JP2017076116A - Polarizer and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarizer having excellent quality while being made thin.SOLUTION: A method for producing a polarizer includes following steps in order of: applying a coating liquid comprising polyvinyl alcohol resin on resin base material 11 to form a resin layer 12 and preparing a laminate 10; improving a saponification degree of polyvinyl alcohol resin included in the resin layer; and dyeing the resin layer.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a polarizer and a method for manufacturing the same.

  There has been proposed a method of obtaining a polarizer by coating a resin base material with a polyvinyl alcohol aqueous solution to form a resin layer, and stretching and dyeing this laminate (for example, Patent Document 1). According to such a method, a thin polarizer (for example, 8 μm or less) can be obtained, and thus, for example, it has been attracting attention as being able to contribute to thinning of the image display device.

JP 2000-338329 A

  However, since the above method uses a resin base material, there is a problem in that it is easily restricted in the manufacturing process. For example, since the coating temperature of the solution is limited according to the glass transition temperature Tg of the resin base material, coating at high temperature is difficult. On the other hand, when the coating temperature is lowered, the gelation of polyvinyl alcohol is promoted, and foreign matter is likely to be generated in the coating film. Moreover, since the viscosity of the solution increases, the occurrence of coating defects such as streaks increases. Thus, since it is easy to receive restrictions in a manufacturing process, there exists a problem that the quality (for example, humidification reliability) of the obtained polarizer is inadequate.

  The present invention has been made to solve the above problems, and a main object thereof is to provide a polarizer having excellent quality while being thin.

The polarizer of this invention is comprised from the resin film containing polyvinyl alcohol-type resin. The saponification degree of the polyvinyl alcohol-based 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 producing a polarizer is provided. In this production method, a coating layer containing a polyvinyl alcohol resin is applied on a resin substrate to form a resin layer, and a laminate is produced. The degree of saponification of the polyvinyl alcohol resin contained in the resin layer is determined. The step of increasing and the step of dyeing the resin layer are included in this order.
In one embodiment, the saponification degree of the polyvinyl alcohol-type resin contained in the said coating liquid is less than 99.5 mol%.
In one embodiment, the saponification degree of the polyvinyl alcohol-type resin contained in the said resin layer is raised by saponification.
In one embodiment, the saponification degree of the polyvinyl alcohol resin is increased by 0.1 mol% or more by the saponification.
In one embodiment, the saponification is performed by bringing a basic solution into contact with the resin layer.
In one embodiment, the manufacturing method further includes a step of stretching the laminate.
In one embodiment, the stretching includes underwater stretching.
In one embodiment, the underwater stretching is performed after the dyeing step.

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

It is a fragmentary sectional view of the layered product by one embodiment of the present invention.

  Hereinafter, although one embodiment of the present invention is described, the present invention is not limited to these embodiments.

A. Polarizer The polarizer of the present invention is composed of a resin film containing a polyvinyl alcohol resin (hereinafter referred to as “PVA resin”). Examples of the PVA resin include polyvinyl alcohol and ethylene-vinyl alcohol copolymer. Polyvinyl alcohol is obtained by saponifying polyvinyl acetate. An ethylene-vinyl alcohol copolymer can be obtained by saponifying an ethylene-vinyl acetate copolymer.

  The saponification degree 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%. When the PVA resin contained in the polarizer satisfies such a saponification degree, excellent humidification reliability can be achieved. The saponification degree can be determined according to JIS K 6726-1994.

  The average degree of polymerization of the PVA-based resin can be appropriately selected according to the purpose. Average polymerization degree is 1000-10000 normally, Preferably it is 1200-6000, More preferably, it is 2000-5000. The average degree of polymerization can be determined according to 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 includes a dichroic material. Specific examples of the dichroic substance include iodine and organic dyes. These may be used alone or in combination of two or more. As the dichroic substance, iodine is preferably used.

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

B. Manufacturing method of polarizer The manufacturing method of the polarizer of this invention forms the resin layer containing a PVA-type resin on a resin base material, and produces a laminated body, and saponification of the PVA-type resin contained in a resin layer A step of increasing the degree. Specifically, a step of increasing the saponification degree of the PVA-based resin is performed after the step of manufacturing the laminate. Thereby, the polarizer which has the outstanding quality (for example, humidification reliability) can be manufactured, ensuring the film forming property of a PVA-type resin layer (for example, prevention of generation | occurrence | production of a foreign material and a stripe).

