KR102400008B1 - Polarizer and Polarizer - Google Patents

Abstract

A polarizer which is thin and has very excellent heat resistance is provided. The polarizer of the present invention is composed of a polyvinyl alcohol-based resin film, has an iodine content of 3.5% by weight or more, and the absolute value of the change in single transmittance ΔTsa after being placed in an environment of 105° C. for 30 hours is 5.0% or less. Here, the single transmittance change amount ΔTsa is expressed by the following formula:
ΔTsa(%)=Ts ₃₀ -Ts ₀
Ts ₀ is the single transmittance before heating, and Ts ₃₀ is the single transmittance after being placed in an environment of 105° C. for 30 hours.

Description

Polarizer and Polarizer

The present invention relates to a polarizer and a polarizing plate.

DESCRIPTION OF RELATED ART In the liquid crystal display device which is a typical image display device, it originates in the image formation method, and the polarizer (actually, the polarizing plate containing a polarizer) is arrange|positioned on both sides of a liquid crystal cell. The polarizer is typically manufactured by dyeing a polyvinyl alcohol (PVA)-based resin film with a dichroic substance such as iodine (eg, Patent Documents 1 and 2). In recent years, the request|requirement of thickness reduction of an image display apparatus is increasing. Therefore, further thinning is calculated|required also about a polarizer. However, as the polarizer becomes thinner, there is a problem of heat resistance in that it is easy to discolor in a high-temperature environment, and cracks and warps are likely to occur in a high-temperature environment.

Japanese Patent Publication No. 5048120 Japanese Laid-Open Patent Publication No. 2013-156391

The present invention has been made in order to solve the above problems, and its main object is to provide a polarizer having a thin shape and very excellent heat resistance.

The polarizer of the present invention is composed of a polyvinyl alcohol-based resin film, has an iodine content of 3.5% by weight or more, and the absolute value of the change in single transmittance ΔTsa after being placed in an environment of 105° C. for 30 hours is 5.0% or less. Here, the single transmittance change amount ΔTsa is expressed by the following formula:

ΔTsa(%)=Ts ₃₀ -Ts ₀

Ts ₀ is the single transmittance before heating, and Ts ₃₀ is the single transmittance after being placed in an environment of 105° C. for 30 hours.

In one embodiment, the polarizer includes at least one selected from a sodium ion, a carbonate ion, and a citrate ion.

According to another aspect of the present invention, a polarizing plate is provided. The polarizing plate includes the polarizer and a protective film laminated on one side or both sides of the polarizer.

ADVANTAGE OF THE INVENTION According to this invention, the polarizer which is thin and has very excellent heat resistance which was desired for a long time but could not be realized was realizable. More specifically, according to the present invention, it was possible to realize a thin polarizer in which color change, cracks, and warpage in a high-temperature environment were remarkably suppressed.

EMBODIMENT OF THE INVENTION Hereinafter, although embodiment of this invention is described, this invention is not limited to these embodiment.

A. Polarizer

A-1. Outline of polarizer

The polarizer according to the embodiment of the present invention is composed of a polyvinyl alcohol (PVA)-based resin film, has an iodine content of 3.5% by weight or more, and the absolute value of the change in single transmittance ΔTsa after being placed in an environment of 105° C. for 30 hours is 5.0 % or less.

