JP2016051173A - Optical film, manufacturing method of optical film, polarizing plate, and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical film that has excellent handleability during manufacture of a polarizing plate and provides good curl of a polarizing plate when bonded to the polarizing plate, a manufacturing method of the optical film, a polarizing plate, and a liquid crystal display device.SOLUTION: There is provided an optical film including a core layer that includes cellulose acylate having an average acyl substitution degree of 2.00 to 2.55, a first skin layer that includes cellulose acylate having an average acyl substitution degree of 2.60 to 3.00 on one surface of the core layer, and a second skin layer that includes cellulose acylate having an average acyl substitution degree of 2.60 to 3.00 on the other surface of the core layer, where the curvature radius of a curl of the film after being left standing for 30 minutes in an environment at 25°C and 60%RH is larger than 25 mm, and the curvature radius of a curl in water of the film after being left standing for 30 minutes in water at 25°C is 10 mm or more and 25 mm or less.SELECTED DRAWING: None

Description

  The present invention relates to an optical film having good polarizing plate curl when used in a polarizing plate. 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.

  In recent years, liquid crystal display devices have become larger in screen, and liquid crystal display devices and their members are becoming thinner. From the viewpoint of design, a design that narrows the frame of the television is preferred. In addition, due to an increase in demand in emerging countries, the transport distance of liquid crystal panels has increased, and the opportunity to move in places with high relative humidity has increased.

In Patent Document 1, by using a cellulose acylate film containing a specific ultraviolet absorber in a predetermined amount, color unevenness at the time of black display after a high-temperature and high-humidity environment and peripheral unevenness generated at a corner of the display unit are disclosed. It is disclosed that it can be suppressed.
In Patent Document 2, as a means of improving the polarizing plate curl, one transparent protective film is bonded to the polarizer, and then the remaining transparent film is bonded to the other side of the two transparent protective films bonded to both sides of the polarizer. A method for producing a polarizing plate in which another transparent protective film is bonded is described.

In Patent Document 3, by laminating the optical film A having a small curl amount at the end on the surface of the optical film B having a relatively large curl amount at the end in the direction (TD) perpendicular to the machine flow direction, A method for producing an optical film laminate X in which curling at the end of TD is suppressed is described. Specifically, the optical film A and B are each transported in a state where tension is applied along the machine flow direction (MD), and the optical film B is optically applied to the surface side where the curl is concave. It is described that the bonding step (B) for bonding the film A is performed. In the bonding step (B), the tension applied to the machine flow direction (MD) in the optical film _B is expressed as T _B , the optical film A. Bonding optical films A and B with tension applied so that tension ratio (T _B / T _A ) <1, where T _A is the tension applied in the machine flow direction (MD) Is described. Patent Document 3 does not describe adjusting the curl of a polarizing plate made of a three-layer laminate.
Patent Document 4 discloses a cellulose acylate having a plasticizer content ratio of 1.2 to 2.0 with respect to one when divided into two in the thickness direction and a curl radius in 25 ° C. water of 25 mm or more. A film is described.

JP 2011-173964 A JP 2004-117482 A JP 2013-11774 A JP 2003-145563 A

  As described above, the transport distance of the liquid crystal panel is increasing, and the opportunity to move in a place where the relative humidity is high is also increasing. However, it is necessary to maintain the uniformity of display quality even after transport. Further, it has been found that when the polarizing plate curl is large, bubbles enter at the end during panel bonding, and light leakage occurs at the end of the polarizing plate after the high temperature and high humidity durability test. In particular, for a large-sized thin polarizing plate, the curl adjustment is insufficient with the conventional method.

  This invention makes it the problem which should be solved to provide the optical film which the bending of the edge part at the time of polarizing plate manufacture is suppressed, and a polarizing plate curl are suppressed, its manufacturing method, and a polarization slope. In addition, the present invention solves the problem of providing an optical film, a method for producing the same, and a polarizing slope, which can prevent bubbles when the optical film is bonded to a liquid crystal panel and can suppress light leakage after a high-temperature and high-humidity durability test. It should be a challenge. Furthermore, this invention makes it the subject which should be solved to provide the said optical film and to provide the liquid crystal display device which has favorable oblique light leakage and the edge part light leakage after time-lapse.

  As a result of intensive studies to solve the above-mentioned problems, the present inventor has found that the polarizing plate curl can be reduced by adjusting it to a predetermined range rather than simply reducing the underwater curl of the film. 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;
A first skin layer containing cellulose acylate having an average acyl substitution degree of 2.60 to 3.00 on one surface of the core layer;
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 radius of curvature of the curl of the film after standing at 25 ° C. and 60% relative humidity for 30 minutes is greater than 25 mm,
An optical film in which the radius of curvature of the underwater curl of the film after standing for 30 minutes in water at 25 ° C. is 10 mm or more and 25 mm or less.
(2) The optical film according to (1), wherein the entire optical film has a thickness of 3 μm or more and 50 μm or less, and each of the first skin layer and the second skin layer has a thickness of 0.3 μm or more and 3 μm or less.
(3) The optical film as described in (1) or (2) in which a core layer contains 1-9 mass parts of polycondensation ester with respect to 100 mass parts of cellulose acylates.
(4) The optical film according to any one of (1) to (3), which satisfies the following formula 1 and the following formula 2:
Formula 1: 30 nm <= Re (550) <= 80nm
Formula 2: 80 nm ≦ Rth (550) ≦ 150 nm
However, Re (550) indicates the in-plane retardation of the optical film at a wavelength of 550 nm, and Rth (550) indicates the retardation in the thickness direction of the optical film at a wavelength of 550 nm.
(5) Dope for forming a core layer containing 1 to 9 parts by mass of a polycondensation ester with respect to 100 parts by mass of cellulose acylate;
A first dope for forming a skin layer containing 0 to less than 0.05 parts by weight of polycondensation ester with respect to 100 parts by weight of cellulose acylate;
A step of forming a film by co-casting a second skin layer forming dope containing 0 to less than 0.05 parts by weight of polycondensation ester with respect to 100 parts by weight of cellulose acylate on a support. The manufacturing method of the optical film in any one of (1) to (4) containing.
(6) The method further includes a step of stretching the film, the residual solvent amount of the film at the start of stretching is 0% by mass to 3% by mass, and the film elastic modulus at the start of stretching is 100 MPa to 1500 MPa. The manufacturing method of the optical film as described in).
(7) A polarizing plate having a polarizer and the optical film according to any one of (1) to (4).
(8) The optical film according to any one of (1) to (4), a polarizer, and a protective film are arranged in the above order, and the underwater curl of the optical film, the underwater curl of the protective film, The polarizing plate according to (7), wherein are curled in the same direction.
(9) The optical film manufactured by the manufacturing method according to (5) or (6), a polarizer, and a protective film are arranged in the above order, and the underwater curl of the optical film and the protective film The polarizing plate according to (7), wherein the underwater curl is curled in the same direction.
(10) A liquid crystal display device comprising the polarizing plate according to any one of (7) to (9).

