JP2007152558A - Cellulose acylate film, its manufacturing method, polarizing plate, optical compensation film, antireflection film and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cellulose acylate film capable of sharply suppressing the display irregularity caused when the cellulose acylate film is incorporated in a liquid crystal display device. <P>SOLUTION: The cellulose acylate film is deposited by a melt flow casting method which keeps projection oblique stripes in a quantity of 0/10-30/10 cm. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

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

  Conventionally, when manufacturing a cellulose acylate film used in a liquid crystal image display device, it is dissolved in a chlorinated organic solvent such as dichloromethane, and this is cast on a substrate and dried to form a film. The enrollment method is mainly implemented. Among the chlorinated organic solvents, dichloromethane is preferably used because it is a good solvent for cellulose acylate and has a low boiling point (about 40 ° C.) and is easy to dry in the film forming process and the drying process.

  On the other hand, in recent years, from the viewpoint of environmental conservation, it has been strongly demanded to suppress the discharge of organic solvents including chlorinated organic solvents. For this reason, a more rigorous closed system is adopted so that the organic solvent does not leak from the system, or even if it leaks from the film forming process, the organic solvent is adsorbed through the gas absorption tower before being released to the outside air, Measures were taken so that organic solvents were hardly discharged by processing such as burning or decomposing with an electron beam. However, even if these measures are taken, complete non-emission has not been reached, and further improvements are required.

Therefore, as a film forming method that does not use an organic solvent, a method for melt-forming cellulose acylate has been developed (Patent Document 1). Here, the melting point is lowered by changing a part of the acetyl group of cellulose acylate to a propionyl group, a butyryl group or the like, thereby enabling melt film formation.
JP 2000-352620 A

However, when a polarizing plate is prepared using a cellulose acylate film melt-formed by this method and incorporated in a liquid crystal display device, there is a problem that display unevenness occurs in a direction oblique to the film forming direction. This is a level that requires improvement in a high-quality liquid crystal display device for television.
In view of such a problem of the prior art, an object is to provide a cellulose acylate film capable of greatly suppressing display unevenness that occurs when incorporated in a liquid crystal display device. Another object of the present invention is to provide a polarizing plate, an optical compensation film, an antireflection film and a liquid crystal display device excellent in optical performance.

The above object of the present invention is achieved by the present invention having the following configuration.
(Aspect 1)
A cellulose acylate film formed by melt film formation, characterized in that the number of oblique projection lines is 0/10 cm to 30/10 cm.
(Aspect 2)
A cellulose acylate film having a projected diagonal stripe of 0/10 cm to 30/10 cm and a residual solvent amount of 0.01% by mass or less.
(Aspect 3)
The cellulose acylate film according to aspect 1 or 2, wherein the thickness unevenness is 0.1% to 1%.
(Aspect 4)
The cellulose acylate film according to any one of aspects 1 to 3, wherein the melt viscosity at 220 ° C. is 100 Pa · s to 2000 Pa · s.
(Aspect 5)
The cellulose acylate film according to any one of aspects 1 to 4, wherein the cellulose acylate has a weight average polymerization degree of 250 to 500.
(Aspect 6)
The cellulose acylate film according to any one of aspects 1 to 5, comprising a cellulose acylate satisfying the following formulas (S-1) to (S-3).
Formula (S-1) 2.6 ≦ X + Y ≦ 3.0
Formula (S-2) 0 ≦ X ≦ 1.8
Formula (S-3) 1.0 ≦ Y ≦ 3
(In the formula, X represents the substitution degree of the acetyl group with respect to the hydroxyl group of cellulose, and Y represents the total substitution degree of the propionyl group, butyryl group, pentanoyl group, and hexanoyl group with respect to the hydroxyl group of cellulose.)

(Aspect 7)
A method for producing a cellulose acylate film having a projected diagonal stripe of 0/10 cm to 30/10/10 cm, comprising a step of melting cellulose acylate and extruding it from a die to form a cast film.
(Aspect 8)
8. The method for producing a cellulose acylate film according to aspect 7, wherein the temperature difference in the width direction of the die is set to 1 ° C. to 10 ° C. to perform melt film formation.
(Aspect 9)
The method for producing a cellulose acylate film according to aspect 7 or 8, wherein the film is formed using a die having a manifold angle of 5 to 45 degrees.
(Aspect 10)
The film is formed using a die having a ratio (a / b) of the die land length (a) to the die land width (b) of 0.005 to 0.2, according to any one of aspects 7 to 9. A method for producing a cellulose acylate film.
(Aspect 11)
The method for producing a cellulose acylate film according to any one of aspects 7 to 10, wherein the cellulose acylate is melted and then formed on a casting drum using a touch roll.
(Aspect 12)
The method for producing a cellulose acylate film according to aspect 11, wherein the film is formed using the touch roll at a linear pressure of 3 kg / cm to 100 kg / cm.
(Aspect 13)
According to any one of aspects 7 to 12, wherein two or more casting drums at 60 ° C to 160 ° C are used, and the film is melted at a peripheral speed difference of 0.001% to 5%. A method for producing a cellulose acylate film.
(Aspect 14)
14. The method for producing a cellulose acylate film according to aspect 13, wherein the line speed of the most upstream casting roll is 25 m / min to 150 m / min.
(Aspect 15)
The method for producing a stretched cellulose acylate film according to any one of aspects 7 to 14, further comprising a step of stretching the film formed by 1% to 500% in at least one direction.

(Aspect 16)
A polarizing plate comprising at least one layer of the cellulose acylate film according to any one of aspects 1 to 6 laminated on a polarizing film.
(Aspect 17)
An optical compensation film, wherein the cellulose acylate film according to any one of aspects 1 to 6 is used as a substrate.
(Aspect 18)
An antireflection film, wherein the cellulose acylate film according to any one of aspects 1 to 6 is used as a substrate.
(Aspect 19)
A liquid crystal display device comprising at least one of the polarizing plate according to aspect 16, the optical compensation film according to aspect 17, and the antireflection film according to aspect 18.

  By incorporating the cellulose acylate film of the present invention into a liquid crystal display device, display unevenness of the liquid crystal display device can be significantly suppressed. Moreover, according to the manufacturing method of this invention, the cellulose acylate film which has such a characteristic can be manufactured simply. Furthermore, the polarizing plate, optical compensation film, and antireflection film of the present invention are excellent in optical properties.

  Hereinafter, the cellulose acylate film of the present invention, its production method and use will be described in detail. The description of the constituent elements described below may be made based on typical embodiments of the present invention, but the present invention is not limited to such embodiments. In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

<Suppression of projected diagonal stripes>
(1) Flow velocity distribution and temperature difference Diagonal unevenness, which has been a problem in the above-described high-quality liquid crystal display devices for television use, is an oblique direction present in a cellulose acylate film used as a protective film for a polarizing plate. It was found that this was caused by streaks (relative to the film forming direction). This is difficult to see with the naked eye and can be confirmed when the sample film is placed in front of the wall and the light from the point light source is projected. The streaks are generated obliquely (10 to 80 degrees with respect to the film forming direction) at intervals of 1 to 30 mm. In the present invention, these streaks are referred to as “projected oblique lines”.
As a result of earnest examination of the cause of “projected oblique stripes”, it was found that it was caused by the flow velocity distribution inside the die of molten cellulose acylate. For example, in the case of a general die, the molten resin (melt) spreads in a fan shape from the die entrance. Compared to the melt flowing in the center of the die, the melt flowing along the periphery of the die has a lower flow rate (solid line in FIG. 1). For this reason, when the positions of the melt that have passed through the die entrance at the same time are connected to each other, an arc is formed obliquely (dotted line in FIG. 1). It has been found that such non-uniformity in flow velocity is a source of projected oblique stripes. If there is something that disturbs the flow of the melt (for example, a baffle inside the die, a filter upstream of the die), the flow velocity inside the die does not necessarily increase at the center, but such uneven flow velocity is also Causes oblique projection streaks.
If there is an oblique projection line, the light from the backlight is refracted in the liquid crystal display (LCD), resulting in uneven display. In order to prevent such display unevenness from being visually recognized when used in an LCD, the projected diagonal stripes are preferably 0/10 cm to 30/10 cm, and more preferably 0/10 cm to 20 lines. / 10 cm, and more preferably 0/10 cm to 10/10/10 cm. The value of the oblique projection line here is a value obtained by counting the number of occurrences over the entire width of the film-forming film and converting it to the number per 10 cm.

In the present invention, it has been found that it is effective to provide a temperature difference in the width direction of the die in order to eliminate the “projected oblique stripe”. That is, in the part where the flow rate is fast, the flow rate is lowered by increasing the melt viscosity by lowering the temperature. On the other hand, at both ends of the die having a low flow rate, the flow rate is increased by increasing the temperature and decreasing the melt viscosity. As a result, the flow velocity in the die becomes uniform, and the oblique projection streaks can be eliminated. Conventionally, in order to suppress the streaks that appear in the die, the temperature inside the die is generally uniform, but in the present invention, conversely, the generation of streaks is suppressed by giving a temperature difference in the width direction. Successful. The temperature difference in the width direction of the die is preferably 1 ° C to 10 ° C, more preferably 2 ° C to 9 ° C, and further preferably 3 ° C to 8 ° C. In the case of a general die, it is preferable to increase the temperature at both ends and lower the center.
Such a temperature distribution in the die can be realized by dividing the heater of the die in the width direction and adjusting these temperatures. Adjustment is performed while measuring the flow rate of the melt exiting the die in the width direction. That is, the flow rate is made uniform by raising the temperature of the heater in the slow flow rate portion. The melt flow rate can be determined by marking (scratching) the melt at the die exit and measuring the time to reach a certain length.
The average temperature of the die is preferably 180 ° C to 250 ° C, more preferably 190 ° C to 240 ° C, and further preferably 200 ° C to 235 ° C.

