JP2010001383A - Optical film and polarizing plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical film which excels in the inhibition of haze when the optical film is stretched at a high draw ratio on widening the film and slit aptitude and a polarizing plate which inhibits dimensional change, warpage, and the occurrence of color shading and excels in face contrast. <P>SOLUTION: The optical film comprises at least a cellulose ester and a (meth)acrylic copolymer or a sugar ester compound obtained by esterifying all OH groups or part of OH groups of a compound having at least one furanose structure or pyranose structure, 1-12 furanose structures or pyranose structures being connected with one another and has an average acetyl substitution degree in the above entire cellulose ester of ≥1.9, an elongation at breakage on stretching in a 23°C, 55%RH environment of not less than 10% in both the TD direction and the MD direction, and a tear strength of not less than 40 mN in both the TD direction and the MD direction. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical film and a polarizing plate using the same, and more specifically, to an optical film excellent in suppression of haze and slit suitability when stretched at a high magnification when the optical film is widened, and the optical film The present invention relates to a polarizing plate excellent in front contrast, in which dimensional change, warpage, and color unevenness generation are suppressed.

  In recent years, the demand for liquid crystal display devices (hereinafter also referred to as LCDs) is vigorous due to the widespread use of liquid crystal displays mounted on automobiles, large liquid crystal television displays, mobile phones, notebook computers, and the like. In such LCDs, various optical films such as a polarizing film and a retardation film are used.

  The demand for LCDs is increasing, and there is a demand for thinner, lighter, and more productive polarizing plates that are used in line with this demand. Furthermore, along with the increase in the screen size of LCDs, the optical film as a member is also required to be thinned and widened with high production, and studies to improve film properties centering on mechanical strength properties are also being promoted. Yes.

  However, as the optical film becomes thinner, widened with higher production, higher speed, and longer winding, failures (eg, haze generation, slit defects, etc.) that were not found in conventional products become apparent. It has become. These failures are failures that must be avoided because they reduce the yield of the optical film and cause defective failures during polarizing plate processing and panel processing.

  In particular, it has been found that when the draw ratio is increased in order to increase the width, a failure that causes a slit failure such as a waved cut surface at the time of slitting is likely to occur.

  It is usually performed to add particles such as silica to the optical film for handling properties such as slit property, imparting smoothness between optical films, transportability, winding quality, and sticking failure prevention (Patent Document 1). ).

  However, if the stretching ratio is increased in order to widen the optical film as described above, a sufficient effect cannot be expected only by the technique of adding the particles.

  On the other hand, it was also found that a polarizing plate using such a widened optical film has problems in physical properties and optical characteristics such as dimensional change, warpage, color unevenness, and decrease in front contrast.

Therefore, an immediate solution to these problems is desired.
JP 2002-194106 A

  Accordingly, an object of the present invention is to provide an optical film excellent in suppression of haze and slit suitability when stretched at a high magnification when the optical film is widened. Another object of the present invention is to provide a polarizing plate excellent in front contrast, in which dimensional change, warpage, and color unevenness generation using the optical film are suppressed.

  The above object of the present invention is achieved by the following configurations.

1. All or part of OH groups in at least a cellulose ester, a (meth) acrylic copolymer, or a compound having at least one furanose structure or pyranose structure and having 1 to 12 furanose structures or pyranose structures bonded thereto An optical film containing an esterified sugar ester compound,
The average acetyl group substitution degree of the whole cellulose ester is ≧ 1.9,
The elongation at break when pulled under an environment of 23 ° C. and 55% RH is 10% or more in both the direction orthogonal to the transport direction (TD direction) and the transport direction (MD direction).
And the tear strength in 23 degreeC55% RH environment is 40 mN or more in TD direction and MD direction, The optical film characterized by the above-mentioned.

  2. The elastic modulus of the optical film is 4.0 GPA or less in both the TD direction and the MD direction (measured in an environment of 23 ° C. and 55 RH%), and the elastic modulus in the TD direction / elastic modulus in the MD direction = 0.90 to 1.1. 2. The optical film as described in 1 above.

  3. 3. The optical film according to 2 above, wherein the optical film has a width of 1.6 to 4 m and is stretched by 1.07 to 2.0 times in at least one of the TD direction or the MD direction. .

4). A polarizing plate having optical films A and B satisfying a) and b) below with a polarizer interposed therebetween.
a) All or one of OH groups in a compound having at least one cellulose ester and a (meth) acrylic copolymer, or at least one furanose structure or pyranose structure and 1 to 12 furanose structures or pyranose structures bonded to each other. An optical film containing a sugar ester compound obtained by esterifying a part,
The average acetyl group substitution degree of the whole cellulose ester is ≧ 1.9,
The elongation at break when pulled in a 23 ° C. and 55% RH environment is 20% or more in both the direction orthogonal to the transport direction (TD direction) and the transport direction (MD direction).
And the optical film A characterized by the tear strength in 23 degreeC55% RH environment being 40 mN or more in TD direction and MD direction.
b) Optical film B characterized by the following retardation Ro = 20 to 100 nm and Rt = 70 to 300 nm.

Ro = (nx−ny) × d
Rt = {(nx + ny) / 2−nz} × d
In the formula, Ro is the retardation value in the film plane, Rt is the retardation value in the film thickness direction, 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 Represents the refractive index in the thickness direction of the film, and d represents the thickness (nm) of the film.

  ADVANTAGE OF THE INVENTION According to this invention, the optical film excellent in suppression of haze at the time of extending | stretching at high magnification when widening an optical film and slit suitability can be provided. In addition, it is possible to provide a polarizing plate excellent in front contrast, in which dimensional change, warpage, and color unevenness generation using the optical film are suppressed.

  The best mode for carrying out the present invention will be described in detail below, but the present invention is not limited thereto.

The optical film of the present invention comprises at least a cellulose ester, a (meth) acrylic copolymer, or an OH in a compound having at least one furanose structure or pyranose structure and 1 to 12 of the furanose structure or pyranose structure bonded thereto. An optical film containing a sugar ester compound obtained by esterifying all or part of a group,
The average acetyl group substitution degree of the whole cellulose ester is ≧ 1.9,
The elongation at break when pulled under an environment of 23 ° C. and 55% RH is 10% or more in both the direction orthogonal to the transport direction (TD direction) and the transport direction (MD direction).
And tear strength in 23 degreeC55% RH environment is 40 mN or more in TD direction and MD direction, It is characterized by the above-mentioned.

  If the width of the optical film is widened by 1.6 m or more in order to improve productivity, a problem that has not occurred in the past occurs. For example, haze generation and slit failure. Moreover, when a polarizing plate is produced using such an optical film, problems such as dimensional changes, warpage, color unevenness, and a decrease in front contrast occur.

  In the present invention, as a result of earnest studies on these problems, at least one of the cellulose ester and the (meth) acrylic copolymer, or at least one furanose structure or pyranose structure, the furanose structure or pyranose structure is 1 to 12. And a sugar ester compound obtained by esterifying all or a part of OH groups in the individually bonded compound, and using a cellulose ester having an average degree of acetyl group substitution of the whole cellulose ester ≧ 1.9, at 23 ° C. and 55% RH The elongation at break when pulled in an environment is 10% or more in both the direction orthogonal to the transport direction (TD direction) and the transport direction (MD direction), and tearing in a 23 ° C. and 55% RH environment The type of cellulose ester, the type of additive and the additive so that the strength is 40 mN or more in both the TD direction and the MD direction. By adjusting the amount and stretching conditions, it has an effect on the occurrence of haze and slit defects, and further suppresses the occurrence of dimensional change, warpage and color unevenness, and an optical film having a high front contrast, and a polarizing plate It is as soon as it has been found that it is obtained and the present invention has been made.

  Hereinafter, the present invention will be described in detail.

<Elongation at break, tear strength>
The elongation at break and tear strength of the optical film focused on in the present invention can be taken as numerical values representing the hardness and brittleness of the film, and by controlling this to a certain range, the slit film aptitude and dimensional stability of the optical film can be obtained. It has been found that the property and warpage can be improved.

(Elongation at break)
The optical film of the present invention has an elongation at break of 23 ° C. and 55% RH, and the direction perpendicular to the transport direction (TD direction) and the transport direction (MD direction) are both 10% or more. More preferably, it is in the range of ˜80%, particularly preferably 10˜50%.

  The elongation at break is measured in an environment of 23 ° C. and 55% RH in accordance with the method described in JIS K 7127. The sample width is cut out to 10 mm and the length is 130 mm, the distance between chucks is set to 100 mm at an arbitrary temperature, and a tensile test is performed at a pulling speed of 100 mm / min.

  As the elongation at break, for example, A & D Tensilon universal testing machine RTF series can be used.

(Tear strength)
The tear strength of the optical film of the present invention is 40 mN or more in both the direction orthogonal to the transport direction (TD direction) and the transport direction (MD direction). Preferably it is 55 mN or more, More preferably, it is 80 mN or more.

  The tear strength can be measured according to ISO 6383 / 2-1983 after the film is conditioned at a temperature of 23 ° C. and a relative humidity of 55% RH for 24 hours, then cut into a sample size of 50 mm × 64 mm.

  For example, Yasuda Seiki Seisakusho Elmendorf Tear Strength Tester can be used to measure the tear strength.

  The elongation at break and tear strength of the optical film deteriorate as the stretching is increased. The reason is considered to be that microvoids generated due to stretching stress or poor compatibility with the plasticizer during stretching, and molecular structures such as cellulose and plasticizer due to stretching stress are oriented in a specific direction. Therefore, as an improvement means, it is possible to select a (meth) acrylic copolymer having good compatibility with cellulose, or a sugar ester compound as a plasticizer, a stretching stress, a stretching direction, a stretching ratio, a stretching temperature, etc. Controlling the molecular orientation direction can be mentioned.

  In particular, when the maximum stress in stretching is 20 MPa or less, it is preferable that the film does not cause void generation or film weakening due to molecular orientation, and the slit property is improved. The maximum stress is more preferably 10 MPa or less.

  In order to reduce the stress during stretching to the above range, the stretching temperature is preferably 140 ° C. or higher, and more preferably 160 ° C. or higher. The average acetyl substitution degree of cellulose is preferably 2.95 or less, but if it is less than 1.9, the film becomes weak and haze increases. The reason is unknown, but it is assumed that the interaction between cellulose molecules weakens and voids are likely to occur.

  The draw ratio is preferably 1.07 times or more and more preferably 1.2 times or more from the viewpoint of productivity. However, when it exceeds 2.0 times, brittle deterioration occurs, which is not preferable.

  Furthermore, in order to suppress the arrangement of molecules in a certain direction, it is also preferable to stretch in two or more directions.

  The maximum stress during stretching can be measured by, for example, a method of attaching a load cell to a clip portion of a tenter that holds the film.

  The absolute value of stress during stretching can be calculated from load measurement, film thickness during stretching, and distance between clips. The value obtained by dividing the maximum load during stretching by the film thickness and the distance between clips is the maximum stress absolute value during stretching, and is expressed in MPa.

