JP5969935B2 - Optical film, roll-shaped optical film, polarizing plate, liquid crystal display device, and method for producing optical film - Google Patents

Description

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

  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.

  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.

  On the other hand, in recent years, there has been an increasing demand for larger and thinner liquid crystal display devices, mainly for TV applications. However, panel warpage due to shrinkage of the polarizing plate has occurred due to the larger and thinner thickness, and light leakage has occurred. Problems are occurring. The contraction force of the conventional polarizing plate is mainly due to the contraction of the polarizing film, but the influence of the protective film is becoming stronger as the thickness is reduced. For this reason, it is necessary to suppress the shrinkage force of the protective film. For example, in Patent Documents 1 to 4, metal oxide particles, non-phosphate ester plasticizer, polyester satisfying a predetermined condition, or predetermined repetition The cellulose ester film which added the compound which has a unit to the cellulose ester is proposed, and patent document 5 proposes performing the heat processing of a predetermined condition to a cellulose ester film.

International Publication No. WO2007 / 088736 International Publication No. WO2007 / 026524 International Publication WO2007 / 000910 JP 2012-42938 A JP 2009-137289 A

As a result of intensive studies by the present inventors, it has been found that it is important to reduce each contraction force represented by the following two formulas of the polarizing plate protective film in order to improve the reliability of the liquid crystal display device. It was.
[Shrink force under high temperature and high humidity] = Elastic modulus after wet heat treatment x film thickness x Humidity dimensional change after wet heat treatment [Shrink force under high temperature and low humidity condition] = Elastic modulus after heat treatment x film thickness x dimensional change (after heat treatment Changes in humidity dimensional change + heat shrinkage after heat treatment)

In Patent Literatures 1 to 5, when an additive is added, the humidity dimensional change (moisture content) and elastic modulus of the film also decrease, so that the shrinkage force can be further suppressed. However, it has been found that when the modulus of elasticity is lowered, a new problem arises that the manufacturing aptitude (conveyability, winding aptitude, roll appearance) is restricted. This phenomenon is particularly remarkable in a film having a low retardation in which the elastic modulus is apt to decrease due to orientation relaxation.
Moreover, the acrylic film using an acrylic resin has some problems in elasticity, brittleness, adhesiveness, and the like, and has problems in transportability and polarizing plate processing suitability.

  The present invention has been made to solve the above-described problems, and provides an optical film having a low shrinkage force and a high elastic modulus.

  As a result of intensive studies to solve the above problems, the present inventors have added a compound having a predetermined repeating unit, thereby increasing the amount of the compound having a repeating unit and reducing the shrinkage force. It has been found that the decrease in elastic modulus can be suppressed, and the present invention has been completed.

The present invention, which is a specific means for solving the above problems, is as follows.
[1] including at least a compound having a repeating unit and a cellulose ester,
In-plane retardation (Re) at a wavelength of 590 nm is 10 nm or less,
The elastic modulus exceeds 3.5 GPa,
An optical film, wherein the compound having a repeating unit is a condensate of a polybasic acid and a polyhydric alcohol, and satisfies the following conditions (1) to (6).
(1) At least a polybasic acid having 5 or less carbon atoms is included as the polybasic acid.
(2) The average carbon number of the polybasic acid is 3 or more and less than 6.
(3) The average carbon number of the polyhydric alcohol is 2 or more and 3 or less.
(4) All repeating units composed of a combination of one kind of polybasic acid and one kind of polyhydric alcohol have 4 to 9 carbon atoms.
(5) Number average molecular weight is 800 or more and 5000 or less.
(6) The hydroxyl value is less than 40 mgKOH / g.
[2] The optical film according to [1] preferably contains 0.1 to 50% by mass of the compound having a repeating unit with respect to the cellulose ester.
[3] In the optical film described in [1] or [2], the ratio of the sound wave propagation speed in the direction in which the sound wave propagation speed is maximum and the direction orthogonal thereto (maximum direction / orthogonal direction in the maximum direction) is 1.10. The above is preferable.
[4] The optical film described in any one of [1] to [3] preferably further includes a compound that improves the wet heat durability of the retardation.
[5] The optical film described in any one of [1] to [4] preferably further includes a humidity dependence reducing agent.
[6] The optical film according to any one of [1] to [5] preferably further includes a retardation adjusting agent.
[7] The optical film according to any one of [1] to [6] preferably includes at least succinic acid as a polybasic acid.
[8] A roll-shaped optical film obtained by winding the optical film according to any one of [1] to [7], and having an elastic modulus in a longitudinal direction exceeding 3.5 GPa.
[9] In the rolled optical film according to [8], the maximum direction of the sound wave propagation speed is preferably the longitudinal direction.
[10] The roll-shaped optical film according to [8] or [9] preferably has a length in the longitudinal direction of 100 to 16000 m.
[11] An optical film formed by unwinding the roll-shaped optical film according to any one of [8] to [10].
[12] A polarizing plate comprising the optical film according to any one of [1] to [7] and [11] and a polarizing film.
[13] The polarizing plate according to [12] is preferably arranged so that the absorption axis of the polarizing film is parallel to the maximum direction of the sound wave propagation speed of the optical film.
[14] A liquid crystal display device comprising the optical film according to any one of [1] to [7] and [11], or the polarizing plate according to [12] or [13].
[15] The method for producing an optical film according to any one of [1] to [7] and [11],
A method for producing an optical film, comprising at least the following steps (a), (b), and (c):
(A) A step of casting a solution containing at least a compound having a repeating unit, a cellulose ester, and a solvent on a support (b) removing the solvent from the solution cast on the support to form a film The step of peeling the film from the support (c) The step of stretching the film in the transport direction [16] The method for producing an optical film according to [15] has a stretching speed of 50 to 10,000% / min. Is preferred.
[17] In the method for producing an optical film according to [15] or [16], it is preferable that the draw ratio is gradually increased between 100% and 150% along the conveyance direction.

  ADVANTAGE OF THE INVENTION According to this invention, it became possible to provide the manufacturing method of the optical film, the roll-shaped optical film, polarizing plate, liquid crystal display device, and optical film which suppressed the contractile force and improved the elasticity modulus.

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

(Optical film)
The optical film of the present invention contains at least a compound having a repeating unit and a cellulose ester, an in-plane retardation (Re) at a wavelength of 590 nm of 10 nm or less, an elastic modulus exceeding 3.5 GPa, and a compound having a repeating unit. , A polybasic acid and a polyhydric alcohol condensate, and satisfying the following conditions (1) to (6).
(1) At least a polybasic acid having 5 or less carbon atoms is included as the polybasic acid.
(2) The average carbon number of the polybasic acid is 3 or more and less than 6.
(3) The average carbon number of the polyhydric alcohol is 2 or more and 3 or less.
(4) All repeating units composed of a combination of one kind of polybasic acid and one kind of polyhydric alcohol have 4 to 9 carbon atoms.
(5) Number average molecular weight is 800 or more and 5000 or less.
(6) The hydroxyl value is less than 40 mgKOH / g.
Since it has such a configuration, the optical film of the present invention has a low shrinkage force and a high elastic modulus.
The optical film of the present invention may be an optical film obtained without being wound into a roll, or may be an optical film obtained by winding a roll of optical film and cutting it into a predetermined size. Good.

The optical film of the present invention can suppress the shrinkage force even when the elastic modulus exceeds 3.5 GPa by containing a cellulose ester with a compound having a predetermined repeating unit. Thereby, the shrinkage | contraction is suppressed and the optical film of this invention is excellent in manufacture aptitude. Further, by including a compound having a predetermined repeating unit, it is possible to suppress crying (bleed out) during film production.
Hereinafter, each material of the optical film will be described.

[Compound having a repeating unit]
The compound having a repeating unit contained in the optical film of the present invention is a condensate of a polybasic acid and a polyhydric alcohol, and satisfies the following conditions (1) to (6).
(1) At least a polybasic acid having 5 or less carbon atoms is included as the polybasic acid.
(2) The average carbon number of the polybasic acid is 3 or more and less than 6.
(3) The average carbon number of the polyhydric alcohol is 2 or more and 3 or less.
(4) All repeating units composed of a combination of one kind of polybasic acid and one kind of polyhydric alcohol have 4 to 9 carbon atoms.
(5) Number average molecular weight is 800 or more and 5000 or less.
(6) The hydroxyl value is less than 40 mgKOH / g.

It is known that when a compound having a repeating unit having a hydroxyl value of less than 40 mg KOH / g subjected to a hydrophobization treatment (end-capping) is used, the moisture content of the film is reduced and the change in humidity is reduced. However, if the amount of compound added is increased in order to sufficiently reduce the shrinkage force, the elastic modulus is lowered, so that both shrinkage force reduction (warp performance) and production suitability (elastic force improvement) have not been achieved.
The present inventors satisfy the above conditions (1) to (6), such as using a dibasic acid having a smaller number of carbons than adipic acid such as succinic acid in place of adipic acid and / or in combination with adipic acid. When using a compound having a repeating unit such as a slightly more hydrophilic oligomer than conventional, it was found that the moisture content of the film is equivalent or slightly lower than expected by those skilled in the art, and more than the effect of reducing the moisture content It was found that the change in humidity dimension was improved.
In addition, the elasticity modulus of the optical film using the compound which has the repeating unit made into the slightly hydrophilic oligomer rather than the conventional which satisfy | fills said conditions (1)-(6) is high (above 3.5 GPa), and conveyance property is good. Easy to secure. Therefore, the addition amount of the compound having a repeating unit can be increased, and it is possible to achieve both shrinkage force improvement (warp performance).

  The condensate of the polyhydric alcohol and the polybasic acid is not particularly limited, but is preferably a condensate (reactant) obtained by a reaction between a dibasic acid and a glycol. Hereinafter, 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 may be specifically described, but the present invention is a reaction of dibasic acid and glycol. It is not limited to the aspect using the condensate obtained by this.

The compound having the repeating unit that can be used in the optical film of the present invention includes (1) at least a polybasic acid having 5 or less carbon atoms as a polybasic acid. That is, the compound having a repeating unit includes a repeating unit derived from a polybasic acid having 5 or less carbon atoms. The compound having a repeating unit can increase the elastic modulus by including a repeating unit derived from a polybasic acid having 5 or less carbon atoms.
When the compound having a repeating unit is a condensate of a polyhydric alcohol and one polybasic acid, the one polybasic acid is a polybasic acid having 5 or less carbon atoms. ) The condition that the average carbon number of the polybasic acid is 3 or more and less than 6 is also satisfied.
On the other hand, when the compound having a repeating unit is a condensate of a polyhydric alcohol and a mixture of two or more polybasic acids, it contains at least one polybasic acid having 5 or less carbon atoms, It is also necessary to satisfy the condition that the average carbon number of the basic acid is 3 or more and less than 6.

  In the compound having the repeating unit that can be used in the optical film of the present invention, (2) the polybasic acid has an average carbon number of 3 or more and less than 6. That is, in the compound having the repeating unit, the average number of carbon atoms of the repeating unit derived from the polybasic acid is 3 or more and less than 6. The average carbon number of the dibasic acid of the compound having a repeating unit used in the present invention is preferably 4 or more and less than 6, and preferably 4 or more and 5 or less. However, when the dibasic acid is one kind, the number of carbon atoms is 5 or less, and 4 or less is preferable. In the present invention, a mixture of two or more dibasic acids may be used, and as described above, in this case, at least a polybasic acid having 5 or less carbon atoms is included, and the average carbon number of the two or more dibasic acids is Within the above range. If the average number of carbon atoms of the dibasic acid is in the above range, in addition to the improvement in luminance unevenness, it is excellent in compatibility with the polymer constituting the optical film of the present invention, and when the optical film is formed, when heated and stretched, and Even when the film is stored for a long time, it is preferable because bleed-out hardly occurs.

