JP5268482B2 - Transparent polymer film and manufacturing method thereof, retardation film, polarizing plate and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transparent polymer film having in-plane retardation with reverse wavelength dispersion and having thickness-direction retardation with normal wavelength dispersion. <P>SOLUTION: The transparent polymer film is characterized in that: the wavelength dispersion of the in-plane retardation shows reverse wavelength dispersion; the thickness-direction retardation shows normal wavelength dispersion; and the film includes an in-plane slow phase axis at a wavelength of 500 nm in a direction perpendicular to the in-plane orientation direction of the polymer. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a method for producing a transparent polymer film in which in-plane retardation is subjected to inverse wavelength dispersion. The present invention also relates to a transparent polymer film, a retardation film, a polarizing plate and a liquid crystal display device produced by the production method.

  The demand for optical films with controlled retardation is expanding rapidly. Examples include λ / 4 plates used for optical disk pickups and PS conversion element applications, and optical compensation films that improve the viewing angle dependency of images of liquid crystal display devices. In these optical films, it is necessary not only to design a retardation at a specific wavelength to a desired value, but also to design a retardation over a wide wavelength range. In particular, a λ / 4 plate, an optical compensation film for a VA mode liquid crystal display device, and an optical compensation film for an IPS mode liquid crystal display device are required to have a longer in-plane retardation (reverse wavelength dispersion). Moreover, in order to improve productivity by bonding the said optical compensation film with a polarizing plate by roll-to-roll, it is calculated | required that the slow axis of the said optical compensation film expresses in a film width direction.

In Patent Documents 1 and 2, as a method of providing a transparent polymer film that has optical anisotropy and can be directly bonded to a polarizing plate, a cellulose acylate film is transported and heat-treated at 200 ° C. or higher. The manufacturing method of the transparent polymer film characterized by including the process is disclosed.
JP 2007-086755 A JP 2007-084804 A

However, it has been found that the above production method has a problem that the degree of freedom in controlling the chromatic dispersion of the in-plane retardation is small. In particular, it has been difficult to produce a film having a larger in-plane retardation for longer wavelengths. In order to solve the problems of the prior art, the present inventors have studied for the purpose of the present invention to provide a method for reverse wavelength dispersion of in-plane retardation of a transparent polymer film. In the present invention, “reverse wavelength dispersion” means changing ΔRe in the positive direction, and specifically means that ΔRe ^ad ₈₀ described later becomes positive.

  The present inventors considered using an additive to solve the problem, but how the various additives are oriented and how they act during the manufacturing process of the transparent polymer film. I could not grasp it easily. As a result of extensive studies, it has been found that the problems of the prior art can be solved by heat-treating a cellulose acylate film containing an additive that satisfies a specific condition under a specific temperature condition. That is, the following present invention has been provided as means for solving the problems.

[1] A cellulose acylate film containing a compound in which the wavelength dispersion parameter ΔΔn ⁰ _{calc of} intrinsic birefringence defined by the following formula (1) is negative is a temperature T (unit; A method for producing a transparent polymer film comprising a step of heat-treating at a temperature of ° C.
Formula (1): ΔΔn ⁰ _calc = Δn ⁰ _calc (630 nm) −Δn ⁰ _calc (450 nm)
[In the above equation, Δn ⁰ _calc (630 nm) represents intrinsic birefringence at a measurement wavelength of 630 nm, and Δn ⁰ _calc (450 nm) represents intrinsic birefringence at a measurement wavelength of 450 nm. ]
Formula (2): Tc ≦ T <Tm ₀
[Wherein, Tc represents the crystallization temperature (unit: ° C.) of the cellulose acylate film before heat treatment, and Tm ₀ represents the melting point (unit: ° C.) of the cellulose acylate film before heat treatment. ]
[2] The method for producing a transparent polymer film according to [1], wherein the compound satisfies the following formula (3).
Formula (3): (A-1) × ΔΔn ⁰ _calc ≦ −0.01
[Wherein, A represents the aspect ratio of the compound. ]
[3] The method for producing a transparent polymer film according to [1] or [2], wherein the cellulose acylate film is stretched in the heat treatment step.
[4] The method for producing a transparent polymer film according to [3], wherein the stretching is longitudinal stretching performed in an apparatus having a heating zone between two or more nip rolls.
[5] The method for producing a transparent polymer film according to any one of [1] to [4], wherein the cellulose acylate constituting the cellulose acylate film satisfies the following formula (4).
Formula (4): 2.70 <SA + SB ≦ 3.00
[Wherein, SA represents the degree of substitution of the acetyl group substituted by the hydroxyl group of cellulose, and SB represents the degree of substitution of the acyl group having 3 or more carbon atoms substituted by the hydroxyl group of cellulose. ]

[6] A transparent polymer film produced by the production method of any one of [1] to [5].
[7] The transparent polymer film according to [6], wherein the following formulas (5) and (6) are satisfied at the same time.
Formula (5): Re (550 nm)> 0
Formula (6): ΔRe> 0
[In the formula, Re (λ) represents an in-plane retardation value (unit: nm) when the measurement wavelength is λ. ΔRe represents the difference between the in-plane retardation values when the measurement wavelengths are 630 nm and 450 nm, Re (630 nm) −Re (450 nm) (unit: nm). ]
[8] The transparent polymer film according to [6] or [7], wherein the following formulas (5a) and (5b) are satisfied simultaneously.
Formula (5a): Re (550 nm) = 20 to 300
Formula (5b): ΔRe = 10 to 100

[9] A retardation film comprising at least one transparent polymer film according to any one of [6] to [8].
[10] A polarizing plate comprising at least one transparent polymer film according to any one of [6] to [8].
[11] The polarizing plate according to [10], wherein the transparent polymer film is directly bonded to a polarizing film.
[12] At least one sheet of the transparent polymer film according to any one of [6] to [8], the retardation film according to [9], or the polarizing plate according to [10] or [11]. A liquid crystal display device comprising:

  According to the production method of the present invention, a transparent polymer film in which in-plane retardation is dispersed in reverse wavelength can be provided. According to the present invention, a transparent polymer film having such properties, a retardation film using the same, a polarizing plate and a liquid crystal display device can also be provided.

  Below, the transparent polymer film of this invention, its manufacturing method, etc. are demonstrated 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.

<< Method for producing transparent polymer film >>
[Cellulose acylate]
First, cellulose acylate that can be used in the method for producing a transparent polymer film of the present invention will be described.
The cellulose acylate film heat-treated by the production method of the present invention is a film in which the polymer as a main component constituting the film is cellulose acylate. Here, the “polymer as the main component” indicates a polymer when the film is composed of a single polymer, and when the film is composed of a plurality of polymers, the most mass fraction of the constituent polymers. This indicates a high polymer.

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. The number of carbon atoms of the acyl group is preferably 2 to 22, more preferably 2 to 4, and most preferably 2. 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 more preferable, and an acetyl group is most preferable.
The cellulose acylate may be an ester of cellulose and a plurality of carboxylic acids. That is, the cellulose acylate may be substituted with a plurality of acyl groups.

When the substitution degree of the acetyl group (carbon number 2) substituted on the hydroxyl group of cellulose of cellulose acylate is SA and the substitution degree of the acyl group of 3 or more carbon atoms substituted on the hydroxyl group of cellulose is SB, By adjusting SA and SB, it is possible to adjust the Re expression of the transparent polymer film produced by the production method of the present invention and the humidity dependency of the retardation. In addition, Tc can be adjusted, whereby the heat treatment temperature can be adjusted. The humidity dependency of retardation is a change in retardation due to humidity.
SA + SB is appropriately adjusted depending on the optical characteristics required for the transparent polymer film produced by the production method of the present invention, which is the film of the present invention, but preferably 2.70 <SA + SB ≦ 3.00, more Is 2.88 ≦ SA + SB ≦ 3.00, more preferably 2.89 ≦ SA + SB ≦ 2.99, still more preferably 2.90 ≦ SA + SB ≦ 2.98, and particularly preferably 2.92. ≦ SA + SB ≦ 2.97. By increasing SA + SB, Re obtained after the heat treatment can be increased, Tc can be further decreased, and the humidity dependency of retardation can also be improved. By setting Tc low, the heat treatment temperature can be set relatively low.
Moreover, the humidity dependence of the retardation of the transparent polymer film manufactured by the manufacturing method of this invention can be adjusted by adjusting SB. By increasing SB, the humidity dependency of retardation can be reduced, and the melting point is lowered. In consideration of the humidity dependence of the retardation and the balance of the melting point, the range of SB is preferably 0 <SB ≦ 3.0, more preferably 0 <SB ≦ 1.0, and still more preferably 0.1 ≦ SB ≦ 0.7. When all the hydroxyl groups of cellulose are substituted, the degree of substitution is 3.

Cellulose acylate can be synthesized by a known method.
For example, the basic principle of the cellulose acylate synthesis method 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 a suitable amount of carboxylic acid such as acetic acid, and then esterified by introducing into a pre-cooled acylated mixture to 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 degree of polymerization 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 degree of polymerization and molecular weight distribution of cellulose acylate can be measured by gel permeation chromatography (GPC) or the like.
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).

As a cellulose acylate used as a raw material when producing a cellulose acylate film, a powder or a particulate material can be used, and a pelletized one can also be used. The water content of cellulose acylate when used as a raw material 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 cellulose acylate is not within the preferred range, it is preferable to use the cellulose acylate after drying it by drying air or heating.
When producing a cellulose acylate film, a single type of polymer may be used, or a plurality of types of polymers may be used.

[Additive compound of the present invention]
In the production method of the present invention, a cellulose acylate film containing a compound satisfying a specific condition as an additive is used. That is, a cellulose acylate film containing a compound having a negative wavelength dispersion parameter ΔΔn ⁰ _{calc of} intrinsic birefringence (hereinafter referred to as an additive compound of the present invention) is used.

The additive compound of the present invention has a negative chromatic dispersion parameter ΔΔn ⁰ _{calc of} intrinsic birefringence, preferably −0.5 <ΔΔn ⁰ _calc <−0.05, more preferably −0.3 <ΔΔn. ⁰ _calc <−0.1. Although the effect of changing the reverse wavelength dispersion direction the chromatic dispersion of as the wavelength dispersion parameter ΔΔn ⁰ _calc intrinsic birefringence is less film is large, ΔΔn ⁰ _calc small additives often have an absorption in the visible light range, the film Since addition causes coloration of the film, ΔΔn ⁰ _calc preferably satisfies the above range. The chromatic dispersion parameter ΔΔn ⁰ _calc of intrinsic birefringence in ΔΔn ⁰ _calc is defined by the following equation (1).
Formula (1): ΔΔn ⁰ _calc = Δn ⁰ _calc (630 nm) −Δn ⁰ _calc (450 nm)
In equation (1), Δn ⁰ _calc (630 nm) represents the intrinsic birefringence at a measurement wavelength of 630 nm, and Δn ⁰ _calc (450 nm) represents the intrinsic birefringence at a measurement wavelength of 450 nm. The intrinsic birefringence Δn ⁰ _calc (λ) [where λ represents the measurement wavelength] is defined by the following equation (1a).
Formula (1a): Δn ⁰ _calc (λ) = n ⁰ _{i calc} (λ) − (n ⁰ _{j calc} (λ) + n ⁰ _{k calc} (λ)) / 2
In equation (1a), n ⁰ _{i calc} (λ), n ⁰ _{j calc} (λ), and n ⁰ _{k calc} (λ) represent main refractive indexes, and in the present invention, values calculated by theoretical calculation are used.
All the theoretical calculations here are performed using Gaussian 03 (Gaussian, USA), and the density functional method is used as the method. In addition, the molecular structure used for the calculation is a structure in which the generation energy is minimized by performing the structure optimization calculation. Using B3LYP / 6-31G ^* as a basis function, a polarizability tensor at wavelengths of 450 nm and 630 nm is obtained. Of the principal axes of the polarizability tensor, the principal axis closest to the molecular major axis direction (the principal axis with the smallest angle with the molecular major axis direction) is i, the other principal axes are j, k, and the polarizability tensor diagonal The components α _ii , α _jj , and α _kk are obtained.
Using the polarizability tensor, n ⁰ _{l calc} (λ) is calculated from the following formulas (1b) and (1c) (Vuks formula, which is an extended version of the Lorentz-Lorenz formula), and the above formula ( Δn ⁰ _calc (λ) is obtained from 1a).

［式（１ｂ）および（１ｃ）において、n_lは主屈折率（n⁰ _{l calc}（λ））、α_llは分極率テンソル成分、ρは密度、N_Aはアボガドロ数、Mは分子量、nは平均屈折率を表す。］

[In the formulas (1b) and (1c), n _l is the principal refractive index (n ⁰ _{l calc} (λ)), α _ll is the polarizability tensor component, ρ is the density, N _A is the Avogadro number, M is the molecular weight, n Represents an average refractive index. ]

It is preferable that the additive compound of the present invention further satisfies the following formula (3).
Formula (3): (A-1) × ΔΔn ⁰ _calc ≦ −0.01
In formula (3), A represents the aspect ratio of the compound molecule. The aspect ratio A is expressed by a / b using the length a of the molecular long axis and the length b of the molecular short axis. The length a of the molecular long axis is the maximum value of the distance between two atoms in the molecule, and the length b of the molecular short axis is 2 of the perpendicular length when a perpendicular is drawn from each atom n to the molecular long axis. This is the maximum value of b (n) when the double is b (n).
The larger the aspect ratio A, the easier the orientation of the additive, so that the retardation anisotropy can be expressed more and the effect of changing the wavelength dispersion of the film is greater. When the orientation of the additive is the same, the smaller the ΔΔn ⁰ _calc is, the greater the effect of changing the wavelength dispersion of the film in the reverse wavelength dispersion direction. Accordingly, (A-1) × ΔΔn ⁰ _calc is preferably small. When (A-1) × ΔΔn ⁰ _calc > −0.01, the effect of changing the wavelength dispersion of the film in the reverse wavelength dispersion direction is small and impractical, so the additive compound of the present invention satisfies the formula (3). preferable.
The additive compound of the present invention more preferably satisfies the following formula (3a), and more preferably satisfies the following formula (3b).
Formula (3a): −1.0 <(A-1) × ΔΔn ⁰ _calc ≦ −0.02
Formula (3b): −0.5 <(A−1) × ΔΔn ⁰ _calc ≦ −0.05

The additive compound of the present invention is expressed by any one of the following general formulas (I) to (VI) in addition to the negative wavelength dispersion parameter ΔΔn ⁰ _{calc of} intrinsic birefringence defined by the above formula (1) being negative. It is preferable that it is a compound. Among general formulas (I) to (VI), compounds represented by general formulas (I), (II), and (III) are more preferable, and compounds represented by general formula (I) are more preferable.

R ¹¹ , R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ , R ¹⁶ , and R ^{17 in the} above general formula (I); R ²¹ , R ²² , R ²³ , R ²⁴ , R ^{25 in the} above general formula (II) , R ²⁶ , R ²⁷ , R ²⁸ , and R ²⁹ ; R ⁴¹ , R ⁴² , R ⁴³ , R ⁴⁴ , R ⁴⁵ , R ⁴⁶ , and R ^{47 in the} above general formula (III); in the above general formula (IV) R ⁵¹ , R ⁵² , R ⁵³ , R ⁵⁴ , R ⁵⁵ , R ⁵⁶ , and R ⁵⁷ ; R ⁶¹ , R ⁶² , R ⁶³ , R ⁶⁴ , R ⁶⁵ , R ⁶⁶ , R ⁶⁷ in the general formula (V) And R ⁶⁸ ; R ⁷¹ , R ⁷² , R ⁷³ , R ⁷⁴ , R ⁷⁵ and R ⁷⁶ in the above general formula (VI) each independently represent a hydrogen atom or a substituent each independently represents a hydrogen atom or a substituent.

These substituents are selected in combination so as to satisfy ΔΔn ⁰ _calc <0. In the above general formulas (I) to (VI), it is preferable to combine the substituents so that the horizontal direction (left-right direction) of the paper surface is the molecular major axis direction.

