TWI498400B - A light diffusion adhesive and a polarizing plate and an optical member using the light diffusion adhesive - Google Patents

Description

Light diffusing adhesive and polarizing plate and optical member using the same

This invention relates to a light diffusing adhesive. More specifically, the present invention relates to a light diffusing adhesive comprising a monomer unit containing an aromatic ring-containing (meth)acrylic monomer as a base polymer. Further, the present invention relates to a polarizing plate and an optical member using such a light diffusing adhesive.

The backlight unit of the liquid crystal display device includes a diffusion sheet for suppressing streaks (streaking) generated at the time of overlapping of regular structures, dot patterns of the light guide plate, and color spots of the liquid crystal panel to improve visibility. However, when it is not possible to ensure sufficient visibility by using the diffusion sheet, a light-diffusing adhesive can be used as the adhesive layer of the polarizing plate. The light diffusing adhesive is imparted with a light diffusing function by adding light diffusing fine particles to the adhesive. The light-diffusing adhesive exhibits a light diffusing function (typically haze) by a difference in refractive index between the adhesive and the light-diffusing fine particles. In many cases, an acrylic adhesive is used as an adhesive in a light-diffusing adhesive, and polyoxyphthalate fine particles are used as light-diffusing fine particles. However, an image display device using a light-diffusing adhesive containing an acrylic adhesive has a problem that corner unevenness occurs in a high-temperature environment and visibility is insufficient.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2012-503077

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2008-144125

The present invention has been made in order to solve the above-mentioned problems, and an object thereof is to provide a light-diffusing adhesive which can realize an image display device which does not cause unevenness in a high-temperature environment and which has excellent visibility.

The light diffusing adhesive of the present invention comprises: an adhesive comprising a base polymer containing a (meth)acrylic polymer; and a light diffusing fine particle having a refractive index lower than the adhesive; and the (methyl The acrylic polymer contains a (meth)acrylic monomer containing an aromatic ring as a monomer unit.

In one embodiment, the aromatic ring-containing (meth)acrylic monomer comprises benzyl (meth)acrylate.

In one embodiment, the content of the aromatic ring-containing (meth)acrylic monomer in the base polymer is from 1% by weight to 35% by weight.

In one embodiment, the (meth)acrylic polymer further contains at least one selected from the group consisting of alkyl (meth)acrylate, carboxyl group-containing monomer, and hydroxyl group-containing monomer as a monomer unit.

In one embodiment, the adhesive has a refractive index of 1.47 or more.

In one embodiment, the light diffusing fine particles are polyoxynized resin fine particles.

In one embodiment, the light-diffusing fine particles have a volume average particle diameter of from 1 μm to 4 μm.

In one embodiment, the haze value of the light-diffusing adhesive after curing is 20% to 95%.

According to another aspect of the present invention, a polarizing plate is provided. The polarizing plate includes a polarizing element, a protective layer, and a light diffusing adhesive layer formed of the light diffusing adhesive.

According to still another aspect of the present invention, an optical member is provided. The optical member includes the polarizing plate and a light diffusing adhesive layer passing through the polarizing plate to be bonded to the polarized light Reflective polarizing element of the board.

In one embodiment, the optical member further includes a gusset on a side of the reflective polarizing element opposite to the light diffusing adhesive layer.

According to the present invention, by using a monomer unit of a base polymer containing an aromatic ring-containing (meth)acrylic monomer as a binder in a light-diffusing adhesive, it is possible to suppress a phase difference change in a high-temperature environment and suppress haze. A light diffusing adhesive with varying values. As a result, a light-diffusing adhesive which can realize an image display device which does not cause unevenness in a high-temperature environment and which has excellent visibility can be obtained. Further, the light-diffusing adhesive of the present invention can increase the refractive index difference between the adhesive and the light-diffusing fine particles by using a monomer unit containing a (meth)acrylic monomer containing an aromatic ring as a base polymer of the adhesive. Therefore, even if the thickness is thin, a light-diffusing adhesive layer having a high haze can be formed.

10‧‧‧Polar plate

11‧‧‧Polarized components

12‧‧‧Protective layer

13‧‧‧Protective layer

14‧‧‧Light diffusing adhesive layer

20‧‧‧Reflective polarizing element

30‧‧‧ Picture

31‧‧‧Parts

32‧‧‧稜鏡

33‧‧‧Units

100‧‧‧Optical components

Fig. 1 is a schematic cross-sectional view showing a polarizing plate according to an embodiment of the present invention.

Fig. 2 is a schematic cross-sectional view showing an optical member according to an embodiment of the present invention.

Fig. 3 is a schematic perspective view showing an example of a reflective polarizing element which can be used in the optical member of the present invention.

4 is an exploded perspective view of the optical member of FIG. 2.

Fig. 5 is a photographic image showing a state in which the corners of Example 1 and Comparative Example 1 are compared.

Hereinafter, preferred embodiments of the present invention will be described, and the present invention is not limited to the embodiments.

A. Summary of light diffusion adhesive

The light diffusing adhesive of the embodiment of the present invention comprises an adhesive and is dispersed in the adhesive Light diffusing fine particles in the agent. The base polymer of the adhesive comprises a (meth)acrylic polymer. The (meth)acrylic polymer contains a (meth)acrylic monomer containing an aromatic ring as a monomer unit. The light diffusing fine particles have a refractive index lower than that of the adhesive. Hereinafter, each constituent component of the light-diffusing adhesive will be described in detail.

A-1. Adhesive A-1-1. Base polymer

As described above, the adhesive contains the (meth)acrylic polymer (A) as a base polymer. The (meth)acrylic polymer (A) contains an alkyl (meth)acrylate (a1) constituting the main skeleton of the (meth)acrylic polymer (A) and a (meth)acrylic acid group containing an aromatic ring. The monomer (a2) is used as a monomer unit. As the aromatic ring-containing (meth)acrylic monomer (a2), for example, benzyl (meth)acrylate can be used. The aromatic ring-containing (meth)acrylic monomer has a positive intrinsic birefringence, and thus is bonded to an alkyl (meth)acrylate having a negative intrinsic birefringence (and optionally other (meth)acrylates) When used in combination, the following effects can be obtained: when the light-diffusing adhesive is used in an image display device, stress is applied to the light-diffusing adhesive due to shrinkage of the polarizing element in a high-temperature environment. In this case, the (meth)acrylic monomer unit having an aromatic ring having positive intrinsic birefringence and the alkyl (meth)acrylate having negative intrinsic birefringence are contained in the light diffusing adhesive ( And other (meth) acrylate monomer units as needed, the birefringence of the monomer units generated by the stress can be eliminated by stress. As a result, it is possible to realize an image display device which is excellent in visibility by suppressing a change in phase difference of a light-diffusing adhesive, suppressing a change in a haze value, and finally suppressing generation of a corner unevenness in a high-temperature environment. Further, when a specific amount of an aromatic ring-containing (meth)acrylic monomer is used together with the following carboxyl group-containing monomer (a3) and a hydroxyl group-containing monomer (a4), it is possible to obtain a desired one. Adhesive of refractive index. Further, (meth) acrylate means acrylate and/or methacrylate.

The alkyl (meth)acrylate (a1) may, for example, be a linear or branched alkyl group having 1 to 18 carbon atoms. For example, as the above alkyl group, a methyl group, an ethyl group, a propyl group, etc. Isopropyl, butyl, isobutyl, pentyl, hexyl, cyclohexyl, heptyl 2-ethylhexyl, isooctyl, decyl, decyl, isodecyl, dodecyl, isotetradecane Base, lauryl, tridecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl and the like. These may be used singly or in combination. The average carbon number of the alkyl groups is preferably from 3 to 9.

The base polymer may further comprise a carboxyl group-containing monomer (a3) and/or a hydroxyl group-containing monomer (a4) as a monomer unit. When the adhesive composition has a crosslinking agent, the carboxyl group-containing monomer (a3) and the hydroxyl group-containing monomer (a4) are sufficiently reactive with the crosslinking agent, so that the light diffusion adhesion after curing is enhanced. The cohesiveness or heat resistance of the agent layer can be preferably used. Further, in terms of both durability and secondary workability, a carboxyl group-containing monomer (a3) is preferred, and a hydroxyl group-containing monomer (a4) is preferred in terms of secondary workability. .

