Adhesive sheet

Abstract

To provide an adhesive sheet in which discoloration is suppressed even when a weathering test using a metal halide lamp is performed under environment containing much water.SOLUTION: An adhesive sheet includes a first adhesive layer, an intermediate resin layer, and a second adhesive layer in order from an observation surface side, wherein the intermediate resin layer or the second adhesive layer contains a colorant, at least one of the first adhesive layer and the second adhesive layer is an acrylic adhesive layer containing an acrylic resin, and the first adhesive layer or the intermediate resin layer located on a side closer to the observation surface side than the layer containing the colorant contains an ultraviolet absorber.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a pressure-sensitive adhesive sheet. [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 optical pressure-sensitive adhesive sheet having a first acrylic pressure-sensitive adhesive surface layer, a polyurethane layer, and a second acrylic pressure-sensitive adhesive surface layer in this order, and at least one of the first acrylic pressure-sensitive adhesive surface layer and the second acrylic pressure-sensitive adhesive surface layer contains a complex oxide pigment.

[0004] Patent Document 2 discloses an optical component with adhesive, in which an adhesive layer is laminated on at least one surface of the optical component, the adhesive layer is laminated via an intermediate layer containing a mixture of a polyurethane resin and an isocyanate compound, and the adhesive layer contains a functional group-containing polymer that can react with the isocyanate compound. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2022-113456 [Patent Document 2] Japanese Patent Application Laid-Open No. 2005-241771 Summary of the Invention [Problem to be solved by the invention]

[0006] Depending on the application, there is a demand for pressure-sensitive adhesive sheets that have optical transparency while also having adjustable 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 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 particularly accelerated 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.

[0007] The present disclosure has been made in consideration of the above-mentioned current situation, and aims to provide an adhesive sheet that suppresses fading even when subjected to a weather resistance test using a metal halide lamp in a humid environment. [Means for solving the problem]

[0008] (1) One embodiment of the present invention is a pressure-sensitive adhesive sheet comprising, in order from the observation side, a first pressure-sensitive adhesive layer, an intermediate resin layer, and a second pressure-sensitive adhesive layer, wherein the intermediate resin layer or the second pressure-sensitive adhesive layer contains a colorant, at least one of the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer is an acrylic pressure-sensitive adhesive layer containing an acrylic resin, and the first pressure-sensitive adhesive layer or the intermediate resin layer located closer to the observation side than the layer containing the colorant contains an ultraviolet absorber.

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

[0010] (3) One embodiment of the present invention is a pressure-sensitive adhesive sheet having the configuration of (2) above, wherein the polyurethane layer is a cured product of a thermosetting polyurethane composition containing a polyol component and a polyisocyanate component.

[0011] (4) One embodiment of the present invention is a pressure-sensitive adhesive sheet having the constitution of any one of (1) to (3) above, wherein the colorant contains a complex oxide pigment or a lactam pigment.

[0012] (5) One embodiment of the present invention is a pressure-sensitive adhesive sheet having a total light transmittance of 80% or less in addition to the configuration of any one of the above (1) to (4).

[0013] (6) One embodiment of the present invention is a pressure-sensitive adhesive sheet having a total light transmittance of 30% or more and 80% or less, in addition to the configuration of any one of (1) to (5) above, which is a pressure-sensitive adhesive sheet for bonding optical components, used to bond optical components. [Effects of the Invention]

[0014] According to the present disclosure, it is possible to provide a pressure-sensitive adhesive sheet that is inhibited from fading even when subjected to a weather resistance test using a metal halide lamp in a moisture-rich environment. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a cross-sectional view schematically illustrating an example of a pressure-sensitive adhesive sheet according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0016] Fig. 1 is a cross-sectional view schematically illustrating an example of a pressure-sensitive adhesive sheet according to an embodiment. As shown in Fig. 1, a pressure-sensitive adhesive sheet 10 according to an embodiment includes, in order from the observation side, a first pressure-sensitive adhesive layer 11, an intermediate resin layer 12, and a second pressure-sensitive adhesive layer 13. In this specification, the observation side refers to the side of the target component that is closer to the viewer when the target component is placed facing the viewer.

