JP2005186289A - Cellulose ester film and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cellulose ester film manufacturing method capable of obtaining a cellulose ester film product of good quality, which is useful as an optical film used in a display device of every kind such as a liquid crystal display device, an organic electroluminescence display or the like, especially a protective film for a polarizing plate and a phase difference film used in this display device and can prevent the occurrence of a surface flaw said to be "white-fog irregularity" or "white-spot irregularity" even in a thin film product, and not stopping a film manufacturing process. <P>SOLUTION: In the manufacturing method of the cellulose ester film by a solution casting method, a film raw material solution is cast on a rotationally driven support made of a metal from a casting plate to form a dope film and a web is peeled from the support so as to continue such as state, that the web (or film) peeling sound in a region of 125-250 Hz measured at a position separated from a web peeling point by 100-150 cm in a shield matter-free state becomes 80-120 dB, for 10-120 min. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical film used for various display devices such as a liquid crystal display device (LCD) or an organic electroluminescence display, in particular, a cellulose ester film useful as a protective film for a polarizing plate and a retardation film used in these display devices, and It relates to the manufacturing method.

  In recent years, thinning and thinning of various display devices such as liquid crystal display devices (LCD) or organic electroluminescence displays have progressed, and accordingly, cellulose ester films used for these devices have been required to be thin.

  However, if the film thickness is made even thinner than the cellulose ester film with a film thickness of 80 μm, which is currently widely used in the market, the surface defects of the product film become more noticeable, and a high-quality product can be obtained. It becomes difficult. In particular, when the cellulose ester film is made into a thin film, irregular white dull defects called “white cloudiness unevenness” and “white spot unevenness” occur, which is a big problem in quality. This unevenness is about 200 to 300 mm at a large size and about several tens of mm at a small size, and gradually increases with time when a cellulose ester film is continuously produced for a long period of time. The cause of the occurrence of such “white cloudiness unevenness” is that impurities contained in trace amounts in the cellulose ester raw material dope accumulate and accumulate on the surface of the support on which the dope is cast. It is presumed that it is generated by being transferred to a film and matted.

Here, in the manufacturing method of the cellulose-ester film used for the conventional protective film for polarizing plates etc., there exist the following as the prior patent document regarding the cleaning method of the stain | pollution | contamination of a support surface.
JP, 2002-28943, A The invention of this patent documents 1 is a method of cleaning the endless metal support side which moves infinitely using a tool, when manufacturing a cellulose-ester film by a solution casting film-forming method, The operation of wiping with pure water in the tool and the operation of wiping with the organic solvent in the tool wipes off the dirt on the support. The tool has the ability to absorb pure water or organic solvent. And a non-woven fabric made of long fibers that are difficult to cause detached fibers.

  However, according to the conventional method for cleaning a metal support described in Patent Document 1, it cannot be performed unless production of the cellulose ester film is stopped, and thus there is a problem that the productivity of the film is greatly reduced. . In addition, there is a problem that it is inevitable that scratches are generated on the surface of the support due to dust floating in the air at the time of wiping, without stopping the manufacturing process of such a cellulose ester film, and depending on the cloth The emergence of cleaning methods that do not rely on wiping work has been strongly desired.

  The object of the present invention is to solve the above-mentioned problems of the prior art and to prevent the occurrence of surface defects called “white cloudiness unevenness” or “white spot unevenness” even in a thin film product of cellulose ester film. An object of the present invention is to provide a cellulose ester film production method and a cellulose ester film produced by this method, which can obtain a product of a high-quality cellulose ester film and do not stop the film production process. is there.

  As a result of intensive studies in view of the above points, the present inventor has completed the solution peeling while keeping the film peeled in a certain state, thereby reducing the contamination on the surface of the support. It has been found that the white cloudiness unevenness of the film is greatly reduced, and the present invention has been completed.

  In order to achieve the above object, the invention of the method for producing a cellulose ester film according to claim 1 of the present invention is such that a cellulose ester film raw material solution (dope) is rotationally driven from a casting die by a solution casting film forming method. Casting on a metal support to form a dope film (web), drying the web until it becomes peelable strength from the support, and then peeling the web from the support when peeling from the support The state in which the web (or film) peeling sound measured in a state without a shielding object at a distance of 100 to 150 cm from the peeling point is 80 dB to 120 dB is continued for 10 minutes to 120 minutes. It is characterized by.

  Next, the cellulose ester film according to claim 2 of the present invention is manufactured by the method according to claim 1.

  The cellulose ester film according to claim 3 of the present invention is characterized in that an antireflection treatment layer (AR) is further provided on the cellulose ester film according to claim 2.

  Furthermore, the invention of the cellulose ester film according to claim 4 of the present invention is that an antireflection layer (metal oxide layer) is further provided on the cellulose ester film according to claim 2 by plasma discharge treatment. It is a feature.

  The invention for producing a cellulose ester film according to claim 1 of the present invention is that, as described above, the cellulose ester film raw material solution (dope) is transferred from the casting die to the rotationally driven metal support by the solution casting film forming method. Cast on top, form a dope film (web), dry the web until it becomes peelable strength from the support, and then peel off from the support. A state in which a web (or film) peeling sound measured in a state without a shield at a distance of 100 to 150 cm is in a range of 80 dB to 120 dB is continued for 10 minutes to 120 minutes. Thus, according to the method for producing a cellulose ester film of the present invention, dirt on the surface of the support is reduced, However, it is possible to prevent the occurrence of surface defects called “white cloudiness unevenness” and “white spot unevenness”, and to obtain a high-quality cellulose ester film product, and to stop the film manufacturing process. There is an effect that there is no.

  Next, the invention according to claim 2 of the present invention is a cellulose ester film produced by the method according to claim 1, and even if it is a thin film product, “white cloudiness unevenness” and “white spot unevenness” There is no generation of surface defects, so it is extremely useful for optical films used in various display devices such as liquid crystal display devices (LCD) or organic electroluminescence displays, especially for polarizing plate protective films and retardation films used in these display devices. The effect that it is.

  Further, the invention according to claim 3 of the present invention is a film in which an antireflection treatment layer (AR) is further provided on the cellulose ester film according to claim 2, and according to the present invention, excellent antireflection is provided. There exists an effect that the cellulose-ester film suitable for the protective film for polarizing plates which has a function, and retardation film is obtained.

