JP5691865B2 - Optical film and method for producing optical film - Google Patents

Description

  The present invention relates to an optical film and a method for producing the optical film.

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

  On the other hand, with the recent advancement of technology, the enlargement of the liquid crystal display device is accelerated, and the use of the liquid crystal display device is diversified. For example, it can be used as a large display installed in a street or a store, or used as an advertising display in a public place using a display device called digital signage.

  In such an application, since it is assumed to be used outdoors, degradation due to moisture absorption of the polarizing film becomes a problem, and higher moisture resistance is required for the polarizing plate protective film. However, it has been difficult to obtain sufficient moisture resistance with cellulose ester films such as cellulose triacetate films that have been used in the past, and there has been a problem that the optical effect increases when the film thickness is increased to obtain moisture resistance. . Furthermore, in recent years, there has been a demand for thinning of the apparatus, so that the thickness of the polarizing plate itself has also become a problem.

  On the other hand, polymethyl methacrylate (hereinafter abbreviated as PMMA), which is a representative of acrylic resin, as an optical film material with low hygroscopicity, exhibits excellent transparency and dimensional stability in addition to low hygroscopicity. It was used suitably for.

  However, as described above, since the liquid crystal display device is enlarged, the width of the film original is wide, and the winding length is required to be long, the brittleness improvement is insufficient when the film original is wide. The processability was poor, and the handleability was not sufficient to produce an optical film used in a large liquid crystal display device.

  As a technique for improving moisture resistance and processability, a resin in which an acrylic resin is combined with an impact-resistant acrylic rubber-methyl methacrylate copolymer or butyl-modified acetyl cellulose has been proposed (see Patent Document 1).

  However, even in this method, improvement in brittleness is insufficient, so that there is a problem in workability, and handling properties are not sufficient for manufacturing an optical film used for a large-sized liquid crystal display device.

  In addition, a technique for manufacturing a mixed composition of a cellulose derivative and a polymer having negative intrinsic birefringence by an extrusion method has been proposed (see Patent Document 2).

  However, when various two resins were mixed by the extrusion molding method proposed in this method and melt film formation was performed, there were cases where the compatibility was estimated to be insufficient depending on the mixed resin components. When used as an optical film, there is a problem that the contrast of the image is lowered due to high haze and insufficient transparency.

  Acrylic resin and cellulose for the purpose of providing an optical film having a low haze and no breakage failure during production, a method for producing the optical film, a polarizing plate using the optical film, and a liquid crystal display device using the polarizing plate Some propose a combination of an ester resin and a specific antioxidant (see Patent Document 3).

  While these methods solve various problems, new problems have arisen.

  According to the inventor's study, when the acrylic resin-based film is wound into a roll shape, the gel-like foreign matter resulting from the cellulose ester becomes a protrusion, particularly under low humidity, and coupled with the non-charging property of the acrylic resin, the film Induce a point sticking failure. In addition, due to the non-electrical resistance characteristics, oblique stripes may occur during winding.

  In order to solve these problems, it is effective to humidify the film positively, but it is not easy to install the humidification process in the existing extrusion process. Further, in the drying step before melting, it is conceivable to keep the amount of dry moisture slightly high, but it is not easy to keep the degree of drying constant continuously.

Japanese Patent Laid-Open No. 5-119217 JP 2008-88417 A JP 2010-112987 A

  Accordingly, an object of the present invention is to provide an optical film composed of an acrylic resin and a cellulose ester resin that does not cause a point sticking failure or an oblique muscle failure even when wound into a roll under low humidity, and a method for producing the optical film. There is.

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

1. An optical film containing an acrylic resin (A) and a cellulose ester resin (B) in a mass ratio of 95: 5 to 50:50, wherein the acrylic resin (A) contains at least A1 and A2 satisfying the following conditions: And an acrylic resin having a structure represented by the following general formula (1):
An optical film having a moisture content in the range of 200 to 500 ppm after drying the optical film with circulating air at 90 ° C. and dew point −50 ° C. for 10 hours .

(1) A1 and A2 are modified acrylic resins containing structural units having an amide group. (2) Both A1 and A2 have a weight average molecular weight of 60000 or more. (3) The content of A1 is greater than that of A2. (4) A1 The structural unit having an amide group is 5% or more and less than 30% by mass ratio. (5) The structural unit having an amide group of A2 is 30% or more and less than 80% by mass ratio.
General formula (1):-(MMA) p- (X) q- (Y) r-
[In General Formula (1), MMA represents methyl methacrylate. X represents a monomer unit copolymerizable with MMA having at least one amide group. Y represents a monomer unit copolymerizable with MMA and X. p, q, and r are mass%, and change depending on the amount of modification of A1 and A2, and p + q + r = 100. ]

2 . 2. The optical film as described in 1 above, wherein the cellulose ester resin (B) has a weight average molecular weight of 100,000 or less.

3 . 3. The method for producing an optical film according to 1 or 2 , wherein the optical film is produced by a melt casting method.

  According to the present invention, it is possible to provide an optical film composed of an acrylic resin and a cellulose ester, which does not cause a point sticking failure or a diagonal stripe failure even when wound into a roll under low humidity, and a method for producing the optical film. it can.

It is the figure which showed typically the process of the melt casting film forming method preferable for this invention.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail, but the present invention is not limited thereto.

<Optical film of the present invention>
The optical film of the present invention is an optical film containing an acrylic resin (A) and a cellulose ester resin (B) at a mass ratio of 95: 5 to 50:50, and the acrylic resin (A) satisfies the following conditions. By containing at least A1 and A2, an optical film made of an acrylic resin and a cellulose ester that does not cause a point sticking failure or an oblique muscle failure even when wound into a roll at low humidity is provided.

(1) Both A1 and A2 are modified acrylic resins containing a structural unit having an amide group. (2) Both A1 and A2 have a weight average molecular weight of 60000 or more. (3) The content of A1 is greater than that of A2. (4) A1 The structural unit having an amide group is 5% or more and less than 30% by mass ratio. (5) The structural unit having an amide group of A2 is 30% or more and less than 80% by mass ratio. When the moisture content after drying for 10 hours with circulating air at a dew point of −50 ° C. is in the range of 200-500 ppm, there is no point sticking failure or oblique muscle failure even when wound in a roll at low humidity. An optical film comprising a resin and a cellulose ester can be provided, which is preferable.

  That is, in the present invention, two or more kinds of specific modified acrylic resins are used and the moisture content at the end point of drying is maintained high, whereby the above-mentioned point sticking failure and oblique muscle failure can be solved.

<Water content at the end of drying>
The optical film of the present invention preferably has a water content in the range of 200 to 500 ppm after being dried for 10 hours with circulating air at 90 ° C. and a dew point of −50 ° C. By being in this range, the moisture content of the film after casting can be maintained at a desired level, and it is possible to reduce point-like sticking failures and oblique stripe failures during winding at low humidity. If it is less than 200 ppm, it is difficult to obtain this effect. Particularly, if it exceeds 500 ppm, intermittent muscle failure that is slightly inclined from the MD direction (casting direction or longitudinal direction) called “oblique muscle failure” is induced.

  The moisture content after drying can be measured by a coulometric titration method by cutting an optical film into an appropriate size and using, for example, a Karl Fischer moisture content measurement device (manufactured by Dia Instruments: CA-06, VA-06). .

<Acrylic resin (A)>
The acrylic resin used in the present invention includes a methacrylic resin.

  The acrylic resin (A) according to the present invention is composed of a modified acrylic resin containing at least A1 and A2 satisfying the following conditions, and the specific acrylic resin (A) and the cellulose ester resin (B) are mixed to mix the acrylic resin (A). We were able to solve the problem.

