JP4419558B2 - Cellulose ester film, method for producing the same, polarizing plate using the same, and display device - Google Patents

Description

  The present invention relates to a cellulose ester film, a production method thereof, a polarizing plate using the same, and a display device. More specifically, the present invention relates to a cellulose ester film (hereinafter also simply referred to as a film) used for optical applications and a method for producing the same, and in particular, a protective film for a polarizing plate, a retardation film, and a viewing angle used for a liquid crystal display device and the like. The present invention relates to a cellulose ester film that can be used for various functional films such as an enlarged film, an antireflection film used in a plasma display, and various functional films used in an organic EL display and the like, and a method for producing the same.

  In recent years, notebook computers have been developed to be thinner and lighter, larger screens, and higher definition. Along with this, there is an increasing demand for thinner, wider and higher quality protective films for liquid crystal polarizing plates. In general, cellulose ester films are widely used as protective films for polarizing plates. Cellulose ester films are usually wound around a core to form a film, which is stored and transported.

  With the recent enlargement of the screen, there is a demand for a film film having a wide film width and a long winding length. When the film width is wide and the winding length is long, the storage stability of the film becomes a problem. For example, a cracking failure in which the films stick to each other and the film is deformed, or a convex failure in which a foreign object is deformed in a convex shape as if a foreign object is sandwiched between the films, is likely to occur. In particular, when the width of the original fabric is increased to 1.4 m or more, the effect of knurling provided on both sides is reduced, and the storage stability of the original fabric is likely to deteriorate.

  In order to prevent these problems, a method of adding fine particles has been proposed in JP-A-2001-114907. However, with these methods, there is a problem in that foreign substances in the cellulose ester film increase when the addition amount is increased. With the recent increase in image quality, the level of film foreign matter requirements has become stricter, and even small foreign matters that have not been considered a problem have come to be regarded as problems. As a result of our study, foreign matter that appears to be about 50 μm visually is analyzed using an electron microscope, etc., and the core of the foreign matter is about several μm in size, and the periphery of the foreign matter is raised. Then I found that it looked big. It has also been found that most of the core foreign matter is an aggregate of fine particles. For this reason, it has been difficult to satisfy both the characteristics of increasing the amount of addition of fine particles to improve slipperiness and removing only agglomerates of fine particles of several μm or more to reduce foreign matter failure.

  On the other hand, a method is disclosed in which a matting agent is dispersed in a solvent, added to a solution containing a resin, a fine particle additive solution is prepared, and this is added inline to the main dope (for example, a patent). (Refer to Reference 1.) If the fine particle additive solution is filtered with a fine filter in order to reduce foreign matter, the aggregates of the fine particles adhere to each other with the filter and further aggregate, and the filter may clog up and the filtration pressure may increase rapidly. There were many problems. Further, in this method, a fine particle agglomeration is generated due to a shock generated when the fine particle additive solution is added in-line to the main dope, and this cannot be removed.

In addition, the method in which the fine particles and the ultraviolet absorber are dispersed together and added to the main dope pot (for example, see Patent Document 2) has a problem that the mixing ratio of the fine particles and the ultraviolet absorber cannot be easily changed. there were. In addition, there is a problem that the dispersion state of the fine particles is poor when the resin and the ultraviolet absorber are dispersed together with the fine particles. Further, since no investigation has been made on the filter medium filtering the main dope, it has been difficult to remove only the aggregates of several μm or more of fine particles.
JP 2001-114907 A JP-A-7-11055

  Accordingly, the present invention has been made in view of the above-mentioned problems, and the object of the present invention is a cellulose ester film that has excellent storage stability of the cellulose ester film raw material, no generation of foreign matters, and excellent productivity. And a cellulose ester film produced by the method. Furthermore, it is providing the polarizing plate and display apparatus using this cellulose-ester film.

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

1. In the method for producing a cellulose ester film containing fine particles, an additive solution containing fine particles is added to the main dope, and then a filter medium with a collected particle size of 0.5 to 5 μm and a drainage time of 10 to 25 sec / 100 ml is used. A method for producing a cellulose ester film, comprising filtering and casting the dope to produce a film.
2. 2. The method for producing a cellulose ester film according to 1, wherein the main dope is filtered with a filter medium, and then an additive solution containing an ultraviolet absorber substantially free of fine particles is added in-line to the main dope.
3. The method for producing a cellulose ester film according to 1 or 2, wherein the filter medium is a filter paper having a collected particle diameter of 0.5 to 5 µm and a drainage time of 10 to 25 sec / 100 ml.
4). 4. The method for producing a cellulose ester film according to any one of 1 to 3, wherein the fine particles are silicon oxide fine particles.
5. The film width of the said cellulose-ester film is 1.4m-5m, The manufacturing method of the cellulose-ester film of any one of 1-4 characterized by the above-mentioned.
6). 6. The method for producing a cellulose ester film according to 5, wherein the cellulose ester film has a retardation value Ro represented by the following formula of 20 to 200 nm and an Rt value of 70 to 400 nm.
Ro = (Nx−Ny) × d
Rt = ((Nx + Ny) / 2−Nz) × d
(In the formula, Nx, Ny, and Nz represent the refractive indexes in the principal axis x, y, and z directions of the refractive index ellipsoid, respectively, and Nx and Ny represent the refractive index in the film in-plane direction, and Nz represents the thickness direction of the film. In addition, Nx ≧ Ny, and d represents the film thickness (nm).

  INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a method for producing a cellulose ester film which is excellent in storage stability of a cellulose ester film raw material, does not generate foreign matter, and is excellent in productivity, and a cellulose ester film produced by the method. . Furthermore, a polarizing plate and a display device using the cellulose ester film can be provided.

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

  As a result of diligent research on these problems, we have dispersed fine particles, prepared a fine particle additive solution, added it to the main dope dissolution vessel, and had a collected particle size of 0.5 to 5 μm and a drainage time of 10 It proposes a method for producing a film by filtering with a specific filter medium of ˜25 sec / 100 ml and casting the dope. In this method, aggregates remaining when fine particles are dispersed and aggregates generated when main dope is added are removed only with a specific filter medium having a collected particle diameter of 0.5 to 5 μm and a drainage time of 10 to 25 sec / 100 ml. I can do it. In the main dope, since the concentration of fine particles is sufficiently thinner than that of the additive solution, aggregates do not adhere to each other during filtration and the filtration pressure does not increase rapidly.

  In addition, by adding an additive solution containing a UV absorber substantially free of fine particles to the main dope, the amount of the UV absorber can be adjusted to an arbitrary amount in a short time without increasing foreign matter. It has become possible.

  Hereinafter, the present invention will be described in more detail.

(Filter material)
The present invention is characterized in that a filter medium having a collected particle diameter of 0.5 to 5.0 μm and a drainage time of 10 to 25 sec / 100 ml is used. In the present invention, the filter medium is preferably filter paper.

By using this filter paper, it is possible to remove only agglomerates such as fine particles that cause foreign matters, and to continuously filter the main dope with high viscosity, so there is no foreign matter failure, excellent raw material storability, and high speed. Film formation becomes possible and productivity is improved. The collected particle diameter of the filter paper is measured in accordance with JIS Z 8901 and refers to the smallest particle diameter among particles that can be collected by 90% or more. The collected particle diameter of the filter paper of the present invention is preferably 1 to 4 μm, and most preferably 2 to 3 μm. If the collected particle diameter of the filter paper is less than 0.5 μm, fine particles that are not foreign substances are trapped, and the filtration pressure increases rapidly, which is not preferable. If the collected particle diameter exceeds 5 μm, fine particles that cause foreign substances Since it passes to the aggregate, it is not preferable. The drainage time of the filter paper is measured in accordance with JIS P 3801. Using a Herzberg filtration rate tester, 20 ml of 100 ml of distilled water is 0.98 kPa on a 10 cm ² filtration surface. It means the time for filtration by the pressure of. The drainage time of the filter paper of the present invention is preferably 10 to 20 sec / 100 ml, and most preferably 12 to 17 sec / 100 ml. If the drainage time is too long, the filtration resistance becomes too high and high flow filtration cannot be performed continuously. Also, if the drainage time is too short, the strength of the filter paper is not sufficient, the filter paper will open at high pressure, and aggregates that cause foreign substances may pass through, or the filter paper may be destroyed, The above range is preferred. The collected particle size and drainage time of the filter paper are the fiber thickness of the filter paper, the selection of fiber materials such as materials (cotton linter, wood pulp, rayon, polyester fiber, etc.), the degree of beating of the fiber material with a beater, and filler It can be arbitrarily adjusted according to the filter paper manufacturing method such as the addition of.

  Even if only one filter paper according to the present invention is used, it is more preferable to use about 2 to 7 filter papers because the filtration efficiency is increased. The same filter paper may be combined, or a filter paper having a small retained particle diameter may be combined inside. Moreover, it is preferable to use a guard filter paper for removing large dust on the outside. The guard filter paper has a large retained particle diameter of 20 μm or more, and a filter paper such as soft cotton can remove large dust without affecting the filtration pressure, and can prevent leakage of the filter. In addition, a two-stage filtration in which the main dope solution that has been filtered once is filtered one more time is preferable because it has a great effect of removing aggregates.

  The additive liquid containing fine particles is an additive liquid containing the fine particles shown below in a dispersed state. If the fine particle powder is added directly to the main dope, the dispersibility becomes insufficient, and the filter medium is clogged with the aggregation of the fine particles, resulting in a rapid increase in the filtration pressure. The present invention is characterized in that after the additive liquid containing fine particles is added to the main dope, it is filtered with a filter medium having a collected particle diameter of 0.5 to 5 μm and a drainage time of 10 to 25 sec / 100 ml. . The addition of the additive liquid containing fine particles may be anywhere before the filtration. For example, it may be added directly to the main dope dissolving pot, or a mixing pot for the main dope and the fine particle additive solution may be provided and mixed separately from the main dope dissolving pot. Or you may mix with a static mixer etc. in piping before filtration.

  FIG. 1 is a diagram schematically showing a dope preparation step, a casting step, and a drying step of the solution casting film forming method according to the present invention. Large agglomerates are removed from the fine particle charging vessel 41 by the filter 44 and fed to the stock vessel 42. Thereafter, the fine particle addition liquid is added from the stock pot 42 to the main dope dissolving pot 1. Thereafter, the main dope solution is filtered by the main filter 3, and the ultraviolet absorbent additive solution is added inline thereto.

  FIG. 2 is a diagram schematically showing a dope preparation step, a casting step, and a drying step of another solution casting film forming method according to the present invention. This is an example in which a mixer 21 is provided immediately before the main filter 3, and the main dope solution and the fine particle additive solution are mixed in a pipe before the mixer.