  Furthermore, the invention according to claim 4 of the present invention is a film in which an antireflection layer (metal oxide layer) is further provided on the cellulose ester film according to claim 2 by plasma discharge treatment. According to this, generation of cracks in the vicinity of both ends of the cellulose ester film can be sufficiently suppressed, and streaky unevenness that easily occurs at the end in the width direction is remarkably reduced. Even if it is for a large display device having a size exceeding the above range, it is possible to provide an antireflection film excellent in yield.

  Hereinafter, the present invention will be specifically described.

  In the method for producing a cellulose ester film by the above solution casting film forming method, the target cellulose ester is cellulose triacetate, cellulose diacetate, cellulose acetate butyrate, cellulose acetate propionate, cellulose acetate propionate butyrate Etc. are preferably used. In the case of cellulose triacetate, cellulose triacetate having a polymerization degree of 250 to 400 and a bound acetic acid amount of 54 to 62.5% is particularly preferable, and a bound acetic acid amount of 58 to 62.5% is more preferable because of its strong base strength. Particularly preferred is a cellulose ester having a total acyl group substitution degree of less than 2.85.

  As the cellulose ester, either cellulose ester synthesized from cotton linter or cellulose ester synthesized from wood pulp can be used alone or in combination.

  In this invention, about the specific manufacturing method of a cellulose ester, it is compoundable by the method described in Unexamined-Japanese-Patent No. 10-45804, for example.

  In the present invention, if the number average molecular weight of the cellulose ester is too low, the strength will be low, and if it is too high, the viscosity of the solution may be too high, so it is preferably 70000-300000, more preferably 80000-200000.

  It is preferable to use a large amount of cellulose ester synthesized from a cotton linter that has good releasability from a support made of an endless belt or a drum because of high productivity efficiency. Since the ratio of cellulose ester synthesized from cotton linter is 60% by mass or more and the effect of releasability becomes remarkable, 60% by mass or more is preferable, more preferably 85% by mass or more, and further, it is used alone. Is most preferred.

  In particular, a cellulose ester film having a total acyl group substitution degree of less than 2.85 is preferred because the dimensional change can be reduced, and a cellulose ester film having a total acyl group substitution degree of less than 2.75 is preferred, and particularly 2.70. A significant effect is observed with less than the cellulose ester film.

  In the present invention, it is preferable to add a plasticizer from the viewpoints of mechanical strength, dimensional stability, and the like. As the addition amount, cellulose ester film or cellulose is acylated with an acetyl group and an acyl group having 3 to 4 carbon atoms. It is preferably 3 to 30% by mass, more preferably 10 to 30% by mass, and particularly preferably 15 to 25% by mass relative to the converted cellulose ester film. In general, when the amount of plasticizer added increases, the dimensional change easily occurs. However, the dimensional change rate can be reduced within the above range.

  Although it does not specifically limit as a plasticizer which can be used by this invention, Phosphate ester plasticizer, phthalate ester plasticizer, trimellitic ester plasticizer, pyromellitic acid plasticizer, glycolate plasticizer Citric acid ester plasticizers, polyester plasticizers, and the like can be preferably used.

  For phosphate esters, triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate, etc.For phthalate esters, diethyl phthalate, dimethoxyethyl phthalate, dimethyl Trimellitic plasticizers such as phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, butyl benzyl phthalate, etc. Tributyl trimellitate, triphenyl trimellitate, triethyl trimellitate, pyromellitic ester Examples of plasticizers include tetrabutyl pyromellitate, tetraphenyl pyromellitate, tetraethyl pyromellitate, In acid ester type, triacetin, tributyrin, ethyl phthalyl ethyl glycolate, methyl phthalyl ethyl glycolate, butyl phthalyl butyl glycolate, etc., citrate ester plasticizers such as triethyl citrate, tri-n-butyl citrate Acetyl triethyl citrate, acetyl tri-n-butyl citrate, acetyl tri-n- (2-ethylhexyl) citrate and the like can be preferably used. As the polyester plasticizer, a copolymer of a dibasic acid and a glycol such as an aliphatic dibasic acid, an alicyclic dibasic acid, or an aromatic dibasic acid can be used. The aliphatic dibasic acid is not particularly limited, and adipic acid, sebacic acid, phthalic acid, terephthalic acid, 1,4-cyclohexyl dicarboxylic acid and the like can be used.

  As the glycol, ethylene glycol, diethylene glycol, 1,3-propylene glycol, 1,2-propylene glycol, 1,4-butylene glycol, 1,3-butylene glycol, 1,2-butylene glycol and the like can be used. These dibasic acids and glycols may be used alone or in combination of two or more. The molecular weight of the polyester is preferably in the range of 500 to 2000 in terms of weight average molecular weight from the viewpoint of compatibility with the cellulose resin.

  In the present invention, it is particularly preferable to use a plasticizer having a vapor pressure of less than 1333 Pa at 200 ° C., more preferably a compound having a vapor pressure of 666 Pa or less, and more preferably 1 to 133 Pa. The non-volatile plasticizer is not particularly limited, and examples thereof include arylene bis (diaryl phosphate) ester, tricresyl phosphate, trimellitic acid tri (2-ethylhexyl), and the like.

  These plasticizers can be used alone or in combination of two or more.

  In the present invention, it is preferable to use an ultraviolet absorber for the cellulose ester film for the purpose of protecting the liquid crystal material, and the ultraviolet absorber has an excellent ability to absorb ultraviolet rays having a wavelength of 370 nm or less from the viewpoint of preventing deterioration of the liquid crystal. In addition, from the viewpoint of good liquid crystal display properties, those that absorb as little visible light as possible with a wavelength of 400 nm or more are preferably used.

  In the present invention, in a film having a film thickness of 20 to 250 μm, a preferable polarizing plate can be provided without deteriorating the durability of the polarizing plate by setting the transmittance at a wavelength of 370 nm to 10% or less. The transmittance at a wavelength of 370 nm is more preferably 5% or less, and particularly preferably 2% or less.

  In the present invention, the ultraviolet absorber added to the cellulose ester film is particularly preferably an ultraviolet absorber having two or more aromatic rings in the molecule.

