Photocurable pressure-sensitive adhesive composition, double-sided pressure-sensitive adhesive sheet and method for producing same, and optical device and method for producing same

Abstract

To provide a colored double-sided adhesive sheet having light absorption to visible light, and a photocurable adhesive composition to be used for manufacturing the sheet.SOLUTION: A photocurable adhesive composition includes a polymer, a photopolymerizable compound, a photoinitiator and a colorant. In the colorant, a transmissivity in an ultraviolet region (wavelength 330-400 nm) is larger than a transmissivity in a visible light region (wavelength 400-700 nm). Through applying this composition onto a substrate and performing a photocoagulation or a removal of a solvent as needed, a colored double-sided adhesive sheet is formed.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a photocurable pressure-sensitive adhesive composition, a double-sided pressure-sensitive adhesive sheet formed from the photocurable pressure-sensitive adhesive composition, and an optical device including the double-sided pressure-sensitive adhesive sheet. [Background technology]

[0002] In optical devices, adhesive sheets are used for laminating between components. For example, in a liquid crystal display device, optical films such as retardation films and polarizing plates are attached to both sides of a liquid crystal cell via an adhesive sheet. In an organic EL display device, a circular polarizing plate is attached to the viewing side surface of the organic EL cell via an adhesive sheet in order to prevent reflection of external light by the metal electrode of the organic EL cell. In addition, optical members such as a touch panel sensor and a cover window are attached to the surface of these image display devices via an adhesive sheet.

[0003] It has been proposed to use a photocurable adhesive composition that is cured by irradiation with active light such as ultraviolet light as an adhesive sheet used for bonding components of an optical device. For example, Patent Document 1 shows an example in which a photopolymerization initiator is added to a monomer component, UV polymerization is performed in a solvent-free system, a multifunctional monomer and a photopolymerization initiator are added to the obtained low-polymerization degree polymer (partially polymerized product) to prepare a photocurable adhesive composition, which is applied to a substrate and then UV polymerization is performed again to obtain a transparent adhesive sheet. Patent Document 2 shows an example in which a solution containing a monomer component and a thermal polymerization initiator is heated to prepare a polymer solution by solution polymerization, an isocyanate-based crosslinking agent, a multifunctional monomer and a photopolymerization initiator are added to this solution to prepare a photocurable adhesive composition, which is applied to a substrate and then the solvent is removed by heating to obtain a transparent adhesive sheet. In this adhesive sheet, the multifunctional monomer is in an unreacted state, and when the adhesive sheet is bonded to an adherend and then irradiated with UV light, the storage modulus increases due to photopolymerization of the multifunctional monomer, thereby improving the adhesion reliability to the adherend. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2011-74308 A [Patent Document 2] JP 2014-227453 A Summary of the Invention [Problem to be solved by the invention]

[0005] As shown in Patent Documents 1 and 2, a transparent adhesive sheet with a total light transmittance of 90% or more is generally used to bond components of an optical device. On the other hand, it is expected that an adhesive sheet that absorbs visible light will be used in an optical device for the purpose of controlling visibility, etc. An adhesive composition containing a colorant is used to prepare an adhesive sheet that absorbs visible light. An object of the present invention is to provide an adhesive composition that contains a colorant and is photocurable, and an adhesive sheet formed using the adhesive composition. [Means for solving the problem]

[0006] The pressure-sensitive adhesive composition of the present invention contains a polymer, a photopolymerizable compound, a photopolymerization initiator, and a colorant, and has photocurability. The colorant contained in the photocurable pressure-sensitive adhesive composition preferably has a maximum transmittance at wavelengths of 330 to 400 nm that is greater than the maximum transmittance at wavelengths of 400 to 700 nm. The colorant preferably has an average transmittance at wavelengths of 330 to 400 nm that is greater than the average transmittance at wavelengths of 400 to 700 nm. As the colorant, a pigment, a dye, or the like is used.

[0007] The photopolymerization initiator preferably has at least one absorption maximum in the wavelength range of 330 to 400 nm. The polymer contained in the pressure-sensitive adhesive composition may be an acrylic polymer. The glass transition temperature of the polymer may be 0° C. or lower. The pressure-sensitive adhesive composition may contain a crosslinking agent capable of crosslinking with the polymer. Examples of the crosslinking agent include an isocyanate crosslinking agent and an epoxy crosslinking agent.

[0008] The pressure-sensitive adhesive composition is formed into a sheet to obtain a double-sided pressure-sensitive adhesive sheet. The double-sided pressure-sensitive adhesive sheet may have a maximum transmittance at wavelengths of 330 to 400 nm that is greater than the maximum transmittance at wavelengths of 400 to 700 nm, and may have an average transmittance at wavelengths of 330 to 400 nm that is greater than the average transmittance at wavelengths of 400 to 700 nm. The double-sided pressure-sensitive adhesive sheet may have an average transmittance at wavelengths of 400 to 700 nm that is 80% or less. The double-sided pressure-sensitive adhesive sheet may have a total light transmittance of 80% or less.

[0009] The double-sided pressure-sensitive adhesive sheet may have a thickness of, for example, about 10 to 500 μm. The double-sided pressure-sensitive adhesive sheet may have a shear storage modulus of 10 to 1000 kPa at a temperature of 25° C. The double-sided pressure-sensitive adhesive sheet may have a shear storage modulus of 3 to 300 kPa at a temperature of 85° C.

[0010] The double-sided pressure-sensitive adhesive sheet of the first embodiment of the present invention is formed by applying the pressure-sensitive adhesive composition in a sheet form on a substrate, and irradiating the sheet-like coating film on the substrate with ultraviolet light to photocure the photopolymerizable compound. That is, the double-sided pressure-sensitive adhesive sheet of the first embodiment is composed of a photocured sheet-like molded product of the photocurable pressure-sensitive adhesive composition. The double-sided pressure-sensitive adhesive sheet of the first embodiment may have a non-volatile content of 90% or more.

[0011] The double-sided pressure-sensitive adhesive sheet of the second embodiment of the present invention is formed by applying the pressure-sensitive adhesive composition described above to a substrate in the form of a sheet and removing the solvent as necessary. The double-sided pressure-sensitive adhesive sheet of the second embodiment is a photocurable pressure-sensitive adhesive sheet that contains a photopolymerizable compound in an unreacted state.

[0012] The double-sided pressure-sensitive adhesive sheet is used, for example, to bond a plurality of members (adherends) in the formation of an optical device such as an image display device. The first adherend is bonded to the first main surface of the double-sided pressure-sensitive adhesive sheet, and the second adherend is bonded to the second main surface, thereby bonding the first adherend and the second adherend via the double-sided pressure-sensitive adhesive sheet. If the double-sided pressure-sensitive adhesive sheet has photocurability, the double-sided pressure-sensitive adhesive sheet may be irradiated with ultraviolet light after bonding to the adherend to photocure the photopolymerizable compound. Effect of the Invention

[0013] The colored adhesive sheet can be obtained by using the adhesive composition containing the colorant. Since the colorant contained in the photocurable adhesive composition has UV transparency, even when photocuring is performed by UV irradiation, curing inhibition is unlikely to occur and the polymerization rate can be increased. [Brief description of the drawings]

[0014] [Figure 1] FIG. 2 is a cross-sectional view showing an example of the configuration of a pressure-sensitive adhesive sheet with a release film. [Diagram 2] 1 is a transmission spectrum of a black colorant used in an example. [Diagram 3] 1 is a graph plotting the relationship between the amount of ultraviolet light irradiation and the non-volatile content of the pressure-sensitive adhesive sheet. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] 1 shows a pressure-sensitive adhesive sheet with release films, in which release films 1, 2 are temporarily attached to both sides of a double-sided pressure-sensitive adhesive sheet 5. The double-sided pressure-sensitive adhesive sheet 5 is formed by forming a pressure-sensitive adhesive composition into a sheet. The pressure-sensitive adhesive composition is generally a viscous liquid containing a polymer, and a double-sided pressure-sensitive adhesive sheet is obtained by applying the pressure-sensitive adhesive composition in the form of a layer onto a substrate and removing the solvent as necessary.

