JP2009179732A - Method for producing cellulose ester film, cellulose ester film, polarizing plate, and liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing cellulose ester films which have reduced internal haze while maintaining good slippage (creaking value) in a roll film state and which achieve haze uniformity in their rolls and an improvement in crossed Nicol transmittance when used as polarizing plate protective films. <P>SOLUTION: The method for producing cellulose ester films produces the films by heating and melting pellets of a resin composition containing a cellulose ester resin by an extruder and casting it from its die. In the method, pellets of the resin composition contains particles with a primary particle size of 0.2-10 μm, and the temperature of the resin composition at the outlet of the die part is higher by 10-60°C than that of the resin composition during heating and melting. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing a cellulose ester film, a cellulose ester film, a polarizing plate, and a liquid crystal display device. More specifically, while maintaining good slipperiness (squeaking value) in a roll film state, the internal haze is reduced and polarized light is obtained. The present invention relates to a method for producing a cellulose ester film capable of improving the crossed Nicols transmittance when used as a plate protective film.

  The optical film is a protective film for polarizing plates of liquid crystal displays, and a retardation film with an optical compensation function, and further provided with an antireflection layer, an antiglare layer, and a hard coat layer, and is the outermost surface of a liquid crystal display, plasma display, etc. Is used.

  The optical film has various properties such as high transparency, flatness, moisture permeation prevention, bleed-out resistance, dimensional stability (does not vary with temperature and humidity and time), and adhesion to the PVA polarizing film used for the polarizing plate. Performance is required. The cellulose ester film for optics is used as a polarizing plate protective film from the viewpoint of adhesion with a PVA polarizing film used for a polarizing plate and appropriate moisture permeation prevention property, but the cellulose ester film is generally halogenated. It is manufactured by a solution casting film forming method using an organic solvent. However, the use of halogen-based organic solvents is being restricted from the environmental and safety aspects.

  For this reason, the manufacturing method of the cellulose-ester film which does not use an organic solvent is calculated | required, and the melt-casting method is proposed (for example, refer patent document 1, 2). The melt casting method is a method in which a cellulose ester resin is extruded while being melted to form a film. However, since the melt casting method is a method of casting a composition having a high viscosity as compared with the solution casting method, it is inferior in uniform dispersibility of inorganic fine particles, and a large amount in order to satisfy slipperiness (squeaking value). When it is contained, the haze increases, and there arises a problem that transparency that is originally required as an optical film is impaired. Therefore, it has become necessary to newly develop a slip agent formulation that ensures sufficient slipperiness (squeeze value) and has reduced haze even in the melt casting method having a heat melting / kneading dispersion function.

Further, when the haze inside the support is increased, the crossed Nicol transmittance when used as a polarizing plate protective film is also lowered, and an optical film excellent in sufficient overall performance of slipperiness and transparency is demanded.
JP 2000-352620 A JP 2005-178194 A

  Therefore, the object of the present invention is to reduce the internal haze while maintaining good sliding property (squeaking value) in the roll film state, to improve the crossed Nicol transmittance when used as a polarizing plate protective film, and to increase the haze in the roll. A method for producing a cellulose ester film that achieves the above uniformity is provided.

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

  1. In a method for producing a cellulose ester film in which pellets of a resin composition containing a cellulose ester resin are melted by heating with an extruder and cast from a die, the pellets of the resin composition have a primary particle size of 0.2. A method for producing a cellulose ester film, comprising particles having a diameter of 10 μm to 10 μm, wherein the resin composition temperature at the outlet of the die part is 10-60 ° C. higher than the resin composition temperature at the time of heating and melting .

  2. The pellet of the resin composition containing the particles and the pellet of the resin composition not containing the particles are mixed in a volume ratio of 0.05: 1 to 2: 1 before being charged into the extruder. 2. The method for producing a cellulose ester film as described in 1 above.

  3. 2. The method according to 2 above, wherein the cellulose ester film is stretched in the range of 1.01 to 2.00 times in the transport direction and 1.01 to 2.00 times in the width direction after casting and film formation. The manufacturing method of the cellulose-ester film of description.

  4). 4. The method for producing a cellulose ester film as described in 3 above, wherein the cellulose ester film is cast from a die in a draw ratio of 5 to 30 to form a film.

  5). A cellulose ester film produced by the method for producing a cellulose ester film according to any one of 1 to 4 above.

  6). 6. A polarizing plate comprising the cellulose ester film described in 5 above on at least one surface.

  7. 7. A liquid crystal display device comprising the polarizing plate according to 6 on at least one surface of a liquid crystal cell.

  According to the present invention, while maintaining good slipperiness (squeaking value) in the roll film state, the internal haze is reduced, the cross Nicol transmittance is improved when used as a polarizing plate protective film, the haze in the roll The manufacturing method of the cellulose-ester film which achieved the uniformity can be provided. Moreover, the cellulose-ester film manufactured by the manufacturing method of this cellulose-ester film can implement | achieve the outstanding handleability and visibility, applying to a polarizing plate and a liquid crystal display device.

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

  The method for producing a cellulose ester film of the present invention is the method for producing a cellulose ester film in which a pellet of a resin composition containing a cellulose ester resin is heated and melted by an extruder and cast from a die to form a film. The pellet of the product contains particles having a primary particle diameter of 0.2 to 10 μm, and the resin composition temperature at the outlet of the die part is 10 to 60 ° C. higher than the resin composition temperature at the time of melting by heating. It is characterized by that.

  As a result of analysis by paying attention to the dispersed particle size of inorganic particles used as a slip agent, the present inventors have found that the dispersed particle size and dispersion of the slip agent in the cellulose ester film obtained in the solution casting method and the melt casting method. We found that the distribution was different. Therefore, when selecting particles having a particle size that can be a dispersion particle size and a dispersion distribution similar to the cellulose ester film obtained by the solution casting method, which has a proven record in slipperiness, and when casting with a die By adjusting the temperature, it has been found that the dispersity of the slip agent can be further improved and the internal haze can be reduced while keeping the slipperiness (squeaking value) well, and the present invention has been achieved.

  That is, particles having a specific particle size range larger than the primary particle size of a slip agent conventionally used in the solution casting method are used. Preferably, a master pellet is prepared in advance as a slip agent, and then mixed with a base pellet to melt. By casting and stretching, it became possible to obtain a cellulose ester film having excellent transparency and ensuring good slipperiness.

  The internal haze of the cellulose ester film of the present invention can be determined according to the following measurement method, and the internal haze value is preferably 0.40 or less, and more preferably 0.30 or less.

(Internal haze)
A few drops of silicone oil are added to the front and back of the film, and two glass plates with a thickness of 1 mm (micro slide glass product number S9111, manufactured by MATSANAMI) are sandwiched from the front and back to obtain two glass plates completely. The obtained film was optically adhered, the haze was measured according to JIS-K7136 with the surface haze removed, and only the silicone oil was sandwiched between two separately measured glass plates to subtract the measured haze. The calculated value is calculated as the internal haze of the film.

  The crossed Nicol transmittance of the cellulose ester film of the present invention can be determined according to the following measurement method, preferably 65% or less, and more preferably 60% or less.

(Cross Nicol transmittance)
Two polarizing plates were arranged in crossed Nicols, and transmittance (T1) at 590 nm was measured using a spectrophotometer U3100 manufactured by Hitachi, Ltd. Furthermore, the evaluation sample was placed between polarizing plates, and the transmittance (T2) at 590 nm was measured. Using the measured T1 and T2, the crossed Nicols transmittance is obtained by the following formula.

Cross Nicol transmittance (%) = T2-T1
Further, the slipperiness (squeaking value) in the present invention can be expressed by the following dynamic friction coefficient.

(Dynamic friction coefficient)
The dynamic friction coefficient between the film surface and the back surface is cut out so that the front and back surfaces of the film are in contact with each other according to JIS-K-7125 (1987), a 200 g weight is placed, the sample moving speed is 100 mm / min, and the contact area is 80 mm × 200 mm. The weight is pulled horizontally under the conditions described above, the average load (F) while the weight is moving is measured, and the dynamic friction coefficient (μ) is obtained from the following equation. The smaller the dynamic friction coefficient, the less “squeaking” occurs. The squeak value is preferably 0.80 or less, more preferably 0.50 to 0.65.

Coefficient of dynamic friction (μ) = F (g) / Weight of weight (g)
The cellulose ester film of the present invention is a functional film used for various display devices such as a liquid crystal display (liquid crystal display device), a plasma display, an organic EL display, a field emission display, and an electronic paper display. Protective film, retardation plate, reflector, viewing angle widening film, optical compensation film, antiglare film, antireflection film, brightness enhancement film, color correction filter, color separation film, ultraviolet or infrared cut film, antistatic film or conductive film Applicable to adhesive film.

  In particular, the cellulose ester film of the present invention is suitable for a protective film for polarizing plate, a viewing angle widening film, an optical compensation film, an antiglare film, and an antireflection film.

  Further, the melt casting method in the present invention is to melt the cellulose ester resin composition by heating to a temperature showing fluidity without using any solvent, and then casting the fluid resin composition. It is defined as the casting method.

<Particles: slip agent>
The cellulose ester film of the present invention (hereinafter also simply referred to as film) uses particles having a primary particle size of 0.2 to 10 μm (slip agent 1) as a slip agent.

  Examples of the particles include inorganic compound particles and organic compound particles. Examples of the particles include inorganic particles such as silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, kaolin, talc, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, and calcium phosphate. , Polymethacrylic acid methyl acrylate resin powder, acrylic styrene resin powder, polymethyl methacrylate resin powder, silicon resin powder, polystyrene resin powder, polycarbonate resin powder, benzoguanamine resin powder, melamine resin powder, polyolefin resin powder Organic particles such as polyester resin powder, polyamide resin powder, polyimide resin powder, and polyfluorinated ethylene resin powder can be exemplified, but not limited thereto.

  Among these, silicon dioxide is preferable because it can reduce the haze of the film. In many cases, particles such as silicon dioxide are surface-treated with an organic substance, but such particles are preferable because they can reduce the haze of the film. Preferred organic substances for the surface treatment include halosilanes, alkoxysilanes, silazane, siloxane and the like.