  Examples of commonly used compounds include, but are not limited to, oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, and the like. Alternatively, polymer ultraviolet absorbers described in JP-A-6-148430 and JP-A-2000-273437 can also be preferably used.

  In the present invention, these ultraviolet absorbers may be used alone or in a mixture of two or more different types.

  The ultraviolet absorber preferably used in the present invention is a benzotriazole ultraviolet absorber, a benzophenone ultraviolet absorber, or the like. An embodiment in which a benzotriazole-based ultraviolet absorber with less unnecessary coloring is added to the cellulose ester film is particularly preferable.

  The ultraviolet absorber may be added to the dope after dissolving the ultraviolet absorber in an organic solvent such as alcohol, methylene chloride, dioxolane, or directly into the dope composition. For an inorganic powder that does not dissolve in an organic solvent, a dissolver or a sand mill is used in the organic solvent and cellulose ester to disperse and then added to the dope.

  The amount of the ultraviolet absorber preferably used in the present invention is preferably 0.1 to 5% by mass, more preferably 0.5% by mass with respect to the cellulose ester from the viewpoint of ultraviolet absorption effect and transparency. It is -2.5 mass%, More preferably, it is 0.8-2.0 mass%.

In the present invention, the cellulose ester film preferably contains a benzotriazole ultraviolet absorber represented by the following general formula (1).

  In the formula, R 1, R 2, R 3, R 4 and R 5 may be the same or different, and are a hydrogen atom, halogen atom (each atom such as chlorine, bromine, iodine, fluorine, etc.), nitro group, hydroxyl group, alkyl group (for example, Methyl, ethyl, n-propyl, iso-propyl, aminopropyl, n-butyl, sec-butyl, tert-butyl, chlorobutyl, n-amyl, iso-amyl, hexyl, octyl, nonyl, stearylamidobutyl, decyl, Groups such as dodecyl, pentadecyl, hexadecyl, cyclohexyl, benzyl, phenylethyl, phenylpropyl), alkenyl groups (eg, vinyl, allyl, methallyl, dodecenyl, tridecenyl, tetradecenyl, octadecenyl, etc.), aryl groups (eg, phenyl) , 4-methylphenyl, 4-eth Siphenyl, 2-hexoxyphenyl, 3-hexoxyphenyl and other groups), alkoxy groups (for example, methoxy, ethoxy, propoxy, butoxy, chlorobutoxy, decoxy, diaminophenoxy, ethoxy, pentadecoxy, octadecoxy, etc.) , Oxycarbonyl groups (for example, carbomethoxy, carbobutoxy, carbohexoxy, carbopentadecoxy, etc.), aryloxy groups (for example, phenoxy, 4-methylphenoxy, 2-propylphenoxy, 3-amylphenoxy, etc.) Group), alkylthio group (for example, methylthio, ethylthio, t-butylthio, t-octylthio, benzylthio, etc.), arylthio group (for example, phenylthio, methylphenylthio, ethylphenylthio, methoxyphene) Ruthio, ethoxyphenylthio, naphthylthio, etc.), mono- or dialkylamino groups (for example, N-ethylamino, Nt-octylamino, N, N-diethylamino, N, N-di-t-butylamino, etc.) Each group), an acylamino group (for example, each group such as acetylamino, benzoylamino, methanesulfonylamino, etc.), a 5- or 6-membered heterocyclic residue containing an oxygen atom or nitrogen atom (for example, piperidino, morpholino, pyrrolidino, A heterocyclic residue such as piperazino), and R4 may form a 5- or 6-membered ring consisting of carbon atoms together with R5.

  In said general formula (1), it is preferable that the substituent shown by R1-R5 is C5-C36, and it is preferable that an alkyl group is C1-C18.

  Next, examples of the compound represented by the above general formula are shown, but the present invention is not limited thereto.

(IV-1): 2- (2′-hydroxy-5′-t-butylphenyl) -benzotriazole (IV-2): 2- (2′-hydroxy-3 ′, 5′-di-t-butyl) Phenyl) -benzotriazole (IV-3): 2- (2'-hydroxy-3'-t-butyl-5'-methylphenyl) -5-chlorobenzotriazole (IV-4): 2- (2'- Hydroxy-3 ', 5'-di-t-butylphenyl) -5-chlorobenzotriazole (IV-5): 2- (2'-hydroxy-5'-isooctylphenyl) -benzotriazole (IV-6) : 2- (2'-hydroxy-5'-n-octylphenyl) -benzotriazole (IV-7): 2- (2'-hydroxy-3 ', 5'-di-t-amylphenyl) -benzotriazole (IV -8): 2- (2'-hydroxy-5'-dodecylphenyl) -benzotriazole (IV-9): 2- (2'-hydroxy-5'-hexadecylphenyl) -benzotriazole (IV-10) : 2- (2′-hydroxy-3′-t-amyl-5′-benzophenyl) -benzotriazole In the present invention, together with the above compound, JP-A-60-128434, page 10 to The compound examples (IV-11) to (IV-39) described on page 12 can be used.

  The benzotriazole-based compound used in the present invention can be easily synthesized, for example, by the method described in Japanese Examined Patent Publication No. 44-29620 or a method analogous thereto.

  In the present invention, the cellulose ester film can be added with fine particles such as silicon oxide as a matting agent as required. It is preferable that fine particles such as silicon oxide are surface-treated with an organic substance because the haze of the film can be reduced. Preferred organic materials for the surface treatment include halosilanes, alkoxysilanes, silazanes, siloxanes, and the like. The larger the average diameter of the fine particles, the greater the mat effect, and the smaller the average diameter, the better the transparency. Therefore, the average diameter of the primary particles of the fine particles is preferably 5 to 50 nm, more preferably 7 to 14 nm.

  Examples of the fine particles of silicon oxide include AEROSIL-200, 200V, 300, R972, R972V, R974, R202, R812, OX50, TT600 manufactured by Aerosil Co., Ltd., preferably AEROSIL-200, 200V, R972, R972V, R974. , R202, R812 and the like.