  In the optical film and the polarization slope of the present invention, it is possible to suppress the bending of the edge during the production of the polarizing plate, and it is possible to suppress the polarizing plate curl. The liquid crystal display device of the present invention has good oblique light leakage and end light leakage after time.

FIG. 1 is a schematic view in the vicinity of a casting die. FIG. 2 is an explanatory diagram of an example of co-casting. FIG. 3 is a diagram showing that the film is cut from four directions so as to be in 45 ° increments. FIG. 4 is a diagram showing a case where the underwater curl of the optical film and the underwater curl of the protective film are curled in the same direction.

  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 an in-plane retardation (nm) and a thickness direction retardation (nm) at a 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 the wavelength 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, a number average molecular weight is defined as a polystyrene conversion value by gel permeation chromatography (GPC) measurement. 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 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. 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 radius of curvature of the curl of the film after standing for 30 minutes at 25 ° C. and 60% relative humidity is larger than 25 mm, and the radius of curvature of the underwater curl of the film after standing for 30 minutes in water at 25 ° C. It is an optical film which is 10 mm or more and 25 mm or less.
In this specification, film curl (including underwater curl of film) is defined below. If the film has a longitudinal direction, the longitudinal direction is the first direction. If the film is the same side length, the direction of the arbitrary side is the first direction. If there is no longitudinal direction, the arbitrary direction is the first direction. Then, it is cut into 35 mm × 3 mm so that the first direction becomes the long side, the radius of curvature in the long side direction is measured, and is set as the radius of curvature in the first direction. Similarly, with respect to the first direction, the radii of curvature in the second to fourth directions are measured with the direction in 45 ° increments being the long sides, respectively. The direction having the minimum curvature radius among the curvature radii in the first to fourth directions is defined as the curl direction of the film, and the curvature radius is referred to as the curvature radius of the film curl.

The measurement of the curvature radius of the curl (also referred to as 25 ° C. 60% relative humidity curl) of the film after standing for 30 minutes in a 25 ° C./60% relative humidity environment can be performed as follows. Cut the film to 35 mm x 3 mm. At this time, it cuts out from the first to fourth directions in which the long side direction is 45 °.
After standing for 30 minutes in an environment of 25 ° C. and 60% relative humidity, it can be measured according to measurement method A of ISO (International Standards Organization) 18910: 2000 (Imaging materials-Photographic film and paper-Decision of curl). The radius of curvature of the cut long side direction (35 mm) is read, and the value in the direction of the smallest value among the curvature radii of the first to fourth directions is defined as the curvature radius of the film 25 ° C. 60% relative humidity curl.
When evaluating the curl in the MD direction (longitudinal direction) of the film, the MD direction of the film is 35 mm, and when evaluating the curl in the TD direction of the film, the TD direction (lateral direction) of the film is 35 mm.

(Measurement method of underwater curl of film)
A film is sampled from the same direction as the above-mentioned 25 ° C. 60% relative humidity curl, immersed in water at 25 ° C. for 30 minutes, and then measured according to ISO 18910: 2000 (Imaging materials-Photographic film and paper- Determination of curl) Measure according to A and measure the radius of curvature. The radius of curvature in the long side direction (35 mm) cut out is read, and the value in the direction in which the radius of curvature is the smallest among the first to fourth directions is defined as the radius of curvature of the underwater curl of the film.
When evaluating the curl in the MD direction (longitudinal direction) of the film, the MD direction of the film is 35 mm, and when evaluating the curl in the TD direction of the film, the TD direction (lateral direction) of the film is 35 mm.

The effects of 25 ° C., 60% relative humidity curl and underwater curl on polarizing plate production and polarizing plate curl are as follows. A polarizing plate is generally produced by the following method. After conveying an optical film, a polarizer, and a protective film in a normal temperature and humidity environment, a polyvinyl alcohol (PVA) adhesive is applied between the optical film and the polarizer and between the protective film and the polarizer. Then, it is heated (40 to 80 ° C.), and the PVA adhesive is dried and bonded to form a laminate.
At the time of conveyance before the film is wetted with the PVA adhesive, if the relative humidity curl at 25 ° C. and 60% is small (the radius of curvature is large), the curl of the film is small and the handling property at the time of producing the polarizing plate can be improved. When the film is heated after being wetted with the PVA adhesive, the film begins to curl under the influence of underwater curling, and even if the film is returned to room temperature and normal humidity, the curling of the film does not return. Further, at the timing when the film starts to curl, it is bonded as a polarizing plate. The polarizing plate is a laminate, and the balance of the stretching force of each layer affects the formation of the polarizing plate curl. Therefore, the force that the film tries to curl after bonding has the effect of correcting the curl as a laminate, and the polarization The curl of the board can be reduced.

  The curvature radius of 25 ° C. 60% relative humidity curl of the optical film of the present invention is larger than 25 mm, preferably 30 mm or more, more preferably 40 mm or more. The upper limit of the curvature radius of the 25 ° C. 60% relative humidity curl of the optical film of the present invention is not particularly limited. By setting the radius of curvature of the 25 ° C. and 60% relative humidity curl within the above range, it is possible to suppress the occurrence of end bending during the production of the polarizing plate.

  The radius of curvature of the underwater curl of the optical film of the present invention is 10 mm or more and 25 mm or less, preferably 10 mm or more and less than 25 mm, more preferably 11 mm or more and 22 mm or less, and more preferably 12 mm or more and 20 mm or less. By setting the radius of curvature of the underwater curl within the above range, the curl after being bonded to the polarizing plate can be reduced.

