JP2011126968A - Cellulose acylate film, retardation film, polarizing plate, and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cellulose acylate film the variation of Re and Rth of which is controlled depending on humidity changes in use environments. <P>SOLUTION: This cellulose acylate film includes cellulose acylate and a compound represented by formula (1) (wherein, R<SP>1</SP>and R<SP>2</SP>are each independently a hydrogen atom, a 1C-20C alkyl group, a 1C-20C alkenyl group, a 2C-20C alkynyl group, a 5C-20C heteroaryl group or a 6-20 aryl group, and X is a substituent in which Hammett's σp and σm value satisfy one of relations of (i) σm<0 and σp≥0, (ii) σp<0 and σm≥0, and (iii) σp≥0 and σm≥0). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a cellulose acylate film, a retardation film, a polarizing plate using the cellulose acylate film, and a liquid crystal display device.

  Liquid crystal display devices are increasingly used year by year as space-saving image display devices with low power consumption. Conventionally, a liquid crystal display device has a major drawback that the viewing angle dependency of a display image is large. However, a wide viewing angle liquid crystal mode such as a VA mode has been put into practical use, and thereby, a high-quality image such as a television can be obtained. In demanded markets, the demand for liquid crystal display devices is expanding rapidly.

  The basic configuration of a liquid crystal display device is one in which polarizing plates are provided on both sides of a liquid crystal cell. The polarizing plate plays a role of allowing only light having a polarization plane in a certain direction to pass through, and the performance of the liquid crystal display device is greatly influenced by the performance of the polarizing plate. The polarizing plate generally has a configuration in which transparent protective films are bonded to both front and back sides of a polarizer made of a polyvinyl alcohol film or the like on which iodine or dye is adsorbed and oriented. A cellulose acylate film typified by cellulose acetate has been widely used as a polarizing plate protective film because it has high transparency and can easily ensure adhesion with polyvinyl alcohol used in a polarizer.

  In addition, it is known that a wider viewing angle can be realized, that is, display characteristics can be improved by arranging an optically biaxial retardation film between a polarizing plate and a liquid crystal cell of a liquid crystal display device. Yes. As such a retardation film, a cellulose acylate film capable of exhibiting excellent optical performance, specifically, in-plane retardation Re (nm) and retardation Rth (nm) in the thickness direction of the retardation film. The cellulose acylate film is also used as a retardation film in a liquid crystal display device.

  On the other hand, the cellulose acylate film has a problem that it easily absorbs water as compared with other synthetic polymers, and therefore the film performance is likely to change with changes in environmental humidity. In recent years, as the application of liquid crystal display devices has been expanded, large-size and high-quality applications such as televisions have been expanded, and demands for the quality of polarizing plates, retardation films and polarizing plate protective films have further increased. In particular, a large-size and high-quality liquid crystal display device is required to be used in various harsh environments as compared with the conventional liquid crystal display device. From such a viewpoint, an improvement in resistance to humidity has been strongly desired for cellulose acylate films used in liquid crystal display devices.

  On the other hand, the method of suppressing the moisture content of a film by adding a hydrophobic compound to a cellulose acylate film until now has been examined. As the additive, a structure having both a polar group and a hydrophobic group, such as a polyhydric alcohol derivative and a polyvalent carboxylic acid derivative, has been proposed.

  Conventionally, as an example of an additive that has been studied from the viewpoint of improving resistance to humidity, Patent Document 1 discloses that a cellulose ester film has a benzenecarboxylic acid or a phenol residue at both ends, and an aliphatic cyclic glycol. And an ester plasticizer having a structure containing an aliphatic cyclic dibasic acid. Further, according to the same document, it is disclosed that by adding such an additive, it is possible to provide a retardation film that suppresses the humidity fluctuation of the retardation value and has a stable display quality.

  On the other hand, for example, an additive containing a heterocyclic ring such as a cyclic imide in a part of the skeleton has hardly been added to the cellulose acylate film from the viewpoint of improving resistance to humidity. In particular, little consideration has been given to the addition of barbituric acids to cellulose acylate films.

  Here, in Patent Document 2, a cellulose acylate film having a good surface shape is provided by adding a so-called oil gelling agent as an additive for increasing the viscosity of the cellulose acylate solution by physical interaction and gelling. It is disclosed that it can be done. The literature includes compounds of barbituric acids as a kind of oil gelling agent for cellulose acylate film. As barbituric acid derivatives, aromatic substituents having 6 to 100 carbon atoms or carbon atoms having 5 to 100 carbon atoms are listed. Aliphatic substituents are mentioned as examples. However, Patent Document 2 does not disclose an example in which barbituric acid is actually used to examine its effect, and for that reason, an additive containing a heterocyclic ring such as a cyclic imide as a part of the skeleton is still present in cellulose. In fact, the effect on humidity fluctuations when added to an acylate film has not been disclosed or suggested.

JP 2007-298916 A JP 2002-322294 A

  When the present inventors added the ester plasticizer described in Patent Document 1, the humidity durability improvement effect of the optical properties was examined. Although the environmental humidity fluctuation of the retardation of the film was suppressed, the effect was It turns out that it is still small and that further improvements are needed.

  An object of the present invention is to provide a cellulose acylate film in which fluctuations in Re and Rth with respect to changes in humidity in a use environment are suppressed. Moreover, it is providing the retardation film using this cellulose acylate film, a polarizing plate, and a liquid crystal display device using the same.

  When the present inventors diligently studied for the purpose of solving the above-mentioned problems, various derivatives of barbituric acid described in Patent Document 2 were investigated as additives for cellulose acylate films. As a result, it was found that the above problems can be solved by using a barbituric acid derivative controlled to a specific range with respect to the Hammett values of some substituents that have a unique structure and have not been studied at all in the literature. It was. That is, the said subject is solved by this invention of the following structures.

（一般式（１）中、Ｒ¹およびＲ²はそれぞれ独立に水素原子、炭素数１〜２０のアルキル基、炭素数１〜２０のアルケニル基、炭素数２〜２０のアルキニル基、炭素数５〜２０のヘテロアリール基または炭素数６〜２０のアリール基を表し、Ｘはハメットのσｐ値およびσｍ値がｉ）σｍ＜０ かつ σｐ≧０、ii）σｐ＜０ かつ σｍ≧０、またはiii）σｐ≧０ かつ σｍ≧０のうちいずれかの関係を満たす置換基を表す。）
［２］ 前記一般式（１）において、前記Ｘがフェニル基を有する置換基であることを特徴とする［１］に記載のセルロースアシレートフィルム。
［３］ 前記一般式（１）において、前記Ｘがハメットのσｐ値およびσｍ値がσｐ≧０ かつ σｍ≧０の関係を満たす置換基を表すことを特徴とする［１］に記載のセルロースアシレートフィルム。
［４］ 前記一般式（１）において、前記Ｒ¹およびＲ²のいずれか一方が水素原子であり、もう一方が炭素数１〜２０の置換または無置換のアルキル基であることを特徴とする［１］〜［３］のいずれか一項に記載のセルロースアシレートフィルム。
［５］ ［１］〜［４］のいずれか一項に記載のセルロースアシレートフィルムを含むことを特徴とする位相差フィルム。
［６］ ［１］〜［４］のいずれか一項に記載のセルロースアシレートフィルムまたは［５］に記載の位相差フィルムを少なくとも１枚含むことを特徴とする偏光板。
［７］ ［１］〜［４］のいずれか一項に記載のセルロースアシレートフィルム、［５］に記載の位相差フィルムまたは［６］に記載の偏光板を少なくとも１枚含むことを特徴とする液晶表示装置。
［８］ 下記一般式（１）で表される化合物を含むことを特徴とするセルロースアシレートフィルム用湿度依存性改良剤。

（一般式（１）中、Ｒ¹およびＲ²はそれぞれ独立に水素原子、炭素数１〜２０のアルキル基、炭素数１〜２０のアルケニル基、炭素数２〜２０のアルキニル基、炭素数５〜２０のヘテロアリール基または炭素数６〜２０のアリール基を表し、Ｘはハメットのσｐ値およびσｍ値が
i）σｍ＜０ かつ σｐ≧０、
ii）σｐ＜０ かつ σｍ≧０、または
iii）σｐ≧０ かつ σｍ≧０のうちいずれかの関係を満たす置換基を表す。） [1] A cellulose acylate film comprising cellulose acylate and a compound represented by the following general formula (1).

(In the general formula (1), R ¹ and R ² are each independently a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 1 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, or 5 carbon atoms. Represents a heteroaryl group having ˜20 or an aryl group having 6 to 20 carbon atoms, and X is Hammett's σp value and σm value i) σm <0 and σp ≧ 0, ii) σp <0 and σm ≧ 0, or iii ) Represents a substituent satisfying any one of σp ≧ 0 and σm ≧ 0. )
[2] The cellulose acylate film according to [1], wherein in the general formula (1), X is a substituent having a phenyl group.
[3] The cellulose acylate as described in [1], wherein, in the general formula (1), the X represents a substituent satisfying the relationship of Hammett's σp value and σm value of σp ≧ 0 and σm ≧ 0 Rate film.
[4] In the general formula (1), any one of R ¹ and R ² is a hydrogen atom, and the other is a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms. The cellulose acylate film according to any one of [1] to [3].
[5] A retardation film comprising the cellulose acylate film according to any one of [1] to [4].
[6] A polarizing plate comprising at least one sheet of the cellulose acylate film according to any one of [1] to [4] or the retardation film according to [5].
[7] The cellulose acylate film according to any one of [1] to [4], the retardation film according to [5], or at least one polarizing plate according to [6], Liquid crystal display device.
[8] A humidity dependency improving agent for a cellulose acylate film, comprising a compound represented by the following general formula (1).

