JP4170015B2 - Polarizer - Google Patents

Description

【００５３】
【表２】

【００５４】
【発明の効果】
本発明の偏光板は、ポリビニルアルコール系偏光フィルムと酢酸セルロース系保護フィルムの中間に設けたビニルアルコール系重合体および無機層状化合物を含有する樹脂組成物からなる接着層が耐水性に優れており、そのため高温・高湿度下においても偏光性能の著しい低下が起こることがなく、耐湿熱性に優れている。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a polarizing plate excellent in moisture and heat resistance.
[0002]
[Prior art]
A polarizing plate having a light transmission and blocking function is a basic component of a liquid crystal display (LCD) together with a liquid crystal having a light switching function. This LCD is also used in a wide range of applications such as notebook computers, word processors, liquid crystal color projectors, in-vehicle navigation systems, and liquid crystal televisions in recent years, from small devices such as calculators and wristwatches in the early stages of development. For this reason, there has been a demand for a polarizing plate that is more durable than conventional products, in particular, has excellent heat and humidity resistance at high temperatures and high humidity.
[0003]
In general, a polarizing plate is obtained by uniaxially stretching a polyvinyl alcohol film (hereinafter, abbreviated as “PVA film” and polyvinyl alcohol as a raw material thereof may be abbreviated as “PVA”) to obtain iodine or dichroism. After dyeing with a dye, or after dyeing and uniaxially stretching, a polarizing film obtained by performing a fixing treatment with a boron compound (the dyeing and fixing treatment may be simultaneous) is applied to cellulose triacetate ( TAC) film and acetic acid / cellulose butyrate (CAB) film.
[0004]
Among these, polarizing films dyed with iodine have excellent polarization performance in the initial stage after production, but have poor durability against heat and water, so the polarization performance decreases at high temperatures and high humidity. There is a problem of doing. In order to improve the durability of the polarizing film, PVA is modified, crosslinked by fixing with a boron compound at the time of manufacturing the polarizing film, subjected to heat treatment, or the polarizing film has a low moisture permeability. Although methods such as bonding films made of compounds have been tried, it is difficult to say that either method is sufficient.
[0005]
In addition, polarizing films dyed with dichroic dyes are more durable against heat and water than iodine-based polarizing films, but the orientation of PVA molecules relaxes at high temperatures and high humidity, and the polarizing performance gradually increases. Has a problem that it will decrease.
[0006]
[Problems to be solved by the invention]
An object of the present invention is to provide a polarizing plate excellent in moist heat resistance that eliminates the disadvantages in the prior art and does not cause a significant decrease in polarizing performance even under high temperature and high humidity.
[0007]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present inventors have repeatedly studied paying attention to an adhesive layer between a polyvinyl alcohol polarizing film and a protective film constituting a polarizing plate, and as a result, vinyl alcohol polymers and inorganic layered compounds. And a resin composition containing a crosslinking agent is used as an adhesive layer, and it has been found that a polarizing plate excellent in moisture and heat resistance can be obtained without causing a significant decrease in polarization performance even under high temperature and high humidity. It came to do. That is, the present invention relates to a resin composition comprising a vinyl alcohol polymer (hereinafter sometimes abbreviated as “PVA polymer”) , an inorganic layered compound, and a crosslinking agent on both sides of a polyvinyl alcohol polarizing film. There is provided a polarizing plate comprising a cellulose acetate-based protective film provided through an adhesive layer made of a product.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described in more detail below.
In the present invention, PVA used as a raw material for a polarizing film is produced, for example, by saponifying a polyvinyl ester obtained by polymerizing a vinyl ester. Modified PVA or vinyl ester obtained by graft copolymerization of unsaturated carboxylic acid or derivative thereof, unsaturated sulfonic acid or derivative thereof, α-olefin having 2 to 30 carbon atoms, etc. in a proportion of less than 15 mol% on the main chain of PVA Modified by saponifying a modified polyvinyl ester obtained by copolymerizing an unsaturated carboxylic acid or a derivative thereof, an unsaturated sulfonic acid or a derivative thereof, an α-olefin having 2 to 30 carbon atoms or the like in a proportion of less than 15 mol%. Examples thereof include PVA and a so-called polyvinyl acetal resin obtained by crosslinking a part of hydroxyl groups of unmodified or modified PVA with aldehydes such as formalin, butyraldehyde, and benzaldehyde.
