CN106133083B

CN106133083B - Double-sided adhesive sheet

Info

Publication number: CN106133083B
Application number: CN201480077481.4A
Authority: CN
Inventors: 渡边旭平; 荒井隆行; 所司悟
Original assignee: Lintec Corp
Current assignee: Lintec Corp
Priority date: 2014-03-26
Filing date: 2014-03-26
Publication date: 2020-03-06
Anticipated expiration: 2034-03-26
Also published as: TWI649395B; CN106133083A; WO2015145634A1; KR20160138101A; KR102215672B1; JP6290377B2; TW201600577A; JPWO2015145634A1

Abstract

The double-sided adhesive sheet (1) of the present invention comprises an adhesive layer (2) disposed between two patterned transparent conductive films or between a patterned transparent conductive film and a cover material or a display module, wherein the adhesive layer (2) is composed of an adhesive composition containing an adhesive component and light diffusion particles, and the haze value of the adhesive layer (2) is 2 to 40%. According to the adhesive layer (2) of the double-sided adhesive sheet (1), a circuit pattern of the transparent conductive film can be hardly observed in a capacitive touch panel or the like.

Description

Double-sided adhesive sheet

Technical Field

The present invention relates to a double-sided adhesive sheet that can be used for a touch panel or the like.

Background

In recent years, in various mobile electronic devices such as smart phones and tablet personal computer terminals, there have been increasing cases where capacitive touch panels are used as displays.

There are various types of structures of a capacitive touch panel, and a typical example thereof includes: a display body module such as a liquid crystal module; a first thin film sensor laminated on the display body module via an adhesive layer; a second thin film sensor laminated on the first thin film sensor via an adhesive layer; and a covering material laminated on the second thin film sensor via an adhesive layer.

Generally, the thin film sensor is composed of a base thin film and a transparent conductive film made of patterned tin-doped indium oxide (ITO). In the touch panel having the transparent conductive film patterned in this way, there is a problem that the appearance is impaired by the circuit pattern of the transparent conductive film, so-called visible light え.

In order to solve the above problem of bone visibility, patent document 1 proposes forming an undercoat layer between a film base and a transparent conductive layer, and suppressing a difference in reflectance between a pattern portion and a non-pattern portion of the transparent conductive layer to a small value by using a difference between a refractive index of the transparent conductive layer and a refractive index of the undercoat layer, thereby suppressing bone visibility.

In patent document 2, an easy adhesion layer and an optical adjustment layer, each having a predetermined content, refractive index and thickness of a polyester resin, are laminated between a polyester film and a transparent conductive layer, and the influence of optical disturbance due to the easy adhesion layer is suppressed, thereby suppressing the bone formation.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2011-142089

Patent document 2: japanese patent laid-open publication No. 2013-184431

Disclosure of Invention

Technical problem to be solved

However, in the invention described in patent document 1, it is difficult to control the film thickness of the primer layer as described above, and it is difficult to obtain a sufficient bone-inhibitory effect. In addition, there is a problem that the cost is increased by providing the undercoat layer. On the other hand, in the invention described in patent document 2, it is difficult to control the refractive index and the film thickness of the easy-adhesion layer, and it is difficult to obtain a sufficient bone-growth inhibiting effect.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a double-sided adhesive sheet in which a circuit pattern of a transparent conductive film can be hardly observed through an adhesive layer in a capacitive touch panel or the like.

(II) technical scheme

In order to achieve the above object, the present invention provides a double-sided adhesive sheet comprising an adhesive layer disposed between two patterned transparent conductive films or between a patterned transparent conductive film and a cover material or a display module, wherein the adhesive layer is composed of an adhesive, the adhesive is composed of an adhesive composition containing an adhesive component and light diffusion particles, and the haze value of the adhesive layer is 2 to 40% (invention 1).

When the adhesive layer of the double-sided adhesive sheet of the invention (invention 1) is disposed between two patterned transparent conductive films or between a patterned transparent conductive film and a cover material or a display module, a high light transmittance can be maintained and a circuit pattern of the transparent conductive film is difficult to observe by setting the haze value of the adhesive layer within the above range.

In the above invention (invention 1), the light diffusing fine particles preferably have an average particle diameter of 0.1 to 20 μm by a centrifugal sedimentation light transmission method (invention 2).

In the above inventions (inventions 1 and 2), the adhesive component preferably contains a (meth) acrylate polymer (invention 3).

In the above invention (invention 3), the (meth) acrylate polymer is preferably crosslinked by a crosslinking agent (invention 4).

In the above inventions (inventions 3 and 4), the content of the light diffusion fine particles is preferably 0.01 to 15 parts by mass with respect to 100 parts by mass of the (meth) acrylate polymer (invention 5).

The present invention also provides a laminate comprising the adhesive layer of the double-sided adhesive sheet (invention 1 to 5) between two patterned transparent conductive films or between a patterned transparent conductive film and a cover material or a display module. In the laminate, the adhesive layer may or may not be in direct contact with the transparent conductive film, the covering material, or the display module.

(III) advantageous effects

According to the adhesive layer of the double-sided adhesive sheet of the present invention, in a capacitive touch panel or the like, the circuit pattern of the transparent conductive film can be hardly observed while maintaining high light transmittance

Drawings

Fig. 1 is a sectional view of an adhesive sheet according to an embodiment of the present invention.

Fig. 2 is a cross-sectional view showing an example of the configuration of the touch panel.

Detailed Description

Hereinafter, embodiments of the present invention will be described.

The double-sided adhesive sheet of the present embodiment includes an adhesive layer disposed between two patterned transparent conductive films or between a patterned transparent conductive film and a cover material or a display module.

As shown in fig. 1, the double-sided adhesive sheet 1 of the present embodiment is composed of two

release sheets

3a and 3b and an adhesive layer 2 sandwiched between the two

release sheets

3a and 3b so as to be in contact with the release surfaces of the two

release sheets

3a and 3 b. However, in the double-sided adhesive sheet 1, the

release sheets

3a and 3b are not essential components, and are released and removed when the double-sided adhesive sheet 1 is used. The release surface of the release sheet in the present specification means a surface having releasability in the release sheet, and includes any one of a surface subjected to a release treatment and a surface showing releasability even if the release treatment is not performed.

1. Adhesive layer

The adhesive layer 2 in the present embodiment is composed of an adhesive formed of an adhesive composition containing an adhesive component and light diffusion particles (hereinafter sometimes referred to as "adhesive composition P"), and has a haze value of 2 to 40%. In the adhesive layer 2 of the present embodiment, by controlling the haze value using the light diffusion fine particles as described above, it is possible to maintain high light transmittance and to make it difficult to observe the circuit pattern of the transparent conductive film in a capacitive touch panel or the like, thereby exhibiting an excellent effect of suppressing the visible light.

