TWI716454B - Polarizer and manufacturing method thereof - Google Patents

Abstract

The present invention provides a thin polarizer with excellent quality. According to the manufacturing method of the polarizer of the present invention, a thin polarizer with excellent quality can be obtained. The manufacturing method of the polarizing element of the present invention includes the following steps in sequence: coating a coating liquid containing polyvinyl alcohol resin on a resin substrate to form a resin layer to produce a laminate; increasing the polyvinyl alcohol contained in the resin layer The step of saponification degree of the similar resin; and the step of dyeing the aforementioned resin layer.

Description

Polarizer and manufacturing method thereof

The invention relates to a polarizer and a manufacturing method thereof.

Background Art A method has been proposed in which a resin layer is formed by coating a polyvinyl alcohol aqueous solution on a resin substrate, and the laminate is stretched and dyed to obtain a polarizer (for example, Patent Document 1). According to such a method, a polarizer with a thin thickness (for example, 8 μm or less) can be obtained, and therefore, it has attracted attention because it can contribute to the thinning of an image display device, for example. Prior technical literature Patent literature

Patent Document 1: Japanese Patent Application Publication No. 2000-338329

Summary of the Invention Problems to be Solved by the Invention However, the above-mentioned method uses a resin base material, and therefore, there is a problem that it is liable to be restricted in the manufacturing process. For example, since the coating temperature of the above-mentioned solution is limited due to the difference in the glass transition temperature Tg of the resin substrate, coating at high temperatures is difficult. On the other hand, if the coating temperature is lowered, the gelation of polyvinyl alcohol is promoted, and impurities are likely to be generated on the coating film. In addition, as the viscosity of the solution increases, coating defects such as streaks will increase. Therefore, since it is easily restricted in the manufacturing process, there is a problem that the quality (for example, humidification reliability) of the obtained polarizer is insufficient.

The present invention was completed in order to solve the above-mentioned problems, and its main purpose is to provide a thin polarizer with excellent quality. Means to solve the problem

The polarizer of the present invention is composed of a resin film containing polyvinyl alcohol resin. The degree of saponification of the polyvinyl alcohol resin is 99.5 mol% or more, and the thickness of the resin film is 8 μm or less. According to another aspect of the present invention, a method for manufacturing a polarizer is provided. The manufacturing method sequentially includes the steps of: coating a coating solution containing polyvinyl alcohol resin on a resin substrate to form a resin layer to produce a laminate; increasing the degree of saponification of the polyvinyl alcohol resin contained in the resin layer的 step; and the step of dyeing the resin layer. In one embodiment, the degree of saponification of the polyvinyl alcohol resin contained in the coating liquid is less than 99.5 mol%. In one embodiment, the degree of saponification of the polyvinyl alcohol-based resin contained in the resin layer is increased by saponification. In one embodiment, the degree of saponification of the polyvinyl alcohol-based resin is increased by 0.1 mol% or more by the above-mentioned saponification. In one embodiment, the saponification is performed by contacting an alkaline solution with the resin layer. In one embodiment, the manufacturing method further includes a step of stretching the laminate. In one embodiment, the aforementioned stretching includes underwater stretching. In one embodiment, the underwater stretching is performed after the dyeing step. Effect of invention

According to the present invention, a thin polarizer with excellent quality can be obtained.

Modes for Implementation Explanation One embodiment of the present invention will be described below, but the present invention is not limited to these embodiments.

A. Polarizing member The polarizing member of the present invention is composed of a resin film containing polyvinyl alcohol-based resin (hereinafter referred to as "PVA-based resin"). Examples of PVA-based resins include polyvinyl alcohol and ethylene-vinyl alcohol copolymers. Polyvinyl alcohol is obtained by saponifying polyvinyl acetate. The ethylene-vinyl alcohol copolymer is obtained by saponifying an ethylene-vinyl acetate copolymer.

The degree of saponification of the PVA-based resin is 99.5 mol% or more, preferably 99.8 mol% or more. The upper limit of the degree of saponification is 100 mol%. By allowing the PVA-based resin contained in the polarizer to satisfy such a degree of saponification, excellent humidification reliability can be achieved. In addition, the degree of saponification can be determined based on JIS K 6726-1994.

