JP2021059711A - Photocurable adhesive composition, double-sided adhesive sheet and manufacturing method thereof, and optical device and manufacturing method thereof - Google Patents

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

The present invention relates to a photocurable pressure-sensitive adhesive composition and a double-sided pressure-sensitive adhesive sheet formed from the photo-curable pressure-sensitive adhesive composition. Furthermore, the present invention relates to an optical device including the double-sided adhesive sheet.

In optical devices, adhesive sheets are used for laminating between members. For example, in a liquid crystal display device, optical films such as a retardation film and a polarizing plate are bonded to both sides of a liquid crystal cell via an adhesive sheet. In the organic EL display device, a circularly polarizing plate is attached to the visible surface of the organic EL cell via an adhesive sheet for the purpose of preventing reflection of external light by the metal electrode of the organic EL cell. Further, 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.

It has been proposed to use a photocurable pressure-sensitive adhesive composition that is cured by irradiation with active light rays such as ultraviolet rays as a pressure-sensitive adhesive sheet used for bonding members of an optical device. For example, in Patent Document 1, a photopolymerization initiator is added to a monomer component and UV polymerization is performed in a solvent-free system, and a polyfunctional monomer and a photopolymerization initiator are added to the obtained polymer (partial polymer) having a low degree of polymerization. Is added to prepare a photocurable pressure-sensitive adhesive composition, which is applied onto a substrate and then UV-polymerized again to obtain a transparent pressure-sensitive adhesive sheet. In Patent Document 2, a solution containing a monomer component and a thermal polymerization initiator is heated to prepare a polymer solution by solution polymerization, and an isocyanate-based cross-linking agent, a polyfunctional monomer, and a photopolymerization initiator are added to this solution. An example is shown in which a photocurable pressure-sensitive adhesive composition is prepared, applied onto a substrate, and then the solvent is removed by heating to obtain a transparent pressure-sensitive adhesive sheet. In this pressure-sensitive adhesive sheet, the polyfunctional monomer is in an unreacted state, and when the pressure-sensitive adhesive sheet is attached to the adherend and then UV-irradiated, the polyfunctional monomer photopolymerizes and the storage elastic modulus increases. Adhesive reliability to the adherend is improved.

Japanese Unexamined Patent Publication No. 2011-74308 Japanese Unexamined Patent Publication No. 2014-227453

As shown in Patent Documents 1 and 2, a transparent adhesive sheet having a total light transmittance of 90% or more is generally used for bonding between members of an optical device. On the other hand, for the purpose of controlling visibility and the like, it is assumed that an adhesive sheet that absorbs visible light is used for an optical device. A pressure-sensitive adhesive composition containing a colorant is used to prepare a pressure-sensitive adhesive sheet that absorbs visible light. An object of the present invention is to provide a pressure-sensitive adhesive composition containing a colorant and capable of photocuring, and a pressure-sensitive adhesive sheet formed by using the pressure-sensitive adhesive composition.

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 a wavelength of 330 to 400 nm higher than a maximum transmittance at a wavelength of 400 to 700 nm. Further, it is preferable that the colorant has an average transmittance at a wavelength of 330 to 400 nm higher than the average transmittance at a wavelength of 400 to 700 nm. As the colorant, pigments, dyes and the like are used.

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 cross-linking agent capable of cross-linking with the polymer. Examples of the cross-linking agent include isocyanate-based cross-linking agents and epoxy-based cross-linking agents.

A double-sided pressure-sensitive adhesive sheet can be obtained by forming the above pressure-sensitive adhesive composition into a sheet shape. The double-sided adhesive sheet may have a maximum transmittance at a wavelength of 330 to 400 nm higher than a maximum transmittance at a wavelength of 400 to 700 nm, and an average transmittance at a wavelength of 330 to 400 nm is an average transmittance at a wavelength of 400 to 700 nm. It may be greater than the rate. The average transmittance of the double-sided pressure-sensitive adhesive sheet at a wavelength of 400 to 700 nm may be 80% or less. The total light transmittance of the double-sided adhesive sheet may be 80% or less.

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

In the double-sided pressure-sensitive adhesive sheet of the first aspect of the present invention, the above-mentioned pressure-sensitive adhesive composition is applied in the form of a sheet on a base material, and the sheet-like coating film provided on the base material is irradiated with ultraviolet rays to be photopolymerizable. It is formed by photocuring a compound. That is, the double-sided pressure-sensitive adhesive sheet of the first form is made of a photo-cured product of a sheet-like molded product of a photo-curable pressure-sensitive adhesive composition. The double-sided pressure-sensitive adhesive sheet of the first form may have a non-volatile content of 90% or more.

The double-sided pressure-sensitive adhesive sheet of the second aspect of the present invention is formed by applying the above-mentioned pressure-sensitive adhesive composition on a substrate in the form of a sheet and removing the solvent if necessary. The double-sided pressure-sensitive adhesive sheet of the second form is a photocurable pressure-sensitive adhesive sheet containing a photopolymerizable compound in an unreacted state.

The double-sided adhesive sheet is used for bonding a plurality of members (adhesive bodies), for example, in forming an optical device such as an image display device. By attaching the first adherend to the first main surface of the double-sided adhesive sheet and attaching the second adherend to the second main surface, the first adherend and the second adherend are attached to the double-sided adhesive sheet. It is pasted together via. When the double-sided pressure-sensitive adhesive sheet has photocurability, the photopolymerizable compound may be photo-cured by irradiating the double-sided pressure-sensitive adhesive sheet with ultraviolet rays after bonding to the adherend.

A colored pressure-sensitive adhesive sheet can be obtained by using a pressure-sensitive adhesive composition containing a colorant. Since the colorant contained in the photocurable pressure-sensitive adhesive composition has ultraviolet transparency, even when photocuring is performed by ultraviolet irradiation, curing inhibition is unlikely to occur and the polymerization rate can be increased.

It is sectional drawing which shows the structural example of the pressure-sensitive adhesive sheet with a release film. It is a transmission spectrum of the black colorant used in the example. It is a graph which plotted the relationship between the ultraviolet irradiation amount and the non-volatile content of an adhesive sheet.

FIG. 1 shows an adhesive sheet with a release film in which release films 1 and 2 are temporarily attached to both sides of the double-sided adhesive sheet 5. The double-sided pressure-sensitive adhesive sheet 5 is formed by molding the pressure-sensitive adhesive composition into a sheet shape. The pressure-sensitive adhesive composition is generally a viscous liquid containing a polymer, and a double-sided pressure-sensitive adhesive sheet can be obtained by applying the pressure-sensitive adhesive composition in layers on a substrate and removing the solvent if necessary. ..

The double-sided pressure-sensitive adhesive sheet of the present invention is formed by using a photocurable pressure-sensitive adhesive composition. The photocurable pressure-sensitive adhesive composition contains a photopolymerizable compound and a photopolymerization initiator in addition to the 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 for forming the colored pressure-sensitive adhesive sheet. That is, the photocurable pressure-sensitive adhesive composition used for forming the double-sided pressure-sensitive adhesive sheet of the present invention contains a colorant in addition to the polymer, the photopolymerizable compound and the photopolymerization initiator.

