JP7156453B2 - Transparent double-sided adhesive sheet and adhesive sheet laminate - Google Patents

Description

TECHNICAL FIELD The present invention relates to a transparent double-sided pressure-sensitive adhesive sheet that can be used as a member for constituting image display devices such as personal computers, mobile terminals (PDAs), game machines, televisions (TVs), car navigation systems, touch panels, and pen tablets. .

In recent years, in order to improve the visibility of image display devices, image display panels such as liquid crystal displays (LCD), plasma displays (PDP), electroluminescence displays (ELD), and protection placed on the front side (visible side) By filling the gap between the panel and the touch panel member with an adhesive, the reflection of the incident light and the emitted light from the display image at the interface of the air layer is suppressed.

As a method of filling the gaps between the constituent members for such an image display device with an adhesive, there is a method of filling the gaps with a liquid adhesive resin composition containing an ultraviolet curable resin and then curing the composition by irradiating with ultraviolet rays. It is known (Patent Document 1).

Also known is a method of filling gaps between constituent members for an image display device using an adhesive sheet. For example, Patent Literature 2 discloses a method of bonding an adhesive sheet that has been primarily crosslinked with ultraviolet light to a constituent member of an image display device, and then irradiating the adhesive sheet with ultraviolet rays through the constituent member of the image display device to perform secondary curing. .

Patent Document 3 describes a pressure-sensitive adhesive sheet made of a hot-melt type adhesive composition having a loss tangent of less than 1 at 25° C. and containing urethane (meth)acrylate having a weight average molecular weight of 20,000 to 100,000 as a main component. is used to fill voids between components for image display devices.

International Publication 2010/027041 Japanese Patent No. 4971529 International publication 2010/038366

By the way, when two image display device constituent members are attached using an adhesive sheet made of an adhesive resin composition containing a base resin, a cross-linking agent, and an ultraviolet polymerization initiator, the two image display device constituent members are After primary attachment via the adhesive sheet, ultraviolet rays are irradiated from the outside of one of the image display device constituent members to UV cure the adhesive sheet through the image display device constituent members, followed by secondary attachment. According to this, it is possible to perform the primary attachment while filling the unevenness of the adherend surface, and to further improve the adhesion reliability by finally curing.
However, when such a UV-sensitive adhesive sheet is exposed to UV rays for a long period of time, the deterioration of the adhesive sheet itself progresses, and there is a possibility that decomposed products may occur, resulting in foaming or peeling.
In addition, since some image display apparatus constituent members are susceptible to deterioration by ultraviolet rays, in such a case, the two image display apparatus constituent members cannot be adhered by the method described above.
Furthermore, when the image display device constituent members have ultraviolet absorption properties, even if ultraviolet rays are irradiated through the member, the ultraviolet rays do not sufficiently reach the adhesive sheet. It is not possible to attach the two image display device constituent members with .

On the other hand, as image display devices become thinner, pressure-sensitive adhesive sheets are required to have new functions. In order to prevent ultraviolet deterioration of liquid crystals, organic EL elements, polarizing plates, etc., image display device constituent members may be required to have an ultraviolet absorbing function, and the ultraviolet absorbing function is generally ensured by a polarizing plate protective film. rice field. However, along with the reduction in the thickness of image display device constituent members, the thickness of polarizing plate protective films has also been reduced, making it difficult to obtain a sufficient ultraviolet absorption function. Therefore, components of image display devices other than polarizing plate protective films, such as adhesives and adhesive sheets, are also required to have an ultraviolet absorbing function.

However, it is difficult to impart an ultraviolet-absorbing function to the above-described ultraviolet-curable pressure-sensitive adhesive sheet. On the other hand, if the adhesive sheet is used to fill in the unevenness of the adherend surface, it is first adhered, and then cured and then secondarily adhered, otherwise the adherend surface of the adherend member may have irregularities. There is a problem that it is not possible to achieve both the step absorbability and the reliability of foaming resistance after lamination.

Accordingly, the present invention aims to provide a new transparent double-sided pressure-sensitive adhesive sheet that has an ultraviolet absorbing function and that can be further cured and secondarily adhered after primary adhesion using an adhesive sheet. be.

The present invention comprises a (meth)acrylic copolymer (A), a cross-linking agent (B), a photopolymerization initiator (C) having an absorption coefficient of 10 mL/(g cm) or more at a wavelength of 405 nm, and an ultraviolet absorber ( D) is a transparent double-sided adhesive sheet having an adhesive layer formed from an adhesive resin composition containing D), wherein the ultraviolet transmittance (JIS K7361-1) of the adhesive sheet is 50% or less at a wavelength of 380 nm. It is a transparent double-sided adhesive sheet.

The transparent double-faced pressure-sensitive adhesive sheet for image display of the present invention has an ultraviolet absorption function, and furthermore, after primary adhesion using the pressure-sensitive adhesive sheet, it can be further photocured for secondary adhesion. It is possible to achieve both step absorbability when the adherend surface has unevenness and foam resistance reliability after lamination.

An example of an embodiment of the present invention will be described in detail below. However, the present invention is not limited to the following embodiments.

<This adhesive sheet>
A transparent double-sided pressure-sensitive adhesive sheet according to an example of an embodiment of the present invention comprises a (meth)acrylic copolymer (A), a cross-linking agent (B), and light having an absorption coefficient of 10 mL/(g cm) or more at a wavelength of 405 nm. A transparent double-sided pressure-sensitive adhesive sheet (referred to as "this pressure-sensitive adhesive sheet") made of a pressure-sensitive adhesive resin composition (referred to as "this pressure-sensitive adhesive composition") containing a polymerization initiator (C) and an ultraviolet absorber (D).

[(Meth)acrylic copolymer (A)]
The glass transition temperature (Tg) of the (meth)acrylic polymer used as the base polymer of this pressure-sensitive adhesive sheet varies depending on the type and composition ratio of the acrylic monomers and methacrylic monomers used to polymerize it, as well as the polymerization conditions. characteristics can be adjusted as appropriate.

The "base polymer" in this pressure-sensitive adhesive sheet means a resin that constitutes the main component of this pressure-sensitive adhesive sheet. It does not specify a specific content. As a guideline, the resin accounts for 50% by mass or more, especially 65% by mass or more, especially 80% by mass or more (including 100% by mass) or more of the resin contained in the pressure-sensitive adhesive sheet. In addition, when two or more base polymers are used, the total amount thereof corresponds to the content.

The (meth)acrylic (co)polymer (A) is, for example, an alkyl (meth)acrylate homopolymer or a copolymer obtained by polymerizing this with a copolymerizable monomer component. More preferably, an alkyl (meth)acrylate and a carboxyl group-containing monomer copolymerizable therewith, a hydroxyl group-containing monomer, an amino group-containing monomer, an epoxy group-containing monomer, an amide group-containing monomer and other vinyl monomers Copolymers containing any one or more selected monomers as monomer components can be mentioned.

More specifically, a linear or branched alkyl (meth)acrylate having 4 to 18 carbon atoms in the side chain (hereinafter also referred to as "copolymerizable monomer A"), a carboxyl group-containing monomer copolymerizable therewith (hereinafter Also referred to as "copolymerizable monomer B".), vinyl monomer (hereinafter also referred to as "copolymerizable monomer C"), (meth)acrylate having 1 to 3 carbon atoms in the side chain (hereinafter referred to as "copolymerizable monomer D ), and a copolymer composed of any one or more monomers selected from hydroxyl group-containing monomers (hereinafter “copolymerizable monomer E)”.

Further, (a) a copolymer composed of a copolymerizable monomer A and a monomer component containing a copolymerizable monomer B and / or a copolymerizable monomer C, or (b) a copolymerizable monomer A and a copolymer A particularly preferred example is a copolymer composed of a monomer component containing a polar monomer B and/or a copolymerizable monomer C and a copolymerizable monomer D and/or a copolymerizable monomer E. Specifically, copolymers of copolymerizable monomers A and B, copolymers of copolymerizable monomers A and C, copolymers of copolymerizable monomers A, B and C, copolymerizable monomers A and B and D, copolymers of copolymerizable monomers A, B and E, copolymers of copolymerizable monomers A, B, D and E, copolymers of copolymerizable monomers A, C and D , copolymers of copolymerizable monomers A, C and E, copolymers of copolymerizable monomers A, C, D and E, copolymers of copolymerizable monomers A, B, C and D, copolymerizable Copolymers of monomers A, B, C and E, copolymers of copolymerizable monomers A, B, C, D and E may be mentioned.

Examples of the above-mentioned "copolymerizable monomer A" include n-butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, neopentyl (meth)acrylate, hexyl (meth)acrylate, cyclohexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate , nonyl (meth)acrylate, isononyl (meth)acrylate, t-butylcyclohexyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate Acrylate, tetradecyl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, isobornyl (meth)acrylate, 3,5,5-trimethylcyclohexane (meth)acrylate, dicyclopentanyl (Meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate and the like can be mentioned. These may be used singly or in combination of two or more.

The copolymerizable monomer A is preferably contained in the total monomer components of the copolymer in an amount of 30% by mass or more and 90% by mass or less, particularly 35% by mass or more or 88% by mass or less, and particularly 40% by mass or more. Alternatively, it is more preferably contained in the range of 85% by mass or less.

Examples of the above-mentioned "copolymerizable monomer B" include, for example, (meth)acrylic acid, 2-(meth)acryloyloxyethylhexahydrophthalic acid, 2-(meth)acryloyloxypropylhexahydrophthalic acid, 2-(meth) acryloyloxyethyl phthalate, 2-(meth)acryloyloxypropyl phthalate, 2-(meth)acryloyloxyethyl maleate, 2-(meth)acryloyloxypropyl maleate, 2-(meth)acryloyloxyethyl succinate, Mention may be made of 2-(meth)acryloyloxypropylsuccinic acid, crotonic acid, fumaric acid, maleic acid, itaconic acid. These may be used alone or in combination of two or more. "(Meth)acryl" is meant to include acryl and methacryl. Similarly, "(meth)acryloyl" is meant to include acryloyl and methacryloyl.