The average degree of polymerization of the PVA-based resin can be appropriately selected according to the purpose. The average degree of polymerization is usually 1000 to 10000, preferably 1200 to 6000, and still more preferably 2000 to 5000. In addition, the average degree of polymerization can be obtained based on JIS K 6726-1994.

The thickness of the polarizer (resin film) of the present invention is 8 μm or less, preferably 5 μm or less. On the other hand, the thickness of the polarizer is preferably 1.0 μm or more, and more preferably 2.0 μm or more.

The polarizer typically contains a dichroic substance. Specific examples of dichroic substances include iodine and organic dyes. These can be used alone or in combination of two or more kinds. As the dichroic substance, iodine is preferably used.

The polarizer preferably exhibits absorption dichroism at any wavelength from 380 nm to 780 nm. The monomer transmittance of the polarizer is preferably 40.0% or more, more preferably 42.0% or more, still more preferably 42.5% or more, particularly preferably 43.0% or more. The degree of polarization of the polarizer is preferably 99.8% or more, more preferably 99.9% or more, and still more preferably 99.95% or more. In addition, the degree of polarization (P) is calculated by measuring the monomer transmittance (Ts), parallel transmittance (Tp), and orthogonal transmittance (Tc) according to the following formula. Here, Ts, Tp, and Tc are Y values measured by a 2-degree field of view (C light source) of JIS Z 8701 and corrected for visibility. Polarization (P) (%) = {(Tp-Tc)/(Tp＋Tc)} ^1/2 ×100

B. The manufacturing method of the polarizing element The manufacturing method of the polarizing element of the present invention includes the following steps: forming a resin layer containing PVA-based resin on a resin substrate to produce a laminate, and increasing the degree of saponification of the PVA-based resin contained in the resin layer A step of. Specifically, the step of increasing the degree of saponification of the PVA-based resin is performed after the step of producing the laminate. As a result, it is possible to manufacture a polarizer with excellent quality (for example, humidification reliability) while ensuring the film formability of the PVA-based resin layer (for example, preventing the generation of impurities and streaks).

B-1. Production of laminated body Fig. 1 is a partial cross-sectional view of a laminated body according to an embodiment of the present invention. The laminate 10 has a resin base material 11 and a resin layer 12. The laminate 10 is typically produced by forming a resin layer 12 on a long resin substrate 11. The resin layer 12 is formed by applying a coating liquid containing a PVA-based resin on the resin substrate 11 and drying if necessary.

As a material for forming the above-mentioned resin substrate, any suitable material can be used. Examples include: ester resins such as polyethylene terephthalate resins, cycloolefin resins, olefin resins such as polypropylene, (meth)acrylic resins, polyamide resins, and polycarbonate resins. Resin, and its copolymer resin.

The glass transition temperature (Tg) of the resin substrate is preferably 120°C or lower, and more preferably 100°C or lower. This is because when the laminate is stretched, it is possible to ensure sufficient stretchability while suppressing the crystallization of the resin layer (PVA-based resin). As a result, a polarizer having excellent polarization characteristics can be manufactured. On the other hand, the glass transition temperature of the resin substrate is preferably 60°C or higher. In addition, the glass transition temperature (Tg) is a value calculated based on JIS K7121.

The thickness of the resin substrate is preferably 20 μm to 300 μm, and more preferably 50 μm to 200 μm. The surface of the resin substrate may be subjected to surface modification treatment (for example, corona treatment, etc.) or an easy-adhesion layer may be formed. By such a treatment, a laminate having excellent adhesion between the resin substrate and the resin layer can be obtained.

As described above, the coating liquid contains PVA-based resin. The degree of saponification of the PVA-based resin contained in the coating liquid is preferably less than 99.5 mol%, and more preferably 99.0 mol% or less. By using a PVA-based resin with such a degree of saponification, it is possible to sufficiently ensure the film-forming properties of the resin substrate. Specifically, when coating a coating liquid on a resin substrate, if the coating temperature is too high, defects such as deformation of the resin substrate may occur. However, by reducing the degree of saponification of the PVA-based resin, the temperature of the coating liquid can be reduced. Lowering the viscosity of the coating liquid can prevent the gelation of the PVA-based resin.

