JP2003268127A - Ethylene-modified polyvinyl alcohol film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyvinyl alcohol film useful as a material for producing a polarizing film having good polarization preformances, reduced in color unevenness, and responding to an increase in the size of a liquid crystal display. <P>SOLUTION: The ethylene-modified polyvinyl alcohol film is prepared from an ethylene-modified polyvinyl alcohol having an ethylene unit content of 1-4 mol%, a degree of polymerization of 2,000-4,000, and a degree of saponification of 99.0-99.99 mol% and has a hot-water cut temperature of 66-73°C. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an ethylene-modified polyvinyl alcohol film which is useful as a raw material for manufacturing a polarizing film, has a high polarization performance, a good durability performance and a small color spot.

[0002]

2. Description of the Related Art A polarizing plate having a light transmitting and shielding function is a basic component of a liquid crystal display (LCD) together with a liquid crystal having a light switching function. The fields of application of this LCD range from small devices such as calculators and wristwatches in the early days of development to laptop computers, word processors, liquid crystal color projectors, in-vehicle navigation systems, liquid crystal televisions, personal phones, and indoor and outdoor measuring devices. There is a demand for a large-area polarizing plate that spreads over a wide range such as, and has higher polarization performance and durability than conventional products and has less color spots.

A polarizing plate is generally obtained by uniaxially stretching a polyvinyl alcohol-based polymer film (hereinafter, a polyvinyl alcohol-based polymer may be abbreviated as "PVA" and a polyvinyl alcohol-based polymer film as "PVA film"). After dyeing or dyeing and uniaxially stretching,
A protective film such as a cellulose triacetate (TAC) film or an acetic acid / cellulose butyrate (CAB) film is attached to the polarizing film obtained by performing a fixing treatment with a boron compound (the dyeing and the fixing treatment may be performed at the same time). It has a combined structure.

[0004]

In recent years, the use of liquid crystal displays has spread to high-definition personal computer monitors and home-use televisions, and the demands for contrast and durability have increased more than ever before, resulting in higher polarization performance and durability. Performance is required.

Further, even if the PVA film looks uniform in appearance, the polarizing film obtained thereby may have color spots which are difficult to distinguish from the outside.
This color spot is difficult to confirm unless it is the final product (polarizing plate) with a protective film laminated. When color spots appear in this final product, a secondary material such as a protective film, which is a good product, is also discarded as a defective product, resulting in a large manufacturing loss. As a conventional method for reducing color spots, Japanese Patent Laid-Open No. 6-13
As described in, for example, Japanese Patent No. 8319, studies have been made from the viewpoint of reducing thickness unevenness and birefringence unevenness of a polyvinyl alcohol film. By reducing the thickness unevenness and birefringence unevenness of the polyvinyl alcohol film, it became possible to reduce the color unevenness to some extent and satisfy the required level at the time, but the final product with improved performance in recent years (polarizer and It has been found difficult to reduce the problematic level of color spots in liquid crystal display devices).

Further, with the increase in size of liquid crystal display devices, a polarizing film having a large area has been required. Since the conventional liquid crystal display device has a relatively small display area and is used as a polarizing plate alone, color spots are not a problem, but when the display area is large, uniformity of the entire display area is required. Due to the fact that it is often used in combination with other films such as a viewing angle correction film, the problem of color spots has become apparent. As described above, until now, the color spots have been reduced by adjusting the various structures and physical properties of the film, but this method alone is not sufficient, and in addition to the adjustment of the various structures and physical properties of the film, the polymer It was concluded that it was necessary to control the structure to a certain extent.

Therefore, an object of the present invention is to provide a polyvinyl alcohol film which is excellent in polarization performance and durability, has less color spots, and is useful as a raw material for manufacturing a polarizing film which can cope with an increase in size of a liquid crystal display. is there.

[0008]

Means for Solving the Problems As a result of intensive studies for solving the above problems, the present inventors have found that the content of ethylene units is 1 to 4 mol%, the degree of polymerization is 2000 to 4000, and the degree of saponification is 99.0 to 99. A film is formed from .99 mol% ethylene-modified polyvinyl alcohol, and the hot water cutting temperature is 66 to 73 ° C.
The present invention was completed by finding an ethylene-modified polyvinyl alcohol film that is This ethylene-modified polyvinyl alcohol film is excellent in polarization performance and durability performance, has few color spots, and is useful as a raw material for manufacturing a polarization film that can cope with an increase in size of a liquid crystal display. Further, in the ethylene-modified polyvinyl alcohol film of the present invention, the difference in hot water cutting temperature between two points 5 cm apart in the TD direction of the film is preferably 1 ° C. or less, in order to reduce color spots, and TD of film
The difference in hot water cutting temperature between two points 1 cm apart in the direction is 0.5
It is even more preferable that the temperature is not higher than 0 ° C. in order to reduce color spots, and the film thickness is 10 to 50 μm.
It is particularly preferable that it is m in order to reduce color spots.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION As the ethylene-modified polyvinyl alcohol (ethylene-modified PVA) used in the present invention, an ethylene-vinyl ester-based polymer obtained by copolymerizing ethylene and a vinyl ester-based monomer is saponified, A vinyl alcohol unit may be used as the vinyl ester unit. Examples of the vinyl ester-based monomer include vinyl formate, vinyl acetate,
Examples thereof include vinyl propionate, vinyl valerate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl pivalate, vinyl versatate, and the like. Among these, vinyl acetate is preferably used.

