JP4800673B2 - Adhesive composition, adhesive layer, adhesive member, adhesive optical member, and image display device - Google Patents

Description

  The present invention relates to a pressure-sensitive adhesive composition. Moreover, this invention relates to the adhesive layer formed with the said adhesive composition. Furthermore, this invention relates to the adhesive member which has the said adhesive layer. The pressure-sensitive adhesive composition of the present invention is used, for example, for adhesion of optical members, and the pressure-sensitive adhesive member is suitably used as a pressure-sensitive adhesive optical member. Examples of the optical member include a polarizing plate, a retardation plate, an optical compensation film, a brightness enhancement film, a light diffusion film, and a laminate of these, and an adhesive optical member includes a liquid crystal display device, an organic It is suitably used for image display devices such as EL display devices and PDPs.

  Adhesives used for bonding various optical members, liquid crystal panels, various light sources, diffusers, etc. are acrylic adhesives based on acrylic copolymers because of their excellent transparency and weather resistance. The agent is being used. However, in an acrylic pressure-sensitive adhesive, the refractive index of an acrylic copolymer usually used as a base polymer is low, usually about 1.47, whereas the refractive index of an optical member is, for example, 1. It is about 52 to 1.55 and about 1.54 for polycarbonate, and there is a large difference in the refractive index between the acrylic adhesive and the optical member. For this reason, when an acrylic adhesive is used as an adhesive for an optical member, a refractive index difference occurs at the interface between the optical member and the acrylic adhesive, and total reflection occurs when light enters at a shallow angle. Therefore, there is a problem that the effective use of light is hindered.

  In order to solve such problems, various attempts have been made to create an acrylic pressure-sensitive adhesive having a high refractive index. Such attempts can be broadly divided into a method of using an acrylic copolymer having a high refractive index by copolymerizing a high refractive index monomer as a base polymer of an acrylic pressure-sensitive adhesive, and an ordinary acrylic polymer having a low refractive index. A method of increasing the refractive index of an acrylic pressure-sensitive adhesive by adding a refractive index adjusting agent to a copolymer has been studied.

  For example, as an example of the former, an acrylic adhesive having a refractive index of 1.48 or more using an acrylic copolymer obtained by copolymerizing a monomer having an aromatic group substituted or not substituted with bromine as a base polymer. An agent is disclosed (Patent Document 1). Further, an acrylic pressure-sensitive adhesive having a refractive index of 1.49 to 1.60 using an acrylic copolymer copolymerized with an aromatic group-containing monomer is disclosed as a base polymer (Patent Document 2). Further, an acrylic pressure-sensitive adhesive having a refractive index of 1.50 to 1.55 using an acrylic copolymer obtained by copolymerizing 40 to 90% by weight of an aromatic group monomer is disclosed (Patent Document 3).

  On the other hand, as the latter example, an acrylic pressure-sensitive adhesive to which a tackifier is added in order to adjust the refractive index and the adhesive strength of the pressure-sensitive adhesive is disclosed (Patent Document 4, Patent Document 5), and an acrylic system. An acrylic pressure-sensitive adhesive in which a styrene oligomer having a molecular weight of 900 or less is added as a refractive index adjusting agent to a polymer is disclosed (Patent Document 6).

Special table 2003-535921 gazette JP 2002-173656 A JP 2003-13029 A JP 2000-321960 A JP 2002-14225 A JP 2003-342546 A

  However, the acrylic pressure-sensitive adhesives disclosed in these patent documents can reduce the total reflection of light at the interface with the optical member by increasing the refractive index. Since the characteristics deteriorated, the compatibility between the high refractive index and the adhesive characteristics was not fully satisfied.

  As in Patent Documents 1 to 3, in an acrylic copolymer obtained by copolymerizing a monomer having an aromatic ring, it is the copolymerization ratio that adjusts the refractive index, and the copolymer is used to increase the refractive index. As the polymerization ratio was increased, a trade-off phenomenon was observed in which the adhesive properties greatly decreased. For this reason, there is a natural limit to satisfy both the high refractive index and the adhesive property by the copolymerization ratio of the monomer having an aromatic ring. In order to increase the refractive index, a monomer substituted with bromine can be used as a monomer having an aromatic ring. However, from the viewpoint of environmental measures, the movement of non-halogen is active mainly in electrical and electronic applications, which is not preferable. In addition, in order to adjust the refractive index of the acrylic copolymer, there is a complication of changing the copolymerization ratio of the copolymer itself.

  On the other hand, Patent Documents 4 to 5 have an operational advantage that the refractive index can be adjusted simply by mixing a tackifier as a refractive index adjuster, but acrylic adhesives generally have poor compatibility with the tackifier. . For this reason, when a large amount of the refractive index adjusting agent is added, the acrylic pressure-sensitive adhesive becomes cloudy and the adhesive strength is lowered, so that the amount of use thereof is limited. Moreover, in patent document 6, the said compatibility is improved by using a low molecular weight refractive index regulator, and even if it adds many refractive index regulators, it does not become cloudy. However, in patent document 6, the problem that the adhesive characteristic (holding power, especially holding power in high temperature) of acrylic adhesive itself falls large also generate | occur | produces.

  In consideration of the above-mentioned conventional technology, the present invention is easy to adjust the refractive index to reduce the total reflection of light at the interface with the optical member, and satisfies the adhesive properties (adhesive force, holding force, etc.). An object of the present invention is to provide a pressure-sensitive adhesive composition. Moreover, an object of this invention is to provide the adhesive layer using the said adhesive composition.

  Another object of the present invention is to provide an adhesive member such as an adhesive optical member having the adhesive layer, and further to provide an image display apparatus using the adhesive optical member.

  In order to achieve the above-mentioned object, the present inventors have intensively studied the constitution of the pressure-sensitive adhesive composition. As a result, the inventors have found that the above-mentioned object can be achieved by using the following pressure-sensitive adhesive composition, and complete the present invention. It came.

That is, the present invention is represented by the general formula (1): CH ₂ = C (R ¹ ) COOR ² (where R ¹ is a hydrogen atom or a methyl group, and R ² is an alkyl group having 2 to 14 carbon atoms). With respect to 100 parts by weight of the acrylic copolymer containing 20 to 80% by weight of the acrylic monomer represented and 80 to 20% by weight of the monomer having an aromatic group as a monomer unit,
An aromatic ring or a hydrogenated product thereof, and 20 to 150 parts by weight of a tackifier having a refractive index of 1.53 to 1.75;
The tackifier is a pressure-sensitive adhesive composition, wherein at least one tackifier is a tackifier having a weight average molecular weight of 1000 or more.

  In the pressure-sensitive adhesive composition, the acrylic copolymer is composed of a monomer unit copolymerizable with these monomers in addition to the acrylic monomer and the monomer having an aromatic group. The content is preferably 30% by weight or less. Examples of the copolymerizable monomer include a monomer having a carboxyl group and / or a monomer having a hydroxyl group, and the monomer having a carboxyl group has a hydroxyl group of 0.2 to 15% by weight. The monomer preferably contains 0.05 to 5% by weight as a monomer unit.

  In the pressure-sensitive adhesive composition, the acrylic copolymer preferably has a refractive index of 1.49 to 1.54.

  The pressure-sensitive adhesive composition preferably further comprises 0.02 to 2 parts by weight of a crosslinking agent with respect to 100 parts by weight of the acrylic copolymer.

  Moreover, this invention relates to the adhesive layer characterized by being formed with the said adhesive composition.

  As for the said adhesive layer, it is preferable that the adhesive composition contains the crosslinking agent and the gel fraction after bridge | crosslinking is 20 to 80 weight%.

  The pressure-sensitive adhesive layer preferably has a refractive index of 1.51 to 1.66.

  Moreover, this invention relates to the adhesive member characterized by having the said adhesive layer on the single side | surface or both surfaces of a support body. The adhesive member is suitable as an adhesive optical member using an optical member as a support.

  The present invention also relates to an image display device using at least one adhesive optical member, which is the adhesive member.