  Projected diagonal streaks due to uneven flow velocity can be effectively suppressed by setting the die manifold angle to 5 to 45 degrees. The manifold angle refers to an angle formed by a straight line connecting the die inlet and the die outlet and the die outlet end (θ in FIG. 2). In a large die having a width of 50 cm or more as used in a manufacturing machine, a compact T die (manifold angle = 0 degree) is generally used, but in the present invention, a die having a manifold angle of 5 degrees to 45 degrees is used. Is preferred. The manifold angle is more preferably 10 to 40 degrees, and further preferably 15 to 35 degrees. As a result, it is possible to suppress a decrease in the flow velocity of the melt flowing along the outer periphery of the die and reduce the projected diagonal stripes. Furthermore, since cellulose acylate is easily pyrolyzed, increasing the flow velocity at the outer periphery of the die in this way also has the effect of reducing coloring due to pyrolysis.

  The ratio (a / b) between the land length inside the die (the length of the portion where the slit interval is narrow in the vicinity of the die exit: a in FIG. 2) and the die land width (die exit width: b in FIG. 2) is 0. It is preferable to set it to 005-0.2, More preferably, it is 0.01-0.15, More preferably, it is 0.015-0.1. Normally, a small value of about 0.001 is used. By increasing the land length in this way, an effect of suppressing the melt flow rate at the center of the die and improving the uniformity of the flow rate distribution can be obtained. As a result, the projected diagonal stripe can be reduced. Increasing the land length in this way is also effective in suppressing the thickness distribution. That is, an internal pressure derived from an upstream extruder is generated in the die, and pressure is also generated in the normal direction (perpendicular to the plane of the die). If this remains up to the die exit, the melt expands in the normal direction due to this internal pressure. If a flow velocity distribution exists in the width direction of the die, this internal pressure is also distributed, resulting in uneven thickness. On the other hand, if the land length is sufficiently long as in the above range, the melt relaxes the stress (internal pressure) during this period, and the expansion at the die exit is suppressed. As a result, even if the speed is uneven, the thickness is hardly uneven, and a film having a uniform thickness can be obtained.

In addition, it is also preferable to use cellulose acylate satisfying the substitution degree of the above formulas (S-1) to (S-3) in order to improve the meltability and achieve a more uniform flow rate. Further, if a propionyl group is selected as a substituent other than the acetyl group, this effect can be obtained more easily. Further preferred substitution degrees will be described later. Furthermore, the weight average polymerization degree of the cellulose acylate is preferably 250 to 500, more preferably 300 to 480, and still more preferably 350 to 450. Cellulose acylate having such a preferable substitution degree and polymerization degree can be prepared by the method described later.
If cellulose acylate having a preferred degree of substitution and degree of polymerization is used, the melt viscosity can be lowered, and uneven flow rate in the die can be reduced. Cellulose acylate is easily decomposed thermally, and it is difficult to lower the melt viscosity by raising the melt temperature. Therefore, the composition as described above is particularly effective. This effect is particularly remarkable when Y is a propionyl group. The preferred melt viscosity of cellulose acylate is 100 Pa · s to 2000 Pa · s, more preferably 150 Pa · s to 1500 Pa · s, and still more preferably 200 Pa · s to 1000 Pa · s. Incidentally, these values are measured at 220 ° C. and a shear rate of 1 sec ⁻¹ .

  In addition, the cellulose acylate film of the present invention is preferably substantially free of residual solvent. Specifically, the residual solvent is preferably 0.1% by mass or less, more preferably 0.5% by mass or less, further preferably 0.01% by mass or less, and 0% by mass. Some are particularly preferred. Unlike the solution casting method using a solvent, if the film is formed by a melt casting method without using a solvent, the amount of residual solvent becomes zero.

(2) Touch roll In the present invention, it is preferable to form a film using a touch roll on a casting drum after extrusion from a die after melting. In this method, the melt discharged from the die is sandwiched between a casting drum and a touch roll to be cooled and solidified.
As described above, the melt expands when the internal pressure is released at the die exit. However, if there is uneven flow velocity, the amount of expansion differs, and the projected oblique stripe becomes more noticeable. If a touch roll is used, it is possible to prepare a cellulose acylate film that suppresses expansion by an iron effect and has few projected diagonal lines. Furthermore, uneven thickness can be reduced by the ironing effect of the touch roll. The preferred thickness unevenness is 0.1% to 1%, more preferably 0.2% to 0.8%, and still more preferably 0.2% to 0.6%.

  In such a touch roll, an elastic body layer is provided on a metal shaft, an outer cylinder is covered thereon, and a liquid medium layer is filled between the elastic body layer and the outer cylinder. The wall thickness Z of the outer cylinder is preferably 0.05 mm to 7.0 mm, more preferably 0.2 mm to 5.0 mm. The casting roll and touch roll preferably have a mirror surface, and the arithmetic average height Ra is usually 100 nm or less, preferably 50 nm or less, more preferably 25 nm or less. Specifically, for example, JP-A-11-314263, JP-A-2002-36332, JP-A-11-235747, JP-A-2004-216717, JP-A-2003-145609, and WO97 / 28950 pamphlet. The one described in can be used.

Thus, since the touch roll is filled with the fluid inside the thin outer cylinder, when the touch roll is brought into contact with the casting roll, it is elastically deformed into a concave shape by the pressing. Therefore, since the touch roll and the casting roll are in surface contact with the cooling roll, the pressure is dispersed and a low surface pressure can be achieved. For this reason, only the unevenness | corrugation of the surface can be corrected, without leaving a residual distortion in the film pinched | interposed between these. The preferred linear pressure of the touch roll is 3 kg / cm -100 kg / cm, more preferably 5 kg / cm to 80 kg / cm, still more preferably 7 kg / cm to 60 kg / cm. The linear pressure here is a value obtained by dividing the force applied to the touch roll by the width of the discharge port of the die. If the linear pressure is less than the above range, the pressing force of the touch roll is weak, and the effect of reducing the projected oblique stripes and thickness unevenness due to the unevenness cannot be sufficiently obtained. If it is in said preferable range, the surface pressure of a touch roll can be maintained uniformly and a projection diagonal stripe and thickness irregularity can be reduced more effectively.
The touch roll is preferably set to 60 ° C to 160 ° C, more preferably 70 ° C to 150 ° C, and still more preferably 80 ° C to 140 ° C. Such temperature control can be achieved by passing a temperature-controlled liquid or gas through these rolls.

Further, in the present invention, it is preferable to use a plurality of casting rolls arranged continuously. These casting rolls are preferably given a peripheral speed difference of 0.01% to 5%, more preferably 0.03% to 3%, and even more preferably 0.05% to 2%. As a result, a slight tension is applied to the melt at the die outlet, and the slow flow rate portion is pulled to reduce the uneven flow rate. As a result, it is possible to reduce the projected diagonal streak caused by the uneven flow velocity.
Furthermore, the line speed of the most upstream casting roll is preferably 25 m / min to 150 m / min, more preferably 30 m / min to 100 m / min, and even more preferably 35 m / min to 80 m / min. The most upstream casting roll refers to the casting roll with which the melt from the extruder first comes into contact. The line speed is usually 10 to 15 m / min. In the present invention, it is preferable to carry out at a high speed as described above. As a result, tension can be applied to the melt in the same way as the above-described difference in peripheral speed, and the portion where the flow velocity is slow is pulled, and uneven flow velocity is reduced. As a result, it is possible to reduce the projected diagonal streak caused by the uneven flow velocity.
The temperature of the casting roll is preferably 60 ° C to 160 ° C, more preferably 70 ° C to 150 ° C, and further preferably 80 ° C to 140 ° C. Such temperature control can be achieved by passing a temperature-controlled liquid or gas through these rolls. Thus, the film can be adhered on the casting drum, and the tension due to the difference in peripheral speed can be transmitted to the melt. Below this temperature, the film tends to solidify and slip on the casting drum, while above this temperature, the film sticks and the effect of the peripheral speed difference cannot be transmitted to the melt.

《Cellulose acylate》
The glucose unit which constitutes cellulose and has β-1,4 bonds has free hydroxyl groups at the 2nd, 3rd and 6th positions. Cellulose acylate is a polymer obtained by esterifying some or all of these hydroxyl groups. The degree of acyl substitution means the sum of the ratios of esterification of cellulose for each of the 2-position, 3-position and 6-position (100% esterification has a degree of substitution of 1). In addition, natural cellulose raw materials may contain components other than cellulose, such as polymers (hemicellulose) of constituent sugars other than glucose (for example, xylose, mannose, etc.) and lignin corresponding to the organisms and purification methods from which they are derived. However, in the present invention, polymers produced by acylating cellulose raw materials containing these are also collectively referred to as cellulose acylate.

(Degree of substitution)
In the present invention, it is preferable to use cellulose acylate that satisfies the following substitution degree conditions (S-1) to (S-3).
Formula (S-1) 2.6 ≦ X + Y ≦ 3.0
Formula (S-2) 0 ≦ X ≦ 1.8
Formula (S-3) 1.0 ≦ Y ≦ 3
(In the formula, X represents the substitution degree of the acetyl group with respect to the hydroxyl group of cellulose, and Y represents the total substitution degree of the propionyl group, butyryl group, pentanoyl group, and hexanoyl group with respect to the hydroxyl group of cellulose.)