The ethylene unit content (copolymerization amount of ethylene) in the ethylene-modified PVA is 1 to 4 mol%, preferably 1.5 to 3 mol%, more preferably 2 to 3 mol%. is there. When the content of the ethylene unit is less than 1 mol%, the effect of improving the polarization performance and durability of the resulting polarizing film and the effect of reducing color spots become small, which is not preferable. On the other hand, when the content of the ethylene unit exceeds 4 mol%, the affinity of the ethylene-modified PVA with water is lowered and the uniformity of the film surface is deteriorated, which is likely to cause color spots of the polarizing film, which is not suitable. Is.

Further, when copolymerizing ethylene and a vinyl ester-based monomer, if necessary, the copolymerizable monomer is added within a range not impairing the effects of the invention (preferably 15 mol% or less, more preferably 5 mol% or less). It is also possible to carry out copolymerization at a ratio of not more than mol%).

Examples of the monomer copolymerizable with the vinyl ester-based monomer include propylene and 1
-Olefins having 3 to 30 carbon atoms such as butene and isobutene; acrylic acid and salts thereof; methyl acrylate, ethyl acrylate, n-propyl acrylate, i-acrylic acid
-Acrylate esters such as propyl, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, octadecyl acrylate; methacrylic acid and its salts; methacrylic Methyl acid, ethyl methacrylate, n-propyl methacrylate, i-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate,
Methacrylic acid esters such as dodecyl methacrylate and octadecyl methacrylate; acrylamide, N-methyl acrylamide, N-ethyl acrylamide, N, N-
Dimethyl acrylamide, diacetone acrylamide,
Acrylamidopropanesulfonic acid and its salts, acrylamidopropyldimethylamine and its salts, N-
Acrylamide derivatives such as methylolacrylamide and its derivatives; methacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, methacrylamidepropanesulfonic acid and its salts, methacrylamidepropyldimethylamine and its salts, N-methylolmethacrylamide and its Methacrylamide derivatives such as derivatives; N-vinylformamide, N-vinylacetamide, N-vinylamides such as N-vinylpyrrolidone; 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, vinylidene chloride , Vinyl fluoride, vinylidene fluoride and other vinyl halides; allyl acetate,
Allyl compounds such as allyl chloride; maleic acid and salts or esters thereof; itaconic acid and salts or esters thereof; vinylsilyl compounds such as vinyltrimethoxysilane; isopropenyl acetate, N-vinylformamide, N-vinylacetamide, N- N-vinyl amides such as vinylpyrrolidone can be mentioned.

The degree of polymerization of the ethylene-modified PVA constituting the ethylene-modified PVA film depends on the PV of the polarizing film.
The polymerization degree of A is 2000 to 40 from the viewpoint of polarization performance and durability.
00, preferably 2200 to 3500, and 2500
~ 3000 is particularly preferred. When the degree of polymerization of ethylene-modified PVA is less than 2000, the polarizing performance and durability of the polarizing film are deteriorated, which is not preferable. When the degree of polymerization is more than 4000, the productivity during polymerization is low, which is not industrially preferable, and the affinity with water may be low, which reduces the uniformity of the film surface and reduces the polarization. It is not preferable because it tends to cause color spots on the film.

The degree of polymerization of the ethylene-modified PVA is GP
It is a weight average polymerization degree obtained from C measurement. This weight average degree of polymerization was determined by using hexafluoroisopropanol (HFIP) prepared by using monodisperse PMMA as a standard and adding 20 mmol / liter of sodium trifluoroacetate to the mobile phase.
It is a value obtained by performing GPC measurement at 0 ° C.

The degree of saponification of the ethylene-modified PVA constituting the ethylene-modified PVA film is 99.0 to 99.99 mol% and 99.9 to 99.99 mol% from the viewpoint of polarization performance and durability of the polarizing film. Is more preferable, and 9
9.95 to 99.99 mol% is particularly preferable. When the saponification degree is lower than 99.0 mol%, the durability of the polarizing film is deteriorated, which is not preferable. The saponification degree is 99.
If it exceeds 99 mol%, there is a problem such as coloring of the resin during the production of the ethylene-modified PVA, and the production is extremely difficult.
The degree of saponification indicates the proportion of units actually saponified into vinyl alcohol units among units that can be converted into vinyl alcohol units by saponification.
The saponification degree of ethylene-modified PVA was measured by the method described in JIS.

As a method for producing an ethylene-modified PVA film using ethylene-modified PVA, in addition to a film forming method by a melt extrusion method using ethylene-modified PVA containing water, for example, ethylene in which ethylene-modified PVA is dissolved in a solvent is used. Using a modified PVA solution, a casting film forming method, a wet film forming method (discharging into a poor solvent), a gel film forming method (ethylene modified P
A method in which the VA aqueous solution is once cooled and gelled, and then the solvent is extracted and removed to obtain an ethylene-modified PVA film), a combination thereof, and the like can be employed. Among these, the casting film forming method and the melt extrusion film forming method are preferable from the viewpoint of obtaining a good ethylene-modified PVA film. The obtained ethylene-modified PVA film is
If necessary, drying and heat treatment are performed.