  In the pressure-sensitive adhesive composition of the present invention, an acrylic copolymer obtained by copolymerizing a monomer having an aromatic group is used as a base polymer, and a tackifier having an aromatic or a hydrogenated product thereof is used as a base polymer. The compatibility between the polymer and the tackifier is greatly improved, and an acrylic pressure-sensitive adhesive composition containing the tackifier can be obtained without impairing the transparency. Further, since the acrylic copolymer contains a monomer having an aromatic group as a monomer unit, the base copolymer itself has a high refractive index and the aromatic or hydrogenated product thereof is used. Since the tackifier it has also has a high refractive index, a high refractive index adhesive layer with a refractive index of 1.51 to 1.66 is obtained.

  Thus, the pressure-sensitive adhesive composition of the present invention has good adhesion because the compatibility between the base polymer and the tackifier is good, and the tackifier includes those having a weight average molecular weight of 1000 or more at high temperatures. Has good holding power (cohesive force), etc., and excellent adhesive properties. In addition, since the obtained pressure-sensitive adhesive layer has a high refractive index, the refractive index can be easily adjusted so that the total reflection of light at the interface with the optical member is reduced even when it is used for adhesion of the optical member. .

The pressure-sensitive adhesive composition of the present invention has a general formula (1): CH ₂ = C (R ¹ ) COOR ² (where R ¹ is a hydrogen atom or a methyl group, R ² has 2 to 14 carbon atoms) as a base polymer. An acrylic copolymer containing 20 to 80% by weight of an acrylic monomer represented by the formula (1) and 80 to 20% by weight of a monomer having an aromatic group as monomer units. To do.

  Specific examples of the acrylic monomer represented by the general formula (1) include, for example, ethyl (meth) acrylate, butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth). Examples thereof include acrylate, isoamyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, in (meth) nonyl acrylate, and isomyristyl (meth) acrylate. These acrylic monomers may be used alone or in combination of two or more.

  The (meth) acrylate in the present invention refers to acrylate and / or methacrylate, and (meth) in the present invention has the same meaning as described above.

  Examples of the monomer having an aromatic group include styrene monomers such as styrene and α-methylstyrene; vinyltoluene monomers such as vinyltoluene and αvinyltoluene; benzyl (meth) acrylate and naphthyl (meth) acrylate. And (meth) acrylic monomers having an aromatic group such as phenoxyethyl (meth) acrylate and phenoxybutyl (meth) acrylate.

  The acrylic copolymer contains 20 to 80% by weight of the acrylic monomer represented by the general formula (1) and 80 to 20% by weight of the monomer having an aromatic group. Preferably, the acrylic monomer is 30 to 70% by weight and the monomer having an aromatic group is 70 to 30% by weight. When the amount of the monomer having an aromatic group is decreased, the compatibility with the tackifier is lowered, and when the tackifier is blended, it becomes cloudy, which is not preferable. On the other hand, when the amount is too large, the adhesive property is decreased.

  The acrylic copolymer contains, in addition to the acrylic monomer and the monomer having an aromatic group, a monomer copolymerizable with these monomers in an amount of 30% by weight or less as a monomer unit. be able to.

  Examples of the copolymerizable monomer include a monomer having a hydroxyl group. Specific examples thereof include, for example, 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth) acrylate, 10-hydroxydecyl ( Examples include meth) acrylate, 12-hydroxylauryl (meth) acrylate, (4-hydroxymethylcyclohexyl) -methyl acrylate, and 2-methyl-3-hydroxypropyl (meth) acrylate.

  Examples of the copolymerizable monomer include monomers having a carboxyl group. Specific examples of the monomer having a carboxyl group include acrylic acid, methacrylic acid, itaconic acid, maleic acid and the like, and acrylic acid and methacrylic acid are particularly preferably used.

  Examples of copolymerizable monomers include epoxy group-containing monomers such as glycidyl (meth) acrylate, methyl glycidyl (meth) acrylate, and 3,4-epoxycyclohexylmethyl (meth) acrylate; Monomer; phosphoric acid group-containing monomer; vinyl ester monomer; amide group-containing monomer, amino group-containing monomer such as dimethylaminomethylacrylamide; imide group-containing monomer; N-acryloylmorpholine, vinyl ether Monomers having functional groups such as monomers, and further functionalities such as methyl (meth) acrylate, methoxyethyl (meth) acrylate, ethoxymethyl (meth) acrylate, (meth) acrylamide, vinyl acetate, (meth) acrylonitrile, etc. Non-group-containing monomers, but limited to these No.

  As the copolymerizable monomer, it is preferable to use a monomer having a carboxyl group and / or a monomer having a hydroxyl group. It is particularly preferable to use both.

  In the acrylic copolymer, the monomer having a carboxyl group is preferable from the viewpoint of improving the adhesive properties of the pressure-sensitive adhesive composition, and is 0.2 to 15% by weight, further 1 to 10% by weight as a monomer unit. % Copolymerization is preferred. In addition, when the copolymerization amount of the monomer which has a carboxyl group increases, there exists a tendency for an adhesive layer to become hard and the adhesiveness in a curved surface etc. is unpreferable from a point.

  The monomer having a hydroxyl group is preferable from the viewpoint of improving the long-term durability of the pressure-sensitive adhesive composition. As a monomer unit, 0.05 to 5% by weight, and further 0.07 to 2% by weight are copolymerized. It is preferable to do this. In addition, when the copolymerization amount of the monomer which has a hydroxyl group increases, there exists a tendency for an adhesive layer to become hard and the adhesiveness in a curved surface etc. is unpreferable from a point.

  The weight average molecular weight of the acrylic copolymer of the present invention is not particularly limited, but is 600,000 or more, preferably 700,000 to 3,000,000. When the weight average molecular weight is less than 600,000, durability tends to be poor. On the other hand, from the viewpoint of workability, the weight average molecular weight is preferably 3 million or less.

  For the production of the acrylic copolymer of the present invention, any known production method such as solution polymerization, bulk polymerization, and emulsion polymerization can be appropriately selected. For example, in solution polymerization, for example, ethyl acetate, toluene or the like is used as a polymerization solvent. Specifically, for example, 0.01 to 0.2 parts by weight of a polymerization disclosure agent such as azobisisobutyronitrile is added to 100 parts by weight of the total amount of the monomer, and usually 50 ° C. to 50 ° C. in a nitrogen stream. It is performed at about 70 ° C. for 8 to 30 hours. In the case of emulsion polymerization, an emulsifier and the like can be appropriately selected and used in addition to the polymerization initiator. A chain transfer agent may be used in the polymerization. By using a chain transfer agent, the molecular weight of the acrylic copolymer can be appropriately adjusted. The emulsifier and the chain transfer agent are not particularly limited.

  The acrylic copolymer preferably has a refractive index of 1.49 to 1.54 because of improved compatibility with the tackifier. The refractive index of the acrylic copolymer is more preferably 1.49 to 1.53. The refractive index of the acrylic copolymer can be controlled to be in the above range by adjusting the copolymerization ratio of the monomer having an aromatic group. In addition, since the acrylic copolymer having the refractive index has good compatibility with the tackifier, the refractive index can be improved by the addition of the tackifier, and the adhesive property can be improved.

  The pressure-sensitive adhesive composition of the present invention contains a tackifier having an aromatic ring or a hydrogenated product thereof and a refractive index of 1.53 to 1.75 in addition to the acrylic copolymer. The refractive index of the tackifier is more preferably 1.53 to 1.65, and further preferably 1.54 to 1.63. In addition, since a colored tackifier colors an adhesive composition, a transparent tackifier is preferably used. As a standard of the transparent tackifier, those having a Gardner hue of 1 or less in a 50 wt% toluene solution of the tackifier are preferably used.

  Specific examples of the tackifier include, for example, styrene oligomers, phenoxyethyl acrylate oligomers, copolymers of styrene and α-methylstyrene, copolymers of vinyltoluene and α-methylstyrene, terpene phenols and hydrogenated products thereof, rosin Examples thereof include phenols and hydrogenated products thereof, aromatic petroleum resins and hydrogenated products thereof. Among these, a styrene oligomer and a copolymer of styrene and α-methylstyrene are preferable.

