JP2005246797A - Method for producing optical film, optical film, and polarizing plate using optical film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical film which is useful as a protective film for the polarizing plate of a liquid crystal display (LCD), improved in physical properties, especially improved in curling resistance, application properties, and adhesion after application, and similarly suitable as a protective film for the polarizing plate improved in the physical properties even when a chlorine-free organic solvent is used in consideration of environmental protection in the production of the film, a method for producing the film, and the polarizing plate which uses the optical film and improves the physical characteristics, appearance and visibility of the liquid crystal display. <P>SOLUTION: In the method for producing the optical film by a solution casting film making method using a cellulose ester solution prepared by dissolving a cellulose ester in organic solvents, when the melting point of a main organic solvent for dissolving the cellulose ester is A (°C), and the melting point of an organic additive contained in a cellulose ester film is B (°C), the formula: -120(°C)≤B-A ≤100(°C) is formed. An organic solvent drying speed from the casting on a support to the peeling from the support is set to 5-15%/s corresponding the reduction of an organic solvent. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention is useful as a protective film for a polarizing plate of a liquid crystal display device (LCD) and has improved physical properties, in particular, an optical film having improved curl resistance, coating properties, and adhesion after coating, and The present invention relates to a production method and a polarizing plate using an optical film.

  A cellulose ester film is used as a protective film for a polarizing plate of a liquid crystal display device (LCD). A conventional method for producing a cellulose ester film by a solution casting film forming method is to use a cellulose ester solution (hereinafter also referred to as a dope), an endless support (stainless steel belt or drum) having a mirror-finished surface. ) Is cast from a casting die, and the dope film (also referred to as web) is peeled off by a peeling roll (peeling point), then the web is introduced into a drying apparatus and dried by a drying wind, and further by a winder The cellulose ester film was manufactured by winding up.

  As the protective film for the polarizing plate of LCD, among the cellulose ester films, cellulose triacetate (TAC) film is mainly used. However, as a solvent for dissolving cellulose ester, a cellulose triacetate (TAC) film is conventionally used. Used methylene chloride (dichloromethane).

  However, in the production of such a cellulose triacetate film, generally, due to the physical properties of the film after drying, the film is curled, and the coating property in the coating process of the coating material on the film, In some cases, the adhesion may be insufficient, and further, defects may occur in the physical properties and appearance of the polarizing plate after processing into the polarizing plate, which may impair the visibility of the liquid crystal display.

By the way, the following patent documents related to the improvement of physical properties of the cellulose ester film used for the protective film for polarizing plate include the following.
JP, 10-152568, A The applicant of the present invention firstly uses a cellulose ester film having improved deformation and having little deformation under high temperature and high humidity, and a polarizing plate having excellent durability comprising the cellulose ester film. The invention of the protective film was proposed.

In the invention described in Patent Document 1, the curl value measured under specific conditions of the cellulose ester film is 20 or less in absolute value, and the phthalate ester plasticizer is 1% by weight with respect to the cellulose ester. It was characterized by containing 7% or less.
In addition, the present applicant has previously proposed a method for producing a cellulose triacetate film having good flatness, applicability, and mechanical properties even when the production rate of the film is high. .

  In the invention described in Patent Document 2, when a cellulose triacetate film is produced by a solution casting method using a dope having a solvent content of 300% by weight or more with respect to a dry web, the web is supported by a casting part. The solvent content is reduced at a rate of 300% by weight or less per minute on the body or in the dry region of the dry part after peeling.

  Next, the cellulose triacetate film is produced from a solution using the above methylene chloride solvent by a solution casting film forming method. In recent years, a chlorinated hydrocarbon solvent such as methylene chloride is used in view of protecting the global environment. Therefore, its use is in a direction to be restricted, and there is an increasing demand for avoiding the use of chlorinated hydrocarbon solvents such as methylene chloride.

Prior patent documents relating to attempts to use non-chlorinated hydrocarbon solvents for cellulose ester films used for protective films for polarizing plates include the following.
JP, 2000-53784, A The applicant of the present invention can adjust a high-concentration solution even if a non-chlorine organic solvent is used, and does not require a special dissolution facility as in the cooling dissolution method, making it transparent. A cellulose ester obtained by acylating cellulose with an acetyl group and an acyl group having 3 to 4 carbon atoms is provided for the purpose of providing a method for producing an optical film having excellent mechanical defects and improved optical defects. The invention of the manufacturing method of the optical film which casts the solution melt | dissolved in the non-chlorine type organic solvent on a support body, evaporates a solvent, and forms a film was proposed.

The invention described in Patent Document 3 is characterized in that it defines the acyl group substitution degree and the cellulose polymerization degree.
JP, 2001-188128, A The applicant of the present invention is a film used for optical applications first, and is excellent in wet heat durability for a protective film, particularly a polarizing plate protective film of a liquid crystal display device and a liquid crystal display device. An invention has been proposed for an optical film made of a cellulose ester film having a high strength, few foreign matter defects, and excellent viewing angle characteristics, and a liquid crystal display device using the same.

The invention described in Patent Document 4 is characterized in that it defines the retardation value of an optical film made of a fatty acid cellulose ester film and also defines the degree of acetyl group substitution.
The invention described in Japanese Patent Application Laid-Open No. 2002-86467 improves the liquid aging stability after dissolution and produces a cellulose ester film, particularly a cellulose acylate film, which is free from problems in the mechanical properties and optical properties of the film. In the method for producing a cellulose acylate film in which cellulose acylate is dissolved in a solvent substantially composed of a non-chlorine organic solvent and then formed into a film, the dielectric constant of the solvent is specified. It was a characteristic.

  However, in the conventional inventions described in Patent Documents 1 and 2, the physical properties of the cellulose triacetate film are insufficiently improved, and in particular, the applicability of the film and the adhesion after application are not improved.

  In addition, in the conventional inventions described in Patent Documents 3 to 5, the mechanical properties of cellulose ester films such as cellulose acylate films (for example, the mechanical properties in the vertical direction and the horizontal direction of the film surface) are improved, and the optical characteristics. In addition, in the inventions described in Patent Documents 3 to 5, the non-chlorine organic solvent has low cellulose ester solubility, and is devised to increase the solubility of the cellulose ester. However, with changes in organic solvents, the physical properties of the film after drying also change, and in particular, the curl resistance, coating properties, and adhesion after coating are not improved. As a result, the physical properties and appearance of the polarizing plate are not improved. And there was a problem that the visibility of the liquid crystal display deteriorated.

  The object of the present invention is to solve the above-mentioned problems of the prior art and improve the physical properties of the optical film comprising a cellulose ester film used as a protective film for a liquid crystal display element, that is, a polarizing plate. An optical film suitable for a protective film for a polarizing plate with improved coating properties and adhesion after coating, and a method for producing the same, and considering the environmental safety when producing these films, is non-chlorine. An optical film suitable for a protective film for a polarizing plate, in which the physical properties of the film are improved in the same manner, even when the organic solvent is used, in particular, the curl resistance, coating properties, and adhesion after coating are improved, and the film Providing a production method, and a polarizing plate using these optical films, the physical properties and appearance, and further a liquid crystal display And to provide a visibility enables improved and the polarizing plate.

