CN115335480A

CN115335480A - Adhesive composition, adhesive, and adhesive sheet

Info

Publication number: CN115335480A
Application number: CN202180023731.6A
Authority: CN
Inventors: 形见普史; 片冈贤一; 西野智哉; 山本祐辅; 野依慎太郎
Original assignee: Nitto Denko Corp
Current assignee: Nitto Denko Corp
Priority date: 2020-03-24
Filing date: 2021-03-24
Publication date: 2022-11-11
Also published as: TW202144526A; KR20220153085A; WO2021193719A1

Abstract

An adhesive composition is provided comprising: acrylic acid seriesA polymer (A) containing an aromatic ring-containing monomer (m 1) as a monomer unit; and, an additive (H) _RO ) And an organic material having a higher refractive index than the acrylic polymer (A). Also provided is a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive formed from the pressure-sensitive adhesive composition.

Description

Adhesive composition, adhesive and adhesive sheet

Technical Field

The invention relates to an adhesive composition, an adhesive and an adhesive sheet.

The present application claims priority based on japanese patent application No. 2020-052408, filed on 3/24/2020, japanese patent application No. 2020-166426, filed on 9/30/2020, and japanese patent application No. 2021-049059, filed on 3/23/2021, which are incorporated in their entirety by reference into the present specification.

Background

In general, an adhesive (also referred to as a pressure-sensitive adhesive, hereinafter) has a property of exhibiting a soft solid (viscoelastic body) state in a temperature region near room temperature and simply adhering to an adherend by pressure. By utilizing such properties, adhesives are widely used for the purpose of bonding, fixing, protection, and the like in various industrial fields from home electric appliances to automobiles, various machines, electric devices, electronic devices, and the like. Examples of the use of the adhesive include the use of a polarizing film, a retardation film, a cover window member, and other various light-transmitting members bonded to other members in a display device such as a liquid crystal display device or an organic EL display device.

Patent documents

1 and 2 are cited as technical documents relating to adhesives for optical members.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open No. 2014-169383

Patent document 2: japanese patent laid-open publication No. 2017-128732

Disclosure of Invention

Problems to be solved by the invention

Patent documents

1 and 2 propose an adhesive composition containing a (meth) acrylate polymer containing a monomer having a plurality of aromatic rings as a monomer unit as a main component, and an adhesive obtained by crosslinking the adhesive composition. However, in the techniques described in

patent documents

1 and 2, it is difficult to obtain a pressure-sensitive adhesive having a refractive index higher than that of the (meth) acrylate polymer. On the other hand, a technique of blending particles made of an inorganic material having a high refractive index (for example, inorganic particles such as zirconia particles and titania particles) into a resin to increase the refractive index is also known, but since the refractive index of a pressure-sensitive adhesive blended with inorganic particles is in a trade-off relationship with adhesive properties (for example, peel strength, flexibility, etc.), application to the field of pressure-sensitive adhesives is difficult. In the case of adhesives for optical applications, there is also a concern about a decrease in optical characteristics due to the incorporation of inorganic particles.

Accordingly, an object of the present invention is to provide an adhesive having a refractive index increased by a technique suitable for optical use. Another object of the present invention is to provide an adhesive composition capable of forming such an adhesive and an adhesive sheet comprising the adhesive.

Means for solving the problems

The adhesive composition provided by the present specification comprises: an acrylic polymer (A) containing an aromatic ring-containing monomer (m 1) as a monomer unit; and an additive (H) _RO ) And an organic material having a higher refractive index than the acrylic polymer (A). The acrylic polymer (a) containing an aromatic ring-containing monomer (m 1) as a monomer unit may have a high refractive index. The adhesive compositions disclosed herein are prepared by reacting an epoxy resin with a polyol in the presence of a catalystThe acrylic polymer (A) further contains an additive (H) which is an organic material having a refractive index higher than that of the acrylic polymer (A) _RO ) Thereby, the additive (H) can be formed in a well-balanced manner _RO ) An adhesive which brings about an increase in refractive index and suppression of a decrease in adhesive properties. Further, according to the above-mentioned additive (H) _RO ) It is possible to suppress a decrease in optical characteristics (e.g., transmittance, haze, etc.) and effectively increase the refractive index of the adhesive.

In some preferred forms of the technology disclosed herein (including adhesive compositions, adhesives, adhesive sheets, and technologies practiced in other forms, the same applies hereinafter), the additive (H) described above _RO ) May have a refractive index of, for example, about 1.60 or more. An additive (H) which is an organic material having a refractive index higher than that of the acrylic polymer (A) and satisfying a refractive index of about 1.60 or more _RO ) The refractive index of the adhesive can be effectively increased.

In some embodiments, the above-mentioned additive (H) is added to 100 parts by weight of the acrylic polymer (A) _RO ) The content of (b) may be, for example, more than 0 part by weight and 60 parts by weight or less. Contains an additive (H) in such an amount _RO ) The adhesive composition of (4) can be easily formed in good balance while maintaining the balance of the additive (H) _RO ) The use of the pressure-sensitive adhesive of (1) is preferable because it improves the refractive index and suppresses the decrease in the adhesive properties and/or optical properties.

In some forms, the additive (H) is _RO ) Comprises at least 1 compound selected from the group consisting of aromatic ring-containing compounds and heterocyclic ring-containing compounds. The technique disclosed herein may preferably be used to use the compound as an additive (H) _RO ) The method (2) is implemented.

In some forms, the additive (H) described above _RO ) Includes a compound having 2 or more aromatic rings in 1 molecule. The technique disclosed herein may preferably be used to use the compound as an additive (H) _RO ) The method (2) is implemented. The compound having 2 or more aromatic rings in 1 molecule may be, for example, a compound satisfying at least one of the following conditions:

(i) A structure in which 2 non-fused aromatic rings are directly chemically bonded; and

(ii) Comprises a structure obtained by fusing 2 aromatic rings.

The technology disclosed herein may preferably be used to use such compounds as additives (H) _RO ) The method (2) is implemented.

In some embodiments, the content of the aromatic ring-containing monomer (m 1) in the monomer components constituting the acrylic polymer (a) is 50% by weight or more. The acrylic polymer (a) composed of the monomer components having such a composition can have a high refractive index, and is therefore suitable as the acrylic polymer (a) in the technique disclosed herein.

In some embodiments, the content of the aromatic ring-containing monomer (m 1) in the monomer components constituting the acrylic polymer (a) is more than 70% by weight and less than 100% by weight. Such an acrylic polymer (a) is preferable because it is easy to increase the refractive index and to form an adhesive having good adhesive properties.

In some embodiments, 50% by weight or more of the aromatic ring-containing monomer (m 1) contained in the monomer components constituting the acrylic polymer (a) may be a monomer having a homopolymer glass transition temperature of 10 ℃ or less. Thus, even if the content of the aromatic ring-containing monomer (m 1) in the monomer component is increased, an adhesive having both a high refractive index and adhesive properties in a well-balanced manner can be easily formed. Hereinafter, the Tg of a homopolymer of a monomer may be referred to as the Tg of the monomer.

In some preferred embodiments, the aromatic ring-containing monomer (m 1) includes an aromatic ring-containing monomer having 2 or more aromatic rings in 1 molecule (hereinafter also referred to as "a monomer containing a plurality of aromatic rings"). By using a monomer containing a plurality of aromatic rings, the refractive index of the adhesive can be effectively increased. The aromatic ring-containing monomer (m 1) may contain only 1 kind of a monomer having a plurality of aromatic rings (for example, a homopolymer having a Tg of 10 ℃ or less and a monomer having a plurality of aromatic rings) or may contain 2 or more kinds of monomers having a plurality of aromatic rings in combination.

In some preferred embodiments, the monomer having 2 or more aromatic rings in 1 molecule includes a monomer having a structural portion in which 2 aromatic rings are bonded via a linking group. The multiple aromatic ring-containing monomer having such a structural portion tends to have a lower Tg of a homopolymer than a multiple aromatic ring-containing monomer having a structural portion (for example, a biphenyl structure) in which 2 aromatic rings are directly chemically bonded instead of the structural portion. According to the aromatic ring-containing monomer (m 1) containing a monomer having a plurality of aromatic rings of this structure, flexibility and a high refractive index which are suitable as an adhesive can be balanced more favorably.

In some embodiments, the monomer component constituting the acrylic polymer (a) may further contain a monomer (m 2) having at least one of a hydroxyl group and a carboxyl group in addition to the aromatic ring-containing monomer (m 1). The acrylic polymer (a) composed of the monomer component having such a composition can easily form an adhesive having good adhesive properties.

In the following, the aromatic ring-containing monomer (m 1) may be referred to as "monomer (m 1)" and the monomer (m 2) having at least one of a hydroxyl group and a carboxyl group may be referred to as "monomer (m 2)".

The adhesive compositions disclosed herein may further comprise a crosslinker. The use of the crosslinking agent imparts appropriate cohesive properties to the pressure-sensitive adhesive, and therefore, handling properties of the pressure-sensitive adhesive sheet in the production, processing, storage, attachment to an adherend, and the like can be improved.

In accordance with the present description, an adhesive is provided, which is formed from any of the adhesive compositions disclosed herein. The adhesive is obtained by adding the additive (H) to the acrylic polymer (A) _RO ) Thereby, it is possible to suppress a decrease in adhesive characteristics and/or optical characteristics and to improve the refractive index. In a preferred embodiment, the refractive index of the binder may be higher than 1.570 (preferably 1.575 or more, and more preferably 1.580 or more), for example.

According to the present specification, there is provided an adhesive sheet comprising an adhesive layer composed of an adhesive (e.g., an adhesive having a refractive index of higher than 1.570, preferably 1.575 or more, more preferably 1.580 or more) formed of any of the adhesive compositions disclosed herein. The adhesive sheet can be preferably used so as to be bonded to a member (e.g., an optical member).

In some embodiments of the adhesive sheet disclosed herein, the adhesive layer has a haze value of 1.0% or less. Such a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer with high transparency can be preferably used in the optical field, for example.

It should be noted that the technical means that the respective elements described in the present specification are appropriately combined may be included in the scope claimed in the present patent application.

Drawings

Fig. 1 is a sectional view schematically showing the structure of an adhesive sheet according to an embodiment.

Fig. 2 is a sectional view schematically showing the constitution of an adhesive sheet of another embodiment.

Fig. 3 is a sectional view schematically showing an optical member with an adhesive sheet in which an adhesive sheet according to one embodiment is attached to the optical member.

Detailed Description

Hereinafter, preferred embodiments of the present invention will be described. Matters necessary for carrying out the present invention other than those specifically mentioned in the present specification can be understood by those skilled in the art based on the teaching of the present specification about the implementation of the invention and common general knowledge at the time of application. The present invention can be implemented based on the contents disclosed in the present specification and the common general knowledge in the art.

In the following drawings, members and portions that exhibit the same function are sometimes described with the same reference numerals, and redundant description may be omitted or simplified. The embodiments shown in the drawings are schematic for clearly illustrating the present invention, and do not necessarily accurately show the size or scale of a product to be actually provided.

In this specification, a self-light emitting element refers to a light emitting element capable of controlling light emission luminance by a value of current flowing therethrough. The self-luminous element may be formed of a single body or an aggregate. Specific examples of the self-light emitting element include, but are not limited to, a Light Emitting Diode (LED) and an organic EL. When a light-emitting device is referred to in this specification, the light-emitting device may include such a self-light-emitting element as a constituent element. Examples of the light-emitting device include a light source module device (for example, a planar light-emitting module) used as illumination and a display device in which pixels are formed, but are not limited thereto.

In the present specification, the "base polymer" of the binder means a main component of the rubbery polymer contained in the binder, and is not to be construed as limiting in any way. The rubbery polymer is a polymer that exhibits rubber elasticity in a temperature range around room temperature. In the present specification, the term "main component" means a component contained in an amount of more than 50% by weight unless otherwise specified.

In the present specification, the "acrylic polymer" refers to a polymer containing, as a monomer unit constituting the polymer, a monomer unit derived from a monomer having at least 1 (meth) acryloyl group in 1 molecule. Hereinafter, a monomer having at least 1 (meth) acryloyl group in 1 molecule is also referred to as an "acrylic monomer". Accordingly, the acrylic polymer in the present specification is defined as a polymer containing a monomer unit derived from an acrylic monomer. Typical examples of the acrylic polymer include polymers in which the ratio of the acrylic monomer in all monomers used for the synthesis of the polymer is higher than 50% by weight (preferably higher than 70% by weight, for example, higher than 90% by weight).

In the present specification, "(meth) acryloyl group" means an acryloyl group and a methacryloyl group collectively. Similarly, "(meth) acrylate" is used in the sense of generically referring to both acrylate and methacrylate, and "(meth) acrylic acid" is used in the sense of generically referring to both acrylic acid and methacrylic acid. Therefore, the concept of the acrylic monomer as referred to herein may include both a monomer having an acryloyl group (acrylic monomer) and a monomer having a methacryloyl group (methacrylic monomer).

< adhesive composition >

The adhesive composition disclosed herein is not particularly limited in form as long as it can form an adhesive containing the acrylic polymer (a) (preferably, an adhesive containing the acrylic polymer (a) as a base polymer). The adhesive composition may be in the following various forms, for example: a solvent-based adhesive composition in the form of an adhesive-forming component contained in an organic solvent; an active energy ray-curable pressure-sensitive adhesive composition prepared so as to form a pressure-sensitive adhesive by curing with an active energy ray such as ultraviolet ray or radiation; an aqueous dispersion type adhesive composition in the form of an adhesive forming component dispersed in water; and a hot-melt adhesive composition which forms an adhesive when applied in a molten state by heating and cooled to a temperature around room temperature.

(acrylic Polymer (A))

The adhesive composition disclosed herein contains an acrylic polymer (a) containing an aromatic ring-containing monomer (m 1) as a monomer unit. The acrylic polymer (a) is a polymer containing an aromatic ring-containing monomer (m 1) as a monomer component constituting the acrylic polymer. In the present specification, the term "monomer component constituting the acrylic polymer" refers to a monomer constituting a repeating unit of the acrylic polymer in the pressure-sensitive adhesive formed from the pressure-sensitive adhesive composition, and is not limited to a monomer contained in the pressure-sensitive adhesive composition in the form of a polymer (which may be an oligomer) formed in advance or a monomer contained in the pressure-sensitive adhesive composition in the form of an unpolymerized monomer. That is, the monomer component constituting the acrylic polymer may be contained in the adhesive composition in any form of a polymer, an unpolymerized polymer, and a partially polymerized polymer. From the viewpoint of ease of production of the pressure-sensitive adhesive composition, and the like, in some embodiments, a pressure-sensitive adhesive composition containing substantially all (for example, 95 wt% or more, preferably 99 wt% or more) of the monomer component in the form of a polymer is preferable. An adhesive composition containing substantially all monomer components in the form of a polymer is also preferable from the viewpoint of easy formation of an adhesive sheet with less deformation and warpage.

(monomer (m 1))

As the monomer (m 1), a compound containing at least 1 aromatic ring and at least 1 ethylenically unsaturated group in 1 molecule is used. As the monomer (m 1), 1 kind of the compound may be used alone or 2 or more kinds may be used in combination.

Examples of the ethylenically unsaturated group include a (meth) acryloyl group, a vinyl group, and a (meth) allyl group. From the viewpoint of polymerization reactivity, a (meth) acryloyl group is preferable, and from the viewpoint of flexibility and adhesiveness, an acryloyl group is more preferable. From the viewpoint of suppressing a decrease in flexibility of the adhesive, it is preferable to use, as the monomer (m 1), a compound (i.e., a monofunctional monomer) in which the number of ethylenically unsaturated groups contained in 1 molecule is 1.

The number of aromatic rings contained in 1 molecule of the compound used as the monomer (m 1) may be 1, or 2 or more. The upper limit of the number of aromatic rings contained in the monomer (m 1) is not particularly limited, and may be, for example, 16 or less. In some embodiments, the number of aromatic rings may be, for example, 12 or less, preferably 8 or less, more preferably 6 or less, 5 or less, 4 or less, 3 or less, or 2 or less, from the viewpoints of ease of preparation of the acrylic polymer (a) and transparency of the adhesive.

The aromatic ring of the compound used as the monomer (m 1) may be, for example, a benzene ring (may be a benzene ring constituting a part of a biphenyl structure or a fluorene structure); fused rings of naphthalene ring, indene ring, azulene ring, anthracene ring and phenanthrene ring; and the like carbon rings, and may be, for example, a pyridine ring, a pyrimidine ring, a pyridazine ring, a pyrazine ring, a triazine ring, a pyrrole ring, a pyrazole ring, an imidazole ring, a triazole ring, an oxazole ring, an isoxazole ring, a thiazole ring, a thiophene ring; and the like. The hetero atom contained as a ring-forming atom in the above-mentioned hetero ring may be, for example, 1 or 2 or more selected from the group consisting of nitrogen, sulfur and oxygen. In some embodiments, the heteroatoms constituting the above-described heterocyclic ring may be one or both of nitrogen and sulfur. The monomer (m 1) may have a structure in which 1 or 2 or more carbocyclic rings and 1 or 2 or more heterocyclic rings are fused, for example, as in a dinaphthothiophene structure.

The aromatic ring (preferably, carbocyclic ring) may have 1 or 2 or more substituents on the ring-constituting atoms, or may have no substituent. When a substituent is present, examples of the substituent include, but are not limited to, an alkyl group, an alkoxy group, an aryloxy group, a hydroxyl group, a halogen atom (e.g., a fluorine atom, a chlorine atom, and a bromine atom), a hydroxyalkyl group, a hydroxyalkyloxy group, and a glycidyloxy group. In the substituent containing a carbon atom, the number of carbon atoms contained in the substituent is preferably 1 to 4, more preferably 1 to 3, and may be 1 or 2, for example. In some forms, the above aromatic ring may have no substituent on the ring-forming atoms, or 1 or 2 or more substituents selected from the group consisting of an alkyl group, an alkoxy group, and a halogen atom (e.g., a bromine atom). Note that the aromatic ring of the monomer (m 1) having a substituent on a ring-forming atom thereof means that the aromatic ring has a substituent other than a substituent containing an ethylenically unsaturated group.

The aromatic ring and the ethylenically unsaturated group may be bonded directly or via a linking group. The linking group may be, for example, a group having 1 or 2 or more structures selected from alkylene, oxyalkylene, poly (oxyalkylene), phenyl, alkylphenyl, alkoxyphenyl, and a group having a structure in which 1 or 2 or more hydrogen atoms in these groups are substituted with hydroxyl groups (for example, hydroxyalkylene), oxy (-O-group), thiooxy (-S-group), and the like. In some modes, it may be preferable to employ an aromatic ring-containing monomer of a structure in which an aromatic ring is bonded to an ethylenically unsaturated group directly or via a linking group selected from the group consisting of an alkylene group, an oxyalkylene group, and a poly (oxyalkylene) group. The number of carbon atoms in the alkylene group and the oxyalkylene group is preferably 1 to 4, more preferably 1 to 3, and may be 1 or 2, for example. The number of repeating oxyalkylene units in the poly (oxyalkylene) group may be, for example, 2 to 3.

Examples of the compound which can be preferably used as the monomer (m 1) include aromatic ring-containing (meth) acrylates and aromatic ring-containing vinyl compounds. The aromatic ring-containing (meth) acrylate and the aromatic ring-containing vinyl compound may be used singly or in combination of 1 or more. It is also possible to use 1 or 2 or more kinds of aromatic ring-containing (meth) acrylates in combination with 1 or 2 or more kinds of aromatic ring-containing vinyl compounds.

The content of the monomer (m 1) in the monomer component constituting the acrylic polymer (a) is not particularly limited, and may be set so as to realize a pressure-sensitive adhesive layer that can achieve both desired refractive index and adhesive properties (e.g., peel strength, flexibility, etc.) and/or optical properties (e.g., total light transmittance, haze value, etc.). In some embodiments, the content of the monomer (m 1) in the monomer component may be, for example, 30% by weight or more, preferably 50% by weight or more, may be 60% by weight or more, or may be 70% by weight or more. In some preferable embodiments, the content of the monomer (m 1) is, for example, higher than 70% by weight, may be 75% by weight or more, may be 80% by weight or more, may be 85% by weight or more, may be 90% by weight or more, and may be 95% by weight or more, from the viewpoint of easily obtaining a higher refractive index. The upper limit of the content of the monomer (m 1) in the monomer component is 100% by weight. From the viewpoint of achieving a good balance between the high refractive index and the adhesive and/or optical properties, the content of the monomer (m 1) is favorably less than 100% by weight, and is preferably about 99% by weight or less, more preferably 98% by weight or less, and may be 97% by weight or less, and may be 96% by weight or less, for example. In some embodiments, the content of the monomer (m 1) may be 93% by weight or less, may be 90% by weight or less, may be 80% by weight or less, or may be 75% by weight or less. In some embodiments where the adhesive property and/or the optical property are more important, the content of the monomer (m 1) in the monomer component may be 70 wt% or less, 60 wt% or less, or 45 wt% or less.

In some embodiments of the technology disclosed herein, a monomer having 2 or more aromatic rings (preferably carbocyclic rings) in 1 molecule can be preferably used as the monomer (m 1) in view of easily obtaining a high refractive index increasing effect. Examples of the monomer having 2 or more aromatic rings in 1 molecule (hereinafter, also referred to as "monomer having a plurality of aromatic rings") include: a monomer having a structure in which 2 or more non-condensed aromatic rings are bonded via a linking group, a monomer having a structure in which 2 or more non-condensed aromatic rings are directly chemically bonded (i.e., without via other atoms), a monomer having a condensed aromatic ring structure, a monomer having a fluorene structure, a monomer having a dinaphthothiophene structure, a monomer having a dibenzothiophene structure, and the like. The aromatic ring-containing monomers may be used alone in 1 kind or in combination of 2 or more kinds.

The above-mentioned linking group is, for example may be an oxy (-O-), sulfo-oxo (-S-), oxyalkylene (e.g. -O- (CH)) ₂ ) _n A group, where n is 1 to 3, preferably 1), a thiooxyalkylene group (e.g. -S- (CH) ₂ ) _n A radical, where n is from 1 to 3, preferably 1), a linear alkylene radical (i.e. - (CH) ₂ ) _n A group wherein n is 1 to 6, preferably 1 to 3), a group in which an alkylene group in the oxyalkylene group, the thiooxyalkylene group and the straight-chain alkylene group is partially halogenated or fully halogenated, or the like. From the viewpoint of flexibility of the adhesive and the like, suitable examples of the linking group include an oxy group, a thioxo group, an oxyalkylene group, and a linear alkylene group. Specific examples of the monomer having a structure in which 2 or more non-condensed aromatic rings are bonded via a linking group include phenoxybenzyl (meth) acrylate (e.g., m-phenoxybenzyl (meth) acrylate), thiophenyloxybenzyl (meth) acrylate, and benzylbenzyl (meth) acrylate).

The monomer having a structure in which 2 or more non-condensed aromatic rings are directly chemically bonded may be, for example, (meth) acrylate having a biphenyl structure, (meth) acrylate having a triphenyl structure, biphenyl having a vinyl group, or the like. Specific examples thereof include o-phenylphenol (meth) acrylate and biphenylmethyl (meth) acrylate.

Examples of the monomer having a condensed aromatic ring structure include (meth) acrylate having a naphthalene ring, (meth) acrylate having an anthracene ring, naphthalene having a vinyl group, anthracene having a vinyl group, and the like. Specific examples thereof include 1-naphthylmethyl (meth) acrylate (also known as 1-naphthylmethyl (meth) acrylate), hydroxyethylated β -naphthol acrylate, 2-naphthylethyl (meth) acrylate, 2-naphthyloxyethyl acrylate, and 2- (4-methoxy-1-naphthyloxy) ethyl (meth) acrylate.

Specific examples of the monomer having a fluorene structure include 9,9-bis (4-hydroxyphenyl) fluorene (meth) acrylate, 9,9-bis [4- (2-hydroxyethoxy) phenyl ] fluorene (meth) acrylate, and the like. The monomer having a fluorene structure includes a structural portion in which 2 benzene rings are directly chemically bonded to each other, and thus is included in the concept of the monomer having a structure in which 2 or more non-condensed aromatic rings are directly chemically bonded to each other.

