JP6670060B2 - Pressure-sensitive adhesive layer for optical member, optical member with pressure-sensitive adhesive layer, and image display device - Google Patents

Description

  The present invention relates to a pressure-sensitive adhesive layer for an optical member having a light diffusion function, and an optical member with a pressure-sensitive adhesive layer having at least one pressure-sensitive adhesive layer for an optical member on at least one surface of the optical member. Further, the present invention relates to an image display device including the optical member with an adhesive layer.

  2. Description of the Related Art In recent years, image display devices such as liquid crystal display devices have been required to be larger and thinner, and similar demands have been made for optical members constituting the image display devices. When each of the large and thin optical members is fixed by an adhesive and laminated, the bonding failure (wrinkles, distortions, etc.) to the optical members is likely to occur, and as a result, the display unit may be defective. There was a case.

  Further, the backlight unit of the image display device generally includes a diffusion sheet for improving visibility, but there are cases where sufficient visibility cannot be ensured with the diffusion sheet alone. In some cases, an adhesive layer having a light diffusion function was used.

  Examples of such a light diffusion pressure-sensitive adhesive include a pressure-sensitive adhesive containing a base polymer containing a (meth) acrylic polymer and light-diffusing fine particles having a lower refractive index than the pressure-sensitive adhesive. A light diffusion adhesive in which an acrylic polymer contains an aromatic ring-containing (meth) acrylic monomer as a monomer unit is disclosed (for example, see Patent Document 1).

JP 2014-224964 A

  Although the pressure-sensitive adhesive layer of Patent Document 1 has a light diffusion function, wrinkles and sagging may occur when various types of optical members having a large size and a thin film are bonded to each other. Further, for example, when an optical member having a step (unevenness) on the surface such as a prism sheet is bonded, a step absorption property is required. However, the pressure-sensitive adhesive layer of Patent Document 1 has a problem in terms of the step absorption property. Was not enough.

  Therefore, an object of the present invention is to provide a pressure-sensitive adhesive layer for an optical member having a light diffusing function, which can be bonded to various optical members or optical members having steps, which have been made larger and thinner. . The present invention also provides an optical member with an adhesive layer having at least one adhesive layer for an optical member on at least one surface of the optical member, and an image display device including the optical member with an adhesive layer. Also aim.

  The present inventors have conducted intensive studies to solve the above problems, and as a result, have found the following pressure-sensitive adhesive layer for an optical member, and have completed the present invention.

That is, the present invention includes at least one light-diffusing pressure-sensitive adhesive layer formed from a base pressure-sensitive adhesive composition containing a (meth) acrylic polymer and light-diffusing fine particles and having a thickness of 5 to 300 μm,
The thickness of the entire pressure-sensitive adhesive layer is 20 μm or more,
The present invention relates to an optical member pressure-sensitive adhesive layer having a haze of 10 to 96%.

  The light diffusing fine particles are preferably silicone resin fine particles.

  It is preferable that the refractive index of the light diffusing fine particles is lower than the refractive index of the base pressure-sensitive adhesive composition.

  It is preferable that the light diffusing fine particles have a volume average particle diameter of 1 to 5 μm.

  The pressure-sensitive adhesive layer of the present invention can be formed by laminating a transparent pressure-sensitive adhesive layer having a haze of 0.01 to 5% on at least one surface of the light-diffusing pressure-sensitive adhesive layer. Is preferably 5 to 30 μm, and the thickness of the transparent pressure-sensitive adhesive layer having a haze of 0.01 to 5% is preferably 50 to 300 μm.

  It is preferable that the content of the light diffusing fine particles in the light diffusing pressure-sensitive adhesive layer is 3 to 30% by weight.

  It is preferable that the (meth) acryl-based polymer contains an alkyl (meth) acrylate and a carboxyl group-containing monomer as monomer components.

  It is preferable that the transparent pressure-sensitive adhesive layer contains a (meth) acryl-based polymer containing an alkyl (meth) acrylate, a hydroxyl group-containing monomer and a nitrogen-containing monomer as monomer components.

  It is preferable that the (meth) acrylic polymer contained in the transparent pressure-sensitive adhesive layer does not contain a carboxyl group-containing monomer as a monomer component.

  The present invention also relates to an optical member with an adhesive layer, comprising at least one optical member adhesive layer on at least one surface of the optical member. Further, the present invention relates to an image display device including the optical member with an adhesive layer.

  The pressure-sensitive adhesive layer for an optical member of the present invention has a light diffusion pressure-sensitive adhesive layer having a specific thickness, and has a specific thickness as a whole pressure-sensitive adhesive. Can be laminated without wrinkles or sagging. Further, since the pressure-sensitive adhesive layer for an optical member of the present invention has a specific thickness, for example, when bonding a member having a step on its surface, such as a prism sheet, following the step, there is no gap. Lamination can be performed. Further, since the pressure-sensitive adhesive layer for an optical member of the present invention has a specific haze, it is excellent in display unevenness and durability required for the pressure-sensitive adhesive layer for an optical member. The optical member with the pressure-sensitive adhesive layer using the pressure-sensitive adhesive layer for an optical member of the present invention and the image display device including the optical member with the pressure-sensitive adhesive layer have high reliability.

(A)-(d) It is sectional drawing which shows embodiment of the adhesive layer for optical members of this invention typically. It is sectional drawing which shows typically one use form of the adhesive layer for optical members of this invention.

The pressure-sensitive adhesive layer for an optical member of the present invention is formed from a base pressure-sensitive adhesive composition containing a (meth) acrylic polymer and light diffusing fine particles, and has at least one light diffusing pressure-sensitive adhesive layer having a thickness of 5 to 300 μm. Including
The thickness of the entire pressure-sensitive adhesive layer is 20 μm or more, and the haze is 10 to 96%.

  The configuration of the pressure-sensitive adhesive layer for an optical member of the present invention is not particularly limited, as long as the pressure-sensitive adhesive layer has at least one light-diffusing pressure-sensitive adhesive layer having a thickness of 5 to 300 μm and the total pressure-sensitive adhesive layer has a thickness of 20 μm or more. It is good. Although a specific configuration is not particularly limited, for example, the following configuration can be given.

  When the thickness of the light diffusion pressure-sensitive adhesive layer is less than 20 μm, a transparent pressure-sensitive adhesive layer other than the light diffusion pressure-sensitive adhesive layer is stuck together with the light diffusion pressure-sensitive adhesive layer, so that the total thickness is 20 μm or more. Thus, the pressure-sensitive adhesive layer for an optical member of the present invention can be formed. In this case, the light diffusion pressure-sensitive adhesive layer or the other transparent pressure-sensitive adhesive layer may be one layer or two or more layers. For example, as shown in FIG. The optical member pressure-sensitive adhesive layer 1 can be formed from the layer 2 and the transparent pressure-sensitive adhesive layer 3. Further, as shown in FIG. 1B, a transparent pressure-sensitive adhesive layer 3 can be formed on both surfaces of the light-diffusing pressure-sensitive adhesive layer 2, and as shown in FIG. And the transparent pressure-sensitive adhesive layer 3 can be alternately laminated. When the thickness of the light-diffusing pressure-sensitive adhesive layer is 20 μm or more, the light-diffusing pressure-sensitive adhesive layer can have the same form as that shown in FIGS. 1A to 1C. However, as shown in FIG. The pressure-sensitive adhesive layer 1 for an optical member of the present invention can be formed of only one of the diffusion pressure-sensitive adhesive layers 2. 1 (a) to 1 (d) show a form in which separators 4 are bonded to both surfaces of the pressure-sensitive adhesive layer 1 for an optical member.

1. Optical member pressure-sensitive adhesive layer The optical member pressure-sensitive adhesive layer of the present invention has a total thickness of the pressure-sensitive adhesive layer of 20 μm or more, preferably 30 μm or more, more preferably 50 μm or more, and more preferably 100 μm or more. More preferably, it is particularly preferably more than 100 μm. When the thickness of the entire pressure-sensitive adhesive layer is 20 μm or more, even if the optical member to be adhered is a member having a step on its surface such as a prism sheet, it is adhered without a gap following the step. This is preferable because the matching can be performed. The upper limit of the thickness of the entire pressure-sensitive adhesive layer is not particularly limited, but is preferably about 300 μm or less, and more preferably about 200 μm or less.

(1) Light-diffusing pressure-sensitive adhesive layer The light-diffusing pressure-sensitive adhesive layer contained in the pressure-sensitive adhesive layer for an optical member of the present invention is formed from a base pressure-sensitive adhesive composition containing a (meth) acrylic polymer and light-diffusing fine particles, The thickness is 5 to 300 μm.

(1-1) Base pressure-sensitive adhesive composition The base pressure-sensitive adhesive composition used in the present invention contains a (meth) acrylic polymer (A) as a base polymer. The (meth) acrylic polymer (A) contains, as a monomer unit, an alkyl (meth) acrylate (a1) constituting the main skeleton of the (meth) acrylic polymer (A). Note that (meth) acrylate refers to acrylate and / or methacrylate.

