CN106916541B - Adhesive sheet - Google Patents

Abstract

The invention provides an adhesive sheet which has good impact resistance and can inhibit light leakage from the end face of the width even if the adhesive sheet is narrow. The invention provides an adhesive sheet comprising a base film and an adhesive layer disposed on at least one surface of the base film. The pressure-sensitive adhesive layer contains a colorant in the pressure-sensitive adhesive layer. The adhesive layer has a thickness of more than 25 [ mu ] m and a light transmittance of 5% or less at a length of 0.6 mm.

Description

Adhesive sheet

Technical Field

The present invention relates to an adhesive sheet. More particularly, the present invention relates to an adhesive sheet suitable for use in bonding a liquid crystal display module unit and a backlight unit in a liquid crystal display device incorporated in a portable electronic device, for example.

The present application claims priority based on Japanese patent application 2015-185813, filed on 18/9/2015, and Japanese patent application 2016-145278, filed on 25/7/2016, which are incorporated herein by reference in their entirety.

Background

In general, an adhesive (also referred to as a pressure-sensitive adhesive, hereinafter) is in a soft solid state (viscoelastic body) in a temperature range around room temperature, and has a property of being easily adhered to an adherend by pressure. Because of these properties, adhesives are widely used for the purpose of bonding, fixing, and protecting members in portable electronic devices such as mobile phones, for example, in the form of a pressure-sensitive adhesive sheet with a substrate. Such a substrate-attached adhesive sheet is used for the purpose of bonding a liquid crystal display module unit (hereinafter also referred to as "LCD unit") and a backlight unit (hereinafter also referred to as "BL unit") in a liquid crystal display device incorporated in a portable electronic device such as a mobile phone. Patent documents 1 to 3 are cited as documents relating to such a technique.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open application No. 2002-235053

Patent document 2: japanese laid-open patent application publication No. 2007-284551

Patent document 3: japanese laid-open patent application publication No. 2009-197124

Disclosure of Invention

Problems to be solved by the invention

When light from the BL unit leaks through the adhesive sheet, the light may deteriorate the visibility of the liquid crystal display surface. In order to prevent this, for example, a light-absorbing colored layer (typically a black layer) or the like is provided on the LCD cell side surface of the substrate constituting the adhesive sheet to shield light transmitted from the BL cell side of the adhesive sheet to the LCD cell side.

From the viewpoint of thinning of portable electronic devices, an adhesive sheet for bonding an LCD unit and a BL unit is also required to be thin (patent document 3 and the like). On the other hand, in recent years, mobile electronic devices tend to be emphasized in large screen size (large area of display screen) and design, and the above adhesive sheet is desired to be narrowed in order to suppress a decrease in portability accompanying the increase in screen size and to improve flexibility of design. In response to such a new demand, it is difficult to achieve both narrowing and bonding reliability of a thin adhesive sheet. For example, the adhesive is a viscoelastic material and contributes to impact absorption, but a thin adhesive sheet tends to have a thin adhesive layer, and the impact absorption capacity is further reduced by narrowing the adhesive layer. Therefore, the impact resistance (the performance of maintaining the joint while withstanding the impact such as the drop impact) of a thin and narrow adhesive sheet tends to be insufficient. Since the LCD unit of a large screen is heavy, it is difficult to achieve both the narrowing and the impact resistance.

The present inventors have studied thickening the adhesive layer in order to realize an adhesive that achieves both narrowing and impact resistance at a higher level. However, it was found that, for an adhesive sheet shape different from the previous one having a narrow width (e.g., a width of about 0.6mm or less), if the adhesive layer is thickened to a certain extent or more, a new problem arises: light from the BL unit leaks from the end face through (penetrates) the adhesive layer in the width direction, and this leaked light causes luminance unevenness on the liquid crystal display surface. As a background thereof, the following can also be considered: in recent years, the performance of the backlight has dramatically improved, and the luminance of light emitted from the backlight has increased.

Accordingly, an object of the present invention is to provide an adhesive sheet having good impact resistance and capable of suppressing light leakage from the end face of the width even when the adhesive sheet is narrow.

Means for solving the problems

The pressure-sensitive adhesive sheet provided by the present specification comprises a base film and a pressure-sensitive adhesive layer disposed on at least one surface of the base film. The adhesive layer typically contains a colorant. The adhesive layer has a thickness of more than 25 [ mu ] m and a light transmittance of 5% or less at a length of 0.6 mm. The pressure-sensitive adhesive sheet thus configured has a pressure-sensitive adhesive layer having a thickness of more than 25 μm, and is therefore suitable for achieving both of narrowing and impact resistance. Further, since the light transmittance of the pressure-sensitive adhesive layer at a length of 0.6mm is limited to 5% or less, the pressure-sensitive adhesive layer having a thickness advantageous for improving impact resistance can be suitably combined with narrowing and suppression of light leakage in the width direction.

Here, in the present specification, "light transmittance at a length Amm" means light transmittance measured for a sample having an optical path length of Amm. Hereinafter, the light transmittance at the length Amm may be expressed as "Amm light transmittance". The specific method for measuring the light transmittance of Amm will be described later. Hereinafter, a phenomenon in which light is prevented or suppressed from being transmitted (penetrated) in the width direction of the adhesive sheet and the transmitted light leaks from the end face of the width may be referred to as "horizontal blocking".

The adhesive sheet disclosed herein can be preferably implemented such that all of the layers having a thickness of more than 25 μm constituting the adhesive sheet have a light transmittance of 5% or less at 0.6 mm. According to this aspect, light leakage in the width direction of the adhesive sheet can be more effectively suppressed. That is, a pressure-sensitive adhesive sheet having more excellent horizontal light-shielding properties can be realized.

In a preferred embodiment, the adhesive sheet includes an adhesive layer having a total thickness of more than 50% of the total thickness of the adhesive sheet. With such a configuration, a pressure-sensitive adhesive sheet exhibiting a higher level of impact resistance can be realized.

The pressure-sensitive adhesive sheet disclosed herein preferably has a vertical light transmittance of 1% or less. According to this adhesive sheet, vertical light shielding and horizontal light shielding can be favorably realized by one member.

The adhesive sheet disclosed herein may be suitably implemented in such a manner that the above-described perpendicular light transmittance of the adhesive layer is higher than 25%. This method is advantageous in view of improving the appearance of the pressure-sensitive adhesive sheet. For example, poor dispersion due to an excessive amount of the colorant can be prevented.

The adhesive sheet disclosed herein may preferably be implemented in a shape at least a portion of which has a narrow portion. The width of the narrow portion is typically less than 2.0mm, preferably less than 1.0 mm. In the pressure-sensitive adhesive sheet having such a shape, light leakage in the width direction is likely to occur at the narrow portion, and the narrow portion is likely to constitute a starting point of peeling (poor bonding) due to impact. Therefore, it is particularly significant to apply the technology disclosed in the present application to achieve both impact resistance and horizontal light-shielding properties at a narrow portion.

The adhesive sheet disclosed herein may preferably be implemented such that the width of the adhesive layer at the narrow portion is 50 times or less the thickness of the adhesive layer. If the ratio of the thickness to the width of the pressure-sensitive adhesive layer is increased, the light transmitted obliquely from bottom to top across the width of the pressure-sensitive adhesive layer constituting the narrow portion increases with the light source side as the lower side, and thus, there is a tendency that unevenness in brightness or the like is likely to occur. Therefore, it is particularly significant to use the technology disclosed herein to achieve both of impact resistance and horizontal light-shielding property.

A pressure-sensitive adhesive sheet according to a preferred embodiment is a double-sided pressure-sensitive adhesive sheet including a1 st pressure-sensitive adhesive layer disposed on one surface of the base film and a2 nd pressure-sensitive adhesive layer disposed on the other surface of the base film. The thickness of each of the 1 st adhesive layer and the 2 nd adhesive layer is preferably larger than 25 μm. The pressure-sensitive adhesive sheet having such a structure is highly practical as a joining member, and even if it is narrow, it is easy to form a pressure-sensitive adhesive sheet having good impact resistance. The 1 st adhesive layer and the 2 nd adhesive layer preferably have a light transmittance of 5% or less at 0.6 mm. Even if the pressure-sensitive adhesive sheet is narrow, a pressure-sensitive adhesive sheet having excellent horizontal light-shielding properties and excellent impact resistance can be easily formed.

The pressure-sensitive adhesive sheet disclosed herein has an advantage that impact resistance and horizontal light-shielding property can be suitably satisfied even when the pressure-sensitive adhesive sheet is narrow, and can be suitably used for bonding an LCD unit and a BL unit in a liquid crystal display device including the LCD unit and the BL unit, for example.

Drawings

Fig. 1 is a sectional view schematically showing one configuration example of an adhesive sheet.

Fig. 2 is a sectional view schematically showing another configuration example of the adhesive sheet.

Description of the reference numerals

1. 2 pressure-sensitive adhesive sheet

10 base material film

10A 1 st surface

10B No. 2

12 resin film (base film)

14 coloured layer

21 st adhesive layer

21A 1 st adhesive surface

22 nd 2 adhesive layer

22A 2 nd adhesive surface

31. 32 Release liner

Detailed Description

Preferred embodiments of the present invention will be described below. It should be noted that matters necessary for carrying out the present invention other than the matters specifically mentioned in the present specification can be understood by those skilled in the art from the teaching of the implementation of the invention described in the present specification and the technical common general knowledge at the time of application. The present invention can be implemented according to the contents disclosed in the present specification and the common general knowledge in the art. In the following drawings, members and portions that perform the same function will be described with the same reference numerals, and redundant description may be omitted or simplified. The embodiments shown in the drawings are schematic for clarity of explanation of the present invention, and do not necessarily show the size or scale of the psa sheet of the present invention actually provided as a product.

In the present specification, the "pressure-sensitive adhesive" refers to a material that is in a soft solid (viscoelastic body) state in a temperature range around room temperature as described above and has a property of easily adhering to an adherend by pressure. As used herein, an adhesive is exemplified by "c.a. dahlquist," adhesive: fundamental and Practice ", McLaren&Sons, (1966) P.143 "can generally be defined as having a modulus E satisfying the complex tensile elasticity^*(1Hz)<10⁷dyne/cm²A material having the above properties (typically a material having the above properties at 25 ℃).

The pressure-sensitive adhesive sheet disclosed herein is a pressure-sensitive adhesive sheet with a substrate in which a pressure-sensitive adhesive layer is provided on at least one surface of a substrate film (support). The concept of the adhesive sheet as referred to herein may cover articles called adhesive tapes, adhesive labels, adhesive films, etc. The pressure-sensitive adhesive sheet disclosed herein may be in the form of a roll or a sheet. Alternatively, the adhesive sheet may be processed into various shapes.

The adhesive sheet disclosed herein may be an adhesive sheet having a cross-sectional structure schematically shown in fig. 1, for example. The adhesive sheet 1 shown in fig. 1 includes a base film 10, and a1 st adhesive layer 21 and a2 nd adhesive layer 22 supported by a1 st surface 10A and a2 nd surface 10B of the base film 10, respectively. The 1 st surface 10A and the 2 nd surface 10B are both non-releasable surfaces (non-releasable surfaces). The psa sheet 1 is used by attaching a surface (1 st adhesive surface) 21A of a1 st psa layer 21 and a surface (2 nd adhesive surface) 22A of a2 nd psa layer 22 to an adherend. That is, the pressure-sensitive adhesive sheet 1 is configured as a double-sided pressure-sensitive adhesive sheet (double-sided pressure-sensitive adhesive sheet). The pressure-sensitive adhesive sheet 1 before use has a structure in which the 1 st pressure-sensitive adhesive surface 21A and the 2 nd pressure-sensitive adhesive surface 22A are protected by release liners 31 and 32, respectively, at least the pressure-sensitive adhesive surface side of which is a surface having releasability (release surface). Alternatively, the following configuration may be adopted: the release liner 32 is omitted, a release liner having both release surfaces is used as the release liner 31, and the pressure-sensitive adhesive sheet 1 is rolled up so that the 2 nd adhesive surface 22A comes into contact with the back surface of the release liner 31, whereby the 2 nd adhesive surface 22A is also protected by the release liner 31.

At least one of the 1 st adhesive layer 21 and the 2 nd adhesive layer 22 is an adhesive layer having a thickness of more than 25 μm and a 0.6mm light transmittance of 5% or less, and contains a colorant. The adhesive layer may have a thickness of more than 25 μm and a 0.6mm light transmittance of 5% or less in both of the 1 st adhesive layer 21 and the 2 nd adhesive layer 22, and may contain a colorant in the adhesive layer. As the colorant, for example, a black colorant can be preferably used.

