JP6310887B2 - Optical film, optical film manufacturing method, polarizing plate, and liquid crystal display device - Google Patents

Description

  The present invention relates to an optical film excellent in adhesiveness with a polarizer. The present invention further relates to a method for producing the optical film, a polarizing plate having the optical film, and a liquid crystal display device.

  Liquid crystal display devices are widely used in monitors for personal computers and portable devices, and for television applications because of their various advantages, such as low voltage and low power consumption, enabling miniaturization and thinning. In general, a liquid crystal display device includes a liquid crystal cell, an optical compensation film, and a polarizer. The optical compensation film is used for eliminating image coloring or expanding the viewing angle, and a stretched birefringent film or a film obtained by applying a liquid crystal to a transparent film is used. A cellulose acylate film may be used as the optical compensation film.

  For example, Patent Document 1 discloses a skin layer containing cellulose acylate of 2.7 <Z2 <3.0 on both surfaces of a core layer containing cellulose acylate having an acyl substitution degree of 2.0 <Z1 <2.5. A cellulose acylate film having an in-plane retardation Ro and a thickness direction retardation Rth of 20 ≦ Ro (nm) ≦ 100 and 40 ≦ Rth (nm) ≦ 200, respectively, and a core layer and a skin layer Each containing the same additive A selected from a discotic compound, a rod-like compound, and a polyester compound, and the content (mass%) of the additive A contained in either one of the core layer and the skin layer is A cellulose acylate film having a content of 1% by mass to 15% by mass and an additive A contained in the other layer of 0.05% by mass to 0.50% by mass is described.

  Patent Document 2 discloses a step of casting a dope containing cellulose acylate on a support, and the surface of the dope not in contact with the support in the dope on the support after casting. Including the step of drying in the drying zone by controlling the surface drying air temperature T1 (unit: ° C.) and controlling the back surface drying temperature T2 (unit: ° C.) of the dope, the surface drying air temperature T1 and the back surface drying A method for producing a cellulose acylate film in which the temperature T2 is controlled to satisfy a predetermined relationship is described.

JP 2012-98646 A JP 2012-71541 A

  As the polarizing plate, a laminate of a polarizer and a cellulose acylate film may be used. As the liquid crystal display device is made thinner, the thickness of the polarizer is also reduced, so that in the polishing step after processing of the polarizing plate and the evaluation step after chip processing, inside the skin layer of the cellulose acylate film There is a problem that the film peels off. In the techniques described in Patent Documents 1 and 2, it is desired to further improve the adhesion with the polarizer.

  This invention makes it the subject which should be solved to provide the optical film excellent in adhesiveness with the polarizer which eliminated the said problem. Furthermore, this invention makes it the subject which should be solved to provide the manufacturing method of the said optical film, the polarizing plate which has the said optical film, and a liquid crystal display device.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that the optical film having the first skin layer, the core layer, and the second skin layer has an amount of plasticizer on the surface of the first skin layer. It has been found that by reducing the amount and difference of the plasticizer on the surface of the second skin layer, it is possible to provide an optical film that solves the above problems. The present invention has been completed based on these findings.

That is, according to the present invention, the following inventions are provided.
(1) a core layer containing cellulose acylate having an average acyl substitution degree of 2.00 to 2.55;
On one surface of the core layer, a first skin layer containing a cellulose acylate having an average acyl substitution degree of 2.60 to 3.00,
An optical film having a second skin layer containing cellulose acylate having an average acyl substitution degree of 2.60 to 3.00 on the other surface of the core layer,
The optical film contains at least one plasticizer;
The plasticizer has an elastic modulus of a film formed by adding 1 part by mass of the plasticizer to 100 parts by mass of cellulose acylate having an average acyl substitution degree of 2.43 to 2.81. Satisfying the condition of lowering by 0.1% or more than the elastic modulus of the film formed without addition,
The amount of the plasticizer in the region from the surface of the first skin layer to a depth of 1 μm and the amount of the plasticizer in the region from the surface of the second skin layer to a depth of 1 μm are expressed by the following formula A Satisfying the optical film.
Formula A: | Amount of plasticizer in the region from the surface of the first skin layer to a depth of 1 μm−Amount of plasticizer in a region from the surface of the second skin layer to a depth of 1 μm | ≦ 2% by mass
(2) The optical film according to (1), wherein the addition amount of the plasticizer in the entire film is 3% by mass or more and 9% by mass or less.
(3) The plasticizer is a polycondensed ester containing an aromatic dicarboxylic acid and an aliphatic diol, and the ratio of aromatic dicarboxylic acid residues to all dicarboxylic acid residues in the polycondensed ester is 60 mol%. The optical film as described in (2) above.
(4) The optical film according to (2) or (3), wherein the polycondensed ester has a number average molecular weight of 1000 to 2000.
(5) The film thickness of the entire film is 3 μm or more and 50 μm or less, and the thicknesses of the first skin layer and the second skin layer are 0.3 μm or more and 3 μm or less, respectively (1) to (4) The optical film described in 1.
(6) The optical film according to any one of (1) to (5), which satisfies the following formula 1 and the following formula 2:
Formula 1: 30 nm ≦ Re (550) ≦ 80 nm
Formula 2: 80 nm ≦ Rth (550) ≦ 150 nm
However, Re (550) represents the in-plane retardation of the optical film at 550 nm, and Rth (550) represents the retardation in the thickness direction of the optical film at a wavelength of 550 nm.
(7) A core layer forming dope containing cellulose acylate, a first skin layer forming dope containing cellulose acylate, and a second skin layer forming dope containing cellulose acylate are co-located on the support. A drying temperature T1 of the dope surface not in contact with the support, and a drying temperature T2 of the dope surface in contact with the support. However, the said drying is performed on the conditions which satisfy | fill 20 <= T2-T1 <= 40, The manufacturing method of the optical film in any one of (1) to (6); However, the unit of drying temperature is (degreeC).
(8) A polarizing plate having a polarizer and the optical film according to any one of (1) to (6).
(9) A liquid crystal display device having the polarizing plate according to (8).

  The optical film of this invention is excellent in adhesiveness with a polarizer by the uniform distribution of the plasticizer of the film cross-sectional direction. The polarizing plate and the liquid crystal display device of the present invention are excellent in adhesion between the optical film and the polarizer.

FIG. 1 is a schematic cross-sectional view of a casting apparatus. FIG. 2 is a schematic cross-sectional view of the casting apparatus. FIG. 3 is a schematic cross-sectional view of the casting apparatus. FIG. 4 is a schematic cross-sectional view of the casting apparatus.

  Hereinafter, the present invention will be described in detail. 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.

In the present specification, Re (λ) and Rth (λ) represent in-plane retardation (nm) and retardation in the thickness direction (nm) at wavelength λ, respectively. Note that the wavelength λ is 550 nm unless otherwise specified in this specification. Re (λ) is measured by making light having a wavelength of λ nm incident in the normal direction of the film in KOBRA 21ADH or WR or KOBRA CCD series (manufactured by Oji Scientific Instruments).
When the film to be measured is represented by a uniaxial or biaxial refractive index ellipsoid, Rth (λ) is calculated by the following method.
Rth (λ) is the above-mentioned Re (λ), with the in-plane slow axis (determined by KOBRA 21ADH or WR or KOBRA CCD series) as the tilt axis (rotary axis) (if there is no slow axis, film A total of 6 points of light of wavelength λ nm are incident from the inclined direction in 10 degree steps from the normal direction to 50 degrees on one side with respect to the film normal direction (with any direction in the plane as the rotation axis). KOBRA 21ADH or WR or KOBRA CCD series is calculated based on the measured retardation value, the assumed value of the average refractive index, and the input film thickness value.
In the above, in the case of a film having a direction in which the retardation value is zero at a certain tilt angle with the in-plane slow axis from the normal direction as the rotation axis, the retardation value at a tilt angle larger than the tilt angle is After changing the sign to negative, KOBRA 21ADH or WR or KOBRA CCD series calculates. In selecting the measurement wavelength λnm, the wavelength selection filter can be exchanged manually, or the measurement value can be converted by a program or the like.
Note that the retardation value is measured from two inclined directions with the slow axis as the tilt axis (rotary axis) (in the case where there is no slow axis, the arbitrary direction in the film plane is the rotary axis), Rth can also be calculated from the following formula (X) and formula (XI) based on the value, the assumed value of the average refractive index, and the input film thickness value.

上記のＲｅ（θ）は法線方向から角度θ傾斜した方向におけるレタデーション値を表す。また、式中、ｎｘは面内における遅相軸方向の屈折率を表し、ｎｙは面内においてｎｘに直交する方向の屈折率を表し、ｎｚはｎｘ及びｎｙに直交する方向の屈折率を表す。ｄは膜厚を表す。

The above Re (θ) represents a retardation value in a direction inclined by an angle θ from the normal direction. In the formula, nx represents the refractive index in the slow axis direction in the plane, ny represents the refractive index in the direction orthogonal to nx in the plane, and nz represents the refractive index in the direction orthogonal to nx and ny. . d represents a film thickness.

In the case where the film to be measured cannot be expressed by a uniaxial or biaxial refractive index ellipsoid, that is, a film having no so-called optical axis, Rth (λ) is calculated by the following method.
Rth (λ) is −50 degrees with respect to the normal direction of the film, with Re (λ) being the in-plane slow axis (determined by KOBRA 21ADH or WR or KOBRA CCD series) as the tilt axis (rotation axis). From 10 degrees to +50 degrees with light of wavelength λ nm incident from each inclined direction and measured 11 points, and based on the measured retardation value, the assumed average refractive index and the input film thickness value KOBRA 21ADH or WR is calculated.
In the above measurement, the assumed value of the average refractive index may be a value in a polymer handbook (John Wiley & Sons, Inc.) or a catalog of various optical films. Those whose average refractive index is not known can be measured with an Abbe refractometer. Examples of the average refractive index values of main optical films are given below:
Cellulose acylate (1.48), cycloolefin polymer (1.52), polycarbonate (1.59), polymethyl methacrylate (1.49), and polystyrene (1.59).
By inputting these assumed values of average refractive index and film thickness, the KOBRA 21ADH or WR or KOBRA CCD series calculates nx, ny, and nz. Nz = (nx−nz) / (nx−ny) is further calculated from the calculated nx, ny, and nz.
The retardation can also be measured using AxoScan (AXOMETRICS).

In the present invention, the “slow axis” of the retardation film or the like means a direction in which the refractive index is maximized. Further, the measurement wavelength of the refractive index is a value at λ = 550 nm in the visible light region unless otherwise specified.
Further, in the present specification, the numerical values and numerical ranges indicating the optical characteristics of the respective members indicate numerical values, numerical ranges and properties including generally allowable errors for the liquid crystal display device and the members used therefor. Shall be interpreted.

  In this specification, the number average molecular weight (Mn) is, for example, HLC-8220 (manufactured by Tosoh Corporation), and TSKgel (registered trademark) Super AWM-H (manufactured by Tosoh Corporation, 6.0 mm ID ×) as a column. Unless otherwise stated, the eluent is measured using a 10 mmol / L lithium bromide NMP (N-methylpyrrolidinone) solution.

[Optical film]
The optical film of the present invention has a core layer containing cellulose acylate having an average acyl substitution degree of 2.00 to 2.55, and an average acyl substitution degree of 2.60 to 3.00 on one surface of the core layer. An optical film having a first skin layer containing cellulose acylate and having a second skin layer containing cellulose acylate having an average acyl substitution degree of 2.60 to 3.00 on the other surface of the core layer The optical film contains at least one plasticizer, and the plasticizer is 1 part by weight of the plasticizer with respect to 100 parts by weight of cellulose acylate having an average acyl substitution degree of 2.43 to 2.81. Satisfying the condition that the elastic modulus of the film formed by adding the agent is 0.1% or more lower than the elastic modulus of the film formed without adding the plasticizer, from the surface of the first skin layer 1μ depth The amount of the plasticizer in the area up to the amount of the plasticizer in the region to a depth of 1μm from the surface of the second skin layer, satisfies the following formula A, is an optical film.
Formula A: | Amount of plasticizer in the region from the surface of the first skin layer to a depth of 1 μm−Amount of plasticizer in a region from the surface of the second skin layer to a depth of 1 μm | ≦ 2% by mass

  The amount of plasticizer in the region from the surface of the skin layer to a depth of 1 μm is obtained by scraping the surface layer from the surface of the film to a depth of 1 μm and taking a predetermined amount (for example, 0.05 g) of the sample. The amount of the plasticizer can be measured by quantifying by an appropriate method according to the type of the plasticizer to be measured. For example, the sample is dissolved in a mixed solution of methylene chloride and methanol in a ratio of 92: 8, and the absorbance at a wavelength of 286 nm is measured with an ultraviolet-visible-near infrared spectrophotometer (UV-3150, Shimadzu Corporation). Can be quantified. Alternatively, the sample can be quantified by dissolving the sample in a mixed solution having a ratio of methylene chloride and methanol of 92: 8, performing high performance liquid chromatography HPLC measurement, and calculating the area.