In the present invention, the dibasic acid used for the condensate of polyhydric alcohol and polybasic acid is not particularly limited as long as it satisfies the above conditions (1), (2) and (4), and is aliphatic. Either a dicarboxylic acid or an aromatic dicarboxylic acid can be used, but an aliphatic dicarboxylic acid residue having 2 to 12 carbon atoms or an alicyclic dicarboxylic acid residue or an aromatic dicarboxylic acid residue having 8 to 12 carbon atoms. Preferably there is. And in order to improve the grade of the bleed-out accompanying heat processing, it is more preferable to contain an aliphatic polybasic acid having at least 5 carbon atoms.
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. . Among these, malonic acid, succinic acid and adipic acid are preferable from the viewpoint of improving compatibility, succinic acid and adipic acid are more preferable from the viewpoint of easily satisfying the above conditions (1) to (6), and succinic acid is particularly preferable.
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 phthalic acid is particularly preferable.
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 combination of succinic acid and phthalic acid, and a combination of succinic acid and terephthalic acid are preferred. The combined use of succinic acid and terephthalic acid is more preferred, and the combined use of succinic acid and phthalic acid is particularly preferred. When aliphatic dicarboxylic acid and aromatic dicarboxylic acid are used in combination, the ratio (molar ratio) of the two is not particularly limited, but is preferably 95: 5 to 40:60, and more preferably 55:45 to 45:55.

  In the compound having the repeating unit that can be used in the optical film of the present invention, (3) the polyhydric alcohol has an average carbon number of 2 or more and 3 or less. That is, in the compound having the repeating unit, the average number of carbon atoms of the repeating unit derived from the polyhydric alcohol is 2 or more and 3 or less. When using 2 or more types of polyhydric alcohols, it is preferable that the average carbon number of 2 or more types falls within the above range. If the average number of carbon atoms of the polyhydric alcohol is in the above range, in addition to the improvement in luminance unevenness, it is excellent in compatibility with the cellulose ester constituting the optical film of the present invention, and also during film formation and heat stretching. This is preferable because bleed-out hardly occurs.

  In addition, the glycol used in the condensate of polyhydric alcohol and polybasic acid in the present invention is not particularly limited as long as the above conditions (3) and (4) are satisfied. It is preferably a 12 aliphatic or alicyclic glycol residue, or an aromatic glycol residue having 6 to 12 carbon atoms.

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 (propylene glycol), 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 (neo Pentyl 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, , 4-cyclohexanedimethanol, 2,2,4-trimethyl-1,3-pentanediol, 2-ethyl-1,3-hexanediol, 2-methyl-1,8-octanediol, 1,9-nonanediol 1,10-decanediol, diethylene glycol and the like.
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 compound having the repeating unit that can be used in the optical film of the present invention has (4) all repeating units constituted by a combination of one kind of polybasic acid and one kind of polyhydric alcohol having 4 to 9 carbon atoms. Therefore, both shrinkage force suppression and elastic modulus improvement can be achieved.
Here, all the repeating units constituted by the combination of the one kind of polybasic acid and one kind of polyhydric alcohol have a carbon number of n ¹ (n ¹ represents a natural number) or more are compounds having the repeating unit. The sum of the carbon number of the polybasic acid having the minimum carbon number among the polybasic acids used and the carbon number of the polyhydric alcohol having the minimum carbon number among the polyhydric alcohols used in the compound having the repeating unit is n ¹ or more. All the repeating units constituted by the combination of the one kind of polybasic acid and one kind of polyhydric alcohol have a carbon number of n ² or less (n ² represents a natural number) or less are those used for compounds having the repeating unit. The sum of the carbon number of the polybasic acid having the maximum carbon number among the basic acids and the carbon number of the polyhydric alcohol having the maximum carbon number among the polyhydric alcohols used in the compound having the repeating unit is n ² or less. It means that.
The compound having a repeating unit preferably has 4 to 8 carbon atoms, more preferably 4 to 7 carbon atoms, as a repeating unit constituted by a combination of one kind of polybasic acid and one kind of polyhydric alcohol.

Since the compound having the repeating unit that can be used in the optical film of the present invention has (6) a hydroxyl value of less than 40 mgKOH / g, it is possible to achieve both shrinkage force suppression and elastic modulus improvement.
The compound having a repeating unit is a condensate (reaction product) of a polyhydric alcohol and a polybasic acid, and both ends of the reaction product may remain as the reaction product, but a monocarboxylic acid or When so-called end sealing is performed by reacting monoalcohol, it is preferable because retardation change can be suppressed when held in a humid heat environment. The compound having a repeating unit can have a lower hydroxyl value than the condensate having an unblocked end and can easily satisfy the above condition (6), that is, the hydroxyl value can easily be less than 40 mgKOH / g. . The compound having a repeating unit preferably has a hydroxyl value of 20 mgKOH / g or less, and more preferably 10 mgKOH / g or less.

  When protecting both ends of the compound having a repeating unit with a monoalcohol residue or a monocarboxylic acid residue, the monoalcohol residue is preferably a substituted or unsubstituted monoalcohol residue having 1 to 30 carbon atoms, Methanol, ethanol, propanol, isopropanol, butanol, isobutanol, pentanol, isopentanol, hexanol, isohexanol, cyclohexyl alcohol, octanol, isooctanol, 2-ethylhexyl alcohol, nonyl alcohol, isononyl alcohol, tert-nonyl alcohol, Substitution of aliphatic alcohols such as decanol, dodecanol, dodecahexanol, dodecaoctanol, allyl alcohol, oleyl alcohol, benzyl alcohol, 3-phenylpropanol Alcohol and the like.

  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, and the weight loss due to heating of the condensate of the polyhydric alcohol and the polybasic acid does not increase, resulting in 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, as a condensate of a specific preferable polyhydric alcohol and polybasic acid, both ends of poly (ethylene glycol / succinic acid) ester are acetate ester and poly (1,2-propanediol / succinic acid) ester. Both ends are acetate ester, poly (ethanediol / 1,2-propanediol / succinic acid / adipic acid) ester Both ends are acetate ester, poly (ethylene glycol / adipic acid) ester, poly (propylene glycol / adipic acid) Ester, poly (1,3-butanediol / adipic acid) ester, poly (propylene glycol / sebatic acid) ester, poly (1,3-butanediol / sebatic acid) ester, poly (1,6-hexanediol / adipine) Acid) ester, poly (propylene glycol / phthalic acid) ester, polyester Both (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) ester Examples thereof include 2-ethyl-hexyl alcohol ester / poly (propylene glycol, adipic acid) ester having both ends having 2-ethyl-hexyl alcohol ester, acetylated poly (butanediol / adipic acid) ester, and the like.

The compound having the repeating unit satisfies the condition (5) above, that is, the number average molecular weight (Mn) of the compound having the repeating unit is from 800 to 5000, more preferably from 800 to 4800, and 800 -2000 is more preferable, and 800-1000 is most preferable. If the number average molecular weight of the compound having a repeating unit is 800 or more, the volatility is low, and the optical film of the present invention is formed, and film failure and process contamination due to volatilization under high temperature conditions when stretched are 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 5000 or less, it is easy to improve the water resistance of an optical film, it is easy to reduce shrinkage force, and compatibility with the cellulose ester which comprises the optical film of this invention can be ensured, and it becomes difficult to produce a bleed-out. .
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.
The compound having a repeating unit may be a liquid or a solid under the ambient temperature or humidity to be used (generally at room temperature, so-called 25 ° C., 60% relative humidity). 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.

  These polyhydric alcohols and polybasic acids can be appropriately selected and used according to the desired retardation, except that the above conditions (1) to (6) are satisfied. You may contain more than a kind. 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 produce a film with an increased retardation, it is preferable to contain an aromatic dicarboxylic acid residue and / or an aromatic glycol residue. In the optical film of the present invention, an aliphatic or alicyclic dicarboxylic acid residue and an aliphatic or alicyclic glycol residue may be selected from the viewpoint of reducing retardation (absolute values of Re and Rth). Preferably, an aliphatic dicarboxylic acid residue and an aliphatic glycol residue are selected.

  Synthesis of a condensate of such a polyhydric alcohol and a polybasic acid is performed by a conventional method, and 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. Condensates of these polyhydric alcohols and polybasic acids are described in detail in Koichi Murai, “Plasticizers, Theory and Applications” (Kobo Publishing Co., Ltd., published on March 1, 1973, first edition). 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 which has the said repeating unit can also be obtained as goods. For example, from Adeka Co., Ltd., Adeka Sizer (various types of Adeka Sizer P series and Adeka Sizer PN series) can be used as a condensate of polyhydric alcohol and polybasic acid described in DIARY 2007, pages 55-27, In addition, Dainippon Ink & Chemicals, Inc. “Polymer-related product list 2007 edition”, page 25, various products of polylite, Dainippon Ink & Chemicals, Inc. “DIC polymer modifier” (2004.4.1. Various types of 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).

In the optical film of the present invention, the total content of the compound having a repeating unit is preferably 0.1 to 50% by mass, more preferably 5 to 40% by mass, and further preferably 15 to 35% by mass with respect to the cellulose ester. preferable.
If the addition amount and film thickness satisfy such conditions, the luminance unevenness can be improved, and if it is 40% by mass or less, bleeding out from the film is easily suppressed. In the case of a thin film, since the bleed out from the film tends to be promoted, the upper limit of the addition amount is set lower.
In addition, when 2 or more types of compounds which have the said repeating unit are contained, the total content of the compound which has the 2 or more types of said repeating unit should just be settled in the said range in the optical film of this invention.

[Cellulose ester]
The optical film of the present invention contains a cellulose ester.
The optical film of the present invention preferably has a cellulose ester content of 30 to 99% by mass, more preferably 40 to 90% by mass, and even more preferably 50 to 80% by mass. An optical film excellent in polarizing plate processability can be produced.
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 ester, examples of the method for measuring the degree of substitution of acetic acid and / or a fatty acid having 3 to 22 carbon atoms substituted with a hydroxyl group of cellulose include a method according to ASTM D-817-91 and an NMR method. it can. In the case of a cellulose ester having about 2 to 22 carbon atoms, a compound having a repeating unit is used. In particular, in the case of a cellulose acetate having 2 carbon atoms, an adduct having a repeating unit is also preferable. By using it, the luminance 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 ester used in the present invention, the degree of substitution of the hydroxyl group of cellulose is not particularly limited, but when used for polarizing plate protective film and optical film, in order to impart appropriate moisture permeability and hygroscopicity to the film, It is preferable that the acyl substitution degree to the hydroxyl group of cellulose 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. Further, the acyl substitution degree (DSs) of the cellulose ester contained in the region of 1 μm from the film surface and the acyl substitution degree (DSc) of the cellulose ester contained in the region of 1 μm from the center in the thickness direction of the optical film are DSs ≦ DSc It is preferable to satisfy the relationship. DSs can be measured, for example, by cutting a region of 1 μm from the film surface with a razor blade or the like, and the obtained powder can be measured by a known method. DSc is also used to cut the film to the center in the thickness direction (for example, 50 μm In the case of this film, after cutting up to 25 μm, a 1 μm region is further cut out).

  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 the cellulose ester preferably used in the present invention is 180 to 700 in terms of viscosity average degree of polymerization. In the 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 ester 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.

  The molecular weight distribution of the cellulose ester preferably used in the present invention is evaluated by gel permeation chromatography, and its polydispersity index Mw / Mn (Mw is the mass average molecular weight, Mn is the number average molecular weight) is small, and the molecular weight distribution is Narrow is preferred. 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 a normal cellulose ester, which is useful. A cellulose ester having a small amount of low molecular components can be obtained by removing low molecular components from a cellulose ester synthesized by an ordinary method. The removal of low molecular components can be carried out by washing the cellulose ester with a suitable organic solvent. In addition, when manufacturing a cellulose ester 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, a cellulose ester that is preferable in terms of molecular weight distribution (narrow molecular weight distribution) can be synthesized. When used in the production of the optical film of the present invention, the moisture content of the cellulose ester is preferably 2% by mass or less, more preferably 1% by mass or less, and particularly preferably 0.7% by mass or less. It is. In general, the cellulose ester 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 ester 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 esters, the raw material cotton and the synthesis method are described in detail on pages 7 to 12 in the Japan Society for Invention and Innovation (Technical Number 2001-1745, published on March 15, 2001, Japan Institute of Invention). ing.

  In the present invention, the cellulose ester can be used by mixing two or more kinds of cellulose esters which are single or different from the viewpoints of substituent, substitution degree, polymerization degree, molecular weight distribution and the like.