The iodine content can be appropriately set according to the thickness of the polarizer from the viewpoint of providing sufficient polarization performance and optimum transmittance. For example, when the thickness of the polarizer exceeds 5 µm and is 10 µm or less, the iodine content is preferably 3.5 wt% to 8.0 wt%; When the thickness of the polarizer exceeds 3 µm and is 5 µm or less, the iodine content is preferably 5.0 wt% to 13.0 wt%; When the thickness of a polarizer is 3 micrometers or less, iodine content becomes like this. Preferably it is 10.0 weight% - 25.0 weight%. ADVANTAGE OF THE INVENTION According to embodiment of this invention, in the polarizer which has such an extremely high iodine content, the very excellent heat resistance which was conventionally difficult can be implement|achieved. More specifically, it is a polarizer which has an extremely high iodine content, and the color change in a high-temperature environment, a crack, and curvature can be suppressed remarkably. Details of the color change will be described later. In this specification, "iodine content" means the amount of all iodine contained in the polarizer (PVA-based resin film). More specifically, iodine in the polarizer exists in the form of iodine ions (I ^- ), iodine molecules (I ₂ ), polyiodine ions (I ₃ ^- , I ₅ ^- ), etc., the iodine content in the present specification is It refers to the amount of iodine including all of these forms. The iodine content can be calculated by, for example, a calibration ray method of fluorescence X-ray analysis. In addition, polyiodine ions exist in the state in which the PVA-iodine complex was formed in the polarizer. By forming such a complex, absorption dichroism can be expressed in the wavelength range of visible light. Specifically, the complex of PVA and triiodide ion (PVA·I ₃ ⁻ ) has an absorption peak around 470 nm, and the complex of PVA and iodide ion (PVA·I ₅ ⁻ ) absorbs light at around 600 nm. has a peak. As a result, polyiodine ions, depending on their form, can absorb light in a wide range of visible light. On the other hand, iodine ion (I ⁻ ) has an absorption peak around 230 nm and does not substantially participate in absorption of visible light. Therefore, polyiodine ions existing in a complex state with PVA may be mainly involved in the absorption performance of the polarizer.

The upper limit of the thickness of the polarizer is 10 µm in one embodiment, 7 µm in another embodiment, 3 µm in another embodiment, and 1 µm in another embodiment. The lower limit of the thickness is 0.5 μm in one embodiment, 0.6 μm in another embodiment, and 0.8 μm in still another embodiment. According to the embodiment of the present invention, even with a thin polarizer, a desired single transmittance as described later can be realized, and very excellent heat resistance can be realized. Typically, color change, cracks, and warpage in a high-temperature environment can be remarkably suppressed.

The absolute value of the single transmittance change amount ΔTsa is preferably 3.0% or less, and more preferably 1.0% or less. The lower limit of the absolute value of ΔTsa is inevitably 0.0% (that is, there is no change in the single transmittance before and after heating). The polarizer which concerns on embodiment of this invention has an extremely high iodine content as mentioned above, and the amount of single transmittance change in a high-temperature environment is suppressed remarkably. Therefore, the polarizer by which the discoloration in a high-temperature environment was suppressed can be implement|achieved. Such an excellent effect can be achieved by using a treatment solution (typically sodium hydrogen carbonate and/or citric acid) having a predetermined pH and a buffering action in the process after dyeing in the method for producing a polarizer as described later on a polyvinyl alcohol-based resin film It is estimated that it is realized by preventing polyenization in a high-temperature environment of the obtained polarizer by processing. This is to solve the problem newly discovered by actually manufacturing a very thin (for example, 7 micrometers or less thickness) polarizer which was conventionally difficult even to manufacture, and is an unexpectedly excellent effect. Incidentally, the amount of change in single transmittance ΔTsa is expressed by the following formula:

ΔTsa(%)=Ts ₃₀ -Ts ₀

Here, Ts ₀ is the single transmittance before the heating test, and Ts ₃₀ is the single transmittance after standing in an environment of 105° C. for 30 hours. In addition, in this specification, when simply describing the single transmittance|permeability as Ts, it means the single transmittance Ts ₀ before heating.

The single transmittance (Ts) of the polarizer is preferably 30.0% to 43.0%, more preferably 35.0% to 41.0%. The polarization degree of the polarizer is preferably 99.9% or more, more preferably 99.95% or more, and still more preferably 99.98% or more. By setting the single transmittance to be low and the polarization degree to be high, the contrast can be increased and the black display can be displayed more black, so that an image display device with excellent image quality can be realized. In addition, the single transmittance is the value measured with the spectrophotometer with an integrating sphere. The single transmittance is a Y value measured with a 2 degree field of view (C light source) of JIS Z8701 and corrected for visibility, for example, it can be measured using a spectrophotometer with an integrating sphere (manufactured by Nippon Bunko Co., Ltd., product name: V7100).

The polarizer preferably has an orthogonal a value of 0.0 to 0.6; The orthogonal b-value is preferably -0.6 to 0.0. The polarizer according to the embodiment of the present invention has such a very neutral hue while realizing the desired single transmittance and polarization degree and extremely excellent heat resistance. With such a color, problems such as blue omission do not occur. In addition, a-value and b-value are a-value and b-value of Lab colorimetric system, respectively. In addition, you may adjust each a value and b value so that it may deviate from the said range according to the objective. Further, in the polarizer, the color change Δab ₃₀ after a heat test at 105° C. for 30 hours is preferably 5.0 or less, and more preferably 4.0 or less.

