JP2013067680A - Cellulose acylate film, polarization plate and liquid crystal display device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cellulose acylate film which exhibits excellent retardation development and low inner haze even when using low-cost low-grade pulp and which can be employed for a high contrast application, as well as a method of manufacturing the same.SOLUTION: The cellulose acylate film including cellulose acylate with 2.2-2.55 acyl substitution degree includes, with respect to 100 mass% sugar composition constituting the film, 0.9 mass% or less xylose and 0.9 mass% or less mannose. By performing a step of depositing and removing compositions other than cellulose acylate contained in the dope during dope preparation (deposition removal process), such a cellulose acylate film can be obtained.

Description

  The present invention relates to a cellulose acylate film, a polarizing plate using the same, and a liquid crystal display device.

  In recent years, the demand for liquid crystal display devices (hereinafter also referred to as “LCD”) has been strong due to the widespread use of liquid crystal displays mounted on automobiles, large liquid crystal television displays, mobile phones, notebook computers, and the like. In such LCDs, various optical films such as a polarizing film and a retardation film are used. With increasing demand for LCDs, there are demands for thinner, lighter, and more productive polarizing plates used therefor. Furthermore, with the increase in the screen size of LCDs, it is required to reduce the thickness and area of polarizing plate protective films and retardation films as members.

  As this polarizing plate protective film and retardation film, a cellulose acylate film is used. Particularly in recent years, the required performance for liquid crystal display devices has increased, and in particular, high contrast performance has become important. Therefore, a retardation film as an optical compensation film (viewing angle widening film) is also used as a polarizing plate protective film. Here, triacetyl cellulose (TAC) having a high degree of acetyl group substitution has low retardation, and performance as an engineering compensation film is not sufficient. On the other hand, when diacetyl cellulose (DAC) having a lower degree of acetyl group substitution is used, sufficient retardation can be ensured, but the internal haze of the film increases, making it difficult to use in high contrast applications. there were.

  Further, in the production of diacetyl cellulose (DAC), it is common to obtain a TAC having a desired substitution degree through an acyl group hydrolysis step after fully acylating cellulose to obtain TAC. In this case, the larger the amount of the metal added in the reaction stopping step, the higher the control and stability of the substituent, but there is also a problem that the addition of a large amount of metal adversely affects the internal haze of the film.

  Patent Documents 1 and 2 disclose cellulose esters having a low content of metal ions and catalyst (sulfuric acid) and methods for producing the same as means for preventing deterioration of internal haze. However, with this method, the temperature stability of vinegar cotton deteriorates due to the decrease in metal ions, and the yield deteriorates. If the amount of catalyst (sulfuric acid) added is reduced, the synthesis takes time and the production cost increases. was there.

  The cellulose acylate film is usually obtained by acetylating cellulose from cotton linter pulp, softwood pulp or hardwood pulp to obtain cellulose acylate, and a solution (dope) containing this cellulose acylate and a solvent is supported. It is produced by a casting method in which the film is cast on and peeled off from the support. At this time, if linter pulp is used as a raw material, the cost of cellulose acylate increases. Further, among softwood pulp, high-purity pulp has a difficulty in stably supplying raw materials, and low-purity pulp tends to increase the internal haze of cellulose acylate and lower transparency. On the other hand, the use of hardwood pulp is advantageous in terms of cost, but it is difficult to improve the surface smoothness and productivity of the film.

Japanese Patent Laid-Open No. 10-316701 JP 2009-161701 A

  The present invention has been made in view of the above-described conventional technology, and even when a low-cost low-purity pulp is used, it has excellent retardation and low internal haze and can be applied to high-contrast applications. An object is to provide a cellulose acylate film and a method for producing the same. Another object of the present invention is to provide a polarizing plate and a liquid crystal display device using the cellulose acylate film.

  The present inventor has conducted extensive research in view of the above-described object. As a result, the presence of impurities such as ultra-low-substituted cellulose acylate and hemicellulose was found as a factor for increasing the internal haze of the film when low-purity pulp was used. And it discovered that the said subject could be solved by depositing and removing these impurities at the time of preparation of dope. Furthermore, it has also been found that the ratio of xylose and mannose in the sugar components constituting the film can be used as an index of the content of these impurities in the film, and the present invention has been completed.

  That is, the above object of the present invention is achieved by the following configuration.

(1) A cellulose acylate film containing a cellulose acylate having an acyl group substitution degree of 2.2 to 2.55,
A cellulose acylate film, wherein the ratio of xylose is 0.9% by mass or less and the ratio of mannose is 0.9% by mass or less with respect to 100% by mass of the sugar component constituting the film;
(2) The cellulose acylate film according to (1), further including a chelating agent;
(3) The cellulose acylate film according to (2), wherein the chelating agent includes a chelate stability constant with Ca ²⁺ of 5 or more;
(4) The cellulose acylate film according to the above (2) or (3), wherein the chelating agent comprises an amino group and a carboxyl group.
(5) a dope preparation step of preparing a dope containing cellulose acylate having an acyl group substitution degree of 2.2 to 2.55;
A deposit removing step of depositing and removing components other than the cellulose acylate contained in the dope; and
After drying the film obtained by casting the dope obtained in the deposit removing step on a support and peeling it, the step of stretching at least in the width direction;
A method for producing a cellulose acylate film, comprising:
(6) The production method according to (5), wherein the deposit removing step is performed by adding a chelating agent to the dope;
(7) The manufacturing method according to (5) or (6), further including a step of adding a matting agent to the dope after the deposit removing step;
(8) The cellulose acylate film according to any one of (1) to (4) above or the cellulose acylate film produced by the production method according to any one of (5) to (7) above And a polarizing plate formed by bonding at least one surface of the polarizer;
(9) A liquid crystal display device comprising the polarizing plate according to (8).

  According to the present invention, there is provided a cellulose acylate film that is excellent in retardation development, has low internal haze, and can be applied to high-contrast applications even when low-cost low-purity pulp is used, and a method for producing the same. sell.

In an Example, it is explanatory drawing for demonstrating the method to measure the internal haze of the obtained film. In an Example, it is explanatory drawing for demonstrating the method to measure the internal haze of the obtained film. In an Example, it is explanatory drawing for demonstrating the method to measure the internal haze of the obtained film. In an Example, it is explanatory drawing for demonstrating the method to measure the internal haze of the obtained film.

  Hereinafter, embodiments of the present invention will be described in detail.

≪Cellulose acylate film≫
One aspect of the present invention provides a cellulose acylate film containing a cellulose acylate having an acyl group substitution degree of 2.2 to 2.55. This film is characterized in that the ratio of xylose is 0.9% by mass or less and the ratio of mannose is 0.9% by mass or less with respect to 100% by mass of the sugar component constituting the film.

<Cellulose acylate>
The cellulose acylate film according to one embodiment of the present invention includes a cellulose acylate having an acyl group substitution degree of 2.2 to 2.55. By adopting cellulose acylate with a low degree of acyl group substitution in this way, high retardation development is exhibited, and even when it is an optical compensation film with high retardation, a thin film can be formed. Even when the phase difference is developed, advantages such as the fact that the draw ratio can be kept low and failures such as fracture can be avoided.

  Here, the cellulose molecule consists of many glucose units connected, and the glucose unit has three hydroxyl groups. The number of acyl groups derived from these three hydroxyl groups is called the degree of substitution.

  Examples of the cellulose acylate used in the present invention include carboxylic acid esters having about 2 to 22 carbon atoms, which may be esters of aromatic carboxylic acids, but are particularly preferably lower fatty acid esters of cellulose. The lower fatty acid in the lower fatty acid ester of cellulose means a fatty acid having 6 or less carbon atoms. The acyl group bonded to the hydroxyl group may be linear or branched or may form a ring. Furthermore, another substituent may be substituted. When the degree of substitution is the same, birefringence decreases when the number of carbon atoms in the acyl group is large. Therefore, the number of carbon atoms is preferably selected from acyl groups having 2 to 6 carbon atoms. The acyl group preferably has 2 to 4 carbon atoms, more preferably 2 to 3 carbon atoms.

  For example, cellulose acetate, cellulose propionate, cellulose butyrate and the like, cellulose acetate propio as described in JP-A Nos. 10-45804, 8-231761, US Pat. No. 2,319,052, etc. It is preferable to use mixed fatty acid esters such as nate, cellulose acetate butyrate, and cellulose acetate phthalate.

  In addition, the measurement of the acyl group substitution degree of a cellulose acylate can be implemented according to ASTM-D817-96, and a preferable acyl group substitution degree is 2.2-2.45.

  When the acyl group substitution degree of cellulose acylate is less than 2.2, deterioration of film surface quality due to increase in dope viscosity, haze-up due to increase in stretching tension, and the like may occur. Further, when the acyl group substitution degree is larger than 2.55, it is difficult to obtain a necessary phase difference.

  The number average molecular weight (Mn) of the cellulose acylate is preferable because the mechanical strength of the film from which a range of 30000 to 300000 is obtained is strong. Furthermore, the thing of 50000-200000 is used preferably.

  The ratio (Mw / Mn) of the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the cellulose acylate is preferably 1.4 to 3.0.

  In addition, the value measured using a gel permeation chromatography (GPC) shall be employ | adopted as a value of the number average molecular weight (Mn) and weight average molecular weight (Mw) of a cellulose acylate. At this time, the measurement conditions are as follows.

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

  Cellulose as a raw material for cellulose acylate is not particularly limited, but is derived from plants such as wood, cotton, hemp, flax, ramie, jute, kenaf, animals such as sea squirts, algae such as seaweed, acetic acid bacteria It may originate from any of these microorganisms. Moreover, these raw materials may be used alone or in combination of two or more. Among these, refined pulp, regenerated cellulose, cotton-derived cotton linter and cotton lint, and bacterial cellulose derived from acetic acid bacteria are preferable from the viewpoint of high cellulose purity. On the other hand, according to the present invention, as described later, by controlling the content of a specific sugar component contained in the film, even when a low-purity pulp is used as a raw material, A cellulose acylate film having excellent properties can be provided. Therefore, the effect of the present invention can be remarkably exhibited when a material that can obtain a relatively low-purity cellulose is used as a raw material.

  There is no restriction | limiting in particular also about the form of a cellulose, Any, such as powder form, granular form, cotton form, thread form, cloth form, paper form, sheet form, film form, may be sufficient. Moreover, you may use the cellulose which gave processes, such as a grinding | pulverization process. Examples of the pulverization method include a dry pulverizer such as a ball mill.

  The content of alkaline earth metals (calcium and magnesium) in cellulose acylate is preferably 150 ppm by mass or less, more preferably 70 ppm by mass or less, and particularly preferably 40 ppm by mass or less. preferable. If the content of the alkaline earth metal is within these ranges, the non-uniformity during the formation of the dope is alleviated, the excessive peeling force from the metal support during casting of the solution, and the resulting film streaks. It is also possible to prevent the occurrence of defects such as or horizontal stages.

Alkaline earth metal (Ca, Mg) content is measured by atomic absorption spectrophotometry after pre-treatment in which ash is dissolved in hydrochloric acid after complete combustion of dried cellulose acylate. To do. The measured value can be obtained in units of mass ppm as the content of each alkaline earth metal in 1 g of the completely dry cellulose ester. The following method is used as a specific pretreatment procedure for measurement.
(1) A magnetic crucible having a capacity of 50 ml that has been washed is immersed in a 2N aqueous nitric acid solution overnight.
(2) The magnetic crucible soaked in 2N nitric acid is washed with pure water, rinsed with ultrapure water, and dried in a drier.
(3) Weigh accurately 2 g of sample into a magnetic crucible.
(4) Carbonize the sample in the magnetic crucible on the electric heater.
(5) The magnetic crucible is put into an electric furnace and incinerated at 500 ° C. for about 1 hour and at 600 ° C. for about 1.5 hours.
(6) When the ash is completely white, stop the electric furnace and let it cool in the furnace.
(7) 10 ml of 0.5N hydrochloric acid aqueous solution is put in a magnetic crucible and dissolved by heating on a sand bath.
(8) The solution is allowed to cool and then transferred to a 50 ml volumetric flask using a washed funnel, and the magnetic crucible is rinsed with ultrapure water to make up the volume (hydrochloric acid concentration: 0.1 N).
(9) As a standard solution, a calcium standard solution having a concentration of 1000 ppm is diluted with a 0.1N hydrochloric acid aqueous solution and prepared at concentrations of 0.1 ppm, 0.75 ppm, and 1.5 ppm.
(10) Measured by flame atomic absorption.
The calibration curve was created by the following method. The standard solution for the calibration curve can be prepared by diluting a commercially available standard solution for atomic absorption with 0.1N hydrochloric acid solution to a concentration of 0.1, 0.75, or 1.5 ppm. For example, an atomic absorption device can be measured by a product name “AA-680” manufactured by Shimadzu Corporation.