  As described above, the optical film of the present invention increases the underwater curl of the optical film (decreases the radius of curvature) for adjusting the curl of the polarizing plate, while at 25 ° C. of the optical film for stabilizing the polarizing plate production. % Relative humidity curl is reduced (curvature radius is increased). Conventionally, the underwater curl of the film and the 25 ° C 60% relative humidity curl are linked (if the underwater curl is large, the 25 ° C 60% relative humidity curl is large, and if the underwater curl is small, the 25 ° C 60% relative humidity curl is also small. ). In the present invention, it has been found that the curl of the polarizing plate can be reduced by adjusting the curvature radius of the curl of 25 ° C. and 60% relative humidity curl to 10 mm to 25 mm and the curvature radius of the underwater curl to be larger than 25 mm.

  In order to reduce the relative humidity curl at 25 ° C. and 60% relative humidity, it is effective to reduce the difference in deformation due to water absorption between the front surface and the back surface at 25 ° C. and 60% relative humidity. It is considered effective to be in the range. It is also effective to make a balance between the physical properties of the front and back surfaces. For this purpose, film formation is performed by co-casting using multiple types of dopes, and the thicknesses of the skin layers on the front and back surfaces are close to each other. It is considered that it is effective to reduce the thickness of the skin layer so as to be a value. On the other hand, in order to increase the underwater curl, it is effective to change the physical properties (water content, elastic modulus) in the film thickness direction. For this purpose, a method of forming a film by co-casting using plural kinds of dopes Is considered effective. It is also effective to increase the difference in residual strain between the front and back surfaces that are released by water immersion. To this end, the glass transition temperature between the front and back surfaces during stretching is adjusted by adjusting the additive amount to a predetermined range. It is considered that it is effective to increase the difference between the above, to not add an additive to the skin layer during film formation, and to stretch in a state where the elastic modulus is high.

(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 45 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.

(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 is
It is preferable to satisfy 30 nm ≦ Re (550) ≦ 80 nm,
It is more preferable to satisfy 35 nm ≦ Re (550) ≦ 70 nm, and it is even more preferable to satisfy 40 nm ≦ Re (550) ≦ 65 nm.
Rth is
80 nm ≦ Rth (550) ≦ 150 nm is preferably satisfied,
More preferably, 90 nm ≦ Rth (550) ≦ 140 nm is satisfied,
More preferably, 100 nm ≦ Rth (550) ≦ 130 nm is satisfied.
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.

<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 method for measuring the degree of acetyl substitution can be carried out according to ASTM (American Society for Testing Materials) D-817-91.

  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 are 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.

(Polycondensed ester)
If desired, a polycondensation ester can be added 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 the aromatic dicarboxylic acid to the aliphatic dicarboxylic acid in the dicarboxylic acid component is preferably 5 to 100 mol%, more preferably 10 to 100 mol% of the aromatic dicarboxylic acid. More preferably, it is mol%.
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 2000, more preferably 700 to 1500, and particularly preferably 700 to 1200. 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 2000 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 the time of 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 1000, 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 950, wherein the dicarboxylic acid unit is terephthalic acid / succinic acid = 45/55, the diol unit is ethylene glycol / propylene glycol = 50/50, and the terminal is an acetyl group;
A dicarboxylic acid unit of terephthalic acid / succinic acid = 20/80, a diol unit of ethylene glycol / propylene glycol = 50/50, a polycondensed ester having a number average molecular weight of 900 having an acetyl group at the end; and a dicarboxylic acid unit of adipic acid, A polycondensation ester having a number average molecular weight of 1000, wherein the diol unit is ethylene glycol / propylene glycol = 50/50 and the terminal is an 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 9 parts by mass of a polycondensed ester (preferably, a polycondensed ester of an aromatic dicarboxylic acid and an aliphatic diol) with respect to 100 parts by mass of cellulose acylate. 8 mass parts is more preferable, and 1-7 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.

(Sugar ester)
A sugar ester may be added to the protective film of the present invention.
Specific examples and preferred ranges of [sugar ester] are as described in JP-A-2011-94098, [0041-0056].

(Retardation expression agent)
A retardation developer may be added to the optical film of the present invention. Although there is no restriction | limiting in particular as a retardation expression agent, The compound etc. which are represented by a rod-shaped compound, a disk-shaped compound, or the following general formula (II-1) 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. 0.1 to 10% by mass is preferable, 0.5 to 4% by mass is more preferable, and 1 to 3% by mass is particularly preferable.

  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 developer preferably has maximum absorption in the wavelength region of 250 to 400 nm, and preferably has substantially no absorption in the visible 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）
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。）
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（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 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, and Q ²¹ represents a single bond, —O—, —S—, or — NRf-, Rf represents a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aromatic ring group or a heterocyclic group, and may be linked to Ra ³¹ to form a ring, X ³¹ , X ³² , And X ³³ each independently represents a single bond or a divalent linking group, and X ³⁴ represents 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).)
A linking group selected from the group consisting of divalent linking groups represented by )
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 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 group. 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 a heterocyclic group, and ligated with Ra ³⁴ ring R ⁶¹ , R ⁶² , R ⁶³ and R ⁶⁴ each independently represents a hydrogen atom, a halogen atom, a hydroxyl group, a carbamoyl group, a sulfamoyl group, an alkyl group having 1 to 8 carbon atoms, An alkoxy group having 8 carbon atoms, an alkylamino group having 1 to 8 carbon atoms, and a dialkylamino group having 1 to 8 carbon atoms.)

<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 includes a dope for forming a core layer containing 1 to 9 parts by mass of a polycondensed ester with respect to 100 parts by mass of cellulose acylate, and 0 mass of the polycondensed ester with respect to 100 parts by mass of cellulose acylate The second skin layer containing 0 part by mass or more and less than 0.05 part by mass of the polycondensed ester with respect to 100 parts by mass of the cellulose acylate, comprising the first dope for forming the skin layer containing at least 5 parts by mass A step of forming a film by co-casting a forming dope on a support is included. The above three kinds of dopes can be subjected to multilayer casting simultaneously or sequentially on a support. In the method for producing an optical film of the present invention, the co-cast dope may be dried to form a film, the film may be peeled from the support, and the peeled film may be stretched.

