JP2007023157A - Transparent film, method for producing the same, and polarizing plate and liquid crystal display device using the transparent film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transparent film having excellent transparency, elastic modulus, moisture permeability and dimensional stability, to provide a method for producing the film, to provide a polarizing plate using the film, and to provide a liquid crystal display device using the film, suppressed in light leakage and excellent in durability. <P>SOLUTION: The transparent film comprises an amino resin and cellulose acylate, which amino resin is selected from a group consisting of urea resins, benzoguanamine resin, glycoluril resin and their mixtures. The method for producing transparent films comprises a step for casting a cellulose acylate solution comprising cellulose acylate and an amino resin precursor (casting step) and a heating step for heating the film cast in the casting step. The polarizing plate uses the transparent film as the protective film for a polarizer. The liquid crystal display device uses at least one of the transparent film or the polarizing plate using the film. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a transparent film and a method for producing the same, and a polarizing plate and a liquid crystal display device using the same.

  Cellulose acylate film is transparent, has excellent physical and mechanical properties, has little dimensional change with respect to temperature and humidity change, and has been conventionally used as a support for silver halide light-sensitive material film, drafting tracing film, electrical insulating material In recent years, it has been used as a protective film for polarizing plates in liquid crystal image display devices.

  In recent years, liquid crystal image display devices have become more precise and larger in size, and have excellent light transmission, optical non-orientation, good adhesion to polarizing elements, and excellent flatness as protective films for polarizing plates. In addition, properties such as ultraviolet absorptivity and antistatic properties, and durability against changes in temperature and humidity are required.

  In addition, an optically anisotropic optical compensation film used in a liquid crystal display device is used to improve the viewing angle characteristic peculiar to a liquid crystal display device that the display performance deteriorates when the liquid crystal display device is viewed from an oblique direction. Increasing importance.

  Various types of optical compensation films have been devised and marketed depending on the operation mode of the liquid crystal display device. For example, the cellulose acylate film itself is provided with optical anisotropy; the cellulose acylate film is used as a support. And a liquid crystal compound or an optically anisotropic polymer compound laminated thereon; and the like are known. Also in this field, the durability of the cellulose acylate film against changes in temperature and humidity is required.

An optical film comprising a cellulose ester film that is three-dimensionally cross-linked by a cross-linking agent as a method for modifying the cellulose acylate film to solve the above problems (Patent Document 1); residual cellulose ester The hydroxyl group forms a crosslinked structure through a covalent bond, has at least one aromatic ring in the crosslinked portion, has an in-plane retardation value Ro of 20 to 300 nm, and is stretched. A cellulose ester film (Patent Document 2); a cellulose ester film (Patent Document 3) characterized in that it is formed in the presence of a thermally crosslinkable organic compound.
JP 2004-109307 A JP 2004-244497 A JP 2004-292558 A

  In these patent documents, divinyl compounds, aldehyde compounds, isocyanate compounds, epoxy compounds, ethyleneimine, and the like are described as crosslinking agents, but the elastic modulus, moisture permeability, and dimensional stability are improved, but still insufficient. It was.

Accordingly, an object of the present invention is to provide a transparent film having excellent elastic modulus, moisture permeability, and dimensional stability.
Another object of the present invention is to provide a polarizing plate and a liquid crystal display device obtained by using the same.
Furthermore, it is providing the liquid crystal display device excellent in durability in which light leakage was suppressed.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that a cellulose acylate film has a resin selected from the group consisting of a urea resin, a benzoguanamine resin, a glycoluril resin, and a mixture thereof (hereinafter also referred to as an amino resin). In addition, the cellulose acylate film in which a crosslinked structure is formed by an amino resin precursor that is a material for forming the amino resin has excellent elasticity, moisture permeability, and dimensional stability. I found.

  In the present invention, the cellulose acylate solution (dope) is crosslinked by co-existing an amino resin precursor and a curing catalyst if necessary, by a solution casting method, and by crosslinking by heat. An amino resin (self-condensate) and / or a crosslinked product of an amino resin and cellulose acylate is formed and contained in a cellulose acylate film. As a result, an optically transparent film having excellent film strength and temperature and humidity characteristics without phase separation is produced.

That is, it has been found that the above problem is solved by the following configuration.
(1) A transparent film comprising an amino resin selected from the group consisting of a urea resin, a benzoguanamine resin, a glycoluril resin, and a mixture thereof and cellulose acylate.

(2) The transparent film as described in (1) above, wherein the amino resin contains a structure formed by crosslinking an amino resin precursor.
(3) The transparent film as described in (1) or (2) above, which contains a structure in which an amino resin and a residual hydroxyl group of cellulose acylate are crosslinked.

(4) The transparent film as described in (2) or (3) above, which contains a structure in which an amino resin precursor and a residual hydroxyl group of cellulose acylate are crosslinked.
(5) A transparent film having a step of casting a cellulose acylate solution containing a cellulose acylate and an amino resin precursor (casting step) and a heating step of heating the film formed by the casting step Production method.

(6) A polarizing plate comprising the transparent film according to any one of (1) to (4) above or the transparent film produced by the production method of (5) above as a protective film for a polarizer. .

(7) Use at least one of the transparent film according to any one of (1) to (4) above, the transparent film produced by the production method according to (5) above, or the polarizing plate according to (6) above. A liquid crystal display device characterized by that.

The transparent film containing the amino resin and cellulose acylate of the present invention is optically transparent, excellent in film strength (elastic modulus), and has good temperature and humidity characteristics such as moisture permeability and dimensional change. The liquid crystal display device comprising the polarizing plate produced by using it is also excellent in durability because light leakage is suppressed.
The transparent film of the present invention includes various functional films such as a protective film for polarizing plates used for liquid crystal display devices, retardation films, field-of-view films, antireflection films used for liquid crystal display devices and plasma displays, and halogenated films. The film can be suitably used for optical applications such as a support film used for a silver photographic light-sensitive material and various functional films that can be used for an organic EL display.

  Hereinafter, the transparent film of the present invention and the production method thereof will be described in more detail.

<Transparent film>
The transparent film of the present invention is formed by a step of casting a cellulose acylate, an amino resin precursor, and, if necessary, a cellulose acylate solution containing a curing catalyst (casting step), and the casting step. And a step of cross-linking the film with heat.

[Cellulose acylate]
Cellulose acylate raw material cellulose includes cotton linter, kenaf, wood pulp (hardwood pulp, softwood pulp), etc., and any cellulose ester obtained from any raw material cellulose can be used, and may be used in some cases. Good.

  In the present invention, cellulose acylate is produced by esterifying cellulose. However, particularly preferable cellulose is not usable as it is, and cotton linter, kenaf, pulp and the like are purified and used.

  In the present invention, cellulose acylate is a carboxylic acid ester having 2 to 22 carbon atoms in total.

[Acyl group]
The acyl group having 2 to 22 carbon atoms of the cellulose acylate used in the present invention may be an aliphatic acyl group or an aromatic acyl group, and is not particularly limited. They are, for example, alkyl carbonyl esters, alkenyl carbonyl esters, cycloalkyl carbonyl esters, aromatic carbonyl esters, aromatic alkyl carbonyl esters, and the like of cellulose, each of which may further have a substituted group.

  Examples of these preferred acyl groups include acetyl, propionyl, butanoyl, heptanoyl, hexanoyl, octanoyl, cyclohexanecarbonyl, adamantanecarbonyl, phenylacetyl, benzoyl, naphthylcarbonyl, (meth) acryloyl, and cinnamoyl groups. Among these, more preferred acyl groups are acetyl, propionyl, butanoyl, pentanoyl, hexanoyl, cyclohexanecarbonyl, phenylacetyl, benzoyl, naphthylcarbonyl, and the like, and particularly preferred acyl groups are acetyl, propionyl, and butanoyl.

  A method for synthesizing cellulose acylate is disclosed in JIII Journal of Technical Disclosure No. 2001-1745 (Invention Association, March 15, 2001) p. 9 is described in detail.

As the cellulose acylate suitably used in the present invention, those in which the degree of substitution of cellulose with a hydroxyl group satisfies the following mathematical formulas (1) and (2) are preferable.
Formula (1): 2.3 ≦ SA ′ + SB ′ ≦ 3.0
Formula (2): 0 ≦ SA ′ ≦ 3.0

  Here, SA ′ is the substitution degree of the acetyl group substituting the hydrogen atom of the hydroxyl group of cellulose, and SB ′ is the substitution degree of the acyl group having 3 to 22 carbon atoms substituting the hydrogen atom of the hydroxyl group of cellulose. Represents. SA represents an acetyl group substituting a hydrogen atom of a hydroxyl group of cellulose, and SB represents an acyl group having 3 to 22 carbon atoms substituting a hydrogen atom of a hydroxyl group of cellulose.

  Glucose units having β-1,4 bonds constituting cellulose have free hydroxyl groups at the 2nd, 3rd and 6th positions. Cellulose acylate is a polymer obtained by esterifying some or all of these hydroxyl groups with acyl groups. The degree of acyl substitution means the proportion of cellulose esterified at each of the 2-position, 3-position and 6-position (100% esterification at each position is substitution degree 1).

  In the present invention, the total sum of substitution degrees of SA and SB (SA ′ + SB ′) is more preferably 2.6 to 3.0, and particularly preferably 2.80 to 3.00. Further, the degree of substitution (SA ′) of SA is more preferably 1.4 to 3.0, and particularly 2.3 to 2.9.

Furthermore, it is preferable that the following mathematical formula (3) is satisfied at the same time.
Formula (3): 0 ≦ SB ”≦ 1.2
Here, SB ″ represents a C 3 or C 4 acyl group substituting a hydrogen atom of a hydroxyl group of cellulose.