[0009]
Examples of the vinyl ester include vinyl acetate, vinyl formate, vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl versatate, vinyl laurate, vinyl stearate, vinyl benzoate and the like.
[0010]
Monomers used for the modified PVA are copolymerized mainly for the purpose of modification, and are used within a range not impairing the gist of the present invention. Examples of such monomers include olefins such as ethylene, propylene, 1-butene and isobutene; acrylic acid and salts thereof; methyl acrylate, ethyl acrylate, n-propyl acrylate, i-propyl acrylate, and n-acrylate. -Acrylic esters such as butyl, i-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, octadecyl acrylate; methacrylic acid and salts thereof; methyl methacrylate, ethyl methacrylate Methacrylic acid such as n-propyl methacrylate, i-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate, octadecyl methacrylate Esters Acrylamide derivatives such as acrylamide, N-methyl acrylamide, N-ethyl acrylamide, N, N-dimethyl acrylamide, diacetone acrylamide, acrylamide propane sulfonic acid and its salts, acrylamide propyl dimethylamine and its salts, N-methylol acrylamide and its derivatives Methacrylamide derivatives such as methacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, methacrylamidepropanesulfonic acid and its salts, methacrylamidepropyldimethylamine and its salts, N-methylolacrylamide and its derivatives; N-vinyl N-vinylamides such as formamide, N-vinylacetamide, N-vinylpyrrolidone; methyl vinyl ether, ethyl Vinyl ethers such as nyl ether, n-propyl vinyl ether, i-propyl vinyl ether, n-butyl vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether, stearyl vinyl ether; nitriles such as acrylonitrile and methacrylonitrile; vinyl chloride, Vinyl halides such as vinylidene chloride, vinyl fluoride and vinylidene fluoride; allyl compounds such as allyl acetate and allyl chloride; maleic acid and its salts or esters thereof; itaconic acid and its salts or esters thereof; vinyltrimethoxysilane and the like And vinyl silyl compounds; isopropenyl acetate and the like. Of these, α-olefins are preferable, and ethylene is particularly preferable.
[0011]
The modified amount of the modified PVA is preferably less than 15 mol%.
[0012]
The saponification degree of PVA is preferably 90 mol% or more from the viewpoint of durability, more preferably 95 mol% or more, further preferably 98 mol% or more, and most preferably 99 mol% or more.
[0013]
The saponification degree indicates the proportion of units that are actually saponified to vinyl alcohol units among the units that can be converted to vinyl alcohol units by saponification. The saponification degree of PVA was measured by the method described in JIS.
[0014]
The polymerization degree of PVA is preferably 500 or more, more preferably 1000 or more, further preferably 1500 or more, and most preferably 2500 or more from the viewpoint of polarization performance. The upper limit of the degree of PVA polymerization is preferably 8000 or less, and more preferably 6000 or less.
[0015]
The degree of polymerization of the PVA is measured according to JIS K 6726. That is, it is obtained from the intrinsic viscosity measured in 30 ° C. water after re-saponifying and purifying PVA.
[0016]
As a method for producing a PVA film using the PVA, for example, using a PVA solution in which PVA is dissolved in a solvent, a casting film forming method, a wet film forming method (discharging into a poor solvent), a gel Melting a membrane method (a method in which a PVA aqueous solution is once cooled and gelled, and then a solvent is extracted and removed to obtain a PVA film), a combination of these methods, and a hydrous PVA (which may contain an organic solvent, etc.) For example, a melt extrusion film forming method can be employed. Among these, the casting film forming method and the melt extrusion film forming method are preferable because a good polarizing film can be obtained.
