JP2006028251A - Cellulose ester film, method for producing the same, polarizing plate and display using cellulose ester film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a cellulose ester film that has excellent preservability of cellulose ester film web, causes no foreign matter and excellent productivity, to provide a method for producing the same, a polarizing plate using the cellulose ester film and a liquid crystal display using the polarizing plate. <P>SOLUTION: The cellulose ester film comprising fine particles has relation of formula 1.0×10<SP>-6</SP>≤A/B≤1.0×10<SP>-2</SP>when the number of projections having height of twice or more average projection height of film surface is A and the total number of projections of film surface is B. The method for producing the cellulose ester film comprises adding a fine particle-containing liquid to a main dope of a cellulose ester so as to add the total amount of fine particle to be added to a film, then filtering the dope by a filter medium having 0.5-5 μm collected particle diameters for 10-25 sec/100 ml filtration time, casting the filtered main dope of the cellulose ester containing the fine particle-containing liquid and producing a film. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a cellulose ester film and a method for producing the same, and a polarizing plate and a display device using the cellulose ester film. 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 polarizing plate protective film used for a liquid crystal display device, a retardation, and the like. Various functional films such as films, viewing angle widening films, antireflection films used in plasma displays, cellulose ester films that can be used in various functional films used in organic EL displays and the like, and methods for producing the same, and The present invention relates to a polarizing plate and a display device using a cellulose ester film.

  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. A cellulose ester film is usually wound around a core to form a film original, 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 width of the original film is wide and the winding length is long, the storage stability in the original 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 film is widened to 1.4 m or more, the knurling effect provided on both sides is reduced, and the storage stability of the original film is likely to deteriorate.

  In particular, with the recent increase in image quality, the level of foreign matter removal required for cellulose ester films has become stricter, and small foreign matters that have not been considered a problem until now have become a problem.

In order to prevent such problems of the prior art, the following method for adding fine particles as a matting agent to a cellulose ester film has been proposed.
JP, 2001-114907, A The applicant of the present invention previously contains cellulose ester film containing fine particles (mat agent) in an amount of 0.04 to 0.3% by weight based on the cellulose ester. A film manufacturing method was proposed.

In the method of Patent Document 1, fine particles are dispersed in a solvent and added to a solution containing a resin to prepare a fine particle addition solution, which is added inline to the main dope.
Japanese Patent Application Laid-Open No. 7-11055 discloses that a dope prepared by dissolving cellulose triacetate in a solvent and fine particles having a methyl group on the surface are dispersed in a solvent or a mixed solution of a solvent and cellulose triacetate. A method for producing a cellulose triacetate film is disclosed in which a dispersion prepared in advance is mixed, the mixture is cast on a support, and then dried. Japanese Patent Laid-Open No. 2003-291161 discloses a technique for forming a film while sampling a part of a continuously formed film, detecting the fine particle concentration, and adjusting the fine particle concentration to a certain amount. A solution casting method is disclosed.

  However, in the above-described conventional method, there is a problem that when the amount of fine particles (matting agent) added in the cellulose ester film is increased, the generation of foreign matter in the cellulose ester film is increased.

  In addition, as in the conventional method described in Patent Document 1, when the fine particle additive solution is filtered with a fine filter in an attempt to reduce foreign matter, the fine particle aggregates adhere to each other with the filter and further aggregate, and the filter is clogged and the filtration pressure is reduced. It was a problem because it often increased rapidly. In addition, the method described in Patent Document 1 has a problem that fine particle aggregation occurs due to a shock that occurs when the fine particle additive solution is added in-line to the main dope, and this cannot be removed.

  In the method of Patent Document 2, there is a problem that the mixing ratio of the fine particles and the ultraviolet absorber cannot be easily changed, and when the resin or the ultraviolet absorber and the fine particles are mixed together and dispersed, the dispersed state of the fine particles There was also a problem that was bad. Furthermore, conventionally, there has been a problem that it is difficult to remove only agglomerates of several μm or more of fine particles because no investigation has been made on the filter medium filtering the main dope.

  In addition, in the method described in Patent Document 3, detection with a film after film formation, although in-line, causes a time lag of about several hours, so that there is a problem that variations in preparation cannot be completely suppressed. there were.

  The object of the present invention is to solve the above-mentioned problems of the prior art, and to provide a cellulose ester film excellent in storage stability of the cellulose ester film raw material, free of foreign matter, and excellent in productivity, and a method for producing the same. Furthermore, another object is to provide a polarizing plate using the cellulose ester film and a liquid crystal display device using the polarizing plate.

  In recent years, the present inventors have eagerly considered that the level of foreign substance removal required for cellulose ester films has become stricter with the increase in image quality, and that small foreign substances that have not been a problem until now have been regarded as problems. As a result of repeated research, 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 foreign matter that is the nucleus is an aggregate of fine particles. Therefore, it is difficult to satisfy both the characteristics of increasing the amount of fine particles added to improve the slipperiness of the film and removing only the fine particle aggregates of several μm or more to reduce foreign matter failure. And the present invention has been completed.

In order to achieve the above object, the cellulose ester film according to claim 1 of the present invention is a cellulose ester film containing fine particles, and has a height of at least twice the average protrusion height of the film surface. When the number of protrusions is A and the total number of protrusions on the film surface is B,
It is characterized by 1.0 × 10 ⁻⁶ ≦ A / B ≦ 1.0 × 10 ⁻² .

  The invention according to claim 2 of the present invention is the cellulose ester film according to claim 1, wherein the average protrusion height on the film surface is 2 to 20 nm.

Invention of Claim 3 of this invention is a cellulose-ester film of the said Claim 1 or 2, Comprising: The protrusion density of 2 nm or more of the film surface is 10,000-100,000 piece / mm < ² >. It is said.

  Invention of Claim 4 of this invention is a cellulose-ester film as described in any one of the said Claims 1-3, Comprising: Fine particle is silicon dioxide fine particle, It is characterized by the above-mentioned.

  Invention of Claim 5 of this invention is a manufacturing method of the cellulose-ester film as described in any one of the said Claims 1-4, Comprising: The additive liquid containing microparticles | fine-particles is made into the main dope of a cellulose ester. Then, the total amount of fine particles to be contained in the film is added, 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, and the cellulose containing the filtered fine particle additive solution A film is produced by casting a main dope solution of an ester.

  The invention according to claim 6 of the present invention is the method for producing a cellulose ester film according to claim 5, wherein the main dope solution containing the additive liquid containing fine particles is filtered with a filter medium, and then the fine particles are substantially removed. An additive liquid containing an ultraviolet absorber that is not included is added in-line to the main dope liquid.

  Invention of the manufacturing method of the cellulose-ester film of Claim 7 of this invention is a manufacturing method of the cellulose-ester film as described in any one of Claims 1-4, Comprising: Fine particle and a ultraviolet absorber are contained. The additive solution is added to the main dope of cellulose ester with the total amount of fine particles and UV absorber to be contained in the film, and thereafter the collected particle diameter is 0.5 to 5 μm and the drainage time is 10 to 25 sec / 100 ml. A film is produced by filtering through a filter medium and casting a main dope liquid of cellulose ester containing an additive liquid containing fine particles and an ultraviolet absorber.

  The invention according to claim 8 of the present invention is the method for producing a cellulose ester film according to claim 5 or 7, wherein the cellulose ester main dope liquid to which an additive liquid containing fine particles is added is filtered. It has the process of quantifying the fine particles in the main dope solution.

  The invention according to claim 9 of the present invention is the method for producing a cellulose ester film according to claim 8, characterized in that the method for quantifying fine particles uses high-sensitivity spectroscopy.

  A tenth aspect of the present invention is the method for producing a cellulose ester film according to the eighth or ninth aspect, wherein the fine particle quantification method measures in-line.

  The invention of the polarizing plate according to claim 11 of the present invention is characterized by having the cellulose ester film according to any one of claims 1 to 4.

  The invention of the display device according to claim 12 of the present invention is characterized by having the cellulose ester film according to any one of claims 1 to 4.

  A display device according to a thirteenth aspect of the present invention includes the polarizing plate according to the eleventh aspect.

As described above, the invention of the cellulose ester film according to claim 1 of the present invention is a cellulose ester film containing fine particles, and the number of protrusions having a height that is at least twice the average protrusion height of the film surface. Is A, and the total number of protrusions on the film surface is B,
Since 1.0 × 10 ⁻⁶ ≦ A / B ≦ 1.0 × 10 ⁻² , according to the invention of the cellulose ester film of the present invention, the slipperiness between the cellulose ester films is good, and the winding is long. Since deformation hardly occurs, the cellulose ester film raw material is excellent in preservability, and distortion or the like hardly occurs when forming a polarizing plate. In addition, the polarizing plate and the display device using the cellulose ester film have the effect that no foreign matter is generated, a spot failure on the liquid crystal screen hardly occurs as a foreign matter failure, and the productivity is excellent.