(In the general formula (1), R ¹ and R ² are each independently a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 1 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, or 5 carbon atoms. Represents a heteroaryl group having ˜20 or an aryl group having 6 to 20 carbon atoms, and X is a Hammett σp value and σm value
i) σm <0 and σp ≧ 0,
ii) σp <0 and σm ≧ 0, or
iii) represents a substituent that satisfies any one of σp ≧ 0 and σm ≧ 0. )

  ADVANTAGE OF THE INVENTION According to this invention, the cellulose acylate film by which the fluctuation | variation of Re and Rth with respect to the change of the humidity of a use environment was suppressed can be provided. The cellulose acylate film of the present invention can be suitably used for a retardation film, a polarizing plate, a liquid crystal display device and the like in a liquid crystal display device, and can be particularly suitably used for the liquid crystal display device of the present invention.

  Hereinafter, the contents of the present invention will be described in detail. The description of the constituent elements described below may be made based on typical embodiments of the present invention, but the present invention is not limited to such embodiments. In the present specification, “to” is used to mean that the numerical values described before and after it are included as a lower limit value and an upper limit value.

（一般式（１）中、Ｒ¹およびＲ²はそれぞれ独立に水素原子、炭素数１〜２０のアルキル基、炭素数１〜２０のアルケニル基、炭素数２〜２０のアルキニル基、炭素数５〜２０のヘテロアリール基または炭素数６〜２０のアリール基を表し、Ｘはハメットのσｐ値およびσｍ値が
i）σｍ＜０ かつ σｐ≧０、
ii）σｐ＜０ かつ σｍ≧０、または
iii）σｐ≧０ かつ σｍ≧０のうちいずれかの関係を満たす置換基を表す。）
以下、本発明のフィルムについて説明する。 [Cellulose Acylate Film]
The cellulose acylate film of the present invention (hereinafter also referred to as the film of the present invention) is characterized by containing a cellulose acylate and a compound represented by the following general formula (1).

(In the general formula (1), R ¹ and R ² are each independently a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 1 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, or 5 carbon atoms. Represents a heteroaryl group having ˜20 or an aryl group having 6 to 20 carbon atoms, and X is a Hammett σp value and σm value
i) σm <0 and σp ≧ 0,
ii) σp <0 and .sigma.m ≧ 0, or
iii) represents a substituent that satisfies any one of σp ≧ 0 and σm ≧ 0. )
The following describes the film of the present invention.

<Compound represented by the general formula (1)>
(Structure of the compound represented by the general formula (1))
The film of this invention is characterized by including the compound represented by the said General formula (1).
Here, the change in Re and Rth with respect to the change in humidity in the use environment of the cellulose acylate film is due to the fact that water molecules are coordinated to the carbonyl group present in the substituent of the cellulose acylate. It is speculated that this is caused by the change. Since the compound represented by the general formula (1) of the present invention has a hydrogen bonding group at an appropriate position, when used as an additive, it effectively interacts with a carbonyl group or a hydroxyl group of cellulose acylate. It is possible to suppress fluctuations in Re and Rth with respect to a change in humidity in the use environment of the acylate film. That is, the compound represented by the general formula (1) can be preferably used as a humidity dependency improving agent for cellulose acylate films.
Details of the structure of the compound represented by the general formula (1) used in the present invention will be described.

In the general formula (1), R ¹ and R ² are each independently a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 1 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, or a carbon number. A 5-20 heteroaryl group or a C6-C20 aryl group is represented.
When R ¹ and R ² are each independently an alkyl group, it is preferably 1 to 15 carbon atoms, more preferably 1 to 10 carbon atoms, and particularly preferably 1 to 5 carbon atoms.
When R ¹ and R ² are each independently an alkenyl group, it preferably has 1 to 15 carbon atoms, more preferably 1 to 10 carbon atoms, and particularly preferably 1 to 5 carbon atoms.
When R ¹ and R ² are each independently an alkynyl group, it is preferably 2 to 15 carbon atoms, more preferably 2 to 10 carbon atoms, and particularly preferably 2 to 5 carbon atoms.
When R ¹ and R ² are each independently an alkyl group, an alkenyl group or an alkynyl group, they may be cyclic, linear or branched, but are preferably linear or branched, More preferably.
When R ¹ and R ² are each independently a heteroaryl group, the number of carbon atoms is preferably 5 to 18, and more preferably 5 to 12.
When R ¹ and R ² are each independently an aryl group, the number of carbon atoms is preferably 6 to 18 and more preferably 6 to 12.

R ¹ and R ² may further have a substituent or may be unsubstituted. The substituent is not particularly limited as long as it is not contrary to the gist of the present invention, but is a halogen atom, an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 1 to 20 carbon atoms, or an alkynyl group having 2 to 20 carbon atoms. And a heteroaryl group having 5 to 20 carbon atoms or an aryl group having 6 to 20 carbon atoms are preferable. Among them, an aryl group having 6 to 20 carbon atoms is more preferable, and in particular, when R ¹ and R ² are alkyl groups having a substituent, the substituent is preferably a phenyl group.

R ¹ and R ² are each independently preferably a hydrogen atom or an alkyl group having 1 to 20 carbon atoms, and one of R ¹ and R ² is a hydrogen atom, and the other is ^{1 to} C 1 A substituted or unsubstituted alkyl group of 20 is more preferable from the viewpoint of suppressing retardation change with respect to environmental humidity.

In the general formula (1), X represents Hammett's σp value and σm value.
i) σm <0 and σp ≧ 0,
ii) σp <0 and σm ≧ 0, or
iii) represents a substituent that satisfies any one of σp ≧ 0 and σm ≧ 0. )
X preferably represents a substituent in which Hammett's σp value and σm value satisfy the relationship of formula ii) or formula iii), Hammett's σp value and σm value satisfy formula ii) or formula iii), and More preferably, both represent substituents of 1 or less.
The Hammett's substituent constants σ _p and σ _m in the present specification refer to the values described in Chemical Review, Vol. 91, pages 165 to 195 (1991).

In the general formula (1), the structure of the X is not particularly limited as long as it satisfies the range of the Hammett's σp value and σm value, but the X is an alkyl group having 1 to 20 carbon atoms and 1 to 20 carbon atoms. Is preferably a substituent containing an aromatic ring having 2 to 20 carbon atoms or an aromatic ring having 6 to 20 carbon atoms,
A substituent containing an alkyl group having 1 to 10 carbon atoms or an aromatic ring having 6 to 12 carbon atoms is more preferable, and a substituent having a phenyl group is more preferable.
When X is a substituent having a phenyl group, the X is a substituent having a phenyl group via a linking group, even if the phenyl group is directly connected to the ring skeleton of barbituric acid. There may be.
Further, X may further have a substituent, and the substituent is not particularly limited, but is a halogen atom, an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 1 to 20 carbon atoms, or a carbon number. A 1-20 alkynyl group, a C5-C20 heteroaryl group, a C6-C20 aryl group, etc. are preferable.
In particular, when X is an alkyl group, it preferably has a halogen atom as a substituent, and more preferably has a chlorine atom as a substituent.
In particular, when X is a substituent having a phenyl group, it is preferable to have an alkyl group as a substituent. Among them, it is more preferable that the phenyl group has an alkyl group, and any position of the phenyl group may be substituted with an alkyl group, but the meta position or para position may be substituted. Preferably, the para position is more preferably substituted.
When X is a substituent having a phenyl group via a linking group, the linking group is preferably an alkyleneoxy group having 1 to 10 carbon atoms or an alkylene group having 1 to 10 carbon atoms, and 1 to 5 carbon atoms. The alkyleneoxy group is more preferable.

(Specific examples of the compound represented by the general formula (1))
Specific examples of the compound represented by the general formula (1) include the following. However, the compound represented by the general formula (1) that can be used in the present invention is not limited thereto.

(Molecular weight of the compound represented by the general formula (1))
The molecular weight of the compound represented by the general formula (1) used in the present invention is preferably 150 to 1500, and more preferably 200 to 1000. By using a compound having a molecular weight in the above range, volatilization of the additive in the film production process can be suppressed and compatibility with cellulose acylate can be easily secured.

(Manufacturing method of the compound represented by the general formula (1))
The details of the method for producing the compound represented by the general formula (1) used in the present invention will be described below including the raw materials, the method for introducing substituents, the solvent, the production process and the like.
The compound represented by the general formula (1) used in the present invention is synthesized by a method of condensing a corresponding urea derivative and a malonic ester derivative in the presence of sodium ethoxide.

  The compound represented by the general formula (1) may be obtained commercially and used in the present invention. For example, among the compounds represented by the general formula (1), the compound 1 can be purchased from Tokyo Chemical Industry Co., Ltd.

