JP2006077113A - Cellulose ester film, manufacturing method, therefor polarizing plate, and liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prepare an optical film having an improved optical property and being able to reduce bright spot foreign matter observed under a condition where polarizing plates are orthogonal, and to provide a method for manufacturing the same; to provide a manufacturing method for the optical film which has a low manufacturing load and equipment load associated with drying and recovery of a solvent; and furthermore to provide the optical film having an additive which is uniformly dispersed, having even distribution of mechanical and optical characteristics, and having excellent dimensional stability, and a method for manufacturing the film. <P>SOLUTION: A cellulose ester film is obtained by melting and extruding a mixture comprising a cellulose ester and at least one kind of the additive. At least a part of the cellulose ester is brought into contact with a liquid, in which the additive is dissolved or finely dispersed, to obtain the mixture, which is then dried. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a cellulose ester film, a production method thereof, a polarizing plate, and a liquid crystal display device.

  A liquid crystal display (LCD) can be directly connected to an IC circuit with low voltage and low power consumption, and can be particularly thin, so that display devices such as word processors, personal computers, televisions, monitors, portable information terminals, etc. Widely adopted. The basic configuration of this LCD is, for example, a polarizing plate provided on both sides of a liquid crystal cell.

  By the way, the polarizing plate allows only light of a polarization plane in a certain direction to pass through. Accordingly, the LCD plays an important role in visualizing the change in the orientation of the liquid crystal due to the electric field. That is, the performance of the LCD is greatly influenced by the performance of the polarizing plate. The polarizing plate generally has a configuration in which both sides of a polarizing film made of a polyvinyl alcohol film or the like on which iodine or dye is adsorbed and oriented are laminated with a transparent resin layer. As this transparent resin layer, a cellulose ester film such as triacetyl cellulose is suitable as a protective film because of its low birefringence, and is often used.

  In recent years, liquid crystal displays have been developed for a large screen and high image quality as a monitor to replace CRT. Along with this, the demand for protective films for polarizing plates for liquid crystals has also become severe, and in particular, there has been a problem of improving foreign matter failure called bright spot foreign matter observed under the orthogonal state of polarizing plates.

  Moreover, the solution casting method is common as a method for producing a cellulose ester film. In this method, a so-called dope solution obtained by dissolving cellulose ester in a solvent such as a halogen solvent is cast on a rotating endless belt or drum as a support to form a film. After casting, a part of the solvent is dried on the support, the film obtained by solidification is peeled off from the support, and the remaining solvent is dried to obtain a cellulose ester film.

  Since this method must remove the solvent remaining inside the film, the equipment and manufacturing costs, such as the drying line, drying energy, and the recovery and regeneration device for the evaporated solvent, are enormous, and these are reduced. That is also an issue.

As means for solving the above problems, for example, the optical film described in Patent Document 1 has a cellulose ester film formed by melt casting. With this configuration, an optical film excellent in optical, physical, and dimensional stability can be obtained. However, improvement of the foreign matter failure is still a problem.
JP 2000-352620 A

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an optical film with improved optical characteristics and reduced bright spot foreign matter observed under an orthogonal state of a polarizing plate, and a method for producing the same. is there. Another object of the present invention is to provide a method for producing an optical film with low production load and equipment load associated with drying and recovery of a solvent. Yet another object is to provide an optical film in which additives are uniformly dispersed, the distribution of mechanical properties and optical properties is uniform, and has excellent dimensional stability, and a method for producing the same.

  In addition, 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, and especially a polarizing plate protective film, retardation film, antireflection film, a brightness improvement. Includes films, optical compensation films for viewing angle expansion, etc. In particular, it is to provide a cellulose ester film of the present invention, a polarizing plate employing the film as a polarizing plate protective film, and a liquid crystal display equipped with the polarizing plate.

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

(Claim 1)
In a cellulose ester film obtained by melt-extruding a mixture comprising a cellulose ester and at least one additive, at least a part of the cellulose ester is brought into contact with a liquid in which the additive is dissolved or finely dispersed. And then dried. A cellulose ester film characterized by being dried.

(Claim 2)
The cellulose ester contains at least one selected from cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate phthalate, and cellulose phthalate. The cellulose ester film according to 1.

(Claim 3)
The additive is at least selected from a plasticizer, an antioxidant, an acid scavenger, a light stabilizer, a peroxide decomposer, a radical scavenger, a metal deactivator, an ultraviolet absorber, a matting agent, a dye, and a pigment. It is 1 type, The cellulose-ester film of Claim 1 or 2 characterized by the above-mentioned.

(Claim 4)
The cellulose ester film according to claim 1, wherein the cellulose ester film is an optical film.

(Claim 5)
5. At least one layer selected from an antistatic layer, a hard coat layer, an antireflection layer, an easy adhesion layer, an antiglare layer and an optical compensation layer is provided on at least one surface of the optical film. The cellulose ester film as described.

(Claim 6)
A polarizing plate using the cellulose ester film according to claim 1 on at least one surface.

(Claim 7)
A liquid crystal display device using the cellulose ester film according to claim 1 or the polarizing plate according to claim 6.

(Claim 8)
In a method for producing a cellulose ester film in which a mixture comprising a cellulose ester and at least one additive is melt-extruded, at least one liquid selected from liquids obtained by dissolving or finely dispersing the additive is added to the cellulose. A method for producing a cellulose ester film, wherein at least a part of an ester is contacted and then dried and melt-extruded at a melting temperature of 150 ° C to 250 ° C.

  According to the present invention, it is possible to provide an optical film having improved optical characteristics and reduced bright spot foreign matter observed under an orthogonal state of a polarizing plate, and a method for producing the same. Moreover, it is possible to provide a method for producing an optical film with low production load and equipment load accompanying drying and recovery of the solvent, and further, the additive is uniformly dispersed, the distribution of mechanical properties and optical properties is uniform, and the dimensions An optical film excellent in stability and a method for producing the same can be provided.

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

  The optical film of the present invention is a cellulose ester film formed by melt casting.

  The solution casting method, which is one of the methods for producing a cellulose ester film, forms a film by casting a solution obtained by dissolving cellulose ester in a solvent, evaporating and drying the solvent. Since this method has to remove the solvent remaining in the film, the capital investment and production cost for the production line such as the drying line, the drying energy, and the recovery and recycling equipment for the evaporated solvent are enormous. Reducing these has become an important issue.

  On the other hand, in the film formation by the melt casting method, since the solvent for adjusting the cellulose ester solution is not used as the solution casting, the above-described drying load and equipment load do not occur. Further, when the cellulose ester film is produced by the above-described solution casting method, a bright spot foreign matter failure may occur. On the other hand, when a cellulose ester film is prepared by the melt casting method of the present invention, the occurrence of bright spot foreign matter is reduced, and in particular, the performance as an optical film is improved. Furthermore, since the cellulose ester and the additive are highly dispersed, the distribution of optical characteristics and mechanical characteristics of the product becomes uniform.

  When adding an additive in melt molding of a cellulose ester, for example, there is a method of pre-dispersing in a powder state and melting with a single screw extruder. However, since this method has a low degree of dispersion of the powder, the effects expected in the melting process such as prevention of thermal deterioration and plasticization do not appear sufficiently. Furthermore, it has a defect that the product physical properties are likely to be uneven. In order to improve the dispersibility of the additive and the cellulose ester, there is a method of kneading and melting using a twin screw extruder. This method can obtain a high degree of dispersion, but due to its high shear force, the molding material is significantly deteriorated, and the flexibility, transparency, coloring, mechanical strength, etc. of the molded product are deteriorated.

  An object of the present invention is to provide a melt-molded product, particularly a polarizing plate protective film, in which an additive is uniformly dispersed and has excellent mechanical properties, optical properties, and dimensional stability. Furthermore, the present invention provides a method for adding an additive that is easy and has a low drying load by reducing the production load and facility load associated with drying and recovery of the solvent in the solution casting film formation. Furthermore, there is an advantage that the melt extruder can be miniaturized.

  As a result of intensive studies, the present inventors have found that the object is to dissolve or finely disperse the additive in a cellulose ester film obtained by melt-extruding a mixture comprising a cellulose ester and at least one additive. The present invention has been found to be achieved by a cellulose ester film characterized in that at least a part of the cellulose ester is brought into contact with the resulting liquid and then dried.

  Here, the melt casting in the present invention is defined as melt casting in which a cellulose ester is heated and melted to a temperature showing fluidity without using a solvent, and then the fluid cellulose ester is cast. More specifically, the heating and melting molding method can be classified into a melt extrusion molding method, a press molding method, an inflation method, an injection molding method, a blow molding method, a stretch molding method, and the like. Among these, in order to obtain an optical film excellent in mechanical strength and surface accuracy, the melt extrusion method is excellent. Here, after the film constituent material is heated to exhibit its fluidity, extrusion film formation on a drum or an endless belt is included in the method for producing a molten film of the present invention as a melt casting film formation method.

  Hereinafter, the present invention will be described in detail.

(Contact between cellulose ester and additive)
Examples of the method of bringing the cellulose ester into contact with a solution obtained by dissolving or finely dispersing the additive in a solvent include a method of immersing the cellulose ester in the additive solution, spraying, applying, and dropping the additive solution onto the cellulose ester. When contacting the additive, it is preferable to carry out the stirring of the cellulose ester.

  Although the example of an apparatus which contacts the cellulose ester and additive which concern on this invention is demonstrated, this invention is not limited to this.

  FIG. 1 is a schematic view of an additive spraying and drying apparatus. The cellulose ester weighed from the hopper 1 is sent to a screw conveyor 3 rotated by a motor 2 and sprayed with a solution in which an additive is dissolved or finely dispersed in a solvent from a spraying device 4 while being stirred and transferred, and then dried by a drying device 5. Then, the mixture is taken out from the outlet 6.

  The additive and the cellulose ester are contacted and then dried. A known method can be used for drying, preferably under heating and under reduced pressure, and more preferably under flow. It is preferable that the residual solvent amount is dried to 1% or less, more preferably 0.5% or less, and still more preferably 0.1% or less. In particular, the residual water content is preferably 1% or less, more preferably 0.5% or less, and still more preferably 0.1% or less. The drying temperature at this time is preferably 100 ° C. or higher and Tg or lower of the material to be dried. Including the viewpoint of avoiding fusion between the materials, the drying temperature is more preferably 100 ° C. or higher (Tg-5) ° C. or lower, and still more preferably 110 ° C. or higher (Tg-20) ° C. or lower. A preferable drying time is 0.5 to 24 hours, more preferably 1 to 18 hours, and still more preferably 1.5 to 12 hours. Below these ranges, the degree of drying may be low, or the drying time may be too long. Also, when Tg is present in the material to be dried, heating to a drying temperature higher than Tg may cause the material to fuse and make handling difficult.

