JP2005313467A - Method for producing cellulose ester film and cellulose ester film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a cellulose ester film which is useful as a protective film for the polarizing plate of liquid crystal display (LCD), can improve winding quality especially in a winding article of at least 5,000 m, and can suppress deterioration in the winding quality even in a winding article with a large load such as for example wind diameter enlargement of at least 5,000 m winding applied and the cellulose ester film. <P>SOLUTION: The method for producing the cellulose ester film includes a process for making the cellulose ester film containing a delustering agent and a process for detecting the friction coefficient of the cellulose ester film immediately after being wound. In the film making process, the amount of the delustering agent to be added is adjusted based on the detected friction coefficient of the film from the detection process. The cellulose ester film, when the friction coefficient of the film immediately after being wound is μ1, and the friction coefficient of the film subjected to temperature and humidity adjustment at a temperature of 23°C and in RH of 55% for 24 h is μ2, meets the formula: 0.5≤μ2/μ1≤1.0. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  INDUSTRIAL APPLICABILITY The present invention is useful as a protective film for a polarizing plate of a liquid crystal display device (LCD), and in particular, a method for producing a cellulose ester film capable of improving winding quality with a wound product of 5000 m or more, and a cellulose ester film It is about.

  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 is, for example, a solution casting film forming method, in which a cellulose ester solution (hereinafter also referred to as a dope) is transferred to an endless support (stainless steel belt or A dope film (also referred to as a web) is peeled off by a peeling roll (peeling point), and then the web is introduced into a drying apparatus and dried while being conveyed to obtain a cellulose ester film. Furthermore, the cellulose ester film was manufactured by winding with a winder. As a protective film for a polarizing plate of LCD, a cellulose triacetate (TAC) film is mainly used among cellulose ester films.

  Conventionally, in the production of a cellulose ester film, the production of a film having a volume of 2000 m has been common, but in recent years, the production of the film has been increased to 2500 m to 4000 m with the expansion of the demand for the cellulose ester film. Because of the high production of film, the film production is expected to exceed 5000 m.

  However, when the winding diameter of the cellulose ester film is increased in this way, the force applied to the wound film is increased, and the appearance of the wound appearance is deteriorated, the slippage between the films is deteriorated, that is, the winding quality is deteriorated. there were.

Prior patent documents relating to the improvement of the surface physical properties of the cellulose ester film used in the protective film for polarizing plate considered to be related to the winding quality of these films include the following.
JP-A-5-53244 has previously proposed an invention for a silver halide photographic support that can be thinned and has excellent film properties without devitrification or adhesion between films.

The invention described in Patent Document 1 is a silver halide photographic support having an undercoat layer containing a matting agent on both sides of the support, the support having a thickness of 50 to 100 μm, One undercoat layer and the other undercoat layer were characterized by containing matting agents having different average particle diameters.
JP, 2001-51378, A The present applicant is the support for a silver halide photographic material which does not cause blocking in the process of winding in the form of a roll and blocking in the process of being wound in the form of a roll and heat-treating. And proposed an invention of a silver halide photographic light-sensitive material that does not cause stains or coating defects in the process of coating and drying of emulsion layers and the like.

In the invention described in Patent Document 2, in a support for a silver halide photographic material having at least one undercoat layer on one side and a back layer on the opposite side, the undercoat layer has an average of A matting agent having a matting agent having a primary particle size of 0.01 to 1.6 μm and a protruding height of the matting agent from the surface of the undercoat layer of 0.002 μm or more. It defined the particle size of the fine particles.
JP, 2001-163994, A The applicant of the present invention previously provided an antistatic layer on a resin film, thereby destroying the antistatic layer in an alkali saponification step when using this as a polarizing plate protective film. Improved film backside, such as the problem that the curl becomes large due to the influence of the coating solvent on the base material and the problem that the additive is deposited at the time of manufacture and contaminates the process or deposits on the film. The invention of the resin film and its manufacturing method with high productivity with sufficient adhesiveness with a polarizer was proposed.

The invention described in Patent Document 3 is characterized in that the concentration of the antistatic agent on at least one surface side is different from the average concentration of the antistatic agent on the entire resin film.
JP, 2004-194106, A The applicant of the present invention, in the case where the polarizing plate protective film is thinned in accordance with the thinning of the liquid crystal display element, the handling property in the film forming step and the polarizing plate making step. Proposed an invention of a cellulose ester film and a method for producing the same.

The invention described in Patent Document 4 is characterized in that 0.04 to 0.3% by mass of fine particles are contained in the film with respect to the cellulose ester. Moreover, it was prescribed | regulated that a mat agent fine particle with an average particle diameter of 1.0-10.0 micrometers was contained in a film.
JP, 2002-265670, A The applicant of the present invention has solved the problems in the film forming process and the polarizing plate making process that occur when the polarizing plate protective film is thinned, and has excellent handling properties. The invention of a cellulose ester film and a method for producing the same was proposed.

In the invention described in Patent Document 5, in the cellulose ester film containing fine particles in the film, the average primary particle size of the fine particles is 5 to 30 nm, and the average major axis size of the fine particles in the film is A. (Nm), when the mass ratio of fine particles to cellulose ester in the film is B (%), A × B is 15 to 120. Further, it was specified that the average particle size of the fine particles in the cellulose ester film was 100 to 2000 nm.
JP, 2002-317059, A The invention of this patent documents 6 dissolved cellulose acylate in a solvent for the purpose of making conveyance nature and scratch resistance good without impairing transparency of cellulose acylate film. In the cellulose acylate film formed by casting the solution, the matting agent content in the cellulose acylate film is 0.03 to 0.15% by weight. Further, it was specified that the matting agent was silicon dioxide having an average particle diameter of 0.5 to 1 μm. The present applicant has previously proposed an invention of a cellulose ester film that does not cause wrinkles or breakage even when the film thickness is thin.

  In the invention described in Patent Document 7, a cellulose ester film having a thickness of 60 μm or less has a coefficient of friction between film contact surfaces at a temperature of 23 ° C. and a humidity of 55% and a coefficient of b at a temperature of 23 ° C. and a humidity of 80%. When the coefficient at the temperature of 23 ° C. and the humidity of 85% is c, 1.0 ≦ b / a ≦ 1.5 and 1.0 ≦ c / a ≦ 5.0, preferably 1.0 ≦ b The relationship of /a≦1.5 and 1.0 ≦ c / a ≦ 2.0 is established. Moreover, the average particle diameter of the microparticles | fine-particles in a cellulose-ester film and the distance between particle | grains were prescribed | regulated.

  However, the conventional inventions described in Patent Documents 1 to 3 above all have a coating layer on the film and relate to the physical properties in the coating layer, and the surface physical characteristics of the film itself have not been improved. Not.

  The conventional inventions described in Patent Documents 4 to 7 all relate to the improvement of the surface physical properties of the cellulose ester film itself, but there is a problem that the effect of the improvement is insufficient.

  The object of the present invention is to solve the above-mentioned problems of the prior art and to improve the winding quality of a cellulose ester film used as a protective film for a liquid crystal display element, that is, a polarizing plate, with a wound product of 5000 m or more. It is in providing the cellulose-ester film which can be manufactured, and its manufacturing method.