(Primary particle size)
The primary particle size of the slip agent 1 used in the present invention is 0.2 to 10 μm. If the primary particle size of the slip agent 1 is less than 0.2 μm, good slipperiness may not be ensured due to the amount added, and if it exceeds 10 μm, haze (turbidity) increases and transparency is increased. May fall. When the primary particle size is within this range, the particles are less likely to aggregate, and the primary particle size and the secondary particle size are almost equal, making it easy to control the degree of dispersion of the particles in the film.

  The primary particle size or the secondary particle size of the particles is observed with a transmission electron microscope, and is represented by a diameter assuming a circle equal to the projected area. For example, in the case of the primary particle size of silica particles, a sample prepared by ultra-thin section method is used to observe a sample using a transmission electron microscope (H-7100FA type, manufactured by Hitachi), and the primary particle size of silica particles is data. It means the average primary particle size determined by the number N = 1000.

  Furthermore, it is preferable that 95% by number or more of the particles in the cellulose ester film fall within the range of the dispersed particle diameter of 0.1 to 1.5 μm.

  The slip agent 1 having a primary particle size in the above range can further improve the dispersibility of the particles by further adjusting the temperature at the time of casting with a die and lowering the viscosity of the heat-melted resin composition, It is considered that by selecting the addition amount appropriately, it is possible to ensure good transparency and slipperiness without increasing haze (turbidity).

  Examples of the slip agent 1 having such a particle size include Sea Hoster KE-P30, 100, 150 manufactured by Nippon Shokubai Co., Ltd.

(Addition amount)
The content of the slip agent 1 in the cellulose ester resin is preferably 0.005 to 5 mass% with respect to the cellulose ester resin. Within the above range, good slipperiness and good transparency can be secured, which is preferable.

  The method of adding the slip agent 1 is that the volume ratio of the resin composition pellets containing particles and the resin composition pellets containing no particles is in the range of 0.05: 1 to 2: 1 before being charged into the extruder. It is preferable to mix with.

  That is, in the present invention, after the slip agent is prepared in advance with master pellets (MP), the master pellets (MP) and the base pellets (BP) are mixed before being put into the extruder, heated and melted and cast, It is preferable to do. In the present invention, the mixing time of the master pellet (MP) and the base pellet (BP) is increased and the dispersibility of the particles in the resin composition is improved. Is preferred.

  Here, the master pellet (MP) is a pellet with a large amount of addition of a slip agent, and the base pellet (BP) is a pellet without the addition of a slip agent. First, a high-concentration pellet is produced by the master pellet method, and then a method of blending an appropriate amount of the base pellet (BP) without addition of a slip agent to a desired concentration obtains a film having a uniform slip agent concentration. It is effective for. For the purpose, MP is preferably produced by a twin-screw extruder, a three-roll, etc. that are excellent in melt mixing / dispersibility. The addition concentration of the target dispersion (in the case of the present invention, particles as a slipping agent) at the time of producing the MP is 5 to 21 times the target addition amount (addition amount to the film as the final target product). preferable. If the amount is less than 5 times, the concentration uniformity of the particles in the MP may be insufficient, and the mixing ratio with BP exceeds the range of 2: 1, so a large amount of MP must be prepared. Inferior in productivity. When the amount exceeds 21 times, for example, when the amount is 40 times, the mixing ratio of MP and BP is less than 0.05: 1, the ratio of MP is small, and the concentration of particles in the film that is the final target product Uniformity may be insufficient.

  In the MB, since some of the particles are very high in volume, when adding more than 21 times the amount, dispersibility becomes insufficient in the premixed stirring with the cellulose ester resin powder and other additives, In addition to not being able to produce a uniform MP, the powder transportability deteriorates. In particular, when manufacturing with a twin-screw extruder, there is a risk that the transport failure in the hopper, clogging at the input port, etc. will cause the productivity to deteriorate significantly. There is.

  Further, in the case of a cellulose ester film obtained by the melt-flow method, better slipperiness is ensured by performing stretching described later. This is presumably because, in the case of the melt casting method, unlike the solution casting method, there is almost no volume reduction in the solvent removal step, and the surface protrusion amount of the slip agent is relatively small. Therefore, the cellulose ester film obtained by the melt-flow method is stretched to reduce the film thickness (reducing the volume per unit area), and the slipping agent present inside is projected onto the film surface, which is better It is thought that slipperiness is secured.

  In the present invention, it is also preferable to use particles smaller than the primary particle diameter of the slip agent 1 as the slip agent 2 in combination. The primary particle size of the particles used in the slip agent 2 is preferably 10 to 200 nm. Preferably, it is 30-100 nm. The slip agent 2 tends to aggregate to a secondary particle size 3 to 20 times the primary particle size, and if the primary particle size is in the range of 10 to 200 nm, good slipperiness and transparency are ensured, which is preferable. . It is preferable that the addition amount is appropriately adjusted in the range of 0.05 to 10% by mass.

  Examples of the slip agent 2 include Aerosil NAX50, OX50, NY50, NA50H, NA50Y, RY50, and RX50 manufactured by Nippon Aerosil Co., preferably Aerosil NAX50 and OX50.

<Cellulose ester resin>
The cellulose ester film of the present invention uses a cellulose ester resin as a main component.

  The cellulose ester resin preferably has the structure of cellulose ester, and is preferably the above-mentioned single or mixed acid ester of cellulose containing at least one of fatty acid acyl group and 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, further 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 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 of 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, 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 number of carbon atoms of the carbonamide group is preferably 1-20, and more preferably 1-12. 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 number of carbon atoms in the ureido group is preferably 1-20, and more preferably 1-12. 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 in 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 of 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 in the acyloxy group is preferably 1-20, and more preferably 2-12. Examples of the acyloxy group include acetoxy and benzoyloxy.

  The alkenyl group has preferably 2 to 20 carbon atoms, and more preferably 2 to 12 carbon atoms. Examples of alkenyl groups include vinyl, allyl and isopropenyl. The number of carbon atoms in the alkynyl group is preferably 2-20, and more preferably 2-12. 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 number of carbon atoms of the arylsulfonyl group is preferably 6-20, and more preferably 6-12. The alkyloxysulfonyl group preferably has 1 to 20 carbon atoms, 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 in 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 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, isobutyryl, valeryl. , Pivaloyl, hexanoyl, octanoyl, lauroyl, stearoyl and the like.

  In the present invention, the aliphatic acyl group is meant to include those having a substituent, and the substituent is a substitution of a benzene ring when the aromatic ring is a benzene ring in the above-mentioned aromatic acyl group. What was illustrated as a group is mentioned.

  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.).

  As the cellulose ester structure used in the present invention, 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. These may be used alone or as a mixed acid ester of cellulose, or a mixture of two or more cellulose esters.

  In the cellulose ester constituting the cellulose ester film of the present invention, 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 that

  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 preferable 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 the propionyl group or butyryl group is Y, it is preferably a cellulose resin containing a cellulose ester that simultaneously satisfies the following formulas (I) and (II).

Formula (I) 2.5 ≦ X + Y ≦ 3.0
Formula (II) 0 ≦ X ≦ 2.0
Of these, cellulose acetate propionate is particularly preferably used, among which 0 ≦ X ≦ 2.0 and 0.7 ≦ Y ≦ 2.8. The part not substituted with the acyl group is usually present as a hydroxyl group. These can be synthesized by known methods. These acyl group substitution degrees can be measured according to the method prescribed in ASTM-D817-96.

  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 weight average molecular weight Mw and the number average molecular weight Mn can be measured by the following methods.

  The measurement conditions are as follows.

Solvent: Tetohydrofuran Equipment: HLC-8220 (manufactured by Tosoh Corporation)
Column: TSKgel SuperHM-M (manufactured by Tosoh Corporation)
Column temperature: 40 ° C
Sample concentration: 0.1% by mass
Injection volume: 10 μl
Flow rate: 0.6 ml / min
Calibration curve: Standard polystyrene: PS-1 (manufactured by Polymer Laboratories) Mw = 2, 560,000 to 580, a calibration curve with 9 samples was used.

  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.

  The cellulose ester resin according to the present invention was charged with 1 g in 20 ml of pure water (electric conductivity 0.1 μS / cm or less, pH 6.8), and had a pH of 6 when stirred in a nitrogen atmosphere at 25 ° C. for 1 hr. It is preferable that the electric conductivity is 1 to 100 μS / cm. If the pH is less than 6, the residual organic acid may accelerate cellulose degradation during heating and melting, and if the pH is higher than 7, hydrolysis may accelerate. In addition, when the electrical conductivity is 100 μS / cm or more, since a relatively large amount of residual ions are present, it is considered to be a factor for degrading cellulose during heating and melting.

  The cellulose acetate propionate preferably used in the present invention is synthesized, for example, by the following method.

  60 kg of acetic acid and 20 kg of propionic acid were added to 30 kg of cellulose (manufactured by Nippon Paper Industries Co., Ltd.) and stirred at 54 ° C. for 30 minutes. After the mixture was cooled, esterification was performed by adding 50 kg of acetic anhydride, 50 kg of propionic anhydride and 1.2 kg of sulfuric acid cooled in an ice bath. Stirring was performed for 150 minutes while adjusting the esterification so as not to exceed 40 ° C. After completion of the reaction, a mixture of 30 kg of acetic acid and 10 kg of water was added dropwise over 20 minutes to hydrolyze excess anhydride. While maintaining the temperature of the reaction solution at 40 ° C., 90 kg of acetic acid and 30 kg of water were added and stirred for 1 hour. The mixture was poured into an aqueous solution containing 2 kg of magnesium acetate, stirred for a while and then filtered and dried. Cellulose acetate propionate (acetyl group substitution degree 2.45, propionyl group substitution degree 0.43, acyl group total substitution degree 2 .88, acyl group total carbon number 6.20, weight average molecular weight 211000).

  The cellulose acetate propionate dissolved in acetic acid is preferably filtered before the step of reprecipitation by increasing the pH by adding water or the like to remove foreign matters (insoluble matter in the acetic acid solution). If this foreign matter is not sufficiently removed, it may remain as a foreign matter in the film during subsequent melt film formation.