[0016] The double-sided pressure-sensitive adhesive sheet of the present invention is formed using a photocurable pressure-sensitive adhesive composition. The photocurable pressure-sensitive adhesive composition contains a photopolymerizable compound and a photopolymerization initiator in addition to a polymer. The double-sided pressure-sensitive adhesive sheet of the present invention is a colored pressure-sensitive adhesive sheet that absorbs visible light. A pressure-sensitive adhesive composition containing a colorant is used to form the colored pressure-sensitive adhesive sheet. That is, the photocurable pressure-sensitive adhesive composition used to form the double-sided pressure-sensitive adhesive sheet of the present invention contains a colorant in addition to a polymer, a photopolymerizable compound, and a photopolymerization initiator.

[0017] Double-sided pressure-sensitive adhesive sheets formed using a photocurable pressure-sensitive adhesive composition are broadly divided into a type in which photocuring is performed on a substrate (first form) and a type in which photocuring is not performed on a substrate but is performed after lamination with an adherend (second form).

[0018] [First form] The double-sided pressure-sensitive adhesive sheet of the first embodiment of the present invention is formed by applying a photocurable pressure-sensitive adhesive composition containing a polymer, a photopolymerizable compound, a photopolymerization initiator, and a colorant onto a substrate, and then photocuring the composition on the substrate.

[0019] <Adhesive composition> (polymer) Examples of the polymer contained in the pressure-sensitive adhesive composition include acrylic polymers, silicone polymers, polyesters, polyurethanes, polyamides, polyvinyl ethers, vinyl acetate / vinyl chloride copolymers, modified polyolefins, epoxy-based, fluorine-based, and rubber-based polymers such as natural rubber and synthetic rubber. In particular, acrylic polymers are preferably used because they exhibit appropriate adhesive properties such as wettability, cohesiveness, and adhesiveness, and are also excellent in weather resistance and heat resistance.

[0020] The acrylic polymer contains a (meth)acrylic acid alkyl ester as a main constituent monomer component. In this specification, "(meth)acrylic" means acrylic and / or methacrylic. The amount of the (meth)acrylic acid alkyl ester relative to the total amount of the monomer components constituting the acrylic polymer is preferably 50% by weight or more, more preferably 55% by weight or more, and even more preferably 60% by weight or more.

[0021] The (meth)acrylic acid alkyl ester is preferably a (meth)acrylic acid alkyl ester having an alkyl group with a carbon number of 1 to 20. The (meth)acrylic acid alkyl ester may have an alkyl group that is branched or may have a cyclic alkyl group.

[0022] Specific examples of (meth)acrylic acid alkyl esters having a chain alkyl group include methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, neopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, and isooctyl (meth)acrylate. Examples of the acrylates include octyl, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, isotridecyl (meth)acrylate, tetradecyl (meth)acrylate, isotetradecyl (meth)acrylate, pentadecyl (meth)acrylate, cetyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, isooctadecyl (meth)acrylate, and nonadecyl (meth)acrylate.

[0023] Specific examples of (meth)acrylic acid alkyl esters having an alicyclic alkyl group include (meth)acrylic acid cycloalkyl esters such as cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, cycloheptyl (meth)acrylate, and cyclooctyl (meth)acrylate; (meth)acrylic acid esters having a bicyclic aliphatic hydrocarbon ring such as isobornyl (meth)acrylate; and (meth)acrylic acid esters having a tricyclic or higher aliphatic hydrocarbon ring such as dicyclopentanyl (meth)acrylate, dicyclopentanyloxyethyl (meth)acrylate, tricyclopentanyl (meth)acrylate, 1-adamantyl (meth)acrylate, 2-methyl-2-adamantyl (meth)acrylate, and 2-ethyl-2-adamantyl (meth)acrylate.

[0024] The acrylic polymer may contain a polar group-containing monomer such as a hydroxyl group-containing monomer, a carboxyl group-containing monomer, or a nitrogen-containing monomer as a constituent monomer component. When the acrylic polymer contains a polar group-containing monomer as a constituent monomer component, the cohesive strength of the adhesive tends to be increased and the adhesive strength tends to be improved. The amount of the polar group-containing monomer (the total of the hydroxyl group-containing monomer, the carboxyl group-containing monomer, and the nitrogen-containing monomer) relative to the total amount of the monomer components constituting the acrylic polymer is, for example, about 3 to 50% by weight, and may be 5 to 40% by weight, or 10 to 30% by weight.

[0025] Examples of hydroxyl group-containing monomers include (meth)acrylic acid esters such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, and (4-hydroxymethylcyclohexyl)-methyl (meth)acrylate. When a crosslinking structure is introduced into the polymer by an isocyanate crosslinking agent, the hydroxyl group can become a reaction point (crosslinking point) with the isocyanate group.

[0026] Examples of the carboxy group-containing monomer include acrylic monomers such as (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, etc., as well as itaconic acid, maleic acid, fumaric acid, crotonic acid, etc. When a crosslinked structure is introduced into a polymer by an epoxy crosslinking agent, the carboxy group can become a reaction point (crosslinking point) with the epoxy group.

[0027] Examples of the nitrogen-containing monomer include vinyl monomers such as N-vinylpyrrolidone, methylvinylpyrrolidone, vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazole, vinyloxazole, vinylmorpholine, (meth)acryloylmorpholine, N-vinylcarboxylic acid amides, and N-vinylcaprolactam, and cyano group-containing monomers such as acrylonitrile and methacrylonitrile.

[0028] The acrylic polymer may contain, as monomer components other than those mentioned above, vinyl monomers such as acid anhydride group-containing monomers, caprolactone adducts of (meth)acrylic acid, sulfonic acid group-containing monomers, phosphoric acid group-containing monomers, vinyl acetate, vinyl propionate, styrene, and α-methylstyrene; epoxy group-containing monomers such as glycidyl (meth)acrylate; glycol-based acrylic ester monomers such as polyethylene glycol (meth)acrylate, polypropylene glycol (meth)acrylate, methoxyethylene glycol (meth)acrylate, and methoxypolypropylene glycol (meth)acrylate; and acrylic ester monomers such as tetrahydrofurfuryl (meth)acrylate, fluorine (meth)acrylate, silicone (meth)acrylate, and 2-methoxyethyl (meth)acrylate.

[0029] The glass transition temperature (Tg) of the polymer contained in the pressure-sensitive adhesive composition is preferably 0°C or lower. The glass transition temperature of the polymer may be -5°C or lower, -10°C or lower, or -15°C or lower. The glass transition temperature of the polymer is the peak top temperature of the loss tangent (tan δ) measured by dynamic viscoelasticity measurement. When a crosslinked structure is introduced into the polymer, the glass transition temperature may be calculated based on the theoretical Tg from the composition of the polymer. The theoretical Tg is the glass transition temperature Tg of a homopolymer of the constituent monomer components of the polymer. i and the weight fraction W of each monomer component i It is calculated using the following Fox formula: 1 / Tg=Σ(W i / Tg i )

[0030] Tg is the glass transition temperature of the polymer (unit: K), W i is the weight fraction of monomer component i that constitutes the polymer (copolymerization ratio by weight), Tg i is the glass transition temperature (unit: K) of a homopolymer of monomer component i. The glass transition temperature of a homopolymer can be determined from the values ​​listed in Polymer Handbook, 3rd Edition (John Wiley & Sons, Inc., 1989). For the Tg of a homopolymer of a monomer not listed in the above literature, the peak top temperature of tan δ measured by dynamic viscoelasticity measurement can be used.

[0031] The monomer components are polymerized by various known methods to obtain a polymer. The polymerization method is not particularly limited, but in the adhesive composition used for preparing the first type of double-sided adhesive sheet in which the adhesive composition is photocured on the substrate, the polymer is preferably prepared by photopolymerization. Since the polymer can be prepared without using a solvent in photopolymerization, it is not necessary to dry and remove the solvent when forming the adhesive sheet, and a thick adhesive sheet can be uniformly formed.