(Addition amount of the compound represented by the general formula (1))
The amount of the compound represented by the general formula (1) is preferably 1 to 20% by mass with respect to cellulose acylate. If it is 1% by mass or more, the effect of improving humidity dependency can be easily obtained, and if it is 20% by mass or less, bleeding out and bleeding are less likely to occur when a cellulose acylate film is formed. The more preferable addition amount of the compound represented by the general formula (1) is 2 to 18% by mass, particularly preferably 3 to 15% by mass with respect to the cellulose acylate.
In addition, the compound represented by the general formula (1) may be added in the cellulose acylate film or plural kinds thereof, but the total addition amount may be within the range of the addition amount. preferable.

<Cellulose acylate>
Next, the cellulose acylate used in the present invention will be described in detail.
The degree of substitution of cellulose acylate means the ratio of acylation of three hydroxyl groups present in the structural unit of cellulose (glucose having a (β) 1,4-glycoside bond). The degree of substitution (acylation degree) can be calculated by measuring the amount of bound fatty acid per unit mass of cellulose. In the present invention, the degree of substitution of the cellulose body is determined from the peak intensity ratio of the carbonyl carbon in the acyl group by dissolving the cellulose body in a solvent such as dimethyl sulfoxide substituted with deuterium and measuring the ¹³ C-NMR spectrum. This can be calculated. This can be determined by ¹³ C-NMR measurement after substituting the remaining hydroxyl group of cellulose acylate with another acyl group different from the acyl group of cellulose acylate itself. Details of the measurement method are described in Tezuka et al. (Carbohydrate. Res., 273 (1995) 83-91).

The cellulose acylate in the present invention preferably has a total acyl substitution degree of 1.50 to 2.98, more preferably 2.00 to 2.97, and 2.40 to 2.95. Is particularly preferred.
As the acyl group of the cellulose acylate of the present invention, an acetyl group, a propionyl group, and a butyryl group are particularly preferable, and an acetyl group is more preferable.

A mixed fatty acid ester composed of two or more kinds of acyl groups can also be preferably used as the cellulose acylate of the present invention. Also in this case, the acyl group is preferably an acetyl group and an acyl group having 3 to 4 carbon atoms. Further, the substitution degree of the acetyl group is preferably less than 2.5, and more preferably less than 1.9.
In the present invention, two types of cellulose acylates having different substituents and / or degree of substitution may be used in combination, mixed, or from a plurality of layers composed of different cellulose acylates by the co-casting method described later. A film may be formed.

  Furthermore, mixed acid esters having a fatty acid acyl group and a substituted or unsubstituted aromatic acyl group described in [0023] to [0038] of JP-A-2008-20896 can also be preferably used in the present invention.

  The cellulose acylate used in the present invention preferably has a mass average degree of polymerization of 250 to 800, more preferably 300 to 600. The cellulose acylate used in the present invention preferably has a number average molecular weight of 70000 to 230,000, more preferably 75000 to 230,000, and most preferably 78,000 to 120,000. preferable.

  The cellulose acylate used in the present invention can be synthesized using an acid anhydride or acid chloride as an acylating agent. When the acylating agent is an acid anhydride, an organic acid (for example, acetic acid) or methylene chloride is used as a reaction solvent. Further, a protic catalyst such as sulfuric acid can be used as the catalyst. When the acylating agent is an acid chloride, a basic compound can be used as a catalyst. In the most common synthetic method in the industry, cellulose is an organic acid corresponding to acetyl group and other acyl groups (acetic acid, propionic acid, butyric acid) or their acid anhydrides (acetic anhydride, propionic anhydride, butyric anhydride). A cellulose ester is synthesized by esterification with a mixed organic acid component containing.

  In the above method, cellulose such as cotton linter or wood pulp is activated with an organic acid such as acetic acid and then esterified using a mixture of organic acid components as described above in the presence of a sulfuric acid catalyst. In many cases. The organic acid anhydride component is generally used in an excess amount relative to the amount of hydroxyl groups present in the cellulose. In this esterification treatment, in addition to the esterification reaction, a hydrolysis reaction (depolymerization reaction) of the cellulose main chain (β) 1,4-glycoside bond) proceeds. When the hydrolysis reaction of the main chain proceeds, the degree of polymerization of the cellulose ester is lowered, and the physical properties of the cellulose ester film to be produced are lowered. Therefore, the reaction conditions such as the reaction temperature are preferably determined in consideration of the degree of polymerization and molecular weight of the resulting cellulose ester.

<Method for producing a cellulose acylate film>
The cellulose acylate film of the present invention can be produced by forming a solution containing cellulose acylate and the compound represented by the general formula (1), for example, by a solvent cast method. In the solvent cast method, a film is produced using a solution (dope) in which cellulose acylate is dissolved in an organic solvent.

The organic solvent is selected from ethers having 3 to 12 carbon atoms, ketones having 3 to 12 carbon atoms, esters having 3 to 12 carbon atoms, and halogenated hydrocarbons having 1 to 6 carbon atoms. It is preferable to include a solvent.
The ether, ketone and ester may have a cyclic structure. A compound having two or more functional groups of the ether, ketone, and ester (that is, —O—, —CO—, and —COO—) can also be used as the organic solvent. The organic solvent may have another functional group such as an alcoholic hydroxyl group. In the case of an organic solvent having two or more kinds of functional groups, the number of carbon atoms is preferably within the above-described preferable range of carbon atoms of the solvent having any functional group.

Examples of the ether having 3 to 12 carbon atoms include diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolane, tetrahydrofuran, anisole and phenetole.
Examples of the ketones having 3 to 12 carbon atoms include acetone, methyl ethyl ketone, diethyl ketone, diisobutyl ketone, cyclohexanone and methylcyclohexanone.
Examples of the esters having 3 to 12 carbon atoms include ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate and pentyl acetate.
Examples of the organic solvent having two or more kinds of functional groups include 2-ethoxyethyl acetate, 2-methoxyethanol and 2-butoxyethanol.

The number of carbon atoms of the halogenated hydrocarbon having 1 to 6 carbon atoms is preferably 1 or 2, and most preferably 1. The halogen of the halogenated hydrocarbon is preferably chlorine. The proportion of halogenated hydrocarbon hydrogen atoms replaced with halogen is preferably 25 to 75 mol%, more preferably 30 to 70 mol%, and more preferably 35 to 65 mol%. More preferably, it is most preferable that it is 40-60 mol%. Methylene chloride is a typical halogenated hydrocarbon.
Two or more kinds of organic solvents may be mixed and used.

  The cellulose acylate solution (dope) can be prepared by a general method comprising processing at a temperature of 0 ° C. or higher (ordinary temperature or high temperature). The cellulose acylate solution can be prepared using a dope preparation method and apparatus in a normal solvent cast method. In the case of a general method, it is preferable to use a halogenated hydrocarbon (particularly methylene chloride) as the organic solvent.

  The amount of cellulose acylate in the cellulose acylate solution is adjusted so that it is contained in an amount of 10 to 40% by mass in the resulting solution. The amount of cellulose acylate is more preferably 10 to 30% by mass. Arbitrary additives described later may be added to the organic solvent (main solvent).

  The cellulose acylate solution can be prepared by stirring cellulose acylate and an organic solvent at room temperature (0 to 40 ° C.). High concentration solutions may be stirred under pressure and heating conditions. Specifically, cellulose acylate and an organic solvent are placed in a pressure vessel and sealed, and stirred while heating to a temperature not lower than the boiling point of the solvent at normal temperature and in a range where the solvent does not boil. The heating temperature is usually 40 ° C. or higher, preferably 60 to 200 ° C., and more preferably 80 to 110 ° C.

  Each component may be coarsely mixed in advance and then placed in a container. Moreover, you may put into a container sequentially. The container must be configured to allow stirring. The container can be pressurized by injecting an inert gas such as nitrogen gas. Moreover, you may utilize the raise of the vapor pressure of the solvent by heating. Or after sealing a container, you may add each component under pressure.

  When heating, it is preferable to heat from the outside of the container. For example, a jacket type heating device can be used. The entire container can also be heated by providing a plate heater outside the container and piping to circulate the liquid.

  Stirring is preferably performed using a stirring blade provided inside the container. The stirring blade preferably has a length that reaches the vicinity of the wall of the container. A scraping blade is preferably provided at the end of the stirring blade in order to renew the liquid film on the vessel wall.

  Instruments such as a pressure gauge and a thermometer may be installed in the container. Each component is dissolved in a solvent in a container. The prepared dope is taken out of the container after cooling, or taken out and then cooled using a heat exchanger or the like.

A cellulose acylate solution can also be prepared by a cooling dissolution method. As for the details of the cooling dissolution method, the techniques described in [0115] to [0122] of JP-A-2007-86748 can be used.
Then, cellulose acylate can be dissolved in an organic solvent in which it is difficult to dissolve cellulose acylate by a normal dissolution method. In addition, even if it is a solvent which can melt | dissolve a cellulose acylate with a normal melt | dissolution method, there exists an effect that a uniform solution can be obtained rapidly according to a cooling melt | dissolution method.

  In the cooling dissolution method, first, cellulose acylate is gradually added to an organic solvent with stirring at room temperature. The amount of cellulose acylate is preferably adjusted so as to be contained in the mixture in an amount of 10 to 40% by mass. The amount of cellulose acylate is more preferably 10 to 30% by mass. Furthermore, you may add the arbitrary additive mentioned later in a mixture.

