JP4951543B2 - Method for producing retardation cellulose acylate film - Google Patents

Description

  The present invention relates to a method for producing a retardation cellulose acylate film, a retardation cellulose acylate film, and an optical film using the same.

  Cellulose acylate film is expanding its application as an optical film for image display devices such as liquid crystal display devices and organic EL display devices because of its transparency, toughness and optical isotropy. As an optical film for a liquid crystal display device, in addition to being used as a protective film for a polarizing plate, as a retardation film, it is stretched to develop in-plane retardation (Re) and thickness direction retardation (Rth). used.

In recent years, there has been a demand for a retardation film having characteristics according to applications, and various production methods have been proposed for producing the retardation film. For example, a retardation film having Rth / Re of 0.5 or less is stretched in the machine direction (MD) without restraining it in the width direction while crystallizing the cellulose acylate by heating to the crystallization temperature. It can manufacture by performing free end uniaxial stretching (for example, refer to patent documents 1 and patent documents 2).
JP 2003-131033 A JP 2006-285136 A

  However, in the above-described manufacturing method, there is a possibility that the film becomes brittle when shrinking in the width direction (Transverse direction: TD), or that the film is not gripped in the width direction, so that vertical wrinkles may occur in the film.

  As a result, there was a problem that the elongation at break was large and a high-quality retardation film could not be produced.

  The present invention has been made in view of such circumstances. The in-plane retardation Re is 100 to 300 nm, the thickness direction retardation Rth is Re × 0.5 or less, and the slow axis deviation is in the width direction (TD). An object of the present invention is to provide a method for producing a cellulose acylate film having a property of ± 5 ° or less and a longitudinal elongation at break measured by Tensilon of 5% or more, a cellulose acylate film, and an optical film.

  In order to achieve the above object, the method for producing a retardation cellulose acylate film of the present invention comprises a step of supplying a cellulose acylate film, and heating the cellulose acylate film to a temperature of Tc to Tc + 80 ° C. in the width direction ( (TD) includes a step of shrinking by 10 to 50%, and a step of stretching the cellulose acylate film shrunk in the width direction by 1 to 30% in the width direction (TD).

  According to the present invention, the cellulose acylate film is shrunk in the width direction (TD) at a high temperature to develop the in-plane retardation Re and the thickness direction retardation Rth, and then stretched in the width direction. The brittleness of the phase difference cellulose acylate film can be improved. This is because the cellulose acylate film shrunk in the width direction is stretched to cause a part of the molecules oriented in the longitudinal direction to be directed in the transverse direction, so that the alignment of molecules disappears in one direction. It is thought that brittleness has been improved. Moreover, the retardation cellulose acylate film excellent in planar shape and planarity can be obtained by performing a extending | stretching process. In the present invention, Tc means a temperature raising crystallization temperature.

  The method for producing a retardation cellulose acylate film of the present invention is the cellulose acylate after the stretching treatment in the invention, in which the stretching treatment step has a film surface temperature of the cellulose acylate film of Tc-50 ° C to Tc + 80 ° C. The stretching ratio is adjusted so that the in-plane retardation Re of the film is 100 to 300 nm and the thickness direction retardation Rth is Re × 0.5 or less.

  It defines the conditions of the stretching step for expressing the in-plane retardation Re and the thickness direction retardation Rth required for the retardation cellulose acylate film.

  The method for producing a retardation cellulose acylate film of the present invention further includes a step of stretching the cellulose acylate film in a longitudinal direction (MD) at a predetermined longitudinal stretching ratio before the shrinkage treatment step in the invention, The shrinking treatment step includes shrinking in a state where the widthwise end of the cellulose acylate film stretched in the longitudinal direction is gripped.

  Before shrinking in the width direction, the film is preliminarily stretched in the machine direction (MD), and the film is shrunk in the width direction while gripping the widthwise ends of the cellulose acylate film during the shrinking process. Thereafter, the brittleness of the film can be improved by stretching in the width direction.

  In the method for producing a retardation cellulose acylate film of the present invention, in the above invention, the shrinking treatment step may be performed by using the cellulose acylate film in a heating furnace with a width direction as a free end and a longitudinal direction at a predetermined longitudinal stretching ratio ( MD) is also included.

  The cellulose acylate film is stretched in the longitudinal direction (MD) without holding the width direction at the free end, that is, the end in the width direction with a tenter or the like, and the cellulose acylate film is contracted in the width direction (TD). . Then, the longitudinal wrinkle which is easy to generate | occur | produce by extending | stretching to a width direction can be reduced by extending | stretching free end longitudinally. Here, when the film is pulled, the wrinkled wrinkles that are generated by the film surface undulating like a corrugated sheet in the flow direction are called vertical wrinkles.

  The retardation cellulose acylate film of the present invention is manufactured by the above-described manufacturing method, and has an in-plane retardation Re of 100 to 300 nm, a thickness direction retardation Rth of Re × 0.5 or less, and a slow axis. It is characterized in that the deviation is ± 5 ° or less with respect to the width direction (TD) and the breaking elongation in the longitudinal direction measured by measuring the breaking elongation with a tensile tester is 5% or more. In the present invention, the longitudinal breaking elongation measured by measuring the breaking elongation with a tensile tester is a distance between chucks of 50 mm under an environment of 25 ° C. and 60% using a tensile tester (Strograph) manufactured by Toyo Seiki. A tensile test was performed at a sample width of 10 mm and a tensile speed of 10 mm / min, and the elongation at the time when the film was broken was defined as the breaking elongation.

  The optical film of the present invention uses the retardation cellulose acylate film.

  According to the present invention, the cellulose acylate film is heated to a temperature of Tc to Tc + 80 ° C., subjected to shrinkage treatment by 10 to 50% in the width direction (TD), and the cellulose acylate film shrunk in the width direction is subjected to the width direction ( By subjecting TD) to a stretch treatment of 1 to 30%, a retardation cellulose acylate film with improved brittleness and excellent planarity and planarity can be produced.

  Hereinafter, an embodiment of a method for producing a retardation cellulose acylate film according to the present invention will be described. The present invention will be described with reference to the following preferred embodiments, but can be modified in many ways without departing from the scope of the present invention, and other embodiments than the present embodiment can be used. be able to. Accordingly, all modifications within the scope of the present invention are included in the claims. In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to”.

《Cellulose acylate film》
[Moisture permeability]
The cellulose acylate film of the present invention has a moisture permeability of 100 to 400 g / (m ² · day) at 40 ° C. and 90% relative humidity, and changes in moisture permeability after being held at 60 ° C. and 95% relative humidity for 1000 hours. Is preferably −100 g / (m ² · day) to 10 g / (m ² · day). “Moisture permeability” refers to the change in mass before and after holding when the cup containing calcium chloride is covered with a film and the whole is placed in a sealed container and kept at 40 ° C. and 90% relative humidity for 24 hours. g / (m ² · day)). The moisture permeability increases as the temperature increases and increases as the humidity increases, but the magnitude relationship of the moisture permeability between the films remains unchanged regardless of the temperature or humidity employed. Therefore, in the present invention, the value of the mass change at 40 ° C. and 90% relative humidity was used as a reference.

The moisture permeability of the cellulose acylate film of the present ^{invention, 100~400g / (m 2 · day} ) are ^{preferred, 120~350g / (m 2 · day} ) , more ^{preferably, 150~300g / (m 2 · day} ) is Further preferred.

Also, the moisture permeability before and after holding when the film was held at 60 ° C. and 95% relative humidity for 1000 hours was measured according to the above-mentioned method, and the value obtained by subtracting the moisture permeability before holding from the moisture permeability after holding was “60 ° C. “Change in moisture permeability after holding for 1000 hours at 95% relative humidity”. The moisture permeability change after holding the cellulose acylate film of the present invention at 60 ° C. and a relative humidity of 95% is −100 g / (m ² · day) to 10 g / (m ² · day), and −50 to 5 g / (M ² · day) is preferable, and -20 to 0 g / (m ² · day) is more preferable.