  The drying process may be separated into two or more stages. For example, the film may be melted and formed through storage of the material in the preliminary drying process and the immediately preceding drying process performed immediately before the melt film formation to 1 week before.

  The shape of the cellulose ester brought into contact with the additive solution may be any of powder, granule, pellet, and film. Preferably, a powder and a granule are good. Moreover, you may mix the return material cut | disconnected in the chip shape as recycling. The recycled material may be produced by either the melt casting method or the solution casting method.

  The solvent for dissolving the additive is not limited as long as it is a good solvent for the additive, but a solvent having a low boiling point is preferable from the viewpoint of drying load. Examples of the solvent include alcohols such as methanol, ethanol and 1-propanol, ethyl acetate, tetrahydrofuran, dichloromethane, trichloromethane, acetone, methyl ethyl ketone, toluene, hexane and the like.

  The concentration of the additive is preferably as high as possible from the viewpoint of drying load. The concentration is preferably 10% or more, more preferably 30% or more, and still more preferably 50% or more.

  The fine dispersion of the additive preferably has a particle size of 1 μm or less, more preferably 0.5 μm or less, and still more preferably 0.1 μm or less.

  The ratio of the cellulose ester to be brought into contact with the additive is preferably 50% or more of the total cellulose ester, more preferably 80% or more, and still more preferably 95% or more of the cellulose ester and the additive.

  The additive is adsorbed on the surface of the cellulose ester in contact with the additive, and the surface coverage is preferably 10% or more, more preferably 30% or more, and even more preferably 50% or more. The evaluation of the cellulose ester surface can be observed with an optical microscope or an electron microscope depending on the particle size of the adsorbed additive. Further, the surface coating may be evaluated by measuring the contact angle and surface energy of the cellulose ester adsorbed with the additive, the cellulose ester, and the additive.

  At least a part of the additive liquid may penetrate into the cellulose ester, and the additive may precipitate inside the cellulose ester. Furthermore, the solvent used for the additive solution may have a cellulose ester solubility, and the additive and the cellulose ester may be in a compatible state in which a part of the cellulose ester is dispersed at the molecular level.

  After the additive solution is added and dried, at least a part of the cellulose ester may be dissolved and the cellulose esters may be bonded to each other. The adhered cellulose ester can be powdered or granulated by performing known dry pulverization or the like.

(Cellulose ester)
The cellulose resin according to the present invention is a single or mixed acid ester of cellulose which shows a structure of a cellulose ester and includes at least one of a fatty acyl group and a substituted or unsubstituted aromatic acyl group.

  Hereinafter, cellulose esters useful for satisfying the object of the present invention will be exemplified, but the present invention is not limited thereto.

In the aromatic acyl group, when the aromatic ring is a benzene ring, examples of the substituent of the benzene ring include halogen atom, cyano, alkyl group, alkoxy group, aryl group, aryloxy group, acyl group, carbonamido group, sulfone. Amido group, ureido group, aralkyl group, nitro, alkoxycarbonyl group, aryloxycarbonyl group, aralkyloxycarbonyl group, carbamoyl group, sulfamoyl group, acyloxy group, alkenyl group, alkynyl group, alkylsulfonyl group, arylsulfonyl group, alkyloxy Sulfonyl group, aryloxysulfonyl group, alkylsulfonyloxy group and aryloxysulfonyl group, -S-R, -NH-CO-OR, -PH-R, -P (-R) ₂ , -PH-O-R, -P (-R) (-O-R), -P ( _{O-R) 2, -PH (} = O) -R-P (= O) (- R) 2, -PH (= O) -O-R, -P (= O) (- R) (- O -R), -P (= O) (-O-R) ₂ , -O-PH (= O) -R, -O-P (= O) (-R) _2- O-PH (= O) —O—R, —O—P (═O) (— R) (— O—R), —O—P (═O) (— O—R) ₂ , —NH—PH (═O) —R , —NH—P (═O) (— R) (— O—R), —NH—P (═O) (— O—R) ₂ , —SiH ₂ —R, —SiH (—R) ₂ , _{-Si (-R) 3, -O-} SiH 2 -R, include -O-SiH (-R) ₂ and -O-Si (-R) _3. R is an aliphatic group, an aromatic group or a heterocyclic group. The number of substituents is preferably 1 to 5, more preferably 1 to 4, more preferably 1 to 3, and most preferably 1 or 2. As the substituent, a halogen atom, cyano, alkyl group, alkoxy group, aryl group, aryloxy group, acyl group, carbonamido group, sulfonamido group and ureido group are preferable, halogen atom, cyano, alkyl group, alkoxy group, An aryloxy group, an acyl group and a carbonamido group are more preferred, a halogen atom, cyano, an alkyl group, an alkoxy group and an aryloxy group are still more preferred, and a halogen atom, an alkyl group and an alkoxy group are most preferred.

  The halogen atom includes a fluorine atom, a chlorine atom, a bromine atom and an iodine atom. The alkyl group may have a cyclic structure or a branch. The number of carbon atoms in the alkyl group is preferably 1-20, more preferably 1-12, still more preferably 1-6, and most preferably 1-4. Examples of the alkyl group include methyl, ethyl, propyl, isopropyl, butyl, t-butyl, hexyl, cyclohexyl, octyl and 2-ethylhexyl. The alkoxy group may have a cyclic structure or a branch. The number of carbon atoms in the alkoxy group is preferably 1-20, more preferably 1-12, still more preferably 1-6, and most preferably 1-4. The alkoxy group may be further substituted with another alkoxy group. Examples of the alkoxy group include methoxy, ethoxy, 2-methoxyethoxy, 2-methoxy-2-ethoxyethoxy, butyloxy, hexyloxy and octyloxy.

  The number of carbon atoms in the aryl group is preferably 6-20, and more preferably 6-12. Examples of the aryl group include phenyl and naphthyl. The aryloxy group preferably has 6 to 20 carbon atoms, and more preferably 6 to 12 carbon atoms. Examples of the aryloxy group include phenoxy and naphthoxy. The number of carbon atoms in the acyl group is preferably 1-20, and more preferably 1-12. Examples of the acyl group include formyl, acetyl and benzoyl. The carbonamide group has preferably 1 to 20 carbon atoms, and more preferably 1 to 12 carbon atoms. Examples of the carbonamido group include acetamide and benzamide. The number of carbon atoms in the sulfonamide group is preferably 1-20, and more preferably 1-12. Examples of the sulfonamide group include methanesulfonamide, benzenesulfonamide, and p-toluenesulfonamide. The ureido group has preferably 1 to 20 carbon atoms, and more preferably 1 to 12 carbon atoms. Examples of ureido groups include (unsubstituted) ureido.

  The number of carbon atoms in the aralkyl group is preferably 7-20, and more preferably 7-12. Examples of the aralkyl group include benzyl, phenethyl and naphthylmethyl. The number of carbon atoms of the alkoxycarbonyl group is preferably 1-20, and more preferably 2-12. Examples of the alkoxycarbonyl group include methoxycarbonyl. The aryloxycarbonyl group preferably has 7 to 20 carbon atoms, and more preferably 7 to 12 carbon atoms. Examples of the aryloxycarbonyl group include phenoxycarbonyl. The number of carbon atoms in the aralkyloxycarbonyl group is preferably 8-20, and more preferably 8-12. Examples of the aralkyloxycarbonyl group include benzyloxycarbonyl. The number of carbon atoms in the carbamoyl group is preferably 1-20, and more preferably 1-12. Examples of the carbamoyl group include (unsubstituted) carbamoyl and N-methylcarbamoyl. The number of carbon atoms in the sulfamoyl group is preferably 20 or less, and more preferably 12 or less. Examples of the sulfamoyl group include (unsubstituted) sulfamoyl and N-methylsulfamoyl. The number of carbon atoms of the acyloxy group is preferably 1-20, and more preferably 2-12. Examples of the acyloxy group include acetoxy and benzoyloxy.

  The number of carbon atoms of the alkenyl group is preferably 2-20, and more preferably 2-12. Examples of alkenyl groups include vinyl, allyl and isopropenyl. The alkynyl group preferably has 2 to 20 carbon atoms, and more preferably 2 to 12 carbon atoms. Examples of alkynyl groups include thienyl. The number of carbon atoms in the alkylsulfonyl group is preferably 1-20, and more preferably 1-12. The arylsulfonyl group preferably has 6 to 20 carbon atoms, and more preferably 6 to 12 carbon atoms. The alkyloxysulfonyl group preferably has 1 to 20 carbon atoms, and more preferably 1 to 12 carbon atoms. The number of carbon atoms of the aryloxysulfonyl group is preferably 6-20, and more preferably 6-12. The number of carbon atoms of the alkylsulfonyloxy group is preferably 1-20, and more preferably 1-12. The number of carbon atoms of the aryloxysulfonyl group is preferably 6-20, and more preferably 6-12.

  In the cellulose ester of the present invention, when the hydrogen atom of the hydroxyl group of cellulose is a fatty acid ester with an aliphatic acyl group, the aliphatic acyl group has 2 to 20 carbon atoms, specifically acetyl, propionyl, butyryl, Examples include isobutyryl, valeryl, pivaloyl, hexanoyl, octanoyl, lauroyl, stearoyl and the like.

  In the present invention, the aliphatic acyl group is meant to include those further having a substituent. When the aromatic ring is a benzene ring in the above-described aromatic acyl group, the substituent of the benzene ring Are exemplified.

  Moreover, when the esterified substituent of the cellulose ester is an aromatic ring, the number of substituents X substituted on the aromatic ring is 0 or 1 to 5, preferably 1 to 3, and particularly preferable. Is one or two. Further, when the number of substituents substituted on the aromatic ring is 2 or more, they may be the same or different from each other, but they may be linked together to form a condensed polycyclic compound (for example, naphthalene, indene, indane, phenanthrene, quinoline). , Isoquinoline, chromene, chroman, phthalazine, acridine, indole, indoline, etc.).

  The cellulose ester has a structure having a structure selected from at least one of a substituted or unsubstituted aliphatic acyl group and a substituted or unsubstituted aromatic acyl group, which is used as the structure used in the cellulose ester of the present invention. These may be a single or mixed acid ester of cellulose, or a mixture of two or more cellulose esters.

  The cellulose ester constituting the optical film of the present invention is at least one selected from cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate phthalate, and cellulose phthalate. It is preferable.

  Among these, particularly preferable cellulose esters include cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, and cellulose acetate butyrate.

  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) and (II).

