JP2014098883A - Optical film and production method of the same, polarizing plate and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical film excellent in durability and capable of reducing permeation and desorption of moisture.SOLUTION: The optical film comprises a cellulose ester and an acrylic resin, in which a mass ratio of the cellulose ester to the acrylic resin ranges from 70:30 to 5:95. The optical film has a moisture permeability of 350 g/m/day or less (calculated for a thickness of 40 μm), and contains a moisture permeability reducing compound having a molecular weight of 200 or more and satisfying an expression (1):A/B≤0.6. In the expression, A represents a moisture permeability of an optical film when the moisture permeability reducing compound is added by 10 mass% with respect to the total mass of the cellulose ester and the acrylic resin; and B represents a moisture permeability of an optical film comprising the cellulose ester and the acrylic resin without addition of the moisture permeability reducing compound. The moisture permeability is a value obtained after the film is left in an atmosphere of 40°C and 90% relative humidity for 24 hours in accordance with the procedure of JIS Z-0208, and calculated for a film thickness of 40 μm.

Description

  The present invention relates to an optical film, a manufacturing method thereof, a polarizing plate, and a liquid crystal display device.

In recent years, liquid crystal display devices have been widely used for liquid crystal panels such as liquid crystal televisions, personal computers, mobile phones, and digital cameras. Usually, a liquid crystal display device has a liquid crystal panel member provided with polarizing plates on both sides of a liquid crystal cell, and display is performed by controlling light from the backlight member with the liquid crystal panel member. Here, the polarizing plate is composed of a polarizer and protective films on both sides thereof, and a general polarizer is obtained by dyeing a stretched polyvinyl alcohol (PVA) film with iodine or a dichroic dye to protect it. A cellulose ester film or the like is used as the film.
In liquid crystal display devices, it is known to use a polymer film as an optical compensation film (retardation film) in order to increase the viewing angle, improve image coloring, and improve contrast. For polymer films used as optical compensation films, depending on the liquid crystal cell mode of the liquid crystal display device such as VA mode or IPS mode, the optical properties of the film (for example, retardation value Re and film thickness in the film plane) It is required to provide desired optical anisotropy by controlling the birefringence such as the retardation value Rth in the vertical direction.

  Recent liquid crystal display devices are becoming more and more demanding, and the demands for durability are becoming stricter as the quality of the liquid crystal display devices increases. For example, when used in outdoor applications, stability against environmental changes is required, and the optical film such as the protective film for polarizing plate and the optical compensation film used in the liquid crystal display device also has dimensions and optical characteristics against temperature and humidity changes. It is required to suppress changes in Problems with liquid crystal display devices exposed to high temperature and high humidity conditions include the occurrence of warping and display unevenness in the liquid crystal cell of the liquid crystal display device. This is because moisture penetrates into the polarizing plate and the optical film constituting it. Desorption causes a difference in the shrinkage balance between the front and back polarizing plates of the liquid crystal cell of the liquid crystal display device, causing the liquid crystal cell to warp, and the four corners and four sides of the liquid crystal cell come into contact with the casing and the back side members. This is considered to be caused by uneven display. For this reason, improvement of humidity dependency and wet heat durability has been demanded for protective films and optical compensation films for polarizing plates. It is necessary to suppress desorption, and in particular, the optical film on the outermost surface of the polarizing plate is required to have a performance that prevents moisture from passing through, that is, a reduction in moisture permeability.

  Patent Document 1 describes an optical device in which a large amount of acrylic resin such as polymethyl methacrylate (PMMA) is added to cellulose ester for the purpose of providing an optical film having high transparency, low moisture absorption, high heat resistance, and high mechanical strength. A film is disclosed.

International Publication No. 2009/047924

Liquid crystal display devices are used not only in conventional indoor applications but also in harsher environments such as outdoors, and for the optical film on the outermost surface of the liquid crystal display device, it is important to have a performance that does not transmit moisture. . In TV applications that are becoming larger in size in recent years, there is an influence of the tendency of the glass of the liquid crystal cell to become thinner, warping tends to increase, and there is concern about the effect on display unevenness. In addition, since small and medium-sized devices such as tablet PCs and mobile applications that have been rapidly spreading in recent years have high demands for thinning and space saving in liquid crystal display devices, it is strongly desired to solve the problem of warping.
However, as described above, the use environment of the liquid crystal display device has become severe year by year, and the optical film described in Patent Document 1 reduces the warpage of the liquid crystal cell and suppresses display unevenness under the recent use environment. It has become difficult.

In view of the situation as described above, an object of the present invention is to provide an optical film that is excellent in durability and can reduce moisture permeation and desorption (hereinafter also referred to as moisture permeability reduction) and a method for producing the same. Is to provide.
Another object of the present invention is to provide a polarizing plate using the optical film. Still another object of the present invention is to provide a liquid crystal display device in which the warpage of the liquid crystal cell and the display unevenness after the high temperature and high humidity environment are improved.

  The object of the present invention can be achieved by the following means.

［一般式（Ａ）中、Ｒ¹¹³，Ｒ¹¹⁴，Ｒ¹¹⁵，Ｒ¹²³，Ｒ¹²⁴およびＲ¹²⁵はそれぞれ独立に水素原子または置換基を表す。］

［一般式（Ｂ）中、Ｒ¹²、Ｒ¹³、Ｒ¹⁴、Ｒ¹⁵、Ｒ¹⁶、Ｒ²¹、Ｒ²³、Ｒ²⁴、Ｒ²⁵、Ｒ³²、Ｒ³³、Ｒ³⁴、Ｒ³⁵、Ｒ³⁶は、それぞれ独立に、水素原子または置換基を表し、Ｒ¹²、Ｒ¹³、Ｒ¹⁴、Ｒ¹⁵、Ｒ¹⁶、Ｒ²¹、Ｒ²³、Ｒ²⁴、Ｒ²⁵、Ｒ³²、Ｒ³³、Ｒ³⁴、Ｒ³⁵およびＲ³⁶のうち少なくとも１つはアミノ基、アシルアミノ基、アルコキシカルボニルアミノ基、アリールオキシカルボニルアミノ基、スルホニルアミノ基、ヒドロキシ基、メルカプト基、カルボキシル基である。］

［一般式（Ｃ）中、Ｘ²はＢ、Ｃ−Ｒ（Ｒは水素原子または置換基を表す。）又はＮを表す。Ｒ²¹¹、Ｒ²¹²、Ｒ²¹³、Ｒ²¹⁴、Ｒ²¹⁵、Ｒ²²¹、Ｒ²²²、Ｒ²²³、Ｒ²²⁴、Ｒ²²⁵、Ｒ²³¹、Ｒ²³²、Ｒ²³³、Ｒ²³⁴およびＲ²³⁵は、それぞれ独立に水素原子または置換基を表す。］
［５］ ［１］〜［４］のいずれかに記載の光学フィルムは、セルロースエステルとアクリル樹脂との合計質量に対し、透湿度低減化合物を１０〜１００質量％含むことが好ましい。
［６］ ［１］〜［５］のいずれかに記載の光学フィルムは、厚みが６０μｍ以下であることが好ましい。
［７］ ［１］〜［６］のいずれかに記載の光学フィルムは、下記式（Ｉ）及び下記式（ＩＩ）で定義されるＲｅ及びＲｔｈが、波長５９０ｎｍにおいて下記式（ＩＩＩ）及び下記式（ＩＶ）を満たすことが好ましい。
式（Ｉ） Ｒｅ＝（ｎｘ−ｎｙ）×ｄ
式（ＩＩ） Ｒｔｈ＝｛（ｎｘ＋ｎｙ）／２−ｎｚ｝×ｄ
式（ＩＩＩ） ｜Ｒｅ｜≦５０ｎｍ
式（ＩＶ） ｜Ｒｔｈ｜≦３００ｎｍ
（式（Ｉ）〜（ＩＶ）中、ｎｘはフィルム面内の遅相軸方向の屈折率であり、ｎｙはフィルム面内の進相軸方向の屈折率であり、ｎｚはフィルムの厚み方向の屈折率であり、ｄはフィルムの厚さ（ｎｍ）である。）
［８］ ［１］〜［７］のいずれかに記載の光学フィルムは、セルロースエステル、アクリル樹脂、透湿度低減化合物および溶媒を含む高分子溶液を支持体上に流延して製膜されてなることが好ましい。
［９］ ［１］〜［８］のいずれかに記載の光学フィルムは、少なくとも一方の表面に、厚み０．１〜２０μｍの機能層を有することが好ましい。
［１０］ ［９］に記載の光学フィルムは、機能層を積層した場合の光学フィルムの透湿度（Ｃ）と、機能層の積層なしの場合の光学フィルムの透湿度（Ｄ）とが、Ｃ／Ｄ≦０．９となることが好ましい。
［１１］ セルロースエステル、アクリル樹脂、および透湿度低減化合物を含む組成物を支持体上に流延して高分子膜を形成する工程を含み、
組成物中における前記セルロースエステルと前記アクリル樹脂との質量比が７０：３０〜５：９５であり、
透湿度低減化合物の分子量が２００以上であり、
透湿度低減化合物が下記式（１）を満たすことを特徴とする光学フィルムの製造方法。
式（１） Ａ／Ｂ≦０．６
（式（１）中、Ａはセルロースエステルとアクリル樹脂との合計質量に対して透湿度低減化合物を１０質量％添加した場合の光学フィルムの透湿度を表し、Ｂはセルロースエステルとアクリル樹脂を含みかつ透湿度低減化合物を添加なしの場合の光学フィルムの透湿度を表す。ただし、透湿度はＪＩＳ Ｚ−０２０８の手法で、４０℃、相対湿度９０％で２４時間経過後の値を４０μｍ厚みに換算した値である。）
［１２］ ［１１］に記載の光学フィルムの製造方法は、光学フィルムが下記式（２）を満たすことが好ましい。
式（２） ａ／Ｂ≦０．６
（式（２）中、ａは光学フィルムの透湿度を表し、Ｂは透湿度低減化合物の添加なしの場合の光学フィルムの透湿度を表す。ただし、透湿度はＪＩＳ Ｚ−０２０８の手法で、４０℃、相対湿度９０％で２４時間経過後の値を４０μｍ厚みに換算した値である。）
［１３］ [１１]または[１２]に記載の光学フィルムの製造方法は、光学フィルムを少なくともフィルムの搬送方向および幅方向のいずれかに延伸する工程を含むことが好ましい。
［１４］ 偏光子の保護フィルムとして［１］〜［１０］のいずれかに記載の光学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。
［１５］ 液晶セルと、
液晶セルの少なくとも一方に配置された［１４］に記載の偏光板とを含み、
光学フィルムが最表層となるように配置されたことを特徴とする液晶表示装置。 [1] An optical film containing a cellulose ester and an acrylic resin,
The mass ratio of cellulose ester to acrylic resin is 70:30 to 5:95,
The moisture permeability of the optical film is 350 g / m ² / day or less (in terms of thickness 40 μm),
An optical film comprising a moisture permeability reducing compound having a molecular weight of 200 or more and satisfying the following formula (1):
Formula (1) A / B <= 0.6
(In formula (1), A represents the moisture permeability of the optical film when the moisture permeability reducing compound is added in an amount of 10% by mass with respect to the total mass of the cellulose ester and the acrylic resin, and B includes the cellulose ester and the acrylic resin. And the moisture permeability of the optical film when no moisture permeability reducing compound is added, but the moisture permeability is JIS Z-0208, and the value after 24 hours at 40 ° C. and 90% relative humidity is 40 μm thickness. (It is a converted value.)
[2] The optical film according to [1] preferably satisfies the following formula (2).
Formula (2) a / B <= 0.6
(In Formula (2), a represents the water vapor transmission rate of an optical film, B represents the water vapor transmission rate of the optical film without the addition of a water vapor transmission reduction compound. However, the water vapor transmission rate is a method of JIS Z-0208. (The value after 24 hours at 40 ° C. and 90% relative humidity is converted to a thickness of 40 μm.)
[3] In the optical film according to [1] or [2], the moisture permeability reducing compound preferably has a structure including one or more aromatic rings.
[4] The optical film according to any one of [1] to [3] has a structure in which the moisture permeability reducing compound is represented by the following general formula (A), general formula (B), or general formula (C). Preferably there is.

[In General Formula (A), ^R113 , ^R114 , ^R115 , ^R123 , ^R124 and ^R125 each independently represents a hydrogen atom or a substituent. ]

[In the general formula (B), R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ , R ¹⁶ , R ²¹ , R ²³ , R ²⁴ , R ²⁵ , R ³² , R ³³ , R ³⁴ , R ³⁵ , R ³⁶ are Each independently represents a hydrogen atom or a substituent, and R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ , R ¹⁶ , R ²¹ , R ²³ , R ²⁴ , R ²⁵ , R ³² , R ³³ , R ³⁴ , R ^At least one of ³⁵ and R ³⁶ is an amino group, an acylamino group, an alkoxycarbonylamino group, an aryloxycarbonylamino group, a sulfonylamino group, a hydroxy group, a mercapto group, or a carboxyl group. ]

[In the general formula (C), X ² represents B, C—R (R represents a hydrogen atom or a substituent) or N. R ²¹¹ , R ²¹² , R ²¹³ , R ²¹⁴ , R ²¹⁵ , R ²²¹ , R ²²² , R ²²³ , R ²²⁴ , R ²²⁵ , R ²³¹ , R ²³² , R ²³³ , R ²³⁴ and R ²³⁵ are each independently hydrogen Represents an atom or substituent. ]
[5] The optical film according to any one of [1] to [4] preferably contains 10 to 100% by mass of the moisture permeability reducing compound with respect to the total mass of the cellulose ester and the acrylic resin.
[6] The optical film according to any one of [1] to [5] preferably has a thickness of 60 μm or less.
[7] In the optical film according to any one of [1] to [6], Re and Rth defined by the following formula (I) and the following formula (II) are represented by the following formula (III) and the following formula at a wavelength of 590 nm. It is preferable to satisfy Formula (IV).
Formula (I) Re = (nx−ny) × d
Formula (II) Rth = {(nx + ny) / 2−nz} × d
Formula (III) | Re | ≦ 50 nm
Formula (IV) | Rth | ≦ 300 nm
(In the formulas (I) to (IV), nx is the refractive index in the slow axis direction in the film plane, ny is the refractive index in the fast axis direction in the film plane, and nz is in the thickness direction of the film. (Refractive index, d is the film thickness (nm).)
[8] The optical film according to any one of [1] to [7] is formed by casting a polymer solution containing a cellulose ester, an acrylic resin, a moisture permeability reducing compound, and a solvent on a support. It is preferable to become.
[9] The optical film according to any one of [1] to [8] preferably has a functional layer having a thickness of 0.1 to 20 μm on at least one surface.
[10] In the optical film according to [9], the moisture permeability (C) of the optical film when the functional layer is laminated and the moisture permeability (D) of the optical film when the functional layer is not laminated are C It is preferable that /D≦0.9.
[11] A step of casting a composition containing a cellulose ester, an acrylic resin, and a moisture permeability reducing compound on a support to form a polymer film,
The mass ratio of the cellulose ester and the acrylic resin in the composition is 70:30 to 5:95,
The molecular weight of the moisture permeability reducing compound is 200 or more,
The method for producing an optical film, wherein the moisture permeability reducing compound satisfies the following formula (1):
Formula (1) A / B <= 0.6
(In formula (1), A represents the moisture permeability of the optical film when the moisture permeability reducing compound is added in an amount of 10% by mass with respect to the total mass of the cellulose ester and the acrylic resin, and B includes the cellulose ester and the acrylic resin. And the moisture permeability of the optical film when no moisture permeability reducing compound is added, but the moisture permeability is JIS Z-0208, and the value after 24 hours at 40 ° C. and 90% relative humidity is 40 μm thickness. (It is a converted value.)
[12] In the method for producing an optical film described in [11], the optical film preferably satisfies the following formula (2).
Formula (2) a / B <= 0.6
(In Formula (2), a represents the water vapor transmission rate of an optical film, B represents the water vapor transmission rate of the optical film without the addition of a water vapor transmission reduction compound. However, the water vapor transmission rate is a method of JIS Z-0208. (The value after 24 hours at 40 ° C. and 90% relative humidity is converted to a thickness of 40 μm.)
[13] The method for producing an optical film according to [11] or [12] preferably includes a step of stretching the optical film in at least one of a conveyance direction and a width direction of the film.
[14] A polarizing plate comprising at least one optical film according to any one of [1] to [10] as a protective film for a polarizer.
[15] a liquid crystal cell;
Including the polarizing plate according to [14] disposed in at least one of the liquid crystal cells,
A liquid crystal display device, wherein the optical film is arranged to be an outermost layer.

