JP4849837B2 - Optical member pressure-sensitive adhesive composition, optical member pressure-sensitive adhesive layer, pressure-sensitive adhesive optical member, method for producing the same, and image display device - Google Patents

Description

  The present invention relates to a pressure-sensitive adhesive composition for optical members. Moreover, this invention relates to the adhesive layer formed with the said adhesive composition for optical members. Furthermore, this invention relates to the adhesive optical member which has the said adhesive layer for optical members. 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 addition, Patent Documents 4 to 5 exemplify various adhesives such as styrene-based elastomers in addition to acrylic adhesives as the adhesive, but only by mixing various adhesives and tackifiers. However, those that satisfy the adhesive properties (adhesive strength, holding power, etc.) have not been obtained. In particular, a product having excellent long-term durability cannot be obtained.

  In consideration of the above-described conventional technology, the present invention can easily adjust the refractive index to reduce the total reflection of light at the interface with the optical member, and has adhesive properties (adhesive force, holding force, etc.) and durability. It aims at providing the adhesive composition which can satisfy property. 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 based on 100 parts by weight of a styrene block elastomer.
40 to 250 parts by weight of a tackifier having an aromatic ring or a hydrogenated product thereof, and 0.01 to 2 parts by weight of a silane coupling agent are blended, and the tackifier has a refractive index of 1.53 to 1.75. It is related with the adhesive composition for optical members characterized by these.

  In the pressure-sensitive adhesive composition for an optical member, the tackifier contains a liquid tackifier at 23 ° C. and a tackifier having a softening point of 50 ° C. or more, and the liquid tackifier is 6 to 75 weight of the total amount of the tackifier. % Content is preferable.

  Further, in the pressure-sensitive adhesive composition for optical members, the styrenic block elastomer has a styrene block unit and a block unit formed of at least one selected from ethylene, propylene, butylene, and alkyl (meth) acrylate. Is preferred.

  Moreover, it is preferable that the said adhesive composition for optical members further mix | blends 0.02-2 weight part with a crosslinking agent with respect to 100 weight part of styrene-type block elastomers. As said crosslinking agent, the photocrosslinking agent which generate | occur | produces a radical by irradiation of a radiation is suitable.

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

  In the optical member pressure-sensitive adhesive layer, the optical member pressure-sensitive adhesive composition preferably contains a crosslinking agent, and the gel fraction after crosslinking is preferably 20 to 65% by weight.

  The optical member pressure-sensitive adhesive layer preferably has a refractive index of 1.52 to 1.66.

  Moreover, this invention relates to the adhesive optical member characterized by having the adhesive layer for optical members in any one of Claims 6-8 in the single side | surface or both surfaces of an optical member.

  Further, the present invention provides the pressure-sensitive adhesive optical member, wherein the pressure-sensitive adhesive composition for an optical member is formed by applying the pressure-sensitive adhesive composition for an optical member to the optical member in a heated and melted state without using a solvent. The manufacturing method.

  In the present invention, the optical member pressure-sensitive adhesive composition is coated on a support that has been peel-treated in a heated and melted state without using a solvent to form an optical member pressure-sensitive adhesive layer, and then the optical member pressure-sensitive adhesive. The present invention relates to a method for producing an adhesive optical member, wherein a layer is transferred to an optical member.

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

  The pressure-sensitive adhesive composition for optical members in the present invention uses a styrene block elastomer as a base polymer. The refractive index of the styrenic block elastomer is 1.50 or higher, which is higher than the refractive index near 1.47 of the acrylic polymer, and has good compatibility with the tackifier having an aromatic or hydrogenated product, An adhesive having good transparency and no coloration is obtained. Since the styrenic block elastomer contains styrene, the pressure-sensitive adhesive composition has a high refractive index of the base polymer itself, and a tackifier having an aromatic or hydrogenated product also has a high refractive index. A pressure-sensitive adhesive layer having a refractive index of 1.52 to 1.66 is obtained.

  As described above, the optical member pressure-sensitive adhesive composition of the present invention has good compatibility between the base polymer and the tackifier, and also has a silane coupling agent in addition to these, so that it has adhesiveness and holding power (cohesive strength). Excellent adhesive properties such as, and excellent durability. Moreover, the retention strength (heat resistance) at high temperature can be satisfied by the blending of the crosslinking agent. 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. . Furthermore, since the pressure-sensitive adhesive composition for optical members of the present invention can be heated and melt coated without using a solvent, it can be blended and coated in a solvent-free environment. There is also an advantage in creating.