B-1. Fabrication of Laminate FIG. 1 is a partial cross-sectional view of a laminate according to one embodiment of the present invention. The laminate 10 includes 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 base material 11. The resin layer 12 is formed by applying a coating solution containing a PVA-based resin on the resin substrate 11 and drying it as necessary.

  Any appropriate material can be adopted as the material for forming the resin base material. Examples thereof include ester resins such as polyethylene terephthalate resins, cycloolefin resins, olefin resins such as polypropylene, (meth) acrylic resins, polyamide resins, polycarbonate resins, and copolymer resins thereof.

  The glass transition temperature (Tg) of the resin substrate is preferably 120 ° C. or lower, more preferably 100 ° C. or lower. This is because, when the laminate is stretched, stretchability can be sufficiently ensured while suppressing 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, a glass transition temperature (Tg) is a value calculated | required according to JISK7121.

  The thickness of the resin substrate is preferably 20 μm to 300 μm, more preferably 50 μm to 200 μm. The surface of the resin base material may be subjected to surface modification treatment (for example, corona treatment) or an easy-adhesion layer may be formed. According to such a process, the laminated body excellent in the adhesiveness of the resin base material and the resin layer can be obtained.

  As described above, the coating liquid contains a PVA resin. The saponification degree of the PVA resin contained in the coating solution is preferably less than 99.5 mol%, more preferably 99.0 mol% or less. By using a PVA-based resin having such a saponification degree, it is possible to sufficiently ensure the film forming property on the resin base material. Specifically, when the coating solution is applied to the resin base material, if the coating temperature is too high, the resin base material may be deformed. However, by reducing the degree of saponification of the PVA resin, the coating solution Thus, the viscosity of the coating solution can be lowered without increasing the temperature, and gelation of the PVA resin can be prevented.

  The coating solution is typically a solution obtained by dissolving the PVA resin in a solvent. Examples of the solvent used in the coating solution include water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, various glycols, polyhydric alcohols such as trimethylolpropane, and amines such as ethylenediamine and diethylenetriamine. It is done. These may be used alone or in combination of two or more. Among these, water is preferable. The PVA resin concentration of the solution can be set to any appropriate value. For example, it is set according to the polymerization degree or saponification degree of the PVA resin. The concentration of the PVA resin in the solution is, for example, 3 to 20 parts by weight with respect to 100 parts by weight of the solvent.

  The coating solution may contain an additive. Examples of the additive include a plasticizer and a surfactant. Examples of the plasticizer include polyhydric alcohols such as ethylene glycol and glycerin. Examples of the surfactant include nonionic surfactants. These can be used for the purpose of further improving the uniformity, dyeability and stretchability of the resulting resin layer. Moreover, as an additive, an easily bonding component is mentioned, for example. By using the easily adhesive component, the adhesion between the resin base material and the resin layer can be improved. As a result, for example, a problem such as peeling of the resin layer from the resin base material can be suppressed and dyeing described later can be performed satisfactorily. As the easily adhesive component, for example, modified PVA such as acetoacetyl-modified PVA is used.

  Any appropriate method can be adopted as a coating method of the coating solution. Examples thereof include 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 knife coating method (comma coating method and the like).

  The application temperature (for example, the temperature of the application liquid when applying the application liquid) can be set to any appropriate value depending on the resin substrate used. The application temperature is, for example, 20 ° C. or higher, preferably 50 ° C. or higher. On the other hand, application | coating temperature is less than Tg with respect to the glass transition temperature (Tg) of a resin base material, for example, Preferably it is Tg (degreeC) -20 degrees C or less, More preferably, it is Tg (degreeC) -30 degrees C or less.

  When drying the applied coating film, the drying temperature is, for example, 20 ° C. or higher, preferably 50 ° C. or higher. On the other hand, the drying temperature is preferably lower than the glass transition temperature (Tg) of the resin base material, and more preferably Tg (° C.) − 10 ° C. or lower.

  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 saponification degree Any appropriate method can be adopted as a method for increasing the saponification degree of the PVA-based resin. Preferably, a method of applying saponification treatment to the PVA resin contained in the resin layer formed on the resin base material is employed. By the saponification treatment, unsaponified groups of the PVA resin can be saponified, and the saponification degree can be increased. As a result, the obtained polarizer can be excellent in humidification reliability while being thin.