<< (Meth) acrylic copolymer >>
The (meth) acrylic copolymer (hereinafter, also referred to as acrylic polymer) contained in the optical film of the present invention is effective for suppressing haze increase, slit failure, dimensional change, and warpage during stretching. It is preferable to contain an acrylic polymer having a weight average molecular weight of 500 or more and 30000 or less. Among them, an ethylenically unsaturated monomer Xa having no aromatic ring and no hydrophilic group in the molecule and hydrophilic without an aromatic ring in the molecule. Polymer X having a weight average molecular weight of 5,000 to 30,000 obtained by copolymerization with ethylenically unsaturated monomer Xb having a functional group, more preferably an ethylenically unsaturated group having no aromatic ring and no hydrophilic group in the molecule Weight average molecular weight of 500 obtained by copolymerizing monomer Xa and ethylenically unsaturated monomer Xb having a hydrophilic group and having no aromatic ring in the molecule 30000 and the following polymers X, preferably contains a weight average molecular weight of 500 to 3,000 of the polymer Y obtained by polymerization of ethylenic unsaturated monomer Ya not having an aromatic ring.

<Polymer X, Polymer Y>
The polymer X of the present invention is a copolymer of an ethylenically unsaturated monomer Xa having no aromatic ring and a hydrophilic group in the molecule and an ethylenically unsaturated monomer Xb having no aromatic ring and having a hydrophilic group in the molecule. The polymer having a weight average molecular weight of 5,000 to 30,000.

  Preferably, Xa is an acrylic or methacrylic monomer that does not have an aromatic ring and a hydrophilic group in the molecule, and Xb is an acrylic or methacrylic monomer that does not have an aromatic ring in the molecule and has a hydrophilic group.

  The polymer X of the present invention is represented by the following general formula (X).

Formula (X)
-(Xa) m- (Xb) n- (Xc) p-
More preferably, it is a polymer represented by the following general formula (X-1).

Formula (X-1)
_{- [CH 2 -C (-R 1} ) (- CO 2 R 2)] m- [CH 2 -C (-R 3) (- CO 2 R 4 -OH) -] n- [Xc] p-
(In the formula, R ₁ and R ₃ represent H or CH _3. R ₂ represents an alkyl group having 1 to 12 carbon atoms or a cycloalkyl group. R ₄ represents —CH ₂ — or —C ₂ H ₄ —. Or -C ₃ H _6- , Xc represents a monomer unit that can be polymerized to Xa and Xb, m, n and p represent molar composition ratios, where m ≠ 0, n ≠ 0, m + n + p = 100 .)
Although the monomer as a monomer unit which comprises the polymer X of this invention is mentioned below, it is not limited to this.

  In X, the hydrophilic group means a group having a hydroxyl group or an ethylene oxide chain.

  Examples of the ethylenically unsaturated monomer Xa having no aromatic ring and no hydrophilic group in the molecule include methyl acrylate, ethyl acrylate, propyl acrylate (i-, n-), and butyl acrylate (n-, i- , S-, t-), pentyl acrylate (n-, i-, s-), hexyl acrylate (n-, i-), heptyl acrylate (n-, i-), octyl acrylate (n- I-), nonyl acrylate (n-, i-), myristyl acrylate (n-, i-), acrylic acid (2-ethylhexyl), acrylic acid (ε-caprolactone), acrylic acid (2-hydroxyethyl) ), Acrylic acid (2-ethoxyethyl), or the like, or those obtained by replacing the acrylic acid ester with a methacrylic acid ester. Among these, methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, and propyl methacrylate (i-, n-) are preferable.

  The ethylenically unsaturated monomer Xb having no aromatic ring in the molecule and having a hydrophilic group is preferably acrylic acid or methacrylic acid ester as a monomer unit having a hydroxyl group. For example, acrylic acid (2-hydroxyethyl), List acrylic acid (2-hydroxypropyl), acrylic acid (3-hydroxypropyl), acrylic acid (4-hydroxybutyl), acrylic acid (2-hydroxybutyl), or those in which these acrylic acids are replaced by methacrylic acid. Acrylic acid (2-hydroxyethyl) and methacrylic acid (2-hydroxyethyl), acrylic acid (2-hydroxypropyl), and acrylic acid (3-hydroxypropyl) are preferable.

  Xc is not particularly limited as long as it is an ethylenically unsaturated monomer other than Xa and Xb and copolymerizable, but preferably has no aromatic ring.

  The molar composition ratio m: n of Xa, Xb and Xc is preferably in the range of 99: 1 to 65:35, more preferably in the range of 95: 5 to 75:25. P of Xc is 0-10. Xc may be a plurality of monomer units.

  When the molar composition ratio of Xa is large, the compatibility with the cellulose ester is improved, but the retardation value Rt in the film thickness direction is increased. When the molar composition ratio of Xb is large, the compatibility is deteriorated, but the effect of reducing Rt is high. Further, if the molar composition ratio of Xb exceeds the above range, haze tends to occur during film formation, and it is preferable to optimize these and determine the molar composition ratio of Xa and Xb.

  As for the molecular weight of the polymer X, the weight average molecular weight is from 5,000 to 30,000, more preferably from 8,000 to 25,000.

  By setting the weight average molecular weight to 5,000 or more, it is preferable because advantages such as little dimensional change under high temperature and high humidity as an optical film and little warpage when used as a protective film for a polarizing plate are obtained. When the weight average molecular weight is within 30000, the compatibility with the cellulose ester is further improved, bleeding out under high temperature and high humidity, and further haze generation during stretching are suppressed.

  The weight average molecular weight of the polymer X of the present invention can be adjusted by a known molecular weight adjusting method. Examples of such a molecular weight adjusting method include a method of adding a chain transfer agent such as carbon tetrachloride, lauryl mercaptan, octyl thioglycolate, and the like. The polymerization temperature is usually room temperature to 130 ° C., preferably 50 ° C. to 100 ° C., and this temperature or the polymerization reaction time can be adjusted.

  The measuring method of a weight average molecular weight can be based on the following method.

(Weight average molecular weight measurement method)
The weight average molecular weight Mw was measured using gel permeation chromatography.

  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 (manufactured by GL Sciences)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corp.) Mw = 100000-500 calibration curves with 13 samples were used. Thirteen samples are used at approximately equal intervals.

  The polymer Y of the present invention is a polymer having a weight average molecular weight of 500 or more and 3000 or less obtained by polymerizing an ethylenically unsaturated monomer Ya having no aromatic ring. A weight average molecular weight of 500 or more is preferable because the residual monomer of the polymer is reduced. Moreover, it is preferable to set it as 3000 or less in order to maintain retardation value Rt fall performance. Ya is preferably an acrylic or methacrylic monomer having no aromatic ring.

  The polymer Y of the present invention is represented by the following general formula (Y).

General formula (Y)
-(Ya) k- (Yb) q-
More preferably, it is a polymer represented by the following general formula (Y-1).

General formula (Y-1)
_{- [CH 2 -C (-R 5} ) (- CO 2 R 6)] k- [Yb] q-
(In the formula, R ₅ represents H or CH _3. R ₆ represents an alkyl group or a cycloalkyl group having 1 to 12 carbon atoms. Yb represents a monomer unit copolymerizable with Ya. K and q Represents a molar composition ratio, where k ≠ 0 and k + q = 100.)
Yb is not particularly limited as long as it is an ethylenically unsaturated monomer copolymerizable with Ya. Yb may be plural. k + q = 100, q is preferably 0-30.

  The ethylenically unsaturated monomer Ya constituting the polymer Y obtained by polymerizing an ethylenically unsaturated monomer having no aromatic ring is, for example, methyl acrylate, ethyl acrylate, propyl acrylate (i- , N-), butyl acrylate (n-, i-, s-, t-), pentyl acrylate (n-, i-, s-), hexyl acrylate (n-, i-), heptyl acrylate (N-, i-), octyl acrylate (n-, i-), nonyl acrylate (n-, i-), myristyl acrylate (n-, i-), cyclohexyl acrylate, acrylic acid (2- Ethyl hexyl), acrylic acid (ε-caprolactone), acrylic acid (2-hydroxyethyl), acrylic acid (2-hydroxypropyl), acrylic acid (3-hydroxypropiyl) ), Acrylic acid (4-hydroxybutyl), acrylic acid (2-hydroxybutyl), methacrylic acid ester, the above acrylic acid ester changed to methacrylic acid ester; unsaturated acid, for example, acrylic acid, methacrylic acid And maleic anhydride, crotonic acid, itaconic acid and the like.

  Yb is not particularly limited as long as it is an ethylenically unsaturated monomer copolymerizable with Ya. Examples of vinyl esters include vinyl acetate, vinyl propionate, vinyl butyrate, vinyl valerate, vinyl pivalate, and vinyl caproate. Vinyl caprate, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, vinyl cyclohexanecarboxylate, vinyl octylate, vinyl methacrylate, vinyl crotonate, vinyl sorbate, vinyl cinnamate and the like are preferred. Yb may be plural.

  In order to synthesize the polymers X and Y, it is difficult to control the molecular weight in normal polymerization, and it is desirable to use a method that can align the molecular weight as much as possible by a method that does not increase the molecular weight too much. Such polymerization methods include a method using a peroxide polymerization initiator such as cumene peroxide and t-butyl hydroperoxide, a method using a polymerization initiator in a larger amount than normal polymerization, and a mercapto compound in addition to the polymerization initiator. And a method using a chain transfer agent such as carbon tetrachloride, a method using a polymerization terminator such as benzoquinone and dinitrobenzene in addition to the polymerization initiator, and further disclosed in JP 2000-128911 or 2000-344823. Examples thereof include a compound having one thiol group and a secondary hydroxyl group, or a bulk polymerization method using a polymerization catalyst in which the compound and an organometallic compound are used in combination. In particular, the polymer Y uses a compound having a thiol group and a secondary hydroxyl group in the molecule as a chain transfer agent. The polymerization method of use is preferred. In this case, the terminal of the polymer Y has a hydroxyl group and a thioether resulting from the polymerization catalyst and the chain transfer agent. The compatibility between Y and cellulose ester can be adjusted by this terminal residue.

  The hydroxyl values of the polymers X and Y are preferably 30 to 150 [mg KOH / g].

(Measurement method of hydroxyl value)
This measurement conforms to JIS K 0070 (1992). This hydroxyl value is defined as the number of mg of potassium hydroxide required to neutralize acetic acid bonded to a hydroxyl group when 1 g of a sample is acetylated. Specifically, sample Xg (about 1 g) is precisely weighed in a flask, and 20 ml of an acetylating reagent (a solution obtained by adding pyridine to 20 ml of acetic anhydride to 400 ml) is accurately added thereto. An air cooling tube is attached to the mouth of the flask and heated in a glycerin bath at 95-100 ° C. After 1 hour and 30 minutes, the mixture is cooled, 1 ml of purified water is added from an air condenser, and acetic anhydride is decomposed into acetic acid. Next, titration is performed with a 0.5 mol / L potassium hydroxide ethanol solution using a potentiometric titrator, and the inflection point of the obtained titration curve is set as the end point. Further, as a blank test, titration is performed without a sample, and an inflection point of the titration curve is obtained. The hydroxyl value is calculated by the following formula.

Hydroxyl value = {(BC) × f × 28.05 / X} + D
(Wherein B is the amount of 0.5 mol / L potassium hydroxide ethanol solution used in the blank test (ml), and C is the amount of 0.5 mol / L potassium hydroxide ethanol solution used in the titration (ml). F is a factor of 0.5 mol / L potassium hydroxide ethanol solution, D is an acid value, and 28.05 is 1/2 of 1 mol amount of potassium hydroxide 56.11)
The above-mentioned polymer X and polymer Y are both excellent in compatibility with cellulose ester, excellent in productivity without evaporation and volatilization, good retention as a protective film for polarizing plates, low moisture permeability, and dimensional stability. Are better.