  The pressure-sensitive adhesive composition for optical members of the present invention contains a styrene block elastomer as a base polymer. As the styrene block elastomer, those having at least a styrene block unit and other units can be used without any particular limitation, but depending on at least one selected from a styrene block unit and ethylene, propylene, butylene and alkyl (meth) acrylate. Those having formed block units are preferred.

  Typical styrene block elastomers include styrene-isoprene-styrene (SIS) and styrene-butadiene-styrene (SBS). Since these have a double bond in the main chain, they have poor weather resistance and may be colored, softened or cured. On the other hand, styrene-ethylene-propylene-styrene (SEPS) and styrene-ethylene-butylene-styrene (SEBS) in a form in which the main chain of SIS or SBS is hydrogenated are preferable because of excellent weather resistance and transparency.

  As the styrene block elastomer, an elastomer having a styrene block unit and an alkyl (meth) acrylate block unit that can be synthesized using living radical polymerization, instead of the combination of styrene block unit and olefin block unit as described above. It is preferably used because of its transparency and good weather resistance.

  Examples of the alkyl (meth) acrylate include ethyl (meth) acrylate, butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, isoamyl (meth) acrylate, 2- Examples thereof include alkyl (meth) acrylates having about 2 to 14 carbon atoms in the alkyl group, such as ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, in (meth) nonyl acrylate, and isomyristyl (meth) acrylate. These alkyl (meth) acrylates 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.

  The weight average molecular weight of the styrene block elastomer of the present invention is not particularly limited, but is usually 50,000 to 300,000. When the weight average molecular weight is less than 50,000, the durability tends to be poor. On the other hand, from the viewpoint of workability, the weight average molecular weight is preferably 300,000 or less.

  The refractive index of the styrenic block elastomer is preferably 1.48 to 1.55, since the compatibility with the tackifier is improved. The refractive index of the styrenic block elastomer is more preferably 1.50 to 1.54. The refractive index of the styrenic block elastomer can be controlled to be in the above range by adjusting the ratio of styrene block units. The content of styrene block units with respect to the styrenic block elastomer is usually preferably 10 to 50% by weight, more preferably 12 to 45% by weight, and further preferably 15 to 40% by weight. Since the styrene block elastomer having the refractive index has good compatibility with the tackifier, the effect of improving the refractive index by adding the tackifier is good, and the adhesive property is also good.

  The pressure-sensitive adhesive composition for an optical member of the present invention contains a tackifier having an aromatic ring or a hydrogenated product thereof in addition to the styrene block elastomer. The tackifier has a refractive index of 1.53 to 1.75. The refractive index of the tackifier is the refractive index of the entire tackifier, and when two or more types are used as the tackifier, the refractive index of the mixture may be 1.53 to 1.75. The refractive index of the fire may not be in the range of 1.53 to 1.75. 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.

  Although the softening point, molecular weight, etc. of the tackifier are not particularly limited, it comprises a liquid tackifier at 23 ° C. and a tackifier having a softening point of 50 ° C. or higher. It is preferable to contain 75% by weight, preferably 10 to 50% by weight. It is preferable to use the liquid tackifier in combination with a tackifier having a softening point of 50 ° C. or higher in terms of improving adhesiveness and holding power (cohesive force). If the content of the liquid tackifier is too small, the adhesiveness tends to decrease, and if too much, the cohesive force tends to decrease.

  “Liquid” in a liquid tackifier means that the softening point is 23 ° C. (room temperature or lower). As such a liquid tackifier, those having a low molecular weight are preferably selected from the above materials. The weight average molecular weight of the liquid tackifier is usually preferably about 300 to 2,000. Various oils and fats, liquid hydrocarbons, and fatty acid esters can be used together with the liquid tackifier.

  The tackifier having a softening point of 50 ° C. or higher preferably has a weight average molecular weight of 1000 or more, more preferably 1000 to 4000. The weight average molecular weight is preferably 1100 or more. The softening point of the tackifier is preferably 60 ° C. or higher, more preferably 70 to 160 ° C.

  The amount of tackifier based on 100 parts by weight of the styrenic block elastomer is 40 to 250 parts by weight, preferably 50 to 200 parts by weight, more preferably 70 to 150 parts by weight. Is adjusted to a predetermined refractive index. That is, the refractive index of the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive layer is adjusted to be 1.52 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.