  FIG. 3 is a diagram schematically showing a dope preparation step, a casting step, and a drying step of a comparative solution casting method. In the conventional method, the fine particles are added to the ultraviolet absorber charging pot 10 and added in-line to the main dope solution.

  In many cases, the main dope may contain about 10 to 50% by mass of the recycled material. Since the return material contains fine particles, it is necessary to control the addition amount of the fine particle addition liquid in accordance with the addition amount of the return material. From the viewpoint of easy control, a method of directly adding the main dope to the dissolution vessel capable of batch control and a method of mixing by providing a mixing vessel of the main dope and the fine particle addition solution are more preferable. The method of adding the main dope directly to the dissolution vessel of the main dope is most preferable because sufficient time can be taken to mix the main dope and the fine particle addition solution and the productivity is excellent. The additive solution containing fine particles preferably contains 0.5 to 10% by mass, more preferably 1 to 5% by mass, and more preferably 1 to 3% by mass. Is most preferred. The above range is preferable because the smaller the content of the fine particles, the lower the viscosity and the easier the handling, and the higher the content of the fine particles, the smaller the addition amount and the easier the addition to the main dope. Recycled material is a finely pulverized cellulose ester film, which is generated when the cellulose ester film is formed, and is obtained by cutting out both sides of the film, or by using a cellulose film raw material that has been speculated out of scratches. Is done.

  It is preferable that the fine particle additive liquid contains a cellulose ester in addition to the fine particles from the viewpoint of adjusting the viscosity of the additive liquid and being excellent in stagnant stability. The concentration of the cellulose ester in the fine particle addition liquid is preferably 2 to 5% by mass, and more preferably 3 to 4% by mass. The same cellulose ester as the main dope can be used. In addition, a recycled material may be used as in the case of the main dope, but preferably a cellulose ester that simultaneously satisfies the following formulas (I) and (II) is excellent in dispersibility and can suppress aggregation of fine particles, and is more preferable. . It is presumed that the reason why the dispersibility is excellent is that a propionyl group or a butyryl group of the cellulose ester is absorbed on the surface of the fine particles and exhibits a dispersant effect.

Formula (I) 2.6 ≦ X + Y ≦ 2.9
Formula (II) 0 ≦ X ≦ 2.5
However, X is a substitution degree of an acetyl group, Y is a substitution degree of a propionyl group and / or a butyryl group. Among them, cellulose acetate propionate (total acyl group substitution degree = X + Y) satisfying 1.9 ≦ X ≦ 2.5 and 0.1 ≦ Y ≦ 0.9 is preferable. The portion not substituted with an acyl group usually exists as a hydroxyl group. These can be synthesized by known methods.

  These acyl group substitution degrees can be measured according to the method prescribed in ASTM-D817-96.

  Cellulose esters contained in the fine particle addition liquid are cellulose acetate propionate and cellulose acetate butyrate as described in JP-A-10-45804, JP-A-8-231761, US Pat. No. 2,319,052, and the like. A mixed fatty acid ester such as can be used. Among the above descriptions, the lower fatty acid ester of cellulose particularly preferably used is cellulose acetate propionate. These cellulose esters can be used as a mixture.

  As examples of the inorganic compound as fine particles used in the present invention, silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, Mention may be made of aluminum silicate, magnesium silicate and calcium phosphate. Fine particles containing silicon are preferable from the viewpoint of low turbidity, and silicon dioxide is particularly preferable. The fine particles of silicon dioxide preferably have a primary average particle diameter of 20 nm or less and an apparent specific gravity of 70 g / liter or more. The average diameter of the primary particles is more preferably 5 to 16 nm, further preferably 5 to 12 nm. A smaller primary particle average diameter is preferred because haze is low. The apparent specific gravity is preferably 90 to 200 g / liter or more, and more preferably 100 to 200 g / liter or more. A higher apparent specific gravity is preferable because a high-concentration dispersion can be produced, and haze and aggregates are improved.

The amount of fine particles added is preferably 0.02 to 1.0 g, more preferably 0.03 to 0.3 g, and most preferably 0.08 to 0.2 g per 1 m ² .

  Silicon dioxide fine particles are commercially available under the trade names of, for example, Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600 (manufactured by Nippon Aerosil Co., Ltd.). I can do it. Zirconium oxide fine particles are commercially available under the trade names of Aerosil R976 and R811 (manufactured by Nippon Aerosil Co., Ltd.) and can be used.

  Examples of the polymer include silicone resin, fluorine resin, and acrylic resin. Silicone resins are preferable, and those having a three-dimensional network structure are particularly preferable. It is marketed by name and can be used.

  Among these, Aerosil 200V and Aerosil R972V are fine particles of silicon dioxide having a primary average particle diameter of 20 nm or less and an apparent specific gravity of 70 g / liter or more, and the coefficient of friction is maintained while keeping the turbidity of the optical film low. It is particularly preferable because it has a great effect of reducing the effect.

Examples of the method for preparing the additive liquid containing fine particles include the following methods, but are not limited thereto.
(Production method A)
After stirring and mixing the solvent and the fine particles, dispersion is performed with a disperser. This is a fine particle dispersion. Dilute the fine particle dispersion with a solvent, and then add a small amount of cellulose ester or main dope and stir well.
(Production method B)
After stirring and mixing the solvent and the fine particles, dispersion is performed with a disperser. This is a fine particle dispersion. Separately, a small amount of cellulose ester or main dope is added to the solvent and dissolved by stirring. The fine particle dispersion is added to this and stirred.
(Production method C)
Add a small amount of cellulose ester or main dope to the solvent and dissolve with stirring. Fine particles are added to this and dispersed by a disperser.
(Production Method D)
After stirring and mixing the solvent and the fine particles, dispersion is performed with a disperser. This is a fine particle dispersion. A solvent is added to this to obtain a fine particle additive solution.

  It is preferable that the fine particle addition liquid contains a small amount of resin such as cellulose ester because of less aggregation occurring when the main dope is added. Furthermore, the production method A is particularly preferable because it causes less aggregation during the preparation of the additive solution.

  As the solvent used when dispersing the fine particles, a solvent used at the time of forming a cellulose ester film can be used. In particular, alcohol is preferable, and examples thereof include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, tert-butanol and the like having 1 to 8 carbon atoms.

  When the fine particles are mixed with a solvent and dispersed, the concentration of the fine particles is preferably 5 to 30% by mass, more preferably 8 to 25% by mass, and most preferably 10 to 15% by mass. A higher dispersion concentration is preferable because liquid turbidity with respect to the added amount tends to be low, and haze and aggregates are improved. The concentration of the fine particles when the fine particles are dispersed by mixing a solvent and a small amount of resin is preferably 0.5 to 10% by mass, more preferably 1 to 5% by mass, and most preferably 1 to 3% by mass. The concentration of the resin is preferably 2 to 10% by mass, more preferably 3 to 7% by mass, and most preferably 4 to 6% by mass. This range is preferable because of excellent dispersibility of the fine particles.

  As the disperser for dispersing the fine particles, a normal disperser can be used. Dispersers can be broadly divided into media dispersers and medialess dispersers. For dispersion of fine particles, a medialess disperser is preferred because of low haze.

  Examples of the media disperser include a ball mill, a sand mill, and a dyno mill.

Examples of the medialess disperser include an ultrasonic type, a centrifugal type, and a high pressure type. In the present invention, a high pressure disperser is preferable. The high pressure dispersion device is a device 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.

  Examples of the high-pressure dispersing apparatus include an ultra-high pressure homogenizer (trade name: Microfluidizer) manufactured by Microfluidics Corporation, a nanomizer manufactured by Nanomizer, or Ultra Turrax, and other Manton Gorin type high-pressure dispersing apparatuses such as Izumi Food Machinery. Examples include a homogenizer, UHN-01 manufactured by Sanwa Machinery Co., Ltd.

  Although an ultraviolet absorber can be contained in the fine particle addition liquid, it is more preferable that the ultraviolet ray absorbent is not substantially contained from the viewpoint of excellent dispersibility of the fine particles.

  The additive liquid containing the ultraviolet absorber is a liquid which contains the ultraviolet absorber shown below and is added inline to the main dope, and preferably contains 1 to 30% by mass of the ultraviolet absorber. 5 to 20% by mass is more preferable, and 10 to 15% by mass is most preferable. The above range is preferred because the content of the ultraviolet absorber is excellent in the solubility of the cellulose ester, and the content of the ultraviolet absorber is small, so that the addition amount is small and in-line addition is easy.

  It is preferable that the ultraviolet absorbent addition liquid contains a cellulose ester in addition to the ultraviolet absorbent from the viewpoint of adjusting the viscosity of the addition liquid. The same cellulose ester as the main dope can be used. Moreover, you may use a return material like main dope.

  In the present invention, an additive liquid containing filtered fine particles is added to the main dope, and then filtered through a filter medium having a collected particle diameter of 0.5 to 5 μm and a drainage time of 10 to 25 sec / 100 ml. It is particularly preferable to add an additive solution containing an ultraviolet absorber containing no fine particles to the main dope in-line. It is desired that the variation in the lot of the transmittance of 400 nm or less of the cellulose ester film is within 1%. However, as described above, the main dope often contains about 10 to 50% of the return material, and the transmittance of 400 nm or less varies due to variations in the ultraviolet absorbent contained in the return material. For this reason, it is important to adjust the amount of the UV absorber in-line, whereby the lot variation can be controlled within 1%. Alternatively, a part of the ultraviolet absorber added to the film may be added to the main dope pot, and the remaining ultraviolet absorber may be added in-line to adjust the amount of the ultraviolet absorber. This method is excellent in productivity because the amount of in-line addition can be reduced. The ultraviolet absorber to be added to the main dope pot may be added as it is with other additives, or may be added in a state dissolved in a solvent. Moreover, you may add the addition liquid of a ultraviolet absorber.

The no and substantially free from fine particles, by the amount of fine particles added into the film is less than 0.02 g / m ^2, preferably from 0.01 g / m ² or less, 0.002 g / m ² or less More preferably, it is most preferable not to contain fine particles. If the ultraviolet absorbent additive solution added in-line contains fine particles, it will aggregate when mixed with the main dope and cause foreign substances.

  The ultraviolet absorber is intended to improve durability by absorbing ultraviolet rays of 400 nm or less, and in particular, the transmittance at a wavelength of 380 nm is preferably 10% or less, more preferably 5% or less, and further Preferably it is 2% or less.

  The ultraviolet absorbent used in the present invention is preferably an ultraviolet absorbent that is liquid at a temperature of 20 ° C. The use of a liquid ultraviolet absorber at a temperature of 20 ° C. is preferable because there is little change in the retardation value Rt when the film is stretched. The structure of the ultraviolet absorber is not particularly limited, and examples thereof include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, and triazine compounds.