The carboxyl group-containing monomer (a3) is a compound containing a carboxyl group in its structure and containing a polymerizable unsaturated double bond such as a (meth)acryl fluorenyl group or a vinyl group. Specific examples of the carboxyl group-containing monomer (a3) include (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, and maleic acid. Fumaric acid, crotonic acid, etc. Among the carboxyl group-containing monomers (a3), acrylic acid is preferred from the viewpoint of copolymerizability, price, and adhesion characteristics.

The hydroxyl group-containing monomer (a4) is a compound containing a hydroxyl group in its structure and containing a polymerizable unsaturated double bond such as a (meth)acryl fluorenyl group or a vinyl group. Specific examples of the hydroxyl group-containing monomer (a4) include 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate. 6-hydroxyhexyl methacrylate, 8-hydroxyoctyl (meth) acrylate, 10-hydroxy decyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate or acrylic acid (4-hydroxymethyl) Cyclohexyl)-methyl ester and the like. In the above hydroxyl group-containing monomer (a4), 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and preferably (methyl) are preferable in terms of durability. ) 4-hydroxybutyl acrylate.

The base polymer contains a specific amount of each of the above monomers as a monomer unit in a weight ratio of the total constituent monomers (100% by weight). Weight ratio of alkyl (meth)acrylate (a1) The remainder of the monomer other than the alkyl (meth) acrylate (a1) may be specifically, 52% by weight to 96.99% by weight, preferably 67% by weight to 96.99% by weight, more preferably 71. Weight%~89.99% by weight. The weight ratio of the (meth)acrylic monomer containing an aromatic ring is preferably from 1% by weight to 35% by weight, more preferably from 1% by weight to 20% by weight, still more preferably from 7% by weight to 18% by weight. When the content of the (meth)acrylic monomer containing an aromatic ring is in the above range, the birefringence generated by the monomer units can be favorably eliminated by the stress caused by the shrinkage of the polarizing element in a high temperature environment. As a result, it is possible to realize an image display device which is capable of suppressing a change in the phase difference of the light-diffusing adhesive, suppressing a change in the haze value, and finally suppressing the occurrence of corner unevenness in a high-temperature environment, and having more excellent visibility. The weight ratio of the carboxyl group-containing monomer (a3) is preferably 2% by weight to 10% by weight, more preferably 3% by weight to 10% by weight, still more preferably 4% by weight to 6% by weight. The weight ratio of the hydroxyl group-containing monomer (a4) is preferably from 0.01% by weight to 3% by weight, more preferably from 0.01% by weight to 1% by weight, still more preferably from 0.03% by weight to 0.5% by weight. If the weight ratio of the hydroxyl group-containing monomer (a4) is less than 0.01% by weight, the durability may not be satisfied.

In the base polymer, in addition to the above monomer unit, in order to improve adhesion or heat resistance, a polymerizable functional group containing an unsaturated double bond such as a (meth)acryl fluorenyl group or a vinyl group may be introduced by copolymerization. One or more kinds of copolymerized monomers of the group. In the case where the adhesive composition contains a crosslinking agent, the copolymerized monomers become a reaction point with the crosslinking agent.

Specific examples of such a copolymerizable monomer include an acid anhydride group-containing monomer such as maleic anhydride or itaconic anhydride; a caprolactone adduct of acrylic acid; allylsulfonic acid and 2-(A) a sulfonic acid group-containing monomer such as acrylamide-2-methylpropanesulfonic acid, (meth)acrylamide, propanesulfonic acid or sulfopropyl (meth)acrylate; 2-hydroxyethylpropene oxime A phosphate group-containing monomer or the like.

Further, examples of the monomer for the purpose of reforming include (meth)acrylamide, N,N-dimethyl(meth)acrylamide, and N-butyl(meth)acrylonitrile. a (N-substituted) guanamine monomer such as an amine, N-methylol (meth) acrylamide or N-methylolpropane (meth) acrylamide; an aminoethyl (meth) acrylate; (A) alkylaminoalkyl (meth) acrylate such as N,N-dimethylaminoethyl (meth)acrylate or tert-butylaminoethyl (meth)acrylate; An alkoxyalkyl (meth) acrylate monomer such as methoxyethyl acrylate or ethoxyethyl (meth) acrylate; N-(methyl) propylene decyloxymethylene amber Amine or N-(methyl)propenylfluorenyl-6-oxyhexamethylene succinimide, N-(methyl)propenyl-8-oxyoctamethylene succinimide, N- Acrylate Amber quinone imine monomer such as porphyrin; N-cyclohexyl maleimide or N-isopropyl maleimide, N-lauryl maleimide or N-benzene a maleimide monomer such as cis-butenylene imine; N-methyl itaconimine, N-ethyl itaconimine, N-butyl itaconimine, N-octyl ketamine, N-2-ethylhexyl ketimine, N-cyclohexyl ketimine, N-lauryl ketimine, etc. Body and so on.

As a monomer to be further modified, a vinyl monomer such as vinyl acetate, vinyl propionate or N-vinyl caprolactam; a cyanoacrylate monomer such as acrylonitrile or methacrylonitrile may be used. ; an epoxy group-containing acrylic monomer such as glycidyl (meth)acrylate; polyethylene glycol (meth) acrylate, polypropylene glycol (meth) acrylate, ethylene glycol (meth) methacrylate a glycol-based acrylate monomer such as a base ester or a polypropylene glycol (meth)acrylic acid methacrylate; tetrahydrofurfuryl (meth)acrylate, fluorine (meth)acrylate, or polyoxy(oxy) (meth)acrylate Or an acrylate monomer such as 2-methoxyethyl acrylate or the like. Further, examples thereof include isoprene, butadiene, isobutylene, and vinyl ether.

Further, examples of the copolymerizable monomer other than the above include a decane-based monomer containing a ruthenium atom. Examples of the decane-based monomer include 3-propenyloxypropyltriethoxydecane, vinyltrimethoxydecane, vinyltriethoxydecane, and 4-vinylbutyltrimethoxydecane. 4-vinylbutyltriethoxydecane, 8-vinyloctyltrimethoxydecane, 8-vinyloctyltriethoxydecane, 10-methylpropenyloxydecyltrimethoxydecane, 10-propenylmethoxydecyltrimethoxydecane, 10-methylpropenyloxydecyltriethoxydecane, 10-propylenedecyloxydecyltriethoxydecane, and the like.

Further, as the copolymerizable monomer, tripropylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, or a double may be used. Phenol A diglycidyl ether di(meth)acrylate, neopentyl glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol IV (Meth)acrylic acid ester, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, caprolactone-modified dipentaerythritol hexa (meth) acrylate, etc. a polyfunctional monomer having two or more (meth)acrylonyl groups or an unsaturated double bond such as a vinyl group, such as an ester of a polyhydric alcohol; or a skeleton such as a polyester, an epoxy or a urethane; A polyester (meth) acrylate, an epoxy (meth) acrylate, or a (meth) acrylate having two or more unsaturated groups such as a (meth) acryl fluorenyl group or a vinyl group, and a functional group having the same monomer component Acrylic urethane and the like.

The base polymer generally uses a weight average molecular weight of 1.6 million or more. In consideration of durability, particularly heat resistance, it is preferred to use a weight average molecular weight of 1.7 to 3,000,000. Further preferably, it is 1.8 million to 2.8 million, and more preferably 1.9 to 2.5 million. If the weight average molecular weight is less than 1.6 million, heat resistance may be insufficient. Further, when the weight average molecular weight is more than 3,000,000, the durability may be insufficient. Further, the weight average molecular weight (Mw) / number average molecular weight (Mn) of the molecular weight distribution is 1.8 or more and 10 or less, preferably 2 to 7, and more preferably 2 to 5. When the molecular weight distribution (Mw/Mn) exceeds 10, there is a case where the durability is insufficient. In addition, the weight average molecular weight and the molecular weight distribution (Mw/Mn) were measured by GPC (Gel Permeation Chromatography) and calculated based on the value calculated from polystyrene conversion.

