JP2009160796A - Optical film, its manufacturing method, and polarizing plate and display using the film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical film manufacturing method which is based on a melting casting film formation method, improves the releasing properties of the film to the metal-made cooling roll and eliminates the possibility of adhesion of sublimated matter to the film by removing the gas from the lip part of the die containing sublimated matter, an optical film manufactured by the method and being free of foreign matter and a polarizing plate and a display using the film. <P>SOLUTION: The optical film manufacturing method based on a melting casting film formation method or a solution casting film formation method comprises subjecting the surface of a casting web casted with a casting die to a high-energy surface treatment with an ordinary-pressure plasma apparatus, an excimer UV apparatus or a laser irradiation apparatus to form an easily peelable treated layer on the surface of the cast web. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention can be used for various functional films such as a protective film for a polarizing plate used for a liquid crystal display (LCD), a retardation film, a viewing angle widening film, and an antireflection film used for a plasma display. The present invention relates to a film, a manufacturing method thereof, a polarizing plate using an optical film, and a display device.

  Conventionally, a liquid crystal image display device (LCD) can be directly connected to an IC circuit with low voltage and low power consumption, and can be thinned, so that it is widely used as a display device for a word processor, a personal computer or the like. Yes.

  By the way, the basic structure of this LCD is one in which polarizing plates are provided on both sides of a liquid crystal cell. 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 A polarizing plate consists of a polarizer and a protective film laminated on both sides of the polarizer. A cellulose acylate film is widely used as a protective film for such a polarizing plate.

  These cellulose acylate films have been produced exclusively by a solution casting film forming method. The solution casting film forming method is a film forming method in which a solution obtained by dissolving cellulose acylate 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 film formation method has high flatness, a high-quality liquid crystal display without unevenness can be obtained using this film.

  In general, in solution casting in which a resin solution (dope) containing a thermoplastic resin and an additive is cast on a metal support (hereinafter referred to as support) made of a rotationally driven stainless steel endless belt or the same drum, Although there are some changes depending on the type of cellulose ester (vinegar cotton), the ratio of poor solvent, etc., the weight ratio of the total solvent amount to the film solid content weight (residual solvent amount) is around 60% by weight. There is a region where the peeling force increases and peeling becomes worse.

  In this region, the film cannot be smoothly peeled off from the support, accompanied by considerable fluttering and peeling noise, and the film has a sharp step-like deformation extending in the width direction generated by this fluttering. In production, the conditions for removing this area had to be taken, and this was a limitation in film production.

  This poorly peeled area varies depending on the type of the dope material, that is, for example, the type of vinegar, the addition ratio of the poor solvent, the temperature of the film at the time of peeling, and the like. This region exists even in the film forming process.

  In order to remove such a poor peeling region, for example, an attempt was made to take film production conditions on the so-called high residual dissolution side of the web (film) (the region where the residual solvent amount is higher than the region where the peeling force increases). In particular, in the case of a film having a film thickness of 40 μm or less, the evaporation rate of methylene chloride, which is a solvent, can be greatly reduced even when the temperature of the drying air blown to dry the cast film on the support is lowered. Since it was not possible, there was a problem that the condition for high residual melt peeling was not possible.

  Therefore, in order to achieve high residual melt peeling, in addition to increasing the production rate of the film, in this case, post-drying is performed in order to increase the capacity of the solvent recovery facility or to reduce the amount of residual solvent in the product film to the limit. There was a problem that a large facility modification was required, such as extending the process.

  For this reason, normally, the manufacturing conditions of the optical film had to be set to the conditions on the low residual melt peeling side. However, in the case of low residual dissolution peeling conditions, the casting film enters the drying rate reduction period, so if the drying time on the support is not made very long, the residual dissolution cannot be lowered. There was a problem that the production speed had to be greatly reduced.

As described above, conventionally, there is a problem in that a poorly peeled residual melted region of the support exists, and thus there is a problem that a film has to be formed at a production rate significantly lower than the apparatus capability.
Japanese Unexamined Patent Publication No. 2003-55501 JP-A-2003-128838 discloses a method for producing a cellulose acylate film in which a peeling aid is added to a dope in order to solve the conventional problems as described above. Japanese Patent Laid-Open No. 2000-239403 discloses an apparatus-like improvement method for manufacturing an optical film, which is a solution casting film forming apparatus for casting having a specific surface roughness (Ra). A method for producing a cellulose acylate film formed using a support is disclosed. Japanese Patent Application Laid-Open No. 2002-264152 similarly discloses an apparatus improvement method for manufacturing an optical film, in which a continuous spiral groove is provided on the surface of a support to provide good peeling. Describes a method of stably producing a smooth optical film for a long period of time while suppressing the accumulation of precipitates and the like on the surface of the support while maintaining the properties.

  By the way, the solution casting film forming method requires a large amount of an organic solvent, and the environmental load is also a problem. The cellulose acylate film is formed using a halogen-based solvent with a large environmental load because of its dissolution characteristics, and therefore, a reduction in the amount of solvent used is particularly required. It has become difficult to increase production.

  Therefore, in recent years, attempts have been made to melt film-form cellulose acylate. 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, plasticizers, antioxidants, ultraviolet absorbers, matting agents, etc. are added to improve film properties.

  However, when such a cellulose acylate melt is extruded into a film form from the lip portion of an extrusion die and cooled and solidified by a cooling roll, a film is produced by a melt casting film forming method in which a film is produced. Hereinafter, a gas containing a sublimate is generated from the melt extruded from the lip portion of the casting die).

  As a method for preventing a similar problem that occurs when heat-melting a general thermoplastic resin, for example, a method of forcibly exhausting air in the vicinity of a die by providing a hood at the top of the die has been proposed.

Patent Document 5 below proposes a method of forcibly evacuating by installing a suction nozzle near the lip.
JP-A-11-48306

  However, in the method for producing an optical film by the conventional solution casting film forming method, the above-described methods described in Patent Documents 1 and 2 have a sufficient effect for the above-described web (film) peeling failure region. There was a problem that it could not be obtained.

  Further, in the methods described in Patent Documents 3 and 4, the accumulation of dirt on the surface of the support can be prevented, but the web (film) separation failure region has not been eliminated.

  On the other hand, in the conventional method for producing an optical film by the melt casting film forming method, in a method in which a hood is provided and the air in the vicinity of the die is forcibly evacuated, the sublimate is present at a low temperature part of the hood or the die peripheral equipment with time. A problem arises due to the deposition and deposition of this volume from time to time.

  In addition, in the method of installing a suction nozzle near the lip, the sublimate adheres and accumulates over time at low-temperature locations such as the nozzle and pipe, and this deposit sometimes causes problems such as the sublimate falling, and the suction pipe There arises a problem that the suction performance is remarkably lowered due to clogging due to the deposition of the sublimate. For this reason, production must be frequently interrupted, and cooling rolls, die lips, etc. must be cleaned and restarted, resulting in a problem that the yield and operating rate of the product are significantly reduced.

  As a means for solving such a problem, a method of further lowering the melting temperature of the thermoplastic resin, a method of increasing a suction amount from a hood provided at the top of the die or a nozzle provided in the vicinity of the lip, and the like can be considered.

  However, the former method is not sufficient as a countermeasure because there are other problems such as generation of unmelted material from the die lip and defects in film quality. Also, in the latter method, the sublimate generated from the die lip outlet is strongly sucked together with the nearby air, so that the molten film extruded from the die lip shakes or has a cooling spot, and the thickness unevenness of the film becomes remarkable. Problems arise.

Patent Document 6 below proposes a method for removing a sublimate by disposing the sublimate by providing a suction nozzle to the entire length of the lip portion of the die and guiding the suction gas to the catalyst installation portion.
By the way, in the manufacturing method of the optical film by the conventional solution casting film forming method, in the manufacturing of the optical film having a film width of 1500 mm or more other than the above-described web (film) peeling failure region, it is supported. The dope casting width on the body is 1700 mm or more, and in the production of such a wide film, variations in the peelability in the width direction of the film appear as fluctuations in the peel position. As a result, retardation (Re ) There is a problem that the value, etc., varies in the width direction and the longitudinal direction of the film. In a liquid crystal panel that is becoming higher in definition year by year, such a variation in the characteristics of the optical film is eventually reduced. It has been a big problem due to a decrease in contrast and uneven density.

  The object of the present invention is to solve the above-mentioned problems of the prior art, and for the production method of an optical film by the solution casting film formation method, by eliminating a so-called peelable defective region of the support, The restrictions are reduced, the range of film production conditions is greatly expanded, and the release properties (peelability) of the film from the support are improved. While the variation in the width direction of the peeling position is reduced, the variation in the retardation (Re) value is greatly reduced, and an optical film having optical characteristics with excellent transparency and flatness can be manufactured and produced. The speed can be increased, the productivity of the film can be improved, and as a result, the demands for thinning, widening, and high quality of protective films for polarizing plates in recent years can be met. Optical film, a method of manufacturing the same, is to provide a polarizing plate and a display device using the optical film.

  In addition, the object of the present invention is to improve the film releasability (peelability) from the metal cooling roll and to remove the gas containing sublimation from the lip portion of the die for the melt casting film forming method. Then, it is providing the manufacturing method of the optical film in which a sublimate does not adhere on a film, the optical film without the foreign material manufactured by this manufacturing method, a polarizing plate using this film, and a display apparatus. .

  In order to achieve the above object, the invention of claim 1 is a method for producing an optical film by a melt casting film forming method or a solution casting film forming method, wherein the casting film is cast from a casting die. The surface of the (web) is subjected to high energy surface treatment by an atmospheric plasma device, an excimer UV device, or a laser irradiation device to form an easily peelable treatment layer on the surface of the cast film.

  Invention of Claim 2 is the manufacturing method of the optical film of Claim 1, Comprising: The melt casting film forming method casts the molten material of a thermoplastic resin on a cooling roll from a casting die, The process includes a step of cooling and solidifying and peeling, wherein the cast film of the melt extruded from the casting die is in contact with the surface of the cooling roll from the start of extrusion or immediately after contacting the surface of the cooling roll. High-energy surface treatment is performed on at least one of the two surfaces by using a normal pressure plasma device, an excimer UV device, or a laser irradiation device to form an easily peelable treatment layer on the surface of the casting film. It is characterized by that.

  Invention of Claim 3 is a manufacturing method of the optical film of Claim 2, Comprising: This casting film is within 5 second after a molten material is extruded from a casting die and a casting film is formed. The surface of the film is subjected to high energy surface treatment by an atmospheric pressure plasma device, an excimer UV device, or a laser irradiation device, and an easily peelable treatment layer is formed on the surface of the cast film.

  Invention of Claim 4 is a manufacturing method of the optical film of Claim 2 or 3, Comprising: The peeling force at the time of casting film peeling from the last cooling roll is 1.0-12.0 (N / M width), and the increase in the peel strength of the cast film after 24 hours of operation of the melt cast film forming apparatus is 0.1 to 2.0 (N / m width). .

  The invention according to claim 5 is the method for producing an optical film according to claim 1, wherein the solution casting method is a method in which a dope (resin solution) in which a thermoplastic resin is dissolved in a solvent is added to a metal from a casting die. A dope formed from a casting die, including a step of casting on a rotating drum made of metal or a rotating endless belt made of metal (hereinafter referred to as a support) to form a cast film, and peeling the cast film from the support. An atmospheric pressure plasma apparatus, an excimer is provided on at least one of the two surfaces of the casting film from the beginning of casting until it comes into contact with the support surface or immediately after contacting the support surface. A high-energy surface treatment is performed by a UV device or a laser irradiation device, and an easily peelable treatment layer is formed on the surface of the cast film.

  Invention of Claim 6 is a manufacturing method of the optical film of Claim 5, Comprising: After dope is cast from a casting die and a casting film is formed, residual solvent amount of this casting film The surface of the cast film is subjected to high-energy surface treatment using a normal pressure plasma apparatus, an excimer UV apparatus, or a laser irradiation apparatus until it reaches 200% by weight, and the surface of the cast film is easily peelable. The treatment layer is formed.

  The invention according to claim 7 is the method for producing an optical film according to claim 5 or 6, wherein the high-energy surface treatment by the atmospheric pressure plasma apparatus, the excimer UV apparatus, or the laser irradiation apparatus is performed at least in the presence of a solvent vapor. It is characterized by what is done below.

  Invention of Claim 8 is a manufacturing method of the optical film as described in any one of Claims 5-7, Comprising: The high energy surface treatment by an atmospheric pressure plasma apparatus or an excimer UV apparatus is carried out at least of a solvent. It is characterized in that it is carried out in the presence of vapor and a reactive gas used in an atmospheric pressure plasma apparatus or a purge gas used in an excimer UV apparatus.

  Invention of Claim 9 is a manufacturing method of the optical film as described in any one of Claims 5-8, Comprising: The peeling force at the time of a casting film peeling from a support body is 1.0. 12.0 (N / m width), and the increase in the peel strength of the casting film after operation for 24 hours of the solution casting film forming apparatus is 0.1 to 2.0 (N / m width). It is characterized by being.

  The invention of an optical film of claim 10 is characterized by being manufactured by the method for manufacturing an optical film according to any one of claims 1 to 9.

The invention of the optical film of claim 11 is the optical film of claim 10, wherein the film is disposed between two polarizing plates orthogonal to each other, and the transmittance of the transmitted light having a wavelength of 600 nm of the film. Is measured in a crossed Nicol state, and the variation of the transmittance of the transmitted light is 2 × 10 ^{−5 to} 60 × 10 ⁻⁵ (%).

  The invention of a polarizing plate according to claim 12 is characterized in that the optical film according to claim 10 or 11 is used as a protective film for a polarizing plate and is provided on at least one of both surfaces of the polarizing film.

  A thirteenth aspect of the present invention is characterized in that the polarizing plate according to the twelfth aspect is used.

  The invention of claim 1 is a method for producing an optical film by a melt casting film forming method or a solution casting film forming method, wherein the surface of a casting film (web) cast from a casting die is subjected to normal pressure. A high-energy surface treatment is performed by a plasma device, an excimer UV device, or a laser irradiation device to form an easily peelable treatment layer on the surface of the casting film. In the film-forming method, the peelability of the web from the cooling roll is improved, the flatness, as well as the variation in crossed Nicols transmittance, which tends to deteriorate if the peel is poor, can be greatly reduced. There is an effect that it is possible to meet the demands for thinning, widening, and improving the quality of the protective film for an automobile.

  In addition, it is possible to eliminate the defect of peeling that occurs when the residual solvent in the web at the time of peeling is in a certain range, as seen in the solution casting film forming method, and the restrictions on the film production conditions so far are reduced. While the selection range of production conditions is greatly expanded, the mold releasability (peelability) of the film from the support is improved, and very smooth releasability can be obtained in the entire peel residual solution region.

  Invention of Claim 2 is the manufacturing method of the optical film of Claim 1, Comprising: The melt casting film forming method casts the molten material of a thermoplastic resin on a cooling roll from a casting die, The process includes a step of cooling and solidifying and peeling, wherein the cast film of the melt extruded from the casting die is in contact with the surface of the cooling roll from the start of extrusion or immediately after contacting the surface of the cooling roll. High-energy surface treatment is performed on at least one of the two surfaces by using a normal pressure plasma device, an excimer UV device, or a laser irradiation device to form an easily peelable treatment layer on the surface of the casting film. Therefore, according to the invention of claim 2, in the melt casting film forming method, the peelability of the web from the cooling roll is improved, and, of course, the flat Nicol permeability has been deteriorated when the peelability is poor. The variation of Rukoto can achieves recent thinning of the protective films for polarizing plate, the effect that it is possible to meet broadening, and demand for higher quality.

  Invention of Claim 3 is a manufacturing method of the optical film of Claim 2, Comprising: This casting film is within 5 second after a molten material is extruded from a casting die and a casting film is formed. The surface of the film is subjected to high energy surface treatment by an atmospheric plasma device, excimer UV device, or laser irradiation device to form an easily peelable treatment layer on the surface of the cast film. According to this, since the film peelability is improved, fluctuations in the width direction of the peeling position are reduced, and variation in retardation value is greatly reduced, so that the optical property having excellent transparency and flatness is obtained. There exists an effect that a film can be manufactured.

  Invention of Claim 4 is a manufacturing method of the optical film of Claim 2 or 3, Comprising: The peeling force at the time of casting film peeling from the last cooling roll is 1.0-12.0 (N / M width), and the increase in the peel strength of the cast film after 24 hours of operation of the melt cast film forming apparatus is 0.1 to 2.0 (N / m width), According to the invention of 4, there is an effect that restrictions on film production conditions are reduced and productivity is improved.

  The invention according to claim 5 is the method for producing an optical film according to claim 1, wherein the solution casting method is a method in which a dope (resin solution) in which a thermoplastic resin is dissolved in a solvent is added to a metal from a casting die. A dope formed from a casting die, including a step of casting on a rotating drum made of metal or a rotating endless belt made of metal (hereinafter referred to as a support) to form a cast film, and peeling the cast film from the support. An atmospheric pressure plasma apparatus, an excimer is provided on at least one of the two surfaces of the casting film from the beginning of casting until it comes into contact with the support surface or immediately after contacting the support surface. A high-energy surface treatment is performed by a UV device or a laser irradiation device to form an easily peelable treatment layer on the surface of the casting film. According to the invention of claim 5, in the solution casting film forming method, There is a certain residual solvent in the web when peeling The defect of peeling that can be seen in the surrounding area has been resolved, the restrictions on the film production conditions so far have been reduced, the range of film production conditions has been greatly expanded, and the film releasability from the support (peelability) Is improved, and there is an effect that a very smooth peelability can be obtained in the entire peel residual dissolution zone.

  Invention of Claim 6 is a manufacturing method of the optical film of Claim 5, Comprising: After dope is cast from a casting die and a casting film is formed, residual solvent amount of this casting film The surface of the cast film is subjected to high-energy surface treatment using a normal pressure plasma apparatus, an excimer UV apparatus, or a laser irradiation apparatus until it reaches 200% by weight, and the surface of the cast film is easily peelable. According to the invention of claim 6, by improving the peelability of the film, the variation in the width direction of the peeling position is reduced and the variation of the retardation value is greatly reduced. Therefore, there is an effect that an optical film having optical properties excellent in transparency and flatness can be produced.