The adhesive sheet 1 preferably has a vertical light transmittance of 1% or less. A colorant may be dispersed (kneaded) in the base film 10 (preferably, a resin film) for the purpose of adjusting the vertical light transmittance, adjusting the reflectance, and the like of the adhesive sheet 1. As the colorant, a black colorant and a white colorant can be preferably used.

The base film may be colored by a colored layer disposed on the surface of the base film (preferably, a resin film). Fig. 2 shows an example of the structure of a psa sheet provided with such a substrate film. The base film 10 of the pressure-sensitive adhesive sheet 2 includes a resin film 12 as a base film and a colored layer 14 provided on one surface of the base film. The colored layer 14 may be, for example, a black printed layer printed on the surface of the resin film 12. The other structure is the same as that of the pressure-sensitive adhesive sheet 1 shown in fig. 1. The resin film 12 may be transparent or may have a colorant dispersed therein. The colored layer may be provided only on one surface of the base film as shown in fig. 2, or the same or different colored layers may be provided on one surface and the other surface of the base film, respectively.

The pressure-sensitive adhesive sheet disclosed herein may be in the form of a single-sided pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer on only one surface of a substrate film. Examples of the form of the single-sided pressure-sensitive adhesive sheet include: in the configuration shown in fig. 1, the configuration does not have any form of either the 1 st pressure-sensitive adhesive layer 21 or the 2 nd pressure-sensitive adhesive layer 22, and in the configuration shown in fig. 2, the configuration does not have any form of either the 1 st pressure-sensitive adhesive layer 21 or the 2 nd pressure-sensitive adhesive layer 22.

< adhesive layer >

The adhesive sheet disclosed herein has an adhesive layer thicker than 25 μm on at least one surface of a base film. The pressure-sensitive adhesive sheet thus configured tends to exhibit good impact resistance even when it is narrow. From the viewpoint of achieving higher impact resistance, the thickness of the pressure-sensitive adhesive layer may be set to, for example, 27 μm or more, 30 μm or more, or 35 μm or more. The upper limit of the thickness of the adhesive layer is not particularly limited. From the viewpoint of ease of processing when the adhesive sheet is prepared into a narrow shape (a shape including a narrowed portion at least in part), the thickness of the adhesive layer is usually suitably 100 μm or less, preferably 75 μm or less, and preferably 60 μm or less (for example, 50 μm or less).

The pressure-sensitive adhesive layer having a thickness of more than 25 μm preferably has a light transmittance of 5% or less at 0.6 mm. This can suitably achieve both narrowing and horizontal light-shielding properties. Here, the light transmittance of 0.6mm can be grasped by preparing a sheet-like measurement sample having a thickness of 0.6mm and measuring the light transmittance in the thickness direction of the measurement sample. The light transmittance is measured by perpendicularly irradiating one surface of a measurement sample with light having a wavelength of 380 to 780nm using a commercially available spectrophotometer, and measuring the intensity of the light transmitted through the other surface. As the spectrophotometer, for example, a spectrophotometer manufactured by hitachi (device name "spectrophotometer model U4100") can be used. The same applies to the later-described examples.

The 0.6mm light transmittance of the adhesive layer was measured using a sheet-like adhesive having a thickness of 0.6mm as a measurement sample. The measurement sample can be prepared, for example, by holding a container having a flat releasable bottom surface horizontally, injecting an adhesive composition into the container, and slowly drying or curing the adhesive composition to form an adhesive layer having a thickness of 0.6mm on the bottom surface. Alternatively, a measurement sample having a thickness of 0.6mm can be prepared by applying the adhesive composition to the release surface of the release liner, drying the adhesive composition to form an adhesive layer having an appropriate thickness (for example, a thickness of about 0.05mm to 0.2 mm) thinner than 0.6mm, and overlapping the adhesive layers. The measurement sample obtained by the above-mentioned superposition is preferably subjected to aging at room temperature for 12 hours or more (for example, about 24 hours) and then subjected to light transmittance measurement. In examples described later, a pressure-sensitive adhesive composition was applied to the release surface of the same release liner as used for producing each pressure-sensitive adhesive sheet, and dried at 100 ℃ for 2 minutes to form a pressure-sensitive adhesive layer having a thickness of about 0.1mm on the release surface, and 6 pressure-sensitive adhesive layers were stacked to prepare a measurement sample having a thickness of 0.6mm, which was aged at room temperature for 24 hours and then measured for light transmittance.

Since the adhesive is generally amorphous and does not exhibit significant optical anisotropy, the light transmittance in the thickness direction measured for an adhesive having a thickness of 0.6mm can be regarded as a characteristic reflecting the light transmittance in the width direction of an adhesive having a width of 0.6 mm. Therefore, the pressure-sensitive adhesive layer having a lower 0.6mm light transmittance, which is determined by the above-mentioned measurement method, tends to exhibit a higher level of light-shielding property. By limiting the light transmittance to 5% or less at 0.6mm, light leakage through the adhesive layer in the width direction can be accurately prevented or suppressed even if the thickness of the adhesive layer is greater than 25 mm. From the viewpoint of further improving the horizontal light-shielding property or enabling sufficient horizontal light-shielding even if it is narrower, the 0.6mm light transmittance of the adhesive layer is preferably 3% or less, more preferably 1% or less, further preferably 0.5% or less, and particularly preferably 0.1% or less. The lower limit of the light transmittance of 0.6mm is not particularly limited, and may be substantially 0%, that is, not more than the detection limit.

The method for adjusting the light transmittance of the adhesive layer to 0.6mm is not particularly limited, and various known methods can be used. As a typical example of this method, a method of containing a colorant in the pressure-sensitive adhesive layer can be cited. This method can easily adjust the 0.6mm light transmittance of the adhesive layer to a desired value by selection and amount of the colorant, and is therefore convenient. As the colorant, various materials capable of attenuating light advancing in the adhesive layer by reflecting and/or absorbing the light can be used. The color of the colorant is not particularly limited, and may be colored or colorless. Here, "colored" means including black and metallic colors. Further, "colorless" is meant to include white. The color of the colorant may be, for example, black, gray, white, red, blue, yellow, green, yellow-green, orange, violet, gold, silver, pearl, or the like. The colorant is typically contained in the binder layer in a state of being dispersed (may be dissolved) in the constituent material of the binder layer.

(base Polymer)

In the technique disclosed herein, the type of the adhesive constituting the adhesive layer is not particularly limited. The pressure-sensitive adhesive layer may contain 1 or 2 or more kinds of various rubbery polymers such as acrylic polymers, rubber polymers, polyester polymers, urethane polymers, polyether polymers, silicone polymers, polyamide polymers, and fluorine polymers, which are known in the pressure-sensitive adhesive field, as base polymers. From the viewpoint of adhesive characteristics, cost, and the like, an adhesive containing an acrylic polymer or a rubber-based polymer as a base polymer may be preferably used. Among them, a pressure-sensitive adhesive (acrylic pressure-sensitive adhesive) containing an acrylic polymer as a base polymer is preferable. Hereinafter, a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer made of an acrylic pressure-sensitive adhesive, that is, an acrylic pressure-sensitive adhesive layer will be mainly described, but the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet disclosed herein is not limited to one made of an acrylic pressure-sensitive adhesive.

The "base polymer" of the binder means a main component of the rubbery polymer contained in the binder. 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 having a content of more than 50% by weight unless otherwise specified.

Further, "acrylic polymer" means a polymer containing, as a monomer unit constituting the polymer, a monomer unit derived from a monomer having at least one (meth) acryloyl group in 1 molecule. Hereinafter, a monomer having at least one (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 comprising a monomer unit derived from an acrylic monomer. Typical examples of the acrylic polymer include acrylic polymers in which the ratio of the acrylic monomer in all monomer components used for synthesizing the acrylic polymer is more than 50% by weight.

In addition, "(meth) acryloyl" means acryloyl and methacryloyl in a general sense. Similarly, "(meth) acrylate" means acrylate and methacrylate in a general manner, and "(meth) acrylic acid" means acrylic acid and methacrylic acid in a general manner.

As the acrylic polymer, for example, a polymer of a monomer raw material containing an alkyl (meth) acrylate as a main monomer and further containing a sub-monomer copolymerizable with the main monomer is preferable. Here, the main monomer means a component accounting for more than 50% by weight in the monomer composition of the above monomer raw materials.

As the alkyl (meth) acrylate, for example, a compound represented by the following formula (1) can be suitably used.

CH₂＝C(R¹)COOR² (1)

Here, R in the above formula (1)¹Is a hydrogen atom or a methyl group. Furthermore, R²Is a chain alkyl group having 1 to 20 carbon atoms. Hereinafter, such a range of the number of carbon atoms may be represented by "C_1-20". R is preferably used from the viewpoint of storage modulus of the adhesive²Is C_1-14(e.g. C)_2-10Typically C_4-8) The alkyl (meth) acrylate of a chain alkyl group as a main monomer. From the viewpoint of adhesive properties, R is preferred¹Is a hydrogen atom, R²Is C_4-8Alkyl acrylate having a chain alkyl group (hereinafter also referred to simply as acrylic acid C)_4-8An alkyl ester. ) As the main monomer.

As R²Is C_1-20Examples of the alkyl (meth) acrylate of the chain alkyl group include: methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, and propyl (meth) acrylateIsobutyl enoate, sec-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, undecyl (meth) acrylate, lauryl (meth) acrylate, tridecyl (meth) acrylate, tetradecyl (meth) acrylate, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate, octadecyl (meth) acrylate, nonadecyl (meth) acrylate, eicosyl (meth) acrylate, and the like. These alkyl (meth) acrylates may be used singly in 1 kind or in combination in 2 or more kinds. Preferred alkyl (meth) acrylates include n-Butyl Acrylate (BA) and 2-ethylhexyl acrylate (2 EHA).

The proportion of the alkyl (meth) acrylate in the total monomer components used for synthesizing the acrylic polymer is preferably 70% by weight or more, more preferably 85% by weight or more, and still more preferably 90% by weight or more. The upper limit of the proportion of the alkyl (meth) acrylate is not particularly limited, and is usually preferably 99.5% by weight or less (for example, 99% by weight or less). Alternatively, the acrylic polymer may be obtained by polymerizing substantially only the alkyl (meth) acrylate. Furthermore, acrylic acid C is used_4-8When an alkyl ester is used as the monomer component, acrylic acid C in the alkyl (meth) acrylate contained in the monomer component_4-8The proportion of the alkyl ester is preferably 70% by weight or more, more preferably 90% by weight or more, and still more preferably 95% by weight or more (typically 99 to 100% by weight). The technique disclosed herein can be preferably carried out in such a manner that 50% by weight or more (typically 60% by weight or more) of the total monomer components is BA. In a preferred embodiment, the ratio of BA in the total monomer components may be 70% by weight or more, may be 80% by weight or more, and may be 90% by weight or more. The total monomer component may further contain 2EHA in a smaller proportion than BA.

For the acrylic polymer in the technology disclosed herein, monomers (other monomers) other than the above may be copolymerized within a range not significantly impairing the effects of the present invention. The other monomer can be used for the purpose of, for example, adjusting the glass transition temperature (Tg) of the acrylic polymer, adjusting the adhesive properties (e.g., releasability), and the like. Examples of the monomer capable of improving the cohesive force and heat resistance of the adhesive include: sulfonic acid group-containing monomers, phosphoric acid group-containing monomers, cyano group-containing monomers, vinyl esters, alicyclic (meth) acrylates, aromatic vinyl compounds, and the like. Among these, vinyl esters are suitable examples. Specific examples of the vinyl esters include: vinyl acetate (VAc), vinyl propionate, vinyl laurate, and the like. Among them, VAc is preferable. The amount of VAc used may be, for example, about 3.5 to 10% by weight (preferably about 4 to 7% by weight) of the total monomer components.

In addition, as other monomers that can introduce a functional group that forms a crosslinking base point into the acrylic polymer or can contribute to improvement of the adhesive strength, there are listed: hydroxyl group (OH group) -containing monomers, carboxyl group-containing monomers, anhydride group-containing monomers, amide group-containing monomers, amino group-containing monomers, imide group-containing monomers, epoxy group-containing monomers, (meth) acryloylmorpholine, vinyl ethers and the like.

As one preferable example of the acrylic polymer in the technique disclosed herein, there is an acrylic polymer obtained by copolymerizing a carboxyl group-containing monomer as the other monomer. Examples of the carboxyl group-containing monomer include: acrylic Acid (AA), methacrylic acid (MAA), carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, isocrotonic acid, and the like. Among them, AA and MAA are preferable.

