JP2007176164A - Transparent polymer film and its manufacturing method, and optical compensation film using it, laminated film, and liquid crystal displaying device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transparent polymer film which has a high elasticity modulus, keeps a dimensional variation by humidity small, and has a proper moisture permeability. <P>SOLUTION: This transparent polymer film is manufactured by drawing by 10% or more a transparent polymer film of which the moisture permeability at 40°C and at a relative humidity of 90% is 100 g/(m<SP>2</SP>×day) by the conversion of a film thickness of 80 μm, at (Tg+50)°C or higher. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a transparent polymer film having a high elastic modulus, small dimensional change, and appropriate moisture permeability, and a method for producing the same. The present invention also relates to an optical compensation film, a laminated film, a polarizing plate using the transparent polymer film, and a liquid crystal display device using the same.

  For silver halide photographic light-sensitive materials, optical compensation films, polarizing plates, and image display devices, polymer films such as cellulose ester, polyester, polycarbonate, cycloolefin polymer vinyl polymer, and polyimide are used. Since these polymers can produce films that are more excellent in terms of flatness and uniformity, the films are widely used as films for optical applications.

  Among these, a cellulose ester film having an appropriate moisture permeability can be directly bonded on-line with the most common polarizing film made of polyvinyl alcohol (PVA) / iodine. Therefore, cellulose acylate, particularly cellulose acetate and cellulose acetate propionate are widely used as a protective film for polarizing plates.

  In a liquid crystal display device using such a polarizing plate, a highly stretched polarizing film is used, and accordingly, the four sides or four corners of the display screen of the liquid crystal display device are accompanied by a change in the size of the polarizing plate due to a change in the external environment. Light leakage may occur. Such light leakage is an important problem to be improved because it is easily visible and greatly affects the quality of the display device.

As a countermeasure against this, a method of reducing optical defects by giving a pressure absorbing / relaxing function to an adhesive that bonds a polarizing plate to another member has been disclosed (for example, see Patent Document 1). However, although this method can reduce defects, improvement in the dimensional change of the polarizing plate, which is an essential cause of the defects, cannot be improved.
JP 2000-109771 A

  An object of the present invention is to provide a transparent polymer film having a high elastic modulus, small dimensional change, and appropriate moisture permeability, and a method for producing the same. Another object of the present invention is to provide an optical compensation film using the transparent polymer film of the present invention, as well as another polymer using the transparent polymer film of the present invention as an optical compensation film, an optical compensation film support, or a laminated film. Another object is to provide a laminated film or a polarizing plate that can be directly bonded to a film and exhibit excellent optical performance. It is another object of the present invention to provide a highly reliable liquid crystal display device in which light leakage occurring in the peripheral portion of the screen due to changes in heat and humidity environment is suppressed.

The above-mentioned problem is solved by the following means.
[Aspect 1]
It includes a step of stretching a transparent polymer film having a moisture permeability at 40 ° C. and a relative humidity of 90% of 100 g / (m ² · day) or more in terms of a film thickness of 80 μm at a temperature of (Tg + 50) ° C. or more and 10% or more. A method for producing a transparent polymer film.
[Aspect 2]
The method for producing a transparent polymer film according to aspect 1, wherein the stretching is performed at (Tg + 60) ° C. or higher.
[Aspect 3]
The method for producing a transparent polymer film according to aspect 1 or 2, wherein the stretching is performed at 200 ° C or higher.
[Aspect 4]
4. The method for producing a transparent polymer film according to any one of aspects 1 to 3, wherein the elastic modulus of the transparent polymer film is 1.1 to 100 times by the stretching.
[Aspect 5]
The method for producing a transparent polymer film according to any one of Embodiments 1 to 4, wherein the stretching is performed at a stretching rate of 20% / min or more.

[Aspect 6]
The method for producing a transparent polymer film according to any one of aspects 1 to 5, wherein the stretching is longitudinal stretching performed in an apparatus having a heating zone between at least two nip rolls having different peripheral speeds.
[Aspect 7]
The transparent polymer film manufactured by the manufacturing method as described in any one of aspects 1-6.
[Aspect 8]
A transparent polymer film having an elastic modulus of 5 GPa or more and a moisture permeability of 100 to 2000 g / (m ² · day) in terms of a film thickness of 80 μm at 40 ° C. and a relative humidity of 90%.
[Aspect 9]
The transparent polymer film according to embodiment 7 or 8, wherein the coefficient of humidity expansion is 6 × 10 ⁻⁵ /% RH or less.
[Aspect 10]
The transparent polymer film according to any one of aspects 7 to 9, wherein the total light transmittance is 90% or more.
[Aspect 11]
Haze is 2% or less, The transparent polymer film as described in any one of aspects 7-10 characterized by the above-mentioned.
[Aspect 12]
The transparent polymer film according to any one of Embodiments 7 to 11, comprising a cellulose ester as a polymer as a main component.
[Aspect 13]
The transparent polymer film according to aspect 12, wherein the cellulose ester is cellulose acetate.
[Aspect 14]
An optical compensation film having at least one transparent polymer film according to any one of aspects 7 to 13.

[Aspect 15]
An optical compensation film, wherein an optically anisotropic layer is provided on the transparent polymer film according to any one of aspects 7 to 13.
[Aspect 16]
16. The optical compensation film according to aspect 15, wherein the optically anisotropic layer contains a discotic liquid crystal.
[Aspect 17]
16. The optical compensation film according to aspect 15, wherein the optically anisotropic layer contains a rod-like liquid crystal.
[Aspect 18]
The optical compensation film according to any one of embodiments 15 to 17, wherein the optically anisotropic layer is made of a polymer film.
[Aspect 19]
The optical film according to aspect 18, wherein the polymer film includes at least one polymer material selected from the group consisting of polyamide, polyimide, polyester, polyetherketone, polyamideimide, polyesterimide, and polyaryletherketone. Compensation film.

[Aspect 20]
A laminated film having at least one transparent polymer film according to any one of aspects 7 to 13.
[Aspect 21]
A laminated film in which at least one of the transparent polymer films according to any one of Embodiments 7 to 13 is bonded to another polymer film.
[Aspect 22]
The laminated film according to aspect 21, wherein an angle formed by a direction in which the elastic modulus of the transparent polymer film is maximized and a direction in which the elastic modulus of the other transparent polymer film is maximized is 15 ° or less. .
[Aspect 23]
The laminated film according to embodiment 21 or 22, wherein the polymer that is a main component of the other transparent polymer film is polyvinyl alcohol.
[Aspect 24]
The laminated film according to any one of aspects 21 to 23, wherein the other transparent polymer film is a polarizing film.
[Aspect 25]
25. The laminated film according to any one of aspects 20 to 24, wherein the total light transmittance is 50% or less.

[Aspect 26]
A polarizing plate having at least one transparent polymer film according to any one of aspects 7 to 13.
[Aspect 27]
A polarizing plate comprising the laminated film according to any one of aspects 20 to 25.
[Aspect 28]
28. The polarizing plate according to aspect 26 or 27, wherein at least one layer selected from the group consisting of a hard coat layer, an antiglare layer and an antireflection layer is provided on the surface.

[Aspect 29]
The transparent polymer film according to any one of aspects 7 to 13, the optical compensation film according to any one of aspects 14 to 19, the laminated film according to any one of aspects 20 to 25, and the aspect 26 A liquid crystal display device comprising at least one film selected from the group consisting of polarizing plates according to any one of -28.

  According to the present invention, it is possible to provide a transparent polymer film having a high elastic modulus, a small dimensional change, and an appropriate moisture permeability, and a method for producing the same. Further, according to the present invention, the optical compensation film using the transparent polymer film of the present invention, and the transparent polymer film of the present invention as an optical compensation film, a support for the optical compensation film, or a laminated film, other polymers. It is also possible to provide a laminated film or a polarizing plate that can be directly bonded on-line with a film and exhibit excellent optical performance. Furthermore, it is possible to suppress light leakage generated in the peripheral portion of the screen due to changes in heat and humidity environment, and to provide a highly reliable liquid crystal display device.

  Hereinafter, the transparent polymer film of the present invention and the production method thereof, the retardation film, the laminated film, the polarizing plate, and the liquid crystal display device will be described in detail. The description of the constituent elements described below may be made based on typical embodiments of the present invention, but the present invention is not limited to such embodiments. In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

<Transparent polymer film>
The transparent polymer film of the present invention has an elastic modulus of 5 GPa or more, and a moisture permeability at 40 ° C. and a relative humidity of 90% is 100 to 2000 g / (m ² · day) in terms of a film thickness of 80 μm. To do.