Formula (I) 2.6 ≦ X + Y ≦ 3.0
Formula (II) 0 ≦ X ≦ 2.5
Of these, cellulose acetate propionate is particularly preferably used. Among them, 1.9 ≦ X ≦ 2.5 and 0.1 ≦ Y ≦ 0.9 are preferable. The portion not substituted with the acyl group is usually present as a hydroxyl group. These can be synthesized by known methods.

  Furthermore, the cellulose ester used in the present invention preferably has a weight average molecular weight Mw / number average molecular weight Mn ratio of 1.5 to 5.5, particularly preferably 2.0 to 5.0, Preferably it is 2.5-5.0, More preferably, the cellulose ester of 3.0-5.0 is used preferably.

  The cellulose ester raw material cellulose used in the present invention may be wood pulp or cotton linter, and the wood pulp may be softwood or hardwood, but softwood is more preferred. A cotton linter is preferably used from the viewpoint of peelability during film formation. The cellulose ester made from these can be mixed suitably or can be used independently.

  For example, the ratio of cellulose ester derived from cellulose linter: cellulose ester derived from wood pulp (coniferous): cellulose ester derived from wood pulp (hardwood) is 100: 0: 0, 90: 10: 0, 85: 15: 0, 50:50: 0, 20: 80: 0, 10: 90: 0, 0: 100: 0, 0: 0: 100, 80:10:10, 85: 0: 15, 40:30:30.

(Bright spot foreign matter)
With the bright spot foreign material of the present invention, two polarizing plates are placed in an orthogonal state (crossed nicols), a cellulose ester film (for example, cellulose acetate propionate) is placed between them, and light is applied from one polarizer side, This is a point that appears white when observed with a microscope from the other side of the polarizer, and if this is present, it becomes a defect of the display, and a smaller number is suitable for a high-definition display. This is considered to be caused by light leaking because the refractive index is different at the foreign substance part of cellulose ester, and one of the causes is presumed that cellulose remaining without being acetylated during the acetylation process is involved Is done.

  The polarizing plate used for measuring bright spot foreign matter is preferably made of glass. This is because, when a polarizing plate made of a cellulose ester film is used, the polarizing plate itself contains bright spot foreign matter, which makes it difficult to distinguish it from the bright spot foreign matter in the sample. In addition, a polarizing plate may be arranged at a distance from the sample. If the polarizing plate is arranged at a distance from the sample, the focused position is shifted by the microscope, so that the bright spot foreign matter in the sample can be specified.

(Additive)
Examples of additives include plasticizers, antioxidants, acid scavengers, light stabilizers, peroxide decomposers, radical scavengers, metal deactivators, ultraviolet absorbers, matting agents, dyes, and pigments. . Moreover, if it has the said function, the additive which is not classified into this is also used.

  It is represented by coloring and molecular weight reduction, including decomposition reactions that have not been elucidated, such as oxidation prevention of film constituent materials, capture of acid generated by decomposition, suppression or prohibition of decomposition reaction due to radical species due to light or heat, etc. Additives are used in order to suppress the generation of volatile components due to deterioration or material decomposition, and to impart functions such as moisture permeability and slipperiness.

  On the other hand, when the film constituent material is heated and melted, the decomposition reaction becomes remarkable, and this decomposition reaction may be accompanied by strength deterioration of the constituent material due to coloring or molecular weight reduction. Moreover, generation | occurrence | production of an unfavorable volatile component may occur by the decomposition reaction of a film constituent material.

When the film constituent material is heated and melted, the presence of the above-mentioned additives is excellent in terms of suppressing the deterioration of the strength based on the deterioration and decomposition of the material, or maintaining the inherent strength of the material. It is necessary that the above-mentioned additives are present from the viewpoint of manufacturing the optical film.
Further, the presence of the above-mentioned additives is not preferable as an optical film such as transmittance and haze value generated by suppressing the generation of colored substances in the visible light region at the time of heating and melting, or by mixing volatile components into the film. It is excellent in that the performance can be suppressed or eliminated.

  In the present invention, the display image of the liquid crystal display image is affected when the optical film is used in the configuration of the present invention exceeding 1%, and therefore the haze value is preferably less than 1%, more preferably less than 0.5%. .

  In the step of imparting retardation during film production, the deterioration of the strength of the film constituting material can be suppressed, or the strength inherent to the material can be maintained. This is because if the film constituent material becomes brittle due to remarkable deterioration, breakage is likely to occur in the stretching step, and the retardation value may not be controlled.

  In the above-described film constituent material storage or film forming process, deterioration reactions due to oxygen in the air may occur simultaneously. In this case, the effect of reducing the oxygen concentration in the air can be used together with the stabilizing action of the additive in realizing the present invention. This includes the use of nitrogen or argon as an inert gas as a known technique, degassing operation under reduced pressure to vacuum, and operation under a sealed environment, and at least one of these three methods includes the above additives. It can be used in combination with the method. By reducing the probability that the film constituent material comes into contact with oxygen in the air, deterioration of the material can be suppressed, which is preferable for the purpose of the present invention.

  Since the optical film of the present invention is used as a polarizing plate protective film, the above-mentioned addition to the film constituting material is also made from the viewpoint of improving the storage stability with time with respect to the polarizing plate of the present invention and the polarizer constituting the polarizing plate. It is preferred that an agent is present.

  In the liquid crystal display device using the polarizing plate of the present invention, since the above-mentioned additives are present in the optical film of the present invention, the aging storage property of the optical film can be improved from the viewpoint of suppressing the above-mentioned deterioration and deterioration, and the liquid crystal Also in improving the display quality of the display device, the optical compensation design provided with the optical film is excellent in that the function can be expressed over a long period of time.

    Hereinafter, the additive will be described in more detail.

(Plasticizer)
It is preferable to add a compound known as a plasticizer to the optical film of the present invention from the viewpoint of film modification such as improvement of mechanical properties, imparting flexibility, imparting water absorption resistance, and reducing moisture permeability. Further, in the melt casting method carried out in the present invention, the purpose of lowering the melting temperature of the film constituting material by adding a plasticizer rather than the glass transition temperature of the cellulose ester used alone, or the plasticizer than the cellulose ester at the same heating temperature. The purpose of reducing the viscosity of the film-constituting material containing is included.

  Here, in the present invention, the melting temperature of the film constituent material means a temperature at which the material is heated in a state where the material is heated and fluidity is developed.

  If the cellulose ester alone is lower than the glass transition temperature, the fluidity for forming a film is not exhibited. However, the cellulose ester has a lower elastic modulus or viscosity due to the absorption of heat at a glass transition temperature or higher, and exhibits fluidity. In order to melt the film constituent material, the plasticizer to be added preferably has a melting point or glass transition temperature lower than the glass transition temperature of the cellulose ester in order to satisfy the above-mentioned purpose.

  As the plasticizer used in the present invention, for example, phosphate ester derivatives and carboxylic acid ester derivatives are preferably used. Further, a polymer obtained by polymerizing an ethylenically unsaturated monomer having a weight average molecular weight of 500 to 10,000 described in JP-A-2003-12859, an acrylic polymer, an acrylic polymer having an aromatic ring in the side chain, or cyclohexyl An acrylic polymer having a group in the side chain is also preferably used.

  Examples of phosphoric acid ester derivatives include phosphoric acid ester plasticizers, ethylene glycol ester plasticizers, glycerin ester plasticizers, diglycerin ester plasticizers (fatty acid esters), polyhydric alcohol esters. Examples thereof include a plasticizer, a dicarboxylic acid ester plasticizer, a polyvalent carboxylic acid ester plasticizer, and a polymer plasticizer. Of these, polyhydric alcohol ester plasticizers, dicarboxylic acid ester plasticizers and polycarboxylic acid ester plasticizers are preferred. Further, the plasticizer may be a liquid or a solid, and is preferably colorless due to restrictions on the composition. Thermally, it is preferably stable at a higher temperature, and the decomposition start temperature is preferably 150 ° C. or higher, more preferably 200 ° C. or higher. The addition amount may be as long as the optical properties and mechanical properties are not adversely affected, and the blending amount is appropriately selected within the range not impairing the object of the present invention, and preferably 0.001 with respect to 100 parts by mass of the polymer according to the present invention. -50 mass parts, More preferably, it is 0.01-30 mass parts. 0.1-15 mass% is especially preferable.

  Hereinafter, the plasticizer used in the present invention will be described. Specific examples are not limited to these examples.

  Phosphate ester plasticizers: specifically, phosphoric acid alkyl esters such as triacetyl phosphate and tributyl phosphate, phosphoric acid cycloalkyl esters such as tricyclobenthyl phosphate and cyclohexyl phosphate, triphenyl phosphate, tricresyl phosphate And phosphoric acid aryl esters such as cresylphenyl 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. Further, it may be a mix of an alkyl group, a cycloalkyl group, and an aryl group, and the substituents may be covalently bonded.

  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 phosphate) ), Arylene bis (dialkyl phosphate) such as biphenylene bis (dioctyl phosphate), phosphate esters such as arylene bis (diaryl phosphate) such as phenylene bis (diphenyl phosphate) and naphthylene bis (ditoluyl phosphate). These substituents may be the same or different, and may be further substituted. Further, it may be a mix of an alkyl group, a cycloalkyl group, and an aryl group, and the substituents may be covalently bonded.

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

  Ethylene glycol ester plasticizer: Specifically, ethylene glycol alkyl ester plasticizers such as ethylene glycol diacetate and ethylene glycol dibutyrate, ethylene glycol dicyclopropyl carboxylate, ethylene glycol dicyclohexyl carboxylate and the like Examples include ethylene glycol cycloalkyl ester plasticizers 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, a mixture of alkylate group, cycloalkylate group and arylate group may be used, and these substituents may be covalently bonded. Further, the ethylene glycol part may be substituted, 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. May be introduced into a part of the molecular structure of the additive.

  Glycerin ester plasticizers: Specifically, glycerol alkyl esters such as triacetin, tributyrin, glycerol diacetate caprylate, glycerol oleate propionate, and glycerin cycloalkyl esters such as glycerol tricyclopropyl carboxylate and glycerol tricyclohexyl carboxylate Glyceryl aryl esters such as glycerin tribenzoate and glycerin 4-methylbenzoate, diglycerin tetraacetylate, diglycerin tetrapropionate, diglycerin acetate tricaprylate, diglycerin alkyl esters such as diglycerin tetralaurate, di Diglycerides such as glycerin tetracyclobutylcarboxylate and diglycerin tetracyclopentylcarboxylate Emissions cycloalkyl esters, 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 mix of alkylate group, cycloalkylcarboxylate group, and arylate group, and these substituents may be bonded by a covalent bond. Furthermore, the glycerin or diglycerin part may be substituted, and the partial structure of the glycerin ester or diglycerin ester may be part of the polymer or regularly pendant, and may be an antioxidant or an acid scavenger. Or may be introduced into a part of the molecular structure of an additive such as an ultraviolet absorber.