  Further, 28% or more of SB "is preferably a 6-position hydroxyl group substituent, more preferably 30% or more is a 6-position hydroxyl group substituent, more preferably 31% or more, and particularly 32% or more. It is also preferable that it is a 6-position hydroxyl group substituent.

  Furthermore, the cellulose acylate having a total substitution degree of SA ′ and SB ″ at the 6-position of the cellulose acylate of 0.8 or more, more preferably 0.85 or more, and particularly preferably 0.90 or more. These cellulose acylates can produce a solution having a preferable solubility, and in particular, a non-chlorine organic solvent can be used to produce a good solution.

The degree of substitution can be obtained by calculating the degree of binding of fatty acids bound to hydroxyl groups in cellulose. As a measuring method, it can measure based on ASTM D-817-91 and ASTM D-817-96. The substitution state of the acyl group with the hydroxyl group is ¹³ C.
Measured by NMR method.

The cellulose acylate film as the transparent film (hereinafter, also simply referred to as a cellulose acylate film) is that the cellulose acylate as a polymer component constituting the film substantially satisfies the above formulas (1) and (2). It is preferable to consist of cellulose acylate.
Here, “substantially” means 55% by mass or more (preferably 70% by mass or more, more preferably 80% by mass or more) of the total cellulose acylate component. The cellulose acylate may be used alone or in combination of two or more.

  The degree of polymerization of the cellulose acylate preferably used in the present invention is a viscosity average degree of polymerization of 200 to 700, preferably 230 to 550, more preferably 230 to 350, and particularly preferably a viscosity average degree of polymerization of 240 to 320. The average degree of polymerization can be measured by the intrinsic viscosity method of Uda et al. (Kazuo Uda, Hideo Saito, “Journal of Textile Society”, Vol. 18, No. 1, pages 105-120, 1962). Further details are described in JP-A-9-95538.

The number average molecular weight Mn of the cellulose acylate is preferably in the range of 7 to 25 × 10 ⁴ , more preferably in the range of 8 to 15 × 10 ⁴ . The ratio (Mw / Mn) of the cellulose acylate to the mass average molecular weight Mw is preferably 1.0 to 5.0, more preferably 1.0 to 3.0. The average molecular weight and molecular weight distribution of the cellulose ester can be measured using high performance liquid chromatography, and the above Mn and M can be measured using this.
w can be calculated and Mw / Mn can be calculated.

[Amino resin]
The transparent film of the present invention is characterized by containing a resin (amino resin) selected from the group consisting of a urea resin, a benzoguanamine resin, a glycoluril resin, and a mixture thereof. The transparent film of the present invention preferably contains a crosslinked structure of the amino resin, and further a crosslinked structure with residual hydroxyl groups of cellulose acylate. The amino resin is preferably formed by condensation of an amino resin precursor. Moreover, it is also a preferable aspect to contain the structure where the amino resin precursor and the residual hydroxyl group of cellulose acylate were crosslinked.

In this specification, the amino resin precursor refers to a compound that can be used to form the amino resin (a resin selected from the group consisting of urea resin, benzoguanamine resin, glycoluril resin, and a mixture thereof). An amino resin is formed by the condensation of the compound.
As an amino resin precursor used for this invention, the following general formula (1), (2), (3), (4) and its polynuclear body are preferable. The average degree of polymerization of the polynuclear body is more than 1 and 5 or less.
General formula (1):

R ¹¹ and R ¹² represent a hydrogen atom or CH ₂ OR ¹⁰ (R ¹⁰ represents a hydrogen atom or an alkyl group having 1 to 12 carbon atoms), and R ¹¹ and R ¹² may be the same or different. Also good. R ¹⁰ of the CH ₂ OR ¹⁰ group may be the same or different in the general formula (1).

When R ¹⁰ is an alkyl group, the number of carbon atoms is 1 to 12, preferably 1 to 8 carbon atoms, and more preferably 1 to 6 carbon atoms. If the number of carbon atoms is within the upper limit, there is no problem that compatibility with cellulose acylate is reduced, which is preferable.

Specific examples of R ¹¹ and R ¹² are shown below.
H, CH ₂ OCH ₃ , CH ₂ OC ₂ H ₅ , CH ₂ OC ₃ H ₇ (n), CH ₂ OC ₃ H ₇ (i), CH ₂ OC ₄ H ₉ (n), CH ₂ OC ₄ H ₉ (i), CH ₂ OH and the like.

  General formula (2):

R ^{21 to} R ²⁴ represent a hydrogen atom or CH ₂ OR ²⁰ (R ²⁰ represents a hydrogen atom or an alkyl group having 1 to 12 carbon atoms), and R ^{21 to} R ²⁴ may be the same or different. Also good. R ²⁰ of the CH ₂ OR ²⁰ group may be the same or different in the general formula (2).

When R ²⁰ is an alkyl group, the carbon number is 1 to 12, preferably 1 to 8, and more preferably 1 to 6. If the number of carbon atoms is within the upper limit, there is no problem that compatibility with cellulose acylate is reduced, which is preferable.

Specific examples of R ^{21 to} R ²⁴ are shown below.
H, CH ₂ OCH 3, CH ₂ OC ₂ H ₅ , CH ₂ OC ₃ H ₇ (n), CH ₂ OC ₃ H ₇ (i), CH ₂ OC ₄ H ₉ (n), CH ₂ OC ₄ H ₉ ( i), CH ₂ OH and the like.

  General formula (3):

R ^{31 to} R ³⁴ represent a hydrogen atom or CH ₂ OR ³⁰ (R ³⁰ represents a hydrogen atom or an alkyl group having 1 to 12 carbon atoms), and R ^{31 to} R ³⁴ may be the same or different. Also good. R ³⁰ of the CH ₂ OR ³⁰ group may be the same or different in the general formula (3).

If R ³⁰ is an alkyl group has a carbon number of 1 to 12, preferably 1 to 8 carbon atoms, 1 to 6 carbon atoms is more preferred. If the number of carbon atoms is within the upper limit, there is no problem that compatibility with cellulose acylate is reduced, which is preferable.

Specific examples of R ^{31 to} R ³⁴ are shown below.
H, CH ₂ OCH 3, CH ₂ OC ₂ H ₅ , CH ₂ OC ₃ H ₇ (n), CH ₂ OC ₃ H ₇ (i), CH ₂ OC ₄ H ₉ (n), CH ₂ OC ₄ H ₉ ( i), CH ₂ OH and the like.

  General formula (4):

R ⁴¹ and R ⁴² represent a hydrogen atom or CH ₂ OR ⁴⁰ (R ⁴⁰ represents a hydrogen atom or an alkyl group having 1 to 12 carbon atoms), and R ⁴¹ and R ⁴² may be the same or different. Also good. R ⁴⁰ of the CH ₂ OR ⁴⁰ group may be the same or different in the general formula (4).
R ⁴³ represents a hydrogen atom or an alkyl group having 1 to 12 carbon atoms.

When R ⁴⁰ is an alkyl group, the number of carbon atoms is 1 to 12, preferably 1 to 8 carbon atoms, and more preferably 1 to 6 carbon atoms. If the number of carbon atoms is within the upper limit, there is no problem that compatibility with cellulose acylate is reduced, which is preferable.

Specific examples of R ⁴¹ and R ⁴² are shown below.
H, CH ₂ OCH 3, CH ₂ OC ₂ H ₅ , CH ₂ OC ₃ H ₇ (n), CH ₂ OC ₃ H ₇ (i), CH ₂ OC ₄ H ₉ (n), CH ₂ OC ₄ H ₉ ( i), CH ₂ OH and the like.

[Preferred example of amino resin precursor]
Examples of preferred amino resin precursors in the present invention are shown below. These polynuclear bodies are also included in preferred compounds. The amino resin precursor used in the present invention is not limited to the following compound examples.

  Among these compounds, the amino resin precursor is at least one of (A-1), (B-1), (C-1) and (D-1) from the viewpoint of easy crosslinking and film strength. Most preferably, is used. A plurality of these may be used.

The amino resin precursor used for this invention is contained in the amino resin formation material marketed by each company. For example, “Nikarak MX-270”, “Nikarak MX-280”, “Nikarak MX-290”, “Nikarak BL-60”, “Nikarak BX-37”, “Nikarak BX-4000” {above, San Co., Ltd. Can be exemplified.

  The addition amount of the amino resin precursor is 3 to 60% by mass, preferably 5 to 50% by mass, and more preferably 7 to 40% by mass with respect to the cellulose acylate. If it is 3% by mass or more, a good addition effect of the melamine resin is exhibited, and if it is 60% by mass or less, there is no problem such that the film becomes brittle and the reworkability is lowered. It is preferable to use it.

The industrial production of amino resin forming materials can be broadly divided into the following two:
(1) Production method of low solid content type amino resin forming material,
(2) A method for producing a high solid content type amino resin forming material.
The low solid content type amino resin forming material is manufactured by a one-stage method, while the high solid content type amino resin forming material is manufactured by a multi-stage method. Due to the difference in the production method, the alkyl etherification substitution degree, average polymerization degree, and free formaldehyde content of the amino resin forming monomer / polynuclear substance contained in the amino resin forming material are different.

Next, the reaction mechanism of the one-step method or the multi-step method will be described below by taking melamine as an example, but an amino resin-forming material containing an amino resin precursor that is suitably used in the present invention can be produced in the same manner.
(1) One-step method:

In the above formulas, R represents an alkyl group having 1 to 4 carbon atoms, X is a hydrogen atom, CH ₂ OH, CH ₂ - represents the melamine (syncytial).