  In an optical film manufactured by a conventional method, the amount of solvent may differ due to the difference in drying conditions between the surface of one skin layer and the surface of the other skin layer, which causes the plasticizer to aggregate on one skin layer. The present inventors have found that the stress when the polarizing plate is bent concentrates on the low elastic modulus portion where the plasticizer is aggregated, and the optical film is peeled off from the polarizer. In the present invention, by making the distribution of the plasticizer in the cross-sectional direction of the film uniform, specifically satisfying the above formula A, the adhesion with the polarizer is improved, and the polarization when the polarizing plate is bent. It is estimated that separation from the child can be suppressed.

Further preferred embodiments of Formula A are Formulas A-1 and A-2.
Formula A-1: | Amount of plasticizer in the region from the surface of the first skin layer to a depth of 1 μm−Amount of plasticizer in the region from the surface of the second skin layer to a depth of 1 μm | ≦ 1.5 mass%
Formula A-2: | Amount of plasticizer in the region from the surface of the first skin layer to a depth of 1 μm−Amount of plasticizer in the region from the surface of the second skin layer to a depth of 1 μm | ≦ 1.0 mass%

  When producing an optical film by solution casting, generally it is easy to dry from the surface not in contact with the band, and since the plasticizer is stably present in a good solvent, there are many on the band surface side where there are many solvents, The amount of plasticizer on the air surface side tends to decrease. In order to equalize the amount of plasticizer on the band surface and air surface, it is effective to equalize the dry state of the band surface and air surface. Therefore, (1) the band surface is also dried, and the band surface is dried at a higher temperature to make the dried state of the band surface and the air surface equal, (2) the film thickness is reduced, (3 It is possible to achieve the condition of formula A by reducing the amount of plasticizer added, (4) using a plasticizer with a high aromatic ratio and a high molecular weight. In the above-mentioned Patent Document 1, there is no description about means for independently controlling the drying state of the band surface and the air surface, and the plasticizer used is different, so that Formula A cannot be achieved. Further, Patent Document 2 described above describes means for independently controlling the dry state of the band surface and the air surface. However, the adhesiveness is further increased due to the large amount of plasticizer used and the thick film thickness. An improvement was desired.

<Layer structure of film>
The optical film of the present invention comprises a core layer containing cellulose acylate having an average acyl substitution degree of 2.00 to 2.55, and cellulose having an average acyl substitution degree of 2.60 to 3.00 on one surface of the core layer. It has a first skin layer containing acylate, and a second skin layer containing cellulose acylate having an average acyl substitution degree of 2.60 to 3.00 on the other surface of the core layer.
In this specification, the “core layer” refers to a layer having the largest film thickness, and the “skin layer” refers to a layer that is thinner than the core layer and is in contact with the core layer. .

The optical film of the present invention can be produced by multilayerly casting a dope containing cellulose acylate on a support simultaneously or sequentially as described later, but even in this case, the layers are mixed with each other. In other words, a clear interface may not be formed.
Moreover, although the cellulose acylate in each layer may use only 1 type, or several cellulose acylates may be mixed in one layer, it is preferable that the cellulose acylate in each layer is 1 type.

<Film thickness>
The film thickness of the entire optical film of the present invention is preferably 3 μm or more and 50 μm or less, more preferably 5 μm or more and 47 μm or less, and further preferably 7 μm or more and 40 μm or less.
By setting the film thickness to 3 μm or more, it is preferable because the strength as a film can be secured, and by setting the film thickness to 50 μm or less, it is easy to cope with a change in humidity and maintain optical characteristics.

The thicknesses of the first skin layer and the second skin layer are each preferably 0.3 μm or more and 3 μm or less. It is more preferably 0.4 μm or more and 2.5 μm or less, and further preferably 0.5 μm or more and 2.0 μm or less.
The film thickness can be measured with an electronic micrometer K402B (manufactured by Anritsu Corporation). The film thickness of the skin layer can be measured by a method of cutting the film with a microtome in the cross-sectional direction and observing with an optical microscope, or a reflection spectral film thickness meter such as FE3000 (manufactured by Otsuka Electronics Co., Ltd.).

<Retardation Re and Rth>
The retardations Re and Rth of the optical film of the present invention are appropriately selected depending on the design of the liquid crystal cell and the optical film.
Re preferably satisfies 30 nm ≦ Re (550) ≦ 80 nm, more preferably satisfies 35 nm ≦ Re (550) ≦ 70 nm, and further preferably satisfies 40 nm ≦ Re (550) ≦ 65 nm.
Rth preferably satisfies 80 nm ≦ Rth (550) ≦ 150 nm, more preferably satisfies 90 nm ≦ Rth (550) ≦ 140 nm, and further preferably satisfies 100 nm ≦ Rth (550) ≦ 130 nm.
Further, Re (630) / Re (440) ≦ 1.000 is preferably satisfied, Re (630) / Re (440) ≦ 0.970 is more preferably satisfied, and Re (630) / Re (440). More preferably, ≦ 0.950 is satisfied. The lower limit value of Re (630) / Re (440) is not particularly limited. For example, 0.850 ≦ Re (630) / Re (440), and preferably 0.900 ≦ Re (630) / Re (440). It is.
Re (550) represents the in-plane retardation of the optical film at a wavelength of 550 nm, and Rth (550) represents the thickness direction retardation of the optical film at a wavelength of 550 nm. Re (630) represents the in-plane retardation of the optical film at a wavelength of 630 nm, and Re (440) represents the in-plane retardation of the optical film at a wavelength of 440 nm.

<Cellulose acylate>
The cellulose acylate used in the present invention is not particularly limited. Examples of cellulose acylate raw materials include cotton linter and wood pulp (hardwood pulp, conifer pulp). Cellulose acylate obtained from any raw material can be used. In some cases, cellulose acylate obtained from multiple types of raw materials is used. You may mix and use. For example, in Marusawa and Uda, “Plastic Materials Course (17) Fibrous Resin”, published by Nikkan Kogyo Shimbun (published in 1970) and the Japan Institute of Invention and Technology Publication No. 2001-1745 (pages 7-8) The cellulose described can be used.

  Glucose units having β-1,4 bonds constituting cellulose have free hydroxyl groups at the 2nd, 3rd and 6th positions. Cellulose acylate is a polymer obtained by acylating part or all of these hydroxyl groups with an acyl group. The average degree of acyl substitution means the ratio of acylation of the hydroxyl groups of cellulose located at the 2nd, 3rd and 6th positions (100% acylation has a degree of substitution of 1).

  The degree of acyl group substitution can be measured in accordance with ASTM-D817-96.

  In the present invention, the average acyl substitution degree of the cellulose acylate of the core layer is 2.00 to 2.55, and the average acyl substitution degree of the cellulose acylate of the first skin layer and the second skin layer is independent of each other. 2.60 to 3.00.

  The acyl group having 2 or more carbon atoms of cellulose acylate in the present invention may be an aliphatic group or an allyl group, and is not particularly limited. These are, for example, cellulose alkylcarbonyl esters, alkenylcarbonyl esters, aromatic carbonyl esters, aromatic alkylcarbonyl esters, and the like, each of which may further have a substituted group. Preferred examples of these 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, isobutanoyl group Group, tert-butanoyl group, cyclohexanecarbonyl group, oleoyl group, benzoyl group, naphthylcarbonyl group, cinnamoyl group and the like. Among these, an acetyl group, a propionyl group, a butanoyl group, a dodecanoyl group, an octadecanoyl group, a tert-butanoyl group, an oleoyl group, a benzoyl group, a naphthylcarbonyl group, a cinnamoyl group, and the like are more preferable, and an acetyl group is particularly preferable. A propionyl group and a butanoyl group (when the acyl group has 2 to 4 carbon atoms), more preferably an acetyl group (when the cellulose acylate is cellulose acetate).

In the acylation of cellulose, when an acid anhydride or acid chloride is used as an acylating agent, an organic acid such as acetic acid or methylene chloride is used as an organic solvent as a reaction solvent.
As the catalyst, when the acylating agent is an acid anhydride, a protic catalyst such as sulfuric acid is preferably used, and when the acylating agent is an acid chloride (for example, CH ₃ CH ₂ COCl), Basic compounds are used.

The most common industrial synthesis method of cellulose mixed fatty acid ester is to use cellulose corresponding to fatty acid corresponding to acetyl group and other acyl groups (acetic acid, propionic acid, valeric acid, etc.) or their anhydrides. This is a method of acylating with a mixed organic acid component.
The cellulose acylate used in the present invention can be synthesized, for example, by the method described in JP-A-10-45804. As the cellulose acylate, for example, commercially available products such as L-70 (Daicel Corporation), LT-55 (Daicel Corporation), CA-394-60LF (Eastman Chemical Company) can also be used.

<Plasticizer>
The optical film of the present invention contains at least one plasticizer. As used herein, the term “plasticizer” refers to an elastic modulus of a film formed by adding 1 part by mass of a plasticizer to 100 parts by mass of cellulose acylate having an average acyl substitution degree of 2.43 to 2.81. This satisfies the condition that the elastic modulus of the film formed without adding the plasticizer is 0.1% or more lower. More specifically, the elastic modulus of a film formed by adding 1 part by mass of a plasticizer to 100 parts by mass of cellulose acylate having an average acyl substitution degree of 2.43 to 2.81 is expressed as “elastic modulus (1 Mass part) ”, and the elastic modulus of the film formed without adding the plasticizer is“ elastic modulus (0 part by mass) ”, the elastic modulus (1 part by mass) / elastic modulus (0 part by mass) ≦ 0.999 is satisfied. The elastic modulus is the stress at 0.1% elongation and 0.5% elongation at 25 ° C, 60RH% atmosphere at a tensile speed of 10% / min using Toyo Baldwin Co., Ltd. universal tensile tester "STM T50BP". Measured and calculated from the slope.
Examples of the plasticizer that satisfies the above conditions include polycondensation esters described below and / or plasticizers as retardation developing agents described below.
The addition amount of the plasticizer in the whole film (meaning the total addition amount when plural kinds of plasticizers are used) is preferably 1% by mass to 12% by mass, and preferably 1% by mass to 10% by mass. % Or less, more preferably 1% by mass or more and 8% by mass or less. By making the addition amount of the plasticizer 1% by mass or more, the brittleness of the film can be improved, and by making the addition amount of the plasticizer 12% by mass or less, the condition of the above formula A can be easily satisfied, and the present invention. It becomes easy to obtain the effect.

(Polycondensed ester)
A polycondensation ester can be added as a plasticizer to the optical film of the present invention.
The polycondensation ester is a polycondensation ester of a dicarboxylic acid component and a diol component. The dicarboxylic acid component may consist of only one dicarboxylic acid or may be a mixture of two or more dicarboxylic acids. Among these, as the dicarboxylic acid component, it is preferable to use a dicarboxylic acid component containing at least one aromatic dicarboxylic acid and at least one aliphatic dicarboxylic acid. On the other hand, the diol component may consist of only one diol component or a mixture of two or more diols. Among them, it is preferable to use ethylene glycol and / or an aliphatic diol having an average carbon atom number greater than 2.0 and 3.0 or less as the diol component.

The ratio of aromatic dicarboxylic acid residues to all dicarboxylic acid residues in the polycondensed ester is preferably 10 mol% or more and 100 mol% or less, more preferably 50 mol% or more and 100 mol% or less, and 60 mol% or more and 100 mol% or less. % Or less is more preferable, and 70 mol% or more and 100 mol% or less is particularly preferable.
Examples of aromatic dicarboxylic acids include phthalic acid, terephthalic acid, isophthalic acid, 1,5-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 2,8-naphthalenedicarboxylic acid and 2,6-naphthalenedicarboxylic acid and the like are included, and phthalic acid and terephthalic acid are preferable. Examples of aliphatic dicarboxylic acids include oxalic acid, malonic acid, succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, and 1,4 -Cyclohexane dicarboxylic acid etc. are contained, and a succinic acid and adipic acid are preferable among these.

