JP2012061722A - Optical film and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical film which has excellent peeling resistance, internal haze resistance and dimensional stability, and also has suitable retardation developability, and to provide a method for producing the optical film.SOLUTION: The optical film is formed by laminating a cellulose ester resin A layer, a cellulose ester resin B layer and a cellulose ester resin C layer (which are respectively defined as [A layer], [B layer] and [C layer]) in the order of the A layer, C layer, B layer, C layer and A layer. The average acyl group substitution degree of the cellulose ester of the A layer lies in the range of 2.8 to 3.0, the average acyl group substitution degree of the cellulose ester of the B layer lies in the range of 1.0 to 2.5, and also, the average acyl group substitution degree of the cellulose ester of the C layer lies in the range of >2.5 to <2.8.

Description

  The present invention relates to an optical film excellent in peel resistance, internal haze resistance, and dimensional stability and having appropriate retardation development and a method for producing the same.

  The demand for liquid crystal display devices is expanding in applications such as liquid crystal televisions and personal computer liquid crystal displays. Usually, a liquid crystal display device is composed of a liquid crystal cell in which a transparent electrode, a liquid crystal layer, a color filter, etc. are sandwiched between glass plates, and two polarizing plates provided on both sides thereof. A child (also referred to as a polarizing film or a polarizing film) is sandwiched between two optical films. As this optical film, a cellulose ester film is usually used.

  In the production of a polarizing plate, generally, a film produced by a co-casting method has been subjected to processing such as punching and cutting on a film provided with a cellulose ester film as a protective film on both sides. The shape of the processed cross section deviates from the shear direction perpendicular to the film, becomes a shape inclined to the film surface, or becomes a rough shape at random, so-called delamination or delamination (that is, delamination) There is a problem that it tends to occur.

  With the recent advancement of technology, the increase in size and functionality of liquid crystal display devices has accelerated, and a film formed by laminating a plurality of layers containing a resin such as cellulose ester in order to enhance the functionality of the optical film. It has been proposed (see, for example, Patent Documents 1 to 3). In addition, as an optical film having high optical development, little optical unevenness, and good releasability from the support, a cellulose ester in which a skin layer and a core layer containing cellulose esters having different degrees of acyl group substitution are laminated A laminated film has been proposed (see, for example, Patent Document 4).

  Specifically, for example, it is known that a co-cast film of triacetyl cellulose (TAC) and diacetyl cellulose (DAC) has phase retardation with diacetyl cellulose and high wet heat resistance with triacetyl cellulose. It has been.

  However, there is a concern that the interface between diacetyl cellulose and triacetyl cellulose may be peeled off in a punching test or a large amount of chips may be generated. In addition, since triacetyl cellulose and diacetyl cellulose have different temperature conditions suitable for stretching, there is a problem that when a co-cast film of triacetyl cellulose and diacetyl cellulose is stretched as it is, distortion occurs and internal haze increases.

JP 2004-315756 A JP 2006-6545 A JP 2005-222076 A JP 2010-58331 A

  The present invention has been made in view of the above problems and situations, and its solution is an optical film having excellent peel resistance, internal haze resistance, dimensional stability, and appropriate retardation development, and its It is to provide a manufacturing method.

  The above-mentioned problem according to the present invention is solved by the following means.

  1. Cellulose ester resin A layer, cellulose ester resin B layer, and cellulose ester resin C layer (referred to as “A layer”, “B layer”, and “C layer”, respectively) are A layer, C layer, B layer, C An optical film formed by laminating a layer and an A layer in this order, wherein the average acyl group substitution degree of the cellulose ester of the A layer is in the range of 2.8 to 3.0, and the cellulose ester of the B layer The average acyl group substitution degree is in the range of 1.0 to 2.5, and the average acyl group substitution degree of the cellulose ester of the C layer is in the range of more than 2.5 and less than 2.8. Optical film.

  2. 2. The optical film according to item 1, wherein the cellulose ester resin C layer is thicker than any resin layer adjacent to the C layer.

  3. The thickness of the cellulose ester resin A layer is in the range of 1 to 3 μm, and the thickness of the cellulose ester resin B layer is thicker than the thickness of the cellulose ester resin A layer. Item 3. The optical film according to Item 2.

  4). The optical film according to any one of Items 1 to 3, wherein the cellulose ester resin A layer contains a matting agent.

  5. 5. The optical film according to any one of items 1 to 4, wherein a thickness of the entire optical film is in a range of 40 to 60 [mu] m.

  6). An optical film manufacturing method for manufacturing the optical film according to any one of items 1 to 4, wherein the optical film includes a step of forming a laminated film by a solution co-casting method. A method for producing a film.

  By the above means of the present invention, it is possible to provide an optical film excellent in peel resistance, internal haze resistance and dimensional stability and having appropriate retardation development and a method for producing the same.

  That is, in the present invention, due to the relative relationship of the average acyl group substitution degree of the cellulose ester, when the C layer is inserted between the A layer and the B layer, the adhesion at the interface is improved, and even if a punching test is performed, the chip is not removed. There is little generation | occurrence | production and favorable adhesiveness can be obtained. Further, even when the obtained co-cast film is stretched, the distortion generated at the interface is reduced, so that the increase in haze is suppressed, and since the distortion is small, the dimensional change under high heat and humidity conditions is suppressed.

  Furthermore, if this C layer is set thicker than the A layer and the B layer, not only the strain due to stretching can be suppressed, but also excessive stretching stress can be reduced, and when a triacetyl cellulose or diacetyl cellulose single film is stretched Therefore, the internal haze can be reduced.

Cross-sectional view of a casting die for laminating films by the solution co-casting method Schematic diagram showing a state in which glycerin is dropped on a slide glass Schematic diagram showing the state of a sample film placed on glycerin Schematic diagram showing the state in which glycerin is dropped on the sample film Schematic diagram showing a state where a cover glass is placed on glycerin

  In the optical film of the present invention, the cellulose ester resin A layer, the cellulose ester resin B layer, and the cellulose ester resin C layer (referred to as “A layer”, “B layer”, and “C layer”, respectively) are the A layer, It is an optical film laminated and formed in the order of C layer, B layer, C layer, and A layer, and the average acyl group substitution degree of the cellulose ester of the A layer is in the range of 2.8 to 3.0, The average acyl group substitution degree of the cellulose ester of the B layer is in the range of 1.0 to 2.5, and the average acyl group substitution degree of the cellulose ester of the C layer is more than 2.5 and less than 2.8. It is characterized by being within. This feature is a technical feature common to the inventions according to claims 1 to 6.

  As an embodiment of the present invention, it is preferable that the cellulose ester resin C layer is thicker than any resin layer adjacent to the C layer, from the viewpoint of manifesting the effects of the present invention. Furthermore, it is preferable that the thickness of the cellulose ester resin A layer is within a range of 1 to 3 μm, and the thickness of the cellulose ester resin B layer is larger than the thickness of the cellulose ester resin A layer.

  In the present invention, it is preferable that the cellulose ester resin A layer contains a matting agent. Moreover, it is preferable that the thickness of the whole optical film exists in the range of 40-60 micrometers.

  The method for producing an optical film for producing the optical film of the present invention is preferably a production method of an embodiment having a step of laminating and forming a film by a solution co-casting method.

  The optical film of the present invention can be suitably used for polarizing plates and liquid crystal display devices.

  Hereinafter, the present invention, its components, and modes and modes for carrying out the present invention will be described in detail. In addition, in this application, "-" is used in the meaning which includes the numerical value described before and behind that as a lower limit and an upper limit.

(Cellulose ester resin layer)
The optical film of the present invention includes a cellulose ester resin A layer, a cellulose ester resin B layer, and a cellulose ester resin C layer (hereinafter, referred to as “A layer”, “B layer”, and “C layer”, respectively). Is formed by stacking layers in the order of A layer, C layer, B layer, C layer, and A layer.

  Moreover, the average acyl group substitution degree of the cellulose ester of the A layer is in the range of 2.8 to 3.0, and the average acyl group substitution degree of the cellulose ester of the B layer is in the range of 1.0 to 2.5. The average acyl group substitution degree of the cellulose ester of the C layer is in the range of more than 2.5 and less than 2.8.

  Of the five layers, two “A layers” may have different average acyl group substitution degrees and different weight average molecular weights within a range satisfying the above requirement of the average acyl group substitution degree. Similarly, the two “C layers” may have different average acyl group substitution degrees and weight average molecular weights within the range satisfying the above-mentioned requirement of the average acyl group substitution degree.

  In addition, as long as the condition that the layers are formed in the order of the A layer, the C layer, the B layer, the C layer, and the A layer is satisfied and the effect of the present invention is not impaired, a different kind of layer is provided between any of the layers. Also good.

  In addition, the glucose unit which comprises cellulose with a β-1,4-glycoside bond has free hydroxyl groups (hydroxyl groups) at the 2nd, 3rd and 6th positions. The cellulose ester according to the present invention is a polymer (polymer) obtained by esterifying some or all of these hydroxyl groups (hydroxyl groups) with an acyl group.

  “Acyl group substitution degree” represents the total of the ratios of esterification of hydroxyl groups (hydroxyl groups) at the 2nd, 3rd and 6th positions of glucose as a repeating unit. Specifically, the degree of substitution is 1 when each of the hydroxyl groups (hydroxyl groups) at the 2nd, 3rd and 6th positions of cellulose is 100% esterified. Therefore, when all of the 2nd, 3rd and 6th positions of cellulose are 100% esterified, the degree of substitution is 3 at the maximum.

  In the present application, the “average acyl group substitution degree” refers to an acyl group substitution degree in which the acyl group substitution degree of a plurality of glucose units constituting the cellulose ester is expressed as an average value per unit.

  In addition, the measuring method of acyl group substitution degree can be measured according to ASTM-D817-96.

  Examples of the acyl group include acetyl group, propionyl group, butanoyl group, heptanoyl group, hexanoyl group, octanoyl group, decanoyl group, dodecanoyl group, tridecanoyl group, tetradecanoyl group, hexadecanoyl group, octadecanoyl group, and isobutanoyl. Group, tert-butanoyl group, cyclohexanecarbonyl group, oleoyl group, benzoyl group, naphthylcarbonyl group, cinnamoyl group and the like.

  Among these, an acetyl group, a propionyl group, a butanoyl group, a dodecanoyl group, an octadecanoyl group, a tert-butanoyl group, an oleoyl group, a benzoyl group, a naphthylcarbonyl group, a cinnamoyl group, and the like are more preferable, and an acetyl group is particularly preferable. A propionyl group and a butanoyl group (when the acyl group has 2 to 4 carbon atoms), more preferably an acetyl group.

  In the case of an aliphatic acyl group, the number of carbon atoms is preferably 2 to 6 and more preferably 2 to 4 from the viewpoint of cellulose synthesis productivity and cost. Moreover, it is preferable that the part which is not substituted by the acyl group exists normally as a hydroxyl group (hydroxyl group).

  Examples of the cellulose ester include cellulose acetate, cellulose propionate, cellulose butyrate, and cellulose pentanate. Further, mixed fatty acid esters such as cellulose acetate, cellulose acetate propionate, cellulose propionate, cellulose acetate butyrate, and cellulose acetate pentanate may be used as long as the above-mentioned side chain carbon number is satisfied.

  Among these, cellulose acetate, cellulose acetate propionate, and cellulose propionate are particularly preferable cellulose esters for optical film applications.

  The cellulose ester according to the present invention preferably has a weight average molecular weight Mw of 50,000 to 500,000, more preferably 50,000 to 300,000, still more preferably 50,000 to 270,000. .

  Since the average molecular weight and molecular weight distribution of a cellulose ester can be measured using high performance liquid chromatography, the weight average molecular weight (Mw) and molecular weight distribution are calculated using this.

  The measurement conditions are as follows.

Solvent: Methylene chloride Column: Shodex K806, K805, K803G (Used by connecting three Showa Denko Co., Ltd.)
Column temperature: 25 ° C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (GL Science Co., Ltd.)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0 ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corporation)
A calibration curve with 13 samples from Mw = 100000 to 500 was used. The 13 samples are preferably used at approximately equal intervals.

  The raw material cellulose of the cellulose ester resin according to the present invention is not particularly limited, and examples thereof include cotton linter, wood pulp, and kenaf. Moreover, the cellulose ester obtained from them can be mixed and used in arbitrary ratios, respectively.

  The cellulose ester resin according to the present invention can be produced by a known method. Generally, cellulose is esterified by mixing cellulose as a raw material, a predetermined organic acid (such as acetic acid or propionic acid), an acid anhydride (such as acetic anhydride or propionic anhydride), and a catalyst (such as sulfuric acid). The reaction proceeds until the triester is formed. In the triester, three hydroxyl groups (hydroxyl groups) of the glucose unit are substituted with an acyl acid of an organic acid. When two kinds of organic acids are used at the same time, a mixed ester type cellulose ester such as cellulose acetate propionate or cellulose acetate butyrate can be produced. Next, cellulose ester resin having a desired degree of acyl group substitution is synthesized by hydrolyzing cellulose triester. Thereafter, a cellulose ester resin is completed through steps such as filtration, precipitation, washing with water, dehydration, and drying.

