JP2006171707A - Polarizing plate and image display using same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polarizing plate which is excellent in adhesiveness between a polarizer and a protective film, has an extremely excellent durability under high temperature and high humidity and has an excellent appearance, and to provide an image display using the polarizing plate. <P>SOLUTION: The polarizing plate comprises a polarizer, an adhesive layer, an easy adhesive layer and a protective film made of a film containing cyclic olefine resin as a main component, wherein the easy adhesive layer contains a silane having reactive radical groups and has a thickness thereof of 1 to 50 nm. The image display is provided with such a polarizing plate. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a polarizing plate and an image display device using the polarizing plate. More specifically, the present invention is a polarizing plate having excellent adhesion between a polarizer and a protective film, having extremely excellent durability under high temperature and high humidity, and having an excellent appearance, and the same. The present invention relates to an image display device.

  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, and then a PVA system is formed on both sides of the polarizer. A material obtained by bonding a protective film such as triacetyl cellulose (TAC) using an adhesive is used.

  However, since TAC does not have sufficient heat-and-moisture resistance, when a polarizing plate using TAC as a protective film is used at a high temperature and / or high humidity, the performance of the polarizing plate (for example, the degree of polarization, the hue) decreases. There is. Furthermore, a TAC film produces a phase difference with respect to incident light in an oblique direction. With the recent increase in the size of liquid crystal displays, the effect on viewing angle characteristics due to such a phase difference has become prominent.

  In order to solve the above problem, a cyclic polyolefin resin has been proposed as a material for the protective film instead of TAC. The cyclic polyolefin-based resin has low moisture permeability, and the film has almost no retardation in the oblique direction. However, the cyclic polyolefin resin has insufficient adhesion to the PVA adhesive.

In order to solve such a problem, a method of adhering a protective film of a cyclic olefin resin and a PVA polarizer via an acrylic adhesive has been proposed (see Patent Document 1). However, this method requires thermocompression bonding and takes a long time for heating. As a result, there is a problem that the PVA polarizer is discolored and the degree of polarization is significantly reduced. Moreover, due to the fact that it takes a long time for heating, there is also a problem that the production efficiency is low and the polarizing plate is deformed. Meanwhile, 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 a PVA polarizer are bonded with a polyvinyl alcohol adhesive have been proposed. (See Patent Document 2). However, this polarizing plate has a problem that many floats and streaks occur when the protective film and the PVA polarizer are bonded. As a result, the appearance of the obtained polarizing plate is not stable, and the yield is poor.
Japanese Patent Laid-Open No. 5-212828 Japanese Patent Laid-Open No. 2001-174637

  The present invention has been made in order to solve the above-described conventional problems. The object of the present invention is to provide excellent adhesion between a polarizer and a protective film, and extremely excellent durability under high temperature and high humidity. And it is providing the polarizing plate which has the outstanding external appearance, and an image display apparatus using the same.

  The polarizing plate of the present invention has a polarizer, an adhesive layer, an easy-adhesive layer, and a protective film made of a film containing a cyclic olefin-based resin as a main component, and the easy-adhesive layer is reacted. A silane having a functional functional group and a thickness of 1 to 50 nm.

  In a preferred embodiment, the silane is an isocyanate group-containing alkoxysilane, an amino group-containing alkoxysilane, a mercapto group-containing alkoxysilane, a carboxy-containing alkoxysilane, an epoxy group-containing alkoxysilane, or a vinyl unsaturated group. It is selected from the group consisting of alkoxysilanes, halogen group-containing alkoxysilanes and isocyanurate group-containing alkoxysilanes. In a more preferred embodiment, the silane is an amino group-containing alkoxysilane.

  In a preferred embodiment, the polarizing plate further includes a second protective film on the side opposite to the protective film of the polarizer, and the second protective film is made of a film containing triacetyl cellulose as a main component. .

  According to another aspect of the present invention, an image display device is provided. The image display device includes the polarizing plate.

