JP5012497B2 - Optical film, method for manufacturing optical film, polarizing plate using the same, and liquid crystal display device - Google Patents

Description

  The present invention relates to an optical film, a method for producing the optical film, a polarizing plate using the same, and a liquid crystal display device.

  In recent years, the rise of liquid crystal display devices (liquid crystal displays), plasma displays, and organic EL displays has been remarkable as thin displays replacing CRT displays.

  These new generation displays are equipped with many optical films, but due to their thinness, demands for improving the performance of various functions of these optical films are becoming stricter year by year. Therefore, the appearance of an optical film with improved performance is awaited.

  On the other hand, the development of thinner and lighter notebook computers, larger screens, and higher definition is progressing. Along with this, there has been an increasing demand for thinner, wider and higher quality optical films for liquid crystal display devices.

  Various resins are used as optical films for liquid crystal display devices. Currently, cellulose ester, polycarbonate, and polyolefin are used for polarizing plate protective films as optical films. Among them, cellulose ester films using cellulose esters are overwhelmingly used.

  Until now, these cellulose ester films have been produced exclusively by the solution casting method. The solution casting method is a film forming method in which a solution obtained by dissolving cellulose ester in a solvent is cast to obtain a film shape, and then the solvent is evaporated and dried to obtain a film. Since a film formed by the solution casting method has high flatness, a high-quality liquid crystal display without unevenness can be obtained using this film.

  However, the solution casting method requires a large amount of an organic solvent and has a problem of a large environmental load. Cellulose ester film is formed using a halogen-based solvent with high environmental impact due to its dissolution characteristics, so it is particularly required to reduce the amount of solvent used, and the production of cellulose ester film is increased by solution casting film formation. It has become difficult to do.

  In addition, since the solvent remaining inside the film must be removed, the capital investment and production cost for the production line such as the drying line, the drying energy, and the recovery and regeneration device for the evaporated solvent are enormous. Reducing energy is also an important issue.

  About the cellulose-ester film for optical uses, there exists a manufacturing load and equipment load accompanying use of the solvent in the manufacturing process, and it is in a state with insufficient optical characteristics and mechanical characteristics.

  In recent years, attempts have been made to melt-cast cellulose ester as a polarizing plate protective film for protecting a polarizer, but cellulose ester is a polymer having a very high viscosity when melted, and Also, because the glass transition temperature is high, the cellulose ester is melted and extruded from a die, and it is difficult to level even if cast on a cooling drum or a cooling belt, and the optical properties and mechanical properties are lower than the solution cast film. There is a problem (see, for example, Patent Document 1).

  By the way, the cellulose ester film is usually wound around a core to form a roll-shaped film original, which is stored and transported.

  For this reason, if the film formed by melt casting is stored for a long time in the state of the film roll wound on the core, the horse's spine failure, the failure called the core transfer on the core portion of the film roll, and the film are rewound. It has been found that there is a problem that a failure such as a wrinkle start wrinkle that is wrinkled at the beginning is likely to occur.

  A horse's back failure is a failure in which the original film is deformed into a U-shape like a horse's back during storage, and a belt-like convex part is formed at a pitch of about 2 to 3 cm near the center. This is a failure in which the surface appears distorted when processed into a polarizing plate.

  The core transfer is a failure due to film deformation due to the irregularities of the core and film.

  The winding start wrinkle is a failure in which a wrinkle is generated at the leading portion when the film is rewinded to another core.

  It has been speculated that these failures due to long-term storage are also promoted by bleedout of film additives.

  In the past, failures caused by long-term storage of films have been reduced by lowering the coefficient of dynamic friction between the bases or adjusting the height of knurling (embossing) on both sides.

  These failures were not a major problem with films produced by solution casting, but it was found that films produced by melt casting had a major problem due to the low flatness of the film.

In particular, in recent years, with the increase in size of the screen, it is desired that the width of the original film is wide and the winding length is long. For this reason, the original film becomes wide and the original film load tends to increase, and these faults are more likely to occur, and therefore improvement is desired.
JP 2006-241428 A

  The present invention has been made in view of the above problems, and the object of the present invention is that haze is good, bleed-out is small even when stored for a long time, horse back failure, core transfer failure, winding start wrinkle failure, etc. An object of the present invention is to provide an optical film in which a deformation failure of the original film does not occur, a method for producing the optical film, a polarizing plate using the optical film, and a liquid crystal display device using the polarizing plate.

  Regarding the above problems, the inventors of the present invention diligently studied, and by adding a phosphate ester metal salt compound to the cellulose ester, haze is good, there is little bleed out even if stored for a long time, horse back failure, It was found that there was no deformation failure of the original film such as a roll transfer failure or a wrinkle failure at the beginning of winding.

  Furthermore, it has been found that the optical film of the present invention can be produced by a melt casting film forming method, and the present invention has been completed. Moreover, it discovered that the polarizing plate and liquid crystal display device which have a favorable characteristic can be provided by using such an optical film.

That is, the said subject of this invention is achieved by the following structures.
1. Following general formula (1), (2) or at least one and a method of manufacturing an optical optical film you containing a cellulose ester of the compound represented by (3), produce films by melt casting film forming method A method for producing an optical film .
(In the formula, R ¹ , R ² and R ³ are each independently an alkyl group having 1 to 30 carbon atoms which may have a substituent, or 6 to 6 carbon atoms which may have a substituent. 30 represents an aryl group, and any of R ¹ , R ² and R ³ may be bonded to each other to form a ring, M is a periodic table selected from Groups 1 to 15 excluding hydrogen and carbon And n represents the valence of the metal atom.)
2. The optical film contains at least one compound selected from the group consisting of lactone, sulfur, phenol, double bond, hindered amine and phosphorus compounds having no metal atom. 2. A method for producing an optical film according to 1.

  According to the present invention, optical films and optical films having good haze, low bleed-out even when stored for a long period of time, and free from deformation failures of the original film such as horse back failure, core transfer failure, winding start wrinkle failure, etc. A method, a polarizing plate using the method, and a liquid crystal display device can be provided.

The best mode for carrying out the present invention will be described in detail below, but the present invention is not limited thereto.
<Optical film>
In this invention, an optical film is a functional film used for various display apparatuses, such as a liquid crystal display, a plasma display, and an organic electroluminescent display. Specifically, it is a polarizing plate protective film for liquid crystal display apparatuses, retardation film, antireflection Films, brightness enhancement films, hard coat films, antiglare films, antistatic films, optical compensation films such as viewing angle expansion, and the like are included.

The optical film of the present invention comprises a compound represented by the general formula (1), (2) or (3), a resin serving as a base material, and other additives.
<Compound represented by formula (1), (2) or (3)>
The compound of the general formula (1), (2) or (3) of the present invention will be described.

In the general formula (1), (2) or (3), R ¹ , R ² and R ³ are each independently methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl, decyl, dodecyl, octadecyl, Carbon having 1 to 30 carbon atoms such as cyclohexyl and stearyl, or carbon which may have a substituent such as phenyl, nonylphenyl, butylphenyl, butylmethylphenyl, dibutylphenyl, dibutylmethylphenyl, biphenyl and octylphenyl Represents an aryl group of 6 to 30, and any one of R ¹ , R ² and R ³ may be bonded to each other to form a ring;

  M represents a metal atom selected from Groups 1 to 15 excluding hydrogen and carbon in the periodic table. Specifically, it represents a metal atom selected from the group consisting of titanium, zirconium, tin, antimony, cerium, germanium, barium, zinc, cobalt, manganese, iron, aluminum, magnesium, calcium, strontium, sodium and potassium, n represents the valence of the metal atom.

The alkyl group or aryl group represented by R ¹ , R ² and R ³ may have a substituent. Examples of the substituent include an alkyl group (for example, a methyl group, an ethyl group, a propyl group, an isopropyl group). Group, t-butyl group, pentyl group, hexyl group, octyl group, dodecyl group, trifluoromethyl group, etc.), cycloalkyl group (eg, cyclopentyl group, cyclohexyl group etc.), aryl group (eg, phenyl group, naphthyl group) Etc.), acylamino group (eg acetylamino group, benzoylamino group etc.), alkylthio group (eg methylthio group, ethylthio group etc.), arylthio group (eg phenylthio group, naphthylthio group etc.), alkenyl group (eg vinyl Group, 2-propenyl group, 3-butenyl group, 1-methyl-3-propenyl group, 3-pentenyl group 1-methyl-3-butenyl group, 4-hexenyl group, cyclohexenyl group, etc.), halogen atom (eg, fluorine atom, chlorine atom, bromine atom, iodine atom etc.), alkynyl group (eg, propargyl group etc.), Heterocyclic group (for example, pyridyl group, thiazolyl group, oxazolyl group, imidazolyl group, etc.), alkylsulfonyl group (for example, methylsulfonyl group, ethylsulfonyl group, etc.), arylsulfonyl group (for example, phenylsulfonyl group, naphthylsulfonyl group, etc.) ), Alkylsulfinyl group (eg, methylsulfinyl group, etc.), arylsulfinyl group (eg, phenylsulfinyl group, etc.), phosphono group, acyl group (eg, acetyl group, pivaloyl group, benzoyl group, etc.), carbamoyl group (eg, Aminocarbonyl group, methylaminocal Nyl group, dimethylaminocarbonyl group, butylaminocarbonyl group, cyclohexylaminocarbonyl group, phenylaminocarbonyl group, 2-pyridylaminocarbonyl group, etc.), sulfamoyl group (for example, aminosulfonyl group, methylaminosulfonyl group, dimethylaminosulfonyl group, Butylaminosulfonyl group, hexylaminosulfonyl group, cyclohexylaminosulfonyl group, octylaminosulfonyl group, dodecylaminosulfonyl group, phenylaminosulfonyl group, naphthylaminosulfonyl group, 2-pyridylaminosulfonyl group, etc.), sulfonamide group (for example, methane) Sulfonamide group, benzenesulfonamide group, etc.), cyano group, alkoxy group (for example, methoxy group, ethoxy group, propoxy group, etc.), aryloxy (Eg, phenoxy group, naphthyloxy group, etc.), heterocyclic oxy group, siloxy group, acyloxy group (eg, acetyloxy group, benzoyloxy group, etc.), aminocarbonyloxy group, amino group (eg, amino group, ethylamino) Group, dimethylamino group, butylamino group, cyclopentylamino group, 2-ethylhexylamino group, dodecylamino group, etc.), anilino group (for example, phenylamino group, chlorophenylamino group, toluidino group, anisidino group, naphthylamino group, 2 -Pyridylamino group, etc.), imide group, ureido group (for example, methylureido group, ethylureido group, pentylureido group, cyclohexylureido group, octylureido group, dodecylureido group, phenylureido group, naphthylureido group, 2-pyridylaminourea Id group etc.), alkoxycarbonylamino group (eg methoxycarbonylamino group, phenoxycarbonylamino group etc.), alkoxycarbonyl group (eg methoxycarbonyl group, ethoxycarbonyl group, phenoxycarbonyl etc.), aryloxycarbonyl group (eg Phenoxycarbonyl group, etc.), heterocyclic thio group, thioureido group, hydroxyl group, mercapto group and the like. These substituents may be further substituted with the same substituent.

R ¹ , R ² and R ³ usually have an alkyl substituent having 6 to 30 carbon atoms such as hexyl, octyl, decyl, dodecyl, hexadecyl, octadecyl, cyclohexyl, stearyl and the like because of their excellent compatibility with polymers. A compound is preferred, and the metal atom is preferably zinc, magnesium, calcium, or aluminum because zinc does not impair the durability of the optical film to be produced. Among these, zinc is particularly preferred.

  Specific examples of the compound of the general formula (1), (2) or (3) are: Mg salt of phosphoric acid methyl ester, Ca salt, Sr salt, Ba salt, Zn salt, Mg salt of phosphoric acid ethyl ester , Ca salt, Sr salt, Ba salt, Zn salt, Mg salt of propyl phosphate ester, Ca salt, Sr salt, Ba salt, Zn salt, Mg salt of isopropyl phosphate ester, Ca salt, Sr salt, Ba salt, Zn salt, Mg salt of butyl phosphate ester, Ca salt, Sr salt, Ba salt, Zn salt, Mg salt of isobutyl phosphate, Ca salt, Sr salt, Ba salt, Zn salt, of sec-butyl phosphate Mg salt, Ca salt, Sr salt, Ba salt, Zn salt, Mg salt of tert-butyl phosphate, Ca salt, Sr salt, Ba salt, Zn salt, Mg salt, Ca salt, Sr salt of pentyl phosphate , Ba salt, Zn salt, isopentyl phosphate Mg salt, Ca salt, Sr salt, Ba salt, Zn salt, Mg salt of neopentyl phosphate, Ca salt, Sr salt, Ba salt, Zn salt, Mg salt of hexyl phosphate, Ca salt, Sr Salt, Ba salt, Zn salt, Mg heptyl phosphate Mg salt, Ca salt, Sr salt, Ba salt, Zn salt, Mg octyl phosphate Mg salt, Ca salt, Sr salt, Ba salt, Zn salt, phosphoric acid Mg salt of nonyl ester, Ca salt, Sr salt, Ba salt, Zn salt, Mg salt of decyl phosphate ester, Ca salt, Sr salt, Ba salt, Zn salt, Mg salt of undecyl phosphate ester, Ca salt, Sr salt, Ba salt, Zn salt, Mg salt of dodecyl phosphate, Ca salt, Sr salt, Ba salt, Zn salt, Mg salt of tridecyl phosphate, Ca salt, Sr salt, Ba salt, Zn salt, Mg salt of tetradecyl phosphate Ca salt, Sr salt, Ba salt, Zn salt, Mg salt of pentadecyl phosphate, Ca salt, Sr salt, Ba salt, Zn salt, Mg salt of hexadecyl phosphate, Ca salt, Sr salt, Ba salt Zn salt, Mg salt of peptadecyl phosphate, Ca salt, Sr salt, Ba salt, Zn salt, Mg salt of octadecyl phosphate, Ca salt, Sr salt, Ba salt, Zn salt, distearyl phosphate Mg salt of ester, Ca salt, Sr salt, Ba salt, Zn salt, Mg salt of nonadecyl phosphate, Ca salt, Sr salt, Ba salt, Zn salt, Mg salt of eicosyl phosphate, Ca salt, Sr salt, Ba salt, Zn salt, Mg salt of heneicosyl phosphate, Ca salt, Sr salt, Ba salt, Zn salt, Mg salt of docosyl phosphate, Ca salt, Sr salt, Ba salt, Zn salt, Mg of phosphoric acid tricosyl ester Salt, Ca salt, Sr salt, Ba salt, Zn salt, Mg salt of phosphoric acid tetracosyl ester, Ca salt, Sr salt, Ba salt, Zn salt, Mg salt of phosphoric acid tricontyl ester, Ca salt, Sr salt, Ba salt, Zn salt, Mg salt of Tetracontyle phosphate, Ca salt, Sr salt, Ba salt, Zn salt, Mg salt of pentacontyl phosphate, Ca salt, Sr salt, Ba salt, Zn salt, phosphoric acid Mg salt of hexacontyl ester, Ca salt, Sr salt, Ba salt, Zn salt, Mg phosphate of vinyl phosphate ester, Ca salt, Sr salt, Ba salt, Zn salt, Mg salt of 1-propenyl phosphate phosphate, Ca Salt, Sr salt, Ba salt, Zn salt, Mg salt of phosphoric acid allyl ester, Ca salt, Sr salt, Ba salt, Zn salt, Mg salt of isopropenyl phosphate, Ca salt, Sr salt, Ba salt, Zn Salt, 1-butenyl phosphate Stell's Mg salt, Ca salt, Sr salt, Ba salt, Zn salt, Mg salt of 2-butenyl phosphate, Ca salt, Sr salt, Ba salt, Zn salt, Mg salt of 2-pentenyl phosphate, Ca salt, Sr salt, Ba salt, Zn salt, Mg salt of ethynyl phosphate, Ca salt, Sr salt, Ba salt, Zn salt, Mg salt of phosphate cyclopropyl ester, Ca salt, Sr salt, Ba salt, Zn salt, Mg salt of cyclopentyl phosphate, Ca salt, Sr salt, Ba salt, Zn salt, Mg salt of cyclohexyl phosphate phosphate, Ca salt, Sr salt, Ba salt, Zn salt, 1-cyclohexenyl phosphate Mg salt, Ca salt, Sr salt, Ba salt, Zn salt and the like.

