JP5821309B2 - Light diffusing adhesive sheet, polarizing plate and liquid crystal display panel - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a light diffusable pressure-sensitive adhesive composition and a light diffusable pressure-sensitive adhesive sheet, and specifically relates to a light diffusable pressure-sensitive adhesive composition and a light diffusable pressure-sensitive adhesive sheet that are suitably used for polarizing plates. The present invention also relates to a polarizing plate with an adhesive layer and a liquid crystal display panel using the light diffusable adhesive composition.

  A polarizing plate is widely used as a member constituting a liquid crystal display device. The use of a liquid crystal display device is rapidly expanding as a thin display device used for a liquid crystal television, a liquid crystal monitor, a notebook personal computer, a desktop personal computer, and the like.

  A typical liquid crystal display device includes a backlight using a cold cathode tube or LED as a light source, one or a plurality of diffusion sheets, a light collecting sheet, and a liquid crystal display panel in which a polarizing plate is bonded to a liquid crystal display cell. Consists of. In recent years, in notebook personal computers and liquid crystal monitors, demands for thinning liquid crystal display devices have become apparent, and correspondingly, it is required to reduce the thickness of members and the number of members to be used.

  For example, Japanese Patent Application Laid-Open No. 11-295714 (Patent Document 1) discloses a technology in which a prism sheet having a light condensing property is directly provided on one surface of a polarizing plate, and the prism surface is directed to a backlight (surface light source device) side. Has been. Japanese Patent Laying-Open No. 2005-17355 (Patent Document 2) discloses a configuration in which a protective film having a condensing prism structure is arranged on the backlight side surface of a polarizing plate arranged on the back side of a liquid crystal display device. ing. Furthermore, Japanese Patent Laid-Open No. 2008-262133 (Patent Document 3) discloses that a microlens film is laminated on the light exit surface of a light guide plate constituting a backlight so that the microlens surface is on the outside, while the back side is A configuration is disclosed in which a microprism film is laminated on the polarizing plate, and the microprism surface (waveform surface) is disposed facing the microlens film. Patent Document 3 also discloses that the backlight-side transparent protective film of the polarizing plate disposed on the back side of the liquid crystal display device is composed of the above-described microprism film. As described above, techniques for reducing the thickness of the liquid crystal display device by omitting one or more members from the liquid crystal display device and reducing the number of members have been actively proposed.

  On the other hand, in the field of pressure-sensitive adhesive (also called pressure-sensitive adhesive) for attaching a polarizing plate to a liquid crystal cell, the acrylic resin constituting the pressure-sensitive adhesive is made a mixture of a high molecular weight body and a low molecular weight body, thereby It is known to suppress peeling and white spots. For example, Japanese Patent Application Laid-Open No. 2004-2782 (Patent Document 4) discloses a high molecular weight acrylic resin having a reactive functional group and a weight average molecular weight in the range of 900,000 to 2.5 million, and a weight average molecular weight of 50,000. It is disclosed that a cross-linking agent is blended in a mixture with a low molecular weight acrylic resin in a range of ˜200,000 to obtain a pressure-sensitive adhesive composition for a polarizing plate. JP-A-2006-77224 (Patent Document 5) discloses a low molecular weight acrylic resin having a weight average molecular weight in the range of 50,000 to 500,000, a polar functional group, and a weight average molecular weight of 1,000,000 to A pressure-sensitive adhesive is obtained by blending a cross-linking agent with a mixture of high molecular weight acrylic resins having a molecular weight distribution Mw / Mn which is a ratio of the weight average molecular weight Mw and the number average molecular weight Mn, which is in the range of 1.5 million, and narrowed to 5 or less. It is disclosed.

  A pressure-sensitive adhesive layer formed from such a pressure-sensitive adhesive is provided on the surface of the polarizing plate to form a polarizing plate with a pressure-sensitive adhesive layer, which is adhered to the liquid crystal cell glass on the pressure-sensitive adhesive layer side to obtain a liquid crystal panel. In this state, when it is placed under high temperature or high temperature and high humidity conditions, or when heating and cooling are repeated, foaming occurs in the adhesive layer with the dimensional change of the polarizing plate, between the optical film and the adhesive layer, Or, since the float or peeling may occur between the adhesive layer and the liquid crystal cell glass, the polarizing plate with the adhesive layer is required not to have such problems and to be excellent in so-called adhesive durability. Also, when exposed to high temperatures, the distribution of residual stress acting on the polarizing plate becomes non-uniform, and stress concentration occurs on the outer periphery of the polarizing plate, resulting in a phenomenon called whitening that causes the outer periphery to become whitish during black display. Or color unevenness may occur, and suppression of such white spots and color unevenness is also required. In addition, when there is a defect when attaching the polarizing plate with the adhesive layer to the liquid crystal cell, the polarizing plate is removed once and then a new polarizing plate is attached again. A so-called rework property is also required that the layer is peeled off along with the polarizing plate, no adhesive remains on the cell glass, and no fogging occurs.

JP-A-11-295714 JP 2005-17355 A JP 2008-262133 A Japanese Patent Laid-Open No. 2004-2882 JP 2006-77224 A

  Now, in the liquid crystal display device using a polarizing plate provided with a member having a concavo-convex surface such as a microprism sheet as disclosed in Patent Documents 1 to 3, moiré was often generated in the display.

  The present invention has been made to solve such problems, and the object of the present invention is also in a liquid crystal display device using a polarizing plate including a member having an uneven surface such as a microprism sheet. In order to suppress the occurrence of moiré, when adhering fine particles to the adhesive for adhering the polarizing plate to the liquid crystal cell glass to provide light diffusibility, and when applied to the polarizing plate, adhesion durability An object of the present invention is to provide a light diffusable pressure-sensitive adhesive composition that can provide a liquid crystal display device excellent in image quality and suppressing moire generated from a sheet member having an uneven surface such as a prism sheet. The present invention also provides a light diffusable pressure-sensitive adhesive sheet using the light diffusable pressure-sensitive adhesive composition, and a polarizing plate with an adhesive layer, and further applies the polarizing plate with an adhesive layer to a liquid crystal display panel. Objective.

  That is, according to the present invention, the acrylic resin and the spherical fine particles are contained; the acrylic resin and the spherical fine particles have a refractive index difference between them exceeding 0.01 and less than 0.09; , A mixture of a high molecular weight acrylic resin having a weight average molecular weight in the range of 500,000 to 2,000,000 and a low molecular weight acrylic resin having a weight average molecular weight in the range of 1,000 to 150,000. The light diffusable pressure-sensitive adhesive composition contains 33% by weight; the spherical fine particles have an average particle diameter in the range of 5 to 15 μm and are blended in an amount of 20 to 50 parts by weight with respect to 100 parts by weight of the acrylic resin. Provided.

  In this light diffusable pressure-sensitive adhesive composition, the high molecular weight acrylic resin comprises 70 to 99.8% by weight of a structural unit derived from a (meth) acrylic acid alkyl ester having an alkyl group having 1 to 14 carbon atoms, and It is preferable to contain 0.2 to 10% by weight of a structural unit derived from a (meth) acrylic acid compound having a crosslinkable polar functional group. The low molecular weight acrylic resin preferably contains 80 to 100% by weight of a structural unit derived from a (meth) acrylic acid alkyl ester having an alkyl group having 1 to 14 carbon atoms. In this case, it can be arbitrarily cross-linked. 0 to 10% by weight of a structural unit derived from a (meth) acrylic acid compound having a polar functional group can be contained.

  These light-diffusing pressure-sensitive adhesive compositions can further contain a crosslinking agent, preferably an isocyanate-based crosslinking agent, and can contain a silane-based compound in order to improve adhesion to the liquid crystal cell glass. Furthermore, an ionic compound can be contained in order to impart antistatic properties.

  A light diffusable pressure-sensitive adhesive sheet can be obtained by forming a pressure-sensitive adhesive layer comprising any of these light diffusable pressure-sensitive adhesive compositions on a base film. In this light diffusable pressure-sensitive adhesive sheet, the pressure-sensitive adhesive layer preferably has a haze in the range of 25 to 50%, and the width of the dark part and the light part is 0.125 mm, 0.5 mm, 1.0 mm, and It is preferable that the total value of transmitted sharpness measured using four types of optical combs of 2.0 mm is 150% or less.

  By providing a light diffusive pressure-sensitive adhesive layer formed from any one of the light diffusable pressure-sensitive adhesive compositions on the surface of the polarizing plate, a polarizing plate with a pressure-sensitive adhesive layer imparted with light diffusibility can be obtained. Moreover, it can be set as a liquid crystal display panel by sticking this polarizing plate with an adhesive layer to liquid crystal cell glass by the light diffusable adhesive layer side.

  The light diffusive pressure-sensitive adhesive composition of the present invention has good adhesion durability and suppresses display defects such as moire when it is applied to a polarizing plate and further applied to a liquid crystal display panel or a liquid crystal display device. Therefore, the display quality is excellent. Moreover, according to this invention, since the light-diffusion function is provided to the adhesion layer, the thickness reduction of a polarizing plate and the liquid crystal display panel to which this is applied can be achieved. The liquid crystal display device to which the polarizing plate having the adhesive layer is applied can be suitably used for a notebook personal computer, a liquid crystal monitor, and the like.

It is a schematic sectional drawing which shows a preferable example of the light diffusable adhesive sheet which concerns on this invention. It is a schematic sectional drawing which shows a preferable example of the polarizing plate with the adhesion layer which concerns on this invention. It is a schematic sectional drawing which shows a preferable example of the liquid crystal display panel which concerns on this invention.

  Hereinafter, the present invention will be described in detail.

[Light-diffusing adhesive composition]
In the present invention, spherical fine particles are blended in an acrylic resin to obtain a light diffusable pressure-sensitive adhesive composition. At this time, the refractive index difference between the acrylic resin and the spherical fine particles is set to be in the range of more than 0.01 and less than 0.09. The acrylic resin is composed of a mixture of a high molecular weight acrylic resin having a weight average molecular weight in the range of 500,000 to 2,000,000 and a low molecular weight acrylic resin having a weight average molecular weight in the range of 1,000 to 150,000. The acrylic resin accounts for 5 to 33% by weight based on the total amount of the acrylic resin. Further, spherical fine particles having an average particle diameter in the range of 5 to 15 μm are selected and blended at a ratio of 20 to 50 parts by weight with respect to 100 parts by weight of the acrylic resin. By setting it as such a specific combination, favorable adhesive performance and optical performance are expressed.

