Adhesive sheet for bonding optical member

Abstract

To provide an adhesive sheet for bonding an optical member in which discoloration is suppressed even if a weathering test using a metal halide lamp is performed in environment containing much water.SOLUTION: An adhesive sheet contains an acrylic resin and a colorant, wherein a change amount ΔL* of L* obtained by subtracting brightness L* in an L*a*b* color space of the adhesive sheet before a weathering test for 24 hours of the total of 20 hours in a bright condition and 4 hours in a dark condition is performed by a method according to JIS K 7350-1 and JIS K 7350-2 using a metering weather meter including a metal halide lamp, from brightness L* of the adhesive sheet after the weathering test is performed is 2.5 or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a pressure-sensitive adhesive sheet for attaching optical members. [Background technology]

[0002] Adhesive sheets are adhesive sheets used to bond multiple components together. Adhesive sheets that are particularly transparent and suitable for bonding optical components are also called optically clear adhesive (OCA) sheets.

[0003] Patent Document 1 discloses an adhesive sheet for attaching transparent members, which contains an acrylic polymer and a colorant, and when the adhesive sheet for attaching transparent members is sandwiched between two glass plates and stored in an environment of 85°C and a relative humidity of 85% for 500 hours, the change in total light transmittance is less than 2%. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2021 / 167010 Summary of the Invention [Problem to be solved by the invention]

[0005] There has been a demand for pressure-sensitive adhesive sheets for bonding optical components that have optical transparency while adjusting transmittance. However, according to the inventors' studies, when a colorant is added to a pressure-sensitive adhesive sheet, the color may fade or disappear when exposed to ultraviolet light or the like. Furthermore, when a pressure-sensitive adhesive sheet is used to bond two optical components, moisture may penetrate from the edges, causing discoloration of the pressure-sensitive adhesive sheet. According to the inventors' studies, it has been found that the discoloration of the pressure-sensitive adhesive sheet is accelerated particularly when the pressure-sensitive adhesive sheet is exposed to moisture and subjected to a weather resistance test using a metal halide lamp with a high acceleration factor.

[0006] The present disclosure has been made in consideration of the above-mentioned current situation, and aims to provide an adhesive sheet for attaching optical components that suppresses discoloration even when subjected to a weather resistance test using a metal halide lamp in a moisture-rich environment. [Means for solving the problem]

[0007] (1) One embodiment of the present invention is an adhesive sheet for laminating optical components, which comprises an acrylic resin and a colorant, and after a weather resistance test is conducted in accordance with JIS K 7350-1 and JIS K 7350-2 using a metaling weather meter equipped with a metal halide lamp for 20 hours under the following light conditions and 4 hours under the following dark conditions for a total of 24 hours, the change in L* ΔL* obtained by subtracting the lightness L* of the adhesive sheet before the weather resistance test from the lightness L* in the L*a*b* color space of the adhesive sheet is 2.5 or less. <Testing machine> Product name: Metaling Weather Meter Model: M6T Light source: Metal halide lamp (horizontal metering lamp 6Kw) Inner filter: Quartz Outer filter: #275 Sample surface filter: #255 <Test conditions> Bright conditions Illuminance: 1.2kW / m 2 Irradiation time: 20 hours Black panel temperature: 53℃ Relative humidity: 40% Rainfall: 10 seconds every 15 minutes Dark conditions No irradiation, no rain Tank temperature: 53℃ Relative humidity: 95%

[0008] (2) One embodiment of the present invention is a pressure-sensitive adhesive sheet comprising, in addition to the configuration of (1) above, a first pressure-sensitive adhesive layer, an intermediate resin layer, and a second pressure-sensitive adhesive layer, wherein at least one of the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer contains the acrylic resin and the colorant.

[0009] (3) One embodiment of the present invention is a pressure-sensitive adhesive sheet having the configuration of (1) or (2) above, wherein the intermediate resin layer is a polyurethane layer containing polyurethane.

[0010] (4) One embodiment of the present invention is a pressure-sensitive adhesive sheet having the configuration of (3) above, wherein the polyurethane layer is a cured product of a thermosetting polyurethane composition containing a polyol component and a polyisocyanate component.

[0011] (5) One embodiment of the present invention is a pressure-sensitive adhesive sheet for attaching optical members, which has the configuration of any one of (1) to (4) above, and in addition, the colorant includes a carbon-based colorant or a compound containing a perylene structure.

[0012] (6) One embodiment of the present invention is a pressure-sensitive adhesive sheet for adhering optical components, which has the configuration of any one of (1) to (5) above, and in which the change in b* Δb* obtained by subtracting the b* of the pressure-sensitive adhesive sheet before the weather resistance test from the b* in the L*a*b* color space of the pressure-sensitive adhesive sheet after the weather resistance test is 1.0 or less.

[0013] (7) One embodiment of the present invention is a pressure-sensitive adhesive sheet for attaching optical components, which has the configuration of any one of (1) to (6) above, and in which the change in total light transmittance, calculated by subtracting the total light transmittance of the pressure-sensitive adhesive sheet before the weather resistance test from the total light transmittance of the pressure-sensitive adhesive sheet after the weather resistance test, is 5% or less.

[0014] (8) One embodiment of the present invention is a pressure-sensitive adhesive sheet for attaching optical members, which has the configuration of any one of the above (1) to (7) and also has a total light transmittance of 30% or more and 80% or less. [Effects of the Invention]

[0015] According to the present disclosure, it is possible to provide a pressure-sensitive adhesive sheet that exhibits reduced discoloration even when subjected to a weather resistance test using a metal halide lamp in a moisture-rich environment. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a cross-sectional view schematically showing an example of a pressure-sensitive adhesive sheet for applying optical members according to embodiment 1. FIG. [Figure 2] FIG. 3 is a cross-sectional view that schematically shows an example of a pressure-sensitive adhesive sheet for applying optical members according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0017] (Embodiment 1) Fig. 1 is a cross-sectional view schematically showing an example of an adhesive sheet for bonding optical members according to embodiment 1. As shown in Fig. 1, an adhesive sheet for bonding optical members 10 according to embodiment 1 (hereinafter also simply referred to as an adhesive sheet) contains an acrylic resin and a colorant. By including a colorant in the adhesive sheet 10, transmittance is reduced, and when the adhesive sheet 10 is used to bond a display panel to another optical member such as a cover panel or a touch panel, the boundary between the frame region of the display panel and the display screen can be made less noticeable when the display panel is not lit.

[0018] The pressure-sensitive adhesive sheet 10 is an acrylic pressure-sensitive adhesive layer containing an acrylic resin as the resin component. The acrylic pressure-sensitive adhesive layer is preferably formed by curing an acrylic resin composition. Examples of the acrylic resin composition include those containing an acrylic resin and a crosslinking agent.