(Preparation of dope)
In the present invention, an optical film can be produced using a solution (dope) obtained by dissolving cellulose acylate in an organic solvent by a solution casting method.
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, the cellulose acylate and the organic solvent are placed in a pressure vessel and sealed, and stirred while being heated to a temperature equal to or higher than the boiling point of the solvent at 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.

(Co-casting)
A cellulose acylate film can be produced from the prepared cellulose acylate solution (dope) by a solution casting method.
The dope is cast on a drum or band and the solvent is evaporated to form a film. It is preferable to adjust the concentration of the dope before casting so that the solid content is 10 to 40% by mass. The surface of the drum or band is preferably finished in a mirror state. Regarding casting and drying methods in the solution casting method, US Pat. No. 2,336,310, US Pat. No. 2,367,603, US Pat. No. 2,429,078, US Pat. No. 2,429,297, US Pat. No. 2,429,978, US Pat. No. 2,607,704, US Japanese Patent No. 2739069, US Patent No. 2739070, British Patent No. 640731, British Patent No. 736892, Japanese Patent Publication No. 45-4554, Japanese Patent Publication No. 49-5614, Japanese Patent Publication No. Sho 60-176634, Japanese Patent Publication There are descriptions in JP-A-60-203430 and JP-A-62-115035.

  In the present invention, the obtained cellulose acylate solution (dope) can be cast on a smooth band or drum as a support to form a film. As a method for producing the optical film of the present invention, a known co-casting method can be used. For example, a film may be produced by laminating and laminating cellulose acylate solutions from a plurality of casting ports provided at intervals in the traveling direction of the metal support. For example, JP-A 61-158414 The methods described in JP-A-1-122419, JP-A-11-198285, and the like can be used. Alternatively, a film may be formed by casting a cellulose acylate solution from two casting ports. For example, JP-B-60-27562, JP-A-61-94724, JP-A-61-947245. It can be carried out by the methods described in JP-A No. 61-104413, JP-A No. 61-158413, and JP-A No. 6-134933. Further, a cellulose acylate in which a flow of a high-viscosity cellulose acylate solution described in JP-A-56-162617 is wrapped with a low-viscosity cellulose acylate solution and the high-viscosity and low-viscosity cellulose acylate solutions are simultaneously extruded. A film casting method may be used. Further, it is also preferable that the outer solution described in JP-A-61-94724 and JP-A-61-94725 contains a larger amount of an alcohol component which is a poor solvent than the inner solution.

  Further, by using two casting ports, the film cast on the metal support by the first casting port is peeled off, and the second casting is performed on the side that is in contact with the metal support surface, thereby the film. Can also be produced (for example, Japanese Patent Publication No. 44-20235).

In the method for producing an optical film of the present invention, a cellulose acylate solution of skin layer / core layer / skin layer can be produced by co-casting a cellulose acylate solution.
The co-cast dope can be dried and peeled off from the support as a film.

(Drying process)
A method for drying a film that has been dried on a drum or belt and peeled off will be described. The film peeled off at the peeling position immediately before the drum or belt makes one round is transported alternately through a group of rolls arranged in a staggered pattern, or both ends of the peeled film are gripped with clips or the like. It is transported by a non-contact transport method. Drying can be performed by a method of applying wind at a predetermined temperature to both sides of the film being conveyed or a method using a heating means such as a microwave. Since rapid drying may impair the flatness of the film to be formed, it is preferable to dry at a temperature at which the solvent does not foam in the initial stage of drying, and to dry at a high temperature after the drying proceeds. In the drying process after peeling from the support, the film tends to shrink in the longitudinal direction or the width direction by evaporation of the solvent. Shrinkage increases with drying at higher temperatures. Drying while suppressing this shrinkage as much as possible is preferable for improving the flatness of the film. From this point, for example, as shown in Japanese Patent Laid-Open No. 62-46625, a method in which all or part of the drying process is performed while holding the width at both ends of the web with clips or pins in the width direction. (Tenter method) is preferable. It is preferable that the drying temperature in the said drying process is 100-145 degreeC. Although the drying temperature, the amount of drying air, and the drying time differ depending on the solvent used, it may be appropriately selected according to the type and combination of the solvents used.

(Stretching)
In the present invention, after the co-cast dope is dried and peeled from the support, the film can be stretched.
In the method for producing a cellulose acylate film, the cellulose acylate film may be stretched in any direction of a film transport direction (hereinafter also referred to as a film MD direction) and a direction orthogonal to the film transport direction (hereinafter also referred to as a film TD direction). From the viewpoint of developing a desired retardation, it is preferable to stretch at least in the film TD direction. Furthermore, biaxial stretching combined with stretching in a direction not coincident with the film TD direction (for example, the film MD direction) may be used. Further, the stretching may be performed in one stage or in multiple stages.

The optical film of the present invention can be biaxially stretched.
When performing biaxial stretching, it is preferable to stretch in the film TD direction (direction perpendicular to the transport direction) after stretching in the film MD direction (transport direction). When the stretching is performed, a residual solvent may be included, or the stretching may be performed in a state not including the residual solvent. When the residual solvent is included, it is preferable that the amount of the solvent is stretched between 0.1% by weight and 50% by weight with respect to the film solid content weight.

The stretching ratio in stretching in the film MD direction is preferably 0 to 20%, more preferably 0 to 15%, and particularly preferably 0 to 10%. The stretching rate of the cellulose acylate web during the stretching can be achieved by making a difference between the film transport speed at the entrance of the stretching zone and the film transport speed at the exit. For example, when an apparatus having two nip rolls is used, the cellulose acylate film is preferably stretched in the MD direction by increasing the rotational speed of the nip roll on the exit side rather than the rotational speed of the nip roll on the entrance side of the stretching zone. Can do. In addition, "stretch rate (%)" means what is calculated | required by the following formula | equation.
Stretch ratio (%) = 100 × {(Length after stretching) − (Length before stretching)} / Length before stretching

The stretching ratio in stretching in the film TD direction is preferably more than 20%, more preferably more than 20% to 60% or less, particularly preferably 22 to 55%, and 23 to 50%. More particularly preferred. By performing such stretching, the expression of retardation can be adjusted.
The film surface temperature at the start of stretching is preferably 100 ° C. or higher and 220 ° C. or lower, and more preferably 120 ° C. or higher and 200 ° C. or lower.
In addition, in this invention, it is preferable to extend | stretch using a tenter apparatus as a method of extending | stretching in the film TD direction.

