JP2002030157A - Production method for cellulose acetate film, and cellulose acetate film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce an excellent cellulose triacetate film by using a stable solution prepared by dissolving cellulose triacetate in an organic solvent containing methyl acetate and no chlorohydrocarbon. SOLUTION: This cellulose triacetate film is produced by a process comprising the step of cooling a mixture of cellulose triacetate having an average degree of acetylation of 58.0-62.5% and an organic solvent substantially not containing a chlorohydrocarbon and containing methyl acetate to -100 to -10 deg.C; the step of dissolving cellulose triacetate by heating the cooled mixture to 0-55 deg.C; if necessary, the step of mixing an additive into the resultant cellulose triacetate solution; the step of casting the solution on a carrier; and the step of evaporating the solvent to give a dried film. In any one of the above steps of preparing the solution, methyl or ethyl acetoacetate in an amount of 3-30 wt.% (based on the solution) is incorporated into the solution.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cellulose triacetate film useful for a silver halide photographic light-sensitive material or a liquid crystal image display and a method for producing the cellulose triacetate film.

[0002]

2. Description of the Related Art Conventionally, a chlorine-containing hydrocarbon such as methylene chloride has been used as an organic solvent for a cellulose triacetate solution used in producing a cellulose triacetate used in a silver halide photographic material or a liquid crystal image display device. Have been. Methylene chloride (boiling point 41
C) has been conventionally used as a good solvent for cellulose triacetate, and is preferably used because it has a low boiling point in the film-forming and drying steps of the production process and thus is easy to dry. Conversely, methylene chloride has a problem that it has a low boiling point and is easily volatilized, so that it is slightly leakable from the hermetic equipment, the recovery is limited, and it cannot be completely prevented from dissipating into the atmosphere. Recently, the use of chlorine-containing compounds such as perchrene and trichlene has been regulated due to suspicion of carcinogenicity.Methylene chloride does not have such a problem, but the chlorine-containing compound, methylene chloride, will be subject to some restrictions in the future. It is becoming a target. Therefore, it has become urgent for those skilled in the art to search for or study a solvent for cellulose triacetate other than methylene chloride. Acetone (boiling point: 56) is known as an organic solvent having solubility in cellulose triacetate.
° C), methyl acetate (boiling point 56.3 ° C), tetrahydrofuran (boiling point 65.4 ° C), 1,3-dioxolane (boiling point 75 ° C), nitromethane (boiling point 101 ° C), 1,4-dioxane (boiling point 101 ° C) , Epichlorohydrin (boiling point: 116 ° C), N-methylpyrrolidone (boiling point: 202 ° C) and the like. When these organic solvents are actually subjected to dissolution tests, some of them are not necessarily good solvents, some of which have a risk of explosion, etc., some have a high boiling point, and there are few that can be put to practical use. Was.

[0003] Among the above organic solvents, acetone having a low boiling point only swells cellulose triacetate by a usual method but does not dissolve it. In recent years, attempts have been made to dissolve cellulose triacetate in acetone to produce fibers and films. J.
M. G. FIG. Cowie et al., Makromol. chem.
143, p. 105 (1971), cellulose triacetate (acetylation degree: 60.1% to 61.3%) was cooled from -80 ° C to -70 ° C in acetone, and then heated to 0.5 to 5% by heating. It is reported that a weight percent dilute solution was obtained. Such a method of melting at a low temperature is called a cooling melting method. In addition, Kenji Ude et al.
Vol. 4, pp. 57-61 (1981), "Dry spinning of cellulose triacetate from acetone solution" describes a spinning technique using a cooling dissolution method.

Further, Japanese Patent Application Laid-Open Nos. 9-95544 and 9-95544
Japanese Patent No. 95557 discloses that, on the background of the above technology, cellulose triacetate is dissolved by an organic solvent substantially consisting of acetone or by a cooling dissolution method using acetone and another organic solvent in common, and is applied to film production. is suggesting. According to the above-mentioned study, it was necessary to lower the temperature to -30 ° C. despite the fact that acetone, which is a good solvent for cellulose triacetate, was originally used. Japanese Patent Application Laid-Open No. 9-95538 discloses a film in which cellulose triacetate is dissolved by a cooling dissolution method using an organic solvent selected from ethers, ketones or esters other than acetone to prepare a film. 2-methoxyethyl acetate,
Preference is given to cyclohexanone, ethyl formate, methyl acetate and the like. In the above method, the transparency and stability of the prepared cellulose triacetate solution are poor and the reproducibility of the cellulose triacetate solution is poor unless the low polymerization degree portion of the cellulose triacetate is removed in advance. There was a complication. As a solution to this,
JP-A-11-60752 discloses the use of a mixed solvent of acetone and fluorine alcohol or methyl acetoacetate. Certainly, it was recognized that the solubility of cellulose cellulose triacetate was improved by this method.However, when a high concentration solution of cellulose cellulose triacetate was prepared, or when the degree of acetylation of cellulose cellulose triacetate was increased, the solubility was improved. The solution was insufficient or the stability of the solution over time was unstable, and a practically stable solution could not be prepared.

[0005]

When a solution of cellulose triacetate is prepared in a mixed solvent system of acetone and another solvent using the above-described cooling dissolution method, the above-mentioned commercially available cellulose triacetate is used as it is. If the low polymerization degree components contained in these components are not removed beforehand, there is a problem in the transparency and stability of the solution.
Such properties are serious drawbacks when using, for example, a cellulose triacetate film produced in a silver halide photographic material or a liquid crystal image display device, and must be eliminated in the production process.

An object of the present invention is to provide an excellent cellulose triacetate film without using a chlorinated hydrocarbon such as methylene chloride. Another object of the present invention is to provide an excellent cellulose triacetate film by using a commercially available photographic grade cellulose triacetate as it is in a cooling dissolution method using methyl acetate.

