JP5079184B2 - Polarized film - Google Patents

Description

【００３７】
【発明の効果】
本発明の偏光フィルムは、可視光線スペクトルの範囲における偏光性能に優れ、さらには高温高湿下に長期間放置した場合の耐久性にも優れており、これらの優れた特性を生かして、ＬＣＤナビゲーションシステムだけでなく、ＬＣＤテレビなどの温度や湿度変化が大きい車載ＬＣＤ用の偏光板の製造に有効に使用することができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a polarizing film comprising a polyvinyl alcohol derivative having a polyvinylene structure.
[0002]
[Prior art]
A polarizing plate having a light transmission and shielding function is a basic component of a liquid crystal display (LCD) together with a liquid crystal having a light switching function. The application field of this LCD is widespread from small devices such as calculators and wristwatches in the early days to laptop computers, word processors, liquid crystal color projectors, in-vehicle navigation systems, liquid crystal televisions, and the like. Since LCDs have been used for a long time on a large screen and used outdoors, there has been a demand for polarizing plates that are superior in optical performance and durability than conventional products.
[0003]
In general, a polarizing plate is a polyvinyl alcohol film (hereinafter, the polyvinyl alcohol film is abbreviated as “PVA film”, and the polyvinyl alcohol as a raw material thereof is referred to as a polyvinyl alcohol polymer, which is abbreviated as “PVA”. A support plate such as a cellulose triacetate (TAC) film is bonded to both surfaces of a polarizing film produced by uniaxially stretching and dyeing. The polarizing film includes an iodine polarizing film obtained by dyeing a PVA film with iodine, a dye polarizing film obtained by dyeing a PVA film with a dichroic dye, etc., and a PVA derivative having a polyvinylene structure obtained by dehydrating the PVA film. There is known a polarizing film comprising (US Pat. No. 2,173,304).
[0004]
Among these conventionally known polarizing films, iodine-based polarizing films and dye-based polarizing films have a problem that the polarizing performance is high but the durability is low. Moreover, although the polarizing film which consists of a polyvinyl alcohol derivative which has a polyvinylene structure is excellent in durability, there existed a problem that polarizing performance was low. In order to solve these problems, a polarizing film made of a polyvinyl alcohol derivative having a polyvinylene structure obtained by using polyvinyl alcohol having a polymerization degree of 2000 or more as a material has been proposed (Japanese Patent Laid-Open No. 10-319236). ), A big improvement effect is recognized.
[0005]
However, in recent years, the development of LCD applications has been remarkably progressed, such as screens becoming larger and being used outdoors for mobile applications, and there is a need for polarizing plates that have better optical performance and durability than ever before. ing.
[0006]
[Problems to be solved by the invention]
An object of the present invention is to provide a polarizing film excellent in durability and polarizing performance.
[0007]
[Means for Solving the Problems]
According to the present invention, the above problem is that the amount of 1,2-glycol bonds is 1.5 mol% or less. With a polymerization degree of 1000 or more From polyvinyl alcohol (hereinafter, this polyvinyl alcohol may be abbreviated as modified PVA to distinguish it from normal PVA). By subjecting the resulting film to dry heat stretching at 100 to 250 ° C. in an atmosphere that prevents oxidation of polyvinyl alcohol Has the resulting polyvinylene structure A polarizing film, when the polarizing film is subjected to a durability test that is allowed to stand for 1000 hours at 80 ° C. and 90% RH, the dichroic ratio before the durability test is 26 or more, and the dichroism after the durability test The ratio is 17 or more Can be achieved by a polarizing film.
The polarizing film of the present invention is excellent in polarizing performance in the visible light spectrum range, and also excellent in durability when left for a long time under high temperature and high humidity.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in more detail.