  Specifically, it can be synthesized with reference to the method described in JP-A-10-45804.

  As an embodiment of the present invention, it is preferable that the cellulose ester resin C layer is thicker than any resin layer adjacent to the C layer, from the viewpoint of manifesting the effects of the present invention. Furthermore, it is preferable that the thickness of the cellulose ester tree A layer is in the range of 1 to 3 μm, and the thickness of the cellulose ester resin B layer is thicker than the thickness of the cellulose ester resin A layer.

  The thickness of the cellulose ester resin B layer is preferably in the range of 1 to 59 μm. The thickness of the cellulose ester resin C layer is preferably in the range of 3 to 59 μm.

  In addition, in this invention, it is preferable that the thickness of the whole optical film exists in the range of 40-60 micrometers.

《Various additives》
In the optical film of the present invention, compounds having various functions can be added as additives depending on the purpose.

  In the present invention, a compound represented by the following general formula (1) having a total average substitution degree of 6.1 to 6.9 may be contained.

In General Formula (1), R _{1 to} R ₈ represent a substituted or unsubstituted alkylcarbonyl group or a substituted or unsubstituted arylcarbonyl group, and R _{1 to} R ₈ may be the same. , May be different.

Preferable specific examples of the compound represented by the general formula (1) include compounds shown in Table 1. In addition, R described in the following table represents any one of R _{1 to} R ₈ . As the substituent for the alkylcarbonyl group and the arylcarbonyl group, substituents such as a phenyl group and an alkoxy group included in the alkylcarbonyl group and the arylcarbonyl group shown in the following table are preferable.

  Although the compound represented by the said General formula (1) and a reference compound are described below, it is not limited to these.

  (Synthesis Example: Synthesis of Compound According to the Present Invention)

A four-headed colben equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen gas inlet tube was mixed with 34.2 g (0.1 mol) of sucrose, 180.8 g (0.8 mol) of benzoic anhydride, 379. 7 g (4.8 mol) was charged, the temperature was raised while bubbling nitrogen gas from a nitrogen gas introduction tube with stirring, and an esterification reaction was carried out at 70 ° C. for 5 hours. Next, the inside of the Kolben was depressurized to 4 × 10 ² Pa or less, and after excess pyridine was distilled off at 60 ° C., the inside of the Kolben was depressurized to 1.3 × 10 Pa or less and the temperature was raised to 120 ° C. Most of the acid and benzoic acid formed were distilled off. Then, 1 L of toluene and 300 g of a 0.5% by mass aqueous sodium carbonate solution were added, and the mixture was stirred at 50 ° C. for 30 minutes and then allowed to stand to separate a toluene layer. Finally, 100 g of water is added to the collected toluene layer, and after washing with water at room temperature for 30 minutes, the toluene layer is separated, and toluene is distilled off at 60 ° C. under reduced pressure (4 × 10 ² Pa or less). A mixture of A-1, A-2, A-3, A-4 and A-5 was obtained. When the obtained mixture was analyzed by HPLC and LC-MASS, A-1 was 7% by mass, A-2 was 58% by mass, A-3 was 23% by mass, A-4 was 9% by mass, A-5. Was 3% by mass. A part of the obtained mixture was purified by column chromatography using silica gel to obtain A-1, A-2, A-3, A-4 and A-5 having a purity of 100%, respectively. .

  The total average substitution degree of the compound represented by the general formula (1) added to the optical film in the present invention is 6.1 to 6.9, and the range of the substitution degree is 4 to 8. preferable. The substitution degree distribution may be adjusted to the desired substitution degree by adjusting the esterification reaction time or mixing compounds having different substitution degrees.

(Phase difference agent)
In the present invention, a retardation (also referred to as “retardation”) developing agent may be included. The phase difference (retardation) developing agent can be contained, for example, in a proportion of 0.5 to 10% by mass, and more preferably in a proportion of 2 to 6% by mass. By adopting a retardation developing agent, high Re developability can be obtained at a low draw ratio. The type of retardation developing agent is not particularly defined, but examples thereof include those made of rod-like or discotic compounds. As the rod-like or discotic compound, a compound having at least two aromatic rings can be preferably used as a retardation developing agent. The addition amount of the retardation developing agent composed of the rod-shaped compound is preferably 0.5 to 10 parts by mass, and 2 to 6 parts by mass with respect to 100 parts by mass of the polymer component containing the cellulose ester. Is more preferable.

  The discotic retardation developing agent is preferably used in a range of 0.5 to 10 parts by mass, and in a range of 1 to 8 parts by mass with respect to 100 parts by mass of the polymer component containing the cellulose ester. It is more preferable to use in the range of 2 to 6 parts by mass.

  Two or more kinds of retardation developing agents may be used in combination.

  The phase difference (retardation) developing agent preferably has maximum absorption in the wavelength region of 250 to 400 nm, and preferably has substantially no absorption in the visible region.

  The discotic compound will be described. As the discotic compound, a compound having at least two aromatic rings can be used.

  In the present specification, the “aromatic ring” includes an aromatic hetero ring in addition to an aromatic hydrocarbon ring.

  The aromatic hydrocarbon ring is particularly preferably a 6-membered ring (that is, a benzene ring).

  The aromatic heterocycle is generally an unsaturated heterocycle. The aromatic heterocycle is preferably a 5-membered ring, 6-membered ring or 7-membered ring, more preferably a 5-membered ring or 6-membered ring. Aromatic heterocycles generally have the most double bonds. As the hetero atom, a nitrogen atom, an oxygen atom and a sulfur atom are preferable, and a nitrogen atom is particularly preferable. Examples of aromatic heterocycles include furan ring, thiophene ring, pyrrole ring, oxazole ring, isoxazole ring, thiazole ring, isothiazole ring, imidazole ring, pyrazole ring, furazane ring, triazole ring, pyran ring, pyridine ring , Pyridazine ring, pyrimidine ring, pyrazine ring and 1,3,5-triazine ring.

  As the aromatic ring, a benzene ring, a condensed benzene ring, and biphenyls are preferable. In particular, a 1,3,5-triazine ring is preferably used. Specifically, for example, compounds disclosed in JP-A No. 2001-166144 are preferably used.

  The number of carbon atoms of the aromatic ring contained in the retardation developing agent is preferably 2-20, more preferably 2-12, further preferably 2-8, and 2-6. Most preferably.

  The bonding relationship between two aromatic rings can be classified into (a) when forming a condensed ring, (b) when directly connecting with a single bond, and (c) when connecting via a linking group (for aromatic rings). , Spiro bonds cannot be formed). The connection relationship may be any of (a) to (c).

  Examples of the condensed ring (a condensed ring of two or more aromatic rings) include an indene ring, a naphthalene ring, an azulene ring, a fluorene ring, a phenanthrene ring, an anthracene ring, an acenaphthylene ring, a biphenylene ring, a naphthacene ring, Pyrene ring, indole ring, isoindole ring, benzofuran ring, benzothiophene ring, indolizine ring, benzoxazole ring, benzothiazole ring, benzimidazole ring, benzotriazole ring, purine ring, indazole ring, chromene ring, quinoline ring, isoquinoline Ring, quinolidine ring, quinazoline ring, cinnoline ring, quinoxaline ring, phthalazine ring, pteridine ring, carbazole ring, acridine ring, phenanthridine ring, xanthene ring, phenazine ring, phenothiazine ring, phenoxathiin ring, phenoxazine ring and thiantole Ring is included. Naphthalene ring, azulene ring, indole ring, benzoxazole ring, benzothiazole ring, benzimidazole ring, benzotriazole ring and quinoline ring are preferred.

  The single bond (b) is preferably a bond between carbon atoms of two aromatic rings. Two aromatic rings may be bonded by two or more single bonds to form an aliphatic ring or a non-aromatic heterocyclic ring between the two aromatic rings.

The linking group in (c) is also preferably bonded to carbon atoms of two aromatic rings. The linking group is preferably an alkylene group, an alkenylene group, an alkynylene group, —CO—, —O—, —NH—, —S—, or a combination thereof. Examples of linking groups composed of combinations are shown below. In addition, the relationship between the left and right in the following examples of the linking group may be reversed.
c1: -CO-O-
c2: —CO—NH—
c3: -alkylene-O-
c4: —NH—CO—NH—
c5: —NH—CO—O—
c6: —O—CO—O—
c7: -O-alkylene-O-
c8: -CO-alkenylene-
c9: -CO-alkenylene-NH-
c10: -CO-alkenylene-O-
c11: -alkylene-CO-O-alkylene-O-CO-alkylene-
c12: -O-alkylene-CO-O-alkylene-O-CO-alkylene-O-
c13: -O-CO-alkylene-CO-O-
c14: -NH-CO-alkenylene-
c15: -O-CO-alkenylene-
The aromatic ring and the linking group may have a substituent.

  Examples of substituents include halogen atoms (F, Cl, Br, I), hydroxyl groups, carboxyl groups, cyano groups, amino groups, nitro groups, sulfo groups, carbamoyl groups, sulfamoyl groups, ureido groups, alkyl groups, alkenyls. Group, alkynyl group, aliphatic acyl group, aliphatic acyloxy group, alkoxy group, alkoxycarbonyl group, alkoxycarbonylamino group, alkylthio group, alkylsulfonyl group, aliphatic amide group, aliphatic sulfonamido group, aliphatic substituted amino group An aliphatic substituted carbamoyl group, an aliphatic substituted sulfamoyl group, an aliphatic substituted ureido group, and a non-aromatic heterocyclic group.

  It is preferable that the alkyl group has 1 to 8 carbon atoms. A chain alkyl group is preferable to a cyclic alkyl group, and a linear alkyl group is particularly preferable. The alkyl group may further have a substituent (for example, a hydroxyl group, a carboxy group, an alkoxy group, an alkyl-substituted amino group). Examples of alkyl groups (including substituted alkyl groups) include methyl, ethyl, n-butyl, n-hexyl, 2-hydroxyethyl, 4-carboxybutyl, 2-methoxyethyl and 2-methoxyethyl. Each group of a diethylaminoethyl group is included.

  The alkenyl group preferably has 2 to 8 carbon atoms. A chain alkenyl group is preferable to a cyclic alkenyl group, and a linear alkenyl group is particularly preferable. The alkenyl group may further have a substituent. Examples of the alkenyl group include a vinyl group, an allyl group, and a 1-hexenyl group.

  The alkynyl group preferably has 2 to 8 carbon atoms. A chain alkynyl group is preferable to a cyclic alkynyl group, and a linear alkynyl group is particularly preferable. The alkynyl group may further have a substituent. Examples of the alkynyl group include ethynyl group, 1-butynyl group and 1-hexynyl group.

  The number of carbon atoms in the aliphatic acyl group is preferably 1-10. Examples of the aliphatic acyl group include an acetyl group, a propanoyl group, and a butanoyl group.

  The number of carbon atoms in the aliphatic acyloxy group is preferably 1-10. Examples of the aliphatic acyloxy group include an acetoxy group.

  The number of carbon atoms of the alkoxy group is preferably 1-8. The alkoxy group may further have a substituent (for example, an alkoxy group). Examples of the alkoxy group (including a substituted alkoxy group) include a methoxy group, an ethoxy group, a butoxy group, and a methoxyethoxy group.

  The number of carbon atoms of the alkoxycarbonyl group is preferably 2-10. Examples of the alkoxycarbonyl group include a methoxycarbonyl group and an ethoxycarbonyl group.

  The number of carbon atoms of the alkoxycarbonylamino group is preferably 2-10. Examples of the alkoxycarbonylamino group include a methoxycarbonylamino group and an ethoxycarbonylamino group.

  The alkylthio group preferably has 1 to 12 carbon atoms. Examples of the alkylthio group include a methylthio group, an ethylthio group, and an octylthio group.

  The alkylsulfonyl group preferably has 1 to 8 carbon atoms. Examples of the alkylsulfonyl group include a methanesulfonyl group and an ethanesulfonyl group.

  The number of carbon atoms in the aliphatic amide group is preferably 1-10. Examples of the aliphatic amide group include acetamide.

  The number of carbon atoms of the aliphatic sulfonamide group is preferably 1-8. Examples of the aliphatic sulfonamide group include a methane sulfonamide group, a butane sulfonamide group, and an n-octane sulfonamide group.

  The number of carbon atoms of the aliphatic substituted amino group is preferably 1-10. Examples of the aliphatic substituted amino group include a dimethylamino group, a diethylamino group, and a 2-carboxyethylamino group.

