JP2012032696A - Composite retardation plate, composite polarizing plate and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a composite retardation plate having excellent adhesiveness between a (meth)acrylic resin layer of a retardation plate and an adhesive layer, and preventing the adhesive layer from remaining on a liquid crystal cell when the composite retardation plate is peeled from the liquid crystal cell, and to provide a composite polarizing plate and a liquid crystal display device using the above retardation plate.SOLUTION: The composite retardation plate comprises a retardation plate including a (meth)acrylic resin layer, and a primer layer and an adhesive layer stacked in this order on the (meth)acrylic resin layer. The composite polarizing plate and the liquid crystal display device use the above composite retardation plate. The retardation plate includes a first (meth)acrylic resin layer as the above (meth)acrylic resin layer, and preferably further includes a retardation layer. A second (meth)acrylic resin layer is preferably further stacked on the retardation layer in an opposite side to the first (meth)acrylic resin layer.

Description

  The present invention relates to a composite retardation plate including an adhesive layer and a retardation plate, and a composite polarizing plate and a liquid crystal display device using the same.

  Recently, a retardation plate including a (meth) acrylic resin layer has been proposed as a retardation plate used in a liquid crystal display device (for example, Patent Document 1).

JP 2009-175222 A

  In general, when an optical member such as a retardation plate is bonded to a liquid crystal cell, an adhesive is used so that the optical member can be peeled off in the event of some trouble. In such an adhesive, while high adhesiveness between an optical member and an adhesive is calculated | required, moderate adhesiveness and peelability between an adhesive and a liquid crystal cell are calculated | required. However, a composite retardation plate (a retardation plate with an adhesive layer) in which an adhesive layer is directly laminated on the (meth) acrylic resin layer of a retardation plate including a (meth) acrylic resin layer is used as the adhesive layer. When the composite phase difference plate is peeled off from the liquid crystal cell, the pressure sensitive adhesive is removed from the liquid crystal cell side because the adhesion between the composite phase difference plate and the pressure sensitive adhesive layer is insufficient. In some cases, it may remain and cause poor appearance.

  Accordingly, the object of the present invention is to provide excellent adhesion between the (meth) acrylic resin layer and the pressure-sensitive adhesive layer, thereby preventing the pressure-sensitive adhesive from remaining on the liquid crystal cell side when peeled from the liquid crystal cell. An object of the present invention is to provide a composite retardation plate that can be used. Another object of the present invention is to provide a composite polarizing plate and a liquid crystal display device using the composite retardation plate having excellent adhesion between a (meth) acrylic resin layer and an adhesive layer. .

  The present invention provides a composite retardation plate in which a primer layer and an adhesive layer are laminated in this order on the (meth) acrylic resin layer of a retardation plate including a (meth) acrylic resin layer. . The primer layer can be made of a cured product of a curable resin or a thermoplastic resin, among which a styrene resin, a polyester resin, a polyvinyl resin, an epoxy resin, a polyolefin resin, a (meth) acrylic resin, It is preferably made of one or more resins selected from the group consisting of urethane resins, imide resins and amino resins.

  The retardation plate in the composite retardation plate of the present invention preferably includes a first (meth) acrylic resin layer as the (meth) acrylic resin layer, and further includes a retardation layer. It is preferable to further laminate a second (meth) acrylic resin layer on the opposite side of the retardation layer from the first (meth) acrylic resin layer. The first (meth) acrylic resin layer and / or the second (meth) acrylic resin layer preferably contains rubber particles.

  The retardation layer is made of, for example, a styrene resin. The thicknesses of the retardation layer, the first (meth) acrylic resin layer, and the second (meth) acrylic resin layer are each preferably 10 to 100 μm. The glass transition temperature of the retardation layer is 120 ° C. or higher, and the glass transition temperatures of the first (meth) acrylic resin layer and the second (meth) acrylic resin layer are preferably 120 ° C. or lower. .

  The present invention also provides a composite polarizing plate comprising the composite retardation plate and a polarizing film disposed on the opposite side of the composite retardation plate from the pressure-sensitive adhesive layer, the composite polarizing plate, and the composite polarizing plate. A liquid crystal display device comprising a liquid crystal cell bonded to each other via an adhesive layer is provided.

  According to the present invention, the phase difference plate including the (meth) acrylic resin layer is excellent in adhesion between the (meth) acrylic resin layer and the pressure-sensitive adhesive layer, and thus when peeled from the liquid crystal cell. In addition, it is possible to provide a composite retardation plate capable of satisfactorily peeling the pressure-sensitive adhesive layer without the pressure-sensitive adhesive remaining on the liquid crystal cell side.

It is a schematic sectional drawing which shows a preferable example of the composite phase difference plate of this invention. It is a schematic sectional drawing which shows a preferable example of the composite polarizing plate of this invention.