  The invention according to claim 2 of the present invention is the cellulose ester film according to claim 1, wherein the average protrusion height on the film surface is 2 to 20 nm. For example, since the surface of the cellulose ester film is not too smooth, the slipperiness between the films is good, and the winding deformation in a long length is difficult to occur. Is less likely to be distorted. Moreover, since the surface of the cellulose ester film is not rough, the haze of the film is small, and there is an effect that it can be effectively used as a film for a liquid crystal display.

The invention according to claim 3 of the present invention is the cellulose ester film according to claim 1 or 2, wherein the protrusion density of 2 nm or more on the film surface is 10,000 to 100,000 pieces / mm ^2. According to the invention of the cellulose ester film of the invention, the surface is not too smooth, the slipperiness between the films is good, and it is difficult to cause winding deformation in a long length, so the cellulose ester film original fabric is excellent in preservability, In addition, distortion and the like hardly occur when forming a polarizing plate. Moreover, since the surface of the cellulose ester film is not rough, the haze of the film is small, and there is an effect that it can be effectively used as a film for a liquid crystal display device.

  Invention of Claim 4 of this invention is a cellulose ester film as described in any one of the said Claims 1-3, Comprising: Since microparticles | fine-particles are silicon dioxide microparticles | fine-particles, the cellulose ester film of this invention According to the invention, since the fine particles of silicon dioxide are contained in the film, there is an effect that the turbidity of the cellulose ester film is lowered.

  Invention of Claim 5 of this invention is a manufacturing method of the cellulose-ester film as described in any one of the said Claims 1-4, Comprising: The additive liquid containing microparticles | fine-particles is made into the main dope of a cellulose ester. Then, the total amount of fine particles to be contained in the film is added, 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, and the cellulose containing the filtered fine particle additive solution Since the main dope solution of ester is cast to produce a film, according to the invention of the method for producing a cellulose ester film of the present invention, the use of the filter paper causes a foreign matter. Since only the agglomerates such as fine particles can be removed and the high viscosity main dope can be continuously filtered, there is no foreign matter failure, excellent raw material preservability, and high-speed film formation is possible. Productivity Rufirumu is an effect that improves.

  The invention according to claim 6 of the present invention is the method for producing a cellulose ester film according to claim 5, wherein the cellulose ester main dope liquid containing the fine particle addition liquid is filtered with a filter medium, and then the fine particles are substantially removed. Since the additive solution containing the ultraviolet absorber not included is added in-line to the main dope solution, according to the invention of the method for producing a cellulose ester film of the present invention, the adjustment of the ultraviolet absorptivity of the resulting cellulose ester film can be adjusted. There is an effect that it is easy.

  Invention of the manufacturing method of the cellulose-ester film of Claim 7 of this invention is a manufacturing method of the cellulose-ester film as described in any one of Claims 1-4, Comprising: Fine particle and a ultraviolet absorber are contained. The additive solution is added to the main dope of cellulose ester with the total amount of fine particles and UV absorber to be contained in the film, and thereafter the collected particle diameter is 0.5 to 5 μm and the drainage time is 10 to 25 sec / 100 ml. Filtering with a filter medium and casting a cellulose ester main dope liquid containing fine particles and an ultraviolet absorber to produce a film. According to the cellulose ester film production method of the present invention, the main dope In addition, since the total amount of the fine particles and the ultraviolet absorber is added together, the process can be simplified.

  The invention according to claim 8 of the present invention is the method for producing a cellulose ester film according to claim 5 or 7, wherein the cellulose ester main dope liquid to which an additive liquid containing fine particles is added is filtered. Since it has a step of quantifying the fine particles in the main dope solution, according to the invention of the method for producing a cellulose ester film of the present invention, fine particles can be quantified immediately after charging, so that variations in the process can be avoided. As a result, it is possible to suppress the fluctuation of the slipperiness of the film to a small extent and to sufficiently cope with the lengthening of the film.

  The invention according to claim 9 of the present invention is the method for producing a cellulose ester film according to claim 8, wherein the method for quantifying fine particles uses a high-sensitivity spectroscopic method. According to the invention of the method for producing an ester film, it is possible to suppress fluctuations in the content of fine particles in the film by using high-sensitivity spectral spectroscopy, and consequently to suppress fluctuations in the slipperiness of the film. Thus, it is possible to sufficiently cope with the lengthening of the film.

  The invention according to claim 10 of the present invention is the method for producing a cellulose ester film according to claim 8 or 9, wherein the fine particle quantification method measures in-line, so that the cellulose ester of the present invention According to the invention of the method for producing a film, since the content immediately after the addition of the fine particles can be known immediately, the variation in the content of the fine particles over time can be minimized.

  Since the invention of the polarizing plate according to claim 11 of the present invention has the cellulose ester film according to any one of claims 1 to 4, according to the invention of the polarizing plate of the present invention, There is no foreign matter generation, and there is an effect that a spot failure on the liquid crystal screen hardly occurs as a foreign matter failure.

  Since the invention of the display device according to claim 12 of the present invention has the cellulose ester film according to any one of claims 1 to 4, according to the invention of the display device of the present invention, There is no foreign matter generation, and there is an effect that a spot failure on the liquid crystal screen hardly occurs as a foreign matter failure.

  Since the invention of the display device according to the thirteenth aspect of the present invention has the polarizing plate according to the eleventh aspect of the present invention, according to the display device of the present invention, there is no generation of foreign matters, and the liquid crystal is regarded as a foreign matter failure. There is an effect that spot failure on the screen hardly occurs.

  The cellulose ester film according to the present invention has little variation in the height and distribution of protrusions due to the fine particles, and accordingly, the polarizing plate according to claim 11 using the cellulose ester film according to the present invention, and further comprising the polarizing plate. According to the display device of No. 13 and No. 13, even if the display device is a large screen, every part shows the same film surface property and transparency, so there is no unevenness in light transmittance and film deformation that occurs during film handling, which is good It is possible to obtain an excellent display quality.

  Next, embodiments of the present invention will be described, but the present invention is not limited thereto.

(Surface shape of cellulose ester film)
The cellulose ester film according to the present invention is a cellulose ester film containing fine particles, wherein the number of protrusions having a height of at least twice the average protrusion height on the film surface is A, and the total protrusion number on the film surface is B. When
It is characterized by 1.0 × 10 ⁻⁶ ≦ A / B ≦ 1.0 × 10 ⁻² .

Here, when A / B is less than 1.0 × 10 ⁻⁶ , the ratio of large protrusions is extremely small, the slipperiness between the cellulose ester films is deteriorated, and a long winding deformation is caused to form a polarizing plate. Distortion is likely to occur. When A / B exceeds 1.0 × 10 ⁻² , the ratio of coarse protrusions is increased, and a spot failure on the liquid crystal screen tends to occur as a foreign matter failure, which is not preferable.

  Means for adjusting A / B within the above range are, for example, sharpening the particle size distribution of fine particles added to the cellulose ester film by changing the dispersion conditions of the disperser, and filtering the fine particle additive solution added to the main dope. It can be adjusted by filtering the dope added with fine particles, using fine particles having a sharp primary particle size distribution, but is not limited thereto.

  Further, the cellulose ester film according to the present invention needs to have an average protrusion height of 2 nm to 20 nm on the film surface, but if the average protrusion height of the cellulose ester film surface is less than 2 nm, the surface is too smooth. Further, it is not preferable because the slipperiness between the films is deteriorated, a long winding deformation is caused, and distortion or the like is likely to occur when forming a polarizing plate. If the average protrusion height on the surface of the cellulose ester film exceeds 20 nm, the surface becomes rough, so that the haze of the film rises and cannot be used as a film for a liquid crystal display device.

  Means for adjusting the average protrusion height within the above range include, for example, selecting the particle size of the fine particles to be added, adjusting the drying speed at the time of drying on the metal support, stretching ratio during stretching, and stretching temperature. Although it can adjust by adjusting etc., it is not limited to these.

The cellulose ester film according to the present invention has a protrusion density of 2 nm or more on the film surface of 10,000 to 100,000 pieces / mm ² .

Here, when the projection density of 2 nm or more on the film surface is less than 10,000 pieces / mm ² , the surface is too smooth, the slipping property between the films deteriorates, a long winding deformation occurs, and a polarizing plate is formed. This is not preferable because distortion or the like is likely to occur. When the density of protrusions of 2 nm or more on the film surface exceeds 100,000 / mm ² , the surface becomes rough, so that the haze of the film increases, and it cannot be used as a film for a liquid crystal display device.

  As means for adjusting the protrusion density within the above range, for example, adjusting the addition amount of fine particles, adjusting the drying speed at the time of drying on a metal support, adjusting the stretching ratio at the time of transverse stretching, the stretching temperature, However, the present invention is not limited to these.