  In the one-stage method, melamine, formaldehyde, and alcohol are subjected to methylolation reaction under acidic conditions, and excess alcohol, formaldehyde, water contained in raw material formaldehyde, and water generated by alkoxylation reaction are distilled off under the same conditions. In this method, an amino resin is obtained by an alkoxylation reaction. Under high temperature conditions such as distilling off alcohol and water under acidic conditions, the reaction rate of multinucleation increases, and alkoxylation and multinucleation proceed simultaneously. Moreover, the water in raw material formaldehyde and the water produced | generated by reaction work in the direction which prevents progress of an alkoxylation reaction, and makes alkoxylation incomplete. Thus, in the one-step method in which the two reactions of methylolation and alkoxylation are carried out in one step, an amino resin forming material (in this example, melamine resin formation) that has a polynuclear resin structure with methylol groups remaining and a large amount of free formaldehyde Material).

(2) Multistage method:

  In said formula, R is a C1-C4 alkyl group.

In the multi-stage method, after the methylolation reaction is performed under alkaline conditions, the alkoxylation reaction is performed incompletely at a relatively low temperature under acidic conditions, and then again in alkaline conditions to prevent multinucleation while in the reaction solution. Alcohol and water (including water produced by alkoxylation)
Excess formaldehyde is distilled off, alcohol is added again, and the alkoxylation reaction is carried out at a relatively low temperature under acidic conditions. Further, volatile components in the reaction solution are distilled off, and a predetermined concentration is obtained as necessary. In this way, a dilute solvent is added. In this way, the production method by the multistage method in which the methylolation reaction and the alkoxylation reaction are performed under different conditions and the reaction and distillation are repeated, the methylol group equivalent with less polynuclear substances is controlled, and the free formaldehyde content is low. Less amino resin forming material (in this example, melamine resin forming material) is obtained. For details, see “Coloring Materials”, Volume 63 [1], p. 19-28 (1990).

  A suitable amino resin-forming material in the present invention is preferably produced by a multistage method because it has a low free formaldehyde content. The preferred free formaldehyde content is 5% by weight or less, more preferably 3% by weight or less, and most preferably 1% by weight or less. A free formaldehyde content of 5% by mass or less is preferable from the viewpoint of reducing environmental burden.

[Curing catalyst]
In the present invention, an acid catalyst may be added as a curing catalyst in the dope. Examples of the acid catalyst include acetic acid, lactic acid, succinic acid, oxalic acid, maleic acid, decanedicarboxylic acid, carboxylic acids such as (meth) acrylic acid; paratoluenesulfonic acid, dodecylbenzenesulfonic acid, dinonylnaphthalene (di) Examples thereof include sulfonic acids such as sulfonic acid; organic alkyl phosphate compounds such as dimethyl phosphoric acid, dibutyl phosphoric acid, dimethyl pyrophosphoric acid, and dibutyl pyrophosphoric acid. Of these organic acids, sulfonic acids, particularly dodecylbenzenesulfonic acid, paratoluenesulfonic acid, and dinonylnaphthalene (di) sulfonic acid are particularly preferable from the viewpoint of curability.

  From the standpoint of the storage stability of the dope, it is preferable to use the above acid catalyst by blocking it with a blocking agent that dissociates at the film-forming temperature of an ordinary general cellulose acylate film. It is preferable to use a blocked acid catalyst because problems such as poor storage stability of the dope do not occur.

  An amine is preferably used as the blocking agent, such as primary, secondary, or tertiary alkylamines, alkanolamines, alicyclic amines having 40 or less carbon atoms, and N-heterocyclic amines are preferred, especially ethylamine, diethylamine, triethylamine, ethanolamine, diethanolamine, triethanolamine, n-, i-, s- and t-butylamine, N, N-dimethylstearylamine, and tri-isopropanol Amines and the like are preferred.

  Examples of commercially available acid catalysts include “Nail Cure 155”, “Nail Cure 1051”, “Nail Cure 5076”, and “Nail Cure 4054J” (manufactured by KING INDUSTRIES, INC). When blocking, these acid catalysts are used by blocking with the above-mentioned blocking agent. Examples of the commercially available products include “Nail Cure 2500”, “Nail Cure 5225”, “Nail Cure X49-110”, “Nail Cure 3525”, “Nail Cure 4167” (manufactured by KING INDUSTRIES, INC) and the like.

  The addition amount of the curing catalyst is not generally determined because it depends on the film drying temperature and drying time, but is 0.1 to 10.0% by mass, preferably 0.2 to 8.0% by mass with respect to the amino resin precursor. %, And more preferably 0.3 to 5.0% by mass. If it is 0.1% or more, curing proceeds sufficiently, and if it is 10.0% by mass or less, problems such as poor liquid stability of the dope do not occur.

〔Additive〕
The transparent film of the present invention has a plasticizer (particularly preferably, a plasticizer having an octanol / water partition coefficient (log P value) of 0 to 10 described later) and fine particles (particularly preferably described later) with respect to the cellulose acylate. At least one kind of fine particles having an average primary particle diameter of 3 to 100 nm.

  Next, in the present invention, various additives such as a plasticizer and fine particles that can be contained in the transparent film will be described.

〔Additive〕
[Plasticizer]
The plasticizer used by this invention is a component added in order to give a softness | flexibility further to a transparent film, to improve dimensional stability, and to improve moisture resistance. A preferable plasticizer is preferably a solid having a boiling point of 200 ° C. or higher and a liquid at 25 ° C. or a melting point of 25 to 250 ° C. More preferred are plasticizers having a boiling point of 250 ° C. or higher and a liquid at 25 ° C. or a solid having a melting point of 25 to 200 ° C. When the plasticizer is a liquid, purification is usually performed by distillation under reduced pressure, and higher vacuum is preferable. In the present invention, it is particularly preferable to use a plasticizer having a vapor pressure of 1333 Pa or less at 200 ° C., more preferably a vapor pressure. A compound of 667 Pa or less, more preferably 133 to 1 Pa is preferred.

  As these plasticizers that are preferably added, phosphate esters, carboxylic acid esters, polyol esters and the like within the above-mentioned physical properties are used. Examples of phosphate esters include triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate, and the like.

  Representative examples of the carboxylic acid ester include phthalic acid esters and citric acid esters. Examples of the phthalic acid ester include dimethyl phthalate, diethyl phthalate, dibutyl phthalate, dioctyl phthalate, diphenyl phthalate, diethyl hexyl phthalate and the like. Examples of the citrate ester include O-acetyl triethyl citrate, O-acetyl tributyl citrate, acetyl triethyl citrate, and acetyl tributyl citrate. These preferred plasticizers are liquid except for TPP (melting point: about 50 ° C.) at 25 ° C., and the boiling point is 250 ° C. or higher.

  Examples of other carboxylic acid esters include butyl oleate, methylacetyl ricinoleate, dibutyl sebacate, and various trimellitic acid esters. Examples of glycolic acid esters include triacetin, tributyrin, butyl phthalyl butyl glycolate, ethyl phthalyl ethyl glycolate, methyl phthalyl ethyl glycolate, butyl phthalyl butyl glycolate, methyl phthalyl methyl glycolate, propyl phthalyl Examples include propyl glycolate, butyl phthalyl butyl glycolate, and octyl phthalyl octyl glycolate.

  JP-A-5-194788, JP-A-60-250053, JP-A-4-227941, JP-A-6-16869, JP-A-5-271471, JP-A-7-286068, JP-A-5-5047. No. 11, JP-A-11-80381, JP-A-7-20317, JP-A-8-57879, JP-A-10-152568, JP-A-10-120824, etc. are also preferably used. It is done. According to these publications, there are many preferable descriptions not only on the plasticizer but also on its usage or characteristics, and it is preferably used in the present invention.

Other plasticizers include (di) pentaerythritol esters described in JP-A-11-124445, glycerol esters described in JP-A-11-246704,
Diglycerol esters described in JP-A No. 2000-63560, citric acid esters described in JP-A No. 11-92574, substituted phenyl phosphate esters described in JP-A No. 11-90946, JP-A No. 2003-165868 An ester compound containing an aromatic ring and a cyclohexane ring described in the gazette is preferably used.

  Furthermore, in the present invention, a plasticizer having an octanol / water partition coefficient (log P value) of 0 to 10 is particularly preferably used. If the log P value of the compound is 10 or less, the compatibility with the cellulose acylate is good, there is no problem such as cloudiness or powder blowing of the film, and if the log P value is greater than 0, the hydrophilicity is high. Since it does not become too high, adverse effects such as deterioration of the water resistance of the transparent film are unlikely to occur. As the logP value, a more preferable range is 1 to 8, and a particularly preferable range is 2 to 7.

  The octanol / water partition coefficient (log P value) can be measured by a flask immersion method described in JIS Z-7260-107 (2000). Further, the octanol / water partition coefficient (log P value) can be estimated by a computational chemical method or an empirical method instead of the actual measurement. As a calculation method, Crippen's fragmentation method ["J. Chem. Inf. Comput. Sci.", Vol. 27, p. 21 (1987)], Viswanadhan's fragmentation method ["J. Chem. Inf. Comput. Sci. "29, 163 (1989)], Broto's fragmentation method [" Eur. J. Med. Chem.-Chim. Theor. ", Vol. 19, p. 71 (1984)], etc., among which Crippen. The 's fragmentation method is more preferred. When the log P value of a certain compound varies depending on the measurement method or calculation method, it is preferable to determine whether or not the compound is within the scope of the present invention by the Crippen's fragmentation method.

  A polymer plasticizer having a resin component having a molecular weight of 1,000 to 100,000 is also preferably used. For example, polyesters and / or polyethers described in JP-A-2002-22956, polyester ethers, polyester urethanes or polyesters described in JP-A-5-97073, copolyester ethers described in JP-A-2-292342, Examples thereof include an epoxy resin or a novolac resin described in JP-A No. 2002-146044.