  This light diffusable pressure-sensitive adhesive composition can contain a cross-linking agent in order to form a good cross-linked structure when used as an adhesive layer. Moreover, in order to improve adhesiveness with liquid crystal cell glass, a silane type compound can be contained. Furthermore, an ionic compound can be contained in order to impart antistatic properties. First, description will be made step by step for each of these components constituting the light diffusable pressure-sensitive adhesive composition.

<acrylic resin>
The acrylic resin constituting the pressure-sensitive adhesive composition is generally composed mainly of a structural unit derived from (meth) acrylic acid ester, such as a heterocyclic group including a free carboxyl group, a hydroxyl group, an amino group, and an epoxy ring, It contains a structural unit derived from an unsaturated monomer having a crosslinkable polar functional group, preferably a (meth) acrylic acid compound having a polar functional group. Here, (meth) acrylic acid means that either acrylic acid or methacrylic acid may be used, and “(meth)” when referred to as (meth) acrylate or the like has the same meaning.

  The (meth) acrylic acid ester constituting the acrylic resin is preferably mainly composed of an alkyl ester or an alkoxyalkyl ester. Specifically, the (meth) acrylic acid alkyl ester represented by the following formula (I) is mainly used. It is preferable to use as a component.

In the formula, R ₁ represents a hydrogen atom or a methyl group, and R ₂ represents an alkyl group having 1 to 14 carbon atoms which may be substituted with an alkoxy group having 1 to 10 carbon atoms.

In the above formula (I), as the (meth) acrylic acid ester in which R ₂ is an alkyl group, specifically, methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, n-octyl acrylate Linear alkyl acrylates such as lauryl acrylate; branched alkyl alkyl esters such as isobutyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate; methyl methacrylate, ethyl methacrylate, methacryl Linear alkyl methacrylates such as propyl acid, n-butyl methacrylate, n-octyl methacrylate and lauryl methacrylate; branched such as isobutyl methacrylate, 2-ethylhexyl methacrylate and isooctyl methacrylate Alkyl methacrylate Such ester are exemplified.

Further, in the above formula (I), as the (meth) acrylic acid ester in which R ₂ is an alkyl group substituted with an alkoxy group, that is, an alkoxyalkyl group, specifically, 2-methoxyethyl acrylate, ethoxy acrylate Examples include methyl, 2-methoxyethyl methacrylate, ethoxymethyl methacrylate and the like.

  These (meth) acrylic acid alkyl esters can be used alone or in combination with a plurality of different ones.

  These alkyl (meth) acrylates can be further copolymerized with an unsaturated monomer having one olefinic double bond and at least one aromatic ring in the molecule. As the group containing an olefinic double bond, those having a (meth) acryloyl group are preferred. Examples of the unsaturated monomer having an aromatic ring are (meth) acrylic acid (meth) acrylic acid 2-phenoxyethyl, (meth) acrylic acid 2- (2-phenoxyethoxy) ethyl, ethylene oxide-modified nonylphenol (meth) acrylic. Acid ester, 2- (o-phenylphenoxy) ethyl (meth) acrylate, benzyl (meth) acrylate, benzoic acid / (meth) acrylic acid mixed ester of neopentyl glycol, and the like. In particular, (meth) acrylic acid ester having a phenoxyethyl group is preferable. These unsaturated monomers having one olefinic double bond and at least one aromatic ring in these molecules may be used alone or in combination with a plurality of different monomers.

  Moreover, (meth) acrylic acid ester which has an alicyclic structure in a molecule | numerator can also be copolymerized. The alicyclic structure is a cycloparaffin structure having usually 5 or more carbon atoms, preferably about 5 to 7 carbon atoms. Specific examples of the acrylate ester having an alicyclic structure include isobornyl acrylate, cyclohexyl acrylate, dicyclopentanyl acrylate, cyclododecyl acrylate, methylcyclohexyl acrylate, trimethylcyclohexyl acrylate, tert-acrylate Examples include butyl cyclohexyl, α-ethoxy acrylate cyclohexyl, cyclohexyl phenyl acrylate, and the like. Specific examples of the methacrylic acid ester having an alicyclic structure include isobornyl methacrylate, cyclohexyl methacrylate, dicyclopentanyl methacrylate, cyclododecyl methacrylate, methyl cyclohexyl methacrylate, trimethyl cyclohexyl methacrylate, tert-methacrylic acid tert- Examples thereof include butylcyclohexyl and cyclohexylphenyl methacrylate.

  As described above, the (meth) acrylic acid ester as described above includes an unsaturated monomer having a crosslinkable polar functional group, preferably a (meth) acrylic acid compound having a polar functional group. Polymerized. Examples of unsaturated monomers having such crosslinkable polar functional groups include unsaturated monomers having free carboxyl groups such as acrylic acid, methacrylic acid, and β-carboxyethyl acrylate; (meth) acrylic Unsaturated monomers having a hydroxyl group such as 2-hydroxyethyl acid, 2-hydroxypropyl (meth) acrylate, 2- or 3-chloro-2-hydroxypropyl (meth) acrylate, and diethylene glycol mono (meth) acrylate Acryloylmorpholine, vinylcaprolactam, N-vinyl-2-pyrrolidone, tetrahydrofurfuryl (meth) acrylate, caprolactone-modified tetrahydrofurfuryl acrylate, 3,4-epoxycyclohexylmethyl (meth) acrylate, glycidyl (meth) acrylate, and Unsaturated monomers having a heterocyclic group such as 1,5-dihydrofuran; unsaturated monomers having an amino group different from the heterocyclic ring such as N, N-dimethylaminoethyl (meth) acrylate . These unsaturated monomers having a polar functional group may be used singly or a plurality of different monomers may be used.

  In the present invention, as described above, a high molecular weight acrylic resin having a weight average molecular weight in the range of 500,000 to 2,000,000 and a low molecular weight acrylic resin having a weight average molecular weight in the range of 1,000 to 150,000 are mixed to obtain an adhesive. The acrylic resin constituting the composition is used. Among these, the high molecular weight acrylic resin is derived from the (meth) acrylic acid alkyl ester described above, particularly the (meth) acrylic acid alkyl ester having an alkyl group having 1 to 14 carbon atoms represented by the formula (I). And a copolymer having at least a structural unit derived from a (meth) acrylic acid-based compound having a crosslinkable polar functional group.

  Specifically, the total non-volatile content of the high molecular weight acrylic resin is 100% by weight, and the structural unit derived from (meth) acrylic acid alkyl ester is usually 60 to 99.9% by weight, preferably 70 to 99.8. A structural unit derived from a (meth) acrylic acid compound having a polar functional group and contained in a percentage by weight is usually 0.1 to 20% by weight, preferably 0.2 to 10% by weight. It can be contained. When copolymerizing an unsaturated monomer having one olefinic double bond and at least one aromatic ring in the molecule, or a (meth) acrylic acid ester having an alicyclic structure The unit is contained at a ratio of about 20% by weight or less based on the entire nonvolatile content of the high molecular weight acrylic resin.

  The high molecular weight acrylic resin may contain a structural unit derived from a monomer other than the (meth) acrylic acid ester including the alkyl ester described above and the (meth) acrylic acid compound having a polar functional group. Examples of these include structural units derived from styrene monomers, structural units derived from vinyl monomers, structural units derived from monomers having a plurality of (meth) acryloyl groups in the molecule, and the like. be able to.

  Examples of styrenic monomers include styrene, methyl styrene, dimethyl styrene, trimethyl styrene, ethyl styrene, diethyl styrene, triethyl styrene, propyl styrene, butyl styrene, hexyl styrene, heptyl styrene, and octyl styrene. Alkyl styrenes; halogenated styrenes such as fluorostyrene, chlorostyrene, bromostyrene, dibromostyrene, and iodostyrene; and nitrostyrene, acetylstyrene, methoxystyrene, divinylbenzene, and the like.

  Examples of vinyl monomers include vinyl acetate, vinyl propionate, vinyl butyrate, vinyl 2-ethylhexanoate and vinyl laurate such as vinyl esters; vinyl halides such as vinyl chloride and vinyl bromide; Examples include vinylidene halides such as vinylidene chloride; nitrogen-containing aromatic vinyls such as vinylpyridine, vinylpyrrolidone, and vinylcarbazole; conjugated diene monomers such as butadiene, isoprene, and chloroprene; and acrylonitrile, methacrylonitrile, and the like.

  Examples of monomers having a plurality of (meth) acryloyl groups in the molecule include 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, and 1,9-nonane. Two diols in the molecule, such as diol di (meth) acrylate, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, and tripropylene glycol di (meth) acrylate A monomer having a (meth) acryloyl group; a monomer having three (meth) acryloyl groups in the molecule, such as trimethylolpropane tri (meth) acrylate.

  When a monomer other than a (meth) acrylic acid ester and a (meth) acrylic acid-based compound having a polar functional group is copolymerized, those described above may be used alone or in combination of two or more. Can do. In the acrylic resin used in the pressure-sensitive adhesive composition, the structural unit derived from a monomer other than the (meth) acrylic acid ester and the monomer having a polar functional group is the weight of the entire nonvolatile content of the high molecular weight acrylic resin. The ratio is usually 20% by weight or less, preferably 10% by weight or less.

  The high molecular weight acrylic resin is an acrylic resin containing a structural unit derived from a (meth) acrylic acid compound having a polar functional group as a main component and derived from a (meth) acrylic acid alkyl ester as described above. Two or more types may be included.

  A low molecular weight acrylic resin having a weight average molecular weight in the range of 1,000 to 150,000 is mixed with the high molecular weight acrylic resin described above to obtain an acrylic resin used in the light diffusable pressure-sensitive adhesive composition of the present invention. The low molecular weight acrylic resin used here is a monomer mainly composed of (meth) acrylic acid alkyl ester, which is also a (meth) acrylic acid alkyl ester having about 1 to 14 carbon atoms represented by the formula (I). Can be. Specific examples thereof are the same as those described above for the high molecular weight acrylic resin. This low molecular weight acrylic resin may be a polymer of only a (meth) acrylic acid alkyl ester, or a copolymer of a (meth) acrylic acid-based compound having a crosslinkable polar functional group. Good.

  The low molecular weight acrylic resin contains a structural unit derived from (meth) acrylic acid alkyl ester, usually in a proportion of 60 to 100% by weight, particularly 80 to 100% by weight, based on the whole nonvolatile content thereof, and is optional. In addition, a structural unit derived from a (meth) acrylic acid-based compound having a crosslinkable polar functional group is usually contained in a proportion of 0 to 20% by weight, preferably 0 to 10% by weight. . When other monomers are copolymerized, it is preferably about 10% by weight or less based on the entire nonvolatile content of the low molecular weight acrylic resin.