<Composite retardation plate>
The composite phase difference plate (phase difference plate with pressure-sensitive adhesive layer) of the present invention has a primer layer and a pressure-sensitive adhesive layer on the (meth) acrylic resin layer of the phase difference plate including the (meth) acrylic resin layer. They are stacked in this order. Here, the retardation plate only needs to include a (meth) acrylic resin layer. For example, a retardation plate in which a (meth) acrylic resin layer also serves as a retardation layer, or a (meth) acrylic resin layer is used. Examples include a retardation plate provided with a resin layer and a retardation layer. Among them, a retardation plate in which a (meth) acrylic resin layer is laminated as a protective layer on one side or both sides of the retardation layer is preferable.

  FIG. 1 is a schematic cross-sectional view showing a preferred example of the composite phase difference plate (phase difference plate with pressure-sensitive adhesive layer) of the present invention. The composite retardation plate of the present invention will be described below with reference to FIG. 1, but the present invention is not limited to this. The composite retardation plate in FIG. 1 is a first retardation layer 103 that provides a retardation function to the composite retardation plate and a layer that protects the retardation layer 103 laminated on both surfaces of the retardation layer 103. The pressure-sensitive adhesive layer 101 is interposed on the first (meth) acrylic resin layer 104a side of the retardation plate 105 composed of the (meth) acrylic resin layer 104a and the second (meth) acrylic resin layer 104b via the primer layer 102. Are laminated. By interposing the primer layer 102 between the first (meth) acrylic resin layer 104a and the pressure-sensitive adhesive layer 101, the first (meth) acrylic resin is compared with the case where the primer layer 102 is not provided. The adhesion between the layer 104a and the pressure-sensitive adhesive layer 101 can be improved. Note that the composite retardation plate of the present invention may not have the second (meth) acrylic resin layer 104b.

(Phase difference plate)
As shown in FIG. 1, the retardation plate 105 constituting the composite retardation plate of the present invention is preferably laminated on the retardation layer 103 and one surface thereof (the side on which the adhesive layer 101 is bonded). 1 (meth) acrylic resin layer 104a, and more preferably, a first (meth) acrylic resin layer 104a and a second (meth) acrylic resin layer 104b laminated on both surfaces of the retardation layer 103. Is provided. Thus, when the (meth) acrylic resin layer and the retardation layer are provided, the retardation layer 103 can be composed of, for example, a styrene resin. A film made of a styrene resin is preferable as a retardation layer because it exhibits a negative retardation with a large refractive index in the thickness direction due to stretching or the like. The thickness direction negative retardation is large refractive index of the refractive direction (fast axis direction) perpendicular to that of the refractive index of the maximum refractive index direction in the plane (slow axis direction) n _x, in a plane when the rate n _y, the refractive index in the thickness direction is n _z, has a relationship of _{n z ≒ n x> n y} , is defined by _{(n x -n z) / (} n x -n y) This means that the Nz coefficient is approximately 0 (zero).

  The styrenic resin can be a homopolymer of styrene or a derivative thereof, and can also be a binary or higher copolymer of styrene or a derivative thereof and another copolymerizable monomer. Styrene derivatives are compounds in which other groups are bonded to styrene, such as o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene, o-ethylstyrene, p-ethylstyrene. Such as hydroxystyrene, tert-butoxystyrene, vinyl benzoic acid, o-chlorostyrene, and p-chlorostyrene, hydroxyl group, alkoxy group, carboxyl group, halogen, etc. were introduced into the benzene nucleus of styrene. Examples thereof include substituted styrene. A terpolymer obtained by copolymerizing an acyclic olefin monomer and a cyclic olefin monomer with styrene or a styrene derivative can also be used. Among them, the styrenic resin is preferably a copolymer of styrene or a styrene derivative and at least one monomer selected from acrylonitrile, maleic anhydride, methyl methacrylate, and butadiene, from the viewpoint of heat resistance. Similarly, from the viewpoint of heat resistance, the styrene resin (retardation layer 103) preferably has a glass transition temperature Tg of 120 ° C. or higher.

  The thickness of the retardation layer 103, particularly the retardation layer 103 made of styrene resin, is preferably 10 to 100 μm. When the thickness is less than 10 μm, a sufficient retardation value is hardly exhibited by stretching. On the other hand, if the thickness exceeds 100 μm, the impact strength of the retardation plate tends to be weak and the retardation change due to external stress tends to increase.

  Examples of the (meth) acrylic resin constituting the first and second (meth) acrylic resin layers 104a and 104b include, for example, a methacrylic acid alkyl ester or a homopolymer of an acrylic acid alkyl ester, a methacrylic acid alkyl ester, Examples thereof include a copolymer with an acrylic acid alkyl ester. Specific examples of the alkyl methacrylate include methyl methacrylate, ethyl methacrylate, and propyl methacrylate, and specific examples of the alkyl acrylate include methyl acrylate, ethyl acrylate, and propyl acrylate. As such a (meth) acrylic resin, a commercially available (meth) acrylic resin can be used. As the (meth) acrylic resin, a so-called impact resistant (meth) acrylic resin may be used.