  These plasticizers may be used alone or in combination of two or more. The addition amount of the plasticizer is preferably 2 to 30 parts by mass, particularly 5 to 20 parts by mass with respect to 100 parts by mass of the cellulose acylate.

[Fine particles]
The fine particles preferably used in the transparent film of the present invention are added to improve the frictional properties, mechanical strength and further dimensional stability and moisture resistance of the film, and are preferably hydrophobic. .

  The primary average particle size of the fine particles is preferably 1 to 100 nm, more preferably 3 to 100 nm, still more preferably 3 to 80 nm, and particularly preferably 5 to 100 nm, from the viewpoint of keeping haze low. 60 nm, most preferably 5-50 nm. The primary average particle diameter of the fine particles can be measured by measuring the particles with a transmission electron microscope and determining the average particle diameter.

The apparent specific gravity of the fine particles is preferably 70 g / L or more, more preferably 90-2.
00 g / L, particularly preferably 100 to 200 g / L.

  The addition amount of the fine particles is preferably 0.005 to 2 parts by mass, particularly 0.01 to 1.0 part by mass with respect to 100 parts by mass of the cellulose acylate.

  Preferable specific examples of the fine particles include inorganic compounds such as compounds containing silicon, silicon dioxide, titanium oxide, zinc oxide, aluminum oxide, barium oxide, zirconium oxide, strontium oxide, antimony oxide, tin oxide, tin oxide / antimony carbonate, Calcium, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate and calcium phosphate are preferred, more preferably inorganic compounds and zirconium oxide containing silicon, which suppress the haze increase of the transparent film. Since it can be used, silicon dioxide is particularly preferably used.

  As the fine particles suitably used for the transparent film of the present invention, the aggregation is suppressed in the cellulose acylate solution (dope) and in the film after film formation, and the surface is stably dispersed as fine particles. Preferably it has been treated. The surface treatment is performed by treating the surface of fine particles with an organic compound. Examples of organic compounds that can be used in this case include surface modification of conventionally known inorganic fillers such as metal oxides and inorganic pigments. Examples are described in, for example, “Pigment Dispersion Stabilization and Surface Treatment Technology / Evaluation”, Chapter 1 (Technical Information Association, 2001). Specifically, an organic compound having a polar group having an affinity for the fine particle surface and a coupling compound can be mentioned.

  Examples of the polar group having an affinity for the fine particle surface include a carboxy group, a phosphono group, a hydroxy group, a mercapto group, a cyclic acid anhydride group, an amino group, and the like, and a compound containing at least one kind in the molecule is preferable. For example, long-chain aliphatic carboxylic acids (eg, stearic acid, lauric acid, oleic acid, linoleic acid, linolenic acid, etc.), polyol compounds (eg, pentaerythritol triacrylate, dipentaerythritol pentaacrylate, ECH (epichlorohydrin) modified glycerol, etc.) And phosphono group-containing compounds {for example, EO (ethylene oxide) -modified phosphoric acid, etc.}, alkanolamines {ethylenediamine EO adduct (5 mol), etc.}, and the like.

As a coupling compound, a conventionally well-known organometallic compound is mentioned, A silane coupling agent, a titanate coupling agent, an aluminate coupling agent, etc. are contained. Silane coupling agents are most preferred. Specific examples include coupling compounds described by Fuzo Yamashita and Tosuke Kaneko “Crosslinking Agent Handbook” (Taiseisha, published in 1981).
In the surface treatment, two or more of the above compounds may be used in combination.

  As the organic compound, for example, polymers such as silicone resin, fluorine resin and acrylic resin are preferable, and among them, silicone resin is preferably used. Among the silicone resins, those having a three-dimensional network structure are particularly preferable. For example, a commercially available product having a trade name of “Tospearl” marketed by Toshiba Silicone Co., Ltd. can be used.

  The shape of the fine particles used in the present invention is not particularly limited, but is preferably a rice grain shape, a spherical shape, a cubic shape, a spindle shape, or an indefinite shape. The fine particles may be used alone or in combination of two or more.

  The fine particles preferably used in the present invention are preferably uniformly dispersed in the film after film formation. Therefore, the fine particles are preferably introduced into the dope solution after preparing a fine particle dispersion in the following manner or the like.

(1) After stirring and mixing the solvent and the fine particles, a fine particle dispersion is prepared with a disperser, and added to the dope solution and stirred.
(2) After stirring and mixing the solvent and the fine particles, the dispersion is made into a fine particle dispersion, and a small amount of cellulose acylate is added to the solvent and dissolved by stirring. The fine particle dispersion obtained by adding the fine particle dispersion and stirring to this is sufficiently mixed with the dope solution using an in-line mixer.
(3) A small amount of cellulose acylate is added to a solvent and dissolved by stirring. Fine particles are added to the solvent and dispersed with a disperser to obtain a fine particle addition solution. The fine particle additive solution is sufficiently mixed with the dope solution using an in-line mixer.

  The mass average diameter of the primary particles of the fine particles in the dispersion is preferably 3 to 200 nm, more preferably 3 to 150 nm, still more preferably 3 to 100 nm, and particularly preferably 5 to 80 nm. In particular, it is preferable that the dispersed fine particles in the wet dispersion in the present invention substantially maintain the fine particles to have a primary particle size or larger so as not to excessively increase the specific surface area of the fine particles during dispersion. Furthermore, the dispersed fine particles in the wet dispersion preferably do not contain large particles having an average particle diameter of 500 nm or more, and particularly preferably do not contain large particles having an average particle diameter of 300 nm or more. Furthermore, it is preferable that large particles having an average particle diameter of 500 nm or more are not included, and it is particularly preferable that large particles having an average particle diameter of 300 nm or more are not included. This makes it possible to form a fine concavo-convex shape that is free from optical defects, has a small haze value, and has no surface roughness.

[Ultraviolet light prevention agent]
In order to improve the light resistance of the film itself or to prevent deterioration of image display members such as a polarizing plate and a liquid crystal compound of a liquid crystal display device, it is preferable to further add an ultraviolet ray inhibitor to the transparent film of the present invention.

  As the ultraviolet absorber, one having an excellent ability to absorb ultraviolet rays having a wavelength of 370 nm or less from the viewpoint of preventing deterioration of the liquid crystal and absorbing as much as possible visible light having a wavelength of 400 nm or more from the viewpoint of good image display properties is used. It is preferable. In particular, the transmittance at a wavelength of 370 nm is desirably 20% or less, preferably 10% or less, and more preferably 5% or less.

  Examples of such ultraviolet absorbers include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, and ultraviolet absorbing groups as described above. Examples thereof include, but are not limited to, polymer ultraviolet absorbing compounds. Two or more kinds of ultraviolet absorbers may be used.

  As a method of adding the ultraviolet absorber to the dope, it may be added after being dissolved in an organic solvent such as alcohol, methylene chloride or dioxolane, or may be added directly into the dope composition. For an inorganic powder that does not dissolve in an organic solvent, a dissolver or a sand mill is used in the organic solvent and cellulose acylate to disperse and then added to the dope.

  In this invention, the usage-amount of a ultraviolet absorber is 0.1-5.0 mass parts with respect to 100 mass parts of cellulose acylates, Preferably it is 0.5-2.0 mass parts, More preferably, it is 0.8-2. 0 parts by mass.

[Retardation adjuster]
The transparent film of the present invention can contain a retardation adjusting agent. By using a retardation adjusting agent, the optical properties of the film can be adjusted to a desired range, and a transparent film suitable for optical applications such as a polarizing plate protective film used in a liquid crystal display device can be obtained.

  The transparent film of the present invention can be developed as a retardation film by adding a compound (retardation increasing agent) that increases retardation and stretching the transparent film. As the retardation increasing agent, a compound having a rod-like structure or a planar structure is preferably used.

  Moreover, a transparent film with small optical anisotropy can be obtained by containing a compound (retardation reducing agent) that suppresses the orientation of cellulose acylate in the film in the plane and in the film thickness direction. It can be preferably used as a support for a plate protective film or an optical compensation film. For this purpose, it is advantageous that the compound for reducing the optical anisotropy is sufficiently compatible with cellulose acylate, and the compound itself does not have a rod-like structure or a planar structure. Specifically, when a plurality of planar functional groups such as aromatic groups are provided, a structure having these functional groups in a non-planar rather than the same plane is advantageous. In this invention, the preferable usage-amount of a retardation regulator is 0.01-30 mass parts with respect to 100 mass parts of cellulose acylates, Preferably it is 1-25 mass parts, More preferably, it is 5-20 mass parts.

[Other additives]
Furthermore, in the cellulose acylate solution (dope) used in the present invention, various other additives depending on the application in each preparation step {for example, deterioration inhibitors (for example, antioxidants, peroxide decomposition agents, Radical inhibitors, metal deactivators, acid scavengers, amines, etc.), release agents, antistatic agents, infrared absorbers, etc.}, which may be solid or oily. That is, the melting point and boiling point are not particularly limited. Furthermore, as an infrared absorber, the thing as described in Unexamined-Japanese-Patent No. 2001-194522 can be used, for example.

  These additives may be added at any time in the dope preparation step, but may be added in the final preparation step of the dope preparation step by adding a preparation step. Furthermore, the amount of each material added is not particularly limited as long as the function is manifested. Moreover, when the transparent film of this invention is formed from a multilayer, the kind and addition amount of the additive of each layer may differ. For example, it is described in Japanese Patent Application Laid-Open No. 2001-151902 and the like, but these are conventionally known techniques. These details including the ultraviolet absorbers described above are the materials described in detail on pages 16 to 22 of the Japan Society for Invention and Innovation Technical Bulletin No. 2001-1745 (issued on March 15, 2001, Japan Institute of Invention). Preferably used.