  Polyhydric alcohol ester plasticizer: Specific examples include polyhydric alcohol ester plasticizers described in paragraphs 30 to 33 of JP-A-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 mix 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.

  Dicarboxylic acid ester plasticizers: Specifically, alkyldocarboxylic acid alkyl ester plasticizers such as didodecyl malonate (C1), dioctyl adipate (C4), dibutyl sebacate (C8), dicyclopentyl succinate, Alkyl dicarboxylic acid cycloalkyl ester plasticizers such as dicyclohexyl adipate, alkyl dicarboxylic acid aryl ester plasticizers such as diphenyl succinate and di4-methylphenyl glutarate, dihexyl-1,4-cyclohexanedicarboxylate, Cycloalkyldicarboxylic acid alkyl ester plasticizers such as didecylbicyclo [2.2.1] heptane-2,3-dicarboxylate, dicyclohexyl-1,2-cyclobutanedicarboxylate, dicyclopropyl-1,2 Cycloalkyldicarboxylic acid cycloalkyl ester plasticizers such as cyclohexyl dicarboxylate, aryl cycloalkyldicarboxylates such as diphenyl-1,1-cyclopropyldicarboxylate, di2-naphthyl-1,4-cyclohexanedicarboxylate Ester plasticizers, aryl dicarboxylic acid alkyl ester plasticizers such as diethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate and di-2-ethylhexyl phthalate, and aryl dicarboxylic acid cycloalkyls such as dicyclopropyl phthalate and dicyclohexyl phthalate Examples include ester plasticizers and aryl dicarboxylic acid aryl ester plasticizers such as diphenyl phthalate and di4-methylphenyl phthalate. 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. Further, the aromatic ring of phthalic acid may be substituted, and a multimer such as a dimer, trimer or tetramer may be used. In addition, the partial structure of phthalate ester may be part of the polymer or regularly pendant to the polymer, and may be part of the molecular structure of additives such as antioxidants, acid scavengers, and UV absorbers. It may be introduced.

  Polycarboxylic acid ester plasticizers: Specifically, alkyl polycarboxylic acid alkyl ester plastics such as tridodecyl tricarbarate and tributyl-meso-butane-1,2,3,4-tetracarboxylate Agents, alkyl polyvalent carboxylic acid cycloalkyl ester type plasticizers such as tricyclohexyl tricarbarate, tricyclopropyl-2-hydroxy-1,2,3-propanetricarboxylate, triphenyl 2-hydroxy-1,2 Alkyl polycarboxylic acid aryl ester plasticizers such as 1,3-propanetricarboxylate, tetra-3-methylphenyltetrahydrofuran-2,3,4,5-tetracarboxylate, tetrahexyl-1,2,3,4 -Cyclobutane tetracarboxylate, tetrabutyl-1,2, , Cycloalkyl polycarboxylic acid alkyl ester plasticizers such as 1,4-cyclopentanetetracarboxylate, tetracyclopropyl-1,2,3,4-cyclobutanetetracarboxylate, tricyclohexyl-1,3, 5-cyclohexyl Cycloalkyl polycarboxylic acid cycloalkyl ester plasticizers such as tricarboxylate, triphenyl-1,3,5-cyclohexyltricarboxylate, hexa-4-methylphenyl-1,2,3,4,5,6 -Cycloalkyl polycarboxylic acid aryl ester plasticizers such as cyclohexyl hexacarboxylate, tridodecylbenzene-1,2,4-tricarboxylate, tetraoctylbenzene-1,2,4,5-tetracarboxylate, etc. Aryl polycarboxylic acid Lester ester plasticizer, tricyclopentylbenzene-1,3,5-tricarboxylate, tetracyclohexylbenzene-1,2,3,5-tetracarboxylate, etc. aryl polycarboxylic acid cycloalkyl ester plasticizer tri Aryl polycarboxylic acid aryl ester plasticizers such as phenylbenzene-1,3,5-tetracartoxylate, hexa-4-methylphenylbenzene-1,2,3,4,5,6-hexacarboxylate Can be mentioned. 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. Further, the aromatic ring of phthalic acid may be substituted, and a multimer such as a dimer, trimer or tetramer may be used. In addition, the partial structure of phthalate ester may be part of the polymer or regularly pendant to the polymer, and may be part of the molecular structure of additives such as antioxidants, acid scavengers, and UV absorbers. It may be introduced.

  Polymer plasticizer: Specifically, aliphatic hydrocarbon polymer, alicyclic hydrocarbon polymer, acrylic polymer such as polyethyl acrylate and polymethyl methacrylate, polyvinyl isobutyl ether, poly N-vinyl pyrrolidone, etc. Examples include vinyl polymers, polystyrene, styrene polymers such as poly-4-hydroxystyrene, polybutylene succinate, polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyethers such as polyethylene oxide and polypropylene oxide, polyamides, polyurethanes, and polyureas. It is done. The number average molecular weight is preferably about 1,000 to 500,000, particularly preferably 5,000 to 200,000. If it is 1,000 or less, a problem arises in volatility, and if it exceeds 500,000, the plasticizing ability is lowered, which adversely affects the mechanical properties of the cellulose ester derivative composition. 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, and other plasticizers, antioxidants, acid scavengers, ultraviolet absorbers, slip agents, matting agents, and the like may be included.

  The addition amount of these compounds is preferably used in the range of 0.5% by mass to less than 50% by mass, more preferably 1% by mass to 30% by mass with respect to the resin in which the plasticizer constitutes the film. %, More preferably in the range of 1% by mass to less than 11% by mass. The addition amount of these compounds can be adjusted from the viewpoint of the above purpose.

  Among the plasticizers, it is preferable that no volatile component is generated during heat melting. Specific examples include non-volatile phosphate esters described in JP-A-6-501040. For example, among arylene bis (diaryl phosphate) esters and the above exemplified compounds, trimethylolpropane tribenzoate is preferable. It is not limited. When the volatile component is due to thermal decomposition of the plasticizer, the thermal decomposition temperature Td (1.0) of the plasticizer is higher than the melting temperature of the film-forming material when defined as the temperature at which the mass decreases by 1.0% by mass. Is required. This is because, for the above purpose, the plasticizer is added to the cellulose ester in a larger amount than other film constituent materials, and the presence of the volatile component has a great influence on the quality of the obtained film. The thermal decomposition temperature Td (1.0) can be measured with a commercially available differential thermal mass spectrometer (TG-DTA) apparatus.

(Antioxidant)
The antioxidant used in the present invention will be described.

  Antioxidants include phenolic antioxidants, phosphorus antioxidants, sulfur antioxidants, heat-resistant processing stabilizers, oxygen scavengers, etc. Among them, phenolic antioxidants, particularly alkyl-substituted phenolic compounds Antioxidants are preferred. By blending these antioxidants, it is possible to prevent coloration and strength reduction of the molded product due to heat during molding or oxidative degradation without lowering transparency, heat resistance and the like. These antioxidants can be used alone or in combination of two or more, and the blending amount thereof is appropriately selected within a range not impairing the object of the present invention, but the polymer 100 according to the present invention. Preferably it is 0.001-5 mass parts with respect to a mass part, More preferably, it is 0.01-1 mass part.

  As antioxidants, hindered phenol antioxidant compounds are known compounds, such as those described in columns 12-14 of US Pat. No. 4,839,405, such as 2, 6-dialkylphenol derivative compounds are included. Such compounds include those of general formula (1) below.

  In the above formula, R 1, R 2 and R 3 represent a further substituted or unsubstituted alkyl substituent. Specific examples of hindered phenol compounds include n-octadecyl 3- (3,5-di-t-butyl-4-hydroxyphenyl) -propionate, n-octadecyl 3- (3,5-di-t-butyl- 4-hydroxyphenyl) -acetate, n-octadecyl 3,5-di-tert-butyl-4-hydroxybenzoate, n-hexyl 3,5-di-tert-butyl-4-hydroxyphenylbenzoate, n-dodecyl 3, 5-di-t-butyl-4-hydroxyphenylbenzoate, neo-dodecyl 3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, dodecyl β (3,5-di-t-butyl- 4-hydroxyphenyl) propionate, ethyl α- (4-hydroxy-3,5-di-t-butylphenyl) isobutyrate, octa Sil α- (4-hydroxy-3,5-di-t-butylphenyl) isobutyrate, octadecyl α- (4-hydroxy-3,5-di-t-butyl-4-hydroxyphenyl) propionate, 2- (n -Octylthio) ethyl 3,5-di-t-butyl-4-hydroxy-benzoate, 2- (n-octylthio) ethyl 3,5-di-t-butyl-4-hydroxy-phenylacetate, 2- (n- Octadecylthio) ethyl 3,5-di-t-butyl-4-hydroxyphenyl acetate, 2- (n-octadecylthio) ethyl 3,5-di-t-butyl-4-hydroxy-benzoate, 2- (2- Hydroxyethylthio) ethyl 3,5-di-t-butyl-4-hydroxybenzoate, diethyl glycol bis- (3,5-di-t-butyl- -Hydroxy-phenyl) propionate, 2- (n-octadecylthio) ethyl 3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, stearamide N, N-bis- [ethylene 3- (3 5-di-t-butyl-4-hydroxyphenyl) propionate], n-butylimino N, N-bis- [ethylene 3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2- (2-stearoyloxyethylthio) ethyl 3,5-di-tert-butyl-4-hydroxybenzoate, 2- (2-stearoyloxyethylthio) ethyl 7- (3-methyl-5-tert-butyl-4- Hydroxyphenyl) heptanoate, 1,2-propylene glycol bis- [3- (3,5-di-t-butyl-4-hydroxy Enyl) propionate], ethylene glycol bis- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], neopentyl glycol bis- [3- (3,5-di-t-butyl-) 4-hydroxyphenyl) propionate], ethylene glycol bis- (3,5-di-t-butyl-4-hydroxyphenyl acetate), glycerin-1-n-octadecanoate-2,3-bis- (3 5-di-t-butyl-4-hydroxyphenyl acetate), pentaerythritol-tetrakis- [3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionate], 1,1,1 -Trimethylolethane-tris- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], sorbite Hexa- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2-hydroxyethyl 7- (3-methyl-5-t-butyl-4-hydroxyphenyl) propionate, 2- Stearoyloxyethyl 7- (3-methyl-5-t-butyl-4-hydroxyphenyl) heptanoate, 1,6-n-hexanediol-bis [(3 ′, 5′-di-t-butyl-4-hydroxy Phenyl) propionate], pentaerythritol-tetrakis (3,5-di-t-butyl-4-hydroxyhydrocinnamate). Hindered phenolic antioxidant compounds of the above type are commercially available from Ciba Specialty Chemicals under the trade names “Irganox 1076” and “Irganox 1010”, for example.

