JP2008088445A - Method for producing cellulose ester film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a cellulose ester film in which even when thinning a polarizing plate protection film following on thinning a liquid crystal display element, the handleability is excellent in a film making process and a polarizing plate creating process. <P>SOLUTION: The method for producing the cellulose ester film is characterized in that a dispersion, in which finely divided particles having a mean particle diameter of 10.0 μm or less are dispersed in a pressure condition of at least 100 kgf/cm<SP>2</SP>by a high pressure dispersing apparatus, is used, in a dope, the methylene chloride ratio in a solvent is 70-95 mass%, the concentration of a cellulose ester is 10-50 mass%, in a range from the surface to the depth of 10 μm of the cellulose ester film which contains the finely divided particles having the mean particle diameter of 10.0 μm or less in a film, the finely divided particles exist by 5-500 pieces/1,000 μm<SP>2</SP>in a cross section perpendicular to the film, and the membrane thickness is 20-65 μm. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a cellulose ester film, and particularly to a film suitable as a protective film for a polarizing plate of a liquid crystal display device.

  In recent years, as liquid crystal display devices (LCDs) are used in various places, they are required to be thinner and lighter, and polarizing plates used in LCDs are also required to be thinner and lighter.

  Incidentally, a cellulose triacetate (TAC) film is mainly used as a protective film for polarizing plates used in LCDs at present, but its thickness is relatively thick at 80 μm or more. Since four protective films are usually used as LCD members, it is highly desired to reduce the thickness.

  However, when the TAC film, which is the protective film, is thinned, wrinkles are generated during the film forming process of the TAC film and the subsequent polarizing plate creation process, for example, in the transport process during film formation, and the winding state. However, it was not easy to reduce the film thickness.

  In addition, when the liquid crystal display device is assembled as the film thickness is reduced, display unevenness is likely to occur. As a result of diligent research, the inventors of the present application have found that the display unevenness is caused by blocking such as sticking between films, and have reached the present invention. As the film becomes thinner, blocking is more likely to occur, and since blocking has occurred, uneven coating, wrinkles, and the like occur, resulting in unevenness on the surface. The uniformity of the surface is a characteristic that is particularly severe in the film for liquid crystal display devices than the film for other uses, and the present inventors have found that the uniformity of the surface in the film for liquid crystal display devices. The present invention has been conceived to improve the above.

  The object of the present invention is to produce a cellulose ester film having excellent handling properties in the film forming process and the polarizing plate making process even when the polarizing plate protective film is made thin with the thinning of the liquid crystal display element. It is to provide a method.

  The above object of the present invention is achieved by the following configurations.

1. Using a dispersion obtained by dispersing fine particles having an average particle size of 10.0 μm or less under a pressure condition of 100 kgf / cm ² or more with a high-pressure dispersion apparatus, the dope has a methylene chloride ratio in the solvent of 70 to 95% by mass. The concentration of the cellulose ester is 10 to 50% by mass, and in the region from the surface of the cellulose ester film containing fine particles having an average particle size of 10.0 μm or less to the depth of 10 μm, the fine particles are applied to the film. A method for producing a cellulose ester film, comprising producing a cellulose ester film having a vertical cross section of 5 to 500 pieces / 1000 μm ² and a film thickness of 20 to 65 μm.

2. Dispersion in which fine particles having an average particle size of 10.0 μm or less are dispersed in a solvent containing 25% by mass to 100% by mass of a lower alcohol selected from methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, and butyl alcohol The dope has a methylene chloride ratio in the solvent of 70 to 95% by mass, the cellulose ester concentration is 10 to 50% by mass, and the film contains fine particles having an average particle size of 10.0 μm or less. In the region from the surface of the ester film to a depth of 10 μm, the fine particles are present in a cross section perpendicular to the film, and 5 to 500 pieces / 1000 μm ² exist, and a cellulose ester film having a thickness of 20 to 65 μm is produced. A method for producing a cellulose ester film.

