JP4954035B2 - Method for producing cellulose acylate film - Google Patents

Description

  The present invention relates to a method for producing a cellulose acylate film, and more particularly to a method for producing a cellulose acylate film having a low Rth.

  Polymer films represented by cellulose ester, polyester, polycarbonate, cycloolefin polymer vinyl polymer, polyimide, and the like are used for silver halide photographic light-sensitive materials, retardation films, polarizing plates, and image display devices. From these polymers, films that are more excellent in terms of flatness and uniformity can be produced, and are therefore widely used as films for optical applications.

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

  On the other hand, when the transparent polymer film is used for a retardation film, a retardation film support, a protective film for a polarizing plate, and an optical application such as a liquid crystal display device, the control of the optical anisotropy is This is a very important factor in determining the performance (for example, visibility) of the display device. Along with the recent demand for wide viewing angle of liquid crystal display devices, it is required to improve the compensation of retardation, and the in-plane direction letter of the retardation film disposed between the polarizing film and the liquid crystal cell It is possible to appropriately control the retardation value (Re; hereinafter simply referred to as “Re”) and the retardation value in the film thickness direction (Rth; hereinafter referred to simply as “Rth”). It is requested. Especially, since the polymer film which shows negative Rth is not easy to manufacture, manufacturing simply is calculated | required.

  As a method of producing a polymer film exhibiting negative Rth, a method of forming a vertically aligned liquid crystal layer using an isotropic polymer film as a support is disclosed (for example, see Patent Document 1). However, the problem is that the yield is reduced due to variations in retardation due to non-uniform orientation and film thickness.

  Further, as a method for producing a polymer film exhibiting negative Rth, a continuous production method is disclosed in which a heat-shrinkable film is adhered to the polymer film, heat-stretched, and then the heat-shrinkable film is peeled off. (For example, refer to Patent Document 2 and Patent Document 3). According to the examples of these documents, it has been clarified that the polycarbonate film or the like produced by this method exhibits negative Rth. However, this method has a problem that a large amount of heat-shrinkable film is consumed and the quality of the obtained film (for example, retardation value and slow axis direction) varies. This problem is particularly remarkable in polymers having a high elastic modulus such as cellulose esters and hydrophilic polymers.

Furthermore, as a method for producing a polymer film exhibiting negative Rth, a method using a cellulose acylate film having a high degree of acetyl substitution is disclosed (for example, see Patent Document 4). According to this method, a film having an appropriate moisture permeability can be obtained, but there are problems that the energy required for dissolving the polymer is large and that Re is not sufficiently developed.
JP-A-6-331826 JP-A-5-157911 Japanese Patent Laid-Open No. 2000-23310 JP 2005-120352 A

  In view of these problems of the prior art, the present inventor aimed to provide a highly productive film having optical properties useful for a retardation film, a polarizing plate and the like. In particular, an object was to provide a film showing a low Rth in the minus direction by a simple method.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that a cellulose acylate film produced according to a specific production method has excellent properties, and that the production method is simple and highly productive. As a result, the inventors have solved the above problems and completed the present invention described below.

[1] A method for producing a cellulose acylate film comprising the following steps (A) to (C):
(A) A step of gelling by casting a cellulose acylate solution on a support.
(B) The web is peeled off from the support, and the ratio (W ₂ / W ₁ ) of the tenter rail width (W ₂ ) after stretching to the tenter rail width (W ₁ ) at the start of stretching is 0.8-2. The process of extending | stretching a web with a tenter in the direction orthogonal to a conveyance direction so that it may become.
(C) The process of heat-processing the produced cellulose acylate film at the temperature T (unit; ° C) of following formula (1).
Formula (1): 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 cellulose acylate film production according to [1], wherein in the step (B), the web peeled off from the support is gripped by a tenter and stretched in a direction perpendicular to the conveying direction. Method.
[3] The method for producing a cellulose acylate film according to [1] or [2], wherein the W ₂ / W ₁ ratio in the step (B) is 1.1 to 1.2.
[4] In any one of [1] to [3], the step (B) includes a step of stretching a web having a residual solvent amount of 60 to 220% by mass in a direction orthogonal to the conveyance direction. The method for producing a cellulose acylate film according to one item.
[5] The solvent according to any one of [1] to [4], wherein the solvent of the cellulose acylate solution in the step (A) contains 1 to 15% by mass of a solvent having a boiling point of 95 ° C. or higher. The manufacturing method of the cellulose acylate film of description.
[6] The process according to any one of [1] to [5], wherein the cellulose acylate solution is cast on a support maintained at −30 to 10 ° C. in the step (A). A method for producing a cellulose acylate film.
[7] The cellulose acylate film according to any one of [1] to [6], wherein the surface temperature of the web on the support in the step (A) is −10 to 0 ° C. Manufacturing method.

  According to the method for producing a cellulose acylate film of the present invention, a cellulose acylate film having a low Rth can be produced with high productivity. In particular, a cellulose acylate film having a negative Rth can be produced with high productivity.

  Below, the manufacturing method of the cellulose acylate film of this invention is 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 Cellulose Acylate Film >>
The cellulose acylate film of the present invention can be produced from a cellulose acylate solution appropriately containing cellulose acylate and various additives by a solution casting film forming method. In the present invention, Rth is optimized by optimizing the chemical structure of cellulose acylate as described below, or by devising the solvent used for film formation and simultaneously controlling the temperature of the support during the film formation process. Cellulose acylate film having a low R (particularly cellulose acylate film having a negative Rth) can be produced with high productivity.

[Cellulose acylate]
In the cellulose acylate film of the present invention, the degree of acyl substitution is 2.50 from the viewpoint of improving the peelability from the support in casting film formation, improving the tensile stress at high temperature, and improving the Re expression of the heat-treated film. It is preferable to use a cellulose acylate of ˜3.00, more preferably a cellulose acylate having an acyl substitution degree of 2.70 to 2.99, more preferably a cellulose acylate of 2.80 to 2.98. A cellulose acylate of .85 to 2.98 is most preferred.

