JP4675591B2 - Cellulose acylate film, method for producing the same, and liquid crystal display device - Google Patents

Description

  The present invention relates to a cellulose acylate film formed by melt casting, a method for producing the same, and a liquid crystal display device using the same.

  Conventionally, in producing a cellulose acylate film used in a liquid crystal image display device, a cellulose acylate resin is dissolved in a chlorinated organic solvent such as dichloromethane, and this is cast on a substrate and dried. The film casting method for forming a film is mainly carried out. Dichloromethane, which is used as a chlorinated organic solvent, has been conventionally used as a good solvent for cellulose acylate, and has a low boiling point (boiling point: about 40 ° C.) in the film-forming and drying steps of the manufacturing process. It is preferably used. In recent years, from the viewpoint of environmental conservation, the amount of chlorinated organic solvents having a low boiling point has been significantly reduced, such as preventing leakage by handling in a closed facility. Furthermore, even in the unlikely event of leakage, install a gas absorption tower to adsorb the organic solvent before releasing it to the outside air, or disassemble the chlorine-based organic solvent by thermal combustion or electron beam before discharging. As a result, almost no organic solvent was discharged to the outside air. However, further research is needed to achieve complete non-emission of chlorinated organic solvents.

  As such a countermeasure, a film forming method in which cellulose acylate is melted and an organic solvent is not used is disclosed (see Patent Document 1). Such a film-forming method is such that the carbon chain of the ester group of cellulose acylate is lengthened to lower the melting point to facilitate melt film formation. Specifically, melt film formation at a low temperature is enabled by changing cellulose acetate to cellulose propionate, cellulose butyrate, or the like. However, in this method by melt film formation, when a polarizing plate is produced using the melt film formation and incorporated in a liquid crystal display device, a display failure occurs in which a bright spot is generated on the screen when black display is performed. was there. That is, it was found that light leaked from the place where it should originally be black and can only be displayed in gray, and an improvement thereof was desired.

JP 2000-352620 A

  The present invention relates to a cellulose acylate film formed by melt casting, and a cellulose acylate film capable of reducing the occurrence of display failure at the time of black display when incorporated in a liquid crystal display device and its production It is an object to provide a method and a liquid crystal display device using the method.

The object of the present invention is achieved by the following constitution.
(1) It is formed by melt casting a cellulose acylate resin, the film density is 1.240 g / cm ^{2 to} 1.350 g / cm ³ , and the retardation (Rth) in the thickness direction is 100 nm to 800 nm. A cellulose acylate film characterized by being:

(2) The cellulose acylate film according to (1), wherein the acylate group of the cellulose acylate resin satisfies a substitution degree represented by the following formulas (1) and (2).
2.5 ≦ A + B ≦ 3.0 Formula (1)
1.25 ≦ B ≦ 3.0 (2)
[In formula, A shows the substitution degree of an acetyl group. B shows the sum total of the substitution degree of a propionyl group, a butyryl group, a pentanoyl group, and a hexanoyl group. ]
(2 ′) The in-plane retardation (Re) and the retardation in the thickness direction (Rth) satisfy all of the following formulas (3) to (5): Cellulose acylate film.
Rth ≧ Re Formula (3)
300 ≧ Re ≧ 0 Formula (4)
500 ≧ Rth ≧ 100 Formula (5)
(3) The cellulose acylate film according to (1) or (2), wherein the in-plane retardation (Re) is 20 nm to 300 nm.

(4) including kneading and melting the cellulose acylate resin using a kneading extruder under conditions of 150 ° C. to 220 ° C., screw rotation speed 100 rpm to 800 rpm, and residence time 5 seconds to 3 minutes. A process for producing cellulose acylate pellets.

(5) The method for producing cellulose acylate pellets according to (4), wherein a vent is provided on the outlet side of the kneading extruder, and the cellulose acylate resin is kneaded and melted while being evacuated.
(6) The cellulose according to (4) or (5), wherein the cellulose acylate resin is melted, then solidified into a strand shape in warm water at 30 ° C. to 90 ° C., and further cut and dried. A method for producing acylate pellets.

(7) A method for producing a cellulose acylate film comprising a step of extruding a melted cellulose acylate resin from a die and then forming a film with a casting drum to a predetermined thickness, comprising: a die lip interval (T) A method for producing a cellulose acylate film, wherein a film is formed so that a ratio (T / D) to a film thickness (D) after film formation is 2 to 10.
(8) The method for producing a cellulose acylate film according to (7), wherein the distance between the lip interval of the die and the casting drum is 1% to 20% of the casting width.
(9) The method for producing a cellulose acylate film according to (7) or (8), wherein the temperature at both ends of the die is set to be 1 ° C. to 20 ° C. higher than the central portion.

(10) A cellulose acylate film produced using the cellulose acylate pellets produced by the method for producing cellulose acylate pellets according to any one of (4) to (6).
(10-2) The cellulose according to any one of (7) to (9), wherein the cellulose acylate pellet produced by the method for producing a cellulose acylate pellet according to any one of (4) to (6) is used. The cellulose acylate film according to any one of (1) to (3), wherein the cellulose acylate film is produced by a method for producing an acylate film.

(11) The cellulose acylate film according to any one of (1) to (3) and (10) to (10-2) is stretched by 10% to 300% in at least one direction. Cellulose acylate film.
(12) It has a polarizing layer and the cellulose acylate film according to any one of (1) to (3) and (10) to (11), which is provided on the polarizing layer. Polarizing plate.
(13) An optical compensation film for a liquid crystal display plate, wherein the cellulose acylate film according to any one of (1) to (3) and (10) to (11) is used as a substrate.
(14) An antireflection film using the cellulose acylate film according to any one of (1) to (3) and (10) to (11) as a substrate.

  According to the present invention, a cellulose acylate film formed by melt casting, which can reduce the occurrence of display failure during black display when incorporated in a liquid crystal display device, and A manufacturing method thereof and a liquid crystal display device using the same can be provided.

  Hereinafter, the contents of the present invention 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, “to” is used to mean that the numerical values described before and after it are included as a lower limit value and an upper limit value. In the present invention, “Tg” indicates the glass transition temperature of the cellulose acylate resin or film unless otherwise specified. Further, in the present invention, “cellulose acylate resin” means cellulose acylate before the physical properties defined in the present invention are expressed, and “cellulose acylate film” is defined in the present invention by means such as stretching. It means a cellulose acylate film exhibiting physical properties.

Analysis of the cause of the display failure that occurs when the liquid crystal display device displays black, that is, the failure that the portion that should be displayed in black is displayed in gray was found to have the following causes.
(1) Light leakage from the oblique direction of the liquid crystal display device In the melt film-forming method, the cellulose acylate resin is immediately solidified in a state in which the orientation is completely lost by melting, so that the plane orientation is difficult to proceed. However, in the conventional solution film formation, the film is formed while the solvent is volatilized, and accordingly, the film is compressed in the thickness direction and the plane orientation proceeds. For this reason, the melt film-forming film exhibits retardation in the thickness direction (Rth: hereinafter, sometimes simply referred to as “Rth”), which is an index of plane orientation expressed below, as compared with the solution film-forming film. It is difficult, and Rth only reaches 80 nm or less.
Rth = | {(n _MD + n _TD ) / 2} −n _th | × d
Here, n _MD , n _TD , and n _th indicate the refractive index in the longitudinal direction (MD), the width direction (TD), and the thickness direction (th), respectively, and d indicates the thickness (expressed in nm). Point to.
Since such Rth is refractive index anisotropy in the thickness direction, the effect of this Rth appears remarkably when a conventional melt-formed film is viewed from an oblique direction. That is, when these conventional melt film-forming films are incorporated in a liquid crystal display device, a general liquid crystal display device is manufactured in accordance with the optical characteristics of a conventional solution film-forming method having a large Rth. When a melt film-forming film is used, light leakage occurs from an oblique direction.
For this reason, it is preferable that Rth calculated | required by a melt film forming film is 100 nm-800 nm, More preferably, it is 140 nm-500 nm, More preferably, it is 160 nm-350 nm.

In the present invention, the above-described low Rth has been solved as follows.
(I) Specifically, using a twin-screw kneading extruder, the temperature is preferably 150 ° C. to 220 ° C., more preferably 160 ° C. to 210 ° C., further preferably 170 ° C. to 200 ° C., and the screw rotation speed. Is preferably 100 rpm to 800 rpm, more preferably 150 rpm to 600 rpm, still more preferably 200 rpm to 400 rpm, and the residence time is preferably 5 seconds to 3 minutes, more preferably 10 seconds to 2 minutes, still more preferably 20 seconds to Cellulose acylate pellets are produced in 90 seconds.