If the haze value is less than 2%, the bone-suppressing effect cannot be obtained, and the circuit pattern of the transparent conductive film can be observed. In addition, if the haze value exceeds 40%, no bone-inhibiting effect is obtained. From this viewpoint, the haze value of the adhesive layer 2 is preferably 3 to 30%, and particularly preferably 6 to 20%. The haze value in the present specification is defined as follows according to JIS K7136: 2000 measured values.

(1) Adhesive composition

The adhesive component is not particularly limited as long as it exhibits a desired adhesive strength and light transmittance in a capacitive touch panel or the like and does not inhibit the effect of the light diffusion fine particles. Examples of such an adhesive component include an acrylic adhesive component, a rubber adhesive component, a silicone adhesive component, a polyurethane adhesive component, and a polyester adhesive component, among which an acrylic adhesive component is preferable from the above viewpoint.

The acrylic pressure-sensitive adhesive component preferably contains a (meth) acrylate polymer (a), and particularly preferably contains a (meth) acrylate polymer (a) crosslinked by a crosslinking agent (B). In the present specification, (meth) acrylic acid refers to both acrylic acid and methacrylic acid. Other similar terms are also the same. In the present specification, the term "polymer" also includes the term "copolymer".

(1-1) (meth) acrylate ester Polymer (A)

In the (meth) acrylate polymer (a), the monomer constituting the polymer is preferably an alkyl (meth) acrylate containing 1 to 20 carbon atoms in the alkyl group. Thus, the obtained adhesive can exhibit good adhesion. The (meth) acrylate polymer (a) is particularly preferably a copolymer of an alkyl (meth) acrylate having 1 to 20 carbon atoms in the alkyl group, a monomer having a functional group reactive with the crosslinking agent (B) (a reactive functional group-containing monomer), and other monomers used as needed. In addition, a hard monomer described later is removed from the alkyl (meth) acrylate.

Examples of the alkyl (meth) acrylate having 1 to 20 carbon atoms in the alkyl group include methyl acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, n-pentyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, n-decyl (meth) acrylate, n-dodecyl (meth) acrylate, tetradecyl (meth) acrylate, hexadecyl (meth) acrylate, and octadecyl (meth) acrylate. Among them, from the viewpoint of further improving the adhesion, a (meth) acrylate having 1 to 8 carbon atoms in the alkyl group is preferable, and methyl acrylate, n-butyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate are particularly preferable. These may be used alone or in combination of two or more.

In the (meth) acrylate polymer (a), the monomer unit constituting the polymer is preferably 30 to 90% by mass, particularly preferably 40 to 75% by mass, and further preferably 50 to 65% by mass of an alkyl (meth) acrylate having 1 to 20 carbon atoms and containing an alkyl group.

The reactive functional group-containing monomer preferably includes a monomer having a hydroxyl group in the molecule (hydroxyl group-containing monomer), a monomer having a carboxyl group in the molecule (carboxyl group-containing monomer), a monomer having an amino group in the molecule (amino group-containing monomer), and the like.

Examples of the hydroxyl group-containing monomer include hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 3-hydroxybutyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate. Among them, 2-hydroxyethyl (meth) acrylate is preferable from the viewpoint of reactivity with a hydroxyl group and a crosslinking agent (B) in the obtained (meth) acrylate polymer (a) and copolymerizability with other monomers. These may be used alone or in combination of two or more.

Examples of the carboxyl group-containing monomer include ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, and citraconic acid. Among these, acrylic acid is preferred from the viewpoint of reactivity of the carboxyl group in the obtained (meth) acrylate polymer (a) with the crosslinking agent (B) and copolymerizability with other monomers. These may be used alone or in combination of two or more.

Examples of the amino group-containing monomer include aminoethyl (meth) acrylate, n-butylaminoethyl (meth) acrylate, and the like. These may be used alone or in combination of two or more.

When the (meth) acrylate polymer (a) contains a hydroxyl group-containing monomer as a reactive functional group-containing monomer constituting the polymer, the content thereof is preferably 15 to 30% by mass, particularly preferably 17 to 28% by mass, from the viewpoint of step difference following property under durable conditions, and further preferably 20 to 25% by mass, from the viewpoint of optimizing the wet-heat whitening resistance in addition to the above-mentioned viewpoint.

When the (meth) acrylate polymer (a) contains a carboxyl group-containing monomer as a reactive functional group-containing monomer constituting the polymer, the content thereof is preferably 5 to 25% by mass, particularly preferably 7 to 20% by mass, from the viewpoint of step difference following property under durable conditions, and further preferably 10 to 15% by mass, from the viewpoint of optimizing wet-heat whitening resistance in addition to the above-mentioned viewpoint.

Here, when the touch panel or the like is placed in a high-temperature and high-humidity environment, moisture enters the adhesive layer, and when the touch panel or the like returns to normal temperature, the adhesive layer whitens, and there is a problem of "wet heat whitening" in which transparency is lowered. When the (meth) acrylate polymer (a) contains the reactive functional group-containing monomer in the above range, a predetermined amount of the reactive functional group remains in the adhesive agent layer. The reactive functional group is usually a hydrophilic group, and when a predetermined amount of such a hydrophilic group is present in the adhesive agent layer, the compatibility with moisture that has entered the adhesive agent layer under high-temperature and high-humidity conditions is good even when the adhesive agent layer is left under high-temperature and high-humidity conditions, and as a result, whitening of the adhesive agent layer is suppressed, and the wet-heat whitening resistance of the adhesive agent layer 2 becomes excellent.

In the (meth) acrylate polymer (a), as a monomer unit constituting the polymer, an acrylate-based hard monomer is preferably contained. The hard monomer is a monomer having a glass transition temperature (Tg) of 70 ℃ or higher, preferably 75 to 200 ℃, and particularly preferably 80 to 180 ℃ as a homopolymer obtained by polymerizing only the hard monomer. By containing the above hard monomer as a monomer unit constituting the (meth) acrylate polymer (a), the obtained adhesive is excellent in durability and blister resistance. Therefore, even when the adherend is a plastic sheet and air leakage occurs from the plastic sheet, foaming phenomenon (blister) such as bubbling, lifting, and peeling can be suppressed.

Examples of the hard monomer include methyl methacrylate (Tg105 ℃ C.), isobornyl acrylate (Tg94 ℃ C.), isobornyl methacrylate (Tg180 ℃ C.), acryloylmorpholine (Tg145 ℃ C.), adamantyl acrylate (Tg115 ℃ C.), adamantyl methacrylate (Tg141 ℃ C.), dimethylacrylamide (Tg89 ℃ C.), and acrylamide (Tg165 ℃ C.). These may be used alone or in combination of two or more.

Among the above hard monomers, methyl methacrylate, isobornyl acrylate and acryloylmorpholine are more preferable, and methyl methacrylate is particularly preferable, from the viewpoint of preventing adverse effects on other properties such as tackiness and transparency and further exhibiting the performance of the hard monomers.