The glass transition temperature of the base polymer is preferably from -60 ° C to -10 ° C, more preferably from -55 ° C to -15 ° C. Appropriate adhesion can be obtained by using a base polymer having the above characteristics.

The base polymer can be obtained by appropriately combining the above monomers and performing polymerization according to the purpose or desired characteristics as long as the effects of the present invention are obtained. In more detail, the basic gathering The compound can be imparted by imparting an adhesive monomer (for example, alkyl (meth) acrylate (a1)), a coagulating comonomer, and a functional group-containing monomer which imparts adhesion and becomes a crosslinking point. (For example, a carboxyl group-containing monomer (a3) and a hydroxyl group-containing monomer (a4)) are obtained by copolymerization. The base polymer obtained may be any of a random copolymer, a block copolymer, and a graft copolymer. The base polymer can be synthesized by any appropriate method. For example, it can be synthesized by referring to the publication of Nakagawa Yoshihiko, "The Chemistry and Application of Adhesive".

As the polymerization method of the base polymer, any appropriate method can be employed. Specific examples include solution polymerization, bulk polymerization, emulsion polymerization, and various radical polymerizations. For example, in the case of using solution polymerization, as the polymerization solvent, for example, ethyl acetate or toluene can be used. Specifically, the solution polymerization is carried out by adding a polymerization initiator to a solution containing a monomer mixture under a flow of an inert gas such as nitrogen, and is carried out under the reaction conditions of usually about 50 to 70 ° C for about 5 to 30 hours.

As the polymerization initiator in the polymerization of the base polymer, any appropriate polymerization initiator can be employed. The weight average molecular weight of the obtained base polymer can be controlled by adjusting the amount of the polymerization initiator.

Examples of the polymerization initiator include 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-amidinopropane) dihydrochloride, and 2,2'-azobis. [2-(5-Methyl-2-imidazolin-2-yl)propane] dihydrochloride, 2,2'-azobis(2-methylpropionamidine) disulfate, 2,2'- Azobis(N,N'-dimethyleneisobutylphosphonium), 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine] hydrate (and pure light) Anthraquinone initiators such as 薬-, VA-057); persulfate such as potassium persulfate or ammonium persulfate; di(2-ethylhexyl) peroxydicarbonate and di-dicarbonate Tertiary butylcyclohexyl) ester, dibutyl phthalate dihydrate, tert-butyl peroxy neodecanoate, third hexyl peroxypivalate, tert-butyl peroxypivalate Oxidized dilaurin, di-n-octyl peroxide, 1,1,3,3-tetramethylbutyl peroxy 2-ethylhexanoate, bis(4-methylbenzhydryl) peroxide, peroxide a benzamidine, a third butyl peroxybutyrate, a 1,1-di(trihexylperoxy)cyclohexane, a third butyl hydroperoxide, a peroxide such as hydrogen peroxide An initiator, a combination of a persulfate and a sodium hydrogen sulfite, a combination of a peroxide and sodium ascorbate, and the like, a redox initiator of a peroxide and a reducing agent. The polymerization initiator may be used singly or in combination of two or more.

The amount of the polymerization initiator to be used is preferably from about 0.005 parts by weight to about 1 part by weight, more preferably from about 0.02 part by weight to about 0.5 part by weight, per 100 parts by weight of the monomer. For example, when 2,2'-azobisisobutyronitrile is used as the polymerization initiator, the amount thereof is preferably from about 0.06 parts by weight to about 0.2 parts by weight, more preferably from about 0.08 parts by weight to about 0.175 parts by weight.

A-1-2. Crosslinker

The adhesive may also contain a crosslinking agent. Examples of the crosslinking agent include an organic crosslinking agent and a polyfunctional metal chelate compound. Examples of the organic crosslinking agent include an isocyanate crosslinking agent, a peroxide crosslinking agent, an epoxy crosslinking agent, and an imide crosslinking agent. Polyfunctional metal chelates are those in which a polyvalent metal is covalently bonded or coordinated to 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. Examples of the organic compound include an alkyl ester, an alcohol compound, a carboxylic acid compound, an ether compound, and a ketone compound. Examples of the atom in the organic compound to carry out the covalent bonding or the coordinate bonding include an oxygen atom. The crosslinking agent is preferably an isocyanate crosslinking agent, an epoxy crosslinking agent or a peroxide crosslinking agent.

The isocyanate crosslinking agent is a compound having two or more isocyanate groups in one molecule. Examples thereof include isocyanate monomers such as toluene diisocyanate, chlorophenyl diisocyanate, tetramethylene diisocyanate, benzodimethyl diisocyanate, diphenylmethane diisocyanate, and hydrogenated diphenylmethane diisocyanate, and An isocyanate compound, an isocyanurate compound, a biuret type compound obtained by adding such an isocyanate monomer to trimethylolpropane or the like; and further, a polyether polyol, a polyester polyol, an acrylic polyol, A urethane prepolymer type isocyanate obtained by an addition reaction such as a polybutadiene polyol or a polyisoprene polyol. Particularly preferred is a polyisocyanate compound, ie, One of the group consisting of hexamethylene diisocyanate, hydrogenated dimethyl diisocyanate, and isophorone diisocyanate or a polyisocyanate compound derived therefrom may be selected. Here, the hexagonal armor is contained in one or a polyisocyanate compound selected from the group consisting of hexamethylene diisocyanate, hydrogenated dimethyl diisocyanate, and isophorone diisocyanate. Diisocyanate, hydrogenated dimethyl diisocyanate, isophorone diisocyanate, polyol modified hexamethylene diisocyanate, polyhydric alcohol modified hydrogenated dimethyl diisocyanate, trimerization The form-type hydrogenated dimethyl dimethyl diisocyanate, and the polyol-modified isophorone diisocyanate. The polyisocyanate compound exemplified is preferably reacted with a hydroxyl group rapidly, in particular, by using an acid or a base contained in the polymer as a catalyst, and thus is particularly advantageous in the speed of crosslinking.

The epoxy-based crosslinking agent is a compound having two or more epoxy groups (glycidyl groups) in one molecule. Examples of the epoxy-based crosslinking agent include ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, diglycidyl terephthalate, spirodiol diglycidyl ether, and diglycidylaminomethyl. Cyclohexane, tetraglycidylbenzenediamine, polyglycidyl metaxylyleneamine, and the like.

As the peroxide, any suitable compound which can form a radical active species by heating or light irradiation to carry out crosslinking of the base polymer can be used. In view of workability and stability, a peroxide having a half-life temperature of 80 ° C to 160 ° C for 1 minute is preferable, and a peroxide having a half-life temperature of 90 ° C to 140 ° C for 1 minute is more preferable. Specific examples of the peroxide include di(2-ethylhexyl)peroxydicarbonate (1 minute half-life temperature: 90.6 ° C), and di(4-tert-butylcyclohexyl)peroxycarbonate. Ester (1 minute half-life temperature: 92.1 ° C), dibutyl phthalate dihydrate (1 minute half-life temperature: 92.4 ° C), peroxy neodecanoic acid tert-butyl ester (1 minute half-life temperature: 103.5 ° C ), perhexyl peroxypivalate (1 minute half-life temperature: 109.1 ° C), perbutyl pivalate peroxylate (1 minute half-life temperature: 110.3 ° C), dilaurin peroxide (1 minute) Half-life temperature: 116.4 ° C), di-n-octogen peroxide (1 minute half-life temperature: 117.4 ° C), peroxide (2- Ethylhexanoic acid) 1,1,3,3-tetramethylbutyl ester (1 minute half-life temperature: 124.3 ° C), bis(4-methylbenzhydryl) peroxide (1 minute half-life temperature: 128.2 ° C) ), benzoyl peroxide (1 minute half-life temperature: 130.0 ° C), isobutyl isobutyrate (1 minute half-life temperature: 136.1 ° C), 1, 1-two (third hexyl peroxide) Cyclohexane (1 minute half-life temperature: 149.2 ° C) and the like. Among them, in particular, in terms of excellent crosslinking reaction efficiency, di(4-tert-butylcyclohexyl)peroxydicarbonate (1 minute half-life temperature: 92.1 ° C) and dilauric peroxide can be preferably used.醯 (1 minute half-life temperature: 116.4 ° C), benzoquinone peroxide (1 minute half-life temperature: 130.0 ° C) and the like. In addition, the half-life of a peroxide is an indicator which shows the decomposition rate of a peroxide, and is a time which the residual amount of peroxide turns into half. Therefore, the 1-minute half-life temperature of a peroxide means a temperature at which the residual amount of the peroxide becomes half in 1 minute. The decomposition temperature for obtaining the half-life at any time or the half-life time at any temperature is described in the Maker catalog, for example, in the Organic Peroxide Catalogue No. 9 of Nippon Oil & Fat Co., Ltd. Edition (May 2003) and so on.