[0017]
Examples of the solvent for dissolving PVA used in producing the PVA film include dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylene glycol, glycerin, propylene glycol, diethylene glycol, triethylene glycol, and tetraethylene. Glycol, trimethylolpropane, ethylenediamine, diethylenetriamine, glycerin, water and the like can be mentioned, and one or more of these can be used. Among these, dimethyl sulfoxide, water, or a mixed solvent of glycerin and water is preferably used.
[0018]
The PVA concentration of the PVA solution or water-containing PVA used for producing the PVA film is preferably 10 to 70% by weight, more preferably 10 to 60% by weight, and further preferably 13 to 55% by weight. In particular, 15 to 50% by weight is most preferred. The PVA solution or the hydrous PVA may contain a plasticizer, a surfactant, a dichroic dye, or the like as necessary.
[0019]
When producing the PVA film, it is preferable to add a polyhydric alcohol as a plasticizer. Examples of the polyhydric alcohol include ethylene glycol, glycerin, propylene glycol, diethylene glycol, diglycerin, triethylene glycol, tetraethylene glycol, trimethylolpropane, etc., and one or more of these are used. can do. Among these, diglycerin, ethylene glycol, and glycerin are preferably used because of the effect of improving stretchability.
[0020]
The addition amount of the polyhydric alcohol is preferably 1 to 30 parts by weight, more preferably 3 to 25 parts by weight, and most preferably 5 to 20 parts by weight with respect to 100 parts by weight of PVA. If the amount is less than 1 part by weight, the dyeability and stretchability may be lowered. If the amount is more than 30 parts by weight, the PVA film becomes too flexible and the handleability may be lowered.
[0021]
When producing a PVA film, it is preferable to add a surfactant. The type of the surfactant is not particularly limited, but an anionic or nonionic surfactant is preferable. As the anionic surfactant, for example, a carboxylic acid type such as potassium laurate, a sulfate type such as octyl sulfate, and a sulfonic acid type anionic surfactant such as dodecylbenzenesulfonate are suitable. Nonionic surfactants include, for example, alkyl ether types such as polyoxyethylene oleyl ether, alkylphenyl ether types such as polyoxyethylene octylphenyl ether, alkyl ester types such as polyoxyethylene laurate, and polyoxyethylene laurylamino. Alkylamine type such as ether, alkylamide type such as polyoxyethylene lauric acid amide, polypropylene glycol ether type such as polyoxyethylene polyoxypropylene ether, alkanolamide type such as oleic acid diethanolamide, polyoxyalkylene allyl phenyl ether, etc. Nonionic surfactants such as allyl phenyl ether type are preferred. These surfactants can be used alone or in combination of two or more.
[0022]
The addition amount of the surfactant is preferably 0.01 to 1 part by weight with respect to 100 parts by weight of PVA, more preferably 0.02 to 0.5 part by weight, and most preferably 0.05 to 0.3 part by weight. . If the amount is less than 0.01 part by weight, the effect of improving stretchability and dyeing property is difficult to appear, and if it is more than 1 part by weight, it may elute on the surface of the PVA film and cause blocking, and the handleability may decrease. .
[0023]
The thickness of the PVA film is preferably 5 to 150 μm, more preferably 20 to 100 μm, still more preferably 30 to 90 μm, and most preferably 35 to 80 μm.
[0024]
In order to produce a polarizing film from a PVA film, for example, the PVA film may be dyed, uniaxially stretched, fixed, dried, and further subjected to heat treatment as necessary. There is no. Moreover, you may perform uniaxial stretching twice or more.
[0025]
Dyeing can be performed before uniaxial stretching, during uniaxial stretching, or after uniaxial stretching. As dyes used for dyeing, iodine-potassium iodide; direct black 17, 19, 154; direct brown 44, 106, 195, 210, 223; direct red 2, 23, 28, 31, 37, 39, 79, 81 , 240, 242, 247; Direct Blue 1, 15, 22, 78, 90, 98, 151, 168, 202, 236, 249, 270; Direct Violet 9, 12, 51, 98; Direct Green 1, 85; Direct Dichroic dyes such as yellow 8, 12, 44, 86, 87; direct orange 26, 39, 106, 107 can be used in one kind or a mixture of two or more kinds. Ordinary dyeing is generally performed by immersing the PVA film in a solution containing the above-mentioned dye, but the processing conditions and processing method are particularly limited, such as mixing with the PVA film to form a film. is not.