<Content of specific impurities>
The cellulose acylate film according to this embodiment is characterized in that the content of specific impurities contained in the film is controlled to a predetermined value. Specifically, in the cellulose acylate film according to the present embodiment, the ratio of xylose in the sugar components constituting the film is 0.9% by mass or less with respect to 100% by mass of the total amount of sugar components, preferably Is 0.5% by mass or less, more preferably 0.1% by mass or less, and particularly preferably 0.05% by mass or less. In addition, the ratio of mannose in the saccharide component constituting the film is 0.9% by mass or less, preferably 0.5% by mass or less, more preferably 0% with respect to 100% by mass of the total amount of saccharide components. 0.1 mass% or less, particularly preferably 0.07 mass% or less.

  Here, xylose is a kind of aldopentose and mannose is a kind of aldohexose. According to the study by the present inventors, if the content of these sugar components in the sugar component contained in the cellulose acylate film is a value within the above-described range, while ensuring the retardation development, It has been found that small cellulose acylate films can be provided. The mechanism by which such effects are obtained by controlling the content of these sugar components as described above is not completely clear, but these sugar components have low solubility. Therefore, it is presumed that deterioration of internal haze is suppressed by reducing the content thereof. In particular, when a matting agent (fine particles), which will be described later, is added to the film, aggregation of the matting agent (fine particles) by these sugar components can be suppressed, and the effect of reducing internal haze can be even more pronounced. It is estimated.

  In addition, as a value of content of the xylose and mannose mentioned above, the value measured by the method as described in the column of the Example mentioned later shall be employ | adopted. Moreover, the detail is mentioned later about an example of the manufacturing method of the cellulose acylate film which satisfies said prescription | regulation.

<Additives>
The cellulose acylate film according to one embodiment of the present invention may contain various additives in addition to the above-described cellulose acylate. Hereinafter, additives that can be used in the present invention will be described.

(Chelating agent)
The cellulose acylate film according to this embodiment preferably contains a chelating agent. When the film contains a chelating agent, there is an advantage that aggregation of various materials contained in the film is alleviated. Moreover, it can utilize also for making it deposit and remove the impurity contained in a cellulose raw material by implementing the process of adding a chelating agent at the time of preparation of dope so that it may mention later, and is especially preferable.

Although there is no restriction | limiting in particular about the specific structure of the chelating agent used in this form, ^That whose chelate stability constant with Ca ^<2+ > is 2 or more is preferable, 5 or more are more preferable, and 10 or more are especially preferable. . About the upper limit of chelate stability constant with Ca ^<2+> of a chelating agent, it is about 12 or less from the difficulty of a compound acquisition.

Examples of the chelating agent having a chelate stability constant of 2 or more with Ca ²⁺ ions include organic carboxylic acid chelating agents, organic phosphoric acid chelating agents, inorganic phosphoric acid chelating agents, and polyhydroxy compounds.

  Specifically, diethylenetriaminepentaacetic acid (stability constant = 10.74), nitrile triacetic acid (stability constant = 6.41) (above, Cylest Co.), hydroxyiminodiacetic acid (stability constant = 5.3) ), Iminodiacetic acid (stability constant = 2.59) (Dojindo Laboratories), aminotrimethylenephosphonic acid (stability constant = 6.44), and the like. Especially, it is preferable that what has an amino group and a carboxy group is included as a chelating agent. Moreover, it is also preferable to include what has a phosphonic acid group as a chelating agent. According to such a form, the chelating agent is preferable because it can form not only a coordination with a metal but also a complex with a sugar component.

Note that the stability constant of the chelating agent with Ca ²⁺ is L. G. Sillen, A.M. E. "Stability Constants of Metal-ion Complexes" by Martell, The Chemical Society, London (1964), S.M. Chaberek, A .; E. This means a constant generally known by Martell's “Organic Sequencing Agents” Wiley (1959) and the like.

  Although there is no restriction | limiting in particular about content of the chelating agent in the cellulose acylate film which concerns on this form, Preferably it is 0.002-0.1 mass% with respect to 100 mass% of cellulose acylates, More preferably, it is 0.00. It is 02-0.05 mass%. If content of a chelating agent is 0.002 mass% or more with respect to a cellulose acylate, the reduction effect of an internal haze can express. On the other hand, when the content of the chelating agent is 1.0% by mass or less with respect to the cellulose acylate, the elution of the chelating agent can be prevented in the saponification step during the production of the polarizing plate.

(Sugar ester compound)
The cellulose acylate film according to this embodiment preferably contains a sugar ester compound. Thus, since a cellulose acylate film contains a sugar ester compound, hydrolysis of cellulose acylate can be prevented, so that the water resistance of the film can be improved. In addition, the film surface is saponified at the time of bonding with a polarizer when constituting a polarizing plate, but hydrolysis of cellulose acylate during the saponification treatment and accompanying elution into an alkaline saponification solution are also possible. Can be prevented.

  As an example of the sugar ester compound, the following general formula (I):

The compound represented by these is mentioned.

  In general formula (I), Q represents a monosaccharide or disaccharide residue, R represents an aliphatic group or an aromatic group, and m is directly bonded to the monosaccharide or disaccharide residue. 1 is the total number of — (O—C (═O) —R) groups directly bonded to the monosaccharide or disaccharide residue, and 3 ≦ m + 1 ≦ 8 and l ≠ 0.

  The compound having the structure represented by the general formula (I) is a single type of compound in which the number of hydroxyl groups (m) and the number of-(O—C (═O) —R) groups (1) are fixed. It is difficult to separate, and it is known that a compound in which several components different in m and l in the formula are mixed is obtained. Therefore, the performance as a mixture in which the number of hydroxyl groups (m) and the number of-(O—C (═O) —R) groups (1) are important is important, and the cellulose acylate film of this embodiment In this case, a compound having a structure represented by the general formula (I) with respect to haze characteristics and a mixing ratio of a component of m = 0 and a component of m> 0 is 45:55 to 0: 100. More preferably, in terms of performance and cost, the mixing ratio of the component m = 0 and the component m> 0 is in the range of 10:90 to 0.1: 99.9. In addition, the component of said m = 0 and the component of m> 0 can be measured by a high performance liquid chromatography by a conventional method.

  In the above general formula (I), Q represents a monosaccharide or disaccharide residue. Specific examples of monosaccharides include allose, altrose, glucose, mannose, gulose, idose, galactose, talose, ribose, arabinose, xylose, lyxose, and the like.

  Although the structural example of the compound which has a monosaccharide residue represented with general formula (I) below is shown, this invention is not limited to these specific examples.

  Specific examples of the disaccharide include trehalose, sucrose, maltose, cellobiose, gentiobiose, lactose, and isotrehalose.

  Although the structural example of the compound which has a disaccharide residue represented with general formula (I) below is shown, this invention is not limited to these specific examples.

  In general formula (I), R represents an aliphatic group or an aromatic group. Here, the aliphatic group and the aromatic group may each independently have a substituent.

  In general formula (I), m is the total number of hydroxyl groups directly bonded to the monosaccharide or disaccharide residue, and l is directly bonded to the monosaccharide or disaccharide residue. The total number of — (O—C (═O) —R) groups. And it is necessary that 3 ≦ m + 1 ≦ 8, and it is preferable that 4 ≦ m + 1 ≦ 8. Also, l ≠ 0. When l is 2 or more, the — (O—C (═O) —R) groups may be the same as or different from each other.

  The aliphatic group in the definition of R may be linear, branched or cyclic, preferably has 1 to 25 carbon atoms, more preferably has 1 to 20 carbon atoms, 15 is particularly preferred. Specific examples of the aliphatic group include, for example, methyl, ethyl, n-propyl, iso-propyl, cyclopropyl, n-butyl, iso-butyl, tert-butyl, amyl, iso-amyl, tert-amyl, n- Examples include hexyl, cyclohexyl, n-heptyl, n-octyl, bicyclooctyl, adamantyl, n-decyl, tert-octyl, dodecyl, hexadecyl, octadecyl, didecyl and the like.

  The aromatic group in the definition of R may be an aromatic hydrocarbon group or an aromatic heterocyclic group, and more preferably an aromatic hydrocarbon group. The aromatic hydrocarbon group preferably has 6 to 24 carbon atoms, and more preferably 6 to 12 carbon atoms. Specific examples of the aromatic hydrocarbon group include benzene, naphthalene, anthracene, biphenyl, terphenyl and the like. As the aromatic hydrocarbon group, benzene, naphthalene, and biphenyl are particularly preferable. As the aromatic heterocyclic group, those containing at least one of an oxygen atom, a nitrogen atom or a sulfur atom are preferable. Specific examples of the heterocyclic ring include, for example, furan, pyrrole, thiophene, imidazole, pyrazole, pyridine, pyrazine, pyridazine, triazole, triazine, indole, indazole, purine, thiazoline, thiadiazole, oxazoline, oxazole, oxadiazole, quinoline, Examples include isoquinoline, phthalazine, naphthyridine, quinoxaline, quinazoline, cinnoline, pteridine, acridine, phenanthroline, phenazine, tetrazole, benzimidazole, benzoxazole, benzthiazole, benzotriazole, and tetrazaindene. As the aromatic heterocyclic group, pyridine, triazine, and quinoline are particularly preferable.

  Next, although the preferable example of a compound represented by general formula (I) is shown below, this invention is not limited to these specific examples.

  (Synthesis Example: Synthesis Example of Compound Represented by General Formula (I))

Four-headed Kolben equipped with a stirrer, a reflux condenser, a thermometer and a nitrogen gas inlet tube was charged with 34.2 g (0.1 mol) of sucrose, 180.8 g (0.8 mol) of benzoic anhydride, 379. 7 g (4.8 mol) was charged, the temperature was raised while bubbling nitrogen gas from a nitrogen gas introduction tube with stirring, and an esterification reaction was carried out at 70 ° C. for 5 hours. Next, the inside of the Kolben was depressurized to 4 × 10 ² Pa or less, and after excess pyridine was distilled off at 60 ° C., the inside of the Kolben was depressurized to 1.3 × 10 Pa or less and the temperature was raised to 120 ° C. Most of the acid and benzoic acid formed were distilled off. Then, 1 L of toluene and 300 g of a 0.5% by mass aqueous sodium carbonate solution were added, and the mixture was stirred at 50 ° C. for 30 minutes and then allowed to stand to separate a toluene layer. Finally, 100 g of water is added to the collected toluene layer, and after washing with water at room temperature for 30 minutes, the toluene layer is collected, and toluene is distilled off at 60 ° C. under reduced pressure (4 × 10 2 Pa or less) to thereby give Exemplified Compound 1 A mixture of (a1), exemplary compound 2 (a2), exemplary compound 3 (a3), exemplary compound 4 (a4), and exemplary compound 5 was obtained. When the obtained mixture was analyzed by HPLC and LC-MASS, Exemplified Compound 1 (a1) was 7% by mass, Exemplified Compound 2 (a2) was 58% by mass, Exemplified Compound 3 (a3) was 23% by mass, Exemplified Compound 4 (a4) was 9% by mass, and Exemplified Compound 5 was 3% by mass. In addition, by purifying a part of the obtained mixture by silica gel column chromatography, exemplary compound 1 (a1), exemplary compound 2 (a2), exemplary compound 3 (a3), exemplary compound 4 (100% purity), respectively a4) and Exemplified Compound 5 were obtained.