  Mg salt of phosphoric acid phenyl ester, Ca salt, Sr salt, Ba salt, Zn salt, Mg salt of diphenyl phosphate, Ca salt, Sr salt, Ba salt, Zn salt, Mg salt of phosphoric acid o-tolyl ester , Ca salt, Sr salt, Ba salt, Zn salt, Mg salt of phosphoric acid m-tolyl ester, Ca salt, Sr salt, Ba salt, Zn salt, Mg salt of phosphoric acid p-tolyl ester, Ca salt, Sr salt Ba salt, Zn salt, Mg salt of 2,4-xylyl phosphate, Ca salt, Sr salt, Ba salt, Zn salt, Mg salt of 2,4,6-mesityl phosphate, Ca salt, Sr Salt, Ba salt, Zn salt, Mg salt of phosphoric acid o-camenyl ester, Ca salt, Sr salt, Ba salt, Zn salt, Mg salt of phosphoric acid m-camenyl ester, Ca salt, Sr salt, Ba salt, Zn Salt, Mg salt, Ca salt, Sr salt of p-camenyl phosphate Ba salt, Zn salt, Mg salt of benzyl phosphate ester, Ca salt, Sr salt, Ba salt, Zn salt, Mg salt of phenethyl phosphate, Ca salt, Sr salt, Ba salt, Zn salt, α-phosphate Mg salt of methyl benzyl ester, Ca salt, Sr salt, Ba salt, Zn salt, Mg salt of diphenyl methyl ester, Ca salt, Sr salt, Ba salt, Zn salt, Mg salt of triphenyl methyl phosphate, Ca salt, Sr salt, Ba salt, Zn salt, Mg salt of styryl phosphate, Ca salt, Sr salt, Ba salt, Zn salt, Mg salt of cinnamyl phosphate, Ca salt, Sr salt, Ba salt, Zn salt, Mg salt of 2-biphenylyl phosphate, Ca salt, Sr salt, Ba salt, Zn salt, Mg salt of 3-biphenylyl phosphate, Ca salt, Sr salt, Ba salt, Zn salt, phosphorus Acid 4-biphenylyl s Mg salt, Ca salt, Sr salt, Ba salt, Zn salt, Mg salt of 1-naphthyl phosphate, Ca salt, Sr salt, Ba salt, Zn salt, Mg salt of 2-naphthyl phosphate, Ca Salt, Sr salt, Ba salt, Zn salt, Mg salt of 1-antilyl phosphate, Ca salt, Sr salt, Ba salt, Zn salt, Mg salt of 2-antilyl phosphate, Ca salt, Sr salt Ba salt, Zn salt, Mg salt of 9-antilyl phosphate, Ca salt, Sr salt, Ba salt, Zn salt, Mg salt of phenanthryl phosphate, Ca salt, Sr salt, Ba salt, Zn Salt, 2,2′-methylenebis (4,6-di-tert-butylphenyl) sodium phosphate, and the like.

  Preferably, a magnesium salt mixture of phosphate mono- and distearyl ester (LBT-1812 manufactured by Sakai Chemical Industry Co., Ltd.), an aluminum salt mixture of mono- and distearyl phosphate phosphate (LBT-1813 manufactured by Sakai Chemical Industry Co., Ltd.) , Calcium salt mixture of phosphoric acid mono- and distearyl ester (LBT-1820, manufactured by Sakai Chemical Industry Co., Ltd.), zinc salt mixture of phosphoric acid mono- and distearyl ester (LBT-1830, manufactured by Sakai Chemical Industry Co., Ltd.), etc. A commercial item is mentioned.

  More preferably, a calcium salt mixture of phosphoric acid mono and distearyl ester (LBT-1820 manufactured by Sakai Chemical Industry Co., Ltd.) and a zinc salt mixture of phosphoric acid mono and distearyl ester (LBT-1830 manufactured by Sakai Chemical Industry Co., Ltd.) ).

In the present invention, the amount of the compound represented by the general formula (1), (2) or (3) is appropriately selected within a range not impairing the object of the present invention. Usually, 0.001 to 2.0 parts by mass, preferably 0.01 to 1.0 parts by mass, and more preferably 0.05 to 0.5 parts by mass. Two or more of these may be used in combination.
<Resin as base material>
As the base resin, in addition to cellulose ester or cellulose ester, polycarbonate resin, polystyrene resin, polysulfone resin, polyester resin, polyarylate resin, acrylic resin (including copolymer), Olefin resin (norbornene resin, cyclic olefin resin, cyclic conjugated diene resin, vinyl alicyclic hydrocarbon resin, etc.), cellulose ether resin, vinyl resin (polyvinyl acetate resin, polyvinyl alcohol resin, etc.) And the like).

  Among these, cellulose ester or cellulose ester in which an acrylic resin is used in combination is preferably used.

  The cellulose ester is contained in an amount of 100 to 30% by mass, preferably 99.9 to 70% by mass, based on the entire resin serving as a base material.

《Cellulose ester》
Next, the cellulose ester of the present invention and the optical film containing the cellulose ester (hereinafter also simply referred to as cellulose ester film) will be described in detail.

  The cellulose ester film used in the present invention is produced by a solution casting method or a melt casting method.

  In the solution casting method, a solution (dope) in which cellulose ester is dissolved in a solvent is cast on a support, and the solvent is evaporated to form a film.

  In the melt casting method, a film obtained by melting cellulose ester by heating (melt) is cast on a support.

  Since the melt casting method can significantly reduce the amount of organic solvent used during film production, the film is much more environmentally friendly than conventional solution casting methods that use large amounts of organic solvents. In the present invention, it is preferable to produce a cellulose ester film by a melt casting method.

  The melt casting in the present invention is a method in which a cellulose ester is heated and melted to a temperature showing fluidity without using a solvent, and a film is formed using this, for example, a film is formed by extruding a fluid cellulose ester from a die. It is a method to do.

  In addition, although a solvent may be used in a part of the process of preparing the molten cellulose ester, in the melt casting film forming process for forming into a film shape, the forming process is performed without using a solvent.

  The cellulose ester constituting the optical film is not particularly limited as long as it is a melt-castable cellulose ester. For example, an aromatic carboxylic acid ester or the like is also used, but the film characteristics such as optical characteristics are obtained. In view of this, it is preferable to use a lower fatty acid ester of cellulose.

  In the present invention, the lower fatty acid in the lower fatty acid ester of cellulose means a fatty acid having 5 or less carbon atoms from the viewpoint of both mechanical properties and melt casting film-forming properties, such as cellulose acetate, cellulose propionate, Cellulose butyrate, cellulose pivalate and the like are preferable as lower fatty acid esters of cellulose.

  In order to achieve both the mechanical properties and the melt casting film-forming properties, mixed fatty acid esters such as cellulose acetate propionate and cellulose acetate butyrate may be used.

  Among the cellulose esters, cellulose acetate propionate and cellulose acetate butyrate are preferably used.

  Next, the substitution degree of the acyl group of the cellulose ester used for this invention is demonstrated.

  Cellulose has a total of three hydroxyl groups, one at each of the 2nd, 3rd and 6th positions of 1 glucose unit. The total degree of substitution is the average number of acyl groups bonded to 1 glucose unit. It is a numerical value indicating whether or not. Therefore, the maximum substitution degree is 3.0.

  These acyl groups may be substituted on the 2nd, 3rd and 6th positions of the glucose unit on average, or may be substituted with a distribution.

  As the substitution degree of the mixed fatty acid ester, more preferred cellulose acetate propionate and lower fatty acid ester of cellulose acetate butyrate have an acyl group having 2 to 4 carbon atoms as a substituent, and the substitution degree of the acetyl group is X, When the substitution degree of propionyl group or butyryl group is Y, it is a cellulose resin containing a cellulose ester that simultaneously satisfies the following formulas (I), (II) and (III).

  In addition, the substitution degree of an acetyl group and the substitution degree of other acyl groups are determined by the method prescribed in ASTM-D817-96.

Formula (I) 2.4 ≦ X + Y ≦ 2.9
Formula (II) 0 ≦ X ≦ 2.4
Formula (III) 0.5 ≦ Y ≦ 2.9
Of these, cellulose acetate propionate is particularly preferably used. Among them, 1.2 ≦ X ≦ 2.1 and 0.6 ≦ Y ≦ 1.4 are preferable. Cellulose esters having different degrees of substitution of acyl groups may be blended so that the entire cellulose ester film may fall within the above range. The part not substituted with the acyl group is usually present as a hydroxyl group. These can be synthesized by known methods.

  The cellulose ester used in the present invention preferably has a number average molecular weight (Mn) of 50,000 to 150,000, more preferably a number average molecular weight of 55,000 to 120,000, and a number average molecular weight of 60000 to 100,000. Most preferred.

  Further, the cellulose ester used in the present invention preferably has a weight average molecular weight (Mw) / number average molecular weight (Mn) ratio of 1.3 to 5.5, particularly preferably 1.5 to 5.0. More preferably, it is 1.7-4.0, More preferably, the cellulose ester of 2.0-3.5 is used preferably.

  Mn and Mw / Mn were calculated by gel permeation chromatography in the following manner.

  The measurement conditions are as follows.

Solvent: Methylene chloride Column: Shodex K806, K805, K803G (Used by connecting three Showa Denko Co., Ltd.)
Column temperature: 25 ° C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (GL Science Co., Ltd.)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corp.) Mw = 2,800,000-500 calibration curves with 13 samples were used. The 13 samples are preferably used at approximately equal intervals.

  The cellulose ester can be obtained, for example, by substituting the hydroxyl group of the raw material cellulose with acetic anhydride, propionic anhydride and / or butyric anhydride in the usual manner using an acetyl group, propionyl group and / or butyl group within the above range. .

  The method for synthesizing such a cellulose ester is not particularly limited, and for example, it can be synthesized with reference to the method described in JP-A-10-45804 or JP-A-6-501040.

  The residual sulfuric acid content in the cellulose ester used in the present invention is preferably in the range of 0.1 to 45 ppm in terms of elemental sulfur. These are considered to be contained in the form of salts.

  If the residual sulfuric acid content exceeds 45 ppm, the deposits on the die lip during heat melting increase, such being undesirable. Moreover, since it becomes easy to fracture | rupture at the time of slitting at the time of hot drawing or after hot drawing, it is not preferable.

  A smaller amount is preferable, but if it is less than 0.1, it is not preferable because the load of the cellulose ester washing process becomes too large, and it is not preferable because it may easily break.

  This is not well understood, although an increase in the number of washings may affect the resin. Furthermore, the range of 1-30 ppm is preferable. The residual sulfuric acid content can be measured by a method prescribed in ASTM-D817-96.

  The free acid content in the cellulose ester used in the present invention is preferably 1 to 500 ppm.

  If it exceeds 500 ppm, deposits on the die lip will increase and breakage will easily occur. It is difficult to make it less than 1 ppm by washing. Furthermore, it is preferable that it is the range of 1-100 ppm, and also it becomes difficult to fracture | rupture. A range of 1 to 70 ppm is particularly preferable.

  The free acid content can be measured by the method prescribed in ASTM-D817-96.

  By washing the synthesized cellulose ester more sufficiently than when it is used in the solution casting method, the residual acid content can be within the above range, and a film is produced by the melt casting method. In this case, adhesion to the lip portion is reduced and a film having excellent flatness can be obtained, and a film having good dimensional change, mechanical strength, transparency, moisture resistance, Rt value and Ro value described later can be obtained. .

  In addition to washing with water, cellulose ester can be washed with a poor solvent such as methanol or ethanol, or as a result, a mixed solvent of a poor solvent and a good solvent can be used as a poor solvent. Low molecular organic impurities can be removed.

  Furthermore, washing of the cellulose ester is preferably performed in the presence of an antioxidant such as a hindered amine or a phosphite, which improves the heat resistance and film forming stability of the cellulose ester.

  In order to improve the heat resistance, mechanical properties, optical properties, etc. of cellulose ester, it can be dissolved in a good solvent of cellulose ester and then reprecipitated in a poor solvent to remove low molecular weight components and other impurities of cellulose ester. it can.

  At this time, it is preferable to carry out in the presence of an antioxidant as in the case of washing the cellulose ester.

  Furthermore, another polymer or a low molecular weight compound may be added after the cellulose ester reprecipitation treatment.

  Moreover, it is preferable that the cellulose ester used by this invention is a thing with few bright spot foreign materials when it is made into a film.

  A bright spot foreign material is an arrangement in which two polarizing plates are arranged orthogonally (crossed Nicols), a cellulose ester film is arranged between them, light from the light source is applied from one side, and the cellulose ester film is applied from the other side. This is the point where the light from the light source appears to leak when observed.

  At this time, the polarizing plate used for the evaluation is desirably composed of a protective film having no bright spot foreign matter, and a polarizing plate using a glass plate for protecting the polarizer is preferably used.

  One of the causes of bright spot foreign matter is the unacetylated or low acetylated cellulose contained in the cellulose ester. Use a cellulose ester with less bright spot foreign matter (use a cellulose ester with a small dispersion degree of substitution). And filtering the melted cellulose ester, or removing the bright spot foreign matters through the filtration process in the same way once in the solution state in at least one of the process of synthesizing the cellulose ester and the process of obtaining the precipitate You can also. Since the molten resin has a high viscosity, the latter method is more efficient.