  On the other hand, in order to improve the reworkability of the polarizing plate using the optical film of the present invention, it is preferable to impart a thickness direction distribution of the additive using, for example, a known co-casting technique. Specifically, it is preferable that the content of the additive near the surface is lower than the content of other portions.

  In addition, as an additive, the additive (for example, invention technical report 2001-1745) normally used for a cellulose ester can be used, and it is a compound which has a repeating unit as mentioned above, Bleed out suppression And from the viewpoint of suppressing volatilization in the film production process.

[Retardation adjuster]
The optical anisotropy of the optical film of the present invention is also controlled by the addition of the compound having the above-mentioned repeating unit, but a different optical anisotropy adjusting agent may be added depending on the target retardation. For example, a compound that reduces Rth described in JP-A 2006-30937, pages 23 to 72 can be added, or a compound that increases Rth (specifically, a compound having one or more aromatic rings is preferable. 2 to 15 and more preferably 3 to 10. The atoms other than the aromatic ring in the compound are preferably arranged in the same plane as the aromatic ring, and there are a plurality of aromatic rings. In the case where the aromatic ring is present, it is preferable that the aromatic rings are arranged in the same plane, and in order to selectively increase Rth, the presence state of the additive in the film is such that the plane of the aromatic ring is the film. It is also preferable to exist in a direction parallel to the surface. Among these retardation adjusting agents, the optical film of the present invention preferably contains a compound that increases Rth.
The retardation adjusting agent may be used alone or in combination of two or more 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. The optical anisotropy control agent (a compound represented by the general formula (10) described later as a retardation durability improving agent described later is preferable among the optical anisotropy control agents). 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. By adding such a compound, Rth wet heat durability described later can be appropriately controlled.
As the retardation adjusting agent having the effect of increasing Rth, a compound represented by the following general formula (10) mentioned as a retardation durability improving agent described later is more preferable. A preferable range of the compound represented by the following general formula (10) as a retardation adjusting agent having an effect of increasing Rth is also preferable for the compound represented by the following general formula (10) as a retardation durability improving agent. Similar to range.

[Retardation durability improver]
The optical film of the present invention preferably contains a compound that improves the durability of the retardation (in particular, the wet heat durability). Although the addition amount of such a compound is not particularly limited, it is preferably 0.001 to 20% by mass with respect to the cellulose ester, preferably 0.01 to 10% by mass, and preferably 0.05 to 5% by mass, 0.1-3 mass% is the most preferable.
The wet heat durability of the 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 forming a polarizing plate. . The former can be improved by using a compound having a repeating unit having the specific molecular weight described above and / or controlling the dimensional change rate described later. The latter can be improved by using a compound having a repeating unit having a specific molecular weight as described above and / or adding a compound that improves the wet heat durability of the retardation.
As a compound for improving the wet heat durability of the retardation, a compound showing basicity can be preferably used, either an inorganic compound or an organic compound, or both may be used, and the compound showing weak basicity Is more preferable.
Examples of the inorganic base (inorganic compound showing basicity) include sodium hydroxide, potassium hydroxide, sodium carbonate, sodium hydrogen carbonate, potassium carbonate, potassium hydrogen carbonate and the like.
As the organic base (organic compound showing basicity), a compound having a basic functional group in the molecule can be used. Examples of the basic functional group include a primary amino group, a secondary amino group, Examples thereof include nitrogen-containing heterocyclic groups such as tertiary amino group, quaternary ammonium group, pyridyl group, pyrimidinyl group and pyrazinyl group, guanidino group, imino group, imidazolyl group, indole group, purine group and pyrimidine group.

<Compound having an amino group>
The optical film of the present invention preferably contains a compound having an amino group as a retardation durability improver.
The compound containing an amino group that is preferably used in the present invention is not particularly limited, but is preferably a triazine mother nucleus having an amino group as a substituent at any substitutable position. The compound represented by (1) or (2) is more preferable.

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.)

Ra represents an alkyl group, an alkenyl group, an alkynyl group, a heterocyclic group or an aryl group, preferably an alkyl group or an aryl group, and more preferably an aryl group.
When said Ra is an alkyl group, it is preferable that it is C1-C20, it is more preferable that it is C3-C15, and it is especially preferable that it is C6-C12.
When said Ra is an alkenyl group, it is preferable that it is C2-C20, it is more preferable that it is C2-C15, and it is especially preferable that it is C2-C12.
When said Ra is an alkynyl group, it is preferable that it is C2-C20, it is more preferable that it is C2-C15, and it is especially preferable that it is C2-C12.
When Ra is an aryl group, it preferably has 6 to 30 carbon atoms, more preferably 6 to 20 carbon atoms, and most preferably a phenyl group.
When Ra is a heterocyclic group, it is preferably a nitrogen-containing heteroaromatic group, and more preferably a pyridyl group.

The Ra may further have a substituent.
The substituent that Ra may have is an alkyl group (preferably having 1 to 20 carbon atoms, more preferably 1 to 12, particularly preferably 1 to 8, such as a methyl group or an ethyl group. , Isopropyl group, tert-butyl group, n-octyl group, n-decyl group, n-hexadecyl group, cyclopropyl group, cyclopentyl, cyclohexyl group, etc.), alkenyl group (preferably having 2 to 20 carbon atoms). , More preferably 2 to 12, particularly preferably 2 to 8, for example, vinyl group, allyl group, 2-butenyl group, 3-pentenyl group, etc.), alkynyl group (preferably having 2 to 2 carbon atoms). 20, more preferably 2 to 12, particularly preferably 2 to 8, and examples thereof include a propargyl group and a 3-pentynyl group.), Aryl (Preferably 6 to 30 carbon atoms, more preferably 6 to 20 carbon atoms, particularly preferably 6 to 12 carbon atoms such as phenyl group, biphenyl group, naphthyl group, etc.), amino group (preferably carbon atom number) 0 to 20, more preferably 0 to 10, particularly preferably 0 to 6, and examples thereof include an amino group, a methylamino group, a dimethylamino group, a diethylamino group, a dibenzylamino group, and the like, and an alkoxy group (preferably). Has 1 to 20 carbon atoms, more preferably 1 to 12 and particularly preferably 1 to 8, and examples thereof include a methoxy group, an ethoxy group, and a butoxy group, and an aryloxy group (preferably having 6 carbon atoms). To 20, more preferably 6 to 16, particularly preferably 6 to 12, and examples thereof include a phenyloxy group and a 2-naphthyloxy group. And an acyl group (preferably having 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, particularly preferably 1 to 12 carbon atoms such as acetyl group, benzoyl group, formyl group, and pivaloyl group). An alkoxycarbonyl group (preferably having 2 to 20 carbon atoms, more preferably 2 to 16 carbon atoms, particularly preferably 2 to 12 carbon atoms such as a methoxycarbonyl group and an ethoxycarbonyl group), an aryloxycarbonyl group ( Preferably, it has 7 to 20 carbon atoms, more preferably 7 to 16, particularly preferably 7 to 10, and examples thereof include a phenyloxycarbonyl group.), An acyloxy group (preferably 2 to 20 carbon atoms, and more). Preferably it is 2 to 16, particularly preferably 2 to 10, such as acetoxy group or benzoyloxy group. And so on. ), An acylamino group (preferably having 2 to 20 carbon atoms, more preferably 2 to 16 carbon atoms, particularly preferably 2 to 10 carbon atoms such as acetylamino group and benzoylamino group), alkoxycarbonylamino group ( The number of carbon atoms is preferably 2 to 20, more preferably 2 to 16, and particularly preferably 2 to 12, and examples thereof include a methoxycarbonylamino group, and an aryloxycarbonylamino group (preferably 7 to 7 carbon atoms). 20, More preferably, it is 7-16, Most preferably, it is 7-12, for example, a phenyloxycarbonylamino group etc. are mentioned, A sulfonylamino group (preferably 1-20 carbon atoms, More preferably, it is 1-16. And particularly preferably 1 to 12, for example, methanesulfonylamino group, benzenesulfonate Amino groups, etc.), sulfamoyl groups (preferably having 0 to 20 carbon atoms, more preferably 0 to 16 carbon atoms, particularly preferably 0 to 12 carbon atoms such as sulfamoyl group, methylsulfamoyl group, dimethylsulfa). And a carbamoyl group (preferably having 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, particularly preferably 1 to 12 carbon atoms such as a carbamoyl group and a methylcarbamoyl group). , Diethylcarbamoyl group, phenylcarbamoyl group, etc.), alkylthio group (preferably having 1 to 20 carbon atoms, more preferably 1 to 16, particularly preferably 1 to 12, such as methylthio group and ethylthio group) An arylthio group (preferably having 6 to 20 carbon atoms, More preferably, it is 6-16, Most preferably, it is 6-12, for example, a phenylthio group etc. are mentioned, A sulfonyl group (Preferably 1-20 carbon atoms, More preferably, it is 1-16, Most preferably, it is 1-1. 12, for example, a mesyl group, a tosyl group, etc.), a sulfinyl group (preferably having 1 to 20 carbon atoms, more preferably 1 to 16, particularly preferably 1 to 12, such as a methanesulfinyl group, A benzenesulfinyl group, etc.), a ureido group (preferably having a carbon atom number of 1-20, more preferably 1-16, particularly preferably 1-12, such as a ureido group, a methylureido group, a phenylureido group, etc. A phosphoric acid amide group (preferably having 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, particularly preferably 1 to 12, for example, diethyl phosphoric acid amide, phenyl phosphoric acid amide and the like. ), Hydroxy group, mercapto group, halogen atom (eg fluorine atom, chlorine atom, bromine atom, iodine atom), cyano group, sulfo group, carboxyl group, nitro group, hydroxamic acid group, sulfino group, hydrazino group, imino group, Heterocyclic group (preferably having 1 to 30 carbon atoms, more preferably 1 to 12 carbon atoms, and examples of the hetero atom include a nitrogen atom, an oxygen atom and a sulfur atom, specifically, for example, an imidazolyl group, a pyridyl group and a quinolyl group. , Furyl group, piperidyl group, morpholino group, benzoxazolyl group, benzimidazolyl group, benzthiazolyl group, etc.), silyl group (preferably having 3 to 40 carbon atoms, more preferably 3 to 30 carbon atoms, especially Preferably it is 3-24, for example, a trimethylsilyl group, a triphenylsilyl group, etc. are mentioned. And the like. These substituents may be further substituted. Moreover, when there are two or more substituents, they may be the same or different. If possible, they may be linked together to form a ring.

Said X < ¹ > -X < ⁴ > represents a single bond or a bivalent coupling group, and may respectively be same or different. X ¹ , X ² , X ³ and X ⁴ are preferably single bonds. The divalent linking group is preferably selected from the following linking group group (L).
Linking group (L)

  (The * side is the linking site with the N atom substituted on the 1,3,5-triazine ring in the compound represented by the general formula (1).)

R ¹ , R ² , 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, A substituted or unsubstituted acyl group or a substituted or unsubstituted heterocyclic group is represented, and R ¹ , R ² , R ³ and R ⁴ are preferably hydrogen atoms.

When R ¹ , R ² , R ³ and R ⁴ are alkyl groups, it is preferably 1 to 12 carbons, more preferably 1 to 6 carbons, and 1 to 4 carbons. Is particularly preferred.
When R ¹ , R ² , R ³ and R ⁴ are alkenyl groups, it is preferably 2 to 12 carbons, more preferably 2 to 6 carbons, and 2 to 4 carbons. Is particularly preferred.
When R ¹ , R ² , R ³ and R ⁴ are alkynyl groups, it is preferably 2 to 12 carbons, more preferably 2 to 6 carbons, and 2 to 4 carbons. Is particularly preferred.
When R ¹ , R ² , R ³ and R ⁴ are aryl groups, it is preferably 6 to 18 carbon atoms, more preferably 6 to 12 carbon atoms, and particularly preferably 6 carbon atoms. preferable.
R ¹ , R ² , R ³ and R ⁴ are preferably a hydrogen atom, an alkyl group or an aryl group, and more preferably a hydrogen atom.
R ¹ , R ² , R ³ and R ⁴ may further have a substituent, and examples of the substituent include the substituent which Ra may have.