  The amount of these additives to be used is preferably suitably used in the range of 0.001 to 20% by mass based on the total solid content in the cellulose acylate solution (dope).

〔solvent〕
Next, the organic solvent for dissolving the cellulose acylate used in the present invention will be described. Examples of the organic solvent to be used include conventionally known organic solvents. For example, those having a solubility parameter in the range of 17 to 22 are preferable. Solubility parameters are described in, for example, J. Brandrup, E .; H. "Polymer Handbook", 4th edition, VII / 671-VII / 714. Lower aliphatic hydrocarbon chloride, lower aliphatic alcohol, ketone having 3 to 12 carbon atoms, ester having 3 to 12 carbon atoms, ether having 3 to 12 carbon atoms, aliphatic having 5 to 8 carbon atoms Hydrocarbons, aromatic hydrocarbons having 6 to 12 carbon atoms, fluoroalcohols (for example, paragraph numbers [0020] of JP-A-8-143709, paragraph number [0037] of JP-A-11-60807, etc.) Compound) and the like.

In the present invention, the cellulose acylate is preferably a solution in which 10 to 30% by mass is dissolved in an organic solvent, more preferably 13 to 27% by mass, and particularly 15 to 25%.
A cellulose acylate solution dissolved in mass% is preferred. The method for preparing cellulose acylate at these concentrations may be prepared so as to be a predetermined concentration at the stage of dissolution, or it is prepared in advance as a low concentration solution (for example, 9 to 14% by mass) and then concentrated later. You may adjust to a predetermined high concentration solution by a process. Furthermore, a cellulose acylate solution having a high concentration may be added to the cellulose acylate solution at a predetermined low concentration by adding various additives, and the cellulose acylate solution concentration of the present invention is obtained by any method. If implemented, there is no particular problem.

[Preparation of dope]
Regarding the preparation of the cellulose acylate solution (dope) of the present invention, the dissolution method is not particularly limited, and it is carried out by a room temperature dissolution method, a cooling dissolution method or a high temperature dissolution method, and further a combination thereof. The Regarding these, for example, JP-A-5-163301, JP-A-61-106628, JP-A-58-127737, JP-A-9-95544, JP-A-10-95854, JP-A-10-45950, JP 2000-53784, JP 11-322946, JP 11-322947, JP 2-276830, JP 2000-273239, JP 11-71463, JP 04-259511, JP JP-A Nos. 2000-273184, 11-323017, and 11-302388 describe methods for preparing cellulose acylate solutions. These techniques for dissolving cellulose acylate in an organic solvent can be applied as appropriate within the scope of the present invention. About these details, especially a non-chlorine type | system | group solvent system, it implements by the method described in detail on the 22-25th pages of the above-mentioned technical numbers 2001-1745.

  Further, the cellulose acylate dope solution of the present invention is usually subjected to solution concentration and filtration, and is also described in detail on page 25 of the aforementioned technical number 2001-1745. In addition, when it melt | dissolves at high temperature, it is the case where it is more than the boiling point of the organic solvent to be used, and in that case, it uses in a pressurized state.

  The amino resin precursor used in the present invention is thermosetting and usually undergoes a curing reaction in the range of 80 ° C to 200 ° C. Therefore, care must be taken not to apply an excessive temperature after the addition of the amino resin precursor. Preferably, after preparing a cellulose acylate solution containing various additives other than the amino resin precursor, it is desirable to add and mix the solution containing the amino resin precursor.

  The solution containing the amino resin precursor is usually filtered, and a mixing device such as a static mixer or a rotary stirring device is preferably used for mixing with the cellulose acylate solution.

The cellulose acylate solution of the present invention preferably has a specific viscosity and dynamic storage modulus. 1 mL of the sample solution was used in a rheometer “CLS500” with a “Steel Cone” having a diameter of 4 cm / 2 ° (both manufactured by TA Instruments), and the measurement conditions were Oscillation Step / Temperature Ramp, and the range of 40 ° C. to −10 ° C. was 2 ° C. Measured at a variable rate per minute, the static non-Newtonian viscosity n ^* (Pa · sec) at 40 ° C. and the storage modulus G ′ (Pa) at 5 ° C. are determined. The sample solution is kept warm until the liquid temperature becomes constant at the measurement start temperature, and then the measurement is started. In the present invention, the viscosity at 40 ° C. is preferably 1 to 300 Pa · sec, and the dynamic storage elastic modulus at −5 ° C. is preferably 10,000 to 1,000,000 Pa. More preferably, the viscosity at 40 ° C. is 1 to 200 Pa · sec, and the dynamic storage elastic modulus at −5 ° C. is 30,000 to 500,000 Pa.

[Method for producing transparent film]
Next, a method for producing a cellulose acylate film as a transparent film of the present invention using the cellulose acylate solution will be described. As the method and equipment for producing the cellulose acylate film, a conventionally known solution casting film forming method and solution casting film forming apparatus called a drum method or a band method used for producing a cellulose triacetate film are used.

  The metal support used in the casting step preferably has a surface having an arithmetic average roughness (Ra) of 0.015 μm or less and a ten-point average roughness (Rz) of 0.05 μm or less. More preferably, the arithmetic average roughness (Ra) is 0.001 to 0.01 μm, and the ten-point average roughness (Rz) is 0.001 to 0.02 μm. More preferably, the (Ra) / (Rz) ratio is 0.15 or more. Thus, the surface shape of the film after film formation can be controlled within a preferable range described later by setting the surface roughness of the metal support within a predetermined range.

Hereinafter, the film forming process will be described using the band method as an example.
The prepared dope (cellulose acylate solution) is once stored in a storage kettle, and the foam contained in the dope is defoamed for final preparation. The dope 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 number of rotations, and the dope is run endlessly from the die (slit) of the pressure die. The dry-dried dope film (also referred to as web) is peeled off from the metal support at a peeling point that is uniformly cast on the metal support and substantially rounds the metal support. The both ends of the obtained web are sandwiched between clips, transported by a tenter while maintaining the width, dried, and then transported by a roll group of a drying device to finish drying, and wound to a predetermined length by a winder. The drying temperature in the drying step is preferably 40 to 250 ° C, particularly preferably 70 to 180 ° C.

  The amino resin curing reaction is preferably caused to proceed by the heat of the drying step. The drying temperature and time suitable for the curing reaction vary depending on the content of the amino resin precursor and the amount of acid catalyst added, but are usually 40 ° C. to 250 ° C. and 3 minutes to 40 minutes. For example, when the drying temperature is 130 ° C., 20 minutes to 30 minutes is preferable.

  Further, in order to remove the residual solvent, it is preferably dried at 50 to 160 ° C., and in that case, the residual solvent is preferably evaporated by drying with high-temperature air whose temperature is changed successively. The above method is described in Japanese Patent Publication No. 5-17844. According to this method, the time from casting to stripping can be shortened. The drying temperature, the amount of drying air, and the drying time vary depending on the solvent used, and can be appropriately selected according to the type and combination of the solvents used. The amount of residual solvent in the final finished film is preferably 2% by mass or less, and more preferably 0.4% by mass or less in order to obtain a film having good dimensional stability. The specific method of these drying processes may use, for example, any of the conventionally known methods and apparatuses described in the above-mentioned Technical Report of the Invention Association, and is not particularly limited. The combination of the tenter and the roll group dryer varies depending on the purpose. Each of these manufacturing processes is described in detail in the above-mentioned official technical numbers 2001-1745, pages 25-30, and is classified into casting (including co-casting), metal support, drying, peeling, stretching, etc. The

  In the casting step, one type of cellulose acylate solution may be cast as a single layer, or two or more types of cellulose acylate solutions may be cast simultaneously and / or sequentially.

  It is preferable that the film thickness of the transparent film of this invention is 20-150 micrometers, More preferably, it is 30-120 micrometers.

[Characteristics of transparent film]
The transparent film of this invention is used suitably as a protective film for polarizing plates, and this transparent film has the following characteristics.

[Film surface properties]
It is preferable that the transparent film used as a protective film for polarizing plates has a specific surface shape. Hereinafter, the surface shape of the transparent film will be described.

  The surface of the transparent film on which the antireflection film is provided has an arithmetic average roughness (Ra) of surface irregularities of the film based on JIS B-0601-1994 of 0.0001 to 0.1 μm, a ten-point average roughness (Rz). ) Is preferably 0.0001 to 0.3 μm and the maximum height (Ry) is 0.5 μm or less, the arithmetic average roughness (Ra) is 0.0001 to 0.08 μm, the ten-point average roughness ( Rz) is preferably 0.0001 to 0.1 μm and the maximum height (Ry) is 0.5 μm or less, and arithmetic average roughness (Ra) is 0.0002 to 0.015 μm, ten-point average roughness More preferably, the thickness (Rz) is 0.002 to 0.05 μm and the maximum height (Ry) is 0.05 μm or less, and the arithmetic average roughness (Ra) is 0.001 to 0.010 μm, ten points. Average roughness (Rz) is 0.002-0. It is particularly preferable that 025 μm and the maximum height (Ry) be 0.04 μm or less. Within these ranges, an antireflection film having a uniform coated surface with no coating unevenness and good adhesion to the protective film for polarizing plate is provided, and is bonded to the polarizer as a transparent protective film for the polarizer. In this case, the adhesiveness is good.

  The concave and convex shapes on the surface can be evaluated by a transmission electron microscope (TEM), an atomic force microscope (AFM), or the like.