The content of the polymer X and the polymer Y in the cellulose ester film is preferably in a range satisfying the following formulas (i) and (ii). When the content of the polymer X is Xg (mass% = the mass of the polymer X / the mass of the cellulose ester × 100) and the content of the polymer Y is Yg (mass%),
Formula (i) 5 ≦ Xg + Yg ≦ 35 (mass%)
Formula (ii) 0.05 ≦ Yg / (Xg + Yg) ≦ 0.4
A preferable range of the formula (i) is 10 to 25% by mass.

  If the total amount of the polymer X and the polymer Y is 5% by mass or more, the polymer X and the polymer Y sufficiently act to reduce the retardation value Rt. Moreover, if it is 35 mass% or less as a total amount, adhesiveness with a polyvinyl alcohol-type polarizer will be favorable.

  The polymer X and the polymer Y can be directly added and dissolved as a material constituting the dope liquid described later, or can be added to the dope liquid after being previously dissolved in an organic solvent for dissolving the cellulose ester.

<< Compound with furanose structure or pyranose structure >>
The optical film of the present invention includes a sugar ester compound obtained by esterifying all or part of OH groups in a compound having at least one furanose structure or pyranose structure and having 1 to 12 furanose structures or pyranose structures bonded thereto. However, preferred examples of the “compound having at least one furanose structure or pyranose structure and 1 to 12 furanose structures or pyranose structures bonded to each other” include the following. The invention is not limited to these examples.

  Examples include glucose, galactose, mannose, fructose, xylose, arabinose, lactose, sucrose, cellobiose, cellotriose, maltotriose, raffinose, and the like, and those having both a furanose structure and a pyranose structure are particularly preferable. An example is sucrose.

  “A sugar ester compound in which all or part of OH groups in a compound having at least one furanose structure or pyranose structure and 1 to 12 furanose structures or pyranose structures bonded to each other” is synthesized. The monocarboxylic acid used at the time is not particularly limited, and the sugar ester compound used in the present invention is esterified with a known aliphatic monocarboxylic acid, alicyclic monocarboxylic acid, aromatic monocarboxylic acid, or the like. Can be synthesized. The carboxylic acid used may be one type or a mixture of two or more types.

  Preferred aliphatic monocarboxylic acids include acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, 2-ethyl-hexanecarboxylic acid, undecylic acid, lauric acid , Saturated fatty acids such as tridecylic acid, 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, Examples include unsaturated fatty acids such as undecylenic acid, oleic acid, sorbic acid, linoleic acid, linolenic acid, arachidonic acid and octenoic acid.

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

  Examples of preferable aromatic monocarboxylic acids include aromatic monocarboxylic acids and cinnamic acids having 1 to 5 substituents such as alkyl groups or alkoxy groups introduced into the benzene ring of benzoic acid such as benzoic acid and toluic acid. An aromatic monocarboxylic acid having two or more benzene rings such as benzyl acid, biphenyl carboxylic acid, naphthalene carboxylic acid, tetralin carboxylic acid, or a derivative thereof may be mentioned, and benzoic acid is particularly preferable.

  Details of the production methods of these compounds are described in JP-A Nos. 62-42996 and 10-237084.

  Specific examples are given below, but the present invention is not limited thereto.

  The optical film of the present invention has at least one furanose structure or pyranose structure in order to suppress the occurrence of haze during stretching, and the OH group of the compound in which 1 to 12 of the furanose structure or pyranose structure is bonded. It is preferable to contain 1 to 35% by mass, particularly 5 to 30% by mass, in the optical film, of a sugar ester compound that is all or partly esterified. Within this range, it is preferable that the excellent effects of the present invention are exhibited and there is no bleeding out during storage of the raw material.

《Cellulose ester》
The cellulose ester used in the optical film of the present invention has an average degree of acetyl group substitution of the whole cellulose ester ≧ 1.9. Preferably, in the case of a cellulose ester having a total acyl group substitution degree that satisfies the relations of the formulas (1) to (3) described later, it contributes to lowering the maximum stress during stretching and obtains the effects of the present invention. Can do. On the other hand, if it is less than 1.9, the cellulose ester becomes too soft and the surface becomes rough when the solvent or additive volatilizes, which is not preferable.

  The measuring method of the substitution degree of the acyl group of a cellulose ester can be measured according to ASTM-D817-96.

  The cellulose ester used in the present invention is not particularly limited as long as it satisfies the above acetyl group substitution degree. However, the cellulose ester is a carboxylic acid ester having about 2 to 22 carbon atoms, and may be an aromatic carboxylic acid ester. A lower fatty acid ester of cellulose is preferable. The lower fatty acid in the lower fatty acid ester of cellulose means a fatty acid having 6 or less carbon atoms. The acyl group bonded to the hydroxyl group may be linear or branched or may form a ring. Furthermore, another substituent may be substituted. When the degree of substitution is the same, birefringence decreases when the number of carbon atoms is large, and therefore, the number of carbon atoms is preferably selected from acyl groups having 2 to 6 carbon atoms. The cellulose ester preferably has 2 to 4 carbon atoms, more preferably 2 to 3 carbon atoms.

  The cellulose ester may be an acyl group derived from a mixed acid, and particularly preferably an acyl group having 2 and 3 carbon atoms or 2 and 4 carbon atoms. In the present invention, as a cellulose ester, a mixed fatty acid ester of cellulose to which a propionate group or a butyrate group is bonded in addition to an acetyl group such as cellulose acetate propionate, cellulose acetate butyrate, or cellulose acetate propionate butyrate is used. Can do. The butyryl group forming butyrate may be linear or branched. As the cellulose ester preferably used in the present invention, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, and cellulose acetate phthalate are particularly preferably used.

  Preferred cellulose esters for the present invention are those that simultaneously satisfy the following formulas (1) to (3).

Formula (1) 2.0 <= X + Y <= 3.0
Formula (2) 1.9 <= X <= 3.0
Formula (3) 0 ≦ Y ≦ 1.1
In the formula, X is the degree of substitution of the acetyl group, Y is the degree of substitution of the propionyl group or butyryl group, and X + Y is the degree of substitution of the total acyl group.

  Of these, triacetyl cellulose and cellulose acetate propionate are particularly preferably used. In the case of cellulose acetate propionate, 1.9 ≦ X ≦ 2.5, and preferably 0.2 ≦ Y ≦ 1.0.

  If the substitution degree of the acetyl group is too low, there will be many unreacted parts with respect to the hydroxyl groups of the pyranose ring constituting the skeleton of the cellulose resin, and a large amount of the hydroxyl groups will leave dimensional changes, warpage, and slits. Problems that occur due to a decrease in physical properties of the binder, such as defects, become significant.

  The optical film of the present invention preferably contains two or more kinds of cellulose esters having a weight average molecular weight (Mw) of Mw ≧ 260000 and different Mw of 10,000 or more.

  The smaller the molecular weight of the cellulose ester, the less the haze increases during stretching, but the peelability from the belt during casting tends to deteriorate. Mixing two or more types of cellulose esters with different molecular weights improves the releasability, and at the same time improves the compatibility between acrylic copolymers or sugar ester compounds with furanose or pyranose structures and cellulose esters. Therefore, there is an effect of suppressing haze rise and improving dimensional stability.

  The weight average molecular weight (Mw) is preferably in the range of 260000-500000, more preferably in the range of 290000-400000. The difference in Mw between two or more cellulose esters is preferably 10,000 or more and 100,000 or less, and more preferably 20,000 or more and 50,000 or less.

  The mixing ratio of the low molecular weight cellulose ester and the high molecular weight cellulose ester can be in the range of 99: 1 to 1:99, preferably 90:10 to 50:50, more preferably 90:10 to 60:40. Especially preferably, it is the range of 85: 15-60: 40.

  The weight average molecular weight (Mw) of a cellulose ester can be measured as follows.

  Measured by high performance liquid chromatography under the following conditions.

Solvent: Acetone Column: MPW × 1 (manufactured by Tosoh Corporation)
Sample concentration: 0.2 (mass / volume)%
Flow rate: 1.0 ml / min Sample injection volume: 300 μl
Standard sample: Standard polystyrene Temperature: 23 ° C
Although there is no limitation in particular as a cellulose of the raw material of the cellulose ester used for this invention, Wood pulp (a softwood pulp, a hardwood pulp), a cotton linter, etc. can be used. The Mw of the cellulose ester can be controlled by the type of cellulose and the use of a plurality of raw material celluloses. For example, if esterification is performed using pre-hydrolysis kraft pulp, the Mw of the cellulose ester increases, and if softwood sulfite pulp is used, the Mw tends to decrease. Therefore, cellulose may be used singly or in combination of two or more. For example, softwood pulp and cotton linter or hardwood pulp may be used in combination. As cellulose, usually pulp (particularly softwood pulp) is often used. In addition, the α-cellulose content (% by mass) of cellulose is usually from 94 to 99 (for example, 95 to 99), preferably from about 96 to 98.5 (for example, 97.3 to 98). .

When the acylating agent of the cellulose raw material is an acid anhydride (acetic anhydride, propionic anhydride, butyric anhydride), the cellulose ester according to the present invention uses an organic solvent such as acetic acid or an organic solvent such as methylene chloride. The reaction is carried out using a protic catalyst such as sulfuric acid. When the acylating agent is acid chloride (CH ₃ COCl, C ₂ H ₅ COCl, C ₃ H ₇ COCl), the reaction is carried out using a basic compound such as an amine as a catalyst. Specifically, it can be synthesized with reference to the method described in JP-A-10-45804.

  The average substitution degree of the acyl group at the 6-position of the glucose unit of the cellulose ester used in the present invention is preferably 0.5 to 0.9.

  Unlike the 2nd and 3rd positions, the glucose unit constituting the cellulose ester has a highly reactive primary hydroxyl group, and this primary hydroxyl group is sulfated during the production of cellulose ester using sulfuric acid as a catalyst. Esters are preferentially formed. Therefore, by increasing the amount of the catalytic sulfuric acid in the cellulose estilation reaction, the average substitution degree at the 2nd and 3rd positions of the glucose unit can be increased as compared with the ordinary cellulose ester. Furthermore, if the cellulose is tritylated as necessary, the hydroxyl group at the 6-position of the glucose unit can be selectively protected. Therefore, the trityl group protects the hydroxyl group at the 6-position, and after esterification, the trityl group (protection) The average substitution degree at the 2nd and 3rd positions can be increased from the 6th position of the glucose unit. Specifically, a cellulose ester produced by the method described in JP-A No. 2005-281645 can also be preferably used.

  In the case of acetylcellulose, it is necessary to extend the time for the acetylation reaction in order to increase the acetylation rate. However, if the reaction time is too long, the decomposition proceeds at the same time, and the polymer chain is broken and the acetyl group is decomposed, resulting in undesirable results. Therefore, it is necessary to set the reaction time within a certain range in order to increase the degree of acetylation and suppress decomposition to some extent. It is not appropriate to define the reaction time because the reaction conditions are various and greatly change depending on the reaction apparatus, equipment and other conditions. As the decomposition of the polymer progresses, the molecular weight distribution becomes wider. Therefore, in the case of cellulose ester, the degree of decomposition can be defined by the value of weight average molecular weight (Mw) / number average molecular weight (Mn) that is usually used. In other words, in the process of acetylation of cellulose triacetate, the weight average molecular weight used as one index of the reaction degree for allowing the acetylation reaction to be carried out for a sufficient time for acetylation without being excessively decomposed too much. The value of (Mw) / number average molecular weight (Mn) can be used.