When stretching in the film TD direction, the residual solvent amount of the film at the start of stretching is preferably 0% by mass to 3% by mass, more preferably 0% by mass to 2.3% by mass, More preferably, it is at least 2.1% by mass.
The amount of residual solvent can be expressed by the following formula.
Residual solvent amount (% by mass) = {(MN) / N} × 100
Here, M is the mass of the film (web) at an arbitrary point in time, and N is the mass when the film whose M is measured is dried at 110 ° C. for 3 hours.

When stretching in the film TD direction, the film elastic modulus at the start of stretching is preferably from 100 MPa to 1500 MPa, more preferably from 100 MPa to 1000 MPa, further preferably from 100 MPa to 500 MPa, more preferably 100 MPa. It is particularly preferable that the pressure is 300 MPa or less.
The film elastic modulus is cut out from the center of the film 15 seconds before stretching so that the film MD direction is 10 mm and the film TD direction is 130 mm, and the distance between chucks is measured using the Tensilon Universal Material Testing Machine RTF series (Orientec). It can be measured by conducting a tensile test at a pulling speed of 100 mm% / min.

[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 well-known polarizer can be used as the polarizer. 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. Although the thickness of a polarizer is not specifically limited, Generally, it is 3 micrometers-35 micrometers, Preferably it is 5 micrometers-25 micrometers, More preferably, it is 5-20 micrometers.

  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.

  In the polarizing plate of the present invention, preferably, the optical film of the present invention, a polarizer, and a protective film are arranged in the above order, and the underwater curl of the optical film is the same as the underwater curl of the protective film. Curling in the direction is preferred. FIG. 4 shows two modes in which the underwater curl direction of the protective film 1 and the underwater curl of the optical film 3 are the same in a polarizing plate in which the protective film 1, the polarizer 2 and the optical film 3 are laminated in this order. Show.

(Curl out of the wave)
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), FLLC (Ferroelectric Liquid Crystal), AFLC (Anti-Ferroelectric Liquid Crystal), OCB (Optical Liquid Crystal). ), 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.
<Cellulose acetate>
Cellulose acetate was synthesized by the method described in JP-A-10-45804 and JP-A-8-231761, and the degree of substitution was measured. Specifically, sulfuric acid (7.8 parts by mass with respect to 100 parts by mass of cellulose) was added as a catalyst, carboxylic acid serving as a raw material for the acyl substituent was added, and an acylation reaction was performed 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. Furthermore, the low molecular weight component of the cellulose acetate was removed by washing with acetone. Table 1 shows the degree of substitution of the synthesized cellulose acetate.

<Preparation of dope>
(Preparation of core layer dope solution C01)
The following composition was put into a mixing tank and stirred to dissolve each component to prepare a core layer dope solution C01.
Cellulose acetate CA01 (substitution degree 2.43) 100 parts by mass plasticizer E1 4.0 parts by mass additive N1 2.3 parts by mass methylene chloride 394.0 parts by mass Methanol 59.0 parts by mass Solid content concentration is 19.0 parts by mass %Met.

(Preparation of core layer dope solutions C02 to C27)
Core layer dope solutions C02 to C27 were prepared in the same manner as in the preparation of the core layer dope solution C01 except that the cellulose acetate, plasticizer, and additives shown in Table 2 were used in the amounts shown in Table 2. . The amount of the solvent was appropriately adjusted so that the cellulose acetate concentration and the solvent composition were the same. The numerical values in the column of addition amount in Table 2 indicate parts by mass when the amount of cellulose acetate is 100 parts by mass.

(Preparation of skin layer dope solution S01)
The following composition was put into a mixing tank and stirred to dissolve each component to prepare a skin layer dope solution S01.
Cellulose acetate CA02 (substitution degree 2.81) 100 parts by mass Methylene chloride 425.0 parts by mass Methanol 63.0 parts by mass

(Dispersion of matting agent solution)
The following composition was charged into a disperser and stirred to dissolve each component to prepare a matting agent dispersion M1.
2.0 parts by mass of silica particles having an average particle size of 20 nm (AEROSIL (registered trademark) R972, manufactured by Nippon Aerosil Co., Ltd.)
Methylene chloride 76.1 parts by mass Methanol 11.4 parts by mass Skin layer dope solution S01 12.6 parts by mass

(Preparation of dope solution S01M)
The skin layer dope solution S01M was prepared by mixing the matting agent dispersion M1 with the prepared skin layer dope solution S01 in the ratio shown below.
Skin layer dope solution S01 100.0 parts by weight Matting agent dispersion M1 7.1 parts by weight

(Preparation of skin layer dope solutions S02 to S06)
Skin layer dope solutions S02 to S06 were prepared by the same method as the preparation of skin layer dope solution S01, except that the cellulose acetate, plasticizer and release accelerator shown in Table 5 were used in the amounts shown in Table 5. . The amount of the solvent was appropriately adjusted so that the cellulose acetate concentration and the solvent composition were the same. The numerical values in the column of addition amount in Table 5 indicate parts by mass when the amount of cellulose acetate is 100 parts by mass. The exfoliation accelerator K-37V indicates Poem I (registered trademark) K-37V, manufactured by Riken Vitamin Co., Ltd.

(Preparation of skin layer dope solutions S02M to S06M)
Skin layer dope solutions S02M to S06M to which a matting agent solution was added were prepared in the same manner as the preparation of skin layer dope solution S01M except that skin layer dope solutions S02 to S06 were used instead of skin layer dope solution S01. .

<Film formation of cellulose acetate film>
(Casting)
The above-prepared dope solutions C01 to C27 and S01M to S06M were used in combinations described in Table 6 and cast using a band casting machine.
When casting the dope solution, as shown in FIG. 1, the dopes described in Table 6 below were co-cast from the casting die 89 on the traveling band 85 as shown in FIG. Here, by adjusting the casting amount of each dope, the core layer was made the thickest, and as a result, the cast film obtained by simultaneous multilayer co-casting so that the film thickness after stretching became the value of Table 6 below. A film 70 was formed.