Examples of the monomer having a dinaphthothiophene structure include (meth) acryloyl group-containing dinaphthothiophene, vinyl group-containing dinaphthothiophene, and (meth) allyl group-containing dinaphthothiophene. Specific examples thereof include (meth) acryloyloxymethyl dinaphthothiophenes (for example, a dinaphthothiophene ring having CH bonded to the 5-or 6-position ₂ CH(R ¹ )C(O)OCH ₂ A compound of the structure of (1). Here, R ¹ Is a hydrogen atom or a methyl group. ) (meth) acryloyloxyethyl dinaphthothiophene (for example, CH is bonded to the 5-or 6-position of the dinaphthothiophene ring ₂ CH(R ¹ )C(O)OCH(CH ₃ ) -or CH ₂ CH(R ¹ )C(O)OCH ₂ CH ₂ A compound of the structure of (1). Here, R ¹ Is a hydrogen atom or a methyl group. ) Vinyl dinaphthothiophene (for example, a compound having a structure in which a vinyl group is bonded to the 5-or 6-position of a naphthothiophene ring), and (meth) allyloxydianaphthothiophene. The monomer having a dinaphthothiophene structure includes a naphthalene structure and also has a structure in which 2 naphthalene structures are fused to a thiophene ring, and therefore, the monomer having a fused aromatic ring structure is included in the concept of the monomer having a fused aromatic ring structure.

Examples of the monomer having the dibenzothiophene structure include (meth) acryloyl group-containing dibenzothiophene and vinyl group-containing dibenzothiophene. The monomer having a dibenzothiophene structure has a structure in which 2 benzene rings are fused to a thiophene ring, and therefore, the monomer having a fused aromatic ring structure is included in the concept of the monomer having a fused aromatic ring structure.

The dinaphthothiophene structure and the dibenzothiophene structure do not belong to a structure in which 2 or more non-condensed aromatic rings are directly chemically bonded.

As the monomer (m 1) in the technology disclosed herein, a monomer having 1 aromatic ring (preferably, a carbocyclic ring) in 1 molecule may also be used. The monomer having 1 aromatic ring in 1 molecule can contribute to, for example, improvement of flexibility, adjustment of adhesive properties, improvement of transparency, and the like of the adhesive. In some embodiments, from the viewpoint of improving the refractive index of the adhesive, a monomer having 1 aromatic ring in 1 molecule is preferably used in combination with a monomer containing a plurality of aromatic rings.

Examples of the monomer having 1 aromatic ring in 1 molecule include (meth) acrylates containing a carbon aromatic ring such as benzyl (meth) acrylate, methoxybenzyl (meth) acrylate, phenyl (meth) acrylate, ethoxylated phenol (meth) acrylate, phenoxypropyl (meth) acrylate, phenoxybutyl (meth) acrylate, cresol (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, and chlorobenzyl (meth) acrylate; bromine-substituted aromatic ring-containing (meth) acrylates such as 2- (4,6-dibromo-2-sec-butylphenyloxy) ethyl (meth) acrylate, 2- (4,6-dibromo-2-isopropylphenoxy) ethyl (meth) acrylate, 6- (4,6-dibromo-2-sec-butylphenyloxy) hexyl (meth) acrylate, 6- (4,6-dibromo-2-isopropylphenoxy) hexyl (meth) acrylate, 2,6-dibromo-4-nonylphenyl acrylate, 2,6-dibromo-4-dodecylphenyl acrylate; vinyl compounds containing a carbon aromatic ring such as styrene, α -methylstyrene, vinyltoluene and t-butylstyrene; compounds having a vinyl substituent on the heteroaromatic ring, such as N-vinylpyridine, N-vinylpyrimidine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, and N-vinyloxazole; and the like.

As the monomer (m 1), a monomer having an oxyethylene chain structure between the ethylenically unsaturated group and the aromatic ring in the above-described various aromatic ring-containing monomers can be used. Such a monomer having an oxyethylene chain sandwiched between an ethylenically unsaturated group and an aromatic ring can be grasped as an ethoxylate of the original monomer. Oxyethylene unit (-CH) in the oxyethylene chain ₂ CH ₂ The number of repetitions of O-) is typically 1 to 4, preferably 1 to 3, more preferably 1 to 2, for example 1. Specific examples of the ethoxylated aromatic ring-containing monomer include ethoxylated o-phenylphenol (meth) acrylateEthoxylated nonylphenol (meth) acrylate, ethoxylated cresol (meth) acrylate, phenoxyethyl (meth) acrylate, phenoxydiethylene glycol di (meth) acrylate, and the like.

The content of the monomer having a plurality of aromatic rings in the monomer (m 1) is not particularly limited, and may be, for example, 5% by weight or more, 25% by weight or more, or 40% by weight or more. In some embodiments, the content of the monomer having a plurality of aromatic rings in the monomer (m 1) may be, for example, 50% by weight or more, preferably 70% by weight or more, 85% by weight or more, 90% by weight or more, or 95% by weight or more, from the viewpoint of easily realizing a binder having a higher refractive index. Substantially 100% by weight of the monomer (m 1) may be a monomer containing a plurality of aromatic rings. That is, as the monomer (m 1), only 1 or 2 or more kinds of monomers containing a plurality of aromatic rings may be used. In some embodiments, for example, in view of the balance between the high refractive index and the adhesive property and/or the optical property, the content of the monomer containing a plurality of aromatic rings in the monomer (m 1) may be less than 100% by weight, may be 98% by weight or less, may be 90% by weight or less, may be 80% by weight or less, or may be 65% by weight or less. In some embodiments, the content of the monomer having a plurality of aromatic rings in the monomer (m 1) may be 70% by weight or less, may be 50% by weight or less, may be 25% by weight or less, or may be 10% by weight or less in consideration of the adhesive property and/or the optical property. The technique disclosed herein can also be carried out in such a manner that the content of the monomer having a plurality of aromatic rings in the monomer (m 1) is less than 5% by weight. A monomer containing a plurality of aromatic rings may not be used.

The content of the monomer containing a plurality of aromatic rings in the monomer components constituting the acrylic polymer (a) is not particularly limited, and may be set so as to realize a pressure-sensitive adhesive layer that can achieve both desired refractive index and adhesive properties (e.g., peel strength, flexibility, etc.) and/or optical properties (e.g., total light transmittance, haze value, etc.). The content of the monomer having a plurality of aromatic rings in the monomer component may be, for example, 3% by weight or more, 10% by weight or more, or 25% by weight or more. In some embodiments, the content of the monomer having a plurality of aromatic rings in the monomer component may be, for example, higher than 35% by weight, preferably higher than 50% by weight, may be higher than 70% by weight, may be 75% by weight or more, may be 85% by weight or more, may be 90% by weight or more, or may be 95% by weight or more, from the viewpoint of easily realizing a binder having a higher refractive index. The content of the monomer having a plurality of aromatic rings in the monomer component may be 100% by weight, but from the viewpoint of well-balanced compatibility between the high refractive index and the adhesive property and/or the optical property, it is favorably less than 100% by weight, preferably about 99% by weight or less, more preferably 98% by weight or less, may be 96% by weight or less, may be 93% by weight or less, may be 90% by weight or less, may be 85% by weight or less, may be 80% by weight or less, or may be 75% by weight or less. In some embodiments, the content of the monomer having a plurality of aromatic rings in the monomer component may be 70% by weight or less, 50% by weight or less, 25% by weight or less, 15% by weight or less, or 5% by weight or less in consideration of the adhesive property and/or the optical property. The technique disclosed herein can also be carried out in such a manner that the content of the monomer having a plurality of aromatic rings in the monomer components is less than 3% by weight.

In some aspects of the technology disclosed herein, it may be preferable to employ a high refractive index monomer as at least a part of the monomer (m 1). Here, the "high refractive index monomer" refers to a monomer having a refractive index of, for example, about 1.510 or more, preferably about 1.530 or more, and more preferably about 1.550 or more. The upper limit of the refractive index of the high refractive index monomer is not particularly limited, and is, for example, 3.000 or less, 2.500 or less, 2.000 or less, 1.900 or less, 1.800 or less, or 1.700 or less, from the viewpoint of ease of preparation of the pressure-sensitive adhesive composition and ease of compatibility with flexibility suitable as a pressure-sensitive adhesive. The high refractive index monomer may be used alone in 1 kind or in combination of 2 or more kinds.

The refractive index of the monomer was measured using an Abbe refractometer at a measurement wavelength of 589nm and a measurement temperature of 25 ℃. As the Abbe refractometer, model number "DR-M4" manufactured by ATAGO or its equivalent can be used. In the case where a nominal value of the refractive index at 25 ℃ is provided by the manufacturer or the like, the nominal value may be adopted.

As the high refractive index monomer, a compound having a suitable refractive index can be suitably used from among compounds (for example, the above exemplified compounds and compound groups) included in the concept of the aromatic ring-containing monomer (m 1) disclosed herein. Specific examples thereof include m-phenoxybenzyl acrylate (refractive index: 1.566, tg of homopolymer: 35 ℃ C.), 1-naphthylmethyl acrylate (refractive index: 1.595, tg of homopolymer: 31 ℃ C.), ethoxylated o-phenylphenol acrylate (repetition number of oxyethylene units: 1, refractive index: 1.578), benzyl acrylate (refractive index (nD 20): 1.519, tg of homopolymer: 6 ℃ C.), phenoxyethyl acrylate (refractive index (nD 20): 1.517, tg of homopolymer: 2 ℃ C.), phenoxydiglycol acrylate (refractive index: 1.510, tg of homopolymer: -35 ℃ C.), 6-acryloyloxymethyl dinaphthothiophene (6 MDNTA, refractive index: 1.75), 6-methacryloyloxymethyl dinaphthothiophene (6 MDNTMA, refractive index: 1.726), 5-acryloyloxyethyl dinaphthothiophene (5 EDNTA, refractive index: 1.786), 6-acryloyloxyethyl dinaphthothiophene (6 MDNTA, 3532), vinyldinaphthothiophene (5 EDNTNT), vinyldinaphthothiophene (refractive index: 3425: 3432, VDNTNT), etc., but these refractive indexes are not limited to VDNTNT 2, VDNTNT).

The content of the high-refractive-index monomer (i.e., aromatic ring-containing monomer having a refractive index of about 1.510 or more, preferably about 1.530 or more, and more preferably about 1.550 or more) in the monomer (m 1) is not particularly limited, and may be, for example, 5% by weight or more, 25% by weight or more, 35% by weight or more, or 40% by weight or more. In some embodiments, the content of the high refractive index monomer in the monomer (m 1) may be, for example, 50% by weight or more, preferably 70% by weight or more, 85% by weight or more, 90% by weight or more, or 95% by weight or more, from the viewpoint of easily obtaining a higher refractive index. Substantially 100% by weight of the monomer (m 1) may be a high refractive index monomer. In some embodiments, for example, from the viewpoint of achieving a good balance between the high refractive index and the adhesive properties and/or optical properties, the content of the high refractive index monomer in the monomer (m 1) may be less than 100% by weight, may be 98% by weight or less, may be 90% by weight or less, may be 80% by weight or less, and may be 65% by weight or less. In some aspects, the content of the high refractive index monomer in the monomer (m 1) may be 70 wt% or less, may be 50 wt% or less, may be 25 wt% or less, may be 15 wt% or less, and may be 10 wt% or less in consideration of adhesive characteristics and/or optical characteristics. The technique disclosed herein may also be carried out in such a manner that the content of the high-refractive-index monomer in the monomer component (m 1) is less than 5% by weight. The high refractive index monomer may not be used.

The content of the high refractive index monomer in the monomer component constituting the acrylic polymer (a) is not particularly limited, and may be set so as to realize a pressure-sensitive adhesive layer that can achieve both a desired refractive index and adhesive properties (e.g., peel strength, flexibility, etc.) and/or optical properties (e.g., total light transmittance, haze value, etc.). The content of the high refractive index monomer in the monomer component may be, for example, 3 wt% or more, 10 wt% or more, or 25 wt% or more. In some embodiments, the content of the high refractive index monomer in the monomer component may be, for example, higher than 35% by weight, preferably higher than 50% by weight, may be higher than 70% by weight, may be 75% by weight or more, may be 85% by weight or more, may be 90% by weight or more, or may be 95% by weight or more, from the viewpoint of easily realizing a binder having a higher refractive index. The content of the high refractive index monomer in the monomer component may be 100% by weight, but from the viewpoint of achieving a good balance between the high refractive index and the adhesive and/or optical properties, it is favorably less than 100% by weight, preferably 99% by weight or less, more preferably 98% by weight or less, and may be 96% by weight or less, may be 93% by weight or less, may be 90% by weight or less, may be 85% by weight or less, may be 80% by weight or less, or may be 75% by weight or less. In some embodiments, the content of the high refractive index monomer in the monomer component may be 70 wt% or less, may be 50 wt% or less, may be 25 wt% or less, may be 15 wt% or less, and may be 5 wt% or less in consideration of the adhesive property and/or the optical property. The technique disclosed herein can also be carried out in such a manner that the content of the high refractive index monomer in the above monomer components is less than 3% by weight.

In some preferred embodiments of the technology disclosed herein, an aromatic ring-containing monomer (hereinafter sometimes referred to as "monomer L") having a homopolymer Tg of 10 ℃ or less (preferably 5 ℃ or less or 0 ℃ or less, more preferably-10 ℃ or less, further preferably-20 ℃ or less, for example-25 ℃ or less) is used as at least a part of the monomer (m 1). When the content of the aromatic ring-containing monomer (m 1) (particularly, the aromatic ring-containing monomer (m 1) corresponding to one or both of the aromatic ring-containing monomer and the high refractive index monomer) in the monomer component is increased, the storage modulus G 'of the adhesive tends to be generally increased, and by using the monomer L as a part or the whole of the monomer (m 1), the increase in the storage modulus G' can be suppressed. This can improve the refractive index while maintaining flexibility suitable as a binder more favorably. The lower limit of the Tg of the monomer L is not particularly limited. In view of the balance with the refractive index-increasing effect, the Tg of the monomer L may be, for example, -70 ℃ or higher, may be-55 ℃ or higher, or may be-45 ℃ or higher in some embodiments. The monomers L may be used alone in 1 kind or in combination of 2 or more kinds.

As the monomer L, a compound having a Tg corresponding to that of the compound included in the concept of the aromatic ring-containing monomer (m 1) disclosed herein (for example, the compound and the compound group exemplified above) can be appropriately used. As a suitable example of the aromatic ring-containing monomer usable as the monomer L, m-phenoxybenzyl acrylate (homopolymer Tg: -35 ℃ C.) can be mentioned. As another suitable example, phenoxydiethylene glycol acrylate (homopolymer Tg: -35 ℃ C.) is cited.

The content of the monomer L in the monomer (m 1) is not particularly limited, and may be, for example, 5% by weight or more, 25% by weight or more, or 40% by weight or more. In some embodiments, the content of the monomer L in the monomer (m 1) may be, for example, 50% by weight or more, 60% by weight or more, 70% by weight or more, 75% by weight or more, 85% by weight or more, 90% by weight or more, or 95% by weight or more, from the viewpoint of easily obtaining a binder having both a high refractive index and flexibility at a higher level. The monomer L may be substantially 100% by weight of the monomer (A1). In some embodiments, for example, from the viewpoint of achieving both flexibility and high refractive index which are suitable as a binder in a good balance, the content of the monomer L in the monomer (m 1) may be less than 100% by weight, may be 98% by weight or less, may be 90% by weight or less, may be 80% by weight or less, may be 70% by weight or less, may be 50% by weight or less, may be 25% by weight or less, or may be 10% by weight or less. The technique disclosed herein can also be carried out in such a manner that the content of the monomer L in the monomer (m 1) is less than 5% by weight. The monomer L may not be used.

The content of the monomer L in the monomer components constituting the acrylic polymer (a) may be, for example, 3 wt% or more, 10 wt% or more, or 25 wt% or more. In some embodiments, the content of the monomer L in the monomer component may be, for example, higher than 35% by weight, preferably higher than 50% by weight, may be higher than 70% by weight, may be 75% by weight or more, may be 85% by weight or more, may be 90% by weight or more, or may be 95% by weight or more, from the viewpoint of easily obtaining a binder having both a high refractive index and flexibility at a higher level. The content of the monomer L in the monomer component may be 100% by weight, but in consideration of the balance between the high refractive index and the adhesive property and/or the optical property, it is advantageous to be less than 100% by weight, preferably about 99% by weight or less, more preferably 98% by weight or less, and may be 96% by weight or less, may be 95% by weight or less, may be 93% by weight or less, may be 90% by weight or less, may be 85% by weight or less, may be 80% by weight or less, and may be 75% by weight or less. In some embodiments, the content of the monomer L in the monomer component may be 70% by weight or less, 50% by weight or less, 25% by weight or less, 15% by weight or less, or 5% by weight or less. The technique disclosed herein can also be carried out in such a manner that the content of the monomer L in the above-mentioned monomer components is less than 3% by weight.

In some embodiments, the glass transition temperature Tg based on the composition of the monomer (m 1) is from the viewpoint of flexibility of the adhesive _m1 Advantageously, the temperature is about 20 ℃ or lower, preferably 10 ℃ or lower (e.g., 5 ℃ or lower), more preferably 0 ℃ or lower, still more preferably-10 ℃ or lower, and may be-20 ℃ or lower, or may be-25 ℃ or lower. Glass transition temperature Tg _m1 The lower limit of (b) is not particularly limited. In some ways, the glass transition temperature Tg is taken into consideration in balance with the refractive index-increasing effect _m1 For example, it may be at least-70 deg.C, at least-55 deg.C, or at least-45 deg.C. The techniques disclosed herein may also be used at the glass transition temperature Tg _m1 For example, at-40 ℃ or higher, -35 ℃ or higher, -33 ℃ or higher, -30 ℃ or higher, or-25 ℃ or higher.

Here, the glass transition temperature Tg based on the composition of the monomer (m 1) _m1 The method comprises the following steps: tg determined by the following Fox equation based only on the composition of the monomer (m 1) in the monomer components constituting the acrylic polymer (A). Glass transition temperature Tg _m1 The following Fox formula can be applied to only the monomer (m 1) among the monomer components constituting the acrylic polymer (A), and the glass transition temperature of a homopolymer of each aromatic ring-containing monomer used as the monomer (m 1) and the weight fraction of each aromatic ring-containing monomer in the total amount of the monomer (m 1) can be calculated. In the mode of using only 1 monomer as the monomer (m 1), tg and glass transition temperature Tg of a homopolymer of the monomer _m1 And (5) the consistency is achieved.

In some embodiments, as the aromatic ring-containing monomer (m 1), a monomer L (i.e., an aromatic ring-containing monomer having a homopolymer Tg of 10 ℃ or less, preferably 5 ℃ or less, or 0 ℃ or less, more preferably-10 ℃ or less, further preferably-20 ℃ or less, for example-25 ℃ or less) and a monomer H having a Tg of more than 10 ℃ may be used in combination. The Tg of the monomer H may, for example, be higher than 10 deg.C, higher than 15 deg.C or higher than 20 deg.C. By using the monomer L and the monomer H in combination, for example, the content of the aromatic ring-containing monomer (m 1) in the monomer component is largeIn the structure (2), the high refractive index and flexibility of the adhesive can be achieved at a higher level. The amount ratio of the monomer L to the monomer H used is not particularly limited, and may be set so as to exhibit the above-mentioned effects. For example, it is preferable to satisfy any one of the above glass transition temperatures Tg _m1 The ratio of the amount of the monomer L to the amount of the monomer H used is set as described in (1).

In some embodiments, the aromatic ring-containing monomer (m 1) may be preferably selected from compounds that do not include a structure in which 2 or more non-fused aromatic rings are directly chemically bonded (e.g., a biphenyl structure). For example, the acrylic polymer is preferably composed of a monomer component having a composition in which the content of a compound having a structure in which 2 or more non-condensed aromatic rings are directly chemically bonded is less than 5% by weight (more preferably less than 3% by weight, and may be 0% by weight). From the viewpoint of realizing an adhesive that has flexibility, adhesion, and a high refractive index in a well-balanced manner, it is advantageous to limit the amount of the compound having a structure in which 2 or more non-condensed aromatic rings are directly chemically bonded to each other.

(monomer (m 2))

In some embodiments of the technology disclosed herein, the monomer component constituting the acrylic polymer (a) may further contain a monomer (m 2) in addition to the monomer (m 1). The monomer (m 2) is a monomer belonging to at least one of a monomer having a hydroxyl group (hydroxyl group-containing monomer) and a monomer having a carboxyl group (carboxyl group-containing monomer). The above-mentioned hydroxyl group-containing monomer is a compound having at least 1 hydroxyl group and at least 1 ethylenically unsaturated group in 1 molecule. The above carboxyl group-containing monomer is a compound containing at least 1 carboxyl group and at least 1 ethylenically unsaturated group in 1 molecule. The monomer (m 2) can contribute to introduction of a crosslinking point into the acrylic polymer (a) or can impart appropriate cohesive properties to the adhesive. The monomer (m 2) may be used alone in 1 kind or in combination of 2 or more kinds. The monomer (m 2) is typically a monomer containing no aromatic ring.

Examples of the ethylenically unsaturated group of the monomer (m 2) include a (meth) acryloyl group, a vinyl group, and a (meth) allyl group. From the viewpoint of polymerization reactivity, a (meth) acryloyl group is preferable, and from the viewpoint of flexibility and adhesiveness, an acryloyl group is more preferable. From the viewpoint of suppressing the decrease in flexibility of the adhesive, it is preferable to use, as the monomer (m 2), a compound having 1 number of ethylenically unsaturated groups contained in 1 molecule (i.e., a monofunctional monomer).

Examples of the hydroxyl group-containing monomer include, but are not limited to, hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate, and (4-hydroxymethylcyclohexyl) methyl (meth) acrylate. Examples of hydroxyl group-containing monomers which can be preferably used include 4-hydroxybutyl acrylate (Tg: -40 ℃) and 2-hydroxyethyl acrylate (Tg: -15 ℃). From the viewpoint of improving flexibility in the room temperature region, 4-hydroxybutyl acrylate having a lower Tg is more preferable. In a preferred embodiment, it is possible that 50% by weight or more (for example, more than 50% by weight, more than 70% by weight, or more than 85% by weight) of the monomer (m 2) is 4-hydroxybutyl acrylate. The hydroxyl group-containing monomers may be used singly in 1 kind or in combination of 2 or more kinds.

In some modes of using a hydroxyl group-containing monomer as the monomer (m 2), the above hydroxyl group-containing monomer may be 1 or 2 or more selected from compounds having no methacryloyl group. Suitable examples of the hydroxyl group-containing monomer having no methacryloyl group include the above-mentioned various hydroxyalkyl acrylates. For example, it is preferable that more than 50% by weight, more than 70% by weight, or more than 85% by weight of the hydroxyl group-containing monomers used as the monomer (m 2) is hydroxyalkyl acrylate. By using the hydroxyalkyl acrylate, a hydroxyl group contributing to the provision of a crosslinking point and imparting appropriate cohesive property can be introduced into the acrylic polymer (a), and a pressure-sensitive adhesive having excellent flexibility and adhesiveness in a room temperature region can be easily obtained as compared with a case where only the corresponding hydroxyalkyl methacrylate is used.

Examples of the carboxyl group-containing monomer include, but are not limited to, acrylic monomers such as (meth) acrylic acid, carboxyethyl (meth) acrylate, and carboxypentyl (meth) acrylate, and itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid. Examples of the carboxyl group-containing monomer that can be preferably used include acrylic acid and methacrylic acid. The carboxyl group-containing monomers may be used alone in 1 kind or in combination of 2 or more kinds. A combination of a hydroxyl group-containing monomer and a carboxyl group-containing monomer may also be used.

The content of the monomer (m 2) in the monomer components constituting the acrylic polymer (a) is not particularly limited and may be set according to the purpose. In some embodiments, the content of the monomer (m 2) may be, for example, 0.01 wt% or more, 0.1 wt% or more, or 0.5 wt% or more. From the viewpoint of obtaining a higher effect of use, the content of the monomer (A2) may be preferably 1% by weight or more, 2% by weight or more, or 4% by weight or more in some embodiments. The upper limit of the content of the monomer (m 2) in the monomer component is set so that the total content of the monomer (m 2) and the content of the monomer (m 1) does not exceed 100% by weight. In some embodiments, the content of the monomer (m 2) is preferably 30% by weight or less or 25% by weight or less, and from the viewpoint of relatively increasing the content of the monomer (m 1) to facilitate the increase in refractive index, the content is preferably 20% by weight or less, more preferably 15% by weight or less, and may be less than 12% by weight, less than 10% by weight, or less than 7% by weight.