  The invention according to claim 7 is the method for producing an optical film according to claim 5 or 6, wherein the high-energy surface treatment by the atmospheric pressure plasma apparatus, the excimer UV apparatus, or the laser irradiation apparatus is performed at least in the presence of a solvent vapor. According to the invention of claim 7, a monolayer treatment film having a pure water contact angle that uses organic solvent vapor or monomer gas as a raw material is formed to reduce the peeling force of the casting film. Therefore, even when the optical thin film is peeled off from the support at high speed, the peeling stress applied to the film can be reduced, and the variation in optical characteristics can be reduced. Specifically, the crossed Nicols transmittance ( The variation width of (CNT) can be reduced.

  Invention of Claim 8 is a manufacturing method of the optical film as described in any one of Claims 5-7, Comprising: The high energy surface treatment by an atmospheric pressure plasma apparatus or an excimer UV apparatus is carried out at least of a solvent. This is performed in the presence of steam and a reaction gas used in an atmospheric pressure plasma apparatus or a purge gas used in an excimer UV apparatus. According to the invention of claim 8, the contact angle of pure water using the reaction gas or purge gas as a raw material is increased. A smaller monolayer treatment film is formed to reduce the peeling force of the casting film, thereby reducing the peeling stress on the film even when the optical thin film is peeled off from the support at high speed. It is possible to reduce the variation in optical characteristics, specifically, to reduce the variation width of the crossed Nicols transmittance (CNT). That.

  Invention of Claim 9 is a manufacturing method of the optical film as described in any one of Claims 5-8, Comprising: The peeling force at the time of a casting film peeling from a support body is 1.0. 12.0 (N / m width), and the increase in the peel strength of the casting film after operation for 24 hours of the solution casting film forming apparatus is 0.1 to 2.0 (N / m width). Therefore, according to the invention of claim 9, restrictions on film production conditions are reduced and productivity is improved. Furthermore, since the peelability of the film is improved, fluctuations in the width direction of the peeling position are reduced, and variation in retardation values is greatly reduced, so that the optical film has optical properties with excellent transparency and flatness. Can be manufactured. Thereby, there is an effect that it is possible to provide an optical film manufacturing method, an optical film, a polarizing plate, and a display device that can meet demands for thinning, widening, and high quality of a protective film for a polarizing plate. .

  Invention of the optical film of Claim 10 was manufactured by the method as described in any one of Claims 1-9, According to invention of the optical film of Claim 10, Since the release property (peelability) of the cast film (web) from the support is improved, very smooth peelability is obtained, and fluctuation in the width direction of the peel position is reduced, the optical film is The variation in crossed Nicols transmittance is greatly reduced, and the effect of excellent transparency and flatness is achieved.

The invention of the optical film of claim 11 is the optical film of claim 10, wherein the film is disposed between two polarizing plates orthogonal to each other, and the transmittance of the transmitted light having a wavelength of 600 nm of the film. Is measured in a crossed Nicol state, and the variation in transmittance of the transmitted light is 2 × 10 ^{−5 to} 60 × 10 ⁻⁵ (%). According to the invention of claim 11, The release property (peelability) of the cast film (web) is improved, very smooth peelability is obtained, and fluctuation in the width direction of the peel position is reduced. As a result, there is an effect of greatly reducing transparency and flatness.

  The invention of the polarizing plate of claim 12 has the optical film of claim 10 or 11 as a protective film for polarizing plate on at least one of the surfaces of the polarizing film. According to the invention, the dispersion of the crossed Nicols transmittance is greatly reduced, and an optical film having excellent transparency and flatness is provided on at least one surface. Therefore, this polarizing plate is incorporated in a liquid crystal panel. At this time, the liquid crystal panel does not cause a decrease in contrast and uneven density, and has an effect of excellent visibility.

  Since the invention of the display device of claim 13 uses a polarizing plate comprising an optical film having excellent optical properties without variation according to claim 12, according to the invention of claim 13, There is an effect that the liquid crystal panel is excellent in visibility without causing a decrease in contrast and uneven density.

  Next, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited thereto.

  The method for producing an optical film according to the present invention is a method for producing an optical film by a melt casting film forming method or a solution casting film forming method, on the surface of a casting film (web) cast from a casting die. Then, a high-energy surface treatment is performed by a normal pressure plasma device, an excimer UV device, or a laser irradiation device to form an easily peelable treatment layer on the surface of the cast film.

  That is, the present invention is so-called on-line during film formation, at least one of both surfaces of the casting film until the casting film comes out of the casting die and contacts the cooling roll or the support or immediately after the contact. One surface is subjected to a high energy surface treatment by a high energy irradiation device (A) comprising an atmospheric pressure plasma device, an excimer UV device, or a laser irradiation device, thereby forming a treatment film on the surface of the casting film, thereby cooling the surface. It improves the peelability from the roll or the support.

  The high-energy irradiation on the casting film may be performed on at least one of both surfaces of the casting film, and preferably, on the both surfaces of the casting film, the side in contact with the cooling roll or the support. High energy irradiation is performed on the surface of

  According to the present invention, in the melt casting film forming method, the additive gas that evaporates when the casting film is extruded from the casting die is decomposed by irradiation with excimer UV or atmospheric pressure plasma, This prevents the device and film from becoming dirty.

  According to the present invention, in the melt casting film forming method, the releasability of the web from the cooling roll is improved, and flatness, as well as the variation of the crossed Nicols transmittance, which tends to deteriorate when the peel is poor, is greatly reduced. Therefore, it is possible to meet the recent demands for thinning, widening, and improving the quality of protective films for polarizing plates.

  In addition, it is possible to eliminate the defect of peeling that occurs when the residual solvent in the web at the time of peeling is in a certain range, as seen in the solution casting film forming method, and the restrictions on the film production conditions so far are reduced. While the selection range of production conditions is greatly expanded, the releasability (peelability) of the film from the support is improved, and a very smooth peelability can be obtained in the entire residual peeling area.

  Hereafter, the manufacturing method of the optical film by this invention is described in detail.

  The optical film according to the present invention can be produced by a melt casting film forming method or a solution casting film forming method.

  First, the manufacturing method of the optical film by the melt casting film forming method of this invention is demonstrated.

  The method for producing an optical film according to the present invention is based on a melt casting film forming method, in which a melt of a thermoplastic resin is cast from a casting die onto a cooling roll, cooled and solidified, and then peeled off. And the molten cast film extruded from the casting die is at least one of both surfaces of the cast film from the start of extrusion until it contacts the surface of the cooling roll or immediately after contacting the surface of the cooling roll. One surface is subjected to a high-energy surface treatment using an atmospheric pressure plasma device, an excimer UV device, or a laser irradiation device to form an easily peelable treatment layer on the surface of the cast film.

  In the method for producing an optical film of the present invention, within 5 seconds after the melt is extruded from the casting die and the casting film is formed, preferably within 0.5 to 3 seconds. It is preferable to subject the surface to a high-energy surface treatment using an atmospheric pressure plasma device, an excimer UV device, or a laser irradiation device to form an easily peelable treatment layer on the surface of the cast film.

  Here, more than 5 seconds after the melt is extruded from the casting die and the cast film is formed, the surface of the cast film is applied to the surface of the cast film by an atmospheric plasma device, an excimer UV device, or a laser irradiation device. When the high energy surface treatment is performed, the cast film surface is hardened, and the effect of surface modification is weakened.

  Moreover, in the manufacturing method of the optical film of this invention, the peeling force at the time of casting film peeling from the last cooling roll is 1.0-12.0 (N / m width), and a melt casting film forming apparatus It is preferable that the increase amount of the peeling force of the cast film after 24 hours of operation is 0.1 to 2.0 (N / m width).

  Here, if the peeling force when the cast film is peeled from the support is less than 1.0 (N / m width), a part of the web may be peeled off in the middle, which is not preferable. Further, if the peeling force exceeds 12.0 (N / m width), the film cannot be smoothly peeled off from the support, and there is considerable flapping and peeling noise. Since sharp step-like deformation extending in the direction occurs, it is not preferable.

  Also, if the increase in the peel strength of the cast film after 24 hours of operation of the melt cast film forming apparatus is less than 0.1 (N / m width), the peel position may be taken downstream. Because there is a case, it is not preferable. In addition, when the amount of increase in the peel strength of the cast film exceeds 2.0 (N / m width), the film cannot be smoothly peeled from the support, accompanied by considerable flapping and peeling noise. This is not preferable because sharp step-like deformation extending in the width direction generated by the flapping occurs.

  According to the method for producing an optical film of the present invention, in the melt casting film forming method, the peelability of the web from the cooling roll is improved, and, of course, the flat Nicol transmittance has been deteriorated when the peel is bad. The variation in the thickness can be greatly reduced, and it is possible to meet the recent demands for thinning, widening, and improving the quality of protective films for polarizing plates.

  Melt casting film forming methods are classified into molding methods that are heated and melted, and melt extrusion molding methods, press molding methods, inflation methods, injection molding methods, blow molding methods, stretch molding methods, and the like can be applied. Among these, in order to obtain an optical film excellent in mechanical strength and surface accuracy, the melt extrusion method is excellent. Hereinafter, the method for producing the film of the present invention will be described by taking the melt extrusion method as an example.

  In the method for producing an optical film by the melt casting film forming method of the present invention, the film constituent material to be used is mainly a pellet-shaped material, and it is preferable to dry before film formation. The moisture content of the pellets after drying is preferably 500 ppm or less, more preferably 200 ppm or less.

  As the dryer, a dehumidifying hot air dryer, a ribbon-type heat transfer vacuum dryer, a screw-type heat transfer vacuum dryer, or the like can be preferably used, but is not limited thereto.

  When using a vacuum dryer, the degree of vacuum is preferably 10 torr or less, more preferably 3 torr or less. The temperature is preferably 50 ° C. or higher and 150 ° C. or lower. More preferably, it is 80 degreeC or more and 120 degrees C or less. It is preferable to put nitrogen gas into the dryer during drying. When returning from the vacuum state to the atmospheric pressure, it is preferable to add dehumidified air or nitrogen gas.

  When using a dehumidifying hot air dryer, the dew point of the dehumidified air is preferably −20 ° C. or lower, more preferably −40 ° C. or lower.

  Pneumatic transportation is preferred as a transfer method from the dryer to the extruder. The air used for transportation is preferably dehumidified. Pellets that are pneumatically transported from the dryer are placed in a hopper above the extruder, but there is a powder collector on the hopper to remove small debris and powder from the pellets that are transported along with the pellets Is preferred. In the collector, pellets and powder are separated by the force of air, and only the powder is removed. The hopper is preferably kept warm. The temperature is preferably 50 ° C. or higher and 150 ° C. or lower. More preferably, it is 80 degreeC or more and 120 degrees C or less. It is preferable to put dehumidified air into the hopper.

  FIG. 1 is a schematic flow sheet showing the overall configuration of an apparatus for carrying out the method for producing an optical film by the melt casting method of the present invention, and FIG. 2 is an enlarged view of a cooling roll portion from the casting die. . Note that the implementation of the present invention is not limited to the process of the drawings shown below.

  1 and 2, for example, a cellulose ester resin dried under hot air, vacuum or reduced pressure is melted at an extrusion temperature of about 200 to 300 ° C. using an extruder (1), and a leaf disk type filter (2) Filter through to remove foreign matter.

  When the feed hopper (not shown) is introduced into the extruder (1), it is preferable to prevent oxidative decomposition or the like by applying a vacuum, a reduced pressure, or an inert gas atmosphere.

  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).

  It is preferable to mix a resin such as a cellulose resin and other additives such as a stabilizer added as necessary before melting. Mixing may be performed by a mixer or the like, or as described above, mixing may be performed in a resin preparation process such as a cellulose resin. When a mixer is used, a general mixer such as a V-type mixer, a conical screw type mixer, a horizontal cylindrical type mixer, or the like can be used.

  After the film constituent materials are mixed as described above, the mixture may be directly melted and formed into a film using an extruder (1). Once the film constituent materials are pelletized, the pellets May be melted with an extruder (1) to form a film. Further, when the film constituent material includes a plurality of materials having different melting points, a so-called braided semi-melt is once produced at a temperature at which only a material having a low melting point is melted, and the semi-melt is extruded (1). ) To form a film. If the film component contains a material that is easily pyrolyzed, in order to reduce the number of times of melting, a method of directly forming a film without producing pellets, or after making a paste-like semi-molten material as described above A method of forming a film is preferred.

  As the extruder (1), various commercially available extruders can be used, but a melt-kneading extruder is preferable, and a single-screw extruder or a twin-screw extruder may be used. When forming a film directly without producing pellets from film constituent materials, it is preferable to use a twin-screw extruder because an appropriate degree of kneading is required. However, even with a single-screw extruder, the screw shape is a Maddock type. By changing to a kneading type screw such as a unimelt type or a dull mage, moderate kneading can be obtained, so that it can be used. When a pellet or braided semi-melt is once used as a film constituent material, it can be used in either a single screw extruder or a twin screw extruder.

  In the extruder (1) and after the extrusion, the cooling step is preferably carried out by substituting with an inert gas such as nitrogen gas or reducing the pressure to reduce the oxygen concentration.

  Although the preferable conditions for the melting temperature of the film constituent material in the extruder (1) vary depending on the viscosity and discharge amount of the film constituent material, the thickness of the sheet to be produced, etc., in general, the glass transition of the film (resin mixture) The temperature (Tg) is Tg or more and Tg + 100 ° C. or less, preferably Tg + 10 ° C. or more and Tg + 90 ° C. or less. The melt viscosity at the time of extrusion is 10 to 100,000 poise, preferably 100 to 10,000 poise. Further, the residence time of the film constituting material in the extruder (1) is preferably short, and is within 5 minutes, preferably within 3 minutes, more preferably within 2 minutes. The residence time depends on the type of the extruder (1) and the extrusion conditions, but it can be shortened by adjusting the material supply amount, L / D, screw rotation speed, screw groove depth, and the like. Is possible.

  The shape, rotation speed, etc. of the screw of the extruder (1) are appropriately selected depending on the viscosity of the film constituting material, the discharge amount, and the like. In this embodiment, the shear rate in the extruder (1) is 1 / second to 10000 / second, preferably 5 / second to 1000 / second, more preferably 10 / second to 100 / second. As the extruder (1), an extruder generally marketed as a plastic molding machine can be used.

  The film constituent material extruded from the extruder (1) is sent to the casting die (4), and is extruded from the casting die (4) into a film shape.

  The melt discharged from the extruder (1) is supplied to the casting die (4). The casting die (4) is not particularly limited as long as it is used for producing a sheet or a film. As the material of the casting die (4), hard chromium, chromium carbide, chromium nitride, titanium carbide, titanium carbonitride, titanium nitride, super steel, ceramic (tungsten carbide, aluminum oxide, chromium oxide), etc. are sprayed or plated. Buffing as surface processing, lapping using a # 1000 or higher grinding wheel, plane cutting using a diamond grinding wheel of # 1000 or higher (cutting direction is perpendicular to the resin flow direction), electrolytic polishing, electrolytic composite polishing, etc. And the like.

  The preferred material of 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.

  In the method for producing an optical film by the melt casting film forming method of the present invention, after the film material such as cellulose resin is mixed, the melt extruded from the die lip of the casting die (4) using the extruder (3). On the surface of at least one of the two surfaces of the cast film, from the start of extrusion until it contacts the surface of the cooling roll (5) or immediately after contacting the surface of the cooling roll (5) By applying a high energy surface treatment with a high energy irradiation device (A) comprising an atmospheric pressure plasma device, an excimer UV device, or a laser irradiation device to form an easily peelable treatment layer on the surface of the casting film, The surface of the cast film is modified to improve the peelability from the cooling roll (5).

  In FIGS. 1 and 2, a high energy irradiation device (A) comprising an atmospheric pressure plasma device, an excimer UV device, or a laser irradiation device is disposed on both sides of the casting film. Irradiation may be performed on at least one of both surfaces of the casting film, and preferably, high-energy irradiation is performed on the surface of the casting film that is in contact with the cooling roll (5). To do.

  A high energy irradiation apparatus (A) comprising an atmospheric pressure plasma apparatus, an excimer UV apparatus, or a laser irradiation apparatus will be described later.

  Next, the cast film that has been subjected to the high energy surface treatment as described above is brought into contact with the first cooling roll (5), circumscribed to the first cooling roll (5), and further, the second cooling roll ( 7) A third total of three cooling rolls (8) are sequentially circumscribed, and are cooled and solidified to form a film (10).

  In order to extrude the melt from the casting die (4) in the form of a film and take out the extruded casting film (film), it is brought into close contact with at least two rotating bodies (cooling rolls) to form a film. .

  Here, in order to correct the flatness, a touch roll (6) for sandwiching the molten film on the surface of the first cooling roll (5) is provided. The touch roll (6) has an elastic surface and forms a nip with the first cooling roll (5).

  The embodiment of the present invention shown in FIG. 1 and FIG. 2 is different in that the cast film first contacts the surface of the first cooling roll (5) and the film contacts the surface of the touch roll (6). The embodiment which has shown is shown.

  In addition, although illustration was abbreviate | omitted, the point which the casting film from an extruder (4) contacted the surface of the 1st cooling roll (5) first, and the casting film contacted the surface of the touch roll (6). The point may be the same.

  Furthermore, in the embodiment of the present invention shown in FIGS. 1 and 2, the cooled and solidified film (10) peeled from the third cooling roll (8) by the peeling roll (9) is a dancer roll (film tension adjusting roll). Through (11), the film is guided to a stretching device (12), 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 stretching the film in the width direction, a known tenter or the like can be preferably used. In particular, it is preferable to set the stretching direction to the width direction because lamination with the polarizing film can be performed in a roll form. By stretching in the width direction, the slow axis of the optical film made of the cellulose ester resin film becomes the width direction.

  After stretching, the end of the film is slit to a product width by a slitter (13) and cut off, and then knurled (embossed) by a knurling device comprising an embossing ring (14) and a back roll (15). By applying to both ends of the film and winding by the winding device (16), sticking in the optical film (original winding) (F) and generation of scratches are prevented. 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.

  Next, the atmospheric pressure plasma apparatus (atmospheric pressure plasma apparatus) will be described in detail.

  In the atmospheric pressure plasma apparatus used in the present invention, a reactive gas is put into a plasma state by applying a high-frequency voltage to discharge between opposing electrodes, and at least one of both surfaces of the casting film Is exposed to the reactive gas in the plasma state to modify the surface of the casting film, particularly the surface of the casting film that contacts the support (first cooling roll) (5). An easily peelable treatment layer is formed on the surface of the cast film.