  The diol component is ethylene glycol and / or a diol having an average number of carbon atoms of more than 2.0 and 3.0 or less. In the diol component, ethylene glycol is preferably 50 mol%, and more preferably 75 mol%. Examples of the aliphatic diol include alkyl diols and alicyclic diols, such as ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, and 1,3-butane. Diol, 2-methyl-1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 2,2-diethyl -1,3-propanediol (3,3-dimethylolpentane), 2-n-butyl-2-ethyl-1,3-propanediol (3,3-dimethylolheptane), 3-methyl-1,5 -Pentanediol, 1,6-hexanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-ethyl-1,3-hexa There are diol, 2-methyl-1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-octadecanediol, diethylene glycol and the like, and these are one or more kinds together with ethylene glycol. It is preferably used as a mixture of

  The diol component is preferably ethylene glycol, 1,2-propanediol, and 1,3-propanediol, and particularly preferably ethylene glycol and 1,2-propanediol.

  Further, the polycondensed ester is preferably a derivative of a polycondensed ester in which the terminal OH of the polycondensed ester forms an ester with a monocarboxylic acid. Monocarboxylic acids used for sealing the both terminal OH groups are preferably aliphatic monocarboxylic acids, preferably acetic acid, propionic acid, butanoic acid, benzoic acid and derivatives thereof, more preferably acetic acid or propionic acid, and acetic acid. Most preferred. When the number of carbon atoms of the monocarboxylic acids used at both ends of the polycondensed ester is 3 or less, the loss on heating of the compound does not increase, and the occurrence of planar failures can be reduced. Moreover, 2 or more types of monocarboxylic acid used for sealing may be mixed. Both ends of the polycondensed ester are preferably sealed with acetic acid or propionic acid, and derivatives of the polycondensed ester in which both ends are acetyl ester residues due to acetic acid sealing are particularly preferred.

  The number average molecular weight of the polycondensed ester is preferably 500 to 3000, more preferably 700 to 2500, and particularly preferably 1000 to 2000. The number average molecular weight of the polycondensed ester is preferably 500 or more from the viewpoint of improving optical expression. Moreover, if it is 3000 or less, compatibility with a cellulose acylate will become high and it will become difficult to produce the bleed out at the time of manufacture and a heat-stretching.

  The number average molecular weight of the polycondensed ester can be measured and evaluated by gel permeation chromatography as described above in the present specification. Further, in the case of a polyester polyol having an unsealed terminal, it can also be calculated from the amount of hydroxyl group per mass (hereinafter referred to as hydroxyl value). The hydroxyl value is determined by measuring the amount (mg) of potassium hydroxide required for neutralizing excess acetic acid after acetylating the polyester polyol.

  The polycondensation ester is a conventional method, either a hot melt condensation method using a polyesterification reaction or transesterification reaction between a dicarboxylic acid component and a diol component, or an interfacial condensation method between an acid chloride of a dicarboxylic acid component and a glycol. Can be easily synthesized. The polycondensation ester is described in detail in Koichi Murai, “Plasticizers, Theory and Applications” (Koshobo Co., Ltd., first published on March 1, 1973). In addition, Japanese Patent Laid-Open Nos. 05-155809, 05-155810, Japanese Patent Laid-Open Nos. 05-97073, 2006-259494, 07-330670, 2006-342227, 2007-003679. It is also possible to use materials described in the above publications.

As a specific example of the polycondensed ester,
Polycondensed ester having a number average molecular weight of 1200, wherein the dicarboxylic acid unit is terephthalic acid / succinic acid = 70/30, the diol unit is ethylene glycol / propylene glycol = 50/50, and the terminal is an acetyl group;
A polycondensed ester having a number average molecular weight of 1200, wherein the dicarboxylic acid unit is terephthalic acid / succinic acid = 50/50, the diol unit is ethylene glycol / propylene glycol = 50/50, and the terminal is an acetyl group;
Polycondensed ester having a number average molecular weight of 800, wherein the dicarboxylic acid unit is terephthalic acid / succinic acid = 70/30, the diol unit is ethylene glycol / propylene glycol = 50/50, and the terminal is an acetyl group;
A dicarboxylic acid unit is terephthalic acid / succinic acid = 60/40, a diol unit is ethylene glycol / propylene glycol = 50/50, a polycondensed ester having a number average molecular weight of 1200 having a terminal acetyl group; and a dicarboxylic acid unit is terephthalic acid / Polycondensed ester with succinic acid = 70/30, diol unit of ethylene glycol / propylene glycol = 50/50, number-average molecular weight 1600 having a terminal acetyl group;
Can be used. The numerical values of dicarboxylic acid and diol indicate the molar ratio.

The optical film of the present invention preferably contains 1 to 12 parts by mass of polycondensation ester (preferably, polycondensation ester of aromatic dicarboxylic acid and aliphatic diol) with respect to 100 parts by mass of cellulose acylate. 10 mass parts is more preferable, and 1-8 mass parts is still more preferable.
In the present invention, the polycondensed ester can be used as a plasticizer, but the polycondensed ester may also serve as a retardation developer.

(Plasticizer as retardation developer)
A plasticizer as a retardation developer may be added to the optical film of the present invention. Although there is no restriction | limiting in particular as a plasticizer as a retardation expression agent, A rod-shaped compound, a disk-shaped compound, the compound represented by the following general formula (II-1), etc. can be used. As the rod-like compound or discotic compound, a compound having at least two aromatic rings is preferably used.

  When a rod-shaped compound is used, the amount of the rod-shaped compound added is preferably 0.1 parts by mass or more and less than 3 parts by mass, and 0.5 parts by mass or more and less than 2 parts by mass with respect to 100 parts by mass of the cellulose acylate component. More preferably. When using the compound represented by a discotic compound or general formula (II-1), the addition amount of the compound represented by a discotic compound or general formula (II-1) is 0 with respect to a cellulose acylate, respectively. It is preferably 1 to 10% by mass, more preferably 0.5 to 7% by mass, and particularly preferably 1 to 4% by mass.

  Since the compound represented by the discotic compound and the general formula (II-1) is superior to the rod-like compound in terms of Rth retardation expression, it is preferably used when a particularly large Rth retardation is required. Two or more types of retardation developing agents may be used in combination. The retardation developing agent preferably has maximum absorption in the wavelength region of 250 to 400 nm, and preferably has substantially no absorption in the visible light region.

The discotic compound will be described. As the discotic compound, a compound having at least two aromatic rings can be used. In the present specification, the “aromatic ring” includes an aromatic hetero ring in addition to an aromatic hydrocarbon ring. The aromatic hydrocarbon ring is particularly preferably a 6-membered ring (that is, a benzene ring).
Specific examples and preferred ranges of the “aromatic ring” are as described in paragraph numbers 0073 to 0077 of JP2013-75401A. The aromatic ring and the linking group may have a substituent, and specific examples of the substituent are as described in paragraph numbers 0078 to 0081 of JP2013-75401A.
The molecular weight of the discotic compound is preferably 300 to 800.
As the discotic compound, a triazine compound represented by the following general formula (I) is preferably used.

In the above general formula (I):
R ²⁰¹ each independently represents an aromatic ring or a heterocyclic ring having a substituent in at least one of the ortho, meta and para positions.
X ²⁰¹ each independently represents a single bond or —NR ²⁰² —. Here, each R ²⁰² independently represents a hydrogen atom, a substituted or unsubstituted alkyl group, an alkenyl group, an aromatic ring group, or a heterocyclic group.

The aromatic ring represented by R ²⁰¹ is preferably phenyl or naphthyl, particularly preferably phenyl. The aromatic ring R ²⁰¹ represents may have at least one substituent at any substitutable position. Examples of the substituent include a halogen atom, hydroxyl group, cyano group, nitro group, carboxyl group, alkyl group, alkenyl group, aryl group, alkoxy group, alkenyloxy group, aryloxy group, acyloxy group, alkoxycarbonyl group, Alkenyloxycarbonyl group, aryloxycarbonyl group, sulfamoyl group, alkyl-substituted sulfamoyl group, alkenyl-substituted sulfamoyl group, aryl-substituted sulfamoyl group, sulfonamide group, carbamoyl, alkyl-substituted carbamoyl group, alkenyl-substituted carbamoyl group, aryl-substituted carbamoyl group, amide Groups, alkylthio groups, alkenylthio groups, arylthio groups and acyl groups.

The heterocyclic group represented by ^R201 preferably has aromaticity. The heterocycle having aromaticity is generally an unsaturated heterocycle, preferably a heterocycle having the largest number of double bonds. The heterocyclic ring is preferably a 5-membered ring, 6-membered ring or 7-membered ring, more preferably a 5-membered ring or 6-membered ring, and most preferably a 6-membered ring. The hetero atom of the heterocyclic ring is preferably a nitrogen atom, a sulfur atom or an oxygen atom, and particularly preferably a nitrogen atom. As the heterocyclic ring having aromaticity, a pyridine ring (2-pyridyl or 4-pyridyl as the heterocyclic group) is particularly preferable. The heterocyclic group may have a substituent. Examples of the substituent of the heterocyclic group are the same as the examples of the substituent of the aromatic ring.
When X ²⁰¹ is a single bond, the heterocyclic group is preferably a heterocyclic group having a free valence on the nitrogen atom. The heterocyclic group having a free valence on the nitrogen atom is preferably a 5-membered ring, 6-membered ring or 7-membered ring, more preferably a 5-membered ring or 6-membered ring, and a 5-membered ring. Is most preferred. The heterocyclic group may have a plurality of nitrogen atoms. Further, the heterocyclic group may have a hetero atom other than the nitrogen atom (for example, O, S).

The alkyl group represented by R ²⁰² may be a cyclic alkyl group or a chain alkyl group, but a chain alkyl group is preferable, and a linear alkyl group is more preferable than a branched chain alkyl group. preferable. The number of carbon atoms in the alkyl group is preferably 1-30, more preferably 1-20, further preferably 1-10, still more preferably 1-8, and 1-6. Most preferred. The alkyl group may have a substituent. Examples of the substituent include a halogen atom, an alkoxy group (for example, methoxy group, ethoxy group) and an acyloxy group (for example, acryloyloxy group, methacryloyloxy group).

The alkenyl group represented by R ²⁰² may be a cyclic alkenyl group or a chain alkenyl group, but is preferably a chain alkenyl group and is more preferably a linear alkenyl group than a branched chain alkenyl group. More preferably it represents a group. The number of carbon atoms in the alkenyl group is preferably 2 to 30, more preferably 2 to 20, still more preferably 2 to 10, still more preferably 2 to 8, 6 is most preferred. The alkenyl group may have a substituent. Examples of the substituent are the same as those of the alkyl group described above.
The aromatic ring group and heterocyclic group represented by R ²⁰² are the same as the aromatic ring and heterocyclic ring represented by R ²⁰¹ , and the preferred range is also the same. The aromatic ring group and the heterocyclic group may further have a substituent, and examples of the substituent are the same as those of the aromatic ring and heterocyclic ring of ^R201 .

  The compound represented by the general formula (I) can be synthesized by a known method such as the method described in JP-A-2003-344655. Details of the retardation developing agent are described on page 49 of published technical bulletin 2001-1745.

  As the discotic compound, it is also preferable to use a compound represented by the following general formula (II-1). In addition, the compound represented with the following general formula (II-1) does not need to be disk shape.

一般式（ＩＩ−１）中、Ｙ¹はメチン基、あるいは−Ｎ−を表す。Ｒａ³¹はアルキル基、アルケニル基、アルキニル基、芳香族環基または複素環基を表す。Ｒｂ³¹、Ｒｃ³¹、Ｒｄ³¹およびＲｅ³¹はそれぞれ独立に水素原子、アルキル基、アルケニル基、アルキニル基、芳香族環基または複素環基を表す。Ｑ²¹は単結合、−Ｏ−、−Ｓ−、あるいは−ＮＲｆ−を示し、Ｒｆは水素原子、アルキル基、アルケニル基、アルキニル基、芳香族環基または複素環基を表し、Ｒａ³¹と連結して環を形成してもよい。Ｘ³¹、Ｘ³²、およびＸ³³は、それぞれ独立に単結合または２価の連結基を表す。Ｘ³⁴は、下記一般式（Ｑ）で表される２価の連結基からなる群から選択される連結基を表す。
一般式（Ｑ）

一般式（Ｑ）中、＊側が上記一般式（ＩＩ−１）で表される化合物中の複素環に置換しているＮ原子との連結部位である。
一般式（ＩＩ−１）におけるアルキル基、アルケニル基、芳香族環基または複素環基は、一般式（Ｉ）におけるアルキル基、アルケニル基、芳香族環基または複素環基と同義である。

In the general formula ^(II-1), Y 1 represents a methine group or-N-,. Ra ³¹ represents an alkyl group, an alkenyl group, an alkynyl group, an aromatic ring group or a heterocyclic group. Rb ^31, Rc ^31, Rd ³¹ and Re ³¹ each independently represent a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aromatic ring group or a heterocyclic group. Q ²¹ represents a single bond, —O—, —S—, or —NRf—, and Rf represents a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aromatic ring group, or a heterocyclic group, and is linked to Ra ^31. To form a ring. X ³¹ , X ³² and X ³³ each independently represent a single bond or a divalent linking group. X ³⁴ represents a linking group selected from the group consisting of divalent linking groups represented by the following general formula (Q).
General formula (Q)

In General Formula (Q), the * side is a linking site with an N atom substituted on the heterocyclic ring in the compound represented by General Formula (II-1).
The alkyl group, alkenyl group, aromatic ring group or heterocyclic group in general formula (II-1) has the same meaning as the alkyl group, alkenyl group, aromatic ring group or heterocyclic group in general formula (I).