In the embodiment using a hydroxyl group-containing monomer as the monomer (m 2), the content of the hydroxyl group-containing monomer in the monomer component is not particularly limited, and may be, for example, 0.01 wt% or more (preferably 0.1 wt% or more, more preferably 0.5 wt% or more). In some embodiments, the content of the hydroxyl group-containing monomer is preferably 1% by weight or more, may be 2% by weight or more, or may be 4% by weight or more of the monomer component. The upper limit of the content of the hydroxyl group-containing monomer in the monomer component is set so that the total content of the hydroxyl group-containing monomer and the content of the monomer (m 1) does not exceed 100% by weight, and is preferably 30% by weight or less or 25% by weight or less, for example, and from the viewpoint of relatively increasing the content of the monomer (m 1) to facilitate the increase in refractive index, the upper limit is preferably 20% by weight or less, more preferably 15% by weight or less, may be less than 12% by weight, may be less than 10% by weight, or may be less than 7% by weight.

In the embodiment using a carboxyl group-containing monomer as the monomer (m 2), the content of the carboxyl group-containing monomer in the monomer component is not particularly limited, and may be, for example, 0.01 wt% or more (preferably 0.1 wt% or more, more preferably 0.3 wt% or more). In some embodiments, the content of the carboxyl group-containing monomer may be 1% by weight or more, 2% by weight or more, or 4% by weight or more. The upper limit of the content of the carboxyl group-containing monomer in the monomer component is set so that the total amount of the carboxyl group-containing monomer and the amount of the monomer (m 1) used does not exceed 100% by weight, and is preferably 30% by weight or less or 25% by weight or less, for example, and from the viewpoint of increasing the content of the monomer (m 1) relatively to facilitate the increase in refractive index, the content is preferably 20% by weight or less, more preferably 15% by weight or less, and may be less than 12% by weight or less than 10% by weight. In some embodiments, the content of the carboxyl group-containing monomer is favorably less than 7% by weight, preferably less than 5% by weight, may be less than 3% by weight, may be less than 1% by weight, or may be less than 0.5% by weight, from the viewpoint of improving the flexibility of the binder. The technique disclosed herein can be preferably carried out, for example, in a manner of using only a hydroxyl group-containing monomer as the monomer (m 2), that is, in a manner of not using a carboxyl group-containing monomer.

The total content of the monomer (m 1) and the monomer (m 2) in the monomer components constituting the acrylic polymer (a) may be, for example, 31 wt% or more, preferably 51 wt% or more, 61 wt% or more, or 71 wt% or more. In some embodiments, from the viewpoint of easily and suitably exhibiting the effects of these monomers, the total content of the monomer (m 1) and the monomer (m 2) in the monomer components constituting the acrylic polymer (a) may be, for example, 76% by weight or more, preferably 81% by weight or more, may be 86% by weight or more, may be 91% by weight or more, may be 96% by weight or more, may be 99% by weight or more, or may be substantially 100% by weight.

(monomer m 3)

The monomer component constituting the acrylic polymer (a) may contain monomers other than the monomer (m 1) and the monomer (m 2) as required. An example of such an optional component is an alkyl (meth) acrylate (hereinafter also referred to as "monomer (m 3)"). The monomer (m 3) can contribute to adjustment of flexibility of the adhesive and improvement of compatibility in the adhesive.

As the monomer (m 3), one having 1 to 20 carbon atoms at the ester terminal (i.e., C) _1-20 Of (b) a linear or branched alkyl (meth) acrylate. As (meth) acrylic acid C _1-20 Specific examples of the alkyl ester include, but are not limited to, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, sec-butyl (meth) acrylate, tert-butyl (meth) acrylate, pentyl (meth) acrylate, isoamyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate, tridecyl (meth) acrylate, tetradecyl (meth) acrylate, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate, stearyl (meth) acrylate, isostearyl (meth) acrylate, nonadecyl (meth) acrylate, and eicosyl (meth) acrylate.

In some embodiments, it may be preferable to use, as at least a part of monomer (m 3), an alkyl (meth) acrylate whose homopolymer has a Tg of-20 ℃ or lower (more preferably-40 ℃ or lower, for example-50 ℃ or lower). Such low Tg alkyl (meth) acrylates can help to improve the flexibility of the adhesive. The lower limit of Tg of the above-mentioned alkyl (meth) acrylate is not particularly limited, and may be, for example, not less than-85 ℃, not less than-75 ℃, not less than-65 ℃ or not less than-60 ℃. Specific examples of the low Tg alkyl (meth) acrylate include n-Butyl Acrylate (BA), 2-ethylhexyl acrylate (2 EHA), isononyl acrylate (iNA), and the like.

In some embodiments using the monomer (m 3), it is preferable that at least a part of the monomer (m 3) is an alkyl acrylate from the viewpoint of flexibility, adhesiveness, and the like. For example, it is preferable that 50% by weight or more (more preferably 75% by weight or more, and still more preferably 90% by weight or more) of the monomer (m 3) is an alkyl acrylate. The method may be one in which only 1 or 2 or more alkyl acrylates are used as the monomer (m 3) and alkyl methacrylates are not used.

In the embodiment where the monomer component contains an alkyl (meth) acrylate, the content of the alkyl (meth) acrylate in the monomer component may be set so as to exhibit its use effect appropriately. In some embodiments, the content of the alkyl (meth) acrylate may be, for example, 1 wt% or more, 3 wt% or more, 5 wt% or more, or 8 wt% or more. In some embodiments, the content of the alkyl (meth) acrylate may be 15 wt% or more, 30 wt% or more, or 45 wt% or more. The upper limit of the content of the monomer (m 3) in the monomer component is set so that the total content thereof with the content of other monomers does not exceed 100% by weight, and may be, for example, less than 50% by weight. In some embodiments, the content of the above monomer (m 3) may be, for example, less than 35% by weight. Since the refractive index of the alkyl (meth) acrylate is generally low, it is advantageous to relatively increase the content of the monomer (m 1) by limiting the content of the monomer (m 3) in the monomer component in order to increase the refractive index. From this viewpoint, the content of the monomer (m 3) is favorably 24% by weight or less of the monomer components, preferably less than 23% by weight, more preferably less than 20% by weight, possibly less than 17% by weight, possibly less than 12% by weight, possibly less than 7% by weight, possibly less than 3% by weight, possibly less than 1% by weight. The monomer (m 3) may be substantially not used.

(other monomers)

The monomer component constituting the acrylic polymer (a) may contain a monomer other than the above-mentioned monomers (m 1), (m 2) and (m 3) (hereinafter referred to as "other monomer") as necessary. The other monomer may be used for the purpose of, for example, adjusting Tg of the acrylic polymer (a), adjusting adhesive performance, improving compatibility in the adhesive layer, and the like. The other monomers can be used alone in 1 or a combination of 2 or more.

Examples of the other monomer include monomers having a functional group other than a hydroxyl group and a carboxyl group (functional group-containing monomers). Examples of the other monomers capable of improving the cohesive force and heat resistance of the adhesive include sulfonic acid group-containing monomers, phosphoric acid group-containing monomers, and cyano group-containing monomers. Examples of the monomer capable of introducing a functional group capable of serving as a crosslinking base point into the acrylic polymer (a), or contributing to an improvement in peel strength and an improvement in compatibility in the pressure-sensitive adhesive layer include an amide group-containing monomer (e.g., (meth) acrylamide, N-methylol (meth) acrylamide, etc.), an amino group-containing monomer (e.g., (meth) aminoethyl acrylate, N-dimethylaminoethyl (meth) acrylate, etc.), a monomer having a nitrogen atom-containing ring (e.g., N-vinyl-2-pyrrolidone, N- (meth) acryloylmorpholine, etc.), an imide group-containing monomer, an epoxy group-containing monomer, a ketone group-containing monomer, an isocyanate group-containing monomer, an alkoxysilyl group-containing monomer, and the like. Among the monomers having a nitrogen atom-containing ring, for example, N-vinyl-2-pyrrolidone is also included in the amide group-containing monomers. The same applies to the relationship between the monomer having a nitrogen atom-containing ring and the amino group-containing monomer.

Examples of the other monomers that can be used in addition to the functional group-containing monomer include vinyl ester monomers such as vinyl acetate; non-aromatic ring-containing (meth) acrylates such as cyclohexyl (meth) acrylate and isobornyl (meth) acrylate; olefin monomers such as ethylene, butadiene, and isobutylene; chlorine-containing monomers such as vinyl chloride; alkoxy group-containing monomers such as methoxyethyl (meth) acrylate, ethoxyethyl (meth) acrylate, and ethoxyethoxyethyl (meth) acrylate; vinyl ether monomers such as methyl vinyl ether; and the like. As a suitable example of the other monomer which can be used for the purpose of improving the flexibility of the adhesive, etc., ethoxyethoxyethoxyethyl acrylate (also known as ethylcarbitol acrylate, homopolymer Tg: -67 ℃ C.) can be mentioned.

When the above-mentioned other monomers are used, the amount thereof to be used is not particularly limited, and may be appropriately set within a range that the total amount of the monomer components does not exceed 100% by weight. In some embodiments, the content of the other monomer in the monomer component may be, for example, about 35% by weight or less, preferably about 25% by weight or less (for example, 0 to 25% by weight), or may be about 20% by weight or less (for example, 0 to 20% by weight), or may be about 10% by weight or less, or may be about 5% by weight or less, or may be about 1% by weight or less, from the viewpoint of easily exerting the refractive index improving effect by the use of the monomer (m 1). The techniques disclosed herein can be preferably carried out in such a manner that the monomer component does not substantially contain the other monomers described above.

In some embodiments, the monomer component constituting the acrylic polymer (a) may have a composition in which the amount of the methacryloyl group-containing monomer used is suppressed to a predetermined level or less. The amount of the methacryloyl group-containing monomer in the monomer component may be, for example, less than 5% by weight, less than 3% by weight, less than 1% by weight, or less than 0.5% by weight. From the viewpoint of realizing a pressure-sensitive adhesive that achieves a good balance of flexibility, adhesiveness, and high refractive index, it may be advantageous to limit the amount of the methacryloyl group-containing monomer used. The monomer component constituting the acrylic polymer (a) may be a composition containing no methacryloyl group-containing monomer (for example, a composition containing only an acryloyl group-containing monomer).

In some embodiments, it is preferable to limit the amount of the carboxyl group-containing monomer to be used, from the viewpoint of suppressing coloring or discoloration (for example, yellowing) of the pressure-sensitive adhesive, with respect to the monomer component constituting the acrylic polymer (a). The amount of the carboxyl group-containing monomer in the monomer component may be, for example, less than 1% by weight, preferably less than 0.5% by weight, more preferably less than 0.3% by weight, less than 0.1% by weight, or less than 0.05% by weight. Such a limitation of the amount of the carboxyl group-containing monomer used is also advantageous from the viewpoint of suppressing corrosion of a metal material (for example, a metal wiring, a metal film, or the like that may be present on an adherend) that may be placed in contact with or in proximity to the pressure-sensitive adhesive disclosed herein. The technique disclosed herein can be preferably carried out in such a manner that the monomer component does not contain a carboxyl group-containing monomer.

For the same reason, in some embodiments, the monomer component constituting the acrylic polymer (a) is preferably limited in the amount of the monomer having an acidic functional group (including a sulfonic acid group, a phosphoric acid group, and the like in addition to a carboxyl group). As the amount of the acidic functional group-containing monomer used in the monomer component of this embodiment, the preferable amount of the carboxyl group-containing monomer can be used. The technique disclosed herein can be preferably carried out in such a manner that the monomer component does not contain an acid group-containing monomer (i.e., in such a manner that the acrylic polymer (a) is acid-free).

(glass transition temperature Tg) _T )

In some embodiments, the glass transition temperature Tg of the monomer component constituting the acrylic polymer (a) is based on the composition of the monomer component _T Suitably at a temperature of about 20 ℃ or lower, preferably at a temperature of about 10 ℃ or lower, more preferably at a temperature of 0 ℃ or lower, and may be at a temperature of-10 ℃ or lower, may be at a temperature of-20 ℃ or lower, may be at a temperature of-25 ℃ or lower, may be at a temperature of-28 ℃ or lower, or may be at a temperature of-30 ℃ or lower. Glass transition temperature Tg _T When the content is low, it may be advantageous from the viewpoint of improving the flexibility of the adhesive. In addition, the glass transition temperature Tg _T For example, it may be-60 ℃ or higher, and from the viewpoint of facilitating the increase in refractive index of the adhesive, it is preferably-50 ℃ or higher, more preferably higher than-45 ℃, and may be higher than-40 ℃, may be higher than-35 ℃, may be higher than-25 ℃, may be-15 ℃ or higher, and may be-5 ℃ or higher.

Here, the glass transition temperature Tg _T Unless otherwise specified, the term "glass transition temperature" refers to the glass transition temperature determined by the Fox equation based on the composition of the monomer component. The Fox formula is a relational expression between Tg of a copolymer and glass transition temperature Tgi of a homopolymer obtained by homopolymerizing monomers constituting the copolymer, as shown below.

1/Tg＝Σ(Wi/Tgi)

In the Fox formula, tg represents the glass transition temperature (unit: K) of the copolymer, wi represents the weight fraction (copolymerization ratio on the weight basis) of the monomer i in the copolymer, and Tgi represents the glass transition temperature (unit: K) of the homopolymer of the monomer i.

As the glass transition temperature of the homopolymer used for calculating Tg, a value described in publicly known data such as "Polymer Handbook" (3 rd edition, john Wiley & Sons, inc., 1989) was used. The highest value was used for the monomers having various values described in the Polymer Handbook. In the case where the Tg of a homopolymer is not described in the publicly known documents, a value obtained by the measurement method described in Japanese patent application laid-open No. 2007-51271 is used.

(method for producing acrylic Polymer (A))

In the techniques disclosed herein, the method for obtaining the acrylic polymer (a) composed of such monomer components is not particularly limited, and various polymerization methods known as a method for synthesizing an acrylic polymer, such as solution polymerization, emulsion polymerization, bulk polymerization, suspension polymerization, and photopolymerization, can be suitably used. For example, the solution polymerization method can be preferably employed. The polymerization temperature in the solution polymerization may be appropriately selected depending on the types of monomers and solvents used, the type of polymerization initiator, and the like, and may be, for example, about 20 to 170 ℃ (typically about 40 to 140 ℃).

The solvent (polymerization solvent) used for the solution polymerization may be appropriately selected from conventionally known organic solvents. For example, aromatic compounds (typically aromatic hydrocarbons) selected from toluene and the like; acetic acid esters such as ethyl acetate; aliphatic or alicyclic hydrocarbons such as hexane and cyclohexane; 1,2-dichloroethane and other halogenated alkanes; lower alcohols such as isopropyl alcohol (e.g., monohydric alcohols having 1 to 4 carbon atoms); ethers such as t-butyl methyl ether; ketones such as methyl ethyl ketone; etc. or a mixed solvent of 2 or more.

The initiator used for the polymerization may be appropriately selected from conventionally known polymerization initiators depending on the kind of the polymerization method. For example, 1 or 2 or more azo polymerization initiators such as 2,2' -Azobisisobutyronitrile (AIBN) can be preferably used. Other examples of the polymerization initiator include: persulfates such as potassium persulfate; peroxide initiators such as benzoyl peroxide and hydrogen peroxide; substituted ethane initiators such as phenyl-substituted ethane; an aromatic carbonyl compound; and the like. As still another example of the polymerization initiator, a redox-type initiator based on a combination of a peroxide and a reducing agent can be cited. The polymerization initiators may be used alone in 1 kind or in combination of 2 or more kinds. The amount of the polymerization initiator to be used may be a usual amount, and may be selected from a range of about 0.005 to 1 part by weight (typically about 0.01 to 1 part by weight) per 100 parts by weight of the monomer component.

In the polymerization, various conventionally known chain transfer agents can be used as needed. For example, mercaptans such as n-dodecyl mercaptan, t-dodecyl mercaptan, thioglycolic acid, and α -thioglycerol can be used. Alternatively, a chain transfer agent containing no sulfur atom (non-sulfur chain transfer agent) may be used. Examples of the non-sulfur chain transfer agent include: anilines such as N, N-dimethylaniline and N, N-diethylaniline; terpenes such as α -pinene and terpinolene; styrenes such as α -methylstyrene and α -methylstyrene dimer; and the like. The chain transfer agent may be used alone in 1 kind or in combination of 2 or more kinds. The amount of the chain transfer agent used may be, for example, about 0.01 to 1 part by weight per 100 parts by weight of the monomer raw material.

The weight average molecular weight (Mw) of the acrylic polymer (A) is not particularly limited, and may be, for example, about 10X 10 ⁴ ～500×10 ⁴ The range of (1). From the viewpoint of adhesive properties, the Mw of the acrylic polymer (A) is preferably at about 20X 10 ⁴ ～400×10 ⁴ (more preferably about 30X 10) ⁴ ～150×10 ⁴ E.g. about 50X 10 ⁴ ～130×10 ⁴ ) The range of (1).

Here, the Mw of the acrylic polymer (a) can be determined in terms of polystyrene by Gel Permeation Chromatography (GPC). Specifically, the measurement was carried out under the following conditions using a GPC measurement apparatus having the trade name "HLC-8220GPC" (manufactured by Tosoh corporation).

[ measurement conditions of GPC ]

Sample concentration: 0.2 wt% (tetrahydrofuran solution)

Sample injection amount: 10 μ L

Eluent: tetrahydrofuran (THF)

Flow rate (flow velocity): 0.6 mL/min

Column temperature (measurement temperature): 40 deg.C

Column:

sample column: trade name "TSKguardcolumn SuperHZ-H"1 root + trade name "TSKgel SuperHZM-H"2 root (manufactured by Tosoh Co., ltd.)

Reference column: trade name "TSKgel SuperH-RC"1 root (manufactured by Tosoh corporation)

A detector: differential Refractometer (RI)

Standard sample: polystyrene

(additive (H) _RO ))

As an additive in the art disclosed herein (H) _RO ) In the opposite relationship to the acrylic polymer (a), an organic material having a higher refractive index is used. Here, the above "H _RO "denotes an Organic material (Organic material) having a High Refractive index (High Refractive index). By using such additives in combination (H) _RO ) The acrylic polymer (a) can provide an adhesive agent having a refractive index and adhesive properties (peel strength, flexibility, etc.) and/or optical properties (total light transmittance, haze value, etc.) at the same time. As additive (H) _RO ) The organic material of (a) may be a polymer or a non-polymer. The functional group may or may not have a polymerizable functional group. Additive (H) _RO ) 1 or more species may be used alone or in combination.

Additive (H) _RO ) The refractive index of (b) is not limited to a specific range, since it can be set to an appropriate range in a relative relationship with the refractive index of the acrylic polymer (a). Additive (H) _RO ) Can be selected, for example, from a range of refractive indices higher than 1.55, higher than 1.56, or higher than 1.57, and higher than that of the acrylic polymer (a). From the viewpoint of increasing the refractive index of the binder, in some embodiments, the additive (H) _RO ) The refractive index of (a) is favorably 1.58 or more, preferably 1.60 or more, more preferably 1.63 or more, may be 1.65 or more, may be 1.70 or more, and may be 1.58 or moreMay be 1.75 or more. Using additives (H) of higher refractive index _RO ) When, even smaller amounts of additive (H) are used _RO ) The target refractive index can also be achieved. This is preferable from the viewpoint of suppressing the decrease in adhesive properties and optical properties. Additive (H) _RO ) The upper limit of the refractive index of (b) is not particularly limited, and from the viewpoint of easiness in compatibility and high refractive index in the adhesive and compatibility with flexibility suitable as an adhesive, for example, it is 3.000 or less, and may be 2.500 or less, and may be 2.000 or less, and may be 1.950 or less, and may be 1.900 or less, and may be 1.850 or less.

The additive (H) is _RO ) The refractive index of (2) was measured at a measurement wavelength of 589nm and a measurement temperature of 25 ℃ using an Abbe refractometer in the same manner as the refractive index of the monomer. When a nominal value of the refractive index at 25 ℃ is provided by a manufacturer or the like, the nominal value may be adopted.

Additive (H) _RO ) Refractive index n of _b Refractive index n with acrylic Polymer (A) _a The difference, i.e. n _b -n _a (hereinafter also referred to as "Δ n _A ". ) Is set to be greater than 0. In some modes, Δ n _A For example, the content is 0.02 or more, may be 0.05 or more, may be 0.07 or more, may be 0.10 or more, may be 0.15 or more, and may be 0.20 or more, or 0.25 or more. By selecting the acrylic polymer (A) and the additive (H) _RO ) So that Δ n _A Become larger with additives (H) _RO ) The effect of improving the refractive index by using (2) tends to be high. In addition, from additives (H) in the adhesive layer _RO ) From the viewpoint of compatibility, in some modes,. DELTA.n _A For example, it may be 0.70 or less, 0.60 or less, 0.50 or less, 0.40 or less, or 0.35 or less.

In some modes, the additive (H) _RO ) Refractive index n of _b And comprising the additive (H) _RO ) Refractive index n of the adhesive layer _T The difference, i.e. n _b -n _T (hereinafter also referred to as "Δ n _B ". ) May be set to be greater than 0. In some modes, Δ n _B For example, the content of the organic solvent is 0.02 or more,may be 0.05 or more, may be 0.07 or more, may be 0.10 or more, may be 0.15 or more, and may be 0.20 or more, or 0.25 or more. By selecting the composition of the adhesive layer and the additives (H) _RO ) So that Δ n _B Become larger with additives (H) _RO ) The effect of improving the refractive index tends to be high. In some embodiments, Δ n is calculated from the viewpoint of compatibility in the pressure-sensitive adhesive layer, transparency of the pressure-sensitive adhesive layer, and the like _B For example, it may be 0.70 or less, 0.60 or less, 0.50 or less, 0.40 or less, or 0.35 or less.

As additive (H) _RO ) The molecular weight of the organic material to be used is not particularly limited and may be selected according to the purpose. In some embodiments, the additive (H) is added in order to balance the effect of increasing the refractive index with other characteristics (e.g., optical characteristics suitable for the adhesive such as flexibility and haze) well _RO ) Suitably, the molecular weight of (a) is less than about 10000, preferably less than 5000, more preferably less than 3000 (e.g. less than 1000), and may be less than 800, may be less than 600, may be less than 500, and may be less than 400. Additive (H) _RO ) When the molecular weight of (b) is not too large, it may be advantageous from the viewpoint of improving compatibility in the adhesive layer. In addition, an additive (H) _RO ) The molecular weight of (b) may be 130 or more, or 150 or more, for example. In some forms, from the additive (H) _RO ) From the viewpoint of increasing the refractive index of (C), an additive (H) _RO ) The molecular weight of (a) is preferably 170 or more, more preferably 200 or more, may be 230 or more, may be 250 or more, may be 270 or more, may be 500 or more, may be 1000 or more, and may be 2000 or more. In some embodiments, a polymer having a molecular weight of about 1000 to 10000 (e.g., 1000 or more and less than 5000) may be used as the additive (H) _RO )。

As additive (H) _RO ) The molecular weight of (2) can be calculated from a non-polymer or a polymer having a low degree of polymerization (for example, about 2 to 5-mer) or can be determined by matrix assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF-MS). Additive (H) _RO ) Is composed ofIn the case of a polymer having a higher polymerization degree, a weight average molecular weight (Mw) based on GPC performed under appropriate conditions can be used. The nominal value of the molecular weight may be used when it is provided by a manufacturer or the like.

Can be used as additive (H) _RO ) Examples of the organic material of (4) include organic compounds having an aromatic ring and heterocyclic rings (which may be aromatic rings or non-aromatic heterocyclic rings). ) The organic compound of (4) and the like, but is not limited thereto.

As additive (H) _RO ) The above organic compound having an aromatic ring (hereinafter also referred to as "aromatic ring-containing compound") is used. ) The aromatic ring to be contained may be selected from the same aromatic rings as those contained in the compound used as the monomer (m 1).

The aromatic ring may have 1 or 2 or more substituents on the ring-forming atoms, or may have no substituent. When a substituent is present, examples of the substituent include, but are not limited to, an alkyl group, an alkoxy group, an aryloxy group, a hydroxyl group, a halogen atom (e.g., a fluorine atom, a chlorine atom, and a bromine atom), a hydroxyalkyl group, a hydroxyalkyloxy group, and a glycidyloxy group. In the substituents containing carbon atoms, the number of carbon atoms contained in the substituent is, for example, 1 to 10, advantageously 1 to 6, preferably 1 to 4, more preferably 1 to 3, and may be, for example, 1 or 2. In some modes, the above aromatic ring may be an aromatic ring having no substituent on a ring-forming atom, or having 1 or 2 or more substituents selected from the group consisting of an alkyl group, an alkoxy group, and a halogen atom (e.g., a bromine atom).