The (meth) acrylate polymer (A) preferably contains 10 to 45 mass% of the above hard monomer, and particularly preferably contains 15 to 30 mass% of the hard monomer as a monomer unit constituting the polymer. By containing the hard monomer in an amount of 10 mass% or more, the effect of improving the durability and blister resistance based on the monomer unit can be expected. On the other hand, by containing the hard monomer in an amount of 45 mass% or less, relative shortage of the other monomer units in the (meth) acrylate polymer (a) can be prevented, and the obtained adhesive is excellent in adhesiveness, step following property and resistance to wet whitening and heat resistance.

In the (meth) acrylate polymer (a), it is preferable that the hydroxyl group-containing monomer and the hard monomer are contained in the above ranges as monomer units constituting the polymer. This makes the resultant adhesive more excellent in blister resistance.

The (meth) acrylate polymer (a) may contain, if necessary, other monomers as monomer units constituting the polymer. As the other monomer, a monomer having no reactive functional group is preferable in order not to hinder the action of the hydroxyl group-containing monomer. Examples of the other monomer include alkoxyalkyl (meth) acrylates such as methoxyethyl (meth) acrylate and ethoxyethyl (meth) acrylate; aliphatic cyclic (meth) acrylates such as cyclohexyl (meth) acrylate; (meth) acrylic esters having a non-crosslinkable tertiary amino group such as N, N-dimethylaminoethyl (meth) acrylate and N, N-dimethylaminopropyl (meth) acrylate; vinyl acetate; styrene, and the like. These may be used alone or in combination of two or more.

The polymerization state of the (meth) acrylate polymer (a) may be a random copolymer or a block copolymer.

The weight average molecular weight of the (meth) acrylate polymer (a) is preferably 10 to 150 ten thousand, particularly preferably 20 to 130 ten thousand, and further preferably 30 to 80 ten thousand. In the present specification, the weight average molecular weight is a polystyrene equivalent value measured by a Gel Permeation Chromatography (GPC) method.

In the adhesive composition P, one kind of the (meth) acrylate polymer (a) may be used alone, or two or more kinds may be used in combination.

When the adhesive composition P contains the (meth) acrylate polymer (a) as the adhesive component and the (meth) acrylate polymer (a) has the above-mentioned predetermined composition and molecular weight, the obtained adhesive layer 2 is also excellent in step following property. Therefore, even when the adhesive layer 2 is attached to a covering material having a step due to a printed layer or the like, a void or air bubbles are not easily formed between the step and the adhesive layer. In addition, even when the laminate is left at a high temperature such as 80 ℃, bubbles and the like can be prevented from being generated in the vicinity of the step.

(1-2) crosslinking agent (B)

When the adhesive component of the adhesive composition P contains the (meth) acrylate polymer (a) containing a reactive functional group-containing monomer as a monomer unit constituting the polymer and the crosslinking agent (B), the crosslinking agent (B) reacts with the reactive functional group of the reactive functional group-containing monomer constituting the (meth) acrylate polymer (a) when the adhesive composition P is heated or the like. This results in a structure in which the (meth) acrylate polymer (a) is crosslinked by the crosslinking agent (B), and the strength and durability of the adhesive layer 2 are improved.

The crosslinking agent (B) may be reacted with the reactive functional group of the (meth) acrylate polymer (a), and examples thereof include isocyanate crosslinking agents, epoxy crosslinking agents, amine crosslinking agents, melamine crosslinking agents, aziridine crosslinking agents, hydrazine crosslinking agents, aldehyde crosslinking agents, oxazoline crosslinking agents, metal alkoxide crosslinking agents, metal chelate crosslinking agents, metal salt crosslinking agents, and ammonium salt crosslinking agents. Among the above, when the reactive functional group of the (meth) acrylate polymer (a) is a hydroxyl group, an isocyanate-based crosslinking agent having excellent reactivity with the hydroxyl group is preferably used, and when the reactive functional group of the (meth) acrylate polymer (a) is a carboxyl group, an epoxy-based crosslinking agent having excellent reactivity with the carboxyl group is preferably used. The crosslinking agent (B) may be used singly or in combination of two or more.

The isocyanate-based crosslinking agent contains at least a polyisocyanate compound. Examples of the polyisocyanate compound include aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate and xylylene diisocyanate; aliphatic polyisocyanates such as hexamethylene diisocyanate; alicyclic polyisocyanates such as isophorone diisocyanate and hydrogenated diphenylmethane diisocyanate, and biuret and isocyanurate products thereof; and adducts which are reactants with low-molecular active hydrogen-containing compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, and castor oil. Among them, trimethylolpropane-modified aromatic polyisocyanates are preferable from the viewpoint of reactivity with hydroxyl groups, and trimethylolpropane-modified tolylene diisocyanate and trimethylolpropane-modified xylylene diisocyanate are particularly preferable.

Examples of the epoxy-based crosslinking agent include 1, 3-bis (N, N ' -diglycidylaminomethyl) cyclohexane, N, N, N ', N ' -tetraglycidyl-m-xylylenediamine, ethylene glycol diglycidyl ether, 1, 6-hexanediol diglycidyl ether, trimethylolpropane diglycidyl ether, diglycidylaniline, and diglycidylamine.

The content of the crosslinking agent (B) in the adhesive composition P is preferably 0.001 to 10 parts by mass, particularly preferably 0.01 to 5 parts by mass, and further preferably 0.02 to 1 part by mass, based on 100 parts by mass of the (meth) acrylate polymer (a).

(2) Light diffusing particles

The light diffusing fine particles may be any particles as long as the haze value of the adhesive layer 2 can be within the above range, and examples thereof include inorganic fine particles such as silica, calcium carbonate, aluminum hydroxide, magnesium hydroxide, clay, talc, and titanium dioxide; organic light-transmitting fine particles such as acrylic resin, polystyrene resin, polyethylene resin, and epoxy resin; and microparticles made of a silicon-containing compound having an intermediate structure between inorganic and organic materials such as silicone resin (for example, TOSPEARL series manufactured by Japan Momentive performance materials Inc. (モメンティブ · パフォーマンス · マテリアルズ · ジャパン)). Among these, acrylic resin fine particles and fine particles composed of a silicon-containing compound having an inorganic and organic intermediate structure are preferable because they are excellent in dispersibility in the adhesive component and can provide uniform optical characteristics. The light diffusion fine particles may be used alone or in combination of two or more.

The shape of the light diffusion fine particles is preferably spherical fine particles with uniform light diffusion. The average particle diameter of the light diffusion fine particles by the centrifugal sedimentation light transmission method is preferably 0.1 to 20 μm, and more preferably 1 to 10 μm. Particularly, when the light diffusion fine particles are fine particles composed of a silicon-containing compound, the average particle diameter by the centrifugal sedimentation light transmission method is preferably 1 to 10 μm. When the average particle diameter is within the above range, the haze value can be set within the above range without impairing the light transmittance of the adhesive layer 2.