  As a result of intensive studies in view of the above points, the present inventor has a specific relationship between the boiling point of the organic solvent to be used and the melting point of the organic additive in the film, and the relationship between the drying rate of the organic solvent. Thus, it has been found that the effect of improving the physical properties of the optical film is great. That is, it has been found that the organic additive distribution during film drying is determined by the relationship between the boiling point of the organic solvent used, the melting point of the organic additive in the film, and the drying speed of the organic solvent. It has been found that the distribution of organic additives in the film determines the physical properties of the optical film, particularly the curl resistance, coating properties, and adhesion after coating of the optical film. Furthermore, the present inventor has less physical distribution of the organic additive in the thickness cross-sectional direction of the optical film, that is, the smaller the existing distribution ratio of the organic additive between the front and back surfaces of the optical film, It has been found that the curl improvement effect is great. Moreover, when the curl value of an optical film is below a specific range, it turns out that applicability | paintability and adhesiveness after application | coating are improved, and it came to complete this invention. In particular, when the boiling point of the organic solvent and the melting point of the material (compound) in the film are in a specific relationship, it has also been found that the improvement effect is great, and it has been found that the effect of the present invention can be further increased. . Furthermore, when producing an optical film, even if the organic solvent to be used is a non-chlorine organic solvent, if the same physical characteristics as described above are obtained, the use of the chlorinated organic solvent is suppressed from the viewpoint of the recent global environmental conservation. Can reduce the burden on the environment. And in the case of the present invention, even if the organic solvent to be used is a non-chlorine organic solvent, it has been found that the same physical characteristics as described above can be obtained, and the use of the chlorinated organic solvent can be suppressed, thereby protecting the global environment. Therefore, the effect of the present invention can be further increased, and the present invention has been achieved.

In order to achieve the above object, the invention of the method for producing an optical film according to claim 1 of the present invention comprises preparing a cellulose ester solution in which cellulose ester is dissolved in an organic solvent, and casting the solution on a support. Then, the boiling point of the main organic solvent for dissolving the cellulose ester is A (° C.) When the melting point of the organic additive contained in the cellulose ester film is B (° C.),
−120 (° C.) ≦ B−A ≦ 100 (° C.), and the organic solvent drying rate from casting to support to peeling from the support is 5-15% / sec in terms of decrease in organic solvent. It is characterized by being.

  Invention of the optical film manufacturing method of Claim 2 of this invention is a manufacturing method of the optical film of said Claim 1, Comprising: The organic type additive contained in a cellulose-ester film is a ultraviolet absorber and / Or a plasticizer or a compound having a plasticizer function.

  Invention of the optical film manufacturing method of Claim 3 of this invention is a manufacturing method of the optical film of said Claim 2, Comprising: A plasticizer is a phosphate ester type compound and a phthalate ester type compound, The compound having a plasticizer function is a compound comprising an ester of a fatty acid polyhydric alcohol and one or more monocarboxylic acids.

  Invention of the manufacturing method of the optical film of Claim 4 of this invention is a manufacturing method of the optical film of the said Claim 1, Comprising: It is a manufacturing method of the optical film which consists of a cellulose-ester film with a film thickness of 50 micrometers or less, The organic solvent drying rate from the casting of the cellulose ester solution to the support to the peeling of the web from the support is 5 to 15% / sec in terms of the decrease in the organic solvent.

  Invention of the optical film manufacturing method of Claim 5 of this invention is a manufacturing method of the optical film of the said Claim 1, Comprising: Manufacture of the optical film which consists of a cellulose-ester film more than 50 micrometers in thickness and below 100 micrometers The method is characterized in that the organic solvent drying rate from the casting of the cellulose ester solution to the support to the peeling of the web from the support is 5 to 10% / sec in terms of the decrease in the organic solvent. .

  The invention of the method for producing an optical film according to claim 6 of the present invention is the method for producing an optical film according to claim 1, wherein −120 (° C.) ≦ B−A ≦ 50 (° C.). It is a feature.

  The optical film manufacturing method according to claim 7 of the present invention is the optical film manufacturing method according to claim 1, wherein the organic solvent is a non-chlorine organic solvent.

  The invention of the optical film according to claim 8 of the present invention is characterized by being manufactured by the method for manufacturing an optical film according to any one of claims 1 to 7.

  Invention of Claim 9 of this invention is an optical film manufactured by the manufacturing method of the optical film as described in any one of the said Claims 1-7, Comprising: Front and back of this optical film The ratio of the distribution of organic additives is 50/50 or more and 65/35 or less.

  The invention of the optical film according to claim 10 of the present invention is an optical film produced by the method for producing an optical film according to any one of claims 1 to 7, and is measured under the following conditions. The curl value of the optical film is 20 or less in absolute value.

<Conditions> A film sample is cut into a width direction of 50 mm and a longitudinal direction of 2 mm, temperature-controlled for 24 hours in an environment of a temperature of 23 ± 2 ° C. and a humidity of 55% RH, and the curvature of the film is measured using a curvature scale. Measure curl value.

  The invention of the polarizing plate according to claim 11 of the present invention is that the optical film comprising the cellulose ester film according to any one of claims 8 to 10 is laminated on at least one surface of the polarizer. It is a feature.

In the invention of the method for producing an optical film according to claim 1 of the present invention, as described above, a cellulose ester solution in which cellulose ester is dissolved in an organic solvent is prepared, and this solution is cast on a support to form a web. In the method for producing an optical film composed of a cellulose ester film formed by peeling the web from the support and then drying it, the boiling point of the main organic solvent for dissolving the cellulose ester is A (° C.) in the cellulose ester film. If the melting point of the organic additive contained in B is B (° C),
−120 (° C.) ≦ B−A ≦ 100 (° C.), and the organic solvent drying rate from casting to support to peeling from the support is 5-15% / sec in terms of decrease in organic solvent. According to the invention described in claim 1, the physical properties of an optical film made of a cellulose ester film used as a protective film for a liquid crystal display element, that is, a polarizing plate are improved. There is an effect that an optical film suitable for a protective film for a polarizing plate having improved resistance, coating property, and adhesion after coating can be produced.

  The organic additive here means an organic compound comprising an ultraviolet absorber and / or a plasticizer or a compound having a plasticizer function.

  As described above, the method for producing an optical film according to claim 3 of the present invention is the method for producing an optical film according to claim 2, wherein the plasticizer is a phosphate ester compound and a phthalate ester. According to the invention of claim 3, wherein the compound having a plasticizer function is a compound comprising an ester of a fatty acid polyhydric alcohol and one or more monocarboxylic acids. In particular, it is possible to produce an optical film suitable for a protective film for a polarizing plate with improved curl resistance, coatability, and adhesion after coating. Particularly, when these compounds are used, the adhesion after coating is improved. There is an effect that the improvement effect is great.

