WO2016121001A1 - Adhesive composition, adhesive and adhesive sheet - Google Patents

Abstract

An adhesive composition which contains an active energy ray-curable adhesive component and organic fine particles, and wherein: the active energy ray-curable adhesive component contains a (meth)acrylic acid ester polymer, an active energy ray-curable compound and a crosslinking agent; the organic fine particles have a refractive index of 1.50-2.00; and the absolute value of the difference between the refractive index of the active energy ray-curable adhesive component and the refractive index of the organic fine particles is 0.02-0.50. An adhesive which is obtained from this adhesive composition enables the achievement of an optical member that has sufficient durability and light diffusibility.

Description

Adhesive composition, adhesive and adhesive sheet

The present invention relates to a pressure-sensitive adhesive composition, a pressure-sensitive adhesive (a material obtained by curing a pressure-sensitive adhesive composition), and a pressure-sensitive adhesive sheet, and in particular, a pressure-sensitive adhesive composition suitable for optical members such as polarizing plates, a pressure-sensitive adhesive, and The present invention relates to an adhesive sheet.

Generally, in a liquid crystal panel, a pressure-sensitive adhesive layer formed from a pressure-sensitive adhesive composition is often used to adhere a polarizing plate or a retardation plate to a glass substrate of a liquid crystal cell. However, since optical members such as polarizing plates and retardation plates tend to shrink due to heat, etc., shrinkage occurs due to thermal history. There has been pointed out a problem of durability such as peeling at the interface (so-called floating or peeling).

On the other hand, the liquid crystal panel has an advantage that it is thin and consumes less power, but has a problem that it is insufficient in terms of luminance and viewing angle. From the viewpoint of improving this problem with the pressure-sensitive adhesive layer, a pressure-sensitive adhesive layer used for the optical member may be required to have light diffusibility.

In order to impart light diffusibility to the pressure-sensitive adhesive layer, fine particles are usually added to the pressure-sensitive adhesive layer. However, when fine particles are added to the pressure-sensitive adhesive layer, due to differences in thermal expansibility or heat-shrinkability between the fine particles and the pressure-sensitive adhesive, misalignment occurs at the interface between the fine particles and the pressure-sensitive adhesive due to thermal history, and bubbles are generated. Such a problem is concerned.

In addition, as described above, in the case of an optical member that is thermally contracted, the pressure-sensitive adhesive layer is also deformed accordingly, and there is a concern that a problem arises in that a gap occurs at the interface between the foreign particles and the pressure-sensitive adhesive, and bubbles are generated. The In fact, when the pressure-sensitive adhesive layer to which fine particles are added is used for an optical member, the floating and peeling due to the heat history are worsened and the durability tends to be lower than when no fine particles are added.

On the other hand, Patent Document 1 provides a pressure-sensitive adhesive that can be bonded with good durability and that the liquid crystal display device has uniform brightness without causing foaming or uneven brightness in the pressure-sensitive adhesive layer over time. As a problem, an adhesive containing an adhesive copolymer containing an acrylic copolymer and an active energy ray-curable compound and fine particles is disclosed.

Japanese Patent No. 4953717

By the way, in recent years, with the development of various mobile electronic devices such as smartphones and tablet terminals, thinning of liquid crystal display devices has been demanded. In response to such demands, there is an increasing need for pressure-sensitive adhesives having sufficient light diffusibility and durability even in the case of pressure-sensitive adhesives for optical members, even when the pressure-sensitive adhesive layer is formed thin.

The present invention has been made in view of such a situation, and is a pressure-sensitive adhesive composition, pressure-sensitive adhesive, and pressure-sensitive adhesive sheet capable of obtaining an optical member having excellent light diffusibility and durability as a light-diffusing pressure-sensitive adhesive. The purpose is to provide.

In order to achieve the above object, first, the present invention provides an adhesive composition containing an active energy ray-curable adhesive component and organic fine particles, wherein the active energy ray-curable adhesive component is (Metal). ) An acrylic ester polymer, an active energy ray-curable compound and a crosslinking agent, the organic fine particles have a refractive index of 1.50 to 2.00, and the active energy ray-curable adhesive component has a refractive index Provided is a pressure-sensitive adhesive composition characterized in that the absolute value of the difference in refractive index from the organic fine particles is 0.02 to 0.50 (Invention 1).

In the above invention (Invention 1), the average particle diameter of the organic fine particles by centrifugal sedimentation light transmission method is preferably 0.5 to 10 μm (Invention 2).

In the above inventions (Inventions 1 and 2), the organic fine particles are preferably fine particles made of a polymer containing methyl methacrylate as a constituent monomer unit (Invention 3).

Secondly, the present invention provides a pressure-sensitive adhesive obtained by curing the pressure-sensitive adhesive composition (Invention 1 to 3) (Invention 4).

In the above invention (Invention 4), the haze value is preferably 20 to 95% (Invention 5).

Thirdly, the present invention provides a pressure-sensitive adhesive sheet comprising a base material and a pressure-sensitive adhesive layer, wherein the pressure-sensitive adhesive layer comprises the pressure-sensitive adhesive (inventions 4 and 5). (Invention 6)

Fourthly, the present invention includes two release sheets and an adhesive layer sandwiched between the release sheets so as to be in contact with the release surfaces of the two release sheets, and the adhesive layer is the adhesive. A pressure-sensitive adhesive sheet comprising (Inventions 4 and 5) is provided (Invention 7).

According to the pressure-sensitive adhesive composition, pressure-sensitive adhesive and pressure-sensitive adhesive sheet according to the present invention, an optical member having sufficient durability and light diffusibility can be obtained.

It is sectional drawing of the adhesive sheet which concerns on the 1st Embodiment of this invention. It is sectional drawing of the adhesive sheet which concerns on the 2nd Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described.
[Adhesive composition]
The adhesive composition according to this embodiment (hereinafter referred to as “adhesive composition P”) contains an active energy ray-curable adhesive component and organic fine particles. The active energy ray-curable adhesive component contains a (meth) acrylic acid ester polymer, an active energy ray-curable compound, and a crosslinking agent. The refractive index of the organic fine particles is 1.50 to 2.00, and the absolute value of the difference between the refractive index of the active energy ray-curable adhesive component and the refractive index of the organic fine particles is 0.02 to 0.50. It is.

In the pressure-sensitive adhesive composition P according to the present embodiment, the refractive index of the organic fine particles is relatively large, and the difference in absolute value between the refractive index of the active energy ray-curable pressure-sensitive adhesive component and the refractive index of the organic fine particles is relatively large. . For this reason, according to the adhesive composition P, high light diffusibility can be achieved. In particular, even when a thin adhesive layer is formed using the adhesive composition P, a sufficiently high light diffusibility can be achieved. Furthermore, since the amount of organic fine particles required to achieve a desired light diffusibility can be reduced, a decrease in durability due to the addition of organic fine particles is suppressed. Moreover, the pressure-sensitive adhesive obtained by curing the pressure-sensitive adhesive composition P is an active energy ray-cured product in which a (meth) acrylic acid ester polymer having a cross-linked structure formed by reaction with a cross-linking agent is formed by irradiation with active energy rays. High cohesive force is exhibited by being trapped in the three-dimensional network structure of the active compound. Excellent durability can be achieved by such a reduction in the amount of organic fine particles used and high cohesion. And the optical member provided with the adhesive layer formed using such an adhesive composition P, especially a polarizing plate has sufficient durability, and is excellent in light diffusibility.