Examples of the above-mentioned "copolymerizable monomer C" include compounds having a vinyl group in the molecule. Examples of such compounds include (meth)acrylic acid alkyl esters in which the alkyl group has 1 to 12 carbon atoms, functional monomers having functional groups such as hydroxyl group, amide group and alkoxyalkyl group in the molecule, and Polyalkylene glycol di(meth)acrylates and vinyl ester monomers such as vinyl acetate, vinyl propionate and vinyl laurate and aromatic vinyl monomers such as styrene, chlorostyrene, chloromethylstyrene, α-methylstyrene and other substituted styrenes can be exemplified. These may be used alone or in combination of two or more.

The copolymerizable monomer B and the copolymerizable monomer C are 1.2% by mass to 15% by mass or less in the total monomer components of the copolymer, and 1.5% by mass or more from the viewpoint of obtaining excellent adhesive properties. Alternatively, it is preferably contained in the range of 10% by mass or less, particularly 2% by mass or more or 8% by mass or less.

Examples of the above-mentioned "copolymerizable monomer D" include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, i-propyl (meth)acrylate and the like. These may be used alone or in combination of two or more.
The copolymerizable monomer D preferably contains 0% by mass or more and 70% by mass or less in the total monomer components of the copolymer, especially 3% by mass or more or 65% by mass or less, especially 5% by mass or more or It is more preferable to contain in the range of 60% by mass or less.

Examples of the "copolymerizable monomer E" include hydroxyalkyls such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 2-hydroxybutyl (meth)acrylate. (Meth)acrylates may be mentioned. These may be used alone or in combination of two or more.

The copolymerizable monomer E is preferably contained in the total monomer components of the copolymer in an amount of 0% by mass or more and 30% by mass or less, especially 0% by mass or more or 25% by mass or less, especially 0% by mass or more or It is more preferable to contain in the range of 20% by mass or less.

In addition to those listed above, acid anhydride group-containing monomers such as maleic anhydride and itaconic anhydride, and epoxies such as glycidyl (meth)acrylate, glycidyl α-ethylacrylate, and 3,4-epoxybutyl (meth)acrylate Group-containing monomers, amino group-containing (meth)acrylic acid ester monomers such as dimethylaminoethyl (meth)acrylate and diethylaminoethyl (meth)acrylate, (meth)acrylamide, Nt-butyl (meth)acrylamide, N-methylol (Meth)acrylamide, N-methoxymethyl (meth)acrylamide, N-butoxymethyl (meth)acrylamide, diacetone (meth)acrylamide, maleic acid amide, monomers containing amide groups such as maleimide, vinylpyrrolidone, vinylpyridine, Heterocyclic basic monomers such as vinylcarbazole can also be used as appropriate, if necessary.

Specific examples of (meth)acrylic (co)polymers include 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, decyl (meth)acrylate, lauryl (meth)acrylate, isostearyl (meth)acrylate, ) Monomer component (a) such as acrylate, butyl (meth)acrylate, ethyl (meth)acrylate, methyl (meth)acrylate, etc., (meth)acrylic acid having a carboxyl group, 2-(meth)acryloyloxyethylhexahydrophthalate acid, 2-(meth)acryloyloxypropylhexahydrophthalic acid, 2-(meth)acryloyloxyethyl phthalate, 2-(meth)acryloyloxypropyl phthalate, 2-(meth)acryloyloxyethyl maleate, 2- (meth) acryloyloxypropyl maleic acid, 2-(meth) acryloyloxyethyl succinic acid, 2-(meth) acryloyloxypropyl succinic acid, crotonic acid, fumaric acid, maleic acid, itaconic acid and the like monomer component (b) , hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, glycerol (meth)acrylate, monomethyl maleate, monomethyl itaconate, vinyl acetate, glycidyl (meth)acrylate with organic functional groups, etc. , (meth)acrylamide, (meth)acrylonitrile, fluorinated (meth)acrylate, silicone (meth)acrylate and other monomer components (c), and (meth)acrylic acid ester copolymers obtained by copolymerizing be able to.

The (meth)acrylic (co)polymer preferably has a mass average molecular weight of 100,000 to 1,500,000, more preferably 150,000 or more or 1,300,000 or less, and more preferably 200,000 or more or 1,200,000 or less.

When it is desired to obtain an adhesive composition with high cohesive force, the mass average molecular weight is 700,000 to 1,500,000, particularly 800,000 or more or 1,300,000 or less, from the viewpoint that the greater the molecular weight, the more cohesive force is obtained by the entanglement of molecular chains. is preferred. On the other hand, when it is desired to obtain a pressure-sensitive adhesive composition having high fluidity and stress relaxation properties, the mass average molecular weight is preferably 70,000 to 700,000, particularly 100,000 or more or 600,000 or less. In addition, when a solvent is not used when molding an adhesive sheet or the like, it is difficult to use a polymer with a large molecular weight. Alternatively, it is preferably 600,000 or less, more preferably 150,000 or more or 500,000 or less.

(Acrylic copolymer (A1))
A preferred example of the base polymer of the pressure-sensitive adhesive sheet is a (meth)acrylic copolymer (A1) comprising a graft copolymer having a macromonomer as a branch component.

By forming the present pressure-sensitive adhesive sheet using the above acrylic copolymer (A1) as a base resin, the present pressure-sensitive adhesive sheet can exhibit self-adhesiveness while maintaining a sheet shape at room temperature, and when heated in an uncrosslinked state, It has a hot-melt property that melts or flows, and can be photo-cured. After photo-curing, it exhibits excellent cohesion and can be adhered.
Therefore, if the acrylic copolymer (A1) is used as the base polymer of the pressure-sensitive adhesive sheet, it exhibits adhesiveness at room temperature (20°C) even in an uncrosslinked state, and is more preferably 50 to 90°C. can have the property of softening or fluidizing when heated to a temperature of 60° C. or higher or 80° C. or lower.

The glass transition temperature of the copolymer constituting the trunk component of the acrylic copolymer (A1) is preferably -70 to 0°C.
At this time, the glass transition temperature of the copolymer component constituting the trunk component refers to the glass transition temperature of the polymer obtained by copolymerizing only the monomer components constituting the trunk component of the acrylic copolymer (A1). . Specifically, it means a value calculated by the Fox formula from the glass transition temperature and composition ratio of a polymer obtained from a homopolymer of each component of the copolymer.
The Fox calculation formula is a calculated value obtained by the following formula, which is described in Polymer Handbook [Polymer Handbook, J. Am. Brandrup, Interscience, 1989].
1/(273+Tg)=Σ(Wi/(273+Tgi))
[In the formula, Wi is the weight fraction of the monomer i, and Tgi is the Tg (° C.) of the homopolymer of the monomer i. ]

The glass transition temperature of the copolymer component constituting the trunk component of the acrylic copolymer (A1) is determined by the flexibility of the pressure-sensitive adhesive sheet at room temperature and the wettability of the pressure-sensitive adhesive sheet to the adherend. Since the adhesiveness is affected, the glass transition temperature is preferably -70°C to 0°C, especially -65°C, in order for the pressure-sensitive adhesive sheet to obtain appropriate adhesiveness (tackiness) at room temperature. or higher or -5°C or lower, particularly preferably -60°C or higher or -10°C or lower.
However, even if the copolymer component has the same glass transition temperature, the viscoelasticity can be adjusted by adjusting the molecular weight. For example, by reducing the molecular weight of the copolymer component, it can be made more flexible.

The (meth)acrylic acid ester monomer contained in the trunk component of the acrylic copolymer (A1) includes, for example, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, sec-butyl (meth) acrylate, t-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, neopentyl (meth) acrylate, hexyl ( meth)acrylate, cyclohexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, isooctyl acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, t-butylcyclohexyl (meth)acrylate , decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, lauryl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, behenyl (meth)acrylate, isobornyl (meth) acrylate, 2-phenoxyethyl (meth) acrylate, 3,5,5-trimethylcyclohexane acrylate, p-cumylphenol EO-modified (meth) acrylate, dicyclopentanyl (meth) acrylate, dicyclopentenyl ( meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, benzyl (meth)acrylate and the like. These include hydroxyl group-containing (meth)acrylates such as hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, and glycerol (meth)acrylate having hydrophilic groups and organic functional groups, and (meth)acrylates. ) acrylic acid, 2-(meth)acryloyloxyethylhexahydrophthalic acid, 2-(meth)acryloyloxypropylhexahydrophthalic acid, 2-(meth)acryloyloxyethyl phthalate, 2-(meth)acryloyloxypropyl phthalate acid, 2-(meth)acryloyloxyethyl maleate, 2-(meth)acryloyloxypropyl maleate, 2-(meth)acryloyloxyethyl succinate, 2-(meth)acryloyloxypropyl succinate, crotonic acid, fumaric acid Acids, maleic acid, itaconic acid, monomethyl maleate, carboxyl group-containing monomers such as monomethyl itaconate, maleic anhydride, acid anhydride group-containing monomers such as itaconic anhydride, glycidyl (meth)acrylate, α-ethyl acrylic acid epoxy group-containing monomers such as glycidyl and 3,4-epoxybutyl (meth)acrylate; amino group-containing (meth)acrylate monomers such as dimethylaminoethyl (meth)acrylate and diethylaminoethyl (meth)acrylate; ) acrylamide, Nt-butyl (meth)acrylamide, N-methylol (meth)acrylamide, N-methoxymethyl (meth)acrylamide, N-butoxymethyl (meth)acrylamide, diacetoneacrylamide, maleic acid amide, maleimide, etc. Monomers containing an amide group, heterocyclic basic monomers such as vinylpyrrolidone, vinylpyridine, vinylcarbazole, and the like can also be used.
In addition, styrene, t-butylstyrene, α-methylstyrene, vinyltoluene, acrylonitrile, methacrylonitonyl, vinyl acetate, vinyl propionate, alkyl vinyl ether, hydroxyalkyl vinyl ether, alkyl vinyl ether, which can be copolymerized with the above acrylic monomers and methacrylic monomers. Various vinyl monomers such as vinyl monomers can also be used as appropriate.