  The obtained cellulose acetate propionate is preferably washed with water, alcohol, etc., and the residual acid component is preferably removed to less than 100 ppm and the low molecular weight substance (molecular weight of 10,000 or less) is removed to less than 5% by mass. When there are many residual acid components and low molecular weight substances, there is a risk that deterioration, coloring, and the like become significant.

  Other preferred cellulose esters, cellulose acetate, cellulose propionate, cellulose butyrate and cellulose acetate butyrate use acetic acid, propionic acid or butyric acid as fatty acid, acetic anhydride, propionic anhydride or anhydrous n as anhydrous fatty acid. -Can be synthesized in the same manner using butyric acid.

<Additive>
The cellulose ester film of the present invention may contain additives such as a plasticizer, an antioxidant, an acid scavenger, a light stabilizer, an ultraviolet absorber, a retardation controller, and a polymer material in addition to the cellulose ester resin. preferable.

  The additives may be mixed by adding the cellulose ester resin fine powder and the additive, respectively, or by adding all the additives in advance by melt mixing and integration, and then adding the cellulose ester resin fine powder. In addition, the cellulose ester resin fine powder and the additive may be tableted or pelletized. The tablet refers to a molded product in which the cellulose ester resin does not melt but the additive is obtained by dispersing and mixing the cellulose ester resin fine powder and the additive at a melting temperature. Pellet refers to a molded product that is melt-mixed and integrated at a temperature at which the cellulose ester resin and the additive melt.

(Plasticizer)
Adding a compound known as a plasticizer to the cellulose ester film of the present invention is not only to obtain the effects of the present invention, but also to improve mechanical properties, impart flexibility, impart water resistance, reduce moisture permeability, etc. This is preferable from the viewpoint of film modification. Further, in the melt casting method carried out in the present invention, the plasticity is higher than that of cellulose ester for the purpose of lowering the melting temperature of the film constituting material by adding a plasticizer, or at the same heating temperature, rather than the glass transition temperature of the cellulose ester used alone. It is preferable at the point which can reduce the viscosity of the film constituent material containing an agent.

  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 heat absorption above the glass transition temperature 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 object.

  As the plasticizer, 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 a cyclohexyl group An acrylic polymer or the like having a 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 higher temperatures, and the decomposition start temperature is preferably 150 ° C. or higher, more preferably 200 ° C. or higher. The addition amount can be adjusted for various performances required for the cellulose ester film, and the blending amount is appropriately selected within a range not impairing the object of the present invention, and preferably 1 to 100 parts by mass of the cellulose ester resin. It is 50 mass%, More preferably, it is 3-30 mass%. 5-15 mass% is especially preferable.

  Hereinafter, the plasticizer used in the present invention will be further 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 cresyl phenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate, trinaphthyl phosphate, trixylyl phosphate, tris ortho-biphenyl phosphate. These substituents may be the same or different, and may be further substituted. Moreover, the mix of an alkyl group, a cycloalkyl group, and an aryl group may be sufficient, and substituents may couple | bond together by the covalent bond.

  Also, alkylene bis (dialkyl phosphate) such as ethylene bis (dimethyl phosphate), butylene bis (diethyl phosphate), alkylene bis (diaryl phosphate) such as ethylene bis (diphenyl phosphate), propylene bis (dinaphthyl phosphate), phenylene bis (dibutyl) And phosphate esters such as arylene bis (diaryl phosphate) such as arylene bis (dialkyl phosphate), phenylene bis (diphenyl phosphate), naphthylene bis (ditoluyl phosphate) such as biphenylene bis (dioctyl phosphate). These substituents may be the same or different, and may be further substituted. Moreover, the mix of an alkyl group, a cycloalkyl group, and an aryl group may be sufficient, and substituents may couple | bond together by the covalent bond.

  Further, the phosphate ester partial structure may be part of the polymer or regularly pendant, and may be introduced into part of the molecular structure of additives such as antioxidants, acid scavengers, and UV absorbers. It 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, it may be a mix of alkylate group, cycloalkylate group and arylate group, and these substituents may be covalently bonded. Furthermore, the ethylene glycol part may be substituted, the partial structure of the ethylene glycol ester may be part of the polymer or regularly pendant, and may be an antioxidant, an acid scavenger, an ultraviolet absorber, etc. It may be introduced into a part of the molecular structure of the additive.

  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 mixture of alkylate group, cycloalkylcarboxylate group, and arylate group, and these substituents may be bonded by a covalent bond. Furthermore, the glycerin and diglycerin part may be substituted, the partial structure of the glycerin ester and the diglycerin ester may be part of the polymer or regularly pendant, and an antioxidant, an acid scavenger, You may introduce | transduce into a part of molecular structure of additives, such as a ultraviolet absorber.

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

  These alkylate groups, cycloalkylcarboxylate groups, and arylate groups may be the same or different, and may be further substituted. Further, it may be a mixture of alkylate group, cycloalkylcarboxylate group, and arylate group, and these substituents may be bonded by a covalent bond. Furthermore, the polyhydric alcohol part may be substituted, the partial structure of the polyhydric alcohol may be a part of the polymer or regularly pendant, an antioxidant, an acid scavenger, an ultraviolet absorber, etc. It 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. Furthermore, 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 introduced into part of the molecular structure of additives such as antioxidants, acid scavengers, UV absorbers, etc. May be.

  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, 1,4-cyclopentanetetracarboxylate and other cycloalkyl polycarboxylic acid alkyl ester plasticizers, tetracyclopropyl-1,2,3,4-cyclobutanetetracarboxylate, tricyclohexyl-1,3,5-cyclohexyl Cycloalkyl polycarboxylic acid cycloalkyl ester plasticizers such as tricarboxylate, triphenyl-1,3,5-cyclohexyl tricarboxylate, 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, aryl polyvalent carboxylic acid cycloalkyl ester plasticizer tri such as tricyclopentylbenzene-1,3,5-tricarboxylate, tetracyclohexylbenzene-1,2,3,5-tetracarboxylate Aryl polycarboxylic acid aryl ester-based plasticizers such as phenylbenzene-1,3,5-tetracartoxylate and 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. Furthermore, 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 introduced into part of the molecular structure of additives such as antioxidants, acid scavengers, UV absorbers, etc. May be.

  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 1000 or less, a problem occurs in volatility, and if it exceeds 500,000, the plasticizing ability is lowered, and the mechanical properties of the cellulose ester derivative composition are adversely affected. These polymer plasticizers may be a homopolymer composed of one type of repeating unit or a copolymer having a plurality of repeating structures. Two or more of the above polymers may be used in combination, and other plasticizers, antioxidants, acid scavengers, ultraviolet absorbers, slip agents, slip agents, and the like may be included.

  Among the plasticizers, it is generally preferable that no volatile component is generated during heat melting. Specific examples include nonvolatile 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 to. When the volatile component is due to the 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 when 1.0% by mass is reduced. 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 thermogravimetric analysis (TG-DTA) apparatus.

(Antioxidant)
In the present invention, a cellulose ester resin or a cellulose ester resin composition containing the cellulose ester resin and an additive is heated and melted to form a film, thereby obtaining a target cellulose ester film. However, in general, cellulose ester resins are susceptible to thermal oxidative degradation. Therefore, it is desirable to use an antioxidant for the purpose of imparting heat resistance to the cellulose ester resin.

  A commercially available antioxidant may be used as the antioxidant used in the present invention. 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 or strength reduction of the molded product due to heat, oxidative degradation, or the like during molding without reducing 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. On the other hand, it is preferably 0.001 to 5 parts by mass, more preferably 0.01 to 1 part by mass.

  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 a compound includes a compound represented by the following general formula (1).

  In the formula, R1, R2 and R3 represent further substituted or unsubstituted alkyl substituents. 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, octade 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-4) -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-tert-butyl-4-hydroxyl Nyl) 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 Ruhexa- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 2-hydroxyethyl 7- (3-methyl-5-tert-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, Inc. under the trade names “Irganox 1076” and “Irganox 1010”, for example.

  As other antioxidants, specific examples of phosphorus compounds include triphenyl phosphite, diphenylisodecyl phosphite, phenyl diisodecyl phosphite, tris (nonylphenyl) phosphite, tris (dinonylphenyl) phosphite, tris. (2,4-di-t-butylphenyl) phosphite, 10- (3,5-di-t-butyl-4-hydroxybenzyl) -9,10-dihydro-9-oxa-10-phosphaphenanthrene- 10-oxide, 6- [3- (3-t-butyl-4-hydroxy-5-methylphenyl) propoxy] -2,4,8,10-tetra-t-butyldibenz [d, f] [1.3 .2] monophosphite compounds such as dioxaphosphine and tridecyl phosphite; 4,4'-butylidene-bis 3-phenyl-6-tert-butylphenyl-di-tridecyl phosphite), 4,4'-isopropylidene-bis (phenyl-di-alkyl (C12-C15) phosphite) and the like; triphenyl Phosphonite, tetrakis (2,4-di-tert-butylphenyl) [1,1-biphenyl] -4,4'-diylbisphosphonite, tetrakis (2,4-di-tert-butyl-5-methylphenyl) ) Phosphonite compounds such as [1,1-biphenyl] -4,4′-diylbisphosphonite; Phosphinite compounds such as triphenylphosphinite and 2,6-dimethylphenyldiphenylphosphinite; Triphenylphosphine, Phosphine compounds such as tris (2,6-dimethoxyphenyl) phosphine; It is.

  Phosphorus compounds of the above type are, for example, “SumilizerGP” from Sumitomo Chemical Co., Ltd., “ADK STAB PEP-24G”, “ADK STAB PEP-36” and “ADK STAB 3010”, Ciba Specialty It is commercially available under the trade name “IRGAFOS P-EPQ” from Chemicals Co., Ltd. and “GSY-P101” from Sakai Chemical Industry Co., Ltd.

  Examples of the acrylate compound include 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 and the like.

