WO2010095518A1 - Optical film manufacturing method, optical film, polarizing plate, and liquid crystal display device - Google Patents

Abstract

Disclosed is a method for manufacturing an optical film for which a fused material adhering to the perimeter of a lip part does not degrade due to oxidation and form an aggregate, and for which sublimates from the fused material do not adhere to the perimeter of the lip part, and for which striped noise is not generated; further disclosed are an optical film manufactured with said method, and a polarizing plate and a liquid crystal display device for which said optical film is used as a protective film. In an extrusion process, an inert gas with a temperature of not less than 110°C and not more than 300°C is supplied to the lip part of a casting die from a supply nozzle.

Description

Optical film manufacturing method, optical film, polarizing plate, and liquid crystal display device

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

Optical films are often used in image display devices such as word processors, personal computers, and TVs. For example, polarizing plates provided on both sides of a liquid crystal cell used in a liquid crystal image display (LCD) are used as protective films that are attached to both sides of a polarizer. Since the polarizing plate allows only light with a polarization plane in a certain direction to pass, it plays an important role in visualizing changes in the orientation of the liquid crystal due to the electric field in the LCD, and the performance of the polarizing plate greatly depends on the performance of the polarizing plate. The Therefore, the optical performance required for the protective film attached to both surfaces of the polarizer is also increasing.

Until now, such optical films have been produced exclusively by the solution casting method. The solution casting method is a film forming method in which a solution obtained by dissolving a resin in a solvent is cast to obtain a film shape, and then the solvent is evaporated and dried to obtain a film. Since a film formed by the solution casting method has high flatness, a high-quality image display device without unevenness can be obtained using this film.

However, since the solution casting method uses a large amount of organic solvent, it has been a problem that equipment for drying and recovering the organic solvent is required. Therefore, in recent years, as an optical film manufacturing method, an attempt of a melt casting method for forming a film by melting a resin has been performed.

For example, in the case of a cellulose acylate film used for a protective film, cellulose acylate as a main resin is melted to form a film. Various additives are added to the melt of cellulose acylate for improving film forming properties and improving properties as a protective film of a polarizing plate. For example, film properties are improved by adding plasticizers, antioxidants, ultraviolet absorbers, matting agents, and the like.

However, when such a cellulose acylate film constituent material is melted at a high temperature and extruded from the lip portion of the casting die onto a cooling roll to be cooled and solidified, the melt casting method for producing a film is used. There was a problem that aggregates adhered to the periphery of the lip part of the die, the film thickness of the melt coming out from the casting die became non-uniform, and streaky noise (film thickness unevenness) occurred in the manufactured film. . The lip portion is a constituent member of an outlet portion that extrudes the molten resin from the casting die, and the periphery of the lip portion indicates the vicinity of the outlet from which the molten resin exits the casting die.

It has been found that the cause of the generation of aggregates around the lip is due to the fact that sublimates generated from the melt extruded from the casting die adhere to the lip.

As a method for preventing the adhesion of the sublimated material, a method (Patent Document 1) has been proposed in which a suction nozzle is installed in the vicinity of the lip portion to forcibly exhaust the generated sublimated material.

Japanese Patent Laid-Open No. 11-48306

However, there is a problem that even if the method of Patent Document 1 is used, aggregates around the lip portion cannot be sufficiently removed, and streaky noise of the film is generated. As a result of earnestly examining the cause of agglomerates other than the adhesion of sublimates, the present inventor also adheres to the periphery of the lip when the melt is pushed out of the casting die, but a part of it deteriorates due to oxidation. It turned out to be an aggregate.

Therefore, the object of the present invention is that the melt adhering to the periphery of the lip portion does not form an agglomerate due to oxidative degradation, and the sublimate from the melt does not adhere to the periphery of the lip portion. It is providing the manufacturing method of the optical film which does not generate | occur | produce, the optical film manufactured by this manufacturing method, the polarizing plate which used this optical film for the protective film, and a liquid crystal display device.

The problems of the present invention can be solved by the following means.

1. In an optical film manufacturing method comprising an extrusion step of extruding a molten resin into a film form from a lip portion of a casting die, and a cooling step of cooling and solidifying the film-like resin extruded in the extrusion step with a cooling drum ,
The extrusion process includes
An optical film manufacturing method, wherein an inert gas having a temperature of 110 ° C. or higher and 300 ° C. or lower is supplied from a supply nozzle to the lip portion.

2. 2. The optical film according to 1 above, wherein the step of supplying the inert gas is characterized in that a wind speed of the inert gas exiting from a tip of the supply nozzle is 0.3 m / s or more and 3 m / s or less. Production method.

3. 3. The method for producing an optical film as described in 1 or 2 above, wherein a heater is disposed in the supply nozzle to heat the inert gas.

4. The suction nozzle is disposed downstream of the supply nozzle in the direction in which the extruded film-like resin flows down, and the suction nozzle sucks the inert gas that exits from the supply nozzle. 4. The method for producing an optical film according to any one of items 1 to 3.

5. 5. The method for producing an optical film according to any one of 1 to 4, wherein the inert gas is nitrogen gas.

6. The cooling step includes providing a touch roll that presses the film-shaped resin on the cooling drum, and pressing the touch roll smoothes the surface of the film-shaped resin. 6. The method for producing an optical film according to any one of items 1 to 5.

7. 7. The method for producing an optical film according to any one of 1 to 6, wherein the resin is cellulose acylate or a cycloolefin polymer.

8. 8. An optical film produced by the method for producing an optical film described in any one of 1 to 7 above.

9. 9. A polarizing plate using the optical film according to 8 as a protective film for a polarizing plate.

10. 10. A liquid crystal display device using the polarizing plate as described in 9 above.

According to the present invention, when extruding the molten resin from the casting die, an inert gas having a temperature of 110 ° C. or higher and 300 ° C. or lower is supplied to the lip portion from the supply nozzle, so that the sublimate adheres to the periphery of the lip portion. Further, it is possible to prevent oxidative deterioration of the melt adhered to the lip portion, and no aggregate is formed around the lip portion. Therefore, it is possible to provide a method for producing an optical film having a uniform thickness that does not generate streak noise, an optical film produced by the production method, a polarizing plate using the optical film as a protective film, and a liquid crystal display device. .

It is a schematic flow sheet which shows the whole structure of the apparatus which enforces the manufacturing method of the optical film of this invention. It is a schematic sectional drawing around the lip | rip part of a casting die. It is a schematic sectional drawing of the state which has pinched the melted film-form resin with the cooling roll and the touch roll. FIG. 3 is a schematic side view and a part of a side view of a casting die 4. It is a schematic sectional drawing of one Embodiment of a touch roll. It is a center sectional view in the plane which intersects perpendicularly with the axis of rotation of another embodiment of a touch roll. It is sectional drawing in the plane containing the rotating shaft of another embodiment of a touch roll.

Hereinafter, although the manufacturing method of the optical film of this invention is demonstrated using embodiment, this invention is not limited to the following embodiment.

FIG. 1 is a schematic flow sheet showing the overall configuration of an apparatus for carrying out the method for producing an optical film of the present invention. In the extrusion process, after the film constituent materials such as the raw material resin are mixed, the melted film constituent material is extruded from the casting die 4 onto the first cooling roll 5 using the extruder 1, and the first cooling is performed as the cooling process. While making it contact with the surface of the roll 5, it is made to contact with the surface of a total of three cooling rolls, the 2nd cooling roll 7 and the 3rd cooling roll 8 in order, and is cooled and solidified, and it is set as the film 10. FIG. Next, as the peeling process, the film 10 is peeled off by the peeling roll 9, and then as the stretching process, the longitudinal stretching is performed by the speed difference between the rolls by the longitudinal stretching apparatus 12a, and then the both ends of the film are held by the lateral stretching apparatus 12b. Then, the film is stretched in the width direction, and then wound by the winding device 16 as a winding process.

In the method for producing an optical film of the present invention, an inert gas having a temperature of 110 ° C. or more and 300 ° C. or less is supplied to the lip portion of the casting die 4 when extruding molten resin from the casting die 4 in the extrusion step. Is supplied from

FIG. 2 is a schematic cross-sectional view of the periphery of the lip portion of the present embodiment. The lip portions 33 and 34 of the casting die 4 and a pair of supply nozzles 70 and 70 for supplying an inert gas to the lip portions 33 and 34 are shown. , A pair of suction nozzles 80, 80 for sucking the inert gas from the supply nozzles 70, 70, a film-like molten resin (film 10) flowing out from the slits 32 of the lip portions 33, 34, and a first one for cooling the molten resin The arrangement of one cooling roll 5 and the flow of inert gas are shown.

The pair of supply nozzles 70, 70 are at their tips at positions separated from the respective surfaces of the melted resin film 10 flowing down from the slits 32 formed by the lip portions 33 and 34 of the casting die 4 by a predetermined distance d. It is arranged so that the part comes.

The tip of the supply nozzle 70 (on the film 10 side) has a shape extending in the width direction of the film 10, like the slit 32 of the casting die 4, specifically, an elongated rectangular opening. As shown in FIG. 2, a side wall in the longitudinal direction of the supply nozzle 70 is formed from the side portion of the casting die 4 and the nozzle side plate 71. The end in the longitudinal direction (not shown) is sealed by another member so that gas from the supply nozzle does not leak. As shown in FIG. 2, an inert gas is supplied to the supply nozzle 70 from a supply pipe 73.