[Elastic modulus]
The elastic modulus in the present invention is prepared by preparing a film sample having a length of 150 mm and a width of 10 mm, adjusting the humidity for 24 hours at 25 ° C. and a relative humidity of 60%, and following an ISO 1184-1983 standard, an initial sample length of 100 mm, a tensile speed It is the tensile elastic modulus measured at 10 mm / min and determined from the initial slope of the stress-strain curve. Although the elastic modulus generally differs depending on how the film sample is taken in the length direction and the width direction, in the present invention, a value obtained by preparing a film sample in the direction in which the elastic modulus is maximum is expressed as the elastic modulus of the present invention.
The elastic modulus of the film of the present invention is 5 GPa or more, preferably 6 to 30 GPa, more preferably 7 to 20 GPa, and still more preferably 8 to 15 GPa. A method for adjusting the elastic modulus within the range of the present invention will be described later.

[Modification of elastic modulus]
The change in elastic modulus in the present invention is calculated by the following formula, where E _{0 is} the elastic modulus of the film before the stretching treatment determined according to the above method and E ₁ is the elastic modulus of the film after the stretching treatment.
Elastic modulus change [times] = E ₁ / E ₀
The elastic modulus change in the present invention is preferably 1.1 to 100 times, more preferably 1.3 to 10 times, further preferably 1.5 to 8 times, and particularly preferably 2 to 5 times. If the elastic modulus change is 1.1 times or more, the orientation of the polymer chain is advanced, which is preferable in that it is possible to reduce the dimensional change when an external force is applied, and the elastic modulus change is 100 times or less. If it exists, when it uses as a protective film of a polarizing plate, it is preferable at the point that the dimensional change of a polarizer can be suppressed efficiently.

[Humidity expansion coefficient]
When measuring the humidity expansion coefficient in the present invention, a film sample having a length of 25 cm (measurement direction) and a width of 5 cm cut out with the direction having the maximum elastic modulus as the longitudinal direction is prepared, and the sample is provided at intervals of 20 cm. After pin holes are made and humidity is adjusted for 24 hours at 25 ° C. and 10% relative humidity, the distance between the pin holes is measured with a pin gauge (measured value is L ₀ ). Next, the sample is conditioned at 25 ° C. and a relative humidity of 80% for 24 hours, and the distance between the pin holes is measured with a pin gauge (measured value is L ₁ ). The humidity expansion coefficient is calculated by the following formula using these measured values.
Humidity expansion coefficient [/% RH] = {(L ₁ −L ₀ ) / L ₀ } / (R ₁ −R ₀ )
The film according to the present invention preferably has a humidity expansion coefficient of 6.0 × 10 ⁻⁵ /% RH or less, more preferably 4.0 × 10 ⁻⁵ /% RH or less, and 3.0 × 10 ⁻⁵ /% RH or less. More preferred is 2.0 × 10 ⁻⁵ /% RH or less. When the humidity expansion coefficient is 6.0 × 10 ⁻⁵ /% RH or less, when used as a protective film for a polarizing plate, a decrease in the degree of polarization or polarization of the peripheral portion occurring before and after the polarizing plate is held in a humid heat environment. This is preferable in that the displacement of the surface can be suppressed.

[Total light transmittance]
The total light transmittance in the present invention is that a sample having a length of 40 mm and a width of 80 mm is conditioned for 24 hours at 25 ° C. and a relative humidity of 60%, and then conforms to the standard of JIS K-6714 at 25 ° C. and a relative humidity of 60%. , Measured with a haze meter (HGM-2DP, Suga tester).
The total light transmittance of the film of the present invention is 90% or more, preferably 91% or more, more preferably 92% or more, further preferably 93%, and particularly preferably 94% or more.

[Haze]
The haze in the present invention is a haze meter in which a sample having a length of 40 mm and a width of 80 mm is conditioned at 25 ° C. and a relative humidity of 60% for 24 hours, and at 25 ° C. and a relative humidity of 60% according to the standard of JIS K-6714 (HGM-2DP, Suga Tester).
The haze of the transparent polymer film of the present invention is preferably 2% or less, more preferably 1% or less, further preferably 0.5% or less, particularly preferably 0.3% or less, and in some cases 0.2% or less. Is most preferred.

[Moisture permeability]
The moisture permeability in the present invention is the change in mass before and after humidity control when a cup containing calcium chloride is covered with a film and sealed, and left for 24 hours at 40 ° C. and 90% relative humidity. It is a value evaluated from (g / (m ² · day)). The moisture permeability increases as the temperature increases and increases as the humidity increases, but the magnitude relationship of moisture permeability between the films remains unchanged regardless of the conditions. Therefore, in the present invention, the value of the mass change at 40 ° C. and 90% relative humidity is used as a reference. In addition, since the moisture permeability decreases as the film thickness increases and increases as the film thickness decreases, the measured moisture permeability is first multiplied by the measured film thickness, and a value obtained by dividing the result by 80 is “ The water vapor transmission rate in terms of a film thickness of 80 μm ”.

The moisture permeability of the film of the present invention is 100 g / (m ² · day) or more in terms of 80 μm. By using a film having a moisture permeability of 80 g in terms of 100 g / (m ² · day) or more, the film can be directly bonded to the polarizing film. The moisture permeability of the 80μm ^{terms, 100~1500g / (m 2 · day} ) , more ^{preferably, 300~1000g / (m 2 · day} ) is more preferred.
When the transparent polymer film of the present invention is used as an outer protective film that is not disposed between the polarizing film and the liquid crystal cell as described later, the moisture permeability of the transparent polymer film of the present invention is 500 g / (m in terms of 80 μm. ² · day), preferably 100 to 450 g / (m ² · day), more preferably 100 to 400 g / (m ² · day), and 150 to 300 g / (m ² · day). Most preferred. By doing in this way, durability of the polarizing plate with respect to humidity or wet heat improves, and a highly reliable liquid crystal display device can be provided.

In order to prepare the film of the present invention having a moisture permeability of 100 g / (m ² · day) or more in terms of 80 μm, it is preferable to appropriately control the hydrophilicity / hydrophobicity of the polymer or to reduce the density of the film. The former method includes, for example, a method of appropriately controlling the hydrophilicity / hydrophobicity of the polymer main chain and further introducing a hydrophobic or hydrophilic side chain. The latter method includes, for example, a side chain in the polymer main chain. And the like, selection of the type of solvent used during film formation, and control of the drying rate during film formation.

[Tg]
The glass transition temperature (Tg) in the present invention is such that 20 mg of a film is placed in a DSC measurement pan, and this is heated from 30 ° C. to 250 ° C. at 10 ° C./min in a nitrogen stream, and then −20 ° C./30° C. It is determined by measuring the temperature at which the baseline starts to deviate from the low temperature side when it is cooled in minutes and heated again from 30 ° C. to 250 ° C.
The Tg of the film of the present invention is preferably 80 ° C to 300 ° C, more preferably 100 ° C to 200 ° C, and further preferably 130 ° C to 180 ° C.

[polymer]
Examples of the polymer that is a constituent element of the transparent polymer film of the present invention include cellulose ester, polyester, polycarbonate, cycloolefin polymer, vinyl polymer, polyamide, and polyimide. The polymer preferably has a hydrophilic structure such as a hydroxyl group, amide, imide or ester in the main chain or side chain in order to achieve appropriate moisture permeability. As the polymer, cellulose ester is preferable.
As said polymer, a powder or a particulate thing can be used, and the pelletized thing can also be used.
The water content of the polymer is preferably 1.0% by mass or less, more preferably 0.7% by mass or less, and most preferably 0.5% by mass or less. Moreover, it is preferable that the said moisture content is 0.2 mass% or less depending on the case. When the water content of the polymer is not within the preferred range, it is preferable to use the polymer after drying it by heating or the like.
These polymers may be used alone or in combination of two or more polymers.

Examples of the cellulose ester include a cellulose ester compound and a compound having an ester-substituted cellulose skeleton obtained by introducing a functional group biologically or chemically from cellulose as a raw material. Among them, cellulose acylate is particularly preferable.
In addition, as a polymer which is a main component of the transparent polymer film of this invention, it is preferable to use the above-mentioned cellulose acylate. Here, the “polymer as the main component” means a polymer when it is composed of a single polymer, and when it is composed of a plurality of polymers, it is the most mass fraction of the constituent polymers. Indicates a high polymer.