The modified PVA used in the present invention is required to have a 1,2-glycol bond amount of 1.5 mol% or less, more preferably 1.4 mol% or less, still more preferably 1.2 mol% or less. Especially preferably, it is 1.0 mol% or less. From the viewpoint of improving the heat resistance, durability, and polarization performance of the polarizing film, the 1,2-glycol bond amount of the modified PVA is preferably as low as possible, but if the 1,2-glycol bond amount is too low, the production of the modified PVA is performed. Since it becomes difficult per se, it is suitable that it is 0.5 mol% or more.
[0009]
In the present invention, the degree of polymerization of the modified PVA is preferably 1000 or more, more preferably 1800 or more, and particularly preferably 2000 or more in consideration of the strength and processing characteristics of the film made of the modified PVA. The degree of polymerization of the modified PVA is preferably 8000 or less, more preferably 4000 or less, and particularly preferably 3000 or less from the viewpoint of processing characteristics such as film formation and stretching. The degree of polymerization of the modified PVA can be determined by the method described in JIS-K6726.
[0010]
The degree of saponification of the modified PVA is preferably 95 mol% or more, more preferably 98 mol% or more, particularly preferably 99 mol% or more, optimal from the viewpoint of the polarizing performance and durability of the film having a polyvinylene structure obtained. Is 99.5 mol% or more. Furthermore, the higher the degree of saponification of the modified PVA, the better. However, if the degree of saponification becomes too high, it becomes difficult to produce the modified PVA itself, so that it is suitably 99.99 mol% or less.
In addition, the saponification degree as used in this specification shows the ratio of the unit which is actually saponified by the vinyl alcohol unit in the unit which can be converted into a vinyl alcohol unit by saponification. The degree of saponification of the modified PVA can be determined by the method described in JIS-K6726.
[0011]
The polarizing film of the present invention preferably has a dichroic ratio of 25 or more, more preferably 30 or more, and particularly preferably 33 or more. As a method for improving the two-color ratio of the polarizing film, there is a method in which a film made of PVA containing a dehydration accelerator and containing a small amount of 1,2-glycol bonds is dry-heat stretched at a high stretch ratio in a low oxygen atmosphere. preferable.
[0012]
The maximum absorption wavelength in the range of the visible light absorption spectrum (wavelength: 380 to 780 nm) of the polarizing film is preferably 500 nm or more, more preferably 520 nm or more, and particularly preferably 540 nm or more. The upper limit of the maximum absorption wavelength is preferably 650 nm, and more preferably 630 nm. As the 1,2-glycol bond amount of the modified PVA decreases, the maximum absorption wavelength tends to move to the higher wavelength side.
When the maximum absorption wavelength is in the above range, the number of vinylene units of a conjugated double bond forming a polyvinylene structure is considered to be about 15 to 30.
[0013]
PVA having a 1,2-glycol bond amount of 1.5 mol% or less used in the present invention is obtained by polymerizing a vinyl ester monomer at a temperature of 50 ° C. or less to obtain a vinyl ester polymer, which is saponified. Can be obtained by:
[0014]
Examples of the polymerization method of the vinyl ester monomer include a low temperature bulk polymerization method, a low temperature suspension polymerization method and a low temperature emulsion polymerization method. In the low temperature polymerization method, in a polymerization system having a large chain transfer such as a vinyl ester monomer, since the chain transfer is suppressed as the polymerization temperature is lowered, the degree of polymerization is usually increased. By using a chain transfer agent in combination, a PVA having a 1,2-glycol bond amount of 1.5 mol% or less and a desired degree of polymerization can be obtained. The polymerization temperature is preferably in the range of −50 to 50 ° C., preferably in the range of −40 to 40 ° C., particularly in the range of −30 to 20 ° C., from the viewpoint of easy polymerization and the performance of the obtained polarizing film. preferable.
Examples of the polymerization catalyst include an azo catalyst, a peroxide catalyst, a redox catalyst, and the like. Further, from the viewpoint of the durability performance and polarization performance of the polarizing film, the polymerization of the vinyl ester monomer is preferably carried out by a low temperature emulsion polymerization method using a redox catalyst.
