JP4302393B2 - Polarized film - Google Patents

Description

【００３９】
【発明の効果】
本発明のポリエン系偏光フィルムは、偏光性能および色相に優れており、この特性を生かして、例えば、ＬＣＤナビゲーションシステムまたはＬＣＤテレビなどの耐久性はもちろんのこと、偏光性能も要求される車載カラーＬＣＤ用の偏光フィルムとして特に有効である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a polarizing film in which a polyene structure is introduced by a dehydration reaction of an ethylene-vinyl alcohol copolymer film and has good optical characteristics and excellent hue.
[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. This LCD can be used in a wide range from small devices such as calculators and watches in the early days to laptop computers, word processors, liquid crystal color projectors, in-vehicle navigation systems, liquid crystal televisions, and measuring devices used indoors and outdoors. In the environment where it is used, the temperature conditions are wide from low to high, the humidity conditions are wide from low to high, and the polarization performance is higher than conventional products, and durability such as heat and humidity resistance An excellent polarizing plate has been demanded.
[0003]
A conventional polarizing film is obtained by uniaxially stretching a vinyl alcohol copolymer film and dyeing with iodine or a dichroic dye, or dyeing and uniaxially stretching and then fixing with a boron compound. (Staining and fixing may be simultaneous). However, the polarizing film dyed with iodine (iodine polarizing film) has a problem that the polarization performance is high but the durability is low, and the polarizing film dyed with a dichroic dye (dye polarizing film) There was a problem that the polarization performance was low although the durability was high. In order to meet the demand for improving the contrast of LCDs, iodine-based polarizing films are often used. In general, polarizing plates are bonded with support plates such as cellulose triacetate (TAC) on both sides of such iodine-based polarizing films. Combined configuration.
[0004]
As another type of polarizing film, a polarizing film (polyene polarizing film) obtained by inducing a dehydration reaction in a polyvinyl alcohol film to form a polyene and stretching it uniaxially is proposed. (For example, U.S. Pat. No. 2,173,304; Patent Document 1). Polyene-based polarizing films do not use unstable substances such as iodine complexes, so they have excellent heat and moisture resistance, and part of the polyvinyl alcohol structure is dehydrated and turned into polyenes, so that it is water resistant. The improvement effect can be expected. However, the conventional polyene polarizing film has a problem that its polarizing performance is lower than that of the iodine polarizing film.
[0005]
As an attempt to improve the polarizing performance of the polyene polarizing film, a method using polyvinyl alcohol having a polymerization degree of 2000 or more as a material of the polyvinyl alcohol film (Japanese Patent Laid-Open No. 10-319236; Patent Document 2), 1,2- A method using polyvinyl alcohol having a small amount of glycol bonds (Japanese Patent Laid-Open No. 2002-174726; Patent Document 3) is known. These methods are intended to improve the polarization performance of the polyene-based polarizing film by improving the orientation of the polyene, but as a result of detailed studies by the present inventors, only raising the orientation of the polyene, It has been found that there is a limit in achieving the objective of obtaining a polyene polarizing film having polarization performance equivalent to that of an iodine polarizing film.
[0006]
Further, in order to perform color display on the LCD, the polarizing plate needs to exhibit a light transmission and shielding function in the entire wavelength range of visible light. For example, if the polarizing plate has insufficient polarization performance at a wavelength corresponding to blue, white light cannot be displayed due to leakage of blue light, resulting in a bluish display. For these reasons, generally, a color LCD polarizing plate is generally adjusted to a gray color so that absorption performance is exhibited in the entire wavelength region.
In the case of an iodine-based polarizing film, by adjusting the concentration of an additive such as potassium iodide, the absorption intensity based on the two types of complexes existing in the visible light region is balanced and adjusted to a gray color. In the case of a dye-based polarizing film, the concentration of several kinds of dyes used is adjusted to balance the absorption intensity based on several complexes existing in the visible light region, and is adjusted to a gray color. However, since polyene is formed by inducing a dehydration reaction in a polyene polarizing film, the chain length of the polyene is determined to some extent depending on the dehydration reaction conditions, and only the absorption of light of a specific wavelength tends to increase. There was a problem. In other words, the polyene polarizing film has a problem that it tends to be bluish or reddish. Since the polyene polarizing film has substantially only one absorption, it is difficult to develop a gray color. The polyene polarizing film also has a plurality of visible light rays such as an iodine polarizing film and a dye polarizing film. There has been a demand for a method of adjusting to a gray color by balancing the absorption intensity.