Examples of the polymer constituting the cellulose acylate film of the present invention include a cellulose acylate compound and a compound having an acyl-substituted cellulose skeleton obtained by introducing a functional group biologically or chemically from cellulose as a raw material. It is done.
As said polymer, a powder or a particulate thing can be used, and the pelletized thing can also be used.
The water content of the polymer is preferably 1.0% by mass or less, more preferably 0.7% by mass or less, and most preferably 0.5% by mass or less. Moreover, it is preferable that the said moisture content is 0.2 mass% or less depending on the case. When the water content of the polymer is not within the preferred range, it is preferable to use the polymer after drying it by heating or the like.
These polymers may be used alone or in combination of two or more polymers.
In addition, it is preferable to use the above-mentioned cellulose acylate as a polymer as a main component of the cellulose acylate film of the present invention. Here, the “polymer as the main component” indicates a polymer when it is composed of a single polymer, and when it is composed of a plurality of polymers, it is the most mass fraction of the constituent polymers. Indicates a high polymer.

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

  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 cellulose acylate raw material cotton and the synthesis method are also described in pages 7 to 12 of the Japan Society for Invention and Technology (Publication No. 2001-1745, published on March 15, 2001, Japan Society of Invention).

[Cellulose acylate solution]
(solvent)
As the solvent of the cellulose acylate solution used for the preparation of the cellulose acylate film of the present invention, a solvent containing 1 to 15% by mass of a solvent having a boiling point of 95 ° C. or higher with respect to the total solvent can be preferably used. It is more preferable to contain 10 mass%, and it is further more preferable to contain 3-8 mass%. And it is preferable that the solvent whose boiling point is 95 degreeC or more is a poor solvent of a cellulose acylate. Specific examples of the solvent having a boiling point of 95 ° C. or higher include solvents having a boiling point of 95 ° C. or higher among the specific examples of the “organic solvent used in combination with the main solvent” described later, but butanol, pentanol, It is preferable to use 1,4-dioxane.
Moreover, it is preferable to contain 10-30 mass% of alcohol, It is more preferable to contain 12-25 mass%, It is more preferable to contain 15-25 mass%.
Furthermore, the main solvent having a boiling point of 80 ° C. or less is preferably contained in an amount of 30 to 90% by mass, more preferably 40 to 85% by mass, and further preferably 50 to 80% by mass.
By using a solvent containing such a solvent having a boiling point of 95 ° C. or higher in an amount of 1 to 15% by mass with respect to the total solvent, the gelation temperature is increased, and the cellulose acylate film solution is gelled in a short time. Become. Furthermore, it can peel off from a support body in the state with the amount of residual solvents in a film high by forming into a film by the below-mentioned casting method. As a result, the conveyance speed can be increased and productivity is improved.
The “gelation” in the step (A) of the production method of the present invention means that the cast cellulose acylate solution becomes a gel and can be suitably peeled off as a web from the support. In particular, it means that there is no breakage or insufficient self-holding property when peeling off as a web. In addition, since it is preferable that gelation proceeds in a short time in a state where a relatively large amount of the solvent is embraced, a gel containing a solvent having a boiling point of 95 ° C. or higher and 1 to 15% by mass with respect to the total solvent is used. Gelation can be carried out not only by shortening the gelation time by raising the gelation temperature, but also by other methods.
As the main solvent of the cellulose acylate solution used for producing the cellulose acylate film of the present invention, an organic solvent which is a good solvent for the polymer can be preferably used. As such an organic solvent, an organic solvent having a boiling point of 80 ° C. or lower is more preferable from the viewpoint of reducing the drying load. The boiling point of the organic solvent is more preferably 10 to 80 ° C, and particularly preferably 20 to 60 ° C. Moreover, the organic solvent whose boiling point is 30-45 degreeC depending on the case can also be used suitably as said main solvent.

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

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.
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.

  Although the example of the combination of the organic solvent preferably used as a solvent of the polymer solution used for preparation of the cellulose acylate film of the present invention is given below, the combination of organic solvents that can be employed in the present invention is limited to these. It is not a thing. 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) Acetone / ethanol / butanol = 80/15/5
(22) Methyl acetate / acetone / methanol / butanol = 75/10/10/5

(Additive)
The said cellulose acylate solution used for preparation of the cellulose acylate film used for the manufacturing method of this invention can contain the various liquid or solid additive according to a use in each preparation process. The additive preferably used in the cellulose acylate film of the present invention is an additive having a molecular weight of 3000 or less, and is suitable for reducing the humidity dependency of retardation or adjusting the balance between Re and Rth. Can be used. In particular, when it is desired to increase the Rth / Re value, the additive having a molecular weight of 3000 or less is preferably a compound having one or more aromatic rings. Examples of the additive include a plasticizer (preferred addition amount is 0.01 to 10% by mass with respect to the polymer, the same shall apply hereinafter), an ultraviolet absorber (0.001 to 1% by mass), and an average particle size. 5 to 3000 nm fine particle powder (0.001 to 1% by mass), fluorosurfactant (0.001 to 1% by mass), release agent (0.0001 to 1% by mass), deterioration inhibitor (0 .0001 to 1% by mass), an optical anisotropy control agent (0.01 to 10% by mass), and an infrared absorber (0.001 to 1% by mass).

  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, when these compounds are used in combination with cellulose acylate particularly preferably used in the present invention, the hydrophobicity of the film can be improved and the change in humidity of retardation can be reduced. Moreover, the wavelength dependence of retardation can be effectively controlled by using the ultraviolet absorber or the infrared absorber in combination. Any additive used in the cellulose acylate film of the present invention is preferably substantially free of volatilization during the drying process.

  Depending on the intended Re and Rth values, an optical anisotropy control agent having an effect of not changing or decreasing the Rth of the film before the heat treatment can be preferably used. By adding such an additive, the mobility of the polymer molecules during the heat treatment can be improved, so that the expression of Re and Rth of the cellulose acylate 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. By combining an optical anisotropy control agent such as a retardation increasing agent, not only a cellulose acylate film having an Nz of 0 to 1, but also a cellulose acylate film having an Nz of less than 0 or greater than 1 should be produced as appropriate. Can do.