  Specific examples of other antioxidants include phosphorus antioxidants such as trisnonylphenyl phosphite, triphenyl phosphite, tris (2,4-di-tert-butylphenyl) phosphite, and dilauryl-3. , 3′-thiodipropionate, dimyristyl-3,3′-thiodipropionate, distearyl-3,3′-thiodipropionate, pentaerythrityltetrakis (3-laurylthiopropionate), etc. System antioxidant, 2-tert-butyl-6- (3-tert-butyl-2-hydroxy-5-methylbenzyl) -4-methylphenyl acrylate, 2- [1- (2-hydroxy-3,5- Di-tert-pentylphenyl) ethyl] -4,6-di-tert-pentylphenyl acrylate 3,4-dihydro-2H-1-benzopyran compound, 3,3′-spirodichroman compound, 1,1-spiroindane compound, morpholine, thiomorpholine, thiomorpholine oxide, described in JP-B-08-27508, Examples thereof include thiomorpholine dioxide, compounds having a piperazine skeleton in the partial structure, oxygen scavengers such as dialkoxybenzene compounds described in JP-A No. 03-174150, and the like. These antioxidant partial structures may be part of the polymer, or may be regularly pendant to the polymer, and introduced into part of the molecular structure of additives such as plasticizers, acid scavengers, and UV absorbers. May be.

(Acid scavenger)
The acid scavenger preferably comprises an epoxy compound as an acid scavenger described in US Pat. No. 4,137,201. Epoxy compounds as such acid scavengers are known in the art and are derived by condensation of various polyglycol diglycidyl ethers, particularly about 8-40 moles of ethylene oxide per mole of polyglycol. Glycol, diglycidyl ether of glycerol, metal epoxy compounds (such as those conventionally used in and together with vinyl chloride polymer compositions), epoxidized ether condensation products, diphenols of bisphenol A Glycidyl ether (i.e., 4,4'-dihydroxydiphenyldimethylmethane), epoxidized unsaturated fatty acid ester (especially an ester of an alkyl of about 4 to 2 carbon atoms of a fatty acid of 2 to 22 carbon atoms (e.g. butyl Epoxy stearate) ), And various epoxidized long chain fatty acid triglycerides and the like (e.g., epoxidized vegetable oils and other unsaturated natural oils, which may be represented and exemplified by compositions such as epoxidized soybean oil, sometimes epoxidized natural) These are referred to as glycerides or unsaturated fatty acids and these fatty acids generally contain 12 to 22 carbon atoms)). Particularly preferred are commercially available epoxy group-containing epoxide resin compounds EPON 815c and other epoxidized ether oligomer condensation products of general formula (2).

  In the above formula, n is equal to 0-12. Further possible acid scavengers that can be used include those described in paragraphs 87 to 105 of JP-A-5-194788.

(Light stabilizer)
Light stabilizers include hindered amine light stabilizer (HALS) compounds, which are known compounds, such as columns 5-11 of US Pat. No. 4,619,956 and US Pat. , 839,405, as described in columns 3 to 5, including 2,2,6,6-tetraalkylpiperidine compounds, or acid addition salts thereof or complexes of them with metal compounds It is. Such compounds include those of the following general formula (3).

  In the above formula, R1 and R2 are H or a substituent. Specific examples of hindered amine light stabilizer compounds include 4-hydroxy-2,2,6,6-tetramethylpiperidine, 1-allyl-4-hydroxy-2,2,6,6-tetramethylpiperidine, 1-benzyl. -4-hydroxy-2,2,6,6-tetramethylpiperidine, 1- (4-t-butyl-2-butenyl) -4-hydroxy-2,2,6,6-tetramethylpiperidine, 4-stearoyl Oxy-2,2,6,6-tetramethylpiperidine, 1-ethyl-4-salicyloyloxy-2,2,6,6-tetramethylpiperidine, 4-methacryloyloxy-1,2,2,6 6-pentamethylpiperidine, 1,2,2,6,6-pentamethylpiperidin-4-yl-β (3,5-di-t-butyl-4-hydroxyphenyl) -propionate, -Benzyl-2,2,6,6-tetramethyl-4-piperidinyl maleate, (di-2,2,6,6-tetramethylpiperidin-4-yl) -adipate, (di- 2,2,6,6-tetramethylpiperidin-4-yl) -sebacate, (di-1,2,3,6-tetramethyl-2,6-diethyl-piperidin-4-yl) -sebacate, (di -1-allyl-2,2,6,6-tetramethyl-piperidin-4-yl) -phthalate, 1-acetyl-2,2,6,6-tetramethylpiperidin-4-yl-acetate, trimellitic acid- Tri- (2,2,6,6-tetramethylpiperidin-4-yl) ester, 1-acryloyl-4-benzyloxy-2,2,6,6-tetramethylpiperidine, dibutyl-malonic acid-di -(1,2,2,6,6-pentamethyl-piperidin-4-yl) -ester, dibenzyl-malonic acid-di- (1,2,3,6-tetramethyl-2,6-diethyl-piperidine- 4-yl) -ester, dimethyl-bis- (2,2,6,6-tetramethylpiperidine-4-oxy) -silane, tris- (1-propyl-2,2,6,6-tetramethylpiperidine- 4-yl) -phosphite, tris- (1-propyl-2,2,6,6-tetramethylpiperidin-4-yl) -phosphate, N, N′-bis- (2,2,6,6- Tetramethylpiperidin-4-yl) -hexamethylene-1,6-diamine, N, N′-bis- (2,2,6,6-tetramethylpiperidin-4-yl) -hexamethylene-1,6- Diacetamide, 1-acetyl -4- (N-cyclohexylacetamide) -2,2,6,6-tetramethyl-piperidine, 4-benzylamino-2,2,6,6-tetramethylpiperidine, N, N'-bis- (2, 2,6,6-tetramethylpiperidin-4-yl) -N, N′-dibutyl-adipamide, N, N′-bis- (2,2,6,6-tetramethylpiperidin-4-yl) -N , N′-dicyclohexyl- (2-hydroxypropylene), N, N′-bis- (2,2,6,6-tetramethylpiperidin-4-yl) -p-xylylene-diamine, 4- (bis-2 -Hydroxyethyl) -amino-1,2,2,6,6-pentamethylpiperidine, 4-methacrylamide-1,2,2,6,6-pentamethylpiperidine, α-cyano-β-methyl-β- [N- (2,2 6,6-tetramethyl-piperidin-4-yl)] - amino - acrylic acid methyl ester. Examples of preferred hindered amine light stabilizers include the following HALS-1 and HALS-2.

  These hindered amine light resistance stabilizers can be used alone or in combination of two or more, and used together with these hindered amine light resistance stabilizers and additives such as plasticizers, acid scavengers, and UV absorbers. Alternatively, it may be introduced into a part of the molecular structure of the additive. The blending amount is appropriately selected within a range not impairing the object of the present invention, but is preferably 0.01 to 20 parts by mass, more preferably 0.02 to 15 parts with respect to 100 parts by mass of the polymer according to the present invention. Part by mass, particularly preferably 0.05 to 10 parts by mass.

(UV absorber)
As an ultraviolet absorber, from the viewpoint of preventing deterioration of a polarizer or a display device with respect to ultraviolet rays, the ultraviolet absorber has an excellent ability to absorb ultraviolet rays having a wavelength of 370 nm or less. Less is preferred. Examples include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, etc., but benzophenone compounds and less colored benzotriazole compounds preferable. Moreover, you may use the ultraviolet absorber of Unexamined-Japanese-Patent No. 10-182621, Unexamined-Japanese-Patent No. 8-337574, and the polymeric ultraviolet absorber of Unexamined-Japanese-Patent No. 6-148430.

  Specific examples of useful benzotriazole ultraviolet absorbers include 2- (2′-hydroxy-5′-methylphenyl) benzotriazole, 2- (2′-hydroxy-3 ′, 5′-di-tert-butylphenyl). ) Benzotriazole, 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'-hydro Cis-3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 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 Examples include, but are not limited to, a mixture of -5- (5-chloro-2H-benzotriazol-2-yl) phenyl] propionate.

  As commercially available products, TINUVIN 109, TINUVIN 171 and TINUVIN 360 (all manufactured by Ciba Specialty Chemicals) can also be used.

  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 the present invention, the ultraviolet absorber is preferably added in an amount of 0.1 to 20% by mass, more preferably 0.5 to 10% by mass, and further preferably 1 to 5% by mass. Two or more of these may be used in combination.

(Matting agent)
In the optical film of the present invention, fine particles such as a matting agent can be added in order to impart slipperiness, and examples of the fine particles include inorganic compound fine particles and organic compound fine particles. The matting agent is preferably as fine as possible. Examples of the fine particles include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, kaolin, talc, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, Examples thereof include inorganic fine particles such as magnesium silicate and calcium phosphate, and crosslinked polymer fine particles. Among these, silicon dioxide is preferable because it can reduce the haze of the film. In many cases, fine particles such as silicon dioxide are surface-treated with an organic substance, but such particles are preferred because they can reduce the haze of the film.

  Preferred organic substances for the surface treatment include halosilanes, alkoxysilanes, silazane, siloxane and 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 particle size of the secondary particles of the fine particles is in the range of 0.05 to 1.0 μm. The average particle size of secondary particles of the fine particles is preferably 5 to 50 nm, more preferably 7 to 14 nm. These fine particles are preferably used in the cellulose ester film in order to generate irregularities of 0.01 to 1.0 μm on the surface of the cellulose ester film. The content of the fine particles in the cellulose ester is preferably 0.005 to 0.3% by mass with respect to the cellulose ester.

  Examples of the fine particles of silicon dioxide include Aerosil 200, 200V, 300, R972, R972V, R974, R202, R812, OX50, TT600 manufactured by Nippon Aerosil Co., Ltd., preferably Aerosil 200V, R972. , R972V, R974, R202, R812. 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. In this case, 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.

  The presence of fine particles in the film used as the matting agent can be used for another purpose to improve the strength of the film. The presence of the fine particles in the film can also improve the orientation of the cellulose ester itself constituting the optical film of the present invention.

(Retardation control agent)
In the optical film of the present invention, an alignment film is formed to provide a liquid crystal layer, and the optical film and the retardation derived from the liquid crystal layer are combined to provide an optical compensation capability, so that such polarization is improved for improving the liquid crystal display quality. Plate processing may be performed. As the compound to be added for adjusting the retardation, an aromatic compound having two or more aromatic rings as described in the specification of European Patent 911,656A2 may be used as a retardation control agent. I can do it. Two or more aromatic compounds may be used in combination. The aromatic ring of the aromatic compound includes an aromatic heterocyclic ring in addition to the aromatic hydrocarbon ring. Particularly preferred is an aromatic heterocycle, and the aromatic heterocycle is generally an unsaturated heterocycle. Of these, a 1,3,5-triazine ring is particularly preferred.

