JP2016206679A - Optical film, polarizing plate, image display device, and method for manufacturing optical film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical film and a method for manufacturing the optical film, which has an excellent appearance of a film roll and can be used as an optical film having desired retardation, moisture dependence of the desired retardation and small dimensional change for a polarizing plate or a liquid crystal display device, and to provide a polarizing plate using the optical film, suppressing peeling or generation of unevenness in stripes like a record and curling, and to provide a liquid crystal panel or a liquid crystal display device that suppresses generation of unevenness of light on a display surface when observed in a frontal or oblique direction.SOLUTION: An optical film includes one or more kinds of additives and cellulose ester. Total content of the additives (Ct mass% with respect to the cellulose ester) and film thickness (d μm) satisfy relationship of Ct<30 and Ct/d≥0.375. When the optical film is treated at 60°C and 90% relative humidity (RH) for 24 hours, the optical film shows a dimensional change rate of 3% or less. The dimensional change rate is an absolute value of a value obtained by dividing dimensional change when the optical film is left standing under conditions of 60°C and 90% RH for 24 hours, by initial length of the film.SELECTED DRAWING: None

Description

  The present invention relates to an optical film comprising a cellulose ester that has excellent adhesion to a polarizing film and can be directly bonded to the polarizing film, and a method for producing the same, a retardation film using the optical film, The present invention relates to a highly reliable polarizing plate, a liquid crystal panel, and a liquid crystal display device using an optical film.

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

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

  When such a film is used in an optical application such as a retardation film, a retardation film support, a protective film for a polarizing plate, and a liquid crystal display device, the control of the optical anisotropy is a performance of the display device. This is a very important factor in determining (for example, visibility). With the recent demand for wider viewing angle of liquid crystal display devices, it is required to improve retardation compensation, and the retardation value in the in-plane direction of the retardation film disposed between the polarizing film and the liquid crystal cell. (Re; hereinafter simply referred to as “Re”) and the retardation value in the film thickness direction (Rth; hereinafter referred to simply as “Rth”) are required to be appropriately controlled. Yes. For example, in an IPS mode liquid crystal display device widely used in liquid crystal television applications, both Re and Rth are required to be reduced. For example, Patent Document 1 discloses that both ends of the cellulose acylate are hydroxyl groups. A technique for containing 5% by mass or more of a certain polyester diol is disclosed. In addition, in the VA mode liquid crystal display device, both Re and Rth are required to be increased. In order to adjust to appropriate Re and Rth, adjustment of the material constituting the film, adjustment of the film forming method, and stretching of the film Techniques for performing the operation are disclosed (for example, see Patent Documents 2 to 5).

  On the other hand, it has been found that as the liquid crystal display device becomes slim, circular light unevenness occurs when the display surface is observed from the front under specific conditions. The generation mechanism of this light unevenness is still unclear, but one reason is that the backlight member and the liquid crystal panel (particularly the backlight side polarizing plate) are in partial contact with each other and in contact with the contacted part. It is mentioned that brightness and color change depending on the part that did not exist. For this reason, Patent Document 6 discloses a method of preventing contact with the backlight member and suppressing the occurrence of light unevenness by providing irregularities on the surface of the backlight-side protective film of the backlight-side polarizing plate.

JP 2009-098674 A European Patent 0911656 JP-A-5-257014 JP 2005-138358 A JP 2001-100039 A JP 2009-169393 A

However, as in Patent Document 6, when a polyethylene terephthalate film is used as a protective film for a polarizing plate, there are difficulties in workability of the polarizing plate, leading to a decrease in the production rate of the polarizing plate, or using such a polarizing plate. In the liquid crystal panel, problems such as panel warpage and light unevenness on the outer periphery of the display surface under specific conditions have been clarified.
Therefore, in order to solve such problems of the prior art, the present inventors have excellent polarizing plate processability, and an optical film that does not cause circular light unevenness or peripheral light unevenness on the display surface of a liquid crystal display device. The production of a polarizing plate was studied for the purpose of the present invention. And it is an optical film containing a cellulose ester, and the elastic modulus by appropriately controlling the relationship between the total content of one or more kinds in the optical film and the film thickness (Ct / d ≧ 0.375), It has been found that these problems can be solved by using an optical film in which the photoelasticity, moisture absorption rate, and humidity dependence of Rth are controlled.

However, when such a film is produced by a conventional method, the film is stored for a long period of time, or when the film is heated or humidified, the dimensions change more than before, for example, the appearance of the roll deteriorates over time, When such a film is processed into a polarizing plate as a protective film, peeling or record streak-like unevenness or curling occurs in the obtained polarizing plate, or when a polarizing plate containing such a film is heated or humidified heat-treated New issues such as curling and dimensional changes became clear.
An object of the present invention is an optical film that is excellent in the appearance of a roll, has a desired retardation, and has a humidity dependency of the desired retardation, and can be used for a polarizing plate and a liquid crystal display device as an optical film having a small dimensional change, and It is in providing the manufacturing method. Another object of the present invention is to provide a polarizing plate that can prevent the occurrence of peeling, record streak-like irregularities, and curls using such an optical film. Another object of the present invention is to provide a liquid crystal panel or a liquid crystal display device in which the occurrence of light unevenness on the display surface when observed from the front and oblique directions is suppressed.

  As a result of intensive studies to solve the above problems, the present inventors have found that the problem of peeling of the polarizing plate is a total of one or more additives in the optical film set to eliminate display unevenness. This is due to weak mechanical strength (low tensile stiffness) and high elastic modulus (hard to creep) that satisfy the relationship between content and film thickness (Ct / d ≧ 0.375). Therefore, it was estimated that the size change rate promoted peeling. Further, the size change rate of the film is determined by the mechanical strength of the web satisfying the relationship between the total content of one or more additives in the optical film and the film thickness (Ct / d ≧ 0.375). This is due to the weakness (low tensile rigidity) and the tendency of residual strain to be accumulated due to the high drying speed, and it was found that it is important to eliminate this. That is, since the web satisfying the relationship between the total content and the film thickness (Ct / d ≧ 0.375) has a high drying speed, the shrinkage speed accompanying the drying is high. Therefore, if the tenter width is not reduced in accordance with the shrinkage, stress is applied to the web and the residual strain is accumulated. Therefore, it is important to match the shrinkage rate with the tenter width profile. In particular, in a web that satisfies the relationship between the total content and the film thickness, the amount of residual solvent in the tenter is small, and the relaxation rate of residual strain is slow. Therefore, such a device is very important. On the other hand, heat treatment (so-called annealing treatment) aimed at removing residual strain is generally known. However, in a film satisfying the relationship between the total content and the film thickness (Ct / d ≧ 0.375), Such a conventionally known process cannot sufficiently reduce the dimensional change rate, and when such a process is performed, a circle that is visible when the liquid crystal display device is observed obliquely. It became clear that another problem that the improvement effect of the light unevenness of the shape may be diminished occurs. Accordingly, it has been found that a film satisfying the relationship between the total content and the film thickness is preferably formed without accumulating residual strain.

Furthermore, the problem of the recording stripe-shaped unevenness of the polarizing plate is caused by the weak mechanical strength (low tensile rigidity) of the film satisfying the relationship between the total content and the film thickness and the size change rate. In particular, it was estimated that the influence of the mechanical strength and the dimensional change rate in the transmission axis direction of the polarizing plate was large.
In addition, the problem of curling of the polarizing plate is that the tensile rigidity, expansion coefficient (humidity expansion coefficient, thermal expansion coefficient), and dimensional change rate between the optical film used on the opposite side of the polarizing film and the film of the present invention are It is estimated that it is preferable to reduce the rate of dimensional change in the film of the present invention because the optical film generally generated on the opposite side has a smaller value than the film of the present invention.
On the other hand, the optical film of the present invention preferably has a certain width or more from an industrial viewpoint. Therefore, for example, it is effective to widen the width of the die or the casting support, but since there is a limit from the viewpoint of cost, it is preferable to stretch in the width direction during film formation. And it discovered that it can extend | stretch, without accumulating residual distortion by adjusting the residual solvent amount in this extending process to a specific range.
And it discovered that the film which solved even the problem of the dimensional change rate was able to be manufactured by combining these suitably, and came to complete this invention.
That is, the present invention can be achieved by the following means.
<1>
An optical film comprising one or more additives and cellulose acetate,
The total content of the additive (Ct; unit: mass% with respect to the cellulose acetate) and the film thickness (d; unit: μm) satisfy the relationship of Ct <30 and Ct / d ≧ 0.375,
The acyl substitution degree of the cellulose acetate is 2.8 to 2.94 (excluding 2.8),
The following formula (IIIa) and formula (IVa) are satisfied,
Formula (I) Re = (nx−ny) × d (nm)
Formula (II) Rth = {(nx + ny) / 2−nz} × d (nm)
Formula (IIIa) Re <10
Formula (IVa) | Rth | <25
(Where nx is the refractive index in the slow axis direction in the film plane, ny is the refractive index in the fast axis direction in the film plane, nz is the refractive index in the thickness direction of the film, and d is (The thickness of the film (nm).)
An optical film having a dimensional change rate of 0.1 to 0.5% when treated at 60 ° C. and 90% RH for 24 hours.
However, the dimensional change rate is an absolute value of a value obtained by dividing the dimensional change when the optical film is allowed to stand for 24 hours under the conditions of 60 ° C. and 90% RH by the initial length.
<2>
The optical film as described in <1> whose film thickness is 5-80 micrometers.
<3>
The optical film as described in <1> or <2> whose tensile elastic modulus is 3.0 GPa or more.
<4>
The optical film according to any one of <1> to <3>, wherein the dimensional change rate is a dimensional change rate in a direction orthogonal to a direction in which the elastic modulus of the film is maximum.
<5>
The optical film according to any one of <1> to <4>, wherein the optical film is a film in which two or more layers containing cellulose acetate and an additive are laminated.
<6>
The optical film according to <5>, wherein the optical film is a film in which a support surface side layer, an intermediate layer, and an air surface side layer are laminated.
<7>
The optical film according to <6>, wherein the amount of additive material in the support surface side layer and the air surface side layer is smaller than the amount of additive material in the intermediate layer.
<8>
A polarizing plate comprising at least the optical film according to any one of <1> to <7>, wherein a direction in which the elastic modulus of the optical film is maximum and an absorption axis direction of the polarizing plate are mutually Polarizing plates that are parallel.
<9>
A polarizing plate comprising at least the optical film according to any one of <1> to <7>, wherein a direction in which the elastic modulus of the optical film is maximum and an absorption axis direction of the polarizing plate are mutually A polarizing plate that is orthogonal.
<10>
An image display device comprising at least the optical film according to any one of <1> to <7>, or the polarizing plate according to <8> or <9>.
<11>
Including one or more additives and cellulose acetate,
The total content of the additive (Ct; unit: mass% with respect to the cellulose acetate) and the film thickness (d; unit: μm) satisfy the relationship of Ct <30 and Ct / d ≧ 0.375,
The acyl substitution degree of the cellulose acetate is 2.8 to 2.94 (excluding 2.8),
The following formula (IIIa) and formula (IVa) are satisfied,
Formula (I) Re = (nx−ny) × d (nm)
Formula (II) Rth = {(nx + ny) / 2−nz} × d (nm)
Formula (IIIa) Re <10
Formula (IVa) | Rth | <25
(Where nx is the refractive index in the slow axis direction in the film plane, ny is the refractive index in the fast axis direction in the film plane, nz is the refractive index in the thickness direction of the film, and d is (The thickness of the film (nm).)
And the manufacturing method of the optical film whose dimensional change rate at the time of processing at 60 degreeC and 90% RH for 24 hours is 0.1-0.5%,
After gripping the web containing at least the additive, cellulose acetate, and residual solvent with a tenter,
(A) The process of extending | stretching in the width direction in the state whose residual solvent amount is 3-250 mass% per total solid of a web,
(B) a step of subsequently reducing the width in the width direction;
(C) 5 to 5,000 seconds at a temperature (T1) set in the range of (Tg−20) to (Tc + 20) ° C. with the residual solvent amount being 0.01 to 30% by mass based on the total solid content of the web. A method for producing an optical film, comprising a step of heating. [Here, Tg represents the glass transition temperature (unit: ° C) of the web, and Tc represents the crystallization temperature (unit: ° C) of the web. ]
<12>
After the steps (A) to (C),
(D) The manufacturing method of the optical film as described in <11> including the process of removing a web (film) from a tenter, and the highest heating temperature (T2) after a (D) process is lower than said T1.
<13>
The method for producing an optical film according to <11> or <12>, wherein the width reduction ratio in the step (B) is 0.5% or more.
<14>
Any of <11> to <13>, wherein the ratio (Wt / Ww) of the width reduction ratio (Wt) to the free shrinkage ratio (Ww) of the web in the step (B) is 0.7 to 1.3. The manufacturing method of the optical film of Claim 1.
Although this invention is invention which concerns on said <1>-<14>, below, other matters are also described.

[1]
An optical film comprising one or more additives and a cellulose ester,
The total content of the additive (Ct; unit: mass% with respect to the cellulose ester) and the film thickness (d; unit: μm) satisfy the relationship of Ct <30 and Ct / d ≧ 0.375,
An optical film having a dimensional change rate of 3% or less when treated at 60 ° C. and 90% RH for 24 hours.
However, the dimensional change rate is an absolute value of a value obtained by dividing the dimensional change when the optical film is allowed to stand for 24 hours under the conditions of 60 ° C. and 90% RH by the initial length.
[2]
The optical film as described in [1] whose film thickness is 5-80 micrometers.
[3]
The optical film according to [1] or [2], which has a tensile modulus of 3.0 GPa or more.
[4]
The optical film according to any one of [1] to [3], wherein the dimensional change rate is a dimensional change rate in a direction orthogonal to a direction in which the elastic modulus of the film is maximum.
[5]
The optical film according to any one of [1] to [4], wherein the optical film is a film in which two or more layers containing a cellulose ester and an additive are laminated.
[6]
A polarizing plate comprising at least the optical film according to any one of [1] to [5], wherein a direction in which the elastic modulus of the optical film is maximum and an absorption axis direction of the polarizing plate are mutually Polarizing plates that are parallel.
[7]
A polarizing plate comprising at least the optical film according to any one of [1] to [5], wherein a direction in which the elastic modulus of the optical film is maximum and an absorption axis direction of the polarizing plate are mutually A polarizing plate that is orthogonal.
[8]
An image display device comprising at least the optical film according to any one of [1] to [5] or the polarizing plate according to [6] or [7].
[9]
Including one or more additives and a cellulose ester,
The total content of the additive (Ct; unit mass% with respect to the cellulose ester) and the film thickness (d; unit μm) satisfy the relationship of Ct <30 and Ct / d ≧ 0.375,
And the manufacturing method of the optical film whose dimensional change rate at the time of processing for 24 hours at 60 degreeC and 90% RH is 3% or less,
After gripping the web containing at least the additive, cellulose ester, and residual solvent with a tenter,
(A) The process of extending | stretching in the width direction in the state whose residual solvent amount is 3-250 mass% per total solid of a web,
(B) a step of subsequently reducing the width in the width direction;
(C) 5 to 5,000 seconds at a temperature (T1) set in the range of (Tg−20) to (Tc + 20) ° C. with the residual solvent amount being 0.01 to 30% by mass based on the total solid content of the web. A method for producing an optical film, comprising a step of heating. [Here, Tg represents the glass transition temperature (unit: ° C) of the web, and Tc represents the crystallization temperature (unit: ° C) of the web. ]
[10]
After the steps (A) to (C),
(D) The manufacturing method of the optical film as described in [9] including the process of removing a web (film) from a tenter, and the highest heating temperature (T2) after a (D) process is lower than said T1.
[11]
Including one or more additives and a cellulose ester,
The total content of the additive (Ct; unit mass% with respect to the cellulose ester) and the film thickness (d; unit μm) satisfy the relationship of Ct <30 and Ct / d ≧ 0.375,
And the manufacturing method of the optical film whose dimensional change rate at the time of processing for 24 hours at 60 degreeC and 90% RH is 3% or less,
After gripping the web containing at least the additive, cellulose ester, and residual solvent with a tenter,
(A) The process of extending | stretching in the width direction in the state whose residual solvent amount is 3-250 mass% per total solid of a web,
(B) a step of subsequently reducing the width in the width direction;
(C) a step of heating to a temperature (T1) set in the range of (Tg-20) to (Tc + 20) ° C. in a state where the residual solvent amount is 0.01 to 30% by mass per total solid content of the web;
(D) including a step of removing the web (film) from the tenter, and (E) after heating to a temperature (T3) set in the range of (Tg-20) to (Tc + 20) ° C. in the roller conveyance zone, (Tg-20) The manufacturing method of the optical film including the process cooled to the temperature (T4) set in the range of (degreeC). [Here, Tg represents the glass transition temperature (unit: ° C) of the web, and Tc represents the crystallization temperature (unit: ° C) of the web. ]
[12]
The method for producing an optical film according to [11], wherein the transport tension during cooling in the step (E) is lower than the transport tension during heating.
[13]
The method for producing an optical film according to any one of [9] to [12], wherein the width reduction ratio in the step (B) is 0.5% or more.
[14]
Any of [9] to [13], wherein the ratio (Wt / Ww) of the width reduction ratio (Wt) and the free shrinkage ratio (Ww) of the web in the step (B) is 0.7 to 1.3. The manufacturing method of the optical film of Claim 1.
[15]
Including one or more additives and a cellulose ester,
The total content of the additive (Ct; unit mass% with respect to the cellulose ester) and the film thickness (d; unit μm) satisfy the relationship of Ct <30 and Ct / d ≧ 0.375,
And the manufacturing method of the optical film whose dimensional change rate at the time of processing for 24 hours at 60 degreeC and 90% RH is 3% or less,
Having a step of casting at least two layers by a co-casting method,
Of the at least two layers, at least one layer is a layer containing an additive and a cellulose ester,
And the manufacturing method of the optical film from which the solid content concentration of the dope solution for forming at least one layer among the said at least 2 layers differs from the solid content concentration of the dope solution for forming another layer.

The present invention preferably further has the following configuration.
[16]
The optical film according to any one of [1] to [5], wherein the moisture permeability at 40 ° C. and 90% RH is 500 to 3000 g / (m ² · day).
[17]
The optical film according to any one of [1] to [5] and [16], wherein the dimensional change rate is a dimensional change rate in a direction in which the elastic modulus of the film is maximized.
[18]
The optical film according to any one of [1] to [5], [16] and [17], wherein the additive is a compound having a repeating unit.
[19]
The optical film according to any one of [1] to [5] and [16] to [18], which contains the compound represented by the general formula (1) or (2).
General formula (1)

(In the general formula (1), Ra is a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkynyl group, a substituted or unsubstituted heterocyclic group, or a substituted or unsubstituted substituent. Represents an aryl group, X ¹ , X ² , X ³ and X ⁴ each independently represents a single bond or a divalent linking group, R ¹ , R ² , R ³ and R ⁴ each independently represent a hydrogen atom or a substituent; Or an unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkynyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted acyl group, or a substituted or unsubstituted heterocyclic group; Represents.)
General formula (2)

(In General Formula (2), Rb and Rc are each independently a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkynyl group, a substituted or unsubstituted heterocyclic group, or Represents a substituted or unsubstituted aryl group, X ⁵ and X ⁶ each independently represents a single bond or a divalent linking group, R ⁵ and R ⁶ each independently represent a hydrogen atom, a substituted or unsubstituted alkyl group, A substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkynyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted acyl group, or a substituted or unsubstituted heterocyclic group.
[20]
The image display device according to [8], wherein the optical film is disposed closer to the liquid crystal cell than the polarizing film.

  The optical film containing the cellulose ester of the present invention is excellent in the appearance of a roll, has a desired retardation, a humidity dependency of the desired retardation, and is used for a polarizing plate or a liquid crystal display device as an optical film having a small dimensional change. Can do. In a polarizing plate using such an optical film, peeling, record streak-like unevenness and curling are suppressed. In addition, the liquid crystal panel using the retardation film and the polarizing plate produced using the optical film of the present invention, and the liquid crystal display device are excellent in suppressing the occurrence of light unevenness on the display surface when observed from the front and oblique directions. Show reliability.