1. Active energy ray-curable adhesive component The adhesive composition P contains an active energy ray-curable adhesive component, and the active energy ray-curable adhesive component is a (meth) acrylic acid ester polymer (A), an active energy ray. Contains a curable compound (B) and a crosslinking agent (C). In this specification, (meth) acrylic acid ester means both acrylic acid ester and methacrylic acid ester. The same applies to other similar terms. Further, the “polymer” includes the concept of “copolymer”.

As described above, the pressure-sensitive adhesive containing organic fine particles often causes problems in durability when applied to an optical member such as a polarizing plate. However, in this embodiment, when the adhesive composition P contains the said active energy ray-curable adhesive component, the obtained adhesive becomes excellent in durability. In addition, the pressure-sensitive adhesive containing organic fine particles generally has a reduced cohesive force, and when the release sheet is peeled from the pressure-sensitive adhesive layer, the pressure-sensitive adhesive layer may be taken to the release sheet side. However, the pressure-sensitive adhesive composition P containing the active energy ray-curable pressure-sensitive adhesive component is less likely to cause the above-described problems when cured, and the resulting pressure-sensitive adhesive layer has excellent handling properties.

(1) (Meth) acrylic acid ester polymer (Meth) acrylic acid ester polymer (A) is a (meth) acrylic acid alkyl ester having 1 to 20 carbon atoms in the alkyl group as a monomer constituting the polymer. It is preferable to contain. Thereby, the obtained adhesive can express preferable adhesiveness. The (meth) acrylic acid ester polymer (A) includes a (meth) acrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms and a monomer having a reactive functional group (reactive functional group-containing monomer). And a copolymer with other monomer used as desired. By including a reactive functional group-containing monomer as a monomer constituting the polymer (meth) acrylic acid ester polymer (A), it is possible to improve adhesion with a glass surface such as a liquid crystal cell, Moreover, it can react with a crosslinking agent (C) described later to form a crosslinked structure.

Examples of (meth) acrylic acid alkyl ester having 1 to 20 carbon atoms in the alkyl group include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, and n- (meth) acrylate. Butyl, n-pentyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, n-decyl (meth) acrylate, (meth) acrylic acid Examples thereof include n-dodecyl, myristyl (meth) acrylate, palmityl (meth) acrylate, stearyl (meth) acrylate, and the like. Among these, from the viewpoint of further improving the adhesiveness, (meth) acrylic acid esters having an alkyl group having 1 to 8 carbon atoms are preferable, and n-butyl (meth) acrylate or 2-ethylhexyl (meth) acrylate is particularly preferable. . In addition, these may be used independently and may be used in combination of 2 or more type.

The (meth) acrylic acid ester polymer (A) contains 50 to 99% by mass of a (meth) acrylic acid alkyl ester having 1 to 20 carbon atoms as the monomer unit constituting the polymer. The content is preferably 65 to 97% by mass, more preferably 80 to 95% by mass.

As the reactive functional group-containing monomer, a monomer having a hydroxyl group in the molecule (hydroxyl group-containing monomer), a monomer having a carboxyl group in the molecule (carboxyl group-containing monomer), a monomer having an amino group in the molecule (amino group-containing) Monomer) and the like. One of these reactive functional group-containing monomers may be used alone, or two or more thereof may be used in combination.

Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, (meth And (meth) acrylic acid hydroxyalkyl esters such as 3-hydroxybutyl acrylate and 4-hydroxybutyl (meth) acrylate. Among them, 2-hydroxyethyl (meth) acrylate is preferred from the viewpoint of the reactivity of the resulting (meth) acrylic acid ester polymer (A) with the crosslinking agent (C) of the hydroxyl group and the copolymerizability with other monomers. Or 4-hydroxybutyl (meth) acrylate is preferable. These may be used alone or in combination of two or more.

Examples of the carboxyl group-containing monomer include ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, and citraconic acid. Of these, acrylic acid is preferred from the viewpoint of the reactivity of the resulting (meth) acrylic acid ester polymer (A) with the crosslinking agent (C) of the carboxyl group and the copolymerizability with other monomers. These may be used alone or in combination of two or more.

Examples of the amino group-containing monomer include aminoethyl (meth) acrylate, n-butylaminoethyl (meth) acrylate, and the like. These may be used alone or in combination of two or more.

As the reactive functional group-containing monomer, it is preferable to use a hydroxyl group-containing monomer and a carboxyl group-containing monomer, particularly acrylic acid in combination. In this case, it is preferable to use an isocyanate-based crosslinking agent as the crosslinking agent (C) described later. Since the hydroxyl group-containing monomer has high reactivity with the isocyanate-based crosslinking agent, it becomes a crosslinking point of the (meth) acrylic acid ester polymer (A). On the other hand, a carboxyl group-containing monomer, particularly acrylic acid, improves the adhesive strength of the resulting adhesive and raises the glass transition temperature to improve the cohesive strength. Moreover, a carboxyl group-containing monomer, particularly acrylic acid, also has an action of promoting a crosslinking reaction between a hydroxyl group derived from a hydroxyl group-containing monomer and an isocyanate-based crosslinking agent.

The (meth) acrylic acid ester polymer (A) preferably contains 1 to 25% by mass, particularly 2 to 15% by mass of a reactive functional group-containing monomer as a monomer unit constituting the polymer. The content is preferably 3 to 10% by mass. When a hydroxyl group-containing monomer and a carboxyl group-containing monomer are used in combination, the hydroxyl group-containing monomer is preferably contained in an amount of 0.05 to 20% by mass, particularly preferably 0.1 to 10% by mass, and more preferably 0.2%. It is preferable to contain ~ 2% by mass. Further, the carboxyl group-containing monomer is preferably contained in an amount of 0.5 to 20% by mass, particularly preferably 1 to 10% by mass, and more preferably 2 to 8% by mass.

Examples of the other monomer include aliphatic rings such as (meth) acrylic acid alkoxyalkyl esters such as methoxyethyl (meth) acrylate and ethoxyethyl (meth) acrylate, and cyclohexyl (meth) acrylate (meth) Non-crosslinkable acrylamide such as acrylic ester, acrylamide, methacrylamide, etc. Non-crosslinkable tertiary such as N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate Examples thereof include (meth) acrylic acid ester having an amino group, vinyl acetate, and styrene. These may be used alone or in combination of two or more.

The polymerization mode of the (meth) acrylic acid ester polymer (A) may be a random copolymer or a block copolymer. In addition, since a (meth) acrylic acid ester polymer (A) is a component which provides adhesiveness, it is preferable not to have active energy ray curability.

The (meth) acrylic acid ester polymer (A) preferably has a weight average molecular weight of 400,000 to 2,500,000, particularly preferably 1,000,000 to 2,200,000, and more preferably 1,400,000 to 2,000,000. preferable. By making the weight average molecular weight of the (meth) acrylic acid ester polymer (A) relatively high, durability can be further improved. In addition, the weight average molecular weight in this specification is the value of polystyrene conversion measured by the gel permeation chromatography (GPC) method.