[0007]

The object of the present invention is to provide a cellulose triacetate having an average acetylation degree of 58.0 to 62.5% and an organic solvent containing substantially no chlorine-containing hydrocarbon and containing methyl acetate. Cooling the mixture to −100 to −10 ° C., heating the cooled mixture to 0 to 55 ° C. to dissolve the cellulose triacetate, and, if necessary, adding additives to the solution and mixing. In forming a cellulose triacetate film through a step of casting the cellulose triacetate solution prepared through the step on a support and a step of evaporating the solvent and drying the film, in any of the steps of preparing the cellulose triacetate solution, Cellulose containing 3 to 30% by weight of methyl acetoacetate or ethyl acetoacetate based on a solution Manufacturing method and film of Li acetate film was achieved by.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The average acetylation degree of cellulose triacetate used in the present invention is 58.0% to 62.5%. In the present invention, this range is referred to as cellulose triacetate. In addition to the degree of acetylation, the indication of the degree of reactivity includes the degree of substitution or the degree of acetylation. The degree of acetylation is expressed in terms of% by weight of acetic acid when acetic acid reacts with the hydroxyl group of cellulose, and 62.5% when the acetic acid is reacted at the maximum. The degree of acetylation is expressed in terms of the acetyl group (CH3CO) weight% at the time of reaction, and is 44.8% at the highest reaction. The degree of substitution represents the degree to which the acetyl group has reacted with the OH group of the cellulose molecule, and the case where all the OH groups have reacted is represented as 3.00. This means that three acetyl groups were substituted for three OH groups in the glucose unit, the minimum unit of the cellulose molecule. Incidentally, in the case of cellulose triacetate having a degree of acetylation of 58.0%, the degree of acetylation is 41.57% and the degree of substitution is 2.63. The degree of acetylation can be measured by the method described in the test method for cellulose triacetate of ASTM D-817-97.

The polymerization degree (viscosity average) of the cellulose triacetate used in the present invention is preferably from 220 to 500. Generally, a cellulose triacetate film containing cellulose triacetate, the degree of polymerization is required to be 200 or more in order for the mechanical strength of the fiber or the molded article to be tough, and the “Cellulose Handbook” edited by Hiroshi Sobue and Nobuhiko Uida Asakura Shobo (1985)
It is described in "Plastic Materials Course 17" edited by Hiroshi Marusawa and Kazuo Uda, Nikkan Kogyo Shimbun (1970). The polymerization degree of the cellulose triacetate film of the present invention is more preferably from 250 to 350. The viscosity average polymerization degree can be measured by an Ostwald viscometer, and is determined by the following equation from the measured intrinsic viscosity [η] of the cellulose triacetate film. DP = [η] / Km (where DP is the viscosity average polymerization degree,
Km is a constant 6 × 10-4)

As the cellulose as a raw material of the cellulose triacetate used in the present invention, there are cotton linter and wood pulp, and any of the cellulose triacetates may be used, or may be used as a mixture. Some raw materials have many low molecular weight components.
JP-A-9-95538, JP-A-9-95544 and JP-A-9-95544
In Japanese Patent No. -5557, cellulose triacetate having a low molecular weight tends to undergo crystallization in the cooling dissolution method.
If microcrystals are present, the dissolution in methyl acetate is reduced, the stability of the obtained cellulose triacetate solution (hereinafter sometimes referred to as dope) is low, and microcrystals are easily generated again. It is further stated that the optical properties of the resulting film are also reduced. The cellulose triacetate used in the present invention is not particularly limited, but is preferably a photographic grade,
Commercially available photographic grades can be obtained with satisfactory viscosities such as viscosity average degree of polymerization, degree of acetylation, and low molecular weight components. Manufacturers of photographic grade cellulose triacetate include Daicel Corporation, Coatles, Hoechst and Eastman Kodak, and any photographic grade cellulose triacetate can be used.
In the present invention, cellulose triacetate is mainly used, but other cellulose derivatives (for example, cellulose acetate propionate (CAP), cellulose acetate butyrate (CAB), cellulose acetate benzoate, etc.) may be used in combination. In that case, the substitution is at most 40% by weight, more preferably at most 30% by weight, based on the cellulose triacetate.

In the present invention, a mixed solvent of methyl acetate and at least one kind of methyl acetoacetate or ethyl acetoacetate is used for preparing the cellulose triacetate solution, but the addition of another solvent is prohibited as described later. Not something. This mixed solvent is substantially free of halogenated hydrocarbons such as methylene chloride. “Substantially free” means that the proportion of halogenated hydrocarbon in the mixed solvent is less than 5% by weight (preferably less than 2% by weight). The at least one mixed solvent of methyl acetoacetate or ethyl acetoacetate used together with methyl acetate will be described in more detail.

The amount of the solvent preferably used in the present invention is 30 to 87% by weight of methyl acetate, and 3 to 60% by weight of at least one kind of methyl acetoacetate or ethyl acetoacetate. preferable. Furthermore, the content of methyl acetate is 50 to 85% by weight,
Preferably, at least one methyl acetoacetate or ethyl acetoacetate is 5 to 40% by weight,
Preferably, the content of methyl acetate is 50 to 75% by weight, and at least one kind of methyl acetoacetate or ethyl acetoacetate is 5 to 25% by weight. In the present invention, another organic solvent may be added to the above-mentioned organic solvent in all steps of the cellulose triacetate solution. For example, alcohols such as methanol, ethanol, propanol, isopropanol, s-butanol, t-butanol, cyclohexanol, hexane, octane,
Aliphatic or alicyclic hydrocarbons such as cyclohexane,
Toluene, aromatic hydrocarbons such as xylene, methyl formate, ethyl formate, ethyl acetate, isopropyl acetate, esters such as butyl acetate, 1,3-dioxolane, tetrahydrofuran, ethers such as 1,4-dioxane, Methoxyethanol, ethoxyethanol, ethylene glycol esters or ethers such as 2-methoxyethyl acetate, methyl ethyl ketone, diethyl ketone, methyl isobutyl ketone, diisobutyl ketone,
It can be suitably selected from ketones such as cyclohexanone and methylcyclohexanone, and mixed solvents thereof. These solvents can be used in the range of 0 to 40% by weight.