3. Using a dispersion in which fine particles having an average particle size of 10.0 μm or less are dispersed in a solvent at a concentration of 1% by mass to 30% by mass, the dope has a methylene chloride ratio in the solvent of 70 to 95% by mass, cellulose The concentration of the ester is 10 to 50% by mass, and the fine particles are perpendicular to the film in the region from the surface of the cellulose ester film containing fine particles having an average particle size of 10.0 μm or less in the film to a depth of 10 μm. A method for producing a cellulose ester film comprising producing a cellulose ester film having a cross section of 5 to 500 pieces / 1000 μm ² and a film thickness of 20 to 65 μm.

  4). 4. The solvent according to any one of 1 to 3, wherein the solvent other than methylene chloride in the dope is a solvent selected from methanol, ethanol, n-propyl alcohol, iso-propyl alcohol, and n-butanol. The manufacturing method of the cellulose-ester film of description.

  According to the present invention, with the thinning of the liquid crystal display element, even when the polarizing plate protective film is thinned, in the film forming process and the polarizing plate making process, the manufacture of a cellulose ester film having excellent handleability Can provide a method.

  The best mode for carrying out the present invention will be described in detail below, but the present invention is not limited thereto.

  Hereinafter, the present invention will be specifically described.

  Examples of the cellulose ester according to the present invention include cellulose triacetate, cellulose diacetate, cellulose acetate butyrate, and cellulose acetate propionate. In the case of cellulose triacetate, cellulose triacetate having a polymerization degree of 250 to 400 and a bound acetic acid amount of 54 to 62.5% is particularly preferable, and a base strength having a bound acetic acid amount of 58 to 62.5% is strong and more preferable. As the cellulose triacetate, either cellulose triacetate synthesized from cotton linter or cellulose triacetate synthesized from wood pulp can be used alone or in combination.

  It is preferable to use a large amount of cellulose triacetate synthesized from a cotton linter that has good releasability from a belt or a drum because of high productivity efficiency. Since the ratio of cellulose triacetate 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 can be used alone. Most preferred.

  Although it does not specifically limit as a plasticizer which can be used by this invention, In a phosphate ester type | system | group, a triphenyl phosphate, a tricresyl phosphate, a cresyl diphenyl phosphate, an octyl diphenyl phosphate, a diphenyl biphenyl phosphate, a trioctyl phosphate, a tributyl phosphate In the phthalate ester system, diethyl phthalate, dimethoxyethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, etc. Use phthalyl ethyl glycolate, methyl phthalyl ethyl glycolate, butyl phthalyl butyl glycolate alone or in combination It is preferred.

  If necessary, two or more plasticizers may be used in combination. In this case, the proportion of phosphate ester plasticizer used is 50% or less, which hardly causes hydrolysis of the cellulose ester film and is durable. It is preferable because of its excellent properties.

  It is more preferable that the ratio of the phosphate ester plasticizer is small, and it is particularly preferable to use only a phthalate ester or glycolate ester plasticizer.

  In the present invention, in order to make the water absorption rate and moisture content within a specific range, the addition amount of the plasticizer is preferably 3% by mass to 30% by mass, more preferably 3% by mass to the cellulose ester. Is 10% by mass to 25% by mass, more preferably 15% by mass to 25% by mass. If it exceeds 30% by mass, the mechanical strength and dimensional stability deteriorate.

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

  In the present invention, in particular, the transmittance at a wavelength of 370 nm needs to be 10% or less, preferably 5% or less, more preferably 2% or less.

  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.

  In this invention, it is preferable to use 1 or more types of these ultraviolet absorbers, and you may contain 2 or more types of different ultraviolet absorbers.

  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 used in the present invention is mass% with respect to the cellulose ester, 0.1 mass% to 2.5 mass%, preferably 0.5 mass% to 2.0 mass%, more preferably 0.8 mass%. It is mass%-2.0 mass%. When the amount of the ultraviolet absorber used is more than 2.5% by mass, the transparency tends to deteriorate, which is not preferable.

  Examples of the solvent for the cellulose ester according to the present invention include lower alcohols such as methanol, ethanol, n-propyl alcohol, iso-propyl alcohol, and n-butanol, cyclohexanedioxanes, and lower aliphatic hydrocarbon chlorides such as methylene chloride. Things can be used.