Furthermore, since the moisture permeability decreases as the film thickness increases and increases as the film thickness decreases, the measured moisture permeability is first multiplied by the actually measured film thickness and divided by 80 in the present invention. The water vapor transmission rate in terms of a film thickness of 80 μm ”. Moisture permeability of the film thickness 80μm in terms of the cellulose acylate film of the present ^{invention, 100~420g / (m 2 · day} ) are ^{preferred, 150~400g / (m 2 · day} ) , more preferably, 180~350g / (m ² · day) is more preferable.

  If a cellulose acylate film satisfying such a moisture permeability condition is used, it is possible to provide a polarizing plate excellent in durability against humidity or heat and a highly reliable liquid crystal display device.

[Cellulose acylate]
In the cellulose acylate film of the present invention, the polymer as a main component is cellulose acylate. Here, the “polymer as the main component” indicates a polymer when it is composed of a single polymer, and when it is composed of a plurality of polymers, it is the most mass fraction of the constituent polymers. Indicates a high polymer.

  As the cellulose acylate used for producing the cellulose acylate film of the present invention, a powder or a particulate one can be used, and a pelletized one can also be used. The water content of cellulose acylate is preferably 1.0% by mass or less, more preferably 0.7% by mass or less, and most preferably 0.5% by mass or less. Moreover, it is preferable that a moisture content is 0.2 mass% or less depending on the case. When the water content of cellulose acylate is not within the preferred range, it is preferably used after drying by heating or the like. These polymers may be used alone or in combination of two or more polymers.

  Examples of the cellulose acylate include a cellulose acylate compound and a compound having an acyl-substituted cellulose skeleton obtained by introducing a functional group biologically or chemically using cellulose as a raw material.

  The cellulose acylate is an ester of cellulose and carboxylic acid. The carboxylic acid constituting the ester is more preferably a fatty acid having 2 to 22 carbon atoms, and most preferably a lower fatty acid having 2 to 4 carbon atoms.

  In the cellulose acylate, all or part of the hydrogen atoms of the hydroxyl groups present at the 2-position, 3-position and 6-position of the glucose unit constituting the cellulose are substituted with acyl groups. Examples of the acyl group include, for example, an aceter group, a propionyl group, a butyryl group, an isobutyryl group, a bivaloyl group, a hebutanoyl group, a hexanoyl group, an octanoyl group, a decanoyl group, a dodecanoyl group, a tridecanoyl group, a tetradecanoyl group, a hexadecanoyl group, Examples include a decanoyl group, an octadecanoyl group, a cyclohexane carbonyl group, an oleoyl group, a benzoyl group, a naphthyl carbonyl group, and a cinnamoyl group. As the acyl group, an acetel group, a propionyl group, a butyryl group, a dodecanoyl group, an octadecanoyl group, a bivaloyl group, an oleoyl group, a benzoyl group, a naphthylcarbonyl group, and a cinnamoyl group are preferable, and an acetyl group, a propionyl group, and a butyryl group. Is most preferred.

  Cellulose acylate may be substituted with a plurality of acyl groups, and specific examples include cellulose acetate propionate, cellulose acetate petitate, cellulose acetate petitate propionate, and cellulose petitate propionate. It is done.

  As the cellulose acylate constituting the cellulose acylate film of the present invention, cellulose acetate having an ester with acetic acid is particularly preferred, and cellulose having an acetyl substitution degree of 2.70 to 2.87 from the viewpoint of solubility in a solvent. Acetate is more preferable, and cellulose acetate of 2.80 to 2.86 is most preferable. The degree of substitution here refers to the degree to which the hydrogen atom of the hydroxyl group existing at the 2nd, 3rd and 6th positions of the glucose unit constituting cellulose is substituted, and the 2nd, 3rd and 6th positions. The degree of substitution when the hydrogen atom of the hydroxyl group present in is substituted is 3.

  The basic principle of the cellulose acylate synthesis method is described in Nakahiko Ueda et al., Wood Chemistry, 180-190 (Kyoritsu Shuppan, 1968). A typical synthesis method of cellulose acylate includes a liquid phase acylation method using a carboxylic acid anhydride-carboxylic acid-sulfuric acid catalyst. Specifically, first, cellulose raw materials such as cotton linter and wood pulp are pretreated with a suitable amount of carboxylic acid such as acetic acid, and then esterified by introducing into a pre-cooled acylated mixture to complete cellulose acylate (2 The total degree of acyl substitution at the 3rd, 6th and 6th positions is approximately 3.00). The acylated mixed solution generally contains a carboxylic acid as a solvent, a carboxylic acid anhydride as an esterifying agent, and sulfuric acid as a catalyst. In addition, the carboxylic acid anhydride is usually used in a stoichiometrically excessive amount with respect to the total amount of cellulose reacting with the carboxylic acid anhydride and moisture present in the system.

  Subsequently, after completion of the acylation reaction, water or hydrous acetic acid is added in order to hydrolyze the excess carboxylic anhydride remaining in the system. Further, in order to partially neutralize the esterification catalyst, an aqueous solution containing a neutralizing agent (for example, calcium, magnesium, iron, aluminum or zinc carbonate, acetate, hydroxide or oxide) is added. Also good. Further, the obtained complete cellulose acylate is saponified by maintaining at 20 to 90 ° C. in the presence of a small amount of acylation reaction catalyst (generally, remaining sulfuric acid), and desired acyl substitution degree and polymerization degree are obtained. To a cellulose acylate having When the desired cellulose acylate is obtained, the catalyst remaining in the system is completely neutralized using the neutralizing agent or the like, or water or dilute acetic acid without neutralizing the catalyst. Cellulose acylate solution is added into the solution (or water or dilute acetic acid is added into the cellulose acylate solution) to separate the cellulose acylate, and the desired cellulose acylate is obtained by washing and stabilizing treatment. Can do.

  The degree of polymerization of the cellulose acylate is preferably from 150 to 500, more preferably from 200 to 400, and even more preferably from 220 to 350 in terms of viscosity average degree of polymerization. The viscosity average degree of polymerization can be measured according to the description of Uda et al.'S intrinsic viscosity method (Kazuo Uda, Hideo Saito, Journal of Textile Science, Vol. 18, No. 1, pages 105-120, 1962). The method for measuring the viscosity average degree of polymerization is also described in JP-A-9-95538.

  In addition, cellulose acylate having a small amount of low molecular components has a high average molecular weight (degree of polymerization), but its viscosity is lower than that of ordinary cellulose acylate. Such a cellulose acylate having a small amount of low molecular components can be obtained by removing the low molecular components from cellulose acylate synthesized by an ordinary method. The removal of the low molecular components can be performed by washing the cellulose acylate with an appropriate organic solvent. In addition, cellulose acylate having a small amount of low molecular components can be obtained by synthesis. When synthesizing cellulose acylate having a small amount of low molecular components, the amount of sulfuric acid catalyst in the acylation reaction is preferably adjusted to 0.5 to 25 parts by mass with respect to 100 parts by mass of cellulose. When the amount of the sulfuric acid catalyst is within the above range, cellulose acylate that is preferable in terms of molecular weight distribution (uniform molecular weight distribution) can be synthesized. The raw material cotton of cellulose ester and the synthesis method are also described in pages 7 to 12 of the Japan Society of Invention Disclosure (Public Technical Number 2001-1745, published on March 15, 2001, Japan Society of Invention).

<< Production of Cellulose Acylate Film >>
The cellulose acylate film of the present invention can be produced from a solution containing cellulose acylate and various additives by a solution casting film forming method. The solution casting film forming method will be described in detail below.

  Further, when the melting point of the cellulose acylate of the present invention or the melting point of the mixture of cellulose acylate and various additives is lower than the decomposition temperature and higher than the stretching temperature, the film is formed by a melt film forming method. It is also possible to make it. The melt film forming method is described in JP-A No. 2000-352620.