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.

  Rb and Rc each independently represents an alkyl group, an alkenyl group, an alkynyl group, a heterocyclic group, or an aryl group. Specific examples are the same as the specific examples of Ra, and an alkyl group or an aryl group is preferable.

X ⁵ and X ⁶ each independently represent a single bond or a divalent linking group, and specific examples and preferred ranges thereof are the same as the specific examples and preferred ranges of the aforementioned X ¹ , X ² , X ³ and X ⁴ .

R ⁵ and R ⁶ 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, and specific examples and preferred ranges thereof include the R ¹ , R ² , R ³ and The specific examples and preferred ranges of R ⁴ are the same.

  Hereinafter, the compound represented by the general formula (1) or (2) that can be preferably used in the present invention as a retardation durability improver is shown.

Moreover, as a compound which has the said amino group, the compound represented by following General formula (3) can be mentioned. In addition, the compound represented by the following general formula (3) includes a compound having an amino group as a substituent at any substitutable position as a pyridine or pyrimidine mother nucleus.
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 substituted or unsubstituted 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 the linking site with the 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.

The compound represented by the general formula (3) is preferably a compound represented by the general formula (4) of JP2012-42938A, and the general formula (5) of JP2012-42938A. The compound represented by general formula (6) of JP 2012-42938 A is particularly preferable, and the compound represented by general formula (7) below is more preferable. More particularly preferred.
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, and more preferably 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, a hydrogen atom or an alkyl group having 1 to 8 carbon atoms is more preferable, and a hydrogen atom is more preferable.

  Hereinafter, compounds that can be preferably used in the present invention are shown as compounds represented by the general formula (3). Other examples of the compound represented by the general formula (3) include compounds described in [0097] to [0106] of JP 2012-42938 A.

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

In the general formula (10), X ^{21 to} X ²⁶ each independently represents a single bond or a divalent linking group. R ^{21 to} R ²⁶ 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.

In General Formula (10), specific examples in the case where X ^{21 to} X ²⁶ represent a divalent linking group are the same as the specific examples in the case where X ¹ in General Formula (1) represents a divalent linking group. is there. In the 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 the general formula (10), R ²¹ , R ²³ , and R ²⁵ are preferably hydrogen atoms, and R ²² , R ²⁴ , and R ²⁶ are preferably aryl groups.
In the general formula (10), R ^{21 to} R ²⁶ may further have a substituent, and examples of the substituent that R ^{21 to} R ²⁶ may have include Ra in the general formula (1). The substituent which may have can be mentioned, The preferable range of each substituent is the same as the preferable range of the substituent which Ra may have in the said General formula (1). Among these, the substituent which R ^{21 to} R ²⁶ may have is preferably an alkyl group or an alkoxy group, two of R ²² , R ²⁴ and R ²⁶ are alkyl groups, and one is an alkoxy group. More preferably, two of R ²² , R ²⁴ and R ²⁶ are methyl groups, and one is particularly preferably a methoxy group.

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

  Examples of other retardation durability improvers used in the present invention include compounds represented by the general formula (8) or (9) in JP 2012-42938 A, and the contents thereof are described in the present invention. Incorporated.

[Retardation humidity dependency improver]
The optical film of the present invention is characterized in that it contains a compound having a repeating unit having a large molecular weight. In such a film, since the humidity dependency of retardation may be slightly increased, it is also preferable to include a compound that further reduces the humidity dependency. As a compound for reducing the humidity dependency, a retardation humidity dependency improving (reducing) agent having ΔRth (A) defined by the following formula (IA) of −100 or more and less than 0 nm may also be included.
Formula (IA) ΔRth (A) = (ΔRth (rh, A) −ΔRth (rh, 0)) / Q
[In the formula, ΔRth (rh, A) represents a value obtained by subtracting Rth at 25 ° C. and 80% relative humidity from Rth at 25 ° C. and relative humidity of 10% of the film to which the compound is added by A mass%, and ΔRth (Rh, 0) represents a value obtained by subtracting Rth at 25 ° C. and 80% relative humidity from Rth at 25 ° C. and 10% relative humidity of the film to which the compound is not added, and Q is a cellulose ester in the film Represents the mass of the compound when the mass 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>
The compound containing a hydroxyl group preferably used as a retardation humidity dependency improving agent in the present invention is preferably a compound containing a phenolic hydroxyl group. Examples of such a compound containing a phenolic hydroxyl group include the compounds represented by the general formula (3) mentioned above as a retardation durability improver, and pages 13 to 19 of JP-A-2008-89860. And a compound represented by the general formula (I) described on pages 7 to 9 of JP-A-2008-233530 can be preferably used, and a compound represented by the general formula (3) can be used. More preferably, it can be used. The preferred range of the compound represented by the general formula (3) as a retardation humidity dependency improver is the same as the preferred range of the compound represented by the general formula (3) as a retardation durability improver.

[Matting agent fine particles]
It is preferable to add fine particles as a matting agent to the optical film of the present invention. Fine particles containing silicon are preferable in terms of low turbidity, and silicon dioxide is particularly preferable. The silicon dioxide fine particles preferably have a primary average particle size of 20 nm or less and an apparent specific gravity of 70 g / liter or more. Those having an average primary particle size as small as 5 to 20 nm are more preferred because they can reduce the haze of the film.
The Mohs hardness of the matting agent is preferably 1-8, and more preferably 5-7.
The addition amount of the matting agent is preferably 0.001% by mass to 0.2% by mass and more preferably 0.01% by mass to 0.1% by mass with respect to the cellulose ester.

  Examples of the matting agent fine particles used in the present invention and other preferred embodiments are the same as those of the matting agent fine particles described in [0148] to [0153] of JP 2012-42938 A, Incorporated into the present invention.

[Other additives]
In addition to the compound having a repeating unit described above, a retardation adjusting agent, a compound that improves the wet heat durability of the retardation, a retardation humidity dependency reducing agent, and a matting agent fine particle, the optical film of the present invention has various other additives. (For example, a plasticizer, an ultraviolet absorber, a deterioration preventing agent, a release agent, an infrared absorber, a wavelength dispersion adjusting agent, and other polymer additives other than a compound having a repeating unit that satisfies the above conditions). They can be solid or oily. That is, the melting point and boiling point are not particularly limited. For example, mixing of ultraviolet absorbing material at 20 ° C. or lower and 20 ° C. or higher, and similarly mixing of a plasticizer is described in, for example, JP-A-2001-151901. Furthermore, infrared absorbing dyes are described in, for example, JP-A No. 2001-194522. Examples of other polymer additives other than the compound having a repeating unit satisfying the above conditions include compounds described in JP-A-2012-42938, [0037] to [0038].

[When additive is added]
When producing the optical film of the present invention, the additive may be added at any time in the dope preparation step, but the step of adding the additive to the final preparation step of the dope preparation step is prepared. In addition, it may be performed. 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.

[Additive amount of additive]
In the optical film of the present invention, when these other additives are added in addition to the compound having the above-mentioned repeating unit, the total amount of additives contained in the optical film of the present invention is the total amount of cellulose ester used. On the other hand, it is preferably 30% by mass or more and 200% by mass or less, and more preferably 35% by mass or more and 150% by mass or less.

[Characteristics of optical film]
<Retardation>
The optical film of the present invention has an in-plane retardation (Re) at a wavelength of 590 nm defined by the following formula (I) of 10 nm or less, preferably 0 to 5 nm, and more preferably 0 to 3 nm. The thickness direction retardation (Rth) at a wavelength of 590 nm defined by the following formula (II) is preferably −25 to 25 nm, more preferably −20 to 5 nm, and −10 to 0 nm. More preferably.
These values are the chemical structure of the polymer constituting the optical film of the present invention (for example, the type and degree of substitution of cellulose ester), the type and amount of the compound having the above-mentioned repeating unit, and the film film. It can be controlled by the 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.
When the optical 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 do. The optical film of the present invention can be particularly preferably used in an IPS liquid crystal display device in which the liquid crystal and the optical film are not directly optically compensated.

  Re and Rth can be measured as follows.

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. At 25 ° C. and 60% relative humidity, the following formula was used: An average refractive index (n) represented by (B) is obtained.
Formula (B): n = (n _TE × 2 + n _TM ) / 3
[ _Where n _TE is a refractive index measured with polarized light in the film plane direction, and n _TM is a 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).

<Elastic modulus>
The optical film of the present invention preferably has an elastic modulus exceeding 3.5 GPa and 4.0 GPa or more. Although there is no restriction | limiting in particular about the upper limit of an elasticity modulus, it is 10 GPa or less. When the elastic modulus exceeds 3.5 GPa, it is possible to improve the production suitability of the film. Moreover, since the optical film of the present invention is wound and stored as a roll-shaped optical film of the present invention, which will be described later, the appearance hardly deteriorates, it is preferable.
The elastic modulus of the optical film of the present invention represents the elastic modulus in the direction in which the sound wave propagation speed becomes maximum. The same applies to the roll-shaped optical film of the present invention described later using the optical film of the present invention.
As a specific method for measuring the elastic modulus, it can be measured by the method described in Examples described later.

<Sound wave propagation speed, ratio of sound wave propagation speed in the direction perpendicular to the direction where the sound wave propagation speed is maximum>
In the optical film of the present invention, the ratio of the sound wave propagation velocity in the direction where the sound wave propagation velocity is maximum and the direction orthogonal thereto (maximum direction / direction orthogonal to the maximum direction) is preferably 1.10 or more, and 1.20. More preferably, it is more preferably 1.24 or more. Although there is no restriction | limiting in particular about an upper limit, It is 2.0 or less. By setting the ratio of the sound wave propagation speed to 1.10 or more, the production suitability of the film can be improved.

In the present invention, the maximum direction of sound wave propagation means that the direction of sound velocity propagation is in an angle range of ± 10 ° with respect to the maximum direction, and preferably intersects at an angle of ± 5 °. More preferably, they intersect at an angle of °.
The direction in which the sound wave propagation velocity is orthogonal to the maximum direction means that the sound velocity propagation direction intersects with the maximum direction at an angle of 90 ° ± 10 °, and intersects with an angle of 90 ° ± 5 °. It is more preferable that they intersect at an angle of 90 ° ± 1 °.

  In the present invention, the direction in which the sound wave propagation speed becomes maximum is adjusted using an orientation measuring machine (SST-2500: manufactured by Nomura Corporation) after conditioning the optical film at 25 ° C. and a relative humidity of 60% for 24 hours. The direction in which the propagation speed of the longitudinal vibration of the ultrasonic pulse is maximized was obtained. In addition, the propagation speed of the longitudinal vibration of the ultrasonic pulse measured at this time is set as the sound wave propagation speed in the direction in which the sound wave propagation speed becomes maximum. Furthermore, after determining the direction orthogonal to the direction in which the propagation velocity of the longitudinal wave vibration of the ultrasonic pulse is maximized, the ultrasonic pulse in the direction orthogonal to the direction in which the propagation velocity of the longitudinal wave vibration of the ultrasonic pulse is maximized is determined. The propagation speed of the longitudinal wave vibration was determined as the sound wave propagation speed in the direction orthogonal to the direction in which the propagation speed of the longitudinal wave vibration of the ultrasonic pulse is maximum.

<Shrink force>
The shrinkage force (unit × 10 N / m) of the optical film of the present invention is represented by the following formula (1). By reducing the contraction force, it is possible to suppress changes in the humidity dimension.
Formula (1) Fw1 = Ew1 × εw1 × dw
[In the formula, all the characteristic quantities are values in which the sound wave propagation speed is in the maximum direction. Ew1 is the elastic modulus after the wet heat treatment, εw1 is the absolute value of the humidity dimensional change rate after the wet heat treatment, and dw is the film thickness after the wet heat treatment. Ew1 is in the range of 2.0 to 8.0 GPa, εw1 is in the range of 0.01 to 0.38%, and dw is in the range of 5 to 80 μm. ]

  Ew1 in the above formula (1) is calculated by the elastic modulus measurement method described in the examples below, after holding the optical film in an environment of 60 ° C. and 90% relative humidity for 48 hours. In the present invention, the elastic modulus (Ew1) after the wet heat treatment in the direction of maximum sound wave propagation speed is preferably 2.0 to 8.0 GPa, more preferably 2.5 to 7.0, and more preferably 3.0 to 5.5. Is more preferable.