  UV absorbers preferably used are benzotriazole-based UV absorbers and benzophenone-based UV absorbers that are highly transparent and excellent in preventing the deterioration of polarizing plates and liquid crystal elements, and have less unnecessary coloration. UV absorbers are particularly preferred. Specific examples of the ultraviolet absorber used in the present invention include, for example, 5-chloro-2- (3,5-di-sec-butyl-2-hydroxylphenyl) -2H-benzotriazole, (2-2H-benzotriazole -2-yl) -6- (linear and side chain dodecyl) -4-methylphenol, 2-hydroxy-4-benzyloxybenzophenone, 2,4-benzyloxybenzophenone, etc., and tinuvin 109, tinuvin 171 Tinuvin such as Tinuvin 234, Tinuvin 326, Tinuvin 327, and Tinuvin 328 are all commercially available from Ciba Specialty Chemicals and can be preferably used. Among these, Tinuvin 109 and Tinuvin 171 are liquid ultraviolet absorbers at a temperature of 20 ° C., and can be more preferably used.

  The cellulose ester film according to the present invention preferably contains two or more ultraviolet absorbers.

  The amount of UV absorber used is not uniform depending on the type of UV absorber, operating conditions, etc., but when the dry film thickness of the cellulose ester film is 30 to 200 μm, it is 0.5 to 4 with respect to the cellulose ester film. 0.0 mass% is preferable, and 0.6 to 2.0 mass% is still more preferable.

Moreover, in this invention, in order to adjust the color of a film, you may use a blue dye etc. as an additive, for example. Preferred examples of the dye include anthraquinone dyes. The anthraquinone dye can have an arbitrary substituent at positions 1 to 8 of the anthraquinone. Preferable substituents include an anilino group, a hydroxyl group, an amino group, a nitro group, or a hydrogen atom that may be substituted. The addition amount of the films of these dyes 0.1 to 1000 / m ² to maintain the transparency of the film is preferably 10-100 [mu] g / m ^2.

  In the present invention, a fluorescent brightening agent may be used as an additive to adjust the color of the film.

  It is preferable to add a blue dye or a fluorescent brightening agent to the additive solution of the ultraviolet absorber because the color of the film can be easily adjusted.

  In the present invention, the main dope is a dope liquid for producing the cellulose ester film of the present invention, and is called a main dope in order to distinguish it from the additive liquid. The additive solution may be mixed with the same resin component as the main dope solution containing the resin component at a high concentration, and in order to distinguish it from the main dope solution that is not an additive solution containing most of the film-forming resin component. Called dope.

  In the in-line addition, it is preferable to appropriately use a filter or a liquid feed pump described in JP-A-2001-213974.

  Examples of the plasticizer include, but are not limited to, phosphate ester plasticizers, phthalate ester plasticizers, and citrate ester plasticizers. Examples of phosphate ester systems include triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate, and the like. Phthalate, dimethoxyethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, butyl benzyl phthalate, dibenzyl phthalate, butyl phthalyl butyl glycolate, ethyl phthalyl ethyl glycolate, methyl phthalyl ethyl glycolate Examples of citrate plasticizers include triethyl citrate and 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.

  These plasticizers may be used singly or in combination of two or more as required. Moreover, the usage-amount of a plasticizer can be made to contain 1-30 mass% with respect to a cellulose ester, Preferably it is 2-25 mass%, Most preferably, it is 8-15 mass%.

  In the optical film of the present invention, in addition to the plasticizer, an additive exhibiting the same action as the plasticizer can be contained. As these additives, for example, if it is a low molecular weight organic compound capable of plasticizing a cellulose ester film, the same effect as that of a plasticizer can be obtained. These components are not added for the purpose of directly plasticizing the film as compared with the plasticizer, but exhibit the same action as the plasticizer depending on the amount.

  Next, the aliphatic polyhydric alcohol ester preferably used in the present invention will be described.

  The aliphatic polyhydric alcohol ester is an ester of a dihydric or higher aliphatic polyhydric alcohol and one or more monocarboxylic acids.

(Aliphatic polyhydric alcohol)
The aliphatic polyhydric alcohol used in the present invention is a dihydric or higher alcohol and is represented by the following general formula (A).

Formula (A) R1- (OH) n
However, R1 represents an n-valent aliphatic organic group, n represents a positive integer of 2 or more, and an OH group represents an alcoholic and / or phenolic hydroxyl group.

  Examples of the n-valent aliphatic organic group include an alkylene group (eg, methylene group, ethylene group, trimethylene group, tetramethylene group, etc.), an alkenylene group (eg, ethenylene group, etc.), an alkynylene group (eg, ethynylene group, etc.), a cycloalkylene group. (For example, 1,4-cyclohexanediyl group) and alkanetriyl group (for example, 1,2,3-propanetriyl group). The n-valent aliphatic organic group includes those having a substituent (for example, a hydroxy group, an alkyl group, a halogen atom, etc.).

  n is preferably from 2 to 20.

  Examples of preferable polyhydric alcohol include, for example, adonitol, arabitol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, tripropylene glycol, 1 , 2-butanediol, 1,3-butanediol, 1,4-butanediol, dibutylene glycol, 1,2,4-butanetriol, 1,5-pentanediol, 1,6-hexanediol, hexanetriol, Examples thereof include galactitol, mannitol, 3-methylpentane-1,3,5-triol, pinacol, sorbitol, trimethylolpropane, trimethylolethane, xylitol and the like. In particular, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, sorbitol, trimethylolpropane, and xylitol are preferable.

(Monocarboxylic acid)
There is no restriction | limiting in particular as monocarboxylic acid which synthesize | combines the polyhydric alcohol ester preferably used for this invention, Well-known aliphatic monocarboxylic acid, alicyclic monocarboxylic acid, aromatic monocarboxylic acid, etc. can be used. Use of an alicyclic monocarboxylic acid or aromatic monocarboxylic acid is preferred in terms of improving moisture permeability and retention.

  Examples of preferred monocarboxylic acids include the following, but the present invention is not limited thereto.

  As the aliphatic monocarboxylic acid, a fatty acid having a straight chain or a side chain having 1 to 32 carbon atoms can be preferably used. The number of carbon atoms is more preferably 1-20, and particularly preferably 1-10. When acetic acid is contained, compatibility with the cellulose ester is increased, and it is also preferable to use a mixture of acetic acid and another monocarboxylic acid.

  Preferred aliphatic monocarboxylic acids include acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, 2-ethyl-hexanecarboxylic acid, undecylic acid, lauric acid, tridecylic acid , Saturated fatty acids such as myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, serotic acid, heptacosanoic acid, montanic acid, melicic acid, laccelic acid, undecylenic acid, Examples thereof include unsaturated fatty acids such as oleic acid, sorbic acid, linoleic acid, linolenic acid and arachidonic acid. These may further have a substituent.

  Examples of preferable alicyclic monocarboxylic acids include cyclopentanecarboxylic acid, cyclohexanecarboxylic acid, cyclooctanecarboxylic acid, and derivatives thereof.

  Examples of preferred aromatic monocarboxylic acids include those in which an alkyl group is introduced into the benzene ring of benzoic acid such as benzoic acid and toluic acid, and two or more benzene rings such as biphenylcarboxylic acid, naphthalenecarboxylic acid, and tetralincarboxylic acid. The aromatic monocarboxylic acid which has, or those derivatives can be mentioned. Benzoic acid is particularly preferable.

(Polyhydric alcohol ester)
Although there is no restriction | limiting in particular in the molecular weight of the polyhydric alcohol ester preferably used for this invention, It is preferable that it is 300-1500, and it is still more preferable that it is 350-750. The larger one is preferable in terms of retention, and the smaller one is preferable in terms of moisture permeability and compatibility with the cellulose ester.

  The carboxylic acid in the polyhydric alcohol ester may be one kind or a mixture of two or more kinds. Moreover, all the OH groups in the polyhydric alcohol may be esterified, or a part of the OH groups may be left as they are. Preferably, it has 3 or more aromatic rings or cycloalkyl rings in the molecule.

  Examples of polyhydric alcohol esters preferably used in the present invention are shown below.

  The amount of the polyhydric alcohol ester used is preferably 3 to 30% by mass, more preferably 5 to 25% by mass, and particularly preferably 5 to 20% by mass with respect to the cellulose ester.

  The manufacturing method of the cellulose-ester film which is a preferable aspect of this invention is demonstrated.

  A preferable film forming process used in the method for producing a cellulose ester film of the present invention includes a dissolution process, a casting process, a solvent evaporation process, a peeling process, a drying process, and a winding process shown below. Each process will be described below.

<Dissolution process of main dope>
The dissolution step of the main dope is a step of forming a dope by dissolving the flakes in cellulose ester flakes in an organic solvent mainly containing a good solvent described later in a dissolution vessel while stirring.

  In the present invention, the solid content concentration in the dope is preferably adjusted to 15% by mass or more, particularly preferably 18 to 35% by mass.

  If the solid content concentration in the dope is too high, the viscosity of the dope becomes too high, and a sharkskin or the like may occur during casting to deteriorate the film flatness. Therefore, it is preferably 35% by mass or less.

  The dope viscosity is preferably adjusted to a range of 10 to 50 Pa · s.

  For dissolution, a method carried out at normal pressure, a method carried out below the boiling point of a preferred organic solvent (that is, a good solvent), a method carried out under pressure above the boiling point of the good solvent, a method carried out by a cooling dissolution method, and carried out at high pressure. There are various dissolution methods and the like. As a method of dissolving at a temperature higher than the boiling point of the good solvent and applying a pressure that does not boil, the foaming is suppressed by pressurizing to 0.11-1.50 MPa at 40.4-120 ° C. and in a short time. It can be dissolved.

  As the cellulose ester used in the present invention, a lower fatty acid ester of cellulose is preferably used.

  The lower fatty acid in the lower fatty acid ester of cellulose ester means a fatty acid having 6 or less carbon atoms, such as cellulose acetate, cellulose propionate, cellulose butyrate, etc., and JP-A Nos. 10-45804 and 8- Examples of lower fatty acid esters of cellulose include mixed fatty acid esters such as cellulose acetate propionate and cellulose acetate butyrate described in US Pat. No. 2,176,61 and US Pat. No. 2,319,052.

  As a measuring method of the substitution degree of the acyl group of a cellulose ester, it can implement according to ASTM-D-817-96.

  Among the above fatty acids, cellulose acetate and cellulose acetate propionate are preferably used. In the case of the cellulose ester film of the present invention, those having a polymerization degree of 250 to 400 are particularly preferably used from the viewpoint of film strength.