  As a solvent ratio, for example, methylene chloride is preferably 70 to 95% by mass, and other solvents are preferably 5 to 30% by mass. The concentration of the cellulose ester is preferably 10 to 50% by mass. The heating temperature with the addition of the solvent is preferably a temperature not lower than the boiling point of the solvent used and in a range where the solvent does not boil, for example, preferably 60 ° C. or higher and 80 to 110 ° C. The pressure is determined so that the solvent does not boil at the set temperature.

  After dissolution, it is taken out from the container while cooling, or extracted from the container with a pump or the like and cooled with a heat exchanger or the like, and used for film formation. The method for producing the cellulose ester film in the present invention 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, 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-B Nos. 45-9074, 49-4554, 49-5614, 60-27562, 61-39890, and 62-4208.

  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.

  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 not lower than the boiling point of the solvent used and in a range where the solvent does not boil, for example, preferably 60 ° C. or higher and 80 to 110 ° C. The pressure is determined so that the solvent does not boil at the set temperature.

  After dissolution, take it out from the container while cooling, or extract it from the container with a pump 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.

  In the present invention, a dope obtained by dissolving cellulose ester is cast on a support (casting process), and then heated to remove a part of the solvent (drying process on the support), and then from the support. It peels and the peeled film is dried (film drying process), and a cellulose-ester film is obtained.

  As the support in the casting process, a support in which a belt-like or drum-like stainless steel is mirror-finished is used. The temperature of the support in the casting process can be cast at a general temperature range of 0 ° C. to less than the boiling point of the solvent, but the dope is gelled by casting on a support at 5 to 30 ° C. In order to increase the peeling limit time, it is preferable, and it is more preferable to cast it on a support at 5 to 15 ° C. The peeling limit time is the time during which the cast dope is on the support at the limit of the casting speed at which a transparent and flat film can be continuously obtained. A shorter peeling limit time is preferable because of excellent productivity.

  In the drying process on the support, the dope is cast, once gelled, and when the time from casting to peeling is 100%, the dope temperature is 40 ° C. to 70 ° C. within 30% from the casting. By doing so, evaporation of the solvent is promoted, and it can be peeled off from the support as soon as possible, and the peel strength is further increased. The dope temperature is more preferably set to 55 ° C. to 70 ° C. within 30%. This temperature is preferably maintained at 20% or more, more preferably 40% or more.

  Drying on the support is preferably peeled from the support with a residual solvent amount of 60% to 150% because the peel strength from the support is reduced, and more preferably 80 to 120%. The dope temperature at the time of peeling is preferably 0 ° C. to 30 ° C., because the base strength at the time of peeling can be increased and the base breakage at the time of peeling can be prevented, and 5 ° C. to 20 ° C. is more preferable.

  The amount of residual solvent in the film is represented by the following formula.

Residual solvent amount = residual volatile matter mass / film mass after heat treatment × 100%
The residual volatile matter mass is a value obtained by subtracting the film mass after the heat treatment from the film mass before the heat treatment when the film is heat treated at 115 ° C. for 1 hour.

  In the film drying step, the film peeled from the support is further dried, and the residual solvent amount is 3% by mass or less, preferably 1% by mass or less, more preferably 0.5% by mass or less. It is preferable for obtaining a good film. In the film drying process, generally, a roll suspension system, a pin tenter system, or a clip tenter system is used for drying while transporting the film. For the liquid crystal display member, it is preferable to dry while maintaining the width by a tenter method in order to improve the dimensional stability. In particular, in order to demonstrate the effect of improving the dimensional stability by holding the width in a large amount of residual solvent immediately after peeling from the support, the film is formed by evaporation of the solvent in the drying process after peeling from the support. Try to shrink in the width direction.

  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 the entire drying process or a part of the drying process as shown in Japanese Patent Application Laid-Open No. 62-46625 is performed while holding the width at both ends of the web with a clip in the width direction. Is preferred.

  The means for drying the film is not particularly limited, and is generally performed with hot air, infrared rays, a heating roll, microwaves, or the like. It is preferable to carry out with hot air in terms of simplicity. The drying temperature is preferably in the range of 40 ° C. to 150 ° C. and divided into 3 to 5 stages, and it is preferable that the drying temperature is increased stepwise. .