As a solvent for dissolving the ethylene-modified PVA used for producing the ethylene-modified PVA film, for example, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone,
Ethylene glycol, glycerin, propylene glycol, diethylene glycol, triethylene glycol,
Tetraethylene glycol, trimethylolpropane,
Examples thereof include ethylenediamine, diethylenetriamine, glycerin, and water, and one or more of these can be used. Among these, dimethyl sulfoxide, water, or a mixed solvent of glycerin and water is preferably used.

The ratio of the ethylene-modified PVA in the ethylene-modified PVA solution used in the production of the ethylene-modified PVA film or the ethylene-modified PVA containing water varies depending on the degree of polymerization of the ethylene-modified PVA.
~ 70 wt% is preferred, 25-60 wt% is more preferred, 30-55 wt% is even more preferred, 35
-50% by weight is most preferred. If the proportion of ethylene-modified PVA exceeds 70% by weight, the viscosity of the ethylene-modified PVA solution or the ethylene-modified PVA containing water becomes too high, making filtration and defoaming difficult when preparing a stock solution of the film, resulting in foreign matters and defects. It will be difficult to obtain a film without If the proportion of ethylene-modified PVA is lower than 20% by weight, the viscosity of the ethylene-modified PVA solution or the ethylene-modified PVA containing water becomes too low, making it difficult to produce a PVA film having a desired thickness. In addition, in the ethylene-modified PVA solution or the ethylene-modified PVA containing water, a plasticizer, a surfactant, and
You may also contain a dichroic dye.

It is preferable to add a polyhydric alcohol as a plasticizer when producing an ethylene-modified PVA film. Examples of the polyhydric alcohol include ethylene glycol, glycerin, propylene glycol, diethylene glycol, diglycerin, triethylene glycol, tetraethylene glycol, trimethylolpropane, and the like.
More than one species can be used. Among these, diglycerin, ethylene glycol, and glycerin are preferably used because of the effect of improving stretchability.

The amount of polyhydric alcohol added is preferably 1 to 30 parts by weight, more preferably 3 to 25 parts by weight, and most preferably 5 to 20 parts by weight, based on 100 parts by weight of ethylene-modified PVA. If it is less than 1 part by weight, the dyeability and stretchability may decrease, and if it is more than 30 parts by weight, the ethylene-modified PVA film may become too soft and the handleability may decrease.

It is preferable to add a surfactant when the ethylene-modified PVA film is produced. The type of surfactant is not particularly limited, but anionic or nonionic surfactant is preferable. As the anionic surfactant, for example, carboxylic acid type anionic surfactants such as potassium laurate, sulfate ester type such as octyl sulfate, and sulfonic acid type anionic surfactants such as dodecylbenzene sulfonate are suitable. Examples of the nonionic surfactant include alkyl ether type such as polyoxyethylene oleyl ether, alkyl phenyl ether type such as polyoxyethylene octyl phenyl ether, alkyl ester type such as polyoxyethylene laurate, and polyoxyethylene lauryl amino. Alkylamine type such as ether, alkylamide type such as polyoxyethylene lauric acid amide, polypropylene glycol ether type such as polyoxyethylene polyoxypropylene ether, alkanolamide type such as oleic acid diethanolamide, polyoxyalkylene allyl phenyl ether, etc. Nonionic surfactants such as allyl phenyl ether type are preferred. These surfactants can be used alone or in combination of two or more.

The amount of the surfactant added is preferably 0.01 to 1 part by weight, more preferably 0.02 to 0.5 part by weight, based on 100 parts by weight of ethylene-modified PVA.
Most preferably 0.05 to 0.3 parts by weight. If it is less than 0.01 part by weight, the effect of improving the film-forming property and peeling property is difficult to appear, and if it is more than 1 part by weight, the surfactant is ethylene-modified P.
It may be eluted on the surface of the VA film to cause blocking, which may deteriorate the handleability.

The hot water cutting temperature of the ethylene-modified PVA film of the present invention is 66 to 73 ° C, preferably 68 to 73 ° C, more preferably 70 ° C to 73 ° C. When the hot water cutting temperature of the ethylene-modified PVA film is lower than 66 ° C., the melted film is in a stretched state and molecular orientation hardly occurs, so that the polarizing performance of the polarizing film becomes insufficient. If the hot water cutting temperature is higher than 73 ℃,
It is not preferable because the film becomes difficult to stretch and the polarizing performance of the polarizing film is lowered. When the ethylene-modified PVA film is dried and heat-treated, the hot water cutting temperature of the film can be adjusted by changing the temperature and time of the treatment.

The ethylene-modified PVA film of the present invention is
The difference in hot water cutting temperature between two points 5 cm apart in the TD direction of the film is preferably 1 ° C or less, more preferably 0.8 ° C or less, and particularly preferably 0.5 ° C or less. preferable. If the difference in hot water cutting temperature exceeds 1 ° C,
When a polarizing film is produced from an ethylene-modified PVA film, color spots are easily noticeable with the naked eye, and when incorporated into a liquid crystal display device, a change in color tone easily occurs, which is not preferable. In order to reduce the difference in hot water cutting temperature between two points separated by 5 cm to 1 ° C. or less, a known method for uniformizing the thermal history applied to the TD direction of the film may be appropriately combined. For example, a method of making the resin temperature, drum temperature, roll temperature, drying temperature, heat treatment temperature, etc. in the TD direction of the film uniform can be mentioned. In the present invention, even if the individual heat history in the TD direction of the film is not uniform, the difference in hot water cutting temperature between two points 5 cm apart in the TD direction of the finally obtained film should be 1 ° C. or less. Good.