The pair of suction nozzles 80, 80 are arranged below the pair of supply nozzles 70, 70. The tip portions of the pair of suction nozzles 80, 80 are disposed on the downstream side in the direction in which the film 10 flows down with respect to the tip portions of the pair of supply nozzles 70, 70. The supplied inert gas flows along the film 10, is sucked by the suction nozzle 80 disposed on the downstream side, and is discharged by the discharge pipe 82. The shape of the opening at the tip of the suction nozzle 80 (film 10 side) is a rectangle parallel to the width direction of the film 10. Further, the side portion of the suction nozzle 80 is also formed by nozzle side plates 71 and 81, and the end portion in the longitudinal direction (not shown) is sealed with another member.

In this way, by supplying the inert gas from the supply nozzle 70 to the lip portions 33 and 34 of the casting die 4, even if the molten resin that has come out of the slit 32 adheres to the periphery of the lip portion, It is not touched and therefore not oxidized and thus solidifies and does not become aggregates. Further, even if a sublimation component sublimated at a high temperature contained in the resin coming out of the slit 32 is sublimated, it does not accumulate on the lip portion because it gets on the flow of inert gas. Therefore, there is no occurrence of aggregates around the lip due to oxidative degradation of the molten resin or accumulation of sublimation components, and no vertical streak-like film thickness unevenness due to aggregates attached to the lip. High-quality optical films can be manufactured.

The temperature of the inert gas supplied from the supply nozzle 70 toward the lip portion is 110 ° C. or higher and 300 ° C. or lower. When the temperature is less than 110 ° C., a problem occurs in that the film becomes uneven as a result of cooling the film.

Examples of the inert gas supplied from the supply nozzle 70 toward the lip portions 33 and 34 include helium, neon, argon, krypton, xenon, radon, and nitrogen gas. In particular, nitrogen gas is more preferable than other inert gases. Is preferable because it is inexpensive and easy to obtain.

Further, in the embodiment of FIG. 2, the suction nozzle 80 is disposed in the vicinity of the supply nozzle 70, but suction and discharge may be performed at a remote position. In order to ensure the safety of the person working in the room, exhausting the melted resin from the casting die 4 to the first cooling roll 5 so that the concentration of the inert gas in the room is not increased. Is preferable. In addition, although the pair of supply nozzles 70 and the pair of suction nozzles 80 are arranged on both lip sides of the casting die 4, the lip portion of the present invention is also provided on either lip side of the casting die 4. There is an effect of suppressing the adhesion of aggregates. However, it is more effective and preferable to arrange them on both lip sides of the casting die.

In addition, the inert gas is preferably supplied at a wind speed of 0.3 m / s or more and 3 m / s or less from the tip of the supply nozzle 70. The calculation of the wind speed of the inert gas is a value obtained by dividing the supply amount Wm ³ / s of the inert gas from the supply pipe 73 by the opening area Sm ² of the tip of the supply nozzle 70.

By setting the wind speed of the inert gas within the above range, the inert gas wind speed is too low, so that there is no risk of oxygen mixing into the lip and no sublimation component adhering to the lip. Since the gas wind speed is too high and there is no fear of disturbing the flow of the extruded film-like molten resin, an optical film with a uniform film thickness without streak noise can be produced, which is preferable.

The wind speed is preferably uniform in the width direction, and the deviation of the wind speed in the width direction is preferably within ± 30%. More preferably, it is within 10%. By making the deviation of the wind speed in the width direction within the above range, it is preferable that there is no fear of disturbing the flow of the film-like molten resin extruded from the casting die.

In the present invention, it is preferable that a heater 72 is disposed in the supply nozzle 70. The inert gas sent to the supply nozzle 70 may be heated to a predetermined temperature in advance and then supplied to the supply nozzle 70 from the supply pipe 73. However, by arranging a heater in the supply nozzle 70, In addition, the temperature of the inert gas that flows from the tip of the supply nozzle 70 toward the lip can be controlled more stably. In addition, a gas heated in advance to a predetermined temperature may be sent and heated again by a heater arranged in the nozzle. As a method of the heater 72, a rubber heater, a cartridge heater, an aluminum cast heater, or the like can be preferably used, but is not limited thereto. A cartridge heater is particularly preferred.

The distance d between the tip of the supply nozzle 70 and the surface of the molten resin film 10 extruded from the slit 32 is preferably 2 mm or more and 15 mm or less.

If the thickness is less than 2 mm, there is a possibility that the film 10 and the supply nozzle 70 come into contact with each other due to a change in the flow rate of the inert gas from the supply nozzle 70. On the other hand, if it exceeds 15 mm, the flow of airflow around the lip due to the inert gas tends to fluctuate, and the adhesion of sublimable components to the lip portions 33 and 34 and the oxidative deterioration of the melt adhering to the lip portions 33 and 34 occur. Occurrence of aggregates can occur.

Also, the distance between the tip of the suction nozzle 80 and the surface of the film 10 is preferably 2 mm or more and 15 mm or less, like the supply nozzle 70.

Further, in the cooling step in the present invention, as shown in FIG. 1, it is preferable to provide a touch roll 6 that presses the film-like resin flowing down on the first cooling drum 5. By pressing the resin on the first cooling drum 5 with the touch roll 6, a film with higher planarity can be formed.

FIG. 3 is an enlarged schematic cross-sectional view for explaining a state in which a melted film-like resin is sandwiched between the first cooling roll 5 and the touch roll 6.

The touch roll 6 that abuts on the first cooling roll 5 has an elastic surface, and is deformed along the surface of the first cooling roll 5 by the pressing force to the first cooling roll 5. A nip is formed in By forming the nip portion and clamping with the touch roll 6 in this way, even if there is a small unevenness in the film thickness of the molten resin flowing down on the first cooling roll 5, it can be smoothed. It is preferable because of improved properties.

Hereinafter, the production method of the optical film of the present invention will be described in detail by taking production of a cellulose acylate film and a cycloolefin polymer film preferably used in the present invention as examples.
<Cellulose acylate film>
First, the constituent materials of the cellulose acylate film will be described.
(Raw material resin)
Cellulose as a cellulose acylate raw material is not particularly limited, and examples thereof include cotton linter, wood pulp, and kefna. Moreover, you may mix and use the raw material cellulose obtained from these in arbitrary ratios. The cellulose acylate is preferably a cellulose acylate having an acetyl group or an acyl group having 3 to 22 carbon atoms. Examples of the acyl group having 3 to 22 carbon atoms include propionyl (C ₂ H ₅ CO—), n-butyryl (C ₃ H ₇ CO—), isobutyryl, valeryl (C ₄ H ₉ CO—), isovaleryl, Includes sec-valeryl, tert-valeryl, octanoyl, dodecanoyl, octadecanoyl and oleoloyl. Propionyl and butyryl are preferred. As the cellulose acylate, cellulose acetate is preferable, and cellulose triacetate is particularly preferable. When the acylating agent for the acyl group is an acid anhydride or acid chloride, an organic acid (eg, acetic acid) or methylene chloride is used as the organic solvent as the reaction solvent. Cellulose acylate preferably has a hydroxyl group substitution degree of 2.6 to 3.0. The degree of polymerization (average viscosity) of cellulose acylate is preferably 200 to 700, and particularly preferably 250 to 550. These cellulose acylates are marketed by Daicel Chemical Industries, Ltd., Courtles, Hoechst, and Eastman Kodak. Photographic grade cellulose acylate is preferably used. The water content of cellulose acylate is preferably 2% by mass or less.

The β-1,4-bonded glucose unit constituting cellulose has free hydroxyl groups at the 2nd, 3rd and 6th positions. Cellulose acylate is a polymer obtained by esterifying some or all of these hydroxyl groups with acetic acid or other acids. The degree of acyl substitution means the proportion of cellulose esterified at each of the 2-position, 3-position and 6-position (100% esterification is 1.00).

The cellulose acylate used is a cellulose acylate having a total acyl substitution degree of 2-position and 3-position of 1.70 to 1.95 and an acyl substitution degree of 6-position of 0.88 or more, and 2-position. It is obtained by blending with a cellulose acylate having a total 3-position acyl substitution degree of 1.70 to 1.95 and a 6-position acyl substitution degree of less than 0.88.

Next, the additive contained in the cellulose acylate film will be described.
(Plasticizer)
The following are mentioned as a plasticizer contained in a cellulose acylate film.

An ester plasticizer comprising a polyhydric alcohol and a monovalent carboxylic acid, and an ester plasticizer comprising a polyvalent carboxylic acid and a monohydric alcohol are preferred because of their high affinity with the cellulose ester.

An ethylene glycol ester plasticizer that is one of polyhydric alcohol esters: specifically, ethylene glycol alkyl ester plasticizers such as ethylene glycol diacetate and ethylene glycol dibutyrate, ethylene glycol dicyclopropylcarboxylate And ethylene glycol cycloalkyl ester plasticizers such as ethylene glycol dicyclohexylcarboxylate, and ethylene glycol aryl ester plasticizers such as ethylene glycol dibenzoate and ethylene glycol di-4-methylbenzoate. These alkylate groups, cycloalkylate groups, and arylate groups may be the same or different, and may be further substituted. Further, it may be a mix of alkylate group, cycloalkylate group and arylate group, and these substituents may be covalently bonded. Further, the ethylene glycol part may be substituted, and the ethylene glycol ester partial structure may be part of the polymer or regularly pendant, and may be an antioxidant, an acid scavenger, an ultraviolet absorber, etc. It may be introduced into a part of the molecular structure of the additive.