In the present invention, it is more preferable to use cellulose acylate that satisfies the following substitution degree conditions (S-4) to (S-6).
Formula (S-4) 2.7 ≦ X + Y ≦ 3.0
Formula (S-5) 0 ≦ X ≦ 1.2
Formula (S-6) 1.5 ≦ Y ≦ 3

In the present invention, it is more preferable to use cellulose acylate that satisfies the following substitution degree conditions (S-7) to (S-9).
Formula (S-7) 2.8 ≦ X + Y ≦ 3.0
Formula (S-8) 0 ≦ X ≦ 0.8
Formula (S-9) 2.0 ≦ Y ≦ 3

By using a cellulose acylate that satisfies the above conditions, the meltability becomes better and it becomes easier to knead uniformly. This effect is particularly remarkable when Y is a propionyl group.
Regarding the method for synthesizing the cellulose acylate used in the present invention, it is possible to refer to the description on pages 7 to 12 of the Japan Society for Invention and Technology (Publication No. 2001-1745, published on March 15, 2001, Japan Society of Invention). . In addition, the addition amount here is the mass% with respect to a cellulose acylate.

(material)
As the cellulose raw material for synthesizing cellulose acylate, those derived from hardwood pulp, softwood pulp and cotton linter are preferably used.

(activation)
Prior to acylation, the cellulose raw material is preferably subjected to a treatment (activation) in contact with an activator. As the activator, acetic acid, propionic acid, or butyric acid is preferable, and acetic acid is particularly preferable. The addition amount of the activator is preferably 5% to 10000%, more preferably 10% to 2000%, and further preferably 30% to 1000%. The addition method can be selected from methods such as spraying, dripping and dipping. The activation time is preferably 20 minutes to 72 hours or less, particularly preferably 20 minutes to 12 hours. The activation temperature is preferably 0 ° C to 90 ° C, particularly preferably 20 ° C to 60 ° C. Furthermore, 0.1 mass%-10 mass% of acylation catalysts, such as a sulfuric acid, can also be added to an activator.

(Acylation)
It is preferable to acylate the hydroxyl group of cellulose by reacting cellulose with a carboxylic acid anhydride using a Bronsted acid or a Lewis acid (refer to "Physical and Chemical Dictionary", fifth edition (2000)) as a catalyst.

  In order to control the temperature rise due to the heat of reaction of acylation, it is preferable to cool the acylating agent in advance. The acylation temperature is preferably -50 ° C to 50 ° C, more preferably -30 ° C to 40 ° C, particularly preferably -20 ° C to 35 ° C. 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 to 24 hours, more preferably 1 hour to 12 hours, and particularly preferably 1.5 hours to 10 hours.

  A method for obtaining a cellulose acylate is a method in which two carboxylic anhydrides are reacted as an acylating agent by mixing or sequential addition, and a mixed acid anhydride of two carboxylic acids (for example, acetic acid / propionic acid mixed acid anhydride). ), A mixed acid anhydride (for example, acetic acid / propionic acid mixed acid anhydride) in a reaction system using a carboxylic acid and an acid anhydride of another carboxylic acid (for example, acetic acid and propionic acid anhydride) as a raw material. A method of forming and reacting with cellulose, a method of once synthesizing cellulose acylate having a degree of substitution of less than 3, and further acylating the remaining hydroxyl group with an acid anhydride or acid halide can be used.

  The synthesis of cellulose acylate having a high degree of substitution at the 6-position is described in JP-A-11-5851, JP-A-2002-212338, JP-A-2002-338601, and the like.

(Acid anhydride)
As an acid anhydride of carboxylic acid, a carboxylic acid having 2 to 22 carbon atoms can be preferably used. Particularly preferred are acetic anhydride, propionic anhydride, and butyric anhydride. The acid anhydride is preferably added in an amount of 1.1 to 50 equivalents, more preferably 1.2 to 30 equivalents, and particularly preferably 1.5 to 10 equivalents based on the hydroxyl group of cellulose. By appropriately adjusting the amount of acid anhydride added, the degree of substitution of the acyl group can be adjusted.

(catalyst)
The acylation catalyst is preferably a Bronsted acid or a Lewis acid, more preferably sulfuric acid or perchloric acid, and a preferred addition amount is 0.1 to 30% by mass, more preferably 1 to 15% by mass. And particularly preferably 3 to 12% by mass.

(solvent)
Carboxylic acid is preferable as the acylating solvent, more preferably carboxylic acid having 2 to 7 carbon atoms, and particularly preferably acetic acid, propionic acid, and butyric acid. These solvents may be used as a mixture.

(Reaction terminator)
It is preferable to add a reaction terminator after the acylation reaction. The reaction terminator is not particularly limited as long as it decomposes acid anhydrides, and examples thereof include water, alcohol (having 1 to 3 carbon atoms), and carboxylic acids (acetic acid, propionic acid, butyric acid, etc.). Among them, water and carboxylic acid ( A mixture with acetic acid) is more preferred. The composition of water and carboxylic acid is preferably 5 to 80% by mass, more preferably 10 to 60% by mass, and particularly preferably 15 to 50% by mass of water.

(Neutralizer)
A neutralizing agent may be added after the acylation reaction is stopped. Preferred examples of the neutralizing agent include ammonium, organic quaternary ammonium, alkali metal, group 2 metal, group 3-12 metal, or group 13-15 element carbonate, bicarbonate, organic acid salt, water An oxide or an oxide can be given. Particularly preferred are sodium, potassium, magnesium or calcium carbonates, bicarbonates, acetates or hydroxides.

(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. In the presence of catalyst) and water, the ester bond is partially hydrolyzed by maintaining the temperature at 20 to 90 ° C. for several minutes to several days, thereby reducing the acyl substitution degree of cellulose acylate to a desired level. Thereafter, partial hydrolysis of the remaining catalyst is stopped using the neutralizing agent. The degree of weight average polymerization can be adjusted by adjusting the time maintained in the presence of the catalyst and water. Specifically, the longer the time maintained in the presence of the catalyst and water, the lower the weight average degree of polymerization.

(Filtration)
Filtration may be performed in any step from completion of acylation to reprecipitation. It is also preferred to dilute with a suitable solvent prior to filtration.

(Reprecipitation)
The cellulose acylate solution is mixed with water or an aqueous solution of carboxylic acid (for example, acetic acid, propionic acid, etc.) and reprecipitated. Reprecipitation may be either continuous or batch.

(Washing)
It is preferable to perform a washing treatment after reprecipitation. Washing can be performed using water or warm water, and the completion of washing can be confirmed by pH, ion concentration, electrical conductivity, elemental analysis, and the like.

(Stabilization)
The cellulose acylate after washing is preferably added with a weak alkali (carbonates such as Na, K, Ca and Mg, bicarbonates, hydroxides and oxides) for stabilization.

(Dry)
It is preferable to dry the moisture content of the cellulose acylate at 50 to 160 ° C. to 2% by mass or less.

"Additive"
(Stabilizer)
In the present invention, it is particularly effective to add a stabilizer in order to maintain the stability of cellulose acylate during high-temperature melt film formation. In particular, it is preferable to add at least one selected from a phenol-based stabilizer having a molecular weight of 500 or more and a phosphite-based stabilizer having a molecular weight of 500 or more or a thioether-based stabilizer having a molecular weight of 500 or more.

  In the present invention, any known phenol-based stabilizer can be used as the phenol-based stabilizer. Preferable phenolic stabilizers include hindered phenolic stabilizers. In particular, it is preferable to have a substituent at a site adjacent to the hydroxyphenyl group. In this case, the substituent is preferably a substituted or unsubstituted alkyl group having 1 to 22 carbon atoms, such as a methyl group, an ethyl group, a propionyl group, An isopropionyl group, a butyl group, an isobutyl group, a tert-butyl group, a pentyl group, an isopentyl group, a tert-pentyl group, a hexyl group, an octyl group, an isooctyl group, and a 2-ethylhexyl group are more preferable. In addition, a stabilizer having a hydroxyphenyl group and a phosphite group in the same molecule is also mentioned as a preferable material.

  These are readily available as commercial products and are sold by the following manufacturers. From Ciba Specialty Chemicals, Irganox 1076, Irganox 1010, Irganox 3113, Irganox 245, Irganox 1135, Irganox 1330, Irganox 259, Irganx 565, Irganx 565, Irganx 565, Ir35x10 Moreover, it can obtain from Asahi Denka Kogyo Co., Ltd. as ADK STAB AO-50, ADK STAB AO-60, ADK STAB AO-20, ADK STAB AO-70, and ADK STAB AO-80. Furthermore, from Sumitomo Chemical Co., Ltd., it can obtain as Sumilizer BP-76, Sumilizer BP-101, Sumilizer GA-80. Also available from Sipro Kasei Co., Ltd. as Sinox 326M and Sinox 336B.

  A phosphite ester stabilizer having a molecular weight of 500 or more has an antioxidant effect. For example, compounds described in JP-A-2004-182979, [0023] to [0039], JP-A-51-70316. The compounds described in JP-A-10-306175, JP-A-57-78431, JP-A-54-157159, and JP-A-55-13765 can be mentioned as preferred compounds. Furthermore, as other phosphite-based stabilizers, materials described in detail on pages 17 to 22 of the Japan Institute of Invention and Technology (Public Technical Number 2001-1745, published on March 15, 2001, Japan Society of Invention) Can be selected and used. These are commercially available from Asahi Denka Kogyo Co., Ltd. as ADK STAB 1178, 2112, PEP-8, PEP-24G, PEP-36G, and HP-10, and Sandostab P-EPQ from Clariant. Is possible.

  In the present invention, any known thioether stabilizer can be used as the thioether stabilizer. For example, it is marketed by Sumitomo Chemical Co., Ltd. as Sumilizer TPL, TPM, TPS, TDP. Also available from Asahi Denka Kogyo Co., Ltd. as ADK STAB AO-412S.