(1) Both A1 and A2 are modified acrylic resins containing a structural unit having an amide group. (2) Both A1 and A2 have a weight average molecular weight of 60000 or more. (3) The content of A1 is greater than that of A2. (4) A1 The structural unit having an amide group is 5% or more and less than 30% by mass ratio. (5) The structural unit having an amide group of A2 is 30% or more and less than 80% by mass ratio. The acrylic resin (A) is represented by the following general formula (1).

General formula (1)
-(MMA) p- (X) q- (Y) r-
MMA represents methyl methacrylate, X represents a monomer unit copolymerizable with MMA having at least one amide group, and Y represents a monomer unit copolymerizable with MMA and X. p, q, and r are mass%, change depending on the amount of modification of A1 and A2 below, and p + q + r = 100.

  X is a vinyl monomer having at least one amide group copolymerizable with MMA, and X may be one type or two or more types, and one monomer unit may have a plurality of functional groups.

  Specific monomers for X include acrylamide, N-methylacrylamide, N-butylacrylamide, N, N-dimethylacrylamide, N, N-diethylacrylamide, acryloylmorpholine, N-hydroxyethylacrylamide, acryloylpyrrolidine, acryloylpiperidine, Methacrylamide, N-methylmethacrylamide, N-butylmethacrylamide, N, N-dimethylmethacrylamide, N, N-diethylmethacrylamide, methacryloylmorpholine, N-hydroxyethylmethacrylamide, methacryloylpyrrolidine, methacryloylpiperidine, N-vinyl Examples include formamide, N-vinylacetamide, N-vinylpyrrolidone and the like.

  Preferably, acryloylmorpholine and N-vinylpyrrolidone are used.

  Commercially available monomers can be used as they are.

  q is 5 ≦ q <30 (mass%) in the case of the modified acrylic resin A1 constituting the acrylic resin (A), and 30 ≦ q <in the case of the modified acrylic resin A2 constituting the acrylic resin (A). 80 (mass%). X may be a plurality of monomers.

  The monomer X contributes to the improvement of moisture retention at the end of drying because the functional group contains oxygen atoms and nitrogen atoms in the structure and is polarized, and the interaction between the materials constituting the film is entangled. It is speculated that the increase is contributing.

  In addition, since the functional group is non-dissociable, it is considered that it is physically stable without acid generation due to decomposition over time.

  Therefore, even if the modified acrylic resin A2 satisfies the q value, if the constituent unit having an amide group of the modified acrylic resin A1 used in combination is less than 5%, the effect of controlling the water content cannot be obtained. Insufficient water resistance and poor durability under wet heat.

  Moreover, even if the modified acrylic resin A1 satisfies the q value, if the structural unit having an amide group of the modified acrylic resin A2 used in combination is less than 30%, the effect of controlling the water content cannot be obtained, and if it exceeds 80% Insufficient water resistance and poor durability under wet heat.

  Y in the acrylic resin (A) according to the present invention represents a monomer unit copolymerizable with MMA and X.

  Examples of Y include acrylic monomers other than MMA, methacrylic monomers, olefins, acrylonitrile, styrene, vinyl acetate, etc., International Publication No. 2009/047924, JP 2009-1744, JP 2009-179731, and the like. These monomers are mentioned. Y may be two or more.

  Y can be used as needed, and is most preferably not used.

  The acrylic resin (A) according to the present invention preferably has a weight average molecular weight (Mw) of 60000 or more from the viewpoint of improving transparency particularly when it is compatible with the cellulose ester resin (B).

  As for the weight average molecular weight (Mw) of the acrylic resin (A), the weight average molecular weight of both A1 and A2 is preferably 60000 to 200000, more preferably 70000 to 150,000, and further preferably 80000 to 100,000. If it is less than 60000, the water resistance is insufficient and the durability under wet heat is poor.

  The weight average molecular weight of the acrylic resin (A) according to the present invention can be measured by 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 = 2,800,000-500 calibration curves with 13 samples were used. The 13 samples are preferably used at approximately equal intervals.

  As the method for producing the acrylic resin (A) in the present invention, any known method such as suspension polymerization, emulsion polymerization, bulk polymerization, or solution polymerization may be used. Here, as a polymerization initiator, a normal peroxide type and an azo type can be used, and a redox type can also be used.

  Regarding the polymerization temperature, suspension or emulsion polymerization may be performed at 30 to 100 ° C, and bulk or solution polymerization may be performed at 80 to 160 ° C. In order to control the reduced viscosity of the obtained copolymer, polymerization can be carried out using alkyl mercaptan or the like as a chain transfer agent.

  In the optical film of the present invention, the content ratio of the A1 and A2 constituting the acrylic resin (A) preferably satisfies A1> A2 in order to improve moisture retention at the end point of drying.

  The mass ratio A1: A2 of A1 and A2 contained in the acrylic resin (A) constituting the optical film of the present invention is preferably 55:45 to 90:10, more preferably 70:30 to 90: 10. The resin containing A1 and A2 may be obtained by mixing separate resins, or may be obtained by synthesizing A1 and A2 in the same reaction vessel.

  The acrylic resin (A) according to the present invention may contain an acrylic resin other than the above A1 and A2, but the ratio of A1 + A2 constituting the acrylic resin (A) is 50% by mass or more of the acrylic resin (A). Preferably, it is 85 mass% or more, more preferably 90 mass% or more, and particularly preferably 100 mass%.

<Cellulose ester resin (B)>
The cellulose ester resin (B) according to the present invention has an acyl group total substitution degree (T) of 2.0 to 3 from the viewpoint of transparency, particularly when improved in brittleness or compatible with the acrylic resin (A). 0.0, the substitution degree of the acyl group having 3 to 7 carbon atoms is 1.2 to 3.0, and the substitution degree of the acyl group having 3 to 7 carbon atoms is 2.0 to 3.0. preferable.

  That is, the cellulose ester resin (B) according to the present invention is a cellulose ester resin substituted with an acyl group having 3 to 7 carbon atoms. Specifically, propionyl, butyryl and the like are preferably used. Is preferably used.

  When the total substitution degree of the acyl group of the cellulose ester resin (B) is less than 2.0, that is, when the residual degree of the hydroxyl groups at the 2, 3, and 6 positions of the cellulose ester molecule is more than 1.0, the acrylic ester When the resin (A) is not sufficiently compatible with the resin (A) and used as an optical film, haze becomes a problem.

  Moreover, even if the total substitution degree of the acyl group is 2.0 or more, if the substitution degree of the acyl group having 3 to 7 carbon atoms is less than 1.2, sufficient compatibility cannot be obtained.

  For example, even when the total substitution degree of the acyl group is 2.0 or more, the substitution degree of the acyl group having 2 carbon atoms, that is, the acetyl group is high, and the substitution degree of the acyl group having 3 to 7 carbon atoms is 1. When it is less than 2, the compatibility is lowered and the haze is increased.

  Even when the total substitution degree of the acyl group is 2.0 or more, the substitution degree of the acyl group having 8 or more carbon atoms is high, and the substitution degree of the acyl group having 3 to 7 carbon atoms is less than 1.2. In such a case, the brittleness deteriorates and desired characteristics cannot be obtained.

  As for the acyl substitution degree of the cellulose ester resin (B) according to the present invention, the total substitution degree (T) is 2.0 to 3.0, and the substitution degree of the acyl group having 3 to 7 carbon atoms is 1.2 to 3.0. If it is 3.0, there is no problem, but the total substitution degree of acyl groups other than those having 3 to 7 carbon atoms, that is, acetyl groups or acyl groups having 8 or more carbon atoms, is preferably 1.3 or less. .

  The total substitution degree (T) of the acyl group of the cellulose ester resin (B) is more preferably in the range of 2.5 to 3.0.

  The cellulose ester resin (B) according to the present invention is preferably at least one selected from cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate benzoate, cellulose propionate, and cellulose butyrate, Those having an acyl group having 3 or 4 carbon atoms as a substituent are preferred.