The double-sided adhesive sheet formed by using the photocurable pressure-sensitive adhesive composition is a type that photocures on the base material (first form) and an adherend that does not photocurerate on the base material. It is roughly classified into the type (second form) in which photo-curing is performed after bonding.

[First form]
In the double-sided pressure-sensitive adhesive sheet of the first embodiment of the present invention, a photocurable pressure-sensitive adhesive composition containing a polymer, a photopolymerizable compound, a photopolymerization initiator, and a colorant is applied onto a base material, and the base material is coated. It is formed by performing photocuring on the above.

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

Acrylic polymers contain (meth) acrylic acid alkyl esters as the main constituent monomer components. In addition, in this specification, "(meth) acrylic" means acrylic and / or methacryl. The amount of the (meth) acrylic acid alkyl ester with respect 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, still more preferably 60% by weight or more.

As the (meth) acrylic acid alkyl ester, a (meth) acrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms is preferably used. The (meth) acrylic acid alkyl ester may have a branched alkyl group or a cyclic alkyl group.

Specific examples of the (meth) acrylic acid alkyl ester having a chain alkyl group include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, and (meth). S-butyl 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, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate , (Meta) undecyl acrylate, (meth) dodecyl acrylate, (meth) isotridecyl acrylate, (meth) tetradecyl acrylate, (meth) isotetradecyl acrylate, (meth) pentadecyl acrylate, (meth) acrylate Examples thereof include cetyl, heptadecyl (meth) acrylate, octadecyl (meth) acrylate, isooctadecyl (meth) acrylate, and nonadecil (meth) acrylate.

Specific examples of the (meth) acrylate alkyl ester having an alicyclic alkyl group include cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate, cycloheptyl (meth) acrylate, cyclooctyl (meth) acrylate and the like. (Meta) acrylic acid cycloalkyl ester; (meth) acrylic acid ester having a bicyclic aliphatic hydrocarbon ring such as (meth) acrylic acid isobornyl; dicyclopentanyl (meth) acrylate, dicyclopentanyloxy Tricycles such as ethyl (meth) acrylate, tricyclopentanyl (meth) acrylate, 1-adamantyl (meth) acrylate, 2-methyl-2-adamantyl (meth) acrylate, 2-ethyl-2-adamantyl (meth) acrylate Examples thereof include (meth) acrylic acid esters having the above aliphatic hydrocarbon rings.

The acrylic polymer may contain a polar group-containing monomer such as a hydroxyl group-containing monomer, a carboxy group-containing monomer, and 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 force of the pressure-sensitive adhesive is enhanced, and the adhesive force tends to be improved. The amount of the polar group-containing monomer (total of the hydroxy group-containing monomer, the carboxy group-containing monomer, and the nitrogen-containing monomer) with respect to the total amount of the monomer components constituting the acrylic polymer is, for example, about 3 to 50% by weight, and is 5 to 40. It may be% by weight or 10 to 30% by weight.

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

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

Nitrogen-containing monomers include N-vinylpyrrolidone, methylvinylpyrrolidone, vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazole, vinyloxazole, vinylmorpholin, (meth) acryloylmorpholin, and N-vinyl. Examples thereof include vinyl-based monomers such as carboxylic acid amides and N-vinylcaprolactam, and cyano group-containing monomers such as acrylonitrile and methacrylonitrile.

Acrylic polymers include acid anhydride group-containing monomers, (meth) acrylic acid caprolactone adducts, sulfonic acid group-containing monomers, phosphoric acid group-containing monomers, vinyl acetate, vinyl propionate, styrene, and α as monomer components other than the above. -Vinyl-based monomers such as methylstyrene; Epoxy group-containing monomers such as glycidyl (meth) acrylate; Polyethylene glycol (meth) acrylate, Polypropylene glycol (meth) acrylate, methoxyethylene glycol (meth) acrylate, (meth) ) Glycol-based acrylic ester monomers such as methoxypolypropylene glycol acrylate; Acrylic acid esters such as tetrahydrofurfuryl (meth) acrylate, fluorine (meth) acrylate, silicone (meth) acrylate and 2-methoxyethyl (meth) acrylate. It may contain a monomer or the like.

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 from the composition of the polymer based on the theoretical Tg. Theoretical Tg is a glass transition temperature Tg _i of the homopolymer constituent monomer components of the polymer, the weight fraction W _i of each monomer component, is calculated by the Fox equation below.
1 / Tg = Σ ( _Wi / Tg _i )

Tg is the glass transition temperature of the polymer (unit: K), _Wi is the weight fraction of the monomer component i constituting the polymer (copolymerization ratio based on the weight), and Tg _i is the glass transition temperature of the homopolymer of the monomer component i ( Unit: K). As the glass transition temperature of the homopolymer, the numerical value described in the third edition of the Polymer Handbook (John Wiley & Sons, Inc., 1989) can be adopted. For the Tg of the monomer homopolymer not described in the above document, the peak top temperature of tan δ measured by dynamic viscoelasticity measurement may be adopted.

A polymer can be obtained by polymerizing the above-mentioned monomer components by various known methods. The polymerization method is not particularly limited, but in the pressure-sensitive adhesive composition used for producing the first-form double-sided pressure-sensitive adhesive sheet in which the pressure-sensitive adhesive composition is photocured on a substrate, it is preferable to prepare a polymer 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 pressure-sensitive adhesive sheet, and a thick pressure-sensitive adhesive sheet can be uniformly formed.

In the production of a pressure-sensitive adhesive sheet in which the pressure-sensitive adhesive composition is photocured on a substrate, it is preferable to prepare a polymer (prepolymer) having a low degree of polymerization in which a part of the monomer components remains unreacted. .. The composition used for preparing the prepolymer (composition for forming the prepolymer) preferably contains a photopolymerization initiator in addition to the monomer. The photopolymerization initiator may be appropriately selected depending on 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, and a photoactive oxime-based photopolymerization initiator. Examples thereof include benzoin-based photopolymerization initiators, benzyl-based photopolymerization initiators, benzophenone-based photopolymerization initiators, ketal-based photopolymerization initiators, thioxanthone-based photopolymerization initiators, and acylphosphine oxide-based photopolymerization initiators.

At the time of polymerization, a chain transfer agent, a polymerization inhibitor (polymerization delaying agent) or the like may be used for the purpose of adjusting the molecular weight. 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. Examples thereof include α-methylstyrene dimer.

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 coating on a substrate. The polymerization rate of the prepolymer can be adjusted to a desired range by adjusting the type and amount of the photopolymerization initiator, the irradiation intensity and irradiation time of active light such as UV light, and the like. The polymerization rate of the prepolymer is a non-volatile component when heated at 130 ° C. for 3 hours, and is calculated by the following formula. The polymerization rate (nonvolatile content) of the pressure-sensitive adhesive sheet is also measured by the same method.
Polymerization rate (%) = weight after heating / weight before heating x 100

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

(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 radically polymerizable, cationically polymerizable or anionically polymerizable, but since it is excellent in reactivity, it is a radically polymerizable functional group having an unsaturated double bond (ethylenically unsaturated group). Is preferable.