  In the present invention, the method for producing the cellulose ester film is not particularly limited, and may be a method generally used in the art. For example, U.S. Pat. Nos. 2,492,978, 2,739,070, and 2,739. , 069, 2,492,977, 2,336,310, 2,367,603, 2,607,704, British Patents 64,071, 735,892, Reference can be made to the methods described in JP 45-9074, 49-4554, 49-5614, 60-27562, 61-39890, 62-4208, and the like.

  In the present invention, the solvent used in the dope solution may be used alone or in combination, but it is preferable to use a mixture of a good solvent and a poor solvent of cellulose ester in terms of production efficiency. It is preferable in terms of the solubility of the ester. The preferable range of the mixing ratio of the good solvent and the poor solvent is 70 to 98% by mass for the good solvent and 30 to 2% by mass for the poor solvent.

  In the present invention, the good solvent and the poor solvent used in the dope liquid are defined as those that dissolve the cellulose ester used alone and those that swell or do not dissolve alone as the poor solvent. Therefore, depending on the average degree of acetylation of the cellulose ester, the good solvent and the poor solvent change. For example, when acetone is used as the solvent, the cellulose acetate becomes a good solvent when the bound acetic acid amount is 55%, and the poor solvent when the bound acetic acid amount is 60%. End up.

  In the present invention, the good solvent used in the dope solution is not particularly limited. For example, in the case of cellulose triacetate, organic halogen compounds such as methylene chloride and dioxolanes, and in the case of cellulose acetate propionate, methylene chloride, acetone, acetic acid. And methyl.

  In the present invention, the poor solvent used in the dope solution is not particularly limited, but for example, methanol, ethanol, i-propyl alcohol, n-butanol, cyclohexane, acetone, cyclohexanone, and the like are preferably used.

  As a method for dissolving the cellulose ester when preparing the dope solution, a general method can be used, but under pressure, a temperature within a range not lower than the boiling point of the solvent at normal pressure and not boiling. The method of heating with stirring and dissolving with stirring is more preferable in order to prevent the generation of massive undissolved materials called gels and mamaco. Further, a method in which cellulose ester is mixed with a poor solvent and wetted or swollen, and then mixed with a good solvent and dissolved is also preferably used.

  The type of the pressure vessel is not particularly limited as long as it can withstand a predetermined pressure and can be heated and stirred under pressure. In addition to the pressure vessel, other instruments such as a pressure gauge and a thermometer are appropriately disposed. The pressurization may be performed by a method of injecting an inert gas such as nitrogen gas or by increasing the vapor pressure of the solvent by heating. Heating is preferably performed from the outside. For example, a jacket type is preferable because temperature control is easy.

  The heating temperature with the addition of the solvent is preferably a temperature in the range where the solvent used is at or above the normal pressure and the solvent does not boil from the viewpoint of the solubility of the cellulose ester, but is necessary if the heating temperature is too high. Increased pressure increases productivity. The range of preferable heating temperature is 45-120 degreeC, 60-110 degreeC is more preferable, and the range of 70-105 degreeC is further more preferable. The pressure is adjusted at a set temperature so that the solvent does not boil.

  In addition to cellulose ester and solvent, additives such as necessary plasticizers and UV absorbers are mixed with the solvent in advance, dissolved or dispersed, and then added to the solvent before dissolving the cellulose ester. You may throw into dope.

  After dissolution, take it out from the container while cooling, or take it out from the container with a pump etc. and cool it with a heat exchanger etc., and use it for film formation, but the cooling temperature at this time may be cooled to room temperature It is more preferable to cool to a temperature 5 to 10 ° C. lower than the boiling point and perform casting at that temperature because the dope viscosity can be reduced.

  A stainless steel endless belt or drum having a mirror-finished surface is used as the film-forming support.

  The dope is fed to the casting die through a pressurized metering gear pump, and the dope is extruded from the casting die at the casting position and cast onto the support. The support can be cast at a temperature in the general temperature range of 0 ° C. to less than the boiling point of the solvent. At this time, it is necessary to control the ambient atmospheric humidity above the dew point.

  Other casting methods include a doctor blade method in which the film thickness of the cast dope film is adjusted with a blade, or a reverse roll coater method in which the film is adjusted with a reverse rotating roll. A pressure die that can be prepared and facilitates uniform film thickness is preferred. Examples of the pressure die include a coat hanger die and a T die, and any of them is preferably used.

  In order to increase the film forming speed, two or more pressure dies may be provided on the casting support, and the dope amount may be divided to form a multilayer film.

  The casting film (dope film) on the support is dried by applying a dope whose temperature is controlled to be lower than the boiling point of the low-boiling solvent in the mixed solvent from the casting die to the support. When the residual solvent amount in the cast film is 200% or more by weight of the solid content, the cast film temperature is below the boiling point of the solvent, and in the range of 100 to 200%, the boiling point of the solvent is + 10 ° C. or below, 100% The cast film is dried with hot air, hot water or an infrared heater so that the boiling point of the solvent is in the range of + 20 ° C. or lower until the peeling is performed.

  On the support, it is desirable that the amount of residual solvent in the cast film is dried to 150% or less, and further, 120% from the viewpoint of reducing the occurrence of film peeling residue on the support and film deformation at the time of peeling. The following is preferred.

  The film temperature when the cast film is peeled from the support is preferably 0 to 30 ° C. in that a high film strength can be obtained, and 5 to 30 ° C. is more preferable in order to prevent water droplet condensation in the air.

  The gap between the casting die / slit and the support surface is preferably in the range of 0.3 to 5 mm. In addition, when the web transport speed of the support is 10 m / min or more, the casting film coming out of the casting die / slit is depressurized so that the casting ribbon (ribbon) at the time of air mixing or dope casting It is desirable to suppress fluttering of the resinous resin solution so that horizontal streaks (transverse film thickness unevenness) do not occur in the width direction of the film. The appropriate point of the vacuum in the vacuum chamber varies depending on the cast film thickness and the web transport speed of the support, but a range of about 50 to 800 Pa is practical.

  The gap between the lower end of the decompression chamber and the support does not increase the suction air volume, that is, if the suction air volume becomes too large, a dry film of dope is formed at the end of the casting die / slit. In order to obtain it, about 0.5-5 mm is preferable, and when depressurizing a decompression chamber to -100 Pa or more, 0.5-3 mm is more preferable.