Glycerin ester plasticizer that is one of polyhydric alcohol esters: Specifically, glycerol alkyl esters such as triacetin, tributyrin, glycerol diacetate caprylate, glycerol oleate propionate, glycerol tricyclopropylcarboxylate, glycerol Glycerin cycloalkyl esters such as tricyclohexylcarboxylate, glycerol aryl esters such as glycerol tribenzoate and glycerol-4-methylbenzoate, diglycerol tetraacetylate, diglycerol tetrapropionate, diglycerol acetate tricaprylate, diglycerol tetra Diglycerol alkyl esters such as laurate, diglycerol tetracyclobutylcarboxylate, diglycerol tetra Diglycerol cycloalkyl esters such as Russia pentyl carboxylate, diglycerin tetrabenzoate, diglycerin aryl ester such as diglycerin 3-methylbenzoate or the like. These alkylate groups, cycloalkylcarboxylate groups, and arylate groups may be the same or different, and may be further substituted. Further, it may be a mixture of alkylate group, cycloalkylcarboxylate group, and arylate group, and these substituents may be bonded by a covalent bond. Furthermore, the glycerin and diglycerin part may be substituted, the partial structure of the glycerin ester and the diglycerin ester may be part of the polymer or regularly pendant, and the antioxidant, acid scavenger, You may introduce | transduce into a part of molecular structure of additives, such as a ultraviolet absorber.

Specific examples of other polyhydric alcohol ester plasticizers include polyhydric alcohol ester plasticizers described in paragraphs 30 to 33 of JP-A No. 2003-12823.

These alkylate groups, cycloalkylcarboxylate groups, and arylate groups may be the same or different, and may be further substituted. Further, it may be a mixture of alkylate group, cycloalkylcarboxylate group, and arylate group, and these substituents may be bonded by a covalent bond. Furthermore, the polyhydric alcohol part may be substituted, and the partial structure of the polyhydric alcohol may be part of the polymer or regularly pendant, and may be an antioxidant, an acid scavenger, an ultraviolet absorber. May be introduced into a part of the molecular structure of the additive.

Among the ester plasticizers composed of the polyhydric alcohol and the monovalent carboxylic acid, alkyl polyhydric alcohol aryl esters are preferred. Specifically, the above-mentioned ethylene glycol dibenzoate, glycerin tribenzoate, diglycerin tetrabenzoate, Examples thereof include the exemplified compound 16 described in paragraph 32 of Kaikai 2003-12823.

Dicarboxylic acid ester plasticizer that is one of polyvalent carboxylic acid esters: Specifically, alkyl dicarboxylic acid alkyl such as didodecyl malonate (C1), dioctyl adipate (C4), dibutyl sebacate (C8), etc. Ester plasticizers, alkyl dicarboxylic acid cycloalkyl ester plasticizers such as dicyclopentyl succinate and dicyclohexyl adipate, and alkyl dicarboxylic acid aryl ester plasticizers such as diphenyl succinate and di-4-methylphenyl glutarate Dialkyl-1,4-cyclohexanedicarboxylate, didecylbicyclo [2.2.1] heptane-2,3-dicarboxylate, and the like, cycloalkyldicarboxylic acid alkyl ester plasticizers, dicyclohexyl-1,2- Cyclobutane deca Cycloalkyldicarboxylic acid cycloalkyl ester type plasticizers such as boxylate, dicyclopropyl-1,2-cyclohexyl dicarboxylate, diphenyl-1,1-cyclopropyldicarboxylate, di-2-naphthyl-1,4- Cycloalkyl dicarboxylic acid aryl ester plasticizers such as cyclohexane dicarboxylate, aryl dicarboxylic acid alkyl ester plasticizers such as diethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, and di-2-ethylhexyl phthalate, dicyclopropyl Aryl dicarboxylic acid cycloalkyl ester plasticizers such as phthalate and dicyclohexyl phthalate, and aryl dicarboxylic acid esters such as diphenyl phthalate and di-4-methylphenyl phthalate Ruesuteru based plasticizers. These alkoxy groups and cycloalkoxy groups may be the same or different, may be mono-substituted, and these substituents may be further substituted. The alkyl group and cycloalkyl group may be mixed, and these substituents may be bonded together by a covalent bond. Furthermore, the aromatic ring of phthalic acid may be substituted, and a multimer such as a dimer, trimer or tetramer may be used. Also, the partial structure of phthalate ester may be part of the polymer or regularly pendant to the polymer, and it may be part of the molecular structure of additives such as antioxidants, acid scavengers, and UV absorbers. It may be introduced.

Other polycarboxylic acid ester plasticizers include alkyl polycarboxylic acid alkyl esters such as tridodecyl tricarbarate and tributyl-meso-butane-1,2,3,4-tetracarboxylate. Plasticizers, alkylpolycarboxylic acid cycloalkyl ester plasticizers such as tricyclohexyltricarbarate, tricyclopropyl-2-hydroxy-1,2,3-propanetricarboxylate, triphenyl-2-hydroxy -1,2,3-propanetricarboxylate, tetra-3-methylphenyltetrahydrofuran-2,3,4,5-tetracarboxylate and other alkyl polyvalent carboxylic acid aryl ester plasticizers, tetrahexyl-1, 2,3,4-cyclobutanetetracarboxylate, te Cycloalkyl polycarboxylic acid alkyl ester plasticizers such as rabutyl-1,2,3,4-cyclopentanetetracarboxylate, tetracyclopropyl-1,2,3,4-cyclobutanetetracarboxylate, tricyclohexyl- Cycloalkyl polycarboxylic acid cycloalkyl ester plasticizers such as 1,3,5-cyclohexyl tricarboxylate, triphenyl-1,3,5-cyclohexyl tricarboxylate, hexa-4-methylphenyl-1,2 , 3,4,5,6-cyclohexylhexacarboxylate and other cycloalkyl polycarboxylic acid aryl ester plasticizers, tridodecylbenzene-1,2,4-tricarboxylate, tetraoctylbenzene-1,2, Ants such as 4,5-tetracarboxylate Polyvalent carboxylic acid alkyl ester plasticizer, aryl polyvalent carboxylic acid cycloalkyl such as tricyclopentylbenzene-1,3,5-tricarboxylate, tetracyclohexylbenzene-1,2,3,5-tetracarboxylate Aryl polyvalent carboxylic acids such as ester plasticizers triphenylbenzene-1,3,5-tetracartoxylate, hexa-4-methylphenylbenzene-1,2,3,4,5,6-hexacarboxylate Examples include aryl ester plasticizers. These alkoxy groups and cycloalkoxy groups may be the same or different, and may be mono-substituted, and these substituents may be further substituted. The alkyl group and cycloalkyl group may be mixed, and these substituents may be bonded together by a covalent bond. Furthermore, the aromatic ring of phthalic acid may be substituted, and a multimer such as a dimer, trimer or tetramer may be used. Also, the partial structure of phthalate ester may be part of the polymer or regularly pendant into the polymer, and introduced into part of the molecular structure of additives such as antioxidants, acid scavengers, UV absorbers, etc. May be.

Among the ester plasticizers composed of the polyvalent carboxylic acid and the monohydric alcohol, dialkyl carboxylic acid alkyl esters are preferred, and specific examples include the dioctyl adipate and tridecyl tricarbalate.

Further examples include phosphate ester plasticizers, carbohydrate ester plasticizers, and polymer plasticizers.

Phosphate ester plasticizers: specifically, phosphoric acid alkyl esters such as triacetyl phosphate and tributyl phosphate, phosphoric acid cycloalkyl esters such as tricyclobenthyl phosphate and cyclohexyl phosphate, triphenyl phosphate, tricresyl phosphate And phosphoric acid aryl esters such as cresylphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate, trinaphthyl phosphate, trixylyl phosphate, tris ortho-biphenyl phosphate. These substituents may be the same or different, and may be further substituted. Moreover, the mix of an alkyl group, a cycloalkyl group, and an aryl group may be sufficient, and substituents may couple | bond together by the covalent bond.

Also, alkylene bis (dialkyl phosphate) such as ethylene bis (dimethyl phosphate), butylene bis (diethyl phosphate), alkylene bis (diaryl phosphate) such as ethylene bis (diphenyl phosphate), propylene bis (dinaphthyl phosphate), phenylene bis (dibutyl phosphate) ), Arylene bis (dialkyl phosphate) such as biphenylene bis (dioctyl phosphate), phosphate esters such as arylene bis (diaryl phosphate) such as phenylene bis (diphenyl phosphate) and naphthylene bis (ditoluyl phosphate). These substituents may be the same or different, and may be further substituted. Moreover, the mix of an alkyl group, a cycloalkyl group, and an aryl group may be sufficient, and substituents may couple | bond together by the covalent bond.

Furthermore, the partial structure of phosphate ester may be part of the polymer, or may be regularly pendant, and also introduced into part of the molecular structure of additives such as antioxidants, acid scavengers, UV absorbers, etc. May be. Among the above-mentioned compounds, phosphoric acid aryl ester and arylene bis (diaryl phosphate) are preferable, and specifically, triphenyl phosphate and phenylene bis (diphenyl phosphate) are preferable.

Next, the carbohydrate ester plasticizer will be described. The carbohydrate means a monosaccharide, disaccharide or trisaccharide in which the saccharide is present in the form of pyranose or furanose (6-membered ring or 5-membered ring). Non-limiting examples of carbohydrates include glucose, saccharose, lactose, cellobiose, mannose, xylose, ribose, galactose, arabinose, fructose, sorbose, cellotriose and raffinose. The carbohydrate ester refers to an ester compound formed by dehydration condensation of a carbohydrate hydroxyl group and a carboxylic acid, and specifically means an aliphatic carboxylic acid ester or an aromatic carboxylic acid ester of a carbohydrate. Examples of the aliphatic carboxylic acid include acetic acid and propionic acid, and examples of the aromatic carboxylic acid include benzoic acid, toluic acid, and anisic acid. Carbohydrates have a number of hydroxyl groups depending on the type, but even if a part of the hydroxyl group reacts with the carboxylic acid to form an ester compound, the whole hydroxyl group reacts with the carboxylic acid to form an ester compound. Also good. In the present invention, it is preferable that all of the hydroxyl groups react with the carboxylic acid to form an ester compound.