  An example of a method for producing a cellulose ester is shown below: 100 parts by mass of a flocculent linter was crushed as a cellulose raw material, 40 parts by mass of acetic acid was added, and pretreatment activation was performed at 36 ° C. for 20 minutes. Thereafter, 8 parts by mass of sulfuric acid, 260 parts by mass of acetic anhydride and 350 parts by mass of acetic acid were added, and esterification was performed at 36 ° C. for 120 minutes. After neutralization with 11 parts by mass of a 24% magnesium acetate aqueous solution, saponification aging was carried out at 63 ° C. for 35 minutes to obtain acetylcellulose. This was stirred for 160 minutes at room temperature using a 10-fold acetic acid aqueous solution (acetic acid: water = 1: 1 (mass ratio)), then filtered and dried to obtain purified acetylcellulose having an acetyl substitution degree of 2.75. . This acetylcellulose had Mn of 92000, Mw of 156000, and Mw / Mn of 1.7. Similarly, cellulose esters having different degrees of substitution and Mw / Mn ratios can be synthesized by adjusting the esterification conditions (temperature, time, stirring) and hydrolysis conditions of the cellulose ester. The Mw / Mn ratio of the cellulose ester is preferably 1.4 to 5.0.

  The synthesized cellulose ester is preferably purified to remove low molecular weight components or to remove unacetylated or low acetylated components by filtration.

  In the case of mixed acid cellulose ester, it can be obtained by the method described in JP-A-10-45804.

  Cellulose esters are also affected by trace metal components in cellulose esters. These are considered to be related to water used in the production process, but it is preferable that there are few components that can become insoluble nuclei, and metal ions such as iron, calcium, and magnesium contain organic acidic groups. Insoluble matter may be formed by salt formation with a polymer degradation product or the like that may be present, and it is preferable that the amount is small. The iron (Fe) component is preferably 1 ppm or less. As for the calcium (Ca) component, it is easy to form a coordination compound, that is, a complex with an acidic component such as carboxylic acid or sulfonic acid, and many ligands. Starch, turbidity).

  The calcium (Ca) component is 60 ppm or less, preferably 0 to 30 ppm. The magnesium (Mg) component is preferably in the range of 0 to 70 ppm, particularly preferably 0 to 20 ppm, since too much will cause insoluble matter. Metal components such as iron (Fe) content, calcium (Ca) content, magnesium (Mg) content, etc. are pre-processed by completely digesting cellulose ester with micro digest wet cracking equipment (sulfuric acid decomposition) and alkali melting. After being performed, it can be analyzed using ICP-AES (Inductively Coupled Plasma Atomic Emission Spectrometer).

(Plasticizer)
The optical film of the present invention can contain an appropriate amount of a plasticizer as necessary to obtain 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 a polyester 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 is composed of 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.

  The polyhydric alcohol used is represented by the following general formula (1).

Formula (1) R1- (OH) n
(In the formula, R1 represents an n-valent organic group, and n represents a positive integer of 2 or more)
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 thereof include 1,3,5-triol, pinacol, sorbitol, trimethylolpropane, trimethylolethane, xylitol, pentaerythritol, dipentaerythritol and the like. Of these, trimethylolpropane and pentaerythritol 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 preferable in terms of improving moisture permeability and retention. Examples of preferred monocarboxylic acids include the following, but are 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. The use of acetic acid is preferred because the compatibility with the cellulose ester is increased, and it is also preferred 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-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, Examples thereof include unsaturated fatty acids such as oleic 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 those derivatives can be mentioned. In particular, benzoic acid is preferred.

  The molecular weight of the polyhydric alcohol ester is preferably in the range of 300 to 1500, and more preferably in the range of 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. The specific compound of a polyhydric alcohol ester is shown below.

  In addition, trimethylolpropane triacetate, pentaerythritol tetraacetate and the like are also preferably used.

  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.

  Examples of the phosphate ester plasticizer include triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate and the like.

  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 (2).

Formula _{(2) R 2 (COOH)} m (OH) n
(Wherein R ₂ is an (m + n) -valent organic group, m is a positive integer of 2 or more, n is an integer of 0 or more, a COOH group is a carboxyl group, and an OH group is 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 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. 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. And aromatic monocarboxylic acids possessed by them, or derivatives thereof. 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 may be one kind or a mixture of two or more kinds.

  The acid value of the polyvalent carboxylic acid ester compound 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.

(Acid value)
The acid value means the number of milligrams of potassium hydroxide necessary for neutralizing the acid (carboxyl group present in the sample) contained in 1 g of the sample. The acid value is measured according to JIS K0070.

  Examples of particularly preferred polyvalent carboxylic acid ester compounds are shown below, but the present invention is not limited thereto. For example, triethyl citrate, tributyl citrate, acetyl triethyl citrate (ATEC), acetyl tributyl citrate (ATBC), benzoyl tributyl citrate, acetyl triphenyl citrate, acetyl tribenzyl citrate, dibutyl tartrate, diacetyl dibutyl tartrate, Examples include tributyl trimellitic acid and tetrabutyl pyromellitic acid.

  The polyester plasticizer is not particularly limited, and a polyester plasticizer having an aromatic ring or a cycloalkyl ring in the molecule can be used. Although it does not specifically limit as a polyester plasticizer, For example, the aromatic terminal ester plasticizer represented by following General formula (3) can be used.

General formula (3) B- (GA) n-GB
(In the formula, B is a benzene monocarboxylic 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 (3), a benzene monocarboxylic acid residue represented by B and an alkylene glycol residue, oxyalkylene glycol residue or aryl glycol residue represented by G, an alkylene dicarboxylic acid residue or aryl dicarboxylic group represented by A It is composed of an acid residue and can be obtained by a reaction similar to that of a normal polyester plasticizer.

  Examples of the benzene monocarboxylic acid component of the polyester plasticizer include benzoic acid, para-tert-butylbenzoic acid, orthotoluic acid, metatoluic acid, p-toluic acid, dimethylbenzoic acid, ethylbenzoic acid, normal propylbenzoic acid, and aminobenzoic acid. And acetoxybenzoic acid and the like, and these can be used as one kind or a mixture of two or more kinds, respectively.

  Examples of the alkylene glycol component having 2 to 12 carbon atoms of the polyester plasticizer include 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-1,3propanediol (3,3-dimethylolheptane), 3-methyl-1, 5-pentanediol 1,6-hexanediol, 2,2,4-trimethyl 1,3-pentanediol, 2-ethyl 1, -Hexanediol, 2-methyl 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-octadecanediol, etc., and these glycols are one kind or two kinds or more 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.

  In addition, examples of the oxyalkylene glycol component having 4 to 12 carbon atoms of the aromatic terminal ester include diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, and tripropylene glycol. It can be used as a seed or a mixture of two or more.

  Examples of the alkylene dicarboxylic acid component having 4 to 12 carbon atoms of the aromatic terminal ester include succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, and dodecanedicarboxylic acid. These are used as one kind or a mixture of two or more kinds. 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 polyester plasticizer has a number average molecular weight of preferably 300 to 1500, more preferably 400 to 1000. The acid value is 0.5 mgKOH / g or less, the hydroxyl value is 25 mgKOH / g or less, more preferably the acid value is 0.3 mgKOH / g or less, and the hydroxyl value is 15 mgKOH / g or less.

  Hereinafter, synthesis examples of the aromatic terminal ester plasticizer will be shown.

<Sample No. 1 (Aromatic terminal ester sample)>
A reaction vessel was charged with 410 parts of phthalic acid, 610 parts of benzoic acid, 737 parts of dipropylene glycol, and 0.40 part of tetraisopropyl titanate as a catalyst. While refluxing the monohydric alcohol, heating was continued at 130 to 250 ° C. until the acid value became 2 or less, and water produced was continuously removed. Next, the distillate was removed at 200-230 ° C. under reduced pressure of 1.33 × 10 4 Pa to 4 × 10 2 Pa or less, and then filtered to obtain an aromatic terminal ester plasticizer having the following properties. .

Viscosity (25 ° C., mPa · s); 43400
Acid value: 0.2
<Sample No. 2 (Aromatic terminal ester sample)>
Sample No. 1 was used except that 410 parts of phthalic acid, 610 parts of benzoic acid, 341 parts of ethylene glycol, and 0.35 part of tetraisopropyl titanate as a catalyst were used in the reaction vessel. In the same manner as in No. 1, an aromatic terminal ester having the following properties was obtained.

Viscosity (25 ° C., mPa · s); 31000
Acid value: 0.1
<Sample No. 3 (Aromatic terminal ester sample)>
Sample No. 1 was used except that 410 parts of phthalic acid, 610 parts of benzoic acid, 418 parts of 1,2-propanediol, and 0.35 part of tetraisopropyl titanate as the catalyst were used in the reaction vessel. In the same manner as in No. 1, an aromatic terminal ester having the following properties was obtained.

Viscosity (25 ° C., mPa · s); 38000
Acid value: 0.05
<Sample No. 4 (Aromatic terminal ester sample)>
Sample No. 4 was used except that 410 parts of phthalic acid, 610 parts of benzoic acid, 418 parts of 1,3-propanediol, and 0.35 part of tetraisopropyl titanate as a catalyst were used in the reaction vessel. In the same manner as in No. 1, an aromatic terminal ester having the following properties was obtained.

Viscosity (25 ° C., mPa · s); 37000
Acid value: 0.05
Although the specific compound of an aromatic terminal ester plasticizer is shown below, this invention is not limited to this.

(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 light having a wavelength of 400 nm or less, and the transmittance at a wavelength of 370 nm is particularly preferably 10% or less, more preferably 5% or less. 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 made by 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. .

  For example, as the benzotriazole ultraviolet absorber, a compound represented by the following general formula (a) can be used.

In the formula, R ₁ , R ₂ , R ₃ , R ₄ and R ₅ may be the same or different, and are a hydrogen atom, a halogen atom, a nitro group, a hydroxyl group, an alkyl group, an alkenyl group, an aryl group, an alkoxyl group, an acyloxy group. Represents a group, aryloxy group, alkylthio group, arylthio group, mono- or dialkylamino group, acylamino group or 5- to 6-membered heterocyclic group, and R ₄ and R ₅ are closed to form a 5- to 6-membered carbocycle May be.

  Moreover, these groups described above may have an arbitrary substituent.

  Although the specific example of the benzotriazole type ultraviolet absorber used for this invention below is given, this invention is not limited to these.

UV-1: 2- (2'-hydroxy-5'-methylphenyl) benzotriazole UV-2: 2- (2'-hydroxy-3 ', 5'-di-tert-butylphenyl) benzotriazole UV-3 : 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) benzotriazole UV-4: 2- (2'-hydroxy-3 ', 5'-di-tert-butylphenyl)- 5-Chlorobenzotriazole UV-5: 2- (2'-hydroxy-3 '-(3 ", 4", 5 ", 6" -tetrahydrophthalimidomethyl) -5'-methylphenyl) benzotriazole UV-6: 2,2-methylenebis (4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol)
UV-7: 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole UV-8: 2- (2H-benzotriazol-2-yl) -6 (Linear and side chain dodecyl) -4-methylphenol (TINUVIN171)
UV-9: Octyl-3- [3-tert-butyl-4-hydroxy-5- (chloro-2H-benzotriazol-2-yl) phenyl] propionate and 2-ethylhexyl-3- [3-tert-butyl- 4-Hydroxy-5- (5-chloro-2H-benzotriazol-2-yl) phenyl] propionate mixture (TINUVIN 109)
Furthermore, as the benzophenone-based ultraviolet absorber, a compound represented by the following general formula (b) is preferably used.