Εw1 in the above formula (1) is a film sample having a length of 12 cm (measurement direction), a width of 3 cm, and a direction orthogonal to the direction in which the direction in which the sound wave propagation speed is maximum or the direction orthogonal thereto is taken as the longitudinal direction. Each sample cut out as a length was prepared, pin holes were made at intervals of 10 cm in the sample, held for 48 hours in an environment of 60% relative humidity and 90% relative humidity, and then conditioned for 24 hours at 25 ° C and 80% relative humidity , the distance between the pin holes to the length measured at a pin gauge (measurements and L _80). Next, the sample is conditioned at 25 ° C. and 60% relative humidity for 24 hours, and the distance between the pin holes is measured with a pin gauge (measured value is L ₆₀ ). Subsequently, the sample was conditioned at 25 ° C. and 10% relative humidity for 48 hours, and the distance between the pin holes was measured with a pin gauge (measured value is L ₁₀ ). The humidity dimensional change rate is calculated by the following formula using these measured values.
Humidity dimensional change rate between 10% and 80% relative humidity (εw1, direction in which sound wave propagation speed becomes maximum) [%] = | L ₁₀ −L ₈₀ | / L ₆₀
The absolute value (εw1; change between relative humidity 10% and 80%; unit%) of the humidity dimension change after wet heat treatment in the direction in which the sound wave propagation speed becomes maximum is preferably 0.01 to 0.38, 0.05 -0.30 is more preferable, and 0.07-0.28 is still more preferable.

  Here, when using the optical film of this invention as a protective film of the polarizing plate arrange | positioned at the visual recognition side among the polarizing plates arrange | positioned on both surfaces of a panel, the shrinkage force accompanying dehydration of a polarizing plate is reduced. Therefore, the Fw1 is preferably 1 to 70, more preferably 10 to 50, and still more preferably 20 to 35.

[Thickness of optical film]
The thickness of the optical film of the present invention is preferably 5 to 80 μm, more preferably 10 to 70 μm, and particularly preferably 25 to 40 μm.

<Width of optical film>
The width of the optical film is preferably 700 to 3000 mm, more preferably 1000 to 2800 mm, and particularly preferably 1300 to 2500 mm.

<Haze of optical 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. The haze can be measured by the method described in Examples described later.

<Equilibrium moisture content of optical 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 moisture content at 25 ° C. and a relative humidity of 80% is preferably 0 to 4% by mass. More preferably, it is 0.1-3.5 mass%, and it is especially preferable that it is 1-3 mass%. When the equilibrium moisture content is 4% by mass or less, it is preferable that the dependency of retardation due to humidity change 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 vapor transmission rate of optical film>
The moisture permeability of the optical film is measured under the conditions of 40 ° C. and 90% RH based on JIS Z-0208. Although the moisture permeability of the optical film of the present invention is not particularly limited, it is preferably 50 to 1500 g / (m ² · 24 h). More preferably ^{100~1000g / (m 2 · 24h)} , particularly preferably ^{200~800g / (m 2 · 24h)} . If the moisture permeability is within this range, it is preferable because both the workability of the polarizing plate and the durability of the polarizing plate against humidity or wet heat can be achieved. Further, the moisture permeability of the protective film used on the opposite side of the optical film of the present invention with the polarizing film interposed therebetween is not particularly limited, but is preferably low and is 3 to 1000 g / (m ² · 24 h) or less. It is preferably 5 to 500 g / (m ² · 24 h), more preferably 10 to 100 g / (m ² · 24 h), and 10 to 50 g / (m ² · 24 h). It is particularly preferred. If it is this range, both polarizing plate workability and durability of a polarizing plate with respect to humidity or wet heat can be made compatible, or the curvature of a panel can be improved more effectively.

<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 due to contraction of the polarizing film. The change in birefringence due to such stress can be measured as a photoelastic coefficient, but the range is preferably 15 × 10 ¹² Pa ⁻¹ or less (15Br or less), and −5 × 10 ¹² Pa ⁻¹ 12 × 10 ¹² Pa ⁻¹ is more preferable, and −2 × 10 ¹² Pa ^{−1 to} 11 × 10 ¹² Pa ⁻¹ is still more preferable.

<Contact angle of optical film surface by alkali saponification treatment>
Since the optical film of the present invention contains a cellulose ester, 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 on the surface of the optical film 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 under a low pressure gas of 10 ^{−3 to} 20 Torr, and plasma treatment under atmospheric pressure is also preferred. A plasma-excitable gas is a gas that is plasma-excited under the above conditions, and includes chlorofluorocarbons such as argon, helium, neon, krypton, xenon, nitrogen, carbon dioxide, tetrafluoromethane, and mixtures thereof. It is done. Details of these are described in detail on pages 30 to 32 in the Japan 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]
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.

[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.

(Roll optical film)
The roll-shaped optical film of the present invention is characterized in that the optical film of the present invention is wound, and the elastic modulus in the longitudinal direction exceeds 3.5 GPa.
The elastic modulus of the roll-shaped optical film of the present invention is defined as the elastic modulus in the direction in which the sound wave propagation speed becomes maximum as described above. Here, in the manufacturing method of the optical film of the present invention, since the stretching process is performed in the transport direction, the roll-shaped optical film of the present invention using the optical film of the present invention has the maximum direction of sound wave propagation speed in the longitudinal direction. It is preferable that In this case, the fact that the elastic modulus in the longitudinal direction of the roll-shaped optical film of the present invention exceeds 3.5 GPa is synonymous with the fact that the elastic modulus (elastic modulus in the maximum direction of sound wave propagation speed) exceeds 3.5 GPa.
Unless there is particular notice, such as the material contained in the roll-shaped optical film of this invention, a physical property, a manufacturing method, it is the same as that of the optical film of this invention, and its preferable range is also the same.
The length of the roll-shaped optical film of the present invention is preferably 100 to 16000 m, more preferably 1000 to 10000 m, and particularly preferably 3000 to 8000 m. Since the roll-shaped optical film of the present invention has a high elastic modulus, transportability is good even when it is manufactured with such a length.
In the roll-shaped optical film of the present invention, the optical film of the present invention may be wound around an arbitrary winding core.

(Optical film manufacturing method)
The method for producing an optical film of the present invention preferably includes at least the following steps (a), (b), and (c) from the viewpoint of reducing the contractile force while suppressing a reduction in elastic modulus. It is more preferable to have the steps (b) and (c) in this order.
(A) A step of casting a solution containing at least a compound having a repeating unit, a cellulose ester, and a solvent on a support (b) removing the solvent from the solution cast on the support to form a film Step of forming a film and stripping the film from the support (c) Step of stretching the film in the transport direction

  From the viewpoint of improving the reworkability of the polarizing plate using the optical film of the present invention, the step (c) of stretching the film in the transport direction is performed in a state where the residual solvent amount is 1.0 to 300% by mass. The residual solvent amount is more preferably 100 to 280% by mass, further preferably 150 to 250% by mass, and still more preferably 180 to 240% by mass.

The draw ratio in the transport direction can be appropriately set according to the properties required for the film, preferably between 100 and 200%, more preferably between 105 and 150%, and even more preferably between 110 and 140%. 115 to 130% is particularly preferable. These stretching operations may be performed in one stage or in multiple stages. Here, “stretch ratio (%)” means that obtained using the following formula.
Stretch ratio (%) = 100 × {(Length after stretching) − (Length before stretching)} / Length before stretching Here, the length before stretching and the length after stretching are the stretching zone. It can also be evaluated as the transport speed of the base before and the transport speed of the base after the stretching zone.
In the method for producing an optical film of the present invention, it is preferable that the stretch ratio is gradually expanded between 100% and 200% along the transport direction. Although there is no restriction | limiting in particular as a method of enlarging draw ratio between 100%-200% along a conveyance direction in particular, For example, the web (film) peeled off from the support body is a cross which has two or more rollers. Multi-stage in which the rotation speed (weekly speed) with respect to the support speed of two or more rollers at the crossing section is increased gradually from upstream to downstream and the draw ratio in the transport direction is sequentially expanded The method of extending | stretching can be mentioned.

  In the method for producing an optical film of the present invention, the stretching speed in stretching in the transport direction is preferably 50 to 10,000% / min, more preferably 100 to 3000% / min, and further preferably 200 to 1500% / min. is there.

  It is preferable to have a heat treatment (post heat treatment) step after the stretching step from the viewpoint of reducing the contraction force while suppressing the reduction of the elastic modulus. From the viewpoint of reducing the residual strain accumulated in the film in a short time, the post-heat treatment temperature is (Tg−10) ° C. or higher and lower than (Tg + 60) ° C. when the glass transition temperature of the optical film is Tg (unit ° C.). Tg to (Tg + 50) ° C. is more preferable, and (Tg + 10) ° C. to (Tg + 40) ° C. is more preferable. When the temperature is lower than (Tg−10) ° C., the heat treatment time necessary for sufficiently reducing the residual strain is remarkably increased, so that the productivity is not preferable, and when it is equal to or higher than (Tg + 60) ° C., retardation deviation may occur. . The time for the heat treatment is not particularly limited as long as it is sufficient to reduce residual strain, but is preferably 0.01 to 60 minutes, and preferably 0.1 to 40 minutes. More preferably, it is more preferably 1 to 30 minutes. If it is 0.01 minutes or more, it is preferable because residual strain can be sufficiently reduced, and if it is 60 minutes or less, productivity can be secured.

[Organic solvent of dope solution]
In this invention, it is preferable to manufacture a film by the solvent cast method, and a film is manufactured using the solution (dope) which melt | dissolved the polymer in the organic solvent. The organic solvent that is preferably used as the main solvent in the present invention is not particularly limited as long as the polymer dissolves. For example, when the main polymer used is a cellulose ester, the organic solvent has 3 to 12 carbon atoms. A solvent selected from esters, ketones, ethers, and halogenated hydrocarbons having 1 to 7 carbon atoms is 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 said dope solution and an optical film 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 preferably used in 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]
Preparation of the dope solution is not particularly limited, and it may be performed at 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 an optical film using the dope solution 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. The both ends of the obtained web are sandwiched between clips, transported with a tenter while holding the width and dried, and then the obtained optical film is mechanically transported by a group of rolls in a heating device and rolled into a roll with a winder Wind up to a predetermined length. The combination of the tenter and the roll group dryer varies depending on the purpose. As another embodiment, 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 is held by a pin-shaped tenter. In the solvent cast method, such as a method in which the optical film obtained is transported and dried, and then the obtained optical film is mechanically transported by a group of rolls in a heating device and wound into a predetermined length by a winder. Various methods for forming a film can be used. In the present invention, a zone between the time after peeling from the metal support and before gripping with the tenter can be preferably used as the stretching step, and the rotation speed of the metal support and the transport speed of the tenter are made different. Thus, the web can be stretched, and preferred stretch ratios are as described above.
A zone that is mechanically transported by a roll group in the heating device can be preferably used as a post-heat treatment step, and the transport tension is preferably low, preferably 10 to 300 N, and preferably 15 to 200 N. More preferably, it is 20-150N. The conveyance tension can be controlled by adding a peripheral speed difference between the rolls in the heating device, and if it is 10 N or more, it prevents slipping between the film and the roll and prevents the film from being scratched. Preferably, if it is 300 N or less, the residual distortion of the film can be effectively reduced, which is preferable. Further, when the transport tension is lowered, residual strain is less likely to accumulate.
The optical film used in the present invention may be a single layer film or may have a laminated structure of two or more layers. For example, it is also preferable that it is a laminated structure composed of two layers of a core layer and a surface layer, and is formed by co-casting.
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 optical 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.

(Polarizer)
The polarizing plate of the present invention has the optical film of the present invention and a polarizing film.
The optical film of the present invention or the retardation film can be used as a protective film for a polarizing plate (polarizing plate of the present invention). The polarizing plate of the present invention has a polarizing film and two polarizing plate protective films (optical films) protecting both surfaces thereof, and the optical film or the retardation film of the present invention is used as at least one polarizing plate protective film. It is particularly preferred.
When the optical film of the present invention is used as a polarizing plate protective film, the optical film of the present invention is subjected to the surface treatment (also described in JP-A-6-94915 and JP-A-6-118232) to make it hydrophilic. For example, it is preferable to perform glow discharge treatment, corona discharge treatment, alkali saponification treatment, or the like. As the surface treatment, alkali saponification treatment is most preferably used.