  According to another aspect of the present invention, a liquid crystal display device is provided. The liquid crystal display device includes a liquid crystal cell and the polarizing plate disposed on at least one side of the liquid crystal cell, and a protective film made of a film containing a cyclic olefin-based resin as a main component of the polarizing plate It is arranged on the liquid crystal cell side.

  As described above, according to the present invention, by forming an easy adhesion layer containing a silane having a reactive functional group on the polarizer side of the protective film, and by making the thickness of the easy adhesion layer very thin, A polarizing plate having excellent adhesion between the polarizer and the protective film, having extremely excellent durability under high temperature and high humidity, and having an excellent appearance can be obtained. Such knowledge was obtained for the first time when a polarizing plate containing a specific silane and having an extremely thin easy-adhesion layer was actually subjected to high temperature and high humidity, which is an unexpectedly excellent effect. .

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

A. Polarizing plate A-1. FIG. 1 is a schematic cross-sectional view of a polarizing plate according to a preferred embodiment of the present invention. The polarizing plate 30 includes a polarizer 31, an adhesive layer 32, an easy-adhesive layer 33, and a protective film 34 in this order. Practically, the polarizing plate 30 may have a second protective film 36 attached via an adhesive layer 35 on the side opposite to the protective film 34 of the polarizer 31.

A-2. Protective film The protective film 34 consists of a film which contains cyclic olefin resin as a main component. In this specification, “containing as a main component” means that the film contains a cyclic olefin resin in a proportion of 50% by weight or more, preferably 60% by weight or more, more preferably 70% by weight or more of the whole. To do. The cyclic olefin-based resin is a general term for resins that are polymerized using a cyclic olefin as a polymerization unit, and examples thereof include resins described in JP-A-3-14882 and JP-A-3-122137. Specific examples include ring-opening (co) polymers of cyclic olefins, addition polymers of cyclic olefins, copolymers of cyclic olefins and α-olefins such as ethylene and propylene (typically random copolymers). And graft modified products in which these are modified with an unsaturated carboxylic acid or a derivative thereof, and hydrides thereof. Specific examples of the cyclic olefin include norbornene monomers.

  Examples of the norbornene-based monomer include norbornene and alkyl and / or alkylidene substituted products thereof such as 5-methyl-2-norbornene, 5-dimethyl-2-norbornene, 5-ethyl-2-norbornene, and 5-butyl. 2-Norbornene, 5-ethylidene-2-norbornene, etc., polar substituents such as halogens; dicyclopentadiene, 2,3-dihydrodicyclopentadiene, etc .; dimethanooctahydronaphthalene, 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-1,4,4a, 5,6,7,8,8a-oct Hydronaphthalene, 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-octahydronaphthalene, 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, 9,9a-octahydro-1H-benzoin 4,11: 5,10: 6,9-trimethano-3a, 4,4a, 5,5a, 6,9,9a, 10,10a, 11,11a-dodecahydro-1H-cyclopentanthracene and the like. It is done.

  In the present invention, other cycloolefins capable of ring-opening polymerization 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 cyclic olefin-based resin preferably has a number average molecular weight (Mn) measured by a gel permeation chromatograph (GPC) method using a toluene solvent, preferably 25,000 to 200,000, more preferably 30,000 to 100,000. 000, most preferably 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 cyclic olefin-based resin is obtained by hydrogenating a ring-opening polymer of a norbornene monomer, the hydrogenation rate is preferably 90% or more, more preferably 95% or more, Most preferably, it is 99% or more. Within such a range, the heat deterioration resistance and light deterioration resistance are excellent.

  As the cyclic olefin 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 protective film 34 may further contain any appropriate additive as necessary. The kind and use amount of the additive can be appropriately set according to the purpose. Specific examples of the additives include plasticizers, antioxidants, tackifiers (for example, terpene resins, phenol resins, terpene-phenol resins, rosin resins, xylene resins), ultraviolet absorbers, heat stabilizers, and the like. .

  The thickness of the protective film 34 is typically 500 μm or less, preferably 1 to 300 μm, and more preferably 5 to 200 μm.

  The smaller the retardation value (in-plane retardation) of the protective film 34, 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 protective film 34 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 protective film 34 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, most preferably 100 g / m ^2. -24 hours or less. 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.

