JP2003213012A - Cellulose ester film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cellulose ester film having a thickness of ≤60 μm, useful e.g. as a protecting film for a polarizing plate of a liquid crystal image display device (LCD), having excellent windability to prevent the generation of winding defects such as wrinkle and crease even by sufficiently increasing the winding length of the film, and having excellent applicability in the application of various coating layer for forming a film for optical use and excellent adhesivity to a light polarizer. <P>SOLUTION: The cellulose ester film satisfies the relationship of b/a≤3.0 wherein (a) is the charge accumulation between the films before saponification and (b) is the charge accumulation between chromium metal and the film before saponification. The film further satisfies the relationship of c/a≤8.0 wherein (a) is the charge accumulation between the films before saponification and (b) is the charge accumulation between the films after saponification. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cellulose ester film, and more particularly to a thin cellulose ester film having remarkably improved winding property, coating property and adhesiveness.

The cellulose ester film according to the present invention is used, for example, as a protective film for a polarizing plate in a liquid crystal image display device (LCD), and has suitability for processing during coating of various coating layers provided for use as an optical film. With excellent, it is possible to reduce the failure in the winding process of the film after saponification and after coating, further excellent adhesion to the polarizer,
The polarizing plate has excellent stability over time, and also has excellent display appreciation in an LCD using the polarizing plate.

[0003]

2. Description of the Related Art Generally, a liquid crystal image display device can be directly connected to an IC circuit with a low voltage and a low power consumption and can be made thin. Therefore, it is widely used as a display device for a word processor, a personal computer or the like. Has been done. As a protective film for such a polarizing plate, a cellulose ester film such as triacetyl cellulose (TAC) is suitable and often used because of its small birefringence.

Further, since liquid crystal image display devices tend to be lighter and thinner, a thinner film is required for the cellulose ester film used for the polarizing plate, and the conventional protective film is used. Has a thickness of 80
It was comparatively thick with a thickness of at least μm. But LCD
Since four protective films are usually used as members, it has been desired to reduce the thickness to, for example, about 40 μm.

[0005]

However, with the thinning (about 40 μm) of the cellulose ester film, which is a protective film for a polarizing plate, in the winding process of winding the film into a roll, a certain winding diameter and a certain winding diameter are used. In order to increase the length, the number of turns increases, and the number of turns increases.
The frequency of occurrence of breakage and failure such as poor appearance also increases. Further, there has been a problem that the appearance of the cellulose ester film is remarkably deteriorated with the deterioration of wrinkles and folds over time.

Therefore, conventionally, the winding length of the cellulose ester film was suppressed to prevent the winding diameter from increasing. However, due to the increased demand for the polarizing plate protective film as described above, the film per winding is increased. There has been a potential need for increased winding length.

Further, conventionally, the occurrence of winding defects has been suppressed by variously adjusting the conditions at the time of production such as the tension at the time of winding the cellulose ester film and the contact pressure of the winding roll. Not enough results have been obtained. Besides, if you leave the roll-shaped film,
There is a problem that the appearance of wrinkles and folds may be further deteriorated and the appearance may be significantly impaired.

The present inventor has conducted extensive studies in view of the above points, and as a result, the winding property of the cellulose ester film was found to be
It was found that in addition to the adjustment of the conditions during production, the physical properties of the cellulose ester film itself are greatly related. In particular,
The smaller the charging characteristics of the cellulose ester film itself, that is, the less the generation and accumulation of charging, the more the amount of charge generated and accumulated between the films during the winding of a large number of thin films is significantly reduced, and the film winding property is improved. It is improved, and winding defects such as wrinkles and folds of the film are reduced. In addition, when using the film as a protective film for a polarizing plate to form a polarizing plate, the adhesion between the film and the polarizer is improved, and further, a functional layer (on the protective film for a polarizing plate) (on the protective film for the polarizing plate). It has been found that the coating properties in coating the antireflection layer and the antiglare layer are improved, and the present invention has been completed.

An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a thin film having a film thickness of 60 μm or less, and even when the winding length of the film is sufficiently long, winding such as wrinkles and folds occurs. It is an object of the present invention to provide a cellulose ester film that does not cause a malfunction.

[0010]

In order to achieve the above object, the invention of claim 1 of the present invention is a cellulose ester film having a thickness of 60 μm or less, wherein the cellulose ester films before saponification are Charge amount: a When the charge amount between the cellulose ester film before saponification and metallic chromium is b: b / a ≦ 3.0.

Here, as described in claim 2, b / a
It is preferable that ≦ 1.5.

The invention according to claim 3 of the present invention is 60 μm.
A cellulose ester film having a thickness of m or less, wherein the charge amount between the cellulose ester films before saponification: a and the charge amount between the cellulose ester films after saponification: c, c / a ≦ 8.0 It is characterized by being.

Here, as described in claim 4, c / a
It is preferable that ≦ 4.0.

The invention according to claim 5 of the present invention is a cellulose ester film having a thickness of 60 μm or less, wherein the amount of charge between the cellulose ester film before saponification and metallic chromium: b the cellulose ester film after saponification It is characterized in that d / b ≦ 4.0, where d is the amount of charge between the metal and chromium metal.

Here, as described in claim 6, d / b
It is preferable that ≦ 2.0.

The invention according to claim 7 of the present invention is a cellulose ester film having a thickness of 60 μm or less, which is measured under the condition 1 at 23 ° C. and 80% RH, before the saponification. : A1 charge amount of cellulose ester films before saponification measured under condition 2 of 23 ° C. and 55% RH: a2, 0 ≦ a1 / a2 ≦ 2.0, and 23 ° C., 80% RH Charge amount between the cellulose ester film before saponification and metallic chromium measured under the condition 1:
b1 Charge amount between cellulose ester film before saponification and metallic chromium measured under condition 2 of 23 ° C. and 55% RH:
When b2, 0 ≦ b1 / b2 ≦ 2.0, and the charge amount between the saponified cellulose ester films measured under the condition 1 of 23 ° C. and 80% RH: c1 23 ° C., 55% RH The amount of charge between the saponified cellulose ester films measured under 2 is 1.0, and c2 is 1.0 ≦ c1 / c2 ≦ 2.0. After saponification measured under the condition 1 of 23 ° C. and 80% RH. Amount of charge between cellulose ester film and chromium metal:
d1 Charge amount between cellulose ester film after saponification and metallic chromium measured under condition 2 of 23 ° C. and 55% RH:
When d2, it is characterized in that 1.0≤d1 / d2≤2.0.