The crosslinking agent is preferably used in an amount of from 0.01 part by weight to 20 parts by weight, more preferably from 0.03 part by weight to 10 parts by weight, per 100 parts by weight of the base polymer. When the amount of the crosslinking agent used is less than 0.01 part by weight, the cohesive force of the adhesive tends to be insufficient, and there is a possibility that foaming occurs upon heating. When the amount of the crosslinking agent used exceeds 20 parts by weight, the moisture resistance is insufficient, and peeling or the like is likely to occur.

As the crosslinking agent, as described above, an isocyanate crosslinking agent, a peroxide crosslinking agent, and an epoxy crosslinking agent are preferable. The reason for this is that the coating liquid has excellent pot life, adhesion characteristics, durability, and crosslinking stability. It is especially preferred to use an isocyanate crosslinking agent and a peroxide crosslinking agent in combination. The reason for this is that it is easy to obtain a balance of adhesion characteristics, durability, and crosslinking stability.

A-1-3. Additives

The adhesive may also contain any suitable additives. As an additive, for example, Antistatic agent, antioxidant, coupling agent. The type, amount, and combination of the additives may be appropriately set as needed.

A-1-4. The whole of the adhesive

The content of the adhesive in the light-diffusing adhesive is preferably from 50% by weight to 99.7% by weight, more preferably from 52% by weight to 97% by weight.

The refractive index of the adhesive is preferably 1.47 or more, more preferably 1.47 to 1.60, and still more preferably 1.47 to 1.55. When the refractive index of the adhesive is in the above range, the difference in refractive index from the light diffusing fine particles can be set to a desired range. As a result, a light-diffusing adhesive having a desired haze value after hardening can be obtained. Further, by combining with light-diffusing fine particles having a desired volume average particle diameter (described later), a light-diffusing adhesive having a desired haze value and having a neutral hue can be obtained.

A-2. Light diffusing fine particles

As the light diffusing fine particles, any appropriate one can be used as long as the effects of the present invention are obtained. Specific examples include inorganic fine particles and polymer fine particles. The light diffusing fine particles are preferably polymer fine particles. Examples of the material of the polymer fine particles include a polyoxyn resin, a methacrylic resin (for example, polymethyl methacrylate), a polystyrene resin, a polyurethane resin, and a melamine resin. These resins have excellent dispersibility with respect to the adhesive and an appropriate refractive index difference with the adhesive, and thus a light-diffusing adhesive layer excellent in diffusing performance can be obtained. Preferred are polyoxynoxy resins and polymethyl methacrylate. The shape of the light diffusing fine particles is, for example, a spherical shape, a flat shape, or an indefinite shape. The light-diffusing fine particles may be used singly or in combination of two or more.

As described above, the refractive index of the light diffusing fine particles is lower than the refractive index of the adhesive. 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. When the refractive index of the light-diffusing fine particles is in the above range, the difference in refractive index from the adhesive can be set to a desired range. As a result, a light-diffusing adhesive having a desired haze value after hardening can be obtained.

The absolute value of the refractive index difference between the light-diffusing fine particles and the adhesive is preferably more than 0 and not more than 0.2, more preferably more than 0 and not more than 0.15, still more preferably from 0.01 to 0.13.

The volume average particle diameter of the light diffusing fine particles is preferably from 1 μm to 4 μm, more preferably from 2 μm to 4 μm, still more preferably about 3 μm. When the volume average particle diameter of the light-diffusing fine particles is in the above range, a light-diffusing adhesive having a desired haze value and having a neutral hue can be obtained by combining with an adhesive having the above-mentioned desired refractive index. Further, the volume average particle diameter can be measured, for example, using an ultracentrifugal automatic particle size distribution measuring apparatus.

The content of the light diffusing fine particles in the light diffusing adhesive is preferably from 0.3% by weight to 50% by weight, more preferably from 3% by weight to 48% by weight. By setting the amount of the light-diffusing fine particles to the above range, a light-diffusing adhesive layer having excellent light diffusing properties can be obtained.

A-3. Characteristics of light diffusing adhesive

The haze value of the light-diffusing adhesive after hardening is preferably from 10% to 99%, more preferably from 20% to 95%. By setting the haze value to the above range, the desired diffusion performance can be obtained, and generation of embossing and glare can be satisfactorily suppressed. The light diffusing property of the light-diffusing adhesive can be controlled by adjusting the constituent material of the substrate (adhesive), the constituent materials of the light-diffusing fine particles, the volume average particle diameter, the blending amount, and the like.

The total light transmittance of the light-diffusing adhesive is preferably 75% or more, more preferably 80% or more, and still more preferably 85% or more.

B. Polarizer

Fig. 1 is a schematic cross-sectional view showing a polarizing plate according to an embodiment of the present invention. The polarizing plate of this embodiment is a polarizing plate with a light-diffusing adhesive layer. The polarizing plate 10 includes a polarizing element 11 , a protective layer 12 disposed on one side of the polarizing element 11 , a protective layer 13 disposed on the other side of the polarizing element 11 , and a side opposite to the polarizing element 11 disposed on the protective layer 12 . The light-diffusing adhesive layer 14 formed of the light-diffusing adhesive described in the above item A. The thickness of the light-diffusing adhesive layer is, for example, 5 μm to 100 μm. One of the protective layers 12 and 13 may be omitted depending on the purpose or the configuration of the polarizing plate. As a representative, the polarizing element is an absorption type polarizing element. Make As a representative, the polarizing plate 10 can be used as a polarizing plate on the backlight side. Specifically, the polarizing plate 10 can be used, for example, by bonding the light-diffusing adhesive layer 14 to the substrate on the backlight side of the liquid crystal cell of the liquid crystal display device.

B-1. Polarizing element

The transmittance of the absorption type polarizing element at a wavelength of 589 nm (also referred to as a monomer transmittance) is preferably 41% or more, and more preferably 42% or more. Furthermore, the theoretical upper limit of the monomer transmittance is 50%. Further, the degree of polarization is preferably from 99.5% to 100%, more preferably from 99.9% to 100%. When it is in the above range, when used in a liquid crystal display device, the contrast in the front direction can be further improved.

The monomer transmittance and the degree of polarization can be measured using a spectrophotometer. As a specific measurement method of the above-described degree of polarization, the parallel transmittance (H ₀ ) and the orthogonal transmittance (H ₉₀ ) of the polarizing element can be measured according to the formula: degree of polarization (%) = {(H _{0 -} H ₉₀ ) /(H ₀ +H ₉₀ )} ^1/2 ×100 is obtained. The parallel transmittance (H ₀ ) is a value of a transmittance of a parallel type laminated polarizing element produced by superimposing two identical polarizing elements such that absorption axes are parallel to each other. Further, the orthogonal transmittance (H ₉₀ ) is a value of a transmittance of an orthogonal type laminated polarizing element produced by superimposing two identical polarizing elements such that absorption axes are orthogonal to each other. Further, the transmittances are Y values obtained by performing a visual sensitivity correction by a 2 degree field of view (C light source) of J1S Z 8701-1982.