  As described above, the method for producing an optical film according to claim 4 of the present invention is the method for producing an optical film according to claim 1, wherein the optical film comprises a cellulose ester film having a thickness of 50 μm or less. It is a production method, characterized in that the organic solvent drying rate from the casting of the cellulose ester solution to the support to the peeling of the web from the support is 5-15% / sec in terms of the decrease in the organic solvent. Therefore, according to the invention described in claim 4, by further narrowing the drying rate of the organic solvent, the physical properties, particularly the curl resistance of the film, the coating property, and the adhesion after coating are improved. There exists an effect that the optical film suitable for a protective film can be manufactured.

  As described above, the method for producing an optical film according to claim 5 of the present invention is the method for producing an optical film according to claim 1, wherein the film has a thickness of more than 50 μm and not more than 100 μm. The organic solvent drying rate between the casting of the cellulose ester solution to the support and the peeling of the web from the support is 5 to 10% / sec in terms of the decrease in the organic solvent. According to the invention described in claim 5, in the case of an optical film having a large film thickness, the physical properties, in particular, of the film, by limiting the drying speed of the organic solvent to a slightly slow range. There is an effect that an optical film suitable for a protective film for a polarizing plate with improved curl resistance, coating property, and adhesion after coating can be produced.

Invention of the optical film manufacturing method of Claim 6 of this invention is a manufacturing method of the optical film of the said Claim 1, as mentioned above,
−120 (° C.) ≦ B−A ≦ 50 (° C.) According to the invention of claim 6, the relationship between the boiling point of the organic solvent used and the melting point of the organic additive By further narrowing down, it is possible to produce an optical film suitable for a protective film for a polarizing plate having improved physical properties, particularly curl resistance, coatability, and adhesion after coating.

  The optical film manufacturing method according to claim 7 of the present invention is, as described above, the optical film manufacturing method according to claim 1, wherein the organic solvent is a non-chlorine organic solvent. According to the invention of claim 7, even if the organic solvent is a non-chlorine organic solvent, there is an effect that the physical properties of the film are not deteriorated. Thus, even if the organic solvent to be used is a non-chlorine organic solvent, since the same physical characteristic is acquired about the optical film which consists of a cellulose ester film, there exists an effect that an environmental load can be reduced.

  The optical film according to claim 8 of the present invention is manufactured by the method for manufacturing an optical film according to any one of claims 1 to 7 as described above. According to the invention of claim 8, an optical film suitable for a protective film for a polarizing plate is obtained in which the physical properties of the optical film are improved, and in particular, the curl resistance, coatability and adhesion after coating are improved. There is an effect that can be.

  The invention of the optical film according to claim 9 of the present invention is an optical film produced by the method for producing an optical film according to any one of claims 1 to 7, as described above, The distribution ratio of the organic additive between the front and back surfaces of the optical film is 50/50 or more and 65/35 or less. According to the invention of claim 9, the physical properties of the optical film The characteristics are improved, and in particular, an effect is obtained that an optical film suitable for a protective film for a polarizing plate having improved curl resistance, coating properties, and adhesion after coating can be obtained.

  The invention of the optical film according to claim 10 of the present invention, as described above, is an optical film produced by the method for producing an optical film according to any one of claims 1 to 7, wherein The curl value of the optical film measured under the above conditions is 20 or less in absolute value.

<Conditions> A film sample is cut into a width direction of 50 mm and a longitudinal direction of 2 mm, temperature-controlled for 24 hours in an environment of a temperature of 23 ± 2 ° C. and a humidity of 55% RH, and the curvature of the film is measured using a curvature scale. Measure curl value.

  According to the invention described in claim 10, when the curl value of the optical film is below a specific range, the physical properties of the film are improved, and in particular, the curl resistance of the film, the coating property, and the adhesion after coating are improved. There exists an effect that the optical film suitable for the protective film for polarizing plates can be obtained.

  In the invention of the polarizing plate according to claim 11 of the present invention, as described above, the optical film comprising the cellulose ester film according to any one of claims 8 to 10 is laminated on at least one surface of the polarizer. According to the invention of claim 11, since the optical film having excellent physical properties is laminated on at least one surface of the polarizer, the physical properties and appearance of the polarizing plate In addition, it is possible to improve the visibility of a liquid crystal display in which a polarizing plate is bonded to a liquid crystal cell, and to produce a liquid crystal display that can maintain stable display performance over a long period of time. There is an effect that it is possible.

  Hereinafter, the present invention will be described in more detail, but the present invention is not limited thereto.

One of the inventions of the method for producing an optical film according to the present invention is to prepare a cellulose ester solution in which cellulose ester is dissolved in an organic solvent, and cast the solution on a support to form a web, and the web is supported on the support. In the method for producing an optical film comprising a cellulose ester film produced by further drying and then drying, the boiling point of the main organic solvent for dissolving the cellulose ester is A (° C.), and the organic additive contained in the cellulose ester film If the melting point of B is B (° C),
−120 (° C.) ≦ B−A ≦ 100 (° C.), and the organic solvent drying rate from casting to support to peeling from the support is 5-15% / sec in terms of decrease in organic solvent. It is.

  Here, if B-A is less than −120 (° C.), the effect of improving the curl resistance, coating properties, and adhesion after coating of the optical film is not observed. On the other hand, when B-A exceeds 100 (° C.), the effect of improving the curl resistance, coating property and adhesion after coating of the optical film is not observed.

The relational expression between the boiling point of the main organic solvent A (° C.) and the melting point of the organic additive contained in the cellulose ester film B (° C.) is as follows:
It is preferable that −120 (° C.) ≦ B−A ≦ 50 (° C.).

  Moreover, in the invention of the method for producing an optical film according to the present invention, the organic solvent drying rate from the casting of the cellulose ester solution to the support until the peeling from the support is 5-15% / sec.

  Here, if the organic solvent drying rate is less than 5% / sec in terms of the decrease in organic solvent, the drying rate is low, which is not preferable in terms of production suitability such as energy load. Also, if the organic solvent drying rate is less than 15% / sec, the decrease in organic solvent, it is not preferable because the drying rate is high, the material distribution in the film changes and the curl resistance of the film deteriorates.

  The organic additive contained in the cellulose ester film is a UV absorber and / or a plasticizer or a compound having a plasticizer function. These will be described later.

  In the manufacturing method of the optical film by this invention, when the optical film obtained consists of a cellulose-ester film with a film thickness of 50 micrometers or less, it is from casting | flow_spread of the cellulose-ester solution to the support body to peeling of the web from a support body. It is preferable that the organic solvent drying rate in the meantime is 5-15% / sec in terms of decrease in organic solvent.