[0007]
Prior art document information related to the invention of this application includes the following.
[Patent Document 1]
U.S. Pat. No. 2,173,304
[Patent Document 2]
JP-A-10-319236
[Patent Document 3]
JP 2002-174726 A
[0008]
[Problems to be solved by the invention]
An object of the present invention is to provide a polarizing film having a polyene structure having high polarization performance and good hue as compared with conventional products.
[0009]
[Means for Solving the Problems]
As a result of intensive studies to solve the above problems, the present inventors have found that an ethylene-vinyl alcohol copolymer (A) having an ethylene content of 4 mol% or less and an ethylene content of more than 4 mol% and 10 mol%. The inventors have found a polarizing film obtained by introducing a polyene structure into a polyvinyl alcohol film comprising the following ethylene-vinyl alcohol copolymer (B), and have completed the present invention.
The present invention dehydrates a polyvinyl alcohol film comprising two kinds of ethylene-vinyl alcohol copolymers having an ethylene content of 4 mol% or less and 4 to 10 mol%, and has substantially two kinds of chain lengths. By producing polyene, it effectively increases the absorption of light in a wide wavelength region, and by controlling the balance of the amount produced, a polyene polarizing film having high polarization performance and excellent hue It is something to be offered.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
The polyvinyl alcohol film used in the present invention includes an ethylene-vinyl alcohol copolymer (A) having an ethylene content of 4 mol% or less and an ethylene-vinyl alcohol having an ethylene content of more than 4 mol% and 10 mol% or less. It consists of a type | system | group copolymer (B), It is characterized by the above-mentioned. By introducing ethylene into the vinyl alcohol polymer, the stretch orientation of the polyvinyl alcohol film is improved, and the polarization performance of the polyene polarizing film is improved. Furthermore, the chain length of polyene can be controlled by adjusting the amount of modification by ethylene, increasing the absorbance in a wider wavelength region than before, and producing a polyene polarizing film with high polarization performance and good hue. Be able to get.
[0011]
The performance (particularly polarization performance and hue) of the polyene polarizing film of the present invention is greatly affected by the ethylene content of the ethylene-vinyl alcohol copolymer. Since the probability that the polyene chain is cleaved by ethylene increases as the ethylene content increases, the chain length of the polyene tends to be shorter. Since the wavelength of light to be absorbed is determined according to the length of the polyene chain, the polarizing film for LCD preferably has various polyene chain lengths so as to absorb light of all wavelengths in the visible light region. From the viewpoint, it is important in the present invention to use two types of ethylene-vinyl alcohol copolymers (A) and (B).
[0012]
In the polarizing film of the present invention, it is necessary to use an ethylene-vinyl alcohol copolymer (A) having an ethylene content of 4 mol% or less in order to produce a polyene having a relatively long chain length. The rate is preferably 3 mol% or less, more preferably 2 mol% or less, and even more preferably 1 mol% or less. When the ethylene content exceeds 4 mol%, the polyene chain length is shortened in the obtained polarizing film, so that the absorption in the long wavelength region of visible light is insufficient and the polarizing performance is deteriorated.
[0013]
In the present invention, it is necessary to use an ethylene-vinyl alcohol copolymer (B) having an ethylene content of more than 4 mol% and not more than 10 mol% in order to produce a polyene having a relatively short chain length, The ethylene content is preferably 5 mol% or more, more preferably 6 mol% or more. When the ethylene content is lower than 4 mol%, the resulting polarizing film is not preferable because the absorption in the short wavelength region of visible light is insufficient and the polarizing performance is deteriorated. When the ethylene content is larger than 10 mol%, the resulting polarizing film is not preferable because the polyene chain length is too short and the absorption of light in the visible light region becomes small.
[0014]
In the present invention, the difference between the ethylene content of the ethylene-vinyl alcohol copolymer (A) and the ethylene content of the ethylene-vinyl alcohol copolymer (B) is preferably 4 mol% or more, preferably 5 mol. % Or more is more preferable. If the difference in ethylene content is less than 4 mol%, the obtained polarizing film is not preferable because the position of the absorption wavelength by the produced polyene is close and it is difficult to adjust the hue.