The aforementioned coating liquid is typically a solution obtained by dissolving the aforementioned PVA-based resin in a solvent. As the solvent used in the coating solution, for example, water, dimethyl sulfide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, various glycols, trimethylolpropane Such as polyols, ethylenediamine, diethylenetriamine and other amines. These can be used alone or in combination of two or more kinds. Among these, water is preferable. The PVA-based resin concentration of the solution can be set to any appropriate value. For example, it is set according to the degree of polymerization, saponification degree, etc. of the PVA-based resin. The PVA-based resin concentration of the solution is, for example, 3 parts by weight to 20 parts by weight with respect to 100 parts by weight of the solvent.

Additives may also be contained in the above-mentioned coating liquid. As an additive, a plasticizer, a surfactant, etc. are mentioned, for example. Examples of plasticizers include polyols such as ethylene glycol and glycerol. Examples of the surfactant include nonionic surfactants. These additives can be used for the purpose of further improving the uniformity, dyeability, and stretchability of the obtained resin layer. Moreover, as an additive, an easy-adhesion component can be mentioned, for example. By using easy-adhesive components, the adhesion between the resin substrate and the resin layer can be improved. As a result, defects such as peeling of the resin layer from the resin substrate can be suppressed, and the dyeing described later can be performed well. As the easy-adhesive component, for example, modified PVA such as acetoxy-modified PVA is used.

As the coating method of the coating liquid, any appropriate method can be adopted. For example, a roll coating method, a spin coating method, a wire bar coating method, a dip coating method, a die coating method, a curtain coating method, a spray coating method, a blade coating method (comma coating method, etc.) can be mentioned.

The coating temperature (for example, the temperature of the coating liquid when the coating liquid is applied) can be set to any appropriate value according to the resin substrate used. The coating temperature is, for example, 20°C or higher, preferably 50°C or higher. On the other hand, the coating temperature is less than Tg with respect to the glass transition temperature (Tg) of the resin substrate, preferably Tg(°C)-20°C or less, and more preferably Tg(°C)-30°C or less.

When drying the coated film obtained by coating, the drying temperature is, for example, 20°C or higher, preferably 50°C or higher. On the other hand, the drying temperature is preferably less than the glass transition temperature (Tg) of the resin substrate, and more preferably Tg (°C)-10°C or less.

The thickness of the resin layer (before stretching) is preferably 3 μm to 40 μm, more preferably 3 μm to 20 μm, and particularly preferably 3 μm to 15 μm.

B-2. Adjustment of the degree of saponification As a method of increasing the degree of saponification of the above-mentioned PVA-based resin, any appropriate method can be adopted. Preferably, a method of saponifying the PVA-based resin contained in the resin layer formed on the resin substrate is adopted. The unsaponified groups of the PVA resin are saponified by the saponification treatment, and the degree of saponification can be increased. As a result, the obtained polarizer is thin and can provide excellent humidification reliability.

Preferably, the degree of saponification of the PVA-based resin contained in the resin layer is increased by more than 0.1 mol% by saponification treatment, more preferably by more than 0.5 mol%, particularly preferably by more than 1.0 mol%. The saponification degree of the PVA-based resin after the saponification treatment is typically more than 99.0 mol%, for example, 99.3 mol% or more, preferably 99.5 mol% or more, and more preferably 99.8 mol% or more.

In one embodiment, the saponification treatment is performed by contacting an alkaline solution with the resin layer. As the contact method of the alkaline solution, any appropriate method can be adopted. For example, a method of dropping, coating, and spraying an alkaline solution to the resin layer; and a method of immersing the resin layer (layered body) in the alkaline solution.

As the basic compound contained in the above-mentioned basic solution, any suitable basic compound can be used. Examples of basic compounds include: hydroxides of alkali metals such as sodium hydroxide, potassium hydroxide, and lithium hydroxide; hydroxides of alkaline earth metals such as calcium hydroxide; inorganic alkali metal salts such as sodium carbonate; acetic acid Organic alkali metal salts such as sodium; ammonia water, etc. These can be used alone or in combination of two or more kinds. Among these, hydroxides of alkali metals are preferred; sodium hydroxide, potassium hydroxide, and lithium hydroxide are more preferred; and sodium hydroxide is particularly preferred.