Among these solvents, the solvents capable of efficiently producing the cellulose triacetate film of the present invention have a carbon number of methanol, ethanol, propanol, isopropanol, n-butanol, s-butanol, t-butanol, cyclohexanol and the like. Examples thereof include lower alcohols of 1 to 6, methyl ethyl ketone, cyclohexanone and cyclohexane. Methanol, ethanol, n-butanol and cyclohexanone are preferred. In general, a cellulose triacetate film solution is cast on a support, the solvent in the dope is evaporated on the support, and the solvent is evaporated. After one round, the dope film (hereinafter also referred to as a web, which cannot be clearly distinguished, cannot be separated on the support, but before and after peeling). , Which will be referred to in the initial drying process, etc.) is separated from the support. Whether or not the separation is possible depends on the strength of the doped film enough to withstand the separation and the amount of the residual solvent near the support surface. Therefore, it is necessary to increase the strength of the dope film on the support and to evaporate the solvent quickly. When a solvent such as the above alcohol or cyclohexane is added, the dope is gelled after casting, and the dope solidifies. The dope film that has lost fluidity can be dried quickly by efficiently applying heat that does not cause foaming, and as a result, peeling can be accelerated. The proportion of such a solvent in the organic solvent is 2% by weight to 30% by weight based on the total organic solvent, preferably 5% by weight.
% To 20% by weight.

The cellulose triacetate solution of the present invention is dissolved in a mixed organic solvent containing methyl acetate and methyl acetoacetate or ethyl acetoacetate by a cooling dissolution method.
It may be prepared by dissolving cellulose triacetate. In that case, first, cellulose triacetate is gradually added to a mixed solvent of methyl acetate and methyl acetoacetate or ethyl acetoacetate at room temperature while stirring. At this stage, the cellulose triacetate is in a state where it is insufficiently swollen in ethyl acetate with methyl acetate alone, whereas the methyl acetoacetate or ethyl acetoacetate of the present invention is used in this stage. It was confirmed that the cellulose triacetate was not only sufficiently swollen but also reached a semi-dissolved state.

The dissolution concentration of cellulose triacetate by the cooling dissolution method in the mixed solvent system of methyl acetate and methyl acetoacetate or ethyl acetoacetate of the present invention can be as high as 25% by weight or more, as disclosed in JP-A-9-95544. Alternatively, the cellulose triacetate solution having a high concentration can be obtained because the solubility is higher than the solubility in acetone alone or a mixed solvent of acetone and another solvent described in JP-A-9-95557. From the viewpoint of drying efficiency during film formation, it is preferable that the concentration is as high as possible. The amount of cellulose triacetate is adjusted so as to contain 10 to 40% by weight as a final dope. However, in the organic solvent composition of the present invention, a high-concentration cellulose triacetate solution can be prepared. Any concentration may be used. If the concentration is too high, the viscosity of the solution may be too large and it may be difficult to form a film. Therefore, the preferred cellulose triacetate concentration of the cellulose triacetate solution is in the range of 15% by weight to 30% by weight. Further, the range is preferably 17% by weight to 25% by weight.

Next, the mixture is heated at -100 to -10 ° C (preferably at -90 to -10 ° C, more preferably at -80 to -2.
(0 ° C., most preferably −80 to −30 ° C.).
Cooling is performed, for example, in a dry ice / methanol bath (−75
° C) or a cooled ethylene glycol solution (-30 to -2
0 ° C.). Further, a mechanical cooling device may be used. When cooled in this way, the mixture of cellulose triacetate and the mixed solvent may solidify in some cases. Next, when this cooled product is heated to 0 to 55 ° C, cellulose triacetate is completely dissolved in the mixed solvent. The temperature may be raised only at room temperature or may be heated in a warm bath. In this way, a homogeneous solution is obtained. The operation of cooling and heating may be repeated in order to accelerate the dissolution. Whether or not the dissolution is sufficient can be determined only by visually observing the appearance of the solution. In the cooling dissolution method,
It is preferable to use a closed container to avoid water contamination due to condensation during cooling. In the cooling and heating operation, if the pressure is increased during cooling and the pressure is decreased during heating, the dissolution time can be further reduced. In order to perform pressurization and decompression, it is desirable to use a pressure-resistant container.

As described above, the concentration of the cellulose triacetate in the dope of the present invention is characterized in that a high concentration of the dope can be obtained, and a cellulose triacetate solution having a high concentration and excellent stability can be obtained without relying on concentration means. What is obtained is also a feature of the present invention. After further dissolving at a low concentration to facilitate dissolution, the solution may be concentrated using a concentration means. The method of concentration is not particularly limited.For example, the low-concentration solution is guided between the cylindrical body and the rotation locus of the outer periphery of the rotating blade rotating in the circumferential direction inside the cylindrical body, and the temperature is set between the solution and the solution. A method of obtaining a high concentration solution while evaporating the solvent by giving a difference (for example, Japanese Patent Application Laid-Open No.
No. 1), a heated low-concentration solution is blown into a container from a nozzle, and the solvent is flash-evaporated until the solution hits the inner wall of the container from the nozzle. A method of extracting from the bottom (for example, U.S. Pat.
No. 8229, No. 4414341, and No. 4504355). In the preparation of the cellulose triacetate solution of the present invention, methyl acetoacetate or ethyl acetoacetate may be mixed and prepared in any of the preparation steps. In other words, during the first mixing, cooling,
Either at the time of raising the temperature or at the time of the subsequent preparation, the effect is hardly changed. When preparing the cellulose triacetate solution of the present invention, the container may be filled with an inert gas such as nitrogen gas. The viscosity of the cellulose triacetate solution immediately before film formation may be in a range that can be cast at the time of film formation, and is usually preferably adjusted to a range of 10 ps · s to 2000 ps · s, and particularly preferably 30 ps · s to 4
00ps · s is preferred.

