JP4851286B2 - Cellulose acylate film and method for producing the same - Google Patents

Description

  The present invention relates to a cellulose acylate film and a method for producing the same, and more particularly to a cellulose acylate film having a quality suitable for a liquid crystal display device and a method for producing the same.

  Conventionally, a cellulose acylate film has been stretched to develop in-plane retardation (Re) and retardation in the thickness direction (Rth), and used as a retardation film for liquid crystal display elements, thereby expanding the viewing angle. Has been.

  As a method of stretching such a cellulose acylate film, a method of stretching in the longitudinal (longitudinal) direction of the film (longitudinal stretching), a method of stretching in the lateral (width) direction of the film (transverse stretching), or longitudinal stretching A method of simultaneously performing transverse stretching (simultaneous stretching) can be mentioned. Of these, longitudinal stretching has been used in the past because of its compact equipment. Normally, longitudinal stretching is performed in the longitudinal direction by heating the film to a glass transition temperature (Tg) or more between two or more pairs of nip rollers and increasing the transport speed on the outlet side from the transport speed of the nip rollers on the inlet side. Is the method.

Patent Document 1 describes a method of longitudinally stretching a cellulose ester. This patent document 1 improves the unevenness of the angle of the slow axis by reversing the longitudinal stretching direction from the casting film forming direction. Patent Document 2 describes a method in which a nip roller installed between short spans having an aspect ratio (L / W) of 0.3 or more and 2 or less is installed in a stretching zone for stretching. According to Patent Document 2, the thickness direction orientation (Rth) can be improved. The aspect ratio here refers to a value obtained by dividing the interval (L) of the nip rollers used for stretching by the width (W) of the film to be stretched.
JP 2002-311240 A JP 2003-315551 A

  By the way, when a cellulose acylate film before stretching (unstretched) is formed by a melt film-forming method, there is a problem that the cellulose acylate resin is difficult to level because the melt viscosity is high. For this reason, the cellulose acylate film formed by the melt film forming method has a problem that streak failure is likely to occur and a problem that the thickness accuracy is lowered.

  The inventor of the present invention paid attention to the polishing roller method as a method for solving these problems. This polishing roller method is a method in which the resin extruded from the die is cooled while being sandwiched between a pair of rollers, and it is possible to prevent the occurrence of streak failure and to improve the thickness accuracy.

  By the way, as the in-plane retardation (Re) and the thickness direction retardation (Rth) of the cellulose acylate film before stretching are smaller, it is easier to control the ratio of longitudinal stretching and lateral stretching in the subsequent process. Moreover, it is preferable that Re and Rth are not expressed in the protective film used in the liquid crystal display device.

  From this, the inventor reduced Re and Rth by reducing the sandwiching roll pressure or increasing the film forming temperature in the polishing roller method in which the molten resin extruded from the die is cooled while sandwiching it with a pair of rollers. Proposed measures to make it smaller.

  However, it has been found that in the polishing roller method, when a cellulose acylate film is formed at a high film forming speed, retardation occurs when sandwiched between a pair of rollers.

  The present invention has been made in view of such circumstances, and provides a cellulose acylate film capable of suppressing the expression of retardation during film formation even when the film is formed at a high speed by a polishing roller method, and a method for producing the same. For the purpose.

In order to achieve the above object, the invention according to claim 1 is a film in which cellulose acylate resin is melted and extruded from a die into a sheet, and the sheet is sandwiched between a pair of metal rollers and cooled and solidified. Is a method for producing a cellulose acylate film which is formed at a film forming speed of 20 m / min or more, wherein the cellulose acylate resin has a weight average molecular weight of 100,000 to 170,000 , and When A is the substitution degree of the acetyl group and B is the substitution degree of the propionyl group, 2.85 ≦ A + B ≦ 2.95, 0 ≦ A ≦ 0.5, 2.5 ≦ B ≦ 3.0 It is characterized by satisfaction.

The inventors of the present invention, as a result of earnest research on the cause of retardation when sandwiched between a pair of rollers when forming a cellulose acylate film at a high film forming speed, It was found that the expression of retardation can be suppressed by adjusting the weight average molecular weight of the resin and the substitution degree of the acetyl group and the substitution degree of the propionyl group. That is, when the weight average molecular weight is 100,000 to 170,000 and A is the substitution degree of acetyl group and B is the substitution degree of propionyl group, 2.85 ≦ A + B ≦ 2.95, 0 ≦ A ≦ Even if a cellulose acylate film satisfying 0.5, 2.5 ≦ B ≦ 3.0 is formed with a polishing roller method at a film forming speed of 20 m / min or more, streak failure occurs. It is possible to prevent the occurrence of retardation and to improve the thickness accuracy, as well as to suppress the expression of retardation.

Therefore, according to the first aspect of the present invention, a cellulose acylate film is produced in which a sheet is sandwiched between a pair of metal rollers and cooled and solidified at a film forming speed of 20 m / min or more to form a film. The cellulose acylate resin has a weight average molecular weight of 100,000 to 170,000 , and when A is a substitution degree of an acetyl group and B is a substitution degree of a propionyl group, 2.85 ≦ A + B By satisfying ≦ 2.95, 0 ≦ A ≦ 0.5, and 2.5 ≦ B ≦ 3.0 , it is possible to suppress the occurrence of streak failure and retardation of the film, and further the retardation of the film. Since the expression of Re and Rth can be suppressed, it is possible to obtain a cellulose acylate film suitable for optical applications having good thickness accuracy and uniform optical characteristics in the width direction and the longitudinal direction.

The invention according to claim 2 is the invention according to claim 1 , wherein the pair of rollers made of metal has a surface property with an arithmetic average height Ra of 100 nm or less, and at least one of the pair of rollers is The outer roller wall thickness is an elastic roller having a thickness in the range of 0.2 mm to 7.0 mm.

According to the second aspect , since the surface property of each of the pair of metal rollers is 100 nm or less in terms of arithmetic average height Ra, the surface property of the film can be improved. And since at least one of a pair of rollers is an elastic roller whose roller outer cylinder thickness is 0.2 mm or more and 7.0 mm or less, the elastic roller is elastically deformed and comes into surface contact with the cooling roll via the sheet. The sheet can be pressed planarly and uniformly with a restoring force that restores the elastically deformed shape. When the sheet is cooled while being pressed in a planar and uniform manner as described above, a film having no residual distortion is formed inside, thereby suppressing the occurrence of retardation during film formation.

The invention according to claim 3 is the invention according to claim 1 or 2 , characterized in that the zero shear viscosity of the thermoplastic resin when discharged from the die is 2000 Pa · sec or less.

According to the invention of claim 3 , when the zero shear viscosity of the cellulose acylate resin when discharged from the die is 2000 Pa · sec or less, it is possible to further prevent streaking failures from occurring in the film. If the zero shear viscosity exceeds 2000 Pa · sec, the molten resin discharged from the die spreads immediately after discharge and tends to adhere to the tip of the die, which becomes dirty and easily causes streak failure. . The zero shear viscosity is measured by measuring the shear rate dependency data of the melt viscosity with a plate cone type melt viscosity measuring device, and the melt viscosity at the zero shear rate from the measured value in the region where the melt viscosity is not dependent on the shear rate. Is obtained by extrapolating.

The invention according to claim 4 is the invention according to any one of claims 1 to 3 , wherein the film thickness obtained by the film formation is 30 to 300 μm, the in-plane retardation Re is 0 to 10 nm, and the thickness direction. The retardation Rth is 0 to 20 nm.

  According to the present invention, it is possible to produce a cellulose acylate film suitable for an optical film having high thickness accuracy, no streak failure, and suppressed retardation, and therefore has a thickness of 30 to 300 μm. A cellulose acylate film having an inner retardation (Re) of 0 to 10 nm and a thickness direction retardation (Rth) of 0 to 20 nm can be produced.

The invention according to claim 5 is a cellulose acylate film produced by the production method according to any one of claims 1 to 4 .

  According to the present invention, a cellulose acylate film having good optical properties can be obtained.

A sixth aspect of the present invention is an optical compensation film for a liquid crystal display panel using the cellulose acylate film according to the fifth aspect as a base material, and a seventh aspect is a polarizing element for the cellulose acylate film according to the fifth aspect. It is a polarizing plate formed using at least one sheet as a protective film for the film.

Since the cellulose acylate film of claim 5 has high optical properties, it is suitable for an optical compensation film for a liquid crystal display panel or a polarizing plate.

  According to the present invention, it is possible to prevent streak failure and suppress retardation when forming a film by sandwiching a molten resin between a pair of rollers and solidifying at a high film forming speed. Further, it is possible to provide a cellulose acylate film capable of obtaining a film for optical use with uniform optical characteristics and a method for producing the same.

  Hereinafter, preferred embodiments of a cellulose acylate film and a method for producing the same according to the present invention will be described with reference to the accompanying drawings. In the present embodiment, a case where a film is formed by a touch roll method in which resin extruded from a die is cooled while being sandwiched between a pair of rollers, and the pressing roller is a metal elastic roller will be described.

  As shown in FIG. 1, the manufacturing apparatus 10 mainly includes a film forming process unit 14 that manufactures an unstretched cellulose acylate film 12 and a winding process unit 20 that winds up the cellulose acylate film 12.

  In the film forming process section 14, the cellulose acylate resin melted by the extruder 22 is discharged from the die 24 into a sheet shape and supplied between a pair of rotating metal rollers 26 and 28. Then, after the cellulose acylate film 12 cooled and solidified on the cooling roller 28 is peeled off from the roller 28, it is wound up in a roll shape by the winding process section 20. Thereby, the stretched cellulose acylate film 12 is manufactured. Hereinafter, details of each process part will be described.

  Here, when a film is formed by cooling and solidifying with a pair of metal rollers 26 and 27 at a film forming speed Y (see FIG. 3) of 20 m / min or more, the cellulose acylate resin has a weight average molecular weight. 70 to 200,000, where A is the substitution degree of the acetyl group and B is the substitution degree of the propionyl group, 2.7 ≦ A + B ≦ 3.0, 0 ≦ A ≦ 0.7. It is adjusted to satisfy 3 ≦ B ≦ 3.0. In general, when a cellulose acylate film is formed at a high film forming speed, retardation occurs when the cellulose acylate resin is sandwiched between the pair of rollers 26 and 28. Therefore, the expression of retardation was suppressed by adjusting the weight average molecular weight of the cellulose acylate resin and the substitution degree of the acetyl group and the substitution degree of the propionyl group. Actually, when the weight average molecular weight is 70,000 to 200,000, and A is the substitution degree of the acetyl group and B is the substitution degree of the propionyl group, 2.7 ≦ A + B ≦ 3.0, 0 ≦ Cellulose acylate resin satisfying A ≦ 0.7 and 2.3 ≦ B ≦ 3.0, and the cellulose acylate film is manufactured with a pair of metal rollers 26 and 28 at a film forming speed of 20 m / min or more. Even if the film is formed, the occurrence of streak failure can be prevented, the thickness accuracy can be improved, and the occurrence of retardation can be suppressed. The cellulose acylate resin has a weight average molecular weight of 100,000 to 170,000, and 2.85 ≦ A + B ≦ 2.95, 0 ≦ A ≦ 0.5, 2.5 ≦ B ≦ 3.0, It is more preferable to satisfy

  FIG. 2 shows a single screw extruder 22 of the film forming process section 14. As shown in FIG. 2, a single screw 38 having a flight 36 on a screw shaft 34 is disposed in the cylinder 32, and cellulose acylate resin is supplied into the cylinder 32 through a supply port 40 from a hopper (not shown). The In the cylinder 32, in order from the supply port 40 side, a supply unit (region indicated by A) for quantitatively transporting the cellulose acylate resin supplied from the supply port 40, and a compression unit (at B) for kneading and compressing the cellulose acylate resin And a measuring section (area indicated by C) for measuring the kneaded and compressed cellulose acylate resin. The cellulose acylate resin melted by the extruder 22 is continuously sent from the discharge port 42 to the die 24.

  The screw compression ratio of the extruder 22 is set to 2.5 to 4.5, and L / D is set to 20 to 50. Here, the screw compression ratio is represented by the volume ratio between the supply unit A and the metering unit C, that is, the volume per unit length of the supply unit A ÷ the volume per unit length of the metering unit C. Is calculated using the outer diameter d1 of the screw shaft 34, the outer diameter d2 of the screw shaft 34 of the measuring section C, the groove diameter a1 of the supply section A, and the groove diameter a2 of the measuring section C. L / D is the ratio of the cylinder length (L) to the cylinder inner diameter (D) in FIG. Moreover, extrusion temperature is set to 190-240 degreeC. When the temperature in the extruder 22 exceeds 240 ° C., a cooler (not shown) may be provided between the extruder 22 and the die 24.

  The extruder 22 may be a single-screw extruder or a twin-screw extruder. However, if the screw compression ratio is less than 2.5 and is too small, the extruder 22 is not sufficiently kneaded, and an undissolved part is generated, or a shear heating is generated. Is small and the melting of the crystals is insufficient, and fine crystals are likely to remain in the cellulose acylate film after production, and bubbles are more likely to be mixed. Thereby, when the cellulose acylate film 12 is stretched, the remaining crystals inhibit the stretchability and the orientation cannot be sufficiently increased. On the other hand, if the screw compression ratio exceeds 4.5 and is too large, the shear stress is excessively applied and the resin is easily deteriorated due to heat generation, so that the cellulose acylate film after production is easily yellowed. On the other hand, if the shear stress is excessively applied, the molecules are cut and the molecular weight is lowered, so that the mechanical strength of the film is lowered. Therefore, the screw compression ratio is preferably in the range of 2.5 to 4.5, more preferably 2.8 to 4. in order to make the cellulose acylate film after production hardly yellow and hardly break. Is in the range of 2, particularly preferably in the range of 3.0 to 4.0.

  On the other hand, if the L / D is less than 20 and is too small, melting and kneading are insufficient, and fine crystals are likely to remain in the cellulose acylate film after production as in the case where the compression ratio is small. Conversely, if the L / D exceeds 50 and is too large, the residence time of the cellulose acylate resin in the extruder 22 becomes too long, and the resin is liable to deteriorate. In addition, when the residence time is long, the molecules are cut, the molecular weight is lowered, and the mechanical strength of the film is lowered. Therefore, L / D is preferably in the range of 20 to 50, preferably in the range of 22 to 45, and particularly preferably in the range of 24 to 45, in order to make the cellulose acylate film after production hardly yellowish and difficult to stretch and break. A range of 40.

  Also, if the extrusion temperature is too low below 190 ° C., the crystals will not be sufficiently melted, and fine crystals will tend to remain in the cellulose acylate film after production, and the cellulose acylate film will be stretched when stretched. The orientation is hindered and the orientation cannot be sufficiently increased. On the other hand, if the extrusion temperature exceeds 240 ° C. and is too high, the cellulose acylate resin is deteriorated and the degree of yellowness (YI value) is deteriorated. Therefore, in order to make the cellulose acylate film after production hardly yellow and stretch and break, the extrusion temperature is preferably 190 ° C to 240 ° C, preferably 195 ° C to 235 ° C, particularly preferably 200 ° C. It is the range of ° C-230 ° C.

  The cellulose acylate resin is melted using the extruder 22 configured as described above, and this molten resin is continuously supplied to the die 24 and discharged from the tip (lower end) of the die 24 in a sheet form. The zero shear viscosity of the cellulose acylate resin when discharged is preferably 2000 Pa · sec or less. If the zero shear viscosity exceeds 2000 Pa · sec, the molten resin discharged from the die spreads immediately after discharge and tends to adhere to the tip of the die, which becomes dirty and easily causes streak failure. . The discharged molten resin is supplied between the rollers 26 and 28 (see FIG. 1).

  FIG. 3 shows an embodiment of the rollers 26 and 28. One of the rollers 26 and 28 is a metal elastic roller 26, and the other roller is a metal cooling roller 28.

  The rollers 26 and 28 are preferably made of a metal material and have a mirror surface or a state close to the mirror surface, and the arithmetic average height Ra is 100 nm or less, preferably 50 nm or less, more preferably 25 nm or less. Mirrored. The rollers 26 and 28 are configured to be able to control their surface temperatures. For example, by circulating a liquid medium such as water inside the rollers 26 and 28, the surface temperatures can be controlled. .

  Of the pair of rollers 26, 28, the roller 26 is formed with a smaller diameter than the other roller 28, and the surface can control the surface temperature with high accuracy. The elastic roller 26 includes an outer cylinder 44, a liquid medium layer 46, an elastic body layer (inner cylinder) 48, and a metal shaft 50 in this order from the outer layer. The outer cylinder 44 and the inner cylinder 48 of the elastic roller 26 are rotated by the rotation of the cooling roller 28 that is in contact with the sheet. When the sheet is sandwiched between the pair of rollers 26, 28, the elastic roller 26 receives a reaction force from the cooling roller 28 via the sheet and elastically deforms into a concave shape following the surface of the cooling roller 28. Accordingly, the elastic roller 26 and the cooling roller 28 are in surface contact with the sheet, and the cooling roller 28 is pressed while the sandwiched sheet is pressed into a planar shape by a restoring force that restores the elastically deformed elastic roller 26 to its original shape. Cooled by. The outer cylinder 44 is made of a metal thin film and preferably has a seamless structure without a welded joint. The wall thickness Z of the outer cylinder 44 is preferably in the range of 0.2 mm to 7.0 mm. Here, when the thickness Z of the outer cylinder 44 of the elastic roller is 0.2 mm or less, not only the restoring force is small and the surface quality improvement effect cannot be obtained, but also the roller strength is weakened. Further, if it is 7.0 mm or more, elasticity is not obtained and the effect of eliminating the residual strain does not appear.

Further, when the glass transition temperature Tg (° C.) of the cellulose acylate resin−the temperature (° C.) of the elastic roller 26 is X (° C.) and the film forming speed in the film forming step is Y (m / min), 0.0043 X It is preferable to set the film forming speed Y and the temperature of the pressure roller 26 so as to satisfy ² + 0.12X + 1.1 <Y <0.019X ² + 0.73X + 24. When the film formation speed Y is 0.0043X ² + 0.12X + 1.1 or less, the pressing time is too long and residual distortion occurs in the film. When the film formation speed Y is 0.019X ² + 0.73X + 24 or more, cooling is performed. This is because the film is too short to slowly cool the film and sticks to the elastic roller 26. For example, when the Tg of the cellulose acylate resin is 120 ° C., when the temperature of the cooling roller 26 is 115 ° C., 90 ° C., and 60 ° C., the residual strain appears in the film because the film forming speed Y is 1 m / min. When the film forming speed Y is 29 m / min, 64 m / min, or 137 m / min, the film is stuck to the elastic roller. Experiments were also performed on various resins, and the relational expression between X and Y was obtained from these experimental data. The temperature of the cooling roller 28 needs to be within ± 20 ° C. with respect to the temperature of the elastic roller 26, preferably within ± 15 ° C., and more preferably ± 10 ° C.