  The high molecular weight acrylic resin has a weight average molecular weight Mw in terms of standard polystyrene as measured by gel permeation chromatography (GPC) in the range of 500,000 to 2,000,000. When the weight average molecular weight is 500,000 or more, the adhesiveness under high temperature and high humidity is improved, and there is a tendency that the possibility of floating or peeling between the glass substrate and the adhesive layer tends to be reduced. It is preferable because the property tends to be improved. In addition, when the weight average molecular weight is 2 million or less, even if the size of the polarizing plate bonded to the adhesive layer changes, the adhesive layer changes following the change in size, so the periphery of the liquid crystal display panel This is preferable because there is no difference between the brightness of the part and the brightness of the center part, and white spots and color unevenness tend to be suppressed. The weight average molecular weight is more preferably in the range of 1,000,000 to 1,800,000. The molecular weight distribution represented by the ratio Mw / Mn of the weight average molecular weight Mw and the number average molecular weight Mn is preferably in the range of 2 to 10, more preferably in the range of 2 to 5.

  On the other hand, the low molecular weight acrylic resin has a weight average molecular weight Mw converted to standard polystyrene by GPC in the range of 1,000 to 150,000. By using a low molecular weight acrylic resin having a weight average molecular weight of 1,000 or more, the entanglement effect of the low molecular weight material is exhibited, and an adhesive layer is formed on the polarizing plate from the adhesive composition containing the low molecular weight acrylic resin. When cutting the sheet, the possibility that the adhesive protrudes from the cross section or the polarizing plate is contaminated by the protruding adhesive is reduced. In addition, by using a low molecular weight acrylic resin having a weight average molecular weight of 150,000 or less, the flexibility of the low molecular weight acrylic resin is maintained, and the gel layer of the high molecular weight acrylic resin is inserted to make the entire adhesive layer dense. Adhesive durability can be improved. The weight average molecular weight is more preferably in the range of 1,000 to 50,000, and more preferably in the range of 1,000 to 10,000. The molecular weight distribution Mw / Mn of the low molecular weight acrylic resin is preferably in the range of 1 to 9, more preferably in the range of 1 to 5, and particularly preferably in the range of 2 to 3.

  The blending amount of the low molecular weight acrylic resin is in the range of 5 to 33% by weight based on the total amount of the acrylic resin including the high molecular weight acrylic resin constituting the pressure-sensitive adhesive composition. When the content is less than 5% by weight, the stress concentration of the polarizing plate can be effectively alleviated when an adhesive layer is formed on the polarizing plate from the pressure-sensitive adhesive composition containing the adhesive and is adhered to the liquid crystal cell glass. On the other hand, if the content exceeds 33% by weight, the cohesive force of the pressure-sensitive adhesive is reduced, which tends to cause foaming or peeling.

  The acrylic resin can be advantageously produced by a method in which a necessary monomer is dissolved in an organic solvent and solution polymerization is performed in the presence of a polymerization initiator. The molecular weight varies depending on the combination of monomers and various polymerization conditions. If the combination of monomers is the same, the molecular weight can be adjusted by changing the amount of the polymerization initiator. For example, if the amount of the polymerization initiator is increased, the polymerization starting point is increased, so that a resin having a small molecular weight can be produced.

<Spherical fine particles>
In the present invention, spherical fine particles are blended in the pressure-sensitive adhesive mainly composed of the acrylic resin described above, and light diffusibility is imparted to the resulting pressure-sensitive adhesive layer. The material of the spherical fine particles is not particularly limited, and known organic fine particles and inorganic fine particles can be used. Examples of the organic fine particles include resin particles made of polyolefin resin such as polystyrene, polyethylene and polypropylene, and (meth) acrylic resin such as polymethacrylate resin and polyacrylate resin. There may be. Furthermore, a copolymer resin obtained by copolymerizing two or more monomers selected from ethylene, propylene, styrene, methyl methacrylate, benzoguanamine, formaldehyde, melamine, butadiene, and the like can also be used. Examples of the inorganic fine particles include particles made of silica, silicone resin, titanium oxide, aluminum oxide, and the like. In consideration of the dispersibility of the acrylic resin, which is a mixture of a high molecular weight acrylic resin and a low molecular weight acrylic resin, the applicability of the adhesive composition, the optical properties of the resulting adhesive layer, etc., the fine particles are based on silicone resin or polymethyl methacrylate. What consists of resin is preferable.

  The spherical fine particles are most preferably completely spherical, but can be used without any problem as long as they are substantially spherical. The average particle size is in the range of 5 to 15 μm. When the average particle size is less than 5 μm, the transmission clearness of the obtained adhesive layer increases, and moire often appears on the display. On the other hand, if the average particle size exceeds 15 μm, the particles protrude from the surface of the adhesive layer, leading to a reduction in display quality and a decrease in adhesion durability. The average particle diameter of the spherical fine particles is more preferably in the range of 7 to 13 μm, more preferably 9 to 11 μm.

The spherical fine particles are selected so that the difference in refractive index from the acrylic resin, which is a mixture of a high molecular weight acrylic resin and a low molecular weight acrylic resin, exceeds 0.01 and less than 0.09. This difference in refractive index means that the following formula (1) is satisfied when the refractive index of the acrylic resin is n1 and the refractive index of the spherical fine particles is n2.
0.01 <| n1-n2 | <0.09 (1)

  This refractive index difference is preferably more than 0.01 and not more than 0.07, and more preferably more than 0.01 and not more than 0.04. If the difference in refractive index between the two is 0.01 or less, the resulting adhesive layer does not exhibit the desired optical performance, and as a result, it becomes close to a transparent adhesive. On the other hand, if the difference in refractive index between the two becomes too large, the light diffusibility is strongly developed, so that the white luminance when the liquid crystal display device is viewed from the front is lowered.

  If the spherical fine particles satisfying the above conditions, they can be used alone or in combination of two or more. When two or more kinds of spherical fine particles are mixed, those having different refractive indexes may be mixed, or those having only different particle diameters may be mixed.

  The blending amount of the spherical fine particles is 20 to 50 parts by weight with respect to 100 parts by weight of the nonvolatile content of the acrylic resin which is a mixture of the high molecular weight acrylic resin and the low molecular weight acrylic resin. If the blending amount is less than 20 parts by weight with respect to 100 parts by weight of the acrylic resin, the desired optical performance, particularly haze, is not expressed. On the other hand, if the blending amount is more than 50 parts by weight, the resulting adhesive layer has an adhesive layer. Reduces adhesive performance such as peeling due to reduced force.

<Crosslinking agent>
Usually, a crosslinking agent is mix | blended with the adhesive composition which has an acrylic resin as a main component. The crosslinking agent is a compound having at least two functional groups in the molecule that can react with polar functional groups constituting the acrylic resin to form a crosslinked structure. Specific examples include isocyanate compounds, epoxy compounds, metal chelate compounds, and aziridine compounds.

  Isocyanate compounds are compounds having at least two isocyanato groups (-NCO) in the molecule, such as tolylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, diphenylmethane diisocyanate, Examples thereof include hydrogenated diphenylmethane diisocyanate, naphthalene diisocyanate, and triphenylmethane triisocyanate. In addition, adducts obtained by reacting these isocyanate compounds with polyols such as glycerol and trimethylolpropane, and those obtained by making isocyanate compounds into dimers and trimers can also be used as a crosslinking agent for the adhesive layer. Further, two or more kinds of isocyanate compounds can be mixed and used.

  The epoxy compound is a compound having at least two epoxy groups in the molecule, for example, bisphenol A type epoxy resin, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether. 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, N, N-diglycidylaniline, N, N, N ′, N′-tetraglycidyl-m-xylenediamine, 1,3-bis ( N, N'-diglycidylaminomethyl) cyclohexane and the like. Two or more types of epoxy compounds can be mixed and used.

  Examples of the metal chelate compound include compounds in which acetylacetone or ethyl acetoacetate is coordinated to a polyvalent metal such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium, and zirconium. Can be mentioned.

  An aziridine-based compound is a compound having at least two skeletons of a three-membered ring composed of one nitrogen atom and two carbon atoms, also called ethyleneimine, for example, diphenylmethane-4,4′-bis ( 1-aziridinecarboxamide), toluene-2,4-bis (1-aziridinecarboxamide), triethylenemelamine, isophthaloylbis-1- (2-methylaziridine), tris-1-aziridinylphosphine oxide, hexamethylene -1,6-bis (1-aziridinecarboxamide), trimethylolpropane tris-β-aziridinylpropionate, tetramethylolmethane tris-β-aziridinylpropionate, and the like.

  Among these crosslinking agents, isocyanate compounds are preferably used. The crosslinking agent is usually about 0.1 to 10 parts by weight, preferably about 0.1 to 7 parts by weight, more preferably 0.1 to 100 parts by weight of the nonvolatile content of the acrylic resin constituting the pressure-sensitive adhesive composition. About 3 parts by weight is blended. Since the amount of the crosslinking agent is also related to the gel fraction described later, it may be appropriately selected from the above range according to the required gel fraction.

<Silane compounds>
In order to improve the adhesion between the pressure-sensitive adhesive layer and the liquid crystal cell glass, the pressure-sensitive adhesive composition mainly composed of an acrylic resin preferably contains a silane-based compound, and in particular, before blending a crosslinking agent, It is preferable to blend a silane compound.

  Silane compounds have a hydrolyzable group such as an alkoxy group bonded to a silicon atom and a reactive functional group such as a vinyl group, amino group, epoxy group, haloalkyl group, (meth) acryloyl group or mercapto group. It may be a compound having an organic group bonded thereto. Illustrating each specific compound, examples of the silane compound having a vinyl group include vinyltrimethoxysilane, vinyltriethoxysilane, and vinyltris (2-methoxyethoxy) silane. Examples of the silane compound having an amino group include N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane, and 3-aminopropyltriethoxy. There are silanes. Silane compounds having an epoxy group include 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropyldimethoxymethylsilane, 3-glycidoxypropylethoxydimethylsilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane and the like. Examples of the silane compound having a haloalkyl group include 3-chloropropylmethyldimethoxysilane and 3-chloropropyltrimethoxysilane. Examples of the silane compound having a (meth) acryloyl group include 3- (meth) acryloyloxypropyltrimethoxysilane. Examples of the silane compound having a mercapto group include 3-mercaptopropyltrimethoxysilane. Two or more types of silane compounds may be used in combination.