[0015]
As the chain transfer agent that can be used for the polymerization of the vinyl ester monomer, a conventionally known one such as an aldehyde compound can be suitably used. In particular, from the viewpoint of durability performance and polarization performance of the polarizing film, R′S— Mercaptan represented by H (R ′ represents a hydrocarbon group having 1 to 18 carbon atoms or a mono- or polyhydroxy hydrocarbon group, and S represents a sulfur atom) is preferably used.
In the mercaptan represented by the above formula, when the carbon number of R ′ is smaller than 1, the reactivity of the mercaptan is too high to be difficult to handle, and when the carbon number exceeds 18, the resulting PVA crystals As a result, the intended polarizing film having excellent durability cannot be obtained.
Examples of mercaptans that can be used include methanethiol, ethanethiol, n-propanethiol, i-propanethiol, n-butanethiol, i-butanethiol, t-butanethiol, n-hexanethiol, n-octane. Thiol, i-octanethiol, n-decanethiol, n-dodecanethiol, t-dodecanethiol, n-tetradecanethiol, n-hexadecanethiol, n-octadecanethiol, 2-mercaptoethanol, 3-mercapto-1-propanol, Examples thereof include 1-mercapto-2-propanol, 3-mercapto-1,2-propanediol, 4-mercapto-1-butanol, and 3-mercapto-2-butanol. Among these, a mercaptan containing a mono- or polyhydroxy hydrocarbon group from the viewpoints that the odor is relatively small, the workability is good, the reactivity is relatively high, and the crystallinity of the obtained PVA is not impaired. Are more preferable, and mercaptans containing a monohydroxy group such as 2-mercaptoethanol, 3-mercapto-1-propanol, 4-mercapto-1-butanol are particularly preferable.
In the process of producing the modified PVA used in the present invention, when a mercaptan is used as a chain transfer agent during the polymerization of the vinyl ester monomer, a mercapto group is introduced into the molecular end of the modified PVA. The reason is not clear from the film in which the mercapto group is introduced at the molecular end of the modified PVA, but a polarizing film having further excellent durability performance and optical performance can be obtained. Therefore, the use of the film is preferable and recommended. The
[0016]
Examples of the vinyl ester monomer that can be used for the production of PVA having a 1,2-glycol bond amount of 1.5 mol% or less in the present invention include vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, and laurin. Examples thereof include vinyl acid vinyl, vinyl stearate, vinyl benzoate, vinyl pivalate, vinyl versatate, and among these, vinyl acetate is preferable.
[0017]
When copolymerizing the vinyl ester monomer, if necessary, the copolymerizable monomer is within a range that does not impair the effects of the invention (preferably 15 mol% or less, more preferably 5 mol% or less). It can be copolymerized.
[0018]
Examples of the monomer copolymerizable with the vinyl ester monomer include olefins having 3 to 30 carbon atoms such as ethylene, propylene, 1-butene and isobutene; acrylic acid and salts thereof; methyl acrylate and acrylic acid. Acrylic acid such as ethyl, n-propyl acrylate, i-propyl acrylate, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, octadecyl acrylate Esters; methacrylic acid and salts thereof; methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, i-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, methacrylic acid 2 -Ethylhexyl, dodecyl methacrylate, Methacrylic acid esters such as octadodecyl tacrylate; acrylamide, N-methylacrylamide, N-ethylacrylamide, N, N-dimethylacrylamide, diacetone acrylamide, acrylamide propanesulfonic acid and its salt, acrylamidopropyldimethylamine and its salt or Quaternary salts thereof, acrylamide derivatives such as N-methylolacrylamide and derivatives thereof; methacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, methacrylamidepropanesulfonic acid and salts thereof, methacrylamidepropyldimethylamine and salts thereof or Methacrylamide derivatives such as quaternary salts, N-methylolacrylamide and derivatives thereof; methyl vinyl ether, ethyl vinyl ether Vinyl ethers such as n-propyl vinyl ether, i-propyl vinyl ether, n-butyl vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether and stearyl vinyl ether; nitriles such as acrylonitrile and methacrylonitrile; vinyl chloride and vinylidene chloride , Vinyl halides such as vinyl fluoride and vinylidene fluoride; allyl compounds such as allyl acetate and allyl chloride; maleic acid and its salts or esters thereof; itaconic acid and its salts or esters thereof; vinylsilyl such as vinyltrimethoxysilane Compounds; isopropenyl acetate and the like.