  Preferably, the substituent is preferably a halogen atom (for example, a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom), an alkyl group (preferably an alkyl group having 1 to 30 carbon atoms, more preferably an alkyl group having 1 to 10 carbon atoms, for example, Methyl group, ethyl group, n-propyl group, isopropyl group, tert-butyl group, n-octyl group, 2-ethylhexyl group), cycloalkyl group (preferably having 3 to 30 carbon atoms, more preferably 3 carbon atoms) 10 to 10 substituted or unsubstituted cycloalkyl groups such as cyclohexyl group, cyclopentyl group, 4-n-dodecylcyclohexyl group, bicycloalkyl group (preferably having 5 to 30 carbon atoms, more preferably 5 to 5 carbon atoms). 10 substituted or unsubstituted bicycloalkyl groups, ie preferably 5 to 30 carbon atoms, more preferably carbon A monovalent group obtained by removing one hydrogen atom from a bicycloalkane having 5 to 10 atoms, for example, bicyclo [1.2.2] heptan-2-yl, bicyclo [2.2.2] octane-3 -Yl), an alkenyl group (preferably a substituted or unsubstituted alkenyl group having 2 to 30 carbon atoms, more preferably 2 to 10 carbon atoms, such as a vinyl group or an allyl group), a cycloalkenyl group (preferably carbon). A substituted or unsubstituted cycloalkenyl group having 3 to 30 atoms, more preferably 3 to 10 carbon atoms, that is, preferably a hydrogen of a cycloalkene having 3 to 30 carbon atoms, more preferably 3 to 10 carbon atoms. Monovalent groups with one atom removed, for example, 2-cyclopenten-1-yl, 2-cyclohexen-1-yl), bicycloalkenyl groups (substituted or unsubstituted) A substituted bicycloalkenyl group, preferably a substituted or unsubstituted bicycloalkenyl group having 5 to 30 carbon atoms, more preferably 5 to 10 carbon atoms, that is, one hydrogen atom of a bicycloalkene having one double bond was removed. Monovalent groups such as bicyclo [2.2.1] hept-2-en-1-yl, bicyclo [2.2.2] oct-2-en-4-yl), alkynyl groups (preferably Is a substituted or unsubstituted alkynyl group having 2 to 30 carbon atoms, more preferably 2 to 10 carbon atoms, such as an ethynyl group or a propargyl group, and an aryl group (preferably having 6 to 30 carbon atoms, more preferably A substituted or unsubstituted aryl group having 6 to 10 carbon atoms, such as a phenyl group, a p-tolyl group or a naphthyl group, or a heterocyclic group (preferably a 5- or 6-membered substituted or unsubstituted group). Is a monovalent group obtained by removing one hydrogen atom from an unsubstituted aromatic or non-aromatic heterocyclic compound, more preferably 3 to 30 carbon atoms, more preferably 3 to 10 carbon atoms. It is a 5- or 6-membered aromatic heterocyclic group. For example, 2-furyl group, 2-thienyl group, 2-pyrimidinyl group, 2-benzothiazolyl group),

A cyano group, a hydroxyl group, a nitro group, a carboxyl group, an alkoxy group (preferably a substituted or unsubstituted alkoxy group having 1 to 30 carbon atoms, more preferably 1 to 10 carbon atoms, such as a methoxy group, an ethoxy group, Isopropoxy group, tert-butoxy group, n-octyloxy group, 2-methoxyethoxy group), aryloxy group (preferably having 6 to 30 carbon atoms, more preferably 6 to 10 carbon atoms, substituted or unsubstituted) Aryloxy groups such as phenoxy group, 2-methylphenoxy group, 4-tert-butylphenoxy group, 3-nitrophenoxy group, 2-tetradecanoylaminophenoxy group), silyloxy group (preferably having 3 to 20 carbon atoms) More preferably a silyloxy group having 3 to 10 carbon atoms, such as a trimethylsilyloxy group, te rt-butyldimethylsilyloxy group), a heterocyclic oxy group (preferably a substituted or unsubstituted heterocyclic oxy group having 2 to 30 carbon atoms, more preferably 2 to 10 carbon atoms, 1-phenyltetrazole-5- Oxy group, 2-tetrahydropyranyloxy group), acyloxy group (preferably formyloxy group, C2-C30, more preferably C2-C10 substituted or unsubstituted alkylcarbonyloxy group, carbon atom A substituted or unsubstituted arylcarbonyloxy group having 6 to 30 carbon atoms, more preferably 6 to 10 carbon atoms, such as formyloxy group, acetyloxy group, pivaloyloxy group, stearoyloxy group, benzoyloxy group, p-methoxyphenyl Carbonyloxy group), carbamoyloxy group (preferably 1 carbon atom) 30, more preferably a substituted or unsubstituted carbamoyloxy group having 1 to 10 carbon atoms, such as N, N-dimethylcarbamoyloxy group, N, N-diethylcarbamoyloxy group, morpholinocarbonyloxy group, N, N- Di-n-octylaminocarbonyloxy group, Nn-octylcarbamoyloxy group), alkoxycarbonyloxy group (preferably substituted or unsubstituted alkoxycarbonyl having 2 to 30 carbon atoms, more preferably 2 to 10 carbon atoms) An oxy group, such as a methoxycarbonyloxy group, an ethoxycarbonyloxy group, a tert-butoxycarbonyloxy group, an n-octylcarbonyloxy group, an aryloxycarbonyloxy group (preferably having 7 to 30 carbon atoms, more preferably a carbon atom) Number 7-10 substitution or nothing Conversion aryloxycarbonyloxy group, e.g., phenoxycarbonyl group, p- methoxyphenoxy carbonyloxy group, p-n-hexadecyloxycarbonyl phenoxycarbonyl group),

An amino group (preferably an amino group, 1 to 30 carbon atoms, more preferably a substituted or unsubstituted alkylamino group having 1 to 10 carbon atoms, 6 to 30 carbon atoms, more preferably 6 to 6 carbon atoms); 10 substituted or unsubstituted anilino groups such as amino group, methylamino group, dimethylamino group, anilino group, N-methyl-anilino group, diphenylamino group), acylamino group (preferably formylamino group, carbon atom) A substituted or unsubstituted alkylcarbonylamino group having 1 to 30 carbon atoms, more preferably 1 to 10 carbon atoms, and a substituted or unsubstituted arylcarbonylamino group having 6 to 30 carbon atoms, more preferably 6 to 10 carbon atoms Group, for example, formylamino group, acetylamino group, pivaloylamino group, lauroylamino group, benzoylamino group) An aminocarbonylamino group (preferably a substituted or unsubstituted aminocarbonylamino group having 1 to 30 carbon atoms, more preferably 1 to 10 carbon atoms, such as a carbamoylamino group, an N, N-dimethylaminocarbonylamino group; , N, N-diethylaminocarbonylamino group, morpholinocarbonylamino group), alkoxycarbonylamino group (preferably a substituted or unsubstituted alkoxycarbonylamino group having 2 to 30 carbon atoms, more preferably 2 to 10 carbon atoms, such as , Methoxycarbonylamino group, ethoxycarbonylamino group, tert-butoxycarbonylamino group, n-octadecyloxycarbonylamino group, N-methyl-methoxycarbonylamino group), aryloxycarbonylamino group (preferably having 7 to 7 carbon atoms) 3 More preferably a substituted or unsubstituted aryloxycarbonylamino group having 7 to 10 carbon atoms, for example, phenoxycarbonylamino group, p-chlorophenoxycarbonylamino group, mn-octyloxyphenoxycarbonylamino group), sulfo Famoylamino group (preferably a substituted or unsubstituted sulfamoylamino group having 0 to 30 carbon atoms, more preferably 0 to 10 carbon atoms, such as sulfamoylamino group, N, N-dimethylamino Sulfonylamino group, Nn-octylaminosulfonylamino group), alkyl and arylsulfonylamino groups (preferably substituted or unsubstituted alkylsulfonylamino having 1 to 30 carbon atoms, more preferably 1 to 10 carbon atoms, 6 to 30 carbon atoms, more preferably 6 carbon atoms 10 substituted or unsubstituted arylsulfonylamino groups, for example, methylsulfonylamino group, butylsulfonylamino group, phenylsulfonylamino group, 2,3,5-trichlorophenylsulfonylamino group, p-methylphenylsulfonylamino group), Mercapto group, alkylthio group (preferably a substituted or unsubstituted alkylthio group having 1 to 30 carbon atoms, more preferably 1 to 10 carbon atoms, such as methylthio group, ethylthio group, n-hexadecylthio group), arylthio group ( Preferably a substituted or unsubstituted arylthio group having 6 to 30 carbon atoms, more preferably 6 to 10 carbon atoms, such as phenylthio group, p-chlorophenylthio group, m-methoxyphenylthio group),

Heterocyclic thio group (preferably a substituted or unsubstituted heterocyclic thio group having 2 to 30 carbon atoms, more preferably 2 to 10 carbon atoms, such as 2-benzothiazolylthio group, 1-phenyltetrazole-5 -Ylthio group), a sulfamoyl group (preferably a substituted or unsubstituted sulfamoyl group having 0 to 30 carbon atoms, more preferably 0 to 10 carbon atoms, such as an N-ethylsulfamoyl group, N- (3- Dodecyloxypropyl) sulfamoyl group, N, N-dimethylsulfamoyl group, N-acetylsulfamoyl group, N-benzoylsulfamoyl group, N- (N′phenylcarbamoyl) sulfamoyl group), sulfo group, alkyl and Arylsulfinyl groups (preferably substituted or unsubstituted 1 to 30 carbon atoms, more preferably 1 to 10 carbon atoms) Or an unsubstituted alkylsulfinyl group, 6-30, more preferably a substituted or unsubstituted arylsulfinyl group having 6-10 carbon atoms, more preferably 6-10 carbon atoms, such as a methylsulfinyl group, ethylsulfinyl group. Group, phenylsulfinyl group, p-methylphenylsulfinyl group), alkyl and arylsulfonyl group (preferably a substituted or unsubstituted alkylsulfonyl group having 1 to 30 carbon atoms, more preferably 1 to 10 carbon atoms, carbon A substituted or unsubstituted arylsulfonyl group having 6 to 30 atoms, more preferably 6 to 10 carbon atoms, such as a methylsulfonyl group, an ethylsulfonyl group, a phenylsulfonyl group, a p-methylphenylsulfonyl group), an acyl group ( Preferably a formyl group, 2 to 30 carbon atoms, more preferably Or a substituted or unsubstituted alkylcarbonyl group having 2 to 10 carbon atoms, 7 to 30 carbon atoms, more preferably a substituted or unsubstituted arylcarbonyl group having 7 to 10 carbon atoms such as an acetyl group, Valoylbenzoyl group), aryloxycarbonyl group (preferably a substituted or unsubstituted aryloxycarbonyl group having 7 to 30 carbon atoms, more preferably 7 to 10 carbon atoms, such as phenoxycarbonyl group, o-chloro Phenoxycarbonyl group, m-nitrophenoxycarbonyl group, p-tert-butylphenoxycarbonyl group),

An alkoxycarbonyl group (preferably a substituted or unsubstituted alkoxycarbonyl group having 2 to 30 carbon atoms, more preferably 2 to 10 carbon atoms, such as methoxycarbonyl group, ethoxycarbonyl group, tert-butoxycarbonyl group, n- Octadecyloxycarbonyl group), a carbamoyl group (preferably a substituted or unsubstituted carbamoyl group having 1 to 30 carbon atoms, more preferably 1 to 10 carbon atoms, such as a carbamoyl group, an N-methylcarbamoyl group, N, N-dimethylcarbamoyl group, N, N-di-n-octylcarbamoyl group, N- (methylsulfonyl) carbamoyl group), aryl and heterocyclic azo groups (preferably having 6 to 30 carbon atoms, more preferably carbon atoms) 6-10 substituted or unsubstituted arylazo groups, 3 carbon atoms To 30 and more preferably a substituted or unsubstituted heterocyclic azo group having 3 to 10 carbon atoms, for example, phenylazo group, p-chlorophenylazo group, 5-ethylthio-1,3,4-thiadiazol-2-ylazo group ), An imide group (preferably an N-succinimide group, an N-phthalimide group), a phosphino group (preferably a substituted or unsubstituted phosphino group having 2 to 30 carbon atoms, more preferably 2 to 10 carbon atoms, such as , Dimethylphosphino group, diphenylphosphino group, methylphenoxyphosphino group), phosphinyl group (preferably a substituted or unsubstituted phosphinyl group having 2 to 30 carbon atoms, more preferably 2 to 10 carbon atoms, for example, Phosphinyl group, dioctyloxyphosphinyl group, diethoxyphosphinyl group), phosphinyloxy (Preferably a substituted or unsubstituted phosphinyloxy group having 2 to 30 carbon atoms, more preferably 2 to 10 carbon atoms, for example, diphenoxyphosphinyloxy group, dioctyloxyphosphinyloxy group) A phosphinylamino group (preferably a substituted or unsubstituted phosphinylamino group having 2 to 30 carbon atoms, more preferably 2 to 10 carbon atoms, such as a dimethoxyphosphinylamino group, dimethylaminophosphine, Finylamino group), silyl group (preferably a substituted or unsubstituted silyl group having 3 to 30 carbon atoms, more preferably 3 to 10 carbon atoms, such as trimethylsilyl group, tert-butyldimethylsilyl group, phenyl Dimethylsilyl group).

  Among the above substituents, those having a hydrogen atom may be substituted with the above groups after removing this. Examples of such functional groups include an alkylcarbonylaminosulfonyl group, an arylcarbonylaminosulfonyl group, an alkylsulfonylaminocarbonyl group, and an arylsulfonylaminocarbonyl group. Examples thereof include a methylsulfonylaminocarbonyl group, a p-methylphenylsulfonylaminocarbonyl group, an acetylaminosulfonyl group, and a benzoylaminosulfonyl group.

Among the above substituents, more preferable are a halogen atom, an alkyl group, an aryl group, an alkoxy group, a cyano group, a hydroxyl group, a carboxyl group, and an arylsulfonyl group, and more preferable are an alkyl group, an alkoxy group, A hydroxyl group, a carboxyl group, and a phenylsulfonyl group;
Moreover, when there are two or more substituents in one molecule, these substituents may be the same or different. Further, if possible, they may be linked to each other to form a ring (including a condensed ring with a ring described in the general formula).

  The molecular weight of the additive compound of the present invention is preferably 100 to 5000, more preferably 150 to 3000, and further preferably 200 to 1000. By adjusting the molecular weight of the additive compound within this range, it is possible to achieve both reduction in volatility of the additive from the film and improvement in solubility in the film (that is, reduction in bleed out).

  The addition amount of the additive compound of the present invention in the cellulose acylate film varies depending on the optical properties and the like imparted to the film, but is preferably 0.1 to 20% by mass, more preferably 0.5 to 15% by mass. Yes, more preferably 1 to 10% by mass. The additive compound of the present invention is preferably added and mixed in advance with a film-forming melt or solution before film formation.

[Cellulose acylate solution]
The cellulose acylate film used in the production method of the present invention (hereinafter also referred to as “cellulose acylate film before heat treatment” in the specification) is, for example, a cellulose acylate solution containing the cellulose acylate and various additives. Can be produced by a solution casting film forming method. Hereinafter, a cellulose acylate solution that can be used in the solution casting film forming method will be described.

(solvent)
As the main solvent of the cellulose acylate solution used for producing the “cellulose acylate film used in the production method 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 cellulose acylate solution used for the production of the “cellulose acylate film used in the production method of the present invention” is composed of a single solvent, it indicates that solvent. In this case, the solvent having the highest mass fraction among the constituent solvents is shown. Preferred examples of the main solvent include halogenated hydrocarbons.

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, toluene and the like.

  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. Preferred is an alcohol having 1 to 4 carbon atoms, more preferred is methanol, ethanol or butanol, and most preferred is methanol or butanol. 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.

Since the polymer constituting the cellulose acylate film of the present invention contains a hydrogen bonding functional group such as a hydroxyl group, an ester, or a ketone, it is 5 to 30% by mass in the total solvent, more preferably 7 to 25% by mass, It is preferable to contain 10-20 mass% alcohol from a viewpoint of the peeling load reduction from a casting support body preferably.
By adjusting the alcohol content, it is possible to easily adjust the expression of Re and Rth of the transparent polymer film produced by the production method of the present invention. Specifically, by increasing the alcohol content, the heat treatment temperature can be set relatively low, and the reach range of Re and Rth can be further increased.
In addition, the cellulose acylate solution used in the production of the cellulose acylate film used in the production method of the present invention has a small proportion of volatilization with the halogenated hydrocarbon at the initial stage of the drying process, and has a boiling point of 95 ° C. or higher. And 1 to 15% by mass, more preferably 1.5 to 13% by mass, and further preferably 2 to 10% by mass of an organic solvent which is a poor solvent for cellulose ester. In the present invention, it is effective to contain a small amount of water to increase the solution viscosity and the film strength of the wet film during drying, or to increase the dope strength during casting by the drum method. 0.1 to 5% by mass, more preferably 0.1 to 3% by mass, and particularly 0.2 to 2% by mass.