[Cellulose acylate solution]
(solvent)
When producing the cellulose acylate film of the present invention by a solution casting film forming method, a cellulose acylate solution is prepared. As the main solvent for the cellulose acylate solution used at this time, an organic solvent which is a good solvent for the cellulose acylate can be preferably used. As such an organic solvent, an organic solvent having a boiling point of 80 ° C. or lower is more preferable from the viewpoint of reducing the drying load. The boiling point of the organic solvent is more preferably 10 to 80 ° C, and particularly preferably 20 to 60 ° C. Moreover, the organic solvent whose boiling point is 30-45 degreeC depending on the case can also be used suitably as said main solvent.

  Examples of such a main solvent include halogenated hydrocarbons, esters, ketones, ethers, alcohols and hydrocarbons, which may have a branched structure or a cyclic structure. The main solvent may have two or more functional groups of esters, ketones, ethers and alcohols (that is, —O—, —CO—, —COO—, —OH). Furthermore, the hydrogen atom in the hydrocarbon portion of the ester, ketone, ether and alcohol may be substituted with a halogen atom (particularly a fluorine atom). The cellulose acylate main solvent used for the production of the cellulose acylate film of the present invention indicates a solvent when it is composed of a single solvent, and is composed of a plurality of solvents. Among the solvents to be used, the solvent having the highest mass fraction is shown.

  As said halogenated hydrocarbon, a chlorinated hydrocarbon is more preferable, for example, a dichloromethane, chloroform, etc. are mentioned, A dichloromethane is further more preferable. Examples of the ester include methyl formate, ethyl formate, methyl acetate, and ethyl acetate. Examples of the ketone include acetone and methyl ethyl ketone. Examples of the ether include diethyl ether, methyl-tert-butyl ether, diisopropyl ether, dimethoxymethane, 1,3-dioxolane, 4-methyldioxolane, tetrahydrofuran, methyltetrahydrofuran, 1,4-dioxane and the like. As said alcohol, methanol, ethanol, 2-propanol etc. are mentioned, for example. Examples of the hydrocarbon include n-pentane, cyclohexane, n-hexane, benzene, toluene and the like.

  Examples of the organic solvent used in combination with these main solvents include halogenated hydrocarbons, esters, ketones, ethers, alcohols and hydrocarbons, which may have a branched structure or a cyclic structure. The organic solvent may have any two or more of ester, ketone, ether and alcohol functional groups (that is, —O—, —CO—, —COO—, —OH). Furthermore, the hydrogen atom in the hydrocarbon portion of the ester, ketone, ether and alcohol may be substituted with a halogen atom (particularly a fluorine atom).

  As said halogenated hydrocarbon, a chlorinated hydrocarbon is more preferable, for example, a dichloromethane, chloroform, etc. are mentioned, A dichloromethane is further more preferable. Examples of the ester include methyl formate, ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate, and pentyl acetate. Examples of the ketone include acetone, methyl ethyl ketone, diethyl ketone, diisoptyl ketone, cyclopentanone, cyclohexanone, and methylcyclohexanone. Examples of the ether include diethyl ether, methyl tert-butyl ether, diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolane, 4-methyldioxolane, tetrahydrofuran, methyltetrahydrofuran, anisole, and phenetole. Etc.

  Examples of the alcohol include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, tert-butanol, 1-pentanol, 2-methyl-2-butanol, cyclohexanol, and 2-fluoro. Examples include ethanol, 2,2,2-trifluoroethanol, 2,2,3,3-tetrafluoro-1-propanol. Examples of the hydrocarbon include n-pentane, cyclohexane, n-hexane, benzene, toluene, xylene and the like. Examples of the organic solvent having two or more kinds of functional groups include 2-ethoxyethyl acetate, 2-methoxyethanol, 2-butoxyethanol, and methyl acetoacetate.

  In the cellulose acylate film of the present invention, it is preferable that 5 to 30% by mass, more preferably 7 to 25% by mass, and still more preferably 10 to 20% by mass of alcohol in the total solvent is peel load from the band. Desirable from the viewpoint of reduction.

Examples of combinations of organic solvents that are preferably used as the solvent for the cellulose acylate solution used in the production of the cellulose acylate film of the present invention are listed below, but the combinations that can be employed in the present invention are limited to these. is not. In addition, the numerical value of a ratio means a mass part.
(1) Dichloromethane / methanol / ethanol / butanol = 80/10/5/5
(2) Dichloromethane / methanol / ethanol / butanol = 80/5/5/10
(3) Dichloromethane / isoptyl alcohol = 90/10
(4) Dichloromethane / acetone / methanol / propanol = 80/5/5/10
(5) Dichloromethane / methanol / butanol / cyclohexane = 80/8/10/2
(6) Dichloromethane / methyl ethyl ketone / methanol / butanol = 80/10/5/5
(7) Dichloromethane / butanol = 90/10
(8) Dichloromethane / acetone / methyl ethyl ketone / ethanol / butanol = 68/10/10/7/5
(9) Dichloromethane / cyclopentanone / methanol / pentanol = 80/2/15/3
(10) Dichloromethane / methyl acetate / ethanol / butanol = 70/12/15/3
(11) Dichloromethane / methyl ethyl ketone / methanol / butanol = 80/5/5/10
(12) Dichloromethane / methyl ethyl ketone / acetone / methanol / pentanol = 50/20/15/5/10
(13) Dichloromethane / 1,3-dioxolane / methanol / butanol = 70/15/5/10
(14) Dichloromethane / dioxane / acetone / methanol / butanol = 75/5/10/5/5
(15) Dichloromethane / acetone / cyclopentanone / ethanol / isoptyl alcohol / cyclohexane = 60/18/3/10/7/2
(16) Dichloromethane / methyl ethyl ketone / acetone / isoptyl alcohol = 70/10/10/10
(17) Dichloromethane / acetone / ethyl acetate / butanol / hexane = 69/10/10/10/1
(18) Dichloromethane / methyl acetate / methanol / isoptyl alcohol = 65/15/10/10
(19) Dichloromethane / cyclopentanone / ethanol / butanol = 85/7/3/5
(20) Dichloromethane / methanol / butanol = 83/15/2
(21) Dichloromethane = 100
(22) Acetone / ethanol / butanol = 80/15/5
(23) Methyl acetate / acetone / methanol / butanol = 75/10/10/5
(24) 1,3-dioxolane = 100
Further, details of the case where a non-halogen organic solvent is used as a main solvent are described in the Invention Association's public technical bulletin (Publication No. 2001-1745, published on March 15, 2001, Invention Association), and the present invention is appropriately described. Can be applied.

(Solution concentration)
The cellulose acylate concentration in the cellulose acylate solution to be prepared is preferably 5 to 40% by mass, more preferably 10 to 30% by mass, and most preferably 15 to 30% by mass. The cellulose acylate concentration can be adjusted to a predetermined concentration at the stage of dissolving the cellulose acylate in a solvent. Further, after preparing a solution with a low concentration (for example, 4 to 14% by mass) in advance, the solution may be concentrated by evaporating the solvent or the like. Furthermore, after preparing a high concentration solution in advance, it may be diluted. Moreover, the density | concentration of a cellulose acylate can also be reduced by adding an additive.

(Additive)
The said cellulose acylate solution used for preparation of the cellulose acylate film of this invention can contain the various liquid or solid additive according to a use in each preparation process. Examples of the additive include a plasticizer (preferred addition amount is 0.01 to 10% by mass with respect to cellulose acylate, the same applies hereinafter), an ultraviolet absorber (0.001 to 1% by mass), and an average particle size. 5 to 3000 nm fine particle powder (0.001 to 1% by mass), fluorosurfactant (0.001 to 1% by mass), release agent (0.0001 to 1% by mass), deterioration inhibitor (0 .0001 to 1% by mass), an optical visibility control agent (0.01 to 10% by mass), and an infrared absorber (0.001 to 1% by mass).

  The plasticizer and the optical anisotropy controlling agent are organic compounds having a molecular weight of 3000 or less, preferably a compound having both a hydrophobic part and a hydrophilic part. These compounds change the retardation value by orienting between cellulose acylate chains. Furthermore, these compounds can improve the hydrophobicity of the film and reduce the humidity change of the retardation. Moreover, the wavelength dependence of retardation can be effectively controlled by using the ultraviolet absorber or the infrared absorber in combination. Any additive used in the cellulose acylate film of the present invention is preferably substantially free of volatilization during the drying process.