The invention according to claim 8 of the present invention is a cellulose ester film having a thickness of 60 μm or less, and the amount of charge between the cellulose ester films before saponification measured under condition 3 at 23 ° C. and 20% RH. : A3 23 ° C., 55% RH Charge amount between cellulose ester films before saponification measured under condition 2: a2, 0 ≦ a3 / a2 ≦ 1.0, 23 ° C., 20% RH Charge amount between the cellulose ester film before saponification and metallic chromium measured under the condition 3:
b3 Amount of charge between cellulose ester film before saponification and metallic chromium measured under condition 2 of 23 ° C. and 55% RH:
b2 is 0 ≦ b3 / b2 ≦ 1.0, and the charge amount between the cellulose ester films after saponification measured under the condition 3 of 23 ° C. and 20% RH: c3 23 ° C., 55% RH The amount of charge between the saponified cellulose ester films measured under 2 is 0 ≦ c3 / c2 ≦ 1.0, and the cellulose after saponification measured under the condition 3 of 23 ° C. and 20% RH The amount of charge between the ester film and metallic chromium:
Charge amount between the saponified cellulose ester film and metallic chromium measured under the condition 2 of d3 23 ° C. and 55% RH:
When d2, it is characterized in that 0≤d3 / d2≤1.0.

The invention according to claim 9 of the present invention is the above-mentioned claim 1.
The cellulose ester film according to any one of claims 1 to 8, wherein fine particles having an average particle diameter of 100 to 500 nm are present in the cellulose ester film within an interparticle distance of 0.5 to 5 μm. It has a feature.

The invention of claim 10 of the present invention is the cellulose ester film according to any one of claims 1 to 8, wherein the cellulose ester film comprises:
It is characterized in that fine particles having an average particle diameter of 500 to 1000 nm are present within a distance between particles of 1 to 5 μm.

An eleventh aspect of the present invention is the cellulose ester film according to any one of the first to tenth aspects, wherein the cellulose ester film has the general formula (1):

[Chemical 4] (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), at least 1
It contains seeds.

The invention of claim 12 of the present invention is the cellulose ester film according to any one of claims 1 to 11, wherein the cellulose ester film has the general formula (1):

[Chemical 5] (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), and at least one plasticizer X, and Formula (1)

[Chemical 6] (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 phenyl groups), and at least one plasticizer Y represented by
Are contained together.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Next, an embodiment of the present invention will be described.

First, the cellulose ester film having a dry film thickness of 60 μm or less according to the present invention is manufactured by the solution casting film forming method, for example, as follows.

Although not shown in the drawings, the apparatus for producing a cellulose ester film according to the present invention comprises a support composed of a driving rotating stainless steel endless belt or a rotating drum, and a dope which is a raw material solution of the cellulose ester film on the support. A casting die, a peeling roll for peeling the web formed on the support by the die from the support, and a web peeled from the support by the peeling roll via at least one transport roll. A drying zone for drying, and a film obtained by drying the web are wound by a winding roll via at least one transport roll, and a moisture conditioning zone for adjusting the water content of the film to an equilibrium water content. ing.

In the production of the cellulose ester film according to the present invention, first, the raw materials for the cellulose ester film are mixed in a raw material mixer to prepare a cellulose ester solution (hereinafter referred to as "dope"). Next, the dope is cast from a casting die onto a support composed of an endless belt to obtain a dope film, that is, a web. Peel off.

The web peeled off by the peeling rolls is conveyed in the drying zone via the conveying rolls, dried by the drying air during the conveyance, and then sent to the humidity control zone. Then, the film sent from the post-drying zone is carried in the housing via the carrying roll and is taken up by the take-up roll, and the water content of the film is appropriately adjusted. The ambient temperature in the drying zone and the humidity control zone is, for example, 5 to 200 ° C, preferably 20 to 150 ° C. In addition, before the winding roll, means such as a static eliminator blower for removing or reducing the surface potential of the film is provided.

In the method for producing a cellulose ester film of the present invention, the cellulose ester which is the main raw material of the cellulose ester film includes cellulose triacetate (TAC), cellulose diacetate,
Examples thereof include cellulose acetate butyrate and cellulose acetate propionate (CAP). In the case of cellulose triacetate (TAC), the degree of polymerization is 2
Cellulose triacetate having 50 to 400 and a bound acetic acid amount of 54 to 62.5% is preferable, and a bound acetic acid amount of 58 to 6
2.5% cellulose triacetate is more preferable because it has a strong base strength. 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. Above all, it is preferable to use cellulose acetate propionate (CAP), which is less likely to cause water-proof charging.

Examples of the solvent for the cellulose ester in the present invention include lower alcohols such as methanol, ethanol, n-propyl alcohol, iso-propyl alcohol and n-butanol, lower aliphatic carbonization such as cyclohexanedioxane and methylene chloride. Hydrogen chlorides and the like can be used.

The solvent ratio is, for example, 70 to 95% by weight of methylene chloride, and 30 to 5% by weight for other solvents.
Is preferred. The concentration of cellulose ester is 10 to 5
0% by weight is preferred. The heating temperature after the addition of the solvent is preferably not lower than the boiling point of the solvent used and in the range in which the solvent does not boil, and is preferably set to 60 ° C. or higher and 80 to 110 ° C., for example. The pressure is set so that the solvent does not boil at the set temperature.

After the dissolution, the product is taken out from the container while being cooled, or is taken out from the container by a pump or the like and cooled by a heat exchanger or the like, and is used for film formation.

