JP2006178132A - Polarizing plate and its use - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polarizing plate which has high adhesive strength with a polarizing film between a transparent protective film, which is less likely to exfoliated, especially even under high temperature and high humidity and is of high quality and high added value at high productivity, and to provide uses of the polarizing plate. <P>SOLUTION: The polarizing plate is constituted, by laminating the transparent protective film on at least one face of the polarizing film and the transparent protective film, and at least one face of the polarizing film are adhered by an adhesive, comprising a polyvinyl alcohol resin and a silane-based coupling agent. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a polarizing plate and its use. More specifically, the present invention relates to a polarizing plate having high adhesive strength between a polarizing film and a transparent protective film and its use.

  In a liquid crystal display device which is a typical image display device, it is indispensable to dispose polarizing plates on both sides of the liquid crystal cell due to the image forming method. As such a polarizing plate, generally, a polyvinyl alcohol (PVA) film is dyed and stretched with a dichroic substance such as iodine or a dichroic dye to form a polarizer (polarizing film), and then the polarizer (polarizing film) A polarizing film is used in which a protective film such as triacetyl cellulose (TAC) is bonded to both surfaces of a polarizing film using a PVA adhesive.

  However, the conventional PVA-based adhesive has a problem that the water resistance is insufficient and peeling between films is likely to occur under high temperature and high humidity.

  In addition, when an amorphous thermoplastic resin film is used as a protective film, there is an advantage that excellent polarizing characteristics can be obtained with little light leakage in a crossed Nicol state even when observed from an oblique direction. However, the amorphous thermoplastic resin film has a problem that the adhesiveness is particularly poor when a conventional PVA adhesive is used.

  In order to solve such problems, a polarizing plate protective film in which a polyurethane resin layer and a polyvinyl alcohol layer are laminated on a thermoplastic saturated norbornene resin film, and a polarizing plate in which the protective film and the polarizing film are bonded with a PVA adhesive. A plate has been proposed (see Patent Document 1). However, this polarizing plate has a problem that many floats and streaks occur when the protective film and the polarizing film are bonded. As a result, since the appearance of the obtained polarizing plate is not stable and the yield is poor, there are problems that productivity is poor and quality is deteriorated.

Moreover, a polarizing plate in which a protective film and a polarizing film are bonded using a polyurethane-based adhesive has been proposed (see Patent Document 2). However, polyurethane-based adhesives require aging for a long time and have a low yield, resulting in poor productivity.
Japanese Patent Laid-Open No. 2001-174637 JP 2000-32432 A

  The present invention has been made in order to solve the above-described conventional problems, and the object is to provide a polarizing plate having a high adhesive strength between the polarizing film and the transparent protective film, and having a high quality and a high added value. It is to provide with high productivity and to provide an application of such a polarizing plate.

A transparent protective film is laminated on at least one surface of the polarizing film,
A polarizing plate formed by adhering at least one surface of the polarizing film and the transparent protective film with an adhesive containing a polyvinyl alcohol resin and a silane coupling agent.

  In a preferred embodiment, the silane coupling agent is an amino group-containing alkoxysilane.

  In a preferred embodiment, at least one of the transparent protective films is an amorphous thermoplastic resin film.

  In a preferred embodiment, the amorphous thermoplastic resin film is a norbornene resin film.

  According to another aspect of the present invention, an image display device is provided. This image display device includes at least one polarizing plate of the present invention.

  According to the present invention, the adhesive strength between the polarizing film and the transparent protective film is high, and it is difficult to peel off even under high temperature and high humidity, providing a high quality, high added value polarizing plate with high productivity, And the use of such a polarizing plate can be provided. In particular, when an amorphous thermoplastic resin film having excellent properties as a transparent protective film is used, the adhesiveness is particularly poor, and there is a problem of quality deterioration and productivity reduction. Such a problem has been solved without providing an easy-adhesive layer on the thermoplastic resin film.

  Hereinafter, although preferable embodiment of this invention is described, this invention is not limited to these embodiment.

  FIG. 1 is a schematic cross-sectional view illustrating a preferred embodiment of a polarizing plate according to the present invention. The polarizing plate 30 includes a polarizing film 31 and a transparent protective film 33 bonded to one of the polarizing films 31 via an adhesive layer 32. Practically, the polarizing plate 30 includes a second transparent protective film 35 bonded to the polarizing film 31 on the side opposite to the transparent protective film 33 via an adhesive layer 34. The second transparent protective film 35 may be the same as the transparent protective film 33 or may be any appropriate other protective film.