As the film thickness decreases, the number of bright spot foreign matter per unit area decreases, and as the cellulose ester content in the film decreases, the bright spot foreign matter tends to decrease. 0.01 mm or more is preferably 200 pieces / cm ² or less, more preferably 100 pieces / cm ² or less, further preferably 50 pieces / cm ² or less, and 30 pieces / cm ² or less. More preferably, it is more preferably 10 / cm ² or less, but most preferably none.

Moreover, it is preferable that it is 200 pieces / cm < ² > or less also about a bright spot of 0.005-0.01 mm or less, it is more preferable that it is 100 pieces / cm < ² > or less, and it is 50 pieces / cm < ² > or less. More preferably, it is more preferably 30 pieces / cm ² or less, still more preferably 10 pieces / cm ² or less, and most preferably none.

  When removing bright spot foreign matter by melt filtration, filtering the cellulose ester composition to which a plasticizer, a deterioration inhibitor, an antioxidant, etc. are added and mixed is more effective than filtering the melted cellulose ester alone. It is preferable because the removal efficiency of point foreign matters is high.

  Of course, the cellulose ester may be dissolved in a solvent during the synthesis and reduced by filtration. What mixed the ultraviolet absorber and other additives suitably can be filtered.

  Filtration is preferably performed at a viscosity of a melt containing cellulose ester of 10,000 Pa · s or less, more preferably 5000 Pa · s or less, even more preferably 1000 Pa · s or less, and even more preferably 500 Pa · s or less. .

  As the filter medium, conventionally known materials such as glass fibers, cellulose fibers, filter paper, and fluorine resins such as tetrafluoroethylene resin are preferably used, and ceramics, metal atoms and the like are particularly preferably used.

  The absolute filtration accuracy is preferably 50 μm or less, more preferably 30 μm or less, still more preferably 10 μm or less, and even more preferably 5 μm or less. These can be used in combination as appropriate.

  The filter medium can be either a surface type or a depth type, but the depth type is preferably used because it is relatively less clogged.

  In another embodiment, a cellulose ester obtained by dissolving the raw material cellulose ester at least once in a solvent and then drying the solvent may be used.

  In that case, the cellulose ester which was made to melt | dissolve in a solvent with at least 1 or more of the plasticizer which is another additive, an ultraviolet absorber, antioxidant, and a mat agent, and is used is used.

  As the solvent, a good solvent used in a solution casting method such as methylene chloride, methyl acetate or dioxolane can be used, and a poor solvent such as methanol, ethanol or butanol may be used at the same time.

  You may cool to -20 degrees C or less in the process of dissolution, or you may heat to 80 degrees C or more. When such a cellulose ester is used, each additive in a molten state can be easily made uniform, and optical characteristics can be made uniform.

The optical film of the present invention may be appropriately mixed with polymer components other than cellulose ester. The polymer component to be mixed is preferably one having excellent compatibility with the cellulose ester, and the transmittance when formed into a film is preferably 80% or more, more preferably 90% or more, and further preferably 92% or more.
<Other additives>
Examples of other additives include antioxidants, plasticizers, particles (matting agents), and ultraviolet absorbers.

"Antioxidant"
Since the resin used as the base material of the optical film of the present invention is decomposed not only by heat but also by oxygen, the optical film of the present invention preferably contains an antioxidant as a stabilizer.
In this invention, it is preferable to use what is generally known as an antioxidant. In particular, lactone, sulfur, phenol, double bond, hindered amine, and phosphorus compounds having no metal atom can be preferably used.

  As the lactone compound of the present invention, those commercially available from Ciba Specialty Chemicals under the trade name HP-136 are preferred.

  The phenolic compound preferably has a 2,6-dialkylphenol structure. For example, Ciba Specialty Chemicals Co., Ltd., “Irganox 1076”, “Irganox 1010”, “Irgafos XP40”, “Irgafos XP60”, (Co., Ltd.) ) What is marketed with the brand name ADEKA "Adeka stub AO-50" is preferable.

  Examples of the phosphorus-based compound having no metal atom include Sumitizer GP from Sumitomo Chemical Co., Ltd., ADK STAB PEP-24G from Adeka Co., Ltd., “ADK STAB PEP-36”, “ADK STAB 2112” and What is marketed under the brand name of “ADK STAB 3010”, “IRGAFOS P-EPQ” from Ciba Specialty Chemicals Co., Ltd., and “GSY-P101” from Sakai Chemical Industry Co., Ltd. is preferable.

  The hindered amine compound is preferably, for example, commercially available from Ciba Specialty Chemicals Co., Ltd. under the trade names of “Tinuvin 144” and “Tinvin 770”, and ADEKA Co., Ltd. as “ADK STAB LA-52”.

  As the sulfur compound, for example, those commercially available from Sumitomo Chemical Co., Ltd. under the trade names of “Sumilizer TPL-R” and “Sumilizer TP-D” are preferable.

  The above-mentioned double bond type compounds are preferably those commercially available from Sumitomo Chemical Co., Ltd. under the trade names of “Sumilizer GM” and “Sumilizer GS”.

  Furthermore, as a commercially available epoxy group-containing epoxide resin compound, a compound having an epoxy group as described in EPON 815C, US Pat. No. 4,137,201 may be contained.

  The amount of these antioxidants and the like to be appropriately added is determined in accordance with the process at the time of recycling, but generally 0.05 to 20% by mass, preferably with respect to the resin as the main raw material of the film Is added in the range of 0.1 to 1% by mass.

  These antioxidants can obtain a synergistic effect by using several different types of compounds in combination rather than using only one kind. For example, the combined use of lactone, phosphorus, phenol and double bond compounds is preferred.

  In the present invention, the preferred embodiment of the cellulose ester is preferably washed in the presence of an antioxidant during suspension washing with a poor solvent.

  The antioxidant to be used is not limited as long as it is a compound that inactivates radicals generated in the cellulose ester or suppresses deterioration of the cellulose ester caused by addition of oxygen to the radical generated in the cellulose ester. be able to.

  The antioxidant used for suspension washing of the cellulose ester may remain in the cellulose ester after washing. The remaining amount is preferably 0.01 to 2000 ppm, more preferably 0.05 to 1000 ppm. More preferably, it is 0.1-100 ppm.

  The antioxidant useful in the present invention can be used without limitation as long as it is a compound that suppresses the deterioration of the film molding material due to oxygen. Among the useful antioxidants, phenolic compounds, hindered amine compounds, Examples thereof include phosphorus compounds having no metal atoms, sulfur compounds, heat-resistant processing stabilizers, oxygen scavengers, etc. Among these, phenol compounds, hindered amine compounds, and phosphorus compounds having no metal atoms are particularly preferable.

  By blending these compounds, it is possible to prevent coloring and strength reduction of the molded product due to heat, thermal oxidation degradation, and the like without reducing transparency, heat resistance, and the like. These antioxidants can be used alone or in combination of two or more.

  The antioxidant is preferably removed from impurities such as residual acids, inorganic salts, organic low molecules, etc. that are carried over from production or generated during storage, and more preferably has a purity of 99% or more, like the cellulose ester described above. It is. The residual acid and water are preferably from 0.01 to 100 ppm, and when melt casting film formation of cellulose ester, thermal deterioration can be suppressed, and film formation stability, film optical properties and mechanical properties are improved. To do.

  In the present invention, these antioxidants are each preferably added in an amount of 0.01 to 10% by mass, more preferably 0.1 to 5% by mass, and further 0.2 to the cellulose ester resin. It is preferable to add ~ 2 mass%. Two or more of these may be used in combination.

<Ultraviolet absorber>
The ultraviolet absorber is excellent in the ability to absorb ultraviolet rays having a wavelength of 370 nm or less from the viewpoint of preventing deterioration of the polarizer and the display device with respect to ultraviolet rays, and has little absorption of visible light having a wavelength of 400 nm or more from the viewpoint of liquid crystal display properties. Those are preferred.

  Examples of the ultraviolet absorber used in the present invention include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, triazine compounds, and the like. However, benzophenone compounds, less colored benzotriazole compounds, and triazine compounds are preferable.

  Further, ultraviolet absorbers described in JP-A Nos. 10-182621 and 8-337574, and polymer ultraviolet absorbers described in JP-A Nos. 6-148430 and 2003-113317 may be used.

  Specific examples of the benzotriazole ultraviolet absorber include 2- (2′-hydroxy-5′-methylphenyl) benzotriazole, 2- (2′-hydroxy-3 ′, 5′-di-tert-butylphenyl) benzo Triazole, 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3 ', 5'-di-tert-butylphenyl) -5 Chlorobenzotriazole, 2- (2′-hydroxy-3 ′-(3 ″, 4 ″, 5 ″, 6 ″ -tetrahydrophthalimidomethyl) -5′-methylphenyl) benzotriazole, 2,2-methylenebis (4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol), 2- (2'-hydroxy- '-Tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2- (2'-hydroxy-3'-tert-butyl-5'-(2-octyloxycarbonylethyl) -phenyl) -5 -Chlorobenzotriazole, 2- (2'-hydroxy-3 '-(1-methyl-1-phenylethyl) -5'-(1,1,3,3, -tetramethylbutyl) -phenyl) benzotriazole, 2- (2H-benzotriazol-2-yl) -6- (linear and side chain dodecyl) -4-methylphenol, octyl-3- [3-tert-butyl-4-hydroxy-5- (chloro-2H) -Benzotriazol-2-yl) phenyl] propionate and 2-ethylhexyl-3- [3-tert-butyl-4-hydroxy-5- (5-chloro- H- benzotriazol-2-yl) can be mentioned mixtures of phenyl] propionate, and the like.

  As commercially available products, TINUVIN 171, TINUVIN 900, TINUVIN 928, TINUVIN 360 (all manufactured by Ciba Specialty Chemicals), LA31 (manufactured by ADEKA Corporation) ), RUVA-100 (manufactured by Otsuka Chemical).

  Specific examples of benzophenone compounds include 2,4-dihydroxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy-5-sulfobenzophenone, bis (2-methoxy-4-hydroxy- 5-benzoylphenylmethane) and the like, but are not limited thereto.

  In this invention, it is preferable to add 0.1-5 mass% of ultraviolet absorbers with respect to resin, Furthermore, it is preferable to add 0.2-3 mass%, Furthermore, 0.5-2 mass% is added. It is preferable. Two or more of these may be used in combination.

  The benzotriazole structure or triazine structure may be part of the polymer, or may be regularly pendant to the polymer, and part of the molecular structure of other additives such as plasticizers, antioxidants, and acid scavengers. May be introduced.

  Although it does not specifically limit as a conventionally well-known ultraviolet absorptive polymer, For example, the polymer which homopolymerized RUVA-93 (made by Otsuka Chemical), the polymer which copolymerized RUVA-93, and another monomer, etc. are mentioned. .

  Specific examples include PUVA-30M obtained by copolymerization of RUVA-93 and methyl methacrylate at a ratio (mass ratio) of 3: 7, and PUVA-50M obtained by copolymerization at a ratio of 5: 5 (mass ratio). It is done. Furthermore, the polymer etc. which are described in Unexamined-Japanese-Patent No. 2003-113317 are mentioned.

《Plasticizer》
In the production of the optical film of the present invention, it is preferable to add at least one plasticizer in the film molding material.

  The plasticizer is generally an additive that has an effect of improving brittleness or imparting flexibility by being added to a polymer. For example, a preferred embodiment of the cellulose ester in the present invention In this case, a plasticizer is added to lower the melting temperature than the melting temperature alone, and to lower the melt viscosity of the film constituent material containing the plasticizer than the cellulose resin alone at the same heating temperature.

  Moreover, since it adds also in order to improve the hydrophilic property of a cellulose ester and to improve the water vapor transmission rate of an optical film, it has a function as a moisture permeation preventive agent.

  Here, the melting temperature of the film constituting material means a temperature at which the material is heated and fluidity is developed. In order to melt and flow the cellulose ester, it is necessary to heat at least a temperature higher than the glass transition temperature.

  Above the glass transition temperature, the elastic modulus or viscosity decreases due to heat absorption, and fluidity is exhibited.

  However, in cellulose esters, the molecular weight of the cellulose ester may decrease due to thermal decomposition at the same time as melting at high temperatures, which may adversely affect the mechanical properties of the resulting film. Therefore, it is necessary to melt the cellulose ester at the lowest possible temperature. is there.

  In order to lower the melting temperature of the film constituent material, it can be achieved by adding a plasticizer having a melting point or glass transition temperature lower than the glass transition temperature of the cellulose ester.

  The optical film of the present invention is preferably an optical film containing 1 to 25% by mass of a plasticizer. When the content is less than 1% by mass, the effect of improving the flatness is not recognized, and when the content is more than 25% by mass, bleeding out easily occurs and the temporal stability of the film decreases, which is not preferable.

  More preferred is an optical film containing 3 to 20% by mass of a plasticizer, and further preferred is an optical film containing 5 to 15% by mass.

  In the present invention, an ester plasticizer composed of a polyhydric alcohol and a monovalent carboxylic acid, and an ester plasticizer composed of a polyvalent carboxylic acid and a monovalent alcohol have a high affinity with the cellulose ester and are preferred.

  Examples of the polyhydric alcohol that is a raw material of the ester plasticizer preferably used in the present invention include the following, but the present invention is not limited thereto.

  Adonitol, arabitol, ethylene glycol, glycerin, diglycerin, 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-1,3,5-triol, pinacol, sorbitol, trimethylolpropane, ditrimethylolpropane, trimethylolethane, pentaerythritol, dipentaerythritol, xyl Mention may be made of the toll and the like.

  In particular, ethylene glycol, glycerin, and trimethylolpropane are preferable.

  Specific examples of ethylene glycol ester plasticizers that are one of the polyhydric alcohol esters include ethylene glycol alkyl ester plasticizers such as ethylene glycol diacetate and ethylene glycol dibutyrate, and ethylene glycol dicyclopropyl. Examples thereof include ethylene glycol cycloalkyl ester plasticizers such as carboxylate and ethylene glycol dicyclohexylcarboxylate, and ethylene glycol aryl ester plasticizers such as ethylene glycol dibenzoate and ethylene glycol di4-methylbenzoate. These alkylate groups, cycloalkylate groups, and arylate groups may be the same or different, and may be further substituted.

  Further, it may be a mix of alkylate group, cycloalkylate group and arylate group, and these substituents may be covalently bonded.

  Further, the ethylene glycol part may be substituted, and the ethylene glycol ester partial structure may be part of the polymer or regularly pendant, and may be an antioxidant, an acid scavenger, an ultraviolet absorber, etc. It may be introduced into a part of the molecular structure of the additive.

  Specific examples of the glycerin ester plasticizer that is one of the polyhydric alcohol esters include glycerol alkyl esters such as triacetin, tributyrin, glycerol diacetate caprylate, glycerol oleate propionate, and glycerol tricyclopropylcarboxylate. Glycerol glycerol esters such as glycerol tricyclohexyl carboxylate, glycerol aryl esters such as glycerol tribenzoate and glycerol 4-methylbenzoate, diglycerol tetraacetylate, diglycerol tetrapropionate, diglycerol acetate tricaprylate, diglycerol Tetralaurate, diglycerin alkyl ester, diglycerin tetracyclobutylcarboxylate, diglycerin tet Diglycerol cycloalkyl esters such as cyclopentyl carboxylate, diglycerin tetrabenzoate, diglycerin aryl ester such as diglycerin 3-methylbenzoate or the like.