  As a result of intensive studies in view of the above points, the present inventor detects the slipperiness of the film related to the winding quality of the cellulose ester film in the manufacturing process of the cellulose ester film, and reflects the result in the manufacturing conditions. As a result, the winding quality of the cellulose ester film can be improved immediately. Especially, even when the load on the wound film is excessive, such as an increase in the film winding diameter, It has been found that the deterioration of the winding quality of the film can be suppressed, and the present invention has been completed.

  In order to achieve the above object, the invention of the method for producing a cellulose ester film according to claim 1 of the present invention comprises a step of forming a cellulose ester film containing a matting agent, and a friction of the cellulose ester film immediately after winding. A coefficient detecting step, and in the film forming step, the addition amount of the matting agent is adjusted based on the detected value of the film friction coefficient from the detecting step.

  The invention according to claim 2 of the present invention is the method for producing a cellulose ester film according to claim 1, wherein in the film friction coefficient detection step, the coefficient of friction between films immediately after winding is measured. Thus, the friction coefficient of the film is detected.

  Invention of Claim 3 of this invention is a manufacturing method of the cellulose-ester film of the said Claim 1, Comprising: The friction coefficient of the cellulose-ester film immediately after winding is 1.00 or less, It is characterized by the above-mentioned.

  Invention of the manufacturing method of the cellulose-ester film of Claim 4 of this invention is equipped with the film frictional resistance detection apparatus in the film conveyance process before winding in the process of forming the cellulose-ester film containing a mat agent, The friction coefficient of the cellulose ester film at the time of conveyance is detected in the middle of the production line (online), and the addition amount of the matting agent is adjusted based on the detected value of the detected film friction coefficient.

  The invention according to claim 5 of the present invention is the method for producing a cellulose ester film according to claim 1 or 4, wherein the matting agent is added in the step of adjusting the amount of the matting agent added to the cellulose ester solution. It is characterized in that the solution to be contained is prepared in advance and the mixing ratio of the matting agent solution added to the cellulose ester main solution is adjusted.

A sixth aspect of the present invention is a cellulose ester film produced by the method for producing a cellulose ester film according to the first aspect, wherein the friction coefficient of the cellulose ester film immediately after winding is μ1, and the temperature is 23. When the friction coefficient of a cellulose ester film conditioned at 24.degree. C. and humidity of 55% RH for 24 hours is .mu.2.
It is characterized by 0.5 ≦ μ2 / μ1 ≦ 1.0.

Invention of Claim 7 of this invention is a cellulose-ester film manufactured by the cellulose-ester film manufacturing method of the said Claim 4, Comprising: Before winding-up detected by the film frictional resistance detection apparatus of a film conveyance process ( Online) When the friction coefficient of cellulose ester film is μP,
It is characterized by 0.5 ≦ μP ≦ 1.0.

  The invention according to claim 8 of the present invention is the cellulose ester film according to claim 6 or 7, wherein the arithmetic average roughness of the film is Ra, the ten-point average roughness is Rz, and the average distance between the local peaks. : Sm is within the following ranges, respectively.

9.0 nm ≦ Ra ≦ 11.0 nm
150 nm ≦ Rz ≦ 250 nm
10nm ≦ Sm ≦ 300nm
Invention of Claim 9 of this invention is the cellulose-ester film as described in any one of the said Claims 6-8, Comprising: The average particle diameter of the matting agent microparticles | fine-particles in a film is 100-500 nm, It is characterized in that the distance between the particles of the matting agent fine particles is 0.3 to 3 μm.

  The invention according to claim 10 of the present invention is the cellulose ester film according to any one of claims 6 to 8, wherein the average particle diameter of the matting agent fine particles in the film is 500 to 1000 nm, It is characterized in that the inter-particle distance of the matting agent fine particles is 1 to 5 μm.

Moreover, invention of Claim 11 of this invention is a cellulose-ester film as described in any one of the said Claims 6-10, Comprising: Furthermore, general formula [I]

(In the formula, A, B and C represent a phenyl group or a biphenyl group, and at least two of A, B and C are biphenyl groups)
It is characterized by containing the compound shown by these.

Invention of Claim 12 of this invention is a cellulose-ester film manufactured by the manufacturing method of the cellulose-ester film as described in any one of the said Claims 6-10, Comprising: Furthermore, general formula [I]

In the compound represented by
Wherein A, B and C represent a phenyl group or a biphenyl group, and at least two of A, B and C are biphenyl groups;
In the formula, A, B and C each represent a phenyl group or a biphenyl group, and at least two of A, B and C contain a compound which is a phenyl group.

  A thirteenth aspect of the present invention is the cellulose ester film according to any one of the sixth to tenth aspects, further comprising an aliphatic polyhydric alcohol and one or more monocarboxylic acids. A compound comprising a polyhydric alcohol ester is contained in an amount of 4.5 to 12.5% by weight with respect to the cellulose ester film.

  A fourteenth aspect of the present invention is the cellulose ester film according to the thirteenth aspect, wherein the monocarboxylic acid is a compound having an aromatic ring or a cycloalkyl ring in the molecule.

  The invention described in claim 15 of the present invention is the cellulose ester film described in claim 13, characterized in that the aliphatic polyhydric alcohol has 2 to 20 valences.

  A sixteenth aspect of the present invention is the cellulose ester film according to the thirteenth aspect, characterized in that the aliphatic polyhydric alcohol has 2-3 valences.

  The invention described in claim 17 of the present invention is the cellulose ester film described in claim 13, characterized in that the aliphatic polyhydric alcohol has 4 or more carbon atoms.

  The invention of the method for producing a cellulose ester film according to claim 1 of the present invention detects the friction coefficient of the cellulose ester film immediately after winding, and the step of forming the cellulose ester film containing the matting agent as described above. In the film forming process, the addition amount of the matting agent is adjusted based on the detected value of the film friction coefficient from the detecting process. According to the invention of claim 1, Film slipperiness related to winding quality is detected from the cellulose ester film immediately after winding, and the result is reflected in the manufacturing conditions, so that the winding quality can be improved immediately and the winding diameter of the cellulose ester film increases. Even if the load on the wound film becomes excessive, the immediate response of the cellulose ester film An effect that reduction and slipperiness of the degradation i.e. the winding quality degradation between the films can be suppressed.

  Moreover, the invention described in claim 2 of the present invention is, as described above, the method for producing a cellulose ester film described in claim 1 above, and in the film friction coefficient detection step, the friction between the films immediately after winding. By measuring the coefficient, the coefficient of friction of the film is detected. According to the invention of claim 2, the coefficient of friction of the film can be reliably detected. Even if the winding diameter is increased and the force applied to the wound film is increased, there is an effect that deterioration of slipperiness between films, that is, deterioration of winding quality can be suppressed.

  Invention of Claim 3 of this invention is a manufacturing method of the cellulose-ester film of the said Claim 1 as mentioned above, Comprising: The friction coefficient of the cellulose-ester film immediately after winding is 1.00 or less According to the invention described in claim 3, since the cellulose ester film immediately after winding has a friction coefficient of 1.00 or less, the winding quality such as deterioration of slipperiness between films is obtained. There is an effect that deterioration can be suppressed.