In the conventional pelletizing process, using a twin-screw kneading extruder at a high temperature such as 250 ° C. to 330 ° C., a low speed such as a screw rotation speed of 10 rpm to 50 rpm and a long residence time of 5 minutes to 15 minutes. It was carried out. That is, it was pelletized without applying a shearing force slowly (at a low rotation) at a high temperature.
In contrast, in the present invention, pelletization is performed at a low temperature, for a short time, and with a high shearing force (high rotation). This method is more effective for melting the low acetyl form. That is, in the method of melting by heat (high temperature x long time) instead of shearing force (low rotation) as in the conventional method, decomposition occurs during melting, and the cross-linking reaction that occurs accompanying this decomposition further reduces the low acetylated form. Make it difficult to melt. In contrast, the low acetylated product can be effectively melted without causing crosslinking due to decomposition by melting with shearing force (high rotation) instead of heat (low temperature × short time) as in the present invention.

(Ii) In the present invention, it is preferable to prepare a pellet while providing a vent on the outlet side of the biaxial kneading extruder and evacuating.
In the step of pelletizing the cellulose acylate, it is generally preliminarily dried beforehand (at 80 ° C. to 150 ° C. for 0.1 to 24 hours). However, since the cellulose acylate powder is hydrophilic, residual moisture of about 0.2% by mass remains, and the low acetylated product is easily decomposed in the presence of water and easily becomes a crosslinkable foreign matter. Therefore, in the present invention, in addition to such preliminary drying, it is preferable to provide a pellet in a twin-screw kneading extruder and pelletize while evacuating. The vacuum degree of the vent part is preferably 0.001 to 0.9 atm, more preferably 0.01 to 0.8 atm, and further preferably 0.1 to 0.7 atm. Such evacuation can be achieved by providing an exhaust port in the screw casing of the twin-screw kneading extruder and piping this to a vacuum pump.

(Iii) Further, in the present invention, after melting, it is preferably solidified in a strand shape in warm water of 30 ° C. to 90 ° C., more preferably 35 ° C. to 80 ° C., and still more preferably 37 ° C. to 60 ° C. And dry.
In a normal process, after being melted by a twin-screw kneading extruder, a die having many holes of several mm is extruded into cold water of 5 ° C. to 20 ° C., solidified, solidified, and then conveyed. It was dehydrated and cut into pellets. At this time, the water temperature for coagulation was generally lowered as described above. This is to increase the elastic modulus as much as possible when transporting the strands, and to facilitate transport.
On the other hand, in this invention, it is preferable to coagulate with the above warm water. Since the low acylated substance has many hydroxyl groups remaining and is easily dissolved in water, the elution is promoted by raising the temperature of the coagulation bath in this way. Such immersion time in warm water is preferably 3 seconds to 10 minutes, more preferably 5 seconds to 5 minutes, and even more preferably 10 seconds to 3 minutes.
After such a coagulation bath, it is preferable that the elastic modulus of the strand is increased by passing it through cold water of 5 ° C. to less than 30 ° C. to facilitate transportation.

(2) Increasing Rth In the present invention, it is preferable to employ at least one of the following (2-1) to (2-3) with increasing Rth.

(2-1) Increase (T / D).
In general, in melt film formation, after melting a resin, the resin is extruded from a slit and solidified on a casting drum, but in the present invention, it is preferable to have a surface orientation on the casting drum to increase Rth. That is, it is preferable to increase the ratio (T / D) (hereinafter sometimes referred to as “T / D ratio”) between the die lip interval (T) and the thickness (D) of the film after film formation. . That is, since the film thickness of the molten resin is reduced from the film thickness (D) to the lip interval (T), the plane orientation is advanced until the thickness is reduced. T / D ratio becomes like this. Preferably it is 2-10, More preferably, it is 2.5-8, More preferably, it is 3-6. In the prior art, the lip interval (T) was set to a value close to D, and the T / D ratio was approximately 1.

  In addition, by drawing the resin extruded from the lip that increases the peripheral speed of the casting drum onto the casting drum (CD) that rotates at high speed, the thickness can be reduced and the surface orientation can be advanced. At this time, the rotation speed of the casting drum is determined by the balance between the extrusion speed and the lip interval, and is adjusted to be the extrusion speed × (T / D). That is, the CD rotation speed may be set so as to be T / D times the linear velocity (V) of the resin at the exit of the extruder die.

(2-2) Adjust the distance between the die lip and the casting drum.
The distance between the die lip and the casting drum is preferably 1% to 20% of the casting width. By setting the distance between the lip and the casting drum within 1 to 20% of the casting width, it is possible to keep the width relatively wide and to make the thickness relatively thin, which is preferable. Specifically, the space between the lip of the die and the casting drum is preferably 1% to 20%, more preferably 2% to 15%, and further preferably 3% to 10% of the casting width. Usually, the film is formed at a distance of about 30%.

(2-3) The temperature at both ends of the die is raised by 1 ° C. to 20 ° C. from the center portion. The T / D ratio is increased, the peripheral speed of the casting drum is increased, and the drawing is performed at a high speed to extend the plane orientation. Will be. On the casting drum where the resin temperature is lowered to the vicinity of the glass transition temperature (Tg), cracks are likely to occur at both ends of the film along with such a stretching operation. As such a measure, in the present invention, it is preferable to increase the temperature at both ends of the die from the center, preferably 1 ° C. to 20 ° C., more preferably 2 ° C. to 15 ° C., more preferably 3 ° C. to 12 ° C. . Such heating of the end of the die can be achieved by adding a panel heater.

(3) Stretching As a method of increasing Rth, a method of increasing the density by reducing the gap (free volume) between cellulose acylate molecules is effective. For this purpose, it is preferable to slow down the cooling rate after stretching. For example, it is preferable to cool at a cooling rate of 2 ° C./min to 60 ° C./min between the drying zone and the exit from the stretching zone to 50 ° C. The cooling temperature is more preferably 3 ° C / min to 40 ° C / min, and further preferably 4 ° C / min to 30 ° C / min. Since the cooling after the conventional stretching is performed at a cooling rate of 100 ° C./min or more, the above-described conditions are considerably slow.
Cellulose acylate shrinks in volume with cooling, but when the glass transition temperature (Tg) is lowered, the mobility of the cellulose acylate molecule is rapidly reduced. For this reason, the shrinkage of molecules does not catch up with the cooling rate, and the free volume tends to increase. By slowly cooling as in the present invention, the free volume can be reduced, and the film density, Re, and Rth can be increased. I think that the.
Such cooling from above Tg to below Tg appears after drying and stretching, and it is necessary to slowly cool them as described above. Here, gradual cooling means cooling at a cooling rate of 2 ° C./min to 60 ° C./min.
Such slow cooling may be carried out by any method, for example, it can be achieved by dividing the heat treatment zone outlet into several parts and cooling it to room temperature. For example, an infrared heater, a halogen heater, a panel heater, etc.) may be provided.

Considering the above, the cellulose acylate film of the present invention is a cellulose acylate film formed by melt casting a cellulose acylate resin, and has a density of 1.240 g / cm ^{2 to} 1.350 g / cm. ³ and the thickness direction retardation (Rth) is 100 nm to 800 nm. The physical properties of the cellulose acylate film of the present invention can be expressed by appropriately combining the above-mentioned means.