  From the viewpoint of reducing the humidity change of the retardation, it is preferable that the amount of these additives is large. However, as the amount of addition increases, the glass transition temperature (Tg) of the cellulose acylate film decreases, and the film production process It becomes easy to cause the volatilization problem of the additive. Therefore, when employing cellulose acetate more preferably used in the present invention, the amount of the additive having a molecular weight of 3000 or less is preferably 30% by mass or less, and 0.1 to 30% by mass with respect to the cellulose acylate. More preferably, 2-20 mass% is further more preferable.

From the viewpoint of increasing the Rth / Re value, specifically, a compound having one or more aromatic rings is preferable, 2 to 15 is more preferable, and 3 to 10 is more preferable. 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 additive.

Additives that can be suitably used in the present invention are described in JP-A-2005-104148. Moreover, about an infrared absorber, Unexamined-Japanese-Patent No. 2001-194522 has description. The timing of adding the additive can be appropriately determined according to the type of the additive.
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 cellulose acylate 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. At least one number average molecular weight selected from a plasticizer, a polyether polyurethane plasticizer, a polyamide plasticizer, a polysulfone plasticizer, a polysulfonamide plasticizer, and other polymer plasticizers described later. Preferably, 500 or more plasticizers can be 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.

(1) Polyester plasticizer 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 preservability that the end capping is performed particularly 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. Be 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).

(2) Polyester polyether plasticizer 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). ).

(3) Polyester polyurethane plasticizer Furthermore, the polyester polyurethane plasticizer used by this invention is demonstrated. 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.

(4) Other polymer plasticizers 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. It is. 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).

(5) Examples of specific polymer plasticizers Specific examples of preferable polymer plasticizers are described below, but the polymer plasticizers that can be used in the present invention are not limited thereto.
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, cellulose acylate and a solvent are mixed and stirred to swell, and optionally cooled or heated to dissolve, and then filtered to obtain a polymer solution.

In this invention, in order to improve the solubility to the solvent of a cellulose acylate, the process of cooling and / or heating the mixture of a cellulose acylate and a solvent may be included.
When a halogen-based organic solvent is used as the solvent and the mixture of cellulose acylate and the solvent is cooled, 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.

(Filtration and defoaming)
Prior to casting, the cellulose acylate solution is preferably filtered to remove foreign matters such as undissolved matter, dust and impurities using a suitable filter medium such as a wire mesh or flannel. For the filtration of the cellulose acylate solution, a filter having an absolute filtration accuracy of 0.1 to 100 μm is used, and a filter having an absolute filtration accuracy of 0.5 to 25 μm is preferably used. In that case, it is preferable to perform filtration at a filtration pressure of 1.56 MPa or less, more preferably 1.17 Mpa or less, and even more preferably 0.98 Mpa or less. The filtration flow rate is preferably 5 liters / hr, more preferably 50 liters / hr.
Regarding defoaming, Japanese Patent Application Laid-Open No. 2003-200445 describes a high-concentration cellulose acylate solution before casting on a casting support in order to prevent failure due to casting bubbles, and saturated dissolved air under 1 atm. A solution casting method characterized by degassing to 90% or less of the amount is described.
More specifically, when transferring or storing the fine particle dispersion stock solution after dispersion, the liquid containing the fine particles and the organic solvent is dissolved or dispersed and stored in order to prevent the dispersion from being exposed to air in either the transfer tube or the storage container. When transporting to a container for storage, it is preferable to raise the temperature in this container slightly or leave it for a long time to release the air contained in the solution as bubbles, especially after mixing It is described that such a defoaming should be performed if the dope (cellulose acylate solution) of this type has equipment or time allowance.
Here, as the vibration device used for defoaming in the present invention, it is preferable to apply vibration as fine and strong as possible, and ultrasonic waves are preferable. Further, it is disclosed that the vibration frequency of a useful vibration device is preferably 100 Hz to 40 kHz, and particularly preferably 10 to 40 kHz as an ultrasonic vibration element. Furthermore, it is considered that by performing the vibration treatment in this way, the solubility of the solution is increased and the gelation temperature is increased.

[Casting, drying]
The cellulose acylate film of the present invention can be produced using a conventional solution casting film forming apparatus according to a conventional solution casting film forming method. Specifically, the dope (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. The casting is uniformly cast on a metal support of a cast part, preferably a band-shaped or drum-shaped metal support, more preferably a metal drum (casting process).

  In the present invention, it is preferable from the viewpoint of improving productivity to keep the temperature of the metal support used when casting the cellulose acylate solution at a relatively low temperature. The temperature of the metal support can be evaluated as the temperature of the metal support surface with which the cellulose acylate solution comes into contact, preferably −30 to 10 ° C., more preferably −20 to 7 ° C., More preferably, it is -15-5 degreeC, and it is especially preferable that it is -10-0 degreeC. The surface temperature of the web that gels on the support can be controlled by adjusting the temperature of the support surface. The surface temperature of the web to be gelled is preferably −30 to 10 ° C., more preferably −20 to 7 ° C., further preferably −15 to 5 ° C., and −10 to 0 ° C. It is particularly preferred. By using the above-mentioned solvent and setting the above metal support temperature, the film forming rate can be remarkably increased.