[0017] <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 an acrylic pressure-sensitive adhesive layer containing an acrylic resin as a resin component, and it is preferable that both the first pressure-sensitive adhesive layer 11 and the second pressure-sensitive adhesive layer 13 are acrylic pressure-sensitive adhesive layers.

[0018] The acrylic pressure-sensitive adhesive layer is preferably formed by curing an acrylic resin composition, such as an acrylic resin composition 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 R 2 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 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. 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 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 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 may not be able to follow dimensional changes in the substrates in response to environmental changes, resulting in peeling. The thickness of the first pressure-sensitive adhesive layer 11 and the second pressure-sensitive adhesive layer 13 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.

[0026] <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 .

[0027] The intermediate resin layer 12 is preferably a polyurethane layer containing polyurethane. By including polyurethane in the intermediate resin layer 12, it is possible to obtain an adhesive sheet 10 with excellent transparency and conformability. Because polyurethane is flexible, the adhesive sheet 10 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.

[0028] 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 make the polyurethane layer thick. Furthermore, by including a thermosetting polyurethane in the polyurethane layer, it is possible to obtain a pressure-sensitive adhesive sheet having excellent flexibility and transparency even when formed into a thick film.

[0029] 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).

[0030] [ka]

[0031] 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.

[0032] 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.

[0033] 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 preparing 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. A pressure-sensitive adhesive sheet having 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.

[0034] 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.).

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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. When only a hydrophobic polyisocyanate is used, the polyurethane layer may whiten due to moisture absorbed from the outside after the pressure-sensitive adhesive sheet is produced. On the other hand, when only a hydrophilic polyisocyanate is used, although whitening due to moisture absorption can be suppressed, the polyisocyanate may be difficult to mix with the polyol component, resulting in reduced transparency.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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 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, etc.

[0043] 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.

[0044] 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.

[0045] 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. Furthermore, if the α ratio is less than 1.0, the adhesive strength required for the pressure-sensitive adhesive sheet 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.

[0046] 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.

[0047] 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.

[0048] The thermosetting polyurethane composition may contain various additives such as tackifiers (tackifiers), stabilizers, antioxidants, antifungals, and flame retardants, as needed, within the range that does not impair the required properties of the pressure-sensitive adhesive sheet.

[0049] 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 decreases, and when one side of the pressure-sensitive adhesive sheet is attached to the surface of an optical component, the pressure-sensitive adhesive sheet 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 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.

[0050] The pressure-sensitive adhesive sheet according to this embodiment is preferably a pressure-sensitive adhesive sheet for bonding optical members, which is 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 thereof include liquid crystal panels and organic electroluminescence panels (organic EL panels). By bonding optical members using the pressure-sensitive adhesive sheet 10, it is possible to eliminate air gaps between the optical members, thereby improving the visibility of the display device.

[0051] The pressure-sensitive adhesive sheet 10 may further include 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.

[0052] The intermediate resin layer 12 or the second pressure-sensitive adhesive layer 13 contains a colorant. In the pressure-sensitive adhesive sheet according to this embodiment, the transmittance is reduced by including a colorant in the intermediate resin layer 12 or the second pressure-sensitive adhesive layer 13. When the pressure-sensitive adhesive sheet is used to bond a display panel to other optical components 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. When the intermediate resin layer 12 is a polyurethane layer, particularly when it contains thermosetting polyurethane, it is preferable to add a colorant to the second pressure-sensitive adhesive layer 13, taking into account the dispersibility of the colorant.

[0053] The first pressure-sensitive adhesive layer 11 or the intermediate resin layer 12, which is located closer to the observation surface than the layer containing the colorant, contains an ultraviolet absorber. That is, when the second pressure-sensitive adhesive layer 13 contains a colorant, the first pressure-sensitive adhesive layer 11 or the intermediate resin layer 12 contains an ultraviolet absorber. When the intermediate resin layer 12 contains a colorant, the first pressure-sensitive adhesive layer 11 contains an ultraviolet absorber. By adding an ultraviolet absorber to a layer located closer to the observation surface than the layer containing the colorant, it is possible to suppress fading of the pressure-sensitive adhesive sheet 10 due to light such as ultraviolet light irradiated from the observation surface side. Furthermore, by adding the colorant and the ultraviolet absorber to different layers, bleed-out and the like are less likely to occur, and the amounts of each added are easier to adjust.