[0026]
For uniaxial stretching, a wet stretching method in which a PVA film is stretched in a warm aqueous solution (may be in a solution containing the dye or a fixing treatment bath described later), or a dry heat stretching method in which the PVA film after water is stretched in air. Can be used. The stretching temperature is not particularly limited, but is preferably 30 to 90 ° C. when the PVA film is stretched (wet stretching) in warm water, and 50 to 180 ° C. when it is dry heat stretched. Further, the stretching ratio of uniaxial stretching (total stretching ratio in the case of multistage uniaxial stretching) is preferably 4 times or more, and most preferably 5 times or more from the viewpoint of polarization performance. The upper limit of the stretching ratio is not particularly limited, but it is preferably 8 times or less because uniform stretching is easily obtained. The thickness of the film after stretching is preferably from 3 to 75 μm, more preferably from 5 to 50 μm.
[0027]
Fixing treatment is often performed for the purpose of strengthening the adsorption of the dye to the PVA film. Usually, boric acid and / or boron compounds are added to the treatment bath used for the fixing treatment. Moreover, you may add an iodine compound in a processing bath as needed.
[0028]
The drying treatment (heat treatment) of the stretched film is preferably performed at 30 to 150 ° C, more preferably 50 to 150 ° C.
[0029]
A polarizing plate is produced by attaching a cellulose acetate-based protective film to both sides of the polarizing film obtained as described above via an adhesive layer. As the cellulose acetate-based protective film, a cellulose triacetate film, a cellulose diacetate film, an acetic acid / butyric acid cellulose film, or the like is used. The cellulose acetate-based protective film has been subjected to a known physical treatment such as plasma treatment, plasma coating treatment, glow discharge treatment, corona discharge treatment, high frequency treatment, electron beam treatment, or chemical treatment with an acid or alkali solution. Also good. There is no restriction | limiting in particular about the thickness of a cellulose acetate type protective film, The thing of thickness of 25-200 micrometers is used normally.
[0030]
In the present invention, the PVA polymer used as a component of the resin composition constituting the adhesive layer is produced by saponifying a polyvinyl ester obtained by polymerizing a vinyl ester. Examples of vinyl esters include vinyl acetate, vinyl formate, vinyl propionate, vinyl butyrate, vinyl pivalate, vinyl versatate, vinyl laurate, vinyl stearate, vinyl benzoate, etc. Used.
[0031]
Moreover, by using a modified PVA polymer produced by saponifying a modified polyvinyl ester copolymerized with a vinyl ester and an α-olefin having 2 to 30 carbon atoms as a component of the resin composition, The heat and humidity resistance under high humidity can be further improved. Examples of such α-olefins include ethylene, propylene, 1-butene, and isobutene. Among these, ethylene is preferable. The α-olefin content in the modified PVA polymer is 1 to 15 mol%, preferably 2 to 15 mol%, more preferably 3 to 15 mol%. When the content of α-olefin is less than 1 mol%, the effect due to the inclusion of α-olefin may not be sufficiently exhibited, and when the content of α-olefin is excessively increased, modified PVA This tendency becomes significant when the water-soluble nature of the polymer decreases and the characteristics inherent to PVA tend to be impaired, and the α-olefin content exceeds 15 mol%.
[0032]
When the vinyl ester and the α-olefin are copolymerized, a copolymerizable unsaturated monomer can be used as long as it does not impair the effects of the present invention. Examples of such unsaturated monomers include acrylic acid, methacrylic acid, phthalic acid, phthalic anhydride, maleic acid, maleic anhydride, itaconic acid, itaconic anhydride, acrylonitrile, methacrylonitrile, acrylamide-2-methylpropane List sulfonic acid and its sodium salt, sodium vinyl sulfonate, sodium allyl sulfonate, ethyl vinyl ether, n-butyl vinyl ether, vinyl chloride, vinyl bromide, vinyl fluoride, vinylidene chloride, vinylidene fluoride, tetrafluoroethylene, etc. Can do.