  The softening point of the tackifier is preferably 40 ° C. or higher from the viewpoint of heat resistance. Furthermore, it is preferable that it is 60 degreeC or more and 70-160 degreeC. The tackifier contains at least one of those having a weight average molecular weight of 1000 or more. The weight average molecular weight is further preferably 1000 to 4000. Further, it is preferably 1100 or more. The tackifier having a weight average molecular weight of 1000 or more is preferably 50% by weight or more, further 60% by weight or more, further 70% by weight or more, and further 80% by weight or more of the total amount of the tackifier.

  The amount of tackifier based on 100 parts by weight of the acrylic copolymer is 20 to 150 parts by weight, preferably 30 to 100 parts by weight, and the pressure-sensitive adhesive composition is adjusted to have a predetermined refractive index by such amount. . That is, the refractive index of the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive layer is adjusted to be 1.51 to 1.66, preferably 1.52 to 1.62. If the amount of the tackifier is too small, the refractive index is not sufficiently increased. On the other hand, if the amount is too large, the pressure-sensitive adhesive layer becomes hard and the pressure-sensitive adhesive properties are deteriorated. When using a tackifier with a softening point of less than 40 ° C., the amount used is less than 20 parts by weight and used in combination with a tackifier with a softening point of 50 ° C. or more. It is preferable that the temperature be 40 ° C or higher.

  The pressure-sensitive adhesive composition of the present invention can contain a crosslinking agent in addition to the acrylic copolymer and the tackifier. By blending the cross-linking agent, the pressure-sensitive adhesive composition can be cross-linked to improve durability such as heat resistance, and the durability can be satisfied even when the pressure-sensitive adhesive composition is applied to a use exposed to high temperature.

  As the crosslinking agent, those having reactivity with the functional group in the acrylic copolymer are suitably used. Examples of the crosslinking agent include isocyanate compounds, epoxy compounds, metal chelate compounds, melamine compounds, aziridine compounds, metal salts, and the like. Among these, an isocyanate compound is preferably used. Isocyanate compounds include diisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, diisocyanate adducts modified with various polyols, isocyanurate rings, burettes, and allophanates. And polyisocyanate compounds.

  Moreover, when there is no functional group in an acrylic copolymer, a peroxide can be used as a crosslinking agent. In addition, the pressure-sensitive adhesive composition can be crosslinked using ultraviolet rays or electron beams.

  In addition, although the said crosslinking agent can use 1 type (s) or 2 or more types, when using a peroxide as a crosslinking agent and using an aromatic isocyanate compound, it was obtained by carrying out the crosslinking process. The pressure-sensitive adhesive layer may be colored. For this reason, aliphatic or alicyclic isocyanate compounds are preferably used in applications requiring transparency.

  The amount of the crosslinking agent is 0.02 to 2 parts by weight, preferably 0.05 to 1 part by weight, based on 100 parts by weight of the acrylic copolymer. If the amount of the crosslinking agent is too small, the crosslinking reaction becomes insufficient and the durability cannot be sufficiently improved. On the other hand, if the amount is too large, crosslinking is excessive and the adhesive properties are poor, which is not preferable.

  Furthermore, the pressure-sensitive adhesive composition of the present invention may contain other known additives. For example, powders such as colorants, pigments, dyes, surfactants, plasticizers, surface lubricants, leveling agents, softeners, antioxidants, anti-aging agents, light stabilizers, ultraviolet absorbers, polymerization inhibitors, The inorganic or organic filler, metal powder, particles, foil, etc. can be added as appropriate depending on the use. At that time, it is necessary to adjust the addition amount to such an extent that the elastic modulus of the pressure-sensitive adhesive layer is not significantly changed.

  The pressure-sensitive adhesive composition of the present invention can be used as a solution. Examples of the solvent used include methyl ethyl ketone, acetone, ethyl acetate, tetrahydrofuran, dioxane, cyclohexanone, n-hexane, toluene, xylene, methanol, ethanol, n-propanol, isopropanol, water and the like. These solvents may be used alone or in combination of two or more. As the solvent, the polymerization solvent can be used as it is, or one or more solvents other than the polymerization solvent may be newly added so that the pressure-sensitive adhesive layer can be uniformly applied.

  The pressure-sensitive adhesive composition is applied on a support and dried to produce a pressure-sensitive adhesive layer. When the pressure-sensitive adhesive composition contains a crosslinking agent, crosslinking treatment is appropriately performed by heat treatment or the like. The crosslinking treatment may be performed at the temperature of the solvent drying step, or may be performed by providing a separate crosslinking treatment step after the drying step. As the support, plastic film, paper and laminated paper, non-woven fabric, metal foil, foamed sheet and the like are used as appropriate. In the case of using a peeled support, it is possible to transfer it to various supports. As such a coating method, any coating method such as a roll coater such as a reverse coater or a gravure coater, a curtain coater, a lip coater or a die coater can be employed.

  In the production of the pressure-sensitive adhesive layer, it is preferable to adjust the addition amount of the cross-linking agent so that the gel fraction of the cross-linked pressure-sensitive adhesive layer is 20 to 80% by weight. It is more preferable to adjust the addition amount of the crosslinking agent. When the gel fraction is small, the cohesive force is inferior and the holding power is not sufficient. On the other hand, when the gel fraction is large, the adhesive strength is not sufficient, and it is not preferable from the viewpoint of adhesive properties.

  The thickness after drying of the said adhesive layer is 2-500 micrometers, Preferably it is about 5-100 micrometers. In addition, the surface of the pressure-sensitive adhesive layer may be subjected to easy attachment processing such as corona treatment, plasma treatment, and easy adhesion layer formation, and formation of an antistatic layer. When such a pressure-sensitive adhesive layer is exposed on the surface, the pressure-sensitive adhesive layer may be protected with a sheet (release sheet, separator, release liner) that has been subjected to a release treatment until practical use.

  An adhesive member provided with an adhesive layer on a support is used as an adhesive sheet and an adhesive tape in various applications. When an optical member is used as the support, it is used as an adhesive optical member.

  As an optical member, what is used for formation of image display apparatuses, such as a liquid crystal display device, is used, Although the kind in particular is not restrict | limited, For example, a film light-guide plate is mentioned. The film light guide plate is exemplified by a film provided with a light guide function by forming a fine uneven shape on one surface of a polycarbonate film. In addition, the refractive index of the film material used for these film light guide plates is 1.49 or more, preferably 1.50 or more, more preferably 1.51 or more, and most preferably 1.52 or more. The upper limit of the refractive index is preferably 1.60. The thickness of a film light-guide plate can be suitably selected from the range of about 10-200 micrometers according to a use, for example.

  In addition, examples of the optical film include an antireflection film, a conductive film, and the like. The material constituting them is preferably one having the above refractive index.

  The pressure-sensitive adhesive optical member of the present invention is bonded and fixed to a display panel (for example, a liquid crystal panel having a configuration in which a plurality of optical members such as a glass substrate, a polarizing plate and a retardation plate are laminated together with a liquid crystal). Can be used. A liquid crystal panel is preferably used as the display panel. As the liquid crystal panel, a liquid crystal panel used in a display screen section of a mobile phone (such as a mobile phone) in mobile communication can be suitably used. As a substrate of such a liquid crystal panel, a glass substrate, a plastic substrate (particularly, a glass substrate) or the like can be used. The refractive index is 1.49 or more, preferably 1.50 or more, more preferably 1.51 or more, most preferably 1.52 or more, and the upper limit is preferably 1.60.

  Examples of the optical member include a polarizing plate. A polarizing plate having a transparent protective film on one or both sides of a polarizer is generally used.

  The polarizer is not particularly limited, and various types can be used. Examples of polarizers include dichroic iodine and dichroic dyes on hydrophilic polymer films such as polyvinyl alcohol films, partially formalized polyvinyl alcohol films, and ethylene / vinyl acetate copolymer partially saponified films. Examples thereof include polyene-based oriented films such as those obtained by adsorbing substances and uniaxially stretched, polyvinyl alcohol dehydrated products and polyvinyl chloride dehydrochlorinated products. Among these, a polarizer composed of a polyvinyl alcohol film and a dichroic material such as iodine is preferable. The thickness of these polarizers is not particularly limited, but is generally about 5 to 80 μm.