  By laminating the first and / or second (meth) acrylic resin layer on the retardation layer, chemical resistance and mechanical strength of the retardation plate can be improved. In order to further improve the mechanical strength, it is also preferable that the first and second (meth) acrylic resin layers 104a and 104b contain rubber particles. The rubber particles are preferably acrylic. Acrylic rubber particles are particles having rubber elasticity obtained by polymerizing an acrylic monomer mainly composed of an alkyl acrylate ester such as butyl acrylate or 2-ethylhexyl acrylate in the presence of a polyfunctional monomer. It is. The acrylic rubber particles may be one in which such rubber elastic particles are formed as a single layer, or may be a multilayer structure having at least one rubber elastic layer. As the acrylic rubber particles having a multilayer structure, particles having rubber elasticity as described above are used as cores, and the periphery thereof is covered with a hard alkyl methacrylate ester polymer, or a hard alkyl methacrylate ester polymer. The core is covered with an acrylic polymer having rubber elasticity as described above, or the hard core is covered with a rubber elastic acrylic polymer, and the periphery thereof is hard alkyl methacrylate. Examples thereof include those covered with a polymer. Such rubber particles generally have an average diameter of particles formed of an elastic layer in the range of about 50 to 400 nm.

  The content of rubber particles in the first and second (meth) acrylic resin layers 104a and 104b is usually about 5 to 50 parts by weight per 100 parts by weight of the (meth) acrylic resin. Since (meth) acrylic resin and acrylic rubber particles are commercially available in a state where they are mixed, commercially available products thereof can be used. Examples of commercially available (meth) acrylic resins containing acrylic rubber particles include “Orograss DR”, which was previously sold by Sumika Haas Co., Ltd., and currently sold by Sumitomo Chemical Co., Ltd. "HT55X", "Technoloy S001", etc. are mentioned.

  The (meth) acrylic resin composition containing the rubber particles and the (meth) acrylic resin as described above generally has a Tg of 120 ° C. or lower, but a (meth) acrylic resin composition having a Tg of 110 ° C. or lower. It is preferable to use a product.

  The thickness of the first and second (meth) acrylic resin layers 104a and 104b is preferably 10 to 100 μm.

  As described above, the Tg of the retardation layer 103 is preferably 120 ° C. or higher, while the Tg of the first and second (meth) acrylic resin layers 104a and 104b is 120 ° C. or lower, particularly 110 ° C. or lower. It is preferable that Moreover, both Tg does not overlap and it is preferable that the phase difference layer 103 has Tg higher than the 1st and 2nd (meth) acrylic-type resin layers 104a and 104b. This is because it becomes easier to manufacture a retardation plate by coextrusion described later.

  The phase difference plate 105 includes, for example, a resin (for example, styrene resin) that forms a phase difference layer and a resin (for example, rubber particles) that forms a first and / or second (meth) acrylic resin layer. (Meth) acrylic resin composition) can be coextruded and then subjected to a stretching treatment for imparting in-plane retardation to the layer to be the retardation layer. In addition, a single-layer film is prepared separately from the resin that forms the retardation layer and the resin that forms the first and / or second (meth) acrylic resin layer, and then is laminated by heat fusion using heat lamination. It can also be produced by a method in which a stretching process is performed. Stretching is not particularly limited as long as a desired in-plane retardation value is obtained, and can be, for example, longitudinal uniaxial stretching, tenter transverse uniaxial stretching, simultaneous biaxial stretching, sequential biaxial stretching, or the like.

  As described above, the retardation plate 105 preferably has a three-layer structure in which the first and second (meth) acrylic resin layers 104 a and 104 b are laminated on both surfaces of the retardation layer 103. In this case, these (meth) acrylic resin layers can have substantially the same thickness. By adopting a three-layer structure, the mechanical strength and chemical resistance of the retardation plate can be further improved.

(Adhesive layer)
The pressure-sensitive adhesive layer 101 is used for bonding the retardation film 105 to a liquid crystal cell. Examples of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer 101 include a pressure-sensitive adhesive having a base polymer such as an acrylic polymer, a silicone polymer, polyester, polyurethane, or polyether. Among them, acrylic pressure-sensitive adhesives based on acrylic polymers are excellent in optical transparency, maintain appropriate wettability and cohesion, and have excellent adhesion to the primer layer, and weather resistance. It is preferably used because it has high heat resistance and heat resistance, and is unlikely to cause peeling problems such as floating and peeling under heating and humidification conditions.

  Examples of the acrylic base polymer contained in the acrylic pressure-sensitive adhesive include acrylic acid alkyl esters in which the alkyl group of the ester moiety is an alkyl group having 20 or less carbon atoms such as a methyl group, an ethyl group, or a butyl group, acrylic acid, An acrylic copolymer with a functional group-containing acrylic monomer such as hydroxyethyl acrylate is preferably used. The pressure-sensitive adhesive layer having such an acrylic copolymer as a base polymer is excellent in adhesion to the primer layer, and when bonded to a glass substrate and then peeled off, a pressure-sensitive adhesive residue ( It can be peeled relatively easily without causing adhesive residue). Tg of the acrylic copolymer is preferably 25 ° C. or less, and more preferably 0 ° C. or less. The weight average molecular weight of the acrylic copolymer is preferably 100,000 or more.