As another suitable example, an acrylic polymer copolymerized with a hydroxyl group-containing monomer as the other monomer is mentioned. 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, and 4-hydroxybutyl (meth) acrylate; polypropylene glycol mono (meth) acrylate; n-hydroxyethyl (meth) acrylamide, and the like. Among them, preferable hydroxyl group-containing monomers include: the alkyl group is a straight-chain hydroxyalkyl (meth) acrylate having 2 to 4 carbon atoms.

The "other monomers" can be used alone in 1 or a combination of 2 or more. The total content of the other monomers is preferably about 40% by weight or less (typically 0.001 to 40% by weight) of the total monomer components, and more preferably about 30% by weight or less (typically 0.01 to 30% by weight, for example, 0.1 to 10% by weight).

When a carboxyl group-containing monomer is used as the other monomer, the content thereof is preferably about 0.1 to 10% by weight (for example, 0.2 to 8% by weight, typically 0.5 to 5% by weight) of the total monomer components. When a hydroxyl group-containing monomer is used as the other monomer, the content thereof is preferably about 0.001 to 10% by weight (for example, 0.01 to 5% by weight, typically 0.02 to 2% by weight) of the total monomer components.

The copolymerization composition of the acrylic polymer is suitably designed so that the glass transition temperature (Tg) of the polymer is-15 ℃ or lower (typically-70 ℃ or higher and-15 ℃ or lower). The Tg of the acrylic polymer is preferably-25 ℃ or lower (for example, -60 ℃ or higher and-25 ℃ or lower), and more preferably-40 ℃ or lower (for example, -60 ℃ or higher and-40 ℃ or lower). It is preferable to set Tg of the acrylic polymer to the upper limit or less from the viewpoint of workability of attaching the adhesive sheet.

The Tg of the acrylic polymer can be adjusted by appropriately changing the monomer composition (i.e., the kind of the monomer used for synthesis of the polymer, the amount ratio used). Here, Tg of the acrylic polymer is a value obtained from the Fox equation based on the composition of the monomer components used for synthesizing the polymer. The Fox formula is a relationship between Tg of a copolymer and the glass transition temperature Tgi of a homopolymer obtained by homopolymerizing each monomer constituting the copolymer, as shown below.

1/Tg＝Σ(Wi/Tgi)

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

The glass transition temperature of the homopolymer used for calculation of Tg was the value described in the publicly known data. For example, for the monomers listed below, as the glass transition temperature of the homopolymer of the monomer, the following values were used.

As the glass transition temperature of a homopolymer of a monomer other than the above-exemplified monomers, the values described in "Polymer Handbook" (3 rd edition, John Wiley & Sons, Inc.,1989) were used. The highest value is used for monomers having various values described in this document.

The above documents do not describe the glass transition temperature of the homopolymer, and the following measurement method is used.

Specifically, 100 parts by weight of a monomer, 0.2 parts by weight of 2, 2' -azobisisobutyronitrile and 200 parts by weight of ethyl acetate as a polymerization solvent were put into a reactor equipped with a thermometer, a stirrer, a nitrogen introduction tube and a reflux condenser, and stirred for 1 hour while introducing nitrogen. After the oxygen in the polymerization system was removed in this manner, the temperature was raised to 63 ℃ to carry out the reaction for 10 hours. Then, the mixture was cooled to room temperature to obtain a homopolymer solution having a solid content of 33% by weight. Subsequently, the homopolymer solution was cast on a release liner and dried to prepare a test sample (sheet-like homopolymer) having a thickness of about 2 mm. The test sample was punched out into a disk shape having a diameter of 7.9mm, and sandwiched between parallel plates, while applying a shear strain having a frequency of 1Hz using a viscoelasticity tester (model name "ARES" manufactured by TA Instruments Japan inc.) and measuring viscoelasticity in a shear mode at a temperature rise rate of 5 ℃/min within a temperature range of-70 to 150 ℃, and the temperature corresponding to the peak top temperature of the shear loss modulus G "(the temperature at which the G" curve reaches the maximum) was taken as Tg of the homopolymer.

The method for obtaining the acrylic polymer is not particularly limited, and various polymerization methods known as a method for synthesizing an acrylic polymer, such as a solution polymerization method, an emulsion polymerization method, a bulk polymerization method, a suspension polymerization method, and a photopolymerization method, can be appropriately used. For example, solution polymerization can be preferably used. As a method of supplying the monomer in the case of performing the solution polymerization, a batch charging method, a continuous supply (dropwise) method, a batch supply (dropwise) method, or the like, in which all the monomer raw materials are supplied at once, can be suitably employed. The polymerization temperature may be appropriately selected depending on the kind of the monomer and the solvent used, the kind of the polymerization initiator, and the like, and may be, for example, about 20 ℃ to 170 ℃ (typically about 40 ℃ to 140 ℃). In a preferred embodiment, a polymerization temperature of about 75 ℃ or less (more preferably about 65 ℃ or less, for example, about 45 ℃ to 65 ℃) can be used.

The solvent (polymerization solvent) used in 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; acetates such as ethyl acetate; aliphatic or alicyclic hydrocarbons such as hexane and cyclohexane; halogenated alkanes such as 1, 2-dichloroethane; lower alcohols (e.g., monohydric alcohols having 1 to 4 carbon atoms) such as isopropyl alcohol; ethers such as t-butyl methyl ether; ketones such as methyl ethyl ketone; and the like, or a mixed solvent of 2 or more solvents.

The initiator used in 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 another example of the polymerization initiator, a redox initiator composed of a combination of a peroxide and a reducing agent may be cited. Such 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 generally used, and may be selected from the range of about 0.005 to 1 part by weight (typically about 0.01 to 1 part by weight) based on 100 parts by weight of the total monomer components.

The solution polymerization described above can provide a polymerization reaction solution in which the acrylic polymer is dissolved in an organic solvent. The pressure-sensitive adhesive layer in the technique disclosed herein may be formed from a pressure-sensitive adhesive composition containing an acrylic polymer solution obtained by subjecting the above-mentioned polymerization reaction liquid or the reaction liquid to an appropriate post-treatment. As the acrylic polymer solution, a solution prepared by preparing the polymerization reaction solution to an appropriate viscosity (concentration) as needed can be used. Alternatively, an acrylic polymer solution prepared by synthesizing an acrylic polymer by a polymerization method other than solution polymerization (for example, emulsion polymerization, photopolymerization, bulk polymerization, or the like) and dissolving the acrylic polymer in an organic solvent may be used.

The weight average molecular weight (Mw) of the base polymer (preferably, acrylic polymer) in the technology disclosed herein is not particularly limited, and may be, for example, 10 × 10⁴～500×10⁴The range of (1). From the viewpoint of adhesive properties, the Mw of the base polymer is preferably 10X 10⁴～150×10⁴(e.g., 20X 10)⁴～75×10⁴Typically 35 x 10⁴～65×10⁴) The range of (1). Here, Mw is a value in terms of standard polystyrene obtained by GPC (gel permeation chromatography). As the GPC apparatus, for example, the type name "HLC-8320 GPC" (column: TSKgelGMH-H (S), manufactured by Tosoh corporation) can be used.

(tackifier)

The adhesive layers disclosed herein may contain a tackifier. The tackifier is not particularly limited, and various tackifier resins such as rosin-based tackifier resin, terpene-based tackifier resin, hydrocarbon-based tackifier resin, epoxy-based tackifier resin, polyamide-based tackifier resin, elastomer-based tackifier resin, phenol-based tackifier resin, and ketone-based tackifier resin can be used. Such tackifiers may be used singly in 1 kind or in combination in 2 or more kinds. When an acrylic polymer is used as the base polymer, a rosin-based tackifying resin (for example, polymerized rosin ester) or a terpene-based tackifying resin (for example, terpene phenol resin) is preferably used.

Specific examples of the rosin-based tackifier resin include: unmodified rosins (raw rosins) such as gum rosin, wood rosin, tall oil rosin and the like; modified rosins (hydrogenated rosins, disproportionated rosins, polymerized rosins, and other chemically modified rosins) obtained by modifying these unmodified rosins by hydrogenation, disproportionation, polymerization, or the like; other various rosin derivatives, and the like. Examples of the rosin derivatives include: rosin esters such as those obtained by esterifying unmodified rosin with an alcohol (i.e., esterified products of rosin), and those obtained by esterifying modified rosin (hydrogenated rosin, disproportionated rosin, polymerized rosin, etc.) with an alcohol (i.e., esterified products of modified rosin); unsaturated fatty acid-modified rosins obtained by modifying unmodified rosins or modified rosins (hydrogenated rosins, disproportionated rosins, polymerized rosins, etc.) with unsaturated fatty acids; unsaturated fatty acid-modified rosin esters obtained by modifying rosin esters with unsaturated fatty acids; rosin alcohols obtained by reducing carboxyl groups in unmodified rosin, modified rosin (hydrogenated rosin, disproportionated rosin, polymerized rosin, etc.), unsaturated fatty acid-modified rosin, or unsaturated fatty acid-modified rosin ester; metal salts of rosins (particularly, rosin esters) such as unmodified rosins, modified rosins, and various rosin derivatives; rosin phenol resins obtained by polymerizing a rosin (such as an unmodified rosin, a modified rosin, and various rosin derivatives) and phenol in the presence of an acid catalyst and thermally polymerizing the resulting products, and the like.

Examples of terpene-based tackifying resins include: terpene resins such as α -pinene polymer, β -pinene polymer, dipentene polymer and the like; modified terpene resins obtained by modifying (e.g., phenol modification, aromatic modification, hydrogenation modification, hydrocarbon modification) these terpene resins, and the like. Examples of the modified terpene resin include: terpene-phenol resins, styrene-modified terpene resins, aromatic-modified terpene resins, hydrogenated terpene resins, and the like.

Examples of hydrocarbon tackifying resins include: various hydrocarbon resins such as aliphatic hydrocarbon resins, aromatic hydrocarbon resins, aliphatic cyclic hydrocarbon resins, aliphatic/aromatic petroleum resins (styrene-olefin copolymers and the like), aliphatic/alicyclic petroleum resins, hydrogenated hydrocarbon resins, coumarone resins, and coumarone indene resins.

The softening point of the tackifier resin is not particularly limited. In one embodiment, the tackifier resin may preferably have a softening point (softening temperature) of about 80 ℃ or higher (preferably about 110 ℃ or higher, and more preferably about 135 ℃ or higher). Terpene-based tackifying resins (terpene-phenol resins, etc.) and rosin-based tackifying resins (esterified products of polymerized rosin, etc.) having such softening points can be preferably used. For example, a terpene-phenol resin having a softening point of about 135 ℃ or higher (further about 140 ℃ or higher) can be preferably used. The upper limit of the softening point of the tackifier resin is not particularly limited, and may be, for example, about 200 ℃ or lower (typically about 180 ℃ or lower). The softening point of the tackifier resin can be measured according to a softening point test method (ring and ball method) specified in JIS K2207.

The amount of the tackifier resin to be used is not particularly limited, and may be appropriately set in accordance with the intended adhesive performance (e.g., adhesive strength). For example, the tackifier resin is preferably used in a proportion of about 10 to 100 parts by weight (more preferably about 15 to 80 parts by weight, and further preferably about 20 to 60 parts by weight) based on 100 parts by weight of the acrylic polymer on a solid content basis.

Examples of suitable compositions for the acrylic adhesive disclosed herein include: the adhesive composition contains a tackifier resin (e.g., a terpene-phenol resin) having a softening point of 135 ℃ or higher in a proportion of 20 to 60 parts by weight relative to 100 parts by weight of an acrylic polymer.

Other examples of suitable compositions for the acrylic adhesive disclosed herein include: a combination of a rosin-based tackifying resin (e.g., a polymerized rosin ester) and a terpene-based tackifying resin (e.g., a terpene phenol resin). With this composition, more excellent adhesive properties can be exhibited. The weight ratio of the rosin-based tackifying resin to the terpene-based tackifying resin may be, for example, in the range of 5/95 to 95/5, in the range of 10/90 to 90/10, in the range of 20/80 to 80/20, or in the range of 30/70 to 70/30.

The acrylic adhesives disclosed herein may contain a tackifying resin T having a hydroxyl value of greater than 50mgKOH/g_H1. Tackifying resin T_H1The hydroxyl value of (B) may be, for example, 60mgKOH/g or more, 70mgKOH/g or more, 80mgKOH/g or more, or 90mgKOH/g or more, from the viewpoint of improving the adhesive properties. Tackifying resin T_H1The hydroxyl value of (B) is usually preferably 300mgKOH/g or less, preferably 250mgKOH/g or less, and may be 200mgKOH/g or less (for example, 150mgKOH/g or less), from the viewpoint of compatibility with an acrylic polymer and the like.