[0019] Examples of the acrylic resin include (meth)acrylic acid ester polymers and copolymers thereof (hereinafter also referred to as (meth)acrylic copolymers).

[0020] The (meth)acrylic copolymer may be, for example, a copolymer of a (meth)acrylic acid alkyl ester and a carboxyl group-containing monomer.

[0021] The (meth)acrylic acid alkyl ester may be a (meth)acrylic acid alkyl ester (CH2=CR 1 -COOR 2 ;R 1 is a hydrogen atom or a methyl group, and R2 is an alkyl group having 1 to 18 carbon atoms), and the alkyl group preferably has 4 to 12 carbon atoms.

[0022] Examples of (meth)acrylic acid alkyl esters having an alkyl group of 1 to 18 carbon atoms include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undeca(meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, and isostearyl (meth)acrylate. These may be used alone or in combination of two or more.

[0023] Examples of the carboxyl group-containing monomer include carboxyl group-containing (meth)acrylates such as β-carboxyethyl (meth)acrylate, 5-carboxypentyl (meth)acrylate, succinic acid mono(meth)acryloyloxyethyl ester, and ω-carboxypolycaprolactone mono(meth)acrylate; acrylic acid, methacrylic acid, itaconic acid, crotonic acid, fumaric acid, and maleic acid. These may be used alone or in combination of two or more.

[0024] The crosslinking agent may be, for example, a component capable of undergoing a crosslinking reaction with the crosslinkable functional group derived from the crosslinkable functional group-containing monomer possessed by the (meth)acrylic copolymer, and specific examples thereof include isocyanate compounds, metal chelate compounds, epoxy compounds, etc. The crosslinking agents may be used alone or in combination of two or more.

[0025] The colorant is added for the purpose of reducing the total light transmittance of the resin layer to which the colorant is added. It is preferable that the colorant reduces the transmittance in the visible light region (wavelengths of 380 to 780 nm). The colorant may be any color; however, when the pressure-sensitive adhesive sheet 10 is used to bond optical components such as display panels, it is preferable to use a black colorant, which is an achromatic color, in order to minimize the effect on the color tone of the displayed image when the display panel is turned on and to achieve harmony between the display screen and the frame region when the display panel is turned off.

[0026] Examples of the colorant include a carbon-based raw material and a perylene-based pigment containing a compound containing a perylene structure. Examples of the carbon-based raw material include those containing carbon black, graphite, etc. Examples of the perylene-based pigment include NPFT-81295 manufactured by Nippon Pigment Co., Ltd. When a carbon-based raw material and a perylene-based pigment containing a compound containing a perylene structure are used as the colorant, fading in a weather resistance test using a metal halide lamp can be suppressed even without containing an ultraviolet absorber.

[0027] The content of the colorant relative to 100 parts by mass of the acrylic resin is preferably 0.1 to 0.6 parts by mass, more preferably 0.15 to 0.40 parts by mass, and even more preferably 0.2 to 0.3 parts by mass.

[0028] The pressure-sensitive adhesive sheet 10 may contain an ultraviolet absorber, but does not need to contain an ultraviolet absorber because the use of a specific colorant can suppress fading during a weather resistance test using a metal halide lamp even without the inclusion of an ultraviolet absorber. If the pressure-sensitive adhesive sheet 10 contains an ultraviolet absorber, the content of the ultraviolet absorber is preferably 3.0 parts by mass or less, and more preferably 1.8 parts by mass or less, per 100 parts by mass of the acrylic resin. From the perspective of suppressing haze, the content of the ultraviolet absorber is preferably 1 part by mass or less, and more preferably no ultraviolet absorber is contained, per 100 parts by mass of the acrylic resin.

[0029] Examples of ultraviolet absorbers include benzotriazole-based ultraviolet absorbers, benzophenone-based ultraviolet absorbers, and triazine-based ultraviolet absorbers. Examples of benzotriazole-based ultraviolet absorbers include ADK STAB LA-29, LA-24, LA-31RG, LA-32, and LA-36 manufactured by ADEKA CORPORATION, and JF79 manufactured by Johoku Chemical Co., Ltd. Examples of benzophenone-based ultraviolet absorbers include ADK STAB 1413 manufactured by ADEKA CORPORATION, and CYASORB UV24 manufactured by Solvay Japan. Examples of triazine-based ultraviolet absorbers include ADK STAB LA-46 and LA-F70 manufactured by ADEKA CORPORATION, and Tinuvin 1600 manufactured by BASF Japan.

[0030] The thickness of the pressure-sensitive adhesive sheet 10 is preferably 10 μm or more and 100 μm or less. If the thickness is less than 10 μm, sufficient adhesive strength may not be obtained. On the other hand, if the thickness exceeds 100 μm, the pressure-sensitive adhesive sheet 10 may not be flexible enough to deform and follow steps present on the surface of the adherend to which it is attached (step-following ability). Furthermore, when the pressure-sensitive adhesive sheet 10 is used to bond substrates with different elasticity in response to environmental changes, such as bonding a glass substrate and a resin substrate, the pressure-sensitive adhesive sheet 10 may not be able to follow dimensional changes in the substrates in response to environmental changes, resulting in peeling. The thickness of the pressure-sensitive adhesive sheet 10 is more preferably 20 μm or more and 80 μm or less. In consideration of flexibility, a thickness of 25 μm or more and 50 μm or less is even more preferable.

[0031] The method for producing the pressure-sensitive adhesive sheet 10 is not particularly limited, and may involve, for example, applying the pressure-sensitive adhesive composition to a film using a general-purpose film-forming device or method such as a coating device, bar coater, doctor blade, etc. Alternatively, the pressure-sensitive adhesive sheet 10 may be produced using a centrifugal molding method.

[0032] A release film may be attached to each side of the pressure-sensitive adhesive sheet 10. The release film can protect both sides of the pressure-sensitive adhesive sheet 10 until just before it is attached to the adherend, preventing a decrease in adhesiveness and the adhesion of foreign matter. It also prevents the pressure-sensitive adhesive sheet 10 from sticking to anything other than the adherend, improving handleability.

[0033] The release film may be, for example, a PET film, etc. The surface of the release film that comes into contact with the pressure-sensitive adhesive sheet 10 may be subjected to an easy-release treatment (release treatment) such as a silicon treatment.

[0034] (Embodiment 2) Fig. 2 is a cross-sectional view schematically showing an example of a pressure-sensitive adhesive sheet for attaching an optical member according to embodiment 2. As shown in Fig. 2, a pressure-sensitive adhesive sheet 20 according to embodiment 2 may include a first pressure-sensitive adhesive layer 11, an intermediate resin layer 12, and a second pressure-sensitive adhesive layer 13, in this order. The first pressure-sensitive adhesive layer 11 may be on the observation side, or the second pressure-sensitive adhesive layer 13 may be on the observation side. In this specification, the observation side refers to the side of the target member that is closer to the viewer when the target member is placed facing the viewer.