In addition, the number of visual optical defects having a size of 100 μm or more in the transparent film is preferably 1 or less per 1 m ² from the viewpoint of obtaining a uniform and clear film with good production rate. This optical defect can be observed using a polarizing microscope with the slow axis of the film parallel to the absorption axis of the polarizer under crossed Nicols. The defects that appear as bright spots are approximated in a circular area, and those having a diameter of 100 μm or more are counted. Bright spots of 100 μm or more can be easily observed with the naked eye.

That is, the surface of the transparent film has an arithmetic average roughness (Ra) of surface irregularities based on JIS B-0601-1994 of 0.0001 to 0.1 μm, and a ten-point average roughness (Rz) of 0.0001. Preferably, the number of visual optical defects having a size of ˜0.3 μm and a size of 100 μm or more is 1 or less per 1 m ² . By using the film having the above-described surface shape, display image non-uniformities such as optical defects and uneven brightness are remarkably reduced, which is preferable.

[Mechanical properties of film]
(Dimension change)
The dimensional stability of the transparent film of the present invention is 24% under the conditions of dimensional change when left standing at 60 ° C. and 90% RH for 24 hours (high humidity) and 90 ° C. and 5% RH. It is preferable that the dimensional change rate after standing for a long time (high temperature) is 0.5% or less. More preferably, it is 0.3% or less, and even more preferably, it is 0.15% or less.

As a specific measurement method, two transparent film samples 30 mm × 120 mm were prepared, humidity-controlled at 25 ° C. and 60% RH for 24 hours, and an automatic pin gauge {Shinto Kagaku Co., Ltd.) with 6 mmφ at both ends. Holes were made at intervals of 100 mm to obtain the original size (L ₀ ) of the punch interval. After one sample was treated at 60 ° C. and 90% RH for 24 hours, the dimension of the punch interval (L ₁ ) was measured, and the other sample was treated at 90 ° C. and 5% RH for 24 hours. The dimension (L ₂ ) of the punch interval was measured. Measurement was made to a minimum scale of 1/1000 mm at all intervals. The dimensional change rate under each condition can be obtained by the following mathematical formulas (4) and (5).
Formula (4): Dimensional change rate of 60 ° C. and 90% RH (high humidity) = {| L ₀ −L ₁ | / L ₀ } × 100,
Formula (5): Dimensional change rate of 90 ° C. and 5% RH (high temperature) = {| L ₀ −L ₂ | / L ₀ } × 100.

(Elastic modulus)
The elastic modulus of the transparent film correlates with the degree of freedom of movement of the cellulose acylate molecular chain in the film, and the greater the modulus of elasticity, the smaller the degree of freedom of movement of the cellulose acylate molecular chain. The diffusion rate of low molecular weight compounds such as water is also reduced. The elastic modulus of the transparent film can be increased by introducing a crosslinked structure. The elastic modulus of the transparent film can be determined by a tensile test.

  Specifically, the sample is conditioned for 24 hours in an environment of 25 ° C. and 60% RH, and the elastic modulus is measured according to the method described in JIS K-7127. As the tensile tester, “Tensilon” manufactured by A & D Co., Ltd. can be used.

The transparent film preferably has an elastic modulus at 25 ° C. and 60% RH of 3800 N / mm ² or more in either the width direction or the longitudinal direction, and is 4410 N / mm ² or more and 5880 N / mm ² or less. It is more preferable. If it is 3800 N / mm ² or more, the moisture permeability does not become too large, and problems such as deterioration of display characteristics such as frame unevenness do not occur. Moreover, if it is 5880 N / mm < ² > or less, the problem that the processability of a film will be impaired does not arise and it is preferable.

(curl)
The curl value in the width direction of the transparent film of the present invention is preferably −10 / m to + 10 / m. When the transparent film of the present invention is coated with a surface treatment and an optically anisotropic layer, which will be described later, when the rubbing treatment is performed, the alignment film, the coating and bonding of the optically anisotropic layer are performed in a long length In addition, when the curl value in the width direction of the transparent film of the present invention is within this range, the handling of the film is hindered, and problems such as film cutting do not occur. In addition, since the film does not come into strong contact with the transport roll at the edge or center of the film, dust generation is not likely to occur or foreign matter adheres to the film. Problems such as point defects and the frequency of coating stripes exceeding allowable values do not occur. Furthermore, curling in this range is preferable because it can reduce color spot failures that are likely to occur when an optically anisotropic layer is installed, and can prevent bubbles from entering when a polarizer is bonded.

  The curl value can be measured according to a measurement method (ANSI / ASCPH1.29-1985) defined by the American National Standards Institute.

(Tear strength)
The tear strength (Elmendorf tear method) based on the tear test method of JIS K-7128-2: 1998 is preferably 2 g or more in the range where the film thickness of the transparent film of the present invention is 20 to 80 μm. More preferably, it is 5-25g, Furthermore, it is 6-25g. Moreover, 8 g or more is preferable at 60 micrometer conversion, More preferably, it is 8-15g. Specifically, a sample piece 50 mm × 64 mm can be measured for 2 hours under conditions of 25 ° C. and 65% RH, and then measured using a light load tear strength tester.

[Optical performance]
(Change in optical performance of film after high humidity treatment)
Regarding the change of the optical performance due to the environmental change of the transparent film of the present invention, it is preferable that the change amount of Re and Rth of the film treated at 60 ° C. and 90% RH for 240 hours is 15 nm or less. More preferably, it is 12 nm or less, and more preferably 10 nm or less.

(Change in optical performance of film after high temperature treatment)
Further, it is preferable that the amount of change in Re and Rth of the film treated at 80 ° C. for 240 hours is 15 nm or less. More preferably, it is 12 nm or less, and more preferably 10 nm or less.

(Humidity dependence of film Re and Rth)
It is preferable that both the in-plane retardation Re and the thickness direction retardation Rth of the transparent film of the present invention have small changes due to humidity. Specifically, the difference ΔRth between the Rth value at 25 ° C. and 10% RH represented by the following formula (6) and the Rth value at 25 ° C. and 80% RH is preferably 0 to 35 nm. More preferably, it is 0-30 nm, More preferably, it is 0-25 nm, Most preferably, it is 0-20 nm.
Formula (6): ΔRth = Rth _{10% RH} −Rth _{80% RH}

In this specification, Re ₍ λ ₎ and Rth ₍ λ ₎ represent in-plane retardation and retardation in the thickness direction at the wavelength λ, respectively. Re ₍ λ ₎ is measured using “KOBRA 21ADH” (manufactured by Oji Scientific Instruments) with light having a wavelength of λ nm incident in the normal direction of the film. Rth ₍ λ ₎ is +40 with respect to the film normal direction with the in-plane retardation Re ₍ λ ₎ and the in-plane slow axis (determined by “KOBRA 21ADH”) as the tilt axis (rotation axis). A retardation value measured in three directions, that is, a retardation value measured by incidence of light having a wavelength of λ nm from a direction inclined by -40 ° and a direction inclined by -40 °, and an assumed value of average refractive index are inputted. “KOBRA 21ADH” is calculated based on the measured film thickness value. Here, as the assumed value of the average refractive index, “Polymer Handbook” (John Wiley & Sons, Inc.) and catalog values of various optical films can be used. Those whose average refractive index is not known can be measured with an Abbe refractometer.

Examples of the average refractive index values of main optical films are given below:
Cellulose acylate (1.48), cycloolefin polymer (1.52), polycarbonate (1.59), polymethyl methacrylate (1.49), and polystyrene (1.59).

By inputting the assumed average refractive index values and thicknesses, "KOBRA 21ADH" calculates the _{n x, n y, n z} . In this specification, unless otherwise specified, the measurement wavelength of the retardation value is 590 nm.

[Water permeability of film]
The transparent film of the present invention has a water vapor transmission rate of 400 to 2000 g / m ² · 24 hours in terms of a film thickness of 80 μm measured according to JIS Z-0208 at a temperature of 60 ° C. and a humidity of 95% RH. It is desirable that More preferably 500~1800g / m ² · 24 hours, particularly preferably 600~1600g / m ² · 24 hours. When the water vapor transmission rate is 2000 g / m ² · 24 hours or less, problems such as the absolute value of the humidity dependency of the Re value and Rth value of the film exceeding 0.5 nm /% RH do not occur. In addition, even when an optically anisotropic film is laminated on the transparent film of the present invention, the absolute value of the humidity dependence of the Re value and Rth value does not exceed 0.5 nm /% RH. preferable. When this optical compensation sheet or polarizing plate is incorporated in a liquid crystal display device, it does not cause a change in color or a decrease in viewing angle. In addition, when the moisture permeability of the transparent film is 400 g / m ² · 24 hours or more, the transparent film does not prevent drying of the adhesive when the polarizer is attached to both sides of the polarizer. Good adhesion.

If the film thickness of the transparent film of the present invention is thick, the moisture permeability becomes small, and if the film thickness is thin, the moisture permeability becomes large. Therefore, it is necessary to convert the sample of any film thickness to a standard of 80 μm. The conversion of the film thickness was determined according to the following formula (7).
Formula (7): Moisture permeability in terms of 80 μm = measured moisture permeability × {measured film thickness (μm) / 80 (μm)}.

The measurement method of moisture permeability is “Polymer Physical Properties II” (“Polymer Experiment Course 4”, Kyoritsu Shuppan), pages 285 to 294: Measurement of vapor permeation (mass method, thermometer method, vapor pressure method, adsorption amount) The transparent film sample 70 mmφ of the present invention is conditioned at 60 ° C. and 95% RH for 24 hours, and the moisture permeability test apparatus “KK-709007” {Toyo Seiki Co., Ltd. }, The moisture content per unit area was calculated (g / m ² ) in accordance with JIS Z-0208, and the moisture permeability was determined as follows: moisture content after humidity conditioning-mass before moisture conditioning.