  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 according to the present invention is generally 20 to 200 [mu] m, but is 20 to 65 [mu] m from the request of thinning and lightening the polarizing plate used in the LCD. Preferably, it is 30-60 micrometers, More preferably, it is 35-50 micrometers. If it is thinner than this, the stiffness of the film will be reduced, so troubles due to wrinkles etc. are likely to occur on the polarizing plate making process, and if it is thicker than this, it will contribute to the thinning of the LCD Few.

  Further, fine particles are added as a matting agent to the cellulose ester film according to the present invention.

  The kind of fine particles may be an inorganic compound or an organic compound. Examples of the inorganic compound include fine particles of silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, tin oxide, and the like. In this, it is preferable that it is a compound containing a silicon atom, and especially a silicon dioxide fine particle is preferable. Examples of the silicon dioxide fine particles include AEROSIL 200, 200V, 300, R972, R972V, R974, R202, R812, R805, OX50, and TT600 manufactured by Aerosil Co., Ltd.

  Examples of the organic compound include acrylic resin, silicone resin, fluorine compound resin, and urethane resin.

  In the present invention, the primary particle size of the fine particles is not particularly limited, but finally the average particle size in the film needs to be 1.0 to 10.0 μm. Preferably, it is 1.0-8.0 micrometers, More preferably, it is 2.0-5.0 micrometers.

  The average particle size of the fine particles refers to the average value of the lengths in the major axis direction of the particles at the observation position of the film when the cellulose ester film is observed with an electron microscope or an optical microscope. As long as it is a particle observed in a film, it may be a primary particle or a secondary particle in which primary particles are aggregated, but most of the particles that are usually observed are secondary particles.

As an example of the measuring method, for example, a portion having an area of 9775 μm ² per film is observed with a microscope, and the average value of the particle diameters of the fine particles at the observation location is obtained.

  In the same film, the same measurement is randomly measured at 10 points, and an average value is obtained. Furthermore, the average particle size was obtained by averaging the 10 average values.

  In the case of fine particles, the primary particle size, the particle size after being dispersed in a solvent, and the particle size added to the film often change. And controlling the particle size formed.

  If the particle size exceeds 10 μm, haze deterioration or the like may be observed, or it may cause a failure in a wound state as a foreign matter. In addition, when the thickness is 1.0 μm or less, a sufficient effect of improving the winding property is not seen, and particularly when the cellulose ester film is 20 to 65 μm, it is remarkable.

  In the present invention, the true specific gravity of the fine particles needs to be 0.8 to 4.0. Preferably it is 0.8-3.0, More preferably, it is 0.85-2.5. The true specific gravity here means the ratio of mass to volume theoretically calculated from the elements constituting the substance. When the true specific gravity is 0.8 or less, the buoyancy of the fine particles is greatly separated in the state of the fine particle dispersion, and the distribution of the fine particles in the film is uneven. When the true specific gravity is 4.0 or more, Since the sedimentation of the fine particles occurs in the state of the fine particle dispersion and a portion where the fine particles are not added is generated in the film, it is necessary to be within the scope of the present invention.

In the present invention, in the region from the surface of the cellulose ester film to a depth of 10 μm, fine particles having an average particle diameter of 1.0 to 10.0 μm are present in a cross section perpendicular to the cellulose ester film in an amount of 5 to 500/1000 μm ^2. is doing. Preferably a 5 to 300 pieces / 1000 .mu.m ^2, more preferably from 10 to 250 pieces / 1000 .mu.m ^2. In the case of 5 or less, the film surface roughness becomes too smooth and blocking occurs due to an increase in the friction coefficient. In the case of 500 or more, the coefficient of friction of the film surface is too low, and winding deviation occurs at the time of winding, or the transparency of the film is low and the haze is high, so it has no value as a film for a liquid crystal display device. The scope of the present invention is essential.

The number of fine particles in the region from the surface of the cellulose ester film to a depth of 10 μm can be measured, for example, as follows. Ten tomographic photographs are taken at random for each film, and the number of each tomographic photograph in 1000 μm ² at a location from the surface to 10 μm is measured. And the average value of 10 places is taken out.