  These alkylate groups, cycloalkylcarboxylate groups, and arylate groups may be the same or different, and may be further substituted.

  Further, it may be a mixture of alkylate group, cycloalkylcarboxylate group, and arylate group, and these substituents may be bonded by a covalent bond.

  Furthermore, the glycerin and diglycerin part may be substituted, the partial structure of the glycerin ester and the diglycerin ester may be part of the polymer or regularly pendant, and the antioxidant, acid scavenger, You may introduce | transduce into a part of molecular structure of additives, such as a ultraviolet absorber.

  Specific examples of other polyhydric alcohol ester plasticizers include polyhydric alcohol ester plasticizers described in paragraphs 30 to 33 of JP-A No. 2003-12823.

  These alkylate groups, cycloalkylcarboxylate groups, and arylate groups may be the same or different, and may be further substituted.

  Further, it may be a mixture of alkylate group, cycloalkylcarboxylate group, and arylate group, and these substituents may be bonded by a covalent bond. Furthermore, the polyhydric alcohol part may be substituted, and the partial structure of the polyhydric alcohol may be part of the polymer or regularly pendant, and may be an antioxidant, an acid scavenger, an ultraviolet absorber. May be introduced into a part of the molecular structure of the additive.

  Among the ester plasticizers composed of the polyhydric alcohol and the monovalent carboxylic acid, alkyl polyhydric alcohol aryl esters are preferable. Specifically, the ethylene glycol dibenzoate, glycerin tribenzoate, diglycerin tetrabenzoate, penta Examples include erythritol tetrabenzoate and exemplified compound 16 described in paragraph 31 of JP-A No. 2003-12823.

  Specific examples of the dicarboxylic acid ester plasticizer that is one of the polyvalent carboxylic acid esters include alkyl dicarboxylic acid alkyl ester plasticizers such as didodecyl malonate, dioctyl adipate, and dibutyl sebacate. Alkyl dicarboxylic acid cycloalkyl ester type plasticizers such as cyclopentyl succinate and dicyclohexyl adipate, alkyl dicarboxylic acid aryl ester type plasticizers such as diphenyl succinate and di4-methylphenyl glutarate, dihexyl-1,4-cyclohexane Cycloalkyl dicarboxylic acid alkyl ester plasticizers such as dicarboxylate and didecylbicyclo [2.2.1] heptane-2,3-dicarboxylate, dicyclohexyl-1,2-cyclobutanedicarboxylate, dicis Cycloalkyldicarboxylic acid cycloalkyl ester plasticizers such as ropropyl-1,2-cyclohexyldicarboxylate, diphenyl-1,1-cyclopropyldicarboxylate, di2-naphthyl-1,4-cyclohexanedicarboxylate, etc. Cycloalkyldicarboxylic acid aryl ester plasticizers, diethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate and other aryl dicarboxylic acid alkyl ester plasticizers, dicyclopropyl phthalate, dicyclohexyl phthalate, etc. Aryl dicarboxylic acid cycloalkyl ester plasticizers, and aryl dicarboxylic acid aryl ester plasticizers such as diphenyl phthalate and di-4-methylphenyl phthalate And the like. These alkoxy groups and cycloalkoxy groups may be the same or different, may be mono-substituted, and these substituents may be further substituted.

  The alkyl group and cycloalkyl group may be mixed, and these substituents may be bonded together by a covalent bond. Furthermore, the aromatic ring of phthalic acid may be substituted, and a multimer such as a dimer, trimer or tetramer may be used.

  Also, the partial structure of phthalate ester may be part of the polymer, or may be regularly pendant to the polymer, and part of the molecular structure of additives such as antioxidants, acid scavengers, UV absorbers It may be introduced.

  Examples of other polycarboxylic acid ester plasticizers include alkyl polycarboxylic acid alkyl esters such as tridodecyl tricarbarate and tributyl-meso-butane-1,2,3,4-tetracarboxylate. Plasticizers, alkylpolycarboxylic acid cycloalkyl ester plasticizers such as tricyclohexyltricarbarate, tricyclopropyl-2-hydroxy-1,2,3-propanetricarboxylate, triphenyl 2-hydroxy- Alkyl polyvalent carboxylic acid aryl ester plasticizers such as 1,2,3-propanetricarboxylate, tetra-3-methylphenyltetrahydrofuran-2,3,4,5-tetracarboxylate, tetrahexyl-1,2, 3,4-cyclobutanetetracarboxylate, tetrabu Cycloalkyl polycarboxylic acid alkyl ester plasticizers such as ru-1,2,3,4-cyclopentanetetracarboxylate, tetracyclopropyl-1,2,3,4-cyclobutanetetracarboxylate, tricyclohexyl- Cycloalkyl polycarboxylic acid cycloalkyl ester plasticizers such as 1,3,5-cyclohexyl tricarboxylate, triphenyl-1,3,5-cyclohexyl tricarboxylate, hexa-4-methylphenyl-1,2, Cycloalkyl polycarboxylic acid aryl ester plasticizers such as 3,4,5,6-cyclohexylhexacarboxylate, tridodecylbenzene-1,2,4-tricarboxylate, tetraoctylbenzene-1,2,4 , 5-tetracarboxylate and other aryl polyvalent Rubinoic acid alkyl ester plasticizers, tricyclopentylbenzene-1,3,5-tricarboxylate, tetracyclohexylbenzene-1,2,3,5-tetracarboxylate and other aryl polyvalent carboxylic acid cycloalkyl esters Plasticizers of aryl polyvalent carboxylic acid aryl esters such as plasticizers triphenylbenzene-1,3,5-tetracarboxylate, hexa-4-methylphenylbenzene-1,2,3,4,5,6-hexacarboxylate Agents.

  These alkoxy groups and cycloalkoxy groups may be the same or different, and may be mono-substituted, and these substituents may be further substituted.

  The alkyl group and cycloalkyl group may be mixed, and these substituents may be bonded together by a covalent bond. Furthermore, the aromatic ring of phthalic acid may be substituted, and a multimer such as a dimer, trimer or tetramer may be used.

  Also, the partial structure of phthalate ester may be part of the polymer or regularly pendant into the polymer, and introduced into part of the molecular structure of additives such as antioxidants, acid scavengers, UV absorbers, etc. May be.

  Among the ester plasticizers composed of the polyvalent carboxylic acid and the monohydric alcohol, alkyl dicarboxylic acid alkyl esters are preferable, and specific examples include the dioctyl adipate.

  Examples of other plasticizers used in the present invention include phosphate ester plasticizers, carbohydrate ester plasticizers, and polymer plasticizers.

  Specific examples of the phosphoric acid ester plasticizer include phosphoric acid alkyl esters such as triacetyl phosphate and tributyl phosphate, phosphoric acid cycloalkyl esters such as tricyclopentyl phosphate and cyclohexyl phosphate, triphenyl phosphate, and trichlorate. Examples thereof include phosphoric acid aryl esters such as zil phosphate, cresyl phenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate, trinaphthyl phosphate, trixylyl phosphate, tris ortho-biphenyl phosphate.

  These substituents may be the same or different, and may be further substituted. Moreover, the mix of an alkyl group, a cycloalkyl group, and an aryl group may be sufficient, and substituents may couple | bond together by the covalent bond.

  Also, alkylene bis (dialkyl phosphate) such as ethylene bis (dimethyl phosphate), butylene bis (diethyl phosphate), alkylene bis (diaryl phosphate) such as ethylene bis (diphenyl phosphate), propylene bis (dinaphthyl phosphate), phenylene bis (dibutyl) And phosphate esters such as arylene bis (diaryl phosphate) such as arylene bis (dialkyl phosphate), phenylene bis (diphenyl phosphate), naphthylene bis (ditoluyl phosphate) such as biphenylene bis (dioctyl phosphate).

  These substituents may be the same or different, and may be further substituted. Moreover, the mix of an alkyl group, a cycloalkyl group, and an aryl group may be sufficient, and substituents may couple | bond together by the covalent bond.

  Furthermore, the partial structure of phosphate ester may be part of the polymer, or may be regularly pendant, and also introduced into part of the molecular structure of additives such as antioxidants, acid scavengers, UV absorbers, etc. May be.

  Among the above-mentioned compounds, phosphoric acid aryl ester and arylene bis (diaryl phosphate) are preferable, and specifically, triphenyl phosphate and phenylene bis (diphenyl phosphate) are preferable.

  Next, the carbohydrate ester plasticizer will be described. The carbohydrate means a monosaccharide, disaccharide or trisaccharide in which the saccharide is present in the form of pyranose or furanose (6-membered ring or 5-membered ring). Non-limiting examples of carbohydrates include glucose, saccharose, lactose, cellobiose, mannose, xylose, ribose, galactose, arabinose, fructose, sorbose, cellotriose and raffinose.

  The carbohydrate ester refers to an ester compound formed by dehydration condensation of a carbohydrate hydroxyl group and a carboxylic acid, and specifically means an aliphatic carboxylic acid ester or an aromatic carboxylic acid ester of a carbohydrate.

  Examples of the aliphatic carboxylic acid include acetic acid and propionic acid, and examples of the aromatic carboxylic acid include benzoic acid, toluic acid, and anisic acid.

  Carbohydrates have a number of hydroxyl groups depending on the type, but even if a part of the hydroxyl group reacts with the carboxylic acid to form an ester compound, the whole hydroxyl group reacts with the carboxylic acid to form an ester compound. Also good. In the present invention, it is preferable that all of the hydroxyl groups react with the carboxylic acid to form an ester compound.

  Specific examples of the carbohydrate ester plasticizer include glucose pentaacetate, glucose pentapropionate, glucose pentabylate, saccharose octaacetate, saccharose octabenzoate and the like. Among these, saccharose octaacetate, saccharose Octabenzoate is more preferred, and sucrose octabenzoate is particularly preferred.

  As these compounds, those commercially available as trade names Monopet SB and Monopet SOA (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) can be preferably used.

  Specific examples of the polymer plasticizer include aliphatic hydrocarbon polymers, alicyclic hydrocarbon polymers, polyethyl acrylate, polymethyl methacrylate, methyl methacrylate and 2-hydroxyethyl methacrylate. Acrylic polymers such as polymers (for example, any ratio between 1:99 and 99: 1), vinyl polymers such as polyvinyl isobutyl ether and poly N-vinyl pyrrolidone, polystyrene, poly 4-hydroxystyrene Styrene polymers such as polybutylene succinate, polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyethers such as polyethylene oxide and polypropylene oxide, polyamides, polyurethanes and polyureas.

  The number average molecular weight is preferably about 1,000 to 500,000, particularly preferably 5,000 to 200,000.

  If it is 1000 or less, a problem arises in volatility, and if it exceeds 500000, the plasticizing ability is lowered, and the mechanical properties of the optical film are adversely affected.

  These polymer plasticizers may be a homopolymer composed of one type of repeating unit or a copolymer having a plurality of repeating structures. Two or more of the above polymers may be used in combination.

  The amount of the other plasticizer added is usually 0.1 to 50 parts by mass, preferably 1 to 30 parts by mass, and more preferably 3 to 15 parts by mass with respect to 100 parts by mass of the cellulose ester.

  The optical film of the present invention preferably contains 1 to 25% by mass of an ester plasticizer comprising a polyhydric alcohol and a monovalent carboxylic acid, and an ester plasticizer comprising a polyvalent carboxylic acid and a monohydric alcohol. , And may be used in combination with other plasticizers.

  In the optical film of the present invention, an ester plasticizer comprising a polyhydric alcohol and a monovalent carboxylic acid is more preferred, and an ester plasticizer comprising a trivalent or higher alcohol and a monovalent carboxylic acid is compatible with the cellulose ester. Because it is high and can be added at a high addition rate, bleed-out does not occur even when other plasticizers and additives are used in combination, and other types of plasticizers and additives can be added as necessary. It is most preferable because it can be easily used together.

  In addition, since the optical film of this invention will affect as an optical use when it colors, Preferably yellow degree (yellow index, YI) is 3.0 or less, More preferably, it is 1.0 or less. Yellowness can be measured based on JIS-K7103.

<Particles (matting agent)>
A matting agent can be added to the optical film of the present invention in order to impart slipperiness, optical and mechanical functions. Examples of the matting agent include inorganic compound fine particles and organic compound fine particles.

  The shape of the matting agent is preferably a spherical shape, a rod shape, a needle shape, a layer shape, a flat shape or the like.

  Examples of the matting agent include metal atoms such as silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, kaolin, talc, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, and calcium phosphate. Inorganic fine particles such as oxides, phosphates, silicates and carbonates and crosslinked polymer fine particles.

  Among these, silicon dioxide is preferable because it can reduce the haze of the film. These fine particles are preferably surface-treated with an organic substance because the haze of the film can be reduced.

  The surface treatment is preferably performed with halosilanes, alkoxysilanes, silazane, siloxane, or the like. The larger the average particle size of the fine particles, the greater the sliding effect, and the smaller the average particle size, the better the transparency.

  The average primary particle size of the fine particles is in the range of 0.01 to 1.0 μm. The average particle size of the primary particles of preferable fine particles is preferably 5 to 50 nm, more preferably 7 to 14 nm.

  These fine particles are preferably used for generating irregularities of 0.01 to 1.0 μm on the optical film surface.

  As the fine particles of silicon dioxide, Aerosil 200, 200V, 300, R972, R972V, R974, R202, R812, OX50, TT600, NAX50, etc. manufactured by Nippon Aerosil Co., Ltd. P10, KE-P30, KE-P100, KE-P150 and the like can be mentioned, and Aerosil 200V, R972V, NAX50, KE-P30 and KE-P100 are preferable. Two or more kinds of these fine particles may be used in combination.

  When using 2 or more types together, it can mix and use in arbitrary ratios. Fine particles having different average particle sizes and materials, for example, Aerosil 200V and R972V can be used in a mass ratio of 0.1: 99.9 to 99.9: 0.1.

  These matting agents are preferably added by kneading. Further, as another form, after mixing and dispersing a matting agent dispersed in a solvent in advance with a resin and / or a plasticizer and / or an antioxidant and / or an ultraviolet absorber, a solid material in which the solvent is volatilized or precipitated is obtained. It is preferable to use this in the process of producing the resin melt from the viewpoint that the matting agent can be uniformly dispersed in the resin.

  The matting agent can also be added to improve the mechanical, electrical and optical properties of the film.

  In addition, although the slipperiness of the film obtained improves, so that these microparticles | fine-particles are added, since a haze raises so that it adds, content is preferably 0.001-5 mass% with respect to resin, and more. Preferably it is 0.005-1 mass%, More preferably, it is 0.01-0.5 mass%.