The average particle size by the centrifugal sedimentation light transmission method was measured using a centrifugal automatic particle size distribution measuring device (HORIBA, Ltd. (HORIBA), japan-700) as a measurement sample obtained by sufficiently stirring 1.2g of fine particles and 98.8g of isopropyl alcohol.

When the adhesive composition P contains the (meth) acrylate polymer (a) as an adhesive component, the content of the light diffusion fine particles is preferably 0.01 to 15 parts by mass, and more preferably 0.1 to 4 parts by mass, based on 100 parts by mass of the (meth) acrylate polymer (a). Further, in the case of light diffusion fine particles composed of a silicon-containing compound having an intermediate structure between organic and inorganic materials, such as silicone resin, it is particularly preferably 0.2 to 1.5 parts by mass, most preferably 0.2 to 0.9 parts by mass, and in the case of organic light-transmitting fine particles, it is most preferably 0.3 to 3 parts by mass. When the content of the light diffusion fine particles is within the above range, the haze value of the adhesive layer 2 can be within the above range, and an excellent visible light suppressing effect can be obtained. When the adhesive component is a component other than the acrylic adhesive component, the content of the light diffusion fine particles is preferably within the above range with respect to 100 parts by mass of the adhesive component.

(3) Various additives

The adhesive composition P (adhesive constituting the adhesive layer 2) may contain various additives, for example, a silane coupling agent, a refractive index adjuster, an antistatic agent, a tackifier, an antioxidant, an ultraviolet absorber, a light stabilizer, a softener, a filler, and the like, as necessary.

The adhesive composition P preferably contains a silane coupling agent from the viewpoint of improving the adhesive force of the obtained adhesive. The silane coupling agent is preferably an organosilicon compound having at least one alkoxysilyl group in the molecule, and has good compatibility with the adhesive component and light transmittance.

Examples of such silane coupling agents include polymerizable unsaturated group-containing silicon compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, and methacryloyl; epoxy-structured silicon compounds such as 3-glycidoxypropyltrimethoxysilane and 2- (3, 4-epoxycyclohexyl) ethyltrimethoxysilane; mercapto-containing silicon compounds such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropyldimethoxymethylsilane, etc.; amino-containing silicon compounds such as 3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane and N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane; 3-chloropropyltrimethoxysilane; 3-isocyanate propyltriethoxysilane, or a condensate of at least one of them with an alkyl silicon-containing compound such as methyltriethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane, or ethyltrimethoxysilane. These may be used alone or in combination of two or more.

When the adhesive composition P contains the (meth) acrylate polymer (a) as an adhesive component, the content of the silane coupling agent is preferably 0.01 to 10 parts by mass, particularly preferably 0.05 to 5 parts by mass, and further preferably 0.1 to 1 part by mass, based on 100 parts by mass of the (meth) acrylate polymer (a). When the adhesive component is a component other than the acrylic adhesive component, the content of the silane coupling agent is preferably within the above range with respect to 100 parts by mass of the adhesive component.

(4) Production of adhesive composition

The adhesive composition can be produced by mixing an adhesive component, light diffusing fine particles, and additives added as needed. When the adhesive component contains the (meth) acrylate polymer (a), the (meth) acrylate polymer (a) is prepared, and if necessary, the crosslinking agent (B) is added.

The (meth) acrylate polymer (a) can be produced by polymerizing a mixture of monomer units constituting the polymer by a general radical polymerization method. The polymerization of the (meth) acrylate polymer (a) can be carried out by a solution polymerization method or the like using a polymerization initiator as necessary. Examples of the polymerization solvent include ethyl acetate, n-butyl acetate, n-isobutyl acetate, toluene, acetone, hexane, and methyl ethyl ketone, and two or more kinds thereof may be used in combination.

The polymerization initiator may, for example, be an azo compound or an organic peroxide, and two or more kinds may be used in combination. Examples of the azo compound include 2,2' -azobisisobutyronitrile, 2,2' -azobis (2-methylbutyronitrile), 1' -azobis (cyclohexane-1-carboxynitrile), 2,2' -azobis (2, 4-dimethylvaleronitrile), 2,2' -azobis (2, 4-dimethyl-4-methoxyvaleronitrile), dimethyl 2,2' -azobis (2-methylpropionate), 4' -azobis (4-cyanovaleric acid), 2,2' -azobis (2-hydroxymethylpropionitrile), and 2,2' -azobis [2- (2-imidazolin-2-yl) propane ].

Examples of the organic peroxide include benzoyl peroxide, t-butyl perbenzoate, cumene hydroperoxide, diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate, di (2-ethoxyethyl) peroxydicarbonate, t-butyl peroxyneodecanoate, t-butyl peroxypivalate, (3,5, 5-trimethylhexanoyl) peroxide, dipropyl peroxide, and diacetyl peroxide.

In the polymerization step, a chain transfer agent such as 2-mercaptoethanol is added to adjust the weight average molecular weight of the obtained polymer.

After the (meth) acrylate polymer (a) is obtained, the light diffusing fine particles, and if necessary, the crosslinking agent (B) and additives are added to a solution of the (meth) acrylate polymer (a), and the mixture is thoroughly mixed to obtain an adhesive composition P (coating solution) diluted with a solvent.

Examples of the diluting solvent include aliphatic hydrocarbons such as hexane, heptane and cyclohexane; aromatic hydrocarbons such as toluene and xylene; chlorinated hydrocarbons such as methylene chloride and ethylene chloride; alcohols such as methanol, ethanol, propanol, butanol, and 1-methoxy-2-propanol; ketones such as acetone, methyl ethyl ketone, 2-pentanone, isophorone, and cyclohexanone; esters such as ethyl acetate and butyl acetate; and cellosolve solvents such as ethyl cellosolve.

The concentration and viscosity of the coating solution prepared in this manner are not particularly limited as long as the coating solution can be applied, and can be appropriately selected according to the situation. For example, the concentration of the adhesive composition P is diluted to 10 to 40 mass%. In addition, when obtaining a coating solution, the addition of a diluting solvent or the like is not an essential condition, and if the adhesive composition P has a coatable viscosity or the like, the diluting solvent may not be added.

(5) Formation of adhesive

The adhesive in the present embodiment is formed of the adhesive composition P. The formation of the adhesive can be generally performed by subjecting the adhesive composition P to a heat treatment. The heat treatment may be performed simultaneously with a drying treatment when a diluent solvent or the like of the adhesive composition P is volatilized.

When the (meth) acrylate polymer (a) is contained in the adhesive composition P, the heating temperature of the heating treatment is preferably 50 to 150 ℃, and particularly preferably 70 to 120 ℃. The heating time is preferably 30 seconds to 10 minutes, and particularly preferably 50 seconds to 2 minutes. After the heat treatment, the curing period may be set to about 1 to 2 weeks at normal temperature (e.g., 23 ℃ C., 50% RH) as necessary. In the case where the curing period is required, the adhesive is formed after the curing period has elapsed, and in the case where the curing period is not required, the adhesive is formed after the heat treatment is completed.