[0035] In embodiment 2, at least one of first pressure-sensitive adhesive layer 11 and second pressure-sensitive adhesive layer 13 is pressure-sensitive adhesive sheet 10 containing the acrylic resin and colorant described in embodiment 1. When intermediate resin layer 12 is a polyurethane layer, particularly when it contains thermosetting polyurethane, in consideration of the dispersibility of the colorant, pressure-sensitive adhesive sheet 10 in which first pressure-sensitive adhesive layer 11 or second pressure-sensitive adhesive layer 13 contains the acrylic resin and colorant described in embodiment 1 is preferred.

[0036] <Adhesive layer> Both the first pressure-sensitive adhesive layer 11 and the second pressure-sensitive adhesive layer 13 are preferably layers that form the outermost surface of the pressure-sensitive adhesive sheet 20. At least one of the first pressure-sensitive adhesive layer 11 and the second pressure-sensitive adhesive layer 13 is preferably an acrylic pressure-sensitive adhesive layer, and it is more preferable that both the first pressure-sensitive adhesive layer 11 and the second pressure-sensitive adhesive layer 13 are acrylic pressure-sensitive adhesive layers.

[0037] The thickness of the first pressure-sensitive adhesive layer 11 and the second pressure-sensitive adhesive layer 13 is preferably 10 μm or more and 100 μm or less, more preferably 20 μm or more and 80 μm or less, and further preferably 25 μm or more and 50 μm or less in consideration of flexibility.

[0038] <Intermediate resin layer> Intermediate resin layer 12 is an intermediate layer disposed between first pressure-sensitive adhesive layer 11 and second pressure-sensitive adhesive layer 13. Intermediate resin layer 12 is preferably a layer that imparts flexibility and conformability to pressure-sensitive adhesive sheet 20.

[0039] The intermediate resin layer 12 is preferably a polyurethane layer containing polyurethane as a resin component. By including polyurethane in the intermediate resin layer 12, it is possible to obtain an adhesive sheet 20 with excellent transparency and conformability. Because polyurethane is flexible, the adhesive sheet 20 stretches well when tensile stress is applied and is very resistant to tearing. This allows it to be peeled off without leaving any adhesive residue.

[0040] The polyurethane layer is preferably a cured product of a polyurethane composition containing a polyol component and a polyisocyanate component, more preferably a cured product of a thermosetting polyurethane composition containing a polyol component and a polyisocyanate component. Thermosetting polyurethane can be formed into a film without using a solvent, making it possible to form a thick polyurethane layer. Furthermore, by including thermosetting polyurethane in the polyurethane layer, it is possible to obtain a pressure-sensitive adhesive sheet 20 that has excellent flexibility and transparency even when formed into a thick film.

[0041] The thermosetting polyurethane is obtained, for example, by reacting a polyol component with a polyisocyanate component, and preferably has a structure shown in the following formula (A).

[0042] [ka]

[0043] In the above formula (A), R represents the moiety excluding the NCO group of the polyisocyanate component, R' represents the moiety excluding the OH group of the polyol component, and n represents the number of repeating units.

[0044] The thermosetting polyurethane is preferably not acrylic-modified, and preferably does not contain moieties derived from acrylic acid esters, methacrylic acid esters, or the like in the main chain. When the thermosetting polyurethane is acrylic-modified, it becomes hydrophobic, making it more susceptible to moisture aggregation. This moisture aggregation can cause whitening, foaming, and the like, and can impair optical properties. In the thermosetting polyurethane, the total amount of monomer units derived from the polyol component and monomer units derived from the polyisocyanate component is preferably 80 mol % or more of the monomer units constituting the entire thermosetting polyurethane.

[0045] The polyol component and the polyisocyanate component can both be liquid at room temperature (23°C), allowing thermosetting polyurethane to be obtained without the use of a solvent. Other components, such as a tackifier, can be added to either the polyol component or the polyisocyanate component, preferably the polyol component. Since solvent removal is not required when producing the polyurethane layer, a uniform, thick sheet can be formed. Furthermore, the polyurethane layer can maintain its optical properties even when formed thick. Furthermore, the polyurethane layer can be thickened and is flexible, resulting in excellent impact resistance. The adhesive sheet 20 with a polyurethane layer can be used to bond a transparent member having a transparent conductive film on its surface to a cover panel. When using other members, it can also be used to bond a display panel or a transparent member having a transparent conductive film on its surface to other members.

[0046] Examples of the polyol component include polyolefin polyol, polyether polyol, polycaprolactone polyol, polycarbonate polyol, and polyester polyol. These may be used alone or in combination of two or more. Among these, it is preferable to use polyolefin polyol. Specific examples of the polyolefin polyol include Epol (manufactured by Idemitsu Kosan Co., Ltd.).

[0047] The polyol component preferably contains 50% by weight or more of a polyol component having an olefin skeleton, and more preferably consists solely of a polyol component having an olefin skeleton.

[0048] The polyolefin polyol preferably has an olefin skeleton. That is, the main chain is preferably composed of a polyolefin or a derivative thereof. The polyolefin polyol preferably contains at least a polyol component having an olefin skeleton. Examples of the polyol component having an olefin skeleton include polybutadiene-based polyols such as 1,2-polybutadiene polyol, 1,4-polybutadiene polyol, 1,2-polychloroprene polyol, and 1,4-polychloroprene polyol, polyisoprene-based polyols, and polyols in which the double bonds are saturated with hydrogen, halogen, or the like. The polyol component having an olefin skeleton may also be a polyol obtained by copolymerizing a polybutadiene-based polyol or the like with an olefin compound such as styrene, ethylene, vinyl acetate, or an acrylic ester, or a hydrogenated product thereof. The polyol component having an olefin skeleton may have a linear structure or a branched structure. The polyol component having an olefin skeleton may be used alone or in combination of two or more types.

[0049] The polyisocyanate component may be either a hydrophilic polyisocyanate or a hydrophobic polyisocyanate, or both. The hydrophilic polyisocyanate is a polyisocyanate having a hydrophilic unit, and the hydrophobic polyisocyanate is a polyisocyanate not having the hydrophilic unit. The hydrophilic polyisocyanate having a hydrophilic unit does not mean a polyisocyanate having improved hydrophilicity solely through a structure derived from an isocyanate group, such as an isocyanurate structure or a biuret structure, but a polyisocyanate to which a functional group (hydrophilic unit) that enhances hydrophilicity has been added. The inclusion of a hydrophilic unit in the polyisocyanate component provides an effect of suppressing whitening due to moisture absorption.