  Examples of the alkyl (meth) acrylate (a1) include those having a linear or branched alkyl group having 1 to 18 carbon atoms. For example, examples of the alkyl group include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, amyl, hexyl, cyclohexyl, heptyl, 2-ethylhexyl, isooctyl, nonyl, and decyl. Groups, isodecyl group, dodecyl group, isomiristyl group, lauryl group, tridecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group and the like. These can be used alone or in combination.

  The mixing ratio of the alkyl (meth) acrylate (a1) is preferably 50% by weight or more based on all the constituent monomers (100% by weight) constituting the (meth) acrylic polymer (A). The content is more preferably 100% by weight, further preferably 60 to 100% by weight, and particularly preferably 70 to 90% by weight.

  The (meth) acrylic polymer (A) is selected from the group consisting of a carboxyl group-containing monomer (a2), a hydroxyl group-containing monomer (a3), and a nitrogen-containing monomer (a4) for the purpose of improving adhesiveness and heat resistance. Preferably, one or more selected monomers are included as monomer components.

  As the carboxyl group-containing monomer (a2), a monomer having a polymerizable functional group having an unsaturated double bond such as a (meth) acryloyl group or a vinyl group and having a carboxyl group can be used without particular limitation. . Examples of the carboxyl group-containing monomer include (meth) acrylic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, isocrotonic acid, and the like. They can be used alone or in combination. These anhydrides can be used for itaconic acid and maleic acid. Among these, acrylic acid and methacrylic acid are preferable, and acrylic acid is particularly preferable.

  The compounding ratio of the carboxyl group-containing monomer (a2) is preferably 10% by weight or less based on all the constituent monomers (100% by weight) constituting the (meth) acrylic polymer (A), and is preferably 0.05% by weight or less. The content is more preferably from 10 to 10% by weight, further preferably from 0.1 to 10% by weight, and particularly preferably from 0.5 to 5% by weight.

  As the hydroxyl group-containing monomer (a3), those having a polymerizable functional group having an unsaturated double bond such as a (meth) acryloyl group or a vinyl group and having a hydroxyl group can be used without particular limitation. . Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 6-hydroxyhexyl ( Hydroxyalkyl (meth) acrylates such as (meth) acrylate, 8-hydroxyoctyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, and 12-hydroxylauryl (meth) acrylate; (4-hydroxymethylcyclohexyl) methyl ( And hydroxyalkylcycloalkane (meth) acrylates such as (meth) acrylate. Other examples include hydroxyethyl (meth) acrylamide, allyl alcohol, 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, diethylene glycol monovinyl ether, and the like. These can be used alone or in combination. Among these, hydroxyalkyl (meth) acrylate is preferred, and 2-hydroxyethyl (meth) acrylate is more preferred.

  The mixing ratio of the hydroxyl group-containing monomer (a3) is preferably 20% by weight or less based on all the constituent monomers (100% by weight) constituting the (meth) acrylic polymer (A), and is 0.05% by weight or less. The content is more preferably from 20 to 20% by weight, further preferably from 0.1 to 15% by weight, and particularly preferably from 1 to 15% by weight.

  As the nitrogen-containing monomer (a4), those having a polymerizable functional group having an unsaturated double bond such as a (meth) acryloyl group or a vinyl group and having a functional group having a nitrogen atom are used without particular limitation. be able to. Examples of the nitrogen-containing monomer (a4) include (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N-isopropyl (meth) acrylamide, and N-butyl (meth) (Meth) acrylamide-based monomers such as acrylamide, N-methylol (meth) acrylamide, N-methylolpropane (meth) acrylamide and (meth) acryloylmorpholine; for example, aminoethyl (meth) acrylate, N (meth) acrylate, N-dimethylaminoethyl, t-butylaminoethyl (meth) acrylate, etc., terminal, primary, secondary or tertiary amino group-containing monomers; for example, cyano group-containing monomers, such as acrylonitrile and methacrylonitrile; -Vinylpyrrolidone, N- (1-methyl Nyl) pyrrolidone-based monomers such as pyrrolidone, and others, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, N-vinyloxazole, Vinyl group-containing heterocyclic compounds such as N-vinyl morpholine; vinyl carboxylic acid amide compounds such as N-vinyl acetamide; for example, maleimides such as N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, N-phenylmaleimide Monomers; for example, N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide, N-cyclohexylitaconimide, N-lauri Itaconic imide monomers such as itacimide; succinimide monomers such as N- (meth) acryloyloxymethylene succinimide, N- (meth) acryloyl-6-oxyhexamethylene succinimide, N- (meth) acryloyl-8-oxyoctamethylene succinimide Monomers; and others, sulfonic acid group-containing (meth) acrylamide-based monomers such as 2- (meth) acrylamide-2-methylpropanesulfonic acid and (meth) acrylamidepropanesulfonic acid, and diacetone acrylamide. Among them, a vinyl group-containing heterocyclic compound is preferable, and N-vinylpyrrolidone is more preferable.

  The compounding ratio of the nitrogen-containing monomer (a4) is preferably 20% by weight or less based on all the constituent monomers (100% by weight) constituting the (meth) acryl-based polymer (A), and is 0.05 to less. The content is more preferably 20% by weight, further preferably 0.1 to 15% by weight, and particularly preferably 1 to 15% by weight.

  The (meth) acrylic polymer (A) further includes, in addition to the alkyl (meth) acrylate (a1), the carboxyl group-containing monomer (a2), the hydroxyl group-containing monomer (a3), and the nitrogen-containing monomer (a4). In order to improve adhesion and heat resistance, one or more copolymerizable monomers having a polymerizable functional group having an unsaturated double bond such as a (meth) acryloyl group or a vinyl group are introduced by copolymerization. be able to. Specific examples of such a copolymerized monomer include, for example, a caprolactone adduct of acrylic acid; a sulfonic acid group-containing compound such as styrenesulfonic acid, allylsulfonic acid, sulfopropyl (meth) acrylate, and (meth) acryloyloxynaphthalenesulfonic acid. Monomer; a phosphoric acid group-containing monomer such as 2-hydroxyethyl acryloyl phosphate;

  Further, as a modifying monomer, vinyl monomers such as vinyl acetate and vinyl propionate; epoxy group-containing acrylic monomers such as glycidyl (meth) acrylate; polyethylene glycol (meth) acrylate, polypropylene glycol (meth) acrylate, ( Glycol-based acrylic ester monomers such as methoxyethylene glycol (meth) acrylate and methoxypolypropylene glycol (meth) acrylate; tetrahydrofurfuryl (meth) acrylate, fluorine (meth) acrylate, silicone (meth) acrylate and 2-methoxyethyl acrylate And the like. Further, isoprene, butadiene, isobutylene, vinyl ether and the like can be mentioned.

  Further, as copolymerizable monomers other than those described above, silane-based monomers containing a silicon atom and the like can be mentioned. Examples of the silane monomer include 3-acryloxypropyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 4-vinylbutyltrimethoxysilane, 4-vinylbutyltriethoxysilane, and 8-vinyloctyltrimethoxysilane. , 8-vinyloctyltriethoxysilane, 10-methacryloyloxydecyltrimethoxysilane, 10-acryloyloxydecyltrimethoxysilane, 10-methacryloyloxydecyltriethoxysilane, 10-acryloyloxydecyltriethoxysilane, and the like.

  Further, in addition to the monofunctional monomer, a polyfunctional monomer may be used as a copolymerizable monomer as needed in order to adjust the cohesive force of the pressure-sensitive adhesive. Here, in the present invention, a monofunctional monomer refers to a monomer having one polymerizable functional group having an unsaturated double bond such as a (meth) acryloyl group or a vinyl group, and a polyfunctional monomer. The term “monomer” means a monomer having at least two polymerizable functional groups having an unsaturated double bond such as a (meth) acryloyl group or a vinyl group, as described later.

  The polyfunctional monomer is a monomer having at least two polymerizable functional groups having an unsaturated double bond such as a (meth) acryloyl group or a vinyl group, and includes, for example, (poly) ethylene glycol di (meth) acrylate, (Poly) propylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, pentaerythritol di (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, 1,2-ethylene Glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,12-dodecanediol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, tetramethylol methane tri (meth) acryle Ester compounds of polyhydric alcohols such as (g) with (meth) acrylic acid; allyl (meth) acrylate, vinyl (meth) acrylate, divinylbenzene, epoxy acrylate, polyester acrylate, urethane acrylate, butyl di (meth) acrylate, hexyl di (meth) A) acrylate and the like. The polyfunctional monomers can be used alone or in combination of two or more.