  In the use of these stabilizers, at least one phenol-based stabilizer and at least one selected from a phosphite-based stabilizer or a thioether-based stabilizer are each 0.02 to 3% by mass with respect to cellulose acylate. It is preferable to use so that it may be contained, and it is made to contain 0.05-1 mass% especially. The content ratio of the phenol stabilizer and the phosphite stabilizer or thioether stabilizer is not particularly limited, but is preferably 1/10 to 10/1 (part by mass), more preferably 1/5 to 5/5. It is 5/1 (parts by mass), more preferably 1/3 to 3/1 (parts by mass), and particularly preferably 1/3 to 2/1 (parts by mass).

  In the present invention, it is also recommended to use a stabilizer having a hydroxyphenyl group and a phosphite group in the same molecule. Those materials are described in JP-A-10-273494. As a commercially available product, Sumilyzer GP (Sumitomo Chemical Co., Ltd.) can be mentioned.

Further, a long-chain aliphatic amine described in JP-A-61-63686, a compound containing a sterically hindered amine group described in JP-A-6-329830, and a hindered dye described in JP-A-7-90270. Peridinyl light stabilizers, organic amines described in JP-A-7-278164, and the like can also be used.
Preferred amine stabilizers are ADK STAB LA-57, LA-52, LA-67, LA-62, LA-77 from Asahi Denka, and TINUVIN 765, 144 from Ciba Specialty Chemicals. It is commercially available. The ratio of amines to stabilizers is usually about 0.01 to 25% by weight.

(Plasticizer)
If a plasticizer is added to cellulose acylate, the crystal melting temperature (Tm) of cellulose acylate can be lowered. Although the molecular weight of the plasticizer used for this invention is not specifically limited, Preferably high molecular weight is mentioned, For example, molecular weight 500 or more is preferable, More preferably, it is 550 or more, Furthermore, 600 or more is preferable. Examples of the plasticizer include phosphate esters, alkylphthalylalkyl glycolates, carboxylic acid esters, and fatty acid esters of polyhydric alcohols. These plasticizers may be solid or oily. That is, the melting point and boiling point are not particularly limited. When performing melt film formation, those having non-volatility can be particularly preferably used.

(UV absorber)
An ultraviolet inhibitor may be added to the cellulose acylate. With respect to the ultraviolet ray inhibitor, JP-A-60-235852, JP-A-3-199201, JP-A-51907073, JP-A-5-194789, JP-A-5-271471, JP-A-6-107854, JP-A-6-118233. 6-148430, 7-11056, 7-11055, 7-11056, 8-29619, 8-239509, and JP-A-2000-204173. . The addition amount is preferably 0.01 to 2% by mass, more preferably 0.01 to 1.5% by mass of the melt (melt) to be prepared.

  These ultraviolet absorbers are available as the following commercial products. As benzotriazoles, TINUBIN P (Ciba Specialty Chemicals), TINUBIN 234 (Ciba Specialty Chemicals), TINUBIN 320 (Ciba Specialty Chemicals), TINUBIN 326 (Ciba Specialty Chemicals) TINUBIN 327 (Ciba Specialty Chemicals), TINUBIN 328 (Ciba Specialty Chemicals), Sumisorb 340 (Sumitomo Chemical), Adekas Type LA-31 (Asahi Denka Kogyo Co., Ltd.), etc. . In addition, as benzophenone-based ultraviolet absorbers, Seasorb 100 (manufactured by Sipro Kasei Co., Ltd.), Seasorb 101 (manufactured by Sipro Kasei Co., Ltd.), Seasorb 101S (manufactured by Sipro Kasei Co., Ltd.), Seasorb 102 (manufactured by Sipro Kasei Co., Ltd.), Seasorb 103 (Sipro Kasei) Kasei Co., Ltd.), Adekas Type LA-51 (Asahi Denka Kogyo Co., Ltd.), Chemisorp 111 (Chemipro Kasei Co., Ltd.), UVINUL D-49 (BASF Corp.), and the like. Examples of oxalic acid anilide UV absorbers include TINUBIN 312 (manufactured by Ciba Specialty Chemicals) and TINUBIN 315 (manufactured by Ciba Specialty Chemicals). In addition, as a salicylic acid ultraviolet absorber, Seasorb 201 (manufactured by Sipro Kasei) and Seasorb 202 (manufactured by Sipro Kasei) are marketed, and as a cyanoacrylate ultraviolet absorber, Seasorb 501 (manufactured by Sipro Kasei), UVINUL N-539 (BASF) is available.

(Fine particles)
In the present invention, fine particles can be added to cellulose acylate. Examples of the fine particles include fine particles of inorganic compounds or fine particles of organic compounds, and any of them may be used. The average primary particle size of preferable fine particles contained in the cellulose acylate in the present invention is 5 nm to 3 μm, preferably 5 nm to 2.5 μm, and particularly preferably 20 nm to 2.0 μm. The addition amount of the fine particles is 0.005 to 1.0% by mass with respect to cellulose acylate, more preferably 0.01 to 0.8% by mass, and further preferably 0.02 to 0.4% by mass. %.

Examples of the inorganic compound include SiO ₂ , ZnO, TiO ₂ , SnO ₂ , Al ₂ O ₃ , ZrO ₂ , In ₂ O ₃ , MgO, BaO, MoO ₂ , V ₂ O ₅ , talc, clay, calcined kaolin, and calcined. Examples include calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, and calcium phosphate. Preferably, at least one of SiO ₂ , ZnO, TiO ₂ , SnO ₂ , Al ₂ O ₃ , ZrO ₂ , In ₂ O ₃ , MgO, BaO, MoO ₂ , and V ₂ O ₅ is preferable, and SiO ₂ is more preferable. , TiO ₂ , SnO ₂ , Al ₂ O ₃ , ZrO ₂ .

As the fine particles of SiO ₂ , for example, commercially available products such as Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600 (above, manufactured by Nippon Aerosil Co., Ltd.) can be used. As the ZrO ₂ fine particles, for example, commercially available products such as Aerosil R976 and R811 (above, manufactured by Nippon Aerosil Co., Ltd.) can be used. Seahoster KE-E10, E30, E40, E50, E70, E70, E150, W10, W30, W50, P10, P30, P50, P100, P150, P250 ) Etc. are also used. Further, silica microbeads P-400 and 700 (catalyst chemical industry products) can also be used. SO-G1, SO-G2, SO-G3, SO-G4, SO-G5, SO-G6, SO-E1, SO-E2, SO-E3, SO-E4, SO-E5, SO-E6, SO- It can also be used as C1, SO-C2, SO-C3, SO-C4, SO-C5, SO-C6 (manufactured by Admatechs Co., Ltd.). Furthermore, silica particles (a powdered water dispersion) 8050, 8070, 8100, and 8150 manufactured by Moritex Corporation can also be used.

  Next, as the fine particles of the organic compound that can be used in the present invention, for example, polymers such as silicone resins, fluororesins, and acrylic resins are preferable, and silicone resins are particularly preferable. The silicone resin preferably has a three-dimensional network structure, such as Tospearl 103, 105, 108, 120, 145, 3120, and 240 (above, manufactured by Toshiba Silicone Co., Ltd.). Commercial products having a trade name can be used.

Furthermore, it is preferable to use fine particles made of an inorganic compound that have been surface-treated in order to stably exist in the cellulose acylate film. The inorganic fine particles are also preferably used after surface treatment. As the surface treatment method, there are chemical surface treatment using a coupling agent and physical surface treatment such as plasma discharge treatment and corona discharge treatment. In the present invention, it is preferable to use a coupling agent. . As the coupling agent, an organoalkoxy metal compound (for example, a silane coupling agent, a titanium coupling agent, etc.) is preferably used. When inorganic fine particles are used as the fine particles (especially when SiO ₂ is used), treatment with a silane coupling agent is particularly effective. An organosilane compound can be used as the silane coupling agent. Although the usage-amount of the said coupling agent is not specifically limited, Preferably it is recommended to use 0.005-5 mass% with respect to an inorganic fine particle, Furthermore, 0.01-3 mass% is preferable.

(Release agent)
A release agent can be added to the cellulose acylate in the present invention. As the release agent, a compound having a fluorine atom is preferable. The compound having a fluorine atom can exhibit an action as a release agent and may be a low molecular weight compound or a polymer. Examples of the polymer include the polymers described in JP-A No. 2001-269564. A polymer having a fluorine atom is preferably a polymer obtained by polymerizing a monomer containing a fluorinated alkyl group-containing ethylenically unsaturated monomer as an essential component. The fluorinated alkyl group-containing ethylenically unsaturated monomer related to the polymer is not particularly limited as long as it is a compound having an ethylenically unsaturated group and a fluorinated alkyl group in the molecule. A surfactant having a fluorine atom can also be used, and a nonionic surfactant is particularly preferable.

<< Manufacture of cellulose acylate film >>
(Pelletized)
The cellulose acylate and additives are preferably mixed and pelletized prior to melt film formation.
Pelletization can be made by melting the cellulose acylate and additives at 150 ° C. to 250 ° C. using a biaxial or uniaxial kneading extruder, then extruding the noodles into water and cutting. it can. You may pelletize with the underwater cut method cut | disconnecting, extruding directly in water. More preferably, the kneading and extruding machine is a vent type and is pelletized while decompressing. Further, it is more preferable to pelletize the inside of the kneading extruder while replacing with nitrogen.

Preferably, the pellet size is such cross-sectional area is 1 mm ² to 300 mm ^2, a length 1Mm～30mm, and more preferably the cross-sectional area of 2 mm ² 100 mm ^2, length 1.5Mm～10mm.
The rotation speed of the kneading extruder is preferably 10 rpm to 1000 rpm, more preferably 30 rpm to 500 rpm. The extrusion residence time in pelletization is usually 10 seconds to 30 minutes, preferably 30 seconds to 3 minutes.

