JP2007231278A - Cellulose ester film, and liquid crystal display device having the cellulose ester film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cellulose ester film which has sufficient durability and little causes bleed-out. <P>SOLUTION: This cellulose ester film is characterized by containing a urethane resin having a polyester as a component, having a urethane group concentration of 0.3 to 1.50 mmol/g in the urethane resin, and containing either of a plasticizer and an anti-oxidizing agent. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a cellulose ester film and a liquid crystal display device having the cellulose ester film.

  Cellulose ester films are preferably used in silver halide photographic light-sensitive materials and liquid crystal image display devices because of their transparency and characteristics free from optical defects. In particular, it is used as a protective film for polarizing plates in liquid crystal image display devices.

  In recent years, information devices equipped with liquid crystal image display devices such as notebook PCs, car navigation systems, and mobile phones have been developed for thinning. For the protective films for polarizing plates used in liquid crystal image display devices However, thinning is required. Therefore, the cellulose ester film is also thinned.

  However, when the cellulose ester film is thinned, the tear strength is lowered, resulting in a problem that durability is lowered.

As countermeasures, Patent Documents 1 and 2 disclose a technique for increasing the tear strength by including a polyurethane resin having polyester as a component in a cellulose ester film.
Japanese Patent Publication No. 47-760 Japanese Patent Publication No. 44-32672

  In the polarizing plate protective film of the liquid crystal display device, the durability of the polarizing plate protective film is also necessary, but it is important that the liquid crystal screen etc. is sufficiently easy to see, and therefore sufficient transparency, retentivity, Flatness is required. Further, it is required that the viewing angle dependency is small.

  In addition, the cellulose ester film containing a polyurethane resin having a polyester as a component is a phenomenon in which the ester bond portion of the polyester in the polyurethane resin is hydrolyzed with time, and the surface of the cellulose ester film becomes white turbid (bleed out) ) May occur, which may reduce the visibility of a liquid crystal display screen or the like.

  The present invention has been made in view of the above problems, and a first object of the present invention is to provide a cellulose ester film having sufficient durability and reduced occurrence of bleed out.

  The second object of the present invention is to provide a highly transparent cellulose ester film.

  The third object of the present invention is to provide a cellulose ester film having a low retentivity.

  A fourth object of the present invention is to provide a cellulose ester film with little color turbidity in an IPS liquid crystal display device.

  The fifth object of the present invention is to provide a cellulose ester film having high flatness.

  The sixth object of the present invention is to provide a liquid crystal display device having a cellulose ester film that achieves at least one of the above objects.

  The present invention achieves at least one of the above objects.

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

  1. It contains a urethane resin having polyester as a component, the urethane group concentration of the urethane resin is in the range of 0.3 to 1.50 mmol / g, and contains either a plasticizer or an antioxidant. Cellulose ester film.

  2. 2. The cellulose ester film as described in 1 above, wherein the urethane group concentration of the urethane resin is in the range of 0.7 to 1.20 mmol / g.

  3. 3. The cellulose ester film as described in 1 or 2 above, wherein the plasticizer or antioxidant is a plasticizer.

  4). 4. The cellulose ester film as described in any one of 1 to 3 above, wherein the urethane resin has a weight average molecular weight of 100,000 or more.

  5. It uses as a polarizing plate protective film, The cellulose-ester film of any one of said 1-4 characterized by the above-mentioned.

  6). 6. A liquid crystal display device comprising the cellulose ester film as described in 5 above.

  7). 7. The liquid crystal display device as described in 6 above, which is an IPS system.

  By at least one of the cellulose ester films of the present invention, it is possible to provide a cellulose ester film having sufficient durability and reduced occurrence of bleed out.

  By at least one of the cellulose ester films of the present invention, a highly transparent cellulose ester film can be provided.

  A cellulose ester film having low retentivity can be provided by at least one of the cellulose ester films of the present invention.

  With at least one of the cellulose ester films of the present invention, a cellulose ester film with little color turbidity can be provided in an IPS liquid crystal display device.

  A cellulose ester film having high planarity can be provided by at least one of the cellulose ester films of the present invention.