  A polarizer obtained by dyeing a polyvinyl alcohol film with iodine and uniaxially stretching it can be prepared by, for example, dying polyvinyl alcohol in an aqueous solution of iodine and stretching it 3 to 7 times the original length. If necessary, it can be immersed in an aqueous solution such as potassium iodide which may contain boric acid, zinc sulfate, zinc chloride or the like. Further, if necessary, the polyvinyl alcohol film may be immersed in water and washed before dyeing. In addition to washing the polyvinyl alcohol film surface with dirt and anti-blocking agents by washing the polyvinyl alcohol film with water, it also has the effect of preventing unevenness such as uneven coloring by swelling the polyvinyl alcohol film. is there. Stretching may be performed after dyeing with iodine, may be performed while dyeing, or may be dyed with iodine after stretching. The film can be stretched even in an aqueous solution such as boric acid or potassium iodide or in a water bath.

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

  Moreover, the polymer film described in JP-A-2001-343529 (WO01 / 37007), for example, (A) a thermoplastic resin having a substituted and / or unsubstituted imide group in the side chain, and (B) a substitution in the side chain And / or a resin composition containing a thermoplastic resin having unsubstituted phenyl and a nitrile group. A specific example is a film of a resin composition containing an alternating copolymer composed of isobutylene and N-methylmaleimide and an acrylonitrile / styrene copolymer. As the film, a film made of a mixed extruded product of the resin composition or the like can be used.

  Although the thickness of a protective film can be determined suitably, generally it is about 1-500 micrometers from points, such as workability | operativity, such as intensity | strength and handleability, and thin film property. In particular, 5 to 200 μm is preferable.

  Moreover, it is preferable that a protective film has as little color as possible. Therefore, Rth = (nx−nz) · d (where nx is the refractive index in the slow axis direction in the film plane, nz is the refractive index in the film thickness direction, and d is the film thickness). A protective film having a direction retardation of −90 nm to +75 nm is preferably used. By using a film having a thickness direction retardation value (Rth) of −90 nm to +75 nm, coloring (optical coloring) of the polarizing plate caused by the protective film can be almost eliminated. The thickness direction retardation (Rth) is more preferably -80 nm to +60 nm, and particularly preferably -70 nm to +45 nm.

  As the protective film, a cellulose polymer such as triacetyl cellulose is preferable from the viewpoints of polarization characteristics and durability. A triacetyl cellulose film is particularly preferable. In addition, when providing a protective film on both sides of a polarizer, the protective film which consists of the same polymer material may be used by the front and back, and the protective film which consists of a different polymer material etc. may be used. The polarizer and the protective film are usually in close contact with each other through an aqueous adhesive or the like. Examples of the water-based adhesive include an isocyanate-based adhesive, a polyvinyl alcohol-based adhesive, a gelatin-based adhesive, a vinyl-based latex, a water-based polyurethane, and a water-based polyester.

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

  The hard coat treatment is applied for the purpose of preventing scratches on the surface of the polarizing plate. For example, a transparent protective film with a cured film excellent in hardness, sliding properties, etc. by an appropriate ultraviolet curable resin such as acrylic or silicone is used. It can be formed by a method of adding to the surface of the film. The antireflection treatment is performed for the purpose of preventing reflection of external light on the surface of the polarizing plate, and can be achieved by forming an antireflection film or the like according to the conventional art. Further, the sticking prevention treatment is performed for the purpose of preventing adhesion between adjacent layers of other members.

  Anti-glare treatment is applied for the purpose of preventing external light from being reflected on the surface of the polarizing plate and obstructing the visibility of the light transmitted through the polarizing plate. For example, the surface is roughened by sandblasting or embossing. It can be formed by imparting a fine concavo-convex structure to the surface of the transparent protective film by an appropriate method such as a method or a compounding method of transparent fine particles. Examples of the fine particles to be included in the formation of the surface fine concavo-convex structure include conductive materials made of silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, antimony oxide, and the like having an average particle diameter of 0.5 to 50 μm. In some cases, transparent fine particles such as inorganic fine particles and organic fine particles (including beads) made of a crosslinked or uncrosslinked polymer are used. When forming a surface fine uneven structure, the amount of fine particles used is generally about 2 to 50 parts by weight, preferably 5 to 25 parts by weight, based on 100 parts by weight of the transparent resin forming the surface fine uneven structure. The anti-glare layer may also serve as a diffusion layer (such as a visual enlargement function) for diffusing the light transmitted through the polarizing plate to enlarge vision.

  The antireflection layer, antisticking layer, diffusion layer, antiglare layer, and the like can be provided on the transparent protective film itself, or can be provided separately from the transparent protective film as an optical layer.

  As an optical member, for example, it is used for forming a liquid crystal display device such as a reflection plate, an anti-transmission plate, a retardation plate (including wavelength plates such as 1/2 and 1/4), a visual compensation film, and a brightness enhancement film. And an optical layer that may be formed. These can be used alone, or can be laminated on the polarizing plate for practical use and used in one or more layers.

  In particular, a reflective polarizing plate or a semi-transmissive polarizing plate in which a polarizing plate is further laminated with a reflecting plate or a semi-transmissive reflecting plate, an elliptical polarizing plate or a circular polarizing plate in which a retardation plate is further laminated on a polarizing plate, a polarizing plate A wide viewing angle polarizing plate in which a visual compensation film is further laminated on a plate, or a polarizing plate in which a luminance enhancement film is further laminated on a polarizing plate is preferable.

  A reflective polarizing plate is a polarizing plate provided with a reflective layer, and is used to form a liquid crystal display device or the like that reflects incident light from the viewing side (display side). Such a light source can be omitted, and the liquid crystal display device can be easily thinned. The reflective polarizing plate can be formed by an appropriate method such as a method in which a reflective layer made of metal or the like is attached to one surface of the polarizing plate via a transparent protective layer or the like as necessary.

  Specific examples of the reflective polarizing plate include those in which a reflective layer is formed by attaching a foil or a vapor deposition film made of a reflective metal such as aluminum on one side of a transparent protective film matted as necessary. In addition, the transparent protective film may contain fine particles to form a surface fine concavo-convex structure, and a reflective layer having a fine concavo-convex structure thereon. The reflective layer having the fine concavo-convex structure has an advantage that incident light is diffused by irregular reflection to prevent directivity and glaring appearance and to suppress unevenness in brightness and darkness. Moreover, the protective film containing fine particles also has an advantage that incident light and its reflected light are diffused when passing through it and light and dark unevenness can be further suppressed. The reflective layer of the fine concavo-convex structure reflecting the surface fine concavo-convex structure of the transparent protective film is formed by, for example, applying metal to the surface of the transparent protective layer by an appropriate method such as a vacuum deposition method, an ion plating method, a sputtering method, or a plating method. It can be performed by a method of attaching directly to the screen.

  Instead of the method of directly applying the reflecting plate to the transparent protective film of the polarizing plate, the reflecting plate can be used as a reflecting sheet provided with a reflecting layer on an appropriate film according to the transparent film. Since the reflective layer is usually made of metal, the usage form in which the reflective surface is covered with a transparent protective film, a polarizing plate or the like is used to prevent the reflectance from being lowered due to oxidation, and thus to maintain the initial reflectance for a long time. In addition, it is more preferable to avoid a separate attachment of the protective layer.

  The semi-transmissive polarizing plate can be obtained by using a semi-transmissive reflective layer such as a half mirror that reflects and transmits light with the reflective layer. A transflective polarizing plate is usually provided on the back side of a liquid crystal cell, and displays an image by reflecting incident light from the viewing side (display side) when a liquid crystal display device is used in a relatively bright atmosphere. In a relatively dark atmosphere, a liquid crystal display device of a type that displays an image using a built-in power source such as a backlight built in the back side of the transflective polarizing plate can be formed. In other words, the transflective polarizing plate can be used to form liquid crystal display devices that can save energy when using a light source such as a backlight in a bright atmosphere and can be used with a built-in power supply even in a relatively dark atmosphere. It is.