  The mixture is then cooled to -100 to -10 ° C (preferably -80 to -10 ° C, more preferably -50 to -20 ° C, most preferably -50 to -30 ° C). The cooling can be performed, for example, in a dry ice / methanol bath (−75 ° C.) or a cooled diethylene glycol solution (−30 to −20 ° C.). The mixture of the cellulose acylate and the organic solvent is solidified by cooling.

  The cooling rate is preferably 4 ° C./min or more, more preferably 8 ° C./min or more, and most preferably 12 ° C./min or more. The faster the cooling rate, the better. However, 10,000 ° C./second is the theoretical upper limit, 1000 ° C./second is the technical upper limit, and 100 ° C./second is the practical upper limit. The cooling rate is a value obtained by dividing the difference between the temperature at the start of cooling and the final cooling temperature by the time from the start of cooling to the final cooling temperature.

  Furthermore, when the cooled mixture is heated to 0 to 200 ° C. (preferably 0 to 150 ° C., more preferably 0 to 120 ° C., most preferably 0 to 50 ° C.), cellulose acylate is dissolved in the organic solvent. The temperature may be increased by simply leaving it at room temperature or in a warm bath. The heating rate is preferably 4 ° C./min or more, more preferably 8 ° C./min or more, and most preferably 12 ° C./min or more. The higher the heating rate, the better. However, 10,000 ° C./second is the theoretical upper limit, 1000 ° C./second is the technical upper limit, and 100 ° C./second is the practical upper limit. The heating rate is the value obtained by dividing the difference between the temperature at the start of heating and the final heating temperature by the time from the start of heating until the final heating temperature is reached. is there.

  As described above, a uniform cellulose acylate solution is obtained. If the dissolution is insufficient, the cooling and heating operations may be repeated. Whether or not the dissolution is sufficient can be determined by merely observing the appearance of the solution with the naked eye.

  In the cooling dissolution method, it is desirable to use a sealed container in order to avoid moisture mixing due to condensation during cooling. In the cooling and heating operation, when the pressure is applied during cooling and the pressure is reduced during heating, the dissolution time can be shortened. In order to perform pressurization and decompression, it is desirable to use a pressure-resistant container.

  In addition, according to the measurement by a differential scanning calorimeter (DSC), the 20 mass% solution which melt | dissolved cellulose acetate (acetylation degree: 60.9%, viscosity average polymerization degree: 299) in methyl acetate by the cooling dissolution method is. In the vicinity of 33 ° C., there exists a quasi-phase transition point between the sol state and the gel state, and a uniform gel state is obtained below this temperature. Therefore, this solution is preferably kept at a temperature equal to or higher than the pseudo phase transition temperature, preferably about 10 ° C. plus the gel phase transition temperature. However, this pseudo phase transition temperature varies depending on the degree of acetylation of cellulose acetate, the degree of viscosity average polymerization, the concentration of the solution, and the organic solvent used.

  It is preferable to produce a cellulose acylate film from the prepared cellulose acylate solution (dope) by a solvent cast method. A compound represented by the general formula (1) is added to the dope. Other additives such as a retardation enhancer may be further added to the dope. The dope is cast on a drum or band and the solvent is evaporated to form a film. The concentration of the dope before casting is preferably adjusted so that the solid content is 18 to 35%. The surface of the drum or band is preferably finished in a mirror state. The dope is preferably cast on a drum or band having a surface temperature of 10 ° C. or less.

  Regarding the drying method in the solvent cast method, US Pat. Nos. 2,336,310, 2,367,603, 2,492,078, 2,492,977, and 2,492,978 Nos. 2,607,704, 2,739,069 and 2,739,070, British Patent Nos. 640731 and 736892, and Japanese Patent Publication No. 45-4554 49-5614, JP-A-60-176834, JP-A-60-203430 and JP-A-62-115035. Drying on the band or drum can be performed by blowing an inert gas such as air or nitrogen.

  Further, the obtained film can be peeled off from the drum or band and further dried with high-temperature air whose temperature is successively changed from 100 ° C. to 160 ° C. to evaporate the residual solvent. The above method is described in Japanese Patent Publication No. 5-17844. According to this method, it is possible to shorten the time from casting to stripping. In order to carry out this method, it is necessary for the dope to gel at the surface temperature of the drum or band during casting.

Using the prepared cellulose acylate solution (dope), two or more layers can be cast to form a film. In this case, it is preferable to produce a cellulose acylate film by a solvent cast method. The dope is cast on a drum or band and the solvent is evaporated to form a film. It is preferable to adjust the concentration of the dope before casting so that the solid content is in the range of 10 to 40% by mass. The surface of the drum or band is preferably finished in a mirror state.
When casting a plurality of cellulose acylate liquids of two or more layers, it is possible to cast a plurality of cellulose acylate solutions, and a plurality of casting ports provided at intervals in the direction of travel of the support Alternatively, a film may be produced while casting and laminating solutions containing cellulose acylate. For example, the methods described in JP-A-61-158414, JP-A-1-122419, and JP-A-11-198285 can be used. Also, a film can be formed by casting a cellulose acylate solution from two casting ports. For example, JP-B-60-27562, JP-A-61-94724, JP-A-61-947245, JP-A-61-104413, JP-A-61-158413, and JP-A-6-158413. The method described in each publication of No. 134933 can be used. Further, a flow of a cellulose acylate film in which a flow of a high-viscosity cellulose acylate solution described in JP-A-56-162617 is wrapped with a low-viscosity cellulose acylate solution and the high-low viscosity cellulose acylate solution is simultaneously extruded. A rolling method can also be used.
Also, using two casting ports, the film formed on the support by the first casting port is peeled off, and the second casting is performed on the side in contact with the support surface to produce a film. You can also For example, the method described in Japanese Patent Publication No. 44-20235 can be mentioned.
As the cellulose acylate solution to be cast, the same solution may be used, or two or more different cellulose acylate solutions may be used. In order to give a function to a plurality of cellulose acylate layers, a cellulose acylate solution corresponding to the function may be extruded from each casting port. Furthermore, the cellulose acylate solution in the present invention can be cast simultaneously with other functional layers (for example, an adhesive layer, a dye layer, an antistatic layer, an antihalation layer, an ultraviolet absorption layer, a polarizing layer, etc.).
In the conventional single-layer solution, it is necessary to extrude a cellulose acylate solution having a high concentration and a high viscosity in order to obtain a necessary film thickness. In that case, the stability of the cellulose acylate solution is poor and solid matter is generated, which often causes problems due to defects or poor flatness. As a solution to this problem, by casting a plurality of cellulose acylate solutions from a casting port, a highly viscous solution can be extruded onto a support at the same time, and the planarity is improved and the film is excellent. Not only can be produced, but also the use of a concentrated cellulose acylate solution can reduce the drying load and increase the production speed of the film.

(Addition of additives)
In this invention, the timing which adds the compound represented by the said General formula (1) to a cellulose acylate film to a cellulose acylate solution will not be specifically limited if it is added at the time of film forming. For example, it may be added at the time of cellulose acylate synthesis, or may be mixed with cellulose acylate during dope preparation.

  Degradation inhibitors (for example, antioxidants, peroxide decomposers, radical inhibitors, metal deactivators, acid scavengers, amines, etc.) may be added to the cellulose acylate film. The deterioration preventing agents are described in JP-A-3-199201, JP-A-51907073, JP-A-5-194789, JP-A-5-271471, and JP-A-6-107854. Moreover, it is preferable that the addition amount of the said deterioration inhibitor is 0.01-1 mass% of the solution (dope) to prepare, and it is further more preferable that it is 0.01-0.2 mass%. If the addition amount is 0.01% by mass or more, the effect of the deterioration inhibitor is sufficiently exhibited, and if the addition amount is 1% by mass or less, the deterioration inhibitor bleeds out to the film surface (bleeding). And the like are less likely to occur. Examples of particularly preferred deterioration inhibitors include butylated hydroxytoluene (BHT) and tribenzylamine (TBA).

  In addition, it is preferable to add fine particles as a matting agent to the cellulose acylate film. The fine particles used in the present invention include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate and Mention may be made of calcium phosphate. Fine particles containing silicon are preferable in terms of low turbidity, and silicon dioxide is particularly preferable. The silicon dioxide fine particles preferably have a primary average particle size of 20 nm or less and an apparent specific gravity of 70 g / liter or more. The apparent specific gravity is preferably 90 to 200 g / liter or more, and more preferably 100 to 200 g / liter or more. A larger apparent specific gravity is preferable because a high-concentration dispersion can be produced, and haze and aggregates are improved.

  These fine particles usually form secondary particles having an average particle diameter of 0.1 to 3.0 μm, and these fine particles are present as aggregates of primary particles in the film, and 0.1 to 0.1 μm on the film surface. An unevenness of 3.0 μm is formed. The secondary average particle diameter is preferably 0.2 μm to 1.5 μm, more preferably 0.4 μm to 1.2 μm, and most preferably 0.6 μm to 1.1 μm. The primary and secondary particle sizes were determined by observing the particles in the film with a scanning electron microscope and determining the diameter of a circle circumscribing the particles as the particle size. In addition, 200 particles were observed at different locations, and the average value was taken as the average particle size.

  As fine particles of silicon dioxide, for example, commercially available products such as Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600 (above Nippon Aerosil Co., Ltd.) can be used. Zirconium oxide fine particles are commercially available, for example, under the trade names Aerosil R976 and R811 (manufactured by Nippon Aerosil Co., Ltd.) and can be used.