Examples of suitable compositions for the acrylic adhesive disclosed herein include: a combination of the above tackifier resin T_H1And hydroxyl value and the tackifying resin T_H1Tackifier resin T with difference of more than 5mgKOH/g_H2The composition of (1). Tackifying resin T_H1With tackifying resins T_H2The difference in hydroxyl value (b) of (a) is preferably 10mgKOH/g or more (for example, 20mgKOH/g or more), and may be 30mgKOH/g or more, or may be 40mgKOH/g or more. Tackifying resin T_H2The hydroxyl value of (A) may be higher or lower than that of the tackifying resin T_H1The hydroxyl value of (2). In one embodiment, a tackifier resin T may be preferably used_H2Has a hydroxyl value higher than that of the tackifying resin T_H1Combinations of hydroxyl numbers of (a). Examples of suitable compositions for the acrylic adhesive disclosed herein include: a tackifier resin T having a hydroxyl value of 75mgKOH/g or less (for example, 70mgKOH/g or less) is used in combination_H1And a tackifier resin T having a hydroxyl value of 80mgKOH/g or more (e.g., 90mgKOH/g or more)_H2The composition of (1).

The acrylic adhesives disclosed herein may contain a tackifying resin T having an acid value of greater than 20mgKOH/g_A1. Tackifying resin T_A1The acid value of (B) may be, for example, 30mgKOH/g or more, or 40mgKOH/g or more. In addition, the tackifier resin T is useful from the viewpoint of weather resistance of the adhesive and the like_A1The acid value of (A) is usually preferably not more than 150mgKOH/g, may be not more than 100mgKOH/g, or may beIs 70mgKOH/g or less.

For tackifying resin T_A1The hydroxyl value of (b) is not particularly limited. Tackifying resin T_A1May correspond to the above tackifier resin T_H1Or tackifying resins T_H2They may be inappropriate. Tackifying resin T_A1The acid value of (B) may be, for example, 50mgKOH/g or less, 30mgKOH/g or less, or 20 mgKOH/g.

Examples of suitable compositions for the acrylic adhesive disclosed herein include: a combination of the above tackifier resin T_H1And the above tackifier resin T_A1The composition of (1).

Tackifying resin T_H1And a tackifying resin T_H2And a tackifying resin T_A1The resins having desired hydroxyl value or acid value can be selected independently from the above-exemplified tackifying resins. For example tackifying resins T_H1And a tackifying resin T_H2And a tackifying resin T_A1Each may be independently selected from the group consisting of rosin-based tackifying resins and terpene-based tackifying resins (e.g., terpene phenol resins).

The acid value and the hydroxyl value of the tackifier resin can be determined by JIS K0070: 1992.

(coloring agent)

The binder layer may contain a colorant. This enables adjustment of the light transmittance (light-shielding property) of the pressure-sensitive adhesive layer. For example, the light transmittance of the adhesive layer can be adjusted to 0.6mm and the vertical light transmittance can be adjusted. Adjusting the light transmittance (e.g., vertical light transmittance) of the adhesive layer may also contribute to the adjustment of the light transmittance of the adhesive sheet containing the adhesive layer.

As the colorant, conventionally known pigments and dyes can be used. Examples of pigments include: zinc carbonate, zinc oxide, zinc sulfide, talc, kaolin, calcium carbonate, titanium oxide, silica, lithium fluoride, calcium fluoride, barium sulfate, alumina, zirconia, iron oxide, iron hydroxide, chromium oxide, spinel-type calcined pigments, chromic acids, molybdate red, ultramarine, aluminum powder, bronze powder, silver powder, calcium phosphate and other inorganic pigments, phthalocyanine, azo, condensed azo, azo lake, anthraquinone, perylene-violanthrone, indigo, thioindigo, isoindolinone, methylamine, dioxazine, quinacridone, nigrosine, triphenylmethane, carbon black and other organic pigments. Examples of the dye include: azo dyes, anthraquinones, quinophthalones, styrene (styryl), diphenylmethane, triphenylmethane, oxazines, triazines, xanthan gum, methane, azomethines, acridines, diazines. The coloring agent may be used alone in 1 kind or in appropriate combination of 2 or more kinds.

Since the light-shadability can be efficiently adjusted by a small amount of the colorant, a black colorant can be preferably used. Specific examples of the black coloring agent include: carbon black (furnace black, channel black, acetylene black, thermal black, lamp black, pine smoke, etc.), graphite, copper oxide, manganese dioxide, aniline black, perylene black, titanium black, cyanine black, activated carbon, ferrite (non-magnetic ferrite, etc.), magnetite, chromium oxide, iron oxide, molybdenum disulfide, chromium complex, anthraquinone-based colorant, etc. Among them, carbon black is preferred.

Since the light-shielding property of the adhesive layer can be efficiently adjusted by a small amount of the colorant, a granular colorant (pigment) can be preferably used. In a preferred embodiment, a pigment (for example, a particulate black colorant such as carbon black) having an average particle diameter of 10nm to 500nm, more preferably 10nm to 120nm can be used. The "average particle diameter" in the present specification means, unless otherwise specified, a particle diameter at 50% of a cumulative value in a particle size distribution measured by a particle size distribution measuring apparatus based on a laser scattering diffraction method (50% volume average particle diameter; hereinafter, it may be abbreviated as "D" in some cases)₅₀。)。

The amount of the colorant to be mixed is not particularly limited, and may be set so as to form an adhesive layer satisfying a desired light transmittance of 0.6 mm. It is usually preferably 0.5 parts by weight or more, preferably 1.0 parts by weight or more, and more preferably 1.5 parts by weight or more, based on 100 parts by weight of the base polymer. The amount of the colorant to be blended may be 15 parts by weight or less based on 100 parts by weight of the base polymer, for example. The amount of the colorant to be blended is preferably 10 parts by weight or less, preferably 5 parts by weight or less, and more preferably 3 parts by weight or less, per 100 parts by weight of the base polymer, from the viewpoint of suppressing a decrease in adhesive properties that may be caused by the blending of the colorant. In a preferred embodiment, the amount of the colorant to be blended is 2.5 parts by weight or less (more preferably 2.3 parts by weight or less, for example, 2 parts by weight or less) per 100 parts by weight of the base polymer.

The content of the colorant in the pressure-sensitive adhesive layer is usually preferably 0.3% by weight or more, preferably 0.5% by weight or more, and more preferably 1.0% by weight or more of the pressure-sensitive adhesive layer. The content of the colorant may be set to, for example, less than 10% by weight, preferably less than 5% by weight, more preferably less than 3.5% by weight, and still more preferably less than 3.0% by weight. In a preferred embodiment, the colorant content of the adhesive layer may be set to less than 2.5 wt% (more preferably less than 2.2 wt%, for example less than 2.0 wt%).

The binder compositions disclosed herein may contain ingredients that help to improve the dispersibility of the above colorants. The dispersibility-enhancing component may be, for example, a polymer, an oligomer, a liquid resin, a surfactant, or the like. The dispersibility-enhancing component is preferably dissolved in the adhesive composition. The oligomer may be, for example, a low-molecular weight polymer (e.g., having an Mw of about less than 10X 10) containing 1 or 2 or more monomer components among the above-mentioned acrylic monomers⁴Preferably less than 5X 10⁴Acrylic oligomer of (ii). The liquid resin may be, for example, a tackifier resin (typically, a tackifier resin such as rosins, terpenes, and hydrocarbons, for example, hydrogenated rosin methyl ester) having a softening point of about 50 ℃ or lower, more preferably about 40 ℃ or lower. By using such a dispersibility-enhancing component, dispersion unevenness of a colorant (for example, a particulate black colorant such as carbon black) can be suppressed, and color unevenness of the pressure-sensitive adhesive layer can be suppressed. Therefore, an adhesive sheet having better appearance quality can be formed.

The content of the dispersibility-enhancing component is not particularly limited, and is usually preferably about 20 wt% or less (preferably about 10 wt% or less, more preferably 7 wt% or less, for example about 5 wt% or less) of the entire adhesive layer, from the viewpoint of suppressing the influence on the adhesive properties (for example, the decrease in cohesion). In one embodiment, the content of the dispersibility-enhancing component may be about 10 times or less (preferably about 5 times or less, for example, about 3 times or less) the weight of the colorant. In view of suitably exhibiting the effect of the dispersibility-enhancing component, the content is usually suitably about 0.2% by weight or more (typically about 0.5% by weight or more, preferably about 1% by weight or more) of the entire pressure-sensitive adhesive layer. In one embodiment, the content of the dispersibility-enhancing component may be about 0.2 times or more (preferably about 0.5 times or more, for example, 1 time or more) the weight of the colorant.

(crosslinking agent)

In the technique disclosed herein, the adhesive composition used for forming the adhesive layer may contain a crosslinking agent as needed. The kind of the crosslinking agent is not particularly limited, and can be appropriately selected from conventionally known crosslinking agents. Examples of such a crosslinking agent include: isocyanate crosslinking agents, epoxy crosslinking agents, oxazoline crosslinking agents, aziridine crosslinking agents, melamine crosslinking agents, peroxide crosslinking agents, urea crosslinking agents, metal alkoxide crosslinking agents, metal chelate crosslinking agents, metal salt crosslinking agents, carbodiimide crosslinking agents, amine crosslinking agents, and the like. The crosslinking agent may be used alone in 1 kind or in combination of 2 or more kinds. Among these, from the viewpoint of improving the cohesive force, an isocyanate-based crosslinking agent and/or an epoxy-based crosslinking agent are preferably used, and a combination of an isocyanate-based crosslinking agent and an epoxy-based crosslinking agent is particularly preferably used. The amount of the crosslinking agent is not particularly limited. For example, the amount of the acrylic polymer is about 10 parts by weight or less, preferably about 0.005 to 10 parts by weight, more preferably about 0.01 to 5 parts by weight, based on 100 parts by weight of the base polymer (preferably, the acrylic polymer).

(other additives)

The pressure-sensitive adhesive composition may contain, as required, various additives commonly used in the field of pressure-sensitive adhesive compositions such as leveling agents, crosslinking aids, plasticizers, softening agents, antistatic agents, antioxidants, ultraviolet absorbers, antioxidants, and light stabilizers. For such various additives, conventionally known additives can be used according to a conventional method, and since they are not particularly components that provide the features of the present invention, detailed descriptions thereof are omitted.

The pressure-sensitive adhesive layer (layer formed of a pressure-sensitive adhesive) disclosed herein may be a pressure-sensitive adhesive layer formed of a water-based pressure-sensitive adhesive composition, a solvent-based pressure-sensitive adhesive composition, a hot-melt pressure-sensitive adhesive composition, or an active energy ray-curable pressure-sensitive adhesive composition. The aqueous pressure-sensitive adhesive composition is a pressure-sensitive adhesive composition in a form containing a pressure-sensitive adhesive (pressure-sensitive adhesive layer-forming component) in a solvent (aqueous solvent) mainly containing water, and typically includes a pressure-sensitive adhesive composition called an aqueous dispersion type pressure-sensitive adhesive composition (a composition in which at least a part of the pressure-sensitive adhesive is dispersed in water) and the like. The solvent-based adhesive composition is in a form containing an adhesive in an organic solvent. The technique disclosed herein can be preferably implemented to have an adhesive layer formed from a solvent-based adhesive composition from the viewpoint of adhesive properties and the like.

The adhesive layer disclosed herein may be formed using a conventionally known method. For example, a method (direct method) of directly applying (typically coating) a pressure-sensitive adhesive composition to such a substrate film and drying the composition to form a pressure-sensitive adhesive layer can be employed. Further, a method (transfer method) may be employed in which a pressure-sensitive adhesive layer is formed on a surface (release surface) having releasability by applying a pressure-sensitive adhesive composition to the surface and drying the pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer is transferred to a base film. The transfer method is preferable from the viewpoint of productivity. The release surface may be the surface of a release liner or the back surface of a base film subjected to a release treatment. The pressure-sensitive adhesive layer disclosed herein is typically formed continuously, but is not limited to this form, and may be formed in a regular pattern such as dots or stripes, or a random pattern.

The application of the adhesive composition can be performed using a conventionally known coater such as a gravure roll coater, a die coater, or a bar coater. Alternatively, the adhesive composition may be applied by dipping, curtain coating, or the like.