  The saponification treatment preferably increases the saponification degree of the PVA resin contained in the resin layer by 0.1 mol% or more, more preferably 0.5 mol% or more, particularly preferably 1.0 mol% or more. Let The saponification degree of the PVA-based resin after saponification treatment typically exceeds 99.0 mol%, for example, 99.3 mol% or more, preferably 99.5 mol% or more, more preferably 99.8 mol%. % Or more.

  In one embodiment, a saponification process is performed by bringing a basic solution into contact with the resin layer. Arbitrary appropriate methods can be employ | adopted as a contact method of a basic solution. For example, the method of dripping, coating, and spraying a basic solution with respect to a resin layer, and the method of immersing a resin layer (laminated body) in a basic solution are mentioned.

  Any appropriate basic compound may be used as the basic compound contained in the basic solution. Examples of the basic compound include alkali metal hydroxides such as sodium hydroxide, potassium hydroxide and lithium hydroxide, alkaline earth metal hydroxides such as calcium hydroxide, and inorganic alkali metal salts such as sodium carbonate. , Organic alkali metal salts such as sodium acetate, aqueous ammonia and the like. These may be used alone or in combination of two or more. Among these, preferred are alkali metal hydroxides, more preferred are sodium hydroxide, potassium hydroxide, and lithium hydroxide, and particularly preferred is sodium hydroxide.

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

  The density | concentration of a basic solution is 0.01N-5N, for example, Preferably it is 0.05N-3N, More preferably, it is 0.1N-2.5N. When the basic solution is an aqueous sodium hydroxide solution, the concentration is preferably 1.0 w% or more, more preferably 2 w% to 8 w%.

  The liquid temperature of a basic solution is 20 degreeC or more, for example, Preferably it is 25 to 50 degreeC. The contact time of the basic solution is set according to, for example, the thickness of the resin layer and the type and concentration of the basic compound contained in the basic solution. The contact time is, for example, 5 seconds to 30 minutes, preferably 5 seconds to 5 minutes.

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

B-3. Dyeing The resin layer can be dyed. As a dyeing method, for example, a method of immersing a resin layer (laminate) in a dye solution containing the dichroic substance, a method of applying the dye solution to the resin layer, and spraying the dye solution onto the resin layer A method is mentioned. Preferably, a method of immersing the resin layer in the staining solution is used.

  The staining solution is preferably an iodine aqueous solution. The compounding amount of iodine is preferably 0.1 part by weight to 0.5 part by weight with respect to 100 parts by weight of water. In order to increase the solubility of iodine in water, it is preferable to add an iodide to the aqueous iodine solution. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide. Etc. Among these, potassium iodide is preferable. The compounding amount of the iodide is preferably 0.02 to 20 parts by weight, more preferably 0.1 to 10 parts by weight with respect to 100 parts by weight of water.

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

  Preferably, the saponification is performed before dyeing the resin layer. This is because sufficient polarization characteristics are imparted to the obtained polarizer.

B-4. Stretching The laminate can be stretched. Any appropriate method can be adopted as a method of stretching the laminate. Specifically, it may be fixed end stretching (for example, a method using a tenter stretching machine) or free end stretching (for example, a method of uniaxial stretching through a laminate between rolls having different peripheral speeds). Moreover, simultaneous biaxial stretching (for example, a method using a simultaneous biaxial stretching machine) or sequential biaxial stretching may be used. The stretching of the laminate may be performed in one stage or in multiple stages. When performed in multiple stages, the stretch ratio of the laminate described later is the product of the stretch ratios of the respective stages.

  Any appropriate direction can be selected as the stretching direction of the laminate. In one embodiment, it extends | stretches in the longitudinal direction of an elongate laminated body. Specifically, the laminate is transported in the longitudinal direction, which is the transport direction (MD). In another embodiment, it extends | stretches in the width direction of an elongate laminated body. Specifically, the laminate is transported in the longitudinal direction, and the direction (TD) is orthogonal to the transport direction (MD).

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

  The stretching method is not particularly limited, and may be, for example, an in-air stretching method or an underwater stretching method in which the laminate is immersed in a stretching bath.