  The silane compound may be of a polymer or oligomer type. Examples of polymer or oligomer type silane compounds in the form of (monomer)-(monomer) copolymer include the following.

  3-mercaptopropyltrimethoxysilane-tetramethoxysilane copolymer, 3-mercaptopropyltrimethoxysilane-tetraethoxysilane copolymer, 3-mercaptopropyltriethoxysilane-tetramethoxysilane copolymer, and 3-mercaptopropyltriethoxysilane-tetraethoxy A copolymer containing a mercaptopropyl group, such as a silane copolymer;

  Mercaptomethyl groups such as mercaptomethyltrimethoxysilane-tetramethoxysilane copolymer, mercaptomethyltrimethoxysilane-tetraethoxysilane copolymer, mercaptomethyltriethoxysilane-tetramethoxysilane copolymer, and mercaptomethyltriethoxysilane-tetraethoxysilane copolymer. Containing copolymers;

  3-methacryloyloxypropyltrimethoxysilane-tetramethoxysilane copolymer, 3-methacryloyloxypropyltrimethoxysilane-tetraethoxysilane copolymer, 3-methacryloyloxypropyltriethoxysilane-tetramethoxysilane copolymer, 3-methacryloyloxypropyltriethoxysilane -Tetraethoxysilane copolymer, 3-methacryloyloxypropylmethyldimethoxysilane-tetramethoxysilane copolymer, 3-methacryloyloxypropylmethyldimethoxysilane-tetraethoxysilane copolymer, 3-methacryloyloxypropylmethyldiethoxysilane-tetramethoxysilane copolymer, and 3-Methacryloyloxypropylmethyldiethoxysilane-tetra Toki bell Ranco polymers such as, methacryloyloxypropyl group containing copolymers;

  3-acryloyloxypropyltrimethoxysilane-tetramethoxysilane copolymer, 3-acryloyloxypropyltrimethoxysilane-tetraethoxysilane copolymer, 3-acryloyloxypropyltriethoxysilane-tetramethoxysilane copolymer, 3-acryloyloxypropyltriethoxysilane -Tetraethoxysilane copolymer, 3-acryloyloxypropylmethyldimethoxysilane-tetramethoxysilane copolymer, 3-acryloyloxypropylmethyldimethoxysilane-tetraethoxysilane copolymer, 3-acryloyloxypropylmethyldiethoxysilane-tetramethoxysilane copolymer, and 3-acryloyloxypropylmethyldiethoxysilane-tetraethoxysilane Rimmer such as, acryloyloxypropyl group-containing copolymer;

  Vinyltrimethoxysilane-tetramethoxysilane copolymer, vinyltrimethoxysilane-tetraethoxysilane copolymer, vinyltriethoxysilane-tetramethoxysilane copolymer, vinyltriethoxysilane-tetraethoxysilane copolymer, vinylmethyldimethoxysilane-tetramethoxysilane copolymer, Vinyl group-containing copolymers such as vinylmethyldimethoxysilane-tetraethoxysilane copolymer, vinylmethyldiethoxysilane-tetramethoxysilane copolymer, and vinylmethyldiethoxysilane-tetraethoxysilane copolymer;

  3-aminopropyltrimethoxysilane-tetramethoxysilane copolymer, 3-aminopropyltrimethoxysilane-tetraethoxysilane copolymer, 3-aminopropyltriethoxysilane-tetramethoxysilane copolymer, 3-aminopropyltriethoxysilane-tetraethoxysilane Copolymer, 3-aminopropylmethyldimethoxysilane-tetramethoxysilane copolymer, 3-aminopropylmethyldimethoxysilane-tetraethoxysilane copolymer, 3-aminopropylmethyldiethoxysilane-tetramethoxysilane copolymer, and 3-aminopropylmethyldiethoxy Amino group-containing copolymers such as silane-tetraethoxysilane copolymers.

  These silane-based compounds are often liquids. The compounding amount of the silane compound in the pressure-sensitive adhesive composition is usually about 0.0001 to 10 parts by weight, preferably 0.01 to 5 parts by weight, with respect to 100 parts by weight of the nonvolatile content of the acrylic resin. Is done. It is preferable that the amount of the silane compound with respect to the nonvolatile content of 100 parts by weight of the acrylic resin is 0.0001 parts by weight or more because adhesion between the adhesive layer and the glass substrate is improved. Moreover, it is preferable for the amount to be 10 parts by weight or less because the silane compound tends to be suppressed from bleeding out from the adhesive layer.

<Ionic compounds>
It is also preferable to add an ionic compound to the pressure-sensitive adhesive composition containing an acrylic resin as a main component. The ionic compound acts as an antistatic agent and imparts antistatic properties to the adhesive layer. This compound is particularly preferably a solid at room temperature (25 ° C.). Moreover, what has an organic cation is preferable.

  The cation component constituting the ionic compound may be an organic cation, and as described above, one that gives an ionic compound that is solid at room temperature is preferable. For example, imidazolium cation, pyridinium cation, ammonium cation, sulfonium cation, phosphonium cation, etc. can be mentioned, but when used in the adhesive layer of a polarizing plate, the viewpoint that it is difficult to be charged when the release film provided thereon is peeled off Therefore, a pyridinium cation, an imidazolium cation or an ammonium cation is preferable.

  On the other hand, in the ionic compound, the anion component serving as a counter ion of the cation component may be an inorganic anion or an organic anion. Again, those that give ionic compounds that are solid at room temperature are preferred. For example, the following anions can be mentioned.

Chloride anion [Cl ⁻ ],
Bromide anion [Br ⁻ ],
Iodide anion [I ⁻ ],
Tetrachloroaluminate anion [AlCl ₄ ⁻ ],
Heptachlorodialuminate anion [Al ₂ Cl ₇ ⁻ ],
Tetrafluoroborate anion [BF ₄ ⁻ ],
Hexafluorophosphate anion [PF ₆ ⁻ ],
Perchlorate anion [ClO ₄ ⁻ ],
Nitrate anion [NO ₃ ⁻ ],
Acetate anion [CH ₃ COO ⁻ ],
Trifluoroacetate anion [CF ₃ COO ⁻ ],
Methanesulfonate anion [CH ₃ SO ₃ ⁻ ],
Trifluoromethanesulfonate anion [CF ₃ SO ₃ ⁻ ],
p-toluenesulfonate anion [p-CH ₃ C ₆ H ₄ SO ₃ ⁻ ],
Bis (trifluoromethanesulfonyl) imide anion [(CF ₃ SO ₂ ) ₂ N ⁻ ],
Tris (trifluoromethanesulfonyl) methanide anion [(CF ₃ SO ₂ ) ₃ C ⁻ ], hexafluoroarsenate anion [AsF ₆ ⁻ ],
Hexafluoroantimonate anion [SbF ₆ ⁻ ],
Hexafluoroniobate anion [NbF ₆ ⁻ ],
Hexafluorotantalate anion [TaF ₆ ⁻ ],
Dimethyl phosphinate anion [(CH ₃ ) ₂ POO ⁻ ],
(Poly) hydrofluorofluoride anion [F (HF) _n ⁻ ] (n is about 1 to 3), dicyanamide anion [(CN) ₂ N ⁻ ],
Thiocyan anion [SCN ⁻ ],
Perfluorobutanesulfonate anion [C ₄ F ₉ SO ₃ ⁻ ],
Bis (pentafluoroethanesulfonyl) imide anion [(C ₂ F ₅ SO ₂ ) ₂ N ⁻ ], perfluorobutanoate anion [C ₃ F ₇ COO ⁻ ],
(Trifluoromethanesulfonyl) (trifluoromethanecarbonyl) imide anion [(CF ₃ SO ₂ ) (CF ₃ CO) N ⁻ ] and the like.

  Among these, in particular, an anion component containing a fluorine atom is preferably used because it provides an ionic compound having excellent antistatic performance, and a bis (trifluoromethanesulfonyl) imide anion is particularly preferable.

  Specific examples of the ionic compound can be appropriately selected from the combination of the cation component and the anion component. Specific examples of the compound that is a combination of a cation component and an anion component include the following.

N-hexylpyridinium hexafluorophosphate,
N-octylpyridinium hexafluorophosphate,
N-butyl-4-methylrupyridinium hexafluorophosphate,
N-butyl-N-methylpyrrolidinium hexafluorophosphate,
1-ethyl-3-methylimidazolium hexafluorophosphate,
1-ethyl-3-methylimidazolium p-toluenesulfonate,
1-butyl-3-methylimidazolium methanesulfonate,
Tetrabutylammonium hexafluorophosphate,
Tetrabutylammonium p-toluenesulfonate,
(2-hydroxyethyl) trimethylammonium dimethylphosphinate,
Tetramethylammonium bis (trifluoromethanesulfonyl) imide,
Tetraethylammonium bis (trifluoromethanesulfonyl) imide,
Tetrabutylammonium bis (trifluoromethanesulfonyl) imide,
Triethylmethylammonium bis (trifluoromethanesulfonyl) imide,
Tributylmethylammonium bis (trifluoromethanesulfonyl) imide,
Trimethyldecyl ammonium bis (trifluoromethanesulfonyl) imide,
Diethyl (2-methoxyethyl) methylammonium bis (trifluoromethanesulfonyl) imide,
Glycidyltrimethylammonium bis (trifluoromethanesulfonyl) imide and the like.

  Such ionic compounds can be used alone or in combination of two or more. Of course, examples of the ionic compound are not limited to those exemplified here.

  As described above, the ionic compound that is solid at room temperature imparts antistatic properties to the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition mainly composed of an acrylic resin, and maintains various physical properties as a pressure-sensitive adhesive. It is particularly effective. Compared with the case of using an ionic compound that is liquid at room temperature, the antistatic performance can be maintained for a long time. From the viewpoint of such antistatic long-term stability, the ionic compound preferably has a melting point of 30 ° C. or higher, more preferably 35 ° C. or higher. On the other hand, if the melting point is too high, the compatibility with the acrylic resin is deteriorated. Therefore, it is preferable to have a melting point of 90 ° C. or lower, more preferably 80 ° C. or lower. Although the molecular weight of an ionic compound is not specifically limited, For example, it is preferable that molecular weight is 700 or less, Furthermore, it is preferable that it is 500 or less.