  The proportion of the copolymerizable monomer other than the carboxyl group-containing monomer (a2), the hydroxyl group-containing monomer (a3), and the nitrogen-containing monomer (a4) is not particularly limited, but may be any one constituting the (meth) acrylic polymer (A). In the monomer, the content is preferably 10% by weight or less, more preferably 0.1 to 10% by weight, and still more preferably 0.1 to 5% by weight.

  The (meth) acrylic polymer (A) can be obtained by polymerizing the above monomers in an appropriate combination according to the purpose and desired properties. The obtained (meth) acrylic polymer (A) may be any of a random copolymer, a block copolymer, and a graft copolymer. The (meth) acrylic polymer (A) can be synthesized by any appropriate method. For example, the (meth) acrylic polymer (A) can be synthesized by referring to “Chemistry and Application of Adhesion and Adhesion” by Katsuhiko Nakamae published by Dainippon Tosho Co., Ltd. .

  For example, as the polymerization method of the (meth) acrylic polymer (A), any appropriate method can be adopted. Specific examples include solution polymerization, bulk polymerization, emulsion polymerization, and various radical polymerizations.

  The polymerization initiator, chain transfer agent, emulsifier and the like used for the radical polymerization are not particularly limited, and can be appropriately selected and used. The weight average molecular weight of the (meth) acrylic polymer can be controlled by the amount of the polymerization initiator and the amount of the chain transfer agent and the reaction conditions, and the amount is appropriately adjusted according to the type.

  For example, in solution polymerization or the like, for example, ethyl acetate, toluene, or the like is used as a polymerization solvent. As a specific example of solution polymerization, the reaction is carried out under a stream of an inert gas such as nitrogen, with a polymerization initiator added, and usually at about 50 to 70 ° C. for about 5 to 30 hours.

  Examples of the thermal polymerization initiator used for solution polymerization and the like include, for example, 2,2′-azobisisobutyronitrile, 2,2′-azobis-2-methylbutyronitrile, 2,2′-azobis (2 -Methylpropionic acid) dimethyl, 4,4'-azobis-4-cyanovaleric acid, azobisisovaleronitrile, 2,2'-azobis (2-amidinopropane) dihydrochloride, 2,2'-azobis [2- (5-methyl-2-imidazolin-2-yl) propane] dihydrochloride, 2,2′-azobis (2-methylpropionamidine) disulfate, 2,2′-azobis (N, N′-dimethyleneisobutyl) Amidine), 2,2'-azobis [N- (2-carboxyethyl) -2-methylpropionamidine] hydrate (VA-057, Wako Pure Chemical Industries, Ltd. Azo initiators such as potassium persulfate and ammonium persulfate, di (2-ethylhexyl) peroxydicarbonate, di (4-t-butylcyclohexyl) peroxydicarbonate, di-sec -Butyl peroxy dicarbonate, t-butyl peroxy neodecanoate, t-hexyl peroxy pivalate, t-butyl peroxy pivalate, dilauroyl peroxide, di-n-octanoyl peroxide, 1,1 , 3,3-tetramethylbutylperoxy-2-ethylhexanoate, di (4-methylbenzoyl) peroxide, dibenzoyl peroxide, t-butylperoxyisobutyrate, 1,1-di (t-hexyl) Peroxy) cyclohexane, t-butyl hydroperoxide, hydrogen peroxide, etc. Compound initiator, a combination of persulfate and sodium hydrogen sulfite, a redox initiator in which a peroxide and a reducing agent such as a combination of peroxide and sodium ascorbate are combined, and the like. It is not limited.

  The polymerization initiator may be used alone, or two or more kinds may be used as a mixture. However, based on 100 parts by weight of all monomer components constituting the (meth) acrylic polymer (A) , Preferably about 1 part by weight or less, more preferably about 0.005 to 1 part by weight, even more preferably about 0.02 to 0.5 part by weight.

  In addition, in order to produce a (meth) acrylic polymer (A) using, for example, 2,2′-azobisisobutyronitrile as a polymerization initiator, the amount of the polymerization initiator used is determined by the total amount of the monomer components. The amount is preferably about 0.2 parts by weight or less, more preferably about 0.06 to 0.2 parts by weight, per 100 parts by weight.

  Examples of the chain transfer agent include lauryl mercaptan, glycidyl mercaptan, mercaptoacetic acid, 2-mercaptoethanol, thioglycolic acid, 2-ethylhexyl thioglycolate, 2,3-dimercapto-1-propanol, and the like. The chain transfer agent may be used alone or as a mixture of two or more kinds, but the total content is 0.1 part by weight with respect to 100 parts by weight of the total amount of the monomer components. Less than or equal.

  Examples of the emulsifier used for emulsion polymerization include, for example, anionic emulsifiers such as sodium lauryl sulfate, ammonium lauryl sulfate, sodium dodecylbenzenesulfonate, ammonium polyoxyethylene alkyl ether sulfate, and sodium polyoxyethylene alkyl phenyl ether sulfate; Nonionic emulsifiers such as ethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene fatty acid ester, and polyoxyethylene-polyoxypropylene block polymer are exemplified. These emulsifiers may be used alone or in combination of two or more.

  Further, a reactive emulsifier into which a radical polymerizable functional group such as a propenyl group or an allyl ether group has been introduced can be used. Specifically, for example, Aqualon HS-10, HS-20, KH-10, BC-05, BC-10, BC-20 (all of which are manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), Adecaria Soap SE10N (Made by ADEKA).

  The amount of the emulsifier to be used is preferably 5 parts by weight or less, more preferably 0.3 to 5 parts by weight, based on 100 parts by weight of the total amount of the monomer components, and the polymerization stability and mechanical stability. From the viewpoint, it is more preferably 0.5 to 1 part by weight.

  When the (meth) acrylic polymer (A) is produced by radiation polymerization, it can be produced by polymerizing the monomer component by irradiating radiation such as an electron beam or UV. When the radiation polymerization is performed by an electron beam, it is not particularly necessary to include a photopolymerization initiator in the monomer component.However, when the radiation polymerization is performed by UV polymerization, particularly, the polymerization time is shortened. Because of the advantages that can be achieved, a photopolymerization initiator can be contained in the monomer component. One photopolymerization initiator can be used alone, or two or more photopolymerization initiators can be used in combination.

  The photopolymerization initiator is not particularly limited, but is not particularly limited as long as it initiates photopolymerization, and a commonly used photopolymerization initiator can be used. For example, benzoin ether-based photopolymerization initiator, acetophenone-based photopolymerization initiator, α-ketol-based photopolymerization initiator, aromatic sulfonyl chloride-based photopolymerization initiator, photoactive oxime-based photopolymerization initiator, benzoin-based photopolymerization initiator Agents, benzyl-based photopolymerization initiator, benzophenone-based photopolymerization initiator, ketal-based photopolymerization initiator, thioxanthone-based photopolymerization initiator, acylphosphine oxide-based photopolymerization initiator and the like can be used.

  Specifically, examples of the benzoin ether-based photopolymerization initiator include benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2,2-dimethoxy-1,2-diphenylethane- 1-one (trade name: Irgacure 651, manufactured by BASF); anisole methyl ether; Examples of the acetophenone-based photopolymerization initiator include 1-hydroxycyclohexylphenyl ketone (trade name: Irgacure 184, manufactured by BASF), 4-phenoxydichloroacetophenone, 4-t-butyl-dichloroacetophenone, 1- [4- ( 2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propan-1-one (trade name: Irgacure 2959, manufactured by BASF), 2-hydroxy-2-methyl-1-phenyl-propane- 1-one (trade name: Darocure 1173, manufactured by BASF), methoxyacetophenone, and the like. Examples of the α-ketol-based photopolymerization initiator include 2-methyl-2-hydroxypropiophenone, 1- [4- (2-hydroxyethyl) -phenyl] -2-hydroxy-2-methylpropane-1-. ON and the like. Examples of the aromatic sulfonyl chloride-based photopolymerization initiator include 2-naphthalenesulfonyl chloride. Examples of the photoactive oxime-based photopolymerization initiator include 1-phenyl-1,1-propanedione-2- (o-ethoxycarbonyl) -oxime and the like.

  The benzoin-based photopolymerization initiator includes, for example, benzoin and the like. Benzyl photopolymerization initiators include, for example, benzyl and the like. The benzophenone-based photopolymerization initiator includes, for example, benzophenone, benzoylbenzoic acid, 3,3'-dimethyl-4-methoxybenzophenone, polyvinylbenzophenone, α-hydroxycyclohexylphenyl ketone, and the like. The ketal-based photopolymerization initiator includes, for example, benzyldimethyl ketal. Examples of the thioxanthone-based photopolymerization initiator include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, 2,4-diethylthioxanthone, isopropylthioxanthone, 2,4-diisopropylthioxanthone, dodecylthioxanthone and the like are included.