The content of the unsaturated monomer in the modified PVA polymer is preferably less than 10 mol%, more preferably less than 5 mol%, and particularly preferably less than 2 mol%.
[0033]
The degree of polymerization of the PVA polymer is preferably 100 to 3000, more preferably 200 to 2000, and particularly preferably 300 to 1500.
When the degree of polymerization of the PVA polymer is less than 100, the adhesive force and strength of the adhesive layer formed from the resin composition containing the PVA polymer and the inorganic layered compound tend to be insufficient. Moreover, when the polymerization degree of the PVA polymer exceeds 3000, the viscosity of the adhesive solution prepared from the resin composition containing the PVA polymer and the inorganic layered compound becomes too high. There is a tendency that the workability at the time of coating is lowered and the productivity of the polarizing plate is lowered.
[0034]
The degree of polymerization of the PVA polymer is measured according to JIS K 6726. That is, it is obtained from the intrinsic viscosity measured in water at 30 ° C. after re-saponifying and purifying the PVA polymer.
[0035]
The saponification degree of the PVA polymer is preferably 90 mol% or more, more preferably 95 mol% or more from the viewpoint of durability of the adhesive layer formed from the resin composition containing the PVA polymer and the inorganic layered compound, 99 mol% or more is particularly preferable.
[0036]
The saponification degree indicates the proportion of units that are actually saponified to vinyl alcohol units among the units that can be converted to vinyl alcohol units by saponification. The saponification degree of the PVA polymer was measured by the method described in JIS.
[0037]
The inorganic layered compound used in the present invention is an inorganic compound having a structure in which atoms are strongly bonded by a covalent bond or the like and densely arranged, and stacked substantially in parallel by weak forces such as van der Waals force and electrostatic force. Say. The inorganic layered compound is the distance between sheets (which can be determined by the X-ray diffraction method) from the viewpoint of the water resistance of the target polarizing plate, and the average particle diameter of the particles (if the particles are plate-like, they are flat surfaces). The value obtained by dividing the average particle diameter in the direction is preferably in the range of 100 to 10000, more preferably in the range of 500 to 9000, and particularly preferably in the range of 1000 to 8000. The inorganic layered compound is preferably used by blending particles having different average particle diameters.
[0038]
Examples of the layered inorganic compound that can be used in the present invention include mica, talc, montmorillonite, kaolinite, vermiculite, and the like.
[0039]
Among the layered inorganic compounds described above, a layered inorganic compound having a property of swelling or cleaving when immersed in an organic solvent or an inorganic solvent (in this specification, such layered inorganic compounds are collectively referred to as “swellable inorganic compounds”). (Referred to as “compound”) is preferably used because it exhibits particularly excellent water resistance when combined with a PVA polymer to form a resin composition. Here, the swelling of the layered inorganic compound refers to a phenomenon in which, when the layered inorganic compound is immersed in a large excess of an organic solvent or an inorganic solvent, the interval between the layers as viewed by X-ray diffraction increases. Cleaving refers to a phenomenon in which a peak indicating the distance between layers is reduced or disappears when a similar operation is performed. Among the swellable inorganic compounds, those that swell or cleave with water are most preferable from the viewpoint of obtaining a polarizing plate excellent in moisture and heat resistance.
[0040]
Examples of the swellable inorganic compound include vermiculite, montmorillonite, and a synthetic swellable fluorinated mica in which lithium, sodium and the like are intercalated between layers. Among them, montmorillonite having a cleaving property in an aqueous solvent and swellable fluorine mica are preferable, and particularly excellent in the cleaving property, and since it has properties such as quality uniformity and high purity due to being a synthetic material, lithium and sodium between the layers. A swellable fluorine mica intercalated with the like is optimal.