  The number of carbon atoms in the aliphatic substituted carbamoyl group is preferably 2-10. Examples of the aliphatic substituted carbamoyl group include a methylcarbamoyl group and a diethylcarbamoyl group.

  The number of carbon atoms in the aliphatic substituted sulfamoyl group is preferably 1-8. Examples of the aliphatic substituted sulfamoyl group include a methylsulfamoyl group and a diethylsulfamoyl group.

  The number of carbon atoms in the aliphatic substituted ureido group is preferably 2-10. Examples of the aliphatic substituted ureido group include a methylureido group.

  Examples of the non-aromatic heterocyclic group include a piperidino group and a morpholino group.

  The molecular weight of the retardation developing agent is preferably 300 to 800.

  As the discotic compound, a triazine compound represented by the following general formula (I) is preferably used.

In the above general formula (I):
R ¹ independently represents an aromatic ring or a heterocyclic ring having a substituent in at least one of the ortho position, the meta position, and the para position.

X represents each independently a single bond or NR < ² >-. Here, each R ² independently represents a hydrogen atom, a substituted or unsubstituted alkyl group, an alkenyl group, an aryl group, or a heterocyclic group.

The aromatic ring represented by R ¹ is preferably phenyl or naphthyl, and particularly preferably phenyl. The aromatic ring represented by R ¹ may have at least one substituent at any substitution position. Examples of the substituent include halogen atom, hydroxyl group, cyano group, nitro group, carboxyl group, alkyl group, alkenyl group, aryl group, alkoxy group, alkenyloxy group, aryloxy group, acyloxy group, alkoxycarbonyl group, Alkenyloxycarbonyl group, aryloxycarbonyl group, sulfamoyl group, alkyl-substituted sulfamoyl group, alkenyl-substituted sulfamoyl group, aryl-substituted sulfamoyl group, sulfonamide group, carbamoyl, alkyl-substituted carbamoyl group, alkenyl-substituted carbamoyl group, aryl-substituted carbamoyl group, amide Groups, alkylthio groups, alkenylthio groups, arylthio groups and acyl groups.

The heterocyclic group represented by R ¹ preferably has aromaticity. The heterocycle having aromaticity is generally an unsaturated heterocycle, preferably a heterocycle having the largest number of double bonds. The heterocyclic ring is preferably a 5-membered ring, 6-membered ring or 7-membered ring, more preferably a 5-membered ring or 6-membered ring, and most preferably a 6-membered ring. The hetero atom of the heterocyclic ring is preferably a nitrogen atom, a sulfur atom or an oxygen atom, and particularly preferably a nitrogen atom. As the heterocyclic ring having aromaticity, a pyridine ring (2-pyridyl or 4-pyridyl as the heterocyclic group) is particularly preferable. The heterocyclic group may have a substituent. Examples of the substituent of the heterocyclic group are the same as the examples of the substituent of the aryl moiety.

  When X is a single bond, the heterocyclic group is preferably a heterocyclic group having a free valence on the nitrogen atom. The heterocyclic group having a free valence on the nitrogen atom is preferably a 5-membered ring, 6-membered ring or 7-membered ring, more preferably a 5-membered ring or 6-membered ring, and a 5-membered ring. Is most preferred. The heterocyclic group may have a plurality of nitrogen atoms. Further, the heterocyclic group may have a hetero atom other than the nitrogen atom (for example, O, S). Examples of heterocyclic groups having free valences on nitrogen atoms are shown below.

The alkyl group represented by R ² may be a cyclic alkyl group or a chain alkyl group, but a chain alkyl group is preferable, and a linear alkyl group is more preferable than a branched chain alkyl group. preferable.

  The number of carbon atoms in the alkyl group is preferably 1-30, more preferably 1-20, further preferably 1-10, still more preferably 1-8, and 1-6. Most preferred. The alkyl group may have a substituent. Examples of the substituent include a halogen atom, an alkoxy group (for example, methoxy group, ethoxy group) and an acyloxy group (for example, acryloyloxy group, methacryloyloxy group).

The alkenyl group represented by R ² may be a cyclic alkenyl group or a chain alkenyl group, but preferably represents a chain alkenyl group, and is a straight chain alkenyl group rather than a branched chain alkenyl group. More preferably it represents a group. The number of carbon atoms in the alkenyl group is preferably 2 to 30, more preferably 2 to 20, still more preferably 2 to 10, still more preferably 2 to 8, 6 is most preferred. The alkenyl group may have a substituent. Examples of the substituent are the same as those of the alkyl group described above.

The aromatic ring group and heterocyclic group represented by R ² are the same as the aromatic ring and heterocyclic ring represented by R ¹ , and the preferred range is also the same. The aromatic ring group and the heterocyclic group may further have a substituent, and examples of the substituent are the same as those of the aromatic ring and heterocyclic ring of R ¹ .

  As the discotic compound, a triphenylene compound represented by the following general formula (II) can also be preferably used.

In the general formula (II), R ¹ , R ² , R ³ , R ⁴ , R ⁵ and R ⁶ each independently represent a hydrogen atom or a substituent.

The substituent represented by each of R ¹ , R ² , R ³ , R ⁴ , R ⁵ and R ⁶ is an alkyl group (preferably having 1 to 40 carbon atoms, more preferably 1 to 30 carbon atoms, and particularly preferably carbon number). 1-20 alkyl groups, such as methyl, ethyl, isopropyl, tert-butyl, n-octyl, n-decyl, n-hexadecyl, cyclopropyl, cyclopentyl, cyclohexyl, etc. ), An alkenyl group (preferably an alkenyl group having 2 to 40 carbon atoms, more preferably 2 to 30 carbon atoms, particularly preferably 2 to 20 carbon atoms, such as a vinyl group, an allyl group, 2- Butenyl group, 3-pentenyl group and the like), alkynyl group (preferably 2 to 40 carbon atoms, more preferably 2 to 30 carbon atoms, particularly preferably 2 carbon atoms). -20 alkynyl group, for example, propargyl group, 3-pentynyl group, etc., aryl group (preferably 6-30 carbon atoms, more preferably 6-20 carbon atoms, particularly preferably 6-6 carbon atoms). 12 aryl groups, for example, phenyl group, p-methylphenyl group, naphthyl group, etc., substituted or unsubstituted amino group (preferably having 0 to 40 carbon atoms, more preferably 0 to 30 carbon atoms). And particularly preferably an amino group having 0 to 20 carbon atoms, such as an unsubstituted amino group, a methylamino group, a dimethylamino group, a diethylamino group, and an anilino group).

  An alkoxy group (preferably an alkoxy group having 1 to 40 carbon atoms, more preferably 1 to 30 carbon atoms, particularly preferably 1 to 20 carbon atoms, and examples thereof include a methoxy group, an ethoxy group, and a butoxy group). Aryloxy group (preferably an aryloxy group having 6 to 40 carbon atoms, more preferably 6 to 30 carbon atoms, particularly preferably 6 to 20 carbon atoms, and examples thereof include a phenyloxy group and a 2-naphthyloxy group. An acyl group (preferably an acyl group having 1 to 40 carbon atoms, more preferably 1 to 30 carbon atoms, and particularly preferably 1 to 20 carbon atoms, such as an acetyl group, a benzoyl group, a formyl group, and a pivaloyl group. Etc.), an alkoxycarbonyl group (preferably having 2 to 40 carbon atoms, more preferably 2 to 30 carbon atoms, and particularly preferably carbon number) To 20 alkoxy groups such as methoxycarbonyl group and ethoxycarbonyl group), aryloxycarbonyl groups (preferably having 7 to 40 carbon atoms, more preferably having 7 to 30 carbon atoms, and particularly preferably carbon atoms). An aryloxycarbonyl group having 7 to 20 carbon atoms, such as a phenyloxycarbonyl group, and an acyloxy group (preferably having 2 to 40 carbon atoms, more preferably 2 to 30 carbon atoms, and particularly preferably 2 carbon atoms). To 20 acyloxy groups, such as an acetoxy group and a benzoyloxy group, and acylamino groups (preferably having 2 to 40 carbon atoms, more preferably 2 to 30 carbon atoms, and particularly preferably 2 to 20 carbon atoms). Acylamino groups such as acetylamino group, benzoylamino group, etc. And an alkoxycarbonylamino group (preferably an alkoxycarbonylamino group having 2 to 40 carbon atoms, more preferably 2 to 30 carbon atoms, particularly preferably 2 to 20 carbon atoms, such as a methoxycarbonylamino group) An aryloxycarbonylamino group (preferably 7 to 40 carbon atoms, more preferably 7 to 30 carbon atoms, particularly preferably 7 to 20 carbon atoms, such as phenyloxycarbonylamino group). Group), a sulfonylamino group (preferably a sulfonylamino group having 1 to 40 carbon atoms, more preferably 1 to 30 carbon atoms, particularly preferably 1 to 20 carbon atoms, such as a methanesulfonylamino group, Benzenesulfonylamino group), sulfamoyl A group (preferably a sulfamoyl group having 0 to 40 carbon atoms, more preferably 0 to 30 carbon atoms, particularly preferably 0 to 20 carbon atoms, such as a sulfamoyl group, a methylsulfamoyl group, a dimethylsulfamoyl group, A phenylsulfamoyl group), a carbamoyl group (preferably a carbamoyl group having 1 to 40 carbon atoms, more preferably 1 to 30 carbon atoms, and particularly preferably 1 to 20 carbon atoms. A carbamoyl group, a methylcarbamoyl group, a diethylcarbamoyl group, a phenylcarbamoyl group, etc.).

  Alkylthio group (preferably having 1 to 40 carbon atoms, more preferably 1 to 30 carbon atoms, particularly preferably 1 to 20 carbon atoms, for example, methylthio group, ethylthio group, propylthio group, butylthio group, pentylthio group, hexylthio group , Heptylthio group, octylthio group and the like), arylthio group (preferably having 6 to 40 carbon atoms, more preferably 6 to 30 carbon atoms, particularly preferably 1 to 20 carbon atoms, for example, phenylthio group). ), A sulfonyl group (preferably a sulfonyl group having 1 to 40 carbon atoms, more preferably 1 to 30 carbon atoms, particularly preferably 1 to 20 carbon atoms, and examples thereof include a mesyl group and a tosyl group), sulfinyl Group (preferably having 1 to 40 carbon atoms, more preferably 1 to 30 carbon atoms, particularly preferably 1 to 2 carbon atoms) Sulfinyl group, for example, methanesulfinyl group, benzenesulfinyl group, etc.), ureido group (preferably having 1 to 40 carbon atoms, more preferably 1 to 30 carbon atoms, particularly preferably 1 to 20 carbon atoms). A ureido group, for example, an unsubstituted ureido group, a methylureido group, a phenylureido group, and the like, a phosphoric acid amide group (preferably having 1 to 40 carbon atoms, more preferably 1 to 30 carbon atoms, and particularly preferably Is a phosphoric acid amide group having 1 to 20 carbon atoms, and examples thereof include a diethylphosphoric acid amide group and a phenylphosphoric acid amide group, a hydroxyl group, a mercapto group, a halogen atom (for example, a fluorine atom, a chlorine atom, bromine). Atom, iodine atom), cyano group, sulfo group, carboxyl group, nitro group, hydroxamic acid group, sulfino , A hydrazino group, an imino group, a heterocyclic group (preferably a heterocyclic group having 1 to 30 carbon atoms, more preferably 1 to 12, for example, a heterocyclic ring having a hetero atom such as a nitrogen atom, an oxygen atom, a sulfur atom, etc. A imidazolyl group, a pyridyl group, a quinolyl group, a furyl group, a piperidyl group, a morpholino group, a benzoxazolyl group, a benzimidazolyl group, a benzthiazolyl group, a 1,3,5-triazyl group, etc.) A silyl group (preferably a silyl group having 3 to 40 carbon atoms, more preferably 3 to 30 carbon atoms, particularly preferably 3 to 24 carbon atoms, and examples thereof include a trimethylsilyl group and a triphenylsilyl group. ) Is included. These substituents may be further substituted with these substituents. Moreover, when it has two or more substituents, they may be the same or different. If possible, they may be bonded to each other to form a ring.

The substituent represented by each of R ¹ , R ² , R ³ , R ⁴ , R ⁵ and R ⁶ is preferably an alkyl group, an aryl group, a substituted or unsubstituted amino group, an alkoxy group, an alkylthio group or a halogen atom. is there.

  Although the specific example of a compound represented by general formula (II) below is given, it is not limited to this.

  The compound represented by the general formula (I) is, for example, a method described in JP-A No. 2003-344655, and the compound represented by the general formula (II) is, for example, a method described in JP-A-2005-134484. Can be synthesized by a known method.