  Next, the cast film 70 was peeled off from the cast band 85 to form a wet film, and then dried by a crossover and a tenter to obtain a film. The amount of residual solvent immediately after stripping the dope was about 25% by mass. The film was sent to a drying chamber, and drying was sufficiently promoted while being conveyed while being wound around a number of rollers.

(Biaxial stretching)
The films (Examples 20 and 21) obtained by casting were stretched by 10% in the MD (longitudinal) direction, held by clips, and stretched by 40% in the TD (transverse) direction under the condition of uniaxial fixed end. At this time, the residual solvent amount at the start of TD stretching and the elastic modulus of the film were as shown in Table 7. The film elastic modulus at the start of stretching was adjusted by the film material, residual solvent amount and temperature.

(TD uniaxial stretching)
The films (Examples 1 to 19 and Comparative Examples 1 to 9) obtained by casting were gripped with a clip and stretched 30% in the TD (lateral) direction under the condition of uniaxial fixed end. At this time, the residual solvent amount at the start of stretching and the elastic modulus of the film were as shown in Table 7. The film elastic modulus at the start of stretching was adjusted by the film material, residual solvent amount and temperature.

(Measurement of film modulus at the start of stretching)
The elastic modulus at the start of stretching was measured as follows. The film obtained by casting was cut out from the center of the film 15 seconds before stretching so that the MD (longitudinal) direction was 10 mm and the TD (transverse) direction was 130 mm. Using a Tensilon universal material testing machine RTF series (Orientec Co., Ltd.), the distance between chucks was set to 100 mm, and a tensile test was performed at a pulling speed of 100 mm% / min.

  About the film obtained by casting, the film surface temperature at the start of stretching was measured using a thermocouple. An oven was installed in the film tension part of the Tensilon universal material testing machine, and the temperature of the oven was adjusted so that the film surface temperature was equal to the temperature at the start of stretching at the start of Tensilon measurement.

(Humid heat treatment)
Each film subjected to the stretching treatment was sequentially subjected to a condensation prevention treatment, a wet heat treatment (water vapor contact treatment) and a heat treatment.
In the anti-condensation treatment, the film temperature Tf0 was adjusted to 120 ° C. by applying dry air to each film.
In the wet heat treatment (water vapor contact treatment), the absolute humidity of the wet gas in the wet gas contact chamber (the wet heat treatment absolute humidity) is 250 g / m ^3, and the dew point of the wet gas is higher than the temperature Tf0 of each film. Each film was conveyed while maintaining the temperature (wet heat treatment temperature) of each film at 100 ° C. for only the treatment time (60 seconds).

In the heat treatment, the absolute humidity of the gas in the heat treatment chamber (heat treatment absolute humidity) is set to 0 g / m ³ , the temperature of each film (heat treatment temperature) is set to the same temperature as the wet heat treatment temperature, and the treatment time (2 minutes) is maintained. did. The film surface temperature was determined from the average value obtained by attaching a tape-type thermocouple surface temperature sensor (ST series manufactured by Anri Keiki Co., Ltd.) to the film at three points.

(Take-up)
Then, after cooling to room temperature, each film was wound up, and rolls having a roll width of 1960 mm and a roll length of 3900 m were produced at least 24 rolls under the above conditions for the purpose of judging the production suitability. Samples of 1 m in length (width 1960 mm) were cut out at intervals of 100 m for one of 24 rolls produced continuously to form films of Examples and Comparative Examples, and measurement of 25 ° C., 60% relative humidity curl and underwater curl were as follows. I went there.

(Measurement method of 25% 60% relative humidity curl)
The obtained film was cut so as to be 35 mm × 3 mm from four directions so that the MD direction was 0 ° and the increment was 45 ° (see FIG. 3). The four cut films were allowed to stand in an environment of 25 ° C. and 60% for 30 minutes, and then the curvature radius of the curl of the film was read. The curl amount on the cut long side (35 mm) was read, and the value with the smallest curvature radius was defined as the curvature radius of the curl of the film.

(Measurement method of underwater curl)
The film was sampled from the same direction as the above-mentioned 25 ° C. 60% relative humidity curl, immersed in water at 25 ° C. for 30 minutes, and then the radius of curvature was read. The curl amount on the cut long side (35 mm) was read, and the value with the smallest curvature radius was defined as the curvature radius of the curl of the film.

(Film retardation)
It measured with automatic birefringence meter KOBRA-21ADH (Oji Scientific Instruments Co., Ltd. product) by said method.

  Table 7 shows the results of measurement of 25 ° C., 60% relative humidity curl, underwater curl, Re (550) and Rth (550).

<Preparation of protective film>
(Preparation of cellulose ester solution for first skin layer and second skin layer)
The following composition was put into a mixing tank, stirred while heating to dissolve each component, and a cellulose ester solution for the first skin layer and the second skin layer was prepared.

Composition of cellulose ester solution for first skin layer and second skin layer:
Cellulose ester (acetyl substitution degree 2.86) 100 parts by weight Sugar ester compound of formula (I) 3 parts by weight Sugar ester compound of formula (II) 1 part by weight UV absorber 2.4 parts by weight silica particle dispersion (average particle size) 16 nm) 0.078 parts by mass (AEROSIL (registered trademark) R972, Nippon Aerosil Co., Ltd. methylene chloride 339 parts by mass Methanol 74 parts by mass Butanol 3 parts by mass

(Preparation of cellulose ester solution for core layer)
The following composition was put into a mixing tank and stirred while heating to dissolve each component to prepare a cellulose ester solution for the core layer.