(Polymer material)
In the optical film of the present invention, polymer materials and oligomers other than cellulose ester may be appropriately selected and mixed. The above polymer materials and oligomers are preferably those having excellent compatibility with the cellulose ester, and the transmittance when formed into a film is 80% or more, more preferably 90% or more, and further preferably 92% or more. The purpose of mixing at least one of polymer materials and oligomers other than cellulose ester includes meanings for controlling viscosity at the time of heating and melting and improving film physical properties after film processing. In this case, it can be included as the above-mentioned other additives.

(Film formation)
Examples of the optical film of the present invention include U.S. Pat. Nos. 2,492,978, 2,739,070, 2,739,069, 2,492,977, and 2,336. 310, No. 2,367,603, No. 2,607,704, British Patent Nos. 64,071, 735,892, No. 45-9074, No. 49-4554, The film can be formed by referring to the methods described in JP 49-5614, JP 60-27562, JP 61-39890, and 62-4208.

  For example, the cellulose ester and additive mixture of the present invention is hot-air dried or vacuum dried, then melt extruded, extruded into a film form from a T-die, and brought into close contact with a cooling drum by an electrostatic application method, etc., and cooled and solidified. An unstretched film is obtained. The temperature of the cooling drum is preferably maintained at 90 to 150 ° C.

  The cellulose ester to which the additive has been adsorbed can be melted by a known melt extruder, and a cellulose ester to which no additive is added and an additive can be further added. For example, if the cellulose ester adsorbed 90% of the additive used is 50% of the total cellulose ester, the remaining 10% additive and 50% untreated cellulose ester are added after the additive adsorption step. It can be added directly during the melt extrusion process. Furthermore, the residual water content of the entire mixture immediately before being charged into the melt extruder is preferably 1% or less, more preferably 0.5% or less, and even more preferably 0.1% or less. Furthermore, the residual solvent amount of the entire mixture is preferably 1% or less, more preferably 0.5% or less, and further preferably 0.1% or less.

  Melt extrusion may be used by connecting a single screw extruder, a twin screw extruder, and a single screw extruder downstream of the twin screw extruder. From the viewpoint of the mechanical properties and optical properties of the obtained film, the single screw extruder is used. Is preferably used. Furthermore, it is preferable to replace or depressurize the raw material supply and melting processes such as the raw material tank, the raw material charging section, and the inside of the extruder with an inert gas such as nitrogen gas.

  The temperature during the melt extrusion of the present invention is preferably in the range of 150 to 250 ° C. Furthermore, it is preferable that it is the range of 200-240 degreeC.

  When a polarizing plate is produced using the optical film of the present invention as a polarizing plate protective film, the cellulose ester film is particularly preferably a film stretched in the width direction or the film forming direction.

  The unstretched film peeled off from the cooling drum described above is heated within a range of Tg + 100 ° C. from the glass transition temperature (Tg) of the cellulose ester via a heating device such as a plurality of roll groups and / or an infrared heater, It is preferable to perform single-stage or multistage longitudinal stretching. Next, the cellulose ester film stretched in the longitudinal direction obtained as described above is preferably stretched transversely within a temperature range of Tg to Tg-20 ° C. and then heat-set.

  In the case of transverse stretching, it is preferable to perform transverse stretching while sequentially raising the temperature difference in the range of 1 to 50 ° C. in a stretching region divided into two or more, because the distribution of physical properties in the width direction can be reduced. Further, after the transverse stretching, it is preferable that the film is held at a temperature of Tg-40 ° C. or higher at a temperature equal to or lower than the final transverse stretching temperature for 0.01 to 5 minutes because the distribution of physical properties in the width direction can be further reduced.

  In the heat setting, heat setting is usually performed for 0.5 to 300 seconds at a temperature higher than the final transverse stretching temperature and within a temperature range of Tg-20 ° C or lower. At this time, it is preferable to heat-fix while sequentially raising the temperature difference in the range of 1 to 100 ° C. in the region divided into two or more.

  The heat-set film is usually cooled to Tg or less, and clip holding portions at both ends of the film are cut and wound. At this time, it is preferable to perform a relaxation treatment of 0.1 to 10% in the horizontal direction and / or the vertical direction within the temperature range of the final heat setting temperature or lower and Tg or higher. Further, the cooling is preferably performed by gradually cooling from the final heat setting temperature to Tg at a cooling rate of 100 ° C. or less per second. Means for cooling and relaxation treatment are not particularly limited, and can be performed by a conventionally known means. In particular, it is preferable to perform these treatments while sequentially cooling in a plurality of temperature ranges from the viewpoint of improving the dimensional stability of the film. The cooling rate is a value obtained by (T1−Tg) / t, where T1 is the final heat setting temperature and t is the time until the film reaches Tg from the final heat setting temperature.

  More optimal conditions of these heat setting conditions, cooling, and relaxation treatment conditions vary depending on the cellulose ester constituting the film, so the physical properties of the obtained biaxially stretched film should be measured and adjusted appropriately to have desirable characteristics. It may be determined by.

(Functional layer)
In the production of the optical film of the present invention, functions such as an antistatic layer, a hard coat layer, an antireflection layer, a slippery layer, an easy adhesion layer, an antiglare layer, a barrier layer, and an optical compensation layer before and / or after stretching. A sex layer may be applied. In particular, it is preferable to provide at least one layer selected from an antistatic layer, a hard coat layer, an antireflection layer, an easy adhesion layer, an antiglare layer, and an optical compensation layer. At this time, various surface treatments such as corona discharge treatment, plasma treatment, and chemical treatment can be performed as necessary.

  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 the same type of film raw material or as a different type of film raw material. It may be reused.

  A cellulose ester film having a laminated structure can also be produced by co-extruding compositions containing cellulose resins having different additive concentrations such as the above-mentioned plasticizer, ultraviolet absorber and matting agent. For example, a cellulose ester 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. More plasticizers and UV absorbers can be added to the core layer than the skin layer, and may be added only to the core layer. It is also possible to change the type of plasticizer and ultraviolet absorber 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 Tg of the skin layer and the core layer may be different, and the Tg of the core layer is preferably lower than the Tg of the skin layer. 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.

  The optical film of the present invention can be used for a polarizing plate protective film. When using as a polarizing plate protective film, the manufacturing method of a polarizing plate is not specifically limited, It can manufacture by a general method. The obtained optical film is alkali-treated, and a polarizer protective film is bonded to both sides of the polarizer using a completely saponified polyvinyl alcohol aqueous solution on both sides of the polarizer produced by immersing and stretching the polyvinyl alcohol film in an iodine solution. There is a method, and the optical film which is a polarizing plate protective film of the present invention is preferable on the viewpoint that it can be directly bonded to a polarizer on at least one side.

  Further, instead of the alkali treatment, easy-adhesion processing as described in JP-A-6-94915 and JP-A-6-118232 may be applied to perform polarizing plate processing.

  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 adhesive layer bonded to a liquid crystal plate, and is used on the surface side which bonds a polarizing plate to a liquid crystal cell.

(Dimensional stability)
The optical film of the present invention has a dimensional stability with a dimensional variation value of less than ± 1.0% at 80 ° C. and 90% RH, based on the dimensions of the film left at 23 ° C. and 55% RH for 24 hours. Yes, more preferably less than 0.5%, and even more preferably less than 0.1%.

  Since the optical film of the present invention is used as a protective film for a polarizing plate, if the optical film itself has a fluctuation beyond the above range, the absolute value of the retardation as a polarizing plate and the orientation angle are shifted from the initial setting. In some cases, the display quality may be reduced or the display quality may be deteriorated.

(Film constituent materials)
In the optical film of the present invention by the melt casting method, the film constituent materials include cellulose esters, plasticizers and antioxidants constituting the film, and UV absorbers, matting agents and films as slipping agents as necessary. In order to control the strength and optical properties, the above fine particles may be added, or the above-mentioned retardation control agent may be added.

  The film constituting material is required to have little or no volatile component in the melting and film forming process. This is because foaming during heating and melting may cause defects inside the film and deterioration of the planarity of the film surface.

  The presence of the additive in the film constituting material is at least one of the materials constituting the film, such as the cellulose ester, plasticizer, antioxidant, and other ultraviolet absorbers, matting agents, retardation control agents, and the like that are added as necessary. It is excellent in terms of suppressing or preventing the generation of volatile components due to alteration or decomposition over the seeds. Further, the additive itself is required not to generate a volatile component in the melting temperature region of the film constituting material.

  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, preferably 0.2% by mass or less, more preferably 0.1% by mass or less. It is desirable to be. In the present invention, a heat loss from 30 ° C. to 350 ° C. is determined using a differential thermal mass measuring apparatus (TG / DTA200 manufactured by Seiko Electronics Industry Co., Ltd.), and the amount is defined as the content of volatile components.

(Stretching operation, refractive index control)
The optical film of the present invention can be controlled in refractive index by a stretching operation. As the stretching operation, the refractive index is controlled within a preferable range by stretching 1.0 to 2.0 times in one direction of the cellulose ester and 1.01 to 2.5 times in the direction perpendicular to the film plane. I can do it.

  For example, the film can be stretched sequentially or simultaneously in the longitudinal direction of the film and the direction perpendicular to the longitudinal direction of the film, that is, the width direction. At this time, if the stretching ratio in at least one direction is too small, a sufficient phase difference cannot be obtained, and if it is too large, stretching becomes difficult and breakage may occur.

  For example, when the film is stretched in the direction of melting and casting, if the contraction in the width direction is too large, the refractive index in the thickness direction of the film becomes too large. In this case, the width shrinkage of the film can be suppressed or improved by stretching in the width direction. When stretching in the width direction, the refractive index may be distributed with a width. This is sometimes seen when the tenter method is used, but it is a phenomenon that occurs when the film is stretched in the width direction, causing contraction force at the center of the film and the ends being fixed. It is thought to be called a phenomenon. Even in this case, by stretching in the casting direction, the bowing phenomenon can be suppressed, and the distribution of the width retardation can be reduced.

  Furthermore, the film thickness fluctuation | variation of the film obtained can be reduced by extending | stretching in the biaxial direction orthogonal to each other. If the variation in the film thickness of the optical film is too large, the retardation will be uneven, and unevenness such as coloring may be a problem when used in a liquid crystal display.

  The film thickness variation of the cellulose ester film support is preferably in the range of ± 3%, 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. preferable.

