JP2012025871A - Optical film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an acrylic resin-containing optical film having composition that does not generate streak failure even during long-time continuous production or production over many times.SOLUTION: The optical film contains an acrylic resin (A) and a cellulose ester resin (B), wherein the acrylic resin (A) is represented by the following general formula (1), and the cellulose ester resin (B) satisfies predetermined conditions (Z). General formula (1):-(MMA)p-(X)q-, wherein MMA represents methyl methacrylate, X represents a monomer unit copolymerizable with MMA, and p and q each represent mol%, and 50≤p≤99 and 0≤q≤50.

Description

  The present invention relates to an optical film containing an acrylic resin, a polarizing plate and a display device using the optical film, and more specifically, by blending an acrylic resin and a cellulose ester resin, the surface is transparent and has high heat resistance. The present invention relates to an optical film containing an acrylic resin with significantly improved productivity and productivity.

  Polymethyl methacrylate (hereinafter abbreviated as PMMA), which is a representative of conventional acrylic resins, has been suitably used for optical films from the viewpoint of its excellent transparency, dimensional stability, low hygroscopicity, and the like. However, the PMMA film has poor heat resistance and has a problem that its shape changes when used under high temperatures or for long-term use.

  This problem is an important issue not only as a physical property of a single film but also in a polarizing plate and a display device using such a film. That is, in the liquid crystal display device, because the polarizing plate curls with the deformation of the film, the entire panel is warped, and the design phase difference changes even when used at the position on the viewing side surface. There was a problem that the viewing angle fluctuated and the color changed.

  In order to improve heat resistance, an optical film in which an acrylic resin and a specific cellulose ester resin are mixed has been proposed (Patent Document 1). In addition, an optical film in which the same material is melt cast and the brittleness, yellowness, and bleed-out are improved at the same time, and a manufacturing method thereof have been proposed (Patent Document 2).

  Although this optical film was excellent in performance as an optical film, a decomposition product was generated when the melt was produced as a long roll film by the melt casting method, and the decomposition product was used to extrude the melt. The problem that streaks occur in the optical film by depositing on the die slip part was revealed.

JP 2009-299075 A JP 2010-122340 A

  Accordingly, an object of the present invention is to provide an acrylic resin-containing optical film having a composition that does not cause streak failure even in continuous production for a long time or in many productions.

  The object of the present invention has been achieved by the following.

1. In the optical film containing the acrylic resin (A) and the cellulose ester resin (B), the acrylic resin (A) is represented by the following general formula (1), and the cellulose ester resin (B) has the following condition (Z): An optical film characterized by satisfying
General formula (1)
-(MMA) p- (X) q-
MMA represents methyl methacrylate, and X represents a monomer unit copolymerizable with MMA. p and q are mol%, and 50 ≦ p ≦ 99 and 0 ≦ q ≦ 50.
Condition (Z)
1) A cellulose ester resin is dissolved in a 10 times amount (mass ratio) dichloromethane / ethanol = 85/15 (mass ratio) mixed solution to obtain a dope.
2) The dope is treated in a centrifuge for 3 hours under the condition of 10,000 G.
3) Remove the supernatant, replenish the same amount (mass ratio) of dichloromethane / ethanol = 85/15 (mass ratio) mixture, and shake and shake.
4) Treat again for 3 hours in a centrifuge at 10,000 G.
5) Remove the supernatant and air-dry the sediment.
6) The dried residue is immersed in a 10 times amount (mass ratio) water / methanol = 1/1 (mass ratio) mixed solution and treated with an ultrasonic cleaner for 1 hour.
7) The mixed solution is filtered with a nonwoven fabric filter having a filtration accuracy of 1 μm.
8) The obtained filtrate is air-dried and the mass of the residual solid is measured.
9) Let P be the content of the finally obtained solid content of cellulose ester resin.
10) 0 ppm ≦ P ≦ 100 ppm.

2. 2. The optical film as described in 1 above, wherein the acrylic resin (A) satisfies the following general formula (2).
General formula (2)
-(MMA) p- (X) q- (Y) r-
MMA represents methyl methacrylate, X represents a monomer unit copolymerizable with MMA having at least one hydroxyl group or amide group, and Y represents a monomer unit copolymerizable with MMA and X. p, q, and r are mol%, and are 50 <= p <= 99, 0 <= q <= 50, and p + q + r = 100.

  ADVANTAGE OF THE INVENTION According to this invention, the acrylic resin containing optical film which has a composition which does not generate a streak failure also in long-time continuous manufacture or manufacture over many times can be obtained.

It is the schematic of the optical film manufacturing apparatus of this invention.