[0050] The polyisocyanate component preferably contains a hydrophilic polyisocyanate and a hydrophobic polyisocyanate. By including both a hydrophilic polyisocyanate and a hydrophobic polyisocyanate in the thermosetting polyurethane composition, the balance between the hydrophilicity and hydrophobicity of the polyurethane layer can be adjusted. If only a hydrophobic polyisocyanate is used, the polyurethane layer may whiten due to moisture absorbed from the outside after the production of the pressure-sensitive adhesive sheet 20. On the other hand, if only a hydrophilic polyisocyanate is used, although whitening due to moisture absorption can be suppressed, it may be difficult to mix with the polyol component, resulting in reduced transparency.

[0051] The weight ratio of the curing agent containing the hydrophilic polyisocyanate to the curing agent containing the hydrophobic polyisocyanate in the thermosetting polyurethane composition is preferably 2:1 to 1:2, more preferably 1:1 to 1:1.5. It is 5.

[0052] The hydrophilic unit contained in the hydrophilic polyisocyanate is preferably a polyalkylene oxide unit, such as a polyethylene oxide unit or a polypropylene oxide unit.

[0053] Examples of hydrophilic units other than polyalkylene oxide units include units containing a carboxylic acid group, an alkali metal salt of carboxylic acid, a sulfonic acid group, an alkali metal salt of sulfonic acid, a hydroxyl group, an amide group, an amino group, etc. More specific examples include polyacrylic acid, an alkali metal salt of polyacrylic acid, a sulfonic acid group-containing copolymer, an alkali metal salt of a sulfonic acid group-containing copolymer, polyvinyl alcohol, polyacrylamide, carboxymethyl cellulose, an alkali metal salt of carboxymethyl cellulose, polyvinylpyrrolidone, etc.

[0054] The hydrophilic polyisocyanate is preferably a modified polyisocyanate containing an ethylene oxide unit, obtained by reacting an aliphatic and / or alicyclic polyisocyanate having an isocyanate group with an ether compound having a polyalkylene oxide unit. The use of an aliphatic and / or alicyclic polyisocyanate makes it less susceptible to coloration or discoloration, and ensures the transparency of the PSA sheet 20 over a long period of time. Furthermore, by reacting an ether compound having a polyalkylene oxide unit to form a modified polyisocyanate, the hydrophilic portion (polyalkylene oxide unit) of the polyisocyanate component can suppress whitening, and the hydrophobic portion (other units) can exhibit compatibility with low-polarity tackifiers, plasticizers, and the like.

[0055] Specific examples of modified polyisocyanates containing ethylene oxide units include Coronate 4022, Aquanate 130, and Aquanate 140, all of which are manufactured by Tosoh Corporation.

[0056] Examples of hydrophobic polyisocyanates include IPDI (isophorone diisocyanate)-based polyisocyanates and HDI-based polyisocyanates. A specific example of IPDI (isophorone diisocyanate)-based polyisocyanates is Desmodur I manufactured by Sumika Bayer Urethane Co., Ltd. A specific example of HDI-based polyisocyanates is HC-247 manufactured by Nippon Polyurethane Industry Co., Ltd.

[0057] The α ratio of the polyurethane layer (molar number of OH groups derived from the polyol component / molar number of NCO groups derived from the polyisocyanate component) is preferably 1.0 or more and 1.8 or less. The lower the α ratio, the harder the polyurethane layer, and the higher the α ratio, the softer the polyurethane layer. By setting the α ratio of the polyurethane layer to 1.0 or more and 1.8 or less, flexibility suitable for bonding optical elements can be obtained. If the α ratio is less than 1.0, the amount of the polyisocyanate component blended is excessive relative to the amount of the polyol component blended, and the polyurethane layer becomes hard. If the polyurethane layer becomes hard, it may be difficult to ensure the flexibility required for the pressure-sensitive adhesive sheet 20. Furthermore, if the α ratio is less than 1.0, the adhesive strength required for the pressure-sensitive adhesive sheet 20 may not be ensured. If the α ratio exceeds 1.8, the thermosetting polyurethane composition may not be sufficiently cured. The α ratio is more preferably 1.0 or more and 1.5 or less.

[0058] The thermosetting polyurethane composition may further contain a plasticizer. The plasticizer is not particularly limited as long as it is a compound used to impart flexibility to the thermosetting polyurethane, but from the viewpoints of compatibility and weather resistance, it is preferable that the plasticizer contain a carboxylic acid-based plasticizer.

[0059] The thermosetting polyurethane composition may further contain a catalyst. The catalyst is not particularly limited as long as it is a catalyst used in a urethanization reaction, and examples thereof include organic tin compounds such as di-n-butyltin dilaurate, dimethyltin dilaurate, dibutyltin oxide, and tin octoate; organic titanium compounds; organic zirconium compounds; tin carboxylates; bismuth carboxylates; and amine catalysts such as triethylenediamine.

[0060] The thermosetting polyurethane composition may contain various additives such as tackifiers, stabilizers, antioxidants, anti-fungals, and flame retardants, as needed, within the range that does not impair the required properties of the adhesive sheet 20.

[0061] The intermediate resin layer 12 may or may not contain an ultraviolet absorber. When the intermediate resin layer 12 contains an ultraviolet absorber, the content of the ultraviolet absorber is preferably 3.0 parts by mass or less, more preferably 1.8 parts by mass or less, per 100 parts by mass of the resin component. From the viewpoint of suppressing haze, the content of the ultraviolet absorber is preferably 1 part by mass or less, per 100 parts by mass of the resin component, more preferably no ultraviolet absorber is contained. As the ultraviolet absorber, those listed in embodiment 1 may be used. When the intermediate resin layer is a cured product of a polyurethane composition containing a polyol component and a polyisocyanate component, the content of the ultraviolet absorber refers to the content per 100 parts by mass of the polyol component.

[0062] The intermediate resin layer 12 is preferably thicker than the first pressure-sensitive adhesive layer 11 and the second pressure-sensitive adhesive layer 13. The thickness of the intermediate resin layer 12 is preferably 100 μm or more and 2000 μm or less. If the thickness is less than 100 μm, the flexibility of the entire pressure-sensitive adhesive sheet 20 decreases, and when one side of the pressure-sensitive adhesive sheet 20 is attached to the surface of an optical component, the pressure-sensitive adhesive sheet 20 may not be able to cover the irregularities or steps present on the surface of the optical component, and the other side of the pressure-sensitive adhesive sheet 20 may not be able to be attached to the surface of the other optical component with sufficient adhesive strength. If the thickness exceeds 2000 μm, it may be difficult to control the thickness accuracy of the intermediate resin layer 12. The thickness of the intermediate resin layer 12 is more preferably 200 μm or more and 1500 μm or less, even more preferably 250 μm or more and 1500 μm or less, and particularly preferably 500 μm or more and 1000 μm or less.