  The invention of the method for producing a cellulose ester film according to claim 4 of the present invention is, as described above, in the step of forming a cellulose ester film containing a matting agent, the film frictional resistance detecting device in the film conveying step before winding. The friction coefficient of the cellulose ester film at the time of conveyance is detected in the middle of the production line (online), and the addition amount of the matting agent is adjusted based on the detected value of the detected film friction coefficient Therefore, according to the invention described in claim 4, for example, a frictional resistance detection system that makes slight contact with the film is mounted immediately before the winding process during conveyance, and the frictional force is calculated from the relational expression of frictional resistance / contact load. By calculating the coefficient (μp) and reflecting the result in the manufacturing conditions, the winding quality can be improved immediately, and the cellulose ester fiber Even when the load on the wound film is excessive, such as when the roll diameter of the film increases, this immediate response suppresses the deterioration of the winding appearance of the cellulose ester film and the slippage between the films, that is, the deterioration of the winding quality. There is an effect that is.

  In addition, the invention according to claim 5 of the present invention is a method for producing a cellulose ester film according to claim 1 or 4 as described above, wherein the addition amount of the matting agent to the cellulose ester solution is adjusted. In the present invention, a solution containing a matting agent is prepared in advance, and the mixing ratio of the matting agent solution added to the cellulose ester main solution is adjusted. It is possible to reliably adjust the amount of matting agent added to the cellulose ester solution, to improve the winding quality immediately, and to increase the winding diameter of the cellulose ester film. Even if it becomes excessive, this immediate response can cause deterioration of the winding appearance of the cellulose ester film and deterioration of slipperiness between films, that is, deterioration of winding quality. There is an effect that Erareru.

The invention according to claim 6 of the present invention is a cellulose ester film produced by the method for producing a cellulose ester film according to claim 1 as described above, wherein the friction coefficient of the cellulose ester film immediately after winding is determined. When the friction coefficient of the cellulose ester film adjusted to μ1 at a temperature of 23 ° C. and a humidity of 55% RH for 24 hours is μ2,
0.5 ≦ μ2 / μ1 ≦ 1.0
According to the invention described in claim 6, by defining the relationship between the friction coefficient μ1 of the film immediately after winding and the friction coefficient μ2 of the film after temperature control and humidity control The film slipperiness relating to the winding quality can be maintained in a good state. For example, even if the winding diameter of the cellulose ester film is increased and the force applied to the winding film is increased, the film winding appearance is deteriorated or the films are There is an effect that it is possible to prevent the deterioration of the slipperiness, that is, the deterioration of the winding quality.

The invention according to claim 7 of the present invention is a cellulose ester film produced by the method for producing a cellulose ester film according to claim 4 as described above, and is detected by a film frictional resistance detecting device in the film conveying step. When the friction coefficient of the cellulose ester film before winding (online) is μP,
0.5 ≦ μP ≦ 1.0
According to the invention of claim 7, the film slipperiness relating to the winding quality is good by defining the friction coefficient μP of the cellulose ester film before winding (online). For example, even if the winding diameter of the cellulose ester film is increased and the force applied to the wound film is increased, deterioration of the film winding appearance and slipperiness of the films, that is, deterioration of the winding quality may be caused. There is an effect that it can be prevented.

  Thus, the ratio between the coefficient of friction μ1 of the film immediately after winding according to claim 6 and the coefficient of friction μ2 of the film after temperature control: μ2 / μ1 is before winding according to claim 7. It was found that the friction coefficient μp of the (online) film showed almost the same tendency.

  The invention according to claim 8 of the present invention is the cellulose ester film according to claim 6 or 7 as described above, wherein the film has arithmetic average roughness: Ra, ten-point average roughness: Rz, The average interval between the local peaks: Sm is within the following range, respectively.

9.0 nm ≦ Ra ≦ 11.0 nm
150 nm ≦ Rz ≦ 250 nm
10nm ≦ Sm ≦ 300nm
According to the cellulose ester film according to claim 8, the number of contact points when the film contacts can be controlled to a specific range by setting the surface state of the film to a specific range, and the winding quality can be controlled. The film slipperiness related to the film can be kept in a good state. For example, even if the winding diameter of the cellulose ester film is increased and the force applied to the wound film is increased, the film winding appearance is deteriorated and the slipping property between the films is increased. It is possible to prevent the deterioration of the winding, that is, the deterioration of the winding quality.

  Invention of Claim 9 of this invention is the cellulose-ester film as described in any one of the said Claims 6-8, Comprising: The average particle diameter of the matting agent microparticles | fine-particles in a film is 100-500 nm, The distance between the particles of the matting agent fine particles is 0.3 to 3 μm.

  Here, in order to set the friction coefficient of the cellulose ester film after winding within a specific range, fine particles having a specific particle diameter are present at a specific inter-particle distance. That is, the fine particles are not defined by the content or content ratio inside the film, but by the degree of the presence of fine particles, that is, the distance between particles.

  According to the cellulose ester film according to the ninth aspect, as described above, by setting the surface state of the film in the specific range, the ratio of the friction coefficients with different humidity control histories is in the specific range, and the humidity control conditions fluctuated. As a result, the film robustness can be increased. As a result, even if the winding diameter of the cellulose ester film is increased and the force applied to the wound film is increased, the film There is an effect that it is possible to prevent the deterioration of the winding appearance and the slipperiness of the films, that is, the deterioration of the winding quality.

  Invention of Claim 10 of this invention is a cellulose-ester film as described in any one of the said Claims 6-8 as mentioned above, Comprising: The average particle diameter of the matting agent microparticles | fine-particles in a film is 500. ˜1000 nm, and the inter-particle distance of the matting agent fine particles is 1 to 5 μm. According to the invention of claim 10, similarly, the surface state of the film is set to a specific range. Because the ratio of the friction coefficient with different humidity control history is in a specific range, it is possible to suppress the fluctuation of the friction coefficient when the humidity control conditions fluctuate, and as a result, the robustness of the film can be increased, Even if the winding diameter of the cellulose ester film increases and the force applied to the wound film increases, the film winding appearance deteriorates and the slipperiness between films, that is, the wound product An effect that it is possible to prevent deterioration.

  Next, a specific plasticizer is used to set the friction coefficient of the cellulose ester film after winding within a specific range. By using a specific plasticizer, the hygroscopicity and moisture permeability are lowered, and the film moisture resistance is improved when the humidity is changed, which is closely related to the reduction of the friction coefficient and the improvement of the slipping property.

That is, the invention according to claim 11 of the present invention is the cellulose ester film according to any one of claims 6 to 10 as described above, and further includes the general formula [I].

(In the formula, A, B and C represent a phenyl group or a biphenyl group, and at least two of A, B and C are biphenyl groups)
It contains the compound shown by these, It is characterized by the above-mentioned.

  According to the eleventh aspect of the present invention, the ratio of the friction coefficients having different humidity control histories is in a specific range, and the fluctuation of the friction coefficient when the humidity control conditions change can be suppressed. As a result, the robustness of the film Therefore, the coefficient of friction of the cellulose ester film after winding can be set within a specific range, thereby increasing the winding diameter of the cellulose ester film and increasing the force applied to the wound film. Even so, it is possible to prevent deterioration in film winding appearance and slippage between films, that is, deterioration in winding quality. In particular, trisbiphenyl phosphate (TBP) improves the hydrophobicity of the film and, as a result, exhibits an effect of improving slipperiness.