<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). The acrylic resin (A) is represented by the following general formula (1), and the cellulose ester resin (B): Satisfies the following condition (Z).
General formula (1)
-(MMA) p- (X) q-
MMA represents methyl methacrylate, and X represents a monomer unit copolymerizable with MMA. p and q are mol%, and 50 ≦ p ≦ 99 and 0 ≦ q ≦ 50.
Condition (Z)
1) A cellulose ester resin is dissolved in a 10 times amount (mass ratio) dichloromethane / ethanol = 85/15 (mass ratio) mixed solution to obtain a dope.
2) The dope is treated in a centrifuge for 3 hours under the condition of 10,000 G.
3) Remove the supernatant, replenish the same amount (mass ratio) of dichloromethane / ethanol = 85/15 (mass ratio) mixture, and shake and shake.
4) Treat again for 3 hours in a centrifuge at 10,000 G.
5) Remove the supernatant and air-dry the sediment.
6) The dried residue is immersed in a 10 times amount (mass ratio) water / methanol = 1/1 (mass ratio) mixed solution and treated with an ultrasonic cleaner for 1 hour.
7) The mixed solution is filtered with a nonwoven fabric filter having a filtration accuracy of 1 μm.
8) The obtained filtrate is air-dried and the mass of the residual solid is measured.
9) Let P be the content of the finally obtained solid content of cellulose ester resin.
10) 0 ppm ≦ P ≦ 100 ppm.
(Mechanism estimation)
The cellulose ester resin satisfying the condition (Z) means that there are few components having a total degree of substitution in the vicinity of 0.5 to 1.5 in the resin. Usually, a cellulose ester resin contains 300 to 3000 ppm of a component having a total substitution degree of about 0.5 to 1.5 (hereinafter simply referred to as “low substitution degree component”).

  The “low substitution component” in the present invention is different from a component having a substitution degree of almost zero, which has been conventionally expressed as “unsubstituted cellulose” or “bright spot foreign matter”.

  On the other hand, streak failures in continuous production for a long time or many times of production are caused by accumulation of thermal decomposition components of the resin in the die slip portion, particularly in the land portion. If this accumulation becomes violent, it can be visually confirmed at the time of die disassembly, but streak failure occurs even if it is extremely mild.

  Since it cannot be visually confirmed, the next manufacturing is performed without removing the accumulation at the time of cleaning, and it is not possible to ensure the elimination of streak failure.

  The present inventors presumed that the low substitution component of the cellulose ester resin promoted thermal decomposition of the acrylic resin, and the acrylic resin thermal decomposition component accumulated in the die slip part. Then, the subject was solved and the present invention was reached by using the cellulose ester resin which reduced the low substitution degree component significantly.

Furthermore, in the case of the acrylic resin which copolymerized the monomer containing an amide group and a hydroxyl group, it estimated that it had the function to protect a cellulose-ester resin from thermal decomposition (it maintains a stable state) with the affinity.
<Acrylic resin (A)>
The acrylic resin used in the present invention includes a methacrylic resin.

  The acrylic resin (A) of the present invention is represented by the following general formula (1), and preferably has a weight average molecular weight Mw of 20,000 or more and 1,000,000 or less. Furthermore, it is preferably represented by the general formula (2).

General formula (2)
-(MMA) p- (X) q- (Y) r-
MMA represents methyl methacrylate, X represents a monomer unit copolymerizable with MMA having at least one hydroxyl group or amide group, and Y represents a monomer unit copolymerizable with MMA and X. p, q, and r are mol%, and are 50 <= p <= 99, 0 <= q <= 50, and p + q + r = 100.

  X is a vinyl monomer having at least one hydroxyl group or 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 Formamide, N-vinylacetamide, vinylpyrrolidone, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, etc. It is below.

  Preferably, acryloyl morpholine, vinyl pyrrolidone, and 2-hydroxyethyl methacrylate are used.

  Commercially available monomers can be used as they are.

  q is 0 ≦ q ≦ 50 and is appropriately selected depending on the properties of the monomer, but preferably 5 ≦ q ≦ 30. X may be a plurality of monomers.

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

  Examples of Y include known monomers such as acrylic monomers other than MMA, methacrylic monomers, olefins, acrylonitrile, styrene, and vinyl acetate. Y may be two or more.

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

  The acrylic resin (A) of the present invention has a weight average molecular weight (Mw) of 20000 or more from the viewpoint of improving transparency particularly when it is compatible with the cellulose ester resin (B).

  The weight average molecular weight (Mw) of the acrylic resin (A) is more preferably in the range of 20000 to 1000000, particularly preferably in the range of 50000 to 300000, and most preferably in the range of 100,000 to 200000. preferable.

  The upper limit of the weight average molecular weight (Mw) of the acrylic resin (A) is preferably 1000000 or less from the viewpoint of production.

  The weight average molecular weight of the acrylic resin of 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.
<Cellulose ester resin (B)>
The cellulose ester resin (B) of the present invention has an acyl group total substitution degree of 1.8 to 3.0, particularly from the viewpoint of transparency when improved in brittleness or compatible with the acrylic resin (A). The degree of substitution of the group is preferably 0.0 to 2.5, and the degree of substitution of the acyl group having 3 to 7 carbon atoms is preferably 0.0 to 2.8. The condition (Z) is satisfied.