[0019]
In the present invention, PVA having a 1,2-glycol bond amount of 1.5 mol% or less can be produced by saponifying the above-described polyvinyl ester polymer according to a known method using an alkali catalyst or an acid catalyst. it can.
[0020]
The polarizing film of the present invention is manufactured using a film obtained by forming PVA having a 1,2-glycol bond amount of 1.5 mol% or less as a material. Examples of a method for forming a film from PVA include a casting method or a die casting method in which a PVA solution is cast on a film formed from a resin, a drying drum, or a drying belt. Examples of the PVA solvent in the film-forming methods of these films include water, an organic solvent, or a mixed solution of water and an organic solvent. Examples of the organic solvent in this case include dimethyl sulfoxide, phenol, methanol, ethanol and the like. If necessary, a plasticizer, a surfactant, a dichroic dye, inorganic salts, and the like can be added to the PVA solution. The formed PVA film may be heat-treated as necessary. The thickness of the PVA film is preferably 5 to 500 μm, more preferably 10 to 200 μm, and particularly preferably 20 to 100 μm.
[0021]
The polarizing film of the present invention is a pre-swelling treatment for a PVA film, a dehydration treatment for generating a polyvinylene structure, a uniaxial stretching treatment (a uniaxial stretching treatment and a dehydration treatment are often performed simultaneously), a fixing treatment with a boron compound, and the like. It can manufacture through processes, such as a process, and there is no restriction | limiting in particular in the order and frequency | count of these processes. The polarizing film manufactured through these steps may be further heat-treated as necessary.
[0022]
The PVA film is dehydrated, thereby forming a polyvinylene structure in the PVA. The PVA film can be dehydrated by stretching a PVA film containing a dehydration accelerator, or by heating the stretched PVA film containing a dehydration accelerator. As a method of adding a dehydration accelerator to the PVA film, a method of immersing the PVA film in an aqueous solution containing the dehydration accelerator, a method of placing the PVA film in an atmosphere of a gaseous dehydration accelerator, and a dehydration accelerator are contained. Examples thereof include a method for forming a PVA solution. Examples of the dehydration accelerator include proton acids such as hydrochloric acid and sulfuric acid, and stannic halides such as stannic chloride and stannic bromide. The dehydration accelerator is preferably added in an amount ranging from 0.001 to 10% by weight with respect to PVA. When the amount of the dehydration accelerator is less than the above range, the polarization performance tends to be difficult to express. If the amount of the dehydration accelerator is larger than the above range, efficient dehydration may be difficult. Examples of the time when the dehydration accelerator is added include when the PVA film is formed, before uniaxial stretching of the PVA film, and before the dehydration treatment of the PVA film. When adding a dehydration accelerator to the film-forming stock solution of the PVA film, care should be taken because the PVA may be thermally oxidized if the drying temperature during film formation is too high.
[0023]
Examples of the method for uniaxially stretching the PVA film include dry heat stretching, wet stretching, stretching in warm water, stretching in the air with the film absorbed in water, and the like.
The stretching temperature when dry-stretching the PVA film is preferably 100 ° C. or higher, more preferably 120 ° C. or higher, and particularly preferably 140 ° C. or higher. The stretching temperature is preferably 250 ° C. or lower, more preferably 230 ° C. or lower, particularly preferably 220 ° C. or lower. The stretching temperature may be changed according to the stretched state of the film being stretched.
In addition, when the PVA film is stretched by dry heat, coloring due to oxidation of PVA may occur, and therefore, it is preferably performed in a nitrogen atmosphere or a low oxygen atmosphere such as in a vacuum. The PVA film changes to a colored film in which a polyvinylene structure having polarization performance is formed during dry-heat stretching.