Examples of the solvent used in the alkaline solution include alcohols such as water, ethanol, and methanol, ethers, benzene, chloroform, and mixed solvents thereof. Among these, water and alcohol are preferably used.

The concentration of the alkaline solution is, for example, 0.01N to 5N, preferably 0.05N to 3N, and still more preferably 0.1N to 2.5N. When the alkaline solution is an aqueous sodium hydroxide solution, its concentration is preferably 1.0w% or more, and more preferably 2w%-8w%.

The liquid temperature of the alkaline solution is, for example, 20°C or higher, preferably 25°C to 50°C. The contact time of the alkaline solution is set according to, for example, the thickness of the resin layer, the type and concentration of the alkaline compound contained in the alkaline solution. The contact time is, for example, 5 seconds to 30 minutes, preferably 5 seconds to 5 minutes.

The alkaline solution can be removed from the resin layer by any appropriate method after contacting the resin layer. Examples of the method of removing the alkaline solution include washing, wiping, suction, and drying. The removal based on cleaning is preferred. As the cleaning liquid used for cleaning, for example, alcohol such as water, methanol, and ethanol is used.

B-3. Dyeing The above resin layer can be dyed. As a method of dyeing, for example, a method of immersing a resin layer (laminate) in a dyeing solution containing the above-mentioned dichroic substance, a method of coating the dyeing solution on the resin layer, and spraying the dyeing solution on the resin layer On the method. The method of impregnating the resin layer in the dyeing liquid is preferably used.

The above-mentioned dyeing liquid is preferably an iodine aqueous solution. The blending amount of iodine is preferably 0.1 parts by weight to 0.5 parts by weight with respect to 100 parts by weight of water. In order to increase the solubility of iodine with respect to water, it is preferable to blend iodide in the iodine aqueous solution. Examples of iodides include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide. Wait. Among these, potassium iodide is preferred. The blending amount of the iodide is preferably 0.02 parts by weight to 20 parts by weight, and more preferably 0.1 parts by weight to 10 parts by weight with respect to 100 parts by weight of water.

The liquid temperature during dyeing of the dyeing liquid is preferably 20°C to 50°C. The immersion time is preferably 5 seconds to 5 minutes. In addition, the dyeing conditions (concentration, liquid temperature, immersion time) can be set so that the degree of polarization or monomer transmittance of the finally obtained polarizer is within a predetermined range.

The above-mentioned saponification is preferably performed before dyeing the resin layer. This is to impart sufficient polarization characteristics to the obtained polarizer.

B-4. Stretching The above-mentioned laminate can be stretched. As the stretching method of the laminate, any appropriate method can be adopted. Specifically, it may be fixed-end stretching (for example, a method using a stretch tenter) or free-end stretching (for example, a method of uniaxially stretching the laminate through rolls with different peripheral speeds). In addition, it may be simultaneous biaxial stretching (for example, a method using a simultaneous biaxial stretching machine) or sequential biaxial stretching. The stretching of the laminate may be performed in one stage or in multiple stages. When it is performed in a plurality of stages, the stretching ratio of the laminate described later is the product of the stretching ratios of each stage.

As the stretching direction of the laminate, any appropriate direction can be selected. In one embodiment, stretching is performed in the longitudinal direction of the elongated laminate. Specifically, conveying the laminate in the longitudinal direction is the conveying direction (MD). In another embodiment, stretching is performed in the width direction of the long laminate. Specifically, the laminated body is conveyed in the longitudinal direction in a direction (TD) orthogonal to the conveying direction (MD).

The laminate is preferably stretched from the original length to 4.0 times or more, and more preferably 5.0 times or more.

The stretching method is not particularly limited. For example, it may be an in-air stretching method or an underwater stretching method that is performed while immersing the laminate in a stretching bath.

The stretching temperature of the laminate can be set to any appropriate value according to the forming material of the resin substrate, the stretching method, and the like. In the air stretching method, the stretching temperature is preferably above the glass transition temperature (Tg) of the resin substrate, more preferably above the glass transition temperature (Tg) of the resin substrate + 10°C or above, particularly preferably Tg + 15 ℃ above. On the other hand, the stretching temperature of the laminate is preferably 170°C or lower. By stretching at such a temperature, it is possible to suppress the rapid progress of the crystallization of the PVA-based resin, and to suppress defects caused by the crystallization (for example, hindering the orientation of the PVA-based resin by stretching).