  In the present invention, the fine particles are used in an amount of 0.04 to 0.3% by mass based on the cellulose ester. Preferably, it is 0.05-0.2 mass%, More preferably, it is 0.05-0.15 mass%. If it is 0.04 or less, the film surface roughness becomes too smooth and blocking occurs due to an increase in the friction coefficient. If it is 0.3 or more, the friction coefficient of the film surface is too low, and winding deviation occurs at the time of winding, or the transparency of the film is low and the haze is high, so it does not have value as a film for a liquid crystal display device. A range is mandatory.

In the present invention, in the region from the surface of the cellulose ester film to 10% of the film thickness, the number A of fine particles in a cross section perpendicular to the film / 100 μm ² and the cross section perpendicular to the film in the remaining 80% region The ratio A / B of the number B of fine particles / 100 μm ² is 1 or more, preferably 1 to 100, more preferably 1.1 to 100.

Wherein A number / 100 [mu] m ² is 0.5 to 50 pieces 100 [mu] m ^2, preferably 0.5 to 40 pieces 100 [mu] m ^2. The B / 100 μm ² is 0 to 25/100 μm ² , more preferably 0 to 5/100 μm ² . It is preferable to reduce the fine particles inside the film that hardly contribute to prevention of blocking because haze of the entire film can be reduced while maintaining blocking properties.

Further, the number of protrusions having a height from the film surface of 0.1 μm or more present on the surface of the cellulose ester film is 10 to 500/100 μm ² , preferably 10 to 400/100 μm ² , more preferably 15 to 300 pieces / 100 μm ² .

  The folding wrinkle in the present invention refers to a wrinkle that is generated when the film is folded from both ends during film conveyance or winding during film production, and is preferably absent.

  The convex pressed failure in the present invention means that air that has entered between the films during winding during film production remains without being removed, or float when foreign matter enters and is preferably absent.

  In the present invention, the winding deviation refers to a phenomenon in which winding occurs at the time of film production due to the meandering of the film, and the film protrudes from the end face during storage or transportation after winding, and the amount of protrusion from the end face Is preferably within 5 mm.

In the present invention, a composition in which fine particles and a solvent are mixed is treated with a high-pressure dispersing device. The high-pressure dispersion apparatus used in the present invention is an apparatus that creates special conditions such as high shear and high pressure by passing a composition in which fine particles and a solvent are mixed at high speed through a narrow tube. It is preferable that the maximum pressure condition inside the apparatus is 100 kgf / cm ² or more in a thin tube having a tube diameter of 1 to 2000 μm, for example, by processing with a high-pressure dispersion apparatus.

More preferably, it is 200 kgf / cm ² or more. At that time, it is preferable that the maximum reaching speed reaches 100 m / sec or more and the heat transfer speed reaches 100 kcal / hr or more.

  The above-described high-pressure fractionation <dispersion apparatus includes an ultra-high-pressure homogenizer (trade name: Microfluidizer) manufactured by Microfluidics Corporation or a nanomizer manufactured by Nanomizer, and a Manton Gorin type high-pressure dispersion apparatus such as a homogenizer manufactured by Izumi Food Machinery Co., Ltd. Can be mentioned.

  In the present invention, the fine particles are dispersed in a solvent containing 25% by mass to 100% by mass of a lower alcohol, and then mixed with a dope obtained by dissolving cellulose ester in a solvent, and the mixed solution is cast on a support. The cellulose ester film is obtained by drying to form a film. The content ratio of the lower alcohol is preferably 50% by mass to 100% by mass, and more preferably 75-100% by mass. Preferred examples of lower alcohols include methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol and the like.

  Although it does not specifically limit as solvents other than a lower alcohol, It is preferable to use the solvent used at the time of film forming of a cellulose ester.

  In the present invention, the fine particles are dispersed in a solvent at a concentration of 1% by mass to 30% by mass. Dispersing at a concentration higher than this is not preferable because the viscosity increases rapidly. The concentration of the fine particles in the dispersion is preferably 5 to 25% by mass, and more preferably 10 to 20% by mass.

  In the present invention, the haze of the film can be measured, for example, according to ASTM-D1003-52.

  In the present invention, the haze is preferably 0 to 0.6%, more preferably 0 to 0.4%, and still more preferably 0.1 to 0.2%.