  In the atmospheric pressure plasma apparatus, a high-frequency power is applied between the electrodes facing each other so as to sandwich the substrate to be processed, and a method called direct type or planar type that converts the supply gas into plasma, and a reactive gas is applied with a high-frequency voltage. There are methods called a remote method and a downstream method in which plasma is generated between the formed electrodes, and both methods can be used in the present invention. However, in the method for producing an optical film of the present invention, a high-energy surface treatment of the cast film surface is performed. It is desirable to use the latter method.

  FIG. 5 is an explanatory diagram for explaining the principle of the atmospheric pressure plasma apparatus.

  In the figure, (a) and (b) are counter electrodes of the atmospheric pressure plasma apparatus, (g) is a reactive gas, and (s) is a cast film.

  As a simple structure of the atmospheric pressure plasma apparatus in FIG. 5, a reactive gas (g) is introduced between the counter electrodes (a) and (b) to which a high-frequency voltage is applied, and is converted into a plasma to form a cast film ( s) A surface treatment layer is formed by spraying on the surface.

  In the embodiment of the present invention, it is necessary to employ an electrode capable of applying such a high power voltage and maintaining a uniform glow discharge state in the atmospheric pressure plasma apparatus.

  Such an electrode is preferably a metal base material coated with a dielectric. It is preferable to coat a dielectric on at least one side of the opposed application electrode and the ground electrode, and more preferably coat both of the opposed application electrode and the ground electrode with a dielectric. The dielectric is preferably an inorganic substance having a relative dielectric constant of 6 to 45. Examples of such a dielectric include ceramics such as alumina and silicon nitride, silicate glass, borate glass, and the like. Glass lining material and the like.

  In addition, when a cellulose ester film, which is a transparent film base material, is placed between electrodes or transported between electrodes and exposed to plasma, the transparent film base material has a roll electrode specification that can be transported in contact with one electrode. Furthermore, the dielectric surface and the gap between the electrodes can be kept constant by polishing the dielectric surface and setting the electrode surface roughness Rmax (JIS B 0601) to 10 μm or less. It is preferable that the discharge state can be stabilized, and further, the distortion and cracking due to the difference in thermal shrinkage and residual stress can be eliminated and the non-porous, highly accurate inorganic dielectric can be coated to greatly improve the durability. .

  The gap between the blow-out slit for performing plasma supply and the surface of the casting film (s) is preferably 0.5 to 6 mm, and more preferably 1 to 4 mm. If it is too close, there is a risk of contacting or damaging the surface of the cast film (s). If it is too far, the effect of modifying the surface is weakened.

  Various reactive gases (g) such as nitrogen, oxygen, argon, and helium can be used. Nitrogen is preferable from the viewpoints of environment, exhaust aftertreatment, and running cost. It is preferable to mix a small amount of oxygen. The mixing ratio of oxygen is preferably 2% by volume or less with respect to the volume of the source gas.

  In addition, as a raw material gas (g) for forming the surface treatment layer, for example, an organic solvent vapor such as methylene chloride or alcohol, or a monomer gas such as acetylene is mixed with nitrogen or oxygen of the reactive gas of the atmospheric pressure plasma. May be introduced. The mixing ratio is preferably in the range of 0.2 to 20% by volume with respect to the total volume of nitrogen and oxygen.

  When the source gas for forming the surface treatment layer is not mixed with the reactive gas of the atmospheric pressure plasma, the source gas is sprayed on the surface of the casting film from the outside of the atmospheric pressure plasma apparatus, and is entrained on the surface of the casting film. It may be fed under the atmospheric pressure plasma apparatus to react and form a film.

  In that case, the gas concentration around the atmospheric plasma apparatus is preferably in the range of 500 ppm to 100,000 ppm, and more preferably 1000 to 50,000 ppm.

  Further, the air volume of the source gas of atmospheric pressure plasma is desirably 20 to 5000 L / min per 1 m of the effective width of plasma irradiation. Furthermore, 40-2500 L / min is more preferable.

  Next, an excimer UV apparatus will be described. FIG. 6 is an explanatory diagram for explaining the principle of the excimer UV apparatus.

  In the figure, (u) is an excimer UV lamp, (r) is a reflector, (p) is a purge gas, (i) is an air curtain / lamp device cooling air, (s) is a casting film, and (e) is an exhaust gas. It is.

In this embodiment, an excimer UV lamp (u) shown in FIG. 6 is used to irradiate the cast film (s) mainly with ultraviolet light having a wavelength of 172 nm with a light quantity of 1 to 3000 mJ / cm ^2. It is. Under such ultraviolet irradiation, oxygen contained in the purge gas (p) generates active oxygen and ozone, and contributes to the modification of the surface of the casting film (s). Further, a raw material gas for generating a surface treatment film such as an organic solvent vapor such as methylene chloride or alcohol, or a monomer gas such as acetylene may be mixed with the purge gas (p) and introduced. When these raw material gases are not mixed with the purge gas (p), these raw material gases may be entrained on the surface of the casting film and sent under the excimer UV device to perform reaction and surface treatment layer formation.

  Further, if the gap between the excimer UV lamp (u) and the casting film (s) is too close, there is a risk of contacting or damaging the surface of the casting film (s). Since the high energy of excimer UV is absorbed in water and the effect of modifying the surface of the cast film (s) becomes weak, 0.5 to 4 mm is preferable, and 1 to 3 mm is more preferable.

  Next, a laser irradiation apparatus will be described. FIG. 7 is an explanatory diagram for explaining the principle of the laser irradiation apparatus.

  In the figure, (L) is a laser irradiation device, (l) is the laser beam, (m) is a variable mirror, and (s) is a casting film.

  In the present invention, using the laser irradiation apparatus (L) shown in FIG. 7, the surface of the casting film (s) is irradiated with laser energy to modify the surface. Under such laser irradiation, in a gas atmosphere such as methylene chloride, alcohol, acetylene, etc., these gases are entrained on the surface of the casting film (s) and sent to the bottom of the laser irradiation apparatus to react with the surface treatment layer. May be formed.

As irradiation conditions of the laser beam (l) by the laser irradiation apparatus (L), it is preferable to set the irradiation energy to about 100 to 200 mJ / cm ² . If the irradiation energy is less than 100 mJ / cm ² , the effect of modifying the surface of the cast film (s) is reduced. On the other hand, if the irradiation energy is larger than 200 mJ / cm ^{2, the} surface of the cast film (s) may be microscopically distorted, which is not preferable.

  In addition, as the laser beam (l) by the laser irradiation apparatus (L), for example, a pulse laser having a pulse width of 20 to 100 ns can be used for one shot or a plurality of shots.

  Laser light (l) from the laser irradiation device (L) is emitted from the laser light source, and is irradiated onto the surface of the casting film (s) through the mirror (m). The variable angle of the mirror (m) is scanned to irradiate the entire surface of the casting film (s) with the laser beam (l).

  Further, the angle of the laser beam (l) incident on the surface of the casting film (s) does not need to be vertical. Further, the laser beam (l) may be simultaneously irradiated from a plurality of directions using a mirror (m) or the like.

  When these high energy irradiation devices (A) are brought into a film production line for optical applications, measures for maintaining cleanliness become a problem. In particular, it is important to take measures to maintain cleanliness in a normal pressure plasma apparatus having a structure in which dust generated is discharged into the line.

  In the method for producing an optical film of the present invention, various resins can be used as the film material. Among them, cellulose ester, particularly cellulose acylate is preferable.

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, 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.

  In the cellulose acylate, the substitution degree of the hydroxyl group of cellulose is preferably 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 commercially available from Daicel Chemical Industries, Ltd., Courtles, Hoechst, and Eastman Kodak. Photographic grade cellulose acylate is preferably used. The water content of the cellulose acylate is preferably 2% by weight or less.

  Glucose units having β-1,4 bonds constituting cellulose have 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 in the present invention has 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, It is obtained by blending cellulose acylate having a total acyl substitution degree at the 2nd and 3rd positions of 1.70 to 1.95 and an acyl substitution degree at the 6th position of less than 0.88. When the total of the 2- and 3-position acyl substitutions is 1.70 or less, the film is likely to absorb moisture and is susceptible to hydrolysis, so the durability of the film is lowered. In addition, the dimensional change due to humidity or the like becomes large. On the other hand, if it exceeds 1.95, the organicity of cellulose acylate increases, so the affinity with the solvent increases and the viscosity of the dope increases. Accordingly, the total of the 2- and 3-position acyl substitutions is preferably 1.70 to 1.95, and more preferably 1.75 to 1.88.

  By the way, since the hydroxyl group at the 6-position is a primary hydroxyl group, unlike the hydroxyl groups at the 2- and 3-positions, it has been found that hydrogen bonding of the hydroxyl group is extremely likely to occur. Therefore, by setting the acyl substitution degree at the 6-position to 0.88 or more, the solubility in a solvent is remarkably improved, and it is possible to obtain a dope that is preferable in terms of castability. The range of the degree of acyl substitution at the 6-position is preferably from 0.88 to 0.99, more preferably from 0.89 to 0.98 in view of synthesis suitability and the like. However, when the degree of acyl substitution at the 6-position is improved, there is a problem that the film strength is lowered, and it is difficult to achieve both. On the other hand, if the acyl substitution degree is less than 0.88, the solubility in a solvent is remarkably lowered, which is not preferable.

  Further, a film made of 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, or 2-position, 3-position In the roll state, an optical film in which a thin film is formed on a film made of cellulose acylate having a total acyl substitution degree of 1.70 to 1.95 and a acyl substitution degree of 6-position of less than 0.88. There has been a problem that flatness such as wrinkles and dents is liable to occur during storage, and the formed metal oxide layer is liable to crack, resulting in uneven film thickness.

  It has been found that these problems can be solved by blending cellulose acylate. In addition, cellulose acylate having an acyl substitution degree at the 6-position of 0.88 or more desirably has a smaller number of carbon atoms in the acyl substituent from the viewpoint of film strength, and is preferably all acetyl groups. In JP-A-11-5851, the total of acetyl substituents at the 2nd, 3rd and 6th positions is 2.67 or more, and the total of the acetyl substituents at the 2nd and 3rd positions is 1.97 or less. Although cellulose acetate is described, the range in which the sum of the 2nd and 3rd positions exceeds 1.90 is a preferred range from the optical suitability of the film, and the casting suitability is described in this specification. The range described is more preferable.

  The basic principle of the cellulose acylate synthesis method is described in Mita et al., Wood chemistry, 180-190 (Kyoritsu Shuppan, 1968). A typical synthesis method is a liquid phase acetylation method using an acetic anhydride-acetic acid-sulfuric acid catalyst. Specifically, a cellulose raw material such as wood pulp is pretreated with an appropriate amount of an organic acid, and then it is esterified by adding it to a pre-cooled acylated mixture to complete cellulose acylate (2nd, 3rd and 6th positions). The total degree of acyl substitution is approximately 3.00). The acylated mixed solution generally contains an organic acid as a solvent, an anhydrous organic acid as an esterifying agent, and sulfuric acid as a catalyst. The organic anhydride is usually used in a stoichiometric excess over the sum of the cellulose that reacts with it and the water present in the system. After completion of the acylation reaction, a neutralizing agent (for example, calcium, magnesium, iron, aluminum or zinc) is used for hydrolysis of excess organic anhydride remaining in the system and neutralization of a part of the esterification catalyst. Of carbonate, acetate or oxide).

  Next, the obtained complete cellulose acylate is saponified and aged by maintaining it at 50 to 90 ° C. in the presence of a small amount of an acetylation reaction catalyst (generally, remaining sulfuric acid), and the desired acyl substitution degree and The cellulose acylate having a polymerization degree is changed. When the desired cellulose acylate is obtained, the catalyst remaining in the system is completely neutralized with the neutralizing agent as described above, or water or dilute sulfuric acid without neutralization. A cellulose acylate solution is introduced into the cellulose acylate solution (or water or dilute sulfuric acid is introduced into the cellulose acylate solution) to separate the cellulose acylate, and the cellulose acylate is obtained by washing and stabilizing treatment.

  In an ordinary cellulose acylate synthesis method, the acyl substitution degree at the 2-position or the 3-position is higher than the acyl substitution degree at the 6-position. Therefore, in order to make the total acyl substitution degree at the 2nd and 3rd positions 1.95 or less and the acyl substitution degree at the 6th position 0.88 or more, the above reaction conditions need to be specifically adjusted. . As specific reaction conditions, it is preferable to reduce the amount of the sulfuric acid catalyst and lengthen the time of the acylation reaction. When the amount of the sulfuric acid catalyst is large, the acylation reaction proceeds faster, but a sulfuric ester is formed between the cellulose and the cellulose according to the amount of the catalyst, and is released at the end of the reaction to form a residual hydroxyl group. Sulfate esters are more produced at the 6-position, which is highly reactive. Therefore, when there is much sulfuric acid catalyst, the acyl substitution degree of 6-position becomes small. Therefore, in order to synthesize the cellulose acylate used in the present invention, it is necessary to extend the reaction time in order to reduce the amount of sulfuric acid catalyst as much as possible and compensate for the reduced reaction rate.

(Plasticizer)
The optical film of the present invention may contain the following plasticizer.

  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. Moreover, the mix of an alkylate group, a cycloalkylate group, and an arylate group may be sufficient, and these substituents may couple | bond together by the covalent bond. Further, the ethylene glycol part may be substituted, 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 tetracycle Diglycerol cycloalkyl esters such as 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. Moreover, the mix of alkylate group, a cycloalkyl carboxylate group, and an arylate group may be sufficient, and these substituents may couple | bond together by the 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. Moreover, the mix of alkylate group, a cycloalkyl carboxylate group, and an arylate group may be sufficient, and these substituents may couple | bond together by the 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, Exemplified compound 16 described in paragraph 32 of Kokai 2003-12823 can be mentioned.

  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 , Dicyclohexyl-1,4-cyclohexanedicarboxylate, didecylbicyclo [2.2.1] heptane-2,3-dicarboxylate, and other cycloalkyldicarboxylic acid alkyl ester plasticizers, dicyclohexyl-1,2- Cyclobutane Cycloalkyldicarboxylic acid cycloalkyl ester plasticizers such as xylate, dicyclopropyl-1,2-cyclohexyl dicarboxylate, diphenyl-1,1-cyclopropyldicarboxylate, di-2-naphthyl-1,4- Cycloalkyldicarboxylic acid aryl ester plasticizers such as cyclohexane dicarboxylate, aryl dicarboxylic acid alkyl ester plasticizers such as diethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, dicyclopropyl Aryl dicarboxylic acid cycloalkyl ester plasticizers such as phthalate and dicyclohexyl phthalate, and aryl dicarboxylic acid aliquots such as diphenyl phthalate and di-4-methylphenyl phthalate Glycol ester-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, or 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. In addition, the partial structure of phthalate ester may be part of the polymer or regularly pendant to the polymer, and may be part of the molecular structure of additives such as antioxidants, acid scavengers, and UV absorbers. It may be introduced.

  Examples of other polycarboxylic acid ester plasticizers include alkyl polycarboxylic acid alkyl esters such as tridodecyl tricarbarate and tributyl-meso-butane-1,2,3,4-tetracarboxylate. Plasticizer, tricyclohexyl-2-carbamate, tricyclopropyl-2-hydroxy-1,2,3-propanetricarboxylate and other alkyl polycarboxylic acid cycloalkyl ester plasticizer, 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, tet Cycloalkyl polycarboxylic acid alkyl ester plasticizers such as butyl-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, Allies such as 4,5-tetracarboxylate Polycarboxylic acid alkyl ester plasticizers, aryl polycarboxylic acid cycloalkyl esters such as tricyclopentylbenzene-1,3,5-tricarboxylate, tetracyclohexylbenzene-1,2,3,5-tetracarboxylate Aryl polyvalent carboxylic acid aryl such as triphenylbenzene-1,3,5-tetracartoxylate, hexa-4-methylphenylbenzene-1,2,3,4,5,6-hexacarboxylate An ester plasticizer may be mentioned. These alkoxy groups and cycloalkoxy groups may be the same or different, and may be monosubstituted, and these substituents may be further substituted. The alkyl group and cycloalkyl group may be mixed, or 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. In addition, the partial structure of phthalate ester may be part of the polymer or may be regularly pendant to 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 preferable, and specific examples include the dioctyl adipate and tridecyl tricarbalate.

  Further, phosphate ester plasticizers, carbohydrate ester plasticizers, polymer plasticizers and the like can be mentioned.

  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 cresyl phenyl 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 phosphate ester partial structure may be part of the polymer, or may be regularly pendant, and may be introduced into part of the molecular structure of additives such as antioxidants, acid scavengers, and UV absorbers. 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 hydroxyl group of a carbohydrate and a carboxylic acid. Specifically, it 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 5,000 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 optical film of this invention will affect as an optical use when it colors, Preferably yellow degree (yellow index, YI) is 3.0 or less, More preferably, it is 1.0 or less. Yellowness can be measured based on JIS-K7103.

  The plasticizer preferably removes impurities such as residual acids, inorganic salts, organic low molecules, etc. that are carried over from production or generated during storage, and more preferably has a purity of 99% or more, like the cellulose ester described above. is there. The residual acid and water are preferably 0.01 to 100 ppm, and when melt-forming the cellulose resin, thermal degradation can be suppressed, and film-forming stability, optical properties of the film, and mechanical properties are improved. .

(Antioxidant)
In the optical film of the present invention, it is also preferable to use an antioxidant as the cellulose ester is decomposed not only by heat but also by oxygen in a high temperature environment where melt film formation is performed. .

  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 molding 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 columns 5 to 11 of US Pat. No. 4,619,956 and columns 3 to 5 of US Pat. No. 4,839,405. 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 weight of the cellulose ester. 0.001 to 10.0 parts by weight, preferably 0.01 to 5.0 parts by weight, and more preferably 0.1 to 3.0 parts by weight.

  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 weight, preferably 0.05 to 5 parts by weight, and more preferably 0.1 to 3 parts by weight with respect to 100 parts by weight 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 8-40 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 ether (ie, 4,4'-dihydroxydiphenyldimethylmethane), epoxidized unsaturated fatty acid ester (especially an ester of an alkyl of about 2 to 2 carbon atoms of a fatty acid of 2 to 22 carbon atoms (e.g. 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, which 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 is excellent in the ability to absorb ultraviolet rays having a wavelength of 370 nm or less, and from the viewpoint of liquid crystal display property, 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'-te t-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, or compounds described in JP-A Nos. 58-185777 and 59-149350, nickel complex compounds, Machine powder, and the like.