The polarizer is preferably sodium hydrogen carbonate (NaHCO ₃ ), potassium hydrogen carbonate (KHCO ₃ ), disodium hydrogen phosphate (Na ₂ HPO ₄ ), potassium carbonate (K ₂ CO ₃ ), sodium carbonate (Na ₂ CO ₃ ) and citric acid; and at least any one of ions derived therefrom. Specific examples of such ions include sodium ion, carbonate ion, potassium ion, phosphate ion, citrate ion, and monosodium carbonate ion. The polarizer may contain 2 or more types of these substances and/or ions. The polarizer may more preferably include sodium ions, carbonate ions and/or citrate ions. This is due to the treatment (section B-1) with the treatment liquid in the production method (section B) described later. When a polarizer contains such a compound (that is, by manufacturing a polarizer by the manufacturing method including the process as described in Item B-1), the discoloration in the high temperature environment of a polarizer can be suppressed remarkably. This can suppress the generation of protons in the PVA-based resin by the buffering action in a predetermined pH range of the treatment solution, and as a result, the occurrence of multiple double bonds (polyenization) in the PVA-based resin under a high-temperature environment is suppressed. Therefore, it is estimated that discoloration can be suppressed. Furthermore, by suppressing polyenization, cracks and warping can be suppressed. This is estimated as follows: When a double bond is formed in a PVA-based resin molecule by polyenization, the distance between monomer units in the vicinity of the double bond becomes small. As a result, the PVA-based resin molecules (chains) partially contract, and such partial shrinkage may cause warpage or cracks. By suppressing polyenization, the formation of such a double bond is suppressed, and as a result, warping or cracking can be suppressed.

A-2. PVA-based resin film

As PVA-type resin which forms a PVA-type resin film, polyvinyl alcohol and ethylene-vinyl alcohol copolymer are mentioned, for example. Polyvinyl alcohol is obtained by saponifying polyvinyl acetate. The ethylene-vinyl alcohol copolymer is obtained by saponifying the ethylene-vinyl acetate copolymer. The saponification degree of PVA-type resin is 85 mol% or more and less than 100 mol% normally, Preferably they are 95.0 mol% - 99.95 mol%, More preferably, they are 99.0 mol% - 99.93 mol%. The degree of saponification can be obtained according to JIS K 6726-1994. By using the PVA-type resin of such a saponification degree, the polarizer excellent in durability can be obtained. When the degree of saponification is too high, there is a possibility of gelation.

The average degree of polymerization of the PVA-based resin may be appropriately selected depending on the purpose. The average degree of polymerization is usually from 1000 to 10000, preferably from 1200 to 4500, more preferably from 1500 to 4300. In addition, an average degree of polymerization can be calculated|required according to JISK6726-1994.

The thickness of the PVA-based resin film is not particularly limited, and may be set according to a desired thickness of the polarizer. The thickness of the PVA-based resin film is, for example, 10 µm to 200 µm.

In one embodiment, the PVA-type resin layer formed on the base material may be sufficient as a PVA-type resin film. The laminate of the substrate and the PVA-based resin layer can be obtained, for example, by a method of applying a coating liquid containing the PVA-based resin to the substrate, a method of laminating a PVA-based resin film on the substrate, or the like.

B. Manufacturing method of polarizer

B-1. Outline of the manufacturing method of a polarizer

The manufacturing method of the polarizer which concerns on embodiment of this invention includes extending|stretching and dyeing a PVA-type resin film at least. Typically, the manufacturing method includes a step of preparing a PVA-based resin film, a stretching step, a swelling step, a dyeing step, a crosslinking step, a washing step, and a drying step. Each process in which the PVA-based resin film is provided may be performed in any suitable order and timing. Therefore, each process may be performed in the above order, and may be performed in a different order from the above. If necessary, one step may be performed a plurality of times. In addition, you may perform processes other than the above (for example, insolubilization process) at arbitrary appropriate timings. Further, when the PVA-based resin film is a PVA-based resin layer formed on a substrate, a laminate of the substrate and the PVA-based resin layer is provided in the above step.