  Examples of the acylphosphine-based photopolymerization initiator include bis (2,6-dimethoxybenzoyl) phenylphosphine oxide, bis (2,6-dimethoxybenzoyl) (2,4,4-trimethylpentyl) phosphine oxide, bis ( 2,6-dimethoxybenzoyl) -n-butylphosphine oxide, bis (2,6-dimethoxybenzoyl)-(2-methylpropan-1-yl) phosphine oxide, bis (2,6-dimethoxybenzoyl)-(1- Methylpropan-1-yl) phosphine oxide, bis (2,6-dimethoxybenzoyl) -t-butylphosphine oxide, bis (2,6-dimethoxybenzoyl) cyclohexylphosphine oxide, bis (2,6-dimethoxybenzoyl) octylphosphine Oxides, bis (2-meth Xybenzoyl) (2-methylpropan-1-yl) phosphine oxide, bis (2-methoxybenzoyl) (1-methylpropan-1-yl) phosphine oxide, bis (2,6-diethoxybenzoyl) (2-methyl Propane-1-yl) phosphine oxide, bis (2,6-diethoxybenzoyl) (1-methylpropan-1-yl) phosphine oxide, bis (2,6-dibutoxybenzoyl) (2-methylpropane-1- Yl) phosphine oxide, bis (2,4-dimethoxybenzoyl) (2-methylpropan-1-yl) phosphine oxide, bis (2,4,6-trimethylbenzoyl) (2,4-dipentoxyphenyl) phosphine oxide , Bis (2,6-dimethoxybenzoyl) benzylphosphine oxide, bis ( , 6-Dimethoxybenzoyl) -2-phenylpropylphosphine oxide, bis (2,6-dimethoxybenzoyl) -2-phenylethylphosphine oxide, bis (2,6-dimethoxybenzoyl) benzylphosphine oxide, bis (2,6- Dimethoxybenzoyl) -2-phenylpropylphosphine oxide, bis (2,6-dimethoxybenzoyl) -2-phenylethylphosphine oxide, 2,6-dimethoxybenzoylbenzylbutylphosphine oxide, 2,6-dimethoxybenzoylbenzyloctylphosphine oxide, Bis (2,4,6-trimethylbenzoyl) -2,5-diisopropylphenylphosphine oxide, bis (2,4,6-trimethylbenzoyl) -2-methylphenylphosphine oxide, bis (2,4,6-trimethylbenzoyl) -4-methylphenylphosphine oxide, bis (2,4,6-trimethylbenzoyl) -2,5-diethylphenylphosphine oxide, bis (2,4,6-trimethylbenzoyl) -2,3,5,6-tetramethylphenylphosphine oxide, bis (2,4,6-trimethylbenzoyl) -2,4-di-n-butoxyphenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine Oxide, bis (2,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide, bis (2,4,6-trimethylbenzoyl) isobutylphosphine oxide, 2,6-dimethoxybenzoyl-2,4 6-trimethylbenzoyl-n-butylphosphineoxy , Bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide, bis (2,4,6-trimethylbenzoyl) -2,4-dibutoxyphenylphosphine oxide, 1,10-bis [bis (2,4, 6-trimethylbenzoyl) phosphine oxide] decane, tri (2-methylbenzoyl) phosphine oxide, and the like.

  The amount of the photopolymerization initiator is not particularly limited, but is preferably, for example, 0.01 to 5 parts by weight, and more preferably 0.05 to 5 parts by weight, based on 100 parts by weight of all the monomers constituting the (meth) acrylic polymer (A). To 3 parts by weight, more preferably 0.05 to 1.5 parts by weight, and particularly preferably 0.1 to 1 part by weight. When the amount of the photopolymerization initiator is within the above range, the polymerization reaction can be sufficiently advanced. In addition, a photopolymerization initiator can be used individually by 1 type or in combination of 2 or more types.

  The weight average molecular weight of the (meth) acrylic polymer (A) used in the present invention is preferably 400,000 to 2.5 million, and more preferably 600,000 to 2.2 million. By setting the weight average molecular weight to be larger than 400,000, the durability of the pressure-sensitive adhesive layer can be satisfied, and the cohesive force of the pressure-sensitive adhesive layer can be reduced to prevent adhesive residue. The weight average molecular weight is a value measured by gel permeation chromatography (GPC) and calculated in terms of polystyrene. In addition, it is difficult to measure the molecular weight of the (meth) acrylic polymer obtained by radiation polymerization.

  The base pressure-sensitive adhesive composition used in the present invention may contain a crosslinking agent. Examples of the crosslinking agent include an organic crosslinking agent and a polyfunctional metal chelate. Examples of the organic crosslinking agent include an isocyanate crosslinking agent, a peroxide crosslinking agent, an epoxy crosslinking agent, and an imine crosslinking agent. Multifunctional metal chelates are those in which a polyvalent metal is covalently or coordinated with an organic compound. Examples of the polyvalent metal include Al, Cr, Zr, Co, Cu, Fe, Ni, V, Zn, In, Ca, Mg, Mn, Y, Ce, Sr, Ba, Mo, La, Sn, and Ti. No. Examples of the organic compound include an alkyl ester, an alcohol compound, a carboxylic acid compound, an ether compound, and a ketone compound. As an atom in the organic compound to be covalently bonded or coordinated, for example, an oxygen atom can be mentioned. Among these, an isocyanate-based crosslinking agent is preferable as the crosslinking agent.

  The isocyanate-based cross-linking agent typically refers to a compound having two or more isocyanate groups in one molecule. For example, tolylene diisocyanate, chlorophenylene diisocyanate, tetramethylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, isocyanate monomers such as hydrogenated diphenylmethane diisocyanate, and isocyanate compounds obtained by adding these isocyanate monomers to trimethylolpropane and the like. Examples include isocyanurates, buret type compounds, and urethane prepolymer-type isocyanates obtained by an addition reaction with polyether polyol, polyester polyol, acrylic polyol, polybutadiene polyol, polyisoprene polyol, and the like. Particularly preferred is a polyisocyanate compound, and one or a polyisocyanate compound selected from the group consisting of hexamethylene diisocyanate, hydrogenated xylylene diisocyanate, and isophorone diisocyanate. Here, hexamethylene diisocyanate, hydrogenated xylylene diisocyanate, and a polyisocyanate compound derived from one or more selected from the group consisting of isophorone diisocyanate include hexamethylene diisocyanate, hydrogenated xylylene diisocyanate, isophorone diisocyanate, and polyol-modified Hexamethylene diisocyanate, polyol-modified hydrogenated xylylene diisocyanate, trimer-type hydrogenated xylylene diisocyanate, polyol-modified isophorone diisocyanate, and the like are included.

  The epoxy-based crosslinking agent typically refers to a compound having two or more epoxy groups (glycidyl groups) in one molecule. Examples of the epoxy crosslinking agent include ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, terephthalic acid diglycidyl ester, spiro glycol diglycidyl ether, diglycidylaminomethylcyclohexane, tetraglycidyl xylene diamine, and polyglycidyl metaxylene. Diamines and the like can be mentioned.

  As the peroxide, any appropriate compound that can generate a radical active species by heating or light irradiation to promote crosslinking of the base polymer can be used. In consideration of workability and stability, a peroxide having a one-minute half-life temperature of 80C to 160C is preferable, and a peroxide having a half-life of 90C to 140C is more preferable. Specific examples of the peroxide include di (2-ethylhexyl) peroxydicarbonate (1 minute half-life temperature: 90.6 ° C.) and di (4-t-butylcyclohexyl) peroxydicarbonate (1 minute half-life Temperature: 92.1 ° C.), di-sec-butyl peroxydicarbonate (1 minute half-life temperature: 92.4 ° C.), t-butyl peroxy neodecanoate (1 minute half-life temperature: 103.5 ° C.) ), T-hexylperoxypivalate (1 minute half-life temperature: 109.1 ° C.), t-butyl peroxypivalate (1 minute half-life temperature: 110.3 ° C.), dilauroyl peroxide (1 minute half-life) Temperature: 116.4 ° C.), di-n-octanoyl peroxide (1 minute half-life temperature: 117.4 ° C.), 1,1,3,3-tetramethylbutylperoxy-2-ethyl Xanoate (1 minute half-life temperature: 124.3 ° C), di (4-methylbenzoyl) peroxide (1 minute half-life temperature: 128.2 ° C), dibenzoyl peroxide (1 minute half-life temperature: 130.0 ° C) ), T-butylperoxyisobutyrate (1 minute half-life: 136.1 ° C.), 1,1-di (t-hexylperoxy) cyclohexane (1 minute half-life: 149.2 ° C.) and the like. No. The half-life of the peroxide is an index indicating the decomposition rate of the peroxide, and refers to the time until the remaining amount of the peroxide becomes half. Therefore, the 1-minute half-life temperature of the peroxide refers to a temperature at which the residual amount of the peroxide is reduced to half in 1 minute. The decomposition temperature for obtaining a half-life at an arbitrary time and the half-life time at an arbitrary temperature are described in a manufacturer's catalog and the like. Edition (May 2003) "and the like.