  Here, if the organic solvent drying rate is less than 5% / sec in terms of the decrease in organic solvent, the drying rate is low, which is not preferable in terms of production suitability such as energy load. Also, if the organic solvent drying rate is less than 15% / sec, the decrease in organic solvent, it is not preferable because the drying rate is high, the material distribution in the film changes and the curl resistance of the film deteriorates.

  Moreover, in the manufacturing method of the optical film of this invention, when the optical film obtained consists of a cellulose-ester film with a film thickness exceeding 50 micrometers and 100 micrometers or less, it casts from a support body from casting to the support body of a cellulose-ester solution. It is preferable that the organic solvent drying speed until peeling of the web is 5 to 10% / sec in terms of the decrease in the organic solvent.

  Here, if the organic solvent drying rate is less than 5% / sec in terms of the decrease in organic solvent, the drying rate is low, which is not preferable in terms of production suitability such as energy load. Further, when the organic solvent drying rate is less than 10% / sec, which is a decrease in the organic solvent, the drying rate is high, the material distribution in the film is changed, and the curl resistance of the film is deteriorated.

  In the invention of the method for producing an optical film according to the present invention, the organic solvent may be a non-chlorine organic solvent. Thus, even if the organic solvent used is a non-chlorine organic solvent, the physical properties of the film An optical film made of a cellulose ester film having no deterioration in characteristics can be obtained, and the environmental load can be reduced.

  Next, the invention of the optical film of the present invention is characterized by being manufactured by the above-described optical film manufacturing method, and according to the optical film of the present invention, the physical properties of the film are improved, especially the film. An optical film suitable for a protective film for a polarizing plate with improved curling resistance, coating properties, and adhesion after coating can be obtained.

  Moreover, the invention of the optical film of the present invention is an optical film produced by the method for producing an optical film, wherein the presence ratio of the organic additive between the front and back surfaces of the optical film is 50/50. It is above 65/35.

  Here, the measuring method of the abundance of organic additives such as phosphate ester compounds on the cellulose ester film is as follows. That is, in the region from the surface of the cellulose ester film to a few nm, the number of organic additives such as phosphate ester compounds can be determined using a time-of-flight secondary ion mass spectrometer, such as phosphate ester compounds. It is measured based on the detection probability of organic additives such as phosphate ester compounds for all components detected when measuring organic additive molecules. As a time-of-flight secondary ion mass spectrometer, TFS-2100 manufactured by Physical Electronics Co., Ltd. is used, and measurement is performed by a specified method shown in the apparatus.

  If the distribution ratio of the organic additive between the front and back surfaces of the optical film according to the present invention is less than 50/50 or more than 65/35, the physical properties of the optical film are improved, particularly the curl resistance of the film, coating The effect of improving the adhesion and adhesion after coating is not sufficient.

  Further, the invention of the optical film of the present invention is an optical film produced by the method for producing an optical film described above, and the curl value of the optical film measured under the following conditions is 20 or less in absolute value. is there.

<Conditions> A film sample is cut into a width direction of 50 mm and a longitudinal direction of 2 mm, temperature-controlled for 24 hours in an environment of a temperature of 23 ± 2 ° C. and a humidity of 55% RH, and the curvature of the film is measured using a curvature scale. Measure curl value.

  Here, if the curl value of the optical film exceeds 20 in absolute value, the effect of improving the physical properties of the optical film is not sufficient.

  In the invention of the polarizing plate of the present invention, the optical film composed of the cellulose ester film is laminated on at least one surface of the polarizer. According to the present invention, since the optical film having excellent physical properties is laminated on at least one surface of the polarizer, the physical properties and appearance of the polarizing plate can be improved. In addition, the visibility of a liquid crystal display in which this polarizing plate is bonded to a liquid crystal cell can be improved, and a liquid crystal display capable of maintaining stable display performance over a long period can be manufactured.

  The present invention will be specifically described below.

  Examples of the cellulose ester that is the main component of the optical film of the present invention include cellulose triacetate (TAC), cellulose diacetate, cellulose acetate butyrate, and cellulose acetate propionate (CAP). In the case of cellulose triacetate, cellulose triacetate having a polymerization degree of 250 to 400 and a bound acetic acid amount of 54 to 62.5% is particularly preferable, and a base strength having a bound acetic acid amount of 58 to 62.5% is strong and more preferable. As the cellulose triacetate, either cellulose triacetate synthesized from cotton linter or cellulose triacetate synthesized from wood pulp can be used alone or in combination. It is preferred that the cellulose ester is substantially cellulose triacetate.

  In the method of the present invention, the solvent used for dissolving the cellulose ester may be used alone or in combination, but it is preferable to use a mixture of a good solvent and a poor solvent in terms of increasing production efficiency, and the more good solvent, This is preferable from the viewpoints of the solubility of cellulose ester and the reduction of film foreign matter due to minute insoluble matter. The preferable range of the mixing ratio of the good solvent and the poor solvent is 70 to 98% by weight for the good solvent and 30 to 2% by weight for the poor solvent.

  Here, the good solvent and the poor solvent used in the present invention define a good solvent that dissolves the cellulose ester used alone, and a poor solvent that swells or does not dissolve alone.

  The good solvent used in the present invention is not particularly limited. For example, in the case of cellulose triacetate (TAC), organic halogen compounds such as methylene chloride (DCM), dioxolanes, and cellulose acetate propionate (CAP). Examples include methylene chloride (DCM), acetone, and methyl acetate (MA). The poor solvent is not particularly limited, but for example, methanol, ethanol (EtOH), i-propyl alcohol, n-butanol, cyclohexane, acetone, cyclohexanone and the like are preferably used.

  Examples of the non-chlorine organic solvent for cellulose ester include acetone, methyl acetate (MA), cyclohexanone, ethyl formate, 1,3-dioxolane, 2,2,2-trifluoroethanol, 2,2,3,3- Tetrafluoro-1-propanol, 1,3-difluoro-2-propanol, 1,1,1,3,3,3-hexafluoro-2-methyl-2-propanol, 1,1,1,3,3 Examples include 3-hexafluoro-2-propanol and 2,2,3,3,3-pentafluoro-1-propanol. These solvents may be used alone or in combination of two or more.

  Among these, methyl acetate (MA) and acetone are most preferable as the non-chlorine organic solvent. Methyl acetate and acetone can obtain a film having good solubility and excellent transparency.

  In the present invention, when the cellulose ester is dissolved in a non-chlorine organic solvent to prepare a cellulose ester solution, the blending weight ratio of the non-chlorine organic solvent to the cellulose ester is 2 or more and 5 or less. The blending weight ratio of the non-chlorine organic solvent to the cellulose ester is preferably 2.5 or more and 4.5 or less, and more preferably 3 or more and 4 or less.