In the manufacturing method of the polarizer which concerns on embodiment of this invention, after dyeing, Preferably, it includes processing a PVA-type resin film with a processing liquid. The treatment with the treatment liquid may be performed at any suitable timing after dyeing. Specifically, the treatment with the treatment liquid may be performed before or after the crosslinking step, or may be performed before or after the washing step. When the stretching step is performed after the dyeing step, the treatment with the treatment liquid may be performed before or after the stretching step. When the swelling step is performed after the dyeing step, the treatment with the treatment liquid may be performed before or after the swelling step. When the insolubilization step is performed after the dyeing step, the treatment with the treatment liquid may be performed before or after the insolubilization step. Typically, the treatment with the treatment liquid may be performed after the washing step and before the drying step, or between the first drying step and the second drying step when the drying step is performed in two steps.

The pH of the treatment liquid is, for example, 3.0 to 8.0, preferably 5.0 to 8.0, more preferably 5.5 to 7.5, still more preferably 5.5 to 6.5. In another embodiment, more preferably, it is 3.5-5.5, More preferably, it is 3.7-4.7. In addition, the treatment solution preferably has a buffering action in the range of the pH (that is, the pH is in the range of 3.0 to 8.0). The treatment liquid may be, for example, an aqueous solution containing sodium hydrogen carbonate, potassium hydrogen carbonate, disodium hydrogen phosphate, potassium carbonate, sodium carbonate, or citric acid. A treatment solution containing these compounds, for example, has a buffering action in a high pH range compared to a treatment solution containing an acetic acid-based compound, and as a result, it can have a better effect of preventing discoloration under a high-temperature environment. Aqueous solution may contain these compounds independently and may contain 2 or more types. The treatment liquid is preferably an aqueous solution of sodium hydrogen carbonate or citric acid. Therefore, the polarizer according to the embodiment of the present invention may contain sodium hydrogen carbonate and/or citric acid as described above. The concentration of the aqueous solution can be appropriately set according to the desired pH and buffering action. For example, the concentration of the aqueous sodium hydrogen carbonate solution may be preferably 0.20 wt% to 2.0 wt%, and the concentration of the aqueous citric acid solution may be preferably 0.10 wt% to 3.0 wt%. Moreover, aqueous solution may contain the pH adjuster as needed. Examples of the pH adjuster include sulfuric acid (to decrease the pH) and sodium hydroxide (to increase the pH). By processing the PVA-type resin film with such a processing liquid, the discoloration in the high temperature environment of a polarizer can be suppressed remarkably. As described above, the generation of protons in the PVA-based resin can be suppressed by the buffering action in the predetermined pH range of the treatment solution, and as a result, the generation of many double bonds in the PVA-based resin under a high-temperature environment (polyenization). ), and it is estimated that discoloration can be suppressed.

The treatment with the treatment liquid typically includes bringing the treatment liquid into contact with the PVA-based resin film. Any suitable method can be mentioned as a contact method. As a specific example, immersion to the processing liquid of a PVA-type resin film, application|coating or spraying of the processing liquid to a PVA-type resin film is mentioned. Application or spraying of the treatment liquid is preferred. It is because the problem called the absorption spectrum change of the polarizer before and behind the immersion in immersion can be prevented, and polyenization of PVA can be prevented still more favorably as a result. Any suitable method (means) can be employed as the method (means) for applying or spraying the treatment liquid onto the PVA-based resin film. Examples of the application means include a reverse coater, a gravure coater (direct, reverse or offset), a bar reverse coater, a roll coater, a die coater, a bar coater, and a rod coater. Any suitable atomizing apparatus (for example, a pressure nozzle type, a rotating disk type) is mentioned as a spraying means.

Hereinafter, although each process is demonstrated, as mentioned above, each process can be performed in any suitable order, and is not limited to the order of description.

B-2. drawing process

In the stretching step, the PVA-based resin film is typically uniaxially stretched 3 to 7 times. The longitudinal direction (MD direction) of a film may be sufficient as an extending|stretching direction, and the width direction (TD direction) of a film may be sufficient as it. Dry extending|stretching may be sufficient as the extending|stretching method, and wet extending|stretching may be sufficient and these may be combined. Moreover, when performing a bridge|crosslinking process, a swelling process, a dyeing|staining process, you may extend|stretch a PVA-type resin film. In addition, the direction of stretching may correspond to the direction of the absorption axis of the polarizer to be obtained.