In addition, in the adhesive composition P, the (meth) acrylic acid ester polymer (A) may be used alone or in combination of two or more.

(2) Active energy ray-curable compound The active energy ray-curable compound (B) contained in the active energy ray-curable adhesive component in the present embodiment is an active energy ray containing the active energy ray-curable compound (B). The absolute value of the difference in refractive index between the curable adhesive component and the organic fine particles may be within the above-described range, and may be any of a monomer, an oligomer or a polymer, or a mixture thereof. Among them, a polyfunctional acrylate monomer having a molecular weight of 1000 or less that is excellent in compatibility with the (meth) acrylic acid ester polymer (A) and the like can be preferably exemplified.

In the adhesive composition P in the present embodiment, the active energy ray-curable compound (B) forms a chemical bond with each other by irradiation with active energy rays to generate a three-dimensional network structure. Then, by capturing the (meth) acrylic acid ester polymer (A) in the structure, the cohesive force is improved, and as a result, the durability is excellent.

Examples of polyfunctional acrylate monomers having a molecular weight of 1000 or less include 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, and polyethylene glycol diene. (Meth) acrylate, neopentyl glycol adipate di (meth) acrylate, hydroxypivalic acid neopentyl glycol di (meth) acrylate, dicyclopentanyl di (meth) acrylate, caprolactone modified dicyclopentenyl di (meth) acrylate, ethylene oxide modified Bifunctional type such as di (meth) acrylate phosphate, di (acryloxyethyl) isocyanurate, allylated cyclohexyl di (meth) acrylate, etc .; trimethylolpropane tri (meth) acrylate Rate, dipentaerythritol tri (meth) acrylate, propionic acid modified dipentaerythritol tri (meth) acrylate, pentaerythritol tri (meth) acrylate, propylene oxide modified trimethylolpropane tri (meth) acrylate, tris (acryloxyethyl) isocyanate Trifunctional type such as nurate and ε-caprolactone modified tris- (2- (meth) acryloxyethyl) isocyanurate; tetrafunctional type such as diglycerin tetra (meth) acrylate and pentaerythritol tetra (meth) acrylate; propionic acid modified 5-functional type such as dipentaerythritol penta (meth) acrylate; dipentaerythritol hexa (meth) acrylate, caprolactone-modified dipentaerythritol hexa (meth) acrylate And hexafunctional types such as cartons. These may be used individually by 1 type and may be used in combination of 2 or more type.

The content of the active energy ray-curable compound (B) is preferably 1 to 50 parts by mass, particularly 5 to 30 parts by mass with respect to 100 parts by mass of the (meth) acrylic acid ester polymer (A). It is preferable that the amount is 10 to 20 parts by mass. When the content of the active energy ray-curable compound (B) is within the above range, the resulting pressure-sensitive adhesive is superior in durability, and the resulting pressure-sensitive adhesive layer has excellent handling properties. Become. Furthermore, the adhesiveness by the (meth) acrylic acid ester polymer (A) is maintained well.

(3) Crosslinking agent In the adhesive composition P in the present embodiment, the active energy ray-curable adhesive component contains a crosslinking agent (C). When the adhesive component of the adhesive composition P contains a (meth) acrylic acid ester polymer (A) containing a reactive functional group-containing monomer as a monomer unit constituting the polymer, and a crosslinking agent (C), When the adhesive composition P is heated, the crosslinking agent (C) reacts with the reactive functional group of the reactive functional group-containing monomer constituting the (meth) acrylic acid ester polymer (A). Thereby, the structure by which (meth) acrylic acid ester polymer (A) was bridge | crosslinked with the crosslinking agent (C) is formed, and the cohesion force of the adhesive which is obtained improves.

In addition, in the adhesive composition P in this embodiment, the above-mentioned active energy ray-curable compound (B) improves the cohesive force of the obtained adhesive to improve durability. Further, by using the crosslinking agent (C) in combination, the cohesive force is further improved while maintaining the appropriate adhesive strength of the adhesive, and the durability is further improved.

The crosslinking agent (C) may be any one that reacts with the reactive functional group of the (meth) acrylic acid ester polymer (A). For example, an isocyanate crosslinking agent, an epoxy crosslinking agent, and an amine crosslinking agent. , Melamine crosslinking agent, aziridine crosslinking agent, hydrazine crosslinking agent, aldehyde crosslinking agent, oxazoline crosslinking agent, metal alkoxide crosslinking agent, metal chelate crosslinking agent, metal salt crosslinking agent, ammonium salt crosslinking agent, etc. Is mentioned. When the (meth) acrylic acid ester polymer (A) has a hydroxyl group as a reactive functional group, among them, it is preferable to use an isocyanate-based crosslinking agent that is excellent in reactivity with a hydroxyl group. In addition, a crosslinking agent (C) can be used individually by 1 type or in combination of 2 or more types.

The isocyanate-based crosslinking agent contains at least a polyisocyanate compound. Examples of the polyisocyanate compound include aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate and xylylene diisocyanate, aliphatic polyisocyanates such as hexamethylene diisocyanate, alicyclic polyisocyanates such as isophorone diisocyanate and hydrogenated diphenylmethane diisocyanate, and the like. , And their biuret bodies, isocyanurate bodies, and adduct bodies that are a reaction product with low molecular active hydrogen-containing compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, and castor oil. Among these, trimethylolpropane-modified aromatic polyisocyanate, particularly trimethylolpropane-modified tolylene diisocyanate is preferable from the viewpoint of reactivity with hydroxyl groups.

The content of the crosslinking agent (C) is preferably 0.01 to 10 parts by weight, particularly 0.05 to 5 parts by weight, with respect to 100 parts by weight of the (meth) acrylic acid ester polymer (A). It is preferable that the amount is 0.1 to 1 part by mass.

(4) Various additives The active energy ray-curable adhesive component may be various additives, for example, a photopolymerization initiator, a silane coupling agent, a refractive index adjusting agent, an antistatic agent, a tackifier, an antioxidant, if desired. You may contain a ultraviolet absorber, a light stabilizer, a softening agent, a filler, etc.

In the case where ultraviolet rays are used as active energy rays for curing the adhesive composition P, the active energy ray-curable adhesive component preferably contains a photopolymerization initiator. By containing the photopolymerization initiator, the active energy ray-curable adhesive component can be efficiently cured, and the polymerization curing time and the irradiation amount of the active energy ray can be reduced.

Examples of the photopolymerization initiator include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin-n-butyl ether, benzoin isobutyl ether, acetophenone, dimethylaminoacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1- [4- (methylthio) phenyl]- 2-morpholino-propan-1-one, 4- (2-hydroxyethoxy) phenyl-2- (hydroxy-2-propyl) ketone, benzophenone, p-phenylbenzophenone, 4,4′-diethyla Nobenzophenone, dichlorobenzophenone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, 2-aminoanthraquinone, 2-methylthioxanthone, 2-ethylthioxanthone, 2-chlorothioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, benzyldimethyl ketal, acetophenone dimethyl ketal, p-dimethylaminobenzoate, oligo [2-hydroxy-2-methyl-1 [4- (1-methylvinyl) phenyl] propanone], 2, 4,6-trimethylbenzoyl-diphenyl-phosphine oxide and the like. These may be used alone or in combination of two or more.