Further, the length Q (cm) that the elastic roller 26 of the pair of rollers 26 and 28 and the cooling roller 27 are in contact with each other via the sheet is set, and the linear pressure that sandwiches the sheet between the elastic roller 26 and the cooling roller 27 is P. It is preferable to set the linear pressure P and the contact length Q so as to satisfy 3 kg / cm ² <P / Q <50 kg / cm ² . Here, if P / Q is 3 kg / cm ² or less, the pressing force for pressing the sheet in a planar shape is too small to have a surface improvement effect, and if P / Q is 50 kg / cm ² or more, the pressing force is If the film is too large, residual distortion occurs in the film and retardation is developed.

  According to the film forming process section 14 configured as described above, by discharging the cellulose acylate resin from the die 24, the discharged cellulose acylate resin has a very slight liquid pool between the pair of rollers 26 and 28. (Bank) is formed, and this cellulose acylate resin is sandwiched between a pair of rollers 26 and 28 to form a sheet while the thickness is adjusted. At that time, the elastic roller 26 receives a reaction force from the cooling roller 28 via the sheet and elastically deforms in a concave shape following the surface of the cooling roller 28, and the sheet is pressed into a surface shape by the elastic roller 26 and the cooling roller 28. The When a film is formed by cooling and solidifying a sheet by sandwiching between a pair of metal rollers configured in this way, cellulose acylate is used even when the film forming speed is as high as 20 m / min or more. The resin has a weight average molecular weight of 70,000 to 200,000, and when A is the substitution degree of the acetyl group and B is the substitution degree of the propionyl group, 2.7 ≦ A + B ≦ 3.0, 0 ≦ A By satisfying ≦ 0.7, 2.3 ≦ B ≦ 3.0, it is possible to suppress the occurrence of streak failure and retardation of the film, and further suppress the expression of retardation Re and Rth of the film. Therefore, it is possible to obtain a cellulose acylate film having good thickness accuracy and suitable for optical applications having uniform optical characteristics in the width direction and the longitudinal direction.

  Further, according to the film forming process section 14 configured as described above, the cellulose acylate film 12 having a film thickness of 20 to 300 μm, an in-plane retardation Re of 20 nm or less, and a thickness direction retardation Rth of 20 nm or less. Can be manufactured.

  Here, the retardations Re and Rth are obtained by the following equations.

Re (nm) = | n (MD) −n (TD) | × T (nm)
Rth (nm) = | {(n (MD) + n (TD)) / 2} −n (TH) | × T (nm)
In the formula, n (MD), n (TD), and n (TH) represent the refractive index in the longitudinal direction, the width direction, and the thickness direction, and T represents the thickness in nm.

The film 12 sandwiched between the pair of rollers 26 and 28 is wound around the cooling roller 28 and cooled, and then peeled off from the surface of the cooling roller 28, and is rolled in the winding process unit 20 via the pass roll 17. Rolled up. At that time, the winding tension of the cellulose acylate film 12 is preferably 0.02 kg / mm ² or less. By setting the winding tension within such a range, the stretched cellulose acylate film 12 can be wound without causing a retardation distribution.

  Below, the cellulose acylate resin suitable for this invention, the processing method of a cellulose acylate film, etc. are demonstrated in detail along a procedure.

(1) Plasticizer It is preferable to add a polyhydric alcohol plasticizer to the resin for producing the cellulose acylate film in the present invention. Such a plasticizer not only lowers the elastic modulus, but also has an effect of reducing the difference in crystal amount between the front and back sides. The content of the polyhydric alcohol plasticizer is preferably 2 to 20% by weight based on the cellulose acylate. The content of the polyhydric alcohol plasticizer is preferably 2 to 20% by weight, more preferably 3 to 18% by weight, and still more preferably 4 to 15% by weight.

When the content of the polyhydric alcohol plasticizer is less than 2% by weight, the above effect is not sufficiently achieved. On the other hand, when the content is more than 20% by weight, crying out (plasticizer surface deposition) occurs.
The polyhydric alcohol plasticizer that can be specifically used in the present invention has good compatibility with cellulose fatty acid esters, and glycerin ester compounds such as glycerin esters and diglycerin esters in which the thermoplastic effect is remarkable, Examples thereof include polyalkylene glycols such as polyethylene glycol and polypropylene glycol, and compounds in which an acyl group is bonded to a hydroxyl group of polyalkylene glycol.

  Specific glycerin esters include glycerin diacetate stearate, glycerin diacetate palmitate, glycerin diacetate myristate, glycerin diacetate laurate, glycerin diacetate caprate, glycerin diacetate nonanate, glycerin diacetate octanoate, Glycerin diacetate heptanoate, glycerol diacetate hexanoate, glycerol diacetate pentanoate, glycerol diacetate oleate, glycerol acetate dicaprate, glycerol acetate dinonanoate, glycerol acetate dioctanoate, glycerol acetate diheptanoate , Glycerol acetate dicaproate, glycerol acetate divalerate, glycerol acetate dibu Glycerol dipropionate caprate, glycerol dipropionate laurate, glycerol dipropionate myristate, glycerol dipropionate palmitate, glycerol dipropionate stearate, glycerol dipropionate oleate, glycerol tributyrate, glycerol tri Examples include but are not limited to pentanoate, glycerin monopalmitate, glycerin monostearate, glycerin distearate, glycerin propionate laurate, glycerin oleate propionate, and these are used alone or in combination. be able to.

  Among these, glycerol diacetate caprylate, glycerol diacetate pelargonate, glycerol diacetate caprate, glycerol diacetate laurate, glycerol diacetate myristate, glycerol diacetate palmitate, glycerol diacetate stearate, glycerol diacetate oleate preferable.

  Specific examples of diglycerin esters include diglycerin tetraacetate, diglycerin tetrapropionate, diglycerin tetrabutyrate, diglycerin tetravalerate, diglycerin tetrahexanoate, diglycerin tetraheptanoate, diglyceride. Glycerin tetracaprylate, diglycerol tetrapelargonate, diglycerol tetracaprate, diglycerol tetralaurate, diglycerol tetramyristate, diglycerol tetrapalmitate, diglycerol triacetate propionate, diglycerol triacetate butyrate, diglycerol Triacetate valerate, diglycerin triacetate hexanoate, diglycerin triacetate heptanoate, diglycerin triacetate caprylate, Glycerin triacetate pelargonate, diglycerol triacetate caprate, diglycerol triacetate laurate, diglycerol triacetate myristate, diglycerol triacetate palmitate, diglycerol triacetate stearate, diglycerol triacetate oleate, diglycerol diacetate dipropionate, diglycerol Diacetate dibutyrate, diglycerol diacetate divalerate, diglycerol diacetate dihexanoate, diglycerol diacetate diheptanoate, diglycerol diacetate dicaprylate, diglycerol diacetate dipelargonate, diglycerol di Acetate dicaprate, diglycerin diacetate dilaurate, diglycerin diacetate dimisti Diglycerin diacetate dipalmitate, diglycerin diacetate distearate, diglycerin diacetate dioleate, diglyceryl acetate tripropionate, diglyceryl acetate tributyrate, diglyceryl acetate trivalerate, diglyceryl acetate tri Hexanoate, diglycerol acetate triheptanoate, diglycerol acetate tricaprylate, diglycerol acetate tripelargonate, diglycerol acetate tricaprate, diglycerol acetate trilaurate, diglycerol acetate trimyristate, diglycerol acetate tri Palmitate, Diglycerol acetate tristearate, Diglycerol acetate trioleate, Diglycerol laurate, Jig Examples include, but are not limited to, mixed acid esters of diglycerin such as glycerin stearate, diglycerin caprylate, diglycerin myristate, and diglycerin oleate, and these can be used alone or in combination.

  Among these, diglycerin tetraacetate, diglycerin tetrapropionate, diglycerin tetrabutyrate, diglycerin tetracaprylate, and diglycerin tetralaurate are preferable.

  Specific examples of the polyalkylene glycol include polyethylene glycol and polypropylene glycol having an average molecular weight of 200 to 1000, but are not limited thereto, and these can be used alone or in combination.

  Specific examples of the compound in which an acyl group is bonded to the hydroxyl group of polyalkylene glycol include polyoxyethylene acetate, polyoxyethylene propionate, polyoxyethylene butyrate, polyoxyethylene valerate, polyoxyethylene caproate, Polyoxyethylene heptanoate, polyoxyethylene octanoate, polyoxyethylene nonanate, polyoxyethylene caprate, polyoxyethylene laurate, polyoxyethylene myristate, polyoxyethylene palmitate, polyoxyethylene stearate , Polyoxyethylene oleate, polyoxyethylene linoleate, polyoxypropylene acetate, polyoxypropylene propionate, polyoxypropylene butyrate, polyoxypropylene Valerate, polyoxypropylene caproate, polyoxypropylene heptanoate, polyoxypropylene octanoate, polyoxypropylene nonanoate, polyoxypropylene caprate, polyoxypropylene laurate, polyoxypropylene myristate, polyoxy Examples thereof include propylene palmitate, polyoxypropylene stearate, polyoxypropylene oleate, and polyoxypropylene linoleate, but are not limited thereto, and these can be used alone or in combination.

  Furthermore, in order to sufficiently develop the above-described effects of these polyhydric alcohols, it is preferable to melt and form a cellulose acylate under the following conditions. That is, pellets obtained by mixing cellulose acylate and polyhydric alcohol are melted with an extruder and extruded from a T die to form a film, but it is preferable that the extruder outlet temperature (T2) is higher than the extruder inlet temperature (T1). More preferably, the die temperature (T3) is higher than T2. That is, it is preferable to raise the temperature as the melting proceeds. When the temperature is rapidly increased from the inlet, the polyhydric alcohol is first dissolved and liquefied. In this, the cellulose acylate becomes floating, and a sufficient shearing force cannot be received from the screw, and insoluble matter is generated. Those which are not sufficiently mixed cannot exhibit the effect of the plasticizer as described above, and the effect of suppressing the difference between the front and back of the melt film after melt extrusion cannot be obtained. Further, such poorly dissolved substances become fish-eye foreign substances after film formation. Such foreign matter does not become a bright spot even when observed with a polarizing plate, but rather can be visually recognized by projecting light from the back of the film and observing it in a screen form. In addition, fisheye causes tailing at the die exit and increases the die line.

  T1 is preferably 150 to 200 ° C, more preferably 160 to 195 ° C, and still more preferably 165 ° C to 190 ° C. T2 is preferably in the range of 190 to 240 ° C, more preferably 200 to 230 ° C, and even more preferably 200 to 225 ° C. It is important that the melting temperatures T1 and T2 are 240 ° C. or lower. When this temperature is exceeded, the elastic modulus of the film-forming film tends to increase. This is probably because cellulose acylate is decomposed due to melting at a high temperature, which causes cross-linking and increases the elastic modulus. The die temperature T3 is preferably 200 to 235 ° C, more preferably 205 to 230 ° C, and still more preferably 205 ° C to 225 ° C.

(2) Stabilizer In the present invention, it is preferable to use either or both of a phosphite compound and a phosphite compound as a stabilizer. Thereby, deterioration over time can be suppressed and the die line can be improved. This is because these compounds function as a leveling agent to eliminate the die line formed by the unevenness of the die. The blending amount of these stabilizers is preferably 0.005 to 0.5% by weight, more preferably 0.01 to 0.4% by weight, still more preferably 0.02 to 0.3% by weight. %.

(I) Phosphite stabilizer The specific phosphite stabilizer is not particularly limited, but the phosphite stabilizer shown in Chemical Formulas 1 to 3 is preferable.

（ここで、Ｒ1、Ｒ2，Ｒ3、Ｒ4、Ｒ5、Ｒ6、Ｒ’1、Ｒ’2、Ｒ’3・・・Ｒ’ｎ、Ｒ’ｎ＋１は水素又は炭素数４〜２３のアルキル、アリール、アルコキシアルキル、アリールオキシアルキル、アルコキシアリール、アリールアルキル、アルキルアリール、ポリアリールオキシアルキル、ポリアルコキシアルキル及びポリアルコキシアリール基から成る群から選択された基を示す。但し、一般式（２）（３）（４）の各同一式中で全てが水素になることはない。一般式（３）中で示されるホスファイト系着色防止剤中のＸは脂肪族鎖、芳香核を側鎖に有する脂肪族鎖、芳香核を鎖中に有する脂肪族鎖及び上記鎖中に２個以上連続しない酸素原子を包含する鎖から成る群から選択された基を示す。また、ｋ、ｑは１以上の整数、ｐは３以上の整数を示す。）
これらのホスファイト系着色防止剤のｋ、ｑの数は好ましくは１〜１０である。ｋ、ｑの数が１以上にすることで加熱時の揮発性が小さくなり、１０以下にすることでセルロースアセテートプロピオネートとの相溶性が向上するため好ましい。また、ｐの値は３〜１０が好ましい。３以上のすることで加熱時の揮発性が小さくなり、１０以下にすることでセルロースアセテートプロピオネートとの相溶性が向上するため好ましい。

(Where R1, R2, R3, R4, R5, R6, R′1, R′2, R′3... R′n, R′n + 1 are hydrogen or alkyl having 4 to 23 carbon atoms, aryl, A group selected from the group consisting of alkoxyalkyl, aryloxyalkyl, alkoxyaryl, arylalkyl, alkylaryl, polyaryloxyalkyl, polyalkoxyalkyl and polyalkoxyaryl groups, provided that they are represented by the general formulas (2) (3) In the same formula (4), not all are hydrogen.X in the phosphite colorant represented by the general formula (3) is an aliphatic having an aliphatic chain and an aromatic nucleus in the side chain. A group selected from the group consisting of a chain, an aliphatic chain having an aromatic nucleus in the chain, and a chain including two or more non-continuous oxygen atoms in the chain, and k and q are integers of 1 or more, p represents an integer of 3 or more.
The numbers of k and q in these phosphite colorants are preferably 1 to 10. When the number of k and q is 1 or more, volatility during heating is reduced, and when it is 10 or less, compatibility with cellulose acetate propionate is improved, which is preferable. The value of p is preferably 3-10. By making it 3 or more, the volatility at the time of a heating becomes small, and since compatibility with a cellulose acetate propionate improves by making it 10 or less, it is preferable.

  As specific examples of the phosphite-based anti-coloring agent represented by the following general formula (2), those represented by the following formulas (5) to (8) are preferable.

また、下記一般式（３）で表されるホスファイト系着色防止剤の具体例としては、下記式（９）（１０）（１１）で表されるものが好ましい。

Moreover, what is represented by following formula (9) (10) (11) as a specific example of the phosphite type | system | group coloring inhibitor represented by following General formula (3) is preferable.

（ii）亜リン酸エステル系安定剤
亜リン酸エステル系安定剤は、例えばサイクリックネオペンタンテトライルビス（オクタデシル）ホスファイト、サイクリックネオペンタンテトライルビス（２，４−ジ−ｔ−ブチルフェニル）ホスファイト、サイクリックネオペンタンテトライルビス（２，６−ジ−ｔ−ブチル−４−メチルフェニル）ホスファイト、２，２−メチレンビス（４，６−ジ−ｔ−ブチルフェニル）オクチルホスファイト、トリス（２，４−ジ−ｔ−ブチルフェニル）ホスファイト等が挙げられる。

(Ii) Phosphite ester stabilizer The phosphite ester stabilizer is, for example, cyclic neopentanetetraylbis (octadecyl) phosphite, cyclic neopentanetetraylbis (2,4-di-t-butyl). Phenyl) phosphite, cyclic neopentanetetraylbis (2,6-di-t-butyl-4-methylphenyl) phosphite, 2,2-methylenebis (4,6-di-t-butylphenyl) octylphos Phyto, tris (2,4-di-t-butylphenyl) phosphite and the like can be mentioned.

(Iii) Other stabilizers A weak organic acid, a thioether compound, an epoxy compound or the like may be added as a stabilizer.
The weak organic acid is not particularly limited as long as it has a pKa of 1 or more, does not interfere with the action of the present invention, and has coloring prevention properties and physical property deterioration prevention properties. Examples thereof include tartaric acid, citric acid, malic acid, fumaric acid, oxalic acid, succinic acid, maleic acid and the like. These may be used alone or in combination of two or more.

  Examples of the thioether compound include dilauryl thiodipropionate, ditridecyl thiodipropionate, dimyristyl thiodipropionate, distearyl thiodipropionate, and palmityl stearyl thiodipropionate. It may be used in combination, or two or more may be used in combination.

  Examples of the epoxy compound include those derived from epichlorohydrin and bisphenol A, such as derivatives from epichlorohydrin and glycerin, vinylcyclohexene dioxide, and 3,4-epoxy-6-methylcyclohexylmethyl-3,4-epoxy-6. -Cyclic ones such as methylcyclohexanecarboxylate can also be used. Epoxidized soybean oil, epoxidized castor oil, long chain α-olefin oxides, and the like can also be used. These may be used alone or in combination of two or more.

(3) Cellulose acylate << cellulose acylate resin >>
(Composition / Degree of substitution)
The cellulose acylate used in the present invention is preferably a cellulose acylate that satisfies all the requirements represented by the following formulas (1) to (3).

2.7 ≦ A + B ≦ 3.0 Formula (1)
0 ≦ A ≦ 0.7 Formula (2)
2.3 ≦ B ≦ 3.0 Formula (3)
(In the above formulas (1) to (3), A represents the substitution degree of the acetyl group, and B represents the total substitution degree of the propionyl group.)
More preferably,
2.85 ≦ A + B ≦ 2.95 Formula (4)
0 ≦ A ≦ 0.5 Formula (5)
2.5 ≦ B ≦ 3.0 Formula (6)
These cellulose acylates may be used alone or in combination of two or more. Further, a polymer component other than cellulose acylate may be appropriately mixed.

  Next, the manufacturing method of the cellulose acylate of this invention is demonstrated in detail. The raw material cotton and the synthesis method of the cellulose acylate of the present invention are also described in detail on pages 7 to 12 of the Journal of the Invention of the Invention (Public Technical Number 2001-1745, issued on March 15, 2001, Invention Association). Are listed.

(Raw material and pretreatment)
As the cellulose raw material, those derived from hardwood pulp, softwood pulp and cotton linter are preferably used. As the cellulose raw material, it is preferable to use a high-purity material having an α-cellulose content of 92% by mass or more and 99.9% by mass or less.

  When the cellulose raw material is in the form of a film or a lump, it is preferable that the cellulose is pulverized in advance, and it is preferable that the pulverization proceeds until the cellulose is in a fluff form.