The ethylene-modified PVA film of the present invention comprises
Further, the difference in hot water cutting temperature between two points 1 cm apart in the TD direction of the film is preferably 0.5 ° C. or less,
It is more preferably 0.4 ° C. or lower, and particularly preferably 0.3 ° C. or lower. The difference in hot water cutting temperature is 0.
When the temperature exceeds 5 ° C, color spots are easily visible when a polarizing film is prepared from an ethylene-modified PVA film, and a color tone change easily occurs when incorporated into a liquid crystal display device, which is not preferable. In order to make the difference in hot water cutting temperature between two points separated by 1 cm to be 0.5 ° C. or less, a known method for uniformizing the heat history applied in the TD direction of the film may be appropriately combined. For example, film T
A method for making the resin temperature in the D direction, the drum temperature, the roll temperature, the drying temperature, the heat treatment temperature, etc. uniform. In the present invention, even if the individual thermal history in the TD direction of the film is not uniform, the difference in hot water cutting temperature between two points 1 cm apart in the TD direction of the finally obtained film is 0.5 ° C. or less. If

The ethylene-modified PVA film of the present invention preferably has a thickness of 10 to 50 μm.
More preferably, it is μm. When the thickness is less than 10 μm, the film strength is too low to make uniform stretching difficult, and color spots are likely to occur on the polarizing film. Thickness is 50
When the thickness exceeds μm, a thickness change due to neck-in of the end portion is likely to occur when an ethylene-modified PVA film is uniaxially stretched to form a polarizing film, and color spots of the polarizing film are easily emphasized, which is not preferable.

In order to produce a polarizing film from the ethylene-modified PVA film of the present invention, for example, the ethylene-modified PVA film may be dyed, uniaxially stretched, fixed and dried, and optionally heat-treated. The order of dyeing, uniaxial stretching and fixing treatment is not particularly limited. In addition, the uniaxial stretching may be performed twice or more.

Dyeing can be performed before uniaxial stretching, during uniaxial stretching, or after uniaxial stretching. Dyes used for dyeing include iodine-potassium iodide; direct black 1
7, 19, 154; Direct Brown 44, 10
6, 195, 210, 223; Direct Red 2,
23, 28, 31, 37, 39, 79, 81, 240,
242, 247; Direct Blue 1, 15, 22,
78, 90, 98, 151, 168, 202, 236,
249, 270; Direct Violet 9, 12,
51, 98; Direct Green 1, 85; Direct Yellow 8, 12, 44, 86, 87; Direct Orange 26, 39, 106, 107 and other dichroic dyes are used in one kind or in a mixture of two or more kinds. it can.
Usually, the dyeing is generally carried out by immersing the PVA film in a solution containing the above dye,
There are no particular restrictions on the processing conditions and processing method, such as mixing the PVA film to form a film.

As the uniaxial stretching, a wet stretching method or a dry heat stretching method can be used, and the ethylene-modified PVA film after warm water such as an aqueous solution of boric acid (in a solution containing the dye or in a fixing treatment bath described later) or after absorbing water. Can be used in the air. The stretching temperature is not particularly limited, but is preferably 30 to 90 ° C. when the ethylene-modified PVA film is stretched in hot water (wet stretching), and is preferably 50 to 180 ° C. when dry heat stretching. In addition, the draw ratio for uniaxial stretching (in the case of multi-stage uniaxial stretching, the total draw ratio)
Is preferably 4 times or more, and particularly preferably 5 times or more, from the viewpoint of the polarization performance of the polarizing film. The upper limit of the stretching ratio is not particularly limited, but if it is 8 times or less, uniform stretching is easily obtained, which is preferable. The thickness of the film after stretching is 2 to
20 μm is preferable, and 5 to 15 μm is more preferable.

Fixing treatment is often carried out for the purpose of strengthening the adsorption of the above dyes to the ethylene-modified PVA film. Boric acid and / or a boron compound are usually added to the treatment bath used for the fixing treatment. Moreover, you may add an iodine compound in a process bath as needed.

The drying treatment of the obtained polarizing film is 30
It is preferable to carry out at 150 to 150 ° C, more preferably at 50 to 150 ° C.

The polarizing film obtained as described above is usually used as a polarizing plate by laminating an optically transparent protective film having mechanical strength on both sides or one side thereof. As a protective film, cellulose triacetate (T
AC) film, cellulose acetate / butyrate (CAB) film, acrylic film, polyester film and the like are used. Further, as the adhesive for bonding, a PVA-based adhesive, a urethane-based adhesive, and the like can be mentioned, and among them, the PVA-based adhesive is preferable.

The polarizing plate obtained as described above is used as a component of a liquid crystal display device after being coated with an adhesive such as an acrylic adhesive and then attached to a glass substrate, or a retardation film or a viewing angle improving film, It is used by bonding with a brightness enhancement film.

[0034]

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited thereto. The hot water cutting temperature, the transmittance of the polarizing film, the degree of polarization and the dichroic ratio in the examples were evaluated by the following methods.