  In the optical film of the present invention, since the molecular orientation in the transport direction is strongly advanced, the molecular orientation degree of the polarizing film and the molecules of the film of the present application are compared with those of conventional optical films used in general polarizing plates. The degree of orientation is close. As a result, in the polarizing plate using the optical film of the present invention, for example, the thermal expansion coefficient and the humidity expansion coefficient of the polarizing film and the optical film of the present invention are closer to those of the conventional product. When an environmental change such as temperature and humidity occurs, internal stress generated in the optical film of the present invention is reduced. As a result, it is possible to obtain a preferable effect that properties such as a change in retardation of the film in a practical form are further suppressed.

  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 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. Moreover, it is preferable that the optical film of this invention is arrange | positioned so that the absorption axis of a polarizing film and the maximum direction of the sound wave propagation speed of the optical film of this invention may become parallel.
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, a low moisture permeability layer, etc. It is preferably used as a polarizing plate protective film on the outermost surface of the display side of the liquid crystal display device. At this time, for the protective film, the protective film of the polarizing plate used on the viewing side of the liquid crystal display device and the protective film of the polarizing plate used on the side opposite to the viewing side have a moisture evaporation rate of, for example, It is preferable that the selection is made so as to be disclosed in Japanese Patent Application Laid-Open No. 2012-133301 from the viewpoint of improvement of warpage and luminance unevenness after wet heat treatment.
The polarizing plate is composed of a polarizing film and a protective film for protecting both surfaces of the polarizing film, and further comprises a protective film on one surface of the polarizing plate and a separate film on 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 liquid crystal display device of the present invention has the optical film of the present invention or the polarizing plate of the present invention.
The optical 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 the optical film of the present invention and the polarizing plate are used will be described below. Among these modes, the optical film and polarizing plate of the present invention can be preferably used in all modes, but are particularly preferably used for 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]
The optical film of the present invention can be 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]
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]
The optical film of the present invention may be used as a retardation film or a support for a retardation film of 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 the same as the optical properties of the optical anisotropic layer, the optical properties of the support, and the optical 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 ester film, it can be preferably used particularly in the latter case.

  The present invention will be described more specifically with reference to the following 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 is not limited to the specific examples shown below.

(Measurement method)
First, characteristics measurement methods and evaluation methods are shown below.

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

[Residual solvent amount]
The residual solvent amount of the web (film) at the time of manufacturing the optical film was calculated based on the following formula.
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. ]

[Haze]
30 points in the width direction of the optical film (positions obtained by equally dividing 30 positions from both ends of the film into 30 parts at equal intervals) are sampled every 100 m in the longitudinal direction, and a sample having a size of 4 cm × 4 cm is taken out and haze The average value measured using a meter (NDH 2000: manufactured by Nippon Denshoku Industries Co., Ltd.) was defined as haze, and (maximum value−minimum value) was defined as haze distribution.

[Sound propagation velocity]
Measurement was performed by the method described above.

[Retardation]
5 points in the width direction of the optical film (center part of film, end part (position of 5% of the total width from each end), and two intermediate parts between the center part and the end part) are sampled every 100 m in the longitudinal direction, and 5 cm A sample having a size of × 5 cm was taken out, the average value of each point evaluated according to the above-described method was calculated, and Re and Rth were obtained, respectively.

[Elastic modulus]
A sample of 200 mm × 10 mm was cut out from the produced optical film so that the conveying direction was long, and the humidity was adjusted for 24 hours at 25 ° C. and 60 RH% atmosphere using Toyo Baldwin Co., Ltd. universal tensile tester “STM T50BP”. Thereafter, the stress at 0.1% elongation and 0.5% elongation was measured at a tensile rate of 10% / min, and the elastic modulus was determined from the slope.

[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

(Manufacture of optical films)
The optical film of the present invention was produced by selecting those listed in Tables 1 and 3 from the materials and production methods shown below.

[Material used for film formation]
<Polymer resin>
Those listed in Table 3 were selected from the following polymer resins. Each polymer resin was heated to 120 ° C. and dried to have a water content of 0.5% by mass or less.

Polymer resin A:
20 parts by mass of cellulose acetate powder derived from pulp having a degree of substitution of 2.86 was used. The polymer resin A has a viscosity average polymerization degree 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 0.2. Viscosity in a mass%, 6 mass% dichloromethane solution 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 content The amount 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.

Polymer resin B:
20 parts by mass of a cellulose acetate powder derived from Lita having a substitution degree of 2.94 and a viscosity average polymerization degree of 280 was used.

Polymer resin C:
20 parts by mass of cellulose acetate powder derived from Lita having a substitution degree of 2.87 and a viscosity average polymerization degree of 310 was used.

Polymer resin D:
According to Production Example 1 of JP 2008-9378 A [0222] to [0224], synthesized from 7500 g of methyl methacrylate and 2500 g of methyl 2- (hydroxymethyl) acrylate, the obtained lactonization rate was 98%, Tg = A 134 ° C. acrylic resin was used.

<Solvent>
80 parts by mass of the solvent described in Table 3 was used from the following solvents. The water content of each solvent was 0.2% by mass or less.
Solvent A dichloromethane / methanol / butanol = 81/18/1 (mass ratio)
Solvent B dichloromethane / methanol = 92/8 (mass ratio)

<Additives>
Those listed in Table 1 and Table 3 were selected from the following additives. However, in Table 3, “addition amount” of the compound having a repeating unit, the retardation increasing agent, the retardation durability improving agent, and the retardation humidity dependency improving agent represents mass% when the cellulose ester is 100 mass%. The addition amount of the additive and retardation increasing agent to the cellulose ester solution was adjusted so as to be the above amount.
Compounds having repeating units:
A-1: Condensate of ethanediol / adipic acid (1/1 molar ratio), number average molecular weight 1000, hydroxyl value 112 mgKOH / g
A-2: Acetate ester at both ends of the condensate of ethanediol / adipic acid (1/1 molar ratio), number average molecular weight 1000, hydroxyl value 0 mgKOH / g
A-3: Acetic ester at both ends of the condensate of ethanediol / succinic acid (1/1 molar ratio), number average molecular weight 1000, hydroxyl value 0 mgKOH / g
A-4: 1,2-propanediol / succinic acid (1/1 molar ratio) condensate at both ends, acetate ester, number average molecular weight 1000, hydroxyl value 0 mg KOH / g
A-5: 1,2-propanediol / succinic acid (1/1 molar ratio) condensate at both ends, acetate ester, number average molecular weight 800, hydroxyl value 0 mg KOH / g
A-6: Acetic ester at both ends of the condensate of ethanediol / 1,2-propanediol / succinic acid / adipic acid (1/1/1/1 molar ratio), number average molecular weight 1000, hydroxyl value 0 mgKOH / G
A-7: Acetic ester at both ends of the condensate of ethanediol / succinic acid (1/1 molar ratio), number average molecular weight 1500, hydroxyl value 0 mgKOH / g
A-8: Acetic ester at both ends of the condensate of ethanediol / succinic acid (1/1 molar ratio), number average molecular weight 4800, hydroxyl value 0 mgKOH / g
A-9: 1,2-propanediol / adipic acid (1/1 molar ratio) condensate at both ends, acetate ester, number average molecular weight 6000, hydroxyl value 0 mgKOH / g
A-10: Acetic ester at both ends of the condensate of ethanediol / adipic acid / phthalic acid (2/1/1 molar ratio), number average molecular weight 760, hydroxyl value 0
The composition of the compound having a repeating unit is shown in Table 1 below. In Table 1 below, PA represents phthalic acid, AA represents adipic acid, SA represents succinic acid, EG represents ethanediol (ethylene glycol), and PG represents 1,2-propanediol (propylene glycol).

<Retardation raising agent>
Compounds with the following structure

<Retardation durability improver>
Compounds with the following structure

<Retardation humidity dependency improver>
Compounds with the following structure

<Matte fine particles>
M-1: silicon dioxide fine particles (particle size 20 nm, Mohs hardness of about 7) (0.02 parts by mass of cellulose ester with respect to 100 parts by mass)
M-2: silicon dioxide fine particles (particle size 20 nm, Mohs hardness about 7) (0.05 parts by mass of cellulose ester with respect to 100 parts by mass)

(Evaluation of forced crying of compounds with repeating units)
17.8 parts by mass of the cellulose ester described in Table 1, 7.1 parts by mass of compound A-1 having a repeating unit, 132.7 parts by mass of dichloromethane, 33.6 parts by mass of methanol, 1.7 parts by mass of butanol and 300 mL of pressure resistance After putting into a container and stirring for 15 minutes at room temperature, it heated at 80 degreeC for 3 hours, and obtained the dope solution. The obtained dope is filtered through a filter paper (# 63, manufactured by Toyo Filter Paper Co., Ltd.) having an absolute filtration accuracy of 10 μm, cast on a glass plate, heated at 70 ° C. for 6 minutes, and then peeled off from the glass plate. Then, after being fixed to a metal frame, it was further heated at 70 ° C. for 15 minutes to obtain a film having a thickness of 60 μm.
The obtained film was cut into 40 mm squares, placed in an oven at 140 ° C. and heated for 20 minutes, and the film was visually observed for crying (forced crying test). Moreover, the crying out of the film produced similarly was investigated except having changed to compound A-2 to A-10 which has a repeating unit. The results are shown in Table 1.
A: No crying is seen at all B: Some crying is seen on a part of the film C: Clear crying is seen on part or the whole film D: The film is crying on the whole

  Using the above materials, the film No. described in Table 3 below was selected from the following film forming processes A to C, and film No. 1-27 were produced. All films were excellent in transparency with a haze of 0.5% or less.

[Film forming process A]
<Preparation of dope solution>
Dissolution process:
The polymer resin was gradually added to a 4000 liter stainless steel dissolution tank having a stirring blade while the solvent and additive were added and stirred and dispersed. 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 dope 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 ]). In addition, an agitation 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 ]) is used. 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 the tank to 50 ° C. with a jacketed pipe, and further heated to 90 ° C. under a pressure of 1.2 MPa to completely dissolve. 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 dope 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 concentration of the dope after flashing was 24.8% 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.

Filtration:
Next, it was first passed through a sintered fiber metal filter having a nominal pore diameter of 10 μm, and then passed through a sintered fiber filter of 10 μm. The dope temperature after filtration was adjusted to 36 ° C. and stored in a 2000 L stainless steel stock tank.

Casting process:
Subsequently, the dope in the stock tank was fed. The casting die had a width of 2.1 m, the casting width was 2000 mm, and the dope flow rate was adjusted by adjusting the flow rate of the dope at the die protrusion. 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 36 ° C. during the work process.

《Casting Die》
The material of the die is a duplex stainless steel with a mixed composition of austenite phase and ferrite phase, with a coefficient of thermal expansion of 2 × 10 ^-6 (° C ^-1 ) or less, and forced corrosion in an aqueous electrolyte solution. In the test, a material having approximately the same corrosion resistance as SUS316 was used.
In addition, the lip tip of the casting die used was a WC coating formed by a thermal spraying method. Further, a mixed solvent, which is a solvent for solubilizing the dope, was supplied at 0.5 ml / min on one side to the gas-liquid interface between the bead end and the slit.

《Metal support》
A mirror surface stainless steel support, which is a drum having a width of 2.1 m and a diameter of 3 m, was used as the 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 drum temperature was set to −5 ° C., and the drum rotation speed was set so that the peripheral speed of the drum was 80 m / min. In addition, when the drum surface became dirty with casting, it cleaned appropriately.