The photopolymerization initiator is used in an amount in the range of 0.1 to 20 parts by weight, particularly 1 to 12 parts by weight with respect to 100 parts by weight of the active energy ray curable compound (B) in the active energy ray curable adhesive component. It is preferable to be used.

In addition, the active energy ray-curable adhesive component preferably contains a silane coupling agent from the viewpoint of improving the adhesive force of the obtained adhesive to the glass surface or the like. The silane coupling agent is preferably an organosilicon compound having at least one alkoxysilyl group in the molecule, having good compatibility with the adhesive component and having light transmittance.

Examples of such silane coupling agents include polymerizable unsaturated group-containing silicon compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, and methacryloxypropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 2- ( 3,4-epoxycyclohexyl) silicon compounds having an epoxy structure such as ethyltrimethoxysilane, mercapto group-containing silicon compounds such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, and 3-mercaptopropyldimethoxymethylsilane Amino group-containing compounds such as 3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane, etc. Elemental compound, 3-chloropropyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane, or at least one of them, and alkyl group such as methyltriethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane Examples include condensates with silicon compounds. These may be used individually by 1 type and may be used in combination of 2 or more type.

The content of the silane coupling agent is preferably 0.01 to 10 parts by mass, particularly 0.05 to 5 parts by mass with respect to 100 parts by mass of the (meth) acrylic acid ester polymer (A). More preferably, the content is 0.1 to 1 part by mass.

2. Organic Fine Particles The refractive index of the organic fine particles contained in the pressure-sensitive adhesive composition P according to the present embodiment is 1.50 to 2.00, preferably 1.52 to 1.80, particularly 1.54 to It is preferably 1.65. When the refractive index is 1.50 or more, sufficient light diffusibility can be imparted without impairing durability even if the adhesive is a thin film. On the other hand, when the refractive index exceeds 2.00, there is a possibility that the optical characteristics are deteriorated due to excessive reflection at the fine particle interface.

Examples of the organic fine particles satisfying the refractive index include organic light-transmitting fine particles such as acrylic resin, polystyrene resin, polyethylene resin, and epoxy resin. Examples of the acrylic resin fine particles include those composed of a homopolymer of methyl methacrylate and a copolymer of monomers such as methyl methacrylate and vinyl acetate, styrene, methyl acrylate, and ethyl (meth) acrylate. It is done. Among them, as the organic fine particles, acrylic resin fine particles are preferable, in particular, fine particles made of a polymer containing methyl methacrylate as a constituent monomer unit are preferable, and fine particles made of a copolymer of methyl methacrylate and styrene are more preferable. . Such fine particles are preferable because they easily satisfy the refractive index. The above organic fine particles may be used individually by 1 type, and may be used in combination of 2 or more type.

The shape of the organic fine particles is preferably spherical fine particles with uniform light diffusion. The average particle diameter of the organic fine particles by the centrifugal sedimentation light transmission method is preferably 0.5 to 10 μm, particularly preferably 1.0 to 4.0 μm, and further preferably 1.2 to 2.5 μm. It is preferable. When the average particle size of the organic fine particles is 10 μm or less, the fineness is improved in the optical member with the pressure-sensitive adhesive layer to which the obtained pressure-sensitive adhesive is applied. On the other hand, when the average particle size of the organic fine particles is 0.5 μm or more, sufficient light diffusibility can be obtained.

In addition, the average particle diameter by the centrifugal sedimentation light transmission method was obtained by sufficiently stirring 1.2 g of fine particles and 98.8 g of isopropyl alcohol as a measurement sample, and using a centrifugal automatic particle size distribution measuring apparatus (manufactured by Horiba, Ltd., Measured using CAPA-700).

The content of the organic fine particles in the adhesive composition P is preferably 1 to 30 parts by mass, particularly 2 to 15 parts by mass with respect to 100 parts by mass of the active energy ray-curable adhesive component. It is preferably 4 to 9 parts by mass. In the adhesive composition P according to this embodiment, the absolute value of the difference between the refractive index of the active energy ray-curable adhesive component and the refractive index of the organic fine particles is relatively large. Therefore, sufficient light diffusibility can be achieved even if the content of the organic fine particles is small. Furthermore, as a result of being able to reduce content, the fall of the durability resulting from addition of organic fine particles is suppressed, and the outstanding durability can be achieved.

3. Refractive index difference The absolute value of the difference between the refractive index of the active energy ray-curable adhesive component and the refractive index of the organic fine particles is 0.02 to 0.50, preferably 0.04 to 0.20. In particular, it is preferably 0.06 to 0.10. Thus, since the absolute value of the refractive index difference between the active energy ray-curable adhesive component and the organic fine particles is relatively large, high light diffusibility can be achieved with a small addition amount. In particular, even when a thin adhesive layer is formed using the adhesive composition P, a sufficiently high light diffusibility can be achieved. Furthermore, since the amount of organic fine particles required to achieve the desired light diffusibility can be reduced, a decrease in durability due to the addition of organic fine particles is suppressed, and excellent durability can be achieved.

The refractive index of the active energy ray-curable adhesive component is preferably 1.40 to 1.55, particularly preferably 1.42 to 1.50, and more preferably 1.44 to 1.49. It is preferable that

Here, the refractive index of the active energy ray-curable adhesive component is a value measured according to JIS K0062 using an Abbe refractometer. In addition, since the refractive index of an active energy ray hardening adhesive component does not change before and after the curing, it may be a value measured before curing or a value measured after curing. On the other hand, the refractive index of the organic fine particles is a value measured using a refractive index standard solution, as shown in Test Examples described later.

4). Manufacturing method of adhesive composition The adhesive composition P is manufactured by mixing the (meth) acrylic acid ester polymer (A), the active energy ray-curable compound (B), the crosslinking agent (C) and the organic fine particles. can do. For example, by preparing the (meth) acrylic acid ester polymer (A) first and blending the active energy ray-curable compound (B), the cross-linking agent (C) and the organic fine particles, and an additive as required, the adhesive Composition P can be produced.

The (meth) acrylic acid ester polymer (A) can be produced by polymerizing a mixture of monomer units constituting the polymer by an ordinary radical polymerization method. The polymerization of the (meth) acrylic acid ester polymer (A) can be performed by a solution polymerization method or the like using a polymerization initiator as desired. Examples of the polymerization solvent include ethyl acetate, n-butyl acetate, isobutyl acetate, toluene, acetone, hexane, methyl ethyl ketone and the like, and two or more kinds may be used in combination.

Examples of the polymerization initiator include azo compounds and organic peroxides, and two or more kinds may be used in combination. Examples of the azo compound include 2,2′-azobisisobutyronitrile, 2,2′-azobis (2-methylbutyronitrile), 1,1′-azobis (cyclohexane 1-carbonitrile), 2 2,2'-azobis (2,4-dimethylvaleronitrile), 2,2'-azobis (2,4-dimethyl-4-methoxyvaleronitrile), dimethyl 2,2'-azobis (2-methylpropionate) 4,4′-azobis (4-cyanovaleric acid), 2,2′-azobis (2-hydroxymethylpropionitrile), 2,2′-azobis [2- (2-imidazolin-2-yl) Propane] and the like.