[0054] 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.

[0055] Examples of the colorant include composite oxide pigments, organic pigments, inorganic pigments, etc. From the viewpoint of suppressing haze, composite oxide pigments are preferred.

[0056] The composite oxide pigment is an inorganic pigment in which two or more metal oxides are chemically bonded by high heat or the like. The composite oxide pigment preferably contains at least one of iron and manganese. Examples of the composite oxide pigment include composite oxide pigments containing iron and manganese, composite oxide pigments containing iron, cobalt, and chromium, and composite oxide pigments containing copper, chromium, and manganese. Among these, composite oxide pigments containing both iron and manganese are more preferred, and composite oxide pigments containing copper, iron, and manganese are even more preferred. A specific example of a colorant containing the composite oxide pigment containing copper, iron, and manganese is "NSP-AY 805B BLACK" manufactured by Nichiko Bix Co., Ltd. The colorant may contain, in addition to the composite oxide pigment, a resin, a solvent, an additive, and the like.

[0057] Examples of the organic pigment include lactam pigments containing compounds with a lactam structure and perylene pigments containing compounds with a perylene structure. Examples of the lactam pigments include NPFT-81294 manufactured by Nippon Pigment Co., Ltd. Examples of the perylene pigments include NPFT-81295 manufactured by Nippon Pigment Co., Ltd.

[0058] Examples of the inorganic pigment include carbonaceous raw materials, such as carbon black, graphite, and diamond.

[0059] From the viewpoint of being able to control the visible light transmittance without increasing the yellowness of the pressure-sensitive adhesive sheet 10 (the b* value when expressed in the L*, a*, b* color system), complex oxide pigments are preferred. It is thought that complex oxide pigments can suppress the yellowness by including multiple types of metal oxides. Because yellowness is a color that is also seen in general resin degradation, pressure-sensitive adhesive sheets with reduced yellowness are sometimes preferred to create a luxurious feel. Since the addition of carbon black tends to increase the b* value, from the viewpoint of suppressing the yellowness, it is preferable that the colorant does not contain carbon black.

[0060] The content of the colorant per 100 parts by mass of the resin components is preferably 0.1 part by mass or more and 1.0 part by mass or less, and more preferably 0.2 part by mass or more and 0.8 part by mass or less. When the intermediate resin layer contains a colorant, the content of the colorant refers to the content per 100 parts by mass of the resin component with the largest content among the resin components contained in the intermediate resin layer. 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 colorant refers to the content per 100 parts by mass of the polyol component. When the second pressure-sensitive adhesive layer contains a colorant, the content of the colorant refers to the content per 100 parts by mass of the resin component with the largest content among the resin components contained in the second pressure-sensitive adhesive layer. In particular, when the second pressure-sensitive adhesive layer is an acrylic pressure-sensitive adhesive layer, the content of the colorant refers to the content per 100 parts by mass of the acrylic resin.

[0061] The ultraviolet absorber has the effect of suppressing photodegradation of the resin component by absorbing ultraviolet light irradiated onto the pressure-sensitive adhesive sheet. 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.

[0062] The content of the UV absorber is preferably 0.5 parts by mass or more and 3.0 parts by mass or less per 100 parts by mass of the resin component. If the content exceeds 3.0 parts by mass, the haze of the pressure-sensitive adhesive sheet may decrease or bleeding may occur. The content of the UV absorber is more preferably 0.8 parts by mass or more and 1.8 parts by mass or less, and even more preferably 1.0 parts by mass or more and 1.5 parts by mass or less, per 100 parts by mass of the resin component. When the intermediate resin layer contains a UV absorber, the content of the UV absorber refers to the content per 100 parts by mass of the resin component with the highest content among the resin components contained in the intermediate resin layer. 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 UV absorber refers to the content per 100 parts by mass of the polyol component. When the second pressure-sensitive adhesive layer contains a UV absorber, the content of the UV absorber refers to the content per 100 parts by mass of the resin component with the highest content among the resin components contained in the pressure-sensitive adhesive composition. In particular, when the second pressure-sensitive adhesive layer is an acrylic pressure-sensitive adhesive layer, the content of the ultraviolet absorber refers to the content relative to 100 parts by mass of the acrylic resin.