(6) Thickness of adhesive layer

The thickness (value measured according to JIS K7130) of the adhesive layer 2 is preferably 5 to 600. mu.m, particularly preferably 20 to 300. mu.m, and more preferably 50 to 150. mu.m. When the thickness of the adhesive layer 2 is 5 μm or more, good adhesiveness can be exhibited. In addition, when the adhesive sheet is attached to an adherend having a step, the step-following property can be exhibited. On the other hand, the adhesive layer 2 has a thickness of 600 μm or less, and thus the processability is improved. The adhesive layer 2 may be formed of a single layer or may be formed by laminating a plurality of layers.

2. Release sheet

The release sheets 12a and 12b are not particularly limited, and examples thereof include a polyethylene film, a polypropylene film, a polybutylene film, a polybutadiene film, a polymethylpentene film, a polyvinyl chloride film, a vinyl chloride copolymer film, a polyethylene terephthalate film, a polyethylene naphthalate film, a polybutylene terephthalate film, a polyurethane film, an ethylene vinyl acetate film, an ionomer resin film, an ethylene/(meth) acrylic acid copolymer film, an ethylene/(meth) acrylic acid ester copolymer film, a polystyrene film, a polycarbonate film, a polyimide film, and a fluororesin film. In addition, crosslinked films of these materials may also be used. Further, a laminated film of these substances may be used.

The release surfaces (particularly, surfaces in contact with the adhesive agent layer 2) of the release sheets 12a and 12b are preferably subjected to a release treatment. Examples of the release agent used for the release treatment include release agents such as alkyd, silicone, fluorine, unsaturated polyester, polyolefin, and wax. In addition, of the release sheets 12a and 12b, one release sheet is preferably a heavy release type release sheet having a large release force, and the other release sheet is preferably a light release type release sheet having a small release force.

The thickness of the release sheets 12a and 12b is not particularly limited, and is usually about 20 to 150 μm.

3. Production of double-sided adhesive sheet

As one example of the production of the double-sided adhesive sheet 1, after a coating layer is formed by applying a coating liquid of the above-described adhesive composition P to the release surface of one release sheet 12a (or 12b) and performing a heat treatment, the release surface of the other release sheet 12b (or 12a) is superimposed on the coating layer. When the curing period is required, the coating layer becomes the adhesive layer 2 by setting the curing period, and when the curing period is not required, the coating layer directly becomes the adhesive layer 2. Thus, the double-sided adhesive sheet 1 was obtained. The conditions for the heat treatment and curing are as described above.

As another production example of the double-sided adhesive sheet 1, a coating layer is formed by applying a coating solution of the above-described adhesive composition P to the release surface of one release sheet 12a and heating the coating layer, to obtain a release sheet 12a with a coating layer. Further, a coating layer is formed by applying the coating liquid of the adhesive composition P to the release surface of the other release sheet 12b and heating the coating layer, thereby obtaining a release sheet 12b with a coating layer. The coated layer-provided release sheet 12a and the coated layer-provided release sheet 12b are bonded so that the two coated layers are in contact with each other. When the curing period is required, the laminated coating layer becomes the adhesive layer 2 by setting the curing period, and when the curing period is not required, the laminated coating layer directly becomes the adhesive layer 2. Thus, the double-sided adhesive sheet 1 was obtained. According to this production example, even when the adhesive layer 2 is thick, stable production can be performed.

Examples of the method of applying the coating liquid of the adhesive composition P include a bar coating method, a blade coating method, a roll coating method, a blade coating method, a die coating method, and a gravure coating method.

4. Use of double-sided adhesive sheet

The double-sided adhesive sheet 1 of the present embodiment can be used for a laminate having a circuit pattern of a transparent conductive film, and can be preferably used for a capacitive touch panel or the like. When the double-sided adhesive sheet 1 is used for a capacitive touch panel, the adhesive layer 2 may be present at any position between the display body module and the cover material of the touch panel, and may be located between two transparent conductive films, between the transparent conductive film and the cover material, or between the transparent conductive film and the display body module. Even when the adhesive layer 2 is present at any of these positions, the circuit pattern of the transparent conductive film is hardly observed due to the excellent bone-formation inhibiting effect of the adhesive layer 2.

By using the double-sided adhesive sheet 1 of the present embodiment, for example, a capacitance type touch panel 10 shown in fig. 2 can be manufactured. The touch panel 10 is configured to include a display module 4, a first thin film sensor 5a laminated thereon via an adhesive layer 2, a second thin film sensor 5b laminated thereon via the adhesive layer 2, and a cover material 6 laminated thereon via the adhesive layer 2.

The three adhesive layers 2 in the touch panel 10 are the adhesive layers 2 of the double-sided adhesive sheet 1, but the touch panel is not limited thereto, and at least one adhesive layer 2 may be the adhesive layer 2 of the double-sided adhesive sheet 1. In the case where one or both of the adhesive layers 2 in the touch panel 10 are the adhesive layers 2 of the double-sided adhesive sheet 1, the other adhesive layer is made of a desired adhesive. As a desired adhesive, an adhesive containing no light diffusion fine particles of the adhesive constituting the adhesive layer 2 can be exemplified.

Examples of the display module 4 include a Liquid Crystal (LCD) module, a Light Emitting Diode (LED) module, an organic electroluminescence (organic EL) module, and electronic paper.

The first thin film sensor 5a and the second thin film sensor 5b are generally composed of a base film 51 and a patterned transparent conductive film 52. The base film 51 is not particularly limited, and for example, a polyethylene terephthalate film, a polycarbonate film, a polymethyl methacrylate film, a polycycloolefin film, a polyolefin film, or a cellulose triacetate film can be used.

Examples of the transparent conductive film 52 include metals such as platinum, gold, silver, and copper; oxides such as tin oxide, indium oxide, cadmium oxide, zinc oxide, and zinc oxide; tin-doped indium oxide (ITO), zinc oxide-doped indium oxide, fluorine-doped indium oxide, antimony-doped tin oxide, fluorine-doped tin oxide, aluminum-doped zinc oxide, and the like; non-oxide compounds such as chalcogenide, lanthanum hexaboride, titanium nitride, and titanium carbide, and among them, tin-doped indium oxide (ITO) is preferable.

One of the transparent conductive film 52 of the first thin-film sensor 5a and the transparent conductive film 52 of the second thin-film sensor 5b generally forms a circuit pattern in the X-axis direction, and the other forms a circuit pattern in the Y-axis direction.