[0063] The pressure-sensitive adhesive sheet 20 may further have other layers, but preferably has a three-layer structure of a first pressure-sensitive adhesive layer 11, an intermediate resin layer 12, and a second pressure-sensitive adhesive layer 13. That is, the first pressure-sensitive adhesive layer 11 and the intermediate resin layer 12 are preferably in contact with each other, and the second pressure-sensitive adhesive layer 13 and the intermediate resin layer 12 are preferably in contact with each other.

[0064] The thickness (total thickness) of the adhesive sheet 20 in embodiment 2 is preferably 120 to 2200 μm. If the thickness is less than 120 μm, the flexibility of the adhesive sheet 20 may decrease. If the thickness exceeds 2200 μm, it may become difficult to control the thickness accuracy of the entire adhesive sheet 10. The thickness of the adhesive sheet 10 is more preferably 240 μm or more and 1660 μm or less, even more preferably 300 μm or more and 1600 μm or less, and particularly preferably 550 μm or more and 1100 μm or less.

[0065] The method for producing the intermediate resin layer 12 is not particularly limited. A specific example of a method for producing the intermediate resin layer 12 as a cured product of a thermosetting polyurethane composition involves mixing a polyol component, a polyisocyanate component, and, if necessary, other components such as a catalyst, and stirring the mixture in a mixer or the like to obtain a liquid or gel-like thermosetting polyurethane composition. If a tackifier is included, the tackifier is first added to the polyol component, and then heated and stirred to dissolve the tackifier, thereby preparing a masterbatch, which is then mixed with the other materials. The thermosetting polyurethane composition is then immediately placed in a molding machine, and the thermosetting polyurethane composition is sandwiched between a pair of release films and moved while undergoing a curing reaction (crosslinking reaction), thereby semi-curing the thermosetting polyurethane composition. The crosslinking reaction is then carried out in an oven for a certain period of time to obtain a polyurethane layer.

[0066] For pressure-sensitive adhesive sheet 20 according to embodiment 2, the method for laminating first pressure-sensitive adhesive layer 11, intermediate resin layer 12, and second pressure-sensitive adhesive layer 13 in this order is not particularly limited, and examples include a method in which first pressure-sensitive adhesive layer 11, second pressure-sensitive adhesive layer 13, and intermediate resin layer 12 are produced separately and then bonded together. In embodiment 2 as well, the above-mentioned release films may be attached to both sides of pressure-sensitive adhesive sheet 20.

[0067] <Optical properties> The optical properties of the pressure-sensitive adhesive sheet 10 according to embodiment 1 and the pressure-sensitive adhesive sheet 20 according to embodiment 2 will be described below. In the following description of the optical properties, when there is no particular distinction between the pressure-sensitive adhesive sheet 10 according to embodiment 1 and the pressure-sensitive adhesive sheet 20 according to embodiment 2, they will simply be referred to as "adhesive sheet." Note that the optical properties of the pressure-sensitive adhesive sheet 20 according to embodiment 2 refer to the optical properties of the entire pressure-sensitive adhesive sheet 20, which is the combination of the first pressure-sensitive adhesive layer 11, the intermediate resin layer 12, and the second pressure-sensitive adhesive layer 13.

[0068] The haze of the pressure-sensitive adhesive sheet is preferably 10% or less, more preferably 6% or less, even more preferably 4% or less, and particularly preferably 2% or less. From the standpoint of visibility, a lower haze is preferable, but considering that the pressure-sensitive adhesive sheet 10 contains a colorant, the haze of the pressure-sensitive adhesive sheet 10 may be 0.5% or more, or even 1.0% or more. Note that the above haze is the value before the weather resistance test described below is conducted. The haze is measured according to a method in accordance with JIS K 7136, and can be measured, for example, using a turbidity meter "HazeMeter NDH5000" manufactured by Nippon Denshoku Industries Co., Ltd.

[0069] The pressure-sensitive adhesive sheet is optically transparent, and preferably has a total light transmittance of 80% or less. By setting the total light transmittance of the pressure-sensitive adhesive sheet 10 to 80% or less, when the pressure-sensitive adhesive sheet is used to bond a display panel to another optical component, the boundary between the frame region of the display panel and the display screen can be made less noticeable. A total light transmittance of 70% or less is more preferable. When the pressure-sensitive adhesive sheet has a total light transmittance of 80% or less, when the pressure-sensitive adhesive sheet is used to bond a display panel to another optical component and the display panel is turned on to display an image or the like in the display area, the image or the like can be sufficiently viewed even when observed through the pressure-sensitive adhesive sheet 10. Note that the total light transmittance is a value measured before the weather resistance test described below is conducted. The total light transmittance is measured according to a method in accordance with JIS K 7361-1, and can be measured, for example, using a turbidity meter "HazeMeter NDH5000" manufactured by Nippon Denshoku Industries Co., Ltd.

[0070] The pressure-sensitive adhesive sheet preferably has a total light transmittance of 30% or more and 80% or less. By setting the total light transmittance of the pressure-sensitive adhesive sheet to 30% or more and 80% or less, when the pressure-sensitive adhesive sheet is used to bond a display panel to another optical component and the display panel is turned on to display an image or the like in the display area, visibility can be further improved. The total light transmittance is more preferably 55% or more and 80% or less.

[0071] The PSA sheet preferably has an L* value of 70 or more and 95 or less, more preferably 68 or more and 92 or less, and even more preferably 80 or more and 90 or less, when expressed in the L*, a*, b* color system. The L* value is the value before the weather resistance test described below is conducted. L* is measured according to a method in accordance with JIS Z 8781-4, and can be measured, for example, using a spectrophotometer CM-3600A manufactured by Konica Minolta.