When an underwater stretching method is adopted as the stretching method, the liquid temperature of the stretching bath is preferably 40°C to 85°C, and more preferably 50°C to 85°C. As long as it is such a temperature, it is possible to stretch to a high magnification while suppressing the dissolution of the PVA-based resin. Specifically, as described above, the glass transition temperature (Tg) of the resin substrate is preferably 60° C. or higher in consideration of the relationship with the formation of the resin layer. In this case, if the stretching temperature is lower than 40°C, there is a concern that stretching cannot be performed well even if the plasticization of the resin base material by water is considered. On the other hand, the higher the temperature of the stretching bath, the higher the solubility of the PVA-based resin, and there is a concern that excellent polarization characteristics cannot be obtained. The immersion time for immersing the laminate in the stretching bath is preferably 15 seconds to 5 minutes.

In the case of adopting the underwater stretching method, it is preferable that the laminate is immersed in a boric acid aqueous solution for stretching (boric acid underwater stretching). By using an aqueous solution of boric acid as a stretching bath, the PVA-based resin layer can be imparted with rigidity against tension applied during stretching and water-insoluble water resistance. The boric acid aqueous solution is preferably obtained by dissolving boric acid and/or borate in water as a solvent. The boric acid concentration is preferably 1 to 10 parts by weight with respect to 100 parts by weight of water. By setting the concentration of boric acid to 1 part by weight or more, the dissolution of the PVA-based resin can be effectively suppressed.

Stretching in water is preferably performed after dyeing the above-mentioned resin layer. The reason is that the stretchability can be made more excellent. In this case, it is preferable to blend iodide in the above-mentioned boric acid aqueous solution. The reason is that the elution of iodine contained in the resin layer can be suppressed. The concentration of iodide is preferably 0.05 to 15 parts by weight, and more preferably 0.5 to 8 parts by weight with respect to 100 parts by weight of water.

It is preferable to perform underwater stretching at least once. By using underwater stretching, the PVA-based resin contained in the resin layer can have a high degree of saponification (for example, 99.0 mol% or more), while ensuring dyeability. Specifically, when a PVA-based resin having a high degree of saponification is stretched at a high temperature (for example, 120° C. or higher), there is a concern that sufficient dyeability cannot be ensured after stretching. In one embodiment, the laminate is stretched in the air at, for example, 95°C to 150°C, and then subjected to the dyeing step, and then stretched by underwater stretching. In this case, the stretching ratio of the laminate by air stretching is, for example, 1.5 times to 3.5 times, preferably 2.0 times to 3.0 times. In addition, the stretching ratio of the laminate by underwater stretching is preferably 2.0 times or more.

The above-mentioned saponification may be performed before or after the stretching step. Saponification is preferably carried out after air stretching. This is to ensure sufficient stretchability and dyeability.

B-5. Others Any appropriate treatment other than the above can be performed on the above-mentioned resin layer (layered body). For example, insolubilization treatment, cross-linking treatment, washing treatment, and drying treatment can be given.

(Insolubilization Treatment) The above-mentioned insolubilization treatment is typically performed by immersing a resin layer in an aqueous boric acid solution. In particular, in the case of adopting the underwater stretching method, water resistance can be imparted to the PVA-based resin by performing insolubilization treatment. The concentration of the boric acid aqueous solution is preferably 1 to 4 parts by weight with respect to 100 parts by weight of water. The liquid temperature of the insolubilization bath (boric acid aqueous solution) is preferably 20°C to 40°C. The insolubilization treatment is preferably performed before dyeing and stretching in water.

(Crosslinking treatment) The above-mentioned crosslinking treatment is typically performed by immersing a resin layer in an aqueous boric acid solution. The crosslinking treatment can impart water resistance to the PVA-based resin. The concentration of the boric acid aqueous solution is preferably 1 to 4 parts by weight with respect to 100 parts by weight of water. In addition, when the crosslinking treatment is performed after the above-mentioned dyeing, it is preferable to further blend an iodide. By blending iodide, it is possible to suppress the elution of iodine adsorbed on the resin layer. The blending amount of iodide is preferably 1 part by weight to 5 parts by weight with respect to 100 parts by weight of water. Specific examples of iodide are as described above. The liquid temperature of the crosslinking bath (boric acid aqueous solution) is preferably 20°C to 50°C. The crosslinking treatment is preferably carried out before stretching in water. In one embodiment, dyeing, cross-linking, and underwater stretching are performed sequentially.