The cellulose ester is an ester of cellulose and acid. As the acid constituting the ester, an organic acid is preferable, a carboxylic acid is more preferable, a fatty acid having 2 to 22 carbon atoms is further preferable, and a lower fatty acid having 2 to 4 carbon atoms is most preferable.
The cellulose acylate is an ester of cellulose and carboxylic acid. In the cellulose acylate, all or part of the hydrogen atoms of the hydroxyl groups present at the 2-position, 3-position and 6-position of the glucose unit constituting the cellulose are substituted with acyl groups. Examples of the acyl group include, for example, acetyl group, propionyl group, butyryl group, isobutyryl group, pivaloyl group, heptanoyl group, hexanoyl group, octanoyl group, decanoyl group, dodecanoyl group, tridecanoyl group, tetradecanoyl group, hexadecanoyl group, and hexadecanoyl group. Examples include a noyl group, an octadecanoyl group, a cyclohexanecarbonyl group, an oleoyl group, a benzoyl group, a naphthylcarbonyl group, and a cinnamoyl group. As the acyl group, acetyl group, propionyl group, butyryl group, dodecanoyl group, octadecanoyl group, pivaloyl group, oleoyl group, benzoyl group, naphthylcarbonyl group, cinnamoyl group are preferable, acetyl group, propionyl group, butyryl group Is most preferred.
The cellulose ester may be an ester of cellulose and a plurality of acids. Cellulose acylate may be substituted with a plurality of acyl groups.

  In the transparent polymer film of the present invention, cellulose acetate which is cellulose acylate having an ester with acetic acid is particularly preferable. From the viewpoint of solubility in a solvent, cellulose acetate having a degree of acetyl substitution of 2.70 to 2.87 is preferable. More preferred is cellulose acetate of 2.80 to 2.86, most preferred. Here, the degree of acetyl substitution means the total of the ratio of the hydrogen atoms of the hydroxyl groups present at the 2-position, 3-position and 6-position of cellulose being substituted with acyl groups, and all the hydroxyl groups are substituted. In this case, the degree of substitution is 3.

  The basic principle regarding the method for synthesizing cellulose acylate is described in Nobuhiko Umeda et al., Wood Chemistry, 180-190 (Kyoritsu Shuppan, 1968). A typical synthesis method of cellulose acylate includes a liquid phase acylation method using a carboxylic acid anhydride-carboxylic acid-sulfuric acid catalyst. Specifically, first, cellulose raw materials such as cotton linter and wood pulp are pretreated with an appropriate amount of carboxylic acid such as acetic acid, and then put into a precooled acylated mixture to be esterified, and complete cellulose acylate (2 The total degree of acyl substitution at the 3rd, 6th and 6th positions is approximately 3.00). The acylated mixed solution generally contains a carboxylic acid as a solvent, a carboxylic acid anhydride as an esterifying agent, and sulfuric acid as a catalyst. In addition, the carboxylic acid anhydride is usually used in a stoichiometrically excessive amount with respect to the total amount of cellulose reacting with the carboxylic acid anhydride and moisture present in the system.

  Subsequently, after completion of the acylation reaction, water or hydrous acetic acid is added in order to hydrolyze the excess carboxylic anhydride remaining in the system. Further, in order to partially neutralize the esterification catalyst, an aqueous solution containing a neutralizing agent (for example, calcium, magnesium, iron, aluminum or zinc carbonate, acetate, hydroxide or oxide) is added. Also good. Furthermore, the obtained complete cellulose acylate is saponified and aged by maintaining it at 20 to 90 ° C. in the presence of a small amount of acylation reaction catalyst (generally, remaining sulfuric acid) to obtain the desired degree of acyl substitution and degree of polymerization. Change to cellulose acylate. When the desired cellulose acylate is obtained, the catalyst remaining in the system is completely neutralized using the neutralizing agent or the like, or water or dilute acetic acid without neutralizing the catalyst. Cellulose acylate solution is added into the solution (or water or dilute acetic acid is added into the cellulose acylate solution) to separate the cellulose acylate, and the desired cellulose acylate is obtained by washing and stabilizing treatment. Can do.

  The degree of polymerization of the cellulose acylate is preferably from 150 to 500, more preferably from 200 to 400, and even more preferably from 220 to 350 in terms of viscosity average degree of polymerization. The viscosity-average polymerization degree can be measured according to the description of Uda et al.'S intrinsic viscosity method (Kazuo Uda, Hideo Saito, Journal of Textile Science, Vol. 18, No. 1, pages 105-120, 1962). The method for measuring the viscosity average degree of polymerization is also described in JP-A-9-95538.

In addition, cellulose acylate having a small amount of low molecular components has a high average molecular weight (degree of polymerization), but its viscosity is lower than that of ordinary cellulose acylate. Such a cellulose acylate having a small amount of low molecular components can be obtained by removing the low molecular components from cellulose acylate synthesized by an ordinary method. The removal of the low molecular components can be performed by washing the cellulose acylate with an appropriate organic solvent. In addition, cellulose acylate having a small amount of low molecular components can be obtained by synthesis. When synthesizing cellulose acylate having a small amount of low molecular components, the amount of sulfuric acid catalyst in the acylation reaction is preferably adjusted to 0.5 to 25 parts by mass with respect to 100 parts by mass of cellulose. When the amount of the sulfuric acid catalyst is within the above range, cellulose acylate that is preferable in terms of molecular weight distribution (uniform molecular weight distribution) can be synthesized.
The raw material cotton of cellulose ester and the synthesis method are also described in pages 7 to 12 of the Japan Society of Invention Disclosure (Public Technical Number 2001-1745, published on March 15, 2001, Japan Society of Invention).

<< Method for producing transparent polymer film >>
The transparent polymer film of the present invention can be produced from a polymer solution containing a polymer and various additives by a solution casting film forming method. Further, when the melting point of the polymer or the melting point of the mixture of the polymer and various additives is lower than the decomposition temperature and higher than the stretching temperature described later, the transparent polymer film of the present invention is obtained by a melt film forming method. It can also be produced by forming a film. The melt film forming method is described in JP-A No. 2000-352620.
Below, the manufacturing method of a transparent polymer film is demonstrated concretely taking the preferable embodiment in this invention as an example.

[Polymer solution]
(solvent)
The transparent polymer film of the present invention can be produced, for example, by forming a polymer solution containing a polymer and, if necessary, various additives by a solution casting film forming method or the like.
As a main solvent of a polymer solution (preferably a cellulose ester solution) used for production of the transparent polymer film of the present invention, an organic solvent which is a good solvent for the polymer can be preferably used. As such an organic solvent, an organic solvent having a boiling point of 80 ° C. or lower is more preferable from the viewpoint of reducing the drying load. The boiling point of the organic solvent is more preferably 10 to 80 ° C, and particularly preferably 20 to 60 ° C. Moreover, the organic solvent whose boiling point is 30-45 degreeC depending on the case can also be used suitably as said main solvent.

  Examples of such a main solvent include halogenated hydrocarbons, esters, ketones, ethers, alcohols and hydrocarbons, which may have a branched structure or a cyclic structure. The main solvent may have two or more functional groups of esters, ketones, ethers and alcohols (that is, —O—, —CO—, —COO—, —OH). Furthermore, the hydrogen atom in the hydrocarbon portion of the ester, ketone, ether and alcohol may be substituted with a halogen atom (particularly a fluorine atom). In addition, when the main solvent of the polymer solution (preferably cellulose ester solution) used for preparation of the transparent polymer film of the present invention is composed of a single solvent, it indicates that solvent, and is composed of a plurality of solvents. In the case, it indicates a solvent having the highest mass fraction among the constituent solvents.

As said halogenated hydrocarbon, a chlorinated hydrocarbon is more preferable, for example, a dichloromethane, chloroform, etc. are mentioned, A dichloromethane is further more preferable.
Examples of the ester include methyl formate, ethyl formate, methyl acetate, and ethyl acetate.
Examples of the ketone include acetone and methyl ethyl ketone.
Examples of the ether include diethyl ether, methyl-tert-butyl ether, diisopropyl ether, dimethoxymethane, 1,3-dioxolane, 4-methyldioxolane, tetrahydrofuran, methyltetrahydrofuran, 1,4-dioxane and the like.
As said alcohol, methanol, ethanol, 2-propanol etc. are mentioned, for example.
Examples of the hydrocarbon include n-pentane, cyclohexane, n-hexane, benzene, and toluene.

  Examples of the organic solvent used in combination with these main solvents include halogenated hydrocarbons, esters, ketones, ethers, alcohols and hydrocarbons, which may have a branched structure or a cyclic structure. The organic solvent may have any two or more of ester, ketone, ether and alcohol functional groups (that is, —O—, —CO—, —COO—, —OH). Furthermore, the hydrogen atom in the hydrocarbon portion of the ester, ketone, ether and alcohol may be substituted with a halogen atom (particularly a fluorine atom).