The drying of the adhesive composition is preferably performed under heating from the viewpoint of accelerating the crosslinking reaction, improving the production efficiency, and the like. The drying temperature may be, for example, about 40 to 150 ℃, and is preferably about 60 to 130 ℃. After drying the pressure-sensitive adhesive composition, the pressure-sensitive adhesive composition may be further cured for the purpose of adjusting the transfer of components in the pressure-sensitive adhesive layer, proceeding of the crosslinking reaction, relaxing of strain which may be present in the substrate film or the pressure-sensitive adhesive layer, and the like.

< substrate film >

As the base film, a film containing a resin film as a base film can be preferably used. The base film is typically a (independent) member that can be independently shape-maintained. The substrate film in the technology disclosed herein may consist essentially of such a base film. Alternatively, the base film may include an auxiliary layer in addition to the base film. Examples of the auxiliary layer include a colored layer, a reflective layer, an undercoat layer, and an antistatic layer provided on the surface of the base film.

The resin film is a film containing a resin material as a main component (for example, a component contained in the resin film in an amount exceeding 50% by weight). Examples of the resin film include: polyolefin resin films such as Polyethylene (PE), polypropylene (PP), and ethylene-propylene copolymers; polyester resin films such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN); vinyl chloride resin films; a vinyl acetate resin film; a polyimide resin film; a polyamide resin film; a fluororesin film; cellophane; and the like. The resin film may be a rubber-based film such as a natural rubber film or a butyl rubber film. Among them, polyester films are preferable from the viewpoint of handling properties and processability, and among them, PET films are particularly preferable. In the present specification, the term "resin film" is typically a non-porous sheet, and is distinguished from the concept of a so-called nonwoven fabric or woven fabric (in other words, a concept excluding a nonwoven fabric or woven fabric).

The resin film may contain a colorant. This makes it possible to adjust the light transmittance (light-shielding property) of the resin film. For example, the vertical light transmittance and the 0.6mm light transmittance of the resin film can be adjusted. Adjusting the light transmittance (e.g., vertical light transmittance) of a resin film also contributes to adjusting the light transmittance of a base film containing the resin film, and further, the light transmittance of a pressure-sensitive adhesive sheet containing the base film.

As the colorant, a conventionally known pigment or dye can be used as well as the colorant that can be contained in the adhesive layer. The color of the colorant is not particularly limited, and may be colored or colorless. The color of the colorant may be, for example, black, gray, white, red, blue, yellow, green, yellow-green, orange, violet, gold, silver, pearl, or the like.

In one embodiment, a black colorant can be preferably used because the light-shielding property (for example, vertical light transmittance) can be efficiently adjusted by a small amount of the colorant. Specific examples of the black coloring agent include coloring agents exemplified as coloring agents that can be contained in the binder layer. In a preferred embodiment, a pigment (for example, a particulate black colorant such as carbon black) having an average particle diameter of 10nm to 500nm, more preferably 10nm to 120nm can be used.

In another embodiment, the resin film may contain a white colorant. Examples of the white colorant include: titanium oxide (titanium dioxide such as rutile type titanium dioxide and anatase type titanium dioxide), zinc oxide, aluminum oxide, silicon oxide, zirconium oxide, magnesium oxide, calcium oxide, tin oxide, barium oxide, cesium oxide, yttrium oxide, magnesium carbonate, calcium carbonate (light calcium carbonate, heavy calcium carbonate, etc.), barium carbonate, zinc carbonate, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide, aluminum silicate, magnesium silicate, calcium silicate, barium sulfate, calcium sulfate, barium stearate, zinc oxide, zinc sulfide, talc, silica, aluminum oxide, clay, kaolin, titanium phosphate, mica, gypsum, white carbon black, diatomaceous earth, bentonite, lithopone, zeolite, sericite, halloysite, etc. inorganic white colorants such as acrylic resin particles, polystyrene resin particles, polyurethane resin particles, amide resin particles, polycarbonate resin particles, etc, Organic white colorants such as silicone resin particles, urea formaldehyde resin particles, melamine resin particles, and the like.

The amount of the colorant used in the resin film is not particularly limited, and may be adjusted appropriately so as to impart desired optical characteristics. The amount of the colorant used is usually preferably about 0.1 to 30% by weight, for example, 0.1 to 25% by weight (typically 0.1 to 20% by weight) of the resin film.

The resin film may contain various additives such as a filler (inorganic filler, organic filler, etc.), a dispersant (surfactant, etc.), an antioxidant, an ultraviolet absorber, an antistatic agent, a lubricant, and a plasticizer, if necessary. The compounding ratio of each additive is usually less than about 30% by weight (e.g., less than 20% by weight, and typically less than 10% by weight).

The resin film may have a single-layer structure, or may have a multilayer structure of 2 or 3 or more layers. From the viewpoint of shape stability, the resin film is preferably a single-layer structure. In the case of a multilayer structure, at least one layer (preferably all layers) is preferably a layer having a continuous structure of the above resin (for example, a polyester resin). The method for producing the resin film is not particularly limited, and any conventionally known method may be suitably used. For example, conventionally known conventional film forming methods such as extrusion molding, inflation molding, T-die casting molding, calender roll molding, and the like can be suitably used.

The base film can be colored by a colored layer disposed on the surface of the base film (preferably, a resin film). In the base film having such a configuration including the base film and the colored layer, the base film may or may not contain a coloring agent. The colored layer may be disposed on either surface of the base film, or may be disposed on both surfaces. In the configuration in which the colored layers are disposed on the surfaces of both sides of the base film, the colored layers may be the same or different in configuration.

Such a colored layer can be formed by applying a composition for forming a colored layer containing a colorant and a binder to a base film. As the colorant, conventionally known pigments and dyes can be used as well as colorants that can be contained in the adhesive layer and the resin film. As the binder, a material known in the field of coating or printing can be used without particular limitation. For example, it can be illustrated that: polyurethane, phenolic resin, epoxy resin, urea melamine resin, polymethyl methacrylate, and the like. The composition for forming a colored layer may be, for example, a solvent type, an ultraviolet curing type, a thermosetting type, or the like. The colored layer can be formed by any means conventionally used for forming colored layers without any particular limitation. For example, a method of forming a colored layer (printed layer) by printing such as gravure printing, flexo printing, and offset printing can be preferably used.

The colored layer may have a single-layer structure in which 1 layer is formed as a whole, or may have a multilayer structure including 2, 3 or more sub-colored layers. The colored layer having a multilayer structure including 2 or more sub-colored layers can be formed by, for example, repeating application (e.g., printing) of the composition for forming a colored layer. The coloring agent contained in each of the subsidiary coloring layers may be the same in color or different in amount of blending. In the colored layer for imparting light-shielding properties, it is particularly significant to form a multilayer structure in terms of preventing the occurrence of pinholes and improving the reliability of light leakage prevention.

The thickness of the entire colored layer is preferably about 1 μm to 10 μm, preferably about 1 μm to 7 μm, and for example, about 1 μm to 5 μm. In the colored layer including two or more sub-colored layers, the thickness of each sub-colored layer is preferably about 1 μm to 2 μm.

The thickness of the base film disclosed herein is not particularly limited. The thickness of the base film may be, for example, 200 μm or less, preferably 150 μm or less, and more preferably 100 μm or less, from the viewpoint of avoiding the pressure-sensitive adhesive sheet from becoming too thick. The thickness of the base film may be 70 μm or less, 50 μm or less, or 30 μm or less (for example, 25 μm or less) depending on the purpose and the mode of use of the pressure-sensitive adhesive sheet. In one embodiment, the thickness of the base film may be 20 μm or less, may be 15 μm or less, and may be 10 μm or less (for example, 5 μm or less). By reducing the thickness of the base film, the thickness of the adhesive layer can be made larger even if the total thickness of the adhesive sheet is the same. This may be advantageous from the viewpoint of impact resistance of the adhesive sheet. The lower limit of the thickness of the base film is not particularly limited. The thickness of the base film is usually 0.5 μm or more (for example, 1 μm or more), preferably 2 μm or more, for example, 4 μm or more, from the viewpoint of handling (handleability), processability, and the like of the pressure-sensitive adhesive sheet. In one embodiment, the thickness of the base film may be 6 μm or more, may be 8 μm or more, and may be 10 μm or more (for example, more than 10 μm).

The pressure-sensitive adhesive sheet disclosed herein can be implemented, for example, in such a manner that the 0.6mm transmittance of the base film (typically, a resin film) is, for example, 15% or less (preferably 10% or less, more preferably 5% or less). An adhesive sheet comprising such a base film can exhibit good horizontal light-shielding properties. It is particularly significant that the 0.6mm light transmittance of the base film satisfies the above-mentioned value in the base film having a thickness of more than 25 μm. From the viewpoint of obtaining a higher level of light-shielding property, the base film preferably has a light transmittance of 3% or less at 0.6mm, more preferably 1% or less, still more preferably 0.5% or less, and particularly preferably 0.1% or less. The lower limit of the 0.6mm transmittance of the base film is not particularly limited, and may be substantially 0%, that is, not more than the detection limit. The 0.6mm transmittance of the base film can be measured in the same manner as the 0.6mm transmittance of the adhesive layer, using the base film as a measurement sample.

The adhesive sheet disclosed herein may be implemented, for example, in such a manner that the perpendicular light transmittance of the substrate film is, for example, less than 5%. Thus, in the adhesive sheet including the substrate film, a good light-shielding property in the vertical direction (thickness direction of the adhesive sheet) can be achieved. From the viewpoint of obtaining a higher level of light-shielding property, the perpendicular light transmittance of the base film is preferably less than 3%, more preferably less than 1%, further preferably less than 0.5%, particularly preferably less than 0.1%. The lower limit of the vertical transmittance is not particularly limited, and may be substantially 0%, that is, a detection limit or less. The vertical light transmittance of the base film can be measured in the same manner as the 0.6mm light transmittance of the pressure-sensitive adhesive layer, using the base film as a measurement sample.

The surface of the base film may be subjected to conventionally known surface treatment such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, and coating with a primer. Such surface treatment may be treatment for improving adhesion between the base film and the pressure-sensitive adhesive layer, in other words, fixation of the pressure-sensitive adhesive layer to the base film.

< Release liner >

In the technique disclosed herein, a release liner may be used for the formation of the pressure-sensitive adhesive layer, the production of the pressure-sensitive adhesive sheet, the storage, distribution, shape processing, and the like of the pressure-sensitive adhesive sheet before use. The release liner is not particularly limited, and examples thereof include release liners having a release treatment layer on the surface of a liner base material such as a resin film or paper, and release liners formed of a low-adhesive material such as a fluorine-based polymer (polytetrafluoroethylene or the like) or a polyolefin-based resin (polyethylene, polypropylene or the like). The release treated layer may be formed by surface-treating the backing material with a release treating agent such as silicone, long chain alkyl, fluorine, or molybdenum sulfide.

< pressure-sensitive adhesive sheet >

The total thickness of the psa sheet disclosed herein (including the psa layer and the substrate film, but not including the release liner) is not particularly limited. The total thickness of the pressure-sensitive adhesive sheet may be, for example, about 25.5 μm or more, or 30 μm or more, or 50 μm or more, or 60 μm or more. The upper limit of the total thickness of the pressure-sensitive adhesive sheet is typically 400 μm or less, preferably 300 μm or less, and may be 250 μm or less (e.g., 200 μm or less). In one embodiment, the total thickness of the pressure-sensitive adhesive sheet may be 120 μm or less, or may be 90 μm or less.

The adhesive sheet disclosed herein may be implemented in such a manner that the vertical light transmittance of the adhesive sheet is, for example, 5% or less. The vertical light transmittance of the adhesive sheet is preferably 3% or less, more preferably 1% or less, further preferably 0.5% or less, and particularly preferably 0.1% or less, from the viewpoint of suitably achieving vertical light shielding and horizontal light shielding by one member. The lower limit of the vertical transmittance is not particularly limited, and may be substantially 0%, that is, a detection limit or less. The vertical light transmittance of the adhesive sheet can be measured in the same manner as the 0.6mm light transmittance of the adhesive layer, using the adhesive sheet as a measurement sample.

The pressure-sensitive adhesive sheet disclosed herein can be suitably implemented in the form of a double-sided pressure-sensitive adhesive sheet (double-sided pressure-sensitive adhesive sheet) including a1 st pressure-sensitive adhesive layer disposed on one surface of a base film and a2 nd pressure-sensitive adhesive layer disposed on the other surface of the base film. The pressure-sensitive adhesive sheet having such a structure has high practicability as a joining member. Further, the total thickness of the pressure-sensitive adhesive layer (the total thickness of the 1 st pressure-sensitive adhesive layer and the 2 nd pressure-sensitive adhesive layer) is easily increased in the proportion of the total thickness of the pressure-sensitive adhesive sheet, and therefore, it is suitable for improving the impact resistance.