(Retardation adjuster)
The cellulose acylate film according to this embodiment may contain a retardation adjusting agent. The retardation adjusting agent is an additive capable of adjusting the retardation development property of the film by its addition. There is no restriction | limiting in particular about the specific structure, A conventionally well-known knowledge can be referred suitably. Moreover, although there exists the retardation adjusting agent which has the effect of adjusting wavelength dispersion simultaneously, you may use this.

  Examples of the retardation adjusting agent that can be used in the present invention include aromatic compounds having two or more aromatic rings as described in EP 911,656A2. Two or more aromatic compounds may be used in combination. The aromatic ring of the aromatic compound includes an aromatic heterocyclic ring in addition to the aromatic hydrocarbon ring. An aromatic heterocyclic ring is particularly preferred, and the aromatic heterocyclic ring is generally an unsaturated heterocyclic ring. Of these, compounds having a 1,3,5-triazine ring are particularly preferred.

  Another example of the retardation adjusting agent is a compound disclosed in Japanese Patent Application Laid-Open No. 2010-163482 as the general formula (I). Specific examples of the general formula (I) are disclosed in paragraphs “0052” to “0058” of the publication. Moreover, the compound currently disclosed by Unexamined-Japanese-Patent No. 2010-163483 as general formula (I) can also be used as a retardation regulator similarly. Specific examples of the general formula (I) are disclosed in paragraphs “0054” to “0068” of the publication.

  It is preferable that a retardation regulator is contained in the quantity of 0.01-20 mass% with respect to 100 mass% of cellulose acylates, More preferably, it is 0.1-10 mass%.

(Plasticizer)
The cellulose acylate film according to this embodiment may contain a plasticizer. Although there is no restriction | limiting in particular about the specific form of a plasticizer, For example, a polyester plasticizer is mentioned. There is no restriction | limiting in particular about the specific structure of a polyester plasticizer, The polyester plasticizer which has an aromatic ring or a cycloalkyl ring in a molecule | numerator can be used. As a polyester plasticizer, the polyester plasticizer represented by following General formula (2) is mentioned, for example.

(Wherein B is a hydroxy group or carboxylic acid residue, G is an alkylene glycol residue having 2 to 12 carbon atoms, an aryl glycol residue having 6 to 12 carbon atoms, or an oxyalkylene glycol residue having 4 to 12 carbon atoms) A represents an alkylenedicarboxylic acid residue having 4 to 12 carbon atoms or an aryldicarboxylic acid residue having 6 to 12 carbon atoms, and n represents an integer of 1 or more.)
In the general formula (2), the alkylene glycol component having 2 to 12 carbon atoms includes ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,2-propanediol, 2-methyl 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 2 , 2-diethyl-1,3-propanediol (3,3-dimethylolpentane), 2-n-butyl-2-ethyl-1,3-propanediol (3,3-dimethylolheptane), 3-methyl- 1,5-pentanediol 1,6-hexanediol, 2,2,4-trimethyl 1,3-pentanediol, 2-ethyl 1, -Hexanediol, 2-methyl 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-octadecanediol, etc., and these glycols are one kind or a mixture of two or more kinds. Used as.

  In particular, an alkylene glycol having 2 to 12 carbon atoms is particularly preferable because of excellent compatibility with cellulose acetate.

  Examples of the aryl glycol component having 6 to 12 carbon atoms include hydroquinone, resorcin, bisphenol A, bisphenol F, bisphenol, and the like, and these glycols can be used singly or as a mixture of two or more.

  Examples of the oxyalkylene glycol component having 4 to 12 carbon atoms include diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, and tripropylene glycol. These glycols may be used alone or as a mixture of two or more. Can be used as

  Examples of the alkylene dicarboxylic acid component having 4 to 12 carbon atoms include succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, and the like. Used as a mixture of seeds and more. Examples of the arylene dicarboxylic acid component having 6 to 12 carbon atoms include phthalic acid, terephthalic acid, isophthalic acid, 1,5 naphthalene dicarboxylic acid, and 1,4 naphthalene dicarboxylic acid.

  The ester compound represented by the general formula (2) has a number average molecular weight of preferably 300 to 1500, and more preferably 400 to 1000.

  In the cellulose acylate according to the present invention, a polyester compound having a hydroxyl group (hydroxyl group) at the end is preferable in terms of compatibility.

  Although the specific compound of the ester compound represented by General formula (2) below is shown, it is not limited to this.

  The cellulose acylate film according to the present embodiment can contain a plasticizer other than the polyester plasticizer represented by the general formula (2) as necessary for obtaining the effects of the present invention.

  The plasticizer is not particularly limited, but is preferably a polycarboxylic acid ester plasticizer, a glycolate plasticizer, a phthalate ester plasticizer, a fatty acid ester plasticizer, a polyhydric alcohol ester plasticizer, or an ester plasticizer. Agent, acrylic plasticizer and the like.

  Of these, when two or more plasticizers are used, at least one plasticizer is preferably a polyhydric alcohol ester plasticizer.

  The polyhydric alcohol ester plasticizer is a plasticizer comprising an ester of a dihydric or higher aliphatic polyhydric alcohol and a monocarboxylic acid, and preferably has an aromatic ring or a cycloalkyl ring in the molecule. Preferably it is a 2-20 valent aliphatic polyhydric alcohol ester.

  The polyhydric alcohol preferably used in the present invention is represented by the following general formula (a).

(In the formula, R ₁₁ represents an n-valent organic group, n represents a positive integer of 2 or more, and the OH group represents an alcoholic and / or phenolic hydroxy group (hydroxyl group).

  Examples of preferred polyhydric alcohols include, but are not limited to, the following.

  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, galactitol, mannitol, 3-methylpentane- Examples include 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.

  There is no restriction | limiting in particular as monocarboxylic acid used for polyhydric alcohol ester, Well-known aliphatic monocarboxylic acid, alicyclic monocarboxylic acid, aromatic monocarboxylic acid, etc. can be used. Use of an alicyclic monocarboxylic acid or aromatic monocarboxylic acid is preferred in terms of improving moisture permeability and retention.

  Examples of preferred monocarboxylic acids include the following, but are 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. The inclusion of acetic acid is preferred because the compatibility with cellulose acetate increases, and it is also preferred to use a mixture of acetic acid and other monocarboxylic acids.

  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-hexanoic 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, olein Examples thereof include unsaturated fatty acids such as acid, sorbic acid, linoleic acid, linolenic acid, and arachidonic acid.

  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 1 to 3 alkoxy groups such as an alkyl group, a methoxy group or an ethoxy group are introduced into the benzene ring of benzoic acid such as benzoic acid or toluic acid, biphenylcarboxylic acid, Examples thereof include aromatic monocarboxylic acids having two or more benzene rings such as naphthalenecarboxylic acid and tetralincarboxylic acid, or derivatives thereof. Benzoic acid is particularly preferable.

  The molecular weight of the polyhydric alcohol ester is not particularly limited, but is preferably 300 to 1500, and more preferably 350 to 750. A higher molecular weight is preferred because it is less likely to volatilize, and a smaller one is preferred in terms of moisture permeability and compatibility with cellulose acetate.

  The carboxylic acid used for 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.

  Below, the specific compound of a polyhydric alcohol ester is illustrated.

  The glycolate plasticizer is not particularly limited, but alkylphthalylalkyl glycolates can be preferably used.

  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, methyl phthalyl butyl glycolate, ethyl phthalyl butyl glycolate, butyl phthalyl methyl glycolate, butyl phthalyl ethyl glycolate, propyl phthalyl butyl glycol Butyl phthalyl propyl glycolate, methyl phthalyl octyl glycolate, ethyl phthalyl octyl glycolate, octyl phthalyl methyl glycolate, octyl phthalate Ethyl glycolate, and the like.

  Examples of the phthalate ester plasticizer include diethyl phthalate, dimethoxyethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, dioctyl phthalate, dicyclohexyl phthalate, and dicyclohexyl terephthalate.

  Examples of the citrate plasticizer include acetyl trimethyl citrate, acetyl triethyl citrate, and acetyl tributyl citrate.

  Examples of fatty acid ester plasticizers include butyl oleate, methylacetyl ricinoleate, and dibutyl sebacate.

  Examples of the phosphate ester plasticizer include triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate and the like.

  The polyvalent carboxylic acid ester compound is composed of an ester of divalent or higher, preferably divalent to 20 valent polyvalent carboxylic acid and alcohol. The aliphatic polyvalent carboxylic acid is preferably 2 to 20 valent, and in the case of an aromatic polyvalent carboxylic acid or an alicyclic polyvalent carboxylic acid, it is preferably 3 to 20 valent.

  The polyvalent carboxylic acid is represented by the following general formula (b).

Formula (b): R ₁₂ (COOH) _m1 (OH) _n1
In the formula, R ₁₂ represents an (m1 + n1) -valent organic group, m1 represents a positive integer of 2 or more, n1 represents an integer of 0 or more, a COOH group represents a carboxy group, and an OH group represents an alcoholic or phenolic hydroxy group.

  Examples of preferred polyvalent carboxylic acids include, but are not limited to, the following.

  Trivalent or higher aromatic polyvalent carboxylic acids such as trimellitic acid, trimesic acid, pyromellitic acid or derivatives thereof, succinic acid, adipic acid, azelaic acid, sebacic acid, oxalic acid, fumaric acid, maleic acid, tetrahydrophthal An aliphatic polyvalent carboxylic acid such as an acid, an oxypolyvalent carboxylic acid such as tartaric acid, tartronic acid, malic acid and citric acid can be preferably used. In particular, it is preferable to use an oxypolycarboxylic acid from the viewpoint of improving retention.

  There is no restriction | limiting in particular as alcohol used for the polyhydric carboxylic acid ester compound which can be used for this invention, Well-known alcohol and phenols can be used.

  For example, an aliphatic saturated alcohol or aliphatic unsaturated alcohol having a straight chain or a side chain having 1 to 32 carbon atoms can be preferably used. It is more preferable that it is C1-C20, and it is especially preferable that it is C1-C10.

  In addition, alicyclic alcohols such as cyclopentanol and cyclohexanol or derivatives thereof, aromatic alcohols such as benzyl alcohol and cinnamyl alcohol, or derivatives thereof can also be preferably used.

  When an oxypolycarboxylic acid is used as the polycarboxylic acid, the alcoholic or phenolic hydroxy group (hydroxyl group) of the oxypolycarboxylic acid may be esterified with a monocarboxylic acid. Examples of preferred monocarboxylic acids include the following, but the present invention is not limited thereto.

  As the aliphatic monocarboxylic acid, a fatty acid having a straight chain or a side chain having 1 to 32 carbon atoms can be preferably used. It is more preferable that it is C1-C20, and it is especially preferable that it is C1-C10.

  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, and laccelic acid, undecylenic acid, olein Examples thereof include unsaturated fatty acids such as acid, sorbic acid, linoleic acid, linolenic acid, and arachidonic acid.

  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 biphenyl carboxylic acid, naphthalene carboxylic acid, and tetralin carboxylic acid. The aromatic monocarboxylic acid which has, or those derivatives can be mentioned. Particularly preferred are acetic acid, propionic acid, and benzoic acid.

  The molecular weight of the polyvalent carboxylic acid ester compound is not particularly limited, but is preferably in the range of 300 to 1000, and more preferably in the range of 350 to 750. The larger one is preferable in terms of improvement in retention, and the smaller one is preferable in terms of moisture permeability and compatibility with cellulose acetate.

  The alcohol used for the polyvalent carboxylic acid ester that can be used in the present invention may be one kind or a mixture of two or more kinds.

  The acid value of the polyvalent carboxylic acid ester compound that can be used in the present invention is preferably 1 mgKOH / g or less, and more preferably 0.2 mgKOH / g or less. Setting the acid value in the above range is preferable because the environmental fluctuation of the retardation is also suppressed.

  In addition, an acid value means the milligram number of potassium hydroxide required in order to neutralize the acid (carboxy group which exists in a sample) contained in 1g of samples. The acid value is measured according to JIS K0070.

  Examples of particularly preferred polyvalent carboxylic acid ester compounds are shown below, but the present invention is not limited thereto.