As the above-mentioned absorption type polarizing element, any appropriate polarizing element can be used as needed. For example, a hydrophilic polymer such as a polyvinyl alcohol-based film, a partially formalized polyvinyl alcohol-based film, or an ethylene-vinyl acetate copolymer-based partially saponified film is adsorbed to a dichroic substance such as iodine or a dichroic dye. A uniaxially stretched film is formed on the film; a polyene-based alignment film such as a dehydrated material of polyvinyl alcohol or a dehydrochlorinated product of polyvinyl chloride. Further, it is also possible to use an E-type and O-type polarizing element of a guest-host type in which a liquid crystal composition containing a dichroic substance and a liquid crystalline compound is aligned in a fixed direction as disclosed in U.S. Patent No. 5,523,863; U.S. Patent No. 6,049,428 E-type and O, which are disclosed to align the liquid crystal to a fixed direction Type polarizing element, etc.

Among the above polarizing elements, a polarizing element using a polyvinyl alcohol (PVA) film containing iodine can be preferably used from the viewpoint of having a high degree of polarization. As the material of the polyvinyl alcohol-based film used for the polarizing element, polyvinyl alcohol or a derivative thereof can be used. Examples of the polyvinyl alcohol derivative include polyvinyl formal, polyvinyl acetal, and the like, and examples thereof include an olefin such as ethylene or propylene, and an unsaturated acid such as acrylic acid, methacrylic acid or crotonic acid. A modifier such as a carboxylic acid, or an alkyl ester thereof, or acrylamide. Usually, the polymerization degree of polyvinyl alcohol is about 1000 to 10,000 and the degree of saponification is about 80 mol% to 100 mol%.

The polyvinyl alcohol-based film (unstretched film) is subjected to at least uniaxial stretching treatment or iodine dyeing treatment according to a conventional method. Further, boric acid treatment or iodide treatment may be carried out. Further, the polyvinyl alcohol-based film (stretched film) subjected to the above treatment is dried by a conventional method to obtain a polarizing element.

The stretching method in the uniaxial stretching treatment is not particularly limited, and any of the wet stretching method and the dry stretching method may be employed. Examples of the extension means of the dry stretching method include a roll stretching method, a heating roll stretching method, a compression stretching method, and the like. The extension can also be carried out in multiple stages. In the above extension means, the unstretched film is usually brought into a heated state. The unstretched film is usually used in an amount of from about 30 μm to about 150 μm. The stretching ratio of the stretched film can be appropriately set as needed, and the stretching ratio (total stretching ratio) is about 2 times to 8 times, preferably 3 times to 6.5 times, and more preferably 3.5 times to 6 times. The thickness of the stretched film is preferably about 5 μm to 40 μm.

The iodine dyeing treatment is carried out by immersing a polyvinyl alcohol-based film in an iodine solution containing iodine and potassium iodide. The iodine solution is usually an aqueous iodine solution containing iodine and potassium iodide as a dissolution aid. The iodine concentration is preferably from about 0.01% by weight to about 1% by weight, more preferably from 0.02% by weight to 0.5% by weight, and the potassium iodide concentration is preferably from about 0.01% by weight to about 10% by weight, more preferably from 0.02% by weight to 8% by weight.

In the iodine dyeing treatment, the temperature of the iodine solution is usually from about 20 ° C to about 50 ° C, preferably from 25 ° C to 40 ° C. The immersion time is usually about 10 seconds to 300 seconds, preferably 20 seconds to 240 seconds. The scope. In the iodine dyeing treatment, the concentration of the iodine solution, the immersion temperature of the polyvinyl alcohol film in the iodine solution, the immersion time, and the like are adjusted, whereby the iodine content and the potassium content in the polyvinyl alcohol film are in a desired range. Make adjustments. The iodine dyeing treatment can be carried out at any stage before the uniaxial stretching treatment, during the uniaxial stretching treatment, or after the uniaxial stretching treatment.

The boric acid treatment is carried out by immersing the polyvinyl alcohol-based film in an aqueous boric acid solution. The boric acid concentration in the aqueous boric acid solution is about 2% by weight to 15% by weight, preferably 3% by weight to 10% by weight. In the aqueous boric acid solution, potassium ions and iodide ions may be contained by potassium iodide. The concentration of potassium iodide in the aqueous boric acid solution is preferably from about 0.5% by weight to about 10% by weight, and further preferably from 1% by weight to 8% by weight. A boric acid aqueous solution containing potassium iodide can obtain a polarizing element having less coloration, that is, a so-called neutral gray polarizing element having substantially constant absorbance throughout a substantially full wavelength region of visible light.

In the iodide ion treatment, for example, an aqueous solution containing iodide ions by potassium iodide or the like is used. The potassium iodide concentration is preferably from about 0.5% by weight to about 10% by weight, and further preferably from 1% by weight to 8% by weight. When the iodide ion is impregnated, the temperature of the aqueous solution is usually from about 15 ° C to about 60 ° C, preferably from 25 ° C to 40 ° C. The immersion time is usually from about 1 second to about 120 seconds, preferably from about 3 seconds to 90 seconds. The stage of the iodide ion treatment is not particularly limited as long as it is before the drying step. It can also be washed after the following water is washed.

The polyvinyl alcohol-based film (stretched film) subjected to the above treatment can be supplied to a water washing step and a drying step according to a conventional method.

The drying step may be carried out by any appropriate drying method such as natural drying, air drying, heat drying or the like. For example, in the case of heat drying, the drying temperature is, as a representative, 20 ° C to 80 ° C, preferably 25 ° C to 70 ° C, and the drying time is preferably about 1 minute to 10 minutes. Further, the moisture content of the polarizing element after drying is preferably from 10% by weight to 30% by weight, more preferably from 12% by weight to 28% by weight, still more preferably from 16% by weight to 25% by weight. When the moisture content is too large, when the polarizing plate is dried, the degree of polarization tends to decrease as the polarizing element is dried. Especially the orthogonal transmittance of short wavelength regions below 500 nm The increase, that is, the light of a short wavelength leaks, and thus the black display tends to be colored blue. On the other hand, if the moisture content of the polarizing element is too small, there is a problem that local unevenness defects (cracking defects) and the like are likely to occur.

As a representative, the polarizing plate 10 is provided in an elongated shape (for example, a roll shape) for the manufacture of an optical member. In one embodiment, the polarizing element has an absorption axis in the longitudinal direction. Such a polarizing element can be obtained by a manufacturing method conventionally used in the industry (for example, a manufacturing method as described above). In another embodiment, the polarizing element has an absorption axis in the width direction. In the case of such a polarizing element, the optical member of the present invention can be produced by laminating a roll-to-roll method and a linear polarization-separating type reflective polarizing element having a reflection axis in the width direction. Therefore, the manufacturing efficiency can be greatly improved.

B-2. Protective layer

The protective layer is formed of any appropriate film which can be used as a protective film for a polarizing plate. Specific examples of the material which is a main component of the film include cellulose resins such as triethyl cellulose (TAC); polyester resins, polyvinyl alcohol resins, polycarbonate resins, polyamido resins, and polycondensates.醯imino, polyether oxime, polyfluorene, polystyrene, polycondensate A transparent resin such as an olefin, a polyolefin, a (meth)acrylic or an acetate. Further, examples thereof include thermosetting resins such as (meth)acrylic acid, urethane-based, (meth)acrylic acid urethane-based, epoxy-based, and polyfluorene-based resins, and ultraviolet curable resins. . Other than this, for example, a glass-based polymer such as a siloxane-based polymer may be mentioned. Further, a polymer film described in JP-A-2001-343529 (WO01/37007) can also be used. As the material of the film, for example, a resin composition containing a thermoplastic resin having a substituted or unsubstituted quinone imine group in a side chain, and a thermoplastic resin having a substituted or unsubstituted phenyl group and a nitrile group in a side chain can be used. Examples of the material include a resin composition containing an alternating copolymer of isobutylene and N-methylbutyleneimine, and an acrylonitrile-styrene copolymer. The polymer film can be, for example, an extrusion molded product of the above resin composition. The respective protective layers may be the same or different.