[0032] In the preparation of a type of adhesive sheet in which the adhesive composition is photocured on a substrate, it is preferable to prepare a polymer (prepolymer) with a low degree of polymerization in which a part of the monomer component remains unreacted. The composition (prepolymer forming composition) used for preparing the prepolymer preferably contains a photopolymerization initiator in addition to the monomer. The photopolymerization initiator may be appropriately selected according to the type of monomer. For example, a photoradical polymerization initiator is used for the polymerization of an acrylic polymer. Examples of the photopolymerization initiator include a benzoin ether-based photopolymerization initiator, an acetophenone-based photopolymerization initiator, an α-ketol-based photopolymerization initiator, an aromatic sulfonyl chloride-based photopolymerization initiator, a photoactive oxime-based photopolymerization initiator, a benzoin-based photopolymerization initiator, a benzyl-based photopolymerization initiator, a benzophenone-based photopolymerization initiator, a ketal-based photopolymerization initiator, a thioxanthone-based photopolymerization initiator, and an acylphosphine oxide-based photopolymerization initiator.

[0033] In the polymerization, a chain transfer agent, a polymerization inhibitor (polymerization retarder), etc. may be used for the purpose of molecular weight adjustment, etc. Examples of the chain transfer agent include thiols such as α-thioglycerol, lauryl mercaptan, glycidyl mercaptan, mercaptoacetic acid, 2-mercaptoethanol, thioglycolic acid, 2-ethylhexyl thioglycolate, and 2,3-dimercapto-1-propanol, and α-methylstyrene dimer.

[0034] The polymerization rate of the prepolymer is not particularly limited, but is preferably 3 to 50% by weight, more preferably 5 to 40% by weight, from the viewpoint of obtaining a viscosity suitable for application onto a substrate. The polymerization rate of the prepolymer can be adjusted to a desired range by adjusting the type and amount of photopolymerization initiator, the irradiation intensity and irradiation time of active light such as UV light, etc. The polymerization rate of the prepolymer is the non-volatile content when heated at 130°C for 3 hours, and is calculated by the following formula. The polymerization rate (non-volatile content) of the pressure-sensitive adhesive sheet is also measured by the same method. Polymerization rate (%) = weight after heating / weight before heating x 100

[0035] As described above, the photocurable adhesive composition used to form the colored adhesive sheet contains a polymer, a photopolymerizable compound, a photopolymerization initiator, and a colorant. For example, the photocurable adhesive composition can be obtained by adding the photopolymerizable compound, the photopolymerization initiator, and the colorant to a prepolymer. Instead of using a prepolymer, a low molecular weight polymer (oligomer) can be used, and the low molecular weight polymer can be mixed with the photopolymerizable compound, the photopolymerization initiator, and the colorant to prepare the adhesive composition.

[0036] (Photopolymerizable compound) The photopolymerizable compound contained in the pressure-sensitive adhesive composition has one or more photopolymerizable functional groups in one molecule. The photopolymerizable functional group may be any of radical polymerizable, cationic polymerizable, and anionic polymerizable, but a radical polymerizable functional group having an unsaturated double bond (ethylenically unsaturated group) is preferred because of its excellent reactivity.

[0037] The prepolymer contains a monomer that has not reacted with the polymer, and the unreacted monomer retains photopolymerizability. Therefore, in the preparation of the pressure-sensitive adhesive composition, it is not necessary to add a photopolymerizable compound. When a photopolymerizable compound is added to the prepolymer, the photopolymerizable compound to be added may be the same as or different from the monomer used in the preparation of the prepolymer.

[0038] When the polymer is an acrylic polymer, the compound added as the photopolymerizable compound is preferably a monomer or oligomer having a (meth)acryloyl group as a photopolymerizable functional group, since it has high compatibility with the polymer. The photopolymerizable compound may be a polyfunctional compound having two or more photopolymerizable functional groups in one molecule. Examples of the photopolymerizable polyfunctional compound include polyfunctional (meth)acrylates. Examples of the polyfunctional (meth)acrylates include bifunctional compounds such as polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, polytetramethylene glycol di(meth)acrylate, bisphenol A ethylene oxide modified di(meth)acrylate, bisphenol A propylene oxide modified di(meth)acrylate, alkanediol di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, pentaerythritol di(meth)acrylate, neopentyl glycol di(meth)acrylate, glycerin di(meth)acrylate, and urethane di(meth)acrylate. functional (meth)acrylic acid esters; trifunctional (meth)acrylic acid esters such as pentaerythritol tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, and ethoxylated isocyanuric acid tri(meth)acrylate; tetrafunctional (meth)acrylic acid esters such as ditrimethylolpropane tetra(meth)acrylate, ethoxylated pentaerythritol tetra(meth)acrylate, and pentaerythritol tetra(meth)acrylate; and penta- or higher functional (meth)acrylic acid esters such as dipentaerythritol penta(meth)acrylate and dipentaerythritol hexa(meth)acrylate.

[0039] When a polyfunctional compound is used as the photopolymerizable compound, the amount of the polyfunctional compound used is preferably 40 parts by weight or less, more preferably 30 parts by weight or less, and even more preferably 25 parts by weight or less, relative to 100 parts by weight of the total amount of monomers (the total of the monomers used to prepare the prepolymer and the photopolymerizable compound added to the prepolymer). If the amount of the polyfunctional monomer used is excessively large, the adhesive sheet after photocuring may have low viscosity and poor adhesive strength. The amount of the polyfunctional compound used may be 20 parts by weight or less, 15 parts by weight or less, 10 parts by weight or less, or 5 parts by weight or less. The amount of the polyfunctional monomer used may be 0, 0.1 parts by weight or more, 0.3 parts by weight or more, or 0.5 parts by weight or more.

[0040] (Photopolymerization initiator) The photocurable pressure-sensitive adhesive composition contains a photopolymerization initiator. The photopolymerization initiator generates radicals, acids, bases, etc., when irradiated with active light such as ultraviolet light, and can be appropriately selected depending on the type of photopolymerizable compound, etc. When the photopolymerizable compound is a compound having a (meth)acryloyl group (e.g., monofunctional or polyfunctional (meth)acrylate), it is preferable to use a photoradical polymerization initiator as the photopolymerization initiator. The photopolymerization initiator may be used alone or in a mixture of two or more kinds.

[0041] In the case where the photopolymerization initiator used in the preparation (polymerization) of the prepolymer remains in the prepolymer composition without being deactivated, the addition of the photopolymerization initiator may be omitted. In the case where a photopolymerization initiator is added to the prepolymer composition, the photopolymerization initiator to be added may be the same as or different from the photopolymerization initiator used in the preparation of the prepolymer.

[0042] The photopolymerization initiator contained in the pressure-sensitive adhesive composition preferably has an absorption maximum in a wavelength region where the light absorption by the colorant described below is small. Specifically, the photopolymerization initiator preferably has an absorption maximum in a wavelength region of 330 to 400 nm. Since the photopolymerization initiator has an absorption maximum in a region where the light absorption by the colorant is small, the curing inhibition by the colorant is suppressed, so that the polymerization rate can be sufficiently increased by photocuring. Examples of photoradical polymerization initiators having an absorption maximum in a wavelength region of 330 to 400 nm include hydroxyketones, benzyl dimethyl ketals, aminoketones, acylphosphine oxides, benzophenones, trichloromethyl group-containing triazine derivatives, and the like.

[0043] The content of the photopolymerization initiator in the photocurable pressure-sensitive adhesive composition is about 0.01 to 10 parts by weight, and preferably about 0.05 to 5 parts by weight, per 100 parts by weight of the total amount of monomers (monomers used to prepare the prepolymer and the photopolymerizable compound added to the prepolymer).

[0044] (Coloring agent) The adhesive composition used to form the colored adhesive sheet contains a colorant. The colorant may be a dye or a pigment as long as it is soluble or dispersible in the adhesive composition. Pigments are preferred because they have high color expression even when added in small amounts.

[0045] The colorant used is one that absorbs visible light and transmits ultraviolet light. The colorant preferably has a maximum transmittance at wavelengths of 330 to 400 nm that is greater than the maximum transmittance at wavelengths of 400 to 700 nm. The colorant preferably has an average transmittance at wavelengths of 330 to 400 nm that is greater than the average transmittance at wavelengths of 400 to 700 nm. The transmittance of the colorant is measured using a solution or dispersion diluted with a suitable solvent or dispersion medium (an organic solvent with low absorption in the wavelength range of 330 to 700 nm) such as tetrahydrofuran (THF) so that the transmittance at a wavelength of 400 nm is about 50 to 60%.