  The amount of the crosslinking agent to be used is preferably 0.01 to 20 parts by weight, more preferably 0.03 to 10 parts by weight, based on 100 parts by weight of the (meth) acrylic polymer (A). If the amount of the crosslinking agent used is less than 0.01 part by weight, the cohesive force of the pressure-sensitive adhesive tends to be insufficient, and foaming may occur during heating. If the amount of the cross-linking agent exceeds 20 parts by weight, the moisture resistance may not be sufficient, and peeling may easily occur.

  The base pressure-sensitive adhesive composition may include any appropriate additive. Examples of the additive include an antistatic agent, an antioxidant, and a coupling agent. The type, amount and combination of the additives can be appropriately set according to the purpose.

  The content of the base pressure-sensitive adhesive composition in the light diffusion pressure-sensitive adhesive layer used in the present invention is preferably 50 to 99.7% by weight, more preferably 52 to 97% by weight, and 70 to 97% by weight. Is more preferable.

  The refractive index of the base pressure-sensitive adhesive composition is preferably 1.47 or more, more preferably from 1.47 to 1.60, and even more preferably from 1.47 to 1.55. When the refractive index of the base pressure-sensitive adhesive composition is in the above range, the difference in refractive index from the light diffusing fine particles described below can be set in a desired range. As a result, a light diffusion pressure-sensitive adhesive layer having a desired haze value after curing can be obtained, which is preferable.

(1-2) Light-Diffusing Fine Particles The light-diffusing pressure-sensitive adhesive layer has light-diffusing fine particles dispersed in a pressure-sensitive adhesive layer formed from the base pressure-sensitive adhesive composition. As the light diffusing fine particles, any appropriate particles can be used as long as the effects of the present invention can be obtained. Specific examples include inorganic fine particles and polymer fine particles. Among these, polymer fine particles are preferable.

  Examples of the material of the polymer fine particles include a silicone resin, a methacrylic resin (for example, polymethyl methacrylate), a polystyrene resin, a polyurethane resin, and a melamine resin. Since these resins have excellent dispersibility in the base pressure-sensitive adhesive composition and an appropriate difference in refractive index from the base pressure-sensitive adhesive composition, a light-diffusing pressure-sensitive adhesive layer having excellent diffusion performance can be obtained. Among these, silicone resins and polymethyl methacrylate are particularly preferred.

  The shape of the light diffusing fine particles can be, for example, a true sphere, a flat shape, or an irregular shape. The light diffusing fine particles may be used alone or in combination of two or more.

  The refractive index of the light diffusing fine particles used in the present invention is preferably lower than the refractive index of the base pressure-sensitive adhesive composition. The refractive index of the light diffusing fine particles is preferably from 1.30 to 1.70, more preferably from 1.40 to 1.65. If the refractive index of the light diffusing fine particles is in the above range, the difference in refractive index from the base pressure-sensitive adhesive composition can be in a desired range, and as a result, the light diffusing pressure-sensitive adhesive layer having a desired haze value after curing. Is preferred because

  The absolute value of the refractive index difference between the light diffusing fine particles and the base pressure-sensitive adhesive composition is preferably more than 0 and 0.2 or less, more preferably more than 0 and 0.15 or less. More preferably, it is 0.01 to 0.13.

  The volume average particle diameter of the light diffusing fine particles is preferably about 1 to 5 μm, more preferably about 2 to 5 μm, and further preferably about 2 to 4 μm. When the volume average particle diameter of the light diffusing fine particles is within the above range, a light diffusing pressure-sensitive adhesive layer having a desired haze value can be obtained by combining with the base pressure-sensitive adhesive composition. The volume average particle diameter can be measured using, for example, an ultracentrifugal automatic particle size distribution analyzer.

  The content of the light diffusing fine particles in the light diffusing pressure-sensitive adhesive layer is not particularly limited, but is preferably 0.3 to 50% by weight, more preferably 3 to 48% by weight, and more preferably 3 to 48% by weight. It is more preferable that the content be 30 to 30% by weight. By setting the amount of the light diffusing fine particles in the above range, a light diffusing pressure-sensitive adhesive layer having excellent light diffusing performance can be obtained.

(1-3) Method of forming light diffusion pressure-sensitive adhesive layer The light diffusion pressure-sensitive adhesive layer is formed, for example, by applying a light diffusion pressure-sensitive adhesive composition in which light-diffusing fine particles are dispersed in the base pressure-sensitive adhesive composition to a support. Then, it can be formed by drying and removing a solvent and the like. In applying the light diffusion pressure-sensitive adhesive composition, one or more solvents may be appropriately added. Further, when the base pressure-sensitive adhesive composition is an active energy ray-curable type, a light-diffusing method in which a prepolymer obtained by polymerizing a part of the base pressure-sensitive adhesive composition and light-diffusing fine particles are dispersed in the prepolymer is prepared. The light-diffusing pressure-sensitive adhesive layer can be formed by applying the pressure-sensitive adhesive composition to a support and irradiating the coating layer with active energy rays such as ultraviolet rays. Further, the light diffusion pressure-sensitive adhesive composition can be directly applied to an optical member such as a polarizing film described later to form a light diffusion pressure-sensitive adhesive layer.

  The thickness of the light diffusion pressure-sensitive adhesive layer is 5 to 300 μm, preferably 5 to 250 μm, more preferably 50 to 250 μm, even more preferably 100 to 200 μm, and more than 100 μm and 200 μm or less. Is more preferable. When the thickness of the light-diffusing pressure-sensitive adhesive layer is within the above range, the light-diffusing pressure-sensitive adhesive layer can be adhered by following fine irregularities of a material to be adhered or irregularities for imparting an optical function. In the case where the transparent pressure-sensitive adhesive layer is bonded to the light-diffusing pressure-sensitive adhesive layer, the thickness of the light-diffusing pressure-sensitive adhesive layer is preferably about 5 to 100 μm because the physical properties of the light-diffusing pressure-sensitive adhesive affect peripheral members. It is preferable because it does not affect the bonding effect, and more preferably about 5 to 30 μm. Further, when the light diffusion pressure-sensitive adhesive layer is composed of two or more layers, the total thickness of all the light diffusion pressure-sensitive adhesive layers may be within the above range.

  Various methods are used for applying the light diffusion pressure-sensitive adhesive composition. Specifically, for example, by 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, etc. A method such as an extrusion coating method may be used.

  The heating and drying temperature is preferably about 30C to 200C, more preferably 40C to 180C, and still more preferably 80C to 160C. By setting the heating temperature within the above range, a pressure-sensitive adhesive layer having excellent pressure-sensitive adhesive properties can be obtained. As the drying time, an appropriate time can be appropriately used. The drying time is preferably about 5 seconds to 20 minutes, more preferably 30 seconds to 10 minutes, and still more preferably 1 minute to 8 minutes.

  When the base pressure-sensitive adhesive composition is an active energy ray-curable pressure-sensitive adhesive, a light diffusion pressure-sensitive adhesive layer can be formed by irradiating an active energy ray such as ultraviolet light. For UV irradiation, a high-pressure mercury lamp, a low-pressure mercury lamp, a metal halide lamp, a chemical light lamp, or the like can be used.

  As the support, for example, a sheet subjected to a release treatment can be used. As the sheet subjected to the release treatment, a silicone release liner is preferably used.

  When the pressure-sensitive adhesive layer is formed on the release-treated sheet, if the pressure-sensitive adhesive layer is exposed, the pressure-sensitive adhesive layer may be protected with a release-treated sheet (separator) until practical use. . In practical use, the sheet subjected to the release treatment is released.

  As a constituent material of the separator, for example, a plastic film, paper, cloth, a porous material such as a nonwoven fabric, a net, a foamed sheet, a metal foil, and a suitable thin leaf such as a laminate of these can be mentioned. A plastic film is preferably used because of its excellent surface smoothness.

  As the plastic film, for example, polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, polyethylene terephthalate film, polybutylene terephthalate film, polyurethane film, ethylene film -Vinyl acetate copolymer films and the like.

  The thickness of the separator is usually 5 to 200 μm, preferably about 5 to 100 μm. The separator may be, if necessary, a silicone-based, fluorine-based, long-chain alkyl-based or fatty acid amide-based release agent, a release and antifouling treatment with silica powder or the like, a coating type, a kneading type, a vapor deposition type. And the like. In particular, by appropriately performing a release treatment such as a silicone treatment, a long-chain alkyl treatment, or a fluorine treatment on the surface of the separator, the releasability from the pressure-sensitive adhesive layer can be further improved.