  For example, triethyl citrate, tributyl citrate, acetyl triethyl citrate (ATEC), acetyl tributyl citrate (ATBC), benzoyl tributyl citrate, acetyl triphenyl citrate, acetyl tribenzyl citrate, dibutyl tartrate, diacetyl dibutyl tartrate, Examples include tributyl trimellitic acid and tetrabutyl pyromellitic acid.

(polyester)
The cellulose acylate film according to the present embodiment preferably contains the following polyester.

(Polyester represented by general formula (d) or (e))
The cellulose acylate film according to the present embodiment preferably contains a polyester represented by the following general formula (d) or (e).

(In the formula, B1 represents a monocarboxylic acid, G represents a divalent alcohol, A represents a dibasic acid, and B1, G, and A do not contain an aromatic ring. M represents the number of repetitions. )

(In the formula, B2 represents a monoalcohol, G represents a divalent alcohol, A represents a dibasic acid, and B2, G, and A do not contain an aromatic ring. N represents the number of repetitions.)
In the general formulas (d) and (e), B1 represents a monocarboxylic acid component, B2 represents a monoalcohol component, G represents a divalent alcohol component, A represents a dibasic acid component, and these are synthesized. It represents what has been done. B1, B2, G, and A are all characterized by containing no aromatic ring. m and n represent the number of repetitions.

  There is no restriction | limiting in particular as monocarboxylic acid represented by B1, Well-known aliphatic monocarboxylic acid, alicyclic monocarboxylic acid, etc. can be used.

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

  As the aliphatic monocarboxylic acid, a straight-chain or side-chain fatty acid having 1 to 32 carbon atoms can be preferably used. The number of carbon atoms is more preferably 1-20, and particularly preferably 1-12. When acetic acid is contained, the compatibility with cellulose acylate is increased, and it is also preferable to use a mixture of acetic acid and another monocarboxylic acid.

  Preferred aliphatic monocarboxylic acids include formic acid, 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, Saturated fatty acids such as tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, serotic acid, heptacosanoic acid, montanic acid, mellicic acid, and laxelic acid; Examples thereof include unsaturated fatty acids such as acid, oleic acid, sorbic acid, linoleic acid, linolenic acid, and arachidonic acid.

  The monoalcohol component represented by B2 is not particularly limited, and known alcohols can be used. For example, an aliphatic saturated alcohol or aliphatic unsaturated alcohol having a straight chain or a side chain having 1 to 32 carbon atoms can be preferably used. The number of carbon atoms is more preferably 1-20, and particularly preferably 1-12.

  Examples of the divalent alcohol component represented by G include the following, but the present invention is not limited thereto. For example, ethylene glycol, diethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, 1,5-pentanediol, , 6-hexanediol, 1,5-pentylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, etc., among which ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1 , 2-butylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, 1,6-hexanediol, diethylene glycol and triethylene glycol are preferred, and 1,3-propylene glycol, 1,4 Butylene glycol 1,6-hexanediol, diethylene glycol is preferably used.

  The dibasic acid (dicarboxylic acid) component represented by A is preferably an aliphatic dibasic acid or an alicyclic dibasic acid. Examples of the aliphatic dibasic acid include malonic acid, succinic acid, glutaric acid, Adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedicarboxylic acid, dodecanedicarboxylic acid, etc., in particular, aliphatic dicarboxylic acid having 4 to 12 carbon atoms, at least one selected from these is used Can be done. That is, two or more dibasic acids may be used in combination.

  m and n represent the number of repetitions and are preferably 1 or more and 170 or less.

(Polyester represented by general formula (f) or (g))
The cellulose acylate film according to the present embodiment preferably contains a polyester represented by the following general formula (f) or (g).

(In the formula, B1 represents a monocarboxylic acid having 1 to 12 carbon atoms, G represents a divalent alcohol having 2 to 12 carbon atoms, and A represents a dibasic acid having 2 to 12 carbon atoms. B1, G , A does not contain an aromatic ring, and m represents the number of repetitions.)

(In the formula, B2 represents a monoalcohol having 1 to 12 carbon atoms, G represents a divalent alcohol having 2 to 12 carbon atoms, and A represents a dibasic acid having 2 to 12 carbon atoms. B2, G, (A does not contain an aromatic ring. N represents the number of repetitions.)
In the general formulas (f) and (g), B1 represents a monocarboxylic acid component, B2 represents a monoalcohol component, G represents a divalent alcohol component having 2 to 12 carbon atoms, and A represents 2 to 2 carbon atoms. Twelve dibasic acid components are represented and synthesized by them. B1, G, and A do not contain an aromatic ring. m and n represent the number of repetitions. B1 and B2 have the same meanings as B1 and B2 in the general formula (d) or (e) described above. G and A correspond to an alcohol component or a dibasic acid component having 2 to 12 carbon atoms in G and A in the general formula (d) or (e).

  The number average molecular weight of the polyester is 1000 or more and 10,000 or less. If the number average molecular weight is less than 1000, breakage tends to occur at high temperature and high magnification stretching, and if it exceeds 10,000, whitening due to phase separation tends to increase.

  Polycondensation of polyester is performed by a conventional method. For example, a direct reaction of the dibasic acid with a glycol, a hot melt condensation method using the dibasic acid or an alkyl ester thereof, for example, a polyesterification reaction or a transesterification reaction between a methyl ester of a dibasic acid and a glycol. Alternatively, it can be easily synthesized by any method of dehydrohalogenation reaction between acid chloride of these acids and glycol, but it is preferable to synthesize a polyester having a weight average molecular weight not so large by direct reaction.

  Polyester having a high distribution on the low molecular weight side has very good compatibility with cellulose acylate, and after film formation, a cellulose acylate film having low moisture permeability and high transparency can be obtained. A conventional method can be used as a method for adjusting the molecular weight without particular limitation. For example, although depending on the polymerization conditions, when a method of blocking the molecular ends with a monovalent acid or monovalent alcohol is used, the molecular weight is adjusted by adjusting the addition amount of these monovalent raw material compounds. be able to. In this case, it is preferable from the viewpoint of the stability of the polymer to adjust the addition amount of the monovalent acid. For example, acetic acid, propionic acid, butyric acid and the like can be mentioned, but it is preferable to select those which are not distilled out of the system during the polycondensation reaction but are easily distilled off when stopped and removed from the reaction system. For this purpose, a plurality of compounds may be used in combination. In the case of a direct reaction, the weight average molecular weight can also be adjusted by measuring the timing for stopping the reaction based on the amount of water produced during the reaction. In addition, the molecular weight can be adjusted by biasing the number of moles of glycol or dibasic acid to be charged, or the molecular weight can be adjusted by controlling the reaction temperature.

  The polyester is preferably contained in an amount of 1 to 40% by mass with respect to 100% by mass of cellulose acylate, and the polyester represented by the general formula (f) or (g) is in an amount of 2 to 30% by mass. It is preferably included. In particular, it is preferably contained in an amount of 5 to 15% by mass.

(UV absorber)
The cellulose acylate film according to this embodiment can also contain an ultraviolet absorber depending on its application. The ultraviolet absorber is intended to improve durability by absorbing ultraviolet light having a wavelength of 400 nm or less. In particular, the transmittance at a wavelength of 370 nm is preferably 10% or less, more preferably 5% or less, Preferably it is 2% or less. In addition, when the retardation film which concerns on this invention contains a ultraviolet absorber, it is preferable that the said ultraviolet absorber is contained 2 or more types.

  Although the ultraviolet absorber used in the present invention is not particularly limited, for example, oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, triazine compounds, nickel complex compounds, inorganic powders Examples include the body.

  For example, 5-chloro-2- (3,5-di-sec-butyl-2-hydroxylphenyl) -2H-benzotriazole, (2-2H-benzotriazol-2-yl) -6- (linear and side Chain dodecyl) -4-methylphenol, 2-hydroxy-4-benzyloxybenzophenone, 2,4-benzyloxybenzophenone, etc., and tinuvin 109, tinuvin 171, tinuvin 234, tinuvin 326, tinuvin 327, tinuvin 328, etc. These are commercially available products made by Ciba Japan Co., Ltd. and can be preferably used.

  The UV absorbers preferably used in the present invention are benzotriazole UV absorbers, benzophenone UV absorbers, and triazine UV absorbers, particularly preferably benzotriazole UV absorbers and benzophenone UV absorbers. . In addition, a discotic compound such as a compound having a 1,3,5 triazine ring is also preferably used as the ultraviolet absorber. As the UV absorber, a polymer UV absorber can also be preferably used, and in particular, a polymer type UV absorber described in JP-A-6-148430 is preferably used.

  The method of adding the UV absorber can be added to the dope after dissolving the UV absorber in an alcohol such as methanol, ethanol or butanol, an organic solvent such as methylene chloride, methyl acetate, acetone or dioxolane or a mixed solvent thereof. Or you may add directly in dope composition. Moreover, what does not melt | dissolve in an organic solvent like an inorganic powder should just add to a dope, after using a dissolver and a sand mill in an organic solvent and a cellulose acetate, disperse | distributing.

  Although there is no restriction | limiting in particular about content of the ultraviolet absorber in the cellulose acylate film which concerns on this form, Preferably it is 0.01-10 mass% with respect to 100 mass% of cellulose acylates, More preferably, it is 0.1. ˜5 mass%.

(Infrared absorber)
The cellulose acylate film according to this embodiment may include an infrared absorber. Also by adopting such a configuration, the reverse wavelength dispersion of the film can be adjusted.

  The infrared absorber preferably has a maximum absorption in a wavelength region of 750 to 1100 nm, and more preferably has a maximum absorption in a wavelength region of 800 to 1000 nm. Moreover, it is preferable that the infrared absorber has substantially no absorption in the visible region.

  As the infrared absorbing agent, it is preferable to use an infrared absorbing dye or an infrared absorbing pigment, and it is particularly preferable to use an infrared absorbing dye.

  The infrared absorbing dye includes an organic compound and an inorganic compound. It is preferable to use an infrared absorbing dye that is an organic compound. Organic infrared absorbing dyes include cyanine compounds, metal chelate compounds, aminium compounds, diimonium compounds, quinone compounds, squarylium compounds, and methine compounds. The infrared absorbing dye is described in Coloring Materials, 61 [4] 215-226 (1988), and Chemical Industry, 43-53 (1986, May).

  Examining the types of dyes from the viewpoint of infrared absorption function or absorption spectrum, infrared absorbing dyes developed in the technical field of silver halide photographic light-sensitive materials are excellent. Examples of infrared absorbing dyes developed in the technical field of silver halide photographic light-sensitive materials include dihydroperimidine squarylium dyes (described in US Pat. No. 5,380,635 and Japanese Patent Application No. 8-189817), cyanine dyes Nos. 62-123454, 3-138640, 3-221542, 3-226636, 5-313305, 6-43583, Japanese Patent Application No. 7-269097 and European Patent No. 0430244), pyrylium dyes (described in JP-A-3-138640 and JP-A-3-21542), diimonium dyes (described in JP-A-3-138640 and JP-A-3-21542), pyrazolopyridone Dyes (described in JP-A-2-282244), indoaniline dyes (JP-A-5-323500) No. 5-323501), polymethine dyes (Japanese Unexamined Patent Publication Nos. 3-26765 and 4-190343 and European Patent No. 377961), and oxonol dyes (Japanese Unexamined Patent Publication No. 3-9346). Description), anthraquinone dyes (described in JP-A-4-13654), naphthalocyanine dyes (described in US Pat. No. 5,099,899) and naphtholactam dyes (described in European Patent 568267). As for these infrared absorbers, only 1 type may be used independently and 2 or more types may be used together.

  Although there is no restriction | limiting in particular about content of the infrared absorber in the cellulose acylate film which concerns on this form, Preferably it is 0.01-10 mass% with respect to 100 mass% of cellulose acylates, More preferably, it is 0.1. ˜5 mass%.

(Matting agent (fine particles))
In the cellulose acylate film according to the present embodiment, for example, silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, kaolin, talc, calcined calcium silicate, hydrated calcium silicate, silica It is preferable to contain inorganic fine particles such as aluminum oxide, magnesium silicate and calcium phosphate and fine particles such as a crosslinked polymer as a matting agent. Of these, silicon dioxide is preferable because it can reduce the haze of the film.