  The stretching temperature of the laminate can be set to any appropriate value depending on the resin base material, the stretching method, and the like. When adopting the air stretching method, the stretching temperature is preferably equal to or higher than the glass transition temperature (Tg) of the resin substrate, more preferably the glass transition temperature (Tg) of the resin substrate + 10 ° C., and particularly preferably Tg + 15 ° C. That's it. 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 rapid progress of crystallization of the PVA-based resin and to suppress problems due to the crystallization (for example, preventing the orientation of the PVA-based resin due to stretching). .

  When the underwater stretching method is employed as the stretching method, the liquid temperature of the stretching bath is preferably 40 ° C to 85 ° C, more preferably 50 ° C to 85 ° C. If it is such temperature, it can extend | stretch at high magnification, suppressing melt | dissolution of PVA-type resin. Specifically, as described above, the glass transition temperature (Tg) of the resin base material is preferably 60 ° C. or higher in relation to the formation of the resin layer. In this case, when the stretching temperature is lower than 40 ° C., there is a possibility that the stretching cannot be satisfactorily performed even in consideration of plasticization of the resin base material with water. 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 possibility that excellent polarization characteristics cannot be obtained. The immersion time of the laminate in the stretching bath is preferably 15 seconds to 5 minutes.

  When employing an underwater stretching method, it is preferable to stretch the laminate by immersing it in an aqueous boric acid solution (stretching in boric acid in water). By using a boric acid aqueous solution as the stretching bath, it is possible to impart to the PVA resin a rigidity that can withstand the tension applied during stretching and a water resistance that does not dissolve in water. 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 boric acid concentration to 1 part by weight or more, dissolution of the PVA-based resin can be effectively suppressed.

  Preferably, the stretching in water is performed after dyeing the resin layer. This is because the stretchability can be improved. In this case, it is preferable to add an iodide to the boric acid aqueous solution. This is because elution of iodine contained in the resin layer can be suppressed. The concentration of iodide is preferably 0.05 to 15 parts by weight, more preferably 0.5 to 8 parts by weight with respect to 100 parts by weight of water.

  Preferably, the underwater stretching is preferably performed at least once. By adopting underwater stretching, it is possible to ensure dyeability while the PVA resin contained in the resin layer has a high degree of saponification (for example, 99.0 mol% or more). Specifically, when a PVA resin having a high degree of saponification is stretched at a high temperature (for example, 120 ° C. or higher), there is a possibility that sufficient dyeability cannot be ensured after stretching. In one embodiment, the laminate is subjected to a dyeing process after being stretched in the air at, for example, 95 ° C to 150 ° C, and then stretched by stretching in water. In this case, the draw ratio of the laminate by air drawing is, for example, 1.5 to 3.5 times, and preferably 2.0 to 3.0 times. Moreover, the draw ratio of the laminate by drawing in water is preferably 2.0 times or more.

  The saponification may be performed before the stretching step or after the stretching step. Preferably, saponification is performed after air drawing. This is to ensure sufficient stretchability and dyeability.

B-5. Others Any appropriate treatment other than the above may be applied to the resin layer (laminate). For example, insolubilization treatment, cross-linking treatment, washing treatment, and drying treatment can be mentioned.

(Insolubilization treatment)
The insolubilization treatment is typically performed by immersing the resin layer in an aqueous boric acid solution. In particular, when an underwater stretching method is employed, water resistance can be imparted to the PVA resin by performing an 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 insolubilizing bath (boric acid aqueous solution) is preferably 20 ° C to 40 ° C. Preferably, the insolubilization treatment is performed before dyeing or stretching in water.

(Crosslinking treatment)
The crosslinking treatment is typically performed by immersing the resin layer in an aqueous boric acid solution. By performing the crosslinking treatment, water resistance can be imparted to the PVA 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. Moreover, when performing a crosslinking process after the said dyeing | staining, it is preferable to mix | blend iodide further. By blending iodide, elution of iodine adsorbed on the resin layer can be suppressed. 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 the iodide are as described above. The liquid temperature of the crosslinking bath (boric acid aqueous solution) is preferably 20 ° C to 50 ° C. Preferably, the crosslinking treatment is performed before stretching in water. In one embodiment, dyeing, crosslinking and stretching in water are performed in this order.

(Cleaning process)
The washing treatment is typically performed by immersing the resin layer in an aqueous potassium iodide solution.