Composition of cellulose ester solution for core layer Cellulose ester (acetyl substitution degree 2.86) 100 parts by mass Sugar ester compound of formula (I) 7.7 parts by mass Sugar ester compound of formula (II) 2.3 parts by mass UV absorber 2.4 parts by mass Methylene chloride 266 parts by mass Methanol 58 parts by mass Butanol 2.6 parts by mass

(Filming by co-casting)
As a casting die, an apparatus equipped with a feed block adjusted for co-casting so that a film having a three-layer structure can be formed was used. The cellulose ester solution for the first skin layer, the cellulose ester solution for the core layer, and the cellulose ester solution for the second skin layer were co-cast on a drum cooled to −7 ° C. from the casting port. At this time, the flow rate of each dope was adjusted so that the thickness ratio would be the first skin layer / core layer / second skin layer = 5/53/2.
It casted on the mirror surface stainless steel support body which is a drum of diameter 3m. A dry air of 34 ° C. was applied on the drum at 270 m ³ / min.
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. At the time of peeling, 5% stretching was performed in the MD direction.

The cellulose ester web held by the pin tenter was conveyed to the drying zone. In the initial drying, a drying air of 45 ° C. was blown and then dried at 110 ° C. for 5 minutes. At this time, the cellulose ester web was conveyed while stretching in the width direction at a magnification of 10%.
After releasing the web from the pin tenter, the portion held by the pin tenter was continuously cut out and dried at 145 ° C. for 10 minutes while applying a 210 N tension in the MD direction. Furthermore, the width direction edge part was continuously cut off so that a web might become desired width, and the unevenness | corrugation of the width of 15 mm and a height of 10 micrometers was attached to the both ends of the width direction of a web, and a film with a film thickness of 60 micrometers was produced. A protective film 2A was obtained.
The radius of curvature of the underwater curl of the protective film 2A produced above was 50 mm.

<Preparation of polarizing plate>
The surface of the optical film produced in Examples 1-21 and Comparative Examples 1-9 was alkali saponified. It was immersed in a 1.5 mol / L aqueous sodium hydroxide solution at 45 ° 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 60 μm was continuously stretched 5 times in an iodine aqueous solution and dried to obtain a polarizer having a thickness of 15 μm. Using the 3% by weight aqueous solution of polyvinyl alcohol (Kuraray PVA-117H) as an adhesive, the above-described alkali saponified optical films of Examples and Comparative Examples, and the protective film 2A similarly alkali saponified were prepared. Then, a laminated laminate was obtained so as to be between the optical film of Example or Comparative Example and the protective film 2A. At this time, the MD direction of the optical film of Example or Comparative Example and the protective film 2A was made parallel to the absorption axis direction of the polarizer.

  An acrylic pressure-sensitive adhesive layer having a thickness of 15 μm was provided on the surface on the optical film side in Examples or Comparative Examples, and a separate film having a thickness of 38 μm was further bonded to the outside thereof. 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 protective film 2A side to produce a polarizing plate.

  When the optical film of Example or Comparative Example, the polarizer, and the protective film 2A are arranged in the vertical direction in this order, the underwater curl of the optical film and the protective film 2A is convex upward when the protective film 2A is viewed from above. Was positive curl, and the case of convex downward was negative curl.

(End breakage during polarizing plate manufacturing)
When the polarizing plate was produced as described above, the frequency of occurrence of edge folding was observed. A polarizing plate having a thickness of 1000 m was prepared and evaluated according to the following criteria.
1: No occurrence 2: Occurrence, but evaluation of polarizing plate is possible 3: Occurrence, evaluation of polarizing plate is impossible

(Evaluation of polarizing plate 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 polarizer was set to the long side direction. The punched polarizing plate was left in an environment of 23 ° C. and 55% relative humidity for 7 days, and then the separate film was peeled off to evaluate curl.
The polarizing plate from which the separate film was peeled was placed on a flat surface with the bottom surface convex, and the floating heights at the four corners and the center of each side were measured, and the maximum absolute value was defined as the polarizing plate curl value. .

  Here, the polarizing plate curl is positive (+) indicates a convex curl on the side of the protective film (that is, the protective film side), and the polarizing plate curl is negative (−) is on the side of the pressure-sensitive adhesive (that is, the first side). It represents a convex curl on the one optical film side).

  The results of the above evaluation are shown in Table 8.

  In the polarizing plate using the optical films of Examples 1 to 6 and 9 to 21 having a curvature radius of 25 ° C. and 60% relative humidity curl of greater than 30 mm, the evaluation of end bending at the time of manufacturing the polarizing plate is 1, It was excellent. In the polarizing plate using the optical films of Examples 7 and 8 having a curvature radius of 25 ° C. and 60% relative humidity curl of greater than 25 mm and 30 mm or less, the evaluation of edge bending at the time of producing the polarizing plate is 2, which is good. there were. On the other hand, in the polarizing plate using the optical films of Comparative Examples 3 and 6 in which the radius of curvature of 25 ° C. and 60% relative humidity curl is 25 mm or less, the evaluation of the end bending at the time of manufacturing the polarizing plate is 3, which is poor. there were.

(Evaluation 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 20 and the polarizing plate 21 using the biaxially stretched optical film were better in wave height and wave number than the polarizing plate 1 and the polarizing plate 2 using the optical film subjected to TD uniaxial stretching.

<Liquid crystal display device>
(Production of liquid crystal display device)
Each of the polarizing plates in the VA liquid crystal cell was prepared so that the pressure-sensitive adhesive side (that is, the optical film side in the example or comparative example) was on the liquid crystal cell side by using two polarizing plates in the above examples and comparative examples. The liquid crystal display devices of Examples and Comparative Examples were fabricated by pasting them so that the absorption axes of the liquid crystal were orthogonal to each other. The VA liquid crystal cell was used by peeling off the front and back polarizing plates and retardation plate of a commercially available VA mode liquid crystal display device (LC-52 G7, manufactured by Sharp Corporation).

(Evaluation of oblique light leakage)
Using the measuring device (EZ-Contrast XL88, manufactured by ELDIM), the luminance of the liquid crystal display device thus produced was measured with a measuring instrument (EZ-Contrast XL88, manufactured by ELDIM). Evaluated by criteria.
1: 0.5 cd / m ² or less 2: Over 0.5 cd / m ² and 1.0 cd / m ² or less 3: Over 1.0 cd / m ² and 1.5 cd / m ² or less 4: 1.5 cd / m ¹ to more than ^{2 and} less than 2.0 cd / m ² 5 to more than 2.0 cd / m ² has no practical problem. 4 to 5 have a large light leakage and have a practical problem.