  In the present invention, the dynamic friction coefficient of the front and back of the film can be measured by a method specified by, for example, JIS-K-7125 (1987).

  In the present invention, when a reference material used for measuring the dynamic friction coefficient of a general film is used as a counterpart material (for example, a metal such as a hard sphere), the effect of adding fine particles to the front and back of the film as in the present invention Cannot be confirmed. It is necessary to measure the dynamic friction coefficient between films. Therefore, in accordance with JIS-K-7125, measurement can be performed by using a film for both the test piece and the counterpart material and arranging the film so that the front and back surfaces of the film are in contact with each other.

  In this invention, it is preferable that a dynamic friction coefficient is 0.5-1.3, More preferably, it is 0.5-1.0, More preferably, it is 0.6-0.8.

  In this invention, what is called a knurling process which gives an unevenness | corrugation to the both ends of the width direction of a cellulose-ester film, and makes an edge part bulky is given.

  When the ratio X (%) of the knurling height (a: μm) to the film thickness (d: μm) X (%) = (a / d) × 100, X = 0 to 25%. .

  Preferably, it is 1 to 15%, more preferably 1 to 10%. From this range, if the knurling height ratio is large, the winding shape is likely to be deformed, and if the ratio is small, the winding property is deteriorated, which is not preferable.

  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.

  The foreign matter recognized in the polarization crossed Nicol state means a material measured by placing two polarizing plates in a direct (crossed Nicol) state and placing a cellulose ester film between them. In the polarization crossed Nicol state, such a foreign substance is observed by shining only the part of the foreign substance in the dark field, so that the size and number 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 0 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, but it can be achieved by filtering a dope composition in which cellulose ester is dissolved in a solvent using the following filter paper. In this case, it is preferable to use a filter paper having a filtering time of 20 sec or more as a kind of filter paper, and to form a film by filtering at a filtration pressure of 16 kg / cm ² or less. More preferably, filtering is performed using a filter paper of 30 sec or more and a filtration pressure of 12 kg / cm ² or less, and more preferably using a filter paper of 40 sec or more and a filtration pressure of 10 kg / cm ² or less. Moreover, it is more preferable to use two or more of the above filter papers. The filtration pressure can be controlled by appropriately selecting the filtration flow rate and the filtration area.

  The production method of the polarizing plate according to 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.

  A liquid crystal display member is a member used in a liquid crystal display device. For example, a polarizing plate, a protective film for a polarizing plate, a retardation plate, a reflective plate, a viewing angle improving film, an antiglare film, an antireflective film, and a charge Prevention film.

  Among them, it is more preferable to apply the present invention to a polarizing plate, a polarizing plate protective film, a retardation plate, and a viewing angle improving film that have strict requirements on dimensional stability.

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

Example 1
<Preparation of sample 1>
(Preparation of dispersion A)
Ethanol 27 parts by mass Fine particle I / silicon dioxide fine particle 3 parts by mass (trade name: Aerosil 200V, primary particle size: 12 nm; manufactured by Nippon Aerosil Co., Ltd.) A dispersion was prepared by dispersing at a pressure of 250 kgf / cm ^{2 with} a gorin type high-pressure disperser.

(Preparation of additive liquid A)
Dispersion A 22 parts by mass Cellulose triacetate synthesized from cotton linter 12 parts by mass 2- (2′-hydroxy-3 ′, 5′-di-t-butylphenyl) benzotriazole (UV absorber I) 26 parts by mass Methylene Chloride 290 parts by mass The above additive solution was measured with a centrifugal particle size distribution analyzer (CAPA500, manufactured by Horiba, Ltd.), and the average particle size was 1.2 μm.