The absolute value of the photoelastic coefficient C [590] (m ² / N) of the protective film 34 is preferably 2.0 × 10 ^{−13 to} 2.0 × 10 ⁻¹¹ , and more preferably 5.0 × 10 10. ^{−13 to} 8.0 × 10 ⁻¹² , particularly preferably 2.0 × 10 ^{−12 to} 6.0 × 10 ⁻¹² , and most preferably 2.0 × 10 ^{−12 to} 5.0 × 10 ^-12 . By having a photoelastic coefficient in such a range, display unevenness when the polarizing plate is used in an image display device (particularly a liquid crystal display device) can be suppressed.

  The surface of the protective film 34 on which the polarizer is not bonded can 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. Such a treatment can also be performed on the second protective film 36 (described later).

A-3. Easy Adhesive Layer The easy adhesive layer 33 includes silane having a reactive functional group. By providing such an easy-adhesive layer, the adhesion between the polarizer 31 and the protective film 34 can be significantly improved. Specific examples of silanes having reactive functional groups include isocyanate groups such as γ-isocyanatopropyltrimethoxysilane, γ-isocyanatopropyltriethoxysilane, γ-isocyanatopropylmethyldiethoxysilane, and γ-isocyanatopropylmethyldimethoxysilane. Alkoxysilanes; γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-aminopropylmethyldimethoxysilane, γ-aminopropylmethyldiethoxysilane, γ- (2-aminoethyl) aminopropyltrimethoxysilane , Γ- (2-aminoethyl) aminopropylmethyldimethoxysilane, γ- (2-aminoethyl) aminopropyltriethoxysilane, γ- (2-aminoethyl) aminopropylmethyldiethoxysilane , Γ-ureidopropyltrimethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, N-benzyl-γ-aminopropyltrimethoxysilane, N-vinylbenzyl-γ-aminopropyltriethoxysilane, etc. Alkoxysilanes; mercapto group-containing alkoxysilanes such as γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, γ-mercaptopropylmethyldimethoxysilane, γ-mercaptopropylmethyldiethoxysilane; γ-glycidoxy Propyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, β- (3,4-epoxy (Cyclohexyl) ethyltriethoxysilane and other epoxy group-containing alkoxysilanes; 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; Modified silyl polymers, silylated amino polymers, unsaturated aminosilane complexes, phenylamino long-chain alkylsilanes, aminosilylated silicones, silylated polyesters, and derivatives thereof.

  The silane can be appropriately selected according to the type of the protective film, the type of adhesive used for bonding the protective film and the polarizer, and the like. For example, when a PVA aqueous adhesive is used as an adhesive, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-aminopropylmethyldimethoxysilane, γ-aminopropylmethyldiethoxysilane, γ- (2-aminoethyl) aminopropyltrimethoxysilane, γ- (2-aminoethyl) aminopropylmethyldimethoxysilane, γ- (2-aminoethyl) aminopropyltriethoxysilane, γ- (2-aminoethyl) Aminopropylmethyldiethoxysilane, γ-ureidopropyltrimethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, N-benzyl-γ-aminopropyltrimethoxysilane, N-vinylbenzyl-γ-aminopropyltriethoxy Contains amino groups such as silane Alkoxysilane are preferred. This is because it is easy to form an easy adhesion layer having good light transmittance, wettability, and adhesive strength. Of these, γ- (2-aminoethyl) aminopropyltriethoxysilane and γ- (2-aminoethyl) aminopropylmethyldiethoxysilane are preferable. This is because it is easy to form an easily adhesive layer having particularly excellent adhesive strength.

  The easy-adhesion layer 33 has a thickness of 1 to 100 nm, preferably 1 to 50 nm, and more preferably 10 to 50 nm. By setting the thickness of the easy-adhesion layer to 100 nm or less, even when the obtained polarizing plate is used under high temperature and high humidity, color loss, floating, unevenness, and streaks do not occur. That is, a polarizing plate having excellent appearance maintenance performance and polarization degree maintenance performance under high temperature and high humidity can be obtained. Such knowledge was obtained for the first time when a polarizing plate containing a specific silane and having an extremely thin easy-adhesion layer was actually subjected to high temperature and high humidity, which is an unexpectedly excellent effect. .