Although the example of the combination of the organic solvent preferably used as a solvent of the cellulose acylate solution used for preparation of the cellulose acylate film used for the manufacturing method of the present invention is given below, the present 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 / butanol / water = 85/18 / 1.5 / 0.5
(26) Dichloromethane / acetone / methanol / butanol / water = 87/5/5 / 2.5 / 0.5
(27) Dichloromethane / methanol = 92/8
(28) Dichloromethane / methanol = 90/10
(29) Dichloromethane / methanol = 87/13
(30) 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 cellulose acylate concentration in the cellulose acylate 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 cellulose acylate concentration can be adjusted to a predetermined concentration at the stage of dissolving the cellulose acylate in a solvent. Further, after preparing a low concentration (for example, 4 to 14% by mass) solution in advance, the solution may be concentrated by evaporating the solvent. Furthermore, after preparing a high concentration solution in advance, it may be diluted. Moreover, the density | concentration of a cellulose acylate can also be reduced by adding an additive.

(Additive)
The polymer solution used for the production of the cellulose acylate film used in the production method of the present invention includes various liquid or solid additives (additives other than the above-described additive compound of the present invention) according to the use in each preparation step. Can further be included. Examples of the additive include an ultraviolet absorber (0.001 to 1% by mass), a fine particle powder (0.001 to 1% by mass) having an average particle size of 5 to 3000 nm, and a fluorosurfactant (0 0.001 to 1% by mass), release agent (0.0001 to 1% by mass), deterioration inhibitor (0.0001 to 1% by mass), optical anisotropy control agent (0.01 to 10% by mass), infrared An absorbent (0.001 to 1% by mass) is included.

  The optical anisotropy controlling agent is an organic compound 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, these compounds can improve the hydrophobicity of the film and reduce the humidity change of the retardation when used in combination with the cellulose acylate particularly preferably used in the present invention. Moreover, the wavelength dependence of retardation can also be controlled effectively by using the ultraviolet absorber or the infrared absorber in combination. Any additive used in the cellulose acylate film of the present invention is preferably substantially free of volatilization during the drying process.

Among the optical anisotropy controlling agents, in the present invention, an optical anisotropy controlling agent that has an effect of increasing Rth of the cellulose acylate film before heat treatment is preferably used according to the intended Re and Rth values. be able to. The Rth increase width is more preferably 8 to 100 nm, further preferably 10 to 50 nm, and most preferably 15 to 30 nm. By adding such an additive, it is possible to selectively increase the Rth of the film (raw material) before the manufacturing method of the present invention is performed. By applying the above, it is possible to increase the Rth / Re value. For example, it is possible to manufacture a film that simultaneously satisfies Rth / Re ≧ −0.39, Re> 0, and Rth <0.
Further, depending on the intended Re and Rth values, an optical anisotropy controlling agent having an effect of not changing or decreasing the Rth of the film before the heat treatment can be preferably used. These Rth fluctuation ranges (Rth of the original fabric with the additive-Rth of the original fabric without the additive) are more preferably −100 or more and less than 8 nm, more preferably −50 to 5 nm, and most preferably −30 to 5 nm. . By adding such an additive, the mobility of polymer molecules during heat treatment can be improved, so that the expression of Re and Rth of the transparent polymer film produced by the production method of the present invention is further adjusted. Therefore, the heat treatment temperature can be set relatively low, and the reach range of Re and Rth can be increased. Therefore, by combining an optical anisotropy control agent such as a retardation increasing agent, not only a transparent polymer film satisfying | Rth | / Re <0.5, but also a transparent polymer film satisfying | Rth | /Re≧0.5 Can also be produced as appropriate.

In the present invention, the variation width of Rth due to the additive is Rth (Rth ₁ ) measured after the film was immersed in methanol at 25 ° C., ultrasonically extracted for 3 hours, and further dried at 80 ° C. for 10 minutes, It can be evaluated by the difference (Rth ₀ -Rth ₁ ) from Rth (Rth ₀ ) before methanol treatment. In addition, in the case of an additive that is difficult to extract with methanol, Rth (Rth ₂ ) before heat treatment of the film formed from the dope solution with the additive and the film formed from the dope solution with no additive added. It can also be evaluated by a difference (Rth ₂ −Rth ₃ ) from Rth (Rth ₃ ) before heat treatment.

Specifically, such an additive is preferably a compound having one or more aromatic rings, more preferably 2 to 15, more preferably 3 to 10. The atoms other than the aromatic ring in the compound are preferably arranged in the same plane as the aromatic ring, and when there are a plurality of aromatic rings, the aromatic rings may be arranged in the same plane. preferable. In order to selectively increase Rth, the presence state of the additive in the film is preferably such that the aromatic ring plane is in a direction parallel to the film surface.
The said additive may be used independently and may be used in combination of 2 or more types of additives.
Specific examples of the additive having an effect of increasing Rth include a plasticizer described on pages 33 to 34 of JP-A-2005-104148 and pages 38 to 89 of JP-A-2005-104148. And an optical anisotropy control agent.

  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 of addition increases, the glass transition temperature (Tg) of the polymer film decreases and the additive in the film production process It becomes easy to cause volatilization problem. 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.

  JP-A-2005-104148 describes an optical anisotropy control agent that can be suitably used when cellulose acylate is used as the polymer in the present invention. The infrared absorber is described in JP-A No. 2001-194522. The timing of adding the additive can be appropriately determined according to the type of the additive.

In the present invention, the following polymeric plasticizers can also be preferably used as additives.
Here, the polymer plasticizer in the present invention is characterized by having a repeating unit portion in the compound. The polymer plasticizer of the present invention has a number average molecular weight of 500 to 3000, preferably a number average molecular weight of 600 to 2800, more preferably a number average molecular weight of 700 to 2500, and particularly preferably a number average molecular weight. 700-2000. However, the high-molecular plasticizer in the present invention is not limited to those composed only of a compound having such a repeating unit portion, and may be a mixture with a compound having no repeating unit.

The polymer plasticizer of the present invention may be a liquid or a solid under the ambient temperature or humidity used (generally room temperature conditions, so-called 25 ° C., relative humidity 60%). Further, the smaller the color, the better, and it is particularly preferable that the color is colorless. Thermally, it is preferably stable at higher temperatures, and the decomposition start temperature is preferably 150 ° C. or higher, more preferably 200 ° C. or higher.
Hereinafter, the polymer plasticizer used in the present invention will be described in detail with specific examples, but the polymer plasticizer that can be used in the present invention is not limited thereto.

  The polymer plasticizer that can be used in the polymer film of the present invention is not particularly limited, but is a polyester plasticizer, a polyether plasticizer, a polyurethane plasticizer, a polyester polyurethane plasticizer, or a polyester polyether plasticizer. A number average molecular weight of 500 or more selected from an agent, a polyether polyurethane plasticizer, a polyamide plasticizer, a polysulfone plasticizer, a polysulfonamide plasticizer, and other polymer plasticizers described later The plasticizer can be preferably mentioned.

  At least one of them is polyester plasticizer, polyether plasticizer, polyurethane plasticizer, polyester polyurethane plasticizer, polyester polyether plasticizer, polyether polyurethane plasticizer, polyamide plasticizer, polysulfone More preferred are plasticizers and polysulfonamide plasticizers, and particularly preferred are polyester plasticizers, polyester polyurethane plasticizers, and polyester polyether plasticizers. Hereinafter, the polymeric plasticizers preferably used in the present invention will be described by type.

  First, the polyester plasticizer used in the present invention will be described. A preferred polyester plasticizer is not particularly limited, and is obtained by reaction of dicarboxylic acid and glycol. Both ends of the reaction product may remain as the reaction product, but a monocarboxylic acid or monoalcohol is further reacted. Thus, so-called end sealing may be performed. It is effective in terms of storage stability that the end capping is performed in order not to contain a free carboxylic acid. The dicarboxylic acid used in the polyester plasticizer of the present invention is preferably an aliphatic dicarboxylic acid residue having 4 to 12 carbon atoms or an aromatic dicarboxylic acid residue having 8 to 12 carbon atoms.

  Examples of the alkylene dicarboxylic acid component having 4 to 12 carbon atoms of the polyester plasticizer preferably used in the present invention include succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, and dodecanedicarboxylic acid. 1,4-cyclohexanedicarboxylic acid and the like. Examples of the arylene dicarboxylic acid component having 8 to 12 carbon atoms include phthalic acid, terephthalic acid, 1,5-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, and the like. These are used as one kind or a mixture of two or more kinds, respectively. Next, the glycol used for the polyester plasticizer will be described as an aliphatic or alicyclic glycol residue having 2 to 12 carbon atoms and an aromatic glycol residue having 6 to 12 carbon atoms.

  Examples of aliphatic glycols or alicyclic glycols having 2 to 12 carbon atoms include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 2-methyl-1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 2,2-diethyl-1 , 3-propanediol (3,3-dimethylolpentane), 2-n-butyl-2-ethyl-1,3-propanediol (3,3-dimethylolheptane), 3-methyl-1,5-pentanediol 1,6-hexanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-ethyl-1,3-hexanediol There are 2-methyl-1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-octadecanediol, etc., and these glycols are used as one kind or a mixture of two or more kinds. Is done.

  Moreover, it is preferable to protect with a monoalcohol residue or a monocarboxylic acid residue so that both ends of the polyester plasticizer of the present invention do not become carboxylic acid. In this case, the monoalcohol residue is preferably a substituted or unsubstituted monoalcohol residue having 1 to 30 carbon atoms, such as methanol, ethanol, propanol, isopropanol, butanol, isobutanol, pentanol, isopentanol, hexanol, isopropanol. Hexanol, cyclohexyl alcohol, octanol, isooctanol, 2-ethylhexyl alcohol, nonyl alcohol, isononyl alcohol, tert-nonyl alcohol, decanol, dodecanol, dodecahexanol, dodecaoctanol, allyl alcohol, oleyl alcohol and other aliphatic alcohols, benzyl alcohol And substituted alcohols such as 3-phenylpropanol.

  The end-capping alcohol residues that can be preferably used are methanol, ethanol, propanol, isopropanol, butanol, isobutanol, isopentanol, hexanol, isohexanol, cyclohexyl alcohol, isooctanol, 2-ethylhexyl alcohol, isononyl alcohol, Oleyl alcohol and benzyl alcohol, especially methanol, ethanol, propanol, isobutanol, cyclohexyl alcohol, 2-ethylhexyl alcohol, isononyl alcohol and benzyl alcohol.

  Moreover, when sealing with a monocarboxylic acid residue, the monocarboxylic acid used as a monocarboxylic acid residue is preferably a substituted or unsubstituted monocarboxylic acid having 1 to 30 carbon atoms. These may be aliphatic monocarboxylic acids or aromatic carboxylic acids. First, preferred aliphatic monocarboxylic acids are described. Examples include acetic acid, propionic acid, butanoic acid, caprylic acid, caproic acid, decanoic acid, dodecanoic acid, stearic acid, and oleic acid. Examples of aromatic monocarboxylic acids include benzoic acid. Acid, p-tert-butylbenzoic acid, orthotoluic acid, metatoluic acid, p-toluic acid, dimethyl benzoic acid, ethyl benzoic acid, normal propyl benzoic acid, aminobenzoic acid, acetoxybenzoic acid, etc., each of which is one or two It can be used as a mixture of seeds or more.

  As described above, specific preferred polyester plasticizers include poly (ethylene glycol / adipic acid) ester, poly (propylene glycol / adipic acid) ester, poly (1,3-butanediol / adipic acid) ester, and poly (propylene). Glycol / sebatic acid) ester, poly (1,3-butanediol / sebatic acid) ester, poly (1,6-hexanediol / adipic acid) ester, poly (propylene glycol / phthalic acid) ester, poly (1,3 -Both ends of butanediol / phthalic acid ester, poly (propylene glycol / terephthalic acid) ester, poly (propylene glycol / 1,5-naphthalene-dicarboxylic acid) ester, poly (propylene glycol / terephthalic acid) ester are 2- Ethyl-hexyl alcohol Examples thereof include 2-ethyl-hexyl alcohol ester and acetylated poly (butanediol / adipic acid) ester at both ends of steal / poly (propylene glycol, adipic acid) ester.

  Such polyesters can be synthesized by a conventional method, such as a hot melt condensation method using a polyesterification reaction or a transesterification reaction between the dibasic acid or an alkyl ester thereof and a glycol, or an acid chloride of these acids and a glycol. It can be easily synthesized by any of the interfacial condensation methods. These polyester plasticizers are described in detail in Koichi Murai, “Plasticizers, Theory and Applications” (Koshobo Co., Ltd., first edition published on March 1, 1973). In addition, Japanese Patent Laid-Open Nos. 05-155809, 05-155810, Japanese Patent Laid-Open Nos. 05-97073, 2006-259494, 07-330670, 2006-342227, 2007-003679. The materials described in each publication can also be used.

  In addition, as a product, ADEKA Co., Ltd. can use Adeka Sizer (various Adeka Sizer P series and Adeka Sizer PN series) as described in DIARY 2007, pages 55-27 as a polyester plasticizer. Kogyo Co., Ltd. “Polymer-related Product List 2007” on page 25, various products of Polylite, Dainippon Ink and Chemicals, Inc. “DIC Polymer Modifier” (issued 2004.4.1.000VIII) 2-5 Various types of polysizers described in (1) can be used. Furthermore, it is available as Plasthall P series made by CP HALL, USA. Benzoyl functionalized polyethers are commercially available from Velsicol Chemicals, Rosemont, Ill. Under the trade name BENZOFLEX (eg, BENZOFLEX 400, polypropylene glycol dibenzoate).

  Next, the polyester polyether plasticizer used in the present invention will be described. The polyester polyether plasticizer of the present invention refers to a condensation polymer of dicarboxylic acid and polyether diol. As the dicarboxylic acid, an aliphatic dicarboxylic acid residue having 4 to 12 carbon atoms or an aromatic dicarboxylic acid residue having 8 to 12 carbon atoms described in the polyester plasticizer is used as it is.

  Next, examples of the polyethers having an aliphatic glycol having 2 to 12 carbon atoms include polyethylene ether glycol, polypropylene ether glycol, polytetramethylene ether glycol, and combinations thereof. Typical useful commercially available polyether glycols include Carbowax resin, Pluronics resin and Niax resin. In the production of the polyester polyether plasticizer used in the present invention, a commonly used polymerization method known to those skilled in the art can be used.

  Examples of these polyester ether plasticizers include polyester polyether plasticizers described in US Pat. No. 4,349,469. Basically, it is a polyester polyether plasticizer synthesized from, for example, 1,4-cyclohexanedicarboxylic acid as dicarboxylic acid and 1,4-cyclohexanedimethanol and polytetramethylene ether glycol as polyether. Other useful polyester polyether plasticizers include commercially available resins such as DuPont's Hytrel copolyesters and copolymers such as GAF's Galflex polymer. For these, the materials described in JP-A-5-197073 can be used. It is commercially available as ADEKA Sizer RS series from ADEKA Corporation. Polyester ether plasticizers that are alkyl functionalized polyalkylene oxides are commercially available from ICI Chemicals, Wilmington, Del., Under the trade name PYCAL (eg, PYCAL 94, a phenyl ester of polyethylene oxide). ).

(Polyester polyurethane plasticizer)
Further, the polyester polyurethane plasticizer used in the present invention will be described. The plasticizer can be obtained by condensation of polyester and an isocyanate compound. First, as the polyester, the polyester plasticizer before sealing both ends can be used as it is, and the materials described above for the polyester plasticizer can be preferably used.