  In the cellulose ester film of the present invention, a cellulose ester having a total acyl group substitution degree of 2.5 to 3.0 is preferably used, and a cellulose ester having a total acyl group substitution degree of 2.55 to 2.85 is particularly preferably used. . When the total acyl group substitution degree is 2.55 or more, the mechanical strength of the film increases, and when it is 2.85 or less, the solubility of the cellulose ester is improved and the generation of foreign substances is more preferable.

  When used as a polarizing plate protective film, cellulose acetate is more preferable, and a molecular weight distribution Mw / Mn obtained by dividing the weight average molecular weight Mw by the number average molecular weight Mn is more preferably 1.8 to 3.0.

  The reason why the molecular weight distribution Mw / Mn of the cellulose acetate used here is limited to the range of 1.8 to 3.0 is that the molecular weight distribution Mw / Mn of the cellulose acetate is less than 1.8. Since crystallization of the cellulose ester occurs partially inside, there is a variation in quality in processability and dimensional stability, which is not preferable. On the other hand, the molecular weight distribution Mw / Mn of cellulose acetate is 3.0. If it exceeds, fine irregularities are likely to occur on the film surface due to stretching, which is not preferable. As the molecular weight of cellulose acetate, those having a number average molecular weight (Mn) of 90,000 to 180,000 are used. More preferably, it is 120,000 to 180,000, particularly preferably 150,000 to 180,000. When the number average molecular weight (Mn) is less than 90000, wrinkles are likely to occur during film formation, and when the number average molecular weight (Mn) exceeds 180000, the dope viscosity becomes very high, which is not preferable for production.

  The average molecular weight and molecular weight distribution of the cellulose ester can be measured by a known method using high performance liquid chromatography. Using this, the number average molecular weight and the weight average molecular weight can be calculated, and the ratio (Mw / Mn) can be calculated.

  The measurement conditions are as follows.

Solvent: Methylene chloride Column: Shodex K806, K805, K803G (Used by connecting three Showa Denko Co., Ltd.)
Column temperature: 25 ° C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (manufactured by GL Sciences)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corp.) Mw = 100000-500 calibration curves with 13 samples were used. It is preferable to obtain 13 samples at approximately equal intervals.

When used as a retardation film, cellulose acetate propionate is more preferable. In the case of cellulose acetate propionate, when the acetyl group substitution degree is X and the propionyl group substitution degree is Y, 2.55 ≦ X + Y ≦ 2.85
1.5 ≦ X ≦ 2.4
Those within the range are preferably used.

  As the cellulose ester, a cellulose ester synthesized from cotton linter, a cellulose ester synthesized from wood pulp, and a cellulose ester synthesized from other raw materials can be used alone or in combination.

  Cellulose esters are also affected by trace metal components in cellulose esters. These are considered to be related to water used in the production process, but it is preferable that there are few components that can become insoluble nuclei, and metal ions such as iron, calcium, and magnesium contain organic acidic groups. Insoluble matter may be formed by salt formation with a polymer degradation product or the like that may be present, and it is preferable that the amount is small. The iron (Fe) component is preferably 1 ppm or less. About calcium (Ca) component, it is contained in a lot of ground water and river water, etc., and it becomes hard water, and it is unsuitable as drinking water. Coordination compounds with ligands, that is, complexes are easily formed, and scum (insoluble starch, turbidity) derived from many insoluble calcium is formed.

  The calcium (Ca) component is 60 ppm or less, preferably 0 to 30 ppm. The magnesium (Mg) component is preferably in the range of 0 to 70 ppm, particularly preferably 0 to 20 ppm, since too much will cause insoluble matter. Metal components such as iron (Fe) content, calcium (Ca) content, magnesium (Mg) content, etc. are pre-processed by completely digesting cellulose ester with micro digest wet cracking equipment (sulfuric acid decomposition) and alkali melting. After performing, it can obtain | require by performing an analysis using ICP-AES (inductively coupled plasma emission spectroscopy analyzer).

  Instead of cellulose ester, a recycled material of cellulose ester film may be used. The use ratio of the recycled material is preferably 0 to 70% by mass, more preferably 10 to 50% by mass, and most preferably 20 to 40% by mass with respect to the solid content of the prescription value such as the main dope. It is preferable to set the amount within the above range because the greater the amount of recycled material used, the better the filterability, and the smaller the amount of recycled material used, the better the slipperiness.

  When the recycled material is used, the additives contained in the cellulose ester film such as plasticizers, ultraviolet absorbers, and fine particles are reduced according to the amount used, and the final cellulose ester film composition becomes the design value. Make adjustments as follows.

  The solvent used for preparing the main dope is not particularly limited as long as it is a solvent that can dissolve the cellulose ester, but even if it cannot be dissolved alone, it can be dissolved by mixing with other solvents. It can be used if possible. In general, a mixed solvent comprising a poor solvent of methylene chloride and cellulose ester, which is a good solvent, is used, and the mixed solvent preferably contains 4 to 30% by mass of the poor solvent.

  Other good solvents that can be used include, for example, methylene chloride, methyl acetate, ethyl acetate, amyl acetate, acetone, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, cyclohexanone, ethyl formate, 2,2,2-trimethyl. Fluoroethanol, 2,2,3,3-tetrafluoro-1-propanol, 1,3-difluoro-2-propanol, 1,1,1,3,3,3-hexafluoro-2-methyl-2-propanol 1,1,1,3,3,3-hexafluoro-2-propanol, 2,2,3,3,3-pentafluoro-1-propanol, nitroethane, and the like. Organohalogen compounds, dioxolane derivatives, methyl acetate, ethyl acetate, acetone and the like are preferred organic solvents (ie, good solubility ) And the like as. The use of methyl acetate is particularly preferred because the resulting film has less curl.

  Examples of the poor solvent for cellulose ester include alcohols having 1 to 8 carbon atoms such as methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, tert-butanol, methyl ethyl ketone, methyl isobutyl ketone, and acetic acid. Examples thereof include ethyl, propyl acetate, monochlorobenzene, benzene, cyclohexane, tetrahydrofuran, methyl cellosolve, and ethylene glycol monomethyl ether. These poor solvents can be used alone or in combination of two or more.

  After dissolution, the cellulose ester solution (dope) is filtered through a filter medium, defoamed, and sent to the next step with a pump. In this case, a plasticizer, an antioxidant, etc. are preferably added to the dope. .

  These additives may be added together with the cellulose ester and the solvent during the preparation of the cellulose ester solution, or may be added during or after the solution preparation.

  Using the dope thus obtained, a cellulose ester film can be obtained through a casting process described below.

《Casting process》
An endless metal belt that feeds the dope through a pressurized metering gear pump to a pressure die and infinitely transfers it at the casting position, or a support for casting a rotating metal drum (hereinafter sometimes referred to simply as a support) This is a step of casting a dope from a pressure die. The surface of the casting support is a mirror surface.

  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, but the slit shape of the die part is prepared. A pressure die that is easy to make uniform in film thickness is preferable. 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 and stacked. Alternatively, the inside of the die can be divided by slits, and a plurality of dope solutions having different compositions can be cast simultaneously (also referred to as co-casting) to obtain a laminated structure cellulose ester film.

  Thus, the obtained dope is cast on a support such as a belt or a drum to form a film. The present invention is particularly effective in a solution casting film forming method using a belt. This is because it is easy to finely adjust the drying conditions on the support as described later.

<< Solvent evaporation process >>
In the present invention, the web (in the present invention, the dope is cast on the casting support, and the formed dope film is called a web) is heated on the casting support to evaporate the solvent. In order to evaporate the solvent, there are a method of blowing air from the web side and / or a method of transferring heat from the back side of the support by a liquid, a method of transferring heat from the front and back by radiant heat, and the like. Drying efficiency is preferred. A method of combining them is also preferable. The web on the support after casting is preferably dried on the support in an atmosphere of 40 to 100 ° C. In order to maintain the atmosphere at 40 to 100 ° C., it is preferable to apply hot air at this temperature to the upper surface of the web or heat by means such as infrared rays.

  In particular, it is desirable for the cellulose ester film of the present invention to peel the web from the support within 30 to 90 seconds after casting. If it peels in less than 30 seconds, not only the surface quality of a film will fall but it is unpreferable also in terms of moisture permeability. Drying over 90 seconds is not preferable because surface quality is deteriorated due to deterioration of peelability and strong curling occurs in the film.

<< Peeling process >>
In this step, the web in which the solvent is evaporated on the support is peeled from the support at the peeling position. The peeled web is sent to the next process. If the residual solvent amount (the following formula) of the web at the time of peeling is too large, peeling will be difficult, or conversely, if it is peeled off after sufficiently drying on the support, part of the web will be peeled off.

  The temperature at the peeling position on the support is preferably 10 to 40 ° C, more preferably 11 to 30 ° C. The residual solvent amount of the web at the peeling position is preferably 25 to 120% by mass, more preferably 40 to 100% by mass.

  The residual solvent amount of the web according to the present invention is defined by the following formula.

Residual solvent amount = (mass before web heat treatment−mass after web heat treatment) / (mass after web heat treatment) × 100%
Note that the heat treatment for measuring the residual solvent amount represents performing heat treatment at 115 ° C. for 1 hour.

  In order to adjust the amount of residual solvent at the time of peeling as described above, the surface temperature of the support for casting after casting is controlled so that the organic solvent can be efficiently evaporated from the web. It is preferable to set the temperature at the peeling position on the support to the above temperature range. In order to control the support temperature, it is preferable to use a heat transfer method with good heat transfer efficiency. For example, a back surface heat transfer method using a liquid is preferable.

  The heat transfer method using radiant heat or hot air is difficult to control the temperature of the support and is not a preferable method. However, in a belt (support) machine, the temperature control at the place where the belt to be transferred has come down is moderate. The belt temperature can be adjusted with a gentle breeze.

  The temperature of the support can be partially changed by dividing the heating means, and can be set to different temperatures such as a casting position, a drying part, and a peeling position of the casting support.

  As a method for increasing the film forming speed (the film forming speed can be increased because the film is peeled off while the residual solvent amount is as large as possible), there is a gel casting method (gel casting) in which even a large amount of residual solvent can be removed.

  For example, a poor solvent for the cellulose ester is added to the dope, and after the dope is cast, the gel is formed, and the temperature of the support is lowered to form a gel. There is also a method of adding a metal salt in the dope.

  By gelling on the support and strengthening the film, peeling can be accelerated and the film forming speed can be increased.