[0046] Examples of ultraviolet-transmitting black pigments that absorb less ultraviolet light than visible light include "9050BLACK" and "UVBK-0001" manufactured by Tokushiki Co., Ltd. Examples of ultraviolet-transmitting black dyes include "SOC-L-0123" manufactured by Orient Chemical Industries Co., Ltd.

[0047] Carbon black and titanium black, which are generally used as black colorants, have a higher ultraviolet absorption than visible light absorption (UV transmittance is lower than visible light transmittance). Therefore, when a colorant such as carbon black is added to a photocurable adhesive composition sensitive to ultraviolet light, most of the ultraviolet light irradiated for photocuring is absorbed by the colorant, the amount of light absorbed by the photopolymerization initiator is small, and photocuring takes time (the cumulative amount of light irradiation increases). In addition, when the thickness of the adhesive sheet is large, there is little ultraviolet light reaching the surface opposite to the light irradiated surface, so that even if light is irradiated for a long time, photocuring tends to be insufficient. In contrast, by using a colorant with a higher ultraviolet transmittance than visible light, the curing inhibition caused by the colorant can be suppressed.

[0048] The content of the colorant in the photocurable pressure-sensitive adhesive composition is, for example, about 0.01 to 20 parts by weight relative to 100 parts by weight of the total amount of monomers, and may be appropriately set depending on the type of colorant, the color tone and light transmittance of the pressure-sensitive adhesive sheet, etc. The colorant may be added to the composition as a solution or dispersion in which it is dissolved or dispersed in an appropriate solvent.

[0049] (Other Ingredients) The photocurable adhesive composition may contain components other than the polymer, the photopolymerizable compound, the photopolymerization initiator, and the colorant. For example, a chain transfer agent may be contained for the purpose of adjusting the photocuring speed. In addition, an oligomer or a tackifier may be contained for the purpose of adjusting the viscosity of the adhesive composition or the adhesive strength of the adhesive sheet. As the oligomer, for example, one having a weight average molecular weight of about 1000 to 30000 is used. As the oligomer, an acrylic oligomer is preferable because it has excellent compatibility with acrylic polymers. The adhesive composition may contain additives such as a silane coupling agent, a plasticizer, a softener, an antidegradant, a filler, an antioxidant, a surfactant, and an antistatic agent.

[0050] <Preparation of double-sided adhesive sheet> A photocurable adhesive composition containing a colorant is applied in a sheet (layer) on a substrate, and the coating of the adhesive composition on the substrate is irradiated with ultraviolet light to perform photocuring, thereby obtaining a double-sided adhesive sheet. When performing photocuring, it is preferable to attach a cover sheet to the surface of the coating, and irradiate the adhesive composition with ultraviolet light while sandwiched between the two sheets, thereby preventing polymerization inhibition due to oxygen. Before photocuring, the sheet-like coating may be heated for the purpose of removing the solvent or dispersion medium of the colorant. When removing the solvent or the like by heating, it is preferable to perform the removal before attaching the cover sheet.

[0051] The substrate and cover sheet used to form the double-sided pressure-sensitive adhesive sheet may be any suitable substrate. The substrate and cover sheet may be a release film having a release layer on the surface that comes into contact with the double-sided pressure-sensitive adhesive sheet.

[0052] As the film substrate of the release film, films made of various resin materials are used. Examples of the resin materials include polyester resins such as polyethylene terephthalate and polyethylene naphthalate, acetate resins, polyethersulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, (meth)acrylic resins, polyvinyl chloride resins, polyvinylidene chloride resins, polystyrene resins, polyvinyl alcohol resins, polyarylate resins, and polyphenylene sulfide resins. Among these, polyester resins such as polyethylene terephthalate are particularly preferred. The thickness of the film substrate is preferably 10 to 200 μm, and more preferably 25 to 150 μm. Examples of materials for the release layer include silicone-based release agents, fluorine-based release agents, long-chain alkyl-based release agents, and fatty acid amide-based release agents. The thickness of the release layer is generally about 10 to 2000 nm.

[0053] As a method for applying the pressure-sensitive adhesive composition onto a substrate, various methods such as roll coating, kiss roll coating, gravure coating, reverse coating, roll brush, spray coating, dip roll coating, bar coating, knife coating, air knife coating, curtain coating, lip coating, and die coater can be used.

[0054] The thickness of the double-sided pressure-sensitive adhesive sheet is not particularly limited and may be set depending on the type and shape of the adherend. The thickness of the double-sided pressure-sensitive adhesive sheet is, for example, about 10 to 500 μm, and may be 20 μm or more, 30 μm or more, 40 μm or more, or 50 μm or more. As described above, since the colorant has ultraviolet light transmittance, even if the thickness of the double-sided pressure-sensitive adhesive sheet is large, it is possible to photocure the photocurable composition uniformly in the thickness direction. The thickness of the double-sided pressure-sensitive adhesive sheet may be 400 μm or less, 300 μm or less, 250 μm or less, or 200 μm or less.

[0055] By irradiating the adhesive composition coated in a layer on the substrate with ultraviolet light, active species are generated from the photopolymerization initiator, the photopolymerizable compound is polymerized, and the liquid adhesive composition becomes a solid (standard) adhesive sheet with an increase in the polymerization rate (a decrease in unreacted monomers). The light source for ultraviolet light irradiation is not particularly limited as long as it can irradiate light in a wavelength range to which the photopolymerization initiator contained in the adhesive composition is sensitive, and LED light sources, high pressure mercury lamps, ultra-high pressure mercury lamps, metal halide lamps, xenon lamps, etc. are used.

[0056] The integrated light amount of the irradiation light is, for example, 100 to 5000 mJ / cm 2 The polymerization rate (non-volatile content) of the double-sided pressure-sensitive adhesive sheet made of the photocured product of the photocurable pressure-sensitive adhesive composition is preferably 80% or more, more preferably 85% or more, and even more preferably 90% or more. The polymerization rate may be 93% or more or 95% or more. In order to reduce the non-volatile content, the pressure-sensitive adhesive sheet may be heated to remove volatile content such as residual monomers, unreacted polymerization initiator, and solvent.

[0057] By laminating release films 1 and 2 to the surface of double-sided adhesive sheet 5, an adhesive sheet with release films is obtained in which release films are temporarily attached to both sides, as shown in Figure 1. The release films used as the substrate or cover sheet when forming the double-sided adhesive sheet may be used as release films 1 and 2 as they are.

[0058] When release films 1, 2 are provided on both sides of the double-sided adhesive sheet 5, the thickness of one release film 1 and the thickness of the other release film 2 may be the same or different. The peeling force when peeling off the release film temporarily attached to one side from the double-sided adhesive sheet 5 and the peeling force when peeling off the release film temporarily attached to the other side from the double-sided adhesive sheet 5 may be the same or different. When the two peeling forces are different, the release film 2 (light release film) with a relatively small peeling force is peeled off from the double-sided adhesive sheet 5 first to be bonded to the first adherend, and the release film 1 (heavy release film) with a relatively large peeling force is peeled off to be bonded to the second adherend, which provides excellent workability.

[0059] <Characteristics of double-sided adhesive sheets> The double-sided pressure-sensitive adhesive sheet containing the colorant has optical absorption in visible light. The total light transmittance of the double-sided pressure-sensitive adhesive sheet is, for example, 80% or less, and may be 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, 20% or less, 10% or less, or 5% or less.

[0060] As described above, the colorant used has a smaller absorption of ultraviolet light than visible light. Therefore, the double-sided pressure-sensitive adhesive sheet has a smaller absorption of ultraviolet light than visible light. Specifically, the maximum transmittance T mUV The maximum transmittance T mVIS It is preferable that the average transmittance T aUV is the average transmittance T for wavelengths from 400 to 700 nm aVIS It is preferable that it is greater than .