  The solvent content in the film when peeling the film from the support is preferably 150% by mass or less, and among them, as described in JP-A-2002-28943, the peeling sound of the film It is desirable to peel off in a low region. This is because, in a state where the peeling sound is large, a very sharp streak is generated in the width direction on the base during peeling.

  Normally, production is not performed under conditions with high peeling noise, but the film forming conditions such as the temperature of the support, cast film thickness, and casting speed are changed to change the solvent content in the film at the time of peeling. To pass through this region in a short time.

  However, as a result of the examination, when the state where the peeling sound was high was continued for 10 minutes or more, the contamination on the surface of the support was reduced, and the white cloudiness unevenness of the finished film was also greatly reduced.

  That is, in the invention of the method for producing a cellulose ester film according to claim 1 of the present invention, the cellulose ester film raw material solution (dope) is flowed from the casting die onto the rotationally driven metal support by the solution casting film forming method. Then, after forming the dope film (web) and drying the web until it becomes peelable strength from the support, when peeling from the support, 100 to 150 cm from the peeling point of the web peeled from the support The state in which the web (or film) peeling sound measured in a state where there is no shielding object at a distance is 80 dB or more and 120 dB or less continues for 10 minutes or more and 120 minutes or less.

  Here, when the web is peeled from the support, the web (or film) peeling sound measured in the state of no shield is measured 100 to 150 cm away from the peeling point of the web peeled from the support. If it is less than 80 dB, since the peeling force of the web (or film) is too low, it is not preferable because the effect of causing the web (or film) to remove the dirt firmly adhered to the surface of the support cannot be obtained. Also, when the web (or film) peeling sound exceeds 120 dB, in a thin film having low strength, the web (or film) is torn from the edge due to noise vibration, or the vibration causes, for example, failure of various sensors. This is not preferable because of fear.

  According to the invention described in claim 1 of the present invention, even a thin film product of a cellulose ester film can prevent occurrence of surface defects called “white cloud unevenness” or “white spot unevenness”, and has a good quality. Since the product of a cellulose ester film can be obtained and the production process of the film is not stopped, the productivity of the cellulose ester film is excellent.

  Further, according to the method of the present invention, it is not necessary to perform cleaning by wiping work using a conventional cloth. Therefore, when wiping with a cloth, the surface of the support is scratched by dust floating in the air. There's nothing to do.

  In the film post-drying step, the film peeled off from the belt is further dried, and the residual solvent amount at the time of winding is 3% by mass or less, preferably 1% by mass or less, more preferably 0.5% by mass or less. It is preferable in terms of film dimensional stability and environment.

  In the post-film drying step, generally, a method of drying while transporting the film by a roll suspension method, a pin tenter method, or a clip tenter method is adopted. For the liquid crystal display member, it is preferable to dry while maintaining the width by a tenter method in order to improve flatness and dimensional stability. In particular, holding the width in a large amount of residual solvent immediately after peeling from the support exhibits a more dimensional stability improving effect.

  In particular, in the drying process after peeling from the support, the film tends to shrink in the width direction by evaporation of the solvent. Shrinkage increases with drying at higher temperatures. In order to improve the flatness of the finished film, it is preferable to dry while suppressing the shrinkage as much as possible. From this point, for example, a method / tenter method in which all or part of the drying process as shown in JP-A-62-46625 is performed while holding the width at both ends of the web with a clip in the width direction. Is preferred.

  When the residual solvent amount is 10 to 100% by mass, and / or when the residual solvent amount is 5 to 10% by mass and the temperature is 110 to 150 ° C. If the stretching is about 1 to 20%, the effect of improving the flatness of the cellulose ester film is particularly preferable.

  The means for drying the film is not particularly limited, and is generally performed with hot air, infrared rays, a heating roll, microwaves, or the like. It is preferable to dry with hot air in terms of simplicity. The drying temperature is preferably in the range of 40 ° C. to 150 ° C. and gradually increased to 3 to 5 steps, and the drying temperature is preferably increased in the range of 80 ° C. to 150 ° C. to improve the flatness and dimensional stability. Therefore, it is more preferable.

  These steps from casting to post-drying may be performed in an air atmosphere or an inert gas atmosphere such as nitrogen gas. It goes without saying that the dry atmosphere is carried out in consideration of the explosion limit concentration of the solvent.

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

  The thickness of the cellulose ester film of the present invention is from 20 to 200 μm, preferably from 25 to 150 μm, from the viewpoint of reducing the thickness and weight of the polarizing plate used in the LCD. If it is thinner than this, the stiffness of the film is lowered, so that troubles such as wrinkles and film breakage are likely to occur in the polarizing plate preparation process. If it is thicker than this, the contribution to thinning of the LCD is small.

  In the present invention, it is preferable that the cellulose ester film has less foreign matter. In particular, it is preferable that there are few foreign substances recognized in the polarization crossed Nicol state.

Foreign matter recognized in the polarization crossed Nicol state means that the two polarizing plates are placed in a straight (crossed Nicol) state, a cellulose ester film is placed between them, light from the light source is applied from the opposite side, and the observed bright spot is Say. Since such foreign matters are observed as bright spots when light from the light source from the opposite side leaks only at the location of the foreign matters, the size and number of the foreign matters can be easily identified.

As for the number of foreign matters, it is preferable that there are 200 or less foreign matters having a size of 5 to 50 μm recognized in a polarization crossed Nicol state and substantially zero foreign matters having a size of 50 μm or more per 250 mm ² area. More preferably, the number of foreign matters of 5 to 50 μm is 100 or less, more preferably 50 or less.

  In order to obtain the cellulose ester film with little foreign matter, any means can be used. For example, it can be achieved by filtering a dope composition obtained by dissolving cellulose ester in a solvent using the following filter paper.

  As the filter medium in the present invention, it is preferable that the absolute filtration accuracy is small in order to remove insoluble matters, but if the absolute filtration accuracy is too small, there is a problem that the filter medium is likely to be clogged. Therefore, a filter medium having an absolute filtration accuracy of 0.008 mm or less is preferable, a filter medium in the range of 0.001 to 0.008 mm is more preferable, and a filter medium in the range of 0.003 to 0.006 mm is more preferable.