[0015]
In the present invention, the ethylene-vinyl alcohol copolymer (B) is preferably used at a ratio of 10 to 50 parts by weight with respect to 100 parts by weight of the ethylene-vinyl alcohol copolymer (A). When the amount of the ethylene-vinyl alcohol copolymer (B) is less than 10 parts by weight, the resulting polarizing film is not preferred because the absorption in the short wavelength region is insufficient and the polarizing performance is lowered. Further, it is not preferable because it is difficult to adjust the hue. When the ethylene-vinyl alcohol copolymer (B) is larger than 50 parts by weight, in the resulting polarizing film, the absorption in the short wavelength region becomes too large, the transmittance is lowered, and the relative polarizing performance is lowered. Therefore, it is not preferable. Further, it is not preferable because it is difficult to adjust the hue.
[0016]
The polarizing film of the present invention is a Lab color system, and the hue a is preferably 2.5 or less, more preferably 2.0 or less, and particularly preferably 1.5 or less. The hue b is preferably 0.5 or less, more preferably 0.4 or less, and particularly preferably 0.3 or less. As described above, these hues are the ethylene contents of the two types of ethylene-vinyl alcohol copolymers (A) and (B), the use ratio of these ethylene-vinyl alcohol copolymers, and the heat treatment temperature. It is adjusted by controlling etc.
[0017]
The performance of the polarizing film of the present invention is also affected by the degree of polymerization of the ethylene-vinyl alcohol copolymer. When the degree of polymerization of the ethylene-vinyl alcohol copolymer is less than 300, the resulting polarizing film has reduced performance such as optical characteristics, water resistance, heat and humidity resistance, and durability, so the degree of polymerization is 300 or more. Is preferable, more preferably 500 or more, and particularly preferably 1000 or more. From the viewpoint of processing characteristics such as film formation and stretching, the degree of polymerization of the ethylene-vinyl alcohol copolymer is preferably 30000 or less. When the copolymer is water-soluble, the degree of polymerization (P) of the ethylene-vinyl alcohol copolymer is measured according to JIS-K6726.
[0018]
The ethylene-vinyl alcohol copolymer used in the present invention is obtained by saponifying an ethylene-vinyl ester copolymer obtained by copolymerization of ethylene and a vinyl ester monomer such as vinyl acetate, and converting the vinyl ester unit into vinyl alcohol. It can be manufactured by converting into units. The degree of saponification of vinyl alcohol units in the ethylene-vinyl alcohol polymer also affects the performance of the polarizing film of the present invention. Here, the degree of saponification represents the proportion of units actually saponified to vinyl alcohol units among the units that can be converted to vinyl alcohol units by saponification. It becomes a residue. The saponification degree is preferably 85 mol% or more, more preferably 90 mol% or more, and particularly preferably 98 mol% or more. If the degree of saponification is too high, a crosslinking reaction tends to occur at the time of dehydration of the polyvinyl alcohol film. Therefore, the degree of saponification is preferably 99.95 mol% or less, more preferably 99.9 mol% or less. Preferably, it is particularly preferably 99 mol% or less.
[0019]
When ethylene and vinyl ester are copolymerized, other monomers may be copolymerized to such an extent that the gist of the present invention is not impaired. Examples of such comonomers include olefins such as propylene, 1-butene, and isobutene; acrylic acid and its salts; methyl acrylate, ethyl acrylate, n-propyl acrylate, i-propyl acrylate, and n-butyl acrylate. Acrylic acid esters such as i-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, octadecyl acrylate; methacrylic acid and salts thereof; methyl methacrylate, ethyl methacrylate, n methacrylate -Methacrylic acid esters such as propyl, i-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate, octadecyl methacrylate; N-methylacrylamide, N-ethylacrylamide, N, N-dimethylacrylamide, diacetoneacrylamide, acrylamidepropanesulfonic acid and its salt, acrylamidopropyldimethylamine and its salt or its quaternary salt, N-methylolacrylamide and its derivative Acrylamide derivatives such as: methacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, methacrylamidepropanesulfonic acid and its salt, methacrylamideamidopropylamine and its salt or quaternary salt thereof, N-methylolmethacrylamide and its Methacrylamide derivatives such as derivatives; methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, n-butyl Vinyl ethers such as vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether and stearyl vinyl ether; Nitriles such as acrylonitrile and methacrylonitrile; Vinyl halides such as vinyl chloride, vinylidene chloride, vinyl fluoride and vinylidene fluoride And allyl compounds such as allyl acetate and allyl chloride; maleic acid and salts thereof or esters thereof; vinylsilyl compounds such as vinyltrimethoxysilane; and isopropenyl acetate.