A-4. Adhesive Layer As the adhesive constituting the adhesive layer 32, any appropriate adhesive can be adopted as long as the protective film 34 and the polarizer 31 are favorably bonded. Preferably, an optically isotropic adhesive can be used. Examples of such adhesives include polyvinyl alcohol (PVA) adhesives, urethane adhesives, acrylic adhesives, and epoxy adhesives. For example, when the polarizer is a PVA film, an adhesive containing a PVA resin is preferable. This is because it is particularly excellent in adhesiveness with a polarizer. Any appropriate PVA-based resin can be adopted as the PVA-based resin. Representative examples include unsubstituted PVA and PVA having a highly reactive functional group. PVA having a highly reactive functional group is particularly preferred. This is because the durability of the polarizing plate can be further significantly improved. Specific examples of PVA having a highly reactive functional group include acetoacetyl-modified PVA resins. The polymerization degree of the binder resin (for example, PVA resin) of the adhesive is preferably 100 to 3000. By having the degree of polymerization in such a range, the adhesion to the polarizer and the protective film can be particularly good. The thickness of the adhesive layer 32 can be appropriately set according to the purpose and application of the LCD in which the polarizing plate is used, but is preferably 30 to 300 nm, and more preferably 50 to 150 nm.

  Preferably, the adhesive constituting the adhesive layer further includes a cross-linking agent. By using a binder resin and a crosslinking agent in combination, adhesion and water resistance can be significantly improved. Specific examples of the crosslinking agent used in the present invention include dialdehydes such as glyoxal, malondialdehyde, succindialdehyde, glutardialdehyde, maleidialdehyde, and phthaldialdehyde, among which glyoxal is preferable; ethylenediamine, triethylenediamine Alkylene diamines having two alkylene groups and two amino groups, such as hexamethylene diamine, among which hexamethylene diamine is preferable; tolylene diisocyanate, hydrogenated tolylene diisocyanate, trimethylolpropane-tolylene diisocyanate adduct, triphenylmethane tri Isocyanates, methylene bis (4-phenylmethane triisocyanate), isophorone diisocyanates, and their ketoxime blocks or phenols Isocyanates such as block products; ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin di or triglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, diglycidyl aniline, diglycidyl amine Epoxys such as: Formaldehyde, acetaldehyde, propionaldehyde, monoaldehydes such as butyraldehyde, etc .; alkylated methylol urea, alkylated methylol melamine, acetoguanamine, amino-formaldehyde resins such as condensates of benzoguanamine and formaldehyde, especially alkyl Methylol melamine is preferred; sodium, potassium, magnesium, calcium, aluminum Beam, iron, divalent metal or salts and oxides of trivalent metals, such as nickel. The crosslinking agent is preferably used in a proportion of 0.1 to 30 parts by weight with respect to 100 parts by weight of the binder resin. If it is less than 0.1 part by weight, the water resistance may not be sufficiently improved. If it exceeds 30 parts by weight, the pot life may be shortened, and excellent adhesiveness may not be obtained.

A-5. Polarizer As the polarizer 31, any appropriate polarizer can be adopted as long as the effects of the present invention are not impaired. As the polarizer, usually, a polymer film is dyed with a dichroic substance (typically iodine or a dichroic dye) and uniaxially stretched. Any appropriate polymer film can be used as the polymer film forming the polarizer. 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 polarizer can be formed by any appropriate method (for example, a casting method in which a solution in which a resin is dissolved in water or an organic solvent is cast, a casting method, an extrusion method). The thickness of the polarizer 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.