  Acrylate compounds of the above type are commercially available from Sumitomo Chemical Co., Ltd. under the trade names “Sumilizer GM” and “Sumilizer GS”, for example.

  Examples of the benzofuranone compounds include 3- [4- (2-acetoxyethoxy) phenyl] -5,7-ditert-butylbenzofuran-2-one, 5,7-ditert-butyl-3- [4- (2 -Stearoyloxyethoxy) phenyl] benzofuran-2-one, 3,3′-bis [5,7-ditert-butyl-3- (4- [2-hydroxyethoxy] phenyl) benzofuran-2-one], 5 , 7-ditert-butyl-3- (4-methoxyphenyl) benzofuran-2-one, 5,7-ditert-butyl-3-phenylbenzofuran-2-one, 5,7-ditert-butyl-4 -Methyl-3-phenylbenzofuran-2-one, 3- (4-acetoxy-3,5-dimethylphenyl) -5,7-ditert-butylbenzofuran-2-one, 3- (3,5-dimethyl- 4-Pivalloy Oxyphenyl) -5,7-ditert-butylbenzofuran-2-one, 3- (3,4-dimethylphenyl) -5,7-ditert-butylbenzofuran-2-one, 3- (2,3- Dimethylphenyl) -5,7-ditert-butyl-benzofuran-2-one and the like.

  The above type of benzofuranone-based compound is commercially available, for example, from Ciba Specialty Chemicals under the trade name “HP-136”.

  Dilauryl-3,3′-thiodipropionate, dimyristyl-3,3′-thiodipropionate, distearyl-3,3′-thiodipropionate, pentaerythrityltetrakis (3-laurylthiopropioate) Nate) and the like, 3,4-dihydro-2H-1-benzopyran compounds, 3,3'-spirodichroman compounds, 1,1-spiroindane compounds described in JP-B-08-27508 , Morpholine, thiomorpholine, thiomorpholine oxide, thiomorpholine dioxide, compounds having a piperazine skeleton in a partial structure, oxygen scavengers such as dialkoxybenzene compounds described in JP-A-03-174150, and the like. These antioxidant partial structures may be part of the polymer or regularly pendant into the polymer and introduced into part of the molecular structure of additives such as plasticizers, acid scavengers, and UV absorbers. It 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 include polyglycols derived by condensation of diglycidyl ethers of various polyglycols, particularly about 8-40 moles of ethylene oxide per mole of polyglycol. Glycol, diglycidyl ether of glycerol, etc., metal epoxy compounds (such as those conventionally used in and 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 are represented and exemplified by compositions such as epoxidized soybean oil) These are referred to as 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 represented by the following general formula (2).

  In the above formula, n is 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 a compound includes a compound represented by 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 stabilizers can be used alone or in combination of two or more, and these hindered amine light stabilizers can be used in combination with 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 weight, more preferably 0.02 to 15 parts by weight, based on 100 parts by weight of the cellulose ester resin. Especially preferably, it is 0.05-10 mass parts.

(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 is excellent in the ability to absorb ultraviolet rays having a wavelength of 370 nm or less, and from the viewpoint of liquid crystal display property, absorption of visible light having a wavelength of 400 nm or more is absorbed. 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 the benzotriazole-based compound 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-chlorobenzo Triazole, 2- (2′-hydroxy-3 ′-(3 ″, 4 ″, 5 ″, 6 ″ -tetrahydrophthalimidomethyl) -5′-methylphenyl) benzotriazole, 2,2-methylenebis (4- (1 , 1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol), 2- (2'-hydroxy-3'- ert-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2- (2'-hydroxy-3'-tert-butyl-5 '-(2-octyloxycarbonylethyl) -phenyl) -5-chloro Benzotriazole, 2- (2′-hydroxy-3 ′-(1-methyl-1-phenylethyl) -5 ′-(1,1,3,3-tetramethylbutyl) -phenyl) benzotriazole, 2- ( 2H-benzotriazol-2-yl) -6- (linear and side chain dodecyl) -4-methylphenol, octyl-3- [3-tert-butyl-4-hydroxy-5- (chloro-2H-benzotriazole) 2-yl) phenyl] propionate and 2-ethylhexyl-3- [3-tert-butyl-4-hydroxy-5- (5-chloro-2H-benzene) Zotoriazoru 2-yl) can be mentioned mixtures of phenyl] propionate, but not limited thereto.

  As commercial products, TINUVIN 326, TINUVIN 109, TINUVIN 171, TINUVIN 900, TINUVIN 928, TINUVIN 928, TINUVIN 360 (all of which are Ciba Specialty Chemicals) Product), LA31 (manufactured by ADEKA), Sumisorb 250 (manufactured by Sumitomo Chemical), and RUVA-100 (manufactured by Otsuka Chemical).

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

  In 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.

(Retardation control agent)
In the cellulose ester film of the present invention, an alignment film is formed, a liquid crystal layer is provided, and a polarizing plate protective film and a retardation derived from the liquid crystal layer are combined to provide an optical compensation capability to improve 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 EP 911,656A2 can be used as a retardation control agent. 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 cellulose ester film of the present invention, polymer materials and oligomers other than cellulose ester may be appropriately selected and mixed. The polymer materials and oligomers described above are preferably those having excellent compatibility with the cellulose ester, and the transmittance when formed into a film is preferably 80% or more, more preferably 90% or more, and further preferably 92% or more. 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 contain as an above-mentioned other additive.

<Film formation by melt casting>
The cellulose ester film of the present invention is characterized by being formed by a melt casting method.

  The molding method by melt casting that heats and melts without using the solvent (for example, methylene chloride, etc.) used in the solution casting method, more specifically, melt extrusion molding method, press molding method, inflation method, injection molding method And can be classified into blow molding, stretch molding and the like. Among these, in order to obtain a polarizing plate protective film having excellent mechanical strength and surface accuracy, the melt extrusion method is excellent.

  Hereinafter, the manufacturing method of the cellulose ester film of the present invention will be described by taking the melt extrusion method as an example.

  FIG. 1 is a schematic flow sheet showing the overall configuration of an apparatus for carrying out the method for producing a cellulose ester film of the present invention.

  In FIG. 1, the cellulose ester film is manufactured by mixing film materials such as cellulose ester resin and then using the extruder 1 to melt and extrude from a die 4 onto a first cooling roll 5. In addition to circumscribing, the film 10 is further circumscribed by a total of three cooling rolls, the second cooling roll 7 and the third cooling roll 8, and solidified by cooling to form a film 10. Next, the film 10 peeled off by the peeling roll 9 is then stretched in the width direction by holding both ends of the film by the stretching device 12, and then wound by the winding device 16. In addition, a touch roll 6 is provided that clamps the molten film on the surface of the first cooling roll 5 in order to correct the flatness. The touch roll 6 has an elastic surface and forms a nip with the first cooling roll 5. Details of the touch roll 6 will be described later.

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

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

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

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

  In the present invention, it is preferable that the cellulose ester resin and other additives such as a stabilizer added as necessary are mixed before melting. More preferably, the cellulose ester resin and the stabilizer are mixed first. Mixing may be performed by a mixer or the like, or may be mixed in the cellulose ester resin preparation process as described above. When using a mixer, general mixers, such as a V type mixer, a conical screw type mixer, a horizontal cylindrical mixer, a Henschel mixer, a ribbon mixer, can be used.

  After the film constituent materials are mixed as described above, the mixture may be directly melted and formed into a film using the extruder 1. In the present invention, after the film constituent materials are pelletized, the pellets are extruded. 1 is melted to form a film. When the film constituent material includes a plurality of materials having different melting points, a so-called braided semi-melt is once produced at a temperature at which only the material having a low melting point is melted, and the semi-melt is supplied to the extruder 1. It is also possible to form a film by introducing it.

  As the extruder 1, various commercially available extruders can be used, but a melt-kneading extruder is preferable, and a single-screw extruder or a twin-screw extruder may be used.

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

  In the present invention, the temperature of the resin composition at the time of heating and melting refers to the temperature of the resin composition immediately after being extruded from the screw in the extruder 1. The temperature of the resin composition and the temperature of the extruder 1 are not necessarily the same temperature, and the temperature of the extruder 1 is adjusted so that the resin composition temperature at the time of heating and melting becomes a desired value.

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

  The melt viscosity at the time of extrusion is 10 to 100,000 poise, preferably 100 to 10,000 poise. Further, the residence time of the film constituting material in the extruder 1 is preferably short, and is within 5 minutes, preferably within 3 minutes, more preferably within 2 minutes. Although the residence time depends on the type of the extruder 1 and the extrusion conditions, it can be shortened by adjusting the material supply amount, L / D, screw rotation speed, screw groove depth, etc. It is.

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

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

  The film constituent material extruded from the extruder 1 is sent to the die 4 and extruded from the slit of the die 4 into a film shape. The die 4 is not particularly limited as long as it is used for producing a sheet or a film. The material of the die 4 is sprayed or plated with hard chromium, chromium carbide, chromium nitride, titanium carbide, titanium carbonitride, titanium nitride, super steel, ceramic (tungsten carbide, aluminum oxide, chromium oxide), etc. Buffing, lapping using # 1000 or higher whetstone, surface cutting using # 1000 or higher diamond whetstone (cutting direction is perpendicular to resin flow direction), electrolytic polishing, electrolytic composite polishing, etc. Etc. A preferable material of the lip portion of the die 4 is the same as that of the die 4. The surface accuracy of the lip is preferably 0.5S or less, and more preferably 0.2S or less.

  The slit of the die 4 is configured so that the die lip clearance can be adjusted. Thickness gauges are installed at the required locations in the wake of the die, and the web thickness information detected thereby is fed back to the control device. The thickness information is compared with the set thickness information by the control device, and correction control comes from the same device. It is also possible to control the power or the ON rate of the heat bolt heating element by the amount signal. The heat bolt preferably has a length of 20 to 40 cm and a diameter of 7 to 14 mm, and a plurality of, for example, several tens of heat bolts are preferably arranged at a pitch of 20 to 40 mm. Instead of the heat bolt, a gap adjusting member mainly composed of a bolt for adjusting the die lip clearance by manually moving back and forth in the axial direction may be provided.