  Among these, cellulose ester resins that are particularly preferred are cellulose acetate propionate and cellulose propionate.

  The portion that is not substituted with an acyl group usually exists as a hydroxyl group. These can be synthesized by known methods.

  In addition, the substitution degree of an acetyl group and the substitution degree of other acyl groups are obtained by a method prescribed in ASTM-D817-96.

  The weight average molecular weight (Mw) of the cellulose ester resin (B) according to the present invention is 75000 or more, particularly from the viewpoint of improving compatibility with the acrylic resin (A) and brittleness, and is in the range of 75,000 to 300,000. Although it is preferable, it is preferable that it is 100,000 or less from a viewpoint of improving winding looseness when wound in a roll shape.

  Due to the effect of the present invention, sticking on the surface of the optical film is suppressed and the film tends to be slippery. By suppressing the cellulose ester to a low molecular weight of 100,000 or less, an effect of moderately suppressing the slipperiness of the optical film surface can be expected, and the occurrence of loosening during winding can be suppressed.

  When the weight average molecular weight (Mw) of the cellulose ester resin is less than 75,000, the effect of improving heat resistance and brittleness decreases. Moreover, when it exceeds 300,000, a viscosity becomes high and film formation becomes difficult.

  In the present invention, two or more kinds of cellulose ester resins can be mixed and used.

  The weight average molecular weight of the cellulose ester resin (B) according to the present invention can be measured by the GPC.

<Acrylic resin (A) and cellulose ester resin (B)>
In the optical film of the present invention, the acrylic resin (A) and the cellulose ester resin (B) are contained in a compatible state at a mass ratio of 95: 5 to 50:50, more preferably 90:10 to 50: 50, particularly preferably a mass ratio of 80:20 to 60:40.

  If the mass ratio of the acrylic resin (A) and the cellulose ester resin (B) is more than 95: 5, the effect of the cellulose ester resin (B) cannot be sufficiently obtained, and the mass ratio is When the amount of acrylic resin is less than 50:50, the photoelastic coefficient is increased.

  In the optical film of the present invention, the acrylic resin (A) and the cellulose ester resin (B) are preferably contained in a compatible state. The physical properties and quality required for an optical film are achieved by supplementing each other by dissolving different resins.

  Whether the acrylic resin (A) and the cellulose ester resin (B) are in a compatible state can be determined by, for example, the glass transition temperature Tg.

  For example, when the two resins have different glass transition temperatures, when the two resins are mixed, there are two or more glass transition temperatures for each resin because there is a glass transition temperature for each resin. When they are compatible, the glass transition temperature specific to each resin disappears and becomes one glass transition temperature, which is the glass transition temperature of the compatible resin.

  In addition, the glass transition temperature here is the intermediate | middle calculated | required according to JISK7121 (1987), using the differential scanning calorimeter (DSC-7 type | mold by Perkin Elmer), measured with the temperature increase rate of 20 degree-C / min. The point glass transition temperature (Tmg).

  In the optical film of the present invention, the weight average molecular weight (Mw) of the acrylic resin (A), the weight average molecular weight (Mw) of the cellulose ester resin (B), and the degree of substitution are different in solubility in the solvent of both resins. It is obtained by measuring each after use.

  When fractionating the resin, it is possible to extract and separate the soluble resin by adding a compatible resin in a solvent that is soluble only in either one. At this time, heating operation or reflux is performed. May be.

  A combination of these solvents may be combined in two or more steps to separate the resin. The dissolved resin and the resin remaining as an insoluble matter are filtered off, and the solution containing the extract can be separated by an operation of evaporating the solvent and drying.

  These fractionated resins can be identified by general structural analysis of polymers. When the optical film of the present invention contains a resin other than the acrylic resin (A) and the cellulose ester resin (B), it can be separated by the same method.

  If the weight average molecular weights (Mw) of the compatible resins are different, the high molecular weight substances are eluted earlier by gel permeation chromatography (GPC), and the lower molecular weight substances are eluted after a longer time. Therefore, it can be easily fractionated and the molecular weight can be measured.

  In addition, the molecular weight of the compatible resin is measured by GPC, and at the same time, the resin solution eluted every time is separated, the solvent is distilled off, and the dried resin is different by quantitatively analyzing the structure. By detecting the resin composition for each molecular weight fraction, it is possible to identify each compatible resin.

  By measuring the molecular weight distribution of each of the resins separated in advance based on the difference in solubility in a solvent by GPC, it is possible to detect each of the compatible resins.

  The total mass of the acrylic resin (A) and the cellulose ester resin (B) in the optical film of the present invention is preferably 55% by mass or more of the optical film, more preferably 60% by mass or more, and particularly preferably 70% by mass or more.

<Other additive resins>
When the resin other than the acrylic resin (A) and the cellulose ester resin (B) is used for the optical film of the present invention, it is preferable to adjust the addition amount within a range that does not impair the function of the optical film of the present invention.

  As a preferred resin, a low molecular acrylic resin obtained by polymerizing an ethylenically unsaturated monomer described in paragraphs (0072) to (0123) of JP 2010-32655 A (weight average molecular weight Mw of 500 or more and 30000 or less) Polymer).

  Most preferably, Mw is 2000-30000. If it is 1000 or less, a problem occurs in bleed-out, and if it exceeds 30000, the transparency deteriorates.

  Also, a vinyl polymer having an amide bond described in Japanese Patent No. 4138854 can be used.

  The said low molecular acrylic resin and the vinyl polymer which has an amide bond are 0-15 mass% with respect to the total mass of an optical film, and it is preferable that it is 0-10 mass%.

<Acrylic particles (C)>
The optical film of this invention may contain the acrylic particle (C) which is a multilayer structure acrylic type granular composite.

  As an example of a commercial item of such a multilayer structure acrylic granular composite, for example, “Metablene W-341” manufactured by Mitsubishi Rayon Co., “Kaneace” manufactured by Kaneka Chemical Co., Ltd., “Paralloid” manufactured by Kureha Chemical Co., Ltd., Examples include “Acryloid” manufactured by Rohm and Haas, “Staffroid” manufactured by Gantz Kasei Kogyo Co., Ltd., Chemisnow MR-2G, MS-300X (manufactured by Soken Chemical Co., Ltd.), and “Parapet SA” manufactured by Kuraray Co., Ltd. These can be used alone or in combination of two or more.

  The optical film of the present invention preferably contains 0 to 30% by mass of acrylic particles (C) with respect to the total mass of the resin constituting the film, and is contained in the range of 1.0 to 15% by mass. More preferably.

<Other additives>
The optical film of the present invention has a retardation control agent for the purpose of controlling retardation, a hydrolysis inhibitor for preventing deterioration of the film against humidity, a plasticizer for imparting processability to the film, and deterioration of the film. It is preferable to contain additives such as an antioxidant for preventing, an ultraviolet absorber for imparting an ultraviolet absorbing function, and fine particles (matting agent) for imparting slipperiness to the film.

<Phase difference control agent>
As the retardation control agent used in the present invention, an aromatic terminal polyester represented by the following general formula (I) can be used.

General formula (I) 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 (I), 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 ordinary polyester.

  Specific examples of the aromatic terminal polyester used in the present invention include paragraphs (0183) to (0186) of JP-A 2010-32655.

  The content of the aromatic terminal polyester used in the present invention is preferably 0 to 20% by mass, particularly preferably 1 to 11% by mass in the optical film.

<Hydrolysis inhibitor>
In the optical film of the present invention, a sugar ester compound can be used as a hydrolysis inhibitor. The sugar ester compound used has at least one pyranose structure or furanose structure of 1 to 12 inclusive. It is preferable to use a sugar ester compound obtained by esterifying all or part of the OH group.