  A liquid crystal display device having the cellulose ester film of the present invention having at least one of the above effects can be provided.

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

  The present invention is described in more detail below.

  This inventor contains the urethane resin which has polyester as a component, the urethane group density | concentration of this urethane resin is the range of 0.3-1.50 mmol / g, and either a plasticizer or antioxidant is added. It has been found that when it is contained in a cellulose ester film, bleeding out of the cellulose ester film hardly occurs.

  The present inventor has found that when a urethane resin having a polyester as a component and having a weight average molecular weight of 100,000 or more is contained in the cellulose ester film, the cellulose ester film is less likely to bleed out.

  Moreover, this inventor also discovered that the bleed-out of a cellulose-ester film becomes difficult to occur by making a cellulose-ester film contain the urethane resin which has polyester as a component, and antioxidant. At this time, it has also been found that it is preferable to make the weight average molecular weight of the urethane resin to be contained 100000 or more because the bleedout of the cellulose ester is more difficult to occur.

  Furthermore, this inventor also discovered that the bleed-out of a cellulose-ester film becomes difficult to occur by making a cellulose-ester film contain the urethane resin which has polyester as a component, and a plasticizer. At this time, it was also found that it is preferable to make the weight average molecular weight of the urethane resin to be contained 100000 or more because the bleedout of the cellulose ester film is less likely to occur. Furthermore, it has been found that the inclusion of an antioxidant is particularly preferable because it is more difficult for bleeding out to occur.

  In the cellulose ester film of the present invention, it is more preferable that the weight average molecular weight of the urethane resin is 200,000 or more, which makes it more difficult for bleeding out to occur.

  Since the cellulose ester film of the present invention contains a urethane resin, it has high tear strength and excellent durability.

  The material of the urethane resin used in the cellulose ester film of the present invention is not particularly limited as long as it contains high tear strength and durability, but it is synthesized by reacting polyester with toluene diisocyanate. It is preferable to be a urethane resin. When this urethane resin is used, the tear strength is further increased, bleeding out can be further suppressed, and the transparency can be increased. Furthermore, moisture permeability can be suppressed.

  Even if a urethane resin synthesized by reacting polyester and p, p'-diphenylmethane diisocyanate as a urethane resin is used, the tear strength is further increased, bleeding out can be further suppressed, and the transparency is increased. be able to. Furthermore, moisture permeability can be suppressed.

  Furthermore, the polyester used for the urethane resin is preferably synthesized with adipic acid and ethylene glycol. As a result, the tear strength is further increased, bleeding out can be further suppressed, and the transparency can be further increased.

  The urethane group concentration of the urethane resin contained in the cellulose ester film of the present invention needs to be 0.3 to 1.50 mmol / g, more preferably 0.7 to 1.20 mmol / g, Thereby, tear strength becomes high and transparency becomes high. The urethane group concentration can be measured by NMR (JEOL Ltd .: Lambda400).

  The cellulose ester film of the present invention preferably contains 1 to 30% by mass of urethane resin, more preferably 15 to 25% by mass. As a result, the tear strength is further increased, bleeding out can be further suppressed, and the transparency can be increased.

  Examples of the plasticizer contained in at least one of the cellulose ester films of the present invention include alkyl phthalyl alkyl glycolates, phosphate esters and carboxylic acid esters.

  Examples of alkyl phthalyl alkyl glycolates include methyl phthalyl methyl glycolate, ethyl phthalyl ethyl glycolate, propyl phthalyl propyl glycolate, butyl phthalyl butyl glycolate, octyl phthalyl octyl glycolate, methyl phthalyl ethyl Glycolate, ethyl phthalyl methyl glycolate, ethyl phthalyl propyl glycolate, propyl phthalyl ethyl glycolate, methyl phthalyl propyl glycolate, methyl phthalyl butyl glycolate, ethyl phthalyl butyl glycolate, butyl phthalyl methyl glycol Butyl phthalyl ethyl glycolate, propyl phthalyl butyl glycolate, butyl phthalyl propyl glycolate, methyl phthalyl octyl glycolate, ethyl phthalyl Chi le glycolate, octyl phthalyl methyl glycolate, and the like octyl phthalyl ethyl glycolate. Examples of phosphate esters include triphenyl phosphate, tricresyl phosphate, phenyl diphenyl phosphate, and the like. Examples of the carboxylic acid ester include phthalic acid ester and citric acid ester. Examples of the phthalic acid ester include dimethyl phthalate, diethyl phosphate, dioctyl phthalate, and diethyl hexyl phthalate. Examples of the citrate ester include acetyl triethyl citrate and citric acid. Mention may be made of acetyltributyl. Other examples include butyl oleate, methylacetyl ricinoleate, dibutyl sebacate, and triacetin.