  Among these, Aerosil 200V and Aerosil R972V are fine particles of silicon dioxide having a primary average particle diameter of 20 nm or less and an apparent specific gravity of 70 g / liter or more, and while maintaining the turbidity of the optical film low, friction This is particularly preferable because the effect of reducing the coefficient is great.

In order to obtain a cellulose acylate film having particles having a small secondary average particle size in the present invention, several methods are conceivable when preparing a fine particle dispersion. For example, a fine particle dispersion prepared by stirring and mixing a solvent and fine particles is prepared in advance, and the fine particle dispersion is added to a separately prepared small amount of cellulose acylate solution and dissolved by stirring. Further, a main cellulose acylate solution (dope solution) and There is a way to mix. This method is a preferred preparation method in that the dispersibility of the silicon dioxide fine particles is good and the silicon dioxide fine particles are more difficult to reaggregate. In addition, after adding a small amount of cellulose ester to the solvent and dissolving with stirring, add fine particles to this and disperse with a disperser. This is used as a fine particle additive solution, and this fine particle additive solution is sufficiently mixed with the dope solution using an inline mixer. There is also a method of mixing. The present invention is not limited to these methods, but the concentration of silicon dioxide when the silicon dioxide fine particles are mixed and dispersed with a solvent or the like is preferably 5 to 30% by mass, more preferably 10 to 25% by mass, and 15 to 20%. Mass% is most preferred. A higher dispersion concentration is preferable because the liquid turbidity with respect to the added amount is lowered, and haze and aggregates are improved. The addition amount of the matting agent fine particles in the final cellulose acylate dope solution is preferably 0.01 to 1.0 g, more preferably 0.03 to 0.3 g, more preferably 0.08 to 0.16 g per m ^3. Is most preferred.
The solvent used is preferably lower alcohols such as methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol and the like. Although it does not specifically limit as solvents other than a lower alcohol, It is preferable to use the solvent used at the time of film forming of a cellulose ester.

  These steps from casting to post-drying may be performed in an air atmosphere or an inert gas atmosphere such as nitrogen gas. The winder used for producing the cellulose acylate film in the present invention may be a commonly used winding machine such as a constant tension method, a constant torque method, a taper tension method, or a program tension control method with a constant internal stress. It can be wound up by a take-up method.

(Extension process)
The cellulose acylate film of the present invention is preferably subjected to a stretching treatment. A desired retardation can be imparted to the cellulose acylate film by stretching. The stretching direction of the cellulose acylate film is preferably either the width direction or the longitudinal direction.
Methods for stretching in the width direction are described in, for example, JP-A-62-115035, JP-A-4-152125, JP-A-2842211, JP-A-298310, and JP-A-11-48271. Yes.

  The stretching of the film is preferably carried out under heating conditions. The film can be stretched by a treatment during drying, and is particularly effective when the solvent remains. In the case of stretching in the longitudinal direction, for example, the film is stretched by adjusting the speed of the film transport roller so that the film winding speed is higher than the film peeling speed. In the case of stretching in the width direction, the film can also be stretched by conveying while holding the width of the film with a tenter and gradually widening the width of the tenter. After the film is dried, it can be stretched using a stretching machine (preferably uniaxial stretching using a long stretching machine).

The cellulose acylate film of the present invention is preferably stretched at a temperature of (Tg−5 ° C.) to (Tg + 40 ° C.) using the glass transition temperature Tg (unit: ° C.) of the cellulose acylate film. (Tg + 35 ° C.) is more preferable, and (Tg + 10 ° C.) to (Tg + 30 ° C.) is particularly preferable. In the case of a dry film, 130 ° C to 200 ° C is preferable.
Moreover, when extending | stretching in the state in which the dope solvent remained after casting, it becomes possible to extend | stretch at temperature lower than a dry film, In this case, 100 to 170 degreeC is preferable.

The stretch ratio of the cellulose acylate film of the present invention (elongation relative to the film before stretching) is preferably 1% to 200%, more preferably 5% to 150%. In particular, stretching in the width direction is preferably 1% to 200%, more preferably 5% to 150%, and particularly preferably 30 to 45%.
The stretching speed is preferably 1% / min to 300% / min, more preferably 10% / min to 300% / min, and most preferably 30% / min to 300% / min.

  In addition, the stretched cellulose acylate film in the present invention is stretched to the maximum stretch ratio and then held for a certain period of time at a stretch ratio lower than the maximum stretch ratio (hereinafter sometimes referred to as “relaxation process”). May be manufactured. The stretching ratio in the relaxation step is preferably 50% to 99% of the maximum stretching ratio, more preferably 70% to 97%, and most preferably 90% to 95%. Moreover, the time of the relaxation process is preferably 1 second to 120 seconds, and more preferably 5 seconds to 100 seconds.

Furthermore, the cellulose acylate film of the present invention can be preferably produced by including a shrinking step of shrinking while gripping the film in the width direction.
In the manufacturing method characterized by including a stretching process for stretching in the width direction of the film and a shrinking process for contracting in the film conveyance direction (longitudinal direction), the film width is held by a pantograph type or linear motor type tenter. The film can be shrunk by gradually narrowing the interval between the clips in the conveying direction while stretching in the direction.

  In the method described above, it can be said that at least a part of the stretching step and the shrinking step are performed simultaneously.

  In addition, Ichikin Kogyo Co., Ltd. is a stretching apparatus that specifically performs a stretching process that stretches either the longitudinal direction or the width direction of the film as described above, simultaneously shrinks the other, and simultaneously increases the film thickness of the film. A company-made FITZ machine or the like can be desirably used. This apparatus is described in (Japanese Patent Laid-Open No. 2001-38802).

The stretching ratio in the stretching step and the shrinkage rate in the shrinking step can be arbitrarily selected depending on the target in-plane retardation Re and the thickness direction retardation Rth. It is preferable that the draw ratio is 10% or more and the shrinkage rate in the shrinking step is 5% or more.
In particular, it preferably includes a stretching step of stretching 10% or more in the width direction of the film and a shrinking step of contracting the transport direction of the film by 5% or more while holding the film in the width direction of the film.
In addition, the shrinkage rate as used in the field of this invention means the ratio of the contracted length of the film after contraction with respect to the length of the film before contraction in the contraction direction.
The shrinkage rate is preferably 5 to 40%, particularly preferably 10 to 30%.

<Characteristics of cellulose acylate film>
(Retardation)
Next, the characteristics of the cellulose acylate film of the present invention will be described in detail.
The preferable range of the optical properties of the cellulose acylate film of the present invention varies depending on the application.
For VA mode, Re measured at 589 nm is preferably 30 to 200 nm, more preferably 30 to 150 nm, and even more preferably 40 to 100 nm. Rth is preferably 70 to 400 nm, more preferably 100 to 300 nm, and even more preferably 100 to 250 nm.
For TN mode, Re measured at 589 nm is preferably 0 to 100 nm, more preferably 20 to 90 nm, and even more preferably 50 to 80 nm. Rth is preferably 20 to 200 nm, more preferably 30 to 150 nm, and even more preferably 40 to 120 nm.

In this specification, Re (λ) and Rth (λ) respectively represent in-plane retardation and retardation in the thickness direction at a wavelength λ. In the present specification, “Re” and “Rth” refer to Re and Rth at a wavelength of 589 nm, unless otherwise specified. 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) The light of wavelength λ nm is incident from each of the inclined directions in steps of 10 degrees from the normal direction to 50 degrees on one side with respect to the film normal direction (with the direction of the rotation axis as the rotation axis). KOBRA 21ADH or WR is calculated based on the measured retardation value, the assumed average refractive index, and the input film thickness value.
In the above case, in the case of a film having a direction in which the retardation value is zero at a certain tilt angle with the in-plane slow axis from the normal direction as the rotation axis, retardation at a tilt angle larger than the tilt angle. The value is calculated by KOBRA 21ADH or WR after changing its sign to negative.
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 assumed value of the average refractive index, and the input film thickness value, Rth can also be calculated from the following equations (21) and (22).

Note:
The above Re (θ) represents a retardation value in a direction inclined by an angle θ from the normal direction. In formula (21), 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. . d represents the thickness of the film.

Rth = ((nx + ny) / 2−nz) × d Formula (22)
In the case where the film to be measured cannot be expressed by a uniaxial or biaxial refractive index ellipsoid, that is, a film having no so-called optical axis, Rth (λ) is calculated by the following method.
Rth (λ) is the above-mentioned Re (λ), and the in-plane slow axis (determined by KOBRA 21ADH or WR) is the tilt axis (rotation axis) from −50 degrees to +50 degrees with respect to the film normal direction. The light of wavelength λ nm is incident from each inclined direction in 10 degree steps and measured at 11 points. Based on the measured retardation value, the assumed average refractive index, and the input film thickness value, KOBRA 21ADH or WR is calculated.
In the above measurement, as the assumed value of the average refractive index, values in the polymer handbook (John Wiley & Sons, Inc.) and catalogs of various optical films can be used. Those whose average refractive index is not known can be measured with an Abbe refractometer. The average refractive index values of main optical films are exemplified below: cellulose acylate (1.48), cycloolefin polymer (1.52), polycarbonate (1.59), polymethyl methacrylate (1.49), Polystyrene (1.59). By inputting these assumed values of 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 thickness of the cellulose acylate film)
The thickness of the cellulose acylate film in the present invention is preferably 30 μm to 100 μm, more preferably 30 μm to 80 μm, and most preferably 30 μm to 60 μm.