In the subsequent step of the cellulose ester film produced as described above, in order to make it into an optical film having various functions, for example, an antistatic layer for giving an antistatic function or a surface hardness The coating step of providing a hard coat layer for improving the coating property, an undercoat layer for improving the film-forming property, or an anti-curl layer for preventing curling is carried out. Alternatively, a saponification step of subjecting the cellulose ester film to an alkali saponification treatment is carried out before the coating of each coating layer.

The alkali saponification treatment may be carried out before or after coating each coating layer. For example, after subjecting the cellulose ester film to alkali saponification treatment, an antistatic layer and / or an ultraviolet curable resin layer, or an antireflection layer may be further applied, or a back coat layer,
After coating the antistatic layer and the ultraviolet curable resin layer, alkali saponification treatment may be performed, and then the antireflection layer may be coated.

According to the first aspect of the present invention, 6
A cellulose ester film having a thickness of 0 μm or less, wherein the amount of charge between the cellulose ester films before saponification: a, the amount of charge between the cellulose ester film before saponification and metallic chromium: b, b / a ≦ 3.0, preferably b / a ≦ 1.
It is set to 5.

As described above, the reason why the charge amount between the cellulose ester films before saponification and the ratio of the charge amount between the film and the metal chromium are regulated is that the charge between the metal chromium-cellulose ester film is small. Is
It means that the original charge generation of the cellulose ester film is small, and there is little charge between the cellulose ester films that lowers this in the first place, and thus it occurs when the cellulose ester film is wound many times in a thin film. And the amount of accumulated charge is greatly reduced, and the film winding property is improved,
It is based on the fact that winding defects such as wrinkles and folds of the film are reduced.

Therefore, when the above ratio b / a exceeds 3.0, the amount of charge between the cellulose ester film before saponification and metallic chromium becomes large, so that the cellulose ester film is generated and accumulated during winding. The electrification amount to be applied becomes large, and winding defects such as wrinkles and folds of the film occur, which is not preferable.

In the invention according to claim 3 of the present invention,
A cellulose ester film having a thickness of 60 μm or less, wherein the amount of charge between the cellulose ester films before saponification: a, the amount of charge between the cellulose ester films after saponification: c, c / a ≦ 8.0, Preferably c / a ≦ 4.
It is set to 0.

As described above, the reason why the ratio of the charge amounts of the cellulose ester films before and after saponification is defined is that the difference in the charge amount between the film before and after saponification of the cellulose ester film is smaller, the influence of water is smaller. This is because there is little influence when the conditions of the charging characteristics are changed, which is preferable.
If the above ratio c / a exceeds 8.0, the charge amount of the cellulose ester films after saponification becomes too large, and wrinkles or folds of the film may occur during winding after the cellulose ester film is subjected to alkali saponification treatment. It is not preferable because a winding failure occurs.

Next, according to the invention of claim 5 of the present invention, a cellulose ester film having a thickness of 60 μm or less, wherein the amount of charge between the cellulose ester film before saponification and metallic chromium is: b saponification When the amount of charge between the subsequent cellulose ester film and metallic chromium is d: d / b ≦ 4.0, preferably d / b ≦ 2.
It is set to 0.

As described above, the reason why the ratio of the charge amount between the cellulose ester film and the metal chromium before and after saponification is defined is that the charge between the metal chromium and the cellulose ester film is small before and after the saponification of the cellulose ester film. That is, the original charge generation of the cellulose ester film is small, and the smaller the difference in the charge amount between the cellulose ester film and the metal chromium, the smaller the influence of water and the change in the conditions of the charging characteristics. This is because it has less influence and is preferable. If the above ratio c / a exceeds 8.0, the charge amount of the cellulose ester films after saponification becomes too large, and wrinkles or folds of the film may occur during winding after the cellulose ester film is subjected to alkali saponification treatment. It is not preferable because a winding failure occurs.

According to the invention of claim 7 of the present invention, 60 μ
A cellulose ester film having a thickness of not more than m, the charge amount between the cellulose ester films before saponification measured under the condition 1 of 23 ° C. and 80% RH: a1 under the condition 2 of 23 ° C. and 55% RH When the amount of charge between the measured cellulose ester films before saponification: a2, 0 ≦ a1 / a2 ≦ 2.0, and the cellulose ester film before saponification measured under condition 1 at 23 ° C. and 80% RH Charge amount with metallic chrome:
b1 Charge amount between cellulose ester film before saponification and metallic chromium measured under condition 2 of 23 ° C. and 55% RH:
When b2, 0 ≦ b1 / b2 ≦ 2.0, and the charge amount between the saponified cellulose ester films measured under the condition 1 of 23 ° C. and 80% RH: c1 23 ° C., 55% RH The amount of charge between the saponified cellulose ester films measured under 2 is 1.0, and c2 is 1.0 ≦ c1 / c2 ≦ 2.0. After saponification measured under the condition 1 of 23 ° C. and 80% RH. Amount of charge between cellulose ester film and chromium metal:
d1 Charge amount between cellulose ester film after saponification and metallic chromium measured under condition 2 of 23 ° C. and 55% RH:
When d2, 1.0≤d1 / d2≤2.0.

Thus, before and after saponification of the cellulose ester film and humidity change (at 23 ° C., 80% R
H and 55% RH), the reason for defining the ratio of the charge amount between the cellulose ester films or the ratio of the charge amount between the cellulose ester film and the metal chromium is that before and after saponification of the cellulose ester film and the humidity. In the change, the smaller the difference in the charge amount between the cellulose ester films, or between the metal chrome-cellulose ester film, the less the influence of water, the less the influence when the conditions of the charging characteristics are changed, which is preferable. Within the range, winding defects such as wrinkles and folds of the cellulose ester film are unlikely to occur.