According to the present invention, an optical film that is excellent in durability and can reduce moisture permeability can be provided. By using the optical film of the present invention, it is possible to provide a liquid crystal display device in which the warpage of the liquid crystal cell and the occurrence of display unevenness after the aging of the high temperature and high humidity environment are suppressed.

It is the schematic of the film manufacturing line for enforcing the solution casting method.

Below, the polarizing plate of this invention, its manufacturing method, the additive used for it, etc. are demonstrated in detail.
The description of the constituent elements described below may be made based on typical embodiments of the present invention, but the present invention is not limited to such embodiments. In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.
“Acrylic resin” means a resin obtained by polymerizing methacrylic acid or a derivative of acrylic acid, and a resin containing the derivative. Further, when not particularly limited, “(meth) acrylate” represents acrylate and methacrylate, and “(meth) acryl” represents acryl and methacryl.
Furthermore, the “slow axis direction” of the film is the direction in which the refractive index is maximum in the film plane, and the “fast axis direction” means the direction perpendicular to the slow axis in the film plane. .

[Optical film]
The optical film of the present invention is an optical film containing a cellulose ester and an acrylic resin, wherein the mass ratio of the cellulose ester and the acrylic resin is 70:30 to 5:95, and the moisture permeability of the optical film is 350 g / m ² / day or less (40 μm thickness equivalent), a molecular weight of 200 or more, and a moisture permeability reducing compound that satisfies the following formula (1).
Formula (1) A / B <= 0.6
(In Formula (1), A represents the moisture permeability of the optical film when the moisture permeability reducing compound is added in an amount of 10% by mass with respect to the total mass of the cellulose ester and the acrylic resin, and B represents the cellulose ester and It represents the moisture permeability of the optical film when the acrylic resin is contained and no moisture permeability reducing compound is added, provided that the moisture permeability is JIS Z-0208 according to the method of JIS Z-0208 after 24 hours at 40 ° C. and 90% relative humidity. (The value is a value converted to a thickness of 40 μm.)
With the above configuration, durability is excellent and moisture permeability can be reduced.

Furthermore, the optical film of the present invention preferably satisfies the following formula (2).
Formula (2) a / B <= 0.6
(In Formula (2), a represents the water vapor transmission rate of an optical film, B represents the water vapor transmission rate of the optical film without the addition of a water vapor transmission reduction compound. However, the water vapor transmission rate is a method of JIS Z-0208. (The value after 24 hours at 40 ° C. and 90% relative humidity is converted to a thickness of 40 μm.)
The a / B is preferably 0.55 or less, and more preferably 0.50 or less.
Hereinafter, the preferable aspect of the structure of the optical film of this invention is demonstrated.

<Components of optical film>
(Cellulose acylate)
The cellulose used as a raw material for the cellulose ester used in the present invention includes cotton linter and wood pulp (hardwood pulp, softwood pulp), etc., and any cellulose ester obtained from any raw material cellulose can be used. May be. As for these raw material celluloses, for example, plastic material course (17) Fibrous resin (Maruzawa, Uda, Nikkan Kogyo Shimbun, published in 1970) and Invention Association Open Technical Report 2001-1745 (pages 7-8). However, the cellulose ester used in the present invention is not particularly limited to that described.

The cellulose ester used in the present invention is preferably an ester of cellulose and a fatty acid (including an aromatic fatty acid), and is in the 2nd, 3rd and 6th positions of β-1,4 bonded glucose units constituting the cellulose. A cellulose acylate acylated by substituting an acyl group of the fatty acid for a certain hydroxyl group is preferred.
For example, cellulose alkyl carbonyl ester, alkenyl carbonyl ester, aromatic carbonyl ester, aromatic alkyl carbonyl ester, etc., and cellulose ester in which acyl groups of two or more fatty acids are substituted are also preferable. These cellulose esters may further have a substituted group.
As the acyl group that substitutes for the hydroxyl group, an acetyl group having 2 carbon atoms and an acyl group having 3 to 22 carbon atoms can be preferably used. From the viewpoint of improving compatibility with the acrylic resin, an acetyl group having 2 carbon atoms and an acyl group having 3 to 7 carbon atoms are preferable.
The total substitution degree of acyl groups in the cellulose ester used in the present invention (the ratio of substitution of acyl groups with hydroxyl groups in the β-glucose unit of cellulose) The number of substituted groups is 3). However, it is preferable that the total substitution degree of the acyl group is higher because the compatibility with the acrylic resin is better and the humidity dependency is reduced. For this reason, the total substitution degree of the acyl group is preferably 2.00 to 3.00, more preferably 2.50 to 3.00, and still more preferably 2.50 to 2.90.
Furthermore, from the viewpoint of compatibility with the acrylic resin, the substitution degree of the acyl group having 3 to 7 carbon atoms is preferably 1.20 to 3.00, more preferably 1.50 to 3.00, and 2.00. -3.00 is more preferable, and 2.00-2.90 is particularly preferable.
In the cellulose ester used in the present invention, examples of the method for measuring the degree of substitution of the acyl group substituted on the hydroxyl group of cellulose include a method according to ASTM D-817-91 and an NMR method.

The acyl group that substitutes for the hydroxyl group of the β-glucose unit of cellulose may be either an aliphatic group or an aromatic group, and is not particularly limited. Moreover, the acyl group substituted on the hydroxyl group may be a single acyl group or two or more kinds.
Examples of the acyl group include acetyl group, propionyl group, butanoyl group, heptanoyl group, hexanoyl group, octanoyl group, decanoyl group, dodecanoyl group, tridecanoyl group, tetradecanoyl group, hexadecanoyl group, octadecanoyl group, iso -Butanoyl group, t-butanoyl group, cyclohexanecarbonyl group, oleoyl group, benzoyl group, naphthylcarbonyl group, cinnamoyl group and the like can be mentioned. Among these, acetyl group, propionyl group, butanoyl group, dodecanoyl group, octadecanoyl group, t-butanoyl group, oleoyl group, benzoyl group, naphthylcarbonyl group, cinnamoyl group and the like are preferable, and acetyl group, propionyl group, butanoyl group are preferable. Group is more preferable, propionyl group or butanoyl group is still more preferable, and propionyl group is particularly preferable.
Acetyl and propionyl groups, acetyl and butanoyl groups, propionyl and butanoyl groups, acetyl, propionyl and butanoyl groups are used in combination for ease of synthesis, cost, and ease of control of substituent distribution. More preferably, acetyl group and propionyl group, acetyl group and butanoyl group, acetyl group, propionyl group and butanoyl group are used in combination, more preferably acetyl group and propionyl group, acetyl group and propionyl group. And a butanoyl group are used in combination, and an acetyl group and a propionyl group are particularly preferably used in combination.
Examples of the cellulose ester substituted with the acyl group include cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, cellulose acetate petitate, cellulose acetate propionate butyrate, and cellulose benzoate. Of these, cellulose propionate, cellulose butyrate, cellulose acetate propionate, cellulose acetate butyrate, and cellulose acetate propionate butyrate are preferable, and cellulose acetate propionate is more preferable.

  The degree of polymerization of the cellulose ester used in the present invention is preferably 180 to 700 in terms of viscosity average degree of polymerization. In particular, in cellulose acetate propionate substituted with an acetyl group and a propionyl group, 180 to 550 is more preferable. 180 to 400 are more preferable, and 180 to 350 are particularly preferable. If the degree of polymerization is within this range, the viscosity of the dope solution containing the cellulose ester can be made suitable for film production by casting, and the compatibility with the acrylic resin is high, and the transparency and mechanical strength are high. It is preferable because a high film can be obtained. The viscosity average degree of polymerization can be measured by Uda et al.'S limiting viscosity method (Kazuo Uda, Hideo Saito, Journal of Textile Science, Vol. 18, No. 1, pages 105-120, 1962). This is described in detail in JP-A-9-95538.

The mass average molecular weight Mw of the cellulose ester used in the present invention is preferably 75000 or more. If the mass average molecular weight Mw of a cellulose ester is 75000 or more, mechanical strength is high and it is excellent in the handling ability at the time of film manufacture. From this viewpoint, the mass average molecular weight Mw of the cellulose ester is more preferably 100,000 or more, and particularly preferably 150,000 or more. Moreover, from a viewpoint of a compatibility improvement with an acrylic resin, it is preferable that the mass mean molecular weight Mw of a cellulose ester is 300000 or less, It is more preferable that it is 270000 or less, It is further more preferable that it is 250,000 or less.
From the viewpoint of achieving both the mechanical strength of the film, the handling suitability, and the compatibility improvement with the acrylic resin, the mass average molecular weight Mw of the cellulose ester is preferably 75,000 or more and 300,000 or less, and preferably 100,000 or more and 270000 or less. More preferably, it is 150,000 or more and 250,000 or less.
From the same viewpoint, the number average molecular weight Mn of the cellulose ester is preferably 18000 or more and 300000 or less, more preferably 25000 or more and 270000 or less, and further preferably 38000 or more and 250,000 or less.
The mass average molecular weight and number average molecular weight of the cellulose ester can be measured by gel permeation chromatography.
Further, regarding the molecular weight distribution of the cellulose ester, it is preferable that the polydispersity index Mw / Mn (Mw is a mass average molecular weight, Mn is a number average molecular weight) is small and the molecular weight distribution is narrow. The specific value of Mw / Mn is preferably 1.0 to 4.0, more preferably 2.0 to 3.5, and even more preferably 2.3 to 3.4. preferable.

When the low molecular weight component of the cellulose ester is removed, the average molecular weight (polymerization degree) is increased, but the viscosity is lower than that of a normal cellulose ester, which is useful. The removal of the low molecular component can be carried out by washing the cellulose ester synthesized by a usual method with an appropriate organic solvent. In addition, when manufacturing a cellulose acylate with few low molecular components, it is preferable to adjust the sulfuric acid catalyst amount in an acetylation reaction to 0.5-25 mass parts with respect to 100 mass parts of cellulose. When the amount of the sulfuric acid catalyst is within the above range, cellulose acylate having a narrow molecular weight distribution can be synthesized.
Regarding the cellulose acylate that can be used in the present invention, the raw material cotton and the synthesis method thereof are disclosed in JIII Journal of Technical Disclosure (Publication No. 2001-1745, published on March 15, 2001, Invention Association), pages 7-12. It is described in detail on the page.

  In the present invention, from the viewpoint of the substituent, substitution degree, polymerization degree, molecular weight distribution, etc. of cellulose ester, a single or different two or more kinds of cellulose esters can be mixed and used.

  The content of the cellulose ester in the optical film of the present invention is preferably 69.9 to 3.3% by mass, more preferably 69.9 to 10.0% by mass in the optical film. It is more preferable that it is 9-20.0 mass%, and it is still more preferable that it is 49.9-20.0 mass%.

(acrylic resin)
The acrylic resin used in the present invention is a resin obtained by polymerizing a derivative of (meth) acrylic acid and a resin containing the derivative, and is not particularly limited as long as the effects of the present invention are not impaired.
Examples of the (meth) acrylic acid derivative include (meth) acrylate. For example, methyl acrylate, ethyl acrylate, N-propyl acrylate, N-butyl acrylate, tert-butyl acrylate, isopropyl acrylate, N-hexyl acrylate, cyclohexyl acrylate, t-butyl cyclohexyl acrylate, methyl methacrylate, ethyl methacrylate, N-propyl methacrylate, Homopolymers of alkyl (meth) acrylates such as N-butyl methacrylate, tert-butyl methacrylate, isopropyl methacrylate, N-hexyl methacrylate, cyclohexyl methacrylate, t-butylcyclohexyl methacrylate; 2-chloroethyl acrylate, 2-hydroxyethyl acrylate, 2,3,4,5-tetrahydroxypentyl acrylate, 2 Any hydrogen atom in alkyl (meth) acrylates such as chloroethyl methacrylate, 2-hydroxyethyl methacrylate, 2,3,4,5-tetrahydroxypentyl methacrylate, etc. substituted with halogen groups, hydroxyl groups and other organic residues Good. Here, the other organic residue is preferably a linear, branched, or cyclic alkyl group having 1 to 20 carbon atoms.

  As a main component of the acrylic resin used in the present invention, alkyl (meth) acrylate is preferable. The alkyl (meth) acrylate is preferably an alkyl (meth) acrylate composed of an alkyl group having 1 to 18 carbon atoms and (meth) acrylic acid, and an alkyl composed of an alkyl group having 1 to 12 carbon atoms and meth) acrylic acid. (Meth) acrylate is more preferred, methyl acrylate and methyl methacrylate are more preferred, and methyl methacrylate is particularly preferred.

The acrylic resin used in the present invention is a copolymer of one (meth) acrylic acid derivative or a copolymer of two or more (meth) acrylic acid derivatives. It may be a copolymer with other possible monomers.
Examples of copolymerizable components that can be copolymerized with (meth) acrylic acid derivatives include α, β-unsaturated acids such as acrylic acid and methacrylic acid, and unsaturated group-containing divalent carboxylic acids such as maleic acid, fumaric acid, and itaconic acid. Unsaturated acids such as acids, styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene, p-ethylstyrene, p-tert-butylstyrene, α-methylstyrene, α- Aromatic vinyl compounds such as methyl-p-methylstyrene, α, β-unsaturated nitriles such as acrylonitrile and methacrylonitrile, lactone ring units, glutaric anhydride units, unsaturated carboxylic acid anhydrides such as maleic anhydride Examples include compounds, maleimides such as maleimide and N-substituted maleimide, and glutarimide units.
From the viewpoint of optical properties, an aromatic vinyl compound is preferable, and styrene is particularly preferable.