一般式（ＩＩ−４）中、Ｙ⁴はメチン基、あるいは−Ｎ−を表す。Ｒａ³⁴はアルキル基、アルケニル基、アルキニル基、芳香族環基または複素環基を表す。Ｑ²⁴は単結合、−Ｏ−、−Ｓ−、あるいは−ＮＲｆ−を示し、Ｒｆは水素原子、アルキル基、アルケニル基、アルキニル基、芳香族環基、または複素環基を表し、Ｒａ³⁴と連結して環を形成してもよい。Ｒ⁶¹、Ｒ⁶²、Ｒ⁶³およびＲ⁶⁴は、それぞれ独立に水素原子、ハロゲン原子、水酸基、カルバモイル基、スルファモイル基、炭素数１から８のアルキル基、炭素数１から８のアルコキシ基、炭素数１から８のアルキルアミノ基、炭素数１から８のジアルキルアミノ基を表す。 Examples of the compound represented by the general formula (II-1) include the general formula (II-2), the general formula (II-4) or the general formula described in paragraph numbers 0092 to 0095 of JP2013-75401A. More preferably, it is represented by the formula (II-5). Especially, it is especially preferable that it represents with the following general formula (II-4).

In the general formula ^(II-4), Y 4 represents a methine group or-N-,. Ra ³⁴ represents an alkyl group, an alkenyl group, an alkynyl group, an aromatic ring group or a heterocyclic group. Q ²⁴ represents a single bond, -O -, - S-, or -NRf- indicates, Rf represents a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aromatic ring group or heterocyclic group, and Ra ³⁴ They may be linked to form a ring. R ⁶¹ , R ⁶² , R ⁶³ and R ⁶⁴ are each independently a hydrogen atom, halogen atom, hydroxyl group, carbamoyl group, sulfamoyl group, alkyl group having 1 to 8 carbon atoms, alkoxy group having 1 to 8 carbon atoms, carbon number An alkylamino group having 1 to 8 carbon atoms and a dialkylamino group having 1 to 8 carbon atoms are represented.

(Durability improver)
The cellulose acylate film of the present invention may contain a compound represented by the following general formula (III).

In general formula (III), R ¹ , R ³ and R ⁵ each independently represents a hydrogen atom, an alkyl group, a cycloalkyl group, an alkenyl group or an aromatic group. The alkyl group, cycloalkyl group, alkenyl group and aromatic group may have a substituent. Provided that any one of R ¹ , R ³ and R ⁵ is an alkyl group or a cycloalkyl group substituted by a group having a ring structure, and the ring structures present in R ¹ , R ³ and R ⁵ are the total 3 or more.

The number of carbon atoms in the alkyl group in the R ^1, R ³ and R ^5, preferably 1 to 20, more preferably 1 to 10, more preferably 1 to 5, particularly preferably 1 to 3, methyl group or ethyl Groups are preferred. However, in the case of an alkyl group substituted by a group having a ring structure, the carbon number is preferably 7 to 20, more preferably 7 to 12, and still more preferably 7 to 10. The ring structure in the alkyl group having a ring structure may be an aromatic ring (including an aromatic heterocyclic ring) or an aliphatic ring, but is preferably an aromatic hydrocarbon group or an aliphatic ring. .
The number of carbon atoms of the cycloalkyl groups represented by R ^1, R ³ and R ⁵ are preferably 3 to 20, more preferably from 3 to 10, more preferably 4 to 8, 5 or 6 is particularly preferred. Specific examples of the cycloalkyl group include, for example, cyclopropyl, cyclopentyl, and cyclohexyl, and cyclohexyl is particularly preferable.
The number of carbon atoms of the alkenyl group in the R ^1, R ³ and R ^5, preferably 2 to 20, more preferably 2 to 10, 2 to 5 is more preferred. For example, vinyl and allyl are mentioned.
The aromatic group in R ¹ , R ³ and R ⁵ may be an aromatic hydrocarbon group or an aromatic heterocyclic group, but is preferably an aromatic hydrocarbon group. 6-20 are preferable, as for carbon number of an aromatic group, 6-16 are more preferable, and 6-12 are more preferable.
As the aromatic group, especially the aromatic hydrocarbon group, phenyl and naphthyl are preferable, and phenyl is more preferable.

Each of the above groups of R ¹ , R ³ and R ⁵ may have a substituent.
The substituent is not particularly limited, and may be an alkyl group (preferably having 1 to 10 carbon atoms such as methyl, ethyl, isopropyl, t-butyl, pentyl, heptyl, 1-ethylpentyl, benzyl, 2-ethoxyethyl, 1 -Carboxymethyl, etc.), alkenyl groups (preferably having 2 to 20 carbon atoms, such as vinyl, allyl, oleyl, etc.), alkynyl groups (preferably having 2 to 20 carbon atoms, such as ethynyl, butadiynyl, phenylethynyl, etc.) A cycloalkyl group (preferably having 3 to 20 carbon atoms, such as cyclopropyl, cyclopentyl, cyclohexyl, 4-methylcyclohexyl, etc.), an aryl group (preferably having 6 to 26 carbon atoms, such as phenyl, 1-naphthyl, 4-methoxyphenyl, 2-chlorophenyl, 3-methylphenyl, etc.), hete A cyclic group (preferably a heterocyclic group having 0 to 20 carbon atoms, wherein the ring-constituting hetero atom is preferably an oxygen atom, a nitrogen atom or a sulfur atom, even if it is a 5- or 6-membered ring and condensed with a benzene ring or a heterocyclic ring. The ring may be a saturated ring, an unsaturated ring, or an aromatic ring, such as 2-pyridinyl, 3-pyridinyl, 4-pyridinyl, 2-imidazolyl, 2-benzimidazolyl, 2-thiazolyl, 2-oxazolyl, etc. ), An alkoxy group (preferably having 1 to 20 carbon atoms, such as methoxy, ethoxy, isopropyloxy, benzyloxy, etc.), an aryloxy group (preferably having 6 to 26 carbon atoms, such as phenoxy, 1-naphthyloxy, 3-methylphenoxy, 4-methoxyphenoxy, etc.).

An alkylthio group (preferably having 1 to 20 carbon atoms, such as methylthio, ethylthio, isopropylthio, benzylthio, etc.), an arylthio group (preferably having 6 to 26 carbon atoms, such as phenylthio, 1-naphthylthio, 3-methylphenylthio, etc. , 4-methoxyphenylthio, etc.), sulfonyl groups (preferably alkyl or aryl sulfonyl groups, preferably having 1 to 20 carbon atoms, such as methylsulfonyl, ethylsulfonyl, benzenesulfonyl, toluenesulfonyl, etc.), acyl groups ( Including alkylcarbonyl group, alkenylcarbonyl group, arylcarbonyl group, and heterocyclic carbonyl group, carbon number is preferably 20 or less, for example, acetyl, pivaloyl, acryloyl, methacryloyl, benzoyl, nicotinoyl, etc.), alkoxy Rubonyl group (preferably having 2 to 20 carbon atoms, for example, ethoxycarbonyl, 2-ethylhexyloxycarbonyl, etc.), aryloxycarbonyl group (preferably having 7 to 20 carbon atoms, for example, phenyloxycarbonyl, naphthyloxycarbonyl, etc.) An amino group (including an amino group, an alkylamino group, an arylamino group and a heterocyclic amino group, preferably having 0 to 20 carbon atoms, such as amino, N, N-dimethylamino, N, N-diethylamino, N- Ethylamino, anilino, 1-pyrrolidinyl, piperidino, morpholinyl, etc.), sulfonamide groups (preferably alkyl or aryl sulfonamide groups, preferably having 0 to 20 carbon atoms, for example, N, N-dimethylsulfonamide, N -Phenylsulfonamide etc.), sulfamoyl group Preferably, it is an alkyl or aryl sulfamoyl group, preferably having 0 to 20 carbon atoms, such as N, N-dimethylsulfamoyl, N-phenylsulfamoyl, etc.), an acyloxy group (preferably having 1 to 20 carbon atoms). , For example, acetyloxy, benzoyloxy, etc.), carbamoyl groups (preferably alkyl or aryl carbamoyl groups, preferably having 1 to 20 carbon atoms, such as N, N-dimethylcarbamoyl, N-phenylcarbamoyl, etc.), acylamino Group (preferably having 1 to 20 carbon atoms, for example, acetylamino, acryloylamino, benzoylamino, nicotinamide, etc.), cyano group, hydroxy group, mercapto group or halogen atom (for example, fluorine atom, chlorine atom, bromine atom, iodine) Atoms).

The above substituent may be further substituted with the above substituent. Examples thereof include a perfluoroalkyl group such as trifluoromethyl, an aralkyl group, and an alkyl group substituted with an acyl group.
In addition, these substituents are applied not only to the substituents that each of R ¹ , R ³ , and R ⁵ may have, but also to the substituents in the compounds described in the present specification.

Here, among the above substituents that each of R ¹ , R ³ and R ⁵ may have, an alkyl group, an aryl group, an alkoxy group, an alkylthio group, an alkylsulfonyl group, a halogen atom, and an acyl group are preferable. , An alkyl group, an aryl group, an alkoxy group, and an acyl group are more preferable, and an alkyl group and an alkoxy group are more preferable.

The compound represented by the general formula (III) is an alkyl group or a cycloalkyl group in which any one of R ¹ , R ³ and R ⁵ is substituted with a group having a ring structure, and any one of them has a ring structure. It is preferable that the group to have is a substituted alkyl group.
Of these, R ⁵ is preferably an alkyl group or a cycloalkyl group substituted with a group having a ring structure.
Here, the ring of the group having a ring structure is a benzene ring, naphthalene ring, cyclopentane ring, cyclohexane ring, nitrogen-containing heteroaromatic ring (for example, pyrrole ring, pyrazole ring, imidazole ring, oxazole ring, thiazole ring, pyridine ring) , Indole ring and isoindole ring) are preferable.
In the compound represented by the general formula (III), at least two of R ¹ , R ³ and R ⁵ are preferably an alkyl group or a cycloalkyl group having a ring structure as a substituent. Furthermore, it is particularly preferable that R ¹ and R ³ are each independently an alkyl group which may have a substituent, an aromatic group which may have a substituent, or a cycloalkyl group.
In the compound represented by the general formula (III), the total of the ring structures present in the substituents of R ¹ , R ³ and R ⁵ is more preferably at most 4.

R ⁵ is preferably an alkyl group or a cycloalkyl group that may be substituted with a ring structure group or an acyl group, an alkyl group substituted with an aryl group, or an alkyl group substituted with an acyl group (preferably an acyl group and an aryl group). Is more preferably an alkyl group substituted with an aryl group or a cycloalkyl group.
Hereinafter, the preferable alkyl group and cycloalkyl group in R ⁵ will be further described.

Among the alkyl groups, examples of the unsubstituted alkyl group include methyl, ethyl, propyl, isopropyl, n-butyl, n-hexyl, 2-ethylhexyl, and n-octyl.
Examples of the alkyl group substituted with a ring structure group include aralkyl groups such as benzyl, phenethyl, 3-phenylpropyl, naphthylmethyl, pyridin-2-ylmethyl, pyridin-3-ylmethyl, pyridin-4-ylmethyl, and indole- 3-ylmethyl is mentioned.

The acyl group in the alkyl group substituted with an acyl group is preferably an alkylcarbonyl group, a cycloalkylcarbonyl group, or an arylcarbonyl group, more preferably a cycloalkylcarbonyl group or an arylcarbonyl group having a ring structure, particularly an arylcarbonyl group. preferable.
Examples of the alkylcarbonyl group include acetyl, propionyl, butyryl, and pivaloyl. Examples of the cycloalkylcarbonyl group include cyclopropylcarbonyl, cyclopentylcarbonyl, and cyclohexylcarbonyl. Examples of the arylcarbonyl group include, for example, , Benzoyl, toluoyl and naphthoyl.
Examples of the alkyl group substituted with an acyl group include a 2-acylethyl group, a 3-acylpropyl group, and a 2-acylpropyl group, with a 2-acylethyl group being preferred.
In the present invention, the alkyl group substituted with an acyl group is preferably an alkyl group substituted with an aryl group together with an acyl group. In this case, the aryl group is preferably a phenyl group.
Examples of the alkyl group substituted with an acyl group and an aryl group include 1-phenyl-2-benzoylethyl and 1-tolyl-2-benzoylethyl.