  The material of the filter medium is not particularly limited, and a normal filter medium can be used. However, a plastic filter medium such as polypropylene and Teflon (registered trademark) and a metal filter medium such as stainless steel are preferable because fibers do not fall off. Moreover, it is more preferable to use two or more of the above filter papers.

  The dope solution can be filtered by a normal method, but the method of filtering while heating at a temperature not lower than the boiling point of the solvent at normal pressure and in a range where the solvent does not boil is the difference between before and after the filter medium. The increase in pressure (hereinafter sometimes referred to as filtration pressure) is small and preferable. A preferable temperature range is 45 to 120 ° C, more preferably 45 to 70 ° C, and still more preferably 45 to 55 ° C.

A smaller filtration pressure is preferred. The filtration pressure is preferably 1.6 × 10 ⁶ Pa or less, more preferably 1.2 × 10 ⁶ Pa or less, and further preferably 1.0 × 10 ⁶ Pa or less. The filtration pressure can be controlled by appropriately selecting the filtration flow rate and the filtration area.

  Next, the invention according to claim 2 of the present invention is a cellulose ester film produced by the method according to claim 1. Even if the cellulose ester film according to the present invention is a so-called thin film product, it has no surface defects called “white cloudiness unevenness” or “white spot unevenness” and has excellent quality.

Further, an antireflection treatment layer (AR) is further provided on the cellulose ester film according to the present invention. Here, it is preferable that a single layer or two or more layers of materials having a refractive index different from the refractive index of the cellulose ester film be laminated on the antireflection treatment layer (AR). In the case of a single layer structure, it is preferable to use a material having a smaller refractive index than that of the cellulose ester film. Moreover, when it is set as the multilayered structure of two or more layers, the layer which adjoins a cellulose-ester film uses the material which has a larger refractive index than a cellulose-ester film, and has a refractive index smaller than this for the layer above this It is better to choose the material. The material constituting such an antireflection treatment layer (AR) is not particularly limited as long as the above refractive index relationship is satisfied regardless of whether it is an organic material or an inorganic material. For example, CaF ₂ , MgF ₂ , NaAiF ₄ , SiO _It is preferable to use a dielectric such as ₂ , ThF ₄ , ZrO ₂ , Nd ₂ O ₃ , SnO ₂ , TiO ₂ , CeO ₂ , ZnS, or In ₂ O ₃ .

  The antireflection treatment layer (AR) may be a dry coating process such as a vacuum deposition method, a sputtering method, a CVD method, or an ion plating method, or a wet coating process such as a gravure method, a reverse method, or a die method.

  The cellulose ester film provided with the antireflection treatment layer (AR) of the present invention is suitable as a protective film for a polarizing plate and a retardation film having an excellent antireflection function.

  Furthermore, an antireflection layer (metal oxide layer) is provided on the cellulose ester film according to the present invention by plasma discharge treatment.

  Here, the method of providing the metal oxide layer on the cellulose ester film is not particularly limited, but it is preferably formed by plasma CVD (plasma discharge) or coating.

  In the present invention, even when the metal oxide layer has a metal oxide content of 70% by mass or more, the occurrence of cracks can be significantly reduced. In particular, cracks were easily generated in the vicinity of both end portions of the cellulose ester film having a width direction exceeding 1 m, but the occurrence of cracks in this portion can be sufficiently suppressed. In addition, streaky irregularities that were likely to occur at the ends in the width direction were significantly reduced. Thereby, an antireflection film excellent in yield can be provided even for a large display device having a size exceeding 20 types.

  In the present invention, the method for providing the metal oxide layer is not particularly limited, but among these, the metal oxide layer is preferably formed by plasma CVD (plasma discharge) treatment.

  The blending amount of the inorganic fine particles is preferably 5 to 90% by mass, more preferably 10 to 70% by mass, and particularly preferably 10 to 50% by mass with respect to the total mass of the low refractive index layer. The inorganic fine particles are preferably used after being subjected to a surface treatment.

  Next, plasma CVD (plasma discharge) treatment under atmospheric pressure or a pressure in the vicinity thereof as a method for forming the metal oxide layer is performed by using a plasma CVD treatment apparatus. The cellulose ester film is subjected to plasma discharge treatment by reciprocating the discharge portion in a state of being in close contact with the rotating electrode. The cellulose ester film conveyed from the former winding roll or the previous process is guided to the rotating electrode through the guide roll and nip roll, and the cellulose ester film is transferred in synchronization with the rotation of the rotating electrode while in contact with the rotating electrode. Then, the reaction gas prepared by the reaction gas generator is supplied from the supply pipe to the discharge portion under atmospheric pressure or a pressure in the vicinity thereof, and a thin film is formed on the surface of the cellulose ester film facing the fixed electrode.

  The cellulose ester film subjected to the plasma discharge treatment is conveyed to the next process or the take-up roll through a nip roll and a guide roll.

  Thus, in this invention, it is preferable that the cellulose-ester film in which a thin film is formed is plasma-discharge-treated, conveying on a rotating electrode.

  Further, the reaction gas for forming the metal oxide layer preferably contains nitrogen or a rare gas. That is, the reactive gas is preferably a mixed gas of nitrogen or a rare gas and a reactive gas described later. Here, specific examples of the rare gas include each element of Group 18 element of the periodic table such as helium, neon, argon, krypton, xenon, and radon. Elements and argon elements can be preferably used. The concentration of the rare gas in the reaction gas is preferably 90% by volume or more in order to generate a stable plasma discharge. The rare gas is used to generate a stable plasma discharge, and the reactive gas is ionized or radicalized in the plasma, and a thin film is formed by depositing or adhering to the substrate surface.

  The reactive gas useful in the present invention can form thin films having various functions on a cellulose ester film by using a reactive gas added with reactive gases of various substances. For example, the low refractive index layer of the antireflection layer can be formed using a fluorine-containing organic compound or a silicon compound as the reactive gas.

  In addition, these metal oxide layers (metal oxide nitride layers) using organometallic compounds, metal hydrides, and metal halides containing Ti, Zr, In, Sn, Zn, Ge, Si or other metals. Or a metal nitride layer or the like, and these layers may be low-refractive index layers, medium-refractive index layers or high-refractive index layers of antireflection layers, or conductive layers or antistatic layers. You can also

  Further, the antifouling layer and the low refractive index layer can be formed with a fluorine-containing organic compound, and the gas barrier layer and the low refractive index layer can be formed with a silicon compound. The present invention is particularly preferably used for forming an antireflection layer formed by alternately laminating high, medium refractive index layers and low refractive index layers.