<A polarizing plate protective film>
(Saponification treatment)
The cellulose acylate film of the present invention can be used as a polarizing plate protective film by imparting adhesion to a polarizer material such as polyvinyl alcohol by alkali saponification treatment. The saponification method is described in [0211] and [0212] of JP-A-2007-86748, and the method of making a polarizer of a polarizing plate, the optical characteristics of the polarizing plate, etc. are described in [0213] to [0255] of the same publication. Based on these descriptions, a polarizing plate using the film of the present invention as a protective film can be produced.

  For example, the alkali saponification treatment for the cellulose acylate film of the present invention is preferably carried out in a cycle in which the film surface is immersed in an alkaline solution, neutralized with an acidic solution, washed with water and dried. Examples of the alkaline solution include a potassium hydroxide solution and a sodium hydroxide solution, and the concentration of hydroxide ions is preferably in the range of 0.1 to 5.0 mol / L, and 0.5 to 4.0 mol / L. More preferably, it is in the range of L. The alkaline solution temperature is preferably in the range of room temperature to 90 ° C, more preferably in the range of 40 to 70 ° C.

[Phase difference film]
The cellulose acylate film of the present invention can be used as a retardation film. The “retardation film or optical compensation film” is generally used for a display device such as a liquid crystal display device and means an optical material having optical anisotropy, and is synonymous with an optical compensation sheet. In a liquid crystal display device, an optical compensation film is used for the purpose of improving the contrast of a display screen or improving viewing angle characteristics and color.
In addition, a plurality of the cellulose acylate films of the present invention may be laminated, or the cellulose acylate film of the present invention and a film other than the present invention may be laminated to appropriately adjust Re and Rth and use as an optical compensation film. You can also. Lamination of the film can be performed using a pressure-sensitive adhesive or an adhesive.

[Polarizer]
The polarizing plate of the present invention includes at least one sheet of the cellulose acylate film of the present invention or the retardation film of the present invention.
A polarizing plate generally comprises a polarizer and two transparent protective films disposed on both sides thereof. As one protective film, the cellulose acylate film of the present invention can be used. The other protective film may be a normal cellulose acetate film. Examples of the polarizer include an iodine polarizer, a dye polarizer using a dichroic dye, and a polyene polarizer. The iodine polarizer and the dye polarizer are generally produced using a polyvinyl alcohol film. When the cellulose acylate film of the present invention is used as a polarizing plate protective film, the method for producing the polarizing plate is not particularly limited, and can be produced by a general method. There is a method in which the obtained cellulose acylate film is treated with an alkali and bonded to both sides of a polarizer prepared by immersing and stretching a polyvinyl alcohol film in an iodine solution using a completely saponified polyvinyl alcohol aqueous solution. Instead of alkali treatment, easy adhesion processing as described in JP-A-6-94915 and JP-A-6-118232 may be performed. Examples of the adhesive used to bond the protective film-treated surface and the polarizer include polyvinyl alcohol adhesives such as polyvinyl alcohol and polyvinyl butyral, vinyl latexes such as butyl acrylate, and the like. The polarizing plate is composed of a polarizer and a protective film that protects both surfaces of the polarizer, and is further constructed by laminating a protective film on one surface of the polarizing plate and a separate film on the opposite surface. The protective film and the separate film are used for the purpose of protecting the polarizing plate at the time of shipping the polarizing plate and at the time of product inspection. In this case, the protect film is bonded for the purpose of protecting the surface of the polarizing plate, and is used on the side opposite to the surface where the polarizing plate is bonded to the liquid crystal plate. Moreover, a separate film is used in order to cover the contact bonding layer bonded to a liquid crystal plate, and is used for the surface side which bonds a polarizing plate to a liquid crystal plate.

The cellulose acylate film of the present invention is preferably bonded to the polarizer so that the transmission axis of the polarizer and the slow axis of the cellulose acylate film of the present invention are substantially parallel.
In the liquid crystal display device of the present invention, it is preferable that the transmission axis of the polarizing plate and the slow axis of the cellulose acylate film of the present invention are substantially parallel. Here, being substantially parallel means that the deviation between the direction of the main refractive index nx of the cellulose acylate film of the present invention and the direction of the transmission axis of the polarizing plate is within 5 °. It is preferable that the angle is within 0 °, preferably within 0.5 °. When the deviation is within 1 °, the polarization degree performance under the polarizing plate crossed Nicols is lowered and light leakage is less likely to occur.

<Functionalization of polarizing plate>
The polarizing plate in the present invention is a function that is combined with an optical film having functional layers such as an antireflection film, a brightness enhancement film, a hard coat layer, a forward scattering layer, and an antiglare (antiglare) layer for improving display visibility. It is also preferably used as a polarizing plate. The antireflection film, brightness enhancement film, other functional optical film, hard coat layer, forward scattering layer, and antiglare layer for functionalization are described in [0257] to [0276] of JP-A-2007-86748. Thus, a functionalized polarizing plate can be created based on these descriptions.

(Antireflection film)
The polarizing plate in the present invention can be used in combination with an antireflection film. As the antireflection film, either a film having a reflectivity of about 1.5% only by applying a single layer of a low refractive index material such as a fluorine-based polymer, or a film having a reflectivity of 1% or less using multilayer interference of a thin film is used. it can. In the present invention, a structure in which a low refractive index layer and at least one layer having a higher refractive index than that of the low refractive index layer (that is, a high refractive index layer and a middle refractive index layer) is laminated on a transparent support is preferably used. The In addition, Nitto Technical Report, vol. 38, no. 1, May, 2000, pages 26 to 28 and JP-A No. 2002-301783.

The refractive index of each layer satisfies the following relationship.
Refractive index of high refractive index layer> refractive index of medium refractive index layer> refractive index of transparent support> refractive index of low refractive index layer

  As the transparent support used for the antireflection film, a transparent polymer film used for the protective film for the polarizer described above can be preferably used.

  The refractive index of the low refractive index layer is preferably 1.20 to 1.55, more preferably 1.30 to 1.50. The low refractive index layer is preferably used as an outermost layer having scratch resistance and antifouling properties. In order to improve the scratch resistance, it is also preferable to impart slipperiness to the surface using a material such as a silicone-containing compound containing a silicone group or a fluorine-containing compound containing fluorine.

Examples of the fluorine-containing compound include JP-A-9-222503 [0018] to [0026], JP-A-11-38202 [0019] to [0030], JP-A 2001-40284 [0027] to [0027]. [0028] The compounds described in JP 2000-284102 A and the like can be preferably used.
The silicone-containing compound is preferably a compound having a polysiloxane structure, such as reactive silicone (for example, Silaplane (manufactured by Chisso Corporation), polysiloxane containing silanol groups at both ends (Japanese Patent Laid-Open No. 11-258403), etc. Alternatively, an organometallic compound such as a silane coupling agent and a specific fluorine-containing hydrocarbon group-containing silane coupling agent may be cured by a condensation reaction in the presence of a catalyst (Japanese Patent Laid-Open No. 58-86). 142958, 58-147483, 58-147484, JP-A-9-157582, 11-106704, JP-A-2000-117902, 2001-48590, 2002 the compounds of JP -53804, etc.).
The low refractive index layer has an average primary particle diameter of 1 to 150 nm such as fillers (for example, silicon dioxide (silica), fluorine-containing particles (magnesium fluoride, calcium fluoride, barium fluoride)) as additives other than the above. And a low refractive index inorganic compound, organic fine particles described in [0020] to [0038] of JP-A No. 11-3820, etc.), silane coupling agents, slip agents, surfactants, and the like are preferably included. Can do.

The low refractive index layer may be formed by a vapor phase method (vacuum deposition method, sputtering method, ion plating method, plasma CVD method, etc.), but may be formed by a coating method because it can be manufactured at low cost. preferable. As the coating method, dip coating, air knife coating, curtain coating, roller coating, wire bar coating, gravure coating, and micro gravure can be preferably used.
The film thickness of the low refractive index layer is preferably 30 to 200 nm, more preferably 50 to 150 nm, and most preferably 60 to 120 nm.

The medium refractive index layer and the high refractive index layer preferably have a configuration in which ultrafine particles of high refractive index having an average particle size of 100 nm or less are dispersed in a matrix material. Inorganic compound fine particles having a high refractive index include inorganic compounds having a refractive index of 1.65 or more, for example, oxides such as Ti, Zn, Sb, Sn, Zr, Ce, Ta, La, and In, and metal atoms thereof. A composite oxide or the like can be preferably used.
Such ultrafine particles may be obtained by treating the particle surface with a surface treatment agent (silane coupling agent, etc .: JP-A Nos. 11-295503, 11-153703, 2000-9908, anionic compounds) Or an organic metal coupling agent (Japanese Patent Laid-Open No. 2001-310432, etc.), a core-shell structure having high refractive index particles as a core (Japanese Patent Laid-Open No. 2001-166104, etc.), or a specific dispersant is used together (for example, , JP-A-11-153703, US Pat. No. 6,210,858B1, JP-A-2002-27776069, etc.).