(activation)
Prior to acylation, the cellulose raw material is preferably subjected to a treatment (activation) for contact with an activator. As the activator, carboxylic acid or water can be used. However, when water is used, an excess of acid anhydride is added after activation to perform dehydration or to replace water. It is preferable to include a step of washing with an acid or adjusting acylation conditions. The activator may be added by adjusting to any temperature, and the addition method can be selected from spraying, dropping, dipping and the like.

  Preferred carboxylic acids as activators are carboxylic acids having 2 to 7 carbon atoms (for example, acetic acid, propionic acid, butyric acid, 2-methylpropionic acid, valeric acid, 3-methylbutyric acid, 2-methylbutyric acid, 2,2 -Dimethylpropionic acid (pivalic acid), hexanoic acid, 2-methylvaleric acid, 3-methylvaleric acid, 4-methylvaleric acid, 2,2-dimethylbutyric acid, 2,3-dimethylbutyric acid, 3,3-dimethylbutyric acid , Cyclopentanecarboxylic acid, heptanoic acid, cyclohexanecarboxylic acid, benzoic acid, etc.), more preferably acetic acid, propionic acid, or butyric acid, and particularly preferably acetic acid.

  In the activation, an acylation catalyst such as sulfuric acid can be further added as necessary. However, when a strong acid such as sulfuric acid is added, depolymerization may be promoted. Therefore, the addition amount is preferably limited to about 0.1% by mass to 10% by mass with respect to cellulose. Two or more kinds of activators may be used in combination, or an acid anhydride of a carboxylic acid having 2 to 7 carbon atoms may be added.

  The addition amount of the activator is preferably 5% by mass or more, more preferably 10% by mass or more, and particularly preferably 30% by mass or more based on cellulose. It is preferable that the amount of the activator is equal to or more than the lower limit value because problems such as a decrease in the degree of activation of cellulose do not occur. The upper limit of the addition amount of the activator is not particularly limited as long as productivity is not lowered, but it is preferably 100 times or less, more preferably 20 times or less, and 10 times or less by mass with respect to cellulose. It is particularly preferred that Activation may be carried out by adding a large excess of activator to cellulose, and then the amount of the activator may be reduced by performing operations such as filtration, air drying, heat drying, distillation under reduced pressure, and solvent substitution.

  The activation time is preferably 20 minutes or more, and the upper limit is not particularly limited as long as it does not affect the productivity, but is preferably 72 hours or less, more preferably 24 hours or less, particularly preferably. 12 hours or less. The activation temperature is preferably 0 ° C. or higher and 90 ° C. or lower, more preferably 15 ° C. or higher and 80 ° C. or lower, and particularly preferably 20 ° C. or higher and 60 ° C. or lower. The step of activating cellulose can also be performed under pressure or reduced pressure. Moreover, you may use electromagnetic waves, such as a microwave and infrared rays, as a heating means.

(Acylation)
In the method for producing cellulose acylate in the present invention, it is preferable to acylate a hydroxyl group of cellulose by adding an acid anhydride of carboxylic acid to cellulose and reacting with Bronsted acid or Lewis acid as a catalyst.

  As a method for obtaining a cellulose mixed acylate, a method of reacting two carboxylic acid anhydrides as an acylating agent by mixing or sequentially adding them, a mixed acid anhydride of two carboxylic acids (for example, acetic acid / propionic acid mixed acid anhydride) Product), mixed acid anhydride (for example, acetic acid / propionic acid mixed acid anhydride) in the reaction system using carboxylic acid and another carboxylic acid anhydride (for example, acetic acid and propionic acid anhydride) as raw materials And a method in which cellulose acylate having a degree of substitution of less than 3 is once synthesized, and a remaining hydroxyl group is further acylated with an acid anhydride or acid halide. .

(Acid anhydride)
The acid anhydride of the carboxylic acid preferably has 2 to 7 carbon atoms as the carboxylic acid. For example, acetic anhydride, propionic anhydride, butyric anhydride, 2-methylpropionic anhydride, valeric anhydride 3-methylbutyric anhydride, 2-methylbutyric anhydride, 2,2-dimethylpropionic anhydride (pivalic anhydride), hexanoic anhydride, 2-methylvaleric anhydride, 3-methylvaleric anhydride 4-methylvaleric anhydride, 2,2-dimethylbutyric anhydride, 2,3-dimethylbutyric anhydride, 3,3-dimethylbutyric anhydride, cyclopentanecarboxylic anhydride, heptanoic anhydride, cyclohexane Examples thereof include carboxylic acid anhydrides and benzoic acid anhydrides. More preferred are acetic anhydride, propionic anhydride, butyric anhydride, valeric anhydride, hexanoic anhydride, heptanoic anhydride and the like, and particularly preferred are acetic anhydride, propionic anhydride, butyric acid. Anhydrous.

  For the purpose of preparing a mixed ester, it is preferable to use these acid anhydrides in combination. The mixing ratio is preferably determined according to the substitution ratio of the target mixed ester. The acid anhydride is usually added in excess equivalent to the cellulose. That is, it is preferable to add 1.2-50 equivalent with respect to the hydroxyl group of a cellulose, It is more preferable to add 1.5-30 equivalent, It is especially preferable to add 2-10 equivalent.

(catalyst)
It is preferable to use a Bronsted acid or a Lewis acid as the acylation catalyst used in the production of cellulose acylate in the present invention. The definitions of Bronsted acid and Lewis acid are described in, for example, “Physical and Chemical Dictionary”, 5th edition (2000). Examples of preferable Bronsted acid include sulfuric acid, perchloric acid, phosphoric acid, methanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid and the like. Examples of preferred Lewis acids include zinc chloride, tin chloride, antimony chloride, magnesium chloride and the like.

  As the catalyst, sulfuric acid or perchloric acid is more preferable, and sulfuric acid is particularly preferable. The preferable addition amount of a catalyst is 0.1-30 mass% with respect to a cellulose, More preferably, it is 1-15 mass%, Most preferably, it is 3-12 mass%.

(solvent)
In carrying out acylation, a solvent may be added for the purpose of adjusting viscosity, reaction rate, stirring property, acyl substitution ratio, and the like. As such a solvent, dichloromethane, chloroform, carboxylic acid, acetone, ethyl methyl ketone, toluene, dimethyl sulfoxide, sulfolane and the like can be used, but preferably carboxylic acid, for example, having 2 to 7 carbon atoms. Carboxylic acids {eg acetic acid, propionic acid, butyric acid, 2-methylpropionic acid, valeric acid, 3-methylbutyric acid, 2-methylbutyric acid, 2,2-dimethylpropionic acid (pivalic acid), hexanoic acid, 2-methylyoshi Herbic acid, 3-methylvaleric acid, 4-methylvaleric acid, 2,2-dimethylbutyric acid, 2,3-dimethylbutyric acid, 3,3-dimethylbutyric acid, cyclopentanecarboxylic acid} and the like. More preferably, acetic acid, propionic acid, butyric acid and the like can be mentioned. These solvents may be used as a mixture.

(Conditions for acylation)
When acylation is performed, an acid anhydride and a catalyst, and further, if necessary, a solvent may be mixed and then mixed with cellulose, or these may be separately mixed with cellulose. It is preferable to prepare a mixture of an acid anhydride and a catalyst or a mixture of an acid anhydride, a catalyst and a solvent as an acylating agent and then react with cellulose. In order to suppress an increase in temperature in the reaction vessel due to reaction heat during acylation, the acylating agent is preferably cooled in advance. The cooling temperature is preferably −50 ° C. to 20 ° C., more preferably −35 ° C. to 10 ° C., and particularly preferably −25 ° C. to 5 ° C. The acylating agent may be added in liquid form or may be frozen and added as a crystal, flake, or block solid.

  Further, the acylating agent may be added to the cellulose at once or dividedly. In addition, cellulose may be added to the acylating agent all at once or in divided portions. When the acylating agent is added in portions, the same acylating agent or a plurality of different acylating agents may be used. As a preferred example, 1) a mixture of acid anhydride and solvent is added first, then the catalyst is added, and 2) a mixture of part of acid anhydride, solvent and catalyst is added first, then the rest of the catalyst and Add solvent mixture 3) Add acid anhydride and solvent mixture first, then add catalyst and solvent mixture 4) Add solvent first, acid anhydride and catalyst mixture or acid For example, a mixture of an anhydride, a catalyst, and a solvent may be added.

  Although acylation of cellulose is an exothermic reaction, in the method for producing the cellulose acylate of the present invention, it is preferable that the maximum temperature reached during acylation is 50 ° C. or lower. If the reaction temperature is lower than this temperature, depolymerization proceeds and it is preferable because there is no inconvenience such as difficulty in obtaining a cellulose acylate having a polymerization degree suitable for the use of the present invention. The maximum temperature reached during acylation is preferably 45 ° C. or lower, more preferably 40 ° C. or lower, and particularly preferably 35 ° C. or lower. The reaction temperature may be controlled using a temperature control device or may be controlled by the initial temperature of the acylating agent. The reaction temperature can also be controlled by reducing the pressure of the reaction vessel and the heat of vaporization of the liquid component in the reaction system. Since the exotherm during the acylation is large in the initial stage of the reaction, it is possible to control such as cooling in the initial stage of the reaction and heating thereafter. The end point of acylation can be determined by means such as light transmittance, solution viscosity, temperature change of the reaction system, solubility of the reaction product in an organic solvent, and observation with a polarizing microscope.

  The minimum reaction temperature is preferably −50 ° C. or higher, more preferably −30 ° C. or higher, and particularly preferably −20 ° C. or higher. The acylation time is preferably 0.5 hours or more and 24 hours or less, more preferably 1 hour or more and 12 hours or less, and particularly preferably 1.5 hours or more and 6 hours or less. If it is 0.5 hours or less, the reaction does not proceed sufficiently under normal reaction conditions, and if it exceeds 24 hours, it is not preferred for industrial production.

(Reaction terminator)
In the method for producing cellulose acylate used in the present invention, it is preferable to add a reaction terminator after the acylation reaction.

  Any reaction terminator may be used as long as it decomposes the acid anhydride, and preferred examples include water, alcohols (eg, ethanol, methanol, propanol, isopropyl alcohol, etc.) or compositions containing these. be able to. Moreover, the reaction terminator may contain a neutralizing agent described later. Upon addition of the reaction terminator, a large exotherm exceeding the cooling capacity of the reaction apparatus may occur, which may cause a decrease in the degree of polymerization of the cellulose acylate or may precipitate the cellulose acylate in an undesired form. In order to avoid such inconveniences, it is preferable to add a mixture of carboxylic acid such as acetic acid, propionic acid, butyric acid and water rather than directly adding water or alcohol, and acetic acid is particularly preferable as the carboxylic acid. The composition ratio of carboxylic acid and water can be used at any ratio, but the water content is 5% by mass to 80% by mass, further 10% by mass to 60% by mass, and particularly 15% by mass to 50% by mass. It is preferable that it is the range of these.

  The reaction terminator may be added to the acylation reaction vessel or the reactant may be added to the reaction terminator vessel. The reaction terminator is preferably added over 3 minutes to 3 hours. If the addition time of the reaction terminator is 3 minutes or more, the exotherm becomes too large, causing a decrease in the degree of polymerization, insufficient hydrolysis of the acid anhydride, and reducing the stability of cellulose acylate. This is preferable because there is no inconvenience. Moreover, it is preferable that the addition time of the reaction terminator is 3 hours or less because problems such as industrial productivity decrease do not occur. The addition time of the reaction terminator is preferably 4 minutes or longer and 2 hours or shorter, more preferably 5 minutes or longer and 1 hour or shorter, and particularly preferably 10 minutes or longer and 45 minutes or shorter. When adding the reaction terminator, the reaction vessel may or may not be cooled, but for the purpose of suppressing depolymerization, it is preferable to cool the reaction vessel to suppress the temperature rise. It is also preferable to cool the reaction terminator.

(Neutralizer)
In order to hydrolyze excess carboxylic anhydride remaining in the system or neutralize part or all of the carboxylic acid and esterification catalyst after the acylation termination step or the acylation termination step, Additives (eg, calcium, magnesium, iron, aluminum or zinc carbonates, acetates, hydroxides or oxides) or solutions thereof may be added. As a solvent for the neutralizing agent, water, alcohol (eg, ethanol, methanol, propanol, isopropyl alcohol, etc.), carboxylic acid (eg, acetic acid, propionic acid, butyric acid, etc.), ketone (eg, acetone, ethyl methyl ketone, etc.), Preferred examples include polar solvents such as dimethyl sulfoxide and mixed solvents thereof.

(Partial hydrolysis)
The cellulose acylate thus obtained has a total degree of substitution close to 3. However, for the purpose of obtaining a desired degree of substitution, a small amount of catalyst (generally, acylation of remaining sulfuric acid or the like) is performed. (Catalyst) and water in the presence of 20 to 90 ° C. for several minutes to several days to partially hydrolyze the ester bond and reduce the degree of acyl substitution of cellulose acylate to the desired degree ( So-called aging) is generally performed. Since the cellulose sulfate ester is also hydrolyzed during the partial hydrolysis, the amount of sulfate ester bound to the cellulose can be reduced by adjusting the hydrolysis conditions.

  When the desired cellulose acylate is obtained, it is preferable to completely neutralize the catalyst remaining in the system using the neutralizing agent as described above or a solution thereof to stop partial hydrolysis. . By adding a neutralizing agent (for example, magnesium carbonate, magnesium acetate, etc.) that generates a salt that is poorly soluble in the reaction solution, a catalyst (for example, sulfate ester) bound to the solution or to cellulose is effectively removed. It is also preferable to remove.

(Filtration)
The reaction mixture (dope) is preferably filtered for the purpose of removing or reducing unreacted substances, hardly soluble salts, and other foreign matters in the cellulose acylate. Filtration may be performed at any step between the completion of acylation and reprecipitation. For the purpose of controlling filtration pressure and handleability, it is also preferable to dilute with an appropriate solvent prior to filtration.

(Reprecipitation)
The cellulose acylate solution thus obtained is mixed in a poor solvent such as water or an aqueous solution of carboxylic acid (for example, acetic acid, propionic acid, etc.), or the poor solvent is mixed in the cellulose acylate solution. As a result, the cellulose acylate can be re-precipitated and the desired cellulose acylate can be obtained by washing and stabilizing treatment. Reprecipitation may be carried out continuously or batchwise by a fixed amount. It is also preferable to control the form and molecular weight distribution of the re-precipitated cellulose acylate by adjusting the concentration of the cellulose acylate solution and the composition of the poor solvent according to the substitution mode of the cellulose acylate or the degree of polymerization.

(Washing)
The produced cellulose acylate is preferably washed. Any washing solvent may be used as long as it has low solubility of cellulose acylate and can remove impurities, but water or warm water is usually used. The temperature of the washing water is preferably 25 ° C to 100 ° C, more preferably 30 ° C to 90 ° C, and particularly preferably 40 ° C to 80 ° C. The washing treatment may be performed by a so-called batch method in which filtration and replacement of the washing liquid are repeated, or may be carried out using a continuous washing apparatus. It is also preferable to reuse the waste liquid generated in the reprecipitation and washing steps as a poor solvent in the reprecipitation step, or to recover and reuse a solvent such as carboxylic acid by means such as distillation.

  The progress of washing may be traced by any means, but preferred examples include methods such as hydrogen ion concentration, ion chromatography, electrical conductivity, ICP, elemental analysis, and atomic absorption spectrum.

  By such treatment, the catalyst (sulfuric acid, perchloric acid, trifluoroacetic acid, p-toluenesulfonic acid, methanesulfonic acid, zinc chloride, etc.) in the cellulose acylate, neutralizing agent (for example, calcium, magnesium, iron, Aluminum or zinc carbonate, acetate, hydroxide or oxide, etc.), reaction product of neutralizing agent and catalyst, carboxylic acid (eg acetic acid, propionic acid, butyric acid), reaction of neutralizing agent with carboxylic acid Can be removed, which is effective to increase the stability of cellulose acylate.

(Stabilization)
Cellulose acylate after washing by hot water treatment is weakly alkaline (for example, carbonates, bicarbonates such as sodium, potassium, calcium, magnesium, aluminum, etc.) in order to further improve the stability or reduce the carboxylic acid odor. It is also preferable to treat with an aqueous solution of hydroxide, oxide, etc.). The amount of residual impurities can be controlled by the amount of cleaning liquid, cleaning temperature, time, stirring method, shape of cleaning container, composition and concentration of stabilizer. In the present invention, conditions for acylation, partial hydrolysis and washing are set so that the amount of residual sulfate radical (as the sulfur atom content) is 0 to 500 ppm.

(Dry)
In the present invention, in order to adjust the water content of the cellulose acylate to a preferable amount, it is preferable to dry the cellulose acylate. The drying method is not particularly limited as long as the desired moisture content can be obtained. However, it is preferable that the drying method be performed efficiently by using means such as heating, air blowing, decompression, and stirring alone or in combination. The drying temperature is preferably 0 to 200 ° C, more preferably 40 to 180 ° C, and particularly preferably 50 to 160 ° C. The cellulose acylate of the present invention has a water content of preferably 2% by mass or less, more preferably 1% by mass or less, and particularly preferably 0.7% by mass or less.

(Form)
The cellulose acylate of the present invention can take various shapes such as particles, powders, fibers and lumps, but it is preferable that the raw materials for film production are particles or powders. Cellulose acylate may be pulverized or sieved for uniform particle size and improved handling. When the cellulose acylate is in the form of particles, 90% by mass or more of the particles used preferably have a particle diameter of 0.5 to 5 mm. Moreover, it is preferable that 50 mass% or more of the particle | grains to be used have a particle diameter of 1-4 mm. The cellulose acylate particles preferably have a shape as close to a sphere as possible. The apparent density of the cellulose acylate particles of the present invention is preferably 0.5 to 1.3, more preferably 0.7 to 1.2, and particularly preferably 0.8 to 1.15. The method for measuring the apparent density is defined in JIS K-7365.

  The cellulose acylate particles of the present invention preferably have an angle of repose of 10 to 70 degrees, more preferably 15 to 60 degrees, and particularly preferably 20 to 50 degrees.

(Degree of polymerization)
The polymerization degree of the cellulose acylate preferably used in the present invention is an average polymerization degree of 100 to 300, preferably 120 to 250, and more preferably 130 to 200. The average degree of polymerization is determined by Uda et al.'S intrinsic viscosity method (Kazuo Uda, Hideo Saito, Journal of Textile Society, Vol. 18, No. 1, pages 105-120, 1962), molecular weight distribution measurement by gel permeation chromatography (GPC), etc. It can be measured by this method. Further details are described in JP-A-9-95538.