[0020]
For the production of the polarizing film of the present invention, a polyvinyl alcohol film obtained by forming an ethylene-vinyl alcohol copolymer is used as a raw material film. As a method for forming a polyvinyl alcohol film from an ethylene-vinyl alcohol copolymer, for example, an ethylene-vinyl alcohol copolymer is contained on a resin film, a drying drum or a drying belt. Examples thereof include a casting method or a die casting method in which the solution is cast. Examples of the solvent of the ethylene-vinyl alcohol copolymer include water, an organic solvent, or a mixed liquid of water and an organic solvent. The polyvinyl alcohol film formed on the resin film, the drying drum or the drying belt may be dried and further subjected to heat treatment as necessary.
[0021]
If necessary, a plasticizer, a surfactant, a dichroic dye, inorganic salts, and the like can be added to the solution containing the ethylene-vinyl alcohol copolymer used for film formation. The thickness of the polyvinyl alcohol film used for the production of the polarizing film is preferably 5 to 150 μm, more preferably 30 to 100 μm.
[0022]
From the polyvinyl alcohol film thus obtained, for example, swelling treatment, treatment for introducing a polyene structure, uniaxial stretching (often performed simultaneously with the treatment for introducing a polyene structure), fixing treatment, and drying treatment A polarizing film can be produced by applying You may heat-process the obtained polarizing film as needed further.
[0023]
As a method for introducing a polyene structure into a polyvinyl alcohol film, a known method is used, and there is no particular limitation, but a method using deacetic acid or dehydration is generally employed. As the method, for example, after impregnating a polyvinyl alcohol film with hydrochloric acid gas, or a methanol solution of a protonic acid such as sulfuric acid, or an aqueous solution of stannic halide such as stannic chloride and stannic bromide A method of heating the film after being immersed in the film is mentioned. The dehydration accelerator (hydrochloric acid gas, protonic acid, stannic halide, etc.) used in this method may be added in advance to a film-forming stock solution used for producing a polyvinyl alcohol film, If the drying temperature is too high, the film may be oxidized by heat. Therefore, the polyvinyl alcohol film is preferably impregnated by the above-described method. The amount of the dehydration accelerator impregnated into the polyvinyl alcohol film is adjusted depending on the type of the dehydration accelerator used and the hue and transmittance of the target polarizing film. Usually, the ethylene-vinyl alcohol copolymer is added to the copolymer. It is used within the range of 0.5 to 10% by weight. If the amount of the dehydration accelerator is less than 0.5% by weight, the amount of polyene to be produced is reduced, so that there is a possibility that the polarizing performance of the obtained polarizing film is difficult to be expressed. There is a possibility that the dehydration accelerator is phase-separated when stretching the film into which is introduced. In order to produce a polyene with a small amount of dehydration accelerator, it is necessary to heat-treat the polyvinyl alcohol film at a temperature higher than usual, so that it is difficult to control intermolecular crosslinking. On the other hand, when there are too many dehydration accelerators, it is difficult to control intermolecular crosslinking even when the polyvinyl alcohol film is heat-treated at a relatively low temperature.
[0024]
The amount of acetic acid and dehydrated from the polyvinyl alcohol film by the above treatment is preferably 1 to 5% by weight when the thickness is about 50 μm, although it depends on the thickness of the film. If the amount of deacetic acid and dehydration from the polyvinyl alcohol film is too small, the amount of visible light absorption is low, the degree of coloring becomes small, and sufficient polarization cannot be expected. In addition, if the amount of deacetic acid and dehydration is too large, the amount of absorption of visible light becomes excessive, and it becomes difficult to obtain a suitably transparent polarizing film, or intermolecular crosslinking proceeds during the reaction, resulting in polyene. Chain length is shortened and film embrittlement occurs. Dehydration tends to occur when the temperature is high, and a preferable temperature range is 90 to 150 ° C, and a more preferable temperature range is 100 to 130 ° C.
[0025]
A dehydration accelerator may remain in the polarizing film thus obtained. If the dehydration accelerator remains, the polarization performance of the film may change upon heating. Therefore, the film may be removed by immersing the film in water, aqueous methanol, saline or a weak alkaline aqueous solution, and extracting the dehydration accelerator. Good. The temperature of the extract at that time is suitably from 0 to 50 ° C.