  Among them, methyl phthalyl methyl glycolate, ethyl phthalyl ethyl glycolate, propyl phthalyl propyl glycolate, butyl phthalyl butyl glycolate, octyl phthalyl octyl glycolate are preferable, and ethyl phthalyl ethyl glycolate is particularly preferable. . These alkyl phthalyl alkyl glycolates may be used in combination of two or more.

  1-30 mass% is preferable with respect to a cellulose ester, and, as for the quantity of the plasticizer contained in the cellulose ester film of this invention, 4-13 mass% is especially preferable. By setting it as this range, durability can be improved, maintaining the retentivity of a cellulose-ester film.

  The antioxidant contained in at least one of the cellulose ester films of the present invention is specifically a phenylenediamine antioxidant (Ouchi Shinsei Chemical Co., Ltd .: Nocrack CD, Nocrack TO, Nocrack GI, Aspic ), Imidazole antioxidants (Ouchi Shinsei Chemical Co., Ltd .: Nocrack MB, Nocrack MMB, etc.), hindered phenol antioxidants (BHT, etc.), dithiocarbamate antioxidants, and the like. Di-t-butylmethylphenol (BHT) is preferred.

  The cellulose ester film of the present invention contains a cellulose ester. Examples of the cellulose ester include cellulose triacetate, cellulose diacetate, cellulose ester propionate, and cellulose propionate. It may contain an acyl group having 4 or more carbon atoms, such as cellulose acetate butyrate and cellulose acetate propionate butyrate. Of these, those consisting only of an acyl group having 2 to 3 carbon atoms are preferred, and cellulose triacetate and cellulose acetate propionate are particularly preferred. The substitution degree of the acyl group is preferably 2.6 to 3.0. By setting the substitution degree within this range, a film having good durability can be obtained. If the degree of substitution of the acetyl group is too small, the breaking strength of the film may be too low, so it is preferably 1.4 or more. The measuring method of the substitution degree of an acyl group can be measured by ASTM-D817-96.

  The cellulose ester used in the present invention can be synthesized by an ordinary method. For example, it can be synthesized by the method described in JP-A-10-45804.

  The cellulose as a raw material for the cellulose ester is not particularly limited, and examples thereof include cotton linter, wood pulp, and kenaf. Moreover, the cellulose ester obtained from them can be mixed and used in arbitrary ratios, respectively. Cellulose esters obtained from cotton linters are preferred because they have particularly good releasability from the support during film formation.

  The weight average molecular weight of the cellulose ester used in the present invention is preferably in the range of 70,000 to 300,000 because the mechanical strength when molded is strong. Furthermore, 80000-200000 are preferable.

  When the cellulose ester film of the present invention is used, for example, in a liquid crystal display device, the opportunity to be used outdoors has increased, and it is also important to impart a function of cutting ultraviolet rays to a protective film for a polarizing plate. . For this purpose, it is preferable to contain an ultraviolet absorber, and the ultraviolet absorber used preferably has no absorption in the visible light region, and examples thereof include benzotriazole compounds, benzophenone compounds, and salicylic acid compounds. For example, 2- (2′-hydroxy-5-methylphenyl) benzotriazole, 2- (2′-hydroxy-3 ′, 5′-di-t-butylphenyl) benzotriazole, 2- (2′-hydroxy- 3'-di-t-butyl-5'-methylphenyl) benzotriazole, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-n-octoxybenzophenone, 4-dodecyloxy 2-hydroxybenzophenone, 2,2 ′, 4,4′-tetrahydroxybenzophenone, 2,2′-dihydroxy-4,4′-dimethoxybenzophenone, phenyl salicylate, methyl salicylate, and the like.