As said halogenated hydrocarbon, a chlorinated hydrocarbon is more preferable, for example, a dichloromethane, chloroform, etc. are mentioned, A dichloromethane is further more preferable.
Examples of the ester include methyl formate, ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate, and pentyl acetate.
Examples of the ketone include acetone, methyl ethyl ketone, diethyl ketone, diisobutyl ketone, cyclopentanone, cyclohexanone, and methylcyclohexanone.
Examples of the ether include diethyl ether, methyl tert-butyl ether, diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolane, 4-methyldioxolane, tetrahydrofuran, methyltetrahydrofuran, anisole, and phenetole. Etc.
Examples of the alcohol include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, tert-butanol, 1-pentanol, 2-methyl-2-butanol, cyclohexanol, and 2-fluoro. Examples include ethanol, 2,2,2-trifluoroethanol, 2,2,3,3-tetrafluoro-1-propanol.
Examples of the hydrocarbon include n-pentane, cyclohexane, n-hexane, benzene, toluene, xylene and the like.
Examples of the organic solvent having two or more kinds of functional groups include 2-ethoxyethyl acetate, 2-methoxyethanol, 2-butoxyethanol, and methyl acetoacetate.

When the polymer which comprises the transparent polymer film of this invention contains a cellulose acylate, Preferably it is 5-30 mass% in all the solvents, More preferably, it is 7-25 mass%, More preferably, it is 10-20 mass% alcohol. It is preferable to contain from the viewpoint of reducing the peeling load from the band.
Further, from the viewpoint of reducing Rth, the polymer solution used for the production of the transparent polymer film of the present invention has a small proportion of volatilizing with the halogenated hydrocarbon at the initial stage of the drying process, and the boiling point gradually concentrated is 95 ° C. or higher. And it is preferable to contain the organic solvent which is a poor solvent of a cellulose ester preferably 1-15 mass%, More preferably, 1.5-13 mass%, More preferably, 2-10 mass%.

  Although the example of the combination of the organic solvent preferably used as a solvent of the polymer solution used for preparation of the transparent polymer film of this invention is given below, the combination which can be used by this invention is not limited to these. In addition, the numerical value of a ratio means a mass part.

(1) Dichloromethane / methanol / ethanol / butanol = 80/10/5/5
(2) Dichloromethane / methanol / ethanol / butanol = 80/5/5/10
(3) Dichloromethane / isobutyl alcohol = 90/10
(4) Dichloromethane / acetone / methanol / propanol = 80/5/5/10
(5) Dichloromethane / methanol / butanol / cyclohexane = 80/8/10/2
(6) Dichloromethane / methyl ethyl ketone / methanol / butanol = 80/10/5/5
(7) Dichloromethane / butanol = 90/10
(8) Dichloromethane / acetone / methyl ethyl ketone / ethanol / butanol = 68/10/10/7/5
(9) Dichloromethane / cyclopentanone / methanol / pentanol = 80/2/15/3
(10) Dichloromethane / methyl acetate / ethanol / butanol = 70/12/15/3
(11) Dichloromethane / methyl ethyl ketone / methanol / butanol = 80/5/5/10
(12) Dichloromethane / methyl ethyl ketone / acetone / methanol / pentanol = 50/20/15/5/10
(13) Dichloromethane / 1,3-dioxolane / methanol / butanol = 70/15/5/10
(14) Dichloromethane / dioxane / acetone / methanol / butanol = 75/5/10/5/5
(15) Dichloromethane / acetone / cyclopentanone / ethanol / isobutyl alcohol / cyclohexane = 60/18/3/10/7/2
(16) Dichloromethane / methyl ethyl ketone / acetone / isobutyl alcohol = 70/10/10/10
(17) Dichloromethane / acetone / ethyl acetate / butanol / hexane = 69/10/10/10/1
(18) Dichloromethane / methyl acetate / methanol / isobutyl alcohol = 65/15/10/10
(19) Dichloromethane / cyclopentanone / ethanol / butanol = 85/7/3/5
(20) Dichloromethane / methanol / butanol = 83/15/2
(21) Dichloromethane = 100
(22) Acetone / ethanol / butanol = 80/15/5
(23) Methyl acetate / acetone / methanol / butanol = 75/10/10/5
(24) 1,3-dioxolane = 100
(25) Dichloromethane / methanol = 85/15
(26) Dichloromethane / methanol = 92/8
(27) Dichloromethane / methanol = 90/10
(28) Dichloromethane / methanol = 87/13
(29) Dichloromethane / ethanol = 90/10

  In addition, the detailed description in the case of using a non-halogen organic solvent as the main solvent is described in the Japan Society for Invention and Innovation (Publication No. 2001-1745, published on March 15, 2001, Japan Institute of Invention), and used as appropriate. can do.

(Solution concentration)
The polymer concentration in the polymer solution to be prepared is preferably 5 to 40% by mass, more preferably 10 to 30% by mass, and most preferably 15 to 30% by mass.
The polymer concentration can be adjusted to a predetermined concentration when the polymer is dissolved in a solvent. Further, after preparing a solution with a low concentration (for example, 4 to 14% by mass) in advance, the solution may be concentrated by evaporating the solvent or the like. Furthermore, after preparing a high concentration solution in advance, it may be diluted. Moreover, the concentration of the polymer can be lowered by adding an additive.

(Additive)
The said polymer solution used for preparation of the transparent polymer film of this invention can contain the various liquid or solid additive according to a use in each preparation process. Examples of the additive include a plasticizer (preferable addition amount is 0.01 to 10% by mass based on the polymer, the same applies hereinafter), an ultraviolet absorber (0.001 to 1% by mass), and an average particle size of 5 to 5. 3000 nm fine particle powder (0.001 to 1% by mass), fluorosurfactant (0.001 to 1% by mass), release agent (0.0001 to 1% by mass), deterioration inhibitor (0.0001 -1 mass%), an optical anisotropy control agent (0.01-10 mass%), and an infrared absorber (0.001-1 mass%).

  The plasticizer and the optical anisotropy controlling agent are organic compounds having a molecular weight of 3000 or less, preferably a compound having both a hydrophobic part and a hydrophilic part. These compounds change the retardation value by orienting between polymer chains. Furthermore, when these compounds are used in combination with cellulose acylate particularly preferably used in the present invention, the hydrophobicity of the film can be improved and the change in humidity of retardation can be reduced. Moreover, the wavelength dependence of retardation can be effectively controlled by using the ultraviolet absorber or the infrared absorber in combination. The additives used for the transparent polymer film of the present invention are preferably those that are substantially free of volatilization during the drying process.

  From the viewpoint of reducing the humidity change of the retardation, it is preferable that the amount of these additives to be added is large. However, as the amount is increased, the glass transition temperature (Tg) of the polymer film is decreased, and the additive is added in the film production process. It becomes easy to cause the volatilization problem of the agent. Therefore, when the cellulose acetate used more preferably in the present invention is used as a polymer, the amount of the additive having a molecular weight of 3000 or less is preferably 0.01 to 30% by mass, more preferably 2 to 30% by mass with respect to the polymer. Preferably, 5 to 20% by mass is more preferable.

  A plasticizer that can be suitably used when cellulose acylate is used as the polymer constituting the transparent polymer film of the present invention is described in JP-A No. 2001-151901. Moreover, about an infrared absorber, Unexamined-Japanese-Patent No. 2001-194522 has description. The timing of adding the additive can be appropriately determined according to the type of the additive. Further, the additive is also described in pages 16 to 22 of the Japan Society of Invention Disclosure Technical Bulletin (Public Technical Number 2001-1745, published on March 15, 2001, Japan Society of Invention).

(Preparation of polymer solution)
The polymer solution can be prepared, for example, according to the preparation method described in JP-A-2005-104148, pages 106-120. Specifically, the polymer and the solvent can be mixed and stirred to swell, and optionally cooled or heated to dissolve, and then filtered to obtain a polymer solution.

[Casting, drying]
The transparent polymer film of the present invention can be produced using a conventional solution casting film forming apparatus according to a conventional solution casting film forming method. Specifically, the dope (polymer solution) prepared in a dissolving machine (kettle) can be filtered and then temporarily stored in a storage kettle, and the foam contained in the dope can be defoamed for final preparation. The dope is kept at 30 ° C., and is sent from the dope discharge port to the pressure die through a pressure metering gear pump capable of delivering a constant amount of liquid with high accuracy, for example, by the rotational speed, and the dope runs endlessly from the die (slit) of the pressure die. It casts uniformly on the metal support body of the cast part currently cast (casting process). Next, the dope film (also referred to as web) is peeled off from the metal support at the peeling point where the metal support has almost gone around, and then transported to the drying zone, and drying is completed while being transported by a roll group. In the present invention, a metal band or a metal drum can be used as the metal support.

  The details of the casting step and the drying step are also described in JP-A-2005-104148, pages 120 to 146, and can be applied to the present invention as appropriate.