As the matrix material, conventionally known thermoplastic resins, curable resin films, and the like can be used, but JP-A-2000-47004, 2001-315242, 2001-31871, 2001-296401. It is also possible to use a curable film obtained from a polyfunctional material described in JP-A-2001-293818 or a metal alkoxide composition described in JP-A-2001-293818.
The refractive index of the high refractive index layer is preferably 1.70 to 2.20. The thickness of the high refractive index layer is preferably 5 nm to 10 μm, and more preferably 10 nm to 1 μm.
The refractive index of the middle refractive index layer is adjusted to be a value between the refractive index of the low refractive index layer and the refractive index of the high refractive index layer. The refractive index of the middle refractive index layer is preferably 1.50 to 1.70.

  The haze of the antireflection film is preferably 5% or less, more preferably 3% or less. Further, the strength of the film is preferably H or more, more preferably 2H or more, and most preferably 3H or more in a pencil hardness test according to JIS K5400.

(Brightness enhancement film)
The polarizing plate in the present invention can be used in combination with a brightness enhancement film. The brightness enhancement film has a function of separating circularly polarized light or linearly polarized light, and is disposed between the polarizing plate and the backlight, and reflects or backscatters one circularly polarized light or linearly polarized light to the backlight side. Re-reflected light from the backlight part partially changes the polarization state and partially transmits when re-entering the brightness enhancement film and the polarizing plate, so the light utilization rate is improved by repeating this process. The front luminance is improved to about 1.4 times. As the brightness enhancement film, an anisotropic reflection system and an anisotropic scattering system are known, and both can be combined with the polarizing plate in the present invention.

  In the anisotropic reflection method, a brightness enhancement film having anisotropy in reflectance and transmittance is known by laminating a uniaxially stretched film and an unstretched film in multiple layers to increase the difference in refractive index in the stretching direction. Multilayer film systems using the principle of dielectric mirrors (described in the specifications of WO95 / 17691, WO95 / 17692, and WO95 / 17699) and cholesteric liquid crystals A system (European Patent No. 606940A2 specification, JP-A-8-271731) is known. DBEF-E, DBEF-D, and DBEF-M (all manufactured by 3M) are used as multi-layer brightness enhancement films using the principle of dielectric mirrors, and NIPOCS (Nitto Denko Corporation) as a cholesteric liquid crystal brightness enhancement film. )) Is preferably used in the present invention. For NIPOCS, see Nitto Giho, vol. 38, no. 1, May, 2000, pages 19 to 21 and the like.

  Further, in the present invention, the specifications of International Publication No. 97/32223, International Publication No. 97/32224, International Publication No. 97/32225, International Publication No. 97/32226, and Japanese Patent Application Laid-Open No. 9-274108. Used in combination with a brightness enhancement film of an anisotropic scattering system in which a positive intrinsic birefringent polymer and a negative intrinsic birefringent polymer are blended and uniaxially stretched as described in each publication of JP-A-11-174231 It is also preferable to do. As the anisotropic scattering system brightness enhancement film, DRPF-H (manufactured by 3M) is preferable.

(Other functional optical film)
The polarizing plate in the present invention is further combined with a functional optical film provided with a hard coat layer, a forward scattering layer, an antiglare (antiglare) layer, a gas barrier layer, a sliding layer, an antistatic layer, an undercoat layer, a protective layer and the like. it is also preferable to use. These functional layers are also preferably used in combination with each other in the same layer as the antireflection layer or the optically anisotropic layer in the above-described antireflection film. These functional layers can be used by providing them on one side or both sides of the polarizer side and the side opposite to the polarizer (the side on the air side).

(Hard coat layer)
Since the polarizing plate in the present invention imparts mechanical strength such as scratch resistance, it is preferably combined with a functional optical film having a hard coat layer provided on the surface of the transparent support. When the hard coat layer is applied to the above-described antireflection film, it is particularly preferable to provide it between the transparent support and the high refractive index layer.
The hard coat layer is preferably formed by a crosslinking reaction or a polymerization reaction of a curable compound by light and / or heat. The curable functional group is preferably a photopolymerizable functional group, or the hydrolyzable functional group-containing organometallic compound is preferably an organic alkoxysilyl compound. As a specific constituent composition of the hard coat layer, for example, those described in JP-A-2002-144913, JP-A-2000-9908, WO 00/46617, etc. can be preferably used.
The film thickness of the hard coat layer is preferably 0.2 μm to 100 μm.
The strength of the hard coat layer is preferably H or higher, more preferably 2H or higher, and most preferably 3H or higher in a pencil hardness test according to JIS K5400. Further, in the Taber test according to JIS K5400, the smaller the wear amount of the test piece before and after the test, the better.

  As the material for forming the hard coat layer, a compound containing an ethylenically unsaturated group or a compound containing a ring-opening polymerizable group can be used, and these compounds can be used alone or in combination. Preferred examples of the compound containing an ethylenically unsaturated group include ethylene glycol diacrylate, trimethylolpropane triacrylate, ditrimethylolpropane tetraacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, dipentaerythritol. Polyacrylates of polyols such as hexaacrylate; epoxy acrylates such as diacrylate of bisphenol A diglycidyl ether, diacrylate of hexanediol diglycidyl ether; obtained by reaction of polyisocyanate and hydroxyl group-containing acrylate such as hydroxyethyl acrylate Examples of preferred compounds include urethane acrylates. Moreover, as a commercially available compound, EB-600, EB-40, EB-140, EB-1150, EB-1290K, IRR214, EB-2220, TMPTA, TMPTMA (above, Daicel UCB Co., Ltd. product), UV -6300, UV-1700B (manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) and the like.

  Preferred examples of the compound containing a ring-opening polymerizable group include ethylene glycol diglycidyl ether, bisphenol A diglycidyl ether, trimethylol ethane triglycidyl ether, trimethylol propane triglycidyl ether, glycerol triglycidyl ether as glycidyl ethers. Triglycidyl trishydroxyethyl isocyanurate, sorbitol tetraglycidyl ether, pentaerythritol tetraglycyl ether, polyglycidyl ether of cresol novolac resin, polyglycidyl ether of phenol novolac resin, etc. Celoxide 2021P, Celoxide 2081 GT-301, Epolide GT-401, EHPE3150CE (above, Oxetanes such as OXT-121, OXT-221, OX-SQ, PNOX-1009 (above, manufactured by Toagosei Co., Ltd.), etc. Can be mentioned. In addition, a polymer of glycidyl (meth) acrylate or a copolymer of a monomer that can be copolymerized with glycidyl (meth) acrylate may be used for the hard coat layer.

  In the hard coat layer, oxide fine particles such as silicon, titanium, zirconium, and aluminum are used to reduce curing shrinkage of the hard coat layer, improve adhesion to the substrate, and reduce curling of the hard coat treated article in the present invention. It is also preferable to add crosslinked fine particles such as crosslinked fine particles such as polyethylene, polystyrene, poly (meth) acrylic acid esters, polydimethylsiloxane, etc., and fine organic particles such as fine crosslinked rubber particles such as SBR and NBR. The average particle size of these crosslinked fine particles is preferably 1 nm to 20000 nm. Further, the shape of the crosslinked fine particles can be used without particular limitation, such as a spherical shape, a rod shape, a needle shape, or a plate shape. The addition amount of the fine particles is preferably 60% by volume or less, more preferably 40% by volume or less of the hard coat layer after curing.

  In the case of adding the inorganic fine particles described above, since the affinity with the binder polymer is generally poor, it contains a metal such as silicon, aluminum, titanium, and the alkoxide group, carboxylic acid group, sulfonic acid group, phosphonic acid group, etc. It is also preferable to perform a surface treatment using a surface treatment agent having a functional group of

  The hard coat layer is preferably cured using heat or active energy rays. Among them, active energy rays such as radiation, gamma rays, alpha rays, electron rays, and ultraviolet rays are more preferred, and safety and productivity are improved. In view of the above, it is particularly preferable to use an electron beam or an ultraviolet ray. In the case of curing with heat, the heating temperature is preferably 140 ° C. or lower, more preferably 100 ° C. or lower, considering the heat resistance of the plastic itself.

(Forward scattering layer)
The forward scattering layer is used to improve the viewing angle characteristics (hue and luminance distribution) in the vertical and horizontal directions when the polarizing plate of the present invention is applied to a liquid crystal display device. In the present invention, the forward scattering layer preferably has a configuration in which fine particles having different refractive indexes are dispersed in a binder. For example, Japanese Patent Application Laid-Open No. 11-38208 in which a forward scattering coefficient is specified, a relative refractive index between a transparent resin and fine particles is in a specific range Japanese Patent Laid-Open No. 2000-199809, Japanese Patent Laid-Open No. 2002-107512, etc. in which the haze value is defined as 40% or more can be used. Moreover, in order to control the viewing angle characteristics of haze, the polarizing plate in the present invention should be used in combination with “Lumisty” described in Sumitomo Chemical Co., Ltd. Technical Report “Optical Functional Film” on pages 31-39. Can also be preferably performed.