[0072] The PSA sheet is subjected to a weather resistance test in accordance with JIS K 7350-1 and JIS K 7350-2 using a metaling weather meter equipped with a metal halide lamp, for a total of 24 hours, consisting of 20 hours under the following light conditions and 4 hours under the following dark conditions. After the test, the PSA sheet has a change in L* ΔL* of 2.5 or less, calculated by subtracting the lightness L* of the PSA sheet before the weather resistance test from the lightness L* in the L*a*b* color space of the PSA sheet. Note that while JIS K 7350-2 is a test method using a xenon arc lamp as the light source, in the present disclosure a metal halide lamp is used as the light source, and the test standards of JIS K 7350-1 and JIS K 7350-2 are applied mutatis mutandis. <Testing machine> Product name: Metaling Weather Meter Model: M6T Light source: Metal halide lamp (horizontal metering lamp 6Kw) Inner filter: Quartz Outer filter: #275 Sample surface filter: #255 <Test conditions> Bright conditions Illuminance: 1.2kW / m 2 Irradiation time: 20 hours Black panel temperature: 53℃ Relative humidity: 40% Rainfall: 10 seconds every 15 minutes Dark conditions No irradiation, no rain Tank temperature: 53℃ Relative humidity: 95%

[0073] When discoloration occurs, the L* of the pressure-sensitive adhesive sheet after the weather resistance test becomes higher than the lightness L* of the pressure-sensitive adhesive sheet before the weather resistance test. The larger the ΔL*, the greater the degree of discoloration. By setting the ΔL* to 2.5 or less, when the pressure-sensitive adhesive sheet 10 is used to bond optical components such as display panels, the boundary between the display screen and the black printed portion of the frame area when the display panel is turned off is made less visible, providing a sense of unity. The pressure-sensitive adhesive sheet of this embodiment suppresses discoloration even when irradiated with ultraviolet light, particularly when subjected to a weather resistance test using a metal halide lamp with a high acceleration factor, making it suitable for use in environments exposed to external light. For example, it can be used to attach to window glass in houses or vehicles, or to bond in-vehicle displays. ΔL* is more preferably 1.0 or less, and even more preferably 0.5 or less.

[0074] The cumulative light intensity in the above weather resistance test was 86.4 MJ / m 2 It is preferable that the above ΔL* is 2.5 or less.

[0075] The change in haze (ΔHaze) obtained by subtracting the haze of the pressure-sensitive adhesive sheet before the weather resistance test from the haze of the pressure-sensitive adhesive sheet after the weather resistance test is preferably 2% or less, more preferably 1% or less.

[0076] The change in total light transmittance (Δtotal light transmittance) obtained by subtracting the total light transmittance of the pressure-sensitive adhesive sheet before the weather resistance test from the total light transmittance of the pressure-sensitive adhesive sheet after the weather resistance test is preferably 5% or less, more preferably 3% or less, and even more preferably 1% or less.

[0077] The change in b* (Δb*) obtained by subtracting the b* of the pressure-sensitive adhesive sheet before the weather resistance test from the b* of the pressure-sensitive adhesive sheet after the weather resistance test is preferably 1.0 or less, more preferably 0.7 or less.

[0078] The pressure-sensitive adhesive sheets 10 and 20 according to the first and second embodiments are pressure-sensitive adhesive sheets for bonding optical members, which are used to bond optical members. Examples of the optical members include various members constituting display devices, such as display panels, touch panels (glass substrates with ITO transparent conductive film), cover glasses, polarizing plates, and retardation films. The type of display panel is not particularly limited, and examples include liquid crystal panels and organic electroluminescence panels (organic EL panels). By bonding optical members using the pressure-sensitive adhesive sheets 10 and 20, it is possible to eliminate air gaps between the optical members, thereby improving the visibility of the display device. [Example]

[0079] The present invention will be explained in more detail below by giving examples, but the present invention is not limited to these examples.

[0080] Table 1 below shows the colorants used in the examples and comparative examples.

[0081] [Table 1]

[0082] The carbon black content in the inorganic black pigment containing carbon black was 10% by mass, and the median diameter D50 of the carbon black (measured with a particle size distribution analyzer) was 71.1 nm. The content of the composite oxide containing copper, iron, and manganese in the composite oxide pigment was 10 to 15% by mass.

[0083] (Preparation of acrylic resin composition) The acrylic resin was prepared by blending acrylic acid ester copolymers ("SK1838" and "SK1875" manufactured by Soken Chemical & Engineering Co., Ltd.) at a solid content ratio of 5:5, and 0.6 parts by mass of an isocyanate curing agent ("DY-70" manufactured by Soken Chemical & Engineering Co., Ltd.) was added to 100 parts by mass of the acrylic resin to prepare acrylic resin composition A.

[0084] Example 1 To the acrylic resin composition A, 0.18 parts by mass of carbon black shown in Table 1 was further added. The content of the carbon black is the content relative to 100 parts by mass of the acrylic resin contained in the acrylic resin composition A. The acrylic resin composition was applied to a 100 μm thick release PET film using a comma coater so that the thickness after drying would be 25 μm, and after drying the solvent, a 50 μm thick release PET film was laminated and cured to produce a single-layer pressure-sensitive adhesive sheet according to Example 1 sandwiched between the release PET films.

[0085] (Examples 2 and 3, Comparative Example 1) Single-layer adhesive sheets according to Examples 2 and 3 and Comparative Example 1 were prepared in the same manner as in Example 1, except that the type and / or amount of colorant added to the adhesive layer was changed as shown in Table 2.

[0086] <Weather resistance test> Test pieces measuring 2 cm x 5 cm were cut from the pressure-sensitive adhesive sheets of Examples 1 to 3 and Comparative Example 1. A 50 μm-thick release PET film was peeled off from each test piece, and the exposed surface of the pressure-sensitive adhesive sheet was placed on the sample stage of a metaling weather meter with the surface facing the observation side. The four sides of each test piece were fixed to the sample stage with aluminum tape, and light was irradiated from the observation side of each pressure-sensitive adhesive sheet. In this weather resistance test, the first pressure-sensitive adhesive layer was exposed and exposed to rain under the following conditions, so that each pressure-sensitive adhesive sheet was irradiated with light while its surface was wet with water. Therefore, fading resistance can be examined under more severe conditions than when a weather resistance test is performed with both sides sandwiched between substrates.

[0087] A weather resistance test was conducted for a total of 24 hours using a metaling weather meter equipped with a metal halide lamp in accordance with JIS K 7350-1 and JIS K 7350-2, with 20 hours under the following light conditions and 4 hours under the following dark conditions. The cumulative light intensity of the above weather resistance test was 86.4 MJ / m 2 It was. <Testing machine> Product name: Metaling Weather Meter Model: M6T Light source: Metal halide lamp (horizontal metering lamp 6Kw) Inner filter: Quartz Outer filter: #275 Sample surface filter: #255 <Test conditions> Bright conditions Illuminance: 1.2kW / m 2 Irradiation time: 20 hours Black panel temperature: 53℃ Relative humidity: 40% Rainfall: 10 seconds every 15 minutes Dark conditions No irradiation, no rain Tank temperature: 53℃ Relative humidity: 95%

[0088] The optical properties of the pressure-sensitive adhesive sheet were measured before and after the weather resistance test, including the haze, total light transmittance, and L*, a*, and b* in the L*a*b* color space. Each optical property was measured at the center of the test piece, and the measured values ​​are summarized in Table 2 below. The change in each parameter before and after the weather resistance test is represented by Δ in Table 2. Haze was measured according to JIS K 7136, and total light transmittance was measured according to JIS K 7361-1 using a turbidity meter "HazeMeter NDH5000" manufactured by Nippon Denshoku Industries Co., Ltd. L*, a*, and b* were measured according to JIS Z 8781-4 using a "spectrophotometer CM-3600A" manufactured by Konica Minolta. Note that the haze, total light transmittance, L*, a*, and b* of the pressure-sensitive adhesive sheet were measured only for the pressure-sensitive adhesive sheet from which the release PET film was removed from each test piece.