  Any appropriate polarizing film can be adopted as the polarizing film as long as the effects of the present invention are not impaired. As the polarizing film, a film obtained by dyeing a polymer film with a dichroic substance (typically iodine or a dichroic dye) and uniaxially stretching is usually used. Any appropriate polymer film can be used as the polymer film forming the polarizing film. Typical examples of the polymer film include a polyvinyl alcohol (PVA) film, a polyethylene terephthalate (PET) film, and an ethylene-vinyl acetate copolymer film. PVA film is preferred. It is because it is excellent in the dyeability by a dichroic substance. The degree of polymerization of the polymer constituting the polymer film is preferably 100 to 5000, more preferably 1400 to 4000. The polymer film constituting the polarizing film can be formed by any appropriate method (for example, a casting method in which a solution obtained by dissolving a resin in water or an organic solvent is cast, a casting method, an extrusion method). The thickness of the polarizing film can be appropriately set according to the purpose and application of the LCD in which the polarizing plate is used, but is typically 5 to 80 μm.

  Any appropriate method can be adopted as a method for producing the polarizing film depending on the purpose, the material used, the conditions, and the like. Typically, a method is employed in which the polymer film (for example, PVA film) is subjected to a series of production steps including swelling, dyeing, crosslinking, stretching, washing with water, and drying. In each processing step except the drying step, the treatment is performed by immersing the polymer film in a bath containing the solution used in each step. The order, frequency, and presence / absence of each treatment of swelling, dyeing, crosslinking, stretching, washing with water, and drying can be appropriately set according to the purpose, materials used, conditions, and the like. For example, several processes may be performed simultaneously in one process, and a specific process may be omitted. More specifically, for example, the stretching process may be performed after the dyeing process, may be performed before the dyeing process, or may be performed simultaneously with the swelling process, the dyeing process, and the crosslinking process. Further, for example, it can be suitably employed to perform the crosslinking treatment before and after the stretching treatment. Further, for example, the water washing process may be performed after all the processes, or may be performed only after a specific process.

  The swelling step is typically performed by immersing the polymer film in a treatment bath (swelling bath) filled with water. By this treatment, dirt on the surface of the polymer film and an anti-blocking agent can be washed and the polymer film can be swollen to prevent unevenness such as uneven dyeing. Glycerin, potassium iodide, or the like can be appropriately added to the swelling bath. The temperature of the swelling bath is typically about 20 to 60 ° C., and the immersion time in the swelling bath is typically about 0.1 to 10 minutes.

  The dyeing step is typically performed by immersing the polymer film in a treatment bath (dye bath) containing a dichroic substance such as iodine. As the solvent used for the dye bath solution, water is generally used, but an appropriate amount of an organic solvent compatible with water may be added. The dichroic substance is typically used at a ratio of 0.1 to 1.0 part by weight with respect to 100 parts by weight of the solvent. When iodine is used as the dichroic substance, the dye bath solution preferably further contains an auxiliary agent such as iodide. This is because the dyeing efficiency is improved. The auxiliary is preferably used in a proportion of 0.02 to 20 parts by weight, more preferably 2 to 10 parts by weight, with respect to 100 parts by weight of the solvent. Specific examples of iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and iodide. Titanium is mentioned. The temperature of the dyeing bath is typically about 20 to 70 ° C., and the immersion time in the dyeing bath is typically about 1 to 20 minutes.

  The crosslinking step is typically performed by immersing the dyed polymer film in a treatment bath (crosslinking bath) containing a crosslinking agent. Arbitrary appropriate crosslinking agents can be employ | adopted as a crosslinking agent. Specific examples of the crosslinking agent include boron compounds such as boric acid and borax, glyoxal, and glutaraldehyde. These can be used alone or in combination. As the solvent used for the solution of the crosslinking bath, water is generally used, but an appropriate amount of an organic solvent having compatibility with water may be added. The crosslinking agent is typically used at a ratio of 1 to 10 parts by weight with respect to 100 parts by weight of the solvent. When the concentration of the crosslinking agent is less than 1 part by weight, sufficient optical properties cannot often be obtained. When the concentration of the crosslinking agent exceeds 10 parts by weight, the stretching force generated in the film during stretching increases, and the resulting polarizing plate may shrink. The solution of the crosslinking bath preferably further contains an auxiliary agent such as iodide. This is because it is easy to obtain uniform characteristics in the plane. The concentration of the auxiliary agent is preferably 0.05 to 15% by weight, more preferably 0.5 to 8% by weight. Specific examples of iodide are the same as in the dyeing step. The temperature of the crosslinking bath is typically about 20 to 70 ° C, preferably 40 to 60 ° C. The immersion time in the crosslinking bath is typically about 1 second to 15 minutes, preferably 5 seconds to 10 minutes.