  Hereinafter, the present invention will be described in detail. In the present specification, when numerical values represent physical property values, characteristic values, etc., the descriptions “(numerical value 1) to (numerical value 2)” and “(numerical value 1) to (numerical value 2)” are “(numerical value 1). ) ”(Numerical value 2) or less”.

  The optical film of the present invention is a film containing at least a cellulose ester and an additive, wherein one or two or more additives are less than 30% by mass with respect to the cellulose ester and Ct / d ≧ 0.375. Contains only the amount that satisfies As an additive, an additive usually used for cellulose ester (for example, JIII Journal of Technical Disclosure 2001-1745) can be used. It is preferable from the viewpoint of suppressing volatilization in the production process.

In the present invention, the additive is a component different from the above-mentioned cellulose ester and a polymer compound different from the cellulose ester described later, and when calculating the total content (Ct) of one or more additives. In addition, a high molecular compound different from a cellulose ester or a cellulose ester described later is not included in the “additive”.
The optical film of this invention can improve the light nonuniformity of a liquid crystal display device by containing an additive (preferably the compound which has a repeating unit) in said amount with respect to a cellulose ester.

The relationship between the total content of one or more additives (preferably a compound having a repeating unit) and the film thickness more preferably satisfies Ct / d ≧ 0.563, and Ct / d ≧ More preferably, it is 0.750.
The upper limit of Ct / d is not particularly limited, but is preferably Ct / d ≦ 3.0, more preferably Ct / d ≦ 2.0, and Ct / d ≦ 1.5. More preferably.

The total content of one or more additives (preferably a compound having a repeating unit) is preferably 2% by mass or more and less than 30% by mass with respect to the cellulose ester, and is 5 to 25% by mass. It is more preferable, and it is still more preferable that it is 6-20 mass%. The content is preferably 2% by mass or more and satisfying Ct / d ≧ 0.375, so that light unevenness can be improved. By being less than 30% by mass, deterioration of roll appearance over time can be easily suppressed. preferable.
When two or more additives are contained, the total content of the two or more additives may be within the above range in the optical film of the present invention. Moreover, when the optical film of this invention contains polymers other than a cellulose ester (for example, polymer blend), polymers other than this cellulose ester shall not be included in an additive.

[Compound having a repeating unit]
The optical film of the present invention preferably contains a compound having a repeating unit.
The number average molecular weight (Mn) of the compound having a repeating unit in the present invention is preferably 600 to 50,000, more preferably 900 to 10,000, and further preferably 1,000 to 5,000. If the number average molecular weight of the compound having a repeating unit is 600 or more, the volatility is low, and the film of the optical film of the present invention is formed, or film failure or process contamination due to volatilization under high temperature conditions when stretched is difficult to occur. At the same time, by increasing the molecular weight, it is possible to suppress a retardation change when held in a moist heat environment. Moreover, if it is 50000 or less, compatibility with a cellulose ester can be ensured, and the humidity dependency of retardation considered to be derived from cellulose ester molecules can be effectively reduced, or bleeding out can be suppressed. it can. However, the compound having a repeating unit in the present invention is not limited to only a compound having such a repeating unit portion, and may be a mixture with a compound having no repeating unit.

The number average molecular weight of the compound having a repeating unit in the present invention can be measured and evaluated by gel permeation chromatography.
In addition, the compound having a repeating unit of the present invention may be liquid or solid under the ambient temperature or humidity used (generally room temperature conditions, so-called 25 ° C., relative humidity 60%). Further, the smaller the color, the better, and it is particularly preferable that the color is colorless. Thermally, it is preferably stable at a higher temperature, and the decomposition start temperature is preferably 150 ° C. or higher, more preferably 200 ° C. or higher.
Hereinafter, although the compound which has a repeating unit used for this invention is demonstrated in detail, giving the specific example, the compound which has a repeating unit which can be used by this invention is not limited to these.

(Types of compounds having repeating units)
Although it does not specifically limit as a compound which has a repeating unit which can be used for the optical film of this invention, A condensate or an adduct can be mentioned, As a condensate, the condensate of a polyhydric alcohol and a polybasic acid is mentioned. Preferred examples include condensates of polyhydric ether alcohols and polybasic acids, condensates of polyhydric alcohols and polybasic acids and isocyanate compounds, and the adduct is an addition of an acrylic ester. And adducts of methacrylic acid esters are preferred. In addition, a number average of at least one selected from polyether compounds, polyurethane compounds, polyether polyurethane compounds, polyamide compounds, polysulfone compounds, polysulfonamide compounds, and other polymer compounds described later. A compound having a molecular weight of 600 or more can also be used.

At least one of them is preferably a condensate of polyhydric alcohol and polybasic acid, a condensate of polyhydric ether alcohol and polybasic acid, an adduct of acrylic ester, an adduct of methacrylic ester, A condensate of polyhydric alcohol and polybasic acid, a condensate of polyhydric ether alcohol and polybasic acid are more preferable, and a condensate of polyhydric alcohol and polybasic acid is still more preferable.
Hereinafter, the compounds having a repeating unit preferably used in the present invention will be described by type.

(Condensate of polyhydric alcohol and polybasic acid)

First, the condensate of polyhydric alcohol and polybasic acid used in the present invention will be described. A preferred condensate of a polyhydric alcohol and a polybasic acid is not particularly limited, and is obtained by a reaction between a dibasic acid and a glycol. Carrying out so-called terminal sealing by reacting carboxylic acid or monoalcohol is preferable because it can suppress a change in retardation when held in a humid heat environment. In such a condensate, the hydroxyl value is lowered as compared with a condensate having an unsealed end, and the hydroxyl value is preferably less than 40 mgKOH / g, more preferably 20 mgKOH / g or less, and 10 mgKOH. / G or less is more preferable.
In the condensate of polyhydric alcohol and polybasic acid used in the present invention, the polyhydric alcohol preferably contains at least a polyhydric alcohol having 3 or more carbon atoms from the viewpoint of suppressing contamination of the casting support.
The condensate of polyhydric alcohol and polybasic acid used in the present invention is preferably synthesized from a glycol having 2 to 12 carbon atoms and a dibasic acid having 4 to 12 carbon atoms.

As a dibasic acid used for the condensate of the polyhydric alcohol and polybasic acid of the present invention, an aliphatic dicarboxylic acid residue or alicyclic dicarboxylic acid residue having 3 to 12 carbon atoms or 8 to 12 carbon atoms is used. The aromatic dicarboxylic acid residue is preferred. And in order to improve the grade of the bleed-out accompanying heat processing, it is more preferable to contain an aliphatic polybasic acid and / or an aromatic polybasic acid having at least 4 carbon atoms. Moreover, as a glycol, it is preferable that it is a C2-C12 aliphatic or alicyclic glycol residue, and a C6-C12 aromatic glycol residue. These may be appropriately selected and used according to the desired retardation, and may contain only one type or two or more types. For example, when it is desired to produce a film with reduced retardation, it is preferable to select an aliphatic or alicyclic dicarboxylic acid residue or phthalic acid residue, and an aliphatic or alicyclic glycol residue. Moreover, when it is desired to create a film with an increased retardation, it is preferable to contain an aromatic dicarboxylic acid residue and / or an aromatic glycol residue.
The dibasic acid and glycol that can be preferably used for the synthesis of the condensate of polyhydric alcohol and polybasic acid in the present invention will be described below.

As the dibasic acid, either an aliphatic dicarboxylic acid or an aromatic dicarboxylic acid can be used.
Examples of the aliphatic dicarboxylic acid include oxalic acid, malonic acid, succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, suberic acid, azelaic acid, cyclohexanedicarboxylic acid, sebacic acid, and dodecanedicarboxylic acid. . Of these, malonic acid, succinic acid and adipic acid are preferably included from the viewpoint of improving compatibility.
Examples of the aromatic dicarboxylic acid include phthalic acid, terephthalic acid, isophthalic acid, 1,5-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, and the like. Of these, phthalic acid and terephthalic acid are preferable, and terephthalic acid is particularly preferable.
The dibasic acid used in the present invention has preferably 3 to 12 carbon atoms, more preferably 4 to 8 carbon atoms, and preferably 4 to 6 carbon atoms. In the present invention, a mixture of two or more dibasic acids may be used. In this case, the average carbon number of the two or more dibasic acids is preferably in the above range. If the number of carbon atoms of the dibasic acid is within the above range, it is preferable because in addition to improving the light unevenness, it is excellent in compatibility with the cellulose ester and bleed-out hardly occurs at the time of film formation and heat stretching of the optical film.
It is also preferable to use an aliphatic dicarboxylic acid and an aromatic dicarboxylic acid in combination. Specifically, a combination of adipic acid and phthalic acid, a combination of adipic acid and terephthalic acid, a combined use of succinic acid and phthalic acid, and a combined use of succinic acid and terephthalic acid are preferred. The combined use of succinic acid and terephthalic acid is more preferable. When the aliphatic dicarboxylic acid and the aromatic dicarboxylic acid are used in combination, the ratio (molar ratio) between the two is not particularly limited, but is preferably 95: 5 to 40:60, and more preferably 55:45 to 45:55.

Examples of the glycol (diol) include aliphatic diols and aromatic diols, and aliphatic diols are preferable.
Examples of the aliphatic diol include alkyl diols and alicyclic diols, such as ethylene glycol (ethanediol), 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 2-methyl-1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 2,2-diethyl-1,3-propanediol (3,3-dimethylolpentane), 2-n-butyl-2-ethyl-1,3-propanediol (3,3-dimethylolheptane), 3- Methyl-1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedi Tanol, 2,2,4-trimethyl-1,3-pentanediol, 2-ethyl-1,3-hexanediol, 2-methyl-1,8-octanediol, 1,9-nonanediol, 1,10- Examples include decanediol and diethylene glycol.
The preferred aliphatic diol is at least one of ethylene glycol, 1,2-propanediol, and 1,3-propanediol, and particularly preferably at least one of ethylene glycol and 1,2-propanediol. . When two types are used, it is preferable to use ethylene glycol and 1,2-propanediol.
The number of carbon atoms of the glycol is preferably 2 to 10, more preferably 2 to 6, and particularly preferably 2 to 4. When using 2 or more types of glycols, it is preferable that the average number of carbons of 2 or more types falls in the above range. If the number of carbon atoms of the glycol is in the above range, in addition to improving the light unevenness, it is excellent in compatibility with the cellulose ester, and bleed-out is unlikely to occur during film formation and heat stretching, which is preferable.

  Moreover, it is preferable to protect both ends of the condensate of the polyhydric alcohol and polybasic acid of the present invention with a monoalcohol residue or a monocarboxylic acid residue. In this case, the monoalcohol residue is preferably a substituted or unsubstituted monoalcohol residue having 1 to 30 carbon atoms, such as methanol, ethanol, propanol, isopropanol, butanol, isobutanol, pentanol, isopentanol, hexanol, isopropanol. Hexanol, cyclohexyl alcohol, octanol, isooctanol, 2-ethylhexyl alcohol, nonyl alcohol, isononyl alcohol, tert-nonyl alcohol, decanol, dodecanol, dodecahexanol, dodecaoctanol, allyl alcohol, oleyl alcohol and other aliphatic alcohols, benzyl alcohol And substituted alcohols such as 3-phenylpropanol.

  Moreover, when sealing with a monocarboxylic acid residue, the monocarboxylic acid used as a monocarboxylic acid residue is preferably a substituted or unsubstituted monocarboxylic acid having 1 to 30 carbon atoms. These may be aliphatic monocarboxylic acids or aromatic carboxylic acids. First, preferred aliphatic monocarboxylic acids are described. Examples include acetic acid, propionic acid, butanoic acid, caprylic acid, caproic acid, decanoic acid, dodecanoic acid, stearic acid, and oleic acid. Examples of aromatic monocarboxylic acids include benzoic acid. Acid, p-tert-butylbenzoic acid, orthotoluic acid, metatoluic acid, p-toluic acid, dimethylbenzoic acid, ethylbenzoic acid, normal propylbenzoic acid, aminobenzoic acid, acetoxybenzoic acid, etc., each of which is one or two It can be used as a mixture of seeds or more.

  At this time, if the number of carbon atoms of the monocarboxylic acid residues at both ends is 3 or less, the volatility decreases, the weight loss due to heating of the condensate of the polyhydric alcohol and the polybasic acid does not increase, and process contamination Occurrence and occurrence of surface failure can be reduced. From such a viewpoint, aliphatic monocarboxylic acids are preferable as monocarboxylic acids used for sealing. The monocarboxylic acid is more preferably an aliphatic monocarboxylic acid having 2 to 22 carbon atoms, more preferably an aliphatic monocarboxylic acid having 2 to 3 carbon atoms, and an aliphatic monocarboxylic acid residue having 2 carbon atoms. Particularly preferred is a group. For example, acetic acid, propionic acid, butanoic acid, benzoic acid and derivatives thereof are preferable, acetic acid or propionic acid is more preferable, and acetic acid (terminal is an acetyl group) is most preferable. Two or more monocarboxylic acids used for sealing may be mixed.

  In addition, when the both ends of the condensate of a polyhydric alcohol and a polybasic acid are unsealed, it is preferable that this condensate is a polyester polyol.

  As mentioned above, specific preferred polyhydric alcohol and polybasic acid condensates include poly (ethylene glycol / adipic acid) ester, poly (propylene glycol / adipic acid) ester, poly (1,3-butanediol / adipine). Acid) ester, poly (propylene glycol / sebatic acid) ester, poly (1,3-butanediol / sebatic acid) ester, poly (1,6-hexanediol / adipic acid) ester, poly (propylene glycol / phthalic acid) Ester, poly (1,3-butanediol / phthalic acid) ester, poly (propylene glycol / terephthalic acid) ester, poly (propylene glycol / 1,5-naphthalene-dicarboxylic acid) ester, poly (propylene glycol / terephthalic acid) Both ends of the ester are 2-ethyl- Hexyl alcohol ester / poly (propylene glycol adipate) both ends of ester 2-ethyl - hexyl alcohol esters, acetylated poly (butanediol / adipic acid) ester, and the like.

  The synthesis of a condensate of such a polyhydric alcohol and a polybasic acid is carried out by a conventional method, a hot melt condensation method using a (poly) esterification reaction or a transesterification reaction between the dibasic acid or an alkyl ester thereof and a glycol. Alternatively, it can be easily synthesized by any of the interfacial condensation methods of acid chlorides of these acids and glycols. Condensation products of these polyhydric alcohols and polybasic acids are described in detail in Koichi Murai, “Plasticizers, Theory and Applications” (Kokai Shobo Co., Ltd., first published on March 1, 1973). There is. In addition, Japanese Patent Laid-Open Nos. 05-155809, 05-155810, Japanese Patent Laid-Open Nos. 05-97073, 2006-259494, 07-330670, 2006-342227, 2007-003679. The materials described in each publication can also be used.

  Moreover, the compound (oligomer) whose molecular weight is the said preferable range can be used as an additive among what is sold by each company as goods. Specifically, from Adeka Corporation, Adeka Sizer (various types of Adeka Sizer P series and Adeka Sizer PN series) described in DIARY 2007, pages 55-27 as condensates of polyhydric alcohols and polybasic acids Dainippon Ink and Chemicals Co., Ltd. “Polymer-related products list 2007 edition” on page 25, various products of polylite, Dainippon Ink and Chemicals Co., Ltd. “DIC polymer modifier” (2004. 4) .1.000VIII issue) Various polycizers described on pages 2 to 5 can be used. Furthermore, it can be obtained as a Plasticall P series manufactured by CP HALL, USA. Benzoyl functionalized polyethers are commercially available from Velsicol Chemicals, Rosemont, Ill. Under the trade name BENZOFLEX (eg, BENZOFLEX 400, polypropylene glycol dibenzoate).

(Condensate of polyhydric ether alcohol and polybasic acid)
Next, the condensate of polyhydric ether alcohol and polybasic acid used in the present invention will be described. The condensate of the polyhydric ether alcohol and polybasic acid of the present invention indicates a condensation oligomer of dicarboxylic acid and polyether diol. As the dicarboxylic acid, an aliphatic dicarboxylic acid residue having 4 to 12 carbon atoms or an aromatic dicarboxylic acid residue having 8 to 12 carbon atoms described as a condensate of a polyhydric alcohol and a polybasic acid is used as it is. is there.

  Next, examples of the polyethers having an aliphatic glycol having 2 to 12 carbon atoms include polyethylene ether glycol, polypropylene ether glycol, polytetramethylene ether glycol, and combinations thereof. Typical useful commercially available polyether glycols include Carbowax resin, Pluronics resin and Niax resin. In the production of the polyester polyether plasticizer used in the present invention, a commonly used polymerization method known to those skilled in the art can be used.

  Examples of condensates of these polyhydric ether alcohols and polybasic acids include condensates of polyhydric ether alcohols and polybasic acids described in US Pat. No. 4,349,469. Basically, for example, a condensate of polybasic acid and polyhydric ether alcohol synthesized from 1,4-cyclohexanedicarboxylic acid as dicarboxylic acid and 1,4-cyclohexanedimethanol and polytetramethylene ether glycol as polyether. It is. As other useful condensates of polyhydric ether alcohols and polybasic acids, for example, compounds (oligomers) having a molecular weight within the above preferred range among those shown below can be used. Specific examples include commercially available resins such as DuPont Hytrel copolyesters and GAF copolymers such as Galflex polymers. For these, the materials described in JP-A-5-197073 can be used. It is commercially available as ADEKA Sizer RS series from ADEKA Corporation. Polyester ether plasticizers that are alkyl functionalized polyalkylene oxides are commercially available from ICI Chemicals, Wilmington, Del., Under the trade name PYCAL (eg, PYCAL 94, a phenyl ester of polyethylene oxide). ).

(Condensate of polyhydric alcohol and polybasic acid and isocyanate compound)
Furthermore, the condensate of the polyhydric alcohol and polybasic acid used in the present invention and the isocyanate compound will be described. The condensate can be obtained by condensation of a polyhydric alcohol and polybasic acid condensate and an isocyanate compound. First, as the condensate of polyhydric alcohol and polybasic acid, the condensate of polyhydric alcohol and polybasic acid before sealing both ends can be used as it is. The above-mentioned materials can be preferably used.

Examples of the diisocyanate component forming the polyurethane structure include OCN (CH ₂ ) _p NCO (p = 2) represented by ethylene diisocyanate, trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate and the like. -8) Polymethylene isocyanate and aromatic diisocyanates such as p-phenylene diisocyanate, tolylene diisocyanate, p, p'-diphenylmethane diisocyanate, 1,5-naphthylene diisocyanate, Although m-xylylene diisocyanate or the like is used, it is not limited thereto. Among these, tolylene diisocyanate, m-xylylene diisocyanate, and tetramethylene diisocyanate are particularly preferable.

  In the present invention, a condensate of a polyhydric alcohol and a polybasic acid and an isocyanate compound can be easily synthesized by a conventional synthesis method in which a raw material polyester diol and diisocyanate are mixed and heated with stirring. You can get to For these, the materials described in JP-A-5-197073, JP-A-2001-122979, JP-A-2004-175971, JP-A-2004-175972 and the like can be used.

(High molecular compounds other than cellulose ester)
In the present invention, in addition to the cellulose ester, other polymer compounds can be used in combination. Examples of the high molecular weight compound include aliphatic hydrocarbon polymers, alicyclic hydrocarbon polymers, acrylic polymers such as polyacrylates and polymethacrylates (the ester groups include methyl, ethyl, propyl Group, butyl group, isobutyl group, pentyl group, hexyl group, cyclohexyl group, octyl group, 2-ethylhexyl group, nonyl group, isononyl group, tert-nonyl group, dodecyl group, tridecyl group, stearyl group, oleyl group, benzyl group , Phenyl group, etc.), polyvinyl isobutyl ether, vinyl polymers such as poly N-vinylpyrrolidone, styrene polymers such as polystyrene and poly 4-hydroxystyrene, polyethers such as polyethylene oxide and polypropylene oxide, polyamides, polyurethanes, polyureas Phenol - formaldehyde condensate, urea - formaldehyde condensate, vinyl acetate, and the like.