The prepolymer contains an unreacted monomer with the polymer, and the unreacted monomer retains photopolymerizability. Therefore, it is not always necessary to add the photopolymerizable compound in the preparation of the pressure-sensitive adhesive composition. When the photopolymerizable compound is added to the prepolymer, the photopolymerizable compound to be added may be the same as or different from the monomer used for preparing the prepolymer.

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 the photopolymerizable functional group because 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) acrylate. Examples of the polyfunctional (meth) acrylate include polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, polytetramethylene glycol di (meth) acrylate, bisphenol A ethylene oxide-modified di (meth) acrylate, and bisphenol A propylene oxide. Modified di (meth) acrylate, alcandiol di (meth) acrylate, tricyclodecanedimethanol di (meth) acrylate, pentaeristol di (meth) acrylate, neopentyl glycol di (meth) acrylate, glycerin di (meth) acrylate , Bifunctional (meth) acrylic acid esters such as urethane di (meth) acrylates; trifunctional (meth) acrylates such as pentaeristol tri (meth) acrylates, trimethyl propanetri (meth) acrylates, and tri (meth) acrylates of ethoxylated isocyanuric acid. Meta) acrylic acid ester; tetrafunctional (meth) acrylic acid ester such as ditrimethylolpropane tetra (meth) acrylate, ethoxylated pentaeristol tetra (meth) acrylate, pentaeristol tetra (meth) acrylate; dipentaeryristol penta Examples thereof include (meth) acrylates and the like, and pentafunctional or higher functional (meth) acrylic acid esters such as dipentaeryristol hexa (meth) acrylate.

When a polyfunctional compound is used as the photopolymerizable compound, the amount of the polyfunctional compound used is 100 parts by weight based on the total amount of the monomers (total of the monomer used for preparing the prepolymer and the photopolymerizable compound added to the prepolymer). , 40 parts by weight or less is preferable, 30 parts by weight or less is more preferable, and 25 parts by weight or less is further preferable. If the amount of the polyfunctional monomer used is excessively large, the viscosity of the pressure-sensitive adhesive sheet after photocuring is low, and the adhesive strength may be poor. 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, and may be 0.1 parts by weight or more, 0.3 parts by weight or more, or 0.5 parts by weight or more.

(Photopolymerization initiator)
The photocurable pressure-sensitive adhesive composition comprises a photopolymerization initiator. The photopolymerization initiator generates radicals, acids, bases, etc. by irradiation with active rays such as ultraviolet rays, and can be appropriately selected depending on the type of the photopolymerizable compound and the like. When the photopolymerizable compound is a compound having a (meth) acryloyl group (for example, a 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 combination of two or more.

If the photopolymerization initiator used in the preparation (polymerization) of the prepolymer remains in the prepolymer composition without being inactivated, the addition of the photopolymerization initiator may be omitted. When a photopolymerization initiator is added to the prepolymer composition, the photopolymerization initiator added may be the same as or different from the photopolymerization initiator used in the preparation of the prepolymer.

The photopolymerization initiator contained in the pressure-sensitive adhesive composition preferably has an absorption maximum in a wavelength region where light absorption by a colorant described later is small. Specifically, the photopolymerization initiator preferably has an absorption maximum in the 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 the photocuring. Examples of the photoradical polymerization initiator having an absorption maximum in the wavelength region of 330 to 400 nm include hydroxyketones, benzyldimethylketals, aminoketones, acylphosphine oxides, benzophenones, trichloromethyl group-containing triazine derivatives and the like. ..

The content of the photopolymerization initiator in the photocurable pressure-sensitive adhesive composition is 0.01 to 100 parts by weight based on 100 parts by weight of the total amount of the monomers (the monomer used for preparing the prepolymer and the photopolymerizable compound added to the prepolymer). It is about 10 parts by weight, preferably about 0.05 to 5 parts by weight.

(Colorant)
The pressure-sensitive adhesive composition used to form the colored pressure-sensitive adhesive sheet contains a colorant. The colorant may be a dye or a pigment as long as it can be dissolved or dispersed in the pressure-sensitive adhesive composition. Pigments are preferable because they have high color development even when added in a small amount.

As the colorant, one that absorbs visible light and has ultraviolet transparency is used. The colorant preferably has a maximum transmittance at a wavelength of 330 to 400 nm higher than a maximum transmittance at a wavelength of 400 to 700 nm. Further, the colorant preferably has an average transmittance at a wavelength of 330 to 400 nm higher than the average transmittance at a wavelength of 400 to 700 nm. The transmittance of the colorant is adjusted by using an appropriate solvent such as tetrahydrofuran (THF) or a dispersion medium (an organic solvent having a small absorption in the wavelength range of 330 to 700 nm) so that the transmittance at a wavelength of 400 nm is about 50 to 60%. Measure with a diluted solution or dispersion.

Examples of the ultraviolet-transmissive black pigment having less absorption of ultraviolet rays than the absorption of visible light include "9050BLACK" and "UVBK-0001" manufactured by Tokushiki. Examples of the ultraviolet-transparent black dye include "SOC-L-0123" manufactured by Orient Chemical Industries.

Carbon black and titanium black, which are generally used as black colorants, absorb ultraviolet rays more than they absorb visible light (the ultraviolet transmittance is smaller than the visible light transmittance). Therefore, when a colorant such as carbon black is added to the photocurable pressure-sensitive adhesive composition having sensitivity to ultraviolet rays, most of the ultraviolet rays irradiated for photocuring are absorbed by the colorant, and the amount of light absorbed by the photopolymerization initiator. Is small, and it takes time to photo-cure (the amount of integrated irradiation light increases). Further, when the thickness of the adhesive sheet is large, the amount of ultraviolet rays reaching the surface opposite to the light irradiation surface is small, so that the photocuring tends to be insufficient even if the light irradiation is performed for a long time. On the other hand, by using a colorant having a higher transmittance of ultraviolet rays than visible light, it is possible to suppress curing inhibition caused by the colorant.

The content of the colorant in the photocurable pressure-sensitive adhesive composition is, for example, about 0.01 to 20 parts by weight with respect to 100 parts by weight of the total amount of the monomers, and the type of the colorant, the color tone of the pressure-sensitive adhesive sheet, and the light transmittance. It may be set appropriately according to the rate and the like. The colorant may be added to the composition as a solution or dispersion dissolved or dispersed in an appropriate solvent.

(Other ingredients)
The photocurable pressure-sensitive 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 rate or the like. Further, an oligomer or a tackifier may be contained for the purpose of adjusting the viscosity of the pressure-sensitive adhesive composition, adjusting the adhesive strength of the pressure-sensitive adhesive sheet, and the like. As the oligomer, for example, one having a weight average molecular weight of about 1000 to 30,000 is used. As the oligomer, an acrylic oligomer is preferable because it has excellent compatibility with an acrylic polymer. The pressure-sensitive adhesive composition may contain additives such as a silane coupling agent, a plasticizer, a softening agent, an antioxidant, a filler, an antioxidant, a surfactant, and an antistatic agent.