  From the viewpoint of reducing the humidity change of the retardation, it is preferable that the amount of these additives is large. However, as the amount of addition increases, the glass transition temperature (Tg) of the cellulose acylate film decreases, and the film production process It becomes easy to cause the volatilization problem of the additive. Therefore, when using cellulose acetate more preferably used in the present invention, the amount of the additive having a molecular weight of 3000 or less is preferably 0.01 to 30% by mass, more preferably 2 to 30% by mass with respect to the cellulose acylate. Preferably, 5 to 20% by mass is more preferable.

  A plasticizer that can be suitably used in the cellulose acylate film of the present invention is described in JP-A No. 2001-151901. The infrared absorber is described in JP-A No. 2001-194522. The timing of adding the additive can be appropriately determined according to the type of the additive. Further, the additive is also described in pages 16 to 22 of the Japan Society of Invention Disclosure Technical Bulletin (Public Technical Number 2001-1745, published on March 15, 2001, Japan Society of Invention).

(Preparation of cellulose acylate solution)
The cellulose acylate solution can be prepared, for example, according to the preparation method described in JP-A-2005-104148, pages 106 to 120. Specifically, the cellulose acylate and the solvent can be mixed and stirred to swell, and optionally cooled or heated to dissolve, and then filtered to obtain a cellulose acylate solution.

[Casting, drying]
The cellulose acylate film of the present invention can be produced using a conventional solution casting film forming apparatus according to a conventional solution casting film forming method. FIG. 1 is a schematic explanatory view showing an example of a casting film production line 10 for producing a cellulose acylate film by a solution casting film production method. The dope (cellulose acylate solution) prepared by a dissolving machine (pot) (not shown) is temporarily stored in the storage pot 11 after filtration. The foam contained in the dope is defoamed and finally prepared. The dope is kept at 30 ° C., and is sent from the dope discharge port to the pressurizing die 14 through the pressurizing quantitative gear pump 12 capable of feeding the liquid with a high accuracy by, for example, the rotational speed. A filter 13 can be provided between the pressurization type fixed gear pump 12 and the pressurization die 14. The dope is uniformly cast from the die (slit) of the pressure die 14 onto the metal support 15 of the casting part running endlessly (casting process). Next, the dough film (also referred to as a web) is peeled off from the metal support 15 at the peeling point where the metal support 15 has made one round. Reference numerals 16 and 17 respectively denote rotating drums on the casting part side and the non-casting part side, 18 a guide roll, and 19 a peeling roll. Subsequently, the dope film is conveyed to the drying zone 22. The dope film is conveyed through the drying zone 22 by the guide roller 20. The dope film is dried by being conveyed through the drying zone 22. The unstretched cellulose acylate film 23 that has been dried is wound up to a predetermined length by the winder 21. In the present invention, a metal band or a metal belt can be used as the metal support 15.

  The details of the casting step and the drying step are also described in JP-A-2005-104148, pages 120 to 146, and can be applied to the present invention as appropriate.

  The amount of residual solvent in the dried film is preferably 0-2% by mass, more preferably 0-1% by mass. After completion of drying, the film may be conveyed to the heat treatment zone as it is, or may be heat treated offline after the film has been wound. The preferable width | variety of the cellulose acylate film before heat processing is 0.5-5 m, More preferably, it is 0.7-3 m. Moreover, when winding up a film once, preferable winding length is 300-30000m, More preferably, it is 500-10000m, More preferably, it is 1000-7000m.

[Stretching and heat treatment]
Next, a first method for shrinking the cellulose acylate film obtained above in the width direction will be described. The first method is a method of stretching in the machine direction (MD) and shrinking in the width direction by heat treatment while gripping the film in the width direction after stretching.

  FIG. 2 schematically shows the configuration of the stretching / heat treatment apparatus. As shown in the drawing, the stretching / heat treatment apparatus 30 includes a preheating unit 34 for heating an unstretched cellulose acylate film 32, a longitudinal stretching unit 36 for stretching the heated film 32 in the longitudinal direction (MD), and a longitudinal direction. It is comprised by the heat processing part 38 which heat-shrinks the stretched film 32 to the width direction, and the horizontal extending | stretching part 90 which extends | stretches a film in the width direction (MD).

  The preheating unit 34 includes rollers 40 and 40 whose surface temperatures can be adjusted. The film 32 is preheated (heated) by winding the film 32 around the rollers 40 and 40. The preheated film 32 is conveyed to the longitudinal stretching unit 36.

  The longitudinally extending portion 36 includes a pair of low speed rollers 42 and 42 and a pair of high speed rollers 44 and 44. The film 32 is sandwiched and conveyed by the rollers 42, 42 and 44, 44. At that time, the film 32 is stretched in the machine direction (MD) due to the speed difference between the low speed roller 42 and the high speed roller 44.

  A non-contact heating device (not shown) is provided between the low speed roller 42 and the high speed roller 44. The film 32 during stretching is heated by the heating device. The configuration of the heating device is not particularly limited. For example, a near-infrared heater such as blowing hot air, a far-infrared heater, or a condensing heater can be used. By the heating device, the temperature of the film 32 is controlled to be (Tg−50 ° C.) or more and (Tg + 50 ° C.) or less.

  The inter-surface distance L between the low speed roller 42 and the high speed roller 44 is preferably 2 mm to 2000 mm. When the distance L is smaller than the above range, a space for placing the heating device cannot be secured. In addition, when the distance L is larger than the above range, the conveyance of the film 32 becomes unstable. As a result, wrinkles are generated in the longitudinal direction of the film, optical characteristics are uneven, or the film has a waveform. There is a possibility that a problem of deformation occurs.

  The film 32 is stretched in the machine direction (MD) by the longitudinal stretching section 36 configured as described above. In this stretching, the longitudinal stretching ratio is preferably 1.05 to 1.6 times. By longitudinally stretching in such a range, when a heat treatment described later is performed, the in-plane retardation Re is 100 to 300 nm, the thickness direction retardation Rth is Re × 0.5 or less, and the slow axis deviation is wide. A retardation cellulose acylate film having a characteristic of ± 5 ° or less with respect to the direction (TD) can be produced. The film 32 longitudinally stretched by the longitudinal stretching unit 36 is sent to the heat treatment unit 38.

  The heat treatment section 38 is provided with a heating furnace (not shown) and controlled so that the temperature T of the film 32 satisfies (Tc) ≦ T ≦ (Tc + 80 ° C.). Here, Tc is a crystallization temperature. By controlling the temperature T of the film 32 within the above range, the film 32 is crystallized and thermally contracted by 10 to 50% in the width direction (TD).

  FIG. 3 is a plan view showing the configuration of the heat treatment apparatus 50 constituting the heat treatment unit 38. As shown in the figure, the heat treatment apparatus 50 includes a pair of endless chains 52 and 52, and the chains 52 and 52 are disposed on both sides in the width direction of the film 32. The chain 52 is wound around two sprockets 54 and 55, respectively. By rotating one of the sprockets 54 and 55 with a driving device (not shown), the chain 52 travels around.

  A plurality of clips 56, 56... Are attached to the pair of chains 52 at a predetermined pitch. The clip 56 is a member that holds the end of the film 32 in the width direction. The clip 56 is moved so as to circulate between the sprockets 54 and 55 together with the chain 52. A guide rail 58 is provided between the sprockets 54 and 55. A clip 56 that moves between the sprockets 54 and 55 is guided by a guide rail 58.

  The guide rails 58 are provided on both sides of the film 32 in the width direction (TD). The interval between the guide rails 58 and 58 is configured to change from the upstream side to the downstream side in the conveyance direction (MD) of the film 32. The heat treatment apparatus 50 includes a wide portion (hereinafter referred to as a heating portion) α formed such that the distance between the guide rails 58 and 58 is substantially constant (or slightly widened) from the upstream side to the downstream side in the conveyance direction of the film 32. , A portion (hereinafter referred to as a contracting portion) β formed so as to be gradually reduced, and a portion (hereinafter referred to as a holding portion) γ formed with a substantially constant narrow width. From the upstream side to the downstream side in the transport direction (MD) of the film 32, the distance between the guide rails 58, 58 is narrowed, and the distance between the clips 56, 56 holding both ends of the film 32 is narrowed.