(Cleaning treatment) The above-mentioned cleaning treatment is typically performed by immersing the resin layer in a potassium iodide aqueous solution.

(Drying treatment) The drying temperature of the above-mentioned drying treatment is, for example, 30°C to 100°C.

C. Polarizing plate The polarizing plate of the present invention has the above-mentioned polarizer. The polarizing plate typically has a polarizer and a protective film arranged on at least one side of the polarizer. As the protective film, the above-mentioned resin substrate may be used as it is, or a film other than the above-mentioned resin substrate may be used. As a material for forming the protective film, for example, cellulose resins such as cellulose diacetate and cellulose triacetate (TAC), cycloolefin resins such as (meth)acrylic resins, norbornene resins, and poly Olefin resins such as ethylene and polypropylene, ester resins such as polyethylene terephthalate resins, polyamide resins, polycarbonate resins, copolymer resins thereof, and the like. In addition, "(meth)acrylic resin" means acrylic resin and/or methacrylic resin.

The thickness of the protective film is typically 10 μm to 100 μm. Various surface treatments can be applied to the protective film. The protective film can function not only as a protective film for the polarizer, but also as a retardation film.

The protective film is typically laminated on the polarizer through an adhesive layer (specifically, an adhesive layer, an adhesive layer). The adhesive layer is typically formed of PVA-based adhesives and active energy ray-curable adhesives. The adhesive layer is typically formed of an acrylic adhesive. Example

Hereinafter, the present invention will be specifically explained based on examples, but the present invention is not limited to these examples. In addition, the measuring method of each characteristic is as follows. 1. Thickness is measured using a digital micrometer (manufactured by ANRITSU CORPORATION, product name "KC-351C"). 2. The glass transition temperature (Tg) is measured in accordance with JIS K 7121.

[Example 1] (Production of laminated body) As a resin substrate, an amorphous isophthalic acid copolymerized polyethylene terephthalate (IPA copolymerized PET) film (thickness: 100 μm) with a Tg of 75°C was used. Corona treatment was performed on one side of the resin substrate, and the corona treated surface was coated at 23°C and contained polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mol%) and acetone in a ratio of 9:1 Acetyl-modified PVA (polymerization degree 1200, saponification degree 99.0 mol% or more, manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "GOHSEFIMER Z200") aqueous solution and dried to form a PVA-based resin layer with a thickness of 12 μm. Layered body. In addition, the degree of saponification of the PVA-based resin contained in the aqueous solution was 99.3 mol%.

(Production of Polarizing Plate) The obtained laminate was uniaxially stretched to 2.0 times (air-assisted stretching) in the longitudinal direction in the longitudinal direction between rollers with different peripheral speeds in an oven at 120°C. Next, the layered body was immersed in a 1 mol/L (1N, 4w%) sodium hydroxide aqueous solution for 10 seconds (saponification treatment). Next, the layered body was immersed in an insolubilization bath (a boric acid aqueous solution obtained by mixing 4 parts by weight of boric acid with respect to 100 parts by weight of water) at a liquid temperature of 30°C for 30 seconds (insolubilization treatment). Next, the iodine concentration and immersion time were adjusted and immersed in a dye bath at a liquid temperature of 30°C so that the obtained polarizing plate had a predetermined transmittance. In this example, it was immersed in an iodine aqueous solution obtained by mixing 0.2 parts by weight of iodine and 1.5 parts by weight of potassium iodide with respect to 100 parts by weight of water for 60 seconds (dyeing treatment). Next, it was immersed in a crosslinking bath (a boric acid aqueous solution obtained by mixing 3 parts by weight of potassium iodide and 3 parts by weight of boric acid with respect to 100 parts by weight of water) at a liquid temperature of 30°C for 30 seconds (crosslinking treatment). After that, the layered body was immersed in a boric acid aqueous solution (an aqueous solution obtained by mixing 4 parts by weight of boric acid and 5 parts by weight of potassium iodide with respect to 100 parts by weight of water) at a liquid temperature of 70°C while running in the longitudinal direction between rolls with different peripheral speeds. Uniaxial stretching (underwater stretching) is performed so that the total stretching ratio becomes 5.5 times. Thereafter, the layered body was immersed in a cleaning bath (an aqueous solution obtained by mixing 4 parts by weight of potassium iodide with respect to 100 parts by weight of water) at a liquid temperature of 30°C (washing treatment).