[0063] <Adhesive sheet> The thickness (total thickness) of the adhesive sheet 10 is preferably 120 μm or more and 2200 μm or less. If the thickness is less than 120 μm, the flexibility of the adhesive sheet 10 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.

[0064] The haze of the pressure-sensitive adhesive sheet 10 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.

[0065] The adhesive sheet 10 preferably has a total light transmittance of 80% or less. By making the adhesive sheet 10 have a total light transmittance of 80% or less, when the 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. The total light transmittance is more preferably 70% or less. If the total light transmittance is 30% or more and 80% or less, when the 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 adhesive sheet 10. The total light transmittance is more preferably 55% or more and 80% or less. Note that the total light transmittance is the value 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.

[0066] The adhesive sheet 10 preferably has a total light transmittance of 80% or less and a haze of 10% or less. By making the adhesive sheet 10 have a total light transmittance of 80% or less and a haze of 10% or less, visibility can be improved when the adhesive sheet is used to bond a display panel to another optical member and the display panel is turned on to display an image or the like in the display area.

[0067] The PSA sheet 10 preferably has an L* value of 70 or more and 95 or less, more preferably 82 or more and 95 or less, and even more preferably 85 or more and 92 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 using, for example, a spectrophotometer CM-3600A manufactured by Konica Minolta, Inc.

[0068] The PSA sheet is subjected to a weather resistance test using a metaling weather meter equipped with a metal halide lamp in accordance with JIS K 7350-1 and JIS K 7350-2 for a total of 24 hours, consisting of 20 hours under the following light conditions and 4 hours under the following dark conditions. The change in L*, 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, is preferably 2.5 or less. Note that JIS K 7350-2 is a test method using a xenon arc lamp as the light source, but 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%

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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 0.5 or less.

[0074] Another embodiment of the present invention is a pressure-sensitive adhesive sheet for bonding optical components, comprising, in order from the observation side, a first resin layer containing an ultraviolet absorber and a second resin layer containing a colorant, wherein the pressure-sensitive adhesive sheet is subjected to a weather resistance test using a metaling weather meter equipped with a metal halide lamp in accordance with JIS K 7350-1 and JIS K 7350-2 for a total of 24 hours, consisting of 20 hours under the above-mentioned light conditions and 4 hours under the above-mentioned dark conditions, and the change in L* ΔL* 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 after the weather resistance test is 2.5 or less.

[0075] When the pressure-sensitive adhesive sheet for optical member attachment comprises the above-mentioned first pressure-sensitive adhesive layer 11, intermediate resin layer 12, and second pressure-sensitive adhesive layer 13, the first resin layer may be the first pressure-sensitive adhesive layer 11, and the second resin layer may be the intermediate resin layer 12. Alternatively, the first resin layer may be the first pressure-sensitive adhesive layer 11, and the second resin layer may be the second pressure-sensitive adhesive layer 13. Alternatively, the first resin layer may be the intermediate resin layer 12, and the second resin layer may be the second pressure-sensitive adhesive layer 13.

[0076] In another embodiment of the pressure-sensitive adhesive sheet for optical member attachment, the first resin layer may be the acrylic pressure-sensitive adhesive layer described above, and the second resin layer may be the polyurethane layer described above. Alternatively, the first resin layer and the second resin layer may be the acrylic pressure-sensitive adhesive layer described above. The first resin layer may be the polyurethane layer described above, and the second resin layer may be the acrylic pressure-sensitive adhesive layer described above. The first resin layer and the second resin layer may be the polyurethane layer described above. In consideration of the dispersibility of the colorant, it is more preferable that the first resin layer is an acrylic pressure-sensitive adhesive layer or a polyurethane layer, and the second resin layer is an acrylic pressure-sensitive adhesive layer.