As useful as additives (H) _RO ) Examples of the aromatic ring-containing compound of (2) include: a compound useful as the monomer (m 1); an oligomer comprising a compound usable as the monomer (m 1) as a monomer unit; a group having an ethylenically unsaturated group (which may be a substituent bonded to a ring-forming atom) or a group in which a part constituting the ethylenically unsaturated group is removed from a compound usable as the monomer (m 1) and replaced with a hydrogen atom or a group having no ethylenically unsaturated group (e.g., a hydroxyl group, an amino group, a halogen atom, an alkyl group, an alkoxy group, a hydroxyalkyl group, a hydroxyalkane)Alkoxy, glycidoxy, etc.); and the like, but are not limited thereto. Can be used as additive (H) _RO ) Non-limiting examples of the aromatic ring-containing compound of (a) may include: aromatic ring-containing monomers such as benzyl acrylate, m-phenoxybenzyl acrylate, 2- (o-phenylphenoxy) ethyl acrylate, phenoxyethyl acrylate, phenoxydiethylene glycol acrylate, phenoxypolyethylene glycol acrylate, 2-hydroxy-3-phenoxypropyl acrylate, the above-mentioned monomer having a fluorene structure, the monomer having a dinaphthothiophene structure, and the monomer having a dibenzothiophene structure; an aromatic ring-containing compound having no ethylenically unsaturated group, such as 3-phenoxybenzyl alcohol, dinaphthothiophene, and derivatives thereof (for example, compounds having a structure in which 1 or 2 or more substituents selected from a hydroxyl group, a carbinol group, a diethanol group, a glycidyl group, and the like are bonded to the dinaphthothiophene ring); and the like. The aromatic ring-containing compound may be an oligomer (preferably an oligomer having a molecular weight of about 5000 or less, more preferably about 1000 or less, for example, an oligomer of about 2 to 5-mer) containing such an aromatic ring-containing monomer as a monomer unit. The above oligomer may be, for example: homopolymers of aromatic ring-containing monomers; a copolymer of 1 or 2 or more aromatic ring-containing monomers; copolymers of 1 or 2 or more aromatic ring-containing monomers with other monomers; and the like. As the other monomer, 1 or 2 or more kinds of monomers having no aromatic ring can be used.

In some forms, as an additive (H) _RO ) From the viewpoint of easily obtaining a high refractive index increasing effect, an organic compound having 2 or more aromatic rings in 1 molecule (hereinafter, also referred to as "a compound containing a plurality of aromatic rings") can be preferably used. ). The compound containing a plurality of aromatic rings may or may not have a polymerizable functional group such as an ethylenically unsaturated group. The compound having a plurality of aromatic rings may be a polymer or a non-polymer. The polymer may be an oligomer containing a monomer having a plurality of aromatic rings as a monomer unit (preferably an oligomer having a molecular weight of about 5000 or less, more preferably about 1000 or less, for example, an oligomer having about 2 to 5 mers). Examples of the above oligomersSuch as may be: homopolymers of monomers containing multiple aromatic rings; 1 or 2 or more aromatic ring-containing monomers; 1 or 2 or more aromatic ring-containing monomers and other monomers; and the like. The other monomer may be an aromatic ring-containing monomer that is not a monomer containing a plurality of aromatic rings, may be a monomer having no aromatic ring, or may be a combination thereof.

Non-limiting examples of compounds containing multiple aromatic rings include: a compound having a structure in which 2 or more non-condensed aromatic rings are bonded via a linking group, a compound having a structure in which 2 or more non-condensed aromatic rings are directly chemically bonded (i.e., without via other atoms), a compound having a condensed aromatic ring structure, a compound having a fluorene structure, a compound having a dinaphthothiophene structure, a compound having a dibenzothiophene structure, and the like. The compounds containing a plurality of aromatic rings may be used alone in 1 kind or in combination of 2 or more kinds.

Specific examples of the compound having a fluorene structure include, in addition to the monomer having a fluorene structure and an oligomer which is a homopolymer or a copolymer of the monomer, 9,9-bisphenylfluorene and derivatives thereof, such as 9,9-bis (4-hydroxyphenyl) fluorene (refractive index: 1.68), 9,9-bis (4-aminophenyl) fluorene (refractive index: 1.73), 9,9-bis (4-hydroxy-3-methylphenyl) fluorene (refractive index: 1.68), 9,9-bis [4- (2-hydroxyethoxy) phenyl ] fluorene (refractive index: 1.65).

Specific examples of the compound having a dinaphthothiophene structure include dinaphthothiophene (refractive index: 1.808) in addition to the monomer having a dinaphthothiophene structure and an oligomer which is a homopolymer or a copolymer of the monomer; hydroxyalkyl dinaphthothiophenes such as 6-hydroxymethyl dinaphthothiophene (refractive index: 1.766); dihydroxydinaphthothiophene such as 2,12-dihydroxydinaphthothiophene (refractive index: 1.750); 2,12-dihydroxyethyloxydianaphthothiophene (refractive index: 1.677) or dihydroxyalkyloxydinaphthothiophene; diglycidyl oxydianaphthothiophenes such as 2,12-diglycidyl oxydianaphthothiophene (refractive index: 1.723); 5363 a dinaphthothiophene having 2 or more ethylenically unsaturated groups, such as 2,12-diallyloxydinaphthothiophene (2,12-DAODNT, refractive index 1.729); and the like dinaphthothiophenes and derivatives thereof.

Specific examples of the compound having a dibenzothiophene structure include dibenzothiophene (refractive index: 1.607), 4-dimethyldibenzothiophene (refractive index: 1.617), 4,6-dimethyldibenzothiophene (refractive index: 1.617), and the like, in addition to the monomer having a dibenzothiophene structure and an oligomer which is a homopolymer or a copolymer of the monomer.

As an additive (H) _RO ) The organic compound having a heterocycle of (1) (hereinafter also referred to as heterocycle-containing organic compound). ) Examples of (3) include thioepoxy compounds, compounds having a triazine ring, and the like. Examples of the thioepoxy compound include bis (2,3-thiocyclopropyl) disulfide and a polymer thereof (refractive index: 1.74) described in japanese patent No. 3712653. Examples of the compound having a triazine ring include compounds having at least 1 triazine ring (for example, 3 to 40, preferably 5 to 20) in 1 molecule. Since the triazine ring is aromatic, a compound having a triazine ring is also included in the concept of the aromatic ring-containing compound, and a compound having a plurality of triazine rings is also included in the concept of the aromatic ring-containing compound.

In some forms, as an additive (H) _RO ) Compounds having no ethylenically unsaturated group can be preferably used. This can suppress the adhesive composition from being deteriorated by heat or light (the leveling property is decreased by the progress of gelation or increase in viscosity), and improve the storage stability. From the presence of a catalyst containing the additive (H) _RO ) From the viewpoint of suppressing the occurrence of dimensional change, deformation (warpage, waviness, etc.), optical distortion, etc. caused by the reaction of the ethylenically unsaturated group in the pressure-sensitive adhesive sheet of the pressure-sensitive adhesive layer (b) and the laminate comprising the pressure-sensitive adhesive sheet, it is also preferable to use an additive (H) having no ethylenically unsaturated group _RO )。

In the use of oligomers as additives (H) _RO ) In the embodiment (1), the oligomer can be prepared by a known methodObtained by polymerizing the monomer components. In the case of producing the oligomer by radical polymerization, a polymerization initiator, a chain transfer agent, an emulsifier, and the like for radical polymerization may be appropriately added to the monomer components to carry out polymerization. The polymerization initiator, chain transfer agent, emulsifier, and the like used for the radical polymerization are not particularly limited, and may be appropriately selected and used. The weight average molecular weight of the oligomer can be controlled by the amount of the polymerization initiator, the amount of the chain transfer agent used, and the reaction conditions, and the amount of the oligomer used is appropriately adjusted depending on the kind of the oligomer.

Examples of the chain transfer agent include lauryl mercaptan, glycidyl mercaptan, thioglycol, 2-mercaptoethanol, α -thioglycerol, thioglycolic acid, 2-ethylhexyl thioglycolate, 2,3-dimercapto-1-propanol, and the like. The chain transfer agent may be used alone in 1 kind, or may be used in combination of 2 or more kinds. The amount of the chain transfer agent to be used may be set so that an oligomer having a desired weight average molecular weight can be obtained, depending on the composition of the monomer component used for synthesizing the oligomer, the kind of the chain transfer agent, and the like. In some embodiments, the amount of the chain transfer agent used is suitably about 15 parts by weight or less, and may be 10 parts by weight or less, or about 5 parts by weight or less, based on 100 parts by weight of the total amount of the monomers used for oligomer synthesis. The lower limit of the amount of the chain transfer agent used is not particularly limited, and may be, for example, 0.01 parts by weight or more, 0.1 parts by weight or more, 0.5 parts by weight or more, or 1 part by weight or more, based on 100 parts by weight of the total amount of the monomers used for synthesizing the oligomer.

Additive (H) _RO ) The amount of the acrylic polymer (a) used (the total amount of the compounds when used in plural kinds) is not particularly limited as long as it is higher than 0 part by weight based on 100 parts by weight of the polymer, and may be set according to the purpose. In some modes, the additive (H) _RO ) The amount of the acrylic polymer (a) used may be, for example, 80 parts by weight or less, and from the viewpoint of achieving a good balance between the increase in refractive index of the adhesive and the suppression of the decrease in adhesive properties and optical properties, it is advantageous to use 60 parts by weight or less, and preferably 45 parts by weight or lessThe following. In some of the ways in which the adhesive property and the optical property are more important, the additive (H) _RO ) The amount of the acrylic polymer (a) used may be, for example, 30 parts by weight or less, 20 parts by weight or less, 15 parts by weight or less, or 10 parts by weight or less based on 100 parts by weight of the acrylic polymer (a). In addition, from the viewpoint of increasing the refractive index of the binder, the additive (H) _RO ) The amount of the acrylic polymer (a) to be used may be, for example, 1 part by weight or more, and is favorably 3 parts by weight or more, and preferably 5 parts by weight or more, and may be 7 parts by weight or more, and may be 10 parts by weight or more, and may be 15 parts by weight or more, and may be 20 parts by weight or more, based on 100 parts by weight of the acrylic polymer (a).

(crosslinking agent)

The adhesive may contain a crosslinking agent as needed for the purpose of adjusting the cohesive force of the adhesive. As the crosslinking agent, crosslinking agents known in the field of adhesives, such as isocyanate-based crosslinking agents, epoxy-based crosslinking agents, aziridine-based crosslinking agents, oxazoline-based crosslinking agents, melamine-based resins, and metal chelate-based crosslinking agents, can be used. Among them, isocyanate-based crosslinking agents can be preferably used. Other examples of the crosslinking agent include a polyfunctional monomer having 2 or more ethylenically unsaturated groups in 1 molecule. The crosslinking agent can be used alone in 1 or a combination of more than 2.

The isocyanate-based crosslinking agent may be a 2-or more-functional isocyanate compound, and examples thereof include aliphatic polyisocyanates such as trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene Diisocyanate (HDI), and dimer acid diisocyanate; alicyclic isocyanates such as cyclopentylene diisocyanate, cyclohexylene diisocyanate, isophorone diisocyanate (IPDI), 1,3-bis (isocyanatomethyl) cyclohexane and the like; 2,4-tolylene diisocyanate, 4,4' -diphenylmethane diisocyanate, xylylene Diisocyanate (XDI) and other aromatic isocyanates; modified polyisocyanates obtained by modifying the above isocyanate compounds with allophanate bonds, biuret bonds, isocyanurate bonds, uretdione bonds, urea bonds, carbodiimide bonds, uretonimine bonds, oxadiazinetrione bonds or the like; and the like. Examples of commercially available products include tradenames Takenate 300S, takenate, takenate 600, takenate D165N, takenate D178N (see above, manufactured by Takara chemical industries, ltd.), sumidur T80, sumidur L, desmodur N3400 (see above, manufactured by Sumika Bayer Urethane Co., ltd.), millionate MR, millionate MT, cornate L, cornate HL, and Cornate HX (see above, manufactured by Tosoh Co., ltd.). The isocyanate compound may be used alone in 1 kind or in combination of 2 or more kinds. It is also possible to use a 2-functional isocyanate compound and a 3-or more-functional isocyanate compound in combination.

Examples of the epoxy crosslinking agent include bisphenol a, epichlorohydrin type epoxy resins, ethylene glycidyl ether, polyethylene glycol diglycidyl ether, glycerol triglycidyl ether, 1,6-hexanediol glycidyl ether, trimethylolpropane triglycidyl ether, diglycidylaniline, diamine glycidyl amine, N' -tetraglycidyl m-xylylenediamine, and 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane. These may be used alone in 1 kind or in combination of 2 or more kinds.

Examples of the polyfunctional monomer include ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, ethylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,12-dodecanediol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, tetramethylolmethane tri (meth) acrylate, allyl (meth) acrylate, vinyl (meth) acrylate, divinylbenzene, bisphenoxyethanolfluorene di (meth) acrylate, bisphenol a di (meth) acrylate, epoxy acrylate, polyester acrylate, urethane acrylate, butyl glycol (meth) acrylate, and hexyldiol di (meth) acrylate. The polyfunctional monomers may be used alone in 1 kind or in combination of 2 or more kinds.

The amount of the crosslinking agent (which may be a polyfunctional monomer) used is not particularly limited, and may be, for example, about 0.001 to 5.0 parts by weight per 100 parts by weight of the monomer component. In some embodiments, the amount of the crosslinking agent used is preferably 3.0 parts by weight or less, more preferably 2.0 parts by weight or less, and may be 1.0 part by weight or less, may be 0.5 part by weight or less, and may be 0.2 part by weight or less, with respect to 100 parts by weight of the monomer component, from the viewpoint of improving flexibility of the adhesive. In some embodiments, the amount of the crosslinking agent used may be, for example, 0.005 parts by weight or more, 0.01 parts by weight or more, 0.05 parts by weight or more, or 0.08 parts by weight or more, relative to 100 parts by weight of the monomer component, from the viewpoint of properly exerting the effect of the crosslinking agent used.

In order to more efficiently perform the crosslinking reaction, a crosslinking catalyst may also be used. Examples of the crosslinking catalyst include metal-based crosslinking catalysts such as tetra-n-butyl titanate, tetra-isopropyl titanate, iron acetylacetonate, butyl tin oxide, and dioctyltin dilaurate. Among them, tin-based crosslinking catalysts such as dioctyltin dilaurate are preferable. The amount of the crosslinking catalyst used is not particularly limited. In view of the balance between the rate of crosslinking reaction and the length of pot life of the adhesive composition, the amount of the crosslinking catalyst used per 100 parts by weight of the monomer component may be, for example, in the range of about 0.0001 part by weight or more and 1 part by weight or less, and preferably in the range of 0.001 part by weight or more and 0.5 part by weight or less.

The adhesive composition may contain a compound that undergoes keto-enol tautomerism as a crosslinking retarder. This can achieve the effect of extending the pot life of the adhesive composition. For example, in the adhesive composition containing an isocyanate-based crosslinking agent, a compound that undergoes keto-enol tautomerism can be preferably used. As the compound which causes keto-enol tautomerism, various β -dicarbonyl compounds can be used. For example, β -diketones (acetylacetone, 2,4-hexanedione, etc.) and acetoacetates (methyl acetoacetate, ethyl acetoacetate, etc.) can be preferably used. The keto-enol tautomerism-inducing compounds may be used in 1 species alone or in combination of 2 or more. The amount of the compound which causes keto-enol tautomerism may be, for example, 0.1 to 20 parts by weight, 0.5 to 10 parts by weight, or 1 to 5 parts by weight, based on 100 parts by weight of the monomer component.

(tackifier)

Tackifiers may be included in the adhesive compositions disclosed herein. As the tackifier, known tackifier resins such as rosin-based tackifier resin, terpene-based tackifier resin, phenol-based tackifier resin, hydrocarbon-based tackifier resin, ketone-based tackifier resin, polyamide-based tackifier resin, epoxy-based tackifier resin, and elastic-based tackifier resin can be used. These may be used alone in 1 kind or in combination of 2 or more kinds. The amount of the tackifier resin to be used is not particularly limited, and may be set so as to exhibit an appropriate adhesive performance according to the purpose and the use. In some embodiments, the amount of the tackifier used is preferably 30 parts by weight or less, more preferably 10 parts by weight or less, and still more preferably 5 parts by weight or less, relative to 100 parts by weight of the monomer component, from the viewpoint of refractive index and transparency. The techniques disclosed herein may preferably be practiced without the use of a tackifier.

(plasticizing Material)

In some forms of the adhesive composition disclosed herein, the adhesive composition may further comprise a plasticizing material having a molecular weight lower than that of the acrylic polymer (a) as an additive used as desired. By using the plasticizing material, the flexibility of the pressure-sensitive adhesive layer, the adhesion to an adherend, the flexibility of the entire pressure-sensitive adhesive sheet, and the ability to follow deformation can be improved. As the plasticizing material, an organic material can be preferably used from the viewpoint of compatibility and transparency in the pressure-sensitive adhesive layer. Plasticizing materials may also be used as the above-mentioned additives (H) _RO ) The material of (1).

The molecular weight of the plasticizing material is not particularly limited as long as it is lower than that of the acrylic polymer (a). In some embodiments, from the viewpoint of easily exhibiting the plasticizing effect, the molecular weight of the plasticizing material may be 30000 or less, may be 25000 or less, may be less than 10000, preferably less than 5000, more preferably less than 3000 (e.g., less than 1000), may be less than 800, may be less than 600, may be less than 500, or may be less than 400. When the molecular weight of the plasticizing material is not excessively large, it may be advantageous from the viewpoint of improvement in compatibility in the pressure-sensitive adhesive layer, or the like. In some embodiments, the molecular weight of the plasticizing material is preferably 130 or more, preferably 150 or more, and may be 170 or more, 200 or more, 250 or more, or 300 or more, from the viewpoint of facilitating the exertion of a sufficient plasticizing effect. In some embodiments, the plasticizing material may have a molecular weight of 500 or more, 1000 or more, or 2000 or more. When the molecular weight of the plasticizer is not too low, it is preferable from the viewpoint of heat resistance of the pressure-sensitive adhesive sheet and suppression of contamination of an adherend.

Non-limiting examples of compounds that may be options for plasticizing materials include: compounds useful as the monomer (m 1) (e.g., (meth) acrylate having an aromatic ring such as benzyl, phenoxy, or naphthyl, a monomer having a fluorene structure, a monomer having a dinaphthothiophene structure, a monomer having a dibenzothiophene structure, or the like); an oligomer comprising a compound usable as the monomer (m 1) as a monomer unit; a compound having a structure in which a moiety having an ethylenically unsaturated group is removed from a compound usable as the monomer (m 1) and replaced with a hydrogen atom or a group having no ethylenically unsaturated group (for example, 3-phenoxybenzyl alcohol); and the like. The oligomer containing a compound usable as the monomer (m 1) as a monomer unit may be copolymerized with a low Tg monomer such as n-butyl acrylate or 2-ethylhexyl acrylate, for example, from the viewpoint of improving flexibility. As the plasticizing material, 1 or 2 or more kinds of known plasticizers (for example, phthalate ester, terephthalate ester, adipate ester, adipic acid polyester, and glycol benzoate) can be used.

In some embodiments, as the plasticizing material, an organic material having a refractive index of about 1.50 or more (more preferably 1.53 or more) can be preferably used. Specific examples of compounds that can be options for plasticizing materials include: diethylene glycol dibenzoate (refractive index 1.55), dipropylene glycol dibenzoate (refractive index 1.54), 3-phenoxytoluene (refractive index 1.57), 3-ethylbiphenyl (refractive index 1.59), 3-methoxybiphenyl (refractive index 1.61), 4-methoxybiphenyl (refractive index 1.57), polyethylene glycol dibenzoate, 3-phenoxybenzyl alcohol (refractive index 1.59), triphenyl phosphate (refractive index 1.56), benzyl benzoate (refractive index 1.57), 4- (tert-butyl) phenyl diphenyl phosphate (refractive index 1.56), trimethylphenyl phosphate (refractive index 1.55), butyl benzyl phthalate (refractive index 1.54), rosin methyl ester (refractive index 1.53), alkylbenzyl phthalate (refractive index 1.53), butyl (benzenesulfonyl) amine (refractive index 1.53), trimethyl trimellitate (refractive index 1.52), benzyl phthalate (refractive index 1.52), 2-ethylhexyl diphenyl phosphate (refractive index 1.51), tris (8978 zxft-butyl benzene) phosphite, 8978-di-tert-butyl benzene phosphate, and the like, but not limited thereto. From the viewpoint of refractive index and compatibility, for example, diethylene glycol dibenzoate can be preferably used. The upper limit of the refractive index of the plasticizing material is not particularly limited, and may be, for example, 3.00 or less. In some embodiments, the refractive index of the plasticizing material is suitably 2.50 or less, and advantageously 2.00 or less, and may be 1.90 or less, and may be 1.80 or less, and may be 1.70 or less, from the viewpoints of ease of preparation of the adhesive composition, compatibility within the adhesive, and the like.

The refractive index of the plasticized material was measured at a measurement wavelength of 589nm and a measurement temperature of 25 ℃ using an Abbe refractometer, similarly to the refractive index of the monomer. When a nominal value of the refractive index at 25 ℃ is provided by a manufacturer or the like, the nominal value may be adopted.

In the embodiment using the plasticizing material, the amount of the plasticizing material to be used is not particularly limited and may be set according to the purpose, based on 100 parts by weight of the acrylic polymer (a). From the viewpoint of enhancing the plasticizing effect, the plasticizing material may be used in an amount of, for example, 0.1 part by weight or more and also 0.5 part by weight or more with respect to 100 parts by weight of the acrylic polymer (a), and from the viewpoint of obtaining a higher plasticizing effect, it is preferably 1 part by weight or more, more preferably 3 parts by weight or more, and also 5 parts by weight or more and also 7 parts by weight or more, and also 10 parts by weight or more, and also 15 parts by weight or more and also 20 parts by weight or more. From the viewpoint of satisfying both the high refractive index of the adhesive and the transparency and plasticizing effect in a well-balanced manner, the amount of the plasticizing material to be used is preferably about 100 parts by weight or less, more preferably 80 parts by weight or less, even more preferably 60 parts by weight or less, and may be 45 parts by weight or less, and may be 35 parts by weight or less, or may be 25 parts by weight or less, based on 100 parts by weight of the acrylic polymer (a). In some embodiments where the adhesion property and the optical property are more important, the amount of the plasticizing material to be used may be 15 parts by weight or less, 10 parts by weight or less, or 5 parts by weight or less with respect to 100 parts by weight of the acrylic polymer (a).

(leveling agent)

The adhesive composition disclosed herein may contain a leveling agent as needed for the purpose of improving the appearance (e.g., improving the uniformity of thickness) of the adhesive layer formed from the composition, improving the coatability of the adhesive composition, and the like. Examples of the leveling agent include, but are not limited to, acrylic leveling agents, fluorine leveling agents, and silicone leveling agents. The leveling agent may be selected from commercially available leveling agents, for example, as appropriate and used by a conventional method.

In some embodiments, as the leveling agent, a polymer (hereinafter, also referred to as "polymer (B)") which is a polymer containing a monomer having a polyorganosiloxane skeleton (hereinafter, also referred to as "monomer S1") and a monomer raw material of an acrylic monomer (hereinafter, also referred to as "monomer raw material B") can be preferably used. The polymer (B) may be a copolymer of the monomer S1 and an acrylic monomer. The polymer (B) may be used singly or in combination of two or more.

The monomer S1 is not particularly limited, and any monomer having a polyorganosiloxane skeleton can be used. As the monomer S1, a monomer having a structure having a polymerizable reactive group at one end can be preferably used. Among these, the monomer S1 having a polymerizable reactive group at one end and having no functional group that can undergo a crosslinking reaction with the acrylic polymer (a) at the other end can be preferably used. Examples of commercially available products include single-terminal reactive silicone oils available from shin-Etsu chemical Co., ltd. (for example, trade names such as X-22-174ASX, X-22-2426, X-22-2475 and KF-2012). The monomers S1 may be used singly or in combination of two or more.

The functional group equivalent of the monomer S1 may be, for example, about 100g/mol to about 30000 g/mol. In some preferred embodiments, the functional group equivalent weight is, for example, 500g/mol or more, 800g/mol or more, 1500g/mol or more, or 2000g/mol or more. The functional group equivalent may be, for example, 20000g/mol or less, less than 10000g/mol, 7000g/mol or less, or 5500g/mol or less. When the functional group equivalent of the monomer S1 is within the above range, a good leveling effect can be easily exhibited.