(Dope composition A)
Cellulose triacetate synthesized from cotton linter (acetylation degree 61.0%)
85 parts by weight Cellulose triacetate synthesized from wood pulp (degree of acetylation 61.0%)
15 parts by mass Ethylphthalyl ethyl glycolate (plasticizer A) 2 parts by mass Triphenyl phosphate (plasticizer B) 8 parts by mass Methylene chloride 475 parts by mass Ethanol 50 parts by mass The dope composition A was put in a sealed container and 70 ° C. While stirring until the cellulose triacetate (TAC) was completely dissolved, the dope was obtained. The time required for dissolution was 4 hours. After the dope composition A is filtered, the dope composition A and the additive liquid A are mixed with an in-line mixer so that the addition ratio of fine particles to cellulose triacetate is 0.05% by mass, and then a belt casting apparatus. Was cast uniformly on a stainless steel band support with a dope temperature of 35 ° C. and a temperature of 30 ° C. After drying to a peelable range, the dope was peeled from the stainless steel band support. At this time, the residual solvent amount of the dope was 25%. The time required from casting the dope to peeling was 3 minutes. After peeling from the stainless steel band support, drying is completed in the drying zone of 50 ° C, 90 ° C, 120 ° C, 130 ° C while being transported by many rolls, and knurling with a width of 10 mm and a height of 4 µm is applied to both ends of the film. Thus, a cellulose triacetate film sample 1 having a thickness of 40 μm was prepared. The film width was 1300 mm and the winding length was 3000 m. The winding tension was an initial tension of 20 kg / 1300 mm and a final winding tension of 10 kg / 1300 mm.

(Preparation of samples 2 to 10)
Film samples 2 to 10 were prepared in the same manner except that the thickness of the cellulose triacetate film and the amount of fine particles added were changed as shown in Table 1 in the preparation of Sample 1.

  The following performance evaluation was performed about the film samples 1-10 created as mentioned above.

(Evaluation methods)
1. Average particle diameter The particles were observed with a scanning electron microscope (magnification 3000 times), and the diameter of the circle circumscribing the particles was defined as the particle diameter. Then, 10 places are measured at 10 places at random locations, and an average value is obtained. Furthermore, the average particle size was obtained by averaging the 10 average values.

  2. Haze: Measured according to ASTM-D1003-52.

  3. Coefficient of dynamic friction: The coefficient of dynamic friction between the film surface and the back surface is cut out so that the front and back surfaces of the film are in contact with each other according to JIS-K-7125 (1987), a 200 g weight is placed, the sample moving speed is 100 mm / min, and the contact area The weight was pulled horizontally under the condition of 80 mm × 200 mm, the average load (F) while the weight was moving was measured, and the dynamic friction coefficient (μ) was determined from the following formula.

Coefficient of dynamic friction = F (gf) / weight of weight (gf)
4). Convex-pressed failure: A film wound up 1500 m in the manufacturing process is stored for 1 month in an atmosphere of 23 ° C.-55% RH, then the film is cut out 1 m in the length direction, and the number of occurrences of convex deformation is determined. evaluated. If it is 3 / m ² or less, it is at a level where there is no practical problem.

  5. Winding deviation: The deviation width of the end of the wound sample was measured. It is preferable that it is 10 mm or less.

6). Number of fine particles: 10 tomographic photographs of the film were taken at random, and for each tomographic picture, the number in 1000 μm ² at a location within 10 μm from the surface was counted, and the average value at 10 locations was calculated.

  7. Folding wrinkles: The number of wrinkles generated in 100 m of the film was visually observed and counted.

8). Fine particle distribution A / B: Take 10 tomographic photographs of cellulose ester film, count the number in 100 μm ² in the area from the surface to 10% of the film thickness, and count it as A, and the remaining 80% in the area The number in 100 μm ² was counted as B, and the ratio A / B was calculated.

  9. Number of protrusions on the film surface: The number of protrusions having a height of 0.1 μm or more from the film surface was counted on the surface of the cellulose ester film using an optical interference type surface roughness meter WYKO.

  As can be seen from Table 1, according to the method of the present invention, it is found that the failure during winding is improved by adding fine particles to the cellulose ester film.

  In particular, when the cellulose ester film is thinned, the effect is noticeable.

(Example 2)
Samples 10 to 18 were prepared in the same manner as shown in Table 2, except that the sample 2 of Example 1 was prepared under the same conditions as those shown in Table 2 except that the dispersion pressure of the Manton Gorin type high-pressure disperser and the fine particles were changed to the following types. And evaluated.