  The amount of residual solvent in the film thus dried is preferably 0 to 2% by mass, more preferably 0 to 1% by mass. After the drying, the film may be transported to the heat treatment zone as it is, or may be heat treated offline after winding the film. The preferred width of the transparent polymer film before heat treatment is 0.5 to 5 m, more preferably 0.7 to 3 m. Moreover, when winding up a film once, preferable winding length is 300-30000m, More preferably, it is 500-10000m, More preferably, it is 1000-7000m.

[Stretching]
In the present invention, in order to achieve the desired elastic modulus, the film-formed transparent polymer film is stretched under high temperature conditions greatly exceeding Tg.

(temperature)
In the manufacturing method of this invention, it has the process of extending | stretching a transparent polymer film above (Tg + 50) degreeC. The heat treatment temperature is more preferably (Tg + 60) ° C. or more, further preferably (Tg + 65) to (Tg + 150) ° C., and particularly preferably (Tg + 70) ° C. to (Tg + 100) ° C. When the polymer that is the main component of the polymer film is cellulose acylate, this temperature is 200 ° C. or higher, preferably 210 to 270 ° C., more preferably 220 to 250 ° C. By setting the stretching temperature in this way, the mobility of the polymer chain can be improved, so that whitening (haze increase) of the film and cutting of the film accompanying an increase in the stretching ratio can be prevented. Moreover, the balance between the aggregation and orientation of polymer chains and the simultaneous thermal relaxation can be appropriately controlled by adjusting the stretching speed and the stretching ratio as described later. Therefore, by following the production method of the present invention, the aggregation and arrangement of polymer chains in the film can be advanced to a high degree, the elastic modulus that could not be achieved in the past is very large, the change in humidity dimension is small, It becomes possible to produce the transparent polymer film of the present invention having an appropriate moisture permeability.

(Stretching method)
Stretching may be carried out by gripping both ends of the film with a chuck and spreading it in a direction perpendicular to the transport direction (lateral stretching), but the preferred stretch direction is the transport direction, for example, the peripheral speed on the outlet side is increased. It is preferable to perform longitudinal stretching (zone stretching) in an apparatus having a heating zone between two or more nip rolls that have been accelerated. The draw ratio can be appropriately set according to the elastic modulus required for the film, preferably 10 to 500%, more preferably 30 to 200%, still more preferably 50 to 150%, and particularly preferably 70 to 100%. These stretching operations may be performed in one stage or in multiple stages. Here, “stretch ratio (%)” means that obtained using the following formula. The stretching speed is preferably 20% / min or more, more preferably 20 to 10000% / min, further preferably 50 to 5000% / min, even more preferably 100 to 1000% / min, particularly 150 to 800% / min. preferable.

  Stretch ratio (%) = 100 × {(Length after stretching) − (Length before stretching)} / Length before stretching

  The transparent polymer film of the present invention preferably has a single layer structure. Here, the “single layer structure” film does not mean that a plurality of film materials are bonded together, but means a single polymer film. And it includes the case where a single polymer film is produced from a plurality of polymer solutions using a sequential casting method or a co-casting method. In this case, a polymer film having a distribution in the thickness direction can be obtained by appropriately adjusting the type and blending amount of the additive, the molecular weight distribution of the polymer, the type of polymer and the like. Moreover, what has various functional parts, such as an optical anisotropy part, a glare-proof part, a gas barrier part, and a moisture-resistant part, in those one film is also included.

[surface treatment]
The transparent polymer film of the present invention can be improved in adhesion with each functional layer (for example, an undercoat layer, a back layer, and an optically anisotropic layer) by appropriately performing a surface treatment. The surface treatment includes glow discharge treatment, ultraviolet irradiation treatment, corona treatment, flame treatment, saponification treatment (acid saponification treatment, alkali saponification treatment), and glow discharge treatment and alkali saponification treatment are particularly preferable. The “glow discharge treatment” here is a treatment for subjecting the film surface to a plasma treatment in the presence of a plasma-excitable gas. The details of these surface treatment methods are described in the Japan Institute of Invention Disclosure Technical Bulletin (Public Technical No. 2001-1745, issued on March 15, 2001, Japan Institute of Invention) and can be used as appropriate.

In order to improve the adhesion between the film surface and the functional layer, an undercoat layer (adhesive layer) can be provided on the transparent polymer film of the present invention in addition to or in place of the surface treatment. About the said undercoat, it describes in an invention association public technical bulletin (public technical number 2001-1745, March 15, 2001 issue, invention association) 32 pages, These can be used suitably.
In addition, the functional layer provided on the transparent polymer film of the present invention is described in pages 32 to 45 of the Japan Society of Invention Disclosure Technical Bulletin (Public Technical Number 2001-1745, published on March 15, 2001, Japan Society of Invention). Yes, those described here can be used as appropriate.

<Optical compensation film>
The transparent polymer film of the present invention can be used as an optical compensation film. The “optical compensation film” is generally used for a display device such as a liquid crystal display device, and means an optical material having optical anisotropy, and is synonymous with a retardation film, a retardation plate, an optical compensation sheet, and the like. It is. In a liquid crystal display device, an optical compensation film is used for the purpose of improving the contrast of a display screen or improving viewing angle characteristics and color.

  The transparent polymer film of the present invention can be used as an optical compensation film as it is. In addition, a plurality of the transparent polymer films of the present invention can be laminated, or the transparent polymer film of the present invention and a film outside of the present invention can be laminated to appropriately adjust Re and Rth to be used as an optical compensation film. . Lamination of the film can be performed using a pressure-sensitive adhesive or an adhesive.

  In some cases, the transparent polymer film of the present invention may be used as a support for an optical compensation film, and an optically anisotropic layer made of liquid crystal or the like may be provided thereon to be used as an optical compensation film. The optically anisotropic layer applied to the optical compensation film of the present invention may be formed from, for example, a composition containing a liquid crystal compound or may be formed from a polymer film having birefringence.

  The liquid crystal compound is preferably a discotic liquid crystal compound or a rod-like liquid crystal compound.

[Discotic liquid crystalline compounds]
Examples of the discotic liquid crystalline compound that can be used as the liquid crystalline compound in the present invention include various documents (for example, C. Destrade et al., Mol. Crysr. Liq. Cryst., Vol. 71, page 111 ( 1981); Edited by Chemical Society of Japan, Quarterly Chemical Review, No. 22, Chemistry of Liquid Crystal, Chapter 5, Chapter 10 Section 2 (1994); B. Kohne et al., Angew. Chem. Soc. Chem. Comm. , page 1794 (1985); J. Zhang et al., J. Am. Chem. Soc., vol. 116, page 2655 (1994)).

  In the optically anisotropic layer, the discotic liquid crystalline molecules are preferably fixed in an aligned state, and most preferably fixed by a polymerization reaction. Further, the polymerization of discotic liquid crystalline molecules is described in JP-A-8-27284. In order to fix the discotic liquid crystalline molecules by polymerization, it is necessary to bond a polymerizable group as a substituent to the discotic core of the discotic liquid crystalline molecules. However, when the polymerizable group is directly connected to the disc-shaped core, it becomes difficult to maintain the orientation state in the polymerization reaction. Therefore, a linking group is introduced between the discotic core and the polymerizable group. Discotic liquid crystalline molecules having a polymerizable group are disclosed in JP-A No. 2001-4387.

[Bar-shaped liquid crystalline compound]
Examples of rod-like liquid crystalline compounds that can be used as the liquid crystalline compound in the present invention include azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexane. , Cyano-substituted phenylpyrimidines, alkoxy-substituted phenylpyrimidines, phenyldioxanes, tolanes and alkenylcyclohexylbenzonitriles. Further, as the rod-like liquid crystal compound, not only the above low molecular liquid crystal compound but also a polymer liquid crystal compound can be used.

  In the optically anisotropic layer, the rod-like liquid crystalline molecules are preferably fixed in an aligned state, and most preferably fixed by a polymerization reaction. Examples of polymerizable rod-like liquid crystalline compounds that can be used in the present invention include, for example, Makromol. Chem., 190, 2255 (1989), Advanced Materials, 5, 107 (1993), US Pat. Nos. 683,327, 5,622,648, 5,770,107, WO 95/22586, 95/24455, 97/00600, 98/23580 pamphlet, 98/52905 pamphlet, JP-A-1-272551, JP-A-6-16616, JP-A-7-110469, JP-A-11-80081, and JP-A-2001-328773. Compounds described in publications and the like are included.