  When cellulose ester that obtains positive birefringence with respect to stress is used, the slow axis of the optical film can be provided in the width direction by stretching in the width direction. In this case, in the present invention, in order to improve display quality, the slow axis of the optical film is preferably in the width direction, and satisfies (stretch ratio in the width direction)> (stretch ratio in the casting direction). is required.

  There is no particular limitation on the method of stretching the web. For example, a method in which a difference in peripheral speed is applied to a plurality of rolls, and the roll peripheral speed difference is used to stretch in the longitudinal direction, the both ends of the web are fixed with clips and pins, and the interval between the clips and pins is increased in the traveling direction. And a method of stretching in the vertical direction, a method of stretching in the horizontal direction and stretching in the horizontal direction, a method of stretching in the vertical and horizontal directions and stretching in both the vertical and horizontal directions, and the like. Of course, these methods may be used in combination. In the case of the so-called tenter method, driving the clip portion by the linear drive method is preferable because smooth stretching can be performed and the risk of breakage and the like can be reduced.

  It is preferable to perform the width maintenance or the transverse stretching in the film forming process by a tenter, and it may be a pin tenter or a clip tenter.

  When the optical film of the present invention is used as a polarizing plate protective film, the thickness of the protective film is preferably 10 to 500 μm. In particular, it is preferably 20 μm or more, more preferably 35 μm or more. Further, it is preferably 150 μm or less, more preferably 120 μm or less. Most preferably, it is 25 or more and 90 micrometers. If the optical film is thicker than the above region, the polarizing plate after polarizing plate processing becomes too thick, so that it is not suitable for the purpose of thin and light in liquid crystal displays used for notebook personal computers and mobile electronic devices. On the other hand, if it is thinner than the above-mentioned region, it is not preferable because it becomes difficult to develop retardation, the moisture permeability of the film becomes high, and the ability to protect the polarizer from humidity decreases.

  The slow axis or the fast axis of the optical film of the present invention is present in the film plane, and θ1 is preferably −1 ° or more and + 1 ° or less, assuming that the angle formed with the film forming direction is θ1. More preferably, it is 5 ° or more and + 0.5 ° or less. This θ1 can be defined as an orientation angle, and θ1 can be measured using an automatic birefringence meter KOBRA-21ADH (Oji Scientific Instruments).

  Each of θ1 satisfying the above relationship can contribute to obtaining high luminance in a display image, suppressing or preventing light leakage, and contributing to obtaining faithful color reproduction in a color liquid crystal display device.

(Liquid crystal display device)
In a liquid crystal display device, a substrate containing liquid crystal is usually disposed between two polarizing plates. However, a polarizing plate protective film to which the optical film of the present invention is applied can provide excellent display properties regardless of the location. . In particular, since a clear hard coat layer, an antiglare layer, an antireflection layer, and the like are provided on the polarizing plate protective film on the display side outermost surface of the liquid crystal display device, it is particularly preferable to use the polarizing plate protective film for this portion.

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

<< Preparation of mixture of cellulose ester and additive >>
(Material used)
<Cellulose ester>
C-1. Cellulose triacetate C-2. Cellulose acetate propionate (acetyl substitution degree 1.9, propionyl group substitution degree 0.8, molecular weight Mn = 70000, molecular weight Mw = 220,000, Mw / Mn = 3)
C-3. Cellulose acetate propionate CAP482-20 (Eastman Chemical)
C-4. Cellulose acetate butyrate CAB171-15 (Eastman Chemical)
<Plasticizer>
P-1. Trimethylolpropane tribenzoate P-2. Triphenyl phosphate <Antioxidant>
A-1. IRGANOX-1010 (Ciba Specialty Chemicals)
<Ultraviolet absorber>
U-1. TINUVIN360 (Ciba Specialty Chemicals)
(Adjustment of cellulose ester / additive mixture)
Example 1
As an additive, 16 g of plasticizer P-1 was dissolved in 64 g of ethanol, and this was sprayed onto 60 g of cellulose ester C-1 with stirring using the apparatus of FIG. 1 and dried at 90 ° C. for 2 hours. This was mixed with 140 g of untreated cellulose ester C-1, dried in air at 120 ° C. for 3 hours, allowed to cool to room temperature, and the cellulose / additive mixture of Example 1 (hereinafter, cellulose ester mixture) was obtained. Obtained.

(Example 2)
In the same manner as in Example 1, 16 g of the plasticizer P-2 was dissolved in 48 g of ethyl acetate, sprayed onto 60 g of cellulose ester C-2 with stirring, and dried at 90 ° C. for 2 hours. This was mixed with 140 g of untreated cellulose ester C-2 and subjected to the same drying treatment as in Example 1 to obtain a cellulose ester mixture of Example 2.

(Example 3)
20 g of plasticizer P-1 was dissolved in 60 g of ethanol, and this was sprayed onto 140 g of cellulose ester C-3 with stirring and dried at 90 ° C. for 2 hours. This was mixed with 60 g of untreated cellulose ester C-3 and subjected to the same drying treatment as in Example 1 to obtain a cellulose ester mixture of Example 3.

Example 4
24 g of plasticizer P-1 was dissolved in 24 g of ethyl acetate, and this was sprayed onto 200 g of cellulose ester C-4 while stirring. This was dried in air at 120 ° C. for 4 hours and then allowed to cool to room temperature to obtain a cellulose ester mixture of Example 4.

(Example 5)
30 g of plasticizer P-2 and 4 g of antioxidant A-1 were dissolved in 30 g of dichloromethane, and this was sprayed onto 200 g of cellulose ester C-2 with stirring. This was subjected to the same drying treatment as in Example 4 to obtain a cellulose ester mixture of Example 5.

(Example 6)
24 g of the plasticizer P-2, 2 g of the antioxidant A-1 and 2 g of the ultraviolet absorber U-12 were dissolved in 24 g of dichloromethane, and this was sprayed onto 200 g of cellulose ester C-2 while stirring. This was dried in air at 110 ° C. for 4 hours and then allowed to cool to room temperature to obtain a cellulose ester mixture of Example 6.

(Comparative Example 1)
16 g of plasticizer P-1 was directly added to 200 g of cellulose ester C-1 and mixed with stirring. Subsequently, after drying at 110 degreeC for 4 hours, it stood to cool to room temperature and the cellulose-ester mixture of the comparative example 1 was obtained.

(Comparative Example 2)
In Comparative Example 1, the same operation was performed except that the cellulose ester was changed to 200 g of C-2 and the plasticizer was changed to 16 g of P-2, so that a cellulose ester mixture of Comparative Example 2 was obtained.

(Comparative Example 3)
In Comparative Example 1, the same procedure was performed except that the cellulose ester was changed to 200 g of C-2, the additive was changed to 20 g of the plasticizer P-1 and the antioxidant A-12, and the cellulose ester mixture of Comparative Example 3 was obtained. Obtained.

(Celous ester melt extrusion)
The cellulose ester mixtures of Examples 1 to 6 and Comparative Examples 1 to 3 were melted by heating to the melting temperatures shown in Table 1 using a melt extruder, and then melt extruded from a T die. Then, cellulose ester films (50 cm × 50 cm × 98 μm) of Examples 1 to 6 and Comparative Examples 1 to 3 were produced.

  The moisture content and residual solvent of the film obtained as described above were measured as follows and are listed in Table 1.

  Moisture content (%): Performed by a conventional method using a moisture measuring device CA-06 and VA-06 (both manufactured by Mitsubishi Chemical Corporation).

  Residual solvent (%): The residual solvent amount was dried at 150 ° C. under reduced pressure, the sum of the solvent and the water content was measured, and calculated from the water content.

<Evaluation>
The following evaluation was performed using the obtained cellulose ester film.

(Bright spot foreign matter)
Two polarizing plates are arranged in an orthogonal state (crossed Nicols) to block the transmitted light, and the prepared sample is placed between the two polarizing plates. The polarizing plate used was a glass protective plate. Light was irradiated from one side, and the number of bright spots having a diameter of 0.01 mm or more per 1 cm ² was counted with an optical microscope (50 times) from the opposite side. In the evaluation, the number of bright spots was 0 to 30, 、 ３, 31 to 50 were ◯, 51 to 80 were △, 81 to 100 were x, and 101 or more were xx.

(Retardation)
Using an automatic birefringence meter KOBRA-21ADH (manufactured by Oji Scientific Instruments), the prepared sample was measured at a wavelength of 590 nm in a 23 ° C. and 55% RH environment to measure the refractive index. Nx and Ny were obtained. In-plane retardation value Ro was calculated according to the following formula (1).

Formula (1) R0 value = (Nx−Ny) × d
In the formula, Nx represents the refractive index of the film in a direction parallel to the film forming direction, Ny represents the refractive index of the film in the direction perpendicular to the film forming direction, and d represents the thickness (nm) of the film.

  The measurement was performed at 10 points in the width direction orthogonal to the film forming direction, and the retardation fluctuation rate shown below was used as an index from the average and standard deviation. In the evaluation, the variation rate was 0 to 2%, ◎, 2 to 5% ◯, 5 to 8% Δ, 8 to 10% x, and 10% or more xx.

Retardation change rate = standard deviation / retardation average value The above evaluation results are shown in Table 1 below.

  From the above table, Comparative Examples 1 to 3 in which the production method or additive particle size is outside the present invention are unsatisfactory in both bright spot foreign matter and retardation variation, but Examples 1 to 6 of the present invention are bright spots. It is clear that both foreign matter and retardation fluctuation are excellent.

<Production of polarizing plate>
Using the films prepared in Example 5 and Example 6, a hard coat layer and an antireflection layer were formed on one surface thereof to prepare an antireflection film with a hard coat. A polarizing plate was produced using this.

<Hard coat layer>
The following hard coat layer composition was applied to a dry film thickness of 3.5 μm and dried at 80 ° C. for 1 minute. Next, it was cured under a condition of 150 mJ / cm ^{2 with} a high-pressure mercury lamp (80 W) to produce a hard coat film having a hard coat layer. The refractive index of the hard coat layer was 1.50.

<Hard coat layer composition (C-1)>
Dipentaerythritol hexaacrylate monomer 108 parts by weight Dipentaerythritol hexaacrylate dimer 36 parts by weight Dipentaerythritol hexaacrylate trimer or higher component 36 parts by weight Irgacure 184 (manufactured by Ciba Specialty Chemicals) 2 parts by weight Propylene glycol monomethyl ether 180 parts by mass Ethyl acetate 120 parts by mass <Medium refractive index layer>
On the hard coat layer of the hard coat film, the following medium refractive index layer composition was applied by an extrusion coater and dried for 1 minute at 80 ° C. and 0.1 m / second. At this time, a non-contact floater was used until completion of touch drying (a state where the coated surface was touched with a finger and felt dry). As the non-contact floater, a horizontal floater type air tumbler manufactured by Belmatik was used. The static pressure in the floater was set to 9.8 kPa, and the floater was lifted uniformly in the width direction of about 2 mm and conveyed. After drying, a medium refractive index layer film having a medium refractive index layer was produced by curing by irradiating ultraviolet rays with 130 mJ / cm ² using a high pressure mercury lamp (80 W). The medium refractive index layer had a thickness of 84 nm and a refractive index of 1.66.