  Examples of the silane coupling agent include epoxy group-containing silanes such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmerlediethoxysilane, and 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane. Coupling agent; such as 3-aminopropyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, 3-triethoxysilyl-N- (1,3-dimethyl-butylidene) propylamine, etc. Amino group-containing silane coupling agent; (meth) acrylic group-containing silane coupling agent such as 3-acryloxypropyltrimethoxysilane and 3-methacryloxypropyltriethoxysilane; and isocyanate group containing 3-isocyanatopropyltriethoxysilane Syrah Coupling agents, and the like.

  The silane coupling agent is blended in an amount of 0.01 to 2 parts by weight, preferably 0.02 to 1 part by weight, based on 100 parts by weight of the styrene block elastomer. If the amount of the silane coupling agent is too large, the adhesive force of the pressure-sensitive adhesive layer to the liquid crystal cell or the like is increased and the removability is poor. On the other hand, if the amount is too small, the durability decreases, which is not preferable.

  Moreover, the adhesive composition for optical members of this invention can contain a crosslinking agent other than the said styrene-type block elastomer and tackifier. By blending the cross-linking agent, the pressure-sensitive adhesive composition can be cross-linked to improve durability such as heat resistance, and durability can be satisfied even when the pressure-sensitive adhesive composition is applied to a use exposed to high temperatures.

  As the crosslinking agent, a photocrosslinking agent that generates radicals when irradiated with radiation is preferably used. The pressure-sensitive adhesive composition in which the photocrosslinking agent is blended is subjected to a crosslinking treatment by a method of causing a crosslinking reaction by applying radiation after coating.

  Examples of the radiation used according to the photocrosslinking agent include ultraviolet rays. Examples of photocrosslinking agents that generate radicals upon irradiation with ultraviolet light include hydroxy ketones, benzyl dimethyl ketals, amino ketones, acylphosphine oxides, benzophenones, trichloromethyl group-containing triazine derivatives, and the like. Examples of triazine derivatives containing trichloromethyl groups include, for example, 2- (p-methoxyphenyl) -4,6-bis- (trichloromethyl) -s-triazine, 2-phenyl-4,6-bis- (trichloromethyl) -S-triazine, 2- (4'-methoxy-1'-naphthyl) -4,6-bis- (trichloromethyl) -s-triazine, 2,4-trichloromethyl- (4'-methoxyphenyl) -6 -Triazine, 2,4-trichloromethyl- (4'-methoxynaphthyl) -6-triazine, 2,4-trichloromethyl (piperonyl) -6-triazine, 2,4-trichloromethyl- (4-methoxystyryl)- Examples include 6-triazine. In particular, an oligomer type photocrosslinking agent of the above compound having a plurality of radical generation points in the molecule is preferable. Specifically, 2-hydroxy-2-methyl- [4- (1-methylvinyl) phenyl] propanol oligomer or the like is preferably used because of its good crosslinking efficiency.

  Such a photocrosslinking agent is generally used in a ratio of 0.02 to 2 parts by weight, preferably 0.05 to 1 part by weight, based on 100 parts by weight of the styrene block elastomer. If the amount of the photocrosslinking agent is too small, the crosslinking reaction by radiation does not proceed sufficiently, and the durability cannot be sufficiently improved. On the other hand, if the amount is too large, the pressure-sensitive adhesive layer becomes hard due to an excessive crosslinking reaction, and the followability to a dimensional change of the optical member (for example, a polarizing plate) is deteriorated.

  In addition to the above, examples of the crosslinking method include a method in which a functional group capable of reacting with a crosslinking agent is introduced into a styrenic block elastomer and a crosslinking agent having a functional group capable of reacting with the functional group is blended. Examples of the crosslinking agent having such a functional group include polyfunctional monomers and oligomers. Such a crosslinking agent can be used alone, or can be used in combination with the photocrosslinking agent in consideration of the adhesiveness in appropriately adjusting the crosslinking. The amount of the crosslinking agent having a functional group is the same as the amount of the photocrosslinking agent. Furthermore, examples of the crosslinking method include a method of crosslinking the pressure-sensitive adhesive composition using radiation such as electron beams and gamma rays. Such a crosslinking method does not require a photocrosslinking agent, but the apparatus is expensive and large.