  As a film thickness of the metal oxide layer formed by this invention, the thing of the range of 1-1000 nm is obtained preferably.

  In the atmospheric pressure plasma treatment, a fluorine compound-containing layer can be formed by using a fluorine-containing organic compound as a raw material gas. As the fluorine-containing organic compound, a fluorocarbon gas, a fluorinated hydrocarbon gas, or the like is preferable. Specifically, examples of the fluorine-containing organic compound include fluorinated hydrocarbon compounds such as carbon tetrafluoride, carbon hexafluoride, and tetrafluoroethylene, monochlorotrifluoride methane, and monochlorodifluoride methane. Examples thereof include halides of fluorinated hydrocarbon compounds, fluorine-substituted products of organic compounds such as alcohols, acids, and ketones, and these may be used alone or in combination.

  When a fluorine-containing organic compound is used for the reactive gas useful in the present invention, from the viewpoint of forming a uniform thin film on the cellulose ester film by plasma discharge treatment, the fluorine-containing organic compound is contained as a reactive gas in the reaction gas. The rate is preferably from 0.01 to 10% by volume, and more preferably from 0.1 to 5% by volume.

  When the fluorine-containing organic compound preferably used in the present invention is a gas at normal temperature and pressure, it can be used as it is as a component of the reactive gas.

  Further, when the fluorine-containing organic compound is liquid or solid at normal temperature and normal pressure, it may be used after being vaporized by vaporization means, for example, by heating, reduced pressure, or the like, and may be used after being dissolved in an appropriate organic solvent. .

  In the present invention, examples of the silicon compound as the reactive gas include organic metal compounds such as dimethylsilane and tetramethylsilane, metal hydrogen compounds such as monosilane and disilane, silane dichloride, silane trichloride, and silicon tetrafluoride. It is preferable to use, but is not limited to, an alkoxysilane such as tetramethoxysilane, tetraethoxysilane, tetraethoxysilane, tetrapropoxysilane, dimethyldiethoxysilane, methyltrimethoxysilane, ethyltriethoxysilane, or the like. . Moreover, these can be used in combination as appropriate. Alternatively, another organic compound can be added to change or control the physical properties of the film.

  In the present invention, when a silicon compound is used as the reactive gas, the content of the silicon compound as the reactive gas in the reactive gas is 0 from the viewpoint of forming a uniform thin film on the cellulose ester film by the discharge plasma discharge treatment. Although it is preferable that it is 0.01-10 volume%, More preferably, it is 0.1-5 volume%.

  Although it does not specifically limit as an organometallic compound as a reactive gas useful for this invention, Al, As, Au, B, Bi, Sb, Ca, Cd, Cr, Co, Cu, Fe, Ga, Ge, Hg Metal compounds for forming metal oxides such as In, Li, Mg, Mn, Mo, Na, Ni, Pb, Pt, Rh, Se, Si, Sn, Ti, Zr, Y, V, W, Zn Can be mentioned.

  For example, a titanium compound is preferable for forming the high refractive index layer of the antireflection layer. Specifically, for example, an organic amino metal compound such as tetradimethylaminotitanium, a metal hydrogen compound such as monotitanium and dititanium, Examples thereof include metal halogen compounds such as titanium chloride, titanium trichloride, and titanium tetrachloride, and metal alkoxides such as tetraethoxy titanium, tetraisopropoxy titanium, and tetrabutoxy titanium.

  In the present invention, the above-mentioned silicon compound and organometallic compound are preferably metal hydride compounds and metal alkoxides from the viewpoint of handling, are not corrosive, do not generate harmful gases, and have little contamination in the process. Alkoxides are preferably used.

  In the present invention, when using an organometallic compound as the reactive gas, from the viewpoint of forming a uniform thin film on the cellulose ester film by plasma discharge treatment, the content of the organometallic compound as the reactive gas in the reactive gas is: Although it is preferable that it is 0.01-10 volume%, More preferably, it is 0.1-5 volume%.

  Further, in order to introduce a metal compound such as a silicon compound or a titanium compound into the discharge part, both can be used in a gas, liquid or solid state at normal temperature and pressure.

  In the case of gas, it can be introduced into the discharge part as it is, but in the case of liquid or solid, it can be used after being vaporized by vaporizing means such as heating, depressurization or ultrasonic irradiation.

  When metal compounds such as silicon compounds and titanium compounds are vaporized by heating, metal alkoxides that are liquid at room temperature and have a boiling point of 200 ° C. or less, such as tetraethoxysilane and tetraisopropoxytitanium, are used in the present invention. It is suitable for a method for forming a metal oxide thin film layer. The metal alkoxide may be used after diluted with an organic solvent. As the organic solvent, an organic solvent such as methanol, ethanol, isopropanol, butanol, n-hexane, or a mixed organic solvent thereof can be used.

  Furthermore, physical properties such as hardness and density of the thin film layer are controlled by containing 0.1 to 10% by volume of oxygen, hydrogen, carbon dioxide, carbon monoxide, nitrogen, nitrogen dioxide, nitrogen monoxide and the like in the reaction gas. be able to.

  According to the cellulose ester fill provided with the antireflection layer (metal oxide layer) by the plasma discharge treatment of the present invention, it is possible to sufficiently suppress the occurrence of cracks in the vicinity of both ends of the cellulose ester film, Streaky unevenness that easily occurs at the end in the width direction is also significantly reduced. Accordingly, an antireflection film excellent in yield can be provided even for a large display device having a size exceeding 20 types.

  The cellulose ester film according to the present invention can be used as a member of an optical element or a display device, and this member is a member used in a liquid crystal display device, for example, a polarizing plate, a protective film for a polarizing plate, and the like. Examples thereof include a phase difference plate, a reflection plate, a viewing angle widening film, an optical compensation film, an antiglare film, an antireflection film, and an antistatic film.

  Among them, it is more preferable to apply the present invention to polarizing plates, protective films for polarizing plates, retardation plates, and viewing angle widening films that have strict requirements on dimensional stability.