According to the invention of claim 8 of the present invention,
A cellulose ester film having a thickness of 60 μm or less, which is the amount of charge between the cellulose ester films before saponification measured under the condition 3 of 23 ° C. and 20% RH: a3 under the condition 2 of 23 ° C. and 55% RH The amount of charge between the measured cellulose ester films before saponification: a2, 0 ≦ a3 / a2 ≦ 1.0, and the cellulose ester film before saponification measured under the condition 3 of 23 ° C. and 20% RH. Charge amount with metallic chrome:
b3 Amount of charge between cellulose ester film before saponification and metallic chromium measured under condition 2 of 23 ° C. and 55% RH:
b2 is 0 ≦ b3 / b2 ≦ 1.0, and the charge amount between the cellulose ester films after saponification measured under the condition 3 of 23 ° C. and 20% RH: c3 23 ° C., 55% RH The amount of charge between the saponified cellulose ester films measured under 2 is 0 ≦ c3 / c2 ≦ 1.0, and the cellulose after saponification measured under the condition 3 of 23 ° C. and 20% RH The amount of charge between the ester film and metallic chromium:
Charge amount between the saponified cellulose ester film and metallic chromium measured under the condition 2 of d3 23 ° C. and 55% RH:
When d2, 0≤d3 / d2≤1.0.

As described above, before and after saponification of the cellulose ester film and at a lower humidity change (23 ° C.).
Under the conditions of 55% RH and 20% RH), the reason why the ratio of the charge amount between the cellulose ester films or the ratio of the charge amount between the cellulose ester film and the metal chromium is defined is the same. Before and after saponification of the film and changes in humidity, the smaller the difference in the charge amount between the cellulose ester films, or the metal chromium-cellulose ester film,
This is because the influence of water is small and the influence when the charging characteristics are changed is small, which is preferable, and within the above range, the winding failure such as wrinkles and folds of the cellulose ester film is unlikely to occur.

Next, according to the invention of claim 9 of the present invention, in the above-mentioned cellulose ester film, the average particle diameter is 100 to 50 in the cellulose ester film.
Fine particles of 0 nm are assumed to exist within the distance between particles of 0.5 to 5 μm.

According to a tenth aspect of the present invention, the above cellulose ester film has an average particle diameter of 500 to 10 in the cellulose ester film.
Fine particles of 00 nm are assumed to exist within the range of the interparticle distance of 1 to 5 μm.

As described above, in the cellulose ester film of the present invention, the fine particles are not defined by the content or content ratio inside the film, but by the degree of existence of the fine particles, that is, the distance between the particles. To adjust the interparticle distance,
Instead of simply adjusting the content of the fine particles, a polar solvent is used as a solvent used when dispersing the fine particles, or the time until the fine particle dispersion is mixed with the cellulose ester main liquid is shortened (preferably the fine particles are used). The method of adding the dispersion liquid to the main liquid in-line) is adopted. The fine particle dispersion is preferably added in-line to the main liquid.

Here, a typical example of the fine particles is a matting agent. The fine particles may have a small particle size (preferably 400 nm or less, particularly 200 to 300 nm) in a large amount, or a large particle size (preferably 600 to 800 nm) may be used in a small amount, but have a small particle size. Is particularly preferable because it is monodisperse.

The type of fine particles is preferably an inorganic compound, and specific examples of the fine particles of an inorganic compound include, for example, silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, kaolin, talc, calcined calcium silicate and water. Examples thereof include inorganic fine particles such as calcium silicate silicate, aluminum silicate, magnesium silicate, and calcium phosphate, and crosslinked polymer fine particles. Of these, silicon dioxide is preferable because it can reduce the haze of the film. The average particle size of the secondary particles of the fine particles is preferably 0.
The content is 01 to 1.0 μm, and the content thereof is preferably 0.005 to 0.3% by weight with respect to the cellulose ester.
Although fine particles such as silicon dioxide are often surface-treated with an organic substance, such particles are preferable because they can reduce the haze of the film. Organic materials for surface treatment of fine particles include halosilanes, alkoxysilanes,
Examples thereof include silazane and siloxane. The larger the average particle size of the fine particles, the greater the matte effect, and conversely, the smaller the average particle size, the better the transparency. The average particle diameter of the primary particles of the fine particles is preferably 5 to 50 nm, more preferably 7 to
It is 14 nm. Examples of commercially available silicon dioxide particles are:
Aerosil-200, 20 manufactured by Aerosil Co., Ltd.
0V, 300, R972, R972V, R974, R2
02, R812, OX50, TT600, etc., and it is particularly preferable to use a fine particle matting agent coated with a hydrophobic group of AEROSIL-R972 type. The presence of such fine particles reduces the resistance at the time of contact and peeling of the film, and suppresses the generation and accumulation of charging. Further, the presence of the above-mentioned fine particles increases the hydrophobicity of the film and increases the water resistance thereof, so that the occurrence of electrification due to water can be prevented.

In the present invention, a specific plasticizer is used. That is, according to the invention of claim 11 of the present invention, the above-mentioned cellulose ester film having the general formula (1)

[Chemical 7] (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), at least 1
Seeds are included.

According to a twelfth aspect of the present invention, in the above cellulose ester film, the general formula (1) is contained in the cellulose ester film.

[Chemical 8] (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), and at least one plasticizer X, and Formula (1)

[Chemical 9] (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 phenyl groups), and at least one plasticizer Y represented by
Are included together.

In the invention of claim 11, the general formula (1)
The compound X in which A, B and C are phenyl groups or biphenyl groups and at least two of A, B and C are biphenyl groups are, for example, bisbiphenylphenylphosphate (BBPP) and trisbiphenylphosphate (TBP). In particular, trisbiphenyl phosphate (TBP) has the effect of improving the hydrophobicity of the film and, as a result, improving the slip property.

In the invention of claim 12, the general formula (1)
The compound Y in which A, B and C in the above represent phenyl groups or biphenyl groups and at least two of A, B and C are phenyl groups are, for example, triphenyl phosphate (TPP) biphenyl diphenyl phosphate (BD
P). And at least 2 of A, B and C
The ratio of the compound X in which one is a biphenyl group and the compound Y in which A, B and C represent a phenyl group or a biphenyl group and at least two of A, B and C are phenyl groups are preferably 8: 2 to 2: 8.