Invention of Claim 12 of this invention is a cellulose-ester film as described in any one of the said Claims 6-10 as above-mentioned, Comprising: Furthermore, general formula [I]

In the compound represented by
Wherein A, B and C represent a phenyl group or a biphenyl group, and at least two of A, B and C are biphenyl groups;
In the formula, A, B and C each represent a phenyl group or a biphenyl group, and at least two of A, B and C contain a phenyl group.

  According to the twelfth aspect of the present invention, the ratio of the friction coefficients having different humidity control histories is in a specific range, and the fluctuation of the friction coefficient when the humidity control conditions change can be suppressed. As a result, the robustness of the film Therefore, even if the winding diameter of the cellulose ester film is increased and the force applied to the wound film increases, deterioration of the film winding appearance and slippage between films, that is, deterioration of winding quality, are prevented. There is an effect that can be done.

  Invention of Claim 13 of this invention is a cellulose-ester film as described in any one of said Claims 6-10 as above-mentioned, Comprising: Furthermore, aliphatic polyhydric alcohol and 1 or more types of The compound comprising a polyhydric alcohol ester with a monocarboxylic acid is contained in an amount of 4.5 to 12.5% by weight based on the cellulose ester film. Since the ratio of the friction coefficients having different moisture histories can be controlled within a specific range, the film winding appearance can be prevented from deteriorating and the slippage between the films, that is, the deterioration of the winding quality can be prevented.

  Invention of Claim 14 of this invention is a cellulose-ester film of the said Claim 13 as mentioned above, Comprising: Monocarboxylic acid is a compound which has an aromatic ring or a cycloalkyl ring in a molecule | numerator. According to the invention described in claim 14, since the ratio of the friction coefficients having different humidity control histories can be controlled within a specific range, the deterioration of the film winding appearance and the slipping property between the films can be controlled. There is an effect that deterioration, that is, deterioration of winding quality can be prevented.

  The invention according to claim 15 of the present invention is the cellulose ester film according to claim 13 as described above, wherein the aliphatic polyhydric alcohol has 2 to 20 valences. Therefore, according to the invention described in claim 15, since the ratio of the friction coefficients having different humidity control histories can be controlled within a specific range, deterioration of the film winding appearance and deterioration of slipperiness between films, that is, winding. There is an effect that deterioration of quality can be prevented.

  A sixteenth aspect of the present invention is the cellulose ester film according to the thirteenth aspect as described above, wherein the aliphatic polyhydric alcohol has 2 to 3 valences. Thus, according to the invention described in claim 16, since the ratio of the friction coefficients with different humidity control histories can be controlled within a specific range, the deterioration of the film winding appearance and the deterioration of slipperiness between films, that is, the winding quality. There is an effect that deterioration can be prevented.

  The invention described in claim 17 of the present invention is, as described above, the cellulose ester film according to claim 13, wherein the aliphatic polyhydric alcohol has 4 or more carbon atoms. Therefore, according to the invention described in claim 17, since the ratio of the friction coefficients having different humidity control histories can be controlled within a specific range, deterioration of the film winding appearance and deterioration of slipperiness between films, that is, winding. There is an effect that deterioration of quality can be prevented.

  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 a cellulose ester film according to the present invention includes a step of forming a cellulose ester film containing a matting agent, and a step of detecting a friction coefficient of the cellulose ester film immediately after winding. In the film process, the addition amount of the matting agent is adjusted based on the detection value of the film friction coefficient from the detection process. Thus, the film slipperiness relating to the winding quality is detected from the cellulose ester film immediately after winding, and the result is reflected in the production conditions, so that the winding quality can be improved immediately. Even when the load on the wound film becomes excessive, such as an increase in the winding diameter, this immediate countermeasure can suppress the deterioration of the winding appearance of the cellulose ester film and the deterioration of the slipperiness between the films, that is, the deterioration of the winding quality.

  In the cellulose ester film production method of the present invention, in the film friction coefficient detection step, the friction coefficient of the film is detected by measuring the friction coefficient between the films immediately after winding. The coefficient of friction can be reliably detected.

  Moreover, in the manufacturing method of the said cellulose-ester film of this invention, it is preferable that the friction coefficient of the cellulose-ester film immediately after winding is 1.00 or less. Thus, since the cellulose-ester film immediately after winding has a friction coefficient of 1.00 or less, deterioration of winding quality, such as deterioration of the slipperiness of films, can be suppressed.

  Next, in the method for producing a cellulose ester film of the present invention, in the step of forming a cellulose ester film containing a matting agent, a film friction resistance detection device is provided in the film conveyance step, and the friction of the cellulose ester film during conveyance is provided. The coefficient is detected in the middle of the production line (online), and the addition amount of the matting agent is adjusted based on the detected value of the detected film friction coefficient.

  Thus, for example, immediately before the winding process during conveyance, a frictional resistance detection system that makes slight contact with the film is mounted, and the friction coefficient (μp) is calculated from the relational expression of frictional resistance / contact load. By reflecting the result on the manufacturing conditions, the winding quality can be improved immediately.

  In the method for producing a cellulose ester film according to the present invention, in the step of adjusting the amount of matting agent added to the cellulose ester solution, a solution containing the matting agent is prepared in advance and added to the cellulose ester main solution. It is preferable to adjust the mixing ratio of the matting agent solution. Thereby, adjustment of the addition amount of the matting agent to a cellulose-ester solution can be implemented reliably, and the immediate improvement of winding quality can be aimed at.

The cellulose ester film according to the present invention has a coefficient of friction of a cellulose ester film immediately after winding as μ1, and a coefficient of friction of a cellulose ester film conditioned at a temperature of 23 ° C. and a humidity of 55% RH for 24 hours as μ2. ,
0.5 ≦ μ2 / μ1 ≦ 1.0.

  Here, if μ2 / μ1 is less than 0.5, the coefficient of friction after humidity control is low, and film slippage tends to occur as a result of film slippage in the wound film, which is not preferable. On the other hand, if μ2 / μ1 exceeds 1.0, the coefficient of dynamic friction after humidity adjustment becomes high, and the appearance of the wound film tends to deteriorate, which is not preferable.

  Note that the ratio of the friction coefficient μ1 of the film immediately after winding and the friction coefficient μ2 of the film after temperature control: μ2 / μ1 is almost the same as the friction coefficient μp of the film immediately before winding (online) It turned out to show a tendency.

  That is, the cellulose ester film according to the present invention has 0.5 ≦ μP ≦ 1.0 when the friction coefficient of the cellulose ester film before winding detected by the film frictional resistance detecting device in the film conveying step is μP. .

  Here, if μP is less than 0.5, the coefficient of friction is low, and as a result of film slippage in the wound film, winding deviation tends to occur, which is not preferable. On the other hand, if μP exceeds 1.0, the dynamic friction coefficient is increased, and the appearance deterioration of the wound film tends to occur, which is not preferable.

  In these cases, the friction coefficient test of the cellulose ester film is performed, for example, as follows.