From the viewpoint of improving compatibility with cellulose ester, the acrylic resin is preferably a methyl methacrylate homopolymer or copolymer, more preferably containing 50% by mass or more of methyl methacrylate-derived repeating units, and 70% by mass or more. More preferably, it is more preferably 90% by mass or more. Furthermore, a copolymer of methyl methacrylate and another monomer is preferable, and the acrylic resin of the copolymer contains 1 to 50% by mass of a repeating unit derived from a monomer copolymerized with methyl methacrylate. Is preferable, it is more preferable that 1-30 mass% is contained, and it is still more preferable that 1-10 mass% is contained.
The monomer copolymerizable with methyl methacrylate comprises, in addition to those exemplified as the monomer copolymerizable with the alkyl (meth) acrylate, an alkyl group having 2 to 18 carbon atoms and methacrylic acid. Examples thereof include alkyl methacrylates and alkyl acrylates comprising an alkyl group having 1 to 18 carbon atoms and acrylic acid, and these can be used alone or in combination of two or more monomers. Of these, methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, s-butyl acrylate, 2-ethylhexyl acrylate, and the like are preferable from the viewpoint of thermal decomposition resistance and fluidity of the copolymer, and methyl acrylate and n- Butyl acrylate is particularly preferably used.
Examples of the acrylic resin and (meth) acrylic acid derivatives and other copolymerizable monomers of the present invention include JP2009-122664, JP2009-139661, JP2009-139754, and JP2009-. 294262, International Publication 2009/054376, and other publications can also be used. In addition, these do not limit this invention, These can be used individually or in combination of 2 or more types.
When two or more types of acrylic resins are used, it is preferable to use at least one type having the above structure.

The mass average molecular weight Mw of the acrylic resin used in the present invention is preferably 80,000 or more. If the mass average molecular weight Mw of an acrylic resin is 80000 or more, mechanical strength is high and it is excellent in the handling ability at the time of film manufacture. In this respect, the acrylic resin preferably has a mass average molecular weight Mw of 100,000 or more. Further, from the viewpoint of improving compatibility with cellulose ester, the mass average molecular weight Mw of the acrylic resin is preferably 3000000 or less, and more preferably 2000000 or less.
The mass average molecular weight of the acrylic resin is measured by gel permeation chromatography.

  There is no restriction | limiting in particular as a manufacturing method of the acrylic resin in this invention, Any of well-known methods, such as suspension polymerization, emulsion polymerization, block polymerization, or solution polymerization, may be used. Here, as a polymerization initiator, a normal peroxide type and an azo type can be used, and a redox type can also be used. Regarding the polymerization temperature, it can be carried out at 30 to 100 ° C. for suspension or emulsion polymerization, and at 80 to 160 ° C. for bulk or solution polymerization. In order to control the reduced viscosity of the obtained copolymer, polymerization can be carried out using alkyl mercaptan or the like as a chain transfer agent.

A commercially available thing can also be used as an acrylic resin used for this invention. For example, Delpet 60N, 80N (Asahi Kasei Chemicals Co., Ltd.), Dianal BR80, BR85, BR88, BR102 (Mitsubishi Rayon Co., Ltd.), KT75 (Electrochemical Industry Co., Ltd.) and the like can be mentioned. Incidentally, Dianal BR88 has a weight average molecular weight of 1,500,000.
Two or more acrylic resins can be used in combination.

  The content of the acrylic resin in the optical film of the present invention is preferably 20.0 to 94.9% by mass, more preferably 20.0 to 84.9% by mass in the optical film, and 20. It is more preferable that it is 0-69.9%, and it is still more preferable that it is 34.0-69.9 mass%.

  In the optical film of the present invention, the ratio (mass ratio) between the cellulose ester and the acrylic resin is 70:30 to 5:95. By making the ratio of cellulose ester 70% by mass or less, humidity dependency is low, durability at high temperature and high humidity is improved, preferable optical characteristics can be obtained, and display unevenness of the liquid crystal display device can be prevented. . Moreover, heat resistance improves by making the ratio of an acrylic resin 95 mass% or less, and it is easy to express desired optical anisotropy. In addition, mechanical strength, mechanical strength, surface shape, hunting suitability, and film surface treatment suitability can be improved. The mass ratio of cellulose ester to acrylic resin is 70:30 to 5:95, preferably 70:30 to 15:85, more preferably 70:30 to 30:70, and even more preferably 49. : 51-30: 70.

In the optical film of the present invention, it is preferable that the cellulose ester and the acrylic resin are contained in a compatible state from the viewpoint of reducing the total haze and internal haze and increasing the transparency.
Whether the cellulose ester and the acrylic resin are in a compatible state can be determined by, for example, the glass transition temperature Tg. For example, when the glass transition temperatures of cellulose ester and acrylic resin are different, when both are mixed, there are two or more glass transition temperatures for each mixture, so that both are compatible. In some cases, the glass transition temperature inherent to each resin disappears and becomes one glass transition temperature, which is the glass transition temperature of the compatible resin.
The glass transition temperature is a temperature at which the baseline derived from the glass transition of the resin begins to change and a temperature at which the glass returns to the baseline again when measured at a heating rate of 10 ° C./min using a differential scanning calorimeter (DSC). It can be calculated as an average value.

  The cellulose ester and the acrylic resin are each preferably an amorphous resin, and either one may be a crystalline polymer or a partially crystalline polymer. It becomes preferable that it becomes a non-crystalline resin by being compatible.

The weight average molecular weight Mw and substitution degree of the cellulose ester in the optical film of the present invention, and the weight average molecular weight Mw of the acrylic resin are obtained by measuring each after separation using the difference in solubility in both solvents. be able to. When fractionating the resin, it is possible to extract and separate the soluble resin by adding a compatible resin in a solvent that is soluble only in either one. At this time, heating operation or reflux is performed. May be. A combination of these solvents may be combined in two or more steps to separate the resin. The dissolved resin and the resin remaining as an insoluble matter are filtered off, and the solution containing the extract can be separated by an operation of evaporating the solvent and drying. These fractionated resins can be identified by general structural analysis of polymers. When the optical film of the present invention contains a resin other than cellulose ester or acrylic resin, it can be separated by the same method.
The optical film of the present invention preferably contains a cellulose ester and an acrylic resin in a compatible state. Further, when the mass average molecular weights Mw of the compatible resins are different from each other, the high molecular weight substances are eluted earlier by gel permeation chromatography, and the lower molecular weight substances are eluted after a longer time. It can be easily fractionated and the molecular weight can be measured.
In addition, the molecular weight of the compatible resin is measured by gel permeation chromatography. At the same time, the resin solution eluted every time is separated, the solvent is distilled off, and the structure of the dried resin is quantitatively analyzed. By detecting the resin composition for each fraction having a different molecular weight, the compatible resins can be respectively identified. The resins that have been separated in advance by the difference in solubility in a solvent can be detected by measuring the molecular weight distribution by gel permeation chromatography, respectively.
In addition, “containing cellulose ester and acrylic resin in a compatible state” means that each resin (polymer) is mixed to result in a compatible state. It is assumed that a mixed resin state by mixing a precursor of acrylic resin such as dimer or oligomer with cellulose ester and then polymerizing it is not included.

  Unless the function as an optical film is impaired, the optical film of this invention may contain resin and additives other than a cellulose ester and an acrylic resin, and may be comprised. When the resin other than the cellulose ester and the acrylic resin is contained, the added resin may be mixed without being dissolved even if the added resin is in a compatible state.

(Moisture permeability reducing compound)
The optical film of the present invention is characterized by containing a moisture permeability reducing compound having a molecular weight of 200 or more and satisfying the following formula (1) in order to reduce moisture permeation and desorption.
Formula (1) A / B <= 0.6
(In Formula (1), A represents the moisture permeability of the optical film when the moisture permeability reducing compound is added in an amount of 10% by mass with respect to the total mass of the cellulose ester and the acrylic resin, and B represents the cellulose ester and It represents the moisture permeability of the optical film when the acrylic resin is contained and no moisture permeability reducing compound is added, provided that the moisture permeability is JIS Z-0208 according to the method of JIS Z-0208 after 24 hours at 40 ° C. and 90% relative humidity. (The value is a value converted to a thickness of 40 μm.)
More preferably, the moisture permeability reducing compound has an A / B of 0.55 or less and an A / B of 0.50 or less. On the other hand, when A / B is larger than 0.6, a sufficient effect is not exhibited in the present invention.

  The moisture permeability reducing compound may have a structure including one or more aromatic rings. Hydrophobic properties can be imparted to the film by the aromatic ring, and moisture permeation and desorption can be suppressed. The moisture permeability reducing compound preferably has a structure represented by the general formula (A), the general formula (B), or the general formula (C). Hereinafter, the moisture permeability reducing compound having a structure represented by the general formula (A), the general formula (B), or the general formula (C) will be described.

［式中、Ｒ¹¹³，Ｒ¹¹⁴，Ｒ¹¹⁵，Ｒ¹²³，Ｒ¹²⁴およびＲ¹²⁵はそれぞれ独立に水素原子または置換基を表す。］ -Benzophenone derivative-
One preferred embodiment of the moisture permeation reducing compound is a benzophenone derivative.
As the benzophenone derivative used in the present invention as the moisture permeability reducing compound, a compound represented by the following general formula (A) is preferably used.

[Wherein, R ¹¹³ , R ¹¹⁴ , R ¹¹⁵ , R ¹²³ , R ¹²⁴ and R ¹²⁵ each independently represent a hydrogen atom or a substituent. ]

R ¹¹³ , R ¹¹⁴ , R ¹¹⁵ , R ¹²³ , R ¹²⁴ and R ¹²⁵ each independently represents a halogen atom (for example, a fluorine atom, a chlorine atom, a bromine atom or an iodine atom), a carbon atom number 1 to 20 alkyl groups (for example, methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, sec-butyl group, t-butyl group, pentyl group, hexyl group, cyclohexyl group, heptyl group, octyl group) Group, 2-ethylhexyl group, t-octyl group, nonyl group, decyl group, undecyl group, dodecyl group, octadecyl group), aryl group having 6 to 20 carbon atoms (for example, phenyl group, tolyl group, naphthyl group, anthranyl) Group), cyano group, hydroxyl group, carboxyl group, alkoxy group having 1 to 20 carbon atoms (for example, methoxy group, ethoxy group, pro Poxy group, butoxy group, octyloxy group, 2-ethylhexyloxy group, t-butoxy group), aryloxy group having 6 to 20 carbon atoms (for example, phenoxy group, tolyloxy group, naphthoxy group), 2 to 2 carbon atoms Examples include 20 alkylcarbonyloxy groups, arylcarbonyloxy groups having 7 to 20 carbon atoms, carbamoyloxy groups, amino groups, alkylamino groups, acylamino groups, alkylcarbonylamino groups, and arylcarbonylamino groups.
R ¹¹³ , R ¹¹⁴ , R ¹¹⁵ , R ¹²³ , R ¹²⁴ and R ¹²⁵ each independently represents a hydroxyl group or an alkoxy group, more particularly preferably a hydroxyl group or a carbon number of 1 to 5 is an alkoxy group, still more preferably a hydroxyl group or a methoxy group.
Of R ¹¹³ , R ¹¹⁴ , R ¹¹⁵ , R ¹²³ , R ¹²⁴ and R ¹²⁵ , at least one of R ¹¹³ , R ¹¹⁴ , R ¹²³ and R ¹²⁴ is preferably a substituent, and one or two are substituents. Is more preferable, and it is particularly preferable that two are substituents.
R ¹¹³ , R ¹¹⁴ , R ¹¹⁵ , R ¹²³ , R ^124, and R ^{125 have} a hydroxyl group in R ¹²⁴ to reduce moisture permeability, and when added to the film, it is easy to suppress an increase in Rth of the film To preferred. Further, from the same viewpoint, it is more preferable that R ¹¹³ , R ¹¹⁴ , R ¹¹⁵ , R ¹²³ , R ¹²⁴ and R ^{125 have} a hydroxyl group at R ¹²⁴ and a substituent at R ¹¹⁴ or R ^123. It is particularly preferable that R ¹²⁴ has a hydroxyl group and R ¹²³ has a substituent.

Although the preferable example of a compound represented by the said general formula (A) below is shown below, this invention is not limited to these specific examples.

-Compound represented by general formula (B)-
As the moisture permeability reducing compound contained in the optical film of the present invention, a compound represented by the following general formula (B) can be preferably used.
General formula (B)

In the general formula ^{(B), R 12, R} 13, R 14, R 15, R 16, R 21, R 23, R 24, R 25, R 32, R 33, R 34, R 35, R 36 are, Each independently represents a hydrogen atom or a substituent (substituent T described below is preferably applicable as the substituent), R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ , R ¹⁶ , R ²¹ , R ²³ , R ^At least one of ²⁴ , R ²⁵ , R ³² , R ³³ , R ³⁴ , R ³⁵ and R ³⁶ is an amino group, acylamino group, alkoxycarbonylamino group, aryloxycarbonylamino group, sulfonylamino group, hydroxy group, mercapto Group, carboxyl group.