Stretching in the casting / conveying direction:
The dope extruded from the die is subsequently cast on a drum placed in a space set at 15 ° C., and the cooled and gelled dope is gelled when it is rotated 320 ° on the drum. It peeled off as a film (web) and the peeled web was conveyed by the transfer part provided with three rollers. At this time, the rotation speed of the roller with respect to the support speed and the driving speed of the tenter described later are adjusted, the stretching in the transport direction is performed at the crossing section, and the film is transported so that the film having the sound wave propagation speed ratio shown in Table 1 is obtained. The draw ratio in the direction was set. The residual solvent amount at the start of stretching was between 180 and 240% by mass, and the stretching speed was 200 to 1,200% / min. With the three rollers in the transition section, the rotational speed (circumferential speed) of the roller with respect to the support speed is sequentially increased from upstream to downstream, and stretching in the transport direction is, for example, 108%, 113%, and 120%. (Corresponding to the final draw ratio) and multi-stage stretching was performed.

Tenter transport and drying process:
The peeled web was conveyed through the drying zone while being fixed at both ends with a tenter having a pin clip, and dried with drying air. Except for the film 8, no positive stretching was performed in this step.
In the film 8, the film is stretched in the transport direction as described above under the same conditions as the film 7, and then the film is stretched in a direction (width direction) orthogonal to the transport direction with a tenter, and the transport direction is more than the transport direction. The draw ratio was set so that a film having a high modulus of elasticity in the orthogonal direction and a sound wave velocity ratio shown in Table 1 was obtained.

Post-drying process:
The optical film after the trimming obtained by the method described above was further dried in the roller transport zone. 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. The produced optical film was post-heat-treated at 110 ° C. with a transport tension of 190N.

Post-processing and winding:
The dried optical film was cooled to 30 ° C. or lower and cut off at both ends. 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. Further, knurling was performed on both ends of the optical film. Knurling was applied by embossing from one side. Thus, an optical film having a final product width of 1490 mm was obtained, wound by a winder, and a 3900 m roll was produced.
In addition, in the film 1, the film 5, and the film 7, the roll of 1000m winding was separately produced for roll external appearance evaluation, and the roll of 7600m was also produced separately in the film 5.

[Film forming process B]
<Preparation of dope solution>
Dissolution:
The polymer resin was gradually added to a 4000 liter stainless steel dissolution tank having a stirring blade while the solvent and additive were added and stirred and dispersed. After completion of the addition, the mixture was stirred at room temperature for 30 minutes, and further stirred for 100 minutes to obtain a dope solution.
The swollen solution was heated from the tank to 50 ° C. with a jacketed pipe, and further heated to 90 ° C. under a pressure of 2 MPa to completely dissolve. 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 dope solution.

Filtration:
Next, it was first passed through a sintered fiber metal filter having a nominal pore diameter of 10 μm, and then passed through a sintered fiber filter of 10 μm. The dope temperature after filtration was adjusted to 36 ° C. and stored in a 2000 L stainless steel stock tank.

Casting process:
Subsequently, the dope in the stock tank was fed. The casting die had a width of 1.7 m, and was cast by adjusting the flow rate of the dope at the die protrusion. 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 36 ° C. during the work process.

《Casting Die》
The material of the die is a duplex stainless steel with a mixed composition of austenite phase and ferrite phase, with a coefficient of thermal expansion of 2 × 10 ^-6 (° C ^-1 ) or less, and forced corrosion in an aqueous electrolyte solution. In the test, a material having approximately the same corrosion resistance as SUS316 was used.
In addition, the lip tip of the casting die used was a WC coating formed by a thermal spraying method. Further, a mixed solvent, which is a solvent for solubilizing the dope, was supplied at 0.5 ml / min on one side to the gas-liquid interface between the bead end and the slit.

《Metal support》
A stainless steel endless band having a width of 2.1 m and a length of 70 m was used as a support. A band having a thickness of 1.5 mm and a surface roughness of 0.05 μm or less was used. The material was made of SUS316 and had sufficient corrosion resistance and strength. The band used was a type driven by two drums, and the drum of the casting part was one having equipment for circulating a heat transfer medium (refrigerant) inside to cool the support. 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.

Stretching in the casting / conveying direction:
The temperature of the casting chamber provided with the casting allowance and the support was maintained at 35 ° C. The dope extruded from the die and cast on the band is first dried by sending parallel-flow drying air, and is peeled off as a film from the casting support when the amount of residual solvent in the dope reaches 50% by mass. did. Subsequently, the obtained film was sent to a longitudinal stretching zone having three driving rollers and a pass roller between the driving rollers, and a stretching ratio in the transport direction so that a film having a sound wave propagation speed ratio described in Table 1 was obtained. It was set. For the three drive rollers, multi-stage stretching was performed, for example, 108%, 113%, and 120% in order to stretch in the transport direction (passed through each roller based on the length of the film before starting stretching). The ratio of the length of the film after the treatment was described as each draw ratio). The film 20 was set so that the stripping roll draw was 1.01 times.

Tenter transport and drying process:
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 inside of the tenter was divided into three zones, and the drying air temperature of each zone was set to 90 ° C, 100 ° C, and 110 ° C from the upstream side. At the exit of the tenter, the amount of residual solvent in the film was adjusted to 10% by mass or less. In this process, no active stretching was performed. The film 20 was stretched 1.05 times in the width direction.

Post-drying process:
The optical film after the trimming obtained by the method described above was further dried in the roller transport zone. 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. The produced optical film was post-dried at 110 ° C. and a conveyance tension of 100N.

Post-processing and winding:
The dried optical film was cooled to 30 ° C. or lower and cut off at both ends. 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. Further, knurling was performed on both ends of the optical film. Knurling was applied by embossing from one side. Thus, an optical film having a final product width of 1490 mm was obtained, wound by a winder, and a 3900 m roll was produced.

[Film forming process C]
Pellet preparation:
The prepared polymer resin is dried with a vacuum dryer at 90 ° C. to make the water content 0.03% or less, and then 0.3% by weight of a stabilizer (Irganox 1010 (Ciba Gaigi Co., Ltd.)) is added at 230 ° C. In a nitrogen stream, a biaxial kneading extruder with a vent was used to extrude into water to form a strand, which was then cut to obtain a pellet having a diameter of 3 mm and a length of 5 mm.

Melt film formation:
The obtained pellets were dried with a 90 ° C. vacuum dryer to a water content of 0.03% or less, and then kneaded using a uniaxial kneading extruder at a supply unit 210 ° C., a compression unit 230 ° C., and a weighing unit 230 ° C. Extruded. At this time, a 300-mesh screen filter, a gear pump, and a leaf disk filter with a filtration accuracy of 7 μm were arranged in this order between the extruder and the die, and these were connected by a melt pipe. Furthermore, a static mixer is installed in the melt pipe immediately before the die, and extruded from the hanger coat die while adjusting the temperature difference between the die ends and the die center temperature, the die lip temperature and the die temperature difference, and the C / T ratio. did.
Thereafter, a melt (molten resin) was extruded onto a triple cast roll. At this time, the touch roll was brought into contact with the most upstream cast roll (chill roll). The touch roll described in Example 1 of Japanese Patent Application Laid-Open No. 11-235747 was used (the one described as a double holding roll, except that the thickness of the thin metal outer cylinder was 2 mm). In addition, the temperature of the triple cast roll containing a chill roll was made into touch roll temperature +3 degreeC, touch roll temperature -2 degreeC, and touch roll temperature -7 degreeC in order from the upstream.
Subsequently, the obtained film was stretched in a longitudinal stretching zone including a pair of nip rolls, and then sent to a roller transport zone to be annealed. In the stretching zone, the stretching ratio was set so that a film having a sound wave propagation speed ratio shown in Table 3 was obtained.
Then, after trimming both ends (5 cm each of the full width) immediately before winding, thicknessing (knurling) with a width of 10 mm and a height of 20 μm was applied to both ends. Further, the film-forming width was 1.5 m, and the film was wound up 3000 m at a film-forming speed of 30 m / min.

(Evaluation in film production)
[Evaluation of transportability]
The transportability in the roller transport zone of the aforementioned film forming processes A to C was evaluated according to the following criteria. The results are shown in Table 3. Practically, the transportability is required to be AC.
A: The film had sufficient rigidity, and 20 rolls could be continuously formed without the film becoming unstable during conveyance.
B: The film was sufficiently rigid and slight flickering was observed, but the film could be formed without any problem.
C: The film was slightly flexible, and some flickering and meandering were observed, but it was not a problem level.
D: The film was slightly soft and fragile, and one or more breaks occurred when film formation was continued.
E: The film was flexible and it was difficult to continue film formation stably.

[Evaluation of roll appearance]
Immediately after producing the roll, the appearance was visually inspected and evaluated according to the following criteria (initial evaluation). Further, the appearance of the roll after being stored in a storage rack at 25 ° C. and a relative humidity of 55% for one month was visually inspected and evaluated according to the following criteria (evaluation with time). The results are shown in Table 2.
A: No winding looseness, bevel, or wrinkle B: Slight winding looseness, bevel, or wrinkle is observed, but no problem in practical use C: Winding looseness, bevel, or wrinkle is severe and cannot be applied as an optical film

(Preparation of polarizing plate)
[Preparation of moisture permeability control film for polarizing plate protective film]
Production of base film 1:
A moisture permeability control film used as a polarizing plate protective film facing the optical film 12 was produced by the following method.
In a reaction vessel having an internal volume of 30 L equipped with a stirrer, a temperature sensor, a cooling pipe and a nitrogen introduction pipe, 8000 g of methyl methacrylate (MMA), 2000 g of methyl 2- (hydroxymethyl) acrylate (MHMA) and 10000 g of toluene as a polymerization solvent Was heated up to 105 ° C. while passing nitrogen through it. When the reflux accompanying the temperature rise began, 10.0 g of t-amylperoxyisonononanoate was added as a polymerization initiator, and a solution comprising 20.0 g of t-amylperoxyisonononanoate and 100 g of toluene was added. While dropping over time, solution polymerization was allowed to proceed under reflux at about 105 to 110 ° C., and further aging was performed for 4 hours. The polymerization reaction rate was 96.6%, and the content (weight ratio) of MHMA in the obtained polymer was 20.0%.

  Next, 10 g of stearyl phosphate / distearyl phosphate mixture (manufactured by Sakai Chemical Industry Co., Ltd., Phoslex A-18) is added to the resulting polymerization solution as a cyclization catalyst, and the mixture is refluxed at about 80 to 100 ° C. for 5 hours. The cyclization condensation reaction was allowed to proceed.

  Next, the obtained polymerization solution was subjected to a barrel type screw twin screw extruder having a barrel temperature of 260 ° C., a rotation speed of 100 rpm, a degree of vacuum of 13.3 to 400 hPa (10 to 300 mmHg), a rear vent number of 1, and a forevent number of 4. (Φ = 29.75 mm, L / D = 30) was introduced at a treatment rate of 2.0 kg / hour in terms of resin amount, and cyclization condensation reaction and devolatilization were performed in the extruder. Next, after completion of devolatilization, the resin in the molten state left in the extruder is discharged from the tip of the extruder, pelletized by a pelletizer, and transparent pellets made of an acrylic resin having a lactone ring structure in the main chain Got. The weight average molecular weight of this resin is 148,000, the melt flow rate (based on JIS K7120, the test temperature is 240 ° C., the load is 10 kg, the same applies to the following production examples) is 11.0 g / 10 min, glass transition The temperature was 130 ° C.

  Next, the obtained pellets and AS resin (product name: Toyo AS AS20, manufactured by Toyo Styrene Co., Ltd.) were kneaded using a single screw extruder (φ = 30 mm) at a weight ratio of pellet / AS resin = 90/10. As a result, transparent pellets having a glass transition temperature of 127 ° C. were obtained.

  The resin composition pellets prepared above were melt-extruded from a coat hanger type T die using a twin-screw extruder to prepare a resin film having a thickness of about 160 μm.

  Next, the obtained unstretched resin film was biaxially stretched 2.0 times in the longitudinal direction and 2.0 times in the transverse direction, thereby producing a transparent plastic film substrate. The biaxially stretchable film thus obtained had a thickness of 40 μm, a total light transmittance of 92%, a haze of 0.3%, and a glass transition temperature of 127 ° C.

<Preparation of composition for forming a low moisture permeable layer>
Prepared as shown below.