  An elliptically polarizing plate or a circularly polarizing plate in which a retardation plate is further laminated on a polarizing plate will be described. A phase difference plate or the like is used when changing linearly polarized light to elliptically polarized light or circularly polarized light, changing elliptically polarized light or circularly polarized light to linearly polarized light, or changing the polarization direction of linearly polarized light. In particular, a so-called quarter-wave plate (also referred to as a λ / 4 plate) is used as a retardation plate that changes linearly polarized light into circularly polarized light or changes circularly polarized light into linearly polarized light. A half-wave plate (also referred to as a λ / 2 plate) is usually used when changing the polarization direction of linearly polarized light.

  The elliptically polarizing plate is effectively used for black and white display without the above color by compensating (preventing) the coloration (blue or yellow) generated by the birefringence of the liquid crystal layer of the super twist nematic (STN) type liquid crystal display device. It is done. Further, the one in which the three-dimensional refractive index is controlled is preferable because it can compensate (prevent) coloring that occurs when the screen of the liquid crystal display device is viewed from an oblique direction. The circularly polarizing plate is effectively used, for example, when adjusting the color tone of an image of a reflective liquid crystal display device in which an image is displayed in color, and also has an antireflection function.

  Examples of the retardation plate include a birefringent film obtained by uniaxially or biaxially stretching a polymer material, a liquid crystal polymer alignment film, and a liquid crystal polymer alignment layer supported by a film. The thickness of the retardation plate is not particularly limited, but is generally about 20 to 150 μm.

  Examples of the polymer material include polyvinyl alcohol, polyvinyl butyral, polymethyl vinyl ether, polyhydroxyethyl acrylate, hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose, polycarbonate, polyarylate, polysulfone, polyethylene terephthalate, polyethylene naphthalate, polyether sulfone, Polyphenylene sulfide, polyphenylene oxide, polyallylsulfone, polyamide, polyimide, polyolefin, polyvinyl chloride, cellulose polymer, norbornene resin, or binary, ternary copolymers, graft copolymers, Examples include blends. These polymer materials become an oriented product (stretched film) by stretching or the like.

  Examples of the liquid crystal polymer include various main chain types and side chain types in which a conjugated linear atomic group (mesogen) imparting liquid crystal alignment is introduced into the main chain or side chain of the polymer. . Specific examples of the main chain type liquid crystal polymer include a nematic alignment polyester liquid crystal polymer, a discotic polymer, and a cholesteric polymer having a structure in which a mesogen group is bonded at a spacer portion that imparts flexibility. Specific examples of the side chain type liquid crystal polymer include polysiloxane, polyacrylate, polymethacrylate, or polymalonate as a main chain skeleton, and a nematic alignment-providing para-substitution through a spacer portion composed of a conjugated atomic group as a side chain. Examples thereof include those having a mesogenic part composed of a cyclic compound unit. These liquid crystal polymers are prepared by, for example, applying a solution of a liquid crystalline polymer on an alignment treatment surface such as a surface of a thin film such as polyimide or polyvinyl alcohol formed on a glass plate, or an oblique deposition of silicon oxide. This is done by developing and heat treatment.

  The retardation plate may have an appropriate retardation according to the purpose of use, such as for the purpose of compensating for coloring, vision, etc. due to birefringence of various wave plates and liquid crystal layers, and may be two or more types. It may be one in which retardation plates are stacked and optical characteristics such as retardation are controlled.

  The elliptical polarizing plate and the reflective elliptical polarizing plate are obtained by laminating a polarizing plate or a reflective polarizing plate and a retardation plate in an appropriate combination. Such an elliptically polarizing plate or the like can also be formed by sequentially laminating them sequentially in the manufacturing process of the liquid crystal display device so as to be a combination of a (reflective) polarizing plate and a retardation plate. An optical member such as a polarizing plate has an advantage that it can improve the production efficiency of a liquid crystal display device and the like because of excellent quality stability and lamination workability.

  The visual compensation film is a film for widening the viewing angle so that the image can be seen relatively clearly even when the screen of the liquid crystal display device is viewed from a slightly oblique direction rather than perpendicular to the screen. Examples of such a visual compensation phase difference plate include a phase difference plate, an alignment film such as a liquid crystal polymer, and a film in which an alignment layer such as a liquid crystal polymer is supported on a transparent substrate. A normal retardation plate uses a birefringent polymer film that is uniaxially stretched in the plane direction, whereas a retardation plate used as a visual compensation film is biaxially stretched in the plane direction. Birefringent polymer film, biaxially stretched film such as polymer with birefringence with a controlled refractive index in the thickness direction that is uniaxially stretched in the plane direction and stretched in the thickness direction, etc. Used. Examples of the inclined alignment film include a film obtained by bonding a heat shrink film to a polymer film and stretching or / and shrinking the polymer film under the action of the contraction force by heating, and a film obtained by obliquely aligning a liquid crystal polymer. can give. The raw material polymer for the phase difference plate is the same as the polymer described in the previous phase difference plate, preventing coloration due to a change in the viewing angle based on the phase difference by the liquid crystal cell and expanding the viewing angle for good visual recognition. An appropriate one for the purpose can be used.

  In addition, from the viewpoint of achieving a wide viewing angle with good visibility, an optical compensation position in which an alignment layer of a liquid crystal polymer, particularly an optically anisotropic layer composed of a tilted alignment layer of a discotic liquid crystal polymer, is supported by a triacetyl cellulose film. A phase difference plate can be preferably used.

  A polarizing plate obtained by bonding a polarizing plate and a brightness enhancement film is usually provided on the back side of a liquid crystal cell. The brightness enhancement film reflects a linearly polarized light with a predetermined polarization axis or a circularly polarized light in a predetermined direction when natural light is incident due to a backlight such as a liquid crystal display device or reflection from the back side, and transmits other light. In addition, a polarizing plate in which a brightness enhancement film is laminated with a polarizing plate allows light from a light source such as a backlight to enter to obtain transmitted light in a predetermined polarization state, and reflects light without transmitting the light other than the predetermined polarization state. The The light reflected on the surface of the brightness enhancement film is further inverted through a reflective layer or the like provided behind the brightness enhancement film and re-incident on the brightness enhancement film, and part or all of the light is transmitted as light having a predetermined polarization state. Luminance can be improved by increasing the amount of light transmitted through the enhancement film and increasing the amount of light that can be used for liquid crystal display image display or the like by supplying polarized light that is difficult to be absorbed by the polarizer. That is, when light is incident through the polarizer from the back side of the liquid crystal cell without using a brightness enhancement film, light having a polarization direction that does not coincide with the polarization axis of the polarizer is almost polarized. It is absorbed by the polarizer and does not pass through the polarizer. That is, although depending on the characteristics of the polarizer used, approximately 50% of the light is absorbed by the polarizer, and accordingly, the amount of light that can be used for liquid crystal image display or the like is reduced and the image becomes dark. The brightness enhancement film reflects light that has a polarization direction that is absorbed by the polarizer without being incident on the polarizer, and is reflected by the brightness enhancement film, and then inverted through a reflective layer or the like provided behind the brightness enhancement film. The brightness enhancement film transmits only the polarized light in which the polarization direction of the light reflected and inverted between the two is allowed to pass through the polarizer. Since the light is supplied to the polarizer, light such as a backlight can be efficiently used for displaying an image on the liquid crystal display device, and the screen can be brightened.

  A diffusion plate may be provided between the brightness enhancement film and the reflective layer. The polarized light reflected by the brightness enhancement film is directed to the reflective layer or the like, but the installed diffuser plate uniformly diffuses the light passing therethrough and simultaneously cancels the polarized state and becomes a non-polarized state. That is, the light in the natural light state is directed toward the reflection layer or the like, reflected through the reflection layer or the like, and again passes through the diffusion plate and reenters the brightness enhancement film. In this way, by providing a diffuser plate that returns polarized light to the original natural light between the brightness enhancement film and the reflective layer, the brightness of the display screen is maintained, and at the same time, the brightness of the display screen is reduced and uniform. Can provide a bright screen. By providing such a diffuser plate, it is considered that the first incident light has a moderate increase in the number of repetitions of reflection, and in combination with the diffusion function of the diffuser plate, a uniform bright display screen can be provided.