Examples of the substituent T include an alkyl group (preferably having 1 to 20 carbon atoms, more preferably 1 to 12 carbon atoms, and particularly preferably 1 to 8 carbon atoms, such as a methyl group, an ethyl group, an isopropyl group, and tert-butyl. Group, n-octyl group, n-decyl group, n-hexadecyl group, cyclopropyl group, cyclopentyl group, cyclohexyl group, etc.), alkenyl group (preferably having 2 to 20 carbon atoms, more preferably 2 carbon atoms). To 12, particularly preferably 2 to 8 carbon atoms, such as vinyl group, allyl group, 2-butenyl group, and 3-pentenyl group), alkynyl group (preferably 2 to 20 carbon atoms, more preferably Has 2 to 12 carbon atoms, particularly preferably 2 to 8 carbon atoms, and examples thereof include a propargyl group and a 3-pentynyl group.), Aryl (Preferably having 6 to 30 carbon atoms, more preferably 6 to 20 carbon atoms, particularly preferably 6 to 12 carbon atoms, and examples thereof include a phenyl group, a p-methylphenyl group, and a naphthyl group.), An amino group (Preferably has 0 to 20 carbon atoms, more preferably 0 to 10 carbon atoms, and particularly preferably 0 to 6 carbon atoms. For example, amino group, methylamino group, dimethylamino group, diethylamino group, dibenzylamino group, etc. And an alkoxy group (preferably having 1 to 20 carbon atoms, more preferably 1 to 12 carbon atoms, particularly preferably 1 to 8 carbon atoms, and examples thereof include a methoxy group, an ethoxy group, and a butoxy group. ), An aryloxy group (preferably having 6 to 20 carbon atoms, more preferably 6 to 16 carbon atoms, particularly preferably 6 to 12 carbon atoms, such as phenyl A xy group, a 2-naphthyloxy group, etc.), an acyl group (preferably having 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, and particularly preferably 1 to 12 carbon atoms, such as an acetyl group, A benzoyl group, a formyl group, a pivaloyl group, etc.), an alkoxycarbonyl group (preferably having a carbon number of 2 to 20, more preferably a carbon number of 2 to 16, particularly preferably a carbon number of 2 to 12, such as methoxycarbonyl Group, an ethoxycarbonyl group, etc.), an aryloxycarbonyl group (preferably having 7 to 20 carbon atoms, more preferably having 7 to 16 carbon atoms, particularly preferably having 7 to 10 carbon atoms, such as a phenyloxycarbonyl group. An acyloxy group (preferably having 2 to 20 carbon atoms, more preferably 2 to 16 carbon atoms, especially Preferably it is C2-C10, for example, an acetoxy group, a benzoyloxy group, etc. are mentioned. ), An acylamino group (preferably having 2 to 20 carbon atoms, more preferably 2 to 16 carbon atoms, particularly preferably 2 to 10 carbon atoms, and examples thereof include an acetylamino group and a benzoylamino group), alkoxycarbonyl. An amino group (preferably having 2 to 20 carbon atoms, more preferably 2 to 16 carbon atoms, particularly preferably 2 to 12 carbon atoms, such as a methoxycarbonylamino group), an aryloxycarbonylamino group (preferably Has 7 to 20 carbon atoms, more preferably 7 to 16 carbon atoms, particularly preferably 7 to 12 carbon atoms, such as a phenyloxycarbonylamino group, and a sulfonylamino group (preferably 1 to 1 carbon atom). 20, more preferably 1 to 16 carbon atoms, particularly preferably 1 to 12 carbon atoms. Nylamino group, benzenesulfonylamino group, etc.), sulfamoyl group (preferably having 0 to 20 carbon atoms, more preferably 0 to 16 carbon atoms, particularly preferably 0 to 12 carbon atoms, such as sulfamoyl group, methyl A sulfamoyl group, a dimethylsulfamoyl group, a phenylsulfamoyl group, etc.), a carbamoyl group (preferably having 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, and particularly preferably 1 to carbon atoms). 12 and examples thereof include a carbamoyl group, a methylcarbamoyl group, a diethylcarbamoyl group, a phenylcarbamoyl group, etc.), an alkylthio group (preferably having 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, and particularly preferably carbon atoms). Examples thereof include methylthio group and ethylthio group. ), An arylthio group (preferably having 6 to 20 carbon atoms, more preferably 6 to 16 carbon atoms, particularly preferably 6 to 12 carbon atoms, such as a phenylthio group), a sulfonyl group (preferably C1-C20, More preferably, it is C1-C16, Most preferably, it is C1-C12, For example, a mesyl group, a tosyl group, etc. are mentioned), a sulfinyl group (preferably C1-C20, More preferably, it is C1-C16, Most preferably, it is C1-C12, for example, a methanesulfinyl group, a benzenesulfinyl group, etc.), a ureido group (preferably C1-C20, more preferably carbon) The number is 1 to 16, particularly preferably 1 to 12, and examples thereof include a ureido group, a methylureido group, and a phenylureido group. ), A phosphoric acid amide group (preferably having 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, and particularly preferably 1 to 12 carbon atoms, such as a diethylphosphoric acid amide group and a phenylphosphoric acid amide group. Hydroxy group, mercapto group, halogen atom (eg fluorine atom, chlorine atom, bromine atom, iodine atom), cyano group, sulfo group, carboxyl group, nitro group, hydroxamic acid group, sulfino group, hydrazino group, imino group Group, heterocyclic group (preferably having 1 to 30 carbon atoms, more preferably 1 to 12 carbon atoms, and examples of the hetero atom include a nitrogen atom, an oxygen atom, and a sulfur atom, specifically, for example, an imidazolyl group, a pyridyl group, and a quinolyl group. Group, furyl group, piperidyl group, morpholino group, benzoxazolyl group, benzimidazolyl group, benzthiazolyl group, etc. ), A silyl group (preferably having 3 to 40 carbon atoms, more preferably 3 to 30 carbon atoms, particularly preferably 3 to 24 carbon atoms, and examples thereof include a trimethylsilyl group and a triphenylsilyl group. For example). Among these, an alkyl group, an aryl group, a substituted or unsubstituted amino group, an alkoxy group, and an aryloxy group are more preferable, and an alkyl group, an aryl group, and an alkoxy group are more preferable.
These substituents may be further substituted with a substituent T. Moreover, when there are two or more substituents, they may be the same or different. If possible, they may be linked together to form a ring.

In addition, at least one of R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ , R ¹⁶ , R ²¹ , R ²³ , R ²⁴ , R ²⁵ , R ³² , R ³³ , R ³⁴ , R ³⁵ , R ³⁶ is amino. Group, acylamino group, alkoxycarbonylamino group, aryloxycarbonylamino group, sulfonylamino group, hydroxy group, mercapto group and carboxyl group, more preferably amino group and hydroxy group, and particularly preferably hydroxy group. These groups may be substituted with a substituent. As the substituent in this case, the above-described substituent T can be applied, and the preferred range is also the same.

  Preferred examples of the compound represented by formula (B) of the present invention are shown below, but the present invention is not limited to these specific examples.

-Trityl type-
One preferred embodiment of the moisture permeability reducing compound is a trityl type compound.
The trityl-type compound used in the present invention as the moisture permeability reducing compound is a compound represented by the following general formula (C).
General formula (C)

(Wherein X ² represents B, C—R (R represents a hydrogen atom or a substituent) or N. R ²¹¹ , R ²¹² , R ²¹³ , R ²¹⁴ , R ²¹⁵ , R ²²¹ , R ²²² , R ²²³ , R ²²⁴ , R ²²⁵ , R ²³¹ , R ²³² , R ²³³ , R ²³⁴ and R ²³⁵ each independently represent a hydrogen atom or a substituent.
One group selected from the group consisting of R ²¹¹ , R ²¹² , R ²¹³ , R ²¹⁴ , R ²¹⁵ , and one selected from the group consisting of R ²²¹ , R ²²² , R ²²³ , R ²²⁴ , R ²²⁵ The group may be bonded via a single bond or a divalent linking group (such as an alkylene group having 1 to 10 carbon atoms) to form a cyclic structure.

X ² represents B, C—R (R represents a hydrogen atom or a substituent), N, and X ² is preferably B, C—R (R is preferably an aryl group, a substituted or unsubstituted amino group) , Alkoxy group, aryloxy group, acyl group, alkoxycarbonyl group, aryloxycarbonyl group, acyloxy group, acylamino group, alkoxycarbonylamino group, aryloxycarbonylamino group, sulfonylamino group, hydroxy group, mercapto group, halogen atom ( For example, fluorine atom, chlorine atom, bromine atom, iodine atom), carboxyl group, more preferably aryl group, alkoxy group, aryloxy group, hydroxy group, halogen atom, more preferably alkoxy group, hydroxy group And particularly preferably a hydroxy group), N, and Are preferably C—R and N, and particularly preferably C—R.

R ²¹¹ , R ²¹² , R ²¹³ , R ²¹⁴ , R ²¹⁵ , R ²²¹ , R ²²² , R ²²³ , R ²²⁴ , R ²²⁵ , R ²³¹ , R ²³² , R ²³³ , R ²³⁴ and R ²³⁵ are each independently Represents a hydrogen atom or a substituent, and is preferably a hydrogen atom. R ²¹¹ , R ²¹² , R ²¹³ , R ²¹⁴ , R ²¹⁵ , R ²²¹ , R ²²² , R ²²³ , R ²²⁴ , R ²²⁵ , R ²³¹ , R ²³² , R ²³³ , R ²³⁴ and R ²³⁵ can be substituted. The above-mentioned substituent T can be applied.
R ²¹¹ , R ²¹² , R ²¹³ , R ²¹⁴ , R ²¹⁵ , R ²²¹ , R ²²² , R ²²³ , R ²²⁴ , R ²²⁵ , R ²³¹ , R ²³² , R ²³³ , R ²³⁴ and R ²³⁵ are each independently Preferably alkyl group, alkenyl group, alkynyl group, aryl group, substituted or unsubstituted amino group, alkoxy group, aryloxy group, acyl group, alkoxycarbonyl group, aryloxycarbonyl group, acyloxy group, acylamino group, alkoxycarbonylamino Group, aryloxycarbonylamino group, sulfonylamino group, sulfamoyl group, carbamoyl group, alkylthio group, arylthio group, sulfonyl group, sulfinyl group, ureido group, phosphoric acid amide group, hydroxy group, mercapto group, halogen atom (eg fluorine atom) , Chlorine atom, bromine atom, iodine atom), cyano group, sulfo group, Carboxyl group, nitro group, hydroxamic acid group, sulfino group, hydrazino group, imino group, heterocyclic group (preferably having 1 to 30 carbon atoms, more preferably 1 to 12 carbon atoms. Atoms, sulfur atoms, specifically imidazolyl, pyridyl, quinolyl, furyl, piperidyl, morpholino, benzoxazolyl, benzimidazolyl, benzthiazolyl, etc.), silyl groups, more preferably alkyl groups, aryl A group, a substituted or unsubstituted amino group, an alkoxy group, and an aryloxy group, and more preferably an alkyl group, an aryl group, or an alkoxy group.
These substituents may be further substituted. Moreover, when there are two or more substituents, they may be the same or different. If possible, they may be linked together to form a ring.

In the compound represented by the general formula (2), R ²¹¹ , R ²¹² , R ²¹³ , R ²¹⁴ , R ²¹⁵ , R ²²¹ , R ²²² , R ²²³ , R ²²⁴ , R ²²⁵ , R ²³¹ , R ²³² , R R ²¹¹ , R ²¹² , R ²¹³ , R ²¹⁴ , R ²¹⁵ , R in one group selected from the group consisting of ²³³ , R ²³⁴ and R ²³⁵ , and another compound represented by the general formula (2) One group selected from the group consisting of ²²¹ , R ²²² , R ²²³ , R ²²⁴ , R ²²⁵ , R ²³¹ , R ²³² , R ²³³ , R ²³⁴ and R ²³⁵ is a single bond or a divalent group (carbon A compound having two X ^{2 in} one molecule which is bonded by an alkylene group of 1 to 10 or the like can also be used in the present invention.

In the general formula (C), R ²¹¹ , R ²¹² , R ²¹³ , R ²¹⁴ , R ²¹⁵ , R ²²¹ , R ²²² , R ²²³ , R ²²⁴ , R ²²⁵ , R ²³¹ , R ²³² , R ²³³ , R ²³⁴ As a substituent for R ²³⁵ , a structure represented by the following general formula (C3) can also be adopted.
General formula (C3)

(In the formula, X ² represents B, C—R (R represents a hydrogen atom or a substituent) or N.
R ²¹¹ , R ²¹² , R ²¹³ , R ²¹⁴ , R ²¹⁵ , R ²²¹ , R ²²² , R ²²³ , R ²²⁴ and R ²²⁵ each independently represent a hydrogen atom or a substituent. )
The preferred range of each substituent in the general formula (C3) is the same as the preferred range of each substituent in the general formula (C).

  Specific examples of the compound represented by formula (C) will be described below in detail, but the present invention is not limited to the following specific examples.

  The moisture permeability reducing compound is preferably contained in the optical film of the present invention in an amount of 10% by mass to 100% by mass with respect to the total mass of the cellulose ester and the acrylic resin. More preferably, it is 15 to 90% by mass, and more preferably 20 to 80% by mass.

  Of the compounds represented by the general formula (A), the general formula (B), or the general formula (C), the compound represented by the general formula (A) or the general formula (B) is preferable. .

(Matting agent fine particles)
Fine particles can be added as a matting agent to the optical film of the present invention. Fine particles used as a matting agent 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 preferred in that the haze of the film is reduced, and silicon dioxide is particularly preferred. 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. Those having an average primary particle size as small as 5 to 16 nm are more preferred because they can reduce the haze of the film. 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 average particle diameter of the secondary particles is preferably from 0.2 μm to 1.5 μm, more preferably from 0.4 μm to 1.2 μm, and most preferably from 0.6 μm to 1.1 μm. The particle diameter of the primary particles and the secondary particles was 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 diameter. 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 (manufactured by 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 an average primary particle diameter of 20 nm or less and an apparent specific gravity of 70 g / liter or more, while keeping the turbidity of the optical film low. This is particularly preferable because the effect of reducing the friction coefficient is great.

In order to obtain an optical film having particles having a small average particle size of secondary particles in the present invention, several methods are conceivable when preparing a dispersion of fine particles. For example, a fine particle dispersion prepared by stirring and mixing a solvent and fine particles is prepared in advance, and this fine particle dispersion is added to a small amount of a separately prepared cellulose ester or acrylic resin solution and dissolved by stirring. Further, a polymer solution for main film preparation There is a method of mixing with (dope solution). 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, a small amount of cellulose ester or acrylic resin is added to the solvent, and dissolved by stirring. Then, fine particles are added to this and dispersed with a disperser. This is used as a fine particle additive solution, and this fine particle additive solution is doped with an in-line mixer. There is also a method of thoroughly mixing with the liquid. 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 in the final dope solution is preferably 0.01 to 1.0 g, more preferably 0.03 to 0.3 g, and most preferably 0.08 to 0.16 g per 1 m ² . The addition amount of the matting agent is preferably 0.001% by mass or more and 0.4% by mass or less, and preferably 0.001% by mass or more and 0% by mass with respect to the total amount of resin used in the dope solution such as cellulose ester resin and acrylic resin. .2% by mass or less is more preferable, and 0.01% by mass or more and 0.1% by mass or less is more preferable. In addition, when the optical film is formed from multiple layers, it is preferable to add only to the surface layer side without adding to the inner layer. In this case, the total amount of resin used for the dope solution such as cellulose ester resin and acrylic resin On the other hand, the addition amount of the matting agent in the surface layer is preferably 0.001% by mass or more and 0.4% by mass or less, more preferably 0.001% by mass or more and 0.2% by mass or less, and 0.01% by mass or more. 0.1 mass% or less is still more preferable.

  As the solvent used for dispersion, lower alcohols are preferable, and examples thereof include methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, and butyl alcohol. 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 an optical film.

(Other additives)
In addition to the mat particles, the optical film of the present invention has other various additives (for example, retardation developing agent, plasticizer, ultraviolet absorber, deterioration inhibitor, release agent, infrared absorber, wavelength dispersion adjustment). Agents), which can be solid or oily. That is, the melting point and boiling point are not particularly limited. For example, mixing of ultraviolet absorbing material at 20 ° C. or lower and 20 ° C. or higher, and similarly mixing of a plasticizer is described in, for example, JP-A-2001-151901. Furthermore, infrared absorbing dyes are described in, for example, JP-A No. 2001-194522. Moreover, the addition time may be added at any time in the dope preparation step, but may be added by adding an additive to the final preparation step of the dope preparation step. Furthermore, the amount of each material added is not particularly limited as long as the function is manifested. Moreover, when an optical film is formed from a multilayer, the kind and addition amount of the additive of each layer may differ. For example, it is described in Japanese Patent Application Laid-Open No. 2001-151902, and these are conventionally known techniques. For these details, materials described in detail on pages 16 to 22 in the Japan Institute of Invention Disclosure Technical Bulletin (Public Technical No. 2001-1745, published on March 15, 2001, Japan Institute of Invention) are preferably used.