<Making double-sided adhesive sheet>
By applying a photocurable pressure-sensitive adhesive composition containing a colorant on a base material in a sheet form (layered form) and irradiating a coating film of the pressure-sensitive adhesive composition on the base material with ultraviolet rays to perform photo-curing. , A double-sided adhesive sheet can be obtained. When photocuring, it is preferable to attach a cover sheet to the surface of the coating film and irradiate ultraviolet rays with the pressure-sensitive adhesive composition sandwiched between the two sheets to prevent polymerization inhibition by oxygen. .. Prior to photo-curing, the sheet-like coating film 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 carry out before attaching the cover sheet.

Any suitable base material is used as the base material and the cover sheet used for forming the double-sided pressure-sensitive adhesive sheet. The base material and the cover sheet may be a release film having a release layer on the contact surface with the double-sided adhesive sheet.

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

As a method of applying the pressure-sensitive adhesive composition on the substrate, roll coat, kiss roll coat, gravure coat, reverse coat, roll brush, spray coat, dip roll coat, bar coat, knife coat, air knife coat, curtain coat , Lip coat, die coater and the like are used.

The thickness of the double-sided adhesive sheet is not particularly limited, and may be set according to 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 transparency, the photocurable composition can be uniformly photocured in the thickness direction even when the thickness of the double-sided pressure-sensitive adhesive sheet is large. 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.

By irradiating the pressure-sensitive adhesive composition layered on the substrate with ultraviolet rays, active species are generated from the photopolymerization initiator, the photopolymerizable compound is polymerized, and the polymerization rate is increased (reduction of unreacted monomers). ), The liquid pressure-sensitive adhesive composition becomes a solid (standard) pressure-sensitive adhesive sheet. The light source for ultraviolet irradiation is not particularly limited as long as the photopolymerization initiator contained in the pressure-sensitive adhesive composition can irradiate light in a sensitive wavelength range, and is an LED light source, a high-pressure mercury lamp, and an ultra-high-pressure mercury. Lamps, metal halide lamps, xenon lamps, etc. are used.

The integrated light amount of the irradiation light is, for example, about ^{100 to 5000 mJ / cm 2.} The polymerization rate (nonvolatile content) of the double-sided pressure-sensitive adhesive sheet made of the photocurable product of the photocurable pressure-sensitive adhesive composition is preferably 80% or more, more preferably 85% or more, still 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 components such as residual monomers, unreacted polymerization initiator, and solvent.

By adhering the release films 1 and 2 to the surface of the double-sided adhesive sheet 5, as shown in FIG. 1, an adhesive sheet with a release film having the release films temporarily attached to both sides can be obtained. The release film used as the base material or the cover sheet when forming the double-sided adhesive sheet may be used as it is as the release films 1 and 2.

When the release films 1 and 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 the release film temporarily attached to one surface from the double-sided adhesive sheet 5 and the peeling force when peeling the release film temporarily attached to the other surface from the double-sided adhesive sheet 5 are It may be the same or different. If the peeling forces of the two are different, the release film 2 (light peeling film) having a relatively small peeling force is peeled off from the double-sided adhesive sheet 5 first and bonded to the first adherend, and then relative to each other. Excellent workability when the release film 1 (heavy release film) having a large peeling force is peeled off and bonded to the second adherend.

<Characteristics of double-sided adhesive sheet>
The double-sided pressure-sensitive adhesive sheet containing a colorant has light absorption in visible light. The total light transmittance of the double-sided adhesive sheet is, for example, 80% or less, 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. You may.

As described above, as the colorant, one that absorbs ultraviolet rays less than that of visible light is used. Therefore, the double-sided adhesive sheet absorbs ultraviolet rays less than it absorbs visible light. Specifically, it is preferable maximum transmittance _{T MUV} wavelength 330~400nm of the adhesive sheet is larger than the maximum transmittance _{T MVIS} wavelength 400 to 700 nm. Further, the average transmittance _{T AUV} wavelength 330~400nm of the adhesive sheet is preferably larger than the average transmittance _{T avis} wavelength 400 to 700 nm.

Average transmittance _{T avis} wavelength 400~700nm the double-sided pressure-sensitive adhesive sheet is, for example, 80% or less, 70% or less, 60% or less, 50% or less, 40% or less, 30% or less than 20% or 10% or less It may be. Average transmittance _{T AUV} wavelength 330~400nm the double-sided pressure-sensitive adhesive sheet is preferably at least 5%, 10% or more, 15% or more, may be 20% or more or 25% or more. _Difference between _TaUV and _{TaVIS The TaUV} - _TaVIS may be 3% or more, 5% or more, 8% or more, or 10% or more.

_{The maximum transmittance T mVIS in} the wavelength range of 400 to 700 nm of the double-sided adhesive sheet is, for example, 85% or less, 80% or less, 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, 20. It may be% or less or 10% or less. _{The maximum transmittance T mUV in} the wavelength range of 330 to 400 nm of the double-sided pressure-sensitive adhesive sheet is preferably 5% or more, and may be 10% or more, 15% or more, 20% or more, or 25% or more. _Difference between T mUV and T _mVIS T _mUV- T _mVIS may be 0.1% or more, 0.5% or more, 1% or more, or 1.5% or more.

The transmittance of the double-sided adhesive sheet may be adjusted according to the application and purpose. For example, when used as a light-shielding seal member of the LED array, the average transmittance _{T avis} wavelength 400~700nm the double-sided pressure-sensitive adhesive sheet is preferably 10% or less, may be 7% or less or 5% or less. When the double-sided adhesive sheet is used for the antireflection application of OLED, the _TaVIS is preferably 80% or less, and may be 78% or less or 75% or less. In either case, the maximum transmittance _{T AUV} wavelength in the range of 330~400nm the double-sided pressure-sensitive adhesive sheet _may be higher than _{T avis.}

_{The shear storage elastic modulus G'25 °} C. at a temperature of the pressure-sensitive adhesive sheet at 25 ° C. is, for example, about 10 to 1000 kPa, may be 30 kPa or more, 50 kPa or more, 70 kPa or more or 100 kPa or more, 700 kPa or less, 500 kPa or less, 300 kPa or less. Alternatively, it may be 200 kPa or less. _{The shear storage elastic modulus G'85 °} C. at a temperature of the pressure-sensitive adhesive sheet at 85 ° C. is, for example, about 3 to 300 kPa, may be 5 kPa or more, 7 kPa or more, or 10 kPa or more, and is 200 kPa or less, 150 kPa or less, or 100 kPa or less. It may be. When the shear storage elastic modulus of the pressure-sensitive adhesive sheet is within the above range, both appropriate flexibility and adhesiveness can be achieved. The shear storage elastic modulus is a value measured by dynamic viscoelasticity measurement at a frequency of 1 Hz.

[Second form]
The double-sided pressure-sensitive adhesive sheet of the second aspect of the present invention is a type of pressure-sensitive adhesive sheet that is not photo-cured on a base material, and is formed in the form of a photo-curable pressure-sensitive adhesive composition. Since the double-sided pressure-sensitive adhesive sheet of the second form contains the photopolymerizable compound in an unreacted state, the pressure-sensitive adhesive sheet has photocurability.