[0077] <Method of manufacturing adhesive sheets> The method for laminating the first adhesive layer 11, the intermediate resin layer 12, and the second adhesive layer 13 in this order is not particularly limited, and examples include a method in which the first adhesive layer 11, the second adhesive layer 13, and the intermediate resin layer 12 are produced separately and then bonded together.

[0078] The method for producing the first pressure-sensitive adhesive layer 11 and the second pressure-sensitive adhesive layer 13 is not particularly limited, and may be, for example, a method in which a pressure-sensitive adhesive composition is applied using a general-purpose film-forming device or film-forming method such as various coating devices, bar coaters, doctor blades, etc. Alternatively, the first pressure-sensitive adhesive layer 11 and the second pressure-sensitive adhesive layer 13 may be produced using a centrifugal molding method.

[0079] 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.

[0080] A release film may be attached to each side of the pressure-sensitive adhesive sheet. The release film can protect both sides of the pressure-sensitive adhesive sheet until just before it is attached to the adherend, preventing a decrease in adhesiveness and the adhesion of foreign matter. In addition, the pressure-sensitive adhesive sheet is prevented from sticking to anything other than the adherend, improving handleability.

[0081] Examples of the release film include PET film, etc. The surface of the release film that comes into contact with the pressure-sensitive adhesive sheet may be subjected to an easy-release treatment (release treatment) such as silicon treatment. [Example]

[0082] The present invention will be explained in more detail below by giving examples, but the present invention is not limited to these examples.

[0083] Table 1 below shows the colorants and ultraviolet absorbers used in the examples and comparative examples.

[0084] [Table 1]

[0085] The content of the composite oxide containing copper, iron, and manganese in the composite oxide pigment was 10 to 15 mass %. The content of carbon black in the inorganic black pigment containing carbon black was 10 mass %, and the median diameter D50 of the carbon black (measured with a particle size distribution analyzer) was 71.1 nm.

[0086] (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.

[0087] (Preparation of Thermosetting Polyurethane Composition) (1-1) 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")

[0088] Example 1 <First and second pressure-sensitive adhesive layers> To prepare the acrylic resin composition for the first pressure-sensitive adhesive layer, 1.3 parts by mass of an ultraviolet absorber UVA-1 shown in Table 1 was further added to the above acrylic resin composition A. To prepare the acrylic resin composition for the second pressure-sensitive adhesive layer, 0.6 parts by mass of a complex oxide pigment shown in Table 1 was further added to the above acrylic resin composition A. The contents of the complex oxide pigment and the ultraviolet absorber are the contents relative to 100 parts by mass of the acrylic resin contained in the acrylic resin composition A. 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 dried thickness would be 25 μm. After drying the solvent, a 50 μm-thick release PET film was laminated and cured to prepare first and second acrylic pressure-sensitive adhesive layers sandwiched between the release PET films.

[0089] <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.

[0090] <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 1 having the first pressure-sensitive adhesive layer, polyurethane layer, and second pressure-sensitive adhesive layer in this order.

[0091] Examples 2 to 4 Pressure-sensitive adhesive sheets according to Examples 2 to 4 were produced in the same manner as in Example 1, except that the thickness of the polyurethane layer and / or the first pressure-sensitive adhesive layer was changed as shown in Table 2.

[0092] Example 5 An adhesive sheet according to Example 5 was produced in the same manner as in Example 1, except that acrylic resin composition A was used as is as the acrylic resin composition for the first adhesive layer, and an ultraviolet absorber was further added to thermosetting polyurethane composition B as the thermosetting polyurethane composition, as shown in Table 2, and the thickness of the polyurethane layer was changed to 1000 μm.

[0093] Examples 6 to 8 Pressure-sensitive adhesive sheets according to Examples 6 to 8 were produced in the same manner as in Example 1, except that the type and amount of colorant added to the second pressure-sensitive adhesive layer was changed as shown in Table 2.