  The transparent film of the present invention can achieve improved adhesion between the transparent film and each functional layer (for example, the undercoat layer and the back layer) by optionally performing a surface treatment. For example, glow discharge treatment, ultraviolet irradiation treatment, corona treatment, flame treatment, acid or alkali treatment can be used.

The glow discharge treatment here may be low-temperature plasma that occurs under a low pressure gas of 10 ^{−3 to} 20 Torr, and plasma treatment under atmospheric pressure is also preferred. A plasma-excitable gas is a gas that is plasma-excited under the above-mentioned conditions, and examples thereof include chlorofluorocarbons such as argon, helium, neon, krypton, xenon, nitrogen, carbon dioxide, tetrafluoromethane, and mixtures thereof. It is done. Details of these are described in detail on pages 30 to 32 in the Journal of the Invention Association (Technology No. 2001-1745, issued on March 15, 2001, Invention Association).

  Note that, in the plasma treatment at atmospheric pressure which has been attracting attention in recent years, for example, irradiation energy of 20 to 500 Kgy is used under 10 to 1000 Kev, and more preferably irradiation energy of 20 to 300 Kgy is used under 30 to 500 Kev. Among these, an alkali saponification treatment is particularly preferable, and it is extremely effective as a surface treatment of a cellulose acylate film.

  The alkali saponification treatment is also preferably performed by applying a saponification solution. Examples of the coating method include a dip coating method, a curtain coating method, an extrusion coating method, a bar coating method, and an E-type coating method.

  The solvent of the alkali saponification coating solution has good wettability because it is applied to the transparent support of the saponification solution, and the surface state remains good without forming irregularities on the surface of the transparent support by the saponification solution solvent. It is preferred to select a solvent to keep. Specifically, an alcohol solvent is preferable, and isopropyl alcohol is particularly preferable. An aqueous solution of a surfactant can also be used as a solvent.

  The alkali of the alkali saponification coating solution is preferably an alkali that dissolves in the above solvent, and more preferably KOH or NaOH. The pH of the saponification coating solution is preferably 10 or more, more preferably 12 or more. The reaction conditions during alkali saponification are preferably 1 second to 5 minutes at room temperature, more preferably 2 seconds to 1 minute, and particularly preferably 3 seconds to 30 seconds.

After the alkali saponification reaction, it is preferable to wash the surface on which the saponification solution is applied, or after washing with an acid. Further, the coating-type saponification treatment and the alignment film uncoating described later can be performed continuously, and the number of steps can be reduced. Furthermore, the cellulose acylate film as a transparent film obtained in the present invention may be subjected to alkali treatment by an immersion method. That is, the surface treatment can be carried out by continuously or intermittently arranging an alkali treatment bath, a water washing bath, an acid treatment bath, a water washing bath, and optionally a rinse bath. In this case, each solution has the same composition as the corresponding solution used in the coating method.

  In order to achieve adhesion between the film and the emulsion layer, after surface activation treatment, a method of directly applying the functional layer on the transparent film to obtain adhesive force, and after some surface treatment Alternatively, there is a method in which an undercoat layer (adhesive layer) is provided and a functional layer is applied thereon without surface treatment. Details of these subbing layers are described on page 32 in the Japan Society for Invention and Innovation (Technical Number 2001-1745, published on March 15, 2001, Japan Institute of Invention). The functional layer that can be provided on the cellulose acylate film as the transparent film of the present invention is also disclosed by the Japan Institute of Invention (Technology No. 2001-1745, published on March 15, 2001, Japan Institute of Invention) 32 pages to 45. Various functional layers described in detail on the page can be applied.

[Use of transparent film]
First, the application of the transparent film produced in the present invention will be briefly described.

[Protective film for polarizing plate]
The cellulose acylate film which is a transparent film of the present invention is particularly useful for a protective film for a polarizing plate. When using as a protective film for polarizing plates, the production method of a polarizing plate is not specifically limited, It can produce by a general method. There is a method in which the obtained cellulose acylate film is treated with an alkali and bonded to both sides of a polarizer prepared by immersing and stretching a polyvinyl alcohol film in an iodine solution using a completely saponified polyvinyl alcohol aqueous solution. Instead of alkali treatment, easy adhesion processing as described in JP-A-6-94915 and JP-A-6-118232 may be performed. Examples of the adhesive used to bond the protective film treated surface and the polarizer include polyvinyl alcohol adhesives such as polyvinyl alcohol and polyvinyl butyral, vinyl latexes such as butyl acrylate, and the like.

  The polarizing plate is composed of a polarizer and a protective film that protects both surfaces of the polarizer, and further includes a protective film bonded to one surface of the polarizing plate and a separate film bonded to the other surface. The protective film and the separate film are used for the purpose of protecting the polarizing plate at the time of shipping the polarizing plate or at the time of product inspection. In this case, the protect film is bonded for the purpose of protecting the surface of the polarizing plate, and is used on the side opposite to the surface where the polarizing plate is bonded to the liquid crystal cell. On the other hand, the separate film is used for the purpose of covering the adhesive layer to be bonded to the liquid crystal cell, and is used on the surface side of the polarizing plate to be bonded to the liquid crystal cell. In a liquid crystal display device, a substrate (liquid crystal cell) containing a liquid crystal is usually disposed between two polarizing plates, but a protective film for polarizing plates to which the transparent film of the present invention is applied is excellent in any part. Display characteristics can be obtained. When used for the protective film for polarizing plate on the outermost surface of the display side of the liquid crystal display device, a transparent hard coat layer, an antiglare layer, an antireflection layer, and the like may be provided thereon.

[Optical compensation sheet]
The cellulose acylate film that is the transparent film of the present invention can be used for various applications, and can also be applied to an optical compensation sheet of a liquid crystal display device.

The transparent film of the present invention can be used for liquid crystal cells in various display modes. TN (Twisted Nematic), IPS (In-Plane Switching), FLC (Ferroelectric Liquid Crystal), AFLC (Anti-Ferroelectric Liquid Crystal), OCB (Optically QuantTampS)
Various display modes such as twisted nematic (VA), VA (vertically aligned), and HAN (hybrid aligned nematic) have been proposed. In addition, a display mode in which the above display mode is oriented and divided has been proposed. The transparent film of the present invention is effective in any display mode liquid crystal display device. Further, it is effective in any of a transmissive type, a reflective type, and a transflective liquid crystal display device.

  The transparent film of the present invention is particularly preferably used as a support for an optical compensation sheet or a polarizing plate protective film of a TN type liquid crystal display device having a TN mode liquid crystal cell. By using the transparent film of the present invention having an improved elastic modulus and the like for a TN liquid crystal display device, unevenness in the frame can be improved and display performance can be improved.

  You may use the transparent film of this invention as a support body of the optical compensation sheet | seat of the STN type liquid crystal display device which has a liquid crystal cell of STN mode. 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 °, 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 sheet used in the STN type liquid crystal display device is described in JP-A-2000-105316.

  The transparent film of the present invention is also advantageously used as a support for an optical compensation sheet of a VA liquid crystal display device having a VA mode liquid crystal cell, or as a polarizing plate protective film. By using the transparent film of the present invention with improved elasticity and the like for a VA liquid crystal display device, it is possible to improve corner unevenness and display performance.

  The transparent film of the present invention may be used as a support for an optical compensation sheet or a polarizing plate protective 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.

  The transparent film of the present invention may be used as an optical compensation sheet or a polarizing plate protective film for a TN type, STN type, HAN type, GH (Guest-Host) type reflective liquid crystal display device. These display modes have been well known since ancient times. The TN type reflection type liquid crystal display device is described in JP-A-10-123478, International Publication No. 98/48320, and Japanese Patent No. 3022477.

  The optical compensation sheet used in the reflective liquid crystal display device is described in International Publication No. 00/65384 pamphlet.

  The transparent film of the present invention is also advantageously used as a support for an optical compensation sheet of an ASM type liquid crystal display device having a liquid crystal cell of an ASM (Axial Symmetrical Microcell) mode. The ASM mode liquid crystal cell is characterized in that the thickness of the cell is maintained by a position-adjustable resin spacer. Other properties are the same as those of the TN mode liquid crystal cell. For the ASM mode liquid crystal cell and the ASM type liquid crystal display device, see Kume et al., “Kume et al.,“ SID 98 Digest ”, p. 1089 (1998)}.

[Support for silver halide photographic material]
The cellulose acylate film which is a transparent film of the present invention is also useful as a support for silver halide photographic light-sensitive materials. The transparent film of the present invention can be used as a support for any silver halide photographic light-sensitive material for printing plate making, medical use, general photographic use and the like. Moreover, it is preferable that the film thickness is 30-250 micrometers. Such silver halide photographic materials are described in T.W. H. James et al., “The Theory of the.
Photographic Process ", 4th edition (Macmillan Publishing Co., Inc. 1977) and the like.

  The detailed description on pages 45 to 59 is applied to the use of these detailed transparent films described above in the Japan Society for Invention and Innovation Technical Report (Public Technical Number 2001-1745, Issued on March 15, 2001, Japan Institute of Invention and Innovation). it can.

  Although the specific Example about the transparent film of this invention is described below, this invention is not limited to these.

<Preparation of cellulose acylate film>
Example 1-1
[Production of Cellulose Acylate Film 001 (Transparent Film of the Present Invention)]
[Preparation of cellulose acylate solution (dope)]
A dope was prepared by gradually adding cellulose acylate powder (average size: 2 mm) to a stainless steel dissolution tank having a stirring blade while containing the following solvent solution and stirring well. After the addition, the mixture was allowed to stand at 35 ° C. for 1 hour at room temperature (25 ° C.) to swell the cellulose acylate. The component ratio of each component used for preparation of the dope of Example 1-1 is shown below.