B-3. swelling process

The swelling process is usually performed before the dyeing process. The swelling step is performed, for example, by immersing the PVA-based resin film in a swelling bath. As the swelling bath, water such as distilled water or pure water is usually used. The swelling bath may contain arbitrary appropriate other components other than water. As other components, solvents, such as alcohol, additives, such as surfactant, iodide, etc. are mentioned. 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, titanium iodide, and the like. Preferably, potassium iodide is used. The temperature of the swelling bath is, for example, 20°C to 45°C. In addition, immersion time is 10 second - 300 second, for example.

B-4. dyeing process

The dyeing process is a process of dyeing a PVA-based resin film with a dichroic substance. Preferably, it carries out by adsorbing a dichroic substance. As the adsorption method, for example, a method of immersing a PVA-based resin film in a dyeing solution containing a dichroic substance, a method of coating the dyeing solution on a PVA-based resin film, a method of spraying the dyeing solution onto a PVA-based resin film, etc. can be heard Preferably, it is a method of immersing a PVA-based resin film in a dyeing solution. It is because a dichroic substance can adsorb|suck favorably.

Examples of the dichroic substance include iodine and dichroic dye. Preferably it is iodine. When using iodine as a dichroic substance, iodine aqueous solution is used preferably as a dyeing solution. Preferably the content of iodine in an iodine aqueous solution is 0.04 weight part - 5.0 weight part with respect to 100 weight part of water. In order to improve the solubility of iodine in water, it is preferable to mix|blend iodide with iodine aqueous solution. As the iodide, potassium iodide is preferably used. To [ content of iodide / 100 weight part of water ], Preferably they are 0.3 weight part - 15 weight part.

The liquid temperature at the time of dyeing a dyeing solution can be set to any suitable value, for example, 20 degreeC - 50 degreeC. In the case of immersing the PVA-based resin film in the dyeing solution, the immersion time is, for example, 5 seconds to 5 minutes.

B-5. crosslinking process

In a crosslinking process, a boron compound is normally used as a crosslinking agent. As a boron compound, boric acid, borax, etc. are mentioned, for example. Preferably it is boric acid. In the crosslinking process, the boron compound is usually used in the form of an aqueous solution.

When an aqueous boric acid solution is used, the boric acid concentration of the boric acid aqueous solution is, for example, 1 wt% to 15 wt%, preferably 1 wt% to 10 wt%. You may make the boric-acid aqueous solution contain zinc compounds, such as iodide, such as potassium iodide, zinc sulfate, and zinc chloride, further.

A crosslinking process can be performed by arbitrary suitable methods. For example, a method of immersing a PVA-based resin film in an aqueous solution containing a boron compound, a method of applying an aqueous solution containing a boron compound to the PVA-based resin film, or a method of spraying an aqueous solution containing a boron compound onto the PVA-based resin film can be heard It is preferable to immerse in the aqueous solution containing a boron compound.

The temperature of the solution used for crosslinking is, for example, 25°C or higher, preferably 30°C to 85°C, and more preferably 40°C to 70°C. Immersion time is 5 second - 800 second, for example, Preferably they are 8 second - 500 second.

B-6. cleaning process

The washing process may be typically performed after the crosslinking process. The washing step is typically performed by immersing the PVA-based resin film in a washing solution. A typical example of the washing liquid is pure water. You may add potassium iodide to pure water.

The temperature of the washing liquid is, for example, 5°C to 50°C. Immersion time is 1 second - 300 second, for example.

B-7. drying process

The drying process can be performed by any suitable method. As a drying method, natural drying, air drying, reduced pressure drying, heat drying etc. are mentioned, for example. Heat drying is preferably used. When heat-drying, a heating temperature is 30 degreeC - 100 degreeC, for example. In addition, the drying time is, for example, between 20 seconds and 10 minutes.

C. Polarizer

The polarizer according to the embodiment of the present invention is typically used in a state in which a protective film is laminated on one side or both sides thereof (that is, as a polarizing plate). Practically, a polarizing plate contains an adhesive layer as an outermost layer. The pressure-sensitive adhesive layer is typically an outermost layer on the side of the image display device. A separator is temporarily attached to an adhesive layer so that peeling is possible, and while protecting an adhesive layer until actual use, roll formation is enabled.