[0026]
Polyvinyl alcohol film is uniaxially stretched by a dry heat stretching method, a wet stretching method or the like, or in a boron compound-containing aqueous solution or warm water, or in the air with the film absorbed. can do. The stretching temperature 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, and particularly preferably 220 ° C. or lower. The temperature during stretching may be changed according to the stretched state of the film being stretched. In addition, when the polyvinyl alcohol film is uniaxially stretched by a dry heat stretching method, the ethylene-vinyl alcohol copolymer may be oxidized and the film may be colored. It is preferable to maintain a low oxygen atmosphere. The polyvinyl alcohol-based film changes into a colored film in which a polyene structure having polarization performance is formed during dry heat stretching.
The temperature at which the polyvinyl alcohol film is uniaxially stretched by a wet stretching method 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. A polyene structure is not formed only by uniaxially stretching a polyvinyl alcohol film by a wet stretching method, and thus 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.
The stretching of the polyvinyl alcohol film can be performed in two or more stages. In that case, the stretching methods of the same type such as dry heat stretching-dry heat stretching, wet stretching-wet stretching may be combined, or the dry process may be performed. Different types of stretching methods such as stretching-wet stretching and wet stretching-dry stretching may be combined.
[0027]
The stretching ratio of uniaxial stretching is preferably 2 times or more, more preferably 4 times or more from the viewpoint of polarization performance. Although there is no upper limit in the strict sense about the draw ratio, it is preferably 8 times or less from the viewpoint of obtaining uniform drawing.
[0028]
Usually, 1 to 6% by weight of boric acid and a boron compound are added to the treatment bath used for the fixing treatment. The temperature of the treatment bath during the fixing treatment is preferably 20 to 70 ° C.
It is preferable to perform the drying process of the polarizing film obtained by the fixing process in a temperature range of 30 to 80 ° C. Moreover, it is preferable to perform the heat processing which can be performed arbitrarily after a drying process in the temperature range of 50-150 degreeC.
[0029]
In order to impart sufficient mechanical strength, the polarizing film of the present invention may be formed as a polarizing plate by laminating a protective film that is optically transparent and has mechanical strength on both sides or one side. As the protective film, a cellulose acetate film, an acrylic film, a polyester film or the like is usually used.
[0030]
【Example】
EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to the examples. In the examples, “%” and “parts” represent “% by weight” and “parts by weight”, respectively, unless otherwise specified. 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. did. In addition, Lab was measured using a spectrophotometer. Although a polarizing film is normally used in the state which bonded a protective film, in the following Examples and comparative examples, physical properties were measured in the state where a protective film was not bonded to a polarizing film.
[0031]
Example 1
100 parts by weight of an ethylene-vinyl alcohol copolymer having a degree of polymerization of 2400, a degree of saponification of 98.5 mol%, and an ethylene content of 1 mol%, and a degree of polymerization of 2400, a degree of saponification of 98.5 mol%, and an ethylene content of 6 30 parts by weight of a mol% ethylene-vinyl alcohol copolymer was dissolved in 800 parts by weight of distilled water by heating under a temperature condition of 95 ° C. to obtain a uniform aqueous solution. The aqueous solution was cast on a metal drum, dried at 80 ° C., and then heat treated at 120 ° C. for 10 minutes to obtain a polyvinyl alcohol film. The obtained polyvinyl alcohol film had a degree of swelling of 190%, a hot water cutting temperature of 69 ° C., and a film thickness of 50 μm. This film was uniaxially stretched 4 times at 80 ° C. to absorb hydrochloric acid gas, and subjected to a heat treatment at 110 ° C. to perform a dehydration reaction, thereby producing a polyene. Next, the film was stretched 1.5 times in an 8% boric acid aqueous solution at 80 ° C., washed with water, and dried at 50 ° C. to obtain a polarizing film. Table 1 shows the polarizing performance and hue of the polarizing film.
A TAC film having a thickness of 50 μm was bonded to one side of the polarizing film using a PVA adhesive to produce a polarizing plate.