A plasticizer having good compatibility with the cellulose ester and the acrylic resin is less likely to bleed out, has a low haze, and is effective for producing a film that realizes a liquid crystal display device excellent in light leakage, front contrast, and luminance.
You may use a plasticizer for the optical film of this invention. Although it does not specifically limit as a plasticizer, A phosphate ester plasticizer, a phthalate ester plasticizer, a polyhydric alcohol ester plasticizer, a polycarboxylic acid ester plasticizer, a glycolate plasticizer, a citrate ester Examples thereof include plasticizers, fatty acid ester plasticizers, carboxylic acid ester plasticizers, polyester oligomer plasticizers, sugar ester plasticizers, and ethylenically unsaturated monomer copolymer plasticizers.
Preferred are phosphate ester plasticizers, glycolate plasticizers, polyhydric alcohol ester plasticizers, polyester oligomer plasticizers, sugar ester plasticizers, ethylenically unsaturated monomer copolymer plasticizers, and more preferred. Is a polyester oligomer plasticizer, sugar ester plasticizer, ethylenically unsaturated monomer copolymer plasticizer, more preferably an ethylenically unsaturated monomer copolymer plasticizer, sugar ester plasticizer, particularly preferably Is an ethylenically unsaturated monomer copolymer plasticizer.
In particular, polyester oligomer plasticizers, ethylenically unsaturated monomer copolymer plasticizers, and sugar ester plasticizers are highly compatible with the optical film of the present invention, and are highly effective in reducing bleed out, low haze, and low moisture permeability. Further, since it is difficult for the plasticizer to be decomposed and the film to be altered or deformed due to changes in temperature and humidity, the film can be preferably used in the present invention.
In the present invention, the plasticizer may be used alone or in combination of two or more.

  The optical film of the present invention may contain acrylic particles. Japanese Patent Publication No. 60-17406, Japanese Patent Publication No. 3-39095 and the like describe that the addition of acrylic particles, particularly a multilayer structure acrylic granular composite, improves impact resistance and stress whitening resistance.

  In the optical film of the present invention, when these additives are added, the total amount of the additives is preferably 100% by mass or less and more preferably 80% by mass or less with respect to the optical film.

<Characteristics of optical film>
(Retardation)
In the optical film of the present invention, Re and Rth (defined by the following formulas (I) and (II)) measured at a wavelength of 590 nm satisfy the formulas (III) and (IV).
Formula (I) Re = (nx−ny) × d
Formula (II) Rth = {(nx + ny) / 2−nz} × d
Formula (III) −50 nm ≦ Re ≦ 50 nm
Formula (IV) Rth ≧ 300 nm
(Where nx is the refractive index in the slow axis direction in the film plane of the optical film, ny is the refractive index in the fast axis direction in the film plane, and nz is the thickness direction of the optical film) (Refractive index, d is the thickness (nm) of the optical film.)
In the optical film of the present invention, the above formulas (III) and (IV) may be satisfied at at least one point in the film plane, but the above formulas (III) and (IV) are arbitrary at any point in the film plane. ) Is preferably satisfied.

Re, Rth, and Nz at the wavelength λnm can be measured as follows.
Re is measured by making light with a wavelength of λ nm incident in the normal direction of the film in KOBRA21ADH (manufactured by Oji Scientific Instruments).
Rth is a letter measured by making light of wavelength λ nm incident from a direction inclined + 40 ° with respect to the film normal direction with the slow axis in the plane (determined by KOBRA21ADH) as the tilt axis (rotation axis). The retardation value and the retardation value measured by making light of wavelength λ nm incident from a direction inclined by −40 ° with respect to the film normal direction with the in-plane slow axis as the tilt axis (rotation axis). Calculated by KOBRA21ADH based on the retardation value measured in (1). Here, as the assumed value of the average refractive index, values in the polymer handbook (JOHNWILEY & 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).
Nz is calculated by the formula (VI) based on Re and Rth. Note that nx, ny, and nz can be calculated by KOBRA21ADH based on the assumed value of the average refractive index and the film thickness, and Nz can be calculated by the formula (II) from these nx, ny, and nz values.
In the measurement of the optical film of the present invention, the retardation is measured by setting the average refractive index of the optical film to 1.48.

  The above Re, Rth, and Nz can be adjusted by the substitution degree of cellulose ester, the ratio of cellulose ester and acrylic resin, the addition of a retardation developer, the film thickness, the stretching direction and stretching ratio of the film, and the like.

(Film thickness)
The thickness of the optical film of the present invention is preferably 60 μm or less, more preferably 40 μm or less, and particularly preferably 30 μm or less. If it is 60 micrometers or less, the curvature of the panel accompanying the environment where a liquid crystal display device is set, ie, temperature / humidity change, can be made small.

(Water permeability of film)
The moisture permeability of the film is measured under the conditions of 40 ° C. and 90% relative humidity based on JIS Z-0208.
In different samples, the moisture permeability needs to be converted by setting the reference to 40 μm. The film thickness can be converted according to the following mathematical formula.
Mathematical formula: moisture permeability in terms of 40 μm = measured moisture permeability × measured film thickness (μm) / 40 (μm).
The moisture permeability of the optical film of the present invention is preferably 350 g / m ² / day or less. It is more preferably 200 g / m ² / day or less, and further preferably 100 g / m ² / day. If the water vapor transmission rate is 350 g / m ² / day or less, warpage of the liquid crystal cell and display unevenness during black display after the normal temperature, high humidity, and high temperature and high humidity environment of the liquid crystal display device can be suppressed.

(Haze of film)
The optical film of the present invention preferably has a total haze value of 2.00% or less. When the total haze value is 2.00% or less, the transparency of the film is high, and the contrast ratio and brightness of the liquid crystal display device are improved. The total haze value is more preferably 1.00% or less, further preferably 0.50% or less, particularly preferably 0.30% or less, and most preferably 0.20% or less.
The internal haze value of the optical film of the present invention is preferably 1.00% or less. By setting the internal haze value to 1.00% or less, the contrast ratio of the liquid crystal display device can be improved and excellent display characteristics can be realized. The internal haze value is more preferably 0.50% or less, further preferably 0.20% or less, particularly preferably 0.10% or less, and most preferably 0.05% or less. From the viewpoint of raw material selection, production control, etc., 0.01% or more is preferable.
In particular, the optical film of the present invention preferably has a total haze value of 0.30% or less and an internal haze value of 0.10% or less.
The total haze value and internal haze value are the types and addition amounts of cellulose ester and acrylic resin of the film material, selection of additives (particularly, the particle size, refractive index, addition amount of matting agent particles), and film production conditions. It can be adjusted by (temperature during stretching, stretching ratio, etc.).
In addition, the measurement of a haze can measure the film sample 40mmx80mm of this invention at 25 degreeC and 60% of relative humidity, and according to JISK-6714 with a haze meter (HGM-2DP, Suga test machine).

(Elastic modulus of film)
The elastic modulus of the optical film of the present invention is preferably 1800 to 7000 MPa in the width direction (TD direction).
In the present invention, when the elastic modulus in the TD direction is within the above range, display unevenness at the time of black display after high humidity and high temperature and high humidity environment aging, transportability at the time of film production, end slit property and difficulty in breaking. It is preferable from the viewpoint of manufacturing suitability. If the TD elastic modulus is too small, display unevenness at the time of black display after high humidity and high temperature and high humidity environment is likely to occur, and there is a problem in manufacturing suitability. The elastic modulus is more preferably 1800 to 5000 MPa, and further preferably 1800 to 4000 MPa.
Moreover, 1800-4000 MPa is preferable and, as for the elasticity modulus of the conveyance direction (MD direction) of the optical film of this invention, it is more preferable that it is 1800-3000 MPa.
Here, the conveyance direction (longitudinal direction) of the film is the conveyance direction (MD direction) during film production, and the width direction is the direction (TD direction) perpendicular to the conveyance direction during film production.
The elastic modulus of the film depends on the type and amount of cellulose ester and acrylic resin used in the film material, selection of additives (particularly the particle size, refractive index, and amount of addition of the matting agent particles), and film production conditions (stretch ratio). Etc.).
For example, the elastic modulus was measured by measuring the stress at 0.5% elongation at a tensile rate of 10% / min in an atmosphere of 23% and a relative humidity of 70% using a universal tensile tester “STMT50BP” manufactured by Toyo Baldwin Co., Ltd. Can be sought.

(Glass transition temperature Tg)
The glass transition temperature Tg of the optical film of the present invention is preferably 100 ° C. or higher and 200 ° C. or lower, more preferably 100 ° C. or higher and 150 ° C. or lower, from the viewpoints of production suitability and heat resistance.
The glass transition temperature is a temperature at which the base line derived from the glass transition of the film starts to change and a temperature at which it returns to the base line again when measured at a heating rate of 10 ° C./min using a differential scanning calorimeter (DSC). It can be calculated as an average value.
Moreover, the measurement of a glass transition temperature can also be calculated | required using the following dynamic viscoelasticity measuring apparatuses. After adjusting the film sample (unstretched) 5 mm × 30 mm of the present invention for 2 hours or more at 25 ° C. and 60% relative humidity, a dynamic viscoelasticity measuring device (Vibron: DVA-225 (produced by IT Measurement Control Co., Ltd.)) ), The distance between the grips is 20 mm, the heating rate is 2 ° C./min, the measurement temperature range is 30 ° C. to 250 ° C., the frequency is 1 Hz, the logarithmic axis is the storage elastic modulus, the horizontal axis is the temperature (° C. ), When the storage elastic modulus transitions from the solid region to the glass transition region, the sharp decrease in the storage elastic modulus is drawn in the solid region and the straight line 1 is drawn in the glass transition region. The intersection of the straight line 1 and the straight line 2 is a temperature at which the storage elastic modulus suddenly decreases and the film starts to soften when the temperature rises, and the temperature at which the film begins to move to the glass transition region. ).

(Equilibrium moisture content of film)
The water content (equilibrium water content) of the optical film of the present invention is 25, regardless of the film thickness, so as not to impair the adhesion with a water-soluble polymer such as polyvinyl alcohol when used as a protective film for a polarizing plate. It is preferable that the moisture content in 0 degreeC and 80% of relative humidity is 0-4 mass%. More preferably, it is 0.1-2.5 mass%, and it is still more preferable that it is 0.5-1.5 mass%. If the equilibrium moisture content is 4% by mass or less, the dependence of retardation on humidity changes does not become too large, and the display unevenness of the liquid crystal display device during black display after normal temperature, high humidity, and high temperature and high humidity environments is suppressed. This is also preferable.
The moisture content was measured by measuring a film sample 7 mm × 35 mm by a Karl Fischer method using a moisture measuring device and sample drying apparatuses “CA-03” and “VA-05” (both manufactured by Mitsubishi Chemical Corporation).

(Dimensional change of film)
The dimensional stability of the optical film of the present invention is as follows: dimensional change rate after standing for 24 hours under conditions of 60 ° C. and 90% relative humidity (high humidity), and 80 ° C., DRY environment (5% relative humidity) The ratio of dimensional change after standing for 24 hours under the following conditions is preferably 0.5% or less.
More preferably, it is 0.3% or less, More preferably, it is 0.15% or less.

(Photoelastic coefficient)
When the optical film of the present invention is used as a protective film for a polarizing plate, birefringence (Re, Rth) may change due to stress caused by the contraction of the polarizer. The change in birefringence due to such stress can be measured as a photoelastic coefficient, but the range is preferably 15 Br or less, more preferably −3 to 12 Br, and further preferably 0 to 11 Br. preferable.

[Method for producing optical film]
The method for producing an optical film of the present invention includes a step of casting a composition containing a cellulose ester, an acrylic resin, and a moisture permeation reducing compound on a support to form a polymer film, The mass ratio of the cellulose ester and the acrylic resin is 70:30 to 5:95, the molecular weight of the moisture permeability reducing compound is 200 or more, and the moisture permeability reducing compound satisfies the following formula (1). And
Formula (1) A / B <= 0.6
Furthermore, the method for producing an optical film of the present invention preferably includes a step of stretching the optical film (or polymer film) in at least one of a film transport direction and a width direction, and the polymer film transport direction. It is more preferable to include a step of stretching the polymer film in the width direction perpendicular to the width direction.
In the polymer film, the mass ratio of cellulose ester to acrylic resin is 70:30 to 5:95, and the cellulose ester and acrylic resin are preferably in a compatible state. The polymer film used for stretching may be a dry film or a wet film, but is preferably a wet film.
As the polymer film used for stretching, the glass transition temperature Tg of the unstretched polymer film after drying is preferably 100 to 200 ° C, more preferably 100 to 150 ° C.
Here, the dried polymer film (dry film) refers to a film having a residual solvent amount of 3.0% by mass or less in the film. The amount of residual solvent is preferably 1.0% by mass or less, more preferably 0.5% by mass or less, still more preferably 0.3% by mass or less, and particularly preferably 0.2% by mass or less.

  As a method for forming the polymer film, an inflation method, a T-die method, a calendar method, a cutting method, a casting method, an emulsion method, a hot press method, and the like can be used. From the viewpoints of suppression and suppression of optical defects such as die lines, solution casting by casting is preferred.

The method for producing the optical film of the present invention may use a solution casting method or a melt casting method.
In the case of the melt casting method, the step of casting a composition containing the cellulose ester, the acrylic resin, and the moisture permeation reducing compound on a support to form a polymer film includes the cellulose ester, the acrylic resin, and the moisture permeation reduction. It is preferably a step of casting a molten compound on a support to form a polymer film.
In the case of the solution casting method, the step of casting the cellulose ester, the acrylic resin, and the moisture permeability reducing compound on a support to form a polymer film includes the cellulose ester, the acrylic resin, the moisture permeability reducing compound, and It is preferably a process of forming a polymer film by casting a polymer solution (dope) containing a solvent on a support.
In the dope, the mass ratio between the cellulose ester and the acrylic resin is 70:30 to 5:95, preferably 70:30 to 15:85, more preferably 70:30 to 30:70. More preferably, it is 49:51 to 30:70.

<Solvent>
Solvents useful for forming the dope can be used without limitation as long as they dissolve cellulose ester, acrylic resin, the moisture permeability reducing compound and other additives at the same time.
In the present invention, any of a chlorinated solvent containing a chlorinated organic solvent as a main solvent and a non-chlorinated solvent not containing a chlorinated organic solvent can be used as the organic solvent. Two or more organic solvents may be mixed and used.

  In producing the dope, a chlorinated organic solvent is preferably used as the main solvent. In the present invention, the kind of the chlorinated organic solvent is not particularly limited as long as the object can be achieved within the range in which raw materials such as cellulose acylate and acrylic resin can be dissolved, cast and film-formed. These chlorinated organic solvents are preferably dichloromethane and chloroform. Particularly preferred is dichloromethane. In addition, there is no particular problem in mixing an organic solvent other than the chlorinated organic solvent. In that case, it is necessary to use at least 50% by mass of dichloromethane in the total amount of the organic solvent. Other organic solvents used in combination with the chlorinated organic solvent in the present invention will be described below. That is, as another preferable organic solvent, a solvent selected from esters, ketones, ethers, alcohols, hydrocarbons and the like having 3 to 12 carbon atoms is preferable. The ester, ketone, ether and alcohol may have a cyclic structure. A compound having two or more functional groups of esters, ketones and ethers (that is, —O—, —CO— and —COO—) can also be used as a solvent. For example, other functional groups such as alcoholic hydroxyl groups can be used. You may have group simultaneously. In the case of a solvent having two or more types of functional groups, the number of carbon atoms may be within the specified range of the compound having any functional group.

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

Further, the alcohol used in combination with the chlorinated organic solvent may be linear, branched or cyclic, and among them, saturated aliphatic hydrocarbon is preferable. The hydroxyl group of the alcohol may be any of primary to tertiary. Examples of the alcohol include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, t-butanol, 1-pentanol, 2-methyl-2-butanol and cyclohexanol. As the alcohol, fluorine-based alcohol is also used. Examples thereof include 2-fluoroethanol, 2,2,2-trifluoroethanol, 2,2,3,3-tetrafluoro-1-propanol and the like. Further, the hydrocarbon may be linear, branched or cyclic. Either aromatic hydrocarbons or aliphatic hydrocarbons can be used. The aliphatic hydrocarbon may be saturated or unsaturated. Examples of hydrocarbons include cyclohexane, hexane, benzene, toluene and xylene.
As other solvents, for example, the solvents described in JP-A-2007-140497 can be used.