  In the present invention, the weight average degree of polymerization / number average degree of polymerization of cellulose acylate by GPC is preferably 1.6 to 3.6, more preferably 1.7 to 3.3. Particularly preferred is 8 to 3.2.

  These cellulose acylates may be used alone or in combination of two or more. Further, a polymer component other than cellulose acylate may be appropriately mixed. The polymer component to be mixed is preferably one having excellent compatibility with the cellulose ester, and the transmittance when formed into a film is 80% or more, more preferably 90% or more, and further preferably 92% or more.

[Examples of cellulose acylate synthesis]
Although the synthesis example of the cellulose acylate used for this invention is demonstrated in detail below, this invention is not limited to these.

Synthesis Example 1 (Synthesis of cellulose acetate propionate)
150 g of cellulose (hardwood pulp) and 75 g of acetic acid were placed in a 5 L separable flask equipped with a reflux apparatus as a reaction vessel and stirred vigorously for 2 hours while heating in an oil bath adjusted to 60 ° C. The cellulose subjected to such pretreatment was swollen and crushed to form a fluff shape. The reaction vessel was placed in a 2 ° C ice water bath for 30 minutes and cooled.

  Separately, a mixture of 1545 g of propionic acid anhydride and 10.5 g of sulfuric acid was prepared as an acylating agent, cooled to −30 ° C., and then added to the reaction vessel containing the above-treated cellulose at once. After 30 minutes, the external temperature was gradually increased, and the internal temperature was adjusted to 25 ° C. after 2 hours from the addition of the acylating agent. The reaction vessel was cooled in an ice water bath at 5 ° C., and the internal temperature was adjusted to 10 ° C. 0.5 hours after the addition of the acylating agent, and the internal temperature was 23 ° C. after 2 hours. Was kept at 23 ° C. and further stirred for 3 hours. The reaction vessel was cooled in an ice water bath at 5 ° C., and 120 g of 25% by mass aqueous acetic acid cooled to 5 ° C. was added over 1 hour. The internal temperature was raised to 40 ° C. and stirred for 1.5 hours. Next, a solution obtained by dissolving magnesium acetate tetrahydrate in 2-fold mol of sulfuric acid in 50% by mass aqueous acetic acid was added to the reaction vessel, and the mixture was stirred for 30 minutes. Cellulose acetate propionate was precipitated by adding 1 L of 25% by mass hydrous acetic acid, 500 mL of 33% by mass hydrous acetic acid, 1 L of 50% by mass hydrous acetic acid and 1 L of water in this order. The obtained cellulose acetate propionate precipitate was washed with warm water. By changing the washing conditions at this time as shown in Table 1, cellulose acetate propionate in which the amount of residual sulfate radicals was changed was obtained. After washing, the mixture is stirred in a 0.005 mass% calcium hydroxide aqueous solution at 20 ° C. for 0.5 hour, further washed with water until the pH of the washing solution becomes 7, and then vacuum dried at 70 ° C. It was.

  According to 1H-NMR and GPC measurement, the obtained cellulose acetate propionate had an acetylation degree of 0.30, a propionylation degree of 2.63, and a polymerization degree of 320. The sulfate radical content was measured according to ASTM D-817-96.

Synthesis Example 2 (Synthesis of cellulose acetate butyrate)
100 g of cellulose (hardwood pulp) and 135 g of acetic acid were placed in a 5 L separable flask equipped with a reflux apparatus as a reaction vessel, and allowed to stand for 1 hour while heating in an oil bath adjusted to 60 ° C. Thereafter, the mixture was vigorously stirred for 1 hour while being heated in an oil bath adjusted to 60 ° C. The cellulose subjected to such pretreatment was swollen and crushed to form a fluff shape. The reaction vessel was placed in a 5 ° C ice water bath for 1 hour to sufficiently cool the cellulose.

  Separately, a mixture of 1080 g of butyric anhydride and 10.0 g of sulfuric acid was prepared as an acylating agent, cooled to −20 ° C., and then added to a reaction vessel containing pretreated cellulose at once. After 30 minutes, the external temperature was raised to 20 ° C. and reacted for 5 hours. The reaction vessel was cooled in an ice water bath at 5 ° C, and 2400 g of 12.5% by mass aqueous acetic acid cooled to about 5 ° C was added over 1 hour. The internal temperature was raised to 30 ° C. and stirred for 1 hour. Next, 100 g of a 50% by mass aqueous solution of magnesium acetate tetrahydrate was added to the reaction vessel, and the mixture was stirred for 30 minutes. 1000 g of acetic acid and 2500 g of 50% by mass aqueous acetic acid were gradually added to precipitate cellulose acetate butyrate. The obtained cellulose acetate butyrate precipitate was washed with warm water. By changing the washing conditions at this time as shown in Table 1, cellulose acetate butyrate in which the amount of residual sulfate radicals was changed was obtained. After washing, the mixture was stirred in a 0.005 mass% calcium hydroxide aqueous solution for 0.5 hour, further washed with water until the pH of the washing solution became 7, and then dried at 70 ° C. The obtained cellulose acetate butyrate had an acetylation degree of 0.84, a butyrylation degree of 2.12, and a polymerization degree of 268.

(4) Other additives (i) Matting agent It is preferable to add fine particles as a matting agent. The fine particles used in the present invention include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, silica Mention may be made of magnesium and calcium phosphates. Fine particles containing silicon are preferable because they can reduce turbidity, and silicon dioxide is particularly preferable. The silicon dioxide fine particles preferably have a primary average particle size of 20 nm or less and an apparent specific gravity of 70 g / liter or more. Those having an average primary particle size as small as 5 to 16 nm are more preferred because they can reduce the haze of the film. The apparent specific gravity is preferably 90 to 200 g / liter or more, and more preferably 100 to 200 g / liter or more. A larger apparent specific gravity is preferable because a high-concentration dispersion can be produced, and haze and aggregates are improved.

  These fine particles usually form secondary particles having an average particle diameter of 0.1 to 3.0 μm, and these fine particles are present as aggregates of primary particles in the film, and 0.1 to 0.1 μm on the film surface. An unevenness of 3.0 μm is formed. The secondary average particle size is preferably from 0.2 μm to 1.5 μm, more preferably from 0.4 μm to 1.2 μm, and most preferably from 0.6 μm to 1.1 μm. The primary and secondary particle sizes were determined by observing the particles in the film with a scanning electron microscope and determining the diameter of a circle circumscribing the particles as the particle size. In addition, 200 particles were observed at different locations, and the average value was taken as the average particle size.

  As the fine particles of silicon dioxide, for example, commercially available products such as Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600 (above Nippon Aerosil Co., Ltd.) can be used. Zirconium oxide fine particles are commercially available, for example, under the trade names Aerosil R976 and R811 (manufactured by Nippon Aerosil Co., Ltd.) and can be used.

  Among these, Aerosil 200V and Aerosil R972V are fine particles of silicon dioxide having a primary average particle diameter of 20 nm or less and an apparent specific gravity of 70 g / liter or more, and the coefficient of friction is maintained while keeping the turbidity of the optical film low. It is particularly preferable because it has a great effect of reducing the effect.

(Ii) Other additives Various additives other than the above, for example, ultraviolet light inhibitors (for example, hydroxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, cyanoacrylate compounds, etc.), infrared absorbers, optical modifiers , Surfactants and odor trapping agents (such as amines) can be added. These details are disclosed in the Invention Association Public Technique No. 2001-1745 (issued March 15, 2001, Invention Association), p. Materials described in detail in 17-22 are preferably used.

  As the infrared absorbing dye, for example, those disclosed in JP-A No. 2001-194522 can be used, and as the ultraviolet absorber, for example, those described in JP-A No. 2001-151901 can be used. It is preferable to contain 001-5 mass%.

  Examples of the optical adjusting agent include a retardation adjusting agent. For example, those described in JP-A Nos. 2001-166144, 2003-344655, 2003-248117, and 2003-66230 can be used. Can control in-plane retardation (Re) and thickness direction retardation (Rth). A preferable addition amount is 0 to 10 wt%, more preferably 0 to 8 wt%, and still more preferably 0 to 6 wt%.

(5) Physical properties of cellulose acylate mixture The cellulose acylate mixture (a mixture of cellulose acylate, plasticizer, stabilizer, and other additives) preferably satisfies the following physical properties.

(I) Weight loss The thermoplastic cellulose acetate propionate composition of the present invention has a heat loss rate at 220 ° C of 5% by weight or less. Here, the heating weight loss rate refers to the weight loss rate at 220 ° C. when the temperature of the sample is raised from room temperature at a rate of temperature increase of 10 ° C./min in a nitrogen gas atmosphere. By setting it as the said cellulose acylate mixture, a heating weight loss rate can be 5 weight% or less. More preferably, it is 3 weight% or less, More preferably, it is 1 weight% or less. By doing in this way, the malfunction (bubble generation) which generate | occur | produces during film forming can be suppressed.

(Ii) Melt Viscosity The thermoplastic cellulose acetate propionate composition of the present invention preferably has a melt viscosity at 220 ° C. and 1 sec ⁻¹ of 100 to 1000 Pa · sec, more preferably 200 to 800 Pa · sec, still more preferably. 300 to 700 Pa · sec. By making such a high melt viscosity, it is not stretched (stretched) by the tension at the die exit, and an increase in optical anisotropy (retardation) due to stretch orientation can be prevented. Such adjustment of the viscosity may be achieved by any method, but can be achieved by, for example, the degree of polymerization of cellulose acylate and the amount of additives such as a plasticizer.

(6) Pelletization The cellulose acylate and additives are preferably mixed and pelletized prior to melt film formation.

  In pelletization, it is preferable to dry the cellulose acylate and additives in advance, but this can be substituted by using a vent type extruder. In the case of drying, a method of heating at 90 ° C. for 8 hours or more in a heating furnace can be used as a drying method, but this is not restrictive. Pelletization can be made by melting the cellulose acylate and additives at 150 ° C. or higher and 250 ° C. or lower using a biaxial kneading extruder and then solidifying and cutting the noodle-like extruded product in water. . Further, pelletization may be performed by an underwater cutting method or the like that is cut while being directly extruded from a die after being melted by an extruder.

  Any known single-screw extruder, non-meshing counter-rotating twin-screw extruder, meshing-type counter-rotating twin-screw extruder, meshing-type co-direction as long as the extruder is sufficiently melt kneaded A rotary twin screw extruder or the like can be used.

The preferred pellet size is preferably a cross-sectional area of 1 mm ^{2 to} 300 mm ² and a length of 1 mm to 30 mm, more preferably a cross-sectional area of 2 mm ^{2 to} 100 mm ² and a length of 1.5 mm to 10 mm. It is.

  Moreover, when pelletizing, the said additive can also be injected | thrown-in from the raw material input port and vent port in the middle of an extruder.

  The number of revolutions of the extruder is preferably from 10 rpm to 1000 rpm, more preferably from 20 rpm to 700 rpm, and even more preferably from 30 rpm to 500 rpm. Accordingly, when the rotational speed is slow, the residence time becomes long, which is not preferable because the molecular weight is lowered due to thermal deterioration or the yellowishness is easily deteriorated. On the other hand, if the rotational speed is too high, molecules are likely to be cut by shearing, which leads to problems such as a decrease in molecular weight and an increase in the generation of cross-linked gel.

  The extrusion residence time in pelletization is 10 seconds or more and 30 minutes or less, more preferably 15 seconds or more and 10 minutes or less, and further preferably 30 seconds or more and 3 minutes or less. If sufficient melting is possible, a shorter residence time is preferable in terms of suppressing resin deterioration and yellowing.

(7) Melt film formation (i) Drying It is preferable to use what was pelletized by the above-mentioned method, and it is preferable to reduce the water | moisture content in a pellet prior to melt film formation.

In the present invention, in order to adjust the water content of the cellulose acylate to a preferable amount, it is preferable to dry the cellulose acylate. The drying method is often dried using a dehumidifying air dryer, but is not particularly limited as long as the desired moisture content can be obtained (heating, blowing, decompressing, stirring, etc. alone or in combination) It is preferable to use it efficiently, and it is more preferable that the drying hopper has a heat insulating structure). The drying temperature is preferably 0 to 200 ° C, more preferably 40 to 180 ° C, and particularly preferably 60 to 150 ° C. When the drying temperature is too low, not only does drying take time, but the moisture content does not fall below the target value, which is not preferable. On the other hand, if the drying temperature is too high, the resin sticks and is not preferable. The amount of drying air used is preferably 20 to 400 m ³ / time, more preferably 50 to 300 m ³ / hour, and particularly preferably 100 to 250 m ³ / hour. If the amount of drying air is small, the drying efficiency is unfavorable. On the other hand, even if the air volume is increased, if the amount is more than a certain amount, further improvement in drying effect is small and not economical. The dew point of air is preferably 0 to −60 ° C., more preferably −10 to −50 ° C., particularly preferably −20 to −40 ° C. The drying time is required to be at least 15 minutes, more preferably 1 hour or more, and particularly preferably 2 hours or more. On the other hand, even if the drying time exceeds 50 hours, the effect of further reducing the moisture content is small, and there is a concern about thermal degradation of the resin, so it is not preferable to unnecessarily increase the drying time. The cellulose acylate of the present invention preferably has a water content of 1.0% by mass or less, more preferably 0.1% by mass or less, and particularly preferably 0.01% by mass or less.

(Ii) Melt Extrusion The cellulose acylate resin described above is supplied into the cylinder via a supply port of an extruder (apart from the above pelletizing extruder). In the cylinder, in order from the supply port side, a supply unit (region I) for quantitatively transporting the cellulose acylate resin supplied from the supply port, a compression unit (region II) for melting and kneading and compressing the cellulose acylate resin, and melt kneading and compression And a measuring section (region III) for measuring the cellulose acylate resin. The resin is preferably dried in order to reduce the water content by the above-mentioned method. However, in order to prevent oxidation of the molten resin by residual oxygen, the inside of the extruder is in an inert (nitrogen or the like) air flow or with a vent. More preferably, it is carried out while evacuating using an extruder. The screw compression ratio of the extruder is set to 2.5 to 4.5, and L / D is set to 20 to 70. Here, the screw compression ratio is represented by the volume ratio between the supply unit A and the metering unit C, that is, the volume per unit length of the supply unit A ÷ the volume per unit length of the metering unit C. It is calculated using the outer diameter d1 of the shaft, the outer diameter d2 of the screw shaft of the measuring part C, the groove part diameter a1 of the supply part A, and the groove part diameter a2 of the measuring part C. L / D is the ratio of the cylinder length to the cylinder inner diameter. Moreover, extrusion temperature is set to 190-240 degreeC. When the temperature in the extruder exceeds 240 ° C., a cooler may be provided between the extruder and the die.

  If the screw compression ratio is less than 2.5 and is too small, it will not be sufficiently melt-kneaded and undissolved parts will occur, or the shear heat generation will be too small and the crystals will not melt sufficiently, resulting in a cellulose acylate film after production In this case, fine crystals are likely to remain, and bubbles are more likely to be mixed. As a result, when the strength of the cellulose acylate film is reduced, or when the film is stretched, the remaining crystals inhibit the stretchability and the orientation cannot be sufficiently increased. On the other hand, if the screw compression ratio exceeds 4.5 and is too large, the shear stress is excessively applied and the resin is easily deteriorated due to heat generation, so that the cellulose acylate film after production is easily yellowed. On the other hand, when too much shear stress is applied, the molecules are cut and the molecular weight is lowered, so that the mechanical strength of the film is lowered. Therefore, the screw compression ratio is preferably in the range of 2.5 to 4.5, more preferably 2 in order to make the cellulose acylate film after production hardly yellowish and the film strength is strong and the stretch breakage is difficult. .8 to 4.2, particularly preferably in the range of 3.0 to 4.0.

On the other hand, if the L / D is less than 20 and is too small, melting and kneading are insufficient, and fine crystals are likely to remain in the cellulose acylate film after production, as in the case where the compression ratio is small. On the other hand, if L / D exceeds 70 and is too large, the residence time of the cellulose acylate resin in the extruder becomes too long, and the resin tends to be deteriorated. In addition, when the residence time is long, the molecules are cut or the molecular weight is lowered, so that the mechanical strength of the cellulose acylate film is lowered. Therefore, L / D is preferably in the range of 20 to 70, and more preferably in the range of 22 to 65, in order to make the cellulose acylate film after production hardly yellow, and the film strength is strong and the stretch breakage is difficult. Especially preferably, it is the range of 24-50.
The extrusion temperature is preferably in the above temperature range. The cellulose acylate film thus obtained has characteristic values having a haze of 2.0% or less and a yellow index (YI value) of 10 or less.

  Here, haze is an index indicating whether the extrusion temperature is too low, in other words, an index for knowing the amount of crystals remaining in the cellulose acylate film after production. If haze exceeds 2.0%, cellulose after production is obtained. Decrease in strength of the acylate film and breakage during stretching are likely to occur. The yellow index (YI value) is an index for knowing whether the extrusion temperature is too high. If the yellow index (YI value) is 10 or less, there is no problem in terms of yellowness.

  In general, single-screw extruders with relatively low equipment costs are often used as the types of extruders, and there are screw types such as full flight, madok, and dalmage, but cellulose acid with relatively poor thermal stability. The rate resin is preferably a full flight type. In addition, although the equipment cost is effective, it is possible to use a twin-screw extruder that can extrude while volatilizing unnecessary volatile components by providing a vent port in the middle by changing the screw segment. There are two types of shaft extruders, the same direction and the different direction, which can be used. However, the type of the same direction rotation with high self-cleaning performance is preferred because a stagnant portion is hardly generated. The twin-screw extruder is effective in equipment, but it is suitable for film formation of cellulose acetate resin because it has high kneadability and high resin supply performance and can be extruded at a low temperature. By appropriately arranging the vent opening, it is possible to use the cellulose acylate pellets and powder in an undried state as they are. Also, film smears produced during film formation can be reused without drying.

  In addition, although the diameter of a preferable screw changes with target extrusion rates per unit time, it is 10 to 300 mm, More preferably, it is 20 to 250 mm, More preferably, it is 30 to 150 mm.