  It is preferable to contain an ionic compound in the ratio of 0.3-12 weight part with respect to 100 weight part of non volatile matters of the acrylic resin which comprises an adhesive composition. When the ionic compound is added in an amount of 0.3 part by weight or more with respect to 100 parts by weight of the non-volatile content of the acrylic resin, the antistatic performance is improved, and when the amount is 12 parts by weight or less, the adhesive durability It is preferable because it is easy to maintain. The amount of the ionic compound relative to 100 parts by weight of the non-volatile content of the acrylic resin is preferably 0.5 parts by weight or more and 5 parts by weight or less.

<Other additives that can be added to the pressure-sensitive adhesive composition>
The light diffusing pressure-sensitive adhesive composition described above may further contain a crosslinking catalyst, a weathering stabilizer, a tackifier, a plasticizer, a softening agent, a dye, a pigment, and the like. In particular, when a crosslinking catalyst is blended with the crosslinking agent in the pressure-sensitive adhesive, the pressure-sensitive adhesive layer can be prepared by aging in a short time, and in the resulting liquid crystal display panel, floating or peeling occurs between the pressure-sensitive adhesive layer and the polarizing plate. Or foaming in the adhesive layer can be suppressed, and the reworkability can be further improved. Examples of the crosslinking catalyst include amine compounds such as hexamethylenediamine, ethylenediamine, polyethyleneimine, hexamethylenetetramine, diethylenetriamine, triethylenetetramine, isophoronediamine, trimethylenediamine, polyamino resin, and melamine resin. When an amine compound is added to the adhesive as a crosslinking catalyst, an isocyanate compound is suitable as the crosslinking agent.

<Preparation of pressure-sensitive adhesive composition>
The light diffusable pressure-sensitive adhesive composition containing each component described above can be prepared in a state in which each component other than spherical fine particles including acrylic resin is dissolved in an organic solvent and the spherical fine particles are dispersed therein. . The solvent for dispersing the spherical fine particles is not particularly limited. For example, the same solvent as that used in the production of the above-described high molecular weight acrylic resin and low molecular weight acrylic resin can be used, and acetate-based, benzene-based, or ketone excellent in dispersibility and resistance to organic fine particles. System solvents such as ethyl acetate, toluene, xylene, and methyl ethyl ketone can also be used.

[Light diffusion adhesive sheet]
The light diffusable pressure-sensitive adhesive composition described above can be applied on a substrate film, the solvent can be removed to form a pressure-sensitive adhesive layer, and a light diffusable pressure-sensitive adhesive sheet can be obtained. Moreover, an adhesive layer can be formed on another film, and it can be transcribe | transferred to a base film and it can also be set as a light diffusable adhesive sheet. The base film can be a release film or various optical films including a polarizing plate. In FIG. 1, the typical structural example of the light diffusable adhesive sheet which concerns on this invention was shown with schematic sectional drawing. The light diffusable pressure-sensitive adhesive sheet 10 shown in FIG. 1 has a heavy release film 12 disposed on one surface of an adhesive layer 11 formed from a light diffusable pressure-sensitive adhesive composition, and a light release film 13 on the other surface. It is an arranged configuration. Here, the heavy release film 12 and the light release film 13 are different in the release level from the adhesive layer 11, and the heavy release film 12 has a relatively high release force from the adhesive layer 11, and The light release film 13 has a relatively small peeling force from the adhesive layer 11.

  The light diffusable pressure-sensitive adhesive sheet 10 thus configured is used in the following form, for example. That is, first, the light release film 13 is peeled off from the pressure-sensitive adhesive layer 11, and the release surface (pressure-sensitive adhesive layer surface) is bonded to the polarizing plate to obtain a polarizing plate with the pressure-sensitive adhesive layer. When the polarizing plate with the adhesive layer is attached to the liquid crystal cell in such a state, the heavy release film 12 is peeled off, and the release surface (adhesive layer surface) is attached to the liquid crystal cell glass.

  In order to obtain appropriate peelability from the adhesive layer 11, each of the films constituting the heavy release film 12 and the light release film 13 is subjected to a mold release treatment on at least the surface in contact with the adhesive layer 11. ing.

  The film constituting the heavy release film 12 remains even after being bonded to the polarizing plate, and the polarizing plate may be inspected in that state, so that the maximum strain of the orientation main axis is uniaxial or biaxial stretching of 10 degrees or less. A polyester film is often used. The polyester is not particularly limited as long as optical properties are maintained, and for example, polyethylene terephthalate, polyethylene naphthalate, polyethylene isophthalate, polybutylene terephthalate, and the like can be used. These resins may be used alone or in combination of two or more. Polyethylene terephthalate or polyethylene naphthalate is preferable from the viewpoint of heat resistance and ease of subsequent release treatment, and polyethylene terephthalate is most practical in view of cost.

  Since the light release film 13 is peeled and removed at the time of bonding to the polarizing plate, the maximum strain of the orientation main axis is not limited to 10 degrees or less. Again, for example, a uniaxially stretched polyester film or a biaxially stretched polyester film can be used, and other unstretched or stretched films can also be used. Examples of other films include polyolefin films, polyamide films, cellulose derivative films, polycarbonate films, polyphenylene sulfide films, various liquid crystal polymer films, polyvinyl chloride films, polyvinylidene chloride films, various films There are biodegradable films.

  As described above, the surface of the heavy release film 12 and the light release film 13 that are in contact with the adhesive layer 11 is subjected to a release treatment using a release agent. As the mold release agent, a silicone type mold release agent having excellent release characteristics is preferably used. Also, the peel strength can be adjusted by the thickness of the silicone-based release agent and the presence or absence of oligomer addition, and it is preferable that the peel strength of the heavy release film 12 is 1.2 times or more compared to the light release film 13.

  Although there is no restriction | limiting in particular also in the thickness of the heavy release film 12 and the light release film 13, From a viewpoint of the ease of handling at the time of use, cost, etc., it is preferable to set it as about 5-100 micrometers.

  For example, the light diffusable pressure-sensitive adhesive sheet 10 shown in FIG. 1 is coated with the light diffusable pressure-sensitive adhesive composition described above on one of the two release films 12 and 13 and dried. Then, after removing the solvent, it can be produced by pasting the release treatment surface of the other release film. Drying of the light diffusable pressure-sensitive adhesive composition formed on one release film 12 or 13 is performed, for example, by heating at a temperature of about 60 to 120 ° C. for about 0.5 to 10 minutes. Subsequently, after the other release film 13 or 12 is pasted, for example, in an atmosphere of a temperature of 23 ° C. and a relative humidity of 65%, the film is aged for about 5 to 20 days, and the crosslinking agent is sufficiently reacted.

  In the light diffusable pressure-sensitive adhesive sheet 10 thus obtained, the pressure-sensitive adhesive layer 11 preferably has a gel fraction in the range of 40 to 75% by weight, more preferably 45 to 70% by weight, especially 50 to 70% by weight. . Here, the gel fraction is a value measured according to the following (I) to (IV).

<Measurement method of gel fraction of adhesive layer>
(I) An adhesive layer having an area of about 8 cm × about 8 cm and a metal mesh made of SUS304 (its weight is Wm) of about 10 cm × about 10 cm are bonded together.
(II) Weigh the bonded product obtained in (I) above, weigh it Ws, then fold it 4 times so as to wrap the adhesive layer, fasten it with a stapler (stapler), weigh it, Let the weight be Wb.
(III) The mesh stapled in (II) above is placed in a glass container, and 60 ml of ethyl acetate is added and immersed, and then the glass container is stored at room temperature for 3 days.
(IV) The mesh is taken out from the glass container, dried at 120 ° C. for 24 hours, weighed, the weight is taken as Wa, and the gel fraction is calculated based on the following formula (2).
Gel fraction (% by weight) = [{Wa− (Wb−Ws) −Wm} / (Ws−Wm)] × 100 (2)

  When the gel fraction of the pressure-sensitive adhesive layer 11 exceeds 75% by weight, the adhesiveness under high temperature and high humidity is lowered, and the liquid crystal cell glass and the pressure-sensitive adhesive layer tend to be easily lifted or peeled off. On the other hand, when the gel fraction of the pressure-sensitive adhesive layer 11 is less than 40% by weight, the cohesive force of the pressure-sensitive adhesive layer is weakened, and bubbles tend to cause cohesive failure under high temperature and high humidity.

  In order to adjust the gel fraction of the pressure-sensitive adhesive layer 11 to 40 to 75% by weight, the types of high molecular weight acrylic resin and low molecular weight acrylic resin that are effective components of the pressure-sensitive adhesive composition, the types of spherical fine particles, and the mixing of each component Although the ratio varies depending on the ratio, the gel fraction increases as the amount of the crosslinking agent is increased. Therefore, the gel fraction can be adjusted by the amount of the crosslinking agent. Specifically, the blending amount of the crosslinking agent with respect to 100 parts by weight of the nonvolatile content of the acrylic resin, which is a mixture of the high molecular weight acrylic resin and the low molecular weight acrylic resin constituting the light diffusing pressure-sensitive adhesive composition, is 0.1 to 3 weights. From the range of about parts, it is preferable to select appropriately according to the type of acrylic resin.

  Although the thickness of the adhesion layer 11 is not specifically limited, Usually, it is preferable that it is 30 micrometers or less, and it is preferable that it is 10 micrometers or more. If the thickness of the pressure-sensitive adhesive layer is 30 μm or less, the adhesiveness under high temperature and high humidity is improved, and there is a tendency that the possibility of floating or peeling between the glass substrate and the pressure-sensitive adhesive layer tends to decrease, and reworkability. It is preferable because the adhesive layer tends to improve, and if the thickness is 10 μm or more, even if the dimension of the polarizing plate bonded thereto changes, the adhesive layer follows the dimensional change and fluctuates. The difference between the brightness at the peripheral edge and the brightness at the center of the liquid crystal display panel is eliminated, and white spots and color unevenness tend to be suppressed, which is preferable.

  In the light diffusable pressure-sensitive adhesive sheet 10, the haze of the pressure-sensitive adhesive layer 11 is in the range of 25 to 50%, and the widths of the dark part and the bright part are 0.125 mm, 0.5 mm, 1.0 mm, and 2.0 mm. It is preferable that the total value of transmitted sharpness measured using four types of optical combs is 150% or less. Furthermore, it is more preferable that the haze is in the range of 25 to 45%, and the total value of the transmission clarity measured using four types of optical combs is 130% or less. In general, the relationship between haze and transmission definition is inversely proportional, and the higher the haze, the lower the transmission definition. The lower the haze, the higher the transmission definition.