In the cellulose triacetate solution of the present invention, various additives depending on the use can be added in each preparation step. For silver halide photographic materials, a plasticizer or a colorant for preventing light piping or an ultraviolet ray inhibitor for improving mechanical properties or imparting water resistance, and for a liquid crystal image display device, a heat and moisture resistance. It is desirable to add an antioxidant to be provided. As the plasticizer, phosphoric acid esters, carboxylic acid esters, glycolic acid esters and the like are preferably used. Examples of phosphate esters include triphenyl phosphate (TP
P), tricresyl phosphate (TCP), cresyl diphenyl phosphate (CDPP), octyl diphenyl phosphate (ODPP), diphenyl biphenyl phosphate (BDP), trioctyl phosphate (TOP), tributyl phosphate (TBP), and the like. Examples of the acid ester include dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), dioctyl phthalate (DOP), and diethylhexyl phthalate (DEH).
P), acetyltriethyl citrate (TEAC), acetyltributyl citrate (TBAC), butyl oleate (BO), methylacetyl ricinoleate (AML),
Examples include dibutyl sebacate (DBS). Examples of glycolic acid esters include triacetin (TA), tributyrin (TB), butylphthalylbutyl glycolate (BPBG), and ethylphthalylethyl glycolate (E).
PEG), methylphthalylethyl glycolate (MPE)
G) such as dipentaerythritol hexaacetate,
Examples include sorbitol hexaacetate and pentaerythritol tetraacetate. Among them, TPP, TCP,
CDPP, TBP, DMP, DEP, DBP, DOP,
DEHP, TA, EPEG, BDP are preferred. Especially T
PP, DEP, EPEG, BDP are preferred. These plasticizers may be used alone or in combination of two or more. The added amount of the plasticizer is preferably 5% by weight or more and 30% by weight or less, particularly preferably 8% by weight or more and 16% by weight or less based on cellulose triacetate. . These compounds may be added together with the cellulose triacetate and the solvent during the preparation of the cellulose triacetate solution, or may be added during or after the solution preparation.

Further, sodium 2,2'-methylenebis (4,6-di-t-butylphenyl) phosphate (ADEKA STAB NA-10, manufactured by Asahi Denka Co., Ltd.) and bis (p-
Methylbenzylidene) sorbitol (Gerol MD,
Shin-Nippon Rika Co., Ltd.) and bis (p-ethylbenzylidene) sorbitol (NC-4, manufactured by Mitsui Toatsu Chemicals, Inc.)
Etc. may be added. The amount of these compounds to be added is 1 ppm by weight based on cellulose triacetate.
1.0% is preferable, and 10 ppm to 1000 ppm is more preferable. In addition, an antioxidant, a colorant for preventing light piping, and the like can be added. The content of the coloring agent is preferably 10 ppm or more and 1000 ppm or less by weight relative to cellulose triacetate.
0 ppm or more and 500 ppm or less are more preferable. By including the coloring agent in this manner, the light piping of the cellulose triacetate film can be reduced, and the yellow color can be improved.

Further, the cellulose triacetate solution of the present invention may optionally contain various additives as described below at the stage of preparation according to the intended use. As additives, ultraviolet absorbers, as stabilizers kaolin, talc,
There are inorganic fine particles such as diatomaceous earth, quartz, calcium carbonate, barium sulfate, titanium oxide, and alumina; salts of alkaline earth metals such as calcium and magnesium; and antistatic agents, flame retardants, lubricants, oils, and the like. Prior to casting,
It is necessary to filter the cellulose triacetate solution using an appropriate filter medium such as a wire mesh or flannel to remove foreign substances such as undissolved matter, dust and impurities.

A method for producing a film using the cellulose triacetate solution of the present invention will be described. As the equipment for producing the cellulose triacetate film of the present invention, those conventionally used for producing cellulose triacetate film can be used. The dope prepared by the above-described preparation apparatus is sent to a pressurized die through a pressurized fixed-quantity gear pump that can perform a high-precision fixed-quantity liquid supply by, for example, the number of rotations. The dope sent from the precision gear pump into the pressing die is evenly cast from a die (slit) of the pressing die onto a support that is rotating endlessly. The film is peeled off from the support as a (web), dried while passing through a rotating roll group, and the dried film is transported and wound up to a predetermined length by a winder.

The casting method useful in the present invention is a method of uniformly extruding the prepared dope from a pressure die onto a support, and adjusting the film thickness of the dope once cast on the support with a blade. There are a method using a doctor blade, a method using a reverse roll coater that adjusts with a roll that rotates in the reverse direction, and the like, but a pressing die is preferable. The pressure die includes a coat hanger type and a T-die type, and any of them is useful in the present invention. In addition to the methods mentioned here, various methods for casting a cellulose triacetate film from a conventionally known cellulose triacetate solution (for example, JP-A-61-94724, and JP-A-6-94724).
1-148013, JP-A-4-85011, JP-A-4-85011
No. 286611, No. 5-185443, No. 5-185
Nos. 445, 6-278149, 8-207210
And the like, can be preferably used, and by setting each condition in consideration of the difference in the boiling point of the solvent to be used, the same effects as those described in the respective publications can be obtained.