[0032]
Example 2
Polymerization degree 2400, saponification degree 98.5 mol%, unmodified (ethylene content 0 mol%) ethylene-vinyl alcohol copolymer 100 parts by weight, polymerization degree 2400, saponification degree 98.5 mol%, 20 parts by weight of an ethylene-vinyl alcohol copolymer having an ethylene content of 7 mol% was dissolved in 800 parts by weight of distilled water by heating at 95 ° C. to obtain a uniform aqueous solution. The aqueous solution was cast on a metal drum, dried at 80 ° C., and then heat treated at 120 ° C. for 10 minutes to obtain a polyvinyl alcohol film. The swelling degree of the obtained polyvinyl alcohol film was 200%, the hot water cutting temperature was 70 ° C., and the thickness of the film was 50 μm. This film was uniaxially stretched 4 times at 80 ° C. to absorb hydrochloric acid gas, and subjected to a heat treatment at 120 ° C. to perform a dehydration reaction to produce a polyene. Next, the film was stretched 1.6 times in an 8% boric acid aqueous solution at 80 ° C., washed with water, and dried at 50 ° C. to obtain a polarizing film. Table 1 shows the polarizing performance and hue of the polarizing film.
A TAC film having a thickness of 50 μm was bonded to one side of the polarizing film using a PVA adhesive to produce a polarizing plate.
[0033]
Example 3
100 parts by weight of an ethylene-vinyl alcohol copolymer having a polymerization degree of 2400, a saponification degree of 98.5 mol% and an ethylene content of 2 mol%, and a polymerization degree of 2400, a saponification degree of 98.5 mol% and an ethylene content of 5 20 parts by weight of a mol% ethylene-vinyl alcohol copolymer was dissolved in 800 parts by weight of distilled water by heating under a temperature condition of 95 ° C. to obtain a uniform aqueous solution. The aqueous solution was cast on a metal drum, dried at 80 ° C., and then heat treated at 120 ° C. for 10 minutes to obtain a polyvinyl alcohol film. The swelling degree of the obtained polyvinyl alcohol film was 200%, the hot water cutting temperature was 70 ° C., and the thickness of the film was 50 μm. This film was uniaxially stretched 4 times at 80 ° C. to absorb hydrochloric acid gas, and subjected to a heat treatment at 120 ° C. to perform a dehydration reaction to produce a polyene. Next, the film was stretched 1.7 times in an 8% boric acid aqueous solution at 80 ° C., washed with water, and dried at 50 ° C. to obtain a polarizing film. Table 1 shows the polarizing performance and hue of the polarizing film.
A TAC film having a thickness of 50 μm was bonded to one side of the polarizing film using a PVA adhesive to produce a polarizing plate.
[0034]
Example 4
100 parts by weight of an ethylene-vinyl alcohol copolymer having a degree of polymerization of 2400, a degree of saponification of 98.5 mol%, and an ethylene content of 1 mol%, and a degree of polymerization of 2400, a degree of saponification of 98.5 mol%, and an ethylene content of 6 60 parts by weight of a mol% ethylene-vinyl alcohol copolymer was dissolved in 900 parts by weight of distilled water by heating under a temperature condition of 95 ° C. to obtain a uniform aqueous solution. The aqueous solution was cast on a dried metal drum, dried at 80 ° C., and then heat treated at 120 ° C. for 10 minutes to obtain a polyvinyl alcohol film. The obtained polyvinyl alcohol film had a degree of swelling of 190%, a hot water cutting temperature of 69 ° C., and a film thickness of 50 μm. This film was uniaxially stretched 4 times at 80 ° C. to absorb hydrochloric acid gas, and subjected to a heat treatment at 110 ° C. to perform a dehydration reaction, thereby producing a polyene. Next, the film was stretched 1.5 times in an 8% boric acid aqueous solution at 80 ° C., washed with water, and dried at 50 ° C. to obtain a polarizing film. Table 1 shows the polarizing performance and hue of the polarizing film.
A TAC film having a thickness of 50 μm was bonded to one side of the polarizing film using a PVA adhesive to produce a polarizing plate.