  In the formula, Y represents a hydrogen atom, a halogen atom or an alkyl group, an alkenyl group, an alkoxyl group, and a phenyl group, and these alkyl group, alkenyl group, and phenyl group may have a substituent. A represents a hydrogen atom, an alkyl group, an alkenyl group, a phenyl group, a cycloalkyl group, an alkylcarbonyl group, an alkylsulfonyl group or a —CO (NH) n-1-D group, and D represents an alkyl group, an alkenyl group or a substituent. Represents a phenyl group which may have m and n represent 1 or 2.

  In the above, the alkyl group represents, for example, a linear or branched aliphatic group having up to 24 carbon atoms, the alkoxyl group represents, for example, an alkoxyl group having up to 18 carbon atoms, and the alkenyl group has, for example, carbon number An alkenyl group up to 16 represents an allyl group, a 2-butenyl group, or the like. In addition, as substituents to alkyl groups, alkenyl groups, and phenyl groups, halogen atoms such as chlorine atoms, bromine atoms, fluorine atoms, etc., hydroxyl groups, phenyl groups (this phenyl group is substituted with alkyl groups or halogen atoms, etc.) May be used).

  Specific examples of the benzophenone-based ultraviolet absorber represented by the general formula (b) are shown below, but the present invention is not limited thereto.

UV-10: 2,4-dihydroxybenzophenone UV-11: 2,2'-dihydroxy-4-methoxybenzophenone UV-12: 2-hydroxy-4-methoxy-5-sulfobenzophenone UV-13: Bis (2-methoxy -4-hydroxy-5-benzoylphenylmethane)
In addition, a discotic compound such as a compound having a 1,3,5 triazine ring, which will be described later, is also preferably used as the ultraviolet absorber.

  It is preferable that the polarizing plate protective film concerning this invention contains 2 or more types of 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 for adding the UV absorber is to add the UV absorber 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 use conditions, etc., but when the dry film thickness of the optical film is 30 to 200 μm, it is 0.5 to 10% by mass with respect to the optical film. Is preferable, and 0.6-4 mass% is still more preferable.

(Fine particles)
The optical film of the present invention preferably contains fine particles.

  As fine particles, examples of inorganic compounds include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, Examples thereof include magnesium silicate and calcium phosphate. Fine particles containing silicon are preferable in terms of low turbidity, and silicon dioxide is particularly preferable.

  The average primary particle diameter of the fine particles is preferably 5 to 400 nm, and more preferably 10 to 300 nm. These may be mainly contained as secondary aggregates having a particle size of 0.05 to 0.3 μm, and may be contained as primary particles without being aggregated if the particles have an average particle size of 100 to 400 nm. preferable. The content of these fine particles in the optical film is preferably 0.01 to 1% by mass, particularly preferably 0.05 to 0.5% by mass. In the case of an optical film having a multilayer structure by the co-casting method, it is preferable to contain fine particles of this addition amount on the surface.

  Silicon dioxide fine particles are commercially available, for example, under the trade names Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600 (above Nippon Aerosil Co., Ltd.). it can.

  Zirconium oxide fine particles are commercially available, for example, under the trade names Aerosil R976 and R811 (manufactured by Nippon Aerosil Co., Ltd.) and can be used.

  Examples of the polymer include silicone resin, fluororesin, and acrylic resin. Silicone resins are preferable, and those having a three-dimensional network structure are particularly preferable. For example, Tospearl 103, 105, 108, 120, 145, 3120, and 240 (manufactured by Toshiba Silicone Co., Ltd.) It is marketed by name and can be used.

  Among these, Aerosil 200V and Aerosil R972V are particularly preferably used because they have a large effect of reducing the friction coefficient while keeping the haze of the optical film low. In the optical film of the present invention, it is preferable that the dynamic friction coefficient of at least one surface is 0.2 to 1.0.

(dye)
A dye may be added to the optical film of the present invention for color adjustment. For example, a blue dye may be added to suppress the yellowness of the film. Preferred examples of the dye include anthraquinone dyes.

  The anthraquinone dye may have an arbitrary substituent at an arbitrary position from the 1st position to the 8th position of the anthraquinone. Preferred substituents include an anilino group, hydroxyl group, amino group, nitro group, or hydrogen atom. In particular, it is preferable to contain a blue dye described in JP-A-2001-154017, particularly an anthraquinone dye.

  Various additives may be batch-added to a dope that is a cellulose ester-containing solution before film formation, or an additive solution may be separately prepared and added in-line. In particular, it is preferable to add a part or all of the fine particles in-line in order to reduce the load on the filter medium.

  When the additive solution is added in-line, it is preferably dissolved in a small amount of cellulose ester in order to improve mixing with the dope. The amount of the cellulose ester is preferably 1 to 10 parts by mass, more preferably 3 to 5 parts by mass with respect to 100 parts by mass of the solvent.

  In order to perform in-line addition and mixing in the present invention, for example, an in-line mixer such as a static mixer (manufactured by Toray Engineering), SWJ (Toray static type in-tube mixer Hi-Mixer) or the like is preferably used.

(Optical film manufacturing method)
Next, the manufacturing method of the optical film of this invention is demonstrated.

  Whether the optical film of the present invention is a film produced by a solution casting method or a film produced by a melt casting method, both can be preferably used.

  Production of the optical film of the present invention by the solution casting method is a step of preparing a dope by dissolving the cellulose ester and the additive in a solvent, a step of casting the dope on an endless metal support that moves infinitely, It is performed by a step of drying the cast dope as a web, a step of peeling from the metal support, a step of stretching or maintaining the width, a step of further drying, and a step of winding up the finished film.

  The process for preparing the dope will be described. The concentration of cellulose ester in the dope is preferably higher because the drying load after casting on the metal support can be reduced. However, if the concentration of cellulose ester is too high, the load during filtration increases and the filtration accuracy is poor. Become. As a density | concentration which makes these compatible, 10-35 mass% is preferable, More preferably, it is 15-25 mass%.

  The solvent used in the dope may be used alone or in combination of two or more, but it is preferable to use a mixture of a good solvent and a poor solvent of cellulose ester in terms of production efficiency, and there are many good solvents. This is preferable from the viewpoint of the solubility of the cellulose ester. The preferable range of the mixing ratio of the good solvent and the poor solvent is 70 to 98% by mass for the good solvent and 2 to 30% by mass for the poor solvent. With a good solvent and a poor solvent, what dissolve | melts the cellulose ester to be used independently is defined as a good solvent, and what poorly swells or does not melt | dissolve is defined as a poor solvent. Therefore, depending on the average acetylation degree (acetyl group substitution degree) of the cellulose ester, the good solvent and the poor solvent change. For example, when acetone is used as the solvent, the cellulose ester acetate ester (acetyl group substitution degree 2.4), cellulose Acetate propionate is a good solvent, and cellulose acetate (acetyl group substitution degree 2.8) is a poor solvent.

  The good solvent is not particularly limited, and examples thereof include organic halogen compounds such as methylene chloride, dioxolanes, acetone, methyl acetate, and methyl acetoacetate. Particularly preferred is methylene chloride or methyl acetate.

  Moreover, although a poor solvent is not specifically limited, For example, methanol, ethanol, n-butanol, cyclohexane, cyclohexanone etc. are used preferably. Moreover, it is preferable that 0.01-2 mass% of water contains in dope. Moreover, the solvent used for melt | dissolution of a cellulose ester collect | recovers the solvent removed from the film by drying at the film-forming process, and uses this again. The recovery solvent may contain trace amounts of additives added to the cellulose ester, such as plasticizers, UV absorbers, polymers, monomer components, etc., but even if these are included, they are preferably reused. Can be purified and reused if necessary.

  A general method can be used as a dissolution method of the cellulose ester when preparing the dope described above. When heating and pressurization are combined, it is possible to heat above the boiling point at normal pressure. It is preferable to stir and dissolve while heating at a temperature that is equal to or higher than the boiling point of the solvent at normal pressure and that the solvent does not boil under pressure, in order to prevent the generation of massive undissolved materials called gels and mamacos. Moreover, after mixing a cellulose ester with a poor solvent and making it wet or swell, the method of adding a good solvent and melt | dissolving is also used preferably.

  The pressurization may be performed by a method of injecting an inert gas such as nitrogen gas or a method of increasing the vapor pressure of the solvent by heating. Heating is preferably performed from the outside. For example, a jacket type is preferable because temperature control is easy.

  The heating temperature with the addition of a solvent is preferably higher from the viewpoint of the solubility of the cellulose ester, but if the heating temperature is too high, the required pressure increases and the productivity deteriorates. A preferable heating temperature is 45 to 120 ° C, more preferably 60 to 110 ° C, and still more preferably 70 ° C to 105 ° C. The pressure is adjusted so that the solvent does not boil at the set temperature.

  Alternatively, a cooling dissolution method is also preferably used, whereby the cellulose ester can be dissolved in a solvent such as methyl acetate.

  Next, this cellulose ester solution is filtered using a suitable filter medium such as filter paper. As the filter medium, it is preferable that the absolute filtration accuracy is small in order to remove insoluble matters and the like, but there is a problem that the filter medium is likely to be clogged if the absolute filtration accuracy is too small. For this reason, a filter medium with an absolute filtration accuracy of 0.008 mm or less is preferable, a filter medium with 0.001 to 0.008 mm is more preferable, and a filter medium with 0.003 to 0.006 mm is still more preferable.

  There are no particular restrictions on the material of the filter medium, and ordinary filter media can be used. However, plastic filter media such as polypropylene and Teflon (registered trademark), and metal filter media such as stainless steel do not drop off fibers. preferable. It is preferable to remove and reduce impurities, particularly bright spot foreign matter, contained in the raw material cellulose ester by filtration.

A bright spot foreign object is placed when two polarizing plates are placed in a crossed Nicols state, an optical film is placed between them, light is applied from one polarizing plate, and the opposite is observed when observed from the other polarizing plate. It is a point (foreign matter) where light from the side appears to leak, and the number of bright spots having a diameter of 0.01 mm or more is preferably 200 / cm ² or less. More preferably, it is 100 pieces / cm < ² > or less, More preferably, it is 50 pieces / m < ² > or less, More preferably, it is 0-10 pieces / cm < ² > or less. Further, it is preferable that the number of bright spots of 0.01 mm or less is small.

  The dope can be filtered by a normal method, but the method of filtering while heating at a temperature not lower than the boiling point of the solvent at normal pressure and in a range where the solvent does not boil under pressure is the filtration pressure before and after filtration. The increase in the difference (referred to as differential pressure) is small and preferable. A preferred temperature is 45 to 120 ° C, more preferably 45 to 70 ° C, and still more preferably 45 to 55 ° C.

  A smaller filtration pressure is preferred. The filtration pressure is preferably 1.6 MPa or less, more preferably 1.2 MPa or less, and further preferably 1.0 MPa or less.

  Here, the dope casting will be described.

  The metal support in the casting (casting) step preferably has a mirror-finished surface. As the metal support, a stainless steel belt or a drum whose surface is plated with a casting is preferably used. The cast width can be 1 to 4 m. Since the width of the optical film of the present invention is preferably 1.6 to 4 m, the cast width is inevitably wide. The surface temperature of the metal support in the casting step is −50 ° C. to a temperature lower than the boiling point of the solvent, and a higher temperature is preferable because the web can be dried faster. May deteriorate. A preferable support body temperature is 0-40 degreeC, and 5-30 degreeC is still more preferable. Alternatively, it is also a preferable method that the web is gelled by cooling and peeled from the drum in a state containing a large amount of residual solvent. The method for controlling the temperature of the metal support is not particularly limited, and there are a method of blowing hot air or cold air, and a method of contacting hot water with the back side of the metal support. It is preferable to use warm water because heat transfer is performed efficiently, so that the time until the temperature of the metal support becomes constant is short. When warm air is used, wind at a temperature higher than the target temperature may be used.