  4 is a perspective view showing the clip 56, and FIG. 5 is a cross-sectional view thereof. As shown in these drawings, the clip 56 mainly includes a main body 60 and a pedestal 62. The pedestal 62 is formed with an attachment portion 62A to which the chain 52 is attached and a guide portion 62B guided by the guide rail 58. By engaging the guide portion 62B with the guide rail 68, the pedestal 42 is formed. It is moved along the guide rail 58.

  A flapper 64 is pivotally attached to the main body 60 so as to be rotatable. The flapper 64 has a pressing portion 64 </ b> A at its lower end, and can grip the end portion of the film 32 between the pressing portion 64 </ b> A and the main body 60. A drive lever 64B is formed at the upper end of the flapper 64. The flapper 64 is swung by the drive lever 64B being pressed laterally by a guide (not shown). The guides are provided at the positions of the sprockets 54 and 54. At this position, the flapper 64 is swung, and the gripping of the film 32 by the pressing portion 64A and the release of the gripped state are switched.

  Specifically, the clip 56 grips the end of the film 32 at the position of the sprocket 54 provided on the upstream side in the transport direction of the film 32. The clip 56 is conveyed to the position of the sprocket 55 on the downstream side while being held. The clip 56 is configured to release the grip of the film 32 at the position of the sprocket 55 on the downstream side. As a result, both ends of the film 32 are gripped at the position of the upstream sprocket 54 and the grip is released at the position of the downstream sprocket 55.

  3, when the film 32 contracts in the width direction, the clip 56 grips the end portion of the film 32, so that “the film 32 is prevented from loosening and the end portion of the film 32 is It is configured not to pull excessively outward. Specifically, the trajectory of the clip 56 such that “the film 32 does not sag in the width direction and the film 32 is not excessively pulled outward” is obtained in advance by a test or the like, and the clip 56 travels along this trajectory. A guide rail 58 is disposed on the side. As a result, the film 32 is shrunk by 10 to 50% in the width direction.

  The state that “the film 32 does not sag in the width direction and the film 32 is not excessively pulled outward” is obtained by detecting the height position of the central portion in the width direction of the film 32 with an optical sensor or the like. be able to. That is, the height position of the central portion when the film 32 is slack and the height position of the central portion when the film 32 is excessively pulled outward by the clip 56 are obtained. The trajectory of the clip 56 is set so that is in the middle.

  According to the heat treatment section 38 configured as described above, the film 32 is heated to near the crystallization temperature, and is thermally contracted in the width direction while being crystallized. At that time, since the clip 56 holds the end of the film 32 in the width direction, the end of the film 32 can be prevented from acting like a free end. It is possible to prevent the film 32 from being deformed into a corrugated shape or the occurrence of uneven optical characteristics as in the prior art. Further, in the present embodiment, the film 32 is prevented from being pulled excessively by the clip 56, so that the film 32 is naturally thermally contracted by crystallization. Therefore, it is possible to prevent the occurrence of uneven optical characteristics as in the case of being pulled outward.

  In the above-described embodiment, the width of the guide rails 58 and 58 in the contraction part β is set to an appropriate value in advance so that “the film 32 does not slack and is not excessively pulled outward”. However, the method is not limited to the above.

  For example, as shown in FIG. 6, the main body 60 and the pedestal 62 may be attached via a rail 66 so that the main body 60 can be slidably supported with respect to the pedestal 62 in the width direction of the film 32. Thereby, in the contraction part β, when the film 32 is thermally contracted, the main body 60 is pulled and moved by the film 32, so that the clip 56 can be prevented from pulling the film 32 too much. Further, by setting the predetermined friction between the main body 60 and the pedestal 62, the clip 56 can prevent the end portion of the film 32 from acting like a free end. It is possible to prevent the occurrence of uneven optical characteristics.

  Moreover, you may comprise a heat processing part as shown in FIG. In the heat treatment part of FIG. 7, the guide rails 68 and 68 are arranged separately from the heating part α and the holding part γ, and the contraction part β has no guide rail. Therefore, the clip 56 can freely move in the width direction at the contraction portion β, and the clip 56 can be prevented from excessively pulling the film 32 outward. Further, since the clip 56 is supported by the chain 52, the clip 56 can prevent the end portion of the film 32 from acting like a free end.

  Next, a second method for shrinking an unstretched cellulose acylate film in the width direction will be described. The second method is a method in which an unstretched cellulose acylate film is stretched in the machine direction (MD) and simultaneously contracted in the width direction without grasping the end in the width direction of the film.

  FIG. 8 schematically shows the configuration of the processing apparatus. As shown in the figure, the processing device 70 includes a delivery device 72 that sends out the cellulose acylate film 32, a pair of low-speed rollers 74 and 74, a pair of high-speed rollers 76 and 76, a low-speed roller 74, and a high-speed roller 76. The heating furnace 78 is disposed in the middle, the cooling furnace 80 is disposed at the rear stage of the heating furnace 78, and the winder 82 is configured to wind up the cellulose acylate film 32 contracted in the width direction.

  The cellulose acylate film 32 is nipped by rollers 74, 74 and 76, 76 and conveyed in the heating furnace 78. At that time, the film 32 is stretched in the machine direction (MD) due to the speed difference between the low speed roller 74 and the high speed roller 76. The cellulose acylate film 32 is stretched in the machine direction (MD) and simultaneously contracted by 10 to 50% in the width direction in the heating furnace 78.

At this time, the cellulose acylate film 32 has a longitudinal stretch ratio in the machine direction (MD) of 1 to 2 times in the machine direction (MD) due to a difference in peripheral speed between the low speed rollers 74 and 74 and the high speed rollers 76 and 76, and the film width / (Longitudinal stretch ratio) ^1/2 > Stretched in the machine direction (MD) so as to satisfy the relational expression of film width after longitudinal stretching.

  The stretching time in the heating furnace 78 is preferably 1 second or more and 100 seconds or less, and the distance between the surfaces of the low speed roller 74 and the high speed roller 76 is preferably 1 m or more and 100 m or less. By using the above-mentioned distance between planes, it is not instantaneous longitudinal stretching that pulls a film in a moment (usually about 0.5 seconds) as in conventional longitudinal stretching, but it takes a long stretching time and a long stretching distance. Long span stretching in which the film A is stretched longitudinally while being slowly pulled can be performed. The stress applied in the longitudinal direction of the cellulose acylate film 32 between the low speed roller 74 and the high speed roller 76 is preferably set in a range of 0.4 MPa to 8 MPa. Moreover, it is preferable that the thickness of the longitudinally unstretched cellulose acylate film 32 is 60 to 120 μm.

  In the heating furnace 78, a plurality of heating nozzles 84, 84... Are arranged at the upper and lower positions of the cellulose acylate film 32 to be conveyed and in the film conveying direction. Hot air is blown out from the heating nozzle 84 toward the cellulose acylate film 32. The temperature in the heating furnace 78 is controlled so as to satisfy a stretching temperature in the range of Tc to Tc + 80 ° C. when the crystallization temperature of the cellulose acylate film 32 is Tc. In this case, it is preferable that the heating rate at which the cellulose acylate film 32 is heated to the stretching temperature in the heating furnace 78 is 10 to 400 ° C./min.

  The cellulose acylate film 32 passing through the heating furnace 78 is floated and conveyed by the pressure of hot air blown from the heating nozzle 84. By floating and transporting, the cellulose acylate film 32 is uniaxially stretched at a free end in a state where a free end is formed in the width direction. The flying height when the cellulose acylate film 32 is floated and conveyed is preferably within 30 mm. In addition, as long as it can extend | stretch at a free end, this invention is not limited to the floating conveyance by a hot air.