  Further, as the pressure-sensitive adhesive forming the pressure-sensitive adhesive layer 101, a diffusion pressure-sensitive adhesive in which a light diffusing agent is dispersed can be used. The light diffusing agent is for imparting light diffusibility to the pressure-sensitive adhesive layer 101. The light diffusing agent may be fine particles having a refractive index different from that of the base polymer constituting the pressure-sensitive adhesive layer 101, and fine particles made of an inorganic compound or fine particles made of an organic compound (polymer) can be used. Since the base polymer constituting the pressure-sensitive adhesive layer 101 including the acrylic base polymer as described above often has a refractive index of around 1.4, the light diffusing agent has a refractive index of 1-2. What is necessary is just to select suitably from the thing of a grade. The difference in refractive index between the base polymer constituting the pressure-sensitive adhesive layer 101 and the light diffusing agent is usually 0.01 or more, and from the viewpoint of the brightness and visibility of the liquid crystal display device, it is 0.01 or more and 0.5. The following is preferable. The fine particles used as the light diffusing agent are preferably spherical and those close to monodisperse. For example, fine particles having an average particle diameter in the range of about 2 to 6 μm are preferably used.

  Examples of the fine particles made of an inorganic compound include aluminum oxide (refractive index 1.76) and silicon oxide (refractive index 1.45).

  Examples of the fine particles made of an organic compound (polymer) include melamine beads (refractive index 1.57), polymethyl methacrylate beads (refractive index 1.49), methyl methacrylate / styrene copolymer resin beads (refractive index). 1.50), polycarbonate beads (refractive index 1.55), polyethylene beads (refractive index 1.53), polystyrene beads (refractive index 1.6), polyvinyl chloride beads (refractive index 1.46) ) And silicone resin beads (refractive index 1.46).

  The amount of the light diffusing agent is appropriately determined in consideration of the haze value required for the pressure-sensitive adhesive layer 101 in which it is dispersed, the brightness of the liquid crystal display device to which it is applied, etc. The amount is about 3 to 30 parts by weight with respect to 100 parts by weight of the resin constituting the pressure-sensitive adhesive layer 101.

  The haze value of the pressure-sensitive adhesive layer 101 in which the light diffusing agent is dispersed ensures the brightness of a liquid crystal display device to which a composite retardation plate or a composite optical member using the same is applied (which will be described later). From the viewpoint of preventing bleeding and blurring of the display image, it is preferable to be in the range of 20 to 80%. The haze value is a value represented by (diffuse transmittance / total light transmittance) × 100 (%), and is measured according to JIS K 7105.

  The pressure-sensitive adhesive layer 101 is formed by applying a pressure-sensitive adhesive solution mainly composed of the base polymer as described above onto the primer layer 102 formed on the surface of the first (meth) acrylic resin layer 104a of the retardation plate 105, In addition to being able to be formed by a drying method, the pressure-sensitive adhesive layer 101 is formed by applying a pressure-sensitive adhesive solution to the release-treated surface of the film that has been subjected to the mold release treatment, and then drying the film. It can also be formed by a method of bonding to the surface of the primer layer 102 so that the pressure-sensitive adhesive layer 101 side becomes the bonding surface. The surface of the primer layer 102 on which the pressure-sensitive adhesive layer 101 is formed and / or the bonding surface of the pressure-sensitive adhesive layer 101 is preferably subjected to corona discharge treatment in advance. Thereby, the adhesiveness of the primer layer 102 and the adhesive layer 101 can further be improved. In the case where a composite optical member is produced by laminating an optical functional layer on the side opposite to the primer layer 102 side of the retardation plate 105, the adhesive layer 101 is formed by attaching the optical functional layer to the retardation plate 105. You may carry out after laminating | stacking.

  The thickness of the pressure-sensitive adhesive layer 101 is determined according to the adhesive force and the like and is not particularly limited, but is usually about 1 to 40 μm. In order to obtain a thin composite phase difference plate and a composite optical member using the same without impairing properties such as workability and durability, the thickness of the pressure-sensitive adhesive layer 101 is preferably about 3 to 25 μm. Further, by setting the thickness of the pressure-sensitive adhesive layer 101 to about 3 to 25 μm, the brightness of the liquid crystal display device when viewed from the front or obliquely is maintained, and the display image is less likely to be blurred or blurred. Can do.