In fig. 2, the transparent conductive film 52 of the first thin-film sensor 5a of the present embodiment is positioned above the first thin-film sensor 5a (on the side of the cover material 6), but is not limited thereto, and may be positioned below the first thin-film sensor 5a (on the side of the display module 4). In fig. 2, the transparent conductive film 52 of the second thin-film sensor 5b is located below the second thin-film sensor 5b (on the side of the module 4), but the present invention is not limited thereto, and may be located above the second thin-film sensor 5b (on the side of the cover material 6).

The covering material 6 is generally a glass plate or a plastic plate as a main body. The glass plate is not particularly limited, and examples thereof include chemically strengthened glass, alkali-free glass, quartz glass, soda-lime glass, barium/strontium-containing glass, aluminosilicate glass acid, lead glass, borosilicate glass, and barium borosilicate glass. The plastic plate is not particularly limited, and examples thereof include acrylic plates and polycarbonate plates made of polymethyl methacrylate.

Further, functional layers such as a hard coat layer, an antireflection layer, and an antiglare layer may be provided on one surface or both surfaces of the glass plate or the plastic plate, or optical members such as a hard coat film, an antireflection film, and an antiglare film may be laminated.

In the present embodiment, the covering material 6 has a step on the surface on the adhesive layer 2 side, specifically, a step formed by the presence or absence of the printed layer 7. The printed layer 7 is generally formed in a frame shape on the adhesive layer 2 side in the covering material 6.

The material constituting the printed layer 7 is not particularly limited, and a known material for printing can be used. The thickness of the printing layer 7, i.e., the step height, is preferably 3 to 45 μm, more preferably 5 to 35 μm, particularly preferably 7 to 25 μm, and further preferably 7 to 15 μm.

The thickness (height of step) of the print layer 7 is preferably 50% or less, particularly preferably 5 to 40%, and further preferably 10 to 30% of the thickness of the adhesive layer 2. When the thickness of the adhesive layer 2 and the thickness of the printed layer 7 satisfy the above relationship, the adhesive layer 2 favorably follows the step difference generated by the printed layer 7, and the occurrence of warpage, bubbles, and the like in the vicinity of the step difference is suppressed.

An example of the method for manufacturing the touch panel 10 will be described below.

As the double-sided adhesive sheet 1, first, second, and third double-sided adhesive sheets 1 are prepared. First, one release sheet 3a (or 3b) is peeled off from the first double-sided adhesive sheet 1, and the exposed adhesive layer 2 is bonded to the thin film sensor 5a so as to be in contact with the patterned transparent conductive film 52 of the thin film sensor 5 a. Next, the other release sheet 3b (or 3a) is peeled off from the first double-sided adhesive sheet 1, and the exposed adhesive layer 2 is bonded to the thin film sensor 5b so as to be in contact with the patterned transparent conductive film 52 of the thin film sensor 5 b. Thus, a laminate in which the thin film sensor 5a, the adhesive layer 2, and the thin film sensor 5b were sequentially laminated was obtained.

Next, one release sheet 3a (or 3b) is peeled from the second double-sided adhesive sheet 1, and the exposed adhesive layer 2 is bonded to the surface of the laminate on the side of the film sensor 5a (the exposed surface of the base film 51 of the film sensor 5 a). Further, one release sheet 3a (or 3b) is peeled from the third double-sided adhesive sheet 1, and the exposed adhesive layer 2 is bonded to the surface of the laminate opposite to the side on which the adhesive layer 2 is laminated (the exposed surface of the base film 51 of the thin-film sensor 5 b).

Thereafter, the other release sheet 3b (or 3a) is peeled off from the third double-sided adhesive sheet 1, and the covering material 6 is bonded to the exposed adhesive layer 2 so that the printed layer 7 side of the covering material 6 is in contact with the adhesive layer 2. Thus, a structure in which the covering material 6, the adhesive layer 2, the thin film sensor 5b, the adhesive layer 2, the thin film sensor 5a, the adhesive layer 2, and the release sheet 3b (or 3a) were sequentially laminated was obtained.

Finally, the release sheet 3b (or 3a) is peeled off from the above-described constituent body, and the constituent body is bonded to the display body module 4 so that the exposed adhesive layer 2 comes into contact with the display body module 4. Thereby, the touch panel 10 shown in fig. 2 is manufactured.

When the adhesive layer 2 in contact with the covering material 6 is composed of the adhesive composition P containing the (meth) acrylate polymer (a) as an adhesive component, the (meth) acrylate polymer (a) has the above-mentioned predetermined composition and molecular weight, and the adhesive layer 2 has a predetermined thickness, the step following property of the adhesive layer 2 is excellent. Therefore, when the adhesive layer 2 and the covering material 6 are bonded in the above-described step, voids or air bubbles are less likely to be formed between the step difference generated by the printed layer 7 and the adhesive layer 2, and the adhesive layer 2 can fill up the step difference. In addition, even when the touch panel 10 is placed under high-temperature and high-humidity conditions, bubbles and the like can be prevented from being generated in the vicinity of the level difference.

In the touch panel 10 described above, since the adhesive layer 2 has a predetermined haze value, an excellent bone-growth inhibiting effect is exhibited, and the circuit pattern of the transparent conductive film 52 is difficult to be observed. In addition, since the adhesive layer 2 has high light transmittance, the screen of the display module 4 can be displayed colorless. Further, when the adhesive layer 2 is composed of the adhesive composition P containing the (meth) acrylate polymer (a) as an adhesive component, the (meth) acrylate polymer (a) having the above-described predetermined composition, the wet heat whitening resistance of the adhesive layer 2 is excellent, and whitening of the touch panel 10 when it is returned to normal temperature after being left under high-temperature and high-humidity conditions is suppressed.

The touch panel 10 may further include other layers exhibiting bone suppression effects in addition to the above layers. For example, a known refractive index adjustment layer (refractive index matching layer) may be provided between the base film 51 and the transparent conductive film 52 in the first thin film sensor 5a and/or the second thin film sensor 5 b.

The above-described embodiments are described for easy understanding of the present invention, and are not intended to limit the present invention. Therefore, it is the gist of the present invention that each element disclosed in the above embodiment includes all design changes and equivalents which fall within the technical scope of the present invention.

For example, one of the

release sheets

3a and 3b of the double-sided adhesive sheet 1 may be omitted.

Examples

The present invention will be further specifically described below with reference to examples and the like, but the scope of the present invention is not limited to these examples and the like.

(example 1)

Preparation of (meth) acrylate copolymer

The (meth) acrylic ester polymer (a) was prepared by copolymerizing 90 parts by mass of n-butyl acrylate and 10 parts by mass of acrylic acid. The molecular weight of the (meth) acrylate polymer (a) was measured by the method described later, and the weight average molecular weight (Mw) was 40 ten thousand.