In the present invention, by using the above-mentioned specific plasticizer, the hygroscopicity and the moisture permeability are lowered, and the moisture resistance of the film when the humidity is changed is improved, which results in the reduction of the friction coefficient and the slipping property. It is closely related to the improvement of the winding performance. In addition, since the hydrophobicity of the cellulose ester film is high and the water resistance is high, it is possible to prevent the occurrence of electrification due to water.

The cellulose ester film of the present invention may contain the following plasticizers in addition to the above specific phosphate ester plasticizers. Specific examples of the other phosphoric acid ester system include tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, trioctyl phosphate, tributyl phosphate, and the like, and among phthalic acid ester systems, diethyl phthalate and dimethoxyethyl phthalate. , Dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate and the like,
Examples of the glycolic acid ester system include triacetin, tributyrin, butylphthalylbutyl glycolate, ethylphthalylethyl glycolate, methylphthalylethyl glycolate, and butylphthalylbutyl glycolate.

In the cellulose ester film of the present invention, if necessary, two or more kinds of plasticizers may be used in combination, including the above-mentioned specific plasticizers X and Y. Preferred in the present invention. The total amount of plasticizer added is
3 to 30% by weight based on the weight of cellulose ester
And more preferably 10 to 25% by weight, and further preferably 15 to 25% by weight. If it exceeds 30% by weight, mechanical strength and dimensional stability deteriorate.

In addition, by incorporating an ultraviolet absorber such as a benzotriazole-based ultraviolet absorber, an antioxidant, and a processing stabilizer into the cellulose ester film, the performance of the liquid crystal image display device due to the cellulose ester film. Can be improved.

[0057]

EXAMPLES Next, examples of the present invention will be described together with comparative examples.

Examples 1 to 3 and Comparative Examples 1 to 3 In producing the cellulose triacetate film of the present invention having a target dry film thickness of 41 μm, dopes were first prepared. That is, the following composition containing triacetyl cellulose dissolved in a solvent was placed in a closed container, dissolved with stirring to prepare a dope, and the prepared dope was filtered with a filter paper.

(Dope composition) Cellulose triacetate having a degree of acetyl substitution of 2.88 (number average molecular weight 150000) 100 parts by weight Plasticizer triphenyl phosphate (TPP) 10 parts by weight Ethylphthalylethyl glycolate (EPEG) 2 parts by weight Silicon dioxide Microparticles (AEROSIL-R972) 0.3 parts by weight Solvent Methylene chloride 475 parts by weight Ethanol 25 parts by weight Next, a cellulose triacetate film was produced in the following manner using the above-mentioned filtered dope by a production apparatus not shown.

In a raw material mixer (not shown), a solution (dope) of cellulose triacetate was prepared, and the dope was cast from a casting die onto a support made of a driving rotating stainless steel endless belt having a mirror-finished surface. The film was cast to obtain a dope film, that is, a web, and when the web reached the lower surface of the support made of an endless belt and made almost one round, it was peeled by a peeling roll.

Next, the web peeled off by the peeling roll is dried by a drying air to form a film while passing through the drying zone, and then the film is wound up on a winding roll and in the humidity control zone. The water content of the film is adjusted appropriately. Here, the target dry film thickness of the cellulose triacetate film is 41 μm,
The ambient temperature of the humidity control zone is 23 ° C, and the ambient humidity is
The three conditions were 80 RH%, 55 RH%, and 20 RH%.

The plasticizer is TPP and EPEG.
Common with. On the other hand, silicon dioxide particles (matting agent particles) having different average particle diameters were used, and the interparticle distance of the matting agent particles in each film was as shown in Table 1.

The cellulose triacetate films of Examples and Comparative Examples according to the present invention were different from each other.
Two humidity control conditions: 80% RH, 55% RH, and 2
The amount of charge between the cellulose triacetate films before and after saponification at 0% RH (μC / g, the same below) and the amount of charge between the cellulose triacetate film before and after saponification and metallic chromium were measured, and the obtained results are shown in the table below. It showed in 1-3.

In Table 1, the cellulose triacetate films (hereinafter simply referred to as films) obtained in Examples 1 to 3 and Comparative Examples 1 to 23 were treated at 23 ° C.
Charge amount between films before saponification measured under condition 2 of 55% RH: a2 Charge amount between films before saponification and metallic chromium: b2 Charge amount between films after saponification: c2 Film after saponification The amount of charge with metallic chrome: d2 is shown, and b2 / a2, c2 / a2, and d2 /
The ratio of the charge amount of b2 was calculated, and these values are shown together.

[0065]

[Table 1]

Similarly, in Table 2, with respect to the cellulose triacetate films obtained in Examples 1 to 3 and Comparative Examples 1 to 3, charging between films before saponification measured under the condition 1 of 23 ° C. and 80% RH. Amount: a1 Charge amount between film before saponification and metallic chromium: b1 Charge amount between films after saponification: c1 Charge amount between saponified film and metallic chromium: d1 a2, b1 / b2, c1 / c2,
And the ratio of the charge amounts of d1 / d2 were calculated, and these values are shown together. In Table 2, the description of the average particle diameter of the matting agent particles and the measured value of the interparticle distance is omitted, but these are the same as those in Table 1.

[0067]

[Table 2]

Similarly, in Table 3, with respect to the cellulose triacetate films obtained in Examples 1 to 3 and Comparative Examples 1 to 3, charging between the films before saponification measured under the condition 3 of 23 ° C. and 20% RH. Amount: a3 Charge amount between the film before saponification and metal chromium: b3 Charge amount between the films after saponification: c3 Charge amount between the film after saponification and metal chromium: d3 a2, b3 / b2, c3 / c2,
And the ratio of the charge amounts of d3 / d2 were calculated, and these values are shown together. In Table 3, the description of the average particle diameter of the matting agent particles and the measured value of the interparticle distance is omitted, but these are the same as those in Table 1.

[0069]

[Table 3]

Examples 4 to 6 and Comparative Examples 4 to 6 The cellulose triacetate film of the present invention is produced in the same manner as in the above Examples, but the silicon dioxide fine particles (matting agent particles) have a matting agent particle size of 500 nm. The distance was 3.5 μm, which was common, and various plasticizers were used in combination in each example. The dope composition is
It is as follows.