Examples of organic peroxides include benzoyl peroxide, t-butyl perbenzoate, cumene hydroperoxide, diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate, and di (2-ethoxyethyl) peroxy. Examples thereof include dicarbonate, t-butyl peroxyneodecanoate, t-butyl peroxybivalate, (3,5,5-trimethylhexanoyl) peroxide, dipropionyl peroxide, diacetyl peroxide and the like.

In the polymerization step, the weight average molecular weight of the resulting polymer can be adjusted by adding a chain transfer agent such as 2-mercaptoethanol.

Once the (meth) acrylic acid ester polymer (A) is obtained, the active energy ray-curable compound (B), the crosslinking agent (C) and the organic fine particles are added to the solution of the (meth) acrylic acid ester polymer (A). In addition, if desired, an additive is added and mixed well to obtain an adhesive composition P (coating solution) diluted with a solvent.

Examples of the dilution solvent for diluting the adhesive composition P to form a coating solution include aliphatic hydrocarbons such as hexane, heptane, and cyclohexane, aromatic hydrocarbons such as toluene and xylene, methylene chloride, ethylene chloride, and the like. Halogenated hydrocarbons, alcohols such as methanol, ethanol, propanol, butanol and 1-methoxy-2-propanol, ketones such as acetone, methyl ethyl ketone, 2-pentanone, isophorone and cyclohexanone, esters such as ethyl acetate and butyl acetate, ethyl A cellosolv solvent such as cellosolve is used.

The concentration / viscosity of the coating solution prepared in this manner is not particularly limited as long as it is within a coatable range, and can be appropriately selected according to the situation. For example, dilution is performed so that the concentration of the adhesive composition P is 10 to 40% by mass. In addition, when obtaining a coating solution, addition of a dilution solvent etc. is not a necessary condition, and if a viscosity etc. which can be coated with the adhesive composition P are not necessary, a dilution solvent does not need to be added.

[Adhesive]
The pressure-sensitive adhesive according to the present embodiment is obtained by curing the pressure-sensitive adhesive composition P. After the pressure-sensitive adhesive composition P is applied to a desired object and dried, the pressure-sensitive adhesive composition is irradiated with active energy rays. It can preferably be obtained by curing the product P.

Although drying of the adhesive composition P may be performed by air drying, it is usually performed by heat treatment (preferably hot air drying). In the case of performing the heat treatment, the heating temperature is preferably 50 to 150 ° C., particularly preferably 70 to 120 ° C. The heating time is preferably 10 seconds to 10 minutes, particularly preferably 50 seconds to 2 minutes.

As active energy rays, ultraviolet rays, electron beams and the like are usually used. The dose of the active energy ray varies depending on the type of the energy ray, for example, in the case of ultraviolet rays, preferably 50 ~ 1000mJ / cm ² in quantity, especially 100 ~ 500mJ / cm ² preferably. In the case of an electron beam, about 10 to 1000 krad is preferable.

In the active energy ray-curable adhesive component of the adhesive composition P, the (meth) acrylate polymer (A) is crosslinked by the crosslinking agent (C) by drying (heating treatment) of the adhesive composition P, A crosslinked structure is formed. Moreover, by irradiating the adhesive composition P with active energy rays, the plurality of active energy ray-curable compounds (B) are bonded to each other to form a three-dimensional network structure, and are crosslinked by the crosslinking agent (C) (meta ) It is presumed that the acrylate polymer (A) is trapped in the three-dimensional network structure.

[Adhesive sheet]
As shown in FIG. 1, the pressure-sensitive adhesive sheet 1 </ b> A according to the first embodiment is laminated on the pressure-sensitive adhesive layer 11, the pressure-sensitive adhesive layer 11 stacked on the release surface of the release sheet 12, and the pressure-sensitive adhesive layer 11. And the formed base material 13.

In addition, as shown in FIG. 2, the adhesive sheet 1B according to the second embodiment includes the two release sheets 12a and 12b and the two release sheets 12a and 12b so as to be in contact with the release surfaces of the two release sheets 12a and 12b. And the pressure-sensitive adhesive layer 11 sandwiched between the release sheets 12a and 12b. In addition, the release surface of the release sheet in this specification refers to a surface having peelability in the release sheet, and includes both a surface that has been subjected to a release treatment and a surface that exhibits peelability without being subjected to a release treatment. .

In any of the pressure- sensitive adhesive sheets 1A and 1B, the pressure-sensitive adhesive layer 11 is made of a pressure-sensitive adhesive formed by curing the above-described pressure-sensitive adhesive composition P.

The thickness of the pressure-sensitive adhesive layer 11 is appropriately determined according to the purpose of use of the pressure- sensitive adhesive sheets 1A and 1B, and is excellent in durability and light diffusibility while reducing the thickness of the pressure- sensitive adhesive sheets 1A and 1B. From the viewpoint, it is preferably 1 to 50 μm, more preferably 3 to 20 μm, and further preferably 5 to 15 μm in addition to the viewpoint of definition. As described above, the pressure-sensitive adhesive obtained by curing the pressure-sensitive adhesive composition P according to the present embodiment exhibits high cohesive force while containing organic fine particles. Therefore, even when the thickness of the pressure-sensitive adhesive layer 11 is reduced, excellent durability can be achieved. That is, according to the pressure-sensitive adhesive composition P according to this embodiment, a thin-film pressure-sensitive adhesive layer having excellent light diffusibility and durability can be obtained.

There is no restriction | limiting in particular as the base material 13, All can be used as a base material sheet of a normal adhesive sheet. For example, in addition to desired optical members, woven or non-woven fabrics using fibers such as rayon, acrylic, polyester, etc .; papers such as fine paper, glassine paper, impregnated paper, coated paper; metal foils such as aluminum and copper; urethane Foams, foams such as polyethylene foams; polyethylene terephthalate films, polybutylene terephthalate films, polyester films such as polyethylene naphthalate films, polyolefin films such as polyethylene films and polypropylene films, cellulose films such as triacetyl cellulose, polyvinyl chloride Film, polyvinylidene chloride film, polyvinyl alcohol film, ethylene-vinyl acetate copolymer film, polyurethane film, polystyrene film, polycarbonate film, acrylic resin film Lum, norbornene resin film, a plastic film such as a cycloolefin resin film; of two or more kinds of those laminates, and the like. The plastic film may be uniaxially stretched or biaxially stretched.

Examples of the optical member include a polarizing plate (polarizing film), a polarizer, a retardation plate (retarding film), a viewing angle compensation film, a brightness enhancement film, a contrast enhancement film, a liquid crystal polymer film, a diffusion film, and a transflective film. Etc. Among these, since the polarizing plate (polarizing film) easily shrinks and has a large dimensional change, it is suitable as a target for forming the pressure-sensitive adhesive of the present embodiment (the pressure-sensitive adhesive layer 11) from the viewpoint of durability.

Although the thickness of the substrate 13 varies depending on the type, for example, in the case of an optical member, it is usually 10 to 500 μm, preferably 50 to 300 μm, and particularly preferably 80 to 150 μm.