  Specific examples of the acyl group having 3 to 7 carbon atoms include propionyl and butyryl, with propionyl group being particularly preferred.

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

  Among these, a cellulose ester resin particularly preferable is cellulose acetate propionate, cellulose propionate, or cellulose acetate.

  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 of the present invention is 75,000 or more, particularly from the viewpoint of improving compatibility with the acrylic resin (A) and brittleness, and is preferably in the range of 75,000 to 300,000. It is more preferable that it is within the range of 240,000, and that of 160000 to 240000 is particularly preferable.

  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 resins can be mixed and used.

The weight average molecular weight of the cellulose ester resin of the present invention can be measured by the GPC.
<Condition (Z)>
Condition (Z) can be obtained by carrying out a purification treatment. In addition, the composition of the cellulose ester resin (B) before and after the purification treatment does not show a difference in the GPC measurement, but it can be determined that it is clearly different depending on the condition (Z).

Condition (Z) is as follows.
1) A cellulose ester resin is dissolved in a 10 times amount (mass ratio) dichloromethane / ethanol = 85/15 (mass ratio) mixed solution to obtain a dope.
2) The dope is treated in a centrifuge for 3 hours under the condition of 10,000 G.
3) Remove the supernatant, replenish the same amount (mass ratio) of dichloromethane / ethanol = 85/15 (mass ratio) mixture, and shake and shake.
4) Treat again for 3 hours in a centrifuge at 10,000 G.
5) Remove the supernatant and air-dry the sediment.
6) The dried residue is immersed in a 10 times amount (mass ratio) water / methanol = 1/1 (mass ratio) mixed solution and treated with an ultrasonic cleaner for 1 hour.
7) The mixed solution is filtered with a nonwoven fabric filter having a filtration accuracy of 1 μm.
8) The obtained filtrate is air-dried and the mass of the residual solid is measured.
9) Let P be the content of the finally obtained solid content of cellulose ester resin.
10) 0 ppm ≦ P ≦ 100 ppm.

  Specifically, the cellulose ester resin (B) satisfying the condition (Z) can be produced as follows.

In the production of the cellulose ester resin, it is possible to reduce the low substitution component that satisfies the condition (Z) by the following approaches (1) to (5) as viewed from the raw material cellulose.
(1) Enhancing the esterification reaction For example, in “C.J. Malm: Svend Kem. Tidskr, 73, 10 (1961)”, cellulose is activated with acetic acid in pretreatment and then treated with butyric acid containing a small amount of sulfuric acid. It is shown that esterification can be enhanced by increasing the concentration of acid anhydride and catalyst sulfuric acid by making the ratio of ester mixed acid and cellulose as small as possible and increasing the concentration of acid anhydride and catalyst sulfuric acid. . Further, US Pat. No. 2,097,954 proposes a pretreatment in which a cellulose ester resin having a high degree of acetylation is activated with acetic acid and then treated with butyric acid containing a small amount of sulfuric acid.

Further, strengthening the pulverization of the raw material cellulose, making it an ultrafine powder using a pulverizer, a disperser or the like contributes to the enhancement of the esterification reaction.
(2) Suppressing excessive hydrolysis in the aging step The aging step is to hydrolyze the primary cellulose ester resin after the esterification reaction to obtain a cellulose ester resin having a desired degree of substitution. By uniformly controlling the hydrolysis reaction at this time, it is possible to suppress the occurrence of low substitution components. For example, Japanese Patent Laid-Open No. 2006-117896 discloses a concept that suppresses the occurrence of low substitution components by adjusting the content of sulfuric acid used as a catalyst and the content of an aqueous solvent in the aging step. Yes.
(3) Suppressing excessive hydrolysis in the precipitation step In the precipitation step, a poor solvent such as water is added to the reaction solution to precipitate the insoluble cellulose ester resin. It is easy to induce a reaction. When the hydrolysis reaction proceeds locally, the low substitution degree component increases. Therefore, the temperature at the time of water addition is suppressed to a low temperature, the addition of water is moderated to suppress the progress of local hydrolysis, and water is jetted into fine particles while stirring the reaction liquid at a high rate. It is effective to add uniformly.

According to Japanese Patent Application Laid-Open No. 2008-56819, it is suggested that contact with water in the precipitation step promotes hydrolysis and easily generates a low substitution degree component. According to the present invention, it is also preferred to obtain a cellulose ester resin by removing the solvent without contact with moisture.
(4) Separating the low substitution component using an appropriate solvent Cellulose ester resin is dissolved in an organic solvent (dichloromethane, tetrahydrofuran, acetone, etc.) in which the main component of the cellulose ester resin is easy to dissolve and the low substitution component is difficult to dissolve. The low substitution component can be removed by dissolving and filtering the insoluble low substitution component.