Haze and transparency are defined in JIS K 7105-1981 “Testing methods for optical properties of plastics”. Haze calculation method is JIS K 7136: 2000 “How to determine haze of plastics and transparent materials” Are also stipulated. The haze is a value defined by the following formula (3).
Haze = (diffuse transmittance / total light transmittance) × 100 (%) (3)

On the other hand, the transmission definition means the image definition measured by the transmission method. As defined in the above standard, the image definition is a value obtained by the following equation (4) from the highest wave height and the lowest wave height recorded on the recording paper when a certain optical comb is used. In the present specification, the average value of the measurement results in the vertical direction and the horizontal direction of the test piece was adopted.
Image definition = [(highest wave height−lowest wave height) / (highest wave height + lowest wave height)] × 100 (%) (4)

  In this standard, the ratio of the width of the dark part to the bright part is 1: 1 and the width is 0.125 mm, 0.5 mm, 1.0 mm, and 2.0 mm as an optical comb used for measuring the image definition. In the present specification, the transmission sharpness is defined as the total value of the image sharpness measured by the transmission method using these four types of optical combs. Thus, since the total value of the values measured using the four types of optical combs is defined as the transmission sharpness, the maximum value, that is, the value measured without the sample (the total value thereof) is 400%.

  The optical characteristics including the above-mentioned haze and transmission clarity in the pressure-sensitive adhesive layer 11 constituting the light-diffusing pressure-sensitive adhesive sheet 10 are as follows: the refractive index difference between the acrylic resin and the spherical fine particles constituting the pressure-sensitive adhesive composition, the blending amount of the fine particles and the particles The above characteristics can be satisfied by adjusting the diameter and the like. For example, if the haze exceeds 50%, the total value of transmitted sharpness measured using four types of optical combs is often 150% or less, but in this case, the haze is too large and the forward scattering property is high. When the liquid crystal display device is viewed from the front, the white luminance is lowered. On the other hand, if the haze is less than 25%, the total value of the transmitted sharpness measured using the four types of optical combs is often 150% or more, but the white luminance when viewed from the front is not a problem. In addition, a moire phenomenon caused by a film having irregularities on the surface of a prism sheet or the like is likely to occur.

[Polarizing plate with diffusion adhesive layer]
As described above, the light diffusable pressure-sensitive adhesive sheet shown in FIG. 1 is peeled off the light release film 13 and the pressure-sensitive adhesive layer exposed on the peeled surface is attached to the polarizing plate to form a polarizing plate with a pressure-sensitive adhesive layer. Can do. This polarizing plate with an adhesive layer can also be regarded as the base film being a polarizing plate in the light diffusable adhesive sheet described above. In FIG. 2, the typical structural example of the polarizing plate with a diffusion adhesion layer which concerns on this invention was shown with schematic sectional drawing. The polarizing plate 30 with a diffusion adhesive layer shown in FIG. 2 has a structure in which the light diffusing adhesive layer 11 formed from the light diffusable adhesive composition according to the present invention described above is formed on the polarizing plate 20. ing. The heavy release film 12 described with reference to FIG. 1 is present on the outer surface of the adhesive layer 11 to protect the adhesive layer 11. The polarizing plate 20 has a structure in which the first protective film 23 is bonded to one surface of the polarizing film 21 and the second protective film 24 is bonded to the other surface.

  The polarizing film 21 constituting the polarizing plate 20 has a function of emitting polarized light with respect to incident light such as natural light. Usually, such a polarized light emission function is manifested by a function of absorbing linearly polarized light having a vibration surface in a certain direction and transmitting linearly polarized light having a vibration surface orthogonal thereto. The polarizing film 21 can be composed of a uniaxially stretched polyvinyl alcohol resin film in which a dichroic dye such as iodine or a dichroic dye is adsorbed and oriented. Such a polarizing film is generally produced by subjecting a polyvinyl alcohol resin film to uniaxial stretching, dyeing with a dichroic dye, and boric acid treatment.

  The 1st protective film 23 and the 2nd protective film 24 are arrange | positioned at both surfaces of the polarizing film 21, respectively. A transparent resin film is used for the protective films 23 and 24. Examples of the transparent resin include acetyl cellulose resins such as triacetyl cellulose and diacetyl cellulose, methacrylic resins such as polymethyl methacrylate, polyester resins, and polyolefins. Resin, polycarbonate resin, polyether ether ketone resin, polysulfone resin and the like. The resin constituting the protective film may contain a UV absorber such as a salicylic acid ester compound, a benzophenone compound, a benzotriazole compound, a triazine compound, a cyanoacrylate compound, or a nickel complex compound. The acetylcellulose-based resin is one preferred form of the resin film constituting the protective films 23 and 24. Among them, a triacetylcellulose film is preferably used. For the first protective film 23 on the liquid crystal cell glass side described later, that is, on the light diffusing adhesive layer 11 side in the state of FIG. 2, a polyolefin-based resin such as a norbornene-based resin is also preferably used. The thickness of the protective films 23 and 24 is not particularly limited, but is preferably in the range of 20 to 90 μm, and more preferably in the range of 30 to 90 μm. When the thickness is less than 20 μm, it becomes difficult to handle the film. On the other hand, when the thickness exceeds 90 μm, the workability is inferior, and it is disadvantageous in reducing the thickness and weight of the resulting polarizing plate.

  For bonding the polarizing film 21 and the protective films 23, 24, a transparent adhesive is usually used. For example, a water-based adhesive such as an aqueous solution of a polyvinyl alcohol-based resin is a suitable one. Further, an ultraviolet curable adhesive that is cured by ultraviolet irradiation may be used.

  The polarizing plate 30 with a diffusion adhesive layer shown in FIG. 2 can be manufactured as follows, for example. That is, first, the polarizing plate 30 having the configuration of the first protective film 23 / polarizing film 21 / second protective film 24 is prepared. Next, what peeled off the light peeling film 13 from the light diffusable adhesive sheet 10 shown in FIG. 1 is the 1st protective film 23 of the polarizing plate 20 by the light diffusable adhesive layer 11 side after the peeling film peeling. By transferring to the side surface, the structure of FIG. 2 is obtained.

  Apart from this, the polarizing plate 30 with a diffusion adhesion layer shown by FIG. 2 as follows can also be manufactured. That is, first, the light diffusable pressure-sensitive adhesive composition according to the present invention described above is prepared in a state diluted with an organic solvent, and this is applied to the release-treated surface of the heavy release film 12 to 60 to 120 ° C. The organic solvent is removed by heating for about 0.5 to 10 minutes, and the light diffusable adhesive layer 11 formed on the heavy release film 12 is obtained. Next, the polarizing plate 20 having the configuration of the first protective film 23 / polarizing film 21 / second protective film 24 was bonded to the light diffusing adhesive layer 11 on the first protective film 23 side. After that, if the atmosphere is room temperature (around 23 ° C.) and the relative humidity is around 65%, the structure shown in FIG. 2 can be obtained by aging for about 5 to 20 days and sufficiently reacting the crosslinking agent.

  On the first protective film 23 side of the polarizing plate 20 composed of the first protective film 23 / polarizing film 21 / second protective film 24, a sheet composed of the heavy release film 12 / light diffusive adhesive layer 11. Is applied to the bonding surface of the light diffusable pressure-sensitive adhesive layer 11 in order to increase the adhesive strength with the first protective film 23 when the light diffusable pressure-sensitive adhesive layer 11 is applied. Is preferred. The corona discharge treatment is a treatment in which a high voltage is applied between the electrodes to discharge and activate the resin film disposed there. The corona discharge treatment is preferably performed with the output set to about 200 to 1,000 W. By setting the output of the corona discharge treatment to 200 W or more, the effect of this treatment becomes remarkable, and the adhesive force between the light diffusable pressure-sensitive adhesive layer 11 and the first protective film 23 is improved. In addition, by setting the output of the corona discharge treatment to 1,000 W or less, generation of dust that is likely to occur due to this treatment can be suppressed. The effect of the corona discharge treatment varies depending on the type of electrode, electrode spacing, voltage, humidity, type of resin film used, etc. For example, the electrode spacing is set to 1 to 5 mm and the moving speed is set to about 3 to 20 m / min. It is preferable to do.

[LCD panel]
The polarizing plate 30 with a diffusion adhesive layer shown in FIG. 2 can be made into a liquid crystal display panel by peeling the heavy release film 12 and then sticking the light diffusable adhesive layer 11 side to the liquid crystal cell glass. . Another polarizing plate can be attached to the other side of the liquid crystal cell glass via the same adhesive layer as the light diffusing adhesive layer described above. It is also effective to bond the polarizing plate through a transparent adhesive layer. In this manner, the state in which the polarizing plate 20 is bonded to at least one surface of the liquid crystal cell glass via the light diffusive adhesive layer may be referred to as an “optical laminate” below.

  FIG. 3 is a schematic cross-sectional view showing a typical configuration example of the liquid crystal display panel according to the present invention. In the liquid crystal display panel 40 shown in FIG. 3, the polarizing plate 30 with a diffusion adhesive layer, that is, the heavy release film 12 peeled off from the state shown in FIG. The polarizing plate 20 is adhered to the other surface of the liquid crystal cell glass 45 through a normal transparent adhesive layer 16 having no light diffusion performance. In FIG. 3, the polarizing plate 20 with the transparent adhesive layer 16 provided on the upper side of the liquid crystal cell glass 45 is displayed as a transparent polarizing plate 31 with an adhesive layer.

  In this liquid crystal display panel 40, which of the polarizing plate 30 with a diffusion adhesive layer and the transparent polarizing plate 31 with a transparent adhesive layer is the front side (viewing side) of the liquid crystal display device, and which is the back side (backlight side). In general, it is preferable that the polarizing plate 30 with the diffusion adhesive layer is on the back side. In this case, as shown in FIG. 3, the surface treatment layer 25 is provided on the outer side of the transparent adhesive layer-attached polarizing plate 31 on the front side (the side opposite to the adhesive layer 16 attached to the liquid crystal cell glass 45). Is preferred.

  The liquid crystal cell glass 45 includes a glass substrate, and generally a liquid crystal display device in which a liquid crystal compound is filled between two glass substrates is used. The liquid crystal display mode in the liquid crystal cell glass 45 is TN (Twisted Nematic), STN (Super Twisted Nematic), IPS (In-Plane Switching), VA (Vertical Alignment), OCB (Optically Compensated Birefringence), etc. It can be a variety of known ones. Examples of the material for the glass substrate include soda lime glass, low alkali glass, non-alkali glass, and the like, and alkali-free glass is suitably used for liquid crystal display.