  In the present invention, the cellulose ester solution contains a lower alcohol having 1 to 6 carbon atoms for the purpose of improving the solubility, adjusting the viscosity, adjusting the drying speed, and promoting gelation when the solution is cast. You may make it contain. Examples of these lower alcohols include methanol, ethanol, 1-propanol, isopropyl alcohol, 1-butanol, isobutyl alcohol, 2-butanol, t-butyl alcohol, and cyclohexanol. Of these, methanol, ethanol, and 1-butanol are preferable. These lower alcohols are preferably contained in an amount of 2 to 20% by weight based on the total organic solvent. A cellulose ester solution containing a lower alcohol having 1 to 6 carbon atoms has a strong film strength even when it contains a large amount of residual solvent during casting, and is a belt or drum that is a support used for casting. Easy to peel off from above.

  The cellulose ester solution may be prepared by an ordinary method, and is obtained by putting the cellulose ester and the solvent in a container and stirring and mixing at room temperature or under a temperature condition where the solvent does not boil. It is preferable that the stirring and mixing be performed by an apparatus and a system in which no liquid film remains inside the container. Further, the inside of the container may be filled with an inert gas such as nitrogen gas to suppress decomposition. If necessary, a pressurized container or the like may be used and stirred and mixed under pressure.

  The cellulose ester concentration in the solution is preferably as high as possible from the viewpoint of drying efficiency during film formation. On the other hand, when the concentration is too high, the viscosity of the solution is too large, and the flatness of the obtained film may deteriorate. Considering these points, the cellulose ester concentration of a preferable solution is in the range of 15% by weight to 40% by weight. Furthermore, the range of 20% by weight to 35% by weight is preferable.

  The viscosity of the cellulose ester solution may be in a range that allows casting during film formation, and is usually preferably adjusted to a range of 5 P (poise) to 500 P (poise).

  The heating temperature with the addition of the solvent is preferably a temperature not lower than the boiling point of the solvent used and in a range where the solvent does not boil, for example, preferably 60 ° C. or higher and 80 to 110 ° C. The pressure is determined so that the solvent does not boil at the set temperature.

  After dissolution, it is taken out from the container while cooling, or extracted from the container with a pump or the like and cooled with a heat exchanger or the like, and used for film formation.

  The optical film according to the present invention contains a compound comprising a polyhydric alcohol ester of an aliphatic polyhydric alcohol and one or more monocarboxylic acids. The content of the polyhydric alcohol ester with respect to the cellulose ester is 4.5 to 12.5% by weight, preferably 6 to 12% by weight, and more preferably 7 to 11% by weight.

  In the optical film of the present invention, the monocarboxylic acid is preferably a compound having an aromatic ring or a cycloalkyl ring in the molecule.

  In the optical film of the present invention, the aliphatic polyhydric alcohol is preferably 2-20.

  Thus, it is considered that the use of the polyhydric alcohol ester contributes greatly to the ability to reduce the amount of the conventional plasticizer.

  Next, the aliphatic polyhydric alcohol ester used in the present invention will be described. The aliphatic polyhydric alcohol ester is an ester of a dihydric or higher aliphatic polyhydric alcohol and one or more monocarboxylic acids.

(Aliphatic polyhydric alcohol)
The aliphatic polyhydric alcohol used in the present invention is a dihydric or higher alcohol represented by the following general formula (1).

R _1- (OH) n (1)
In the formula, R ₁ represents an n-valent aliphatic organic group, n represents a positive integer of 2 or more, and an OH group represents an alcoholic and / or phenolic hydroxyl group.

  Here, as the n-valent aliphatic organic group, an alkylene group (for example, methylene group, ethylene group, trimethylene group, tetramethylene group, etc.), an alkenylene group (for example, ethenylene group, etc.), an alkynylene group (for example, ethynylene group, etc.), Examples include cycloalkylene groups (for example, 1,4-cyclohexanediyl group) and alkanetriyl groups (for example, 1,2,3-propanetriyl group). The n-valent aliphatic organic group includes those having a substituent (for example, a hydroxy group, an alkyl group, a halogen atom, etc.).

  n is preferably from 2 to 20. Examples of preferable polyhydric alcohol include, for example, 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, Examples thereof include galactitol, mannitol, 3-methylpentane-1,3,5-triol, pinacol, sorbitol, trimethylolpropane, trimethylolethane, xylitol and the like. In particular, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, sorbitol, trimethylolpropane, and xylitol are preferable.

(Monocarboxylic acid)
In the present invention, the monocarboxylic acid in the polyhydric alcohol ester is not particularly limited, and known aliphatic monocarboxylic acid, alicyclic monocarboxylic acid, aromatic monocarboxylic acid and the like 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, compatibility with the cellulose ester is increased, and it is also preferable to use a mixture of acetic acid and another monocarboxylic acid.

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

  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. The aromatic monocarboxylic acid which has, or those derivatives can be mentioned. Benzoic acid is particularly preferable.

(Polyhydric alcohol ester)
The molecular weight of the polyhydric alcohol ester used in the present invention is not particularly limited, but is preferably 300 to 1500, and more preferably 350 to 750. The larger one is preferable in terms of retention, and the smaller one is preferable in terms of moisture permeability and compatibility with the cellulose ester.

  In the present invention, the carboxylic acid in 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. Preferably, it has 3 or more aromatic rings or cycloalkyl rings in the molecule.

Examples of the polyhydric alcohol ester used in the present invention are shown below.

  Among the above polyhydric alcohol esters, trimethylolpropane tribenzoate (TMPTB), trimethylolpropane triacetate, trimethylolpropane tripropionate, dipropylene glycol dibenzoate, tripropylene glycol dibenzoate, 1,3-dibutylene glycol dibenzoate Tetraethylene glycol dibenzoate, mixed ester of trimethylolpropane with acetic acid and benzoic acid, ester of trimethylolpropane with cyclohexanecarboxylic acid, mixed ester of trimethylolpropane with acetic acid and cyclohexanecarboxylic acid, 3-methylpentane- Esters of 1,3,5-triol and cyclohexanecarboxylic acid, S of 3-methylpentane-1,3,5-triol and benzoic acid Le, esters of xylitol and benzoic acid, esters of xylitol and cyclohexanecarboxylic acid.

  In addition, the usage-amount of a polyhydric alcohol ester is preferable 4.5-12.5 weight% with respect to a cellulose ester, 6-12 weight% is further more preferable, Most preferably, it is 7-11 weight%.

  The optical film according to the present invention contains additives such as a plasticizer and an ultraviolet absorber in addition to the cellulose ester, the solvent and the compound comprising the polyhydric alcohol ester.

  Additives such as compounds composed of polyhydric alcohol esters, plasticizers, UV absorbers, etc. can be mixed with a solvent in advance and dissolved or dispersed, and then added to the solvent before dissolving the cellulose ester, or the dope after dissolving the cellulose ester It may be thrown into.