<Preparation of dope>
The dope can be prepared by a general method including processing at a temperature of 0 ° C. or higher (ordinary temperature or high temperature). The dope that can be used in the present invention can be prepared using a dope preparation method and apparatus in a normal solvent cast method. In the case of a general method, halogenated hydrocarbon (especially dichloromethane) and alcohol (especially methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, t-butanol, 1) -Pentanol, 2-methyl-2-butanol and cyclohexanol) are preferably used.
The total amount of cellulose ester and acrylic resin is preferably adjusted so as to be contained in the obtained polymer solution in an amount of 10 to 40% by mass. 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 solution can be prepared by stirring the cellulose ester and the acrylic resin and the organic solvent at room temperature (0 to 40 ° C.). The high concentration solution may be stirred under pressure and heating conditions. Specifically, cellulose ester and acrylic resin and an organic solvent are placed in a pressure vessel and sealed, and stirred while being heated to a temperature equal to or higher than the boiling point of the solvent at room temperature and not boiling.
The heating temperature is usually 40 ° C or higher, preferably 60 to 200 ° C, 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 needs to be configured so that it can be stirred. 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.
It is preferable to provide a stirring blade inside the container and stir using this. 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 the 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.

<Production of film-solution casting method->
Next, a method for producing the optical film of the present invention using the dope obtained above will be described.
FIG. 1 is a schematic view showing a film production line 20. However, the present invention is not limited to the film production line as shown in FIG. The film production line 20 includes a stock tank 21, a filtration device 30, a casting die 31, a casting band 34 stretched around rotating rollers 32 and 33, a tenter dryer 35, and the like. Further, an ear-cutting device 40, a drying chamber 41, a cooling chamber 42, a winding chamber 43, and the like are arranged.

  An agitator 61 that is rotated by a motor 60 is attached to the stock tank 21. The stock tank 21 is connected to the casting die 31 via the pump 62 and the filtration device 30.

  The width of the casting die 31 is not particularly limited, but is preferably 1.1 to 2.0 times the width of the film as the final product.

  A casting band 34 is provided below the casting die 31 so as to span the rotating rollers 32 and 33. The rotating rollers 32 and 33 are rotated by a driving device (not shown), and the casting band 34 travels endlessly with the rotation.

  In order to set the surface temperature of the casting band 34 to a predetermined value, it is preferable that a heat transfer medium circulation device 63 is attached to the rotary rollers 32 and 33. The casting band 34 is preferably one whose surface temperature can be adjusted to -20 ° C to 40 ° C.

The width of the casting band 34 is not particularly limited, but it is preferable to use a band having a range of 1.1 to 2.0 times the casting width of the dope 22. Further, it is preferable that the length is 20 m to 200 m, the thickness is 0.5 mm to 2.5 mm, and the surface roughness is polished to be 0.05 μm or less. The casting band 34 is preferably made of stainless steel, and more preferably made of SUS316 so as to have sufficient corrosion resistance and strength. Moreover, it is preferable to use the thickness unevenness of the entire casting band 34 of 0.5% or less.
It is also possible to use the rotating rollers 32 and 33 directly as a support.

  The casting die 31, the casting band 34 and the like are accommodated in the casting chamber 64. The casting chamber 64 is provided with a temperature control facility 65 for keeping the internal temperature at a predetermined value, and a condenser (condenser) 66 for condensing and recovering the volatile organic solvent. A recovery device 67 for recovering the condensed and liquefied organic solvent is provided outside the casting chamber 64. Further, it is preferable that a decompression chamber 68 for controlling the pressure of the back surface of the casting bead formed from the casting die 31 to the casting band 34 is disposed, and this is also used in this embodiment. .

  Air blowing ports 70, 71, 72 are provided near the peripheral surface of the casting band 34 in order to evaporate the solvent in the casting film 69.

  The crossover portion 80 is provided with a blower 81, and the ear-cutting device 40 downstream of the tenter dryer 35 is used for finely cutting the waste at the side end (referred to as an ear) of the cut film 82. Crusher 90 is connected.

  The drying chamber 41 is provided with a number of rollers 91, and an adsorption / recovery device 92 for adsorbing / recovering the solvent gas generated by evaporation is attached. A forced static elimination device (static elimination bar) 93 for adjusting the charged voltage of the film 82 to a predetermined range (for example, −3 kV to +3 kV) is provided downstream of the cooling chamber 42. Furthermore, in this embodiment, a knurling application roller 94 for applying knurling to both edges of the film 82 by embossing is appropriately provided downstream of the forced static elimination device 93. Further, a winding roller 95 for winding the film 82 and a press roller 96 for controlling the tension at the time of winding are provided in the winding chamber 43.

Next, an example of a method for producing the film 82 using the film production line 20 will be described below.
The dope 22 is always made uniform by the rotation of the stirrer 61. The dope 22 may be mixed with additives such as a retardation developer, a plasticizer, and an ultraviolet absorber even during the stirring.

The dope 22 is sent to the filtration device 30 by the pump 62 and filtered there, and then is cast from the casting die 31 onto the casting band 34.
A casting bead is formed from the casting die 31 to the casting band 34, and a casting film 69 is formed on the casting band 34. The temperature of the dope 22 during casting is preferably −10 ° C. to 57 ° C.
The dope 22 from the casting die 31 forms a casting bead and is cast on the casting band 34.
The casting film 69 moves as the casting band 34 moves.

  Next, the casting film 69 is continuously transported to the place where the air blowing port 73 is disposed at the upper part. Dry air is blown toward the casting film 69 from the nozzle of the air blowing port 73.

The casting film 69 is self-supporting as a result of evaporation of the solvent by drying, and is then peeled off from the casting band 34 while being supported by the peeling roller 75 as a wet film 74. The amount of residual solvent at the time of stripping is preferably 20% by mass to 250% by mass based on the solid content.
Thereafter, the transfer section 80 provided with a large number of rollers is conveyed, and the wet film 74 is fed into the tenter dryer 35. In the transfer part 80, the drying of the wet film 74 is advanced by sending the drying air of desired temperature from the air blower 81. FIG. At this time, the temperature of the drying air is preferably 20 ° C to 250 ° C.

It is preferable that the manufacturing method of the optical film of this invention includes the process of extending | stretching the said optical film.
The wet film 74 is preferably stretched in either the transport direction (MD direction) or the orthogonal width direction (TD direction). The moisture permeability can be reduced by stretching in the transport direction and the width direction. In addition, unevenness generated during drying and peeling off on the support can be reduced, and a good surface shape can be obtained within the film plane.
The wet film 74 sent to the tenter dryer 35 is dried while being conveyed by being gripped by clips at both ends thereof. In this case, stretching in the width direction can be performed using a tenter dryer 35.
It is preferable to divide the inside of the tenter dryer 35 into temperature zones and adjust the drying conditions appropriately for each of the zones.
As described above, the wet film 74 can be stretched in the width direction by the crossover 80 and / or the tenter dryer 35.
Further, the film may be stretched in the transport direction, and by making the rotation speed of the downstream roller faster than the rotation speed of the upstream roller at the crossing section 80, the wet film 74 is given draw tension in the transport direction. It can be carried out.
Here, in the transfer section 80 and / or the tenter dryer 35, the wet film 74 is dried without being stretched, and the residual solvent amount in the film is 3.0% by mass or less, preferably 1.0% by mass or less, Stretching may be performed after a dry film of 0.5% by mass or less, more preferably 0.3% by mass or less, and particularly preferably 0.2% by mass or less is more preferable.
In addition, when extending | stretching a dry film, after producing a dry film with unstretched and winding up once, you may extend | stretch further.
The polymer film used for stretching may be a dry film or a wet film, but is more preferably a wet film.

  The draw ratio in the width direction is preferably 10 to 500%, more preferably 20 to 500%, and particularly preferably 30 to 500%. The draw ratio in the transport direction is preferably 1 to 500%. In addition, since the tension | tensile_strength by conveyance is applied even when it does not stretch | stretch by drawing tension in the conveyance direction intentionally, the film stretched | stretched by the magnification of about 1 to 10% may be obtained as a result.

  The temperature during stretching is preferably in the temperature range of Tg ± 30 ° C. with respect to the glass transition temperature Tg of the unstretched polymer film after drying. Here, the glass transition temperature of the unstretched polymer film after drying is the glass transition temperature in a compatible state of the cellulose ester and the acrylic resin, and as described above, 100 to 200 ° C. is preferable, and 100 to 150 ° C. is more preferable. Stretching in this temperature range has good film handling suitability, and a desired optical film can be produced without breaking the polymer film. By stretching at (Tg−30 ° C.) or more, the film can be prevented from being broken, and variations in Rth within the film can be suppressed. Moreover, by extending | stretching below (Tg + 30 degreeC), extending | stretching can be prevented by the dead weight of a film, and the dispersion | variation in Rth within a film can be suppressed. Moreover, the increase in the total haze and internal haze due to phase separation in the film can be suppressed.

As described above, the stretching treatment may be performed in a drying process after the wet film 74 is formed and then passed through the transfer section 80 and the tenter dryer 35, or may be performed after the wet film 74 is wound up after being dried.
Casting conditions are preferably performed under such a condition that the film thickness is 10 to 200 μm when the film is produced without being stretched, more preferably 20 to 150 μm, still more preferably 30 to 120 μm, and even more preferably 40 to 100 μm. Most preferably, the conditions are as follows.
If it is within this range, the film thickness after stretching can be reduced, the change in retardation at the time of humidity change, high temperature and high temperature and high humidity environment is reduced, and an inexpensive film with less resin to be used can be produced. Therefore, it is preferable.

  The wet film 74 is dried to a predetermined residual solvent amount by the tenter dryer 35 and then sent to the downstream side as a film 82. Both ends of the film 82 are cut at both edges by the edge-cutting device 40. The cut side end portion is sent to the crusher 90 by a cutter blower (not shown). The crusher 90 pulverizes the film side end portion into a chip. Since this chip is reused for dope preparation, this method is effective in terms of cost. In addition, although it can also abbreviate | omit about the cutting process of this film both ends, it is preferable to carry out in any one from the said casting process to the process of winding up the said film.

  The film 82 from which both side ends have been removed is sent to the drying chamber 41 and further dried. Although the temperature in the drying chamber 41 is not specifically limited, It is preferable that it is the range of 50 to 160 degreeC. In the drying chamber 41, the film 82 is conveyed while being wound around a roller 91, and the solvent gas generated by evaporation here is adsorbed and recovered by an adsorption recovery device 92. The air from which the solvent component has been removed is blown again as dry air inside the drying chamber 41. The drying chamber 41 is more preferably divided into a plurality of sections in order to change the drying temperature.

  The film 82 is cooled to approximately room temperature in the cooling chamber 42. A humidity control chamber (not shown) may be provided between the drying chamber 41 and the cooling chamber 42, and air adjusted to a desired humidity and temperature can be blown onto the film 82 in the humidity control chamber. It is preferable. Thereby, generation | occurrence | production of the curling of the film 82 and the winding defect at the time of winding can be suppressed.

  Further, the forcible charge removal device (charge removal bar) 93 sets the charged voltage while the film 82 is being conveyed to a predetermined range (for example, −3 kV to +3 kV). Furthermore, it is preferable to provide a knurling roller 94 and to impart knurling to both edges of the film 82 by embossing.

  Finally, the film 82 is taken up by the take-up roller 95 in the take-up chamber 43. At this time, it is preferable to wind the sheet while applying a desired tension with the press roller 96. More preferably, the tension is gradually changed from the start to the end of winding. The film 82 to be wound is preferably at least 100 m in the longitudinal direction (casting direction). The width of the film 82 is preferably 600 mm or more, more preferably 1100 mm or more and 2900 mm or less, and further preferably 1800 mm or more and 2500 mm or less.

  In the solution casting method in the method for producing an optical film of the present invention, when casting a dope, two or more kinds of dopes can be simultaneously laminated or sequentially laminated. Furthermore, you may combine both casting. When performing simultaneous lamination and co-casting, a casting die to which a feed block is attached may be used, or a multi-manifold casting die may be used. It is preferable that at least one of the thickness of the layer on the air surface side and the thickness of the layer on the support side is 0.5% to 30% of the thickness of the entire film of the film composed of multiple layers by co-casting. Furthermore, when performing simultaneous lamination co-casting, it is preferable that the high-viscosity dope is wrapped with the low-viscosity dope when the dope is cast from the die slit to the support. Moreover, when performing simultaneous lamination | stacking co-casting, it is preferable that the dope which contact | connects an external field has a larger alcohol composition ratio than an internal dope among the casting beads formed from a die slit to a support body.

From casting die, decompression chamber, support structure, co-casting, peeling method, stretching, drying conditions for each process, handling method, curl, winding method after flatness correction, solvent recovery method, film recovery method The details are described in paragraphs [0617] to [0889] of JP-A-2005-104148.
Moreover, although the example of the manufacturing method of the optical film of this invention demonstrated above by the example which cast the dope on the band, you may cast a dope on a drum.

<Contact angle of film surface by alkali saponification>
One effective means of surface treatment when the optical film of the present invention is used as a protective film for a polarizing plate is alkali saponification treatment. In this case, the contact angle of the film surface after the alkali saponification treatment is preferably 55 ° or less. More preferably, it is 50 ° or less, and further preferably 45 ° or less.
As one example of the alkali saponification treatment, an optical film is immersed in an aqueous 1.5 N sodium hydroxide solution at 55 ° C. for 2 minutes, washed in a water bath at room temperature, and 0.05 N sulfuric acid at 30 ° C. Was neutralized. Although the method etc. which wash | clean again in the water-washing bath at room temperature and also dry with 100 degreeC warm air are mentioned, In this invention, it is not limited to this conditions and a method.
The alkali saponification solution is not particularly limited, but other than sodium hydroxide, for example, potassium hydroxide can also be used.
The concentration of the alkali saponification solution is not particularly limited, but from the viewpoint of the film surface and saponification performance, 0.1 to 10 rules are preferable, 1.0 to 8.0 rules are more preferable, and 1.0 to The 5.0 regulations are particularly preferred.

<Surface treatment>
The optical film can achieve improved adhesion between the optical film and other layers (for example, a polarizer, an undercoat layer, and a back layer) by optionally performing a surface treatment. For example, glow discharge treatment, ultraviolet irradiation treatment, corona treatment, flame treatment, acid or alkali treatment can be used. The glow discharge treatment here may be low-temperature plasma that occurs under a low pressure gas of 10 ^{−3 to} 20 Torr, and plasma treatment under atmospheric pressure is also preferred. A plasma-excitable gas is a gas that is plasma-excited under the above conditions, and includes chlorofluorocarbons such as argon, helium, neon, krypton, xenon, nitrogen, carbon dioxide, tetrafluoromethane, and mixtures thereof. It is done. Details of these are described in detail on pages 30 to 32 in the Japan Society for Invention and Innovation Technical Report (Public Technical Number 2001-1745, issued on March 15, 2001, Japan Society for Invention), and are preferably used in the present invention. be able to.