Specific examples of the carbohydrate ester plasticizer include glucose pentaacetate, glucose pentapropionate, glucose pentabtylate, saccharose octaacetate, saccharose octabenzoate, and of these, saccharose octaacetate is more preferred. preferable.

Polymer plasticizer: Specifically, aliphatic hydrocarbon polymer, alicyclic hydrocarbon polymer, polyethyl acrylate, polymethyl methacrylate, copolymer of methyl methacrylate and 2-hydroxyethyl methacrylate (For example, an arbitrary ratio between copolymer ratios 1:99 to 99: 1), vinyl polymers such as polyvinyl isobutyl ether, poly N-vinyl pyrrolidone, polystyrene, poly 4-hydroxystyrene, etc. Examples thereof include styrene-based polymers, polybutylene succinates, polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyethers such as polyethylene oxide and polypropylene oxide, polyamides, polyurethanes, and polyureas. The number average molecular weight is preferably about 1,000 to 500,000, particularly preferably 5000 to 200,000. If it is 1000 or less, a problem arises in volatility, and if it exceeds 500000, the plasticizing ability is lowered, and the mechanical properties of the cellulose ester film are adversely affected. These polymer plasticizers may be a homopolymer composed of one type of repeating unit or a copolymer having a plurality of repeating structures. Two or more of the above polymers may be used in combination.

In addition, since the cellulose acylate film of the present invention has an effect as an optical application when colored, the yellowness (yellow index, YI) is preferably 3.0 or less, more preferably 1.0 or less. Yellowness can be measured based on JIS-K7103.

It is preferable that the plasticizer removes impurities such as residual acids, inorganic salts, organic low molecules, etc. that are carried over from the time of manufacture or generated during storage, and more preferably has a purity of 99% or more. is there. Residual acid and water are preferably 0.01 to 100 ppm, and when melt-forming cellulose resin, thermal deterioration can be suppressed, and film-forming stability, optical physical properties and mechanical properties of the film are improved. .
(Antioxidant)
In the cellulose acylate film of the present invention, an antioxidant is used as a stabilizer because cellulose ester is decomposed not only by heat but also by oxygen in a high temperature environment where melt film formation is performed. Is also preferable.

The antioxidant useful in the present invention can be used without limitation as long as it is a compound that suppresses deterioration of the melt-molded material due to oxygen, but among the useful antioxidants, phenolic compounds, hindered amine compounds, Examples thereof include phosphorus compounds, sulfur compounds, heat-resistant processing stabilizers, oxygen scavengers, etc. Among these, phenol compounds, hindered amine compounds, phosphorus compounds, and lactone compounds are particularly preferable.

The hindered amine compound (HALS) is described, for example, in US Pat. No. 4,619,956, columns 5 to 11 and US Pat. No. 4,839,405, columns 3 to 5. Thus, 2,2,6,6-tetraalkylpiperidine compounds, or their acid addition salts or complexes of them with metal compounds are preferred. As a commercial item, LA52 (made by Asahi Denka Co., Ltd.) can be mentioned.

As the lactone compound, compounds described in JP-A-7-233160 and JP-A-7-247278 are preferable.

These stabilizers can be used singly or in combination of two or more, and the blending amount is appropriately selected within a range not impairing the object of the present invention, but is usually 0 with respect to 100 parts by mass of the cellulose ester. 0.001 to 10.0 parts by mass, preferably 0.01 to 5.0 parts by mass, and more preferably 0.1 to 3.0 parts by mass.

By blending these compounds, it is possible to prevent coloring and strength reduction of the molded product due to heat and thermal oxidative degradation during melt molding without reducing transparency and heat resistance.

The addition amount of the antioxidant is usually 0.01 to 10 parts by mass, preferably 0.05 to 5 parts by mass, and more preferably 0.1 to 3 parts by mass with respect to 100 parts by mass of the cellulose ester.
(Acid scavenger)
The acid scavenger is an agent that plays a role of trapping an acid (protonic acid) remaining in the cellulose ester brought in from the production. When the cellulose ester is melted, side chain hydrolysis is promoted by moisture and heat in the polymer, and acetic acid and propionic acid are generated in the case of CAP. A compound having an epoxy structure, a tertiary amine, an ether structure, or the like may be used as long as it can be chemically bonded to an acid, but is not limited thereto.

Specifically, it is preferable to comprise an epoxy compound as an acid scavenger described in US Pat. No. 4,137,201. Epoxy compounds as such acid scavengers are known in the art and are derived by condensation of diglycidyl ethers of various polyglycols, particularly about 8 to 40 moles of ethylene oxide per mole of polyglycol. Metal glycol compounds such as polyglycols, diglycidyl ethers of glycerol (eg, those conventionally used in and together with vinyl chloride polymer compositions), epoxidized ether condensation products, bisphenol A Diglycidyl ethers (ie, 4,4'-dihydroxydiphenyldimethylmethane), epoxidized unsaturated fatty acid esters (especially esters of alkyls of about 2 to 2 carbon atoms of fatty acids of 2 to 22 carbon atoms (eg Butyl epoxy stearate ), And various epoxidized long chain fatty acid triglycerides and the like (e.g., epoxidized vegetable oils and other unsaturated natural oils, which may be represented and exemplified by compositions such as epoxidized soybean oil, sometimes epoxidized natural) These are referred to as glycerides or unsaturated fatty acids and these fatty acids generally contain 12 to 22 carbon atoms)).
(UV absorber)
As an ultraviolet absorber, from the viewpoint of preventing deterioration of a polarizer or a display device with respect to ultraviolet rays, the ultraviolet absorber has an excellent ability to absorb ultraviolet rays having a wavelength of 370 nm or less, and from the viewpoint of liquid crystal display properties, absorption of visible light having a wavelength of 400 nm or more is absorbed. Less is preferred.

For example, salicylic acid ultraviolet absorbers (phenyl salicylate, p-tert-butyl salicylate, etc.) or benzophenone ultraviolet absorbers (2,4-dihydroxybenzophenone, 2,2′-dihydroxy-4,4′-dimethoxybenzophenone, etc.), Benzotriazole UV absorber (2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2- (2'-hydroxy-3 ', 5'-di) -Tert-butylphenyl) -5-chlorobenzotriazole, 2- (2'-hydroxy-3 ', 5'-di-tert-amylphenyl) benzotriazole, 2- (2'-hydroxy-3'-dodecyl- 5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3'-t rt-butyl-5 '-(2-octyloxycarbonylethyl) -phenyl) -5-chlorobenzotriazole, 2- (2'-hydroxy-3'-(1-methyl-1-phenylethyl) -5'- (1,1,3,3-tetramethylbutyl) -phenyl) benzotriazole, 2- (2'-hydroxy-3 ', 5'-di- (1-methyl-1-phenylethyl) -phenyl) benzotriazole ), Cyanoacrylate ultraviolet absorbers (2′-ethylhexyl-2-cyano-3,3-diphenyl acrylate, ethyl-2-cyano-3- (3 ′, 4′-methylenedioxyphenyl) -acrylate, etc.) , Triazine ultraviolet absorbers, compounds described in JP-A Nos. 58-185777 and 59-149350, nickel complex compounds, inorganic powders Etc. The.

As the UV absorber, a benzotriazole UV absorber and a triazine UV absorber that are highly transparent and excellent in preventing deterioration of a polarizing plate and a liquid crystal element are preferable, and a benzotriazole UV light having a more appropriate spectral absorption spectrum. Absorbents are particularly preferred.

Also, it can be used in combination with a conventionally known ultraviolet absorbing polymer. The conventionally known UV-absorbing polymer is not particularly limited, and examples thereof include a polymer obtained by homopolymerizing RUVA-93 (manufactured by Otsuka Chemical Co., Ltd.) and a polymer obtained by copolymerizing RUVA-93 and other monomers. It is done. Specifically, PUVA-30M obtained by copolymerizing RUVA-93 and methyl methacrylate in a ratio (mass ratio) of 3: 7, and PUVA-50M copolymerized in a ratio of 5: 5 (mass ratio). It is done. Furthermore, the polymer etc. which are described in Unexamined-Japanese-Patent No. 2003-113317 are mentioned.

As commercially available products, TINUVIN 109, TINUVIN 171, TINUVIN 360, TINUVIN 900, TINUVIN 928 (all manufactured by Ciba Japan), LA-31 (Asahi) Denka Co., Ltd.) and RUVA-100 (Otsuka Chemical Co., Ltd.) can also be used.

Specific examples of benzophenone compounds include 2,4-dihydroxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy-5-sulfobenzophenone, bis (2-methoxy-4-hydroxy-) 5-benzoylphenylmethane) and the like, but are not limited thereto.

The ultraviolet absorber is preferably added in an amount of 0.1 to 20% by mass, more preferably 0.5 to 10% by mass, and further preferably 1 to 5% by mass. Two or more of these may be used in combination.
(Viscosity reducing agent)
For the purpose of reducing the melt viscosity, a hydrogen bonding solvent can be added. 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” that occurs between an electronegative atom and a covalently bonded hydrogen atom, that is, a bond having a large bonding moment and containing hydrogen, such as OH (Oxygen hydrogen bond), N—H (nitrogen hydrogen bond), FH (fluorine hydrogen bond), and an organic solvent that can arrange adjacent molecules. 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. .