  These polymer compounds may be a homopolymer composed of one type of repeating unit or a copolymer having a plurality of repeating structures. Two or more of the above polymers may be used in combination. These high molecular compounds may be used alone, or the same effect can be obtained by using them in combination. Among these, a polyacrylic acid ester, a polymethacrylic acid ester, or a copolymer with another vinyl monomer is preferable, and in particular, an acrylic polymer such as polyacrylic acid ester and polymethacrylic acid ester (the ester group is methyl). Group, ethyl group, propyl group, butyl group, hexyl group, cyclohexyl group, 2-ethylhexyl group, isononyl group, oleyl group).

[Humidity dependency reducing agent]
In addition to the additives described above, the optical film of the present invention is a humidity dependency reducing agent having ΔRth (A) defined by the following formula (A) of −100 or more and less than 0 nm as a compound that further reduces humidity dependency Can also be included. When such an additive is used in combination, the humidity dependency of Rth can be more efficiently reduced, so that the total amount of the additive can also be reduced. And it is preferable also from a viewpoint of a dimensional change rate reduction to reduce the total amount of an additive.
Formula (A) ΔRth (A) = (ΔRth (rh, A) −ΔRth (rh, 0)) / Q [wherein ΔRth (rh, A) is 25 ° C. relative to the film to which the compound is added. This represents a value obtained by subtracting Rth at 25 ° C. and 80% relative humidity from Rth at 10% humidity, and ΔRth (rh, 0) is 25 from Rth at 25 ° C. and 10% relative humidity of the film to which the compound is not added. It represents a value obtained by subtracting Rth at 80 ° C. and relative humidity of 80%, and Q represents the mass of the compound when the mass of the cellulose ester in the film is 100. ]
When such a compound is used, ΔRth can be effectively reduced even with a small addition amount, so that the total amount of the additive with respect to the cellulose ester can be reduced, for example, suppressing the volatilization of the additive during the film forming process. Or improving the film transportability, or suppressing the bleeding out of the film. ΔRth (A) is more preferably −50 to 10 nm, and further preferably −30 to 0 nm.
Examples of such a compound include a compound having a hydrogen bonding group and a high density of hydrogen bonding groups per molecular weight. The hydrogen bonding group is preferably a group containing at least one —OH group or —NH group. For example, a hydroxyl group (—OH), a carboxyl group (—COOH), a carbamoyl group (—CONHR), A sulfamoyl group (—SONHR), a ureido group (—NHCONHR), an amino group (—NHR), a urethane group (—NHCOOR), and an amide group (—NHCOR) are more preferable. However, R represents a hydrogen atom, a hydroxy group, an amino group, an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 15 carbon atoms, or a heterocyclic group, and preferably represents a hydrogen atom. More preferred are an amino group, a hydroxyl group, a carboxyl group, a carbamoyl group, a sulfamoyl group or a ureido group, and even more preferred are an amino group and a hydroxyl group. It is further preferred that at least one of the hydroxyl groups is a phenolic hydroxyl group.
Specific examples of the compound that reduces the humidity dependency of retardation include the following compounds.

(Compound having a hydroxyl group)
Examples of the compound containing a hydroxyl group preferably used in the present invention, more preferably a compound containing a phenolic hydroxyl group, include, for example, Compound A described in pages 13 to 19 of JP-A-2008-89860, and JP-A A compound represented by the general formula (I) described on pages 7 to 9 of 2008-233530 can be preferably used.

(Compound having an amino group)
Although it does not specifically limit as a compound containing the amino group preferably used by this invention, It is preferable that it is a compound represented by the following general formula (1) or (2).

  General formula (1)

(In the general formula (1), Ra represents an alkyl group, an alkenyl group, an alkynyl group, a heterocyclic group or an aryl group. X ¹ , X ² , X ³ and X ⁴ are each independently a single bond or a divalent linkage. R ¹ , R ² , R ³ and R ⁴ each independently represents a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aryl group, an acyl group or a heterocyclic group.

  General formula (2)

(In general formula (2), Rb and Rc each independently represents an alkyl group, an alkenyl group, an alkynyl group, a heterocyclic group or an aryl group. X ⁵ and X ⁶ each independently represent a single bond or a divalent linking group. R ⁵ and R ⁶ each independently represents a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aryl group, an acyl group or a heterocyclic group.
X ^{1 to} X ⁶ represent a single bond or a divalent linking group, and may be the same or different from each other, and the divalent linking group is represented by the following general formula (3). It is preferable to be selected from the group.

  General formula (3)

  Hereinafter, compounds that can be preferably used in the present invention are shown as compounds having an amino group.

The compound having an amino group is preferably a compound represented by the following general formula (3) having a pyridine or pyrimidine mother nucleus and an amino group as a substituent at any substitutable position. Is also preferable.
General formula (3)

In general formula (3), Y represents a methine group or a nitrogen atom. Qa, Qb and Qc each independently represent a single bond or a divalent linking group. Ra, Rb and Rc are each independently a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkynyl group, a substituted or unsubstituted aryl group, a cyano group, or a halogen atom. Represents a substituted or unsubstituted heterocyclic group or —N (Rd) (Rd ′), Rd and Rd ′ each independently represent a hydrogen atom or a substituent, and Rd and Rd ′ are linked to each other to form a ring; May be formed. Ra and Rb may be connected to each other to form a ring. X ¹ represents a single bond or a divalent linking group selected from the following divalent linking group group (L). X ² represents a single bond or a divalent linking group. R ¹ and R ² are each independently a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkynyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted group And R ¹ and R ² may be linked to each other to form a ring.
Linking group (L)

(In each formula, the * side is a linking site with a nitrogen atom substituted on the nitrogen-containing aromatic ring in the compound represented by the general formula (3), and R ^g is a substituted or unsubstituted alkyl group, substituted Or an unsubstituted alkenyl group, a substituted or unsubstituted alkynyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heterocyclic group.

  In general formula (3), Y represents a methine group or a nitrogen atom. From the viewpoint of increasing hydrogen bonding properties, Y preferably represents a nitrogen atom.

In general formula (3), Qa, Qb and Qc each independently represent a single bond or a divalent linking group.
When Qa, Qb, and Qc represent a divalent linking group, the divalent linking group is preferably an oxygen atom, a sulfur atom, or —N (Rf) — (Rf represents a hydrogen atom or an alkyl group). ).
When Rf represents an alkyl group, an alkyl group having 1 to 10 carbon atoms is preferable, and an alkyl group having 1 to 5 carbon atoms is more preferable.
Qa preferably represents a single bond, an oxygen atom, or —NH—, and more preferably represents a single bond or an oxygen atom.
Qb preferably represents a single bond.
Qc preferably represents a single bond.

In general formula (3), Ra, Rb, and Rc are each independently a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkynyl group, substituted or unsubstituted aryl A group, a cyano group, a halogen atom, a substituted or unsubstituted heterocyclic group, or —N (Rd) (Rd ′), Rd and Rd ′ each independently represent a hydrogen atom or a substituent, and Rd and Rd 'May be linked to each other to form a ring. Ra and Rb may be connected to each other to form a ring.
When Ra, Rb, and Rc represent an alkyl group, it is preferably 1 to 12 carbon atoms, more preferably 1 to 8 carbon atoms, still more preferably 1 to 6 carbon atoms, It is especially preferable that it is 1-4.
When Ra, Rb, and Rc represent an alkenyl group, it is preferably 2 to 12 carbon atoms, more preferably 2 to 6 carbon atoms, and particularly preferably 2 to 4 carbon atoms.
When Ra, Rb, and Rc represent an alkynyl group, it is preferably 2 to 12 carbon atoms, more preferably 2 to 6 carbon atoms, and particularly preferably 2 to 4 carbon atoms.
When Ra, Rb, and Rc represent an aryl group, it preferably has 6 to 18 carbon atoms, more preferably 6 to 12 carbon atoms, and particularly preferably 6 carbon atoms (phenyl group).
When Ra, Rb, and Rc represent a heterocyclic group, a morpholinyl group and the like can be mentioned.
When Ra, Rb, and Rc represent -N (Rd) (Rd '), it is preferable that Rd or Rd' is a hydrogen atom.

  Ra, Rb, and Rc may have a substituent, and the substituent is the same as the substituent that Ra in the general formula (1) may have.

  Ra and Rb may be connected to each other to form a ring. In the case of forming a ring, the ring is preferably a nitrogen-containing aromatic ring, more preferably an imidazole ring.

Ra is preferably a hydrogen atom, an alkyl group, or an aryl group, and more preferably a hydrogen atom or an alkyl group.
Rb is preferably a hydrogen atom.
Rc is preferably —N (Rd) (Rd ′).

  Rd and Rd ′ each independently represent a hydrogen atom or a substituent, and Rd and Rd ′ may be linked to each other to form a ring. When Rd and Rd ′ represent a substituent, the substituent is the same as the substituent which Ra, Rb and Rc may have. Rd and Rd ′ may further have a substituent, and the further substituent is the same as the substituent which Ra, Rb and Rc may have.

In General Formula (3), X ¹ represents a single bond or a divalent linking group selected from the linking group group (L).
X ¹ is more preferably any of the following three linking groups, and even more preferably a carbonyl group.

(In each formula, the * side is a linking site with a nitrogen atom substituted on the nitrogen-containing aromatic ring in the compound represented by the general formula (3), and R ^g is a substituted or unsubstituted alkyl group, substituted Or an unsubstituted alkenyl group, a substituted or unsubstituted alkynyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heterocyclic group.
In General Formula (3), X ² represents a single bond or a divalent linking group. Specific examples and preferred ranges when X ² represents a divalent linking group are the same as the specific examples and preferred ranges when Qa, Qb and Qc represent a divalent linking group.
X ² preferably represents a single bond.

In general formula (3), R ¹ and R ² are each independently a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkynyl group, a substituted or unsubstituted aryl group Or a substituted or unsubstituted heterocyclic group, and R ¹ and R ² may be linked to each other to form a ring.

When R ¹ and R ² represent an alkyl group, an alkenyl group, an alkynyl group, an aryl group, or a heterocyclic group, specific examples and preferred ranges of the alkyl group, alkenyl group, alkynyl group, aryl group, or heterocyclic group include , Ra, Rb, and Rc are the same as the specific examples and preferred ranges in the case where each represents an alkyl group, an alkenyl group, an alkynyl group, an aryl group, or a heterocyclic group. Examples of the substituent that R ¹ and R ² may have are the same as the examples of the substituent that Ra, Rb, and Rc may have.

R ¹ preferably represents a substituted or unsubstituted aryl group. The substituent that the aryl group may have is preferably an alkyl group, an alkoxy group, a cyano group, a nitro group, a halogen atom, a substituted or unsubstituted carbamoyl group, or a substituted or unsubstituted sulfamoyl group, An alkyl group having 1 to 8 atoms, an alkoxy group having 1 to 8 carbon atoms, a halogen atom, a substituted or unsubstituted carbamoyl group, or a substituted or unsubstituted sulfamoyl group is more preferable. The substituent that the carbamoyl group or sulfamoyl group may have is preferably an alkyl group.

R ² preferably represents a hydrogen atom.

The compound represented by the general formula (3) is preferably a compound represented by the following general formula (4).
General formula (4)

Y, Qa, Qb, Ra, Rb, X ¹ , X ² , R ¹ , and R ² in the general formula (4) are respectively Y, Qa, Qb, Ra, Rb, in the general formula (3). ^{X 1, X 2, R 1} , or the same meaning as ^{R 2.} X ³ represents a single bond or a linking group selected from the divalent linking group group (L). X ⁴ represents a single bond or a divalent linking group. R ³ and R ⁴ are each independently a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkynyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted group And R ³ and R ⁴ may be linked to each other to form a ring.

Y, Qa, Qb, Ra, Rb, X ¹ , X ² , R ¹ , and R ² in the general formula (4) are respectively Y, Qa, Qb, Ra, Rb, in the general formula (3). ^{X 1, X 2, R 1} , and ^{R 2} in the above formula, the same applies to specific examples and preferred ranges.
In General Formula (4), X ³ represents a single bond or the divalent linking group group. Specific examples and preferred ranges of X ³ are the same as the specific examples and preferred ranges of X ^{1 in} the general formula (3).
In General Formula (4), X ⁴ represents a single bond or a divalent linking group. Specific examples and preferred ranges of X ⁴ are the same as the specific examples and preferred ranges of X ^{2 in} the general formula (1).
In general formula (4), R ³ and R ⁴ are each independently a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkynyl group, or a substituted or unsubstituted aryl group. Or a substituted or unsubstituted heterocyclic group, and R ³ and R ⁴ may be linked to each other to form a ring. Specific examples and preferred ranges of R ³ and R ⁴ are the same as the specific examples and preferred ranges of R ¹ and R ^{2 in} the general formula (3).

The compound represented by the general formula (4) is preferably a compound represented by the following general formula (5).
General formula (5)

Y, Qa, and Ra in general formula (5) are respectively synonymous with Y, Qa, and Ra in general formula (4). Ar ¹ and Ar ² each independently represent a substituted or unsubstituted aryl group.

Y, Qa, and Ra in the general formula (5) are respectively synonymous with Y, Qa, and Ra in the general formula (4), and specific examples and preferred ranges are also the same.
In General Formula (5), Ar ¹ and Ar ² each independently represent a substituted or unsubstituted aryl group. Specific examples and preferred ranges of the aryl group are the same as the specific examples and preferred ranges in the case where R ¹ in the general formula (3) represents an aryl group.

The compound represented by the general formula (5) is preferably a compound represented by the following general formula (6).
General formula (6)

Formula (6) in the Qa, Ra, Ar ^1, and Ar ² respectively, in formula (5) in Qa, Ra, and Ar ^1, and Ar ² synonymous.

Formula (6) in the Qa, Ra, Ar ^1, and Ar ² are each, Qa in the general formula (5), Ra, Ar ^1, and Ar ² in the above formula, specific examples and preferred ranges are also the same is there.

The compound represented by the general formula (6) is preferably a compound represented by the following general formula (7).
General formula (7)

In the general formula (7), ^{Q d} represents a single bond, an oxygen atom, or -NH-. R ^a8 represents an alkyl group having 1 to 8 carbon atoms. R ¹¹ , R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ and R ¹⁶ are each independently a hydrogen atom, a halogen atom, a substituted or unsubstituted carbamoyl group, a substituted or unsubstituted sulfamoyl group, or a group having 1 to 8 carbon atoms. An alkyl group or an alkoxy group having 1 to 8 carbon atoms is represented.

In the general formula (7), ^{Q d} represents a single bond, an oxygen atom, or -NH-. Q ^d is preferably a single bond or an oxygen atom.
In the general formula (7), R ¹¹ , R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ and R ¹⁶ are each independently a hydrogen atom, a halogen atom, a substituted or unsubstituted carbamoyl group, a substituted or unsubstituted sulfamoyl group, An alkyl group having 1 to 8 carbon atoms or an alkoxy group having 1 to 8 carbon atoms is represented. R ¹¹ , R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ and R ¹⁶ are a hydrogen atom, a substituted or unsubstituted carbamoyl group, a substituted or unsubstituted sulfamoyl group, an alkyl group having 1 to 8 carbon atoms, or carbon An alkoxy group having 1 to 8 atoms is preferable, and a hydrogen atom or an alkyl group having 1 to 8 carbon atoms is more preferable.

  Hereinafter, compounds that can be preferably used in the present invention are shown as compounds represented by the general formula (3).

The compound having an amino group is also preferably a compound represented by the following general formula (8).
General formula (8)

In General Formula (8), Qa ₈ and Qc ₈ each independently represent a single bond or a divalent linking group. Ra ₈ and Rc ₈ are each independently a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkynyl group, a substituted or unsubstituted aryl group, a cyano group, a halogen atom, A substituted or unsubstituted heterocyclic group, or -N (Rd) (Rd '), Rd and Rd' each independently represent a hydrogen atom or a substituent, and Rd and Rd 'are linked to each other to form a ring; It may be formed. X ⁸¹ represents a single bond or a divalent linking group selected from the divalent linking group group. ^X82 represents a single bond or a divalent linking group. R ⁸¹ and R ⁸² are each independently a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkynyl group, a substituted or unsubstituted aryl group, or substituted or unsubstituted And R ⁸¹ and R ⁸² may be linked to each other to form a ring.

In General Formula (8), specific examples of Qa ₈ and Qc ₈ are the same as Qa in General Formula (3).
In General Formula (8), specific examples of Ra ₈ and Rc ₈ are the same as Ra in General Formula (3).
In the general formula ^(8), the preferred range of ^{X 81} are the same as ^{X 1} in general formula (3).
In the general formula ^(8), the preferred range of ^{X 82} are the same as ^{X 2} in general formula (3).
In the general formula ^(8), the preferred range of ^{R 81} is the same as ^{R 1} in general formula (3).
In the general formula ^(8), the preferred range of ^{R 82} is the same as ^{R 2} in general formula (3).

The compound having an amino group is also preferably a compound represented by the following general formula (9).
General formula (9)

In general formula (9), Qa ₉ represents a single bond or a divalent linking group. Ra ₉ is a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkynyl group, a substituted or unsubstituted aryl group, a cyano group, a halogen atom, a substituted or unsubstituted complex. A ring group or —N (Rd) (Rd ′) is represented, Rd and Rd ′ each independently represent a hydrogen atom or a substituent, and Rd and Rd ′ may be linked to each other to form a ring. X ⁹¹ represents a single bond or a linking group selected from the divalent linking group group (L). X ^{92 to} X ⁹⁴ each independently represents a single bond or a divalent linking group. R ^{91 to} R ⁹⁴ are each independently a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkynyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted group Represents a heterocyclic group. R ⁹¹ and R ⁹² , and R ⁹³ and R ⁹⁴ may be connected to each other to form a ring.

In General Formula (9), specific examples of Qa ₉ are the same as Qa in General Formula (3).
In General Formula (9), specific examples of Ra ₉ are the same as Ra in General Formula (3).
In the general formula ^(9), the preferred range of ^{X 91} are the same as ^{X 1} in general formula (3).
In the general formula ^(9), the preferred range of X 92 ^{to X 94} are the same as ^{X 2} in general formula (3).
In general formula (9), the preferred range of R ⁹¹ is the same as R ¹ in general formula (3).
In the general formula ^(9), the preferred range of R 92 ^{to R 94} are the same as ^{R 2} in general formula (3).

  Although the specific example of a compound represented by General formula (8) or (9) is shown below, it is not limited to these.

The compound having an amino group is also preferably a compound represented by the following general formula (10).
General formula (10)

In General Formula (10), X ^{21 to} X ²⁶ each independently represent a single bond or a divalent linking group. R ^{21 to} R ²⁶ each independently represent a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aryl group, an acyl group, or a heterocyclic group.

In General Formula (10), the specific example in which X ^{21 to} X ²⁶ represent a divalent linking group is the same as the specific example in which X ¹ in General Formula (1) represents a divalent linking group. is there. In general formula (10), X ^{21 to} X ²⁶ are preferably single bonds.
In the general formula (10), specific examples of R ^{21 to} R ²⁶ are the same as the specific examples of R ¹ in the general formula (1). In general formula (10), it is preferable that R <^21> , R <^23> , and R <^25> are hydrogen atoms, and R <^22> , R <^24> , and R < ²⁶ > are aryl groups.

  Specific examples of the compound represented by the general formula (10) include, but are not limited to, the following compounds.