(Dry)
Prior to melt film formation, it is preferable to dry the moisture in the pellets so that the moisture content is 0.1% by mass or less, more preferably 0.01% by mass or less.
Drying temperature is preferably 40 to 180 ° C. for this, amount of drying air is preferably available in 20 to 400 m ³ / hour, and particularly preferably 100 to 250 m ³ / hour. The dew point of the drying wind is preferably 0 to -60 ° C, more preferably -20 to -40 ° C.

(Melt extrusion)
The dried cellulose acylate resin is supplied into the cylinder from the supply port of the kneading extruder.
The screw compression ratio of the kneading extruder is preferably 2.5 to 4.5, more preferably 3.0 to 4.0. L (screw length) / D (screw diameter) is preferably 20 to 70. More preferably, it is 24-50. The melting temperature is preferably performed at the above-described temperature.
As the screw, a full flight, a mudock, a dull image, or the like can be used.
In order to prevent the oxidation of the resin, it is more preferable that the inside of the kneading extruder is carried out in an inert (nitrogen or the like) air flow or while being evacuated using a vented extruder.

(filtration)
It is preferable to perform breaker plate type filtration at the outlet of the extruder.
For high-precision filtration, it is preferable to provide a leaf type disk filter type filtration device after passing through the gear pump. Filtration may be performed in a single stage or in multiple stages. The filtration accuracy of the filter medium is preferably 3 μm to 15 μm, more preferably 3 μm to 10 μm. The filter medium is preferably stainless steel or steel, and stainless steel is particularly preferable. As the filter medium, a knitted wire or a sintered metal filter medium can be used, and the latter is particularly preferable.

(Gear pump)
It is preferable to install a gear pump between the kneading extruder and the die in order to improve the thickness accuracy (reduction in fluctuation of the discharge amount). Thereby, the resin pressure fluctuation width of the die portion can be made 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 is also preferable. A high-precision gear pump using three or more gears is also effective. Since the staying part in the gear pump causes resin deterioration, a structure with less staying is preferable.
In order to stabilize the extrusion pressure, it is preferable to reduce the temperature fluctuation of the adapter connecting the kneading extruder and the gear pump and the gear pump and the die. For this purpose, it is more preferable to use an aluminum cast heater.

(Die)
In the present invention, it is preferable to use a die as described above. The clearance at the die outlet is generally 1.0 to 5.0 times the film thickness, more preferably 1.3 to 2 times.
The clearance of the die is preferably adjustable at intervals of 40 to 50 mm, more preferably at most 25 mm. A method of measuring the downstream film thickness and feeding it back to the die thickness adjustment is also effective in reducing the thickness variation.
Since the functional layer is provided on the outer layer, it is possible to produce a film having two or more kinds of structures using a multilayer film forming apparatus.
The preferable residence time of the resin from the supply port through the kneading extruder to the exit of the die is 2 minutes to 60 minutes, preferably 4 minutes to 30 minutes. Further, a static mixer for improving the uniformity of the resin temperature may be inserted immediately before the die.

(cast)
The molten resin extruded from the die onto the sheet is cooled and solidified on a casting drum to obtain a film. At this time, it is preferable to use a touch roll as described above.
The casting drum is set as described above. The number of preferable casting rolls is 1 to 8, more preferably 2 to 5. It is preferable that the temperature of the casting roll is gradually lowered from the upstream toward the downstream. The diameter of the casting roll and the touch roll is preferably 50 mm to 5000 mm, more preferably 150 mm to 1000 mm. The interval between the plurality of casting rolls is preferably 0.3 mm to 300 mm, more preferably 3 mm to 30 mm between the surfaces.
Then, it peels off from a casting drum, winds up after passing through a nip roll. The thickness of the unstretched film thus obtained is preferably 30 μm to 400 μm, more preferably 50 μm to 200 μm.

(Winding)
It is preferable to trim both ends before winding. The trimmed portion may be reused as a film raw material. As the trimming cutter, any rotary cutter, shear blade, knife, or the like may be used. Regarding the material, carbon steel, stainless steel, and ceramic can be used.
A preferable winding tension is 1 kg / m width to 50 kg / width, more preferably 3 kg / m width to 20 kg / m width. The take-up tension may be taken up with a constant take-up tension, but it is more preferable that the take-up tension be taper according to the take-up diameter.
It is also necessary to adjust the draw ratio between the nip rolls so that the film does not receive a tension higher than the specified tension in the middle of the line.
Prior to winding, a laminated film may be attached to at least one side.

  FIG. 3 shows a schematic view of an apparatus for carrying out melt film formation that can be preferably employed in the present invention. In the figure, 101 is a kneading extruder, 102 is a gear pump, 103 is a filtration unit, 104 is a die, 105 is a touch roll, 106 is a casting cooling drum, 107 is cellulose acylate, 108 is a longitudinal stretching process unit, and 109 is lateral stretching. The process part 110 shows a winding process part. The stretching will be described later. In the case of forming an unstretched film, the film can be wound without passing through the stretched portions (108, 109) after passing through the casting cooling drum (106).

<Physical properties of unstretched cellulose acylate film>
The unstretched cellulose acylate film thus obtained preferably has Re = 0 to 20 nm and Rth = 0 to 60 nm, more preferably Re = 0 to 10 nm, Rth = 0 to 40 nm, and more preferably Re = 0 to 10 nm. , Rth = 0 to 20 nm. Re and Rth represent in-plane retardation and retardation in the thickness direction, respectively, and are represented by the following formula.
Re = (nx−ny) × d
Rth = [{(nx + ny) / 2} -nz] × d
(In the above formula, nx is the refractive index in the slow axis direction, ny is the refractive index in the deep window axis direction, nz is the refractive index in the thickness direction, and d is the thickness (nm).)

  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 the direction 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 of the unstretched cellulose acylate film is preferably 90% to 100%. The haze is usually 0 to 1%, preferably 0 to 0.6%.
The tensile elastic modulus is preferably 1.0 kN / mm ^{2 to} 3.5 kN / mm ² , more preferably 1.4 kN / mm ^{2 to} 2.6 kN / mm ² . The elongation at break is preferably 8% to 400%, more preferably 10% to 300%, and still more preferably 15% to 200%.
Tg is preferably 95 ° C to 145 ° C. The thermal dimensional change at 80 ° C. for 1 day is preferably 0% to ± 1% in both the vertical and horizontal directions, and more preferably 0% to ± 0.3%.
40 ° C., water permeability at 90% relative humidity, preferably 300 g / m ² · day to 1000 g / m ² · day, more preferably from 500 g / m ² · day ~800g / m ² · day. The equilibrium water content at 25 ° C. and 80% relative humidity is preferably 1% by mass to 4% by mass, and more preferably 1.5% by mass to 2.5% by mass.

<Physical properties of stretched and stretched cellulose acylate film>
(Stretching)
An unstretched film can be stretched to control Re and Rth.
The stretching temperature is preferably (Tg to Tg + 50 ° C.), more preferably (Tg + 5 ° C.) to (Tg + 20 ° C.). A preferable draw ratio is 1% to 300%, more preferably 3% to 200%, at least one side. It is more preferable to stretch with one stretching ratio larger than the other, and the smaller stretching ratio is preferably 1% to 30%, more preferably 3% to 20%, and the larger stretching ratio is 30% to 30%. 300% is preferable, and 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 can be carried out using a nip roll, a tenter or the like. Moreover, you may use the simultaneous biaxial stretching method as described in Unexamined-Japanese-Patent No. 2000-37772, Unexamined-Japanese-Patent No. 2001-113591, and Unexamined-Japanese-Patent No. 2002-103445.

Re and Rth of the stretched cellulose acylate film preferably satisfy the following formula.
Rth ≧ Re
200 ≧ Re ≧ 0
500 ≧ Rth ≧ 30

It is more preferable that Re and Rth of the cellulose acylate film after stretching satisfy the following formula.
Rth ≧ Re × 1.2
100 ≧ Re ≧ 20
350 ≧ Rth ≧ 80

  In addition, the angle θ formed by the film forming direction (longitudinal direction) and the slow axis is preferably 0 ± 3 °, more preferably 0 ± 1 ° in the case of longitudinal stretching. In the case of transverse stretching, 90 ± 3 ° or −90 ± 3 ° is preferable, and 90 ± 1 ° or −90 ± 1 ° is more preferable.

  The thickness of the cellulose acylate film after stretching is preferably 15 μm to 200 μm, more preferably 40 μm to 140 μm. The thickness unevenness is preferably 0% to 3% in both the longitudinal direction and the width direction, and more preferably 0% to 1%.

(Physical properties)
The physical properties of the stretched cellulose acylate film are preferably in the following ranges.
The tensile elastic modulus is preferably 1.0 kN / mm ² or more and less than 3.0 kN / mm ² , more preferably 1.3 kN / mm ^{2 to} 2.6 kN / mm ² .
The breaking elongation is preferably 3% to 200%, more preferably 8% to 150%.
Tg is preferably 95 ° C to 145 ° C, more preferably 105 ° C to 135 ° C.
The thermal dimensional change after standing at 80 ° C. for 1 day is preferably 0% to ± 1% in both the vertical and horizontal directions, and more preferably 0% to ± 0.3%.

40 ° C., water permeability at 90% relative humidity, preferably 300 g / m ² · day to 1000 g / m ² · day, more preferably from 500 g / m ² · day ~800g / m ² · day.
The equilibrium water content at 25 ° C. and 80% relative humidity is preferably 1% by mass to 4% by mass, and more preferably 1.5% by mass to 2.5% by mass.
The haze is preferably 0% to 3%, more preferably 0% to 1% or less. The total light transmittance is preferably 90% to 100%.