Fine particle II / silicon dioxide fine particle (trade name: Aerosil R972V, primary particle size: 16 nm; manufactured by Nippon Aerosil Co., Ltd.)
Fine particle III / silicon dioxide fine particle (trade name: Aerosil TT600, primary particle size: 40 nm; manufactured by Nippon Aerosil Co., Ltd.)
Fine particle IV / silicone resin fine particle (trade name: Tospearl 105, primary particle size: 0.5 μm; manufactured by Toshiba Silicone Co., Ltd.)
Fine particles V / PMMA fine particles (trade name: MX-150, primary particle size: 1.5 μm; manufactured by Soken Chemical Co., Ltd.)
Fine particle VI / silicone resin fine particle (trade name: KMP605, primary particle size: 2.0 μm; manufactured by Koshi Chemical Industry Co., Ltd.)

  As can be seen from Table 2, according to the method of the present invention, it is found that the failure during winding is improved by adding fine particles to the cellulose ester film.

(Example 3)
Samples 19 to 23 were similarly prepared and evaluated as shown in Table 3 except that the height of the knurling was changed as shown in Table 3 under the preparation conditions of Sample 2 of Example 1.

  As can be seen from Table 3, in the present invention, the knurling height ratio is more preferably 0 to 25%.

Example 4
Except that the fine particles were dispersed in a solvent in which the mixing ratio (parts by mass / mass%) of ethanol and methylene chloride as shown in Table 4 was changed at the time of preparation of the fine particle dispersion A under the preparation conditions of the sample 2 of Example 1. Similarly, samples 24-28 were prepared as shown in Table 4.

  Further, in the preparation of Sample 2 of Example 1, dispersion was performed while changing the concentration of the fine particles as shown in Table 4 when the dispersion A was prepared. At this time, samples 29 to 32 are prepared as shown in Table 4 by changing the amount of dispersion added to the additive so that the amount of fine particles added to cellulose triacetate is the same as that of sample 2 of Example 1. did.

  Samples 24-32 were evaluated in the same manner as in Example 1.

  As can be seen from Table 4, when preparing the fine particle dispersion, the failure during winding is improved within the scope of the present invention.

Claims (4)

Using a dispersion obtained by dispersing fine particles having an average particle size of 10.0 μm or less under a pressure condition of 100 kgf / cm ² or more with a high-pressure dispersion apparatus, the dope has a methylene chloride ratio in the solvent of 70 to 95% by mass. The concentration of the cellulose ester is 10 to 50% by mass, and in the region from the surface of the cellulose ester film containing fine particles having an average particle size of 10.0 μm or less to the depth of 10 μm, the fine particles are applied to the film. A method for producing a cellulose ester film, comprising producing a cellulose ester film having a vertical cross section of 5 to 500 pieces / 1000 μm ² and a film thickness of 20 to 65 μm. Dispersion in which fine particles having an average particle size of 10.0 μm or less are dispersed in a solvent containing 25% by mass to 100% by mass of a lower alcohol selected from methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, and butyl alcohol The dope has a methylene chloride ratio in the solvent of 70 to 95% by mass, the cellulose ester concentration is 10 to 50% by mass, and the film contains fine particles having an average particle size of 10.0 μm or less. In the region from the surface of the ester film to a depth of 10 μm, the fine particles are present in a cross section perpendicular to the film, and 5 to 500 pieces / 1000 μm ² exist, and a cellulose ester film having a thickness of 20 to 65 μm is produced. A method for producing a cellulose ester film. Using a dispersion in which fine particles having an average particle size of 10.0 μm or less are dispersed in a solvent at a concentration of 1% by mass to 30% by mass, the dope has a methylene chloride ratio in the solvent of 70 to 95% by mass, cellulose The concentration of the ester is 10 to 50% by mass, and the fine particles are perpendicular to the film in the region from the surface of the cellulose ester film containing fine particles having an average particle size of 10.0 μm or less in the film to a depth of 10 μm. A method for producing a cellulose ester film comprising producing a cellulose ester film having a cross section of 5 to 500 pieces / 1000 μm ² and a film thickness of 20 to 65 μm. 4. The solvent other than methylene chloride in the dope is a solvent selected from methanol, ethanol, n-propyl alcohol, iso-propyl alcohol, and n-butanol. The manufacturing method of the cellulose-ester film of description.