(Optically anisotropic layer made of polymer film)
The optically anisotropic layer may be formed from a polymer film. The polymer film can be formed from a polymer that can exhibit optical anisotropy. Examples of the polymer capable of expressing the optical anisotropy include polyolefin (for example, polyethylene, polypropylene, norbornene-based polymer), polycarbonate, polyarylate, polysulfone, polyvinyl alcohol, polymethacrylic acid ester, polyacrylic acid ester, and Cellulose esters (for example, cellulose triacetate, cellulose diacetate) are included. Moreover, as the polymer, a copolymer or polymer mixture of these polymers may be used.

<Laminated film>
The transparent polymer film or optical compensation film of the present invention can be laminated by laminating with the transparent polymer film or optical compensation film of the present invention. Moreover, the transparent polymer film or optical compensation film of the present invention can be laminated by being laminated with a transparent polymer film or optical compensation film outside the present invention. Lamination of the film can be performed using a pressure-sensitive adhesive or an adhesive.
Lamination of the films can be performed online or offline, but it is preferable to perform the film online from the viewpoint of productivity. In this case, if the angle between the direction in which the elastic modulus of the transparent polymer film of the present invention is maximum and the direction in which the elastic modulus of the transparent polymer film outside of the present invention is maximum is small, the transparent polymer film outside of the present invention It is preferable because dimensional changes due to the environment can be suppressed, and the angle formed by the direction in which the elastic modulus of the transparent polymer film of the present invention is maximum and the direction in which the elastic modulus of the transparent polymer film outside the present invention is maximum is 15 ° or less. It is preferably 10 ° or less, more preferably 5 ° or less, and most preferably 2 ° or less.

  Examples of the polymer that is the main component of the transparent polymer film outside the present invention include cellulose esters, polyesters, polycarbonates, cycloolefin polymers, vinyl polymers, polyamides, polyimides, and amyloses. Polyethylene terephthalate and polyvinyl alcohol are more preferable, and polyvinyl alcohol obtained by hydrolyzing polyvinyl acetate is more preferable.

  The total light transmittance of the laminated film of the present invention is not particularly limited, but is preferably 50% or less, more preferably 30 to 50%, and further preferably 40 to 49%.

Moreover, it is preferable that a dichroic molecule is introduced into the transparent polymer film outside the present invention. As the dichroic molecule, higher-order iodine ions such as I ³⁻ and I ⁵⁻ or dichroic dyes can be preferably used. Furthermore, the film in which the dichroic molecule is introduced is preferably stretched, and more preferably a so-called polarizing film having a polarization separation function.

"Polarizer"
The transparent polymer film, optical compensation film, or laminated film of the present invention can be used as a protective film for a polarizing plate (the polarizing plate of the present invention). The polarizing plate of the present invention comprises a polarizing film and two polarizing plate protective films (transparent polymer films) that protect both surfaces thereof, and the transparent polymer film or retardation film of the present invention is used as at least one polarizing plate protective film. be able to. Moreover, the transparent polymer film, optical compensation film, or laminated film of the present invention can be bonded with a polarizing film by roll-to-roll using an adhesive.

  When the transparent polymer film of the present invention is used as the polarizing plate protective film, the transparent polymer film of the present invention is subjected to the surface treatment (also described in JP-A-6-94915 and JP-A-6-118232) to make it hydrophilic. For example, it is preferable to perform glow discharge treatment, corona discharge treatment, or alkali saponification treatment. In particular, when the polymer constituting the transparent polymer film of the present invention is cellulose acylate, alkali saponification treatment is most preferably used as the surface treatment.

  As the polarizing film, for example, a film obtained by immersing and stretching a polyvinyl alcohol film in an iodine solution can be used. When using a polarizing film obtained by immersing and stretching a polyvinyl alcohol film in an iodine solution, the surface-treated surface of the transparent polymer film of the present invention can be directly bonded to both surfaces of the polarizing film using an adhesive. In the present invention, it is preferable that the transparent polymer film is directly bonded to the polarizing film as described above. As the adhesive, an aqueous solution of polyvinyl alcohol or polyvinyl acetal (for example, polyvinyl butyral) or a latex of vinyl polymer (for example, polybutyl acrylate) can be used. A particularly preferred adhesive is an aqueous solution of fully saponified polyvinyl alcohol.

  In general, a liquid crystal display device includes four polarizing plate protective films because a liquid crystal cell is provided between two polarizing plates. The transparent polymer film of the present invention can be suitably used for any of the four polarizing plate protective films. When the transparent polymer film of the present invention is used as an outer protective film that is not disposed between the polarizing film and the liquid crystal layer (liquid crystal cell) in the liquid crystal display device, a transparent hard coat layer, an antiglare layer, and an antireflection layer are used. In particular, it is preferably used as a polarizing plate protective film on the outermost surface of the display side of the liquid crystal display device.

<Liquid crystal display device>
The transparent polymer film, optical compensation film, laminated film and polarizing plate of the present invention can be used for liquid crystal display devices in various display modes. Since the transparent polymer film, the optical compensation film and the laminated film of the present invention have a high elastic modulus and a small coefficient of humidity expansion, the film of the present invention exhibits a dimensional change due to heat and humidity of the polarizer. Suppress. Therefore, it is possible to suppress light leakage that occurs in the periphery of the screen due to changes in heat and humidity environment.

  Each liquid crystal mode in which these films are used will be described below. These liquid crystal display devices may be any of a transmissive type, a reflective type, and a transflective type.

(TN type liquid crystal display device)
The transparent polymer film of the present invention can be used as a support for an optical compensation film of a TN type liquid crystal display device having a TN mode liquid crystal cell. TN mode liquid crystal cells and TN type liquid crystal display devices have been well known for a long time. With respect to the optical compensation film used in the TN type liquid crystal display device, each of JP-A-3-9325, JP-A-6-148429, JP-A-8-50206 and JP-A-9-26572, and Mori. It is described in other papers (Jpn.J.Appl.Phys.Vol.36 (1997) p.143 and Jpn.J.Appl.Phys.Vol.36 (1997) p.1068).

(STN type liquid crystal display)
The transparent polymer film of the present invention may be used as a support for an optical compensation film of an STN type liquid crystal display device having an STN mode liquid crystal cell. In general, in a STN type liquid crystal display device, rod-like liquid crystalline molecules in a liquid crystal cell are twisted in the range of 90 to 360 degrees, and the refractive index anisotropy (Δn) and cell gap (d) of the rod-like liquid crystalline molecules. Product (Δnd) is in the range of 300 to 1500 nm. The optical compensation film used for the STN type liquid crystal display device is described in JP-A No. 2000-105316.

(VA type liquid crystal display device)
The transparent polymer film of the present invention can be used as an optical compensation film for a VA liquid crystal display device having a VA mode liquid crystal cell or as a support for the optical compensation film. The VA-type liquid crystal display device may be an alignment-divided system as described in, for example, JP-A-10-123576.

(IPS liquid crystal display device and ECB liquid crystal display device)
The transparent polymer film of the present invention is particularly advantageous as an optical compensation film for an IPS liquid crystal display device having an IPS mode and an ECB mode liquid crystal cell, an ECB liquid crystal display device, a support for the optical compensation film, or a protective film for a polarizing plate. Used for. In these modes, the liquid crystal material is aligned substantially in parallel during black display, and black is displayed by aligning liquid crystal molecules parallel to the substrate surface in the absence of voltage.

(OCB type liquid crystal display device and HAN type liquid crystal display device)
The transparent polymer film of the present invention is also advantageously used as a support for an optical compensation film of an OCB type liquid crystal display device having an OCB mode liquid crystal cell or a HAN type liquid crystal display device having a HAN mode liquid crystal cell. In the optical compensation film used for the OCB type liquid crystal display device or the HAN type liquid crystal display device, it is preferable that the direction in which the absolute value of retardation is minimum does not exist in the plane of the optical compensation film or in the normal direction. The optical properties of the optical compensation film used in the OCB type liquid crystal display device or HAN type liquid crystal display device are the same as the optical properties of the optical anisotropic layer, the optical properties of the support, and the optical anisotropic layer and the support. Is determined by the arrangement of An optical compensation film used for an OCB type liquid crystal display device or a HAN type liquid crystal display device is described in JP-A-9-197397. It is also described in Mori et al. (Jpn. J. Appl. Phys. Vol. 38 (1999) p. 2837).

(Reflective liquid crystal display)
The transparent polymer film of the present invention is also advantageously used as an optical compensation film for TN-type, STN-type, HAN-type, and GH (Guest-Host) -type reflective liquid crystal display devices. These display modes have been well known since ancient times. The TN-type reflective liquid crystal display device is described in JP-A-10-123478, WO98 / 48320 pamphlet, and Japanese Patent No. 3022477. The optical compensation film used in the reflective liquid crystal display device is described in International Publication No. 00/65384 pamphlet.