Measuring method Surface property tester manufactured by Shinto Chemical Co., Ltd. TYPE14S, TYPE18L, TYPE32, Trispostation, and similar models, applying an arbitrary load using a contact indenter as appropriate, and conducting a friction coefficient test It can ask for. For the contact indenter, various optional tools can be used. The coefficient of friction can be obtained by a predetermined method specified in the apparatus.

  Note that the above measurement method is an example, and is not limited to this. The dynamic friction coefficient and the static friction coefficient can be appropriately determined by a similar method using a similar measuring machine. . Further, the friction coefficient μ1 of the cellulose ester film immediately after winding may be measured online or may be measured offline.

  In the cellulose ester film according to the present invention, the arithmetic average roughness of the film: Ra, the ten-point average roughness: Rz, and the average interval between local peaks: Sm are within the following ranges, respectively.

9.0 nm ≦ Ra ≦ 11.0 nm
150 nm ≦ Rz ≦ 250 nm
10nm ≦ Sm ≦ 300nm
By maintaining the arithmetic average roughness (Ra), ten-point average roughness (Rz), and the average distance (Sm) between the local peaks in the above ranges, the film slipperiness related to the winding quality is in a good state. For example, even if the winding diameter of the cellulose ester film is increased and the force applied to the wound film is increased, the deterioration of the film winding appearance and the slipperiness of the films, that is, the deterioration of the winding quality is prevented. be able to.

  In addition, the cellulose ester film according to the present invention has an average particle diameter of the matting agent fine particles in the film (an average value of so-called secondary particle diameters of the matting agent fine particles in the film) of 100 to 500 nm, and between the particles of the matting agent fine particles. The distance (the distance between the so-called secondary particles of the matting agent fine particles in the film) is 0.3 to 3 μm.

  Here, if the average particle diameter of the matting agent fine particles in the film is less than 100 μm, the number of contact points when the films are overlapped decreases, and the friction resistance between the films increases. This is not preferable because it tends to cause appearance deterioration. On the other hand, if the average particle size of the matting agent fine particles exceeds 500 nm, the transparency of the film deteriorates and the appearance of the film deteriorates, which is not preferable. Further, if the inter-particle distance of the matting agent fine particles is less than 0.3 μm, the transparency of the film deteriorates and the appearance of the film deteriorates, which is not preferable. Further, when the distance between the particles of the matting agent fine particles exceeds 3 μm, the number of contact points when the films are overlapped decreases, and as a result of increasing the frictional resistance between the films, it is easy to cause deterioration of the appearance of the film in the wound film. Therefore, it is not preferable.

  Furthermore, in the cellulose ester film according to the present invention, the average particle diameter of the matting agent fine particles in the film is 500 to 1000 nm, and the interparticle distance of the matting agent fine particles is 1 to 5 μm.

  Here, if the average particle diameter of the matting agent fine particles in the film is less than 500 nm, the number of contact points when the films are overlapped decreases, and the frictional resistance between the films increases. As a result, the appearance of the film in the wound film Since it tends to cause deterioration, it is not preferable. Further, if the average particle size of the matting agent fine particles exceeds 1000 nm, the transparency of the film deteriorates and the appearance of the film deteriorates, which is not preferable. Further, if the inter-particle distance of the matting agent fine particles is less than 1 μm, the transparency of the film deteriorates and the appearance of the film deteriorates, which is not preferable. Further, when the inter-particle distance of the matting agent fine particles exceeds 5 μm, the number of contact points when the films are overlapped with each other is reduced, and as a result, the frictional resistance between the films is increased. It is not preferable.

  The present invention will be specifically described below.

  Examples of the cellulose ester that is the main component of the cellulose ester 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, 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 cellulose ester film according to the present invention further has the general formula [I].

(In the formula, A, B and C represent a phenyl group or a biphenyl group, and at least two of A, B and C are biphenyl groups)
The compound shown by these is contained. In particular, trisbiphenyl phosphate (TBP) improves the hydrophobicity of the film and, as a result, exhibits an effect of improving slipperiness.

The cellulose ester film according to the present invention further has the general formula [I].

In the compound represented by
Wherein A, B and C represent a phenyl group or a biphenyl group, and at least two of A, B and C are biphenyl groups;
In the formula, A, B and C each represents a phenyl group or a biphenyl group, and at least two of A, B and C contain a phenyl group.

  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.

  The cellulose ester film according to the present invention further 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 cellulose ester 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 cellulose ester 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 2-20 valent aliphatic polyhydric alcohol and one or more monocarboxylic acids.

The aliphatic polyhydric alcohol used in the present invention is a divalent to 20-valent alcohol represented by the following general formula [II].

R _1- (OH) n ... [II]
In the formula, R ₁ represents an n-valent aliphatic organic group, n represents a positive integer of 2 to 20, and the 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 300-1500, and more preferably 350-750. 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 cellulose ester film according to the present invention contains an additive such as 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 and UV absorbers are mixed with a solvent in advance, dissolved or dispersed, and then added to the solvent before dissolving the cellulose ester, or added to the dope after dissolving the cellulose ester. May be.

  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.

  The fine particles added as a matting agent for the purpose of improving the slipperiness and preventing blocking after winding of the cellulose ester film of the present invention may be added to the main dope. Is preferable. 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. And 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. Further, 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 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. 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 winder related to the production of the cellulose ester film of the present invention may be a commonly used winder such as a constant tension method, a constant torque method, a taper tension method, a program tension control method with a constant internal stress. It can be wound up by the method.

  The thickness of the cellulose ester film according to the present invention is not particularly limited, but is usually preferably 100 μm or less because it is used for a protective film for a liquid crystal display element used for LCD, that is, a polarizing plate. A cellulose ester film having a thickness of 20 to 80 μm is preferred.

  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 1-3
(Preparation of dope solution)
A dope solution of cellulose triacetate (TAC) was prepared as follows.

Cellulose triacetate (acetyl substitution degree 2.88) 100 parts by weight Tinuvin T-326 (manufactured by Ciba Specialty Chemicals) 1 part by weight Triphenyl phosphate (TPP) (phosphate ester plasticizer)
Ethyl phthalyl ethyl glycolate (EPEG) (phthalate ester plasticizer)
Trimethylolpropane tribenzoate (TMPTB) (polyhydric alcohol ester)
Total 10 parts by weight of plasticizer and / or polyhydric alcohol ester Aerosil 200V 0.02 to 0.30 parts by weight (silicon dioxide matting agent, manufactured by Nippon Aerosil Co., Ltd.)
Methylene chloride (DCM) 320 parts by weight Methyl acetate (MA) 320 parts by weight Ethanol (EtOH) 20 parts by weight A cellulose triacetate film is produced from the above materials, but a plasticizer, triphenyl phosphate (TPP) (phosphate ester) System plasticizer), ethyl phthalyl ethyl glycolate (EPEG) (phthalate ester plasticizer), and trimethylolpropane tribenzoate (TMPTB) which is a polyhydric alcohol ester, as shown in Table 1, Three types of dope materials were set.

  Then, each of these materials was put into a sealed container and completely dissolved while maintaining and stirring at 80 ° C. under pressure.

(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 web formed on the support was peeled off from the support with a peeling roll and dried while being conveyed by a number of rolls. At this time, drying was performed using a clip tenter while stretching the film in the width direction. After drying, three types of cellulose triacetate films having a film thickness of 40 μm were obtained by winding up into a roll.