As a protective film, arbitrary appropriate resin films are used. Examples of the material for forming the resin film include cellulose resins such as (meth)acrylic resins, diacetyl cellulose and triacetyl cellulose, cycloolefin resins such as norbornene resins, olefinic resins such as polypropylene, and polyethylene terephthalate. Ester-type resins, such as resin, polyamide-type resin, polycarbonate-type resin, these copolymer resin, etc. are mentioned. In addition, "(meth)acrylic-type resin" means an acrylic resin and/or a methacryl-type resin.

In one embodiment, as said (meth)acrylic-type resin, the (meth)acrylic-type resin which has a glutarimide structure is used. (Meth)acrylic resins having a glutarimide structure (hereinafter also referred to as glutarimide resins) are, for example, in Japanese Patent Laid-Open Nos. 2006-309033, 2006-317560, and Japanese Unexamined Patent Publication (Kokai). No. 2006-328329, Japanese Unexamined Patent Publication No. 2006-328334, Japanese Unexamined Patent Publication No. 2006-337491, Japanese Unexamined Patent Publication No. 2006-337492, Japanese Unexamined Patent Publication No. 2006-337493, Japanese Unexamined Patent Publication It is described in No. 2006-337569, Japanese Unexamined Patent Publication No. 2007-009182, Japanese Unexamined Patent Publication No. 2009-161744, and Japanese Unexamined Patent Publication No. 2010-284840. Their descriptions are incorporated herein by reference.

When manufacturing a polarizer using the laminated body of a base material and a PVA-type resin layer, you may use as a protective film as it is, without peeling a base material.

[Example]

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) Iodine content

The fluorescence X-ray intensity (kcps) of the polarizers of the laminates obtained in Examples, Comparative Examples and Reference Examples using a fluorescence X-ray analyzer (manufactured by Rigaku, trade name "ZSX-PRIMUS II", measurement diameter: Φ20 mm) was measured. In addition, the thickness (micrometer) of the said polarizer was measured using the spectroscopic film thickness meter (The Otsuka Electronics company make, brand name "MCPD-3000"). The iodine content (weight%) was calculated|required using the following formula from the obtained fluorescent X-ray intensity and thickness.

(iodine concentration)=20.5×(fluorescence X-ray intensity)/(film thickness)

In addition, although the coefficient at the time of calculating iodine content changes with a measuring apparatus, the said coefficient can be calculated|required using an appropriate analytical curve.

(2) ΔTsa and ΔTsa'

The reflection type polarizer (the 3M company make, brand name "DBEF") was pasted together to the polarizer side of the laminated body obtained by the Example, the comparative example, and the reference example. Next, the thermoplastic resin base material was peeled, and the alkali-free glass of thickness 1.3mm was bonded together to the said peeling surface through the acrylic adhesive layer of thickness 20 micrometers, and it was set as the test sample. This test sample was heated under the conditions of 105 degreeC for 30 hours (heating test). The single transmittance of the polarizer before the test and after the heating test was measured using a spectrophotometer with an integrating sphere (manufactured by Nippon Bunko Co., Ltd., product name: V7100), respectively. From the single transmittance Ts ₀ before heating and the single transmittance Ts ₃₀ after the heating test, the amount of change in the single transmittance ΔTsa was calculated using the following formula.

ΔTsa(%)=Ts ₃₀ -Ts ₀

In addition, ΔTsa' (%) = Ts ₂₀ -Ts ₀ when the heating time of the heating test was set to 20 hours was also obtained.

(3) color change Δab

For the laminates obtained in Examples, Comparative Examples, and Reference Examples, a-values and b-values were measured using an ultraviolet and visible spectrophotometer (manufactured by Nippon Bunko, V-7100). These were made into a ₀ value and b ₀ value. In addition, a ₂₀ value and b ₂₀ value after heating at 105° C. for 20 hours, and a ₃₀ value and b ₃₀ value after heating at 105° C. for 30 hours were respectively obtained. Color change amounts Δab ₂₀ and Δab ₃₀ were respectively calculated from these values using the following equation.