When two or more monomers having different functional group equivalents are used as the monomer S1, the functional group equivalent of the monomer S1 may be the sum of the products of the functional group equivalents of the respective monomers and the weight fractions of the monomers.

Here, "functional group equivalent" means the weight of the main skeleton (for example, polydimethylsiloxane) bonded per 1 functional group. The labeling unit g/mol was converted to 1mol of the functional group. The functional group equivalents of the monomers S1 can be determined, for example, by means of Nuclear Magnetic Resonance (NMR) ¹ The spectral intensity of H-NMR (proton NMR) was calculated. Based on ¹ The functional group equivalent (g/mol) of the monomer S1 of the spectral intensity of H-NMR can be calculated based on ¹ A general structure analysis technique for H-NMR spectroscopy is described in Japanese patent No. 5951153, if necessary. In the functional group equivalent of the monomer S1, the functional group means a polymerizable functional group (for example, an ethylenically unsaturated group such as a (meth) acryloyl group, vinyl group, or allyl group).

The content of the monomer S1 in the monomer raw material B may be an appropriate value within a range in which the desired effect is exerted by using the monomer S1, and is not limited to a specific range. In some embodiments, the content of the monomer S1 in the monomer raw material B may be, for example, 5 to 60% by weight, 10 to 50% by weight, or 15 to 40% by weight.

The monomer raw material B contains an acrylic monomer copolymerizable with the monomer S1 in addition to the monomer S1. This improves the compatibility of the polymer (B) in the adhesive layer. Examples of the acrylic monomer that can be used as the monomer raw material B include alkyl acrylates. The "alkyl" as used herein means a chain (including straight-chain and branched-chain) alkyl (group), and does not include the alicyclic hydrocarbon group described later. In some embodiments, monomer feed B can comprise (meth) acrylic acid C _4-12 Alkyl esters (preferably (meth) acrylic acid C) _4-10 Alkyl esters, e.g. C (meth) acrylate _6-10 Alkyl ester). In other embodiments, the monomer feed B may comprise methacrylic acid C _1-18 Alkyl esters (preferably methacrylic acid C) _1-14 Alkyl esters, e.g. methacrylic acid C _1-10 Alkyl esters). The monomer raw material B may contain, for example, one or two or more selected from Methyl Methacrylate (MMA), n-Butyl Methacrylate (BMA), and 2-ethylhexyl methacrylate (2 EHMA) as an acrylic monomer.

As another example of the acrylic monomer, a (meth) acrylate having an alicyclic hydrocarbon group is exemplified. For example, cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, dicyclopentanyl (meth) acrylate, 1-adamantyl (meth) acrylate, and the like can be used. The (meth) acrylate having an alicyclic hydrocarbon group may not be used.

The content of the alkyl (meth) acrylate and the (meth) acrylate having an alicyclic hydrocarbon group in the monomer raw material B may be, for example, 10 wt% or more and 95 wt% or less, 20 wt% or more and 95 wt% or less, 30 wt% or more and 90 wt% or less, 40 wt% or more and 90 wt% or less, or 50 wt% or more and 85 wt% or less.

Other examples of monomers which can be contained in the monomer raw material B together with the monomer S1 include: examples of the monomer that can be used in the acrylic polymer include the above-mentioned carboxyl group-containing monomer, acid anhydride group-containing monomer, hydroxyl group-containing monomer, epoxy group-containing monomer, cyano group-containing monomer, isocyanate group-containing monomer, amide group-containing monomer, nitrogen atom-containing ring-containing monomer, aminoalkyl (meth) acrylate, vinyl ester, vinyl ether, olefin, (meth) acrylate having an aromatic hydrocarbon group, halogen atom-containing (meth) acrylate, and the like.

The Mw of the polymer (B) may be, for example, 5000 or more, preferably 10000 or more, or 15000 or more. The Mw of the polymer (B) may be, for example, 200000 or less, preferably 100000 or less, 50000 or less, or 30000 or less. By setting the Mw of the polymer (B) in an appropriate range, appropriate compatibility and leveling property can be exhibited.

The polymer (B) can be produced by polymerizing the above-mentioned monomers by a known method such as solution polymerization, emulsion polymerization, bulk polymerization, suspension polymerization, or photopolymerization, for example.

In order to adjust the molecular weight of the polymer (B), a chain transfer agent may be used as necessary. Examples of chain transfer agents to be used include: compounds having a mercapto group such as n-dodecylmercaptan, mercaptoethanol, and α -thioglycerol; thioglycolates such as thioglycolic acid and methyl thioglycolate; alpha-methylstyrene dimer; and so on. The amount of the chain transfer agent to be used is not particularly limited, and may be appropriately set so as to obtain the polymer (B) having a desired molecular weight. In some embodiments, the chain transfer agent may be used in an amount of, for example, 0.1 to 5 parts by weight, 0.2 to 3 parts by weight, or 0.5 to 2 parts by weight, based on 100 parts by weight of the monomer.

The amount of the polymer (B) used may be, for example, 0.001 parts by weight or more relative to 100 parts by weight of the acrylic polymer (a), and from the viewpoint of obtaining a higher effect in use, may be 0.01 parts by weight or more, or may be 0.03 parts by weight or more. The amount of the polymer (B) used may be, for example, 3 parts by weight or less, and is preferably 1 part by weight or less, and may be 0.5 parts by weight or less, or 0.1 parts by weight or less, from the viewpoint of reducing the influence on the refractive index.

(inorganic particles)

The technique disclosed herein can be preferably carried out without substantially using inorganic particles for increasing the refractive index, but within limits that do not significantly impair the effect of the technique disclosed herein, the additive (H) may be added _RO ) In addition, inorganic particles having a high refractive index may be used as an auxiliary. Examples of the inorganic particles include titanium oxide (titanium oxide, tiO) ₂ ) Zirconium oxide (zirconium oxide, zrO) ₂ ) Aluminum oxide, zinc oxide, tin oxide, copper oxide, barium titanate, niobium oxide (Nb) ₂ O ₅ Etc.) or the like (specifically, metal oxides). The average particle diameter of the inorganic particles (which means 50% volume average particle diameter by laser scattering/diffraction method) may be selected from a range of about 10nm to 100nm, for example. The amount of the inorganic particles used is preferably less than 5 parts by weight, more preferably less than 1 part by weight, based on 100 parts by weight of the acrylic polymer (a). In the presence of an additive (H) _RO ) In the embodiment (b), the amount of the inorganic particles used is preferably the additive (H) on a weight basis _RO ) Is 2 times or less, more preferably 1 time or less or 0.5 time or less.

(other additives)

The adhesive composition disclosed herein may contain, as necessary, known additives that can be used in adhesive compositions, such as plasticizers, softeners, colorants, antistatic agents, age resistors, ultraviolet absorbers, antioxidants, light stabilizers, and preservatives, within a range that does not significantly interfere with the effects of the present invention. The various additives can be conventionally known additives, and the present invention is not particularly characterized, and therefore, detailed description thereof is omitted.

< adhesive agent >

The adhesives disclosed herein may be formed, for example, using any of the adhesive compositions described above. The pressure-sensitive adhesive may be a pressure-sensitive adhesive obtained by curing a pressure-sensitive adhesive composition in the form of a solvent type, an active energy ray-curable type, a water-dispersible type, a hot-melt type or the like by drying, crosslinking, polymerization, cooling or the like, that is, a cured product of the pressure-sensitive adhesive composition. The curing means (for example, drying, crosslinking, polymerization, cooling, etc.) of the adhesive composition may be applied in only 1 kind, or may be applied in 2 or more kinds simultaneously or in multiple stages. For solvent-based adhesive compositions, the composition can typically be dried (preferably further crosslinked) to form an adhesive. In the active energy ray-curable adhesive composition, typically, an adhesive is formed by performing a polymerization reaction and/or a crosslinking reaction by irradiation with active energy rays. When the active energy ray-curable adhesive composition needs to be dried, it is preferable to irradiate the active energy ray after drying.

(refractive index)

The adhesive disclosed herein may be an adhesive exhibiting a refractive index above a prescribed value. According to the technology disclosed herein, an adhesive having a refractive index of, for example, 1.560 or more (preferably 1.570 or more, more preferably higher than 1.570), an adhesive composition capable of forming the adhesive, and an adhesive sheet including the adhesive can be provided.

In the present specification, the refractive index of the adhesive refers to the refractive index of the surface (bonding surface) of the adhesive. The refractive index of the adhesive can be measured using a commercially available refractive index measuring apparatus (Abbe refractometer) at a measurement wavelength of 589nm and a measurement temperature of 25 ℃. As the Abbe refractometer, for example, a model number "DR-M4" manufactured by ATAGO or a product equivalent thereof can be used. As the measurement sample, an adhesive layer formed of an adhesive to be evaluated may be used. The refractive index of the binder can be measured specifically by the method described in the examples below. The refractive index of the binder can be adjusted, for example, by the composition of the binder.

In some embodiments, the refractive index of the adhesive may be preferably 1.575 or more (e.g., higher than 1.575), more preferably 1.580 or more, further preferably 1.585 or more, and particularly preferably 1.590 or more (e.g., 1.595 or more). According to the pressure-sensitive adhesive having such a refractive index, the behavior of light can be effectively controlled by the difference in refractive index between the pressure-sensitive adhesive and the adherend. In some versions of the adhesives disclosed herein, the adhesive may have a refractive index of, for example, 1.600 or greater than 1.600, 1.605 or greater than 1.605, or 1.610 or greater than 1.610. The preferable upper limit of the refractive index of the pressure-sensitive adhesive is not limited to a specific range, since it may vary depending on the refractive index of the adherend, etc. In some embodiments, the refractive index of the adhesive may be, for example, 1.700 or less, 1.670 or less, or 1.650 or less in consideration of balance between the adhesive property and the transparency.

< pressure-sensitive adhesive sheet >

According to the present specification, there is provided an adhesive sheet having an adhesive layer. The adhesive constituting the adhesive layer may be an adhesive formed from any of the adhesive compositions disclosed herein (e.g., a cured product of the adhesive composition).

The pressure-sensitive adhesive sheet may be a substrate-attached pressure-sensitive adhesive sheet in the form of having a pressure-sensitive adhesive layer on one or both sides of a non-releasable substrate (support substrate), or a substrate-free pressure-sensitive adhesive sheet in the form of having the pressure-sensitive adhesive layer held on a release liner (i.e., a pressure-sensitive adhesive sheet having no non-releasable substrate). The concept of the adhesive sheet as referred to herein may include objects called adhesive tapes, adhesive labels, adhesive films, etc. The adhesive sheet disclosed herein may be in the form of a roll or a sheet. Alternatively, the pressure-sensitive adhesive sheet may be further processed into various shapes.

Fig. 1 shows an example of the structure of the pressure-sensitive adhesive sheet disclosed herein. The adhesive sheet 1 is configured as a one-sided adhesive sheet (one-sided adhesive sheet), and includes: the 1 st surface 10A is a pressure-sensitive adhesive layer 10 serving as a bonding surface (pressure-sensitive adhesive surface) to an adherend, and a support base material 20 laminated on the 2 nd surface 10B of the pressure-sensitive adhesive layer 10. The 2 nd surface 10B of the pressure-sensitive adhesive layer 10 is bonded to the 1 st surface (non-releasable surface) 20A of the supporting base material 20. As the support base 20, for example, a plastic film such as a polyester film can be used. The support substrate 20 may be an optical film such as a polarizing plate. The psa sheet 1 before use (before application to an adherend) may be, for example, as shown in fig. 1, in the form of a release-lined psa sheet 50 having a psa surface 10A protected by a release liner 30 which forms a releasable surface (release surface) at least on the psa layer side. Alternatively, the 2 nd surface 20B (the surface opposite to the 1 st surface 20A, also referred to as the back surface) of the support base 20 may be a release surface, and the adhesive surface 10A may be protected by winding or laminating the support base so that the adhesive surface 10A abuts against the 2 nd surface 20B. The adhesive layer 10 may have a single-layer structure or a laminated structure in which two or more sub-adhesive layers having different compositions are laminated in direct contact with each other (i.e., without being separated by a layer made of a non-adhesive material).

The release liner is not particularly limited, and examples thereof include release liners obtained by subjecting the surface of a liner base material such as a resin film or paper to a release treatment, and release liners formed of a low-adhesion material such as a fluorine-based polymer (polytetrafluoroethylene or the like) or a polyolefin-based resin (polyethylene, polypropylene or the like). For example, a silicone-based or long-chain alkyl-based release agent may be used for the release treatment. In some cases, a resin film subjected to a release treatment may be preferably used as the release liner.

The pressure-sensitive adhesive sheet disclosed herein may be a substrate-less double-sided pressure-sensitive adhesive sheet formed of a pressure-sensitive adhesive layer. As shown in fig. 2, the substrate-less double-sided adhesive sheet 2 may be in the form of: before use, the 1 st surface (1 st adhesive surface) 10A and the 2 nd surface (2 nd adhesive surface) 10B of the adhesive layer 10 are protected by

release liners

31, 32 which become releasable surfaces (release surfaces) at least on the adhesive layer side. Alternatively, the back surface (the surface opposite to the pressure-sensitive adhesive side) of the release liner 31 may be a release surface, and the pressure-

sensitive adhesive surfaces

10A and 10B may be protected by winding or laminating the release liner 31 so that the pressure-sensitive adhesive surface 10B comes into contact with the back surface of the release liner 31. Such a substrate-less double-sided pressure-sensitive adhesive sheet can be used, for example, by bonding a substrate (which may be an optical member such as an optical film) to at least one of the 1 st pressure-sensitive adhesive surface and the 2 nd pressure-sensitive adhesive surface. The pressure-sensitive adhesive layer constituting the substrate-less double-sided pressure-sensitive adhesive sheet may have a single-layer structure or a laminated structure in which two or more sub-pressure-sensitive adhesive layers having different compositions are directly in contact and laminated, as in the pressure-sensitive adhesive layer 10 in the pressure-sensitive adhesive sheet 1 shown in fig. 1.

The pressure-sensitive adhesive sheet disclosed herein may be a component of an optical member of a pressure-sensitive adhesive sheet with an optical member bonded to at least one surface of a pressure-sensitive adhesive layer. For example, the adhesive sheet 1 shown in fig. 1 may be a component of an optical member 100 with an adhesive sheet in which an optical member 70 is bonded to one surface 10A of an adhesive layer 10 as shown in fig. 3. The optical member may be, for example, a glass plate, a resin film, a metal plate, or the like. In the psa sheet 1 shown in fig. 1, when the support substrate 20 is an optical member such as an optical film, the psa sheet 1 can be regarded as an optical member with a psa sheet in which the optical member is bonded to the 2 nd surface 10B of the psa layer 10.

Further, although not particularly shown, the pressure-sensitive adhesive sheet disclosed herein may be in the form of a substrate-attached double-sided adhesive pressure-sensitive adhesive sheet (substrate-attached double-sided pressure-sensitive adhesive sheet) including a support substrate having non-peelable 1 st and 2 nd surfaces, the 1 st pressure-sensitive adhesive layer being fixedly laminated on the 1 st surface, and the 2 nd pressure-sensitive adhesive layer being fixedly laminated on the 2 nd surface. Examples of the configuration of such a double-sided pressure-sensitive adhesive sheet with a substrate include the following: in the single-sided psa sheet 1 shown in fig. 1, the 2 nd surface 20B of the support substrate 20 is a non-releasable surface, and the 2 nd surface 20B is provided with a2 nd psa layer, the 2 nd surface of the 2 nd psa layer being bonded to the 2 nd surface 20B of the support substrate 20, and the 1 st surface (the surface on the opposite side of the 2 nd surface) of the 2 nd psa layer being the 2 nd psa surface of the substrate-attached double-sided psa sheet. The composition of the adhesive constituting the 2 nd adhesive layer may be the same as or different from that of the adhesive constituting the 1 st adhesive layer. As for the double-sided psa sheet with a substrate before use, the 1 st adhesive surface and the 2 nd adhesive surface may be protected by release liners, as in the case of the substrate-less double-sided psa sheet.

When the psa sheet disclosed herein is a double-sided psa sheet (including both substrate-less double-sided psa sheets and substrate-attached double-sided psa sheets, unless otherwise specified, the same applies hereinafter), the refractive index of the 1 st psa surface and the 2 nd psa surface is not particularly limited. In some embodiments, at least the 1 st adhesive surface preferably satisfies any of the above refractive indices, and the 1 st adhesive surface and the 2 nd adhesive surface may both satisfy any of the above refractive indices.

In some modes, the refractive index n of the 2 nd adhesion surface ₂ Refractive index n of the 1 st adhesive surface ₁ To approximately the same extent. More specifically, | n, which is the absolute value of the difference in refractive index between the two adhesive surfaces ₁ -n ₂ For example, | may be less than 0.05, or less than 0.03, or less than 0.01.| n ₁ -n ₂ The lower limit of |, may be 0.00 or more than 0.00. The relative relationship of the refractive indices of the two adhesive surfaces may be n ₁ >n ₂ May be n ₁ <n ₂ May also be n ₁ ＝n ₂ 。

In some other modes, the refractive index n of the 1 st adhesive surface of the adhesive sheet ₁ Refractive index n of 2 nd adhesive surface ₂ The difference, i.e. n ₁ -n ₂ For example, the average molecular weight may be more than 0.00, or may be 0.01 or more, or may be 0.03 or more, or may be 0.05 or more, or may be 0.10 or more, or may be 0.15 or more, or may be 0.20 or more, or may be 0.25 or more. n is a radical of an alkyl radical ₁ And n ₂ The magnitude relationship of (c) may also be reversed. The double-sided adhesive sheet having different refractive indices in the 1 st adhesive side and the 2 nd adhesive side can be realized, for example, by: in the double-sided adhesive sheet with a substrate, 1 st and 2 nd adhesive layers with different refractive indexes are laminated on a non-peeling supporting substrate; the pressure-sensitive adhesive layer constituting the substrate-less double-sided pressure-sensitive adhesive sheet has a laminated structure of two or more sub-pressure-sensitive adhesive layers having different refractive indices.

The adhesive layer of the adhesive sheet disclosed herein can be formed by imparting (e.g., coating) an adhesive composition to an appropriate surface and then curing the composition. The application of the adhesive composition can be carried out using a conventional coating machine such as a gravure roll coater, a reverse roll coater, a dip roll coater, a bar coater, a knife coater, or a spray coater.

The adhesive layer of the adhesive sheet disclosed herein may be an adhesive layer having post-curing properties or an adhesive layer having no post-curing properties. Here, the adhesive layer having post-curing properties refers to an adhesive layer that can be further cured by irradiation with heat or active energy rays (e.g., ultraviolet rays). Examples of the pressure-sensitive adhesive layer having post-curing properties include a pressure-sensitive adhesive layer having an unreacted ethylenically unsaturated group in a side chain of a base polymer (for example, the acrylic polymer (a)), and a pressure-sensitive adhesive layer containing an unreacted polyfunctional monomer. In some embodiments, the adhesive layer preferably has no post-cure properties. The pressure-sensitive adhesive layer having no post-curing property does not undergo dimensional change accompanying the subsequent curing reaction (i.e., dimensional stability is good), and therefore warpage of the pressure-sensitive adhesive sheet or the adherend to which the pressure-sensitive adhesive sheet is attached is easily suppressed. When dimensional change (for example, cure shrinkage) due to post-curing does not occur, it may also be advantageous from the viewpoint of suppressing optical distortion of the pressure-sensitive adhesive layer.

The thickness of the pressure-sensitive adhesive layer is not particularly limited, and may be, for example, 3 μm or more. In some embodiments, the thickness of the pressure-sensitive adhesive layer may be, for example, 5 μm or more, 10 μm or more, 20 μm or more, 30 μm or more, 50 μm or more, 70 μm or more, or 85 μm or more. In some embodiments, the thickness of the pressure-sensitive adhesive layer may be, for example, 300 μm or less, 250 μm or less, 200 μm or less, 150 μm or less, or 120 μm or less. If the thickness of the pressure-sensitive adhesive layer is not too large, it may be advantageous from the viewpoint of thinning of the pressure-sensitive adhesive sheet. The technique disclosed herein can be preferably carried out so that the thickness of the pressure-sensitive adhesive layer is in the range of, for example, 3 μm to 200 μm (more preferably, 5 μm to 100 μm). In the case of a psa sheet having a1 st psa layer and a2 nd psa layer on the 1 st and 2 nd sides of the substrate, the thickness of the psa layer may be at least as great as the thickness of the 1 st psa layer. The thickness of the 2 nd adhesive layer may be selected from the same range. In the substrate-less double-sided pressure-sensitive adhesive sheet formed of the pressure-sensitive adhesive layer, the thickness of the pressure-sensitive adhesive layer is the thickness of the pressure-sensitive adhesive sheet.

(Total light transmittance)

In the technique disclosed herein, it is appropriate that the total light transmittance of the adhesive layer is, for example, higher than 50%, and preferably 70% or more. In some preferred embodiments, the total light transmittance of the adherend is 85% or more, preferably 86% or more, more preferably 88% or more, and still more preferably 90% or more (for example, higher than 90.0%), and may be 90.5% or more. Such a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer with high transparency can be suitably used in applications requiring high light transmittance (for example, optical applications) and applications requiring good visual recognition of an adherend through the pressure-sensitive adhesive sheet, in a configuration having a substrate or a configuration not having a substrate. In some embodiments, the total light transmittance of the adhesive layer may be 93% or more, or may be 95% or more. The upper limit of the total light transmittance is theoretically a value obtained by subtracting the optical loss (fresnel loss) due to reflection occurring at the air interface from 100%, and may be practically about 98% or less, about 96% or less, or about 95% or less. In some embodiments, the total light transmittance of the adhesive layer may be about 94% or less, about 93% or less, or about 92% or less, in consideration of the refractive index and the adhesive property. Total light transmittance was measured according to JIS K7136: 2000, measured using a commercially available transmittance meter. As the transmittance meter, a product name "HAZEMETER HM-150" available from the color technology research on villages or a product equivalent thereof can be used. More specifically, the total light transmittance of the adhesive layer can be measured, for example, in accordance with the examples described later. The total light transmittance of the adhesive layer can be adjusted, for example, by selection of the composition, thickness, and the like of the adhesive layer.

When the psa sheet disclosed herein is in the form of a double-sided psa sheet with a substrate, in which the 1 st and 2 nd psa layers are fixedly laminated to a support substrate, it is preferable that at least the 1 st psa layer satisfies any of the above total light transmittances. In the use mode of light passing through the thickness direction of the adhesive sheet, it is preferable that both the 1 st adhesive layer and the 2 nd adhesive layer satisfy any of the above-described total light transmittances. The relative relationship between the total light transmittance of the two adhesive layers may be 1 st adhesive layer > 2 nd adhesive layer, may be 1 st adhesive layer < 2 nd adhesive layer, or may be 1 st adhesive layer = 2 nd adhesive layer.

(haze value)

In some embodiments, the haze value of the pressure-sensitive adhesive layer constituting the pressure-sensitive adhesive sheet may be, for example, 5.0% or less, preferably 3.0% or less (for example, 2.0% or less), more preferably 1.0% or less, and further preferably 0.9% or less. The pressure-sensitive adhesive sheet having such a pressure-sensitive adhesive layer with high transparency can be suitably used in applications requiring high light transmittance (for example, optical applications) and applications requiring good visual recognition of an adherend through the pressure-sensitive adhesive sheet, in structures having or not having a substrate. In some embodiments, the haze value of the adhesive layer may be 0.8% or less, may be 0.5% or less, and may be 0.3% or less. The lower limit of the haze value of the pressure-sensitive adhesive layer is not particularly limited, and from the viewpoint of improving transparency, the smaller the haze value, the more preferable. On the other hand, in some embodiments, the haze value may be, for example, 0.05% or more, 0.1% or more, 0.2% or more, 0.3% or more, or 0.4% or more, in consideration of the refractive index and the adhesive property. These haze values relating to the adhesive layer can also be preferably applied to the haze value of an adhesive sheet when the technology disclosed herein is carried out in the form of a substrate-free adhesive sheet (typically, an adhesive sheet formed of an adhesive layer).

Here, the "haze value" refers to a ratio of diffuse transmitted light to total transmitted light when the measurement target is irradiated with visible light. Also known as turbidity. The haze value can be expressed by the following equation.