  Although it does not specifically limit as a plasticizer which can be used by this invention, In a phosphate ester type | system | group, a triphenyl phosphate (TPP), a biphenyl diphenyl phosphate (BDP), a tricresyl phosphate, a cresyl diphenyl phosphate, an octyl diphenyl phosphate, For phthalate esters such as trioctyl phosphate and tributyl phosphate, diethyl phthalate, dimethoxyethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, butyl phthalyl butyl glycolate, ethyl phthalyl ethyl glycolate (EPEG), methyl phthalyl ethyl glycolate, butyl phthalyl butyl glycolate and the like can be used.

  The above plasticizers may be used in combination of two or more as required. By containing these plasticizers, a film having excellent dimensional stability and water resistance can be obtained, which is particularly preferable.

  In the present invention, in order to make the water absorption rate and the moisture content within a specific range, the preferable addition amount of the plasticizer is 12% by weight or less with respect to the cellulose ester. When two or more kinds of plasticizers are used in combination, the total amount of these plasticizers may be 12% by weight or less.

  In the present invention, the polyhydric alcohol ester has a plasticizer function, and such a polyhydric alcohol ester and a conventional plasticizer can be used simultaneously. In this case, the polyhydric alcohol ester can be used in the range of 4.5 to 12.5% by weight with respect to the cellulose ester as described above, but the total amount of the polyhydric alcohol ester and the plasticizer is It is preferable that it is 12.5 weight% or less in the weight% with respect to a cellulose ester. In this case, the amount of the plasticizer used is preferably 8.0% by weight or less based on the cellulose ester. Especially, it is preferable that the usage-amount of polyhydric alcohol ester is 7 weight% or more with respect to a cellulose ester, Furthermore, the usage-amount of a plasticizer shall be 5.5 weight% or less with respect to a cellulose ester. Is preferred. The reason is that the use of the polyhydric alcohol ester makes it possible to reduce the amount of the conventional plasticizer used, and the effects of the present invention can be exhibited.

  In addition, the cellulose ester film contains at least one selected from a phosphate ester compound, a phthalate ester compound, a compound comprising a polyhydric alcohol ester of a fatty acid polyhydric alcohol and one or more monocarboxylic acids, Content with respect to the cellulose-ester film of this compound whole quantity is 8.0 weight% or more and 13 weight% or less.

  Here, if the content of the total amount of the above compound relative to the cellulose ester film is less than 8.0% by weight, the effect of the present invention is reduced, which is not preferable. On the other hand, if it exceeds 13% by weight, the dimensional stability is deteriorated.

  Next, the ultraviolet absorber that can be used in the present invention is not particularly limited, but is excellent in the ability to absorb ultraviolet rays having a wavelength of 370 nm or less from the viewpoint of preventing deterioration of the liquid crystal, and has a wavelength of 400 nm or more from the viewpoint of good liquid crystal display properties. Those that absorb as little visible light as possible are preferably used.

  Examples of commonly used compounds include, but are not limited to, oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, and the like.

  Further, fine particles added as a matting agent for the purpose of improving slipperiness and preventing blocking after winding to the optical film of the present invention may be added to the main dope, but it is added to the additive solution from the viewpoint of productivity. Is preferred. Add to additive solution and add to film. Moreover, although it may be contained in the main dope, any fine particles can be used.

  As fine particles used in the present invention, examples of inorganic compounds include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, and hydrated calcium silicate. Mention may be made of aluminum silicate, magnesium silicate and calcium phosphate. Zirconium oxide fine particles are commercially available, for example, under the trade names Aerosil R976 and R811 (manufactured by Nippon Aerosil Co., Ltd.), and can be used. Among these, fine particles containing silicon are preferable in terms of low turbidity, and silicon dioxide is particularly preferable. Examples of these are those commercially available under the trade names Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600 (above, Nippon Aerosil Co., Ltd.). Can do. Furthermore, the silicon dioxide fine particles are preferably silicon dioxide fine particles having a primary average particle diameter of 20 nm or less and an apparent specific gravity of 70 g / liter or more. Examples of the silicon dioxide fine particles that satisfy these requirements include Aerosil 200V and Aerosil R972V, which are particularly preferable because they have a great effect of reducing the friction coefficient while keeping the turbidity of the film low.

  In the present invention, the fine particles are used by adding 0.04 to 0.4% by weight to the cellulose ester. Preferably, it is 0.05 to 0.3% by weight, more preferably 0.05 to 0.2% by weight.

  In the present invention, a dope obtained by dissolving cellulose ester is cast on a support (casting process), and then heated to remove a part of the solvent (drying process on the support), and then from the support. It peels and the peeled film is dried (film drying process), and a cellulose-ester film is obtained.

  As the support in the casting process, a support in which a belt-like or drum-like stainless steel is mirror-finished is used. The temperature of the support in the casting process can be cast in a general temperature range of 0 ° C. to a temperature lower than the boiling point of the solvent, but the dope is gelled by casting on a support at 5 to 30 ° C. Therefore, it is preferable to cast it on a support at 5 to 15 ° C.

  In the drying process on the support, the dope is cast, once gelled, and when the time from casting to peeling is 100%, the dope temperature is 40 ° C. to 70 ° C. within 30% from the casting. By doing so, evaporation of the solvent is promoted, and it can be peeled off from the support as soon as possible, and the peel strength is further increased. The dope temperature is more preferably set to 55 ° C. to 70 ° C. within 30%. This temperature is preferably maintained at 20% or more, more preferably 40% or more.

  Drying on the support is preferably peeled from the support with a residual solvent amount of 60% to 150% because the peel strength from the support is reduced, and more preferably 80 to 120%. The dope temperature at the time of peeling is preferably 0 ° C. to 30 ° C., because the base strength at the time of peeling can be increased and the base breakage at the time of peeling can be prevented, and 5 ° C. to 20 ° C. is more preferable.

  In the film drying step, the film peeled from the support is further dried, and the residual solvent amount is 3% by weight or less, preferably 1% by weight or less, more preferably 0.5% by weight or less. It is preferable for obtaining a good film. In the film drying process, generally, a roll suspension system, a pin tenter system, or a clip tenter system is used for drying while transporting the film. For the liquid crystal display member, it is preferable to dry while maintaining the width by a tenter method in order to improve the dimensional stability.

  The means for drying the film is not particularly limited, and is generally performed with hot air, infrared rays, a heating roll, microwaves, or the like. It is preferable to carry out with hot air in terms of simplicity. The drying temperature is preferably in the range of 40 ° C. to 150 ° C. and divided into 3 to 5 stages, and it is preferable to increase the temperature step by step, more preferably in the range of 80 ° C. to 140 ° C. in order to improve 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.

  The winding machine relating to the production of the optical film of the present invention may be a generally used winding method such as a constant tension method, a constant torque method, a taper tension method, a program tension control method with a constant internal stress. Can be rolled up.

  Although the thickness of the optical film according to the present invention is not particularly limited, it is usually preferably 100 μm or less because it is used for a protective film for a liquid crystal display element used for an LCD, that is, a polarizing plate. An optical film of 20 to 80 μm is preferable.