  The primary average particle diameter of the fine particles is preferably 20 nm or less, more preferably 5 to 16 nm, and particularly preferably 5 to 12 nm.

  These fine particles preferably form secondary particles having a particle size of 0.1 to 5 μm and are contained in the film, and a preferable average particle size is 0.1 to 2 μm, more preferably 0.2 to 0. .6 μm. Thereby, the unevenness | corrugation about 0.1-1.0 micrometer high can be formed in the film surface, and this can give appropriate slipperiness to the film surface.

  The primary average particle diameter of the fine particles used in the present invention is measured by observing the particles with a transmission electron microscope (magnification 500,000 to 2,000,000 times), observing 100 particles, measuring the particle diameter, and measuring the average. Let the value be the primary average particle size.

  The apparent specific gravity of the fine particles is preferably 70 g / liter or more, more preferably 90 to 200 g / liter, and particularly preferably 100 to 200 g / liter. A higher apparent specific gravity is preferable because a high-concentration dispersion can be produced and haze and aggregates are improved, and it is particularly preferably used when preparing a dope having a high solid content concentration.

  Silicon dioxide fine particles having an average primary particle diameter of 20 nm or less and an apparent specific gravity of 70 g / liter or more are, for example, a mixture of vaporized silicon tetrachloride and hydrogen burned in air at 1000 to 1200 ° C. Can be obtained. For example, Aerosil R812, Aerosil 200V, Aerosil R972V (above, manufactured by Nippon Aerosil Co., Ltd.) are commercially available and can be used.

  The apparent specific gravity described above is calculated by the following equation by taking a certain amount of silicon dioxide fine particles in a graduated cylinder, measuring the weight at this time.

  Examples of the method for preparing the fine particle dispersion used in the present invention include the following three types.

<< Preparation Method A >>
After stirring and mixing the solvent and fine particles, dispersion is performed with a disperser. This is a fine particle dispersion. The fine particle dispersion is added to the dope solution and stirred.

<< Preparation Method B >>
After stirring and mixing the solvent and fine particles, dispersion is performed with a disperser. This is a fine particle dispersion. Separately, a small amount of cellulose acylate is added to the solvent and dissolved by stirring. The fine particle dispersion is added to this and stirred. This is a fine particle addition solution. The fine particle additive solution is sufficiently mixed with the dope solution using an in-line mixer.

<< Preparation Method C >>
Add a small amount of cellulose acylate to the solvent and stir to dissolve. Fine particles are added to this and dispersed by a disperser. This is a fine particle addition solution. The fine particle additive solution is sufficiently mixed with the dope solution using an in-line mixer.

  Preparation method A is excellent in dispersibility of silicon dioxide fine particles, and preparation method C is excellent in that silicon dioxide fine particles are difficult to re-aggregate. Among them, the preparation method B described above is a preferable preparation method that is excellent in both dispersibility of the silicon dioxide fine particles and difficulty in reaggregation of the silicon dioxide fine particles.

《Distribution method》
The concentration of silicon dioxide when the silicon dioxide fine particles are mixed and dispersed with a solvent is preferably 5 to 30% by mass, more preferably 10 to 25% by mass, and most preferably 15 to 20% by mass. A higher dispersion concentration is preferable because liquid turbidity with respect to the added amount tends to be low, and haze and aggregates are improved.

  The solvent used is preferably lower alcohols such as methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol and the like. Although it does not specifically limit as solvents other than a lower alcohol, It is preferable to use the solvent used at the time of film formation of a cellulose acylate.

  The addition amount of fine particles (matting agent) with respect to cellulose acylate is preferably 0.01 to 5.0% by mass, and 0.05 to 1.0% by mass with respect to 100% by mass of cellulose acylate. More preferred is 0.1 to 0.5% by mass. The larger the amount added, the better the dynamic friction coefficient, and the smaller the amount added, the less aggregate.

  As the disperser, a normal disperser can be used. Dispersers can be broadly divided into media dispersers and medialess dispersers. For dispersing the silicon dioxide fine particles, a medialess disperser is preferable from the viewpoint of reducing 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.

  When processing with a high-pressure dispersion apparatus, for example, the maximum pressure condition inside the apparatus is preferably 9.807 MPa or more in a thin tube having a tube diameter of 1 to 2000 μm. More preferably, it is 19.613 MPa or more. Further, at that time, those having a maximum reaching speed of 100 m / second or more and those having a heat transfer speed of 420 kJ / hour or more are preferable. Examples of the high-pressure dispersion apparatus include an ultra-high pressure homogenizer (trade name: Microfluidizer) manufactured by Microfluidics Corporation and a nanomizer manufactured by Nanomizer, and other manton gorin type high-pressure dispersion apparatuses such as Izumi Food Machinery Co., Ltd. Examples thereof include a homogenizer and UHN-01 manufactured by Sanwa Machinery Co., Ltd.

  In addition, casting a dope containing fine particles so as to be in direct contact with the casting support is preferable because a film having high slip properties and low haze can be obtained.

(Coloring agent)
The retardation film according to the present invention may contain a colorant. The “colorant” means a dye or a pigment. In the present invention, those having an effect of making the color tone of the liquid crystal screen blue, adjusting the yellow index, and reducing haze are particularly preferable. Various dyes and pigments can be used as the colorant, and anthraquinone dyes, azo dyes, phthalocyanine pigments and the like are particularly effective.

≪Method for producing cellulose acylate film≫
Although there is no restriction | limiting in particular about the manufacturing method of the cellulose acylate film which concerns on this invention, For example, it is possible to manufacture the cellulose acylate film which concerns on this invention by performing the process which deposits an impurity in the state of dope. . That is, the method for producing a cellulose acylate film according to another embodiment of the present invention includes:
A dope preparation step of preparing a dope containing cellulose acylate having an acyl group substitution degree of 2.2 to 2.55;
A deposit removing step of depositing and removing components other than the cellulose acylate contained in the dope; and
The film obtained by casting the dope obtained in the deposit removing step on a support is dried, peeled, and then stretched at least in the width direction.

  Hereafter, the preferable form of this manufacturing method is demonstrated in detail.

  The cellulose acylate film is obtained by stretching a film obtained by casting a cellulose composition containing a cellulose acylate and an additive on a support in the longitudinal direction and / or the transverse direction simultaneously or sequentially. It is obtained by this. Examples of such a production method include a solution casting method and a melt casting method, both of which can be employed, and a solution casting method is particularly preferably used.

  First, the process for preparing the dope (dope preparation process) will be described. In this step, a dope containing cellulose acylate having an acyl group substitution degree of 2.2 to 2.55 is prepared. Since the details of the cellulose acylate used in this case are as described above, the description thereof is omitted here.

  The concentration of cellulose acylate in the dope is preferably higher because the drying load after casting on the metal support can be reduced, but if the concentration of cellulose acylate is too high, the load during filtration increases and the filtration accuracy Becomes worse. As a density | concentration which makes these compatible, 10-35 mass% is preferable, More preferably, it is 15-25 mass%.

  The solvent used for the preparation of the dope may be used alone or in combination of two or more, but it is preferable in terms of production efficiency to use a mixture of a good solvent and a poor solvent of cellulose acylate, A larger amount of good solvent is preferred from the viewpoint of the solubility of cellulose acylate.

  The preferable range of the mixing ratio of the good solvent and the poor solvent is 70 to 98% by mass for the good solvent and 2 to 30% by mass for the poor solvent. Here, regarding the good solvent and the poor solvent, those that dissolve the cellulose acylate used alone are defined as good solvents, and those that swell or do not dissolve alone are defined as poor solvents. Therefore, depending on the substitution degree of cellulose acylate, even the same solvent may be a good solvent or a poor solvent.

  The good solvent candidate is not particularly limited, and examples thereof include organic halogen compounds such as methylene chloride, dioxolanes, acetone, methyl acetate, and methyl acetoacetate. Particularly preferred is methylene chloride or methyl acetate.

  Moreover, although it does not specifically limit as a candidate of a poor solvent, For example, methanol, ethanol, n-butanol, cyclohexane, cyclohexanone etc. are used preferably. Moreover, it is preferable that 0.01-2 mass% of water is contained in dope. In addition, the solvent used for melt | dissolving a cellulose acylate at the time of preparation of dope is collect | recovered after removing from a film by drying at the film-forming process, and is normally recycled.

  The recovered solvent may contain trace amounts of additives added to cellulose acylate, such as plasticizers, UV absorbers, polymers, and monomer components. Can be purified and reused if necessary.

  As a method for dissolving cellulose acylate when preparing the dope described above, a general method can be used. When heating and pressurization are combined, it is possible to heat above the boiling point at normal pressure.

  It is preferable to stir and dissolve while heating at a temperature that is equal to or higher than the boiling point of the solvent at normal pressure and that the solvent does not boil under pressure, in order to prevent the generation of massive undissolved materials called gels and mamaco.

  In addition, a method in which cellulose acetate is mixed with a poor solvent and wetted or swollen, and then a good solvent is added and dissolved is also preferably used.

  The pressurization may be performed by a method of injecting an inert gas such as nitrogen gas or a method of increasing the vapor pressure of the solvent by heating. Heating is preferably performed from the outside. For example, a jacket type is preferable because temperature control is easy.

  A higher heating temperature with the addition of a solvent is preferable from the viewpoint of the solubility of cellulose acylate, but if the heating temperature is too high, the required pressure increases and the productivity deteriorates.

  A preferable heating temperature is 45 to 120 ° C, more preferably 60 to 110 ° C, and still more preferably 70 ° C to 105 ° C. The pressure is adjusted so that the solvent does not boil at the set temperature. Alternatively, a cooling dissolution method is also preferably used, whereby cellulose acylate can be dissolved in a solvent such as methyl acetate.

  Next, a deposit removing step is performed. In this step, at least one component other than cellulose acylate contained in the dope prepared above is deposited to remove the deposit. Here, the impurity to be deposited in the deposition removing step is not particularly limited as long as it is a component other than cellulose acylate. However, according to the study by the present inventors, the dope containing cellulose acylate contains ultra-low-substituted cellulose acylate derived from the cellulose acylate production process, hemicellulose derived from a cellulose raw material, and the like. It was found that the internal haze of the resulting cellulose acylate film was increased, and as a result, when the film was used for applications such as an optical compensation film, problems such as a decrease in contrast were caused. Therefore, in the deposit removal step in the production method according to this embodiment, it is preferable to deposit and remove at least one (preferably both) of the above-described ultra-low-substituted cellulose acylate and hemicellulose. The “ultra-low-substituted cellulose acylate” means a cellulose acylate having a smaller degree of substitution than the cellulose acylate contained essentially in the cellulose acylate film in the present invention, specifically, acyl group substitution. Cellulose acylate having a degree of less than 2.2. “Hemicellulose” is a general term for water-insoluble polysaccharides obtained by removing cellulose and pectin from the constituents of plant cell wall polysaccharides. These include pentose homopolysaccharides (xylan, araban, etc.) and hexose homopolysaccharides (mannan). Etc.) as well as heteropolysaccharides composed of a plurality of different monosaccharides (mannose, galactose, xylose, arabinose, etc.).

  The mechanism by which the contents of xylose and mannose in the resulting film are reduced by depositing and removing components other than cellulose acylate as described above is not completely clear, but is added in the present invention. Since it can be removed only in the region, in addition to chelation with metal, it is considered that the chelating agent interacts with the hydroxyl group of xylose and mannose to form a complex and is efficiently removed in that form.

  There is no particular limitation on a specific method for depositing components other than cellulose acylate, as typified by those described above, and conventionally known knowledge can be referred to as appropriate. For example, a method of adding a chelating agent to a dope containing cellulose acylate at the time of preparation of the dope, as described in Examples described later, can be mentioned. Thereby, components other than the cellulose acylate as described above can be deposited. At this time, the specific form (and its preferred form) of the chelating agent that can be added is as described above, and therefore the description thereof is omitted here.