(Primer layer)
The primer layer 102 constituting the composite phase difference plate of the present invention is interposed between the phase difference plate 105 and the pressure-sensitive adhesive layer 101, and adheres to the phase difference plate 105 (first (meth) acrylic resin layer 104a). Adhesion with the agent layer 101 is improved. Thereby, even when it peels from this glass surface, after bonding a composite phase difference plate to glass surfaces, such as a liquid crystal cell, using the adhesive layer 101, also, the phase difference plate 105 and the adhesive layer 101, It can be peeled without the pressure-sensitive adhesive remaining on the glass surface while maintaining a strong bonded state (showing good peelability to the glass surface). The primer generally means undercoating, but the primer layer 102 in the present invention functions as an undercoating layer for the pressure-sensitive adhesive layer 101 bonded to the retardation plate 105 and can be said to be an easy adhesion layer.

  The primer layer 102 is formed of a resin (primer resin) that can form a transparent coating film by coating and exhibits good adhesion to the first (meth) acrylic resin layer 104a and the pressure-sensitive adhesive layer 101. It can be made of a cured product of a thermoplastic resin or a curable resin. Examples of the thermoplastic resin include a styrene resin; a polyester resin such as polyethylene terephthalate; a polyvinyl resin such as polyvinyl alcohol and polyvinyl chloride; an epoxy resin such as a water-soluble epoxy resin; and may be chlorinated. Examples include polyolefin resins such as acid-modified polyolefin resins; (meth) acrylic resins; urethane resins; imide resins; amino resins such as urea resins, melamine resins, and amide resins. Examples of the curable resin include active energy ray curable resins such as a cationic polymerizable compound and a radical polymerizable compound. The primer layer 102 may be composed of two or more kinds of resins. Of these, styrene resins are preferably used.

  The styrenic resin constituting the primer layer 102 can be a homopolymer of styrene or a derivative thereof, or can be a binary or higher copolymer of styrene or a derivative thereof and another copolymerizable monomer. There can also be. Styrene derivatives are compounds in which other groups are bonded to styrene, such as o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene, o-ethylstyrene, p-ethylstyrene. Such as hydroxystyrene, tert-butoxystyrene, vinyl benzoic acid, o-chlorostyrene, and p-chlorostyrene, hydroxyl group, alkoxy group, carboxyl group, halogen, etc. were introduced into the benzene nucleus of styrene. Examples thereof include substituted styrene.

  The preferred number average molecular weight of the styrenic resin is 5,000 to 600,000, more preferably 10,000 to 500,000. When the number average molecular weight is less than 5000, the primer layer 102 becomes brittle and the primer layer 102 may be tacked. On the other hand, when the number average molecular weight exceeds 600,000, the viscosity of the coating solution in which the primer resin is dissolved becomes high, and the leveling tends to be deteriorated.

  As such a styrene-based resin, commercially available products such as polystyrene (manufactured by Sigma Aldrich Japan Co., Ltd .: Typical Mn = 14000, typical Mw = 230,000, Tg = 94 ° C.) can be used.

  The formation of the primer layer 102 on the surface of the first (meth) acrylic resin layer 104a can be performed by coating the surface with a coating solution obtained by dissolving a primer resin constituting the primer layer 102 in a solvent. Solvents include aromatic solvents such as toluene and xylene; aliphatic solvents such as cyclohexane, methylcyclohexane, ethylcyclohexane, heptane, nonane and decane; ester solvents such as ethyl acetate and butyl acetate; acetone, methyl ethyl ketone and methyl Examples thereof include ketone solvents such as butyl ketone; alcohol solvents such as methanol, ethanol, propanol and butanol; water, and mixed solvents thereof. The solid content concentration of the coating liquid can be appropriately selected from the range of 1 to 50% by mass.

  The method for applying the primer layer forming coating solution is not particularly limited. For example, spin coating, bar coating, roll coating, curtain coating, and die coating methods such as slot coating and extrusion coating are adopted. can do. After applying the coating liquid, it is preferable to provide a solvent removal (drying) step by a method such as heating with a heater or spraying hot air, and removing the solvent by drying it appropriately. When the primer resin is a curable resin, the coating layer is cured by irradiation with active energy rays or the like after drying as necessary.

  In forming the primer layer 102, it is preferable to perform corona discharge treatment on the coating surface of the first (meth) acrylic resin layer 104a in advance. Thereby, the adhesiveness between the primer layer 102 and the phase difference plate 105 can be further improved.

  The thickness of the primer layer 102 is not particularly limited, but is about 0.1 to 10 μm in order to obtain good adhesion to the first (meth) acrylic resin layer 104a and the pressure-sensitive adhesive layer 101. It is preferable.

<Composite optical member>
The composite retardation plate of the present invention can be made into a composite optical member by laminating optical functional layers having other optical functions. As the optical functional layer, for example, a retardation plate (half-wave plate, 1 / wave plate, half-transmission plate, condensing plate, light reflection plate, retardation plate 105 different from the retardation plate 105 constituting the composite retardation plate). 4 wavelength plate, etc.), viewing angle compensation film, brightness enhancement film, polarizing plate (linear polarizing plate) and the like. The optical function layer can be used in combination of one layer or two or more layers according to the purpose of use. The optical functional layer can be integrated with the composite retardation plate using an adhesive or a pressure-sensitive adhesive.