  The surface treatment layer 25 provided on the outer side of the polarizing plate 31 having the transparent adhesive layer 16 as necessary reflects the light emitted from an external light source such as a fluorescent lamp in order to improve display characteristics and surface properties. Is provided in order to reduce the visibility of the liquid crystal display device. Specifically, the anti-glare (AG) layer that provides unevenness on the surface and scatters the reflected light, the anti-reflection (AR) layer that prevents reflection using light interference, and the low reflection that reduces the reflectance by the coating ( LR) layer. Further, when a hard coat layer is directly provided on the surface of the polarizing plate 20, or when a hard coat layer is further provided on the antiglare layer, the antireflection layer, the low reflection layer, etc. The hard coat layer can also be the surface treatment layer 25.

  The polarizing plate 30 with the diffusion adhesive layer and the polarizing plate 31 with the transparent adhesive layer are usually such that the liquid crystal cell glass 45 is in the TN mode, IPS mode or VA mode so that the respective transmission axes form a predetermined angle. If there is, it is bonded to both surfaces of the liquid crystal cell glass 45 via the respective adhesive layers 11 and 16 so that the respective transmission axes are orthogonal to each other.

[Liquid Crystal Display]
The liquid crystal display panel of the present invention taking the one shown in FIG. 3 as an example is advantageously used as a transmissive liquid crystal display device. In this case, with the structure shown in FIG. 3, the outer side of the polarizing plate 30 with the diffusion adhesive layer or the outer side of the transparent polarizing plate 31 with the adhesive layer, preferably the side opposite to the liquid crystal cell glass 45 of the polarizing plate 30 with the diffusion adhesive layer. A backlight is provided to form a liquid crystal display device.

  The liquid crystal display device formed from this liquid crystal display panel is, for example, a notebook type, desktop type, personal computer display including PDA (Personal Digital Assistance), television, in-vehicle display, electronic dictionary, digital camera, digital video It can be used for cameras, electronic desk calculators, watches, etc.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further more concretely, this invention is not limited by these examples. In the examples, parts and% indicating the amount used or content are based on weight unless otherwise specified.

In the following examples, the weight average molecular weight and the number average molecular weight are measured by placing two “TSK gel GMH _HR- H (S)” manufactured by Tosoh Corporation as a column in a GPC apparatus in series. Was used as an eluent and converted into standard polystyrene under the conditions of a sample concentration of 5 mg / ml, a sample introduction amount of 100 μl, a temperature of 40 ° C., and a flow rate of 1 ml / min. The refractive index was measured using an Abbe refractometer Type No. 2007 manufactured by Atago Co., Ltd.

  First, the example which manufactured the high molecular weight acrylic resin prescribed | regulated by this invention and the low molecular weight acrylic resin is shown.

[Polymerization Example 1: High molecular weight acrylic resin]
In a reactor equipped with a condenser, a nitrogen inlet, a thermometer and a stirrer, 169.8 parts ethyl acetate, 98.6 parts butyl acrylate, 1.0 part 2-hydroxyethyl acrylate, and 0.4 acrylic acid The internal temperature was increased to 55 ° C. while the air in the apparatus was replaced with nitrogen gas and oxygen-free. Next, a total amount of a solution prepared by dissolving 0.14 part of azobisisobutyronitrile (polymerization initiator) in 5 parts of ethyl acetate was added. Thereafter, the inner temperature was kept at 54 to 56 ° C. for 12 hours, and finally ethyl acetate was added to adjust the acrylic resin concentration to 28%. The obtained acrylic resin had a polystyrene equivalent weight average molecular weight Mw of 1.34 million, Mw / Mn of 1.7, and a refractive index of 1.46 by GPC. This is designated as acrylic resin A1. In this acrylic resin A1, when the total weight of the monomers is 100, the weight ratio of each monomer is butyl acrylate / 2-hydroxyethyl acrylate / acrylic acid = 98.6 / 1.0 / 0. .4.

[Polymerization Example 2: High molecular weight acrylic resin]
Polymerization examples, except that the monomer composition was changed to 78.6 parts butyl acrylate, 20.0 parts 2-phenoxyethyl acrylate, 1.0 part 2-hydroxyethyl acrylate, and 0.4 parts acrylic acid In the same manner as in Example 1, an acrylic resin ethyl acetate solution was obtained. The resulting acrylic resin had a polystyrene-equivalent weight average molecular weight Mw of 1.32 million, Mw / Mn of 2.3, and a refractive index of 1.48 by GPC. This is designated as acrylic resin A2. In this acrylic resin A2, the weight ratio of each monomer when the total weight of the monomers is 100 is butyl acrylate / 2-phenoxyethyl acrylate / 2-hydroxyethyl acrylate / acrylic acid = 78. 6 / 20.0 / 1.0 / 0.4.

[Polymerization Example 3: Low molecular weight acrylic resin]
In the same reactor used in Polymerization Example 1, a mixed solution of 215 parts of ethyl acetate, 33 parts of butyl acrylate, 38 parts of butyl methacrylate, 28 parts of methyl acrylate and 1 part of 2-hydroxyethyl acrylate was charged. The internal temperature was raised to 75 ° C. while replacing the air inside the apparatus with nitrogen gas so as not to contain oxygen. Next, a total amount of a solution prepared by dissolving 0.67 parts of azobisisobutyronitrile (polymerization initiator) in 10 parts of ethyl acetate was added. Thereafter, the inner temperature was kept at 74 to 76 ° C. for 8 hours, and finally ethyl acetate was added to adjust the concentration of the acrylic resin to 30%. The obtained acrylic resin had a polystyrene equivalent weight average molecular weight Mw by GPC of 100,000, Mw / Mn of 2.5, and a refractive index of 1.46. This is designated as acrylic resin B1. In this acrylic resin B1, the weight ratio of each monomer when the total weight of the monomers is 100 is butyl acrylate / butyl methacrylate / methyl acrylate / 2-hydroxyethyl acrylate = 33/38 / 28/1.

[Polymerization Example 4: Low molecular weight acrylic resin]
An acrylic resin ethyl acetate solution was obtained in the same manner as in Polymerization Example 3 except that the amount of the polymerization initiator azobisisobutyronitrile was changed to 0.13 part. The obtained acrylic resin had a polystyrene equivalent weight average molecular weight Mw of 365,000, Mw / Mn of 4.5, and a refractive index of 1.46 by GPC. This is called acrylic resin B2. The weight ratio of the monomer in this acrylic resin B2 is the same as in Polymerization Example 3.

  In addition, as a low molecular weight acrylic resin, the following product name was also used.

  “Alfon UP-1000”: an all-acrylic liquid polymer having no functional group (non-volatile content of 98% or more), having a weight average molecular weight Mw of 3,000, Mw / Mn of 1.4, and a refractive index of 1.46 From Toagosei Co., Ltd. In Table 1 below, this polymer is abbreviated as “UP1000”.

  “Alfon UH-2000”: an all-acrylic liquid polymer having a hydroxyl group as a functional group (nonvolatile content: 98% or more), having a weight average molecular weight Mw of 11,000, Mw / Mn of 1.5, and a refractive index. 1.46, obtained from Toagosei Co., Ltd. In Table 1 below, this polymer is abbreviated as “UH2000”.

  Moreover, the following product names were used as spherical fine particles.

  “MX-1000”: Spherical acrylic particles having an average particle size of 10 μm and a refractive index of 1.49, obtained from Soken Chemical Co., Ltd. In Table 1 below, this fine particle is abbreviated as “MX1000”.

“MX-500”: spherical type acrylic fine particles having an average particle diameter of 6 μm and a refractive index of 1.49, obtained from Soken Chemical Co., Ltd. In Table 1 below, this fine particle is referred to as “MX-500”.

“MX-180TA”: spherical acrylic fine particles with an average particle size of 2 μm and a refractive index of 1.49, obtained from Soken Chemical Co., Ltd. In Table 1 below, this fine particle is abbreviated as “MX180TA”.

  “MX-3000”: Spherical acrylic particles having an average particle size of 30 μm and a refractive index of 1.49, obtained from Soken Chemical Co., Ltd. In Table 1 below, this fine particle is abbreviated as “MX3000”.

  “Tospearl 1110”: spherical type silicone resin fine particles with an average particle size of 10 μm and a refractive index of 1.43, obtained from Momentive Performance Materials Japan LLC. In Table 1 below, this fine particle is abbreviated as “TP1110”.

  “EMB-20”: spherical type low alkali glass fine particles having an average particle diameter of 10 μm and a refractive index of 1.56, obtained from Potters Barotini Co., Ltd. In Table 1 below, this fine particle is referred to as “EMB-20”.

  Further, as other additives, those having the following trade names were used.

Isocyanate-based crosslinking agent:
“Coronate L”: Ethylene acetate solution of trimethylolpropane adduct of tolylene diisocyanate (solid content concentration 75%), obtained from Nippon Polyurethane Industry Co., Ltd.

Silane compounds:
“KBM-403”: 3-glycidoxypropyltrimethoxysilane (liquid), obtained from Shin-Etsu Chemical Co., Ltd.

Ionic compounds:
“FC-4400”: tributylmethylammonium bis (trifluoromethanesulfonyl) imide having the structure of formula (C ₄ H ₉ ) ₃ (CH ₃ ) N ⁺ (CF ₃ SO ₂ ) ₂ N ⁻ , from Sumitomo 3M Limited obtain. Melting point 26 ° C.

[Examples 1 to 9 and Comparative Examples 1 to 8]
(Preparation of adhesive liquid)
As the high molecular weight acrylic resin, the acrylic resins A1 and A2 prepared in the polymerization examples 1 and 2, and as the low molecular weight acrylic resin, the acrylic resins B1 and B2 prepared in the polymerization examples 3 and 4, and “Alfone UP” shown above. -1000 "and" Alfon UH-2000 "were blended in the proportions shown in Table 1 so that the total solid content of the acrylic resin was 100 parts. To this acrylic resin solution, 0.16 parts of the above-mentioned isocyanate crosslinking agent “Coronate L”, 0.5 parts of silane compound “KBM-403” and 1.0 part of ionic compound “FC-4400” were added. Part and the amount of spherical fine particles described in Table 1 were blended to prepare an adhesive solution.

  The pressure-sensitive adhesive liquid of Example 9 was blended in a proportion of 83% of high molecular weight acrylic resin A1 having a refractive index of 1.48 and 17% of low molecular weight acrylic resin “Alfon UP-1000” having a refractive index of 1.46. However, the refractive index of the entire acrylic resin after mixing was 1.48 in terms of a weighted average taking into account the blending ratio of both.