  Moreover, in such a form, there is no restriction | limiting in particular about the addition amount of the chelating agent to dope, However, Preferably it is 0.2-2.0 mass% with respect to 100 mass% of cellulose acylate, More preferably 0.5 to 1.2% by mass. When the addition amount of the chelating agent is 0.2% by mass or more with respect to the cellulose acylate, components (impurities) other than the cellulose acylate can be sufficiently deposited. On the other hand, if the content of the chelating agent is 2.0% by mass or less based on the cellulose acylate, it is preferable from the viewpoint of removal efficiency.

  In addition, the method for depositing components other than cellulose acylate in the deposition removing step is not limited to the addition of the chelating agent described above. Other methods include, for example, a method in which the dope is cooled to crystallize and precipitate components other than cellulose acylate, and the solid content concentration of the dope is increased by removing the solvent, so that components other than cellulose acylate The method of crystallizing and precipitating is also exemplified. Of course, other methods may be used.

  In the deposit removing step, as described above, after depositing components other than cellulose acylate, the deposit is removed. There is no particular limitation on the method for removing the deposit, and conventionally known knowledge can be referred to as appropriate, but preferably removal by filtration can be employed.

  Specifically, the dope containing the deposit is filtered using an appropriate filter medium such as filter paper. As the filter medium, it is preferable that the absolute filtration accuracy is small. However, if the absolute filtration accuracy is too small, there is a problem that the filter medium is likely to be clogged. For this reason, a filter medium with an absolute filtration accuracy of 0.008 mm or less is preferable, a filter medium with 0.001 to 0.008 mm is more preferable, and a filter medium with 0.003 to 0.006 mm is more preferable. There are no particular restrictions on the material of the filter medium, and ordinary filter media can be used. However, plastic filter media such as polypropylene and Teflon (registered trademark), and metal filter media such as stainless steel do not drop off fibers. preferable. The dope can be filtered by a normal method, but the method of filtering while heating at a temperature not lower than the boiling point of the solvent at normal pressure and in a range where the solvent does not boil under pressure is the filtration pressure before and after filtration. The increase in the difference (referred to as differential pressure) is small and preferable. The preferable temperature at the time of filtration is 45-120 degreeC, 45-70 degreeC is more preferable, and it is further more preferable that it is 45-55 degreeC. A smaller filtration pressure is preferred. The filtration pressure is preferably 1.6 MPa or less, more preferably 1.2 MPa or less, and further preferably 1.0 MPa or less.

  When a matting agent (fine particles) is added to the dope, the step of adding the matting agent (fine particles) to the dope is preferably performed after the above-described deposit removal step. This is because, for example, when the deposit is to be removed by filtration and the mat agent (fine particles) is already included in the dope, the mat agent (fine particles) is also removed together with the deposit. On the other hand, if components other than cellulose acylate are removed as a deposit by filtration or the like in the deposit removing step and then a matting agent (fine particles) is added, the above-described problems can be prevented. In addition, there is no particular limitation on the timing of adding a component that can be dissolved in the dope (such as a sugar ester compound or a plasticizer) to the dope, but in order to deposit components other than cellulose acylate as a deposit, The solubility of the various additives is preferably small. For this reason, it is preferable to add the additive component that can be dissolved in the dope after the deposit removing step, similarly to the matting agent (fine particles).

Note that if the matting agent (fine particles) contains even a small amount of coarse particles having a relatively large particle size, there is a possibility that bright spot foreign matter may be generated when the cellulose acylate film is used for an optical compensation film or the like. . For this reason, it is preferable to add the matting agent (fine particles) to the dope after removing coarse particles in advance, or to perform a filtration step for removing the coarse particles after addition to the dope. In addition, the bright spot foreign matter is arranged in a crossed Nicols state with two polarizing plates, a cellulose acylate film is placed between them, and light is applied from one polarizing plate side, from the other polarizing plate side. It is a point (foreign matter) where light from the opposite side appears to leak when observed, and the number of bright spots having a diameter of 0.01 mm or more is preferably 200 / cm ² or less. Further, the number of bright spots is more preferably 100 pieces / cm ² or less, further preferably 50 pieces / m ² or less, and particularly preferably 0 to 10 pieces / cm ² . Further, it is preferable that the number of bright spots of 0.01 mm or less is small.

  Subsequently, the dope prepared above is cast on an endless metal support that moves infinitely (casting process; casting process).

  The metal support in the casting process preferably has a mirror-finished surface, and a stainless steel belt or a drum whose surface is plated with a casting is preferably used as the metal support.

  The cast width can be 1 to 4 m. The surface temperature of the metal support in the casting step is −50 ° C. to a temperature lower than the boiling point of the solvent, and a higher temperature is preferable because the web can be dried faster. May deteriorate.

  A preferable support temperature is 0 to 55 ° C, and more preferably 25 to 50 ° C. Alternatively, it is also a preferable method that the web is gelled by cooling and peeled from the drum in a state containing a large amount of residual solvent.

  The method for controlling the temperature of the metal support is not particularly limited, and there are a method of blowing hot air or cold air, and a method of contacting hot water with the back side of the metal support. It is preferable to use warm water because heat transfer is performed efficiently, so that the time until the temperature of the metal support becomes constant is short. When warm air is used, wind at a temperature higher than the target temperature may be used.

  In order for the cellulose acylate film to exhibit good flatness, the residual solvent amount when peeling the web from the metal support is preferably 10 to 150% by mass, more preferably 20 to 40% by mass or 60 to 130% by mass. %, Particularly preferably 20 to 30% by mass or 70 to 120% by mass.

  In the present invention, the residual solvent amount is defined by the following formula.

(In the formula, M represents the mass of a sample collected during or after the production of the web or film, and N is the mass after heating the sample at 115 ° C. for 1 hour.)
Furthermore, the film obtained by casting the dope is dried as a web. In this drying step, it is preferable that the web is peeled off from the metal support and further dried to make the residual solvent amount 1% by mass or less. More preferably, it is 0.1 mass% or less, Most preferably, it is 0-0.01 mass%. In the drying process, a roll drying method (a method in which webs are alternately passed through a plurality of rolls arranged above and below) and a method of drying while transporting the web by a tenter method are adopted. The means for drying the web is not particularly limited, and can be generally performed with hot air, infrared rays, a heating roll, microwave, or the like, but from the viewpoint of simplicity, it is preferably performed with hot air. The drying temperature in the web drying process is preferably increased stepwise from 40 to 200 ° C.

  Subsequently, the obtained web is stretched. In this stretching process, it is particularly preferable to perform stretching in the width direction (lateral direction) by a tenter method in which both ends of the web are gripped by clips or the like. Peeling is preferably performed at a peeling tension of 300 N / m or less.

  The means for drying the web is not particularly limited, and can be generally performed with hot air, infrared rays, a heating roll, microwave, or the like, but it is preferably performed with hot air in terms of simplicity.

  The drying temperature in the web drying step is preferably increased stepwise from 40 to 200 ° C.

  The film thickness of the cellulose acylate film of the present invention is not particularly limited, but is preferably 10 to 200 μm, more preferably 10 to 100 μm, and further preferably 20 to 60 μm.

  The cellulose acylate film of the present invention has a width of 1 to 4 m. In particular, those having a width of 1.4 to 4 m are preferably used, and particularly preferably 1.6 to 3 m. If it exceeds 4 m, conveyance becomes difficult.

  The cellulose acylate film of the present invention has a retardation Ro defined by the formula (I) in the in-plane direction from the viewpoint of taking advantage of high retardation development, although the required retardation is different depending on the required optical compensation effect. Is preferably 30 nm or more, more preferably in the range of 30 to 200 nm, and still more preferably in the range of 30 to 90 nm. On the other hand, the retardation Rth in the thickness direction defined by the formula (II) is preferably 70 nm or more, and more preferably in the range of 70 to 300 nm. In addition, about the measuring method of retardation, it describes in the column of the Example mentioned later.

(Where nx is the refractive index in the slow axis direction in the film plane, ny is the refractive index in the fast axis direction in the film plane, nz is the refractive index in the thickness direction of the film, and d is (The thickness of the film (nm).)
Although there is no restriction | limiting in particular as an adjustment method of a phase difference, The method of adjusting with the conditions (drawing ratio etc.) at the time of extending | stretching process is common.

  In order to obtain the target retardation values Ro and Rth in the present invention, it is preferable that the cellulose acylate film has the structure of the present invention, and the refractive index is controlled by controlling the transport tension and stretching. For example, the retardation value can be changed by lowering or increasing the tension in the longitudinal direction.

  In addition, the retardation value can be changed by biaxially stretching or uniaxially stretching sequentially or simultaneously with respect to the longitudinal direction (film forming direction) of the film and the direction orthogonal to the film plane, that is, the width direction. it can.

  The draw ratios in the biaxial directions perpendicular to each other are preferably in the range of 0.8 to 1.5 times in the casting direction and 1.1 to 2.5 times in the width direction, respectively. It is preferable to carry out in the range of 0.8 to 1.0 times in the direction and 1.25 to 2.5 times in the width direction.

  The stretching temperature is preferably 120 ° C. to 200 ° C., more preferably 130 ° C. to 180 ° C., and more preferably 140 ° C. to 170 ° C. or less. The amount of residual solvent in the film during stretching is preferably 15 to 0%, and more preferably 10 to 0%. Specifically, it is preferable to stretch at 155 ° C. with a residual solvent amount of 11%, or at 155 ° C. with a residual solvent amount of 2%. Alternatively, it is preferable to stretch at 160 ° C. with a residual solvent amount of 11%, or at 160 ° C. with a residual solvent amount of less than 1%.

  There is no particular limitation on the method of stretching the web. For example, a method in which a difference in peripheral speed is applied to a plurality of rolls, and the roll peripheral speed difference is used to stretch in the longitudinal direction between the rolls. And a method of stretching in the vertical direction, a method of stretching in the horizontal direction and stretching in the horizontal direction, a method of stretching in the vertical and horizontal directions and stretching in both the vertical and horizontal directions, and the like. Of course, these methods may be used in combination.

  In the case of the so-called tenter method, driving the clip portion by a linear drive method is preferable because smooth stretching can be performed and the risk of breakage and the like can be reduced.

  These width maintenance or lateral stretching in the film forming step is preferably performed by a tenter, and may be a pin tenter or a clip tenter.

  The slow axis or the fast axis of the cellulose acylate film of the present invention is present in the film plane, and θ1 is preferably −1 ° or more and + 1 ° or less when the angle formed with the film forming direction is θ1. More preferably, it is 0.5 ° or more and + 0.5 ° or less.

  This θ1 can be defined as an orientation angle, and θ1 can be measured using an automatic birefringence meter KOBRA-21ADH (Oji Scientific Instruments). Each of θ1 satisfying the above relationship can contribute to obtaining high luminance in a display image, suppressing or preventing light leakage, and contributing to obtaining faithful color reproduction in a color liquid crystal display device.

<Physical properties of cellulose acylate film>
The moisture permeability of the cellulose acylate film of the present invention is preferably 300 to 1800 g / m ² · 24 h at 40 ° C. and 90% RH, more preferably 400 to 1500 g / m ² · 24 h, and 40 to 1300 g / m ² · 24 h. Is particularly preferred. The moisture permeability can be measured according to the method described in JIS Z 0208.

  The cellulose acylate film of the present invention preferably has a breaking elongation of 10 to 80%, more preferably 20 to 50%.

  The visible light transmittance of the cellulose acylate film of the present invention is preferably 90% or more, and more preferably 93% or more.

  The internal haze of the cellulose acylate film of the present invention is preferably less than 1%, particularly preferably 0 to 0.1%, and most preferably 0 to 0.03%.

≪Usage≫
(Liquid crystal display device)
The retardation film according to the present invention is used in, for example, a liquid crystal display device. In this case, the retardation film preferably has a function as a polarizing plate protective film for a liquid crystal display device. In this case, the in-plane retardation Ro described above is obtained when the two polarizing plates are arranged in crossed Nicols and the liquid crystal cell is arranged between the polarizing plates when observed obliquely from the normal line of the display surface. It mainly compensates for light leakage due to deviation of the polarizing plate from the crossed Nicols state. On the other hand, the retardation Rth in the thickness direction is mainly caused by the birefringence of the liquid crystal cell similarly observed when viewed from an oblique direction when the liquid crystal cell is in a black display state in the TN mode or VA mode, particularly in the MVA mode. To help compensate.