  The surface shape of the cellulose ester film can be measured by, for example, New-View 5010 manufactured by ZYGO. Measurement conditions and data analysis conditions are as follows.

<Measurement conditions>
Objective lens: 50x Intermediate lens zoom: 1x Camera resolution: 320x240 30Hz
Scan length: 5 μm (5 sec)
Minimum modulation tolerance (min mod): 7%
<Data analysis conditions>
Software used: advanced texture
Surface shape: remover
High FFT Filter: Auto
Low FFT Filter: Auto
Remove Spokes: off
Noise Filter Size: 0
Fill Data: off
Trim: 0
Reference Band: 4nm
(Filter material)
In the method for producing the cellulose ester film according to the present invention, the total amount of fine particles to be contained in the film is added to an additive solution containing fine particles as a main dope. The film is produced by filtering through a filter medium having a water time of 10 to 25 sec / 100 ml and casting the dope. 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 matter and continuously filter the main dope with high viscosity, so there is no foreign matter failure, excellent raw material storage stability, and high speed Film formation becomes possible and productivity is improved.

  Here, 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.

  Moreover, the method for producing a cellulose ester film according to the present invention comprises adding an additive solution containing fine particles and an ultraviolet absorber to the main dope of cellulose ester, and adding the total amount of fine particles and ultraviolet absorber to be contained in the film, Filtering with a filter medium having a collected particle size of 0.5 to 5 μm and a drainage time of 10 to 25 sec / 100 ml, casting a main dope solution of cellulose ester containing an additive solution containing fine particles and an ultraviolet absorber, It is characterized by producing a film.

  In the present invention, the collected particle diameter of the filter paper is 0.5 to 5 μm, 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, it is not preferable because fine particles that are not foreign matter are trapped and the filtration pressure rapidly increases, and if the collected particle size exceeds 5 μm, fine particles that cause foreign matter are collected. This is not preferable because it passes through the aggregates.

Here, the drainage time of the filter paper is measured in accordance with JIS P 3801. Using a Herzberg filtration rate tester, 20 ml of distilled water is added at a filtration surface of 10 cm ^2. This is the time for filtration with a pressure of 0.98 kPa.

  In the method of the present invention, the drainage time of the filter paper 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 will not be sufficient, and the filter paper will open at high pressure and aggregates that cause foreign matter 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 material (cotton linter, wood pulp, rayon, polyester fiber, etc.), the degree of beating of the fiber material with a beating machine, It can be arbitrarily adjusted by the filter paper manufacturing method such as addition of filler.

  In the present invention, even if one filter paper is used, the effect is exhibited. However, it is more preferable to use about two to seven filter papers because the filtration efficiency increases. 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 is preferable because the retained particle diameter is as large as 20 μm or more, and a filter paper such as soft cotton does not affect the filtration pressure, can remove large dust, and can prevent liquid leakage of the filter. In addition, a two-stage filtration in which the main dope solution that has been filtered once is filtered once more is preferable because it has a large effect of removing aggregates.

  In the present invention, the additive liquid containing fine particles is an additive liquid containing the following fine particles dispersed. It is not preferable to add fine powder directly to the main dope because the dispersibility becomes insufficient, the filter medium is clogged with fine particles and the filtration pressure is rapidly increased.

  In the present invention, after the additive liquid containing fine particles is added to the main dope of cellulose ester, 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. It is characterized by.

  The addition of the additive liquid containing fine particles may be anywhere before the filtration. For example, it may be added directly to the dissolution vessel of the cellulose ester main dope, or separately from the main dope dissolution vessel, a mixing vessel of the main dope and the fine particle addition solution may be provided and mixed. Or you may mix with a static mixer etc. in piping before filtration.

  Next, the method for producing a cellulose ester film of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic view of a solution casting film forming apparatus for carrying out the method for producing a cellulose ester film of the present invention.

  Referring to the figure, in the method of the present invention, in the dope preparation step, first, an additive solution containing fine particles is prepared in the fine particle charging pot 1. Subsequently, the addition liquid containing fine particles is sent from the fine particle charging vessel 1 to the subfilter 3 by the operation of the liquid feed pump 2, and after removing large agglomerates there, it is led to the main dope dissolving vessel 4, and the fine particle addition solution is converted into cellulose. The total amount of fine particles to be contained in the film is added to the ester main dope. Thereafter, the main dope liquid containing the fine particle addition liquid is filtered by the main filter 5 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 main dope liquid of cellulose ester containing the filtered fine particle addition liquid is introduced into the main dope liquid stock pot 6.

  On the other hand, an additive liquid containing an ultraviolet absorber substantially free of fine particles is prepared in the ultraviolet absorber dissolving pot 8. Then, by operating the liquid feed pump 2, the main dope liquid of cellulose ester containing the fine particle addition liquid is taken out from the main dope liquid stock pot 6, filtered through the filter 7, and then sent to the static mixer 11. On the way, after the ultraviolet absorbent additive liquid taken out from the ultraviolet absorbent dissolving pot 8 by the operation of the liquid feeding pump 10 is once filtered through the filter 10, the filtered ultraviolet absorbent additive liquid is filtered as described above. Add inline to the main dope solution. Next, the main dope liquid of cellulose ester containing the fine particle addition liquid and the ultraviolet absorbent addition liquid are mixed by the static mixer 11, and the mixed main dope liquid is introduced into the casting die 102.

  In addition, the following description of the casting process for manufacturing the cellulose-ester film by a solution casting film-forming method is mentioned later.

  Although not shown, a cellulose ester containing fine particles and an ultraviolet absorber is added to the main dope, and the total amount of fine particles and ultraviolet absorber to be contained in the film is added to the main dope. In some cases, the main dope solution is 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, and the dope is cast to produce a film. According to such a method for producing a cellulose ester film of the present invention, since the whole amount of the fine particles and the ultraviolet absorber is added together to the main dope, the process can be simplified.

  In many cases, the main dope of cellulose ester may contain about 10 to 50% by weight of 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. Here, the return material is a finely pulverized cellulose ester film, which is generated when the cellulose ester film is formed. The original fabric is used.

  In the present invention, from the viewpoint of easy control, a method of directly adding to the main dope dissolving pot capable of batch management and a method of mixing by providing a mixing pot of the main dope and the fine particle additive solution are more preferable. The method of adding the main dope directly to the dissolution vessel of the main dope is most preferable because it takes a sufficient time to mix the main dope and the fine particle addition solution and is excellent in productivity.

  In the present invention, the additive solution containing fine particles preferably contains 0.5 to 10% by weight, more preferably 3 to 7% by weight, and more preferably 5 to 7% by weight. Most preferably.

  The fine particle addition liquid may contain a cellulose ester in addition to the fine particles, or may be a diluted fine particle dispersion. When the cellulose ester is contained in the fine particle addition liquid, the concentration of the cellulose ester is preferably 2 to 5% by weight, and more preferably 3 to 4% by weight. The same cellulose ester as the main dope can be used. Further, the recycled material may be used in the same manner as the main dope, but preferably a cellulose ester that simultaneously satisfies the following formulas (I) and (II) is excellent in dispersibility, and the aggregation of fine particles is suppressed, which 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.

2.6 ≦ X + Y ≦ 2.9 (I)
0 ≦ X ≦ 2.5 (II)
In the above formula, X is the substitution degree of the acetyl group, and Y is the substitution degree of the propionyl group and / or the 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.

  The cellulose ester contained in the fine particle addition liquid is cellulose acetate propionate as described in JP-A Nos. 10-45804, 8-231761, U.S. Pat. No. 2,319,052, and the like. Further, mixed fatty acid esters such as cellulose acetate butyrate can be used. Among these, a cellulose lower fatty acid ester that is particularly preferably used is cellulose acetate propionate. These cellulose esters can also be mixed and used.

  In the method of the present invention, the fine particles used are, as examples of inorganic compounds, silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated silicic acid Mention may be made of calcium, aluminum silicate, magnesium silicate and calcium phosphate. Fine particles containing silicon are preferable in terms 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 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 0.06 to 0.5% by weight, more preferably 0.08 to 0.4% by weight, most preferably 0.1 to 0.3% by weight, based on the content in the film. . Since the content of fine particles in the film greatly affects the slipperiness of the film, it is necessary to minimize the variation.

  In the present invention, before filtering the main dope liquid of cellulose ester to which an additive liquid containing fine particles is added in order to reduce the fluctuation, a step of quantifying the fine particles in the main dope liquid and a method for quantifying the fine particles However, by using a high-sensitivity spectroscopic method, fluctuations in the content of fine particles in the film can be suppressed.

  Silicon dioxide fine particles are commercially available, for example, under the trade names Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600 (above, Nippon Aerosil Co., Ltd.). it can. Zirconium oxide fine particles are commercially available, for example, under the trade names 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. For example, Tospearl 103, 105, 108, 120, 145, 3120 and 240 (manufactured by Toshiba Silicone Co., Ltd.) 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.