  Examples of the sugar ester compound used in the present invention include glucose, galactose, mannose, fructose, xylose, arabinose, lactose, sucrose, cellobiose, cellotriose, maltotriose, raffinose and the like. What has is preferable. An example is sucrose.

  The sugar ester compound used in the present invention is one in which part or all of the hydroxyl groups of the sugar compound are esterified or a mixture thereof.

  Specific examples of the sugar ester compound include paragraphs (0060) to (0070) of JP 2010-32655 A.

<Other additives>
The optical film of the present invention may further contain a plasticizer, a retardation control agent, an antioxidant, an ultraviolet absorber, matte particles, and the like.

  Examples of the plasticizer include polyhydric alcohol esters, phthalates, fatty esters, trimellitic esters, phosphate esters, polyesters, and epoxies.

  A polyhydric alcohol ester compound is preferred as the plasticizer contained in the optical film of the present invention. Examples of the polyhydric alcohol ester compounds include paragraphs (0218) to (0170) of JP 2010-32655 A.

  Similarly, polyester and phthalate plasticizers are preferably used. Polyester plasticizers are superior in non-migration and extraction resistance compared to phthalate ester plasticizers such as dioctyl phthalate, but are slightly inferior in plasticizing effect and compatibility.

  Therefore, it can be applied to a wide range of uses by selecting or using these plasticizers according to the use.

  The polyester plasticizer is a reaction product of a monovalent or tetravalent carboxylic acid and a monovalent or hexavalent alcohol, and is mainly obtained by reacting a divalent carboxylic acid with a glycol. . Representative divalent carboxylic acids include glutaric acid, itaconic acid, adipic acid, phthalic acid, azelaic acid, sebacic acid and the like.

  In particular, when adipic acid, phthalic acid or the like is used, those having excellent plasticizing properties can be obtained. Examples of the glycol include glycols such as ethylene, propylene, 1,3-butylene, 1,4-butylene, 1,6-hexamethylene, neopentylene, diethylene, triethylene, and dipropylene. These divalent carboxylic acids and glycols may be used alone or in combination.

  The ester plasticizer may be any of ester, oligoester and polyester types, and the molecular weight is preferably in the range of 100 to 10000, but preferably in the range of 600 to 3000, the plasticizing effect is large.

  The viscosity of the plasticizer has a correlation with the molecular structure and molecular weight. In the case of an adipic acid plasticizer, the viscosity is preferably in the range of 200 to 5000 mPa · s (25 ° C.) in view of compatibility and plasticization efficiency. Furthermore, some polyester plasticizers may be used in combination.

  For phosphate plasticizers, triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenylbiphenyl phosphate, trioctyl phosphate, tributyl phosphate, etc. For phthalate ester plasticizers, diethyl phthalate, dimethoxy Ethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate and the like can be used.

  The plasticizer is preferably added in an amount of 0.5 to 30 parts by mass with respect to 100 parts by mass of the composition containing an acrylic resin. If the added amount of the plasticizer exceeds 30 parts by mass, the surface becomes sticky, which is not preferable for practical use. These plasticizers may be used alone or in combination of two or more.

<Other phase difference control agents>
Other than the above retardation control agent, those containing bisphenol A in the molecule are preferred. A compound in which ethylene oxide or propylene oxide is added to both ends of bisphenol A can be used.

  For example, BP series such as New Pole BP-2P, BP-3P, BP-23P, BP-5P, BPE-20 (F), BPE-20NK, BPE-20T, BPE-40, BPE-60, BPE-100, There are BPE series (manufactured by Sanyo Chemical Co., Ltd.) such as BPE-180, and BPX series (manufactured by Adeka Co., Ltd.) such as Adeka polyether BPX-11, BPX-33, BPX-55.

  Diallyl bisphenol A, dimethallyl bisphenol A, tetrabromobisphenol A with bisphenol A substituted with bromine, oligomers and polymers obtained by polymerizing this, bisphenol A bis (diphenyl phosphate) substituted with diphenyl phosphate, etc. Can be used.

  Polycarbonate obtained by polymerizing bisphenol A, polyarylate obtained by polymerizing bisphenol A with a dibasic acid such as terephthalic acid, and an epoxy oligomer or polymer polymerized with an epoxy-containing monomer can also be used.

  Modiper CL130D or L440-G obtained by graft polymerization of bisphenol A and styrene, styrene acrylic, or the like can also be used.

  Those having a triazine structure are also preferred. The compounds described in JP 2001-166144 A can be used.

<Antioxidant>
In this invention, what is generally known can be used as an antioxidant. In particular, lactone, sulfur, phenol, double bond, hindered amine, and phosphorus compounds can be preferably used.

  For example, those including those commercially available from BASF Japan under the trade names of “IrgafosXP40” and “IrgafosXP60” are preferable.

  The phenolic compound preferably has a 2,6-dialkylphenol structure. For example, BASF Japan Ltd., “Irganox 1076”, “Irganox 1010”, and ADEKA “ADEKA STAB AO-50” are trade names. What is marketed is preferable.

  The phosphorous compounds are, for example, from Sumitomo Chemical Co., Ltd., “Sumizer GP”, from ADEKA Co., Ltd., “ADK STAB PEP-24G”, “ADK STAB PEP-36” and “ADK STAB 3010”, from BASF Japan Co., Ltd. IRGAFOS P-EPQ ", commercially available from Sakai Chemical Industry Co., Ltd. under the trade name" GSY-P101 "is preferred.

  As the hindered amine compound, for example, those commercially available from BASF Japan Ltd. under the trade names “Tinuvin 144” and “Tinvin 770”, and ADEKA Co., Ltd. under the name “ADK STAB LA-52” are preferable.

  The sulfur compound is preferably commercially available from Sumitomo Chemical Co., Ltd. under the trade names “Sumilizer TPL-R” and “Sumilizer TP-D”.

  The above-mentioned double bond type compounds are preferably those commercially available from Sumitomo Chemical Co., Ltd. under the trade names “Sumilizer GM” and “Sumilizer GS”.

  Furthermore, it is possible to contain a compound having an epoxy group as described in US Pat. No. 4,137,201 as an acid scavenger.

  The amount of these antioxidants and the like to be appropriately added is determined in accordance with the process at the time of recycling, but generally 0.05 to 20% by mass, preferably with respect to the resin as the main raw material of the film Is added in the range of 0.1 to 1% by mass.

  These antioxidants can obtain a synergistic effect by using several different types of compounds in combination rather than using only one kind. For example, the combined use of lactone, phosphorus, phenol and double bond compounds is preferred.

<Colorant>
In the present invention, it is preferable to use a colorant. The colorant means a dye or a pigment. In the present invention, the colorant refers to a colorant having an effect of making the color tone of a liquid crystal screen a blue tone, adjusting a yellow index, and reducing haze.

  Various dyes and pigments can be used as the colorant, but anthraquinone dyes, azo dyes, phthalocyanine pigments and the like are effective.

<Ultraviolet absorber>
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. It is good also as a polymer type ultraviolet absorber.

<Matting agent>
In the present invention, it is preferable to add a matting agent in order to impart film slipperiness.

  The matting agent used in the present invention may be either an inorganic compound or an organic compound as long as it does not impair the transparency of the obtained film and has heat resistance during melting. These matting agents can be used alone or in combination of two or more.

  By using particles having different particle sizes and shapes (for example, acicular and spherical), both transparency and slipperiness can be made highly compatible.

  Among these, silicon dioxide is particularly preferably used because it has a refractive index close to that of cellulose ester and is excellent in transparency (haze).

  Specific examples of silicon dioxide include Aerosil 200V, Aerosil R972V, Aerosil R972, R974, R812, 200, 300, R202, OX50, TT600, NAX50 (manufactured by Nippon Aerosil Co., Ltd.), Sea Hoster KEP-10, Sea Hoster KEP- 30, Seahoster KEP-50 (manufactured by Nippon Shokubai Co., Ltd.), Silo Hovic 100 (manufactured by Fuji Silysia), Nip Seal E220A (manufactured by Nippon Silica Industry), Admafine SO (manufactured by Admatechs), etc. Goods etc. can be preferably used.