Examples of the hydrogen bonding solvent include alcohols such as methanol, ethanol, propanol, isopropanol, n-butanol, sec-butanol, t-butanol, 2-ethylhexanol, heptanol, octanol, nonanol, dodecanol, ethylene glycol, Propylene glycol, hexylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, methyl cellosolve, ethyl cellosolve, butyl cellosolve, hexyl cellosolve, glycerin, etc., ketones: acetone, methyl ethyl ketone, etc., carboxylic acids: eg formic acid, acetic acid, propionic acid, Butyric acid, etc., ethers: eg, diethyl ether, tetrahydrofuran, dioxane, etc., Pyrrolidones: eg, N-methyl Pyrrolidone, etc., amines: for example, can be exemplified trimethylamine, pyridine, etc., and the like. These hydrogen bonding solvents can be used alone or in admixture of two or more. Among these, alcohol, ketone, and ether are preferable, and methanol, ethanol, propanol, isopropanol, octanol, dodecanol, ethylene glycol, glycerin, acetone, and tetrahydrofuran are particularly preferable. Furthermore, water-soluble solvents such as methanol, ethanol, propanol, isopropanol, ethylene glycol, glycerin, acetone, and tetrahydrofuran are particularly preferable. Here, water-soluble means that the solubility in 100 g of water is 10 g or more.
(Retardation control agent)
An alignment film may be formed in the cellulose acylate film, a liquid crystal layer may be provided, and polarizing plate processing may be performed in which the cellulose acylate film and the retardation derived from the liquid crystal layer are combined to provide an optical compensation capability. The compound to be added to control the retardation is an aromatic compound having two or more aromatic rings as described in EP 911,656A2, which is used as a retardation control agent. You can also. Two or more aromatic compounds may be used in combination. The aromatic ring of the aromatic compound includes an aromatic heterocyclic ring in addition to the aromatic hydrocarbon ring. An aromatic heterocyclic ring is particularly preferred, and the aromatic heterocyclic ring is generally an unsaturated heterocyclic ring. Of these, compounds having a 1,3,5-triazine ring are particularly preferred.
(Matting agent)
Fine particles such as a matting agent can be added to the cellulose acylate film in order to impart slipperiness, and examples of the fine particles include inorganic compound fine particles and organic compound fine particles. The matting agent is preferably as fine as possible. Examples of the fine particles include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, kaolin, talc, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, Examples thereof include inorganic fine particles such as magnesium silicate and calcium phosphate, and crosslinked polymer fine particles. Among these, silicon dioxide is preferable because it can reduce the haze of the film. In many cases, fine particles such as silicon dioxide are surface-treated with an organic material, but such a material is preferable because it can reduce the haze of the film.

Preferred organic materials for the surface treatment include halosilanes, alkoxysilanes, silazanes, siloxanes, and the like. The larger the average particle size of the fine particles, the greater the sliding effect, and the smaller the average particle size, the better the transparency. The average particle size of the secondary particles of the fine particles is in the range of 0.05 to 1.0 μm. The average particle size of secondary particles of preferable fine particles is preferably 5 to 50 nm, more preferably 7 to 14 nm. These fine particles are preferably used in the cellulose acylate film in order to produce an unevenness of 0.01 to 1.0 μm on the surface of the cellulose acylate film. The content of the fine particles in the cellulose ester is preferably 0.005 to 0.3% by mass with respect to the cellulose ester.

Examples of the fine particles of silicon dioxide include Aerosil 200, 200V, 300, R972, R972V, R974, R202, R812, OX50, TT600 manufactured by Nippon Aerosil Co., Ltd., preferably Aerosil 200V, R972. , R972V, R974, R202, R812. Two or more kinds of these fine particles may be used in combination. When using 2 or more types together, it can mix and use in arbitrary ratios. In this case, fine particles having different average particle sizes and materials, for example, Aerosil 200V and R972V can be used in a mass ratio of 0.1: 99.9 to 99.9: 0.1.

The presence of fine particles in the film used as the matting agent can be used for another purpose to improve the strength of the film. In addition, the presence of the fine particles in the film can improve the orientation of the cellulose ester constituting the cellulose acylate film of the present invention.
(Polymer material)
For the cellulose acylate film, polymer materials other than cellulose esters and oligomers may be appropriately selected and mixed. The above polymer materials and oligomers are preferably those having excellent compatibility with the cellulose ester, and the transmittance when formed into a film is 80% or more, more preferably 90% or more, and further preferably 92% or more. The purpose of mixing at least one of polymer materials and oligomers other than cellulose ester includes meanings for controlling viscosity at the time of heating and melting and improving film physical properties after film processing.

Thus, what added various additives to the raw material resin of a cellulose acylate film is formed into a film with the film forming apparatus using the melt casting method shown in FIG. 1, and a cellulose acylate film is manufactured.
(Extrusion process)
It is preferable to mix the cellulose resin as a raw material and other additives such as a stabilizer added as necessary before melting. For mixing, a general mixer such as a V-type mixer, a conical screw type mixer, a horizontal cylindrical type mixer, a Henschel mixer, or a ribbon mixer can be used. The mixed film constituent material is melted at an extrusion temperature of about 200 to 300 ° C. using the extruder 1 and filtered through a leaf disk type filter 2 to remove foreign matters. When additives such as a plasticizer are not mixed in advance, they may be kneaded in the middle of the extruder. In order to add uniformly, it is preferable to use a mixing apparatus such as a static mixer 3.

The film constituent material extruded from the extruder 1 and filtered by the metal filter 2 is sent to the casting die 4 and extruded from the slit of the casting die 4 into a film shape. The casting die 4 is not particularly limited as long as it is used for producing a sheet or a film. The material of the casting die 4 is sprayed or plated with hard chromium, chromium carbide, chromium nitride, titanium carbide, titanium carbonitride, titanium nitride, super steel, ceramic (tungsten carbide, aluminum oxide, chromium oxide), etc. Processing such as buffing, lapping using a # 1000 or higher grinding wheel, surface cutting using a # 1000 or higher diamond grinding wheel (the cutting direction is perpendicular to the resin flow direction), electrolytic polishing, electrolytic composite polishing, etc. And so on. A preferred material for the lip portion of the casting die 4 is the same as that of the casting die 4. The surface accuracy of the lip is preferably 0.5S or less, and more preferably 0.2S or less.

The slit of the casting die 4 is configured so that the gap can be adjusted.

4 shows a schematic view of the casting die 4, FIG. 4 (a) shows a part of a side view, and FIG. 4 (b) shows a cross-sectional view. Of the pair of lips 33, 34 forming the slit 32 of the casting die 4, one is a flexible lip 33 that has low rigidity and is easily deformed, and the other is a fixed lip 34. A large number of heat bolts 35 are arranged at a constant pitch in the width direction of the casting die 4, that is, in the length direction of the slits 32. Each heat bolt 5 is provided with a block 36 having an embedded electric heater 37 and a cooling medium passage, and each heat bolt 35 penetrates each block 36 vertically. The base of the heat bolt 35 is fixed to the die body 31, and the tip is in contact with the outer surface of the flexible lip 33. While the block 36 is always air-cooled, the input of the embedded electric heater 37 is increased or decreased to raise or lower the temperature of the block 36, thereby causing the heat bolt 35 to thermally expand and contract, thereby displacing the flexible lip 33 to change the film thickness. Adjust. Thickness gauges are installed at the required locations in the wake of the die, and the web thickness information detected thereby is fed back to the control device. The thickness information is compared with the set thickness information by the control device, and correction control comes from the same device. It is also possible to control the power or ON rate of the heating element of the heat bolt 35 by the amount signal. The heat bolt 35 preferably has a length of 20 to 40 cm and a diameter of 7 to 14 mm, and a plurality of, for example, several tens of heat bolts are preferably arranged at a pitch of 20 to 40 mm. Instead of the heat bolt 35, a gap adjusting member mainly composed of a bolt for adjusting the gap of the slit 32 by manually moving back and forth in the axial direction may be provided. The gap of the slit 32 adjusted by the gap adjusting member is usually 500 to 1500 μm, preferably 800 to 1300 μm, more preferably 900 to 1200 μm.

In the method for producing an optical film of the present invention, a resin that is provided with a supply nozzle 70 for supplying an inert gas to the lip portion in the vicinity of the lips 33 and 34 of the casting die 4 and is melted from the slit 32 of the casting die 4. The step of supplying an inert gas having a temperature of 110 ° C. or more and 300 ° C. or less from the supply nozzle 70 to the lip portion is extruded. Details are described here and are omitted here.
(Cooling process)
The film-like resin extruded from the casting die 4 in the extrusion process is sandwiched between the first cooling roller 5 and the touch roll 6 to be cooled and the surface thereof is flattened.

FIG. 5 shows a schematic cross section of an embodiment of the touch roll 6 (hereinafter, touch roll A). As shown in the drawing, the touch roll A has an elastic roller 42 disposed inside a flexible metal sleeve 41.

The metal sleeve 41 is made of stainless steel having a thickness of 0.3 mm and has flexibility. If the metal sleeve 41 is too thin, the strength is insufficient, whereas if it is too thick, the elasticity is insufficient. For these reasons, the thickness of the metal sleeve 41 is preferably 0.1 mm or more and 1.5 mm or less. The elastic roller 42 is formed in a roll shape by providing a rubber 44 on the surface of a metal inner cylinder 43 that is rotatable via a bearing. When the touch roll A is pressed toward the first cooling roll 5, the elastic roller 42 presses the metal sleeve 41 against the first cooling roll 5, and the metal sleep 41 and the elastic roller 42 have the shape of the first cooling roll 5. It deforms corresponding to the familiar shape, and forms a nip with the first cooling roll. A cooling liquid 45 flows in a space formed between the metal sleeve 41 and the elastic roller 42.

6 and 7 show a touch roll B which is another embodiment of the touch roll. 6 is a central sectional view in a plane orthogonal to the rotation axis, and FIG. 7 is a sectional view in a plane including the rotation axis.