  In the present invention, the method for preparing the additive liquid containing fine particles includes the following methods, but is not limited thereto.

(Production method A)
After stirring and mixing the solvent and the fine particles, the dispersion is performed with a disperser. This is a fine particle dispersion. The fine particle dispersion is diluted with a solvent, and then a small amount of cellulose ester or main dope is added and sufficiently stirred.

(Production method B)
After stirring and mixing the solvent and the fine particles, the 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.

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

  When the fine particles are mixed with a solvent and dispersed, the concentration of the fine particles is preferably 5 to 30% by weight, more preferably 8 to 25% by weight, and most preferably 10 to 15% by weight. 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.

  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 dispersion apparatus include an ultra-high pressure homogenizer (trade name: Microfluidizer) manufactured by Microfluidics Corporation, a nanomizer manufactured by Nanomizer, or Ultra Turrax. In addition, a Manton Gorin type high-pressure dispersion apparatus such as Izumi Examples include food machinery homogenizers, Sanwa Machinery Co., Ltd. UHN-01, and the like.

  In the present invention, the ultraviolet absorber is intended to improve durability by absorbing ultraviolet light having a wavelength of 400 nm or less. Particularly, the transmittance at a wavelength of 380 nm is preferably 10% or less, more preferably 5 % Or less, more preferably 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.

  In the present invention, preferably used UV absorbers are benzotriazole UV absorbers and benzophenone UV absorbers that are highly transparent and excellent in preventing the deterioration of polarizing plates and liquid crystal elements, and more unnecessary coloring. Less benzotriazole ultraviolet 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 ultraviolet absorbers that are liquid at a temperature of 20 ° C., and can be used more preferably.

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

  In the present invention, the amount of the UV absorber used is not uniform depending on the type of UV absorber, use conditions, etc., but when the dry film thickness of the cellulose ester film is 30 to 200 μm, it is 0 with respect to the cellulose ester film. 0.5 to 4.0% by weight is preferable, and 0.6 to 2.0% by weight is more preferable.

  In the present invention, the ultraviolet absorber is added by a method of adding it together with the fine particles to the cellulose ester main dope, or a method of adding them in-line to the main dope of the cellulose ester separately from the fine particles. The method of adding the fine particles and the ultraviolet absorber together to the main dope is preferable from the viewpoint of simplifying the process. The in-line addition method is preferable because it is easy to adjust the ultraviolet absorption rate of the film.

  In the present invention, the additive solution containing an ultraviolet absorber is a solution containing the ultraviolet absorber shown below and added in-line to the main dope of the cellulose ester, and the ultraviolet absorber is contained in an amount of 1 to 30% by weight. It is preferably contained, more preferably 5 to 20% by weight, and most preferably 10 to 15% by weight. 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, 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 is more preferable, and most preferably no fine particles are contained. If the ultraviolet absorbent additive solution added in-line contains fine particles, it is aggregated to cause foreign substances when mixed with the main dope of the cellulose ester, so it is preferable that the amount is smaller.

In the present invention, for example, a blue dye may be used as an additive in order to adjust the color of the film. 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 the blue dye and the fluorescent brightening agent in the additive solution of the ultraviolet absorber so that the color of the film can be easily adjusted.

  In this invention, the main dope of a cellulose ester is a dope liquid at the time of manufacturing the cellulose ester film of this invention, and it calls a main dope in order to distinguish with an 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.

  The cellulose ester film according to the present invention can contain a compound comprising a polyhydric alcohol ester of an aliphatic polyhydric alcohol and one or more monocarboxylic acids. The content of the polyhydric alcohol ester with respect to the cellulose ester is 4.5 to 12.5% by weight, preferably 6 to 12% by weight, and more preferably 7 to 11% by weight.

  In the cellulose ester film of the present invention, the monocarboxylic acid is preferably a compound having an aromatic ring or a cycloalkyl ring in the molecule.

  In the cellulose ester film of the present invention, the aliphatic polyhydric alcohol is preferably 2-20.

  Thus, the use of a polyhydric alcohol ester greatly contributes to the ability to reduce the amount of conventional plasticizers.

  Next, the aliphatic polyhydric alcohol ester 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 represented by the following general formula (1).

R _1- (OH) n (1)
In the formula, R ₁ 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.

  Here, as the n-valent aliphatic organic group, an alkylene group (for example, methylene group, ethylene group, trimethylene group, tetramethylene group, etc.), an alkenylene group (for example, ethenylene group, etc.), an alkynylene group (for example, ethynylene group, etc.), Examples include cycloalkylene groups (for example, 1,4-cyclohexanediyl group) and alkanetriyl groups (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)
In the present invention, the monocarboxylic acid in the polyhydric alcohol ester is not particularly limited, and known aliphatic monocarboxylic acid, alicyclic monocarboxylic acid, aromatic monocarboxylic acid and the like 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 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 preferred alicyclic monocarboxylic acids include cyclopentane carboxylic acid, cyclohexane carboxylic acid, cyclooctane carboxylic acid, or 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)
The molecular weight of the polyhydric alcohol ester used in the present invention is not particularly limited, but is preferably 300 to 1500, and more preferably 350 to 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.

  In the present invention, 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 the polyhydric alcohol ester used in the present invention are shown below.

  Among the above polyhydric alcohol esters, trimethylolpropane tribenzoate (TMPTB), trimethylolpropane triacetate, trimethylolpropane tripropionate, dipropylene glycol dibenzoate, tripropylene glycol dibenzoate, 1,3-dibutylene glycol dibenzoate Tetraethylene glycol dibenzoate, mixed ester of trimethylolpropane with acetic acid and benzoic acid, ester of trimethylolpropane with cyclohexanecarboxylic acid, mixed ester of trimethylolpropane with acetic acid and cyclohexanecarboxylic acid, 3-methylpentane- Esters of 1,3,5-triol and cyclohexanecarboxylic acid, S of 3-methylpentane-1,3,5-triol and benzoic acid Le, esters of xylitol and benzoic acid, esters of xylitol and cyclohexanecarboxylic acid.

  In addition, the usage-amount of a polyhydric alcohol ester is preferable 4.5-12.5 weight% with respect to a cellulose ester, 6-12 weight% is further more preferable, Most preferably, it is 7-11 weight%.

  The cellulose ester film according to the present invention contains additives such as a plasticizer and an ultraviolet absorber in addition to the cellulose ester, the solvent, and the compound comprising the polyhydric alcohol ester.

  Additives such as compounds composed of polyhydric alcohol esters, plasticizers, UV absorbers, etc. can be mixed with a solvent in advance and dissolved or dispersed, and then added to the solvent before dissolving the cellulose ester, or the dope after dissolving the cellulose ester It may be thrown into.

  Although it does not specifically limit as a plasticizer which can be used by this invention, In a phosphate ester type | system | group, a triphenyl phosphate (TPP), a biphenyl diphenyl phosphate (BDP), a tricresyl phosphate, a cresyl diphenyl phosphate, an octyl diphenyl phosphate, For phthalate esters such as trioctyl phosphate and tributyl phosphate, diethyl phthalate, dimethoxyethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, butyl phthalyl butyl glycolate, ethyl phthalyl ethyl glycolate (EPEG), methyl phthalyl ethyl glycolate, butyl phthalyl butyl glycolate and the like can be used.

  The above plasticizers may be used in combination of two or more as required. By containing these plasticizers, a film having excellent dimensional stability and water resistance can be obtained, which is particularly preferable.

  In the present invention, in order to make the water absorption rate and the moisture content within a specific range, the preferable addition amount of the plasticizer is 12% by weight or less with respect to the cellulose ester. When two or more kinds of plasticizers are used in combination, the total amount of these plasticizers may be 12% by weight or less.

  Moreover, the said polyhydric alcohol ester has a plasticizer function, Such polyhydric alcohol ester and the conventional plasticizer can be used simultaneously. In this case, the polyhydric alcohol ester can be used in the range of 4.5 to 12.5% by weight with respect to the cellulose ester as described above, but the total amount of the polyhydric alcohol ester and the plasticizer is It is preferable that it is 12.5 weight% or less in the weight% with respect to a cellulose ester. In this case, the amount of the plasticizer used is preferably 8.0% by weight or less based on the cellulose ester. Especially, it is preferable that the usage-amount of polyhydric alcohol ester is 7 weight% or more with respect to a cellulose ester, Furthermore, the usage-amount of a plasticizer shall be 5.5 weight% or less with respect to a cellulose ester. Is preferred. The reason is that the use of the conventional plasticizer can be reduced by using the polyhydric alcohol ester.

  Below, preferable embodiment is described about the manufacturing method of the cellulose-ester film of this invention.

  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. Below, each process is demonstrated.