[0071] (Dope composition)       Cellulose triacetate with acetyl substitution of 2.88         (Number average molecular weight 150,000) 100 parts by weight       Plasticizer (various) 12 parts by weight       Silicon dioxide fine particles (AEROSIL-R972) 0.3 parts by weight       solvent         Methylene chloride 475 parts by weight         25 parts by weight of ethanol

The cellulose triacetate films of Examples and Comparative Examples according to the present invention were different from each other.
Two humidity control conditions: 80% RH, 55% RH, and 2
The amount of charge between the cellulose triacetate films before and after saponification at 0% RH and the amount of charge between the cellulose triacetate film before and after saponification and metallic chromium were measured,
The obtained results are shown in Tables 4-6.

In Table 4, the cellulose triacetate films (hereinafter, simply referred to as films) obtained in Examples 4 to 6 and Comparative Examples 4 to 6 were prepared at 23 ° C.
Charge amount between films before saponification measured under condition 2 of 55% RH: a2 Charge amount between films before saponification and metallic chromium: b2 Charge amount between films after saponification: c2 Film after saponification The amount of charge with metallic chrome: d2 is shown, and b2 / a2, c2 / a2, and d2 /
The ratio of the charge amount of b2 was calculated, and these values are shown together.

In Table 4, the symbols of plasticizers represent the following compounds.

TPP: triphenyl phosphate (number of biphenyl groups 0, number of phenyl groups 3) BDP: biphenyl diphenyl phosphate (number of biphenyl groups 1, number of phenyl groups 2) BBPP: bisbiphenylphenyl phosphate (number of biphenyl groups 2, number of phenyl groups 1) TBP: trisbiphenyl Phosphate (3 biphenyl groups, 0 phenyl groups) EPEG: Ethylphthalylethyl glycolate

[0076]

[Table 4]

Similarly, in Table 5, the cellulose triacetate films obtained in Examples 4 to 6 and Comparative Examples 4 to 6 were charged with each other before saponification, as measured under condition 1 at 23 ° C. and 80% RH. Amount: a1 Charge amount between film before saponification and metallic chromium: b1 Charge amount between films after saponification: c1 Charge amount between saponified film and metallic chromium: d1 a2, b1 / b2, c1 / c2,
And the ratio of the charge amounts of d1 / d2 were calculated, and these values are shown together. In Table 5, the description of the combination of plasticizers is omitted, but these are the same as in Table 4.

[0078]

[Table 5]

Similarly, in Table 6, the cellulose triacetate films obtained in Examples 4 to 6 and Comparative Examples 4 to 6 were charged with each other before saponification, measured under condition 3 at 23 ° C. and 20% RH. Amount: a3 Charge amount between the film before saponification and metal chromium: b3 Charge amount between the films after saponification: c3 Charge amount between the film after saponification and metal chromium: d3 a2, b3 / b2, c3 / c2,
And the ratio of the charge amounts of d3 / d2 were calculated, and these values are shown together. In Table 5, the description of the combination of plasticizers is omitted, but these are the same as in Table 4.

[0080]

[Table 6]

Evaluation Test The performance of the rolls of the cellulose triacetate film obtained in Examples 1 to 6 and Comparative Examples 1 to 6 was evaluated for the following items. The evaluation results are shown in Table 7.

The evaluation was performed as follows.

(1) Failure-free m-number of windings: The presence or absence of a failure is confirmed in an automatic failure detection system utilizing infrared irradiation and its reflection, and the number of continuous windings in the absence of failure is calculated.

(2) Appearance during winding: The appearance of the film during winding is judged by visual inspection.

(3) Appearance after winding: The appearance of the film after winding is judged by visual inspection.

(4) Applicability test: Toluene, methyl ethyl ketone, cyclohexane, 2-propanol and methanol were applied to a film cut into a size of length 200 mm x width 50 mm, respectively, and the wettability of each solvent and the presence or absence of cloudiness. Is judged by visual inspection.

(5) Adhesion of polarizer: Cellulose triacetate film was used as a protective film for polarizing plate,
After producing a polarizing plate from a polarizer film and a protective film for a polarizing plate by a known method, a forced peeling force is applied between the polarizer film and the protective film for a polarizing plate to visually check the difficulty of peeling. Determine by inspection.

(6) Adhesion of coating film: An acrylic resin-based coating liquid dissolved in a preliminarily adjusted organic solvent was applied onto a cellulose triacetate film and dried.
After solidification, a forced peeling force is applied to the coated product, and the difficulty of peeling is judged by visual inspection.

In Table 7, the evaluation was made into the following four stages.

◯: Good, Δ: Normal, ×: Bad, XX: Very bad

[0091]

[Table 7]

As is clear from the results in Table 7 above, according to Examples 1 to 6 of the present invention, the cellulose triacetate film has any of the number of failure-free m rolls, the appearance during winding, and the appearance after winding. Thigh is good. in this way,
The winding property of the cellulose triacetate film is such that, in addition to the adjustment of the conditions during production, the physical properties of the cellulose triacetate film itself, in particular, the charging property of the cellulose triacetate film itself, that is, the smaller the occurrence and accumulation of charging, the more the film is wound in a thin film The amount of charge generated and accumulated between the films during winding is greatly reduced, and the film winding property is improved. Even though the film is thin and thin, the film winding length can be made sufficiently long. It is clear that winding defects such as wrinkles and folds do not occur.

Further, according to Examples 1 to 6 of the present invention, the cellulose triacetate film was good in all of the coating property test, the polarizer adhesion and the coating film adhesion. When used as a protective film for a polarizing plate to form a polarizing plate, the adhesion between the film and the polarizer is improved.
It is apparent that the coatability when the functional layer (antireflection layer, antiglare layer) is coated on the polarizing plate (protective film for polarizing plate) is improved.