  Further, the pressure-sensitive adhesive composition for optical members 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 for optical members of the present invention can be used as a solution dissolved in a solvent. Moreover, since it melts by heating, it can be used in a heated and melted state without using a solvent. Examples of the solvent 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.

  The above-mentioned pressure-sensitive adhesive composition can be directly applied to an optical member to form a pressure-sensitive adhesive layer for an optical member to produce a pressure-sensitive adhesive optical member. After forming the pressure-sensitive adhesive layer for members, the pressure-sensitive adhesive layer for optical members can be transferred to the optical member to produce a pressure-sensitive adhesive optical member.

  Examples of the optical member include those described below, and the support subjected to the release treatment is suitably used, such as a plastic film, paper and laminated paper, nonwoven fabric, metal foil, and foamed sheet.

  When using the adhesive composition for optical members as a solution, it dries after application | coating and forms an adhesive layer. 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. As a method of applying the pressure-sensitive adhesive composition for an optical member in a molten state without using a solvent, for example, it is kneaded with a heating kneader or a uniaxial / biaxial kneader to be uniform, and then applied with a heated die coater. The method of crafting is given.

  When the pressure-sensitive adhesive composition contains a crosslinking agent, a crosslinking treatment is appropriately performed by a heat treatment or the like. In the case of using a solution as the pressure-sensitive adhesive composition, the crosslinking treatment may be performed at the temperature of the solvent drying step, or may be performed by separately providing a crosslinking treatment step after the drying step.

When a photocrosslinking agent is blended as a crosslinking agent in the pressure-sensitive adhesive composition, a crosslinking treatment by ultraviolet irradiation is performed. The ultraviolet irradiation can be performed using an appropriate ultraviolet ray source such as a high pressure mercury lamp, a low pressure mercury lamp, an excimer laser, or a metal halide lamp. In this case, the irradiation amount of ultraviolet rays can be appropriately selected according to the required degree of crosslinking as described above, but is usually selected within the range of 0.2 to 10 J / cm ² for ultraviolet rays. Is desirable. The temperature at the time of irradiation is not particularly limited, but is preferably about 140 ° C. or less in consideration of heat resistance of the support and the like. The irradiation amount is the sum of the light amounts of UVA, UVB, and UVC when the light amount is measured using a UV power pack manufactured by Fusion Japan.

  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 65% by weight, so as to be 25 to 60% 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.

  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 conjugated atomic groups as side chains. 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 styrenic block elastomer and tackifier were measured under the following conditions of the GPC (gel permeation chromatography) method.

Analyzing device: manufactured by Tosoh Corporation, HLC-8120GPC
Column (styrene block elastomer): 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 was taken and weighed to determine 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
(Styrene block elastomer)
A block polymer of styrene-ethylene butylene-styrene having a styrene content of 30% by weight (Taftec HI141, manufactured by Asahi Kasei Co., Ltd.) was used. The refractive index was 1.53.

(Preparation of adhesive composition)
After dissolving 100 parts of the styrene block elastomer in 300 parts of toluene, a hydrogenated terpene resin at room temperature (softening point below room temperature, weight average molecular weight 650, refractive index 1.50, Yashara Chemical Co., Ltd.) was used as a tackifier. Manufactured by Clearon LH) and 40 parts of styrene oligomer (softening point 72-77 ° C., weight average molecular weight 1350, refractive index 1.59, Picorastic A75 manufactured by Eastman Chemical Co.) dissolved in 40 parts of toluene. And 0.2 part of 3-glycidoxypropylmethyldiethoxysilane were uniformly mixed to obtain a pressure-sensitive adhesive composition (solution) of the present invention. The refractive index of the entire tackifier composed of 10 parts of the room temperature liquid hydrogenated terpene resin and 40 parts of the styrene oligomer is 1.57.

(Preparation of adhesive layer)
The pressure-sensitive adhesive composition (solution) was applied to a 38 μm-thick polyethylene terephthalate film that had been subjected to silicone release treatment so that the dry thickness of the pressure-sensitive adhesive layer was 20 μm, dried at 140 ° C. for 3 minutes, and gel A pressure-sensitive adhesive layer having a fraction of 0% by weight was obtained.