  In the method for producing a cellulose triacetate film of the present invention, in the film friction coefficient detection step, a device for detecting the friction coefficient immediately after winding the film is equipped, and the frictional resistance force immediately after winding the film is offline. The friction coefficient was calculated from the friction resistance force / contact load, and the friction coefficient (μ1) immediately after winding the film was detected.

  The measurement of the coefficient of friction (μ1) immediately after winding the cellulose triacetate film was performed as follows.

Measurement method Using a surface property tester TYPE14S, TYPE18L, TYPE32, Trispostation, manufactured by Shinto Chemical Co., Ltd., and applying a desired load using a contact indenter, and performing a friction coefficient test. For the contact indenter, various optional tools can be used. The coefficient of friction was determined by a predetermined method specified in the apparatus.

  And in this invention, in the process of forming the cellulose triacetate film containing a mat agent, the addition amount of the mat agent was adjusted based on the detected value of the film friction coefficient from the detection process. In this case, a correlation line (correlation equation) between the addition amount of the matting agent and the friction coefficient is prepared in advance, an appropriate addition amount is obtained according to the detected value of the friction coefficient, the addition amount is determined accordingly, and the mat The addition amount of the agent was adjusted.

  In Examples 1 to 3 of the present invention, in the step of adjusting the amount of matting agent added to the cellulose triacetate solution, a matting agent is prepared in advance and added to the cellulose triacetate main solution. The mixing ratio of the solution was adjusted.

  Table 1 below shows the types of plasticizers and polyhydric alcohol esters used, the coefficient of friction (μ1) of the film immediately after winding, a temperature of 23 ° C., and a humidity of 55% RH. The friction coefficient (μ2) of each film was shown. The ratio of the coefficient of friction (μ2) of the film after temperature control and the coefficient of friction (μ1) of the film immediately after winding: μ2 / μ1 was calculated and shown in Table 1.

Comparative Examples 1-3
For comparison, a cellulose triacetate film having a film thickness of 40 μm is produced in the same manner as in Example 1 above. In Comparative Examples 1 and 2, the coefficient of friction (μ 2) of the film after temperature control and winding is taken up. The ratio with the coefficient of friction (μ1) of the film immediately after this: the case where μ2 / μ1 exceeds 1.0, which is outside the range of the present invention. In Comparative Example 3, μ2 / μ1 is outside the range of the present invention. A case of less than 0.5 is shown.

(Evaluation of winding quality)
The winding quality of each cellulose triacetate film of Examples 1 to 3 and Comparative Examples 1 to 3 according to the present invention was evaluated. Here, as an evaluation method of the winding quality, each cellulose triacetate film was used as a wound film, the appearance was confirmed, and the evaluation was performed based on the number of protrusions observed on the protrusions. In Table 1, the evaluation was made in the following four stages.

◎: 0-5, ○: 6-10, Δ: 11-20, x: 21 or more (arithmetic average roughness: Ra, ten-point average roughness: Rz, average interval between local peaks: Sm Measurement)
Moreover, in this invention, the surface roughness of a film is adjusted by addition of the said microparticles | fine-particles, 1m2 of each cellulose triacetate film obtained in the said Examples 1-3 and Comparative Examples 1 and ² was sampled. Then, the average value of arithmetic average roughness (Ra) on both sides of the film, the average value of ten-point average roughness (Rz), and the average distance (Sm) between local peaks were measured according to the method of JIS K7125.

That is, using a film surface roughness measuring machine (WYKO-NT1100) manufactured by Veeco, the measurement was carried out on each side of the film at a magnification of 20 times, and the average value was calculated as the arithmetic average roughness ( Ra) and ten-point average roughness (Rz). Moreover, the point which becomes a trough from the peak of a roughness curve was made into the change point, and the average value of the space | interval from a change point to the next change point was made into the average space | interval (Sm) of a local peak. The results obtained are summarized in Table 1 below.

  As is apparent from the results in Table 1 above, in Examples 1 to 3 of the present invention, the ratio between the friction coefficient μ1 of the cellulose triacetate film immediately after winding and the friction coefficient μ2 of the cellulose triacetate film after temperature adjustment. : Μ2 / μ1 are both 1.00 or less. Therefore, in Examples 1 to 3 of the present invention, the film slipperiness relating to the winding quality can be maintained in a good state. For example, the winding diameter of the cellulose triacetate film is increased, and the force applied to the winding film is increased. However, it is possible to prevent the deterioration of the film winding appearance and the slipperiness of the films, that is, the deterioration of the winding quality.

  Moreover, in Examples 1-3 of this invention, the winding quality of a cellulose triacetate film is favorable, and it turns out that the film has the outstanding physical property and is suitable for the protective film for polarizing plates. . Further, in Examples 1 to 3 of the present invention, the arithmetic average roughness (Ra) of the cellulose triacetate film is 9.5, the ten-point average roughness (Rz) is 170, and the average interval (Sm) between the local peaks. Is 250, it is presumed that the contact area when the films are superposed is in an appropriate state, the coefficient of friction between the films is within the scope of the present invention, and the winding quality is good.

  On the other hand, in Comparative Examples 1-3, it turns out that the winding quality of a cellulose triacetate film is inferior, the surface physical property of a film is inferior, and it is not suitable for the protective film for polarizing plates. In Comparative Examples 1 and 2, the arithmetic average roughness (Ra) of the cellulose triacetate film is as low as 6.0 and 8.0, and the ten-point average roughness (Rz) is as low as 80 and 110. On the contrary, since the average distance (Sm) between the local peaks is as high as 650 and 400, it is estimated that the contact area when the films are superposed is reduced, and the friction coefficient between the films is within the scope of the present invention. The roll quality deteriorates.

  Furthermore, in Comparative Example 3, the arithmetic average roughness (Ra) of the cellulose triacetate film is as high as 13.0, and the ten-point average roughness (Rz) is as high as 300. The average interval (Sm) was as low as 100 and the winding quality was good, but the film smoothness deteriorated and was unbearable for practical use.

Examples 4-6
In the same manner as in Examples 1 to 3 above, a cellulose triacetate film having a film thickness of 40 μm is obtained. In this example, in the step of forming a cellulose triacetate film containing a matting agent, the winding of the film transport step A frictional resistance detection system that makes slight contact with the film is installed immediately before the film is taken, and the friction coefficient of the cellulose triacetate film during conveyance is detected on the production line (online). The addition amount of the matting agent was adjusted based on the detected value of μp). In this case, a correlation line (correlation equation) between the addition amount of the matting agent and the friction coefficient is prepared in advance, an appropriate addition amount is obtained according to the detected value of the friction coefficient, the addition amount is determined accordingly, and the mat The addition amount of the agent was adjusted.

  In Examples 4 to 6 of the present invention, in the step of adjusting the amount of matting agent added to the cellulose triacetate solution, a matting agent is prepared in advance and added to the cellulose triacetate main solution. The mixing ratio of the solution was adjusted.

  Table 2 below shows the types of plasticizer and polyhydric alcohol ester used, and the friction coefficient (μp) of the film immediately before winding (online).