As the release sheets 12, 12a, 12b, for example, polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, polyethylene terephthalate film, polyethylene naphthalate film, Polybutylene terephthalate film, polyurethane film, ethylene vinyl acetate film, ionomer resin film, ethylene / (meth) acrylic acid copolymer film, ethylene / (meth) acrylic acid ester copolymer film, polystyrene film, polycarbonate film, polyimide film A fluororesin film or the like is used. These crosslinked films are also used. Furthermore, these laminated films may be sufficient.

The release surface of the release sheet (particularly the surface in contact with the pressure-sensitive adhesive layer 11) is preferably subjected to a release treatment. Examples of the release agent used for the release treatment include alkyd, silicone, fluorine, unsaturated polyester, polyolefin, and wax release agents. Of the release sheets 12a and 12b, one release sheet is preferably a heavy release release sheet having a high release force, and the other release sheet is preferably a light release release sheet having a low release force.

The thickness of the release sheets 12, 12a and 12b is not particularly limited, but is usually about 20 to 150 μm.

In order to manufacture the pressure-sensitive adhesive sheet 1A, a solution (coating solution) containing the pressure-sensitive adhesive composition P is applied to the release surface of the release sheet 12 and dried to form a coating layer of the pressure-sensitive adhesive composition P. A base material 13 is laminated on the coating layer. And it hardens | cures by irradiating an active energy ray to the said coating-film layer through the peeling sheet 12, and the adhesive layer 11 is formed. The active energy ray irradiation conditions are as described above.

Moreover, in order to manufacture the said adhesive sheet 1B, the coating solution containing the said adhesive composition P is apply | coated and dried on the peeling surface of one peeling sheet 12a (or 12b), and the coating film of the adhesive composition P After forming the layer, the other release sheet 12b (or 12a) is laminated on the coating layer. And it hardens | cures by irradiating the said coating-film layer to an active energy ray through the peeling sheet 12a (or 12b), and the adhesive layer 11 is formed.

Moreover, it replaces with forming an adhesive layer 11 by irradiating an active energy ray through a peeling sheet as mentioned above, and forms the coating-film layer of the adhesive composition P on a peeling sheet, The coating-film layer With the exposed state, the active energy ray may be irradiated to form the pressure-sensitive adhesive layer 11, and then a base material or a release sheet may be laminated on the pressure-sensitive adhesive layer 11. Furthermore, the adhesive layer 11 may be formed by directly forming a coating layer of the adhesive composition P on the substrate and irradiating the coating layer with active energy rays.

As a method for applying the coating solution, for example, a bar coating method, a knife coating method, a roll coating method, a blade coating method, a die coating method, a gravure coating method, or the like can be used.

The pressure-sensitive adhesive strength of the pressure-sensitive adhesive sheet according to this embodiment is preferably 0.5 to 20 N / 25 mm, particularly preferably 1 to 15 N / 25 mm, and more preferably 3 to 10 N. / 25 mm or more is preferable. In addition, adhesive force here means 180 degree peeling adhesive force (peeling speed 300mm / min) according to JIS Z0237: 2009, affixed to a to-be-adhered body, and pressurizes for 20 minutes at 0.5 MPa and 50 degreeC. After that, it is measured after being left for 24 hours under conditions of 23 ° C. and 50% RH. When the adhesive force is within the above range, it is possible to prevent floating or peeling when applied to an optical member such as a polarizing plate.

The transmission clarity (image definition) of the pressure-sensitive adhesive layer in the pressure-sensitive adhesive sheet according to the present embodiment is transmission clarity by optical combs having comb widths of 0.125 mm, 0.25 mm, 0.5 mm, 1.0 mm, and 2.0 mm. When expressed in terms of the total degree, it is preferably 200 to 500%, particularly preferably 290 to 490%, and more preferably 400 to 480%. At this time, the thickness of the pressure-sensitive adhesive layer is, for example, 5 to 15 μm. In addition, the transmission definition here means the transmission definition measured according to the transmission method of JIS K7374: 2007.

The haze value (measured according to JIS K7136: 2000) of the pressure-sensitive adhesive layer in the pressure-sensitive adhesive sheet according to this embodiment is preferably 20 to 95%, particularly preferably 40 to 90%, Is preferably 50 to 85%. When the haze value is in the above range, the pressure-sensitive adhesive according to this embodiment can achieve both light diffusibility and fineness. At this time, the thickness of the pressure-sensitive adhesive layer is, for example, 5 to 15 μm.

Here, for example, to manufacture a liquid crystal display device composed of a liquid crystal cell and a polarizing plate, a polarizing plate is used as the base material 13 of the pressure-sensitive adhesive sheet 1A, and the release sheet 12 of the pressure-sensitive adhesive sheet 1A is peeled off. What is necessary is just to bond the exposed adhesive layer 11 and a liquid crystal cell.

For example, in order to manufacture a liquid crystal display device in which a retardation plate is disposed between a liquid crystal cell and a polarizing plate, as an example, first, one release sheet 12a (or 12b) of the adhesive sheet 1B is released. Then, the pressure-sensitive adhesive layer 11 exposed from the pressure-sensitive adhesive sheet 1B and the phase difference plate are bonded together. Next, the release sheet 12 of the pressure-sensitive adhesive sheet 1A using a polarizing plate as the base material 13 is peeled off, and the pressure-sensitive adhesive layer 11 exposed from the pressure-sensitive adhesive sheet 1A and the retardation plate are bonded. Furthermore, the other release sheet 12b (or 12a) is peeled from the pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet B, and the pressure-sensitive adhesive layer 11 exposed from the pressure-sensitive adhesive sheet B is bonded to the liquid crystal cell.

According to the above pressure- sensitive adhesive sheets 1A and 1B, an optical member exhibiting excellent light diffusibility can be obtained by the pressure-sensitive adhesive layer 11. In addition, since the pressure-sensitive adhesive layer 11 is extremely excellent in form stability, even when applied to adhesion of a polarizing plate, for example, deformation of the polarizing plate can be suppressed by the pressure-sensitive adhesive layer 11, thereby exhibiting high durability. It is estimated to be. Thereby, it is possible to impart excellent light diffusibility and excellent temporal stability to the optical member even in an environment where a heat history is applied.

The embodiment described above is described for facilitating understanding of the present invention, and is not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

For example, the release sheet 12 of the adhesive sheet 1A may be omitted, or one of the release sheets 12a and 12b in the adhesive sheet 1B may be omitted.

Hereinafter, the present invention will be described more specifically with reference to examples and the like, but the scope of the present invention is not limited to these examples and the like.

[Example 1]
1. Preparation of (meth) acrylic acid ester polymer 94.5 parts by mass of n-butyl acrylate, 5 parts by mass of acrylic acid and 0.5 parts by mass of 2-hydroxyethyl acrylate were copolymerized to give (meth) acrylic acid ester. A polymer (A) was prepared. When the molecular weight of this (meth) acrylic acid ester polymer (A) was measured by the method described later, the weight average molecular weight was 1.8 million.