Hereinafter, the present invention will be described along the film forming procedure.
(Cellulose acylate resin)
The cellulose acylate resin used in the present invention preferably has the following characteristics.
In the cellulose acylate resin used in the present invention, the acylate group preferably satisfies the substitution degree represented by the following (1) and (2).
2.5 ≦ A + B <3.0 Formula (1)
1.25 ≦ B <3.0 Formula (2)
[In formula, A shows the substitution degree of an acetyl group. B shows the sum total of the substitution degree of a propionyl group, a butyryl group, a pentanoyl group, and a hexanoyl group. ]

More preferably, it is a cellulose acylate resin that satisfies the following conditions.
When 1/2 or more of B is a propionyl group 2.6 ≦ A + B ≦ 2.95
2.0 ≦ B ≦ 2.95
When less than 1/2 of B is a propionyl group 2.6 ≦ A + B ≦ 2.95
1.3 ≦ B ≦ 2.5

More preferably, it is a cellulose acylate resin that satisfies the following conditions.
When 1/2 or more of B is a propionyl group 2.7 ≦ A + B ≦ 2.95
2.4 ≦ B ≦ 2.9
When less than 1/2 of B is a propionyl group 2.7 ≦ A + B ≦ 2.95
1.3 ≦ B ≦ 2.0

  In the present invention, it is preferable to reduce the degree of substitution of the acetyl group and increase the sum of the degree of substitution of the propionyl group, butyryl group, pentanoyl group, and hexanoyl group. As a result, unevenness in elongation is less likely to occur during stretching, Re and Rth unevenness are less likely to occur, crystal melting temperature (Tm) can be lowered, and yellowing caused by thermal decomposition of melt film formation is suppressed. You can also. These effects can be achieved by using as large a substituent as possible (substituent having a large number of carbon atoms), but if it is too large, the glass transition temperature (Tg) and the elastic modulus are excessively lowered, which is not preferable. For this reason, a propionyl group, a butyryl group, a pentanoyl group, and a hexanoyl group larger than an acetyl group are preferable, a propionyl group and a butyryl group are more preferable, and a butyryl group is more preferable.

  The basic principle of these cellulose acylate synthesis methods is described in Mita et al., Wood Chemistry, pages 180-190 (Kyoritsu Shuppan, 1968). A typical synthesis method is a liquid phase acetylation method using a carboxylic acid anhydride-acetic acid-sulfuric acid catalyst. Specifically, cellulose raw materials such as cotton linter and wood pulp are pretreated with an appropriate amount of acetic acid, and then put into a pre-cooled carboxylated mixed solution to be esterified to complete cellulose acylate (2nd, 3rd and 6th). The total degree of acyl substitution at the position is approximately 3.00). The carboxylated mixed solution generally contains acetic acid as a solvent, carboxylic anhydride as an esterifying agent, and sulfuric acid as a catalyst. The carboxylic anhydride is usually used in a stoichiometric excess over the sum of the cellulose that reacts with it and the water present in the system. After completion of the acylation reaction, a neutralizing agent (for example, calcium, magnesium, iron, aluminum or zinc) is used for hydrolysis of excess carboxylic anhydride remaining in the system and neutralization of a part of the esterification catalyst. Of carbonate, acetate or oxide). Next, the obtained complete cellulose acylate is saponified and aged by maintaining it at 50 to 90 ° C. in the presence of a small amount of an acetylation reaction catalyst (generally, remaining sulfuric acid) to obtain the desired degree of acyl substitution and polymerization. The cellulose acylate having a degree is changed. When the desired cellulose acylate is obtained, the catalyst remaining in the system is completely neutralized by using the neutralizing agent as described above, or in water or dilute sulfuric acid without neutralization. Cellulose acylate can be obtained by charging the cellulose acylate solution (or adding water or dilute sulfuric acid into the cellulose acylate solution) to separate the cellulose acylate, and washing and stabilizing treatment.

The degree of polymerization of the cellulose acylate preferably used in the present invention is preferably 200 to 700 in terms of viscosity average degree of polymerization, more preferably 250 to 550, particularly preferably 250 to 400, and most preferably 250 to 350. is there. The average viscosity polymerization degree can be measured by Uda et al.'S intrinsic viscosity method (Kazuo Uda, Hideo Saito, Journal of Textile Science, Vol. 18, No. 1, pages 105-120, 1962). This is described in detail in Japanese Patent No. 95538.
Adjustment of such a viscosity average polymerization degree can also be achieved by removing low molecular weight components. When the low molecular component is removed, the average molecular weight (degree of polymerization) of the cellulose acylate is increased, but the viscosity is lower than that of ordinary cellulose acylate, which is useful. The removal of the low molecular component can be carried out by washing the cellulose acylate with an appropriate organic solvent. Further, the molecular weight can be adjusted by a polymerization method. For example, when producing a cellulose silicate with a small amount of low molecular components, the amount of sulfuric acid catalyst in the acetylation reaction is preferably adjusted to 0.5 to 25 parts by mass with respect to 100 parts by mass of cellulose. When the amount of the sulfuric acid catalyst is in the above range, cellulose acylate that is preferable in terms of molecular weight distribution (uniform molecular weight distribution) can be synthesized.

The cellulose acylate resin used in the present invention preferably has a weight average molecular weight Mw / number average molecular weight Mn ratio of 1.5 to 5.5, particularly preferably 2.0 to 5.0, Preferably it is 2.5-5.0 and the cellulose acylate of 3.0-5.0 is used especially preferably.
These cellulose acylate resins may be used alone or in combination of two or more. Further, a polymer component other than cellulose acylate may be appropriately mixed. The polymer component to be mixed preferably has excellent compatibility with the cellulose ester, and the transmittance when formed into a film is preferably 80% or more, more preferably 90% or more, and 92% or more. Is particularly preferred.

Furthermore, in the present invention, it is preferable to add a plasticizer to the cellulose acylate resin. Examples of the plasticizer include alkyl phthalyl alkyl glycolates, phosphate esters and carboxylic acid esters.
Examples of the alkyl phthalyl alkyl glycolates include methyl phthalyl methyl glycolate, ethyl phthalyl ethyl glycolate, propyl phthalyl propyl glycolate, butyl phthalyl butyl glycolate, octyl phthalyl octyl glycolate, methyl phthalyl ethyl glycol Rate, ethyl phthalyl methyl glycolate, ethyl phthalyl propyl glycolate, methyl phthalyl butyl glycolate, ethyl phthalyl butyl glycolate, butyl phthalyl methyl glycolate, butyl phthalyl ethyl glycolate, propyl phthalyl butyl glycolate , Butyl phthalyl propyl glycolate, methyl phthalyl octyl glycolate, ethyl phthalyl octyl glycolate, octyl phthalyl methyl glycolate, octyl phthalate Ethyl glycolate, and the like.

Examples of the phosphate ester include triphenyl phosphate, tricresyl phosphate, phenyl diphenyl phosphate, and the like. Furthermore, it is preferable to use the phosphate ester plasticizer described in claims 3 to 7 of JP-T-6-501040.
Examples of the carboxylic acid ester include phthalic acid esters such as dimethyl phthalate, diethyl phthalate, dibutyl phthalate, dioctyl phthalate, and diethylhexyl phthalate; citrate esters such as acetyl trimethyl citrate, acetyl triethyl citrate, and acetyl tributyl citrate. Adipic acid esters such as dimethyl adipate, dibutyl adipate, diisobutyl adipate, bis (2-ethylhexyl) adipate, diisodecyl adipate, bis (butyl diglycol adipate) and the like. In addition, butyl oleate, methylacetyl ricinoleate, dibutyl sebacate, triacetin and the like are preferably used alone or in combination.
The addition amount of these plasticizers is preferably 0% by mass to 20% by mass with respect to the cellulose acylate resin, more preferably 1% by mass to 20% by mass, and further preferably 2% by mass to 15% by mass. . These plasticizers may be used in combination of two or more if necessary.

  In addition to the plasticizer, the cellulose acylate resin includes various additives (for example, UV inhibitors, fine particles, deterioration inhibitors, optical anisotropy control agents, infrared absorbers, surfactants, odor trapping agents). (Such as amines) can be added. As the infrared absorbing dye, for example, those disclosed in JP-A No. 2001-194522 can be used. Moreover, as said ultraviolet-ray inhibitor, the thing of Unexamined-Japanese-Patent No. 2001-151901 can be used, for example, It is preferable to make it contain 0.001-5 mass% with respect to a cellulose acylate resin, respectively. The fine particles preferably have an average particle size of 5 to 3000 nm. As said microparticles | fine-particles, what consists of a metal oxide and a crosslinked polymer can be used, and it is preferable to make it contain 0.001-5 mass% with respect to a cellulose acylate resin. As the degradation inhibitor, an amine degradation inhibitor, a guanidine degradation inhibitor, a peroxide degradation agent degradation inhibitor, a radical chain inhibitor degradation inhibitor, and an activator degradation inhibitor for metal are used. It is preferable to make it contain 0.0001-2 mass% with respect to cellulose acylate resin. As the optical anisotropy control agent, for example, those described in JP-A Nos. 2003-66230 and 2002-49128 can be used, and the optical anisotropy control agent is contained in an amount of 0.1 to 15% by mass with respect to the cellulose acylate resin. Is preferred.