Examples of the diisocyanate component forming the polyurethane structure include OCN (CH ₂ ) _p NCO (p = 2) represented by ethylene diisocyanate, trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate and the like. -8) Polymethylene isocyanate and aromatic diisocyanates such as p-phenylene diisocyanate, tolylene diisocyanate, p, p'-diphenylmethane diisocyanate, 1,5-naphthylene diisocyanate, Although m-xylylene diisocyanate or the like is used, it is not limited thereto. Among these, tolylene diisocyanate, m-xylylene diisocyanate, and tetramethylene diisocyanate are particularly preferable.

  In the present invention, the polyester polyurethane plasticizer can be easily synthesized by a conventional synthesis method in which the raw material polyester diol and diisocyanate are mixed and heated with stirring. For these, the materials described in JP-A-5-197073, JP-A-2001-122979, JP-A-2004-175971, JP-A-2004-175972 and the like can be used.

  In the present invention, not only the polyester plasticizer, polyester polyether plasticizer and polyester polyurethane plasticizer described above, but also other polymer plasticizers can be used. Examples of the polymer plasticizer include aliphatic hydrocarbon polymers, alicyclic hydrocarbon polymers, acrylic polymers such as polyacrylates and polymethacrylates (the ester groups include methyl, ethyl, Propyl, butyl, isobutyl, pentyl, hexyl, cyclohexyl, octyl, 2-ethylhexyl, nonyl, isononyl, tert-nonyl, dodecyl, tridecyl, stearyl, oleyl, benzyl Group, phenyl group, etc.), vinyl polymers such as polyvinyl isobutyl ether and poly N-vinyl pyrrolidone, styrene polymers such as polystyrene and poly 4-hydroxystyrene, polyethers such as polyethylene oxide and polypropylene oxide, polyamides, polyurethanes and polyureas Phenol - formaldehyde condensate, urea - formaldehyde condensate, vinyl acetate, and the like.

  These polymer plasticizers may be a homopolymer composed of one type of repeating unit or a copolymer having a plurality of repeating structures. Two or more of the above polymers may be used in combination. These high molecular weight plasticizers may be used singly, or the same effect can be obtained by using them in combination. Among these, a polyacrylic acid ester, a polymethacrylic acid ester, or a copolymer with another vinyl monomer is preferable, and in particular, an acrylic polymer such as polyacrylic acid ester and polymethacrylic acid ester (the ester group is methyl). Group, ethyl group, propyl group, butyl group, hexyl group, cyclohexyl group, 2-ethylhexyl group, isononyl group, oleyl group).

Specific examples of preferred polymer plasticizers are described below, but the polymer plasticizers that can be used in the present invention are not limited to these.
PP-1: Condensation product with ethanediol / succinic acid (1/1 molar ratio) (number average molecular weight 2500)
PP-2: Condensate with 1,3-propanediol / glutaric acid (1/1 molar ratio) (number average molecular weight 1500)
PP-3: Condensate with 1,3-propanediol / adipic acid (1/1 molar ratio) (number average molecular weight 1300)
PP-4: Condensate with 1,3-propanediol / ethylene glycol / adipic acid (1/1/2 molar ratio) (number average molecular weight 1500)
PP-5: Condensation product with 2-methyl-1,3-propanediol / adipic acid (1/1 molar ratio) (number average molecular weight 1200)
PP-6: Condensate with 1,4-butanediol / adipic acid (1/1 molar ratio) (number average molecular weight 1500)
PP-7: Condensate with 1,4-cyclohexanediol / succinic acid (1/1 molar ratio) (number average molecular weight 800)

PP-8: butyl esterified product (number average molecular weight 1300) at both ends of the condensate with 1,3-propanediol / succinic acid (1/1 molar ratio)
PP-9: Cyclohexyl esterified compound (number average molecular weight 1500) at both ends of the condensate with 1,3-propanediol / glutaric acid (1/1 molar ratio)
PP-10: 2-ethylhexyl esterified product (number average molecular weight 3000) at both ends of the condensate with ethanediol / succinic acid (1/1 molar ratio)
PP-11: isononyl esterified product (number average molecular weight 1500) at both ends of the condensate with 1,3-propanediol / ethylene glycol / adipic acid (1/1/2 molar ratio)
PP-12: Propyl ester of both ends of the condensate with 2-methyl-1,3-propanediol / adipic acid (1/1 molar ratio) (number average molecular weight 1300)
PP-13: 2-ethylhexyl esterified compound (number average molecular weight 1300) at both ends of the condensate with 2-methyl-1,3-propanediol / adipic acid (1/1 molar ratio)
PP-14: Isononyl esterified product (number average molecular weight 1300) at both ends of the condensate with 2-methyl-1,3-propanediol / adipic acid (1/1 molar ratio)
PP-15: butyl esterified product (number average molecular weight 1800) at both ends of the condensate with 1,4-butanediol / adipic acid (1/1 molar ratio)

PP-16: Condensation product with ethanediol / terephthalic acid (1/1 molar ratio) (number average molecular weight 2000)
PP-17: Condensate with 1,3-propanediol / 1,5-naphthalenedicarboxylic acid (1/1 molar ratio) (number average molecular weight 1500)
PP-18: Condensation product with 2-methyl-1,3-propanediol / isophthalic acid (1/1 molar ratio) (number average molecular weight 1200)
PP-19: Condensate with 1,3-propanediol / terephthalic acid (1/1 molar ratio) benzyl esterified compound at both ends (number average molecular weight 1500)
PP-20: 1,3-propanediol / 1,5-naphthalenedicarboxylic acid condensate with a propyl esterified product (1/1 molar ratio) at both ends (number average molecular weight 1500)
PP-21: Condensation product of 2-methyl-1,3-propanediol / isophthalic acid (1/1 molar ratio) at both ends butyl esterified product (number average molecular weight 1200)

PP-22: Condensation with poly (average polymerization degree 5) propylene ether glycol / succinic acid (1/1 molar ratio) (number average molecular weight 1800)
PP-23: Condensation product (number average molecular weight 1600) with poly (average polymerization degree 3) ethylene ether glycol / glutaric acid (1/1 molar ratio)
PP-24: Condensation product (number average molecular weight 2200) with poly (average polymerization degree 4) propylene ether glycol / adipic acid (1/1 molar ratio)
PP-25: Condensation product (number average molecular weight 1500) with poly (average polymerization degree 4) propylene ether glycol / phthalic acid (1/1 molar ratio)

PP-26: Condensation product of poly (average polymerization degree 5) propylene ether glycol / succinic acid (1/1 molar ratio) at both ends butyl esterified product (number average molecular weight 1900)
PP-27: Condensation product with poly (average polymerization degree 3) ethylene ether glycol / glutaric acid (1/1 molar ratio) 2-ethylhexyl esterified compound (number average molecular weight 1700) at both ends
PP-28: Poly (average polymerization degree 4) tert-nonyl esterified product (number average molecular weight 1300) at both ends of the condensate with propylene ether glycol / adipic acid (1/1 molar ratio)
PP-29: Condensation product of poly (average polymerization degree 4) propylene ether glycol / phthalic acid (1/1 molar ratio) at both ends propyl esterified compound (number average molecular weight 1600)
PP-29 ′: Condensation product with ethanediol / adipic acid (1/1 molar ratio) (number average molecular weight 1000)

PP-30: A polyester urethane compound obtained by condensing a condensate (number average molecular weight 1500) with 1,3-propanediol / succinic acid (1/1 molar ratio) with trimethylene diisocyanate (1 mol),
PP-31: Polyester-urethane compound PP-32 obtained by condensing a condensate (number average molecular weight 1200) with 1,3-propanediol / glutaric acid (1/1 molar ratio) with tetramethylene diisocyanate (1 mol). : Polyester-urethane compound PP-33 obtained by condensing a condensate (number average molecular weight 1000) with 1,3-propanediol / adipic acid (1/1 molar ratio) with p-phenylene diisocyanate (1 mol): 1 Polyester-urethane compound PP-34 obtained by condensing a condensate (number average molecular weight 1500) with 1,3-propanediol / ethylene glycol / adipic acid (1/1/2 molar ratio) with tolylene diisocyanate (1 mol): A condensate (number average molecular weight 1200) with 2-methyl-1,3-propanediol / adipic acid (1/1 molar ratio) Polyester-urethane compound PP-35 condensed with m-xylylene diisocyanate (1 mol): a condensate (number average molecular weight 1500) with 1,4-butanediol / adipic acid (1/1 molar ratio) is tetramethylene. Polyester-urethane compound condensed with diisocyanate (1 mole)

PP-36: Polyisopropyl acrylate (number average molecular weight 1300)
PP-37: Polybutyl acrylate (number average molecular weight 1300)
PP-38: Polyisopropyl methacrylate (number average molecular weight 1200)
PP-39: Poly (methyl methacrylate / butyl methacrylate (molar ratio 8/2, number average molecular weight 1600)
PP-40: Poly (methyl methacrylate / 2-ethylhexyl methacrylate (molar ratio 9/1, number average molecular weight 1600)
PP-41: poly (vinyl acetate (number average molecular weight 2400)

(Preparation of cellulose acylate solution)
Preparation of the cellulose acylate solution is, for example, disclosed in JP-A-58-127737, JP-A-61-106628, JP-A-2-276830, JP-A-4-259511, JP-A-5-163301, No. 9-95544, No. 10-45950, No. 10-95854, No. 11-71463, No. 11-302388, No. 11-322946, No. 11-322947, No. 11 No.-323017, JP-A 2000-53784, 2000-273184, 2000-273239, and the like. Specifically, the polymer and the solvent are mixed and stirred to swell, and optionally cooled or heated to dissolve and then filtered to obtain a cellulose acylate solution.

In the present invention, in order to improve the solubility of the polymer in the solvent, a step of cooling and / or heating the mixture of the polymer and the solvent may be included.
When a mixture of a polymer and a solvent is cooled using a halogen-based organic solvent as a solvent and cellulose acylate as a polymer, the mixture is preferably cooled to −100 to 10 ° C. Moreover, it is preferable to include the process swollen at -10-39 degreeC in the process before a cooling process, and the process heated to 0-39 degreeC in the process after cooling.

When using a halogen-based organic solvent as a solvent and heating a mixture of cellulose acylate and solvent, the method includes dissolving cellulose acylate in the solvent by one or more methods selected from the following (a) or (b): It is preferable.
(A) Swell at −10 to 39 ° C. and warm the resulting mixture to 0 to 39 ° C.
(B) Swell at −10 to 39 ° C., heat the obtained mixture to 40 to 240 ° C. at 0.2 to 30 MPa, and cool the heated mixture to 0 to 39 ° C.
Furthermore, when a non-halogen organic solvent is used as the solvent and the mixture of cellulose acylate and the solvent is cooled, it is preferable to include a step of cooling the mixture to −100 to −10 ° C. Moreover, it is preferable to include the process of swelling at -10-55 degreeC in the process before a cooling process, and the process heated to 0-57 degreeC in the process after cooling.

When using a halogen-based organic solvent as a solvent and heating a mixture of cellulose acylate and solvent, the method includes dissolving cellulose acylate in the solvent by one or more methods selected from the following (c) or (d) It is preferable.
(C) Swell at −10 to 55 ° C. and warm the resulting mixture to 0 to 57 ° C.
(D) Swell at −10 to 55 ° C., heat the obtained mixture to 40 to 240 ° C. at 0.2 to 30 MPa, and cool the heated mixture to 0 to 57 ° C.

[Film Formation of Cellulose Acylate Film Used for Production Method of the Present Invention]
The cellulose acylate film used in the production method of the present invention can be produced by the solution casting film formation method using the above cellulose acylate solution. In carrying out the solution casting film forming method, a conventional apparatus can be used in accordance with the conventional method. Specifically, the dope (cellulose acylate solution) prepared in a dissolving machine (kettle) is filtered, and then temporarily stored in a storage kettle, and the foam contained in the dope is defoamed and finally prepared. it can. 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 number of rotations. 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. Details of the casting process and the drying process of the solution casting film-forming method are also described in pages 120 to 146 of JP-A-2005-104148, and can be applied to the present invention as appropriate.

  Moreover, the cellulose acylate film used for the production method of the present invention can be produced by a melt casting film production method without using the cellulose acylate solution. The melt casting film forming method is a method in which a polymer melted by heating is cast on a support and cooled to form a film. If 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, it is possible to employ a melt casting film forming method. The melt casting film forming method is described in JP-A No. 2000-352620.

  In the present invention, a metal band or a metal drum can be used as a metal support used in forming a cellulose acylate film before heat treatment. When a cellulose acylate film formed using a metal band is used, there is a tendency that Rth of the film after heat treatment tends to be low, and depending on factors such as the above-mentioned additives and other retardation adjusting factors, Rth Is negative and a film with | Rth | / Re <0.5 can be produced. In addition, when a cellulose acylate film formed using a metal drum is used, there is a tendency that the Rth of the film after heat treatment tends to be high, and it depends on other retardation adjusting elements such as the additive. , Rth is close to zero, negative or positive, and in some cases, a film satisfying | Rth | / Re <0.5 can be produced. The difference in Rth after the heat treatment of the cellulose acylate film used in the production method of the present invention is due to the different external forces applied to the web during the film formation process, and the plane orientation of the polymer chains present in the film before the heat treatment Presumed to be due to the difference in state.

When controlling the retardation of the transparent polymer film produced by the production method of the present invention, the mechanical history applied to the cellulose acylate film before heat treatment, that is, the external force applied to the polymer web in the film forming process is controlled. It is preferable to keep it. Specifically, when the transparent polymer film produced by the production method of the present invention exhibits large Re and negative Rth, the polymer web is preferably 0.1% or more and less than 15%, more preferably Stretching is 0.5 to 10%, more preferably 1 to 8%. In addition, when producing while conveying the cellulose acylate film before heat processing, it is preferable to extend | stretch in the said conveyance direction. The residual solvent amount of the polymer web at the time of stretching is calculated based on the following formula and is 5 to 1000%. The amount of residual solvent is preferably 10 to 200%, more preferably 30 to 150%, and still more preferably 40 to 100%.
Residual solvent amount (% by mass) = {(MN) / N} × 100
[Wherein, M is the mass of the cellulose acylate film just before being inserted into the stretching zone, and N is the mass when the cellulose acylate film just before being inserted into the stretching zone is dried at 110 ° C. for 3 hours. Represent]
Moreover, when showing large Re and positive Rth, a polymer web is preferably extended | stretched 15 to 300%, More preferably, it is 18 to 200%, More preferably, it is 20 to 100%. In addition, when producing while conveying the cellulose acylate film before heat processing, it is preferable to extend | stretch in the said conveyance direction. The residual solvent amount of the polymer web at the time of stretching is calculated based on the above formula and is 5 to 1000%. The residual solvent amount is preferably 30 to 500%, more preferably 50 to 300%, and still more preferably 80 to 250%.
The draw ratio (elongation) of the polymer web during the drawing can be achieved by the difference in peripheral speed between the metal support speed and the peeling speed (peeling roll draw). By performing such stretching, the expression of retardation can be adjusted.

  If the residual solvent amount is stretched in a state of 5% or more, haze is hardly increased. There exists a tendency for the effect of retardation expression property adjustment by polymer web extending | stretching to become large. The residual solvent amount of the polymer web is appropriately adjusted by changing the concentration of the cellulose acylate solution, the temperature and speed of the metal support, the temperature and air volume of the drying air, the solvent gas concentration in the drying atmosphere, and the like. be able to.

Further, in the step of stretching the polymer web, the film surface temperature of the web is preferably low from the viewpoint of transmitting external force to the polymer, and the temperature of the web is set to (Ts-100) to (Ts-0.1) ° C. Preferably, (Ts-50) to (Ts-1) ° C is more preferable, and (Ts-20) to (Ts-3) ° C is more preferable. Here, Ts represents the surface temperature of the casting support, and when the temperature of the casting support is set to a partially different temperature, it represents the surface temperature at the center of the support.
The polymer web that has been subjected to the stretching process in this manner is then conveyed to the drying zone, and drying is terminated while both ends are clipped by a tenter or conveyed by a roll group.

  The amount of residual solvent in the film thus dried is preferably 0 to 2% by mass, and more preferably 0 to 1% by mass. This film may be conveyed to the heat treatment zone as it is, or may be heat treated offline after the film is wound. The preferable width | variety of the cellulose acylate film before heat processing is 0.5-5 m, More preferably, it is 0.7-3 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.