2. Preparation of Adhesive Composition 100 parts by mass of the (meth) acrylic acid ester polymer (A) obtained in the above process (solid content converted value; the same applies hereinafter) and Tris (as an active energy ray-curable compound (B)) Acryloxyethyl) isocyanurate (manufactured by Toagosei Co., Ltd., product name “Aronix M-315”; molecular weight 423) and 15 parts by mass of trimethylolpropane modified tolylene diisocyanate (manufactured by Nippon Polyurethane Co., Ltd., product) (Name “Coronate L”) 0.3 parts by mass, and then a mixture of benzophenone and 1-hydroxycyclohexyl phenyl ketone as a photopolymerization initiator at a mass ratio of 1: 1 (manufactured by Ciba Specialty Chemicals, Product name “Irgacure 500”) 1.5 parts by mass, 3-glycidoxyp as silane coupling agent 0.2 parts by mass of pyrrole trimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., product name “KBM-403”) (above, active energy ray-curable adhesive component), and styrene as organic fine particles (acrylic resin fine particles) 5 parts by mass of resin beads made of a copolymer with methyl methacrylate (manufactured by Sekisui Plastics Co., Ltd., product name “XX-16LA”, average particle size: 2.5 μm, refractive index 1.555) are added sufficiently. The mixture was stirred and diluted with ethyl acetate to obtain a coating solution of the adhesive composition.

Here, Table 1 shows the composition of the adhesive composition. Details of the abbreviations and the like described in Table 1 are as follows.
[Styrene / PMMA copolymer fine particles]
XX-16LA: Resin beads made of a copolymer of styrene and methyl methacrylate (manufactured by Sekisui Plastics Co., Ltd., product name “XX-16LA”, average particle size: 2.5 μm, refractive index: 1.555)
XX-11LA: resin beads made of a copolymer of styrene and methyl methacrylate (manufactured by Sekisui Plastics Co., Ltd., product name “XX-11LA”, average particle size: 3.5 μm, refractive index: 1.555)
XX-06LA: Resin beads made of a copolymer of styrene and methyl methacrylate (manufactured by Sekisui Plastics Co., Ltd., product name “XX-06LA”, average particle size: 6 μm, refractive index: 1.555)
[PMMA fine particles]
XX-28LA: Resin beads made of crosslinked methacrylic acid polymer (manufactured by Sekisui Plastics Co., Ltd., product name “XX-28LA”, average particle size: 1.5 μm, refractive index: 1.525)
SSX-103: Resin beads made of crosslinked methacrylic acid polymer (manufactured by Sekisui Plastics Co., Ltd., product name “SSX-103”, average particle size: 3.0 μm, refractive index: 1.490)
[Silicone fine particles]
Tospearl 120: Fine particles composed of a silicon-containing compound having an intermediate structure between inorganic and organic (manufactured by Momentive Performance Materials Japan, product name “Tospearl 120”, average particle size: 2.0 μm, refractive index: 1.430)
Tospearl 145: Fine particles composed of a silicon-containing compound having an intermediate structure between inorganic and organic (manufactured by Momentive Performance Materials Japan, product name “Tospearl 145”, average particle size: 4.5 μm, refractive index: 1.430)

3. Production of polarizing plate with pressure-sensitive adhesive layer A release sheet (SP-PET3811, manufactured by Lintec Corporation, thickness) of a coating solution of the pressure-sensitive adhesive composition obtained in the above-described process was prepared by peeling one side of a polyethylene terephthalate film with a silicone-based release agent. : 38 μm) was applied to the release-treated surface with a knife coater, followed by heat treatment at 90 ° C. for 1 minute to form a coating layer of the adhesive composition.

Next, a polarizing plate made of a polarizing film with a discotic liquid crystal layer and integrated with a polarizing film and a viewing angle widening film was bonded to the exposed surface side of the coating layer. Then, the polarizing plate with an adhesive layer was obtained by irradiating an ultraviolet-ray on the following conditions through a peeling sheet, and making the said coating-film layer into an adhesive layer. In addition, the thickness of the formed adhesive layer was 15 micrometers.
<Ultraviolet irradiation conditions>
Fusion Co. electrodeless lamp H bulb used, illuminance 600 mW / cm ^2, light quantity 150 mJ / cm ²
・ UV illuminance / light meter uses "UVPF-36" manufactured by Eye Graphics.

[Examples 2 to 12, Comparative Examples 1 to 6]
A polarizing plate with a pressure-sensitive adhesive layer was produced in the same manner as in Example 1 except that the type and blending amount of the organic fine particles were changed as shown in Table 1.

Here, the above-mentioned weight average molecular weight (Mw) is a polystyrene-reduced weight average molecular weight measured under the following conditions (GPC measurement) using gel permeation chromatography (GPC).
<Measurement conditions>
GPC measurement device: manufactured by Tosoh Corporation, HLC-8020
GPC column (passed in the following order): TSK guard column HXL-H manufactured by Tosoh Corporation
TSK gel GMHXL (× 2)
TSK gel G2000HXL
・ Measurement solvent: Tetrahydrofuran ・ Measurement temperature: 40 ° C.

[Test Example 1] (Measurement of refractive index and calculation of refractive index difference)
The refractive index of the organic fine particles used in Examples and Comparative Examples was measured by the following method. Fine particles were placed on a slide glass, a refractive index standard solution was dropped on the fine particles, and a cover glass was put on to prepare a sample. The sample was observed with a microscope, and the refractive index of the refractive index standard solution in which the outline of the fine particles was most difficult to see was taken as the refractive index of the fine particles.

On the other hand, the refractive index of the adhesive component used in Examples and Comparative Examples was measured by the following method. In each adhesive composition of Examples and Comparative Examples, organic fine particles were not added, and instead of the polarizing plate used for the preparation of the polarizing plate with the adhesive layer, one side of the polyethylene terephthalate film was replaced with a silicone-based release agent. A release sheet (SP-PET3801, manufactured by Lintec Corporation, thickness: 38 μm) subjected to a release treatment was used, the pressure-sensitive adhesive layer was set to 25 μm, and the others were similarly performed. The release sheet (SP-PET3801) / the pressure-sensitive adhesive layer ( A pressure-sensitive adhesive sheet having a structure of (thickness: 25 μm) / release sheet (SP-PET3811) was produced.

A single pressure-sensitive adhesive layer obtained by peeling two release sheets from the pressure-sensitive adhesive sheet was used as a measurement sample. With respect to this measurement sample, the refractive index was measured according to JIS K0062-1992 using an Abbe refractometer, and this was taken as the refractive index of the active energy ray-curable adhesive component.

From the above measurement results, the refractive index difference between the active energy ray-curable adhesive component and the organic fine particles was calculated.

Table 2 shows the refractive index of the organic fine particles and the adhesive component measured as described above, and the absolute value of the difference in the produced refractive index.

[Test Example 2] (Measurement of haze value)
Instead of the polarizing plate used for the preparation of the polarizing plate with the pressure-sensitive adhesive layer in Examples and Comparative Examples, a release sheet (SP-PET 3801, manufactured by Lintec Co., Ltd., thickness) on which one side of the polyethylene terephthalate film was treated with a silicone-based release agent. The pressure-sensitive adhesive sheet having a structure of release sheet (SP-PET3801) / adhesive layer / release sheet (SP-PET3811) was prepared.

About the adhesive layer of the obtained adhesive sheet, haze value (%) was measured according to JISK7136: 2000 using the haze meter (Nippon Denshoku Industries Co., Ltd. make, NDH2000). The results are shown in Table 2.