Here, at least one of the 1 st adhesive layer and the 2 nd adhesive layer is an adhesive layer having a thickness of more than 25 μm and a 0.6mm light transmittance of 5% or less. The thickness of the other pressure-sensitive adhesive layer is not particularly limited, and may be, for example, 2 μm or more, typically 5 μm or more, preferably 10 μm or more, and more preferably 15 μm or more. If the thickness of the other pressure-sensitive adhesive layer is increased, the impact resistance of the pressure-sensitive adhesive sheet tends to be improved. From this viewpoint, the thickness of the other pressure-sensitive adhesive layer may be 20 μm or more, may be 25 μm or more, or may exceed 25 μm (for example, 27 μm or more, further 30 μm or more, or 35 μm or more) as with the one pressure-sensitive adhesive layer.

In the case where the thickness of the above-mentioned other adhesive layer is larger than 25 μm, the 0.6mm light transmittance of the other adhesive layer is also preferably 5% or less. Thus, even if the thickness is small, both impact resistance and horizontal light-shielding property can be suitably satisfied. On the other hand, in the case where the thickness of the other adhesive layer is 25 μm or less, the 0.6mm light transmittance of the other adhesive layer is not particularly limited. The pressure-sensitive adhesive layer disclosed herein can be preferably implemented, for example, such that the pressure-sensitive adhesive layer disposed on one surface has a thickness of more than 25 μm and a light transmittance of 0.6mm of 5% or less, and the pressure-sensitive adhesive layer disposed on the other surface has a thickness of 25 μm or less and a light transmittance of 0.6mm of more than 5%.

Preferred examples of the pressure-sensitive adhesive sheet (single-sided pressure-sensitive adhesive sheet or double-sided pressure-sensitive adhesive sheet) disclosed herein include: the light transmittance of the pressure-sensitive adhesive sheet at 0.6mm for a layer having a thickness of more than 25 μm is 5% or less (more preferably 3% or less, still more preferably 1% or less, and typically 0.1% or less). According to the pressure-sensitive adhesive sheet having such a configuration, even if the pressure-sensitive adhesive sheet is narrow, both good light-shielding properties and impact resistance tend to be achieved. From the viewpoint of achieving a higher level of light-shielding property, preferable examples of the preferred embodiment include: and (c) a mode in which the 0.6mm light transmittance of each of the layers having a thickness of 20 μm or more (more preferably, a layer having a thickness of 15 μm or more, and still more preferably, a layer having a thickness of 10 μm or more) among the layers contained in the adhesive sheet is 5% or less (more preferably, 3% or less, still more preferably, 1% or less, and typically, 0.1% or less).

When the pressure-sensitive adhesive sheet disclosed herein is used for light reflection applications, the light reflectance of the surface of the pressure-sensitive adhesive sheet may be, for example, 40% or more, preferably 60% or more, and more preferably 70% or more. The upper limit of the light reflectance is preferably 100%, and may be about 99% or less (for example, 95% or less, typically 92% or less) from the practical viewpoint.

The light reflectance (%) of the surface of the adhesive sheet was determined by irradiating one surface of the adhesive sheet (light reflectance measurement surface) with light having a wavelength of 550nm using a commercially available spectrophotometer and measuring the intensity of light reflected on the surface irradiated with the light. As the spectrophotometer, for example, a spectrophotometer manufactured by Shimadzu corporation (device name "MPS-2000") can be used. The same applies to the later-described examples.

The total thickness of the 1 st adhesive layer and the 2 nd adhesive layer is not particularly limited. The total thickness of the above adhesive layers may be, for example, more than 27 μm, typically more than 30 μm, preferably more than 35 μm, and more preferably more than 40 μm. If the total thickness of the adhesive layer is increased, the impact resistance of the adhesive sheet tends to be improved. From this viewpoint, the total thickness of the pressure-sensitive adhesive layer may be more than 40 μm, more than 50 μm, more than 60 μm, and further more than 70 μm.

The ratio of the total thickness of the pressure-sensitive adhesive layer contained in the pressure-sensitive adhesive sheet to the total thickness of the pressure-sensitive adhesive sheet is not particularly limited. Here, the total thickness of the adhesive layer contained in the adhesive sheet means the total thickness of the adhesive layer provided on one surface of the substrate film and the adhesive layer provided on the other surface. In the case of a single-sided pressure-sensitive adhesive sheet in which a pressure-sensitive adhesive layer is provided only on one surface of a base film, the thickness of the pressure-sensitive adhesive layer provided on the other surface is 0, and the thickness of the pressure-sensitive adhesive layer provided on the one surface corresponds to the total thickness of the pressure-sensitive adhesive layers. The pressure-sensitive adhesive sheet disclosed herein can be implemented, for example, in such a manner that the total thickness of the pressure-sensitive adhesive layer accounts for 40% or more (preferably 50% or more, typically more than 50%, more preferably 60% or more, and still more preferably 70% or more) of the total thickness of the pressure-sensitive adhesive sheet. With such a configuration, even if the thickness of the pressure-sensitive adhesive sheet is smaller than the total thickness thereof, the sheet tends to exhibit impact resistance at a higher level. In one embodiment, the ratio of the total thickness of the pressure-sensitive adhesive layer to the total thickness of the pressure-sensitive adhesive sheet may be 75% or more, and more preferably 80% or more. The upper limit of the ratio of the total thickness of the pressure-sensitive adhesive layer to the total thickness of the pressure-sensitive adhesive sheet is not particularly limited, and is usually preferably 95% or less, and more preferably 90% or less.

The pressure-sensitive adhesive layer contained in the pressure-sensitive adhesive sheet disclosed herein has a thickness of more than 25 μm and a light transmittance of 0.6mm of 5% or less, and the perpendicular light transmittance of the pressure-sensitive adhesive layer is not particularly limited. The perpendicular light transmittance of the pressure-sensitive adhesive layer may be, for example, 10% or more, 15% or more, or 20% or more. The adhesive sheet disclosed herein may be preferably implemented in such a manner that the perpendicular light transmittance of the adhesive layer exceeds 25% (more preferably exceeds 30%). The upper limit of the vertical light transmittance of the pressure-sensitive adhesive layer is not particularly limited, and the light transmittance of the pressure-sensitive adhesive layer of 0.6mm may be 5% or less. By thus increasing the allowable limit value of the vertical light transmittance within a range satisfying 5% or less of the light transmittance of 0.6mm, the amount of the colorant required for adjusting to the vertical light transmittance can be reduced. This is preferable from the viewpoint of suppressing dispersion unevenness of the colorant (even color unevenness of the adhesive layer) and obtaining an adhesive sheet having good appearance quality. The vertical light transmittance of the adhesive layer can be measured in the same manner as the above-mentioned 0.6mm light transmittance of the adhesive layer, using the adhesive layer as a measurement sample.

The adhesive sheet disclosed herein preferably has a 180-degree peel strength of 3.0N/20mm or more. The pressure-sensitive adhesive sheet exhibiting the above characteristics tends to have a highly durable bond structure even when the pressure-sensitive adhesive sheet is narrow. The peel strength is preferably 3.5N/20mm or more, and more preferably 4.0N/20mm or more. The peel strength referred to herein means 180 degree peel strength (180 degree peel adhesion) with respect to the stainless steel plate.

The 180 degree peel strength can be measured as follows. Specifically, a sample obtained by cutting the pressure-sensitive adhesive sheet into pieces having a width of 20mm and a length of 100mm was subjected to pressure contact with the adhesive surface of a stainless steel plate (SUS304BA plate) by reciprocating a 2kg roller 1 time at 23 ℃ and 50% RH. After leaving in this environment for 30 minutes, the molded article was measured using a universal tensile compression tester according to JIS Z0237: 2000, the peel strength (N/20mm) was measured under the conditions of a tensile rate of 300 mm/min and a peel angle of 180 degrees. As the universal tensile compression tester, for example, "tensile compression tester, TG-1 kN" manufactured by Minebea Co., Ltd. The same measurement method is also used in the examples described below.

< use >

The pressure-sensitive adhesive sheet disclosed herein has good impact resistance even when it is narrow, and has excellent horizontal light-shielding properties. With such a feature, the adhesive sheet can be suitably used for, for example, an electronic device having a liquid crystal display device which requires predetermined optical characteristics. More specifically, in a liquid crystal display device including an LCD unit and a BL unit, it may be preferable to bond the LCD unit and the BL unit.

The adhesive sheet disclosed herein can be preferably used for bonding an LCD unit and the BL unit of a portable electronic device, for example. Non-limiting examples of such portable electronic devices include: a mobile phone, a smart phone, a tablet personal computer, a notebook personal computer, various wearable devices (e.g., a wrist-worn type such as a wristwatch, a modular type worn on a part of the body with a clip, a band, or the like, an eye-worn (eyewear) type including a glasses type (monocular type, binocular type, also including a helmet type), a clothing type attached to a shirt, a sock, a hat, or the like in the form of a decoration, an ear-worn type such as an earphone, or the like), a digital camera, a digital video camera, an audio device (e.g., a portable music player, a recording pen, or the like), a calculator (e.g., a desktop calculator), a portable game device, an electronic dictionary, an electronic organizer, an electronic book, an in-vehicle information device, a portable radio, a portable television, a portable printer, a portable scanner, a portable modem, or the like. It should be noted that "portable" in this specification is interpreted as being insufficient if it is merely portable, which means having a level of portability at which an individual (a standard adult) can move relatively easily.

The pressure-sensitive adhesive sheet disclosed herein can be used for bonding of an LCD unit and a BL unit and other bonding applications, for example, in the form of a bonding member processed into various shapes. Preferred examples of such a joining member include: has a narrow portion with a width of less than 2.0mm (e.g., less than 1.0 mm). The pressure-sensitive adhesive sheet disclosed herein has a pressure-sensitive adhesive layer having a thickness of more than 25 μm and a light transmittance of 0.6mm of 5% or less, and therefore can exhibit excellent performance (impact resistance, horizontal light-shielding property, etc.) even when used as a joining member having a shape (e.g., a frame shape) including such a narrow portion. In one embodiment, the width of the narrow portion may be 0.7mm or less, may be 0.5mm or less, or may be about 0.3mm or less. The lower limit of the width of the narrowed portion is not particularly limited, and is usually preferably 0.1mm or more (typically 0.2mm or more) from the viewpoint of workability of the adhesive sheet.

The narrow portion is typically linear. Here, linear means a concept including linear, curved, and polygonal (for example, L-shaped) shapes, as well as annular shapes such as frame shapes and circular shapes, and a composite shape or an intermediate shape thereof. The ring shape is not limited to a shape formed by a curved line, and includes a concept in which a part or all of the ring shape is formed in a straight line, such as a shape along the outer periphery of a square (frame shape) or a shape along the outer periphery of a fan shape. The length of the narrow portion is not particularly limited. For example, in the case where the length of the narrow portion is 10mm or more (typically 20mm or more, for example, 30mm or more), the effect of applying the technology disclosed herein can be exhibited as appropriate.

The pressure-sensitive adhesive sheet disclosed herein can be preferably used in a shape in which the width W of the pressure-sensitive adhesive layer at the narrowed portion is 50 times or less the thickness T of the pressure-sensitive adhesive layer. That is, the adhesive sheet can be used in a form of being stuck to an adherend in a shape in which the W/T value is preferably 50 or less (more preferably 40 or less, further preferably 30 or less, for example, 25 or less). In the case of a ring-shaped adhesive sheet for bonding an LCD cell and a BL cell of a liquid crystal display device, for example, when the adhesive sheet has an adhesive layer with high light transmittance, part of light emitted from the BL cell passes obliquely through the adhesive layer (reaches the LCD cell side) from the BL cell side end on the inner periphery of the adhesive layer to the LCD cell side end on the outer periphery of the adhesive layer. Such light obliquely transmitted through the adhesive layer to the LCD cell side is liable to cause disadvantages such as uneven brightness of the liquid crystal display surface. If the value of W/T is decreased, the proportion of light transmitted through the adhesive layer in the width direction to the LCD unit side obliquely to the adhesive layer tends to increase. Therefore, the significance of applying the technology disclosed herein to prevent or suppress light leakage in the width direction of the adhesive sheet increases.

The matters disclosed in this specification include the following.

(1) An adhesive sheet comprising a base film and an adhesive layer disposed on at least one surface of the base film,

the adhesive layer contains a colorant in the adhesive layer,

the adhesive layer has a thickness of more than 25 [ mu ] m and a light transmittance of 5% or less at 0.6 mm.