[0089] In Table 2, the content of the colorant is the content relative to 100 parts by mass of the acrylic resin contained in the acrylic resin composition A.

[0090] [Table 2]

[0091] In Comparative Example 1, the ΔL* value before and after the weather resistance test was high, and discoloration occurred due to the weather resistance test, whereas in Examples 1 to 3, no discoloration occurred.

[0092] The weather resistance of a pressure-sensitive adhesive sheet having a first pressure-sensitive adhesive layer, a polyurethane layer, and a second pressure-sensitive adhesive layer laminated in this order was examined below.

[0093] (Preparation of Thermosetting Polyurethane Composition) Thermosetting polyurethane composition B 100 parts by weight of the following polyol component, 4.7 parts by weight of hydrophilic polyisocyanate, 4.7 parts by weight of hydrophobic polyisocyanate, 10 parts by weight of tackifier, and 0.01 parts by weight of catalyst were stirred and mixed using a reciprocating rotary mixer Ajiter to prepare a thermosetting polyurethane composition B having an α ratio of 1.5. Polyolefin polyol (EPOL (registered trademark) manufactured by Idemitsu Kosan Co., Ltd.) Hydrophilic polyisocyanate Modified polyisocyanate containing ethylene oxide units (Tosoh's "Coronate 4022") Hydrophobic polyisocyanate IPDI (isophorone diisocyanate) polyisocyanate ("Desmodur I" manufactured by Sumika Bayer Urethane Co., Ltd.) Tackifier Idemitsu Kosan's "Imarv P-100" ·catalyst Dimethyltin dilaurate (Momentive's "Fomrez catalyst UL-28")

[0094] Example 4 <First and second pressure-sensitive adhesive layers> To prepare the acrylic resin composition for the first pressure-sensitive adhesive layer, 0.6 parts by mass of carbon black shown in Table 1 was further added to the above acrylic resin composition A. The carbon black content is the content relative to 100 parts by mass of the acrylic resin contained in acrylic resin composition A. As the acrylic resin composition for the second pressure-sensitive adhesive layer, acrylic resin composition A was used as is. The acrylic resin compositions for the first and second pressure-sensitive adhesive layers were each applied to a 100-μm-thick release PET film using a comma coater so that the thickness after drying would be 25 μm, and a 50-μm-thick release PET film was laminated on top and dried to prepare first and second acrylic pressure-sensitive adhesive layers sandwiched between release PET films.

[0095] <Polyurethane layer> A polyurethane layer was prepared as an intermediate resin layer. The thermosetting polyurethane composition B prepared above was sandwiched between a pair of release films and transported while being crosslinked and cured at an oven temperature of 50 to 90°C for several minutes to obtain a sheet with a release film. A 100 μm-thick PET film with a release-treated surface was used as the release film. The crosslinking reaction was then carried out in a heating device for 10 to 15 hours to produce a 500 μm-thick polyurethane layer with release films on both sides.

[0096] <Adhesive sheet> The release films on both sides of the polyurethane layer were peeled off, and 50 μm-thick release PET films were peeled off from each of the first and second acrylic pressure-sensitive adhesive layers with release films attached, and laminated so as to be in contact with the surface of the polyurethane layer, thereby producing a pressure-sensitive adhesive sheet according to Example 4 having the first pressure-sensitive adhesive layer, polyurethane layer, and second pressure-sensitive adhesive layer in this order.

[0097] Example 5 An adhesive sheet according to Example 5 was produced in the same manner as in Example 4, except that the thickness of the first adhesive layer was changed to 50 μm.

[0098] (Examples 6 to 8) Pressure-sensitive adhesive sheets according to Examples 5 to 8 were produced in the same manner as in Example 4, except that the amount of carbon black added to the first pressure-sensitive adhesive layer was changed as shown in Table 3.

[0099] (Example 9, Comparative Example 2) Pressure-sensitive adhesive sheets according to Example 9 and Comparative Example 2 were prepared in the same manner as in Example 4, except that the colorant added to the first pressure-sensitive adhesive layer was changed as shown in Tables 3 and 4.

[0100] Example 10 As the acrylic resin composition for the first pressure-sensitive adhesive layer, acrylic resin composition A was used as is. As the acrylic resin composition for the second pressure-sensitive adhesive layer, 0.4 parts by mass of carbon black shown in Table 1 was further added to the above acrylic resin composition A. A pressure-sensitive adhesive sheet according to Example 10 was produced in the same manner as in Example 4, using the acrylic resin compositions for the first and second pressure-sensitive adhesive layers.

[0101] Example 11 The acrylic resin composition A was used as is for the first pressure-sensitive adhesive layer. The pressure-sensitive adhesive sheet of Example 11 was produced in the same manner as in Example 4, except that the acrylic resin composition A was used as the acrylic resin composition for the second pressure-sensitive adhesive layer, and 0.4 parts by mass of carbon black and 1.3 parts by mass of an ultraviolet absorber (UVA) shown in Table 1 were further added to the acrylic resin composition A in an amount relative to 100 parts by mass of the acrylic resin.

[0102] Example 12 An adhesive sheet of Example 12 was produced in the same manner as Example 4, except that the acrylic resin composition for the second adhesive layer of Example 11 was used as the acrylic resin composition for the first adhesive layer, and the acrylic resin composition for the first adhesive layer of Example 11 was used as the acrylic resin composition for the second adhesive layer.

[0103] (Comparative Examples 3 to 5) The pressure-sensitive adhesive sheets according to Comparative Examples 3 to 5 were prepared in the same manner as in Example 4, except that acrylic resin composition A was used as is as the acrylic resin composition for the first pressure-sensitive adhesive layer, and a colorant was further added to thermosetting polyurethane composition B as shown in Table 4 as the thermosetting polyurethane composition.

[0104] <Weather resistance test> Test pieces measuring 2 cm x 5 cm were cut from the pressure-sensitive adhesive sheets of Examples 4 to 12 and Comparative Examples 2 to 5. The release film on the side of the first pressure-sensitive adhesive layer was peeled off from each test piece, and the test piece was placed on the sample stage of a metaling weather meter so that the first pressure-sensitive adhesive layer faced the observation side. The four edges of each test piece were fixed to the sample stage using aluminum tape. In the weather resistance test, light was irradiated from the observation side of each pressure-sensitive adhesive sheet. The weather resistance test was performed in the same manner as in Example 1 above, and the optical properties were evaluated in the same manner as in Example 1. The results are shown in Tables 3 and 4 below. In Tables 3 and 4, the content of the colorant is the content per 100 parts by mass of the acrylic resin contained in the acrylic resin composition A.