  When used as a polarizing plate protective film, after film formation, when the residual solvent amount is 40% by mass or more, the film starts to be stretched in the MD direction, and the residual solvent amount is less than 40% by mass. It is preferable to stretch in the TD direction. When the residual solvent amount is 40% by mass or more, the film is stretched in the MD direction, and when the residual solvent amount is less than 40% by mass, it is stretched in the TD direction. If the film is stretched in both the MD direction and the TD direction in the state, even if it is stretched in the MD direction and the orientation of the cellulose ester is increased, the orientation of the cellulose ester is disturbed by the stretching in the TD direction. This is because it becomes lower. The cellulose ester film of the present invention can maintain an improvement in elastic modulus without disturbing the orientation of the cellulose ester. It is more preferable to start stretching the film in the MD direction when the residual solvent amount is 60 to 120% by mass, and most preferably 90 to 110% by mass. When the residual solvent amount is less than 1 to 30% by mass, it is more preferable to stretch in the TD direction, and most preferably 5 to 20% by mass.

  When used as a polarizing plate protective film, the stretching ratio of the cellulose ester film is 1.05 to 1.3 times in both the MD direction and the TD direction, and more preferably 1.05 to 1.15 times. The area is preferably 1.12 times to 1.44 times by MD direction and TD direction stretching, and preferably 1.15 times to 1.32 times. This can be determined by MD-direction stretching ratio × TD-direction stretching ratio. If the draw ratio in the MD direction is less than 1.05 times, the effect of improving the elastic modulus is small and not preferable. If the draw ratio in the TD direction is less than 1.05 times, the effect of reducing Ro is small and not preferable. Moreover, since a haze will also increase even if a draw ratio exceeds 1.3 times, it is unpreferable.

  In order to stretch in the MD direction, it is preferable to peel at a peeling tension of 130 N / m or more, and particularly preferably 150 to 170 N / m. Since the web after peeling is also in a high residual solvent state, stretching in the MD direction can be performed by maintaining the same tension as the peeling tension. As the web dries and the residual solvent amount decreases, the draw ratio in the MD direction decreases.

When used as a polarizing plate protective film, the roll span of the stretching zone for stretching the cellulose ester film in the MD direction is preferably 1.0 m or less. When a cellulose ester film having a molecular weight distribution as in the present invention is stretched in the MD direction in the state of a high residual solvent amount, slipping in the MD direction is likely to occur, and slipping is prevented when the roll span is 1.0 m or less. I can do it. Moreover, 10-40 degreeC is preferable for the film temperature when extending | stretching to MD direction, It is because the planarity of a film becomes good by setting it as this range.
The draw ratio in the MD direction of the present invention was calculated from the rotation speed of the belt support and the tenter operation speed.

  In order to stretch in the TD direction, for example, the entire drying process as shown in JP-A-62-46625 or a part of the process is dried while holding the width at both ends of the web with clips or pins in the width direction. Among them, a tenter method using a clip and a pin tenter method using a pin are preferably used.

  The drying temperature when performing the tenter is preferably 30 to 150 ° C, more preferably 80 to 150 ° C, and most preferably 100 to 140 ° C. The lower the drying temperature, the less the transpiration of the UV absorber, the plasticizer, etc., the better the process contamination, and the higher the drying temperature, the better the flatness and elastic modulus of the film. When the cellulose ester film is stretched, foreign matters are likely to protrude on the surface, and foreign matter failures occur more often than usual. Therefore, this invention exhibits an effect especially in the cellulose-ester film which has the process to extend | stretch.

  In the present invention, the in-plane retardation value Ro is obtained by performing a three-dimensional refractive index measurement at a wavelength of 590 nm using an automatic birefringence meter KOBRA-21ADH (manufactured by Oji Scientific Instruments). It can be calculated from Nx, Ny, Nz.

  The in-plane retardation value Ro is preferably 20 to 200 nm, and the retardation value Rt in the thickness direction is preferably in the range of 70 to 400 nm.

Ro = (Nx−Ny) × d
Rt = ((Nx + Ny) / 2−Nz) × d
(In the formula, Nx, Ny, and Nz represent the refractive indexes in the principal axis x, y, and z directions of the refractive index ellipsoid, respectively, and Nx and Ny represent the refractive index in the film in-plane direction, and Nz represents the thickness direction of the film. In addition, Nx ≧ Ny, and d represents the film thickness (nm).
In the cellulose ester film of the present invention, the angle θ (radian) formed between the slow axis direction and the film forming direction and the retardation Ro in the in-plane direction have the following relationship, and particularly as an optical film such as a protective film for a polarizing plate. Preferably used.

P ≦ 1-sin2 (2θ) sin2 (πRo / λ)
P is 0.9999 or less.

  θ is the angle (° radians) formed between the slow axis direction in the film plane and the film forming direction (straight direction of the film), and λ is the three-dimensional refractive index measurement for obtaining the above Nx, Ny, Nz, and θ. The wavelength of light is 590 nm, and π is the circumference.

<< Drying process >>
It is a step of drying the web while holding the width using a drying device that alternately conveys the web through rolls arranged in a staggered pattern and / or a tenter device that conveys while holding both ends of the web with clips or pins. . It is preferable to maintain the conveyance tension in the drying process as low as possible, since Ro can be maintained low, and is preferably 190 N / m or less. More preferably, it is 170 N / m or less, More preferably, it is 140 N / m or less, It is especially preferable that it is 100-130 N / m. In particular, it is effective to maintain it below the transport tension until the amount of residual solvent in the film is at least 5% by mass or less.

  As a drying means, hot air is generally blown on both sides of the web, but there is also a means of heating by applying microwaves instead of wind. Too much drying tends to impair the flatness of the finished film. Drying at a high temperature is preferably performed from about 8% by mass or less of residual solvent. Throughout the whole, the drying temperature is approximately 40-250 ° C. It is particularly preferable to dry at 40 to 160 ° C.

  In the drying process after peeling from the casting support surface, the web tends to shrink in the width direction by evaporation of the solvent. Shrinkage increases as the temperature rapidly dries.

  Drying while suppressing this shrinkage as much as possible is preferable for improving the flatness of the finished film.

  From this point of view, for example, a method of drying all or part of the drying process as disclosed in Japanese Patent Application Laid-Open No. 62-46625 while holding the width at both ends of the web with clips or pins in the width direction (tenter) Among them, a tenter method using a clip and a pin tenter method using a pin are preferably used.

  At this time, the stretching ratio in the width direction is preferably 0% to 100%, more preferably 5% to 20%, most preferably 8% to 15% when used as a polarizing plate protective film, and as a retardation film. When used, 10% to 40% is more preferable, and 20% to 30% is most preferable. R0 can be controlled by the draw ratio, and a higher draw ratio is preferable because the flatness of the finished film is excellent. The present invention is particularly effective for a film having a high stretch ratio in which fine particle aggregates tend to become foreign matters.

  When the tenter is used, the residual solvent amount of the web is preferably 20 to 100% by mass at the start of the tenter, and drying is performed while the tenter is applied until the residual solvent amount of the web becomes 10% by mass or less. Preferably, it is 5 mass% or less more preferably.

  30-150 degreeC is preferable, as for the drying temperature in the case of performing a tenter, 50-120 degreeC is more preferable, and 70-100 degreeC is the most preferable. The lower the drying temperature, the less the transpiration of UV absorbers, plasticizers, etc., the better the process contamination, and the higher the drying temperature, the better the flatness of the film. Since the ultraviolet absorber represented by the general formula (1) hardly evaporates even when the drying temperature is high, the effect is remarkably exerted under the production conditions where the tenter drying temperature is high and the draw ratio is high.

  In the film drying step, the film peeled off from the support is further dried, and the residual solvent amount is preferably 0.5% by mass or less, more preferably 0.1% by mass or less, and still more preferably. Is 0 to 0.01 mass% or less.

  In the film drying process, generally, a roll suspension method or a method of drying while conveying the film by the pin tenter method as described above is adopted. 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 divided into 3 to 5 stages in the range of 40 to 150 ° C. and gradually increased, and more preferably in the range of 80 to 140 ° C. in order to improve dimensional stability.

  In the process from immediately after casting through the solution casting film forming method to drying, the atmosphere in the drying apparatus may be air, but may be performed in an inert gas atmosphere such as nitrogen gas, carbon dioxide gas, argon, etc. Good.

  Of course, the danger of the explosion limit of the evaporating solvent in the dry atmosphere must always be taken into account.

<Winding process>
This is a step of winding up as a cellulose ester film after the residual solvent amount in the web is 2% by mass or less, and a film having good dimensional stability can be obtained by making the residual solvent amount 0.4% by mass or less. I can do it.

  As a winding method, a generally used method may be used. There are a constant torque method, a constant tension method, a taper tension method, a program tension control method with a constant internal stress, and the like.

  To adjust the film thickness, it is necessary to control the dope concentration, the pumping amount of the pump, the slit gap of the die base, the extrusion pressure of the die, the speed of the casting support, etc. so as to obtain the desired thickness. Good.

  Further, as a means for making the film thickness uniform, it is preferable to use a film thickness detection means to feed back and adjust the programmed feedback information to each of the above devices.

  The film thickness of the cellulose ester film varies depending on the purpose of use, but the finished film is usually in the range of 5 to 500 μm, more preferably in the range of 10 to 250 μm, and particularly in the range of 10 to 120 μm as the film for a liquid crystal image display device. Is used. The cellulose ester film of the present invention is particularly effective in the range of a thin film having a thickness of 10 to 60 μm.

The moisture permeability of the cellulose ester film of the present invention is defined as a value at 25 ° C. and 90 RH% measured by the method described in JIS Z 0208. Moisture permeability is preferably 20~250g / m ² · 24 hours, but is preferably in particular 20~200g / m ² · 24 hours. When the moisture permeability exceeds 250 g / m ² · 24 hours, the durability of the polarizing plate is remarkably deteriorated. On the other hand, when the moisture permeability is less than 20 g / m ² · 24 hours, it is used as an adhesive for producing a polarizing plate. It is not preferable because a solvent such as water becomes difficult to dry and the drying time becomes long. More preferably, it is 25 to 200 g / m ² · 24 hours.

  In the cellulose ester film of the present invention, the dimensional stability can be further improved by reducing the mass change at 80 ° C. and 90% RH.

  In the cellulose ester film of the present invention, it is more preferable that the mass change rate before and after the heat treatment at 80 ° C. and 90% RH for 48 hours is within ± 2%, which is a thin film with improved moisture permeability. However, a cellulose ester film having an excellent dimensional change rate can be obtained.

  The dimensional change rate of the cellulose ester film of the present invention when heated at 80 ° C. in a 90% RH atmosphere for 48 hours is ± 0 in both the MD direction (film forming direction) and the TD direction (film width direction). It is preferably within 5%, more preferably within ± 0.3%, further preferably within ± 0.1%, and further preferably within ± 0.05%.