  The haze value of the formed light diffusion pressure-sensitive adhesive layer is preferably from 10 to 99%, more preferably from 10 to 96%, further preferably from 20 to 96%, and more preferably from 40 to 80%. It is particularly preferred that there is. By setting the haze value within the above range, desired diffusion performance can be obtained, and the occurrence of moiré and glare can be favorably suppressed, which is preferable. The light diffusion performance of the light diffusion pressure-sensitive adhesive can be controlled by adjusting the constituent material of the matrix (pressure-sensitive adhesive), the constituent material of the light-diffusing fine particles, the volume average particle diameter, the compounding amount, and the like.

  The total light transmittance of the light diffusion pressure-sensitive adhesive layer is preferably 75% or more, more preferably 80% or more, and even more preferably 85% or more.

(2) Transparent pressure-sensitive adhesive layer As described above, the pressure-sensitive adhesive layer for an optical member of the present invention can include a transparent pressure-sensitive adhesive layer other than the light diffusion pressure-sensitive adhesive layer.

  The transparent pressure-sensitive adhesive layer is not particularly limited, and examples thereof include those formed from a pressure-sensitive adhesive composition containing a base polymer and a crosslinking agent. The pressure-sensitive adhesive composition may be a pressure-sensitive adhesive such as an acrylic, a synthetic rubber, a rubber, or a silicone. However, from the viewpoints of transparency, heat resistance, and the like, a (meth) acryl-based polymer is used as a base polymer. Is preferred.

  As the monomer component contained in the (meth) acryl-based polymer, those listed in the base pressure-sensitive adhesive composition can be suitably used, and an alkyl (meth) acrylate (a1), a hydroxyl group-containing monomer (a3), And a (meth) acrylic polymer containing a nitrogen-containing monomer (a4) as a monomer component. The monomer component contained in the (meth) acrylic polymer preferably does not contain a carboxyl group-containing monomer. The mixing ratio of each monomer and the method for forming the transparent pressure-sensitive adhesive layer may be the same as those for the light diffusion pressure-sensitive adhesive layer.

  The haze of the transparent pressure-sensitive adhesive layer is not particularly limited, but is preferably 0.01 to 5%, more preferably 0.05 to 5%, and 0.1 to 3%. Is more preferable. When the haze of the transparent pressure-sensitive adhesive layer is in the above range, optical design such as haze becomes easy, which is preferable.

  Further, the thickness of the transparent pressure-sensitive adhesive layer is not particularly limited, and when the pressure-sensitive adhesive layer is formed by laminating with the light-diffusing pressure-sensitive adhesive layer, the total thickness may be 20 μm or more, particularly Although not limited, it is preferably 20 to 300 μm, and more preferably 50 to 300 μm. It is preferable that the thickness of the transparent pressure-sensitive adhesive layer be in the above range, since the transparent adhesive layer can be adhered following minute irregularities of a material to be laminated or irregularities for imparting an optical function.

(3) Pressure-Sensitive Adhesive Layer for Optical Member The pressure-sensitive adhesive layer for an optical member of the present invention may be formed from only one light-diffusing pressure-sensitive adhesive layer, as described above, and may include at least one light-diffusing pressure-sensitive adhesive layer. It may be formed from at least one transparent pressure-sensitive adhesive layer.

  The pressure-sensitive adhesive layer for an optical member of the present invention is preferably applied to an optical member, and the optical member is as described later. Among optical members, it can be preferably used for a brightness enhancement film and a polarizing film.

  The haze value of the entire pressure-sensitive adhesive layer for an optical member of the present invention is from 10 to 96%, preferably from 20 to 96%, and more preferably from 30 to 96%. If the haze value is less than 10%, display unevenness occurs because the light from the backlight and the prism sheet has a bias, and the bias of the light cannot be completely eliminated. When the haze value of the pressure-sensitive adhesive layer exceeds 96%, it is necessary to add a large amount of particles to the pressure-sensitive adhesive layer. In this case, the stress relaxation property and adhesiveness of the pressure-sensitive adhesive layer are reduced, and the durability is poor. .

2. Optical Member with Adhesive Layer The optical member with an adhesive layer of the present invention is characterized in that at least one surface of the optical member has at least one adhesive layer for the optical member.

  As the optical member, those used in the production of various image display devices and the like are used, and the type thereof is not particularly limited. Examples thereof include a polarizing film, a retardation plate, a brightness enhancement film, and an antiglare sheet. Can be. Incidentally, the optical member is a laminate of a polarizing film and a retardation plate or a laminate of a retardation plate, a laminate of a polarizing film and a brightness enhancement film or a laminate of an anti-glare sheet, and two or more optical material seed layers. There may be. Among these, a brightness enhancement film and a polarizing film are preferable.

  As the polarizing film, those having a transparent protective film on one side or both sides of a polarizer are generally used.

  The polarizer is not particularly limited, and various types can be used. Examples of the polarizer include, for example, a polyvinyl alcohol-based film, a partially formalized polyvinyl alcohol-based film, a hydrophilic polymer film such as an ethylene-vinyl acetate copolymer-based partially saponified film, and dichroic properties of iodine and a dichroic dye. Examples thereof include a uniaxially stretched film obtained by adsorbing a substance, and a polyene-based oriented film such as a dehydrated product of polyvinyl alcohol and a dehydrochlorinated product of polyvinyl chloride. Among these, a polarizer composed of a polyvinyl alcohol-based film and a dichroic substance such as iodine is preferable. The thickness of these polarizers is not particularly limited, but is generally about 5 to 80 μm.

  A polarizer obtained by dyeing a polyvinyl alcohol-based film with iodine and uniaxially stretching the dye can be produced by, for example, dyeing polyvinyl alcohol by immersing it in an aqueous solution of iodine, and stretching the film to 3 to 7 times its original length. If necessary, it can be immersed in an aqueous solution of potassium iodide or the like which may contain boric acid, zinc sulfate, zinc chloride or the like. Further, if necessary, the polyvinyl alcohol-based film may be immersed in water and washed with water before dyeing. By washing the polyvinyl alcohol-based film with water, dirt on the surface of the polyvinyl alcohol-based film and an anti-blocking agent can be washed, and by swelling the polyvinyl alcohol-based film, the effect of preventing unevenness such as uneven dyeing can be obtained. is there. Stretching may be performed after dyeing with iodine, may be performed while dyeing, or may be dyed with iodine after stretching. Stretching can be performed in an aqueous solution of boric acid or potassium iodide or in a water bath.

  In the present invention, a thin polarizer having a thickness of 10 μm or less can also be used. From the viewpoint of thinning, the thickness is preferably 1 to 7 μm. Such a thin polarizer is preferable in that it has little thickness unevenness, is excellent in visibility, is small in dimensional change, has excellent durability, and can be made thinner as a polarizing plate.

  Representative examples of the thin polarizer include Japanese Patent Application Laid-Open Nos. 51-069694 and 2000-338329, International Patent Publication No. 2010/100917, the specification of PCT / JP2010 / 001460, and Japanese Patent Application Publication No. Examples include thin polarizing films described in Japanese Patent Application No. 2010-269002 and Japanese Patent Application No. 2010-263692. These thin polarizing films can be obtained by a manufacturing method including a step of stretching a polyvinyl alcohol-based resin (hereinafter, also referred to as a PVA-based resin) layer and a stretching resin substrate in a laminated state, and a step of dyeing. According to this manufacturing method, even if the PVA-based resin layer is thin, it can be stretched without any trouble such as breakage due to stretching because it is supported by the stretching resin base material.

  WO 2010/100917 brochure of the thin polarizing film, which can be stretched at a high magnification to improve the polarization performance among manufacturing methods including a stretching step in a state of a laminate and a dyeing step. , PCT / JP2010 / 001460, or those obtained by a production method including a step of stretching in a boric acid aqueous solution as described in Japanese Patent Application No. 2010-269002 or Japanese Patent Application No. 2010-263692. Preferred are those obtained by a production method including a step of auxiliary stretching in air before stretching in a boric acid aqueous solution described in Japanese Patent Application No. 2010-269002 or Japanese Patent Application No. 2010-263892.

  As a material for forming the transparent protective film provided on one side or both sides of the polarizer, a material having excellent transparency, mechanical strength, heat stability, moisture blocking property, isotropy and the like is preferable. For example, polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, cellulose polymers such as diacetyl cellulose and triacetyl cellulose, acrylic polymers such as polymethyl methacrylate, and styrene such as polystyrene and acrylonitrile-styrene copolymer (AS resin). Polymers, polycarbonate polymers and the like. In addition, polyethylene, polypropylene, polyolefin having a cyclo- or norbornene structure, polyolefin-based polymers such as ethylene-propylene copolymer, vinyl chloride-based polymers, amide-based polymers such as nylon and aromatic polyamide, imide-based polymers, and sulfone-based polymers , Polyether sulfone polymer, polyether ether ketone polymer, polyphenylene sulfide polymer, vinyl alcohol polymer, vinylidene chloride polymer, vinyl butyral polymer, arylate polymer, polyoxymethylene polymer, epoxy polymer, or Blends of the above-mentioned polymers and the like are also mentioned as examples of the polymer forming the transparent protective film. The transparent protective film can also be formed as a cured layer of a thermosetting resin or an ultraviolet curable resin such as an acrylic, urethane, acrylic urethane, epoxy, or silicone resin.