  The addition amount of the ultraviolet absorber is preferably in the range of 0.5 to 20% by mass, more preferably in the range of 0.6 to 5% by mass with respect to the cellulose ester.

  For the purpose of improving the heat and heat resistance of the film, hindered phenol compounds are preferably used, and 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di- t-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-t-butylanilino) -1 , 3,5-triazine, 2,2-thio-diethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], octa Sil-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, N, N'-hexamethylenebis (3,5-di-t-butyl-4-hydroxy-hydrocinnamamide) 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, tris- (3,5-di-t-butyl-4-hydroxy Benzyl) -isocyanurate and the like. In particular, 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate] is preferred. Further, for example, hydrazine-based metal deactivators such as N, N′-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyl] hydrazine and tris (2,4-di-t A phosphorus-based processing stabilizer such as -butylphenyl) phosphite may be used in combination. The amount of these compounds added is preferably 1 ppm to 1.0%, more preferably 10 to 1,000 ppm in terms of mass ratio with respect to the cellulose ester. In addition, a heat stabilizer such as a salt of an alkaline earth metal such as calcium or magnesium may be added.

  In addition, a dye may be added to the cellulose ester film of the present invention for the purpose of improving the yellowness of the film. The tint is preferably one that can be colored gray as seen on a normal photographic support. However, unlike the photographic support, it is not necessary to prevent light piping, so the content may be small, and the mass ratio to the cellulose ester is preferably 1 to 100 ppm, more preferably 2 ppm to 50 ppm. Since the cellulose ester is slightly yellowish, a blue or purple dye is preferably used. A plurality of dyes may be appropriately combined so as to become gray.

  If the film is difficult to slip, the films may block and handleability may be poor. In this case, inorganic fine particles such as silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, kaolin, talc, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, calcium phosphate, etc. It is preferable to include a matting agent such as a molecule. Of these, silicon dioxide is preferable because it can reduce the haze of the film. The matting agent is preferably blended so that the haze of the film is 0.6% or less and the dynamic friction coefficient is 0.5 or less. The matting agent used for this purpose preferably has an average particle size of 0.01 to 1.0 μm and a content of 0.005 to 0.3% by mass with respect to the cellulose ester.

  In addition to the above, an antistatic agent, a flame retardant, a lubricant, an oil agent, and the like may be added as appropriate.

  The cellulose ester film of the present invention preferably has a haze value of 0.01 to 0.2% in consideration of use for a protective film for a polarizing plate such as a liquid crystal display device. This makes it easier to see the liquid crystal display device. The haze value can be measured with a commercially available measuring instrument such as TURBIDITY METER T-2600DA manufactured by Tokyo Denshoku Co., Ltd.

  The cellulose ester film of the present invention needs to have a certain degree of strength and improved durability in order to cope with the reduction in thickness in consideration of use for a protective film for a polarizing plate such as a liquid crystal display device. Therefore, the tear strength according to the Elmendle method when converted to a thickness of 40 μm is preferably 0.05 N or more. Here, the tear strength according to the Elmendle method when converted to a thickness of 40 μm is 0.05 N or more, as described in JIS K7128-1991, method A (trouser tear method), method B (element It shows that the value measured using a 40 μm thick film using the B method of the Dorf tear method and the C method (right angle tear method) is 0.05 N or more.

The cellulose ester film of the present invention preferably has a moisture permeability of 300 g / m ² · 24 hr or less in consideration of use for a protective film for a polarizing plate such as a liquid crystal display device. Thereby, the penetration | invasion of the water vapor | steam from a polarizing plate can be suppressed and durability of a liquid crystal display device can be improved. The moisture permeability is a value measured under conditions of 25 ° C. and 90% RH according to JIS Z0208-76.

  Since the cellulose acetate film of the present invention has the above performance, it is useful when used as a protective film for a polarizing plate, and particularly useful when used as a protective film for a polarizing plate of a liquid crystal display device.

  The cellulose ester film of the present invention is preferably manufactured using a solution casting film forming method. Thereby, it can be set as the cellulose-ester film which was more excellent in planarity, and the visibility of a liquid crystal display device etc. can be improved.