Moreover, the trunk component of the acrylic copolymer (A1) preferably contains a hydrophobic (meth)acrylate monomer and a hydrophilic (meth)acrylate monomer as structural units.
If the trunk component of the acrylic copolymer (A1) is composed only of hydrophobic monomers, it tends to whiten under wet heat. Therefore, it is preferable to introduce a hydrophilic monomer into the trunk component to prevent whitening under wet heat. .

Specifically, as the trunk component of the acrylic copolymer (A1), a hydrophobic (meth)acrylate monomer, a hydrophilic (meth)acrylate monomer, and a polymerizable functional group at the end of the macromonomer are A copolymer component formed by random copolymerization can be mentioned.

Examples of the hydrophobic (meth)acrylate monomers include n-butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, and pentyl (meth)acrylate. ) acrylate, isopentyl (meth) acrylate, neopentyl (meth) acrylate, hexyl (meth) acrylate, cyclohexyl (meth) acrylate, heptyl (meth) acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, isooctyl acrylate, nonyl (meth) ) acrylate, isononyl (meth) acrylate, t-butylcyclohexyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, undecyl (meth) acrylate, lauryl (meth) acrylate, cetyl (meth) acrylate, stearyl ( meth)acrylate, isostearyl (meth)acrylate, behenyl (meth)acrylate, isobornyl (meth)acrylate, cyclohexyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate and methyl methacrylate.
Examples of hydrophobic vinyl monomers include vinyl acetate, styrene, t-butylstyrene, α-methylstyrene, vinyltoluene, and alkyl vinyl monomers.

Examples of the hydrophilic (meth)acrylate monomers include methyl acrylate, (meth) acrylic acid, tetrahydrofurfuryl (meth) acrylate, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, and hydroxybutyl (meth) acrylate. ) acrylates, hydroxyl group-containing (meth) acrylates such as glycerol (meth) acrylate, (meth) acrylic acid, 2-(meth) acryloyloxyethylhexahydrophthalic acid, 2-(meth) acryloyloxypropyl hexahydrophthalic acid, 2-(meth)acryloyloxyethyl phthalate, 2-(meth)acryloyloxypropyl phthalate, 2-(meth)acryloyloxyethyl maleate, 2-(meth)acryloyloxypropyl maleate, 2-(meth)acryloyl Carboxyl group-containing monomers such as oxyethylsuccinic acid, 2-(meth)acryloyloxypropylsuccinic acid, crotonic acid, fumaric acid, maleic acid, itaconic acid, monomethyl maleate, monomethyl itaconate, maleic anhydride, itaconic anhydride, etc. acid anhydride group-containing monomers, epoxy group-containing monomers such as glycidyl (meth)acrylate, glycidyl α-ethyl acrylate, 3,4-epoxybutyl (meth)acrylate, alkoxy such as methoxypolyethylene glycol (meth)acrylate Examples include polyalkylene glycol (meth)acrylate, N,N-dimethylacrylamide, hydroxyethylacrylamide and the like.

(Branch component: macromonomer)
The acrylic copolymer (A1) preferably contains repeating units derived from the macromonomer by introducing a macromonomer as a branch component of the graft copolymer.
A macromonomer is a macromonomer having a terminal polymerizable functional group and a high molecular weight backbone component.

The glass transition temperature (Tg) of the macromonomer is preferably higher than the glass transition temperature of the copolymer component constituting the acrylic copolymer (A1).
Specifically, since the glass transition temperature (Tg) of the macromonomer affects the heat melting temperature (hot melt temperature) of the pressure-sensitive adhesive sheet, the glass transition temperature (Tg) of the macromonomer is 30°C to 120°C. , preferably 40°C or higher or 110°C or lower, more preferably 50°C or higher or 100°C or lower.
With such a glass transition temperature (Tg), by adjusting the molecular weight, it is possible to maintain excellent workability and storage stability, and it is possible to adjust it so that it hot melts at around 50°C to 80°C. .
The glass transition temperature of the macromonomer refers to the glass transition temperature of the macromonomer itself, which can be measured with a differential scanning calorimeter (DSC).

In addition, at room temperature, the branch components attract each other to maintain a state of physical cross-linking as a pressure-sensitive adhesive composition. In order to obtain fluidity, it is also preferable to adjust the molecular weight and content of the macromonomer.
From this point of view, the macromonomer is preferably contained in the acrylic copolymer (A1) at a rate of 5% to 30% by mass, especially 6% by mass or more or 25% by mass or less, and among them 8% by mass. It is preferably 20% by mass or more or 20% by mass or less.
The number average molecular weight of the macromonomer is preferably 500 or more and less than 8,000, more preferably 800 or more and less than 7,500, and more preferably 1,000 or more and less than 7,000.
Commonly produced macromonomers (for example, macromonomers manufactured by Toagosei Co., Ltd.) can be used as appropriate.

The high molecular weight skeleton component of the macromonomer is preferably composed of an acrylic polymer or a vinyl polymer.
Examples of the high-molecular-weight backbone component of the macromonomer include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, and isobutyl (meth)acrylate. , sec-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, neopentyl (meth)acrylate, hexyl (meth)acrylate, cyclohexyl (meth)acrylate, heptyl (meth)acrylate ) acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, isooctyl acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, t-butylcyclohexyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, Undecyl (meth) acrylate, Lauryl (meth) acrylate, Cetyl (meth) acrylate, Stearyl (meth) acrylate, Isostearyl (meth) acrylate, Behenyl (meth) acrylate, Isobornyl (meth) acrylate, 2-Phenoxyethyl (meth) Acrylates, 3,5,5-trimethylcyclohexane acrylate, p-cumylphenol EO-modified (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate , benzyl (meth)acrylate, hydroxyalkyl (meth)acrylate, (meth)acrylic acid, glycidyl (meth)acrylate, (meth)acrylamide, N,N-dimethyl (meth)acrylamide, (meth)acrylonitrile, alkoxyalkyl ( (Meth)acrylate monomers such as meth)acrylates and alkoxypolyalkylene glycol (meth)acrylates, styrene, t-butylstyrene, α-methylstyrene, vinyltoluene, alkylvinyl monomers, alkylvinylesters, alkylvinylethers, hydroxyalkylvinylethers and various vinyl monomers, and these can be used alone or in combination of two or more.

Examples of the terminal polymerizable functional group of the macromonomer include a methacryloyl group, an acryloyl group, and a vinyl group.

[Crosslinking agent (B)]
The cross-linking agent (B) is selected from, for example, (meth)acryloyl groups, epoxy groups, isocyanate groups, carboxyl groups, hydroxyl groups, carbodiimide groups, oxazoline groups, aziridine groups, vinyl groups, amino groups, imino groups, and amide groups. Cross-linking agents having at least one cross-linkable functional group may be mentioned, and may be used singly or in combination of two or more.
The crosslinkable functional group may be protected with a deprotectable protective group.

Examples of such polyfunctional (meth)acrylates include 1,4-butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, glycerin di(meth)acrylate, glycerin glycidyl ether di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, tricyclodecanedimethanol di(meth)acrylate, bisphenol A polyethoxydi(meth)acrylate, bisphenol A polyalkoxy di(meth)acrylate ) acrylate, bisphenol F polyalkoxydi(meth)acrylate, polyalkylene glycol di(meth)acrylate, trimethylolpropane trioxyethyl (meth)acrylate, ε-caprolactone-modified tris(2-hydroxyethyl) isocyanurate tri(meth) Acrylates, pentaerythritol tri(meth)acrylate, propoxylated pentaerythritol tri(meth)acrylate, ethoxylated pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, propoxylated pentaerythritol tetra(meth)acrylate, ethoxylated Pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, polyethylene glycol di(meth)acrylate, tris(acryloxyethyl) isocyanurate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate , dipentaerythritol penta(meth)acrylate, tripentaerythritol hexa(meth)acrylate, tripentaerythritol penta(meth)acrylate, neopentyl glycol hydroxybivalate di(meth)acrylate, ε of neopentyl glycol hydroxybivalate - UV-curable polyfunctional monomers such as caprolactone adduct di(meth)acrylate, trimethylolpropane tri(meth)acrylate, alkoxylated trimethylolpropane tri(meth)acrylate, and ditrimethylolpropane tetra(meth)acrylate In addition, polyfunctional acrylic oligomers such as polyester (meth)acrylate, epoxy (meth)acrylate, urethane (meth)acrylate, polyether (meth)acrylate, polyfunctional acrylamide, etc. can be mentioned.

Among the above, from the viewpoint of improving the adhesion to the adherend and the effect of suppressing wet heat whitening, among the above polyfunctional (meth)acrylic acid ester monomers, hydroxyl groups, carboxyl groups, polar functional groups such as amide groups Polyfunctional monomers or oligomers containing are preferred. Among them, it is preferable to use a polyfunctional (meth)acrylic acid ester having a hydroxyl group or an amide group.
From the viewpoint of preventing wet heat whitening, the (meth)acrylic acid ester copolymer (A1), ie, the graft copolymer, contains a hydrophobic acrylate monomer and a hydrophilic acrylate monomer as the main components. is preferred, and more preferably, a polyfunctional (meth)acrylic acid ester having a hydroxyl group is used as the cross-linking agent (B).
In addition, a monofunctional or polyfunctional (meth)acrylic acid ester that reacts with the cross-linking agent (B) may be further added in order to adjust effects such as adhesion, moist heat resistance, and heat resistance.