As the optical film of the present invention, if the haze value exceeds 1.0%, the optical material is affected. Therefore, the haze value is preferably less than 1.0%, more preferably less than 0.5%. . The haze value can be measured based on JIS-K7136.
<Melt casting method>
The melt casting film forming method of the optical film of the present invention will be described.

  The film constituent material is required to have little or no volatile component in the melting and film forming process. This is for foaming during heating and melting to reduce or avoid defects inside the film and flatness deterioration of the film surface.

  The content of the volatile component when the film constituent material is melted is 1% by mass or less, preferably 0.5% by mass or less, more preferably 0.2% by mass or less, and even more preferably 0.1% by mass or less. It is desirable that In the present invention, a heat loss from 30 ° C. to 250 ° C. is obtained using a differential thermogravimetric measuring device (TG / DTA200 manufactured by Seiko Electronics Industry Co., Ltd.), and this amount is used as the content of volatile components.

  It is preferable that the film constituent material used removes volatile components typified by the moisture and the solvent before film formation or during heating.

  A known drying method can be applied to the removal method, and it can be performed by a method such as a heating method, a reduced pressure method, a heated reduced pressure method, or the like, and may be performed in air or in an atmosphere in which nitrogen is selected as an inert gas.

  When these known drying methods are performed, it is preferable in terms of film quality to be performed in a temperature range where the film constituting material does not decompose.

  By drying prior to film formation, the generation of volatile components can be reduced, and the resin can be divided into a single resin, or at least one mixture or compatible material other than resin, and dried. You can also

  The drying temperature is preferably 70 ° C. or higher. When a material having a glass transition temperature is present in the material to be dried, heating to a drying temperature higher than the glass transition temperature may cause the material to melt and become difficult to handle. It is preferable that it is below the temperature.

  When a plurality of substances have a glass transition temperature, the glass transition temperature with the lower glass transition temperature is used as a reference. More preferably, it is 70 degreeC or more (glass transition temperature-5 degrees C or less), More preferably, it is 110 degreeC or more (glass transition temperature-20 degrees C or less).

  The drying time is preferably 0.5 to 24 hours, more preferably 1 to 18 hours, still more preferably 1.5 to 12 hours. If the drying temperature is too low, the removal rate of volatile components will be low, and it will take too much time to dry.

  Further, the drying process may be divided into two or more stages. For example, the drying process includes a preliminary drying process for storage of materials and a just-before drying process performed immediately before film formation to one week before film formation. Also good.

  The optical film comprising the cellulose ester which is a preferred embodiment of the present invention is preferably produced by melt casting as described above. The molding method by melt casting, which is heated and melted without using the solvent used in the solution casting method (for example, methylene chloride, etc.), more specifically, melt extrusion molding method, press molding method, inflation method, injection molding method And can be classified into blow molding, stretch molding and the like.

  Among these, in order to obtain a polarizing plate protective film having excellent mechanical strength and surface accuracy, the melt extrusion method is excellent.

  Hereinafter, the melt casting film forming method of the optical film of the present invention will be described by taking the melt extrusion method as an example.

  FIG. 1 is a schematic flow sheet showing the overall configuration of an apparatus for carrying out the method for producing an optical film of the present invention, and FIG. 2 is an enlarged view of a cooling roll portion from a casting die.

  In FIG. 1 and FIG. 2, the manufacturing method of the optical film by this invention is melt-extruded from the casting die 4 on the 1st cooling roll 5 using the extruder 1, after mixing film materials, such as a cellulose resin, While circumscribing the 1st cooling roll 5, it is further circumscribed by the total of 3 cooling rolls of the 2nd cooling roll 7 and the 3rd cooling roll 8 in order, and it cools and solidifies to make the film 10.

  Next, the film 10 peeled off by the peeling roll 9 is then stretched in the width direction by holding both ends of the film by the stretching device 12 and then wound by the winding device 16.

  In addition, a touch roll 6 is provided that clamps the molten film on the surface of the first cooling roll 5 in order to correct the flatness. The touch roll 6 has an elastic surface and forms a nip with the first cooling roll 5. Details of the touch roll 6 will be described later.

  In the method for producing an optical film according to the present invention, the conditions for melt extrusion can be carried out in the same manner as the conditions used for other thermoplastic resins such as polyester. The material is preferably dried beforehand. It is desirable to dry the moisture to 1000 ppm or less, preferably 200 ppm or less by using a vacuum or reduced pressure drier or a dehumidifying hot air drier.

  For example, the cellulose ester resin dried under hot air, vacuum or reduced pressure is melted at an extrusion temperature of about 200 to 300 ° C. using the extruder 1, filtered through a leaf disk type filter 2, etc. to remove foreign matters.

  When introducing into the extruder 1 from a supply hopper (not shown), it is preferable to prevent oxidative decomposition or the like under vacuum, reduced pressure, or inert gas atmosphere.

  When additives such as a plasticizer are not mixed in advance, they may be kneaded in the middle of the extruder. In order to add uniformly, it is preferable to use a mixing apparatus such as a static mixer 3.

  In the present invention, the cellulose ester-based resin and other additives such as a stabilizer added as necessary are preferably mixed before melting, and the cellulose ester-based resin and the additive are mixed before heating. More preferably.

  Mixing may be performed by a mixer or the like, or may be mixed in the cellulose resin preparation process as described above. When a mixer is used, a general mixer such as a V-type mixer, a conical screw type mixer, a horizontal cylindrical type mixer, a Henschel mixer, or a ribbon mixer can be used.

  After the film constituent materials are mixed as described above, the mixture may be melted directly using the extruder 1 to form a film. Once the film constituent materials are pelletized, the pellets are extruded. The film may be melted by the machine 1 to form a film.

  When the film constituent material includes a plurality of materials having different melting points, a so-called braided semi-melt is once produced at a temperature at which only the material having a low melting point is melted, and the semi-melt is supplied to the extruder 1. It is also possible to form a film by introducing it.

  If the film component contains a material that is easily pyrolyzed, in order to reduce the number of times of melting, a method of directly forming a film without producing pellets, or after making a paste-like semi-molten material as described above A method of forming a film is preferred.

  As the extruder 1, various commercially available extruders can be used, but a melt-kneading extruder is preferable, and a single-screw extruder or a twin-screw extruder may be used. When forming a film directly without producing pellets from film constituent materials, it is preferable to use a twin-screw extruder because an appropriate degree of kneading is necessary, but even with a single-screw extruder, the screw shape is a Maddock type. By changing to a kneading type screw such as a unimelt type or a dull mage, moderate kneading can be obtained, so that it can be used.

  When a pellet or braided semi-melt is once used as a film constituent material, it can be used in either a single screw extruder or a twin screw extruder.

  In the extruder 1 and the cooling step after extrusion, it is preferable to reduce the oxygen concentration by replacing with an inert gas such as nitrogen gas or by reducing the pressure.

  The melting temperature of the film constituent material in the extruder 1 varies depending on the viscosity and discharge amount of the film constituent material, the thickness of the sheet to be produced, etc., but generally, with respect to the glass transition temperature Tg of the film, Tg or more and Tg + 100 ° C. or less, preferably Tg + 10 ° C. or more and Tg + 90 ° C. or less. The melt viscosity at the time of extrusion is 1 to 10000 Pa · s, preferably 10 to 1000 Pa · s.

  Further, the residence time of the film constituting material in the extruder 1 is preferably short, and is within 5 minutes, preferably within 3 minutes, more preferably within 2 minutes. The residence time depends on the type of the extruder 1 and the extrusion conditions, but can be shortened by adjusting the material supply amount, L / D, screw rotation speed, screw groove depth, and the like. is there.

  The shape, rotation speed, and the like of the screw of the extruder 1 are appropriately selected depending on the viscosity, the discharge amount, and the like of the film constituent material. In the present invention, the shear rate in the extruder 1 is 1 / second to 10000 / second, preferably 5 / second to 1000 / second, more preferably 10 / second to 100 / second.

  The extruder 1 that can be used in the present invention is generally available as a plastic molding machine.

  The film constituent material extruded from the extruder 1 is sent to the casting die 4 and extruded from the slit of the casting die 4 into a film shape.

  The casting die 4 is not particularly limited as long as it is used for producing a sheet or a film.

  The material of the casting die 4 is sprayed or plated with hard chromium, chromium carbide, chromium nitride, titanium carbide, titanium carbonitride, titanium nitride, super steel, ceramic (tungsten carbide, aluminum oxide, chromium oxide), etc. Processing such as buffing, lapping using a # 1000 or higher grinding wheel, plane cutting using a # 1000 or higher diamond grinding wheel (the cutting direction is perpendicular to the resin flow direction), electrolytic polishing, electrolytic composite polishing, etc. And the like.

  A preferred material for the lip portion of the casting die 4 is the same as that of the casting die 4. The surface accuracy of the lip is preferably 0.5S or less, and more preferably 0.2S or less.

  The slit of the casting die 4 is configured so that the gap can be adjusted. This is shown in FIG. Of the pair of lips forming the slit 32 of the casting die 4, one is a flexible lip 33 having low rigidity and easily deformed, and the other is a fixed lip 34.

  A large number of heat bolts 35 are arranged at a constant pitch in the width direction of the casting die 4, that is, in the length direction of the slits 32.

  Each heat bolt 5 is provided with a block 36 having an embedded electric heater 37 and a cooling medium passage, and each heat bolt 35 penetrates each block 36 vertically.

  The base of the heat bolt 35 is fixed to the die body 31, and the tip is in contact with the outer surface of the flexible lip 33.

  While constantly cooling the block 36, the input to the embedded electric heater 37 is increased or decreased to increase or decrease the temperature of the block 36, thereby causing the heat bolt 35 to thermally expand and contract, thereby displacing the flexible lip 33 and thereby increasing the film thickness. adjust.

  Thickness gauges are installed at the required locations in the wake of the die, and the web thickness information detected thereby is fed back to the control device. The thickness information is compared with the set thickness information by the control device, and correction control comes from the same device. It is also possible to control the power or the ON rate of the heat bolt heating element by the amount signal.

  The heat bolt preferably has a length of 20 to 40 cm and a diameter of 7 to 14 mm, and a plurality of, for example, several tens of heat bolts are preferably arranged at a pitch of 20 to 40 mm. Instead of the heat bolt, a gap adjusting member mainly composed of a bolt for adjusting the slit gap by manually moving back and forth in the axial direction may be provided.

  The slit gap adjusted by the gap adjusting member is usually 200 to 1000 μm, preferably 300 to 800 μm, more preferably 400 to 600 μm.

  The first to third cooling rolls are made of seamless steel pipe having a wall thickness of about 20 to 30 mm, and the surface is finished to a mirror surface.

  Inside, a pipe for flowing a coolant is arranged so that heat can be absorbed from the film on the roll by the coolant flowing through the pipe. Of the first to third cooling rolls, the first cooling roll 5 corresponds to the rotary support of the present invention.

  On the other hand, the touch roll 6 in contact with the first cooling roll 5 has an elastic surface and is deformed along the surface of the first cooling roll 5 by the pressing force to the first cooling roll 5. A nip is formed between the two.

  That is, the touch roll 6 corresponds to the pinching rotary body of the present invention.

  In FIG. 4, the schematic cross section of one Embodiment (henceforth, touch roll A) of the touch roll 6 is shown. As shown in the drawing, the touch roll A has an elastic roller 42 disposed inside a flexible metal sleeve 41.

  The metal sleeve 41 is made of stainless steel having a thickness of 0.3 mm and has flexibility. If the metal sleeve 41 is too thin, the strength is insufficient, whereas if it is too thick, the elasticity is insufficient. For these reasons, the thickness of the metal sleeve 41 is preferably 0.1 to 1.5 mm.

  The elastic roller 42 is formed in a roll shape by providing a rubber 44 on the surface of a metal inner cylinder 43 that is rotatable via a bearing.

  When the touch roll A is pressed toward the first cooling roll 5, the elastic roller 42 presses the metal sleeve 41 against the first cooling roll 5, and the metal sleep 41 and the elastic roller 42 have the shape of the first cooling roll 5. It deforms corresponding to the familiar shape, and forms a nip with the first cooling roll.

  Cooling water 45 flows in a space formed between the metal sleeve 41 and the elastic roller 42.

  5 and 6 show a touch roll B which is another embodiment of the pinching rotator. The touch roll B includes a flexible, seamless stainless steel pipe (thickness 4 mm) outer cylinder 51, and a highly rigid metal inner cylinder 52 arranged on the same axis as the inner side of the outer cylinder 51. It is roughly composed.

  A coolant 54 flows in the space 53 between the outer cylinder 51 and the inner cylinder 52.

  Specifically, in the touch roll B, outer cylinder support flanges 56a and 56b are attached to the rotation shafts 55a and 55b at both ends, and a thin metal outer cylinder 51 is attached between the outer peripheral portions of the both outer cylinder support flanges 56a and 56b. Yes.

  A fluid supply pipe 59 is disposed in the same axial center in a fluid discharge hole 58 formed in the axial center portion of one rotary shaft 55a and forming a fluid return passage 57. The fluid supply pipe 59 is thin-walled. It is connected and fixed to a fluid shaft cylinder 60 arranged at the axial center in the metal outer cylinder 51.

  Inner cylinder support flanges 61a and 61b are attached to both ends of the fluid shaft cylinder 60, respectively, and a thickness of about 15 to 20 mm between the outer periphery of the inner cylinder support flanges 61a and 61b and the other end side outer cylinder support flange 56b. A metal inner cylinder 52 having a thickness is attached.

  A cooling liquid flow space 53 of, for example, about 10 mm is formed between the metal inner cylinder 52 and the thin metal outer cylinder 51, and the metal inner cylinder 52 has a flow space 53 and an inner space near both ends. An outlet 52a and an inlet 52b are formed to communicate with the intermediate passages 62a and 62b outside the cylinder support flanges 61a and 61b, respectively.

  Further, the outer cylinder 51 is thinned within a range in which the thin cylinder theory of elastic mechanics can be applied in order to have flexibility, flexibility, and resilience close to rubber elasticity.

  The flexibility evaluated by the thin-walled cylinder theory is expressed by the thickness t / roll radius r, and the flexibility increases as t / r decreases. In this touch roll B, the flexibility is the optimum condition when t / r ≦ 0.03.

  Usually, the touch roll generally used has a roll diameter R = 200 to 500 mm (roll radius r = R / 2), a roll effective width L = 500 to 1600 mm, and a horizontally long shape with r / L <1. is there.

  As shown in FIG. 6, for example, when the roll diameter R = 300 mm and the roll effective width L = 1200 mm, the appropriate range of the wall thickness t is 150 × 0.03 = 4.5 mm or less, but the molten sheet width is 1300 mm. On the other hand, when the average linear pressure is clamped at 98 N / cm, the equivalent spring constant is equal by setting the wall thickness of the outer cylinder 51 to 3 mm compared to the rubber roll of the same shape. The nip width k in the roll rotation direction of the nip is also about 9 mm, which is almost the same as the nip width of this rubber roll of about 12 mm. The deflection amount at the nip width k is about 0.05 to 0.1 mm.