After cleaning, coat the PVA resin aqueous solution (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., brand name "GOHSEFIMER (registered trademark) Z-200", resin concentration: 3% by weight) on the surface of the PVA resin layer of the laminate, and paste the laminate A thin film (thickness 40 μm, moisture permeability 80 g/m ² /24H) was heated in an oven maintained at 60° C. for 5 minutes to produce a polarizing plate having a polarizer with a thickness of 5 μm.

[Example 2] (Preparation of laminate) As the resin substrate, a cycloolefin resin film (manufactured by JSR Corporation, ARTON) having a Tg of about 135°C was used. On one side of the resin substrate, an aqueous solution of polyvinyl alcohol with a degree of polymerization of 2400 and a degree of saponification of 98.0% was applied at 80°C and dried to form a PVA-based resin layer with a thickness of 12 μm to produce a laminate.

(Production of polarizing plate) The obtained laminate was stretched to a stretching ratio of 5.0 times by free-end uniaxial stretching under heating at 160°C. The thickness of the PVA-based resin layer after the stretching treatment was 5 μm (in-air stretching). Next, the layered body was immersed in a 1 mol/L (1N, 4w%) sodium hydroxide aqueous solution for 10 seconds (saponification treatment). Next, the layered body was immersed in a dyeing bath at a liquid temperature of 30°C (an iodine aqueous solution obtained by mixing 0.5 parts by weight of iodine and 3.5 parts by weight of potassium iodide with respect to 100 parts by weight of water) for 60 seconds (dyeing treatment). Next, the layered body was immersed in a crosslinking bath at a liquid temperature of 60°C (a boric acid aqueous solution obtained by blending 5 parts by weight of potassium iodide and 5 parts by weight of boric acid with respect to 100 parts by weight of water) for 60 seconds (crosslinking treatment). After that, the layered body was immersed in a cleaning bath (aqueous solution obtained by mixing 3 parts by weight of potassium iodide with respect to 100 parts by weight of water) (washing treatment).

After cleaning, the PVA resin aqueous solution (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., brand name "GOHSEFIMER (registered trademark) Z-200", resin concentration: 3% by weight) is coated on the surface of the PVA resin layer of the laminate, and pressed A thin film (thickness 40 μm, moisture permeability 80 g/m ² /24H) was heated in an oven maintained at 80° C. for 5 minutes to produce a polarizing plate having a polarizer with a thickness of 5 μm.

[Comparative Example 1] A polarizing plate was obtained in the same manner as in Example 1 except that the layered body was not subjected to saponification treatment.

[Comparative Example 2] A polarizing plate was obtained in the same manner as in Example 2 except that the layered body was not subjected to saponification treatment.

[Comparative Example 3] When forming a PVA-based resin layer, instead of polyvinyl alcohol with a polymerization degree of 4200 and a saponification degree of 99.2 mol%, a polyvinyl alcohol with a polymerization degree of 4200 and a saponification degree of 99.9 mol% was used (contained in the aqueous solution). The degree of saponification of the PVA-based resin was 99.9 mol%), and other than that, it was performed in the same manner as in Example 1, and the production of a polarizing plate was tried.

[Comparative Example 4] When forming a PVA resin layer, instead of polyvinyl alcohol with a degree of polymerization of 2400 and a degree of saponification of 98.0%, a polyvinyl alcohol with a degree of polymerization of 4200 and a degree of saponification of 99.9 mol% was used. In the same way, the production of a polarizing plate was tried.

(Reference Example 1) Polyvinyl alcohol (polymerization degree 4200, saponification degree 99.9 mol%) and acetyl acetyl modified PVA (polymerization degree 1200, saponification degree 99.0 mol% or more) will be contained in a ratio of 9:1. An aqueous solution (80°C), manufactured by Nippon Synthetic Chemical Industry Co., Ltd., with the trade name "GOHSEFIMER Z200") is coated on a metal plate heated to 80°C in an atmosphere of 80°C so that the thickness after drying is 12μm to obtain PVA Resin-like film. Various treatments were performed on the obtained PVA-based resin film, and an attempt was made to produce a polarizer, but the resin film was broken when stretched in water.