The moisture permeability in terms of film thickness of 80 μm of the cellulose acylate film used in the production method of the present invention is preferably 100 g / (m ² · day) or more, and is 100 to 1500 g / (m ² · day). more preferably in, more preferably from ^{200~1000g / (m 2 · day)} , particularly preferably ^{300~800g / (m 2 · day)} . 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.
The moisture permeability in the present invention refers to the change in mass before and after humidity control when a lid is sealed with a film for evaluating a cup containing calcium chloride and left for 24 hours at 40 ° C. and 90% relative humidity. 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 actually measured film thickness and divided by 80 in the present invention. The water vapor transmission rate in terms of thickness of 80 μm ”.

[Pre-stretching]
The cellulose acylate film formed before the heat treatment in which the amount of the residual solvent calculated based on the above formula is less than 5% after drying the solvent is before the heat treatment at the temperature T satisfying Tc ≦ T <Tm _0. May be stretched (hereinafter, this stretching is also referred to as “preliminary stretching”). By performing the preliminary stretching, it is possible to further adjust the expression of Re and Rth in the heat treatment step. Specifically, within the range described below, the heat treatment temperature can be set relatively low, or the reach range of Re and Rth can be increased by lowering the stretching temperature or increasing the stretching ratio. It becomes possible. Moreover, within the range which does not deviate from the meaning of this invention, another process may be included between the pre-drawing process and the heat treatment process.

In the production method of the present invention, pre-stretching is performed at (Tg-20) to (Tg + 50) ° C., where Tg (unit: ° C.) is the glass transition temperature of the cellulose acylate film used in the production method of the present invention. Is preferred. The pre-drawing temperature is more preferably (Tg-10) to (Tg + 45) ° C., further preferably Tg to (Tg + 40) ° C., and most preferably (Tg + 5) to (Tg + 35) ° C. However, the preliminary stretching temperature does not exceed the crystallization temperature (Tc) described later. The pre-stretching temperature is preferably 5 ° C. or lower than Tc, more preferably 10 ° C. or lower than Tc, and more preferably 15 ° C. or lower than Tc. It is particularly preferable to carry out at a temperature 20 ° C. or more lower than Tc, and most preferred to carry out at a temperature 35 ° C. or more lower than Tc.
In the present invention, the glass transition temperature is a boundary temperature at which the mobility of the polymer constituting the cellulose acylate film of the present invention changes greatly. As for the glass transition temperature in the present invention, 20 mg of a cellulose acylate film used in the production method of the present invention is placed in a measurement pan of a differential scanning calorimeter (DSC), and this is 30 ° C. to 120 ° C. at 10 ° C./min in a nitrogen stream. The temperature is raised to 30 ° C., held for 15 minutes, cooled to −30 ° C./min to 30 ° C., and then heated again from 30 ° C. to 250 ° C., where the baseline starts to deviate from the low temperature side. .
In the production method of the present invention, it is presumed that by making the cellulose acylate film used in the production method of the present invention Tc or more, a structure observed by X-ray diffraction can be grown and the retardation can be adjusted. By preliminarily stretching the film in advance, the polymer can be arranged to some extent in the prestretching direction, so that the structure observed by X-ray diffraction can be efficiently and anisotropically treated in the heat treatment step described later. Can grow into. In addition, by setting the pre-stretching temperature lower than the heat treatment temperature, the polymer can be oriented without growing the structure observed by X-ray diffraction, so that the X-ray diffraction can be performed more efficiently in the subsequent heat treatment step. There is an advantage that the structure observed in can be grown. Therefore, it is more preferable that the stretching direction in the pre-stretching is the same as the stretching direction or the transport direction in the heat treatment described later from the viewpoint of reducing the heat treatment temperature and extending the reach range of Re and Rth. Conversely, when these directions do not match, the reach range of Re and Rth can be reduced.

The direction of the preliminary stretching is not particularly limited, and when the cellulose acylate film before heat treatment is being transported, even if it is longitudinal stretching that is stretched in the transport direction, Although it may be stretching, it is preferably longitudinal stretching. For the longitudinal stretching and lateral stretching methods and preferred embodiments, reference can be made to the section of heat treatment described later. The prestretch ratio is preferably 1 to 500%, more preferably 3 to 400%, still more preferably 5 to 300%, and particularly preferably 10 to 100%. These preliminary stretchings may be performed in one stage or in multiple stages. Here, “preliminary stretch ratio (%)” means that obtained by the following formula.
Pre-stretch ratio (%) = 100 × {(length after stretching) − (length before stretching)} / length before stretching The stretching speed in the pre-stretching is preferably 10 to 10,000% / min, more preferably. Is 20 to 1000% / min, more preferably 30 to 800% / min.

[Heat treatment]
The method for producing a transparent polymer film of the present invention includes a step of heat-treating a cellulose acylate film at a temperature T (unit: ° C.) that satisfies the following formula (2). Here, the heat treatment is preferably performed while being conveyed.
Formula (2): Tc ≦ T <Tm ₀
In the formula (2), Tc represents the crystallization temperature of the cellulose acylate film before the heat treatment, and the unit is ° C. In the present invention, the crystallization temperature indicates a temperature at which the polymer constituting the cellulose acylate film forms a regular periodic structure, and when this temperature is exceeded, a structure observed by X-ray diffraction grows. The crystallization temperature in the present invention is that after 20 mg of cellulose acylate film before heat treatment is placed in a DSC measurement pan, and this is heated from 30 ° C. to 120 ° C. at 10 ° C./min and held for 15 minutes. This is the starting temperature of the exothermic peak observed when the temperature was cooled to 30 ° C. at −20 ° C./min and then heated again from 30 ° C. to 300 ° C. Tc usually appears on the higher temperature side than the glass transition temperature (Tg). For example, the crystallization temperature of a cellulose triacetate film having a total degree of substitution of 2.85 varies depending on additives and film forming conditions, but is about 190 ° C., and the crystallization temperature of a cellulose triacetate film having a total degree of substitution of 2.92 is increased. The temperature is about 170 ° C.
In the formula (2), Tm ₀ represents the melting point of the cellulose acylate film before the heat treatment, and the unit is ° C. The melting point in the present invention was determined by adding 20 mg of a cellulose acylate film before heat treatment to a DSC measurement pan, raising the temperature from 30 ° C. to 120 ° C. at 10 ° C./min in a nitrogen stream, and holding it for 15 minutes. This is the end temperature of the endothermic peak observed when the temperature is cooled to -20 ° C / min to ℃, and then heated again from 30 ℃ to 300 ℃. Tm ₀ usually appears on the higher temperature side than the above-mentioned crystallization temperature (Tc). For example, the melting point of a cellulose triacetate film having a total degree of substitution of 2.85 slightly varies depending on the additives and film forming conditions, but is about 285 ° C., and the melting point of a cellulose triacetate film having a total degree of substitution of 2.92 is about 290 ° C.

Heat treating the cellulose acylate film at a temperature T satisfying the condition of the formula (2), and adjusting the retardation value of the transparent polymer film and the development of retardation wavelength dispersion by adding the additive of the present invention. Can do. As a result, it has become possible to produce a transparent polymer film having a retardation value and retardation wavelength dispersion, which has not been easy to produce, by a simple method. In particular, a transparent polymer film of | Rth | / Re <0.5, which could not be produced only by a complicated production method, can be produced with a simple method and in a planar shape.
The heat treatment temperature in the production method of the present invention preferably satisfies the following formula (7a), more preferably satisfies the following formula (7b), and further preferably satisfies the following formula (7c). By selecting a temperature that satisfies these formulas, there are advantages that the Re expression is increased, and in some cases, the stretching direction and the direction of the slow axis are orthogonal to each other.
Formula (7a): Tc ≦ T <Tm ₀ −5
Formula (7b): Tc ≦ T <Tm ₀ −10
Formula (7c): Tc + 5 ≦ T <Tm ₀ −15

By stretching at a temperature T satisfying Tc ≦ T <Tm ₀ according to the production method of the present invention, the mobility of the polymer chain can be improved. Cutting of the film 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 will be described later. Therefore, by following the production method of the present invention, the polymer chains can be highly aggregated and arranged in the film, and a transparent polymer film having a high elastic modulus, a small humidity dimensional change, and an appropriate moisture permeability can be produced. It becomes possible to do.

  The heat treatment in the production method of the present invention is preferably performed while conveying the cellulose acylate film. The means for transporting the cellulose acylate film is not particularly limited, but typical examples include means for transporting by a nip roll or a suction drum, means for transporting while gripping with a tenter clip (means for transporting by air pressure), and the like. . When the target Rth / Re value is small, a means for conveying by nip roll is preferable. Specifically, a mode in which nip rolls are installed at least before and after the zone where heat treatment is performed and the cellulose acylate film is conveyed by passing between the nip rolls (shrink heat treatment, that is, unconstrained heat treatment) can be exemplified. ). Further, when the target Rth / Re value is large, a means for conveying while holding with a tenter clip is preferable. Specifically, an embodiment in which both ends of the film are passed through a heat treatment zone while being gripped by a tenter clip (constrained heat treatment), and a dimensional change rate in a direction perpendicular to the transport direction is set to −10% or more. Is preferred.

  The conveyance speed is usually 1 to 500 m / min, preferably 5 to 300 m / min, more preferably 10 to 200 m / min, and still more preferably 20 to 100 m / min. If the conveyance speed is 1 m / min or more, which is the lower limit value, it tends to be preferable in terms of industrially sufficient productivity, and the upper limit value is 500 m / min or less. If it exists, there exists a tendency which becomes preferable at the point that a crystal growth can fully be advanced with a practical heat treatment zone length. If the conveying speed is increased, the color of the film tends to be suppressed, and if the conveying speed is decreased, the heat treatment zone length tends to be shortened. It is preferable to keep the conveyance speed during heat treatment (the speed of devices such as nip rolls and suction drums that determine the conveyance speed) constant.

As a heat treatment method in the production method of the present invention, for example, a method of passing a cellulose acylate film through a zone of temperature T, a method of applying hot air to the cellulose acylate film being conveyed, a cellulose being conveyed Examples thereof include a method of irradiating the acylate film with heat rays and a method of bringing the cellulose acylate film into contact with a heated roll.
Preferred is a method in which the cellulose acylate film is passed through the zone of temperature T while applying hot air. This method has an advantage that the cellulose acylate film can be heated uniformly. The temperature in the zone can be maintained at the temperature T by controlling it to a constant temperature with a heater while monitoring it with a temperature sensor, for example. The transport length of the cellulose acylate film in the zone of temperature T varies depending on the properties of the transparent polymer film to be manufactured and the transport speed, but usually the ratio of (transport length) / (width of the cellulose acylate film to be transported) Is preferably set to be 0.1 to 100, more preferably 0.5 to 50, and still more preferably 1 to 20. This ratio may be abbreviated as an aspect ratio in this specification. The passage time (heat treatment time) of the zone of temperature T is usually 0.01 to 60 minutes, preferably 0.03 to 10 minutes, and more preferably 0.05 to 5 minutes. By setting it as the said range, it is excellent in the expression of retardation and coloring of a film can be suppressed.

  In the manufacturing method of this invention, you may extend | stretch simultaneously with heat processing. The stretching direction during heat treatment is not particularly limited, but when the cellulose acylate film before heat treatment has anisotropy, it is stretching in the orientation direction of the polymer in the cellulose acylate film before heat treatment. It is preferable. Here, the film having anisotropy means that the ratio of the sound wave propagation speed in the direction in which the sound wave propagation speed is maximum and the sound wave propagation speed in the direction orthogonal thereto is preferably 1.01 to 10.0. More preferably, it is 1.1-5.0, More preferably, it indicates 1.2-2.5. The direction in which the sound wave propagation speed becomes maximum and the sound wave propagation speed in each direction are determined by adjusting the orientation of the film for 24 hours at 25 ° C. and 60% relative humidity, and then measuring the orientation (SST-2500: manufactured by Nomura Corporation). ) Can be obtained as the direction in which the propagation speed of the longitudinal vibration of the ultrasonic pulse is maximized and the propagation speed in each direction.

  For example, when heat treatment is performed while a cellulose acylate film is conveyed using a device having a heating zone between two nip rolls, the nip roll on the outlet side of the heating zone is faster than the rotational speed of the nip roll on the inlet side of the heating zone. By increasing the rotation speed, the cellulose acylate film can be stretched in the transport direction (longitudinal direction). Further, the cellulose acylate film can be stretched by gripping both ends with a tenter clip and passing it through a heating zone while spreading it in a direction (lateral direction) perpendicular to the transport direction. By stretching the cellulose acylate film in the conveying direction during the heat treatment, the retardation expression can be further adjusted. The draw ratio in the conveying direction is usually 0.8 to 100 times, preferably 1.0 to 10 times, more preferably 1.2 to 5 times. Moreover, the planar shape of the transparent polymer film after heat processing can be improved by extending | stretching a cellulose acylate film in the direction orthogonal to a conveyance direction during heat processing. The draw ratio in the direction orthogonal to the transport direction is usually 0.5 to 10 times, preferably 0.7 to 1.0 times, more preferably 0.8 to 1.0 times. In addition, the draw ratio (%) here means what was calculated | required using the following formula | equation.

Stretch ratio (%) = 100 × {(Length after stretching) − (Length before stretching)} / Length before stretching The stretching speed in the stretching is preferably 10 to 10,000% / min, more preferably. Is 20 to 1000% / min, more preferably 30 to 800% / min.

The cellulose acylate film may be shrunk during the heat treatment. Such shrinkage may be performed without being controlled by the shrink heat treatment (that is, unconstrained heat treatment) or may be performed while being controlled by the restraint heat treatment. The contraction is preferably performed during heat treatment. By shrinking the cellulose acylate film during the heat treatment, the optical properties and / or mechanical properties can be adjusted. The step of shrinking in the width direction can be performed not only during the heat treatment but also before and after the heat treatment. Moreover, the process of contracting in the width direction may be performed in one step, and the contracting process and the stretching process may be repeated.
When shrinking, the shrinkage rate is preferably 5 to 80%, more preferably 10 to 70%, still more preferably 20 to 60%, and most preferably 25 to 50%. The direction of shrinkage is not particularly limited, but when the cellulose acylate film before heat treatment is produced by being conveyed, it is preferably performed in a direction perpendicular to the conveying direction. Moreover, when extending | stretching (preliminary extending | stretching etc.) before shrinkage | contraction, it is preferable to make it shrink | contract in the direction orthogonal to the said extending | stretching direction. The shrinkage rate can be controlled by adjusting the heat treatment temperature or adjusting the external force applied to the film. Specifically, when the end of the film is held by a tenter clip, it can be controlled by the rail widening rate or the like. In addition, when the end of the film is not fixed and is held only by a device such as a nip roll that fixes the film in the transport direction, the distance between the devices fixed in the transport direction and the tension applied to the film And adjustment of the amount of heat given to the film. The shrinkage in the width direction is obtained from the following equation by measuring the full width immediately before and after the film shrinks.

  Shrinkage rate (%) in the width direction = 100 × (full width immediately before shrinkage−full width immediately after shrinkage) / full width just before shrinkage

[Constrained heat treatment]
During the heat treatment, the cellulose acylate film may or may not be stretched in a direction orthogonal to the orientation direction of the film. When the cellulose acylate film is stretched in the direction perpendicular to the orientation direction of the film by the constraining heat treatment, the dimensional change rate in the direction perpendicular to the orientation direction of the film in the heat treatment zone is preferably −10% or more. -10 to 100%, preferably -10 to 50%, more preferably -5 to 30%, and still more preferably -3 to 10%. By doing so, it is possible to improve the ease of cracking of the film and the iron plate-like wrinkles while ensuring the retardation development property and to secure a wider product width. Moreover, the effect that the humidity dependence of Re and Rth can be improved significantly is also acquired. In this case, it is preferable that the film is preliminarily stretched before entering the heat treatment zone, and the direction of the prestretch and the direction giving the dimensional change in the heat treatment zone are substantially orthogonal. preferable.

The dimensional change rate in the direction orthogonal to the prestretching direction in the heat treatment step is, for example, as follows as the dimensional change rate in the width direction accompanying heat treatment when the direction orthogonal to the prestretching direction is the film width direction: Can be obtained.
When the overall width of the film is shorter than that immediately before the heat treatment, the dimensional change rate in the width direction accompanying the heat treatment can be obtained from the minimum overall width during the heat treatment and the overall width immediately before the heat treatment by the following equation.
Dimensional change rate in the width direction (%) = 100 × (minimum full width during heat treatment−full width immediately before heat treatment) / full width immediately before heat treatment The minimum full width during heat treatment referred to here is the film in the width direction during the heat treatment step. It means the width when it shrinks the shortest. For example, if a film with a total width of 200 cm shrinks to 180 cm during heat treatment and then expands (stretches) to 190 cm, the minimum full width during heat treatment is 180 cm.