A-6. Second protective film As the second protective film 36, any appropriate protective film can be adopted as long as the effects of the present invention are not impaired. Specific examples of the material constituting the second protective film 36 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, polyoxy Examples include methylene polymers and epoxy polymers. These may be used alone or in combination of two or more. In addition, it is also possible to use an acrylic, urethane-based, epoxy-based, or silicone-based thermosetting or ultraviolet curable resin film. Furthermore, the same protective film as the protective film 34 described in the above section A-2 may be used. Cellulosic polymer films are preferred, and triacetyl cellulose (TAC) films are particularly preferred. By using such a protective film as the second protective film 36, the appearance maintaining performance and polarization degree maintaining performance under high temperature and high humidity can be further improved. The TAC film has an appropriate water vapor transmission rate (that is, larger than that of the cyclic olefin-based resin film), so that the evaporation of water in the manufacturing process of the polarizing plate is very good, and the undesired moisture is very good when the polarizing plate is completed. It is because it is removed. That is, by using the protective film 34 of the cyclic olefin resin on one side of the polarizer and the protective film 36 of TAC on one side, it is possible to prevent moisture from entering from the outside, and to prevent unwanted moisture inside. A polarizing plate that can be discharged well can be obtained. The thickness of the second protective film 36 is typically 500 μm or less, preferably 1 to 300 μm, and more preferably 5 to 200 μm. Note that the adhesive layer 35 that bonds the second protective film 36 and the polarizer 31 may be formed of any appropriate adhesive. For example, the adhesive which comprises said adhesive bond layer 32 is used. The adhesives constituting the adhesive layer 35 and the adhesive layer 32 may be the same or different. In addition, an easy-adhesive layer may be formed on the surface of the second protective film 36 bonded by the adhesive layer 35. The easy-adhesion layer can be made of any material as appropriate. For example, the material which comprises said easily adhesive layer 33 is used. The materials constituting the easy-adhesive layer and the easy-adhesive layer 33 may be the same or different.

A-7. Hereinafter, a preferable example of the method for producing a polarizing plate of the present invention will be described. First, the polarizer 31 is produced. As a method for producing a polarizer, any appropriate method can be adopted depending on the purpose, materials used, conditions, and the like. Typically, a method in which a polymer film (for example, a PVA film) is subjected to a series of production steps including swelling, dyeing, crosslinking, stretching, washing with water, and drying steps is employed. 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. The polarizer 31 is obtained as described above.

  On the other hand, the protective film 34 is prepared. The protective film 34 is formed by any appropriate method using the cyclic olefin resin described in the section A-2. Specific examples of the method for forming the protective film include a solution casting method, an extrusion method, and a calendar method. Alternatively, a commercially available cyclic olefin resin film may be used as the protective film 34.

  Next, the easy adhesion layer 33 is formed on the protective film 34. Typically, the easy-adhesion layer 33 is formed by applying a solution obtained by dissolving the silane described in the above section A-3 in a solvent or a dispersion obtained by dispersing silane in a dispersion medium on the surface of the protective film and drying it. Is done. Examples of the solvent or dispersion medium include water and organic solvents. As the organic solvent, an organic solvent capable of uniformly dissolving or dispersing the silane and having appropriate volatility is preferable. Specific examples of such organic solvents include alcohols such as methanol, ethanol and propyl alcohol, ketones such as acetone and methyl ethyl ketone, aromatic hydrocarbons such as benzene, toluene and xylene, and halogens such as methylene chloride and chloroform. Hydrocarbons. These may be used alone or in combination of two or more. When a PVA adhesive is used as the adhesive layer 32, methanol, ethanol, propyl alcohol, toluene or a mixed solvent thereof is preferable. As a concentration of the silane solution or the dispersion, any appropriate concentration capable of forming an easy-adhesion layer can be adopted, but it is typically 10 to 70% by weight.

  Any appropriate method can be adopted as a method of applying the silane solution or dispersion on the protective film. Specific examples include a gravure coating method, a dip coating method, a spray coating method, and a casting method. Examples of the method for drying the coating solution include natural drying and heat treatment. The heating temperature in the heat treatment is preferably 20 ° C. or higher and Tg or lower of the protective film, more preferably 80 to 130 ° C. The heating time can vary depending on the heating temperature, but is preferably 30 seconds to 1 hour, more preferably 1 minute to 10 minutes.