(Melting film formation)
The cellulose acylate film of the present invention is preferably produced through a film forming step of forming a melted cellulose acylate resin into a predetermined thickness on a support. Specifically, it is preferable to go through steps of drying, kneading extrusion and casting.
(I) Drying In the present invention, it is preferable to use cellulose acylate pelletized by the above-described method as the meltable cellulose acylate resin. Prior to melt film formation, the moisture content in the pellets is preferably 1% or less, more preferably 0.5% or less, and then charged into a hopper of a melt extruder. At this time, the hopper is set to (Tg-50 ° C) to (Tg + 30 ° C), more preferably (Tg-40 ° C) to (Tg + 10 ° C), and further preferably (Tg-30 ° C) to Tg. Thereby, the re-adsorption of moisture in the hopper can be suppressed, and the drying efficiency can be more easily expressed.

(Ii) Kneading and Extruding The kneading and extruding step is a step of melting cellulose acylate (preferably in a pellet form) while kneading in a melt extruder. In the present invention, kneading and melting are preferably performed at 120 ° C to 250 ° C, more preferably 140 ° C to 220 ° C, and further preferably 150 ° C to 200 ° C. At this time, the melting temperature may be a constant temperature or may be divided into several parts and controlled. A preferable kneading time is 2 minutes to 60 minutes, more preferably 3 minutes to 40 minutes, and particularly preferably 4 minutes to 30 minutes. Further, the kneading extrusion is preferably carried out while filling the inside of the melt extruder with an inert (nitrogen or the like) air flow or evacuating using a vented extruder.

(Iii) Casting In the casting process, melted cellulose acylate resin is passed through a gear pump, the pulsation of the extruder is removed, and then filtered with a metal mesh filter or the like. Extrude into a film. Extrusion may be performed in a single layer, or multiple layers may be extruded using a multi-manifold die or a feed block die. At this time, the thickness unevenness in the width direction can be adjusted by adjusting the distance (T) between the lips of the die.
When extruding a melt-extruded film onto a casting drum, electrostatic contact method, air knife method, air chamber method, vacuum nozzle method, touch roll method, etc. are used to increase the adhesion between the cooling drum and the melt-extruded sheet. It is preferable. Such an adhesion improving method may be performed on the entire surface of the melt-extruded sheet or a part thereof.

  The surface temperature of the casting drum is preferably 60 ° C to 160 ° C, more preferably 70 ° C to 150 ° C, and further preferably 80 ° C to 150 ° C. Thereafter, the sheet is peeled off from the casting drum, passed through a nip roll, and then wound. The winding speed is preferably 10 m / min to 100 m / min, more preferably 15 m / min to 80 m / min, and still more preferably 20 m / min to 70 m / min.

The film forming width of the cellulose acylate resin film is preferably 1 m to 5 m, more preferably 1.2 m to 4 m, and particularly preferably 1.3 m to 3 m. The thickness of the unstretched film thus obtained is preferably 30 μm to 400 μm, more preferably 40 μm to 300 μm, and particularly preferably 50 μm to 200 μm.
The film thus obtained is preferably trimmed at both ends and wound up. The trimmed part is pulverized, or after granulation, depolymerization / repolymerization, etc., if necessary, as a raw material for film of the same type or as a raw material for film of a different type It may be reused. Moreover, it is also preferable from a viewpoint of scratch prevention to attach a lami film to at least one surface before winding.

(Stretching)
In the present invention, in order to express Re and Rth, it is preferable to go through a stretching step of stretching the cellulose acylate resin formed in the film forming step. The stretching may be performed in a state where the film during film formation is in an undried state (for example, after being peeled off from the support after casting and until completion of drying), or may be performed after completion of drying. These stretching may be performed on-line during the film-forming process, or may be performed off-line after winding up once after the film-forming is completed.
Further, the stretching may be uniaxial stretching in which only the width direction is stretched or axial stretching to be stretched in the longitudinal (conveyance) direction and the width direction.

The stretching is preferably performed at Tg to (Tg + 50 ° C.), more preferably (Tg + 1 ° C.) to (Tg + 30 ° C.), and still more preferably (Tg + 2 ° C.) to (Tg + 20 ° C.). The draw ratio is preferably 1% to 500%, more preferably 3% to 400%, and even more preferably 5% to 300%. These stretching may be carried out in one stage or in multiple stages. The “stretch ratio” here is determined using the following formula.
Stretch ratio (%) = 100 × {(Length after stretching) − (Length before stretching)} / Length before stretching

  Such stretching may be performed in the longitudinal direction (longitudinal stretching) using two or more pairs of nip rolls in which the peripheral speed of the lip roll on the outlet side is faster than that on the inlet side, and both ends of the film are chucked. It may be gripped and stretched in the orthogonal direction (perpendicular to the longitudinal direction) (lateral stretching). In general, in any case, Rth can be increased by increasing the draw ratio. Further, Re can be increased by increasing the difference in magnification between longitudinal stretching and lateral stretching.

  As a method of increasing Rth, as described above, a method of reducing the gap (free volume) between cellulose acylate molecules and increasing the density is effective. For this purpose, it is preferable to provide a cooling step of gradually cooling the cellulose acylate resin stretched in the stretching step. As described above, slow cooling means cooling at a cooling rate of 2 ° C./min to 60 ° C./min, and the cooling rate is preferably 10 ° C./min to 60 ° C./min, 15 ° C./min to More preferred is 40 ° C./min.

Rth of the cellulose acylate film of the present invention expressed by such stretching is in the above range, and Re is preferably 20 nm to 300 nm, more preferably 30 nm to 250 nm, and further preferably 40 nm to 200 nm.
Here, “Re” is defined by the following equation.
Re = | n _MD −n _TD | × d
Here, n _MD and n _TD indicate the refractive indexes in the longitudinal direction (MD) and the width direction (TD), respectively, and d indicates the thickness (expressed in nm).

In the relationship between Re and Rth in the present invention, Re ≦ Rth is preferable, Re × 1.5 ≦ Rth is more preferable, and Re ≦ Rth × 2 is more preferable. Such Re and Rth are achieved by fixed end uniaxial stretching, more preferably by longitudinal and transverse biaxial stretching. That is, by stretching in the vertical direction and the horizontal direction, the difference in in-plane refractive index (n _MD , n _TD ) can be reduced and Re can be reduced. Furthermore, by extending in the vertical direction and the horizontal direction and increasing the area ratio, Rth can be increased by strengthening the orientation in the thickness direction accompanying the decrease in thickness. By controlling Re and Rth in this way, light leakage in black display can be further reduced.

Thus, the film thickness of the cellulose acylate film after extending | stretching has preferable 10-300 micrometers, More preferably, they are 20 micrometers-200 micrometers, More preferably, 30 micrometers-100 micrometers are preferable.
The angle θ formed by the film forming direction (longitudinal direction) and the slow axis of Re of the film is preferably closer to 0 °, + 90 °, or −90 °. That is, in the case of longitudinal stretching, it is preferably as close to 0 °, preferably 0 ± 3 °, more preferably 0 ± 2 °, and further preferably 0 ± 1 °. In the case of transverse stretching, 90 ± 3 ° or −90 ± 3 ° is preferable, 90 ± 2 ° or −90 ± 2 ° is more preferable, and 90 ± 1 ° or −90 ± 1 ° is more preferable.

  These unstretched and stretched cellulose acylate films may be used alone or in combination with a polarizing plate, etc., and a liquid crystal layer or a layer with a controlled refractive index (low reflection layer) ) Or a hard coat layer may be used.

(surface treatment)
The cellulose acylate film of the present invention 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 is a treatment for subjecting the film surface to a plasma treatment in the presence of a plasma-excitable gas. The glow discharge treatment may be low-temperature plasma that occurs under a low pressure gas of 10 ^{−3 to} 20 Torr (0.13 to 2700 Pa), and plasma treatment under atmospheric pressure is also preferable. The plasma-excitable gas refers to a gas that is plasma-excited under the above-described conditions, for example, chlorofluorocarbons such as argon, helium, neon, krypton, xenon, nitrogen, carbon dioxide, tetrafluoromethane, and mixtures thereof. Etc.
Details of these are described in detail on pages 30 to 32 in the Journal of the Invention Association (Technology No. 2001-1745, issued on March 15, 2001, Invention Association). 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 surface treatments, the alkali saponification treatment is particularly preferable, and is extremely effective as the surface treatment of the cellulose acylate film.