(Iii) Filtration It is preferable to perform a so-called breaker plate type filtration in which a filter medium is provided at the exit of the extruder in order to filter foreign matter in the resin and avoid damage to the gear pump due to foreign matter. In order to filter foreign matter with higher accuracy, it is preferable to provide a filtration device incorporating a so-called leaf type disk filter after passing through the gear pump. Filtration can be performed by providing one filtration section, or multistage filtration performed by providing a plurality of places. The filtration accuracy of the filter medium is preferably higher, but the filtration accuracy is preferably 15 μm to 3 μm, more preferably 10 μm to 3 μm, from the viewpoint of the pressure resistance of the filter medium and the increase in the filtration pressure due to clogging of the filter medium. In particular, when using a leaf-type disk filter device that finally filters foreign matter, it is preferable to use a filter medium with high filtration accuracy in terms of quality, and it is adjusted by the number of loaded sheets to ensure the suitability of pressure resistance and filter life. Is possible. The type of filter medium is preferably a steel material because it is used under high temperature and high pressure. Among steel materials, stainless steel, steel, etc. are particularly preferable, and stainless steel is particularly preferable in terms of corrosion. . As a configuration of the filter medium, for example, a sintered filter medium formed by sintering metal long fibers or metal powder can be used in addition to a knitted wire, and a sintered filter medium is preferable in terms of filtration accuracy and filter life.

(Iv) Gear pump In order to improve the thickness accuracy, it is important to reduce the fluctuation of the discharge amount. A gear pump is provided between the extruder and the die, and a certain amount of cellulose acylate resin is supplied from the gear pump. That is effective. A gear pump is accommodated in a state where a pair of gears consisting of a drive gear and a driven gear are engaged with each other, and the drive gear is driven to engage and rotate the two gears so that a melted state is generated from the suction port formed in the housing. Resin is sucked into the cavity, and a certain amount of the resin is discharged from a discharge port formed in the housing. Even if there is a slight fluctuation in the resin pressure at the front end of the extruder, the fluctuation is absorbed by using a gear pump, the fluctuation in the resin pressure downstream of the film forming apparatus becomes very small, and the thickness fluctuation is improved. By using a gear pump, it is possible to keep the fluctuation range of the resin pressure in the die portion within ± 1%.

  In order to improve the quantitative supply performance by the gear pump, a method of controlling the pressure before the gear pump to be constant by changing the number of rotations of the screw can also be used. A high-precision gear pump using three or more gears that eliminates gear fluctuations of the gear pump is also effective.

  Other advantages of using a gear pump are that the pressure at the screw tip can be reduced to form a film, reducing energy consumption, preventing rise in resin temperature, improving transport efficiency, shortening the residence time in the extruder, L / D can be expected to be shortened. Also, when using a filter to remove foreign matter, if there is no gear pump, the amount of resin supplied from the screw may fluctuate as the filtration pressure increases. It can be resolved. On the other hand, the disadvantages of gear pumps are that the length of the equipment will be longer depending on the equipment selection method, the resin residence time will be longer, and the shearing stress of the gear pump may cause the molecular chain to break. is required.

  The preferred residence time of the resin from the supply port through the extruder until it exits the die is 2 minutes or more and 60 minutes or less, more preferably 3 minutes or more and 40 minutes or less, and even more preferably 4 minutes or more and 30 minutes. Is less than a minute.

  Cellulose acylate resin because the flow of the polymer for bearing circulation of the gear pump becomes worse, and the sealing by the polymer in the drive part and the bearing part becomes worse, and the fluctuation of the metering and liquid feeding pressure increases. It is necessary to design a gear pump (especially clearance) in accordance with the melt viscosity. In some cases, the staying portion of the gear pump causes deterioration of the cellulose acylate resin, and therefore a structure with as little staying as possible is preferable. The polymer pipes and adapters that connect the extruder and gear pump or gear pump and die also need to be designed with as little stagnation as possible, and to stabilize the extrusion pressure of cellulose acylate resin, which has a high temperature dependence of melt viscosity. It is preferable to make the temperature fluctuation as small as possible. Generally, a band heater having a low equipment cost is often used for heating the polymer tube, but it is more preferable to use an aluminum cast heater with less temperature fluctuation. Furthermore, in order to stabilize the discharge pressure in the extruder as described above, it is preferable to heat and melt the barrel of the extruder with a heater divided into 3 or more and 20 or less.

(V) Die The cellulose acylate resin is melted by the extruder configured as described above, and the molten resin is continuously fed to the die via a filter and a gear pump as necessary. As long as the die is designed so that the molten resin stays in the die, any type of commonly used T die, fishtail die, and hanger coat die may be used. Also, there is no problem to insert a static mixer for improving the uniformity of the resin temperature immediately before the T die. The clearance at the exit of the T die is generally 1.0 to 5.0 times the film thickness, preferably 1.2 to 3 times, and more preferably 1.3 to 2 times. When the lip clearance is less than 1.0 times the film thickness, it is difficult to obtain a sheet having a good surface shape by film formation. Further, when the lip clearance is larger than 5.0 times the film thickness, the sheet thickness accuracy is lowered, which is not preferable. The die is a very important facility for determining the thickness accuracy of the film, and a die that can control the thickness adjustment severely is preferable. Normally, the thickness can be adjusted at intervals of 40 to 50 mm, but preferably a type capable of adjusting the film thickness at intervals of 35 mm or less, more preferably at intervals of 25 mm or less. In addition, since the cellulose acylate resin is highly dependent on the temperature and shear rate of the melt viscosity, it is important to design as little as possible in the temperature variation of the die and the flow rate variation in the width direction. In addition, an automatic thickness adjustment die that measures the downstream film thickness, calculates the thickness deviation, and feeds back the result to the die thickness adjustment is also effective in reducing the thickness fluctuation in long-term continuous production.

(Vi) Cast The molten resin extruded from the die onto the sheet by the above method is extruded into a sheet on the cooling drum. At this time, the thickness unevenness in the width direction can be adjusted by adjusting the distance between the lips of the die.

  At this time, it is necessary to cool and solidify by sandwiching between a pair of metal rollers having a surface property with an arithmetic average height Ra of 100 nm or less. When a cooling roller having a surface property with an arithmetic average height Ra exceeding 100 nm is used, the transparency of the film decreases, which is not preferable. Preferably it is 50 nm or less, More preferably, it is 25 nm.

  The cooling drum is preferably 60 ° C. or higher and 160 ° C. or lower, more preferably 70 ° C. or higher and 150 ° C. or lower, and further preferably 80 ° C. or higher and 140 ° C. or lower. Then, it peels off from a cooling drum, winds up after passing through a take-off roller (nip roller). The winding speed is preferably from 10 m / min to 100 m / min, more preferably from 15 m / min to 80 m / min, still more preferably from 20 m / min to 70 m / min.

  The film forming width is 0.7 m or more and 5 m or less, more preferably 1 m or more and 4 m or less, and further preferably 1.3 m or more and 3 m or less. The thickness of the unstretched film thus obtained is preferably 30 μm or more and 400 μm or less, more preferably 40 μm or more and 300 μm or less, and still more preferably 50 μm or more and 200 μm or less.

  When the so-called touch roll method is used, the surface of the touch roll may be a resin such as rubber or Teflon, or a metal roll. Further, it is possible to use a roll called a flexible roll because the roll surface is slightly dented by the pressure when touched by reducing the thickness of the metal roll, and the crimping area is widened.

  The touch roll temperature is preferably 60 ° C. or higher and 160 ° C. or lower, more preferably 70 ° C. or higher and 150 ° C. or lower, and further preferably 80 ° C. or higher and 140 ° C. or lower.

(Vii) Winding The sheet thus obtained is preferably trimmed at both ends and wound. The trimmed part is recycled as a raw material for the same type of film or as a raw material for a film of a different type after being pulverized or after being subjected to a granulation process or a depolymerization / repolymerization process as necessary. May be used. As the trimming cutter, any type of rotary cutter, shear blade, knife, or the like may be used. As for the material, either carbon steel or stainless steel may be used. In general, it is preferable to use a cemented carbide blade or a ceramic blade because the life of the blade is long and the generation of chips is suppressed.

  Moreover, it is also preferable from a viewpoint of scratch prevention to attach a lami film to at least one surface before winding. The winding tension is preferably 1 kg / m width to 50 kg / width, more preferably 2 kg / m width to 40 kg / width, and still more preferably 3 kg / m width to 20 kg / width. When the winding tension is smaller than 1 kg / m width, it is difficult to wind the film uniformly. On the other hand, when the winding tension exceeds 50 kg / width, the film becomes tightly wound, not only the appearance of the winding is deteriorated, but also the bump portion of the film extends due to the creep phenomenon, and the film wave This is not preferable because it causes a cause or residual birefringence due to the elongation of the film. The winding tension is preferably detected by tension control in the middle of the line and is wound while being controlled to have a constant winding tension. If there is a difference in film temperature depending on the location of the film production line, the length of the film may be slightly different due to thermal expansion. It is necessary to prevent tension.

  The winding tension can be wound at a constant tension by controlling the tension control. However, it is more preferable that the winding tension is tapered to an appropriate winding tension according to the wound diameter. Generally, the tension is gradually reduced as the winding diameter increases, but in some cases, it may be preferable to increase the tension as the winding diameter increases.

(Viii) Physical Properties of Unstretched Cellulose Acylate Film The unstretched cellulose acylate film thus obtained preferably has Re = 0 to 10 nm and Rth = 0 to 20 nm when the film longitudinal direction is the slow axis. Re and Rth represent in-plane retardation and retardation in the thickness direction, respectively. Re is measured with KOBRA 21ADH (manufactured by Oji Scientific Instruments) by making light incident in the normal direction of the film. Rth is the above-mentioned Re and the retardation measured by injecting light from directions inclined by + 40 ° and −40 ° with respect to the film normal direction with the in-plane slow axis as the tilt axis (rotation axis). Calculation is based on the retardation value measured from three directions. The angle θ formed by the film forming direction (longitudinal direction) and the slow axis of Re of the film is preferably closer to 0 °, + 90 °, or −90 °.

  The total light transmittance is preferably 90% to 100%, more preferably 91 to 99%, and still more preferably 92 to 98%. The preferred haze is 0 to 1%, more preferably 0 to 0.8%, still more preferably 0 to 0.6%.

  The thickness unevenness is preferably 0% or more and 4% or less in both the longitudinal direction and the width direction, more preferably 0% or more and 3% or less, and further preferably 0% or more and 2% or less.

Preferably, the modulus in tension is 1.5 kN / mm ² or more 3.5 kN / mm ² or less, more preferably 1.7 kN / mm ² or more 2.8 kN / mm ² or less, more preferably 1.8 kN / mm ² or more 2 .6 kN / mm ² or less.

  The breaking elongation is preferably 3% to 100%, more preferably 5% to 80%, and still more preferably 8% to 50%.

  Tg (Tg of film, that is, Tg of cellulose acylate and additive) is preferably 95 ° C or higher and 145 ° C or lower, more preferably 100 ° C or higher and 140 ° C or lower, and further preferably 105 ° C. It is 135 degrees C or less.

  The thermal dimensional change at 80 ° C for one day is preferably 0% or more and ± 1% or less in both the vertical and horizontal directions, more preferably 0% or more and ± 0.5% or less, and further preferably 0% or more and ± 0.3% or less. It is.

The water permeability at 40 ° C. and 90% rh is preferably 300 g / m ² · day to 1000 g / m ² · day, more preferably 400 g / m ² · day to 900 g / m ² · day, more preferably 500 g / m. m ² · day to 800 g / m ² · day.

  The equilibrium water content at 25 ° C 80% rh is preferably 1 wt% or more and 4 wt% or less, more preferably 1.2 wt% or more and 3 wt% or less, and further preferably 1.5 wt% or more and 2.5 wt% or less.

(8) Stretching The film formed by the above method may be stretched. Thereby, Re and Rth can be controlled.

  The stretching is preferably performed at Tg or more and Tg + 50 ° C or less, more preferably Tg + 3 ° C or more and Tg + 30 ° C or less, and further preferably Tg + 5 ° C or more and Tg + 20 ° C or less. A preferred draw ratio is 1% or more and 300% or less on at least one side, more preferably 2% or more and 250% or less, and further preferably 3% or more and 200% or less. Although it may be stretched evenly in the vertical and horizontal directions, it is more preferable to stretch one of the stretch ratios more than the other and stretch the same. Either longitudinal (MD) or lateral (TD) may be increased, but the smaller stretch ratio is preferably 1% or more and 30% or less, more preferably 2% or more and 25% or less, and further preferably 3%. It is 20% or less. The larger draw ratio is 30% to 300%, more preferably 35% to 200%, and still more preferably 40% to 150%. These stretching operations may be performed in one stage or in multiple stages. The draw ratio here is determined using the following equation.

Stretch ratio (%) = 100 × {(Length after stretching) − (Length before stretching)} / (Length before stretching)
Such stretching may be performed in the longitudinal direction using two or more pairs of nip rolls with increased peripheral speed on the outlet side (longitudinal stretching), and both ends of the film are gripped by chucks and are orthogonally crossed (longitudinal direction). (Perpendicular direction). Moreover, you may use the simultaneous biaxial stretching method of Unexamined-Japanese-Patent No. 2000-37772, Unexamined-Japanese-Patent No. 2001-113591, and Unexamined-Japanese-Patent No. 2002-103445.

  The ratio of Re and Rth can be freely controlled by controlling the value (aspect ratio) obtained by dividing the space between nip rolls by the film width in the case of longitudinal stretching. That is, the Rth / Re ratio can be increased by reducing the aspect ratio. Also, Re and Rth can be controlled by combining longitudinal stretching and lateral stretching. That is, Re can be reduced by reducing the difference between the longitudinal draw ratio and the transverse draw ratio, and Re can be increased by increasing this difference.

  It is preferable that Re and Rth of the cellulose acylate film thus stretched satisfy the following formula.

Rth ≧ Re
500 ≧ Re ≧ 0
500 ≧ Rth ≧ 30
More preferably, Rth ≧ Re × 1.1
150 ≧ Re ≧ 10
400 ≧ Rth ≧ 50
More preferably, Rth ≧ Re × 1.2
100 ≧ Re ≧ 20
350 ≧ Rth ≧ 80
The angle θ formed by the film forming direction (longitudinal direction) and the slow axis of Re of the film is preferably closer to 0 °, + 90 °, or −90 °. That is, in the case of longitudinal stretching, it is preferably as close to 0 °, preferably 0 ± 3 °, more preferably 0 ± 2 °, and further preferably 0 ± 1 °. In the case of transverse stretching, 90 ± 3 ° or −90 ± 3 ° is preferable, 90 ± 2 ° or −90 ± 2 ° is more preferable, and 90 ± 1 ° or −90 ± 1 ° is more preferable.

  The thickness unevenness of the cellulose acylate film after stretching is preferably 0% or more and 3% or less in both the longitudinal direction and the width direction, more preferably 0% or more and 2% or less, and further preferably 0% or more and 1% or less.

  The physical properties of the stretched cellulose acylate film are preferably in the following ranges.

The tensile modulus is preferably less than 1.5 kN / mm ² or more 3.0 kN / mm ^2, more preferably 1.7 kN / mm ² or more 2.8 kN / mm ² or less, more preferably 1.8 kN / mm ² or more 2 .6 kN / mm ² or less.

  The breaking elongation is preferably 3% to 100%, more preferably 5% to 80%, and still more preferably 8% to 50%.

  Tg (Tg of film, that is, Tg of cellulose acylate and additive) is preferably 95 ° C or higher and 145 ° C or lower, more preferably 100 ° C or higher and 140 ° C or lower, and further preferably 105 ° C. It is 135 degrees C or less.

  The thermal dimensional change at 80 ° C for one day is preferably 0% or more and ± 1% or less in both the vertical and horizontal directions, more preferably 0% or more and ± 0.5% or less, and further preferably 0% or more and ± 0.3% or less. It is.

The water permeability at 90 ° C. at 40 ° C. is preferably 300 g / m ² · day to 1000 g / m ² · day, more preferably 400 g / m ² · day to 900 g / m ² · day, more preferably 500 g / m. ² · day to 800 g / m ² · day.

  The equilibrium water content at 25 ° C 80% rh is preferably 1 wt% or more and 4 wt% or less, more preferably 1.2 wt% or more and 3 wt% or less, and further preferably 1.5 wt% or more and 2.5 wt% or less.

  The thickness is preferably 30 μm to 200 μm, more preferably 40 μm to 180 μm, and still more preferably 50 μm to 150 μm.

  The haze is 0% to 2.0%, more preferably 0% to 1.5%, and still more preferably 0% to 1%.

  The total light transmittance is preferably 90% to 100%, more preferably 91% to 99%, and still more preferably 92% to 98%.

(9) Surface treatment An unstretched and stretched cellulose acylate film can achieve improved adhesion to each functional layer (for example, a primer layer and a back layer) by performing a surface treatment. For example, glow discharge treatment, ultraviolet irradiation treatment, corona treatment, flame treatment, acid or alkali treatment can be used. The glow discharge treatment here may be low-temperature plasma that occurs under a low pressure gas of 10 ^{−3 to} 20 Torr, and plasma treatment under atmospheric pressure is also preferred. A plasma-excitable gas is a gas that is plasma-excited under the above conditions, and includes chlorofluorocarbons such as argon, helium, neon, krypton, xenon, nitrogen, carbon dioxide, tetrafluoromethane, and mixtures thereof. It is done. Details of these are described in detail on pages 30 to 32 in the technical report of the Invention Association (Public Technical Number 2001-1745, published on March 15, 2001, Invention Association). Note that, in the plasma treatment at atmospheric pressure which has been attracting attention in recent years, for example, irradiation energy of 20 to 500 Kgy is used under 10 to 1000 Kev, and more preferably irradiation energy of 20 to 300 Kgy is used under 30 to 500 Kev. Among these, an alkali saponification treatment is particularly preferable, and it is extremely effective as a surface treatment of a cellulose acylate film. Specifically, JP-A-2003-3266, 2003-229299, 2004-322928, 2005-76088 and the like can be used.

  The alkali saponification treatment may be immersed in a saponification solution or coated with a saponification solution. In the case of the dipping method, an aqueous solution having a pH of 10 to 14 such as NaOH or KOH is passed through a tank heated to 20 ° C. to 80 ° C. for 0.1 to 10 minutes, and then neutralized, washed with water, and dried. Can be achieved.

  In the case of the coating method, a dip coating method, a curtain coating method, an extrusion coating method, a bar coating method, and an E-type coating method can be used. The solvent of the alkali saponification coating solution has good wettability because it is applied to the transparent support of the saponification solution, and the surface state remains good without forming irregularities on the surface of the transparent support by the saponification solution solvent. It is preferred to select a solvent to keep. Specifically, an alcohol solvent is preferable, and isopropyl alcohol is particularly preferable. An aqueous solution of a surfactant can also be used as a solvent. The alkali of the alkali saponification coating solution is preferably an alkali that dissolves in the above solvent, and more preferably KOH or NaOH. The pH of the saponification coating solution is preferably 10 or more, more preferably 12 or more. The reaction conditions during alkali saponification are preferably 1 second to 5 minutes at room temperature, more preferably 5 seconds to 5 minutes, and particularly preferably 20 seconds to 3 minutes. After the alkali saponification reaction, it is preferable to wash the surface on which the saponification solution is applied with water or with an acid and then with water. Further, the coating-type saponification treatment and the alignment film uncoating described later can be performed continuously, and the number of steps can be reduced. Specific examples of these saponification methods are described in JP-A-2002-82226 and WO02 / 46809.