[Compounds that improve the durability of retardation]
The optical film of the present invention may contain a compound that improves the durability of retardation. The durability of retardation includes the durability observed as a retardation change when the film is held in a wet heat environment, and the retardation change when the film is held in a wet heat environment after being in the form of a polarizing plate. Regarding the former, it can be improved by using the above-mentioned condensate containing a polyhydric alcohol component having at least 3 carbon atoms and / or controlling the dimensional change rate described later. Further, regarding the latter, the above-mentioned condensate containing at least a polyhydric alcohol component having 3 or more carbon atoms is used, and / or within the preferred (number average) molecular weight range (600 to 50,000) of the compound having the above repeating unit. ) And / or a compound that improves the durability of retardation can be improved. As such a compound, a compound having a basic functional group in the molecule can be used. For example, the following compounds can be mentioned as specific examples.

[Cellulose ester]
Next, the cellulose ester in the present invention will be described.
The optical film of the present invention contains a cellulose ester, and the cellulose ester content is preferably 30 to 98% by mass, more preferably 50 to 95% by mass, and still more preferably 70 to 92% by mass. 80 to 90% by mass is most preferable. By this, moderate moisture permeability can be provided to a film and the optical film excellent in polarizing plate workability can be manufactured.
The cellulose ester used in the optical film of the present invention is an ester of cellulose and acid as raw materials, and is preferably a carboxylic acid ester (so-called cellulose acylate) having about 2 to 22 carbon atoms, and has 6 or less carbon atoms. More preferably, it is a lower fatty acid ester. In the cellulose acylate of the present invention, as a method for measuring the degree of substitution of acetic acid and / or a fatty acid having 3 to 22 carbon atoms to be substituted with a hydroxyl group of cellulose, a method according to ASTM D-817-91, or an NMR method Can be mentioned. In the case of cellulose acylate having about 2 to 22 carbon atoms, a condensate having a repeating unit is used, and in particular, in the case of cellulose acetate having 2 carbon atoms, in addition to this, an adduct having a repeating unit is used. Also preferably, the light unevenness of the liquid crystal display device can be improved.
Examples of the cellulose used as a raw material for the cellulose ester used in the present invention include cotton linter and wood pulp (hardwood pulp, softwood pulp). Cellulose esters obtained from any of the raw material cellulose can be used. May be. Detailed descriptions of these raw material celluloses can be found in, for example, Plastic Materials Course (17) Fibrous Resin (Maruzawa, Uda, Nikkan Kogyo Shimbun, published in 1970) and Invention Association Open Technical Report 2001-1745 (page 7). To page 8) can be used, and the optical film of the present invention is not particularly limited.

  In the cellulose acylate of the present invention, the degree of substitution of cellulose with a hydroxyl group is not particularly limited, but when used for polarizing plate protective film and optical film, cellulose is imparted with appropriate moisture permeability and hygroscopicity. It is preferable that the acyl substitution degree to the hydroxyl group is 2.00 to 3.00. Furthermore, the substitution degree is preferably 2.30 to 2.98, more preferably 2.70 to 2.96, and still more preferably 2.80 to 2.94.

  Of the acetic acid and / or the fatty acid having 3 to 22 carbon atoms substituted for the hydroxyl group of cellulose, the acyl group having 2 to 22 carbon atoms may be an aliphatic group or an aromatic group, and is not particularly limited. It may be a mixture of more than one type. 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. These preferred acyl groups include acetyl, propionyl, butanoyl, heptanoyl, hexanoyl, octanoyl, decanoyl, dodecanoyl, tridecanoyl, tetradecanoyl, hexadecanoyl, octadecanoyl, iso-butanoyl, t-butanoyl, cyclohexanecarbonyl, Examples include oleoyl, benzoyl, naphthylcarbonyl, and cinnamoyl groups. Among these, acetyl, propionyl, butanoyl, dodecanoyl, octadecanoyl, t-butanoyl, oleoyl, benzoyl, naphthylcarbonyl, cinnamoyl and the like are preferable, and acetyl, propionyl and butanoyl are more preferable.

  Among these, acetyl groups, mixed esters of acetyl groups and propyl groups are preferred, and acetyl groups are particularly preferred from the viewpoints of ease of synthesis, cost, ease of control of substituent distribution, and the like.

  The degree of polymerization of cellulose acylate preferably used in the present invention is 180 to 700 in terms of viscosity average polymerization degree, and in cellulose acetate, 180 to 550 is more preferable, 180 to 400 is more preferable, and 180 to 350 is particularly preferable. . If the degree of polymerization is too high, the viscosity of the cellulose acylate dope solution tends to be high, and film production tends to be difficult due to casting. If the degree of polymerization is too low, the strength of the produced film tends to decrease. The average degree of polymerization can be measured by Uda et al.'S intrinsic viscosity method (Kazuo Uda, Hideo Saito, Journal of Textile Society, Vol. 18, No. 1, pages 105-120, 1962). This is described in detail in JP-A-9-95538.

  Further, the molecular weight distribution of cellulose acylate preferably used in the present invention is evaluated by gel permeation chromatography, and its polydispersity index Mw / Mn (Mw is mass average molecular weight, Mn is number average molecular weight) is small, and molecular weight distribution. Is preferably narrow. The specific value of Mw / Mn is preferably 1.0 to 4.0, more preferably 2.0 to 3.5, and most preferably 2.3 to 3.4. preferable.

  When the low molecular component is removed, the average molecular weight (degree of polymerization) increases, but the viscosity becomes lower than that of normal cellulose acylate, which is useful. Cellulose acylate having a small amount of low molecular components can be obtained by removing low molecular components from cellulose acylate synthesized by a usual method. The removal of the low molecular component can be carried out by washing the cellulose acylate with an appropriate organic solvent. In addition, when manufacturing a cellulose acylate with few low molecular components, it is preferable to adjust the sulfuric acid catalyst amount in an acetylation reaction to 0.5-25 mass parts with respect to 100 mass parts of cellulose. When the amount of the sulfuric acid catalyst is within the above range, cellulose acylate that is preferable in terms of molecular weight distribution (narrow molecular weight distribution) can be synthesized. When used in the production of the cellulose acylate film of the present invention, the moisture content of the cellulose acylate is preferably 2% by mass or less, more preferably 1% by mass or less, and particularly preferably 0.7%. It is below mass%. In general, cellulose acylate contains water, and its water content is known to be 2.5 to 5% by mass. In order to obtain the moisture content of the cellulose acylate as described above in the present invention, it is necessary to dry, and the method is not particularly limited as long as the desired moisture content is obtained. Regarding these cellulose acylates of the present invention, the raw material cotton and the synthesis method thereof are disclosed on the 7th to 12th pages of the Japan Society for Invention and Innovation (public technical number 2001-1745, published on March 15, 2001, Japan Institute of Invention). It is described in detail.

  In the present invention, cellulose acylate can be used by mixing two or more different types of cellulose acylates from the viewpoint of substituents, substitution degree, polymerization degree, molecular weight distribution, and the like.

[Retardation adjuster]
The optical anisotropy of the optical film of the present invention can be controlled by adding the compound having the above-mentioned repeating unit, but a different optical anisotropy adjusting agent may be further added depending on the target retardation. For example, a compound for reducing Rth described in JP-A-2006-30937, pages 23 to 72 can be added, or a compound that increases Rth, specifically, has one or more aromatic rings. A compound is preferable, it is more preferable to have 2-15, and it is still more preferable to have 3-10. The atoms other than the aromatic ring in the compound are preferably arranged in the same plane as the aromatic ring, and when there are a plurality of aromatic rings, the aromatic rings may be arranged in the same plane. preferable. In order to selectively increase Rth, the presence state of the additive in the film is preferably such that the aromatic ring plane is in a direction parallel to the film surface.
The said additive may be used independently and may be used in combination of 2 or more types of additives.
Specific examples of the additive having an effect of increasing Rth include a plasticizer described on pages 33 to 34 of JP-A-2005-104148 and pages 38 to 89 of JP-A-2005-104148. And an optical anisotropy control agent. Although the detailed reason is not known, in the present invention, a small molecule that has an effect of increasing Rth in order to suppress the visibility of circular light unevenness that is visually recognized when the liquid crystal display device is observed obliquely. It is preferable to contain a compound.

[Retardation]
In the optical film of the present invention, it is important to appropriately adjust Re and Rth (defined by the following formula (I) and formula (II)) measured at a wavelength of 590 nm according to the application. Can be controlled by the type and degree of substitution of the cellulose ester substituent, the type and amount of the compound having the above-mentioned repeating unit, the film thickness, the process conditions during film formation, the stretching process, and the like.
When the retardation of the optical film of the present invention is reduced, for example, when used for an IPS mode liquid crystal panel, it is preferable to satisfy the following formulas (IIIa) and (IVa), and further an optical film used as a protective film: A functional layer to be described later can also be provided as the support. Thereby, for example, the contrast of the display screen of the liquid crystal display device can be improved, and viewing angle characteristics and color can be improved.
Formula (I) Re = (nx−ny) × d (nm)
Formula (II) Rth = {(nx + ny) / 2−nz} × d (nm)
Formula (IIIa) Re <10
Formula (IVa) | Rth | <25
(Where nx is the refractive index in the slow axis direction in the film plane, ny is the refractive index in the fast axis direction in the film plane, nz is the refractive index in the thickness direction of the film, and d is (The thickness of the film (nm).)
In this case, the orientation of the in-plane slow axis is not particularly limited, but is preferably substantially parallel or substantially orthogonal to the orientation in which the elastic modulus of the film is maximum in the in-plane. Re is more preferably 0 to 5 nm. Rth is more preferably -20 to 5 nm, and further preferably -10 to 0 nm. When the cellulose acylate film of the present invention is used as a protective film on the liquid crystal cell side of a polarizing plate of a liquid crystal display device, if Re and Rth are in the above ranges, light leakage from an oblique direction is further improved and display quality is improved. Can be made.

When the retardation of the optical film of the present invention is positively expressed, for example, when used for a VA mode liquid crystal panel, it is preferable to satisfy the following formulas (IIIb) and (IVb), and further used as a protective film. A functional layer described later can also be provided using the optical film as a support. Thereby, for example, the contrast of the display screen of the liquid crystal display device can be improved, and viewing angle characteristics and color can be improved.
Formula (IIIb): 30 ≦ Re ≦ 85
Formula (IVb): 80 ≦ Rth ≦ 300
In this case, the orientation of the in-plane slow axis is not particularly limited, but it is preferably substantially parallel or substantially orthogonal to the orientation in which the elastic modulus of the film is maximum in the plane, and more preferably substantially in parallel. preferable.

Furthermore, when the retardation of the optical film of the present invention is positively expressed and used in, for example, an IPS mode liquid crystal panel, it is preferable to satisfy the following formulas (IIIc) and (Vc), and as a protective film: A functional layer described later can also be provided using the optical film used as a support. Thereby, for example, the contrast of the display screen of the liquid crystal display device can be improved, and viewing angle characteristics and color can be improved.
Formula (IIIc): 60 ≦ Re ≦ 400
Formula (IVc): −0.5 ≦ Rth / Re ≦ 0.5
In this case, the orientation of the in-plane slow axis is not particularly limited, but is preferably substantially parallel or substantially orthogonal to the orientation in which the elastic modulus of the film is maximum in the in-plane.

Re and Rth can be measured as follows.
(Retardation)
In this specification, Re and Rth (unit: nm) are determined according to the following method. First, the film was conditioned at 25 ° C. and 60% relative humidity for 24 hours, and then a prism coupler (MODEL2010 Prism Coupler: manufactured by Metricon) was used. The average refractive index (n) represented by (2) is obtained.
Formula (2): n = ( _nTE * 2 + _nTM ) / 3
[ _Where n _TE is the refractive index measured with polarized light in the film plane direction, and n _TM is the refractive index measured with polarized light in the film surface normal direction. ]

In this specification, Re (λnm) and Rth (λnm) respectively represent in-plane retardation and retardation in the thickness direction at a wavelength λ (unit: nm). Re (λnm) is measured by making light having a wavelength of λnm incident in the normal direction of the film in KOBRA 21ADH or WR (manufactured by Oji Scientific Instruments).
When the film to be measured is represented by a uniaxial or biaxial refractive index ellipsoid, Rth (λnm) is calculated by the following method.
Rth (λnm) is Re (λnm), and the in-plane slow axis (determined by KOBRA 21ADH or WR) is the tilt axis (rotation axis) (if there is no slow axis, any in-plane film The light is incident at a wavelength of λ nm in 10 ° steps from the normal direction to 50 ° on one side with respect to the normal direction of the film (with the direction of the rotation axis as the rotation axis), and a total of 6 points are measured. KOBRA 21ADH or WR calculates based on the measured retardation value, average refractive index, and input film thickness value.
In the above, there is no description regarding λ, and when only Re and Rth are described, it represents a value measured using light having a wavelength of 590 nm. In addition, in the case of a film having a direction in which the retardation value is zero at a certain tilt angle with the in-plane slow axis as the rotation axis from the normal direction, the retardation value at a tilt angle larger than the tilt angle is After changing the sign to negative, KOBRA 21ADH or WR calculates.
In addition, 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), Based on the value, the average refractive index, and the input film thickness value, Rth can also be calculated from the following equations (3) and (4).

Formula (3)

[In the formula, Re (θ) represents a retardation value in a direction inclined by an angle θ from the normal direction. Further, nx represents the refractive index in the slow axis direction in the plane, ny represents the refractive index in the direction orthogonal to nx in the plane, nz represents the refractive index in the thickness direction orthogonal to nx and ny, and d Represents the film thickness of the film. ]
Formula (4): Rth = ((nx + ny) / 2−nz) × d
When the film to be measured cannot be expressed by a uniaxial or biaxial refractive index ellipsoid, that is, a film without a so-called optical axis, Rth (λnm) is calculated by the following method.
Rth (λnm) is from -50 degrees to +50 degrees with respect to the film normal direction, with Re (λnm) as the slow axis (indicated by KOBRA 21ADH or WR) in the plane and the tilt axis (rotation axis). In 11 degrees, light of wavelength λ nm is incident from each inclined direction and measured at 11 points, and KOBRA 21ADH or WR is calculated based on the measured retardation value, average refractive index, and input film thickness value. . By inputting these average refractive index and film thickness, KOBRA 21ADH or WR calculates nx, ny, and nz. Nz = (nx−nz) / (nx−ny) is further calculated from the calculated nx, ny, and nz.
In the above measurement, the average refractive index may be a value in a polymer handbook (John Wiley & Sons, Inc.) or a catalog of various optical films. About the thing whose average refractive index value is not known, it can measure by the above-mentioned method. The average refractive index values of main optical films are exemplified below: cellulose acylate (1.48), cycloolefin polymer (1.52), polycarbonate (1.59), polymethyl methacrylate (1.49), Polystyrene (1.59).

(Humidity dependency)
In the present invention, the humidity dependence (ΔRe) of Re and the humidity dependence (ΔRth) of Rth are the retardation values in the in-plane direction and the film thickness direction when the relative humidity is H (unit:%): Re (H %) And Rth (H%) based on the following formula.
ΔRe = Re (10%) − Re (80%)
ΔRth = Rth (10%) − Rth (80%)
Re (H%) and Rth (H%) are bonded to a glass plate through an adhesive at 25 ° C and 60% relative humidity after the film is conditioned for 24 hours at 25 ° C and 60% relative humidity. . After adjusting the humidity at 60 ° C. and 90% relative humidity for 48 hours, and adjusting the humidity at 25 ° C. and relative humidity H% for 24 hours, at 25 ° C. and relative humidity H% in the same manner as described above, This is a value obtained by measuring and calculating a retardation value when the measurement wavelength at a relative humidity of H% is 590 nm. In addition, when it is simply described as Re without specifying the relative humidity, it represents a value measured at the above-described relative humidity of 60%.
The retardation value when the humidity of the cellulose acylate film of the present invention is changed preferably satisfies the following relational expression.
| ΔRe | <30, and
| ΔRth | <30
It is more preferable to satisfy the following relational expression.
| ΔRe | <15 and
| ΔRth | <15
It is more preferable to satisfy the following relational expression.
| ΔRe | <10 and
| ΔRth | <10
It is most preferable that the following relational expression is satisfied.
| ΔRe | <5 and
| ΔRth | <5
By controlling the retardation value when the humidity is changed, the retardation change when the external environment changes can be reduced, and a highly reliable liquid crystal display device can be provided. Further, by reducing ΔRth of the optical film of the present invention, it is possible to obtain a preferable effect of improving circular color unevenness that is visually recognized when the liquid crystal display device is observed obliquely on a display surface under specific conditions. . In order to effectively reduce ΔRe and ΔRth, it is also preferable to use the aforementioned humidity dependency reducing agent in combination.

[Dimensional change rate of film]
The dimensional change rate of the optical film of the present invention can be measured as an absolute value of a value obtained by dividing the dimensional change when left to stand for 24 hours under the conditions of 60 ° C. and 90% RH by the initial length. By suppressing the deterioration of the roll appearance over time, by using such a film as a protective film for the polarizing plate, it is possible to suppress peeling and curling during polarizing plate processing, and further to the obtained polarizing plate The present inventors have found that it is possible to suppress the recording stripe-like unevenness, curl, and dimensional change rate. At this time, it is particularly effective to suppress the dimensional change rate in the width direction of the roll.
Therefore, the dimensional change of the optical film of the present invention is preferably 3% or less, but considering compatibility with productivity, it is preferably 0.05 to 2%, and preferably 0.1 to 1%. Is more preferable, and it is still more preferable that it is 0.1 to 0.5%.

Specifically, the dimensional change rate of the optical film of the present invention can be measured by the following method. First, prepare a film sample having a length of 25 cm (measurement direction) cut out with the direction in which the elastic modulus of the film is maximized as the longitudinal direction, a width of 5 cm, and a film sample cut out with the direction orthogonal thereto as the longitudinal direction, Pin holes are formed in the sample at intervals of 20 cm, the humidity is adjusted for 24 hours at 25 ° C. and a relative humidity of 60%, and the distance between the pin holes is measured with a pin gauge (measured value is L ₀ ). Next, after holding the sample for 24 hours in a moist heat environment of 60 ° C. and 90% relative humidity, after adjusting the humidity for 2 hours at 25 ° C. and 60% relative humidity, the distance between the pin holes is measured with a pin gauge (measured value). is referred to as _{L 1).} Using these measured values, the dimensional change rate is calculated by the following formula.
Dimensional change rate [%] = | (L ₁ −L ₀ ) / L ₀ | × 100

[Humidity coefficient of film]
In the present invention, the circular color unevenness that is visually recognized when the liquid crystal display device is observed from an oblique direction is obtained by bringing the humidity expansion coefficient of the film closer to the humidity expansion coefficient of the polarizing film in addition to the humidity dependency of Rth described above. It became clear that it became harder to see. However, since the polarizing plate curl may be affected by the balance with the optical film used on the opposite side across the polarizing film, the humidity expansion coefficient of the optical film of the present invention is preferably set as appropriate. In the present invention, the humidity expansion coefficient is prepared by preparing a film sample having a length of 25 cm (measurement direction) cut out with the direction having the maximum elastic modulus as the longitudinal direction and a width of 5 cm, and a sample cut out with the direction orthogonal thereto as the longitudinal direction. Then, pin holes are formed in the sample at intervals of 20 cm, the humidity is adjusted for 24 hours at 25 ° C. and a relative humidity of 10%, and the distance between the pin holes is measured with a pin gauge (measured value is L ₀ ). Next, the sample is conditioned at 25 ° C. and a relative humidity of 80% for 24 hours, and the distance between the pin holes is measured with a pin gauge (measured value is L ₁ ). The humidity expansion coefficient is calculated by the following formula using these measured values.
Humidity expansion coefficient [ppm /% RH] = {(L ₁ −L ₀ ) / L ₀ } / 70 × 10 ⁶
70 is the measured humidity difference (%).
The humidity expansion coefficient of the film of the present invention is preferably 55 ppm /% RH or less, more preferably 3 to 50 ppm /% RH, and more preferably 5 to 45 ppm, although it depends on the type of polarizing film to be used and the type of the facing optical film. /% RH is more preferable. The humidity expansion coefficient of the present invention can be lowered, for example, by increasing the crystallinity of the cellulose acylate contained in the optical film of the present invention or stretching the optical film of the present invention.