(Drying process)
The drying temperature of the said drying process is 30 to 100 degreeC, for example.

C. Polarizing plate The polarizing plate of this invention has the said polarizer. The polarizing plate typically includes a polarizer and a protective film disposed on at least one side of the polarizer. As the protective film, the resin base material may be used as it is, or a film different from the resin base material may be used. Examples of the material for forming the protective film include cellulose resins such as diacetyl cellulose and triacetyl cellulose (TAC), cycloolefin resins such as (meth) acrylic resins and norbornene resins, and olefin resins such as polyethylene and polypropylene. And ester resins such as polyethylene terephthalate resins, polyamide resins, polycarbonate resins, and copolymer resins thereof. The “(meth) acrylic resin” refers to an acrylic resin and / or a methacrylic resin.

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

  The protective film is typically laminated on the polarizer via an adhesive layer (specifically, an adhesive layer or an adhesive layer). The adhesive layer is typically formed of a PVA adhesive or an activated energy ray curable adhesive. The pressure-sensitive adhesive layer is typically formed of an acrylic pressure-sensitive adhesive.

EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited by these Examples. In addition, the measuring method of each characteristic is as follows.
1. Thickness Measured using a digital micrometer (manufactured by Anritsu, product name “KC-351C”).
2. Glass transition temperature (Tg)
It measured according to JIS K7121.

[Example 1]
(Production of laminate)
As the resin base material, an amorphous isophthalic acid copolymerized polyethylene terephthalate (IPA copolymerized PET) film (thickness: 100 μm) having a Tg of 75 ° C. was used.
One side of the resin base material is subjected to corona treatment, and polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mol%) and acetoacetyl-modified PVA (polymerization degree 1200, saponification degree 99.0 mol) are applied to the corona-treated surface. % Of an aqueous solution containing 9% of Nippon Synthetic Chemical Industry's trade name “Gosefimer Z200”) is applied and dried at 23 ° C. to form a PVA resin layer having a thickness of 12 μm. The body was made. The degree of saponification of the PVA resin contained in the aqueous solution is 99.3 mol%.

(Preparation of polarizing plate)
The resulting laminate was uniaxially stretched free end 2.0 times in the machine direction between rolls having different peripheral speeds in an oven at 120 ° C. (air-assisted stretching).
Next, the laminate was immersed in a 1 mol / L (1N, 4 w%) sodium hydroxide aqueous solution for 10 seconds (saponification treatment).
Next, the laminate was immersed in an insolubilization bath (a boric acid aqueous solution obtained by blending 4 parts by weight of boric acid with respect to 100 parts by weight of water) for 30 seconds (insolubilization treatment).
Subsequently, it was immersed in a dyeing bath having a liquid temperature of 30 ° C. while adjusting the iodine concentration and the immersion time so that the obtained polarizing plate had a predetermined transmittance. In this example, 0.2 parts by weight of iodine was blended with 100 parts by weight of water and immersed in an aqueous iodine solution obtained by blending 1.5 parts by weight of potassium iodide (dyeing treatment). .
Subsequently, it was immersed for 30 seconds in a crosslinking bath having a liquid temperature of 30 ° C. (a boric acid aqueous solution obtained by blending 3 parts by weight of potassium iodide and 3 parts by weight of boric acid with respect to 100 parts by weight of water). (Crosslinking treatment).
Thereafter, the laminate was immersed in a boric acid aqueous solution (an aqueous solution obtained by blending 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. However, uniaxial stretching was performed in the longitudinal direction between rolls having different peripheral speeds so that the total stretching ratio was 5.5 times (in-water stretching).
Thereafter, the laminate was immersed in a cleaning bath (an aqueous solution obtained by blending 4 parts by weight of potassium iodide with respect to 100 parts by weight of water) at a liquid temperature of 30 ° C. (cleaning treatment).

After washing, a PVA-based resin aqueous solution (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name “GOHSEFIMAR (registered trademark) Z-200”, resin concentration: 3% by weight) is applied to the surface of the PVA-based resin layer of the laminate. Then, an acrylic film (thickness 40 μm, moisture permeability 80 g / m ² / 24H) was bonded, and this was heated in an oven maintained at 60 ° C. for 5 minutes to produce a polarizing plate having a polarizer having a thickness of 5 μm.