  In order for the optical film to exhibit good flatness, the residual solvent amount when peeling the web from the metal support is preferably 10 to 150% by mass, more preferably 20 to 40% by mass or 60 to 130% by mass. Yes, particularly preferably 20 to 30% by mass or 70 to 120% by mass.

  In the present invention, the amount of residual solvent is defined by the following formula.

Residual solvent amount (% by mass) = {(MN) / N} × 100
M is the mass of a sample collected during or after the production of the web or film, and N is the mass after heating M at 115 ° C. for 1 hour.

  Further, in the optical film drying step, the web is peeled off from the metal support and further dried, and the residual solvent amount is preferably 1% by mass or less, more preferably 0.1% by mass or less, particularly Preferably it is 0-0.01 mass% or less.

  In the film drying process, generally, a roll drying method (a method in which a plurality of rolls arranged on the upper and lower sides are alternately passed through and dried) or a method of drying while transporting the web by a tenter method is adopted.

  In order to produce the optical film of the present invention, the tenter system is stretched in the transport direction (MD direction) where the amount of residual solvent of the web immediately after peeling from the metal support is large, and further, the both ends of the web are gripped with clips or the like. It is preferable to perform stretching in a direction (TD direction) orthogonal to the transport direction.

  In order to stretch in the MD direction immediately after peeling, it is preferable to peel at a peeling tension of 210 N / m or more, particularly preferably 220 to 300 N / m.

  The means for drying the web is not particularly limited, and can be generally performed with hot air, infrared rays, a heating roll, microwave, or the like, but it is preferably performed with hot air in terms of simplicity.

  The drying temperature in the web drying step is preferably 90 ° C to 200 ° C, more preferably 110 ° C to 160 ° C. The drying temperature is preferably increased stepwise.

  Although preferable drying time is based also on drying temperature, 5 minutes-60 minutes are preferable and 10 minutes-30 minutes are more preferable.

  Although the film thickness of an optical film is not specifically limited, 10-200 micrometers is used. In particular, the film thickness is particularly preferably 10 to 100 μm. More preferably, it is 20-80 micrometers.

  The optical film of the present invention has a width of 1 to 4 m. From the viewpoint of productivity, those having a width of 1.6 to 4 m are preferably used, and particularly preferably 1.8 to 3.6 m. If it exceeds 4 m, conveyance becomes difficult.

(Stretching operation, refractive index control)
The optical film of the present invention is preferably stretched at a high magnification in order to widen the width, and even when stretched at a high magnification, generation of haze is suppressed and an optical film excellent in slit suitability can be provided.

  Stretching is also an important operation in adjusting retardation as an optical film. In the optical film of the present invention, the retardation value Ro represented by the following formula is preferably 0 to 20 nm and Rt is preferably −100 to 100 nm, more preferably Ro ≦ 5 nm, −10 nm ≦ Rt ≦ 10 nm. More preferably.

Formula (i) Ro = (nx−ny) × d
Formula (ii) Rt = ((nx + ny) / 2−nz) × d
(In the formula, Ro is the retardation value in the film plane, Rt is the retardation value in the film thickness direction, 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 represents the refractive index in the thickness direction of the film, and d represents the thickness (nm) of the film.)
The refractive index can be obtained at a wavelength of 590 nm under an environment of 23 ° C. and 55% RH using, for example, KOBRA-21ADH (Oji Scientific Instruments).

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

  For example, the film can be stretched sequentially or simultaneously with respect to the MD direction and the TD direction of the film.

  The draw ratios in the biaxial directions perpendicular to each other are preferably 1.07 to 2.0 times in the MD direction and 1.07 to 2.0 times in the TD direction, respectively. It is preferable to carry out in the range of 1.07 to 1.5 times and 1.05 to 2.0 times in the TD direction.

  There is no particular limitation on the method of stretching the web. For example, a method in which peripheral speed differences are applied to a plurality of rolls and a roll peripheral speed difference is used to stretch in the MD direction, both ends of the web are fixed with clips and pins, and the distance between the clips and pins is increased in the traveling direction. And a method of stretching in the MD direction, a method of stretching in the transverse direction and stretching in the TD direction, a method of stretching in the MD / TD direction simultaneously and stretching in both the MD / TD directions, and the like. 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.

  It is preferable to perform the width maintenance or the transverse stretching in the film forming process by a tenter, and it may be a pin tenter or a clip tenter.

  The film transport tension in the film forming process such as in the tenter depends on the temperature, but is preferably 120 N / m to 200 N / m, and more preferably 140 N / m to 200 N / m. 140 N / m to 160 N / m is most preferable.

  When stretching, assuming that the glass transition temperature of the film of the present invention is Tg, it is heated in the range of (Tg-30) to (Tg + 100) ° C., more preferably (Tg-20) to (Tg + 80) ° C. in the MD direction. Or it is preferable to extend in the TD direction.

  The Tg of the optical film can be controlled by the material type constituting the film and the ratio of the constituting materials. In the application of the present invention, the Tg when the film is dried is preferably 110 ° C. or higher, more preferably 120 ° C. or higher. This is because when the optical film of the present invention is used for a liquid crystal display device, if the Tg of the film is lower than the above, the temperature and humidity of the use environment and the influence of the heat of the backlight cause the molecules fixed inside the film. The orientation state is affected, and there is a high possibility that the retardation value and the dimensional stability and shape as a film are greatly changed. In addition, the shape of the film may not be maintained. Conversely, if the Tg of the film is too high, it becomes difficult to produce because it approaches the decomposition temperature of the film constituting material, and the presence of a volatile component or coloring may occur due to the decomposition of the material itself used when forming a film. Accordingly, the glass transition temperature is preferably 180 ° C. or lower, more preferably 150 ° C. or lower. At this time, the Tg of the film can be determined by the method described in JIS K7121.

  In the present invention, the temperature during stretching is not particularly limited, but is preferably 150 ° C. or higher because the haze stability is further improved.

  The optical film is preferably heat-set after stretching, but the heat-setting may be performed at a temperature higher than the final TD direction stretching temperature and usually within 0.5 to 300 seconds within a temperature range of Tg-20 ° C or lower. preferable. Under the present circumstances, it is preferable to heat-fix, heating up sequentially in the range from which a temperature difference is set to 1-100 degreeC in the area | region divided into 2 or more.

  The heat-set film is usually cooled to Tg or less, and clip holding portions at both ends of the film are cut and wound. At this time, it is preferable to perform a relaxation treatment of 0.1 to 10% in the TD direction and / or the MD direction within a temperature range not higher than the final heat setting temperature and not lower than Tg. In addition, it is preferable that the cooling is gradually performed from the final heat setting temperature to Tg at a cooling rate of 100 ° C. or less per second. Means for cooling and relaxation treatment are not particularly limited, and can be performed by a conventionally known means. In particular, it is preferable to carry out these treatments while sequentially cooling in a plurality of temperature ranges from the viewpoint of improving the dimensional stability of the film. The cooling rate is a value obtained by (T1-Tg) / t, where T1 is the final heat setting temperature and t is the time until the film reaches Tg from the final heat setting temperature.

  The more optimal conditions of these heat setting conditions, cooling, and relaxation treatment conditions vary depending on the cellulose ester constituting the film, the compound according to the present invention, and the additive species such as a plasticizer. What is necessary is just to determine by measuring and adjusting suitably so that it may have a preferable characteristic.

  The slow axis or the fast axis of the optical film of the present invention is present 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. More preferably, it is 5 ° or more and + 0.5 ° or less. This θ1 can be defined as an orientation angle, and θ1 can be measured using an automatic birefringence meter KOBRA-21ADH (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>
Moisture permeability of the optical film of the present invention, 40 ° C., preferably 10~1200g ^/ m 2 · 24h at 90% RH, further 20~1000g ^/ m 2 · 24h are preferred, 20~850g ^/ m 2 · 24h is particularly preferable. The moisture permeability can be measured according to the method described in JIS Z 0208.

  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%.

"Polarizer"
The polarizing plate of the present invention and a liquid crystal display device using the same will be described.

  The polarizing plate of the present invention is a polarizing plate having the optical film of the present invention on at least one surface of a polarizer.

  The polarizing plate can be produced by a general method. The optical film of the present invention is preferably bonded to at least one surface of a polarizer prepared by subjecting the polarizer side of the optical film to alkali saponification treatment and immersion drawing in an iodine solution using a completely saponified polyvinyl alcohol aqueous solution. The optical film may be used on the other surface, or another optical film may be used. Commercially available cellulose ester films (for example, Konica Minoltak KC8UX, KC4UX, KC5UX, KC8UY, KC4UY, KC12UR, KC8UCR-3, KC8UCR-4, KC8UCR-5, KC4FR-1, KC8UY-HA, KC8UTA-HA, KC8UX Opt Co., Ltd.) is also preferably used.

  Furthermore, when the optical film of the present invention is an optical film A, the optical film B is an in-plane measured at a wavelength of 590 nm when the optical film used for the polarizing plate on the opposite side through the liquid crystal cell is the optical film B. It is preferable that the retardation Ro is an optical film having a retardation function of 20 to 100 nm and Rt = 70 to 300 nm.

  The optical film B is not particularly limited, and these can be produced, for example, by the methods described in JP-A Nos. 2005-196149 and 2005-275104. It is also preferable to use an optical film that also serves as an optical compensation film having an optically anisotropic layer formed by aligning a liquid crystal compound such as a discotic liquid crystal. For example, the optically anisotropic layer can be formed by the method described in JP-A-2005-275083. When the optical film B is used in combination with the optical film A of the present invention, a polarizing plate and a liquid crystal display device having a stable viewing angle expansion effect can be obtained.

  A polarizer, which is a main component of a polarizing plate, is an element that allows only light of a plane of polarization in a certain direction to pass. A typical polarizer currently known is a polyvinyl alcohol-based polarizing film, which is polyvinyl alcohol. There are one in which iodine is dyed on a system film and one in which dichroic dye is dyed. For the polarizer, a polyvinyl alcohol aqueous solution is formed into a film and dyed by uniaxial stretching or dyed or uniaxially stretched and then preferably subjected to a durability treatment with a boron compound. The film thickness of the polarizer is preferably 5 to 30 μm, particularly preferably 10 to 20 μm.

  Further, the ethylene unit content described in JP-A-2003-248123, JP-A-2003-342322, etc. is 1 to 4 mol%, the degree of polymerization is 2000 to 4000, and the degree of saponification is 99.0 to 99.99 mol%. Ethylene-modified polyvinyl alcohol is also preferably used. Among them, an ethylene-modified polyvinyl alcohol film having a hot water cutting temperature of 66 to 73 ° C. is preferably used. The difference in hot water cutting temperature between two points 5 cm away in the TD direction of the film is more preferably 1 ° C. or less in order to reduce color spots, and two points separated 1 cm in the TD direction of the film. In order to reduce color spots, it is more preferable that the difference in the hot water cutting temperature is 0.5 ° C. or less.

  A polarizer using this ethylene-modified polyvinyl alcohol film is excellent in polarization performance and durability, and has few color spots, and is particularly preferably used for a large-sized liquid crystal display device.