  The dimensional change rate referred to in the present invention is a characteristic value representing a dimensional change in the film vertical direction and the horizontal direction under conditions where temperature and humidity conditions are severe. Specifically, the film is placed under heating conditions, humidifying conditions, and hot humidity conditions, and the longitudinal and horizontal dimensional changes as forced deterioration are measured. For example, a film sample to be measured is cut into a size of 150 mm in the width direction and 120 mm in the length direction, and the film surface is crossed with two sharp edges such as a razor at 100 mm intervals in the width direction and the length direction. Mark the mold. The film is conditioned for 24 hours or more in an environment of 23 ° C. and 55% RH, and the distance L1 between the marks in the width direction and the longitudinal direction before processing is measured with a factory microscope. Next, the sample is subjected to high-temperature and high-humidity treatment (conditions: left at 48 ° C. and 90% RH for 48 hours) in an electric thermostat. Again, the sample is conditioned for 24 hours in an environment of 23 ° C. and 55% RH, and the distance L2 between the marks in the width direction and the longitudinal direction after processing is measured with a factory microscope. The rate of change before and after this processing is obtained by the following equation.

Dimensional change rate (%) = (L2−L1) / L1 × 100
In the formula, L1 represents the distance between marks before processing, and L2 represents the distance between marks after processing.

  That is, a desired dimensional change rate measurement can be performed by attaching the marks to be attached in the longitudinal direction and the width direction of the film.

  The dimensional change rate when treated at 105 ° C. for 5 hours is preferably within ± 0.5% in both the MD and TD directions, more preferably within ± 0.3%, and more preferably ± 0.1%. % Is preferable, and more preferably within ± 0.05%.

The cellulose ester film of the present invention preferably has a tensile strength of 90 to 170 N / mm ² in both the MD and TD directions, particularly preferably 120 to 160 N / mm ² .

  The moisture content is preferably 0.1 to 5%, more preferably 0.3 to 4%, and still more preferably 0.5 to 2%.

  The cellulose ester film of the present invention desirably has a transmittance of 90% or more, more preferably 92% or more, and still more preferably 93% or more. Further, the haze is preferably 0.5% or less, particularly preferably 0.1% or less, and more preferably 0%.

  In the cellulose ester film of the present invention, the curl value preferably has a smaller absolute value, and the deformation direction may be the + direction or the-direction. The absolute value of the curl value is preferably 30 or less, more preferably 20 or less, and particularly preferably 10 or less. The curl value is represented by a radius of curvature (1 / m).

  Below, the manufacturing method by the solution casting film forming method of the cellulose ester film of this invention is demonstrated still in detail using figures.

  FIG. 4 is a schematic view showing a preferred example of a solution casting method for film. Fig.4 (a) is a schematic diagram in the case of drying by a roll conveyance and drying process after casting. FIG. 4B is a schematic diagram in the case of drying in a roll conveyance / drying process after casting and then drying in a tenter conveyance / drying process. FIG. 4 (c) is a schematic diagram in the case of drying in the tenter transport / drying process after casting and then drying in the roll transport / drying process. FIG. 4D is a schematic diagram in the case of drying in a roll conveyance / drying process after casting, then drying in a tenter conveyance / drying process, and then drying in a roll conveyance / drying process.

  In the present invention, the process including the tenter conveyance / drying process and the roll conveyance / drying process is a process of drying and stretching the film somewhere in the process until the film peeled off from the support is dried and wound up. The process which has the tenter conveyance and drying process and roll conveyance and drying process to adjust. The tenter transport / drying process is the process of adjusting the drying expansion and contraction rate while transporting with the tenter transport device, and the roll transporting / drying process is the drying and stretching with simultaneous transport while transporting with the roll transport device. This refers to the process of adjusting the rate.

  In FIG. 4, reference numeral 101 denotes a support that runs endlessly. A mirror band metal is used as the support. Reference numeral 102 denotes a die for casting a dope obtained by dissolving a cellulose ester resin in a solvent to the support 1. Reference numeral 103 denotes a peeling point at which the dope cast on the support 101 is solidified, and 104 denotes the peeled film. Reference numeral 105 denotes a tenter conveying / drying step, 151 denotes an exhaust port, and 152 denotes a dry air intake. In addition, the exhaust port 151 and the dry air intake port 152 may be reversed. Reference numeral 106 denotes a tension cutting means. Examples of the tension cutting means include a nip roll and a suction roll. Note that the tension cut means may be provided between the steps.

  Reference numeral 108 denotes a roll conveyance / drying process, 181 denotes a drying box, 182 denotes an exhaust port, and 183 denotes a dry air intake. In addition, the exhaust port 182 and the dry air intake port 183 may be reversed. Reference numeral 184 denotes an upper conveyance roll, and 185 denotes a lower conveyance roll. The transport rolls 184 and 185 are a pair of upper and lower, and are composed of a plurality of sets. Reference numeral 107 denotes a wound roll film.

  In the process shown in FIG. 4D, the roll conveyance / drying process before the tenter conveyance / drying process 105 is referred to as a first roll conveyance / drying process, and the roll conveyance / drying process after the tenter conveyance / drying process 105 is performed. Is called a second roll conveyance / drying step. In addition, you may provide the cooling process which is not shown by FIG.4 (a)-(d) as needed before winding up.

  In this invention, you may manufacture a cellulose-ester film with the form by any solution casting film forming method mentioned above.

  The cellulose ester film of the present invention is preferably used for a liquid crystal display member, specifically a protective film for a polarizing plate, from the viewpoint of good moisture permeability and dimensional stability. In particular, the cellulose ester film of the present invention is preferably used in a protective film for a polarizing plate which has strict requirements for both moisture permeability and dimensional stability.

  The polarizing plate according to the present invention can be produced by a general method. For example, there is a method in which an optical film or a cellulose ester film is subjected to alkali saponification treatment, and a polyvinyl alcohol film is dipped in an iodine solution and stretched on both sides of a polarizing film prepared by using a completely saponified polyvinyl alcohol aqueous solution. is there. The alkali saponification treatment refers to a treatment of immersing the cellulose ester film in a high-temperature strong alkaline solution in order to improve the wetness of the water-based adhesive and improve the adhesiveness.

  The cellulose ester film of the present invention includes a hard coat layer, an antiglare layer, an antireflection layer, an antifouling layer, an antistatic layer, a conductive layer, an optical anisotropic layer, a liquid crystal layer, an alignment layer, an adhesive layer, an adhesive layer, and an undercoat. Various functional layers such as a layer can be provided. These functional layers can be provided by methods such as coating or vapor deposition, sputtering, plasma CVD, and atmospheric pressure plasma treatment.

  Thus, the obtained polarizing plate is provided in the one or both surfaces of a liquid crystal cell, and the liquid crystal display device of this invention is obtained using this.

  By using the protective film for polarizing plates comprising the cellulose ester film of the present invention, it is possible to provide a polarizing plate excellent in durability, dimensional stability, and optical isotropy as well as in a thin film. Furthermore, the liquid crystal display device using the polarizing plate or retardation film of the present invention can maintain stable display performance over a long period of time.

  The cellulose ester film of the present invention can also be used as a base material for an antireflection film or an optical compensation film.

  Hereinafter, the present invention will be described more specifically by way of examples. However, the embodiments of the present invention are not limited to these examples.

Example 1
<Film formation of samples 1 to 22>
(Silicon oxide dispersion)
Aerosil 972V (Nippon Aerosil Co., Ltd.)
(Average primary particle diameter 16 nm, apparent specific gravity 90 g / liter) 12 parts by mass Ethanol 88 parts by mass The above was stirred and mixed with a dissolver for 30 minutes, and then dispersed with Manton Gorin. The liquid turbidity after dispersion was 120 ppm. 88 parts by mass of methylene chloride was added to the silicon oxide dispersion while stirring, and the mixture was stirred and mixed with a dissolver for 30 minutes to prepare a silicon oxide dispersion dilution.

(Silicon oxide additive A)
100 parts by mass of methylene chloride was charged into an airtight container, and 36 parts by mass of the silicon oxide dispersion diluted liquid was charged while stirring, and stirred and mixed with a dissolver for 30 minutes. Thereafter, 6 parts by mass of cellulose acetate propionate (total acyl group substitution degree 2.65, acetyl group 1.90, propionyl group 0.75) was added with stirring, and the mixture was further stirred for 120 minutes, and then Advantech Toyo Corp. Was filtered through a polypropylene wind cartridge filter TCW-PPS-1N to prepare a silicon oxide additive solution A.

(Preparation of inline additive solution A)
Tinuvin 109 11 parts by weight Tinuvin 171 5 parts by weight Methylene chloride 88 parts by weight Ethanol 12 parts by weight The above is put into a sealed container, heated and stirred to completely dissolve, and cellulose acetate propionate (substitution degree 2.65). , Acetyl group 1.90, propionyl group 0.75) 6 parts by mass with stirring, and further stirred for 120 minutes, then filtered with SL filter cartridge SL-100 manufactured by Loki Techno Co., Ltd., in-line additive A Was prepared.

(Preparation of main dope solution A)
Cellulose triacetate synthesized from linter cotton (Mn = 148000, Mw = 310000, Mw / Mn = 2.1) 100 parts by mass Polyhydric alcohol ester exemplified compound 16 5 parts by mass Ethylphthalyl ethyl glycolate 5.5 parts by mass Methylene Chloride 440 parts by mass Ethanol 40 parts by mass The above is put into a closed container, and while stirring, 19 parts by mass of silicon oxide additive A is added by the process flow of FIG. 1 and dissolved while heating and stirring. Two guard filters having a collected particle size of 30 μm and a drainage time of less than 1 sec / 100 ml were used in the apparatus, and three sheets of filter papers listed in Table 1 were used on the inner side for filtration to prepare a main dope solution A. . The filtration area of the press filter was 50 m ² .