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

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

In order to introduce a crosslinked structure with a crosslinking agent described later, it is preferable that the monomer component constituting the polymer contains a hydroxy group-containing monomer and / or a carboxy group-containing monomer. For example, when an isocyanate-based cross-linking agent is used, it is preferable to contain a hydroxy group-containing monomer as a monomer component. When an epoxy-based cross-linking agent is used, it is preferable to contain a carboxy group-containing monomer as the monomer.

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

Since the high molecular weight polymer is a solid, the pressure-sensitive adhesive composition is preferably a solution in which the polymer is dissolved in an organic solvent in order to be applied onto a substrate. For example, a polymer solution can be obtained by solution-polymerizing the monomer components. A polymer solution may be prepared by dissolving a solid polymer in an organic solvent.

Ethyl acetate, toluene and the like are generally used as the solvent for solution polymerization. The solution concentration is usually about 20 to 80% by weight. The polymerization initiator includes an azo-based initiator, a peroxide-based initiator, a redox-based initiator that combines a peroxide and a reducing agent (for example, a combination of a persulfate and sodium hydrogen sulfite, a peroxide and an ascorbin). A thermal polymerization initiator such as (combination of sodium acid acid) 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. preferable.

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

(Photopolymerization initiator)
The photopolymerization initiator contained in the pressure-sensitive adhesive composition in the second form is the same as that described above for the first form, 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, preferably about 0.05 to 5 parts by weight, based on 100 parts by weight of the polymer.

(Colorant)
The colorant contained in the pressure-sensitive adhesive composition in the second form is the same as that described above for the first form, and it is preferable that the transmittance at a wavelength of 330 to 400 nm is larger than the transmittance at a wavelength of 400 to 700 nm.

(Crosslinking agent)
The pressure-sensitive adhesive composition of the second form preferably contains a cross-linking agent capable of cross-linking with the above polymer. Specific examples of the cross-linking agent for introducing a cross-linked structure into the polymer include an isocyanate-based cross-linking agent, an epoxy-based cross-linking agent, an oxazoline-based cross-linking agent, an aziridine-based cross-linking agent, a carbodiimide-based cross-linking agent, and a metal chelate-based cross-linking agent. Be done. Of these, isocyanate-based cross-linking agents and epoxy-based cross-linking agents are preferable because they have high reactivity with the hydroxyl groups and carboxy groups of the polymer and the cross-linked structure can be easily introduced. These cross-linking agents react with functional groups such as hydroxyl groups and carboxy groups introduced into the polymer to form a cross-linked structure.

As the isocyanate-based cross-linking agent, polyisocyanate having two or more isocyanate groups in one molecule is used. Examples of the isocyanate-based cross-linking agent include lower aliphatic polyisocyanates such as butylene diisocyanate and hexamethylene diisocyanate; alicyclic isocyanates such as cyclopentylene diisocyanate, cyclohexylene diisocyanate and isophorone diisocyanate; 2,4-tolylene diisocyanate. Aromatic isocyanates such as isocyanate, 4,4'-diphenylmethane diisocyanate, xylylene diisocyanate; trimethylolpropane / trimylene diisocyanate trimer adduct (eg, "Coronate L" manufactured by Toso), trimethylolpropane / hexamethylene Diisocyanate trimeric adduct (eg, Tosoh's "Coronate HL"), xylylene diisocyanate trimethylolpropane adduct (eg, Mitsui Chemicals' "Takenate D110N", hexamethylene diisocyanate isocyanurate (eg, Tosoh's "Coronate HL") Examples thereof include isocyanate additives such as "Coronate HX").

As the epoxy-based cross-linking agent, a polyfunctional epoxy compound having two or more epoxy groups in one molecule is used. The epoxy group of the epoxy-based cross-linking agent may be a glycidyl group. Examples of the epoxy-based cross-linking agent include N, N, N', N'-tetraglycidyl-m-xylene diamine, diglycidyl aniline, 1,3-bis (N, N-diglycidyl aminomethyl) 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, penta Ellisritol polyglycidyl ether, polyglycerol polyglycidyl ether, sorbitan polyglycidyl ether, trimethylolpropane polyglycidyl ether, adipate diglycidyl ester, o-phthalic acid diglycidyl ester, triglycidyl-tris (2-hydroxyethyl) isocyanurate, Examples thereof include resorcin diglycidyl ether and bisphenol-S-diglycidyl ether. As the epoxy-based cross-linking agent, commercially available products such as "Denacol" manufactured by Nagase ChemteX and "Tetrad X" and "Tetrad C" manufactured by Mitsubishi Gas Chemical Company may be used.

The amount of the cross-linking agent is about 0.01 to 5 parts by weight with respect to 100 parts by weight of the polymer, 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. It may be 3 parts by weight or less, 2 parts by weight or less, or 1 part by weight or less.

(Other ingredients)
In addition to the above components, the pressure-sensitive adhesive composition of the second form includes oligomers, tackifiers, silane coupling agents, chain transfer agents, plasticizers, softeners, deterioration inhibitors, fillers, antioxidants, and surfactants. It may contain an agent, an antistatic agent and the like.

<Making double-sided adhesive sheet>
A double-sided pressure-sensitive adhesive sheet is formed on the base material by applying the pressure-sensitive adhesive composition on the base material and, if necessary, drying and removing the solvent. As the base material, a release film is preferably used as in the first form.

When the pressure-sensitive adhesive composition contains a solvent, it is preferable to dry the pressure-sensitive adhesive composition after applying the pressure-sensitive adhesive composition on the substrate. As the drying method, an appropriate method can be appropriately 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, an appropriate time can be adopted as appropriate. 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.

After the solvent is dried, it is preferable to attach a cover sheet in order to protect the surface of the double-sided pressure-sensitive adhesive sheet. As the cover sheet, it is preferable to use a release film having a release layer on the contact surface with the adhesive sheet, as in the case of the base film.

A crosslinked structure is introduced into the polymer by applying the pressure-sensitive adhesive composition on the substrate and then heating it as necessary. The heating temperature and heating time may be appropriately set depending on the type of the cross-linking agent used, and are usually in the range of 20 ° C. to 160 ° C. for about 1 minute to 7 days. The heating for drying the solvent may also serve as the heating for crosslinking. The introduction of the crosslinked structure does not necessarily have to be accompanied by heating.

<Characteristics of double-sided adhesive sheet>
The double-sided pressure-sensitive adhesive sheet of the second form preferably has the same thickness, light transmittance, and shear storage elastic modulus as the double-sided pressure-sensitive adhesive sheet of the first form. Since the double-sided pressure-sensitive adhesive sheet of the second form is not photocured on the base material, the photopolymerizable compound is contained in an unreacted state. That is, the double-sided pressure-sensitive adhesive sheet of the second form is a photocurable pressure-sensitive adhesive sheet containing a polymer, a photopolymerizable compound, a photopolymerization initiator, and a colorant.