  The brightness enhancement film has a characteristic of transmitting linearly polarized light having a predetermined polarization axis and reflecting other light, such as a multilayer thin film of dielectric material or a multilayer laminate of thin film films having different refractive index anisotropies. Such as an alignment film of a cholesteric liquid crystal polymer or an alignment liquid crystal layer supported on a film substrate, which reflects either left-handed or right-handed circularly polarized light and transmits other light. Appropriate things, such as a thing, can be used.

  Therefore, in the brightness enhancement film of the type that transmits linearly polarized light having the predetermined polarization axis as described above, the transmitted light is incident on the polarizing plate with the polarization axis aligned as it is, thereby efficiently transmitting while suppressing absorption loss due to the polarizing plate. Can be made. On the other hand, in a brightness enhancement film of a type that transmits circularly polarized light such as a cholesteric liquid crystal layer, it can be incident on a polarizer as it is, but from the point of suppressing absorption loss, the circularly polarized light is converted into linearly polarized light through a retardation plate. It is preferably incident on the polarizing plate. Note that circularly polarized light can be converted to linearly polarized light by using a quarter wave plate as the retardation plate.

  A retardation plate that functions as a quarter-wave plate at a wide wavelength in the visible light region or the like exhibits, for example, a retardation plate that functions as a quarter-wave plate for light-colored light having a wavelength of 550 nm and other retardation characteristics. It can be obtained by a method in which a phase difference layer, for example, a phase difference layer that functions as a half-wave plate is superimposed. Therefore, the retardation plate disposed between the polarizing plate and the brightness enhancement film may be composed of one or more retardation layers.

  In addition, a cholesteric liquid crystal layer having a reflection structure that reflects circularly polarized light in a wide wavelength range such as a visible light range can be obtained by combining two or more layers with different reflection wavelengths to form an overlapping structure. Based on this, transmitted circularly polarized light in a wide wavelength range can be obtained.

  Further, the polarizing plate may be formed by laminating a polarizing plate and two or more optical layers as in the above-described polarization separation type polarizing plate. Therefore, a reflective elliptical polarizing plate or a semi-transmissive elliptical polarizing plate in which the above-described reflective polarizing plate or semi-transmissive polarizing plate and a retardation plate are combined may be used.

  The optical member in which the optical layer is laminated on the polarizing plate can be formed by a method of sequentially laminating separately in the manufacturing process of a liquid crystal display device or the like. There is an advantage that the manufacturing process of a liquid crystal display device or the like can be improved because of excellent stability and assembly work. For the lamination, an appropriate adhesive means such as an adhesive layer can be used. When bonding the polarizing plate and the other optical layer, their optical axes can be set at an appropriate arrangement angle in accordance with the target retardation characteristics.

  In addition, each layer such as an optical member or an adhesive layer of the pressure-sensitive adhesive optical member of the present invention includes, for example, ultraviolet rays such as a salicylic acid ester compound, a benzophenol compound, a benzotriazole compound, a cyanoacrylate compound, and a nickel complex compound. What gave the ultraviolet absorptivity by systems, such as a system processed with an absorber, may be used.

  The pressure-sensitive adhesive optical member of the present invention can be preferably used for forming various image display devices such as a liquid crystal display device. The liquid crystal display device can be formed according to the conventional method. That is, a liquid crystal display device is generally formed by appropriately assembling components such as a liquid crystal cell, an adhesive optical member, and an illumination system as necessary, and incorporating a drive circuit. There is no particular limitation except that an adhesive type optical member is used, and the conventional method can be applied. As the liquid crystal cell, an arbitrary type such as an arbitrary type such as a TN type, an STN type, or a π type can be used.

  An appropriate liquid crystal display device such as a liquid crystal display device in which an adhesive optical member is disposed on one side or both sides of a liquid crystal cell, or a backlight or a reflector used in an illumination system can be formed. In that case, the optical member by this invention can be installed in the one side or both sides of a liquid crystal cell. When optical members are provided on both sides, they may be the same or different. Further, when forming a liquid crystal display device, for example, a single layer or a suitable part such as a diffusing plate, an antiglare layer, an antireflection film, a protective plate, a prism array, a lens array sheet, a light diffusing plate, a backlight, etc. Two or more layers can be arranged.

  Next, an organic electroluminescence device (organic EL display device) will be described. The optical member (polarizing plate or the like) of the present invention can also be applied to an organic EL display device. Generally, in an organic EL display device, a transparent electrode, an organic light emitting layer, and a metal electrode are sequentially laminated on a transparent substrate to form a light emitter (organic electroluminescent light emitter). Here, the organic light emitting layer is a laminate of various organic thin films, for example, a laminate of a hole injection layer made of a triphenylamine derivative and the like and a light emitting layer made of a fluorescent organic solid such as anthracene, Alternatively, a structure having various combinations such as a laminate of such a light-emitting layer and an electron injection layer composed of a perylene derivative or the like, or a laminate of these hole injection layer, light-emitting layer, and electron injection layer is known. It has been.

  In organic EL display devices, holes and electrons are injected into the organic light-emitting layer by applying a voltage to the transparent electrode and the metal electrode, and the energy generated by recombination of these holes and electrons excites the phosphor material. Then, light is emitted on the principle that the excited fluorescent material emits light when returning to the ground state. The mechanism of recombination in the middle is the same as that of a general diode, and as can be predicted from this, the current and the emission intensity show strong nonlinearity with rectification with respect to the applied voltage.

  In an organic EL display device, in order to extract light emitted from the organic light emitting layer, at least one of the electrodes must be transparent, and a transparent electrode usually formed of a transparent conductor such as indium tin oxide (ITO) is used as an anode. It is used as. On the other hand, in order to facilitate electron injection and increase luminous efficiency, it is important to use a material having a small work function for the cathode, and usually metal electrodes such as Mg—Ag and Al—Li are used.

  In the organic EL display device having such a configuration, the organic light emitting layer is formed of a very thin film having a thickness of about 10 nm. For this reason, the organic light emitting layer transmits light almost completely like the transparent electrode. As a result, light that is incident from the surface of the transparent substrate at the time of non-light emission, passes through the transparent electrode and the organic light emitting layer, and is reflected by the metal electrode is again emitted to the surface side of the transparent substrate. The display surface of the organic EL display device looks like a mirror surface.

  In an organic EL display device comprising an organic electroluminescent light emitting device comprising a transparent electrode on the surface side of an organic light emitting layer that emits light upon application of a voltage and a metal electrode on the back side of the organic light emitting layer, the surface of the transparent electrode While providing a polarizing plate on the side, a retardation plate can be provided between the transparent electrode and the polarizing plate.

  Since the retardation plate and the polarizing plate have a function of polarizing light incident from the outside and reflected by the metal electrode, there is an effect that the mirror surface of the metal electrode is not visually recognized by the polarization action. In particular, the mirror surface of the metal electrode can be completely shielded by configuring the retardation plate with a quarter-wave plate and adjusting the angle formed by the polarization direction of the polarizing plate and the retardation plate to π / 4. .

  That is, only the linearly polarized light component of the external light incident on the organic EL display device is transmitted by the polarizing plate. This linearly polarized light becomes generally elliptically polarized light by the phase difference plate, but becomes circularly polarized light particularly when the phase difference plate is a quarter wavelength plate and the angle formed by the polarization direction of the polarizing plate and the phase difference plate is π / 4. .

  This circularly polarized light is transmitted through the transparent substrate, the transparent electrode, and the organic thin film, is reflected by the metal electrode, is again transmitted through the organic thin film, the transparent electrode, and the transparent substrate, and becomes linearly polarized light again on the retardation plate. And since this linearly polarized light is orthogonal to the polarization direction of a polarizing plate, it cannot permeate | transmit a polarizing plate. As a result, the mirror surface of the metal electrode can be completely shielded.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. In each example, parts are parts by weight. The molecular weight, refractive index, softening point, and gel fraction were measured by the following methods.

(Molecular weight measurement method)
The weight average molecular weights of the acrylic copolymer and tackifier were measured under the following conditions of the GPC (gel permeation chromatography) method.