  In the present invention, rod-like compounds having a linear molecular structure can be preferably used in addition to the above-mentioned discotic compounds. The linear molecular structure means that the molecular structure of the rod-like compound is linear in the most thermodynamically stable structure. The most thermodynamically stable structure can be obtained by crystal structure analysis or molecular orbital calculation. For example, molecular orbital calculation is performed using molecular orbital calculation software (for example, WinMOPAC2000, manufactured by Fujitsu Limited), and a molecular structure that minimizes the heat of formation of a compound can be obtained. The molecular structure being linear means that in the thermodynamically most stable structure obtained by calculation as described above, the angle of the main chain constituting the molecular structure is 140 degrees or more.

  As the rod-shaped compound having at least two aromatic rings, a compound represented by the following general formula (III) is preferable.

Formula (III): Ar ₁ -L ₁ -Ar ₂
In the general formula (III), Ar ₁ and Ar ₂ are each independently an aromatic group. In the present specification, the aromatic group includes an aryl group (aromatic hydrocarbon group), a substituted aryl group, an aromatic heterocyclic group, and a substituted aromatic heterocyclic group.

  An aryl group and a substituted aryl group are more preferable than an aromatic heterocyclic group and a substituted aromatic heterocyclic group. The heterocyclic ring of the aromatic heterocyclic group is generally unsaturated. The aromatic heterocycle is preferably a 5-membered ring, 6-membered ring or 7-membered ring, more preferably a 5-membered ring or 6-membered ring. Aromatic heterocycles generally have the most double bonds. As a hetero atom, a nitrogen atom, an oxygen atom or a sulfur atom is preferable, and a nitrogen atom or a sulfur atom is more preferable.

  As the aromatic ring of the aromatic group, a benzene ring, a furan ring, a thiophene ring, a pyrrole ring, an oxazole ring, a thiazole ring, an imidazole ring, a triazole ring, a pyridine ring, a pyrimidine ring and a pyrazine ring are preferable, and a benzene ring is particularly preferable. .

  Examples of the substituent of the substituted aryl group and the substituted aromatic heterocyclic group include a halogen atom (F, Cl, Br, I), a hydroxyl group, a carboxyl group, a cyano group, an amino group, an alkylamino group (for example, methyl Amino group, ethylamino group, butylamino group, dimethylamino group), nitro group, sulfo group, carbamoyl group, alkylcarbamoyl group (for example, N-methylcarbamoyl group, N-ethylcarbamoyl group, N, N-) Dimethylcarbamoyl group), sulfamoyl group, alkylsulfamoyl group (eg, N-methylsulfamoyl group, N-ethylsulfamoyl group, N, N-dimethylsulfamoyl group), ureido Group, alkylureido group (for example, N-methylureido group, N, N-dimethylureido group, N, N, N′-trimethyl group) Each group of a ureido group), an alkyl group (for example, methyl group, ethyl group, propyl group, butyl group, pentyl group, heptyl group, octyl group, isopropyl group, s-butyl group, tert-amyl group, cyclohexyl group, cyclopentyl) Group), alkenyl group (for example, vinyl group, allyl group, hexenyl group), alkynyl group (for example, ethynyl group, butynyl group), acyl group (for example, formyl group, acetyl group, butyryl group, Hexanoyl group, lauryl group), acyloxy group (for example, acetoxy group, butyryloxy group, hexanoyloxy group, lauryloxy group), alkoxy group (for example, methoxy group, ethoxy group, propoxy group, butoxy group) Pentyloxy group, heptyloxy group, octyloxy group), arylo Si group (for example, phenoxy group), alkoxycarbonyl group (for example, methoxycarbonyl group, ethoxycarbonyl group, propoxycarbonyl group, butoxycarbonyl group, pentyloxycarbonyl group, heptyloxycarbonyl group), aryloxycarbonyl group ( For example, phenoxycarbonyl group), alkoxycarbonylamino group (for example, butoxycarbonylamino group, hexyloxycarbonylamino group), alkylthio group (for example, methylthio group, ethylthio group, propylthio group, butylthio group, pentylthio group, heptylthio group, octylthio group) Each group), arylthio group (for example, phenylthio group), alkylsulfonyl group (for example, methylsulfonyl group, ethylsulfonyl group, propylsulfonyl group, butylsulfonyl group) Group, pentylsulfonyl group, heptylsulfonyl group, octylsulfonyl group), amide group (for example, acetamido group, butyramide group, hexylamide group, laurylamide group) and non-aromatic heterocyclic group ( For example, a morpholyl group and a pyrazinyl group) are included.

  Among these, preferable substituents include a halogen atom, a cyano group, a carboxyl group, a hydroxyl group, an amino group, an alkylamino group, an acyl group, an acyloxy group, an amide group, an alkoxycarbonyl group, an alkoxy group, an alkylthio group, and an alkyl group. Can be mentioned.

  The alkyl moiety of the alkylamino group, alkoxycarbonyl group, alkoxy group, and alkylthio group and the alkyl group may further have a substituent. Examples of the alkyl moiety and the substituent of the alkyl group include halogen atom, hydroxyl group, carboxyl group, cyano group, amino group, alkylamino group, nitro group, sulfo group, carbamoyl group, alkylcarbamoyl group, sulfamoyl group, alkylsulfur group. Famoyl group, ureido group, alkylureido group, alkenyl group, alkynyl group, acyl group, acyloxy group, alkoxy group, aryloxy group, alkoxycarbonyl group, aryloxycarbonyl group, alkoxycarbonylamino group, alkylthio group, arylthio group, An alkylsulfonyl group, an amide group and a non-aromatic heterocyclic group are included. As the substituent for the alkyl moiety and the alkyl group, a halogen atom, a hydroxyl group, an amino group, an alkylamino group, an acyl group, an acyloxy group, an acylamino group, an alkoxycarbonyl group, and an alkoxy group are preferable.

In the general formula (III), L ₁ is a divalent linking group selected from an alkylene group, an alkenylene group, an alkynylene group, —O—, —CO—, and a combination thereof.

  The alkylene group may have a cyclic structure. As the cyclic alkylene group, cyclohexylene is preferable, and 1,4-cyclohexylene is particularly preferable. As the chain alkylene group, a linear alkylene group is more preferable than a branched alkylene group.

  The number of carbon atoms of the alkylene group is preferably 1-20, more preferably 1-15, still more preferably 1-10, still more preferably 1-8, and most preferably 1-6. It is.

  The alkenylene group and the alkynylene group preferably have a chain structure rather than a cyclic structure, and more preferably have a linear structure rather than a branched chain structure.

  The alkenylene group and the alkynylene group preferably have 2 to 10 carbon atoms, more preferably 2 to 8, more preferably 2 to 6, still more preferably 2 to 4, and most preferably 2. (Vinylene group or ethynylene group).

  The arylene group preferably has 6 to 20 carbon atoms, more preferably 6 to 16, and still more preferably 6 to 12.

In the molecular structure of the general formula (III), the angle formed by Ar ₁ and Ar ₂ across L ₁ is preferably 140 degrees or more.

  As the rod-like compound, a compound represented by the following formula (IV) is more preferable.

Formula _{(IV): Ar 1 -L 2} -X-L 3 -Ar 2
In the general formula (IV), Ar ₁ and Ar ₂ are each independently an aromatic group. The definition and examples of the aromatic group are the same as those of Ar ₁ and Ar _{2 in} the general formula (III).

In General Formula (IV), L ₂ and L ₃ are each independently a divalent linking group selected from an alkylene group, —O—, —CO—, and a group consisting of a combination thereof.

  The alkylene group preferably has a chain structure rather than a cyclic structure, and more preferably has a linear structure rather than a branched chain structure.

  The alkylene group preferably has 1 to 10 carbon atoms, more preferably 1 to 8, more preferably 1 to 6, still more preferably 1 to 4, and 1 or 2 (methylene group). Or an ethylene group) is most preferable.

L ₂ and L ₃ are particularly preferably —O—CO— or CO—O—.

  In the general formula (IV), X represents a 1,4-cyclohexylene group, a vinylene group or an ethynylene group.

  Specific examples of the compound represented by the general formula (III) or (IV) include compounds described in [Chemical Formula 1] to [Chemical Formula 11] of JP-A No. 2004-109657.

  Two or more rod-shaped compounds whose maximum absorption wavelength (λmax) is longer than 250 nm in the ultraviolet absorption spectrum of the solution may be used in combination.

  The rod-like compound can be synthesized with reference to methods described in literature. As literature, Mol. Cryst. Liq. Cryst. 53, 229 (1979), 89, 93 (1982), 145, 111 (1987), 170, 43 (1989), J. Am. Am. Chem. Soc. 113, p. 1349 (1991), p. 118, p. 5346 (1996), p. 92, p. 1582 (1970). Org. Chem. 40, 420 pages (1975), Tetrahedron, Vol. 48, No. 16, page 3437 (1992).

  Moreover, you may use the rod-shaped aromatic compound of the 11-11 pages of Unexamined-Japanese-Patent No. 2004-50516 as said retardation (retardation) developing agent.

  When the optical film is produced by a solvent cast method, the retardation developing agent may be added to the dope. The addition may be performed at any timing. For example, a retardation developing agent may be dissolved in an organic solvent such as alcohol, methylene chloride, dioxolane, etc., and then added to the cellulose ester solution (dope). Or may be added directly into the dope composition.

  In addition, specific examples of preferable compounds of rod-like compounds other than those described in the above-mentioned publications are shown below.

  The specific examples (1) to (34), (41), and (42) have two asymmetric carbon atoms at the 1-position and the 4-position of the cyclohexane ring. However, since the specific examples (1), (4) to (34), (41), and (42) have a symmetrical meso type molecular structure, there are no optical isomers (optical activity), and geometric isomers (trans Type and cis type). The trans type (1-trans) and cis type (1-cis) of specific example (1) are shown below.

  As described above, the rod-like compound preferably has a linear molecular structure. Therefore, the trans type is preferable to the cis type.

  Specific examples (2) and (3) have optical isomers (a total of four isomers) in addition to geometric isomers. As for geometric isomers, the trans type is similarly preferable to the cis type. The optical isomer is not particularly superior or inferior, and may be D, L, or a racemate.

  In specific examples (43) to (45), the central vinylene bond includes a trans type and a cis type. For the same reason as above, the trans type is preferable to the cis type.

(Plasticizer)
The optical film according to the present invention preferably contains, as a plasticizer, an ester compound represented by the following general formula (PL) from the viewpoint of dimensional stability in an environmental change that causes unevenness of the polarizing plate.

Formula (PL) B- (GA) n-GB
(In the formula, B is a hydroxyl group or carboxylic acid residue, G is an alkylene glycol residue having 2 to 12 carbon atoms, an aryl glycol residue having 6 to 12 carbon atoms, or an oxyalkylene glycol residue having 4 to 12 carbon atoms. A represents an alkylene dicarboxylic acid residue having 4 to 12 carbon atoms or an aryl dicarboxylic acid residue having 6 to 12 carbon atoms, and n represents an integer of 1 or more.)
In the general formula (PL), as the alkylene glycol component having 2 to 12 carbon atoms, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,2-propanediol, 2-methyl 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 2 , 2-diethyl-1,3-propanediol (3,3-dimethylolpentane), 2-n-butyl-2-ethyl-1,3-propanediol (3,3-dimethylolheptane), 3-methyl- 1,5-pentanediol 1,6-hexanediol, 2,2,4-trimethyl 1,3-pentanediol, 2-ethyl 1 There are 3-hexanediol, 2-methyl 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-octadecanediol, etc., and these glycols are one kind or two or more kinds Used as a mixture.

  In particular, an alkylene glycol having 2 to 12 carbon atoms is particularly preferable because of excellent compatibility with a cellulose ester.

  Examples of the aryl glycol component having 6 to 12 carbon atoms include hydroquinone, resorcin, bisphenol A, bisphenol F, bisphenol, and the like, and these glycols can be used as one kind or a mixture of two or more kinds.

  Examples of the oxyalkylene glycol component having 4 to 12 carbon atoms include diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, and tripropylene glycol. These glycols may be used alone or as a mixture of two or more. Can be used as

  Examples of the alkylene dicarboxylic acid component having 4 to 12 carbon atoms include succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, and the like. Used as a mixture of seeds and more. Examples of the arylene dicarboxylic acid component having 6 to 12 carbon atoms include phthalic acid, terephthalic acid, isophthalic acid, 1,5 naphthalene dicarboxylic acid, and 1,4 naphthalene dicarboxylic acid.

  The ester compound represented by the general formula (PL) has a number average molecular weight of preferably 300 to 1500, and more preferably 400 to 1000.

  In the cellulose ester according to the present invention, a polyester compound having a hydroxyl group at the terminal is preferable in terms of compatibility.

  Although the specific compound of the ester compound represented with general formula (PL) which concerns on this invention below is shown, this invention is not limited to this.

<Other plasticizers>
The optical film according to the present invention can contain a plasticizer other than the compound represented by the general formula (PL) as necessary for obtaining the effects of the present invention.