  On the contrary, the cellulose ester resin powder is suspended in an organic solvent (such as methanol) in which the main component of the cellulose ester resin is difficult to dissolve and the low substitution component is easily dissolved. It can also be removed by washing. At this time, in order to promote dissolution, it is preferable to add ultrasonic waves, shearing, pulverization treatment or the like.

For example, it is preferable to roughly pulverize the cellulose ester resin, add 5 times the amount of water / methanol = 1/1 (mass ratio) thereto, and treat the suspended liquid with a bead mill disperser.
(5) Strengthen filtration at each process In the reaction solution before the precipitation process, the low substitution component exists as an insoluble component. Therefore, the low substitution component can also be reduced by performing strong filtration here. Can do. As an example of strengthening filtration, Japanese Patent Application Laid-Open No. 2003-221455 discloses that two or more filtration steps are effective.

  Japanese Patent Application Laid-Open No. 2003-213004 discloses that the minimum particle size of the retained particle size is 3 μm or less and 0.5 μm or more, the thickness is 3.5 to 4.5 mm, and the drainage time is 150 to 350 seconds. The use of cellulose filter paper is disclosed.

  Furthermore, in JP-A-11-254466, a filter medium having an absolute filtration accuracy in the range of 0.005 mm or less (particularly 0.001 to 0.005 mm) is preferable. By filtering with a filter medium having a high filtration accuracy, It is said that minute insoluble matters such as cellulose that has not been esterified and impurities can be effectively removed.

  In addition, filter aids described in JP-A No. 2004-107629 and others are also preferably used. As a filter aid, diatomaceous earth or silica gel is preferable. The filter aid may be used by adding it to the reaction solution side, or may be spread using the filter as a support.

  A plurality of these means may be selected. When the cellulose ester resin is precipitated from the dope after the filtration steps (4) and (5), it is preferable to suppress new hydrolysis by the method described in (3).

As described above, it is necessary for the present invention to reduce the low substitution component in the cellulose ester resin and satisfy the condition (Z).
<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) can exert an effect when the problem of the present invention occurs regardless of the mixing ratio. It is preferable that A) and cellulose ester resin (B) are contained in a mass ratio of 95: 5 to 30:70. More preferably, it is 70: 30-60: 40.

  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 material 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. 413895 can be used.

The low molecular acrylic resin of the present invention and the vinyl polymer having an amide bond are 0 to 15% by mass, preferably 0 to 10% by mass, based on the total mass of the optical film.
<Acrylic particles (D)>
The optical film of the present invention may contain acrylic particles (D) described in Patent Document 1.

  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, Chemisnow MR-2G, MS-300X (manufactured by Soken Chemical Co., Ltd.), and “Parapet SA” manufactured by Kuraray 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 (D) 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 includes a retardation control agent for controlling retardation, a plasticizer for imparting processability to the film, an antioxidant for preventing deterioration of the film, and an ultraviolet ray for imparting an ultraviolet absorbing function. It is preferable to contain additives such as fine particles (matting agent) that impart slipperiness to the absorbent and film.

<Polyester polyol of glycol and dibasic acid>
The polyester polyol that can be used in the present invention includes a dehydration condensation reaction between a glycol having an average carbon number of 2 to 3.5 and a dibasic acid having an average carbon number of 4 to 5.5, or the glycol. It is preferable to be produced by a conventional method by addition of a dibasic anhydride having an average carbon number of 4 to 5.5 and a dehydration condensation reaction.

<Polyester of aromatic dicarboxylic acid and alkylene glycol>
As the retardation control agent of 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.

  As specific compounds of the aromatic terminal polyester of the present invention, paragraphs (0183) to (0186) of JP 2010-32655 A can be mentioned.

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

<Polyhydric ester compound>
The optical film of the present invention can contain a polyhydric alcohol ester compound.

  Examples of the polyhydric alcohol ester compounds include paragraphs (0218) to (0170) of JP 2010-32655 A.

<Sugar ester compound>
As the sugar ester compound of the present invention, it is possible to use a sugar ester compound having at least one pyranose structure or at least one furanose structure and esterifying all or part of the OH groups of the structure. preferable.

  Examples of the sugar ester compound used in the present invention include glucose, galactose, mannose, fructose, xylose, arabinose, lactose, sucrose, cellobiose, cellotriose, maltotriose, raffinose, etc. 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 of the present invention include paragraphs (0060) to (0070) of JP-A 2010-32655.

<Other additives>
In the optical film of the present invention, a plasticizer, a retardation control agent, an antioxidant, an ultraviolet absorber, matte particles, and the like can be used in combination.

  Examples of the plasticizer include phthalate ester, fatty acid ester, trimellitic ester, phosphate ester, polyester, and epoxy.

  For phosphate ester plasticizers, triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl 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.

  Of these, 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.