  It is also preferable to provide an undercoat layer for adhesion to the functional layer. This layer may be coated after the above surface treatment or may be coated without the surface treatment. Details of the undercoat layer are described on page 32 of the Japan Society for Invention and Innovation (Public Technical Number 2001-1745, published on March 15, 2001, Japan Institute of Invention).

  These surface treatment and undercoating processes can be incorporated at the end of the film forming process, can be performed alone, or can be performed in the functional layer application process described later.

(10) Functional layer imparting The stretched and unstretched cellulose acylate film of the present invention has pages 32 to 45 in the Japan Society for Invention and Technology (public technical number 2001-1745, published on March 15, 2001, Japan Society for Invention). It is preferable to combine the functional layers described in detail in. Among these, application of a polarizing layer (polarizing plate), application of an optical compensation layer (optical compensation film), application of an antireflection layer (antireflection film), and application of a hard coat layer are preferred.

(I) Application of polarizing layer (creation of polarizing plate)
[Material used for polarizing layer]
Currently, a commercially available polarizing layer is generally prepared by immersing a stretched polymer in a solution of iodine or dichroic dye in a bath and allowing the iodine or dichroic dye to penetrate into the binder. It is. As the polarizing film, a coating type polarizing film represented by Optiva Inc. can also be used. Iodine and dichroic dye in the polarizing film exhibit deflection performance by being oriented in the binder. As the dichroic dye, an azo dye, a stilbene dye, a pyrazolone dye, a triphenylmethane dye, a quinoline dye, an oxazine dye, a thiazine dye, or an anthraquinone dye is used. The dichroic dye is preferably water-soluble. The dichroic dye preferably has a hydrophilic substituent (eg, sulfo, amino, hydroxyl). For example, the compound as described in Invention Association public technique, public technical number 2001-1745, page 58 (issue date March 15, 2001) can be mentioned.

  As the binder for the polarizing film, either a polymer that can be crosslinked per se or a polymer that is crosslinked by a crosslinking agent can be used, and a plurality of combinations thereof can be used. Examples of the binder include methacrylate copolymer, styrene copolymer, polyolefin, polyvinyl alcohol and modified polyvinyl alcohol, poly (N-methylolacrylamide) described in paragraph No. [0022] of JP-A-8-338913. , Polyester, polyimide, vinyl acetate copolymer, carboxymethyl cellulose, polycarbonate and the like. Silane coupling agents can be used as the polymer. Water-soluble polymers (eg, poly (N-methylolacrylamide), carboxymethylcellulose, gelatin, polyvinyl alcohol, modified polyvinyl alcohol) are preferred, gelatin, polyvinyl alcohol and modified polyvinyl alcohol are more preferred, and polyvinyl alcohol and modified polyvinyl alcohol are most preferred. . It is particularly preferable to use two types of polyvinyl alcohol or modified polyvinyl alcohol having different degrees of polymerization. The saponification degree of polyvinyl alcohol is preferably 70 to 100%, more preferably 80 to 100%. It is preferable that the polymerization degree of polyvinyl alcohol is 100-5000. The modified polyvinyl alcohol is described in JP-A-8-338913, JP-A-9-152509 and JP-A-9-316127. Two or more kinds of polyvinyl alcohol and modified polyvinyl alcohol may be used in combination.

  The lower limit of the binder thickness is preferably 10 μm. The upper limit of the thickness is preferably as thin as possible from the viewpoint of light leakage of the liquid crystal display device. It is preferably not more than a commercially available polarizing plate (about 30 μm), preferably 25 μm or less, and more preferably 20 μm or less.

  The binder of the polarizing film may be cross-linked. A polymer or monomer having a crosslinkable functional group may be mixed in the binder, or a crosslinkable functional group may be imparted to the binder polymer itself. Crosslinking can be performed by light, heat, or pH change, and a binder having a crosslinked structure can be formed. The crosslinking agent is described in US Reissue Patent 23297. Boron compounds (eg, boric acid, borax) can also be used as a crosslinking agent. The addition amount of the crosslinking agent in the binder is preferably 0.1 to 20% by mass with respect to the binder. The orientation of the polarizing element and the wet heat resistance of the polarizing film are improved.

  Even after the crosslinking reaction is completed, the unreacted crosslinking agent is preferably 1.0% by mass or less, and more preferably 0.5% by mass or less. By doing in this way, a weather resistance improves.

[Stretching of polarizing film]
The polarizing film is preferably dyed with iodine or a dichroic dye after the polarizing film is stretched (stretching method) or rubbed (rubbing method).

  In the stretching method, the stretching ratio is preferably 2.5 to 30.0 times, and more preferably 3.0 to 10.0 times. Stretching can be performed by dry stretching in air. Moreover, you may implement wet extending | stretching in the state immersed in water. The stretch ratio of dry stretching is preferably 2.5 to 5.0 times, and the stretch ratio of wet stretching is preferably 3.0 to 10.0 times. Stretching may be performed in parallel to the MD direction (parallel stretching) or may be performed in an oblique direction (oblique stretching). These stretching operations may be performed once or divided into several times. By dividing into several times, it is possible to stretch more uniformly even at high magnification. More preferred is oblique stretching in which the film is stretched with an inclination of 10 to 80 degrees in the oblique direction.

(I) Parallel stretching method Prior to stretching, the PVA film is swollen. The degree of swelling is 1.2 to 2.0 times (mass ratio before swelling and after swelling). Thereafter, the film is stretched at a bath temperature of 15 to 50 ° C., preferably 17 to 40 ° C. in an aqueous medium bath or a dyeing bath for dissolving a dichroic substance while being continuously conveyed through a guide roll or the like. Stretching can be achieved by gripping with two pairs of nip rolls and increasing the conveyance speed of the subsequent nip roll to be higher than that of the previous nip roll. The draw ratio is based on the length ratio after stretching / initial state (hereinafter the same), but the draw ratio is preferably 1.2 to 3.5 times, preferably 1.5 to 3.0 times from the viewpoint of the above-mentioned effects. is there. Thereafter, the film is dried at 50 ° C. to 90 ° C. to obtain a polarizing film.

(II) Diagonal Stretching Method A method of stretching using a tenter projecting obliquely in an oblique direction as described in JP-A No. 2002-86554 can be used. Since this stretching is performed in the air, it is necessary to make it easy to stretch by adding water in advance. The moisture content is preferably 5% to 100%, the stretching temperature is preferably 40 ° C to 90 ° C, and the humidity during stretching is preferably 50% rh to 100% rh.

  The absorption axis of the polarizing film thus obtained is preferably 10 to 80 degrees, more preferably 30 to 60 degrees, and still more preferably 45 degrees (40 to 50 degrees).

[Lamination]
A stretched polarizing plate is prepared by laminating the stretched and unstretched cellulose acylate film after saponification and the polarizing layer prepared by stretching. There are no particular restrictions on the direction of bonding, but it is preferable that the direction of the casting axis of the cellulose acylate film and the direction of the stretching axis of the polarizing plate be 0 °, 45 °, or 90 °.

  The adhesive for bonding is not particularly limited, but examples thereof include PVA resins (including modified PVA such as acetoacetyl group, sulfonic acid group, carboxyl group, oxyalkylene group) and boron compound aqueous solution. preferable. The thickness of the adhesive layer is preferably 0.01 to 10 μm after drying, and particularly preferably 0.05 to 5 μm.

  Examples of the laminated layer structure include the following.

B) A / P / A
B) A / P / B
C) A / P / T
D) B / P / B
E) B / P / T
A represents an unstretched film of the present invention, B represents a stretched film of the present invention, T represents a cellulose triacetate film (Fujitac), and P represents a polarizing layer. In the case of the constitutions b) and b), A and B may be the same composition or different cellulose acetates. In the case of the construction d), B may be different in cellulose acetate having the same composition, or may be different in the same draw ratio. In the case of use in a liquid crystal display device, either may be used as the liquid crystal surface, but in the case of configurations b) and e), it is more preferable that B is on the liquid crystal side.

  When incorporating a liquid crystal display device, a substrate containing liquid crystal is usually disposed between two polarizing plates, but it is possible to freely combine a) to e) of the present invention and a normal polarizing plate (T / P / T). it can. However, it is preferable to provide a transparent hard coat layer, an antiglare layer, an antireflection layer, and the like on the film on the outermost surface of the display side of the liquid crystal display device.

  The polarizing plate thus obtained preferably has a higher light transmittance, and preferably has a higher degree of polarization. The transmittance of the polarizing plate is preferably in the range of 30 to 50%, more preferably in the range of 35 to 50%, and most preferably in the range of 40 to 50% with respect to light having a wavelength of 550 nm. . The degree of polarization is preferably in the range of 90 to 100%, more preferably in the range of 95 to 100%, and most preferably in the range of 99 to 100% in light having a wavelength of 550 nm.

  Furthermore, the polarizing plate thus obtained can be laminated with a λ / 4 plate to produce circularly polarized light. In this case, lamination is performed so that the slow axis of λ / 4 and the absorption axis of the polarizing plate are 45 degrees. At this time, λ / 4 is not particularly limited, but more preferably has a wavelength dependency such that the lower the wavelength, the smaller the retardation. Furthermore, it is preferable to use a polarizing film having an absorption axis inclined by 20 ° to 70 ° with respect to the longitudinal direction and a λ / 4 plate made of an optically anisotropic layer made of a liquid crystalline compound.

  A protective film may be bonded to one surface of these polarizing plates, and a separate film may be bonded to the other surface. The protective film and the separate film are used for the purpose of protecting the polarizing plate at the time of shipping the polarizing plate and at the time of product inspection.

(Ii) Application of optical compensation layer (preparation of optical compensation film)
The optically anisotropic layer is for compensating the liquid crystal compound in the liquid crystal cell in the black display of the liquid crystal display device, and forms an alignment film on the stretched and unstretched cellulose acylate film, and further optically anisotropic It is formed by providing a sex layer.

[Alignment film]
An alignment film is provided on the surface-treated stretched and unstretched cellulose acylate film. This film has a function of defining the alignment direction of liquid crystalline molecules. However, if the alignment state is fixed after aligning the liquid crystalline compound, the alignment film plays the role, and thus is not necessarily an essential component of the present invention. That is, it is possible to produce the polarizing plate of the present invention by transferring only the optically anisotropic layer on the alignment film in which the alignment state is fixed onto the polarizer.

  The alignment film is an organic compound (eg, ω-tricosanoic acid) formed by rubbing treatment of an organic compound (preferably a polymer), oblique deposition of an inorganic compound, formation of a layer having a microgroove, or Langmuir-Blodgett method (LB film). , Dioctadecylmethylammonium chloride, methyl stearylate). Furthermore, an alignment film in which an alignment function is generated by application of an electric field, application of a magnetic field or light irradiation is also known.

  The alignment film is preferably formed by polymer rubbing treatment. In principle, the polymer used for the alignment film has a molecular structure having a function of aligning liquid crystal molecules.

  In the present invention, in addition to the function of aligning liquid crystalline molecules, a cross-linking having a function of aligning a side chain having a crosslinkable functional group (eg, double bond) to the main chain or aligning liquid crystalline molecules. It is preferable to introduce a functional functional group into the side chain.

  As the polymer used for the alignment film, either a polymer that can be crosslinked by itself or a polymer that is crosslinked by a crosslinking agent can be used, and a plurality of combinations thereof can be used. Examples of the polymer include methacrylate copolymers, styrene copolymers, polyolefins, polyvinyl alcohol and modified polyvinyl alcohol, poly (N-methylol) described in paragraph No. [0022] of JP-A-8-338913. Acrylamide), polyester, polyimide, vinyl acetate copolymer, carboxymethylcellulose, polycarbonate and the like. Silane coupling agents can be used as the polymer. Water-soluble polymers (eg, poly (N-methylolacrylamide), carboxymethylcellulose, gelatin, polyvinyl alcohol, modified polyvinyl alcohol) are preferred, gelatin, polyvinyl alcohol and modified polyvinyl alcohol are more preferred, and polyvinyl alcohol and modified polyvinyl alcohol are most preferred. . It is particularly preferable to use two types of polyvinyl alcohol or modified polyvinyl alcohol having different degrees of polymerization. The saponification degree of polyvinyl alcohol is preferably 70 to 100%, more preferably 80 to 100%. It is preferable that the polymerization degree of polyvinyl alcohol is 100-5000.

  A side chain having a function of aligning liquid crystal molecules generally has a hydrophobic group as a functional group. The specific type of functional group is determined according to the type of liquid crystal molecule and the required alignment state. For example, the modifying group of the modified polyvinyl alcohol can be introduced by copolymerization modification, chain transfer modification or block polymerization modification. Examples of modifying groups include hydrophilic groups (carboxylic acid groups, sulfonic acid groups, phosphonic acid groups, amino groups, ammonium groups, amide groups, thiol groups, etc.), hydrocarbon groups having 10 to 100 carbon atoms, fluorine atoms Substituted hydrocarbon groups, thioether groups, polymerizable groups (unsaturated polymerizable groups, epoxy groups, azirinidyl groups, etc.), alkoxysilyl groups (trialkoxy, dialkoxy, monoalkoxy) and the like can be mentioned. As specific examples of these modified polyvinyl alcohol compounds, for example, paragraph numbers [0022] to [0145] in JP-A No. 2000-155216 and paragraph numbers [0018] to [0018] in JP-A No. 2002-62426 are described. [0022] and the like.

  When a side chain having a crosslinkable functional group is bonded to the main chain of the alignment film polymer, or a crosslinkable functional group is introduced into a side chain having a function of aligning liquid crystalline molecules, the alignment film polymer and the optically anisotropic film The polyfunctional monomer contained in the conductive layer can be copolymerized. As a result, not only between the polyfunctional monomer and the polyfunctional monomer, but also between the alignment film polymer and the alignment film polymer and between the polyfunctional monomer and the alignment film polymer is firmly bonded by a covalent bond. Therefore, the strength of the optical compensation film can be remarkably improved by introducing the crosslinkable functional group into the alignment film polymer.

  The crosslinkable functional group of the alignment film polymer preferably contains a polymerizable group in the same manner as the polyfunctional monomer. Specific examples include those described in paragraphs [0080] to [0100] in JP-A-2000-155216. Apart from the crosslinkable functional group, the alignment film polymer can also be crosslinked using a crosslinking agent.

  Examples of the crosslinking agent include aldehydes, N-methylol compounds, dioxane derivatives, compounds that act by activating carboxyl groups, active vinyl compounds, active halogen compounds, isoxazole, and dialdehyde starch. Two or more kinds of crosslinking agents may be used in combination. Specific examples include compounds described in paragraphs [0023] to [024] in JP-A-2002-62426. Aldehydes having high reaction activity, particularly glutaraldehyde are preferred.

  0.1-20 mass% is preferable with respect to a polymer, and, as for the addition amount of a crosslinking agent, 0.5-15 mass% is more preferable. The amount of the unreacted crosslinking agent remaining in the alignment film is preferably 1.0% by mass or less, and more preferably 0.5% by mass or less. By adjusting in this way, even if the alignment film is used for a long time in a liquid crystal display device or left in a high temperature and high humidity atmosphere for a long time, sufficient durability without reticulation can be obtained.

  The alignment film can be basically formed by applying the polymer on the transparent support containing the alignment film forming material and the crosslinking agent, followed by drying by heating (crosslinking) and rubbing treatment. As described above, the crosslinking reaction may be carried out at any time after coating on the transparent support. When a water-soluble polymer such as polyvinyl alcohol is used as the alignment film forming material, the coating solution is preferably a mixed solvent of an organic solvent (eg, methanol) having a defoaming action and water. The ratio of water: methanol is preferably 0: 100 to 99: 1, and more preferably 0: 100 to 91: 9. Thereby, generation | occurrence | production of a bubble is suppressed and the defect of the layer surface of an orientation film and also an optically anisotropic layer reduces remarkably.

  The alignment film is preferably applied by spin coating, dip coating, curtain coating, extrusion coating, rod coating, or roll coating. A rod coating method is particularly preferable. The film thickness after drying is preferably 0.1 to 10 μm. Heating and drying can be performed at 20 ° C to 110 ° C. In order to form sufficient crosslinking, 60 ° C to 100 ° C is preferable, and 80 ° C to 100 ° C is particularly preferable. The drying time can be 1 minute to 36 hours, preferably 1 minute to 30 minutes. The pH is preferably set to an optimum value for the crosslinking agent to be used. When glutaraldehyde is used, the pH is 4.5 to 5.5, and 5 is particularly preferable.

  The alignment film is provided on the stretched / unstretched cellulose acylate film or on the undercoat layer. The alignment film can be obtained by rubbing the surface after crosslinking the polymer layer as described above.

  For the rubbing treatment, a treatment method widely adopted as a liquid crystal alignment treatment process of LCD can be applied. That is, a method of obtaining the orientation by rubbing the surface of the orientation film in a certain direction using paper, gauze, felt, rubber, nylon, polyester fiber or the like can be used. Generally, it is carried out by rubbing several times using a cloth or the like in which fibers having a uniform length and thickness are planted on average.

  When industrially implemented, this is achieved by bringing a rotating rubbing roll into contact with the film with the polarizing layer being transported. However, the roundness, cylindricity, and deflection (eccentricity) of the rubbing roll can be any. Is preferably 30 μm or less. The wrap angle of the film on the rubbing roll is preferably 0.1 to 90 °. However, as described in JP-A-8-160430, a stable rubbing treatment can be obtained by winding 360 ° or more. As for the conveyance speed of a film, 1-100 m / min is preferable. It is preferable to select an appropriate rubbing angle in the range of 0 to 60 °. When used in a liquid crystal display device, the angle is preferably 40 to 50 °. 45 ° is particularly preferred.

  The film thickness of the alignment film thus obtained is preferably in the range of 0.1 to 10 μm.

  Next, the liquid crystalline molecules of the optically anisotropic layer are aligned on the alignment film. Thereafter, as necessary, the alignment film polymer and the polyfunctional monomer contained in the optically anisotropic layer are reacted, or the alignment film polymer is crosslinked using a crosslinking agent.

  The liquid crystalline molecules used in the optically anisotropic layer include rod-like liquid crystalline molecules and discotic liquid crystalline molecules. The rod-like liquid crystal molecules and the disk-like liquid crystal molecules may be high-molecular liquid crystals or low-molecular liquid crystals, and further include those in which low-molecular liquid crystals are cross-linked and no longer exhibit liquid crystallinity.