  Then, the detail of the polarizing plate which used the cellulose acylate film which concerns on this invention as an optical compensation film and the protective film of one side of a polarizer is demonstrated.

  The polarizing plate can be produced by a general method. The back surface side of the cellulose acylate film according to the present invention is subjected to alkali saponification treatment, and the treated film is bonded to at least one surface of the polarizer to produce a polarizing plate.

  Here, the polarizer, which is the main component of the polarizing plate, is an element that passes only light having a plane of polarization in a certain direction, and a typical polarizer currently known is a polyvinyl alcohol polarizing film. There are one in which iodine is dyed on a polyvinyl alcohol film and one in which a dichroic dye is dyed. For the polarizer, a polyvinyl alcohol aqueous solution is formed into a film and dyed by uniaxial stretching or dyed or uniaxially stretched and then preferably subjected to a durability treatment with a boron compound. . On the surface of the polarizer, one side of the cellulose ester film according to the present invention is bonded to form a polarizing plate. It is preferably bonded with a water-based adhesive mainly composed of completely saponified polyvinyl alcohol or the like.

  The cellulose acylate film according to the present invention may be used on the other surface of the polarizer (see Examples described later), or another polarizing plate protective film may be used. With respect to the cellulose acylate film according to the present invention, a commercially available cellulose acylate film can be used as the polarizing plate protective film used on the other surface. As a commercially available cellulose acylate film, for example, Konica Minoltak KC8UX, KC5UX, KC8UCR3, KC8UCR4, KC8UCR5, KC8UY, KC4UA, KC4UY, KC4UE, KC8UE, KC8UY-HA, HC8UY-HA, KC8UY-HA, KC8UY-HA, KC8UY-HA RHA-NC, KC4UXW-RHA-NC (manufactured by Konica Minolta Opto Co., Ltd.) and the like are preferably used. Alternatively, it is also preferable to use a polarizing plate protective film that also serves as an optical compensation film having an optical anisotropic layer formed by aligning liquid crystal compounds such as discotic liquid crystal, rod-shaped liquid crystal, and cholesteric liquid crystal. For example, the optically anisotropic layer can be formed by the method described in JP-A-2003-98348. By using it in combination with the cellulose acylate film according to the present invention, it is possible to obtain a polarizing plate having excellent flatness and a stable viewing angle expansion effect. In addition, as a polarizing plate protective film located in the side far from a liquid crystal cell, or on the said film, it is also possible to arrange | position the film which has other functionality, when improving the quality of a display apparatus. For example, anti-reflection (anti-reflection (AR)), anti-glare (anti-glare (AG)), scratch resistance (hard coat (HC)), low reflection (low reflection (LR)), dust adhesion prevention, brightness improvement, anti-static A film containing a known functional layer as a display for antifouling and back coating can be used as a polarizing plate protective film. Or you may affix separately the film containing these functional layers on the surface of polarizing plate protective films, such as a general purpose TAC film.

  The polarizing plate produced as described above can be constituted by further bonding a protective film on one surface and a separate film on the other surface. The protective film and the separate film are used for the purpose of protecting the polarizing plate at the time of shipping the polarizing plate and at the time of product inspection. In this case, the protect film is bonded for the purpose of protecting the surface of the polarizing plate, and is used on the side opposite to the surface where the polarizing plate is bonded to the display panel. Moreover, a separate film is used in order to cover the contact bonding layer bonded to a panel, and is used for the surface side which bonds a polarizing plate to a liquid crystal cell.

  This polarizing plate is used for MVA (Multi-domain Vertical Alignment) mode, PVA (Patterned Vertical Alignment) mode, CPA (Continuous Pinweal Alignment-P) mode, OCB (Optical Compensated InP) Can be.

  By incorporating the polarizing plate bonded with the cellulose acylate film according to the present invention into a liquid crystal display device, a liquid crystal display device with improved backlight transmission can be produced. It is preferably used for liquid crystal display devices for outdoor use such as liquid crystal display devices and digital signage.

  In addition, the use in the liquid crystal display device of the cellulose acylate film which concerns on this invention is not restricted to what was mentioned above. Depending on the case, in the polarizing plate of a liquid crystal display device, it may be used as an optical film which is located in the opposite side to the liquid crystal cell of the said polarizing plate, and has only a function as a protective film. In this case, since retardation development is not required, strict control of the retardation value as described above is unnecessary. However, since the above-described operational effects that the film develops are obtained in the same manner, such a form is also a preferred embodiment of the present invention.

  Further, when considering application to a polarizing plate used in, for example, a three-dimensional (3D) liquid crystal display device, in the polarizing plate of the above-described form, for example, the retardation film (polarizing plate) according to the present invention with respect to a polarizer. A retardation film (λ / 4 film) can be disposed in place of the protective film located on the surface (viewing side) opposite to the surface (also having a function as a protective film).

  According to such a form, it is possible to reduce crosstalk, luminance reduction, color change, etc. when tilting the head when viewing a stereoscopic (3D) image, and it is possible to maintain excellent visibility in the usage environment. Thus, a three-dimensional (3D) liquid crystal display device having higher durability against the use environment can be obtained.

  At this time, the retardation film that can be disposed in place of the protective film is not particularly limited, and for example, a conventionally known retardation film can be used. Examples of such conventionally known retardation films include those made of cycloolefin resin, those made by tilting a liquid crystal polymer made of discotic liquid crystal or rod-like nematic liquid crystal, and those made of polycarbonate. Of course, the cellulose acylate film according to the present invention may be disposed in place of the protective film described above. Here, for the retardation film formed by tilting the liquid crystal polymer, a layer (support layer) that functions as a support and an alignment film formed thereon are formed to form the retardation film. A phase difference film is required by separately preparing a body and further applying a liquid crystal polymer thereon. For this reason, in a form in which a retardation film made of a liquid crystal polymer is disposed on one side of a polarizer, a layer derived from a laminate of the support layer and the alignment film is also provided on at least one surface of the retardation film. It will also exist. Therefore, it can be said that this form is not necessarily preferable from the viewpoint of thinning the liquid crystal display device. However, such a form may be employed as long as the liquid crystal polymer can be directly processed.

  In any of these forms, similarly to the above, antireflection (antireflection (AR)), antiglare (antiglare (AG)), scratch resistance (hard coat (HC)), low reflection (low reflection (LR) (LR) )) Retardation film placed in place of a protective film on the viewing side instead of a film containing a known functional layer as a display for preventing dust adhesion, improving brightness, preventing antistatic, antifouling, and back coating You may laminate | stack further on. However, it is not advisable to directly arrange these functional layers on a retardation film made of the above-mentioned cycloolefin resin or a retardation film formed by tilting and aligning a liquid crystal polymer made of a discotic liquid crystal or a rod-like nematic liquid crystal. It is difficult from the viewpoint. Therefore, when providing a functional layer on these retardation films, it is preferable to laminate | stack the said functional layer, for example after apply | coating the hard-coat layer containing a cellulose ester on a retardation film as an adhesive layer. On the other hand, when the cellulose acylate film according to the present invention is arranged in place of the protective film on the viewing side, the arrangement of such an intermediate layer (adhesive layer) is derived from its excellent adhesion to the polarizer. Can be omitted, which is preferable. However, in some cases, a hard coat layer containing cellulose acylate may be provided as an adhesive layer.

  As mentioned above, although the usage form of the cellulose acylate film which concerns on this invention was demonstrated in detail, it can be used also for another use. For example, the cellulose acylate film according to the present invention can also be used as a brightness enhancement film. As a layer configuration in which the cellulose acylate film according to the present invention is used as a brightness enhancement film, the cellulose acylate film according to the present invention is disposed on one surface of a polarizer and the other surface is used as a protective film for a polarizing plate. A conventionally known cellulose acylate film (for example, cellulose acetate having no or small retardation) is disposed, and further, on the surface opposite to the polarizer of the retardation film according to the present invention, cholesteric The form of disposing a layer made of liquid crystal is exemplified.

(Organic EL display device)
The retardation film according to the present invention can also be used for an antireflection film disposed in an organic EL display device. In this case, the Ro of the retardation film preferably satisfies 100 ≦ Ro ≦ 150. The cellulose acylate film having such a high in-plane retardation (Ro) can function as a circularly polarizing plate (λ / 4 plate). Here, the circularly polarizing plate (λ / 4 plate) refers to a retardation plate having a function of converting linearly polarized light having a specific wavelength into circularly polarized light (or circularly polarized light into linearly polarized light). The circularly polarizing plate (λ / 4 plate) is designed so that the in-plane retardation (Ro) of the layer is about 1/4 with respect to a predetermined wavelength of light (usually in the visible light region).

  When the cellulose acylate film according to the present invention has a function of a circularly polarizing plate (λ / 4 plate), the angle (θ2) of the slow axis with respect to the longitudinal direction of the film is “substantially 45 °”. The retardation film according to the present invention having a function as a polarizing plate (λ / 4 plate) can be produced with high productivity.

  In other words, the above-described θ2 is preferably “substantially 45 °”, and “substantially 45 °” means 40 to 50 °. More specifically, the angle (θ2) of the slow axis with respect to the longitudinal direction of the film is preferably 41 to 49 °, more preferably 42 to 48 °, and further preferably 43 to 47 °. Preferably, it is 44 to 46 degrees.

  Thus, the cellulose acylate film whose slow axis angle (θ2) with respect to the longitudinal direction of the film is substantially 45 ° can be produced, for example, by adopting an oblique stretching process. Specifically, for example, a method of giving an inclination angle to the orientation axis by stretching with a feeding force at different speeds in the horizontal and vertical directions using a tenter can be used (for example, Japanese Patent Laid-Open No. 3-182701, Japanese Patent Laid-Open No. 3-182701). 2000-9912, JP-A-1-237601, JP-A-2003-342384, JP-A-2008-110573, JP-A-2002-86554, JP-A-2011-11434, and the like. Moreover, you may use the method of giving the inclination-angle to an orientation axis | shaft by the path | route difference as described in the patent 4270429 gazette.

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

≪Method for evaluating physical properties of cellulose acylate film≫
(Acyl group substitution degree of cellulose acylate)
The acyl group substitution degree of cellulose acylate was measured according to ASTM-D817-96.

(Method for measuring content ratio of xylose and mannose)
The content ratio of xylose and mannose in the cellulose acylate film was measured by the following method.

  That is, the product was hydrolyzed with 72% sulfuric acid at room temperature for 4 hours and then with 6% sulfuric acid at 110 ° C. for 3 hours, and liquid chromatographic analysis was performed to determine glucose, xylose and mannose. The content ratios of xylose and mannose relative to the total amount were calculated.

≪Method for evaluating physical properties of cellulose acylate film≫
(Ro (590) and Rth (590))
A 35 mm × 35 mm sample was cut out from the obtained film, conditioned at 25 ° C. and 55% RH for 2 hours, and measured with an automatic birefringence meter (KOBRA-21ADH, manufactured by Oji Scientific Instruments) from the vertical direction at 590 nm. From the extrapolation value of the retardation value measured in the same manner while tilting the film surface, the following formula was used.

(Where nx is the refractive index in the slow axis direction in the film plane, ny is the refractive index in the fast axis direction in the film plane, nz is the refractive index in the thickness direction of the film, and d is (The thickness of the film (nm).)
(Internal haze)
The obtained film was conditioned for 8 hours in an environment of 23 ° C. and 55% RH, and then the internal haze value was evaluated by the following method. The measurement was performed according to JIS K-7136. The internal haze was measured at 23 ° C. and 55% RH.

<Internal haze measuring device>
Haze meter (turbidity meter): Model NDH 2000, manufactured by Nippon Denshoku Co., Ltd. Light source: 5V9W halogen bulb, light receiving part is a silicon photocell (with a relative sensitivity filter)
<Internal haze measurement method>
The internal haze measurement is performed as follows. A description will be given with reference to FIGS.

  First, the blank haze 1 of a measuring instrument other than a film is measured.

  1. Drip a drop (0.05 ml) of glycerin on a cleaned glass slide. At this time, care is taken so that bubbles do not enter the droplet. Even if the glass looks clean, it may be dirty, so be sure to use glass that has been washed with a detergent (see Figure 1).