[Example 2]
(Production of laminate)
A cycloolefin resin film (manufactured by JSR, ARTON) having a Tg of about 135 ° C. was used as the resin base material.
An aqueous solution of polyvinyl alcohol having a polymerization degree of 2400 and a saponification degree of 98.0% was applied to one side of the resin base material at 80 ° C. and dried to form a PVA resin layer having a thickness of 12 μm, thereby preparing a laminate.

(Preparation of polarizing plate)
The obtained laminate was stretched to a stretch ratio of 5.0 times by free end uniaxial stretching under heating at 160 ° C. The thickness of the PVA resin layer after the stretching treatment was 5 μm (air stretching).
Next, the laminate was immersed in a 1 mol / L (1N, 4 w%) sodium hydroxide aqueous solution for 10 seconds (saponification treatment).
Subsequently, the laminate was dyed at 30 ° C. (an iodine aqueous solution obtained by blending 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 laminate was placed in a crosslinking bath having 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. Immersion (crosslinking treatment).
Thereafter, the laminate was immersed in a cleaning bath (an aqueous solution obtained by blending 3 parts by weight of potassium iodide with respect to 100 parts by weight of water) (cleaning treatment).

After washing, a PVA-based resin aqueous solution (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name “GOHSEFIMAR (registered trademark) Z-200”, resin concentration: 3% by weight) is applied to the surface of the PVA-based resin layer of the laminate. Then, an acrylic film (thickness 40 μm, moisture permeability 80 g / m ² / 24H) was bonded, and this was heated in an oven maintained at 80 ° C. for 5 minutes to prepare a polarizing plate having a polarizer having a thickness of 5 μm.

[Comparative Example 1]
A polarizing plate was obtained in the same manner as in Example 1 except that the saponification treatment was not performed on the laminate.

[Comparative Example 2]
A polarizing plate was obtained in the same manner as in Example 2 except that the saponification treatment was not performed on the laminate.

[Comparative Example 3]
In forming the PVA-based resin layer, polyvinyl alcohol having a polymerization degree of 4200 and a saponification degree of 99.9 mol% was used in place of the polyvinyl alcohol having a polymerization degree of 4200 and a saponification degree of 99.2 mol% (included in the aqueous solution). An attempt was made to produce a polarizing plate in the same manner as in Example 1 except that the degree of saponification of the PVA-based resin was 99.9 mol%.

[Comparative Example 4]
Example 2 except that polyvinyl alcohol having a polymerization degree of 4200 and a saponification degree of 99.9 mol% was used in place of the polyvinyl alcohol having a polymerization degree of 2400 and a saponification degree of 98.0% in forming the PVA resin layer. In the same manner, an attempt was made to produce a polarizing plate.

(Reference Example 1)
Polyvinyl alcohol (polymerization degree 4200, saponification degree 99.9 mol%) and acetoacetyl-modified PVA (polymerization degree 1200, saponification degree 99.0 mol% or more, manufactured by Nippon Gosei Kagaku Kogyo Co., Ltd., trade name “Gosefimer Z200” )) In a ratio of 9: 1 was applied on a metal plate heated to 80 ° C. in an 80 ° C. atmosphere so that the thickness after drying was 12 μm, and a PVA resin A membrane was obtained.
Various treatments were applied to the obtained PVA-based resin film to attempt to produce a polarizer, but the resin film was broken during stretching in water.

The degree of saponification and humidification reliability of the polarizers of each Example and Comparative Example were evaluated. The evaluation results are shown in Table 1 together with the production conditions.
1. Method for measuring degree of saponification A sample obtained by cutting out a predetermined portion of the obtained polarizer (PVA) is immersed in heavy water and heated, and the sample for measurement obtained by dissolving the sample is used for ¹ H-NMR measurement. Provided. The measurement conditions are as follows.
Apparatus: ¹ H-NMR (Bruker Biospin, AVANCE III-400)
・ Observation frequency: 400 MHz
・ Chemical shift standard: TSP-d ₄ (0.00ppm)
・ Measurement solvent: heavy water ・ Measurement temperature: 80 ° C.
Using each of the identified peak areas, the unsaponified group strength [VAc] and the saponified group strength [VOH] are obtained by the following formulas (1) and (2), and the saponification degree is obtained by the following formula (3). Asked.
Unsaponified group [VAc] = (3.9-4.1 ppm peak area) / 3 (1)
Saponification group [VOH] = {(1.6-1.9 ppm peak area) − (2.1 ppm peak area × 2/3)} / 2 (2)
100: (degree of saponification) = [VOH] + [VAc]: [VOH] (3)
2. Humidity Reliability Evaluation Method A resin base material was peeled from the obtained polarizer, and a release surface of the resin base material was attached to a glass plate via an adhesive to obtain a sample. The transmittance (Ts) immediately after bonding was 42.5%. This sample was allowed to stand for 240 hours in an environment at 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. A spectral transmittance meter (manufactured by Murakami Color Research Laboratory, product name “DOT-3C”) was used as a measuring machine.