[0035]
Example 5
100 parts by weight of an ethylene-vinyl alcohol copolymer having a degree of polymerization of 2400, a degree of saponification of 98.5 mol%, and an ethylene content of 1 mol%, and a degree of polymerization of 2400, a degree of saponification of 98.5 mol%, and an ethylene content of 6 A homogeneous aqueous solution was prepared by dissolving 5 parts by weight of a mol% ethylene-vinyl alcohol copolymer in 900 parts by weight of distilled water by heating under a temperature condition of 95 ° C. The aqueous solution was cast on a metal drum, dried at 80 ° C., and then heat treated at 120 ° C. for 10 minutes to obtain a polyvinyl alcohol film. The obtained polyvinyl alcohol film had a degree of swelling of 190%, a hot water cutting temperature of 69 ° C., and a film thickness of 50 μm. This film was uniaxially stretched 4 times at 80 ° C. to absorb hydrochloric acid gas, and subjected to a heat treatment at 110 ° C. to perform a dehydration reaction, thereby producing a polyene. Next, the film was stretched 1.7 times in an 8% boric acid aqueous solution at 80 ° C., washed with water, and dried at 50 ° C. to obtain a polarizing film. Table 1 shows the polarizing performance and hue of the polarizing film.
A TAC film having a thickness of 50 μm was bonded to one side of the polarizing film using a PVA adhesive to produce a polarizing plate.
[0036]
Comparative Example 1
100 parts by weight of an ethylene-vinyl alcohol copolymer having a polymerization degree of 2400, a saponification degree of 98.5 mol%, and an unmodified (ethylene content of 0 mol%) is heated to 900 parts by weight of distilled water at a temperature of 95 ° C. Dissolved to make a uniform aqueous solution. The aqueous solution was cast on a metal drum, dried at 80 ° C., and then heat treated at 120 ° C. for 10 minutes to obtain a polyvinyl alcohol film. The degree of swelling of the obtained polyvinyl alcohol film was 210%, the hot water cutting temperature was 66 ° C., and the thickness of the film was 50 μm. This film was uniaxially stretched 4 times at 80 ° C. to absorb hydrochloric acid gas, and subjected to a heat treatment at 120 ° C. to perform a dehydration reaction to produce a polyene. Next, the film was stretched 1.8 times in an 8% boric acid aqueous solution at 80 ° C., washed with water, and dried at 50 ° C. to obtain a polarizing film. Table 1 shows the polarizing performance and hue of the polarizing film.
A TAC film having a thickness of 50 μm was bonded to one side of the polarizing film using a PVA adhesive to produce a polarizing plate.
[0037]
Comparative Example 2
100 parts by weight of an ethylene-vinyl alcohol copolymer having a polymerization degree of 2400, a saponification degree of 98.5% by mole, and an ethylene content of 6% by mole was dissolved in 900 parts by weight of distilled water by heating at a temperature of 95 ° C. A uniform aqueous solution was obtained. The aqueous solution was cast on a metal drum, dried at 80 ° C., and then heat treated at 120 ° C. for 10 minutes to obtain a polyvinyl alcohol film. The degree of swelling of the obtained polyvinyl alcohol film was 210%, the hot water cutting temperature was 66 ° C., and the thickness of the film was 50 μm. This film was uniaxially stretched 4 times at 80 ° C. to absorb hydrochloric acid gas, and subjected to a heat treatment at 110 ° C. to perform a dehydration reaction, thereby producing a polyene. Next, the film was stretched 1.8 times in an 8% boric acid aqueous solution at 80 ° C., washed with water, and dried at 50 ° C. to obtain a polarizing film. Table 1 shows the polarizing performance and hue of the polarizing film.
A TAC film having a thickness of 50 μm was bonded to one side of the polarizing film using a PVA adhesive to produce a polarizing plate.
[0038]
[Table 1]

[0039]
【The invention's effect】
The polyene polarizing film of the present invention is excellent in polarization performance and hue. Taking advantage of this property, for example, in-vehicle color LCDs that require polarization performance as well as durability such as an LCD navigation system or an LCD TV. It is particularly effective as a polarizing film for use.

Claims (4)

Polyvinyl alcohol comprising an ethylene-vinyl alcohol copolymer (A) having an ethylene content of 4 mol% or less and an ethylene-vinyl alcohol copolymer (B) having an ethylene content of more than 4 mol% and 10 mol% or less. A polarizing film formed by introducing a polyene structure into a film. The polarizing film according to claim 1, wherein the ethylene content difference between the ethylene-vinyl alcohol copolymer (A) and the ethylene-vinyl alcohol copolymer (B) is 4 mol% or more. The weight ratio {(B) / (A)} of the ethylene-vinyl alcohol copolymer (A) and the ethylene-vinyl alcohol copolymer (B) is 10/100 to 50/100. Polarized film. The polarizing film according to claim 1, wherein the hue a is 2.5 or less and the hue b is 0.5 or less.