[0061] Average transmittance T of double-sided adhesive sheet at wavelengths of 400 to 700 nm aVIS is, for example, 80% or less, and may be 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, 20% or less, or 10% or less. aUV is preferably 5% or more, and may be 10% or more, 15% or more, 20% or more, or 25% or more. aUV and T aVIS Difference with T aUV -T aVIS may be 3% or more, 5% or more, 8% or more, or 10% or more.

[0062] Maximum transmittance T of the double-sided adhesive sheet in the wavelength range of 400 to 700 nm mVIS is, for example, 85% or less, and may be 80% or less, 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, 20% or less, or 10% or less. mUVis preferably 5% or more, and may be 10% or more, 15% or more, 20% or more, or 25% or more. mUV and T mVIS Difference with T mUV -T mVIS may be 0.1% or more, 0.5% or more, 1% or more, or 1.5% or more.

[0063] The transmittance of the double-sided adhesive sheet may be adjusted according to the application or purpose. For example, when used as a light-shielding sealing member for an LED array, the average transmittance T aVIS is preferably 10% or less, and may be 7% or less or 5% or less. When the double-sided pressure-sensitive adhesive sheet is used for anti-reflection of OLED, T aVIS is preferably 80% or less, and may be 78% or less, or 75% or less. In any case, the maximum transmittance T aUV is T aVIS The higher the better.

[0064] Shear storage modulus G' of adhesive sheet at 25℃ 25℃ The shear storage modulus G' of the pressure-sensitive adhesive sheet at a temperature of 85° C. is, for example, about 10 to 1000 kPa, and may be 30 kPa or more, 50 kPa or more, 70 kPa or more, or 100 kPa or more, and may be 700 kPa or less, 500 kPa or less, 300 kPa or less, or 200 kPa or less. 85℃ is, for example, about 3 to 300 kPa, and may be 5 kPa or more, 7 kPa or more, or 10 kPa or more, and may be 200 kPa or less, 150 kPa or less, or 100 kPa or less. If the shear storage modulus of the pressure-sensitive adhesive sheet is within the above range, it is possible to achieve both appropriate flexibility and adhesiveness. The shear storage modulus is a value measured by dynamic viscoelasticity measurement at a frequency of 1 Hz.

[0065] [Second form] The double-sided pressure-sensitive adhesive sheet of the second embodiment of the present invention is a pressure-sensitive adhesive sheet of a type that does not undergo photocuring on a substrate, and is a photocurable pressure-sensitive adhesive composition formed into a sheet shape. The double-sided pressure-sensitive adhesive sheet of the second embodiment contains a photopolymerizable compound in an unreacted state, so that the pressure-sensitive adhesive sheet has photocurability.

[0066] <Adhesive composition> The pressure-sensitive adhesive composition used to form the double-sided pressure-sensitive adhesive sheet of the second embodiment contains a polymer, a photopolymerizable compound, a photopolymerization initiator, and a colorant.

[0067] (polymer) As the polymer contained in the pressure-sensitive adhesive composition, various polymers can be used as in the first embodiment, and an acrylic polymer is preferably used. The monomer components constituting the acrylic polymer are the same as in the first embodiment.

[0068] In order to introduce a crosslinked structure by a crosslinking agent described later, the monomer components constituting the polymer preferably contain a hydroxyl group-containing monomer and / or a carboxyl group-containing monomer. For example, when an isocyanate-based crosslinking agent is used, it is preferable to contain a hydroxyl group-containing monomer as a monomer component. When an epoxy-based crosslinking agent is used, it is preferable to contain a carboxyl group-containing monomer as a monomer.

[0069] In the second embodiment, since photocuring is not performed on the substrate, a polymer having a relatively large molecular weight is used as the polymer contained in the photocurable adhesive composition in order to form a solid (standard) adhesive sheet. The weight average molecular weight of the polymer is, for example, about 100,000 to 2,000,000.

[0070] Since the high molecular weight polymer is a solid, in order to apply the adhesive composition to a substrate, it is preferable that the adhesive composition is a solution in which the polymer is dissolved in an organic solvent. For example, the polymer solution can be obtained by solution polymerization of the monomer components. The polymer solution may be prepared by dissolving a solid polymer in an organic solvent.

[0071] As the solvent for solution polymerization, ethyl acetate, toluene, etc. are generally used. The solution concentration is usually about 20 to 80% by weight. As the polymerization initiator, a thermal polymerization initiator such as an azo initiator, a peroxide initiator, or a redox initiator combining a peroxide and a reducing agent (for example, a combination of a persulfate and sodium hydrogen sulfite, or a combination of a peroxide and sodium ascorbate) is preferably used. The amount of the polymerization initiator used is not particularly limited, but for example, it is preferably about 0.005 to 5 parts by weight, more preferably about 0.02 to 3 parts by weight, based on 100 parts by weight of the total amount of the monomer components forming the polymer.

[0072] (Photopolymerizable compound) The photopolymerizable compound contained in the pressure-sensitive adhesive composition in the second embodiment is the same as that described above for the first embodiment, and a compound having one or more photopolymerizable functional groups is used.

[0073] (Photopolymerization initiator) The photopolymerization initiator contained in the pressure-sensitive adhesive composition in the second embodiment is the same as that described above for the first embodiment, and preferably has an absorption maximum in the wavelength region of 330 to 400 nm. The amount of the photopolymerization initiator is about 0.01 to 10 parts by weight, and preferably about 0.05 to 5 parts by weight, based on 100 parts by weight of the polymer.

[0074] (Coloring agent) The colorant contained in the pressure-sensitive adhesive composition in the second embodiment is the same as that described above for the first embodiment, and preferably has a higher transmittance at wavelengths of 330 to 400 nm than at wavelengths of 400 to 700 nm.

[0075] (Crosslinking agent) The second type of pressure-sensitive adhesive composition preferably contains a crosslinking agent capable of crosslinking with the polymer. Specific examples of the crosslinking agent for introducing a crosslinked structure into the polymer include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, carbodiimide-based crosslinking agents, and metal chelate-based crosslinking agents. Among them, isocyanate-based crosslinking agents and epoxy-based crosslinking agents are preferred because they have high reactivity with the hydroxyl group or carboxyl group of the polymer and are easy to introduce a crosslinked structure. These crosslinking agents react with functional groups such as hydroxyl groups and carboxyl groups introduced into the polymer to form a crosslinked structure.

[0076] As the isocyanate crosslinking agent, a polyisocyanate having two or more isocyanate groups in one molecule is used. Examples of the isocyanate crosslinking agent include lower aliphatic polyisocyanates such as butylene diisocyanate and hexamethylene diisocyanate; alicyclic isocyanates such as cyclopentylene diisocyanate, cyclohexylene diisocyanate, and isophorone diisocyanate; aromatic isocyanates such as 2,4-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, and xylylene diisocyanate; trimethylolpropane / Examples of isocyanate adducts include tolylene diisocyanate trimer adducts (e.g., "Coronate L" manufactured by Tosoh), trimethylolpropane / hexamethylene diisocyanate trimer adducts (e.g., "Coronate HL" manufactured by Tosoh), trimethylolpropane adducts of xylylene diisocyanate (e.g., "Takenate D110N" manufactured by Mitsui Chemicals, and isocyanurate of hexamethylene diisocyanate (e.g., "Coronate HX" manufactured by Tosoh).

[0077] The epoxy crosslinking agent is a polyfunctional epoxy compound having two or more epoxy groups in one molecule. The epoxy group of the epoxy crosslinking agent may be a glycidyl group. Examples of epoxy crosslinking agents include N,N,N',N'-tetraglycidyl-m-xylylenediamine, diglycidylaniline, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, 1,6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, sorbitol polyglycidyl ether, glycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, polyglycerol polyglycidyl ether, sorbitan polyglycidyl ether, trimethylolpropane polyglycidyl ether, adipic acid diglycidyl ester, o-phthalic acid diglycidyl ester, triglycidyl-tris(2-hydroxyethyl)isocyanurate, resorcinol diglycidyl ether, and bisphenol-S-diglycidyl ether. As the epoxy-based crosslinking agent, commercially available products such as "Denacol" manufactured by Nagase ChemteX, and "Tetrad X" and "Tetrad C" manufactured by Mitsubishi Gas Chemical may be used.