  The cellulose ester film of the present invention is preferably formed by casting from a die in a draw ratio range of 5-30. The draw ratio here is a value obtained by dividing the lip clearance of the die by the average film thickness of the film solidified on the cooling roll.

  A melt containing a cellulose ester resin has a high melt viscosity and is difficult to stretch as compared with other thermoplastic resins. For this reason, when the draw ratio is large, the film thickness is likely to vary in the conveying direction, and the dispersion of the slip agent and the variation in stretching are likely to occur. Therefore, the range of the draw ratio is preferable.

  The draw ratio can be adjusted by the die lip clearance and the take-up speed of the cooling roll. The die lip clearance is preferably 900 μm or more, and more preferably 1 mm or more and 2 mm or less from the viewpoint of controlling the film thickness unevenness.

  The first to third cooling rolls are made of seamless steel pipe having a wall thickness of about 20 to 30 mm, and the surface is finished to a mirror surface. Inside, a pipe for flowing a coolant is arranged so that heat can be absorbed from the film on the roll by the coolant flowing through the pipe. Of the first to third cooling rolls, the first cooling roll 5 corresponds to a rotating support.

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

  The touch roll 6 has an elastic roller disposed inside a flexible metal sleeve.

  The metal sleeve is made of stainless steel having a thickness of 0.3 mm and has flexibility. If the metal sleeve is too thin, the strength is insufficient. Conversely, if the metal sleeve is too thick, the elasticity is insufficient. For these reasons, the thickness of the metal sleeve is preferably 0.1 to 1.5 mm. The elastic roller is a roll formed by providing rubber on the surface of a metal inner cylinder that is rotatable through a bearing. When the touch roll 6 is pressed toward the first cooling roll 5, the elastic roller presses the metal sleeve against the first cooling roll 5, and the shape of the metal sleep and elastic roller conforms to the shape of the first cooling roll 5. To form a nip with the first cooling roll. Cooling water flows through a space formed between the metal sleeve and the elastic roller.

  In the present invention, preferred materials for the first roll 5 and the second roll 6 include carbon steel, stainless steel, resin, and the like. Further, the surface accuracy is preferably increased, and the surface roughness is 0.3 S or less, more preferably 0.01 S or less.

  In the present invention, by reducing the pressure from the opening (lip) of the die 4 to the first roll 5 to 70 kPa or less, the die line correction effect becomes larger, which is preferable. More preferably, the reduced pressure is 50 to 70 kPa. There is no particular limitation on the method of keeping the pressure in the portion from the opening (lip) of the die 4 to the first roll 5 at 70 kPa or less. is there. At this time, the suction device is preferably subjected to a treatment such as heating with a heater so that the device itself does not become a place where the sublimate is attached. In the present invention, if the suction pressure is too small, the sublimate cannot be sucked effectively, so it is necessary to set the suction pressure to an appropriate value.

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

  In the embodiment of the present invention shown in FIG. 1, the cooled and solidified unstretched film 10 peeled from the third cooling roll 8 by the peeling roll 9 is guided to a stretching apparatus 12 via a dancer roll (film tension adjusting roll) 11. Therefore, the film 10 is stretched in the transverse direction (width direction). By this stretching, the molecules in the film are oriented and the effect of the added slip agent is improved. After stretching, after slitting the edge of the film to a product width by the slitter 13, the film is subjected to knurling (embossing) on both ends of the film by a knurling device comprising an embossing ring 14 and a back roll 15. By winding with the winding device 16, the sticking in the original winding F and the generation of scratches are prevented.

  The winding length of the cellulose ester film of the present invention is preferably 500 to 5000 m, and more preferably 1000 to 5000 m. It is also preferable to wind up by providing a knurling with a height of 0 to 25% of the film thickness at both ends of the width.

  In order to stably produce such a very long film, it is important how the molecular weight is not reduced during melt film formation. When the molecular weight is reduced, the film becomes brittle and breakage tends to occur, and it is difficult to obtain a film having the above length. In order to prevent the decrease in molecular weight, not only the above-mentioned stabilizers are added, but also solvents, impurities, oxygen, moisture, etc., mixed before the material purchase or synthesis are removed as much as possible before the melting process. It is important to keep it. Film formation by the melt casting method has a significantly higher temperature at the time of film formation compared to the solution casting method. Therefore, if oxygen, moisture, or chemically active impurities are mixed, the cellulose ester is decomposed. This is because it will be promoted.

  It is preferable that volatile components such as moisture and impurities are removed before film formation or before melting. A method by drying can be applied to this removal method, and a method such as a heating method, a reduced pressure method, or a heated reduced pressure method can be used. Drying may be performed in air or in an atmosphere in which an inert gas such as nitrogen or argon is selected as the inert gas. These inert gases preferably have a low water or oxygen content. The oxygen concentration is preferably 0.1% or less, and the dew point of the gas is preferably −30 ° C. or less. Most preferably, it does not contain substantially. When these known drying methods are performed, it is preferable in terms of film quality to be performed in a temperature range where the film constituting material does not decompose. For example, the moisture or impurities remaining after the removal in the drying step is preferably 1% by mass or less, more preferably 0.5% by mass or less, based on the total mass of the film constituent materials. It is.

  In particular, the moisture content of the cellulose ester resin is preferably less than 0.3% by mass. These characteristic values can be measured by ASTM-D817-96. The cellulose ester is preferably used as 0.1 to 1000 ppm by further reducing the moisture by heat treatment.

  The amount of residual organic impurities can be measured by a headspace gas chromatography method. That is, a known amount of cellulose ester film is heated in a sealed container at 120 ° C. for 20 minutes, and the organic solvent contained in the gas phase in the sealed container is quantified by gas chromatography. From this result, the amount of residual organic solvent can be calculated.

  The film constituent material can reduce the generation of volatile components by drying before film formation, and the resin alone or at least one mixture or compatible material other than the resin among the resin and the film constituent material. It can be divided and dried. The preferable drying temperature is preferably 80 ° C. or higher and the Tg or melting point of the material to be dried. Including the viewpoint of avoiding fusion between materials, the drying temperature is more preferably 100 to (Tg-5) ° C, and still more preferably 110 to (Tg-20) ° C. A preferable drying time is 0.5 to 24 hours, more preferably 1 to 18 hours, and further preferably 1.5 to 12 hours. Below these ranges, the removal rate of volatile components may be low, or drying may take too long, and when Tg is present in the material to be dried, heating to a drying temperature higher than Tg will cause the material to be removed. May be difficult to handle due to fusion. Drying is preferably performed at 1 atm or less, and particularly preferably performed while reducing the pressure from vacuum to 1/2 atm. Drying is preferably performed while appropriately stirring the material such as resin, and the fluidized bed system in which drying air or dry nitrogen is fed from the lower part in the drying container can perform necessary drying in a shorter time. This is preferable because it is possible.

  The drying process may be separated into two or more stages. For example, the material may be formed using a material that has been subjected to storage of the material in the preliminary drying process and drying immediately before film formation to immediately before a week. .

  After removing volatile components such as moisture and impurities in the film-forming material by the drying process, the film-forming material is individually or pre-mixed / pelleted and sent to a heated barrel to melt and flow Then, it is extruded into a sheet by a die, and is brought into close contact with a cooling drum or an endless belt by an electrostatic application method or the like, and is cooled and solidified to be solidified into a sheet to obtain an unstretched sheet. These processes are called casting processes.

  In view of the physical properties of the obtained cellulose ester film and the effect of the present invention, the melting temperature (temperature in the barrel) is preferably in the range of 150 to 250 ° C, more preferably 180 to 230 ° C, and further Preferably it is 190-220 degreeC.

  Moreover, it is necessary for obtaining the effect of the present invention that the resin composition temperature at the outlet of the die portion is 10 to 60 ° C. higher than the melting temperature.

  As a method of increasing the resin composition temperature at the die outlet, a method of setting the set temperature of the die part higher than the resin composition temperature at the time of heating and melting, a method of setting the set temperature of the lip heater similarly, and a gear pump For example, a method for reducing the cooling capacity. In the present invention, among them, a method of increasing the set temperature of the die part is desirable.

  The temperature of the cooling drum is preferably maintained at 80 to 150 ° C. If the temperature of the drum is 90 ° C. or lower, the sheet extruded from the die is rapidly cooled, and the structure in the film may become uneven or brittle in the film thickness direction. It is preferable. On the other hand, when the temperature is 150 ° C. or higher, the cooling rate of the unstretched sheet becomes slow and the productivity is lowered, which is not preferable.

  When the cellulose ester 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. 10-100 micrometers is especially preferable, 20-80 micrometers is preferable, Especially preferably, it is 30-60 micrometers. When the cellulose ester film is thicker than the above region, for example, when used as a polarizing plate protective film, the polarizing plate after polarizing plate processing becomes too thick, and is particularly thin in liquid crystal displays used for notebook computers and mobile electronic devices. Not suitable for lightweight purposes. On the other hand, if the thickness is smaller than the above region, the film has high moisture permeability, and the ability to protect the polarizer from humidity decreases, which is not preferable. Moreover, in retardation film, since expression of retardation becomes difficult, it is not preferable.

  In the solution casting method, when the film thickness is increased, the drying (solvent removal) load is remarkably increased. However, in the present invention, a drying (solvent removal) step is not required, so a film having a large film thickness is improved in productivity. Can be manufactured. Therefore, there is an advantage that it is easier than ever to increase the thickness of the film in accordance with the purpose of providing a necessary phase difference or reducing moisture permeability. Moreover, even if it is a thin film, it has the effect that it can be produced with high productivity by extending | stretching such a thick film. In addition, the film thickness of the film at the time of extending | stretching becomes thin in inverse proportion to the draw ratio. For example, when the unstretched sheet is 200 μm, a 100 μm film can be obtained by stretching twice.

  The film thickness variation of the cellulose ester film support is preferably within a range of ± 3%, further ± 1%, and more preferably ± 0.1%. These film thickness fluctuations can be reduced by stretching.