  A plurality of cooling nozzles 86, 86 are disposed in the cooling furnace 80 in the film transport direction (longitudinal direction). Cool air is blown out from the cooling nozzle 86 toward the cellulose acylate film 32. By disposing the cooling furnace 80 at the subsequent stage of the heating furnace 78, the cellulose acylate film 32 in which the free end uniaxial stretching is finished is promptly cooled below the stretching temperature while being floated and conveyed. Since it is levitated and conveyed by cold air, Rth and Re hardly change. Moreover, since it floats and conveys, a film surface is hard to be damaged compared with the case where there is a conveyance roller.

  The cellulose acylate film 32 cooled to room temperature in the cooling furnace 80 is taken up by a winder 82.

  In the present invention, the cellulose acylate film heat-shrinked in the width direction is characterized in that the film surface temperature of the film is Tc to Tc + 80 ° C. and the film is stretched 1 to 30% of the entire width in the width direction (TD). By re-stretching the film contracted in the width direction in the width direction, the brittleness of the film is improved. It is considered that by subjecting the cellulose acylate film shrunk in the width direction to stretching, the longitudinal orientation is lost and the brittleness of the film is improved. Moreover, the cellulose acylate film excellent in planar shape and planarity can be obtained by performing a extending | stretching process.

  For example, a heat treatment apparatus 92 shown in FIG. 9 is applied to the transverse stretching unit 90 that performs stretching in the width direction. The heat treatment apparatus 92 includes a pair of endless chains 52 and 52, and the chains 52 and 52 are disposed on both sides of the film 32 in the width direction. The chain 52 is wound around two sprockets 54 and 55, respectively. By rotating one of the sprockets 54 and 55 with a driving device (not shown), the chain 52 travels around.

  A plurality of clips 56, 56... Are attached to the pair of chains 52 at a predetermined pitch. The clip 56 is a member that holds the end of the film 32 in the width direction. The clip 56 is moved so as to circulate between the sprockets 54 and 55 together with the chain 52. A guide rail 58 is provided between the sprockets 54 and 55. A clip 56 that moves between the sprockets 54 and 55 is guided by a guide rail 58.

  The guide rails 58 are provided on both sides of the film 32 in the width direction (TD). The interval between the guide rails 58 and 58 is configured to change from the upstream side to the downstream side in the conveyance direction (MD) of the film 32. The heat treatment apparatus 92 has a narrow portion (hereinafter referred to as a heating section) α formed such that the distance between the guide rails 58 and 58 is substantially constant (or slightly widened) from the upstream side to the downstream side in the conveyance direction of the film 32. And a portion (hereinafter referred to as a stretched portion) β ′ formed so as to be gradually widened and a portion (hereinafter referred to as a holding portion) γ ′ formed with a substantially constant wide width. The distance between the guide rails 58 and 58 increases from the upstream side to the downstream side in the transport direction (MD) of the film 32, and the distance between the clips 56 and 56 that grip both ends of the film 32 increases.

  The heat treatment apparatus 92 has basically the same configuration as the heat treatment apparatus 50. The difference between the two apparatuses is that the transport direction of the film 32 is reversed. In the heat treatment apparatus 50, the film 32 is conveyed from the α portion where the distance between the guide rails 58 is wide to the γ portion where the distance between the guide rails 58 is narrow. On the other hand, in the heat treatment apparatus 92, the film 32 is transported from the α ′ portion where the distance between the guide rails 58 is narrow to the γ ′ portion where the distance between the guide rails 58 is wide. The distance between the guide rails 58 of the heat treatment apparatus 92 is determined so that the film 32 is stretched by 1 to 30% in the width direction when the film 32 is transported from the α ′ portion to the γ ′ portion. Is done.

  When the film 32 is contracted in the width direction by the heat treatment apparatus 50, the film 32 can be continuously stretched in the width direction by the heat treatment apparatus 92 in a state where both ends are held. Further, after the film 32 is shrunk in the width direction by the heat treatment apparatus 50 and wound once, the film 32 can be set in the heat treatment apparatus 92 and stretched in the width direction.

  In this case, the stretching ratio in the transverse direction is determined so that the in-plane retardation Re of the film after stretching is 100 to 300 nm and the thickness direction retardation Rth is Re × 0.5 or less. Further, by controlling the temperature during stretching to Tc to Tc + 80 ° C., it is possible to prevent the cellulose acylate film 32 from having a thickness direction retardation RTh / in-plane retardation Re larger than 0.5.

  By the method described above, the in-plane retardation Re is 100 to 300 nm, the thickness direction retardation Rth is Re × 0.5 or less, the slow axis deviation is ± 5 ° or less with respect to the width direction, and the fracture is caused by a tensile tester. A cellulose acylate film 32 having a characteristic that the elongation at break in the longitudinal direction measured by the elongation measurement is 5% or more is produced.

  The longitudinal elongation measured by measuring the elongation at break with a tensile tester is a distance between chucks of 50 mm, a sample width of 10 mm, and an environment of 25 ° C. and 60% using a tensile tester (Strograph) manufactured by Toyo Seiki. A tensile test was conducted at a pulling speed of 10 mm / min, and the elongation at the time when the film broke was defined as the breaking elongation.

  The cellulose acylate film (hereinafter, reference numerals are omitted) preferably has a single layer structure. Here, the film of “single layer structure” means a single cellulose acylate film, not a plurality of film materials bonded together or a coating layer on the surface. And the case where one sheet of a cellulose acylate film is produced from a plurality of cellulose acylate solutions using a sequential casting method or a co-casting method is included. In this case, a cellulose acylate film having a distribution in the thickness direction can be obtained by appropriately adjusting the type and blending amount of additives, the molecular weight distribution of cellulose acylate, the type of cellulose acylate, and the like. Moreover, what has various functional parts, such as an optical anisotropy part, a glare-proof part, a gas barrier part, and a moisture-resistant part, in those one film is also included.

[surface treatment]
The cellulose acylate film of the present invention can be appropriately surface-treated to improve adhesion with each functional layer (for example, an undercoat layer, a back layer, and an optically anisotropic layer). The surface treatment includes glow discharge treatment, ultraviolet irradiation treatment, corona treatment, flame treatment, saponification treatment (acid saponification treatment, alkali saponification treatment), and glow discharge treatment and alkali saponification treatment are particularly preferable. The “glow discharge treatment” here is a treatment for subjecting the film surface to a plasma treatment in the presence of a plasma-excitable gas. The details of these surface treatment methods are described in the Japan Institute of Invention Disclosure Technical Bulletin (Public Technical No. 2001-1745, issued on March 15, 2001, Japan Institute of Invention) and can be used as appropriate.

  In order to improve the adhesion between the film surface and the functional layer, an undercoat layer (adhesive layer) may be provided on the cellulose acylate film of the present invention in addition to or in place of the surface treatment. About the said undercoat, it describes in an invention association public technical bulletin (public technical number 2001-1745, March 15, 2001 issue, invention association) 32 pages, These can be used suitably. Moreover, about the functional layer provided on the cellulose acylate film of the present invention, it is described in pages 32 to 45 of the Japan Society for Invention and Technology (Public Technical Number 2001-1745, published on March 15, 2001, Japan Society of Invention). And those described herein can be used as appropriate.

<Optical compensation film>
The cellulose acylate film of the present invention can also be used as an optical compensation film. The “optical compensation film” generally means an optical material having optical anisotropy, which is used in a display device such as a liquid crystal display device, and is a retardation film, a retardation plate, an optical compensation film, an optical compensation. Synonymous with sheet. In a liquid crystal display device, an optical compensation film is used for the purpose of improving the contrast of a display screen or improving viewing angle characteristics and color.

  The cellulose acylate film of the present invention can be used as an optical compensation film as it is. In addition, a plurality of the cellulose acylate films of the present invention may be laminated, or the cellulose acylate film of the present invention and a film other than the present invention may be laminated to appropriately adjust Re and Rth to be used as an optical compensation film. You can also. Lamination of the film can be performed using a pressure-sensitive adhesive or an adhesive.