  2. Place the cover glass on top of it. Glycerin spreads without pressing the cover glass.

  3. Set on a haze meter and measure blank haze 1. Next, the haze 2 including the sample is measured.

  4). 0.05 ml of glycerin is dropped on a slide glass (see FIG. 1).

  5). A sample film to be measured is placed thereon (see FIG. 2).

  6). 0.05 ml of glycerin is dropped on the sample film (see FIG. 3).

  7). A cover glass is placed thereon (see FIG. 4).

  8). Set in a haze meter and measure haze 2.

  9. (Haze 2) − (Haze 1) = (Internal haze according to the present invention) is calculated.

  Here, the glass and glycerin used in the above measurement are as follows.

Glass: MICRO SLIDE GLASS S9213 MATUNAMI
Glycerin: Kanto Kagaku Deer Special Grade (Purity> 99.0%) Refractive index 1.47
Table 1 shows this value as internal haze. The internal haze is preferably 0.04 or less.

(Recyclability (recyclability))
As in Japanese Patent Application Laid-Open No. 2010-241142, materials other than those wound up as a final cellulose acylate film roll and sent to the next process as a product are returned materials. For example, film scraps called ears cut off at both ends of the web in the middle of manufacturing, reusable unfinished film that comes out if interrupted by some defect or accident, etc. are added during dope preparation May be reused.

  Therefore, the film whose internal haze was measured above was re-dissolved in a solvent, and the returnability (recycling performance) of the obtained film was evaluated based on the increase in internal haze in the film prepared again by the same method. .

  Under the present circumstances, the ratio of the crushed product which crushed the material which has a cellulose acylate as a main component with respect to the total cellulose acylate in a film was 30%. The evaluation was performed based on the increasing range of the internal haze, and the evaluation was performed by subtracting the internal haze value of the film when the recycled material was not used from the internal haze value when the recycled material was used. The evaluation criteria are as follows.

○: Difference is 0.03 or less Δ: Difference is 0.04 or more to 0.8 or less ×: Difference is 0.09 or more << Preparation of Optical Compensation Film >>
Hereinafter, examples in which a cellulose acylate film is used as an optical compensation film will be given.

(Preparation of optical compensation film 1)
<Synthesis Example 1: Synthesis of cellulose acylate>
Kraft method-dissolved pulp (α-cellulose content: 93%) was disintegrated with water, then substituted with acetone and dried. With respect to 100 parts by mass of this pulp, 500 parts by mass of acetic acid was uniformly dispersed and mixed at 40 ° C. for 30 minutes to activate the pretreatment.

  On the other hand, a mixture of 250 parts by mass of acetic anhydride and 4.0 parts by mass of sulfuric acid was added, and esterification was performed by a conventional method. The contents are exothermic due to the reaction between water and acetic anhydride accompanied by the raw pulp, and the reaction between cellulose and acetic anhydride. The contents are adjusted by external cooling, and then 125 parts by mass of an organic solvent is added. The acetylation reaction was allowed to proceed.

  Next, after removing the organic solvent as the reaction solution by heat, 35 parts by mass of a 20% calcium acetate aqueous solution was added and mixed to completely neutralize the sulfuric acid in the system and to make the calcium acetate excess (to the sulfuric acid). 1.09 times equivalent).

  After maintaining the completely neutralized reaction mixture at 150 ° C. for 50 minutes, the reaction mixture was brought to 100 ° C. under the atmosphere. The reaction mixture was added with a dilute aqueous acetic acid solution with stirring, separated as flaky cellulose acylate, sufficiently washed with water, taken out and dried. The degree of acetyl group substitution of the obtained flaky cellulose acylate was 2.4, the number average molecular weight was 47500, and the weight average molecular weight was 166000.

<Fine particle dispersion 1>
Fine particles (Aerosil R972V manufactured by Nippon Aerosil Co., Ltd.) 11 parts by weight Ethanol 89 parts by weight The above was stirred and mixed with a dissolver for 50 minutes, and then dispersed with Manton Gorin.

<Fine particle addition liquid 1>
The fine particle dispersion 1 was slowly added to the dissolution tank containing methylene chloride with sufficient stirring. Further, the particles were dispersed by an attritor so that the secondary particles had a predetermined particle size. This was filtered through Finemet NF manufactured by Nippon Seisen Co., Ltd. to prepare a fine particle additive solution 1.

Methylene chloride 99 parts by mass Fine particle dispersion 1 5 parts by mass <Preparation of dope>
A main dope solution having the following composition was prepared. First, methylene chloride and ethanol were added to the pressure dissolution tank. The cellulose acetate prepared in Synthesis Example 1 and the chelating agent were charged into a pressurized dissolution tank containing a solvent while stirring. This was heated and stirred to dissolve completely, and this was dissolved in Azumi Filter Paper No. After filtering using 244, the remaining components were added and stirred to dissolve to prepare the main dope solution.

<Composition of main dope solution>
Methylene chloride 340 parts by weight Ethanol 64 parts by weight Cellulose acylate (synthesized in Synthesis Example 1) 100 parts by weight Chelating agent (DTPA) 0.3 part by weight Exemplary compound 2-14 (compound represented by formula (2)) ) 4 parts by weight Exemplified Compound 4 (a4) (sugar ester compound) 8 parts by weight Fine Particle Additive Solution 1 1 part by mass Next, using an endless belt casting apparatus, the dope solution is placed on a stainless steel belt support at a temperature of 33 ° C. and a width of 1500 mm. Were uniformly cast. The temperature of the stainless steel belt was controlled at 30 ° C.

  On the stainless steel belt support, the solvent was evaporated until the residual solvent amount in the cast (cast) film was 75%, and then peeled off from the stainless steel belt support with a peeling tension of 180 N / m.

  The peeled cellulose acetate film was stretched in the width direction using a tenter while applying heat at 148 ° C. The draw ratio was 1.5 times, and the residual solvent amount at the start of drawing was 7%.

Next, drying was terminated while the drying zone was conveyed by a number of rolls. The drying temperature was 140 ° C. and the transport tension was 100 N / m. Thereby, an optical compensation film 1 having a dry film thickness of 40 μm was obtained. In addition, when the content of Ca ^<2+> and Mg ^{< 2+>} in the obtained film was measured by the atomic absorption photometry, they were 65 mass ppm and 35 mass ppm, respectively.

(Production of optical compensation films 2 to 16)
Cellulose acylate species, acyl group substitution degree (propionyl group substitution degree), Ca ²⁺ content, Mg ²⁺ content, type of chelating agent and addition amount are as described above except that they are changed as shown in Table 1 below. Optical compensation films 2 to 22 were produced in the same manner as the production of the optical compensation film 1. In addition, control of Ca ^<2+> and Mg ^<2+> content was performed by adjusting the addition amount of calcium acetate and magnesium for neutralization used at the time of a cellulose acylate synthesis | combination.

  As is apparent from the results shown in Table 1, it can be seen that when the cellulose acylate film of the present invention is used as an optical compensation film, the retardation development is excellent and the internal haze is low as compared with the comparative example. It can also be seen that even better results can be obtained especially when NTA or DTPA having a chelate stability constant of 5 or more is used. In other words, according to the present invention, even when low-cost low-purity pulp is used, the cellulose acylate film is excellent in retardation development, has low internal haze, and can be applied as an optical compensation film for high-contrast applications. And a method for manufacturing the same.

≪Preparation of polarizing plate≫
(Preparation of polarizing plates 1 to 16)
A 120 μm-thick polyvinyl alcohol film was uniaxially stretched (temperature: 110 ° C., stretch ratio: 5 times).

  This was immersed in an aqueous solution composed of 0.075 g of iodine, 5 g of potassium iodide and 100 g of water for 60 seconds, and then immersed in an aqueous solution of 68 ° C. composed of 6 g of potassium iodide, 7.5 g of boric acid and 100 g of water. This was washed with water and dried to obtain a polarizer.

  Next, according to the following steps 1 to 5, either one of the optical compensation films 1 to 16 prepared above is applied to one surface of the polarizer obtained above, and Konica Minolta Tack KC4UY (Konica Minolta Opt ( The polarizing plate 1-16 was produced by bonding together a cellulose ester film).

  Step 1: It was immersed in a 2 mol / L sodium hydroxide solution at 60 ° C. for 90 seconds, then washed with water and dried to obtain optical compensation films 1 to 16 having a saponified side to be bonded to a polarizer. Similarly, KC4UY on the back side was also saponified.

  Process 2: The said polarizer was immersed in the polyvinyl alcohol adhesive tank of 2 mass% of solid content for 1-2 seconds.

  Step 3: Excess adhesive adhered to the polarizer in Step 2 was gently wiped off, and this was placed on the optical compensation films 1 to 16 processed in Step 1.

Step 4: optical compensation film 1-16 polarizer and the back-side cellulose ester film pressure 20-30 N / cm ² were laminated in step 3, the conveying speed was pasted at approximately 2m / min.

  Process 5: The laminated body produced at the process 4 was dried for 2 minutes in the 80 degreeC dryer, and the polarizing plates 1-16 respectively corresponding to the optical compensation films 1-16 were produced.

≪Production of liquid crystal display device≫
(Production of liquid crystal display devices 1 to 16)
A liquid crystal panel for viewing angle measurement was produced as follows, and the characteristics as a liquid crystal display device were evaluated.

  The polarizing plates on both sides of the 40-inch display BRAVIA X1 made in advance were peeled off, and the polarizing plates 1 to 16 prepared above were bonded to both surfaces of the glass surface of the liquid crystal cell.

  At that time, the direction of bonding of the polarizing plate is such that the surface of the optical compensation film of the present invention is on the liquid crystal cell side, and the absorption axis is in the same direction as the polarizing plate previously bonded. Thus, liquid crystal display devices 1 to 16 respectively corresponding to the polarizing plates 1 to 16 were produced.

(Evaluation of front contrast)
The liquid crystal display device produced above was evaluated for front contrast.

  Specifically, the measurement was performed with a front contrast measurement device (EZ-contrast) manufactured by ELDIM, and the light quantity during white display and black display was measured. The measurement results were ranked according to superiority or inferiority according to the value of the front contrast as follows. It is preferable that it is more than (triangle | delta). The obtained results are shown in Table 2 below.

A: Front contrast ratio = 3000: 1 or more B: Front contrast ratio = 2999: 1 to 2000: 1
Δ: Front contrast ratio = 1999: 1 to 1000: 1
X: Front contrast ratio = 999: 1 or less

  As shown in Table 2, it was confirmed that when the cellulose acylate film according to the present invention was used as an optical compensation film, a liquid crystal display device having sufficient contrast and excellent visibility could be provided.

Claims (9)

A cellulose acylate film comprising a cellulose acylate having an acyl group substitution degree of 2.2 to 2.55,
A cellulose acylate film characterized in that the ratio of xylose is 0.9% by mass or less and the ratio of mannose is 0.9% by mass or less with respect to 100% by mass of the sugar component constituting the film.   The cellulose acylate film according to claim 1, further comprising a chelating agent. The cellulose acylate film according to claim 2, wherein the chelating agent includes a chelate stability constant with Ca ²⁺ of 5 or more.   The cellulose acylate film according to claim 2 or 3, wherein the chelating agent comprises one having an amino group and a carboxy group. A dope preparation step of preparing a dope containing cellulose acylate having an acyl group substitution degree of 2.2 to 2.55;
A deposit removing step of depositing and removing components other than the cellulose acylate contained in the dope; and
After drying the film obtained by casting the dope obtained in the deposit removing step on a support and peeling it, the step of stretching at least in the width direction;
A method for producing a cellulose acylate film, comprising:   The manufacturing method according to claim 5, wherein the deposit removing step is performed by adding a chelating agent to the dope.   The manufacturing method according to claim 5 or 6, further comprising a step of adding a matting agent to the dope after the deposit removing step.   The cellulose acylate film according to any one of claims 1 to 4, or the cellulose acylate film produced by the production method according to any one of claims 5 to 7, and at least one surface of a polarizer. And a polarizing plate.   A liquid crystal display device comprising the polarizing plate according to claim 8.

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