[0041]
Viewpoint using PVA polymer and inorganic laminar compound in manufacturing the resin composition, For the compounding ratio of the PVA polymer and the inorganic layered compound, impart barrier properties to the adhesive layer formed from the resin composition Thus, the weight ratio of the inorganic layered compound to both the PVA polymer and the inorganic layered compound (inorganic layered compound / (PVA polymer + inorganic layered compound)) is 3% by weight or more, and 5% by weight or more is particularly preferable. 8% by weight is most preferred. In addition, the weight ratio of the inorganic layered compound to both the PVA polymer and the inorganic layered compound is from the viewpoint of realizing the uniform application by suppressing the increase in the viscosity of the adhesive solution and the transparency of the adhesive layer. 30% by weight or less. When the weight ratio of the inorganic layered compound exceeds 30% by weight , the viscosity of the adhesive solution becomes too high, and the workability when applying the adhesive solution tends to be lowered .
[0042]
In the present invention, as a component of the resin composition, a PVA polymer crosslinking agent is further added to the PVA polymer and the layered inorganic compound to improve the water resistance of the adhesive layer . As the crosslinking agent that can be used for this purpose include tetraisopropyl titanate, a diisopropoxy bis (acetylacetone) titanium, such as titanate compound.
[0043]
Of the above-mentioned crosslinking agents , titanium compounds such as tetraisopropyl titanate and diisopropoxybis (acetylacetone) titanate are optimal because of their excellent balance between viscosity and adhesive strength.
[0044]
The amount of the crosslinking agent added is 0.5% by weight or more, more preferably 1% by weight or more , and particularly preferably 2% by weight or more in terms of (crosslinking agent / (PVA polymer + crosslinking agent)). When the weight ratio of the crosslinking agent to both the PVA polymer and the crosslinking agent is less than 0.5% by weight, the effect is not exhibited by adding the crosslinking agent. Further, the weight ratio of the crosslinking agent to both the PVA polymer and the crosslinking agent is 30% by weight or less . When the weight ratio of the crosslinking agent exceeds 30% by weight , the transparency and water resistance of the adhesive layer formed from the resin composition tend to be lowered.
[0045]
There is no particular limitation on the method for producing the adhesive solution from the resin composition containing the PVA polymer and the inorganic layered compound. For example, (1) the PVA polymer is dispersed in the layered inorganic compound in water in advance. (2) A method of preparing a dispersion of a layered inorganic compound and a PVA polymer solution separately and blending them, (3) Water, PVA polymer and layered Examples include a method in which an inorganic compound is charged into a container at a time and dissolved. When a cross-linking agent is further added, the cross-linking agent is added at an arbitrary stage when the adhesive solution is manufactured according to the above-described method, or when the adhesive solution manufactured according to the above-described method is applied. Examples of the method include, but are not limited to, a method in which a solution of a crosslinking agent prepared separately in advance in an adhesive solution is applied while mixing.
[0046]
As for the application amount of the adhesive solution, the thickness (the thickness of the adhesive layer) measured in a dry state is 0.5 to 20 μm , and more preferably 1 to 5 μm. When the thickness of the adhesive layer is less than 0.5 μm, sufficient water resistance may not be exhibited. On the other hand, when it exceeds 20 μm, the load during drying of the adhesive solution tends to increase, which is a problem in producing a polarizing plate. It is.
[0047]
【Example】
EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In the following examples and comparative examples, “%” and “parts” are based on weight unless otherwise specified. Moreover, the dichroic ratio in an Example and a comparative example was evaluated with the following method.
[0048]
Dichroic ratio:
The dichroic ratio was used as an index for evaluating the polarization performance of the obtained polarizing film. This dichroic ratio is a transmittance Ts obtained by measuring and calculating with a spectrophotometer in a C light source and a two-degree field of view in accordance with the Japan Electronic Machinery Manufacturers Association (EIAJ) LD-201-1983. (%) And polarization degree P (%) were used to obtain the following formula.
Dichroic ratio = log (Ts / 100− (Ts / 100) × P / 100) / log (Ts / 100 + (Ts / 100) × P / 100)
[0049]
Example 1
1) Preparation of adhesive solution As a vinyl alcohol polymer, ethylene-modified polyvinyl alcohol having a polymerization degree of 500, a saponification degree of 99.0 mol%, and an ethylene content of 8 mol% was dissolved in hot water, and a 20% solution (resin solution) was obtained. A) was prepared.