[Tensile modulus of film]
The tensile elastic modulus of the optical film of the present invention is preferably 3.0 GPa or more, more preferably 3.0 to 10.0 GPa, from the viewpoint of maintaining the appearance when aged over time. More preferably, it is 0.1 to 5.0 GPa, and most preferably 3.2 to 4.5 GPa. As a specific measurement method, a film sample having a length of 200 mm (measurement direction) and a width of 10 mm is cut out, the distance between chucks is set to 100 mm, and a universal tensile tester “STM T50BP” manufactured by Toyo Baldwin Co., Ltd. is used. The elastic modulus can be calculated from the slope by measuring the stress at 0.1% elongation and 0.5% elongation in an atmosphere at 25 ° C. and 60 RH% at a tensile rate of 10% / min. In the measurement of elastic modulus, the anisotropy of the elastic modulus can be obtained by changing the orientation in which the sample is cut out, and the angle θ formed by the transport direction during production and the orientation in which the elastic modulus is maximized is particularly limited. However, it is preferably 0 ± 10 ° or 90 ± 10 °. The direction with the maximum elastic modulus can also be evaluated as the direction in which the sound wave propagation speed described later is maximized. In the present invention, unless otherwise specified, the direction in which the sound wave propagation speed is maximized is assumed. Can do. The value of the elastic modulus in the present invention represents the value of the elastic modulus in the direction where the elastic modulus is maximum unless otherwise specified.

  The relationship between the humidity expansion coefficient and tensile elastic modulus of the film and the visibility of color unevenness when the liquid crystal display device is observed obliquely is unknown, but by adjusting the film's humidity expansion coefficient and tensile elastic modulus, The internal stress generated when the environmental humidity changes while the film is fixed to a highly rigid support like glass can be reduced, and as a result, the retardation change of the film can be further suppressed, and the color unevenness is It can be reduced.

[Matting agent fine particles]
It is preferable to add fine particles as a matting agent to the optical film of the present invention. The fine particles used in the present invention include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate and Mention may be made of calcium phosphate. Fine particles containing silicon are preferable from the viewpoint of reducing turbidity, and silicon dioxide is particularly preferable. The silicon dioxide fine particles preferably have a primary average particle size of 20 nm or less and an apparent specific gravity of 70 g / liter or more. Those having an average primary particle size as small as 5 to 16 nm are more preferred because they can reduce the haze of the film. The apparent specific gravity is preferably 90 to 200 g / liter or more, and more preferably 100 to 200 g / liter or more. A larger apparent specific gravity is preferable because a high-concentration dispersion can be produced, and haze and aggregates are improved.

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

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

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

In order to obtain an optical film having particles having a small secondary average particle size in the present invention, several methods are conceivable when preparing a dispersion of fine particles. For example, there is a method in which a fine particle dispersion prepared by stirring and mixing a solvent and fine particles is prepared in advance, and this fine particle dispersion is added to a small amount of a separately prepared solution, dissolved by stirring, and further mixed with the main dope solution. This method is a preferred preparation method in that the dispersibility of the silicon dioxide fine particles is good and the silicon dioxide fine particles are more difficult to reaggregate. In addition, after adding a small amount of cellulose ester to the solvent and dissolving with stirring, add the fine particles to this and disperse with a disperser to make this fine particle additive solution, and mix this fine particle additive solution with the dope solution using an in-line mixer. There is also a way to do it. The present invention is not limited to these methods, but the concentration of silicon dioxide when the silicon dioxide fine particles are mixed and dispersed with a solvent or the like is preferably 5 to 30% by mass, more preferably 10 to 25% by mass, and 15 to 20%. Mass% is most preferred. A higher dispersion concentration is preferable because the liquid turbidity with respect to the added amount is lowered, and haze and aggregates are improved.
The addition amount of the matting agent in the final dope solution is preferably as much as possible within the range allowed by the haze of the film, preferably 0.01 to 1.0 g per 1 m ² , more preferably 0.03 to 0.3 g, 0.08 to 0.16 g is most preferable. Further, when the cellulose acylate film is formed from multiple layers by a film forming method such as co-casting, it is preferable not to add to the inner layer, but to add only to the surface layer side. As addition amount of an agent, 0.001-1.0 mass% is preferable with respect to solid content contained in dope for surface layers, 0.005-0.5 mass% is more preferable, 0.01-0.3 mass % Is more preferable, and 0.02 to 0.1% by mass is most preferable.

  As the solvent used for dispersion, lower alcohols are preferable, and examples thereof include methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, and butyl alcohol. Although it does not specifically limit as solvents other than a lower alcohol, It is preferable to use the solvent used at the time of film formation of a cellulose acylate.

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

[Total content of additives]
In the optical film of the present invention, when other additives are added in addition to the compound having the above-mentioned repeating unit, the total content (Ct) of the additives is 2% by mass or more and 30% by mass with respect to the cellulose acylate. % Is more preferable, 5 to 25% by mass is more preferable, and 6 to 20% by mass is still more preferable.

[Method for producing optical film]
(Organic solvent of dope solution)
In this invention, it is preferable to manufacture the film containing a cellulose ester by the solvent cast method, and a film is manufactured using the solution (dope) which melt | dissolved the polymer containing a cellulose ester in the organic solvent. The organic solvent preferably used as the main solvent of the present invention is not particularly limited as long as a polymer containing a cellulose ester is dissolved, but is an ester having 3 to 12 carbon atoms, a ketone, an ether, and 1 carbon atom. Solvents selected from ˜7 halogenated hydrocarbons are preferred. Esters, ketones and ethers may have a cyclic structure. A compound having two or more functional groups of esters, ketones and ethers (that is, —O—, —CO— and —COO—) can also be used as a main solvent. It may have a functional group of

  As described above, chlorine-based halogenated hydrocarbons may be used as the main solvent for the optical film of the present invention, and as described in JIII Journal of Technical Disclosure 2001-1745 (pages 12-16), non-chlorine. A system solvent may be used as the main solvent, and is not particularly limited for the optical film of the present invention.

  In addition, the solvent about the dope solution and film of this invention is disclosed by the following patents including the melt | dissolution method, and is a preferable aspect. They are, for example, JP 2000-95876, JP 12-95877, JP 10-324774, JP 8-152514, JP 10-330538, JP 9-95538, JP 9-95557, JP 10-10. -235664, JP-A-12-63534, JP-A-11-21379, JP-A-10-182853, JP-A-10-278056, JP-A-10-279702, JP-A-10-323853, JP-A-10-237186, JP-A-11-60807. JP-A-11-152342, JP-A-11-292988, JP-A-11-60752, JP-A-11-60752, and the like. According to these patents, not only the preferred solvent for the cellulose ester of the present invention, but also the physical properties of the solution and coexisting substances to be coexisted are described, which is also a preferred embodiment in the present invention.

(Dissolution process)
In the preparation of the dope solution of the present invention, the dissolution method is not particularly limited, and may be room temperature, and further, a cooling dissolution method or a high temperature dissolution method, and further a combination thereof. Regarding the preparation of the dope solution according to the present invention, and further the solution concentration and filtration steps involved in the dissolution step, the Technical Report of the Invention Association (Public Technical Number 2001-1745, published on March 15, 2001, Invention Association) Production processes described in detail on pages 22 to 25 are preferably used.

(Casting, drying, winding process)
Next, a method for producing a film using the dope solution of the present invention will be described. The method and equipment for producing the optical film of the present invention can use a solution casting film forming method and a solution casting film forming apparatus conventionally used for producing a cellulose triacetate film. The dope solution prepared from the dissolving machine (kettle) is temporarily stored in a storage kettle, and the foam contained in the dope is defoamed for final preparation. The dope is fed from the dope discharge port to the pressure die through a pressure metering gear pump capable of delivering a constant amount of liquid with high accuracy, for example, by the number of rotations. The dry-dried dope film (also referred to as web) is peeled off from the metal support at a peeling point that is uniformly cast on the metal support and substantially rounds the metal support. While sandwiching both ends of the obtained web with clips, holding the width and transporting with a tenter and drying, remove the obtained film from the clips, mechanically transporting with a roll group in the heating device and using a winder It is wound up to a predetermined length in a roll shape. The combination of the tenter and the roll group dryer varies depending on the purpose. As another aspect, the metal support described above is a drum cooled to 5 ° C. or less, and after the dope extruded from the die is gelled on the drum, it is peeled off after about one turn and stretched with a pin-shaped tenter. Various methods for forming a film by a solvent cast method, such as a method of transporting and drying the solution, can be used.

  Since the optical film of the present invention preferably has a certain width or more, it is preferably stretched in the width direction during the film forming process (specifically, the tenter zone). On the other hand, in order to suppress the dimensional change rate of the film, it is important not to accumulate residual strain. For this reason, the residual solvent amount is stretched in the width direction in a state of 3 to 250 mass% per total solid content of the web. It is preferable. If stretched in a state where the amount of residual solvent is very large, even in a web containing a polymer having a crystallization temperature, which will be described later, such as cellulose ester, crystallization accompanying stretching is suppressed, and the relaxation of the polymer is preferentially caused. Therefore, the width can be increased without accumulating residual strain. The residual solvent amount is preferably 5 to 150% by mass, more preferably 7 to 100% by mass, and still more preferably 10 to 70% by mass based on the total solid content of the web. In order to achieve such a residual solvent amount, for example, the drying air is weakened, the metal support temperature is lowered, the film forming speed is increased, the film thickness is increased, or the co-casting is performed as described later. It is effective to do.

In the process after stretching with such residual solvent amount, the relaxation rate of the polymer becomes slower as the residual solvent amount decreases. Therefore, in order not to accumulate residual strain, tension is applied to the web. It is important not to. Therefore, in this step, it is important to reduce the tenter width, preferably 0.5% or more, preferably 0.7 to 50%, and 1.0 to 20%. Is more preferable, 1.5 to 10% is further preferable, and 2 to 5% is still more preferable. If the reduction ratio is too large, wrinkles may occur on the web or it may come off from the tenter, so it is more preferably 50% or less.
The following concept can also be applied to the tenter width reduction method. That is, it is an idea to adjust the ratio (Wt / Ww) of the reduction ratio (Wt) of the tenter width and the free shrinkage ratio (Ww) of the web to an appropriate range, and this ratio is 0.7 to 1.3, Preferably it is 0.8-1.2, More preferably, it is 0.9-1.1, More preferably, it is 0.95-1.0. The free shrinkage rate of the web can be estimated by an offline experiment (observing the actual free shrinkage amount).

  Next, heating is performed at a temperature (T1) set in the range of (Tg-20) to (Tc + 20) ° C. in a state where the residual solvent amount of the web is 0.01 to 30% by mass based on the total solid content of the web. It is preferable to do. The T1 is preferably (Tg-10) to Tc ° C, more preferably Tg to (Tc-5) ° C, and further preferably (Tg + 5) to (Tc-10) ° C. In this process, heat relaxation is promoted by heating, and the dimensional change rate of the film is reduced. However, if the temperature is too high, the effect of improving the circular light unevenness that is visible when the liquid crystal display device is observed from an oblique direction is diminished. In some cases, the additive may bleed out, so that T1 is preferably set in this way. In the film of the present invention, the heating time is preferably 5 to 5,000 seconds, more preferably 20 to 3,000 seconds, and more preferably 30 to 1 in order to achieve both thermal relaxation by heating and productivity. More preferred is 1,000 seconds.

  Subsequently, the web is cooled and the web (film) is removed from the tenter. In this cooling process, residual strain is more likely to accumulate than in the heating process described above, so the dimensional change rate in the direction perpendicular to the conveying direction is likely to change depending on the setting of the tenter width, and the tenter width in this process Preferably satisfies the above-mentioned range consisting of Wt and Ww. Also, in the process after the film is removed from the tenter, the maximum heating up to the tenter zone is required to suppress deterioration of the dimensional change rate in the film transport direction, reduce the effect of light unevenness improvement, and prevent additive bleed out. It is preferable to carry at a temperature lower than the temperature.

In the method for producing an optical film of the present invention, in order to adjust the residual solvent amount in the web, it is preferable to cast by a co-casting method, and at least two kinds of dopes having different solid content concentrations are simultaneously used. Alternatively, it is preferable to cast a plurality of layers by sequentially extruding from a die die. In particular, in a film forming method in which a dope is extruded onto a cooled metal support and gelled and peeled off, it is preferable to increase the solid content concentration because a certain level of web strength is required. On the other hand, in order to reduce the rate of dimensional change of the film, it is preferable that the web containing a large amount of additives is conveyed into the tenter in a state where the amount of residual solvent is larger (solid content concentration is lower). As a means for achieving both of these, a method of co-casting layers having different solid content concentrations, ensuring the web strength with a high concentration layer, and ensuring the solid content concentration with a low concentration layer is effective. Therefore, the concentration difference between the concentration of the dope solution forming the layer having a high solid content concentration and the solid content concentration of the dope solution forming another layer is preferably 1% by mass or more, and 2 to 20% by mass. It is more preferable that it is 3 to 10% by mass. The upper limit of the solid content concentration difference is not particularly limited, but if it exceeds 20% by mass, the surface state of the film may be deteriorated. It is also preferable to adjust the solid content concentration by adjusting the thickness of each layer.
In the case of co-casting, for example, a feed block method in which the number of layers can be easily adjusted or a multi-manifold method having excellent thickness accuracy of each layer can be used. In the present invention, the feed block method is more preferable. Can be used.
In the solution casting film forming method used for the functional polarizing plate protective film and the silver halide photographic light-sensitive material, which are optical members for electronic displays, which are the main uses of the optical film of the present invention, the solution casting film forming apparatus In addition, a coating apparatus is often added for surface processing on films such as an undercoat layer, an antistatic layer, an antihalation layer, and a protective layer. These are described in detail on pages 25 to 30 in the Japan Society for Invention and Innovation Technical Report (Public Technical Number 2001-1745, published on March 15, 2001, Japan Society of Inventions). Including), metal support, drying, peeling and the like, and can be preferably used in the present invention.
When forming a three-layer film by laminating on both sides in addition to the mainstream, the layer formed from the mainstream is referred to as the intermediate layer, the layer on the support surface side is referred to as the support surface, and the opposite surface is the air surface. Called.
The amount of additive in the support surface side layer and air surface side layer is preferably smaller than the amount of additive in the intermediate layer. More preferably, it is 0.1-20 phr, More preferably, it is 0.5-15 phr, Most preferably, 1-10 phr. Here, “phr” represents the content (mass%) of the additive with respect to the cellulose ester.
The thickness of the support surface and the air surface is preferably 0.5 to 30 μm, more preferably 1 to 20 μm, and still more preferably 3 to 15 μm.

[Heat treatment process]
In the method for producing an optical film of the present invention, a step of further heat-treating the optical film can be applied as necessary. At this time, when performing film conveyance by the roller conveyance conveyed by the roll group in a heating apparatus, it is preferable that the temperature (T3) in a heating apparatus is the range of (Tg-20)-(Tc + 20) degreeC. . The T3 is preferably (Tg-10) to Tc ° C, more preferably Tg to (Tc-5) ° C, and further preferably (Tg + 5) to (Tc-10) ° C. However, in the film satisfying the relationship between the addition amount and the film thickness of the present invention, when the treatment is performed at a temperature of T3 without sufficiently reducing the tension applied in the transport direction, the dimensional change rate of the film described above is deteriorated. In such a case, T3 is preferably (Tg-20) to (Tc-10) ° C, more preferably (Tg-15) to (Tc-20) ° C, and (Tg-10). ) To (Tc-25) ° C.
In addition, the deterioration of the dimensional change rate of the film related to the tension applied in the transport direction occurs specifically in the process of moving to the subsequent cooling process, so that the tension of the entire roller transport zone is reduced. If this is difficult, it is preferable to partially reduce the transport tension in this process. In this case, the tension may be lowered by partially reducing the transport speed using a device such as a nip roll or a suction roll, and the holding force is increased by adjusting the film wrap angle using a normal pass roll. The tension may be lowered by partially reducing the transport speed. The temperature after cooling (T4) is not particularly limited, but is preferably 10 to (Tg-20) ° C.
The effect of the heat treatment step is not particularly limited, but by changing the temperature and tension controlled heat treatment according to the type of film, the orientation and crystallization of the contained cellulose ester molecules can be changed. It is considered that the amount of residual solvent can be reduced and the humidity expansion coefficient can be changed.

[Film thickness]
The thickness of the optical film of the present invention is preferably 5 to 120 μm, more preferably 5 to 90 μm, and particularly preferably 5 to 80 μm. Moreover, when using as a polarizer protective film bonded to a liquid crystal panel, it is preferably 5 to 80 μm, more preferably 5 to 65 μm, and more preferably 35 to 50 μm in improving light unevenness. Is particularly preferred. Furthermore, if it is in this range, the warpage of the panel accompanying the change in temperature and humidity can be reduced.

[Haze of film]
The haze of the optical film of the present invention is preferably as small as possible, and is preferably 0.01 to 2.0%. More preferably, it is 1.0% or less, More preferably, it is 0.5% or less. However, even if the haze value is higher than these preferred ranges, the haze of the film of the present invention is dominated by the surface haze component due to the surface shape, and therefore, for example, an adhesive is used to adhere to the polarizing film. Or by applying an adhesive and changing the surface shape, it disappears without affecting the display characteristics of the liquid crystal display device. The haze can be measured according to JIS K-6714 by using a haze meter (HGM-2DP, Suga Tester), etc., at 25 ° C. and 60% RH for the optical film sample 40 mm × 80 mm of the present invention.

[Glass transition temperature (Tg) and crystallization temperature (Tc)]
In the present invention, the glass transition temperature (Tg) is a boundary temperature at which the mobility of the polymer constituting the web or film of the present invention changes greatly. In the present invention, 20 mg of a web or film is placed in a sealed measuring pan of a differential scanning calorimeter (DSC) at 25 ° C. and 10% RH, and this is −100 ° C. to 230 ° C. at 10 ° C./min in a nitrogen stream. The temperature at which the baseline begins to deviate from the low temperature side is defined as Tg, and the temperature is further increased, and the observed exothermic peak start temperature is defined as Tc.

[Spectral characteristics, Spectral transmittance]
An optical film sample of 13 mm × 40 mm can be measured for transmittance at a wavelength of 300 to 450 nm with a spectrophotometer “U-3210” {Hitachi, Ltd.} at 25 ° C. and 60% RH. The inclination width can be obtained at a wavelength of 72% -5%. The limiting wavelength can be represented by a wavelength of (gradient width / 2) + 5%, and the absorption edge can be represented by a wavelength having a transmittance of 0.4%. From this, the transmittances at 380 nm and 350 nm can be evaluated.
When the optical film of the present invention is used on the opposite side of the protective film facing the liquid crystal cell of the polarizing plate, the spectral transmittance at a wavelength of 380 nm measured by the above method is 45% or more and 95% or less and a wavelength of 350 nm. The spectral transmittance at is preferably 10% or less.

[Equilibrium moisture content of film]
The water content (equilibrium water content) of the optical film of the present invention is not particularly limited, but when used as a protective film for a polarizing plate, the film is used in order not to impair the adhesiveness with a water-soluble polymer such as polyvinyl alcohol. Regardless of the thickness, the water content at 25 ° C. and 80% RH is preferably 0.1 to 6% by mass. It is more preferably 1 to 4.5% by mass, and particularly preferably 2 to 4% by mass. If the equilibrium moisture content is 6% by mass or less, it is preferable that the dependence of retardation due to a change in humidity does not become too large when used as a support for a retardation film.
The moisture content is measured by the Karl Fischer method using the optical film sample 7 mm × 35 mm of the present invention with a moisture measuring device, sample drying apparatus “CA-03” and “VA-05” (both manufactured by Mitsubishi Chemical Corporation). It was measured. It was calculated by dividing the amount of water (g) by the sample mass (g).