  The shape of the particles can be used without particular limitation, such as indefinite shape, needle shape, flat shape, spherical shape, etc. However, the use of spherical particles is particularly preferable because the transparency of the resulting film can be improved.

  When the particle size is close to the wavelength of visible light, light is scattered and the transparency is deteriorated. Therefore, the particle size is preferably smaller than the wavelength of visible light, and more preferably ½ or less of the wavelength of visible light. . If the size of the particles is too small, the slipperiness may not be improved.

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

<Viscosity reducing agent>
In the present invention, a hydrogen bonding solvent can be added for the purpose of reducing the melt viscosity.

  The hydrogen bonding solvent is J.I. N. As described in Israel Ativili, “Intermolecular Forces and Surface Forces” (Takeshi Kondo, Hiroyuki Oshima, Maglow Hill Publishing, 1991) and electrically negative atoms (oxygen, nitrogen, fluorine, chlorine) An organic solvent capable of producing a hydrogen atom-mediated “bond” between a hydrogen atom covalently bonded to an electronegative atom, ie, a bond having a large bond moment and containing hydrogen, such as O—H (Oxygen hydrogen bond), N—H (nitrogen hydrogen bond), and organic solvent that can arrange adjacent molecules by including F—H (fluorine hydrogen bond).

  These can reduce the viscosity by replacing part of the intermolecular hydrogen bonds of the cellulose ester resin with the above-described solvent having hydrogen bonding properties.

  The hydrogen bonding solvent used in the melt casting method performed in the present invention desirably has low volatility or is non-volatile when used as a melting step or film. In the melt casting method performed in the present invention, the melting temperature of the cellulose ester resin composition can be lowered by the addition of a hydrogen-bonding solvent or the same melting temperature than the glass transition temperature of the cellulose ester resin alone used. The melt viscosity of the cellulose ester resin composition containing a hydrogen bonding solvent can be lowered than that of the cellulose ester resin.

(Physical properties of optical film)
Hereinafter, the characteristics of the optical film according to the present invention will be described.

<transparency>
As an index for judging the transparency of the optical film in the present invention, haze value (turbidity) is used.

  In particular, liquid crystal display devices used outdoors are required to have sufficient brightness and high contrast even in a bright place. Therefore, the haze value is required to be 1.0% or less, and 0.5% or less. More preferably.

  Moreover, it is preferable that the total light transmittance is 90% or more, More preferably, it is 93% or more. Moreover, as a realistic upper limit, it is about 99%.

  According to the optical film of the present invention containing the acrylic resin (A) and the cellulose ester resin (B), high transparency can be obtained, but when using acrylic particles for the purpose of improving another physical property, By reducing the difference in refractive index between the resin (acrylic resin (A) and cellulose ester resin (B)) and acrylic particles (D), an increase in haze value can be prevented.

  In the optical film of the present invention, it is preferable that the number of defects in a film plane of 5 μm or more is 1/10 cm square or less. More preferably, it is 0.5 piece / 10 cm square or less, more preferably 0.1 piece / 10 cm square or less.

  Here, the diameter of the defect indicates the diameter when the defect is circular, and when the defect is not circular, the range of the defect is determined by observing with a microscope by the following method, and the maximum diameter (diameter of circumscribed circle) is determined.

  The range of the defect is the size of the shadow when the defect is observed with the transmitted light of the differential interference microscope when the defect is a bubble or a foreign object. When the defect is a change in the surface shape, such as transfer of a roll flaw or an abrasion, the size is confirmed by observing the defect with the reflected light of a differential interference microscope.

  In addition, when observing with reflected light, if the size of the defect is unclear, aluminum or platinum is deposited on the surface for observation.

  In order to obtain a film excellent in the quality expressed by such a defect frequency with high productivity, it is effective to highly accurately filter the polymer solution immediately before casting or to increase the cleanliness around the casting machine. .

  When the number of defects is greater than 1/10 cm square, for example, when the film is tensioned during processing in a later process, the film may break with the defects as a starting point, and productivity may decrease. Moreover, when the diameter of a defect becomes 5 micrometers or more, it can confirm visually by polarizing plate observation etc., and when used as an optical member, a bright spot may arise.

<Retardation>
For the retardation, a 35 mm × 35 mm sample was cut from the produced optical film, conditioned for 2 hours at 25 ° C. and 55% RH, and measured from the vertical direction at 590 nm with an automatic birefringence meter (KOBRA WR, Oji Scientific Co., Ltd.). Ro and Rth at each wavelength were calculated from the measured values and the extrapolated values of the retardation values measured in the same manner while tilting the film surface.

The optical film of the present invention has an in-plane retardation value Ro (590) defined by the following formula (I) in the range of 0 to 100 nm, and a retarder in the thickness direction defined by the following formula (II). It is preferable to adjust so that the foundation value Rth (590) is in the range of −100 to 100 nm.
Formula (I): Ro (590) = (nx−ny) × d (nm)
Formula (II): Rth (590) = {(nx + ny) / 2−nz} × d (nm)
[In the above formula, Ro (590) represents the in-plane retardation value in the film at a measurement wavelength of 590 nm, and Rth (590) represents the retardation value in the thickness direction in the film at 590 nm.

D represents the thickness (nm) of the optical film, nx represents the maximum refractive index in the plane of the film at 590 nm, and is also referred to as the refractive index in the slow axis direction. ny represents the refractive index in the direction perpendicular to the slow axis in the film plane at 590 nm, and nz represents the refractive index of the film in the thickness direction at 590 nm. ]
The in-plane retardation value Ro (590) is more preferably in the range of 0 to 50 nm.

  On the other hand, the retardation value Rth (590) in the thickness direction is more preferably in the range of −50 to 50 nm.

  The desired retardation is adjusted by adjusting the ratio of each resin within the mass ratio of 95: 5 to 50:50 for the acrylic resin (A) and the cellulose ester resin (B). This is done by adjusting the combination of the control agents and the amount to be added.

  Furthermore, by adjusting and controlling the stretching temperature (combination of the temperatures of the respective sections), the magnification, the stretching speed, the stretching order, the residual solvent amount of the film when stretching, and the like according to the composition of the film. The retardation value can be set to a desired value.

  By adjusting the retardation to such a range, the viewing angle of the liquid crystal display device using the film of the present invention can be widened and the front contrast can be improved.

Front contrast = (brightness of white display measured from normal direction of display device) / (brightness of black display measured from normal direction of display device)
The viewing angle is an angle at which a certain level of contrast can be maintained when the viewing direction of the liquid crystal display device is tilted from the normal direction.

  The uniformity in the slow axis direction is also important, and the angle is preferably −5 to + 5 ° with respect to the film width direction, more preferably in the range of −1 to + 1 °, and particularly −0. It is preferably in the range of 5 to + 0.5 °, particularly preferably in the range of −0.1 to + 0.1 °. These variations can be achieved by optimizing the stretching conditions.

  In the optical film of the present invention, it is preferable that the height from the top of the adjacent mountain to the bottom of the valley is 300 nm or more and there is no streak continuous in the longitudinal direction with an inclination of 300 nm / mm or more.

  The shape of the streak was measured using a surface roughness meter. Specifically, using a Mitutoyo SV-3100S4, a stylus (diamond needle) having a tip shape of a cone of 60 ° and a tip curvature radius of 2 μm was used. The film is scanned in the width direction of the film at a measurement speed of 1.0 mm / sec while applying a load of 0.75 mN, and a cross-sectional curve is measured with a Z-axis (thickness direction) resolution of 0.001 μm.