  The polarizer obtained as described above is generally used as a polarizing plate with a protective film pasted on both sides or one side thereof. As an adhesive used for pasting, a PVA-based adhesive is used. In particular, a PVA-based adhesive is preferably used.

(Liquid crystal display device)
By incorporating the polarizing plate of the present invention into a display device, the liquid crystal display device of the present invention having various visibility can be manufactured. In particular, it is preferably applied to a VA type (MVA type, PVA type) liquid crystal display device.

  The liquid crystal display device using the polarizing plate of the present invention is particularly effective for use in a multi-domain liquid crystal display device, more preferably a multi-domain liquid crystal display device with a birefringence mode. Can do.

  Multi-domain is a method of dividing a liquid crystal cell that constitutes one pixel into a plurality of parts, and is suitable for improving the viewing angle dependency and the symmetry of image display. Various methods have been reported. “Okita, Yamauchi: Liquid Crystal, 6 (3), 303 (2002)”. The liquid crystal display cell is also shown in “Yamada, Yamabara: Liquid Crystal, 7 (2), 184 (2003)”, but is not limited thereto.

  The display quality of the display cell is preferably symmetrical with respect to human observation. Therefore, when the display cell is a liquid crystal display cell, it is possible to multiplex domains by giving priority to the symmetry on the observation side. A known method can be used to divide the domain, and can be determined in consideration of the properties of a known liquid crystal mode by a two-part dividing method, more preferably a four-part dividing method.

  The polarizing plate of the present invention is effective in the MVA (Multi-domain Vertical Alignment) mode represented by the vertical alignment mode, in particular, the MVA mode divided into four, and the known PVA (Patterned Vertical Alignment) mode multi-domained by electrode arrangement. Can be used.

  In particular, a polarizing plate using the optical film of the present invention can impart excellent front contrast when used in a large-screen liquid crystal display device.

  In a large-screen liquid crystal display device with a 17-inch or larger screen, especially a 30-inch or larger screen, there is no distortion such as color unevenness and wavy unevenness in addition to the effects of the present invention, so eyes are not tired even during long-time viewing. There was an effect.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

Example 1
<Synthesis of (meth) acrylic copolymer>
(Synthesis of AC1-5)
A glass flask equipped with a stirrer, two dropping funnels, a gas introduction tube and a thermometer was charged with 40 g of a monomer mixture of the types and ratios described in Table 1, 3.0 g of a mercaptopropionic acid chain transfer agent and 30 g of toluene, The temperature was raised to 90 ° C. Thereafter, from one dropping funnel, 60 g of a monomer mixture of the types and ratios shown in Table 1 was dropped over 3 hours, and at the same time, 0.6 g of azobisisobutyronitrile dissolved in 14 g of toluene was added from the other funnel. The solution was added dropwise over 3 hours. Thereafter, 0.6 g of azobisisobutyronitrile dissolved in 56 g of toluene was added dropwise over 2 hours, and the reaction was further continued for 2 hours to obtain a (meth) acrylic copolymer AC1. Subsequently, in the synthesis | combination of AC1, the same synthesis | combination was performed by changing the addition amount of the chain transfer agent mercaptopropionic acid, and (meth) acrylic-type copolymer AC2-5 was obtained.

  The weight average molecular weights of AC1 to AC5 were measured by the following measuring method and are shown in Table 1.

  In Table 1, MMA, HEMA, and HEA are abbreviations for the following compounds, respectively.

MMA: Methyl methacrylate HEMA: 2-hydroxyethyl methacrylate HEA: β-hydroxyethyl acrylate (molecular weight measurement)
The weight average molecular weight was measured using high performance liquid chromatography.

  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 (manufactured by GL Sciences)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corp.) Mw = 100000-500 calibration curves with 13 samples were used. Thirteen samples are used at approximately equal intervals.

<Production of optical film>
<Preparation of optical film 101>
The flow sheet of the manufacturing apparatus of the cellulose-ester film used for the Example at FIG. 1 is shown.

(Silicon dioxide dispersion)
Aerosil 972V (manufactured by Nippon Aerosil Co., Ltd.) 10 parts by mass (average primary particle diameter 16 nm, apparent specific gravity 90 g / liter)
90 parts by mass of ethanol or more was stirred and mixed with a dissolver for 30 minutes, and then dispersed with Manton Gorin. 88 parts by mass of methylene chloride was added to the silicon dioxide dispersion while stirring, and the mixture was stirred and mixed for 30 minutes with a dissolver to prepare a silicon dioxide dispersion dilution. It filtered with the fine particle dispersion | distribution dilution liquid filter 14 (Advantech Toyo Co., Ltd .: Polypropylene wind cartridge filter TCW-PPS-1N) in FIG.

(Production of in-line additive solution)
Tinuvin 928 (manufactured by Ciba Japan Co., Ltd.) 15 parts by mass Methylene chloride 100 parts by mass The above was put into a hermetic container, heated, stirred and completely dissolved and filtered.

  To this was added 36 parts by mass of the silicon dioxide dispersion diluted solution with stirring, and further stirred for 30 minutes. Then, 6 parts by mass of the following cellulose triacetate was added with stirring, and the mixture was further stirred for 60 minutes. The in-line additive solution was filtered with a filter 8 (Finemet NF manufactured by Nippon Seisen Co., Ltd.). A filter medium with a nominal filtration accuracy of 20 μm was used.

(Dope composition)
Cellulose ester A (cellulose triacetate synthesized from linter cotton, acetyl group substitution degree 2.92, Mw = 290000) 100 parts by mass Additive AC1 ((meth) acrylic copolymer) 10 parts by mass Methylene chloride 430 parts by mass Ethanol 40 parts by mass or more was put into a closed container, heated and stirred to dissolve completely, and Azumi Filter Paper No. No. 24 was used for filtration to prepare a dope solution.

  Next, the inline additive solution was filtered with an inline additive solution feed filter 8 (Finemet NF manufactured by Nippon Seisen Co., Ltd.). A filter medium with a nominal filtration accuracy of 20 μm was used. Add 2.5 parts by weight of the filtered in-line additive to 100 parts by weight of the filtered dope and mix thoroughly with the in-line mixer 10 (Toray static type in-pipe mixer Hi-Mixer, SWJ), then belt casting Using the apparatus, the film was uniformly cast on the stainless steel band support 101 at a temperature of 35 ° C. and a width of 2.0 m. With the stainless steel band support 101, the solvent was evaporated until the residual solvent amount reached 100%, and the stainless steel band support 101 was peeled off. The web of the peeled cellulose ester film was evaporated at 35 ° C., slit to 1.80 m width, and then stretched 1.4 times in the TD direction (direction perpendicular to the film transport direction) with a tenter, It was dried at a drying temperature of 135 ° C. At this time, the residual solvent amount when starting stretching with a tenter was 20%. The maximum stress during TD stretching was 10 MPa. Then, after drying for 15 minutes while transporting the inside of the drying apparatus 105 at 120 ° C. with many rolls, slitting to a width of 1.7 m, applying a knurling process with a width of 15 mm and a height of 10 μm at both ends of the film, The optical film 101 was obtained by winding. The residual solvent amount of the optical film was 0.2%, the film thickness was 80 μm, and the winding number was 6000 m.

  In addition, the draw ratio of MD direction computed from the rotational speed of a stainless steel band support body and the driving speed of a tenter was 1.1 times.

<Preparation of optical films 102-125>
Optical films 102 to 125 were produced in the same manner as the optical film 101 except that the type of cellulose ester, the type of additive, the stretching conditions, and the product width were changed as shown in Table 2.

  The materials used for the optical films 101 to 125 are as follows.

Cellulose ester B: The following cellulose acetate propionate <Synthesis of cellulose acetate propionate>
In a reaction vessel equipped with a stirrer and a cooling device, 80 parts by mass of cellulose (linter) and 33 parts by mass of acetic acid were taken and treated at 60 ° C. for 4 hours to activate the cellulose. 33 parts by mass of acetic anhydride, 518 parts by mass of propionic acid, 536 parts by mass of propionic anhydride and 4 parts by mass of sulfuric acid were mixed, cooled to −20 ° C., and then added to the reaction vessel.

  Esterification was performed so that the maximum temperature of the reaction was 35 ° C., and the time when the viscosity of the reaction solution reached 840 cP was taken as the end point of the reaction. The temperature of the reaction mixture at the end point was adjusted to 15 ° C. The reaction terminator which cooled the mixture of 133 mass parts of water and 133 mass parts of acetic acid to -5 degreeC was added so that the temperature of a reaction mixture might not exceed 23 degreeC.

  The temperature of the reaction mixture was 60 ° C., and the mixture was stirred for 2 hours for partial hydrolysis. The polymer compound obtained by mixing with an acetic acid aqueous solution was reprecipitated, and washing with warm water at 70 to 80 ° C. was repeated. After removing the liquid, it was immersed in a 0.001% by mass calcium hydroxide aqueous solution, stirred for 30 minutes, and then removed again. Drying was performed at 70 ° C. to obtain cellulose acetate propionate.

  The obtained cellulose acetate propionate had an acetyl group substitution degree of 1.40, a propionyl group substitution degree of 2.40, a total acyl group substitution degree of 2.80, and MW = 125900.

Cellulose ester C: The following cellulose acetate propionate synthesis recipe was changed, acetyl group substitution degree 0.50, propionyl group substitution degree 2.30, total acyl group substitution degree 2.80, MW = 186000 cellulose acetate propionate was synthesized.

Cellulose ester D: Cellulose acetate butyrate below <Synthesis of cellulose acetate butyrate>
Cellulose was activated by taking 200 parts by mass of cellulose (wood pulp) and 100 parts by mass of acetic acid in a reaction vessel equipped with a stirrer and a cooling device, and treating the mixture at 60 ° C. for 4 hours. 161 parts by mass of acetic acid, 449 parts by mass of acetic anhydride, 742 parts by mass of butyric acid, 1349 parts by mass of butyric anhydride, and 14 parts by mass of sulfuric acid were mixed and cooled to −20 ° C., and then added to the reaction vessel.

  Esterification was performed so that the maximum temperature of the reaction was 30 ° C., and the time when the viscosity of the reaction solution reached 1050 cP was taken as the end point of the reaction. The temperature of the reaction mixture at the end point was adjusted to 10 ° C. A reaction stopper obtained by cooling a mixture of 297 parts by mass of water and 558 parts by mass of acetic acid to −5 ° C. was added so that the temperature of the reaction mixture did not exceed 23 ° C.

  The temperature of the reaction mixture was set to 60 ° C., and the mixture was stirred for 2 hours and 30 minutes for partial hydrolysis. The polymer compound obtained by mixing with an acetic acid aqueous solution was reprecipitated, and washing with warm water at 70 to 80 ° C. was repeated. After removing the liquid, it was immersed in a 0.002% by mass calcium hydroxide aqueous solution, stirred for 30 minutes, and then removed again. Drying was performed at 70 ° C. to obtain cellulose acetate butyrate.

  The obtained cellulose acetate butyrate had an acetyl group substitution degree of 1.51, a butyryl substitution degree of 1.19, a total acyl substitution degree of 2.70, and a MW = 139000.

AsSc: sugar ester compound, exemplified compound 1
BzSc: Sugar ester compound, exemplified compound 3
P: Trimethylolpropane tribenzoate EPEG: Ethylphthalylethyl glycolate

  The following evaluation was implemented about the obtained optical films 101-125.