[Water permeability of film]
The moisture permeability of the film is measured under the conditions of 40 ° C. and 90% RH based on JIS Z-0208. Preferably the moisture permeability of the optical film of the present invention is ^{200~3000g / (m 2 · day)} , more preferably ^{550~2000g / (m 2 · day)} , 600~1500g / (m 2 · day), more preferably 650 to 1300 g / (m ² · day). If the moisture permeability is within this range, the polarizing plate processability (processing speed, polarizing plate curl) and the durability of the polarizing plate against humidity or wet heat can be achieved, which is preferable. The moisture permeability of the film increases when the test environment becomes a high-temperature and high-humidity side or the film becomes thin. For example, the moisture permeability at 40 ° C. and 90% RH is 500 g / (m ² · day). If the film contains a cellulose ester, the moisture permeability at 25 ° C. and 90% RH is 250 g / (m ² · day). In addition, when using the optical film of this invention with an image display apparatus, it is preferable to arrange | position to the liquid crystal cell side rather than a polarizing film.

[Sound wave velocity (sound velocity)]
In the present invention, the direction in which the speed of sound wave propagation is maximum is that the film is conditioned at 25 ° C. and a relative humidity of 60% for 24 hours, and then an orientation measuring device (SST-2500: manufactured by Nomura Corporation) is used. The direction in which the propagation speed of the longitudinal vibration of the ultrasonic pulse is maximized was obtained. In the present invention, the direction in which the elastic modulus is maximum and the direction in which the sound wave propagation speed is maximum can be regarded as substantially parallel.

[Photoelastic coefficient]
When the optical film of the present invention is used as a polarizing plate protective film, birefringence (Re, Rth) may change due to stress caused by the contraction of the polarizer. Although the change in birefringence accompanying such stress can be measured as a photoelastic coefficient, the range is preferably 15 × 10 ⁻¹² Pa ⁻¹ or less (15 Br or less), and −5 × 10 ⁻¹² Pa ^−. It is more preferably ^{1 to} 12 × 10 ⁻¹² Pa ⁻¹ , and further preferably −2 × 10 ⁻¹² Pa ^{−1 to} 11 × 10 ⁻¹² Pa ⁻¹ .

[Contact angle of film surface by alkali saponification]
Since the optical film of the present invention contains cellulose acylate, an alkali saponification treatment is one of effective means for surface treatment when used as a polarizing plate protective film. In this case, the contact angle of the film surface after the alkali saponification treatment is preferably 55 ° or less. More preferably, it is 50 ° or less, and further preferably 45 ° or less.

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

[Functional layer]
The optical film of the present invention is applied to, for example, optical applications and photographic photosensitive materials. In particular, the optical application is preferably a liquid crystal display device, and the liquid crystal display device has a liquid crystal cell in which liquid crystal is supported between two electrode substrates, two polarizing elements disposed on both sides thereof, and the liquid crystal It is more preferable that at least one optical compensation sheet is disposed between the cell and the polarizing element. As these liquid crystal display devices, TN, IPS, FLC, AFLC, OCB, STN, ECB, VA and HAN are preferable.
In that case, when using the optical film of this invention for the above-mentioned optical use, providing various functional layers is implemented. These are, for example, an antistatic layer, a cured resin layer (transparent hard coat layer), an antireflection layer, an easy adhesion layer, an antiglare layer, an optical compensation layer, an alignment layer, a liquid crystal layer, and the like. Examples of these functional layers and materials thereof include surfactants, slip agents, matting agents, antistatic layers, hard coat layers, etc., and are disclosed by the Japan Institute of Technology (Technical Number 2001-1745, March 15, 2001). (Nippon Issuance, Invention Association), page 32 to page 45, and can be preferably used in the present invention.

<Phase difference film>
The retardation film of the present invention contains at least one optical film of the present invention.
Moreover, the optical film of the present invention can be used as a retardation film. The “retardation film” is generally used for a display device such as a liquid crystal display device, and means an optical material having optical anisotropy, and is synonymous with a retardation plate, an optical compensation film, an optical compensation sheet, and the like. It is. In a liquid crystal display device, a retardation film is used for the purpose of improving the contrast of a display screen or improving viewing angle characteristics and color.
By using the optical film of the present invention, retardation can be freely controlled, and a retardation film excellent in adhesiveness with a polarizing film can be produced.

  Further, a plurality of optical films of the present invention can be laminated, or an optical film of the present invention and a film outside of the present invention can be laminated, and Re and Rth can be appropriately adjusted and used as a retardation film. Lamination of the film can be performed using a pressure-sensitive adhesive or an adhesive.

In some cases, the optical film of the present invention may be used as a support for a retardation film, and an optically anisotropic layer made of liquid crystal or the like may be provided thereon to be used as a retardation film. The optically anisotropic layer applied to the retardation film of the present invention may be formed from, for example, a composition containing a liquid crystal compound, a polymer film having birefringence, You may form from the optical film of invention.
The liquid crystal compound is preferably a discotic liquid crystal compound or a rod-like liquid crystal compound.

[Discotic liquid crystalline compounds]
Examples of the discotic liquid crystalline compound that can be used as the liquid crystalline compound in the present invention include various documents (for example, C. Destrade et al., Mol. Crysr. Liq. Cryst., Vol. 71, page 111 ( 1981); edited by The Chemical Society of Japan, Quarterly Chemical Review, No. 22, Chemistry of Liquid Crystal, Chapter 5, Chapter 10 Section 2 (1994); B. Kohne et al., Angew. Chem. Soc. , Page 1794 (1985); J. Zhang et al., J. Am. Chem. Soc., Vol. 116, page 2655 (1994)).

  In the optically anisotropic layer, the discotic liquid crystalline molecules are preferably fixed in an aligned state, and most preferably fixed by a polymerization reaction. Further, the polymerization of discotic liquid crystalline molecules is described in JP-A-8-27284. In order to fix the discotic liquid crystalline molecules by polymerization, it is necessary to bond a polymerizable group as a substituent to the discotic core of the discotic liquid crystalline molecules. However, when the polymerizable group is directly connected to the disc-shaped core, it becomes difficult to maintain the orientation state in the polymerization reaction. Therefore, a linking group is introduced between the discotic core and the polymerizable group. Discotic liquid crystalline molecules having a polymerizable group are disclosed in JP-A No. 2001-4387.

[Bar-shaped liquid crystalline compound]
Examples of rod-like liquid crystalline compounds that can be used as the liquid crystalline compound in the present invention include azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexane. Cyano-substituted phenylpyrimidines, alkoxy-substituted phenylpyrimidines, phenyldioxanes, tolanes and alkenylcyclohexylbenzonitriles. Further, as the rod-like liquid crystal compound, not only the above low molecular liquid crystal compound but also a polymer liquid crystal compound can be used.

  In the optically anisotropic layer, the rod-like liquid crystalline molecules are preferably fixed in an aligned state, and most preferably fixed by a polymerization reaction. Examples of polymerizable rod-like liquid crystalline compounds that can be used in the present invention are described in, for example, Makromol. Chem. 190, 2255 (1989), Advanced Materials 5, 107 (1993), U.S. Pat. Nos. 4,683,327, 5,622,648, 5,770, No. 107 specification, International Publication No. 95/22586 pamphlet, No. 95/24455 pamphlet, No. 97/00600 pamphlet, No. 98/23580 pamphlet, No. 98/52905 pamphlet, JP-A-1-272551, The compounds described in JP-A-6-16616, JP-A-7-110469, JP-A-11-80081, JP-A-2001-328773, and the like are included.

"Polarizer"
The polarizing plate of the present invention contains at least one optical film of the present invention or a retardation film of the present invention.
The optical film or retardation film of the present invention can be used as a protective film for a polarizing plate (polarizing plate of the present invention). The polarizing plate of the present invention comprises a polarizing film and two polarizing plate protective films (optical films) that protect both surfaces thereof, and the optical film or retardation film of the present invention is used as at least one polarizing plate protective film. Particularly preferred.
When the optical film of the present invention is used as the polarizing plate protective film, the optical film of the present invention is hydrophilized by applying the surface treatment (also described in JP-A-6-94915 and 6-118232). For example, it is preferable to perform glow discharge treatment, corona discharge treatment, or alkali saponification treatment. As the surface treatment, alkali saponification treatment is most preferably used.

As the polarizing film, for example, a film obtained by immersing and stretching a polyvinyl alcohol film in an iodine solution can be used. When using a polarizing film obtained by immersing and stretching a polyvinyl alcohol film in an iodine solution, the surface-treated surface of the optical film of the present invention can be directly bonded to both surfaces of the polarizing film using an adhesive. In the production method of the present invention, it is preferable that the optical film is directly bonded to the polarizing film as described above. As the adhesive, an aqueous solution of polyvinyl alcohol or polyvinyl acetal (for example, polyvinyl butyral) or a latex of a vinyl-based polymer (for example, polybutyl acrylate) can be used. A particularly preferred adhesive is an aqueous solution of fully saponified polyvinyl alcohol.
In the bonding process between the polarizing film and the optical film that is the protective film, the protective film functions to suppress the shrinkage of the polarizing film due to heating, but if there is a difference in dimensional change between the two protective films, Curling occurs on the plate. The cause of the difference in dimensional change can be the difference in dimensional change rate, elastic modulus and film thickness of the protective film. It is an important factor that affects sex. Therefore, when the direction in which the elastic modulus is maximum in the optical film of the present invention coincides with the transport direction, it is preferable to reduce the dimensional change rate in the direction orthogonal thereto, and the elastic modulus in the optical film of the present invention When the direction in which the maximum value is the direction orthogonal to the transport direction, it is preferable to reduce the rate of dimensional change in that direction. Moreover, it is also effective to reduce the heating temperature in the drying zone after polarizing plate bonding as a method of reducing curling by suppressing the shrinkage of the polarizing film itself.

  In addition, the film satisfying the relationship between the addition amount and the film thickness (Ct / d ≧ 0.375) in the present invention is excellent in the light unevenness improvement effect as compared with the conventional cellulose ester film, but the tensile rigidity is lowered. Therefore, the function of suppressing the contraction of the polarizing film tends to be reduced. Along with this, the dimensional change rate of the polarizing plate also increases, so it is easy for record streaky surface failure running in the absorption axis direction of the polarizing plate and peeling (adhesion failure) near the interface between the polarizing film and the optical film. Become. On the other hand, in the present invention, these failures can be suppressed by setting the dimensional change rate of the film to 3% or less.

In general, a liquid crystal display device includes four polarizing plate protective films because a liquid crystal cell is provided between two polarizing plates. The optical film of the present invention may be used for any of the four polarizing plate protective films, but the optical film of the present invention is disposed between the polarizing film and the liquid crystal layer (liquid crystal cell) in the liquid crystal display device. It can be used particularly advantageously as a protective film. Further, the protective film disposed on the opposite side of the optical film of the present invention with the polarizing film interposed therebetween can be provided with a transparent hard coat layer, an antiglare layer, an antireflection layer, and the like. It is preferably used as a polarizing plate protective film on the side outermost surface.
The polarizing plate is composed of a polarizer and a protective film that protects both surfaces of the polarizer, and further includes a protective film bonded to one surface of the polarizing plate and a separate film bonded to the other surface. The protective film and the separate film are used for the purpose of protecting the polarizing plate at the time of shipping the polarizing plate and at the time of product inspection. In this case, the protect film is bonded for the purpose of protecting the surface of the polarizing plate, and is used on the side opposite to the surface where the polarizing plate is bonded to the liquid crystal plate. Moreover, a separate film is used in order to cover the adhesive layer bonded to a liquid crystal plate, and is used for the surface side which bonds a polarizing plate to a liquid crystal plate.
In a liquid crystal display device, a substrate containing liquid crystal is usually disposed between two polarizing plates. However, a polarizing plate protective film to which the optical film of the present invention is applied can provide excellent display properties regardless of the location. . In particular, since the polarizing plate protective film on the outermost surface of the display side of the liquid crystal display device is provided with a transparent hard coat layer, an antiglare layer, an antireflection layer, and the like, the polarizing plate protective film is particularly preferably used in this portion.

<Liquid crystal display device>
The optical film, retardation film and polarizing plate of the present invention can be used for liquid crystal display devices in various display modes. Each liquid crystal mode in which these films are used will be described below. Among these modes, the optical film, retardation film and polarizing plate of the present invention can be preferably used in all modes, but are particularly preferably used for VA mode and IPS mode liquid crystal display devices. These liquid crystal display devices may be any of a transmissive type, a reflective type and a transflective type.

(TN type liquid crystal display device)
The optical film of the present invention is preferably used as a support for a retardation film of a TN type liquid crystal display device having a TN mode liquid crystal cell. TN mode liquid crystal cells and TN type liquid crystal display devices have been well known for a long time. Regarding the retardation film used in the TN type liquid crystal display device, each of JP-A-3-9325, JP-A-6-148429, JP-A-8-50206, and JP-A-9-26572, and Mori. Other papers (Jpn. J. Appl. Phys. Vol. 36 (1997) p. 143 and Jpn. J. Appl. Phys. Vol. 36 (1997) p. 1068) are described.

(STN type liquid crystal display device)
The optical film of the present invention may be used as a support for a retardation film of an STN type liquid crystal display device having an STN mode liquid crystal cell. In general, in a STN type liquid crystal display device, rod-like liquid crystalline molecules in a liquid crystal cell are twisted in the range of 90 to 360 degrees, and the refractive index anisotropy (Δn) and cell gap (d) of the rod-like liquid crystalline molecules. Product (Δnd) is in the range of 300 to 1500 nm. The retardation film used in the STN type liquid crystal display device is described in JP-A No. 2000-105316.

(VA type liquid crystal display device)
The optical film of the present invention is particularly advantageously used as a retardation film or a support for a retardation film in a VA liquid crystal display device having a VA mode liquid crystal cell. The VA-type liquid crystal display device may be an alignment-divided system as described in, for example, JP-A-10-123576. In these embodiments, the polarizing plate using the optical film of the present invention contributes to widening the viewing angle and improving the contrast.

(IPS liquid crystal display device and ECB liquid crystal display device)
The optical film of the present invention is particularly advantageous as an IPS liquid crystal display device having an IPS mode and an ECB mode liquid crystal cell, a retardation film of the ECB liquid crystal display device, a support for the retardation film, or a protective film for a polarizing plate. Used. In these modes, the liquid crystal material is aligned substantially in parallel during black display, and black is displayed by aligning liquid crystal molecules in parallel with the substrate surface in the absence of applied voltage. In these embodiments, the polarizing plate using the optical film of the present invention contributes to widening the viewing angle and improving the contrast.
Further, although | Rth | <25 is preferable, in the region of 450 to 650 nm, it is particularly preferable that Rth is 0 nm or less because the change in color is small.

  In this aspect, among the protective films for the polarizing plates above and below the liquid crystal cell, the polarizing film using the optical film of the present invention as a protective film (cell-side protective film) disposed between the liquid crystal cell and the polarizing plate. It is preferable to use plates above and below the liquid crystal cell. More preferably, an optically anisotropic layer in which the retardation value of the optically anisotropic layer between the protective film of the polarizing plate and the liquid crystal cell is set to not more than twice the value of Δn · d of the liquid crystal layer is provided on one side. It is preferable to arrange in the above.

(OCB type liquid crystal display device and HAN type liquid crystal display device)
The optical film of the present invention is also advantageously used as a support for a retardation film of an OCB type liquid crystal display device having an OCB mode liquid crystal cell or a HAN type liquid crystal display device having a HAN mode liquid crystal cell. In the retardation film used for the OCB type liquid crystal display device or the HAN type liquid crystal display device, it is preferable that the direction in which the absolute value of the retardation is minimum does not exist in the plane of the retardation film or in the normal direction. The optical properties of the retardation film used in the OCB type liquid crystal display device or the HAN type liquid crystal display device are also the optical properties of the optically anisotropic layer, the optical properties of the support, and the optically anisotropic layer and the support. Is determined by the arrangement of A retardation film used for an OCB type liquid crystal display device or a HAN type liquid crystal display device is described in JP-A-9-197397. Moreover, it is described in Mori et al. (Jpn. J. Appl. Phys. Vol. 38 (1999) p. 2837).

(Reflective liquid crystal display)
The optical film of the present invention is also advantageously used as a retardation film of a reflective liquid crystal display device of TN type, STN type, HAN type, and GH (Guest-Host) type. These display modes have been well known since ancient times. The TN-type reflective liquid crystal display device is described in JP-A-10-123478, WO98 / 48320 pamphlet, and Japanese Patent No. 3022477. The retardation film used in the reflective liquid crystal display device is described in International Publication No. 00/65384 pamphlet.

(Other liquid crystal display devices)
The optical film of the present invention is also advantageously used as a support for a retardation film of an ASM type liquid crystal display device having a liquid crystal cell in an ASM (Axial Symmetrical Microcell) mode. The ASM mode liquid crystal cell is characterized in that the thickness of the cell is maintained by a resin spacer whose position can be adjusted. Other properties are the same as those of the TN mode liquid crystal cell. The ASM mode liquid crystal cell and the ASM type liquid crystal display device are described in a paper by Kume et al. (Kume et al., SID 98 Digest 1089 (1998)).
Furthermore, the optical film of the present invention can also be used as a retardation film preferably used in an image display panel capable of displaying a 3D stereoscopic image display, or as a support for the retardation film. Specifically, a λ / 4 layer can be formed on the entire surface of the optical film of the present invention, or, for example, a patterned retardation layer having different birefringences can be alternately formed in a line shape. Since the optical film of the present invention has a smaller dimensional change rate with respect to humidity change than the conventional cellulose acylate film, it can be preferably used particularly in the latter case.

(Hard coat film, antiglare film, antireflection film)
The optical film of the present invention can be applied to a hard coat film, an antiglare film, and an antireflection film. For the purpose of improving the visibility of flat panel displays such as LCD, PDP, CRT, EL, etc., any or all of a hard coat layer, an antiglare layer and an antireflection layer are provided on one or both sides of the optical film of the present invention. be able to. Preferred embodiments of such an antiglare film and antireflection film are described in detail in pages 54 to 57 of the Japan Institute of Invention and Technology (Publication No. 2001-1745, published on March 15, 2001, Japan Society of Invention). The optical film of the present invention can be preferably used.

(Transparent substrate)
Since the optical film of the present invention can make optical anisotropy close to zero, has excellent transparency, and has little retardation change even when held in a humid heat environment, the liquid crystal of the liquid crystal display device It can also be used as an alternative to the cell glass substrate, that is, as a transparent substrate for enclosing the driving liquid crystal.
Since the transparent substrate enclosing the liquid crystal needs to be excellent in gas barrier properties, a gas barrier layer may be provided on the surface of the optical film of the present invention as necessary. The form and material of the gas barrier layer are not particularly limited, but a gas having a relatively high gas barrier property such as SiO ₂ or the like is vapor-deposited on at least one surface of the optical film of the present invention, or a vinylidene chloride polymer or a vinyl alcohol polymer. These coating layers can be provided, or a method of laminating these inorganic and organic layers can be considered, and these can be used as appropriate.
In order to use as a transparent substrate for enclosing liquid crystal, a transparent electrode for driving the liquid crystal by applying a voltage may be provided. Although it does not specifically limit as a transparent electrode, A transparent electrode can be provided by laminating | stacking a metal film, a metal oxide film, etc. on the at least single side | surface of the optical film of this invention. Among these, a metal oxide film is preferable from the viewpoint of transparency, conductivity, and mechanical properties, and an indium oxide thin film mainly containing 2 to 15% of zinc oxide can be preferably used. Details of these techniques are disclosed in, for example, Japanese Patent Application Laid-Open Nos. 2001-125079 and 2000-227603.

  The features of the present invention will be described more specifically with reference to examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

<Measurement method>
First, characteristics measurement methods and evaluation methods are shown below.