Examples of the cycloalkyl group include the groups exemplified for R ¹ , R ³ and R ⁵ .

Although the mechanism is not clear, it is considered that the absorption wavelength of the compound represented by the general formula (III) is shortened by suppressing the expansion of the conjugated structure by R ⁵ . By using such a compound, it is considered that it effectively acts with cellulose acylate and contributes to suppression of deterioration during storage at high temperature and high humidity.

Among the compounds represented by the general formula (III), preferred compounds are listed as follows.
A compound in which any one of R ¹ , R ³ and R ⁵ is an alkyl group substituted with an aromatic ring. Among the alkyl groups substituted with an aromatic ring, one or two aryl groups in the alkyl group Preferred is a group substituted (when two aryl groups are substituted, it is preferably substituted on the same carbon atom). Further, an alkyl group substituted with an aryl group and an acyl group (preferably an aryloyl group) is also preferable.
A compound in which any one of R ¹ , R ³ and R ⁵ is a group containing a cycloalkyl group, and preferably the group containing a cycloalkyl group is a cycloalkyl group is preferable.

In the ring structure in the case where “the total number of ring structures present in R ¹ , R ³ and R ⁵ is 3 or more”, the basic skeleton itself of the substituent of R ¹ , R ³ or R ⁵ has a ring structure. In addition to the case, as already exemplified, a form in which the substituent of R ¹ , R ³ or R ⁵ has a ring structure is also included.
The ring structure is preferably a cyclic saturated hydrocarbon structure or an aromatic ring structure (aromatic hydrocarbon structure or aromatic heterocyclic structure). The ring structure may be a condensed ring structure.
When the ring structure is a cyclic saturated hydrocarbon structure, the cyclic saturated hydrocarbon structure is preferably present as a cycloalkyl group having 3 to 20 carbon atoms. More specifically, it is more preferably present as a cyclopropyl group, a cyclopentyl group or a cyclohexyl group, and particularly preferably as a cyclohexyl group.
Moreover, when the said ring structure is an aromatic ring structure, it is preferable that it is an aromatic hydrocarbon structure. The aromatic hydrocarbon structure preferably exists as an aryl group having 6 to 20 carbon atoms. More specifically, it is more preferably present as a phenyl group or a naphthyl group, and particularly preferably as a phenyl group.
The ring structure may have a substituent, but is preferably unsubstituted. When it has a substituent, the preferable range is the same as the substituent which each group of R < ¹ >, R < ³ > and R < ⁵ > may have.

In the compound represented by the general formula (III), R ¹ , R ³ and R ⁵ are more preferably an alkyl group, an alkenyl group or an aryl group. R ¹ , R ³ and R ⁵ each preferably have one or more ring structures, and more preferably each have one ring structure.

The molecular weight of the compound represented by the general formula (III) is preferably 250 to 1200, more preferably 300 to 800, and particularly preferably 350 to 600.
By setting the molecular weight in such a preferable range, it is possible to obtain a highly transparent film excellent in suppressing volatilization from the film in the compound of the present invention.

  Specific examples of the compound represented by the general formula (III) are shown below, but the present invention is not limited thereto.

It is known that the compound represented by the general formula (III) can be synthesized using a barbituric acid synthesis method in which a urea derivative and a malonic acid derivative are condensed. Barbituric acid having two substituents on the nitrogen atom can be obtained by heating N, N 'disubstituted urea and malonic acid chloride, or by heating in combination with an activator such as malonic acid and acetic anhydride. For example, Journal of the American Chemical Society, 61, 1015 (1939), Journal of Medicinal Chemistry, 54, 2409 (2011), Tetrahedron Letters 99, 80 The method described in International Publication No. 2007/150011 pamphlet and the like can be preferably used.
In addition, the malonic acid used for the condensation may be unsubstituted or substituted, and if malonic acid having a substituent corresponding to R ⁵ is used, a barbituric acid is constructed to construct a general formula (III In addition, the condensation of an unsubstituted malonic acid and a urea derivative yields an unsubstituted barbituric acid at the 5-position, which can be modified to modify the general formula (III) You may synthesize | combine the compound represented by these.

As a method for modifying the 5-position, an addition reaction such as a nucleophilic substitution reaction with an alkyl halide or the like or a Michael addition reaction can be used. In addition, a method in which an alkylidene or arylidene compound is produced by dehydration condensation with an aldehyde or a ketone and then a double bond is reduced can be preferably used. For example, a reduction method using zinc is described in Tetrahedron Letters, 44, 2203 (2003), and a reduction method using catalytic reduction is Tetrahedron Letters, 42, 4103 (2001) or Journal of the American Chemical, 119, 12849 (1997), a reduction method using NaBH ₄ is described in Tetrahedron Letters, 28, 4173 (1987), etc., respectively. These are all synthetic methods that can be preferably used in the case of having an aralkyl group at the 5-position or a cycloalkyl group.
The method for synthesizing the compound represented by the general formula (III) used in the present invention is not limited to the above.

The content of the compound represented by the general formula (III) in the cellulose acylate film is not particularly limited, but is preferably 0.1 to 10 parts by mass with respect to 100 parts by mass of cellulose acylate. More preferably, it is 2-9 mass parts, and it is especially preferable that it is 0.3-8 mass parts.
By making the addition amount of the compound represented by the general formula (III) in the above range, it is possible to effectively reduce the moisture permeability and to suppress the generation of haze.

  In the case of co-casting, an embodiment in which the compound represented by the general formula (III) is added only to the skin layer is also preferably used in terms of adjusting the optical characteristics. The preferable range of the content when added only to the skin layer is the same as the above content.

  The scope of the present invention includes a cellulose acylate film obtained by adding the compound represented by the general formula (III) in the form of a hydrate, a solvate or a salt. In the present invention, the hydrate may contain an organic solvent, and the solvate may contain water. That is, “hydrate” and “solvate” include mixed solvates containing both water and organic solvents.

Examples of the solvent included in the solvate include any common organic solvent. Specifically, alcohol (for example, methanol, ethanol, 2-propanol, 1-butanol, 1-methoxy-2-propanol, t-butanol), ester (for example, ethyl acetate), hydrocarbon (aliphatic or aromatic) Any of hydrocarbons may be used, and examples thereof include toluene, hexane, heptane), ether (eg, diethyl ether, tetrahydrofuran), nitrile (eg, acetonitrile), ketone (eg, acetone, 2-butanone) and the like. Preferred are alcohol solvates, and more preferred are methanol, ethanol, 2-propanol, and 1-butanol. These solvents may be a reaction solvent used in the synthesis of the compound represented by the general formula (III), a solvent used in crystallization purification after synthesis, or a mixture thereof. There may be.
Two or more kinds of solvents may be included at the same time, or water and a solvent (for example, water and alcohol (for example, methanol, ethanol, t-butanol), etc.) may be used.

  Salts include acid addition salts formed with inorganic or organic acids. Examples of the inorganic acid include hydrohalic acid (hydrochloric acid, hydrobromic acid), sulfuric acid, phosphoric acid and the like. Examples of organic acids include acetic acid, trifluoroacetic acid, oxalic acid, and citric acid. Alkanesulfonic acid (methanesulfonic acid), arylsulfonic acid (benzenesulfonic acid, 4-toluenesulfonic acid, 1,5-naphthalenedisulfonic acid) Acid).

  A salt may also have an acidic moiety present in the parent compound such as a metal ion (eg, an alkali metal salt, such as a sodium or potassium salt, an alkaline earth metal salt, such as a calcium or magnesium salt, an ammonium salt, an alkali metal ion, alkaline earth Examples include, but are not limited to, salts formed when substituted with metal ions or aluminum ions, or prepared with organic bases (ethanolamine, diethanolamine, triethanolamine, morpholine, piperidine). Of these, sodium salts and potassium salts are preferred.

<Other additives>
If necessary, a matting agent can be added to the optical film of the present invention. The matting agent is not particularly limited as long as it is a material exhibiting a function of preventing scratches during handling or deterioration of transportability, and an inorganic compound or an organic compound matting agent can be used.
Preferred specific examples of the inorganic compound matting agent include silicon-containing inorganic compounds (eg, silicon dioxide, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, etc.), titanium oxide, zinc oxide, Aluminum oxide, barium oxide, zirconium oxide, strongtium oxide, antimony oxide, tin oxide, tin oxide / antimony, calcium carbonate, talc, clay, calcined kaolin, calcium phosphate, etc. are preferred, and more preferably inorganic compounds containing silicon and zirconium oxide However, since the turbidity of the cellulose acylate film can be reduced, silicon dioxide is particularly preferably used. As the silicon dioxide fine particles, for example, commercially available products having a trade name such as Aerosil (registered trademark) R972, R974, R812, 200, 300, R202, OX50, TT600 (above Nippon Aerosil Co., Ltd.) can be used. . As the fine particles of zirconium oxide, for example, those commercially available under trade names such as Aerosil R976 and R811 (manufactured by Nippon Aerosil Co., Ltd.) can be used.

  Preferable specific examples of the organic compound matting agent are, for example, polymers such as silicone resin, fluorine resin and acrylic resin, and among them, silicone resin is preferably used. Among silicone resins, those having a three-dimensional network structure are particularly preferable. For example, Tospearl (registered trademark) 103, Tospearl 105, Tospearl 108, Tospearl 120, Tospearl 145, Tospearl 3120, and Tospearl 240 (above Toshiba Silicone Co., Ltd.) A commercial product having a trade name such as “made” can be used.

  The method for adding the matting agent to the cellulose acylate solution is not particularly limited. For example, an additive may be contained at the stage of mixing cellulose acylate and a solvent, or an additive may be added after preparing a mixed solution with cellulose acylate and a solvent. Furthermore, a matting agent may be added and mixed immediately before casting the dope, and the mixing can be performed by installing a screw type mixer on-line. Specifically, a static mixer such as an in-line mixer is preferable, and as the in-line mixer, for example, a static mixer SWJ (Toray static type in-pipe mixer Hi-Mixer) (manufactured by Toray Engineering) or the like is preferable. A preferable mode of mixing the matting agent is as described in paragraph No. 0127 of JP2013-75401A.

  The optical film of the present invention contains a matting agent in at least one of the two skin layers, and is resistant to scratches by reducing the coefficient of friction on the film surface. From the viewpoint of preventing film breakage, it is particularly preferable to contain a matting agent in both of the two skin layers from the viewpoint of effectively reducing scratch resistance and creaking.

  The content of the matting agent in the optical film of the present invention is preferably 0.01 to 5.0% by mass, more preferably 0.03 to 3.0% by mass, and particularly preferably 0.05 to 1.0% by mass. By setting it as the above range, it is possible to realize the effect of reducing creaking and scratch resistance without increasing the haze of the optical film.

[Method for producing optical film]
The method for producing an optical film of the present invention comprises a core layer forming dope containing cellulose acylate, a first skin layer forming dope containing cellulose acylate, and a second skin layer forming dope containing cellulose acylate. And a step of drying the dope on the support after the co-casting.
<Dope manufacturing method>
In the present invention, a solution (dope) obtained by dissolving cellulose acylate in an organic solvent by a solution casting method is used as a core layer forming dope, a first skin layer forming dope, and a second skin layer forming dope. Thus, an optical film can be manufactured.
The organic solvent is a solvent selected from ethers having 3 to 12 carbon atoms, ketones having 3 to 12 carbon atoms, esters having 3 to 12 carbon atoms, and halogenated hydrocarbons having 1 to 6 carbon atoms. It is preferable to contain. The ether, ketone and ester may have a cyclic structure. A compound having two or more functional groups of ether, ketone and ester (that is, —O—, —CO— and —COO—) can also be used as the organic solvent. The organic solvent may have another functional group such as an alcoholic hydroxyl group. In the case of an organic solvent having two or more 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 ether having 3 to 12 carbon atoms include diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolane, tetrahydrofuran, anisole and phenetole.
Examples of the ketone having 3 to 12 carbon atoms include acetone, methyl ethyl ketone, diethyl ketone, diisobutyl ketone, cyclohexanone and methylcyclohexanone.
Examples of the ester having 3 to 12 carbon atoms include ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate and pentyl acetate.
Examples of the organic solvent having two or more kinds of functional groups include 2-ethoxyethyl acetate, 2-methoxyethanol and 2-butoxyethanol.
The number of carbon atoms of the halogenated hydrocarbon is preferably 1 or 2, and most preferably 1. The halogen of the halogenated hydrocarbon is preferably chlorine. The proportion of halogen atoms substituted by halogen in the halogenated hydrocarbon is preferably 25 to 75 mol%, more preferably 30 to 70 mol%, and more preferably 35 to 65 mol%. More preferably, it is most preferable that it is 40-60 mol%. Methylene chloride is a typical halogenated hydrocarbon.
Two or more organic solvents may be mixed and used.