(2) The adhesive sheet according to the item (1), wherein all of the layers constituting the adhesive sheet have a light transmittance of 5% or less at 0.6mm, the light transmittance being greater than 25 μm.

(3) The adhesive sheet according to the above (1) or (2), wherein the total thickness of the adhesive layer contained in the adhesive sheet exceeds 50% of the total thickness of the adhesive sheet.

(4) The adhesive sheet according to any one of the above (1) to (3), wherein the adhesive sheet has a vertical light transmittance of 1% or less.

(5) The adhesive sheet according to any one of the above (1) to (4), wherein the perpendicular light transmittance of the adhesive layer is higher than 25%.

(6) The adhesive sheet according to any one of the above (1) to (5), wherein the adhesive sheet has a narrow portion having a width of less than 2.0 mm.

(7) The adhesive sheet according to the item (6), wherein the width of the adhesive layer at the narrowed portion is 50 times or less the thickness of the adhesive layer.

(8) The adhesive sheet according to any one of the above (1) to (7), which is a double-sided adhesive sheet comprising a1 st adhesive layer disposed on one surface of the base film and a2 nd adhesive layer disposed on the other surface of the base film,

the thickness of each of the 1 st adhesive layer and the 2 nd adhesive layer is larger than 25 μm, and the light transmittance at 0.6mm is 5% or less.

(9) The adhesive sheet according to any one of the above (1) to (8), wherein the LCD unit and the BL unit are bonded to each other in a liquid crystal display device including the LCD unit and the BL unit.

(10) The adhesive sheet according to any one of the above (1) to (9), wherein the adhesive layer is an acrylic adhesive layer containing an acrylic polymer.

(11) The adhesive sheet according to any one of the above (1) to (10), wherein the adhesive layer contains an acrylic polymer at a ratio of more than 50% by weight of a polymer component contained in the adhesive layer,

the acrylic polymer contains an alkyl (meth) acrylate represented by formula (1) as a monomer component at a ratio of 70 wt% or more:

CH₂＝C(R¹)COOR² (1)

(R in the above formula (1))¹Is a hydrogen atom or a methyl group. Furthermore, R²Is a chain alkyl group having 1 to 20 carbon atoms. ).

(12) The adhesive sheet according to the item (11), wherein the acrylic polymer further contains a functional group-containing monomer as the monomer component,

the functional group-containing monomer is at least 1 selected from the group consisting of acrylic acid, methacrylic acid, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate.

(13) The adhesive sheet according to any one of the items (10) to (12), wherein the adhesive layer contains a terpene-phenol resin having a softening point of 135 ℃ or higher in an amount of 20 to 60 parts by weight based on 100 parts by weight of the acrylic polymer.

(14) The adhesive sheet according to any one of the above (1) to (13), wherein the colorant contains carbon black as a black colorant.

(15) The adhesive sheet according to any one of the above (1) to (14), wherein the content of the colorant in the adhesive layer is 0.3 wt% or more and less than 3.0 wt%.

(16) An adhesive sheet having double-sided adhesiveness for bonding an LCD unit and a BL unit in a liquid crystal display device having the LCD unit and the BL unit, comprising:

a base material film,

A1 st pressure-sensitive adhesive layer disposed on one surface of the base film, and

a2 nd adhesive layer disposed on the other surface of the base film,

the base film has a thickness of more than 25 μm and a light transmittance of 5% or less at 0.6mm, or has a thickness of 25 μm or less,

the thickness of the 1 st adhesive layer and the 2 nd adhesive layer is more than 25 μm, and the light transmittance of 0.6mm is less than 5%,

the adhesive sheet has a vertical light transmittance of 1% or less,

the total thickness of the 1 st adhesive layer and the 2 nd adhesive layer is more than 50% of the total thickness of the adhesive sheet,

at least one of the 1 st pressure-sensitive adhesive layer and the 2 nd pressure-sensitive adhesive layer is an acrylic pressure-sensitive adhesive layer containing an acrylic polymer in a proportion exceeding 50% by weight of a polymer component contained in the pressure-sensitive adhesive layer,

the acrylic pressure-sensitive adhesive layer contains 0.3 wt% or more and less than 3.0 wt% of carbon black.

Examples

The present invention will be described below with reference to a few examples, but the present invention is not limited to these examples. In the following description, "part" and "%" are based on weight unless otherwise specified.

< example 1>

92 parts of BA, 5 parts of vinyl acetate, 2.9 parts of AA, 0.1 part of 2-hydroxyethyl acrylate, and 30 parts of ethyl acetate and 120 parts of toluene as polymerization solvents were put into a reaction vessel equipped with a stirrer, a thermometer, a nitrogen inlet, a reflux condenser, and a dropping funnel, and stirred for 2 hours while introducing nitrogen. After the oxygen in the polymerization system was removed in this manner, 0.2 part of AIBN as a polymerization initiator was added and solution polymerization was carried out at 60 ℃ for 6 hours to obtain an acrylic polymer solution. The Mw of the acrylic polymer is about 50X 10⁴。

To 100 parts of the acrylic polymer contained in the acrylic polymer solution were added 10 parts of a rosin resin A (a polymerized rosin ESTER, trade name "PENSEL D-125", softening point 120-130 ℃, manufactured by Mikania chemical Co., Ltd.), 10 parts of a rosin resin B (a disproportionated rosin ESTER, trade name "SUPER ESTER A-100", softening point 95-105 ℃, manufactured by Mikania chemical Co., Ltd.), and 15 parts of a terpene phenol resin (trade name "TAMANOL 803L", softening point 145-160 ℃, manufactured by Mikania chemical Co., Ltd.) as a tackifier resin, and 2 parts of a carbon black dispersion (trade name "N-DYM 8715 black", manufactured by Dai Nippon Kogyo Co., Ltd.) and 2 parts of an isocyanate-based crosslinking agent (trade name "CORONATE L", manufactured by Nippon polyurethane Kogyo Co., Ltd., solid content 75%) to obtain an adhesive composition A1. This pressure-sensitive adhesive composition A1 contained 2 parts of carbon black as a colorant per 100 parts of the acrylic polymer.

As the release liner, 2 sheets of polyester charging films (trade name "DIAFOIL MRF", thickness 38 μm, manufactured by mitsubishi polyester corporation) each having one side thereof treated as a release surface were prepared. The release surface of each of these release liners was coated with the adhesive composition a1 so that the thickness after drying was 28 μm, and dried at 100 ℃ for 2 minutes. In this manner, adhesive layers were formed on the release surfaces of the 2 release liners, respectively.

As the base film, a base film having a total thickness of about 10 μm, which was formed from a transparent PET film (trade name "Lumirror", manufactured by Toray corporation) having a thickness of 4.5 μm and a black printed layer (colored layer) provided on the 2 nd surface of the PET film (base film), was prepared. The black printed layer is formed by printing by a gravure printing method using an ink composition containing a black colorant. The pressure-sensitive adhesive layers formed on the 2 release liners were adhered to the 1 st surface (the 1 st surface of the base film) and the 2 nd surface (the surface of the colored layer) of the base film, respectively, to obtain the pressure-sensitive adhesive sheet of this example (transfer method). The release liner is left directly on the adhesive layer for protecting the surface (adhesive surface) of the adhesive layer.

< example 2>

In this example, a substrate film having a total thickness of about 30 μm, which was formed from a transparent PET film (trade name "Lumirror", manufactured by Toray corporation) having a thickness of 25 μm and a black printed layer (colored layer) provided on the 2 nd surface of the PET film in the same manner as in example 1, was used as the substrate film. The amount of the adhesive composition A1 applied to the release film was adjusted so that the thickness after drying was 36 μm. Otherwise, the procedure was carried out in the same manner as in the preparation of the pressure-sensitive adhesive sheet of example 1 to obtain a pressure-sensitive adhesive sheet of this example.

< example 3>

In this example, a substrate film having a total thickness of about 45 μm, which was formed of a 38 μm thick PET film (trade name "Lumiror", manufactured by Toray corporation) obtained by kneading a white pigment, and a printing layer (coloring layer) provided on the 2 nd surface of the PET film in this order of white, silver, and black, was used as the substrate film. The amount of the adhesive composition A1 applied to the release film was adjusted so that the thickness after drying was 30 μm. The pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition a1 was adhered only to the 1 st surface of the base film. Otherwise, the procedure was carried out in the same manner as in the preparation of the pressure-sensitive adhesive sheet of example 1 to obtain a pressure-sensitive adhesive sheet (single-sided pressure-sensitive adhesive sheet) of this example.

< example 4>

95 parts of BA and 5 parts of AA as monomer components and 150 parts of toluene as a polymerization solvent were put into a reaction vessel equipped with a stirrer, a thermometer, a nitrogen introduction tube, a reflux condenser and a dropping funnel, and stirred for 2 hours while introducing nitrogen. After the oxygen in the polymerization system was removed in this manner, 0.2 part of benzoyl peroxide as a polymerization initiator was added thereto, and solution polymerization was carried out at 60 ℃ for 6 hours to obtain an acrylic polymer solution. The acrylic polymer has a Mw of about 60X 10⁴。

To the acrylic polymer solution, 10 parts of a terpene-phenol resin (trade name "YS polymer S-145", softening point about 145 ℃, YASUHARA chemcal co., ltd., manufactured) and 30 parts of a terpene-phenol resin (trade name "TAMANOL 803L", softening point 145 to 160 ℃, manufactured by seikagawa CHEMICAL co., ltd.) as tackifier resins, and 2 parts of the carbon black dispersion (containing carbon black as a colorant) (2 parts.), an isocyanate-based crosslinking agent (trade name "CORONATE L", manufactured by japan polyurethane industries, ltd., 75%) and 0.03 part of an epoxy-based crosslinking agent (trade name "TETRAD-C", manufactured by mitsubishi gas CHEMICAL corporation) were added and mixed with stirring to 100 parts of the acrylic polymer contained in the solution to obtain a pressure-sensitive adhesive composition a 2.

As the base film, a 75 μm thick PET film (trade name "Lumiror", manufactured by Toray corporation) kneaded with a black pigment was used. The amount of the adhesive composition A2 applied to the release film was adjusted so that the thickness after drying was 38 μm. Otherwise, the procedure was carried out in the same manner as in the preparation of the pressure-sensitive adhesive sheet of example 1 to obtain a pressure-sensitive adhesive sheet of this example.

< example 5>

A colorant-free adhesive composition a0 was obtained in the same manner as in the preparation of the adhesive composition a1, except that the carbon black dispersion was not added.

As the base film, a transparent PET film (trade name "Lumirror", manufactured by Toray corporation) having a thickness of 12 μm was used. The amount of the adhesive composition A0 applied to the release film was adjusted so that the thickness after drying was 19 μm. Otherwise, the procedure was carried out in the same manner as in the preparation of the pressure-sensitive adhesive sheet of example 1 to obtain a pressure-sensitive adhesive sheet of this example.

< example 6>

70 parts of BA, 27 parts of 2EHA, and AA3 parts of monomer components, 0.05 part of 4-hydroxybutyl acrylate, and 135 parts of toluene as a polymerization solvent were put into a reaction vessel equipped with a stirrer, a thermometer, a nitrogen introduction tube, a reflux condenser, and a dropping funnel, and stirred for 2 hours while introducing nitrogen. After the oxygen in the polymerization system was removed in this manner, 0.1 part of AIBN as a polymerization initiator was added, and solution polymerization was carried out at 60 ℃ for 6 hours to obtain a toluene solution of an acrylic polymer. The Mw of the acrylic polymer A was about 40X 10⁴。

To 100 parts of the acrylic polymer contained in the toluene solution were added 30 parts of a rosin resin A (a polymerized rosin ester, trade name "PENSEL D-125", softening point 120 to 130 ℃ C., manufactured by Mitsuwa chemical Co., Ltd.) and 2 parts of an isocyanate crosslinking agent (trade name "CORONATE L", manufactured by Nippon polyurethane industries, Ltd., solid content 75%) as tackifier resins to obtain an acrylic pressure-sensitive adhesive composition A3.

As the base film, a transparent PET film (trade name "Lumirror", manufactured by Toray corporation) having a thickness of 25 μm was used. The amount of the adhesive composition A3 applied to the release film was adjusted so that the thickness after drying was 38 μm. Otherwise, the procedure was carried out in the same manner as in the preparation of the pressure-sensitive adhesive sheet of example 1 to obtain a pressure-sensitive adhesive sheet of this example.