(Anti-glare layer)
The antiglare (antiglare) layer is used to scatter reflected light and prevent reflection. The antiglare function is obtained by forming irregularities on the outermost surface (display side) of the liquid crystal display device. The haze of the optical film having an antiglare function is preferably 3 to 30%, more preferably 5 to 20%, and most preferably 7 to 20%.
The method for forming irregularities on the film surface is, for example, a method of forming irregularities on the film surface by adding fine particles (for example, JP 2000-271878 A), relatively large particles (particle size 0.05-2 μm). ) Is added in a small amount (0.1 to 50% by mass) (for example, Japanese Patent Application Laid-Open Nos. 2000-281410, 2000-95893, 2001-100004, and 2001). No. 281407, etc.), a method of physically transferring the uneven shape onto the film surface (for example, as an embossing method, JP-A-63-278839, JP-A-11-183710, JP-A-2000-275401) Etc.) can be preferably used.

[Liquid Crystal Display]
Next, the liquid crystal display device of the present invention will be described. The liquid crystal display device of the present invention includes at least one sheet of the cellulose acylate film of the present invention, the retardation film of the present invention, or the polarizing plate of the present invention.

(VA mode)
The liquid crystal cell of the liquid crystal display device of the present invention is preferably in the VA mode.

  The features of the VA mode are high-speed response and high contrast. However, the contrast is high in the front, but there is a problem that it is deteriorated in the oblique direction. During black display, the liquid crystal molecules are aligned perpendicular to the substrate surface. When observed from the front, the liquid crystal molecules have almost no birefringence, so the transmittance is low and a high contrast can be obtained. However, when observed obliquely, birefringence occurs in the liquid crystal molecules. Further, the crossing angle of the upper and lower polarizing plate absorption axes is 90 ° perpendicular to the front, but is larger than 90 ° when viewed from an oblique direction. Because of these two factors, leakage light occurs in the oblique direction, and the contrast is lowered. In order to solve this, the cellulose acylate film of the present invention is disposed as an optical compensation sheet (retardation film).

  In addition, the liquid crystal molecules are tilted during white display, but the birefringence of the liquid crystal molecules when viewed from an oblique direction differs between the tilt direction and the opposite direction, resulting in differences in luminance and color tone. In order to solve this, it is also preferable to adopt a structure called multi-domain in which one pixel of a liquid crystal display device is divided into a plurality of regions.

(Multi-domain)
For example, in the VA system, the viewing angle characteristics are averaged by inclining liquid crystal molecules into a plurality of different regions within one pixel by applying an electric field. In order to divide the orientation within one pixel, the electrode is provided with slits or protrusions, and the electric field direction is changed or the electric field density is biased. In order to obtain a uniform viewing angle in all directions, the number of divisions may be increased, but a substantially uniform viewing angle can be obtained by dividing into four or eight or more. In particular, it is preferable that the polarizing plate absorption axis can be set at an arbitrary angle when dividing into eight.

  Also, the liquid crystal molecules are difficult to respond at the alignment division region boundary. For this reason, in normally black display, since black display is maintained, a reduction in luminance becomes a problem. Therefore, it is possible to reduce the boundary region by adding a chiral agent to the liquid crystal material.

  Hereinafter, 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.

[Example 1]
[Film formation of cellulose acylate film]

(Preparation of cellulose acylate solution)
The following composition was put into a mixing tank and stirred to dissolve each component to prepare a cellulose acylate solution 1.
―――――――――――――――――――――――――――――――――――
Composition of Cellulose Acylate Solution 1 ――――――――――――――――――――――――――――――――――――
Cellulose acetate with an acetyl substitution degree of 2.43 and a polymerization degree of 340
100.0 parts by mass Compound 1 4.0 parts by mass Methylene chloride (first solvent) 402.0 parts by mass Methanol (second solvent) 60.0 parts by mass ――――――――――――― ―――――――――――――――――――――

  The cellulose acylate solution 1 was cast using a band casting machine, dried at 100 ° C. to a residual solvent content of 40%, and then the film was peeled off. The peeled film was further dried at an ambient temperature of 140 ° C. for 20 minutes. The dried film was stretched 35% in a direction orthogonal to the transport direction in an atmosphere of 195 ° C. using a tenter stretching apparatus to produce a cellulose acylate film of Example 1. The film thickness of the produced cellulose acylate film was 50 μm.

[Examples 2 to 21, Comparative Examples 1 to 11]
Cellulose acylate films of Examples 2 to 21 and Comparative Examples 1 to 11 were produced in the same manner as in Example 1 except that the types and amounts of the additives were changed as described in Table 1 below. Moreover, about the Hammett value of the substituent X in the said General formula (1) of the said compounds 1-5, (sigma) p value and (sigma) m value were combined with following Table 1, respectively. In the case of a barbituric acid derivative different from the general formula (1), the Hammett value of such a barbituric acid derivative is that of the substituent substituted on the hydrogen atom of the —CH ₂ — portion of the ring of the barbituric acid skeleton. Corresponds to Hammett value.

  In addition, in the following Table 1, the addition amount of the additive represents a part by mass with respect to 100 parts by mass of the cellulose acylate resin.

  Below, the structure of the additive used in the comparative example is described.

Compound 5: Comparative barbituric acid derivative which is outside the range of the general formula (1)

Compound 6: Comparative compound described as plasticizer C in the examples of JP-A 2007-84692

Compound 7: Triphenyl phosphate (a known comparative compound)

<Evaluation>

(Measurement of retardation)
About the cellulose acylate film of each Example and Comparative Example manufactured as described above, three points in the width direction (center, end portion (position of 5% of the total width from both ends)) are repeated three times every 10 m in the longitudinal direction. Sampling was performed, and nine samples having a size of 3 cm square were taken out and obtained from the average value of each point obtained according to the following method.
After adjusting the sample film for 24 hours at 25 ° C. and 60% relative humidity, the film surface was measured at 25 ° C. and 60% relative humidity using an automatic birefringence meter (KOBRA-21ADH: manufactured by Oji Scientific Instruments). In contrast, the retardation at a wavelength of 589 nm is measured from the direction inclined in increments of 10 ° from + 50 ° to −50 ° from the normal to the film plane with the slow axis as the vertical direction and the slow axis as the rotation axis. Re) and the retardation value (Rth) in the film thickness direction were calculated. The obtained results are shown in Table 1 below.

(Measurement of humidity dependence of retardation)
Regarding the change in retardation value with humidity, Re, Rth (respectively Re (respectively Re (R))) were measured in the same manner as above except that the film was conditioned at 25 ° C. and 10% relative humidity for 12 hours. 10%), Rth (10%)), and Re and Rth (respectively Re (80%)) measured and measured in the same manner as above except that the humidity was adjusted for 12 hours at 25 ° C. and 80% relative humidity. , Rth (80%)), the humidity dependence ΔRe of Re and the humidity dependence ΔRth of Rth were calculated. The obtained results are shown in Table 1 below.

  From the results of Table 1 above, the cellulose acylate films of Examples 1 to 21 using the additives used in the present invention were compared with the film of Comparative Example 1 in terms of Re and Rth with respect to changes in humidity in the usage environment. It was found that the fluctuation was suppressed. Further, Comparative Example 2 using a compound deviating from the general formula (1) of the present invention, Comparative Example 3 using an additive used in Japanese Patent Application Laid-Open No. 2007-84692, and Comparative Example 11 adding a double amount thereof. The cellulose acylate film of Comparative Example 4 known as a retardation enhancer for cellulose acylate film had a small effect of improving humidity dependency from the case of no additive added in Comparative Example 1. That is, it was found that the compound represented by the general formula (1) of the present invention has a higher humidity dependency improving effect than the additive used in each comparative example.

Claims (8)

Cellulose acylate;
A cellulose acylate film comprising a compound represented by the following general formula (1).

(In the general formula (1), R ¹ and R ² are each independently a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 1 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, or 5 carbon atoms. Represents a heteroaryl group having ˜20 or an aryl group having 6 to 20 carbon atoms, and X is Hammett's σp value and σm value i) σm <0 and σp ≧ 0,
ii) σp <0 and σm ≧ 0, or
iii) σp ≧ 0 and σm ≧ 0
The substituent which satisfy | fills any relationship among these is represented. )   In the said General formula (1), the said X is a substituent which has a phenyl group, The cellulose acylate film of Claim 1 characterized by the above-mentioned.   2. The cellulose acylate film according to claim 1, wherein, in the general formula (1), the X represents a substituent satisfying a relationship of Hammett σp value and σm value of σp ≧ 0 and σm ≧ 0. In the general formula (1), one of the R ¹ and R ² is a hydrogen atom, and the other is a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms. The cellulose acylate film according to any one of to 3.   A retardation film comprising the cellulose acylate film according to claim 1.   A polarizing plate comprising at least one sheet of the cellulose acylate film according to claim 1 or the retardation film according to claim 5.   A liquid crystal display device comprising at least one sheet of the cellulose acylate film according to claim 1, the retardation film according to claim 5, or the polarizing plate according to claim 6. A humidity-dependent improving agent for cellulose acylate films, comprising a compound represented by the following general formula (1).

(In the general formula (1), R ¹ and R ² are each independently a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 1 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, or 5 carbon atoms. Represents a heteroaryl group having ˜20 or an aryl group having 6 to 20 carbon atoms, and X is a Hammett σp value and σm value
i) σm <0 and σp ≧ 0,
ii) σp <0 and σm ≧ 0, or
iii) represents a substituent that satisfies any one of σp ≧ 0 and σm ≧ 0. )