Next, the dope film (also referred to as web) is peeled off from the metal support at the peeling point where the metal support has almost gone around, and then transported to the drying zone, and drying is completed while being transported by a roll group.
In the present invention, when the web is peeled from the metal support, the amount of residual solvent in the web (mixture containing cellulose acylate and solvent) is preferably 101 to 400% by mass, and 120 to 230% by mass. More preferably, it is more preferably 150 to 200% by mass. The residual solvent amount in the cellulose acylate web in the present invention is calculated based on the following formula.
Residual solvent amount (% by mass) = {(MN) / N} × 100
[In the formula, M represents the mass of the cellulose acylate web sampled immediately after peeling from the support, and the mass when this film is dried at 130 ° C. for 2 hours is N. ]

In the present invention, the ratio (W ₂ / W ₁ ratio) of the width (W ₂ ) of the tenter rail after stretching to the tenter rail width (W ₁ ) at the start of stretching from the support is 0.8-2. It is preferable to include the process of extending | stretching a web in the direction orthogonal to the conveyance direction of a film. Considering the width shrinkage accompanying the solvent volatilization (usually the width shrinks to about 0.6 times), even if the W ₂ / W ₁ ratio is 0.8, it is stretched in the width direction.
Moreover, it is preferable that this invention includes the process of hold | gripping the web peeled off from the support body with a clip or a pin tenter.
In order to negatively control the Rth of the film after heat treatment, it is most important to control the width of the peeled web. That is, the ratio of the aforementioned W ₂ / W ₁ ratio or the width (W ₁ ) of the web just before gripping with the tenter and the width (W ₂ ) of the web after gripping with the tenter when the web is gripped by the tenter ( It is important to control the (W ₂ / W ₁ ratio) within a specific range. The W ₂ / W ₁ ratio in the present invention is 0.8 to ₂ , preferably 1 to 1.5, and more preferably 1 to 1.2. By doing in this way, it can be considered that the plane orientation of crystals having negative birefringence that are present in the film after the heat treatment advances, and the Rth of the film becomes negative.

Also, the amount of residual solvent in the web when stretching in the web width direction by the tenter is important. The amount of residual solvent in the web when starting stretching is preferably 60% by mass to 220% by mass, more preferably 100% by mass to 210% by mass, and 150% by mass to 200% by mass. Is more preferable. The residual solvent amount in the web in the present invention is calculated based on the following formula.
Residual solvent amount (% by mass) = {(MN) / N} × 100
[In the formula, M represents the mass of the web, and the mass when this web is dried at 130 ° C. for 2 hours is N. ]
Stretching in the film width direction or simultaneous biaxial stretching in the above residual solvent amount region relaxes the orientation of amorphous with positive birefringence and increases the contribution of orientation of crystals with negative birefringence. Therefore, it can be considered that the Rth of the film is lowered.
The ratio (v ₂ / v ₁ ) between the support speed (v ₁ ) and the film winding speed (v ₂ ) is preferably 1.2 to 3, preferably 1.25 to 2.5. More preferably, it is 1.3-2.

  The film thus dried may be conveyed to a heat treatment zone, or may be heat treated off-line after the film is wound up. 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.

[Pre-stretching]
In the present invention, pre-stretching refers to stretching the cellulose acylate film before the heat treatment step, and it does not matter whether or not further stretching is performed after the pre-stretching. In the production method of the present invention, pre-stretching may or may not be performed. However, if pre-stretching is performed, the optical anisotropy developed in the heat treatment step can be increased. 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.

Pre-stretching is performed at (Tg-20) to (Tg + 50) ° C., where Tg is the glass transition temperature of cellulose acylate. The pre-stretching 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. Since the cellulose acylate polymer can be arranged to some extent in the pre-stretching direction by pre-stretching the film in this way, in the heat treatment step described later, the structure observed by X-ray diffraction can be efficiently and Can grow anisotropically. The preliminary stretching temperature is preferably lower than the heat treatment temperature described later. By making the pre-stretching temperature lower than the heat treatment temperature, the cellulose acylate polymer can be oriented without growing the structure observed by X-ray diffraction. There is an advantage that a structure observed by diffraction can be grown.
The residual solvent amount of the cellulose acylate film before pre-stretching is preferably 3.0% by mass or less, more preferably 2.0% by mass or less, and more preferably 1.0% by mass or less. Is more preferable, and 0.5% by mass or less is particularly preferable. The residual solvent amount in the cellulose acylate film in the present invention is calculated based on the following formula.
Residual solvent amount (% by mass) = {(MN) / N} × 100
[In formula, M represents the mass of a cellulose acylate film, and the mass when this film is dried at 110 degreeC for 3 hours is N. ]

The preliminary stretching may be horizontal stretching performed in a direction orthogonal to the transport direction, for example, tenter stretching performed in an apparatus having a heating zone by holding both ends of a film with a tenter clip, but is performed in the transport direction. Longitudinal stretching is preferably performed, for example, longitudinal stretching performed between two or more apparatuses (for example, nip rolls or suction drums) that hold a film whose peripheral speed on the outlet side is increased in the transport direction. 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 using 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 production method of the present invention includes a step of heat-treating the cellulose acylate film at a temperature T (unit: ° C.) that satisfies the condition of the following formula (1). Here, the heat treatment is preferably performed while being conveyed.
Formula (1): Tc ≦ T <Tm ₀
In Formula (1), Tc represents the crystallization temperature of the cellulose acylate film before heat treatment, and the unit is ° C. In the present invention, the crystallization temperature refers to a temperature at which the polymer constituting the cellulose acylate film of the present invention forms a regular periodic structure, and the structure observed by X-ray diffraction exceeds this temperature. grow up. The crystallization temperature in the present invention is such that 20 mg of a polymer film before heat treatment is put in a DSC measurement pan, and this is heated from 30 ° C. to 120 ° C. at 10 ° C./min and held for 15 minutes in a nitrogen stream, then 30 This is the starting temperature of the exothermic peak observed when the temperature was cooled to -20 ° C / min to ° C and further raised 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 (1), 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.

By heat-treating the cellulose acylate film at a temperature T satisfying the condition of the formula (1), the expression of retardation of the cellulose acylate film can be adjusted. As a result, it has become possible to produce a cellulose acylate film having a retardation value that was not easy to produce by a simple method. In particular, a cellulose acylate film of | Rth | /Re≦0.5, which could not be produced without a complicated production method in the past, can be produced in a good surface by a simple method.
The heat treatment temperature in the production method of the present invention preferably satisfies the following formula (1-1), more preferably satisfies the following formula (1-2), and further preferably satisfies the following formula (1-3). . 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 (1-1): Tc ≦ T <Tm ₀ −5
Formula (1-2): Tc ≦ T <Tm ₀ −10
Formula (1-3): 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, Rth can be lowered (especially Rth is negative), and the aggregation and arrangement of polymer chains in the film can be advanced to a high degree. It becomes possible to produce a cellulose acylate film having a small dimensional change and an appropriate moisture permeability.
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. . Preference is given to means for conveying by nip rolls. Specifically, a mode in which a nip roll is installed at least before and after the zone where heat treatment is performed and the polymer film is conveyed by passing between the nip rolls can be exemplified.