  If necessary, any appropriate surface treatment may be applied to the surface of the protective film before applying the silane solution or dispersion. Specific examples of the surface treatment include corona discharge treatment, glow discharge treatment, primer treatment, coating treatment, and chemical treatment. As described above, the protective film 34 on which the easy adhesion layer 33 is formed is obtained.

  Finally, a polarizer is obtained by bonding the polarizer 31 and the protective film 34 through an adhesive (as a result, the adhesive layer 32). At that time, the polarizer 31 and the protective film 34 are bonded so that the easy-adhesion layer 33 and the adhesive layer 32 are adjacent to each other. Usually, the second protective film 36 is bonded to the surface of the polarizer on which the protective film is not bonded via an adhesive (adhesive layer 35). In addition, arbitrary appropriate methods may be employ | adopted as a bonding method of a polarizer and a protective film.

  A pressure-sensitive adhesive layer can be provided on one side or both sides of the polarizing plate obtained as described above. Arbitrary appropriate adhesives can be employ | adopted as an adhesive which forms an adhesive layer. For example, an acrylic adhesive, a silicone adhesive, a rubber adhesive, etc. are mentioned. Among these, an acrylic adhesive is preferable. This is because it has high optical transparency and good adhesion to a liquid crystal cell or the like. Practically, the surface of the pressure-sensitive adhesive layer is covered with any appropriate separator until the polarizing plate is bonded to a retardation film, an image display device, or the like, which will be described later, and contamination can be prevented. The separator can be formed by, for example, a method of providing a release coat with a release agent such as silicone-based, long-chain alkyl-based, fluorine-based, molybdenum sulfide, or the like on any appropriate film as necessary.

B. Image Display Device Next, the image display device of the present invention will be described. 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 described in the above section A is employed as at least one of the polarizing plates 30 and 30 '.

  In the polarizing plate described in the item A, the protective film 34 is preferably disposed on the liquid crystal cell 10 side. With such an arrangement, display unevenness of the liquid crystal display device can be suppressed and viewing angle characteristics can be greatly improved due to the protective film 34 having a low photoelastic coefficient and a low phase difference. As described above, when the pressure-sensitive adhesive layer is formed on the surface of the protective film 34, the protective film 34 is bonded to the liquid crystal cell side via the pressure-sensitive adhesive layer.

  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.

(1) Adhesion state of polarizer and protective film A peel test was performed manually on the bonded polarizer and protective film. After the test, the case where the polarizer and the protective film were well adhered was evaluated as “Good”, and the case where the polarizer and the protective film were separated was evaluated as “Poor”.
(2) Durability The polarizing plate was placed in an environment of 60 ° C., 90% RH or 100% RH, and the time until color loss, unevenness or lifting was confirmed was measured. Note that “color loss” and “unevenness” refer to a state where black display is not possible when the polarizing plate is arranged in crossed Nicols. “Float” refers to a state where the polarizer and the protective film are not in close contact. “Streak” refers to a state in which the protective film and / or the polarizer are adhered to each other with a very small area.

(Reference Example 1: Production of polarizer)
A polyvinyl alcohol film having a thickness of 80 μm (manufactured by Kuraray Co., Ltd.) in a 5% iodine compound aqueous solution (iodine (I) / potassium iodide (KI) weight ratio = 1/10) is a predetermined single polarizer. 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% boric acid + 2% KI aqueous solution for 10 seconds, and the draw ratio is 5 in 4% boric acid + 3% KI aqueous solution. The film was stretched to 5 times, and finally immersed in a 5% KI aqueous solution for 10 seconds. The obtained stretched film was dried in an oven at 40 ° C. for 3 minutes to obtain a polarizer having a thickness of 30 μm.