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

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

  If the solid content concentration in the dope of the cellulose ester 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. . The viscosity of the main dope of the cellulose ester is preferably adjusted to a range of 10 to 50 Pa · s.

  In the present invention, the dissolution is carried out at normal pressure, the method carried out below the boiling point of the preferred organic solvent (that is, the good solvent), the method carried out under pressure above the boiling point of the above-mentioned good solvent, and the method carried out by the cooling dissolution method. There are various dissolution methods such as a method performed at high pressure. 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. 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-10-45804, 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 Japanese Patent No. -231761 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 is increased, 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 the cellulose ester film according to the present invention is used as a polarizing plate protective film, cellulose acetate is more preferable, and the molecular weight distribution Mw / Mn obtained by dividing the weight average molecular weight Mw by the number average molecular weight Mn is 1.8 to 3.0. Is more preferable.

  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 when the molecular weight distribution Mw / Mn of the cellulose acetate is less than 1.8, the film surface or 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.

  The molecular weight of cellulose acetate is 90000-180000 in terms of number average molecular weight (Mn). Those having 120,000 to 180,000 are more preferred, and 150,000 to 180,000 are particularly preferred. 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
(Showa Denko Co., Ltd., 3 connected and used)
Column temperature: 25 ° C
Sample concentration: 0.1% by weight
Detector: RI Model 504 (GL Science Co., Ltd.)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0 ml / min
Calibration curve: Standard polystyrene STK standard polystyrene
(Made by Tosoh Corporation) Mw = 100000 to 500
A calibration curve with 13 samples was used.

            In addition, it is preferable to obtain 13 samples at substantially equal intervals.

  When the cellulose ester film according to the present invention is used as a retardation film, cellulose acetate propionate is more preferable.

Here, 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 used in the present invention, 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 in the cellulose ester used in the present invention 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. Ligand and coordination compounds, that is, complexes are easily formed, and scum (insoluble starch, turbidity) derived from many insoluble calcium is formed.

  The calcium (Ca) component in the cellulose ester used in the present invention is 60 ppm or less, preferably 0 to 30 ppm. The magnesium (Mg) component in the cellulose ester used in the present invention is preferably from 0 to 70 ppm, and particularly preferably from 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 optical emission spectrometry).

  In this invention, you may use the return material of a cellulose-ester film instead of a cellulose ester. The use ratio of the recycled material is preferably 0 to 70% by weight, more preferably 10 to 50% by weight, and most preferably 20 to 40% by weight based on 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.

  In the present invention, the solvent used for producing the main dope is not particularly limited as long as it is a solvent capable of dissolving the cellulose ester, but it may be mixed with other solvents even if the solvent cannot be dissolved alone. As long as it can be dissolved, it can be used. In general, a mixed solvent composed of a good solvent, methylene chloride and a poor solvent of cellulose ester, is used, and the mixed solvent preferably contains 4 to 30% by weight of the poor solvent.

  In the present invention, 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-trifluoroethanol, 2,2,3,3-tetrafluoro-1-propanol, 1,3-difluoro-2-propanol, 1,1,1,3,3,3-hexafluoro-2- Examples include methyl-2-propanol, 1,1,1,3,3,3-hexafluoro-2-propanol, 2,2,3,3,3-pentafluoro-1-propanol, and nitroethane. Organic halogen compounds such as methylene chloride, dioxolane derivatives, methyl acetate, ethyl acetate, acetone and the like are preferable. The solvent (i.e., good solvent), and 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.

  In the method of the present invention, after dissolution, the cellulose ester solution (dope) is preferably filtered through a filter medium, defoamed, and sent to the next step with a pump. An inhibitor or the like is preferably added.

  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.

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

<Casting process>
A dope is fed to a pressure type casting die through a pressure type fixed gear pump, and an endless metal belt for infinite transfer or a rotating metal drum support for casting (hereinafter, simply referred to as a support) at the casting position. It is a step of casting a dope from a pressure die casting on top. 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. A pressure type casting die that can be prepared and can easily make the film thickness uniform is preferable. The pressure type casting die includes a coat hanger die and a T die, and any of them is preferably used.

  In the present invention, two or more pressure-type casting dies may be provided on the casting support in order to increase the film forming speed, and the dope amount may be divided and stacked. Or the inside of die | dye can be divided | segmented by a slit, and several dope liquids from which a composition differs can be cast simultaneously (it is also called co-casting), and the cellulose-ester film of a laminated structure can also be obtained.

  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 dope is cast on a casting support, the formed dope film (hereinafter referred to as web) is heated on the casting support, and the solvent is evaporated. For evaporating 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 liquid, a method of transferring heat from the front and back by radiant heat, and the like. However, drying efficiency is preferable. 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 that the cellulose ester film of the present invention peels 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. If the drying time is longer than 90 seconds, it 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 weight, more preferably 40 to 100% by weight.

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

Residual solvent amount = {(weight before heat treatment of web−weight after heat treatment of web))
/ (Weight after heat treatment of the web)} × 100%
Note that the heat treatment for measuring the amount of residual solvent means performing heat treatment at 115 ° C. for 1 hour.

  In order to adjust the residual solvent amount at the time of peeling as described above, the surface temperature of the casting support after casting is controlled, and the casting of the organic solvent from the web can be performed efficiently. The temperature at the peeling position on the support is preferably set 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.

  Note that the heat transfer method using radiant heat, hot air, etc. is difficult to control the support temperature, and is not a preferable method. However, in the belt (support) machine, the temperature control at the place where the belt to be transferred has come to the lower side. The belt temperature can be adjusted with gentle wind.

  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 amount of residual solvent 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, it is possible to accelerate the peeling and increase the film forming speed.

  When the cellulose ester film according to the present invention is used as a polarizing plate protective film, when the residual solvent amount is 40% by weight or more after film formation, the film starts to be stretched in the MD direction, and the residual solvent amount. When is less than 40% by weight, stretching in the TD direction is preferred. Here, when the residual solvent amount is 40% by weight or more, the film is stretched in the MD direction, and when the residual solvent amount is less than 40% by weight, the stretched film is stretched in the TD direction. Is stretched in both the MD direction and the TD direction in a high residual solvent state, and even if the orientation of the cellulose ester is enhanced by stretching in the MD direction, the orientation of the cellulose ester is disturbed by the stretching in the TD direction. This is because the improvement effect is reduced.

  The cellulose ester film of the present invention can maintain an improvement in elastic modulus without disturbing the orientation of the cellulose ester. When the amount of residual solvent is 60 to 120% by weight, it is more preferable to start stretching the film in the MD direction, and most preferably 90 to 110% by weight. When the residual solvent amount is less than 1 to 30% by weight, it is more preferable to stretch in the TD direction, and most preferably 5 to 20% by weight.

  When the cellulose ester film according to the present invention is 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 1.05 to 1.15 times. Further preferred. 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 the draw ratio in the MD direction × the draw ratio in the TD direction. Here, if the draw ratio in the MD direction is less than 1.05 times, the effect of improving the elastic modulus is small, which is not preferable. When the draw ratio in the TD direction is less than 1.05 times, the effect of reducing the in-plane retardation value Ro is small, which is 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 using the cellulose-ester film by this invention as a polarizing plate protective film, it is preferable that the roll span of the extending | stretching zone which extends | stretches a cellulose-ester film in MD direction is 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 a state of a high residual solvent amount, slippage in the MD direction is likely to occur, and slippage is prevented when the roll span is 1.0 m or less. can do. 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.

  In the above, the draw ratio in the MD direction 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 or a part of the process as shown in Japanese Patent Application Laid-Open No. 62-46625 is performed while the width ends of the web are held with clips or pins in the width direction. A drying method (referred to as a tenter method), among them, a tenter method using clips and a pin tenter method using pins 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, the foreign matters are likely to protrude on the surface, and foreign matter failures occur more than usual. Therefore, this invention exhibits an effect especially in the cellulose-ester film which has the process to extend | stretch.

  The in-plane retardation value Ro of the cellulose ester film according to the present invention 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 the refractive indexes Nx, Ny, and Nz.

  The in-plane retardation value Ro of the cellulose ester film according to the present invention 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 film thickness direction. Refractive index, Nx ≧ Ny, and d represents film thickness (nm).
In the cellulose ester film according to the present invention, the angle θ (radian) formed between the slow axis direction and the film forming direction and the in-plane retardation value Ro have the following relationship, and in particular, an optical film such as a protective film for a polarizing plate. Are preferably used.

P ≦ 1-sin2 (2θ) sin2 (πRo / λ)
Here, 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 scale 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>
In the method of the present invention, the width is held using a drying device that alternately conveys the web through rolls arranged in a staggered manner and / or a tenter device that conveys while holding both ends of the web with clips or pins. The step of drying the web. Maintaining the conveyance tension in the drying step as low as possible is preferable because the retardation value Ro in the in-plane direction 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 weight 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. Drying too rapidly tends to impair the flatness of the finished film. Drying at a high temperature is preferably carried out from about 8% by weight or less of residual solvent. Throughout the whole, the drying temperature is approximately 40 to 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 viewpoint, for example, a method of drying all or part of the drying process as shown in JP-A-62-46625 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.