Δab ₂₀ ={(a ₂₀ -a ₀ ) ² +(b ₂₀ -b ₀ ) ² } ^1/2

Δab ₃₀ ={(a ₃₀ -a ₀ ) ² +(b ₃₀ -b ₀ ) ² } ^1/2

(4) Initial appearance of polarizer

The external appearance of the polarizer (namely, the polarizer before the heating test of said (2)) of the laminated body obtained by the Example, the comparative example, and the reference example was observed visually, and the following reference|standard evaluated.

(circle): Cloudiness was not confirmed

(triangle|delta): cloudiness was confirmed slightly

x: cloudiness was remarkable

(5) crack

After heating the laminated body obtained by the Example, the comparative example, and the reference example at 115 degreeC for 72 hours, the state of the crack of a polarizer was observed visually, and the following reference|standard evaluated.

(circle): No crack was confirmed

x: a crack was confirmed

(6) Warp

The surface by the side of the polarizer of the laminated body obtained by Example 1 and the comparative example 1 was bonded together through the 20-micrometer-thick acrylic adhesive layer, and the alkali free glass of thickness 0.55mm was made into the test sample. After heating this test sample at 115 degreeC for 72 hours, the amount of warpage was measured. Deflection amount measured the height from a glass plate with respect to 4 corners of a test piece, respectively, and made the largest value into deflection amount. The warpage amount of Example 1 was 0.0 mm, which was "good", and the warpage amount of Comparative Example 1 was 0.75 mm, which was "poor (remarkable warpage)".

[Example 1]

As a thermoplastic resin substrate, an amorphous isophthalic acid copolymerized polyethylene terephthalate (IPA copolymerized PET) film (thickness: 100 µm) having a water absorption rate of 0.75% and Tg75°C was used. Corona treatment is performed on one side of the substrate, and polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mol%) and acetoacetyl-modified PVA (polymerization degree 1200, acetoacetyl modification degree 4.6%, saponification degree 99.0 mol% or more) is performed on the corona-treated surface. , manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "Gosepimer Z200") was coated and dried at 25° C. with an aqueous solution containing a 9:1 ratio to form a PVA-based resin layer having a thickness of 11 μm, thereby preparing a laminate.

The obtained laminated body was air-stretched 4.5 times in the direction orthogonal to the longitudinal direction of the laminated body at 140 degreeC using the tenter stretching machine (stretching process).

Next, the laminate was immersed for 12 seconds in a dyeing bath (aqueous solution having an iodine concentration of 1.4 wt% and a potassium iodide concentration of 9.8 wt%) at a liquid temperature of 25°C for dyeing (dyeing treatment).

Next, the laminate was immersed in a washing bath (pure water) at a liquid temperature of 25°C for 6 seconds (first washing treatment).

Then, it was immersed in a crosslinking bath (aqueous solution with a boron concentration of 1 weight% and potassium iodide concentration of 1 weight%) of 60 degreeC for 16 second (crosslinking process).

Next, the laminate was immersed in a washing bath (aqueous solution having a potassium iodide concentration of 1% by weight) having a liquid temperature of 25°C for 3 seconds (second washing treatment).

Next, the laminate was dried in an oven at 60° C. for 21 seconds (first drying treatment).

Next, a treatment solution (aqueous solution of 0.5% by weight of sodium bicarbonate and 50% by weight of isopropyl alcohol: pH=6.0) was applied to the PVA-based resin layer of the laminate using a bar coater. In addition, the pH of the treatment liquid was adjusted by mixing dilute sulfuric acid.

Finally, the laminate was dried in an oven at 50° C. for 60 seconds to obtain a laminate including a PVA-based resin layer (polarizer) having a thickness of 1.2 μm. The iodine content of the obtained polarizer was 20.9 weight%, and the single transmittance|permeability was 39.3 %.

The obtained laminated body was used for evaluation of said (2)-(6). A result is shown in Table 1.

[Example 2]

Except having used the aqueous solution (pH=6.0) of 0.2 weight% of citric acid and 50 weight% of isopropyl alcohol as a process liquid, it carried out similarly to Example 1, and obtained the laminated body containing a polarizer. In addition, the pH of a process liquid was adjusted by mixing sodium hydroxide. The iodine content of the obtained polarizer was 20.5 weight%, and the single transmittance|permeability was 39.5 %. The obtained laminate was subjected to evaluation similar to Example 1. A result is shown in Table 1.