The photocurable pressure-sensitive adhesive sheet can be photo-cured by irradiating it with ultraviolet rays after it is attached to an adherend. The adhesive force between the adhesive sheet and the adherend can be changed by photocuring. For example, since the adhesive sheet before photo-curing has high flexibility, it is possible to fill the surface irregularities and steps of the adherend, and after photo-curing, the adhesive strength and adhesive reliability to the adherend can be improved.

Ultraviolet rays are used as the active rays for photocuring the adhesive sheet. Similar to the pressure-sensitive adhesive sheet of the first form, since the colorant has a higher transmittance of ultraviolet rays than visible light, it is possible to suppress curing inhibition during photo-curing even when the pressure-sensitive adhesive sheet is thick.

The thickness of the double-sided adhesive sheet is not particularly limited, and may be set according to 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 transparency, curing inhibition is unlikely to occur, and process efficiency can be improved.

[Use of adhesive sheet]
The double-sided adhesive sheets of the first form and the second form can be used for bonding various transparent members and opaque members. The type of the adherend is not particularly limited, and examples thereof include various resin materials, glass, and metal. The double-sided adhesive sheet is used, for example, for bonding members of an optical device such as an image display device. Since the adhesive sheet is colored, it may have an effect of reducing the emission of scattered light or reflected light in the device to the outside to improve visibility.

The double-sided adhesive sheet can also be used as an embedding member between members or as a sealing member, and can also be used for sealing an optical semiconductor element. Examples of the optical semiconductor element include a light emitting diode (LED). For example, when an adhesive sheet is used to seal a micro LED array in which a plurality of LED elements are arranged in a tile shape, the plurality of LEDs are collectively used because they are excellent in following irregularities such as gaps between LEDs. Can be sealed. Further, since the adhesive sheet reduces the scattering and reflection of visible light, it can be expected to have an effect of suppressing the decrease in visibility due to the scattering and reflection of light in the gap between the LEDs.

When the double-sided adhesive sheet is photocurable, it may be photocured by irradiating it with ultraviolet rays after it is attached to the adherend. Since the adhesive sheet before photo-curing has high flexibility, it has excellent ability to follow irregularities such as gaps between LEDs. By performing photo-curing after making the adhesive sheet follow the unevenness, improvement in adhesive reliability can be expected.

The double-sided adhesive sheet can also be put into practical use in a state of being laminated and integrated with other members. For example, an optical film such as a polarizing plate may be attached to one surface of a double-sided adhesive sheet to be put into practical use as an optical film with an adhesive. A laminate in which an adherend is bonded to each of the main surfaces of both side adhesive sheets can also be used as a constituent member of the optical device.

The double-sided adhesive sheet may be laminated with a material having ultraviolet absorption. 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 absorber include a benzotriazole-based ultraviolet absorber, a benzophenone-based ultraviolet absorber, a triazine ultraviolet absorber, a salicylate-based ultraviolet absorber, a cyanoacrylate-based ultraviolet absorber, and the like.

In order to protect members with low UV durability, the adhesive sheet or the like may be required to have UV shielding properties. An ultraviolet absorber can be added to the photocurable pressure-sensitive adhesive composition for forming the double-sided pressure-sensitive adhesive sheet 5, but the photo-curing is inhibited by the UV-absorbing agent absorbing the ultraviolet rays for photo-curing the pressure-sensitive adhesive. Therefore, the significance of using an ultraviolet-transparent colorant is lost. Therefore, it is preferable to shield the ultraviolet rays by laminating an ultraviolet absorbing layer on the double-sided adhesive sheet.

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 may be laminated on both sides. When the ultraviolet absorbing layer is laminated on the pressure-sensitive adhesive composition before photocuring (for example, the double-sided pressure-sensitive adhesive sheet of the second form), the ultraviolet absorbing layer is laminated on one side and the pressure-sensitive adhesive is irradiated with ultraviolet rays from the other side. It may be photo-cured.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

[Evaluation method]
(Measurement of polymerization rate)
A predetermined amount (initial weight W1) of the pressure-sensitive adhesive was collected from the pressure-sensitive adhesive layer, heated in an aluminum cup (weight W2) weighed in advance for 2 hours in an oven at 130 ° C., and then taken out. After allowing to cool for 30 minutes in an atmosphere of 50% RH, the weight (W3) after drying was measured, and the polymerization rate (nonvolatile content) was calculated by the following formula.
Polymerization rate (%) = 100 × (W3-W2) / W1

(Transmittance)
The release film on one side was peeled off from the adhesive sheet, and non-alkali glass was attached to the exposed side. Then, the release film on the other surface was peeled off from the pressure-sensitive adhesive sheet to obtain a sample in which the pressure-sensitive adhesive sheet was bonded on a non-alkali glass plate. Using this sample, the transmission spectrum of the evaluation sample was measured with a visible ultraviolet spectrophotometer (manufactured by Hitachi High-Technologies Corporation, trade name "U-4100"). With the non-alkali glass (single substance) as the baseline, the ratio of the transmittance (transmitted light amount) of the evaluation sample to the transmittance (transmitted light amount) of the non-alkali glass was defined as the transmittance of the adhesive sheet. From the transmission spectrum of the adhesive sheet, the arithmetic average of the transmittance in the wavelength range of 400 to 700 nm and the arithmetic average of the transmittance in the wavelength range of 330 to 400 nm, and the maximum value of the transmittance in the wavelength range of 400 to 700 nm and the wavelength of 330 to 400 nm. The maximum value of transmittance was calculated. The transmission spectrum of the colorant was measured using a quartz cell having an optical path length of 1 cm using a dispersion liquid diluted to 0.1% by weight with THF as a sample.

[Reference example: Preparation of transparent adhesive sheet]
(Polymerization of prepolymer)
2-Ethylhexyl acrylate (2EHA): 28.5 parts by weight, isostearyl acrylate (ISTA): 28.5 parts by weight, isobornyl acrylate (IBHX): 22 parts by weight, and acrylic as monomer components for prepolymer formation. 4-Hydroxybutyl acid (4HBA): 21 parts by weight and a photopolymerization initiator (BASF "Irgacure 184": 0.05 parts by weight, and BASF "Irgacure 651": 0.05 parts by weight) were blended. Polymerization was carried out by irradiating with ultraviolet rays to obtain a prepolymer composition A (polymerization rate 5 to 15%).

(Preparation of adhesive composition and preparation of adhesive sheet)
After adding an additional photopolymerization initiator (BASF's "Irgacure 184": 0.05 parts by weight and BASF's "Irgacure 651": 0.05 parts by weight) to the above prepolymer composition A, defoaming is performed. Was done. This composition is based on a polyethylene terephthalate (PET) film ("Diafoil MRF75" manufactured by Mitsubishi Chemical Corporation) with a thickness of 75 μm provided with a silicone-based release layer on the surface, and the above-mentioned photocurable adhesive is applied onto the base material. The agent composition was applied so as to have a thickness of 100 μm to form a coating layer. On this coating layer, a PET film having a thickness of 75 μm (“Diafoil MRE75” manufactured by Mitsubishi Chemical Corporation) having one side treated with silicone peeling as a cover sheet was laminated. This laminate was photocured by irradiating this laminate with ultraviolet rays for 4 minutes from the cover sheet side with a black light whose position was adjusted so that the irradiation intensity on the irradiation surface directly under the lamp was 3.7 mW / cm ^2. Amount: 880 mJ / cm ² ), a transparent double-sided adhesive sheet with a release film attached to both sides was obtained. The non-volatile content of the adhesive sheet was 98.0%.