The endless support used for producing the cellulose triacetate film of the present invention may be a drum whose surface is mirror-finished by chrome plating,
A stainless belt (also referred to as a band), which is mirror-finished by surface polishing, is used. The pressure die used for the production of the cellulose triacetate film of the present invention may be disposed on a support or one or more pressure dies. Preferably, it is one or two. When two or more dope units are installed, the amount of the dope to be cast may be divided into various ratios for each die, and the dope is sent to the dice at a respective ratio from a plurality of precision metering gear pumps.

The drying of the dope on the support in the production of the cellulose triacetate film of the present invention is generally carried out by heating the dope from the surface of the drum or belt, that is, from the surface of the web on the support. There is a method in which air is blown from the back surface, and a liquid heat transfer method in which the liquid is brought into contact with the back surface opposite to the dope surface of the belt or the drum to transfer the temperature to the surface of the drum or the belt. The surface temperature of the support before casting may be any number of times as long as it is lower than the boiling point of the solvent used for the dope. However, in order to promote drying and to lose fluidity on the support, it is preferable to set the temperature slightly lower than that of methyl acetate. The speed at which the cellulose triacetate film is produced depends on factors such as the length of the belt, the drying method, and the composition of the dope solvent, but it can be said that it almost depends on the amount of the residual solvent when the web is separated from the belt. Depending on the heating method, if the solvent concentration near the belt surface in the dope film thickness direction is too high, the dope will remain on the belt when peeled off and hinder the next casting, so the peeling residue is Absolutely not. Therefore, the entire thickness of the web at the time of peeling must be strong enough to withstand peeling. The residual solvent at the time of peeling differs depending on the method of drying on the belt, and a method of transferring heat from the belt or the back surface of the drum is better than a method of drying by blowing air from the surface of the dope. In the present invention, the residual solvent ratio (%) for peeling is determined by measuring the residual solvent at the time of peeling by an efficient backside heat transfer method (the measuring method will be described later).

The film drying method for producing the cellulose triacetate film of the present invention will be described. The web peeled at the peeling position immediately before the support makes one round is alternately transported through rolls arranged in a staggered manner, or
The peeled web may be transported in a non-contact manner by carrying both ends of the web with a clip-shaped material. Drying is performed by blowing air of a predetermined temperature to both sides of the web (film) being transported. However, in the case of rapid drying, first drying is performed at a temperature that does not cause foaming, followed by high-temperature drying. In the drying step after peeling from the support, the film shrinks in the width direction due to evaporation of the solvent, but in order to improve the flatness of the finished film, it is necessary to dry the film while suppressing shrinkage as much as possible. In order to manufacture at a high speed, it is necessary to apply a high temperature. In such a case, for example, the entire drying process or a part of the process as disclosed in JP-A-62-46625 is required. It is preferable to use a method (tenter method) in which the web is dried while holding both ends of the web width with a clip in the direction. Furthermore, there is also a method of positively stretching in the width direction. In the present invention, for example,
JP-A-62-115035, JP-A-4-152125
And the stretching methods described in JP-A Nos. 4-284221 and 4-298310 can also be used.

The drying temperature in the drying step of the cellulose triacetate film of the present invention is preferably from 80 to 250 ° C, particularly preferably from 100 to 180 ° C. The drying temperature, the amount of drying air, and the drying time vary depending on the solvent used, and may be appropriately selected according to the type and combination of the solvents used. The residual solvent content of the final film is preferably 2% by weight or less, more preferably 0.4% by weight or less, particularly preferably 0.1% by weight or less. By setting the amount of the residual solvent of the film in this range, a film having good dimensional stability can be obtained. The steps from casting to post-drying may be performed under an air atmosphere or under an inert gas atmosphere such as nitrogen gas. As the winding machine for producing the cellulose triacetate film of the present invention, a generally used constant tension type winding machine can be employed.

Although the film thickness of the finished film of the present invention varies depending on the purpose of use, the solid content contained in the dope, the slit width of the die, the slit width of the die, and the like are set to 5 to 500 μm. Die pressure, casting speed, etc. may be adjusted, and preferably the film thickness after drying is 20 to 200 μm, more preferably the film thickness after drying is 40 μm.
１８０180 μm.

The film produced according to the present invention is preferably applied as an optical protective film for a liquid crystal. In particular, TF
Adaptation to a protective film for T liquid crystal is extremely important, and the cellulose ester film of the present invention is important. Recently, it has become an important protective layer for use as a support for optical viewing angle compensation introduced to the market from FUJIFILM Corporation. Furthermore, for example, a transparent protective film, a polarizing film, a transparent support, and an optically anisotropic layer formed from liquid crystal molecules are applied to a liquid crystal display device or the like used for an elliptically polarizing plate in which the optically anisotropic layer is laminated in this order. It is also applied to cells, polarizing elements, and optical compensation sheets (retardation plates). Here, in the transmission type liquid crystal display device, two polarizing elements are attached to both sides of the liquid crystal cell, and one or two optical compensation sheets are arranged between the liquid crystal cell and the polarizing element. In a reflection type liquid crystal display device, a reflection plate, a liquid crystal cell, one optical compensation sheet,
The polarizing elements are arranged in the order of one polarizing element. The liquid crystal cell is composed of rod-like liquid crystal molecules, two substrates for enclosing the same, and an electrode layer for applying a voltage to the rod-like liquid crystal molecules. The liquid crystal cell has a different alignment state of rod-like liquid crystal molecules.
tic), IPS (In-Plane Switching), FLC (Ferro
electric Liquid Crystal), OCB (Optically Compe
nsatory Bend), STN (Supper Twisted Nematic),
For VA (Vertically Aligned) and reflection type, HA
Various display modes such as N (Hybrid Aligned Nematic) have been proposed.