Example 2
(Preparation of adhesive composition)
In the preparation of the pressure-sensitive adhesive composition of Example 1, 0.2 parts of 2-hydroxy-2-methyl- [4- (1-methylvinyl) phenyl] propanol oligomer was further added as a photocrosslinking agent and mixed uniformly. Except for this, a pressure-sensitive adhesive composition (solution) was prepared in the same manner as in Example 1.

(Preparation of adhesive layer)
After the pressure-sensitive adhesive composition (solution) was applied to a 38 μm-thick polyethylene terephthalate film subjected to silicone release treatment so that the pressure-sensitive adhesive layer had a dry thickness of 20 μm and dried at 140 ° C. for 3 minutes. The pressure-sensitive adhesive layer having a gel content of 42% by weight was obtained by irradiating ultraviolet rays with an irradiation light amount of 2.3 J / cm ² with a metal halide lamp.

Example 3
(Preparation of adhesive composition)
In the preparation of the pressure-sensitive adhesive composition of Example 2, the pressure-sensitive adhesive was the same as Example 2 except that toluene was not used and the mixture was made uniform by mixing at a temperature of 180 ° C. for 2 hours with a small heating kneader. A composition was prepared.

(Preparation of adhesive layer)
The pressure-sensitive adhesive composition was heated to 160 ° C. and applied to a 38 μm-thick polyethylene terephthalate film subjected to silicone release treatment so that the pressure-sensitive adhesive layer had a thickness of 20 μm. Irradiation was performed with an irradiation light amount of 2.3 J / cm ² to obtain a pressure-sensitive adhesive layer having a crosslinked gel content of 42% by weight.

Example 4
(Styrene block elastomer)
A block polymer of styrene-ethylene-butylene-styrene having a styrene content of 29% by weight (Taftec H1053, manufactured by Asahi Kasei) was used. The refractive index was 1.53.

(Preparation of adhesive composition)
After dissolving 100 parts of the above styrenic block elastomer in 300 parts of toluene, as a tackifier, a styrene oligomer in a room temperature liquid (softening point below room temperature, weight average molecular weight 430, refractive index 1.60, manufactured by Eastman Chemical Co., Ltd.) 30 parts of picolastic A5) and 70 parts of a copolymer of α-methylstyrene and styrene (softening point 82-88 ° C., weight average molecular weight 1200, refractive index 1.61, Crystallex 3085 manufactured by Eastman Chemical) -Glycidoxypropylmethyldiethoxysilane 0.4 part, 2-hydroxy-2-methyl- [4- (1-methylvinyl) phenyl] propanol oligomer 0.5 part as photocrosslinking agent, Irganox as anti-aging agent 0.31 of 1010 (manufactured by Ciba Specialty Chemicals) To obtain a uniform pressure-sensitive adhesive composition was mixed for 2 hours at a temperature of 200 ° C. at small heating kneader without.

(Preparation of adhesive layer)
The pressure-sensitive adhesive composition was heated to 160 ° C. and applied to a 38 μm-thick polyethylene terephthalate film subjected to silicone release treatment so that the pressure-sensitive adhesive layer had a thickness of 20 μm. Irradiation was performed with an irradiation light amount of 3.0 J / cm ² to obtain a pressure-sensitive adhesive layer having a crosslinked gel content of 38% by weight.

Example 5
(Styrene block elastomer)
After adding 35 parts of styrene to a four-necked flask equipped with a mechanical stirrer, nitrogen inlet, cooling pipe and rubber septum, 1.3 parts of 2,2′-bipyridine was added thereto, Was replaced with nitrogen. After adding 0.41 part of copper bromide to this under nitrogen stream, the reaction system was heated to 90 ° C., and 0.6 g of 2-hydroxyethyl 2-bromo-2-methylpropionate was added as an initiator. Polymerization was started, and polymerization was performed at 90 ° C. for 12 hours under a nitrogen stream without adding a solvent. After confirming that the polymerization rate (a ratio defined by a value obtained by dividing the polymer weight obtained by heating and removing the volatile component by the polymer weight of the polymerization solution before removing the volatile component) is 80% by weight or more, To this was added 140 parts of butyl acrylate from a rubber septum, which was further heated at 110 ° C. for 20 hours. After confirming that the polymerization rate was 80% by weight or more, 35 parts of styrene was added to the polymerization system from a rubber septum, and this was further heated at 90 ° C. for 20 hours. In this manner, a styrene-butyl acrylate-styrene triblock polymer was obtained. The obtained block polymer was heated to 120 ° C. and centrifuged at 20000 g for 1 hour to obtain a supernatant block polymer (green). After adding 10 parts of a sulfonic acid type cation exchange resin to 100 parts of this block polymer and stirring at 120 ° C. for 2 hours, the ion exchange resin is removed, the polymerization catalyst and the like are further removed, and a colorless and transparent styrene content 33 A weight percent styrenic block elastomer was obtained. The weight average molecular weight was 90,000 and the refractive index was 1.50.