Comparative Examples 4-6
For comparison, a cellulose triacetate film having a film thickness of 40 μm is produced in the same manner as in Examples 4 to 6, but in Comparative Examples 4 and 5, the friction coefficient (μp) of the film immediately before winding (online). Shows a case of exceeding 1.0, which is outside the scope of the present invention. In Comparative Example 6, the friction coefficient (μp) of the film immediately before winding (online) is less than 0.5, which is outside the scope of the present invention. The case is shown.

(Evaluation of winding quality)
The winding quality of each cellulose triacetate film of Examples 4 to 6 and Comparative Examples 4 to 6 according to the present invention was evaluated in the same manner as in Examples 1 to 3 above.

(Arithmetic mean roughness: Ra, Ten-point mean roughness: Rz, Average distance between local peaks: Measurement of Sm)
In the present invention, which surface roughness of the film by the addition of the fine particles is adjusted, by sampling 1 m ² of the cellulose triacetate films obtained in 5 as in Example 4-6 and Comparative Example 4 The average value of the arithmetic average roughness (Ra) on both sides of the film, the average value of the ten-point average roughness (Rz), and the average interval (Sm) of the local summits are the same as in Examples 1 to 3 above. Measured. The results obtained are summarized in Table 2 below.

  As is clear from the results in Table 2 above, in Examples 4 to 6 of the present invention, the friction coefficient μP of the cellulose triacetate film immediately before winding is 1.00 or less. Therefore, in Examples 4 to 6 of the present invention, the film slipperiness relating to the winding quality can be maintained in a good state. For example, the winding diameter of the cellulose triacetate film is increased, and the force applied to the winding film is increased. However, it is possible to prevent the deterioration of the film winding appearance and the slipperiness of the films, that is, the deterioration of the winding quality.

  Moreover, in Examples 4-6 of this invention, the winding quality of a cellulose triacetate film is favorable, and it turns out that the film has the outstanding physical property and is suitable for the protective film for polarizing plates. . Furthermore, in Examples 4 to 6 of the present invention, the arithmetic average roughness (Ra) of the cellulose triacetate film is 9.5, the ten-point average roughness (Rz) is 170, and the average distance (Sm) between the local peaks. Is 250, it is presumed that the contact area when the films are superposed is in an appropriate state, the friction coefficient between the films is within the scope of the present invention, and the winding quality is good.

  Thus, the friction coefficient (μp) of the film immediately before winding (online), the friction coefficient (μ2) of the film after temperature adjustment in Examples 1 to 3 above, and the friction coefficient of the film immediately after winding (μ2) It was found that the ratio to μ1): μ2 / μ1 showed almost the same tendency.

  On the other hand, in Comparative Examples 4-6, it turns out that the winding quality of a cellulose triacetate film is bad, the surface physical property of a film is inferior, and it is not suitable for the protective film for polarizing plates. In Comparative Examples 4 and 5, the arithmetic average roughness (Ra) of the cellulose triacetate film is as low as 6.0 and 8.0, and the ten-point average roughness (Rz) is as low as 80 and 110. On the contrary, since the average distance (Sm) between the local peaks is as high as 650 and 400, it is estimated that the contact area when the films are superposed is reduced, and the friction coefficient between the films is within the scope of the present invention. The roll quality deteriorates.

  Further, in Comparative Example 5, the arithmetic average roughness (Ra) of the cellulose triacetate film is as high as 13.0, and the ten-point average roughness (Rz) is as high as 300. The average interval (Sm) was as low as 100, and the winding quality was good, but the film smoothness deteriorated and it was not practical.

Example 7
In the same manner as in Example 1, a cellulose triacetate film having a thickness of 40 μm was obtained. As in Example 1, the film friction coefficient detection step is equipped with a frictional resistance detection system that makes slight contact with the film immediately after the film is wound, and the frictional force / contact load causes friction. The coefficient of friction was calculated and the coefficient of friction between the films immediately after winding was measured to detect the coefficient of friction (μ1) immediately after winding the film. In addition, the friction coefficient test of the cellulose triacetate film was implemented similarly to the case of the said Examples 1-3.

  Table 3 below shows the types of plasticizers and polyhydric alcohol esters used, and after adjusting the temperature for 24 hours at a coefficient of friction (μ1) of the film immediately after winding, a temperature of 23 ° C., and a humidity of 55% RH. The friction coefficient (μ2) of each film was shown. Further, the ratio of the coefficient of friction (μ2) of the film after temperature control and the coefficient of friction (μ1) of the film immediately after winding: μ2 / μ1 was calculated and shown in Table 3.

Comparative Examples 7 and 8
For comparison, a cellulose triacetate film having a film thickness of 40 μm is produced in the same manner as in Example 7. In Comparative Example 7, the coefficient of friction (μ 2) of the film after temperature adjustment and immediately after winding. The ratio with the coefficient of friction (μ1) of the film: the case where μ2 / μ1 exceeds 1.0, which is outside the scope of the present invention, is shown. In Comparative Example 8, the ratio of the coefficient of friction (μ2) of the film after temperature adjustment and the coefficient of friction (μ1) of the film immediately after winding is less than 0.5, which is outside the scope of the present invention. The case is shown.

(Evaluation of winding quality)
For each cellulose triacetate film of Example 7 and Comparative Examples 7 and 8 according to the present invention, the winding quality of the film was evaluated in the same manner as in Example 1 above, and the results obtained are shown in Table 3. .

For each cellulose triacetate film obtained in Example 7 and Comparative Examples 7 and 8, the average particle diameter of the matting agent (silicon dioxide fine particles) was measured, and the interparticle distance of the fine particles was measured. The interparticle distance was measured by observing the film surface and cross section with a scanning electron microscope. That is, the average of the interparticle distance per observation place on a 20 μm square plane was determined. Furthermore, the average of the distance between particles was calculated by taking five observation points. The average of the values thus obtained was defined as the interparticle distance. The obtained results are shown in Table 3 below.

  As is apparent from the results of Table 3 above, according to the cellulose triacetate film according to Example 7 of the present invention, the winding quality of the cellulose triacetate film is good, and the film has excellent physical properties. It can be seen that the film is suitable for a protective film. In Example 7, the average particle diameter of the matting agent (silicon dioxide fine particles) in the cellulose triacetate film was 700 nm, and the distance between the fine particles in the film was 3 μm.

  On the other hand, in Comparative Examples 7 and 8, it can be seen that in any case, the winding quality of the cellulose triacetate film is poor, the surface physical properties of the film are inferior, and it is not suitable for a protective film for polarizing plate. In Comparative Example 7, the average particle size of the matting agent (silicon dioxide fine particles) in the cellulose triacetate film was 250 nm, and in Comparative Example 8, it was 1200 nm. Further, the distance between the fine particles in the film was 4 μm in Comparative Example 7 and 2 μm in Comparative Example 8.

  As a result, according to the cellulose triacetate film according to Example 7 of the present invention, compared to the cellulose triacetate films of Comparative Examples 7 and 8, it is estimated that the contact area when the films are overlapped is in an appropriate state. The coefficient of friction between films is within the scope of the present invention, and the winding quality is good.