The content of the cross-linking agent (B) is 0.1 to 20 with respect to 100 parts by mass of the (meth)acrylic copolymer (A) from the viewpoint of balancing the flexibility and cohesive strength of the pressure-sensitive adhesive composition. It is preferably contained in a proportion of 0.5 parts by mass or more or 15 parts by mass or less, and particularly preferably in a proportion of 1 part by mass or more or 13 parts by mass or less.

[Photoinitiator (C)]
The photopolymerization initiator (C) used in the present pressure-sensitive adhesive sheet functions as a reaction initiation aid in the crosslinking reaction of the crosslinking agent (B), and is visible light, for example light in the wavelength region of 380 nm to 700 nm. It is preferable to use a material that generates radicals upon irradiation and serves as a starting point for the polymerization reaction of the base resin. However, radicals may be generated only by irradiation with visible light, or radicals may be generated by irradiation with light in a wavelength region other than the visible light region.

From this point of view, the photopolymerization initiator (C) has an absorption coefficient at a wavelength of 405 nm of 10 mL/(g cm) or more, especially 15 mL/(g cm) or more, especially 25 mL/(g cm) or more. is particularly preferred.
The absorption coefficient in the present invention corresponds to the absorbance at an optical path length of 1 cm when the photopolymerization initiator is a methanol solution having a concentration of 1 g/L.

Examples of photopolymerization initiators having an absorption coefficient of 10 mL/(g cm) or more at a wavelength of 405 nm include 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butan-1-one, 2-( 4-methylbenzyl)-2-dimethylamino-1-(4-morpholinophenyl)butan-1-one, bis(η ⁵ -2,4-cyclopentadien-1-yl)-bis(2,6-difluoro -3-(1H-pyrrol-1-yl)phenyl)titanium, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, (2,4 ,6-trimethylbenzoyl)ethoxyphenylphosphine oxide, bis(2,6-dimethoxybenzoyl) 2,4,4-trimethylpentylphosphine oxide, thioxanthone, 2-chlorothioxanthone, 3-methylthioxanthone, 2,4-dimethylthioxanthone , anthraquinone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, 2-aminoanthraquinone, 1,2-octanedione, 1-(4-(phenylthio),2-(o-benzoyloxime)) , 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-ethanone 1-(O-acetyloxime), camphorquinone, triazine-based photopolymerization initiators, and the like. be able to.
Any one of these or derivatives thereof may be used, or two or more of these may be used in combination. In addition, it may be used in combination with a photopolymerization initiator having an absorption coefficient of less than 10 mL/(g·cm) at a wavelength of 405 nm.

Photopolymerization initiators are broadly classified into two groups according to the radical generation mechanism: cleavage-type photopolymerization initiators that can generate radicals by cleaving and decomposing the single bond of the photopolymerization initiator itself, and photoexcited initiators. and a hydrogen abstraction type photopolymerization initiator capable of forming an exciplex with a hydrogen donor in the system and transferring hydrogen of the hydrogen donor.
Among these, the cleavage-type photopolymerization initiator decomposes into a different compound when radicals are generated by light irradiation, and once excited, it loses its function as a reaction initiator. Therefore, when the intramolecularly cleavable type is used as the photopolymerization initiator (C) having an absorption wavelength in the visible light region, the photoreaction occurs after the adhesive sheet is crosslinked by light irradiation, compared to the case of using the hydrogen abstraction type. This is preferable because the photopolymerizable initiator remains in the present pressure-sensitive adhesive composition as an unreacted residue, and is less likely to cause unexpected changes in the pressure-sensitive adhesive sheet over time or acceleration of cross-linking. In addition, regarding the coloring peculiar to the photopolymerization initiator, it is preferable because it becomes a reaction decomposition product so that the absorption in the visible light region disappears and the color can be appropriately selected.
On the other hand, hydrogen abstraction type photopolymerization initiators do not produce decomposed products like cleavage type photopolymerization initiators during the radical generation reaction caused by irradiation with active energy rays such as ultraviolet rays. Damage to the body can be reduced.

Examples of the cleavage-type photopolymerization initiator include 2,2-dimethoxy-1,2-diphenylethan-1-one, 1-hydroxycyclohexylphenylketone, and 2-hydroxy-2-methyl-1-phenyl-propane-1. -one, 1-(4-(2-hydroxyethoxy)phenyl)-2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-1-[4-{4-(2-hydroxy- 2-methyl-propionyl)benzyl}phenyl]-2-methyl-propan-1-one, oligo(2-hydroxy-2-methyl-1-(4-(1-methylvinyl)phenyl)propanone), phenylglyoxy Methyl ricate, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butan-1-one, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropane-1 -one, 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl]-1-butanone, bis(2,4,6-trimethylbenzoyl) -phenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, (2,4,6-trimethylbenzoyl)ethoxyphenylphosphine oxide, bis(2,6-dimethoxybenzoyl) 2,4,4-trimethyl Examples include pentylphosphine oxide and derivatives thereof.

Among these, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide and 2,4,6-trimethylbenzoyldiphenylphosphine are preferred because they are cleavage-type photopolymerization initiators and become decomposed after the reaction, resulting in discoloration. Acylphosphine oxide photoinitiators such as fin oxide, (2,4,6-trimethylbenzoyl)ethoxyphenylphosphine oxide and bis(2,6-dimethoxybenzoyl)2,4,4-trimethylpentylphosphine oxide are preferred.
Furthermore, from the compatibility with the acrylic copolymer consisting of a graft copolymer having a macromonomer as a branch component, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, (2 ,4,6-trimethylbenzoyl)ethoxyphenylphosphine oxide, bis(2,6-dimethoxybenzoyl)2,4,4-trimethylpentylphosphine oxide and the like are preferably used.

The content of the photopolymerization initiator (C) is not particularly limited. For example, the (meth)acrylic copolymer (A) is 0.1 to 10 parts by mass with respect to 100 parts by mass, especially 0.2 parts by mass or more or 5 parts by mass or less, among which 0.5 parts by mass or more or 3 parts by mass It is particularly preferable to contain it in a proportion of 1 part or less. However, this range may be exceeded in balance with other factors. A photoinitiator can be used 1 type or in combination of 2 or more types.

[Ultraviolet absorber (D)]
The ultraviolet absorber (D) may be any substance capable of absorbing ultraviolet light. 5 or more, preferably 1 or more among them.

Incidentally, the absorbance at a wavelength of 380 nm is obtained from the following formula.
A ₃₈₀ =−Log(T ₃₈₀ /100)
A ₃₈₀ : absorbance at wavelength 380 nm
T ₃₈₀ ; Transmittance (%) at 380 nm of transparent double-sided pressure-sensitive adhesive sheet

As the ultraviolet absorber (D), for example, one or two or more structures selected from the group consisting of a benzotriazole structure, a benzophenone structure, a triazine structure, a benzoate structure, an oxalanilide structure, a salicylate structure and a cyanoacrylate structure. It is preferable to have
Among them, those having one or more structures selected from the group consisting of a benzotriazole structure, a triazine structure and a benzophenone structure are preferred from the viewpoint of ultraviolet absorption.
From the viewpoint of compatibility with an acrylic copolymer comprising a graft copolymer having a macromonomer as a branch component, it is preferable to use a benzotriazole structure or a benzophenone structure as the ultraviolet absorber (D).

The content of the ultraviolet absorber (D) is not particularly limited. For example, the (meth)acrylic copolymer (A) is 0.01 to 10 parts by mass with respect to 100 parts by mass, among which 0.1 parts by mass or more or 5 parts by mass or less, among which 0.2 parts by mass or more or 3 parts by mass It is particularly preferable to contain it in a ratio of 1 part or less. However, this range may be exceeded in balance with other factors.

From the viewpoint of absorbing ultraviolet rays and initiating photopolymerization in the visible light region excluding the ultraviolet rays, the ratio of the ultraviolet absorber (D) to 100 parts by weight of the photopolymerization initiator (C) is 25 to 400 parts by weight. However, it is preferably 50 parts by mass or more and 300 parts by mass or less, and particularly preferably 80 parts by mass or more and 250 parts by mass or less. Ultraviolet absorbers can be used singly or in combination of two or more.

[Other ingredients]
The pressure-sensitive adhesive sheet may contain, as components other than those described above, known components blended in ordinary pressure-sensitive adhesive compositions. For example, tackifying resins, antioxidants, light stabilizers, metal deactivators, rust inhibitors, anti-aging agents, moisture absorbers, hydrolysis inhibitors, sensitizers, antistatic agents, antifoaming agents, Various additives such as inorganic particles can be appropriately contained.
In addition, reaction catalysts (tertiary amine-based compounds, quaternary ammonium-based compounds, tin laurate compounds, etc.) may be appropriately contained as necessary.

[Preferred composition example]
As an example of a particularly preferred composition of the present pressure-sensitive adhesive composition, the (meth)acrylic copolymer (A) contains an acrylic copolymer composed of a graft copolymer having a macromonomer as a branch component, and is crosslinked. The agent (B) contains a polyfunctional (meth)acrylic acid ester compound such as bifunctional or trifunctional, the photopolymerization initiator (C) contains a cleavage type photopolymerization initiator, and an ultraviolet absorber (D ) can include a composition example containing an ultraviolet absorber having a benzotriazole structure or a benzophenone structure. However, the composition is not limited in this way.

[Lamination structure]
The pressure-sensitive adhesive sheet may be a single-layer sheet or a multi-layer sheet in which two or more layers are laminated.
When the present pressure-sensitive adhesive sheet is a multi-layered pressure-sensitive adhesive sheet, that is, when forming a pressure-sensitive adhesive sheet having a laminated structure comprising an intermediate layer and an outermost layer, the outermost layer is formed from the pressure-sensitive adhesive composition. is preferred.