  Although the thickness of the protective film can be determined as appropriate, it is generally about 1 to 500 μm from the viewpoint of workability such as strength and handleability, and thinness.

  Usually, the polarizer and the protective film are in close contact with each other via an aqueous adhesive or the like. Examples of the water-based adhesive include an isocyanate-based adhesive, a polyvinyl alcohol-based adhesive, a gelatin-based adhesive, a vinyl-based latex, a water-based polyurethane, and a water-based polyester. In addition to the above, examples of the adhesive between the polarizer and the transparent protective film include an ultraviolet curable adhesive, an electron beam curable adhesive, and the like. The adhesive for an electron beam-curable polarizing film exhibits suitable adhesiveness to the above various transparent protective films. The adhesive used in the present invention can contain a metal compound filler.

  The surface of the transparent protective film on which the polarizer is not adhered may be subjected to a hard coat layer, an antireflection treatment, a treatment for preventing sticking, and a treatment for diffusion or antiglare.

  FIG. 2 shows an example of a specific usage pattern of the optical member with a pressure-sensitive adhesive layer of the present invention. The polarizing film 10 having the pressure-sensitive adhesive layer 1 for an optical member of the present invention (optical member with a pressure-sensitive adhesive layer) can be used by bonding the pressure-sensitive adhesive layer surface to the step surface of the prism sheet 20. Since the optical member with a pressure-sensitive adhesive layer of the present invention has the pressure-sensitive adhesive layer for an optical member of the present invention, it can be bonded without gaps following the step. In FIG. 2, the polarizing film 10 has a protective film 12 on both surfaces of the polarizer 11, but may be a single-sided protective polarizing film having the protective film 12 on one surface of the polarizer 11. The prism sheet 20 typically has a substrate 22 and a prism portion 21.

  Since the pressure-sensitive adhesive layer 1 for an optical member of the present invention has a light diffusing function, it can be used instead of a diffusion sheet that is usually provided on the backlight side of an image display device.

3. Image Display Device An image display device according to the present invention includes the optical member with an adhesive layer. The image display device of the present invention only needs to include the optical member with a pressure-sensitive adhesive layer of the present invention, and other configurations may be the same as those of the conventional image display device.

  The image display device of the present invention has high reliability because it includes the optical member with an adhesive layer. Further, since the pressure-sensitive adhesive layer for an optical member of the present invention has a light diffusion function, the optical member with a pressure-sensitive adhesive layer can be used in place of a diffusion sheet provided on the backlight side, and the image display device is reduced in thickness. be able to.

Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to these Examples. In addition, all parts and% in each example are based on weight. Evaluation items in Examples and the like were measured as follows.

Production Example 1 (Production of light diffusion pressure-sensitive adhesive composition (A-1))
In a separable flask equipped with a thermometer, a stirrer, a reflux condenser, and a nitrogen gas inlet tube, 70 parts of 2-ethylhexyl acrylate (2EHA), 15 parts of N-vinyl-2-pyrrolidone (NVP), After mixing 15 parts of hydroxyethyl acrylate (HEA) and 0.1 part of a photopolymerization initiator (trade name: Irgacure 184, manufactured by BASF), the viscosity (measurement conditions: BH viscometer No. rotor, 10 rpm, measurement temperature 30) C) was about 20 Pa · s to obtain a prepolymer composition in which a part of the monomer components was polymerized.

  Next, 0.2 part of an isocyanate crosslinking agent (trade name: Coronate L, adduct of tolylene diisocyanate of trimethylolpropane, manufactured by Nippon Polyurethane Industry Co., Ltd.) was added to 100 parts of the obtained prepolymer composition. By mixing, a base pressure-sensitive adhesive composition (A-1) was obtained. The refractive index of the obtained base pressure-sensitive adhesive composition (A-1) was 1.475.

  Based on 100 parts of the obtained base pressure-sensitive adhesive composition (A-1), silicone resin fine particles (trade name: Tospearl 145, volume average particle diameter: 4 μm, refractive index: 1.43, silicone) 14 parts of resin-based fine particles (manufactured by Momentive Performance Materials) were added to obtain a light-diffusing pressure-sensitive adhesive composition (A-1).

Production Examples 2 to 5 (Production of light diffusion pressure-sensitive adhesive compositions (A-2) to (A-5))
Light-diffusing pressure-sensitive adhesive compositions (A-2) to (A-5) in Production Example 1 in the same manner as in Production Example 1 except that the amount of light-diffusing fine particles was changed as shown in Table 1. Was manufactured.

Production Example 6 (Production of light diffusion pressure-sensitive adhesive composition (A-6))
100 parts of butyl acrylate, 5 parts of acrylic acid, 1 part of hydroxyethyl acrylate, and 2,2′-azobisisopropane as a polymerization initiator were placed in a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a condenser. 0.1 parts of butyronitrile were charged together with 100 parts of ethyl acetate (monomer concentration: 50%), nitrogen gas was introduced while gently stirring to replace the nitrogen, and the liquid temperature in the flask was maintained at about 55 ° C. A polymerization reaction was carried out for 8 hours to prepare a solution of an acrylic polymer (A-6) having a weight average molecular weight (Mw) of 1.8 million.

  An isocyanate-based crosslinking agent (trade name: Coronate L, trimethylolpropane / tolylene diisocyanate trimer adduct, Nippon Polyurethane Industry) based on 100 parts of the solid content of the acrylic polymer (A-6) solution obtained above. 0.66 parts, benzoyl peroxide (Niper BMT, manufactured by NOF Corporation) 0.3 parts, silane coupling agent (trade name: KBM403, manufactured by Shin-Etsu Chemical Co., Ltd.) 0.2 Was added to obtain a base pressure-sensitive adhesive composition (A-6).

  Silicone resin fine particles (trade name: Tospearl 145, volume average particle diameter: 4 μm, refractive index: 1.90 parts) as light diffusing fine particles with respect to 100 parts of solid content of the obtained base pressure-sensitive adhesive composition (A-6). 43, silicone resin-based fine particles, manufactured by Momentive Performance Materials Co., Ltd.) (26 parts) to prepare a light-diffusing pressure-sensitive adhesive composition (A-6).

Production Example 7 (Production of light diffusion pressure-sensitive adhesive composition (A-7))
In Production Example 6, as shown in Table 1, a light diffusion pressure-sensitive adhesive composition (A-7) was produced in the same manner as in Production Example 6, except that the addition amount of the light diffusing fine particles was changed.

Production Examples 8 to 12 (Production of light diffusion pressure-sensitive adhesive compositions (A-8) to (A-12))
Light-diffusing pressure-sensitive adhesive compositions (A-8) to (A-12) in Production Example 1 in the same manner as in Production Example 1 except that the amount of the light-diffusing fine particles was changed as shown in Table 1. Was manufactured.

Example 1 (production of light diffusion pressure-sensitive adhesive layer)
Release treatment of a 38 μm-thick polyester film (trade name: Diafoil MRF, manufactured by Mitsubishi Plastics, Inc.) obtained by peeling one side of the light diffusion pressure-sensitive adhesive composition (A-1) obtained in Production Example 1 with silicone. The surface was coated so that the thickness of the obtained light diffusion pressure-sensitive adhesive layer was 23 μm to form a coating layer. Next, a 38 μm-thick polyester film (trade name: Diafoil MRE, manufactured by Mitsubishi Plastics, Inc.), one surface of which was peeled off with silicone, was coated on the surface of the formed coating layer. And coated. Thereby, the coating layer of the light diffusion pressure-sensitive adhesive composition was shielded from oxygen. Ultraviolet light of 100 mW / cm ² (measured by Topcon UVR-T1 having a maximum sensitivity at about 350 nm) using a chemical light lamp (manufactured by Toshiba Corporation) on the sheet having the coating layer thus obtained. Irradiation was performed for 30 seconds to cure the coating layer to form a light diffusion pressure-sensitive adhesive layer, thereby producing a pressure-sensitive adhesive sheet. The polyester film coated on both sides of the pressure-sensitive adhesive layer functions as a release liner.

Examples 2 to 12, Comparative Examples 1 to 3, 6, 7
A pressure-sensitive adhesive sheet was prepared in the same manner as in Example 1, except that the light-diffusing pressure-sensitive adhesive composition to be used and the thickness after drying were changed as shown in Table 2.

Example 13
(Manufacture of 1st layer, 3rd layer (transparent adhesive layer))
For the transparent pressure-sensitive adhesive layer, in the same manner as in Example 1 except that the light-diffusing pressure-sensitive adhesive composition (A-8) obtained in Production Example 8 was used and the thickness of the obtained pressure-sensitive adhesive layer was 50 μm. Was prepared. Two identical products were produced.