(End light leakage after 1000 hours at 50 ° C. and 90% relative humidity)
The liquid crystal cell to which the polarizing plate of the example and the comparative example was bonded was taken out after being left in a constant temperature layer of 50 ° C. and 90% relative humidity for 1000 hours, taken out, and observed from the front of the liquid crystal display in a black display state in a dark room. Was measured using a measuring machine (EZ-Contrast XL88, manufactured by ELDIM). A position 3 cm from the edge of the four sides of the screen was measured at four points in the center of the top, bottom, left and right, and the maximum value was defined as edge light leakage, and evaluation was performed according to the following criteria.
1: 0.2 cd / m ² or less 2: Over 0.2 cd / m ² and 0.3 cd / m ² or less 3: Over 0.3 cd / m ² and 0.4 cd / m ² or less 4: 0.4 cd / m ¹ to more than ² and 0.5 cd / m ² or less and 5 to more than 0.5 cd / m ² have no practical problem. 4 to 5 have a noticeable light leakage and have a practical problem.

  The results of the above evaluation are shown in Table 10.

(Summary of Examples)
Liquid crystal display devices 1 to 4, 17, 20 and 21 having a curvature radius of underwater curl of the film of 10 mm or more and 20 mm or less and a polarizing plate curl of −5 mm or more and 5 mm or less are at 50 ° C. and 90% relative humidity after 1000 hours. The evaluation of the end light leakage was 1 and was particularly excellent.
The liquid crystal display devices 5 to 16, 18 and 19 having a curvature radius of underwater curl of 20 mm to 25 mm and a polarizing plate curl of −10 mm to −5 mm or 5 mm to 10 mm are 50 ° C. and 90% relative humidity 1000 The evaluation of edge light leakage after time was 2 or 3, which was good.
On the other hand, the curvature radius of the underwater curl is larger than 25 mm, the polarizing plate curl is smaller than −10 mm, or larger than 10 mm, and the liquid crystal display devices 22 to 27 have the edge light leakage after 1000 hours at 50 ° C. and 90% relative humidity. Evaluation was 4 or 5, and was bad.

  In addition, the liquid crystal display devices 1 to 17, 20 and 21 in which the underwater curl of the optical film and the underwater curl of the protective film are curled in the same direction in the polarizing plate all show good results. The liquid crystal display devices 18 and 19 in which the underwater curl and the underwater curl of the protective film are curled in different directions were also at an acceptable level.

The optical film of Example 5 has a slightly higher amount of polycondensed polyester, and the optical film of Example 6 has a slightly lower amount of polycondensed polyester and slightly inferior curl in water, but there is no practical problem.
The optical film of Example 7 contains no plasticizer, the optical film of Example 8 contains an aliphatic polycondensation polyester, and the optical film of Example 9 contains an aromatic polycondensation polyester with a low aromatic ratio. Therefore, the underwater curl is slightly inferior, but there is no problem in practical use.
The optical film of Example 10 is slightly thicker as a whole, and the optical film of Example 11 is slightly inferior in curling at 25 ° C. and 60% relative humidity and underwater due to the slightly thicker skin layer. Is no problem.
The optical film of Example 14 contains a plasticizer in the skin layer, so that the underwater curl is slightly inferior, but there is no practical problem.
The optical film of Example 15 has a slightly high average acyl substitution degree, and the optical film of Example 16 has a slightly low average acyl substitution degree and slightly inferior curl in water, but there is no practical problem.

70 Casting film 85 Casting band 89 Casting die 120 Core layer dope 121 First skin layer dope 122 Second skin layer dope 120a Core layer 121a First skin layer 122a Second skin layer 150 First Second skin layer (support layer) die 151 Core layer (base layer) die 152 First skin layer (air surface layer) die

Claims (9)

A core layer comprising cellulose acylate having an average acyl substitution degree of 2.00 to 2.55;
A first skin layer containing cellulose acylate having an average acyl substitution degree of 2.60 to 3.00 on one surface of the core layer;
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 radius of curvature of the curl of the film after standing at 25 ° C. and 60% relative humidity for 30 minutes is greater than 25 mm,
An optical film in which the radius of curvature of the underwater curl of the film after standing for 30 minutes in water at 25 ° C. is 10 mm or more and 25 mm or less. 2. The optical film according to claim 1, wherein a thickness of the entire optical film is 3 μm or more and 50 μm or less, and thicknesses of the first skin layer and the second skin layer are 0.3 μm or more and 3 μm or less, respectively. The optical film of Claim 1 or 2 in which the said core layer contains 1-9 mass parts of polycondensation ester with respect to 100 mass parts of cellulose acylates. The optical film according to any one of claims 1 to 3, which satisfies the following formula 1 and the following formula 2:
Formula 1: 30 nm <= Re (550) <= 80nm
Formula 2: 80 nm ≦ Rth (550) ≦ 150 nm
However, Re (550) indicates the in-plane retardation of the optical film at a wavelength of 550 nm, and Rth (550) indicates the retardation in the thickness direction of the optical film at a wavelength of 550 nm. A core layer forming dope containing 1 to 9 parts by weight of a polycondensation ester with respect to 100 parts by weight of cellulose acylate;
A first dope for forming a skin layer containing 0 to less than 0.05 parts by weight of polycondensation ester with respect to 100 parts by weight of cellulose acylate;
A step of forming a film by co-casting a second skin layer forming dope containing 0 to less than 0.05 parts by weight of polycondensation ester with respect to 100 parts by weight of cellulose acylate on a support. The manufacturing method of the optical film of any one of Claim 1 to 4 containing. Furthermore, the process of extending | stretching a film is included, The residual solvent amount of the film at the time of an extending | stretching start is 0 mass% or more and 3 mass% or less, The film elastic modulus at the time of an extending | stretching start is 100 MPa or more and 1500 MPa or less. Manufacturing method of the optical film. The polarizing plate which has a polarizer and the optical film of any one of Claim 1 to 4. 5. The optical film according to claim 1, a polarizer, and a protective film are arranged in the order, and the underwater curl of the optical film and the underwater curl of the protective film are in the same direction. The polarizing plate according to claim 7, wherein the polarizing plate is curled. A liquid crystal display device comprising the polarizing plate according to claim 7.

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