For example, as optical compensatory sheets using discotic liquid crystal molecules, those corresponding to various display modes have already been proposed. For example, an optical compensation sheet for a TN mode liquid crystal cell is disclosed in JP-A-6-2141.
No. 16, U.S. Pat. Nos. 5,583,679 and 56,467.
No. 03, German Patent Publication No. 391620A1. Further, an optical compensation sheet for a liquid crystal cell of IPS mode or FLC mode is disclosed in
No. 82 publication. Further, an optical compensatory sheet for an OCB mode or HAN mode liquid crystal cell is disclosed in US Pat. No. 5,805,253 and International Patent Application WO 96/378.
No. 04 is described in each specification. Furthermore, an optical compensation sheet for an STN mode liquid crystal cell is disclosed in Japanese Patent Application Laid-Open No. 9-265.
No. 72 is described. An optical compensation sheet for a VA mode liquid crystal cell is described in Japanese Patent No. 2866372. A polarizing element generally has a structure in which two transparent protective films are attached to both sides of a polarizing film, and the cellulose ester film of the present invention is applied to these protective layers.

An important point of the cellulose ester film prepared by using the plasticizer of the present invention is its optical property, which is observed as in-plane retardation (Re) of the film. The measurement method is obtained by multiplying the in-plane vertical and horizontal refractive index difference at a wavelength of 632.8 nm by a film thickness using an ellipsometer (Analysis analyzer AEP-100: manufactured by Shimadzu Corporation). It is obtained by the following equation. Re = (nx−ny) × d nx: refractive index in the horizontal direction, ny: refractive index in the vertical direction
0 nm or less, more preferably 80 to 0 nm, particularly preferably 30 to 0 nm, particularly preferably 20 to 0 nm.
0 nm. Also important is the retardation (Rth) in the thickness direction of the film, which is obtained by multiplying the birefringence in the thickness direction at a wavelength of 632.8 nm by the film thickness, and is obtained by the following equation. Rth = {(nx + ny) / 2-nz} × d nx: refractive index in the horizontal direction, ny: refractive index in the vertical direction, nz:
The smaller the refractive index in the thickness direction, the better because there is no optical anisotropy in the thickness direction. Rth of the cellulose ester film of the present invention is 150
nm to 0 nm, more preferably Rth is 12
It is 0 nm to 0 nm, particularly preferably 100 nm to 0 nm. In this case, the retension in the thickness direction is preferably 0.5 nm to 0 nm per 1 μm, more preferably 0.2 nm to 0 nm per 1 μm, and particularly preferably 0.2 nm to 0 nm per 1 μm.
It is 1 nm to 0 nm. The cellulose ester film of the present invention can be preferably used as a support for a silver halide photographic light-sensitive material.

[0031]

EXAMPLES In each of the examples, the chemical and physical properties of cellulose triacetate, solutions and films were measured and calculated as follows.

(1) Degree of acetylation (%) of cellulose triacetate The degree of oxidation was measured by a saponification method. The dried cellulose triacetate was precisely weighed and dissolved in a mixed solvent of acetone and dimethyl sulfoxide (volume ratio: 4: 1), and then a predetermined amount of a 1N aqueous solution of sodium hydroxide was added, followed by saponification at 25 ° C for 2 hours. . Phenolphthalein was added as an indicator, and excess sodium hydroxide was titrated with 1N-sulfuric acid (concentration factor: F). A blank test was performed in the same manner as described above. Then, the degree of acetylation (%) was calculated according to the following equation. Degree of acetylation (%) = (6.05 × (BA) × F) / W In the formula, A is the amount of 1N-sulfuric acid (ml) required for titration of the sample,
B is the amount of 1N sulfuric acid (ml) required for the blank test, F
Represents a factor of 1N-sulfuric acid, and W represents a sample weight.

(2) Average molecular weight and molecular weight distribution of cellulose triacetate A high performance liquid chromatography system (GPC) in which a gel filtration column is connected to a detector for detecting refractive index and light scattering.
-LALLS). The measurement conditions are as follows. Solvent: methylene chloride Column: GMH × 1 (manufactured by Tosoh Corporation) Sample concentration: 0.1 W / v% Flow rate: 1 ml / min Sample injection volume: 300 μl Standard sample: polymethyl methacrylate (Mw = 188,
200) Temperature: 23 ° C

(3) Viscosity-average degree of polymerization (DP) of cellulose triacetate About 0.2 g of absolutely dried cellulose triacetate is precisely weighed, and methylene chloride: ethanol = 9: 1 (weight ratio).
Was dissolved in 100 ml of a mixed solvent. This was measured for drop seconds at 25 ° C. using an Ostwald viscometer, and the degree of polymerization was determined by the following equation. ηrel = T / T0 T: Falling seconds of the measurement sample [η] = (1nηrel) / C T0: Falling seconds of the solvent alone DP = [η] / Km C: Concentration (g / l) Km: 6 × 10 -Four

(4) Stability of Solution A 100 parts by weight of a cellulose ester sample is added to a total of 400 parts by weight of a target solvent and a plasticizer, and stirred at room temperature (23 ° C.) for 3 hours. The state of the obtained solution or slurry was observed while standing at normal temperature (23 ° C.) and evaluated in the following four grades of A, B, C and D. A: Transparency and liquid uniformity are shown even after 20 days. B: Transparency and liquid uniformity were maintained for 10 days, but slight cloudiness was observed after 20 days. C: At the end of liquid preparation, the liquid is transparent and uniform, but after one day, it gels and becomes a non-uniform liquid. D: The liquid is opaque and non-uniform with no swelling or dissolution.