(Production of the second layer (light diffusion adhesive layer))
Release treatment of a 38 μm-thick polyester film (trade name: Diafoil MRF, manufactured by Mitsubishi Plastics, Inc.) obtained by peeling one side of the light diffusion pressure-sensitive adhesive composition (A-7) obtained in Production Example 7 with silicone. The surface was coated so that the thickness of the obtained light diffusion pressure-sensitive adhesive layer was 23 μm to form a coating layer, and dried at 155 ° C. for 1 minute to form a light diffusion pressure-sensitive adhesive layer.

  One of the release sheets of the pressure-sensitive adhesive layer for the transparent pressure-sensitive adhesive layer obtained above is peeled off, and a transparent pressure-sensitive adhesive layer is attached to both sides of the light diffusion pressure-sensitive adhesive layer obtained above, and a pressure-sensitive adhesive layer for an optical member. Was formed.

Example 14
A pressure-sensitive adhesive sheet was produced in the same manner as in Example 13, except that the light-diffusing pressure-sensitive adhesive composition to be used and the thickness after drying were changed as shown in Table 2.

Example 15
(Production of the second layer (light diffusion adhesive layer))
Peeling treatment of a 38 μm-thick polyester film (trade name: Diafoil MRF, manufactured by Mitsubishi Plastics, Inc.) obtained by peeling one side of the light diffusion pressure-sensitive adhesive composition (A-10) obtained in Production Example 10 with silicone. The surface was coated so that the thickness of the obtained light diffusion pressure-sensitive adhesive layer was 23 μm to form a coating layer. Next, a 38 μm-thick polyester film (trade name: Diafoil MRE, manufactured by Mitsubishi Plastics, Inc.), one surface of which was peeled off with silicone, was coated on the surface of the formed coating layer. And coated. Thereby, the coating layer of the light diffusion pressure-sensitive adhesive composition was shielded from oxygen. Ultraviolet light of 100 mW / cm ² (measured by Topcon UVR-T1 having a maximum sensitivity at about 350 nm) using a chemical light lamp (manufactured by Toshiba Corporation) on the sheet having the coating layer thus obtained. Irradiation was performed for 30 seconds to cure the coating layer to form a light diffusion pressure-sensitive adhesive layer, thereby producing a pressure-sensitive adhesive sheet. The polyester film coated on both sides of the pressure-sensitive adhesive layer functions as a release liner.

  A pressure-sensitive adhesive sheet was prepared in the same manner as in Example 13, except that the pressure-sensitive adhesive layer was used as the second layer (light diffusion pressure-sensitive adhesive layer).

Examples 16 and 17, Comparative Examples 4 and 5
A pressure-sensitive adhesive sheet was produced in the same manner as in Example 15, except that the light-diffusing pressure-sensitive adhesive composition used and the thickness were changed as shown in Table 2.

  The pressure-sensitive adhesive layers obtained in Examples and Comparative Examples were evaluated as follows. The evaluation results are shown in Table 2.

<Refractive index of base pressure-sensitive adhesive composition>
It was measured by Abbe refractometer (trade name: DR-M2, manufactured by Atago Co., Ltd.).

<Haze value>
The haze value of each light diffusion pressure-sensitive adhesive layer used in Examples and Comparative Examples, the haze value of the transparent pressure-sensitive adhesive layer, and the total haze value of the pressure-sensitive adhesive layers obtained in Examples and Comparative Examples were determined by a haze meter according to the method specified in JIS 7136. (Consumption name: HN-150, manufactured by Murakami Color Science Laboratory Co., Ltd.).

<Lamination>
A polarizing film was prepared, in which a brightness enhancement film (trade name: DBEF-Q, manufactured by 3M) was bonded onto a polarizing film (trade name: CVT, manufactured by Nitto Denko Corporation). One of the release films of the pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples was peeled off and bonded to the brightness enhancement film side of the polarizing film. Further, the other release film of the pressure-sensitive adhesive sheet was peeled off, bonded to a prism sheet having irregularities of 50 μm or 5 μm with a hand roller, and subjected to an autoclave treatment at 50 ° C. and 5 atm for 15 minutes. The state after bonding was visually checked and evaluated according to the following evaluation criteria.
：: Even when a prism sheet having irregularities of 50 μm was used, bonding was possible without generating bubbles of 200 μm or more.
：: When a prism sheet having 50 μm irregularities is used, bubbles of 200 μm or more may be generated. However, when a prism sheet having 5 μm irregularities is used, bubbles of 200 μm or more are not generated. I was able to stick them together.
×: Even when a prism sheet having irregularities of 5 μm was used, bonding was not possible without generating bubbles of 200 μm or more.

<Display unevenness>
The adhesive sheet obtained in each of the examples and the comparative examples, on which the polarizing film was bonded, was cut into a size of 400 mm long × 250 mm wide to obtain a sample. This sample was bonded to a non-alkali glass plate having a thickness of 0.07 mm with a laminator, and a polarizing plate with a transparent pressure-sensitive adhesive layer was bonded to the opposite surface so as to be in a crossed Nicol state. An autoclave treatment was performed to prepare an evaluation sample. Then, it was placed on a 10,000 candela backlight, light leakage was visually observed, and corner unevenness was evaluated based on the following criteria.
◎: No unevenness, no problem in practical use. ：: Non-uniformity occurred and slightly appeared in the display area, but no practical problem.
C: Unevenness is noticeable in the display area due to occurrence of a problem, and there is a problem in practical use.

<Durability>
Glass / Polarizing film (trade name: CVT, manufactured by Nitto Denko Corporation) / Brightness improving film (trade name: DBEF-Q, manufactured by 3M) / Adhesive layer / prism sheet obtained in Examples and Comparative Examples 80 ° C, 60 ° C / 90% R. H. The condition after 240 hours in the environment of the above was visually observed. Evaluation was made according to the following evaluation criteria.
〇: No foaming exceeding 100 μm and no peeling occurred.
×: Foaming exceeding 100 μm, peeling occurred.

<Workability>
The pressure-sensitive adhesive layers obtained in Examples and Comparative Examples with a separator were punched out with a punching blade having a size of 10 cm × 20 cm. The state at the time of punching was visually checked and evaluated according to the following evaluation criteria.
：: Punching could be performed without any problem.
X: The sample adhered to the blade and could not be punched.

DESCRIPTION OF SYMBOLS 1 Adhesive layer for optical members 2 Light-diffusion adhesive layer 3 Transparent adhesive layer 4 Separator 10 Polarizing film 11 Polarizer 12 Protective film 20 Prism sheet 21 Prism part 22 Substrate

Claims (10)

(Meth) formed from a base adhesive composition and the light diffusing fine particles containing an acrylic polymer, a light diffusing adhesive layer has a thickness of 5~300μm and at least So含no optical member for the pressure-sensitive adhesive layer ,
At least one surface of the light diffusion pressure-sensitive adhesive layer has a transparent pressure-sensitive adhesive layer having a haze of 0.01 to 5%,
The thickness of the light diffusion pressure-sensitive adhesive layer is 5 to 30 μm,
The thickness of the transparent pressure-sensitive adhesive layer is 50 to 300 μm,
The thickness of the entire pressure-sensitive adhesive layer is 20 μm or more,
An adhesive layer for an optical member, wherein the haze is 10 to 96%.   The pressure-sensitive adhesive layer according to claim 1, wherein the light diffusing fine particles are silicone resin fine particles.   The pressure-sensitive adhesive layer for an optical member according to claim 1, wherein a refractive index of the light diffusing fine particles is lower than a refractive index of the base pressure-sensitive adhesive composition.   The pressure-sensitive adhesive layer according to any one of claims 1 to 3, wherein the light-diffusing fine particles have a volume average particle diameter of 1 to 5 µm. The pressure-sensitive adhesive layer for an optical member according to any one of claims 1 to 4 , wherein the content of the light-diffusing fine particles in the light-diffusing pressure-sensitive adhesive layer is 3 to 30% by weight. The pressure-sensitive adhesive layer for an optical member according to any one of claims 1 to 5 , wherein the (meth) acrylic polymer contains an alkyl (meth) acrylate and a carboxyl group-containing monomer as monomer components. The transparent adhesive layer contains a (meth) acrylic polymer containing an alkyl (meth) acrylate, a hydroxyl-containing monomer and a nitrogen-containing monomer as a monomer component, according to any one of claims 1 to 6 , wherein Adhesive layer for optical members. The pressure-sensitive adhesive layer according to claim 7 , wherein the (meth) acrylic polymer contained in the transparent pressure-sensitive adhesive layer does not contain a carboxyl group-containing monomer as a monomer component. An optical member with an adhesive layer, comprising at least one optical member adhesive layer according to any one of claims 1 to 8 on at least one surface of the optical member. An image display device comprising the optical member with an adhesive layer according to claim 9 .

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