  The stretching process may be performed at any stage as described above. Specifically, it may be performed after the dyeing process, may be performed before the dyeing process, may be performed simultaneously with the swelling process, the dyeing process, and the crosslinking process, or may be performed after the crosslinking process. The cumulative draw ratio of the polymer film needs to be 5 times or more, preferably 5 to 7 times, and more preferably 5 to 6.5 times. When the cumulative draw ratio is less than 5 times, it may be difficult to obtain a polarizing plate with a high degree of polarization. When the cumulative draw ratio exceeds 7 times, the polymer film (polarizer) may be easily broken. Arbitrary appropriate methods may be employ | adopted as a specific method of extending | stretching. For example, when the wet stretching method is adopted, the polymer film is stretched at a predetermined magnification in a treatment bath (stretching bath). As the stretching bath solution, a solution in which various metal salts, iodine, boron or zinc compounds are added to a solvent such as water or an organic solvent (for example, ethanol) is preferably used.

  The water washing step is typically performed by immersing the polymer film subjected to the above-described various treatments in a treatment bath (water washing bath). An unnecessary residue of the polymer film can be washed away by the washing step. The washing bath may be pure water or an aqueous solution of iodide (for example, potassium iodide or sodium iodide). The concentration of the iodide aqueous solution is preferably 0.1 to 10% by mass. An auxiliary agent such as zinc sulfate or zinc chloride may be added to the aqueous iodide solution. The temperature of the washing bath is preferably 10 to 60 ° C, more preferably 30 to 40 ° C. The immersion time is typically 1 second to 1 minute. The water washing step may be performed only once, or may be performed a plurality of times as necessary. When implemented several times, the kind and density | concentration of the additive contained in the washing bath used for each process can be adjusted suitably. For example, the water washing step includes a step of immersing the polymer film in an aqueous potassium iodide solution (0.1 to 10% by mass, 10 to 60 ° C.) for 1 second to 1 minute, and a step of rinsing with pure water.

  Any appropriate drying method (for example, natural drying, air drying, heat drying) may be employed as the drying step. For example, in the case of heat drying, the drying temperature is typically 20 to 80 ° C., and the drying time is typically 1 to 10 minutes. A polarizing film is obtained as described above.

  As the transparent protective film, any appropriate transparent resin can be adopted as long as the effects of the present invention can be obtained, but in order to further exhibit the effects of the present invention, an amorphous thermoplastic resin film is preferable. .

  Examples of the amorphous thermoplastic resin constituting the amorphous thermoplastic resin film include olefin resins such as cycloolefin resins such as norbornene resins, polymers of olefins with maleic anhydride, N-alkylmaleimides, and the like. , Acrylic resins such as methyl methacrylate polymer, acrylic ester polymer obtained by esterifying alcohol having norbornene skeleton and acrylic acid, polyester resin, polycarbonate resin, polyamide resin, polysulfone resin, polyimide Resin, etc., and among these, norbornene resin is preferably used. These amorphous thermoplastic resins may be used alone or in combination of two or more. In addition, a polymer means a homopolymer or a copolymer.

  Examples of norbornene resins include ring-opening (co) polymers of norbornene monomers, addition polymers of norbornene monomers, and copolymers of norbornene monomers and α-olefins such as ethylene and propylene (typically , Random copolymers), graft modified products obtained by modifying these with an unsaturated carboxylic acid or a derivative thereof, and hydrides thereof.