(5) Film surface condition The film was visually observed, and the surface condition was evaluated as follows. A: The film surface is smooth. B: The film surface is smooth, but some foreign matter is observed. C: Weak irregularities are seen on the film surface, and the presence of foreign matter is clearly observed. D: Irregularities are seen on the film, and many foreign matters are seen.

(7) Film tear test A sample cut into a size of 50 mm × 64 mm was subjected to ISO 638.
The tear load required for tearing was determined according to the standard of 3 / 2-1983.

(8) Folding test of film A sample cut to 120 mm was subjected to ISO 8776 / 2-1.
According to the standard of 988, the number of reciprocations until cutting by bending was determined.

(9) Moisture and heat resistance of the film 1 g of the sample was folded and placed in a 15 ml glass bottle.
After humidity control at a temperature of 90 ° C. and a relative humidity of 100%, the container was sealed. This was taken out after 10 days at 90 ° C. The state of the film was visually checked, and the following judgment was made. A: No abnormality is observed. B: Slightly decomposed odor is observed. C: Remarkably decomposed odor is observed. D: Decomposed odor and shape change due to decomposition are observed.

(10) Film retardation (R
e) Value A front retardation value measured from a direction perpendicular to the film surface at a wavelength of 632.8 nm was determined using an ellipsometer (Ellipsometer AEP-100: manufactured by Shimadzu Corporation).

(11) The haze of the film was measured using a haze meter (Model 1001DP, manufactured by Nippon Denshoku Industries Co., Ltd.).

[0042]

EXAMPLES Example 1 (1-1) Preparation of Cellulose Triacetate Solution A cellulose triacetate solution was prepared according to the following formulation. To a solution in which methyl acetate and methyl acetoacetate or ethyl acetoacetate had been previously mixed, cellulose triacetate powder (average size: 2 mm) was gradually added with good stirring. After the addition, stirring was further continued at room temperature (25 ° C.) for 1 hour. The obtained heterogeneous gel-like solution was cooled at -70 ° C for 6 hours, then heated to 50 ° C and stirred to obtain a solution or a gel-like liquid.

──────────────────────────────────── Cellulose triacetate (average acetylation degree 60.5% , Viscosity average degree of polymerization 300) Amount described in Table 1 Methyl acetate Amount described in Table 1 Methyl acetoacetate Amount described in Table 1 Ethyl acetoacetate Amount described in Table 1 ─────────── ─────────────────────────

(1-2) Preparation of Cellulose Triacetate Film The cellulose triacetate ester solution prepared in (1-1) was cast on a glass plate so as to have a dry film thickness of 100 μm. After drying at 70 ° C. for 3 minutes and 130 ° C. for 5 minutes, the film was peeled off from the glass plate, and then dried at 160 ° C.
The solution was dried stepwise at 30 ° C. for 30 minutes to evaporate the solvent. The properties of the cellulose triacetate film thus obtained are described in Table 1.

(1-3) Results The properties of the obtained cellulose triacetate solution and its film were evaluated, and the results are shown in Table 1. The sample 1-1 containing neither methyl acetoacetate nor ethyl acetoacetate of the present invention could not be made into a solution and a film could not be produced. On the other hand, the solutions of Comparative Samples 1-2 and 1-3 using acetone as a comparative solvent are in a state in which a considerable amount of gel is present, the liquid stability with time is poor, and the film state and tear test of the obtained film are poor. , Cutting resistance test and haze were inferior. On the other hand, the sample 1-4 of the present invention using the methyl setoacetate or ethyl acetoacetate of the present invention.
Nos. 1-12 satisfied the solution properties and the film properties. From the above, it is clear that the present invention is extremely excellent.

[0046]

[Table 1]

Example 2 Sample 1 of the present invention of Example 1
In step 10, the cellulose triacetate was acetylated at a degree of acetylation of 5
A cellulose triacetate solution and a sample 2-1 of the present invention, which is a film thereof, were produced in the same manner as in Example 1 except that the viscosity average polymerization degree was changed to 9.5% and the viscosity average polymerization degree was changed to 320. When the characteristics were evaluated, they were excellent in all points as shown in Table 2. In particular, although within the scope of the present invention, by lowering the degree of acetylation, the fluidity was further increased, the bubbles in the solution could be removed in a short time, and film production was easy.

[0048]

[Table 2]

Example 3 Sample 1 of the present invention of Example 1
In step 10, the cellulose triacetate was converted to a degree of acetylation of 6
A cellulose triacetate solution and a film 3-1 of the present invention, which is a film thereof, were produced in exactly the same manner as in Example 1 except that the viscosity average polymerization degree was changed to 0.5% and the viscosity average polymerization degree was changed to 220. When the properties were evaluated, as shown in Table 2, the solution properties were excellent. The film properties tended to be slightly inferior in the tear test and the cut resistance test. Although this is within the scope of the present invention, it is an effect due to the decrease in the degree of polymerization, but did not cause a serious problem in practical use.

Example 4 Sample 1 of the present invention of Example 1
10, exactly the same as Example 1, except that triphenyl phosphate / diphenyl biphenyl phosphate (2/1 weight ratio) was added as a plasticizer, with 10% by weight of cellulose triacetate being replaced by methyl acetate. In this way, a cellulose triacetate solution and a film 4-1 of the present invention as a film thereof were produced. When the properties were evaluated, as shown in Table 2, the properties were excellent in all of the solution properties and the film properties, and in particular, improvements were observed in the tear test and the cut resistance test. This is a result of imparting flexibility of the film by adding a plasticizer in the present invention, and is a preferred embodiment in the present invention.