  At this time, the stretching ratio in the width direction of the film is preferably 0% to 100%, more preferably 5% to 20%, and most preferably 8% to 15% when used as a polarizing plate protective film. When used as a film, 10% to 40% is more preferable, and 20% to 30% is most preferable. R0 can be controlled by the draw ratio, and the 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 web is dried with a tenter, the residual solvent amount of the web is preferably 20 to 100% by weight at the start of the tenter, and is dried while applying the tenter until the residual solvent amount of the web is 10% by weight or less. Preferably it is carried out, more preferably 5% by weight or less.

  The drying temperature when the web is dried with a tenter is preferably 30 to 150 ° C, more preferably 50 to 120 ° C, and most preferably 70 to 100 ° C. 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.

  Even when the drying temperature is high, the use of an ultraviolet absorber that is difficult to evaporate exhibits a remarkable effect under production conditions with a high tenter drying temperature and a high draw ratio.

  In the film drying step, the film peeled from the support is further dried, and the residual solvent amount is preferably 0.5% by weight or less, more preferably 0.1% by weight or less, and still more preferably Is 0 to 0.01% by weight 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 it may be performed in an inert gas atmosphere such as nitrogen gas, carbon dioxide gas, argon or the like. 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>
It is a step of winding up as a cellulose ester film after the residual solvent amount in the web is 2% by weight or less, and a film with good dimensional stability can be obtained by making the residual solvent amount 0.4% by weight or less. it can.

  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 weight change at 80 ° C. and 90% RH.

  In the cellulose ester film of the present invention, it is more preferable that the rate of change in weight before and after the heat treatment at 80 ° C. and 90% RH for 48 hours is within ± 2%, whereby a thin film having improved moisture permeability. Nevertheless, 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 a high-temperature and high-humidity treatment (condition: left at 48 ° C. and 90% RH for 48 hours) in an electric thermostat. Again, the sample was 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 was 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 a distance between marks before processing, and L2 represents a distance between marks after processing.

  That is, the desired dimensional change rate can be measured by attaching the mark positions 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 further within ± 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 direction and the TD direction, and 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).

  FIG. 1 is a schematic view showing a preferred example of a solution casting film forming apparatus for carrying out the method for producing a cellulose ester film of the present invention. After casting a cellulose ester dope, a peeled web is subjected to a tenter conveying / drying step. It is a schematic diagram in the case of drying and then drying in a roll conveyance / drying process.

  In the method of the present invention, the process including the tenter transport / drying process and the roll transport / drying process is a process of drying / stretching the film somewhere in the process of drying and winding the film peeled off from the support. This refers to a process having a tenter conveyance / drying process and a roll conveyance / drying process for adjusting the rate. The tenter transport / drying process is a process of performing drying simultaneously while transporting with a tenter transport apparatus and adjusting the drying expansion / contraction rate, and the roll transport / drying process is simultaneously drying while transporting with a roll transport apparatus, The process of adjusting the drying expansion / contraction rate.

  In FIG. 1, reference numeral 101 denotes a support that travels endlessly. As the support, for example, a stainless steel mirror strip metal is used. 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 web (film) solidified by the dope cast on the support 101 is peeled off, and 104 denotes the peeled web (film). Reference numeral 105 denotes a tenter conveyance / drying step. Reference numeral 106 denotes a roll conveyance / drying process. Reference numeral 107 denotes a wound roll film.

  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 according to 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. The cellulose ester film of the present invention is preferably used in a protective film for a polarizing plate that 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 immersed and stretched in an iodine solution and bonded to both sides of a polarizing film using a completely saponified polyvinyl alcohol aqueous solution. .

  Here, 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 according to 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, a lower layer Various functional layers such as a pulling layer can be provided. These functional layers can be provided by a method such as coating or vapor deposition, sputtering, plasma CVD, or 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 made of the cellulose ester film according to the present invention, it is possible to provide a polarizing plate excellent in durability, dimensional stability, and optical isotropy as well as thinning.

  Furthermore, the liquid crystal display device using the polarizing plate or retardation film according to the present invention can maintain stable display performance over a long period of time.

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

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited thereto.

Examples 1-10 and Comparative Examples 1-4
(Preparation of fine particle dispersion A)
Aerosil 972V (fine particles of silicon dioxide, manufactured by Nippon Aerosil Co., Ltd.)
(Average diameter of primary particles 16 nm, apparent specific gravity 90 g / liter) 12 parts by weight Ethanol 88 parts by weight The above materials were 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 weight of methylene chloride was added to the silicon dioxide dispersion with stirring, and the mixture was stirred and mixed with a dissolver for 30 minutes to prepare a fine particle dispersion diluent A.

(Preparation of fine particle dispersion B)
Aerosil 200V (fine particles of silicon dioxide, manufactured by Nippon Aerosil Co., Ltd.)
(Average diameter of primary particles 12 nm, apparent specific gravity 100 g / liter) 12 parts by weight Ethanol 88 parts by weight The above materials were 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 weight of methylene chloride was added to the silicon dioxide dispersion with stirring, and the mixture was stirred and mixed with a dissolver for 30 minutes to prepare a fine particle dispersion diluent B.

(Preparation of additive liquid A)
100 parts by weight of methylene chloride was put into a sealed container, and 36 parts by weight of the fine particle dispersion diluted solution was added while stirring, followed by stirring and mixing with a dissolver for 30 minutes. Thereafter, 6 parts by weight 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. Filtration was performed using a polypropylene wind cartridge filter TCW-PPS-1N to prepare a fine particle additive solution A.

(Preparation of additive liquid B)
Tinuvin 109 (ultraviolet absorber) 11 parts by weight Tinuvin 171 (ultraviolet absorber) 5 parts by weight Methylene chloride 88 parts by weight Ethanol 12 parts by weight The above materials are put into a sealed container, heated, stirred and completely dissolved. And filtered.

  To this, 4 parts by weight of a silicon dioxide dispersion diluted solution was added with stirring, followed by further stirring 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 weight 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 a fine particle additive solution B.

(Preparation of additive liquid C)
Tinuvin 109 (ultraviolet absorber) 11 parts by weight Tinuvin 171 (ultraviolet absorber) 5 parts by weight Methylene chloride 88 parts by weight Ethanol 12 parts by weight The above materials are put into a sealed container, heated, stirred and completely dissolved. , 6 parts by weight of cellulose acetate propionate (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 an SL filter cartridge manufactured by Loki Techno Co., Ltd. Filtration was performed with SL-100 to prepare inline additive solution C.

(Preparation of main dope solution A)
100 parts by weight of cellulose triacetate synthesized from linter cotton (Mn = 148000, Mw = 310000, Mw / Mn = 2.1)
Polyhydric alcohol ester exemplified compound No. 16 (supra) 5 parts by weight Ethylphthalyl ethyl glycolate 5.5 parts by weight Methylene chloride 440 parts by weight Ethanol 40 parts by weight The above materials are put into a sealed container and stirred, and the fine particle additive solution is added according to the process flow of FIG. Alternatively, an additive solution is added and dissolved while heating and stirring. Thereafter, two guard filters having a collected particle diameter of 30 μm and a drainage time of less than 1 sec / 100 ml are used in the press filter device, and the collected particles are placed inside the guard filter. A main dope solution A was prepared by using three filter papers each having a diameter of 2 μm, a thickness of 1.2 mm, and a filtering time of 25 sec / 100 ml, followed by filtration. The filtration area of the press filter was 50 m ² .

  When fine particles are added to the main dope after dissolution, measure the content using a fine particle quantitative monitoring system. When the amount was outside the specified amount, the amount of fine particles added to the main dope was adjusted.

(Preparation of main dope solution B)
Cellulose acetate propionate 100 parts by weight (acetyl group substitution degree 1.9, propionyl group substitution degree 0.8, 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 materials are put into a closed container and stirred, and the fine particle addition solution or addition is performed by the process flow of FIG. Main dope liquid B was prepared in the same manner as main dope liquid A, except that the liquid was added and dissolved while heating and stirring.

(Film formation of cellulose ester film sample)
In Examples 1 to 4 and Examples 9 and 10, fine particle dispersions A and B and additive liquids A and B were added to the main dope A of cellulose triacetate in combinations shown in Table 1. In the filter 7 in the solution casting film forming line shown in FIG. 1, the main dope liquid A, the fine particle dispersions A and B, and any of the additive liquids A and B are used with Finemet NF manufactured by Nippon Seisen Co., Ltd. The mixture was filtered.