<Functional layer>
In the optical film of the present invention, a functional layer may be laminated on at least one surface. The type of the functional layer is not particularly limited, but a hard coat layer, an antireflection layer (a layer having a adjusted refractive index such as a low refractive index layer, a medium refractive index layer, or a high refractive index layer), an antiglare layer, an antistatic layer, Examples include an ultraviolet absorption layer, a low moisture permeability layer (moisture permeability reduction layer), and the like.
The functional layer may be a single layer or a plurality of layers. The method for laminating the functional layer is not particularly limited, but is preferably co-cast with an optical film containing a cellulose ester and an acrylic resin, or coated on an optical film containing a cellulose ester and an acrylic resin. .
When the functional layer is formed by coating and drying, it is preferable to use a monomer having an ethylenically unsaturated group as a binder. The monomer may be monofunctional or polyfunctional. Among them, it is preferable to use a polymerizable polyfunctional monomer, more preferably a photopolymerizable polyfunctional monomer, and particularly preferably a coating solution containing a monomer having two or more (meth) acryloyl groups. .

Specific examples of the monomer having two or more (meth) acryloyl groups include (meth) alkylene glycols such as neopentyl glycol acrylate, 1,6-hexanediol (meth) acrylate, and propylene glycol di (meth) acrylate. Acrylic acid diesters;
(Meth) acrylic acid diesters of polyoxyalkylene glycols such as triethylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate;
(Meth) acrylic acid diesters of polyhydric alcohols such as pentaerythritol di (meth) acrylate;
(Meth) acrylic acid diesters of ethylene oxide or propylene oxide adducts such as 2,2-bis {4- (acryloxy · diethoxy) phenyl} propane and 2-bis {4- (acryloxy · polypropoxy) phenyl} propane ;
Etc.

  Furthermore, epoxy (meth) acrylates, urethane (meth) acrylates, and polyester (meth) acrylates are also preferably used as the photopolymerizable polyfunctional monomer.

Among these, esters of polyhydric alcohol and (meth) acrylic acid are preferable. A polyhydric alcohol means a dihydric or higher alcohol.
More preferably, a polyfunctional monomer having 3 or more (meth) acryloyl groups in one molecule is preferable. For example, pentaerythritol tetra (meth) acrylate, pentaerythritol tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, ethylene oxide modified trimethylolpropane tri (meth) acrylate, propylene oxide modified trimethylolpropane tri (meth) acrylate, Ethylene oxide modified tri (meth) acrylate phosphate, trimethylolethane tri (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, dipentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (Meth) acrylate, 1,2,3-cyclohexanetetramethacrylate, polyurethane polyacrylate, Li ester polyacrylate, caprolactone-modified tris (acryloyloxyethyl) isocyanurate.

  Furthermore, resins having three or more (meth) acryloyl groups, such as relatively low molecular weight polyester resins, polyether resins, acrylic resins, epoxy resins, urethane resins, alkyd resins, spiroacetal resins, polybutadiene resins, polythiol polyene resins And oligomers or prepolymers such as polyfunctional compounds such as polyhydric alcohols.

  As other polyfunctional monomers, for example, dendrimers described in JP-A-2005-76005 and JP-A-2005-36105 can be used.

As the polyfunctional monomer, esters of polyhydric alcohol and (meth) acrylic acid, and amides of polyhydric alcohol and isocyanate containing a plurality of (meth) acryloyl groups are also preferably used.
The polyhydric alcohol is not particularly limited, but is preferably an aliphatic alcohol, and more preferably an alcohol having a cyclic aliphatic hydrocarbon group. The aliphatic group of the monocyclic alicyclic alcohol is preferably a cycloalkyl group having 3 to 8 carbon atoms, and examples thereof include a cyclopentyl group, a cyclohexyl group, a cyclobutyl group, and a cyclooctyl group.
Examples of the aliphatic group of the polycyclic alicyclic alcohol include a group having a bicyclo, tricyclo, tetracyclo structure or the like having 5 or more carbon atoms, and a cycloalkyl group having 6 to 20 carbon atoms is preferable. Adamantyl group, norbornyl group, dicyclopentyl group, tricyclodecanyl group, tetracyclododecyl group, central skeleton of compounds described in claims of JP-A-2006-215096, compound described in JP-A-2001-10999 And the like. A part of carbon atoms in the cycloalkyl group may be substituted with a hetero atom such as an oxygen atom.
Among them, examples of the polycyclic alcohol include an adamantyl group, a norbornyl group, a dicyclopentyl group, a tricyclodecanyl group, a tetracyclododecyl group, and a central skeleton of the compound described in the claims of JP-A-2006-215096. Polyhydric alcohols having a central skeleton of the compounds described in JP-A No. 2001-10999 are particularly preferred from the viewpoint of reducing moisture permeability.

  Two or more kinds of polymerizable polyfunctional monomers may be used in combination. Polymerization of the monomer having an ethylenically unsaturated group can be performed by irradiation with ionizing radiation or heating in the presence of a photo radical initiator or a thermal radical initiator.

  It is preferable to use a photopolymerization initiator for the polymerization reaction of the photopolymerizable polyfunctional monomer. As the photopolymerization initiator, a photoradical polymerization initiator and a photocationic polymerization initiator are preferable, and a photoradical polymerization initiator is particularly preferable.

  It is also preferable to use the polymerizable polyfunctional monomer in combination with a monofunctional monomer.

  As the monofunctional monomer, a monomer having one (meth) acryloyl group is preferable, and a monomer having one (meth) acryloyl group is usually obtained from a monovalent alcohol and acrylic acid.

The monohydric alcohol may be an aromatic alcohol or an aliphatic alcohol.
As monohydric alcohol, methyl alcohol, n-propyl alcohol, iso-propyl alcohol, n-butyl alcohol, tert-butyl alcohol, n-amyl alcohol, diacetone alcohol, 1-methoxy-2-propanol, furfuryl alcohol 2-octanol, 2-ethylhexanol, nonanol, n-decanol, undecanol, n-dodecanol, trimethylnonyl alcohol, benzyl alcohol, phenethyl alcohol, ethylene glycol monoisoamyl ether, ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, Examples include ethylene glycol monohexyl ether.
Moreover, about the aliphatic part of aliphatic alcohol, cycloaliphatic may be sufficient. The cycloaliphatic may be monocyclic, polycyclic, or may be bridged in the case of polycyclic. As the monocyclic type, a cycloalkyl group having 3 to 8 carbon atoms is preferable, and examples thereof include a cyclopentyl group, a cyclohexyl group, a cyclobutyl group, and a cyclooctyl group. Examples of the polycyclic type include groups having a bicyclo, tricyclo or tetracyclo structure having 5 or more carbon atoms, and a cycloalkyl group having 6 to 20 carbon atoms is preferable, for example, an adamantyl group, norbornyl group, dicyclopentyl group. , Tricyclodecanyl group, tetracyclododecyl group, central skeleton of the compound described in the claims of JP-A-2006-215096, central skeleton of the compound described in JP-A-2001-10999, and the like. . A part of carbon atoms in the cycloalkyl group may be substituted with a hetero atom such as an oxygen atom.

  The monovalent alcohol, whether it is an aromatic alcohol or an aliphatic alcohol, preferably has 6 or more carbon atoms.

  As (meth) acrylic acid, acrylic acid and methacrylic acid are preferable.

  In addition, as a functional layer, an antireflection layer (a layer having a refractive index adjusted such as a low refractive index layer, a middle refractive index layer, a high refractive index layer), an antiglare layer, an antistatic layer, an ultraviolet absorbing layer, a low moisture permeable layer (transparent In order to obtain a humidity reduction layer, various additives may be added.

  The thickness of the functional layer is more preferably 0.01 to 100 μm, and particularly preferably 0.02 to 50 μm. Furthermore, as a functional layer which reduces a water vapor transmission rate, it is more preferable that it is 0.1-20 micrometers in thickness.

  When the functional layer for reducing the moisture permeability is used, the moisture permeability (C) of the optical film laminated with the functional layer and the moisture permeability (D) of the optical film without lamination are 0.9 or less. It is desirable to become. More preferably, it is 0.85 or less, and more preferably 0.8 or less.

The optical film of the present invention can also be used as an optical compensation film for liquid crystal display devices. A liquid crystal display device includes a liquid crystal cell having a liquid crystal supported between two electrode substrates, two polarizing elements disposed on both sides thereof, and at least one sheet between the liquid crystal cell and the polarizing element. It is more preferable that the optical film of the present invention is arranged as an optical compensation film. These liquid crystal display devices are preferably TN, IPS, FLC, AFLC, OCB, STN, ECB, VA and HAN mode liquid crystal display devices, more preferably TN, OCB, IPS and VA mode liquid crystal display devices. A mode liquid crystal display device is more preferable.
In that case, you may provide various functional layers to the optical film of this invention. Examples of the functional layer include an antistatic layer, a cured resin layer (transparent hard coat layer), an antireflection layer, an easy adhesion layer, an antiglare layer, an optically anisotropic layer, an alignment layer, and a liquid crystal layer. These functional layers and materials thereof include surfactants, slip agents, matting agents, antistatic layers, hard coat layers, etc., and are disclosed by the Japan Institute of Technology (Technical No. 2001-1745, March 15, 2001). (Nippon Issuance, Invention Association), page 32 to page 45, and can be preferably used in the present invention.

[Polarizer]
The polarizing plate of the present invention includes at least one optical film of the present invention as a protective film for a polarizer.
The optical film of the present invention can be used as a protective film for a polarizing plate. In this case, it can serve as an optical compensation film for a liquid crystal display device and a protective film for a polarizing plate. When using as a protective film for polarizing plates, the production method of a polarizing plate is not specifically limited, It can produce by a general method. There is a method in which the obtained optical 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. Further, the surface treatment as described above may be performed.
Examples of the adhesive used to bond the protective film treated surface and the polarizer include polyvinyl alcohol adhesives such as polyvinyl alcohol and polyvinyl butyral, vinyl latexes such as butyl acrylate, and the like.
The polarizing plate is composed of a polarizer and a protective film that protects both surfaces of the polarizer, and further includes a protective film bonded to one surface of the polarizing plate and a separate film bonded to the other surface. The protective film and the separate film are used for the purpose of protecting the polarizing plate at the time of shipping the polarizing plate 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 adhesive layer bonded to a liquid crystal plate, and is used for the surface side which bonds a polarizing plate to a liquid crystal plate.
In a liquid crystal display device, a substrate including a liquid crystal cell is usually disposed between two polarizing plates. The protective film for polarizing plates to which the optical film of the present invention is applied is a protective film for any of the two polarizing plates. Although it can be used, it is preferable to use it as a protective film arrange | positioned at the liquid crystal cell side with respect to a polarizer among the two protective films of each polarizing plate.

(Optical compensation film)
The optical film of the present invention can be used in various applications, and is particularly effective when used as an optical compensation film for liquid crystal display devices. The optical compensation film is generally used for a liquid crystal display device and refers to an optical material that compensates for a retardation, and is synonymous with a retardation plate, an optical compensation sheet, and the like. The optical compensation film has birefringence and is used for the purpose of removing the color of the display screen of the liquid crystal display device or improving the viewing angle characteristics.

  The optical film of the present invention may itself be an optical compensation film, or may be used as a support for the optical compensation film, and an optically anisotropic layer may be provided thereon. The optically anisotropic layer is not limited to the optical performance or driving method of the liquid crystal cell of the liquid crystal display device in which the optical film of the present invention is used, and any optically anisotropic layer required as an optical compensation film Can be used together. The optically anisotropic layer used in combination may be formed from a composition containing a liquid crystalline compound or may be formed from a polymer film having birefringence.

[Liquid Crystal Display]
The liquid crystal display device of the present invention includes a liquid crystal cell and the polarizing plate of the present invention disposed in at least one of the liquid crystal cells, so that the optical film of the present invention contained in the polarizing plate is the outermost layer. It is arranged.

(General liquid crystal display device configuration)
The liquid crystal display device includes a liquid crystal cell having a liquid crystal supported between two electrode substrates, two polarizing plates disposed on both sides thereof, and, if necessary, between the liquid crystal cell and the polarizing plate. At least one optical compensation film is arranged.
The liquid crystal layer of the liquid crystal cell is usually formed by sealing liquid crystal in a space formed by sandwiching a spacer between two substrates. The transparent electrode layer is formed on the substrate as a transparent film containing a conductive substance. The liquid crystal cell may further be provided with a gas barrier layer, a hard coat layer, or an undercoat layer (undercoat layer) (used for adhesion of the transparent electrode layer). These layers are usually provided on the substrate. The substrate of the liquid crystal cell generally has a thickness of 50 μm to 2 mm.

(Types of liquid crystal display devices)
The optical film of the present invention can be used for liquid crystal cells in various display modes. TN (TwistedNematic), IPS (In-PlaneSwitching), FLC of (FerroelectricLiquidCrystal), AFLC (Anti-ferroelectricLiquidCrystal), OCB (OpticallyCompensatoryBend), STN (SuperTwistedNematic), VA (VerticallyAligned), ECB (ElectricallyControlledBirefringence), and HAN (HybridAlignedNematic) Various display modes have been proposed. In addition, a display mode in which the above display mode is oriented and divided has been proposed. The optical film of the present invention is effective in any display mode liquid crystal display device. Further, it is effective in any of a transmissive type, a reflective type, and a transflective liquid crystal display device.

  Hereinafter, the present invention will be specifically described based on examples. The materials, reagents, amounts and ratios of substances, operations, and the like shown in the following examples can be appropriately changed without departing from the gist of the present invention. Therefore, the present invention is not limited to the following examples.

  First, the cellulose ester and acrylic resin used in the examples will be described.

(Cellulose ester)
A cellulose ester having an acyl group total substitution degree of 2.75, an acetyl substitution degree of 0.19, a propionyl substitution degree of 2.56, and a weight average molecular weight of 200,000 was used.
This cellulose ester was synthesized as follows.
Sulfuric acid (7.8 parts by mass with respect to 100 parts by mass of cellulose) was added to cellulose as a catalyst, and carboxylic acid serving as a raw material for the acyl substituent was added to carry out an acylation reaction at 40 ° C. At this time, the substitution degree of the acetyl group and the propionyl group was adjusted by adjusting the amount of the carboxylic acid. In addition, aging was performed at 40 ° C. after acylation. Further, the low molecular weight component of this cellulose ester was removed by washing with acetone.
The obtained cellulose ester (cellulose acetate propionate, CAP) was designated as cellulose ester CE-1. In Table 1 below, it is described as CAP.

(acrylic resin)
The acrylic resin AC-1 described below was used. This acrylic resin is commercially available.
-Dianal BR88 (trade name), manufactured by Mitsubishi Rayon Co., Ltd., weight average molecular weight 1500,000
In Table 1 below, this acrylic resin AC-1 is described as PMMA.

(Moisture permeability reducing compound)
The moisture permeability reducing compound having the structure shown below was used.
The A / B values of Compounds A-5 to A-10, B-7, C-7 and C-21 are 10 for A-5 to A-10, B-7, C-7 and C-21, respectively. An optical film added by mass% is separately manufactured and its moisture permeability in terms of thickness of 40 μm is designated as A, and the moisture permeability in terms of thickness of 40 μm of Comparative Example 1 described later without addition of the moisture permeability reducing compound is designated as B. It was obtained from the value of
In addition, when the A / B value of TPP used as an additive in Comparative Example 3 was determined in the same manner, it was 0.64.