The touch roll B includes a flexible and seamless stainless steel pipe (for example, 4 mm thick) outer cylinder 51 and a highly rigid metal inner cylinder 52 arranged on the same axis as the inner side of the outer cylinder 51. It is roughly composed of The cooling liquid 45 flows in the space 53 between the outer cylinder 51 and the inner cylinder 52.

The touch rolls A and B are urged toward the first cooling roll by urging means (not shown). The urging force of the urging means is F, and the value F / W (linear pressure) obtained by dividing the width W of the film in the nip along the rotation axis of the first cooling roll 5 is 1 N / cm or more and 150 N / cm. Set to According to the present embodiment, a nip is formed between the touch rolls A and B and the first cooling roll 5, and planarity may be corrected while the film passes through the nip. Accordingly, since the film is sandwiched over a long time with a small linear pressure compared to the case where the touch roll is formed of a rigid body and no nip is formed between the first cooling roll and the flatness is more reliably corrected. Can do. That is, when the linear pressure is less than 1 N / cm, it is impossible to sufficiently eliminate the die line (vertical stripe-like film thickness unevenness parallel to the film conveyance direction). On the other hand, if the linear pressure is greater than 150 N / cm, the film is difficult to pass through the nip, resulting in unevenness in place of the film thickness.

In addition, since the surfaces of the touch rolls A and B are made of metal, the surfaces of the touch rolls A and B can be made smoother than when the surface of the touch roll is rubber. Obtainable. In addition, as a material of the elastic body 44 of the elastic roller 42, ethylene propylene rubber, neoprene rubber, silicon rubber, or the like can be used.

Now, in order to satisfactorily eliminate the die line by the touch roll 6, it is important that the viscosity of the film when the touch roll 6 clamps the film is in an appropriate range. Cellulose resins are known to have a relatively large change in viscosity with temperature. Therefore, in order to set the viscosity when the touch roll 6 clamps the film to an appropriate range, it is important to set the film temperature when the touch roll 6 clamps the film to an appropriate range. Further, when the glass transition temperature of the cellulose acylate film is Tg, the temperature T of the film immediately before the film is sandwiched between the touch rolls 6 may be set so as to satisfy Tg + 80 ° C. <T <Tg + 140 ° C. If the film temperature T is lower than Tg, the viscosity of the film is too high and the die line cannot be corrected. On the contrary, when the temperature T of the film is higher than Tg + 140 ° C., the film surface and the roll do not adhere uniformly, and the die line cannot be corrected. Preferably Tg + 100 ° C. <T <Tg + 130 ° C., more preferably Tg + 110 ° C. <T <Tg + 130 ° C. In order to set the temperature of the film when the touch roll 6 sandwiches the film to an appropriate range, the first cooling roll 5 from the position P1 at which the melt extruded from the casting die 4 contacts the first cooling roll 5 is used. What is necessary is just to adjust the length L along the rotation direction of the 1st cooling roll 5 of the nip with the touch roll 6.

Preferred materials for the first roll 5 and the second roll 6 include carbon steel, stainless steel, resin, and the like. The surface accuracy is preferably increased, and the surface roughness is set to 0.3 S or less, more preferably 0.01 S or less.

The film-like cellulose ester-based resin in a molten state from the casting die 4 is brought into close contact with the first roll (first cooling roll) 5, the second cooling roll 7, and the third cooling roll 8 in order to be cooled and solidified. An unstretched cellulose ester resin film 10 is obtained.
(Peeling process)
As the peeling step, the cooled and solidified film 10 is peeled off from the third cooling roll 8 by the peeling roll 9.
(Stretching process)
The peeled and solidified unstretched film 10 is guided to a longitudinal stretching machine 12a through a dancer roll (film tension adjusting roll) 11, where it is longitudinally stretched. Subsequently, the film is guided to the transverse stretching machine 12b, where the film 10 is stretched in the transverse direction (width direction). By this stretching, the molecules in the film are oriented.

As a method of longitudinally stretching the film, a method of stretching by a speed difference between two rolls can be preferably used.

For the method of stretching the film in the width direction, a known tenter or the like can be preferably used.

The glass transition temperature Tg of the film constituting material can be controlled by making the material type constituting the film and the ratio of the constituting material different. When a retardation film is produced as an optical film, Tg is preferably 120 ° C. or higher, preferably 135 ° C. or higher. In the liquid crystal display device, in the image display state, the temperature environment of the film changes due to the temperature rise of the device itself, for example, the temperature rise derived from the light source. At this time, if the Tg of the film is lower than the use environment temperature of the film, the retardation value derived from the orientation state of the molecules fixed inside the film by stretching and the dimensional shape as the film are greatly changed. If the Tg of the film is too high, the temperature is increased when the film constituent material is made into a film, so that the energy consumption for heating is increased, and the material itself may be decomposed when it is made into a film, resulting in coloring. Therefore, Tg is preferably 250 ° C. or lower.

In the stretching step, known heat setting conditions, cooling, and relaxation treatment may be performed, and it may be appropriately adjusted so as to have characteristics required for the target optical film.

In order to provide the physical properties of the phase film and the function of the phase film for expanding the viewing angle of the liquid crystal display device, the stretching step and the heat setting treatment are appropriately selected and performed. When such a stretching step and heat setting treatment are included, the heating and pressing step of the present invention is performed before the stretching step and heat setting treatment.

When producing a retardation film as an optical film and further combining the functions of a polarizing plate protective film, it is necessary to control the refractive index. However, the refractive index can be controlled by a stretching operation. Is a preferred method. Hereinafter, the stretching method will be described.

In the retardation film stretching step, the required litter is stretched by 1.0 to 2.0 times in one direction of the cellulose resin and 1.01 to 2.5 times in the direction perpendicular to the film plane. The foundation Ro and Rt can be controlled. Here, Ro indicates in-plane retardation, the difference between the refractive index in the longitudinal direction MD in the plane and the refractive index in the width direction TD is multiplied by the thickness, and Rt indicates the thickness direction retardation, The difference between the refractive index (average of the longitudinal direction MD and the width direction TD) and the refractive index in the thickness direction is multiplied by the thickness.

Stretching can be performed sequentially or simultaneously with respect to, for example, the longitudinal direction of the film and the direction orthogonal to the longitudinal direction of the film, that is, the width direction. At this time, if the stretching ratio in at least one direction is too small, a sufficient phase difference cannot be obtained, and if it is too large, stretching becomes difficult and film breakage may occur.

Stretching in biaxial directions perpendicular to each other is an effective method for putting the refractive indexes nx, ny, and nz of the film within a predetermined range. Here, nx is the refractive index in the longitudinal MD direction, ny is the refractive index in the width TD direction, and nz is the refractive index in the thickness direction.

For example, when the film is stretched in the melt casting direction, if the shrinkage in the width direction is too large, the value of nz becomes too large. In this case, it can be improved by suppressing the width shrinkage of the film or stretching in the width direction. When stretching in the width direction, the refractive index may be distributed in the width direction. This distribution may appear when the tenter method is used. By stretching the film in the width direction, a shrinkage force is generated at the center of the film, and the phenomenon is caused by the end being fixed. It is thought to be called the Boeing phenomenon. Even in this case, by stretching in the casting direction, the bowing phenomenon can be suppressed and the distribution of the phase difference in the width direction can be reduced.

The film thickness variation of the obtained film can be reduced by stretching in the biaxial directions perpendicular to each other. When the film thickness variation of the retardation film is too large, the retardation becomes uneven, and unevenness such as coloring may be a problem when used in a liquid crystal display.

The film thickness variation of the cellulose resin film is preferably in the range of ± 3%, more preferably ± 1%.
(Winding process)
After the stretching step, the end of the film is slit into a product width by the slitter 13 and cut off, and knurled (embossing) is applied to both ends of the film by a knurling device including the embossing ring 14 and the back roll 15. Thereafter, as a winding process, the film is wound by the winder 16 to obtain a cellulose acylate film (original winding) F. The knurling method can process a metal ring having an uneven pattern on its side surface by heating or pressing. In addition, since the grip part of the clip of the both ends of a film is deform | transforming normally and cannot be used as a film product, it is cut out and reused as a raw material.
<Cycloolefin polymer film>
First, the constituent material of a cycloolefin polymer film is demonstrated.

The cycloolefin polymer used in the present invention is made of a polymer resin containing an alicyclic structure.

A preferred cycloolefin polymer is a resin obtained by polymerizing or copolymerizing a cyclic olefin. Examples of the cyclic olefin include norbornene, dicyclopentadiene, tetracyclododecene, ethyltetracyclododecene, ethylidenetetracyclododecene, tetracyclo [7.4.0.110, 13.02,7] trideca-2,4, Polycyclic unsaturated hydrocarbons such as 6,11-tetraene and derivatives thereof; cyclobutene, cyclopentene, cyclohexene, 3,4-dimethylcyclopentene, 3-methylcyclohexene, 2- (2-methylbutyl) -1-cyclohexene, cyclo Examples thereof include monocyclic unsaturated hydrocarbons such as octene, 3a, 5,6,7a-tetrahydro-4,7-methano-1H-indene, cycloheptene, cyclopentadiene, cyclohexadiene, and derivatives thereof. These cyclic olefins may have a polar group as a substituent. Examples of the polar group include a hydroxyl group, a carboxyl group, an alkoxyl group, an epoxy group, a glycidyl group, an oxycarbonyl group, a carbonyl group, an amino group, an ester group, and a carboxylic acid anhydride group. Or a carboxylic anhydride group is preferred.