(Production of light diffusable adhesive sheet)
The release treatment surface of the polyethylene terephthalate film (trade name “MRV (08)”, obtained from Shin-Tac Kasei Co., Ltd .; called heavy release film) that has been subjected to release treatment for each adhesive solution prepared above. Then, it was applied using an applicator so that the thickness after drying was 25 μm, and dried at 90 ° C. for 2 minutes to obtain a sheet-like pressure-sensitive adhesive. Next, the sheet-like adhesive obtained above was applied to the release-treated surface of another polyethylene terephthalate film (trade name “MRF38”, obtained from Shin-Tac Kasei Co., Ltd .; called light release film) that had been subjected to a release treatment. The surface opposite to the heavy release film of the agent (adhesive surface) was pasted with a laminator and then aged for 10 days under the conditions of a temperature of 23 ° C. and a relative humidity of 65% to prepare a light diffusable adhesive sheet. In the heavy release film and the light release film used here, the latter (light release film) has a lower release force from the adhesive, that is, it is easier to release.

(Preparation of polarizing plate with diffusion adhesive layer)
A light release film from the light diffusable adhesive sheet prepared above is applied to one side of a polarizing plate having a three-layer structure in which both sides of a polarizing film made of polyvinyl alcohol to which iodine is adsorbed and oriented are sandwiched between protective films made of triacetyl cellulose. The polarizing plate with a diffusion adhesion layer was produced by peeling off and sticking the pressure-sensitive adhesive surface after peeling off the light release film with a laminator.

[Evaluation test]
(1) Evaluation of gel fraction of light diffusable pressure-sensitive adhesive sheet The pressure-sensitive adhesive layer was cut out from the light diffusable pressure-sensitive adhesive sheet (after aging) prepared in each Example and Comparative Example, and the gel fraction was determined by the method described above. The results are shown in Table 2.

(2) Adhesive strength evaluation in polarizing plate with diffusion adhesive layer A 25 mm x 150 mm test piece was cut from the polarizing plate with diffusion adhesive layer prepared in each Example and Comparative Example. Using a sticking device ["Lamipacker" (trade name) manufactured by Fuji Plastics Co., Ltd.], the glass substrate for a liquid crystal cell [manufactured by Corning Inc.] It was attached to “Eagle XG” (trade name)] and autoclaved at a temperature of 50 ° C. and a pressure of 5 kg / cm ² (490.3 kPa) for 20 minutes. Subsequently, after being stored at room temperature (23 ° C.) for 24 hours, in the atmosphere at a temperature of 23 ° C. and a relative humidity of 50%, a 25 mm wide end of the polarizing plate was grasped from the adhesion test piece together with the adhesive layer, and 300 mm / min. A 180 ° peel test was performed to peel in the 180 ° direction (direction folded and along the glass substrate surface) at a speed of 1 mm to evaluate the adhesive strength. The results are also shown in Table 2.

(3) Adhesive durability evaluation of polarizing plate with diffusion adhesive layer The polarizing plate with diffusion adhesive layer (thickly peeled film peeled off) prepared in each Example and Comparative Example was used in (2) above. Was attached to one side of the same glass substrate for a liquid crystal cell to produce an optical laminate (corresponding to a liquid crystal display panel). The optical laminate was subjected to a heat shock resistance test in which the process of lowering the temperature from 70 ° C. to −30 ° C. and then raising the temperature to 70 ° C. as one cycle (one hour) was repeated 100 cycles. The latter optical laminated body was observed visually. The results were classified according to the following criteria and summarized in Table 2.

A: No change in appearance such as floating, peeling or foaming is observed.
○: Almost no change in appearance such as floating, peeling, foaming or the like.
Δ: Appearance changes such as floating, peeling and foaming are slightly noticeable.
X: Appearance changes such as floating, peeling and foaming are remarkably recognized.

(4) Measurement of haze Murakami Color Research Laboratory Co., Ltd. conforms to JIS K 7136: 2000 “How to determine haze of plastics and transparent materials” for the optical laminate produced in the same manner as (3) above. The total haze was measured using a manufactured haze meter “HM-150 type”. In addition, since the haze of a glass substrate and a polarizing plate can be disregarded substantially, the haze value measured here may be considered as the value of an adhesion layer. The obtained haze values themselves are shown in Table 2, and are classified according to the following criteria based on the haze values, and are also shown in the “determination” column of “haze” in Table 2.

○: The total haze is in the range of 25 to 50%.
X: All hazes are out of the range of 25 to 50%.

(5) Measurement of transmission clarity The optical laminate produced in the same manner as in (3) above was manufactured by Suga Test Instruments Co., Ltd., which conforms to JIS K 7105-1981 “Plastic Optical Properties Test Method”. Using the image clarity measuring device “ICM-1DP”, light was incident from the polarizing plate side and the transmission clarity was measured. Here, the ratio of the width of the dark part to the bright part is 1: 1, and the transmission sharpness is measured using four types of optical combs whose widths are 0.125 mm, 0.5 mm, 1.0 mm, and 2.0 mm. The respective values and their total values are shown in Table 2. The maximum total value is 400%. Note that the transmission clarity of the glass substrate and the polarizing plate is almost 100% when any optical comb is used. Therefore, the transmission clarity obtained here may be regarded as the value of the adhesive layer. Further, based on the total value of transmitted sharpness measured using four types of optical combs, they were classified according to the following criteria, and are also shown in the “determination” column of “transparent sharpness” in Table 2.

○: Transmission clarity (total value) is less than 150%.
X: Transmission clarity (total value) is 150% or more.

  As can be seen from Tables 1 and 2, Comparative Example 1 in which the low molecular weight acrylic resin was not blended and Comparative Example 2 in which the blending amount of the low molecular weight acrylic resin was as large as 41% of the total acrylic resin were adhesive durability. Sex is not enough. Comparative Example 3 with a small amount of spherical fine particles gives insufficient values of haze and extremely high transmission clarity. On the other hand, Comparative Example 4 in which the compounding amount of the spherical fine particles is 58 parts with respect to 100 parts of the acrylic resin is not sufficient in adhesion durability and the haze is too large. Comparative Example 5 using spherical fine particles having a small average particle diameter gives a value where the transmission sharpness is too high. On the other hand, Comparative Example 6 using spherical fine particles having a large average particle diameter does not have sufficient adhesion durability. Comparative Example 7 using an acrylic resin B2 having a high weight average molecular weight Mw of 365,000 as a low molecular weight acrylic resin has insufficient adhesion durability. In Comparative Example 8 in which the difference in refractive index between the acrylic resin and the spherical fine particles was as large as 0.10, the haze was too large.

  In contrast, the refractive index difference between the acrylic resin and the spherical fine particles, the molecular weight of the low molecular weight acrylic resin, the blending ratio of the high molecular weight acrylic resin and the low molecular weight acrylic resin, the average particle size of the spherical fine particles, and the blending amount of the spherical fine particles In Examples 1 to 9 within the range specified in, each test item gave good results.

10: Light diffusive adhesive sheet,
11: Light diffusive adhesive layer,
12 ... heavy release film,
13. Light release film,
16 …… Transparent adhesive layer,
20 …… Polarizing plate,
21 …… Polarizing film,
23 …… First protective film,
24 …… Second protective film,
25 …… Surface treatment layer
30: Polarizing plate with diffusion adhesive layer,
31 …… Polarizing plate with transparent adhesive layer,
40 …… LCD panel,
45 …… Liquid crystal cell glass.

Claims (8)

Containing acrylic resin and spherical fine particles,
The acrylic resin and the spherical fine particles have a refractive index difference of more than 0.01 and less than 0.09,
The acrylic resin is a mixture of a high molecular weight acrylic resin having a weight average molecular weight in the range of 500,000 to 2,000,000 and a low molecular weight acrylic resin having a weight average molecular weight in the range of 1,000 to 150,000. Containing 5 to 33% by weight of resin,
The spherical particles is in the range of the average particle diameter of 5 to 15 [mu] m, that is 20 to 50 parts by weight blended with respect to the acrylic resin 100 parts by weight
It consists of a light diffusing adhesive composition ,
Transmission clarity measured using four types of optical combs with haze in the range of 25-50% and dark and bright widths of 0.125 mm, 0.5 mm, 1.0 mm and 2.0 mm. An adhesive layer having a total value of 150% or less
A light diffusable pressure-sensitive adhesive sheet formed on a base film . The high molecular weight acrylic resin has 70 to 99.8% by weight of a structural unit derived from a (meth) acrylic acid alkyl ester having an alkyl group having 1 to 14 carbon atoms and a crosslinkable polar functional group (meth). The light diffusable adhesive sheet of Claim 1 which contains the structural unit derived from an acrylic acid type compound 0.2 to 10weight%. The low molecular weight acrylic resin contains 80 to 100% by weight of a structural unit derived from a (meth) acrylic acid alkyl ester having an alkyl group having 1 to 14 carbon atoms, and optionally has a polar functional group capable of crosslinking. 0 to 10 structural units derived from (meth) acrylic acid compounds
The light diffusable adhesive sheet of Claim 1 or 2 containing weight%. The light diffusable adhesive sheet in any one of Claims 1-3 in which the said light diffusable adhesive composition contains an isocyanate type crosslinking agent further. The light diffusable adhesive sheet in any one of Claims 1-4 in which the said light diffusable adhesive composition contains a silane type compound further. The light diffusable pressure- sensitive adhesive sheet according to claim 1, wherein the light diffusable pressure-sensitive adhesive composition further contains an ionic compound. On the surface of the polarizing plate,
Contains acrylic resin and spherical fine particles,
The acrylic resin and the spherical fine particles have a refractive index difference of more than 0.01 and less than 0.09,
The acrylic resin is a mixture of a high molecular weight acrylic resin having a weight average molecular weight in the range of 500,000 to 2,000,000 and a low molecular weight acrylic resin having a weight average molecular weight in the range of 1,000 to 150,000. Containing 5 to 33% by weight of resin,
The spherical fine particles have an average particle size in the range of 5 to 15 μm, and the acrylic resin has a weight of 100
Is formed from a light diffusing pressure-sensitive adhesive composition is 20 to 50 parts by weight blended with respect to the amount unit,
Transmission clarity measured using four types of optical combs with haze in the range of 25-50% and dark and bright widths of 0.125 mm, 0.5 mm, 1.0 mm and 2.0 mm. The polarizing plate with the adhesion layer characterized by having a light diffusable adhesion layer whose total value is 150% or less . A liquid crystal display panel, wherein the polarizing plate with an adhesive layer according to claim 7 is adhered to the surface of the liquid crystal cell glass on the light diffusing adhesive layer side.

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