  The solution can be prepared by using a dope preparation method and apparatus in a normal solution casting method. In the case of a general method, it is preferable to use a halogenated hydrocarbon (particularly, methylene chloride) as the organic solvent.

The amount of cellulose acylate is preferably adjusted so as to be contained in the obtained solution in an amount of 10 to 40% by mass, and more preferably 10 to 30% by mass. Arbitrary additives may be added to the organic solvent.
The solution can be prepared by stirring the cellulose acylate and the organic solvent at room temperature (0 to 40 ° C.). High concentration solutions may be stirred under pressure and heating conditions. Specifically, cellulose acylate and an organic solvent are placed in a pressure vessel and sealed, and stirred while heating to a temperature not lower than the boiling point of the solvent at normal temperature and in a range where the solvent does not boil. The heating temperature is usually 40 ° C. or higher, preferably 60 to 200 ° C., and more preferably 80 to 110 ° C.

Each component may be roughly mixed in advance and then put into a container, or may be 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 a container. The prepared dope may be taken out of the container after cooling, or may be cooled using a heat exchanger or the like after taking out.

<Solution casting method>
A method for producing a film using the dope produced by the above method will be described. FIG. 1 is a schematic view showing a film casting equipment. However, although the present invention may be described below with reference to FIGS. 1 to 4, the present invention is not limited to the form shown in FIG. 1.

(Casting)
The production method of the present invention includes a step of casting a dope containing cellulose acylate on a support. The equipment of FIG. 1 showing an example of a film casting film-forming equipment includes a co-casting die 21, a casting band stretched around a rotating roller, an initial drying device 22 that applies drying air immediately after casting, and A plurality of drying devices 23 are provided. The drying device 23 will be described later with reference to another drawing. Further, it is preferable that a tenter-type dryer, an edge-cutting device, a drying chamber, a cooling chamber, a winding chamber, and the like are arranged downstream (not shown). The tenter dryer may be further installed after the drying chamber.

The material of the co-casting die 21 is preferably a precipitation hardening type stainless steel, and its thermal expansion coefficient is preferably 2 × 10 ⁻⁵ (° C. ⁻¹ ) or less. In a forced corrosion test with an electrolyte aqueous solution, it has a corrosion resistance substantially equivalent to that of SUS316, and even when immersed in a mixture of dichloromethane, methanol, and water for 3 months, it does not cause pitting (perforation) at the gas-liquid interface. What has corrosivity can also be used as a material of this co-casting die 21. In addition, it is preferable to produce the co-casting die 21 by grinding a material that has passed one month or more after casting. Thereby, it is possible to prevent the dope from flowing uniformly in the co-casting die 21 and causing streaks or the like in the casting film described later.

  The finishing accuracy of the wetted surface of the co-casting die 21 is preferably 1 μm or less in terms of surface roughness and the straightness is 1 μm / m or less in any direction. The clearance of the slit of the co-casting die 21 can be adjusted within a range of 0.5 to 3.5 mm by automatic adjustment. About the corner | angular part of the liquid-contact part of the lip tip of the co-casting die 21, the R is 50 micrometers or less over the whole width. Moreover, it is preferable that the shear rate inside the co-casting die 21 is adjusted to be 1 to 5000 (1 / second).

Although the width | variety of the co-casting die 21 is not specifically limited, It is preferable that it is 1.1 to 2.0 times the width | variety of the film used as a final product. Moreover, it is preferable to attach a temperature controller to the co-casting die 21 so that the temperature during film formation is maintained at a predetermined temperature, and it is preferable to use a coat hanger type for the co-casting die 21. . Here, in the production method of the present invention, the casting width is preferably 1900 mm or more, and may be 2100 mm or more in some cases.
Moreover, in the manufacturing method of this invention, it is preferable to cast so that a dry film thickness may be set to 3-50 micrometers. Therefore, it is more preferable that the thickness adjusting bolts (heat bolts) are provided at predetermined intervals in the width direction of the co-casting die 21 and the automatic thickness adjusting mechanism using the heat bolt is provided in the co-casting die 21. The heat bolt is preferably formed by setting a profile in accordance with a pumping amount according to a preset program. The pump is preferably a high precision gear pump.

  At this time, feedback control may be performed by an adjustment program based on the profile of the thickness gauge. Examples of the thickness gauge include an infrared thickness gauge, but are not particularly limited. The thickness difference between any two points in the width direction of the product film excluding the casting edge is preferably adjusted to within 1 μm so that the difference between the minimum value and the maximum value in the width direction thickness is 3 μm or less. It is more preferable to adjust to 2 μm or less. In addition, it is preferable to use the one whose thickness accuracy is adjusted to ± 1.5 μm or less.

More preferably, a cured film is formed at the lip end of the co-casting die 21. A method for forming the cured film is not particularly limited, and examples thereof include ceramic coating, hard chrome plating, and a nitriding method. In the case of using ceramics as the cured film, it can be ground, has low porosity, is not brittle and excellent in corrosion resistance, and has good adhesion to the co-casting die 21, but has good adhesion to the dope. Is preferable. Specific examples include tungsten carbide (WC), Al ₂ O ₃ , TiN, and Cr ₂ O ₃ , among which WC is preferable. This WC coating can be performed by a thermal spraying method.

  A solvent supply device (not shown) is preferably attached to the slit end of the co-casting die 21 in order to prevent the outflowing dope from locally drying and solidifying. Moreover, it is preferable to supply the solvent which solubilizes the dope to both ends of the casting bead, the end of the die slit, and the periphery of the three-phase contact line formed by the outside air. As this solvent, for example, a mixed solvent of 86.5 parts by mass of dichloromethane, 13 parts by mass of acetone, and 0.5 parts by mass of n-butanol is preferably used. At this time, it is preferable to supply at 0.1 to 1.0 ml / min to one side of the end portion, because mixing of foreign matters into the cast film can be prevented. In addition, as a pump which supplies this liquid, it is preferable to use a pump with a pulsation rate of 5% or less.

  Below the co-casting die 21, a casting band stretched around the rotating roller 24 is provided. The rotating roller 24 is rotated by a driving device (not shown), and the casting band travels endlessly with this rotation. The casting band is preferably one that can move at a moving speed, that is, a casting speed of 10 to 200 m / min, more preferably one that can move at 20 m / min or more, and movement at 40 m / min or more. It is particularly preferable that it is possible. In order to set the surface temperature of the casting band to a predetermined value, it is preferable that a heat transfer medium circulation device is attached to the rotating roller 24. The casting band is preferably one whose surface temperature can be adjusted to -20 to 40 ° C. A heat transfer medium flow path (not shown) is formed in the rotating roller 24 used in the present embodiment, and the heat transfer medium maintained at a predetermined temperature passes through it. The temperature of the rotating roller 24 is held at a predetermined value.

  The width of the casting band is not particularly limited, but it is preferable to use a dope having a width of 1.1 to 2.0 times the casting width, and the length is 20 to 200 m. Is preferably 0.5 to 2.5 mm and polished so that the surface roughness is 0.05 μm or less. The casting band 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 that the thickness unevenness of the entire casting band is 0.5% or less.

  The co-casting die 21 and the casting band are preferably housed in the casting chamber. The casting chamber is preferably provided with a temperature control facility for keeping the internal temperature at a predetermined value and a condenser (condenser) for condensing and recovering the volatile organic solvent. And it is preferable that the collection | recovery apparatus for collect | recovering the condensed organic solvents is provided in the exterior of the casting chamber. It is preferable to arrange a decompression chamber for controlling the pressure of the back surface of the casting bead formed from the co-casting die to the casting band.

(Dry)
The production method of the present invention preferably comprises:
(1) A step of drying the dope on the support after co-casting (initial drying step);
(2) The step of drying the dope dried in (1) above at the drying temperature T1 (° C.) on the surface of the dope not in contact with the support and the drying temperature T2 on the surface of the dope in contact with the support (medium-term drying step And (3) a step of further drying the dope dried in the above (2) (late drying step):
It can be set as the method containing.
The drying (1) is preferably performed at a drying temperature of 30 to 50 ° C., and can be performed by applying a drying air at a temperature of 30 to 50 ° C. It is preferable to transfer to the step (2) after drying to 300 to 400% DB in the amount of residual solvent by drying at the above temperature.
In the drying (2), the drying temperature T1 (° C.) of the dope surface not in contact with the support and the drying temperature T2 (° C.) of the dope surface in contact with the support are 20 ≦ T2−T1 ≦ 40. It is preferable to perform drying under conditions that satisfy the above conditions, and it is more preferable to perform the above drying under conditions that satisfy 25 ≦ T2−T1 ≦ 35. It is preferable to move to step (3) after drying to 80% DB by residual solvent amount by drying at the above temperature.
The drying (3) is preferably performed at 80 to 150 ° C.

Specifically, a dope containing a polymer and a solvent is cast on a support that runs endlessly to form a cast film, and then the cast film is peeled off from the support to contain a solvent. In the cellulose acylate manufacturing method of forming a film and drying the film, after the casting film is formed on the support, drying to dry the casting film from the surface, and the non-casting film side of the support It is preferable that drying is performed in which the casting film is dried by heating the support from the back surface while adjusting the drying temperature of the heating device disposed on the back surface so as to satisfy the above-described conditions.
Here, when the thermal conductivity of the support is high, the drying temperature T2 on the dope surface in contact with the support (hereinafter also referred to as the back surface drying temperature T2) may be treated as the support back surface temperature.
The drying temperature T1 on the surface of the dope not in contact with the support is equal to the surface drying air temperature T1.
The drying temperature T1 means the temperature of the air in contact with the surface of the dope. Even if the air having the surface drying air temperature T1 (hot air) is intentionally blown to the dope surface, the air is not moved intentionally (air blowing). (Without) the temperature near the surface of the dope may be controlled to the surface drying air temperature T1. Among them, it is preferable to intentionally blow air having a surface drying air temperature T1 (hot air) to the dope surface from the viewpoint of efficient drying.
0-30 degreeC is preferable, as for the drying temperature T1 (namely, surface drying wind temperature T1) of the dope surface which is not in contact with a support body, 10-30 degreeC is more preferable, and 15-25 degreeC is further more preferable.
40-70 degreeC is preferable and, as for the drying temperature T2 of the dope surface which is in contact with the support body, 40-60 degreeC is more preferable.

  FIG. 1 shows a schematic view around the casting band. A plurality of drying devices 23 are provided side by side along the casting band. Details of the drying device 23 are shown in FIG. It is preferable that a slit nozzle 27 for blowing dry air and an exhaust means 28 are provided on the casting film side (front surface) and the non-casting film side (back surface) of the casting band, respectively. The slit nozzle 27 preferably has a structure attached to the chamber box so that the wind speed distribution is uniform. Each drying device 23 is preferably provided with two support rollers 26 each. The entire drying apparatus is preferably covered with a heat insulating wall 30 so that the internal temperature can be kept constant.

  As described above, in the present invention, the surface drying air temperature T1 means the temperature of the air in contact with the dope surface, and is not limited to an aspect in which the drying air having the surface drying air temperature T1 is blown to the dope surface. Among them, in the manufacturing method of the present invention, the drying air having the above-mentioned surface drying air temperature T1 is supplied from the slit nozzle (surface side) 27 to the surface side of the casting band in FIG. It is preferable to perform a drying step of spraying the surface of the cast film to promote drying of the cast film.

  The temperature of the drying air blown from the slit nozzle 27 (drying temperature, that is, the temperature of each heating zone) is adjusted by the temperature adjustment device 29 so as to satisfy a predetermined temperature range. In the present invention, it is preferable to control the drying temperature so that the temperature T2 of the drying air on the back surface is higher by 20 ° C. or more and 40 ° C. or less than the temperature T1 of the drying air on the surface. This drying step is preferably performed in the first half of the cast film, and further in the cast film (also referred to as a web, which means a state before the cast dope is completely dried and formed into a film). The residual solvent amount is preferably 300 to 400% DB (the definition of% DB will be described later). It can measure by installing a thermometer in each heating zone. A thermometer is not specifically limited, A well-known thing can be used.