  In some cases, the cellulose acylate film of the present invention may be used as a support for an optical compensation film, and an optically anisotropic layer made of liquid crystal or the like may be provided thereon to be used as an optical compensation film. The optical viewing layer applied to the optical compensation film of the present invention may be formed from, for example, a composition containing a liquid crystal compound or may be formed from a cellulose acylate film having birefringence.

  The liquid crystal compound is preferably a discotic liquid crystal compound or a rod-like liquid crystal compound.

[Discotic liquid crystalline compounds]
Examples of discotic liquid crystalline compounds that can be used as the liquid crystalline compound in the present invention include various documents (for example, C. Destradedeal., Mol. Crysr. Liq. Cryst., VOL. 71, pagelll (1981); Edited by Chemical Society of Japan, Quarterly Chemical Review, No. 22, Chemistry of Liquid Crystal, Chapter 5, Chapter 10 Section 2 (1994); B. Kohne et al., Angew. Chem. Soc. Chem. Comm., Page 1794. (1985); J. Zhang et al., J. Am.

  In the optically anisotropic layer, the discotic liquid crystalline molecules are preferably fixed in an aligned state, and most preferably fixed by a polymerization reaction. Further, the polymerization of discotic liquid crystalline molecules is described in JP-A-8-27284. In order to fix the discotic liquid crystalline molecules by polymerization, it is necessary to bond a polymerizable group as a substituent to the discotic core of the discotic liquid crystalline molecules. However, when the polymerizable group is directly connected to the disc-shaped core, it becomes difficult to maintain the orientation state in the polymerization reaction. Therefore, a linking group is introduced between the discotic core and the polymerizable group. Discotic liquid crystalline molecules having a polymerizable group are disclosed in JP-A No. 2001-4387.

[Bar-shaped liquid crystalline compound]
Examples of rod-like liquid crystalline compounds that can be used as the liquid crystalline compound in the present invention include azomethenes, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexane. , Cyano-substituted phenylpyrimidines, alkoxy-substituted phenylpyrimidines, phenyldioxanes, tolanes and alkenylcyclohexylbenzonitriles. Further, as the rod-like liquid crystal compound, not only the above low molecular liquid crystal compound but also a polymer liquid crystal compound can be used.

  In the optically anisotropic layer, the rod-like liquid crystalline molecules are preferably fixed in an aligned state, and most preferably fixed by a polymerization reaction. Examples of polymerizable rod-like liquid crystalline compounds that can be used in the present invention are described in, for example, Makrotnol. Chem. . 190, 2255 (1989), Advanced Materials 5, 107 (1993), U.S. Pat. Nos. 4,683,327, 5,622,648, 5,770,107 No., WO95 / 22586 pamphlet, 95/24455 pamphlet, 97/00600 pamphlet, 98/23580 pamphlet, 98/52905 pamphlet, JP-A-1-272551, The compounds described in JP-A-6-16616, JP-A-7-110469, JP-A-11-80081, JP-A-2001-328773, and the like are included.

(Optically anisotropic layer made of polymer film)
The optically anisotropic layer may be formed from a polymer film. The polymer film can be formed from a polymer that can exhibit optical anisotropy. Examples of the polymer that can exhibit the optical anisotropy include polyolefin (eg, polyethylene, polypropylene, norbornene-based polymer), polycarbonate, polyarylate, polysulfone, polyvinyl alcohol, polymethacrylic acid ester, polyacrylic acid ester, and Cellulose esters (eg, cellulose triacetate, cellulose diacetate) are included. Moreover, as the polymer, a copolymer or polymer mixture of these polymers may be used.

"Polarizer"
The cellulose acylate film or optical compensation film of the present invention can be used as a protective film for a polarizing plate (polarizing plate of the present invention). The polarizing plate of the present invention comprises a polarizing film and two polarizing plate protective films (cellulose acylate film) protecting both surfaces thereof, and the cellulose acylate film or optical compensation film of the present invention is at least one polarizing plate protective film. Can be used as Moreover, the cellulose acylate film of this invention can be bonded by a polarizing film and roll-to-roll using an adhesive agent.

  When the cellulose acylate film of the present invention is used as the polarizing plate protective film, the cellulose acylate film of the present invention is subjected to the surface treatment (also described in JP-A Nos. 6-94915 and 6-118232). For example, glow discharge treatment, corona discharge treatment, or alkali saponification treatment is preferably performed, and alkali saponification treatment is most preferably used as the surface treatment.

  As the polarizing film, for example, a film obtained by immersing and stretching a polyvinyl alcohol film in an iodine solution can be used. When using a polarizing film obtained by immersing and stretching a polyvinyl alcohol film in an iodine solution, the surface-treated surface of the cellulose acylate film of the present invention can be directly bonded to both surfaces of the polarizing film using an adhesive. In the production method of the present invention, it is preferable that the cellulose acylate film is directly bonded to the polarizing film as described above. As the adhesive, an aqueous solution of polyvinyl alcohol or polyvinyl acetal (eg, polyvinyl butyral) or a latex of a vinyl polymer (eg, polybutyl acrylate) can be used. A particularly preferred adhesive is an aqueous solution of fully saponified polyvinyl alcohol.

  In general, a liquid crystal display device includes four polarizing plate protective films because a liquid crystal cell is provided between two polarizing plates. The cellulose acylate film of the present invention can be suitably used for any of the four polarizing plate protective films. Among them, the cellulose acylate film of the present invention is particularly preferably used as an outer protective film that is not disposed between the polarizing film and the liquid crystal layer (liquid crystal cell) in the liquid crystal display device. In this case, the transparent hard coat layer, the antiglare layer are used. A layer, an antireflection layer, or the like can be provided.

<Liquid crystal display device>
The cellulose acylate film, optical compensation film and polarizing plate of the present invention can be used for liquid crystal display devices in various display modes. The cellulose acylate film and optical compensation film of the present invention have a low moisture permeability, and this moisture permeability does not increase even when exposed to wet heat. Therefore, a polarizing plate using the same suppresses a decrease in the degree of polarization over a long period of time. can do. Therefore, a highly reliable liquid crystal display device can be provided.

  Each liquid crystal mode in which these films are used will be described below. These liquid crystal display devices may be any of a transmissive type, a reflective type, and a transflective type.

(TN type liquid crystal display device)
The cellulose acylate film of the present invention can be used as a support for an optical compensation film of a TN type liquid crystal display device having a TN mode liquid crystal cell. TN mode liquid crystal cells and TN type liquid crystal display devices have been well known for a long time. As for the optical compensation film used in the TN type liquid crystal display device, each of JP-A-3-9325, JP-A-6-148429, JP-A-8-50206, and JP-A-9-26572, and Mori. Other papers (Jpn. J. Appl. Phys. Vol. 36 (1997) p. 143 and Jpn. J. Appl. Phys. Vol. 36 (1997) p. 1068) are described.

(STN type liquid crystal display device)
The cellulose acylate film of the present invention may be used as a support for an optical compensation film of an STN type liquid crystal display device having an STN mode liquid crystal cell. In general, in a STN type liquid crystal display device, rod-like liquid crystalline molecules in a liquid crystal cell are twisted in the range of 90 to 360 degrees, and the refractive index anisotropy (Δn) and cell gap (d ) In the range of 300 to 1500 nm. The optical compensation film used for the STN type liquid crystal display device is described in JP-A No. 2000-105316.

(VA type liquid crystal display device)
The cellulose acylate film of the present invention can be used as an optical compensation film of a VA liquid crystal display device having a VA mode liquid crystal cell or a support for the optical compensation film. The VA-type liquid crystal display device may be an alignment-divided system as described in, for example, JP-A-10-123576.

(IPS liquid crystal display device and ECB liquid crystal display device)
The cellulose acylate film of the present invention is particularly an IPS liquid crystal display device having an IPS mode and ECB mode liquid crystal cell, an optical compensation film for an ECB liquid crystal display device, a support for the optical compensation film, or a protective film for a polarizing plate. It is advantageously used. In these modes, the liquid crystal material is aligned substantially in parallel during black display, and black is displayed by aligning liquid crystal molecules in parallel with the substrate surface in the absence of applied voltage.