Measurement of hot water cutting temperature An ethylene-modified PVA film was cut into a length of 5 cm and a width of 5 mm in the width direction. A weight of 1 g per 1 mm ² in cross-sectional area in the width direction was attached to the lower part of the film, and the film was hung in water. Water was heated at a rate of 3 ° C. per minute, and the temperature at which the film was dissolved and cut was measured. Measurement of transmittance, polarization degree and dichroic ratio of polarizing film:
Polarizing film made by Shimadzu spectrophotometer UV-220
0 (attached to integrating sphere)
IAJ) LD-201-1983, C light source,
The transmittance (T) and the degree of polarization (V) were determined by measuring and calculating in a 2 degree visual field. Further, if necessary, the dichroic ratio (Rd) was calculated from the following formula. Rd = log (T−T × V) / log (T + T × V)

Example 1 Content of ethylene unit 2.5 mol%, degree of saponification 99.9
Ethylene-modified PVA100 with 5 mol% and degree of polymerization 2400
What was impregnated with 10 parts by weight of glycerin and 170 parts by weight of water was melt-kneaded, defoamed, and then melt-extruded from a T-die to a metal roll to form a film. The ethylene-modified PVA film obtained after drying and heat treatment has a thickness of 40μ.
m, and the average hot water cutting temperature of the film was 70 ° C.

Ethylene-modified PV thus obtained
The A film was continuously treated in the order of pre-swelling, dyeing, uniaxial stretching, fixing treatment, drying and heat treatment to prepare a polarizing film. That is, the ethylene-modified PVA film was immersed in water at 30 ° C. for 60 seconds to be pre-swelled, and then immersed in a 35 ° C. aqueous solution having a boric acid concentration of 40 g / liter, an iodine concentration of 0.4 g / liter, and a potassium iodide concentration of 60 g / liter. Soak for 2 minutes. Then, uniaxial stretching was performed 6 times in a 55 ° C. aqueous solution with a boric acid concentration of 4% to obtain a potassium iodide concentration of 6%.
The fixing treatment was carried out by immersing in an aqueous solution of 0 g / liter, boric acid concentration of 40 g / liter, and zinc chloride concentration of 10 g / liter at 30 ° C. for 5 minutes. After this, ethylene modified PVA
The film was taken out, dried under constant length with hot air at 40 ° C., and further heat treated at 100 ° C. for 5 minutes.

The transmittance of the obtained polarizing film was 44.3.
The degree of polarization was 4%, the degree of polarization was 99.46%, and the dichroic ratio calculated was 49.13. The obtained polarizing film was placed at an angle of 10 degrees between two polarizing plates arranged in parallel with the stretching axis direction (0 degree). The difference in luminance was small and the color spots were small, which was good. The uniaxially stretched direction was fixed, and a moist heat resistance test was performed in an environment of 60 ° C. and 90% RH. The transmittance of the polarizing film after 24 hours is 4
The degree of polarization was 6.50%, the degree of polarization was 91.24%, and the dichroic ratio determined by calculation was 27.27.

A 4% polyvinyl alcohol aqueous solution was used to adhere a triacetate film to the obtained polarizing film to obtain a polarizing plate. The obtained polarizing plate was placed at an angle of 10 degrees between two polarizing plates arranged in parallel to the stretching axis direction (0 degree). The difference in luminance was small and the color spots were small, which was good.

Example 2 Content of ethylene unit 2.1 mol%, degree of saponification 99.9
Ethylene-modified PVA100 with 2 mol% and degree of polymerization 3000
What was impregnated with 10 parts by weight of glycerin and 200 parts by weight of water was melt-kneaded, defoamed, and then melt-extruded from a T-die to a metal roll to form a film. The thickness of the ethylene-modified PVA film obtained after drying and heat treatment is 35μ.
m, and the average hot water cutting temperature of the film was 68 ° C.

Ethylene-modified PV thus obtained
The A film was continuously treated in the order of pre-swelling, dyeing, uniaxial stretching, fixing treatment, drying and heat treatment to prepare a polarizing film. That is, the ethylene-modified PVA film was immersed in water at 30 ° C. for 60 seconds to be pre-swelled, and then immersed in a 35 ° C. aqueous solution having a boric acid concentration of 40 g / liter, an iodine concentration of 0.4 g / liter, and a potassium iodide concentration of 60 g / liter. Soak for 2 minutes. Then, uniaxial stretching was performed 6 times in a 55 ° C. aqueous solution with a boric acid concentration of 4% to obtain a potassium iodide concentration of 6%.
The fixing treatment was carried out by immersing in an aqueous solution of 0 g / liter, boric acid concentration of 40 g / liter, and zinc chloride concentration of 10 g / liter at 30 ° C. for 5 minutes. After this, ethylene modified PVA
The film was taken out, dried under constant length with hot air at 40 ° C., and further heat treated at 100 ° C. for 5 minutes.

The transmittance of the obtained polarizing film is 43.6.
The degree of polarization was 3%, the degree of polarization was 99.85%, and the dichroic ratio calculated was 53.51. The obtained polarizing film was placed at an angle of 10 degrees between two polarizing plates arranged in parallel with the stretching axis direction (0 degree). The difference in luminance was small and the color spots were small, which was good. The uniaxially stretched direction was fixed, and a moist heat resistance test was performed in an environment of 60 ° C. and 90% RH. The transmittance of the polarizing film after 24 hours is 4
The degree of polarization was 5.21%, the degree of polarization was 96.82%, and the dichroic ratio calculated was 36.34.