  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 of the present invention, those containing bisphenol A in the molecule are also 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 means an effect of making the color tone of a liquid crystal screen blue, adjusting the 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 since it has a refractive index close to that of cellulose ester and is excellent in transparency (haze).

  Specific examples of silicon dioxide include Aerosil 200V, Aerosil R972V, Aerosil R972, R974, R812, 200, 300, R202, OX50, TT600, 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, so the range of 80 nm to 180 nm is particularly preferable.

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

<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 have the ability to form stronger hydrogen bonds with cellulose than intermolecular hydrogen bonds of cellulose resin. In the melt casting method performed in the present invention, the glass transition temperature of the cellulose resin used alone is higher than that. The melting temperature of the cellulose resin composition can be lowered by the addition of a hydrogen bonding solvent, or the melt viscosity of the cellulose resin composition containing a hydrogen bonding solvent can be lowered at the same melting temperature as the cellulose resin. .
<Characteristics of optical film>
Hereafter, the characteristic about the characteristic of the optical film of this invention is demonstrated.

<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 refractive index difference 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 with excellent quality expressed by the frequency of such defects with high productivity, it is necessary to filter the polymer solution with high precision immediately before casting, to increase the cleanliness around the casting machine, It is effective to set drying conditions after rolling stepwise and to dry efficiently while suppressing foaming.

  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 Rt 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 Rt (590) is in the range of −100 to 100 nm.
Formula (I): Ro (590) = (nx−ny) × d (nm)
Formula (II): Rt (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 Rt (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 preferably in the range of 0 to 250 nm.

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

  The desired retardation is adjusted by adjusting the ratio of each resin within the range of 95: 5 to 50:50 mass ratio of acrylic resin and cellulose ester resin. This is done by adjusting 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 thickness of the optical film of the present invention is preferably 20 μm or more and 150 μm or less. More preferably, it is 30 μm or more and 80 μm or less.

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 is preferably produced by a melt casting method from the viewpoint of flatness and thinning.
<Method for producing optical film by melt casting 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.

  The entire manufacturing method will be described below.

<Melted pellet manufacturing process>
The mixture of acrylic resin (A), cellulose ester (including cellulose ester resin (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, dry acrylic resin (A), dry cellulose ester, plasticizer, and other additives are fed to an extruder with a feeder and kneaded using a single or twin screw extruder. Then, it can be extruded from a die into a strand, cooled with water or air, and cut.

  It is important to dry the raw material before extruding to prevent decomposition of the raw material. 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, and if necessary, the antioxidant may be dissolved in a solvent and mixed by impregnating the acrylic resin (A) and cellulose ester, or You may spray and mix.

  A vacuum nauter mixer or the like is preferable because drying and mixing can be performed simultaneously. Moreover, when touching with air, such as an exit from a feeder part or die | dye, it is preferable to set it as atmosphere, such as dehumidified air and dehumidified N2 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 acrylic resin (A) from the molten mixture to the casting die and a line for introducing the cellulose tellur resin from the molten mixture to the casting die are provided side by side, and each molten mixture is laminated in 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 coextruded into a film, solidified on a cooling roll, and cast while pressing 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.

  In addition to the problems of the present invention, streaky defects may occur when foreign matters such as scratches and plasticizer aggregates adhere to the die. 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.

  The cooling roll of the present invention is not particularly limited, but is a roll having a structure in which a heat medium or a coolant that can be controlled in temperature flows through a highly rigid metal roll, and the size is not limited. The size 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 of 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, JP-A-11-235747. A silicon rubber roll coated with a thin-film metal sleeve can be used as described in JP-A-2002-36332, JP-A-2005-172940 and JP-A-2005-280217.

  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 3.0 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 adjusting the retardation of the optical film produced by the above method and reducing the dimensional change rate, 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
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. .

  In addition, an acrylic resin, a cellulose ester resin, and, in some cases, acrylic particles kneaded into pellets can be preferably used.

  The optical film of the present invention is preferably a long film. Specifically, the optical film has a thickness of about 100 m to 5000 m and is usually provided in a roll shape.

  Moreover, it is preferable that the width | variety of a long film is 1.3-4m, and it is more preferable that it is 1.4-2m.

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 20-200 micrometers, it is more preferable that it is 25-100 micrometers, and it is 30-80 micrometers. It is particularly preferred.
<Polarizing plate>
When using the optical film of this invention as a protective film for polarizing plates, a polarizing plate can be produced by a general method.

  It is preferable that an adhesive layer is provided on the back side of the optical film of the present invention, and is bonded to at least one surface of a polarizer produced by immersion and stretching in an iodine 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, KC12UR, KC8UCR-3, KC8UCR-4, KC8UCR-5, KC8UE, KC4R-4, KC4FR-3, KC4FR-3, KC4FR-3, KC4FR-3, KC4FR-3, KC4FR-3, -1, KC8UY-HA, KC8UX-RHA, manufactured by Konica Minolta Opto Co., Ltd.) and the like are preferably used.