  The production method of the polarizing plate of the present invention is not particularly limited, and can be produced by a general method. For example, there is a method in which a cellulose triester film is treated with an alkali and bonded to both surfaces of a polarizing film produced by immersing and stretching in an iodine solution using a completely saponified polyvinyl alcohol aqueous solution. Instead of the alkali treatment, a method for improving adhesiveness as described in JP-A-6-94915 and JP-A-6-118232 may be used.

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

Example 1
(Preparation of dope)
Cellulose triacetate synthesized from cotton linter (acetylation degree 61.0%) 100kg
2- (2'-hydroxy-3 ', 5'-di-t-butylphenyl)
1kg of benzotriazole
Triphenyl phosphate 8.5kg
Ethyl phthalyl ethyl glycolate 2kg
AEROSIL-200V 0.1kg
475 kg of methylene chloride
Ethanol 50kg
These were put into a sealed kettle and heated to 70 ° C., and cellulose triacetate (TAC) was completely dissolved while stirring to obtain a dope. This dope is cast on a support made of a stainless steel endless belt through a casting die kept at 30 ° C., hot air is applied from the front and back of the belt to dry the web (dope film), and the cast film remains. When the amount of solvent reached about 100%, the web was peeled off by a peeling roll. When peeling from the support, the web (or film) peeling sound measured in the state without a shield at a distance of 120 cm from the peeling point of the web peeled from the support is 90 to 100 dB. For 30 minutes.

  In the post-drying step of the film, the film peeled off from the support composed of the endless belt is further dried, and dried so that the residual solvent amount at the time of winding is 1% by mass or less, and a cellulose triacetate film having a film thickness of 80 μm is obtained. Obtained.

  Thus, according to the method of the present invention, it is possible to prevent the occurrence of surface defects called “white cloudiness unevenness” and “white spot unevenness” even for a thin film product of cellulose triacetate film, and to protect the polarizing plate. A cellulose triacetate film having excellent quality suitable for the film could be produced continuously for a long time. And according to the method of this invention, it was able to implement, without stopping the manufacturing process of a film.

Comparative Example 1
Next, for comparison, a cellulose triacetate film is produced in the same manner as in Example 1, but when the web is peeled from the support, it is shielded at a distance of 120 cm from the peeling point of the web to be peeled from the support. The web (or film) peeling sound in the region of 125 to 250 Hz measured in the absence of an object was set to 75 dB.

  In this way, when the cellulose triacetate film was produced for 24 hours, stains adhered and accumulated over time on the surface of the support on which the dope was cast. In addition, an irregular white dull defect called “white spot unevenness” occurred, and when used as a protective film for a polarizing plate of a liquid crystal display device (LCD), a quality problem occurred.

Example 2
A Y ₂ O ₃ layer having a thickness of 730 nm and a refractive index of 1.89 is provided on one side of the cellulose triacetate film produced in Example 1, and TiO ₂ having a thickness of 1200 nm and a refractive index of 2.3 is provided thereon. Furthermore, SiO ₂ having a thickness of 940 nm and a refractive index of 1.46 was formed thereon by high-frequency sputtering to form an antireflection treatment layer (AR). And this polarizing plate was produced using this cellulose triacetate film as a protective film for polarizing plates.

Example 3
Formation of Metal Oxide Layer (Antireflection Layer) A metal oxide layer (antireflection layer) was formed on the cellulose triacetate film produced in Example 1 by atmospheric pressure plasma CVD. As the metal oxide layer (antireflection layer), the first titanium oxide layer (refractive index 2.15, average film thickness 15 nm), the first silicon oxide layer (refractive index 1.46, average film thickness 33 nm), the second A titanium oxide layer (refractive index 2.15, average film thickness 119 nm) and a second silicon oxide layer (refractive index 1.46, average film thickness 86 nm) were formed in this order.

  For the roll electrode of the atmospheric pressure plasma discharge apparatus, a stainless steel jacket roll base material having a cooling function by circulating silicon oil was used. On the other hand, as a counter electrode, a hollow stainless steel pipe was covered with a dielectric to form an opposing electrode group. As a power source for the plasma CVD processing apparatus, a high frequency power source manufactured by Pearl Industry was used, the continuous frequency was 2 MHz, and power of 4 W / cm 2 was supplied to the discharge electrode. However, the roll electrode was rotated in synchronization with the conveyance of the cellulose ester film using a drive.

  The electrode gap was 2 mm, and the reaction gas pressure was atmospheric pressure + 1 kPa. The composition of the reaction gas used for the plasma discharge treatment is described below.

Reaction gas for forming titanium oxide layer (high refractive index layer):
Inert gas (helium) 99.4% by volume
Reaction gas (hydrogen gas) 0.3% by volume
Reaction gas (tetraisopropoxytitanium vapor) 0.3% by volume
Reaction gas for forming silicon oxide layer (low refractive index layer):
Inert gas (helium) 99.4% by volume
Reaction gas (oxygen gas) 0.3% by volume
Reaction gas (tetraethoxysilane vapor) 0.3% by volume
Cracks generated in the metal oxide layer (antireflection layer) formed on the surface of the sample film by subjecting the obtained antireflection cellulose triacetate film to a temperature and humidity control treatment at a temperature of 80 ° C. and a humidity of 90% RH for 72 hours. When observed visually and with a microscope, almost no cracks were observed.

Claims (4)

  Using a solution casting film forming method, a cellulose ester film raw material solution (dope) is cast from a casting die onto a rotationally driven metal support (hereinafter referred to as “support”) to form a dope film (web). Then, after drying the web until it has a peelable strength from the support, when peeling from the support, it is measured 100 to 150 cm away from the peeling point of the web to be peeled from the support, with no shielding. A method for producing a cellulose ester film, wherein the state in which the web (or film) peeling sound in the 125 to 250 Hz region is 80 dB to 120 dB is continued for 10 minutes to 120 minutes.   A cellulose ester film produced by the method according to claim 1.   A cellulose ester film, further comprising an antireflection treatment layer (AR) provided on the cellulose ester film according to claim 2.   A cellulose ester film, wherein an antireflection layer (metal oxide layer) is further provided on the cellulose ester film according to claim 2 by plasma discharge treatment.