A triacetate film was attached to the obtained polarizing film using a 4% aqueous polyvinyl alcohol solution to obtain a polarizing plate. The obtained polarizing plate was placed at an angle of 10 degrees between two polarizing plates arranged in parallel to the stretching axis direction (0 degree). The difference in luminance was small and the color spots were small, which was good.

Comparative Example 1 PVA1 having a saponification degree of 99.95 mol% and a polymerization degree of 2400
One having 100 parts by weight of glycerin impregnated with 170 parts by weight of water was melt-kneaded, defoamed, and then melt-extruded from a T-die to a metal roll to form a film. The thickness of the PVA film obtained after drying and heat treatment was 40 μm, and the average hot water cutting temperature of the film was 70 ° C.

The PVA film was continuously treated in the order of pre-swelling, dyeing, uniaxial stretching, fixing treatment, drying and heat treatment to prepare a polarizing film. That is, the PVA film was immersed in water at 30 ° C. for 60 seconds to be pre-swelled, and then for 2 minutes in a 35 ° C. aqueous solution having a boric acid concentration of 40 g / liter, an iodine concentration of 0.4 g / liter, and a potassium iodide concentration of 40 g / liter. Soaked Then, 5 with a boric acid concentration of 4%
It is uniaxially stretched 5.8 times in an aqueous solution at 5 ° C and fixed by immersing it in an aqueous solution of potassium iodide concentration of 40 g / liter, boric acid concentration of 40 g / liter, and zinc chloride concentration of 10 g / liter at 30 ° C for 5 minutes. Processed. After this, PVA
The film was taken out, dried under constant length with hot air at 40 ° C., and further heat treated at 100 ° C. for 5 minutes.

The polarizing film thus obtained had a transmittance of 43.5.
The degree of polarization was 2%, the degree of polarization was 99.76%, and the dichroic ratio calculated was 49.03. The obtained polarizing film was placed at an angle of 10 degrees between two polarizing plates arranged in parallel with the stretching axis direction (0 degree). It had a large difference in brightness and large color spots, and was not suitable as a polarizing film for a large-sized liquid crystal display. The uniaxially stretched direction was fixed, and a moist heat resistance test was performed in an environment of 60 ° C. and 90% RH. The transmittance of the polarizing film after 24 hours is 47.9.
The degree of polarization was 9%, the degree of polarization was 85.51%, and the dichroic ratio calculated was 22.93.

A triacetate film was attached to the obtained polarizing film using a 4% aqueous polyvinyl alcohol solution to obtain a polarizing plate. The obtained polarizing plate was placed at an angle of 10 degrees between two polarizing plates arranged in parallel to the stretching axis direction (0 degree). The difference in brightness was large and the color spots were large, which was unsatisfactory as a polarizing film for a large-sized liquid crystal display.

Comparative Example 2 Ethylene unit content 2.5 mol%, degree of saponification 99.9
Ethylene-modified PVA100 with 5 mol% and degree of polymerization 2400
What was impregnated with 10 parts by weight of glycerin and 170 parts by weight of water was melt-kneaded, defoamed, and then melt-extruded from a T-die to a metal roll to form a film. The thickness of the ethylene-modified PVA film obtained after drying and heat treatment is 40μ.
m, and the average hot water cutting temperature of the film was 75 ° C.

Ethylene-modified PV thus obtained
The A film was continuously treated in the order of pre-swelling, dyeing, uniaxial stretching, fixing treatment, drying and heat treatment to prepare a polarizing film. That is, the ethylene-modified PVA film was immersed in water at 30 ° C. for 60 seconds to be pre-swelled, and then immersed in a 35 ° C. aqueous solution having a boric acid concentration of 40 g / liter, an iodine concentration of 0.4 g / liter, and a potassium iodide concentration of 60 g / liter. Soak for 2 minutes. Subsequently, it was uniaxially stretched 5.8 times in an aqueous solution of boric acid concentration of 4% at 60 ° C. to obtain potassium iodide concentration of 60 g / liter, boric acid concentration of 40 g / liter, and zinc chloride concentration of 10 g / liter at 30 ° C. Immobilization treatment was performed by immersing in an aqueous solution for 5 minutes. After this, ethylene modified P
The VA film was taken out, dried under constant length with hot air at 40 ° C., and further heat-treated at 100 ° C. for 5 minutes.

The transmittance of the obtained polarizing film is 52.3.
The degree of polarization was 6%, the degree of polarization was 73.04%, and the dichroic ratio determined by calculation was 19.82. The obtained polarizing film was placed at an angle of 10 degrees between two polarizing plates arranged in parallel with the stretching axis direction (0 degree). It had a large difference in brightness and large color spots, and was not suitable as a polarizing film for a large-sized liquid crystal display. The uniaxially stretched direction was fixed, and a moist heat resistance test was performed in an environment of 60 ° C. and 90% RH. The transmittance of the polarizing film after 24 hours is 85.4.
The degree of polarization was 9%, the degree of polarization was 12.62%, and the dichroic ratio determined by calculation was 7.69.

The obtained polarizing film was laminated with a triacetate film using a 4% aqueous polyvinyl alcohol solution to obtain a polarizing plate. The obtained polarizing plate was placed at an angle of 10 degrees between two polarizing plates arranged in parallel to the stretching axis direction (0 degree). The difference in brightness was large and the color spots were large, which was unsatisfactory as a polarizing film for a large-sized liquid crystal display.