  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 for 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 preferably used. A curable pressure-sensitive adhesive that forms a high molecular weight body or a crosslinked structure by various chemical reactions after applying and bonding the pressure-sensitive adhesive is suitably used.

  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.

  The acrylic resin (A) in Table 1 was produced by a known method. In the table, MA is methyl acrylate, St is styrene, ACMO is acryloylmorpholine, VP is vinyl pyrrolidone, and HEMA is 2-hydroxyethyl methacrylate.

  Table 2 describes the composition of the cellulose ester resin (B) that satisfies the condition (Z). The cellulose ester resin (B) was produced by the following method. In addition, Ac group: An acetyl group, Pr group: A propionyl group is represented.

Cellulose ester resin (B) is obtained by subjecting the production method of a reference cellulose ester resin obtained as follows to the following operations and treatments.
Production of (reference cellulose ester resin = cellulose ester resin 6) [pretreatment]
A sheet of softwood pulp (α cellulose content 95%) (water content 8%) was pulverized with a pulverizer of Comparative Example 1 of JP2009-11967A to obtain a cotton-like shape. 24 parts by mass of acetic acid was sprayed on 100 parts by mass of cotton-like softwood pulp, and left for 14 hours to obtain pretreated softwood pulp.
[Esterification]
74 parts by mass of propionic acid, 370 parts by mass of propionic anhydride, and 3.6 parts by mass of sulfuric acid were mixed and cooled to minus 20 ° C. This mixture was transferred to a biaxial stirring reactor, and pretreated softwood pulp was added over 10 minutes with stirring.

The completion of addition of pretreated softwood pulp to the reactor was defined as esterification time 0, and the temperature in the reactor was 10 ° C. for esterification time 0 to 10 minutes. Further, after the esterification time of 10 minutes, the reactor internal temperature was raised from 10 ° C. to 40 ° C. over 55 minutes. Furthermore, the reactor internal temperature was kept at 40 ° C., and 150 minutes after the start of esterification, 180 parts by mass of a 75% by mass acetic acid aqueous solution was added dropwise over 10 minutes to hydrolyze excess propionic anhydride.
[Aging]
The reaction mixture in which excess propionic anhydride was hydrolyzed was kept at 60 ° C. for 130 minutes. In this comparative example, as the neutralization method in the ripening step, a multi-stage neutralization method, more specifically, a continuous neutralization method was used. That is, 20 minutes were required, and 43 parts by mass of a 24% by mass magnesium acetate aqueous solution was added to neutralize sulfuric acid.
[Filtration]
No. No. manufactured by Toyo Roshi Kaisha, Ltd. using the reaction mixture as a filter medium. Filtration was performed at a gauge pressure of 0.2 MPa / cm ² using one piece of 6B filter paper.
[Precipitation / Washing / Drying]
Acetic acid was dissolved in pure water to prepare a 10% by mass acetic acid solution. 2,400 parts by mass of a 10% by mass aqueous acetic acid solution was added to the filtered reaction mixture with stirring to obtain a flaky precipitate. The precipitate was drained with a sieve. This was immersed in warm water of pure water adjusted to 50 ° C. and further drained. After this operation was repeated 6 times, the liquefied cellulose mixed fatty acid ester was vacuum dried at 60 ° C. to obtain a reference cellulose ester resin (cellulose ester resin 6).
1. (Raw material pulverization = pretreatment step) Cellulose ester resins 2, 4
For the raw material cellulose, the crusher described in Example 1 of JP2009-11967A was applied instead of the above crusher.
2. (Reaction promotion = esterification step) Cellulose ester resin 3
The operation of the activation step and the acylation step described in Example 1 of JP-A-2008-127535 was applied.
3. (Aging control = aging process) Cellulose ester resin 4
The conditions described in Example 1 of JP-A No. 2006-117896 (all reaction conditions such as aging sulfuric acid amount, aging water amount, aging temperature, time, etc.) were applied.
4). (Filter aid = Filtration step) Cellulose ester resin 4
0.2% of the filter aid described in Example 3 of JP-A-2004-107629 was added to the reaction solution.
5). (Filtration = filtration step) Cellulose ester resins 1, 2, 4, 5
Prior to the precipitation step, among the examples described in JP-A No. 2003-221455, filter paper having a filtering time of 500 seconds and a metal filter having a collected particle diameter of 5 μm were applied in this order.
6). (Solvent washing = precipitation / washing / drying step) Cellulose ester resins 1, 3
The reference cellulose ester resin was suspended in 10 times the amount of acetone / water = 5/5 solvent, filtered, washed and dried.
7). (Dry spinning) Cellulose ester resin 3
The method described in Example 1 of Japanese Patent Application Laid-Open No. 2008-56819 was applied to the reference cellulose ester resin, and dry spinning was performed to obtain a fiber bundle of cellulose ester resin 3.
8). (Adjustment) Cellulose ester resin 7
0.1% of acetylcellulose having an average degree of substitution of 1.1 and a molecular weight of 50,000 was added.
[Calculation method of P]
In order to determine the condition (Z), P was determined according to the following operation.