  Although the example of the slit wind blowing system was shown as the drying apparatus 23, there exist a parallel flow system (FIG. 3), a counterflow system (FIG. 4), etc., and it is good also as a structure which combined these.

In the production method of the present invention, the drying step is preferably performed after casting the dope until the residual solvent amount R represented by the following formula of the dope becomes 80% DB.
R (% DB) = {(film thickness during drying−film thickness of completely dried film) / film thickness of completely dried film} × 100%,
Here, the completely dried film refers to a film that is 0.1% DB or less when the residual material R is calculated again by the above formula.

  More specifically, the residual solvent amount of the casting film is the residual solvent amount of all the solvents in the casting film. Usually, this residual solvent amount may be measured on a dry basis (mass basis), where x is the film mass at the time of sampling and y is the mass after drying the sampling film {(xy) / It is calculated with a value calculated by y} × 100. However, the dry weight standard is the content of the solvent when the mass when the dope is completely dried and solidified is 100%. However, in the production method of the present invention, at the time of film formation, it is preferable to collect a part of the cast film as a sample and finish the drying process from the back and front of the dope at a specific timing. Instead of the measured value, the residual solvent amount is determined on the basis of the film thickness by the above method. The residual solvent amount of the cast film obtained by the above method employed in the present invention is almost the same value as the residual solvent amount based on a normal dry amount.

(Peeling)
The film dried by the drying device 23 is peeled off from the casting band at the peeling point and sent to an arbitrary downstream process. At the time of peeling, it is preferable that the film is supported by a roller for peeling (hereinafter referred to as a peeling roller), and the peeling position where the casting film is peeled off from the casting band is kept constant. The stripping roller may be a driving roller that includes driving means and rotates in the circumferential direction. The stripping is preferably performed with a casting band on a rotating roller that supports the casting band. When the casting band circulates and returns from the stripping position to the casting position, a new dope is cast again.

(Stretching)
The film peeled from the support can be stretched.
Stretching can be 5% or more and 40% or less in the width direction (lateral direction) orthogonal to the longitudinal direction (corresponding to the transport direction for transporting the film). Furthermore, biaxial stretching combined with stretching in a direction that does not coincide with the width direction (for example, the longitudinal direction) may be used. The stretch ratio in the width direction is 5 to 40%, preferably 8 to 40%. When performing biaxial stretching, it is preferable to stretch in the width direction after stretching in the film longitudinal direction. The stretching ratio in the longitudinal direction is preferably 0 to 20%, more preferably 0 to 15%, and still more preferably 0 to 10%. The stretching ratio in the width direction is 5 to 40%, and preferably 8 to 40%. As used herein, “stretch rate (%)” means that obtained by the following formula regarding the length of the film in the stretching direction.
Stretch rate (%) = 100 × {(length after stretching) − (length before stretching)} / (length before stretching).

  Solvent recovery method, film recovery from co-casting die, decompression chamber, support structure, etc., co-casting, peeling method, stretching, drying conditions of each process, handling method, curl, winding method after flatness correction The method is described in detail in paragraphs [0617] to [0889] of JP-A-2005-104148, and these descriptions can also be applied to the present invention.

<Surface treatment>
In the method for producing an optical film of the present invention, at least one surface may be surface-treated. The surface treatment is preferably at least one of vacuum glow discharge treatment, atmospheric pressure plasma discharge treatment, ultraviolet irradiation treatment, corona discharge treatment, flame treatment, acid treatment or alkali treatment.

[Polarizer]
The optical film of the present invention can be used as a polarizing plate film. The polarizing plate can be produced by laminating and laminating the optical film of the present invention on at least one surface of the polarizer. A conventionally known polarizer can be used. For example, a hydrophilic polymer film such as a polyvinyl alcohol film is treated with a dichroic dye such as iodine and stretched. The bonding of the cellulose acylate film and the polarizer is not particularly limited, but can be performed with an adhesive made of an aqueous solution of a water-soluble polymer. The water-soluble polymer adhesive is preferably a completely saponified polyvinyl alcohol aqueous solution. The thickness of the polarizer is not particularly limited, but is generally 5 μm to 30 μm, preferably 5 μm to 20 μm, and more preferably 5 to 15 μm.

  The optical film of the present invention is composed of protective film / polarizer / protective film / liquid crystal cell / optical film of the present invention / polarizer / protective film, or protective film / polarizer / optical film of the present invention / liquid crystal cell / present. It can be preferably used in the constitution of the optical film / polarizer / protective film of the invention.

  As the protective film, any film can be used as long as it has a function as a polarizing plate protective film. As a material constituting the polarizing plate protective film, for example, a thermoplastic resin excellent in transparency, mechanical strength, thermal stability, moisture barrier property, isotropy and the like is used. Specific examples of such thermoplastic resins include cellulose resins such as triacetyl cellulose, polyester resins, polyethersulfone resins, polysulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, (meth) acrylic resins, cyclic Examples thereof include polyolefin resins (norbornene resins), polyarylate resins, polystyrene resins, polyvinyl alcohol resins, and mixtures thereof. In addition, a polarizing plate protective film is usually bonded to the polarizer by an adhesive layer.

(Wave curl on polarizing plate)
The curl is the end of the polarizing plate when the polarizing plate laminated in the order of the protective film, protective film, polarizer, optical film, adhesive, and separate film is placed in a high humidity environment. As a result of the water absorption, the end of the polarizing plate is deformed by the hygroscopic expansion and becomes a wave-like phenomenon.

  It was found that when the polarizer has a thickness of 5 to 15 μm and a biaxially stretched optical film is used, curling of the polarizing plate can be suppressed. Although the mechanism is not clear, when the thickness of the polarizer is 5 to 15 μm, the expansion force is suppressed, and when an optical film stretched biaxially is used, the optical film acts to suppress the expansion of the polarizer. It seems to be.

[Liquid Crystal Display]
The polarizing plate of the present invention can be used for liquid crystal display devices in various display modes. As the display mode of the liquid crystal display device, TN (Twisted Nematic), IPS (In-Plane Switching Crystal), FLC (Ferroelectric Liquid Crystal), AFLC (Anti-Ferroelectric Liquid Crystal), OCB (Optical STP). ), VA (Vertical Aligned) and HAN (Hybrid Aligned Nematic), and the display mode of the liquid crystal display device of the present invention is not particularly limited. Particularly preferably, the liquid crystal display device of the present invention is a VA mode liquid crystal display device.

The present invention will be described more specifically with reference to the following examples, but the present invention is not limited to the examples.
<Preparation of cellulose acetate>
7.8 parts by mass of sulfuric acid was added to 100 parts by mass of cellulose, and acetic acid 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 acyl group was adjusted by adjusting the amount of acetic acid. In addition, aging was performed at 40 ° C. after acylation. Further, the low molecular weight component of the cellulose acylate was removed by washing with acetone.
As a result, cellulose acetate having an average acetyl substitution degree of 2.43 and cellulose acetate having an average acetyl substitution degree of 2.81 were obtained.

<Preparation of cellulose acylate dope for core layer>
The following composition was put into a mixing tank and stirred to dissolve each component to prepare a cellulose acylate dope for the core layer.
Cellulose acetate (average acetyl substitution degree 2.43) 100.0 parts by mass plasticizer (type and amount shown in Table 1)
Methylene chloride 403.0 parts by mass Methanol 60.2 parts by mass

<Preparation of cellulose acylate dope for skin layer>
The following composition was put into a mixing tank and stirred to dissolve each component to prepare a cellulose acylate dope for a skin layer.
Cellulose acetate (average acetyl substitution degree 2.81) 100.0 parts by mass plasticizer (type and amount shown in Table 1)
Methylene chloride 388.0 parts by mass Methanol 58.0 parts by mass

<Preparation of matting agent dispersion>
The following composition was charged into a disperser and stirred to dissolve each component to prepare a matting agent dispersion.
Matting agent (Aerosil (registered trademark) R972) 0.2 parts by mass Methylene chloride 72.4 parts by mass Methanol 10.8 parts by mass Cellulose acylate dope for skin layer 10.3 parts by mass

<Preparation of cellulose acylate dope for skin layer added with matting agent>
The cellulose acylate dope for skin layer prepared above was mixed with a matting agent dispersion at the ratio shown below to prepare a cellulose acylate dope for skin layer to which a matting agent was added.
Cellulose acylate dope for skin layer 100.0 parts by weight Matting agent dispersion 7.1 parts by weight

<Film formation of cellulose acetate film>
(Casting and drying)
Using the band casting machine, the above-prepared cellulose acylate dope for the core layer and the cellulose acylate dope for the skin layer to which the matting agent was added were used for the first skin layer / core layer / second skin layer 3 Co-cast to form a layer structure. Here, by adjusting the casting amount of each dope, the core layer was made the thickest, and as a result, the film thickness after stretching was subjected to simultaneous multilayer casting so that the film thickness shown in Table 4 was obtained. . In each example and comparative example, the film thickness of the first skin layer and the second skin layer was 1.5 μm, and the remainder was the core layer.

  In the initial drying zone 22 immediately after the start of casting, a drying wind of 10 m / s was applied at 40 ° C. The front-and-back drying in the medium-term drying zone 31 is performed by blowing dry air from the two-dimensional nozzle to the band (support) from the direction perpendicular to both the surface drying and the back surface drying, and the wind speed of each drying air is 10 m / s. Was dried under the conditions shown in Table 1 below. At this time, drying was performed while controlling the residual solvent amount to be 80% DB when it passed through the intermediate drying zone 31 in the first half of the band casting machine of FIG. Thereafter, the film was further dried in the late drying zone 41, and the cellulose ester film cast and rotated 50 cm before the end point of the casting part was peeled off from the drum, and then both ends were clipped with a pin tenter. In peeling, in Examples 1 to 13 and Comparative Examples 1 to 8, stretching in the MD direction was not performed, and in Example 14, 5% stretching was performed in the MD direction. Then, after transversely stretching at a stretching ratio of 8% using a tenter under the condition of 140 ° C., the clip was removed and dried at 130 ° C. for 20 minutes, and then Examples 1 to 13 and Comparative Examples 1 to 1 were further performed under the condition of 175 ° C. 8 was a stretch rate of 25%, and Example 14 was stretched transversely at a stretch rate of 30% to produce a cellulose acylate film. The film thickness was measured as described above in this specification.

  In Table 1, the amount of plasticizer indicates parts by mass with respect to 100 parts by mass of cellulose acetate.

<Quantification of plasticizer>
(Quantification of amount of polycondensed ester in skin layer)
A surface layer from the surface of the film to a depth of 1 μm was scraped to obtain a 0.05 g sample.
The sample was dissolved in a mixed solution having a ratio of methylene chloride and methanol of 92: 8, and absorbance at a wavelength of 286 nm was measured with an ultraviolet-visible near-infrared spectrophotometer (UV-3150, manufactured by Shimadzu Corporation). The polycondensed ester concentration was determined by obtaining a calibration curve.

(Quantification of plasticizer A in skin layer)
A surface layer from the surface of the film to a depth of 1 μm was scraped to obtain a 0.05 g sample. The sample was dissolved in a mixed solution having a ratio of methylene chloride and methanol of 92: 8, and the absorbance at a wavelength of 250 nm was measured with an ultraviolet-visible near-infrared spectrophotometer (UV-3150, Shimadzu Corporation). The additive A concentration was determined by obtaining a calibration curve.

(Quantification of plasticizer B in skin layer)
A 0.05 g sample was taken by scraping the surface layer from the surface of the film to a depth of 1 μm. The sample was dissolved in a mixed solution of methylene chloride and methanol in a ratio of 92: 8, and high performance liquid chromatography (HPLC) measurement was performed to calculate the area.
<HPLC conditions>
Column: ODS-80TS (Tosoh Corporation) 4.6mmφ × 150mm 5μm
Column temperature: 40 ° C
Solution A: Distilled water (Acetic acid, triethylamine 0.1% by volume each)
Solution B: acetonitrile (contains 0.1% by volume of acetic acid and triethylamine)

Flow rate: 1.0 ml / min Measurement time: 7.5 to 10.3 min Detection wavelength: 270 nm
Injection volume: 10 μL

(Quantification of plasticizer C in skin layer)
The film is measured using attenuated total reflection infrared spectroscopy (ATR-IR method). JP Hobbs, CSP Sung (JP Hobbs, CSPSung, K. Krishan, and S. Hill, Macromolecules, 16, 193, (1983)) can be referred to for the calculation method.
Using Nicolet 6700 (manufactured by Thermo Fisher Scientific Co., Ltd.), the reflected light intensity of 1689 [cm-1] of the reflected light spectrum when incident on each of the air surface and the band surface of the film was measured under the following measurement conditions. The concentration of additive C was determined by obtaining a calibration curve.
<ATR-IR measurement conditions>
Prism: Germanium incident angle: 45 °
Number of reflections: 32 times Measurement range: 400cm-1 to 4000cm-1

  The results of the above measurements are shown in Table 4 below.