When the pressure-sensitive adhesive sheet has a multilayer structure, the ratio of the thickness of each outermost layer to the thickness of the intermediate layer is preferably 1:1 to 1:20, more preferably 1:2 to 1:10. is more preferred.
If the thickness of the intermediate layer is within the above range, the contribution of the thickness of the adhesive material layer in the laminate is not too large, and workability in cutting and handling is not deteriorated due to excessive flexibility, which is preferable.
Further, when the outermost layer is within the above range, the conformability to uneven or curved surfaces is not inferior, and the adhesive strength and wettability to the adherend can be maintained, which is preferable.

[Sheet thickness]
Regarding the thickness of this pressure-sensitive adhesive sheet, it is possible to meet the demand for thinner thickness by reducing the thickness of the sheet. It may not be possible, or it may not be possible to exhibit sufficient adhesive strength.
From this point of view, the thickness of the pressure-sensitive adhesive sheet is preferably 20 to 500 μm, more preferably 25 μm or more or 350 μm or less, and particularly preferably 50 μm or more or 250 μm or less.

(Characteristic)
The UV transmittance (JIS K7361-1) of this pressure-sensitive adhesive sheet at a wavelength of 380 nm is preferably 50% or less, more preferably 30% or less, and more preferably 10% or less.

<Adhesive sheet laminate>
This adhesive sheet can also be used alone as it is. Moreover, it is also possible to laminate and use with other members.

(Present adhesive sheet laminate)
For example, it is possible to form a pressure-sensitive adhesive sheet laminate (referred to as "this pressure-sensitive adhesive sheet laminate") by laminating a release film on one side or both sides of the present pressure-sensitive adhesive sheet.

In this case, one or both of the release films preferably have a light transmittance of 40% or less for light having a wavelength of 410 nm or less. If at least one of the release films has a light transmittance of 40% or less for light with a wavelength of 410 nm or less, by laminating the release film on this pressure-sensitive adhesive sheet, the absorption coefficient of this pressure-sensitive adhesive sheet at a wavelength of 405 nm is 10 mL. This is because even if the photopolymerization initiator (C) having a weight of 1/(g·cm) or more is contained, the progress of photopolymerization due to irradiation with visible light can be effectively prevented.
From this point of view, one or both of the release films preferably has a light transmittance of 40% or less for light having a wavelength of 410 nm or less, more preferably 30% or less, and more preferably 20% or less.

Here, as a release film having a light transmittance of 40% or less for light with a wavelength of 410 nm or less, that is, a release film having an effect of partially blocking the transmission of visible light and ultraviolet light, for example, an ultraviolet absorber is blended. A cast film or stretched film made of a polyester, polypropylene or polyethylene resin coated with a silicone resin and subjected to release treatment can be mentioned. In addition, a multilayer cast film or stretched film formed by molding a layer made of a resin that does not contain an ultraviolet absorber on one or both sides of a layer made of a polyester, polypropylene, or polyethylene resin containing an ultraviolet absorber. One surface may be coated with a silicone resin for release treatment. In addition, a cast film or stretched film made of polyester, polypropylene, or polyethylene resin is coated on one side with a coating containing an ultraviolet absorber to form an ultraviolet absorbing layer, and a silicone resin is placed on the ultraviolet absorbing layer. can be mentioned. Also, a cast film or stretched film made of polyester, polypropylene, or polyethylene resin is coated with a paint containing an ultraviolet absorber on one side to form an ultraviolet absorption layer, and the other side is coated with a silicone resin. Examples include those subjected to release treatment. In addition, the other side of a resin film made of polyester, polypropylene, or polyethylene resin with one side subjected to mold release treatment and a separately prepared resin film not subjected to mold release treatment were bonded together using an ultraviolet absorber. A laminate obtained by interposing a layer or an adhesive layer can be mentioned.

The release film may have other layers such as an antistatic layer, a hard coat layer, and an anchor layer, if necessary.
If the thickness of the release film is too thick, the cutting processability will be poor, and if it is too thin, the handleability will be poor and the pressure-sensitive adhesive sheet may easily be dented. From this point of view, the thickness of the release film is preferably 20 μm or more and 300 μm or less, more preferably 25 μm or more or 250 μm or less, and more preferably 38 μm or more or 200 μm or less.
In the case where the release films are laminated on both sides, it is preferable that the thickness and peel strength of one release film and the other release film are different.

Moreover, as a preferable configuration example, there is a configuration in which a surface protection film having a light transmittance of 40% or less for light having a wavelength of 410 nm or less is laminated on one or both sides of the adhesive sheet laminate.
By laminating a surface protective film having a light transmittance of 40% or less for light with a wavelength of 410 nm or less on at least one surface of the adhesive sheet laminate, the absorption coefficient of the adhesive sheet at a wavelength of 405 nm is 10 mL/(g. cm) or more, it is possible to effectively prevent the progress of photopolymerization due to irradiation with visible light.
From this point of view, the surface protection film laminated on one or both sides of the adhesive sheet laminate preferably has a light transmittance of 40% or less, especially 30% or less, especially 20% or less for light having a wavelength of 410 nm or less. More preferably:

Here, the surface protective film having a light transmittance of 40% or less for light having a wavelength of 410 nm or less, that is, the surface protective film having the effect of partially blocking the transmission of visible light and ultraviolet light includes, for example, polyester-based and polypropylene-based films. , A laminated film with an ultraviolet absorbing layer, which is made by applying a slightly adhesive resin with removability to one surface of a polyethylene-based cast film or stretched film, and applying a paint containing an ultraviolet absorber to the other surface. can be mentioned. In addition, a cast film or stretched film of polypropylene or polyethylene may be coated with a removably slightly tacky resin containing an ultraviolet absorber on one side thereof. In addition, cast films and stretched films made of polyester, polypropylene or polyethylene resins containing an ultraviolet absorber are coated with releasable, slightly tacky resins. In addition, a multilayer cast film or stretched film formed by molding a layer made of a resin that does not contain an ultraviolet absorber on one or both sides of a layer made of a polyester, polypropylene, or polyethylene resin containing an ultraviolet absorber. One surface may be coated with a slightly adhesive resin having removability. In addition, a coating containing an ultraviolet absorber is applied to one surface of a cast film or stretched film made of polyester-, polypropylene-, or polyethylene-based resin to form an ultraviolet-absorbing layer, and the ultraviolet-absorbing layer is re-peeled. For example, a resin coated with a slightly sticky resin having properties can be mentioned. In addition, a cast film or stretched film made of polyester, polypropylene, or polyethylene resin is coated with a paint containing an ultraviolet absorber on one side to form an ultraviolet absorbing layer, and the other surface is a microscopic layer with removability. Examples include those coated with an adhesive resin. In addition, the other side of a resin film made of polyester, polypropylene, or polyethylene resin coated with a slightly adhesive resin having removability on one side and a separately prepared resin film are bonded together with an ultraviolet absorber. Examples include those laminated via a layer or an adhesive layer.
The surface protective film may have other layers, such as an antistatic layer, a hard coat layer, and an anchor layer, as necessary.

(Laminate for constituting the present image display device)
It is also possible to form an image display device-constituting laminate (referred to as "this image display device-constituting laminate") by laminating two constituent members for an image display device via the present pressure-sensitive adhesive sheet. .

At this time, as the two constituent members for the image display device, for example, any one of the group consisting of a touch sensor, an image display panel, a surface protection panel and a polarizing film, or a combination of two or more types can be mentioned.

Specific examples of the laminate for constituting the image display device include release sheet/adhesive sheet/touch panel, release sheet/adhesive sheet/protective panel, release sheet/adhesive sheet/image display panel, and image display. Panel/Adhesive sheet/Touch panel, Image display panel/Adhesive sheet/Protective panel, Image display panel/Adhesive sheet/Touch panel/Adhesive sheet/Protective panel, Polarizing film/Adhesive sheet/Touch panel, Polarizing film/Adhesive Configurations such as sheet/touch panel/this pressure-sensitive adhesive sheet/protective panel can be mentioned. However, it is not limited to these lamination examples.
The touch panel includes a structure in which a touch panel function is inherent in a protective panel, and a structure in which a touch panel function is inherent in an image display panel.

(This image display device)
An image display device (referred to as "this image display device") can be configured using the present pressure-sensitive adhesive sheet or the laminate for constituting an image display device as described above.
Image display devices such as a liquid crystal display, an organic EL display, an inorganic EL display, an electronic paper, a plasma display, and a microelectromechanical system (MEMS) display can be used as the image display device.

<Characteristics and usage of this adhesive sheet>
This pressure-sensitive adhesive sheet has an ultraviolet absorbing function and a curability to be cured by irradiation with light having a wavelength other than the ultraviolet region, particularly visible light. Utilizing such characteristics of the present pressure-sensitive adhesive sheet, a laminate for constituting an image display device can be produced, for example, as follows.

After forming the present pressure-sensitive adhesive composition into a sheet (sheet preparation step), two image display device constituent members are laminated via the present pressure-sensitive adhesive sheet before photocuring (primary adhesion step), and then visible light is applied. A laminate for constituting an image display device can be produced by irradiating light containing light having a wavelength in the region to photocrosslink and cure the present pressure-sensitive adhesive sheet (secondary adhesion step).
The light containing light rays with wavelengths in the visible light region may contain light with wavelengths in the ultraviolet region, that is, wavelengths of 380 nm or less. It is preferable to irradiate the PSA sheet with a light beam substantially free of light having a wavelength of 380 nm or less, that is, a visible light beam to photocrosslink and cure the PSA sheet (secondary attaching step).

(Sheet manufacturing process)
The pressure-sensitive adhesive sheet can be produced by molding the pressure-sensitive adhesive composition into a sheet.
As a method for forming the present pressure-sensitive adhesive resin composition into a sheet, any method known at present can be employed.

At this time, as described above, the present pressure-sensitive adhesive resin composition may be formed into a sheet on the release film to produce the present pressure-sensitive adhesive sheet.
Alternatively, the present pressure-sensitive adhesive resin composition may be formed into a sheet on an image display device constituent member, and the present pressure-sensitive adhesive sheet may be laminated on the image display device constituent member.