The stretching temperature when wet-stretching the PVA film is preferably 20 ° C. or higher, more preferably 40 ° C. or higher, and particularly preferably 50 ° C. or higher. The stretching temperature is preferably 90 ° C. or lower, and more preferably 80 ° C. Since the polyvinylene structure is difficult to be formed only by wet-stretching the PVA film, a separate heat treatment is required.
When the stretching temperature is low, it is difficult to stretch at a high magnification, and the polarization performance is difficult to improve. On the other hand, when the stretching temperature is high, the film is likely to be cut during stretching. When stretching is performed twice or more, a combination of the same types of stretching such as dry heat stretching-dry heat stretching, wet stretching-wet stretching may be repeated, or dry stretching-wet stretching, wet Different combinations of stretching, such as stretching-dry stretching, may be repeated.
The draw ratio is preferably 4 times or more, and more preferably 5 times or more. As the draw ratio increases, the maximum absorption wavelength in the film moves to the higher wavelength side, and the optical properties are improved. The upper limit of the draw ratio is preferably 10 times and more preferably 9 times from the viewpoint of uniform stretchability.
[0024]
If the PVA film is not sufficiently dehydrated during stretching and the formation of the polyvinylene structure is insufficient, a dehydration accelerator is added to the stretched PVA film and then heated to further dehydrate the PVA film. Process. In this case, the heating temperature is preferably in the range of 90 to 180 ° C, more preferably in the range of 130 to 170 ° C.
When the thickness of the PVA film is 30 to 100 μm, the amount of dehydration from the PVA film is preferably 1 to 5% by weight with respect to the PVA film. When the amount of dehydration from the PVA film is small, the amount of absorption of visible light is reduced, and sufficient polarization performance is not exhibited. On the other hand, if the amount of dehydration is too large, the amount of visible light absorption becomes excessive, making it difficult to obtain a reasonably transparent polarizing film or causing a cross-linking reaction between molecules, resulting in a decrease in the number of conjugated double bonds. And the film becomes brittle.
[0025]
If the dehydration accelerator remains in the polarizing film, the polarizing performance may change when the polarizing film is left at a high temperature. To prevent this, the polarizing film is made of water, weak alkaline aqueous solution, aqueous methanol, saline solution. It is preferable to remove the dehydration accelerator by dipping in an aqueous inorganic material such as
[0026]
The PVA film in which the polyvinylene structure is formed on PVA is preferably immersed in a fixed treatment bath containing 1 to 6% by weight of a boron compound (eg, boric acid). This immersion treatment may be performed according to the required level of water resistance. The temperature of the fixing treatment bath is preferably kept in the range of 20 to 70 ° C. The PVA film after taking out from the fixing treatment bath is subjected to drying, and the temperature at the time of drying is preferably in the range of 30 to 80 ° C. After drying, the PVA film may be further heat-treated at a temperature in the range of 50 to 150 ° C.
[0027]
The thickness of the polarizing film of the present invention is preferably in the range of 5 to 200 μm, and more preferably in the range of 10 to 100 μm.
In order to impart further sufficient water resistance to the polarizing film of the present invention, a polarizing plate may be obtained by laminating a protective film having transparency and mechanical strength on both sides or one side. As the protective film used for this purpose, a cellulose acetate film, an acrylic film, a polyester film and the like are usually mentioned.
[0028]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited at all by an Example. In the examples, “%” and “part” mean “% by weight” and “part by weight”, respectively, unless otherwise specified.
The polyvinylene structure in the polarizing film was confirmed by measuring the maximum absorption wavelength in a visible light absorption spectrum (wavelength: 380 to 780 nm) using an ultraviolet-visible spectrum.
The transmittance, polarization degree, and dichroism ratio of the polarizing film are measured in accordance with the Japan Electronic Machinery Manufacturers Association (EIAJ) LD-201-1983, using a spectrophotometer with a C light source and a two-degree field of view. Calculated.