  450 g of cellulose ester resin was dissolved in 4500 g of a mixed solution of dichloromethane / ethanol = 85/15 (mass ratio) to prepare a dope.

  200 g of the dope was fractionated and placed in a 250 ml centrifuge tube, and treated at 6700 rpm (10000 G) for 3 hours in a centrifuge (HIMAC CENTRIFUGE SCR20B, manufactured by Hitachi Koki Co., Ltd .: rotor radius 20 cm). 4800 g of dope was processed by setting 4 centrifuge tubes at a time and processing 6 times.

  For each centrifuge tube, the supernatant was removed, the same amount of dichloromethane / ethanol = 85/15 mixed solution was replenished, and the mixture was stirred and shaken to obtain a uniform state.

  For each centrifuge tube, the supernatant was removed again, and the remaining sedimented portion was air-dried. After calculating the weight W1 (g) of the dry residue and taking out the dry residue while lightly pulverizing with a spatula, rinse out with a water / methanol = 1/1 mixed solution to treat all the residue in the centrifuge tube. did. The mass of the final water / methanol = 1/1 mixture was adjusted to be W1 × 10 (g) so that the total amount of the dry residue was immersed in this solution.

  Thereafter, this liquid was treated in an ultrasonic cleaner for 1 hour, and filtered with a nonwoven fabric filter having a filtration accuracy of 1 μm. The obtained filtrate was air-dried, and the mass W2 (g) of the residual solid content was measured.

Finally,
P (ppm) = W2 / 436.4 × 1,000,000
P was determined according to

<Creation of optical film sample>
The following materials were further dried while being mixed at 90 ° 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 1 (dried at 90 ° C. for 3 hours and water content 1000 ppm) 60 parts by weight Cellulose ester resin B 1 (dried at 100 ° C. for 3 hours and water content 500 ppm)
40 parts by mass ADK STAB LA-31 (manufactured by ADEKA Corporation) 2.0 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 (manufactured by Nippon Aerosil Co., Ltd.) 0.4 parts by mass The obtained pellets are dried by circulating 70 ° C. dehumidified air for 5 hours or more. While maintaining the temperature of 100 ° C., it was introduced into the single-screw extruder in the next step. A small amount of the pellet was taken out and the water content was measured and found to be 120 ppm.

  The cellulose ester film was produced by the production apparatus shown in FIG.

  The pellet was melt-extruded from the T die lip portion into a film using a single screw extruder, and then melt-extruded into a film on a first cooling roll having a surface temperature of 90 ° C. to obtain a cast film of 185 μm. 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 2.1 times in the transport direction at 175 ° 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 175 ° 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 an optical film sample 1 having a film thickness of 40 μm and a film width of 2500 mm.

  In order to evaluate the deterioration of streaks over time, three points were obtained when the melt extrusion time was 12 hours and 72 hours, and 12 hours after the extrusion was temporarily interrupted and the inside of the T die was cleaned. Compared. To clean the inside of the T-die, the resin was carefully removed using a copper spatula and a brass brush and wiped with a cotton cloth. In the visual check, the die slip portion is not dirty.

  The optical film sample 1 was pulverized and mixed with the pellets of the same formulation in a ratio of 3: 7 to obtain an optical film (using recycled material) using the above single screw extruder.

  In the same manner, acrylic resin A and cellulose ester resin B were mixed as shown in Table 3 to prepare an optical film sample.

  In Samples 5 and 10, 5 parts by mass of 70 parts by mass of the acrylic resin were replaced with acrylic resin particle Methbrene W-341 (manufactured by Mitsubishi Rayon Co., Ltd.) *.

The melting temperature was set for each resin mixture as a temperature at which the melt viscosity becomes 1000 Pa · s.
<Evaluation of optical film sample>
All evaluations were performed in an atmosphere of 23 ° C. and 55% RH unless otherwise specified. The sample used was stored in advance in the same atmosphere for 24 hours. The results are shown in Table 3.
<Suji>
For each of the optical film samples, when the melt extrusion time is 12 hours and 72 hours have elapsed, and further, the extrusion is temporarily interrupted, and the three points when 12 hours have elapsed after cleaning the inside of the T die, The degree of streaks was evaluated according to the following criteria.

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

  For the streak height, the vertical distance (H) from the top of the mountain to the bottom of the valley is read. 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 streak height and streak slope are expressed as average values of the predetermined streak height and slope existing with respect to the entire film width, respectively.

  The number of streaks is obtained by counting the number of streaks having a predetermined height and inclination in a range divided every 10 mm with respect to the entire width of the film, and obtaining the average of the streaks with respect to the total width.