  The film conveyance speed in the production method of the present invention is usually 1 to 500 m / min, including not only during heat treatment but also during film formation, preferably 5 to 300 m / min, more preferably 10 to 200 m / min, More preferably, it is 20-100 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 and transport speed of the cellulose acylate film to be manufactured, but usually (transport length) / (width of the cellulose acylate film to be transported). The ratio (also referred to as aspect ratio) is preferably set to 0.1 to 100, more preferably 0.5 to 50, and still more preferably 1 to 20. 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 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 the heat treatment is not particularly limited, but when the polymer film before the heat treatment has anisotropy, it is preferably stretched in the orientation direction of the polymer in the polymer film before the heat treatment. 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. More preferably, it is 1.1-5, 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 cellulose acylate 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 0.8 to 10 times, preferably 1 to 5 times, more preferably 1.1 to 3 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 and the stretching speed in the stretching is preferably 10 to 10,000% / min, more preferably. It is 20 to 1000% / min, and more preferably 30 to 800% / min.

The cellulose acylate film may be shrunk during the 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 polymer 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

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.
The residual solvent amount of the cellulose acylate film after the heat treatment is preferably 1.0% by mass or less, more preferably 0.5% by mass or less, and more preferably 0.3% by mass or less. Is more preferably 0.1% by mass or less.

[Stretching]
In order to adjust Re and Rth, the cellulose acylate film transported in the heat treatment zone can be stretched simultaneously with the heat treatment, or the cellulose acylate film after the heat treatment can be further stretched.

(Stretching method)
Stretching is, for example, longitudinal stretching performed in the transport direction in a device having a heating zone between two or more devices (for example, nip rolls or suction drums) that hold the film whose peripheral speed on the exit side is increased in the transport direction. Alternatively, the stretching may be performed by gripping both ends of the film with a chuck and spreading the film in a direction perpendicular to the conveyance direction, or a combination thereof.
When the cellulose acylate film after the heat treatment is further stretched, it is preferable that the film is once cooled after the heat treatment and further moved to a stretching step. In this case, the heat treatment is preferably carried out by passing it through a heat treatment zone while being conveyed, and the stretching is preferably carried out by gripping both ends of the film with a chuck and spreading it in a direction perpendicular to the conveyance direction.

The draw ratio can be appropriately set according to the retardation required for the film, preferably 3 to 500%, more preferably 5 to 100%, still more preferably 10 to 80%, and particularly preferably 20 to 60%. These stretching operations may be performed in one stage or in multiple stages. Here, “stretch ratio (%)” means that obtained using the following formula.
Stretch ratio (%) = 100 × {(Length after stretching) − (Length before stretching)} / Length before stretching

  The stretching speed in the stretching is preferably 10 to 10000% / min, more preferably 20 to 1000% / min, and further preferably 30 to 800% / min.

《Cellulose acylate film》
The cellulose acylate film produced by the production method of the present invention has a low Rth. In particular, a cellulose acylate film having a negative Rth can be provided. Rth can be adjusted in the positive or negative direction by adding an additive as described above. Therefore, by adding an additive, it is possible to convert a film originally showing negative Rth into a film showing positive Rth. Films in which Rth is adjusted by adding additives as described above are also included in the scope of the present invention.

[Retardation]
Next, each retardation in the present invention will be described. 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. At 25 ° C. and 60% relative humidity, the following formula was used: An average refractive index (n) represented by (a) is obtained.
Formula (a): 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) represent in-plane retardation and retardation in the thickness direction at a wavelength λ, respectively. 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 (manufactured 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) Measurements were made at 11 points in total by making light of wavelength λ nm incident from each inclined direction in steps of 10 ° from −50 ° to + 50 ° from the normal direction to the normal direction of the film). Then, KOBRA 21ADH or WR is calculated 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 retardation value of zero at a certain tilt angle with the in-plane slow axis from the normal direction as the rotation axis, the retardation value at a tilt angle larger than that tilt angle. After changing its sign to negative, KOBRA 21ADH or WR calculates.
In addition, the retardation value is measured from the two inclined directions, with the slow axis as the tilt axis (rotation axis) (when there is no slow axis, the arbitrary direction in the film plane is the rotation axis), Based on the value, the average refractive index, and the input film thickness value, Rth can also be calculated from the following formulas (b) and (c).
Formula (b):

［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に直交する方向の屈折率を表す。］
式（ｃ）： Ｒｔｈ＝(（ｎｘ＋ｎｙ）／２−ｎｚ)×ｄ
測定されるフィルムが一軸や二軸の屈折率楕円体で表現できないもの、いわゆる光学軸（ｏｐｔｉｃ ａｘｉｓ）がないフィルムの場合には、以下の方法によりＲｔｈ（λ）は算出される。
Ｒｔｈ（λ）は前記Ｒｅ（λ）を、面内の遅相軸（ＫＯＢＲＡ ２１ＡＤＨまたはＷＲにより判断される）を傾斜軸（回転軸）としてフィルム法線方向に対して−５０度から＋５０度まで１０度ステップで各々その傾斜した方向から波長λｎｍの光を入射させて１１点測定し、その測定されたレターデーション値と平均屈折率および入力された膜厚値を基にＫＯＢＲＡ ２１ＡＤＨまたはＷＲが算出する。
これら平均屈折率と膜厚を入力することで、ＫＯＢＲＡ ２１ＡＤＨまたはＷＲはｎｘ、ｎｙ、ｎｚを算出する。この算出されたｎｘ、ｎｙ、ｎｚよりＮｚ＝（ｎｘ−ｎｚ）／（ｎｘ−ｎｙ）がさらに算出される。

[In the formula, Re (θ) represents a retardation value in a direction inclined by an angle θ from the normal direction. Further, 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, and nz represents the refractive index in the direction perpendicular to nx and ny. ]
Formula (c): 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. Measured at 11 points by making light of wavelength λ nm incident from the inclined direction in 10 degree steps, and KOBRA 21ADH or WR is calculated based on the measured retardation value, average refractive index, and input film thickness value. To do.
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 retardation value of the cellulose acylate film of the present invention is preferably in-plane retardation of 15 to 600 nm, more preferably in-plane retardation of 30 to 600 nm, and in-plane retardation. More preferably, it is 50-600 nm, and it is most preferable that it is 100-400 nm.