  As a phase difference plate different from the phase difference plate 105, for example, a resin film having birefringence stretched uniaxially in the surface direction can be used. Similar to the retardation plate 105, this retardation plate is an optical member for preventing coloring and the like due to a change in viewing angle caused by the phase difference caused by the liquid crystal cell. In combination with the retardation plate 105 as necessary. used.

  The viewing angle compensation film is a film for widening the viewing angle so that an 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. The viewing angle compensation film can be a retardation film composed of a retardation film such as a stretched resin film, an alignment film such as a liquid crystal polymer, or a film in which an alignment layer such as a liquid crystal polymer is formed on a transparent substrate film. Specifically, a birefringent resin film biaxially stretched in the plane direction, or a birefringent resin with a controlled refractive index in the thickness direction stretched uniaxially in the plane direction and also stretched in the thickness direction Examples thereof include bi-directionally stretched films such as films, and tilted oriented films. Examples of the tilted alignment film include a film obtained by bonding a heat shrink film to a resin film and stretching and / or shrinking the resin film under the action of the contraction force by heating, and a film obtained by obliquely aligning a liquid crystal polymer. Is mentioned.

  Examples of the resin material constituting the retardation plate different from the retardation plate 105 and the retardation plate used as a viewing angle compensation film include, for example, polyvinyl alcohol, polyvinyl butyral, polymethyl vinyl ether, polyhydroxyethyl acrylate, hydroxy Ethyl cellulose, hydroxypropyl cellulose, methyl cellulose, polycarbonate, polyarylate, polysulfone, polyethylene terephthalate, polyethylene naphthalate, polyether sulfone, polyphenylene sulfide, polyphenylene oxide, polyallyl sulfone, polyamide, polyimide, polyolefin, polyvinyl chloride, cellulose resin, Cyclic polyolefin resin (norbornene resin), or binary, ternary copolymer and graft copolymer of these , And the like blend. By subjecting a film made of these resin materials to a predetermined stretching treatment, a retardation plate or a viewing angle compensation film can be obtained.

  A brightness enhancement film is a film that reflects linearly polarized light having a predetermined polarization axis or circularly polarized light in a predetermined direction and transmits other light among light incident from a backlight of a liquid crystal display device or the like. The brightness enhancement film is usually laminated with the polarizing plate of the present invention in combination with a polarizing plate to form a composite optical member. This composite optical member is used as a backlight side polarizing plate of a liquid crystal cell. This composite optical member including a brightness enhancement film as a backlight-side polarizing plate transmits light of a predetermined polarization state and reflects light other than the predetermined polarization state among incident light from a light source such as a backlight. . The light reflected on the surface of the brightness enhancement film is inverted through a reflective layer or the like provided on the back surface of the backlight and re-incident on the brightness enhancement film, and part or all of the light is transmitted as light in 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 absorb to the polarizing plate.

  As the brightness enhancement film, a reflective polarization separation sheet designed to produce anisotropy in reflectance by laminating a plurality of thin film films having different refractive index anisotropies, an alignment film of a cholesteric liquid crystal polymer, and the like A circularly polarized light separating sheet or the like in which an alignment liquid crystal layer is supported on a film substrate can be used.

  A polarizing plate (linear polarizing plate) is an optical functional film having a property of transmitting linearly polarized light that vibrates in a certain direction toward the film surface and blocking linearly polarized light that vibrates in a direction orthogonal thereto by absorption or the like. In addition, typically, it can include a polarizing film in which a dichroic dye such as iodine or a dichroic organic dye is adsorbed and oriented on a polyvinyl alcohol resin.

  FIG. 2 shows a composite retardation plate having a polarizing plate (linear polarizing plate) as an optical functional layer (in this specification, a composite optical member including a composite retardation plate and a polarizing plate is referred to as “composite polarizing plate”). It is a schematic sectional drawing which shows a preferable example. As shown in FIG. 2, the composite polarizing plate of the present invention includes the above-described composite retardation plate and a polarizing plate 201 disposed on the opposite side of the composite retardation plate from the adhesive layer 101. The polarizing plate (linear polarizing plate) 201 may be composed of only a polarizing film, or an adhesive layer or the like is provided on one side (in this case, usually opposite to the retardation plate 105) or both sides of the polarizing film. The transparent protective film may be bonded. As the transparent protective film, a film made of an amorphous polyolefin resin, a polyester resin, a (meth) acrylic resin, a polycarbonate resin, a chain polyolefin resin, or the like is used in addition to a cellulose resin such as triacetyl cellulose. be able to.

  Among them, a composite polarizing plate in which a transparent resin film is bonded to one surface of a polarizing film via an adhesive layer or the like, and the composite retardation plate of the present invention is bonded to the other surface via an adhesive layer or the like. The plate is one of the preferred forms from the viewpoint of thinning the composite polarizing plate because the composite retardation plate also functions as a transparent protective film for the polarizing film.