[Comparative Example 1]
To 100 parts by weight of the prepolymer composition prepared in the same manner as in the reference example, 0.1 part by weight of a black dye (“VALIFAST BLACK 3810” manufactured by Orient Chemical Industries Co., Ltd.) and an additional photopolymerization initiator are added, and then defoaming is performed. Was done. 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 irradiation with ultraviolet rays for 4 minutes, and an adhesive sheet could not be obtained.

[Comparative Example 2]
A 20% solution was prepared by dissolving 0.1 parts by weight of a black dye (“VALIFAST BLACK 3810” manufactured by Orient Chemical Industries Co., Ltd.) in 4 parts by weight of 2EHA. This solution was added to 100 parts by weight of the prepolymer composition prepared in the same manner as in the reference example, and an additional photopolymerization initiator was further added, and then defoaming was performed. An attempt was made to prepare a pressure-sensitive adhesive sheet using this composition, but as in Comparative Example 1, the composition was liquid after irradiation with ultraviolet rays for 4 minutes, and a pressure-sensitive adhesive sheet could not be obtained.

[Example 1]
To 100 parts by weight of the prepolymer composition prepared in the same manner as in the reference example, 0.5 parts by weight of a 20% dispersion of black pigment (“9050BLACK” manufactured by Tokushiki) (0.1 parts by weight as a black pigment), and additional After adding the photopolymerization initiator, defoaming was performed. This composition was applied onto a substrate so as to have a thickness of 100 μm, and then heated at 80 ° C. for 1 minute in order to remove the dispersion medium. Then, the cover sheets were pasted together to prepare an adhesive sheet in the same manner as in Reference Example 1. The non-volatile content of the adhesive sheet was 97.1%.

[Example 2]
(Polymerization of prepolymer)
As monomer components for prepolymer formation, butyl acrylate (BA): 67 parts by weight, cyclohexyl acrylate (CHA): 14 parts by weight, and 4HBA: 19 parts by weight, and a photopolymerization initiator (BASF "Irgacure 184": 0.09 parts by weight and BASF's "Irgacure 651": 0.09 parts by weight) were blended and polymerized by irradiating with ultraviolet rays to obtain a prepolymer composition B (polymerization rate 5 to 15%).

(Preparation of adhesive composition)
2-Hydroxyethyl acrylate (2HEA): 9 parts by weight, 4HBA: 8 parts by weight, dipentaerythritol hexaacrylate as a polyfunctional monomer: 0.02 parts by weight, as a silane coupling agent in the above prepolymer composition B. 3-glycidoxypropyltrimethoxysilane ("KBM-403" manufactured by Shinetsu Silicone): 0.35 parts by weight, photopolymerization initiator ("Irgacure 651" manufactured by BASF): 0.5 parts by weight, and 20 parts by weight of black pigment. % Dispersion (“9050 BLACK” manufactured by Tokushiki) was added by 4 parts by weight (0.8 parts by weight as a black pigment), mixed, and then defoamed to prepare a photopolymerizable pressure-sensitive adhesive composition.

(Making an adhesive sheet)
Using the above pressure-sensitive adhesive composition, a pressure-sensitive adhesive sheet was produced in the same manner as in Reference Example 1 except that ^{the irradiation time of ultraviolet rays was changed to 6 minutes and the integrated irradiation amount was changed to 1320 mJ / cm 2.}

[Example 3 and Example 4]
A pressure-sensitive adhesive sheet was produced in the same manner as in Example 2 except that the amount of the black pigment added and the thickness of the pressure-sensitive adhesive sheet were changed as shown in Table 1.

[Example 5]
(Polymerization of prepolymer)
Lauryl acrylate (LA): 36.5 parts by weight, 2EHA: 60 parts by weight, N-vinylpyrrolidone (NVP): 2.5 parts by weight, and 4HBA: 1 part by weight, and light as monomer components for prepolymer formation. A polymerization initiator (BASF's "Irgacure 184": 0.05 parts by weight and BASF's "Irgacure 651": 0.05 parts by weight) was blended and polymerized by irradiating with ultraviolet rays to carry out polymerization, and the prepolymer composition C ( Polymerization rate 5 to 15%) was obtained.

(Preparation of adhesive composition)
In the above prepolymer composition C, 1,6-hexanediol diacrylate as a polyfunctional monomer: 0.08 parts by weight, and 3-glycidoxypropyltrimethoxysilane as a silane coupling agent (manufactured by Shinetsu Silicone, trade name " KBM-403 ") 0.3 parts by weight, photopolymerization initiator (BASF" Irgacure 651 ") 0.3 parts by weight, and 20% dispersion of black pigment (Tokushiki" 9050 BLACK ") 4 parts by weight (black pigment) 0.8 parts by weight) was added, mixed, and then defoamed to prepare a photopolymerizable pressure-sensitive adhesive composition.

(Making an adhesive sheet)
Using the above pressure-sensitive adhesive composition, a pressure-sensitive adhesive sheet was produced in the same manner as in Reference Example 1 except that ^{the irradiation time of ultraviolet rays was changed to 6 minutes and the integrated irradiation amount was changed to 1320 mJ / cm 2.}

[Example 6 and Example 7]
A pressure-sensitive adhesive sheet was produced in the same manner as in Example 5 except that the amount of the black pigment added and the thickness of the pressure-sensitive adhesive sheet were changed as shown in Table 1.

[Ultraviolet irradiation amount and polymerization rate]
With respect to Reference Example 1, Comparative Example 1, Comparative Example 2, and Example 1, the irradiation time (integrated irradiation amount) of ultraviolet rays was changed to prepare an adhesive sheet, and the relationship between the integrated irradiation amount and the non-volatile component was investigated. The results are shown in FIG. In Comparative Example 2, the pressure-sensitive adhesive composition was liquid even after irradiation with ultraviolet rays for 10 minutes (2200 mJ / cm ² ), and the non-volatile content of the pressure-sensitive adhesive sheet after irradiation with ultraviolet rays for ^{25 minutes (5500 mJ / cm 2).} Was 87.6%.

[Evaluation results]
The transmission spectrum of the black pigment dispersion used in Examples 1 to 7 is shown in FIG. The type of prepolymer used in the preparation of the pressure-sensitive adhesive compositions of the above reference examples, comparative examples and examples, the type and amount of the colorant added, the thickness of the pressure-sensitive adhesive sheet, the non-volatile content of the pressure-sensitive adhesive sheet after irradiation with ultraviolet rays, and Table 1 shows the average transmittance and the maximum transmittance calculated from the transmittance spectrum of the pressure-sensitive adhesive sheet. The irradiation time of ultraviolet rays was 4 minutes for Reference Example 1 and Example 1 (integrated irradiation amount 880 mJ / cm ² ), 6 minutes for Examples 2 to 7 (integrated irradiation amount 1320 mJ / cm ² ), and 7 minutes for Comparative Example 1 (integrated irradiation amount 1320 mJ / cm 2). The integrated irradiation dose was 1540 mJ / cm ² ). The transmission spectrum was measured using a sample irradiated with ultraviolet rays for 7 minutes for Comparative Example 1 and a sample irradiated with ultraviolet rays for 25 minutes for Comparative Example 2.