  The manufacturing method of the cellulose ester film by the solution casting film forming method concerning this invention is demonstrated.

  The solution casting film forming method includes a dissolution step, a casting step, a solvent evaporation step, a peeling step, a drying step, and a winding step.

  1. Dissolution step: a step of dissolving the flakes in an organic solvent mainly composed of a good solvent for the flakes of cellulose ester in a dissolution vessel while stirring to form a dope.

  The dissolution method useful in the present invention is a method performed at a temperature not lower than the boiling point of the main solvent and under a pressure that does not boil (hereinafter referred to as a high temperature dissolution method), cooling the cellulose ester and the organic solvent to −100 ° C. to −10 ° C. Or after mixing the cellulose ester with an organic solvent at −100 ° C. to −10 ° C. and then heating to 0 ° C. to 120 ° C. (hereinafter referred to as cooling dissolution method), the cellulose ester and the organic solvent at 50 atm. Examples include a method of pressurizing to 2,000 atmospheres (hereinafter referred to as a high-pressure dissolution method).

  For example, in the case of using methyl acetate (boiling point 56.32 ° C.) as the main solvent in the high temperature dissolution method, the temperature is preferably 56.32 ° C. to 120 ° C., more preferably 60 ° C. to 90 ° C. At this time, the pressure that does not boil may be about 2 atm or more, and there is no particular upper limit, but the effect is saturated at about 50 atm, so 2 to 50 atm is preferable. Further, 2 to 10 atm is preferable.

  Further, when the cellulose ester has a substitution degree of acetyl group of 2.5 or more, it is preferable to use a cooling dissolution method or a high pressure dissolution method.

  For the cooling dissolution method, a method of forming a dope using a solvent such as acetone, methyl acetate, ethyl formate described in JP-A Nos. 9-95538, 9-95544, and 9-95557 is used. I can do it.

  As for the high-pressure dissolution method, the high-pressure dissolution method described in JP-A No. 11-21379 can be used. In the publication, acetone is used as the organic solvent, but the same can be applied to methyl acetate.

  The cellulose ester dope preferably contains 0.1 to 30% by mass of an alcohol having 1 to 4 carbon atoms. As a result, after the dope is cast on the casting support, the solvent starts to evaporate, and when the alcohol ratio increases, the web (dope film) gels, making the web strong and easy to peel off from the casting support. Furthermore, the effect of promoting the dissolution of the cellulose ester of the non-chlorine organic solvent can be obtained. Examples of the alcohol having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, and tert-butanol. Of these, ethanol is most preferable because of the stability of the dope, the boiling point is relatively low, the drying property is good, and there is no toxicity.

  The solid content concentration of the dope is usually preferably 10 to 40% by mass, and the dope viscosity is preferably adjusted to a range of 100 to 500 poise from the viewpoint of obtaining good film flatness.

  The dope prepared as described above is filtered with a filter medium, defoamed, and sent to the next process with a pump.

  2. Casting process: a dope is fed to a pressure die through a pressurized metering gear pump, and an endless metal belt for infinite transfer or a rotating metal drum casting support at the casting position (hereinafter simply referred to as a support). It may be a step of casting a dope from a pressure die on the 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, but the slit shape of the die part is adjusted. A pressure die that is easy to make uniform in film thickness is preferable. Examples of the pressure die include a coat hanger die and a T die, and any of them is preferably used. In order to increase the film forming speed, two or more pressure dies may be provided on the casting support, and the dope amount may be divided and stacked.

  3. Solvent evaporation step: This is a step of evaporating the solvent by heating the web (the dope film after the dope is cast on the casting support is referred to as the web) on the casting support. In order to evaporate the solvent, there are a method of blowing air from the web side and / or a method of transferring heat from the back side of the support by a liquid, a method of transferring heat from the front and back by radiant heat, and the like. The drying efficiency is good and preferable. A method of combining them is also preferable.

  4). Peeling step: A step in which the web in which the solvent has evaporated on the support is peeled 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 is difficult, or conversely, if it is peeled off after sufficiently drying on the support, part of the web is peeled off.