(UV absorber)
The ultraviolet absorber described below was used.
UV agent 1: Tinuvin 328 (Ciba Specialty Chemicals Co., Ltd.)

[Example 1]
<Preparation of optical film 006>
(Preparation of dope 1)
The composition described below was put into a mixing tank and stirred while heating to dissolve each component to prepare Dope 1.
(Composition of dope 1)
Cellulose ester CE-1 30 parts by mass Acrylic resin AC-1 70 parts by mass (Cellulose ester and acrylic resin total 100 parts by mass)
Moisture permeability reducing compound B-7 10 parts by mass UV absorber UV agent 1 2 parts by mass Dichloromethane 447 parts by mass Ethanol 61 parts by mass

  The solid content concentration of dope 1 (total concentration of cellulose ester, acrylic resin, moisture permeability reducing compound, and UV absorber) was 18% by mass.

  Using the band casting apparatus as shown in FIG. 1, the prepared dope 1 was uniformly cast from a casting die onto a stainless steel endless band (casting support) having a width of 2000 mm. When the amount of residual solvent in the dope 1 reaches 40% by mass, it is peeled off from the casting support as a polymer film, conveyed without being actively stretched by a tenter, and dried at 130 ° C. in a drying zone. The optical film 006 was obtained.

<Evaluation of optical film>
Thereafter, the film thickness, moisture permeability, Re and Rth of the obtained unstretched film were measured. The obtained results are shown in Table 1 below.

(Moisture permeability)
The moisture permeability was determined according to JIS Z-0208 after 24 hours at 40 ° C. and 90% relative humidity. When the film was not 40 μm, the value converted to 40 μm thickness was used.
Further, the value of a / B was calculated with the moisture permeability of the obtained film as a and the moisture permeability of the film 102 of Comparative Example 2 described later as B.

(Re, Rth)
After adjusting the sample film for 24 hours at 25 ° C. and 60% relative humidity, the film surface was measured using an automatic birefringence meter (KOBRA-21ADH: manufactured by Oji Scientific Instruments) at 25 ° C. and 60% relative humidity. The phase difference at a wavelength of 590 nm was measured from the direction inclined in increments of 10 ° from + 50 ° to −50 ° from the normal to the film surface with the vertical direction and the slow axis as the rotation axis. ) And the retardation value (Rth) in the film thickness direction.

<Preparation of Polarizing Plate 006 Using Optical Film 006>
1) Production of Polarizer According to Example 1 of Japanese Patent Application Laid-Open No. 2001-141926, iodine was adsorbed to a stretched polyvinyl alcohol film to produce a polarizer having a thickness of 20 μm.

2) Cellulose ester-based protective film A commercially available optical film (Fujitack ZRD40, manufactured by FUJIFILM Corporation) was immersed in a 1.5 mol / L NaOH aqueous solution (saponified solution) kept at 55 ° C. for 2 minutes, and then the film Then, the film was immersed in a 0.05 mol / L sulfuric acid aqueous solution at 25 ° C. for 30 seconds, and then a water-washing bath was passed under running water for 30 seconds to make the film neutral. Then, draining with an air knife was repeated three times, and after dropping water, the film was retained in a drying zone at 70 ° C. for 15 seconds and dried to prepare a saponified cellulose ester-based protective film.

3) Bonding After applying a corona treatment to the optical film 006 of the present invention using an acrylic adhesive on one side of the polarizer, bonding was performed. The saponified commercially available optical film was attached to the other surface using a polyvinyl alcohol-based adhesive, and dried at 70 ° C. for 10 minutes or more to produce a polarizing plate 006 using the film 001. Here, it arrange | positioned so that the transmission axis of a polarizer and the conveyance direction of the film 006 may orthogonally cross.

[Examples 2 to 15, Comparative Examples 2 and 3]
(Production of optical films 009 to 022, optical films 102 to 103 of comparative examples)
In the production of the optical film 006 of the present invention, the type and amount of the moisture permeability reducing compound were changed as shown in Table 1 to obtain a dope having a solid content concentration of 18% by mass. At this time, the solvents dichloromethane and ethanol were made the same at a solid concentration of 18% by mass so as to be constant at the same mixing weight ratio as in the production of the optical film 006. The other casting conditions were the same as the optical film 006, and optical films 009 to 022 of Examples 2 to 15 and optical films 102 to 103 of Comparative Examples 2 and 3 were produced.
The film thickness, water vapor transmission rate, Re, and Rth of the obtained optical films of Examples and Comparative Examples were measured in the same manner as in Example 1. The obtained results are shown in Table 1 below.

(Preparation of polarizing plates 009-022, 102-103)
In the same manner as the polarizing plate 001, polarizing plates 009 to 022 using the optical films 009 to 022 of Examples 2 to 15 and polarizing plates 102 to 103 using the optical films 102 to 103 of the comparative examples were also prepared in the same manner. .

[Comparative Example 1]
<Production of Optical Film 101 of Comparative Example and Polarizing Plate 101 Using the Same>
(Dope 2 preparation)
The composition described below was put into a mixing tank and stirred while heating to dissolve each component to prepare a dope.
(Composition of dope 2)
Cellulose ester CE-1 100 parts by mass UV absorber UV agent 1 2 parts by mass Dichloromethane 447 parts by mass Ethanol 61 parts by mass

  The solid content concentration of dope 2 (total concentration of cellulose ester, acrylic resin, and UV absorber) was 17% by mass.

  The optical film 101 of the comparative example was produced by the same process as producing the optical film 006 except that the dope 2 was used.

The film thickness, moisture permeability, Re, and Rth of the optical film 101 of Comparative Example 1 were measured in the same manner as in Example 1. The obtained results are shown in Table 1 below. In Table 1 below, “tack” is described in the polymer column of the optical film 101 of Comparative Example 1. However, cellulose ester CE-1 is cellulose acetate propionate.
A saponified cellulose ester-based protective film obtained by the method 2) of production of the polarizing plate 006 using the optical film 006 in Example 1 and the saponified film 101 of Comparative Example 1 under the same conditions. Two protective films are attached to both sides of the polarizer obtained by the method 1) for producing the polarizing plate 006 using the optical film 006 in Example 1 using a polyvinyl alcohol-based adhesive. And dried at 70 ° C. for 10 minutes or longer to produce the polarizing plate 101 of Comparative Example 1.

[Panel Evaluation]
<Implementation to IPS panel>
The upper and lower polarizing plates of a 47-inch IPS mode liquid crystal cell (47LM5800 manufactured by LGC) were peeled off, and the polarizing plate was attached to the liquid crystal cell so that the optical film of the present invention was on the outside. The crossed nicols were arranged so that the transmission axis of the upper polarizing plate was in the vertical direction and the transmission axis of the lower polarizing plate was in the horizontal direction. The panel warpage at the time of humidity change of the liquid crystal display device produced as described above was evaluated by the following method.

(Panel warpage after aging in high temperature and high humidity environment)
The liquid crystal display device was allowed to elapse for 72 hours at 50 ° C. and a relative humidity of 80%, and then the liquid crystal display device was disassembled in an environment of 25 ° C. and a relative humidity of 60%.
The obtained results are shown in Table 1 below.

  From Table 1 above, as a result of mounting the polarizing plates 006, 009-022 using the optical films 006, 009-022 of the present invention in a 47 inch liquid crystal cell, panel warpage was reduced as compared with the optical film of the comparative example. It was confirmed that display unevenness was reduced.

[Examples 201 to 203]
Next, optical films 201 to 203 of Examples 201 to 203 were obtained in the same manner as the optical film 009 of Example 1 except that the dope 1 was used and the stretching step shown in Table 2 below was provided. The thickness of the stretched optical film was 40 μm.

The polarizing plate 201-203 of Examples 201-203 was produced similarly to Example 1 except having used the optical films 201-203 of Examples 201-203, and the results of the same evaluation as in Table 1 above were as follows. Table 3 shows.
In the evaluation of moisture permeability, the reference films 1 to 3 were formed in the same manner as in Comparative Example 2 except that the optical film 102 in Comparative Example 2 was stretched under the same stretching conditions as in Examples 201 to 203. The optical film was separately manufactured, and the value of a / B in each example was calculated with B as the moisture permeability in terms of a thickness of 40 μm.

  From Table 3 above, it was found that the effect of the present invention was also obtained in the evaluation of the polarizing plate using the polarizing plates 201 to 203 of Examples 201 to 203 in which the stretching step was provided during the production of the optical film.

20 Film Production Line 21 Stock Tank 22 Dope 30 Filtration Device 31 Casting Die 32 Rotating Roller 33 Rotating Roller 34 Casting Band 35 Denter 40 Dryer 41 Drying Chamber 42 Cooling Chamber 43 Winding Chamber 60 Motor 61 Stirrer 62 Pump 63 Heat transfer medium circulation device 64 Casting chamber 65 Temperature control equipment 66 Condenser (condenser)
67 Recovery device 68 Decompression chamber 69 Casting film 70 Blower port 71 Blower port 72 Blower port 73 Blower port 74 Wet film 75 Stripping roller 80 Crossing part 81 Blower 82 Film 90 Crusher 91 Roller 92 Adsorption / recovery device 93 bar)
94 Knurling roller 95 Winding roller 96 Press roller

Claims (15)

An optical film comprising a cellulose ester and an acrylic resin,
The mass ratio of the cellulose ester and the acrylic resin is 70:30 to 5:95,
The optical film has a moisture permeability of 350 g / m ² / day or less (in terms of thickness 40 μm),
An optical film comprising a moisture permeability reducing compound having a molecular weight of 200 or more and satisfying the following formula (1):
Formula (1) A / B <= 0.6
(In Formula (1), A represents the moisture permeability of the optical film when the moisture permeability reducing compound is added in an amount of 10% by mass with respect to the total mass of the cellulose ester and the acrylic resin, and B represents the cellulose ester and It represents the moisture permeability of the optical film when the acrylic resin is contained and no moisture permeability reducing compound is added, provided that the moisture permeability is JIS Z-0208 according to the method of JIS Z-0208 after 24 hours at 40 ° C. and 90% relative humidity. (The value is a value converted to a thickness of 40 μm.) The optical film according to claim 1, wherein the optical film satisfies the following formula (2).
Formula (2) a / B <= 0.6
(In Formula (2), a represents the water vapor transmission rate of an optical film, B represents the water vapor transmission rate of the optical film without the addition of a water vapor transmission reduction compound. However, the water vapor transmission rate is a method of JIS Z-0208. (The value after 24 hours at 40 ° C. and 90% relative humidity is converted to a thickness of 40 μm.)   The optical film according to claim 1, wherein the moisture permeability reducing compound has a structure including one or more aromatic rings. The said moisture-permeation reducing compound is a structure represented by the following general formula (A), general formula (B), or general formula (C), As described in any one of Claims 1-3 characterized by the above-mentioned. Optical film.

[In General Formula (A), ^R113 , ^R114 , ^R115 , ^R123 , ^R124 and ^R125 each independently represents a hydrogen atom or a substituent. ]

[In the general formula (B), R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ , R ¹⁶ , R ²¹ , R ²³ , R ²⁴ , R ²⁵ , R ³² , R ³³ , R ³⁴ , R ³⁵ , R ³⁶ are Each independently represents a hydrogen atom or a substituent, and R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ , R ¹⁶ , R ²¹ , R ²³ , R ²⁴ , R ²⁵ , R ³² , R ³³ , R ³⁴ , R ^At least one of ³⁵ and R ³⁶ is an amino group, an acylamino group, an alkoxycarbonylamino group, an aryloxycarbonylamino group, a sulfonylamino group, a hydroxy group, a mercapto group, or a carboxyl group. ]

[In the general formula (C), X ² represents B, C—R (R represents a hydrogen atom or a substituent) or N. R ²¹¹ , R ²¹² , R ²¹³ , R ²¹⁴ , R ²¹⁵ , R ²²¹ , R ²²² , R ²²³ , R ²²⁴ , R ²²⁵ , R ²³¹ , R ²³² , R ²³³ , R ²³⁴ and R ²³⁵ are each independently hydrogen Represents an atom or substituent. ]   5. The optical film according to claim 1, wherein the moisture permeability reducing compound is included in an amount of 10 to 100% by mass with respect to a total mass of the cellulose ester and the acrylic resin.   A thickness is 60 micrometers or less, The optical film as described in any one of Claims 1-5 characterized by the above-mentioned. Re and Rth defined by the following formula (I) and the following formula (II) satisfy the following formula (III) and the following formula (IV) at a wavelength of 590 nm. An optical film according to item.
Formula (I) Re = (nx−ny) × d
Formula (II) Rth = {(nx + ny) / 2−nz} × d
Formula (III) | Re | ≦ 50 nm
Formula (IV) | Rth | ≦ 300 nm
(In the formulas (I) to (IV), nx is the refractive index in the slow axis direction in the film plane, ny is the refractive index in the fast axis direction in the film plane, and nz is in the thickness direction of the film. (Refractive index, d is the film thickness (nm).)   The film formation is carried out by casting a polymer solution containing the cellulose ester, the acrylic resin, the moisture permeability reducing compound and a solvent on a support. The optical film as described.   The optical film according to claim 1, which has a functional layer having a thickness of 0.1 to 20 μm on at least one surface.   The moisture permeability (C) of the optical film when the functional layer is laminated and the moisture permeability (D) of the optical film when the functional layer is not laminated satisfy C / D ≦ 0.9. The optical film according to claim 9. Casting a composition comprising a cellulose ester, an acrylic resin, and a moisture permeation reducing compound on a support to form a polymer film,
The mass ratio of the cellulose ester and the acrylic resin in the composition is 70:30 to 5:95,
The molecular weight of the moisture permeability reducing compound is 200 or more,
The method for producing an optical film, wherein the moisture permeability reducing compound satisfies the following formula (1).
Formula (1) A / B <= 0.6
(In Formula (1), A represents the moisture permeability of the optical film when the moisture permeability reducing compound is added in an amount of 10% by mass with respect to the total mass of the cellulose ester and the acrylic resin, and B represents the cellulose ester and It represents the moisture permeability of the optical film when the acrylic resin is contained and no moisture permeability reducing compound is added, provided that the moisture permeability is JIS Z-0208 according to the method of JIS Z-0208 after 24 hours at 40 ° C. and 90% relative humidity. (The value is a value converted to a thickness of 40 μm.) The said optical film satisfy | fills following formula (2), The manufacturing method of the optical film of Claim 11 characterized by the above-mentioned.
Formula (2) a / B <= 0.6
(In Formula (2), a represents the water vapor transmission rate of an optical film, B represents the water vapor transmission rate of the optical film without the addition of a water vapor transmission reduction compound. However, the water vapor transmission rate is a method of JIS Z-0208. (The value after 24 hours at 40 ° C. and 90% relative humidity is converted to a thickness of 40 μm.)   The method for producing an optical film according to claim 11, wherein the optical film is stretched in at least one of a film transport direction and a width direction.   A polarizing plate comprising at least one optical film according to any one of claims 1 to 10 as a protective film for a polarizer. A liquid crystal cell;
The polarizing plate according to claim 14 disposed in at least one of the liquid crystal cells,
A liquid crystal display device, wherein the optical film is arranged to be an outermost layer.

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