  As the ultraviolet absorber according to the present invention, a benzotriazole-based ultraviolet absorber or a triazine-based ultraviolet absorber that is highly transparent and excellent in preventing deterioration of a polarizing plate or a liquid crystal element is preferable, and a spectral absorption spectrum is more appropriate. Benzotriazole ultraviolet absorbers are particularly preferred.

  A conventionally known benzotriazole-based ultraviolet absorber particularly preferably used together with the ultraviolet absorber according to the present invention may be bisified, for example, 6,6′-methylenebis (2- (2H-benzo [d ] [1,2,3] triazol-2-yl))-4- (2,4,4-trimethylpentan-2-yl) phenol, 6,6'-methylenebis (2- (2H-benzo [d] And [1,2,3] triazol-2-yl))-4- (2-hydroxyethyl) phenol.

  Moreover, in this invention, it can also use in combination with a conventionally well-known ultraviolet absorbing polymer. Although it does not specifically limit as a conventionally well-known ultraviolet absorbing polymer, For example, the polymer which homopolymerized RUVA-93 (made by Otsuka Chemical Co., Ltd.), the polymer which copolymerized RUVA-93, and another monomer, etc. are mentioned. It is done. Specifically, PUVA-30M obtained by copolymerization of RUVA-93 and methyl methacrylate at a ratio (weight ratio) of 3: 7, and PUVA-50M copolymerized at a ratio of 5: 5 (weight ratio). It is done. Furthermore, the polymer etc. which are described in Unexamined-Japanese-Patent No. 2003-113317 are mentioned.

  In addition, as commercially available products, TINUVIN 109, TINUVIN 171, TINUVIN 360, TINUVIN 900, TINUVIN 928 (all manufactured by Ciba Specialty Chemicals), LA-31 (Manufactured by Asahi Denka Co., Ltd.) and RUVA-100 (manufactured by 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.

  In the present invention, the ultraviolet absorber is preferably added in an amount of 0.1 to 20% by weight, more preferably 0.5 to 10% by weight, and further preferably 1 to 5% by weight. Two or more of these may be used in combination.

(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 film forming method performed in the present invention, the glass transition temperature of the cellulose resin used alone is used. In addition, 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 the hydrogen bonding solvent is lower than that of the cellulose resin at the same melting temperature. Can do.

  Examples of the hydrogen bonding solvent include alcohols: for example, 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: for example 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)
In the optical film of the present invention, an alignment film may be formed to provide a liquid crystal layer, and a polarizing plate process may be performed in which a cellulose acylate film and a retardation derived from the liquid crystal layer are combined to provide an optical compensation capability. As the compound to be added for controlling the retardation, an aromatic compound having two or more aromatic rings as described in EP 911,656A2 can be used as a retardation control agent. . 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)
In the optical film of the present invention, fine particles such as a matting agent can be added 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 substances for the surface treatment include halosilanes, alkoxysilanes, silazane, siloxane 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 the secondary particles of the 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 weight 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, etc. manufactured by Nippon Aerosil Co., preferably Aerosil 200V, R972, R972V, R974, R202, and 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 weight 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. The presence of the fine particles in the film can also improve the orientation of the cellulose ester itself constituting the optical film of the present invention.

(Polymer material)
In the optical film of the present invention, polymer materials and oligomers other than cellulose ester may be appropriately selected and mixed. The polymer material or oligomer is preferably one having excellent compatibility with the cellulose ester, and the transmittance when formed into a film is preferably 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.

  Below, the manufacturing method of the optical film by the solution casting film forming method of this invention is demonstrated.

  The method for producing an optical film according to the present invention is based on a solution casting film forming method, in which a dope (resin solution) in which a thermoplastic resin is dissolved in a solvent is added to a metal from a casting die. A dope casted from a casting die, including a step of casting on a rotating drum or metal rotating endless belt (support) to form a cast film, and peeling the cast film from the support Between the start of casting and the contact with the support surface or immediately after contacting the support surface, on at least one of the two surfaces of the casting film, an atmospheric plasma device, an excimer UV device, Alternatively, a high-energy surface treatment is performed by a laser irradiation device to form an easily peelable treatment layer on the surface of the cast film.

  Here, the high energy irradiation with respect to the casting film may be performed on at least one of both surfaces of the casting film, and preferably, the both surfaces of the casting film are in contact with the cooling roll or the support. High energy irradiation is performed on the side surface.

  And in the manufacturing method of the optical film of this invention, after dope is cast from a casting die and a casting film is formed, the residual solvent amount of this casting film is 200 weight% from the excess solvent amount. The surface of the cast film is subjected to high-energy surface treatment using an atmospheric pressure plasma apparatus, excimer UV apparatus, or laser irradiation apparatus, and the surface of the cast film is easily peelable. Is preferably formed.

  Here, after the cast film is formed, the residual solvent amount of the cast film is reduced to less than 200% by weight, and then the surface of the cast film is irradiated with an excimer UV device, a normal pressure plasma device, or laser irradiation. If a high energy surface treatment is performed by a high energy irradiation device comprising an apparatus, the cast film surface is hardened and the effect of surface modification becomes weak, which is not preferable.

  In the method for producing an optical film of the present invention, it is preferable to perform high-energy surface treatment with a high-energy irradiation device comprising an atmospheric plasma device, an excimer UV device, or a laser irradiation device in the presence of at least a solvent vapor.

  Furthermore, in the method for producing an optical film of the present invention, high-energy surface treatment using an atmospheric pressure plasma apparatus or an excimer UV apparatus is used for at least a solvent vapor and a reaction gas used for the atmospheric pressure plasma apparatus or an excimer UV apparatus. It is preferable to carry out in the presence of a purge gas.

  In the method for producing an optical film of the present invention, the peeling force when the cast film is peeled from the support is 1.0 to 12.0 (N / m width), and the solution casting film forming apparatus has 24 hours. It is preferable that the increase amount of the peeling force of the cast film after operation is 0.1 to 2.0 (N / m width).

  Here, if the peeling force when the cast film is peeled off from the support is less than 1.0 (N / m width), the peeling position may be taken downstream, which is not preferable. . When the peel strength exceeds 1.0 to 12.0 (N / m width), the film cannot be smoothly peeled off from the support, and there is considerable flapping and peeling noise. Since a sharp step-like deformation extending in the width direction is generated, it is not preferable.

  Moreover, if the increase amount of the peeling force of the casting film after 24 hours of operation of the solution casting film forming apparatus is less than 0.1 (N / m width), the peeling position may be taken downstream. Since it may be, it is not preferable. Moreover, when the amount of increase in the peel strength of the cast film exceeds 2.0 (N / m width), the film tends to shrink in the width direction, and when drying and shrinkage overlap, the end curls and folds. This is not preferable because wrinkles tend to enter.

  According to the method for producing an optical film by the solution casting film forming method of the present invention, as seen in the solution casting film forming method, the peeling is observed when the residual solvent in the web at the time of peeling is in a specific range. Defects are eliminated, restrictions on film production conditions so far are reduced, the range of film production conditions is greatly expanded, film releasability (peelability) from the support is improved, and the entire residual film area after peeling Thus, very smooth peelability can be obtained.

  FIG. 3 is a flow sheet showing a specific example of an apparatus for carrying out the method for producing an optical film of the present invention by a solution casting film forming method.

  In the figure, first, in a dissolution vessel (21), for example, a cellulose ester resin is dissolved in a mixed solvent of a good solvent and a poor solvent, and an additive such as a plasticizer or an ultraviolet absorber is added to the resin solution. (Dope) is prepared.

  Next, a support comprising an endless belt made of, for example, a rotationally driven stainless steel, in which the dope adjusted in the melting pot is fed to the casting die (23) by a conduit through, for example, a pressurized metering gear pump (22) and transferred infinitely. (27) The dope is cast from the casting die (23) to the upper casting position.

  For casting the dope by the casting die (23), there is a doctor blade method in which the film thickness of the cast dope film (web) is adjusted with a blade, or a reverse roll coater method in which the film is adjusted with a reverse rotating roll. However, it is preferable to use a pressure die that can adjust the slit shape of the die part and easily make the film thickness uniform. Examples of the pressure die include a coat hanger die and a T die, and any of them is preferably used.

  In addition, as a casting die (23), the pressure die which can adjust the slit shape of a nozzle | cap | die part and is easy to make a film thickness uniform is preferable. The casting die (23) is usually provided with a decompression chamber (not shown).

  Here, it is preferable that the solid content concentration of the cellulose ester solution (dope) is 15 to 30% by weight. If the solid content concentration of the cellulose ester solution (dope) is less than 15% by weight, sufficient drying cannot be performed on the support (27), and a part of the dope film remains on the support (27) during peeling. This is not preferable because it leads to belt contamination. Further, when the solid content concentration exceeds 30%, the dope viscosity is increased, filter clogging is accelerated in the dope adjustment process, or the pressure is increased during casting on the support (27), so that extrusion is not preferable. Absent.

  In the method for producing an optical film by the solution casting film forming method of the present invention, the dope casting film coming out of the casting die (23) is formed on the surface of the support (27) composed of a rotationally driven endless belt from the beginning of casting. Until the contact or immediately after contact with the surface of the support (27), at least one of the two surfaces of the casting film is formed of a high-pressure plasma device, an excimer UV device, or a laser irradiation device. High-energy surface treatment is performed by the energy irradiation device (A), and an easy-peelable treatment layer is formed on the surface of the casting film, so that the high-energy surface treatment is performed and the casting film is easily peeled off. By forming a treatment layer, the surface of the cast film is modified to improve the peelability from the support (27).

  In FIG. 3, a high energy irradiation device (A) comprising an atmospheric pressure plasma device, an excimer UV device, or a laser irradiation device is disposed on both sides of the casting film. May be performed on at least one of both surfaces of the casting membrane, and preferably, high energy irradiation is performed on the surface of the casting membrane on the side in contact with the support (27). To do.

  Further, as the high energy irradiation device (A) comprising the atmospheric pressure plasma device, the excimer UV device, or the laser irradiation device, those described in detail with reference to FIGS.

  Next, the cast film subjected to the high energy surface treatment as described above is brought into contact with a support (27) made of a rotationally driven endless belt. The belt support (27) is held by a pair of front and rear drums (25) and (25) and a plurality of intermediate rolls (not shown). The drum (25) at both ends of the belt support (27) is wound around the belt support (27). One or both of (25) is provided with a driving device for applying tension (not shown) to the belt support (27), whereby the belt support (27) is used in a tensioned state. The

  Here, it is preferable that the width of the support (27) is 1700 to 2500 mm, the casting width of the cellulose ester solution is 1600 to 2400 mm, and the width of the film after winding is 1400 to 2400 mm. Thereby, the optical film for liquid crystal display devices with a wide width | variety can be manufactured with a support body system.

  When an endless belt is used as the support (27), the belt temperature during film formation is a general temperature range of 0 ° C. to a temperature lower than the boiling point of the solvent, and a mixed solvent having a temperature lower than the boiling point of the lowest boiling solvent. The range of 5 ° C. to the boiling point of the solvent −5 ° C. is more preferable. At this time, it is necessary to control the ambient atmospheric humidity above the dew point. In addition, it is preferable that the peripheral speed of a support body (27) is 40-200 m / min.

  The dope cast on the surface of the support (27) as described above also increases the strength (film strength) of the gel film by promoting the drying until peeling.

  In the system using an endless belt as the support (27), the web (29) is dried and solidified on the support (27) until the web (29) has a peelable film strength from the support (27) by the peeling roll (28). Therefore, it is preferable to dry the residual solvent amount in the web (29) to 150% by weight or less, and more preferably 80 to 120% by weight. Moreover, as for the web temperature when peeling a web (29) from a support body (27), 0-30 degreeC is preferable. Further, immediately after the web (29) is peeled off from the support (27), the temperature once decreases rapidly due to solvent evaporation from the contact surface side of the support (27), and volatile components such as water vapor and solvent vapor in the atmosphere. Is easy to condense, the web temperature during peeling is more preferably 5 to 30 ° C.

  Here, the residual solvent amount can be expressed by the following equation.

Residual solvent amount (% by weight) = {(M−N) / N} × 100
In the formula, M is the weight of the web at an arbitrary time point, and N is the weight when a weight M is dried at a temperature of 110 ° C. for 3 hours.

  The dope film (web) (29) formed by the dope cast on the support (27) is heated on the support (27), and the web is removed from the support (27) by the peeling roll (28). Evaporate the solvent until it can be stripped.

  For evaporating the solvent, there are a method in which air is blown from the web side, a method in which heat is transferred from the back surface of the support (27) by liquid, a method in which heat is transferred from the front and back by radiant heat, and the like. Can be used.

  In the method using an endless belt for the support (27), the peeling tension when the support (27) and the web (29) are peeled by the peeling roll (28) is obtained by measuring the peeling force as in JIS Z 0237. It is peeled off with a tension greater than the peeling force to be obtained, but this may cause the peeling position to be taken downstream if the peeling tension is made equal to the peeling force obtained by the JIS measurement method during high-speed film formation. Higher for stability. However, even if the film is formed with the same peeling tension in the process, it is confirmed that the variation in the crossed Nicols transmittance (CNT) of the film is greatly reduced when the peeling force by the JIS measuring method is lowered.

  As the peeling tension value in the process, peeling is usually performed at 50 to 250 N / m. However, in the optical film produced according to the present invention which is made thinner than the conventional one, the web (29) is peeled off at the time of peeling. Since the amount of residual solvent is large and easily stretches in the transport direction, the film tends to shrink in the width direction, and when drying and shrinkage overlap, the edge curls and folds, making it easy to wrinkle, so it can be peeled off. Peeling at a tension of 170 N / m is preferable, and peeling at a minimum tension of 140 N / m is more preferable.

  In the present invention, the web (29) is dried and solidified on the support (27) until the web (29) has a peelable film strength, and then the web (29) is peeled off by the peeling roll (28). The web (29) is stretched in the tenter (32).

  FIG. 4 is a flow sheet showing another specific example of an apparatus for carrying out the method for producing an optical film of the present invention by a solution casting film forming method. As a support, for example, stainless steel whose surface is subjected to hard chrome plating treatment. The case where the steel rotational drive drum (26) is used is illustrated.

  Since the other points of the optical film manufacturing apparatus in FIG. 4 are the same as those in the optical film manufacturing apparatus in FIG. 3, the same components are denoted by the same reference numerals in the drawings.

  In FIG. 4, in the method for producing an optical film by the solution casting film forming method of the present invention, the dope casting film coming out of the casting die (23) is a support (26 ) Until the contact with the surface or immediately after the contact with the surface of the support (26), the atmospheric pressure plasma device, the excimer UV device, or the laser irradiation device is provided on at least one of both surfaces of the casting film. The surface of the cast film is subjected to a high energy surface treatment by forming an easily peelable treatment layer on the surface of the casting film by performing a high energy surface treatment with the high energy irradiation device (A) comprising By forming an easily peelable treatment layer, the surface of the cast film is modified to improve the peelability from the support (26).

  In FIG. 4, a high energy irradiation device (A) comprising an atmospheric pressure plasma device, an excimer UV device, or a laser irradiation device is disposed on both sides of the casting film. May be performed on at least one of the two surfaces of the casting film, and preferably, the surface of the casting film on the side in contact with the support (26) is irradiated with high energy. To do.

  Further, as the high energy irradiation device (A) comprising the atmospheric pressure plasma device, the excimer UV device, or the laser irradiation device, those described in detail with reference to FIGS.

  Next, in the method for producing an optical film by the solution casting method of the present invention, a resin solution (dope) containing a resin such as cellulose ester resin as a main material, a plasticizer, a retardation adjusting agent, an ultraviolet absorber, At least one kind of fine particles and low molecular weight substances and a solvent are included. Hereinafter, these will be described.

  In the method for producing an optical film by the solution casting film forming method of the present invention, various resins can be used as the film material, and among them, cellulose ester is preferable.

  A cellulose ester is a cellulose ester in which a hydroxyl group derived from cellulose is substituted with an acyl group or the like. Examples thereof include cellulose acylates such as cellulose acetate, cellulose triacetate, cellulose acetate propionate, cellulose acetate butyrate and cellulose acetate propionate butyrate, and cellulose acetate having an aliphatic polyester graft side chain. Among these, cellulose acetate, cellulose acetate propionate, and cellulose acetate having an aliphatic polyester graft side chain are preferable. Other substituents may be included as long as the effects of the present invention are not impaired.

  As an example of cellulose triacetate, the substitution degree of acetyl group is preferably 2.0 or more and 3.0 or less. By setting the degree of substitution within this range, good moldability can be obtained, and desired in-plane retardation (Ro) and thickness direction retardation (Rt) can be obtained. If the substitution degree of the acetyl group is lower than this range, the heat resistance as a retardation film, particularly the dimensional stability under wet heat may be inferior, and if the substitution degree is too large, the necessary retardation characteristics will not be exhibited. There is a case.

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

  In the present invention, the number average molecular weight of the cellulose ester is preferably in the range of 60000 to 300000, since the mechanical strength of the resulting film is strong. Furthermore, 70000-200000 are preferable.

  In the present invention, various additives can be added to the cellulose ester.

  In the method for producing an optical film according to the present invention, it is preferable to use a dope composition containing a cellulose ester and an additive for reducing the thickness direction retardation (Rt).

  In the present invention, reducing the thickness direction retardation (Rt) of the cellulose ester film is important in terms of increasing the viewing angle of the liquid crystal display device operating in the IPS mode. In the present invention, such thickness direction retardation is used. The following are mentioned as an additive which reduces (Rt).

  In general, retardation of a cellulose ester film appears as the sum of retardation derived from a cellulose ester and retardation derived from an additive. Therefore, an additive for reducing the retardation of the cellulose ester is an additive that disturbs the orientation of the cellulose ester and is difficult to orient itself and / or has a small polarizability anisotropy. It is a compound that effectively reduces it. Therefore, as an additive for disturbing the orientation of the cellulose ester, an aliphatic compound is preferable to an aromatic compound.

  Here, as a specific retardation reducing agent, for example, a polyester represented by the following general formula (1) or (2) may be mentioned.

General formula (1) B1- (GA-) mG-B1
General formula (2) B2- (GA-) nG-B2
In the above formula, B1 represents a monocarboxylic acid component, B2 represents a monoalcohol component, G represents a divalent alcohol component, A represents a dibasic acid component, and these are synthesized. B1, B2, G, and A are all characterized by not containing an aromatic ring. m and n represent the number of repetitions.