Th(％)＝Td/Tt×100

In the above formula, th is a haze value (%), td is a scattered light transmittance, and Tt is a total light transmittance. The haze value can be measured by the method described in examples below. The haze value of the adhesive layer can be adjusted by, for example, selection of the composition, thickness, and the like of the adhesive layer.

In the case where the psa sheet disclosed herein is in the form of a double-sided psa sheet with a substrate in which the 1 st psa layer and the 2 nd psa layer are fixedly laminated on a support substrate, at least the 1 st psa layer may satisfy any of the above-described haze values, and the haze value of the 2 nd psa layer is not particularly limited. In the use mode of the adhesive sheet in which light passes through the thickness direction thereof, the haze value of the 2 nd adhesive layer preferably satisfies any one of the haze values of the 1 st adhesive layer. The relative relationship between the haze values of the two adhesive layers may be 1 st adhesive layer > 2 nd adhesive layer, may be 1 st adhesive layer < 2 nd adhesive layer, or may be 1 st adhesive layer = 2 nd adhesive layer.

(surface smoothness of pressure-sensitive adhesive surface)

In some embodiments of the adhesive sheet disclosed herein, the adhesive surface of the adhesive sheet preferably has high surface smoothness.

For example, the adhesive surface is preferably limited to have an arithmetic average roughness Ra of a predetermined value or less. A configuration having a pressure-sensitive adhesive surface designed to have a low arithmetic average roughness Ra is preferable from the viewpoint of optical homogeneity. By limiting the arithmetic average roughness Ra, for example, in a use mode (an adhesive sheet or the like disposed closer to the viewing point than the self-light emitting element in the light emitting device) in which light is extracted through the adhesive surface, an effect of suppressing the occurrence of luminance unevenness due to the surface state of the adhesive layer can be exhibited. When the arithmetic average roughness Ra of the adhesive surface is low, it is also advantageous to suppress optical distortion, and suppression of optical distortion contributes to improvement of optical homogeneity. When the psa sheet disclosed herein is in the form of a double-sided psa sheet having a1 st psa surface and a2 nd psa surface, the arithmetic mean roughness Ra of at least the 1 st psa surface is preferably limited to a predetermined value or less, more preferably both psa surfaces are limited to a predetermined value or less. By imparting high surface smoothness to each pressure-sensitive adhesive surface of the double-sided pressure-sensitive adhesive sheet, it is possible to preferably realize bonding with excellent optical homogeneity.

In some embodiments, the adhesive surface preferably has an arithmetic average roughness Ra of about 70nm or less, more preferably about 65nm or less, even more preferably about 55nm or less, and may be less than 50nm, less than 45nm, or less than 40nm. From the viewpoint of production efficiency and the like, the arithmetic average roughness Ra of the adhesive surface of the adhesive sheet may be, for example, about 10nm or more, about 20nm or more, or about 30nm or more (e.g., about 40nm or more). In the embodiment where the psa sheet has the 1 st psa surface and the 2 nd psa surface, the arithmetic average roughness Ra of the 1 st psa surface and the arithmetic average roughness Ra of the 2 nd psa surface may be the same or different.

For example, the maximum height Rz of the pressure-sensitive adhesive surface is preferably limited to a predetermined value or less. A configuration having an adhesive surface designed to have a low maximum height Rz is preferable from the viewpoint of optical homogeneity. By limiting the maximum height Rz, for example, in the use mode in which light is extracted through the pressure-sensitive adhesive surface as described above, the effect of suppressing the occurrence of luminance unevenness due to the surface state of the pressure-sensitive adhesive layer can be exhibited. When the maximum height Rz of the pressure-sensitive adhesive surface is low, suppression of optical distortion is also advantageous. When the pressure-sensitive adhesive sheet disclosed herein is in the form of a double-sided pressure-sensitive adhesive sheet having a1 st pressure-sensitive adhesive surface and a2 nd pressure-sensitive adhesive surface, it is preferable that at least the maximum height Rz of the 1 st pressure-sensitive adhesive surface is limited to a predetermined value or less, and more preferably, the maximum height Rz of both pressure-sensitive adhesive surfaces is limited to a predetermined value or less. By providing each pressure-sensitive adhesive surface of the double-sided pressure-sensitive adhesive sheet with high surface smoothness, it is possible to preferably realize bonding with excellent optical homogeneity.

In some embodiments, the maximum height Rz of the adhesive surface is preferably about 600nm or less, more preferably about 500nm or less, further preferably about 450nm or less, particularly preferably about 400nm or less, and may be less than 350nm, less than 300nm, or less than 250nm. From the viewpoint of production efficiency and the like, the maximum height Rz of the pressure-sensitive adhesive surface of the pressure-sensitive adhesive sheet in some embodiments may be, for example, about 10nm or more, about 50nm or more, about 100nm or more, or about 200nm or more. In the embodiment of the psa sheet having the 1 st psa surface and the 2 nd psa surface, the maximum height Rz of the 1 st psa surface and the maximum height Rz of the 2 nd psa surface may be the same or different.

The arithmetic average roughness Ra and the maximum height Rz of the adhesion surface were measured using a noncontact surface roughness measuring apparatus. As the noncontact surface roughness measuring device, a surface roughness measuring device using an optical interference system, for example, a three-dimensional optical profiler (trade name "NewView7300", manufactured by ZYGO) or a product equivalent thereof can be used. Specifically, the arithmetic average roughness Ra and the maximum height Rz can be measured, for example, by the following measurement method or by setting the measurement operation and measurement conditions so as to obtain the same or corresponding results as those obtained by the measurement method.

That is, the surface shape of the measurement sample was measured under the following conditions using a three-dimensional optical profiler (trade name "New View7300", manufactured by ZYGO Co., ltd.) in an environment of 23 ℃ and 50% RH. From the measured data, the arithmetic surface roughness Ra was calculated in accordance with JIS B0601-2001. The maximum height Rz is obtained as the sum of the height Rp of the highest peak on the upper side from the average line of the roughness curve and the depth Rv of the deepest valley on the lower side from the average line, with respect to the data (roughness curve) obtained by the above measurement. Ra and Rz were measured 5 times (i.e., N = 5), and their average values were used.

The measurement sample can be prepared by, for example, cutting a pressure-sensitive adhesive layer to be measured or a pressure-sensitive adhesive sheet including the pressure-sensitive adhesive layer into a size of about 150mm in length and about 50mm in width. When the pressure-sensitive adhesive surface is protected by the release liner, the pressure-sensitive adhesive surface is exposed by peeling off the release liner gently (for example, under conditions of a stretching speed of 300 mm/min and a peeling angle of 180 °). It is preferable to perform the measurement after leaving the adhesive surface to stand for about 30 minutes after exposing the adhesive surface.

[ measurement conditions ]

Area measurement: 5.62mm by 4.22mm

(Objective lens: 2.5 times, inner lens: 0.5 times)

Analysis mode:

Remove：Cylinder

Data Fill：ON(Max：25)

Remove Spikes：ON(xRMS：1)

Filter：OFF

the arithmetic average roughness Ra and the maximum height Rz of the pressure-sensitive adhesive surface can be adjusted by the composition and properties (viscosity, leveling property, and the like) of the pressure-sensitive adhesive composition used for forming the pressure-sensitive adhesive layer, the properties of the surface (release surface) of the release liner for protecting the pressure-sensitive adhesive surface, and the like.

(storage modulus G')

In the psa sheet disclosed herein, the storage modulus G '(hereinafter also referred to as "storage modulus G' (25)") at 25 ℃ of the psa constituting the psa layer may be appropriately set depending on the intended use, the mode of use, and the like, and is not limited to a specific range. The storage modulus G' (25) of the adhesive may be, for example, about 700kPa or less. In some embodiments, the storage modulus G' (25) of the pressure-sensitive adhesive is favorably not more than about 600kPa, preferably not more than 500kPa, and more preferably not more than 400kPa (for example, not more than 350 kPa) from the viewpoint of ease of adhesion to an adherend, and the like. In some embodiments, the storage modulus G' (25) of the pressure-sensitive adhesive is favorably not more than about 330kPa, preferably not more than 300kPa, from the viewpoint of improving the flexibility of the pressure-sensitive adhesive in a room temperature region (e.g., 25 ℃) and facilitating adhesion to an adherend. In some embodiments where adhesion and flexibility in the warm-room region are more important, the storage modulus G' (25) of the adhesive may be, for example, less than 270kPa or less than 250kPa, advantageously less than 200kPa, preferably less than 180kPa, more preferably less than 160kPa (e.g. less than 140 kPa). In some embodiments, the adhesive has a storage modulus G' (25) of less than 100kPa, and also less than 90kPa. The lower limit of the storage modulus G' (25) of the binder is not particularly limited, and may be, for example, 30kPa or more, 50kPa or more, or 70kPa or more from the viewpoint of processability, handleability, or the like. In some embodiments, the storage modulus G' (25) may be 100kPa or more, 150kPa or more, 200kPa or more, 250kPa or more, or 300kPa or more in view of increasing the refractive index.

In the psa sheet disclosed herein, the storage modulus G '(hereinafter also referred to as "storage modulus G' (50)") at 50 ℃ of the psa constituting the psa layer is not particularly limited, and may be, for example, less than 100kPa.

In some forms, a storage modulus G' (50) of less than 60kPa is suitable, preferably less than 40kPa, more preferably less than 38kPa (e.g. less than 36 kPa). The pressure-sensitive adhesive having the storage modulus G' (50) restricted in this way can be easily improved in adhesiveness to an adherend by appropriately heating it as necessary, and thus can be improved in adhesiveness to an adherend. The lower limit of the storage modulus G' (50) of the adhesive is not particularly limited.

In some embodiments, the storage modulus G' (50) may be, for example, 10kPa or more, 15kPa or more, 20kPa or more, or 23kPa or more, from the viewpoint of the heat resistance characteristics of the binder.

In some versions of the adhesive disclosed herein, the adhesive preferably satisfies at least one of the following conditions:

(a) A storage modulus G' (25) at 25 ℃ of 350kPa or less (preferably less than 200kPa, for example, 180kPa or less); and

(b) The storage modulus G' (50) at 50 ℃ is lower than 60kPa (preferably lower than 50kPa, more preferably lower than 40kPa, for example lower than 38 kPa).

From the viewpoint of adhesion to an adherend in a room temperature region (e.g., 25 ℃), a pressure-sensitive adhesive satisfying at least the above condition (a) is preferable. A pressure-sensitive adhesive satisfying at least the above condition (b) is preferable because adhesiveness (adhesiveness) to an adherend can be easily improved by heating to a temperature slightly higher than room temperature. The pressure-sensitive adhesive that does not satisfy the above condition (a) and satisfies the above condition (b) has good reworkability (re-adherability) at the initial stage of attachment in the room temperature region, and can be used as a heat-activated pressure-sensitive adhesive that can effectively improve the peel strength from an adherend by heating to a temperature slightly higher than room temperature. The heat activation can be performed by heating the pressure-sensitive adhesive to a temperature slightly higher than room temperature at the time of attachment to an adherend. The temperature slightly higher than room temperature is, for example, about 60 ℃ or lower, preferably about 55 ℃ or lower (for example, about 50 ℃ or lower).

In some embodiments of the pressure-sensitive adhesive sheet disclosed herein, the storage modulus ratio G '(50)/G' (25), which is the ratio of the storage modulus G '(50) [ kPa ] to the storage modulus G' (25) [ kPa ], of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer is, for example, 70% or less, 40% or less, 30% or less, or 20% or less. The adhesive having a small G '(50)/G' (25) ratio is suitable for use as the above-mentioned heat-activated adhesive. The lower limit of G '(50)/G' (25) is not particularly limited. G '(50)/G' (25) is, for example, 5% or more, preferably 10% or more, and may be 12% or more, and may be 15% or more, from the viewpoint of the heat resistance of the adhesive.

The storage moduli G '(25) and G' (50) can be obtained by dynamic viscoelasticity measurement, and from the results, G '(50)/G' (25) can be calculated. The dynamic viscoelasticity can be measured by a conventional method using a commercially available dynamic viscoelasticity measuring apparatus, and for example, "Advanced Rheological Expansion System (ARES)" manufactured by TA Instruments or a product equivalent thereof can be used under the following measurement conditions. As a sample for measurement, a sample prepared to have a thickness of about 1.5mm by laminating the adhesive layer to be evaluated as necessary, or the like, was used.

[ measurement conditions ]

Deformation mode: torsion

Measuring frequency: 1Hz

Temperature rise rate: 5 deg.C/min

Shape: parallel plates

The storage modulus G '(25), G' (50) and storage modulus ratio of the pressure-sensitive adhesive layer can be determined by selection of the composition of the monomer component constituting the acrylic polymer (a) (for example, selection of the type and content of the monomer (m 1)), selection of whether or not to use a crosslinking agent, selection of the type and amount to use, and the above-mentioned additive (H) _RO ) And whether or not the plasticizing material is used, and selection of the type and amount of the plasticizing material to be used. For example, in the case where the 1 st monomer is used as the monomer (m 1) in combination with the 1 st monomer in a smaller amount in addition to the 1 st monomer which is the main component of the monomer (m 1), the use of the 2 nd monomer having a different chemical structure from the 1 st monomer can reduce G ' (50) and G ' (50)/G ' (25) in addition to the use of the 1 st monomer alone as the monomer (m 1).

When the psa sheet disclosed herein is a double-sided psa sheet having a1 st adhesive surface and a2 nd adhesive surface (for example, a substrate-less double-sided psa sheet having a1 st adhesive layer and a2 nd adhesive layer, a substrate-less double-sided psa sheet in which a sub-psa layer constituting the 1 st adhesive surface and a sub-psa layer constituting the 2 nd adhesive surface are laminated without interposing a non-adhesive substrate therebetween, and the like), the storage modulus G '(25), G' (50) and the storage modulus ratio can be applied to at least the psa layer constituting the 1 st adhesive surface, and preferably to both the psa layer constituting the 1 st adhesive surface and the psa layer constituting the 2 nd adhesive surface. The storage modulus G 'of the pressure-sensitive adhesive layer constituting the 1 st pressure-sensitive adhesive surface and the storage modulus G' of the pressure-sensitive adhesive layer constituting the 2 nd pressure-sensitive adhesive surface may be the same or different.

In some embodiments of the technology disclosed herein, the peak temperature of tan δ of the adhesive constituting the adhesive layer is preferably about-50 ℃ or higher, and further, preferably about 50 ℃ or lower. Here, tan δ (loss tangent) of an adhesive means a ratio of loss modulus G ″ of the adhesive to storage modulus G'. That is, tan δ = G "/G'. The tan δ of the adhesive can be determined as follows: a disk-shaped adhesive sample having a thickness of about 2mm and a diameter of 7.9mm was sandwiched between parallel plates, and a temperature dispersion test of the adhesive was performed in a shear mode using a viscoelasticity test apparatus under conditions of a measurement temperature range of-60 ℃ to 60 ℃ and a temperature rise rate of 5 ℃/min while applying a shear strain having a frequency of 1Hz, and based on the storage modulus G' (Pa) and the loss modulus G "(Pa) at that time, the following formula was applied: tan δ = G "/G'. The peak temperature of tan δ of the adhesive (hereinafter sometimes referred to as tpeak.) can be determined from the transition of tan δ in the above temperature range. As the viscoelastic testing apparatus, ARES manufactured by TA Instruments, inc. or its equivalent can be used.

In some embodiments, the binder advantageously has a Tpeak of 45 ℃ or less or 35 ℃ or less, preferably 30 ℃ or less (e.g., 25 ℃ or less), and can be 20 ℃ or less, or can be 15 ℃ or less. With a binder having a lower Tpeak, good initial adhesiveness and adhesion tend to be easily obtained in a room temperature region. On the other hand, from the viewpoint of imparting appropriate cohesive properties to the adhesive, it is preferable that Tpeak of the adhesive is not too low, and that Tpeak is also suitable for achieving both a high refractive index and the like. From this viewpoint, in some embodiments, the Tpeak of the binder may be, for example, -40 ℃ or higher, may be-30 ℃ or higher, may be-20 ℃ or higher, may be-5 ℃ or higher, may be 15 ℃ or higher, and may be 25 ℃ or higher. The pressure-sensitive adhesive having a high Tpeak can be preferably used in a form in which one or both of the pressure-sensitive adhesive and the adherend are heated to a temperature slightly higher than room temperature as necessary at the time of attachment to the adherend. Tpeak of the adhesive can be generalThe composition of the adhesive is selected (for example, the composition of the monomer component constituting the acrylic polymer (A), and the additive (H) _RO ) And whether or not a plasticizing material is used, and selection of the type and amount of the plasticizing material used).

When the psa sheet disclosed herein is in the form of a double-sided psa sheet having a1 st psa surface and a2 nd psa surface, tpeak of the above-mentioned psa is preferably applied to at least the psa layer constituting the 1 st psa surface, and more preferably to both the psa layer constituting the 1 st psa surface and the psa layer constituting the 2 nd psa surface. The Tpeak of the adhesive layer constituting the 1 st adhesive surface may be the same as or different from the Tpeak of the adhesive layer constituting the 2 nd adhesive surface.

(Water absorption)

In some embodiments of the pressure-sensitive adhesive sheet disclosed herein, the water absorption of the pressure-sensitive adhesive layer constituting the pressure-sensitive adhesive sheet is preferably limited to a predetermined value or less. By limiting the water absorption rate of the pressure-sensitive adhesive layer, dimensional change of the pressure-sensitive adhesive layer due to fluctuation of the moisture content in the pressure-sensitive adhesive layer (for example, absorption and release of moisture such as moisture in the environment) tends to be suppressed. This can suppress warping of the pressure-sensitive adhesive sheet or the adherend to which the pressure-sensitive adhesive sheet is attached, which is caused by non-uniformity in dimensional changes between the pressure-sensitive adhesive layer and a layer adjacent thereto (which may be a support base, a release liner, an adherend, or the like). From the viewpoint of maintaining the flatness, transparency, refractive index, and the like of the pressure-sensitive adhesive layer constant, it is also preferable that the variation in the amount of moisture in the pressure-sensitive adhesive layer be suppressed. The pressure-sensitive adhesive layer having a low water absorption rate is less likely to absorb moisture, and therefore is suitable as a pressure-sensitive adhesive sheet for use in members or products including moisture-disturbing elements such as organic EL elements.

In some embodiments, the water absorption of the pressure-sensitive adhesive layer is suitably about 1.0% or less, preferably 0.7% or less, more preferably 0.5% or less (e.g., less than 0.5%), and may be 0.4% or less, may be 0.3% or less, may be 0.2% or less, and may be 0.1% or less. The lower limit of the water absorption rate of the pressure-sensitive adhesive layer is not particularly limited, and may be, for example, 0.01% or more, 0.05% or more, 0.1% or more, or 0.15% or more, from the viewpoint of practical use, for example, in consideration of compatibility with adhesive properties. When the pressure-sensitive adhesive sheet disclosed herein is in the form of a double-sided pressure-sensitive adhesive sheet having a1 st pressure-sensitive adhesive surface and a2 nd pressure-sensitive adhesive surface, the water absorption of at least the pressure-sensitive adhesive layer constituting the 1 st pressure-sensitive adhesive surface is preferably limited to a predetermined value or less. From the viewpoint of obtaining higher effects, it is more preferable that the water absorption rates of both the pressure-sensitive adhesive layer constituting the 1 st pressure-sensitive adhesive surface and the pressure-sensitive adhesive layer constituting the 2 nd pressure-sensitive adhesive surface are limited to a predetermined value or less.

The water absorption rate (also referred to as a moisture rate) of the pressure-sensitive adhesive layer was measured by the following method.

[ measurement of moisture content ]

The pressure-sensitive adhesive layer to be evaluated was cut out to 4cm × 5cm (area: 20 cm) together with 2 sheets of release liners disposed on one surface and the other surface thereof ² ) The size of (2) was measured by removing the release liner on one side and attaching the same to a previously weighed aluminum foil. Subsequently, the release liner on the other surface of the adhesive layer was put into a constant temperature and humidity chamber at a temperature of 60 ℃ and a relative humidity of 90%, and taken out after 72 hours. After weighing a test piece in which an adhesive layer and an aluminum foil were laminated, the moisture content was measured by karl fischer coulometry using a moisture meter (model CA-200 of mitsubishi chemical Analytech) equipped with a heat vaporizer (model VA-200 of mitsubishi chemical Analytech).

Anode liquid: AQUAMICRON AKX (Mitsubishi chemical)

And (3) catholyte: AQUAMICRON CXU (Mitsubishi chemical)

Heating and gasifying temperature: 150 ℃ C

(gel fraction)

The gel fraction of the pressure-sensitive adhesive layer is appropriately set depending on the purpose of use, the mode of use, and the like, and is not limited to a specific range. The gel fraction is preferably about 99% or less, and about 97% or less, for example. In some preferred embodiments, the gel fraction is about 95% or less, and more preferably about 92% or less (for example, about 90% or less), from the viewpoint of easily and suitably satisfying both the high refractive index and the adhesive property. The gel fraction is preferably not too high from the viewpoint of suitably following irregularities that may be present on the surface of an adherend (for example, an irregular structure provided in a light-emitting device for the purpose of improving light extraction efficiency) and achieving good adhesion. In some embodiments, the gel fraction may be about 88% or less, may be about 75% or less, or may be about 65% or less. From the viewpoint of imparting appropriate cohesive properties to the pressure-sensitive adhesive and appropriately exhibiting adhesive properties, the gel fraction of the pressure-sensitive adhesive layer is, for example, about 10% or more, preferably about 20% or more, and may be about 30% or more. From the viewpoint of deformation resistance of the pressure-sensitive adhesive layer (prevention of overflow due to pressure, bubbles due to mixing of foreign substances, and the like), the gel fraction is preferably about 30% or more, more preferably about 40% or more, and may be about 45% or more, and may be about 50% or more, and may be about 65% or more, and may be about 75% or more. The gel fraction of the pressure-sensitive adhesive sheet (typically, a substrate-free pressure-sensitive adhesive sheet) is also preferably within the above-exemplified range. The gel fraction can be adjusted by the molecular weight, molecular structure, concentration, crosslinking degree, etc. of the acrylic polymer (a). The gel fraction was measured by the following method.

[ measurement of gel fraction ]

A prescribed amount of the adhesive sample (weight Wg) ₁ ) A porous polytetrafluoroethylene film (weight Wg) having an average pore diameter of 0.2 μm was used ₂ ) Wrapping into a purse shape, and tying the kite with a kite string (weight Wg) ₃ ) And (5) tightening. As the porous Polytetrafluoroethylene (PTFE) membrane, a product of NITOFLON (registered trademark) NTF1122 (average pore diameter 0.2 μm, porosity 75%, thickness 85 μm) available from Ninto electric corporation or a product equivalent thereof was used.

The coating was immersed in a sufficient amount of ethyl acetate, and kept at room temperature (typically 23 ℃) for 7 days to elute only the sol component in the binder out of the film, and then the coating was taken out and wiped off the ethyl acetate adhered to the outer surface, and the coating was dried at 130 ℃ for 2 hours to measure the weight (Wg) of the coating ₄ ). The gel fraction of the pressure-sensitive adhesive layer was determined by substituting each value into the following formula.

Gel fraction (%) = [ (Wg) ₄ -Wg ₂ -Wg ₃ )/Wg ₁ ]×100

When the psa sheet disclosed herein is in the form of a double-sided psa sheet having a1 st psa surface and a2 nd psa surface, the above-mentioned gel fraction is applied to at least the psa layer constituting the 1 st psa surface, preferably to both the psa layer constituting the 1 st psa surface and the psa layer constituting the 2 nd psa surface. The gel fraction of the pressure-sensitive adhesive layer constituting the 1 st pressure-sensitive adhesive surface may be the same as or different from the gel fraction of the pressure-sensitive adhesive layer constituting the 2 nd pressure-sensitive adhesive surface.

(Peel Strength)

In some embodiments of the pressure-sensitive adhesive sheet disclosed herein, the peel strength of the pressure-sensitive adhesive sheet to a glass plate is suitably about 1.0N/25mm or more (e.g., 1.5N/25mm or more), preferably 2N/25mm or more, more preferably 3N/25mm or more, and may be 4N/25mm or more, and may be 6N/25mm or more, and may be 8N/25mm or more, and may be 10N/25mm or more, and may be 12N/25mm or more. The upper limit of the peel strength is not particularly limited, and may be, for example, 30N/25mm or less, 25N/25mm or less, or 20N/25mm or less.