(Cellulose acylate solution composition)
Cellulose triacetate 18 parts by weight Substitution degree 2.83, 6-position acylation substitution degree 0.93, 2,3-position acylation substitution degree 1.90, viscosity average polymerization degree 320, water content 0.4 mass% , 6 mass% viscosity in methylene chloride solution 305 mPa · s
80 parts by mass of methylene chloride Amino resin precursor (A-1) 3.6 parts by mass Curing catalyst (paratoluenesulfonic acid) 0.18 parts by mass

  Next, bubbles were removed by irradiating the dope with weak ultrasonic waves. The degassed dope was first passed through a sintered metal filter having a nominal pore size of 5 μm and then passed through a sintered metal filter having a nominal pore size of 2.5 μm in a state of being pressurized to 1.5 MPa. Respective primary pressures were 1.6 and 1.3 MPa, and secondary pressures were 0.9 and 0.7 MPa, respectively. The temperature of the dope after filtration was adjusted to 35 ° C. and stored in a stainless steel stock tank. The stock tank had an anchor blade on the central axis and was constantly stirred at a peripheral speed of 0.3 m / sec.

[Film casting]
The dope obtained by the above-described dissolution method was set to 40 ° C., and cast on a mirror surface stainless steel support having a surface temperature of 20 ° C. through a casting Giesser to form a film. The dope cast on the band was first dried by sending parallel-flow drying air. The overall heat transfer coefficient from the drying air to the dope during drying was 24 kcal / m ² · hr · ° C. The temperature of the drying air was 140 ° C. at the upper part of the band and 100 ° C. at the lower part.

  For 5 seconds after casting, dry air is prevented from directly hitting the dope by a wind shield device, and thereafter, a cellulose acylate film (001) having a thickness of 80 μm is produced by conveying a drying zone having a large number of rolls. did. The temperature of the drying zone was 140 ° C. and the drying time was 20 minutes.

Examples 1-2 to 1-10 and Comparative Examples 1-1 to 1-3
In Example 1, as shown in Table 1, except that the type of solvent, the type and / or amount of the crosslinking agent in the cellulose acylate solution blend were changed, or this was not used, and a curing catalyst was used or not used. In the same manner as in Example 1, cellulose acylate films (002) to (010), which are transparent films of the present invention, and cellulose acylate films (101) to (103) of comparative examples were produced. The composition of the cellulose acylate solution is shown in Table 1.

[Evaluation of film]
The following characteristics evaluation was performed about the obtained cellulose acylate film sample. Table 2 shows the measurement results of the characteristic values of each film sample.

[Elastic modulus measurement]
The prepared film sample was conditioned for 24 hours in an environment of 25 ° C. and 60% RH, and the elastic modulus was measured according to the method described in JIS K-7127. As the tensile tester, “Tensilon” manufactured by A & D Co., Ltd. was used.

[Moisture permeability measurement]
The prepared film sample 70 mmφ was conditioned at 60 ° C. and 95% RH for 24 hours, respectively, and per unit area according to JIS Z-0208 using a moisture permeation test apparatus “KK-709007” {manufactured by Toyo Seiki Co., Ltd.}. The amount of water was calculated (g / m ² ), and the moisture permeability was obtained by the following equation: moisture permeability = mass after conditioning−mass before conditioning.

[Measurement of dimensional change]
The prepared film sample 30 mm × 120 mm was conditioned at 25 ° C. and 60% RH for 24 hours, and 6 mmφ holes were opened at both ends with an automatic pin gauge {manufactured by Shinto Kagaku Co., Ltd.) at intervals of 100 mm. The original size (L ₀ ). The dimension (L ₁ ) of the punch interval after the film sample was treated at 60 ° C. and 90% RH for 24 hours was measured. Measurement was made to a minimum scale of 1/1000 mm at all intervals. Using the obtained dimensions (L ₀ ) and (L ₁ ), the dimensional change rate of 60 ° C. and 90% RH (high humidity) was determined according to the mathematical formula (4).
The film sample 90 ° C., and the hole interval after treatment for 24 hours at 5% RH (L ₂₎ was measured. Measurement was made to a minimum scale of 1/1000 mm at all intervals. Using the obtained dimensions, the dimensional change rate of 90 ° C. and 5% RH (high temperature) was determined according to the mathematical formula (5).

[Rth humidity measurement]
The film thickness direction retardation value Rth of the produced film sample was measured with “KOBRA 21ADH” (manufactured by Oji Scientific Instruments) at a measurement wavelength of 590 nm according to the description of the text, and according to the above formula (6), 25 ° C. The difference between the Rth value at 10% RH and the Rth value at 25 ° C. and 80% RH was determined.

<Preparation of polarizing plate>
Example 2-1
(Production of polarizer)
The PVA film was immersed in an aqueous solution of 2.0 g / L of iodine and 4.0 g / L of potassium iodide at 25 ° C. for 240 seconds, and further immersed in an aqueous solution of boric acid 10 g / L at 25 ° C. for 60 seconds. The film was introduced into a stretching machine and stretched 5.3 times. Thereafter, the width was kept constant, and the film was dried in an atmosphere at 80 ° C. while being contracted, and then separated from the tenter and wound up.
The moisture content of the PVA film before starting stretching was 31%, and the moisture content after drying was 1.5%. The difference in transport speed between the left and right tenter clips was less than 0.05%. Wrinkles and film deformation at the tenter exit were not observed.
The obtained polarizer had a transmittance of 43.7% at 550 nm and a degree of polarization of 99.97%.

[Production of Polarizing Plate (P001)]
The cellulose acylate film (001), which is the transparent film of the present invention formed as described above, was immersed in a 1.5 mol / L NaOH aqueous solution at 55 ° C. for 1 minute to saponify both surfaces, and then diluted with sulfuric acid and water. After washing and drying, a polyvinyl alcohol adhesive is applied to one side of each cellulose acylate to a thickness of about 30 μm, bonded to both sides of the polarizer, and further dried at 80 ° C. to obtain a polarizing plate (P001) Was made.

Examples 2-2 to 2-10 and comparative examples 2-1 to 2-3
In Example 2-1, instead of using the cellulose acylate film (001), a polarizing plate (P002) using any of the cellulose acylate films (002) to (010) and (101) to (103) To (P010) and (P101) to (P103).

[Evaluation of mounting on liquid crystal display]
A pair of polarizing plates provided on a 20-inch liquid crystal display device “LC-20V1” {manufactured by Sharp Corporation} using a TN type liquid crystal cell is peeled off, and instead of the above Examples 2-1 to 2-10, Each of the polarizing plates (P001) to (P0010) and (P101) to (P103) prepared in Comparative Examples 2-1 to 2-3 is placed on the viewer side and the backlight side one by one through the adhesive. A liquid crystal display device was manufactured by pasting. At this time, the transmission axis of the polarizing plate on the observer side and the transmission axis of the polarizing plate on the backlight side were arranged to be orthogonal to each other.

  The manufactured liquid crystal display device was treated for 48 hours in an environment of temperature 60 ° C. and humidity 90% RH, and then the backlight was lit continuously for 24 hours under the environmental conditions of temperature 25 ° C. and humidity 60% RH to display the entire surface in black. The state was visually observed in a dark room, and light leakage was evaluated according to the following criteria. The results are shown in Table 3.

(Evaluation criteria)
○: No light leakage is observed.
(Triangle | delta): Light leakage is observed a little, but it is not a problem practically.
X: There is a light leakage, which may cause a practical problem.

  As shown in Table 3, frame-like light leakage was observed on the display screen of the liquid crystal display device in the polarizing plate of the comparative example, whereas it was not observed or very slight in the polarizing plate of the present invention.

  The strength (elastic modulus), moisture permeability and dimensional change of the cellulose acylate film which is the transparent film of the present invention are good, and the liquid crystal display device comprising a polarizing plate produced using them has good durability. there were. It is considered that the large elastic modulus of the transparent film of the present invention and the small moisture permeability and dimensional change contributed to the improvement of light leakage.

On the other hand, the cellulose acylate films of Comparative Examples 1-1 to 1-3 were inferior in elastic modulus, moisture permeability, and dimensional change as compared with the cellulose acylate film of the present invention. Moreover, when it was set as the liquid crystal display device, durability was inadequate. Furthermore, in Comparative Example 1-2, the amount of the crosslinking agent increased to 20% was not able to be evaluated because the cellulose acylate film became brittle.

  As described above, the transparent film of the present invention and the liquid crystal display device using the same exhibited excellent performance.

Claims (7)

  A transparent film comprising an amino resin selected from the group consisting of a urea resin, a benzoguanamine resin, a glycoluril resin, and a mixture thereof, and cellulose acylate.   The transparent film according to claim 1, wherein the amino resin contains a structure formed by crosslinking an amino resin precursor.   The transparent film of Claim 1 or 2 containing the structure where the amino resin and the residual hydroxyl group of the cellulose acylate were bridge | crosslinked.   The transparent film of Claim 2 or 3 containing the structure where the amino resin precursor and the residual hydroxyl group of the cellulose acylate were bridge | crosslinked.   Transparent having a step of casting a cellulose acylate solution containing a cellulose acylate and an amino resin precursor (casting step) and a heating step of heating a film formed by the casting step A method for producing a film.   A polarizing plate using the transparent film according to any one of claims 1 to 4 or the transparent film produced by the production method according to claim 5 as a protective film for a polarizer.   A liquid crystal display using at least one of the transparent film according to any one of claims 1 to 4, the transparent film produced by the production method according to claim 5, or the polarizing plate according to claim 6. apparatus.