Composition of composition B-1 for forming a low moisture permeable layer:
A-DCP (100%) 97.0 g
Irgacure 907 (100%) 3.0g
SP-13 0.04g
MEK (methyl ethyl ketone) 81.8 g

The materials used are shown below.
A-DCP: tricyclodecane dimethanol dimethacrylate [manufactured by Shin-Nakamura Chemical Co., Ltd.]
・ Irgacure 907: Polymerization initiator [Ciba Specialty Chemicals Co., Ltd.]
SP-13 (leveling agent):

<Production of moisture permeability control film>
The base film 1 prepared above as a base film is unwound from a roll form, and the low moisture-permeable layer forming composition B-1 is used. The slot die described in Example 1 of JP-A-2006-122889 The coating was performed under the condition of a conveyance speed of 30 m / min by a die coating method using, and dried at 60 ° C. for 150 seconds. Thereafter, using an air-cooled metal halide lamp (manufactured by Eye Graphics Co., Ltd.) with an oxygen concentration of about 0.1% under a nitrogen purge, ultraviolet rays with an illuminance of 400 mW / cm ² and an irradiation amount of 300 mJ / cm ² are irradiated. Then, the coating layer was cured and wound up. The coating amount was adjusted so that the thickness of the low moisture-permeable layer was 5 μm.
The obtained film was used as a moisture permeability control film.

<Evaluation of moisture permeability control film>
The physical property measurement and evaluation of the produced moisture permeability control film were performed. In addition, the film thickness of the low moisture-permeable layer measured the film thickness before and behind lamination | stacking of a low moisture-permeable layer, and calculated | required from the difference.
―――――――――――――――――――――――――――――――――――――――
Film thickness (μm) Water vapor transmission rate (g / m ² / day)
―――――――――――――――――――――――――――――――――――――――
Base film 1 40 95
Low moisture permeable layer 5 230
Moisture permeability control film 45 67
―――――――――――――――――――――――――――――――――――――――

(Preparation of polarizing plate)
[Saponification of optical film]
Opposite the produced optical films 1 to 27 (the optical film 20 (acrylic film) used as a polarizing plate protective film facing the optical film 20), the optical films 1 to 11 and 13 to 20, and 22 to 24 and 26. FUJITAC TDP40UT (manufactured by FUJIFILM Corporation) used as a polarizing plate protective film and 4.5 mol / L of hydroxylated water adjusted to 37 ° C. each of the above moisture permeability control films used as a polarizing plate protective film facing the optical film 12 After immersing in an aqueous sodium solution (saponification solution) for 1 minute, the film was washed with water, then immersed in a 0.05 mol / L sulfuric acid aqueous solution for 30 seconds, and then passed through a rinsing bath. Then, draining with an air knife was repeated three times, and after dropping the water, it was kept in a drying zone at 70 ° C. for 15 seconds and dried to produce a saponified optical film.

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

[Paste]
Two sheets of the polarizing film thus obtained and the saponified optical film were selected from the combinations shown in Table 1, and after sandwiching the polarizing film between them, PVA (manufactured by Kuraray Co., Ltd., PVA- 117H) Using a 3% aqueous solution as an adhesive, a polarizing plate was produced by laminating with a roll-to-roll so that the polarization axis and the maximum sound velocity direction of the optical film were parallel.
In addition, in the polarizing plate using an acrylic film, the adhesive surface with the polarizing film was subjected to corona treatment instead of saponification treatment.

(Evaluation of polarizing plate)
[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%.

[Time polarization 1]
The optical film (the optical film produced in the above Examples and Comparative Examples) side of the polarizing plate is bonded to a glass plate with an adhesive and left for 500 hours at 60 ° C. and 90% relative humidity. When the subsequent polarization degree (time-dependent polarization degree 1) was calculated by the above-mentioned method, the polarization degree of all the polarizing plates was 99.9%.

[Time polarization 2]
Similar to the evaluation of the degree of polarization over time 1, the polarizing plate was bonded to a glass plate, left in a dry environment at 90 ° C. for 500 hours, and the degree of polarization after standing (degree of polarization over time 2) was calculated by the method described above. However, the polarization degree of all the polarizing plates except Comparative Example 5 was 99.9%.

[Retardation Reliability (Retardation Wet Heat Durability) Evaluation]
The polarizing plate was bonded to a glass plate with the optical film side shown in Table 3 through an adhesive, and allowed to stand for 120 hours at 80 ° C. and 90% relative humidity. The opposing optical film and polarizing film were peeled off from the sample after standing, and the retardation was measured by the method described above after visually confirming that the film remaining on the glass plate was transparent. The Rth change (retardation reliability) before and after the wet heat treatment was evaluated according to the following criteria, and the results are shown in Table 3.
A: Rth change is less than 3 nm and does not affect display characteristics.
B: Rth change is less than 5 nm and does not affect display characteristics.
C: Rth change is less than 10 nm, and display characteristics are hardly affected.
D: Rth change is less than 20 nm, which may slightly affect the display characteristics.
E: Rth change is 20 nm or more, which affects display characteristics.

(Mounting on IPS liquid crystal display)
A pair of polarizing plates sandwiching the liquid crystal cell are peeled off from a commercially available liquid crystal television (IPS mode slim type 42-type liquid crystal television; LG Electronics 42LS5600). It was re-bonded to the liquid crystal cell via an adhesive so as to be disposed on the liquid crystal cell side. The display characteristics of the re-assembled liquid crystal television were confirmed, and the brightness and color from the front and diagonal were confirmed (initial display characteristics), and it was confirmed that there was no abnormality. Also, the initial display characteristics were favorable when only the viewing-side polarizing plate of the pair of polarizing plates sandwiching the liquid crystal cell was peeled off and re-bonded. However, when the polarizing plate containing the film 26 was used, it was confirmed that the color change when viewed from an oblique direction was very large.

[Evaluation of mounting on IPS liquid crystal display device 1 (warp performance, shrinkage evaluation of optical film)]
The prepared liquid crystal display device is held for 3 days in an environment of 50 ° C. and a relative humidity of 90%, then moved to an environment of 25 ° C. and a relative humidity of 60%, kept on in a black display state, and visually observed after 4 hours. Then, luminance unevenness in the front direction was evaluated according to the following criteria (wet evaluation). The evaluation results are shown in Table 3. In addition, when only the polarizing plate on the visual recognition side was peeled off and re-bonded, it was confirmed that there was an improvement effect. Further, the polarizing plate including the film 1 and the polarizing plate including the film 5 are arranged so that the optical film side described in Table 3 is disposed on the side opposite to the liquid crystal cell side (the opposing optical film described in Table 3 is a liquid crystal cell). It was confirmed that the unevenness of luminance was suppressed in the polarizing plate including the film 5 even when the film was re-bonded to the liquid crystal cell via the adhesive (as arranged on the side). Practically, it is required to be an evaluation of A to C.
A: Unevenness is not visually recognized at all in the environment of illuminance of 100 lx.
B: Unevenness is hardly visually recognized in an environment with an illuminance of 100 lx.
C: Pale unevenness is visually recognized in an environment with an illuminance of 100 lx.
D: Clear unevenness is visually recognized in an environment with an illuminance of 100 lx.
E: Clear unevenness is visually recognized in an environment with an illuminance of 300 lx.

[Evaluation of mounting on IPS-type liquid crystal display device 2 (Egg performance and humidity dependency of optical film)]
After mounting evaluation 1 (evaluation after 4 hours), lighting continues in a black display state, and lighting continues in an environment of 25 ° C. and a relative humidity of 60%. Luminance unevenness and color unevenness at the time of black display in an angular direction of 45 degrees and a polar angle direction of 70 degrees were visually observed, and light unevenness was evaluated based on the same criteria as the mounting evaluation 1 (forced evaluation). The evaluation results are shown in Table 3.

From the above Table 3, it can be seen that the liquid crystal display device having the optical film of the present invention has a good mounting evaluation 1 and thus the optical film of the present invention has suppressed shrinkage. It can be seen that the optical film of the present invention also has an elastic modulus exceeding 3.5 GPa and a high elastic modulus. Moreover, since an elasticity modulus also exceeds 3.5 GPa, it turns out that the manufacture aptitude of a roll-shaped optical film is excellent.
The elastic modulus of the optical film whose transportability evaluation is D or E is all 3.5 GPa or less, whereas the elastic modulus of the optical film whose transportability evaluation is C or higher may exceed 3.5 GPa. Recognize. From this, it can be seen that when the elastic modulus exceeds 3.5 GPa, the production suitability of the roll-shaped optical film is excellent.
On the other hand, it can be seen that the optical film of the comparative example is inferior in transportability to the examples, or the liquid crystal display device having the optical film of the comparative example is inferior in mounting evaluation 1 to the examples.

Claims (18)

Including at least a compound having a repeating unit and a cellulose ester,
In-plane retardation (Re) at a wavelength of 590 nm is 10 nm or less,
The elastic modulus exceeds 3.5 GPa,
The compound having a repeating unit, a condensate of a polybasic acid and polyhydric alcohol, and meets the following conditions (1) to (6),
The ratio of the sound wave propagation velocity in the direction in which the sound wave propagation velocity is maximum and the direction orthogonal thereto (maximum direction / orthogonal direction in the maximum direction) is 1.10 or more,
An optical film having a thickness direction retardation (Rth) of -10 to 0 nm at a wavelength of 590 nm .
(1) The polybasic acid includes at least a polybasic acid having 5 or less carbon atoms.
(2) The polybasic acid has an average carbon number of 3 or more and less than 6.
(3) The polyhydric alcohol has an average carbon number of 2 or more and 3 or less.
(4) All repeating units composed of a combination of one kind of polybasic acid and one kind of polyhydric alcohol have 4 to 9 carbon atoms.
(5) Number average molecular weight is 800 or more and 5000 or less.
(6) The hydroxyl value is less than 40 mgKOH / g. The compound having a Repetitive return units, optical film according to claim 1 containing 0.1 to 50 wt% with respect to the cellulose ester. The optical film according to claim 1 or 2, wherein a ratio of a sound wave propagation speed in a direction in which the sound wave propagation speed is maximum and a direction perpendicular thereto (maximum direction / direction orthogonal to the maximum direction) is 1.10 or more and 1.24 or less. .   4. The optical film according to claim 3, wherein the ratio of the sound wave propagation velocity in the direction in which the sound wave propagation velocity is maximum and the direction orthogonal thereto (maximum direction / orthogonal direction in the maximum direction) is 1.20 or more and 1.24 or less. Furthermore, the optical film of any one of Claims 1-4 containing the compound which improves the wet heat durability of a retardation. Furthermore, the optical film of any one of Claims 1-5 containing a humidity dependence reducing agent. Furthermore, the optical film of any one of Claims 1-6 containing a retardation regulator. The optical film according to any one of claims 1 to 7 including at least succinic acid as the polybasic acid. A roll-shaped optical film obtained by winding the optical film according to any one of claims 1 to 8 , and having an elastic modulus in a longitudinal direction exceeding 3.5 GPa. The roll-shaped optical film according to claim 9 , wherein the maximum direction of sound wave propagation speed is the longitudinal direction. The roll-shaped optical film according to claim 9 or 10 , wherein the length in the longitudinal direction is 100 to 16000 m. Optical film be unwound rolled optical film according to any one of claims 9-11. A polarizing plate comprising the optical film according to any one of claims 1 to 8 and 12 , and a polarizing film. The polarizing plate of Claim 13 arrange | positioned so that the absorption axis of the said polarizing film and the maximum direction of the sound wave propagation speed of the said optical film may become parallel. A liquid crystal display device comprising the optical film according to any one of claims 1 to 8 and 12 , or the polarizing plate according to claim 13 or 14 . It is a manufacturing method of the optical film of any one of Claims 1-8 and 12 ,
A method for producing an optical film, comprising at least the following steps (a), (b), and (c):
(A) a compound having a Repetitive return units, cellulose esters, and the solvent was removed the solvent from the solution the solution was cast on a step (b) the support casting on a support including at least Step of forming a film and stripping the film from the support (c) Step of stretching the film in the transport direction The method for producing an optical film according to claim 16 , wherein the stretching speed is 50 to 10,000% / min. The method for producing an optical film according to claim 16 or 17 expands the forward between 100% to 200% of the draw ratio along the conveying direction.