  Here, t / r ≦ 0.03. However, in the case of a general roll diameter R = 200 to 500 mm, flexibility is sufficiently obtained especially in the range of 2 mm ≦ t ≦ 5 mm. Thinning by processing can be easily performed, and it is an extremely practical range. If the wall thickness is 2 mm or less, high-precision processing cannot be performed due to elastic deformation during processing.

  The converted value of 2 mm ≦ t ≦ 5 mm is 0.008 ≦ t / r ≦ 0.05 with respect to a general roll diameter, but in practical use, the roll diameter under the condition of t / r≈0.03. The wall thickness should be increased in proportion to For example, when roll diameter: R = 200, t = 2 to 3 mm, and when roll diameter: R = 500, t = 4 to 5 mm.

  The touch rolls A and B are urged toward the first cooling roll by urging means (not shown). The urging force of the urging means is F, and the value F / W (linear pressure) obtained by dividing the width of the film in the nip in the direction along the rotation axis of the first cooling roll 5 is 9.8 to 147 N / cm. Set to

  According to the present embodiment, a nip is formed between the touch rolls A and B and the first cooling roll 5, and the flatness may be corrected while the film passes through the nip.

  Accordingly, since the film is sandwiched over a long time with a small linear pressure compared to the case where the touch roll is formed of a rigid body and no nip is formed between the first cooling roll and the flatness is more reliably corrected. Can do.

  That is, when the linear pressure is smaller than 9.8 N / cm, the die line cannot be sufficiently eliminated.

  On the other hand, if the linear pressure is greater than 147 N / cm, the film is difficult to pass through the nip, resulting in unevenness in place of the film thickness.

  Moreover, since the surface of the touch rolls A and B can be made smoother than the case where the surface of the touch rolls is made of rubber, the surface of the touch rolls A and B can be made smoother. Can be obtained.

  In addition, as a material of the elastic body 44 of the elastic roller 42, ethylene propylene rubber, neoprene rubber, silicon rubber, or the like can be used.

  Now, in order to satisfactorily eliminate the die line by the touch roll 6, it is important that the viscosity of the film when the touch roll 6 clamps the film is in an appropriate range.

  Cellulose esters are known to have a relatively large change in viscosity with temperature.

  Therefore, in order to set the viscosity when the touch roll 6 clamps the optical film to an appropriate range, it is important to set the temperature of the film when the touch roll 6 clamps the cellulose film to an appropriate range. Become.

  And when the glass transition temperature of an optical film is set to Tg, it is preferable to set the temperature T of the film just before a film is pinched by the touch roll 6 so that Tg <T <Tg + 110 degreeC may be satisfied.

  Preferably, Tg + 10 ° C. <T2 <Tg + 90 ° C., more preferably Tg + 20 ° C. <T2 <Tg + 70 ° C. In order to set the temperature of the film when the touch roll 6 clamps the optical film to an appropriate range, the first cooling roll starts from the position P1 at which the melt extruded from the casting die 4 contacts the first cooling roll 5. What is necessary is just to adjust the length L along the rotation direction of the 1st cooling roll 5 of the nip of 5 and the touch roll 6. FIG.

  In the present invention, preferred materials for the first roll 5 and the second roll 6 include carbon steel, stainless steel, resin, and the like.

  The surface accuracy is preferably increased, and the surface roughness is set to 0.3 S or less, more preferably 0.01 S or less.

  In the present invention, it is preferable to reduce the pressure from the opening (lip) of the casting die 4 to the first roll 5 to 70 kPa or less. More preferably, the reduced pressure is 50 to 70 kPa.

  Although there is no restriction | limiting in particular as a method of keeping the pressure of the part from the opening part (lip | rip) of the casting die 4 to the 1st roll 5 below 70 kPa, Cover the roll periphery from the casting die 4 with a pressure | voltage resistant member, and reduce pressure. There are methods.

  At this time, the suction device is preferably subjected to a treatment such as heating with a heater so that the device itself does not become a place where the sublimate is attached.

  In the present invention, if the suction pressure is too small, the sublimate cannot be sucked effectively, so it is necessary to set the suction pressure to an appropriate value.

  In the present invention, a film-like cellulose ester resin in a molten state is transferred from the T die 4 to the first roll (first cooling roll) 5, the second cooling roll 7, and the third cooling roll 8 in order and conveyed. Cooling and solidification is performed while the unstretched cellulose ester resin film 10 is obtained.

  In the embodiment of the present invention shown in FIG. 1, the cooled and solidified unstretched film 10 peeled from the third cooling roll 8 by the peeling roll 9 is guided to a stretching machine 12 via a dancer roll (film tension adjusting roll) 11. Therefore, the film 10 is stretched in the transverse direction (width direction). By this stretching, the molecules in the film are oriented.

  As a method for stretching the film in the width direction, a known tenter or the like can be preferably used. In particular, it is preferable to set the stretching direction to the width direction because lamination with a polarizing film can be performed in a roll form.

  By stretching in the width direction, the slow axis of the optical film made of the cellulose ester resin film is in the width direction.

  On the other hand, the transmission axis of the polarizing film is also usually in the width direction. By incorporating a polarizing plate in which the transmission axis of the polarizing film and the slow axis of the optical film are parallel to each other into the liquid crystal display device, the display contrast of the liquid crystal display device can be increased and a good viewing angle can be obtained. Is obtained.

  The glass transition temperature Tg of the film constituting material can be controlled by varying the material type constituting the film and the ratio of the constituting material.

  When a retardation film is produced as an optical film, Tg is preferably 120 ° C. or higher, preferably 135 ° C. or higher. In the liquid crystal display device, in the image display state, the temperature environment of the film changes due to the temperature rise of the device itself, for example, the temperature rise derived from the light source.

  At this time, if the Tg of the film is lower than the use environment temperature of the film, the retardation value derived from the orientation state of the molecules fixed inside the film by stretching and the dimensional shape as the film are greatly changed.

  If the Tg of the film is too high, the temperature is increased when the film constituent material is made into a film, so that the energy consumption for heating is increased, and the material itself may be decomposed when it is made into a film, resulting in coloring. Therefore, Tg is preferably 250 ° C. or lower.

  The stretching step may be performed by known heat setting conditions, cooling, and relaxation treatment, and may be appropriately adjusted so as to have the characteristics required for the target optical film.

  In order to provide the physical properties of the phase film and the function of the phase film for expanding the viewing angle of the liquid crystal display device, the stretching step and the heat setting treatment are appropriately selected and performed.

  When such a stretching step and heat setting treatment are included, the heating and pressurizing step is performed before the stretching step and heat setting treatment.

  When producing a retardation film as an optical film and further combining the functions of a polarizing plate protective film, it is necessary to control the refractive index. However, the refractive index can be controlled by a stretching operation. Is a preferred method. Hereinafter, the stretching method will be described.

  In the retardation film stretching process, the required retardation is obtained by stretching 1.0 to 2.0 times in one direction of the cellulose resin and 1.01 to 2.5 times in the direction perpendicular to the film plane. Ro and Rt can be controlled. Here, Ro indicates in-plane retardation, and Rt indicates thickness direction retardation.

  Retardation Ro and Rt are calculated | required by a following formula.

Formula (i) Ro = (nx−ny) × d
Formula (ii) Rt = ((nx + ny) / 2−nz) × d
(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 (refractive index is 23 ° C., 55%) (Measured at a wavelength of 590 nm in an RH environment), d represents the thickness (nm) of the film.)
The refractive index of the optical film is an Abbe refractometer (4T), the thickness of the film is a commercially available micrometer, and the retardation value is an automatic birefringence meter KOBRA-21ADH (manufactured by Oji Scientific Instruments). ) Etc., and each can be measured.

  Stretching can be performed, for example, sequentially or simultaneously in the longitudinal direction of the film and the direction orthogonal to the longitudinal direction of the film, that is, the width direction.

  When stretching in the width direction, the refractive index may be distributed in the width direction. This distribution may appear when the tenter method is used. By stretching the film in the width direction, a shrinkage force is generated at the center of the film, and the phenomenon is caused by the end being fixed. It is thought to be called the Boeing phenomenon.

  Even in this case, by stretching in the casting direction, the bowing phenomenon can be suppressed and the distribution of the phase difference in the width direction can be reduced.

  By stretching in the biaxial directions perpendicular to each other, the film thickness variation of the obtained film can be reduced. When the film thickness variation of the retardation film is too large, the retardation becomes uneven, and unevenness such as coloring may be a problem when used in a liquid crystal display.

  The film thickness variation of the optical film is preferably in the range of ± 3%, and more preferably ± 1%. For the purposes as described above, the method of stretching in the biaxial directions perpendicular to each other is effective, and the stretching ratio in the biaxial directions perpendicular to each other is finally 1.0 to 2.0 times in the casting direction. The width direction is preferably 1.01 to 2.5 times, the casting direction is 1.01 to 1.5 times, and the width direction is 1.05 to 2.0 times. It is more preferable to obtain the required retardation value.

  When the absorption axis of the polarizer exists in the longitudinal direction, the transmission axis of the polarizer coincides with the width direction. In order to obtain a long polarizing plate, the retardation film is preferably stretched so as to obtain a slow axis in the width direction.

  When cellulose ester that obtains positive birefringence with respect to stress is used, the slow axis of the retardation film can be provided in the width direction by stretching in the width direction from the above configuration.

In this case, in order to improve the display quality, the slow axis of the retardation film is preferably in the width direction, and in order to obtain the desired retardation value,
Formula (stretch ratio in the width direction)> (stretch ratio in the casting direction)
It is necessary to satisfy the following conditions.

  After stretching, after slitting the edge of the film to a product width by the slitter 13, the film is subjected to knurling (embossing) on both ends of the film by a knurling device comprising an embossing ring 14 and a back roll 15. By winding with the winder 16, sticking in the optical film (original winding) F and generation of scratches are prevented.

  The knurling method can process a metal ring having an uneven pattern on its side surface by heating or pressing.

  In addition, since the grip part of the clip of the both ends of a film is deform | transforming normally and cannot be used as a film product, it is cut out and reused as a raw material.

  Next, in the film winding process, the film is wound on the take-up roll while keeping the shortest distance between the outer peripheral face of the cylindrical roll film and the outer peripheral face of the mobile transport roll immediately before the roll. It is.

  In addition, a means such as a static elimination blower for removing or reducing the surface potential of the film is provided in front of the winding roll.

  The winder related to the production of the optical film of the present invention may be generally used, and it may be a winding method such as a constant tension method, a constant torque method, a taper tension method, or a program tension control method with a constant internal stress. Can be wound up.

  In addition, it is preferable that the initial winding tension at the time of winding of a polarizing plate protective film is 90.2-300.8 N / m.

  In the film winding step in the method of the present invention, the film is preferably wound under environmental conditions of a temperature of 20 to 30 ° C. and a humidity of 20 to 60% RH. Thus, the tolerance of the humidity change of the thickness direction retardation (Rt) improves by prescribing | regulating the temperature and humidity in the winding-up process of a film.

  If the temperature in the winding process is less than 20 ° C., wrinkles are generated and the film winding quality is deteriorated, which is unpractical. If the temperature in the film winding process exceeds 30 ° C., wrinkles are also generated, and the film winding quality is deteriorated, so that it cannot be put into practical use.

  Moreover, if the humidity in the film winding process is less than 20% RH, it is not preferable because it is easily charged and cannot be put into practical use due to deterioration in film winding quality.

  If the humidity in the film winding process exceeds 60% RH, the winding quality, sticking failure, and transportability deteriorate, which is not preferable.

  When winding the polarizing plate protective film in a roll shape, the winding core may be any material as long as it is a cylindrical core, but is preferably a hollow plastic core, as a plastic material May be any heat-resistant plastic that can withstand the heat treatment temperature, and examples thereof include phenol resins, xylene resins, melamine resins, polyester resins, and epoxy resins.

  A thermosetting resin reinforced with a filler such as glass fiber is preferred. For example, a hollow plastic core: a wound core made of FRP and having an outer diameter of 6 inches (hereinafter, inch represents 2.54 cm) and an inner diameter of 5 inches is used.

  The number of windings to these winding cores is preferably 100 windings or more, more preferably 500 windings or more, the winding thickness is preferably 5 cm or more, and the width of the film substrate is 80 cm or more. It is preferably 1 m or more.

  Although the thickness of the film of the optical film of the present invention varies depending on the purpose of use, the finished film is preferably 10 to 500 μm.

  In particular, the lower limit is 20 μm or more, preferably 35 μm or more. The upper limit is 150 μm or less, preferably 120 μm or less. A particularly preferable range is 25 to 90 μm.

  When the retardation film also serves as a polarizing plate protective film, if the film is thick, the polarizing plate after polarizing plate processing becomes too thick, especially for liquid crystal displays used in notebook computers and mobile electronic devices for thin and lightweight purposes. Not suitable.

  On the other hand, if the film is thin, it is difficult to develop retardation as a retardation film, and in addition, the moisture permeability of the film is increased, and the ability to protect the polarizer from humidity is reduced.

  When the slow axis or the fast axis of the retardation film exists in the film plane and the angle formed with the film forming direction is θ1, θ1 is −1 to + 1 °, preferably −0.5 to + 0.5 °. To be.

  This θ1 can be defined as an orientation angle, and θ1 can be measured using an automatic birefringence meter KOBRA-21ADH (manufactured by Oji Scientific Instruments).

  When each θ1 satisfies the above relationship, it contributes to obtaining high luminance in a display image, suppressing or preventing light leakage, and contributing to faithful color reproduction in a color liquid crystal display device.

  When the retardation film is used for the multi-domain VA mode, the retardation film is arranged in the above region with the fast axis of the retardation film being θ1, which contributes to the improvement of display image quality. When the plate and the liquid crystal display device are in the MVA mode, for example, the configuration shown in FIG. 7 can be adopted.

  In FIG. 7, 21a and 21b are protective films, 22a and 22b are retardation films, 25a and 25b are polarizers, 23a and 23b are slow axis directions of the film, 24a and 24b are transmission axis directions of the polarizer, 26a, Reference numeral 26b denotes a polarizing plate, 27 denotes a liquid crystal cell, and 29 denotes a liquid crystal display device.

  The retardation Ro distribution in the in-plane direction of the optical film is preferably adjusted to 5% or less, more preferably 2% or less, and particularly preferably 1.5% or less.

  Further, the retardation Rt distribution in the thickness direction of the film is preferably adjusted to 10% or less, more preferably 2% or less, and particularly preferably 1.5% or less.

  In the retardation film, it is preferable that the retardation value distribution fluctuation is small. When a polarizing plate including a retardation film is used in a liquid crystal display device, the retardation distribution fluctuation is preferably small from the viewpoint of preventing color unevenness and the like.