  There is no restriction | limiting in particular as a monocarboxylic acid component represented by B1, Well-known aliphatic monocarboxylic acid, alicyclic monocarboxylic acid, etc. can be used.

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

  As the aliphatic monocarboxylic acid, a fatty acid having a straight chain or a side chain having 1 to 32 carbon atoms can be preferably used. The number of carbon atoms is more preferably 1-20, and particularly preferably 1-12. When acetic acid is contained, the compatibility with the cellulose ester is increased, and it is also preferable to use a mixture of acetic acid and another monocarboxylic acid.

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

  The monoalcohol component represented by B2 is not particularly limited, and known alcohols can be used. For example, an aliphatic saturated alcohol or aliphatic unsaturated alcohol having a straight chain or a side chain having 1 to 32 carbon atoms can be preferably used. The number of carbon atoms is more preferably 1-20, and particularly preferably 1-12.

  Examples of the divalent alcohol component represented by G include the following, but the present invention is not limited thereto. For example, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, 1,5-pentanediol, 1,6- Hexanediol, 1,5-pentylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol and the like can be mentioned. Among these, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1 1,2-butylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, 1,6-hexanediol, diethylene glycol, and triethylene glycol are preferred, and 1,3-propylene glycol, 1,4-butylene glycol Lumpur, 1,6-hexanediol, diethylene glycol is preferably used.

  The dibasic acid (dicarboxylic acid) component represented by A is preferably an aliphatic dibasic acid or an alicyclic dibasic acid. Examples of the aliphatic dibasic acid include malonic acid, succinic acid, glutaric acid, and adipic acid. , Pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedicarboxylic acid, dodecanedicarboxylic acid and the like, in particular, aliphatic carboxylic acid having 4 to 12 carbon atoms, at least one selected from these To do. That is, two or more dibasic acids may be used in combination.

  The number of repetitions m and n in the above general formula (1) or (2) is preferably 1 or more and 170 or less.

  The weight average molecular weight of the polyester is preferably 20000 or less, and more preferably 10,000 or less. In particular, polyesters having a weight average molecular weight of 500 to 10,000 have good compatibility with cellulose esters, and neither evaporation nor volatilization occurs during film formation.

  Polycondensation of polyester is carried out by a conventional method. For example, a direct reaction of the dibasic acid and glycol, a hot melt condensation method by the polyesterification reaction or transesterification reaction of the dibasic acid or alkyl esters thereof, for example, a methyl ester of dibasic acid and glycols, or Although it can be easily synthesized by any method of dehydrohalogenation reaction between acid chloride of these acids and glycol, it is preferable that polyester having a weight average molecular weight not so large is by direct reaction. Polyester having a high distribution on the low molecular weight side has a very good compatibility with the cellulose ester, and after forming the film, a moisture permeability is small, and a cellulose ester film rich in transparency can be obtained.

  The method for adjusting the molecular weight is not particularly limited, and a conventional method can be used. For example, although depending on the polymerization conditions, the amount of these monovalent compounds can be controlled by a method of blocking the molecular ends with a monovalent acid or monovalent alcohol. In this case, a monovalent acid is preferable from the viewpoint of polymer stability. For example, acetic acid, propionic acid, butyric acid, etc. can be mentioned, but during the polycondensation reaction, it is not distilled out of the system, but is stopped and such monovalent acid is removed from the reaction system. The one that is easy to accumulate is selected. These may be used in combination. In the case of direct reaction, the weight average molecular weight can also be adjusted by measuring the timing of stopping the reaction by the amount of water distilled off during the reaction. In addition, it can be adjusted by biasing the number of moles of glycol or dibasic acid to be charged, or can be adjusted by controlling the reaction temperature.

  The polyester represented by the general formula (1) or (2) is preferably contained in an amount of 1 to 40% by weight based on the cellulose ester. It is particularly preferable to contain 5 to 15% by weight.

  In the present invention, examples of the additive for reducing the thickness direction retardation (Rt) include the following.

  The dope used for the production of the optical film of the present invention is mainly a cellulose ester, a polymer as an additive for reducing retardation (Rt) (a polymer obtained by polymerizing an ethylenically unsaturated monomer, an acrylic polymer), And an organic solvent.

  In the present invention, in order to synthesize a polymer as an additive for reducing the thickness direction retardation (Rt), it is difficult to control the molecular weight in normal polymerization, and a method that can make the molecular weight as uniform as possible by a method that does not increase the molecular weight too much. It is desirable to use it. Such polymerization methods include a method using a peroxide polymerization initiator such as cumene peroxide and t-butyl hydroperoxide, a method using a polymerization initiator in a larger amount than normal polymerization, and a mercapto compound in addition to the polymerization initiator. And a method using a chain transfer agent such as carbon tetrachloride, a method using a polymerization terminator such as benzoquinone and dinitrobenzene in addition to the polymerization initiator, and JP-A No. 2000-128911 or JP-A No. 2000-344823. Examples include a compound having a single thiol group and a secondary hydroxyl group as described in the publication, or a bulk polymerization method using a polymerization catalyst in which the compound and an organometallic compound are used in combination. In particular, the method described in the publication is preferred.

  In the present invention, monomers as monomer units constituting a polymer as an additive for reducing useful thickness direction retardation (Rt) are listed below, but are not limited thereto.

  As the ethylenically unsaturated monomer unit constituting the polymer as an additive for reducing the thickness direction retardation (Rt) obtained by polymerizing an ethylenically unsaturated monomer, first, as a vinyl ester, for example, vinyl acetate, propionic acid, etc. Vinyl, vinyl butyrate, vinyl valerate, vinyl pivalate, vinyl caproate, vinyl caprate, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl stearate, vinyl cyclohexanecarboxylate, vinyl octylate, vinyl methacrylate, Examples include vinyl crotonate, vinyl sorbate, vinyl benzoate, and vinyl cinnamate.

  Next, as acrylate ester, for example, methyl acrylate, ethyl acrylate, propyl acrylate (i-, n-), butyl acrylate (n-, i-, s-, t-), pentyl acrylate ( n-, i-, s-), hexyl acrylate (n-, i-), heptyl acrylate (n-, i-), octyl acrylate (n-, i-), nonyl acrylate (n-, i-), myristyl acrylate (n-, i-), cyclohexyl acrylate, acrylic acid (2-ethylhexyl), benzyl acrylate, phenethyl acrylate, acrylic acid (ε-caprolactone), acrylic acid (2-hydroxyethyl) ), Acrylic acid (2-hydroxypropyl), acrylic acid (3-hydroxypropyl), acrylic acid (4-hydroxybutyl), acrylic acid (2- Dorokishibuchiru) acrylate-p-hydroxymethylphenyl,-p-acrylic acid (2-hydroxyethyl) phenyl and the like; as methacrylic acid ester, the acrylic acid ester include those changed to methacrylic acid esters.

  Furthermore, examples of the unsaturated acid include acrylic acid, methacrylic acid, maleic anhydride, crotonic acid, itaconic acid, and the like.

  The polymer composed of the above monomers may be a copolymer or a homopolymer, and is preferably a vinyl ester homopolymer, a vinyl ester copolymer, or a copolymer of vinyl ester and acrylic acid or methacrylic acid ester.

  In the present invention, an acrylic polymer (simply referred to as an acrylic polymer) refers to a homopolymer or copolymer of acrylic acid or alkyl methacrylate having no monomer unit having an aromatic ring or a cyclohexyl group.

  Examples of the acrylate monomer having no aromatic ring and cyclohexyl group include, for example, methyl acrylate, ethyl acrylate, propyl acrylate (i-, n-), butyl acrylate (n-, i-, s-, t-), pentyl acrylate (n-, i-, s-), hexyl acrylate (n-, i-), heptyl acrylate (n-, i-), octyl acrylate (n-, i-) , Nonyl acrylate (n-, i-), myristyl acrylate (n-, i-), acrylic acid (2-ethylhexyl), acrylic acid (ε-caprolactone), acrylic acid (2-hydroxyethyl), acrylic acid (2-hydroxypropyl), acrylic acid (3-hydroxypropyl), acrylic acid (4-hydroxybutyl), acrylic acid (2-hydroxybutyl), acrylic acid 2-methoxy-ethyl), acrylic acid (2-ethoxyethyl), or the acrylic acid ester may include those obtained by changing the methacrylic acid ester.

  The acrylic polymer is a homopolymer or copolymer of the above-mentioned monomers, but it is preferable that the acrylic acid methyl ester monomer unit has 30% by weight or more, and the methacrylic acid methyl ester monomer unit has 40% by weight or more. It is preferable. In particular, a homopolymer of methyl acrylate or methyl methacrylate is preferred.

  Polymers obtained by polymerizing the above ethylenically unsaturated monomers and acrylic polymers are both highly compatible with cellulose ester, excellent in productivity without evaporation and volatilization, and retainability as a protective film for polarizing plates The moisture permeability is small, and the dimensional stability is excellent.

  In the present invention, an acrylic acid or methacrylic acid ester monomer having a hydroxyl group is not a homopolymer but a constituent unit of a copolymer. In this case, the acrylic acid or methacrylic acid ester monomer unit having a hydroxyl group is preferably contained in the acrylic polymer in an amount of 2 to 20% by weight.

  In the method for producing an optical film of the present invention, the dope composition contains a cellulose ester and an acrylic polymer having a weight average molecular weight of 500 or more and 3000 or less as an additive for reducing the thickness direction retardation (Rt). Is preferred.

  In the method for producing an optical film of the present invention, the dope composition contains a cellulose ester and an acrylic polymer having a weight average molecular weight of 5000 or more and 30000 or less as an additive for reducing the thickness direction retardation (Rt). It is preferable.

  In the present invention, if the weight average molecular weight of the polymer as an additive for reducing the thickness direction retardation (Rt) is 500 or more and 3000 or less, or if the polymer has a weight average molecular weight of 5000 or more and 30000 or less, the cellulose ester Is compatible with the material, and neither evaporation nor volatilization occurs during film formation. Moreover, the transparency of the cellulose ester film after film formation is excellent, the moisture permeability is extremely low, and it exhibits excellent performance as a protective film for polarizing plates.

  In the present invention, a polymer having a hydroxyl group in the side chain can also be preferably used as an additive for reducing the thickness direction retardation (Rt). The monomer unit having a hydroxyl group is the same as the monomer described above, but acrylic acid or methacrylic acid ester is preferable. For example, acrylic acid (2-hydroxyethyl), acrylic acid (2-hydroxypropyl), acrylic acid (3 -Hydroxypropyl), acrylic acid (4-hydroxybutyl), acrylic acid (2-hydroxybutyl), acrylic acid-p-hydroxymethylphenyl, acrylic acid-p- (2-hydroxyethyl) phenyl, or these acrylic acids. The thing replaced by methacrylic acid can be mentioned, Preferably, it is 2-hydroxyethyl acrylate and 2-hydroxyethyl methacrylate. The acrylic acid ester or methacrylic acid ester monomer unit having a hydroxyl group in the polymer is preferably contained in the polymer in an amount of 2 to 20% by weight, more preferably 2 to 10% by weight.

  The polymer as described above containing 2 to 20% by weight of the monomer unit having the above hydroxyl group, of course, is excellent in compatibility with cellulose ester, retention, dimensional stability, and low moisture permeability. It is particularly excellent in adhesion with a polarizer as a protective film for a polarizing plate, and has an effect of improving the durability of the polarizing plate.

  In the present invention, it is preferable that at least one terminal of the main chain of the polymer has a hydroxyl group. The method of having a hydroxyl group at the end of the main chain is not particularly limited as long as it has a hydroxyl group at the end of the main chain, but radical polymerization having a hydroxyl group such as azobis (2-hydroxyethylbutyrate). A method of using an initiator, a method of using a chain transfer agent having a hydroxyl group such as 2-mercaptoethanol, a method of using a polymerization terminator having a hydroxyl group, a method of having a hydroxyl group at the terminal by living ion polymerization, Using a polymerization catalyst in which a compound having one thiol group and a secondary hydroxyl group as disclosed in JP-A No. 2000-128911 or JP-A No. 2000-344823, or a combination of the compound and an organometallic compound is used. It can be obtained by a polymerization method or the like, and the method described in the publication is particularly preferable. The polymer produced by the method related to the description in this publication is commercially available as Act Flow Series manufactured by Soken Chemical Co., Ltd., and can be preferably used.

  In the present invention, the polymer having a hydroxyl group at the terminal and / or the polymer having a hydroxyl group in a side chain has an advantage of significantly improving the compatibility and transparency of the polymer with respect to the cellulose ester.

  In the present invention, useful additives for reducing the thickness direction retardation (Rt) include, in addition to the above, for example, an ester compound of diglycerin polyhydric alcohol and fatty acid described in JP-A No. 2000-63560, An ester or ether compound of a hexose sugar alcohol described in JP-A-2001-247717, a trialiphatic alcohol phosphate compound described in JP-A-2004-315613, and a general formula (1) described in JP-A-2005-41911 A phosphoric acid ester compound described in JP-A No. 2004-315605, a styrene oligomer described in JP-A No. 2005-105139, and a polymer of a styrene monomer described in JP-A No. 2005-105140. .

  In the method for producing an optical film according to the present invention, an organic solvent having good solubility with respect to the cellulose derivative is referred to as a good solvent, and has a main effect on dissolution. Organic) solvent or main (organic) solvent.

  Examples of good solvents include ketones such as acetone, methyl ethyl ketone, cyclopentanone, cyclohexanone, ethers such as tetrahydrofuran (THF), 1,4-dioxane, 1,3-dioxolane, 1,2-dimethoxyethane, formic acid Esters such as methyl, ethyl formate, methyl acetate, ethyl acetate, amyl acetate, γ-butyrolactone, methyl cellosolve, dimethylimidazolinone, dimethylformamide, dimethylacetamide, acetonitrile, dimethyl sulfoxide, sulfolane, nitroethane, methylene chloride And 1,3-dioxolane, THF, methyl ethyl ketone, acetone, methyl acetate and methylene chloride are preferable.

  In addition to the organic solvent, the dope preferably contains 1 to 40% by weight of an alcohol having 1 to 4 carbon atoms. After casting the dope onto the support, the solvent starts to evaporate and the alcohol ratio increases, so that the web (the dope film after the casting of the cellulose derivative dope on the support is called the web Is used as a gelling solvent that makes the web strong and makes it easy to peel off from the support, or when these ratios are small, dissolve the cellulose derivative of the non-chlorine organic solvent. There is also a role to promote.

  Examples of the alcohol having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, tert-butanol, and propylene glycol monomethyl ether. Of these, ethanol is preferred because it has excellent dope stability, has a relatively low boiling point, good drying properties, and no toxicity. These organic solvents alone are not soluble in cellulose derivatives and are called poor solvents.

  The most preferable solvent for dissolving the cellulose derivative, which is a preferable polymer compound satisfying such conditions, at a high concentration is a mixed solvent having a ratio of methylene chloride: ethyl alcohol of 95: 5 to 80:20. Alternatively, a mixed solvent of methyl acetate: ethyl alcohol 60:40 to 95: 5 is also preferably used.

  The film according to the present invention includes a plasticizer that imparts processability, flexibility, and moisture resistance to the film, fine particles that impart slipperiness to the film (matting agent), an ultraviolet absorber that imparts an ultraviolet absorbing function, and deterioration of the film. You may contain the antioxidant etc. which prevent.

  The plasticizer used in the present invention is not particularly limited. However, a cellulose derivative or a reactive metal compound capable of hydrolytic polycondensation can be used so as not to cause haze, bleed out or volatilize from the film. It preferably has a functional group capable of interacting with the condensate by hydrogen bonding or the like.

  Examples of such functional groups include hydroxyl groups, ether groups, carbonyl groups, ester groups, carboxylic acid residues, amino groups, imino groups, amide groups, imide groups, cyano groups, nitro groups, sulfonyl groups, sulfonic acid residues, Examples thereof include a phosphonyl group and a phosphonic acid residue, and a carbonyl group, an ester group and a phosphonyl group are preferred.

  Examples of such plasticizers include phosphate ester plasticizers, phthalate ester plasticizers, trimellitic acid ester plasticizers, pyromellitic acid plasticizers, polyhydric alcohol ester plasticizers, glycolate plasticizers. Agents, citric acid ester plasticizers, fatty acid ester plasticizers, carboxylic acid ester plasticizers, polyester plasticizers, etc. can be preferably used, but polyhydric alcohol ester plasticizers, glycolate plasticizers are particularly preferred. And non-phosphate ester plasticizers such as polycarboxylic acid ester plasticizers.

  The polyhydric alcohol ester is composed of an ester of a dihydric or higher aliphatic polyhydric alcohol and a monocarboxylic acid, and preferably has an aromatic ring or a cycloalkyl ring in the molecule.

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

Formula (1) R1- (OH) n
(However, R1 represents an n-valent organic group, and n represents a positive integer of 2 or more.)
Examples of preferred polyhydric alcohols include the following, but the present invention is not limited to these.

  Examples of preferred polyhydric alcohols include adonitol, arabitol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, tripropylene glycol, 1, 2-butanediol, 1,3-butanediol, 1,4-butanediol, dibutylene glycol, 1,2,4-butanetriol, 1,5-pentanediol, 1,6-hexanediol, hexanetriol, gallium Examples include lactitol, mannitol, 3-methylpentane-1,3,5-triol, pinacol, sorbitol, trimethylolpropane, trimethylolethane, and xylitol. In particular, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, sorbitol, trimethylolpropane, and xylitol are preferable.

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

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

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

  Examples of preferred aliphatic monocarboxylic acids include acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, 2-ethyl-hexanecarboxylic acid, undecylic acid, lauric acid, Tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, serotic acid, heptacosanoic acid, montanic acid, mellicic acid, laccellic acid, etc., undecylen Examples thereof include unsaturated fatty acids such as acid, oleic acid, sorbic acid, linoleic acid, linolenic acid, and arachidonic acid.

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

  Examples of preferred aromatic monocarboxylic acids include those in which an alkyl group is introduced into the benzene ring of benzoic acid such as benzoic acid and toluic acid, and two or more benzene rings such as biphenylcarboxylic acid, naphthalenecarboxylic acid, and tetralincarboxylic acid. Examples thereof include aromatic monocarboxylic acids and derivatives thereof, and benzoic acid is particularly preferable.