(Film formation of samples 1-20)
In the film forming line shown in FIG. 1, the main dope solution A was filtered with Finemet NF manufactured by Nippon Seisen Co., Ltd. In-line additive solution line was filtered with Finemet NF manufactured by Nippon Seisen Co., Ltd. Add 2.0 parts by mass of the filtered in-line additive liquid A to 100 parts by mass of the filtered main dope liquid A, mix thoroughly with an in-line mixer (Toray static type in-pipe mixer Hi-Mixer, SWJ), and then belt flow Using a rolling apparatus, the film was uniformly cast on a stainless steel band support at a temperature of 22 ° C. and a width of 1800 mm. With the stainless steel band support, the solvent was evaporated until the residual solvent amount reached 100% by mass, and the film was peeled from the stainless steel band support with a peeling tension of 162 N / m. The peeled cellulose triacetate web was evaporated at 35 ° C., slit to 1650 mm width, and then dried at a drying temperature of 135 ° C. while stretching 1.07 times in the width direction with a tenter. At this time, the residual solvent amount when starting stretching with a tenter was 10% by mass. Then, drying was terminated while transporting the drying zone of 110 ° C. and 120 ° C. with many rolls, slitting to a width of 1430 mm, a knurling process with a width of 10 mm and a height of 5 μm was applied to both ends of the film, an initial tension of 220 N / m, A cellulose ester film sample 1 was obtained by winding it around a 6-inch inner diameter core with a final tension of 110 N / m. The draw ratio in the MD direction calculated from the rotational speed of the stainless steel band support and the operating speed of the tenter was 1.08. The residual solvent amount of the cellulose ester film sample 1 was 0.004% by mass, the film thickness was 40 μm, and the number of turns was 5200 m.

  Samples 2 to 20 were prepared in the same manner except that the main dope solution, in-line additive solution, and film forming line (addition method) described in Table 1 were used.

The produced sample was evaluated according to the measurement method shown below. The results are shown in Table 2.
(Preparation of inline additive solution B)
Tinuvin 109 11 parts by weight Tinuvin 171 5 parts by weight Methylene chloride 88 parts by weight Ethanol 12 parts by weight The above was put into a sealed container, heated, stirred and completely dissolved and filtered.

  To this was added 4 parts by mass of a silicon oxide dispersion diluted solution with stirring, and after further stirring for 30 minutes, cellulose acetate propionate (total acyl group substitution degree 2.65, acetyl group 1.90, propionyl group 0.75). ) 6 parts by mass was added with stirring, and the mixture was further stirred for 120 minutes, and then filtered through an SL filter cartridge SL-100 manufactured by Loki Techno Co., to prepare an in-line additive solution B.

(Preparation of inline additive solution C)
Tinuvin 109 11 parts by weight Tinuvin 171 5 parts by weight Methylene chloride 88 parts by weight Ethanol 12 parts by weight The above was put into a sealed container, heated, stirred and completely dissolved and filtered.

  To this, 2 parts by mass of a silicon oxide dispersion diluted solution was added with stirring, and after further stirring for 30 minutes, cellulose acetate propionate (total acyl group substitution degree 2.65, acetyl group 1.90, propionyl group 0.75). ) 6 parts by mass was added with stirring, and the mixture was further stirred for 120 minutes, and then filtered through an SL filter cartridge SL-100 manufactured by Loki Techno Co., to prepare an in-line additive solution C.

(Preparation of inline additive solution D)
Tinuvin 109 11 parts by weight Tinuvin 171 5 parts by weight Methylene chloride 88 parts by weight Ethanol 12 parts by weight The above was put into a sealed container, heated, stirred and completely dissolved and filtered.

  To this was added 0.5 parts by mass of a silicon oxide dispersion diluted solution with stirring, and the mixture was further stirred for 30 minutes, and then cellulose acetate propionate (total acyl group substitution degree 2.65, acetyl group 1.90, propionyl group 0). .75) 6 parts by mass were added with stirring, and the mixture was further stirred for 120 minutes, followed by filtration with an SL filter cartridge SL-100 manufactured by Loki Techno Co., Ltd. to prepare an in-line additive solution D.

(Preparation of inline additive solution E)
Tinuvin 109 11 parts by weight Tinuvin 171 5 parts by weight Methylene chloride 62 parts by weight Ethanol 10 parts by weight The above is put into a sealed container, heated and stirred to dissolve completely, and 35.4 parts by weight of the main dope solution A is stirred. The mixture was further stirred for 120 minutes, and then filtered through an SL filter cartridge SL-100 manufactured by Loki Techno Co., to prepare an in-line additive solution E.

(Preparation of inline additive solution F)
Tinuvin 109 11 parts by mass Tinuvin 171 5 parts by mass Methylene chloride 100 parts by mass The above was put into a sealed container, heated, stirred and completely dissolved, and filtered.

  To this, 36 parts by mass of silicon oxide dispersion diluted solution was added with stirring, and further stirred for 30 minutes, and then 6 parts by mass of cellulose acetate propionate (substitution degree 2.65, acetyl group 1.90, propionyl group 0.75). The mixture was added with stirring, and further stirred for 120 minutes, and then filtered through a polypropylene wind cartridge filter TCW-PPS-1N manufactured by Advantech Toyo Co., Ltd. to prepare an in-line additive solution F.

(Silicon oxide additive solution B)
100 parts by mass of methylene chloride was charged into an airtight container, and 71.2 parts by mass of a silicon oxide dispersion diluted solution was charged while stirring, and the mixture was stirred and mixed with a dissolver for 30 minutes. Thereafter, 35.4 parts by mass of the main dope was added with stirring, and the mixture was further stirred for 120 minutes, followed by filtration with Advantech Toyo Co., Ltd. polypropylene wind cartridge filter TCW-PPS-1N to prepare a silicon oxide additive solution B.

(Preparation of main dope solution B)
Cellulose triacetate synthesized from linter cotton (Mn = 148000, Mw = 310000, Mw / Mn = 2.1) 60 parts by mass Returning material obtained by pulverizing the film of sample 6 with a pulverizer 45.5 parts by mass Polyhydric alcohol ester Compound 16 3.0 parts by mass Ethylphthalylethyl glycolate 3.3 parts by mass Methylene chloride 440 parts by mass Ethanol 40 parts by mass The above was put into a sealed container, and 11.4 parts by mass of silicon oxide additive A was added while stirring. Then, a main dope solution B was prepared in the same manner as the main dope solution A except that it was dissolved while heating and stirring.

(Preparation of main dope solution C)
Cellulose triacetate synthesized from linter cotton (Mn = 148000, Mw = 310000, Mw / Mn = 2.1) 100 parts by mass Polyhydric alcohol ester exemplified compound 16 5 parts by mass Ethylphthalyl ethyl glycolate 5.5 parts by mass Methylene Chloride 440 parts by mass Ethanol 40 parts by mass The above was put into a sealed container, and while stirring, 19 parts by mass of silicon oxide additive B was added and dissolved while heating and stirring. A dope solution C was prepared.

(Preparation of main dope solution D)
Cellulose triacetate synthesized from linter cotton (Mn = 148000, Mw = 310000, Mw / Mn = 2.1) 100 parts by mass Polyhydric alcohol ester exemplified compound 16 5 parts by mass Ethylphthalyl ethyl glycolate 5.5 parts by mass Methylene Chloride 440 parts by mass Ethanol 40 parts by mass The above was put into a sealed container, dissolved while heating and stirring, and main dope liquid D was prepared in the same manner as main dope liquid A, except that silicon oxide additive A was not added. Film formation using the main dope liquid D was performed according to the process flow of FIG.

(Preparation of main dope liquid E)
Cellulose ester (cellulose acetate propionate acetyl group substitution degree 1.9, propionyl group substitution degree 0.8) 100 parts by mass (Mn = 70000, Mw = 220,000, Mw / Mn = 3.14)
Triphenyl phosphate 8 parts by weight Ethyl phthalyl ethyl glycolate 2 parts by weight Methylene chloride 300 parts by weight Ethanol 60 parts by weight The above is put into a closed container, and while stirring, 13 parts by weight of silicon oxide additive A is added, heated, Main dope liquid E was prepared in the same manner as main dope liquid A except that it was dissolved while stirring.

(Film formation of sample 21)
Sample 21 was produced in the same manner except that the filter paper for filtering the main dope of sample 6 was changed from three to one.

(Film formation of sample 22)
The main dope solution E was filtered with Finemet NF manufactured by Nippon Seisen Co., Ltd. in the film production line. In-line additive solution line was filtered with Finemet NF manufactured by Nippon Seisen Co., Ltd. 1.7 parts by mass of the filtered in-line additive liquid A is added to 100 parts by mass of the filtered main dope liquid E, and sufficiently mixed with an in-line mixer (Toray static type in-tube mixer Hi-Mixer, SWJ). Using a rolling apparatus, the film was uniformly cast on a stainless steel band support at a temperature of 35 ° C. and a width of 1800 mm. With the stainless steel band support, the solvent was evaporated until the residual solvent amount reached 100% by mass, and peeling was performed from the stainless steel band support with a peeling tension of 140 Newton / m. The peeled cellulose triacetate web was evaporated at 55 ° C., slit to 1650 mm width, and then stretched 1.30 times at 130 ° C. in the width direction with a tenter. At this time, the residual solvent amount when starting stretching with a tenter was 18% by mass. Thereafter, drying was completed while transporting the drying zone at 120 ° C. and 110 ° C. with a number of rolls, slitting to a width of 1430 mm, knurling with a width of 15 mm and an average height of 10 μm was applied to both ends of the film, and an initial tension of 220 N / m. The cellulose ester film sample 22 was obtained by winding it around a 6-inch inner diameter core with a final tension of 110 N / m. The residual solvent amount of the cellulose ester film sample 22 was 0.1% by mass, the film thickness was 80 μm, and the winding number was 4000 m. The retardation values of this cellulose ester film were Ro 43 nm and Rt 132 nm.

  From Tables 1 and 2, an additive solution containing fine particles is added to the main dope, and then filtered through a filter medium having a collected particle diameter of 0.5 to 5 μm and a drainage time of 10 to 25 sec / 100 ml. It can be seen that the extended sample is excellent in both foreign matter and filter life.

  When the collected particle diameter is less than 0.5 μm, the initial pressure is low, but the increase in filtration pressure is large, and the filter life is short, which is a problem. Moreover, when the collected particle diameter exceeds 5 μm, it can be seen that there are many foreign matters.

  If the drainage time is less than 10 sec / 100 ml, the strength of the filter paper is weak. Therefore, it can be seen that the filter paper is opened by the pressure and the foreign matter is getting worse. Also, it can be seen that if the drainage time is long, the initial pressure is high, and thus the filter life is short.

  It can be seen that the sample 20 produced by the step of adding fine particles from the in-line solution (FIG. 3) without adding fine particles to the main dope solution has a significantly large number of foreign matters.

  If the in-line additive liquid contains fine particles, it can be seen that there are many foreign matters. If fine particles are not included in the in-line additive solution, the number of foreign matters is greatly reduced to a level at which there is no practical problem, and it is found that a sample containing no fine particles is the best. Moreover, it turns out that the sample containing a returned material is the most excellent in a foreign material.

"Measuring method"
(Foreign matter failure)
An on-line defect inspection machine was installed immediately before the winding part of the belt casting apparatus, 10 cellulose acetate raw films were inspected, and the average number of foreign matter failures of 20 μm or more per 100 m ^{2 of} the cellulose acetate film was calculated. .