[0078] The amount of the crosslinking agent is about 0.01 to 5 parts by weight, and may be 0.05 parts by weight or more, 0.1 parts by weight or more, or 0.2 parts by weight or more, and may be 3 parts by weight or less, 2 parts by weight or less, or 1 part by weight or less, relative to 100 parts by weight of the polymer.

[0079] (Other Ingredients) The pressure-sensitive adhesive composition of the second embodiment may contain, in addition to the above-mentioned components, an oligomer, a tackifier, a silane coupling agent, a chain transfer agent, a plasticizer, a softener, an antidegradant, a filler, an antioxidant, a surfactant, an antistatic agent, etc.

[0080] <Preparation of double-sided adhesive sheet> The pressure-sensitive adhesive composition is applied onto a substrate, and the solvent is removed by drying as necessary to form a double-sided pressure-sensitive adhesive sheet on the substrate. As in the first embodiment, a release film is preferably used as the substrate.

[0081] When the pressure-sensitive adhesive composition contains a solvent, it is preferable to dry the solvent after applying the pressure-sensitive adhesive composition onto the substrate. As the drying method, a suitable method can be adopted depending on the purpose. The heating and drying temperature is preferably 40°C to 200°C, more preferably 50°C to 180°C, and particularly preferably 70°C to 170°C. As the drying time, a suitable time can be adopted. The drying time is preferably 5 seconds to 20 minutes, more preferably 5 seconds to 15 minutes, and particularly preferably 10 seconds to 10 minutes.

[0082] After drying the solvent, it is preferable to attach a cover sheet to protect the surface of the double-sided pressure-sensitive adhesive sheet. As the cover sheet, it is preferable to use a release film that has a release layer on the surface that comes into contact with the pressure-sensitive adhesive sheet, similar to the base film.

[0083] After applying the pressure-sensitive adhesive composition onto the substrate, heating is performed as necessary to introduce a crosslinked structure into the polymer. The heating temperature and heating time may be appropriately set depending on the type of crosslinking agent used, and are usually in the range of 20°C to 160°C and about 1 minute to 7 days. Heating for drying the solvent may also serve as heating for crosslinking. The introduction of a crosslinked structure does not necessarily require heating.

[0084] <Characteristics of double-sided adhesive sheets> The double-sided pressure-sensitive adhesive sheet of the second embodiment preferably has the same thickness, light transmittance, and shear storage modulus as the double-sided pressure-sensitive adhesive sheet of the first embodiment. The double-sided pressure-sensitive adhesive sheet of the second embodiment does not undergo photocuring on the substrate, and therefore contains the photopolymerizable compound in an unreacted state. That is, the double-sided pressure-sensitive adhesive sheet of the second embodiment is a photocurable pressure-sensitive adhesive sheet containing a polymer, a photopolymerizable compound, a photopolymerization initiator, and a colorant.

[0085] The photocurable adhesive sheet can be photocured by irradiating ultraviolet light after being attached to an adherend. The adhesive strength between the adhesive sheet and the adherend can be changed by photocuring. For example, since the adhesive sheet before photocuring is highly flexible, it is possible to fill in the surface irregularities and steps of the adherend, and after photocuring, the adhesive strength and adhesive reliability to the adherend can be improved.

[0086] Ultraviolet rays are used as the actinic rays for photocuring the pressure-sensitive adhesive sheet. As in the pressure-sensitive adhesive sheet of the first embodiment, the colorant has a higher transmittance for ultraviolet rays than for visible light, so that photocuring inhibition can be suppressed even when the pressure-sensitive adhesive sheet is thick.

[0087] The thickness of the double-sided pressure-sensitive adhesive sheet is not particularly limited and may be set depending on the type and shape of the adherend. The thickness of the double-sided pressure-sensitive adhesive sheet is, for example, about 10 to 500 μm, and may be 20 μm or more, 30 μm or more, 40 μm or more, or 50 μm or more. As described above, since the colorant has ultraviolet light transmittance, curing inhibition is unlikely to occur, and process efficiency can be improved.

[0088] [Uses of adhesive sheets] The double-sided pressure-sensitive adhesive sheet of the first and second forms can be used to bond various transparent and opaque members. The type of the adherend is not particularly limited, and examples include various resin materials, glass, metal, and the like. The double-sided pressure-sensitive adhesive sheet is used, for example, to bond members of an optical device such as an image display device. Since the pressure-sensitive adhesive sheet is colored, it can have the effect of reducing the emission of scattered light and reflected light to the outside within the device, thereby improving visibility.

[0089] The double-sided adhesive sheet can be used as a filling material between components or as a sealing material, and can also be used to seal optical semiconductor elements. An example of an optical semiconductor element is a light-emitting diode (LED). For example, when an adhesive sheet is used to seal a micro LED array in which multiple LED elements are arranged in a tiled pattern, it is possible to seal multiple LEDs at once because the adhesive sheet has excellent conformability to unevenness such as gaps between the LEDs. In addition, the adhesive sheet reduces the scattering and reflection of visible light, so it is expected to have an effect of suppressing the decrease in visibility caused by the scattering and reflection of light in the gaps between the LEDs.

[0090] If the double-sided adhesive sheet is photocurable, it may be photocured by irradiating it with ultraviolet light after bonding it to the adherend. The adhesive sheet before photocuring is highly flexible, so it has excellent conformability to unevenness such as the gaps between LEDs. By allowing the adhesive sheet to conform to the unevenness and then photocuring it, improved adhesion reliability can be expected.

[0091] The double-sided pressure-sensitive adhesive sheet can also be used in a state where it is laminated and integrated with other members. For example, an optical film such as a polarizing plate can be attached to one side of the double-sided pressure-sensitive adhesive sheet to be used as an optical film with a pressure-sensitive adhesive. A laminate in which an adherend is attached to each of the two main sides of the double-sided pressure-sensitive adhesive sheet can also be used as a component of an optical device.

[0092] The double-sided adhesive sheet may be laminated with a material having ultraviolet absorbing properties. The ultraviolet absorbing layer may be a resin film, an adhesive layer, or the like. The ultraviolet absorbing layer may contain an ultraviolet absorbing agent. Examples of the ultraviolet absorbing agent include a benzotriazole-based ultraviolet absorbing agent, a benzophenone-based ultraviolet absorbing agent, a triazine ultraviolet absorbing agent, a salicylate-based ultraviolet absorbing agent, and a cyanoacrylate-based ultraviolet absorbing agent.

[0093] In order to protect members with low ultraviolet resistance, ultraviolet shielding properties may be required for adhesive sheets and the like. Although an ultraviolet absorber can be added to the photocurable adhesive composition for forming the double-sided adhesive sheet 5, the ultraviolet absorber will absorb the ultraviolet light for photocuring the adhesive, inhibiting photocuring, and thus eliminating the significance of using an ultraviolet-transmitting colorant. For this reason, it is preferable to block ultraviolet rays by laminating an ultraviolet absorbing layer on the double-sided adhesive sheet.