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

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

  The glycolate plasticizer is not particularly limited, but a glycolate plasticizer having an aromatic ring or a cycloalkyl ring in the molecule can be preferably used. As preferred glycolate plasticizers, for example, butyl phthalyl butyl glycolate, ethyl phthalyl ethyl glycolate, methyl phthalyl ethyl glycolate and the like can be used.

  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, dicyclohexyl phthalate, and the like can be used, but in the present invention, it is preferable that a phosphate ester plasticizer is not substantially contained.

  Here, “substantially does not contain” means that the content of the phosphoric ester plasticizer is less than 1% by weight, preferably 0.1% by weight, and particularly preferably not added.

  These plasticizers can be used alone or in combination of two or more.

  The amount of the plasticizer used is preferably 1 to 20% by weight. 6 to 16% by weight is further preferable, and 8 to 13% by weight is particularly preferable. If the amount of the plasticizer used is less than 1% by weight relative to the cellulose derivative, the effect of reducing the moisture permeability of the film is small, so this is not preferred. If it exceeds 20% by weight, the plasticizer bleeds out from the film, and the film Since the physical properties of the material deteriorate, it is not preferable.

  In order to impart slipperiness to the cellulose derivative in the present invention, it is preferable to add fine particles such as a matting agent. Examples of the fine particles include fine particles of an inorganic compound or fine particles of an organic compound.

  Examples of the fine particles of the inorganic compound include fine particles of silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, tin oxide and the like. Of these, fine particles of a compound containing a silicon atom are preferred, and fine silicon dioxide particles are particularly preferred. Examples of the silicon dioxide fine particles include Aerosil 200, 200V, 300, R972, R972V, R974, R202, R812, R805, OX50, and TT600 manufactured by Aerosil Co., Ltd.

  Examples of the organic compound fine particles include fine particles such as acrylic resin, silicone resin, fluorine compound resin, and urethane resin.

  The primary particle size of the fine particles is not particularly limited, but the average particle size in the film is preferably about 0.05 to 5.0 μm. More preferably, it is 0.1-1.0 micrometer.

  When the cellulose ester film is observed with an electron microscope or an optical microscope, the average particle diameter of the fine particles indicates an average value of the lengths in the major axis direction of the particles at the observation position of the film. As long as the particles are observed in the film, they may be primary particles or secondary particles in which the primary particles are aggregated, but most of the particles that are usually observed are secondary particles.

  As an example of the measurement method, 10 vertical cross-sectional photographs are taken at random for one film, and the number of particles in 100 μm 2 whose major axis length is in the range of 0.05 to 5 μm is taken for each cross-sectional photograph. Count. The average value of the major axis lengths of the particles counted at this time is obtained, and a value obtained by averaging the average values of 10 locations is defined as the average particle size.

  In the case of fine particles, the primary particle size, the particle size after being dispersed in a solvent, and the particle size added to the film often change, and what is important is that the fine particles are finally combined with the cellulose ester in the film to aggregate. And controlling the particle size formed.

  Here, if the average particle size of the fine particles exceeds 5 μm, haze deterioration or the like may be observed, or it may cause a failure in a wound state as a foreign matter. Moreover, when the average particle diameter of fine particles is less than 0.05 μm, it becomes difficult to impart slipperiness to the film.

  The fine particles are used by adding 0.04 to 0.5% by weight to the cellulose ester. Preferably, 0.05 to 0.3% by weight, more preferably 0.05 to 0.25% by weight is added. When the amount of fine particles added is 0.04% by weight or less, the film surface roughness becomes too smooth and blocking occurs due to an increase in the friction coefficient. If the amount of fine particles added exceeds 0.5% by weight, the coefficient of friction on the film surface will be too low, causing winding misalignment during winding, and the transparency of the film will be low and haze will be high. The above range is essential because it has no value as a film.

  For the dispersion of the fine particles, it is preferable to treat the composition in which the fine particles and the solvent are mixed with a high-pressure dispersion apparatus. The high-pressure dispersion apparatus used in the present invention is an apparatus that creates special conditions such as high shear and high pressure by passing a composition in which fine particles and a solvent are mixed at high speed through a narrow tube.

  It is preferable that the maximum pressure condition inside the apparatus is 980 N / cm 2 or more in a thin tube having a tube diameter of 1 to 2000 μm, for example, by processing with a high-pressure dispersion apparatus. More preferably, the maximum pressure condition inside the apparatus is 1960 N / cm 2 or more. Further, at that time, those having a maximum reaching speed of 100 m / sec or more and those having a heat transfer speed of 100 kcal / hr or more are preferable.

  Examples of the high-pressure dispersing device as described above include an ultra-high pressure homogenizer (trade name: Microfluidizer) manufactured by Microfluidics Corporation, or a nanomizer manufactured by Nanomizer, and also a Manton Gorin type high-pressure dispersing device such as Izumi Food Machinery. A homogenizer etc. are mentioned.

  In the present invention, the fine particles are dispersed in a solvent containing 25 to 100% by weight of a lower alcohol, then mixed with a dope in which a cellulose ester (cellulose derivative) is dissolved in a solvent, and the mixed solution is allowed to flow on the support. A cellulose ester film is obtained which is formed by stretching and drying.

  Here, the content ratio of the lower alcohol is preferably 50 to 100% by weight, more preferably 75 to 100% by weight.

  Examples of lower alcohols preferably include methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol and the like.

  Although it does not specifically limit as solvents other than a lower alcohol, It is preferable to use the solvent used at the time of film formation of a cellulose ester.

  The fine particles are dispersed in the solvent at a concentration of 1 to 30% by weight. Dispersing at a concentration higher than this is not preferable because the viscosity increases rapidly. The concentration of the fine particles in the dispersion is preferably 5 to 25% by weight, more preferably 10 to 20% by weight.

  The ultraviolet absorbing function of the film is preferably imparted to various optical films such as a polarizing plate protective film, a retardation film, and an optical compensation film from the viewpoint of preventing deterioration of the liquid crystal. For such an ultraviolet absorbing function, a material that absorbs ultraviolet rays may be included in the cellulose derivative, and a layer having an ultraviolet absorbing function may be provided on a film made of the cellulose derivative.

  Examples of ultraviolet absorbers that can be used in the present invention include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, and the like. A benzotriazole-based compound with little coloring is preferable. In addition, ultraviolet absorbers described in JP-A-10-182621 and JP-A-8-337574 and polymer ultraviolet absorbers described in JP-A-6-148430 are also preferably used.

  As the ultraviolet absorber, those having excellent absorption ability of ultraviolet rays having a wavelength of 370 nm or less from the viewpoint of preventing deterioration of a polarizer or liquid crystal and those having little absorption of visible light having a wavelength of 400 nm or more from the viewpoint of liquid crystal display properties. preferable.

  Specific examples of useful UV absorbers in the present invention include 2- (2′-hydroxy-5′-methylphenyl) benzotriazole, 2- (2′-hydroxy-3 ′, 5′-di-tert-). Butylphenyl) benzotriazole, 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3 ', 5'-di-tert-butylphenyl) ) -5-chlorobenzotriazole, 2- (2'-hydroxy-3 '-(3 ", 4", 5 ", 6" -tetrahydrophthalimidomethyl) -5'-methylphenyl) benzotriazole, 2,2- Methylenebis (4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol, 2- (2'-hydroxy) 3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2- (2H-benzotriazol-2-yl) -6- (linear and side chain dodecyl) -4-methylphenol, octyl -3- [3-tert-butyl-4-hydroxy-5- (chloro-2H-benzotriazol-2-yl) phenyl] propionate and 2-ethylhexyl-3- [3-tert-butyl-4-hydroxy-5 A mixture of-(5-chloro-2H-benzotriazol-2-yl) phenyl] propionate can be mentioned, but is not limited thereto.

  Further, as commercially available products of ultraviolet absorbers, TINUVIN 109, TINUVIN 171 and TINUVIN 326 (all manufactured by Ciba Specialty Chemicals) can be preferably used.

  Specific examples of the benzophenone-based compound that is an ultraviolet absorber that can be used in the present invention include 2,4-dihydroxybenzophenone, 2,2′-dihydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy-5- Examples thereof include, but are not limited to, sulfobenzophenone and bis (2-methoxy-4-hydroxy-5-benzoylphenylmethane).

  In this invention, the compounding quantity of these ultraviolet absorbers has the preferable range of 0.01 to 10 weight% with respect to a cellulose ester (cellulose derivative), and also 0.1 to 5 weight% is preferable. If the amount of the ultraviolet absorber used is too small, the ultraviolet absorbing effect may be insufficient. If the amount of the ultraviolet absorber is too large, the transparency of the film may be deteriorated. The ultraviolet absorber is preferably one having high heat stability.

  Further, as the ultraviolet absorber that can be used in the optical film of the present invention, the polymer ultraviolet absorber (or ultraviolet absorbing polymer) described in JP-A-6-148430 and JP-A-2002-47357 is preferably used. be able to. In particular, it is represented by the general formula (1) described in JP-A-6-148430, the general formula (2), or the general formulas (3), (6), and (7) described in JP-A-2002-47357. A polymer ultraviolet absorber is preferably used.

  In general, the antioxidant is also referred to as a deterioration inhibitor, but is preferably contained in a cellulose ester film as an optical film. That is, when a liquid crystal image display device or the like is placed in a high humidity and high temperature state, the cellulose ester film as an optical film may be deteriorated. The antioxidant has a role of delaying or preventing the film from being decomposed by, for example, halogen in the residual solvent in the film or phosphoric acid of the phosphoric acid plasticizer, so that it is preferably contained in the film. .

  As such an antioxidant, a hindered phenol compound is preferably used. For example, 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di- -T-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-bis [3 -(3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-t-butylanilino)- 1,3,5-triazine, 2,2-thio-diethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], octa Sil-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, N, N'-hexamethylenebis (3,5-di-t-butyl-4-hydroxy-hydrocinnamamide) 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, tris- (3,5-di-t-butyl-4-hydroxy Benzyl) -isocyanurate and the like. In particular, 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3 -(3-t-butyl-5-methyl-4-hydroxyphenyl) propionate] is preferred. Further, for example, hydrazine-based metal deactivators such as N, N′-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyl] hydrazine and tris (2,4-di-t A phosphorus-based processing stabilizer such as -butylphenyl) phosphite may be used in combination.

  The amount of these compounds added is preferably 1 ppm to 1.0% by weight, more preferably 10 to 1000 ppm by weight with respect to the cellulose derivative.

  In addition, in the apparatus which implements the manufacturing method of the optical film of the present invention shown in FIG. 3 and FIG. 4, the stretching step is a film for a liquid crystal display device. A tenter method in which the film is fixed and stretched is preferable in order to improve the flatness and dimensional stability of the film.

  It is preferable that the residual solvent amount of the web (film) (29) immediately before entering the tenter (32) in the stretching step is 10 to 35% by weight.

  The stretch ratio of the web in the tenter (32) in the stretching process is 3 to 100%, preferably 5 to 80%, and more preferably 5 to 60%. Moreover, the temperature of the warm air blown from the warm air blowing slit port in the tenter (32) is 100 to 200 ° C, preferably 110 to 190 ° C, and more preferably 115 to 185 ° C.

  A drying device (30) is preferably provided after the tenter (32) in the stretching step. In the drying device (30), the web (29) is meandered by a plurality of conveying rolls arranged in a staggered manner as viewed from the side, and the web (29) is dried in the meantime. The film transport tension in the drying apparatus (30) is affected by the physical properties of the dope, the amount of residual solvent in the peeling and film transport process, the drying temperature, etc., but the film transport tension during drying is 10 to 300 N. / M width, and 20 to 270 N / m width is more preferable.

  The means for drying the web (film) (29) is not particularly limited, and is generally performed by hot air, infrared rays, a heating roll, microwaves, or the like. It is preferable to dry with hot air from the viewpoint of simplicity, for example, it is dried by the drying air (31) blown from the warm air inlet at the front portion of the bottom of the drying device (30), and is dried on the ceiling of the drying device (30). It is dried by exhaust air being discharged from the outlet of the rear portion. The temperature of the drying air (31) is preferably 40 to 160 ° C, and more preferably 50 to 160 ° C in order to improve the flatness and dimensional stability.

  These steps from casting to post-drying may be performed in an air atmosphere or in an inert gas atmosphere such as nitrogen gas. In this case, it goes without saying that the dry atmosphere is carried out in consideration of the explosion limit concentration of the solvent.

  For example, a cellulose ester film that has finished the transport drying process is generally processed to form an emboss on the film by an embossing apparatus before the introduction to the winding process.

  Here, the height h (μm) of the emboss is set in the range of 0.05 to 0.3 times the film thickness T, and the width W is set in the range of 0.005 to 0.02 times the film width L. . Embossing may be formed on both sides of the film. In this case, the height h1 + h2 (μm) of the emboss is set in the range of 0.05 to 0.3 times the film thickness T, and the width W is set in the range of 0.005 to 0.02 times the film width L. For example, when the film thickness is 40 μm, the emboss height h 1 + h 2 (μm) is set to 2 to 12 μm. The emboss width is set to 5 to 30 mm.

  The film after drying is wound up by a winding device (33) to obtain the original roll of the optical film. A film having good dimensional stability can be obtained by setting the residual solvent amount of the film to be dried to 0.5% by weight or less, preferably 0.1% by weight or less.

  The winding method of the film may be a generally used winder, and there are methods for controlling the tension such as a constant torque method, a constant tension method, a taper tension method, a program tension control method with a constant internal stress, etc. Use it properly.

  The film may be bonded to the winding core (winding core) by either a double-sided adhesive tape or a single-sided adhesive tape.

  In the optical film according to the present invention, the width of the film after winding is preferably 1200 to 2500 mm.

  In this invention, the film thickness after drying of a cellulose-ester film has the preferable range of 20-150 micrometers as a finished film from a viewpoint of thickness reduction of a liquid crystal display device. Here, the film thickness after drying refers to a film in which the amount of residual solvent in the film is 0.5% by weight or less.

  Here, when the film thickness of the cellulose ester film after winding is too thin, for example, the required strength as a protective film for a polarizing plate may not be obtained. If the film thickness is too thick, the advantage of thinning the film becomes less than the conventional cellulose ester film. In order to adjust the film thickness, the dope concentration, the pumping amount, the slit gap of the die of the casting die, the extrusion pressure of the casting die, the speed of the support, etc. are controlled so as to obtain the desired thickness. Is good. Further, as a means for making the film thickness uniform, it is preferable to use a film thickness detection means to feed back and adjust the programmed feedback information to each of the above devices.

  In the process from immediately after casting through the solution casting film-forming method to drying, the atmosphere in the drying apparatus may be air, but may be performed in an inert gas atmosphere such as nitrogen gas or carbon dioxide gas. . However, of course, the danger of the explosion limit of the evaporating solvent in the dry atmosphere must always be considered.

  In the present invention, the cellulose ester film preferably has a moisture content of 0.1 to 5%, more preferably 0.3 to 4%, and even more preferably 0.5 to 2%.

  In the present invention, the cellulose ester film desirably has a transmittance of 90% or more, more preferably 92% or more, and further preferably 93% or more.

  Moreover, the optical film manufactured by the method of the present invention has a haze of 0.3 to 2.0 when three sheets are stacked. According to the optical film of the present invention, the haze of the film is very high. It is low and has optical characteristics excellent in transparency and flatness.

  Here, the haze of the optical film may be measured using, for example, a haze meter (1001DP type, manufactured by Nippon Denshoku Industries Co., Ltd.) according to the method defined in JIS K6714.

  Moreover, the tensile elastic modulus in the machine direction (MD direction) of the cellulose ester film produced by the method for producing an optical film according to the present invention is 1500 to 3500 MPa, and the tensile elastic modulus in the direction perpendicular to the machine direction (TD direction) is It is preferably 3000 MPa to 4500 MPa, and the ratio of the elastic modulus in the TD direction / the elastic modulus in the MD direction of the film is preferably 1.40 to 1.90.

  Here, if the ratio of the elastic modulus in the TD direction / the elastic modulus in the MD direction of the optical film is less than 1.40, the winding of the film having a width exceeding 1650 mm increases the sag of the central portion, and the winding core film Since sticking increases, it is not preferable. Further, when the ratio of the elastic modulus in the TD direction / the elastic modulus in the MD direction exceeds 1.90, warpage after overheating in the polarizing plate occurs, or the backlight is heated by the heat of the backlight when incorporated in a liquid crystal panel. Since the dimensional change behavior of the polarizing plate on the side and the surface side is greatly different, unevenness occurs at the corner, which is not preferable.

  As a specific method for measuring the tensile modulus of elasticity in the MD direction and TD direction of the film, for example, the method of JIS K7217 can be mentioned.

  That is, using a tensile tester (TG-2KN, manufactured by Minebea Co., Ltd.), a sample was set at a chucking pressure: 0.25 MPa, a distance between marked lines: 100 ± 10 mm, and a pulling speed: 100 ± 10 mm / min. Pull on. As a result, from the obtained tensile stress-strain curve, the elastic modulus calculation start point is 10N, the end point is 30N, and the tangent line drawn between them is extrapolated to calculate the elastic modulus.

  In the optical film of the present invention, the in-plane retardation (Ro) defined by the following formula is 30 to 300 nm under the conditions of a temperature of 23 ° C. and a humidity of 55% RH, and the thickness direction retardation (Rt) is a temperature of 23 ° C. and humidity. It is preferably 70 to 400 nm under the condition of 55% RH.

Ro = (nx−ny) × d
Rt = {(nx + ny) / 2−nz} × d
In the formula, Ro is the retardation value in the film plane, Rt is the retardation value in the film thickness direction, nx is the refractive index in the slow axis direction in the film plane, ny is the refractive index in the fast axis direction in the film plane, and nz is the film. The refractive index in the thickness direction (refractive index measured at a wavelength of 590 nm), d represents the thickness (nm) of the film.

  The retardation values Ro and Rt can be measured using an automatic birefringence meter. For example, using KOBRA-21ADH (manufactured by Oji Scientific Instruments Co., Ltd.), the wavelength can be obtained at 590 nm in an environment of a temperature of 23 ° C. and a humidity of 55% RH.

  The optical film according to the present invention is manufactured by the above-described optical film manufacturing method, and the thickness of the film is preferably 30 to 200 μm.

The optical film according to the present invention has a film disposed between two polarizing plates orthogonal to each other, and the transmittance of the transmitted light having a wavelength of 600 nm is measured in a crossed Nicols state. The variation is 2 × 10 ^{−5 to} 60 × 10 ⁻⁵ (%).