(Reference Example 2: Production of protective film having an easy-adhesion layer)
One surface of a cyclic olefin-based resin film (manufactured by Nippon Zeon Co., Ltd., trade name: ZEONOR, thickness: 40 μm) was subjected to corona treatment. On the other hand, 67 parts of isopropyl alcohol was mixed with 100 parts of silane (product name: APZ6601 manufactured by Nihon Unicar Co., Ltd.) represented by the chemical formula: NH ₂ CH ₂ NHCH ₂ CH ₂ Si (OC ₂ H ₅ ) ₃ , and 60 parts % Silane solution was prepared. A predetermined amount of the silane solution was applied to the corona-treated surface of the cyclic olefin resin film and dried at 120 ° C. for 2 minutes to obtain a protective film 1 having an easy adhesion layer. The thickness of the easy-adhesion layer after drying was 30 nm. The thickness of the easy adhesion layer was adjusted by changing the coating amount of the silane solution.

(Reference Example 3: Production of protective film having an easy-adhesion layer)
A protective film 2 was produced in the same manner as in Reference Example 2 except that the thickness of the easy-adhesion layer after drying was 300 nm.

  The protective film 1 was bonded to one side of the polarizer obtained in Reference Example 1 with a PVA adhesive so that the easy adhesion layer was on the polarizer side. At the same time, a saponified TAC film (manufactured by Fuji Photo Film Co., Ltd., trade name: Fuji Tac UV80) was bonded to the other surface of the polarizer via the PVA adhesive. After pasting, it was dried at 70 ° C. for 10 minutes to obtain a polarizing plate. The obtained polarizing plate was subjected to the above-described adhesion state evaluation and durability evaluation. The results are shown in Table 1 together with the results of Example 2 and Comparative Examples 1 and 2 described later.

  A polarizing plate was obtained in the same manner as in Example 1 except that an acetoacetyl group-modified PVA adhesive was used in place of the PVA adhesive. The obtained polarizing plate was subjected to the same evaluation as in Example 1. The results are shown in Table 1 above.

(Comparative Example 1)
A polarizing plate was obtained in the same manner as in Example 1 except that the protective film 2 was used instead of the protective film 1. The obtained polarizing plate was subjected to the same evaluation as in Example 1. The results are shown in Table 1 above.

(Comparative Example 2)
A polarizing plate was obtained in the same manner as in Example 2 except that the protective film 2 was used instead of the protective film 1. The obtained polarizing plate was subjected to the same evaluation as in Example 1. The results are shown in Table 1 above.

  As is clear from Table 1, it can be seen that the polarizing plate of the present invention is excellent in adhesion between the polarizer and the protective film. As a result, the polarizing plate of the present invention is excellent in durability (appearance maintaining performance and polarization degree maintaining performance) under high temperature and high humidity. That is, it can be seen that by reducing the thickness of the easy-adhesion layer, both adhesion and durability are remarkably improved.

  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' Retardation film 30, 30 'Polarizing plate 31 Polarizer 32 Adhesive layer 33 Easy-adhesion layer 34 Protective film 100 Liquid crystal display device

Claims (6)

A polarizer, an adhesive layer, an easy adhesive layer, and a protective film made of a film containing a cyclic olefin-based resin as a main component,
The polarizing plate whose said adhesive layer contains the silane which has a reactive functional group, and the thickness is 1-50 nm.   The silane is an isocyanate group-containing alkoxysilane, an amino group-containing alkoxysilane, a mercapto group-containing alkoxysilane, a carboxy-containing alkoxysilane, an epoxy group-containing alkoxysilane, a vinyl unsaturated group-containing alkoxysilane, a halogen group. The polarizing plate according to claim 1, which is selected from the group consisting of containing alkoxysilanes and isocyanurate group-containing alkoxysilanes.   The polarizing plate according to claim 2, wherein the silane is an amino group-containing alkoxysilane.   The second polarizer according to claim 1, further comprising a second protective film on a side opposite to the protective film of the polarizer, wherein the second protective film is made of a film mainly composed of triacetyl cellulose. Polarizing plate.   An image display device comprising the polarizing plate according to claim 1. A liquid crystal cell, and a polarizing plate according to any one of claims 1 to 4 disposed on at least one side of the liquid crystal cell,
The liquid crystal display device by which the protective film which consists of a film which contains the cyclic olefin resin of this polarizing plate as a main component is arrange | positioned at this liquid crystal cell side.

Images