[Rod-like liquid crystalline molecules]
Examples of rod-like liquid crystalline molecules include azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, alkoxy-substituted phenylpyrimidines. , Phenyldioxanes, tolanes and alkenylcyclohexylbenzonitriles are preferably used.

  The rod-like liquid crystalline molecule includes a metal complex. In addition, a liquid crystal polymer containing a rod-like liquid crystalline molecule in a repeating unit can also be used as the rod-like liquid crystalline molecule. In other words, the rod-like liquid crystal molecule may be bonded to a (liquid crystal) polymer.

  For rod-like liquid crystalline molecules, see Chapter 4, Chapter 7 and Chapter 11 of the Chemistry of the Quarterly Chemistry Vol. 22 (1994) The Chemical Society of Japan, and the 142th Committee of the Japan Society for the Promotion of Science. Described in Chapter 3.

  The birefringence of the rod-like liquid crystal molecule is preferably in the range of 0.001 to 0.7.

  The rod-like liquid crystalline molecule preferably has a polymerizable group in order to fix its alignment state. The polymerizable group is preferably a radically polymerizable unsaturated group or a cationically polymerizable group. Specifically, for example, the polymerizable groups described in paragraphs [0064] to [0086] of JP-A-2002-62427 are described. Group and a polymerizable liquid crystal compound.

[Disc liquid crystalline molecules]
For discotic liquid crystal molecules, C.I. Destrade et al., Mol. Cryst. 71, 111 (1981), benzene derivatives described in C.I. Destrade et al., Mol. Cryst. 122, 141 (1985), Physics lett, A, 78, 82 (1990); Kohne et al., Angew. Chem. 96, page 70 (1984) and the cyclohexane derivatives described in J. Am. M.M. Lehn et al. Chem. Commun. , 1794 (1985), J. Am. Zhang et al., J. Am. Chem. Soc. 116, 2655 (1994), azacrown type and phenylacetylene type macrocycles are included.

  As a discotic liquid crystalline molecule, a compound having liquid crystallinity having a structure in which a linear alkyl group, an alkoxy group, and a substituted benzoyloxy group are radially substituted as a side chain of the mother nucleus with respect to the mother nucleus at the center of the molecule Is also included. The molecule or the assembly of molecules is preferably a compound having rotational symmetry and imparting a certain orientation. In the optically anisotropic layer formed from the discotic liquid crystalline molecules, the compound finally contained in the optically anisotropic layer does not need to be a discotic liquid crystalline molecule. Also included are compounds having a group that reacts with heat or light and, as a result, polymerized or cross-linked by reaction with heat or light, resulting in a high molecular weight and loss of liquid crystallinity. Preferred examples of the discotic liquid crystalline molecules are described in JP-A-8-50206. The polymerization of discotic liquid crystalline molecules is described in JP-A-8-27284.

  In order to fix the discotic liquid crystalline molecules by polymerization, it is necessary to bond a polymerizable group as a substituent to the discotic core of the discotic liquid crystalline molecules. A compound in which the discotic core and the polymerizable group are bonded via a linking group is preferable, whereby the orientation state can be maintained even in the polymerization reaction. Examples thereof include compounds described in paragraphs [0151] to “0168” in JP-A No. 2000-155216.

  In the hybrid alignment, the angle between the major axis (disk surface) of the discotic liquid crystalline molecule and the surface of the polarizing film increases or decreases in the depth direction of the optically anisotropic layer and with increasing distance from the surface of the polarizing film. is doing. The angle preferably decreases with increasing distance. Further, the change in angle can be a continuous increase, a continuous decrease, an intermittent increase, an intermittent decrease, a change including a continuous increase and a continuous decrease, or an intermittent change including an increase and a decrease. The intermittent change includes a region where the inclination angle does not change in the middle of the thickness direction. Even if the angle includes a region where the angle does not change, the angle only needs to increase or decrease as a whole. Furthermore, it is preferable that the angle changes continuously.

  The average direction of the major axis of the discotic liquid crystalline molecules on the polarizing film side can be generally adjusted by selecting a discotic liquid crystalline molecule or an alignment film material, or by selecting a rubbing treatment method. In addition, the major axis (disk surface) direction of the surface-side (air-side) discotic liquid crystalline molecules is generally adjusted by selecting the type of additive used together with the discotic liquid crystalline molecules or discotic liquid crystalline molecules. be able to. Examples of the additive used together with the discotic liquid crystalline molecule include a plasticizer, a surfactant, a polymerizable monomer and a polymer. The degree of change in the major axis orientation direction can also be adjusted by selecting liquid crystalline molecules and additives as described above.

"Other composition of optically anisotropic layer"
Along with the liquid crystal molecules, a plasticizer, a surfactant, a polymerizable monomer, etc. can be used in combination to improve the uniformity of the coating film, the strength of the film, the orientation of the liquid crystal molecules, and the like. It is preferable that the compound has compatibility with the liquid crystal molecules and can change the tilt angle of the liquid crystal molecules or does not inhibit the alignment.

  Examples of the polymerizable monomer include radically polymerizable or cationically polymerizable compounds. Preferably, it is a polyfunctional radically polymerizable monomer and is preferably copolymerizable with the above-described polymerizable group-containing liquid crystal compound. Examples thereof include those described in paragraph numbers [0018] to [0020] in JP-A No. 2002-296423. The amount of the compound added is generally in the range of 1 to 50% by mass and preferably in the range of 5 to 30% by mass with respect to the discotic liquid crystalline molecules.

  Examples of the surfactant include conventionally known compounds, and fluorine compounds are particularly preferable. Specific examples include compounds described in paragraph numbers [0028] to [0056] in JP-A-2001-330725.

  The polymer used together with the discotic liquid crystalline molecule is preferably capable of changing the tilt angle of the discotic liquid crystalline molecule.

  A cellulose ester can be mentioned as an example of a polymer. Preferable examples of the cellulose ester include those described in paragraph [0178] of JP-A No. 2000-155216. The addition amount of the polymer is preferably in the range of 0.1 to 10% by mass, and in the range of 0.1 to 8% by mass with respect to the liquid crystal molecule so as not to inhibit the alignment of the liquid crystal molecules. It is more preferable.

  The discotic nematic liquid crystal phase-solid phase transition temperature of the discotic liquid crystalline molecules is preferably 70 to 300 ° C, and more preferably 70 to 170 ° C.

[Formation of optically anisotropic layer]
The optically anisotropic layer can be formed by applying a coating liquid containing liquid crystalline molecules and, if necessary, a polymerization initiator described later and optional components on the alignment film.

  As a solvent used for preparing the coating solution, an organic solvent is preferably used. Examples of organic solvents include amides (eg, N, N-dimethylformamide), sulfoxides (eg, dimethyl sulfoxide), heterocyclic compounds (eg, pyridine), hydrocarbons (eg, benzene, hexane), alkyl halides (eg, , Chloroform, dichloromethane, tetrachloroethane), esters (eg, methyl acetate, butyl acetate), ketones (eg, acetone, methyl ethyl ketone), ethers (eg, tetrahydrofuran, 1,2-dimethoxyethane). Alkyl halides and ketones are preferred. Two or more organic solvents may be used in combination.

  The coating liquid can be applied by a known method (eg, wire bar coating method, extrusion coating method, direct gravure coating method, reverse gravure coating method, die coating method).

  The thickness of the optically anisotropic layer is preferably 0.1 to 20 μm, more preferably 0.5 to 15 μm, and most preferably 1 to 10 μm.

[Fixing the alignment state of liquid crystalline molecules]
The aligned liquid crystalline molecules can be fixed while maintaining the alignment state. The immobilization is preferably performed by a polymerization reaction. The polymerization reaction includes a thermal polymerization reaction using a thermal polymerization initiator and a photopolymerization reaction using a photopolymerization initiator. A photopolymerization reaction is preferred.

  Examples of the photopolymerization initiator include α-carbonyl compounds (described in US Pat. Nos. 2,367,661 and 2,367,670), acyloin ether (described in US Pat. No. 2,448,828), α-hydrocarbon substituted aromatic acyloin. Compound (described in US Pat. No. 2,722,512), polynuclear quinone compound (described in US Pat. Nos. 3,046,127 and 2,951,758), a combination of triarylimidazole dimer and p-aminophenyl ketone (US Pat. No. 3,549,367) Acridine and phenazine compounds (JP-A-60-105667, U.S. Pat. No. 4,239,850) and oxadiazole compounds (U.S. Pat. No. 4,212,970).

  The amount of the photopolymerization initiator used is preferably in the range of 0.01 to 20% by mass, more preferably in the range of 0.5 to 5% by mass, based on the solid content of the coating solution.

  It is preferable to use ultraviolet rays for light irradiation for polymerization of liquid crystalline molecules.

The irradiation energy is preferably in the range of 20 mJ / cm ² to 50 J / cm ^2, more preferably in the range of 20 to 5000 mJ / cm ^2, and still more preferably in the range of 100 to 800 mJ / cm ² . In order to accelerate the photopolymerization reaction, light irradiation may be performed under heating conditions.

  A protective layer may be provided on the optically anisotropic layer.

  It is also preferable to combine this optical compensation film and a polarizing layer. Specifically, the optically anisotropic layer is formed by applying the coating liquid for the optically anisotropic layer as described above to the surface of the polarizing film. As a result, without using a polymer film between the polarizing film and the optically anisotropic layer, a thin polarizing plate having a small stress (strain × cross-sectional area × elastic modulus) associated with the dimensional change of the polarizing film is produced. . When the polarizing plate according to the present invention is attached to a large liquid crystal display device, an image with high display quality can be displayed without causing problems such as light leakage.

  The inclination angle of the polarizing layer and the optical compensation layer may be stretched so as to match the angle formed between the transmission axis of the two polarizing plates bonded to both sides of the liquid crystal cell constituting the LCD and the vertical or horizontal direction of the liquid crystal cell. preferable. A normal inclination angle is 45 °. Recently, however, devices that are not necessarily 45 ° have been developed for transmissive, reflective, and transflective LCDs, and it is preferable that the stretching direction can be arbitrarily adjusted in accordance with the design of the LCD.

"Liquid Crystal Display"
Each liquid crystal mode in which such an optical compensation film is used will be described.

(TN mode liquid crystal display)
It is most frequently used as a color TFT liquid crystal display device and is described in many documents. The alignment state in the liquid crystal cell in the TN mode black display is an alignment state in which the rod-like liquid crystalline molecules rise at the center of the cell and the rod-like liquid crystalline molecules lie in the vicinity of the cell substrate.

(OCB mode liquid crystal display)
This is a bend alignment mode liquid crystal cell in which rod-like liquid crystal molecules are aligned in a substantially opposite direction (symmetrically) between the upper part and the lower part of the liquid crystal cell. Liquid crystal display devices using a bend alignment mode liquid crystal cell are disclosed in US Pat. Nos. 4,583,825 and 5,410,422. Since the rod-like liquid crystal molecules are symmetrically aligned at the upper and lower portions of the liquid crystal cell, the bend alignment mode liquid crystal cell has a self-optical compensation function. Therefore, this liquid crystal mode is also called an OCB (Optically Compensatory Bend) liquid crystal mode.

  Similarly to the TN mode, the liquid crystal cell in the OCB mode is in a black display, and the alignment state in the liquid crystal cell is such that the rod-like liquid crystal molecules rise in the center of the cell and the rod-like liquid crystal molecules lie in the vicinity of the cell substrate. .

(VA mode liquid crystal display device)
The feature is that the rod-like liquid crystalline molecules are oriented substantially vertically when no voltage is applied. In the VA mode liquid crystal cell, (1) the rod-like liquid crystalline molecules are oriented substantially vertically when no voltage is applied. In addition to a narrowly defined VA mode liquid crystal cell (described in JP-A-2-176625) that is aligned substantially horizontally when a voltage is applied, (2) the VA mode is multi-domained to expand the viewing angle ( Liquid crystal cell (in MVA mode) (SID97, Digest of tech. Papers 28 (1997) 845), (3) Rod-like liquid crystal molecules are substantially vertically aligned when no voltage is applied, and twisted A liquid crystal cell in a domain alignment mode (n-ASM mode) (described in the proceedings 58-59 (1998) of the Japan Liquid Crystal Society) and (4) a SURVAVAL mode liquid crystal cell (LCD interface) Published in the relational 98) are included.

(IPS mode liquid crystal display)
The feature is that the rod-like liquid crystalline molecules are aligned substantially horizontally in the plane when no voltage is applied, and this is characterized by switching by changing the orientation direction of the liquid crystal with or without voltage application. Specifically, those described in JP-A No. 2004-365941, JP-A No. 2004-12731, JP-A No. 2004-215620, JP-A No. 2002-221726, JP-A No. 2002-55341, JP-A No. 2003-195333, etc. Can be used.

(Other liquid crystal display devices)
The ECB mode, STN (Supper Twisted Nematic) mode, FLC (Ferroelectric Liquid Crystal) mode, AFLC (Anti-ferroelectric Liquid Crystal) mode, and ASM (Axially Symmetric Aligned Microcell) mode are optical in the same way as described above. Can be compensated for. Further, it is effective in any of a transmissive, reflective, and transflective liquid crystal display device. It is also advantageously used as an optical compensation sheet for a GH (Guest-Host) type reflective liquid crystal display device.

  The uses of these detailed cellulose derivative films described above are described in detail in pages 45 to 59 in the Japan Institute of Technology Open Technical Report (Technical No. 2001-1745, published on March 15, 2001, Japan Society of Inventions). ing.

“Applying an antireflection layer (antireflection film)”
The antireflection film generally comprises a low refractive index layer which is also an antifouling layer, and at least one layer having a higher refractive index than that of the low refractive index layer (that is, a high refractive index layer and a medium refractive index layer). It is provided above.

  Colloidal metal by multilayer deposition of transparent thin films of inorganic compounds (metal oxides, etc.) with different refractive indexes by chemical vapor deposition (CVD) method, physical vapor deposition (PVD) method, sol-gel method of metal compounds such as metal alkoxides Examples include a method of forming a thin film by post-processing (ultraviolet irradiation: JP-A-9-157855, plasma processing: JP-A-2002-327310) after forming an oxide particle film.

  On the other hand, various antireflection films formed by laminating thin films in which inorganic particles are dispersed in a matrix have been proposed as antireflection films with high productivity.

  The antireflection film which consists of the antireflection layer which provided the anti-glare property which the antireflection film by application | coating as mentioned above provided the surface of the uppermost layer with the shape of a fine unevenness | corrugation is also mentioned.

  The cellulose acylate film of the present invention can be applied to any of the above methods, but a coating method (coating type) is particularly preferable.

[Layer structure of coating type antireflection film]
An antireflection film comprising a layer structure of at least a middle refractive index layer, a high refractive index layer, and a low refractive index layer (outermost layer) on the substrate is designed to have a refractive index satisfying the following relationship.

  Refractive index of high refractive index layer> refractive index of medium refractive index layer> refractive index of transparent support> refractive index of low refractive index layer Alternatively, a hard coat layer is provided between the transparent support and the intermediate refractive index layer. Also good.

  Furthermore, it may consist of a medium refractive index hard coat layer, a high refractive index layer and a low refractive index layer.

  Examples thereof include JP-A-8-122504, JP-A-8-110401, JP-A-10-300902, JP-A-2002-243906, JP-A-2000-11706, and the like. Other functions may be imparted to each layer, for example, an antifouling low refractive index layer or an antistatic high refractive index layer (eg, JP-A-10-206603, JP-A-2002). -243906 publication etc.) etc. are mentioned.

  The haze of the antireflection film is preferably 5% or less, more preferably 3% or less. Further, the strength of the film is preferably H or more, more preferably 2H or more, and most preferably 3H or more in a pencil hardness test according to JIS K5400.

[High refractive index layer and medium refractive index layer]
The layer having a high refractive index of the antireflection film is composed of a curable film containing at least an ultrafine particle of an inorganic compound having a high refractive index having an average particle size of 100 nm or less and a matrix binder.

  Examples of the high refractive index inorganic compound fine particles include inorganic compounds having a refractive index of 1.65 or more, preferably those having a refractive index of 1.9 or more. Examples thereof include oxides such as Ti, Zn, Sb, Sn, Zr, Ce, Ta, La, and In, and composite oxides containing these metal atoms.

  In order to obtain such ultrafine particles, the surface of the particles is treated with a surface treatment agent (for example, silane coupling agents, etc .: JP-A Nos. 1-295503, 11-153703, 2000-9908). , Anionic compounds or organometallic coupling agents: Japanese Patent Application Laid-Open No. 2001-310432, etc., a core-shell structure with high refractive index particles as a core (for example, Japanese Patent Application Laid-Open No. 2001-166104, etc.), a specific dispersant Combined use (for example, Unexamined-Japanese-Patent No. 11-153703, patent number US6210858B1, Unexamined-Japanese-Patent No. 2002-27776069 etc.) etc.

  Examples of the material forming the matrix include conventionally known thermoplastic resins and curable resin films.

  Furthermore, it is selected from a polyfunctional compound-containing composition containing at least two radically polymerizable and / or cationically polymerizable groups, an organometallic compound containing a hydrolyzable group, and a partial condensate composition thereof. At least one composition is preferred. Examples thereof include compounds described in JP-A Nos. 2000-47004, 2001-315242, 2001-31871, and 2001-296401.

  A curable film obtained from a colloidal metal oxide obtained from a hydrolyzed condensate of metal alkoxide and a metal alkoxide composition is also preferred. For example, it describes in Unexamined-Japanese-Patent No. 2001-293818.

  The refractive index of the high refractive index layer is generally 1.70 to 2.20. The thickness of the high refractive index layer is preferably 5 nm to 10 μm, and more preferably 10 nm to 1 μm.

  The refractive index of the middle refractive index layer is adjusted to be a value between the refractive index of the low refractive index layer and the refractive index of the high refractive index layer. The refractive index of the middle refractive index layer is preferably 1.50 to 1.70.

[Low refractive index layer]
The low refractive index layer is formed by sequentially laminating on the high refractive index layer. The refractive index of the low refractive index layer is 1.20 to 1.55. Preferably it is 1.30-1.50.

  It is preferable to construct as the outermost layer having scratch resistance and antifouling property. As means for greatly improving the scratch resistance, imparting slipperiness to the surface is effective, and conventionally known thin film layer means such as introduction of silicone or introduction of fluorine can be applied.

  The refractive index of the fluorine-containing compound is preferably 1.35 to 1.50. More preferably, it is 1.36-1.47. The fluorine-containing compound is preferably a compound containing a crosslinkable or polymerizable functional group containing fluorine atoms in the range of 35 to 80% by mass.