<Medium refractive index layer composition>
ELCOM V-2504 (manufactured by Catalyst Kasei Kogyo Co., Ltd., ITO sol, solid content 20%)
100g
Dipentaerythritol hexaacrylate 6.4g
Irgacure 184 (Ciba Specialty Chemicals Co., Ltd.) 1.6g
Tetrabutoxy titanium 4.0g
10% FZ-2207 (Nihon Unicar Co., Ltd., propylene glycol monomethyl ether solution) 3.0 g
Isopropyl alcohol 530g
90g of methyl ethyl ketone
265 g of propylene glycol monomethyl ether
<High refractive index layer>
On the medium refractive index layer, the following high refractive index layer composition was applied by an extrusion coater and dried for 1 minute at 80 ° C. and 0.1 m / second. At this time, a non-contact floater was used until completion of touch drying (a state where the coated surface was touched with a finger and felt dry). The non-contact floater was under the same conditions as the formation of the middle refractive index layer. After drying, ultraviolet rays were irradiated by 130 mJ / cm ² using a high pressure mercury lamp (80 W) and cured to produce a high refractive index layer film having a high refractive index layer.

<High refractive index layer composition>
95 parts by mass of tetra (n) butoxytitanium dimethylpolysiloxane (KF-96-1000CS manufactured by Shin-Etsu Chemical Co., Ltd.) 1 part by mass of γ-methacryloxypropyltrimethoxysilane (KBM503 manufactured by Shin-Etsu Chemical Co., Ltd.)
5 parts by mass Propylene glycol monomethyl ether 1750 parts by mass Isopropyl alcohol 3450 parts by mass Methyl ethyl ketone 600 parts by mass The thickness of the high refractive index layer of this high refractive index layer film was 50 μm and the refractive index was 1.82.

<Low refractive index layer>
First, silica-based fine particles (cavity particles) were prepared.

(Preparation of silica-based fine particles P-1)
A mixture of 100 g of silica sol having an average particle diameter of 5 nm and a SiO ₂ concentration of 20% by mass and 1900 g of pure water was heated to 80 ° C. The pH of this reaction mother liquor was 10.5, and 9000 g of 0.98 mass% sodium silicate aqueous solution as SiO ₂ and 9000 g of 1.02 mass% sodium aluminate aqueous solution as Al ₂ O ₃ were simultaneously added to the mother liquor. did. Meanwhile, the temperature of the reaction solution was kept at 80 ° C. The pH of the reaction solution rose to 12.5 immediately after the addition, and hardly changed thereafter. After completion of the addition, the reaction solution was cooled to room temperature and washed with an ultrafiltration membrane to prepare a SiO ₂ .Al ₂ O ₃ core particle dispersion having a solid content concentration of 20% by mass. (Process (a))
1700 g of pure water is added to 500 g of this core particle dispersion and heated to 98 ° C., and while maintaining this temperature, a silicic acid solution (SiO ₂₎ obtained by dealkalizing a sodium silicate aqueous solution with a cation exchange resin. A dispersion of core particles in which 3000 g (concentration of 3.5% by mass) was added to form a first silica coating layer was obtained. (Process (b))
Next, 1125 g of pure water is added to 500 g of the core particle dispersion liquid that has been washed with an ultrafiltration membrane to form a first silica coating layer having a solid content concentration of 13% by mass, and concentrated hydrochloric acid (35.5%) is further added dropwise. The pH was adjusted to 1.0 and dealumination was performed. Next, the aluminum salt dissolved in the ultrafiltration membrane was separated while adding 10 L of hydrochloric acid aqueous solution of pH 3 and 5 L of pure water, and SiO ₂ · Al from which some of the constituent components of the core particles forming the first silica coating layer were removed. A dispersion of ₂ O ₃ porous particles was prepared (step (c)). A mixture of 1500 g of the above porous particle dispersion, 500 g of pure water, 1,750 g of ethanol, and 626 g of 28% ammonia water is heated to 35 ° C., and then 104 g of ethyl silicate (SiO ₂ 28 mass%) is added. The surface of the porous particles on which the first silica coating layer was formed was coated with a hydrolyzed polycondensate of ethyl silicate to form a second silica coating layer. Next, a dispersion of silica-based fine particles having a solid content concentration of 20% by mass was prepared by replacing the solvent with ethanol using an ultrafiltration membrane.

Table 2 shows the thickness, average particle diameter, MOx / SiO ₂ (molar ratio), and refractive index of the first silica coating layer of the silica-based fine particles. Here, the average particle diameter was measured by a dynamic light scattering method, and the refractive index was measured by the following method using Series A, AA made by CARGILL as a standard refractive liquid.

<Measuring method of particle refractive index>
(1) The particle dispersion is taken in an evaporator and the dispersion medium is evaporated.

  (2) This is dried at 120 ° C. to obtain a powder.

  (3) A standard refraction liquid having a known refractive index is dropped on a glass plate of a few drops, and the above powder is mixed therewith.

  (4) The operation of (3) above is performed with various standard refractive liquids, and the refractive index of the standard refractive liquid when the mixed liquid becomes transparent is taken as the refractive index of the colloidal particles.

(Formation of a low refractive index layer)
Si (OC ₂ H _{5) 4} to _{95mol%, C 3 F 7 -} (OC 3 F 6) 24 -O- (CF 2) 2 -C 2 H 4 -O-CH 2 Si (OCH 3) 3 to 5mol A low-refractive-index coating agent obtained by adding 35% by mass of the silica-based fine particles P-1 having an average particle diameter of 60 nm to a matrix mixed at%, using 1.0N-HCl as a catalyst, and further diluted with a solvent. Produced. A coating solution is applied at a film thickness of 100 nm on the actinic radiation curable resin layer or the high refractive index layer by using a die coater method, dried at 120 ° C. for 1 minute, and then irradiated with ultraviolet rays to have a refractive index of 1.37. The low refractive index layer was formed.

  An antireflection film was produced as described above.

  Next, a 120 μm thick polyvinyl alcohol film was uniaxially stretched (temperature: 110 ° C., stretch ratio: 5 times). This was immersed in an aqueous solution composed of 0.075 g of iodine, 5 g of potassium iodide, and 100 g of water for 60 seconds, and then immersed in an aqueous solution of 68 ° C. composed of 6 g of potassium iodide, 7.5 g of boric acid, and 100 g of water. This was washed with water and dried to obtain a polarizing film.

  Subsequently, according to the following processes 1-5, the polarizing film, the said antireflection film, and the cellulose ester film of the back side were bonded together, and the polarizing plate was produced. As the polarizing plate protective film on the back side, Konica Minolta Tack KC8UX (manufactured by Konica Minolta Opto Co., Ltd.), which is a commercially available cellulose ester film, was used as a polarizing plate.

  Step 1: The optical film was immersed in a 2 mol / L sodium hydroxide solution at 60 ° C. for 90 seconds, then washed with water and dried to saponify the side to be bonded to the polarizer.

  Step 2: The polarizing film was immersed in a polyvinyl alcohol adhesive tank having a solid content of 2% by mass for 1 to 2 seconds.

  Step 3: Excess adhesive adhered to the polarizing film in Step 2 was gently wiped, and this was placed on the optical film treated in Step 1 and laminated.

Step 4: The antireflection film sample, the polarizing film, and the cellulose ester film laminated in Step 3 were bonded at a pressure of 20 to 30 N / cm ² and a conveyance speed of about 2 m / min.

  Process 5: The sample which bonded the polarizing film produced in the process 4, the cellulose-ester film, and the optical film in the 80 degreeC dryer was dried for 2 minutes, and the polarizing plate was produced.

<Production of liquid crystal display device>
A liquid crystal panel for viewing angle measurement was produced as follows, and the characteristics as a liquid crystal display device were evaluated.

  The polarizing plates on both sides of the Fujitsu 15-type display VL-150SD that had been bonded in advance were peeled off, and the prepared polarizing plates were bonded to the glass surfaces of the liquid crystal cells.

  At that time, the direction of bonding of the polarizing plate is performed so that the surface of the optical film is on the liquid crystal cell side and the absorption axis is directed in the same direction as the polarizing plate previously bonded. Each of the liquid crystal display devices was produced.

  The obtained polarizing plate had good bright spot foreign matter, and the liquid crystal display device using the polarizing plate had excellent visibility because the bright spot foreign matter and retardation had little fluctuation.

  Furthermore, the polarizing plate and liquid crystal display device using the cellulose ester film of Example 6 containing an ultraviolet absorber were excellent in temporal stability such as ultraviolet resistance.

It is the schematic of the spraying and drying apparatus of the additive which concerns on this invention.

Explanation of symbols

1 Hopper 2 Motor 3 Screw conveyor 4 Spraying device 5 Drying device 6 Discharge port

Claims (8)

In a cellulose ester film obtained by melt-extruding a mixture comprising a cellulose ester and at least one additive, at least a part of the cellulose ester is brought into contact with a solution in which the additive is dissolved or finely dispersed. And then dried. A cellulose ester film characterized by being dried. The cellulose ester contains at least one selected from cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate phthalate, and cellulose phthalate. The cellulose ester film according to 1. The additive is at least selected from a plasticizer, an antioxidant, an acid scavenger, a light stabilizer, a peroxide decomposer, a radical scavenger, a metal deactivator, an ultraviolet absorber, a matting agent, a dye, and a pigment. It is 1 type, The cellulose-ester film of Claim 1 or 2 characterized by the above-mentioned. The cellulose ester film according to claim 1, wherein the cellulose ester film is an optical film. 5. At least one layer selected from an antistatic layer, a hard coat layer, an antireflection layer, an easy adhesion layer, an antiglare layer and an optical compensation layer is provided on at least one surface of the optical film. The cellulose ester film as described. A polarizing plate using the cellulose ester film according to claim 1 on at least one surface. A liquid crystal display device using the cellulose ester film according to claim 1 or the polarizing plate according to claim 6. In a method for producing a cellulose ester film in which a mixture comprising a cellulose ester and at least one additive is melt-extruded, at least one liquid selected from liquids obtained by dissolving or finely dispersing the additive is added to the cellulose. A method for producing a cellulose ester film, wherein at least a part of an ester is contacted and then dried and melt-extruded at a melting temperature of 150 ° C to 250 ° C.

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