[0094] (Comparative Example 1) A pressure-sensitive adhesive sheet according to Comparative Example 1 was prepared in the same manner as in Example 1, except that no ultraviolet absorber was added and acrylic resin composition A was used as is as the acrylic resin composition for the first pressure-sensitive adhesive layer.

[0095] (Comparative Example 2) An adhesive sheet according to Comparative Example 2 was prepared in the same manner as in Example 1, except that no ultraviolet absorber was added as the acrylic resin composition for the first adhesive layer, and acrylic resin composition A was used as is, and the type and amount of colorant added to the second adhesive layer was changed as shown in Table 3.

[0096] <Weather resistance test> Test pieces measuring 2 cm x 5 cm were cut from the pressure-sensitive adhesive sheets of the Examples and Comparative Examples. 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 with the first pressure-sensitive adhesive layer exposed on 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 test pieces were exposed to rain under the following conditions with the first pressure-sensitive adhesive layer exposed, so that the pressure-sensitive adhesive sheets were irradiated with light while their surfaces were 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.

[0097] A weather resistance test was conducted for a total of 24 hours using a metalling weather meter equipped with a metal halide lamp in accordance with JIS K 7350-1 and JIS K 7350-2, consisting of 20 hours under the following light conditions and 4 hours under the following dark conditions. The metalling weather meter used was an "MT6" manufactured by Suga Test Instruments. The cumulative light intensity of the 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%

[0098] 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.

[0099] In Table 2, the contents of the colorant and the ultraviolet absorber are the contents relative to 100 parts by mass of the acrylic resin contained in the acrylic resin composition A, or the contents relative to 100 parts by mass of the polyol component.

[0100] [Table 2]

[0101] [Table 3]

[0102] The results of Examples 1 to 3 and 5 to 8 confirmed that discoloration of the pressure-sensitive adhesive sheet can be suppressed by adding a colorant to the second pressure-sensitive adhesive layer and an ultraviolet absorber to the first pressure-sensitive adhesive layer. Furthermore, the results of Example 4 confirmed that discoloration of the pressure-sensitive adhesive sheet can also be suppressed by adding a colorant to the second pressure-sensitive adhesive layer and an ultraviolet absorber to the polyurethane layer. On the other hand, the results of Comparative Examples 1 and 2 confirmed that discoloration of the pressure-sensitive adhesive sheet occurs when no ultraviolet absorber is added to either the first pressure-sensitive adhesive layer or the polyurethane layer. [Explanation of symbols]

[0103] 10: Adhesive sheet 11: First adhesive layer 12: Intermediate resin layer 13: Second adhesive layer

Claims

1. The optical disc comprises, in order from the observation surface side, a first pressure-sensitive adhesive layer, an intermediate resin layer, and a second pressure-sensitive adhesive layer, the intermediate resin layer or the second pressure-sensitive adhesive layer contains a colorant, at least one of the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer is an acrylic pressure-sensitive adhesive layer containing an acrylic resin; A pressure-sensitive adhesive sheet, wherein the first pressure-sensitive adhesive layer or the intermediate resin layer located on the observation surface side of the layer containing the colorant contains an ultraviolet absorber.

2. The pressure-sensitive adhesive sheet according to claim 1 , wherein the intermediate resin layer is a polyurethane layer.

3. The pressure-sensitive adhesive sheet according to claim 2 , wherein the polyurethane layer is a cured product of a thermosetting polyurethane composition containing a polyol component and a polyisocyanate component.

4. The pressure-sensitive adhesive sheet according to claim 1 , wherein the colorant comprises a complex oxide pigment or a lactam pigment.

5. The pressure-sensitive adhesive sheet according to claim 1 , which has a total light transmittance of 80% or less.

6. The total light transmittance is 30% or more and 80% or less, The pressure-sensitive adhesive sheet according to any one of claims 1 to 5, which is a pressure-sensitive adhesive sheet for bonding optical members, used for bonding optical members.

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