(Initial pressure)
With a filter press filter, the pressure on the press filter entering side after 1 hour from the start of the filter when a constant flow rate filtration of 2000 liters / hour was performed was measured with a pressure gauge installed in the inlet side pipe.

(Press filter life)
Using a filter press filter, the time from the start of the filter when the constant flow rate filtration at 2000 liters / hour was performed until the pressure on the press filter side exceeded 2500 kPa was measured. The longer the time, the better the productivity. In 24 hours or less, continuous production is difficult.

Example 2
A polarizing plate sample was prepared from the cellulose ester film original fabric sample of Example 1 according to the alkali saponification treatment and the polarizing plate preparation method described below. The combinations of the outer protective film of the polarizing plate (outside of the liquid crystal cell) and the inner protective film of the polarizing plate (liquid crystal cell side) were as shown in Table 3, and the polarizing plate yield and image quality were evaluated.

  Moreover, the antireflection film which coated the backcoat layer, hard-coat layer, and antireflection layer which were shown below was used for the outer side protective film of a polarizing plate.

《Coating back coat layer》
The following back coat layer composition has a wet film thickness of 13 μm on the A side of each cellulose ester film (referring to the air side web surface while the web is dried on the metal support after peeling the web). In this way, a back coat layer was applied by using a die coater and dried at a drying temperature of 90 ° C.

<Backcoat layer composition>
Acetone 30 parts by mass Ethyl acetate 45 parts by mass Isopropyl alcohol 10 parts by mass Diacetylcellulose 0.5 part by mass Ultrafine silica 2% acetone dispersion (Aerosil 200V, manufactured by Nippon Aerosil Co., Ltd.)
0.2 parts by mass << Coating of hard coat layer >>
The following hard coat layer composition was applied with a die coater on the opposite side of the cellulose ester film on which the back coat layer was coated, dried at 80 ° C. for 5 minutes, and then applied to a high pressure mercury lamp (80 W). 160 mJ / cm ² of ultraviolet light was applied to provide a hard coat layer having a dry film thickness of 7 μm.

<Hard coat layer composition>
Dipentaerythritol hexaacrylate monomer 120 parts by weight Dimer 40 parts by weight Trimer or higher component 40 parts by weight Diethoxybenzophenone (UV photoinitiator) 20 parts by weight Propylene glycol monomethyl ether 110 parts by weight Ethyl acetate 110 parts by weight 《Coating of medium refractive index layer》
On the hard coat layer, the following medium refractive index layer composition was coated with a die coater and dried for 1 minute at 80 ° C. and 0.1 m / second. After drying, using a high-pressure mercury lamp (80 W), it was cured by irradiation with ultraviolet rays of 130 mJ / cm ² to form an intermediate refractive index layer.

<Preparation of tetraethoxysilane hydrolyzate A>
After mixing 29 parts by mass of tetraethoxysilane and 55 parts by mass of ethanol, and adding 16 parts by mass of a 1.6% by mass aqueous solution of acetic acid to this, the mixture is stirred at 25 ° C. for 25 hours to hydrolyze tetraethoxysilane A Was prepared.

<Medium refractive index layer composition>
Tetraethoxysilane hydrolyzate A 500 parts by mass Solid content 15% titanium oxide fine particle dispersion (RTSPNB15WT% -GO, manufactured by CI Kasei Kogyo Co., Ltd.) 300 parts by mass Linear dimethyl silicone-EO block copolymer (FZ-2207 Nihon Unicar) 1 part by weight Propylene glycol monomethyl ether 1470 parts by weight Isopropyl alcohol 2720 parts by weight Methyl ethyl ketone 490 parts by weight Medium refractive index layer thickness: 86 nm
Refractive index of medium refractive index layer: 1.64
<Coating of high refractive index layer>
Next, the following high refractive index layer composition was applied on the middle refractive index layer with a die coater and dried for 1 minute at 80 ° C. and 0.1 m / second. After drying, ultraviolet rays were irradiated at 130 mJ / cm ² using a high pressure mercury lamp (80 W), and heat treatment was performed at 100 ° C. for 1 minute to form a high refractive index layer.

<High refractive index layer composition>
Solid content 15% titanium oxide fine particle dispersion (RTSPNB15WT% -G0, manufactured by CI Chemical Industry Co., Ltd.) 530 parts by mass Tetra (n) butoxytitanium 50 parts by mass γ-methacryloxypropyltrimethoxysilane (KBM503, manufactured by Shin-Etsu Chemical Co., Ltd.)
10 parts by weight Linear dimethylsilicone-EO block copolymer (FZ-2207 manufactured by Nippon Unicar) 1 part by weight Propylene glycol monomethyl ether 1470 parts by weight Isopropyl alcohol 2490 parts by weight Methyl ethyl ketone 490 parts by weight High refractive index layer film thickness: 80 nm
Refractive index of the high refractive index layer: 1.85
<Coating of low refractive index layer>
On the obtained high refractive index layer, the following low refractive index layer composition was applied by a die coater and dried for 1 minute at 80 ° C. and 0.1 m / second. After drying, a low-refractive index layer was formed by curing by irradiating with ultraviolet rays of 130 mJ / cm ² using a high-pressure mercury lamp (80 W) and further thermally curing at 120 ° C. for 5 minutes. Next, an aging treatment was performed at 65 ° C. for 120 hours to produce an antireflection film.

<Low refractive index layer composition>
Tetraethoxysilane hydrolyzate A 100 parts by mass Hollow silica fine particle dispersion (P-4 manufactured by Catalytic Chemical Industry Co., Ltd.) 180 parts by mass 10% propylene glycol of linear dimethyl silicone-EO block copolymer (FZ-2207 manufactured by Nihon Unicar) Monomethyl ether solution 3 parts by mass Propylene glycol monomethyl ether 380 parts by mass Isopropyl alcohol 380 parts by mass Low refractive index layer thickness: 100 nm
Refractive index of the low refractive index layer: 1.38
<Alkali saponification treatment>
Saponification step 2N-NaOH 50 ° C. 90 seconds Water washing step Water 30 ° C. 45 seconds Step inside 10 mass% HCl 30 ° C. 45 seconds Water washing step Water 30 ° C. 45 seconds Saponification, water washing, neutralization, water washing under the above conditions And then dried at 80 ° C.

(Preparation of polarizing plate)
A 120 μm thick polyvinyl alcohol film was immersed in 100 kg of an aqueous solution containing 1 kg of iodine and 4 kg of boric acid and stretched 6 times at 50 ° C. to form a polarizing film. Cellulose ester film samples subjected to alkali saponification treatment on both surfaces of this polarizing film were bonded to each other using a completely saponified polyvinyl alcohol 5% aqueous solution as an adhesive to prepare polarizing plates.

  The following evaluation was performed about the obtained polarizing plate samples 1-6.

<< Evaluation of polarizing plate and display device >>
(Polarizing plate yield)
The produced polarizing plate was punched into 30 inches (1 inch represents 2.54 cm), and visual inspection was performed one by one. In the appearance inspection, when one or more defects of 20 μm or more existed in one polarizing plate, it was regarded as a defective product. The yield was determined by the following formula.

Yield (%) = Number of good products / (Number of good products + Number of defective products) × 100
(image quality)
30 type liquid crystal television LC-30BV3 (manufactured by Sharp Corporation) is peeled off, and the produced polarizing plate is pasted so as to be orthogonal to each other so that the polarizing axis of the polarizing plate does not change. A liquid crystal television was produced.

  The liquid crystal display was displayed in white, and visual image quality was evaluated.

  A: There is no foreign matter on the surface, and the screen is easy to see.

  B: There are a few small foreign objects on the surface and it looks shining, so the screen is a little difficult to see.

  C: Since there are many small foreign substances on the surface and it looks shining, the screen is clearly difficult to see.

  From Table 3, it is clear that the polarizing plate sample of the present invention has a high polarizing plate yield and excellent display device image quality.

It is the figure which showed typically the dope preparation process of the solution casting film forming method concerning this invention, a casting process, and a drying process. It is the figure which showed typically the dope preparation process, casting process, and drying process of another solution casting film forming method concerning this invention. It is the figure which showed typically the dope preparation process, casting process, and drying process of the comparative solution casting film forming method. It is a schematic diagram of the solution casting film forming method of a film.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Melting pot 3, 6, 12, 15 Filter 4, 13 Stock tank 5, 14 Liquid feed pump 8, 16 Conduit 10 Ultraviolet absorber charging pot 20 Merge pipe 21 Mixer 30 Die 31 Metal support 32 Web 33 Peeling position 34 Tenter Device 35 Roll Drying Device 41 Fine Particle Charger 42 Stock Tank 43 Pump 44 Filter 101 Mirror Surface Metal Casting Support Body 102 Die 103 Film Peeling Point 104 Peeled Film 105 Tenter Transporting / Drying Process 106 Tension Cutting Means 107 Winding Rolled film taken 108 Roll conveyance / drying process 151, 182 Exhaust port 152, 183 Dry air intake port 181 Drying box 184 Upper conveyance roll 185 Lower conveyance roll

Claims (6)

In the method for producing a cellulose ester film containing fine particles, an additive solution containing fine particles is added to the main dope, and then a filter medium with a collected particle size of 0.5 to 5 μm and a drainage time of 10 to 25 sec / 100 ml is used. A method for producing a cellulose ester film, comprising filtering and casting the dope to produce a film. 2. The method for producing a cellulose ester film according to claim 1, wherein after the main dope is filtered with a filter medium, an additive solution containing an ultraviolet absorber substantially free of fine particles is added in-line to the main dope. The method for producing a cellulose ester film according to claim 1 or 2, wherein the filter medium is a filter paper having a collected particle diameter of 0.5 to 5 µm and a drainage time of 10 to 25 sec / 100 ml. The method for producing a cellulose ester film according to any one of claims 1 to 3, wherein the fine particles are fine particles of silicon oxide. The film width of the said cellulose-ester film is 1.4m-5m, The manufacturing method of the cellulose-ester film of any one of Claims 1-4 characterized by the above-mentioned. 6. The cellulose ester film according to claim 5, wherein the cellulose ester film has a retardation value Ro represented by the following formula of 20 to 200 nm and an Rt value of 70 to 400 nm. Method.
  Ro = (Nx−Ny) × d
  Rt = ((Nx + Ny) / 2−Nz) × d
(In the formula, Nx, Ny, and Nz represent the refractive indexes of the principal axes x, y, and z of the refractive index ellipsoid, respectively, and Nx and Ny represent the refractive index in the film in-plane direction, and Nz represents the thickness direction of the film. In addition, Nx ≧ Ny, and d represents the film thickness (nm).

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