The thickness of the protective layer is preferably from 20 μm to 100 μm. The protective layer may be laminated on the polarizing element via an adhesive layer (specifically, an adhesive layer or an adhesive layer), or may be laminated (not via the adhesive layer) to the polarizing element. The subsequent layer is formed from any suitable adhesive. The adhesive agent is, for example, a water-soluble adhesive containing a polyvinyl alcohol-based resin as a main component. The water-soluble adhesive containing a polyvinyl alcohol-based resin as a main component preferably further contains a metal compound colloid. The metal compound colloid may be one in which the metal compound fine particles are dispersed in the dispersion medium, and may be electrostatically stabilized and persistently stable due to mutual repulsion of the same kinds of charges of the fine particles. The average particle diameter of the fine particles forming the metal compound colloid may be any appropriate value as long as it does not adversely affect optical characteristics such as polarization characteristics. It is preferably 1 nm to 100 nm, and more preferably 1 nm to 50 nm. The reason for this is that fine particles can be uniformly dispersed in the adhesive layer and adhesion can be ensured and cracking can be suppressed. In addition, the "crack point" refers to a local unevenness defect generated at the interface between the polarizing element and the protective layer.

C. Optical components C-1. Overall composition of optical components

Fig. 2 is a schematic cross-sectional view showing an optical member according to an embodiment of the present invention. The optical member 100 includes a polarizing plate 10 and a reflective polarizing element 20 that is bonded to the polarizing plate 10 via the light diffusing adhesive layer 14 of the polarizing plate 10. The polarizing plate 10 is the polarizing plate of the present invention described in the above item B. The optical member 100 may further include a cymbal sheet 30 on the opposite side of the light diffusing adhesive layer 14 of the reflective polarizing element 20 as needed. Hereinafter, the reflective polarizing element and the cymbal sheet used in the optical member of the present embodiment will be described in detail.

C-2. Reflective polarizing element

The reflective polarizing element 20 has a function of transmitting polarized light in a specific polarization state (polarizing direction) and reflecting light in other polarized states. The reflective polarizing element 20 may be of a linear polarization separation type or a circularly polarized light separation type. Hereinafter, a linear polarization-separating type reflective polarizing element will be described as an example. In addition, examples of the circularly polarizing light-separating type of reflective polarizing element include a film in which cholesteric liquid crystal is immobilized and a λ/4 plate. Laminated body.

Fig. 3 is a schematic perspective view showing an example of a reflective polarizing element. The reflective polarizing element is a multilayer laminated body in which a layer A having birefringence and a layer B having substantially no birefringence are alternately laminated. For example, the total number of layers of such a multilayer laminate may range from 50 to 1000. In the illustrated example, the refractive index nx of the A layer in the x-axis direction is larger than the refractive index ny of the y-axis direction, and the refractive index nx of the B layer in the x-axis direction is substantially the same as the refractive index ny of the y-axis direction. Therefore, the difference in refractive index between the A layer and the B layer is large in the x-axis direction and substantially zero in the y-axis direction. As a result, the x-axis direction becomes the reflection axis, and the y-axis direction becomes the transmission axis. The difference in refractive index between the A layer and the B layer in the x-axis direction is preferably 0.2 to 0.3. Further, the x-axis direction corresponds to the extending direction of the reflective polarizing element in the following manufacturing method.

The above A layer preferably contains a material which exhibits birefringence by stretching. Typical examples of such materials include naphthalene dicarboxylic acid polyesters (for example, polyethylene naphthalate), polycarbonates, and acrylic resins (for example, polymethyl methacrylate). Preferred is polyethylene naphthalate. The layer B preferably contains a material which does not substantially exhibit birefringence even when extended. A typical example of such a material is a copolyester of naphthalene dicarboxylic acid and terephthalic acid.

The reflective polarizing element is disposed at an interface between the A layer and the B layer, and transmits light including a first polarization direction (for example, a p-wave) so as to include light (for example, s-wave) in a second polarization direction orthogonal to the first polarization direction. reflection. The reflected light is transmitted between the A layer and the B layer, and a part of the light is transmitted as light including the first polarization direction, and a part is reflected as light including the second polarization direction. In the inside of the reflective polarizing element, the above-described reflection and transmission are repeated a plurality of times, whereby the light use efficiency can be improved.

In one embodiment, the reflective polarizing element may include a reflective layer R as the outermost layer on the opposite side of the polarizing plate 10 as shown in FIG. By providing the reflective layer R, it is possible to further utilize the light that is finally returned to the outermost portion of the reflective polarizing element without being used, so that the light use efficiency can be further improved. As a representative, the multilayer structure of the reflective layer R by the polyester resin layer And the performance of the reflection function.

The overall thickness of the reflective polarizing element can be appropriately set depending on the purpose, the total number of layers included in the reflective polarizing element, and the like. The overall thickness of the reflective polarizing element is preferably from 10 μm to 150 μm. When the overall thickness is in the above range, an image display device (for example, a liquid crystal display device) that suppresses generation of moiré and has high brightness can be realized.

In one embodiment, in the optical member 100, the reflective polarizing element 20 is disposed to transmit light parallel to the polarization direction of the transmission axis of the polarizing plate 10. In other words, the reflective polarizing element 20 is disposed such that its transmission axis and the transmission axis direction of the polarizing plate 10 are substantially parallel to each other. With such a configuration, the light absorbed by the polarizing plate 10 can be recovered, and the utilization efficiency can be further improved, and the brightness can be improved.

As a representative, the reflective polarizing element can be fabricated by combining coextrusion and lateral stretching. Coextrusion can be carried out in any suitable manner. For example, it can be a feed module or a multi-manifold. For example, in the feed module, the material constituting the layer A and the material constituting the layer B are extruded, and then multilayered using a multiplier. Furthermore, such multilayer devices are well known to the practitioner. Then, as a representative, the obtained long multilayer laminated body is extended in a direction (TD) orthogonal to the conveying direction. The material constituting the layer A (for example, polyethylene naphthalate) is increased in refractive index only in the extending direction by the lateral stretching, and as a result, birefringence is exhibited. The material constituting the layer B (for example, a copolyester of naphthalene dicarboxylic acid and terephthalic acid) does not increase in refractive index in either direction even by the lateral extension. As a result, a reflective polarizing element having a reflection axis in the extending direction (TD) and a transmission axis in the transport direction (MD) can be obtained (TD corresponds to the x-axis direction of FIG. 3, and MD corresponds to the y-axis direction). Furthermore, the stretching operation can be performed using any suitable device.

As the reflective polarizing element, for example, those described in Japanese Laid-Open Patent Publication No. Hei 9-507308 can be used.

As the reflective polarizing element, a commercially available product can be used as it is, or a commercially available product can be used for secondary processing (for example, elongation). As a commercial item, the brand name by 3M company is mentioned, for example. DBEF, 3M company's trade name APF.

C-3. Picture

As described above, the cymbal 30 can be used as needed. When the cymbal sheet 30 is used, the cymbal sheet 30 is disposed on the opposite side of the light diffusing adhesive layer 14 of the reflective polarizing element 20. As a representative, the cymbal sheet 30 has a base portion 31 and a dam portion 32. Further, in the present embodiment, since the reflective polarizing element 20 can function as a base portion for supporting the crotch portion 32, it is not necessary to provide the base portion 31. When the optical member of the present invention is disposed on the backlight side of an image display device (for example, a liquid crystal display device), the squeegee 30 emits the polarized light emitted from the light guide plate of the backlight unit while maintaining the polarization state thereof. The polarized light having the maximum intensity in the substantially normal direction of the liquid crystal display device is introduced into the polarizing plate 10 via the reflective polarizing element 20 and the light diffusing adhesive layer 14 by total reflection inside the crotch portion 32. In addition, the "substantial normal direction" includes a direction in which the normal direction deviates from a certain angle, for example, within a range of ±10° from the normal direction.

The cymbal sheet 30 is bonded to the reflective polarizing element 20 via any appropriate adhesive layer (for example, an adhesive layer or an adhesive layer: not shown).