In addition, although a polarizing film is normally used in the state which laminated | stacked the protective film, in the following examples, it measured in the state of the polarizing film independent without a protective film.
[0029]
In addition, calculation of the dichroism ratio of the polarizing film described in the Example was performed to the following method.
Dichroic ratio:
The dichroic ratio was used as an index for evaluating the polarizing performance of the obtained polarizing film. This dichroic ratio is a transmittance obtained by measuring and calculating in a C light source and a two-degree field of view using a spectrophotometer in accordance with the Japan Electronic Machinery Manufacturers Association (EIAJ) LD-201-1983. It calculated | required from the following formula using TS (%) and polarization degree P (%).
Dichroic ratio = log (TS / 100-TS / 100 × P / 100)
/ Log (TS / 100 + TS / 100 × P / 100)
[0030]
Example 1
By using 2-mercaptoethanol as a chain transfer agent and performing low temperature emulsion polymerization at −20 ° C., the 1,2-glycol bond amount is 0.7 mol%, the saponification degree is 99.9 mol%, and the polymerization degree is 2400. A modified PVA having a hydroxyethylthio group was obtained. Using this modified PVA, a PVA film having a thickness of 100 μm was prepared, immersed in a hydrochloric acid aqueous solution (0.01 N) at 20 ° C. for 10 minutes, and then dried at 20 ° C. for 30 minutes. The obtained PVA film was stretched 6.8 times in a uniaxial direction in nitrogen at 190 ° C., and then the stretched PVA film was immersed in 4% boric acid aqueous solution for 10 minutes to remove and fix hydrochloric acid. Processing was performed simultaneously. Finally, the obtained film was dried with warm air of 40 ° C. to obtain a polarizing film having a polyvinylene structure having a thickness of 20 μm.
The transmittance, polarization degree, dichroism ratio and maximum absorption wavelength of the obtained polarizing film were measured, and the polarizing film was allowed to stand for 1000 hours at 80 ° C. and 90% RH. The chromaticity ratio was measured. The results are shown in Table 1.
[0031]
Example 2
By using 4-mercapto-1-butanol as a chain transfer agent and performing low-temperature emulsion polymerization at -20 ° C., the amount of 1,2-glycol bonds is 0.8 mol%, the degree of saponification is 99.9 mol%, and the polymerization A modified PVA having a hydroxybutylthio group with a degree of 1900 was obtained. Using this modified PVA, a PVA film having a thickness of 75 μm was prepared, and immersed in a 20 ° C. sulfuric acid aqueous solution (0.01 N) for 10 minutes, and then dried at 20 ° C. for 30 minutes. The obtained PVA film was stretched 6.5 times in a uniaxial direction in nitrogen at 220 ° C., and then the stretched PVA film was washed with distilled water. Finally, the obtained film was dried with warm air at 40 ° C. to obtain a polarizing film having a polyvinylene structure having a thickness of 18 μm.
Table 1 shows the results of evaluating the optical properties of the polarizing film in the same manner as in Example 1.
[0032]
Example 3
By using n-butanethiol as a chain transfer agent and performing low temperature solution polymerization at 30 ° C., butylthio having a 1,2-glycol bond content of 1.3 mol%, a saponification degree of 99.9 mol%, and a polymerization degree of 1700. A modified PVA having a group was obtained. Using this modified PVA, a PVA film having a thickness of 75 μm was produced, immersed in a 20 ° C. sulfuric acid aqueous solution (0.1 N) for 10 minutes, and then dried at 20 ° C. for 30 minutes. The obtained PVA film was stretched 5.2 times in a uniaxial direction in nitrogen at 160 ° C., and then the stretched PVA film was washed with distilled water. Finally, the obtained film was dried with 40 ° C. hot air to obtain a polarizing film having a polyvinylene structure having a thickness of 24 μm.
Table 1 shows the results of evaluating the optical properties of the polarizing film in the same manner as in Example 1.