Analyzing device: manufactured by Tosoh Corporation, HLC-8120GPC
Column (acrylic copolymer): manufactured by Tosoh Corporation, G7000H _XL -H + GMH _XL -H + GMH _XL
Column (tackifier): GM _HR- H + GMH _HR + G2000MH _HR manufactured by Tosoh Corporation
Column size: 7.8mmφ × 30cm each 90cm in total
Column temperature: 40 ° C
Flow rate: 0.8mL / min
Eluent: Tetrahydrofuran solution concentration: about 0.1% by weight
Injection volume: 100 μL
Detector: Differential refractometer (RI)
Standard sample: Polystyrene data processor: GPC-8020, manufactured by Tosoh Corporation

(Refractive index)
Sodium D line was irradiated in an atmosphere at 25 ° C., and the refractive index was measured with an Abbe refractometer (manufactured by ATAGO, DM-M4).

(Softening point)
It was measured by the ring and ball method described in JIS K5902.

(Gel fraction)
About 0.1 g of the pressure-sensitive adhesive layer immediately after the crosslinking treatment was taken and weighed to obtain the weight (W ₁ ). Next, this was wrapped in a microporous tetrafluoroethylene membrane (membrane weight W ₂ ), immersed in about 50 ml of ethyl acetate at 23 ° C. for 2 days, and then the soluble component was extracted. Then removed the adhesive layer with the film, which was dried for 2 hours at 120 ° C., was measured total weight (W _3). From these measured values, the gel fraction (% by weight) of the pressure-sensitive adhesive layer was determined according to the following formula.
Gel fraction (% by weight) = {(W ₃ −W ₂ ) / W ₁ } × 100

Example 1
(Preparation of acrylic copolymer)
In a reaction vessel equipped with a condenser, a nitrogen inlet tube, a thermometer and a stirrer, 233 parts of ethyl acetate as a solvent, 49 parts of 2-ethylhexyl acrylate, 50 parts of phenoxyethyl acrylate, 1 part of acrylic acid, 2-hydroxyethyl acrylate 0 .2 parts and 0.1 part of 2,2′-azobisisobutyronitrile were added, and after nitrogen substitution, the temperature was raised to 55 ° C. and a polymerization reaction was carried out for 15 hours to obtain a weight average molecular weight of 880,000. An acrylic copolymer solution was obtained. The refractive index of this acrylic copolymer was 1.51.

(Preparation of adhesive composition)
A styrene oligomer (softening point 72-77 ° C., weight average molecular weight 1350, refractive index 1.59, Picorastic A75 manufactured by Eastman Chemical Co., Ltd.) is used as a tackifier for 100 parts of the solid content of the acrylic copolymer. 60 parts were added, and further 0.4 parts of isocyanurate trimer of hexamethylene diisocyanate was added as a crosslinking agent to obtain a pressure-sensitive adhesive composition of the present invention.

(Preparation of adhesive layer)
The composition was applied to a polyethylene terephthalate film having a thickness of 38 μm subjected to silicone release treatment so that the adhesive layer had a dry thickness of 20 μm, dried and crosslinked at 140 ° C. for 3 minutes, and a gel fraction of 38 A transparent pressure-sensitive adhesive layer of wt% was obtained.

Example 2
In Example 1, a pressure-sensitive adhesive composition was prepared in the same manner as in Example 1 except that the amount of tackifier was 30 parts. Moreover, the transparent adhesive layer whose gel fraction is 45 weight% was obtained like Example 1 using the said adhesive composition.

Example 3
In Example 1, a pressure-sensitive adhesive composition was prepared in the same manner as in Example 1 except that the amount of tackifier was 100 parts. Moreover, the transparent adhesive layer whose gel fraction is 32 weight% was obtained like Example 1 using the said adhesive composition.

Example 4
In Example 1, 70 parts of α-methylstyrene / styrene copolymer (softening point 82-88 ° C., weight average molecular weight 1200, refractive index 1.61, Crystallex 3085 manufactured by Eastman Chemical Co., Ltd.) was used as a tackifier. A pressure-sensitive adhesive composition was prepared in the same manner as in Example 1 except that 0.2 part of benzoyl peroxide and 0.6 part of an isophorone diisocyanate adduct of trimethylolpropane were used as a crosslinking agent. Moreover, the transparent adhesive layer whose gel fraction is 45 weight% was obtained like Example 1 using the said adhesive composition.

Example 5
(Preparation of acrylic copolymer)
In a reaction vessel equipped with a condenser, a nitrogen inlet tube, a thermometer and a stirrer, 233 parts of ethyl acetate as a solvent, 79 parts of butyl acrylate, 20 parts of styrene, 1 part of acrylic acid, 0.3 part of 4-hydroxybutyl acrylate, And 0.22 parts of 2,2′-azobisisobutyronitrile were added, and after nitrogen substitution, the temperature was raised to 55 ° C. and a polymerization reaction was carried out for 15 hours to obtain an acrylic copolymer having a weight average molecular weight of 570,000. A combined solution was obtained. The refractive index of this acrylic copolymer was 1.49.

(Preparation of adhesive composition)
As a tackifier, a copolymer of vinyltoluene and α-methylstyrene (softening point 88-94 ° C., weight average molecular weight 1500, refractive index 1.60, Eastman, 100 parts by weight of the acrylic copolymer) 50 parts of Picotex LC manufactured by Chemical Co., Ltd. and 10 parts of styrene oligomer (softening point below room temperature, weight average molecular weight 430, refractive index 1.60, Eastman Chemical Co. Picolastic A5) were added as a crosslinking agent. 0.8 parts of isocyanurate trimer of hexamethylene diisocyanate was added to obtain a pressure-sensitive adhesive composition of the present invention.

(Preparation of adhesive layer)
The composition was applied to a polyethylene terephthalate film having a thickness of 38 μm subjected to silicone release treatment so that the dry thickness of the pressure-sensitive adhesive layer was 20 μm, dried and crosslinked at 140 ° C. for 3 minutes, and a gel fraction of 36 A transparent pressure-sensitive adhesive layer of wt% was obtained.

Example 6
In Example 5, as a tackifier, hydrogenated terpene phenol (softening point 110-115 ° C., weight average molecular weight 1450, refractive index 1.54, Clearon MI15 manufactured by Yashara Chemical Co., Ltd.), and styrene oligomer (softening point) A pressure-sensitive adhesive composition was prepared in the same manner as in Example 5 except that 10 parts of room temperature or lower, weight average molecular weight of 430, refractive index of 1.60, and Picorastic A5) manufactured by Eastman Chemical Co. were used. Moreover, the transparent adhesive layer whose gel fraction is 41 weight% was obtained like Example 1 using the said adhesive composition.

Example 7
(Preparation of acrylic copolymer)
In a reaction vessel equipped with a condenser, a nitrogen inlet tube, a thermometer and a stirrer, 233 parts of ethyl acetate as a solvent, 30 parts of butyl acrylate, 70 parts of phenoxyethyl acrylate, 0.5 part of acrylic acid, 4-hydroxybutyl acrylate 0 .3 parts and 2,2′-azobisisobutyronitrile 0.2 part, and after carrying out nitrogen substitution, the temperature was raised to 55 ° C. and the polymerization reaction was carried out for 15 hours to obtain a weight average molecular weight of 810,000. An acrylic copolymer solution was obtained. The refractive index of this acrylic copolymer was 1.53.

(Preparation of adhesive composition)
As a tackifier, a copolymer of α-methylstyrene and styrene (softening point 82-88 ° C., weight average molecular weight 1200, refractive index 1.61, Eastman Chemical) is used as a tackifier with respect to a solid content of 100 parts of the acrylic copolymer. 80 parts of Crystallex 3085) manufactured by the company, and 10 parts of styrene oligomer (softening point below room temperature, weight average molecular weight 430, refractive index 1.60, Picorastic A5 manufactured by Eastman Chemical Co., Ltd.) 0.6 part of an isophorone diisocyanate adduct of trimethylolpropane was added to obtain a pressure-sensitive adhesive composition of the present invention.