[0094]

As described above, the invention of claim 1 of the present invention is a cellulose ester film having a thickness of 60 μm or less, wherein the amount of charge between the cellulose ester films before saponification is: a Cellulose before saponification When the charge amount between the ester film and the chromium metal is b: b / a ≦ 3.0. According to the invention of claim 1 of the present invention, cellulose before saponification is used. The charge amount between the ester films and the ratio of the charge amount between the film and the metal chromium are regulated, and the fact that the charge between the metal chromium and the cellulose ester film is small means that the original charge generation of the cellulose ester film occurs. This means that there is little charge between the cellulose ester films that lowers this in the first place. The amount of charge generated and accumulated during winding of the rewound cellulose ester film is greatly reduced, the winding property of the film is improved, and winding defects such as wrinkles and folds of the film are reduced. .

The invention of claim 3 of the present invention is, as described above, a cellulose ester film having a thickness of 60 μm or less, wherein the amount of charge between the cellulose ester films before saponification is: a The cellulose ester film after saponification When the charge amount between the two: c / a ≦ 8.0, the charge amount between the cellulose ester films before and after saponification is determined by the invention of claim 3 of the present invention. The ratio is defined, and the smaller the difference in the charge amount between the films before and after the saponification of the cellulose ester film, the smaller the influence of water and the smaller the influence when the conditions of the charging characteristics change.

The invention of claim 5 of the present invention is, as described above, a cellulose ester film having a thickness of 60 μm or less, wherein the amount of charge between the cellulose ester film before saponification and metallic chromium: b saponification When the amount of charge between the subsequent cellulose ester film and metallic chromium is d: d / b ≦ 4.0, according to the invention of claim 1, saponification It defines the ratio of the amount of charge between the front and rear cellulose ester films and metal chromium, and before and after saponification of the cellulose ester film, there is little charge between the metal chromium-cellulose ester film, which means that the cellulose ester film is originally It means that there is less charge generation of, the one where the difference in the charge amount between the cellulose ester film and the metal chromium is small, Small effect, an effect that the influence of the time of changing conditions of the charging characteristics is reduced.

The invention of claim 7 of the present invention is, as described above, a cellulose ester film having a thickness of 60 μm or less, which is the cellulose ester film before saponification measured under the condition 1 of 23 ° C. and 80% RH. Charge amount between films: a1 23 ° C., charge amount between cellulose ester films before saponification measured under condition 2 of 55% RH: a2, 0 ≦ a1 / a2 ≦ 2.0, 23 ° C. , The amount of charge between the cellulose ester film before saponification and metallic chromium measured under the condition 1 of 80% RH:
b1 Charge amount between cellulose ester film before saponification and metallic chromium measured under condition 2 of 23 ° C. and 55% RH:
When b2, 0 ≦ b1 / b2 ≦ 2.0, and the charge amount between the saponified cellulose ester films measured under the condition 1 of 23 ° C. and 80% RH: c1 23 ° C., 55% RH The amount of charge between the saponified cellulose ester films measured under 2 is 1.0, and c2 is 1.0 ≦ c1 / c2 ≦ 2.0. After saponification measured under the condition 1 of 23 ° C. and 80% RH. Amount of charge between cellulose ester film and chromium metal:
d1 Charge amount between cellulose ester film after saponification and metallic chromium measured under condition 2 of 23 ° C. and 55% RH:
When d2, 1.0 ≦ d1 / d2 ≦ 2.0, and according to the invention of claim 7 of the present invention, the change in humidity before and after saponification of the cellulose ester film (23 At 80 ° RH and 55% RH), the ratio of the charge amounts of the cellulose ester films to each other,
Or it defines the ratio of the charge amount between the cellulose ester film and the metal chromium, before and after saponification of the cellulose ester film and in the humidity change, between the cellulose ester films, or between the metal chromium-cellulose ester film of the charge amount. The smaller the difference is, the smaller the influence of water and the smaller the influence when the conditions of the charging characteristics change.

The invention of claim 8 of the present invention is, as described above, a cellulose ester film having a thickness of 60 μm or less, which is the cellulose ester before saponification measured under the condition 3 of 23 ° C. and 20% RH. Amount of charge between films: a3 23 ° C., amount of charge between cellulose ester films before saponification measured under condition 2 of 55% RH: a2, 0 ≦ a3 / a2 ≦ 1.0, 23 ° C. , The amount of charge between the cellulose ester film before saponification and metallic chromium measured under the condition 3 of 20% RH:
b3 Amount of charge between cellulose ester film before saponification and metallic chromium measured under condition 2 of 23 ° C. and 55% RH:
b2 is 0 ≦ b3 / b2 ≦ 1.0, and the charge amount between the cellulose ester films after saponification measured under the condition 3 of 23 ° C. and 20% RH: c3 23 ° C., 55% RH The amount of charge between the saponified cellulose ester films measured under 2 is 0 ≦ c3 / c2 ≦ 1.0, and the cellulose after saponification measured under the condition 3 of 23 ° C. and 20% RH The amount of charge between the ester film and metallic chromium:
Charge amount between the saponified cellulose ester film and metallic chromium measured under the condition 2 of d3 23 ° C. and 55% RH:
When d2, 0≤d3 / d2≤1.0, and according to the invention of claim 8 of the present invention, before and after saponification of the cellulose ester film and at a lower humidity change (23 Under the conditions of 55% RH and 20% RH), the ratio of the charge amount between the cellulose ester films or the ratio of the charge amount between the cellulose ester film and the metal chromium is defined. Before and after saponification of the ester film and humidity change, the smaller the difference in the charge amount between the cellulose ester films or between the metal chrome and the cellulose ester film, the smaller the influence of water and the less the influence when the conditions of the charging characteristics change. Has the effect of becoming.

Further, in the invention of claim 9 of the present invention, as described above, fine particles having an average particle diameter of 100 to 500 nm are present in the cellulose ester film at an interparticle distance of 0.5 to 5;
According to the invention of claim 10 of the present invention, the fine particles having an average particle diameter of 500 to 1000 nm have an interparticle distance of 1 to 5 μm. According to the invention of claims 9 and 10 of the present invention, the degree of presence of the fine particles is not defined by the content or content ratio of the fine particles inside the cellulose ester film. That is, it is defined by the distance between particles, and the presence of such fine particles reduces the resistance at the time of contact and peeling of the film, suppresses the generation and accumulation of electrification, and the presence of the fine particles makes the film hydrophobic. Since it becomes higher and the water resistance becomes higher, it is possible to prevent the occurrence of electrification due to water.