[Example 3]

Except having changed the conditions of the dyeing|dyeing process so that the single transmittance of the obtained polarizer might be set to 43 % vicinity, it carried out similarly to Example 1, and obtained the laminated body containing a polarizer. The iodine content of the obtained polarizer was 6.5 weight%, and the single transmittance|permeability was 43.2%. The obtained laminate was subjected to evaluation similar to Example 1. A result is shown in Table 1.

[Example 4]

Except having changed the conditions of the dyeing|dyeing process so that the single transmittance of the obtained polarizer might be set to 43 % vicinity, it carried out similarly to Example 2, and obtained the laminated body containing a polarizer. The iodine content of the obtained polarizer was 6.5 weight%, and the single transmittance|permeability was 42.8%. The obtained laminate was subjected to evaluation similar to Example 1. A result is shown in Table 1.

[Example 5]

Except having made the sodium hydrogencarbonate of a process liquid into 1.0 weight, it carried out similarly to Example 1, and obtained the laminated body containing a polarizer. The iodine content of the obtained polarizer was 20.5 weight%, and the single transmittance|permeability was 39.5 %. The obtained laminate was subjected to evaluation similar to Example 1. A result is shown in Table 1.

[Comparative Example 1]

Except not having performed the process by a process liquid, it carried out similarly to Example 1, and obtained the laminated body containing a polarizer. The iodine content of the obtained polarizer was 21.5 weight%, and the single transmittance|permeability was 39.3%. The obtained laminate was subjected to evaluation similar to Example 1. A result is shown in Table 1.

[Comparative Example 2]

A laminate containing a polarizer was obtained in the same manner as in Example 1, except that the treatment with the treatment liquid was not performed and the conditions of the dyeing treatment were changed so that the single transmittance of the obtained polarizer was around 43%. The iodine content of the obtained polarizer was 6.7 weight%, and the single transmittance|permeability was 43.2 %. The obtained laminate was subjected to the same evaluation as in Example 1. A result is shown in Table 1.

[Reference Example 1]

In the same manner as in Example 1, except that the coating thickness of the PVA aqueous solution was changed so that the thickness of the obtained polarizer was 12 μm, and the dyeing treatment conditions were changed so that the single transmittance of the obtained polarizer was around 43%, the polarizer was included A laminate was obtained. The iodine content of the obtained polarizer was 3.3 weight%, and the single transmittance|permeability was 43.0%. The obtained laminate was subjected to evaluation similar to Example 1. A result is shown in Table 1.

[Reference Example 2]

A layered product containing a polarizer was obtained in the same manner as in Example 1 except that the treatment with the treatment liquid was not performed, and the conditions of the dyeing treatment were changed so that the single transmittance of the obtained polarizer was 45% or more. The iodine content of the obtained polarizer was 2.1 weight%, and the single transmittance|permeability was 45.7%. The obtained laminate was subjected to evaluation similar to Example 1. A result is shown in Table 1.

[Table 1]

As is clear from Table 1, it can be seen that the polarizer of the Example of the present invention is excellent in any of single transmittance change, color change, crack, and warpage after the heating test, and has very excellent heat resistance. Moreover, when Examples 1 and 2 are referred, it turns out that heat resistance is a thin shape, and it is a subject peculiar to a polarizer with a very large iodine content evidently.

The polarizer of the present invention can be widely applied to liquid crystal panels such as liquid crystal TVs, liquid crystal displays, mobile phones, digital cameras, video cameras, portable game machines, car navigation systems, copiers, printers, fax machines, watches, and microwave ovens.

Claims (3)

It is composed of a polyvinyl alcohol-based resin film,
The iodine content is 3.5% by weight or more,
The thickness is 0.5㎛ ~ 1.2㎛,
A polarizer in which the absolute value of the single transmittance change amount ΔTsa after being placed in an environment of 105° C. for 30 hours is 5.0% or less, and the single transmittance change amount ΔTsa is represented by the following formula:
ΔTsa(%)=Ts ₃₀ -Ts ₀
Here, Ts ₀ is the single transmittance before heating, and Ts ₃₀ is the single transmittance after being placed in an environment of 105° C. for 30 hours. The method of claim 1,
A polarizer comprising at least one selected from a sodium ion, a carbonate ion, and a citrate ion. The polarizing plate containing the polarizer of Claim 1 or 2, and the protective film laminated|stacked on one side or both sides of the said polarizer.