  As a manufacturing method of the polarizing plate, a general method may be used. Hereinafter, the polarizing plate of the present invention and a liquid crystal display device using the same will be described.

  A conventionally well-known thing can be used as a polarizer used for the polarizing plate of this invention. For example, a film made of a hydrophilic polymer such as polyvinyl alcohol is treated with a dichroic dye such as iodine and stretched, or a plastic film such as vinyl chloride is treated and oriented. The polarizer thus obtained is laminated with a cellulose ester film.

  The polarizing plate of the present invention is configured as an optical compensation film made of a cellulose ester film laminated on at least one side of the polarizer, and in the case of only one side, the cellulose ester film support in which no liquid crystal layer is coated on the other side Body or other transparent support or cellulose triacetate (TAC) film may be used.

  Thus, the obtained polarizing plate may be provided in the cell side surface of a liquid crystal cell, and may be provided in both surfaces side. When provided on one side, a liquid crystal display device can be obtained by attaching an optical compensation film made of a cellulose ester film to the polarizer closer to the liquid crystal cell.

  Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited thereto.

Examples 1-5
(Preparation of dope solution)
A dope solution of cellulose triacetate was prepared as follows.

Cellulose triacetate (TAC): 100 parts by weight UV absorber Tinuvin T-326 (manufactured by Ciba Specialty Chemicals): listed in Table 1 Tinuvin T-171 (manufactured by Ciba Specialty Chemicals): listed in Table 1 Tinuvin T-109 (Manufactured by Ciba Specialty Chemicals): listed in Table 1 Triphenyl phosphate (TPP) (phosphate plasticizer): listed in Table 1 Ethylphthalylethyl glycolate (EPEG) (phthalate plasticizer) : Described in Table 1 Trimethylolpropane tribenzoate (TMPTB) (polyhydric alcohol ester): described in Table 1 Aerosil 200V (manufactured by Nippon Aerosil Co., Ltd.): 0.09 parts by weight Methylene chloride (DCM): 320 parts by weight Acetic acid Methyl (MA): 320 parts by weight Ethanol ( EtOH): 20 parts by weight A cellulose triacetate (TAC) film is produced from the above materials, but the plasticizer is triphenyl phosphate (TPP) (phosphate ester plasticizer), and ethylphthalylethyl glycolate (EPEG). ) (Phthalate ester plasticizer) and trimethylolpropane tribenzoate (TMPTB), which is a polyhydric alcohol ester, were combined as shown in Table 1 to set five types of dope materials.

  When the boiling point of the main organic solvent for dissolving cellulose triacetate is A (° C.) and the melting point of the compound contained in the cellulose triacetate film is B (° C.), the value of B−A is calculated and −120 (° C. ) ≦ B−A ≦ 100 (° C.). In addition, B-A is displayed from the minimum to the maximum.

  Here, the melting point of the plasticizer, the compound having a plasticizer function, and the ultraviolet absorber, and the boiling point of the main organic solvent are as follows.

Boiling point A (° C) of the main organic solvent
Methylene chloride (DCM) = 39.8 ° C.
Methyl acetate (MA) = 57.5 ° C.
Melting point B (° C) of compound contained in film
Triphenyl phosphate (TPP) = 49.5 ° C.
Ethyl phthalyl ethyl glycolate (EPEG) = 13 ° C.
Trimethylolpropane tribenzoate (TMPTB) = 87.1 ° C.
UV absorber Tinuvin T-326 = 141 ° C
Tinuvin T-109 = -56 ° C
Tinuvin T-171 = −56 ° C.
Then, each of these materials was put into a sealed container and completely dissolved while maintaining and stirring at 80 ° C. under pressure.

Table 1 below summarizes the contents of the plasticizer and polyhydric alcohol ester in each example, the type and content of the ultraviolet absorber, the type of organic solvent, and the value of B-A. Here, the content of the polyhydric alcohol ester or the polyhydric alcohol ester and the plasticizer represents parts by weight with respect to 100 parts by weight of cellulose triacetate (TAC).

(Production of film sample)
After the dope solution was filtered, it was cast from a casting die onto a support made of a stainless steel endless belt at a dope temperature of 33 ° C. using a belt casting apparatus (not shown). The support after being held on the support so that the organic solvent drying rate from casting to support is peeled off from the support is 5.2 to 6.0% / sec in terms of decrease in organic solvent It peeled from the top and dried, conveying with many rolls. At this time, using a clip tenter, the film was dried while being stretched 1.07 times in the width direction. After drying, five types of cellulose triacetate (TAC) films having a film thickness of 40 μm were obtained by winding in a roll.

Examples 6 and 7
A dope solution having the same composition as in Example 1 was cast on a support, but the organic solvent drying rate from casting to support to peeling from the support was 9% decrease in organic solvent. . Similar to the case of Example 1, except that the film was held on the support so as to be 5% / sec and 14.5% / sec and then peeled off from the support. A cellulose triacetate (TAC) film was obtained.

Comparative Example 1
For comparison, the same procedure as in Example 1 was performed, but methylene chloride (dichloromethane: DCM) was used as the main organic solvent. As a result, when the boiling point of the main organic solvent for dissolving cellulose triacetate is A (° C) and the melting point of the compound contained in the cellulose triacetate film is B (° C), the value of B-A is -96 ° C to 101 ° C. Thus, the value was out of the range of the present invention. In Table 1, the plasticizer and polyhydric alcohol ester content in Comparative Example 1, the type and content of the ultraviolet absorber, the type of organic solvent, and the value of B-A are also shown. .

  This dope solution is cast on a support, and the organic solvent drying rate from casting to support to peeling from the support is 4.5% / sec. After being held on the body, it was peeled off from the support, and a 40 μm-thick cellulose triacetate (TAC) film was obtained in the same manner.

Comparative Example 2
A dope solution having the same composition as in Example 1 was cast on a support, but the organic solvent drying rate from casting to support to peeling from the support was reduced by 16 Cellulose triacetate (TAC) having a film thickness of 40 μm in the same manner as in Example 1 except that the film was held on the support so as to be 5% / sec (outside the scope of the present invention) and then peeled off from the support. ) A film was obtained.

Examples 8-12
Five types of dope solutions having the same composition as in Examples 1 to 5 are used, but by adjusting the amount of the dope solution supplied from the casting die, five types of cellulose triacetate (TAC) with a film thickness of 80 μm are used. A film was obtained.

Examples 13 and 14
Although it implemented similarly to the case of the said Examples 6 and 7, two types of cellulose triacetate (TAC) films with a film thickness of 80 micrometers were obtained by adjusting the supply amount of the dope solution from a casting die.

Comparative Examples 3 and 4
Although it implemented similarly to the case of the said Comparative Examples 1 and 2, two types of cellulose triacetate (TAC) films with a film thickness of 80 micrometers were obtained by adjusting the supply amount of the dope solution from a casting die.