  In Examples 1 to 3 and Examples 9 and 10, the inline additive solution C was added, and the additive solution C was filtered with Finemet NF manufactured by Nippon Seisen Co., Ltd. with the filter 10 in the inline additive solution line. The addition amount and the in-line addition flow rate were adjusted so that the fine particle dispersions A and B and the additive solution A were added to the main dope so that the fine particle content in the film would be the value shown in Table 1. Moreover, in in-line addition, it fully mixed with the in-line mixer 11 (Toray's static type in-tube mixer Hi-Mixer, SWJ). In Example 4, additive liquid B was added to main dope A of cellulose triacetate, and inline additive liquid C was not added.

  The main dope solution of each cellulose triacetate thus obtained was introduced into the casting die 102, and then uniformly cast on the stainless steel band support 101 at a temperature of 22 ° C. and a width of 1800 mm using a belt casting apparatus. The solvent was evaporated on the stainless steel band support 101 until the amount of residual solvent reached 100% by weight, and the film was peeled off from the stainless steel band support 101 with a peeling tension of 162 N / m.

  The peeled cellulose triacetate web (film) 104 was evaporated at 35 ° C., slit to 1650 mm width, and then stretched 1.07 times in the width direction of the web with a tenter 105 while drying at 135 ° C. And dried. At this time, when the tenter 105 started stretching, the residual solvent amount was 10% by weight. Thereafter, drying is completed while the drying zone 106 at 110 ° C. and 120 ° C. is conveyed by a number of rolls, slit to a width of 1430 mm, a knurling process with a width of 10 mm and a height of 5 μm is applied to both ends of the film, and an initial tension of 220 N / m. The sample was wound around a 6-inch inner diameter core with a final tension of 110 N / m to obtain a roll-shaped cellulose ester film sample 107.

  The MD draw ratio calculated from the rotational speed of the stainless steel band support 101 and the operating speed of the tenter 105 was 1.08. The residual solvent amount of the cellulose ester film sample was 0.004% by weight, the film thickness was 40 μm, and the number of turns was 5200 m.

  In Examples 5 to 8, the fine particle dispersions A and B and the additive liquids A and B were added to the main dope B of cellulose acetate propionate. The main dope solution B was filtered with Finemet NF manufactured by Nippon Seisen Co., Ltd. in the main filter 5 in the solution casting film forming line shown in FIG. In Examples 1 to 3, the inline additive solution C was added, and the additive solution C was filtered with a fine met NF manufactured by Nippon Seisen Co., Ltd. with the filter 10 in the inline additive solution line. The addition amount and the in-line addition flow rate were adjusted so that the fine particle dispersions A and B and the additive solution A were added to the main dope so that the fine particle content in the film would be the value shown in Table 1. Moreover, in in-line addition, it fully mixed with the in-line mixer 11 (Toray's static type in-tube mixer Hi-Mixer, SWJ). In Example 8, additive liquid B was added to main dope B of cellulose acetate propionate, and inline additive liquid C was not added.

  The main dope solution of each cellulose acetate propionate thus obtained was introduced into the casting die 102, and then uniformly cast on the stainless steel band support 101 at a temperature of 22 ° C. and a width of 1800 mm using a belt casting apparatus. did. The solvent was evaporated on the stainless steel band support 101 until the amount of residual solvent reached 100% by weight, and the film was peeled off from the stainless steel band support 101 with a peeling tension of 162 N / m.

  The peeled cellulose acetate propionate web (film) 104 was evaporated at 35 ° C., slit to 1650 mm width, and then stretched 1.5 times in the width direction of the web with a tenter 105 while being 135 ° C. It dried at the drying temperature of. At this time, when the tenter 105 started stretching, the residual solvent amount was 10% by weight. Thereafter, drying is completed while the drying zone 106 at 110 ° C. and 120 ° C. is conveyed by a number of rolls, slit to a width of 1430 mm, a knurling process with a width of 10 mm and a height of 10 μm is applied to both ends of the film, and an initial tension of 220 N / m. The sample was wound around a 6-inch inner diameter core with a final tension of 110 N / m to obtain a roll-shaped cellulose ester film sample 107.

  The MD draw ratio calculated from the rotational speed of the stainless steel band support 101 and the operating speed of the tenter 105 was 0.98. The residual solvent amount of the cellulose ester film sample was 0.1% by weight, the film thickness was 80 μm, and the number of turns was 2600 m.

Comparative Examples 1-4
For comparison, in Comparative Example 1, the additive liquid B was added inline to the main dope A of cellulose triacetate without adding the fine particle dispersion. In Comparative Example 2, the fine particle dispersion B was added to the main dope B of cellulose acetate propionate, and the additive liquid C was added in-line. In Comparative Example 3, the additive liquid B was added in-line to the main dope B of cellulose acetate propionate without adding the fine particle dispersion. In Comparative Example 4, the fine particle dispersion A was added to the main dope A of cellulose triacetate, and the additive B was added in-line. In each comparative example, the addition amount and the in-line addition flow rate were adjusted so that the fine particle content in the film became the value shown in Table 1 with respect to the main dope of the fine particle dispersion and the additive solution.

  In Comparative Examples 1 to 4, the fine particle monitoring system for quantifying fine particles in the main dope solution was not used before filtering the main dope solution of cellulose ester to which the additive solution containing fine particles was added.

Next, for the produced cellulose ester film samples of Examples 1 to 10 and Comparative Examples 1 to 4, the type of main dope used, the type of additive solution, the type of in-line additive solution, and the content of fine particles (% by weight) The average projection height (nm) on the film surface, the A / B value when the number of projections having a height more than twice the average projection height is A and the total number of projections on the film surface is B, Table 1 summarizes the variations in the protrusion density (pieces / mm ² ) of the surface of 2 nm or more, the number of foreign matters (pieces / m ² ), and the fine particle content for each winding.

(Surface roughness)
The surface shape of the cellulose ester film can be measured by, for example, New-View 5010 manufactured by ZYGO. Measurement conditions and data analysis conditions are as follows.

The cellulose ester films of Examples 1 to 10 and Comparative Examples 1 to 4 wound up after film formation were sampled, and 10 arbitrary locations were measured using the New-View 5010 manufactured by ZYGO under the following measurement conditions. The average projection height (nm) on the film surface, the A / B value when the number of projections having a height more than twice the average projection height is A and the total number of projections on the film surface is B, The protrusion density (pieces / mm ² ) of 2 nm or more on the surface was calculated using the average value of data measured at 10 locations.

Measurement conditions Objective lens: 50x Intermediate lens zoom: 1x Camera resolution: 320x240 30Hz
Scan length: 5 μm (5 sec)
Minimum modulation tolerance (min mod): 7%
Data analysis conditions Software used: advanced texture
Surface shape: remover
High FFT Filter: Auto
Low FFT Filter: Auto
Remove Spokes: off
Noise Filter Size: 0
Fill Data: off
Trim: 0
Reference Band: 4nm
(Foreign matter failure)
An on-line defect inspection machine is installed immediately before the winding part of the belt casting film forming apparatus, and 10 pieces of cellulose acetate raw film are inspected and, on average, a foreign matter failure of 20 μm or more per 1.0 m ^{2 of} the cellulose acetate film. Numbers were calculated.

(Fine particle content in film and fine particle content variation for each winding)
The final film of 2600 m was sampled, 0.5 g of the sample was melted with alkali, prepared into a 50 ml aqueous solution, and quantitative analysis of Si was performed by ICP-AES (inductively coupled plasma emission spectrometer). The apparatus used is SPS-4000 manufactured by Seiko Denshi Kogyo. It was converted into the amount of Si2 before and after the winding of 10 samples, and the average value of the difference was shown.

As is apparent from the results in Table 1, in the cellulose ester film samples according to Examples 1 to 10 of the present invention, the average protrusion height (nm) on the film surface, and protrusions having a height more than twice the average protrusion height. The value of A / B, where A is the number of protrusions and B is the total number of protrusions on the film surface, and the protrusion density of 2 nm or more (pieces / mm ² ) on the film surface are within the scope of the present invention, and The number of failures is very small, and the dispersion of the fine particle content for each winding of the cellulose ester film is small, the slippage between the cellulose ester films is good, and the winding deformation in the long length is difficult to occur. It is excellent in the storage stability of the original fabric, and is hardly distorted when it is made into a polarizing plate. Moreover, in the polarizing plate and the display device using the cellulose ester film, it can be seen that no foreign matter is generated, a spot failure on the liquid crystal screen hardly occurs as a foreign matter failure, and the productivity is excellent.

  In Examples 1 to 10 according to the present invention, a fine particle monitoring system for performing a step of quantifying fine particles in the main dope solution before filtering the main dope solution of cellulose ester to which an additive solution containing fine particles is added. Therefore, according to the method of the present invention, fine particles can be quantified immediately after preparation, so that fluctuations in the slipperiness of the film can be kept small with respect to fluctuations in the process, and the length of the film It can cope with scaling.