<Treatment for cellulose acylate film>
Next, the treatment that can be performed on the cellulose acylate film of the present invention will be described with reference to preferred embodiments.

(surface treatment)
The cellulose acylate film can achieve improved adhesion between the cellulose acylate film and each functional layer (for example, the undercoat layer and the back layer) by optionally 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 in a low-pressure gas of 10 ^{−3 to} 20 Torr, or may be plasma treatment under atmospheric pressure. Plasma-excitable gas refers to 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. Can be mentioned. Details of these are described in detail in pages 30 to 32 of the Japan Society of Invention Disclosure Technical Bulletin (Public Technical Number 2001-1745, published on March 15, 2001, Japan Institute of Invention). 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.

  The alkali saponification treatment may be immersed in a saponification solution or coated with a saponification solution. In the case of the immersion method, it is achieved by passing an aqueous solution of pH 10 to 14 such as NaOH or KOH through a bath heated to 20 ° C. to 80 ° C. for 0.1 minutes to 10 minutes, followed by neutralization, washing with water and drying. it can.

  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 at the time of 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. Specifically, these saponification methods are described in, for example, JP-A No. 2002-82226 and WO 02/46809 pamphlet.

  It is also preferable to provide an undercoat layer for adhesion to the functional layer. This layer may be applied after the above surface treatment or may be applied without the surface treatment. The 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.

<< Use of Cellulose Acylate Film of the Present Invention >>
The cellulose acylate film of the present invention is combined with the functional layer described in detail on pages 32 to 45 of the Japan Institute of Invention (Technology No. 2001-1745, published on March 15, 2001, Japan Institute of Invention). It is preferable. Among these, application of a polarizing film (polarizing plate), application of an optical compensation layer (optical compensation sheet), and application of an antireflection layer (antireflection film) are preferable. This will be described in order below.

(1) Application of polarizing film (preparation of polarizing plate)
(Material used)
Currently, a commercially available polarizing film is generally produced 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. is there. 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 polarizing performance by being oriented in the binder. As the dichroic dye, an azo dye, stilbene dye, pyrazolone dye, triphenylmethane dye, quinoline dye, oxazine dye, thiazine dye or anthraquinone dye is used. The dichroic dye is preferably water-soluble. The dichroic dye preferably has a hydrophilic substituent (for example, sulfo, amino, hydroxyl). For example, the compounds described in page 58 of the Japan Society of Invention Disclosure Technique (Public Technical Number 2001-1745, Issue Date: March 15, 2001, Japan Society of Invention) are listed.

  As the binder for the polarizing 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 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 (for example, poly (N-methylolacrylamide), carboxymethylcellulose, gelatin, polyvinyl alcohol, and modified polyvinyl alcohol) are preferable, gelatin, polyvinyl alcohol, and modified polyvinyl alcohol are more preferable, and polyvinyl alcohol and modified polyvinyl alcohol are most preferable. . 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 (for example, boric acid and 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)
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. 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. Stretching can be carried out by the following 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., particularly 17 to 40 ° C. in an aqueous medium bath or a dye 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 preferred draw ratio is 1.2 to 3.5 times, particularly 1.5 to 3.0 times in view of the above-mentioned effects. . Thereafter, the film is dried at 50 ° C. to 90 ° C. to obtain a polarizing film.

[Lamination]
The saponified cellulose acylate film and a polarizing film prepared by stretching are bonded to prepare a polarizing plate. The laminating direction is preferably such that the casting axis direction of the cellulose acylate film and the stretching axis direction of the polarizing plate are 45 degrees.

  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, and particularly preferably 0.05 to 5 μm after drying.

  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% in 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.

(2) Application of optical compensation layer (creation of optical compensation sheet)
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 cellulose acylate film, and further provides an optically anisotropic layer. It is formed by doing.

(Alignment film)
An alignment film is provided on the surface-treated 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 (for example, 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-Blodget 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 crosslink having a function of aligning a side chain having a crosslinkable functional group (for example, a 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 (for example, poly (N-methylolacrylamide), carboxymethylcellulose, gelatin, polyvinyl alcohol, and modified polyvinyl alcohol) are preferable, gelatin, polyvinyl alcohol, and modified polyvinyl alcohol are more preferable, and polyvinyl alcohol and modified polyvinyl alcohol are most preferable. . 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 sheet 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 No. 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 generation of 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 performed 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 liquid is preferably a mixed solvent of an organic solvent (for example, 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 alignment film and also an optically anisotropic layer reduces significantly.

  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 cross-linking, 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 transparent support or 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 film being transported. However, the roundness, cylindricity, and deflection (eccentricity) of the rubbing roll can be any. Is preferably 30 μm or less. The film wrap angle 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, 40 to 50 ° is preferable. 45 ° is particularly preferred.
The 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)
As rod-like liquid crystalline molecules, 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 group described in paragraphs [0064] to [0086] of JP-A-2002-62427 is described. And polymerizable liquid crystal compounds.

(Discotic 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 paragraph numbers [0151] to [0168] in JP-A 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 orientation direction of the major axis 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, and the like 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, 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 polymerizable initiator described later and optional components on the alignment film.

  As the 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 (for example, a wire bar coating method, an extrusion coating method, a direct gravure coating method, a reverse gravure coating method, or a 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 crystal 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.

Light irradiation for polymerizing liquid crystalline molecules is preferably performed using ultraviolet rays. The irradiation energy is preferably in the range of ^{20mJ / cm 2 ~50J / cm 2} , more preferably in the range of 20~5000mJ / cm ^2, 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 film. 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 tilt angle of the polarizing film and the optical compensation layer may be stretched so as to match the angle formed by 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.

(3) Application of antireflection layer (antireflection film)
The antireflection film generally includes 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 has the structure 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 an antireflection film which gave the anti-glare property which the surface of the uppermost layer has the shape of a fine unevenness to the antireflection film by application | coating as mentioned above 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 having a layer structure of at least a medium 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 Also, 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 (for example, 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. The strength of the film 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.

(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 inorganic compound ultrafine particle 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, as described in JP-A Nos. 11-295503, 11-153703, and 2000-9908). Silane coupling agent, etc .: Anionic compounds or organometallic coupling agents described in JP 2001-310432 A, etc., and a core-shell structure with high refractive index particles as a core (JP 2001-166104 A) Etc.) and specific dispersants (for example, JP-A-11-153703, US Pat. No. 6,210,858B1, JP-A-2002-27776069, etc.) and the like.

  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 sequentially laminated on the high refractive index layer. The refractive index of the low refractive index layer is usually 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 means for thin film layers including introduction of silicone, introduction of fluorine, and the like 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 (for example, Silaplane (manufactured by Chisso Corporation), silanol group-containing polysiloxane (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 carried out at the same time or after the coating composition for forming the outermost layer containing a polymerization initiator, a sensitizer, etc. 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 located 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 transparent support in order to impart physical strength to the antireflection film. In particular, it is preferably provided between the transparent support and the high refractive index 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 hydrolyzable 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 composition of the hard coat layer include those described in JP-A Nos. 2002-144913, 2000-9908, and WO 00/46617.

  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 Application Laid-Open No. 11-38208 specifying a forward scattering coefficient, Japanese Patent Application Laid-Open No. 2000-199809 having a relative refractive index of a transparent resin and fine particles in a specific range, and Japanese Patent Application 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.

(Application method)
Each layer of the antireflection film is formed by dip coating, air knife coating, curtain coating, roller coating, wire bar coating, gravure coating, micro gravure method or extrusion coating method (US Pat. No. 2,681,294). According to the specification, 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 small amount (0.1 to 50% by mass) of relatively large particles (particle size 0.05 to 2 μm) is added to the hard coat layer to form a surface uneven film, and these shapes are maintained thereon. 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, JP-A-63-278839, JP-A-11-183710, JP-A-2000-275401) Wherein) and the like.

<Liquid crystal display device>
The cellulose acylate film of the present invention can be suitably used for a liquid crystal display device. In particular, the cellulose acylate film of the present invention is effective when used as an optical compensation sheet for liquid crystal display devices. When the film itself is used as an optical compensation sheet, the transmission axis of a polarizing element (described later) and the slow axis of the optical compensation sheet made of a cellulose acylate film are arranged so as to be substantially parallel or perpendicular. It is preferable. Such an arrangement of the polarizing element and the optical compensation sheet is described in JP-A-10-48420. The liquid crystal display device includes a liquid crystal cell having a liquid crystal supported between two electrode substrates, two polarizing elements disposed on both sides thereof, and at least one sheet between the liquid crystal cell and the polarizing element. An optical compensation sheet is arranged.
Below, the kind of liquid crystal display device which can apply the cellulose acylate film of this invention is demonstrated.

(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 Japanese Liquid Crystal Society) and (4) a SURVAVAL mode liquid crystal cell (LCD interface) Announced at National 98).

(Other liquid crystal display devices)
The ECB mode and STN mode liquid crystal display devices can be optically compensated in the same way as described above.

<< Measurement method and evaluation method >>
Below, it describes about the measuring method and evaluation method of a cellulose acylate and a cellulose acylate film. The measurement values described in the present application are those measured by the method described below.

(1) Projected oblique stripes A cellulose acylate film (film formation width x MD 30 cm) was placed in front of a white screen with a spacing of 10 mm in parallel with the screen. The light was projected toward the film from a slide projector (for example, Color Cabin III manufactured by Cabin Kogyo Co., Ltd.) installed 1 m away from the center of the film in a direction of 32.5 degrees. Of the streaks (light brightness) parallel to the film forming direction (MD) projected on the screen, the number of streaks generated at intervals of 1 to 30 mm in the diagonal direction (10 to 80 degrees with respect to the film forming direction) Counting over the entire width, the number per 10 cm width was determined.