(Other liquid crystal display devices)
The transparent polymer film of the present invention is also advantageously used as a support for an optical compensation film of an ASM type liquid crystal display device having an ASM (Axially Symmetric Aligned Microcell) mode liquid crystal cell. The ASM mode liquid crystal cell is characterized in that the thickness of the cell is maintained by a resin spacer whose position can be adjusted. Other properties are the same as those of the TN mode liquid crystal cell. The ASM mode liquid crystal cell and the ASM type liquid crystal display device are described in Kume et al. (Kume et al., SID 98 Digest 1089 (1998)).

[Other uses]
(Hard coat film, antiglare film, antireflection film)
The transparent polymer film of the present invention may be applied to a hard coat film, an antiglare film and an antireflection film depending on circumstances. For the purpose of improving the visibility of flat panel displays such as LCD, PDP, CRT, EL, etc., any or all of a hard coat layer, an antiglare layer and an antireflection layer are provided on one or both sides of the transparent polymer film of the present invention. can do. Preferred embodiments of such an antiglare film and antireflection film are described in detail on pages 54 to 57 of the Japan Society for Invention and Innovation (Publication No. 2001-1745, published on March 15, 2001, Japan Society of Invention and Innovation). It can be preferably used also in the transparent polymer film of the present invention.

  The features of the present invention will be described more specifically with reference to examples and comparative examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Accordingly, the scope of the present invention should not be construed as being limited by the specific examples shown below.

<Measurement method>
First, measurement methods and evaluation methods of characteristics used in the following examples and comparative examples are shown below.

[Elastic modulus]
Three points in the width direction (center, edge (each 5% of the total width from both ends) were sampled every 100 m in the longitudinal direction, and the average value of each point evaluated according to the above-mentioned method was determined to be the elastic modulus of the film. Unless otherwise specified, sampling was performed so that the transport direction was the longitudinal direction.

[Modification of elastic modulus]
The change in elastic modulus of the film before and after the stretching treatment determined according to the above method was calculated.

[Humidity expansion coefficient]
Three points in the width direction (center, end (5% of the total width from both ends) were sampled every 100 m in the longitudinal direction, and the average value of each point evaluated according to the above-mentioned method was obtained to determine the humidity expansion coefficient of the film. did.

[Total light transmittance]
5 points in the width direction (center, end (5% of the total width from both ends) and 2 points in the middle and end) were sampled every 100 m in the longitudinal direction and evaluated according to the method described above. The average value of each point was calculated | required and it was set as the total light transmittance of the film.

[Haze]
5 points in the width direction (center, end (5% of the total width from both ends) and 2 points in the middle and end) were sampled every 100 m in the longitudinal direction and evaluated according to the method described above. The average value of each point was calculated | required and it was set as the haze of the film.

[Moisture permeability]
The value evaluated according to the above-mentioned method was taken as the moisture permeability in terms of film thickness of 80 μm.

[Tg]
The value evaluated according to the above-mentioned method was defined as Tg of the film.

[Surface shape]
The film surface state was evaluated by observing the surface of the obtained transparent polymer film visually and according to the following evaluation scale.
○: The film has a good surface shape and can be preferably applied as an optical film.
there were.
×: The film is completely clouded and cannot be applied as an optical film.
It was.

[Retardation]
5 points in the width direction (center, end (5% of the total width from both ends) and 2 middle points between the center and the end) are sampled every 100 m in the longitudinal direction, and the size is 2 cm □ A sample was taken out, and the average value of each point evaluated according to the following method was obtained and set as Re and Rth. That is, first, the film was conditioned at 25 ° C. and a relative humidity of 60% for 24 hours, and then a prism coupler (MODEL2010 Prism Coupler: manufactured by Metricon) was used. The average refractive index (n) represented by the following formula (a) was determined using a laser.
Formula (a): n = (n _TE × 2 + n _TM ) / 3
[ _Where n _TE is the refractive index measured with polarized light in the film plane direction, and n _TM is the refractive index measured with polarized light in the film surface normal direction. ]
Subsequently, using a birefringence measuring apparatus (ABR-10A: manufactured by UNIOPT Co., Ltd.), the humidity-controlled film was perpendicular to the sample film surface and in the film plane at 25 ° C. and a relative humidity of 60%. The retardation value was measured using a He-Ne laser of 632.8 nm from the direction tilted ± 40 ° from the normal to the film surface with the slow axis as the tilt axis (rotation axis), and the average refractive index determined above. Nx, ny, and nz, respectively, and the in-plane retardation value (Re) and the thickness direction retardation value (Rth) represented by the following formulas (b) and (c), respectively. Was calculated.
Formula (b): Re = (nx−ny) × d
Formula (c): Rth = {(nx + ny) / 2−nz} × d
[Wherein nx is the refractive index in the slow axis (x) direction in the film plane, ny is the refractive index in the direction perpendicular to the x direction in the film plane, and nz is the film thickness direction of the film (film (Surface normal direction) and d is the film thickness (nm). The slow axis is the direction in which the refractive index is maximum in the film plane. ]

[Degree of polarization]
The transmittance (Tp) when the produced two polarizing plates are superposed in parallel with the absorption axis and the transmittance (Tc) when the absorption axes are superposed with each other perpendicular to each other are measured and expressed by the following formula: The degree of polarization (P) was calculated.
Polarization degree P = ((Tp−Tc) / (Tp + Tc)) ^0.5

[Examples 101 to 114, Comparative examples 101 to 106]
(Film production)
The following films were used in each example and comparative example (see Table 1).

Film A: Film according to Example 1 of JP-A-2005-104148
To make a film A.
Film B: Commercially available Fuji Tac (T80UZ; manufactured by Fuji Photo Film Co., Ltd.)
Used as is.
Film C: Fill according to Example 12 of JP-A-2005-104148
A film C was prepared.
Film D: Commercially available Fuji Tac (TD80UL; manufactured by Fuji Photo Film Co., Ltd.)
Used as is.
Film E: Commercially available polyvinyl alcohol film (film thickness 75 μm, Kuraray Co., Ltd.)
Product: Moisture permeability at 40 ° C. and relative humidity 90% = 3300 g / (m ^2.
day) (film thickness 80 μm equivalent)) was used as it was (Comparative Example 105).
Film F: Commercially available ZEONOR film (film thickness 100 μm, manufactured by ZEON CORPORATION; 40 ° C.,
Moisture permeability at 90% relative humidity = 0 g / (m ² · day) (film thickness 80
μm conversion)) was used as is (Comparative Example 106).

(Stretching)
The following stretching steps were used in each example and comparative example (see Table 1).
Drawing A:
About transparent film AD, the vertical uniaxial stretching process was implemented on the conditions described in Table 1 using the roll extending machine. The roll stretching machine was composed of two nip rolls, and an induction heating jacket roll having a mirror-finished surface was used for each roll. In addition, the temperature of each roll can be adjusted individually. The stretching zone was covered with a casing, and the temperatures shown in Table 1 were set. The roll before the stretching part was set so that it could be gradually heated to the stretching temperature described in Table 1. The distance between the stretching was adjusted so that the aspect ratio was 3.3, and stretching was performed at the stretching speed shown in Table 1. After stretching, the film was cooled and wound up. The draw ratio is shown in Table 1.
Stretch B:
About the obtained transparent film, it extended | stretched using the apparatus which has a heating zone adjusted to the temperature of Table 1 between two nip rolls. The draw ratio was controlled by adjusting the peripheral speed of the nip roll, and the aspect ratio (distance between nip rolls / base width) was adjusted to 3.3. After stretching, the film was cooled and wound up. The draw ratio is shown in Table 1.

(Evaluation of transparent polymer film)
Each transparent polymer film obtained was evaluated. The results are shown in Table 1 below.
In addition, the water vapor transmission rate in terms of the film thickness of 80 μm of the films of Examples 101 to 114 and Comparative Examples 101 to 104 were all in the range of 300 to 1000 g / (m ² · day). In all the examples, the angle formed by the direction in which the elastic modulus of the film is maximum and the film transport direction was 3 ° or less.

  As shown in Table 1, a film having a high elastic modulus and a small humidity dimensional change can be produced by the method of the present invention.

[Examples 201 to 214, Comparative Examples 202 to 205]

(Preparation of polarizing plate)
The obtained films were saponified according to the following to produce polarizing plates. The polarizing plates produced using the films of Examples 101 to 114 were designated as Examples 201 to 214, respectively, and the films of Comparative Examples 102 to 104 were used. The polarizing plates prepared in this manner were designated as Comparative Examples 202 to 204, and the polarizing plate produced using the film E was designated as Comparative Example 205. In addition, the total light transmittance of these polarizing plates was 40 to 45%.