Here, the transmittance variation in the crossed Nicols state of the transmitted light having a wavelength of 600 nm of the optical film of the present invention is preferably as small as possible, and if the transmittance variation exceeds 60 × 10 ⁻⁵ (%), it is transparent. This is not preferable because the flatness is reduced.

  According to the invention of the optical film of the present invention, the releasability (peelability) of the cast film (web) from the cooling roll or the support surface is improved, and a very smooth peelability is obtained. Since the variation in the width direction is reduced, the optical film has excellent transparency and flatness because the variation in crossed Nicols transmittance is greatly reduced.

  The optical film targeted by the present invention is a functional film used for various displays such as a liquid crystal display, a plasma display, and an organic EL display, particularly a liquid crystal display. A polarizing plate protective film, a retardation film, an antireflection film, It includes an optical compensation film such as a brightness enhancement film and a viewing angle expansion.

  The optical film according to the present invention is preferably used for a liquid crystal display member, specifically, a protective film for a polarizing plate. In particular, in a protective film for a polarizing plate that has strict requirements for both moisture permeability and dimensional stability, the optical film produced by the method of the present invention is preferably used.

  By using the protective film for a polarizing plate comprising the optical film of the present invention, it is possible to provide a polarizing plate excellent in durability, dimensional stability, and optical isotropy as well as thinning.

  By the way, the polarizing film is a film that has been conventionally stretched by treating a film that can be stretched and oriented, such as a polyvinyl alcohol film, with a dichroic dye such as iodine. Since the polarizing film itself does not have sufficient strength and durability, a polarizing plate is generally obtained by adhering a cellulose ester film having no anisotropy as a protective film to both surfaces thereof.

  The polarizing plate may be prepared by laminating the optical film produced by the method of the present invention as a retardation film, and the optical film produced by the method of the present invention is a retardation film and a protective film. Alternatively, it may be produced by directly bonding to a polarizing film. The method of bonding is not particularly limited, but can be performed with an adhesive composed of an aqueous solution of a water-soluble polymer. The water-soluble polymer adhesive is preferably a completely saponified polyvinyl alcohol aqueous solution. Furthermore, a long polarizing plate can be obtained by laminating a long polarizing film stretched in the longitudinal direction and treated with a dichroic dye and a long retardation film produced by the method of the present invention. . The polarizing plate is a sticking type in which a peelable sheet is laminated on one or both sides thereof via a pressure sensitive adhesive layer (for example, an acrylic pressure sensitive adhesive layer). Or the like can be easily attached).

  The polarizing plate thus obtained can be used for various display devices. In particular, a liquid crystal display device using a VA mode liquid crystal molecule in which liquid crystal molecules are substantially vertically aligned when no voltage is applied, or a TN mode liquid crystal cell in which liquid crystal molecules are substantially horizontal and twisted when no voltage is applied. Is preferred.

  By the way, a polarizing plate can be produced by a general method. For example, there is a method in which an optical film or a cellulose ester film is subjected to alkali saponification treatment, and a polyvinyl alcohol film is immersed and stretched in an iodine solution and bonded to both surfaces of a polarizing film using a completely saponified polyvinyl alcohol aqueous solution. is there. The alkali saponification treatment refers to a treatment of immersing the cellulose ester film in a high-temperature strong alkaline solution in order to improve the wetness of the water-based adhesive and improve the adhesiveness.

  The optical film produced by the method of the present invention includes a hard coat layer, an antiglare layer, an antireflection layer, an antifouling layer, an antistatic layer, a conductive layer, an optical anisotropic layer, a liquid crystal layer, an alignment layer, an adhesive layer, Various functional layers such as an adhesive layer and an undercoat layer can be provided. These functional layers can be provided by a method such as coating or vapor deposition, sputtering, plasma CVD, or atmospheric pressure plasma treatment.

  Thus, the obtained polarizing plate is provided in the one or both surfaces of a liquid crystal cell, and a liquid crystal display device is obtained using this.

  In the present invention, the liquid crystal display device comprises two sheets comprising a liquid crystal cell in which rod-like liquid crystal molecules are sandwiched between a pair of glass substrates, a polarizing film disposed so as to sandwich the liquid crystal cell, and transparent protective layers disposed on both sides thereof. It has a polarizing plate.

  By using the protective film for polarizing plates made of the optical film produced by the method of the present invention, it is possible to provide a polarizing plate excellent in durability, dimensional stability, and optical isotropy as well as thinning. Furthermore, a liquid crystal display device using this polarizing plate or retardation film can maintain stable display performance over a long period of time.

  The optical film produced by the method of the present invention can be used as a base material for an antireflection film or an optical compensation film.

  Examples of the present invention will be described below, but the present invention is not limited thereto.

Example 1
First, the manufacturing method of the optical film of this invention was implemented by the melt casting film forming method.

(Preparation of pellets)
Cellulose acetate propionate 100 parts by weight (acetyl group substitution degree 1.95, propionyl group substitution degree 0.7,
Number average molecular weight 75000, temperature 130 ° C., dried for 5 hours,
Glass transition temperature point Tg = 174 ° C.)
10 parts by weight of plasticizer [trimethylolpropane tris (3,4,5-trimethoxybenzoate)]
1 part by weight of antioxidant (IRGANOX-1010, manufactured by Ciba Specialty Chemicals)
1 part by weight of antioxidant (Sumilizer GP, manufactured by Sumitomo Chemical Co., Ltd.)
To the above material, 0.05 part by weight of silica particles (Aerosil R972V, manufactured by Nippon Aerosil Co., Ltd.) and 0.5 part by weight of an ultraviolet absorber (TINUVIN360, manufactured by Ciba Specialty Chemicals) are added as a matting agent, and nitrogen gas is added. After mixing with an enclosed V-shaped mixer for 30 minutes, it was melted at 240 ° C. using a twin screw extruder (PCM30, manufactured by Ikegai Co., Ltd.) equipped with a strand die, and a cylindrical shape having a length of 4 mm and a diameter of 3 mm. A pellet was prepared. The shear rate at this time was set to 25 / second.

(Production of film)
Using the above molten resin, a cellulose acetate propionate film having a thickness of 40 μm was produced as follows.

  Film formation was performed with the manufacturing apparatus shown in FIG. Referring to the figure, the first cooling roll (5) and the second cooling roll (7) were made of stainless steel having a diameter of 40 cm, and the surface was subjected to hard chrome plating. Further, oil for temperature adjustment (cooling fluid) was circulated inside to control the roll surface temperature. The elastic touch roll (6) had a diameter of 20 cm, the inner cylinder and the outer cylinder were made of stainless steel, and the outer cylinder surface was subjected to hard chrome plating. 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 (6).

  The obtained pellets (water content 50 ppm) were melted in a single screw extruder (1) and subjected to pressure filtration using a leaf disk type metal filter (2).

  A casting die (4) having a lip clearance of 1.0 mm and a lip portion average surface roughness Ra of 0.01 μm was used as the casting die (4). Further, silica fine particles as a slip agent were added from the hopper opening in the middle of the extruder so as to be 0.1 parts by weight.

  The resin melt was melt extruded from the casting die (4) into a film at a melting temperature of 250 ° C.

  And in this Example 1, the atmospheric pressure plasma apparatus which is a high energy irradiation apparatus (A) is applied to the surface of the casting film (web) cast at a speed of 20 m / min from the casting die (4). The plasma was irradiated and before the molten resin of the cast film contacted the first cooling roll (5), a high energy surface treatment was applied to form an easily peelable treatment layer on the surface of the cast film.

  This high energy surface treatment was performed on one surface of the casting film, that is, the surface in contact with the first cooling roll (5).

(Normal pressure plasma treatment)
The resin melt is cast from the casting die (4) under the condition that the gap from the plasma injection slit to the surface of the casting film (s) is 4 mm in the atmospheric plasma device which is the high energy irradiation device (A). However, plasma irradiation treatment was performed on substantially the entire width of the cast film. Here, the amount of reaction gas used in the atmospheric pressure plasma apparatus was 1 m ³ per 1 m of irradiation width. The composition of the mixed gas (reactive gas) used for the plasma treatment is described below. The atmospheric pressure was 1.0 atm.

Nitrogen 99.98% by volume
Oxygen 0.02% by volume
The time from casting to the start of high energy irradiation by the atmospheric plasma device which is the high energy irradiation device (A) is set to 0.5 seconds, 3.0 seconds, and 5.0 seconds, respectively. Three high energy irradiation surface treatments were performed.

  Next, the cast film subjected to the high-energy surface treatment as described above is brought into contact with the first cooling roll (5) having a surface temperature of 100 ° C. at a draw ratio of 10, and a cast film having a film thickness of 100 μm ( Cast film) was obtained.

  In addition, the glass transition temperature (Tg) of the cellulose acetate propionate film of this Example 1 is 136 degreeC, and the glass transition temperature of the cast film extruded from the casting die (4) is made by Seiko Co., Ltd. It measured by DSC method (in nitrogen, temperature rising temperature 10 degreeC / min) using DSC6200.

  Furthermore, the cast film (film) was pressed on the first cooling roll (5) with an elastic touch roll (6) having a metal surface with a thickness of 2 mm at a linear pressure of 10 kg / cm. The film temperature on the touch roll (6) side at the time of pressing was 180 ° C. ± 1 ° C.

  In addition, the surface temperature of the 2nd cooling roll (7) was 30 degreeC. And the surface temperature of each roll of an elastic touch roll (6), a 1st cooling roll (5), and a 2nd cooling roll (7) is with respect to a rotation direction from the position where a cast film (film) contact | connects a roll first. The surface temperature of each roll was an average value obtained by measuring the temperature of the roll surface at a position 90 ° before 10 points in the width direction using a non-contact thermometer.

  The cooled and solidified film (10) peeled from the third cooling roll (8) by the peeling roll (9) is guided to a stretching device (12) through a dancer roll (film tension adjusting roll) (11), where the film ( 10) is stretched in the transverse direction (width direction). By this stretching, the molecules in the film are oriented.

  After stretching, the end of the film is slit to a product width by a slitter (13) and cut off, and then knurled (embossed) by a knurling device comprising an embossing ring (14) and a back roll (15). It applied to the both ends of the film, and it wound up with the winding apparatus (16), and produced three types of cellulose acetate propionate films with film thickness of 40 micrometers.

Example 2
(Normal pressure plasma treatment)
A cellulose acetate propionate film was produced in the same manner as in Example 1, but a monomer (acetylene) was added to the source gas of the atmospheric pressure plasma apparatus.

Nitrogen 94.98% by volume
Oxygen 0.02% by volume
Acetylene 5.00% by volume
In addition, the time from casting to the start of high energy irradiation by the atmospheric plasma device which is the high energy irradiation device (A) is set to 0.5 seconds, 3.0 seconds, and 5.0 seconds, respectively. Steps such as three high energy irradiation surface treatments were carried out in the same manner as in Example 1, and three types of cellulose acetate propionate films having a thickness of 40 μm were produced.

Example 3
(Excimer UV treatment)
In this example, an excimer UV irradiation device was used as the high energy irradiation device (A). The excimer UV irradiation apparatus is as shown in FIG. 6, and the Xe ₂ wavelength has an irradiance of 40 mW / cm ² in quartz glass (q) having a length of about 300 mm in the conveyance direction of the cooling roll (5). An apparatus containing four 172 nm excimer UV lamps, with a gap of 4 mm from the quartz glass surface of the lamp to the surface of the casting film, while casting the resin melt from the casting die (4), Further, before the molten resin of the cast film comes into contact with the first cooling roll (5) by irradiating the excimer UV to the substantially full width by the excimer UV irradiating apparatus which is the high energy irradiating apparatus (A). Then, a high energy surface treatment was applied to form an easily peelable treatment layer on the surface of the cast film.

  This high energy surface treatment was performed on one surface of the casting film, that is, the surface in contact with the first cooling roll (5).

  Moreover, the time from casting to the start of high energy irradiation by the excimer UV irradiation apparatus which is a high energy irradiation apparatus (A) is set to 0.5 seconds, 3.0 seconds, and 5.0 seconds, respectively. Three high energy irradiation surface treatments were performed.

  Next, the casting film subjected to the high energy surface treatment as described above was brought into contact with the first cooling roll (5) in the same manner as in Example 1 to cast a casting film (100 μm thick) ( Cast film).

  Thereafter, these cast films were treated in the same manner as in Example 1 to prepare three types of cellulose acetate propionate films having a film thickness of 40 μm.

Example 4
(Laser irradiation treatment)
In this example, a laser irradiation apparatus was used as the high energy irradiation apparatus (A). The laser irradiation apparatus is as shown in FIG. 7. While casting a resin melt from the casting die (4), a high energy irradiation apparatus (on the surface of the casting film with respect to substantially the entire width of the casting film ( A) A laser beam (wavelength: 248 nm) of a KrF excimer laser irradiation apparatus and a pulse laser with a pulse width of 100 ns is irradiated in one shot, and the molten resin of the cast film comes into contact with the first cooling roll (5). Before, high-energy surface treatment was performed, and an easily peelable treatment layer was formed on the surface of the cast film.

  This high energy surface treatment was performed on one surface of the casting film, that is, the surface in contact with the first cooling roll (5).

  Further, the time from casting to the start of high energy irradiation by the laser irradiation apparatus as the high energy irradiation apparatus (A) is set to 0.5 seconds, 3.0 seconds, and 5.0 seconds, respectively. High energy irradiation surface treatment was performed.

  Next, the casting film subjected to the high energy surface treatment as described above was brought into contact with the first cooling roll (5) in the same manner as in Example 1 to cast a casting film (100 μm thick) ( Cast film).

  Thereafter, these cast films were treated in the same manner as in Example 1 to prepare three types of cellulose acetate propionate films having a film thickness of 40 μm.

Comparative Example 1
For comparison, a cellulose acetate propionate film is prepared in the same manner as in Example 1, except that the high energy surface treatment is not performed in Comparative Example 1 except for the case of Example 1. In addition, the film is formed.

  Next, in order to evaluate the effect of the high energy surface treatment on the cast film surface of the melt according to the present invention shown in the above Examples 1 to 4, the peel strength of the cast film, the obtained cellulose acetate propio Measurements were made on the transmittance variation of the crossed Nicols (CNT) of the Nate film. Further, the film obtained in Comparative Example 1 was measured in the same manner. The method of each evaluation is shown below.

(Measurement method of peeling force)
About the various cast films in Examples 1 to 4 and Comparative Example 1, the sample from which the release film was peeled was bonded to the object, and peeled off by 90 degrees in accordance with JIS Z 0237, peeling speed of 300 mm / The adhesive strength of min was measured.

  Here, when measuring the peel force of a cast film, the difference between the adhesive tape and the adhesive tape is that the solvent in the film evaporates every moment and the amount of residual solvent at the time of peeling decreases with time. It changes depending on the amount of solvent. Therefore, a sheet such as a food wrap was attached to the film surface side at the start of peeling to temporarily stop the evaporation of the solvent so that measurement with an arbitrary amount of residual solvent was possible.

[Method for measuring variation in crossed Nicols (CNT) transmittance]
About the various cellulose acetate propionate films obtained in Examples 1 to 4 and Comparative Example 1, the width of the film was measured using a polarizing film measuring device (VAP-7070) manufactured by JASCO Corporation at a measurement wavelength of 600 nm. Cross nicol (CNT) transmittance was measured at intervals of 50 mm in the direction and at intervals of 50 mm in the longitudinal direction of 300 mm, and the difference between the average value of all the data and the most deviated value was defined here as variation.

Production of Polarizing Plate Using the cellulose acetate propionate film produced in each of Examples 1 to 4 and Comparative Example 1, a polarizing plate was produced and evaluated according to the method described below.

  According to the following method, the polarizing plate of this invention which used the cellulose acetate propionate film as a protective film for polarizing plates was produced.

1. Production of Polarizing Film A polyvinyl alcohol film having a thickness of 120 μm was uniaxially stretched (temperature: 110 ° C., stretch ratio: 5 times). This was immersed in an aqueous solution composed of 0.075 g of iodine, 5 g of potassium iodide, and 100 g of water for 60 seconds, and then immersed in an aqueous solution of 68 ° C. composed of 6 g of potassium iodide, 7.5 g of boric acid, and 100 g of water. . This was washed with water and dried to obtain a polarizing film.

  Subsequently, according to the following processes 1-5, the polarizing film and the cellulose acetate propionate film were bonded together, and the polarizing plate was produced.

  Step 1: The cellulose acetate propionate films prepared in Examples 1 to 4 and Comparative Example 1 were each immersed in a 2 mol / L sodium hydroxide solution at 50 ° C. for 90 seconds, then washed with water and dried. A protective film (made of polyethylene terephthalate) that can be removed again was attached to the surface provided with the antireflection film in advance for protection.

  Similarly, the cellulose ester film was immersed in a 2 mol / L sodium hydroxide solution at 50 ° C. for 90 seconds, then washed with water and dried.

  Process 2: The above-mentioned polarizing film was immersed in a polyvinyl alcohol adhesive tank having a solid content of 2% by weight for 1 to 2 seconds.

  Step 3: Excess adhesive adhered to the polarizing film in Step 2 was lightly removed, and it was sandwiched between a cellulose acetate propionate film and a cellulose ester film that had been subjected to alkali treatment in Step 1 and laminated.

  Process 4: It bonded together at the speed | rate of about 2 m / min with the pressure of 20-30 N / cm <2> with the two rotating rollers. At this time, care was taken to prevent bubbles from entering.

  Step 5: The sample prepared in Step 4 in a dryer at 80 ° C. was dried for 2 minutes to prepare a polarizing plate.

(Evaluation of polarizing plate)
Next, the polarizing plate on the outermost surface of a commercially available liquid crystal display panel (NEC color liquid crystal display, MultiSync, LCD1525J, model name LA-1529HM) was carefully peeled off, and the polarization direction was adjusted here. A polarizing plate using the cellulose acetate propionate film of No. 4 and a polarizing plate using the cellulose acetate propionate film of Comparative Example 1 were attached to each other. Each liquid crystal display panel thus obtained was visually observed by a plurality of evaluators to look whitish when viewed from the front and obliquely.

Evaluation criteria for unevenness ◎ None of the evaluators can see the unevenness at all ○ Some evaluators may see slight unevenness, but the level is usable as a product △ Many evaluators have seen unevenness even though it was faint × Many evaluations Unevenness was seen.