If the total width of the film does not become shorter than that immediately before the heat treatment due to the heat treatment, or if the film only shrinks during the heat treatment process and does not expand, the dimensional change rate in the width direction is the film width at the heat treatment zone inlet and the film at the heat treatment zone outlet. From the total width, it can also be obtained by the following equation.
Dimensional change rate in the width direction (%) = 100 × (full width immediately after heat treatment−full width immediately before heat treatment) / full width immediately before heat treatment

Without being bound by any theory, the humidity dependency of retardation is reduced by suppressing the rate of dimensional change in the direction (preferably the width direction of the film) perpendicular to the direction of pre-stretching accompanying heat treatment. The reason is considered as follows. That is, by performing the heat treatment at the temperature T satisfying the condition of Tc ≦ T <Tm ₀ as described above, the crystal grows while preferentially orientating in the same direction as the pre-stretching of the film, and at the same time, orienting around it. It is considered that an amorphous part is formed, and the oriented amorphous part tends to be formed in that direction, particularly when an external force is applied during cooling. Among these, the crystalline portion exhibits negative birefringence, and the amorphous portion has positive birefringence, so there is an effect of canceling birefringence with each other. In the cellulose acylate film of the present invention, Since the influence of the crystal part is large, the retardation expression can be improved by reducing the oriented amorphous part. On the other hand, the oriented amorphous part interacts with water molecules, and it is considered that the retardation changes when the environmental humidity changes. Therefore, reducing the oriented amorphous part also reduces the humidity dependence of the retardation. It is considered possible.
In order to reduce the oriented amorphous part, it is considered to be very effective to suppress the dimensional change rate in the direction orthogonal to the direction of pre-stretching in the heat treatment. It is considered effective to reduce the conveyance tension in the subsequent cooling process and to reduce the external force applied to the film. As a result, the humidity dependency of retardation can be reduced.

The step of heat-treating the cellulose acylate film at the temperature T may be performed only once or a plurality of times in the production method of the present invention. Performing a plurality of times means that the temperature is once lowered to less than Tc after the previous heat treatment is completed, and then the heat treatment is performed again while the temperature is set to Tc or more and less than Tm ₀ again. When performing the heat treatment a plurality of times, it is preferable to satisfy the above-mentioned range of the draw ratio when all the heat treatments are completed. The heat treatment in the production method of the present invention is preferably 3 times or less, more preferably 2 times or less, and most preferably 1 time.

[Cooling after heat treatment]
The polymer film after the heat treatment is cooled to a temperature lower than Tc. The cooling temperature is not particularly limited, but is preferably 100 to 1,000,000 ° C./min, more preferably 1,000 to 100,000 ° C./min, and further preferably 3,000 to 50,000 ° C. Cool film at / min. The temperature range for cooling the film at such a cooling rate is preferably 50 ° C. or more, more preferably 100 to 300 ° C., further preferably 150 to 280 ° C., and 180 to 250 ° C. It is particularly preferred.
By adjusting the cooling rate in this way, it is possible to further adjust the expression of retardation of the transparent polymer film (particularly, cellulose acylate film) to be obtained. Specifically, the retardation can be improved by increasing the cooling rate. Moreover, the distribution of the orientation of polymer chains in the thickness direction in the cellulose acylate film can be reduced, and the humidity curl of the film can be suppressed. Such an effect can be obtained more sufficiently by controlling the temperature range at which the cooling is performed at a relatively high cooling rate within the above-described preferable range. As a result, for example, a transparent polymer film satisfying both the relational expressions | Rth | / Re <0.5 and Re ≧ 30 can be obtained. Further, a transparent polymer film satisfying both the relational expressions of | Rth | / Re <0.5 and Re ≧ 60, a transparent polymer film satisfying both the relational expressions of | Rth | / Re <0.5 and Re ≧ 100, A transparent polymer film satisfying both the relational expressions | Rth | / Re <0.5 and Re ≧ 150, and a transparent polymer film satisfying both the relational expressions | Rth | / Re <0.5 and Re ≧ 200. Can do.

  For the cooling rate, a cooling zone maintained at a temperature lower than the heating zone is provided after the heating zone, and the transparent polymer film is sequentially conveyed to these zones, the cooling roll is brought into contact with the film, It can be controlled by blowing air on the film or immersing the film in a cooled liquid. The cooling rate is not always required to be constant during the cooling step, and the cooling rate may be reduced at the beginning and the end of the cooling step, and the cooling rate may be increased in the meantime. The cooling rate can be determined by measuring the temperature at a plurality of points with a thermocouple arranged on the film membrane surface as described in the examples described later.

[Stretching after heat treatment]
In the production method of the present invention, the cellulose acylate film may be stretched following the heat treatment. The stretching performed following the heat treatment may be performed after the transparent polymer film is cooled to a temperature lower than Tc after the heat treatment, or may be performed without being cooled while maintaining the heat treatment temperature. Once the polymer film is cooled, the cooling may be naturally cooled to a temperature lower than Tc, or may be forced to cool to a temperature lower than Tc. Moreover, the state once heated to less than Tc after cooling once may be sufficient. The cooling temperature when the film is once cooled is preferably 50 ° C. or more lower than the heat treatment temperature, more preferably 100 to 300 ° C., and even more preferably 150 to 250 ° C. There is a tendency that the Rth / Re value of the film after the heat treatment can be easily controlled by lowering the cooling temperature by 50 ° C. or more than the heat treatment temperature. Further, it is preferable that the film is once cooled to a cooling temperature and then heated again to a temperature lower than Tc and then stretched. The difference between the heat treatment temperature and the stretching temperature is preferably 1 ° C. or more, more preferably 10 to 200 ° C., further preferably 30 to 150 ° C., and particularly preferably 50 to 100 ° C. By appropriately setting the temperature difference, the Rth / Re value can be controlled. Specifically, if the difference between the heat treatment temperature and the stretching temperature is increased, the Rth / Re value tends to increase, and if the difference is decreased, the change in the Rth / Re value tends to decrease.

  As the stretching method, the method described in the explanation of stretching during the heat treatment can be employed. Stretching may be performed in one stage or in multiple stages. Preferable are a method of stretching in the transport direction by changing the rotational speed of the nip roll and a method of stretching by gripping both ends of the polymer film with tenter clips and spreading them in a direction perpendicular to the transport direction. It is particularly preferable that the film is not stretched during the heat treatment, or is stretched in the transport direction by changing the rotation speed of the nip roll, and after the heat treatment, both ends of the polymer film are gripped with tenter clips, and this is transported. It is the aspect extended | stretched by extending in the direction orthogonal to.

  The draw ratio can be appropriately set according to the retardation required for the transparent polymer film, preferably 1 to 500%, more preferably 3 to 400%, still more preferably 5 to 300%, and particularly preferably 10 to 100%. . The stretching speed is preferably 10 to 10000% / min, more preferably 20 to 1000% / min, and further preferably 30 to 800% / min.

  By stretching after the heat treatment, Re and Rth of the obtained transparent film can be adjusted. For example, by increasing the stretching temperature after heat treatment, Rth can be lowered without changing Re much. Further, by increasing the draw ratio after the heat treatment, Re can be lowered and Rth can be raised. Since these show a substantially linear correlation, it becomes easy to achieve the intended Re and Rth by appropriately selecting the stretching conditions after the heat treatment. After the heat treatment is finished, Re and Rth of the transparent polymer film in a state before stretching are not particularly limited.

<Transparent polymer film>
(Optical characteristics of the transparent polymer film of the present invention)
According to the production method of the present invention, a transparent polymer film having in-plane retardation with inverse wavelength dispersion can be obtained. That is, ΔRe can be changed in the positive direction by adding the additive compound of the present invention to the film and producing a transparent polymer film by the production method of the present invention. When the additive compound of the present invention is added and the production method of the present invention is carried out, ΔRe of a transparent polymer film having a negative ΔRe can be made close to zero or made positive. The transparent polymer film obtained by the production method of the present invention is preferably a film in which ΔRe is positive and wavelength dispersion is reverse dispersion.

(Retardation)
In this specification, Re and Rth (unit: nm) are determined according to the following method. First, the film was conditioned at 25 ° C. and 60% relative humidity for 24 hours, and then a prism coupler (MODEL2010 Prism Coupler: manufactured by Metricon) was used. The average refractive index (n) represented by (8) is obtained.
Formula (8): n = (n _TE × 2 + n _TM ) / 3
[ _Where n _TE is a refractive index measured with polarized light in the film plane direction, and n _TM is a refractive index measured with polarized light in the film surface normal direction. ]

In this specification, Re (λ) and Rth (λ) each represent in-plane retardation and retardation in the thickness direction at a wavelength λ (unit: nm). Re (λ) is measured by making light having a wavelength of λ nm incident in the normal direction of the film in KOBRA 21ADH or WR (produced by Oji Scientific Instruments).
When the film to be measured is represented by a uniaxial or biaxial refractive index ellipsoid, Rth (λ) is calculated by the following method.
Rth (λ) is Re (λ), with the in-plane slow axis (determined by KOBRA 21ADH or WR) as the tilt axis (rotation axis) (in the absence of the slow axis, any in-plane value) The light is incident at a wavelength of λ nm in 10 ° steps from the normal direction to 50 ° on one side with respect to the normal direction of the film (with the direction of the rotation axis as the rotation axis), and a total of 6 points are measured. KOBRA 21ADH or WR calculates based on the measured retardation value, average refractive index, and input film thickness value.
In the above, there is no description regarding λ, and when only Re and Rth are described, it represents a value measured using light having a wavelength of 590 nm. In addition, in the case of a film having a direction in which the retardation value is zero at a certain tilt angle with the in-plane slow axis as the rotation axis from the normal direction, the retardation value at a tilt angle larger than the tilt angle is After changing the sign to negative, KOBRA 21ADH or WR calculates.
In addition, the retardation value is measured from two inclined directions with the slow axis as the tilt axis (rotary axis) (in the case where there is no slow axis, the arbitrary direction in the film plane is the rotary axis), Based on the value, the average refractive index, and the input film thickness value, Rth can also be calculated from the following equations (9) and (10).

［式中、Ｒｅ（θ）は法線方向から角度θ傾斜した方向におけるレタ−デーション値を表す。また、ｎｘは面内における遅相軸方向の屈折率を表し、ｎｙは面内においてｎｘに直交する方向の屈折率を表し、ｎｚはｎｘおよびｎｙに直交する厚み方向の屈折率を表し、ｄはフィルムの膜厚を表す。］
式（１０）： Ｒｔｈ＝(（ｎｘ＋ｎｙ）／２−ｎｚ)×ｄ Formula (9)

[In the formula, Re (θ) represents a retardation value in a direction inclined by an angle θ from the normal direction. Nx represents the refractive index in the slow axis direction in the plane, ny represents the refractive index in the direction perpendicular to nx in the plane, nz represents the refractive index in the thickness direction perpendicular to nx and ny, and d Represents the film thickness of the film. ]
Formula (10): Rth = ((nx + ny) / 2−nz) × d

When the film to be measured cannot be expressed by a uniaxial or biaxial refractive index ellipsoid, that is, a film having no so-called optical axis, Rth (λ) is calculated by the following method.
Rth (λ) is the above-mentioned Re (λ), and the in-plane slow axis (determined by KOBRA 21ADH or WR) is the tilt axis (rotation axis) from −50 degrees to +50 degrees with respect to the film normal direction. The light of wavelength λnm is made incident from each inclined direction in 10 degree steps and measured at 11 points, and KOBRA 21ADH or WR is calculated based on the measured retardation value, average refractive index, and input film thickness value. .
Here, as the assumed value of the average refractive index, values of “Polymer Handbook” (John Wiley & Sons, Inc.) and catalogs of various optical films can be used. If the average refractive index is not known, it can be measured with an Abbe refractometer. In this specification, the assumed value of the average refractive index of cellulose acylate was 1.48. By inputting these average refractive index and film thickness, KOBRA 21ADH or WR calculates nx, ny, and nz. Nz = (nx−nz) / (nx−ny) is further calculated from the calculated nx, ny, and nz.

The transparent polymer film produced by the production method of the present invention has a difference ΔRe [= between the in-plane retardation Re (550 nm) when the measurement wavelength is 550 nm and the in-plane retardation value when the measurement wavelengths are 630 nm and 450 nm. Re (630 nm) -Re (450 nm)] preferably satisfies the following formulas (5) and (6) at the same time.
Formula (5): Re (550 nm)> 0
Formula (6): ΔRe> 0
Furthermore, it is more preferable that the transparent polymer film produced by the production method of the present invention satisfies the following formulas (5a) and (5b) at the same time.
Formula (5a): Re (550 nm) = 20 to 300
Formula (5b): ΔRe = 10 to 100

(X-ray diffraction intensity)
In the present invention, the X-ray diffraction intensity of the cellulose acylate film is determined by adjusting the film for 24 hours at 25 ° C. and a relative humidity of 60%, and then an X-ray diffractometer with an imaging plate reader (R-AXIS Rapid-S :( (Made by Rigaku Co., Ltd.), and was obtained from a diffraction photograph of the beam transmitted through the film (Cu Kα ray 50 kV 100 mA 3 minutes collimator 0.8 mmφ). A two-dimensional diffraction image when a beam was incident on the film surface from the vertical direction was photographed, and the two-dimensional diffraction image of the blank measurement was subtracted. In addition, a slice sample cut to 20 mm × 0.30 mm with the film transport direction as the longitudinal direction is prepared, and a two-dimensional diffraction image is photographed when a beam is incident on the center of the cross section of the sample from the vertical direction, and blank measurement is performed. The two-dimensional diffraction image was subtracted. Similarly, a slice sample cut to 20 mm × 0.30 mm with the direction orthogonal to the film transport direction as the longitudinal direction is prepared, and a two-dimensional diffraction image when a beam is incident from the vertical direction on the center of the cross section of the sample is obtained. Photographed and subtracted 2D diffraction image of blank measurement.
A two-dimensional diffraction image obtained by averaging the above three measurement results was calculated, and a diffraction profile I (2θ) obtained by averaging the diffraction profiles with azimuth angles of 90 to 270 ° was obtained for the two-dimensional diffraction image. Here, the direction in which the beam was removed by the beam stopper was defined as an azimuth angle of 0 °. Here, θ represents a Bragg angle.
Regarding the 2θ profile, a straight line connecting plots I (24.9 °) and I (28.7 °) at 2θ = 24.9 ° and 28.7 ° is defined as a baseline f (2θ), and 2θ is 24. The area intensity Ic of the peak existing between .9 and 28.7 ° was determined according to the following formula (I). However, when Ic is a negative value, Ic = 0. Moreover, area intensity It of all the diffraction signals which exist in 2 (theta) between 24.9-28.7 degrees was calculated | required according to following formula (II).

［式中、Ｉ（２θ）は、全方位について平均化したフィルムのＸ線回折プロファイル、ｆ（２θ）は上記回折プロファイルＩ（２θ）について、２θ＝２４．９°および２８．７°におけるプロットＩ（２４．９°）およびＩ（２８．７°）の間を結ぶ直線（ベースライン）である。但し、θはブラッグ角である。］

[Wherein I (2θ) is the X-ray diffraction profile of the film averaged in all directions, and f (2θ) is a plot at 2θ = 24.9 ° and 28.7 ° for the diffraction profile I (2θ). A straight line (baseline) connecting between I (24.9 °) and I (28.7 °). Where θ is the Bragg angle. ]

In the cellulose acylate film of the invention, it is preferable that the Ic and It satisfy the following formula (III).
Formula (III): 0.08 ≦ Ic / It ≦ 0.4
By heat-treating the cellulose acylate film at a temperature T satisfying the condition of the formula (2), the peak intensity of X-ray diffraction at 2θ = 24.9 ° to 28.7 ° can be appropriately controlled, and Ic / It is By setting it to 0.08 or more, negative intrinsic birefringence can be effectively expressed. Further, by setting Ic / It to be 0.4 or less, a transparent film can be obtained without impairing the brittleness of the film.
In the cellulose acylate film of the invention, it is more preferable that the Ic and It satisfy the following formula (IIIa).
Formula (IIIa): 0.08 ≦ Ic / It ≦ 0.3
In the cellulose acylate film of the invention, it is more preferable that the Ic and It satisfy the following formula (IIIb).
Formula (IIIb): 0.10 ≦ Ic / It ≦ 0.2

(Humidity dependency)
In the present invention, the retardation values in the in-plane direction and the film thickness direction when the relative humidity is H (unit:%): Re (H%) and Rth (H%) are 25 ° C. and relative humidity H%. After adjusting the humidity for 24 hours, at 25 ° C. and relative humidity H%, the retardation value when the measurement wavelength at relative humidity H% is 590 nm was measured and calculated in the same manner as described above.