<Evaluation>
<Measurement of elastic modulus>
The bi-directional elastic modulus in the film transport direction (MD direction) and the direction orthogonal to the transport direction (TD direction) is 23 ° C., 55 using a tensile tester manufactured by Toyo Seiki Seisakusho Co., Ltd. according to ISO 527-3. A tensile test was conducted at% RH, and the strength was obtained from 10% strain.

  For example, the elastic modulus in the MD direction of the optical film 101 was 3.6 GPA, the elastic modulus in the TD direction was 3.9 GPA, and the elastic modulus in the TD direction / elastic modulus in the MD direction was 1.08.

<Elongation at break>
Under the conditions of 23 ° C. and 55% RH, in the direction orthogonal to the film transport direction (TD direction) and in the transport direction (MD direction), the sample width is 10 mm and the length is 130 mm according to the method described in JIS K 7127. The distance between chucks was set to 100 mm at an arbitrary temperature, and a tensile test was performed at a pulling speed of 100 mm / min. For the elongation at break, A & D Tensilon universal testing machine RTF series was used.

<Measurement method of tear strength>
Under conditions of 23 ° C. and 55% RH, the tear load of the Elmendorf method was applied according to JIS K 7128-1991 in both the film transport direction (MD direction) and the direction orthogonal to the transport direction (TD direction). The tear strength was measured with a light load tearing device manufactured by (1).

<Haze>
From the result of measurement using a haze meter (1001DP type, manufactured by Nippon Denshoku Industries Co., Ltd.), it was converted to a haze value when the thickness of the sample was 80 μm.

<Slit property>
In both the film transport direction (MD direction) and the direction orthogonal to the transport direction (TD direction), slitting is performed with a cutter, and the slit portion is observed with an optical microscope from above, and the worse one in the MD direction and the TD direction is illustrated. According to the sample of the observation result of the slit portion of 2, evaluation was made by ○, ○ △, Δ, ×.

  The above results are shown in Table 3.

  From Table 3, it can be seen that the optical films 101 to 117 of the present invention are excellent in haze and slit suitability.

Example 2
<Preparation of polarizing plate>
The optical films 101 to 125 produced above were alkali treated with a 2.5 mol / L sodium hydroxide aqueous solution at 40 ° C. for 60 seconds, washed with water for 3 minutes and saponified to obtain an alkali treated film.

  Next, a 120 μm-thick polyvinyl alcohol film was uniaxially stretched (temperature: 110 ° C., stretch ratio: 5 times). This was immersed in an aqueous solution composed of 0.075 g of iodine, 5 g of potassium iodide and 100 g of water for 60 seconds, and then immersed in an aqueous solution of 68 ° C. composed of 6 g of potassium iodide, 7.5 g of boric acid and 100 g of water. This was washed with water and dried to obtain a 3.0 m wide polarizer.

  Next, the optical compensation film 201 produced below was saponified by the above method, and the optical films 101 to 125, the polarizer, and the optical compensation film 201 were laminated in this order using a fully saponified polyvinyl alcohol 5% aqueous solution as an adhesive. The polarizing plates 101 to 125 on the viewing side were prepared.

(Preparation of optical compensation film 201)
<Fine particle dispersion>
Fine particles (Aerosil R972V manufactured by Nippon Aerosil Co., Ltd.) 11 parts by weight Ethanol 89 parts by weight The above was stirred and mixed with a dissolver for 50 minutes, and then dispersed with Manton Gorin.

<In-line additive solution>
The following cellulose acetate propionate 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 solution. Further, the particles were dispersed by an attritor so that the secondary particles had a predetermined particle size. This was filtered with Finemet NF manufactured by Nippon Seisen Co., Ltd. to prepare an in-line additive solution.

Methylene chloride 99 parts by weight Cellulose acetate propionate (acetyl group substitution degree 1.90, propionyl group substitution degree 0.80, total acyl group substitution degree 2.70) 4 parts by weight Fine particle dispersion 11 parts by weight Main dope having the following composition A liquid was prepared. First, methylene chloride and ethanol were added to the pressure dissolution tank. Cellulose acetate propionate was added to a pressurized dissolution tank containing a solvent while stirring. This is completely dissolved with heating and stirring. This was designated as Azumi Filter Paper No. The main dope solution was prepared by filtration using 244.

<Composition of main dope solution>
Methylene chloride 380 parts by mass Ethanol 70 parts by mass Cellulose acetate propionate (acetyl group substitution degree 1.90, propionyl group substitution degree 0.80, total acyl group substitution degree 2.70) 100 parts by mass Trimethylolpropane tribenzoate 5. 5 parts by mass Ethyl phthalyl ethyl glycolate 5.5 parts by mass The above was put into a closed container, heated and stirred, and dissolved completely. Azumi filter paper No. Azumi filter paper No. No. 24 was used for filtration to prepare a dope solution.

  The dope solution was filtered with Finemet NF manufactured by Nippon Seisen Co., Ltd. in the film production line. In the inline additive solution line, the inline additive solution was filtered with Finemet NF manufactured by Nippon Seisen Co., Ltd. Add 2 parts by weight of the filtered in-line additive to 100 parts by weight of the filtered dope solution, mix thoroughly with an in-line mixer (Toray static type in-pipe mixer Hi-Mixer, SWJ), and then use a belt casting apparatus. Used at a temperature of 35 ° C. and a width of 2.0 m and uniformly cast on a stainless steel band support. With the stainless steel band support, the solvent was evaporated until the residual solvent amount became 120%, and then peeled off from the stainless steel band support. The peeled cellulose ester web was evaporated at 50 ° C. and the solvent was slit to a width of 1.9 m, and then stretched 1.7 times at 160 ° C. in the TD direction (direction perpendicular to the film transport direction). Stretched at a magnification. Drying is completed while transporting through a 120 ° C drying zone with many rolls, slitting to a width of 3.0m, knurling at both ends of the film with a width of 15mm and an average height of 10μm, and optical compensation with an average film thickness of 40μm A film 201 was produced. The film winding length was 5000 m.

  The retardation of the optical compensation film 201 was Ro = 60 nm and Rt = 130 nm by the following measurement.

<Measurement of retardation>
Using KOBRA-21ADH (Oji Scientific Instruments Co., Ltd.), the wavelength was measured at 590 nm in an environment of 23 ° C. and 55% RH, and the following formula was used.

Formula (i) Ro = (nx−ny) × d
Formula (ii) Rt = ((nx + ny) / 2−nz) × d
(In the formula, Ro is the retardation value in the film plane, Rt is the retardation value in the film thickness direction, 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 represents the refractive index in the thickness direction of the film, and d represents the thickness (nm) of the film.)
Incidentally, the optical films 101 to 125 were all in the range of Ro ≦ 5 nm and −10 nm ≦ Rt ≦ 10 nm.

(Production of liquid crystal display device)
A liquid crystal panel for viewing angle measurement was produced as follows, and the characteristics as a liquid crystal display device were evaluated.

  The polarizing plate 101-125 produced as described above was peeled off so that the polarizing plate on the viewing side of the 40-inch display KLV-40J3000 made by SONY, which is a VA mode type liquid crystal display device, was bonded in advance so that the absorption axes of the polarizing plates coincided. Was bonded to the glass surface of the liquid crystal cell to produce a VA mode liquid crystal display device. In that case, it bonded so that the optical compensation film 201 might become the liquid crystal cell side.

<Evaluation>
<Dimensional change>
The produced polarizing plate is cut into 10 cm × 10 cm and placed in an environment of 80 ° C. and 90% RH for 300 hours. Then, the dimension of MD direction and TD direction is measured, and the rate of change from the initial stage (10 cm × 10 cm) is calculated.

<warp>
The sample placed for 300 hours in the environment of 80 ° C. and 90% RH is raised on a flat surface so that the optical films 101 to 125 are on the bottom, and the floating height from the four flat surfaces is measured to obtain an average value. Is used as an index of warpage.

<Color unevenness>
The produced liquid crystal display device is displayed in black in a dark room, and the uniformity of the screen color (black) is subjected to sensory evaluation.

◎: No color unevenness is observed at all ○: Some color unevenness is present but acceptable for practical use △: Color unevenness is observed and anxious ×: Color unevenness is clearly observed <Front contrast evaluation of liquid crystal display device>
For evaluation of the front contrast, EZ-contrast manufactured by ELDIM was used, and the amount of transmitted light during black display and white display in the normal direction of the film surface was measured. The front contrast was evaluated by calculating the front contrast = (transmitted light amount when displaying white) / (transmitted light amount when displaying black).

  From Table 4, the polarizing plate and the liquid crystal display device using the optical films 101 to 117 of the present invention are a polarizing plate and a liquid crystal display device that are small in dimensional change and warp, have no color unevenness, and have excellent front contrast. I understand that there is.

It is a flow sheet which shows the manufacturing method of the cellulose resin film of this invention. It is an observation result sample which evaluates slit suitability.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Main dope preparation tank 2 Dope liquid feed pump 3 Dope stationary tank 4 Main filter 5 Dope filter 6 Inline additive liquid tank 7 Inline additive liquid circulation filter 8 Inline additive liquid liquid filter 9 Inline additive liquid liquid pump DESCRIPTION OF SYMBOLS 10 Static mixer 101 Stainless steel band 102 Peeling roll 103 Film 104 Tenter and drying apparatus 105 Roll conveyance and drying apparatus 106 Film winding apparatus

Claims (4)

All or part of OH groups in at least a cellulose ester, a (meth) acrylic copolymer, or a compound having at least one furanose structure or pyranose structure and having 1 to 12 furanose structures or pyranose structures bonded thereto An optical film containing an esterified sugar ester compound,
The average acetyl group substitution degree of the whole cellulose ester is ≧ 1.9,
The elongation at break when pulled under an environment of 23 ° C. and 55% RH is 10% or more in both the direction orthogonal to the transport direction (TD direction) and the transport direction (MD direction).
And the tear strength in 23 degreeC55% RH environment is 40 mN or more in TD direction and MD direction, The optical film characterized by the above-mentioned. The elastic modulus of the optical film is 4.0 GPA or less in both the TD direction and the MD direction (measured in an environment of 23 ° C. and 55 RH%), and the elastic modulus in the TD direction / elastic modulus in the MD direction = 0.90 to 1.1 The optical film according to claim 1. The optical film according to claim 2, wherein the optical film has a width of 1.6 to 4 m and is stretched by 1.07 to 2.0 times in at least one of the TD direction or the MD direction. the film. A polarizing plate having optical films A and B satisfying a) and b) below with a polarizer interposed therebetween.
a) All or one of OH groups in a compound having at least one cellulose ester and a (meth) acrylic copolymer, or at least one furanose structure or pyranose structure and 1 to 12 furanose structures or pyranose structures bonded to each other. An optical film containing a sugar ester compound obtained by esterifying a part,
The average acetyl group substitution degree of the whole cellulose ester is ≧ 1.9,
The elongation at break when pulled in a 23 ° C. and 55% RH environment is 20% or more in both the direction orthogonal to the transport direction (TD direction) and the transport direction (MD direction).
And the optical film A characterized by the tear strength in 23 degreeC55% RH environment being 40 mN or more in TD direction and MD direction.
b) Optical film B characterized by the following retardation Ro = 20 to 100 nm and Rt = 70 to 300 nm.
Ro = (nx−ny) × d
Rt = {(nx + ny) / 2−nz} × d
In the formula, Ro is the retardation value in the film plane, Rt is the retardation value in the film thickness direction, 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 Represents the refractive index in the thickness direction of the film, and d represents the thickness (nm) of the film.