Preferred cycloolefin polymers may be those obtained by addition copolymerization of monomers other than cyclic olefins. Addition copolymerizable monomers include ethylene or α-olefins such as ethylene, propylene, 1-butene and 1-pentene; 1,4-hexadiene, 4-methyl-1,4-hexadiene, 5-methyl- And dienes such as 1,4-hexadiene and 1,7-octadiene.

The cyclic olefin is obtained by an addition polymerization reaction or a metathesis ring-opening polymerization reaction. The polymerization is carried out in the presence of a catalyst. Examples of the addition polymerization catalyst include a polymerization catalyst composed of a vanadium compound and an organoaluminum compound. As a catalyst for ring-opening polymerization, a polymerization catalyst comprising a metal halide such as ruthenium, rhodium, palladium, osmium, iridium, platinum, nitrate or acetylacetone compound, and a reducing agent; or titanium, vanadium, zirconium, tungsten, molybdenum Examples thereof include a polymerization catalyst comprising a metal halide such as acetylacetone compound and an organoaluminum compound. The polymerization temperature, pressure and the like are not particularly limited, but the polymerization is usually carried out at a polymerization temperature of −50 ° C. to 100 ° C. and a polymerization pressure of 0 to 490 N / cm ² .

The cycloolefin polymer used in the present invention is preferably a polymer obtained by polymerizing or copolymerizing a cyclic olefin, followed by a hydrogenation reaction to change the unsaturated bond in the molecule to a saturated bond. The hydrogenation reaction is performed by blowing hydrogen in the presence of a known hydrogenation catalyst. Examples of hydrogenation catalysts include cobalt acetate / triethylaluminum, nickel acetylacetonate / triisobutylaluminum, transition metal compounds such as titanocene dichloride / n-butyllithium, zirconocene dichloride / sec-butyllithium, tetrabutoxytitanate / dimethylmagnesium / alkyl. Homogeneous catalyst consisting of a combination of metal compounds; heterogeneous metal catalyst such as nickel, palladium, platinum; nickel / silica, nickel / diatomaceous earth, nickel / alumina, palladium / carbon, palladium / silica, palladium / diatomaceous earth And a heterogeneous solid-supported catalyst in which a metal catalyst such as palladium / alumina is supported on a carrier.

Alternatively, examples of the cycloolefin polymer include the following norbornene polymers. The norbornene-based polymer preferably has a norbornene skeleton as a repeating unit, and specific examples thereof include JP-A-62-252406, JP-A-62-2252407, and JP-A-2-133413. JP-A-63-145324, JP-A-63-264626, JP-A-1-240517, JP-B-57-8815, JP-A-5-39403, JP-A-5-43663 JP-A-5-43834, JP-A-5-70655, JP-A-5-279554, JP-A-6-206985, JP-A-7-62028, JP-A-8-176411, Although what was described in Kaihei 9-241484 etc. can be utilized preferably, it is not limited to these. Moreover, these may be used individually by 1 type and may use 2 or more types together.

In the present invention, among the norbornene-based polymers, those having a repeating unit represented by any of the following structural formulas (I) to (IV) are preferable.

In the structural formulas (I) to (IV), A, B, C and D each independently represent a hydrogen atom or a monovalent organic group.

Among the norbornene-based polymers, a polymer obtained by metathesis polymerization of at least one compound represented by the following structural formula (V) or (VI) and an unsaturated cyclic compound copolymerizable therewith. A hydrogenated polymer obtained by hydrogenating is also preferred.

In the structural formula, A, B, C and D each independently represent a hydrogen atom or a monovalent organic group.

Here, A, B, C and D are not particularly limited, but preferably an organic group may be linked via a hydrogen atom, a halogen atom, a monovalent organic group, or at least a divalent linking group. These may be the same or different. A or B and C or D may form a monocyclic or polycyclic structure. Here, the at least divalent linking group includes a hetero atom typified by an oxygen atom, a sulfur atom, and a nitrogen atom, and examples thereof include ethers, esters, carbonyls, urethanes, amides, and thioethers. It is not limited. In addition, the organic group may be further substituted via the linking group.

Other monomers copolymerizable with the norbornene monomer include, for example, ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, Α-olefins having 2 to 20 carbon atoms such as 1-hexadecene, 1-octadecene, 1-eicocene, and derivatives thereof; cyclobutene, cyclopentene, cyclohexene, cyclooctene, 3a, 5,6,7a-tetrahydro-4,7 Cycloolefins such as methano-1H-indene, and derivatives thereof; non-such as 1,4-hexadiene, 4-methyl-1,4-hexadiene, 5-methyl-1,4-hexadiene, 1,7-octadiene, etc. Conjugated dienes; and the like are used. Of these, α-olefins, particularly ethylene, are preferred.

These other monomers copolymerizable with the norbornene-based monomer can be used alone or in combination of two or more. In the case of addition copolymerization of a norbornene monomer and another monomer copolymerizable therewith, the ratio of the structural unit derived from the norbornene monomer and the structural unit derived from the other monomer copolymerizable in the addition copolymer However, it is appropriately selected so that the mass ratio is usually 30:70 to 99: 1, preferably 50:50 to 97: 3, and more preferably 70:30 to 95: 5.

When the unsaturated bond remaining in the molecular chain of the synthesized polymer is saturated by a hydrogenation reaction, the hydrogenation rate is 90% or more, preferably 95% or more, particularly from the viewpoint of light resistance deterioration, weather resistance deterioration, etc. Preferably it is 99% or more.

In addition, examples of the cycloolefin polymer used in the present invention include thermoplastic saturated norbornene resins described in paragraph Nos. [0014] to [0019] of JP-A-5-2108, and paragraph Nos. [0015] of JP-A-2001-277430. ] To [0031] thermoplastic norbornene polymers, JP 2003-14901 paragraph Nos. [0008] to [0045] thermoplastic norbornene resins, JP 2003-139950 paragraph Nos. [0014] to [0028] The norbornene-based resin composition described in JP-A-2003-161832, the norbornene-based resins described in paragraph numbers [0029] to [0037], and the paragraph numbers [0027] to [0036] described in JP-A-2003-195268. Norbornene-based resin, JP2003-21158 Paragraph Nos. [0009] to [0023] cycloaliphatic structure-containing polymer resin, norbornene polymer resin or vinyl alicyclic hydrocarbon described in JP-A-2003-212588, paragraph Nos. [0008] to [0024] Polymer resin etc. are mentioned.

Specifically, ZEONEX, ZEONOR manufactured by Nippon Zeon Co., Ltd., Arton manufactured by JSR Corporation, APPEL manufactured by Mitsui Chemicals, Inc. (APL8008T, APL6509T, APL6013T, APL5014DP, APL6015T) and the like are preferably used.

The molecular weight of the cycloolefin polymer used in the present invention is appropriately selected according to the purpose of use, and was measured by a gel permeation chromatography method of a cyclohexane solution (or a toluene solution when the polymer resin does not dissolve). When the weight average molecular weight in terms of polyisoprene or polystyrene is usually in the range of 5,000 to 500,000, preferably 8,000 to 200,000, more preferably 10,000 to 100,000, the mechanical strength and molding processability of the molded body are high. Balanced and suitable.

In addition, when a low-volatile antioxidant is blended in an amount of 0.01 to 5 parts by mass with respect to 100 parts by mass of the cycloolefin polymer, it can effectively prevent the polymer from being decomposed or colored during the molding process. I can do it.

The cycloolefin polymer film contains various additives in the same manner as the cellulose acylate film in order to improve the film characteristics.

Since the production method of the cycloolefin polymer film using the constituent material of the cycloolefin polymer film is the same as that of the cellulose acylate film, the explanation is omitted here.

As described above, by using the method for producing an optical film of the present invention, no agglomerates adhere to the lip portions 33 and 34 of the casting die 4, there is little foreign matter mixed in the film, and the film is conveyed. It is possible to produce a film having no directional stripe-shaped film thickness unevenness. In particular, the cellulose acylate film as the optical film of the present invention has no generation of foreign matter that is reflected in white by irradiation light, and there is a wave of reflected light reflected on the film surface due to the stripe-like film thickness unevenness of the film. High quality film can be produced. Therefore, a liquid crystal display device with high display quality can be obtained by using the optical film of the present invention for a polarizing plate as a protective film for a polarizing plate.

Moreover, the optical film manufactured using the method for manufacturing an optical film of the present invention can be used for various display devices such as a liquid crystal display device, a plasma display device, and an organic EL display device. It can also be used as an optical compensation film such as a retardation film, an antireflection film, a brightness enhancement film, and a viewing angle expansion.

Next, a polarizing plate using the optical film of the present invention as a protective film and a liquid crystal display device using the polarizing plate will be described.
(Polarizer)
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, KC4FR-4, KC4FR-3, KC4FR-3, KC4FR-4 -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 transmits only light having a plane of polarization in a certain direction. A typical polarizing film known at present is a polyvinyl alcohol polarizing film, which is a polyvinyl alcohol. There are one in which iodine is dyed on a system film and one in which dichroic dye is dyed.

The polarizer is formed by forming a polyvinyl alcohol aqueous solution into a film and dyeing the film by uniaxial stretching or dyeing or uniaxially stretching, and then performing 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 above-mentioned pressure-sensitive adhesive may be a one-component type or a type in which two or more components are mixed 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 concentration of the pressure-sensitive adhesive liquid may be appropriately determined depending on the film thickness after adhesion, the coating method, the coating conditions, and the like, and is usually 0.1 to 50% by mass.
(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 according to the present invention is bonded to a liquid crystal cell via the adhesive layer or the like.

The polarizing plate according to the present invention includes a reflective type, a transmissive type, a transflective type LCD or a TN type, an STN type, an OCB type, a HAN type, a VA type (PVA type, MVA type), an IPS type (including an FFS type), and the like. It is preferably used in various drive LCDs.