  Examples of the norbornene-based monomer used to obtain the norbornene-based resin include norbornene and alkyl and / or alkylidene substituted products thereof such as 5-methyl-2-norbornene, 5-dimethyl-2-norbornene, and 5-ethyl. 2-norbornene, 5-butyl-2-norbornene, 5-ethylidene-2-norbornene, etc., polar group substitution products such as halogens; dicyclopentadiene, 2,3-dihydrodicyclopentadiene, etc .; dimethanooctahydro Naphthalene, its alkyl and / or alkylidene substituents, and polar group substituents such as halogen such as 6-methyl-1,4: 5,8-dimethano-1,4,4a, 5,6,7,8, 8a-octahydronaphthalene, 6-ethyl-1,4: 5,8-dimethano-1, , 4a, 5,6,7,8,8a-octahydronaphthalene, 6-ethylidene-1,4: 5,8-dimethano-1,4,4a, 5,6,7,8,8a-octahydronaphthalene 6-chloro-1,4: 5,8-dimethano-1,4,4a, 5,6,7,8,8a-octahydronaphthalene, 6-cyano-1,4: 5,8-dimethano-1 , 4,4a, 5,6,7,8,8a-octahydronaphthalene, 6-pyridyl-1,4: 5,8-dimethano-1,4,4a, 5,6,7,8,8a-octa Hydronaphthalene, 6-methoxycarbonyl-1,4: 5,8-dimethano-1,4,4a, 5,6,7,8,8a-octahydronaphthalene and the like; 3-pentamer of cyclopentadiene, for example, 4,9: 5,8-dimethano-3a, 4,4a, 5,8,8a, 9, a-Octahydro-1H-benzoindene, 4,11: 5, 10: 6,9-trimethano-3a, 4,4a, 5,5a, 6,9,9a, 10,10a, 11,11a-dodecahydro-1H -Cyclopentaanthracene etc. are mentioned. These may be used alone or in combination of two or more.

  In order to obtain a norbornene-based resin, in addition to the norbornene-based monomer, other cycloolefins that can be ring-opening polymerized as cyclic olefins can be used in combination as long as the object of the present invention is not impaired. Specific examples of such cycloolefins include compounds having one reactive double bond such as cyclopentene, cyclooctene, and 5,6-dihydrodicyclopentadiene.

  The norbornene-based resin preferably has a number average molecular weight (Mn) measured by a gel permeation chromatography (GPC) method using a toluene solvent, preferably 25,000 to 200,000, more preferably 30,000 to 100,000. Most preferably, it is 40,000-80,000. When the number average molecular weight is in the above range, a material having excellent mechanical strength and good solubility, moldability and operability can be obtained.

  When the norbornene-based resin is obtained by hydrogenating a ring-opening polymer of a norbornene-based monomer, the hydrogenation rate is preferably 90% or more, more preferably 95% or more, and most preferably Is 99% or more. Within such a range, the heat deterioration resistance and light deterioration resistance are excellent.

  As the norbornene resin, various products are commercially available. Specific examples include trade names ZEONEX and ZEONOR manufactured by Nippon Zeon, Arton manufactured by JSR, and TOPAS manufactured by TICONA.

  The thickness of the transparent protective film that can be used in the present invention is typically 500 μm or less, preferably 1 to 300 μm, and more preferably 5 to 200 μm.

  The method for producing the transparent protective film is not particularly limited, and examples thereof include a solution casting method, an extrusion molding method, a calender molding method, and the like, and a raw material resin typified by the norbornene resin is extruded with an extruder. A method of extruding the film is preferable. Any appropriate method can be adopted as the extrusion. Any appropriate format can be adopted as the format of the extruder. For example, a single screw type extruder or a twin screw type extruder may be used. The set temperature (melting temperature), kneading time, screw speed, and the like of the extruder can be appropriately set according to the type of raw material resin used. For example, the melting temperature of the raw material resin is typically 240 to 300 ° C, and preferably 260 to 280 ° C. Any appropriate additive (for example, a plasticizer or an antioxidant) can be added to the raw material resin as necessary. Furthermore, tackifiers (for example, terpene resins, phenol resins, terpene-phenol resins, rosin resins, xylene resins), ultraviolet absorbers, heat stabilizers, and the like can be added to the raw material resin as necessary. The raw material resin melted by the extruder is extruded from a T-die, cooled (for example, water-cooled), and taken out to form a film. The temperature of the T die can also be set as appropriate according to the type of raw material resin used. The T die temperature is typically 240 to 300 ° C, preferably 260 to 280 ° C. The thickness of the film can be appropriately controlled by adjusting the clearance of the T die.

  The transparency protective film may be stretched as necessary to adjust the phase difference.

  The transparent protective film may be a film formed by modifying at least one side. The reforming treatment is not particularly limited, and examples thereof include corona discharge treatment, ultraviolet irradiation treatment, plasma treatment, laser treatment, flame treatment, high frequency treatment, glow discharge treatment, ozone oxidation treatment, and alkali treatment.

  The smaller the retardation value (in-plane retardation) of the transparent protective film, the better. This is because the influence on the polarization performance of the polarizing plate can be minimized. More specifically, the retardation value is preferably 20 nm or less, more preferably 10 nm or less, and most preferably 5 nm or less.