[0094] When the ultraviolet absorbing layer is laminated after the pressure-sensitive adhesive composition is photocured, the ultraviolet absorbing layer may be laminated on one side of the double-sided pressure-sensitive adhesive sheet, or on both sides. When the ultraviolet absorbing layer is laminated before the pressure-sensitive adhesive composition is photocured (for example, the double-sided pressure-sensitive adhesive sheet of the second type), the ultraviolet absorbing layer may be laminated on one side, and ultraviolet light may be irradiated from the other side to photocure the pressure-sensitive adhesive. EXAMPLES

[0095] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0096] [Evaluation method] (Measurement of polymerization rate) A predetermined amount of adhesive (initial weight W1) was collected from the adhesive layer and heated in an oven at 130°C for 2 hours in an aluminum cup (weight W2) whose weight had been measured in advance, and then removed and allowed to cool for 30 minutes in an atmosphere of 23°C and 50% RH. The weight after drying (W3) was then measured, and the polymerization rate (non-volatile content) was calculated using the following formula. Polymerization rate (%)=100×(W3-W2) / W1

[0097] (transmittance) The release film on one side was peeled off from the adhesive sheet, and alkali-free glass was attached to the exposed surface. Then, the release film on the other side was peeled off from the adhesive sheet, and a sample was obtained in which the adhesive sheet was attached to the alkali-free glass plate. Using this sample, the transmission spectrum of the evaluation sample was measured with a visible ultraviolet spectrophotometer (manufactured by Hitachi High-Technologies, product name "U-4100"). The alkali-free glass (single) was used as a baseline, and the ratio of the transmittance (amount of transmitted light) of the evaluation sample to the transmittance (amount of transmitted light) of the alkali-free glass was taken as the transmittance of the adhesive sheet. From the transmission spectrum of the adhesive sheet, the arithmetic mean of the transmittance in the wavelength range of 400 to 700 nm and the arithmetic mean of the transmittance in the wavelength range of 330 to 400 nm, as well as the maximum value of the transmittance in the wavelength range of 400 to 700 nm and the maximum value of the transmittance in the wavelength range of 330 to 400 nm were obtained. The transmission spectrum of the colorant was measured using a dispersion diluted to 0.1% by weight with THF as a sample in a quartz cell with an optical path length of 1 cm.

[0098] [Reference example: Preparation of transparent adhesive sheet] (Polymerization of prepolymer) As monomer components for forming a prepolymer, 28.5 parts by weight of 2-ethylhexyl acrylate (2EHA), 28.5 parts by weight of isostearyl acrylate (ISTA), 22 parts by weight of isobornyl acrylate (IBHX), and 21 parts by weight of 4-hydroxybutyl acrylate (4HBA) were mixed with photopolymerization initiators (BASF's "Irgacure 184": 0.05 parts by weight, and BASF's "Irgacure 651": 0.05 parts by weight), and polymerization was carried out by exposure to ultraviolet light to obtain prepolymer composition A (polymerization rate 5 to 15%).

[0099] (Preparation of Adhesive Composition and Fabrication of Adhesive Sheet) To the prepolymer composition A, additional photopolymerization initiators (BASF's "Irgacure 184": 0.05 parts by weight, and BASF's "Irgacure 651": 0.05 parts by weight) were added, and then degassing was performed. This composition was applied to a substrate of a 75 μm-thick polyethylene terephthalate (PET) film (Mitsubishi Chemical's "Diafoil MRF75") with a silicone-based release layer on the surface, to form a coating layer of 100 μm in thickness. On this coating layer, a 75 μm-thick PET film (Mitsubishi Chemical's "Diafoil MRE75") with one side treated with silicone release was attached as a cover sheet. The laminate was then irradiated with 3.7 mW / cm2 of radiation intensity on the irradiated surface directly under the lamp from the cover sheet side. 2 The black light was adjusted so that the resin was cured by irradiating it with ultraviolet light for 4 minutes (cumulative irradiation amount: 880 mJ / cm 2 ) to obtain a transparent double-sided pressure-sensitive adhesive sheet with release films on both sides. The non-volatile content of the pressure-sensitive adhesive sheet was 98.0%.

[0100] [Comparative Example 1] 0.1 parts by weight of a black dye ("VALIFAST BLACK 3810" manufactured by Orient Chemical Industries) and an additional photopolymerization initiator were added to 100 parts by weight of a prepolymer composition prepared in the same manner as in Reference Example, and then degassing was performed. Using this composition, an attempt was made to prepare an adhesive sheet in the same manner as in Reference Example 1, but the composition was liquid after 4 minutes of ultraviolet irradiation, and an adhesive sheet could not be obtained.

[0101] [Comparative Example 2] 0.1 parts by weight of black dye ("VALIFAST BLACK 3810" manufactured by Orient Chemical Industries) was dissolved in 4 parts by weight of 2EHA to prepare a 20% solution. This solution was added to 100 parts by weight of a prepolymer composition prepared in the same manner as in the Reference Example, and additional photopolymerization initiator was added, followed by degassing. An attempt was made to prepare an adhesive sheet using this composition, but as in Comparative Example 1, the composition was liquid after 4 minutes of ultraviolet irradiation, and an adhesive sheet could not be obtained.

[0102] [Example 1] To 100 parts by weight of a prepolymer composition prepared in the same manner as in Reference Example, 0.5 parts by weight (0.1 parts by weight as black pigment) of a 20% dispersion of black pigment (Tokushiki's "9050BLACK") and additional photopolymerization initiator were added, and then degassing was performed. This composition was applied to a substrate to a thickness of 100 μm, and then heated at 80° C. for 1 minute to remove the dispersion medium. Thereafter, a cover sheet was attached, and an adhesive sheet was produced in the same manner as in Reference Example 1. The non-volatile content of the adhesive sheet was 97.1%.

[0103] [Example 2] (Polymerization of prepolymer) As monomer components for forming a prepolymer, 67 parts by weight of butyl acrylate (BA), 14 parts by weight of cyclohexyl acrylate (CHA), and 19 parts by weight of 4HBA were mixed with photopolymerization initiators (0.09 parts by weight of BASF's "Irgacure 184" and 0.09 parts by weight of BASF's "Irgacure 651"), and polymerization was carried out by exposure to ultraviolet light to obtain prepolymer composition B (polymerization rate 5-15%).

[0104] (Preparation of Pressure-Sensitive Adhesive Composition) To the above prepolymer composition B, 9 parts by weight of 2-hydroxyethyl acrylate (2HEA), 8 parts by weight of 4HBA, 0.02 parts by weight of dipentaerythritol hexaacrylate as a polyfunctional monomer, 0.35 parts by weight of 3-glycidoxypropyltrimethoxysilane ("KBM-403" manufactured by Shin-Etsu Silicones) as a silane coupling agent, 0.5 parts by weight of a photopolymerization initiator ("Irgacure 651" manufactured by BASF), and 4 parts by weight of a 20% dispersion of black pigment ("9050BLACK" manufactured by TOKUSHIKI) (0.8 parts by weight as black pigment) were added, mixed, and degassed to prepare a photopolymerizable pressure-sensitive adhesive composition.

[0105] (Preparation of adhesive sheet) The above pressure-sensitive adhesive composition was used, and the ultraviolet irradiation time was 6 minutes, with an accumulated irradiation dose of 1320 mJ / cm 2 A pressure-sensitive adhesive sheet was produced in the same manner as in Reference Example 1, except for changing the above.

[0106] [Examples 3 and 4] Except for changing the amount of black pigment added and the thickness of the adhesive sheet as shown in Table 1, adhesive sheets were produced in the same manner as in Example 2.

[0107] [Example 5] (Polymerization of prepolymer) As monomer components for forming a prepolymer, 36.5 parts by weight of lauryl acrylate (LA), 60 parts by weight of 2EHA, 2.5 parts by weight of N-vinylpyrrolidone (NVP), and 1 part by weight of 4HBA were mixed with photopolymerization initiators (0.05 parts by weight of BASF's "Irgacure 184" and 0.05 parts by weight of BASF's "Irgacure 651"), and polymerization was carried out by exposure to ultraviolet light to obtain prepolymer composition C (polymerization rate 5-15%).

[0108] (Preparation of Pressure-Sensitive Adhesive Composition) To the above prepolymer composition C, 0.08 parts by weight of 1,6-hexanediol diacrylate as a multifunctional monomer, 0.3 parts by weight of 3-glycidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Silicones, product name "KBM-403") as a silane coupling agent, 0.3 parts by weight of a photopolymerization initiator (manufactured by BASF, "Irgacure 651"), and 4 parts by weight of a 20% dispersion of black pigment (manufactured by Tokushiki, "9050BLACK") (0.8 parts by weight as black pigment) were added, mixed, and then degassed to prepare a photopolymerizable pressure-sensitive adhesive composition.

[0109] (Preparation of adhesive sheet) The above pressure-sensitive adhesive composition was used, and the ultraviolet irradiation time was 6 minutes, with an accumulated irradiation dose of 1320 mJ / cm 2 A pressure-sensitive adhesive sheet was produced in the same manner as in Reference Example 1, except for changing the above.