  As a method for increasing the film forming speed (the film forming speed can be increased because the film is peeled off while the residual solvent amount is as large as possible), there is a gel casting method (gel casting) in which even a large amount of residual solvent can be removed. For example, a poor solvent for the cellulose ester is added to the dope, and after the dope is cast, the gel is formed, and the temperature of the support is lowered to form a gel. There is also a method of adding a metal salt in the dope. By gelling on the support and strengthening the film, it is possible to speed up the peeling and increase the film forming speed. When peeling at a time when the amount of residual solvent is larger, if the web is too soft, the flatness at the time of peeling will be impaired, or slippage and vertical stripes due to peeling tension are likely to occur. It is decided.

  5. Drying step: a step of drying the web using a drying device that alternately conveys the web through rolls arranged in a staggered pattern and / or a tenter device that clips and conveys both ends of the web with a clip. As a drying means, hot air is generally blown on both sides of the web, but there is also a means for heating by applying a microwave instead of the wind. Too much drying tends to impair the flatness of the finished film. Drying at a high temperature is preferably performed from about 8% by mass or less of the residual solvent. Throughout, the drying temperature is usually 40 to 250 ° C, preferably 70 to 180 ° C. The drying temperature, the amount of drying air, and the drying time differ depending on the solvent used, and the drying conditions may be appropriately selected according to the type and combination of the solvents used.

  In the drying step after peeling from the casting support surface, the web tends to shrink in the width direction due to evaporation of the solvent. Shrinkage increases as the temperature rapidly dries. Drying while suppressing this shrinkage as much as possible is preferable for improving the flatness of the finished film. From this point of view, for example, a method of drying the entire drying process or a part of the process as shown in Japanese Patent Application Laid-Open No. 62-46625 while holding the width at both ends of the web with a clip in the width direction (tenter method) ) Is preferred.

  6). Winding step: The step of winding the web as a film after the residual solvent amount becomes 2% by mass or less. By setting the residual solvent amount to 0.4% by mass or less, a film having good dimensional stability can be obtained. 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.

  The amount of residual solvent can be expressed by the following formula.

Residual solvent amount (% by mass) = {(MN) / N} × 100
Here, M is the mass of the web at any point, and N is the mass when M is dried at 110 ° C. for 3 hours.

  To adjust the film thickness of the cellulose ester film, adjust the dope concentration, the pumping amount, the slit gap of the die base, the extrusion pressure of the die, the speed of the casting support, etc. It is good to control. 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.

  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, or may be performed in an inert gas atmosphere such as nitrogen gas or carbon dioxide gas. .

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

1. Production of Film Samples 1 to 23 <Film Samples 1 to 20>
A dope composition 1 having the following composition was put into a sealed container, heated to 70 ° C., and stirred to completely dissolve cellulose triacetate (TAC) to obtain a dope. The time required for dissolution was 4 hours. After the dope composition was filtered, it was uniformly cast on a stainless band support having a dope temperature of 35 ° C. and a temperature of 22 ° C. using a belt casting apparatus. The temperature of the stainless steel band support was 20 ° C.

  Then, after making it dry to the range which can be peeled, dope was peeled from the stainless steel band support body. At this time, the residual solvent amount of the dope was 25%. The time required from casting the dope to peeling was 3 minutes. After peeling from the stainless steel band support, after drying at 120 ° C while holding in the width direction, release the width holding and finish drying at 120 ° C and 135 ° C drying zones while transporting with many rolls. Then, a knurling process having a width of 10 mm and a height of 5 μm was applied to both ends of the film to prepare a cellulose triacetate film sample 1 having a thickness of 40 μm. The film width of the film sample was 1300 mm, and the winding length was 3000 m. The winding tension was an initial tension of 1.5 N / 1300 mm and a final winding tension of 1 N / 1300 mm. In the same manner, film samples 2 to 20 were prepared for the dope compositions 2 to 20. In this way, film samples 1 to 20 were obtained.