Further, claim 11 and claim 1 of the present invention.
In the invention of No. 2, as described above, by using a specific plasticizer, the hygroscopicity and moisture permeability are reduced, and the moisture resistance of the film is improved when the humidity changes, which results in a reduction in the friction coefficient and an improvement in the slipperiness. As a result, it is closely linked to the improvement of the winding property. Also, the hydrophobicity of the cellulose ester film becomes high,
Since the water resistance is high, it is possible to prevent the occurrence of electrification due to water.

Therefore, according to the cellulose ester film of the present invention, for example, a liquid crystal image display device (LC
When used as a protective film for a polarizing plate in D), it is excellent in processability at the time of coating various coating layers provided for forming an optical film, and
It is possible to reduce failures in the film winding process after saponification and coating, and further, the adhesiveness to the polarizer is excellent, the stability of the polarizing plate with time is excellent, and the LCD using the polarizing plate is excellent. It has the effect of having display appreciation.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G02B 5/30 G02B 5/30 // B29K 1:00 B29K 1:00 B29L 7:00 B29L 7:00 F Term (reference) 2H049 BA02 BB18 BB33 BC01 BC22 4F071 AA09 AB26 AC15 AD02 AE04 AE22 AF38 AF58 AH19 BA02 BB02 BC01 BC12 4F205 AA01 AB07 AB11 AC05 AG01 AH73 GA07 GB02 GE21 4J002 AB021 DE096 DE1360 DJ2060 DH0

Claims (12)

[Claims] 1. A cellulose ester film having a thickness of 60 μm or less, wherein the amount of charge between the cellulose ester films before saponification is: a, and the amount of charge between the cellulose ester film before saponification and metallic chromium: b And b / a ≦ 3.0,
Cellulose ester film. 2. The cellulose ester film according to claim 1, wherein b / a ≦ 1.5. 3. A cellulose ester film having a thickness of 60 μm or less, wherein the amount of charge between the cellulose ester films before saponification is: a, and the amount of charge between the cellulose ester films after saponification is c: c / a ≦ 8.0,
Cellulose ester film. 4. The cellulose ester film according to claim 3, wherein c / a ≦ 4.0. 5. A cellulose ester film having a thickness of 60 μm or less, wherein the amount of charge between the cellulose ester film before saponification and metallic chromium is: b The charge between the cellulose ester film after saponification and metallic chromium. Amount: d, where d / b ≦ 4.0,
Cellulose ester film. 6. The cellulose ester film according to claim 5, wherein d / b ≦ 2.0. 7. A cellulose ester film having a thickness of 60 μm or less, wherein the amount of charge between the cellulose ester films before saponification measured under the condition 1 of 23 ° C. and 80% RH: a1 23 ° C., 55% RH Before saponification measured under the condition 1 of 23 ° C. and 80% RH, where 0 is the charge amount between the cellulose ester films before saponification measured under the condition 2 of the above: a2 Amount of charge between cellulose ester film and chromium metal:
b1 Charge amount between cellulose ester film before saponification and metallic chromium measured under condition 2 of 23 ° C. and 55% RH:
When b2, 0 ≦ b1 / b2 ≦ 2.0, and the charge amount between the saponified cellulose ester films measured under the condition 1 of 23 ° C. and 80% RH: c1 23 ° C., 55% RH The amount of charge between the saponified cellulose ester films measured under 2 is 1.0, and c2 is 1.0 ≦ c1 / c2 ≦ 2.0. After saponification measured under the condition 1 of 23 ° C. and 80% RH. Amount of charge between cellulose ester film and chromium metal:
d1 Charge amount between cellulose ester film after saponification and metallic chromium measured under condition 2 of 23 ° C. and 55% RH:
Cellulose ester film, characterized in that when d2, 1.0≤d1 / d2≤2.0. 8. A cellulose ester film having a thickness of 60 μm or less, wherein the amount of charge between the cellulose ester films before saponification measured under the condition 3 of 23 ° C. and 20% RH: a3 23 ° C., 55% RH Before the saponification measured under the condition 3 of 23 ° C. and 20% RH, the charge amount between the cellulose ester films before saponification measured under the condition 2 is 0 ≦ a3 / a2 ≦ 1.0. Amount of charge between cellulose ester film and chromium metal:
b3 Amount of charge between cellulose ester film before saponification and metallic chromium measured under condition 2 of 23 ° C. and 55% RH:
b2 is 0 ≦ b3 / b2 ≦ 1.0, and the charge amount between the cellulose ester films after saponification measured under the condition 3 of 23 ° C. and 20% RH: c3 23 ° C., 55% RH The amount of charge between the saponified cellulose ester films measured under 2 is 0 ≦ c3 / c2 ≦ 1.0, and the cellulose after saponification measured under the condition 3 of 23 ° C. and 20% RH The amount of charge between the ester film and metallic chromium:
Charge amount between the saponified cellulose ester film and metallic chromium measured under the condition 2 of d3 23 ° C. and 55% RH:
Cellulose ester film, characterized in that when d2, 0≤d3 / d2≤1.0. 9. A cellulose ester film having fine particles having an average particle diameter of 100 to 500 nm with an interparticle distance of 0.
It exists in the range of 5-5 micrometers, The cellulose ester film as described in any one of Claims 1-8 characterized by the above-mentioned. 10. A cellulose ester film, wherein fine particles having an average particle diameter of 500 to 1000 nm are present within a distance between particles of 1 to 5 μm. Item 7. A cellulose ester film. 11. A cellulose ester film having the general formula (1): (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), at least 1
The cellulose ester film according to any one of claims 1 to 10, which contains a seed. 12. A cellulose ester film having the general formula (1): (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), and at least one plasticizer X, and Formula (1) (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 phenyl groups), and at least one plasticizer Y represented by
The cellulose ester film according to any one of claims 1 to 10, which further comprises: