JP3425484B2 - Cellulose acetate laminated film and method for producing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fatty acid-substituted cellulose film used for photographic light-sensitive materials, polarizing plate protection, general packaging materials and the like. In particular, the present invention relates to a fatty acid-substituted cellulose film having a laminated structure and excellent in transparency and wet heat resistance.

[0002]

BACKGROUND OF THE INVENTION Fatty acid-substituted cellulose films, especially cellulose triacetate films, have good transparency, excellent mechanical strength, and small dimensional variation due to changes in humidity and heat (also referred to as good dimensional stability). ) So
It is used as a support for photographic light-sensitive materials and as a protective film for polarizing plates. Usually, a commercially available cellulose acetate film contains 15 to 20% by weight of a phosphoric acid ester-based plasticizer and / or a phthalic acid ester-based plasticizer. Japanese Patent Laid-Open No. 61-243407 discloses that
When a cellulosic film containing 15 to 20% by weight of a plasticizer is used as a polarizing plate protective film, dimensional changes occur due to factors such as migration and volatilization of the plasticizer under high temperature and high humidity conditions. Since it causes curling to cause problems such as deterioration in adhesive strength, it has been proposed that the content of the plasticizer be 10% by weight or less. Further, in JP-A 1-214802, in the above-mentioned commercially available cellulose acetate film as a polarizing plate protective film, the plasticizer contained therein changes color due to severe wet heat treatment, and thus is plasticized as a polarizing plate protective film. Cellulose triacetate without additives (hereinafter TA
It is proposed to use a film (also called C).

A cellulose triacetate film containing no plasticizer or having a reduced amount of plasticizer has poor flexibility, and when used as a polarizing plate protective film, it causes problems such as generation of cracks in the punching process of production. There is a problem that it becomes easier. Furthermore, as a knowledge on the film forming technology of the cellulose triacetate film, when the plasticizer which promotes the diffusion of the solvent is not added or the amount of the plasticizer is reduced, the drying rate of the solvent is decreased in the solvent drying step of the film formation. It is known that, as a result, the amount of solvent remaining in the film is increased. At present, methylene chloride is usually used as a solvent in the process of forming a cellulose triacetate film. Therefore, when the amount of the plasticizer is reduced as described above, when methylene chloride is used as the main solvent in the film forming step, the amount of methylene chloride remaining in the film immediately after production increases. Furthermore, when another organic chlorine-based solvent such as ethylene chloride is used as the auxiliary solvent, a larger amount of the organic chlorine-based solvent remains in the film. As described above, the increase of the residual organic chlorine-based solvent is not preferable in terms of environmental impact and working environment. On the other hand, if the drying time is extended to reduce the residual solvent, the production efficiency will be reduced and the cost will be increased, which is not preferable.

In order to avoid the above-mentioned problems in the process of forming a cellulose triacetate film, JP-A-61-61
In JP-127740, N-methyl-2-pyrrolidone (hereinafter, also referred to as NMP) is used as a main solvent for TAC film formation.
Is proposed to be used. However, since the boiling point of NMP is higher than that of methylene chloride, the amount of NMP remaining in the obtained film is higher. Therefore, if haze is generated in the film or if the drying time is extended in order to reduce the residual solvent, the production efficiency is greatly reduced and the cost is increased, which is not preferable. Further, it is known that cellulose diacetate can be solution-cast even with a non-chlorine organic solvent, but a film using this material has a problem in moist heat resistance and is hardly used at present.

In the current technology, the organic solvent contained in the cellulose acetate film obtained by solution casting is
The present situation is that the amount of residual organic solvent is reduced by evaporating to a certain extent in the drying process. However, in this case, the amount of the residual solvent can be reduced to about 1000 ppm at most in the case of the organic chlorine solvent and about 25,000 ppm in the case of NMP, which is still insufficient, and the above problems due to the residual solvent occur. Resulting in. Furthermore, since a large load is applied to the drying process, the production efficiency is greatly reduced and the cost is increased. As mentioned above,
Excellent in transparency and dimensional stability for a long time as a polarizing plate protective film or photographic light-sensitive material support,
There are many problems in the cellulose acetate film having a small amount of residual organic solvent (particularly, organic chlorine solvent) and the existing technology for producing the film.

[0006]

SUMMARY OF THE INVENTION The object of the present invention is to solve the above-mentioned drawbacks of the prior art and to provide fatty acid cellulose ester,
Especially for cellulose acetate film, it maintains excellent transparency, dimensional stability, and moist heat resistance (durability against coloring or decomposition due to heat and humidity) for a long period of time, and
A film that can significantly reduce the amount of solvent contained in a film immediately after production (especially, the amount of chlorine-based solvent is 10 ppm or less) and can be practically used as a polarizing plate protective film or a support for a photographic light-sensitive material, and the film. The object of the present invention is to provide a manufacturing method capable of obtaining high productivity and at low cost.

[0007]

The above object of the present invention has a core portion made of cellulose acetate having a degree of substitution of 2.7 or less, and 0.5 μm on at least one side of the core portion.
It is achieved by a cellulose acetate laminated film characterized by having a surface layer made of cellulose acetate having a thickness of ˜15 μm and a substitution degree of 2.8 or more. Further, the above-mentioned object is a dope prepared by a solvent containing 70% or more of methylene chloride or N-methyl-2-pyrrolidone for the surface layer made of cellulose acetate having a film thickness of 0.5 μm to 15 μm and a substitution degree of 2.8 or more. The core portion made of cellulose acetate having a degree of substitution of 2.7 or less is achieved by a method for producing a cellulose acetate laminated film, which is characterized in that a solution is formed with a dope prepared from a solvent containing 60% or more of acetone.

In the cellulose acetate laminated film of the present invention, a film having a laminated structure comprising a surface layer having a cellulose triacetate having a substitution degree of 2.8 or more and a core portion having a cellulose acetate having a substitution degree of 2.7 or less is obtained. In addition, the amount of the contained solvent can be remarkably reduced, and at the same time, a cellulose acetate film having excellent wet heat resistance can be obtained. A film formed from a cellulose acetate having a degree of substitution of 2.8 or more (hereinafter, also referred to as TAC) has significantly less moisture permeability than a film having a degree of substitution of 2.7 or less (hereinafter, also referred to as DAC). There are excellent characteristics. Therefore, by providing a TAC with low moisture permeability on the surface layer of the DAC, the invasion of moisture from the external atmosphere can be prevented.
Can be prevented, and DAC with insufficient resistance to moist heat is protected. As a result, the film as a whole has good resistance to humidity and heat over time. TAC
The degree of substitution is preferably 2.8 to 3.0, more preferably 2.9 to 3.0. The degree of substitution of DAC is preferably 2.0 to 2.7, and more preferably 2.5.
Is about 2.7.

In the present invention, the cellulose ester film having the above laminated structure has a two-layered film having a surface layer made of TAC and a layer made of DAC adjacent thereto, and a core portion of the DAC. The film of the triple layer structure in which the surface layer of TAC is provided on both sides of the film is included. Further, it also includes a film composed of three or more layers. In the case of the film having the triple-layer structure of the present invention, the upper and lower surface layers may not have the same thickness, but the same thickness is preferable because the mechanical properties of the film can be balanced. In the film of the present invention, if a functional layer such as a polarizing film or a photosensitive layer is provided on the film surface of the DAC, which is the core portion, the film having a double-layered structure can sufficiently achieve the purpose of preventing moisture. The problem of moisture-proof storage of a double-layered film can be solved by rolling the film and storing it in moisture-proof packaging. In the present invention, a film having a layered structure of three or more layers in which a surface layer of TAC is preferably provided on both surfaces of the core portion of the DAC is preferable. As a result, invasion of moisture into the film can be prevented in any storage state, and excellent transparency, dimensional stability, and moist heat resistance can be maintained for a long period of time.

Further, the surface layer having TAC is 0.5 to 1
Since it is a thin layer of 5 μm, the amount of organic solvent used can be significantly reduced even if it has a triple-layer structure, and it is safe in terms of working environment and impact on the environment, and problems such as haze caused by residual solvent Can be improved. Here, the thickness of the layer having TAC is preferably 0.
5 to 10 μm, more preferably 1.0 to 5.0 μm
m.

In the present invention, when a chlorine-based organic solvent is used for forming the TAC film, the chlorine-based organic solvent contained in the film immediately after the production is the same as the drying conditions in the conventional production of cellulose triacetate film. The amount of solvent can be 10 ppm or less. The amount of this chlorine-based organic solvent is preferably 5 ppm or less. This makes it even safer in terms of work environment and environmental impact,
Furthermore, the residual solvent can remarkably improve the problems such as haze that occur. In the present invention, even when the film has a triple layer structure in which the upper and lower surface layers are formed from cellulose acetate in which methylene chloride is dissolved, the organic chlorine solvent (usually mainly methylene chloride) contained in the film immediately after production is The amount can be 10 ppm or less. Providing a cellulose acetate film having an organochlorine solvent content of 10 ppm or less as described above provides a significantly long drying time when a film of 50 μm or more is formed from a dope of a solution containing methylene chloride. Otherwise, a film of 10 ppm or less cannot be produced, which is practically impossible.

Further, N-methyl-2-pyrrolidone (NM
The boiling point of P) is higher than that of methylene chloride,
The amount of residual solvent increases significantly. In the present invention, TA
Since the thickness of the layer having C is as thin as 15 μm at the maximum, the amount of residual NMP immediately after production can be 2000 ppm or less even in the case of a triple-layered film having upper and lower surface layers.
The amount of residual NMP is preferably 1500 ppm or less. As a result, the drying load for drying the surface layer is not large, and there is no problem in manufacturing. Also, since the amount of residual solvent is small and it is not necessary to use chlorine-based solvent for film formation, there is no problem of chlorine-based solvent remaining. Furthermore, haze generated due to a large amount of residual NMP can be prevented, and the transparency of the film during storage can be maintained.

In the present invention, as the deterioration preventing agent for cellulose acetate, the following general ones can be used. That is, epoxy compounds, weak organic acids, saturated polyhydric alcohols and antioxidants of general organic materials, for example, phosphite ester compounds, hindered phenols,
Sulfur-based antioxidants such as thioether, UV absorbers,
Light stabilizers, metal deactivators, radical chain inhibitors, peroxide decomposers, secondary amines and tertiary amines are known (US Pat. Nos. 2,917,398 and 3,72).
3,147, 4,269,629, 4,13
7,201, 3,723,147, JP-A-63-
128036, 57-78431, 55-13.
765, JP-B-61-45654, JP-A-59-1
2703, 56-18940, and 60-2358.
52, JP-A-3-199201, and 3-19804.
4, ibid. 4-174841, ibid. 5-194789, etc.). In the present invention, any of these can be used as a deterioration inhibitor.

In the present invention, it is preferable to add a tertiary amine compound having a pKa (negative logarithm of acid dissociation constant) of 4 or more. As a result, it is possible to eliminate the disadvantage that the film is excellent in transparency and resistance to moist heat, and that the film is colored after long-term use, which has been difficult to overcome in the past. Of course, in the present invention, the tertiary amine may be added uniformly throughout the film. Further, when a tertiary amine compound having a pKa of 4 or more is added to the surface layer portion, and particularly when the cellulose acetate film having a multilayer structure of the present invention is used as a support for a silver halide photographic light-sensitive material, an adjacent layer is It is a hydrophilic undercoat layer, and this is advantageous because it prevents the bleeding of the tertiary amine compound to the photosensitive layer as a barrier layer, and the influence on the photographic properties is reduced. In the present invention, preferred tertiary amine compounds as deterioration inhibitors for cellulose acetate films include tribenzylamine, tributylamine and the like, as well as JP-A-5-1.
The tertiary amine compounds and the like described in JP-A-94789 can be mentioned, and specifically, the compounds shown below can be mentioned.

[0015]

[Chemical 1]

[0016]

[Chemical 2]

[0017]

[Chemical 3]

[0018]

[Chemical 4]

[0019]

[Chemical 5]

[0020]

[Chemical 6]

[0021]

[Chemical 7]

[0022]

[Chemical 8]

[0023]

[Chemical 9]

[0024]

[Chemical 10]

[0025]

[Chemical 11]

[0026]

[Chemical 12]

[0027]

[Chemical 13]

[0028]

[Chemical 14]

As a method of adding the deterioration preventing agent to the cellulose acetate, there may be mentioned a method of adding it as a kind of additive during the solution film-forming step for obtaining a film molded article.
This method is advantageous in manufacturing because it can simultaneously perform deterioration prevention treatment during the film forming process, and can impart stability to the film itself without requiring new equipment.

In the present invention, the tertiary amine compound is used in an amount of 0.05-3.
It is preferable to add 0 part by weight. Further, it is preferable to add 0.05 to 2.0 parts by weight of other deterioration preventing agents to 100 parts by weight of cellulose acetate. It is more desirable to add 0.1 to 1.0 part by weight. The tertiary amine compound and other deterioration preventive agents are
It can be mixed and used. When the addition amount of the deterioration preventing agent in the present invention is less than the above, the deterioration preventing effect is not sufficiently exerted, and when the addition amount is increased, the deterioration preventing effect gradually increases, but when the addition amount exceeds a certain amount, the deterioration preventing effect is deteriorated. Not only the prevention effect is reduced, but also it becomes cloudy beyond the compatibility limit of the additive, and bleeds on the surface of the film-formed product, and coloring cannot be ignored, so it is not possible to add more than the above-mentioned addition amount. Not appropriate.

In the present invention, the thickness of the core portion having the DAC is preferably 10 to 500 μm, more preferably 50 to 200 μm. The total thickness of the cellulose acetate film having the laminated structure is preferably 10 to 500 μm, and particularly preferably 50 to 200 μm.

As the method for forming a solution of a cellulose acetate film in the present invention, a method generally used in the art can be used. Regarding a solution casting method for a cellulose ester film, for example, US Pat.
No. 92978, No. 2739070, No. 27390
No. 69, No. 2492977, No. 2336310
No. 2367603, No. 2492978, No. 2607704, British Patent No. 640731, No. 735892, Japanese Patent Publication No. 45-9074, No. 49-4.
The description of No. 554, No. 49-5614, etc. can be referred to.

In the film having a laminated structure of the present invention, the layer having TAC is methylene chloride or N.
It is preferable that a dope prepared with a solvent containing 70% or more of methyl-2-pyrrolidone is formed by solution film formation.
The layer having DAC is preferably formed by solution casting a dope prepared from a solvent containing 60% or more of acetone. Thereby, the above film can be obtained with high productivity and at low cost. When solution casting a TAC dope, a solvent containing 70% by weight or more of methylene chloride or NMP is preferably used, and more preferably 80 to 100% by weight. In this case, the content of TAC which is a solid content is preferably 10 to 30% by weight. Other solvents that can be used include, in the case of TAC, lower aliphatic hydrocarbon chlorides, methanol, ethanol, n-propyl alcohol, inpropyl alcohol, lower aliphatic alcohols such as n-butanol, cyclohexane, dioxane, Dimethylacetamide or the like can be used.

Further, in the case of solution casting a DAC dope, it is preferable to use a solvent containing 60% or more of acetone, more preferably 80 to 100% by weight. In this case, the content of the DAC which is a solid content is 10 to 10.
It is preferably 50% by weight. Other solvents that can be used include, in the case of DAC, lower aliphatic hydrocarbon chlorides such as acetone, methyl acetate, ethyl acetate and methylene chloride, methanol, ethanol,
n-propyl alcohol, inpropyl alcohol, n
In addition to lower aliphatic alcohols such as butanol, many other types of solvents such as ethylene glycol monomethyl ether, n-hexane, cyclohexane, methyl ethyl ketone and dioxane can be mixed and used.
Among these solvents, it is preferable to use an acetone-methanol system from the viewpoint of drying load and economical aspects.

In the present invention, as a method for forming a solution as a cellulose acetate film having a laminated structure, a co-casting method, a sequential casting method, a coating method or the like can be used. In the case of production by the co-casting method and the sequential casting method, first, a cellulose acetate dope for each layer is prepared. The co-casting method (multi-layer simultaneous casting) is performed on a casting support (band or drum),
Simultaneously extruding the casting dope of each layer (three layers or more) from another slit etc. Dope is extruded from the casting gisa, and each layer is simultaneously cast and peeled from the support at an appropriate time. It is a casting method of drying and molding a film. FIG. 1 is a cross-sectional view showing a state in which three layers of the surface layer dope 1 and the core layer dope 2 are simultaneously extruded and cast on the casting support 4 by using the co-casting caster 3.

In the sequential casting method, a casting dope for the first layer is first extruded from a casting gisa on a casting support and then cast and dried or dried without drying. The casting dope for the second layer is extruded from the casting gisa, and if necessary, the dope for casting is sequentially cast and laminated up to the third layer or more, and peeled from the support at an appropriate time. It is a casting method of forming a film by drying. The coating method is generally a method of forming a film of the core layer into a film by a solution film-forming method, preparing a coating solution for coating on the surface layer, and coating the film on one side or on both sides simultaneously using an appropriate coating machine. This is a method of forming a laminated film by applying and drying the liquid.

Generally, it is difficult to maintain the flatness of the film because the coating method increases the drying load after coating and the sequential casting method complicates the process. On the other hand, the co-casting method has the advantages that the steps are simple, the productivity is high, and the flatness of the film can be obtained relatively easily. Therefore, in the present invention, the co-casting method is preferable.
There are a feed block method and a multi-manifold method as the type of gysa used in the co-casting method, but either type can be used.

Usually, in the case of solution film-forming of cellulose triacetate, the film is formed by adding a plasticizer such as triphenyl phosphate as a component which becomes a solid after drying and other various additives which are added as necessary. Further, in the case of forming a film of a solution of normal cellulose acetate, a plasticizer such as triphenyl phosphate or dibutyl phthalate as a component that becomes a solid after drying, other various additives and cellulose acetate propionate, if necessary,
Cellulose derivatives such as cellulose acetate butyrate can also be added.

Examples of the plasticizer in the present invention include:
Tricresyl phosphate, or dimethyl phthalate, diethyl phthalate, dibutyl phthalate, dioctyl phthalate, dimethoxyethyl phthalate, glycerol triacetate, o- or p-toluene ethyl sulfonamide, butyl phthalyl butyl glycolate, ethyl phthalyl ethyl Glycolate, methylphthalylethyl glycolate, trimethyl trimellitate,
Examples include compounds such as trioctyl trimellitate. Among these, phthalate-based and trimellitate-based compounds are particularly desirable from the viewpoints of compatibility and resistance to moist heat. A dialkyl phthalate compound having an alkyl chain having 1 to 8 carbon atoms is preferable, and diethyl phthalate is more preferable. In order to prevent quality deterioration of the product during long-term storage, it is desirable to use an additive such as the plasticizer having high thermal stability. In the present invention, it is preferable not to add the plasticizer. In addition to the above, a peeling accelerator from the casting support, a dye, and the like can be added to the cellulose ester solution, if necessary.

The addition of the deterioration preventive agent in the present invention to the cellulose acetate film having a laminated structure means that when the surface layer and the core layer are simultaneously cast in a multilayer structure, the deterioration preventive agent is added as an additive of the composition of the dope for the surface layer. Preferably, it can be achieved by adding a tertiary amine compound or a mixture of a tertiary amine compound and another deterioration inhibitor. Of course, in addition to the method by the co-casting method, when a cellulose acetate film having a laminated structure is produced by the sequential casting method, it is added as an additive of the composition of the dope for the surface layer, and a deterioration inhibitor is added to the laminated structure. It can also be added to the cellulose acetate film.

The cellulose acetate film of the present invention having a laminated structure in which a tertiary amine is added to at least the surface layer,
Since it is an excellent cellulose acetate film that has good transparency and small birefringence over a long period of time, and that it retains moist heat resistance, it is suitable for use as a support for silver halide photographic light-sensitive materials or as a polarizing plate protective film. is there. Here, the moist heat resistance means durability against coloring or decomposition of the (cellulose acetate film) in an environment of high temperature and high humidity. In general, a silver halide photographic light-sensitive material having a cellulose triacetate film as a support has a hydrophilic and gelatin-affinitive undercoat layer on both sides of the cellulose triacetate film, on which both sides are silver halide photographic light-sensitive emulsions. The silver halide photographic light-sensitive material is obtained by coating and drying the layer, or by coating a silver halide photographic light-sensitive emulsion layer on one side and coating a back layer on the other side and drying. In addition, since the display quality of a polarizing plate used in a liquid crystal display device or the like remarkably deteriorates due to evaporation of iodine or scratches on the surface, it is generally protected by sticking a thin film that is transparent and colorless and has good flatness. Has been done. This is called a polarizing plate protective film, and a cellulose acetate film is most often used. As this cellulose acetate film, a film having a thickness of about 0.1 mm produced by the above method is often used. The polarizing plate and the protective film are attached to each other with an adhesive interposed.

Next, the conditions in the film forming process will be described in more detail. Dope used for solution casting is, for example,
It can be obtained by putting cellulose acetate and the above solvent in a pressure vessel and sealing the mixture, heating under pressure to a temperature above the boiling point of the solvent at normal pressure and in a range not boiling the solvent, and stirring. Cellulose acetate, a solvent, and other additives that may be added if necessary may be roughly mixed in advance and then placed in a pressure vessel, or may be placed separately. The type of the pressurizing container does not matter, as long as it can withstand a predetermined pressure. This pressure vessel needs to be able to pressurize and also to stir. After melting, cool and take out from the container, or pull out from the container with a pump and cool with a heat exchanger,
This is subjected to film formation. In this dissolution method, by applying pressure, it is possible to heat above the boiling point at normal pressure, and to prevent gelation by suppressing boiling and preventing an over-concentrated state. The heating increases the solubility and the dissolution rate, and enables complete dissolution in a short time.

The pressurization applied to dissolve the dope may be performed by injecting an inert gas such as nitrogen gas, or may be performed only by increasing the vapor pressure of the solvent by heating. In addition, it is also possible to utilize the decrease in the volume of the gas phase in the container by sealing the pressurized container and then press-fitting a part or all of the cellulose acetate, solvent and other additives. Heating is preferably performed from the outside, and for example, a jacket type is suitable. In addition, a plate heater or the like may be provided outside and connected by piping to circulate the heating.

The stirring blade installed in the pressure dissolution vessel used for dissolving the dope should have a length reaching the vicinity of the vessel wall, and a scraping blade at the end for renewing the liquid film on the vessel wall. It is preferable to provide. In addition to the pressure dissolution vessel, other instruments such as a pressure gauge and a thermometer are properly installed. The above raw materials are placed in a pressure dissolution vessel and heated under pressure. The heating temperature is a temperature which is equal to or higher than the boiling point of the solvent and does not boil the solvent. This temperature is preferably 60 ° C. or higher, particularly 80
It is preferably about 110 ° C. The pressure is set so that the solvent does not boil at this set temperature. After casting the obtained dope on the substrate as described above,
By cooling to a temperature of 0 ° C. or less, gelation of the dope is caused, and peeling can be facilitated, which is preferable. At this time, the gelling temperature of the dope, which depends on the concentration of cellulose acetate and the solvent composition, needs to be higher than the support temperature.

In the case of cooling the casting part, JP-A-62-3
As disclosed in Japanese Patent No. 7113, a method using a refrigerant or cold air, a method using a heat pipe, or the like can be used. The cooling temperature is such that the surface temperature of the support is 10 ° C. or lower, preferably 5 ° C. or lower. Dry air may not be used, but may be used as long as the surface temperature of the support is not increased. After peeling after casting, JP-A-62-115
As disclosed in Japanese Patent No. 035, it is preferable that the film is dried while applying a constant tension in the width direction of the film, and is manufactured in a state where a predetermined residual solvent is contained in the film.

[0046]

EXAMPLES The present invention will be specifically described below with reference to examples, but the contents of the present invention are not limited thereto. [Example 1] (Composition of dope for surface layer) Cellulose acetate (substitution degree 2.9) ... 100 parts by weight Triphenyl phosphate ... 13 parts by weight Tribenzylamine ... 0.5 parts by weight Methylene chloride・ ・ ・ 314 parts by weight Methanol ・ ・ ・ 44 parts by weight n-Butanol ・ ・ ・ 12 parts by weight (composition of core layer dope) Cellulose acetate (substitution degree 2.5) ・ ・ ・ 100 parts by weight Triphenyl phosphate ・··· 10 parts by weight diethyl phthalate ・ ・ ・ 5 parts by weight tribenzylamine ・ ・ ・ 0.5 parts by weight Acetone ・ ・ ・ 256 parts by weight Methanol ・ ・ ・ 110 parts by weight

Dope solutions having the respective compositions described above were prepared by a well-known method, and after filtration, a co-casting method was used to form a dry film having an outer layer (upper and lower surface layers) of 3 μm on both sides of the core layer of 74 μm. Was cast on a support so that In the co-casting, each dope was heated to 35 ° C. using a feed block type die and cast on a stainless steel support. After casting, it was dried at 80 ° C for 3 minutes and then peeled off.
It was dried at 20 ° C. for 10 minutes to obtain a dry film sample.

Examples 2 to 7 and Comparative Examples 1 to 5 shown below
Was cast in the same manner as in Example 1 except for the following conditions. [Example 2] In Example 1, the thickness of the upper and lower surface layers was set to 0.
A film sample having a thickness of 5 μm and a core layer of 79 μm. [Example 3] In Example 1, the thickness of the upper and lower surface layers was changed to 15
A film sample in which the thickness of the core layer is 50 μm. [Example 4] A film sample obtained by changing the substitution degree of the surface layer dope cellulose acetate in Example 1 to 2.8. [Example 5] A film sample produced with a dope excluding tribenzylamine as the core layer dope in Example 1. Example 6 A film sample in which the same amount of tributylamine was added instead of the doped tribenzylamine for the surface layer and the core layer in Example 1. [Example 7] A film sample obtained by removing the core layer dope tribenzylamine from Example 6.

Comparative Example 1 A film sample obtained in Example 1 except that the upper and lower surface layers have a thickness of 0.3 μm and the core layer has a thickness of 79.4 μm. [Comparative Example 2] In Example 1, the upper and lower surface layers had a thickness of 20.
A film sample in which the thickness of the core layer is 40 μm. [Comparative Example 3] A film sample having a thickness of 80 µm prepared by using only the surface layer dope of Example 1. [Comparative Example 4] A film sample having a thickness of 80 µm prepared by using only the core dope of Example 1. [Comparative Example 5] A film sample obtained by changing the substitution degree of the surface layer dope cellulose acetate in Example 1 to 2.7.

Example 8 The core dope composition was the same as in Example 1, and the composition of the surface layer dope was as follows. A sample film was prepared with the upper and lower surface layers having a thickness of 3 μm and the core layer having a thickness of 74 μm. (Dope composition for surface layer) Cellulose acetate (substitution degree 2.9): 100 parts by weight Triphenyl phosphate: 13 parts by weight Tribenzylamine: 0.5 parts by weight N-methyl-2-pyrrolidone ..252 parts by weight Methanol ...

Example 9 In Example 8, a film sample was prepared in which the upper and lower surface layers had a thickness of 0.5 μm and the core layer had a thickness of 79 μm. [Example 10] In Example 8, the thickness of the upper and lower surface layers was changed to 15
A film sample in which the core layer has a thickness of 50 μm. [Example 11] A film sample in which the degree of substitution of the cellulose acetate in the surface layer in Example 8 was 2.8.

Comparative Example 6 A film sample in which the thickness of the upper and lower surface layers was set to 20 μm and the thickness of the core layer was set to 40 μm in Example 8. [Comparative Example 7] In Example 8, the thickness of the upper and lower surface layers was 0.3.
A film sample having a thickness of 7 μm and a core layer thickness of 79.4 μm. [Comparative Example 8] A film sample in which the substitution degree of the cellulose acetate in the surface layer in Example 8 was 2.7.

The various films obtained above were evaluated by the following methods. [Evaluation Method] A moist heat resistant evaluation sample film was cut into 100 mm × 100 mm,
After left in an atmosphere of 85 ° C. and 90% RH for 500 hours, the colored state was observed. The results were evaluated as follows. A: Not colored. B: Slight coloring is observed. C: Remarkable coloring is observed.

Residual amount of chlorine-based organic solvent 0.5 g of a sample film was sampled and quantitatively analyzed by a purge and trap method using a gas chromatograph. The gas chromatograph used was GC1 made by Shimadzu Corporation.
5A, FID was used as the detector, and Porapack Q was used as the column. Transparency Measured by the method of an AKA photoelectric tube colorimeter manufactured by Kotaki Seisakusho. As a result, in any film sample,
The total light transmittance was 84% or more, and the haze was 1% or less, showing good transparency. As the solvent for the surface layer dope, the properties of the cellulose acetate film formed by using a methylene chloride-methanol system and the amount of the organochlorine solvent contained in the product film are shown in Table 1, and the solvent for the surface layer dope is NMP type. Table 2 summarizes the properties and residual solvent amount of the cellulose acetate film formed by using. The residual solvent amount is the chlorine-based solvent that remains immediately after manufacturing,
The amount was NMP.

[0055]

[Table 1]

[0056]

[Table 2]

From the results shown in Table 1, Example 1 has good resistance to moisture and heat, and the amount of the organic chlorine solvent contained in the product film is 2 ppm or less. Example 2 is slightly inferior in moist heat resistance, but is in a range in which it is practically acceptable. The residual chlorine-based organic solvent is also 2 ppm or less. In Example 3, the resistance to moist heat is good, and the amount of the organic chlorine solvent in the product film is 10 ppm. In Comparative Example 1, the surface layer is provided with 0.3 μm, and it can be seen that the moist heat resistance is a problem and the thickness of the surface layer is insufficient. Comparative Example 2 has a surface layer portion of 20 μm and has good wet heat resistance, but the amount of chlorine-based organic solvent is 10
This is a problem because it exceeds ppm. In Comparative Example 3, since the layer containing methylene chloride becomes thick, the amount of the organic chlorine-based solvent becomes very large. In Comparative Example 4, the organochlorine-based solvent was not included, but the cellulose acetate layer having a low degree of substitution was deteriorated and the moist-heat resistance was poor. In Comparative Example 5, the degree of substitution of the surface layer was lowered to 2.7, and it was found that the wet heat resistance was inferior.