Furthermore, it is preferable that the following formulas (A), (B) and (C) are satisfied at the same time.
Formula (A): | Rth | /Re≦0.5
Formula (B): Re ≧ 30
Formula (C): Rth ≦ −7.5
[In the formula, Re represents the retardation value (unit: nm) in the in-plane direction of the cellulose acylate film, and Rth represents the retardation value (unit: nm) in the film thickness direction of the cellulose acylate film. ]

Moreover, it is preferable that the cellulose acylate film of the present invention further satisfies the following formulas (Aa), (Ba), and (Ca).
Formula (Aa): | Rth | /Re≦0.5
Formula (Ba): 30 ≦ Re ≦ 600
Formula (Ca): −300 ≦ Rth ≦ −15

  The variation width of the in-plane slow axis of the cellulose acylate film of the present invention is preferably less than 5 °, more preferably less than 3 °, still more preferably less than 1 °, and more preferably 0.5 It is particularly preferred that the angle is less than °.

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

[Film thickness]
The film thickness of the cellulose acylate film of the present invention is preferably 20 μm to 180 μm, more preferably 40 μm to 160 μm, and even more preferably 60 μm to 140 μm. When the film thickness is thinner than 20 μm, handling property and curling of the polarizing plate when processing into a polarizing plate or the like are not preferable. The film thickness unevenness of the cellulose acylate film of the present invention is preferably 0.01 to 3 μm in both the transport direction and the width direction, more preferably 0.01 to 1.5 μm, and more preferably 0.1 to 1 μm. It is particularly preferred that

[Configuration of cellulose acylate film]
The cellulose acylate 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.

[surface treatment]
The cellulose acylate film of the present invention can be appropriately surface-treated to improve adhesion with each functional layer (for example, an undercoat layer, a back layer, and an optically anisotropic layer). 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) may be provided on the cellulose acylate 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 cellulose acylate film of the present invention.

<Phase difference film>
The cellulose acylate 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 cellulose acylate 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 cellulose acylate films of the present invention are laminated, or the cellulose acylate film of the present invention and a film other than the present invention are laminated, and Re and Rth are appropriately adjusted and used as a retardation film. You can also. Lamination of the film can be performed using a pressure-sensitive adhesive or an adhesive.

In some cases, the cellulose acylate 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 cellulose acylate 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 The 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. , 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 are described in, for example, Makromol. Chem. 190, 2255 (1989), Advanced Materials 5, 107 (1993), U.S. Pat. Nos. 4,683,327, 5,622,648, 5,770, No. 107 specification, International Publication No. 95/22586 pamphlet, No. 95/24455 pamphlet, No. 97/00600 pamphlet, No. 98/23580 pamphlet, No. 98/52905 pamphlet, JP-A-1-272551, The compounds described in JP-A-6-16616, JP-A-7-110469, JP-A-11-80081, JP-A-2001-328773, and the like are included.

"Polarizer"
The cellulose acylate film or retardation film of the present invention can be used as a protective film for a polarizing plate (the polarizing plate of the present invention). The polarizing plate of the present invention comprises a polarizing film and two polarizing plate protective films (cellulose acylate film) protecting both surfaces thereof, and the cellulose acylate film or retardation film of the present invention is at least one polarizing plate protective film. Can be used as
When the cellulose acylate film of the present invention is used as the polarizing plate protective film, the cellulose acylate film of the present invention is subjected to the surface treatment (also described in JP-A Nos. 6-94915 and 6-118232). For example, glow discharge treatment, corona discharge treatment, or alkali saponification treatment is preferably performed. 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 cellulose acylate 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 cellulose acylate 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 cellulose acylate film of the present invention may be used for any of the four polarizing plate protective films, but the cellulose acylate film of the present invention is provided 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 disposed on the substrate. Further, the protective film disposed on the opposite side of the cellulose acylate film of the present invention across the polarizing film can be provided with a transparent hard coat layer, an antiglare layer, an antireflection layer, and the like, particularly a liquid crystal display device. It is preferably used as a polarizing plate protective film on the outermost surface of the display side.

<Liquid crystal display device>
The cellulose acylate 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 cellulose acylate 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 cellulose acylate film of the present invention may be used as a support for a retardation film of a TN 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. Other papers (Jpn. J. Appl. Phys. Vol. 36 (1997) p. 143 and Jpn. J. Appl. Phys. Vol. 36 (1997) p. 1068) are described.

(STN type liquid crystal display device)
The cellulose acylate 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 cellulose acylate 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 cellulose acylate 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 cellulose acylate film of the present invention is particularly used 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. It is advantageously used. 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 cellulose acylate 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 cellulose acylate 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 retardation is minimum does not exist in the plane of the retardation film and 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. Moreover, it is described in Mori et al. (Jpn. J. Appl. Phys. Vol. 38 (1999) p. 2837).

(Reflective liquid crystal display)
The cellulose acylate 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 cellulose acylate 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 a liquid crystal cell of an ASM (Axial Symmetrical Microcell) mode. The ASM mode liquid crystal cell is characterized in that the thickness of the cell is maintained by a 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 a paper by Kume et al. (Kume et al., SID 98 Digest 1089 (1998)).

(Hard coat film, antiglare film, antireflection film)
In some cases, the cellulose acylate film of the present invention may be applied to a hard coat film, an antiglare film, and an antireflection film. 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 cellulose acylate film of the present invention. Can be granted. 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 cellulose acylate film of the present invention.

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

[Melting point (Tm ₀ )]
8 mg of 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 and held for 15 minutes, and then −10 ° C./30° C. to 30 ° C. Cooled in minutes. Then, the temperature at the top of the endothermic peak that appeared when the temperature was raised again from 30 ° C. to 300 ° C. was taken as the melting point of the film.