< example 7>

In example 3, adhesive composition A3 was used in place of adhesive composition a 1. The amount of the adhesive composition A3 applied to the release film was adjusted so that the thickness after drying was 20 μm. As the base film, a base film having a total thickness of about 20 μm, which was formed of a PET film (trade name "Lumiror", manufactured by Toray corporation) having a thickness of 13 μm and obtained by kneading a white pigment, and a printing layer (coloring layer) provided on the 2 nd surface of the PET film in this order of white, silver and black, was used. Otherwise, the procedure was carried out in the same manner as in the preparation of the pressure-sensitive adhesive sheet of example 3 to obtain a pressure-sensitive adhesive sheet (single-sided pressure-sensitive adhesive sheet) of this example.

< example 8>

In this example, a base film having a total thickness of about 17 μm, which was formed from a transparent PET film (trade name "Lumirror", manufactured by Toray corporation) having a thickness of 12 μm and a black printed layer (colored layer) provided on the 2 nd surface of the PET film in the same manner as in example 1, was used as the base film. The amount of the adhesive composition A3 applied to the release film was adjusted so that the thickness after drying was 17 μm. Otherwise, the procedure of example 6 was repeated to obtain a pressure-sensitive adhesive sheet of this example.

< example 9>

In example 2, adhesive composition A3 was used in place of adhesive composition a 1. Otherwise, the procedure of example 2 was repeated to obtain a pressure-sensitive adhesive sheet of this example.

< example 10>

Adhesive layers having a thickness of 20 μm formed from adhesive composition A3 were attached to the 1 st and 2 nd surfaces of the same base film used in example 7. Otherwise, the procedure of example 6 was repeated to obtain a pressure-sensitive adhesive sheet of this example.

[ evaluation ]

For the adhesive sheets of the respective examples, the 0.6mm light transmittance (%) of the adhesive layer, the vertical light transmittance (%) of the adhesive sheet, and the impact resistance were measured or evaluated. The reflectance (%) of the 2 nd side of the pressure-sensitive adhesive sheets of examples 3 and 7 was also measured.

The impact resistance was evaluated for the adhesive sheets of examples 1,2, 4 to 6 and 8 to 10 as follows.

That is, the adhesive sheets of the examples were processed into a frame shape having an outer periphery of 40mm in width, 60mm in length, and 1mm in width. The release liner covering one adhesive surface of the frame-shaped adhesive sheet was peeled off, and the exposed adhesive surface was pressure-bonded to a stainless steel plate (SUS304BA plate) having a transverse length of 60mm, a longitudinal length of 80mm, and a thickness of 1mm by reciprocating a 2kg roller 1 time. Immediately thereafter, the release liner covering the other adhesive surface was peeled off, and an acrylic resin sheet having a width of 40mm, a length of 60mm and a thickness of 2mm was placed on the exposed adhesive surface, and pressure-bonding was carried out by applying a load of 50N from the acrylic sheet side for 10 seconds. The sample was aged at 23 ℃ and 50% RH for 24 hours to obtain a product.

By freely dropping the above-described sample for evaluation from a height of 1m and applying an impact to the sample, the presence or absence of peeling between the adhesive sheet and the stainless steel plate and between the adhesive sheet and the acrylic resin plate was visually confirmed. When no peeling was observed, the sample was allowed to fall freely again from a height of 1m, and the presence or absence of peeling was similarly observed. This drop test was repeated up to a maximum of 40 times and the number of times until peeling occurred was recorded. From the results, the impact resistance was evaluated as E (Excellent) in which no peeling was observed even after 40 drops, G (Good) in which peeling was observed 31 to 40 times, a (Acceptable) in which peeling was observed 21 to 30 times, and P (Poor) in which peeling was observed 20 times or less.

The results obtained are shown in tables 1 and 2 together with the schematic structure of the psa sheet of each example.

[ Table 1]

[ Table 2]

From the results shown in tables 1 and 2, it is clear that the pressure-sensitive adhesive sheets of examples 1,2 and 4 having a pressure-sensitive adhesive layer thicker than 25 μm all exhibited good bonding durability against drop impact even when the pressure-sensitive adhesive sheets were narrow. Further, it is found that the adhesive sheets of examples 1 to 4 each have a light transmittance of 5% or less (specifically, less than 0.1%) at 0.6mm in the adhesive layer, and exhibit a high level of light-shielding property even when the thickness is small.

On the other hand, the pressure-sensitive adhesive sheets of examples 5, 8 and 10 having a pressure-sensitive adhesive layer thickness of 25 μm or less tend to have inferior impact resistance to the pressure-sensitive adhesive sheets of examples 1,2 and 4. Further, it was confirmed that the adhesive sheets of examples 5 to 10 each had a high 0.6mm light transmittance of the adhesive layer, and thus had lower horizontal light-shielding properties than those of examples 1 to 4, and in particular, examples 6 and 9 having an adhesive layer thickness of more than 25 μm were poor in horizontal light-shielding properties.

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 techniques described in the claims include various modifications and alterations to the specific examples illustrated above.

Claims (20)

1. An adhesive sheet comprising a base film and an adhesive layer disposed on at least one surface of the base film,

the adhesive layer contains a colorant in the adhesive layer,

the adhesive layer has a thickness of more than 25 μm and a light transmittance at a length of 0.6mm of 5% or less,

the pressure-sensitive adhesive layer is formed from a solvent-based pressure-sensitive adhesive composition, a hot-melt pressure-sensitive adhesive composition, or an active energy ray-curable pressure-sensitive adhesive composition, the pressure-sensitive adhesive layer contains an acrylic polymer, the pressure-sensitive adhesive composition used for forming the pressure-sensitive adhesive layer contains an isocyanate-based crosslinking agent as a crosslinking agent, and the amount of the crosslinking agent is 2 parts by weight or more and 10 parts by weight or less based on 100 parts by weight of the acrylic polymer,

the base film contains a resin film as a base film, the resin film being a polyethylene terephthalate film,

the adhesive sheet has a narrow portion having a width of less than 2.0mm,

the width of the adhesive layer at the narrow portion is 50 times or less the thickness of the adhesive layer,

the thickness of the base material film is 38 [ mu ] m or less,

the total thickness of the adhesive sheet is 150 [ mu ] m or less.

2. The adhesive sheet according to claim 1, wherein each of the layers constituting the adhesive sheet, which have a thickness of more than 25 μm, has a light transmittance of 5% or less at a length of 0.6 mm.

3. The adhesive sheet according to claim 1 or 2, wherein the total thickness of the adhesive layer contained in the adhesive sheet exceeds 50% of the total thickness of the adhesive sheet.

4. The adhesive sheet according to claim 1 or 2, wherein the adhesive sheet has a vertical light transmittance of 1% or less.

5. The adhesive sheet according to claim 1 or 2, wherein the perpendicular light transmittance of the adhesive layer is higher than 25%.

6. The adhesive sheet according to claim 1 or 2, wherein the adhesive sheet is configured as a double-sided adhesive sheet comprising a1 st adhesive layer disposed on one surface of the base film and a2 nd adhesive layer disposed on the other surface of the base film,

the 1 st adhesive layer and the 2 nd adhesive layer each have a thickness of more than 25 μm and a light transmittance at a length of 0.6mm of 5% or less.

7. The adhesive sheet according to claim 1 or 2, wherein the adhesive layer is an acrylic adhesive layer containing an acrylic polymer.

8. The adhesive sheet according to claim 7, wherein the adhesive layer contains the acrylic polymer in a proportion of more than 50% by weight of a polymer component contained in the adhesive layer,

the acrylic polymer contains an alkyl (meth) acrylate represented by the formula (1) as a monomer component at a ratio of 70 wt% or more:

CH₂＝C(R¹)COOR² (1)

r in the formula (1)¹Is a hydrogen atom or a methyl group; furthermore, R²Is a chain alkyl group having 1 to 20 carbon atoms.

9. The adhesive sheet according to claim 8, wherein the acrylic polymer further contains a functional group-containing monomer as the monomer component,

the functional group-containing monomer is at least 1 selected from the group consisting of acrylic acid, methacrylic acid, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate.

10. The adhesive sheet according to claim 7, wherein the adhesive composition for forming the adhesive layer contains an isocyanate-based crosslinking agent and at least one crosslinking agent selected from the group consisting of an epoxy-based crosslinking agent, an oxazoline-based crosslinking agent, an aziridine-based crosslinking agent, a melamine-based crosslinking agent, a peroxide-based crosslinking agent, a urea-based crosslinking agent, a metal alkoxide-based crosslinking agent, a metal chelate-based crosslinking agent, a metal salt-based crosslinking agent, a carbodiimide-based crosslinking agent, and an amine-based crosslinking agent.

11. The adhesive sheet according to claim 10, wherein the adhesive composition for forming the adhesive layer contains an isocyanate-based crosslinking agent and an epoxy-based crosslinking agent in combination.

12. The adhesive sheet according to claim 7, wherein the adhesive layer contains at least one tackifier resin selected from the group consisting of rosin-based tackifier resins, terpene-based tackifier resins, hydrocarbon-based tackifier resins, epoxy-based tackifier resins, polyamide-based tackifier resins, elastomer-based tackifier resins, phenol-based tackifier resins, and ketone-based tackifier resins.

13. The adhesive sheet according to claim 12, wherein the adhesive layer contains a rosin-based tackifying resin and a terpene phenol resin in a weight ratio of 5/95 to 95/5.

14. The adhesive sheet according to claim 12 or 13, wherein the adhesive layer contains 20 to 60 parts by weight of a terpene-phenol resin having a softening point of 135 ℃ or higher, based on 100 parts by weight of the acrylic polymer.

15. The adhesive sheet according to claim 12 or 13, wherein the adhesive layer combination comprises a tackifying resin T having a hydroxyl value of more than 50mgKOH/g_H1And hydroxyl value and the tackifying resin T_H1Tackifier resins T differing by 5mgKOH/g or more_H2。

16. The adhesive sheet according to claim 12 or 13, wherein the adhesive layer combination comprises a tackifying resin T having a hydroxyl value of more than 50mgKOH/g_H1And tackifying resin T with acid value higher than 20mgKOH/g_A1。

17. The adhesive sheet according to claim 1 or 2, wherein the colorant contains carbon black as a black colorant.

18. The adhesive sheet according to claim 17, wherein the content of the colorant in the adhesive layer is 0.3 wt% or more and less than 3.0 wt%.

19. The adhesive sheet according to claim 1 or 2, which is used for bonding a liquid crystal display module unit and a backlight unit in a liquid crystal display device provided with the liquid crystal display module unit and the backlight unit.

20. An adhesive sheet for bonding double-sided adhesiveness between a liquid crystal display module unit and a backlight unit in a liquid crystal display device including the liquid crystal display module unit and the backlight unit, comprising:

a base material film,

A1 st adhesive layer disposed on one surface of the base film, and

a2 nd adhesive layer disposed on the other surface of the base film,

the base film contains a resin film as a base film, the resin film being a polyethylene terephthalate film,

the pressure-sensitive adhesive layer is formed from a solvent-based pressure-sensitive adhesive composition, a hot-melt pressure-sensitive adhesive composition, or an active energy ray-curable pressure-sensitive adhesive composition, the pressure-sensitive adhesive layer contains an acrylic polymer, the pressure-sensitive adhesive composition used for forming the pressure-sensitive adhesive layer contains an isocyanate-based crosslinking agent as a crosslinking agent, and the amount of the crosslinking agent is 2 parts by weight or more and 10 parts by weight or less based on 100 parts by weight of the acrylic polymer,

the substrate film has a thickness of more than 25 μm and a light transmittance of 0.6mm of 5% or less, or has a thickness of 25 μm or less, and each of the 1 st adhesive layer and the 2 nd adhesive layer has a thickness of more than 25 μm and a light transmittance of 0.6mm of 5% or less,

the adhesive sheet has a vertical light transmittance of 1% or less,

the total thickness of the 1 st adhesive layer and the 2 nd adhesive layer is greater than 50% of the total thickness of the adhesive sheet,

at least one of the 1 st adhesive layer and the 2 nd adhesive layer is an acrylic adhesive layer containing an acrylic polymer at a ratio exceeding 50% by weight of a polymer component contained in the adhesive layer,

the acrylic pressure-sensitive adhesive layer contains 0.3 wt% or more and less than 3.0 wt% of carbon black,

the adhesive sheet has a narrow portion having a width of less than 2.0mm,

the width of the adhesive layer at the narrow portion is 50 times or less the thickness of the adhesive layer,

the thickness of the base material film is 38 [ mu ] m or less,

the total thickness of the adhesive sheet is 150 [ mu ] m or less.

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