The degree of saponification and humidification reliability of the polarizers of the respective Examples and Comparative Examples were evaluated. The evaluation results are shown in Table 1 together with the production conditions. 1. Method for measuring the degree of saponification: A cut piece obtained by cutting a predetermined portion of the polarizer (PVA) obtained is immersed in heavy water and heated, and the measurement sample obtained by dissolving the cut piece is submitted to ¹ H-NMR Determination. The measurement conditions are as follows.・Device: ¹ H-NMR (Bruker Biospin､AVANCE III-400) ・Observation frequency: 400MHz ・Chemical shift standard: TSP-d ₄ (0.00ppm) ・Measurement solvent: heavy water ・Measurement temperature: 80℃

The unsaponified group strength [VAc] and the saponified group strength [VOH] were obtained using the peak areas after identification and assignment, and the saponification degree was obtained according to the following formula.

100: (degree of saponification)=[VOH]+[VAc]:[VOH]

2. Evaluation method of humidification reliability

The resin substrate was peeled off from the obtained polarizer, and the peeled surface of the resin substrate was stuck to a glass plate through an adhesive to obtain a sample. The transmittance (Ts) just after pasting is 42.5%. This sample was left for 240 hours in an environment with a temperature of 85°C and a humidity of 85%, and the amount of change (ΔP) in the degree of polarization of the polarizer before and after being left in a humidified environment was measured. In addition, a spectroscopic transmittance meter (manufactured by Murakami Color Research Institute, product name "DOT-3C") was used as a measuring machine.

When comparing Example 1 and Comparative Example 1, and Example 2 and Comparative Example 2, respectively, the polarizer of the example is thin and has excellent humidification reliability.

In Comparative Examples 3 and 4, gelation occurred when an aqueous solution containing PVA-based resin was applied to the resin substrate, and many defects that could cause breakage were generated in the subsequent stretching step, and the resin could not be formed well. Floor.

Regarding the "dyeability" in the table, when the iodine concentration of the dyeing bath is separately set to 0.5% by weight and the immersion time in the dyeing bath is set to 60 seconds, the monomer transmittance of the polarizer obtained ( Ts) is 42.0% or less, it is judged as "good".

Industrial availability

The polarizing member of the present invention is suitable as liquid crystal panels, organic LCD televisions, liquid crystal displays, mobile phones, digital cameras, video cameras, portable game consoles, car navigation systems, photocopiers, printers, fax machines, watches, microwave ovens, etc. Use of anti-reflection film for EL device.

10: Laminated body

11: Resin substrate

12: Resin layer (polarizer)

Fig. 1 is a partial cross-sectional view of a laminate according to an embodiment of the present invention.

10‧‧‧Layered body

11‧‧‧Resin substrate

12‧‧‧Resin layer (polarizer)

Claims (8)

A method for manufacturing a polarizing member, which sequentially includes the following steps: coating a coating solution containing polyvinyl alcohol resin on a resin substrate to form a resin layer to produce a laminate; increasing the polyethylene contained in the resin layer The step of saponification degree of alcohol resin; and the step of dyeing the aforementioned resin layer. The manufacturing method according to claim 1, wherein the degree of saponification of the polyvinyl alcohol resin contained in the coating liquid is less than 99.5 mol%. The manufacturing method of claim 1, wherein the degree of saponification of the polyvinyl alcohol resin contained in the resin layer is increased by saponification. The manufacturing method of claim 3, wherein the saponification degree of the polyvinyl alcohol-based resin is increased by 0.1 mol% or more by the aforementioned saponification. The manufacturing method of claim 3, wherein the saponification is performed by contacting an alkaline solution with the resin layer. The manufacturing method according to any one of claims 1 to 5, which further includes a step of stretching the aforementioned laminate. The manufacturing method of claim 6, wherein the stretching includes underwater stretching. The manufacturing method of claim 7, which performs the aforementioned underwater stretching after the aforementioned dyeing step.

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