[0105] [Table 3]

[0106] [Table 4]

[0107] Examples 4 to 8, in which carbon black was added as a colorant to the first pressure-sensitive adhesive layer, and Example 9, in which perylene black was added as a colorant to the first pressure-sensitive adhesive layer, did not experience discoloration. On the other hand, Comparative Example 2, in which a black dye was added as a colorant to the first pressure-sensitive adhesive layer, experienced discoloration. Furthermore, Comparative Examples 2 to 4, in which a complex oxide pigment, lactam black, or black dye was added as a colorant to the second pressure-sensitive adhesive layer, also experienced discoloration.

[0108] Of the examples in which no discoloration occurred in the weather resistance test, Examples 4 to 9 were examined for their sense of unity with the frame region and visibility by the following method.

[0109] (Comparative Example 6) A colorless pressure-sensitive adhesive sheet of Comparative Example 6 was produced in the same manner as in Example 4, except that no colorant was added.

[0110] <Integration with the frame area> A display panel having a display area and a frame area and equipped with a backlight was prepared as the display panel. In addition, a glass cover panel was prepared, the portion of which overlaps with the frame area of ​​the display panel when bonded to the display panel and which was printed in black.

[0111] The cover panel and the display panel were bonded to each other using the pressure-sensitive adhesive sheets of Examples 4 to 9 and Comparative Example 6 before the weather resistance test to produce a display device. With the backlight turned off, the L*a*b* of the display area of ​​the display device using the pressure-sensitive adhesive sheets of Examples 4 to 9 and Comparative Example 6 was measured. The L*a*b* of the black printed area was also measured. The L* of the black printed area was 11.6, a* was -0.33, and b* was -1.16. The values ​​obtained by subtracting the L*a*b* of the black printed area from the L*a*b* of the display area of ​​each display device when the light was off are summarized in Table 5 below.

[0112] <Visibility> The backlight of the display device, in which the cover panel and the display panel were bonded together with the adhesive sheets of Examples 4 to 9 and Comparative Example 6 before the weather resistance test, was turned on, and black letters (each approximately 2 mm long and 2 mm wide) spelling out the letters "ABCDE" were displayed against a white background. The letters were then visually observed from a distance of 30 cm from the viewing surface of the display device indoors. Visibility was evaluated according to the following criteria, and the results are summarized in Table 5 below. 〇: The outline of the characters is clearly visible △: The outline of the letters appeared blurred ×: The letters looked cloudy

[0113] <Sense of unity> For the display devices bonded in Examples 4 to 9, with the backlight turned off, the boundary between the frame area (black printed area) and the display surface area was visually observed from a position 30 cm away from the display panel and evaluated according to the following criteria. ○: No boundary between the frame area and the display surface area was observed △: A slight boundary between the frame area and the display surface area was observed ×: The boundary between the frame area and the display surface area was clearly observed.

[0114] [Table 5]

[0115] With regard to visibility, Examples 4 to 9 had good visibility, with the outlines of the characters clearly visible. Comparative Examples 2 to 5 also had good visibility. On the other hand, Example 5 had lower visibility than Example 1. It is thought that Example 5 had higher haze and lower total light transmittance than the other Examples, which resulted in low visibility of the characters. In the display devices bonded in Examples 4 to 9, the frame region and the display region were well integrated when the light was off. On the other hand, the display device bonded with the colorless adhesive sheet of Comparative Example 6 did not have a sense of unity between the frame region and the display region when the light was off. [Explanation of symbols]

[0116] 10, 20: Adhesive sheet 11: First adhesive layer 12: Intermediate resin layer 13: Second adhesive layer

Claims

1. A pressure-sensitive adhesive sheet containing an acrylic resin and a colorant, A pressure-sensitive adhesive sheet for attaching optical members, wherein a weather resistance test is conducted in accordance with JIS K 7350-1 and JIS K 7350-2 using a metaling weather meter equipped with a metal halide lamp for 20 hours under the following light conditions and 4 hours under the following dark conditions for a total of 24 hours, and the change in L*, obtained by subtracting the lightness L* of the pressure-sensitive adhesive sheet before the weather resistance test from the lightness L* in the L*a*b* color space of the pressure-sensitive adhesive sheet, is 2.5 or less. <Testing machine> Product name: Metaling weather meter Model: M6T Light source: Metal halide lamp (horizontal metering lamp 6Kw) Inner filter: Quartz Outer filter: #275 Sample surface filter: #255 <Test conditions> ・Light conditions Illuminance: 1.2 kW / m ２ Irradiation time: 20 hours Black panel temperature: 53°C Relative humidity: 40% Rainfall: 10 seconds every 15 minutes - Dark conditions No irradiation, no rain Tank temperature: 53℃ Relative humidity: 95%

2. A first pressure-sensitive adhesive layer, an intermediate resin layer, and a second pressure-sensitive adhesive layer, The pressure-sensitive adhesive sheet for attaching an optical member according to claim 1 , wherein at least one of the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer contains the acrylic resin and the colorant.

3. The pressure-sensitive adhesive sheet for attaching optical members according to claim 2 , wherein the intermediate resin layer is a polyurethane layer containing polyurethane.

4. The pressure-sensitive adhesive sheet for attaching optical members according to claim 3 , wherein the polyurethane layer is a cured product of a thermosetting polyurethane composition containing a polyol component and a polyisocyanate component.

5. The pressure-sensitive adhesive sheet for attaching optical members according to claim 1 or 2, wherein the colorant comprises a carbon-based colorant or a compound containing a perylene structure.

6. 3. The pressure-sensitive adhesive sheet for adhering optical components according to claim 1 or 2, wherein the change in b* Δb* obtained by subtracting the b* of the pressure-sensitive adhesive sheet before the weather resistance test from the b* in the L*a*b* color space of the pressure-sensitive adhesive sheet after the weather resistance test is 1.0 or less.

7. 3. The pressure-sensitive adhesive sheet for attaching optical components according to claim 1 or 2, wherein the change in total light transmittance obtained by subtracting the total light transmittance of the pressure-sensitive adhesive sheet before the weather resistance test from the total light transmittance of the pressure-sensitive adhesive sheet after the weather resistance test is 5% or less.

8. The pressure-sensitive adhesive sheet for attaching optical members according to claim 1 or 2, which has a total light transmittance of 30% or more and 80% or less.

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