The alkali saponification treatment may be immersed in a saponification solution (immersion method) or a saponification solution may be applied (application method). In the case of the immersion method, an aqueous solution having a pH of 10 to 14 such as NaOH or KOH is passed through a bath heated to 20 to 80 ° C. for 0.1 to 10 minutes, and then neutralized, washed with water, and dried. Can be achieved.
In the case of the coating method, a dip coating method, a curtain coating method, an extrusion coating method, a bar coating method, and an E-type coating method can be used. The solvent of the alkali saponification coating solution has good wettability because it is applied to the transparent support of the saponification solution, and the surface state remains good without forming irregularities on the surface of the transparent support by the saponification solution solvent. It is preferred to select a solvent to keep. Specifically, an alcohol solvent is preferable, and isopropyl alcohol is particularly preferable.
An aqueous solution of a surfactant can also be used as a solvent. The alkali of the alkali saponification coating solution is preferably an alkali that dissolves in the 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. Also, the coating-type saponification treatment and the alignment film uncoating described later can be performed continuously, and the number of steps can be reduced. Specific examples of these saponification methods include the description of the contents described in JP-A-2002-82226 and International Publication WO02 / 46809.

Moreover, it is also preferable to pass through the undercoat process which provides an undercoat layer for adhesion | attachment with a functional layer. This layer may be coated after the surface treatment or may be coated without the surface treatment. Details of the undercoat layer are described on page 32 of the Japan Society for Invention and Innovation (Technical Number 2001-1745, published on March 15, 2001, Japan Institute of Invention).
These surface treatments and the undercoating process for forming the undercoating layer 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.

(Functional layer added)
The functional layer described in detail in pages 32 to 45 of the cellulose acylate film of the present invention in the technical report of the Japan Society of Invention (Public Technical Number 2001-1745, published on March 15, 2001, Japan Society of Invention). Are preferably combined. Among these, application of a polarizing layer (polarizing plate), application of an optical compensation layer (optical compensation sheet for liquid crystal display plate), and application of an antireflection layer (antireflection film) are preferable.
(1) Application of polarizing layer (preparation of polarizing plate)
[Material used]
Currently, a commercially available polarizing layer is generally prepared by immersing a stretched polymer in a solution of iodine or dichroic dye in a bath and allowing the iodine or dichroic dye to penetrate into the binder. It is. As the polarizing layer, a coating type polarizing film represented by Optiva Inc. can also be used. Iodine and dichroic dye in the polarizing layer exhibit deflection performance by being oriented in the binder. As the dichroic dye, an azo dye, a stilbene dye, a pyrazolone dye, a triphenylmethane dye, a quinoline dye, an oxazine dye, a thiazine dye, or an anthraquinone dye is used. The dichroic dye is preferably water-soluble. The dichroic dye preferably has a hydrophilic substituent (eg, sulfo, amino, hydroxyl). Examples of the dichroic dye include the compounds described in JIII Journal of Techniques, Technical No. 2001-1745, page 58 (issue date March 15, 2001).

  As the binder for the polarizing layer, 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. Moreover, a silane coupling agent can be used as a polymer. The binder is preferably a water-soluble polymer (eg, poly (N-methylolacrylamide), carboxymethylcellulose, gelatin, polyvinyl alcohol, modified polyvinyl alcohol), more preferably gelatin, polyvinyl alcohol, and modified polyvinyl alcohol, and polyvinyl alcohol and modified. Polyvinyl alcohol is most preferred. It is particularly preferable to use two types of polyvinyl alcohol or modified polyvinyl alcohol having different mass average polymerization degrees. The saponification degree of polyvinyl alcohol is preferably 70 to 100%, more preferably 80 to 100%. Furthermore, the mass average polymerization degree of polyvinyl alcohol is preferably 100 to 5,000. The modified polyvinyl alcohol is described in JP-A-8-338913, 9-152509 and 9-316127. Two or more kinds of polyvinyl alcohol and modified polyvinyl alcohol may be used in combination.

In the polarizing layer, the lower limit of the binder thickness is preferably 10 μm. From the viewpoint of light leakage of the liquid crystal display device, the upper limit of the thickness is preferably as thin as possible. .
The binder of the polarizing layer may be cross-linked. For this reason, the polymer and monomer which have a crosslinkable functional group may be mixed in a binder, and a crosslinkable functional group may be provided to binder polymer itself. Crosslinking can be performed by light, heat, or pH change, whereby a binder having a crosslinked structure can be formed. The crosslinking agent is described in US Reissue Patent 23297. Boron compounds (eg, boric acid, borax) can also be used as a crosslinking agent. The addition amount of the crosslinking agent in the binder is preferably 0.1 to 20% by mass with respect to the binder. The orientation of the polarizing element and the moisture and heat resistance of the polarizing layer 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 layer is preferably dyed with iodine or a dichroic dye after stretching the polarizing film (stretching method) or rubbing (rubbing method).
In the stretching method, the stretching ratio is preferably 2.5 to 30.0 times, and more preferably 3.0 to 10.0 times. Stretching can be performed by dry stretching in air. Moreover, you may implement wet extending | stretching in the state immersed in water. The stretch ratio of dry stretching is preferably 2.5 to 5.0 times, and the stretch ratio of wet stretching is preferably 3.0 to 10.0 times. Stretching may be performed in parallel to the MD direction (parallel stretching), or may be performed in an oblique direction (oblique stretching). These stretching operations may be performed once or divided into several times. By dividing into several times, it is possible to stretch more uniformly even at high magnification.
A more preferred stretching method is oblique stretching in which the film is stretched with an inclination of 10 ° to 80 ° in the oblique direction.

(A) Parallel stretching method Prior to stretching, it is preferable to swell the PVA film. The degree of swelling is 1.2 to 2.0 times (mass ratio between before swelling and after swelling). Thereafter, it is preferably stretched at a bath temperature of 15 to 50 ° C., especially 17 to 40 ° C. in an aqueous medium bath or a dye bath for dissolving a dichroic material 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 of the stretched / initial state (hereinafter the same), but is preferably 1.2 to 3.5 times, particularly 1.5 to 3.0 times from the viewpoint of the above effects. Then, it is made to dry at 50 to 90 degreeC, and a polarizing layer is obtained.

(B) Diagonal stretching method As the oblique stretching method, a method of stretching using a tenter protruding in an oblique direction in an oblique direction described in JP-A-2002-86554 can be used. Since this stretching is performed in the air, it is necessary to make it easy to stretch by adding water in advance. The preferred water content is 5% to 100%, more preferably 10% to 100%.
The temperature during stretching is preferably 40 ° C to 90 ° C, more preferably 50 ° C to 80 ° C. The humidity is preferably 50% to 100% relative humidity, more preferably 70% to 100% relative humidity, and still more preferably 80% to 100% relative humidity. The traveling speed in the longitudinal direction is preferably 1 m / min or more, more preferably 3 m / min or more.
After the completion of stretching, the film is dried at 50 ° C. to 100 ° C., more preferably 60 ° C. to 90 ° C., for 0.5 to 10 minutes. More preferably, it is 1 minute to 5 minutes.
The absorption axis of the polarizing layer thus obtained is preferably 10 ° to 80 °, more preferably 30 ° to 60 °, and still more preferably 45 ° (40 ° to 50 °).

[Lamination]
The saponified cellulose acylate film and a polarizing layer prepared by stretching can be bonded to produce 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 °.
The adhesive for bonding is not particularly limited, but examples thereof include PVA resins (including modified PVA such as acetoacetyl group, sulfonic acid group, carboxyl group, oxyalkylene group) and boron compound aqueous solution. preferable. The thickness of the adhesive layer is preferably 0.01 to 10 μm after drying, and particularly preferably 0.05 to 5 μm.
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 the light with a wavelength of 590 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 with a wavelength of 590 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 °. 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 λ / 4 plate comprising a polarizing layer having an absorption axis inclined by 20 ° to 70 ° with respect to the longitudinal direction and an optically anisotropic layer made of a liquid crystalline compound.