C-3-1. Department

In one embodiment, as shown in FIGS. 2 and 4, the cymbal sheet 30 (substantially the dam portion 32) is formed by juxtaposing a plurality of units 稜鏡33 which are convex on the opposite side of the reflective polarizing element 20. Composition. Preferably, the unit crucible 33 has a columnar shape, and its longitudinal direction (ridge direction) is oriented in a direction substantially perpendicular to the transmission axis of the polarizing plate 10 and the transmission axis of the reflective polarizing element 20. In the present specification, the expressions of "substantially orthogonal" and "substantially orthogonal" include the case where the angle formed in two directions is 90° ± 10°, preferably 90° ± 7°, and further preferably 90. °±5°. The expression "substantially parallel" and "substantially parallel" includes the case where the angle formed in the two directions is 0 ° ± 10 °, preferably 0 ° ± 7 °, and further preferably 0 ° ± 5 °. Further, in the present specification, when only "orthogonal" or "parallel" is used, it is assumed that the state may be substantially orthogonal or substantially parallel. Furthermore, the cymbal 30 can also be in the ridgeline direction of the unit 稜鏡33 with the polarizing plate The transmission axis of 10 and the transmission axis of the reflective polarizing element 20 are arranged at a specific angle (so-called oblique placement). By adopting such a configuration, there is a case where the occurrence of moiré can be prevented more favorably. The range of the inclined arrangement is preferably 20 or less, more preferably 15 or less.

The shape of the unit 稜鏡 33 may be any suitable configuration as long as the effect of the present invention is obtained. Regarding the cross section of the unit 稜鏡 33 parallel to the direction in which it is arranged and parallel to the thickness direction, the cross-sectional shape may be a triangular shape, or may be other shapes (for example, one side of the triangle or a slope of both sides has a plurality of different inclination angles) The shape of the flat surface). As the triangular shape, it may be a shape that is asymmetrical with respect to a line passing through the apex of the unit 并 and orthogonal to the sheet surface (for example, an equilateral triangle), and a shape symmetrical with respect to the straight line (for example, an isosceles triangle) ). Further, the apex of the unit 可 may be chamfered or curved, or may be cut so as to have a flat surface to form a cross-sectional shape. The detailed shape of the unit 稜鏡 33 can be appropriately set as needed. For example, as the unit 稜鏡33, the configuration described in Japanese Laid-Open Patent Publication No. Hei 11-84111 can be employed.

The distance between the crotch portion 32 and the light diffusing adhesive layer 14 is preferably from 75 μm to 250 μm. By ensuring the above distance between the crotch portion and the light-diffusing adhesive layer, the front contrast and brightness can be maintained and the generation of the moiré can be suppressed satisfactorily. The distance between the crotch portion 32 and the light diffusing adhesive layer 14 can be adjusted, for example, by adjusting the thickness of the adhesive layer between the reflective polarizing element 20 and the substrate portion 31, and/or between the reflective polarizing element 20 and the cymbal sheet 30. control. Further, the distance between the crotch portion 32 and the light diffusing adhesive layer 14 means the flat surface of the crotch portion 32 (the surface opposite to the apex of the unit crucible 33) and the reflective type of the light diffusing adhesive layer 14. The distance of the surface on the side of the polarizing element 20.

C-3-2. Substrate part

When the base material portion 31 is provided on the cymbal sheet 30, the base portion 31 and the dam portion 32 can be integrally formed by extrusion molding or the like of a single material, and the dam portion can be formed on the base portion. The material is used on the film. The thickness of the base material portion is preferably 25 μm to 150 μm. If the above is thick The degree of distance between the light-diffusing adhesive layer and the crotch portion can be set to a desired range. Further, from the viewpoint of workability and strength, the above thickness is also preferable.

As a material constituting the base material portion 31, any appropriate material can be employed depending on the purpose and the configuration of the cymbal sheet. In the case where the dam portion is formed on the film for the base portion, examples of the film for the base portion include cellulose triacetate (TAC) and polymethyl methacrylate (PMMA). A film formed of a methyl acrylate resin or a polycarbonate (PC) resin. The film is preferably an unstretched film.

When the base portion 31 and the crotch portion 32 are integrally formed by a single material, the material for forming the crotch portion can be used as the material for forming the crotch portion when the crotch portion is formed on the film for the base portion. Material. Examples of the material for forming the crotch portion include an epoxy acrylate-based or urethane-based reactive resin (for example, an ionizing radiation curable resin). In the case of forming a sheet having an integral structure, a polyester resin such as PC or PET, an acrylic resin such as PMMA or MS, or a light-transmitting thermoplastic resin such as a cyclic polyolefin can be used.

The base material portion 31 preferably has substantially optical isotropic properties. In the present specification, "there is substantially optical anisotropy", and the phase difference value is small to the extent that it does not substantially affect the optical characteristics of the liquid crystal display device. For example, the in-plane retardation Re of the base material portion is preferably 20 nm or less, more preferably 10 nm or less. Further, the in-plane phase difference Re is a phase difference value in the plane measured by light having a wavelength of 590 nm at 23 °C. The in-plane phase difference Re is represented by Re = (nx - ny) × d. Here, nx is a refractive index in a direction in which the refractive index of the optical member becomes maximum (ie, a direction of the slow axis), and ny is in a direction perpendicular to the slow axis in the plane (ie, the direction of the phase axis) The refractive index of d, the thickness (nm) of the optical member.

Further, the photoelastic coefficient of the base portion 31 is preferably -10 × 10 ^-12 m ² /N to 10 × 10 ^-12 m ² /N, more preferably -5 × 10 ^-12 m ² /N to 5 × 10 ^-12 m ² /N, further preferably -3 × 10 ^-12 m ² /N to 3 × 10 ^-12 m ² /N.

C-4. Phase difference layer

The optical member 100 may have any appropriate retardation layer (not shown) at any appropriate position as needed. The arrangement position, the number, the birefringence (refractive index 楕 round body) of the retardation layer, and the like can be appropriately selected depending on the type of the image display device, the display mode, the desired characteristics, and the like. The retardation layer may also have a protective layer of the polarizing element as needed.

[Examples]

Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to the examples. The test and evaluation methods in the examples are as follows. Further, the "parts" and "%" in the examples are based on weight unless otherwise specified.

(1) Refractive index of the adhesive

The refractive index of the adhesive which does not contain the diffusion microparticles coated on the transparent substrate was measured by the Abbe refractometer (DR-M2, manufactured by Atago Corporation).

(2) Uneven corners

The polarizing plate with the light-diffusing adhesive layer obtained in the examples and the comparative examples was cut into a size of 183 mm in length × 137 mm in width as a sample. Two samples of this sample were prepared. Two sheets of the sample were bonded to both sides of an alkali-free glass plate having a thickness of 0.07 mm by means of a laminator so as to be a crossed polarizer. Then, autoclaving was performed at 5 atm for 15 minutes at 50 ° C to prepare a secondary sample (initial). Then, the secondary sample was subjected to heat treatment at 100 ° C for 24 hours. The initial and heated secondary samples were placed on a backlight of 10,000 candelas, and the light leakage was visually observed, and the angular unevenness was evaluated on the basis of the following criteria.

◎: There is no unevenness in the corners, and there is no problem in practical use.

○: The corner unevenness was slightly generated, but it was not expressed in the display area, so there was no problem in practical use.

△: Corner angle unevenness was generated and slightly expressed in the display area, but there was no problem in practical use.

×: An uneven angle is generated and is apparently expressed in the display area, which is problematic in practical use.

(3) Haze value

The light-diffusing adhesives used in the examples and the comparative examples were subjected to a method specified in JIS 7136, and were measured by a fog meter (manufactured by Murakami Color Research Institute Co., Ltd., trade name "HN-150"). Determination.

<Example 1> 1. Preparation of light diffusion adhesive 1-1. Preparation of base polymer (acrylic polymer) of adhesive

In a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas introduction tube, and a cooler, 74.9 parts of butyl acrylate, 20 parts of benzyl acrylate, 5 parts of acrylic acid, and 0.1 part of 4-hydroxybutyl acrylate were used as a polymerization initiator. 0.1 part of 2,2'-azobisisobutyronitrile was added together with 100 parts of ethyl acetate (concentration of monomer 50%), nitrogen gas was introduced while slowly stirring, and nitrogen substitution was performed. Thereafter, the inside of the flask was placed. The liquid temperature was maintained at around 55 ° C for 8 hours to prepare a solution of an acrylic polymer having a weight average molecular weight (Mw) of 2.04 million and Mw/Mn of 3.2.