(2) Unevenness in thickness The sample was sampled with a width of 35 mm over the entire width of the cellulose acylate film (TD sample), and the central portion in the width direction was sampled with a width of 35 mm and a length of 2 m (MD sample). The TD sample and the MD sample were measured with a continuous thickness meter (FILM THICKNESS TESTER KG601A, manufactured by ANRITSU (Anritsu Electric Co., Ltd.)), and the maximum value, minimum value, and average value were determined. The average of (maximum value−average value) and (average value−minimum value) was defined as thickness unevenness.

(3) Elongation at break The cellulose acylate film was cut into a 1 cm width, and the elongation at break was measured at 10 mm / min with 2 cm between the chucks at 25 ° C. and a relative humidity of 60%. This was measured five times each in the MD direction and TD direction and averaged.

(4) Residual solvent amount A sample film of 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. About these samples, it measured using the gas chromatography (GC) on the following conditions.
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
From the measurement result of sample A, the content rate was determined for each peak other than the solvent (methyl acetate) using a calibration curve, and the sum was defined as Sa. Further, from the measurement result of sample B, the content rate was obtained using a calibration curve for each peak in the region hidden by the solvent peak in the measurement result of sample A, and the sum total was Sb.
The sum of Sa and Sb was defined as the residual solvent amount.

(5) Melt Viscosity A sample was prepared by adding 0.3% by mass of a heat stabilizer (Sumitomo Chemical Co., Ltd.) to the resin and stirring well. Using a plate type rheometer (for example, MCR301 type manufactured by Physica), the melt viscosity was measured under the following conditions within 10 minutes after the sample was set.
Measurement temperature: 220 ° C
Plate: 25mmφ parallel plate Gap: 1mm
Shear rate: 1 sec ^-1

(6) Weight average degree of polymerization (DPw)
The resin was dissolved in THF to prepare a 0.5% by mass sample solution. Using this solution, the weight average molecular weight (Mw) was determined by GPC under the following conditions. The calibration curve was prepared using polystyrene (TSK standard polyester: molecular weight 1050, 5970, 18100, 37900, 190000, 706000). The value obtained by dividing Mw by the molecular weight per segment determined from the degree of substitution determined by the following method was defined as DPw.
Column: TSK GEL Super HZ4000, TSK GEL Super HZ2000,
TSK GEL Super HZM-M, TSK Guard Column Super HZ-L,
Column temperature: 40 ° C
Eluent: THF
Flow rate: 1 ml / min Detector: RI

(7) Degree of substitution of cellulose acylate
It was measured by a method according to ASTM D-817-91 (cellulose acylate was completely hydrolyzed and the free carboxylic acid or its salt was determined by GC or LC).

  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. Accordingly, the scope of the present invention should not be construed as being limited by the specific examples shown below.

[Synthesis Example 1] Synthesis of cellulose acetate propionate 80 parts by weight of cellulose (pulp) and 33 parts by weight of acetic acid were placed in a reaction vessel equipped with a stirrer and a cooling device, and the cellulose was activated by treating at 60 ° C for 4 hours. Turned into. 32 parts by mass of acetic anhydride, 540 parts by mass of propionic acid, 558 parts by mass of propionic acid anhydride, and 4 parts by mass of sulfuric acid were mixed, cooled to −20 ° C., and then added to the reaction vessel.
Esterification was carried out so that the maximum temperature of the reaction was 35 ° C., and the time when the viscosity of the reaction solution reached 910 cP was taken as the end point of the reaction. The temperature of the reaction mixture at the end point was adjusted to 15 ° C. The reaction terminator which cooled the mixture of 133 mass parts of water and 133 mass parts of acetic acid to -5 degreeC was added so that the temperature of a reaction mixture might not exceed 23 degreeC.
The temperature of the reaction mixture was 60 ° C., and the mixture was stirred for 2 hours for partial hydrolysis. The polymer compound obtained by mixing with an acetic acid aqueous solution was reprecipitated, and washing with warm water at 70 to 80 ° C. was repeated. After removing the liquid, it was immersed in a 0.001% by mass calcium hydroxide aqueous solution, stirred for 30 minutes, and then removed again. Drying was performed at 70 ° C. to obtain cellulose acetate propionate. This cellulose acetate propionate was used as a raw material for producing a cellulose acylate film (Examples 1 to 28 and 40 to 45, Comparative Examples 1 and 2) described later.
As a result of observing the film cast from the dichloromethane solution with a polarizing microscope, almost no insoluble matter derived from unreacted cellulose was observed.
When manufacturing the cellulose acylate films (Examples 29 to 34 and 39) described later, cellulose acetate propionate having a composition different from that prepared in Synthesis Example 1 was used as a manufacturing raw material. Cellulose acetate propionate was synthesized according to the same method as in Synthesis Example 1 by adjusting the addition amount of the raw material and the esterification reaction time to control the composition ratio and the degree of polymerization.

[Synthesis Example 2] Synthesis of cellulose acetate butyrate In a reaction vessel equipped with a stirrer and a cooling device, 200 parts by mass of cellulose (linter) and 100 parts by mass of acetic acid were taken, and the cellulose was activated by treating at 60 ° C for 4 hours. Turned into. 161 parts by mass of acetic acid, 449 parts by mass of acetic anhydride, 742 parts by mass of butyric acid, 1349 parts by mass of butyric anhydride, and 14 parts by mass of sulfuric acid were mixed and cooled to −20 ° C., and then added to the reaction vessel.
Esterification was performed so that the maximum temperature of the reaction was 30 ° C., and the time when the viscosity of the reaction solution reached 1050 cP was taken as the end point of the reaction. The temperature of the reaction mixture at the end point was adjusted to 10 ° C. A reaction stopper obtained by cooling a mixture of 297 parts by mass of water and 558 parts by mass of acetic acid to −5 ° C. was added so that the temperature of the reaction mixture did not exceed 23 ° C.
The temperature of the reaction mixture was set to 60 ° C., and the mixture was stirred for 2 hours and 30 minutes for partial hydrolysis. The polymer compound obtained by mixing with an acetic acid aqueous solution was reprecipitated, and washing with warm water at 70 to 80 ° C. was repeated. After removing the liquid, it was immersed in a 0.002% by mass calcium hydroxide aqueous solution, stirred for 30 minutes, and then removed again. Drying was performed at 70 ° C. to obtain cellulose acetate butyrate. The obtained cellulose acetate butyrate was used as a raw material for producing a cellulose acylate film (Example 35) described later.
As a result of observing the film cast from the dichloromethane solution with a polarizing microscope, almost no insoluble matter was observed.
When cellulose acylate films (Examples 36 and 37) described later were produced, cellulose acetate butyrate having a composition different from that prepared in Synthesis Example 2 was used as a raw material for production. According to the same method as in Synthesis Example 2, the rate was also synthesized by adjusting the addition amount of the raw material and the esterification reaction time to control the composition ratio and the degree of polymerization.

  Moreover, when manufacturing the cellulose acylate film (Example 38) mentioned later, mixed cellulose acylate was used as a manufacturing raw material, but this mixed cellulose acylate is also added in amount, type, and ester of carboxylic acid to be added. The synthesis was performed by adjusting the reaction time.

[Examples and Comparative Examples]
1. Production of Unstretched Cellulose Acylate Film (1) Preparation of Cellulose Acylate Mixture Each of these cellulose acylates is 0.3% by mass of a heat stabilizer (Sumitomo Chemical's Sumilizer GP), silicon dioxide particles (Aerosil R972V) 0 0.05% by mass and 1% by mass of ADK STAB LA-31 (manufactured by Asahi Denka Kogyo Co., Ltd.) as a UV absorber was added and stirred well.

(2) Melt Film Formation After the cellulose acylate was formed into cylindrical pellets having a diameter of 3 mm and a length of 5 mm, the cellulose acylate was dried with a vacuum dryer at 110 ° C. for 6 hours to reduce the residual moisture to 0.01% by mass or less. This was put into a hopper adjusted to 80 ° C., and kneaded with a full flight screw with a compression ratio of 4 under a nitrogen stream at the following melting temperature and L (screw length) / D (screw diameter) = 30. Melted.
Melting temperature: Supply section = 180 ° C.
Compression part = 210 ° C
Measuring unit = 220 ° C
Further, after the breaker plate type filtration was performed at the outlet of the extruder, after passing through the gear pump, it was passed through a 4 μm stainless leaf type disk filter type filtration device.

This was extruded under the die conditions described in Table 1. The temperature difference in the width direction was given as follows. First, the melt flow rate was measured at 10 points at equal intervals over the entire width at the die exit. Measurements were made by marking the melt and measuring the length of time it progresses to unit time. Of the measured flow rates, the maximum value was V (M), the minimum value was V (m), and the velocity at each measurement point was V (p). Here, ΔT is a temperature difference in the width direction, and ΔT of each sample is as shown in Table 1.
{(V (M) −V (p)) / (V (M) −V (m))} × ΔT
At this time, the lower speed part is set to a higher temperature and the higher speed part is set to a lower temperature. As apparent from the above equation, the temperature difference (ΔT) in the width direction shown in Table 1 is obtained at the maximum speed and the minimum speed.
Thereafter, the melt was extruded onto a casting drum having the conditions described in Table 1. Under the present circumstances, it formed into a film with the linear pressure of Table 1 using the touch roll of Example 1 of Unexamined-Japanese-Patent No. 11-235747. The temperature of the touch roll was the same as that of the most upstream casting roll. Thereafter, the film was peeled off from the casting roll and wound up. In addition, after trimming both ends (each 3% of the total width) immediately before winding, after applying thickness processing (knurling) of 10 mm width and 50 μm height to both ends, a film having a width of 1.5 m was wound up to 3000 m. .