Example 5 Sample 1 of the present invention of Example 1
At 10, the resulting solution is further heated to 180 ° C., 1.2
Except for heating at Mps for 3 minutes, a cellulose triacetate solution and a sample 5-1 of the present invention, which is a film thereof, were prepared in exactly the same manner as in Example 1. When the properties were evaluated, as shown in Table 2, both the solution properties and the film properties were excellent, and particularly, the solution properties and the surface properties were significantly improved. In addition, improvement in haze has been observed, and it is apparent that in the present invention, it is preferable to further perform high-temperature and high-pressure treatment after cooling and melting.

Example 6 Sample 1 of the present invention of Example 1
10, a cellulose triacetate solution and a film thereof according to the present invention in exactly the same manner as in Example 1 except that methyl acetate is changed to 57.5 parts by weight, methyl acetate is changed to 47.5 parts by weight, and ethanol is changed to 10 parts by weight. Sample 6-1
Was prepared. When the properties were evaluated, they were excellent in all of the solution properties and the film properties as shown in Table 2, and in particular, the solution viscosity was reduced, and the excellent casting resulted in a significant improvement in the surface condition and haze. Was done. Therefore, in the present invention, it is apparent that it is also preferable to add ethanol, which is an alcohol solvent, in addition to methyl acetoacetate.

Example 7 Sample 1 of the present invention of Example 1
In the same manner as in Example 10, except that methyl acetate was changed to 60 parts by weight and 55 parts by weight of butyl acetate and 5 parts by weight of butanol were added, a cellulose triacetate solution and a film of the inventive sample 7- 1 was produced. When the properties were evaluated, as shown in Table 2, it was excellent in all of the solution properties and the film properties. The surface state and haze were greatly improved by casting. Therefore, it is clear that in the present invention, it is preferable to add butanol, which is another solvent, in addition to methyl acetoacetate.

Example 8 Sample 1 of the present invention of Example 1
10. Preparation of a sample 8-1, 8-2 or 8-3 for comparison as a cellulose triacetate solution and its film in exactly the same manner as in Example 1, except that methyl acetoacetate was changed to methanol, ethanol or butanol. It was investigated. However, a solution of the acetyltriacetate solution was not obtained, and the film could not be produced. Therefore, it became clear that the present invention cannot be achieved with alcohols other than the methyl acetoacetate of the present invention.

Example 9 Sample 1 of the present invention of Example 1
In Example 10, an attempt was made to prepare a cellulose triacetate solution and a sample 9-1 of the present invention, which is a film thereof, in exactly the same manner as in Example 1 except that methyl acetate was changed to acetone, but no solution was obtained. Therefore, it is clear that methyl acetate is an excellent main solvent in the present invention.

Example 10 Sample 4 of the present invention of Example 4
-1, a sample 10-1 of the present invention, which is a film thereof, was produced in exactly the same manner as in Example 4 except that the film thickness was changed to 120 μm. One of the obtained films was provided with the first layer and the second layer (composition of the back layer) of Example 1 of JP-A-4-73736 to form a back layer having a cationic polymer as a conductive layer. Further, the sample 105 of Example 1 of JP-A-11-38568 was applied on the opposite side of the film base to which the obtained back layer was provided, to produce a silver halide color photographic light-sensitive material. The obtained color film was excellent in image quality and had no problem in handling.

Example 11 Sample 4 of the present invention of Example 1
-1, a sample 11-1 of the present invention, which is a film thereof, was produced in exactly the same manner as in Example 4 except that the film thickness was changed to 80 μm. Except that the obtained cellulose triester film was changed from the cellulose triacetate manufactured by Fuji Photo Film Co., Ltd. of Example 1 of JP-A-7-333433 to the cellulose triacetate film of Sample 11-1 of the present invention, -333433
An optical compensation filter film sample was produced in exactly the same manner as in Example 1 of Example 1. The obtained filter film had excellent viewing angles in the right, left, up and down directions. Therefore, it is understood that the cellulose triacetate film of the present invention is excellent for optical use.

[0058]

According to the present invention, a cellulose triester film having excellent optical anisotropy and excellent film strength can be provided. Further, a cellulose triacetate solution swelled and dissolved at room temperature using a non-halogen solvent can be provided. Further, the present invention can provide a cellulose triacetate solution in which a cellulose ester is dissolved in a stable state without using a halogenated hydrocarbon-based organic solvent such as methylene chloride. Further, a cellulose triacetate film having small optical anisotropy which can be used for optical purposes can be produced, and a cellulose triacetate film excellent as a support for a light-sensitive material can be produced.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08L 1:12 C08L 1:12

Claims (4)

[Claims] 1. A mixture of cellulose triacetate having an average acetylation degree of 58.0 to 62.5% and an organic solvent containing substantially no chlorine-containing hydrocarbon and containing methyl acetate.
Cooling the mixture to 0-10 ° C,
A step of dissolving the cellulose triacetate by heating to 55 ° C., and, if necessary, a step of casting the cellulose triacetate solution prepared through a step of adding an additive to the solution and mixing, and a solvent. In forming the cellulose triacetate film through the step of evaporating and drying the film, in any of the processes of preparing the cellulose triacetate solution, 3 to 30% by weight of methyl acetoacetate or ethyl acetoacetate is contained in the solution. A method for producing a cellulose triacetate film and a film thereof. 2. The method according to claim 1, wherein the cellulose triacetate is 220
The method for producing a cellulose triacetate film according to claim 1, wherein the film has a viscosity average degree of polymerization of ~ 500. 3. The concentration of cellulose triacetate in the cellulose triacetate solution is 15% by weight to 30%.
The method for producing a cellulose triacetate film according to any one of claims 1 to 2, and a film thereof. 4. The cellulose triacetate solution,
5% by weight of plasticizer based on cellulose triacetate
4. The composition according to claim 1, wherein the content is 30% by weight.
A method for producing a cellulose triacetate film according to any one of the above and a film thereof.