<Retardation>
With respect to the obtained film, Re and Rth were measured at wavelengths of 450 nm, 550 nm, and 630 nm by KOBRA 21ADH (manufactured by Oji Scientific Instruments) by the above method. The results obtained and Re (450) / Re (630) were calculated and listed in Table 6.

<Brittleness>
The obtained film was cut into 35 mm × 140 mm, adjusted for 2 hours under conditions of a temperature of 25 ° C. and a relative humidity of 60%, and then the flexibility of the film due to cracks or cracks generated when rolled into a cylinder with a diameter of 40 mm. Was examined and evaluated. The results are shown in Table 6 as “brittle”. Symbols in the column of “brittleness” in the table mean the following. If it is A or B, there is no practical problem.
A: No cracks or cracks B: Cracks can be confirmed with a microscope C: Film cracks can be visually confirmed

<Polarizing plate>
(Preparation of polarizing plate)
The surface of the first skin layer of the film produced above was subjected to alkali saponification treatment. It was immersed in a 1.5 mol / L aqueous sodium hydroxide solution at 55 ° C. for 2 minutes, washed in a water bath at room temperature, and neutralized with 0.05 mol / L sulfuric acid at 30 ° C. Again, it was washed in a water bath at room temperature and further dried with hot air at 100 ° C. Subsequently, a roll-shaped polyvinyl alcohol film having a thickness of 80 μm was continuously stretched 5 times in an aqueous iodine solution and dried to obtain a polarizer having a thickness of 20 μm. Using the 3% by weight aqueous solution of polyvinyl alcohol (Kuraray PVA-117H) as an adhesive, the above-mentioned alkali saponified cellulose acylate film sample and the same alkali saponified Fujitac TD80UL (manufactured by Fujifilm) were prepared. The polarizer is sandwiched with the saponified surface facing the polarizer, and an acrylic adhesive layer having a thickness of 15 μm is provided on the surface of the retardation film of the polarizing plate. A separate film having a thickness of 38 μm was bonded. In the above polarizing plate, a protective film having a thickness of 60 μm composed of an acrylic pressure-sensitive adhesive layer and a polyethylene terephthalate film was bonded to the surface on the outer film side to prepare a polarizing plate 201 for evaluation. Polarizers 202 to 204 were produced in the same manner as the polarizer 201 except that the thickness of the polarizer and the optical film were changed as shown in the table below.

<Peel test>
The obtained polarizing plate is conditioned at 25 ° C. and 60% for 24 hours, cut into 20 sheets of 120 mm × 120 mm, and bonded to glass using an adhesive sheet. The ratio at which the film and the polarizer were peeled when the film was cut with a cutter and peeled was calculated. The results are shown as “Peel test” in Table 6 below. The numbers in the column of “Peel Test” in the table mean the following. If it is 4 or 5, there is no practical problem.
5: not peeled 4: 0% <peeling rate ≦ 10%
3: 10% <Peeling rate ≦ 20%
2: 20% <Peeling rate ≦ 50%
1: 50% <rate of peeling

<Change in polarization performance after storage at high temperature and high humidity>
For the polarizing plates of Examples and Comparative Examples prepared above, the orthogonal transmittance Tc (730) of the polarizer at a wavelength of 730 nm was measured by the following method.
The orthogonal transmittance Tc (730) of the polarizing plate was measured at a wavelength of 730 nm by the following method using an automatic polarizing film measuring device VAP-7070 manufactured by JASCO Corporation.
In general, the orthogonal transmittance is
(A) a measuring method using two polarizing plates and measuring the absorption axis of the polarizer orthogonally;
(B) Using two types of measurement methods: a measurement method in which a single polarizing plate is used, and the absorption axis of the Grand Taylor prism attached to the apparatus and the polarizer absorption axis of one polarizing plate are arranged orthogonally. Can be measured. Here, the measurement method of (B) was employ | adopted among the measurement methods of said (A) and (B).

Two samples (5 cm × 5 cm) in which a polarizing plate was attached on glass via an adhesive were prepared. Under the present circumstances, it affixed so that the film of the produced said Example and a comparative example might become the glass side. After adjusting the humidity for 24 hours in an environment of 25 ° C. and a relative humidity of 60%, the glass side of this sample was set facing the light source, and the orthogonal transmittance Tc (730) was measured. Two samples were measured respectively, and the average value was defined as the orthogonal transmittance.
Thereafter, the film was stored for 72 hours in an environment of 85 ° C. and a relative humidity of 85%, and then, after the humidity was adjusted for 24 hours in an environment of 25 ° C. and a relative humidity of 60%, the orthogonal transmittance was measured by the same method. The amount of change ΔTc (730) of the orthogonal transmittance before and after aging was obtained and evaluated according to the following criteria. The result is shown in Table 6 below as the polarizer durability. If it is 0-3, it is a level which is satisfactory practically.
0: Change in orthogonal transmittance at wavelength 730 nm is less than 0.15% 1: Change in orthogonal transmittance at wavelength 730 nm is less than 0.3% 2: Change in orthogonal transmittance at wavelength 730 nm is 0.3% or more and less than 0.5% 3: Orthogonal transmittance change at a wavelength of 730 nm is 0.5% or more and less than 1.0% 4: Orthogonal transmittance change at a wavelength of 730 nm is 1.0% or more

(Evaluation method of wave curl)
The polarizing plate produced above was punched into a rectangle having a long side direction of 1150 mm and a short side direction of 645 mm. At this time, the absorption axis of the polarizing plate was made parallel to the short side. The punched polarizing plate was allowed to stand on a flat surface for 24 hours in a 23 ° C. and 55% relative humidity environment with the separate film on the bottom. The maximum value of the floating amount from the flat surface for each wave was taken as the height of the wave, and the measurement was performed using straight silver (manufactured by Shinwa Measurement Co., Ltd.). The measurement of the height of each wave on each side of the polarizing plate was carried out in a state in which the separate film was placed on the bottom and a state in which the separate film was placed on the top.

  A portion where the height of the wave is 1 mm or more was measured as one wave, and the number of waves on each side of the polarizing plate and the height of the wave were measured. The measurement results are shown in the following table. Among the number of waves on each side, the maximum value is called “wave number”, and the maximum wave height of all measurement results is called “wave height”. If the wave height is 3 mm or less and the wave number is 3 or less, there is no practical problem.

  The polarizing plate using the biaxially stretched optical film (Example 14) had better wave height and wave number than the uniaxially stretched optical film (Example 11). Further, the polarizing plate having a polarizer thickness of 10 μm was better in both wave height and wave number than the polarizing plate having a thickness of 25 μm.

<Liquid crystal display device>
(Production of liquid crystal display device)
The polarizing plates produced above were attached to the VA liquid crystal cell side so that the absorption axes of the respective polarizing plates were orthogonal to each other so that the cellulose acylate films of the examples and comparative examples were on the VA liquid crystal cell side. Each display device was created. The VA liquid crystal cell was used by peeling off the polarizing plate and the retardation plate on the front and back of the VA mode liquid crystal TV (LC-40H9, manufactured by Sharp Corporation).

(Evaluation of viewing angle color)
About each produced liquid crystal display device, the brightness | luminance and color at the time of black display are measured using EZ-Contrast XL88 (made by ELDIM) after humidity control for 24 hours in an environment of 25 degreeC and 60% of relative humidity. Then, the luminance value and chromaticity value (u′v ′) of each point are measured by 5 ° for each of the polar angle 0 to 80 ° and the azimuth angle 0 to 360 °, and the color change Δu′v ′ is expressed by the following formula Was measured based on each. Here, u′max (v′max) is the maximum of u ′ (v ′) and u′min (v′min) among the values measured in the range of azimuth angle 0 to 360 ° when the polar angle is 60 °. Is the smallest u ′ (v ′) among the values measured in the range of azimuth angle 0 to 360 ° at a polar angle of 60 °. Further, an arbitrary direction in the plane with respect to the surface of the display device was set to an azimuth angle of 0 °, and a vertical direction to the plane of the display was set to a polar angle of 0 °. The results are shown in Table 6 below. If it is 3 to 5, there is no practical problem.

１： ０．０８０≦Δｕ’ｖ’
２： ０．０６０≦Δｕ’ｖ’＜０．０８０
３： ０．０４０≦Δｕ’ｖ’＜０．０６０
４： ０．０２０≦Δｕ’ｖ’＜０．０４０
５： Δｕ’ｖ’＜０．０２０

1: 0.080 ≦ Δu′v ′
2: 0.060 ≦ Δu′v ′ <0.080
3: 0.040 ≦ Δu′v ′ <0.060
4: 0.020 ≦ Δu′v ′ <0.040
5: Δu′v ′ <0.020

(Summary of Examples)
When the optical films of Examples 1 to 12 having a value of | band surface addition amount−air surface addition amount | of 2.0 or less are used, the brittleness is A or B, and the evaluation of the peel test is 4 or 5 In addition, the evaluation of the viewing angle color tone was 3 to 5, showing good performance. In Example 13, in addition to the above performance, the polarization performance change after 85 hours at 85 ° C. and 85% relative humidity showed good performance. In Example 14, as shown in Table 5 above, the wavy curl of the polarizing plate was good. On the other hand, when the optical films of Comparative Examples 1 to 4 and 6 to 8 having a value of | band surface addition amount−air surface addition amount | of greater than 2.0 were used, the performance of the peel test was inferior. Moreover, the evaluation of brittleness was inferior in the optical film of Comparative Example 5 to which no plasticizer was added.

21 Co-casting die 22 Initial drying zone 23 Drying device 24 Rotating roller 25 Stripping roller 26 Support roller 27 Slit nozzle 28 Exhaust means 29 Temperature control device 30 Heat insulation wall 31 Middle front and back drying zone 41 Late drying zone

Claims (8)

A core layer comprising cellulose acylate having an average acyl substitution degree of 2.00 to 2.55;
On one surface of the core layer, a first skin layer containing cellulose acylate having an average acyl substitution degree of 2.7 to 3.00,
An optical film having a second skin layer containing cellulose acylate having an average acyl substitution degree of 2.7 to 3.00 on the other surface of the core layer,
The optical film contains at least one plasticizer;
The amount of the plasticizer in the region from the surface of the first skin layer to a depth of 1 μm and the amount of the plasticizer in the region from the surface of the second skin layer to a depth of 1 μm are represented by the following formula A Meet
The addition amount of the plasticizer in the whole film is 1% by mass to 12% by mass,
An optical film having a uniform distribution of the plasticizer in a cross-sectional direction of the film.
Formula A: | Amount of plasticizer in the region from the surface of the first skin layer to a depth of 1 μm−Amount of plasticizer in a region from the surface of the second skin layer to a depth of 1 μm | ≦ 2% by mass The plasticizer is a polycondensed ester containing an aromatic dicarboxylic acid and an aliphatic diol, and the ratio of aromatic dicarboxylic acid residues to all dicarboxylic acid residues in the polycondensed ester is 60 mol% or more. The optical film according to claim 1 . The optical film of Claim 2 whose number average molecular weights of the said polycondensation ester are 1000-2000. The film thickness of the entire film is at 3μm or 50μm or less, the thickness of the first skin layer and said second skin layer is 0.3μm or more 3μm or less, any one of claims 1 to 3 The optical film described in 1. The optical film according to any one of claims 1 to 4 , which satisfies the following formula 1 and the following formula 2:
Formula 1: 30 nm ≦ Re (550) ≦ 80 nm
Formula 2: 80 nm ≦ Rth (550) ≦ 150 nm
However, Re (550) represents the in-plane retardation of the optical film at a wavelength of 550 nm, and Rth (550) represents the retardation in the thickness direction of the optical film at a wavelength of 550 nm. A core layer forming dope containing cellulose acylate, a first skin layer forming dope containing cellulose acylate, and a second skin layer forming dope containing cellulose acylate are co-cast on a support. And a step of drying the dope on the support after co-casting, and a drying temperature T1 of the dope surface not in contact with the support and a drying temperature T2 of the dope surface in contact with the support are 20 The method for producing an optical film according to any one of claims 1 to 5, wherein the drying is performed under a condition satisfying ≤T2-T1≤40; however, the unit of the drying temperature is ° C. A polarizing plate comprising a polarizer and the optical film according to claim 1 . A liquid crystal display device comprising the polarizing plate according to claim 7 .

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