[Dope Compositions 1-20]
Triacetylcellulose (acetylation degree 61.0%) 100 parts by mass 2- (2′-hydroxy-3 ′, 5′-di-t-butylphenyl) bezotriazole 2 parts by mass Urethane resin described in Table 1 below 20 5 parts by mass of the plasticizer described in Table 1 below 0.5 parts by mass of the antioxidant described in Table 1 Methylene chloride 475 parts by mass Ethanol 50 parts by mass

<Film sample 21>
A film sample 21 was produced in the same manner as the production of the film sample 1 except that the dope composition 1 was changed to the following dope composition 21 in the production of the film sample 1.

[Dope composition 21]
Triacetyl cellulose (acetylation degree 61.0%) 100 parts by mass 2- (2′-hydroxy-3 ′, 5′-di-t-butylphenyl) bezotriazole 1 part by mass Triphenyl phosphate 15 parts by mass Methylene Chloride 475 parts by mass Ethanol 50 parts by mass <Film sample 22>
A film sample 22 was produced in the same manner except that the dove composition 1 was changed to the following dope composition 22 in the production of the film sample 1.

[Dope composition 22]
Triacetylcellulose (acetylation degree 61.0%) 100 parts by mass 2- (2′-hydroxy-3 ′, 5′-di-t-butylphenyl) bezotriazole 1 part by mass Ethylphthalylethyl glycolate 4 parts by mass Part Methylene chloride 475 parts by mass Ethanol 50 parts by mass <Film sample 23>
A film sample 23 was produced in the same manner except that the dope composition 1 was changed to the following dope composition 23 in the production of the film sample 1.

[Dope composition 23]
Triacetyl cellulose (acetylation degree 61.0%) 100 parts by mass 2- (2′-hydroxy-3 ′, 5′-di-t-butylphenyl) bezotriazole 1 part by mass Triphenyl phosphate 10 parts by mass Lauryl Benzene sulfonate 2 parts by weight Methylene chloride 475 parts by weight Ethanol 50 parts by weight Preparation of Polarizing Plate Samples 1 to 23 Film sample 1 was alkali-treated with a 2.5 M sodium hydroxide aqueous solution at 40 ° C. for 60 seconds, washed with water for 3 minutes to form a saponification layer, and an alkali-treated film was obtained.

  Next, a 120 μm-thick polyvinyl alcohol film was immersed in 100 parts by mass of an aqueous solution containing 1 part by mass of iodine and 4 parts by mass of boric acid, and stretched 4 times at 50 ° C. to form a polarizing film. A polarizing plate sample 1 was prepared by laminating the alkali-treated film on both surfaces of this polarizing film with a 5% aqueous solution of a completely saponified polyvinyl alcohol as an adhesive. Regarding the film samples 2 to 23, polarizing plate samples 2 to 23 were prepared in the same manner as described above.

3. Evaluation of Film Samples 1 to 23 and Polarizing Plate Samples 1 to 23 The following (1) to (6) were evaluated for the film samples 1 to 23, and the following (7) was evaluated for the polarizing plate samples 1 to 23.

(1) Haze The haze value was measured using TURBIDITY METER T-2600DA manufactured by Tokyo Denshoku Co., Ltd.

(2) Tear strength The tear strength of the Elmendorf method was measured with a light load tear device manufactured by Toyo Seiki Co., Ltd. according to JIS K 7128-1991.

(3) Moisture permeability The moisture permeability of each film sample was measured according to the method described in JIS Z 0208. The temperature and humidity conditions for the test are 25 ° C. and 90% RH.

(4) Retention (plasticizer precipitation)
A film sample was cut out in a size of 10 cm in the width direction and 10 cm in the longitudinal direction, and the mass after standing for 24 hours at 23 ° C. and 55% RH was measured. Then, the sample was 48 under the conditions of 80 ° C. and 90% RH. Time processed. Further, the mass of the treated film sample after standing for 24 hours at 23 ° C. and 55% RH was measured, and the retention was calculated by the following method.

Retention property = (mass before treatment−mass after treatment) / mass before treatment × 100%
(5) Bleed-out value A film sample was cut out in a size of 10 cm in the width direction and 10 cm in the longitudinal direction, treated for 48 hours at 80 ° C. and 90% RH, and then manufactured by Tokyo Denshoku Co., Ltd. The haze value measured using TURBIDITY METER T-2600DA was taken as the bleed-out value.