  In view of the recent increase in the size of liquid crystal displays, the width of the polarizing plate protective film is preferably 1 m or more. On the other hand, if it exceeds 4 m, the apparatus becomes large and difficult to convey, so the width of the cellulose ester film of the present invention is preferably 1 to 4 m, particularly preferably 1.4 to 3 m.

  Next, the stretching process will be described.

  After the cellulose ester film of the present invention is cast and formed, it is possible to stretch the film in the range of 1.01 to 2.00 times in the transport direction and 1.01 to 2.00 times in the width direction. It is preferable for achieving both haze.

  After the film is extruded from the barrel and brought into close contact with the cooling drum, the film peeled off from the cooling drum is subjected to transverse stretching, longitudinal stretching, or stretching in an oblique direction as disclosed in JP-A-2004-226465. By doing so, the flatness can be improved and the production speed can be improved. These stretching operations may be performed a plurality of times, and may be performed simultaneously or sequentially when the stretching is performed a plurality of times. When stretching is performed a plurality of times, the product of all the stretching ratios becomes the final stretching ratio. For example, if 2 times of stretching is performed twice, the final stretching ratio is 4 times.

  The cellulose ester has a refractive index that increases in the stretched direction, and forms a slow axis. Therefore, the draw ratio is determined within the range of optical properties to be satisfied by the finally obtained film.

  When it is desired to reduce the retardation in the film plane as much as possible, biaxial stretching is preferred. By stretching at the same magnification in the direction orthogonal to the first stretching axis, birefringence due to the first stretching is canceled, and an isotropic film can be obtained.

  On the other hand, when obtaining a retardation film that has the effect of expanding the viewing angle of the liquid crystal display, the ratio of the first stretching and the second stretching is changed, and one of the stretching ratios is the other stretching An optically anisotropic film can be obtained by stretching so as to be larger than the magnification. In this case, the draw ratio between the width direction and the conveyance direction is preferably 1.1 to 2.0, and more preferably 1.2 to 1.5.

  When stretching multiple times, it may be stretched from the transport direction or from the width direction, but after the stretching process in the width direction, the transport width of the film becomes large, In order to increase the size, it is preferable to perform stretching in the width direction after stretching in the transport direction.

  Moreover, it is preferable that the final draw ratio of a cellulose-ester film shall be 5-100% of longitudinal (MD) direction draw ratio + width (TD) direction draw ratio. If it is less than 5%, the planarity of the resulting film may be inferior. On the other hand, stretching more than 100% is not preferable because the possibility of breakage during the stretching process increases.

  Initially, the extending | stretching method of a conveyance direction (MD) is demonstrated.

  After the film is extruded from the barrel and brought into close contact with the cooling drum, the film peeled off from the cooling drum is heated again in the transport direction through one or more roll groups and / or a heating device such as an infrared heater. Single-stage or multistage MD stretching may be performed.

  When stretching, if the glass transition temperature of the cellulose ester film of the present invention is Tg, it is heated within the range of (Tg-30) to (Tg + 100) ° C., more preferably (Tg-20) to (Tg + 80) ° C. It is preferable to extend in the transport direction (MD) or the width direction (TD). It is preferable to perform transverse stretching within the temperature range of (Tg-20) to (Tg + 20) ° C. and then heat-set. It is also preferable to perform relaxation treatment after the stretching step.

  The Tg of the cellulose ester film can be controlled by the material type constituting the film and the ratio of the constituting materials. In the use of the present invention, the Tg when the cellulose ester film is dried is preferably 110 ° C. or higher, more preferably 120 ° C. or higher. This is because when the cellulose ester film of the present invention is used in a liquid crystal display device, if the Tg of the film is lower than the above, molecules fixed inside the film due to the influence of the temperature and humidity of the use environment and the heat of the backlight. The orientation state of the film is affected, and there is a high possibility that the retardation value and the dimensional stability and shape of the film will greatly change. In addition, the shape of the film may not be maintained. On the other hand, if the Tg of the film is too high, it becomes difficult to produce because it approaches the decomposition temperature of the film constituting material, and the presence of the volatile component or coloring may occur due to the decomposition of the material itself used when forming a film. Accordingly, the glass transition temperature is preferably 180 ° C. or lower, more preferably 150 ° C. or lower. At this time, the Tg of the film can be determined by the method described in JIS K7121.

  Next, the extending | stretching method of a lateral direction (TD) is demonstrated.

  In the case of TD 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 in the range of Tg-40 ° C. or higher at a temperature equal to or lower than the final TD stretching temperature for 0.01 to 5 minutes because the distribution of physical properties in the width direction can be further reduced.

  The heat setting is performed at a temperature higher than the final TD stretching temperature and usually within 0.5 to 300 seconds within a temperature range of Tg-20 ° C. or less. Under the present circumstances, it is preferable to heat-fix, heating up sequentially in the range from which a temperature difference is set to 1-100 degreeC in the area | region divided into 2 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 lateral direction and / or the longitudinal direction within a temperature range of not more than the final heat setting temperature and not less than Tg. In addition, it is preferable that the cooling is gradually performed 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 carry out 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 type of additives such as cellulose ester and plasticizer constituting the film, so the physical properties of the obtained biaxially stretched film are measured and preferable characteristics are obtained. What is necessary is just to determine by adjusting suitably so that it may have.

  The in-plane retardation value (Ro) and thickness direction retardation value (Rt) of the cellulose ester film of the present invention are preferably 0 ≦ Ro and Rt ≦ 70 nm when used as a polarizing plate protective film. More preferably, 0 ≦ Ro ≦ 20 nm and 0 ≦ Rt ≦ 50 nm, and more preferably 0 ≦ Ro ≦ 10 nm and 0 ≦ Rt ≦ 30 nm. When used as a retardation film, 30 ≦ Ro ≦ 100 nm and 70 ≦ Rt ≦ 400 nm, and more preferably 35 ≦ Ro ≦ 65 nm and 90 ≦ Rt ≦ 180 nm. Further, the variation of Rt and the width of distribution are preferably less than ± 10%, more preferably less than ± 5%. More preferably, it is less than ± 1%, and most preferably, there is no fluctuation of Rt.

  The retardation values Ro and Rt can be obtained by the following equations.

Ro = (nx−ny) × d
Rt = ((nx + ny) / 2−nz) × d
Here, d is the thickness (nm) of the film, the refractive index nx (also referred to as the maximum refractive index in the plane of the film, the refractive index in the slow axis direction), ny (in the direction perpendicular to the slow axis in the film plane). ) (Refractive index of the film in the thickness direction).

  The retardation values (Ro) and (Rt) can be measured using an automatic birefringence meter. For example, it can be obtained at a wavelength of 590 nm using KOBRA-21ADH (Oji Scientific Instruments) under an environment of 23 ° C. and 55% RH.

  The slow axis is preferably in the width direction ± 1 ° of the film or in the transport direction ± 1 °. More preferably, it is ± 0.7 ° with respect to the width direction or the transport direction, and further preferably ± 0.5 ° with respect to the width direction or the transport direction. By setting it as such a range, the contrast of the liquid crystal display obtained can be raised.

  Since the cellulose ester film of the present invention does not substantially use a solvent in the film forming step, the amount of residual organic solvent contained in the cellulose ester film wound up after film formation is stably less than 0.1% by mass. Accordingly, it is possible to provide a cellulose ester film having more stable flatness and Rt than before. In particular, it becomes possible to provide a cellulose ester film having stable flatness and Rt even in a long roll of 100 m or more.

  It is difficult to reduce the amount of residual organic solvent in the cellulose ester film produced by the solution casting method to 0.1% by mass or less, and this requires a long drying step. Thus, a cellulose ester film having a very low residual organic solvent content can be obtained, and a cellulose ester film having excellent characteristics as an optical film can be obtained.

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

(Functional layer)
In producing the cellulose ester film of the present invention, before and / or after stretching, an antistatic layer, a hard coat layer, an antireflection layer, a slippery layer, an easy adhesion layer, an antiglare layer, a barrier layer, an optical compensation layer, etc. The functional layer may be provided. 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.

  Moreover, the cellulose ester film of 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 slip agent. For example, a cellulose ester film having a structure of skin layer / core layer / skin layer can be produced. For example, the slip agent can be included in the skin layer more or only in the skin layer. The plasticizer and the ultraviolet absorber can be contained in the core layer more than the skin layer, and may be contained only in the core layer. In addition, the type of plasticizer and ultraviolet absorber can be changed between the core layer and the skin layer. For example, the skin layer contains a low-volatile plasticizer and / or an ultraviolet absorber, and the core layer has excellent plasticity. It is also possible to add a plasticizer or an ultraviolet absorber excellent in ultraviolet absorption. The 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 may be used.

<Polarizer>
The production method of the polarizing plate using the cellulose ester film of the present invention is not particularly limited, and can be produced by a general method. The obtained cellulose ester film is alkali-treated, and the cellulose ester film of the present invention is bonded to at least one surface of a polarizer prepared by immersing and stretching a polyvinyl alcohol film in an iodine solution using a completely saponified polyvinyl alcohol aqueous solution. To do. The cellulose ester film of the present invention may be bonded to both sides of the polarizer as a polarizing plate protective film.

  In addition, as a conventional polarizing plate protective film used for the other surface, Konica Minoltak KC8UX, KC4UX, KC5UX, KC8UY, KC4UY, KC8UCR-3, KC8UCR-4, KC12UR, KC8UXW-H, KC8UYW-X8, Cellulose ester films such as -RHA (manufactured by Konica Minolta Opto Co., Ltd.) can be used.

  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 contact bonding layer bonded to a liquid crystal board, and is used for the surface side which bonds a polarizing plate to a liquid crystal cell.

<Liquid crystal display device>
In a liquid crystal display device, a substrate containing a liquid crystal is usually disposed between two polarizing plates. Since a polarizing plate protective film to which the cellulose ester film of the present invention is applied has high flatness and retardation uniformity, An excellent display property can be obtained even if it is disposed in the position. A polarizing plate protective film provided with a clear hard coat layer, an antiglare layer, an antireflection layer, or the like is preferably used for this portion of the polarizing plate protective film on the outermost display side of the liquid crystal display device. In the case of a polarizing plate protective film provided with an optical compensation layer, or a polarizing plate protective film provided with an appropriate optical compensation capability by stretching operation or the like, it is excellent in being disposed at a site in contact with the liquid crystal cell. Displayability is obtained. In particular, the use of the present invention for a multi-domain type liquid crystal display device, more preferably a multi-domain type liquid crystal display device with a birefringence mode, can further exhibit the effects of the present invention.