In the present invention, the number of streaks having a height of 100 nm or more and an inclination exceeding 200 nm / mm was used as an evaluation index. The results are shown in Table 3.
<Lip cleanability>
When the extrusion was temporarily interrupted and the inside of the T die was cleaned, a part of the land portion of the die slip was washed with acetone, the washing liquid was evaporated to dryness, and the residue was visually evaluated. The results are shown in Table 3.
○: Nothing remains in particular △: A white object remains slightly ×: An apparently white object remains <Preparation of polarizing plate>
Of the optical film samples prepared above, those used for each return material were subjected to the alkali saponification treatment described below to prepare a polarizing plate.

<Alkali saponification treatment>
Saponification step 2M-NaOH 50 ° C. 90 seconds Water washing step Water 30 ° C. 45 seconds Neutralization 10% HCl 30 ° C. 45 seconds Water washing step Water 30 ° C. 45 seconds After saponification treatment, water washing, neutralization, water washing are performed in this order. Subsequently, it dried at 80 degreeC.
<Production of polarizer>
A 120 μm-thick long roll polyvinyl alcohol film was immersed in 100 parts by mass of an aqueous solution containing 1 part by mass of iodine and 4 parts by mass of boric acid, and stretched 6 times at 50 ° C. in the transport direction to produce a polarizer.

The KC4UY manufactured by Konica Minolta Opto Co., Ltd. was similarly saponified on one side of the polarizer, and the optical film sample of the present invention subjected to the alkali saponification treatment was bonded to the opposite side with a completely saponified polyvinyl alcohol 5% aqueous solution. As the agent, the polarizer was bonded to each other so that the transmission axis of the polarizer and the in-plane slow axis of the film were parallel, and dried to prepare a polarizing plate.
<Production of liquid crystal display device>
The obtained polarizing plate carefully peels off the viewing-side polarizing plate previously bonded to the liquid crystal display device Wooo W32L-H90 manufactured by Hitachi, which is an IPS type liquid crystal display device, and transmits the polarizing plate originally applied. In accordance with the axis, a polarizing plate was attached so that the optical film of the present invention produced through an adhesive was on the viewing side, and a liquid crystal display device was produced.

Thereafter, the contrast was evaluated in an environment of 23 ° C. and 55% RH. The results are shown in Table 3.
<contrast>
The measurement was performed after the backlight of each liquid crystal display device was lit continuously for 1 hour in an environment of 23 ° C. and 55% RH. For measurement, EZ-Contrast 160D manufactured by ELDIM was used to measure the luminance from the normal direction of the display screen of white display and black display with a liquid crystal display device, and the ratio was defined as the front contrast.
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 front contrast at any five points of the liquid crystal display device was measured and evaluated according to the following criteria.
○: 1000-1200
Δ: 900 to less than 1000 ×: less than 900

  When the optical film sample of the present invention was used, it was confirmed that the streak was greatly improved.

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 Film (web)
16 Winding device F Rolled film

Claims (2)

In the optical film containing the acrylic resin (A) and the cellulose ester resin (B), the acrylic resin (A) is represented by the following general formula (1), and the cellulose ester resin (B) has the following condition (Z): An optical film characterized by satisfying
General formula (1)
-(MMA) p- (X) q-
MMA represents methyl methacrylate, and X represents a monomer unit copolymerizable with MMA. p and q are mol%, and 50 ≦ p ≦ 99 and 0 ≦ q ≦ 50.
Condition (Z)
1) A cellulose ester resin is dissolved in a 10 times amount (mass ratio) dichloromethane / ethanol = 85/15 (mass ratio) mixed solution to obtain a dope.
2) The dope is treated in a centrifuge for 3 hours under the condition of 10,000 G.
3) Remove the supernatant, replenish the same amount (mass ratio) of dichloromethane / ethanol = 85/15 (mass ratio) mixture, and shake and shake.
4) Treat again for 3 hours in a centrifuge at 10,000 G.
5) Remove the supernatant and air-dry the sediment.
6) The dried residue is immersed in a 10 times amount (mass ratio) water / methanol = 1/1 (mass ratio) mixed solution and treated with an ultrasonic cleaner for 1 hour.
7) The mixed solution is filtered with a nonwoven fabric filter having a filtration accuracy of 1 μm.
8) The obtained filtrate is air-dried and the mass of the residual solid is measured.
9) Let P be the content of the finally obtained solid content of cellulose ester resin.
10) 0 ppm ≦ P ≦ 100 ppm. The optical film according to claim 1, wherein the acrylic resin (A) satisfies the following general formula (2).
General formula (2)
-(MMA) p- (X) q- (Y) r-
MMA represents methyl methacrylate, X represents a monomer unit copolymerizable with MMA having at least one hydroxyl group or amide group, and Y represents a monomer unit copolymerizable with MMA and X. p, q, and r are mol%, and are 50 <= p <= 99, 0 <= q <= 50, and p + q + r = 100.

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