  For example, paragraph numbers [0018] to [0026] of Japanese Patent Application Laid-Open No. 9-222503, paragraph numbers [0019] to [0030] of Japanese Patent Application Laid-Open No. 11-38202, and paragraph numbers of Japanese Patent Application Laid-Open No. 2001-40284. [0027] to [0028], JP-A 2000-284102, and the like.

  The silicone compound is a compound having a polysiloxane structure, preferably containing a curable functional group or a polymerizable functional group in the polymer chain and having a crosslinked structure in the film. For example, reactive silicone (eg, Silaplane (manufactured by Chisso Corporation), etc.), polysiloxane containing silanol groups at both ends (Japanese Patent Laid-Open No. 11-258403, etc.) and the like can be mentioned.

  The crosslinking or polymerization reaction of the fluorine-containing and / or siloxane polymer having a crosslinking or polymerizable group is performed simultaneously with or after the application of the coating composition for forming the outermost layer containing a polymerization initiator, a sensitizer and the like. It is preferable to carry out by light irradiation or heating.

  Also preferred is a sol-gel cured film in which an organometallic compound such as a silane coupling agent and a specific fluorine-containing hydrocarbon group-containing silane coupling agent are cured by a condensation reaction in the presence of a catalyst.

  For example, a polyfluoroalkyl group-containing silane compound or a partially hydrolyzed condensate thereof (Japanese Patent Laid-Open Nos. 58-142958, 58-147483, 58-147484, Japanese Patent Laid-Open Nos. 9-157582, 11) -106704), silyl compounds containing a poly "perfluoroalkyl ether" group which is a fluorine-containing long chain group (Japanese Patent Application Laid-Open Nos. 2000-117902, 2001-48590, 2002) 53804), and the like.

  The low refractive index layer has an average primary particle diameter of 1 to 150 nm such as a filler (for example, silicon dioxide (silica), fluorine-containing particles (magnesium fluoride, calcium fluoride, barium fluoride)) as an additive other than the above. Low refractive index inorganic compounds, organic fine particles described in paragraphs [0020] to [0038] of JP-A-11-3820, etc.), silane coupling agents, slip agents, surfactants, and the like can be contained.

  When the low refractive index layer is positioned below the outermost layer, the low refractive index layer may be formed by a vapor phase method (vacuum deposition method, sputtering method, ion plating method, plasma CVD method, etc.). The coating method is preferable because it can be manufactured at a low cost.

  The film thickness of the low refractive index layer is preferably 30 to 200 nm, more preferably 50 to 150 nm, and most preferably 60 to 120 nm.

[Hard coat layer]
The hard coat layer is provided on the surface of the stretched / unstretched cellulose acylate film in order to impart physical strength to the antireflection film. In particular, it is preferably provided between the stretched / unstretched cellulose acylate film and the high refractive index layer. Moreover, it is also preferable to coat directly on a stretched / unstretched cellulose acylate film without providing an antireflection layer.

  The hard coat layer is preferably formed by a crosslinking reaction or a polymerization reaction of a light and / or heat curable compound. The curable functional group is preferably a photopolymerizable functional group, and the hydrous functional group-containing organometallic compound is preferably an organic alkoxysilyl compound.

  Specific examples of these compounds are the same as those exemplified for the high refractive index layer.

  Specific examples of the constituent composition of the hard coat layer include those described in JP-A Nos. 2002-144913, 2000-9908, and WO00 / 46617.

  The high refractive index layer can also serve as a hard coat layer. In such a case, it is preferable to form fine particles dispersed in the hard coat layer using the method described for the high refractive index layer.

  The hard coat layer can also serve as an antiglare layer (described later) provided with particles having an average particle size of 0.2 to 10 μm to provide an antiglare function (antiglare function).

  The film thickness of the hard coat layer can be appropriately designed depending on the application. The film thickness of the hard coat layer is preferably 0.2 to 10 μm, more preferably 0.5 to 7 μm.

  The strength of the hard coat layer is preferably H or higher, more preferably 2H or higher, and most preferably 3H or higher in a pencil hardness test according to JIS K5400. Further, in the Taber test according to JIS K5400, the smaller the wear amount of the test piece before and after the test, the better.

[Forward scattering layer]
The forward scattering layer is provided in order to give a viewing angle improvement effect when the viewing angle is inclined in the vertical and horizontal directions when applied to a liquid crystal display device. By dispersing fine particles having different refractive indexes in the hard coat layer, it can also serve as a hard coat function.

  For example, Japanese Patent Laid-Open No. 11-38208 specifying a forward scattering coefficient, Japanese Patent Laid-Open No. 2000-199809 having a relative refractive index of a transparent resin and fine particles in a specific range, and Japanese Patent Laid-Open No. 2002 specifying a haze value of 40% or more. -107512 gazette etc. are mentioned.

[Other layers]
In addition to the above layers, a primer layer, an antistatic layer, an undercoat layer, a protective layer, and the like may be provided.

[Coating method]
Each layer of the antireflection film is formed by a dip coating method, an air knife coating method, a curtain coating method, a roller coating method, a wire bar coating method, a gravure coating, a micro gravure method or an extrusion coating method (US Pat. No. 2,681,294). It can be formed by coating.

[Anti-glare function]
The antireflection film may have an antiglare function that scatters external light. The antiglare function is obtained by forming irregularities on the surface of the antireflection film. When the antireflection film has an antiglare function, the haze of the antireflection film is preferably 3 to 30%, more preferably 5 to 20%, and most preferably 7 to 20%.

  As a method for forming irregularities on the surface of the antireflection film, any method can be applied as long as these surface shapes can be sufficiently maintained. For example, a method of forming irregularities on the film surface using fine particles in the low refractive index layer (for example, JP 2000-271878 A), a lower layer of the low refractive index layer (high refractive index layer, medium refractive index layer) Alternatively, a relatively large particle (particle size 0.05 to 2 μm) is added to a hard coat layer in a small amount (0.1 to 50% by mass) to form a surface uneven film, and these shapes are maintained on it. A method of providing a low refractive index layer (for example, JP 2000-281410 A, JP 2000-95893 A, JP 2001-100004 A, 2001-281407, etc.), an uppermost layer (antifouling layer) A method of physically transferring an uneven shape onto the surface after coating (for example, as an embossing method, described in JP-A-63-278839, JP-A-11-183710, JP-A-2000-275401, etc.) And the like.

[Usage]
The unstretched and stretched cellulose acylate film of the present invention is an optical film, particularly for a polarizing plate protective film, an optical compensation sheet for a liquid crystal display device (also referred to as a retardation film), an optical compensation sheet for a reflective liquid crystal display device, and a halogenated film. It is useful as a support for silver photographic light-sensitive materials.

  The measurement method used in the present invention is described below.

(1) Elastic modulus The elastic modulus was determined by measuring the stress at 0.5% elongation in a 23 ° C, 70% rh atmosphere at a tensile rate of 10% / min. It measured by MD and TD and this average value was made into the elasticity modulus.

(2) Degree of substitution of cellulose acylate The degree of substitution of each acyl group of cellulose acylate and the degree of substitution of these 6-positions are described in Carbohydr. Res. 273 (1995) 83-91 (Tezuka et al.).

(3) Residual solvent A sample film (300 mg) dissolved in 30 ml of methyl acetate (sample A) and a sample film dissolved in 30 ml of dichloromethane (sample B) were prepared.
These were measured under the following conditions using gas chromatography (GC).

Column: DB-WAX (0.25 mmφ × 30 m, film thickness 0.25 μm)
Column temperature: 50 ° C
Carrier gas: Nitrogen Analysis time: 15 minutes Sample injection volume: 1 μml
The amount of solvent was determined by the following method.

  For each peak of sample A other than the solvent (methyl acetate), a calibration curve is used to determine the content, and the sum is Sa. In sample B, the content rate is determined using a calibration curve for each peak in the region hidden by the solvent peak in sample A, and the sum is Sb. The sum of Sa and Sb is defined as the residual solvent amount.

(4) Heat loss rate at 220 ° C. When TG-DTA2000S manufactured by Mac Science Co., Ltd. was used and the sample was heated from room temperature to 400 ° C. at a rate of temperature increase of 10 ° C./min under nitrogen, 220 The change in weight of 10 mg of the sample at ° C was defined as the heating weight loss rate.

(5) Melt viscosity Measured under the following conditions using a viscoelasticity measuring device using a cone plate (for example, modular compact rheometer manufactured by Anton Paar: Physica MCR301).
The resin is sufficiently dried to make the water content 0.1% or less, and then measured at a gap of 500 μm and a temperature of 220 ° C. at a shear rate (1 / second).

(6) Re, Rth
10 points were sampled at equal intervals in the width direction of the film, and after adjusting the humidity for 4 hours at 25 ° C. and 60% rh, using an automatic birefringence meter (KOBRA-21ADH: manufactured by Oji Scientific Instruments) At 25 ° C. and 60% RH, the retardation value at a wavelength of 590 nm from the direction perpendicular to the sample film surface and the slow axis as the rotation axis and tilted in increments of 10 ° from + 50 ° to −50 ° from the normal to the film surface From the measurement, an in-plane retardation value (Re) and a retardation value in the film thickness direction (Rth) were calculated.

  The features of the present invention will be described more specifically with reference to examples and comparative examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

[Cellulose acylate resin]
Cellulose acylates with different types of acyl groups and different degrees of substitution described in Table 1 of FIG. 4 were prepared. This was carried out by adding sulfuric acid (7.8 parts by weight with respect to 100 parts by weight of cellulose) as a catalyst, adding carboxylic acid as a raw material for the acyl substituent, and carrying out an acylation reaction at 40 ° C. At this time, the kind and substitution degree of the acyl group were adjusted by adjusting the kind and amount of the carboxylic acid. Moreover, it age | cure | ripened at 40 degreeC after acylation. The Tg of the cellulose acylate thus obtained was measured by the following method and listed in Table 1 of FIG. In addition, the value measured after plasticizer addition is shown.

(Tg measurement)
20 mg of sample is placed in a DSC measuring pan. This is heated from 30 ° C. to 250 ° C. at 10 ° C./min in a nitrogen stream (1st-run), and then cooled to 30 ° C. at −10 ° C./min. Thereafter, the temperature is raised again from 30 ° C. to 250 ° C. (2nd-run). The temperature at which the baseline starts to change from the low temperature side in 2nd-run is shown in Table 1 as the glass transition temperature (Tg). Moreover, 0.05 mass% of silicon dioxide part particles (Aerosil R972V) were added to all levels.

[Melting film formation]
The synthesized cellulose acylate in Table 1 was blown and dried at 120 ° C. for 3 hours to adjust the water content to 0.1% by mass. To this, 3 wt% of triphenyl phosphate (TPP) as a plasticizer, 0.05 mass% of silicon dioxide part particles (Aerosil R972V), 0.20 mass% of phosphite stabilizer (P-1), "UV absorption Agent a "2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-tert-butylanilino) -1,3,5-triazine (0.8% by mass)," UV Absorber b "2 (2'-hydroxy-3 ', 5'-di-tert-butylphenyl) -5-chlorobenzotriazole (0.25 wt%) is added and the mixture is used in a twin screw kneader extruder And kneaded at 190 ° C. The biaxial kneading extruder was provided with a vacuum vent and evacuated (set to 0.3 atm). It was extruded into a strand having a diameter of 3 mm in a water bath and cut into a length of 5 mm.

  The kneaded resin is dried for 3 hours using dehumidified air at 90 ° C., and the moisture content is adjusted to 0.1 wt%. Then, a full flight screw with L / D = 35, a compression rate of 3.5, and a screw diameter of 65 mm is used. After melting at 210 ° C. using the inserted single-screw extruder, a certain amount was fed out using a gear pump in order to increase the thickness accuracy. The molten polymer sent from the gear pump passes through a 4 μm sintered filter to remove foreign matter, and then sent to a die having a slit-like gap, cooled and solidified by a cooling roller, and a cellulose acylate film having a film thickness of 80 μm. It was. The solidified sheet was peeled off from the cooling roller (second roller) 28 and wound into a roll. The cooling roller 28 is a metal roller having a diameter of 500 mm, a wall thickness of 25 mm, and a surface roughness Ra = 25 nm, and the set temperature was a glass transition temperature of the resin of −5 ° C. The elastic roller (first roller) 26 has a diameter of 300 mm, and the wall thickness is as described in Table 1 of FIG. In addition, after trimming both ends (each 3% of the total width) just before winding, the both ends were subjected to thicknessing (knurling) with a width of 10 mm and a height of 50 μm. In each level, the width was 1.5 m, and 3000 m was wound at 30 m / min.

  Here, the extrudability of the molten polymer and the formed cellulose acylate film were evaluated as follows, and comprehensive evaluation was performed from these evaluations and the values of the developed retardation (Re, Rth). It was described in.

(Extrudability)
◎: Extruder motor load has no problem ○: Extrusion has no problem, Extruder motor load is slightly high △: Extruder motor load is high, but somehow can be extruded ×: Extruder Motor load exceeds specified value and film formation is difficult (film strength)
◎: When the film edge during film formation is trimmed with a cutter, no trouble occurs. ○: The film is not broken at all, but the trimmed portion of the trim is seen. Δ: Trimmed. Film breaks occur sporadically as well as the edges. X: Film breaks are severe and trimming with a cutter is difficult. (Productivity)
◎: Film forming speed of 35 m / min or more ○: Film forming speed of 25 m / min or more to less than 35 m Δ: Film forming speed of 15 m / min or more to less than 25 m / min x: Film forming speed of less than 15 m / min (Comprehensive evaluation)
◎: When film formation evaluation, film strength, and productivity are all ◎, in-plane retardation Re is less than 3 nm, and thickness direction retardation Rth is less than 10 nm. ○: Evaluation is equivalent to ◎. In the evaluation of film formation, film strength, and productivity, when there is at least one, or when Re is 3 nm or more and less than 5 nm and retardation Rth in the thickness direction is 10 nm or more and less than 15 nm, Δ: equivalent to ○ In the film formation evaluation, film strength, and productivity evaluation, when Δ is even one, or when Re is 5 nm to 10 nm and thickness direction retardation Rth is 15 nm to 20 nm: Among the evaluations of film formation, film strength, and productivity, there is at least one x, or Re is greater than 10 nm, and the thickness direction retardation Rth is When larger than 20 nm As can be seen from Table 1 of FIG. 4, Experiments 1 to 7 are cellulose acylates having the same substitution degree, but the overall evaluation of those having a weight average molecular weight in the range of 70,000 to 200,000 is Δ to ◎. In contrast, the overall evaluation is x for those not in the range. Further, it can be seen that the overall evaluation of the weight average molecular weight in the range of 100,000 to 170,000 is ◯ to ◎.

  Experiments 8 to 15 are the cases where the substitution degree (B) of the propionyl group of the cellulose acylate resin was shaken, and Experiments 16 to 20 were the substitution degree (A) of the acetyl group of the cellulose acylate resin and the substitution of the propionyl group. This is a case where the degree (B) is swung and A + B is constant (2.85), but 2.7 ≦ A + B ≦ 3.0, 0 ≦ A ≦ 0.7, 2.3 ≦ B ≦ 3.0. Comprehensive evaluation of what is satisfied is Δ to ◎, while dissatisfied evaluation is X. Further, it can be seen that a composite satisfying 2.85 ≦ A + B ≦ 2.95, 0 ≦ A ≦ 0.5, 2.5 ≦ B ≦ 3.0 has a good overall evaluation.

  In Experiments 21 to 26, the thickness of the outer cylinder of the elastic roller 26 was varied. In Experiments 21 to 23, the sum (A + B) of the substitution degree (A) of the acetyl group and the substitution degree (B) of the propionyl group of the cellulose acylate resin is 2.9, and in Experiments 24 to 26, the sum (A + B) is 2.7. However, the experiments 23 and 26 in which the roller outer cylinder thickness of the elastic roller 26 is in the range of 0.2 mm or more and 7.0 mm or less show the expression of retardation (Re, Rth) as compared with those not in the range. Is suppressed.

  In Experiments 27 to 33, the film forming speed was varied. In Experiments 27 to 30, the substitution degree (B) of the propionyl group is 2.75, and in Experiments 31 to 33, the substitution degree (B) of the propionyl group is 2.35. Experiments 29 and 30 in which the film forming speed was set to 20 m / min or more are better results than those having a film forming speed of less than 20 m / min. In addition, the cellulose acylate resin in Experiments 31 to 33 does not satisfy 2.7 ≦ A + B ≦ 3.0.

The block diagram which shows the structure of the film manufacturing apparatus with which this invention is applied Schematic showing the configuration of the extruder Schematic showing a pair of metal rollers in the film forming process section Explanatory drawing of the Example of this invention

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Film manufacturing apparatus, 12 ... Cellulose acylate film, 14 ... Film forming process part, 20 ... Winding process part, 22 ... Extruder, 24 ... Die, 26 ... Roller (elastic roller), 28 ... Roller (cooling roller) 44 ... outer cylinder, 46 ... liquid medium layer, 48 ... elastic body layer, 50 ... metal shaft, Q ... length in contact, Y ... film forming speed, Z ... wall thickness of outer cylinder

Claims (7)

When cellulose acylate resin is melted and extruded from a die into a sheet, the sheet is sandwiched between a pair of metal rollers and solidified by cooling to form a film, with a film forming speed of 20 m / min or more. A method for producing a cellulose acylate film to be formed,
The cellulose acylate resin has a weight average molecular weight of 100,000 to 170,000 , 2.85 ≦ A + B ≦ 2.95 when A is the substitution degree of acetyl group and B is the substitution degree of propionyl group. 0 ≦ A ≦ 0.5 and 2.5 ≦ B ≦ 3.0 are satisfied, A method for producing a cellulose acylate film, The pair of metal rollers has a surface property with an arithmetic average height Ra of 100 nm or less,
2. The method for producing a cellulose acylate film according to claim 1, wherein at least one of the pair of rollers is an elastic roller having a roller outer cylinder thickness of 0.2 mm or more and 7.0 mm or less. The method for producing a cellulose acylate film according to claim 1 or 2 , wherein a zero shear viscosity of the cellulose acylate resin when discharged from the die is 2000 Pa · sec or less. The film formation by the resulting film thickness is 30 to 300 [mu] m, retardation Re is 0~10nm plane, according to any one of claims 1 to 3 in which retardation Rth in the thickness direction, characterized in that a 0~20nm A method for producing a cellulose acylate film. Cellulose acylate film characterized by being manufactured by the manufacturing method according to any one of claims 1-4. An optical compensation film for a liquid crystal display panel, comprising the cellulose acylate film according to claim 5 as a base material. A polarizing plate formed using at least one sheet of the cellulose acylate film according to claim 5 as a protective film of a polarizing film.

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