  Multi-domain is a method of dividing a liquid crystal cell that constitutes one pixel into a plurality of parts, and is also suitable for improving viewing angle dependency and improving symmetry of image display. Various methods have been reported. “Okita, Yamauchi: Liquid Crystal, 6 (3), 303 (2002)”. The liquid crystal display cell is also shown in “Yamada, Yamabara: Liquid Crystal, 7 (2), 184 (2003)”, but is not limited thereto.

  The display quality of the display cell is preferably symmetrical with respect to human observation. Therefore, when the display cell is a liquid crystal display cell, it is possible to multiplex domains by giving priority to the symmetry on the observation side. A known method can be used to divide the domain, and can be determined in consideration of the properties of a known liquid crystal mode by a two-part dividing method, more preferably a four-part dividing method.

  The polarizing plate of the present invention includes an MVA (Multi-domain Vertical Alignment) mode represented by a vertical alignment mode, in particular, a MVA mode divided into four, a known PVA (Patterned Vertical Alignment) mode and an electrode multi-domained by an electrode arrangement. It can be effectively used in a CPA (Continuous Pinwheel Alignment) mode in which arrangement and chiral ability are fused. In addition, a proposal of an optically biaxial film in the adaptation to the OCB (Optical Compensated Bend) mode has been disclosed, and “T. Miyashita, T. Uchida: J. SID, 3 (1), 29 ( 1995) ”, the effect of the present invention can be exhibited in the display quality by the polarizing plate of the present invention. If the effect of this invention can be expressed by using the polarizing plate of this invention, arrangement | positioning of a liquid crystal mode and a polarizing plate will not be limited.

  Since the liquid crystal display device has high performance as a device for colorization and moving image display, the display quality of the liquid crystal display device using the cellulose ester film of the present invention, particularly a large-sized liquid crystal display device, is less fatigued and faithful. Image display is possible.

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

Example 1
[Production of cellulose ester film]
Cellulose ester resin P1 as cellulose acetate propionate (acetyl group substitution degree = 1.41, propionyl group substitution degree = 1.32, total acyl group substitution degree = 2.73) 100 parts by mass, trimethylolpropane as plasticizer 8 parts by mass of tribenzoate, 0.25 parts by mass of Sumizer GS (manufactured by Sumitomo Chemical Co., Ltd.) as a carbon radical scavenger, and pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-hydroxy) as a phenolic compound Phenyl) propionate] (as a commercially available product, Irganox 1010 (manufactured by Ciba Specialty Chemicals)) 0.5 parts by mass, and tetrakis (2,4-di-t-butyl-5-methylphenyl) -4 as a phosphorus compound 4'-biphenylenediphosphonite (as a commercial product) , GSY-P101 (manufactured by Sakai Chemical Industry Co., Ltd.)) 0.25 parts by mass, Tinuvin-928 (manufactured by Ciba Specialty Chemicals Co., Ltd.) as an ultraviolet absorber, 1.5 parts by mass, Sea Hoster KE-P10 (Japan) 0.02 part by mass of catalyst (primary particle size 0.1 μm) was mixed and dried under reduced pressure at 60 ° C. for 5 hours. This cellulose ester composition was melt-mixed at 235 ° C. using a twin-screw extruder and then dried to obtain pellets. At this time, an all screw type screw was used instead of a kneading disk in order to suppress heat generation due to shear during kneading. In addition, evacuation was performed from the vent hole, and volatile components generated during kneading were removed by suction. In addition, the moisture between the feeder, hopper, and the extruder die supplied to the extruder and the cooling tank was set as a dry nitrogen gas atmosphere to prevent moisture from being absorbed into the resin.

<Synthesis of Cellulose Ester Resin P1>
60 kg of acetic acid and 20 kg of propionic acid were added to 30 kg of cellulose (manufactured by Nippon Paper Industries Co., Ltd.) and stirred at 54 ° C. for 30 minutes. After the mixture was cooled, esterification was performed by adding 50 kg of acetic anhydride, 50 kg of propionic anhydride and 1.2 g of sulfuric acid cooled in an ice bath. In the esterification, stirring was performed for 150 minutes while adjusting the temperature so as not to exceed 40 ° C. After completion of the reaction, a mixed solution of 30 g of acetic acid and 10 g of water was added dropwise over 20 minutes to hydrolyze excess anhydride. While maintaining the temperature of the reaction solution at 40 ° C., 90 g of acetic acid and 30 g of water were added and stirred for 1 hour. The mixture was poured into an aqueous solution containing 2 g of magnesium acetate and stirred for a while, followed by filtration and drying. Cellulose acetate propionate (acetyl group substitution degree 1.41, propionyl group substitution degree 1.32, acyl group total substitution degree) 2.73, number average molecular weight Mn = 79124, weight average molecular weight Mw = 2111307, Mw / Mn = 2.67). This cellulose acetate propionate is designated as a cellulose ester resin P1.

  Film formation was performed with the manufacturing apparatus shown in FIG.

  While supplying the pellets from the hopper to the extruder 1 at a temperature of 180 ° C., the temperature of the melting portion of the extruder 1 is set so that the temperature of the resin composition at the time of heating and melting is 250 ° C. A melt was obtained.

  Furthermore, foreign matters and insoluble matters were removed through a filter 2 equipped with a leaf type disk filter having an opening of 5 μm through a gear pump.

  The first cooling roll 5, the second cooling roll 7, and the third cooling roll 8 were made of stainless steel having a diameter of 40 cm, and the surface was subjected to hard chrome plating. Further, oil for temperature adjustment was circulated inside to control the roll surface temperature. The elastic touch roll 6 had a diameter of 20 cm, the inner cylinder and the outer cylinder were made of stainless steel, and the surface of the outer cylinder was subjected to hard chrome plating. The wall thickness of the outer cylinder was 2 mm, and the surface temperature of the elastic touch roll was controlled by circulating oil for temperature adjustment in the space between the inner cylinder and the outer cylinder.

  The die temperature was adjusted so that the temperature of the resin composition at the outlet of the die 4 was 270 ° C., and melt-extruded into a film on a first cooling roll having a surface temperature of 130 ° C. to obtain a cast film with a draw ratio of 20. . At this time, a die having a lip clearance of 1.5 mm and a lip portion average surface roughness Ra of 0.01 μm was used.

Further, an elastic touch roll having a metal surface with a thickness of 2 mm was pressed on the first cooling roll at a linear pressure of 10 kg / cm. The film temperature on the touch roll side during pressing was 180 ° C. ± 1 ° C. (The film temperature on the touch roll side at the time of pressing here refers to the temperature of the film at the position where the touch roll on the first cooling roll comes into contact with the touch roll by using a non-contact thermometer, and there is no touch roll. (The average value of the film surface temperature measured 10 points in the width direction from a position 50 cm away in the state.) The glass transition temperature Tg of this film was 136 ° C. (The glass transition temperature of the film extruded from the die was measured by DSC method (in nitrogen, temperature rising temperature 10 ° C./min) using DSC6200 manufactured by Seiko Co., Ltd.)
The surface temperature of the elastic touch roll was 130 ° C., and the surface temperature of the second cooling roll was 100 ° C. The surface temperature of each roll of the elastic touch roll, the first cooling roll, the second cooling roll, and the third cooling roll is the temperature of the roll surface at a position 90 ° before the rotation direction from the position where the film first contacts the roll. The average value obtained by measuring 10 points in the width direction using a non-contact thermometer was defined as the surface temperature of each roll.

  The obtained film was heated to 160 ° C. and stretched 1.01 times in the conveying direction by the dancer roll 11, followed by a preheating zone, a stretching zone, a holding zone, and a cooling zone (between each zone, between each zone). It is introduced into a tenter (stretching device 12) having a neutral zone for ensuring heat insulation), stretched 1.20 times at 160 ° C in the width direction, and then cooled to 70 ° C while relaxing 2% in the width direction. Thereafter, the film was released from the clip, the clip gripping part was cut off, a knurling process having a width of 10 mm and a height of 5 μm was applied to both ends of the film, and a cellulose ester film 1 having a thickness of 80 μm slit to a width of 1430 mm was produced.

  Similarly, cellulose ester films 2 to 18 were prepared by using a slipping agent having a primary particle size (per volume) shown in Table 1 and further changing the temperature conditions of the extruder and the cellulose ester resin composition at the die outlet. .

  In addition, the primary particle diameter of the slip agent 1 was observed with a transmission electron microscope (H-7100FA type manufactured by Hitachi), and the primary particle diameter of the particles was determined by the number of data N = 1000.

<Evaluation>
The following evaluation was performed using the obtained cellulose ester films 1 to 18, and the results are shown in Table 1.

(Internal haze)
The internal haze of the obtained film was measured by the following measurement.

  A few drops of silicone oil are added to the front and back surfaces of the obtained film, and two glass sheets are completely sandwiched between the front and back surfaces using two 1 mm-thick glass plates (micro slide glass product number S 9111, manufactured by MATSANAMI). The plate and the obtained film were optically adhered, and the haze was measured in accordance with JIS-K7136 with the surface haze removed, and only the silicone oil was sandwiched between two separately measured glass plates. The value obtained by subtracting haze was calculated as the internal haze of the film.

  The internal haze value is preferably 0.40 or less, and more preferably 0.30 or less.

(Cross Nicol transmittance)
Two polarizing plates were arranged in crossed Nicols, and transmittance (T1) at 590 nm was measured using a spectrophotometer U3100 manufactured by Hitachi, Ltd. Furthermore, the evaluation sample was placed between polarizing plates, and the transmittance (T2) at 590 nm was measured. Using the measured T1 and T2, the crossed Nicols transmittance is obtained by the following formula. It is preferably 65% or less, and more preferably 60% or less.