Comparative Example 3 Ethylene unit content 2.5 mol%, degree of saponification 99.9
Ethylene-modified PVA100 with 5 mol% and degree of polymerization 2400
What was impregnated with 10 parts by weight of glycerin and 170 parts by weight of water was melt-kneaded, defoamed, and then melt-extruded from a T-die to a metal roll to form a film. The thickness of the ethylene-modified PVA film obtained after drying and heat treatment is 40μ.
The average hot water cutting temperature of the film was 65 ° C.

Ethylene-modified PV thus obtained
The A film was continuously treated in the order of pre-swelling, dyeing, uniaxial stretching, fixing treatment, drying and heat treatment to prepare a polarizing film. That is, the ethylene-modified PVA film was immersed in water at 30 ° C. for 60 seconds to be pre-swelled, and then immersed in a 35 ° C. aqueous solution having a boric acid concentration of 40 g / liter, an iodine concentration of 0.4 g / liter, and a potassium iodide concentration of 60 g / liter. Soak for 2 minutes. Then, it was uniaxially stretched 5.8 times in a 60 ° C. aqueous solution with a boric acid concentration of 4% to obtain a potassium iodide concentration of 50 g / liter, a boric acid concentration of 40 g / liter, and a zinc chloride concentration of 10 g / liter at 30 ° C. Immobilization treatment was performed by immersing in an aqueous solution for 5 minutes. After this, ethylene modified P
The VA film was taken out, dried under constant length with hot air at 40 ° C., and further heat-treated at 100 ° C. for 5 minutes.

The transmittance of the obtained polarizing film was 44.3.
The degree of polarization was 4%, the degree of polarization was 98.42%, and the dichroic ratio calculated was 38.78. The obtained polarizing film was placed at an angle of 10 degrees between two polarizing plates arranged in parallel with the stretching axis direction (0 degree). It had a large difference in brightness and large color spots, and was not suitable as a polarizing film for a large-sized liquid crystal display. The uniaxially stretched direction was fixed, and a moist heat resistance test was performed in an environment of 60 ° C. and 90% RH. The transmittance of the polarizing film after 24 hours is 53.03.
%, The degree of polarization was 35.12%, and the dichroic ratio determined by calculation was 3.20.

A triacetate film was attached to the obtained polarizing film using a 4% polyvinyl alcohol aqueous solution to obtain a polarizing plate. The obtained polarizing plate was placed at an angle of 10 degrees between two polarizing plates arranged in parallel to the stretching axis direction (0 degree). The difference in brightness was large and the color spots were large, which was unsatisfactory as a polarizing film for a large-sized liquid crystal display.

Comparative Example 4 100 parts by weight of ethylene-modified PVA having an ethylene content of 2.5 mol%, a saponification degree of 99.95 mol% and a polymerization degree of 1700 were impregnated with 10 parts by weight of glycerin and 170 parts by weight of water, and melted. After kneading and defoaming, a T-die was melt-extruded into a metal roll to form a film. The thickness of the ethylene-modified PVA film obtained after drying and heat treatment was 40 μm, and the average hot water cutting temperature of the film was 70 ° C.

The thus obtained ethylene-modified PVA film was continuously treated in the order of pre-swelling, dyeing, uniaxial stretching, fixing treatment, drying and heat treatment to prepare a polarizing film. That is, the ethylene-modified PVA film was immersed in water at 30 ° C. for 60 seconds to be pre-swelled, and then immersed in a 35 ° C. aqueous solution having a boric acid concentration of 40 g / liter, an iodine concentration of 0.4 g / liter, and a potassium iodide concentration of 60 g / liter. Soak for 2 minutes. Then 60 with boric acid concentration of 4%
Uniaxially stretched 5.8 times in an aqueous solution at 30 ° C, and immersed in an aqueous solution of potassium iodide concentration of 60 g / liter, boric acid concentration of 40 g / liter and zinc chloride concentration of 10 g / liter at 30 ° C for 5 minutes for fixation treatment. I went. Thereafter, the ethylene-modified PVA film was taken out, dried under constant length with hot air at 40 ° C., and further heat-treated at 100 ° C. for 5 minutes.

The transmittance of the obtained polarizing film was 43.6.
The degree of polarization was 1%, the degree of polarization was 99.75%, and the dichroic ratio calculated was 49.43. The obtained polarizing film was placed at an angle of 10 degrees between two polarizing plates arranged in parallel with the stretching axis direction (0 degree). It had a large difference in brightness and large color spots, and was not suitable as a polarizing film for a large-sized liquid crystal display. The uniaxially stretched direction was fixed, and a moist heat resistance test was performed in an environment of 60 ° C. and 90% RH. The transmittance of the polarizing film after 24 hours is 55.98.
%, The degree of polarization was 30.05%, and the calculated dichroic ratio was 2.95.

A triacetate film was attached to the obtained polarizing film using a 4% aqueous polyvinyl alcohol solution to obtain a polarizing plate. The obtained polarizing plate was placed at an angle of 10 degrees between two polarizing plates arranged in parallel to the stretching axis direction (0 degree). The difference in brightness was large and the color spots were large, which was unsatisfactory as a polarizing film for a large-sized liquid crystal display.