[Degree of substitution]
The degree of acyl substitution of cellulose acylate is described in Carbohydr. Res. Was determined by ¹³ C-NMR according to the method described in 273 (1995) 83-91 (Tezuka et al.).

[Glass transition temperature (Tg)]
Webs with varying amounts of residual solvent were prepared, and these were measured by the method described above to prepare and read a graph showing the relationship between the amount of residual solvent and Tg.

[Crystallization temperature (Tc)]
Webs with varying amounts of residual solvent were prepared, and these were measured by the method described above to produce and read a graph showing the relationship between the amount of residual solvent and Tc.

[Free web shrinkage]
Estimated as the square root of the amount of residual solvent.

[Dimensional change rate]
Measured by the above-described method, the dimensional change rate in the direction in which the elastic modulus is maximum is D1, and the dimensional change rate in the direction perpendicular thereto is D2.

[Retardation]
5 points in the width direction of the film were sampled every 100 m in the longitudinal direction (5 cm × 5 points in the center of the film, end (5% of the total width from both ends) and 2 points in the middle between the center and the end). A sample having a size of 5 cm was taken out, average values of each point evaluated according to the above-described method were calculated, and Re, Rth, and ΔRth were calculated, respectively.

[Photoelastic coefficient]
A 1 cm × 5 cm sample was cut out from the produced optical film, and the retardation value in the film plane was measured using a spectroscopic ellipsometer (M-220, manufactured by JASCO Corporation) while applying stress to the sample at 25 ° C. It was calculated from the slope of the retardation value and the stress function.

[Tensile modulus]
Universal tensile testing machine "STM" manufactured by Toyo Baldwin Co., Ltd.
Using T50BP ", stresses at 0.1% elongation and 0.5% elongation were measured in an atmosphere of 25 ° C and 60RH% at a tensile speed of 10% / min, and the tensile elastic modulus was determined from the inclination.

[Moisture content]
A 7 mm x 35 mm sample was cut out from the produced optical film and conditioned for 24 hours at 25 ° C and a relative humidity of 60%, then a moisture meter, sample drying equipment "CA-03" and "VA-05" The water content was measured by the Karl Fischer method.

<< 1 >> Manufacture and Evaluation of Optical Film The optical film of the present invention was manufactured by selecting those listed in Table 1 from the materials shown below.

<Material used for film formation>
1] Cellulose acylate Those listed in Table 1 were selected from the following cellulose acylates. Each cellulose acylate was heated to 120 ° C. and dried to adjust the water content to 0.5% by mass or less.

Cellulose acylate A:
20 parts by mass of cellulose acetate powder derived from pulp having a degree of substitution of 2.86 was used. Cellulose acylate A has a viscosity average degree of polymerization of 300, an acetyl group substitution degree at the 6-position of 0.89, an acetone extract of 7% by mass, a mass average molecular weight / number average molecular weight ratio of 2.3, and a water content of 0.3. Viscosity in 2 mass% and 6 mass% dichloromethane solutions is 305 mPa · s, residual acetic acid content is 0.1 mass% or less, Ca content is 65 ppm, Mg content is 26 ppm, iron content is 0.8 ppm, sulfate ion The content was 18 ppm, the yellow index was 1.9, and the amount of free acetic acid was 47 ppm. The average particle size of the powder was 1.5 mm, and the standard deviation was 0.5 mm.

Cellulose acylate B:
20 parts by mass of a cellulose acetate powder derived from linter having a degree of substitution of 2.87 and a viscosity average degree of polymerization of 310 was used.

Cellulose acylate C:
20 parts by mass of a cellulose acetate propionate powder derived from linder having an acetyl substitution degree of 1.90, a propionyl substitution degree of 0.90 and a viscosity average polymerization degree of 270 was used.

2] Solvent The following solvent A was used in (Film preparation A) and (Film preparation C) described later, and the following solvent B was used in (Film preparation B). The water content of each solvent was 0.2% by mass or less, and 80 parts by mass was used.
Solvent A dichloromethane / methanol / butanol = 81/18/1 (mass ratio)
Solvent B dichloromethane / methanol = 92/8 (mass ratio)

3] Additives The additives listed in Table 1 were used. In addition, the following additive M was added to the dope for the support surface and the air surface. However, in Table 1, “parts by mass” of each additive represents parts by mass when the cellulose acylate is 100 parts by mass. In addition, in the case of the film cast by the single layer, the following additive M was added to the whole film.
(Compound having a repeating unit)
A-1: Condensate of ethanediol / adipic acid (1/1 molar ratio), number average molecular weight 1000, hydroxyl value 112 mgKOH / g

(Other additives)
B-1: Triphenyl phosphate / biphenyl diphenyl phosphate (2/1 mass ratio) mixture (plasticizer)

M: silicon dioxide fine particles (particle size 20 nm, Mohs hardness about 7) (0.02 parts by mass)

4] Dissolution The cellulose acylate was gradually added to a 4000 liter stainless steel dissolution tank having a stirring blade while stirring and dispersing the solvent and additive. After completion of the addition, the mixture was stirred at room temperature for 2 hours, swollen for 3 hours, and then stirred again to obtain a cellulose acylate solution.
For stirring, a dissolver type eccentric stirring shaft that stirs at a peripheral speed of 5 m / sec (shear stress 5 × 10 ⁴ kgf / m / sec ² [4.9 × 10 ⁵ N / m / sec ² ]). And a stirring shaft having an anchor blade on the central axis and stirring at a peripheral speed of 1 m / sec (shear stress 1 × 10 ⁴ kgf / m / sec ² [9.8 × 10 ⁴ N / m / sec ² ]) It was. Swelling was carried out with the high speed stirring shaft stopped and the peripheral speed of the stirring shaft having anchor blades set at 0.5 m / sec.
The swollen solution was heated from a tank to 50 ° C. with a jacketed pipe, and further heated to 90 ° C. with 1.2 MPa pressurization to be completely dissolved. The heating time was 15 minutes. At this time, a filter, a housing, and a pipe that are exposed to a high temperature were made of Hastelloy alloy (registered trademark) and had excellent corrosion resistance, and a thing having a jacket for circulating a heat medium for heat retention and heating was used.
Next, the temperature was lowered to 36 ° C. to obtain a cellulose acylate solution.

  The pre-concentration dope thus obtained was flushed at 80 ° C. in a normal pressure tank, and the evaporated solvent was recovered and separated by a condenser. The solid content concentration of the dope after the flash was 23.5 to 26.0% by mass. The condensed solvent was sent to a recovery process to be reused as a solvent in the preparation process (recovery is carried out by a distillation process, a dehydration process, etc.). In the flash tank, defoaming was carried out by stirring by rotating a shaft having an anchor blade on the central shaft at a peripheral speed of 0.5 m / sec. The temperature of the dope in the tank was 25 ° C., and the average residence time in the tank was 50 minutes.

5] Filtration Next, foam removal was performed by irradiating the dope with weak ultrasonic waves. Thereafter, under a pressure of 1.3 MPa, first, a sintered fiber metal filter having a nominal pore diameter of 10 μm was passed, and then, a 10 μm sintered fiber filter was also passed. Respective primary pressures were 1.4 MPa and 1.1 MPa, and secondary pressures were 1.0 MPa and 0.7 MPa. The dope temperature after filtration was adjusted to 36 ° C. and stored in a 2000 L stainless steel stock tank. In the stock tank, stirring was performed by constantly rotating a shaft having an anchor blade on the central shaft at a peripheral speed of 0.3 m / sec. In addition, when the dope was prepared from the dope before concentration, no problem such as corrosion occurred at all in the wetted part of the dope.

(Film preparation A)
In the following table, films 1 to 14 were prepared in (Film Preparation A).
1) Casting step Subsequently, the dope in the stock tank was fed by a feedback pump control using an inverter motor so that the primary pressure of the high precision gear pump was 0.8 MPa with a gear pump for primary pressure increase. The high precision gear pump had a volumetric efficiency of 99.3% and a discharge rate variation of 0.4% or less. Moreover, the discharge pressure was 1.4 MPa. The casting die has a width of 2.1m and is equipped with a feed block adjusted for co-casting. In addition to the mainstream, a device that can be laminated on both sides to form a three-layer film is used. It was.
In addition, the dope liquid supply flow path uses three flow paths for the intermediate layer, the support surface, and the air surface, and the solid content concentration is lowered by adding a solvent or a solution having a high solid content concentration. Was adjusted appropriately by adding. In Table 1, in the production of a film in which the items of “support surface” and “air surface” are described as “−”, a die for co-casting is not used, but for casting in a single layer. Film formation was carried out using a die.

And casting was performed by adjusting the flow rate of the dope at the die projection opening with a casting width of 2000 mm. In order to adjust the dope temperature to 36 ° C., a jacket was provided on the casting die, and the inlet temperature of the heat transfer medium supplied into the jacket was set to 36 ° C.
The die, feed block, and piping were all kept at 29 ° C. during the work process. The die was a coat hanger type die, with thickness adjusting bolts provided at a pitch of 20 mm, and having an automatic thickness adjusting mechanism using a heat bolt. This heat bolt can also set a profile according to the liquid feed amount of the high precision gear pump by a preset program, and feedback control can also be performed by an adjustment program based on the profile of the infrared thickness gauge installed in the film forming process It has performance. The thickness difference between two arbitrary points 50 mm apart in the film excluding the casting edge portion 20 mm was within 1 μm, and the largest difference in the width direction thickness was adjusted to 2 μm / m or less. In addition, a chamber for decompressing was installed on the primary side of the die. The decompression degree of the decompression chamber can apply a pressure difference of 1 to 5000 Pa before and after the casting bead, and can be adjusted according to the casting speed. At that time, the pressure difference was set such that the bead length was 2 to 50 mm.

2) Casting die The material of the die is a two-phase stainless steel having a mixed composition of an austenite phase and a ferrite phase, a material having a thermal expansion coefficient of 2 × 10 ⁻⁶ (° C. ⁻¹ ) or less, and an electrolyte. A material having corrosion resistance substantially equivalent to that of SUS316 was used in a forced corrosion test in an aqueous solution. The finishing precision of the wetted surfaces of the casting die and the feed block is 1 μm or less in surface roughness, the straightness is 1 μm / m or less in any direction, and the slit clearance is 0.5-3. It was adjustable up to 5 mm. The production of this film was performed at 0.7 mm. About the corner | angular part of the liquid-contact part of die-tip tip, it processed so that R might be 50 micrometers or less over the slit full width. The shear rate inside the die was in the range of ^{1 to} 5000 (sec ⁻¹ ).
Further, a casting die provided with a cured film was used at the lip tip. There are tungsten carbide (WC), Al ₂ O ₃ , TiN, Cr ₂ O _{3 and the} like, and particularly preferably WC. In the present invention, a WC coating formed by a thermal spraying method was used. A mixed solvent (dichloromethane / methanol / butanol (81/18/1 part by mass)), which is a solvent for solubilizing the dope, was supplied to the gas-liquid interface between the bead end and the slit at 0.5 ml / min on one side. Furthermore, in order to make the temperature of the decompression chamber constant, a jacket was attached and a heat transfer medium adjusted to 35 ° C. was supplied. The edge suction air volume was adjusted in the range of 1 L / min to 100 L / min, and was adjusted appropriately in the range of 30 L / min to 40 L / min in the production of this film.

3) Metal support The dope extruded from the die used a mirror surface stainless steel support that is a drum having a width of 2.1 m and a diameter of 3 m as a support. The surface was nickel cast and hard chrome plated. The surface roughness of the drum is polished to 0.01 μm or less, there are no pinholes of 50 μm or more, pinholes of 10 μm to 50 μm are 1 / m ² or less, and pinholes of 10 μm or less are 2 / m ² or less A support was used. At this time, the temperature of the drum was set to −5 ° C., the rotation speed of the drum was set so that the peripheral speed of the drum was 80 m / min, the speed fluctuation was 2% or less, and the position fluctuation was 200 μm or less.

4) Casting drying Subsequently, the dope which has been cast on a drum placed in a space set at 15 ° C., cooled and gelled is rotated by 320 ° on the drum, and then the gelated film (web) ). The peeling tension at this time was 3 kgf / m, and the peeling speed was set to 106% with respect to the support speed. 5) Tenter Conveying / Drying Process Conditions The peeled web was conveyed through the drying zone while being fixed at both ends with a tenter having a pin clip, and dried for about 180 seconds with drying air. The tenter was driven by a chain, and the speed fluctuation of the sprocket was 0.5% or less. Further, the inside of the tenter was divided into 4 zones (stretching zone, reduced width zone, heating zone, cooling zone), and the drying air temperature in each zone could be controlled independently. The gas composition of the drying air was a saturated gas concentration of −40 ° C. Stretching was performed by expanding or contracting in the width direction while transporting in the tenter.
The ratio of the length of the base end fixed by the tenter was 70%. Further, the tenter clip was transported while being cooled so as not to exceed 50 ° C. The solvent evaporated in the tenter part was condensed and liquefied at a temperature of −10 ° C. and recovered. The water contained in the solvent was adjusted to 0.5% by mass or less and reused.
Then, the ears were cut at both ends within 30 seconds from the tenter exit. Ears 50 mm on both sides were cut with an NT type cutter. The oxygen concentration in the dry atmosphere of the tenter part was kept at 5 vol%.
In addition, the residual solvent amount described in Table 2 is a value obtained by calculating the residual solvent amount at the entrance of each zone based on the following formula. However, when sampling was difficult, the amount of residual solvent (mass% per total solid content of the web) at each zone entrance was estimated using a web drying simulation.
Residual solvent amount (% by mass) = {(MN) / N} × 100
[Wherein, M represents the mass of the web (film), and N represents the mass when the web (film) is dried at 110 ° C. for 3 hours. ]

6) Post-drying process conditions The polymer film after the end cutting obtained by the method described above was further dried in the roller transport zone. The roller conveyance zone was divided into four zones so that the drying air temperature in each zone could be controlled independently. At this time, the roller conveyance tension of the film was 80 N / width and dried for about 10 minutes. The wrap angle of the roller was 90 degrees and 180 degrees. The material of the roller was made of aluminum or carbon steel, and hard chrome plating was applied to the surface. As the surface shape of the roller, a flat one and a mat formed by blasting were used. All the shakes due to the rotation of the roller were 50 μm or less. The roller deflection at a tension of 80 N / width was selected to be 0.5 mm or less.
A forced charge removal device (charge removal bar) was installed during the process so that the film voltage during conveyance was always in the range of −3 to 3 kV. In the winding unit, not only the charge removal bar but also ion wind charge removal was installed so that the charge was -1.5 to 1.5 kV.
In Table 1, films having different dimensional change rates were prepared by changing the conditions in the tenter zones (stretching zone, width-reducing zone, heating zone, cooling zone) and post-drying zone of each example and comparative example. .
In Table 2 below, “temperature” represents the temperature at the outlet of the dry air, and “film surface temperature” represents the temperature of the film measured with an infrared thermometer installed in the process. The “stretch ratio” represents a value calculated as (W2−W1) / W1 × 100, where the tenter width (W1) at each zone entrance and the tenter width (W2) at the exit.
In Table 2 below, in all the films except for the films 5 to 10, the tenter widths in the reduced width zone and the heating zone were set to be narrowed so as not to loosen while looking at the state of the film. Moreover, the ratio (Wt / Ww) of the width reduction ratio (Wt) of the width reduction zone and the free shrinkage ratio (Ww) of the web was in the range of 0.7 to 1.3.
Note that the width reduction ratio (Wt) is a value obtained by multiplying the draw ratio by -1 (a value in which positive and negative are opposite).

7) Post-treatment and winding conditions The polymer film after drying was cooled to 30 ° C. or lower and both ends were cut off. For the edge-cutting, two devices for slitting the film edge were installed at the left and right ends of the film (two slit devices per side), and the film edge was slit. Here, the slitting device is composed of a disk-shaped rotating upper blade and a roll-shaped rotating lower blade, and the material of the rotating upper blade is a super steel material, the diameter of the rotating upper blade is 200 mm, and cutting The thickness of the blade at the place was 0.5 mm. The material of the roll-shaped rotary lower blade was a super steel material, and the roll diameter of the rotary lower blade was 100 mm. The slit film cross-section was relatively smooth and free from chips. Further, in the film production, there was no breakage of the film during transportation. Further, knurling was performed on both ends of the film. The knurling was applied by embossing from one side, the knurling width was 10 mm, and the pressing pressure was set so that the maximum height was 5 μm higher than the average thickness on average. Thus, a film having a final product width of 1500 mm was obtained and wound up by a winder.
Thus, a film having a final product width of 1500 mm was obtained and wound up by a winder. The winding chamber was kept at a room temperature of 25 ° C. and a humidity of 60%. The tension pattern was such that the diameter of the winding core was 168 mm, the winding start tension was 230 N / width, and the winding end was 190 N / width. The total winding length was 3900 m. The oscillating period during winding was 400 m, and the oscillating width was ± 5 mm. Moreover, the pressing pressure of the press roll with respect to the winding roll was set to 50 N / width. At this time, the roll appearance was inspected and shown in Table 1 as “immediately after the roll appearance”. Furthermore, the rolls were stored in a storage rack at 25 ° C. and a relative humidity of 55% for 1 month, the same inspection was performed, and the results are shown in Table 1 as “Roll appearance aging”.

(Roll appearance)
The roll appearance was inspected and evaluated according to the following criteria.
A: Loose winding, no wrinkles B: Slight loosening or wrinkles are confirmed, but no problem in practical use C: Winding loose or wrinkles is severe and cannot be applied as an optical film. On the drum, which was the body, no peeling residue of the cast film formed from the dope was observed.

(Film preparation B)
In the following table, films 16 to 19 were prepared in (Film Preparation B).
1) Casting process The dope in the stock tank was fed by a feedback pump control using an inverter motor so that the primary pressure of the high precision gear pump was 0.8 MPa with a gear pump for primary pressure increase. The high-precision gear pump had a volume efficiency of 99.2% and a discharge rate variation of 0.5% or less. Moreover, the discharge pressure was 1.4 MPa. The casting die has a width of 1.8m and is equipped with a feed block adjusted for co-casting. In addition to the mainstream, a device that can be laminated on both sides to form a three-layer film is used. It was.
In addition, the dope liquid supply flow path uses three flow paths for the intermediate layer, the support surface, and the air surface, and the solid content concentration is lowered by adding a solvent or a solution having a high solid content concentration. Was adjusted appropriately by adding. In Table 1, in the production of a film in which the items of “support surface” and “air surface” are described as “−”, a die for co-casting is not used, but for casting in a single layer. Film formation was carried out using a die.

The casting was performed by setting the casting width to 1700 mm and adjusting the flow rate of the dope at the die protrusion. In order to adjust the dope temperature to 25 ° C., a jacket was provided on the casting die, and the inlet temperature of the heat transfer medium supplied into the jacket was 25 ° C.
The die, feed block, and piping were all kept at 25 ° C. during the work process. The die was a coat hanger type die, with thickness adjusting bolts provided at a pitch of 20 mm, and having an automatic thickness adjusting mechanism using a heat bolt. This heat bolt can also set a profile according to the liquid feed amount of the high precision gear pump by a preset program, and feedback control can also be performed by an adjustment program based on the profile of the infrared thickness gauge installed in the film forming process It has performance. The thickness difference between two arbitrary points 50 mm apart in the film excluding the casting edge portion 20 mm was within 1 μm, and the largest difference in the width direction thickness was adjusted to 2 μm / m or less. In addition, a chamber for decompressing was installed on the primary side of the die. The decompression degree of the decompression chamber can apply a pressure difference of 1 to 5000 Pa before and after the casting bead, and can be adjusted according to the casting speed. At that time, the pressure difference was set such that the bead length was 5 to 50 mm.