(3) Evaluation The melt viscosity, thickness unevenness, and projected diagonal stripes of the unstretched cellulose acylate film thus obtained were measured by the above methods, and the results are shown in Table 1.
In addition, the residual solvent amount of all the samples of Examples and Comparative Examples was 0% by mass.

  All of the inventions (Examples 1 to 45) exhibited good characteristics. On the other hand, those outside the scope of the present invention (Comparative Examples 1 to 3) had low optical properties. In particular, sample No. Comparative Example 3 carried out according to 3-1 had particularly low optical properties.

  All of the above are results of films obtained by film formation at 30 m / min, but the same results were obtained for films formed at 50 m / min and 80 m / min, respectively. It was confirmed that the present invention can be applied to high-speed film formation.

2. Creation of a stretched cellulose acylate film The unstretched sheet was stretched at 300% / minute at (Tg + 10 ° C.) at the following magnification. Tg is the glass transition temperature of each film, which is measured at 10 ° C./min using DSC and refers to the temperature at which the baseline begins to deviate from the low temperature side.
The stretched film was measured at 25 ° C. and a relative humidity of 60% using an automatic birefringence meter (KOBRA-21ADH: manufactured by Oji Scientific Instruments). Although the results of Example 1 are shown here, similar results were obtained in other examples.

3. Preparation of Polarizing Plate (1) Saponification of Cellulose Acylate Film The following immersion saponification was performed on the unstretched cellulose acylate film and the stretched cellulose acylate film. Similar results were obtained when coating saponification was performed.

(1-1) Immersion Saponification Using a 1.5 mol / L NaOH aqueous solution adjusted to 60 ° C. as a saponification solution, a cellulose acylate film was immersed in the solution for 2 minutes. Then, after being immersed in 0.05 mol / L sulfuric acid aqueous solution for 30 seconds, it was passed through a water-washing bath.

(1-2) Coating Saponification 20 parts by mass of water was added to 80 parts by mass of isopropanol, and KOH was dissolved in this to 1.5 mol / L, and the temperature was adjusted to 60 ° C. and used as a saponification solution. This saponification solution was applied onto a cellulose acylate film at 60 ° C. at 10 g / m ² and saponified for 1 minute. Thereafter, hot water at 50 ° C. was sprayed at 10 L / m ² · min for 1 minute for washing.

(2) Creation of Polarizing Film According to Example 1 of Japanese Patent Application Laid-Open No. 2001-141926, a circumferential speed difference was given between two pairs of nip rolls, and a polarizing film having a thickness of 20 μm was prepared by stretching in the longitudinal direction.

(3) Bonding The polarizing film obtained in this way and the saponified unstretched and stretched cellulose acylate film were combined with a 3% by mass aqueous solution of PVA (PVA-117H manufactured by Kuraray Co., Ltd.) as an adhesive. The polarizing axis and the cellulose acylate film were laminated so that the longitudinal direction was 45 degrees. The polarizing plate thus prepared is attached to the 20-inch VA liquid crystal display device described in FIGS. 2 to 9 of Japanese Patent Laid-Open No. 2000-154261, and is confirmed by visual evaluation from an oblique angle of 32 degrees where the projected oblique stripe is most visible. The number of generated streaks is shown in Table 1. Good performance was obtained with the present invention. On the other hand, when the projected diagonal streaks exceeded 10, the number of visible streaks on the LCD increased extremely.

4). Preparation of Optical Compensation Film (1) Unstretched Film When the unstretched cellulose acylate film of the present invention is used for the first transparent support of Example 1 of JP-A-11-316378, a good optical compensation film is obtained. Obtained.

(2) Stretched cellulose acylate film When the stretched cellulose acylate film of the present invention was used instead of the cellulose acetate film coated with the liquid crystal layer of Example 1 of JP-A-11-316378, a good optical compensation film was gotten.

  An optical compensation filter film was produced using the stretched cellulose acylate film of the present invention instead of the cellulose acetate film coated with the liquid crystal layer of Example 1 of JP-A-7-333433. The obtained optical compensation film showed good optical properties.

  On the other hand, those outside the scope of the present invention have deteriorated optical characteristics. In particular, sample No. What was implemented according to 3-1, especially the fall of the optical characteristic was remarkable.

5. Preparation of Low Reflective Film The cellulose acylate film of the present invention was stretched and unstretched cellulose of the present invention in accordance with Example 47 of the Japan Institute of Invention and Technology (Publication No. 2001-1745, published on March 15, 2001, Japan Society of Invention). When a low reflection film was prepared using an acylate film, good optical performance was obtained.

6). Preparation of liquid crystal display element The polarizing plate of the present invention is applied to the liquid crystal display device described in Example 1 of JP-A-10-48420 and the discotic liquid crystal molecule described in Example 1 of JP-A-9-26572. Including an optically anisotropic layer, an alignment film coated with polyvinyl alcohol, a 20-inch VA liquid crystal display device described in FIGS. 2 to 9 of JP-A-2000-154261, and FIGS. 10 to 10 of JP-A-2000-154261. 15 in the 20-inch OCB type liquid crystal display device. Furthermore, when the low reflection film of the present invention was applied to the outermost layer of these liquid crystal display devices and visual evaluation was performed, good visual recognition performance was obtained.

  ADVANTAGE OF THE INVENTION According to this invention, the cellulose acylate film which can suppress significantly the display nonuniformity generate | occur | produced when incorporating in a liquid crystal display device can be provided with an environmentally friendly melt film-forming method. Therefore, the present invention has very high industrial applicability.

It is front sectional drawing which shows the flow of the melt in die | dye. In the figure, the solid line indicates the flow of the melt in the die, and the dotted line simultaneously connects the positions of the melt that have passed through the die entrance after a certain time. It is front sectional drawing of the die | dye preferably used for manufacture of the cellulose acylate film of this invention. It is the schematic of the example of an apparatus for implementing the melt film forming of this invention.

Explanation of symbols

a ... land length, b ... land width, θ ... manifold angle 101 ... kneading extruder, 102 ... gear pump, 103 ... filtration unit, 104 ... die, 105 ... touch roll, 106 ... casting cooling drum, 107 ... cellulose acylate, 108: Longitudinal stretching process section 109: Horizontal stretching process section 110: Winding process section

Claims (19)

  A cellulose acylate film formed by melt film formation, characterized in that the number of oblique projection lines is 0/10 cm to 30/10 cm.   A cellulose acylate film having a projected diagonal stripe of 0/10 cm to 30/10 cm and a residual solvent amount of 0.01% by mass or less.   The cellulose acylate film according to claim 1 or 2, wherein the thickness unevenness is 0.1% to 1%.   The cellulose acylate film according to any one of claims 1 to 3, wherein the melt viscosity at 220 ° C is 100 Pa · s to 2000 Pa · s.   The cellulose acylate film according to any one of claims 1 to 4, wherein the cellulose acylate has a weight average polymerization degree of 250 to 500. The cellulose acylate film according to any one of claims 1 to 5, comprising a cellulose acylate satisfying the following formulas (S-1) to (S-3).
Formula (S-1) 2.6 ≦ X + Y ≦ 3.0
Formula (S-2) 0 ≦ X ≦ 1.8
Formula (S-3) 1.0 ≦ Y ≦ 3
(In the formula, X represents the substitution degree of the acetyl group with respect to the hydroxyl group of cellulose, and Y represents the total substitution degree of the propionyl group, butyryl group, pentanoyl group, and hexanoyl group with respect to the hydroxyl group of cellulose.)   A method for producing a cellulose acylate film having a projected oblique stripe of 0/10 cm to 30/10/10 cm, comprising a step of melting cellulose acylate and extruding it from a die to form a cast film.   The method for producing a cellulose acylate film according to claim 7, wherein the temperature difference in the width direction of the die is set to 1 ° C. to 10 ° C. for melt film formation.   The method for producing a cellulose acylate film according to claim 7 or 8, wherein the film is formed using a die having a manifold angle of 5 to 45 degrees.   The film formation is performed using a die having a ratio (a / b) of a die land length (a) to a die land width (b) of 0.005 to 0.2. The manufacturing method of the cellulose acylate film of description.   The method for producing a cellulose acylate film according to any one of claims 7 to 10, wherein the cellulose acylate is melted and then formed on a casting drum using a touch roll.   The method for producing a cellulose acylate film according to claim 11, wherein the film is formed using the touch roll at a linear pressure of 3 kg / cm to 100 kg / cm.   13. The film formation according to claim 7, wherein two or more casting drums of 60 ° C. to 160 ° C. are used and melt film formation is performed at a peripheral speed difference of 0.001% to 5%. A method for producing a cellulose acylate film.   14. The method for producing a cellulose acylate film according to claim 13, wherein the line speed of the most upstream casting roll is 25 m / min to 150 m / min.   The method for producing a stretched cellulose acylate film according to any one of claims 7 to 14, further comprising a step of stretching the film formed by 1% to 500% in at least one direction.   A polarizing plate comprising at least one layer of the cellulose acylate film according to any one of claims 1 to 6 laminated on a polarizing film.   An optical compensation film using the cellulose acylate film according to claim 1 as a base material.   An antireflection film, wherein the cellulose acylate film according to any one of claims 1 to 6 is used as a substrate.   A liquid crystal display device using at least one of the polarizing plate according to claim 16, the optical compensation film according to claim 17, and the antireflection film according to claim 18.

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