  From this curve, the streak height reads the vertical distance (H) from the top of the mountain to the bottom of the valley. The slope of the streak is obtained by reading the horizontal distance (L) from the top of the mountain to the bottom of the valley and dividing the vertical distance (H) by the horizontal distance (L).

  The optical film of the present invention can be particularly preferably used as a polarizing plate protective film for a large-sized liquid crystal display device or a liquid crystal display device for outdoor use as long as the above physical properties are satisfied.

<Method for producing optical film>
The optical film of the present invention can be produced by a solution casting method or a melt casting method, but the drying process before casting is general and the water content control preferably performed in the present invention is easy, In order to effectively suppress the occurrence of a point sticking failure, it is preferable to manufacture by a melt casting extrusion film forming method.

  The manufacturing method of the following optical film is an example, and the present invention is not limited to this.

<Method for producing optical film by melt casting extrusion film forming method>
The method for producing an optical film of the present invention is a method for producing an optical film in which at least an acrylic resin (A) and a cellulose ester resin (B) are melted and coextruded from a die and cast on a cooling roll.

  FIG. 1 is a diagram schematically showing the steps of a melt casting film forming method preferable for the present invention.

  In FIG. 1, the manufacturing method of the optical film by this invention is the 1st cooling from the casting die 4 using the extruder 1 after mixing film materials, such as an acrylic resin (A) and a cellulose-ester resin (B). It is melt extruded on the roll 5 and circumscribed to the first cooling roll 5, and is further circumscribed by a total of three cooling rolls, the second cooling roll 7 and the third cooling roll 8, in order to cool and solidify the film 10. To do. Next, the film 10 peeled off by the peeling roll 9 is then stretched in the width direction by holding both ends of the film by the stretching device 12 and then wound by the winding device 16. In addition, a touch roll 6 is provided that clamps the molten film on the surface of the first cooling roll 5 in order to correct the flatness. The touch roll 6 has an elastic surface and forms a nip with the first cooling roll 5.

  The entire manufacturing method will be described below.

<Melted pellet manufacturing process>
The mixture of acrylic resin (A), cellulose ester (B), plasticizer and other additives used for melt extrusion is usually preferably kneaded in advance and pelletized.

  Pelletization may be performed by a known method. For example, a dry acrylic resin (A), a dry cellulose ester resin (B), a plasticizer, and other additives are fed to an extruder with a feeder, and a single or twin screw extruder is used. It can be kneaded, extruded from a die into a strand, cooled with water or air, and cut.

  In order to obtain the effects of the present invention, it is important that the raw material is dried before extrusion. In particular, since the cellulose ester easily absorbs moisture, it is preferable to dry it at 70 to 140 ° C. for 3 hours or more with a dehumidifying hot air dryer or a vacuum dryer to keep the moisture content at 200 ppm or less, and further 100 ppm or less.

  Additives may be fed into the extruder and fed into the extruder, or may be fed by individual feeders. A small amount of an additive such as an antioxidant is preferably mixed in advance in order to mix uniformly.

  Mixing of the antioxidants may be performed by mixing solids, or if necessary, the antioxidant may be dissolved in a solvent, and the acrylic resin (A) or cellulose ester resin (B may be impregnated and mixed). Or may be mixed by spraying.

A vacuum nauter mixer or the like is preferable because drying and mixing can be performed simultaneously. Further, if the contact with air, such as the exit from the feeder unit or die, it is preferable that the atmosphere such as dehumidified air and dehumidified N ₂ gas.

  The extruder is preferably processed at as low a temperature as possible so that the shearing force is suppressed and the resin can be pelletized so as not to deteriorate (molecular weight reduction, coloring, gel formation, etc.). For example, in the case of a twin screw extruder, it is preferable to rotate in the same direction using a deep groove type screw. From the uniformity of kneading, the meshing type is preferable.

  A film is formed using the pellets obtained as described above. It is also possible to feed the raw material powder directly to the extruder with a feeder and form a film as it is without pelletization.

<Process for extruding molten mixture from die to cooling roll>
A line for introducing the molten mixture of the acrylic resin (A) and the cellulose tellurium resin (B) to the casting die is provided, and the molten mixture is extruded from the casting die.

  First, using a single-screw or twin-screw type extruder, the melt temperature Tm when extruding the pellet is about 200 to 300 ° C., filtered through a leaf disk type filter or the like to remove foreign matters, The film is extruded into a film, solidified on a cooling roll, and cast while being pressed with an elastic touch roll.

  When introducing from the supply hopper to the extruder, it is preferable to prevent oxidative decomposition or the like under vacuum or reduced pressure or in an inert gas atmosphere. Tm is the temperature of the die exit portion of the extruder.

  When foreign matter such as scratches or plasticizer aggregates adheres to the die, streak-like defects may occur. Such defects are also referred to as die lines, but in order to reduce surface defects such as die lines, it is preferable to have a structure in which the resin retention portion is minimized in the piping from the extruder to the die. . It is preferable to use a die that has as few scratches as possible inside the lip.

  The inner surface that contacts the molten resin such as an extruder or a die is preferably subjected to surface treatment that makes it difficult for the molten resin to adhere to the surface by reducing the surface roughness or using a material having a low surface energy. Specifically, a hard chrome plated or ceramic sprayed material is polished so that the surface roughness is 0.2 S or less.

  Although there is no particular limitation on the cooling roll used in the present invention, it is a roll having a structure in which a heat medium or a refrigerant body whose temperature can be controlled flows with a highly rigid metal roll, and its size is not limited, The film may be of a size sufficient to cool the melt-extruded film, and the diameter of the cooling roll is usually about 100 mm to 1 m.

  Examples of the surface material of the cooling roll include carbon steel, stainless steel, aluminum, and titanium. Further, in order to increase the surface hardness or improve the releasability from the resin, it is preferable to perform a surface treatment such as hard chrome plating, nickel plating, amorphous chrome plating, ceramic spraying, or the like.

  The surface roughness of the chill roll surface is preferably 0.1 μm or less in terms of Ra, and more preferably 0.05 μm or less. The smoother the roll surface, the smoother the surface of the resulting film. Of course, it is preferable that the surface processed is further polished to have the above-described surface roughness.

  Examples of the elastic touch roll used in the present invention include JP-A-03-124425, JP-A-08-224772, JP-A-07-1000096, JP-A-10-272676, WO97-028950, JP-A-11-235747, As described in JP-A-2002-36332, JP-A-2005-172940 and JP-A-2005-280217, a thin-film metal sleeve-covered silicon rubber roll can be used.

  When peeling the film from the cooling roll, it is preferable to control the tension to prevent deformation of the film.

<Extension process>
In the present invention, it is preferable that the film obtained as described above is further stretched 1.01 to 3.0 times in at least one direction after passing through the step of contacting the cooling roll. The sharpness of the streaks becomes gentle by stretching and can be highly corrected.

  Preferably, the film is stretched 1.1 to 2.0 times in both the longitudinal (film transport direction) and lateral (width direction) directions.

  As a method of stretching, a known roll stretching machine or tenter can be preferably used. In particular, in the case where the optical film is a retardation film that also serves as a polarizing plate protective film, it is preferable to stack the polarizing film in a roll form by setting the stretching direction to the width direction.

  By stretching in the width direction, the slow axis of the optical film becomes the width direction.

  Usually, the draw ratio is 1.1 to 3.0 times, preferably 1.2 to 1.5 times, and the draw temperature is usually Tg to Tg + 50 ° C. of the resin constituting the film, preferably Tg to Tg + 40 ° C. Performed in the temperature range.

  The stretching is preferably performed under a uniform temperature distribution controlled in the width direction. The temperature is preferably within ± 2 ° C, more preferably within ± 1 ° C, and particularly preferably within ± 0.5 ° C.