(Primary sticking process)
If the present pressure-sensitive adhesive sheet has self-adhesiveness (tackiness), it is possible to perform primary sticking by merely stacking two image display device constituent members via the present pressure-sensitive adhesive sheet.

For example, if the present pressure-sensitive adhesive sheet uses an acrylic copolymer (A1) made of a graft copolymer having a macromonomer as a branch component as a base polymer, it can maintain its sheet shape at room temperature and self-adhere. Not only can it exhibit good adhesion properties, but it can also provide moderate adhesiveness, for example, adhesiveness to the extent that it can be peeled off (referred to as "tackiness") in a normal state, that is, around room temperature in an uncrosslinked state. , it is possible to facilitate positioning and the like when sticking. Furthermore, since it can be melted or flowed by heating in an uncrosslinked state (hot-melt property), it is possible to fill the adhesive so as to follow uneven portions such as printing steps, and to fill without generating air bubbles. be able to.

A well-known device can be used as a bonding device used for lamination. For example, an electric heat press equipped with a heating plate, a diaphragm type laminator, a roll laminator, a vacuum bonding machine, a hand roll, and the like can be used.

In addition, when the acrylic copolymer (A1) made of a graft copolymer having a macromonomer as a branch component is used as the base polymer for the present pressure-sensitive adhesive sheet, excellent storage stability is obtained under normal conditions, that is, at room temperature. and cutting workability can be imparted. Moreover, since it has self-adhesiveness (tackiness), it is possible to obtain adhesiveness to the extent that it can be easily attached simply by pressing the present adhesive sheet against an adherend. Easy to use and very convenient to work with.
Furthermore, since it is excellent in shape retention, it is possible to process it into an arbitrary shape in advance. It can also be pre-cut to match.
The cutting method at this time is generally punching with a Thomson blade, cutting with a super cutter or laser. is more preferred.

If the pressure-sensitive adhesive sheet has hot-melt properties, i.e., the property of being softened or fluidized by heating, even if the surface to be adhered has unevenness, the pressure-sensitive adhesive sheet can be heated to follow the unevenness. Even unevenness can be filled without gaps.
At this time, as means for heating the pressure-sensitive adhesive sheet, for example, various constant temperature baths, hot plates, electromagnetic heating devices, heating rolls, and the like can be used. For more efficient lamination and heating, for example, an electric heat press, a diaphragm-type laminator, a roll laminator, or the like is preferably used.

At this time, when the softening temperature of the pressure-sensitive adhesive sheet is 50° C. or higher, sufficient processing characteristics and room temperature storage characteristics can be obtained. On the other hand, if the softening temperature of the present pressure-sensitive adhesive sheet is 100° C. or less, it is possible not only to suppress heat damage to the image display panel and the front panel, but also to prevent the pressure-sensitive adhesive sheet from flowing out too much. can.
Therefore, the softening temperature of the adhesive sheet is preferably 50 to 100°C, more preferably 55°C or higher or 95°C or lower, and more preferably 60°C or higher or 90°C or lower.

When heating the pressure-sensitive adhesive sheet, it is preferable to stack the two image display device constituent members via the pressure-sensitive adhesive sheet and then heat the laminate in a reduced pressure environment.
By heating the laminate in a reduced pressure environment, it is possible to prevent air bubbles or foreign matter from entering the pressure-sensitive adhesive sheet after lamination.

(Secondary sticking process)
In the secondary adhesion step, a laminate obtained by laminating two image display device constituent members via the pressure-sensitive adhesive sheet is attached from the outside of at least one image display device constituent member to the image display device constituent member. Through the adhesive sheet, the pressure-sensitive adhesive sheet is irradiated with light containing light having a wavelength in the visible light region, preferably light substantially not containing light having a wavelength of 380 nm or less, that is, visible light, to photocrosslink and cure the pressure-sensitive adhesive sheet. .

Since the present pressure-sensitive adhesive sheet can be firmly cross-linked by photo-crosslinking in this way, it has an adhesive strength sufficient to withstand the gas pressure of outgassing generated from image display device constituent members such as protective panels. It can have cohesion. Moreover, since the present pressure-sensitive adhesive sheet has ultraviolet absorbability, it is possible to suppress the deterioration of the pressure-sensitive adhesive sheet itself and the constituent members of the image display device due to ultraviolet rays.

When irradiating with visible light, it is preferable to irradiate with visible light that does not substantially contain light with a wavelength in the ultraviolet region, for example, light with a wavelength of less than 365 nm.
Here, "substantially does not contain light with a wavelength of less than 365 nm" means that the emission intensity of light with a wavelength of less than 365 nm is less than 1 mW/cm ² .

As a method of irradiating visible light that does not include light with a wavelength in the ultraviolet region, a light source that emits only visible light that does not include light with a wavelength in the ultraviolet region may be used, as described above.
Examples of light sources that emit only visible light include fluorescent lamps, LEDs, organic ELs, and inorganic ELs.
Further, irradiation may be performed through a filter that does not transmit light having a wavelength in the ultraviolet region. For example, a high-pressure mercury lamp, a metal halide lamp, a xenon arc lamp, a carbon arc lamp, or the like, which also emits light in the ultraviolet region, or sunlight is used as a light source, and the light transmittance at a wavelength of 380 nm is less than 10%. and a method of irradiating the adhesive composition with visible light through a filter having a light transmittance of 60% or more at a wavelength of 405 nm.
The filter may be a release film that constitutes the adhesive sheet laminate, or a surface protective film that is used by being laminated on the surface of the adhesive sheet laminate.

In order to adjust the degree of visible light cross-linking, in addition to the method of controlling the irradiation amount of visible light, visible light is irradiated through the filter so as to partially block the transmission of visible light. It is also possible to adjust the degree of cross-linking.

<Explanation of terms, etc.>
In general, "sheet" is defined in JIS as a thin, flat product whose thickness is smaller than its length and width. A thin, flat product with an arbitrarily limited maximum thickness, usually supplied in the form of a roll (Japanese Industrial Standard JIS K6900). However, the boundary between a sheet and a film is not clear, and there is no need to distinguish between the two in the present invention. “Film” shall be included even in cases where
In addition, the expression "panel" such as an image display panel, a protective panel, etc. includes a plate, a sheet and a film.

In this specification, when described as "X to Y" (X and Y are arbitrary numbers), unless otherwise specified, "X or more and Y or less" and "preferably larger than X" or "preferably It also includes the meaning of "smaller than Y".
In addition, when described as "X or more" (X is an arbitrary number), it includes the meaning of "preferably greater than X" unless otherwise specified, and is described as "Y or less" (Y is an arbitrary number). If not otherwise specified, it also includes the meaning of "preferably smaller than Y".

Examples and comparative examples will be described below in more detail. However, the present invention is not limited to these.

The integrated amount of light at a wavelength of 405 nm and a wavelength of 365 nm measured in this example was measured using an integrated photometer (UIT-250, manufactured by Ushio Inc.).

[Example 1]
As the (meth)acrylic copolymer (A), a copolymer consisting of 15 parts by mass of polymethyl methacrylate macromonomer (Tg 80 ° C.) having a number average molecular weight of 3000, 81 parts by mass of butyl acrylate, and 4 parts by mass of acrylic acid (A-1, mass average molecular weight of 300,000), 100 g of glycerin dimethacrylate (Blenmer GMR, manufactured by NOF Corporation) (B-1) as a cross-linking agent (B), and Ezacure KTO46 as a photopolymerization initiator (C) 15 g of (C-1) (manufactured by Lamberti), 2,6-diphenyl-4-(2-hydroxy-4-hexyloxyphenyl)-1,3,5-triazine (BASF) as an ultraviolet absorber (D) 5 g of Tinuvin 1577) (D-1) was added and uniformly mixed to obtain an adhesive composition 1.
The absorption coefficient of the photopolymerization initiator (C-1) at 405 nm was 7.4×10 ¹ (mL/(g·cm)).

Next, the pressure-sensitive adhesive composition 1 is formed into a sheet having a thickness of 100 μm on a release-treated polyethylene terephthalate film (Mitsubishi Plastics, Diafoil MRV, thickness: 100 μm). A terephthalate film (Mitsubishi Plastics Co., Ltd., Diafoil MRQ, thickness 75 μm) was coated to prepare a pressure-sensitive adhesive sheet laminate 1 .

[Example 2]
As the (meth)acrylic copolymer (A), 10 parts by weight of a polymethyl methacrylate macromonomer (Tg55°C) having a number average molecular weight of 1400 and 90 parts by weight of 2-ethylhexyl acrylate (Tg: -70°C) are randomly mixed. 1 kg of a polymerized acrylic graft copolymer (A-2) (weight average molecular weight: 230,000) and tricyclodecane dimethacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., product name: DCP) ( B-2) 50 g, Irgacure 369 (C-2) (manufactured by BASF) 15 g as a photopolymerization initiator (C), and 2-(2H-benzotriazol-2-yl)-4 as an ultraviolet absorber (D). ,6-di-tert-pentylphenol (manufactured by Johoku Kagaku Co., Ltd., JF-80) (D-2) 20 g was uniformly mixed to prepare an adhesive resin composition 2.

Next, the pressure-sensitive adhesive composition 4 was applied to a release-treated polyethylene terephthalate film (Mitsubishi Plastics Co., Ltd., Diafoil MRV, thickness 100 μm) to a thickness of 100 μm, and then the release-treated polyethylene terephthalate film (Mitsubishi A pressure-sensitive adhesive sheet laminate 2 was prepared by covering with Diafoil MRQ (manufactured by Jisin Co., Ltd., thickness: 75 μm).
The absorption coefficient of the photopolymerization initiator (C-2) at 405 nm was 1.6×10 ² (mL/(g·cm)).