(2) Application of optical compensation layer (production of optical compensation sheet for liquid crystal display panel)
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 can be 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 also possible to produce an optical compensation sheet using the cellulose acylate film of the present invention by transferring only the optically anisotropic layer on the alignment film in which the alignment state is fixed onto the polarizer.
The alignment film is an organic compound (eg, ω-tricosanoic acid) formed by rubbing treatment of an organic compound (preferably polymer), oblique deposition of an inorganic compound, formation of a layer having a microgroove, or Langmuir-Blodgett method (LB film). , Dioctadecylmethylammonium chloride, methyl stearylate). Furthermore, an alignment film in which an alignment function is generated by application of an electric field, application of a magnetic field, or light irradiation is also known.
The alignment film is preferably formed by polymer rubbing treatment. In principle, the polymer used for the alignment film has a molecular structure having a function of aligning liquid crystal molecules.
In the present invention, in addition to the function of aligning liquid crystalline molecules, the cross-linking has a function of binding a side chain having a crosslinkable functional group (eg, double bond) to the main chain, or aligning liquid crystal 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. Moreover, a silane coupling agent can be used as a polymer. The polymer is preferably a water-soluble polymer (eg, poly (N-methylolacrylamide), carboxymethylcellulose, gelatin, polyvinyl alcohol, modified polyvinyl alcohol), more preferably gelatin, polyvinyl alcohol and modified polyvinyl alcohol, and polyvinyl alcohol and modified. Polyvinyl alcohol is most preferred. It is particularly preferable to use two types of polyvinyl alcohol or modified polyvinyl alcohol having different degrees of polymerization. The saponification degree of polyvinyl alcohol is preferably 70 to 100%, more preferably 80 to 100%. The mass average polymerization degree of polyvinyl alcohol is preferably 100 to 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 can be 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 for a liquid crystal display panel 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 [0024] in JP-A-2002-62426. As the crosslinking agent, an aldehyde having a high reaction activity, particularly glutaraldehyde is preferable.
0.1-20 mass% is preferable with respect to a polymer, and, as for the addition amount of a crosslinking agent, 0.5-15 mass% is more preferable. The amount of the unreacted crosslinking agent remaining in the alignment film is preferably 1.0% by mass or less, and more preferably 0.5% by mass or less. By adjusting in this way, even if the alignment film is used for a long time in a liquid crystal display device or left in a high temperature and high humidity atmosphere for a long time, sufficient durability without reticulation can be obtained.
The alignment film can be basically formed by applying the polymer as an alignment film forming material and a transparent support containing a crosslinking agent, followed by drying by heating (crosslinking) and rubbing treatment. As described above, the crosslinking reaction can be carried out at any time after coating on the cellulose acylate film of the present invention. When a water-soluble polymer such as polyvinyl alcohol is used as the alignment film forming material, the coating solution is preferably a mixed solvent of an organic solvent (eg, methanol) having a defoaming action and water. The ratio of water: methanol is preferably 0: 100 to 99: 1, and more preferably 0: 100 to 91: 9. Thereby, generation | occurrence | production of a bubble is suppressed and the defect of the layer surface of an alignment film and also an optically anisotropic layer reduces remarkably.

The alignment film is preferably applied by spin coating, dip coating, curtain coating, extrusion coating, rod coating, or roll coating. A rod coating method is particularly preferable. The film thickness after drying is preferably 0.1 to 10 μm. Heating and drying can be performed at 20 ° C to 110 ° C. In order to form sufficient cross-linking, the heat drying is preferably 60 ° C to 100 ° C, particularly preferably 80 ° C to 100 ° C. 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 cellulose acylate film of the present invention or on the undercoat layer. The alignment film can be obtained by rubbing the surface after crosslinking the polymer layer as described above.

For the rubbing treatment, a treatment method widely adopted as a liquid crystal alignment treatment process of LCD can be applied. That is, a method of obtaining the orientation by rubbing the surface of the orientation film in a certain direction using paper, gauze, felt, rubber, nylon, polyester fiber or the like can be used. Generally, it is carried out by rubbing several times using a cloth or the like in which fibers having a uniform length and thickness are planted on average.
When industrially implemented, this is achieved by bringing a rotating rubbing roll into contact with the film with the alignment 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 for 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 crystal molecule includes a metal complex. In addition, a liquid crystal polymer containing a rod-like liquid crystalline molecule in a repeating unit can also be used as the rod-like liquid crystalline molecule. In other words, the rod-like liquid crystal molecule may be bonded to a (liquid crystal) polymer.
For rod-like liquid crystalline molecules, see Chapter 4, Chapter 7 and Chapter 11 of the Chemistry of the Quarterly Chemistry Vol. 22 (1994) The Chemical Society of Japan, and the 142th Committee of the Japan Society for the Promotion of Science. Described in Chapter 3.
The birefringence of the rod-like liquid crystal molecule is preferably in the range of 0.001 to 0.7.
The rod-like liquid crystalline molecule preferably has a polymerizable group in order to fix its alignment state. The polymerizable group is preferably a radically polymerizable unsaturated group or a cationically polymerizable group. Specifically, for example, the polymerizable groups described in paragraphs [0064] to [0086] of JP-A-2002-62427 are described. Group and a polymerizable liquid crystal compound.

[Disc liquid crystalline molecules]
For discotic liquid crystal molecules, C.I. Destrade et al., Mol. Cryst. 71, 111 (1981), benzene derivatives described in C.I. Destrade et al., Mol. Cryst. 122, 141 (1985), Physics lett, A, 78, 82 (1990); Kohne et al., Angew. Chem. 96, page 70 (1984) and the cyclohexane derivatives described in J. Am. M.M. Lehn et al. Chem. Commun. , 1794 (1985), J. Am. Zhang et al., J. Am. Chem. Soc. 116, 2655 (1994), azacrown type and phenylacetylene type macrocycles are included.
As a discotic liquid crystalline molecule, a compound having liquid crystallinity having a structure in which a linear alkyl group, an alkoxy group, and a substituted benzoyloxy group are radially substituted as a side chain of the mother nucleus with respect to the mother nucleus at the center of the molecule Is also included. The discotic liquid crystalline molecule is preferably a compound in which a molecule or an assembly of molecules has rotational symmetry and can impart 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. The discotic core and the polymerizable group are preferably compounds that are bonded via a linking group, 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 hybrid alignment, the angle between the major axis (disk surface) of the discotic liquid crystalline molecule and the surface of the alignment film increases or decreases in the depth direction of the optically anisotropic layer and with increasing distance from the surface of the alignment film. is doing. The angle preferably decreases with increasing distance. Further, the change in angle can be continuous increase, continuous decrease, intermittent increase, intermittent decrease, change including continuous increase and continuous decrease, or intermittent change including increase and decrease. The intermittent change includes a region where the inclination angle does not change in the middle of the thickness direction. Even if the said angle includes the area | region where an angle does not change, it should just 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 alignment film side can be generally adjusted by selecting the discotic liquid crystalline molecules or the material of the alignment film, or by selecting the 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 the discotic liquid crystalline molecules. be able to. Examples of the additive used together with the discotic liquid crystalline molecule include a plasticizer, a surfactant, a polymerizable monomer and a polymer. The degree of change in the major axis orientation direction can also be adjusted by selecting liquid crystalline molecules and additives as described above.

[Other compositions 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. These are preferably compatible with the liquid crystalline molecules and can change the tilt angle of the liquid crystalline molecules or do 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 more preferable is one that is copolymerizable with the liquid crystal compound containing the polymerizable group. Examples of the polymerizable monomer include those described in paragraph numbers [0018] to [0020] in JP-A-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.
Examples of such polymers include cellulose esters. 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 preferably in the range of 0.1 to 8% by mass with respect to the liquid crystal molecule so as not to disturb 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 polymerization initiator described later and optional components on the alignment film.
As a solvent used for preparing the coating solution, an organic solvent is preferably used. Examples of organic solvents include amides (eg, N, N-dimethylformamide), sulfoxides (eg, dimethyl sulfoxide), heterocyclic compounds (eg, pyridine), hydrocarbons (eg, benzene, hexane), alkyl halides (eg, , Chloroform, dichloromethane, tetrachloroethane), esters (eg, methyl acetate, butyl acetate), ketones (eg, acetone, methyl ethyl ketone), ethers (eg, tetrahydrofuran, 1,2-dimethoxyethane). Alkyl halides and ketones are preferred. Two or more organic solvents may be used in combination.
The coating liquid can be applied by a known method (eg, wire bar coating method, extrusion coating method, direct gravure coating method, reverse gravure coating method, die coating method).
The thickness of the optically anisotropic layer is preferably 0.1 to 20 μm, more preferably 0.5 to 15 μm, and most preferably 1 to 10 μm.