On the other hand, in the cellulose ester film samples of Comparative Examples 1 to 4, the average protrusion height (nm) on the film surface, the number of protrusions having a height more than twice the average protrusion height, and the total number of protrusions on A and the film surface. The A / B value when the number of protrusions is B, and the protrusion density (pieces / mm ² ) of 2 nm or more on the film surface are both outside the scope of the present invention. In particular, the cellulose ester films of Comparative Examples 1 to 3 In the sample, the number of foreign matter failures is large, and the dispersion of the fine particle content for each winding of the cellulose ester film is large. In the polarizing plate and the display device using the cellulose ester film, no foreign matter is generated and the foreign matter failure occurs. As such, there is a drawback that a spot failure tends to occur on the liquid crystal screen. Incidentally, in the cellulose ester film sample of Comparative Example 4, the number of foreign matter failures is small and the dispersion of the fine particle content for each winding of the cellulose ester film is small, but the projection density on the film surface is very small, Therefore, the film ratio is too smooth, the slipperiness between the cellulose ester films is poor, and winding deformation in a long length is likely to occur, so that the storage stability of the original cellulose ester film is inferior, and when making a polarizing plate There is a drawback that distortion is likely to occur.

  In Comparative Examples 1 to 4, before filtering the main dope solution of cellulose ester to which an additive solution containing fine particles was added, a fine particle monitoring system for performing a step of quantifying the fine particles in the main dope solution was used. Therefore, the fine particles could not be quantified immediately after the preparation, and the film could not be made longer.

Examples 11-17,
Using the cellulose ester film original fabric samples of Examples 1 to 8, polarizing plate samples were prepared according to the alkali saponification treatment and the polarizing plate preparation method described below. As shown in Table 2, the combination 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) is a cellulose ester film of Examples 1-4 and Examples 5-8. Any one of the original fabric samples was used in combination. In Comparative Examples 5 and 6, the combination of the outer protective film and the inner protective film of the polarizing plate was a combination of the cellulose ester film original fabric samples of Comparative Examples 1 and 3 and Comparative Example 2.

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

<Coating of 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). As described above, the coating was performed using a die coater, followed by drying at a drying temperature of 90 ° C. to form a backcoat layer.

<Backcoat layer composition>
Acetone 30 parts by weight Ethyl acetate 45 parts by weight Isopropyl alcohol 10 parts by weight Diacetylcellulose 0.5 part by weight Ultrafine silica 2% acetone dispersion 0.2 part by weight (Aerosil 200V manufactured by Nippon Aerosil Co., Ltd.)
<Coating of hard coat layer>
The following hard coat layer composition was applied to the surface of the cellulose ester film opposite to the back coat layer by a die coater, dried at 80 ° C. for 5 minutes, and then a high pressure mercury lamp (80 W). Were irradiated with 160 mJ / cm ² of ultraviolet light 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, the medium refractive index layer was formed by irradiating with an ultraviolet ray of 130 mJ / cm ² using a high-pressure mercury lamp (80 W).

<Preparation of tetraethoxysilane hydrolyzate A>
A mixture of 29 parts by weight of tetraethoxysilane and 55 parts by weight of ethanol, 16 parts by weight of a 1.6% by weight aqueous solution of acetic acid added thereto, and then stirred for 25 hours at 25 ° C. A was prepared.

<Medium refractive index layer composition>
Tetraethoxysilane hydrolyzate A 500 parts by weight Solid content 15% titanium oxide fine particle dispersion 300 parts by weight (RTSPNB15WT% -G0 manufactured by CII Kasei Kogyo Co., Ltd.)
1 part by weight of linear dimethyl silicone-EO block copolymer (FZ-2207 manufactured by Nihon Unicar)
Propylene glycol monomethyl ether 1470 parts by weight Isopropyl alcohol 2720 parts by weight Methyl ethyl ketone 490 parts by weight Film thickness of middle refractive index layer: 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 coated 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 530 parts by weight (RTSPNB15WT% -G0 manufactured by CII Kasei Kogyo Co., Ltd.)
Tetra (n) butoxytitanium 50 parts by weight γ-methacryloxypropyltrimethoxysilane 10 parts by weight (KBM503 manufactured by Shin-Etsu Chemical Co., Ltd.)
1 part by weight of linear dimethyl silicone-EO block copolymer (FZ-2207 manufactured by Nihon Unicar)
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 weight Hollow silica fine particle dispersion (P-4 manufactured by Catalytic Chemical Industry Co., Ltd.) 180 parts by weight 10% propylene glycol monomethyl ether solution of linear dimethyl silicone-EO block copolymer (listed above) 3 parts by weight Part Propylene glycol monomethyl ether 380 parts by weight Isopropyl alcohol 380 parts by weight Low refractive index layer film 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 wt% HCl 30 ° C. 45 seconds Water washing step Water 30 ° C. 45 seconds Saponification, water washing, neutralization, water washing under the above conditions Then, drying was performed 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 together using a 5% aqueous solution of completely saponified polyvinyl alcohol as an adhesive to produce a polarizing plate.

  About the obtained polarizing plate sample (Examples 11-17, Comparative Examples 5 and 6), polarizing plate yield and the image quality of the liquid crystal display device were evaluated.

<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 of liquid crystal display)
The 30-inch liquid crystal television LC-30BV3 (manufactured by Sharp Corporation) is peeled off, and the produced polarizing plates are pasted so as to be orthogonal to each other so that the polarizing axes of the polarizing plates are not changed. A television was made.

  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.

The obtained results are summarized in Table 2 below.

  As is clear from the results in Table 2, it is clear that the polarizing plates according to Examples 11 to 17 of the present invention have a high polarizing plate yield and excellent display device image quality. On the other hand, in the polarizing plates according to Comparative Examples 5 and 6, the polarizing plate yield is low, and there are many small foreign substances on the surface of the display device, and it looks shiny. Was clearly inferior.

It is a schematic diagram of the solution casting film forming apparatus which enforces the manufacturing method of the cellulose-ester film of this invention.

1: Matting agent dissolving pot 2: Liquid feed pump 3: Sub-filter 4: Main dope charging pot 5: Main filter 6: Main dope stock tank 7: Filter 8: Ultraviolet absorber dissolving pot 9: Liquid feeding pump 10: Filter 11: Static mixer 101: Metal support 102: Casting die 103: Peeling roll 104: Film 105: Tenter / drying device 106: Roll conveying / drying device

Claims (13)

A cellulose ester film containing fine particles, where A is the number of protrusions having a height of at least twice the average protrusion height of the film surface, and B is the total number of protrusions on the film surface,
1.0 * 10 < ^-6 ><= A / B <= 1.0 * 10 ^<-2 > The cellulose-ester film characterized by the above-mentioned.   The cellulose ester film according to claim 1, wherein an average protrusion height on the film surface is 2 to 20 nm. 2nm or more protrusions density of the film surface, 10,000 characterized in that it is a 10 million cells / mm ^2, a cellulose ester film according to claim 1 or 2 wherein.   The cellulose ester film according to claim 1, wherein the fine particles are silicon dioxide fine particles.   It is the manufacturing method of the cellulose-ester film as described in any one of Claims 1-4, Comprising: The whole quantity of the microparticles | fine-particles which should be contained in a film is added to the main dope of a cellulose ester to the additive liquid containing microparticles | fine-particles. Thereafter, the mixture is 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, and a cellulose ester main dope solution containing the filtered fine particle additive solution is cast to form a film. The manufacturing method of the cellulose-ester film characterized by manufacturing.   6. The cellulose ester main dope solution containing the fine particle additive solution 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 solution. Of manufacturing cellulose ester film.   It is the manufacturing method of the cellulose-ester film as described in any one of Claims 1-4, Comprising: The fine particle which should be contained in a film for the main dope of a cellulose ester, and the additive liquid containing a microparticle and a ultraviolet absorber, The total amount of the ultraviolet absorber is added, and then filtered through a filter medium having a collected particle diameter of 0.5 to 5 μm and a filtering time of 10 to 25 sec / 100 ml, and a main dope liquid of cellulose ester containing fine particles and the ultraviolet absorber A method for producing a cellulose ester film, characterized in that a film is produced by casting.   The method for producing a cellulose ester film according to claim 5 or 7, further comprising a step of quantifying the fine particles in the main dope liquid before filtering the main dope liquid of the cellulose ester to which the additive liquid containing fine particles is added.   The method for producing a cellulose ester film according to claim 8, wherein the method for quantifying the fine particles uses a high-sensitivity spectroscopic method.   The method for producing a cellulose ester film according to claim 8 or 9, wherein the fine particle quantification method is measured in-line.   A polarizing plate comprising the cellulose ester film according to claim 1.   A display device comprising the cellulose ester film according to claim 1.   A display device comprising the polarizing plate according to claim 11.

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