When Example 1 and Comparative Example 1 are compared with Example 2 and Comparative Example 2, respectively, the polarizer of the Example is thin and excellent in humidification reliability.
In Comparative Examples 3 and 4, gelation occurs when an aqueous solution containing a PVA resin is applied to the resin base material, and a number of defects that cause breakage occur in the subsequent stretching step, resulting in a satisfactory resin layer. Could not be formed.
The “dyeability” in the table separately indicates the single transmittance (Ts) of the obtained polarizer when the iodine concentration in the dyeing bath is 0.5% by weight and the immersion time in the dyeing bath is 60 seconds. ) Was 42.0% or less, it was judged as “good”.

  The polarizer of the present invention is a liquid crystal television, a liquid crystal display, a mobile phone, a digital camera, a video camera, a portable game machine, a car navigation system, a copier, a liquid crystal panel such as a printer, a fax machine, a clock, a microwave oven, etc. It is suitably used as a prevention film.

DESCRIPTION OF SYMBOLS 10 Laminated body 11 Resin base material 12 Resin layer (polarizer)

The degree of saponification and humidification reliability of the polarizers of each Example and Comparative Example were evaluated. The evaluation results are shown in Table 1 together with the production conditions.
1. Method for measuring degree of saponification A sample obtained by cutting out a predetermined portion of the obtained polarizer (PVA) is immersed in heavy water and heated, and the sample for measurement obtained by dissolving the sample is used for ¹ H-NMR measurement. Provided. The measurement conditions are as follows.
Apparatus: ¹ H-NMR (Bruker Biospin, AVANCE III-400)
・ Observation frequency: 400 MHz
・ Chemical shift standard: TSP-d ₄ (0.00ppm)
・ Measurement solvent: heavy water ・ Measurement temperature: 80 ° C.
Using each peak area was assigned identification, seeking unsaponified groups strength [VAc] and Ken groups strength [VOH], was determined more saponification degree in the following equation.
100: (degree of saponification) = [VOH] + [VAc]: [VOH ]
2. Humidity Reliability Evaluation Method A resin base material was peeled from the obtained polarizer, and a release surface of the resin base material was attached to a glass plate via an adhesive to obtain a sample. The transmittance (Ts) immediately after bonding was 42.5%. This sample was allowed to stand for 240 hours in an environment at 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. A spectral transmittance meter (manufactured by Murakami Color Research Laboratory, product name “DOT-3C”) was used as a measuring machine.

Claims (8)

Applying a coating liquid containing a polyvinyl alcohol-based resin on a resin substrate to form a resin layer, and producing a laminate;
Increasing the saponification degree of the polyvinyl alcohol resin contained in the resin layer;
And a step of dyeing the resin layer in this order.   The manufacturing method of Claim 1 whose saponification degree of the polyvinyl alcohol-type resin contained in the said coating liquid is less than 99.5 mol%.   The manufacturing method of Claim 1 or 2 which raises the saponification degree of the polyvinyl alcohol-type resin contained in the said resin layer by saponification.   The manufacturing method of Claim 3 which increases the saponification degree of polyvinyl alcohol-type resin 0.1 mol% or more by the said saponification.   The manufacturing method of Claim 3 or 4 which performs the said saponification by making a basic solution contact the said resin layer.   The manufacturing method in any one of Claim 1 to 5 which further includes the process of extending | stretching the said laminated body.   The manufacturing method according to claim 6, wherein the stretching includes underwater stretching. The manufacturing method according to claim 7, wherein the underwater stretching is performed after the dyeing step.

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