[Crystallization temperature (Tc)]
8 mg of 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 −10 ° C./30° C. Then, the temperature at which the exothermic peak appeared when the temperature was raised again from 30 ° C. to 300 ° C. was taken as the crystallization temperature of the cellulose acylate film before the heat treatment.

[Degree of substitution]
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.).

[Degree of polymerization]
After absolute drying of the cellulose acylate, 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 for the sample to fall, T ₀ is the number of seconds for the solvent alone, ln is the natural logarithm, C is the concentration (g / L), and Km is 6 × 10 ⁻⁴ . ]

[Residual solvent amount]
According to the above-mentioned method, the mass at a specific time point and the mass after drying at 130 ° C. for 2 hours were measured and determined.

[Retardation]
5 points in the width direction of the film (the central part and the end part of the film (positions of 5% of the total width from both ends) and the middle part of the center part and the end part) are sampled every 100 m in the longitudinal direction and 5 cm A sample having a size of × 5 cm was taken out, the average value of each point evaluated according to the above-described method was calculated, and Re and Rth and the direction of the in-plane slow axis were obtained.

  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.

<< Examples 101-113, Comparative Examples 101-106
[Preparation of polymer solution]
1) Cellulose acylate A cellulose acetate powder having a substitution degree of 2.86 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 size of the powder was 1.5 mm, and the standard deviation was 0.5 mm.

2) Solvent Dichloromethane is selected as the halogenated hydrocarbon, butanol is selected as the solvent having a boiling point of 95 ° C. or higher, methanol is selected as the other alcohol, the amount of methanol is fixed at 16.3 parts by mass, and the amount of butanol is shown in Table 1. The amount of dichloromethane was adjusted so that the total amount of dichloromethane, methanol, and butanol was 100 parts by mass. The water content of the solvent was 0.2% by mass or less.

3) Additives The additives listed in Table 1 were selected from the following additives A to C and used.
・ Additive A
Triphenyl phosphate (1.6 parts by mass)
Biphenyl diphenyl phosphate (0.8 parts by mass)
Silicon dioxide fine particles (particle size 20 nm, Mohs hardness about 7) (0.08 parts by mass)
・ Additive B
Silicon dioxide fine particles (particle size 20 nm, Mohs hardness about 7) (0.08 parts by mass)
・ Additive C
PP-29 ′ (2.4 parts by mass)
Silicon dioxide fine particles (particle size 20 nm, Mohs hardness about 7) (0.08 parts by mass)

4) Preparation of cellulose triacetate solution (hereinafter referred to as “dope”) A cellulose triacetate powder (flakes) was prepared by mixing the plurality of solvents in a 4000 L stainless steel dissolution tank having a stirring blade and stirring and dispersing well as a mixed solvent. ) Was gradually added to prepare a total of 2000 kg. In addition, all the solvents used that the water content is 0.5 mass% or less. First, powder of cellulose triacetate is charged into a dispersion tank, and a stirring shear rate is initially 5 m / sec (shear stress 5 × 10 ⁴ kgf / m / sec ² ). Dispersion was carried out for 30 minutes under the condition of having a core stirring shaft and an anchor blade on the central shaft and stirring at a peripheral speed of 1 m / sec (shear stress 1 × 10 ⁴ kgf / m / sec ² ). The starting temperature of dispersion was 25 ° C., and the final temperature reached 48 ° C. After completion of the dispersion, the high-speed stirring was stopped, and the peripheral speed of the anchor blade was set to 0.5 m / sec and further stirred for 100 minutes to swell the cellulose triacetate flakes. Until the end of swelling, the inside of the tank was pressurized to 0.12 MPa with nitrogen gas. At this time, the oxygen concentration in the tank was less than 2 vol%, and the state of no problem was maintained in terms of explosion protection. The water content in the dope was confirmed to be 0.5% by mass or less, and 0.3% by mass in this experiment.

5) Dissolution / filtration step The swollen solution was heated from the tank to 50 ° C. with a jacketed pipe, and further heated to 90 ° C. under a pressure of 2 MPa to completely dissolve. The heating time was 15 minutes.
Next, the temperature was lowered to 36 ° C., and a dope was obtained by passing through a filter medium having a nominal pore diameter of 8 μm. At this time, the primary pressure of filtration was 1.5 MPa, and the secondary pressure was 1.2 MPa. The filters, housings, and pipes that are exposed to high temperatures were made of Hastelloy (registered trademark) and had excellent corrosion resistance, and had a jacket through which a heat transfer heating medium was circulated.

6) Concentration and filtration The pre-concentration dope thus obtained was flushed at 80 ° C. in a normal pressure tank, and the evaporated solvent was recovered and separated by a condenser. The solid concentration of the dope after flashing was 23.5% by mass. In addition, the condensed solvent was sent to a recovery process to be reused as a solvent in the preparation process (recovery is performed by a distillation process, a dehydration process, and the like). The flash tank had an anchor blade on the central axis, and deaerated by stirring at a peripheral speed of 0.5 m / sec. The temperature of the dope in the tank was 25 ° C., and the average residence time in the tank was 50 minutes. The shear viscosity measured at 25 ° C. after collecting this dope was 450 (Pa · s) at a shear rate of 10 (sec ⁻¹ ).

  Next, this dope was defoamed by irradiating weak ultrasonic waves. Thereafter, under a pressure of 1.5 MPa, a sintered fiber metal filter having a nominal pore diameter of 10 μm was first passed, and then a 10 μm sintered fiber filter was also passed. Respective primary pressures were 1.5 MPa and 1.2 MPa, and secondary pressures were 1.0 MPa and 0.8 MPa. The dope temperature after filtration was adjusted to 36 ° C. and stored in a 2000 L stainless steel stock tank. The stock tank had an anchor blade on the central axis and was constantly stirred at a peripheral speed of 0.3 m / sec. In addition, when the dope was prepared from the dope before concentration, no problem such as corrosion occurred at all in the wetted part of the dope.