  The plasticizer is not particularly limited, but is preferably a polycarboxylic acid ester plasticizer, a glycolate plasticizer, a phthalate ester plasticizer, a fatty acid ester plasticizer, a polyhydric alcohol ester plasticizer, or an ester plasticizer. Agent, acrylic plasticizer and the like.

  Of these, when two or more plasticizers are used, at least one plasticizer is preferably a polyhydric alcohol ester plasticizer.

  The polyhydric alcohol ester plasticizer is a plasticizer comprising an ester of a dihydric or higher aliphatic polyhydric alcohol and a monocarboxylic acid, and preferably has an aromatic ring or a cycloalkyl ring in the molecule. Preferably it is a 2-20 valent aliphatic polyhydric alcohol ester.

  The polyhydric alcohol preferably used in the present invention is represented by the following general formula (a).

Formula _{(a) R 11 - (OH} ) n
However, R ₁₁ represents an n-valent organic group, n represents a positive integer of 2 or more, and the OH group represents an alcoholic and / or phenolic hydroxyl group.

  Examples of preferred polyhydric alcohols include the following, but the present invention is not limited to these.

  Adonitol, arabitol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, tripropylene glycol, 1,2-butanediol, 1,3- Butanediol, 1,4-butanediol, dibutylene glycol, 1,2,4-butanetriol, 1,5-pentanediol, 1,6-hexanediol, hexanetriol, galactitol, mannitol, 3-methylpentane- Examples include 1,3,5-triol, pinacol, sorbitol, trimethylolpropane, trimethylolethane, xylitol and the like.

  In particular, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, sorbitol, trimethylolpropane, and xylitol are preferable.

  There is no restriction | limiting in particular as monocarboxylic acid used for polyhydric alcohol ester, Well-known aliphatic monocarboxylic acid, alicyclic monocarboxylic acid, aromatic monocarboxylic acid, etc. can be used. Use of an alicyclic monocarboxylic acid or aromatic monocarboxylic acid is preferred in terms of improving moisture permeability and retention.

  Examples of preferred monocarboxylic acids include the following, but the present invention is not limited thereto.

  As the aliphatic monocarboxylic acid, a fatty acid having a straight chain or a side chain having 1 to 32 carbon atoms can be preferably used. The number of carbon atoms is more preferably 1-20, and particularly preferably 1-10. When acetic acid is contained, the compatibility with the cellulose ester is increased, and it is also preferable to use a mixture of acetic acid and another monocarboxylic acid.

  Preferred aliphatic monocarboxylic acids include acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, 2-ethyl-hexanoic acid, undecylic acid, lauric acid, tridecylic acid, Saturated fatty acids such as myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, serotic acid, heptacosanoic acid, montanic acid, melicic acid, laccelic acid, undecylenic acid, olein Examples thereof include unsaturated fatty acids such as acid, sorbic acid, linoleic acid, linolenic acid, and arachidonic acid.

  Examples of preferred alicyclic monocarboxylic acids include cyclopentane carboxylic acid, cyclohexane carboxylic acid, cyclooctane carboxylic acid, or derivatives thereof.

  Examples of preferred aromatic monocarboxylic acids include those in which 1 to 3 alkoxy groups such as an alkyl group, a methoxy group or an ethoxy group are introduced into the benzene ring of benzoic acid such as benzoic acid or toluic acid, biphenylcarboxylic acid, Examples thereof include aromatic monocarboxylic acids having two or more benzene rings such as naphthalenecarboxylic acid and tetralincarboxylic acid, or derivatives thereof. Benzoic acid is particularly preferable.

  The molecular weight of the polyhydric alcohol ester is not particularly limited, but is preferably 300 to 1500, and more preferably 350 to 750. A higher molecular weight is preferred because it is less likely to volatilize, and a smaller one is preferred in terms of moisture permeability and compatibility with cellulose ester.

  The carboxylic acid used for the polyhydric alcohol ester may be one kind or a mixture of two or more kinds. Moreover, all the OH groups in the polyhydric alcohol may be esterified, or a part of the OH groups may be left as they are.

  Below, the specific compound of a polyhydric alcohol ester is illustrated.

  The glycolate plasticizer is not particularly limited, but alkylphthalylalkyl glycolates can be preferably used.

  Examples of alkyl phthalyl alkyl glycolates include methyl phthalyl methyl glycolate, ethyl phthalyl ethyl glycolate, propyl phthalyl propyl glycolate, butyl phthalyl butyl glycolate, octyl phthalyl octyl glycolate, methyl phthalyl ethyl Glycolate, ethyl phthalyl methyl glycolate, ethyl phthalyl propyl glycolate, methyl phthalyl butyl glycolate, ethyl phthalyl butyl glycolate, butyl phthalyl methyl glycolate, butyl phthalyl ethyl glycolate, propyl phthalyl butyl glycol Butyl phthalyl propyl glycolate, methyl phthalyl octyl glycolate, ethyl phthalyl octyl glycolate, octyl phthalyl methyl glycolate, octyl phthalate Ethyl glycolate, and the like.

  Examples of the phthalate ester plasticizer include diethyl phthalate, dimethoxyethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, dioctyl phthalate, dicyclohexyl phthalate, and dicyclohexyl terephthalate.

  Examples of the citrate plasticizer include acetyl trimethyl citrate, acetyl triethyl citrate, and acetyl tributyl citrate.

  Examples of fatty acid ester plasticizers include butyl oleate, methylacetyl ricinoleate, and dibutyl sebacate.

  The polyvalent carboxylic acid ester compound is composed of an ester of divalent or higher, preferably divalent to 20 valent polyvalent carboxylic acid and alcohol. The aliphatic polyvalent carboxylic acid is preferably 2 to 20 valent, and in the case of an aromatic polyvalent carboxylic acid or an alicyclic polyvalent carboxylic acid, it is preferably 3 to 20 valent.

  The polyvalent carboxylic acid is represented by the following general formula (b).

Formula (b) R ₁₂ (COOH) _m1 (OH) _n1
In the formula, R ₁₂ represents an (m1 + n1) -valent organic group, m1 represents a positive integer of 2 or more, n1 represents an integer of 0 or more, a COOH group represents a carboxyl group, and an OH group represents an alcoholic or phenolic hydroxyl group.

  Examples of preferred polyvalent carboxylic acids include the following, but the present invention is not limited to these.

  Trivalent or higher aromatic polyvalent carboxylic acids such as trimellitic acid, trimesic acid, pyromellitic acid or derivatives thereof, succinic acid, adipic acid, azelaic acid, sebacic acid, oxalic acid, fumaric acid, maleic acid, tetrahydrophthal An aliphatic polyvalent carboxylic acid such as an acid, an oxypolyvalent carboxylic acid such as tartaric acid, tartronic acid, malic acid and citric acid can be preferably used. In particular, it is preferable to use an oxypolycarboxylic acid from the viewpoint of improving retention.

  There is no restriction | limiting in particular as alcohol used for the polyhydric carboxylic acid ester compound which can be used for this invention, Well-known alcohol and phenols can be used.

  For example, an aliphatic saturated alcohol or aliphatic unsaturated alcohol having a straight chain or side chain having 1 to 32 carbon atoms can be preferably used. It is more preferable that it is C1-C20, and it is especially preferable that it is C1-C10.

  In addition, alicyclic alcohols such as cyclopentanol and cyclohexanol or derivatives thereof, aromatic alcohols such as benzyl alcohol and cinnamyl alcohol, or derivatives thereof can also be preferably used.

  When an oxypolycarboxylic acid is used as the polycarboxylic acid, the alcoholic or phenolic hydroxyl group of the oxypolycarboxylic acid may be esterified with a monocarboxylic acid. Examples of preferred monocarboxylic acids include the following, but the present invention is not limited thereto.

  As the aliphatic monocarboxylic acid, a fatty acid having a straight chain or a side chain having 1 to 32 carbon atoms can be preferably used. It is more preferable that it is C1-C20, and it is especially preferable that it is C1-C10.

  Preferred aliphatic monocarboxylic acids include acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, 2-ethyl-hexanecarboxylic acid, undecylic acid, lauric acid, tridecylic acid, Saturated fatty acids such as myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, serotic acid, heptacosanoic acid, montanic acid, melicic acid, and laccelic acid, undecylenic acid, olein Examples thereof include unsaturated fatty acids such as acid, sorbic acid, linoleic acid, linolenic acid, and arachidonic acid.

  Examples of preferred alicyclic monocarboxylic acids include cyclopentane carboxylic acid, cyclohexane carboxylic acid, cyclooctane carboxylic acid, or derivatives thereof.

  Examples of preferred aromatic monocarboxylic acids include those in which an alkyl group is introduced into the benzene ring of benzoic acid such as benzoic acid and toluic acid, and two or more benzene rings such as biphenyl carboxylic acid, naphthalene carboxylic acid, and tetralin carboxylic acid. The aromatic monocarboxylic acid which has, or derivatives thereof can be mentioned. Particularly preferred are acetic acid, propionic acid, and benzoic acid.

  The molecular weight of the polyvalent carboxylic acid ester compound is not particularly limited, but is preferably in the range of 300 to 1000, and more preferably in the range of 350 to 750. The larger one is preferable in terms of improvement in retention, and the smaller one is preferable in terms of moisture permeability and compatibility with cellulose ester.

  The alcohol used for the polyvalent carboxylic acid ester that can be used in the present invention may be one kind or a mixture of two or more kinds.

  The acid value of the polyvalent carboxylic acid ester compound that can be used in the present invention is preferably 1 mgKOH / g or less, and more preferably 0.2 mgKOH / g or less. Setting the acid value in the above range is preferable because the environmental fluctuation of the retardation is also suppressed.

  In addition, an acid value means the milligram number of potassium hydroxide required in order to neutralize the acid (carboxyl group which exists in a sample) contained in 1g of samples. The acid value is measured according to JIS K0070.

(UV absorber)
The optical film according to the present invention can also contain an ultraviolet absorber. The ultraviolet absorber is intended to improve durability by absorbing ultraviolet rays of 400 nm or less, and in particular, the transmittance at a wavelength of 370 nm is preferably 10% or less, more preferably 5% or less, and further Preferably it is 2% or less.

  Although the ultraviolet absorber used in the present invention is not particularly limited, for example, oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, triazine compounds, nickel complex compounds, inorganic powders Examples include the body.

  For example, 5-chloro-2- (3,5-di-sec-butyl-2-hydroxylphenyl) -2H-benzotriazole, (2-2H-benzotriazol-2-yl) -6- (linear and side Chain dodecyl) -4-methylphenol, 2-hydroxy-4-benzyloxybenzophenone, 2,4-benzyloxybenzophenone, etc., and tinuvin 109, tinuvin 171, tinuvin 234, tinuvin 326, tinuvin 327, tinuvin 328, etc. These are commercially available products from Ciba Japan and can be preferably used.

  The UV absorbers preferably used in the present invention are benzotriazole UV absorbers, benzophenone UV absorbers, and triazine UV absorbers, particularly preferably benzotriazole UV absorbers and benzophenone UV absorbers. .

  In addition, a discotic compound such as a compound having a 1,3,5 triazine ring is also preferably used as the ultraviolet absorber.

  The polarizing plate protective film according to the present invention preferably contains two or more ultraviolet absorbers.

  As the UV absorber, a polymer UV absorber can also be preferably used, and in particular, a polymer type UV absorber described in JP-A-6-148430 is preferably used.

  The method of adding the UV absorber can be added to the dope after dissolving the UV absorber in an alcohol such as methanol, ethanol or butanol, an organic solvent such as methylene chloride, methyl acetate, acetone or dioxolane or a mixed solvent thereof. Or you may add directly in dope composition.

  For an inorganic powder that does not dissolve in an organic solvent, a dissolver or a sand mill is used in the organic solvent and cellulose ester to disperse and then added to the dope.

  The amount of the UV absorber used is not uniform depending on the type of UV absorber, the operating conditions, etc., but when the dry film thickness of the polarizing plate protective film is 30 to 200 μm, it is 0.5 with respect to the polarizing plate protective film. -10 mass% is preferable, and 0.6-4 mass% is still more preferable.

(Antioxidant)
Antioxidants are also referred to as deterioration inhibitors. When a liquid crystal image display device or the like is placed in a high humidity and high temperature state, the optical film may be deteriorated.

  The antioxidant has a role of delaying or preventing the optical film from being decomposed by, for example, the residual solvent amount of halogen in the optical film or phosphoric acid of the phosphoric acid plasticizer. It is preferable to contain.

  As such an antioxidant, a hindered phenol compound is preferably used. For example, 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di- -T-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-bis [3 -(3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-t-butylanilino)- 1,3,5-triazine, 2,2-thio-diethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], octa Sil-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, N, N'-hexamethylenebis (3,5-di-t-butyl-4-hydroxy-hydrocinnamamide) 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, tris- (3,5-di-t-butyl-4-hydroxy Benzyl) -isocyanurate and the like.