Table 1 below shows the types of high-energy treatment by the high-energy irradiation device (A) consisting of an atmospheric pressure plasma device, excimer UV device, or laser irradiation device, the time from casting to the start of high-energy irradiation (seconds), melting The peeling force (N / m width) of the web after the start of film formation by a casting film forming apparatus and after 24 hours of operation, variation in crossed Nicol transmittance (%) for the obtained cellulose acetate propionate film, And the polarizing plate visual evaluation about the liquid crystal display panel equipped with the polarizing plate produced using this film was described collectively.

  As is clear from the results in Table 1 above, in Examples 1 to 4 of the present invention, before the cast film contacts the cooling roll (5), the surface of the cast film is subjected to the atmospheric pressure plasma apparatus, the excimer UV. When high-energy surface treatment is performed by a high-energy irradiation device (A) composed of a laser irradiation device or a laser irradiation device, and then the cast film is brought into contact with the surface of the cooling roll (5), the flow is generally reduced. The spread film (film) can be peeled off from the cooling roll (5), and the area that can be taken as production conditions has expanded. And since the release property (peelability) of the cast film from the cooling roll (5) has been improved in this way, the variation in the peel position is reduced, and thereby the longitudinal deviation of expansion and contraction in the width direction of the film. The variation in the crossed Nicols transmittance of the film could be made very small.

  On the other hand, in Comparative Example 1 in which the high energy surface treatment was not performed, there was not much decrease in the peel strength of the cast film, and the variation in the crossed Nicols transmittance of the obtained film was not reduced.

  Conventionally, in the span of several weeks to several months, when the resin melt is extruded from the casting die into a film, the additive gas that evaporates causes the peripheral device to become contaminated, which accumulates and periodically accumulates. However, in Examples 1-4 of the present invention, as a result of performing high-energy surface treatment on the casting film, the additive gas generated simultaneously with the treatment of the casting film surface is decomposed, It was possible to prevent contamination of the device and film.

  Moreover, the liquid crystal display panel equipped with the polarizing plate produced using the cellulose acetate propionate film obtained in Examples 1 to 4 of the present invention has no defects due to foreign matters, and the cellulose acetate obtained in Comparative Example 1 It was confirmed that the liquid crystal display panel equipped with the polarizing plate produced using the propionate film is excellent in display performance.

Example 5
Next, the method for producing the optical film of the present invention was carried out by a solution casting film forming method.

(Preparation of dope)
The following materials were put into a closed container, heated, stirred and completely dissolved and filtered to prepare a dope. Silicon dioxide fine particles (Aerosil R972V) were added after being dispersed in ethanol.

(Dope composition)
Cellulose triacetate (acetyl substitution degree 2.88) 100 parts by weight Triphenyl phosphate 8 parts by weight Biphenyl diphenyl phosphate (liquid plasticizer) 4 parts by weight 5-chloro-2- (3,5-di-sec-butyl-2- Hydroxyphenyl)
-2H-benzotriazole (liquid UV absorber) 1 part by weight Methylene chloride 418 parts by weight Ethanol 23 parts by weight Aerosil R972V 0.1 part by weight (production of cellulose triacetate film)
Using the above dope, a cellulose triacetate film having a thickness of 40 μm was produced as follows.

  Film formation was performed with the manufacturing apparatus shown in FIG. Referring to the figure, the filtered dope was cast into a film from a casting die (23) made of a coat hanger die at a dope temperature of 35 ° C.

  In Example 5, the surface of the casting film (web) cast from the casting die (23) is irradiated with plasma by a normal pressure plasma device which is a high energy irradiation device (A). Before the molten resin of the cast film contacted the support (27), a high energy surface treatment was applied to form an easily peelable treated layer on the surface of the cast film.

  This high energy surface treatment was performed on one surface of the casting film, that is, the surface in contact with the support (27).

  In addition, the residual solvent amount (% by weight) of the web at the start of irradiation of the high energy treatment by the atmospheric plasma device which is the high energy irradiation device (A) and the residual solvent amount (% by weight) at the time of web peeling are as follows. Nine kinds of high energy irradiation surface treatments were carried out by setting as shown in Table 2.

  Next, the cast film subjected to the high-energy surface treatment as described above was cast by being brought into contact with a support body (27) made of SUS316 having a temperature of 20 ° C. and having an ultra-mirror surface polished to an endless belt. .

  After the cast film was peeled from the support (27), it was dried while being conveyed in a roll at 90 ° C., and it was 1.06 times in the width direction in a 100 ° C. atmosphere when the residual solvent amount was 10%. After stretching, release the width holding, finish drying in a 125 ° C. drying zone while transporting rolls, apply a 10 mm width and 8 μm height knurling to both ends of the film, and form a 40 μm-thick cellulose triacetate film. Produced. The film width was 1300 mm, and the winding length was 1500 m.

  Here, as the atmospheric plasma apparatus which is the high energy irradiation apparatus (A), the apparatus shown in FIG.

The point from the plasma injection slit of the atmospheric pressure plasma apparatus to the surface of the casting film (s) is 4 mm, the amount of reaction gas used is 1 m ³ per 1 m of irradiation width, and the atmospheric pressure is 1.0 atm. The points are the same as in the case of the first embodiment.

  In Example 5, the solvent gas concentration around the atmospheric pressure plasma apparatus was 4000 ppm of methylene chloride and 2000 ppm of ethanol in the vicinity of the cast film surface before entering the atmospheric pressure plasma apparatus.

Example 6
(Normal pressure plasma treatment)
Although it implemented similarly to the case of Example 5, the monomer (acetylene) was added to the atmospheric pressure plasma raw material gas.

Nitrogen 94.98% by volume
Oxygen 0.02% by volume
Acetylene 5.00% by volume
In addition, the residual solvent amount (% by weight) of the web at the start of irradiation of the high energy treatment by the atmospheric plasma device which is the high energy irradiation device (A) and the residual solvent amount (% by weight) at the time of web peeling are as follows: As shown in Table 2, each of the nine high energy irradiation surface treatments was performed in the same manner as in Example 5 above, and three types of cellulose triacetate films having a thickness of 40 μm were produced. did.

Example 7
(Excimer UV treatment)
In this example, an excimer UV irradiation device was used as the high energy irradiation device (A). The excimer UV irradiation apparatus is as shown in FIG. 6, and the Xe ₂ wavelength having an irradiance of 40 mW / cm ² in quartz glass (q) having a length in the transport direction of the support (27) of about 300 mm. An apparatus containing four 172 nm excimer UV lamps, with a gap of 4 mm from the quartz glass surface of the lamp to the surface of the casting film and casting the dope from the casting die (23), The substantially full width is irradiated with excimer UV by an excimer UV irradiation device which is a high energy irradiation device (A), and the high energy surface treatment is performed before the cast film of the dope contacts the support (27). Then, an easily peelable treatment layer was formed on the surface of the cast film.

  This high energy surface treatment was performed on one surface of the casting film, that is, the surface in contact with the support (27).

  In addition, the solvent vapor | steam density | concentration of the circumference | surroundings of an excimer UV apparatus was methylene chloride 4000ppm and ethanol 2000ppm in the vicinity of the casting film surface before entering an excimer UV apparatus.

  Moreover, the residual solvent amount (% by weight) of the web at the start of irradiation of the high energy treatment by the excimer UV irradiation device, which is the high energy irradiation device (A), and the residual solvent amount (% by weight) at the time of peeling the web are Nine kinds of high energy irradiation surface treatments were carried out by setting as shown in Table 2.

  Subsequently, the casting film subjected to the high energy surface treatment as described above was brought into contact with the support (27) in the same manner as in Example 1 to form a casting film.

  Thereafter, these cast films were treated in the same manner as in Example 5 to prepare three types of cellulose triacetate films having a film thickness of 40 μm.

Example 8
(Laser irradiation treatment)
In this example, a laser irradiation apparatus was used as the high energy irradiation apparatus (A). The laser irradiation apparatus is as shown in FIG. 7. While casting the dope from the casting die (23), the high energy irradiation apparatus (A) is applied to the surface of the casting film with respect to the substantially entire width of the casting film. A high-energy surface treatment is performed before the cast film comes into contact with the support (27) by irradiating with a laser beam (wavelength 248 nm) of a KrF excimer laser irradiation device and a pulse laser with a pulse width of 100 ns in one shot. Then, an easily peelable treatment layer was formed on the surface of the cast film.

  In addition, the solvent vapor | steam density | concentration of the circumference | surroundings of an excimer UV apparatus was methylene chloride 4000ppm and ethanol 2000ppm in the vicinity of the casting film surface before entering an excimer UV apparatus.

  This high energy surface treatment was performed on one surface of the casting film, that is, the surface in contact with the support (27).

  Further, the following table shows the residual solvent amount (% by weight) of the web at the start of irradiation of the high energy treatment by the laser irradiation device which is the high energy irradiation device (A) and the residual solvent amount (% by weight) at the time of web peeling. Nine kinds of high energy irradiation surface treatments were carried out by setting as shown in FIG.

  Subsequently, the casting film subjected to the high energy surface treatment as described above was brought into contact with the support (27) in the same manner as in Example 1 to form a casting film (cast film). .

  Thereafter, these cast films were processed in the same manner as in Example 1 to prepare three types of cellulose triacetate films having a thickness of 40 μm.

Comparative Example 2
For comparison, a cellulose triacetate film is prepared in the same manner as in Example 5. However, the difference from Example 5 is that Comparative Example 5 was manufactured without performing high-energy surface treatment. The point is that the film was applied.

  Next, in order to evaluate the effect of the high energy surface treatment on the cast film surface of the melt according to the present invention shown in the above Examples 5 to 8, the casting is performed in the same manner as in the above Examples 1 to 4. The peel strength of the film and the transmittance variation of the crossed Nicols (CNT) of the obtained cellulose triacetate film were each measured. Further, the film obtained in Comparative Example 2 was measured in the same manner. The obtained results are shown in Table 2 below.

Production of Polarizing Plate Using the cellulose triacetate film produced in Examples 5 to 8 and Comparative Example 2, in the same manner as in Examples 1 to 4, a polarizing plate was produced, and the evaluation of the polarizing plate was performed. It carried out similarly to the case of the said Examples 1-4. The obtained results are shown in Table 2 below.

Table 2 below shows the type of high-energy treatment by the high-energy irradiation device (A) comprising an atmospheric plasma device, excimer UV device, or laser irradiation device, and the amount of residual solvent (weight) at the start of irradiation of the high-energy treatment. %), Residual solvent amount (% by weight) at the time of web peeling, web peeling force (N / m width) at the start of film formation by a solution casting film forming apparatus and after 24 hours of operation, and cellulose triacetate obtained The variation in crossed Nicols transmittance (%) for the film and the polarizing plate visual evaluation for the liquid crystal display panel equipped with the polarizing plate produced using the film are collectively described.

  As is apparent from the results in Table 2 above, in Examples 5 to 8 of the present invention, the surface of the casting film was contacted with the atmospheric pressure plasma apparatus and the excimer UV before the casting film contacted the support (27). When a high energy surface treatment is performed by a high energy irradiation device (A) comprising an apparatus or a laser irradiation device, and then the dope is brought into contact with the surface of the support (27), the film is peeled off with a low tension as a whole. In the past, there was no area that could not be used as production conditions due to poor peeling, and the area that could be taken as production conditions expanded. Further, as described above, the release property of the cast film from the support (27) has been improved, so that the fluctuation of the peeling position is reduced, thereby reducing the longitudinal deviation of expansion and contraction in the width direction of the film. The variation in crossed Nicols transmittance (CNT) could be made very small.

  On the other hand, in Comparative Example 2 where no high-energy surface treatment was applied, the peel force was not significantly reduced, and the variation in crossed Nicols transmittance (CNT) was not reduced.

  Moreover, the liquid crystal display panel equipped with the polarizing plate produced using the cellulose triacetate film obtained in Examples 5 to 8 of the present invention has no defect due to foreign matter, and the cellulose acetate propionate obtained in Comparative Example 2 It was confirmed that the liquid crystal display panel equipped with the polarizing plate produced using the film was excellent in display performance.

  As is clear from the embodiments of the present invention described above, in the present invention, the casting film is always in a state of being cast from the casting die to the support or immediately after casting. When high-energy treatment is performed with pressure plasma, excimer UV, laser, etc., the peeling force from the cooling roll or support of the casting film is reduced, which can reduce the peeling stress applied to the film during peeling. It is considered that the variation in characteristics can be reduced, specifically, the variation width of the crossed Nicols transmittance (CNT) can be reduced.

  This phenomenon is not fully analyzed because it is difficult to analyze the liquid film that changes its state over time, but the chemical composition of the casting film on the contact surface side with the cooling roll or support changes. Alternatively, it is presumed that the peeling force has decreased due to the formation of the monolayer treatment film.

It is a general | schematic flow sheet which shows 1st Embodiment of the apparatus which enforces the manufacturing method of the optical film of this invention. It is a principal part expansion flow sheet of the manufacturing apparatus of FIG. It is a flow sheet which shows 2nd Embodiment of the apparatus which enforces the manufacturing method of the optical film of this invention. It is a flow sheet which shows the modification of the apparatus of FIG. It is explanatory drawing for demonstrating the principle of the atmospheric pressure plasma apparatus used in the manufacturing method of the optical film of this invention. It is explanatory drawing for demonstrating the principle of the excimer UV apparatus used in the manufacturing method of the optical film of this invention. It is explanatory drawing for demonstrating the principle of the laser irradiation apparatus used in the manufacturing method of the optical film of this invention.

Explanation of symbols

1 Extruder 2: Filter 3: Static mixer 4: Casting die 5: First cooling roll 6: Touch roll 7: Second cooling roll 8: Third cooling roll 9: Peeling roll 10: Film (web)
12: Stretching device 13: Slitter 14: Embossing ring 15: Back roll 16: Winding device F: Optical film (original winding)
21: Melting pot 22: Pump 23: Casting die 24: Depressurization chamber 25: Front and rear winding drum 26: Casting rotationally driven stainless steel drum (support)
27: Stainless steel endless belt for casting (support)
28: peeling roll 29: web 30: roll transport drying device 31: warm air (dry air)
32: Tenter 33: Winder a: Counter electrode of the reactor of the atmospheric pressure plasma apparatus b: Counter electrode of the reactor of the atmospheric pressure plasma apparatus g: Reaction gas s: Casting film u: Excimer UV lamp of the excimer UV apparatus r: Reflector plate p: purge gas i: air curtain / lamp device cooling air e: exhaust q: quartz glass L: laser irradiation device l: laser beam m: variable mirror

Claims (13)

  A method for producing an optical film by a melt casting film forming method or a solution casting film forming method, wherein a surface of a casting film (web) cast from a casting die has an atmospheric pressure plasma device, an excimer UV device, Alternatively, a high energy surface treatment is performed by a laser irradiation device, and an easily peelable treatment layer is formed on the surface of the cast film.   The melt casting film forming method includes a step of casting a melt of a thermoplastic resin from a casting die onto a cooling roll, cooling and solidifying, and peeling off, and casting the melt extruded from the casting die. The atmospheric pressure plasma apparatus, the excimer UV apparatus, on the surface of at least one of both surfaces of the cast film from the start of extrusion until it contacts the surface of the cooling roll or immediately after contacting the surface of the cooling roll, Alternatively, the method for producing an optical film according to claim 1, wherein a high-energy surface treatment is performed by a laser irradiation device to form an easily peelable treatment layer on the surface of the cast film.   Within 5 seconds after the melt is extruded from the casting die and the cast film is formed, the surface of the cast film is subjected to high-energy surface treatment by an atmospheric pressure plasma apparatus, excimer UV apparatus, or laser irradiation apparatus. The method for producing an optical film according to claim 2, wherein an easily peelable treatment layer is formed on the surface of the cast film.   The peeling force when the cast film is peeled from the final cooling roll is 1.0 to 12.0 (N / m width), and the cast film is peeled off after 24 hours of operation of the melt casting film forming apparatus. The method for producing an optical film according to claim 2 or 3, wherein an increase in force is 0.1 to 2.0 (N / m width).   In the solution casting film forming method, a dope (resin solution) in which a thermoplastic resin is dissolved in a solvent is cast from a casting die onto a metal rotating drum or a metal rotating endless belt (hereinafter referred to as a support). A step of forming a casting film and peeling the casting film from the support, wherein the dope casting film coming out of the casting die is in contact with the support surface from the start of casting or the support surface Immediately after contact, at least one of the two surfaces of the cast film is subjected to a high-energy surface treatment using a normal pressure plasma device, an excimer UV device, or a laser irradiation device to The method for producing an optical film according to claim 1, wherein an easily peelable treatment layer is formed.   After the dope is cast from the casting die and the cast film is formed, the atmospheric pressure plasma is formed on the surface of the cast film until the residual solvent amount of the cast film reaches 200% by weight. 6. An optical film according to claim 5, wherein a high-energy surface treatment is performed by an apparatus, an excimer UV apparatus, or a laser irradiation apparatus to form an easily peelable treatment layer on the surface of the cast film. Method.   The method for producing an optical film according to claim 5 or 6, wherein the high-energy surface treatment by an atmospheric pressure plasma apparatus, an excimer UV apparatus, or a laser irradiation apparatus is performed in the presence of at least a solvent vapor.   The high-energy surface treatment by the atmospheric pressure plasma apparatus or the excimer UV apparatus is performed in the presence of at least a solvent vapor and a reaction gas used for the atmospheric pressure plasma apparatus or a purge gas used for the excimer UV apparatus. Item 8. The method for producing an optical film according to any one of Items 5 to 7.   The peel force when the cast film is peeled from the support is 1.0 to 12.0 (N / m width), and the peel force of the cast film after 24 hours of operation of the solution casting film forming apparatus. The method of manufacturing an optical film according to any one of claims 5 to 8, wherein an increase amount of is 0.1 to 2.0 (N / m width).   An optical film manufactured by the method for manufacturing an optical film according to claim 1. It is an optical film of Claim 10, Comprising: A film is arrange | positioned between two polarizing plates orthogonal to each other, the transmittance | permeability of the transmitted light of wavelength 600nm of this film is measured in a crossed Nicol state, and this transmission The optical film is characterized in that the variation in light transmittance is 2 × 10 ^{−5 to} 60 × 10 ⁻⁵ (%).   A polarizing plate comprising the optical film according to claim 10 or 11 as a polarizing plate protective film on at least one of both surfaces of a polarizing film.   A display device comprising the polarizing plate according to claim 12.

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