2) Casting die The material of the die is a two-phase stainless steel having a mixed composition of an austenite phase and a ferrite phase, a material having a thermal expansion coefficient of 2 × 10 ⁻⁵ (° C. ⁻¹ ) or less, and an electrolyte. A material having corrosion resistance substantially equivalent to that of SUS316 was used in a forced corrosion test in an aqueous solution. The finishing precision of the wetted surfaces of the casting die and the feed block is 1 μm or less in surface roughness, the straightness is 1 μm / m or less in any direction, and the slit clearance is 0.5-3. It was adjustable up to 5 mm. The production of this film was performed at 1.0 mm. About the corner | angular part of the liquid-contact part of die-tip tip, it processed so that R might be 50 micrometers or less over the slit full width. The shear rate inside the die was in the range of ^{1 to} 5000 (sec ⁻¹ ).
Further, a casting die provided with a cured film was used at the lip tip. There are tungsten carbide (WC), Al ₂ O ₃ , TiN, Cr ₂ O _{3 and the} like, and particularly preferably WC. In the present invention, a WC coating formed by a thermal spraying method was used. A mixed solvent (dichloromethane / methanol (92/8 parts by mass)), which is a solvent for solubilizing the dope, was supplied to the gas-liquid interface between the bead end and the slit at 0.5 ml / min on one side. Furthermore, in order to make the temperature of the decompression chamber constant, a jacket was attached and a heat transfer medium adjusted to 35 ° C. was supplied. The edge suction air volume was adjusted in the range of 1 L / min to 100 L / min, and was adjusted appropriately in the range of 30 L / min to 40 L / min in the production of this film.

3) Metal support The dope extruded from the die utilized a stainless endless band having a width of 2.1 m and a length of 70 m as a support. The thickness of the band is 1.5 mm, the surface roughness is polished to 0.05 μm or less, there are no pinholes of 30 μm or more, and the number of pinholes of 10 μm to 30 μm is 1 / m ² or less, 10 μm or less A support having 2 holes / m ² or less was used. The band uses a type driven by two drums, and the tension of the band at that time is adjusted to 1.5 × 10 ⁴ kg / m, and the relative speed difference between the band and the drum becomes 0.01 m / min or less. It was a thing. The band drive speed fluctuation was 0.5% or less. In addition, the meandering in the width direction of one rotation was controlled by detecting the positions of both ends of the band so as to be limited to 1.5 mm or less. Further, the positional fluctuation in the vertical direction accompanying the drum rotation on the support surface just below the casting die was set to 200 μm or less. Three layers of dope were co-cast from this die on this support. As the casting drum, one having a facility for circulating a heat transfer medium (refrigerant) inside to cool the support was used. Further, since the other drum supplies heat for drying, the heat transfer medium can pass water. The temperature of each heat transfer medium was 5 ° C. (casting die side) and 40 ° C. The surface temperature of the central part of the support just before casting was 15 ° C. The temperature difference between both ends was 6 ° C. or less.

4) Casting drying The temperature of the casting chamber provided with the casting die, the support and the like was kept at 35 ° C. The dope cast on the band was first dried by sending parallel-flow drying air. The temperature of the drying air was 135 ° C on the upstream side of the upper part of the band, and 140 ° C on the downstream side. The lower part of the band was set to 65 ° C. The saturation temperature of each gas was around -8 ° C. The oxygen concentration in the dry atmosphere on the support was kept at 5 vol%. Note that the air was replaced with nitrogen gas in order to maintain the oxygen concentration at 5 vol%. Moreover, in order to condense and collect the solvent in the casting chamber, a condenser (condenser) was provided, and the outlet temperature was set to −10 ° C.

For 5 seconds after casting, the static pressure fluctuation in the immediate vicinity of the casting die was suppressed to ± 1 Pa or less so that the dry wind did not directly hit the dope with a wind shield. When the solvent ratio in the dope was 150% by mass on the dry basis, the film was peeled off from the casting support. The peeling tension at this time was 10 kgf / m, and the peeling speed (peeling roll draw) with respect to the support speed was set so as to be properly peeled in the range of 100.1% to 105%. The surface temperature of the peeled film was 15 ° C. The drying rate on the support was an average of 180% by weight of dry weight standard solvent / minute. The solvent gas generated by drying was led to a condenser, liquefied at -10 ° C, recovered and reused as a solvent for charging. The drying air from which the solvent was removed was heated again and reused as drying air. At that time, the water content in the solvent was adjusted to 0.5% or less and reused.
The peeled film was conveyed by the transfer part provided with many rollers. The transition part was provided with three rollers, and the temperature of the transition part was kept at 40 ° C. During conveyance with the roller at the crossing portion, a tension of 16N to 160N was applied to the film.

5) Tenter Transport / Drying Process Conditions The peeled film was transported in the drying zone of the tenter while being fixed at both ends with a tenter having a clip, and dried with drying air. The clip was cooled by supplying a heat transfer medium at 20 ° C. The tenter was driven by a chain, and the speed fluctuation of the sprocket was 0.5% or less. Further, the inside of the tenter was divided into 4 zones (stretching zone, reduced width zone, heating zone, cooling zone), and the drying air temperature in each zone could be controlled independently. The gas composition of the drying air was set to a saturated gas concentration of −10 ° C. The average drying rate in the tenter was 120% by mass (dry weight reference solvent) / min. The conditions of the drying zone were adjusted so that the amount of residual solvent in the film at the outlet of the tenter was not more than the value shown in the table. While transported in the tenter, stretching and shrinking were also performed in the width direction. The ratio of the length of the base end fixed by the tenter was 90%. Further, the tenter clip was transported while being cooled so as not to exceed 50 ° C. The solvent evaporated in the tenter part was condensed and liquefied at a temperature of −10 ° C. and recovered. A condenser (condenser) was provided for condensation recovery, and the outlet temperature was set to -8 ° C. The water content contained in the solvent was adjusted to 0.5% by mass or less and reused.

Then, the ears were cut at both ends within 30 seconds from the tenter exit. Ears 50 mm on both sides were cut with an NT-type cutter, and the cut ears were blown to a crusher by a cutter blower and crushed into chips of an average of about 80 mm ² and stored in an ear silo. A solvent concentration meter is provided in the ear silo, and the solvent concentration in the ear silo is constantly monitored. If the solvent concentration in the ear silo exceeds 25% by volume, which is the lower limit of explosion (LEL), explosion may occur. However, in this film formation, it was always less than 25% by volume and there was no possibility of explosion at all. This chip was again used as a raw material in the preparation process together with cellulose triacetate flakes as a raw material for preparation. The oxygen concentration in the dry atmosphere of the tenter part was kept at 5 vol%. Note that the air was replaced with nitrogen gas in order to maintain the oxygen concentration at 5 vol%. Prior to high temperature drying in the roller transport zone of the post-drying step, the film was pre-heated in a pre-drying zone supplied with 100 ° C. drying air.

6) Post-drying process conditions The process was carried out in the same manner as (Film Preparation A).

7) Post-treatment and winding conditions The rolls were evaluated in the same manner as in (Film Preparation A).

(Film preparation C)
A film (film 15) having a film thickness of 15 μm or less was obtained by filtering the dope before concentration in the step of 4) dissolution in accordance with the step of 5) filtration in the above (preparation of polymer solution) column. A dope was formed by the following process. 1) Casting step The obtained dope is fed to a casting die having a width of 1 m and capable of co-casting, and the dope for the intermediate layer, the support surface, and the air surface are respectively fed to the dope having a three-layer structure. Was extruded from a casting die and cast on a glass plate set at 15 ° C. as a support. Then, 45 ° C. drying air was blown off and peeled off from the support after 4 minutes, fixed to a metal frame, dried at 100 ° C. for 5 minutes, and further at 140 ° C. for 10 minutes, then cooled to room temperature, 3 A layered film was obtained.

<< 2 >> Preparation and evaluation of polarizing plate (Preparation of polarizing plate)
1] Saponification of Film Each film prepared in Examples and Comparative Examples and FUJITAC TD60UL (manufactured by FUJIFILM Corporation) were heated in a 4.5 mol / L sodium hydroxide aqueous solution (saponification solution) adjusted to 37 ° C. for 1 minute. After dipping, the film was washed with water, then dipped in a 0.05 mol / L sulfuric acid aqueous solution for 30 seconds, and then passed through a water washing bath. Then, draining with an air knife was repeated three times, and after dropping the water, the film was retained in a drying zone at 70 ° C. for 15 seconds and dried to produce a saponified film.

2] Production of Polarizing Film According to Example 1 of Japanese Patent Application Laid-Open No. 2001-141926, a circumferential speed difference was given between two pairs of nip rolls and stretched in the longitudinal direction to prepare a polarizing film having a thickness of 20 μm.

3] Bonding After selecting two polarizing films from the polarizing film thus obtained and the saponified film and sandwiching the polarizing film therebetween, PVA (manufactured by Kuraray Co., Ltd., PVA-117H) 3% Using an aqueous solution as an adhesive, a polarizing plate was prepared by laminating with a roll-to-roll so that the polarization axis and the longitudinal direction of the film were orthogonal to each other. Here, one film of the polarizing film was a saponified film selected from the film group shown in Table 1, and the other film was a saponified film of Fujitac TD60UL.

(Evaluation of polarizing plate)

  The obtained polarizing plate was reflected and observed under a fluorescent lamp, and the polarizing plate was peeled off visually (the presence or absence of peeling was judged by visually checking whether air was contained between the optical film and the polarizing film) And the presence or absence of record streak-like irregularities extending in the absorption axis direction of the polarizing plate were examined. Table 1 shows A when not visually recognized, and B when visually recognized slightly (when 1 to 5 people were visible among 10 testers) and when visually recognized (10 testers). C is described in the case where the number of people who can be visually recognized is 6 or more.

[Degree of polarization]
The transmittance (Tp) when the produced two polarizing plates are superposed in parallel with the absorption axis and the transmissivity (Tc ′) when the absorption axes are superposed with each other perpendicular to each other are measured. (P) was calculated.
Polarization degree P = ((Tp−Tc ′) / (Tp + Tc ′)) ^0.5
1] Initial polarization degree When the polarization degree of the polarizing plate was calculated by the method described above, the polarization degree of all the polarizing plates was 99.9%.

2] Degree of polarization with time The side of the polarizing plate described in Table 1 (films produced in the above examples and comparative examples) was bonded to a glass plate with an adhesive and allowed to stand for 500 hours at 60 ° C. and 90% relative humidity. When the degree of polarization after standing (time-dependent degree of polarization) was calculated by the method described above, the degree of polarization of all the polarizing plates was 99.9%.

3] Forced curling When curling when the polarizing plate was heated at 80 ° C. for 10 minutes was examined, it was confirmed that the curling of the polarizing plate of each example was suppressed according to the dimensional change rate. On the other hand, in the polarizing plate using the film 9 and the film 12 which are comparative examples, severe curling occurred.
Further, in the polarizing plate using the film 6 and the film 10 having a relatively large dimensional change rate, a relatively large curl was generated, and the curl was more noticeable in the film 6 having a thin film thickness. When heated after being bonded to a glass plate via an agent, there was no problem in practical characteristics because the glass plate was not peeled off or the warpage of the glass plate was not larger than that of other polarizing plates. It was.

4] Mounting evaluation on liquid crystal display device (mounting on IPS liquid crystal display device)
Of the pair of polarizing plates sandwiching the liquid crystal cell from a commercially available liquid crystal television (IPS mode LED slim type 42-inch liquid crystal television), the polarizing plate on the backlight side is peeled off, and the produced polarizing plate is shown in Table 1. The film side described was re-bonded to the liquid crystal cell via an adhesive so that the film side was placed on the liquid crystal cell side. When the display characteristics of the re-assembled liquid crystal television were confirmed and the brightness and color from the front and oblique directions were confirmed, the characteristics were the same as before removing the polarizing plate. Further, luminance unevenness during black display when observed from the front of the apparatus was observed and evaluated according to the following criteria (initial evaluation). The evaluation results are shown in Table 1.

(Light unevenness level in the front direction)
When observed from the front of the apparatus, luminance unevenness during black display was observed and evaluated according to the following criteria.
A: Unevenness is not visually recognized in an environment with an illuminance of 100 lx B: Unevenness is hardly visually recognized in an environment with an illuminance of 100 lx C: Light unevenness is visually recognized in an environment with an illuminance of 100 lx Unevenness is visible E: Clear unevenness is visible in an environment with an illuminance of 300 lx

Furthermore, after holding for 3 days in an environment of 50 ° C. and 80% relative humidity, it was transferred to an environment of 25 ° C. and 60% relative humidity, and kept on in a black display state. (Forced evaluation). The evaluation results are shown in Table 1.
(Light unevenness level in the front direction)
When observed from the front of the apparatus, luminance unevenness during black display was observed and evaluated according to the following criteria.
A: Unevenness is not visually recognized in an environment with an illuminance of 100 lx B: Unevenness is hardly visually recognized in an environment with an illuminance of 100 lx C: Light unevenness is visually recognized in an environment with an illuminance of 100 lx Unevenness is visually recognized E: Clear unevenness is visually recognized in an environment of illuminance of 300 lx (light unevenness level in an oblique direction)
Luminance unevenness and color unevenness during black display in an azimuth direction of 45 degrees and a polar angle direction of 70 degrees from the front of the apparatus were observed and evaluated according to the following criteria.
A: Unevenness is not visually recognized in an environment with an illuminance of 100 lx B: Unevenness is hardly visually recognized in an environment with an illuminance of 100 lx C: Light unevenness is visually recognized in an environment with an illuminance of 100 lx Unevenness is visually recognized E: Clear unevenness is visually recognized in an environment with an illuminance of 300 lx. In Table 1 below, the total amount (Ct) is the content in the total of the three layers, and the film thickness (d) is the total of the three layers. Total thickness.

Films 5, 6 and 18 shall be read as “reference examples” instead of “examples”.
In Tables 1 and 2, all films were preferable as optical films having a haze of 0.5% or less. And when the film produced by co-casting and the film produced by the single layer were compared, the film produced by co-casting tended to have a lower haze value. Moreover, when the film was produced exactly like Example 17 except having changed the cellulose acylate B of Example 17 into the cellulose acylate C, it was confirmed that the effects of the present invention were obtained.

As is apparent from the results shown in Tables 1 and 2, Comparative Films 7 to 9 having a dimensional change rate exceeding 3% when treated at 60 ° C. and 90% RH for 24 hours are appearances of the roll after aging. However, it is understood that a recording stripe and peeling occur in a polarizing plate using this as a protective film, and light unevenness occurs when a liquid crystal display device using the polarizing plate is observed from the front. The film 10 of the comparative example that does not satisfy Ct / d ≧ 0.375 has a poor appearance after the lapse of time, and the liquid crystal display device using the roll has uneven light when observed from the front and oblique directions. I understand. Moreover, the film 12 of the comparative example which does not satisfy Ct <30 has poor appearance after the lapse of time, and the polarizing plate using the roll as a protective film generates record streaks, and the liquid crystal display device using the film has a front surface. It can be seen that light unevenness occurs when observed.
On the other hand, the optical film of the example is excellent in the appearance of the roll, and the polarizing plate using this as a protective film is less likely to cause record streaks and peeling, and the liquid crystal display device incorporating the same is observed from the front and oblique directions. It can be seen that there is little unevenness of light. However, the roll appearance of the film 15 is not evaluated because no roll is formed.
Also, after disassembling the liquid crystal display device immediately after the forced test and comparing the degree of warping of the panel, in the liquid crystal display device using the film of the example, compared with the liquid crystal display device using the film of the comparative example, It was possible to visually confirm that there was little warping, and this tendency was particularly remarkable when a thin film was used.

Claims (14)

An optical film comprising one or more additives and cellulose acetate,
The total content of the additive (Ct; unit: mass% with respect to the cellulose acetate) and the film thickness (d; unit: μm) satisfy the relationship of Ct <30 and Ct / d ≧ 0.375,
The acyl substitution degree of the cellulose acetate is 2.8 to 2.94 (excluding 2.8),
The following formula (IIIa) and formula (IVa) are satisfied,
Formula (I) Re = (nx−ny) × d (nm)
Formula (II) Rth = {(nx + ny) / 2−nz} × d (nm)
Formula (IIIa) Re <10
Formula (IVa) | Rth | <25
(Where nx is the refractive index in the slow axis direction in the film plane, ny is the refractive index in the fast axis direction in the film plane, nz is the refractive index in the thickness direction of the film, and d is (The thickness of the film (nm).)
An optical film having a dimensional change rate of 0.1 to 0.5% when treated at 60 ° C. and 90% RH for 24 hours.
However, the dimensional change rate is an absolute value of a value obtained by dividing the dimensional change when the optical film is allowed to stand for 24 hours under the conditions of 60 ° C. and 90% RH by the initial length.   The optical film according to claim 1, wherein the film thickness is 5 to 80 μm.   The optical film according to claim 1 or 2, wherein the tensile elastic modulus is 3.0 GPa or more.   The optical film according to claim 1, wherein the dimensional change rate is a dimensional change rate in a direction orthogonal to a direction in which the elastic modulus of the film is maximum.   The optical film according to any one of claims 1 to 4, wherein the optical film is a film in which two or more layers containing cellulose acetate and an additive are laminated.   The optical film according to claim 5, wherein the optical film is a film in which a support surface side layer, an intermediate layer, and an air surface side layer are laminated.   The optical film according to claim 6, wherein the amount of additive in the support surface side layer and the air surface side layer is smaller than the amount of additive in the intermediate layer.   It is a polarizing plate containing the optical film of any one of Claims 1-7, Comprising: The direction in which the elasticity modulus of the said optical film becomes the maximum, and the absorption-axis direction of this polarizing plate are mutually parallel. A polarizing plate.   It is a polarizing plate containing the optical film of any one of Claims 1-7, Comprising: The direction in which the elasticity modulus of the said optical film becomes the maximum, and the absorption-axis direction of this polarizing plate are mutually orthogonally crossed A polarizing plate.   An image display device comprising at least the optical film according to any one of claims 1 to 7 or the polarizing plate according to claim 8 or 9. Including one or more additives and cellulose acetate,
The total content of the additive (Ct; unit: mass% with respect to the cellulose acetate) and the film thickness (d; unit: μm) satisfy the relationship of Ct <30 and Ct / d ≧ 0.375,
The acyl substitution degree of the cellulose acetate is 2.8 to 2.94 (excluding 2.8),
The following formula (IIIa) and formula (IVa) are satisfied,
Formula (I) Re = (nx−ny) × d (nm)
Formula (II) Rth = {(nx + ny) / 2−nz} × d (nm)
Formula (IIIa) Re <10
Formula (IVa) | Rth | <25
(Where nx is the refractive index in the slow axis direction in the film plane, ny is the refractive index in the fast axis direction in the film plane, nz is the refractive index in the thickness direction of the film, and d is (The thickness of the film (nm).)
And the manufacturing method of the optical film whose dimensional change rate at the time of processing at 60 degreeC and 90% RH for 24 hours is 0.1-0.5%,
After gripping the web containing at least the additive, cellulose acetate, and residual solvent with a tenter,
(A) The process of extending | stretching in the width direction in the state whose residual solvent amount is 3-250 mass% per total solid of a web,
(B) a step of subsequently reducing the width in the width direction;
(C) 5 to 5,000 seconds at a temperature (T1) set in the range of (Tg−20) to (Tc + 20) ° C. with the residual solvent amount being 0.01 to 30% by mass based on the total solid content of the web. A method for producing an optical film, comprising a step of heating. [Here, Tg represents the glass transition temperature (unit: ° C) of the web, and Tc represents the crystallization temperature (unit: ° C) of the web. ] After the steps (A) to (C),
(D) The manufacturing method of the optical film of Claim 11 including the process of removing a web (film) from a tenter, and the highest heating temperature (T2) after the (D) process is lower than said T1.   The manufacturing method of the optical film of Claim 11 or 12 whose width reduction ratio in the said (B) process is 0.5% or more.   The ratio (Wt / Ww) of the width reduction ratio (Wt) and the free shrinkage ratio (Ww) of the web in the step (B) is 0.7 to 1.3. The manufacturing method of the optical film of description.