1) Saponification of film The film was immersed in a 1.5 mol / L NaOH aqueous solution (saponification solution) adjusted to 55 ° C. for 2 minutes, then washed with water, and then in a 0.05 mol / L sulfuric acid aqueous solution for 30 seconds. After soaking, it was further passed through a washing bath. Then, draining with an air knife was repeated three times, and after dropping the water, the film was retained in a drying zone at 70 ° C. for 15 seconds and dried to produce a saponified film.

2) Production of Polarizing Film According to Example 1 of Japanese Patent Application Laid-Open No. 2001-141926, a circumferential speed difference was given between two pairs of nip rolls and stretched in the longitudinal direction to prepare a polarizing film having a thickness of 20 μm.

3) Bonding The obtained polarizing film was bonded to PVA (manufactured by Kuraray Co., Ltd., PVA-117H) 3% aqueous solution so that the longitudinal direction of the film and the longitudinal direction of the polarizing film were parallel to each other. The films were laminated on-line by being sandwiched between the saponified films. When film F was used, a polarizing plate could not be produced due to poor adhesion with the polarizing film.

[Comparative Example 207]
Using the film of Example 101, a polarizing plate was prepared in the same manner as in Comparative Example 201 except that “3) Bonding” in the above (Preparation of polarizing plate) was changed as described below. .

3) Bonding On both sides of the obtained polarizing film, the saponified film of Example 101 that had been cut out using a 3% aqueous solution of PVA (manufactured by Kuraray Co., Ltd., PVA-117H) as an adhesive, Bonding was performed so that the direction in which the elastic modulus was maximum and the longitudinal direction of the polarizing film were orthogonal to each other.

(Evaluation of polarizing plate)
[Initial polarization degree]
When the polarization degree of the said polarizing plate was computed by the above-mentioned method, all the polarizing plates of Examples 201-214, Comparative Examples 202-205, and Comparative Example 207 had a polarization degree of 99.9% or more. However, when the film of Comparative Example 106 was used, a polarizing plate could not be produced due to poor adhesion with the polarizing film.

[Time polarization 1]
The polarizing plate was bonded to a glass plate with an adhesive, and allowed to stand for 500 hours at 60 ° C. and 95% relative humidity. The degree of polarization (degree of polarization with time) after the standing was calculated by the method described above. All of the polarizing plates of -214 and Comparative Examples 202-204 and Comparative Example 207 had a polarization degree of 99.9% or more. However, in the polarizing plate of Comparative Example 205, the degree of polarization decreased to less than 10%.

[Time polarization 2]
The polarizing plate was bonded to a glass plate with an adhesive, and allowed to stand for 500 hours under the conditions of 90 ° C. and relative humidity 0%, and the degree of polarization (degree of polarization with time) after standing was calculated by the method described above. All of the polarizing plates of -214 and Comparative Examples 202-204 and Comparative Example 207 had a polarization degree of 99.9% or more. In the polarizing plate of Comparative Example 205, the degree of polarization was reduced to less than 90%, and the polarizing plate was not applicable to display device applications.

(Evaluation of mounting on TN type liquid crystal display)
The polarizing plate is incorporated in place of the polarizing plate incorporated in the TN type liquid crystal display device (AQUAS LC20C1S, manufactured by Sharp Corporation), held at 60 ° C. and 0% relative humidity for 1 day, and visually observed after 1 hour. When the polarizing plates of Examples 201 to 213 were incorporated, no frame-like light leakage was observed on the four sides of the screen as compared with the other parts of the screen. When the polarizing plates of Examples 202 to 203 were incorporated, frame-like light leakage was observed on the four sides of the screen as compared with other parts of the screen, and when the polarizing plate of Comparative Example 204 was incorporated, Some frame-like light leakage was observed. When the polarizing plate of Example 214 was incorporated, a slight frame-like light leakage was observed in the dark room, and there was no practical problem. When the polarizing plate of Comparative Example 207 was incorporated, the frame The shape of light leakage was observed severely. Further, when the polarizing plate of Comparative Example 202 was incorporated using the adhesive described in Example 1 of JP-A 2000-109771, the light leakage in the frame shape was reduced, but the light leakage was visually observed. Was confirmed. On the other hand, when the polarizing plate of the present invention was incorporated using the pressure-sensitive adhesive described in Example 1 of JP-A-2000-109771, no frame-like light leakage was observed.

(Evaluation of mounting on VA liquid crystal display)
The polarizing plate was incorporated into a VA liquid crystal display device (32V type high-definition liquid crystal television monitor (W32-L7000), manufactured by Hitachi, Ltd.) and held at 60 ° C. and a relative humidity of 95% for 1 week, then at 25 ° C. When the polarizing plate of Examples 201 to 213 was incorporated, the light leakage was observed at the four corners of the screen as compared with the other portions of the screen when the relative humidity was maintained at 60% and visually observed after one day. In contrast, when the polarizing plates of Comparative Examples 202 to 203 were incorporated, light leakage was observed at the four corners of the screen as compared with other parts of the screen, and the polarizing plate of Comparative Example 204 was When incorporated, light leakage at some four corners was observed. When the polarizing plate of Example 214 was incorporated, light leakage at only four corners was observed in a dark room, but there was no problem in practical use. When the polarizing plate of Comparative Example 207 was incorporated, it was severe 4 Corner light leakage was observed.

  According to the present invention, it is possible to provide a transparent polymer film having a high elastic modulus, a small change in humidity and a suitable moisture permeability, and an excellent optical compensation film and laminated film. Moreover, since the transparent polymer film of this invention has moderate moisture permeability, it can be bonded together with a polarizing film on-line, and can provide an excellent polarizing plate with high productivity. Furthermore, it is possible to suppress light leakage generated in the peripheral portion of the screen due to changes in heat and humidity environment, and to provide a highly reliable liquid crystal display device. Therefore, the present invention has high industrial applicability.

Claims (21)

It includes a step of stretching a transparent polymer film having a moisture permeability at 40 ° C. and a relative humidity of 90% of 100 g / (m ² · day) or more in terms of a film thickness of 80 μm at a temperature of (Tg + 50) ° C. or more and 10% or more. A method for producing a transparent polymer film.   The method for producing a transparent polymer film according to claim 1, wherein the stretching is performed at (Tg + 60) ° C. or more.   The method for producing a transparent polymer film according to claim 1, wherein the stretching is performed at 200 ° C. or more.   The method for producing a transparent polymer film according to any one of claims 1 to 3, wherein the stretching causes an elastic modulus of the transparent polymer film to be 1.1 to 100 times.   The method for producing a transparent polymer film according to any one of claims 1 to 4, wherein the stretching is performed at a stretching rate of 20% / min or more.   The method for producing a transparent polymer film according to any one of claims 1 to 5, wherein the stretching is longitudinal stretching performed in an apparatus having a heating zone between at least two nip rolls having different peripheral speeds. .   The transparent polymer film manufactured by the manufacturing method as described in any one of Claims 1-6. A transparent polymer film having an elastic modulus of 5 GPa or more and a moisture permeability of 100 to 2000 g / (m ² · day) in terms of a film thickness of 80 μm at 40 ° C. and a relative humidity of 90%. 9. The transparent polymer film according to claim 7, wherein the humidity expansion coefficient is 6 × 10 ⁻⁵ /% RH or less.   The transparent polymer film according to any one of claims 7 to 9, wherein the total light transmittance is 90% or more.   Haze is 2% or less, The transparent polymer film as described in any one of Claims 7-10 characterized by the above-mentioned.   The transparent polymer film according to any one of claims 7 to 11, comprising a cellulose ester as a polymer as a main component.   The transparent polymer film according to claim 12, wherein the cellulose ester is cellulose acetate.   An optical compensation film comprising at least one transparent polymer film according to any one of claims 7 to 13.   A laminated film having at least one transparent polymer film according to any one of claims 7 to 13.   A laminated film in which at least one of the transparent polymer films according to any one of claims 7 to 13 and another polymer film are bonded.   The lamination according to claim 16, wherein an angle formed by a direction in which the elastic modulus of the transparent polymer film is maximized and a direction in which the elastic modulus of the other transparent polymer film is maximized is 15 ° or less. the film.   The laminated film according to claim 16 or 17, wherein the polymer which is a main component of the other transparent polymer film is polyvinyl alcohol.   The laminated film according to any one of claims 16 to 18, wherein the other transparent polymer film is a polarizing film.   Total light transmittance is 50% or less, The laminated | multilayer film as described in any one of Claims 15-19 characterized by the above-mentioned.   It is selected from the group consisting of the transparent polymer film according to any one of claims 7 to 13, the optical compensation film according to claim 14, and the laminated film according to any one of claims 15 to 19. A liquid crystal display device comprising at least one film.