[Example 3]
(Meth)acrylic copolymer (A) is a copolymer (A-3, mass average molecular weight 400,000) consisting of 76 parts by mass of 2-ethylhexyl acrylate, 20 parts by mass of vinyl acetate, and 4 parts by mass of acrylic acid. For 1 kg, 200 g of propoxylated pentaerythritol tetraacrylate (ATM-4P, manufactured by Shin-Nakamura Chemical Co., Ltd.) (B-3) as a cross-linking agent (B), and Irgacure 819 (C-3) as a photopolymerization initiator (C). (manufactured by BASF) 7 g, 2,2'-dihydroxy-4-methoxybenzophenone (Kemisorb 111, manufactured by Chemipro Kasei Co., Ltd.) (D-3) 10 g as an ultraviolet absorber (D) was added and uniformly mixed to obtain an adhesive composition. got 3.
The absorption coefficient of the photopolymerization initiator (C-3) at 405 nm was 9.0×10 ² (mL/(g·cm)).

Adhesive resin composition 3 was sandwiched between two peel-treated polyethylene terephthalate films (Mitsubishi Plastics Co., Ltd., Diafoil MRF, thickness 75 μm/Mitsubishi Plastics Co., Ltd., Diafoil MRT, thickness 38 μm), and the thickness was 100 μm. An intermediate layer sheet (α) was formed by shaping into a sheet so as to have a uniform shape.

L as an isocyanate-based cross-linking agent for 1 kg of an adhesive solution (SK Dyne 1882 manufactured by Soken Chemical Co., Ltd., solid content concentration of about 17%) made of a commercially available acrylic copolymer (A-4, mass average molecular weight of 1.3 million) 1.85 g of -45 (B-5) (manufactured by Soken Chemical Co., Ltd.) and 0.5 g of E-5XM (B-6) (manufactured by Soken Chemical Co., Ltd.) as an epoxy-based cross-linking agent were added to obtain pressure-sensitive adhesive composition 4. was prepared.
After coating the adhesive layer coating solution on a release-treated polyethylene terephthalate film (Mitsubishi Plastics, Diafoil MRV, thickness 100 μm) so that the film thickness after drying is 20 to 30 μm. and dried at 80° C. for 5 minutes. This was cured at 23° C. for 7 days to react the cross-linking agent, thereby preparing a sheet for adhesive layer (β).
Furthermore, on a polyethylene terephthalate film (manufactured by Mitsubishi Plastics Co., Ltd., Diafoil MRQ, thickness 75 μm) that has been peeled, the adhesive composition 4 is applied in the same manner so that the film thickness after drying is 20 to 30 μm. After applying the layer-forming coating liquid, it was dried at 80° C. for 5 minutes. This was cured at 23° C. for 7 days to react the cross-linking agent, thereby producing a sheet for adhesive layer (β′).

The PET films on both sides of the intermediate layer resin sheet (α) are sequentially peeled off, and the adhesive surfaces of the adhesive layer resin sheets (β) and (β') are sequentially attached to both surfaces of the intermediate layer sheet (α). A laminate (thickness: 150 μm) consisting of (β)/(α)/(β′) was produced.

Through the PET films remaining on the surfaces of (β) and (β'), light was emitted from a high-pressure mercury lamp so that the integrated light intensity at a wavelength of 365 nm was 1000 mJ/cm ² and the integrated light intensity at a wavelength of 405 nm was 1400 mJ/cm ² . The intermediate layer resin sheet (α) was photocrosslinked by irradiation to produce a pressure-sensitive adhesive sheet laminate 3 .

[Example 4]
Example 1 except that a release film obtained by applying a silicone release agent to a PET film (thickness 100 µm) containing an ultraviolet absorber was used instead of the release-treated polyethylene terephthalate film (diafoil MRV, thickness 100 µm). Adhesive sheet laminate 4 was prepared in the same manner as above.

[Example 5]
On the surface of the polyethylene terephthalate film (Diafoil MRV, thickness 100 μm) of the pressure-sensitive adhesive sheet laminate prepared in Example 1, a surface consisting of a slightly adhesive layer (5 μm) / polyethylene terephthalate film (25 μm) / ultraviolet absorption layer (3 μm) The slightly adhesive layer surface of the protective film was laminated to prepare an adhesive sheet laminate 5 having a configuration of release film/adhesive sheet/release film/surface protective film.

[Comparative Example 1]
A pressure-sensitive adhesive sheet laminate 6 was prepared in the same manner as in Example 1, except that 15 g of Esa-cure TZT (C-5) was added as a photopolymerization initiator instead of Esa-cure KTO46 (C-1).
The absorption coefficient of the photopolymerization initiator (C-5) at 405 nm was less than 10 (mL/(g·cm)), which was too low to measure.

[Comparative Example 2]
Adhesive sheet laminate 7 was prepared in the same manner as in Example 2, except that the ultraviolet absorber (D-2) was not added.

[Comparative Example 3]
L as an isocyanate-based cross-linking agent for 1 kg of an adhesive solution (SK Dyne 1882 manufactured by Soken Chemical Co., Ltd., solid content concentration of about 17%) made of a commercially available acrylic copolymer (A-4, mass average molecular weight of 1.3 million) -45 (B-5) (manufactured by Soken Chemical Co., Ltd.) 1.85 g and E-5XM (B-6) (manufactured by Soken Chemical Co., Ltd.) as an epoxy cross-linking agent 0.5 g, ultraviolet light as an ultraviolet absorber (D) As an absorbent (D), 10 g of 2,2′-dihydroxy-4-methoxybenzophenone (Kemisorb 111, manufactured by Chemipro Kasei Co., Ltd.) (D-3) was added and uniformly mixed to prepare an adhesive composition 7.

Next, on a polyethylene terephthalate film (Mitsubishi Plastics Co., Ltd., Diafoil MRV, thickness 100 μm) that has been peeled off, the pressure-sensitive adhesive composition is applied so that the thickness after drying becomes 50 μm, and then at 80° C. After drying for 5 minutes, a sheet-like adhesive composition 7 having a thickness of 50 µm was obtained.
Similarly, on a polyethylene terephthalate film (manufactured by Mitsubishi Plastics Co., Ltd., Diafoil MRQ, thickness 75 μm) that has been peeled, it is applied so that the thickness after drying becomes 50 μm, and then dried at 80 ° C. for 5 minutes. A sheet-like adhesive composition 7 having a thickness of 50 μm was obtained. After laminating these to a thickness of 100 μm, a release-treated polyethylene terephthalate film (Diafoil MRQ, manufactured by Mitsubishi Plastics Co., Ltd., thickness 75 μm) was coated. This was cured at room temperature (23° C.) for 7 days to react the cross-linking agent, and a pressure-sensitive adhesive sheet laminate 8 was produced.

<Evaluation>
[optical properties]
The PET films on both sides of the pressure-sensitive adhesive sheet laminates prepared in Examples and Comparative Examples were sequentially peeled off, and the pressure-sensitive adhesive sheet was attached so as to be sandwiched between two sheets of soda lime glass (thickness 0.5 mm), and autoclaved (70 ° C.). , a gauge pressure of 0.2 MPa for 20 minutes) to perform the final adhesion. The adhesive sheet laminates 1, 2, 4, 5, 6, and 7 were irradiated with light using a high-pressure mercury lamp through a UV cut filter so that the integrated light amount at a wavelength of 405 nm was 3000 mJ/cm ² , and the optical properties were measured. A sample for evaluation was created.

The light transmittance of the prepared test piece in a wavelength range of 360 to 430 nm was measured with a spectrophotometer (manufactured by Shimadzu Corporation; equipment name "UV2450").
Those having a light transmittance at 380 nm of less than 50% were judged to have UV absorption "good", and those having 50% or more were judged to have UV absorption "x (poor)". The results are shown in Table 1.

[Adhesive force]
For the pressure-sensitive adhesive sheets prepared in Examples and Comparative Examples, one of the release films was peeled off, and a polyethylene terephthalate film (manufactured by Toyobo Co., Ltd.; trade name “Cosmo Shine A4300”, thickness 100 μm) was roll-bonded with a hand roller as a backing film. did. This was cut into strips having a width of 10 mm and a length of 100 mm, and the adhesive surface exposed by peeling off the remaining release film was roll-bonded to soda-lime glass using a hand roller. After autoclave treatment (70 ° C., gauge pressure 0.2 MPa, 20 minutes) and finish attachment, pressure-sensitive adhesive sheet laminates 1, 2, 4, 5, 6, and 7 were treated with high-pressure mercury through a UV cut filter. A lamp was used to irradiate visible light so that the integrated amount of light at a wavelength of 405 nm was 3000 mJ/cm ² and the integrated amount of light at a wavelength of 365 nm was 5 mJ/cm ² or less to prepare adhesive force measurement samples.

The pressure-sensitive adhesive sheet was peeled from the glass while pulling the backing film at an angle of 180° at a peeling speed of 60 mm/min, and the tensile strength was measured with a load cell to measure the 180° peel strength (N/cm) of the pressure-sensitive adhesive sheet against the glass. was measured and shown in Table 1 as "Glass Adhesion". Results are shown in Table 1.