As an inorganic layered compound, swellable fluorine mica (ME-100 manufactured by Coop Chemical Co., Ltd.) is dispersed in water so as to have a concentration of 6%, and this is stirred for 15 minutes using a home-use mixer to obtain a dispersion (filler dispersion). Liquid B) was prepared.
Resin solution A and filler dispersion B are mixed so that the ratio of fluorine mica to the total solid content is 20%, and further, tetraisopropyl titanate as a crosslinking agent is mixed at a ratio of 2% by weight with respect to the total solid content. Then, an adhesive solution was prepared.
2) Preparation of polarizing plate The polyvinyl alcohol polarizing film was gravure coated with the adhesive solution prepared in 1) above, and a cellulose triacetate film having a saponified surface was bonded thereto. This cellulose triacetate film is bonded twice on each side, and after the cellulose triacetate film is bonded to both sides of the polarizing film, it is dried and bonded at 50 ° C., and the cellulose triacetate film is attached to both sides of the polarizing film. A combined polarizing plate was obtained. When the cross section of the polarizing plate was observed, the thickness of the adhesive layer was 3 μm, and no coating spots of the adhesive solution were observed.
The transmittance of the obtained polarizing plate was 42.57%, the degree of polarization was 99.98%, and the dichroic ratio calculated from these values was 58.22. The polarizing plate was put in a constant temperature and humidity machine at 80 ° C. and 90% RH, and a durability test for 1000 hours was performed. The polarization performance after 1000 hours was 43.64%, the degree of polarization 99.85%, and the dichroic ratio 53.51.
[0050]
Example 2 and Reference Examples 1-3
A polarizing plate was produced in the same manner as in Example 1 except that the types and addition amounts of the vinyl alcohol polymer, the inorganic layered compound, and the crosslinking agent used in the adhesive solution were changed as shown in Table 1. Table 2 shows the results obtained for the transmittance, the degree of polarization, and the dichroic ratio of the obtained polarizing plate. Further, a durability test was conducted in the same manner as in Example 1, and the obtained results are shown in Table 2.
[0051]
Comparative Examples 1 and 2
A polarizing plate was produced in the same manner as in Example 1 except that the types and addition amounts of the vinyl alcohol polymer, the inorganic layered compound, and the crosslinking agent used in the adhesive solution were changed as shown in Table 1. Table 2 shows the results obtained for the transmittance, the degree of polarization, and the dichroic ratio of the obtained polarizing plate. Further, a durability test was conducted in the same manner as in Example 1, and the obtained results are shown in Table 2.
[0052]
[Table 1]

[0053]
[Table 2]

[0054]
【The invention's effect】
In the polarizing plate of the present invention, an adhesive layer comprising a resin composition containing a vinyl alcohol polymer and an inorganic layered compound provided between the polyvinyl alcohol polarizing film and the cellulose acetate protective film has excellent water resistance, Therefore, the polarization performance does not significantly decrease even under high temperature and high humidity, and the heat and moisture resistance is excellent.

Claims (1)

On both sides of the polyvinyl alcohol polarizing film, 3 to 30 wt% of an inorganic layered compound having modified vinyl alcohol polymer containing 15 mol% of the α- olefin units having 2 to 30 carbon atoms, a swellable (inorganic laminar Compound / (modified vinyl alcohol polymer + inorganic layered compound)) and a crosslinking agent comprising a titanium compound in an amount of 0.5 to 30% by weight (crosslinking agent / (modified vinyl alcohol polymer + crosslinking agent)) . An adhesive solution containing a resin composition is coated, and a cellulose acetate-based protective film is bonded to the adhesive solution . The adhesive layer has a thickness of 0.5 to 20 μm and is placed in a constant temperature and humidity machine at 80 ° C. and 90% RH. A polarizing plate having a dichroic ratio of 53.46 or more when subjected to a durability test for 1000 hours.