  The retardation film is adjusted so as to have a retardation value suitable for improving the display quality of the liquid crystal cell of VA mode or TN mode, and is preferably used in the MVA mode by dividing the retardation film into the above multi-domain as the VA mode. For this purpose, it is required to adjust the in-plane retardation Ro to a value greater than 30 nm and 95 nm or less, and the thickness direction retardation Rt to a value greater than 70 nm and 400 nm or less.

  The in-plane retardation Ro is observed from the normal direction of the display surface when the two polarizing plates are arranged in crossed Nicols and the liquid crystal cell is arranged between the polarizing plates, for example, in the configuration shown in FIG. When in a crossed Nicol state with respect to time, when observed obliquely from the normal line of the display surface, the polarizing plate deviates from the crossed Nicol state, and light leakage caused by this is mainly compensated.

  The retardation in the thickness direction mainly compensates for the birefringence of the liquid crystal cell similarly observed when viewed from an oblique direction when the liquid crystal cell is in the black display state in the TN mode or VA mode, particularly in the MVA mode. Contribute to.

  As shown in FIG. 7, in the liquid crystal display device, when two polarizing plates are arranged above and below the liquid crystal cell, 22a and 22b in the figure can select the distribution of the thickness direction retardation Rt. The total value of both of the above-mentioned ranges and the thickness direction retardation Rt is preferably larger than 140 nm and 500 nm or less.

  In this case, in-plane retardation Ro and thickness direction retardation Rt of 22a and 22b are preferably the same for improving productivity of an industrial polarizing plate. Particularly preferably, the in-plane retardation Ro is larger than 35 nm and not larger than 65 nm, and the thickness direction retardation Rt is larger than 90 nm and not larger than 180 nm, and is applied to the MVA mode liquid crystal cell in the configuration of FIG.

  In the liquid crystal display device, a TAC film having an in-plane retardation Ro = 0 to 4 nm and a thickness direction retardation Rt = 20 to 50 nm and a thickness of 35 to 85 μm as, for example, a commercially available polarizing plate protective film on one polarizing plate, for example, FIG. When used at the position 22b, the polarizing film disposed on the other polarizing plate, for example, the retardation film disposed on 22a in FIG. 7, has an in-plane retardation Ro of more than 30 nm and not more than 95 nm, and The thickness direction retardation Rt is larger than 140 nm and 400 nm or less. The display quality is improved, and this is preferable from the viewpoint of film production.

  In the film forming process, the clip gripping portions at both ends of the cut film are pulverized or granulated as necessary, and then used as a film material of the same product type or as a film material of a different product type. It may be reused.

  An optical film having a laminated structure can also be produced by coextruding compositions containing cellulose esters having different additive concentrations such as the plasticizer, ultraviolet absorber, and matting agent.

  For example, an optical film having a structure of skin layer / core layer / skin layer can be produced.

  For example, the matting agent can be contained in the skin layer in a large amount or only in the skin layer. The plasticizer and the ultraviolet absorber can be contained in the core layer more than the skin layer, and may be contained only in the core layer.

  In addition, the type of plasticizer and ultraviolet absorber can be changed between the core layer and the skin layer. For example, the skin layer contains a low-volatile plasticizer and / or an ultraviolet absorber, and the core layer has excellent plasticity. It is also possible to add a plasticizer or an ultraviolet absorber excellent in ultraviolet absorption.

  The glass transition temperature of the skin layer and the core layer may be different, and the glass transition temperature of the core layer is preferably lower than the glass transition temperature of the skin layer.

  At this time, the glass transition temperatures of both the skin and the core can be measured, and an average value calculated from these volume fractions can be defined as the glass transition temperature Tg and similarly handled.

  Also, the viscosity of the melt containing the cellulose ester during melt casting may be different between the skin layer and the core layer, and the viscosity of the skin layer> the viscosity of the core layer or the viscosity of the core layer ≧ the viscosity of the skin layer may be used.

  In consideration of productivity and transportability, the roll length of the optical film of the present invention is 10 to 5000 m, preferably 50 to 4500 m. The width of the film at this time is suitable for the width of the polarizer and the production line. The width can be selected.

  A film with a width of 0.5 to 4.0 m, preferably 0.6 to 3.0 m, may be wound into a roll shape and used for polarizing plate processing. After being manufactured and wound on a roll, it may be cut to obtain a roll having a desired width, and such a roll may be used for polarizing plate processing.

  In the production of the polarizing plate protective film, functional layers such as an antistatic layer, a hard coat layer, a slippery layer, an adhesive layer, an antiglare layer, and a barrier layer may be coated before and / or after stretching.

At this time, various surface treatments such as corona discharge treatment, plasma treatment, and chemical treatment can be performed as necessary.
<Polarizing plate>
When using the optical film of this invention as a polarizing plate protective film, the preparation methods of a polarizing plate are not specifically limited, It can manufacture by a general method. The back side of the optical film of the present invention is subjected to alkali saponification treatment, and the treated optical film is bonded to at least one surface of a polarizer produced by immersing and stretching in an iodine solution using a completely saponified polyvinyl alcohol aqueous solution. It is preferable.

  The optical film of the present invention may be used on the other surface, or another polarizing plate protective film may be used. With respect to the optical film of the present invention, a commercially available optical film can be used as the polarizing plate protective film used on the other surface.

  For example, as a commercially available optical film, KC8UX2M, KC4UX, KC5UX, KC4UY, KC8UY, KC12UR, KC8UCR-3, KC8UCR-4, KC4FR-1, KC8UY-HA, KC8UX-RHA (above, Konica Minolta Opto) Etc. 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 in combination with the optical film of the present invention, a polarizing plate having excellent flatness and a stable viewing angle expansion effect can be obtained.

  Or you may use films, such as cyclic olefin resin other than the optical film which has a cellulose ester, an acrylic resin, polyester, a polycarbonate, as a polarizing plate protective film of the other surface.

  Instead of the alkali treatment, polarizing plate processing may be performed by performing easy adhesion processing as described in JP-A-6-94915 and JP-A-6-118232.

  A polarizer, which is a main component of a polarizing plate, is an element that allows only light of a plane of polarization in a certain direction to pass. A typical polarizer currently known is a polyvinyl alcohol-based polarizing film, which is polyvinyl alcohol. There are one in which iodine is dyed on a system film and one in which 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. The film thickness of the polarizer is 5 to 40 μm, preferably 5 to 30 μm, and particularly preferably 5 to 20 μm.

  On the surface of the polarizer, one surface of the optical film of the present invention is bonded to form a polarizing plate. It is preferably bonded with an aqueous adhesive mainly composed of completely saponified polyvinyl alcohol or the like.

  Since the polarizer is stretched in a uniaxial direction (usually the longitudinal direction), when the polarizing plate is placed in a high-temperature and high-humidity environment, the stretching direction (usually the longitudinal direction) shrinks, and the direction perpendicular to the stretching (usually the width direction) ) Will grow.

  As the thickness of the polarizing plate protective film decreases, the expansion / contraction ratio of the polarizing plate increases, and in particular, the amount of contraction in the stretching direction of the polarizer increases. Normally, the direction of stretching of the polarizer is bonded to the casting direction (MD direction) of the polarizing plate protective film. Therefore, when thinning the polarizing plate protective film, it is particularly important to suppress the stretch rate in the casting direction. It is.

  Since the optical film of the present invention is extremely excellent in dimensional stability, it is suitably used as such a polarizing plate protective film.

  That is, even when the durability test is performed at 60 ° C. and 90% RH, the wavy unevenness does not increase, and even if the polarizing plate has an optical compensation film on the back side, the viewing angle characteristics fluctuate after the durability test. Good visibility can be provided without doing so.

  The polarizing plate is composed of a polarizer and a protective film for protecting both surfaces of the polarizer, and can further be constructed by laminating a protective film on one surface of the polarizing plate and a separate film on the opposite 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 liquid crystal plate.

  Moreover, a separate film is used in order to cover the contact bonding layer bonded to a liquid crystal board, and is used for the surface side which bonds a polarizing plate to a liquid crystal cell.

  The optical film of the present invention has a dimensional stability of ± 2.0% in terms of dimensional variation at 80 ° C. and 90% RH, based on the dimensions of the film left at 23 ° C. and 55% RH for 24 hours. Less than, preferably less than 1.0%, more preferably less than 0.5%.

When using the optical film of the present invention as a retardation film for a polarizing plate protective film, if the retardation film itself is within the above range, the initial value of the absolute value and orientation angle of retardation as a polarizing plate is set. Since it does not shift, it is preferable because it does not cause a decrease in display quality improvement capability or display quality deterioration.
<Liquid crystal display device>
A polarizing plate including a polarizing plate protective film (including a case where it also serves as a retardation film) using the optical film of the present invention can exhibit high display quality as compared with a normal polarizing plate, particularly a multi-domain type. The liquid crystal display device is more suitable for use in a multi-domain liquid crystal display device, more preferably by a birefringence mode.

  The polarizing plate of the present invention includes MVA (Multi-domain Vertical Alignment) mode, PVA (Patterned Vertical Alignment) mode, CPA (Continuous Pinweal Alignment B) mode, OCB (Optical Compensation B) mode, OCB (Optical Compensation B mode, etc.). It can be used, and is not limited to a specific liquid crystal mode and the arrangement of polarizing plates.

  Liquid crystal display devices are being applied as devices for colorization and moving image display, and the display quality is improved by the present invention, and the improvement of contrast and the resistance of polarizing plates improve the display of moving images that are less fatigued and faithful. It becomes possible.

  In a liquid crystal display device including at least a polarizing plate including a retardation film, one polarizing plate including a polarizing plate protective film as the optical film of the present invention is disposed on the liquid crystal cell, or on both sides of the liquid crystal cell. Place two in a row. At this time, it can contribute to the improvement of display quality by using the polarizing plate protective film side included in the polarizing plate so as to face the liquid crystal cell of the liquid crystal display device.

  In FIG. 7, the films 22a and 22b face the liquid crystal cell of the liquid crystal display device.

  In such a configuration, the polarizing plate protective film as the optical film of the present invention can optically compensate the liquid crystal cell. When the polarizing plate of the present invention is used in a liquid crystal display device, at least one polarizing plate in the liquid crystal display device may be the polarizing plate of the present invention. By using the polarizing plate of the present invention, a liquid crystal display device with improved display quality and excellent viewing angle characteristics can be provided.

  In the polarizing plate of the present invention, a polarizing plate protective film of a cellulose derivative is used on the surface opposite to the polarizing plate protective film as the optical film of the present invention as viewed from the polarizer, and a general-purpose TAC film or the like is used. Can do. The polarizing plate protective film located on the side far from the liquid crystal cell can be provided with another functional layer in order to improve the quality of the display device.

  For example, it may be affixed to a film containing a known functional layer as a constituent for display in order to prevent reflection, anti-glare, scratch resistance, dust adhesion prevention, brightness improvement, or the polarizing plate surface of the present invention. It is not limited to.

  In general, a retardation film is required to obtain a stable optical characteristic such that the above-described retardation Ro or Rt has little fluctuation.

  In particular, in a liquid crystal display device in a birefringence mode, these fluctuations may cause image unevenness.

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.
Example 1
[Production of Optical Film Having Cellulose Ester (hereinafter, simply referred to as Cellulose Ester Film) 1]
As described below, a cellulose ester film 1 was produced by melt casting using a cellulose ester and various additives.

Cellulose ester C-1 100 parts by mass PETB 8.0 parts by mass Compound P-1 represented by the general formula (1), (2) or (3) of the present invention
0.10 parts by mass TINUVIN 928 (manufactured by Ciba Specialty Chemicals) 1.5 parts by mass The cellulose ester was dried under reduced pressure at 70 ° C. for 3 hours and cooled to room temperature, and then the additives were mixed.

  The above mixture was melt-mixed at 230 ° C. using a twin-screw extruder and pelletized. In addition, the glass transition temperature Tg of this pellet was 136 degreeC.

  Using this pellet, it was melted at 250 ° C. in a nitrogen atmosphere, extruded from the casting die 4 onto the first cooling roll 5, and formed by pressing the film between the first cooling roll 5 and the touch roll 6. .

  Further, silica particle Aerosil 200V (manufactured by Nippon Aerosil Co., Ltd.) was added as a slip agent from the hopper opening in the middle of the extruder 1 so as to be 0.5 parts by mass.

  The heat bolt was adjusted so that the gap width of the casting die 4 was 0.5 mm within 30 mm from the end in the width direction of the film and 1 mm at other locations.

  The touch roll A was used as the touch roll, and 80 ° C. water was poured as cooling water therein.

  From the position P1 at which the resin extruded from the casting die 4 contacts the first cooling roll 5 to the position P2 at the upstream end in the rotation direction of the first cooling roll 5 in the nip between the first cooling roll 5 and the touch roll 6. 1 The length L along the peripheral surface of the cooling roller 5 was set to 20 mm.

  Thereafter, the touch roll 6 was separated from the first cooling roll 5, and the temperature T of the melted part immediately before being sandwiched between the first cooling roll 5 and the touch roll 6 was measured.

  In the present embodiment, the temperature T of the melted part immediately before being sandwiched between the nips of the first cooling roll 5 and the touch roll 6 is 1 mm upstream from the nip upstream end P2, and a thermometer (an independent meter). (Measured by HA-200E).

  As a result of the measurement in this example, the temperature T was 141 ° C. The linear pressure of the touch roll 6 against the first cooling roll 5 was 14.7 N / cm. Furthermore, after being introduced into a tenter and stretched 1.3 times at 160 ° C in the width direction, it was cooled to 30 ° C while relaxing 3% in the width direction, then released from the clip, the clip gripping part was cut off, and both ends of the film Was subjected to a knurling process with a width of 10 mm and a height of 5 μm, and wound on a winding core with a winding tension of 220 N / m and a taper of 40%.

  In addition, the extrusion amount and the take-up speed were adjusted so that the film had a thickness of 80 μm, and the finished film width was slit and wound up so as to have a width of 1430 mm.

  The winding core had an inner diameter of 152 mm, an outer diameter of 165 to 180 mm, and a length of 1550 mm. A prepreg resin obtained by impregnating glass fibers and carbon fibers with an epoxy resin was used as the core material for the core.

  The surface of the core was coated with an epoxy conductive resin, the surface was polished, and the surface roughness Ra was finished to 0.3 μm. The winding length was 2500 m. The film original fabric sample of the present invention is referred to as a cellulose ester film 1.

[Production of Cellulose Ester Films 2 to 11]
Cellulose ester film 1 was prepared in the same manner as in Table 1 except that the type of cellulose ester and the compound represented by general formula (1), (2) or (3) of the present invention were changed as shown in Table 1. Films 2 to 15 were produced.