  In particular, 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3 -(3-t-butyl-5-methyl-4-hydroxyphenyl) propionate] is preferred. Further, for example, hydrazine-based metal deactivators such as N, N′-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyl] hydrazine and tris (2,4-di- A phosphorus processing stabilizer such as t-butylphenyl) phosphite may be used in combination.

  The addition amount of these compounds is preferably 1 ppm to 1.0%, more preferably 10 to 1000 ppm in terms of mass ratio with respect to the cellulose derivative.

(Matting agent)
It is preferable to add a matting agent in order to impart the slipperiness of the film. The matting agent may be either an inorganic compound or an organic compound without impairing the transparency of the resulting film, such as talc, mica, zeolite, diatomaceous earth, calcined siliceous earth, kaolin, sericite, bentonite, smectite. , Clay, silica, quartz powder, glass beads, glass powder, glass flake, milled fiber, wollastonite, boron nitride, boron carbide, titanium boride, magnesium carbonate, heavy calcium carbonate, light calcium carbonate, calcium silicate, silicic acid Aluminum, magnesium silicate, magnesium aluminosilicate, alumina, silica, zinc oxide, titanium dioxide, iron oxide, magnesium oxide, zirconium oxide, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, calcium sulfate, barium sulfate, carbonized carbon Arsenide, aluminum carbide, titanium carbide, aluminum nitride, silicon nitride, titanium nitride, and white carbon. These matting agents can be used alone or in combination of two or more. By using particles having different particle sizes and shapes (for example, acicular and spherical), both transparency and slipperiness can be made highly compatible. Among these, silicon dioxide is particularly preferably used since it has a refractive index close to that of cellulose ester and is excellent in transparency (haze). Specific examples of silicon dioxide include Aerosil 200V, Aerosil R972V, Aerosil R972, R974, R812, 200, 300, R202, OX50, TT600 (above Nippon Aerosil Co., Ltd.), Sea Hoster KEP-10, Sea Hoster KEP-30, Commercial products having trade names such as Seahoster KEP-50 (above, made by Nippon Shokubai Co., Ltd.), Silo Hovic 100 (made by Fuji Silysia), Nip Seal E220A (made by Nippon Silica Kogyo), Admafine SO (made by Admatechs), etc. Can be preferably used.

  The shape of the particles can be used without particular limitation, such as indefinite shape, needle shape, flat shape, spherical shape, etc. However, the use of spherical particles is particularly preferable because the transparency of the resulting film can be improved. When the particle size is close to the wavelength of visible light, light is scattered and the transparency is deteriorated. Therefore, the particle size is preferably smaller than the wavelength of visible light, and more preferably ½ or less of the wavelength of visible light. .

  If the size of the particles is too small, the slipperiness may not be improved, so the range of 80 nm to 180 nm is particularly preferable.

  The particle size means the size of the aggregate when the particle is an aggregate of primary particles. Moreover, when a particle is not spherical, it means the diameter of a circle corresponding to the projected area.

(Phase difference (retardation))
The optical film of the present invention has a retardation Ro defined by the formula (I) in the in-plane direction of 30 nm from the viewpoint of taking advantage of high retardation development, although the required retardation is different depending on the required optical compensation effect. Preferably, the thickness is in the range of 30 to 200 nm, more preferably in the range of 30 to 90 nm, and the retardation Rt in the thickness direction defined by the formula (II) is 70 nm or more. It is preferable that it is in the range of 70 to 300 nm.

Formula (I) Ro = (nx−ny) × d
Formula (II) Rt = {(nx + ny) / 2−nz} × d
(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, d Is the film thickness (nm).)
<Measurement of retardation Ro and Rt>
A 35 mm × 35 mm sample was cut out from the obtained film, conditioned at 25 ° C. and 55% RH for 2 hours, and measured with an automatic birefringence meter (KOBRA-WR, Oji Scientific Co., Ltd.) from the vertical direction at 590 nm. And the extrapolated value of the retardation value measured in the same manner while tilting the film surface.

  A method for adjusting the phase difference is not particularly limited, but a method of adjusting by a stretching process is common.

  In order to obtain the target retardation values Ro and Rt in the present invention, it is preferable that the optical film has the configuration of the present invention, and the refractive index is controlled by controlling the transport tension and stretching.

  For example, the retardation value can be changed by lowering or increasing the tension in the longitudinal direction.

  In addition, the retardation value can be changed by biaxially stretching or uniaxially stretching sequentially or simultaneously with respect to the longitudinal direction of the film (film forming direction) and the direction orthogonal to the film plane, that is, the width direction. it can.

  The draw ratios in the biaxial directions perpendicular to each other are preferably in the range of 0.8 to 1.5 times in the casting direction and 1.1 to 2.5 times in the width direction, respectively. It is preferable to carry out in the range of 0.8 to 1.0 times in the direction and 1.2 to 2.0 times in the width direction.

  The stretching temperature is preferably 120 ° C. to 200 ° C., more preferably 150 ° C. to 200 ° C., and more preferably 150 ° C. to 190 ° C. or less.

  The residual solvent in the film is preferably 20 to 0%, more preferably 15 to 0%.

  Specifically, it is preferable that the residual solvent is stretched by 11% at 155 ° C., or the residual solvent is stretched by 2% at 155 ° C. Alternatively, it is preferable that the residual solvent is stretched at 11% at 160 ° C, or the residual solvent is stretched at less than 1% at 160 ° C.

  There is no particular limitation on the method of stretching the web. For example, a method in which a difference in peripheral speed is applied to a plurality of rolls, and the roll peripheral speed difference is used to stretch in the longitudinal direction, the both ends of the web are fixed with clips and pins, and the interval between the clips and pins is increased in the traveling direction. And a method of stretching in the vertical direction, a method of stretching in the horizontal direction and stretching in the horizontal direction, a method of stretching in the vertical and horizontal directions and stretching in both the vertical and horizontal directions. Of course, these methods may be used in combination.

  In the case of the so-called tenter method, driving the clip portion by the linear drive method is preferable because smooth stretching can be performed and the risk of breakage and the like can be reduced.

  These width maintenance or lateral stretching in the film forming step is preferably performed by a tenter, and may be a pin tenter or a clip tenter.

  The slow axis or the fast axis of the optical film according to the present invention exists in the film plane, and θ1 is preferably −1 ° or more and + 1 ° or less, assuming that the angle formed with the film forming direction is θ1, −0 More preferably, it is 5 ° or more and + 0.5 ° or less.

  This θ1 can be defined as an orientation angle, and the measurement of θ1 can be performed using an automatic birefringence meter KOBRA-WR (Oji Scientific Instruments). Each of θ1 satisfying the above relationship can contribute to obtaining high luminance in a display image, suppressing or preventing light leakage, and contributing to obtaining faithful color reproduction in a color liquid crystal display device.

<Physical properties of optical film>
The moisture permeability of the optical film according to the present invention is preferably 300 to 1800 g / m ² · 24h at 40 ° C. and 90% RH, more preferably 400 to 1500 g / m ² · 24 h, and 40 to 1300 g / m ² · 24 h. Particularly preferred. The moisture permeability can be measured according to the method described in JIS Z 0208.

  The breaking elongation of the optical film according to the present invention is preferably 10 to 80%, more preferably 20 to 50%.

  The optical film according to the present invention preferably has a visible light transmittance of 90% or more, and more preferably 93% or more.

  The haze of the optical film according to the present invention is preferably less than 1%, particularly preferably 0 to 0.1%.

(Method for producing cellulose ester laminated film)
The optical film of the present invention includes a cellulose ester resin A layer, a cellulose ester resin B layer, and a cellulose ester resin C layer (hereinafter, referred to as “A layer”, “B layer”, and “C layer”, respectively). Is formed by stacking layers in the order of A layer, C layer, B layer, C layer, and A layer.

  In the method for producing an optical film of the present invention (hereinafter also referred to as “manufacturing method according to the present invention”), a dope containing a cellulose ester satisfying the average acyl group substitution degree of each of the above layers is formed on the support in the order described above. It has the process of carrying out multilayer casting simultaneously or sequentially, the process which dries the dope which carried out multilayer casting, and exfoliates from a support, and the process of extending the film after exfoliation.

<Preparation of dope>
As the production method according to the present invention, it is preferable to produce the film of the present invention using a solution (dope) obtained by dissolving a cellulose ester in an organic solvent by a solution co-casting method (solvent cast method).

  The organic solvent is selected from ethers having 3 to 12 carbon atoms, ketones having 3 to 12 carbon atoms, esters having 3 to 12 carbon atoms, and halogenated hydrocarbons having 1 to 6 carbon atoms. It is preferable to include a solvent. The ether, ketone and ester may have a cyclic structure. A compound having two or more functional groups of ether, ketone and ester (that is, —O—, —CO— and COO—) can also be used as the organic solvent. The organic solvent may have another functional group such as an alcoholic hydroxyl group (hydroxyl group). In the case of an organic solvent having two or more types of functional groups, the number of carbon atoms may be within the specified range of the compound having any functional group.

  Examples of the ether having 3 to 12 carbon atoms include diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolane, tetrahydrofuran, anisole and phenetole.

  Examples of ketones having 3 to 12 carbon atoms include acetone, methyl ethyl ketone, diethyl ketone, diisobutyl ketone, cyclohexanone and methylcyclohexanone.

  Examples of the esters having 3 to 12 carbon atoms include ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate and pentyl acetate.

  Examples of the organic solvent having two or more kinds of functional groups include 2-ethoxyethyl acetate, 2-methoxyethanol and 2-butoxyethanol.

  The number of carbon atoms of the halogenated hydrocarbon is preferably 1 or 2, and most preferably 1. The halogen of the halogenated hydrocarbon is preferably chlorine. The proportion of halogen atoms substituted by halogen in the halogenated hydrocarbon is preferably 25 to 75 mol%, more preferably 30 to 70 mol%, and more preferably 35 to 65 mol%. More preferably, it is most preferable that it is 40-60 mol%. Methylene chloride is a representative halogenated hydrocarbon.

  Two or more organic solvents may be mixed and used.

  A cellulose ester solution can be prepared by a general method. A general method means processing at a temperature of 0 ° C. or higher (ordinary temperature or high temperature). The solution can be prepared by using a dope preparation method and apparatus in a normal solvent cast method. In the case of a general method, it is preferable to use a halogenated hydrocarbon (particularly, methylene chloride) as the organic solvent.

  The quantity of a cellulose ester is adjusted so that it may be contained in 10-40 mass% in the solution obtained. The amount of the cellulose ester is more preferably 10 to 30% by mass. Arbitrary additives described later may be added to the organic solvent (main solvent).

  The solution can be prepared by stirring the cellulose ester and the organic solvent at room temperature (0 to 40 ° C.). The high concentration solution may be stirred under pressure and heating conditions. Specifically, the cellulose ester and the organic solvent are placed in a pressure vessel and sealed, and stirred while heating to a temperature not lower than the boiling point of the solvent at normal temperature and in a range where the solvent does not boil. The heating temperature is usually 40 ° C. or higher, preferably 60 to 200 ° C., and more preferably 80 to 110 ° C.

  Each component may be coarsely mixed in advance and then placed in a container. Moreover, you may put into a container sequentially. The container needs to be configured so that it can be stirred. The container can be pressurized by injecting an inert gas such as nitrogen gas. Moreover, you may utilize the raise of the vapor pressure of the solvent by heating. Or after sealing a container, you may add each component under pressure.

  When heating, it is preferable to heat from the outside of the container. For example, a jacket type heating device can be used. The entire container can also be heated by providing a plate heater outside the container and piping to circulate the liquid.

  It is preferable to provide a stirring blade inside the container and stir using this. The stirring blade preferably has a length that reaches the vicinity of the wall of the container. A scraping blade is preferably provided at the end of the stirring blade in order to renew the liquid film on the vessel wall.

  Instruments such as a pressure gauge and a thermometer may be installed in the container. Each component is dissolved in a solvent in a container. The prepared dope is taken out of the container after cooling, or taken out and then cooled using a heat exchanger or the like.

  A solution can also be prepared by a cooling dissolution method. In the cooling dissolution method, the cellulose ester can be dissolved in an organic solvent that is difficult to dissolve by a normal dissolution method. In addition, even if it is a solvent which can melt | dissolve a cellulose ester with a normal melt | dissolution method, there exists an effect that a uniform solution can be obtained rapidly according to a cooling melt | dissolution method.

  In the cooling dissolution method, first, a cellulose ester is gradually added to an organic solvent with stirring at room temperature. The amount of the cellulose ester is preferably adjusted so that it is contained in the mixture in an amount of 10 to 40% by mass. The amount of the cellulose ester is more preferably 10 to 30% by mass. Furthermore, you may add the arbitrary additive mentioned later in a mixture.