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.
(Examples 1 to 6, Comparative Examples 1 and 2)
(Pellet creation)
100 parts by mass of cellulose acetate propionate (acetyl group substitution degree 1.95, propionyl group substitution degree 0.7, number average molecular weight 75000, dried at 130 ° C. for 5 hours, glass transition temperature Tg = 174 ° C.)
Trimethylolpropane tris (3,4,5-trimethoxybenzoate) 10 parts by weight IRGANOX-1010 (manufactured by Ciba Japan) 1 part by weight Sumizer GP (manufactured by Sumitomo Chemical) 1 part by weight Silica particles as a matting agent in the above materials (Aerosil R972V (manufactured by Nippon Aerosil Co., Ltd.)) 0.05 parts by mass, 0.5 part by mass of TINUVIN 360 (manufactured by Ciba Japan Co., Ltd.) is added as an ultraviolet absorber, and mixed for 30 minutes with a V-type mixer containing nitrogen gas. After that, it was melted at 240 ° C. using a twin screw extruder (PCM30, Ikegai Co., Ltd.) attached with a strand die to produce a cylindrical pellet having a length of 4 mm and a diameter of 3 mm. The shear rate at this time was set to 25 (/ s).
(Production of film)
The film was manufactured using the manufacturing apparatus shown in FIG.

The produced pellets (water content 50 ppm) were melted in a single screw extruder and subjected to pressure filtration using a leaf disk type metal filter.

A cast film having a film thickness of 100 μm was obtained by melting and extruding the film from a casting die into a film at a melting temperature of 250 ° C. on a first cooling roll having a surface temperature of 100 ° C. At this time, the gap between the slits 32 of the casting die 4 was 1.0 mm, and the average surface roughness Ra of the lip portions 33 and 34 was 0.01 μm. Further, silica fine particles as a slip agent were added from the hopper opening in the middle of the extruder 1 so as to be 0.1 part by mass.

The supply of the inert gas to the lip portion by the supply nozzle 70 was performed using the apparatus shown in FIG. 2, and nitrogen gas was used as the gas. The gap d between the tip of the supply nozzle 70 and the film was 5 mm, and the cartridge heater 72 was used to heat the nitrogen gas having the temperature shown in Table 1 so that it would come out of the tip of the supply nozzle 70. Further, the nitrogen gas was adjusted by a regulating valve (not shown) so as to come out from the tip of the supply nozzle 70 at the wind speed shown in Table 1.

The suction nozzle 80 is arranged so that the tip of the suction nozzle 80 has a gap of 5 mm from the film, and the suction force at the tip of the suction nozzle 80 is not so high that the wind speed is the same as the wind speed of the tip of the supply nozzle 70. It adjusted with the adjustment valve of illustration and sucked.

The first cooling roll and the second cooling roll were made of carbon steel having a diameter of 40 cm, and the surface was hard chrome plated. In addition, temperature adjusting oil (cooling fluid) was circulated inside to control the roll surface temperature. The elastic touch roll had a diameter of 35 cm, the inner cylinder and the outer cylinder were made of carbon steel, and the outer cylinder surface was hard chrome plated. The wall thickness of the outer cylinder was 2 mm, and oil for cooling (cooling fluid) was circulated in the space between the inner cylinder and the outer cylinder to control the surface temperature of the elastic touch roll.

Furthermore, the film on the 1st cooling roll 5 was pressed using the touch roll B shown in FIG. 6, FIG. The outer cylinder 51 of the touch roll B was a carbon steel pipe having a thickness of 2 mm and was pressed at a linear pressure of 5 N / cm. The film temperature on the touch roll B side during pressing was 245 ° C. ± 1 ° C. (The film temperature on the side of the touch roll B at the time of pressing here refers to the temperature of the film at the position where the touch roll B on the first cooling roll 5 is in contact with the touch roll B by using a non-contact thermometer. The average value of the film surface temperature measured at 10 points in the width direction from a position 50 cm away without the touch roll B.) The glass transition temperature Tg of this film was 136 ° C. (The glass transition temperature of the film extruded from the die was measured by DSC method (in nitrogen, temperature rising temperature 10 ° C./min) using DSC6200 manufactured by Seiko Corporation.)
The surface temperature of the touch roll B was 100 ° C., and the surface temperature of the second cooling roll 7 was 80 ° C. The surface temperature of each roll of the touch roll B, the first cooling roll 5, and the second cooling roll 7 is the non-contact temperature of the roll surface at a position 90 ° before the rotation direction from the position where the film first contacts the roll. The average value measured at 10 points in the width direction using a thermometer was defined as the surface temperature of each roll.

The film forming speed was 20 m / min.

The obtained film was introduced into a tenter as a stretching apparatus, stretched 1.3 times at 160 ° C. in the width direction, and wound into a roll to produce an optical film.
(Evaluation)
The optical film was continuously produced with the manufacturing apparatus of FIG. 1, and the vertical streak-like noise on the film surface before the winding process was visually observed, and the continuous film formation time until the occurrence of noise was observed was evaluated. . As for the evaluation rank, those exceeding 400 hours were marked with ◎, those exceeding 50 hours were marked with ◯, and those with 50 hours or less were marked with ×. When the time is less than 50 hours, it is necessary to frequently stop the apparatus and clean the lip portion of the casting die, which causes a problem as a manufacturing apparatus due to extremely low productivity.

Evaluation results are shown in Table 1.

From the results shown in Table 1, by supplying an inert gas having a temperature of 110 ° C. or higher and 300 ° C. or lower to the lip portion of the casting die from the supply nozzle, vertical streak-like noise on the film surface is generated for a long time. I understand that there is no. Comparing Examples 3 to 6, it can be seen that the gas wind speed is preferably 0.3 m / s or more and 3 m / s or less.
(Example 7)
As Example 7, the optical film was manufactured and evaluated in the same manner as Example 4 except that the touch roll B was not used in the manufacture of the optical film of Example 4. The evaluation result is rank ◯, and the length of time during which vertical streak-like noise is generated is shorter than in Example 4. From this, it can be seen that it is preferable to use a touch roll, because it is difficult to generate vertical stripe noise.
(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 in the transport direction 6 times at 50 ° C. to produce a polarizer.

The cellulose acylate film produced in Example 1 was bonded to both sides of the polarizer from both sides with the alkali saponified surface as the polarizer side and a 5% by mass aqueous solution of a fully saponified polyvinyl alcohol as an adhesive. A polarizing plate to which a film was bonded was produced.
(Characteristic evaluation as a liquid crystal display device)
The polarizing plate of 32 type TFT type color liquid crystal display Vega (manufactured by Sony Corporation) was peeled off, and each polarizing plate produced above was cut according to the size of the liquid crystal cell. A liquid crystal cell is sandwiched, and the two polarizing plates thus prepared are pasted so as to be orthogonal to each other so that the polarizing axes of the polarizing plates are not changed from each other, thereby producing a 32-type TFT color liquid crystal display, and a cellulose acylate film. When the characteristics of the polarizing plate were evaluated, the polarizing plate produced from the cellulose acylate film, which is the optical film of the present invention, exhibited excellent display properties without streak-like color unevenness and image distortion. Thereby, it was confirmed that it is excellent as a polarizing plate for image display devices.

DESCRIPTION OF SYMBOLS 1 Extruder 2 Filter 3 Static mixer 4 Casting die 5 1st cooling roll 6 Touch roll 7 2nd cooling roll 8 3rd cooling roll 9 Peeling roll 11, 13, 14, 15 Conveyance roll 12a Longitudinal stretching apparatus 12b Horizontal stretching Device 10 Film 16 Winding device 32 Slit 33, 34 Lip part 41 Metal sleeve 42 Elastic roller 43 Metal inner cylinder 44 Rubber 45 Cooling water 51 Outer cylinder 52 Inner cylinder 53 Space 70 Supply nozzle 71, 81 Nozzle side plate 72 Heater 73 Supply pipe 82 Discharge pipe

Claims (10)

1. In an optical film manufacturing method comprising an extrusion step of extruding a molten resin into a film form from a lip portion of a casting die, and a cooling step of cooling and solidifying the film-like resin extruded in the extrusion step with a cooling drum ,
   The extrusion process includes
   An optical film manufacturing method, wherein an inert gas having a temperature of 110 ° C. or higher and 300 ° C. or lower is supplied from a supply nozzle to the lip portion.
2. 2. The optical film according to claim 1, wherein in the step of supplying the inert gas, a wind speed of the inert gas exiting from a tip of the supply nozzle is 0.3 m / s or more and 3 m / s or less. Manufacturing method.
3. The method for producing an optical film according to claim 1, wherein a heater is disposed in the supply nozzle to heat the inert gas.
4. The suction nozzle is disposed downstream of the supply nozzle in the direction in which the extruded film-like resin flows down, and the suction nozzle sucks an inert gas from the supply nozzle. The method for producing an optical film according to any one of 1 to 3.
5. The method for producing an optical film according to any one of claims 1 to 4, wherein the inert gas is nitrogen gas.
6. The cooling step includes a touch roll that presses the film-like resin on the cooling drum, and the surface of the film-like resin is smoothed by pressing with the touch roll. The method for producing an optical film according to any one of 1 to 5.
7. The said resin is a cellulose acylate or a cycloolefin polymer, The manufacturing method of the optical film of any one of Claim 1 to 6 characterized by the above-mentioned.
8. An optical film manufactured by the method for manufacturing an optical film according to claim 1.
9. A polarizing plate using the optical film according to claim 8 as a protective film for a polarizing plate.
10. A liquid crystal display device using the polarizing plate according to claim 9.

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