Example 8
In the same manner as in Example 7, a cellulose triacetate film having a thickness of 40 μm was obtained. That is, in the process of forming a cellulose triacetate film containing a matting agent, a frictional resistance detection system that makes slight contact with the film immediately before winding of the film transporting process is installed, and the friction coefficient of the cellulose triacetate film during transporting is determined. It was detected in the middle of the production line (online), and the amount of matting agent added was adjusted based on the detected value of the coefficient of film friction (μp) immediately before winding. In this case, a correlation line (correlation equation) between the addition amount of the matting agent and the friction coefficient is prepared in advance, an appropriate addition amount is obtained according to the detected value of the friction coefficient, the addition amount is determined accordingly, and the mat The addition amount of the agent was adjusted. In addition, the friction coefficient test of the cellulose triacetate film was implemented similarly to the case of the said Examples 1-3.

  Table 4 below shows the types of plasticizers and polyhydric alcohol esters used, and the friction coefficient (μp) of the film immediately before winding (online).

Comparative Examples 9 and 10
For comparison, a cellulose triacetate film having a film thickness of 40 μm is produced in the same manner as in Example 8. In Comparative Example 9, the film friction coefficient (μp) immediately before winding is outside the range of the present invention. The case of exceeding 1.0 was shown. In Comparative Example 10, the case where the film friction coefficient (μp) immediately before winding was less than 0.5, which is outside the scope of the present invention, was shown.

(Evaluation of winding quality)
For each of the cellulose triacetate films of Example 8 and Comparative Examples 9 and 10 according to the present invention, the roll quality of each film was evaluated in the same manner as in Example 7 above, and the results obtained are shown in Table 4.

  For each cellulose triacetate film obtained in Example 8 and Comparative Examples 9 and 10, the average particle diameter of the matting agent (silicon dioxide fine particles) was measured, and the distance between the fine particles was measured.

The interparticle distance was measured by observing the film surface and cross section with a scanning electron microscope. That is, the average of the interparticle distance per observation place on a 20 μm square plane was determined. Furthermore, the average of the distance between particles was calculated by taking five observation points. The average of the values thus obtained was defined as the interparticle distance. The obtained results are shown in Table 4 below.

  As is apparent from the results of Table 4 above, according to the cellulose triacetate film according to Example 8 of the present invention, the winding quality of the cellulose triacetate film is good, the film has excellent physical properties, and the polarizing plate It can be seen that the film is suitable for a protective film. In Example 8, the average particle diameter of the matting agent (silicon dioxide fine particles) in the cellulose triacetate film was 700 nm, and the distance between the fine particles in the film was 3 μm.

  On the other hand, in any of Comparative Examples 9 and 10, it can be seen that the winding quality of the cellulose triacetate film is poor, the surface physical properties of the film are inferior, and the film is not suitable for a protective film for a polarizing plate. In Comparative Example 9, the average particle size of the matting agent (silicon dioxide fine particles) in the cellulose triacetate film was 250 nm, and in Comparative Example 10, it was 1200 nm. Furthermore, the interparticle distance of the fine particles in the film was 4 μm in Comparative Example 9 and 2 μm in Comparative Example 10.

  As a result, according to the cellulose triacetate film according to Example 8 of the present invention, compared to the cellulose triacetate films of Comparative Examples 9 and 10, it is estimated that the contact area when the films are overlapped is in an appropriate state. The coefficient of friction between films is within the scope of the present invention, and the winding quality is good.

Claims (17)

  It has a step of forming a cellulose ester film containing a matting agent and a step of detecting the friction coefficient of the cellulose ester film immediately after winding, and in the film forming step, based on the detected value of the film friction coefficient from the detection step And adjusting the addition amount of the matting agent.   The method for producing a cellulose ester film according to claim 1, wherein in the film friction coefficient detection step, the friction coefficient of the film is detected by measuring the friction coefficient between the films immediately after winding.   The method for producing a cellulose ester film according to claim 1 or 2, wherein the coefficient of friction of the cellulose ester film immediately after winding is 1.00 or less.   In the process of forming a cellulose ester film containing a matting agent, a film friction resistance detection device is provided in the film transport process before winding, and the friction coefficient of the cellulose ester film during transport is determined on the production line (online). A method for producing a cellulose ester film, which comprises detecting and adjusting an addition amount of a matting agent based on a detected value of a detected film friction coefficient (μP).   In the step of adjusting the amount of matting agent added to the cellulose ester solution, a solution containing the matting agent is prepared in advance, and the mixing ratio of the matting agent solution added to the cellulose ester main solution is adjusted. The cellulose-ester film manufacturing method of Claim 1 or 4. A cellulose ester film produced by the method for producing a cellulose ester film according to claim 1, wherein the friction coefficient of the cellulose ester film immediately after winding is μ1, and the temperature is adjusted at a temperature of 23 ° C. and a humidity of 55% RH for 24 hours. When the friction coefficient of the wet cellulose ester film is μ2,
0.5 ≦ μ2 / μ1 ≦ 1.0
A cellulose ester film characterized by being: The cellulose ester film manufactured by the cellulose ester film manufacturing method according to claim 4, wherein the friction coefficient of the cellulose ester film before winding (on-line) detected by the film frictional resistance detection device in the film transporting process is μP. and when,
0.5 ≦ μP ≦ 1.0
A cellulose ester film characterized by being: The cellulose ester film according to claim 6 or 7, wherein the arithmetic average roughness of the film: Ra, the ten-point average roughness: Rz, and the average distance between the local peaks: Sm are within the following ranges, respectively.
9.0 nm ≦ Ra ≦ 11.0 nm
150 nm ≦ Rz ≦ 250 nm
10nm ≦ Sm ≦ 300nm   9. The average particle diameter of the matting agent fine particles in the film is 100 to 500 nm, and the interparticle distance of the matting agent fine particles is 0.3 to 3 μm. 9. The cellulose ester film as described.   9. The average particle size of the matting agent fine particles in the film is 500 to 1000 nm, and the interparticle distance of the matting agent fine particles is 1 to 5 μm. 9. Cellulose ester film. Furthermore, the general formula [I]

(In the formula, A, B and C represent a phenyl group or a biphenyl group, and at least two of A, B and C are biphenyl groups)
The cellulose ester film according to claim 6, comprising a compound represented by the formula: Furthermore, the general formula [I]

In the compound represented by
Wherein A, B and C represent a phenyl group or a biphenyl group, and at least two of A, B and C are biphenyl groups;
Wherein A, B, and C represent a phenyl group or a biphenyl group, and at least two of A, B, and C are phenyl groups. The cellulose ester film according to any one of the above.   Furthermore, the compound comprising a polyhydric alcohol ester of an aliphatic polyhydric alcohol and one or more monocarboxylic acids is contained in an amount of 4.5 to 12.5% by weight based on the cellulose ester film. The cellulose ester film according to any one of Items 6 to 10.   The cellulose ester film according to claim 13, wherein the monocarboxylic acid is a compound having an aromatic ring or a cycloalkyl ring in the molecule.   14. The cellulose ester film according to claim 13, wherein the aliphatic polyhydric alcohol has 2 to 20 valences.   The cellulose ester film according to claim 13, wherein the aliphatic polyhydric alcohol has 2 to 3 valences.   The cellulose ester film according to claim 13, wherein the aliphatic polyhydric alcohol has 4 or more carbon atoms.