  The mixture is then cooled to -100 to -10 ° C (preferably -80 to -10 ° C, more preferably -50 to -20 ° C, most preferably -50 to -30 ° C). The cooling can be performed, for example, in a dry ice / methanol bath (−75 ° C.) or a cooled diethylene glycol solution (−30 to −20 ° C.). When cooled in this manner, the mixture of cellulose ester and organic solvent solidifies.

  The cooling rate is preferably 4 ° C./min or more, more preferably 8 ° C./min or more, and most preferably 12 ° C./min or more. The faster the cooling rate, the better. However, 10,000 ° C./second is the theoretical upper limit, 1000 ° C./second is the technical upper limit, and 100 ° C./second is the practical upper limit. The cooling rate is a value obtained by dividing the difference between the temperature at the start of cooling and the final cooling temperature by the time from the start of cooling to the final cooling temperature.

  Further, when this is heated to 0 to 200 ° C. (preferably 0 to 150 ° C., more preferably 0 to 120 ° C., most preferably 0 to 50 ° C.), the cellulose ester is dissolved in the organic solvent. The temperature can be raised by simply leaving it at room temperature or in a warm bath. The heating rate is preferably 4 ° C./min or more, more preferably 8 ° C./min or more, and most preferably 12 ° C./min or more. The higher the heating rate, the better. However, 10,000 ° C./second is the theoretical upper limit, 1000 ° C./second is the technical upper limit, and 100 ° C./second is the practical upper limit. The heating rate is a value obtained by dividing the difference between the temperature at the start of heating and the final heating temperature by the time from the start of heating until the final heating temperature is reached. .

  A uniform solution is obtained as described above. If the dissolution is insufficient, the cooling and heating operations may be repeated. Whether or not the dissolution is sufficient can be determined by merely observing the appearance of the solution with the naked eye.

  In the cooling dissolution method, it is desirable to use a sealed container in order to avoid moisture mixing due to condensation during cooling. In the cooling and heating operation, when the pressure is applied during cooling and the pressure is reduced during heating, the dissolution time can be shortened. In order to perform pressurization and decompression, it is desirable to use a pressure-resistant container.

(Co-casting)
A cellulose acylate film can be produced from the prepared three or more kinds of cellulose ester solutions (dope) by a solvent cast method.

  The dope is cast on a drum or band and the solvent is evaporated to form a film. The concentration of the dope before casting is preferably adjusted so that the solid content is 18 to 35% by mass. The surface of the drum or band is preferably finished in a mirror state. For casting and drying methods in the solvent casting method, U.S. Pat. No. 736892, JP-B Nos. 45-4554, 49-5614, JP-A-60-176834, No. 60-203430, and No. 62-1115035.

  The dope is preferably cast on a drum or band having a surface temperature of 10 ° C. or less. After casting, it is preferable to dry it by applying air for 2 seconds or more. The obtained film can be peeled off from the drum or band and further dried with high-temperature air whose temperature is successively changed from 100 ° C. to 160 ° C. to evaporate the residual solvent. The above method is described in Japanese Patent Publication No. 5-17844. According to this method, it is possible to shorten the time from casting to stripping. In order to carry out this method, it is necessary for the dope to gel at the surface temperature of the drum or band during casting.

  In the present invention, the obtained cellulose ester solution (dope) is formed into a film by casting the three or more cellulose ester solutions on a smooth band or drum as a support.

  There is no restriction | limiting in particular as a manufacturing method of the film of this invention other than the above, A well-known co-casting method can be used. For example, a film may be produced while casting and laminating a solution containing a cellulose ester from a plurality of casting openings provided at intervals in the traveling direction of the metal support. The methods described in JP-A Nos. 158414, 1-122419, and 11-198285 can be applied. Further, it may be formed into a film by casting a cellulose ester solution from two casting ports. For example, JP-B-60-27562, JP-A-61-94724, JP-A-61-947245, This can be carried out by the methods described in JP-A Nos. 61-104813, 61-158413, and 6-134933. Also, an optical film casting method described in Japanese Patent Application Laid-Open No. 56-162617 may be used in which a flow of a high-viscosity cellulose ester solution is wrapped with a low-viscosity cellulose ester solution and the high- and low-viscosity cellulose ester solutions are simultaneously extruded. . Furthermore, it is also a preferred embodiment that the outer solution described in JP-A-61-94724 and JP-A-61-94725 contains a larger amount of an alcohol component which is a poor solvent than the inner solution.

  Alternatively, by using two casting ports, the film cast on the metal support is peeled off by the first casting port, and the second casting is performed on the side in contact with the metal support surface. Further, a film may be prepared, for example, a method described in Japanese Patent Publication No. 44-20235. The cellulose ester solution to be cast may be the same solution or different cellulose ester solutions and is not particularly limited. In order to give a function to a plurality of cellulose ester layers, a cellulose ester solution corresponding to the function may be extruded from each casting port. Further, the cellulose ester solution according to the present invention can be cast simultaneously with other functional layers (for example, an adhesive layer, a dye layer, an antistatic layer, an antihalation layer, a UV absorbing layer, a polarizing layer). As a method for producing the film of the present invention, it is preferred that the film formation is simultaneous or sequential multilayer casting film formation.

  In the case of co-casting, the inner and outer thicknesses are not particularly limited, but preferably the outer side is preferably 0.2 to 50% of the total film thickness, more preferably 2 to 30%. . Here, in the case of co-casting with three or more layers, the total thickness of the layer in contact with the metal support and the layer in contact with the air side is defined as the outer thickness.

  In the case of co-casting, an optical film having a laminated structure can be produced by co-casting cellulose ester solutions having different additive concentrations such as the above-mentioned plasticizer, ultraviolet absorber and matting agent.

  For example, the matting agent can be contained in the A layer more or only in the A layer.

  More plasticizers and ultraviolet absorbers can be added to the B layer or C layer than the A layer, or only to the B layer or C layer. In addition, the type of plasticizer and ultraviolet absorber can be changed between the B layer or C layer and the A layer. For example, the A layer contains a low-volatile plasticizer and / or an ultraviolet absorber, A plasticizer excellent in plasticity or an ultraviolet absorber excellent in ultraviolet absorption can also be added to the layer. Moreover, it is also a preferable aspect that a release agent is contained only in the A layer on the metal support side. Moreover, in order to cool a metal support body by a cooling drum method and to gelatinize a solution, it is also preferable to add more alcohol which is a poor solvent to A layer than B layer or C layer. The Tg of the A layer and the B layer or the C layer may be different, and the Tg of the B layer or the C layer is preferably lower than the Tg of the A layer. Further, the viscosity of the solution containing the cellulose ester during casting may be different between the A layer and the B layer or C layer, and the viscosity of the A layer is preferably smaller than the viscosity of the B layer or C layer. The viscosity of the layer or C layer may be smaller than the viscosity of the A layer.

  In the present invention, the multi-layer cast dope is dried and peeled from the support.

(Drying process)
A method of drying a web which has been dried on a drum or belt and peeled off will be described. The web peeled at the peeling position just before the drum or belt makes one round is conveyed by alternately passing through a group of rolls arranged in a staggered manner, or the both ends of the peeled web are gripped by clips or the like and are not contacted. It is conveyed by the method of conveying it automatically. Drying is performed by a method of applying wind at a predetermined temperature to both sides of the web (film) being conveyed or a method using a heating means such as a microwave. Since rapid drying may impair the flatness of the film to be formed, it is preferable to dry at a temperature at which the solvent does not foam in the initial stage of drying, and to dry at a high temperature after the drying proceeds. In the drying process after peeling from the support, the film tends to shrink in the longitudinal direction or the width direction by evaporation of the solvent. Shrinkage increases with drying at higher temperatures. Drying while suppressing this shrinkage as much as possible is preferable for improving the flatness of the finished film. From this point, for example, as shown in Japanese Patent Laid-Open No. 62-46625, a method in which all or part of the drying process is performed while holding the width at both ends of the web with clips or pins in the width direction. (Tenter method) is preferred. It is preferable that the drying temperature in the said drying process is 100-145 degreeC. The drying temperature, the amount of drying air, and the drying time vary depending on the solvent used, but may be appropriately selected according to the type and combination of the solvents used. In the production of the film of the present invention, the web (film) peeled from the support is preferably stretched when the amount of residual solvent in the web is less than 120% by mass.

  The residual solvent amount can be expressed by the following formula.

Residual solvent amount (% by mass) = {(MN) / N} × 100
Here, M is the mass of the web at an arbitrary point in time, and N is the mass when the web of which M is measured is dried at 110 ° C. for 3 hours.

(Stretching)
The manufacturing method which concerns on this invention includes the process of extending | stretching the film after peeling after the process of drying the dope which carried out multilayer casting, and peeling from a support body.

  In the present invention, the solution cast film can be stretched without being heated to a high temperature as long as the residual solvent amount is in a specific range, but it is preferable because drying and stretching can shorten the process. . That is, the stretching process may be performed in a state where the solvent remains, or the stretching process after drying may be performed. However, if the temperature of the web is too high, the plasticizer will volatilize, so a range of 120 to 180 ° C is preferred. In addition, stretching in biaxial directions perpendicular to each other is an effective method for bringing the refractive indexes Nx, Ny, and Nz of the film within the scope of the present invention.

  For example, when stretching in the casting direction, if the shrinkage in the width direction is too large, the value of Nz becomes too large. In this case, it can be improved by suppressing the width shrinkage of the film or stretching in the width direction. When stretching in the width direction, the refractive index may be distributed with a width. This is sometimes seen when using, for example, the tenter method, but it is a phenomenon that occurs when the film is stretched in the width direction and contraction force is generated at the center of the film and the end is fixed. It is thought to be called the Boeing phenomenon. Even in this case, by stretching in the casting direction, the bowing phenomenon can be suppressed, and the distribution of the width retardation can be improved. Furthermore, the film thickness fluctuation | variation of the film obtained by extending | stretching in the biaxial direction orthogonal to each other can be reduced. If the film thickness variation of the optical film is too large, the retardation will be uneven. The film thickness variation of the optical film is preferably in the range of ± 3%, and more preferably ± 1%. For the purposes as described above, a method of stretching in the biaxial directions orthogonal to each other is effective, and the stretching ratios in the biaxial directions orthogonal to each other are 1.2 to 2.0 times and 0.7 to 1.0, respectively. It is preferable that the range be doubled. Here, stretching to 1.2 to 2.0 times with respect to one direction and making the other perpendicular to 0.7 to 1.0 times means that the distance between the clip or pin supporting the film is This means that the distance is 0.7 to 1.0 times the interval before stretching.

  In general, when a biaxial stretching tenter is used to stretch in the width direction so as to have an interval of 1.2 to 2.0 times, a contracting force acts in the longitudinal direction that is the perpendicular direction.

  Therefore, if the force is applied in only one direction and the stretching is continued, the width in the perpendicular direction is reduced, but this means that the amount of shrinkage is suppressed with respect to the amount that shrinks without restricting the width. This means that the interval between the clip or pin whose width is restricted is restricted to a range of 0.7 to 1.0 times that before stretching. At this time, in the longitudinal direction, a force is exerted to shrink the film by stretching in the width direction. By taking the interval between the clips or pins in the longitudinal direction, an excessive tension is not applied in the longitudinal direction. There is no particular limitation on the method of stretching the web. For example, a method in which a difference in peripheral speed is applied to a plurality of rolls, and the roll peripheral speed difference is used to stretch in the longitudinal direction, the both ends of the web are fixed with clips and pins, and the interval between the clips and pins is increased in the traveling direction. And a method of stretching in the vertical direction, a method of stretching in the horizontal direction and stretching in the horizontal direction, a method of stretching in the vertical and horizontal directions and stretching in both the vertical and horizontal directions. Of course, these methods may be used in combination. That is, the film may be stretched in the transverse direction, longitudinally, or in both directions with respect to the film forming direction, and when stretched in both directions, simultaneous stretching or sequential stretching may be used. May be. In the case of the so-called tenter method, driving the clip portion by the linear drive method is preferable because smooth stretching can be performed and the risk of breakage and the like can be reduced.

  Moreover, it is preferable from viewpoints, such as expansion of an optical expression area, that the manufacturing method concerning this invention includes the process of extending | stretching the film after the said extending process again.

(Description of optical member)
[Polarizer]
Since the optical film of the present invention has high optical expression, it is preferably used as a retardation film as a protective film for a polarizing plate. The polarizing plate is formed by laminating and laminating a protective film on at least one surface of the polarizer. A conventionally known polarizer can be used. For example, a hydrophilic polymer film such as a polyvinyl alcohol film is treated with a dichroic dye such as iodine and stretched. The bonding of the optical film and the polarizer is not particularly limited, but can be performed with an adhesive made of an aqueous solution of a water-soluble polymer. The water-soluble polymer adhesive is preferably a completely saponified polyvinyl alcohol aqueous solution.