Comparative Example 5 100 parts by weight of ethylene-modified PVA having an ethylene content of 2.5 mol%, a saponification degree of 98.5 mol% and a polymerization degree of 2400 were impregnated with 10 parts by weight of glycerin and 170 parts by weight of water, and melted. After kneading and defoaming, a T-die was melt-extruded into a metal roll to form a film. The thickness of the ethylene-modified PVA film obtained after drying and heat treatment was 40 μm, and the average hot water cutting temperature of the film was 70 ° C.

Ethylene-modified PV thus obtained
The A film was continuously treated in the order of pre-swelling, dyeing, uniaxial stretching, fixing treatment, drying and heat treatment to prepare a polarizing film. That is, 30 ethylene-modified PVA film
Pre-swell by immersing in 60 ℃ water for 60 seconds, boric acid concentration 40
g / liter, iodine concentration 0.4 g / liter, potassium iodide concentration 60 g / liter
Soaked for a minute. Then, uniaxial stretching was performed 5.9 times in a 60 ° C. aqueous solution with a boric acid concentration of 4% to obtain a potassium iodide concentration of 5%.
The fixing treatment was carried out by immersing in an aqueous solution of 0 g / liter, boric acid concentration of 40 g / liter, and zinc chloride concentration of 10 g / liter at 30 ° C. for 5 minutes. After this, ethylene modified PVA
The film was taken out, dried under constant length with hot air at 40 ° C., and further heat treated at 100 ° C. for 5 minutes.

The transmittance of the obtained polarizing film was 44.2.
The degree of polarization was 3%, the degree of polarization was 99.48%, and the dichroic ratio calculated was 48.51. The obtained polarizing film was placed at an angle of 10 degrees between two polarizing plates arranged in parallel with the stretching axis direction (0 degree). It had a large difference in brightness and large color spots, and was not suitable as a polarizing film for a large-sized liquid crystal display. The uniaxially stretched direction was fixed, and a moist heat resistance test was performed in an environment of 60 ° C. and 90% RH.
The transmittance of the polarizing film after 24 hours was 55.01%, the degree of polarization was 37.51%, and the dichroic ratio calculated was 3.83.

The obtained polarizing film was laminated with a triacetate film using a 4% aqueous polyvinyl alcohol solution to obtain a polarizing plate. The obtained polarizing plate was placed at an angle of 10 degrees between two polarizing plates arranged in parallel to the stretching axis direction (0 degree). The difference in brightness was large and the color spots were large, which was unsatisfactory as a polarizing film for a large-sized liquid crystal display.

Example 3 An ethylene-modified PVA film was prepared in the same manner as in Example 1 except that the heat history in the width direction was changed. The average value of the hot water cutting temperature of the obtained film is 70 ° C.
Further, when the hot water cutting temperature in the width direction of the film was measured for each 1 cm width, it was 5 c in the TD direction of the film.
The difference in hot water cutting temperature between two points separated by m was 0.4 ° C at the largest place, and the difference in hot water cutting temperature between two points separated by 1 cm in the TD direction of the film was 0. It was 2 ° C. When a polarizing film was prepared using this film in the same manner as in Example 1, the color spots by visual observation were very small and very good.

Example 4 An ethylene-modified PVA film was prepared in the same manner as in Example 1 except that the heat history in the width direction was changed. The average value of the hot water cutting temperature of the obtained film is 70 ° C.
Further, when the hot water cutting temperature in the width direction of the film was measured for each 1 cm width, it was 5 c in the TD direction of the film.
The difference in hot water cutting temperature between two points separated by m was 0.6 ° C at the largest place, and the difference in hot water cutting temperature between two points separated by 1 cm in the TD direction of the film was 0. It was 3 ° C. When a polarizing film was prepared using this film in the same manner as in Example 1, the color spots by visual observation were small and good.

Example 5 An ethylene-modified PVA film was prepared in the same manner as in Example 1 except that the heat history in the width direction was changed. The average value of the hot water cutting temperature of the obtained film is 70 ° C.
Further, when the hot water cutting temperature in the width direction of the film was measured for each 1 cm width, it was 5 c in the TD direction of the film.
The difference in hot water cutting temperature between two points separated by m was 0.9 ° C at the largest place, and the difference in hot water cutting temperature between two points separated by 1 cm in the TD direction of the film was 0. It was 5 ° C. When a polarizing film was produced using this film in the same manner as in Example 1, the color spots by visual observation were small and at a usable level.

[0067]

EFFECTS OF THE INVENTION According to the present invention, an ethylene-modified PVA film having good polarization performance when used as a polarizing film and capable of reducing color spots can be obtained. Then, using this ethylene-modified PVA film, a polarizing film suitable for a large-sized liquid crystal display with few color spots can be obtained.

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Claims (4)

[Claims] 1. An ethylene unit content of 1 to 4 mol%, a polymerization degree of 2000 to 4000, and a saponification degree of 99.0 to 99.9.
An ethylene-modified polyvinyl alcohol film formed from 9 mol% ethylene-modified polyvinyl alcohol and having a hot water cutting temperature of 66 to 73 ° C. 2. The ethylene-modified polyvinyl alcohol film according to claim 1, wherein the difference in hot water cutting temperature between two points separated by 5 cm in the TD direction of the film is 1 ° C. or less. 3. The ethylene-modified polyvinyl alcohol film according to claim 1, wherein a difference in hot water cutting temperature between two points separated by 1 cm in the TD direction of the film is 0.5 ° C. or less. 4. The ethylene-modified polyvinyl alcohol film according to claim 1, having a thickness of 10 to 50 μm.