2. Preparation of adhesive composition

100 parts by mass (in terms of solid content; the same applies hereinafter) of the (meth) acrylate polymer (A) obtained in the step (1), 0.057 part by mass of 1, 3-bis (N, N' -diglycidylaminomethyl) cyclohexane (manufactured by Mitsubishi Gas Chemical Company, Mitsubishi ガス Chemical Co., Ltd., product name "TETRAD C-5") as a crosslinking agent (B) (an epoxy crosslinking agent), 0.25 part by mass of 3-glycidyloxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., (product name "KBM-403" manufactured by Shin-Chemicals Co., Ltd.) as a silane coupling agent, and 0.25 part by mass of fine particles (manufactured by Japan molecular dynamics materials Inc. having an inorganic and organic intermediate structure (モメンティブ, パフォーマンス, マテリアルズ, ジャパン) as light diffusion fine particles were mixed, trade name "TOSPEARL 120", average particle diameter: 2.0 μm, refractive index: 1.42)0.1 part by mass and sufficiently stirred, and diluted with methyl ethyl ketone, thereby obtaining a coating solution of the adhesive composition having a solid content concentration of 34 mass%.

The formulation of the adhesive composition is shown in table 1. The abbreviations and the like described in table 1 are as follows.

[ (meth) acrylic ester Polymer (A) ]

BA: n-butyl acrylate;

AA: acrylic acid;

2 EHA: 2-ethylhexyl acrylate;

MMA: methyl methacrylate;

HEA: 2-hydroxyethyl acrylate.

[ crosslinking agent (B) ]

And (3) epoxy: 1, 3-bis (N, N' -diglycidylaminomethyl) cyclohexane (product name "TETRAD C-5" manufactured by Mitsubishi Gas chemical company);

isocyanate: a xylylene diisocyanate-based crosslinking agent (TOYO INK co., LTD. (manufactured by boeing インキ corporation), product name "BHS 8515").

[ light diffusing microparticles ]

TOSPEARL 120: fine particles composed of a silicon-containing compound having an intermediate structure of inorganic and organic (manufactured by Japan mechanical Performance Materials Inc., trade name "TOSPEARL 120", average particle diameter: 2.0 μm, refractive index: 1.43);

tospearll 145: fine particles composed of a silicon-containing compound having an intermediate structure of inorganic and organic (manufactured by Japan mechanical Performance Materials Inc., trade name "TOSPEARL 145", average particle diameter: 4.5 μm, refractive index: 1.43);

SSX 102: crosslinked acrylic resin beads (manufactured by SEKISUI PLASTICS co., LTD. (product name: of hydrator corporation), trade name "SSX 102", average particle diameter: 2.5 μm, refractive index: 1.49);

SSX 104: crosslinked acrylic resin beads (Sekisui PLASTICS CO., LTD., trade name "SSX 104", average particle diameter: 4.0 μm, refractive index: 1.49).

3. Production of double-sided adhesive sheet

The obtained coating solution of the adhesive composition was applied to a release-treated surface of a heavy release type release sheet (product name "SP-PET 752150", manufactured by linetec Corporation (リンテック)) obtained by releasing one surface of a polyethylene terephthalate film with a silicone-based release agent by a blade coater so that the thickness after drying became 25 μm, and then heat-treated at 90 ℃ for 1 minute, thereby forming a coating layer. Similarly, the obtained coating solution of the adhesive composition was applied to a release-treated surface of a light release type release sheet (product name "SP-PET 382120", manufactured by linetec corporation) obtained by release-treating one surface of a polyethylene terephthalate film with a silicone-based release agent by a blade coater so that the thickness after drying became 25 μm, and then heat-treated at 90 ℃ for 1 minute, thereby forming a coating layer.

Subsequently, the obtained heavy release sheet with a coating layer and the obtained light release sheet with a coating layer were bonded so that the two coating layers were in contact with each other, and cured at 23 ℃ and 50% RH for seven days, thereby producing a double-sided adhesive sheet having a structure of a heavy release sheet/an adhesive layer (thickness: 50 μm)/a light release sheet. The thickness of the adhesive layer was measured in accordance with JIS K7130 using a constant pressure thickness measuring instrument (product name "PG-02" manufactured by teclockccompany Inc. (テクロック)).

(examples 2 to 14, comparative examples 1 to 8)

A double-sided adhesive sheet was produced in the same manner as in example 1, except that the kind, ratio and polymerization average molecular weight (Mw) of each monomer constituting the (meth) acrylate polymer (a), the kind and blending amount of the crosslinking agent (B), and the kind and blending amount of the light diffusion fine particles were changed as shown in table 1.

Here, the weight average molecular weight (Mw) is a weight average molecular weight in terms of polystyrene measured by Gel Permeation Chromatography (GPC) under the following conditions (GPC measurement).

< measurement Condition >

GPC measurement apparatus: HLC-8020, manufactured by Tosoh Corporation;

GPC column (passage in the following order): tosoh Corporation (manufactured by imperial ソー Co., Ltd.);

TSK guardcolumn HXL-H；

TSK gel GMHXL(×2)；

TSK gel G2000HXL；

determination of the solvent: tetrahydrofuran;

measurement temperature: at 40 ℃.

(test example 1) (measurement of haze value)

The adhesive layer of the double-sided adhesive sheet obtained in examples and comparative examples was measured using a haze meter (NDH 2000, manufactured by nippon color maker ) in accordance with JIS K7136: haze value (%) was measured at 2000. The results are shown in Table 2.

(test example 2) (see evaluation of bone inhibitory Effect)

A plurality of polyimide adhesive tapes (1 cm in width) were attached to an ITO film (ITO film, manufactured by OIKE & co., Ltd., manufactured by shikoku corporation) having a thickness of 125 μm and a transparent conductive film (ITO film) made of tin-doped indium oxide (ITO) provided on one surface of a polyethylene terephthalate film, in such a manner that the adhesive tapes were arranged in parallel at intervals of 1 cm.

The obtained laminate was immersed in 1mol/l hydrochloric acid for 2 minutes, and the portion of the ITO film to which the polyimide pressure sensitive adhesive tape was not attached was etched. Subsequently, the laminate was sufficiently washed with ion-exchanged water and dried at 120 ℃ for 10 minutes, and then the polyimide pressure-sensitive adhesive tape was peeled from the transparent conductive film. Thus, a transparent conductive thin film was obtained in which the ITO film was patterned so that the ITO film portion having a width of 1cm and the ITO film non-existing portion having a width of 1cm repeatedly alternated.

Next, the transparent conductive thin film in which the ITO film was patterned as described above was subjected to annealing treatment at 150 ℃ for 90 minutes to crystallize the patterned ITO film.

On the other hand, the double-sided adhesive sheets obtained in examples and comparative examples were cut into a width of 45mm and a length of 70mm, and then the light-release type release sheet was peeled off. The exposed adhesive layer was bonded to the patterned ITO film (crystallized) of the transparent conductive thin film obtained in the above. The heavy-release type release sheet was peeled off from the laminate, and the exposed adhesive layer was attached to a glass plate made of alkali-free glass and having a thickness of 0.5mm, which was used as a sample.