[0033]
Example 4
A 75 μm-thick PVA film produced from PVA having a 1,2-glycol bond content of 1.3 mol%, a saponification degree of 99.9 mol%, and a polymerization degree of 1700 obtained by low temperature solution polymerization at 30 ° C. It was immersed in a sulfuric acid aqueous solution (0.1 N) for 10 minutes. Dry at 20 ° C. for 30 minutes. The film was stretched 5.2 times in a uniaxial direction in 160 ° C nitrogen. Next, it was washed with distilled water. Finally, a polarizing film having a polyvinylene structure having a thickness of 24 μm was obtained by drying with hot air of 40 ° C. The evaluation results of the polarizing film are shown in Table 1.
[0034]
Comparative Example 1
A PVA film having a thickness of 100 μm obtained by forming a PVA having a polymerization degree of 1700, a saponification degree of 99.9 mol%, and a 1,2-glycol bond amount of 1.6 mol% was converted into a 20 ° C. sulfuric acid aqueous solution (0. 0. (5 normal) for 10 minutes and then dried at 20 ° C. for 30 minutes. The obtained PVA film was stretched 4.3 times uniaxially in air at 130 ° C., and then the stretched PVA film was washed with distilled water. Finally, the obtained film was dried with 40 ° C. warm air to obtain a polarizing film having a polyvinylene structure having a thickness of 51 μm.
Table 1 shows the results of evaluating the optical properties of the polarizing film in the same manner as in Example 1.
[0035]
Comparative Example 2
A 75 μm-thick PVA film obtained by forming a PVA film having a polymerization degree of 4000, a saponification degree of 99.7 mol%, and a 1,2-glycol bond amount of 1.6 mol% was formed into a dye aqueous solution (iodine 0 2 g / l, potassium iodide 20 g / l, boric acid 40 g / l) for 3 minutes. Thereafter, the PVA film was stretched 4 times in a uniaxial direction in a 50 ° C. boric acid aqueous solution (40 g / l), and a 30 ° C. treated aqueous solution (potassium iodide 20 g / l, boric acid 40 g / l, zinc chloride 10 g / l). l) soaked in 4 minutes. Finally, the obtained film was dried with hot air of 40 ° C. to obtain an iodine-based polarizing film having a thickness of 16 μm (not having a polyvinylene structure).
Table 1 shows the results of evaluating the optical properties of the polarizing film in the same manner as in Example 1.
[0036]
[Table 1]

[0037]
【Effect of the invention】
The polarizing film of the present invention has excellent polarization performance in the visible light spectrum range, and also has excellent durability when left for a long period of time in a high temperature and high humidity environment. It can be effectively used not only for the system but also for the production of polarizing plates for in-vehicle LCDs such as LCD TVs that have large temperature and humidity changes.

Claims (4)

Polyvinylene structure obtained by dry-heat stretching a film made of polyvinyl alcohol having a 1,2-glycol bond amount of 1.5 mol% or less and a polymerization degree of 1000 or more at 100 to 250 ° C. in an atmosphere that prevents oxidation of polyvinyl alcohol. A polarizing film having a dichroic ratio of 26 or more before the endurance test and 2 after the endurance test when the endurance test is performed for 1000 hours at 80 ° C. and 90% RH. polarizing film color-ratio Ru der 17 or more. Polyvinyl alcohol having a 1,2-glycol bond amount of 1.5 mol% or less has an RS-group (R represents a mono- or polyhydroxy hydrocarbon group, and S represents a sulfur atom) at its terminal. polarizing film sections 1 Symbol placement. The polarizing film according to claim 1 or 2 , wherein a maximum absorption wavelength in a visible light absorption spectrum range is 500 nm or more. 1,2-glycol bond content of the polymerization degree of 1.5 mol% or less of polyvinyl alcohol 1000 or more and 4000 or less, saponification degree of any one of claims 1 to 3 is 95 mol% or more Polarized film.