The retardation value when the humidity of the transparent polymer film of the present invention is changed preferably satisfies the following relational expression.
| Re (10%) − Re (80%) | <50, and
| Rth (10%)-Rth (80%) | <50
It is more preferable to satisfy the following relational expression.
| Re (10%) − Re (80%) | <30, and
| Rth (10%)-Rth (80%) | <40
It is more preferable to satisfy the following relational expression.
| Re (10%) − Re (80%) | <20, and
| Rth (10%)-Rth (80%) | <30
It is most preferable that the following relational expression is satisfied.
| Re (10%) − Re (80%) | <10 and
| Rth (10%)-Rth (80%) | <15

The retardation value when the humidity of the transparent polymer film of the present invention is changed preferably satisfies the following relational expression.
| Re (10%) − Re (80%) | / Re <3 and
| Rth (10%)-Rth (80%) | / Rth <3
It is more preferable to satisfy the following relational expression.
| Re (10%) − Re (80%) | / Re <1, and
| Rth (10%)-Rth (80%) | / Rth <1
It is more preferable to satisfy the following relational expression.
| Re (10%) − Re (80%) | / Re <0.5, and
Rth (10%) − Rth (80%) | / Rth <0.7
It is most preferable that the following relational expression is satisfied.
| Re (10%) − Re (80%) | / Re <0.2 and
| Rth (10%)-Rth (80%) | / Rth <0.4
By controlling the retardation value when the humidity is changed, the retardation change when the external environment changes can be reduced, and a highly reliable liquid crystal display device can be provided.

(Slow axis)
In the transparent polymer film of the present invention, the angle θ formed between the transport direction during production and the slow axis of Re of the film is preferably 0 ± 10 ° or 90 ± 10 °, and 0 ± 5 ° or 90 ± 5 More preferably, it is 0 ± 3 ° or 90 ± 3 °, more preferably 0 ± 1 ° or 90 ± 1 °, and preferably 90 ± 1 °. Most preferred.

(Film thickness)
The film thickness of the transparent polymer film of the present invention is preferably 20 μm to 180 μm, more preferably 30 μm to 160 μm, and further preferably 40 μm to 120 μm. A film thickness of 20 μm or more is preferable from the viewpoint of handling properties when processing into a polarizing plate and curling of the polarizing plate. The film thickness unevenness of the transparent polymer film of the present invention is preferably 0 to 2% in both the transport direction and the width direction, more preferably 0 to 1.5%, and more preferably 0 to 1%. Particularly preferred.

(Moisture permeability)
The moisture permeability of the transparent polymer film of the present invention is preferably 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 easily bonded directly to the polarizing film. The moisture permeability of the 80μm ^{terms, 100~1500g / (m 2 · day} ) , more ^{preferably, 200~1000g / (m 2 · day} ) , and even more preferably 300~800g / (m ² · day) .
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.

(Configuration of transparent polymer film)
The transparent polymer film of the present invention may have a single layer structure or a plurality of layers, but 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 cellulose acylate 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.

  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 cellulose acylate film is described in Invention Technical Disclosure Bulletin (Public Technical No. 2001-1745, published on March 15, 2001, Invention Association), pages 32 to 45. Those described in (2) can be appropriately used on the transparent polymer film of the present invention.

<< retardation film >>
The transparent polymer film of the present invention can be used as a retardation film. The “retardation 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 plate, an optical compensation film, an optical compensation sheet, and the like. It is. In a liquid crystal display device, a retardation film is used for the purpose of improving the contrast of a display screen or improving viewing angle characteristics and color.
By using the transparent polymer film of the present invention, a retardation film in which the Re value and the Rth value are freely controlled can be easily produced. 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 a retardation 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 a retardation film, and an optically anisotropic layer made of liquid crystal or the like may be provided thereon to be used as a retardation film. The optically anisotropic layer applied to the retardation film of the present invention may be formed from, for example, a composition containing a liquid crystal compound, a polymer film having birefringence, You may form from the transparent polymer film of invention.
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.

"Polarizer"
The transparent polymer film or retardation film of the present invention can be used as a protective film for a polarizing plate (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.
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. As the surface treatment, alkali saponification treatment is most preferably used.

  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 production method of 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 may be used for any of the four polarizing plate protective films, but the transparent polymer film of the present invention is disposed between the polarizing film and the liquid crystal layer (liquid crystal cell) in the liquid crystal display device. It can be used particularly advantageously as a protective film. Further, the protective film disposed on the opposite side of the transparent polymer film of the present invention across the polarizing film can be provided with a transparent hard coat layer, an antiglare layer, an antireflection layer, etc. It is preferably used as a polarizing plate protective film on the outermost surface of the display side.

<Liquid crystal display device>
The transparent polymer film, retardation film and polarizing plate of the present invention can be used for liquid crystal display devices in various display modes. Each liquid crystal mode in which these films are used will be described below. Among these modes, the transparent polymer film, retardation film and polarizing plate of the present invention are particularly preferably used for VA mode and IPS mode liquid crystal display devices. 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 may be used as a support for a retardation 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. Regarding the retardation 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 device)
The transparent polymer film of the present invention may be used as a support for a retardation 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 retardation film used in 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 is particularly advantageously used as a retardation film or a support for a retardation film in a VA liquid crystal display device having a VA mode liquid crystal cell. The VA-type liquid crystal display device may be an alignment-divided system as described in, for example, JP-A-10-123576. In these embodiments, the polarizing plate using the transparent polymer film of the present invention contributes to widening the viewing angle and improving the contrast.

(IPS liquid crystal display device and ECB liquid crystal display device)
The transparent polymer film of the present invention is particularly advantageous as a retardation film, a retardation film support or a protective film for a polarizing plate of an IPS liquid crystal display device and an ECB liquid crystal display device having IPS mode and ECB mode liquid crystal cells. 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 in parallel with the substrate surface in the absence of applied voltage. In these embodiments, the polarizing plate using the transparent polymer film of the present invention contributes to widening the viewing angle and improving the contrast.

(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 a retardation 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 retardation 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 the retardation is minimum does not exist in the plane of the retardation film or in the normal direction. The optical properties of the retardation film used in the OCB type liquid crystal display device or the 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 A retardation 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 a retardation film of a reflective liquid crystal display device of TN type, STN type, HAN type, and GH (Guest-Host) type. 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 retardation 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 a retardation 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)).

(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. Therefore, 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 Examples and Comparative Examples are shown below.

[Replacement degree]
The acyl substitution degree of cellulose acylate was determined by ¹³ C-NMR by the method described in Carbohydr. Res. 273 (1995) 83-91 (Tezuka et al.).

[Tm ₀ ]
20 mg of a cellulose acylate film before heat treatment was put in a DSC measurement pan, and this was heated from 30 ° C. to 120 ° C. at 10 ° C./min in a nitrogen stream, held for 15 minutes, and then kept at −20 ° C./30° C. Then, the temperature of the endothermic peak that appeared when the temperature was raised again from 30 ° C. to 300 ° C. was defined as Tm ₀ of the cellulose acylate film before heat treatment.

[Tc]
20 mg of a cellulose acylate film before heat treatment was placed in a DSC measurement pan, and this was heated from 30 ° C. to 120 ° C. at 10 ° C./min in a nitrogen stream, held for 15 minutes, and then −20 ° C. / After cooling in minutes, the starting temperature of the exothermic peak that appeared when the temperature was raised again from 30 ° C. to 300 ° C. was defined as Tc of the cellulose acylate film before heat treatment.

[Degree of polymerization]
After the produced cellulose acylate was absolutely dried, about 0.2 g was precisely weighed and dissolved in 100 mL of a mixed solvent of dichloromethane: ethanol = 9: 1 (mass ratio). This was measured with an Ostwald viscometer at 25 ° C. for the number of seconds to drop, and the degree of polymerization DP was determined by the following equation.
η _rel = T / T ₀
[Η] = ln (η _rel ) / C
DP = [η] / Km
[In the formula, T is the number of seconds that the sample is dropped, T ₀ is the number of seconds that the solvent is dropped, ln is the natural logarithm, C is the concentration (g / L), and Km is 6 × 10 ⁻⁴ . ]

[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. The degree of polarization (P) was calculated.
Polarization degree P = ((Tp−Tc) / (Tp + Tc)) ^0.5

[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)).

Synthesis Example 1 Synthesis of Cellulose Acetate Propionate 150 g of cellulose (hardwood pulp) and 75 g of acetic acid were placed in a 5 L separable flask equipped with a reflux apparatus as a reaction vessel and heated in an oil bath adjusted to 60 ° C. The mixture was stirred vigorously for 2 hours. The cellulose subjected to such pretreatment was swollen and crushed to form a fluff shape. The reaction vessel was placed in an ice water bath at 2 ° C. for 30 minutes and cooled.
Separately, a mixture of 1545 g of propionic acid anhydride and 10.5 g of sulfuric acid was prepared as an acylating agent, cooled to −30 ° C., and then added to the reaction vessel containing the above-treated cellulose at once. After 30 minutes, the external temperature was gradually increased, and the internal temperature was adjusted to 25 ° C. after 2 hours from the addition of the acylating agent. The reaction vessel was cooled in an ice water bath at 5 ° C., the internal temperature was adjusted to 10 ° C. 0.5 hours after addition of the acylating agent, and the internal temperature was 23 ° C. after 2 hours, and the internal temperature was 23 ° C. The mixture was further stirred for 3 hours. The reaction vessel was cooled in an ice water bath at 5 ° C., and 120 g of 25% by mass hydrous acetic acid cooled to 5 ° C. was added over 1 hour. The internal temperature was raised to 40 ° C. and stirred for 1.5 hours. Next, a solution obtained by dissolving magnesium acetate tetrahydrate in 2-fold mol of sulfuric acid in 50% by mass aqueous acetic acid was added to the reaction vessel, and the mixture was stirred for 30 minutes. Cellulose acetate propionate was precipitated by adding 1 L of 25% by mass hydrous acetic acid, 500 mL of 33% by mass hydrous acetic acid, 1 L of 50% by mass hydrous acetic acid and 1 L of water in this order. The obtained cellulose acetate propionate precipitate was washed with warm water. By changing the washing conditions at this time, cellulose acetate propionate in which the amount of residual sulfate radicals is changed can be obtained. After washing, the mixture was stirred in a 0.005 mass% calcium hydroxide aqueous solution at 20 ° C. for 0.5 hour, further washed with water until the pH of the washing solution became 7, and then vacuum dried at 70 ° C.
According to ¹ H-NMR and GPC measurement, the obtained cellulose acetate propionate had an acetylation degree of 0.30, a propionylation degree of 2.63, and a polymerization degree of 320. The sulfate radical content was measured according to ASTM D-817-96.

Synthesis Example 2 Synthesis of Cellulose Acetate Butyrate 100 g of cellulose (hardwood pulp) and 135 g of acetic acid were placed in a 5 L separable flask equipped with a reflux apparatus as a reaction vessel and heated in an oil bath adjusted to 60 ° C. Left for 1 hour. Thereafter, the mixture was vigorously stirred for 1 hour while being heated in an oil bath adjusted to 60 ° C. The cellulose subjected to such pretreatment was swollen and crushed to form a fluff shape. The reaction vessel was placed in an ice water bath at 5 ° C. for 1 hour to sufficiently cool the cellulose.
Separately, a mixture of 1080 g of butyric anhydride and 10.0 g of sulfuric acid was prepared as an acylating agent, cooled to −20 ° C., and then added to a reaction vessel containing pretreated cellulose at once. After 30 minutes, the external temperature was raised to 20 ° C. and reacted for 5 hours. The reaction vessel was cooled in an ice water bath at 5 ° C., and 2400 g of 12.5% by mass aqueous acetic acid cooled to about 5 ° C. was added over 1 hour. The internal temperature was raised to 30 ° C. and stirred for 1 hour. Next, 100 g of a 50% by mass aqueous solution of magnesium acetate tetrahydrate was added to the reaction vessel, and the mixture was stirred for 30 minutes. 1000 g of acetic acid and 2500 g of 50% by mass aqueous acetic acid were gradually added to precipitate cellulose acetate butyrate. The obtained cellulose acetate butyrate precipitate was washed with warm water. By changing the washing conditions at this time, cellulose acetate butyrate in which the amount of residual sulfate radicals is changed can be obtained. After washing, the mixture was stirred in a 0.005 mass% calcium hydroxide aqueous solution for 0.5 hour, further washed with water until the pH of the washing solution became 7, and then dried at 70 ° C. The obtained cellulose acetate butyrate had an acetylation degree of 0.84, a butyrylation degree of 2.12, and a polymerization degree of 268.

<< Examples 1-20, Comparative Examples 1-12 >> Production of Transparent Polymer Film (Preparation of Cellulose Acylate Solution)
1) Cellulose acylate In each of the examples and comparative examples, those listed in Table 2 were selected from the following cellulose acylates A to D and used. Each cellulose acylate was produced by the same method as in the above synthesis example. In addition, each cellulose acylate was heated to 120 ° C. and dried to adjust the water content to 0.5% by mass or less, and then 15 parts by mass was used.
Cellulose acylate A:
A cellulose acetate powder having a substitution degree of 2.85 was used. Cellulose acylate A has a viscosity average degree of polymerization of 300, an acetyl group substitution degree at the 6-position of 0.89, an acetone extract of 7% by mass, a mass average molecular weight / number average molecular weight ratio of 2.3, and a water content of 0.3. Viscosity in 2 mass% and 6 mass% dichloromethane solutions is 305 mPa · s, residual acetic acid content is 0.1 mass% or less, Ca content is 65 ppm, Mg content is 26 ppm, iron content is 0.8 ppm, sulfate ion The content was 18 ppm, the yellow index was 1.9, and the amount of free acetic acid was 47 ppm. The average particle diameter of the powder was 1.5 mm, and the standard deviation was 0.5 mm.
Cellulose acylate B:
A cellulose acetate powder having a substitution degree of 2.95 was used. Cellulose acylate B had a viscosity average polymerization degree of 300 and a substitution degree of acetyl group at the 6-position of 0.94 (moisture permeability at 40 ° C. and 90% relative humidity was 400 to 1200 g / (m ^{2 in} terms of film thickness 80 μm). -Within the range of day)).
Cellulose acylate C:
Cellulose acetate propionate having an acetyl substitution degree of 2.55 and a propionyl substitution degree of 0.3 was used.
Cellulose acylate D:
Cellulose acetate butyrate having an acetyl substitution degree of 2.55 and a butyryl substitution degree of 0.3 was used.

2) Solvent In each example and comparative example, a mixed solvent of dichloromethane / methanol / butanol (83/15/2 parts by mass) was used. The water content of the solvent was 0.2% by mass or less.

3) Additive In each example and comparative example, 0.08 parts by mass of silicon dioxide fine particles (particle size 20 nm, Mohs hardness of about 7) was used. Moreover, as an additive compound of this invention, what was described in Table 2 from the additives AJ shown in Table 1 was selected, it mixed so that it might become the addition amount shown in Table 2, and dope for film forming might be used. Prepared. Table 1 also shows ΔΔn ⁰ _calc , aspect ratio A, (A-1) × ΔΔn ⁰ _{calc of the} additives A to J. The definition and calculation method of ΔΔn ⁰ _calc and aspect ratio A are as described in the section of “Additional compound of the present invention” above. Here, the density ρ is 1.