Cross Nicol transmittance (%) = T2-T1
(Squeeze value: Dynamic friction coefficient)
The dynamic friction coefficient between the film surface and the back surface is cut out so that the front and back surfaces of the film are in contact with each other according to JIS-K-7125 (1987), a 200 g weight is placed, the sample moving speed is 100 mm / min, and the contact area is 80 mm × 200 mm. The weight is pulled horizontally under the conditions described above, the average load (F) while the weight is moving is measured, and the dynamic friction coefficient (μ) is obtained from the following equation. The smaller the dynamic friction coefficient, the less “squeaking” occurs. The squeak value is preferably 0.80 or less, more preferably 0.50 to 0.65.

    Coefficient of dynamic friction (μ) = F (g) / Weight of weight (g)

  From Table 1, it can be seen that the cellulose ester film of the present invention is generally excellent in internal haze, crossed Nicol transmittance, squeak value: dynamic friction coefficient, and is excellent in handleability and transparency.

Example 2
<Production of BP1>
The base pellet (BP) is a pellet containing no slip agent as described above.

  The following composition was stirred and mixed with a tumbler mixer. The obtained mixture was pelleted under the conditions of 250 ° C., screw rotation speed 220 rpm, residence time 30 seconds using a twin screw extruder PCM-30 (Ikegai Co., Ltd.) equipped with a 4 mm × 5 hole pellet molding round die. Turned into.

(Composition of BP1)
Cellulose ester resin P1 92 parts by weight Trimethylolpropane tribenzoate 8 parts by weight Irganox 1010 (manufactured by Ciba Specialty Chemicals) 0.5 part by weight GSY-P101 (manufactured by Sakai Chemical Industry) 0.3 parts by weight Smilizer-GS (Sumitomo Chemical product) 0.3 parts by mass Tinuvin-900 (Ciba Specialty Chemicals)
2 parts by mass <Preparation of MP1>
The master pellet (MP) is a pellet having a high concentration of slip agent as described above.

  The following composition was stirred and mixed with a tumbler mixer. The resulting mixture was pelletized using a twin screw extruder PCM-30 (manufactured by Ikegai Co., Ltd.) equipped with a 4 mm x 5 hole pellet molding round die at 250 ° C, screw rotation speed 220 rpm, and residence time 30 seconds. did.

(Composition of MP1)
Cellulose ester resin P1 92 parts by weight Trimethylolpropane tribenzoate 8 parts by weight Irganox 1010 (manufactured by Ciba Specialty Chemicals) 0.5 part by weight GSY-P101 (manufactured by Sakai Chemical Industry) 0.3 parts by weight Smilizer-GS (Sumitomo Chemical product) 0.3 parts by mass Tinuvin-900 (Ciba Specialty Chemicals)
2 parts by mass KE-P100 (manufactured by Nippon Shokubai Co., Ltd .: primary particle size 1.0 μm silica particles) 0.2 parts by mass The mixing ratio of the base pellet (BP1) and the master pellet (MP1) is described in Table 2 before the extruder is charged. Cellulose ester films 19 to 25 were produced in the same manner as the cellulose ester film 5 of Example 1 except that the mixture was changed and mixed.

  About the obtained film, in addition to the evaluation of internal haze, crossed Nicol transmittance, squeak value: dynamic friction coefficient, internal haze variation was evaluated and shown in Table 2.

(Internal haze variation)
A total of 35 internal hazes were measured, 7 points at intervals of 30 cm in the width direction and 5 points at intervals of 3 m in the casting direction, and then the standard deviation of the measured values was obtained to determine internal haze variation. The smaller the value, the better.

  From Table 2, it can be seen that the cellulose ester film of the present invention has an internal haze, crossed Nicol permeability, and squeak value: in addition to a dynamic friction coefficient, it is excellent in internal haze variation, and a cellulose ester film excellent in handleability and transparency can be obtained. .

Example 3
In the production of the cellulose ester film 21 of Example 2, cellulose ester films 26 to 32 were produced in the same manner except that the draw ratio was changed as shown in Table 3 in the conveying direction and the width direction, and Examples were produced. Evaluation similar to 2 was performed. The results are shown in Table 3.

  From Table 3, it can be seen that the cellulose ester film of the present invention is capable of obtaining a cellulose ester film having excellent internal haze, crossed Nicol permeability, squeak value: dynamic friction coefficient, internal haze variation, and excellent handleability and transparency.

Example 4
In producing the cellulose ester film 21 of Example 2, cellulose ester films 33 to 38 were produced in the same manner except that the draw ratio was changed as shown in Table 4, and the same evaluation as in Example 2 was performed. The results are shown in Table 4.

  From Table 4, it can be seen that the cellulose ester film of the present invention is excellent in internal haze, crossed Nicol transmittance, squeak value: dynamic friction coefficient, internal haze variation, and excellent in handleability and transparency.

Example 5
In preparation of the cellulose ester film 21 of Example 2, the master pellet (MP1) is replaced with the following master pellet (MP2), and further added to the primary particle diameter of particles used for the following slipping agents 1 and 2 and 100 parts by mass of the cellulose ester. Cellulose ester films 39 to 43 were produced in the same manner except that the amount was changed as shown in Table 5.

  The cellulose ester film 43 was prepared by further adding the slip agent 3 as shown in Table 5.

(Composition of MP2)
Cellulose ester resin P1 92 parts by weight Trimethylolpropane tribenzoate 8 parts by weight Irganox 1010 (manufactured by Ciba Specialty Chemicals) 0.5 part by weight GSY-P101 (manufactured by Sakai Chemical Industry) 0.3 parts by weight Smilizer-GS (Sumitomo Chemical product) 0.3 parts by mass Tinuvin-900 (Ciba Specialty Chemicals)
2 parts by mass Sliding agent 1: KE-P100 (manufactured by Nippon Shokubai Co., Ltd .: primary particle size 1.0 μm silica particles)
0.2 parts by mass Sliding agent 2: NAX50 (Nippon Aerosil Co., Ltd .: primary particle size 20 nm)
0.2 part by mass The same evaluation as in Example 2 was performed using the obtained cellulose ester film. The results are shown in Table 5.

  From Table 5, it can be seen that the cellulose ester film of the present invention has an internal haze, a crossed Nicol transmittance, a squeak value: a dynamic friction coefficient, particularly an excellent internal haze variation, and a cellulose ester film excellent in handleability and transparency.

Example 6
<Production of polarizing plate>
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 at 68 ° C. composed of 6 g of potassium iodide, 7.5 g of boric acid, and 100 g of water. . This was washed with water and dried to obtain a polarizer.

  Next, polarizing plates 1 to 43 were produced using the polarizer and the cellulose ester films 1 to 43 produced in Examples 1 to 5 on both sides according to the following steps 1 to 5, respectively.

  Step 1: The cellulose ester 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.

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

  Step 3: Excess adhesive adhered to the polarizer in Step 2 was gently wiped, and this was placed on each cellulose ester film treated in Step 1 and laminated.

Step 4: The cellulose ester film and the polarizer 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.

  Step 5: A sample in which the cellulose ester film prepared in Step 4 and the polarizer were bonded together in a dryer at 80 ° C. was dried for 2 minutes to prepare a polarizing plate.

  The cellulose ester film of the present invention exhibited excellent handling properties and suitability for polarizing plate processing without surface scratches.

<Production of liquid crystal display device>
Next, a liquid crystal display device was produced as follows using the produced polarizing plate.

  In Fujitsu's 15-inch liquid crystal display VL-1530S, the polarizing plate previously bonded to the liquid crystal television is peeled off, and the above-prepared polarizing plates 1 to 43 are bonded to the glass surface of the liquid crystal cell, respectively. did.

  At that time, with the liquid crystal cell being sandwiched, the two produced polarizing plates were pasted so as to be orthogonal to each other so that the polarizing axes of the polarizing plates were not changed, so that liquid crystal display devices 1 to 43 were produced.

  When the characteristics of the liquid crystal display device were evaluated, the liquid crystal display device equipped with the polarizing plate using the cellulose ester film of the present invention had high contrast and showed excellent display properties. Thereby, it was confirmed that the cellulose ester film of the present invention is useful as a polarizing plate for an image display device such as a liquid crystal display and can provide excellent visibility as a liquid crystal display device.

It is a schematic flow sheet which shows the whole structure of the apparatus which enforces the manufacturing method of the cellulose-ester film of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Extruder 2 Filter 3 Static mixer 4 Dies 5 Rotating support body (1st cooling roll)
6 Nipping pressure rotating body (touch roll)
7 Rotating support (second cooling roll)
8 Rotating support (3rd cooling roll)
9 Peeling roll 10 Film 11 Dancer roll 12 Stretching device 13 Slitter 14 Embossing ring 15 Back roll 16 Winding device F Original winding

Claims (7)

In a method for producing a cellulose ester film in which pellets of a resin composition containing a cellulose ester resin are melted by heating with an extruder and cast from a die, the pellets of the resin composition have a primary particle size of 0.2. A method for producing a cellulose ester film, comprising particles having a diameter of 10 μm to 10 μm, wherein the resin composition temperature at the outlet of the die part is 10-60 ° C. higher than the resin composition temperature at the time of heating and melting . The pellet of the resin composition containing the particles and the pellet of the resin composition not containing the particles are mixed in a volume ratio of 0.05: 1 to 2: 1 before being charged into the extruder. The method for producing a cellulose ester film according to claim 1. The cellulose ester film is cast and formed, and then stretched in a range of 1.01 to 2.00 times in the transport direction and 1.01 to 2.00 times in the width direction. The manufacturing method of the cellulose-ester film of description. The method for producing a cellulose ester film according to claim 3, wherein the cellulose ester film is cast from a die in a draw ratio of 5 to 30 to form a film. A cellulose ester film produced by the method for producing a cellulose ester film according to claim 1. A polarizing plate comprising the cellulose ester film according to claim 5 on at least one surface. A liquid crystal display device comprising the polarizing plate according to claim 6 on at least one surface of a liquid crystal cell.

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