[0110] [Examples 6 and 7] Except for changing the amount of black pigment added and the thickness of the adhesive sheet as shown in Table 1, adhesive sheets were prepared in the same manner as in Example 5.

[0111] [UV irradiation dose and polymerization rate] For Reference Example 1, Comparative Example 1, Comparative Example 2, and Example 1, the ultraviolet irradiation time (accumulated irradiation amount) was changed to prepare adhesive sheets, and the relationship between the accumulated irradiation amount and the non-volatile content was examined. The results are shown in Figure 3. For Comparative Example 2, the ultraviolet irradiation time (accumulated irradiation amount) was changed to prepare adhesive sheets, and the relationship between the accumulated irradiation amount and the non-volatile content was examined. The results are shown in Figure 3. 2 The adhesive composition remained liquid even after being exposed to ultraviolet light for 25 minutes (5500 mJ / cm 2 ) The non-volatile content of the adhesive sheet after exposure to ultraviolet light was 87.6%.

[0112] [Evaluation Results] The transmission spectrum of the dispersion of the black pigment used in Examples 1 to 7 is shown in Figure 2. The types of prepolymers used in the preparation of the pressure-sensitive adhesive compositions in the above Reference Examples, Comparative Examples, and Examples, the types and amounts of colorants added, the thicknesses of the pressure-sensitive adhesive sheets, the non-volatile content of the pressure-sensitive adhesive sheets after irradiation with ultraviolet light, and the average transmittance and maximum transmittance calculated from the transmission spectrum of the pressure-sensitive adhesive sheets are shown in Table 1. The ultraviolet light irradiation time was 4 minutes (cumulative irradiation amount 880 mJ / cm2) in Reference Example 1 and Example 1. 2 ), and Examples 2 to 7 were 6 minutes (cumulative irradiation dose 1320 mJ / cm 2 ) Comparative Example 1 is 7 minutes (accumulated irradiation amount 1540 mJ / cm 2 The transmission spectrum was measured using a sample irradiated with ultraviolet light for 7 minutes for Comparative Example 1 and a sample irradiated with ultraviolet light for 25 minutes for Comparative Example 2.

[0113] [Table 1]

[0114] The adhesive sheet of Reference Example 1, which does not contain a colorant, has a higher average transmittance of visible light (wavelength 400-700 nm) than that of ultraviolet light (wavelength 330-400 nm), whereas in Examples 1-7, in which an ultraviolet-transmitting black pigment was added to the adhesive composition, the average transmittance of ultraviolet light was higher than that of visible light. Furthermore, in Examples 1-7, the maximum transmittance of the ultraviolet region was higher than that of the visible light region. On the other hand, in Comparative Example 1 and Comparative Example 2, the average transmittance of ultraviolet light was lower than that of visible light, and the maximum transmittance of the ultraviolet region was lower than the maximum average transmittance of the visible light region.

[0115] In Comparative Example 1, the colorant (dye) was not uniformly dissolved in the adhesive composition, so the measured transmittance was high. In Comparative Example 2, in which a colorant dissolved in a monomer (2EHA) was added in advance, the visible light transmittance was sufficiently reduced, but the ultraviolet light transmittance was also significantly reduced, reaching 25 minutes (5,500 mJ / cm 2 ) the adhesive was not sufficiently solidified. These results show that in Comparative Examples 1 and 2, the colorant absorbs ultraviolet light, which significantly reduces the photocuring speed (photocuring efficiency) of the adhesive.

[0116] 3, it can be seen that Example 1 has sufficiently high photocurability compared to Comparative Examples 1 and 2. Moreover, it can be seen that Examples 2 to 7 have a small amount of unreacted monomer and high photocurability even when the nonvolatile content is high, the colorant content is high, or the visible light transmittance is low, as in Example 1.

[0117] These results show that by preparing a photocurable pressure-sensitive adhesive composition using a colorant that has relatively low ultraviolet absorption compared to the visible light region, the inhibition of curing by the colorant is suppressed, and a colored double-sided pressure-sensitive adhesive sheet that absorbs visible light can be obtained with the same productivity as when no colorant is used.

[0118] When the pressure-sensitive adhesive sheets of the Reference Example and Examples 1 to 7 were attached to a stainless steel substrate and visually inspected, it was confirmed that the metallic luster of the stainless steel substrate was less and the reflectance was lower in Examples 1 to 7 than in the Reference Example. From these results, it is understood that pressure-sensitive adhesive sheets with low visible light transmittance can be applied as anti-reflection members for light-emitting elements, displays, etc.

Claims

1. A photocurable pressure-sensitive adhesive composition comprising a polymer, a photopolymerizable compound, a photopolymerization initiator, and a colorant, The colorant has a maximum transmittance at wavelengths of 330 to 400 nm that is greater than the maximum transmittance at wavelengths of 400 to 700 nm.

2. The photocurable adhesive composition according to claim 1, wherein the colorant has an average transmittance at wavelengths of 330 to 400 nm that is greater than the average transmittance at wavelengths of 400 to 700 nm.

3. 3. The photocurable pressure-sensitive adhesive composition according to claim 1, wherein the photopolymerization initiator has at least one absorption maximum in a wavelength range of 330 to 400 nm.

4. The photocurable pressure-sensitive adhesive composition according to any one of claims 1 to 3, wherein the colorant is a pigment.

5. The photocurable pressure-sensitive adhesive composition according to any one of claims 1 to 4, wherein the polymer is an acrylic polymer.

6. The photocurable pressure-sensitive adhesive composition according to any one of claims 1 to 5, wherein the polymer has a glass transition temperature of 0°C or lower.

7. The photocurable pressure-sensitive adhesive composition according to any one of claims 1 to 6, further comprising a crosslinking agent capable of crosslinking with the polymer.

8. A double-sided pressure-sensitive adhesive sheet which is a sheet-shaped product of the photocurable pressure-sensitive adhesive composition according to any one of claims 1 to 7.

9. A double-sided pressure-sensitive adhesive sheet comprising a photocured product of a sheet-shaped product of the photocurable pressure-sensitive adhesive composition according to any one of claims 1 to 7.

10. 10. The double-sided pressure-sensitive adhesive sheet according to claim 9, having a non-volatile content of 90% by weight or more.

11. The double-sided pressure-sensitive adhesive sheet according to any one of claims 8 to 10, wherein the maximum transmittance at wavelengths of 330 to 400 nm is greater than the maximum transmittance at wavelengths of 400 to 700 nm.

12. The double-sided pressure-sensitive adhesive sheet according to any one of claims 8 to 11, wherein the average transmittance at wavelengths of 330 to 400 nm is greater than the average transmittance at wavelengths of 400 to 700 nm.

13. The double-sided pressure-sensitive adhesive sheet according to any one of claims 8 to 12, having a total light transmittance of 80% or less.

14. The double-sided pressure-sensitive adhesive sheet according to any one of claims 8 to 13, having a thickness of 10 to 500 µm.

15. The double-sided pressure-sensitive adhesive sheet according to any one of claims 8 to 14, having a shear storage modulus at a temperature of 25°C of 10 to 1000 kPa.

16. The double-sided pressure-sensitive adhesive sheet according to any one of claims 8 to 15, having a shear storage modulus at a temperature of 85°C of 3 to 300 kPa.

17. The photocurable pressure-sensitive adhesive composition according to any one of claims 1 to 7 is applied onto a substrate in the form of a sheet, A method for producing a double-sided pressure-sensitive adhesive sheet, comprising irradiating a sheet-like coating film provided on a substrate with ultraviolet light to photocure the photopolymerizable compound.

18. An optical device comprising a first adherend and a second adherend bonded together via the double-sided pressure-sensitive adhesive sheet according to any one of claims 8 to 16.

19. A method for producing an optical device in which a first adherend and a second adherend are bonded together via a double-sided pressure-sensitive adhesive sheet, comprising: a first adherend and a second adherend are bonded to the first main surface and the second main surface of the double-sided pressure-sensitive adhesive sheet according to any one of claims 8 to 16, respectively; The double-sided pressure-sensitive adhesive sheet is irradiated with ultraviolet light to photocure the photopolymerizable compound.

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