In addition, the addition amount of the cellulose ester replaced with the used cellulose ester C-1 is the same mass part as the cellulose ester C-1, and is represented by the general formula (1), (2) or (3) used in the present invention. The addition amount of the additive in place of the compound P-1 represented by For comparison, a comparative sample 11 containing no compound of the present invention was prepared.
P-1: LBT-1830 (manufactured by Sakai Chemical Industry Co., Ltd.)
(Mixture of zinc salt of monostearyl phosphate and zinc salt of distearyl phosphate)
P-2: LBT-1822 (manufactured by Sakai Chemical Industry Co., Ltd.)
(Mixture of zinc salt of monobehenyl phosphate and zinc salt of dibehenyl phosphate)
P-3: LBT-1813 (manufactured by Sakai Chemical Industry Co., Ltd.)
(Mixture of monostearyl phosphate aluminum salt and distearyl phosphate aluminum salt)
P-4: LBT-1820 (manufactured by Sakai Chemical Industry Co., Ltd.)
(Mixture of calcium salt of monostearyl phosphate and calcium salt of distearyl phosphate)
C-1: Cellulose acetate propionate (acetyl group substitution degree 1.4, propionyl group substitution degree 1.3, Mn = 86,000, Mw / Mn = 2.5)
C-2: Cellulose acetate propionate (acetyl group substitution degree 1.3, propionyl group substitution degree 1.2, Mn = 66,000, Mw / Mn = 3.0)
C-3: Cellulose acetate propionate (acetyl group substitution degree 1.6, propionyl group substitution degree 1.2, Mn = 79,000, Mw / Mn = 2.9)
C-4: Cellulose acetate propionate (acetyl group substitution degree 2.0, propionyl group substitution degree 0.7, Mn = 91,000, Mw / Mn = 2.4)

  The obtained cellulose ester film original fabric sample was evaluated by the following method. The results are shown in Table 1.

  In addition, a part of the cellulose ester film was cut out from the raw fabric sample, and bleed out and haze were evaluated by the following methods.

(Horse spine failure, core transfer)
The wound cellulose ester film original sample is wrapped in a polyethylene sheet at 25 ° C. and 50% in a double manner, and stored at 25 ° C. by the storage method as shown in FIGS. 8 (a), (b) and (c). And stored for 30 days under 50% condition.

  Then, it was taken out of the box, the polyethylene sheet was opened, and the fluorescent lamp tube that was lit on the surface of the film original sample was reflected and imaged.

A: Fluorescent lamps appear straight B: Fluorescent lamps appear to be bent partially C: Fluorescent lamps appear to be mottled In addition, the original film sample after storage is rewound to form a spot-like deformation of 50 μm or more, Alternatively, it was measured how many meters of the core transfer, in which the strip-shaped deformation in the width direction was clearly visible, from the core portion, and was ranked according to the following levels.

A: Less than 15 m from the core part B: Less than 15 to 30 m from the core part C: Less than 30 to 50 m from the core part D: 50 m or more from the core part (winding wrinkle)
Work to rewind the original film on the core under the conditions of 25 ° C and 50%. If wrinkles occur at the beginning of the roll and become defective, remove the original film from the core and rewind it. Went.

  The number of defects at this time was counted. This operation was averaged 10 times and ranked to the following levels.

A: 0 to less than 1 B: 1 to less than 3 C: 3 to less than 5 D: 5 or more (bleed out)
A cellulose ester film conditioned at 25 ° C. and 50% for 24 hours is allowed to stand in a high-temperature and high-humidity atmosphere at 80 ° C. and 90% RH for 1000 hours. Were visually observed and evaluated according to the following criteria.

A: No bleed-out is observed on the surface B: Partial bleed-out is slightly observed on the surface C: Slight bleed-out is observed on the entire surface D: On the entire surface A clear bleedout is recognized (Haze)
From the result of measurement using a haze meter (1001DP type, manufactured by Nippon Denshoku Industries Co., Ltd.), it is proportionally converted to the haze value when the thickness of the sample is 80 μm (eg, 1% at 20 μm) And 4% in terms of 80 μm), and the evaluation was performed according to the following criteria.

A: Haze is less than 0.5% B: Haze is less than 0.5-1.0% Table C: Haze is less than 1.0-1.5% D: Haze is 1.5% or more

  From Table 1, cellulose ester film original fabric samples 1 to 10 containing the compound represented by the general formula (1), (2) or (3) of the present invention are cellulose ester film original fabric samples 11 of comparative examples. On the other hand, it is found that the film is a cellulose ester film that has few horse back failures and core transfer even when stored for a long period of time and is less likely to cause deformation failures of the original film such as wrinkles at the beginning of winding.

Moreover, it turns out that the cellulose-ester film itself cut out from the original fabric is excellent in bleed-out and haze characteristics with respect to the comparative example.
Example 2
[Production of Optical Film Having Cellulose Ester (hereinafter, simply referred to as Cellulose Ester Film) 21]
As described below, a cellulose ester film 21 was produced by melt casting using a cellulose ester and various additives.

Cellulose ester C-1 100 parts by mass PETB 8.0 parts by mass IRGANOX1010 (manufactured by Ciba Specialty Chemicals)
0.50 parts by mass Sumizer GS (manufactured by Sumitomo Chemical Co., Ltd.) 0.20 parts by mass GSY-P101 (manufactured by Sakai Chemical Industry Co., Ltd.) 0.25 parts by mass General formula (1), (2) or ( Compound P-1 represented by 3)
0.10 parts by mass TINUVIN 928 (manufactured by Ciba Specialty Chemicals) 1.5 parts by mass The cellulose ester was dried under reduced pressure at 70 ° C. for 3 hours and cooled to room temperature, and then the additives were mixed.

  The above mixture was melt-mixed at 230 ° C. using a twin-screw extruder and pelletized. In addition, the glass transition temperature Tg of this pellet was 136 degreeC.

  Using this pellet, it was melted at 250 ° C. in a nitrogen atmosphere, extruded from the casting die 4 onto the first cooling roll 5, and formed by pressing the film between the first cooling roll 5 and the touch roll 6. . Further, silica particle Aerosil 200V (manufactured by Nippon Aerosil Co., Ltd.) was added as a slip agent from the hopper opening in the middle of the extruder 1 so as to be 0.5 parts by mass.

  The heat bolt was adjusted so that the gap width of the casting die 4 was 0.5 mm within 30 mm from the end in the width direction of the film and 1 mm at other locations.

  The touch roll A was used as the touch roll, and 80 ° C. water was poured as cooling water therein.

  From the position P1 at which the resin extruded from the casting die 4 contacts the first cooling roll 5 to the position P2 at the upstream end in the rotation direction of the first cooling roll 5 in the nip between the first cooling roll 5 and the touch roll 6. 1 The length L along the peripheral surface of the cooling roller 5 was set to 20 mm.

  Thereafter, the touch roll 6 was separated from the first cooling roll 5, and the temperature T of the melted part immediately before being sandwiched between the first cooling roll 5 and the touch roll 6 was measured.

  In the present embodiment, the temperature T of the melted part immediately before being sandwiched between the nips of the first cooling roll 5 and the touch roll 6 is 1 mm upstream from the nip upstream end P2, and a thermometer (an independent meter). (Measured by HA-200E).

  As a result of the measurement in this example, the temperature T was 141 ° C. The linear pressure of the touch roll 6 against the first cooling roll 5 was 14.7 N / cm. Furthermore, after being introduced into a tenter and stretched 1.3 times at 160 ° C in the width direction, it was cooled to 30 ° C while relaxing 3% in the width direction, then released from the clip, the clip gripping part was cut off, and both ends of the film Was subjected to a knurling process with a width of 10 mm and a height of 5 μm, and wound on a winding core with a winding tension of 220 N / m and a taper of 40%.

  In addition, the extrusion amount and the take-up speed were adjusted so that the film had a thickness of 80 μm, and the finished film width was slit and wound up so as to have a width of 1430 mm.

  The winding core had an inner diameter of 152 mm, an outer diameter of 165 to 180 mm, and a length of 1550 mm.

  A prepreg resin obtained by impregnating glass fibers and carbon fibers with an epoxy resin was used as the core material for the core. The surface of the core was coated with an epoxy conductive resin, the surface was polished, and the surface roughness Ra was finished to 0.3 μm. The winding length was 2500 m.

  The film original fabric sample of the present invention is referred to as a cellulose ester film 21.

[Production of Cellulose Ester Films 22 to 31]
In the production of the cellulose ester film 21, the same applies except that the type of cellulose ester, the compound represented by the general formula (1), (2) or (3) of the present invention, and other additives are changed as shown in Table 2. Thus, cellulose ester films 21 to 35 were produced.

  In addition, the addition amount of the cellulose ester replaced with the used cellulose ester C-1 is the same mass part as the cellulose ester C-1, and is represented by the general formula (1), (2) or (3) used in the present invention. The addition amount of the additive in place of the compound P-1 represented by formula (II) and the types and addition amounts of other additives were set to parts by mass shown in Table 2. For comparison, a comparative sample 31 containing no compound of the present invention was prepared.

  Evaluation similar to Example 1 was performed with respect to the obtained cellulose-ester-film original fabric sample. The results are shown in Table 2.

  From Table 2, cellulose ester film original fabric samples 21 to 30 containing the compound represented by the general formula (1), (2) or (3) of the present invention are cellulose ester film original fabric samples 31 of comparative examples. On the other hand, it is found that the film is a cellulose ester film that has few horse back failures and core transfer even when stored for a long period of time and is less likely to cause deformation failures of the original film such as wrinkles at the beginning of winding.

Moreover, it turns out that the cellulose-ester film itself cut out from the original fabric is excellent in bleed-out and haze characteristics with respect to the comparative example.
Example 3
(Production and evaluation of polarizing plate)
A 120 μm-thick polyvinyl alcohol film was immersed in an aqueous solution containing 1 part by mass of iodine, 2 parts by mass of potassium iodide, and 4 parts by mass of boric acid, and stretched 4 times at 50 ° C. to produce a polarizer.

  The cellulose ester film original fabric samples 1 to 10, 21 to 30 of the present invention prepared in Examples 1 and 2 and the comparative cellulose ester film original fabric samples 11 and 31 are double-wrapped with a polyethylene sheet, as shown in FIG. And then stored under conditions of 25 ° C. and 50% RH for 30 days, and then stored under conditions of 40 ° C. and 80% RH.

  Then, each polyethylene sheet was removed, and the cellulose ester film unwound from each original fabric sample was alkali treated with a 2.5 mol / L sodium hydroxide aqueous solution at 40 ° C. for 60 seconds, and further washed with water and dried to be alkali treated. did.

  The alkali-treated surfaces of Samples 1 to 10, 21 to 30, and Comparative Samples 11 and 31 of the present invention were bonded to both sides of the polarizer from both sides using a completely saponified polyvinyl alcohol 5% aqueous solution as an adhesive, Polarizing plates PL-1 to 10, 21 to 30 of the present invention on which a protective film was formed and comparative polarizing plates PL-11 and 31 were prepared.

  The obtained polarizing plates PL-1 to 10 and 21 to 30 of the present invention are protected on both sides by a protective film that is physically superior to the polarizing plates PL-11 and 31 of the comparative polarizing plate. Therefore, it has a remarkably excellent effect of having very good polarizing plate characteristics.

(Characteristic evaluation as a liquid crystal display device)
The polarizing plate of the 32-inch television AQ-32AD5 manufactured by Sharp Corporation, which is a VA type liquid crystal display device, was peeled off, and each of the polarizing plates produced above was cut according to the size of the liquid crystal cell.

  With the liquid crystal cell sandwiched, the two polarizing plates prepared as described above were attached so that the polarizing axes of the polarizing plates were not perpendicular to each other so as to be orthogonal to each other to produce a 32-inch VA color liquid crystal display, and the polarization of the cellulose ester film Sensory evaluation of the characteristic as a board was carried out with the rough feeling.

The results are shown in Table 3.
<Evaluation of roughness>
Images of white, black, red, green, blue, and color bars were displayed on the liquid crystal display device, and visual sensory evaluation was performed from a position 1 m away to see if there was a rough feeling on the pixels.

◎ ・ ・ ・ I don't mind the feeling of roughness at all ○ ・ ・ ・ I almost don't care about the feeling of roughness × ・ ・ ・ I feel that there is a feeling of roughness

  The liquid crystal display device using the polarizing plates PL-1 to 10 and 21 to 30 of the present invention has high contrast and excellent display properties compared to the liquid crystal display device using the comparative polarizing plates PL-11 and 31. It was.

  Thereby, it was confirmed that it is excellent as a polarizing plate for image display apparatuses, such as a liquid crystal display.

It is a general | schematic flow sheet which shows one embodiment of the apparatus which enforces the manufacturing method of the cellulose-ester film of this invention. It is a principal part expansion flow sheet of the manufacturing apparatus of FIG. 3A is an external view of the main part of the casting die, and FIG. 3B is a cross-sectional view of the main part of the casting die. It is sectional drawing of 1st Embodiment of a pinching rotary body. It is sectional drawing in the plane perpendicular | vertical to the rotating shaft of 2nd Embodiment of a pinching rotary body. It is sectional drawing in the plane containing the rotating shaft of 2nd Embodiment of a pinching rotary body. It is a disassembled perspective view which shows the outline of the block diagram of a liquid crystal display device. It is a figure which shows the state of the storage of a cellulose-ester film original fabric.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Extruder 2 Filter 3 Static mixer 4 Casting die 5 Rotating support body (1st cooling roll)
6 Nipping pressure rotating body (touch roll)
7 Rotating support (second cooling roll)
8 Rotating support (3rd cooling roll)
9, 11, 13, 14, 15 Transport roll 10 Cellulose acylate film 12 Stretcher 16 Winding device 21a, 21b Protective film 22a, 22b Retardation film 23a, 23b Film slow axis direction 24a, 24b Transmission of polarizer Axial direction 25a, 25b Polarizers 26a, 26b Polarizer 27 Liquid crystal cell 29 Liquid crystal display device 31 Die body 32 Slit 41 Metal sleeve 42 Elastic roller 43 Metal inner cylinder 44 Rubber 45 Cooling water 51 Outer cylinder 52 Inner cylinder 53 Space 54 Coolant 55a, 55b Rotating shaft 56a, 56b Outer cylinder support flange 60 Fluid shaft cylinder 61a, 61b Inner cylinder support flange 62a, 62b Intermediate passage 110 Winding core body 117 Support plate 118 Base 120 Cellulose ester film original fabric

Claims (2)

Following general formula (1), (2) or at least one and a method of manufacturing an optical optical film you containing a cellulose ester of the compound represented by (3), produce films by melt casting film forming method A method for producing an optical film .
(In the formula, R ¹ , R ² and R ³ are each independently an alkyl group having 1 to 30 carbon atoms which may have a substituent, or 6 to 6 carbon atoms which may have a substituent. 30 represents an aryl group, and any of R ¹ , R ² and R ³ may be bonded to each other to form a ring, M is a periodic table selected from Groups 1 to 15 excluding hydrogen and carbon And n represents the valence of the metal atom.) The optical film contains at least one compound selected from the group consisting of lactone, sulfur, phenol, double bond, hindered amine, and phosphorus compounds having no metal atom. Item 2. A method for producing an optical film according to Item 1.