(Preparation of adhesive layer)
The composition was applied to a polyethylene terephthalate film having a thickness of 38 μm subjected to silicone release treatment so that the dry thickness of the pressure-sensitive adhesive layer was 20 μm, dried and crosslinked at 140 ° C. for 3 minutes, and a gel fraction of 41 A transparent pressure-sensitive adhesive layer of wt% was obtained.

Comparative Example 1
(Preparation of acrylic copolymer)
In a reaction vessel equipped with a condenser, a nitrogen inlet tube, a thermometer and a stirrer, 233 parts of ethyl acetate as a solvent, 97 parts of butyl acrylate, 3 parts of acrylic acid, 0.2 part of 2-hydroxyethyl acrylate, and 2,2 After adding 0.1 part of ′ -azobisisobutyronitrile and carrying out nitrogen substitution, the temperature was raised to 55 ° C. and a polymerization reaction was carried out for 15 hours to obtain an acrylic copolymer solution having a weight average molecular weight of 570,000. Obtained. The refractive index of this acrylic copolymer was 1.47.

(Preparation of adhesive composition)
A styrene oligomer (softening point 72-77 ° C., weight average molecular weight 1200, refractive index 1.59, Picorastic A75 manufactured by Eastman Chemical Co., Ltd.) as a tackifier with respect to 100 parts of the solid content of the acrylic copolymer. 30 parts were added, and 0.4 parts of isocyanurate trimer of hexamethylene diisocyanate was further added as a crosslinking agent to obtain a pressure-sensitive adhesive composition.

(Preparation of adhesive layer)
The composition was applied to a 38 μm-thick polyethylene terephthalate film that had been subjected to silicone release treatment so that the pressure-sensitive adhesive layer had a dry thickness of 20 μm, dried and crosslinked at 140 ° C. for 3 minutes, and a gel fraction of 43 A weight percent pressure-sensitive adhesive layer was obtained. However, since the pressure-sensitive adhesive layer was cloudy and diffusely reflected, the refractive index was not measured.

Comparative Example 2
In Comparative Example 1, Comparative Example 1 was used except that 30 parts of a styrene oligomer (softening point at room temperature or lower, weight average molecular weight 430, refractive index 1.60, Picorastic A5 manufactured by Eastman Chemical Co.) was used as a tackifier. Similarly, a pressure-sensitive adhesive composition was prepared. Moreover, the transparent adhesive layer whose gel fraction is 40 weight% was obtained like the comparative example 1 using the said adhesive composition.

Comparative Example 3
In Example 7, a pressure-sensitive adhesive composition was prepared in the same manner as in Example 7 except that no tackfire was added. Moreover, using the said adhesive composition, it carried out similarly to Example 7, and obtained the transparent adhesive layer whose gel fraction is 69 weight%.

Comparative Example 4
(Preparation of adhesive composition)
As a tackifier, petroleum resin (softening point 98-102 ° C., weight average molecular weight 1650, refractive index 1) is used as a tackifier for 100 parts of the solid content of the acrylic copolymer having a refractive index of 1.49 obtained in Example 5. .52, 30 parts of Eastman Chemical Co. Picotac 1098) and 0.8 parts of isocyanurate trimer of hexamethylene diisocyanate as a crosslinking agent were added to obtain a pressure-sensitive adhesive composition.

(Preparation of adhesive layer)
The composition was applied to a polyethylene terephthalate film having a thickness of 38 μm subjected to silicone release treatment so that the dry thickness of the pressure-sensitive adhesive layer was 20 μm, dried and crosslinked at 140 ° C. for 3 minutes, and a gel fraction of 39 A weight percent pressure-sensitive adhesive layer was obtained. However, since the pressure-sensitive adhesive layer was cloudy and diffusely reflected, the refractive index was not measured.

Comparative Example 5
In Example 1, Example 1 was used except that 60 parts of a styrene oligomer (softening point below room temperature, weight average molecular weight 430, refractive index 1.60, Picorastic A5 manufactured by Eastman Chemical Co.) was used as a tackifier. Similarly, a pressure-sensitive adhesive composition was prepared. Moreover, the transparent adhesive layer whose gel fraction is 35 weight% was obtained like Example 1 using the said adhesive composition.

  The following evaluation test was done about the adhesive layer obtained by the Example and the comparative example. The results are shown in Table 1. Table 1 shows the refractive index of the pressure-sensitive adhesive layer.

(Adhesive strength)
Adhesive layer is attached to a polyester film with a thickness of 38μ to make a backing film, cut to 20mm x 100mm, and a 2kg roller makes a round trip to the adherend (a stainless steel plate sanded with # 280 sandpaper). Then, after 20 minutes at 23 ° C., the adhesive force (N / 20 mm) required for the peeling was measured. The peeling conditions were 180 degree peeling, 300 mm / min pulling speed, 23 ° C., and 50% RH atmosphere.

(Holding power)
Adhesive layer is attached to a polyester film with a thickness of 38μ to form a backing film, attached to a baking plate with an adhesive area of 10mm x 20mm, and under the condition of 80 ° C, a load of 500g is applied vertically until the tape falls. Was measured.

  As shown in Table 1, in the examples, the refractive index of the pressure-sensitive adhesive layer can be easily adjusted by adjusting the amount of tackifier. Moreover, in the Examples, a pressure-sensitive adhesive layer having good compatibility between the acrylic copolymer and the tackifier and having excellent adhesive properties of adhesive strength and holding power is obtained. On the other hand, in Comparative Examples 1 and 4, the compatibility between the acrylic copolymer and the tackifier is poor, the pressure-sensitive adhesive layer is cloudy, and the adhesive force is also poor. In Comparative Examples 2 and 5, the refractive index of the pressure-sensitive adhesive layer can be adjusted without becoming cloudy, but the softening point of the tackifier is low (weight average molecular weight is low), and the pressure-sensitive adhesive properties (retention force) are not sufficient. In Comparative Example 3, there was no tackiness.

Claims (12)

General formula (1): Acrylic system represented by CH ₂ = C (R ¹ ) COOR ² (where R ¹ is a hydrogen atom or a methyl group, and R ² is an alkyl group having 2 to 14 carbon atoms). For 100 parts by weight of an acrylic copolymer containing 20 to 80% by weight of monomer and 80 to 20% by weight of monomer having an aromatic group as a monomer unit,
An aromatic ring or a hydrogenated product thereof, and 20 to 150 parts by weight of a tackifier having a refractive index of 1.53 to 1.75;
At least one tackifier is a tackifier having a weight average molecular weight of 1000 or more.   The acrylic copolymer contains, in addition to the acrylic monomer and the monomer having an aromatic group, a monomer copolymerizable with these monomers in an amount of 30% by weight or less as a monomer unit. The pressure-sensitive adhesive composition according to claim 1. Copolymerizable monomer, the pressure-sensitive adhesive composition according to claim 2, characterized in that organic monomers 0.2 to 15% by weight having a carboxyl group. The pressure-sensitive adhesive composition according to claim 2 or 3, wherein the copolymerizable monomer contains 0.05 to 5% by weight of a monomer having a hydroxyl group. The pressure-sensitive adhesive composition according to any one of claims 1 to 4, wherein an acrylic copolymer has a refractive index of 1.49 to 1.54. The pressure-sensitive adhesive composition according to any one of claims 1 to 5 , further comprising 0.02 to 2 parts by weight of a crosslinking agent based on 100 parts by weight of the acrylic copolymer. It is formed with the adhesive composition in any one of Claims 1-6 , The adhesive layer characterized by the above-mentioned. The pressure-sensitive adhesive layer according to claim 7 , wherein the pressure-sensitive adhesive composition contains a crosslinking agent, and the gel fraction after crosslinking is 20 to 80% by weight. Refractive index is 1.51-1.66, The adhesive layer of Claim 7 or 8 characterized by the above-mentioned. A pressure-sensitive adhesive member comprising the pressure-sensitive adhesive layer according to claim 7 on one side or both sides of a support. The pressure-sensitive adhesive member according to claim 10 , wherein the support is an optical member. 111. An image display device using at least one adhesive optical member as the adhesive member according to claim 110 .