The pressure-sensitive adhesive sheet of Reference Example 1 containing no colorant has an average transmittance of visible light (wavelength 400 to 700 nm) larger than the average transmittance of ultraviolet rays (wavelength 330 to 400 nm), whereas the pressure-sensitive adhesive sheet has a pressure-sensitive adhesive composition. In Examples 1 to 7 to which the ultraviolet-transmissive black pigment was added, the average transmittance of ultraviolet rays was larger than the average transmittance of visible light. Further, in Examples 1 to 7, the maximum transmittance in the ultraviolet region was larger than the maximum transmittance in the visible light region. On the other hand, in Comparative Example 1 and Comparative Example 2, the average transmittance of ultraviolet rays was smaller than the average transmittance of visible light, and the maximum transmittance in the ultraviolet region was smaller than the maximum average transmittance in the visible light region.

In Comparative Example 1, since the colorant (dye) was not uniformly dissolved in the pressure-sensitive adhesive composition, the measured value of the transmittance was large. In Comparative Example 2 in which a colorant dissolved in a monomer (2EHA) was added in advance, the transmittance of visible light was sufficiently reduced, but the transmittance of ultraviolet rays was also significantly reduced, and it took 25 minutes (25 minutes). Even after irradiation with ultraviolet rays of 5500 mJ / cm ² ), the adhesive was not sufficiently solidified. From these results, it can be seen that in Comparative Examples 1 and 2, the photocuring rate (photocuring efficiency) of the pressure-sensitive adhesive is significantly reduced due to the colorant absorbing ultraviolet rays.

From the results shown in Table 1 and FIG. 3, it can be seen that Example 1 has sufficiently high photocurability as compared with Comparative Example 1 and Comparative Example 2. Further, in Examples 2 to 7, as in Example 1, there are few unreacted monomers and high photocuring even when the non-volatile content is large and the content of the colorant is large or the transmittance of visible light is low. It can be seen that it has sex.

From these results, by preparing a photocurable pressure-sensitive adhesive composition using a colorant that absorbs ultraviolet rays relatively less than in the visible light region, curing inhibition by the colorant is suppressed, and the colorant can be used. It can be seen that a colored double-sided adhesive sheet having light absorption in visible light can be obtained with the same productivity as when it is not contained.

When the adhesive sheets of Reference Examples and Examples 1 to 7 were attached to the stainless steel substrate and visually confirmed, in Examples 1 to 7, the metallic luster of the stainless steel substrate was less than that of the reference example, and the reflectance was lowered. It was confirmed that it was done. From these results, it can be seen that the adhesive sheet having a low visible light transmittance can be applied as an antireflection member for a light emitting element, a display, or the like.

Claims (20)

A photocurable pressure-sensitive adhesive composition containing a polymer, a photopolymerizable compound, a photopolymerization initiator, and a colorant.
The colorant is a photocurable pressure-sensitive adhesive composition in which the maximum transmittance at a wavelength of 330 to 400 nm is larger than the maximum transmittance at a wavelength of 400 to 700 nm. A photocurable pressure-sensitive adhesive composition containing a polymer, a photopolymerizable compound, a photopolymerization initiator, and a colorant.
The colorant is a photocurable pressure-sensitive adhesive composition in which the average transmittance at a wavelength of 330 to 400 nm is larger than the average transmittance at a wavelength of 400 to 700 nm. The photocurable pressure-sensitive adhesive composition according to claim 2, wherein the colorant has a maximum transmittance at a wavelength of 330 to 400 nm higher than a maximum transmittance at a wavelength of 400 to 700 nm. The photocurable pressure-sensitive adhesive composition according to any one of claims 1 to 3, wherein the photopolymerization initiator has at least one absorption maximum in the wavelength range of 330 to 400 nm. The photocurable pressure-sensitive adhesive composition according to any one of claims 1 to 4, wherein the colorant is a pigment. The photocurable pressure-sensitive adhesive composition according to any one of claims 1 to 5, wherein the polymer is an acrylic polymer. The photocurable pressure-sensitive adhesive composition according to any one of claims 1 to 6, wherein the glass transition temperature of the polymer is 0 ° C. or lower. The photocurable pressure-sensitive adhesive composition according to any one of claims 1 to 7, further comprising a cross-linking agent capable of cross-linking with the polymer. A double-sided pressure-sensitive adhesive sheet which is a sheet-like molded product of the photocurable pressure-sensitive adhesive composition according to any one of claims 1 to 8. A double-sided pressure-sensitive adhesive sheet comprising a photocurable product of a sheet-like molded product of the photocurable pressure-sensitive adhesive composition according to any one of claims 1 to 8. The double-sided adhesive sheet according to claim 10, wherein the non-volatile content is 90% by weight or more. The double-sided pressure-sensitive adhesive sheet according to any one of claims 9 to 11, wherein the maximum transmittance at a wavelength of 330 to 400 nm is larger than the maximum transmittance at a wavelength of 400 to 700 nm. The double-sided pressure-sensitive adhesive sheet according to any one of claims 9 to 12, wherein the average transmittance at a wavelength of 330 to 400 nm is larger than the average transmittance at a wavelength of 400 to 700 nm. The double-sided adhesive sheet according to any one of claims 9 to 13, wherein the total light transmittance is 80% or less. The double-sided adhesive sheet according to any one of claims 9 to 14, which has a thickness of 10 to 500 μm. The double-sided pressure-sensitive adhesive sheet according to any one of claims 9 to 15, wherein the shear storage elastic modulus at a temperature of 25 ° C. is 10 to 1000 kPa. The double-sided pressure-sensitive adhesive sheet according to any one of claims 9 to 16, wherein the shear storage elastic modulus at a temperature of 85 ° C. is 3 to 300 kPa. The photocurable pressure-sensitive adhesive composition according to any one of claims 1 to 8 is applied onto a substrate in the form of a sheet.
A method for producing a double-sided pressure-sensitive adhesive sheet, wherein a sheet-shaped coating film provided on a base material is irradiated with ultraviolet rays to photo-cure the photopolymerizable compound. An optical device in which a first adherend and a second adherend are bonded to each other via the double-sided adhesive sheet according to any one of claims 9 to 17. A method for manufacturing an optical device in which a first adherend and a second adherend are bonded together via a double-sided adhesive sheet.
A first adherend and a second adherend are attached to the first main surface and the second main surface of the double-sided adhesive sheet according to any one of claims 9 to 17, respectively.
A method for manufacturing an optical device, wherein the double-sided pressure-sensitive adhesive sheet is irradiated with ultraviolet rays to photo-cure the photopolymerizable compound.

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