  In the composite polarizing plate, between the retardation plate 105 and the polarizing plate 201, one or more other optical functional layers such as a retardation plate or a viewing angle compensation film different from the retardation plate 105 as described above are provided. One or more other optical functional layers such as a brightness enhancement film can be disposed on the side of the polarizing plate 201 opposite to the phase difference plate 105. An angle formed by the absorption axis of the polarizing plate 201, which is a linear polarizing plate, and the slow axis of the retardation plate (the retardation plate 105 and / or a retardation plate different from this) included in the composite polarizing plate is set to a predetermined value. By adjusting the angle, the composite polarizing plate can function as a linear polarizing plate or an elliptical polarizing plate (including a circular polarizing plate).

  When using a linear polarizing plate with a transparent protective film laminated on both sides of the polarizing film as an optical functional layer, or a polarizing plate on the polarizing film itself or a linear polarizing plate with a transparent protective film laminated on the polarizing film. In the case where the combined layer is used as an optical functional layer, when the optical functional layer is prepared in advance and bonded to a composite retardation plate, this bonding is usually performed using an adhesive. .

  Any one or more of the layers (polarizing film, transparent protective film, retardation plate, pressure-sensitive adhesive layer, etc.) constituting the composite optical member are, for example, a salicylic acid ester compound, a benzophenol compound, a benzotriazole compound, It may be provided with ultraviolet absorbing ability by containing an ultraviolet absorber such as a cyanoacrylate compound or a nickel complex salt compound.

<Image display device>
The composite retardation plate and the composite optical member (composite polarizing plate, etc.) of the present invention can be suitably applied to various image display devices such as a liquid crystal display device. The image display device including the composite retardation plate or the composite optical member of the present invention is excellent in durability because the adhesiveness between the retardation plate 105 and the pressure-sensitive adhesive layer 101 is excellent. The liquid crystal display device according to the present invention can adopt a conventionally known configuration except that it includes the composite retardation plate or the composite optical member of the present invention. For example, the liquid crystal display device is disposed on the front side (viewing side) of the liquid crystal cell. The composite polarizing plate of the present invention can be used as a polarizing plate and / or a polarizing plate disposed on the backlight side. Or the composite phase difference plate or composite optical member of this invention can also be used as a phase difference plate arrange | positioned between a front side polarizing plate and / or a backlight side polarizing plate, and a liquid crystal cell. When the composite phase difference plate or the composite optical member of the present invention is used on both surfaces of the liquid crystal cell, they may have the same configuration or different configurations. Bonding between the liquid crystal cell and the composite retardation plate or the composite optical member of the present invention is performed using the pressure-sensitive adhesive layer 101 included in the liquid crystal cell. The liquid crystal cell may be of an arbitrary type such as a TN (Twisted Nematic) type, a STN (Super-Twisted Nematic) type, a VA (Vertical Alignment) type, or an IPS (In-Plane Switching) type.

  The liquid crystal display device can include conventionally known appropriate components such as a diffusion plate, an antiglare layer, an antireflection film, a protective plate, a prism array, a lens array sheet, a light diffusion plate, a reflection plate, and a backlight. .

  Since the retardation plate and the linear 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. Therefore, a composite polarizing plate having a retardation plate that is a quarter-wave plate (a retardation plate different from the retardation plate 105) is used, and polarization between the linear polarizing plate and the retardation plate is used. If the angle formed by the direction is adjusted to π / 4, the mirror surface of the metal electrode can be completely shielded.

  EXAMPLES Hereinafter, although an Example is shown and this invention is demonstrated further in detail, this invention is not limited by these examples.

<Example 1>
[Production of retardation plate]
As the first resin component, styrene-maleic anhydride copolymer resin ["Dylark D332" (Tg = 131 [deg.] C.) manufactured by Nova Chemical Co.] is used, and acrylic rubber particles having an average particle diameter of 200 [mu] m are used as the second resin component. A layer formed from the first resin component (retardation layer) using an acrylic resin composition (“Technoloy S001” (Tg = 105 ° C.) manufactured by Sumitomo Chemical Co., Ltd.) Layer) is the central layer, and the two layers formed from the first resin component (the first and second (meth) acrylic resin layers) sandwich the central layer. Three-layer coextrusion was performed to obtain a multilayer resin film in which a (meth) acrylic resin layer having a thickness of 40 μm on each side of the central layer was 80 μm. The multilayer resin film was stretched twice at 142 ° C., the total thickness was 80 μm (retardation layer 40 μm, first and second (meth) acrylic resin layers 20 μm), and in-plane retardation was 140 nm. A phase difference plate having a negative retardation with an Nz coefficient of 0.0 was obtained.

[Preparation of primer layer coating solution]
3 parts by weight of polystyrene (manufactured by Sigma Aldrich Japan Co., Ltd .: Typical Mn = 14000, typical Mw = 230,000, Tg = 94 ° C.) are dissolved in 100 parts by weight of toluene (Wako Pure Chemical Industries, Ltd .: reagent grade). A primer layer coating solution was obtained.

[Formation of primer layer]
After applying the primer layer coating solution on one side of the retardation plate using a bar coater (manufactured by Daiichi Rika Co., Ltd .: Bar coater No. 02), it is dried at 80 ° C. for 2 minutes. Thus, a phase difference plate with a primer layer was obtained. The thickness of the primer layer after drying was about 0.2 μm.

[Corona discharge treatment]
A corona discharge treatment was performed on the surface of the primer layer of the retardation layer with the primer layer under conditions of 280 W and 10 m / min. Further, on the pressure-sensitive adhesive layer surface of NSS5-3M (manufactured by New Tack Kasei Co., Ltd .: thickness 20 μm) composed of an acrylic pressure-sensitive adhesive layer formed on a polyethylene terephthalate (PET) film (separate film) that has been subjected to a release treatment. Also, the corona discharge treatment was performed under the same conditions.

[Production of composite retardation plate]
The primer layer surface subjected to the corona discharge treatment and the pressure-sensitive adhesive layer surface subjected to the corona discharge treatment were bonded together to obtain a composite retardation plate. The composition of the composite retardation plate thus obtained is negative retardation plate composed of three multilayer films / primer layer composed of styrene / adhesive layer / separate film.

<Comparative Example 1>
A composite retardation plate was prepared in the same manner as in Example 1 except that the primer layer was not provided on the surface of the (meth) acrylic resin layer of the retardation plate and the corona discharge treatment was performed under the conditions of 280 W and 10 m / min. Obtained. The composition of the composite retardation plate thus obtained is a negative retardation plate / adhesive layer / separate film composed of a multilayer film of three layers.

[Evaluation of adhesion between retardation plate and adhesive layer (adhesion test)]
The composite phase difference plate of Example 1 and Comparative Example 1 was cut to a width of 25 mm and a length of about 200 mm, and then the separate film was peeled off to produce an evaluation test piece. The test piece was evaluated for adhesion at three points in the length direction using an adhesion evaluation device (manufactured by Nippon System Group Co., Ltd.). The evaluation of the adhesion force is that the pressure-sensitive adhesive layer is a test piece when it is slid 20 times in a certain direction while pressing the surface of the pressure-sensitive adhesive layer with a pressing force of 0.4 MPa using styrene rubber having a hardness of 60 degrees. The three-point average of the length peeled from the retardation plate was obtained as the peel distance. The measurement was carried out in an atmosphere having a temperature of 23 ° C. and a humidity of 60% RH. The shorter the peel distance, the better the adhesion between the retardation plate and the pressure-sensitive adhesive layer. The results are shown in Table 1.

  101 pressure-sensitive adhesive layer, 102 primer layer, 103 phase difference layer, 104a first (meth) acrylic resin layer, 104b second (meth) acrylic resin layer, 105 phase difference plate, 201 polarizing plate.

Claims (11)

  A composite retardation plate in which a primer layer and an adhesive layer are laminated in this order on the (meth) acrylic resin layer of a retardation plate including a (meth) acrylic resin layer.   The composite phase difference plate according to claim 1, wherein the primer layer is made of a cured product of a curable resin or a thermoplastic resin.   The primer layer is selected from the group consisting of a styrene resin, a polyester resin, a polyvinyl resin, an epoxy resin, a polyolefin resin, a (meth) acrylic resin, a urethane resin, an imide resin, and an amino resin. The composite phase difference plate of Claim 1 which consists of 1 or more types of resin.   The composite retardation plate according to claim 1, wherein the retardation plate includes a first (meth) acrylic resin layer as the (meth) acrylic resin layer, and further includes a retardation layer.   The composite retardation plate according to claim 4, wherein a second (meth) acrylic resin layer is further laminated on the opposite side of the retardation layer from the first (meth) acrylic resin layer.   The composite phase difference plate according to claim 5, wherein the first (meth) acrylic resin layer and / or the second (meth) acrylic resin layer contains rubber particles.   The said phase difference layer is a composite phase difference plate in any one of Claims 4-6 comprised from a styrene resin.   The composite layer according to any one of claims 5 to 7, wherein each of the retardation layer, the first (meth) acrylic resin layer, and the second (meth) acrylic resin layer has a thickness of 10 to 100 µm. Phase difference plate.   The glass transition temperature of the retardation layer is 120 ° C or higher, and the glass transition temperatures of the first (meth) acrylic resin layer and the second (meth) acrylic resin layer are 120 ° C or lower. The composite phase difference plate in any one of 5-8.   A composite polarizing plate comprising: the composite retardation plate according to claim 1; and a polarizing film disposed on a side opposite to the pressure-sensitive adhesive layer of the composite retardation plate.   A liquid crystal display device comprising: the composite polarizing plate according to claim 10; and a liquid crystal cell bonded to the composite polarizing plate via the pressure-sensitive adhesive layer.

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