4) Swelling and dissolution In each of the examples and comparative examples, the one shown in Table 2 was selected from the following dissolution steps A and B and used.
・ Dissolution process A
The cellulose acylate was gradually added to the 400 liter stainless steel dissolution tank having stirring blades and circulating cooling water around the outer periphery, while stirring and dispersing the solvent and additive. After completion of the addition, the mixture was stirred at room temperature for 2 hours, swollen for 3 hours, and then stirred again to obtain a cellulose acylate solution.
For the stirring, a dissolver type eccentric stirring shaft that stirs at a peripheral speed of 15 m / sec (shear stress 5 × 10 ⁴ kgf / m / sec ² [4.9 × 10 ⁵ N / m / sec ² ]). And an agitation shaft having an anchor blade on the central axis and stirring at a peripheral speed of 1 m / sec (shear stress 1 × 10 ⁴ kgf / m / sec ² [9.8 × 10 ⁴ N / m / sec ² ]) It was. Swelling was carried out with the high speed stirring shaft stopped and the peripheral speed of the stirring shaft having anchor blades set at 0.5 m / sec.
The swollen solution was heated from a tank to 50 ° C. with a jacketed pipe, and further heated to 90 ° C. under a pressure of 2 MPa to be completely dissolved. The heating time was 15 minutes. At this time, filters, housings, and pipes that were exposed to high temperature were made of Hastelloy alloy and had excellent corrosion resistance, and those having a jacket for circulating a heat medium for heat retention and heating were used.
Next, the temperature was lowered to 36 ° C. to obtain a cellulose acylate solution.
・ Dissolution process B
The cellulose acylate was gradually added to the 400 liter stainless steel dissolution tank having stirring blades and circulating cooling water around the outer periphery, while stirring and dispersing the solvent and additive. After completion of the addition, the mixture was stirred at room temperature for 2 hours, swollen for 3 hours, and then stirred again to obtain a cellulose acylate solution.
For the stirring, a dissolver type eccentric stirring shaft that stirs at a peripheral speed of 15 m / sec (shear stress 5 × 10 ⁴ kgf / m / sec ² [4.9 × 10 ⁵ N / m / sec ² ]). And an agitation shaft having an anchor blade on the central axis and stirring at a peripheral speed of 1 m / sec (shear stress 1 × 10 ⁴ kgf / m / sec ² [9.8 × 10 ⁴ N / m / sec ² ]) It was. Swelling was carried out with the high speed stirring shaft stopped and the peripheral speed of the stirring shaft having anchor blades set at 0.5 m / sec.
The swollen solution was fed from the tank with a screw pump whose center part was heated to 30 ° C., cooled from the outer periphery of the screw, and passed through the cooling part at −70 ° C. for 3 minutes. Cooling was performed using a -75 ° C refrigerant cooled by a refrigerator. The solution obtained by cooling was heated to 30 ° C. in the liquid feed column with a screw pump and transferred to a stainless steel container.
Next, the temperature was lowered to 30 ° C., and the mixture was stirred at 30 ° C. for 2 hours to obtain a cellulose acylate solution.

5) Filtration The obtained solution was filtered with a filter paper (# 63, manufactured by Toyo Filter Paper Co., Ltd.) having an absolute filtration accuracy of 10 μm, and further filtered to a sintered metal filter (FH025, manufactured by Pall) with an absolute filtration accuracy of 2.5 μm. And filtered to obtain a cellulose acylate solution.

(Production of film)
The cellulose acylate solution was heated to 30 ° C. and cast on a mirror surface stainless steel support having a band length of 60 m set at 15 ° C. through a casting Giesser (described in JP-A-11-314233). The casting speed was 50 m / min and the coating width was 200 cm. The space temperature of the entire casting part was set to 15 ° C. Then, the cellulose acylate film that had been cast and rotated 50 cm before the end point of the casting part was peeled off from the band, and 45 ° C. dry air was blown. Next, it was dried at 110 ° C. for 5 minutes and further at 140 ° C. for 10 minutes to obtain a transparent film of cellulose acylate having a thickness of 80 μm.

(Preliminary stretching)
In Example 20 and Comparative Example 12, the following pre-stretching step A was used.
The pre-stretch ratio of the film was determined from the following formula by placing marked lines at regular intervals in a direction orthogonal to the film transport direction, measuring the intervals before and after heat treatment.
Film pre-stretch ratio (%) = 100 × (interval between marked lines after heat treatment−interval between marked lines before heat treatment) / interval between marked lines before heat treatment Further, in each example, the film width after pre-stretching The reduction rate was 10 to 25%.

・ Preliminary stretching process A
The cellulose acylate film thus formed was subjected to longitudinal uniaxial stretching using a roll stretching machine. The roll of the roll drawing machine was an induction heating jacket roll having a mirror-finished surface, and the temperature of each roll could be adjusted individually. The stretching zone was covered with a casing, and the temperatures shown in Table 1 were used. The roll before the stretching part was set so that it could be gradually heated to 160 ° C. The draw ratio was controlled to 40% by adjusting the peripheral speed of the nip roll. The aspect ratio (distance between nip rolls / base inlet width) was adjusted to 0.5, and the stretching speed was 10% / min with respect to the distance between stretching.

(Heat treatment)
The following heat treatment steps A or B were selected and listed in Table 2.

・ Heat treatment process A
The resulting film was heat treated using an apparatus having a heating zone between two nip rolls. The aspect ratio (distance between nip rolls / base width) was adjusted to 3.3, the heating zone was set to the temperature shown in Table 2, and after passing through the two nip rolls, the film was 1000 ° C./min to 25 ° C. Cooled down. Further, the elongation of the film was determined from the following formula by placing marked lines at regular intervals in a direction orthogonal to the film transport direction, measuring the intervals before and after the heat treatment.
Elongation of film (%) = 100 × (interval of marked lines after heat treatment−interval of marked lines before heat treatment) / interval of marked lines before heat treatment / heat treatment step B
After gripping both ends of the obtained film with a tenter clip, the film was passed through the heating zone. The dimensional change rate in the width direction was adjusted by changing the expansion / contraction rate of the tenter. Table 2 shows the temperature of the heating zone, the temperature of the heating zone determined according to the above-described method, and the elongation of the film in the film transport direction determined according to the above-described method.

(Restretch)
In all examples and the following redrawing steps were used. After gripping both ends of the obtained film with a tenter clip, the film was stretched in a direction perpendicular to the transport direction in the heating zone. The draw ratio calculated from the temperature of the heating zone and the expansion / contraction rate of the tenter was 2%. When heat treatment step A was used, after gripping with a tenter clip at the heat treatment zone inlet, the sample was conveyed to the redrawing zone as it was without removing the tenter clip.

(Evaluation of transparent polymer film)
Re (550 nm), ΔRe, Re ₈₀ (550 nm), ΔRe ₈₀ , Re ^ad ₈₀ (550 nm), ΔRe ^ad ₈₀ , Re ^ad _80,% (550 nm), ΔRe ^ad _{80,% of} each obtained transparent polymer film, Rth (550 nm) and Rth ₈₀ (550 nm) were measured and calculated. The meaning of each is as follows. d is the thickness of the transparent polymer film.
Re (550 nm): plane retardation at a measurement wavelength of _{550nm [(n x -n y)} × d; n x is a refractive index in the perpendicular direction to the stretching direction, n _y is a refractive index in the stretching direction, d is the film thickness]
ΔRe = Re (630 nm) −Re (450 nm)
[ΔRe is the chromatic dispersion parameter of in-plane retardation]
Re ₈₀ (550 nm) = Re (550 nm) × 80 / d
[Re ₈₀ (550 nm) is the value converted to 80 μm thickness of Re (550 nm)]
Re ^ad ₈₀ (550 nm) = [Re ₈₀ with additive (550 nm)] − [Re ₈₀ without additive (550 nm)]
ΔRe ^ad ₈₀ = [Re ^ad _{80 with} additive] − [Re ^ad ₈₀ without additive]
Re ^ad _80,% (550 nm) = Re ^ad ₈₀ (550 nm) / addition amount of additive ΔRe ^ad _80,% = ΔRe ^ad ₈₀ / addition amount of additive Rth (550 nm): thickness direction retardation at a measurement wavelength of 550 nm [{ ( _Nx + _ny ) / 2- _nz } × d; _nz is the refractive index in the thickness direction]
Rth ₈₀ (550 nm) = Rth (550 nm) × 80 / d
[Rth ₈₀ (550 nm) is Rth (550 nm) 80 μm thickness equivalent value]

  The results are shown in Table 3 below. In all examples and comparative examples, the slow axis of the film was observed in the width direction of the film.

(ΔRe change due to additives)
As shown in Table 2, the condition is satisfied Examples 1 to 20 of the present invention, [Delta] Re ₈₀ is increased by the addition of additive compounds of the present invention, [Delta] Re ^ad ₈₀ and [Delta] Re ^ad _80,% is a positive value showed that. That is, it was confirmed that the in-plane retardation was inversely wavelength-dispersed by adding the additive compound of the present invention. On the other hand, in Comparative Examples 8 and 11, in which ΔΔn ⁰ _calc was 0 and a compound not satisfying the conditions of the present invention was added, ΔRe ₈₀ decreased and ΔRe ^ad ₈₀ and ΔRe ^ad _80,% showed negative values. Even when a compound satisfying the conditions of the present invention is added, in Comparative Examples 9 and 10 in which heat treatment was performed at a temperature outside the range of the present invention, ΔRe ^ad ₈₀ and ΔRe ^ad _80,% were negative values. showed that.
In all examples, a slow axis was developed in the film width direction. These retardation films are preferable because they can be bonded together with a polarizing plate by roll-to-roll.

Also, shown in FIG. 1 reverse dispersion expressing [Delta] Re ^ad _80,% of the relationship between the per added amount of ^{(A-1) × ΔΔn 0} calc. Correlation between the two was observed, (A-1) in _{^{× ΔΔn 0 calc ≦ -0.01 ΔRe ad}} 80,% becomes positive in-plane retardation it was confirmed that reverse wavelength dispersion of .

<< Example 101 >> Production and Evaluation of Laminated Retardation Film The transparent polymer film of the present invention can be used as it is as a retardation film, but here, the film is bonded by roll-to-roll using an adhesive. Thus, a retardation film with a controlled Rth / Re ratio was produced. Roll using Fujitac TD80UF (manufactured by Fuji Film Co., Ltd.) and the transparent polymer film of Example 1 with adhesive (poly (methyl acrylate / butyl acrylate / hydroxyethyl acrylate), toluene diisocyanate and diglycidyl ethylene glycol) Bonded with two rolls. The slow axis of Re of the retardation film was observed in the width direction of the film, and was an excellent planar shape as a polarizing plate.

Example 102 Preparation and Evaluation of Polarizing Plate 1) Saponification of Film The film obtained in Example 101 was immersed in a 1.5 mol / L NaOH aqueous solution (saponification solution) maintained at 55 ° C. for 2 minutes. Thereafter, the film was washed with water, then immersed in a 0.05 mol / L sulfuric acid aqueous solution at 25 ° C. for 30 seconds, and then passed through a washing bath under running water for 30 seconds to make the film neutral. Then, draining with an air knife was repeated three times, and after dropping water, the film was retained in a drying zone at 70 ° C. for 15 seconds and dried to produce a saponified film. The obtained film had an excellent surface shape, and the optical characteristics and the like almost maintained the characteristics before saponification.

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 polarizing film obtained in this way and the saponified film were placed on the polarizing film side of the saponified surface of the film, and after sandwiching the polarizing film between them, PVA (Kuraray Co., Ltd.) Manufactured, PVA-117H) 3% aqueous solution was used as an adhesive, and the polarizing axis was prepared so that the longitudinal direction of the film was orthogonal to the polarizing plate.

4) Evaluation of polarizing plate (initial polarization degree)
The polarization degree of the polarizing plate was calculated by the following method. The initial polarization degree, the temporal polarization degree 1 and the temporal polarization degree 2 were all 99.9%, indicating excellent polarizing plate characteristics.
(Time polarization 1)
The saponified film side of the polarizing plate is bonded to a glass plate with an adhesive, and left for 500 hours at 60 ° C. and a relative humidity of 95%. Calculated. In any case, the viewing angle characteristics were good.
(Time polarization 2)
The saponified film side of the polarizing plate is bonded to a glass plate with an adhesive and left for 500 hours at 90 ° C. and 0% relative humidity. As a result of the calculation, the decrease in the degree of polarization was 0.1% ≦, which was a level that would not cause a problem as a product.

Example 103 Production and Evaluation of Liquid Crystal Display Device The polarizing plate produced in Example 102 was incorporated into an IPS type liquid crystal display device (32V type high-definition liquid crystal television monitor (W32-L7000), manufactured by Hitachi, Ltd.). When incorporated in place of a polarizing plate, the viewing angle characteristics were improved. This effect is observed when the liquid crystal display device is observed after being left for 500 hours under low humidity conditions (25 ° C. and relative humidity of 10%), and after being left for 500 hours under high humidity conditions (25 ° C. and relative humidity of 80%). Also confirmed when.

  According to the production method of the present invention, a transparent polymer film in which in-plane retardation is dispersed in reverse wavelength can be provided. According to the present invention, a transparent polymer film having such properties, a retardation film using the same, a polarizing plate and a liquid crystal display device can also be provided. Therefore, the present invention can be widely applied to λ / 4 plates used for optical disk pickups and PS conversion element applications, optical compensation films that improve the viewing angle dependency of images of liquid crystal display devices, and the like. Therefore, the present invention has high industrial applicability.

Is a graph showing the ^{(A-1) × ΔΔn 0} calc and ΔRe ^ad _80,% of the relationship.

Claims (5)

A cellulose acylate film containing a compound having a negative chromatic dispersion parameter ΔΔn ⁰ _{calc of} intrinsic birefringence defined by the following formula (1) at a temperature T (unit: ° C.) that satisfies the following formula (2): The manufacturing method of the transparent polymer film characterized by including the process to heat-process.
Formula (1): ΔΔn ⁰ _calc = Δn ⁰ _calc (630 nm) −Δn ⁰ _calc (450 nm)
[In the above equation, Δn ⁰ _calc (630 nm) represents intrinsic birefringence at a measurement wavelength of 630 nm, and Δn ⁰ _calc (450 nm) represents intrinsic birefringence at a measurement wavelength of 450 nm. Here, Δn ⁰ _calc (λ) is defined by the following formula (1a) (λ is 630 nm or 450 nm). ]

[In Formula (1a), n ⁰ _{i calc} (λ), n ⁰ _{j calc} (λ), and n ⁰ _{k calc} (λ) are density functionalities using a molecular structure that generates a minimum energy by structure optimization calculation. This is the main refractive index calculated by the function method. The principal refractive index is the principal axis having the smallest angle between the polarizability tensor obtained using B3LYP / 6-31G ^* as the basis function and the polarizability tensor at a wavelength of λ nm and the principal axis system of the polarizability tensor. It is calculated from the following formulas (1b) and (1c) by using polarizability tensor diagonal components α _ii , α _jj , and α _kk obtained with i and other principal axes as j and k . ]

[In the formulas (1b) and (1c), n _l represents the main refractive index, α _ll represents the polarizability tensor component, ρ represents the density, N _A represents the Avogadro number, M represents the molecular weight, and n represents the average refractive index. ]
Formula (2): Tc ≦ T <Tm ₀
[Wherein, Tc represents the crystallization temperature (unit: ° C.) of the cellulose acylate film before heat treatment, and Tm ₀ represents the melting point (unit: ° C.) of the cellulose acylate film before heat treatment. ] The method for producing a transparent polymer film according to claim 1, wherein the compound satisfies the following formula (3).
Formula (3): (A-1) × ΔΔn ⁰ _calc ≦ −0.01
[Wherein, A represents the aspect ratio of the compound. ]   The method for producing a transparent polymer film according to claim 1, wherein the cellulose acylate film is stretched in the heat treatment step.   The method for producing a transparent polymer film according to claim 3, wherein the stretching is longitudinal stretching performed in an apparatus having a heating zone between two or more nip rolls. The method for producing a transparent polymer film according to any one of claims 1 to 4, wherein the cellulose acylate constituting the cellulose acylate film satisfies the following formula (4).
Formula (4): 2.70 <SA + SB ≦ 3.00
[Wherein, SA represents the degree of substitution of the acetyl group substituted by the hydroxyl group of cellulose, and SB represents the degree of substitution of the acyl group having 3 or more carbon atoms substituted by the hydroxyl group of cellulose. ]

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