(6) Retardation value (Rt value)
Using an automatic birefringence meter KOBRA-21AH (manufactured by Oji Scientific Instruments), a film sample is subjected to three-dimensional refractive index measurement at a wavelength of 590 nm under the conditions of 23 ° C. and 55% RH. Nx, Ny, and Nz are obtained.

  The retardation value Rt in the thickness direction was calculated according to the following formula.

Rt = {(Nx + Ny) / 2−Nz} × d
In the formula, Nx is the refractive index of the film in the direction parallel to the film forming direction, Ny is the refractive index of the film in the direction perpendicular to the film forming direction, Nz is the refractive index of the film in the film thickness direction, d Represents the thickness (nm) of the film.

(7) Polarizing plate durability test Two polarizing plate samples having a size of 10 cm x 10 cm were subjected to high-temperature and high-humidity treatment (conditions: 80 ° C-90% RH, 50 hours), and the surface state was observed.

A: Less than 5% of the polarizing plate surface is cloudy due to bleed out
○: The portion where the surface of the polarizing plate becomes cloudy due to bleed-out is 5% or more and less than 10%.
Δ: The portion where the surface of the polarizing plate becomes cloudy due to bleed-out is 10% or more and less than 20% (a level that can be managed as a polarizing plate)
X: 20% or more of the portion where the surface of the polarizing plate becomes cloudy due to bleed out
If it is more than △, it is a level where there is no practical problem.

  The results are shown in Tables 2 and 3.

  Further, the polarizing plate samples 3 and 22 were incorporated in an IPS module and evaluated for color. The results are shown in Table 4.

  From the results of Tables 2 and 3, the film sample of the present invention has very high transparency with a haze of 0.1%, so that it is very useful particularly when used for a polarizing plate of a liquid crystal display device. I understood.

  Moreover, since the film sample of this invention has high tear strength and high durability, it turned out that it is very useful especially when used for the polarizing plate etc. of a liquid crystal display device.

  Furthermore, since the film sample of the present invention has low retentivity, it has been found that it is very useful particularly when used for a polarizing plate of a liquid crystal display device.

  Further, since the film sample of the present invention has a low water vapor transmission rate, it can prevent deterioration of the function of the liquid crystal display device due to the intrusion of water vapor, particularly when used for a polarizing plate of a liquid crystal display device. It was found that can be improved.

  Furthermore, since the film sample of the present invention suppresses the occurrence of bleed-out, it has been found that the film sample is very useful particularly when used for a polarizing plate of a liquid crystal display device.

  Further, it was found that the polarizing plate sample 3 of the present invention has a particularly small Rt and is very useful when used for a polarizing plate of an IPS liquid crystal display device because color turbidity is suppressed.

  Furthermore, since the film sample of the present invention is manufactured using a solution casting film forming method, it has high flatness and is very useful when used for a polarizing plate protective film of a liquid crystal display device.

  Furthermore, since the polarizing plate sample of this invention can suppress generation | occurrence | production of bleed-out, it turned out that it is very useful when used for the polarizing plate protective film of a liquid crystal display device.

  Furthermore, each of the polarizing plate samples of the present invention was set and used in a liquid crystal display device, and was confirmed to be very useful due to the above-described effects.

Claims (7)

It contains a urethane resin having polyester as a component, the urethane group concentration of the urethane resin is in the range of 0.3 to 1.50 mmol / g, and contains either a plasticizer or an antioxidant. Cellulose ester film. The cellulose ester film according to claim 1, wherein a urethane group concentration of the urethane resin is in a range of 0.7 to 1.20 mmol / g. The cellulose ester film according to claim 1 or 2, wherein the plasticizer or the antioxidant is a plasticizer. The weight average molecular weight of the said urethane resin is 100,000 or more, The cellulose-ester film of any one of Claims 1-3 characterized by the above-mentioned. It uses as a polarizing plate protective film, The cellulose-ester film of any one of Claims 1-4 characterized by the above-mentioned. A liquid crystal display device comprising the cellulose ester film according to claim 5. The liquid crystal display device according to claim 6, wherein the liquid crystal display device is an IPS system.