[Unevenness absorption]
A printed stepped glass plate 1 with an opening of 52 mm × 80 mm is prepared by printing a 20 μm thick print on the peripheral edge (long side 3 mm, short side 15 mm) of 58 mm × 110 mm × 0.8 mm thick glass. did.
In addition, a printed stepped glass plate 2 with an opening of 52 mm × 80 mm was printed with a thickness of 10 μm on the peripheral edge (long side 3 mm, short side 15 mm) of 58 mm × 110 mm × 0.8 mm thick glass. prepared.
The release film on one side of the pressure-sensitive adhesive sheet laminate was peeled off, and the adhesive sheet laminate was roll-bonded to soda-lime glass of 54 mm×82 mm and 0.5 mm in thickness.
Next, the remaining release film is peeled off, and the printed surfaces of the glass plates 1 and 2 with printing steps are press-bonded using a vacuum press so that the four sides of the adhesive surface are applied to the printing steps (absolute pressure 5 kPa, temperature 70° C., press pressure 0.04 MPa), autoclave treatment (70° C., gauge pressure 0.2 MPa, 20 minutes), followed by finishing adhesion. For adhesive sheet laminates 1, 2, 4, 5, 6, and 7, from the printed glass side, using a high-pressure mercury lamp through a UV cut filter, the integrated light amount at a wavelength of 405 nm was 3000 mJ/cm ² . A sample for evaluation was prepared by irradiating light so as to

Regarding the evaluation samples, those that were able to be laminated without air bubbles near the step of the glass plate 1 with a 20 μm printing step have an unevenness absorbency of “Excellent”, and the glass plate 2 with a printing step of 10 μm Those that could be laminated without air bubbles were judged to have unevenness absorbency "Good", and the glass with printed steps 1 and 2 were judged to have unevenness absorbency "X (poor)" if air bubbles were observed near the steps. Table 1 shows the results.

[Heat-resistant]
The release film on one side of the pressure-sensitive adhesive sheets prepared in Examples and Comparative Examples was peeled off, and a COP film (100 μm, manufactured by Nippon Zeon Co., Ltd.) was adhered to the exposed surface using a hand roller. Next, after cutting out the adhesive sheet to 50 mm × 80 mm, the remaining release film was peeled off, attached to soda lime glass having a thickness of 0.5 mm with a hand roller, and autoclaved (temperature 80 ° C., atmospheric pressure 0 .4 MPa for 30 minutes) was applied. Adhesive sheet laminates 1, 2, 4, 5, 6, and 7 were irradiated with light from the COP surface using a high-pressure mercury lamp through a UV cut filter so that the integrated amount of light at a wavelength of 405 nm was 3000 mJ/cm ² . Then, a sample for evaluation was created.

The evaluation sample was cured at 85 ° C. for 6 hours, and when no change in appearance was observed without foaming, heat resistance was "○ (good)", and when foaming or peeling was observed, heat resistance was "× ( poor)”. Table 1 shows the results.

[Lightfastness]
The release film on one side of the pressure-sensitive adhesive sheet laminate was peeled off, and the adhesive sheet laminate was roll-bonded to soda-lime glass having a size of 150 mm×200 mm and a thickness of 2 mm. Then, the remaining release film was peeled off, and the exposed adhesive surface was roll-bonded to soda lime glass of 150 mm×200 mm and 2 mm in thickness, and subjected to autoclave treatment (temperature 80° C., air pressure 0.4 MPa, 30 minutes).
The pressure-sensitive adhesive sheet laminates 1, 2, 4, 5, 6, and 7 were irradiated with light using a high-pressure mercury lamp so that the integrated amount of light at a wavelength of 405 nm was 3000 mJ/cm ² to prepare samples for evaluation.

The evaluation sample was irradiated with ultraviolet light for 24 hours using a xenon light resistance tester (Suntest CPS, manufactured by Atlas). , and those in which lifting or peeling was observed were judged as light resistance "poor". Table 1 shows the results.

Release-treated polyethylene terephthalate film (manufactured by Mitsubishi Plastics, Inc., Diafoil MRV, thickness 100 μm) used in Example 1, PET film containing ultraviolet absorber used in Example 4 (thickness 100 μm), silicone release agent For the release film coated with and the surface protective film used in Example 5, the light transmittance in the wavelength range of 380 to 450 nm was measured with a spectrophotometer (manufactured by Shimadzu Corporation; instrument name "UV2450"). Results are shown in Table 2.

For the adhesive sheet laminate 1, the adhesive sheet laminate 4, and the adhesive sheet laminate 5, respectively, a release-treated polyethylene terephthalate film (Mitsubishi Plastics, Diafoil MRV, thickness 100 μm), the ultraviolet absorber used in Example 4 A PET film (thickness: 100 μm) with a silicone release agent applied thereto was left standing with the release film and the surface protection film side facing upward. The film was irradiated with light from a fluorescent lamp (illuminance of 1100 Lx) for 7 days. The integrated amount of light at a wavelength of 405 nm of the irradiated light was about 43 J/cm ² , and the integrated amount of light at a wavelength of 365 nm was about 1 mJ/cm ² or less, which was unmeasurable.

With respect to PSA sheet laminates 1 and 4 before and after the light irradiation treatment, the gel fraction of the PSA material was obtained by the following method. Results are shown in Table 2.

1) Weigh the adhesive composition (W1) and wrap it in a pre-weighed SUS mesh (W0).
2) The SUS mesh is immersed in 100 mL of ethyl acetate for 24 hours.
3) Take out the SUS mesh and dry it at 75°C for 4.5 hours.
4) Calculate the weight (W2) after drying, and measure the gel fraction of the pressure-sensitive adhesive composition according to the following formula.
Gel fraction (%) = 100 x (W2-W0)/W1

Regarding storage stability, "○ (good)" indicates that the change in gel fraction was less than 5 points before and after irradiation with a fluorescent lamp, and "X (poor)" indicates that the gel fraction increased by 5 points or more after light irradiation. ” was determined. Table 2 shows the results.

The pressure-sensitive adhesive sheet laminates of Examples 1 to 5 not only had excellent ultraviolet absorption performance, but also had excellent quality, in which unevenness absorbability during lamination and reliability after lamination of members were compatible. .
On the other hand, Comparative Example 1 uses a photopolymerization initiator with an absorption coefficient of less than 10 mL / (g cm) at a wavelength of 405 nm, that is, the absorption coefficient at a wavelength of 405 nm is 10 mL / (g cm) or more. Since no agent was used, the adhesive material was not cured even when irradiated with light, and the adhesive strength after the secondary attachment and the reliability after the attachment could not be obtained.
Comparative Example 2 did not contain the ultraviolet absorber (D) and could not obtain ultraviolet absorption performance. Therefore, foaming of the pressure-sensitive adhesive sheet was observed in the light resistance test, and the lamination reliability was poor.
Comparative Example 3 is a pressure-sensitive adhesive sheet obtained by cross-linking the pressure-sensitive adhesive composition by thermal crosslinking. Since it did not have a photocurable layer, it was inferior in absorbing unevenness during lamination.

In Example 4, a PET film containing an ultraviolet absorber is used as the release film. As a result, it was possible to suppress the progress of the photo-curing reaction of the adhesive composition before bonding to the member, and it was possible to obtain an adhesive sheet laminate having excellent storage stability.

In Example 5, a surface protective film having an ultraviolet absorbing layer is laminated on the surface of the release film. As a result, it was possible to suppress the progress of the photo-curing reaction of the adhesive composition before bonding to the member, and it was possible to obtain an adhesive sheet laminate having excellent storage stability.

Claims (12)

A (meth)acrylic copolymer (A), a cross-linking agent (B), a photopolymerization initiator (C) having an absorption coefficient of 10 mL/(g cm) or more at a wavelength of 405 nm, and an ultraviolet absorber (D). A transparent double-sided pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer formed from a pressure-sensitive adhesive resin composition containing
The ultraviolet absorber (D) has one or more structures selected from the group consisting of a benzotriazole structure, a benzophenone structure, a triazine structure, a benzoate structure, an oxalanilide structure, a salicylate structure and a cyanoacrylate structure. There is
A transparent double-sided pressure-sensitive adhesive sheet having a UV transmittance (JIS K7361-1) of 50% or less at a wavelength of 380 nm and a thickness of 20 to 500 μm (excluding those containing a triazole phosphor). 2. The transparent double-sided pressure-sensitive adhesive sheet according to claim 1, wherein the (meth)acrylic copolymer (A) is an acrylic copolymer comprising a graft copolymer having a macromonomer as a branch component. 3. The transparent double-sided pressure-sensitive adhesive sheet according to claim 1, wherein the photopolymerization initiator (C) generates radicals upon irradiation with visible light. 4. The transparent double-sided pressure-sensitive adhesive sheet according to any one of claims 1 to 3, wherein the UV absorber (D) is contained in a ratio of 25 to 400 parts by mass based on 100 parts by mass of the photopolymerization initiator (C). . The (meth)acrylic copolymer (A) contains an acrylic copolymer composed of a graft copolymer having a macromonomer as a branch component, and the cross-linking agent (B) is polyfunctional (meth)acrylic acid. It contains an ester compound, contains a cleavage-type photopolymerization initiator as the photopolymerization initiator (C), and contains an ultraviolet absorber having a benzotriazole structure or a benzophenone structure as the ultraviolet absorber (D). The transparent double-sided pressure-sensitive adhesive sheet according to any one of claims 1 to 4. Claim 1, wherein the pressure-sensitive adhesive resin composition, even in an uncrosslinked state, exhibits adhesiveness at room temperature (20°C) and softens or fluidizes when heated to a temperature of 50 to 100°C. 6. The transparent double-sided pressure-sensitive adhesive sheet according to any one of 1 to 5. A pressure-sensitive adhesive sheet laminate comprising a structure in which the pressure-sensitive adhesive sheet according to any one of claims 1 to 6 and a release film are laminated. 8. The pressure-sensitive adhesive sheet laminate according to claim 7, wherein at least one release film has a light transmittance of 40% or less for light having a wavelength of 410 nm or less. 8. The pressure-sensitive adhesive sheet laminate according to claim 7, wherein a surface protection film having a light transmittance of 40% or less for light having a wavelength of 410 nm or less is laminated on the surface of at least one release film. A laminate for image display device construction, comprising two image display device constituent members laminated with the transparent double-sided pressure-sensitive adhesive sheet according to any one of claims 1 to 6 interposed therebetween. 11. According to claim 10, the image display device constituent member is a laminated body made of one or a combination of two or more of the group consisting of a touch sensor, an image display panel, a surface protection panel and a polarizing film. A laminate for constituting an image display device as described above. 12. An image display device constructed using the laminate for image display device construction according to claim 10 or 11.