  For the purpose of reducing retardation adjustment and dimensional change rate of the optical film produced by the above method, the film may be contracted in the longitudinal direction or the width direction.

  In order to shrink in the longitudinal direction, for example, there is a method of contracting the film by temporarily clipping out the width stretching and relaxing in the longitudinal direction, or by gradually narrowing the interval between adjacent clips of the transverse stretching machine.

  Since the optical film of the present invention is produced by the melt casting coextrusion film forming method, the amount of the solvent contained is 0.01% by mass or less when wound up as a roll film. The amount of the solvent can be measured by the following method.

<Contained solvent amount>
Each sample was placed in a 20 ml sealed glass container, treated under the following headspace heating conditions, and then a calibration curve was prepared and measured for the solvent used in advance by the following gas chromatography. The amount of solvent contained was expressed in parts by mass relative to the total mass of the optical film.
Equipment: HP 5890SERIES II
Column: J & W Company DB-WAX (inner diameter 0.32 mm, length 30 m)
Detection: FID
GC temperature rising condition: held at 40 ° C. for 5 minutes, then heated to 80 ° C./min to 100 ° C. Headspace heating condition: 120 ° C. for 20 min
In the optical film of the present invention, the return material can be used in the production process. The return material is a product obtained by finely pulverizing the optical film, which is generated when the optical film is formed, and is obtained by cutting off both sides of the film, or by using an optical film original that has been speculated out due to scratches, etc. .

  The optical film of the present invention is preferably a long film. Specifically, the optical film has a thickness of about 100 m to 10000 m and is usually provided in a roll shape.

  Moreover, it is preferable that the width | variety of an optical film is 1.3-4m, and it is more preferable that it is 1.4-3m.

  Although there is no restriction | limiting in particular in the film thickness of the optical film of this invention, when using for the polarizing plate protective film mentioned later, it is preferable that it is 10-200 micrometers, it is more preferable that it is 15-100 micrometers, and it is 20-80 micrometers. It is particularly preferred.

<Functional layer>
The optical film of the present invention includes a hard coat layer, an antistatic layer, a back coat layer, a slippery layer, an adhesive layer, a barrier layer, an antiglare layer, an antireflection layer, an optical compensation layer and the like before or after stretching. A functional layer may be applied.

<Polarizing plate>
The optical film of the present invention can be used for a polarizing plate and a liquid crystal display device using the polarizing plate.

  The polarizing plate is characterized in that it is a polarizing plate in which the optical film of the present invention is bonded to at least one surface of a polarizer. The liquid crystal display device of the present invention is characterized in that the polarizing plate is bonded to at least one liquid crystal cell surface via an adhesive layer.

  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.

  On the other surface, the optical film of the present invention may be used, or another polarizing plate protective film may be used. For example, a commercially available cellulose ester film (for example, Konica Minoltack KC8UX, KC4UX, KC5UX, KC8UY, KC4UY, KC4UA, KC6UA, KC12UR, KC8UCR-3, KC8UCR-4, KC8UCR-5, KC8UE, C4, R4 -4, KC4HR-1, KC8UY-HA, KC8UX-RHA, manufactured by Konica Minolta Opto Co., Ltd.) and the like are preferably used.

  A preferred embodiment of the present invention is a polarizing plate in which the optical film of the present invention is bonded to one surface of a polarizer and a cellulose ester film having a thickness of 20 μm to 75 μm is bonded to the other surface.

  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.

As the pressure-sensitive adhesive used in the pressure-sensitive adhesive layer, a pressure-sensitive adhesive having a storage elastic modulus at 25 ° C. in the range of 1.0 × 10 ⁴ Pa to 1.0 × 10 ⁹ Pa in at least a part of the pressure-sensitive adhesive layer is used. It is preferable to use a curable pressure-sensitive adhesive that forms a high molecular weight body or a crosslinked structure by various chemical reactions after the pressure-sensitive adhesive is applied and bonded.

  Specific examples include, for example, urethane adhesives, epoxy adhesives, aqueous polymer-isocyanate adhesives, curable adhesives such as thermosetting acrylic adhesives, moisture-curing urethane adhesives, polyether methacrylate types, Examples include anaerobic pressure-sensitive adhesives such as ester-based methacrylate type and oxidized polyether methacrylate, cyanoacrylate-based instantaneous pressure-sensitive adhesives, and acrylate-peroxide-based two-component instantaneous pressure-sensitive adhesives.

  The pressure-sensitive adhesive may be a one-component type or a type that is used by mixing two or more components before use.

  The pressure-sensitive adhesive may be a solvent system using an organic solvent as a medium, or an aqueous system such as an emulsion type, a colloidal dispersion type, or an aqueous solution type that is a medium containing water as a main component. It may be a solvent type. The density | concentration of the said adhesive liquid should just be suitably determined with the film thickness after adhesion, the coating method, the coating conditions, etc., and is 0.1-50 mass% normally.

<Liquid crystal display device>
By incorporating the polarizing plate bonded with the optical film of the present invention into a liquid crystal display device, it is possible to produce various liquid crystal display devices with excellent visibility, but particularly outdoors such as large liquid crystal display devices and digital signage. It is preferably used for a liquid crystal display device for use. The polarizing plate of the present invention is bonded to a liquid crystal cell via the adhesive layer or the like.

  The polarizing plate of the present invention includes various types such as a reflective type, a transmissive type, a transflective type LCD, a TN type, an STN type, an OCB type, a HAN type, a VA type (PVA type, MVA type), and an IPS type (including an FFS type). It is preferably used in a drive type LCD. In particular, in a large-screen display device having a VA type screen of 30 type or more, particularly 30 type to 54 type, there is no white spot in the periphery of the screen and the effect is maintained for a long time.

  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 Acrylic Resin (A) Containing Amide Group Represented by General Formula (1)>
Acrylic resins A1 and A2 in Table 1 were produced by a known method. In the table, ACMO is acryloylmorpholine, and VP is N-vinylpyrrolidone.

<Production of optical film>
(Preparation of optical film 1)
The following materials were further dried while being mixed at 80 ° C. and 1 Torr for 3 hours with a vacuum nauter mixer, and the resulting mixture was melt-mixed at 235 ° C. using a twin-screw extruder and pelletized.

Acrylic resin (A) represented by general formula (1):
A1: Modified group ACMO, modified amount 25% by mass, weight average molecular weight 80000 40 parts by mass A2: Modified group ACMO, modified amount 40% by mass, weight average molecular weight 80000 15 parts by mass Cellulose ester resin (B): CE1 (cellulose acetate Pionate: acyl group total substitution degree 2.75, acetyl group substitution degree 0.19, propionyl group substitution degree 2.56, Mw = 220,000) 45 parts by mass Tinuvin 928 (manufactured by BASF Japan Ltd.) 1.1 parts by mass GSY -P101 (manufactured by Sakai Chemical Industry Co., Ltd.) 0.25 parts by mass Irganox 1010 (manufactured by BASF Japan Ltd.) 0.5 parts by mass Sumilizer GS (manufactured by Sumitomo Chemical Co., Ltd.) 0.24 parts by mass Aerosil R972V (Japan Aerosil ( 0.4 mass parts Metablen W341 (Mitsubishi Rayon ( 1.0 mass part Metablen P-530A (Mitsubishi Rayon Co., Ltd.) 1.0 mass part The obtained pellets were circulated with 90 ° C dehumidified air (dew point -50 ° C) for 10 hours or more. It dried and it introduce | transduced into the single screw extruder of the next process, maintaining the temperature of 90 degreeC.

  Film formation was performed with the manufacturing apparatus shown in FIG.

  The pellet was melt extruded from a T die onto a first cooling roll having a surface temperature of 90 ° C. at a melting temperature of 240 ° C. using a single screw extruder to obtain a 100 μm cast film. At this time, the film was pressed on the first cooling roll with an elastic touch roll having a 2 mm thick metal surface.