[Production of film]
The polymer solution was heated to 30 ° C., and cast on a mirror surface stainless steel support, which was a drum having a diameter of 3 m, through a casting Giuser. The temperature of the support was set to the temperature shown in Table 1, the casting speed was 100 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 which had been cast and rotated 50 cm before the end point of the casting part was peeled off from the drum. Table 1 shows the amount of residual solvent at the time of stripping. In addition, when the surface temperature of the web which gelatinized on the support body at the time of film forming was measured with the non-contact thermometer, it was in the range of -10 degreeC-0 degreeC.
Thereafter, both ends of the peeled web were gripped with a pin tenter. The cellulose acylate film held by the pin tenter was conveyed to the drying zone. In the initial drying, a drying air of 45 ° C. 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. The ratio (W ₂ / W ₁ ) of the tenter rail width (W ₂ ) after stretching to the tenter rail width (W ₁ ) at the start of stretching was set to the values shown in Table 1, respectively.
The amount of residual solvent of the peeled web was measured by sampling the web immediately after the peeling point, and is shown in Table 1. Table 1 also shows the results of measuring Tc and Tm ₀ for the film before heat treatment.

[Heat treatment]
The obtained film was heat-treated using an apparatus having a heating zone between two nip rolls, and the film was contracted in the width direction. The aspect ratio (distance between nip rolls / base width) is adjusted to 3.3, the base temperature before entering the heating zone is set to 25 ° C., and the heating zone temperature T is set to the temperature shown in Table 1 and heated for 1 minute. did.
At the same time, for Examples 101～104,111～113 and Comparative Example 104, the ratio between the delivery nip rolls speed (v ₁₀₎ and the take-up nip roll speed (v ₁₁₎ to (v ₁₁ / v ₁₀₎ 1 The film was stretched in the machine direction. Table 1 shows the results of measuring the draw ratio in the film conveyance direction (MD direction) in each Example.

[Evaluation of manufactured cellulose acylate film]
Each cellulose acylate film obtained in each example and comparative example was evaluated. The results are shown in Table 1 below.
In Table 1, the dissolved state of the dope was evaluated visually according to the following.
○: A small gel or insoluble matter is dissolved uniformly. ×: A large number of small gels or insoluble matters are seen.
◯: There is no peeling residue on the support and can be peeled off. ×: Many peeling residues are seen on the support, and the surface state that cannot be peeled off was evaluated visually according to the following.
◎: Excellent in surface shape, good film thickness unevenness of 0.5μm, as an optical film
What can be preferably applied ○: It is in the form of a plane that can be applied as an optical film. ×: Waviness and wrinkles of the film are severe, and is not preferable as an optical film. The direction was 90 ° with respect to the film transport direction.
Table 1 shows the results of measuring the film thickness of the heat-treated film.

As shown in Table 1, according to the method of the present invention, it was confirmed that a cellulose acylate film having a large Rth optical property in the minus direction and having a good surface shape can be produced with good productivity (Example 101). ~ 113). When the solvent ratio with a boiling point of 95 ° C. or higher was not appropriate, gelation did not occur on the support, or the solution was not completely dissolved, making it impossible to form a film (Comparative Examples 101 and 102). ). In addition, even when the temperature of the support was not appropriate, the solution did not gel and the web could not be peeled off (Comparative Example 103). When the W ₂ / W ₁ ratio is set lower within the range of the present invention, a film having a good surface shape can be obtained, but the Rth of the film after heat treatment tends to increase in the positive direction (Examples 104 and 105). . On the other hand, when the W ₂ / W ₁ ratio was significantly lowered or significantly increased beyond the range of the present invention, the surface condition deteriorated (Comparative Example 104) or the film was broken (Comparison). Example 105). In addition, when the temperature during the heat treatment was not appropriate, Rth after the heat treatment had a positive value (Comparative Example 106). Furthermore, when the amount of residual solvent at the time of stretching is low, the Rth of the film increases in the minus direction, but the transport speed must be lowered (Examples 110 and 111), so the amount of residual solvent at the time of stretching is 60 to 220. The mass% was more advantageous in terms of productivity (Examples 101 to 109, 112, 113). Moreover, even when the kind of additive in the solution was changed, a film having a good surface shape and a low Rth could be produced with high productivity (Examples 112 and 113).

Claims (7)

The manufacturing method of the cellulose acylate film whose Rth is -7.5 nm or less characterized by including each process of following (A)-(C).
(A) A step of gelling by casting a cellulose acylate solution on a support.
(B) The web is peeled off from the support, and the ratio (W ₂ / W ₁ ) of the tenter rail width (W ₂ ) after stretching to the tenter rail width (W ₁ ) at the start of stretching is 0.8-2. The process of extending | stretching a web with a tenter in the direction orthogonal to a conveyance direction so that it may become.
(C) The process of heat-processing the produced cellulose acylate film at the temperature T (unit; ° C) of following formula (1).
Formula (1): 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. ]   In the said process (B), the web peeled off on the support body is hold | gripped with a tenter, and is extended | stretched in the direction orthogonal to a conveyance direction, The manufacturing method of the cellulose acylate film of Claim 1 characterized by the above-mentioned. 3. The method for producing a cellulose acylate film according to claim 1, wherein the W ₂ / W ₁ ratio in the step (B) is 1.1 to 1.2.   In the said process (B), the process of extending | stretching the web whose residual solvent amount is 60-220 mass% in the direction orthogonal to a conveyance direction is included, The cellulose as described in any one of Claims 1-3 characterized by the above-mentioned. A method for producing an acylate film.   The cellulose acylate according to any one of claims 1 to 4, wherein the solvent of the cellulose acylate solution in the step (A) contains 1 to 15% by mass of a solvent having a boiling point of 95 ° C or higher. A method for producing a film.   In the said process (A), a cellulose acylate solution is cast on the support body hold | maintained at -30-10 degreeC, The cellulose acylate film as described in any one of Claims 1-5 characterized by the above-mentioned. Manufacturing method.   The method for producing a cellulose acylate film according to any one of claims 1 to 6, wherein the surface temperature of the web gelled on the support in the step (A) is -10 to 0 ° C. .