(Preparation of adhesive composition)
100 parts of the above styrenic block elastomer, as a tackifier, a liquid phenoxyethyl acrylate oligomer (softening point room temperature or less, weight average molecular weight 1800, refractive index 1.52; / 100 parts of phenoxyethyl acrylate 2 parts of 2 mercaptoethanol and 0.1 part of 4,4′-azobisisobutylnitrile and 30 parts of polymer obtained by polymerization at 60 ° C. for 8 hours under a nitrogen stream and a copolymer of α-methylstyrene and styrene (softening point 82) -88 ° C, weight average molecular weight 1200, refractive index 1.61, 50 parts by Crystallex 3085) manufactured by Eastman Chemical Co., further 0.5 parts 3-glycidoxypropylmethyldiethoxysilane, 2- photocrosslinking agent Hydroxy-2-methyl- [4- (1-methylvinyl) phenyl] propa A uniform pressure-sensitive adhesive composition was obtained by mixing 0.7 parts of the oligomer in a small heating kneader at 200 ° C. for 2 hours without using a solvent. The tackifier comprising 30 parts of the room temperature liquid phenoxyethyl acrylate oligomer and 50 parts of a copolymer of α-methylstyrene and styrene has a refractive index of 1.58.

(Preparation of adhesive layer)
The pressure-sensitive adhesive composition was heated to 160 ° C. and applied to a 38 μm-thick polyethylene terephthalate film subjected to silicone release treatment so that the pressure-sensitive adhesive layer had a thickness of 20 μm. Irradiation was performed with an irradiation light amount of 3.0 J / cm ² to obtain a pressure-sensitive adhesive layer having a crosslinked gel content of 45% by weight.

Comparative Example 1
A pressure-sensitive adhesive composition was prepared in the same manner as in Example 3 except that 3-glycidoxypropylmethyldiethoxysilane was not used in the preparation of the pressure-sensitive adhesive composition of Example 3. Moreover, the adhesive layer was obtained like Example 3 using the said adhesive composition. The gel content of the pressure-sensitive adhesive layer was 42% by weight.

Comparative Example 2
In the preparation of the pressure-sensitive adhesive composition of Example 1, as a tackifier, a petroleum resin having no aromatic ring (softening point 98-102 ° C., weight average molecular weight 1500, refractive index 1.52, yeast instead of styrene oligomer) A pressure-sensitive adhesive composition (solution) was prepared in the same manner as in Example 1 except that Picotac 1098) manufactured by Man Chemical Co. was used. Moreover, the adhesive layer was obtained like Example 1 using the said adhesive composition (solution). The gel content of the pressure-sensitive adhesive layer was 0% by weight.

  The pressure-sensitive adhesive layer obtained in Examples and Comparative Examples was transferred to a polarizing plate to prepare a pressure-sensitive adhesive optical member. In addition, as a polarizing plate, the polarizing plate of the structure which sandwiched both sides of the polarizer (The film which dye | stained the polyvinyl alcohol film with the iodine and performed the extending | stretching process) with the triacetyl cellulose film was used.

  The following evaluation test was performed on the obtained adhesive optical member. The results are shown in Table 1. Table 1 shows the refractive index of the pressure-sensitive adhesive layer.

(Adhesive strength)
A pressure-sensitive adhesive optical member (width: 25 mm), which is pressure-bonded to a non-alkali glass plate (# 1737 manufactured by Corning) by reciprocating a 2 kg roller, is processed in an autoclave at 50 ° C. and 0.5 Mpa for 30 minutes. Further, after being left for 3 hours under conditions of 23 ° C. and 50% RH, the peel adhesive strength (N / 20 mm) was measured at a peel angle of 90 ° and a peel speed of 300 mm / min.