  The obtained film was first stretched 2.2 times in the transport direction at 140 ° C. by a stretching machine utilizing the difference in peripheral speed of the roll. Next, it is introduced into a tenter having a preheating zone, a stretching zone, a holding zone, and a cooling zone (there is also a neutral zone for ensuring thermal insulation between the zones), and the width is increased at 145 ° C. at 2 ° C. Then, the film was cooled to 30 ° C., then released from the clip, and the clip holding part was cut off to obtain a roll-shaped optical film sample 1 having a film thickness of 20 μm, a film width of 2500 mm, and a winding length of 3000 m. The roll-shaped optical film was wound by installing the winding device 16 in FIG. 1 in a winding chamber adjusted to 25 ° C. and 20% RH.

(Preparation of optical films 2 to 11)
As in the production of the optical film 1, the types and amounts of the acrylic resin (A) and the cellulose ester resin (B) were changed as shown in Table 1, and mixed to produce optical film samples 2 to 11.

(Preparation of optical film 12)
In preparation of the said optical film 4, it changed to the following dope liquid without preparing and using a heated melt, and produced the optical film 12 by the solution casting method.

<Dope solution 1>
Acrylic resin (A) represented by general formula (1):
A1: Modified group ACMO, modified amount 15% by mass, weight average molecular weight 80000 60 parts by mass A2: Modified group ACMO, modified amount 40% by mass, weight average molecular weight 80000 20 parts by mass Cellulose ester resin (B): CE2 (cellulose acetate Pionate: acyl group total substitution degree 2.92, acetyl group substitution degree 1.08, propionyl group substitution degree 1.84, Mw = 18000) 20 parts by mass Tinuvin 928 (manufactured by BASF Japan Ltd.) 1.1 parts by mass Aerosil NAX50 (manufactured by Nippon Aerosil Co., Ltd.) 0.2 parts by mass Methylene chloride 380 parts by mass Ethanol 70 parts by mass The above materials were put into a sealed container and dissolved while stirring to prepare a dope solution. The dope was then cast on a stainless steel support at a temperature of 35 ° C.

  After casting, an endless belt casting apparatus was used to uniformly cast the dope solution on a stainless steel belt support at a temperature of 33 ° C. and a width of 2000 mm. The temperature of the stainless steel belt was controlled at 30 ° C.

  On the stainless steel belt support, the solvent was evaporated until the residual solvent amount in the cast (cast) film became 75%, and then peeled off from the stainless steel belt support with a peeling tension of 150 N / m.

  The peeled web was stretched 36% in the width direction using a tenter while applying heat at 160 ° C. The residual solvent at the start of stretching was 10%.

  Next, drying was terminated while the drying zone was conveyed by a number of rolls. The drying temperature was 130 ° C. and the transport tension was 100 N / m.

  The clip holding part was cut off to obtain a roll-shaped optical film sample 12 having a film thickness of 40 μm, a film width of 2500 mm, and a winding length of 3000 m.

(Preparation of optical film 13)
An optical film 13 was prepared by a solution casting method in the same manner except that the optical film 12 was changed to the following dope solution in the production of the optical film 12.

<Dope solution 2>
Acrylic resin (A) represented by general formula (1):
A1: Modified group ACMO, modified amount 30% by mass, weight average molecular weight 80,000 60 parts by weight Cellulose ester resin (B): CE2 (cellulose acetate propionate: acyl group total substitution degree 2.92, acetyl group substitution degree 1.08 , Propionyl group substitution degree 1.84, Mw = 18000) 40 parts by mass Tinuvin 928 (manufactured by BASF Japan Ltd.) 1.1 parts by mass Aerosil NAX50 (manufactured by Nippon Aerosil Co., Ltd.) 0.2 parts by mass Methylene chloride 380 parts by mass << Evaluation of optical film >>
<Water content at the end of drying>
After unwinding the produced roll-shaped optical films 1 to 11, and cutting out a 50 cm square film at 5 locations from an arbitrary winding length, and drying the film with circulating air at 90 ° C. and dew point −50 ° C. for 10 hours, The water content was measured by a coulometric titration method using a Karl Fischer water content measuring device (Dia Instruments Co., Ltd .: CA-06, VA-06), and the average value was obtained to obtain the water content at the end point of drying.

<Fail with point sticking>
The optical film wound up in a roll shape was drawn out, and 10 m near the core portion 100 m was visually observed. A pair of point-like failures corresponding to the winding diameter was regarded as a sticking failure, and the rank was evaluated from the frequency.

◎: 0 pieces ○: 1-3 pieces △: 4-15 pieces ×: 16-30 pieces XX: 31 pieces or more <oblique muscle failure>
The optical film was projected on a screen with a projector light source, and the intensity of MD direction streaks (characterized by being slightly inclined) was sensory evaluated.

○: No muscle failure is observed at any angle. Δ: Muscle failure can be detected depending on the orientation of the optical film. X: Muscle failure is found by holding the film vertically in the projection direction.

  From the above table, the optical film of the present invention containing the two modified acrylic resins A1 and A2 according to the present invention in a content A1> A2 and having a water content at the end of drying of 200 to 500 ppm is It can be seen that it is excellent in failure with sticking and slanting stripe failure.

Example 2
Roll-shaped optical film samples 21 to 23 were prepared in the same manner except that the cellulose ester resin used for the optical film sample 4 was changed to a cellulose ester resin having the following weight average molecular weight changed. In addition, the following winding looseness was evaluated.

<Loose winding>
The amount of deviation of the roll end of the wound optical film sample was measured and evaluated according to the following criteria. The practical allowable range is Δ or more.

○: Less than 3 mm Δ: 3 mm or more and less than 10 mm ×: 10 mm or more

  From the above table, it can be seen that the optical film samples 22 to 23 in which the weight average molecular weight of the cellulose ester resin is 70,000 to 100,000 are excellent not only in the point-like sticking failure and the oblique muscle failure but also in the loosening of the winding. .

DESCRIPTION OF SYMBOLS 1 Extruder 2 Filter 3 Static mixer 4 Casting die 5 Rotating support body (1st cooling roll)
6 Nipping pressure rotating body (touch roll)
7 Rotating support (second cooling roll)
8 Rotating support (3rd cooling roll)
9, 11, 13, 14, 15 Transport roll 10 Optical film 12 Stretching device 16 Winding device

Claims (3)

An optical film containing an acrylic resin (A) and a cellulose ester resin (B) in a mass ratio of 95: 5 to 50:50, wherein the acrylic resin (A) contains at least A1 and A2 satisfying the following conditions: And an acrylic resin having a structure represented by the following general formula (1):
An optical film having a moisture content in the range of 200 to 500 ppm after drying the optical film with circulating air at 90 ° C. and dew point −50 ° C. for 10 hours .
(1) A1 and A2 are modified acrylic resins containing structural units having an amide group. (2) Both A1 and A2 have a weight average molecular weight of 60000 or more. (3) The content of A1 is greater than that of A2. (4) A1 The structural unit having an amide group is 5% or more and less than 30% by mass ratio. (5) The structural unit having an amide group of A2 is 30% or more and less than 80% by mass ratio.
General formula (1):-(MMA) p- (X) q- (Y) r-
[In General Formula (1), MMA represents methyl methacrylate. X represents a monomer unit copolymerizable with MMA having at least one amide group. Y represents a monomer unit copolymerizable with MMA and X. p, q, and r are mass%, and change depending on the amount of modification of A1 and A2, and p + q + r = 100. ] The weight average molecular weight of the said cellulose-ester resin (B) is 100,000 or less, The optical film of Claim 1 characterized by the above-mentioned. A method for producing an optical film according to claim 1 or 2, process for producing an optical film characterized in that the optical film is produced by melt casting method.

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