  The light transmittance of the transparent protective film is preferably as large as possible (that is, 100% is ideal). Practically, the light transmittance is preferably 85% or more, more preferably 90% or more, and most preferably 95% or more. If the light transmittance is 85% or more, the amount of light transmitted through the polarizing plate can be sufficiently secured, and there is very little possibility of causing a decrease in polarization performance, which causes a practical problem.

The water vapor transmission rate of the transparent protective film at 70 ° C. and 90% RH is 25 μm, preferably 300 g / m ² · 24 hr or less, more preferably 200 g / m ² · 24 hr or less, and most preferably 100 g / m. ² · 24hr is less than or equal to. If it is such a range, the polarizing plate which has the outstanding durability can be obtained. On the other hand, the water vapor permeability is preferably 0.05g ^/ m 2 · 24hr or more, more preferably 0.1g ^/ m 2 · 24hr or more. In such a range, the moisture contained in the polarizer and the adhesive is sufficiently transmitted through the protective film in the drying process in the production of the polarizing plate, so that there is a problem that the adhesiveness is lowered due to residual moisture and the polarization performance is lowered. Is very unlikely to occur.

  If necessary, an adhesive layer may be provided on the surface to which the polarizing film of the transparent protective film is attached, but if an adhesive containing a polyvinyl alcohol resin and a silane coupling agent in the present invention is used, Strong adhesive strength can be obtained without providing an easy-adhesive layer.

  The surface of the transparent protective film on which the polarizing film is not bonded may be subjected to a hard coat treatment, an antireflection treatment, an antisticking treatment, or a diffusion treatment (also referred to as an antiglare treatment) as necessary. The above-mentioned hard coat treatment is performed for the purpose of preventing scratches on the polarizing plate surface, and is a cured film excellent in hardness, sliding properties, etc., by any appropriate ultraviolet curable resin (for example, acrylic or silicone). Is performed on the surface of the protective film. The antireflection treatment is performed for the purpose of preventing reflection of external light on the surface of the polarizing plate. The anti-sticking treatment is performed for the purpose of preventing adhesion with an adjacent layer. The anti-glare treatment is performed for the purpose of preventing the outside light from being reflected on the surface of the polarizing plate and obstructing the viewing of the light transmitted through the polarizing plate, and any appropriate method (for example, sandblasting or embossing). It is carried out by imparting a fine concavo-convex structure to the surface of the transparent protective film by a roughening method by a processing method, a blending method of transparent fine particles). The antiglare layer (layer formed by antiglare treatment) may also serve as a diffusion layer (viewing angle expanding function or the like) for diffusing the light transmitted through the polarizing plate to expand the viewing angle.

  In the present invention, it is important that at least one surface of the polarizing film and the transparent protective film are bonded with an adhesive containing a polyvinyl alcohol resin and a silane coupling agent. Thus, even if an easy-adhesive layer is not provided on the transparent protective film, the adhesive strength between the polarizing film and the transparent protective film is high, and a high-quality, high-value-added polarizing plate is provided with high productivity. And the use of such a polarizing plate can be provided.

  The polyvinyl alcohol resin only needs to be water-soluble. For example, in addition to ordinary polyvinyl alcohol (PVA), silane-modified PVA, epoxy-modified PVA, carboxyl group-modified PVA, amino group-modified PVA, and acetoacetyl group-modified PVA etc. are mentioned. From the viewpoint of excellent reactivity with a silane coupling agent, acetoacetyl group-modified PVA is preferable.

  Although it does not specifically limit as a polymerization degree of a polyvinyl alcohol resin, Usually, 100-5000 are preferable and 500-3500 are more preferable.

  Although it does not specifically limit as a saponification degree of polyvinyl alcohol resin, Usually, 70-100 mol% is preferable and 90-100 mol% is more preferable.

  In the case of using acetoacetyl group-modified PVA, the degree of polymerization is preferably 100 to 5000, more preferably 500 to 4000, and still more preferably 1000 to 3500 in order to further exert the effects of the present invention. The degree of conversion is preferably 70 to 100 mol%, more preferably 90 to 100 mol%, still more preferably 95 to 100 mol%, and the degree of acetoacetylation is preferably 0.1 to 40 mol%, more preferably Is 0.1 to 30 mol%, more preferably 0.5 to 10 mol%.