[Fixing the alignment state of liquid crystalline molecules]
The aligned liquid 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. The polymerization reaction is preferably a photopolymerization reaction.
Examples of the photopolymerization initiator include α-carbonyl compounds (described in US Pat. Nos. 2,367,661 and 2,367,670), acyloin ether (US Pat. No. 2,448, 828), α-hydrocarbon-substituted aromatic acyloin compounds (described in US Pat. No. 2,722,512), polynuclear quinone compounds (US Pat. Nos. 3,046,127 and 2,951). , 758), a combination of triarylimidazole dimer and p-aminophenyl ketone (described in US Pat. No. 3,549,367), acridine and phenazine compound (Japanese Patent Laid-Open No. 60-105667). Publication, U.S. Pat. No. 4,239,850) and oxadiazole compounds (U.S. Pat. No. 4,212,970).
The amount of the photopolymerization initiator used is preferably in the range of 0.01 to 20% by mass, more preferably in the range of 0.5 to 5% by mass, based on the solid content of the coating solution.
It is preferable to use ultraviolet rays for light irradiation for polymerization of liquid crystalline molecules.
The irradiation energy is preferably in the range of ^{20mJ / cm 2 ~50J / cm 2} , more preferably in the range of ^{20mJ / cm 2 ~5000mJ / cm 2} , a range of 100mJ / cm ² ~800mJ / cm ² More preferably. In order to accelerate the photopolymerization reaction, light irradiation may be performed under heating conditions.
A protective layer may be provided on the optically anisotropic layer.

It is also preferable to combine this optical compensation film and a polarizing layer. Specifically, the optically anisotropic layer is formed by applying the coating liquid for the optically anisotropic layer as described above to the surface of the polarizing layer. As a result, a thin polarizing plate having a small stress (strain × cross-sectional area × elastic modulus) associated with the dimensional change of the polarizing layer can be produced without using a polymer film between the polarizing layer and the optically anisotropic layer. When a polarizing plate including the cellulose acylate film of 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 between the polarizing layer and the optical compensation layer should be stretched so as to match the angle formed between the transmission axis of the two polarizing layers bonded to both sides of the liquid crystal cell constituting the LCD and the vertical or horizontal direction of the liquid crystal cell. Is preferred. A normal inclination angle is 45 °. Recently, however, devices that are not necessarily 45 ° have been developed for transmissive, reflective, and transflective LCDs, and it is preferable that the stretching direction can be arbitrarily adjusted in accordance with the design of the LCD.

[Liquid Crystal Display]
Each liquid crystal mode in which such an optical compensation film is used will be described.
(TN mode liquid crystal display)
The TN mode liquid crystal display device 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)
The OCB mode liquid crystal display device is a bend alignment mode liquid crystal cell in which rod-like liquid crystal molecules are aligned (symmetrically) in substantially opposite directions at the upper and lower portions of the liquid crystal cell. A liquid crystal display device using a bend alignment mode liquid crystal cell is 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. For this reason, 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 VA mode liquid crystal display device is characterized in that the rod-like liquid crystalline molecules are aligned substantially vertically when no voltage is applied. (1) No voltage is applied to the VA mode liquid crystal cell. In addition to a narrowly-defined VA mode liquid crystal cell (described in JP-A-2-176625), which is sometimes aligned substantially vertically and aligned substantially horizontally when a voltage is applied, Liquid crystal cell with multi-domain mode (MVA mode) (SID97, Digest of tech. Papers (Preliminary Collection) 28 (1997) 845), (3) Substantially vertical alignment of rod-like liquid crystalline molecules when no voltage is applied Mode (n-ASM mode) liquid crystal cell (described in Proceedings 58-59 (1998) of the Japanese Liquid Crystal Society) and (4) SURVAIVAL mode Liquid crystal cells (announced at LCD International 98).

(IPS mode liquid crystal display)
The IPS mode liquid crystal display device is characterized in that rod-like liquid crystalline molecules are substantially aligned horizontally in the plane when no voltage is applied, and this is switched by changing the alignment direction of the liquid crystal with and without voltage application. Is the feature. Specifically, Japanese Patent Application Laid-Open Nos. 2004-365941, 2004-12731, 2004-215620, 2002-221726, 2002-55341, and 2003-195333. Those described in the publication can be used.

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

(3) Application of antireflection layer (antireflection film)
The antireflection layer generally comprises a low refractive index layer which is also an antifouling layer, and at least one layer having a higher refractive index than that of the low refractive index layer (ie, a high refractive index layer and a medium refractive index layer). It is provided above.
Colloidal metal by multilayer deposition of transparent thin films of inorganic compounds (metal oxides, etc.) with different refractive indexes by chemical vapor deposition (CVD) method, physical vapor deposition (PVD) method, sol-gel method of metal compounds such as metal alkoxides Examples include a method of forming a thin film by post-processing (ultraviolet irradiation: JP-A-9-157855, plasma processing: JP-A-2002-327310) after forming an oxide particle film.
On the other hand, various antireflection layers formed by laminating and applying thin layers in which inorganic particles are dispersed in a matrix have been proposed as antireflection layers with high productivity.
Further, examples of the antireflection layer include an antireflection film comprising an antireflection layer provided with an antiglare property in which the surface of the uppermost layer has a fine uneven shape on the antireflection film formed by coating as described above. It is done.
The cellulose acylate film of the present invention can be applied to any of the above-mentioned methods, but a coating method (coating type) is particularly preferable.

[Layer structure of coating type antireflection film]
The antireflection layer comprising a layer structure of at least a middle refractive index layer, a high refractive index layer, and a low refractive index layer (outermost layer) on the substrate which is a cellulose acylate film in the present invention satisfies the following relational expression. It is designed to have a refractive index.
Relational expression: 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 Transparent support (cellulose acylate film of the present invention) and medium refraction A hard coat layer may be provided between the rate layers. Further, the antireflection layer may comprise a medium refractive index hard coat layer, a high refractive index layer and a low refractive index layer.
Examples of the antireflection film include JP-A-8-122504, JP-A-8-110401, JP-A-10-300902, JP-A-2002-243906, JP-A-2000-11706, and the like. . Other functions may be imparted to each layer, for example, an antifouling low refractive index layer or an antistatic high refractive index layer (eg, JP-A-10-206603, JP-A-2002). -243906 publication etc.) etc. are mentioned.
The haze of the antireflection layer is preferably 5% or less, more preferably 3% or less. The strength of the film is preferably H or more, more preferably 2H or more, and most preferably 3H or more in a pencil hardness test according to JIS K5400.

[High refractive index layer and medium refractive index layer]
The layer having a high refractive index (high refractive index layer) of the antireflection layer is composed of a curable film containing at least inorganic compound ultrafine particles 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 of the high refractive index inorganic compound ultrafine particles include oxides such as Ti, Zn, Sb, Sn, Zr, Ce, Ta, La, and In, and composite oxides containing these metal atoms.
In order to obtain such ultrafine particles, the surface of the particles is treated with a surface treatment agent (for example, silane coupling agents, etc. (JP-A Nos. 1-295503, 11-153703, 2000-9908). ), An anionic compound or an organometallic coupling agent (JP 2001-310432 A, etc.), a core-shell structure with a high refractive index particle as a core (JP 2001-166104 A, etc.), specific dispersion (For example, JP-A-11-153703, US Pat. No. 6,210,858, JP-A-2002-27776069, etc.) and the like.
Examples of the material forming the matrix include conventionally known thermoplastic resins and curable resin films.
Further, the material forming the matrix includes a polyfunctional compound-containing composition having at least two radically polymerizable and / or cationically polymerizable groups, an organometallic compound containing a hydrolyzable group, and a portion thereof. At least one composition selected from condensate compositions 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. Such a curable film is described in, for example, JP-A-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 preferably adjusted to be a value between the refractive index of the low refractive index layer and the refractive index of the high refractive index layer. The refractive index of the middle refractive index layer is preferably 1.50 to 1.70.

[Low refractive index layer]
The low refractive index layer is formed by sequentially laminating on the high refractive index layer. The refractive index of the low refractive index layer is 1.20 to 1.55. Preferably it is 1.30-1.50.
The low refractive index layer is preferably constructed as an outermost layer having scratch resistance and antifouling properties. As a means for greatly improving the scratch resistance, it is effective to impart slipperiness to the surface, and it is possible to apply a thin film layer means including introduction of silicone by a conventionally known silicone compound, introduction of fluorine by a fluorine-containing compound, or the like.
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.
Examples of the fluorine compound include paragraphs [0018] to [0026] of JP-A-9-222503, paragraphs [0019] to [0030] of JP-A-11-38202, and JP-A-2001-40284. And the compounds described in paragraph numbers [0027] to [0028] of JP-A No. 2000-284102.