(durability)
An adhesive optical member (12-inch wide size) was affixed to a non-alkali glass (Corning # 1737) having a thickness of 0.5 mm, treated in an autoclave at 50 ° C. and 0.5 Mpa for 30 minutes, and further, 60 ° C., After putting in an atmosphere of 90% RH for 500 hours, the state of the optical member was evaluated. If there was no peeling or floating, “○” was given, and if there was peeling or floating, “X” was given.

(Holding power)
The pressure-sensitive 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 10 mm x 20 mm, and a load of 500 g is applied vertically at 70 ° C or 100 ° C. The time until the tape fell was measured. Each evaluation was made into 70 degreeC retention strength and 100 degreeC retention strength. A holding power of 100 ° C. was used as a measure of heat resistance.

  The pressure-sensitive adhesive optical member using the pressure-sensitive adhesive layer of the examples is excellent in adhesive properties such as adhesion and holding power (cohesive force), and excellent in durability. In Examples 2 to 5 in which a crosslinking agent was blended, the 100 ° C. holding power was good and the heat resistance was also excellent. In addition, since the pressure-sensitive adhesive layer of the example 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. is there. In Examples 3 to 5, the pressure-sensitive adhesive layer is formed by heat-melt coating without using a solvent, which is advantageous in terms of environmental aspects and the production of a pressure-sensitive adhesive optical member. On the other hand, in Comparative Example 1, since no silane coupling agent was used, the durability was not satisfied. In Comparative Example 2, a tackifier having no aromatic ring or hydrogenated product thereof is used, and the durability is not satisfied.

Claims (11)

For 100 parts by weight of styrene block elastomer,
A pressure-sensitive adhesive composition for an optical member of an image display device comprising 40 to 250 parts by weight of a tackifier having an aromatic ring or a hydrogenated product thereof and 0.01 to 2 parts by weight of a silane coupling agent (however, the pressure-sensitive adhesive) the composition is a free wax), wherein the tackifier is I refractive index 1.53 to 1.75 der, the tackifier is higher than the softening point of 50 ° C. and tackifiers liquid at 23 ° C. tackifier A pressure-sensitive adhesive composition for an optical member of an image display device, comprising a fire and containing the liquid tackifier in an amount of 6 to 75% by weight based on the total amount of the tackifier. Styrenic block elastomers, styrene block, ethylene, propylene, butylene and the alkyl (meth) image display according to claim 1, characterized in that it comprises a block which is formed by any of at least one selected from acrylate A pressure-sensitive adhesive composition for an optical member of an apparatus . Furthermore a crosslinking agent, relative to 100 parts by weight of styrenic block elastomers, adhesive for optical members of the image display apparatus according to claim 1 or 2, characterized in that by blending 0.02 to 2 parts by weight Agent composition. The pressure-sensitive adhesive composition for an optical member of an image display device according to claim 3 , wherein the crosslinking agent is a photocrosslinking agent that generates radicals upon irradiation with radiation. An adhesive layer for an optical member of an image display device, which is formed of the adhesive composition for an optical member of an image display device according to any one of claims 1 to 4 . 6. The optical member for an image display device according to claim 5 , wherein the pressure-sensitive adhesive composition for an optical member of the image display device contains a crosslinking agent, and the gel fraction after crosslinking is 20 to 65% by weight. Adhesive layer. The pressure-sensitive adhesive layer for an optical member of an image display device according to claim 5 or 6 , wherein the refractive index is 1.52 to 1.66. On one or both sides of the optical member of an image display apparatus, according to claim 5-7 for an image display device adhesive optical member comprising an optical member for a pressure-sensitive adhesive layer of the image display apparatus according to any one of. An optical member for pressure-sensitive adhesive composition of the image display apparatus according to any one of claims 1 to 4, applied to an optical member for an image display device in a heated molten state without using a solvent, the optical member of an image display device A method for producing a pressure-sensitive adhesive optical member for an image display device according to claim 8 , wherein a pressure-sensitive adhesive layer is formed. The pressure-sensitive adhesive composition for an optical member of an image display device according to any one of claims 1 to 4 is applied to a support that has been subjected to a release treatment in a heated and melted state without using a solvent, and the pressure-sensitive adhesive for an optical member of an image display device. 9. The method for producing a pressure-sensitive adhesive optical member for an image display device according to claim 8 , wherein after the agent layer is formed, the pressure-sensitive adhesive layer for the optical member of the image display device is transferred to the optical member for the image display device . An image display device using at least one adhesive optical member for an optical member of an image display device according to claim 8 .