The sample was pressurized at 0.5MPa and 50 ℃ for 30 minutes in an autoclave, and then placed in an atmosphere of 85 ℃ and 85% RH for 72 hours. Thereafter, whether or not the circuit pattern was visually observed from the polyethylene terephthalate film side was confirmed, and the bone-growth inhibiting effect was evaluated by the following criteria. The results are shown in Table 2.

◎ No pattern was observed;

○ the pattern can be observed invisibly;

x: a pattern can be observed.

(test example 3) (evaluation of step-by-step tracking ability)

(a) Preparation of evaluation sample

An ultraviolet curable ink (Teikoku Printing Inks Mfg. Co., Ltd., product name "POS-911 ink") was screen-printed on the surface of a glass plate (manufactured by NSG Precision Co., Ltd. (NSG プレシジョン Co., Ltd.) in a frame shape (outer shape: 90mm in length × 50mm in width 5mm) so that the coating thickness could be 5 μm, 10 μm, 15 μm and 20 μm. Then, ultraviolet rays (80W/cm) were irradiated²Two metal halide lamps having a lamp height of 15cm and a belt speed of 10 to 15 m/min), and curing the printed ultraviolet curable ink to produce a cured product having a step (height of step: any one of 5 μm, 10 μm, 15 μm, and 20 μm).

The light release type release sheet was peeled from the double-sided adhesive sheet obtained in examples and comparative examples, and the exposed adhesive layer was bonded to an easy-adhesive layer of a polyethylene terephthalate film (manufactured by Toyobo co., Ltd. (division of imperial corporation), PET a4300, thickness: 100 μm) having an easy-adhesive layer. Then, the heavy-release type release sheet is peeled off to expose the adhesive layer. Further, the laminate was laminated on each step glass plate by a laminating machine (product name "LPD 3214" manufactured by Fujipura Company Inc. (フジプラ)) so that the adhesive layer covered the entire printed surface in a frame shape, to obtain a sample for evaluation.

(b) Evaluation of evaluation sample

The obtained evaluation sample was autoclaved at 50 ℃ and 0.5MPa for 30 minutes and then stored under a moist heat condition of 85 ℃ and 85% RH for 72 hours. Thereafter, the adhesive layer (particularly in the vicinity of the level difference generated by the printed layer) was visually confirmed, and the level difference following property was evaluated by the following criteria. The results are shown in Table 2.

◎, no bubbles, lifting and peeling;

○, generating bubbles with diameter less than 0.2 mm;

x: bubbles, lifting or flaking are generated with a diameter exceeding 0.2 mm.

(test example 4) (evaluation of blister resistance)

The adhesive layers of the double-sided adhesive SHEETs obtained in examples and comparative examples were sandwiched between a transparent conductive film of a polyethylene terephthalate film (OIKE & Co., Ltd., manufactured by Ltd., ITO film thickness: 125 μm) having a transparent conductive film of tin-doped indium oxide (ITO) provided on one side and an acrylic plate (manufactured by Mitsubishi Gas Chemical Company, IUPILON SHEET (ユーピロン & シート) MR200, thickness: 1mm) or a Polycarbonate (PC) plate (manufactured by Mitsubishi Gas Chemical Company, IUPILONSHEET MR58, thickness: 1mm) made of polymethyl methacrylate (PMMA), thereby obtaining a double-sided adhesive SHEET.

The resulting laminate was autoclaved at 50 ℃ and 0.5MPa for 30 minutes and then allowed to stand at 23 ℃ and 50% RH for 15 hours under normal pressure. Then, the resultant was stored at 85 ℃ and 85% RH for 72 hours. Thereafter, the presence or absence of bubbles, lifting or peeling in the adhesive agent layer was visually confirmed, and the blister resistance was evaluated by the following criteria. The results are shown in Table 2.

○, no bubbles, lifting and peeling, or only bubbles with diameter less than 0.1mm are generated;

x: bubbles, lifting or peeling of more than 0.1mm in diameter are generated.

(test example 5) (evaluation of resistance to whitening by Damp Heat)

Two polyethylene terephthalate films (OIKE & co., ltd., ITO film, thickness: 125 μm) each having a transparent conductive film made of tin-doped indium oxide (ITO) provided on one surface thereof were prepared, and the adhesive layer of the double-sided adhesive sheet obtained in example or comparative example was sandwiched so that the transparent conductive film of these ITO films was in contact with the adhesive layer, and the laminate was used as a sample.

First, the haze value (haze value before moist heat condition) of the obtained sample was measured. Next, the sample was stored under the moist heat condition of 85 ℃ and 85% RH for 72 hours. Thereafter, the atmosphere was returned to 23 ℃ and 50% RH (normal temperature and normal humidity), and the haze value (haze value after moist heat condition) of the sample was measured within 30 minutes. Haze value was according to JIS K7136: 2000, measured using a haze meter (NIPPON DENSHOKU INDUSTRIES Co., Ltd., product name "NDH 2000" manufactured by Ltd.).

The haze value increase (percentage) after the moist heat condition was calculated by subtracting the haze value before the moist heat condition from the haze value after the moist heat condition. The results are shown in Table 2. When the haze value is increased by less than 1.0%, the resistance to wet-heat whitening is said to be good.

(Table 1)

(Table 2)

As is clear from table 2, the adhesive layer of the double-sided adhesive sheet obtained in the examples was excellent in bone growth inhibitory performance, and had good step following property and wet heat whitening resistance. In addition, the adhesive agent layers of examples 8 to 14 using a hydroxyl group-containing monomer and a hard monomer as monomer units constituting the (meth) acrylate polymer (a) were also excellent in blister resistance.

Industrial applicability

The double-sided adhesive sheet of the present invention is useful for forming an adhesive layer used for a capacitive touch panel.

Description of the reference numerals

11: double-sided adhesive sheet

2: adhesive layer

3a, 3 b: release sheet

4: display body module

5 a: first film sensor

5 b: second film sensor

51: base film

52: transparent conductive film

6: covering material

7: printing layer

10: touch panel

Claims

1. A laminate characterized by comprising an adhesive layer between two patterned transparent conductive films or between a patterned transparent conductive film and a cover material or a display module,

the adhesive layer is composed of an adhesive formed of an adhesive composition containing an adhesive component and light diffusion particles,

the haze value of the adhesive layer is 2-40%.

2. The laminate according to claim 1,

the light diffusion particles have an average particle diameter of 0.1 to 20 [ mu ] m by a centrifugal sedimentation light transmission method.

3. The laminate according to claim 1,

the adhesive component contains a (meth) acrylate polymer.

4. The laminate according to claim 3,

the (meth) acrylate polymer is crosslinked by a crosslinking agent.

5. The laminate according to claim 3,

the content of the light diffusion particles is 0.01-15 parts by mass relative to 100 parts by mass of the (methyl) acrylate polymer.