Here, the peel strength can be grasped as follows: an alkali glass plate as an adherend was pressure-bonded thereto, and left to stand in an atmosphere of 23 ℃ and 50% RH for 30 minutes, then put into a pressure defoaming apparatus (autoclave), and autoclave-treated at 50 ℃ and 0.5MPa for 30 minutes, and further left to stand in an atmosphere of 23 ℃ and 50% RH for 24 hours, and then the 180 DEG peel adhesion was measured under conditions of a peel angle of 180 DEG and a tensile rate of 300 mm/min. In the measurement, an appropriate backing material (for example, a polyethylene terephthalate (PET) film having a thickness of about 25 μm to about 50 μm) may be bonded to the pressure-sensitive adhesive sheet to be measured and reinforced as necessary. The peel strength can be measured more specifically by the method described in the examples below.

When the adhesive sheet disclosed herein is in the form of a double-sided adhesive sheet having a1 st adhesive side and a2 nd adhesive side, in some embodiments, the peel strength is preferably applied to at least the 1 st adhesive side, more preferably to both the 1 st adhesive side and the 2 nd adhesive side. The peel strength of the 1 st adhesive surface to the glass plate may be the same as or different from the peel strength of the 2 nd adhesive surface to the glass plate.

(supporting base Material)

Some embodiments of the pressure-sensitive adhesive sheet may be in the form of a substrate-attached pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer on one or both sides of a support substrate. The material of the support substrate is not particularly limited, and may be appropriately selected depending on the purpose of use, the mode of use, and the like of the adhesive sheet. Non-limiting examples of the usable substrate include plastic films such as polyolefin films mainly composed of polyolefins such as polypropylene (PP) and ethylene-propylene copolymers, polyester films mainly composed of polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT) and polyethylene naphthalate (PEN), and polyvinyl chloride films mainly composed of polyvinyl chloride; foam sheets formed of foams such as polyurethane foam, polyethylene (PE) foam, and polychloroprene foam; woven and nonwoven fabrics based on various fibrous materials (natural fibers such as hemp and cotton, synthetic fibers such as polyester and vinylon, and semisynthetic fibers such as acetate fibers) alone or in a blend; paper such as japanese paper, fine paper, kraft paper, crepe paper, and the like; metal foils such as aluminum foil and copper foil; and the like. The substrate may be a composite substrate. Examples of such composite substrates include substrates having a structure in which a metal foil and the plastic film are laminated, and plastic substrates reinforced with inorganic fibers such as glass cloth.

In some embodiments, various film substrates may be preferred. The film substrate may be a porous substrate such as a foamed film or a nonwoven fabric sheet, a non-porous substrate, or a substrate having a structure in which a porous layer and a non-porous layer are laminated. In some embodiments, as the film substrate, a substrate including a resin film (self-supporting or independent) capable of independently maintaining the shape as a base film can be preferably used. Here, the "resin film" refers to a (non-porous) resin film having a non-porous structure, typically containing substantially no air bubbles. Therefore, the resin film is a concept different from a foamed film and a nonwoven fabric. As the resin film, a film (self-supporting type or independent type) capable of independently maintaining the shape can be preferably used. The resin film may have a single-layer structure or a multilayer structure having 2 or more layers (for example, a 3-layer structure).

Examples of the material constituting the resin film include polyester resins mainly composed of polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN), polyolefin resins mainly composed of polyolefins such as Polyethylene (PE), polypropylene (PP), ethylene-propylene copolymers, and ethylene-butene copolymers, cellulose resins such as triacetyl cellulose, cellulose resins such as acetate resins, polysulfone resins, polyethersulfone resins, polycarbonate resins, polyamide (PA) resins such as nylon 6, nylon 66, and partially aromatic polyamides, polyimide (PI) resins, transparent polyimide resins, polyamideimide (PAI), polyether ether ketone (PEEK), polyether Sulfone (PEs), and cyclic polyolefin resins such as norbornene resins, (meth) acrylic resins, polyvinyl chloride resins, polyvinylidene chloride resins, polystyrene resins, polyvinyl alcohol resins, ethylene-vinyl acetate copolymer resins, ethylene-vinyl alcohol copolymer resins, polyvinyl sulfide resins, polyphenylene Sulfide (PPs), polyethylene Urethane (PU), ethylene-vinyl acetate copolymers (EVA), and fluorinated polyimides.

The resin film may be formed using a resin material containing 1 kind of such resin alone, or may be formed using a resin material obtained by blending 2 or more kinds of such resins. The resin film may be unstretched or stretched (for example, uniaxially stretched or biaxially stretched). For example, a PET film, a PBT film, a PEN film, an unstretched polypropylene (CPP) film, a biaxially oriented polypropylene (OPP) film, a Low Density Polyethylene (LDPE) film, a Linear Low Density Polyethylene (LLDPE) film, a PP/PE blend film, or the like can be preferably used. Examples of the resin film preferable from the viewpoint of strength and dimensional stability include a PET film, a PEN film, a PPS film, and a PEEK film. From the viewpoint of easy acquisition, etc., a PET film and a PPS film are particularly preferable, and among them, a PET film is preferable.

The resin film may contain known additives such as a light stabilizer, an antioxidant, an antistatic agent, a colorant (dye, pigment, etc.), a filler, a lubricant, and an antiblocking agent, as necessary, within a range not significantly impairing the effects of the present invention. The amount of the additive to be blended is not particularly limited, and may be appropriately set according to the use of the pressure-sensitive adhesive sheet and the like.

The method for producing the resin film is not particularly limited. For example, conventionally known general resin film forming methods such as extrusion molding, inflation molding, T-die casting molding, calender roll molding, and the like can be suitably used.

The substrate may consist essentially of such a base film. Alternatively, the base film may further include an auxiliary layer. Examples of the auxiliary layer include optical property adjusting layers (for example, a colored layer and an antireflection layer), printing layers for giving a desired appearance to a substrate, lamination layers, antistatic layers, undercoating layers, release layers, and other surface treatment layers.

In some embodiments, a substrate having light-transmitting properties (hereinafter also referred to as a light-transmitting substrate) can be preferably used as the supporting substrate. This makes it possible to form a pressure-sensitive adhesive sheet with a substrate having light-transmitting properties. The total light transmittance of the light-transmitting substrate may be, for example, higher than 50% or 70% or more. In some preferred embodiments, the total light transmittance of the support substrate is 80% or more, more preferably 90% or more, and may be 95% or more (e.g., 95 to 100%). The above total light transmittance is measured according to JIS K7136: 2000, measured using a commercially available transmittance meter. As the transmittance meter, the product name "HAZEMETER HM-150" manufactured by the color technology research on village or the equivalent thereof was used. A preferable example of the light-transmitting substrate is a resin film having light-transmitting properties. The light-transmitting substrate may be an optical film.

The thickness of the substrate is not particularly limited, and may be selected according to the purpose of use, the mode of use, and the like of the adhesive sheet. The thickness of the substrate may be, for example, 500 μm or less, and is preferably 300 μm or less, may be 150 μm or less, may be 100 μm or less, may be 50 μm or less, may be 25 μm or less, and may be 10 μm or less from the viewpoint of handling property and processability of the pressure-sensitive adhesive sheet. When the thickness of the base material is reduced, the following property to the surface shape of the adherend tends to be improved. From the viewpoint of handling properties, processability, and the like, the thickness of the base material may be, for example, 2 μm or more, 10 μm or more, or 25 μm or more.

The surface of the substrate on the side on which the pressure-sensitive adhesive layer is laminated may be subjected to conventionally known surface treatment such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, formation of a primer layer by coating with a primer (primer), or the like, as necessary. Such a surface treatment may be a treatment for improving the anchoring property of the adhesive layer to the substrate. The composition of the primer used for forming the undercoat layer is not particularly limited, and may be appropriately selected from known compositions. The thickness of the undercoat layer is not particularly limited, and is usually about 0.01 μm to 1 μm, preferably about 0.1 μm to 1 μm. As other treatments that can be performed on the base material as needed, antistatic layer formation treatment, coloring layer formation treatment, printing treatment, and the like can be cited. These treatments may be applied alone or in combination.

When the pressure-sensitive adhesive sheet disclosed herein is in the form of a substrate-attached pressure-sensitive adhesive sheet, the thickness of the pressure-sensitive adhesive sheet may be, for example, 1000 μm or less, 350 μm or less, 200 μm or less, 120 μm or less, 75 μm or less, or 50 μm or less. From the viewpoint of handling properties and the like, the thickness of the pressure-sensitive adhesive sheet may be, for example, 10 μm or more, 25 μm or more, 80 μm or more, or 130 μm or more.

The thickness of the pressure-sensitive adhesive sheet is the thickness of the portion to be adhered to the adherend. For example, the psa sheet 1 having the structure shown in fig. 1 has a thickness from the 1 st surface (psa surface) 10A of the psa layer to the 2 nd surface 20B of the support substrate, excluding the thickness of the release liner 30.

< Release liner-equipped adhesive sheet >

The psa sheet disclosed herein may be in the form of a psa article in which the surface (psa surface) of the psa layer is in contact with the release surface of the release liner. Thus, according to the present specification, there is provided a release-liner-equipped adhesive sheet (adhesive article) comprising: any of the pressure-sensitive adhesive sheets disclosed herein, and a release liner having a release surface that comes into contact with the pressure-sensitive adhesive surface of the pressure-sensitive adhesive sheet.

The release liner is not particularly limited, and examples thereof include a release liner having a release layer on the surface of a liner base material such as a resin film or paper (which may be paper laminated with a resin such as polyethylene), and a release liner comprising a resin film made of a low-adhesion material such as a fluorine-based polymer (polytetrafluoroethylene or the like) or a polyolefin-based resin (polyethylene, polypropylene or the like). From the viewpoint of excellent surface smoothness, a release liner having a release layer on the surface of a resin film as a liner base material, or a release liner including a resin film made of a low-adhesion material can be preferably used. The resin film is not particularly limited as long as it can protect the pressure-sensitive adhesive layer, and examples thereof include a Polyethylene (PE) film, a polypropylene (PP) film, a polybutylene film, a polybutadiene film, a polymethylpentene film, a polyvinyl chloride film, a vinyl chloride copolymer film, a polyester film (a PET film, a PBT film, and the like), a polyurethane film, an ethylene-vinyl acetate copolymer film, and the like. For forming the release layer, for example, a known release treatment agent such as a silicone release treatment agent, a long-chain alkyl release treatment agent, an olefin release treatment agent, a fluorine release treatment agent, a fatty acid amide release treatment agent, molybdenum sulfide, or silica powder can be used.

< use >

The pressure-sensitive adhesive sheet disclosed herein can be used by being bonded to various adherends. The constituent material of the adherend (adherend material) is not particularly limited, and examples thereof include: examples of the metal material include metal materials such as copper, silver, gold, iron, tin, palladium, aluminum, nickel, titanium, chromium, indium, zinc, and alloys containing 2 or more of these metals, polyimide resins, acrylic resins, polyether nitrile resins, polyether sulfone resins, polyester resins (PET resins, polyethylene naphthalate resins, and the like), polyvinyl chloride resins, polyphenylene sulfide resins, polyether ether ketone resins, polyamide resins (so-called aramid resins, and the like), polyarylate resins, fluorine resins, polycarbonate resins, and diacetylcelluloseVarious resin materials (typically, plastic materials) such as cellulose polymers such as triacetyl cellulose, polyvinyl butyral, liquid crystal polymers, and carbon materials such as graphene, alumina, zirconia, titania, and SiO ₂ Metal oxides such as ITO (indium tin oxide) and ATO (antimony doped tin oxide) and mixtures thereof, nitrides such as aluminum nitride, silicon nitride, titanium nitride, gallium nitride and indium nitride and composites thereof, and inorganic materials such as alkali glass, alkali-free glass, quartz glass, borosilicate glass and sapphire glass. The adhesive sheet disclosed herein can be used by being stuck to a member (for example, an optical member) having at least a surface made of the above-mentioned material.

The pressure-sensitive adhesive sheet disclosed herein can be used in an adhesive form that does not require a treatment of heating to a temperature higher than a temperature range of about room temperature (for example, 20 to 35 ℃) after being bonded to an adherend. Depending on the constituent material (e.g., material of the substrate) of the pressure-sensitive adhesive sheet and the type of the adherend, the heat treatment may be carried out at least one of after the pressure-sensitive adhesive sheet is bonded to the adherend, at the time of bonding, and before the bonding, if allowable. The heat treatment may be performed for the purpose of improving the adhesion of the pressure-sensitive adhesive to the adherend, promoting adhesion, or the like. The heat treatment temperature may be appropriately set within an allowable range in consideration of the surface state of the adherend to obtain a desired effect, for example, about 100 ℃ or less, 80 ℃ or less, 60 ℃ or less, or 50 ℃ or less, depending on the constituent material of the pressure-sensitive adhesive sheet and the kind of the adherend.

The member or material to which the pressure-sensitive adhesive sheet is attached (at least one adherend in the case of a double-sided pressure-sensitive adhesive sheet) may have optical transparency. In such an adherend, the use of the technology disclosed herein easily provides advantages of suppressing a decrease in optical characteristics (transparency, etc.) and improving the refractive index. The total light transmittance of the adherend may be, for example, higher than 50% or 70% or more. In some preferred embodiments, the total light transmittance of the adherend is 80% or more, more preferably 90% or more, and still more preferably 95% or more (e.g., 95 to 100%). The pressure-sensitive adhesive sheet disclosed herein can be preferably used by being stuck to an adherend (for example, an optical member) having a total light transmittance of a predetermined value or more. The above total light transmittance is measured according to JIS K7136: 2000, measured by using a commercially available transmittance meter. As the transmittance meter, a product name "HAZEMETER HM-150" manufactured by the color technology research on villages or a product equivalent thereof was used.

The refractive index of the pressure-sensitive adhesive layer may be the same as or different from that of the adherend. For example, by increasing the refractive index of the pressure-sensitive adhesive layer relatively compared to the refractive index of the adherend, light incident on the pressure-sensitive adhesive layer at an angle equal to or less than the critical angle from the adherend side can be refracted on the front side, and the front luminance can be improved. In this case, the refractive index of the adherend may be, for example, 1.55 or less, 1.50 or less, 1.48 or less, 1.45 or less, or less than 1.45, or, for example, 1.10 or more, 1.20 or more, 1.30 or more, or 1.35 or more. In addition, by using an adherend having a relatively higher refractive index than the pressure-sensitive adhesive layer, light incident on the adherend from the pressure-sensitive adhesive layer side can be refracted on the front side, and the front luminance can be improved. In this case, the refractive index of the adherend may be, for example, 1.60 or more, 1.65 or more, or 1.70 or more, and may be, for example, 3.00 or less, or 2.50 or less, or 2.00 or less. On the other hand, by reducing the difference in refractive index between the pressure-sensitive adhesive layer and the adherend, reflection of light at the interface can be suppressed. In this case, the refractive index of the adherend may be about 1.55 to 1.80, about 1.55 to 1.75, or about 1.60 to 1.70. The refractive index of the adherend can be measured by the same method as the refractive index of the pressure-sensitive adhesive.

In some preferred embodiments, the adherend may have any of the refractive indices described above and any of the total light transmittances described above. In the mode of attachment to such an adherend, the effects brought by the technology disclosed herein can be particularly preferably exhibited.

As an example of preferable applications, optical applications are cited. More specifically, the pressure-sensitive adhesive sheet disclosed herein can be preferably used, for example, as a pressure-sensitive adhesive sheet for optical use used for applications of bonding optical members (for bonding optical members), applications of manufacturing products (optical products) using the optical members, and the like.

The optical member is a member having optical characteristics (for example, polarization, light refraction, light scattering, light reflection, light transmittance, light absorption, light diffraction, optical rotation, visibility, and the like). The optical member is not particularly limited as long as it has optical properties, and examples thereof include members constituting devices (optical devices) such as display devices (image display devices) and input devices, and members used in these devices, such as polarizing plates, wavelength plates, phase difference plates, optical compensation films, brightness enhancement films, light guide plates, reflection films, reflection prevention films, hard Coat (HC) films, impact absorption films, stain-proofing films, photochromic films, light control films, transparent conductive films (ITO films), appearance films, decorative films, surface protection plates, prisms, lenses, color filters, transparent substrates, and members further laminated with these (these may be collectively referred to as "functional films"). The "plate" and the "film" each include a plate-like, film-like, sheet-like form, and the like, and for example, "polarizing film" includes "polarizing plate", "polarizer", and the like, and "light guide plate" includes "light guide film", "light guide sheet", and the like. In addition, the "polarizing plate" includes a circular polarizing plate.

Examples of the display device include a liquid crystal display device, an organic EL (electroluminescence) display device, a micro LED (μ LED), a mini LED (miniLED), a PDP (plasma display panel), and electronic paper. The input device may be a touch panel.

The optical member is not particularly limited, and examples thereof include members formed of glass, acrylic resin, polycarbonate, polyethylene terephthalate, metal film, and the like (for example, sheet-shaped, film-shaped, plate-shaped members). The term "optical member" as used herein includes a member (e.g., a design film, a decorative film, and a surface protective film) that plays a role of decoration and protection while maintaining the visibility of a display device and an input device.

The technology disclosed herein can be preferably used, for example, for joining an optical film such as a film having 1 or 2 or more functions of light transmission, reflection, diffusion, wave guiding, light collection, diffraction, or the like, a fluorescent film, or the like to another optical member (which may be another optical film). Among these, in the bonding of optical thin films having at least 1 function of light waveguide, light collection, and diffraction, the entire volume of the bonding layer is desirably high in refractive index, and this can be a preferable application object of the technology disclosed herein.

The adhesive disclosed herein can be preferably used for bonding optical films such as a light guide film, a diffusion film, a fluorescent film, a color control film, a prism sheet, a lenticular film, and a microlens array film. In these applications, from the viewpoint of the tendency toward miniaturization and high performance of optical members, thinning and improvement of light extraction efficiency are required. As an adhesive that can cope with this demand, the adhesive disclosed herein can be preferably utilized. More specifically, for example, in bonding a light guide film and a diffusion film, the refractive index of the pressure-sensitive adhesive layer serving as a bonding layer is adjusted (for example, the refractive index is increased), thereby contributing to the reduction in thickness. When the fluorescent film is bonded, the light extraction efficiency (which can also be grasped as the light emission efficiency) can be improved by appropriately adjusting the refractive index difference between the fluorescent light-emitting body and the adhesive. In the joining of the color adjusting film, the refractive index of the binder is appropriately adjusted so that the difference in refractive index between the color adjusting film and the color adjusting pigment is small, whereby the scattering component can be reduced, and the improvement of the light transmittance can be contributed. In joining a prism sheet, a lenticular film, a microlens array film, or the like, by appropriately adjusting the refractive index of the adhesive, it is possible to control diffraction of light and contribute to improvement in luminance and/or viewing angle.

The pressure-sensitive adhesive sheet disclosed herein is preferably used to be stuck to an adherend having a high refractive index (which may be a layer, a member or the like having a high refractive index), and can suppress interfacial reflection with the adherend. As described above, the pressure-sensitive adhesive sheet used in this manner preferably has a small refractive index difference from an adherend and high adhesion at the interface with the adherend. In addition, from the viewpoint of improving the homogeneity of the appearance, the thickness uniformity of the pressure-sensitive adhesive layer is preferably high, and for example, the surface smoothness of the pressure-sensitive adhesive surface is preferably high. In the case where the thickness of the adherend having a high refractive index is small (for example, 5 μm or less, 4 μm or less, or 2 μm or less), it is particularly significant to suppress reflection at the interface from the viewpoint of suppressing coloring and color unevenness caused by interference of reflected light. Examples of such a use mode include: in the polarizing plate with a retardation layer, which comprises a polarizer, a1 st retardation layer and a2 nd retardation layer in this order, the method is used for bonding the polarizer and the 1 st retardation layer and/or bonding the 1 st retardation layer and the 2 nd retardation layer.

The adhesive sheet disclosed herein is suitable for increasing the refractive index, and therefore can be preferably used by being attached to a light-emitting layer (for example, a highly refractive light-emitting layer mainly composed of an inorganic material) of an optical semiconductor or the like. By reducing the difference in refractive index between the light-emitting layer and the binder layer, reflection at the interface therebetween can be suppressed, and light extraction efficiency can be improved. The pressure-sensitive adhesive sheet used in this manner preferably has a pressure-sensitive adhesive layer having a high refractive index. In addition, from the viewpoint of preventing deterioration of the self-light emitting element due to moisture in advance, the water absorption rate of the pressure-sensitive adhesive layer is preferably low. From the viewpoint of improving brightness, the pressure-sensitive adhesive sheet is preferably low colored. This may also be advantageous from the viewpoint of suppressing unintentional coloring due to the adhesive sheet.

The adhesive disclosed herein can be preferably used as a coating layer for covering a lens surface, a bonding layer for a member facing the lens surface (for example, a member having a surface shape corresponding to the lens surface), a filling layer for filling between the lens surface and the member, and the like, in a microlens and other lens members (for example, a lens member such as a microlens constituting a microlens array film or a microlens for a camera) used as a constituent member of a camera, a light-emitting device, and the like. The adhesive disclosed herein is suitable for increasing the refractive index, and therefore, even a lens having a high refractive index (for example, a lens made of a high refractive index resin or a lens having a surface layer made of a high refractive index resin) can reduce the refractive index difference from the lens. This is advantageous from the viewpoint of reducing the thickness of the lens and a product including the lens, and contributes to suppressing aberrations and increasing the abbe number. The adhesive disclosed herein can also be used by itself as a lens resin, for example, in the form of filling in recesses or voids of a suitable transparent member.

The method for bonding an optical member using the adhesive sheet disclosed herein is not particularly limited, and examples thereof include (1) a method for bonding optical members to each other via the adhesive sheet disclosed herein, (2) a method for bonding an optical member to a member other than an optical member via the adhesive sheet disclosed herein, and (3) a method for bonding an optical member or a member other than an optical member via the adhesive sheet disclosed herein. In the embodiment (3), the pressure-sensitive adhesive sheet including the optical member may be a pressure-sensitive adhesive sheet in which the support is an optical member (e.g., an optical film). Such an adhesive sheet containing an optical member as a support can also be regarded as an adhesive optical member (e.g., an adhesive optical film). In addition, when the pressure-sensitive adhesive sheet disclosed herein is a type of pressure-sensitive adhesive sheet having a support and the functional film is used as the support, the pressure-sensitive adhesive sheet disclosed herein can be also known as an "adhesive type functional film" having the pressure-sensitive adhesive layer disclosed herein on at least one side of the functional film.

As described above, according to the technology disclosed herein, a laminate is provided which includes the adhesive sheet disclosed herein and a member to which the adhesive sheet is attached. The member to which the adhesive sheet is attached may have a refractive index of the adherend material. The difference (refractive index difference) between the refractive index of the pressure-sensitive adhesive sheet and the refractive index of the member may be the refractive index difference between the adherend and the pressure-sensitive adhesive sheet. The members constituting the laminate are not described repeatedly, since they are described as the above-described members, materials, and adherends.

As can be understood from the above description and the following examples, matters disclosed in the present specification include the following.

[ 1] an adhesive sheet comprising an adhesive layer,

which has an adhesive surface comprising the adhesive layer,

the adhesive layer has a refractive index of higher than 1.570, a total light transmittance of 86% or more, and a haze value of 3.0% or less.

The adhesive sheet according to [ 1] above, wherein the thickness of the adhesive layer is 5 μm or more.

[ 3 ] the adhesive sheet according to the above [ 1] or [ 2], which has a peel strength (adhesive force) of 3N/25mm or more with respect to a glass plate.

The pressure-sensitive adhesive sheet according to any one of [ 1] to [ 3 ] above, wherein the arithmetic average roughness Ra of the pressure-sensitive adhesive surface is 100nm or less.

The pressure-sensitive adhesive sheet according to any one of [ 1] to [4 ] above, wherein the water absorption of the pressure-sensitive adhesive layer is 1.0% or less.

The pressure-sensitive adhesive sheet according to any one of [ 1] to [ 5 ] above, which is configured in the form of a laminate comprising the pressure-sensitive adhesive layer and a light-transmitting substrate.

[ 7 ] the adhesive sheet according to [ 6 ], wherein the light-transmissive substrate is a resin film.

The pressure-sensitive adhesive sheet according to any one of [ 1] to [ 5 ] above, which is a double-sided adhesive pressure-sensitive adhesive sheet formed of the pressure-sensitive adhesive layer.

[ 9 ] A release liner-equipped adhesive sheet comprising:

the adhesive sheet according to any one of [ 1] to [ 8 ] above, and

a release liner disposed on the pressure-sensitive adhesive surface of the pressure-sensitive adhesive sheet.