(OCB type liquid crystal display device and HAN type liquid crystal display device)
The cellulose acylate film of the present invention is also advantageously used as a support for an optical compensation film of an OCB type liquid crystal display device having an OCB mode liquid crystal cell or a HAN type liquid crystal display device having a HAN mode liquid crystal cell. In the optical compensation film used for the OCB type liquid crystal display device or the HAN type liquid crystal display device, it is preferable that the direction in which the absolute value of retardation is minimum does not exist in the plane of the optical compensation film or in the normal direction. The optical properties of the optical compensation film used in the OCB type liquid crystal display device or the HAN type liquid crystal display device are the optical properties of the optically anisotropic layer, the optical properties of the support, and the optically anisotropic layer and the support. Is determined by the arrangement of An optical compensation film used for an OCB type liquid crystal display device or a HAN type liquid crystal display device is described in JP-A-9-197397. Moreover, it is described in Mori et al. (Jpn. J. Appl. Phys. Vol. 38 (1999) p. 2837).

(Reflective liquid crystal display)
The cellulose acylate film of the present invention is also advantageously used as an optical compensation film for TN type, STN type, HAN type, and GH (Guest-Host) type reflective liquid crystal display devices.

  These display modes have been well known since ancient times. The TN-type reflective liquid crystal display device is described in JP-A-10-123478, WO98 / 48320 pamphlet, and Japanese Patent No. 3022477. The optical compensation film used in the reflective liquid crystal display device is described in International Publication No. 00/65384 pamphlet.

(Other liquid crystal display devices)
The cellulose acylate film of the present invention is also advantageously used as a support for an optical compensation film of an ASM type liquid crystal display device having a liquid crystal cell in an ASM (Axial Synthetic Aligned Microcell) mode. The ASM mode liquid crystal cell is characterized in that the thickness of the cell is maintained by a position-adjustable resin spacer. Other properties are the same as those of the TN mode liquid crystal cell. The ASM-mode liquid crystal cell and the ASM-type liquid crystal display device are described in a paper by Kume et al. (Kume et al., SID98DigestlO89 (1998)).

《Hard coat film, antiglare film, antireflection film》
In some cases, the cellulose acylate film of the present invention may be applied to a hard coat film, an antiglare film, and an antireflection film. For the purpose of improving the visibility of flat panel displays such as LCD, PDP, CRT, EL, etc., any or all of a hard coat layer, an antiglare layer and an antireflection layer are provided on one or both sides of the cellulose acylate film of the present invention. Can be granted. Preferred embodiments of such an antiglare film and antireflection film are described in detail on pages 54 to 57 of the Japan Society for Invention and Innovation (Publication No. 2001-1745, published on March 15, 2001, Japan Society of Invention and Innovation). It can be preferably used also in the cellulose acylate film of the present invention.

  As a pre-stretch film, a Fujitac film Fujitac film (thickness 80 μm, Tg 140 ° C., Tc 195 ° C.) was used. The film before stretching was subjected to longitudinal stretching treatment and heat treatment under the longitudinal stretching conditions and heat treatment conditions shown in the table of FIG. 8 to obtain a film product.

The table of FIG. 10 shows longitudinal stretching conditions, film heating conditions, width shrinkage conditions, re-lateral stretching conditions for Examples (1 to 4 ) , Reference Examples 5 and 6 and Comparative Examples (1 to 4 ) of the present invention, and The evaluation (Re, Rth) of the manufactured stretched cellulose triacetate film is summarized and listed.

  In FIG. 10, “span” means the distance between the surfaces of a pair of stretching rollers, and “breaking elongation” means the breaking elongation in the longitudinal direction measured by measuring the breaking elongation with a tensile tester. Specifically, a tensile test was performed by using a tensile tester (Strograph) manufactured by Toyo Seiki, under an environment of 25 ° C. and 60%, a distance between chucks of 50 mm, a sample width of 10 mm, and a tensile speed of 10 mm / min. The brittleness was evaluated by the elongation at break in the tensile test. A: Greater than 6%, B: 5-6%, evaluated as a level of less than 5%.

Examples 1 to 4 are cases where all of the longitudinal stretching conditions, film heating conditions, and width shrinkage conditions in the table of FIG. 10 are satisfied. In the table of FIG. 10, Reference Examples 5 and 6 are examples in which the film is contracted in the width direction while stretching at the free end in the vertical direction.

  Comparative Example 1 is a case where the width contraction is performed at the lower limit magnification (10%) or less of the width contraction step which is an essential condition of the present invention, and re-lateral stretching is not performed. The comparative example 2 is a case where width shrinkage is performed below the lower limit temperature (Tc) of the width shrinkage step, which is an essential condition of the present invention. Comparative Example 3 is a case where re-lateral stretching was performed at an upper limit ratio (30%) of re-horizontal stretching which is an essential condition of the present invention. Comparative Example 4 is a case where width contraction is performed at a lower limit magnification (10%) or less of the width contraction step which is an essential condition of the present invention.

As a result, Examples 1 to 4 were improved in brittleness, and all were evaluated as ◯ or more. In addition, Re was 100 nm or more, which is the target of the present invention. Furthermore, Examples 1 to 4 all satisfied Rth <Re / 2, which is the target of the present invention, when calculated from the relationship between Re and Rth in FIG.

  On the other hand, the comparative example 1 was x in brittle evaluation. Comparative Example 2 was evaluated as ◯ for brittleness, but Re was 80 nm, which did not satisfy the target of the present invention of 100 nm or more. Comparative Example 3 broke during re-lateral stretching and could not be measured. In Comparative Example 4, Re was 75 nm and did not satisfy the target of the present invention of 100 nm or more.

The figure which shows the schematic structure of a casting film forming line The figure which shows schematic structure of the extending | stretching and heat processing apparatus to which this invention is applied Plan view showing heat treatment part Perspective view showing clip Vertical section showing clip FIG. 4 is a longitudinal sectional view showing a clip having a structure different from that of FIG. FIG. 2 is a plan view showing a heat treatment part having a structure different from FIG. FIG. 2 is a plan view showing a heat treatment part having a structure different from FIG. Plan view showing the structure of the transverse stretch Table showing the results of the examples

Explanation of symbols

  DESCRIPTION OF SYMBOLS 30 ... Stretching / heat treatment apparatus, 32 ... Film, 34 ... Preheating part, 36 ... Longitudinal stretching part, 38 ... Heat treatment part, 50 ... Heat treatment apparatus, 52 ... Chain, 54 ... Sprocket, 56 ... Clip, 58 ... Guide rail, 60 ... Main body, 62 ... Pedestal, 70 ... Processing device, 78 ... Heating furnace, 90 ... Horizontal stretching section, 92 ... Heat treatment device

Claims (3)

In the method for producing a retardation cellulose acylate film,
A step of obtaining a shrinking trajectory of the cellulose acylate film in advance;
Supplying a cellulose acylate film;
The cellulose acylate film is heated to a temperature of Tc to Tc + 80 ° C. and subjected to a shrinkage treatment of 10 to 50% in the width direction (TD) along the trajectory while gripping the width direction end of the cellulose acylate film. When,
A step of stretching the cellulose acylate film shrunk in the width direction in the width direction (TD) by 1 to 30%, and a method for producing a retardation cellulose acylate film.   In the stretching treatment step, the film surface temperature of the cellulose acylate film is Tc-50 ° C. to Tc + 80 ° C., the in-plane retardation Re of the cellulose acylate film after the stretching treatment is 100 to 300 nm, and the thickness direction position The method for producing a retardation cellulose acylate film according to claim 1, wherein the stretching ratio is adjusted so that the phase difference Rth is Re × 0.5 or less. The method for producing a cellulose acylate film according to claim 1 or 2, wherein further, the shrinkage treatment step the longitudinal direction (MD) including a phase difference step of stretching the cellulose of the cellulose acylate film at a predetermined longitudinal draw ratio before A method for producing an acylate film.

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