1-2. Preparation of light diffusion adhesive

The isocyanate crosslinking agent (Coronate L, manufactured by Japan Polyurethane Industry Co., Ltd., toluene diisocyanate of trimethylolpropane) is blended with respect to 100 parts of the solid content of the acrylic polymer solution obtained above. 0.45 parts and 0.1 parts of benzoyl peroxide (manufactured by Nippon Oil & Fats Co., Ltd., Nyper BMT), 0.1 part of decane coupling agent (KBM403 manufactured by Shin-Etsu Chemical Co., Ltd.), and polyoxynoxy resin as light-diffusing fine particles 9 parts of microparticles (Tospearl 130 manufactured by Momentive Performance Materials Japan Co., Ltd., volume average particle diameter: 3 μm) was prepared, and a coating liquid of a light-diffusing adhesive (solid content: 11%) was prepared.

2. Fabrication of a polarizing plate with a light diffusing adhesive layer 2-1. Production of polarizing plate

A polyvinyl alcohol film having a thickness of 80 μm was dyed in a 0.3% iodine solution at 30 ° C for 1 minute, and extended to 3 times between rolls having different speed ratios. Thereafter, at 60 ° C, including The aqueous solution of boric acid of 4% concentration and potassium iodide of 10% concentration was immersed for 0.5 minutes, and extended until the total stretching ratio was 6 times. Then, it was washed by immersing in an aqueous solution containing potassium iodide at a concentration of 1.5% at 30 ° C for 10 seconds, and then dried at 50 ° C for 4 minutes to obtain a polarizing element. A saponified 80 μm-thick triethylene fluorene cellulose film was bonded to both surfaces of the polarizing element by a polyvinyl alcohol-based adhesive to prepare a polarizing plate.

2-2. Fabrication of a polarizing plate with a light diffusing adhesive layer

Then, the coating liquid obtained in the above was applied to a 38 μm polyethylene terephthalate (PET) film which was subjected to polyfluorination treatment so that the thickness of the dried light diffusion adhesive layer was 12 μm. (One side of Mitsubishi Chemical Polyester Film Co., Ltd., MRF38) was dried at 155 ° C for 1 minute, and then transferred onto the polarizing plate obtained above to prepare a polarizing plate with a light-diffusing adhesive layer. (Polarizing plate according to an embodiment of the present invention).

An adhesive, a light-diffusing adhesive, and a polarizing plate with a light-diffusing adhesive layer were provided for the above evaluation. The results are shown in Table 1. Further, a photographic image in a state in which the angle 隅 is uneven is shown in Fig. 5 .

<Example 2>

A light diffusion adhesive was prepared according to the formulation shown in Table 1. A polarizing plate with a light-diffusing adhesive layer was produced in the same manner as in Example 1 except that the light-diffusing adhesive was used. The adhesive, the light-diffusing adhesive, and the polarizing plate with the light-diffusing adhesive layer were provided for the same evaluation as in Example 1. The results are shown in Table 1.

<Example 3>

A light diffusion adhesive was prepared according to the formulation shown in Table 1. A polarizing plate with a light-diffusing adhesive layer was produced in the same manner as in Example 1 except that the light-diffusing adhesive was used. The adhesive, the light-diffusing adhesive, and the polarizing plate with the light-diffusing adhesive layer were provided for the same evaluation as in Example 1. The results are shown in Table 1.

<Example 4>

A light diffusion adhesive was prepared according to the formulation shown in Table 1. In addition to using the light diffusion adhesive A polarizing plate with a light-diffusing adhesive layer was produced in the same manner as in Example 1. The adhesive, the light-diffusing adhesive, and the polarizing plate with the light-diffusing adhesive layer were provided for the same evaluation as in Example 1. The results are shown in Table 1.

<Example 5>

A light diffusion adhesive was prepared according to the formulation shown in Table 1. A polarizing plate with a light-diffusing adhesive layer was produced in the same manner as in Example 1 except that the light-diffusing adhesive was used. The adhesive, the light-diffusing adhesive, and the polarizing plate with the light-diffusing adhesive layer were provided for the same evaluation as in Example 1. The results are shown in Table 1.

<Example 6>

A light diffusion adhesive was prepared according to the formulation shown in Table 1. A polarizing plate with a light-diffusing adhesive layer was produced in the same manner as in Example 1 except that the light-diffusing adhesive was used. The adhesive, the light-diffusing adhesive, and the polarizing plate with the light-diffusing adhesive layer were provided for the same evaluation as in Example 1. The results are shown in Table 1.

<Example 7>

A light diffusion adhesive was prepared according to the formulation shown in Table 1. A polarizing plate with a light-diffusing adhesive layer was produced in the same manner as in Example 1 except that the light-diffusing adhesive was used. The adhesive, the light-diffusing adhesive, and the polarizing plate with the light-diffusing adhesive layer were provided for the same evaluation as in Example 1. The results are shown in Table 1.

<Example 8>

A light diffusion adhesive was prepared according to the formulation shown in Table 1. A polarizing plate with a light-diffusing adhesive layer was produced in the same manner as in Example 1 except that the light-diffusing adhesive was used and the thickness of the light-diffusing adhesive layer was changed to 21 μm. The adhesive, the light-diffusing adhesive, and the polarizing plate with the light-diffusing adhesive layer were provided for the same evaluation as in Example 1. The results are shown in Table 1.

<Comparative Example 1>

A light diffusion adhesive was prepared according to the formulation shown in Table 1. Use the light diffusion adhesive and A polarizing plate with a light-diffusing adhesive layer was produced in the same manner as in Example 1 except that the thickness of the light-diffusing adhesive layer was changed to 23 μm. The adhesive, the light-diffusing adhesive, and the polarizing plate with the light-diffusing adhesive layer were provided for the same evaluation as in Example 1. The results are shown in Table 1. Further, a photographic image in a state in which the angle 隅 is uneven is shown in Fig. 5 .

<evaluation>

As is clear from Table 1, the light-diffusing adhesive of the embodiment of the present invention does not cause angular unevenness even in a high-temperature environment. Further, it is understood that the light-diffusing adhesive of the embodiment of the present invention can form a light-diffusing adhesive layer having a high haze even if the thickness is thin.

[Industrial availability]

The light-diffusing adhesive of the present invention can be preferably used for the bonding of members of an image display device to each other. The polarizing plate and the optical member of the present invention can be preferably used as a polarizing plate on the opposite side to the viewing side of an image display device (for example, a liquid crystal display device).

10‧‧‧Polar plate

11‧‧‧Polarized components

12‧‧‧Protective layer

13‧‧‧Protective layer

14‧‧‧Light diffusing adhesive layer

Claims (10)

A light diffusing adhesive comprising: an adhesive comprising a base polymer containing a (meth)acrylic polymer; and a light diffusing fine particle having a refractive index lower than the adhesive; the (methyl) The acrylic polymer comprises a (meth)acrylic monomer containing an aromatic ring as a monomer unit; the light diffusing adhesive further comprises an alkyl (meth)acrylate as a monomer unit, and is relative to all the constituent monomers The weight ratio of the alkyl (meth)acrylate is from 71% by weight to 89.99% by weight. The light-diffusing adhesive of claim 1, wherein the aromatic ring-containing (meth)acrylic monomer comprises benzyl (meth)acrylate. The light-diffusing adhesive according to claim 1, wherein the content of the aromatic ring-containing (meth)acrylic monomer in the base polymer is from 1% by weight to 35% by weight. The light-diffusing adhesive of claim 1, wherein the adhesive has a refractive index of 1.47 or more. The light-diffusing adhesive of claim 1, wherein the light-diffusing fine particles are polyoxynized resin fine particles. The light-diffusing adhesive according to claim 1, wherein the light-diffusing fine particles have a volume average particle diameter of from 1 μm to 4 μm. The light-diffusing adhesive of claim 1 has a haze value of 20% to 95% after hardening. A polarizing plate comprising a polarizing element, a protective layer, and a light diffusing adhesive layer formed of the light diffusing adhesive of claim 1. An optical member comprising the polarizing plate of claim 8 and a reflective polarizing element bonded to the polarizing plate via a light diffusing adhesive layer of the polarizing plate. The optical member according to claim 9, wherein the reflective polarizing element further comprises a gusset on a side opposite to the light diffusing adhesive layer.