In Example 4, the degree of acetyl group substitution of the cellulose acetate in the surface layer was 2.8, and although the moist-heat resistance was slightly inferior, there was no problem in practical use, and the amount of the organic chlorine solvent was 2 ppm or less. . Example 8 and below are systems containing no organic chlorine solvent. From the results of Table 2, Example 8 has good wet heat resistance. Example 9 is slightly inferior in moist heat resistance, but is at a level where there is no practical problem. The wet heat resistance of Example 10 is inferior to that of Example 8, but is practically acceptable. In Comparative Example 6, N-methyl-2-pyrrolidone was not sufficiently dried, so that haze was generated in the surface layer, and the moist-heat resistance was significantly poor. In Comparative Example 7, the solvent of the surface layer can be dried, but the moist heat resistance is poor because the surface layer is too thin. Example 11 is the same as Example 8 except that the substitution degree of the surface layer is set to 2.8. In this case as well, the moist heat resistance is inferior to that of Example 8, but at a practically no problem level.

In Comparative Example 8, the degree of substitution of the surface layer of Example 11 was changed to 2.7. In this case, the resistance to moist heat is poor. As can be seen from the results in Table 1, Example 5 is Example 1
In the case where the tribenzylamine in the core layer dope was removed, the moist heat resistance was inferior to that of Example 1, but at a practically acceptable level. Example 6 is a case where the same amount of tributylamine was added instead of tribenzylamine in Example 1. In this case, good wet heat resistance can be obtained. Example 7 is a case where the tributylamine in the core layer dope of Example 6 was removed. In this case, Example 6
Although it has a lower moist heat resistance than that, there is no problem in practical use.

[0060]

EFFECTS OF THE INVENTION According to the present invention, excellent transparency, dimensional stability, and moist heat resistance (durability against coloring or decomposition due to heat or humidity) are maintained for a long period of time, and the film is contained immediately after production. A film that can significantly reduce the amount of solvent (especially, the amount of chlorine-based solvent is 10 ppm or less) and can be practically used as a protective film for polarizing plates and a support for photographic light-sensitive materials, and a film with high productivity and low cost. It is possible to provide the production method obtained in.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of a situation in which a triple-layer structure cellulose acetate film is cast by simultaneous casting using a co-casting gisa.

[Explanation of symbols]

1 Dope for surface layer 2 Dope for core layer 3 co-casting gyusa 4 Casting support

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI // B29K 1:00 B29K 1:00 B29L 9:00 B29L 9:00 11:00 11:00 (56) References 6-134933 (JP, A) JP 5-200942 (JP, A) JP 5-194789 (JP, A) JP 5-193052 (JP, A) JP 61-243407 (JP, A) JP 61-148013 (JP, A) JP 61-94725 (JP, A) JP 61-94724 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) ) B32B 1/00-35/00 B29C 41/00-41/52 G02B 5/30 C08L 1/12

Claims (6)

(57) [Claims] 1. A core portion made of cellulose acetate having a degree of substitution of 2.7 or less, having a film thickness of 0.5 μm to 15 μm and a degree of substitution of 2.8 on at least one surface of the core portion.
A cellulose acetate laminated film having a surface layer made of the above cellulose acetate. 2. The cellulose acetate laminated film according to claim 1, wherein the amount of the organic chlorine solvent contained in the film immediately after production is 10 ppm or less. 3. The cellulose acetate laminated film according to claim 1, wherein the amount of N-methyl-2-pyrrolidone contained in the film immediately after production is 1500 ppm or less. 4. The cellulose acetate laminated film according to claim 1, wherein at least the surface layer contains a tertiary amine compound having a negative logarithm pKa of an acid dissociation constant of 4 or more. . 5. The surface layer made of cellulose acetate having a thickness of 0.5 μm to 15 μm and a substitution degree of 2.8 or more,
Dope prepared with a solvent containing 70% or more of methylene chloride or N-methyl-2-pyrrolidone, degree of substitution 2.7.
The method for producing a cellulose acetate laminated film, wherein the following core portion made of cellulose acetate is solution-cast with a dope prepared from a solvent containing 60% or more of acetone. 6. The method for producing a cellulose acetate laminated film having a laminated structure according to claim 5, wherein each layer of the cellulose acetate film having the laminated structure is cast by co-casting method. .