  Examples of silane coupling agents include isocyanate group-containing alkoxysilanes such as γ-isocyanatopropyltrimethoxysilane, γ-isocyanatopropyltriethoxysilane, γ-isocyanatopropylmethyldiethoxysilane, and γ-isocyanatopropylmethyldimethoxysilane. Γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-aminopropylmethyldimethoxysilane, γ-aminopropylmethyldiethoxysilane, γ- (2-aminoethyl) aminopropyltrimethoxysilane, γ- (2-aminoethyl) aminopropylmethyldimethoxysilane, γ- (2-aminoethyl) aminopropyltriethoxysilane, γ- (2-aminoethyl) aminopropylmethyldiethoxysilane, Amino group-containing alkoxysilanes such as ureidopropyltrimethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, N-benzyl-γ-aminopropyltrimethoxysilane, N-vinylbenzyl-γ-aminopropyltriethoxysilane Mercapto group-containing alkoxysilanes such as γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, γ-mercaptopropylmethyldimethoxysilane, γ-mercaptopropylmethyldiethoxysilane; γ-glycidoxypropyltri Methoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, β- (3,4-epoxy (Rohexyl) epoxy group-containing alkoxysilanes such as ethyltriethoxysilane; β-carboxyethyltriethoxysilane, β-carboxyethylphenylbis (2-methoxyethoxy) silane, N-β- (carboxymethyl) aminoethyl-γ- Carboxy-containing alkoxysilanes such as aminopropyltrimethoxysilane; vinyl-type unsaturated groups such as vinyltrimethoxysilane, vinyltriethoxysilane, γ-methacryloyloxypropylmethyldimethoxysilane, and γ-acryloyloxypropylmethyltriethoxysilane Alkoxysilanes; halogen group-containing alkoxysilanes such as γ-chloropropyltrimethoxysilane; isocyanurate group-containing alkoxysilanes such as tris (trimethoxysilyl) isocyanurate; Silyl polymers, silylated amino polymers, unsaturated aminosilane complexes, phenylamino long-chain alkylsilanes, aminosilylated silicones, silylated polyesters, and derivatives thereof.

  The silane coupling agent can be appropriately selected according to the type of the transparent protective film, and for example, when a norbornene resin film is used as the transparent protective film, γ-aminopropyltrimethoxysilane, γ -Aminopropyltriethoxysilane, γ-aminopropylmethyldimethoxysilane, γ-aminopropylmethyldiethoxysilane, γ- (2-aminoethyl) aminopropyltrimethoxysilane, γ- (2-aminoethyl) aminopropylmethyldimethoxy Silane, γ- (2-aminoethyl) aminopropyltriethoxysilane, γ- (2-aminoethyl) aminopropylmethyldiethoxysilane, γ-ureidopropyltrimethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane N-benzyl-γ-amino Amino group-containing alkoxysilanes such as nopropyltrimethoxysilane and N-vinylbenzyl-γ-aminopropyltriethoxysilane are preferred. When these are used, the effect of the present invention is further exhibited, and in particular, strong adhesive strength can be obtained.

  The adhesive in the present invention may contain other additives in addition to the polyvinyl alcohol resin and the silane coupling agent as long as the effects of the present invention are not impaired.

  The content ratio of the polyvinyl alcohol resin and the silane coupling agent in the adhesive containing the polyvinyl alcohol resin and the silane coupling agent is preferably 0.1 to 100 parts by weight with respect to 100 parts by weight of the polyvinyl alcohol resin. More preferably, it is 0.1-50 weight part, More preferably, it is 0.1-30 weight part.

  The total content of the polyvinyl alcohol resin and the silane coupling agent in the adhesive containing the polyvinyl alcohol resin and the silane coupling agent is preferably 0.5 to 10 with respect to 100 parts by weight of the total amount of the adhesive. Parts by weight, more preferably 1 to 6 parts by weight, still more preferably 1 to 4 parts by weight.

  The method for producing the adhesive containing the polyvinyl alcohol resin and the silane coupling agent is not particularly limited. However, from the viewpoint of using a water-soluble polyvinyl alcohol resin, the silane coupling agent is preferably added to the aqueous solution of the polyvinyl alcohol resin. It is a method of adding.

  In the polarizing plate according to the present invention, in the polarizing plate in which the transparent protective film is laminated on at least one surface of the polarizing film, at least one surface of the polarizing film and the transparent protective film are bonded to each other. It is adhered by an agent.

  That is, in the polarizing plate according to the present invention, the transparent protective film may be laminated on both surfaces of the polarizing film, or the transparent protective film may be laminated only on one surface of the polarizing film. In the latter case, any appropriate protective film can be employed on the other surface as long as the effects of the present invention are not impaired. Examples of the resin constituting such a protective film include cellulose polymers (for example, diacetyl cellulose and triacetyl cellulose), acrylic polymers (for example, polymethyl methacrylate), and styrene polymers (for example, polystyrene, acrylonitrile-styrene). Copolymer (AS resin)), sulfone polymer, polyether sulfone polymer, polyether ether ketone polymer, polyphenylene sulfide polymer, vinyl alcohol polymer, vinylidene chloride polymer, vinyl butyral polymer, polyoxymethylene polymer Examples thereof include polymers and epoxy polymers. These may be used alone or in combination of two or more. Furthermore, it is also possible to use an acrylic, urethane-based, epoxy-based, or silicone-based thermosetting or ultraviolet curable resin film. The thickness of such a protective film is typically 500 μm or less, preferably 1 to 300 μm, and more preferably 5 to 200 μm.

  As a method of adhering at least one surface of the polarizing film and the transparent protective film with the above adhesive, any appropriate adhering method can be adopted as long as the effects of the present invention are not impaired. For example, there is a method in which an adhesive in an aqueous solution state is applied after being applied to an adhesive surface using a gravure coating method, a dip coating method, a spray method, a casting method, or the like.

  Next, the image display apparatus of the present invention will be described. The image display device of the present invention includes at least one polarizing plate of the present invention. Here, a liquid crystal display device will be described as an example, but it goes without saying that the present invention can be applied to any display device that requires a polarizing plate. Specific examples of the image display device to which the polarizing plate of the present invention can be applied include a self-luminous display device such as an electroluminescence (EL) display, a plasma display (PD), and a field emission display (FED). Can be mentioned. FIG. 2 is a schematic cross-sectional view of a liquid crystal display device according to a preferred embodiment of the present invention. In the illustrated example, a transmissive liquid crystal display device will be described, but it goes without saying that the present invention is also applied to a reflective liquid crystal display device and the like.

  The liquid crystal display device 100 includes a liquid crystal cell 10, retardation films 20 and 20 ′ disposed across the liquid crystal cell 10, and polarizing plates 30 and 30 ′ disposed outside the retardation films 20 and 20 ′. A light guide plate 40, a light source 50, and a reflector 60 are provided. The polarizing plates 30 and 30 'are arranged so that their polarization axes are orthogonal to each other. The liquid crystal cell 10 includes a pair of glass substrates 11 and 11 ′ and a liquid crystal layer 12 as a display medium disposed between the substrates. One substrate 11 is provided with a switching element (typically a TFT) for controlling the electro-optical characteristics of the liquid crystal, a scanning line for supplying a gate signal to the active element, and a signal line for supplying a source signal ( Neither is shown). The other glass substrate 11 ′ is provided with a color layer constituting a color filter and a light shielding layer (black matrix layer) (both not shown). The distance (cell gap) between the substrates 11 and 11 ′ is controlled by the spacer 13. In the liquid crystal display device of the present invention, the polarizing plate of the present invention described above is employed as at least one of the polarizing plates 30 and 30 '.

  For example, in the case of the TN mode, in such a liquid crystal display device 100, when no voltage is applied, the liquid crystal molecules of the liquid crystal layer 12 are arranged in a state where the polarization axis is shifted by 90 degrees. In such a state, incident light that is transmitted through only light in one direction by the polarizing plate is twisted 90 degrees by liquid crystal molecules. As described above, since the polarizing plates are arranged so that the polarization axes thereof are orthogonal to each other, the light (polarized light) reaching the other polarizing plate is transmitted through the polarizing plate. Therefore, when no voltage is applied, the liquid crystal display device 100 performs white display (normally white method). On the other hand, when a voltage is applied to such a liquid crystal display device 100, the arrangement of liquid crystal molecules in the liquid crystal layer 12 changes. As a result, the light (polarized light) that has reached the other polarizing plate cannot be transmitted through the polarizing plate, resulting in black display. An image is formed by switching such display for each pixel using an active element.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these Examples. Unless otherwise indicated, parts and percentages in the examples are based on weight. Evaluation items in the examples are as follows.

<Adhesion evaluation by hand peeling>
The adhesive strength between the polarizing film and the protective film was confirmed by manual peeling.
○: No peeling at all.
X: Peeled off at the interface between the polarizer and the protective film.

<60 ° C hot water immersion test>
The produced polarizing plate was cut | disconnected to 25 mm x 50 mm (TDxMD), immersed in 60 degreeC warm water, and the time until a protective film peeled was measured.

[Reference Example 1]
A 80 μm-thick polyvinyl alcohol film (manufactured by Kuraray Co., Ltd.) is used in a 5 wt% iodine compound aqueous solution (iodine (I) / potassium iodide (KI) weight ratio = 1/10). The dyeing is carried out by adjusting the time so that the transmittance (43% in this case) is obtained, and it is immersed in 3 wt% boric acid + 2 wt% KI aqueous solution for 10 seconds, and the draw ratio is 5 in 4 wt% boric acid + 3 wt% KI aqueous solution. The film was stretched to 5 times and finally immersed in a 5 wt% KI aqueous solution for 10 seconds. The obtained stretched film was dried in an oven at 40 ° C. for 3 minutes to obtain a polarizing film having a thickness of 30 μm.

[Example 1]
100 parts of an acetoacetyl group-modified polyvinyl alcohol resin (polymerization degree 1200, saponification degree 99 mol%, acetoacetylation degree 5 mol%) was dissolved in 3000 parts of water to prepare an aqueous polyvinyl alcohol solution. While stirring this aqueous solution, 10 parts of γ-aminopropyltriethoxysilane was added dropwise to produce an adhesive.
Using the obtained adhesive, one side of the polarizing film obtained in Reference Example 1 was subjected to corona treatment with a discharge amount of 100 W · min / m ^{2 and} a 40 μm-thick norbornene resin film (trade name: ZEONOR, Japan) Zeon Co., Ltd.) and a saponified 40 μm thick triacetyl cellulose film (trade name: Fujitac, manufactured by Fuji Photo Film Co., Ltd.) are bonded together and dried at 70 ° C. for 10 minutes to form a polarizing plate. Produced. In the saponification treatment, the triacetyl cellulose film was immersed in a 10% aqueous sodium hydroxide solution at 60 ° C. for 1 minute, washed with pure water, and then dried at 70 ° C. for 3 minutes.
About the obtained polarizing plate, the adhesive evaluation by hand peeling and the 60 degreeC warm water immersion test were done.
The results are shown in Table 1.

[Example 2]
Instead of 100 parts of acetoacetyl group-modified polyvinyl alcohol resin (polymerization degree 1200, saponification degree 99 mol%, acetoacetylation degree 5 mol%), polyvinyl alcohol resin (polymerization degree 1700, saponification degree 99 mol%, acetoacetyl A polarizing plate was produced in the same manner as in Example 1 except that 100 parts of a conversion degree of 5 mol% were used.
About the obtained polarizing plate, the adhesive evaluation by hand peeling and the 60 degreeC warm water immersion test were done.
The results are shown in Table 1.

[Comparative Example 1]
A polarizing plate was produced in the same manner as in Example 1 except that γ-aminopropyltriethoxysilane was not added dropwise.
About the obtained polarizing plate, the adhesive evaluation by hand peeling and the 60 degreeC warm water immersion test were done.
The results are shown in Table 1.

As is clear from Table 1, according to the present invention, the polarizing film and the transparent protective film have a high adhesive strength, and are particularly difficult to peel off even under high temperature and high humidity. It can be provided with high productivity and can be used for such a polarizing plate. In particular, according to the present invention, even when an amorphous thermoplastic resin film with poor adhesion is used as a transparent protective film, sufficient adhesion can be obtained without bothering to provide an easy-adhesive layer. Particularly, it is difficult to peel off even under high temperature and high humidity, and a high-quality, high-value-added polarizing plate can be obtained with high productivity.

  The polarizing plate of the present invention can be suitably used for an image display device such as a liquid crystal display device (LCD) or a self-luminous display device.

It is a schematic sectional drawing of the polarizing plate by preferable embodiment of this invention. 1 is a schematic cross-sectional view of a liquid crystal display device according to a preferred embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Liquid crystal cell 11, 11 'Glass substrate 12 Liquid crystal layer 13 Spacer 20, 20' Phase difference film 30, 30 'Polarizing plate 31 Polarizing film 32 Adhesive layer 33 Transparency protective film 34 Adhesive layer 35 2nd transparency protection Film 40 Light guide plate 50 Light source 60 Reflector 100 Liquid crystal display device

Claims (5)

A transparent protective film is laminated on at least one surface of the polarizing film,
A polarizing plate formed by adhering at least one surface of the polarizing film and the transparent protective film with an adhesive containing a polyvinyl alcohol resin and a silane coupling agent.   The polarizing plate according to claim 1, wherein the silane coupling agent is an amino group-containing alkoxysilane.   The polarizing plate according to claim 1 or 2, wherein at least one of the transparent protective films is an amorphous thermoplastic resin film.   The polarizing plate according to claim 3, wherein the amorphous thermoplastic resin film is a norbornene-based resin film. An image display device comprising at least one polarizing plate according to claim 1.

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