[Test Example 3] (Measurement of transmission clarity)
Instead of the polarizing plate used for the preparation of the polarizing plate with the pressure-sensitive adhesive layer in Examples and Comparative Examples, a release sheet (SP-PET 3801, manufactured by Lintec Co., Ltd., thickness) on which one side of the polyethylene terephthalate film was treated with a silicone-based release agent. The pressure-sensitive adhesive sheet having a structure of release sheet (SP-PET3801) / adhesive layer / release sheet (SP-PET3811) was prepared.

For the pressure-sensitive adhesive surface of the pressure-sensitive adhesive layer within 1 minute after peeling off the release sheet from the obtained pressure-sensitive adhesive sheet, an image clarity measuring device (ICM-1DP, manufactured by Suga Test Instruments Co., Ltd.) was applied in accordance with the transmission method of JIS K7374: 2007. The transmission sharpness (image sharpness) was measured. The comb widths of the optical combs in the image clarity measuring device used were 0.125 mm, 0.25 mm, 0.5 mm, 1.0 mm and 2.0 mm. Table 2 shows the total value (%) of transmission clarity measured for each optical comb.

[Test Example 4] (Durability evaluation)
The polarizing plate with the pressure-sensitive adhesive layer obtained in Examples and Comparative Examples was cut into a size of 233 mm × 309 mm using a cutting device (Super Cutter manufactured by Hadano Seisakusho, PN1-600). After peeling off the release sheet from the above polarizing plate with the pressure-sensitive adhesive layer and pasting the exposed pressure-sensitive adhesive layer on alkali-free glass (Corning Corp., Eagle XG), 0.5 MPa and 50 ° C. in an autoclave manufactured by Kurihara Seisakusho, The sample was pressurized for 20 minutes and used as an evaluation sample.

The evaluation sample was put in an environment of 80 ° C. in a dry state (relative humidity of less than 35%) for 500 hours, and then the presence or absence of lifting or peeling was confirmed using a 10 × loupe. And durability was evaluated by the following evaluation criteria. The results are shown in Table 2.
A: No lifting or peeling was confirmed.
○: Lifting or peeling of a size of 0.5 mm or less was confirmed.
X: Floating or peeling of a size exceeding 0.5 mm was confirmed.

[Test Example 5] (Evaluation of definition)
A metal-deposited layer was provided on the glass plate, and a resist pattern and an etching process were performed to form a lattice pattern having a light transmission portion with a size of 60 ppi (pixels / inch). The glass plate provided with the lattice pattern was placed on a backlight (Bright Box 5000, manufactured by King Corp.).

Next, the release sheet of the polarizing plate with the pressure-sensitive adhesive layer obtained in Examples and Comparative Examples is peeled off, and placed on the lattice pattern so that the polarizing plate side of the polarizing plate with the pressure-sensitive adhesive layer is down, The location where glare occurred was confirmed. And when the polarizing plate with the pressure-sensitive adhesive layer is moved in a direction parallel to the glass plate on the lattice pattern, and the occurrence of glare that has been confirmed in advance has moved together with the polarizing plate with the pressure-sensitive adhesive layer, It was judged that the occurrence of the glare was due to the polarizing plate with the pressure-sensitive adhesive layer.

In addition, when the occurrence of glare due to the polarizing plate with the adhesive layer was not confirmed in the lattice pattern of 60 ppi, the occurrence of glare due to the lattice pattern of 70 ppi and still the polarizing plate with the adhesive layer was observed. If it was not confirmed, the same operation was performed until the occurrence of glare caused by the polarizing plate with the pressure-sensitive adhesive layer was confirmed using a lattice pattern of 10 ppi in sequence, such as a lattice pattern of 80 ppi. Went. Table 2 shows the largest lattice pattern (ppi) of ppi in which the occurrence of glare due to the polarizing plate with the pressure-sensitive adhesive layer is not confirmed.

Here, the glare caused by the polarizing plate with the pressure-sensitive adhesive layer is more likely to occur as ppi in the lattice pattern increases, in other words, as the display becomes higher definition. Therefore, it means that generation | occurrence | production of glare can be suppressed effectively, so that the value of ppi shown in Table 2 is large. In addition, what exceeds 100 ppi can be called a high-definition polarizing plate.

[Test Example 6] (Measurement of adhesive strength)
The pressure-sensitive adhesive layer-attached polarizing plate obtained in Examples or Comparative Examples was cut to prepare samples having a width of 25 mm and a length of 100 mm. After peeling the release sheet from this sample and pasting the sample on alkali-free glass (Corning, Eagle XG) through the exposed adhesive layer, 0.5 MPa at 50 ° C. in an autoclave manufactured by Kurihara Seisakusho, Pressurized for 20 minutes. Then, after leaving for 24 hours under the conditions of 23 ° C. and 50% RH, using a tensile tester (Orientec Co., Ltd., Tensilon), the adhesive strength (adhesion) under the conditions of a peeling speed of 300 mm / min and a peeling angle of 180 °. The adhesive strength after 1 day; N / 25 mm) was measured. The results are shown in Table 2.

From Table 2, it can be seen that the polarizing plate with the pressure-sensitive adhesive layer of the examples has excellent light diffusibility and excellent durability. Furthermore, it turns out that the polarizing plate with an adhesive layer of an Example also has sufficient definition and adhesive force.

The pressure-sensitive adhesive composition, pressure-sensitive adhesive, and pressure-sensitive adhesive sheet according to the present invention are suitable for optical members having light diffusibility, and are particularly used for uniformly diffusing light from a backlight in a liquid crystal display device. Suitable for optical members.

1A, 1B ... Adhesive sheet 11 ... Adhesive layer 12, 12a, 12b ... Release sheet 13 ... Base material

Claims (7)

1. An adhesive composition containing an active energy ray-curable adhesive component and organic fine particles,
   The active energy ray-curable adhesive component contains a (meth) acrylic acid ester polymer, an active energy ray-curable compound and a crosslinking agent,
   The organic fine particles have a refractive index of 1.50 to 2.00,
   A pressure-sensitive adhesive composition, wherein an absolute value of a difference between a refractive index of the active energy ray-curable pressure-sensitive adhesive component and a refractive index of the organic fine particles is 0.02 to 0.50.
2. 2. The pressure-sensitive adhesive composition according to claim 1, wherein the average particle diameter of the organic fine particles by a centrifugal sedimentation light transmission method is 0.5 to 10 μm.
3. 3. The pressure-sensitive adhesive composition according to claim 1 or 2, wherein the organic fine particles are fine particles composed of a polymer containing methyl methacrylate as a constituent monomer unit.
4. A pressure-sensitive adhesive obtained by curing the pressure-sensitive adhesive composition according to any one of claims 1 to 3.
5. The pressure-sensitive adhesive according to claim 4, having a haze value of 20 to 95%.
6. A pressure-sensitive adhesive sheet comprising a base material and a pressure-sensitive adhesive layer,
   The said adhesive layer consists of an adhesive of Claim 4 or 5, The adhesive sheet characterized by the above-mentioned.
7. Two release sheets,
   An adhesive layer sandwiched between the release sheets so as to be in contact with the release surfaces of the two release sheets;
   The said adhesive layer consists of an adhesive of Claim 4 or 5, The adhesive sheet characterized by the above-mentioned.

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