  Next, for each cellulose triacetate film obtained in Examples 1 to 14 and Comparative Examples 1 to 4 of the present invention, the abundance distribution ratio of the plasticizer (including the compound having a plasticizer function) in the thickness cross-sectional direction of the film, That is, the distribution ratio of the plasticizer between the front and back surfaces of the film was measured, and the obtained results are shown in Tables 2 and 3 below.

(Measurement of distribution ratio of plasticizer)
The amount of plasticizer present on the cellulose ester film is measured by measuring the number of plasticizers in the region from the surface of the cellulose ester film to several nanometers using a time-of-flight secondary ion mass spectrometer. It is measured by the detection probability of the plasticizer for all the components detected. As a time-of-flight secondary ion mass spectrometer, TFS-2100 manufactured by Physical Electronics Co., Ltd. was used, and measurement was performed by a specified method shown in the apparatus.

  Next, for each of the cellulose triacetate films of Examples 1 to 14 and Comparative Examples 1 to 4 according to the present invention, the curl value of the film, the curl suitability at the time of coating, the coating property, and the adhesion of the coating film are measured, The obtained results are shown in Tables 2 and 3 below.

(Measurement of curl value of film)
Each film sample is cut into a width direction of 50 mm and a longitudinal direction of 2 mm. Further, the film pieces were conditioned for 24 hours in an environment of a temperature of 23 ° C. ± 2 ° C. and a humidity of 55% RH, and the curl value of the film was measured using a curvature scale.

(Measurement of film applicability)
Toluene, methyl ethyl ketone, cyclohexane, 2-propanol, and methanol are applied to each cellulose triacetate film that has been cut to a size of 200 mm in length x 50 mm in width, and comprehensive visual inspection is performed for the wettability of each solvent and the presence or absence of cloudiness. Was judged.

(Measurement of curl suitability during film application)
When the above solvent was applied to each cellulose triacetate film, whether or not the film was curled was determined by visual inspection.

(Measurement of film coating film adhesion)
On each of the above cellulose triacetate films, an acrylic resin-based coating solution dissolved in a pre-adjusted organic solvent is applied, dried, and solidified. Was determined by visual inspection.

  In Tables 2 and 3, the evaluation was performed in the following four stages.

◎: Good, ○: Normal, △: Bad, ×: Wrinkle bad (Evaluation of liquid crystal display visibility)
Polarization characteristics of each cellulose triacetate film of Examples 1 to 14 and Comparative Examples 1 to 4 according to the present invention were evaluated. Here, as a method for evaluating polarization characteristics, each cellulose triacetate film was used as a protective film for a polarizing plate, a polarizing plate was prepared from the film according to a conventional method, and further used for a liquid crystal display. The image obtained by the liquid crystal display was observed visually, graded with ◎, ○, Δ, and × according to the visibility of the image, and the obtained results are shown in Table 2 and Table 3 above. .

  As is clear from the results in Tables 2 and 3 above, according to the cellulose triacetate films according to Examples 1 to 14 of the present invention, the curl value, curl suitability, coatability, and coat film adhesion of the film are all. It can be seen that the film is improved, the physical properties of the film are improved, and the film is suitable for a protective film for a polarizing plate.

  In particular, in Examples 1, 3, 5, 6, 7, 8, 10, 12, 13, and 14 of the present invention, the organic solvents used are methyl acetate (MA) and ethyl alcohol (EtOH), both of which are not. Although it is a chlorinated organic solvent, the same physical characteristics have been obtained using these non-chlorinated organic solvents. Therefore, the use of conventional chlorinated organic solvents can be suppressed, and the burden on the global environment is reduced. Can be reduced.

  Furthermore, according to each cellulose triacetate film of Examples 1 to 14 according to the present invention, it can be seen that the visibility of images obtained by a liquid crystal display is good and the polarization characteristics of the film are improved.

  On the other hand, according to the cellulose triacetate films according to Comparative Examples 1 to 4, none of the curl value, curl suitability, coating property, and coating film adhesion of the film was improved, and the physical properties of the film were good. Therefore, these films are not suitable for a protective film for polarizing plates. Moreover, in the cellulose triacetate film of Comparative Examples 1-4, it turns out that the visibility of the image obtained with a liquid crystal display is deteriorated.

Claims (11)

A cellulose ester solution in which cellulose ester is dissolved in an organic solvent is prepared, and this solution is cast on a support to form a web. After the web is peeled off from the support, the cellulose ester film is prepared by drying. In the method for producing an optical film, the boiling point of the main organic solvent for dissolving the cellulose ester is A (° C.), and the melting point of the organic additive contained in the cellulose ester film is B (° C.).
−120 (° C.) ≦ B−A ≦ 100 (° C.), and the organic solvent drying rate from casting to support to peeling from the support is 5-15% / sec in terms of decrease in organic solvent. The manufacturing method of the optical film characterized by the above-mentioned.   The method for producing an optical film according to claim 1, wherein the organic additive contained in the cellulose ester film is an ultraviolet absorber and / or a plasticizer or a compound having a plasticizer function.   The plasticizer is a phosphate ester compound and a phthalate ester compound, and the compound having a plasticizer function is a compound comprising an ester of a fatty acid polyhydric alcohol and one or more monocarboxylic acids. The method for producing an optical film according to claim 2.   A method for producing an optical film comprising a cellulose ester film having a thickness of 50 μm or less, wherein the organic solvent drying rate from the casting of the cellulose ester solution to the support to the peeling of the web from the support is reduced by the organic solvent. The method for producing an optical film according to claim 1, wherein the rate is 5 to 15% / sec.   A method for producing an optical film comprising a cellulose ester film having a film thickness of more than 50 μm and not more than 100 μm, wherein the organic solvent drying speed is from the casting of the cellulose ester solution to the support until the web is peeled from the support. The method for producing an optical film according to claim 1, wherein the organic solvent is reduced by 5 to 10% / sec.   The method for producing an optical film according to claim 1, wherein −120 (° C.) ≦ B−A ≦ 50 (° C.).   The method for producing an optical film according to claim 1, wherein the organic solvent is a non-chlorine organic solvent.   An optical film manufactured by the method for manufacturing an optical film according to claim 1.   It is an optical film manufactured by the manufacturing method of the optical film as described in any one of Claims 1-7, Comprising: The distribution ratio of the organic type additive between the front and back of this optical film is 50/50. The optical film characterized by being 65/35 or less. It is an optical film manufactured by the manufacturing method of the optical film as described in any one of Claims 1-7, Comprising: The curl value of this optical film measured on condition of the following is 20 or less in absolute value An optical film characterized in that
<Conditions> A film sample is cut into a width direction of 50 mm and a longitudinal direction of 2 mm, temperature-controlled for 24 hours in an environment of a temperature of 23 ± 2 ° C. and a humidity of 55% RH. Measure curl value.   The optical film as described in any one of Claims 8-10 is laminated | stacked on the at least single side | surface of a polarizer, The polarizing plate characterized by the above-mentioned.