[ 10 ] an adhesive composition for forming an adhesive layer of the adhesive sheet according to any one of [ 1] to [ 8 ] above.

[ 11 ] an adhesive composition comprising:

an acrylic polymer (A) containing an aromatic ring-containing monomer (m 1) as a monomer unit; and

additive (H) _RO ) And an organic material having a higher refractive index than the acrylic polymer (A).

[ 12 ] the adhesive composition according to [ 11 ] above, wherein the additive (H) is _RO ) Has a refractive index of 1More than 60.

[ 13 ] the adhesive composition according to the above [ 11 ] or [ 12 ], wherein the additive (H) is added to 100 parts by weight of the acrylic polymer (A) _RO ) Is more than 0 part by weight and 60 parts by weight or less.

[ 14 ] the adhesive composition according to any one of [ 11 ] to [ 13 ] above, wherein the additive (H) _RO ) Comprises at least 1 compound selected from the group consisting of aromatic ring-containing compounds and heterocyclic ring-containing compounds.

[ 15 ] the adhesive composition according to any one of [ 11 ] to [ 14 ] above, wherein the additive (H) _RO ) Contains a compound having 2 or more aromatic rings in 1 molecule.

[ 16 ] the adhesive composition according to [ 15 ] above, wherein the additive (H) is _RO ) A compound having 2 or more aromatic rings in the 1 molecule, which satisfies at least one of the following conditions:

(ii) Comprises a structure obtained by fusing 2 aromatic rings.

The adhesive composition according to any one of [ 11 ] to [ 16 ] above, wherein a content of the aromatic ring-containing monomer (m 1) in the monomer components constituting the acrylic polymer (A) is 50% by weight or more.

The adhesive composition according to any one of [ 11 ] to [ 17 ] above, wherein the content of the aromatic ring-containing monomer (m 1) in the monomer components constituting the acrylic polymer (A) is more than 70% by weight and less than 100% by weight,

50% by weight or more of the aromatic ring-containing monomer (m 1) is a monomer having a homopolymer glass transition temperature of 10 ℃ or lower.

The pressure-sensitive adhesive composition according to any one of [ 11 ] to [ 18 ] above, wherein the monomer component constituting the acrylic polymer (A) further contains a monomer (m 2) having at least one of a hydroxyl group and a carboxyl group.

The adhesive composition according to any one of [ 11 ] to [ 18 ] above, which is used for forming an adhesive layer of the adhesive sheet according to any one of [ 1] to [ 8 ].

An adhesive comprising the adhesive composition according to any one of [ 11 ] to [ 20 ] above, wherein the refractive index of the adhesive is higher than 1.570.

[ 22 ] an adhesive sheet comprising an adhesive layer composed of an adhesive agent formed from the adhesive composition according to any one of [ 11 ] to [ 20 ] above.

The pressure-sensitive adhesive sheet according to [ 22 ] above, wherein the haze value of the pressure-sensitive adhesive layer is 1.0% or less.

[ 24 ] an interlayer sheet which is used by being disposed between layers of a laminate in optical use,

comprising a refractive index n ₁ A viscoelastic layer V of 1.570 or more ₁ And the interlayer sheet satisfies:

the total light transmittance is more than 86%;

a haze value of 1.0% or less; and,

The storage modulus G' at 25 ℃ is 30 to 700kPa.

[ 25 ] the interlayer sheet according to [ 24 ] above, which has a thickness of 5 μm or more.

[ 26 ] the interlayer sheet according to the above [ 24 ] or [ 25 ], wherein the viscoelastic layer V ₁ Comprising a main polymer and a plasticising material having a lower molecular weight than the main polymer.

[ 27 ] the interlayer sheet according to [ 26 ], wherein the weight average molecular weight of the plasticizing material is 30000 or less.

The interlayer sheet according to any one of [ 24 ] to [ 27 ] above, further comprising a viscoelastic layer V laminated on the viscoelastic layer ₁ Viscoelastic layer V ₂ ，

The above viscoelastic layer V ₂ Storage modulus G 'at 25℃' _V2 Lower than the above viscoelastic layer V ₁ Storage modulus G 'at 25℃' _V1 。

[ 29 ] the interlayer sheet according to [ 28 ], wherein the viscoelastic layer V ₂ Refractive index n of ₂ Below the viscoelastic layer V ₁ Refractive index n of ₁ 。

[ 30 ] the interlayer sheet according to any one of [ 24 ] to [ 29 ], wherein the viscoelastic layer V ₁ Is a layer formed from the adhesive composition according to any one of [ 11 ] to [ 18 ] above.

[ 31 ] the interlayer sheet according to any one of [ 24 ] to [ 29 ], wherein the viscoelastic layer V ₁ Is the adhesive layer in the adhesive sheet according to any one of [ 1] to [ 5 ] above.

[ 32 ] an optical laminate comprising:

the interlayer sheet according to any one of [ 24 ] to [ 31 ] above, and

and a resin film laminated on the interlayer sheet.

[ 33 ] an interlayer sheet with a release liner, comprising:

the interlayer sheet according to any one of [ 24 ] to [ 31 ] above, and

and a release liner covering at least one surface of the interlayer sheet.

Examples

The following examples are illustrative of the present invention, but are not intended to limit the invention to the scope of the specific examples. In the following description, "part(s)" and "%" indicating the amount and content of the compound are based on weight unless otherwise specified.

< example 1>

(preparation of acrylic Polymer solution)

Into ase:Sub>A four-necked flask equipped with ase:Sub>A stirring blade, ase:Sub>A thermometer, ase:Sub>A nitrogen inlet tube and ase:Sub>A condenser, m-phenoxybenzyl acrylate (trade name "LIGHT ACRYLATE POB-A" manufactured by Kyoeishase:Sub>A chemical Co., ltd., refractive index: 1.566, tg of homopolymer: -35 ℃ C., hereinafter abbreviated as "POB-A") was charged as ase:Sub>A monomer component ". ) 95 parts of 4-hydroxybutyl acrylate (4 HBA) 5 parts, 2,2' -Azobisisobutyronitrile (AIBN) 0.2 part as a polymerization initiator, and 100 parts of toluene as a polymerization solvent were gradually stirred while introducing nitrogen gas, and polymerization was carried out for 6 hours while maintaining the liquid temperature in the flask at about 60 ℃ to prepare a solution (50%) of acrylic polymer A1. The weight average molecular weight (Mw) of the acrylic polymer A1 was 50 ten thousand. Tg (i.e., tg) of the acrylic polymer A1 based on the composition of the monomer components _T ) At-35 ℃ and a Tg (i.e., tg) based on the composition of the aromatic ring-containing monomer _m1 ) Is-35 ℃.

(preparation of adhesive composition)

The solution (50%) of the acrylic polymer A1 was diluted with ethyl acetate to 30%, and 334 parts (100 parts of nonvolatile matter) of the solution was added as an additive (H) _RO ) 5 parts of 6-acryloyloxymethyl dinaphthothiophene (Sugai Chemical IND. CO., dinaphthothiophene-6-methacrylate product manufactured by LTD., trade name "6MDNTA", refractive index 1.75), 10 parts (non-volatile component) of a 1% ethyl acetate solution of isocyanurate of hexamethylene diisocyanate (product of Tosoh Corona corporation, trade name "Coronate HX", 3-functional isocyanate compound) as a crosslinking agent, 2 parts of acetylacetone as a crosslinking retarder, and 1 part (non-volatile component 0.01 part) of a 1% ethyl acetate solution of iron acetylacetonate as a crosslinking catalyst were mixed with stirring to prepare an acrylic adhesive composition C1.

(preparation of adhesive sheet)

The acrylic pressure-sensitive adhesive composition C1 prepared above was coated on a silicone-treated surface of a polyethylene terephthalate (PET) film R1 (thickness 50 μm) having silicone-treated one surface, and heated at 130 ℃ for 2 minutes to form a pressure-sensitive adhesive layer having a thickness of 25 μm. Next, a silicone-treated surface of the PET film R2 (thickness 25 μm) having silicone-treated one surface was bonded to the surface of the pressure-sensitive adhesive layer. In this way, a substrate-less double-sided adhesive sheet S1 formed of the adhesive layer was obtained. Both sides of the pressure-sensitive adhesive sheet S1 are protected by PET films (release liners) R1, R2.

< examples 2 to 5>

Adding additive (H) _RO ) And the amount used relative to 100 parts of acrylic polymer (phr; perrounded resin) was changed as shown in table 1, and the acrylic pressure-sensitive adhesive compositions C2 to C5 of examples 2 to 5 were prepared in the same manner as the preparation of the acrylic pressure-sensitive adhesive composition C1 of example 1. In Table 1, "BPFL" means 9,9-bis (4-hydroxyphenyl) fluorene (Osaka Gas Chemicals Co., manufactured by Ltd., refractive index 1.68) and "BAFL" means 9,9-bis (4-aminophenyl) fluorene (Osaka Gas Chemicals Co., manufactured by Ltd., refractive index 1.73).

Adhesive sheets (substrate-less double-sided adhesive sheets formed of an adhesive layer) S2 to S5 of examples 2 to 5 were produced in the same manner as in the production of the adhesive sheet of example 1, except that the acrylic adhesive compositions C2 to C5 were used instead of the acrylic adhesive composition C1.

< example 6>

20 parts of POB-A, 80 parts of 1-naphthylmethyl acrylate (trade name "LIGHT ACRYLATE NMT-A" manufactured by Kyoeisha chemical Co., ltd., refractive index: 1.595, tg of homopolymer: 31 ℃ C., hereinafter abbreviated as "NMT-A") were charged into a separable flask equipped with a thermometer, a stirrer, a reflux condenser and a nitrogen gas inlet, 0.2 parts of AIBN as a polymerization initiator, 3.5 parts of α -thioglycerol as a chain transfer agent, and 67 parts of methyl ethyl ketone were introduced, and nitrogen substitution was performed for about 1 hour while stirring. Then, the flask was heated to 70 ℃ to carry out a reaction for 12 hours, thereby obtaining an acrylic oligomer (hereinafter referred to as oligomer B) having a weight average molecular weight (Mw) 4000 and a refractive index of 1.63.

Adding additive (H) _RO ) The acrylic pressure-sensitive adhesive composition C6 of this example was prepared in the same manner as in the preparation of the acrylic pressure-sensitive adhesive composition C1 of example 1 except that the oligomer B was used in an amount of 30 parts (30 phr) based on 100 parts of the acrylic polymer.

A psa sheet (substrate-less double-sided psa sheet formed of a psa layer) S6 of this example was produced in the same manner as in the production of the psa sheet in example 1, except that an acrylic psa composition C6 was used instead of the acrylic psa composition C1.

< example 7>

Without using additives (H) _RO ) In addition, an acrylic adhesive composition C7 of this example was prepared in the same manner as the preparation of the acrylic adhesive composition C1 of example 1.

A psa sheet (substrate-less double-sided psa sheet formed of a psa layer) S7 of this example was produced in the same manner as in example 1, except that an acrylic psa composition C7 was used instead of the acrylic psa composition C1, and the thickness of the psa layer was set to 20 μm.

< example 8>

A solution of acrylic polymer A2 was prepared in the same manner as in the preparation of the acrylic polymer solution in example 1, except that the monomer component compositions were changed to POB-A72 parts, NMT-A23 parts, and 4HBA 5 parts. The weight average molecular weight (Mw) of the acrylic polymer A2 was 45 ten thousand.

An acrylic adhesive composition C8 of this example was prepared in the same manner as the preparation of the adhesive composition in example 1, except that a solution of the acrylic polymer A2 was used instead of the solution of the acrylic polymer A1.

A psa sheet (substrate-less double-sided psa sheet formed of a psa layer) S8 according to this example was produced in the same manner as in the production of the psa sheet in example 1, except that an acrylic psa composition C8 was used instead of the acrylic psa composition C1.

< examples 9 to 13>

Adding additive (H) _RO ) Acrylic adhesive compositions C9 to C13 of examples 9 to 13 were prepared in the same manner as the preparation of the acrylic adhesive composition C8 of example 8 except that the kinds and amounts of (a) and (b) were changed as shown in table 1.

Adhesive sheets (substrate-less double-sided adhesive sheets formed of an adhesive layer) S9 to S13 of examples 9 to 13 were produced in the same manner as the production of the adhesive sheet of example A1, except that the acrylic adhesive compositions C9 to C13 were used instead of the acrylic adhesive composition C1, respectively.

< example 14>

No additive (H) _RO ) In addition to that, the acrylic pressure-sensitive adhesive composition C in example 8Preparation of 8 the acrylic adhesive composition C14 of example 14 was prepared in the same manner.

A psa sheet (substrate-less double-sided psa sheet formed of a psa layer) S14 of this example was produced in the same manner as in the production of the psa sheet in example 8, except that an acrylic psa composition C14 was used instead of the acrylic psa composition C8.

< example 15>

A solution (40%) of an acrylic polymer A3 was prepared in the same manner as the preparation of the acrylic polymer solution in example 1, except that the composition of the monomer component was changed to 90 parts of 2-ethylhexyl acrylate (2 EHA) and 10 parts of 4 hba.

The solution (40%) of the acrylic polymer A3 was diluted with ethyl acetate to 20%, and to 500 parts (100 parts of nonvolatile matter) of the solution, 10 parts, based on solids, of a dispersion of zirconia particles, 10 parts, based on solids, of a 1% ethyl acetate solution (0.1 part of nonvolatile matter) of isocyanurate of hexamethylene diisocyanate (product name "Coronate HX" manufactured by tokyo co., 3-functional isocyanate compound) as a crosslinking agent, 2 parts of acetylacetone as a crosslinking retarder, and 1 part, based on iron acetylacetonate as a crosslinking catalyst, of a 1% ethyl acetate solution (0.01 part of nonvolatile matter) were added and mixed with stirring to prepare an acrylic adhesive composition C15. As the dispersion liquid of zirconia particles, a dispersion liquid of surface-treated zirconia particles (average particle diameter 20nm, refractive index of solid: 1.64, surface-treated carboxylic acid-based/phosphoric acid-based hydrophobization treatment, manufactured by Kyowa Kagaku Co., ltd.) dispersed in Propylene Glycol Monomethyl Ether (PGME) was used.

A psa sheet (substrate-less double-sided psa sheet formed of a psa layer) S15 of example 15 was produced in the same manner as in the production of the psa sheet in example 1, except that an acrylic psa composition C15 was used instead of the acrylic psa composition C1, and the thickness of the psa layer was 20 μm.

< example 16>

ase:Sub>A solution of an acrylic polymer ase:Sub>A 4 was prepared in the same manner as in the preparation of the acrylic polymer solution in example 1, except that the composition of the monomer component was changed to POB-ase:Sub>A/n-butyl acrylate (base:Sub>A)/4 hbase:Sub>A = 79/20/1. The weight average molecular weight (Mw) of the acrylic polymer A4 was 52 ten thousand.

An acrylic pressure-sensitive adhesive composition C16 of this example was prepared in the same manner as in example 2 except that a solution of the acrylic polymer A4 was used instead of the solution of the acrylic polymer A1, and a pressure-sensitive adhesive sheet (a substrate-less double-sided pressure-sensitive adhesive sheet formed of a pressure-sensitive adhesive layer) S16 was produced.

< example 17>

ase:Sub>A solution of an acrylic polymer ase:Sub>A 5 was prepared in the same manner as in the preparation of the acrylic polymer solution in example 1, except that the composition of the monomer component was changed to POB-ase:Sub>A/ethyl carbitol acrylate (cbase:Sub>A)/4 hbase:Sub>A = 79/20/1. The weight average molecular weight (Mw) of the acrylic polymer A5 was 46 ten thousand.

An acrylic pressure-sensitive adhesive composition C17 of this example was prepared in the same manner as in example 2 except that a solution of the acrylic polymer A4 was used instead of the solution of the acrylic polymer A1, and a pressure-sensitive adhesive sheet (substrate-free double-sided pressure-sensitive adhesive sheet formed of a pressure-sensitive adhesive layer) S17 was produced.

< example 18>

ase:Sub>A solution of an acrylic polymer ase:Sub>A 6 was prepared in the same manner as in the preparation of the acrylic polymer solution in example 1, except that the composition of the monomer component was changed to POB-ase:Sub>A/phenoxydiglycol acrylate/4hbase:Sub>A =79/20/1. As the phenoxy diethylene glycol acrylate, a product name "LIGHT ACRYLATE P H-A" made by Kyoeisha chemical Co., ltd was used. The weight average molecular weight (Mw) of the acrylic polymer A6 was 48 ten thousand.

An acrylic pressure-sensitive adhesive composition C18 of this example was prepared in the same manner as in example 2 except that a solution of the acrylic polymer A6 was used instead of the solution of the acrylic polymer A1, and a pressure-sensitive adhesive sheet (substrate-free double-sided pressure-sensitive adhesive sheet formed of a pressure-sensitive adhesive layer) S18 was produced.

< example 19>

Adding additive (H) _RO ) The variant was 2,12-diallyloxydinaphthothiophene (Sugai Chemical ind. Co., ltd. System, abbreviation: 2,12-DAODNT, refractive index: 1.729 Except for this, the acrylic pressure-sensitive adhesive composition C19 of this example was prepared in the same manner as in example 2,a pressure-sensitive adhesive sheet (substrate-less double-sided pressure-sensitive adhesive sheet formed of a pressure-sensitive adhesive layer) S19 was produced.

< examples 20 to 22>

Without using additives (H) _RO ) Except for this, acrylic pressure-sensitive adhesive compositions C20 to 22 were prepared and pressure-sensitive adhesive sheets (substrate-less double-sided pressure-sensitive adhesive sheets formed of a pressure-sensitive adhesive layer) S20 to 22 were produced in the same manner as in examples 16 to 18, respectively.

< measurement and evaluation >

(refractive index)

The refractive index of the pressure-sensitive adhesive layer (substrate-less double-sided pressure-sensitive adhesive sheet) of each example was measured using an Abbe refractometer (model number "DR-M4" manufactured by ATAGO) under conditions of a measurement wavelength of 589nm and a measurement temperature of 25 ℃. The results are shown in tables 1 and 2.

(Total light transmittance and haze value)

The total light transmittance and haze of each test piece obtained by bonding the adhesive layer of each example to alkali-free glass (thickness of 0.8 to 1.0mm, total light transmittance of 92%, haze of 0.4%) was measured using a haze meter (trade name "HAZEMETER HM-150", manufactured by color technology research in village) under a measurement environment of 23 ℃. The total light transmittance and haze of the alkali-free glass were subtracted from the measured values to obtain values as the total light transmittance and haze value of the pressure-sensitive adhesive layer. The results are shown in tables 1 and 2.

(storage modulus G')

The pressure-sensitive adhesive layers of the examples were stacked to a thickness of about 1.5mm, and used as a sample for measurement. Dynamic viscoelasticity was measured under the following conditions using ARES manufactured by TA Instruments. The storage modulus G' at 25 ℃ was read based on the measurement results. The results are shown in tables 1 and 2.

[ measurement conditions ]

Deformation mode: torsion

Measuring frequency: 1Hz

Temperature rise rate: 5 ℃ per minute

Shape: parallel plates

(Peel Strength)

The peel strength to a glass plate was measured for each adhesive sheet of each example. That is, the release liner was peeled from one side of the pressure-sensitive adhesive sheet in a measuring environment of 23 ℃ and 50% RH, and a PET film having a thickness of 50 μm was attached and lined, and then cut into a size of 25mm in width and 100mm in length to prepare a test piece. The release liner on the other side was peeled from the test piece, and a 2kg roller was reciprocated 1 time and pressure-bonded to the surface of an alkali glass plate (a product having a thickness of 1.35mm and a green plate edge, manufactured by Songlanzui industries) as an adherend. The resultant was allowed to stand in this atmosphere for 30 minutes, then charged into a pressure defoaming apparatus (autoclave), and subjected to autoclave treatment at a temperature of 50 ℃ and a pressure of 0.5MPa for 30 minutes, and further allowed to stand in an atmosphere of 23 ℃ and 50% RH for 24 hours, and then subjected to a tensile compression testing machine in accordance with JIS Z0237: the peel strength (adhesive force) [ N/25mm ] was measured at a tensile rate of 300 mm/min and a peel angle of 180 degrees. As a universal tensile compression tester, "tensile compression tester, TG-1kN", manufactured by Minebea corporation, was used. The results are shown in tables 1 and 2.

[ Table 1]

TABLE 1

Acrylic polymer A1: POB-A/4HBA =95/5

Acrylic polymer A2: POB-A/NMT-A/4HBA =72/23/5

Acrylic polymer A3:2EHA/4HBA =90/10

[ Table 2]

TABLE 2

Acrylic polymer A1: POB-A/4HBA =95/5

Acrylic polymer A4: POB-A/BA/4HBA =79/20/1

Acrylic polymer A5: POB-A/CBA/4HBA =79/20/1

Acrylic polymer A6: POB-A/P2H-A/4HBA =79/20/1

As shown in Table 1, the additive (H) was not added _RO ) The adhesive of example 7 was supplemented with an additive (H) _RO ) The adhesives of examples 1 to 6 showed a higher refractive index than that of example 7. These adhesives have high transparency and good peel strength. The same tendency was observed in the comparison between example 14 and examples 8 to 13. On the other hand, example 15 in which the refractive index was increased by blending the high-refractive-index inorganic particles was remarkably inferior in transparency (particularly, remarkably high in haze) and did not show an adhesive property (peel strength) suitable for practical use as an adhesive, as compared with examples 1 to 14.

In examples 16 to 19 shown in table 2, it was also confirmed that: by additives (H) _RO ) The use of (2) can exhibit an effect of increasing the refractive index. The adhesives of examples 16 to 19 had high transparency and good peel strength.

As described above, the adhesives of examples 1 to 6, 8 to 13, and 16 to 19 can suppress a decrease in optical characteristics and increase the refractive index, and are therefore suitable for applications such as bonding of optical members (for example, optical films having at least 1 function of light waveguide, light collecting, and diffraction).

Specific examples of the present invention have been described above in detail, but these are merely examples and do not limit the scope of the claims. The embodiments described in the claims include various modifications and changes made to the specific examples illustrated above.

Description of the reference numerals

1.2 pressure-sensitive adhesive sheet

10. Adhesive layer

10A No. 1 surface (adhesive surface)

10B No. 2 surface

20. Supporting substrate

20A 1 st surface

20B No. 2 (Back)

30. 31, 32 release liner

50. Release liner-equipped adhesive sheet

70. Optical member

100. Adhesive sheet-attached member

Claims

1. An adhesive composition comprising:

additive (H) _RO ) An organic material having a higher refractive index than the acrylic polymer (A).

2. Adhesive composition according to claim 1, wherein the additive (H) _RO ) Has a refractive index of 1.60 or more.

3. The adhesive composition according to claim 1 or 2, wherein the additive (H) is added to 100 parts by weight of the acrylic polymer (a) _RO ) Is more than 0 part by weight and 60 parts by weight or less.

4. Adhesive composition according to any one of claims 1 to 3, wherein the additive (H) _RO ) Comprising at least 1 compound selected from the group consisting of aromatic ring-containing compounds and heterocyclic ring-containing compounds.

5. Adhesive composition according to any one of claims 1 to 4, wherein the additive (H) _RO ) Includes a compound having 2 or more aromatic rings in 1 molecule.

6. Adhesive composition according to claim 5, wherein the additive (H) _RO ) Containing, as the compound having 2 or more aromatic rings in 1 molecule, a compound satisfying at least one of the following,

(ii) Comprises a structure obtained by fusing 2 aromatic rings.

7. The adhesive composition according to any one of claims 1 to 6, wherein the aromatic ring-containing monomer (m 1) is contained in an amount of 50% by weight or more in monomer components constituting the acrylic polymer (A).

8. The adhesive composition according to any one of claims 1 to 7, wherein the content of the aromatic ring-containing monomer (m 1) in the monomer components constituting the acrylic polymer (A) is more than 70% by weight and less than 100% by weight,

9. The adhesive composition according to any one of claims 1 to 8, wherein the monomer component constituting the acrylic polymer (a) further contains a monomer (m 2) having at least one of a hydroxyl group and a carboxyl group.

10. An adhesive formed from the adhesive composition of any one of claims 1-9, having a refractive index greater than 1.570.

11. An adhesive sheet comprising an adhesive layer composed of an adhesive formed from the adhesive composition according to any one of claims 1 to 9.

12. The adhesive sheet according to claim 11, wherein the haze value of the adhesive layer is 1.0% or less.