  The film of the present invention is a protective film for polarizing plate / polarizer / protective film for polarizing plate / liquid crystal cell / film of the present invention / polarizer / protective film for polarizing plate, or protective film for polarizing plate / polarizer / It can use preferably by the structure of the film / liquid crystal cell of this invention / film of this invention / polarizer / protective film for polarizing plates. In particular, by bonding to a liquid crystal cell such as a TN type, a VA type, or an OCB type, it is possible to provide a display device that is further excellent in viewing angle and visibility with little coloring. In particular, a polarizing plate using the protective film for a polarizing plate according to the present invention has little deterioration under high temperature and high humidity conditions, and can maintain stable performance for a long time.

[Liquid Crystal Display]
The optical film of the present invention and the polarizing plate using the film can be used for liquid crystal cells and liquid crystal display devices in various display modes. TN (Twisted Nematic), IPS (In-Plane Switching), FLC (Ferroelectric Liquid Crystal), AFLC (Anti-Ferroelectric Liquid Nyst) Various display modes such as HAN (Hybrid Aligned Nematic) have been proposed.

  The OCB mode liquid crystal cell is a liquid crystal display device using a bend alignment mode liquid crystal cell in which rod-like liquid crystalline molecules are aligned in a substantially opposite direction (symmetrically) between an upper portion and a lower portion of the liquid crystal cell. OCB mode liquid crystal cells are disclosed in US Pat. Nos. 4,583,825 and 5,410,422. Since the rod-like liquid crystal molecules are aligned symmetrically between the upper part and the lower part of the liquid crystal cell, the bend alignment mode liquid crystal cell has a self-optical compensation function. The bend alignment mode liquid crystal display device has an advantage of high response speed.

  In a VA mode liquid crystal cell, rod-like liquid crystalline molecules are aligned substantially vertically when no voltage is applied.

  The VA mode liquid crystal cell includes (1) a narrowly defined VA mode liquid crystal cell in which rod-like liquid crystalline molecules are aligned substantially vertically when no voltage is applied, and substantially horizontally when a voltage is applied (Japanese Patent Laid-Open No. Hei 2-). 176625) (2) Liquid crystal cell (SID97, Digest of tech.Papers 28) (1997) 845 in which the VA mode is converted into a multi-domain (MVA mode) for widening the viewing angle. ), (3) a liquid crystal cell in a mode (n-ASM mode) in which rod-like liquid crystalline molecules are substantially vertically aligned when no voltage is applied and twisted multi-domain alignment is applied when a voltage is applied (Sharp Technical Report No. 80, page 11); (4) A SURVAVAL mode liquid crystal cell (Monthly Display May 14th page (1999)) is included.

  The VA mode liquid crystal display device includes a liquid crystal cell and two polarizing plates disposed on both sides thereof. The liquid crystal cell carries a liquid crystal between two electrode substrates. In one aspect of the transmission type liquid crystal display device of the present invention, the film of the present invention is disposed between the liquid crystal cell and one polarizing plate, or between the liquid crystal cell and both polarizing plates. Arrange two.

  In another aspect of the transmissive liquid crystal display device according to the present invention, an optical compensation sheet made of the film of the present invention is used as a transparent protective film for a polarizing plate disposed between a liquid crystal cell and a polarizer. The above optical compensation sheet may be used only for the protective film (between the liquid crystal cell and the polarizer) of one polarizing plate, or two (between the liquid crystal cell and the polarizer) of both polarizing plates. You may use said optical compensation sheet for a sheet of protective film. When the optical compensation sheet is used for only one polarizing plate, it is particularly preferable to use it as a protective film for the liquid crystal cell side of the backlight side polarizing plate of the liquid crystal cell. For the lamination to the liquid crystal cell, the film of the present invention is preferably on the VA cell side. The protective film may be a normal optical film, and is preferably thinner than the film of the present invention. For example, 40-60 μm is preferable, and examples include, but are not limited to, commercially available KC4UY (40 μm manufactured by Konica Minolta Opto), KC5UX (60 μm manufactured by Konica Minolta Opto), and the like.

  The features of the present invention will be described more specifically with reference to examples and comparative examples.

<Preparation of laminated film>
(Preparation of composition solution for each layer)
(First layer: A layer)
Cellulose ester A 100 parts by mass Silica fine particles 0.13 parts by mass Methylene chloride 314 parts by mass Ethanol 56 parts by mass (second layer: C layer)
Cellulose ester C 100 parts by mass Methylene chloride 314 parts by mass Ethanol 56 parts by mass (third layer: B layer)
Cellulose ester B 100 parts by weight Methylene chloride 314 parts by weight Ethanol 56 parts by weight (Fourth layer: C layer)
Cellulose ester C 100 parts by mass Methylene chloride 314 parts by mass Ethanol 56 parts by mass (Fifth layer: A layer)
Cellulose ester A 100 parts by mass Silica fine particles 0.13 parts by mass Methylene chloride 314 parts by mass Ethanol 56 parts by mass The details of cellulose esters A, B, and C are as shown in Table 1.

<Fine particle dispersion>
Silica fine particles (Aerosil R972V manufactured by Nippon Aerosil Co., Ltd.) 11 parts by mass Ethanol 89 parts by mass The above was stirred and mixed with a dissolver for 50 minutes, and then dispersed with Manton Gorin.

<Fine particle additive solution>
The following cellulose ester was added to a dissolution tank containing methylene chloride and heated to completely dissolve, and this was then added to Azumi Filter Paper No. Filtered using 244. The fine particle dispersion was slowly added thereto while sufficiently stirring the filtered cellulose ester A solution. Further, the particles were dispersed by an attritor so that the secondary particles had a predetermined particle size. This was filtered through Finemet NF manufactured by Nippon Seisen Co., Ltd. to prepare a fine particle additive solution.

Methylene chloride 99 parts by weight Cellulose ester A 4 parts by weight Fine particle dispersion 11 parts by weight The cellulose ester resin solution of the first layer and the fifth layer was filtered using filter paper (Azumi Filter Paper Co., Ltd., Azumi Filter Paper No. 244). Thereafter, the fine particle addition liquid was mixed with respect to cellulose ester A so as to be 0.13 parts by mass.

  These 1st-5th layer cellulose-ester resin solutions were formed into a film in 5 layer co-casting equipment.

  In addition, in FIG. 1, sectional drawing which shows the principal part of the casting die 1 of the 5-layer co-casting equipment used with the solution casting method is shown. Here, the casting die 1 is a feed block system having a single slot, and can form five layers simultaneously. Two feed blocks 2 and 3 are placed on the back of the casting die 1, and the feed blocks 2 and 3 have dope supply ports 2a, 2b, 3a to 3c. Dopes (not shown) for forming the first to fifth layers are supplied from the supply ports 2a, 2b, 3a to 3c, respectively. Inside the feed block 3, the slots that continue from the supply ports 3a to 3c merge, and further, inside the feed block 2, the dope from the feed block 3 and the dope from the supply ports 2a and 2b form five layers. The five types of dope that have joined together are simultaneously cast from the tip lip 6 to the drum (band) 7 as a support through a single slot 5.

(Punching test)
About each obtained film, the film was cut | disconnected perpendicularly and the shear cut surface was observed visually. Moreover, the generation | occurrence | production state of the cutting waste was investigated in that case. The processing characteristics of the film were evaluated in three stages, ◎, ○, and ×.
◎: There is almost no bulge on a smooth surface. ○: There are some irregularities but there is no problem in actual use. ×: Many surfaces are rolled up (phase difference measurement).
Using an automatic birefringence meter KOBRA-WR (manufactured by Oji Scientific Instruments Co., Ltd.), the film was allowed to stand for 24 hours in an environment of 23 ° C. and 55% RH, and then the retardation of the film at a wavelength of 590 nm was measured in the same environment. .

  Retardation was calculated using the following formula (i).

Formula (i): Rt = ((nx + ny) / 2−nz) × d
(Where nx is the refractive index in the slow axis direction in the film plane, ny is the refractive index in the direction perpendicular to the slow axis in the plane, nz is the refractive index in the film thickness direction, and d is the thickness of the film. (Nm)
(Dimensional stability)
The hygroscopicity of the optical film shall be evaluated by dimensional change (dimensional stability) with respect to humidity change.

  The following method is used as an evaluation method of dimensional change with respect to humidity change.

  In the casting direction of the produced optical film, two marks (crosses) were attached and treated at 60 ° C. and 90% RH for 1000 hours, and the distance between the mark (cross) before and after treatment was measured with an optical microscope. Obtain the dimensional change rate (%). The dimensional change rate (%) is expressed by the following formula.

Dimensional change rate (%) = [(a1-a2) / a1] × 100
a1: Distance before heat treatment a2: Distance after heat treatment When an optical film is used as a protective film for a polarizing plate of a liquid crystal display device, unevenness or a change in retardation value occurs in the protective film for liquid crystal polarizing plate due to a dimensional change due to moisture absorption. This causes problems such as a decrease in contrast and uneven color. In particular, the above problem becomes significant when the polarizing plate protective film is used in a liquid crystal display device used outdoors. However, if the dimensional change rate (%) under the above conditions is less than 0.5%, it can be evaluated as a protective film for a liquid crystal polarizing plate exhibiting sufficiently low hygroscopicity. Furthermore, it is preferable that it is less than 0.3%.

(Internal haze)
The internal haze was measured according to JIS K-7136.

  The internal haze is a haze generated by a scattering factor inside the film, and the internal is a portion of 5 μm or more from the film surface.

  The internal haze is measured by a haze meter by dropping a solvent having a refractive index of film refractive index ± 0.05 on the film interface so that the haze on the film surface can be ignored as much as possible.

<Internal haze measuring device>
Haze meter (turbidity meter): Model NDH 2000, manufactured by Nippon Denshoku Co., Ltd. Light source: 5V9W halogen bulb, light receiving part is a silicon photocell (with a relative sensitivity filter)
The internal haze measurement is performed as follows. This will be described with reference to FIGS.

  First, the blank haze 1 of a measuring instrument other than a film is measured.

  1. Drip a drop (0.05 ml) of glycerin on a cleaned glass slide. At this time, care is taken so that bubbles do not enter the droplet. Glass must be washed with a detergent (see Fig. 2).

  2. Place the cover glass on top of it. Glycerin spreads without pressing the cover glass.

  3. Set on a haze meter and measure blank haze 1. Next, the haze 2 including the sample is measured.

  4). 0.05 ml of glycerin is dropped on the slide glass (see FIG. 2).

  5. A sample film to be measured is placed thereon (see FIG. 3).

  6). 0.05 ml of glycerin is dropped on the sample film (see FIG. 4).

  7). A cover glass is placed thereon (see FIG. 5).

  8). Set in a haze meter and measure haze 2.

  9. (Haze 2) − (Haze 1) = (Internal haze according to the present invention) is calculated.

  The glass and glycerin used in the above measurement are as follows.

Glass: MICRO SLIDE GLASS S9213 MATUNAMI
Glycerin: Kanto Chemical Deer Special Grade The above evaluation results are summarized in Table 2.

  From the results shown in Table 2, the examples of the present invention are superior in the peel resistance, internal haze resistance, and dimensional stability compared to the comparative examples, and have an appropriate retardation development and a method for producing the same. It can be seen that can be provided.

1 Casting die 2, 3 Feed block 2a, 2b, 3a, 3b, 3c Supply port 5 Slot 6 Tip lip 7 Band (drum)

Claims (6)

  Cellulose ester resin A layer, cellulose ester resin B layer, and cellulose ester resin C layer (referred to as “A layer”, “B layer”, and “C layer”, respectively) are A layer, C layer, B layer, C An optical film formed by laminating a layer and an A layer in this order, wherein the average acyl group substitution degree of the cellulose ester of the A layer is in the range of 2.8 to 3.0, and the cellulose ester of the B layer The average acyl group substitution degree is in the range of 1.0 to 2.5, and the average acyl group substitution degree of the cellulose ester of the C layer is in the range of more than 2.5 and less than 2.8. Optical film.   2. The optical film according to claim 1, wherein the cellulose ester resin C layer is thicker than any resin layer adjacent to the C layer.   The thickness of the cellulose ester resin A layer is in the range of 1 to 3 µm, and the thickness of the cellulose ester resin B layer is thicker than the thickness of the cellulose ester resin A layer. 2. The optical film according to 2.   The optical film according to any one of claims 1 to 3, wherein the cellulose ester resin A layer contains a matting agent.   The optical film according to any one of claims 1 to 4, wherein a thickness of the entire optical film is in a range of 40 to 60 µm.   It is a manufacturing method of the optical film which manufactures the optical film as described in any one of Claim 1- Claim 4, Comprising: It has the process of carrying out lamination | stacking film formation by the solution co-casting method, Optical film characterized by the above-mentioned. Manufacturing method.

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