The silicone compound is a compound having a polysiloxane structure, preferably containing a curable functional group or a polymerizable functional group in the polymer chain and having a crosslinked structure in the film. For example, reactive silicone (eg, Silaplane (manufactured by Chisso Corporation), silanol group-containing polysiloxane (Japanese Patent Laid-Open No. 11-258403, etc.) and the like can be mentioned.
In the crosslinking or polymerization reaction of the fluorine-containing and / or siloxane polymer having a crosslinking group or a polymerizable group, the coating composition for forming the outermost layer containing a polymerization initiator, a sensitizer, or the like is applied simultaneously or after coating. It is preferable to carry out by light irradiation or heating later.
Further, as the low refractive index layer, 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 is also preferable.
Examples of these silane coupling agents include polyfluoroalkyl group-containing silane compounds or partially hydrolyzed condensates thereof (Japanese Patent Laid-Open Nos. 58-142958, 58-147483, 58-147484, and Japanese Patent Laid-Open No. 58-147484). 9-157582, 11-106704, etc.), silyl compounds containing a (poly) perfluoroalkyl ether group which is a fluorine-containing long chain group (Japanese Patent Laid-Open No. 2000-117902, 2001) Compounds described in JP-A-48590 and 2002-53804).
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 can be provided on the surface of the substrate which is the cellulose acylate film of the present invention in order to impart physical strength to the antireflection film. In particular, it is preferably provided between the base material 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 of the curable compound 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 International Publication WO00 / 46617.
The high refractive index layer described above 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 layer thickness of the hard coat layer can be appropriately designed depending on the application. The layer 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]
When applied to a liquid crystal display device, the forward scattering layer can be provided in order to provide an effect of improving the viewing angle when the viewing angle is inclined in the vertical and horizontal directions. By dispersing fine particles having different refractive indexes in the hard coat layer, it can also serve as a hard coat function.
Examples of the forward scattering layer include, for example, Japanese Patent Application Laid-Open No. 11-38208 in which a forward scattering coefficient is specified, Japanese Patent Application Laid-Open No. 2000-199809 in which a relative refractive index between a transparent resin and fine particles is in a specific range, and a haze value of 40%. The thing as described in Unexamined-Japanese-Patent No. 2002-107512 etc. which were prescribed | regulated as mentioned above is mentioned.

[Other layers]
In addition to the above layers, a primer layer, an antistatic layer, an undercoat layer, a protective layer, and the like may be provided.
[Coating method]
Each layer of the antireflection film is formed by 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 can be 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 retained. 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 layer, and these shapes are maintained on the surface uneven layer. 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.

[Measuring method]
The measurement method used in the present invention is described below.
(1) Re and Rth measurements After the sample film was conditioned at 25 ° C. and 60% relative humidity for 3 hours or more, an automatic birefringence meter (KOBRA-21ADH / PR: manufactured by Oji Scientific Instruments) was used. At a temperature of 60 ° C. and a relative humidity of 60%, the retardation value at a wavelength of 590 nm is measured from the direction perpendicular to the sample film surface and ± 40 ° from the film surface normal. The in-plane retardation (Re) is calculated from the vertical direction, and the retardation (Rth) in the thickness direction is calculated from the measured value in the ± 40 ° direction from the film surface ray. Let these be Re (60) and Rth (60). Unless otherwise specified, Re and Rth refer to this value. Further, in order to observe the degree of change in Rth due to humidity change, Rth was measured at relative humidity of 25% and 80%, respectively, and the degree of change was shown as Rth (80) / Rth (25), which is shown in Table 1. did. The closer the value is to 100%, the higher the environmental resistance. The environmental resistance is preferably 98% or more, and more preferably 99% or more.

(2) Degree of substitution of cellulose acylate The degree of acyl substitution of cellulose acylate is determined according to Carbohydr. Res. 273 (1995) 83-91 (Tezuka et al.).

Specific embodiments of the cellulose acylate film of the present invention are described below. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.
1. Formation of Cellulose Acylate Film (1) Preparation of Cellulose Acylate Cellulose acylates with different types of acyl groups and different degrees of substitution described in Table 1 were prepared. This was carried out by adding sulfuric acid (7.8 parts by mass with respect to 100 parts by mass of cellulose) as a catalyst, adding carboxylic acid as a raw material for the acyl substituent, and carrying out an acylation reaction at 40 ° C. At this time, the kind and substitution degree of the acyl group were adjusted by adjusting the kind and amount of the carboxylic acid. After acylation, aging was performed at 40 ° C. The cellulose acylate thus obtained is shown in Table 1.

(2) Cellulose acylate pelletization The cellulose acylate was dried at 120 ° C. for 3 hours to a water content of 0.1% by mass, and a plasticizer: 6 parts by mass of triphenyl phosphate was added. 0.05% by mass of silicon dioxide fine particles (trade name: Aerosil R972V, manufactured by Nippon Aerosil Co., Ltd.) was added.
A mixture of these was put into a hopper of a twin-screw kneading extruder and kneaded.
The mixture thus melted was extruded into a strand having a diameter of 3 mm in a water bath and immersed for 1 minute (strand solidification). Thereafter, the strand-solidified mixture was passed through water at 10 ° C. for 30 seconds to lower the temperature, and then cut into a length of 5 mm. The pellets thus formed were dried at 100 ° C. for 10 minutes and then packed in bags.

(Measurement of glass transition temperature (Tg))
Tg of the obtained pellet was measured by the following method, and the results are shown in Table 1.
20 mg of a sample was placed in a DSC measurement pan. This was heated from 30 ° C. to 250 ° C. at 10 ° C./min in a nitrogen stream (1st-run), and then cooled to 30 ° C. at −10 ° C./min. Thereafter, the temperature was raised again from 30 ° C. to 250 ° C. (2nd-run). The glass transition temperature (Tg) was determined for the 2nd-run. The Tg refers to the temperature at which the baseline begins to deviate from the low temperature side. The results are shown in Table 1.

(3) Melt Film Formation Cellulose acylate pellets formed by the above method were dried with a vacuum dryer at 110 ° C. for 3 hours. This was put into a hopper adjusted to (Tg-10 ° C.) based on the Tg measured above, and melt-cast at 190 ° C. for 5 minutes. At this time, a film having a desired thickness (D) was obtained by setting the speed of the casting drum to T / D times the extrusion speed. The surface temperature of the casting drum was Tg-10 ° C., on which the cellulose acylate was solidified to form a film. At this time, an electrostatic application method (a 10 kV wire was placed 10 cm from the point where the melt was attached to the casting drum) was used. Next, the solidified film was peeled off from the casting drum, and both ends (5% of the total width) were trimmed immediately before winding. Then, the both ends of the film were subjected to a thicknessing process (knurling) having a width of 10 mm and a height of 50 μm, and wound up by 3000 m at 30 m / min. The width of the unstretched film thus obtained was 1.5 m at each level.

(4) Stretching The unstretched films thus obtained were each stretched at the magnifications shown in Table 1 to prepare cellulose acylate films. After stretching, both ends of the film were further trimmed by 5% each. Table 1 shows Re and Rth of these cellulose acylate films. The stretching was performed at a temperature 10 ° C. higher than the Tg measured above and at 300% / min. The slow cooling was performed under the conditions described in Table 1. The thickness of the stretched film (cellulose acylate film) thus obtained is shown in Table 1.

(Density measurement)
In addition, the density of the cellulose acylate was measured with an automatic densimeter (MINIDENS: manufactured by Ipros). The results are shown in Table 1.

2. Production of Polarizing Plate (1) Saponification of Cellulose Acylate Film The unstretched and stretched cellulose acylate films were saponified by the following immersion saponification method.
(I) Immersion saponification A 1.5 N aqueous solution of NaOH was used as a saponification solution.
The temperature was adjusted to 60 ° C., and the cellulose acylate film was immersed for 2 minutes.
Then, it was immersed in a 0.1N sulfuric acid aqueous solution for 30 seconds and passed through a water washing bath.

(Ii) 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 N, and the temperature was adjusted to 60 ° C. as a saponification solution.
This saponification solution was applied to 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 for 1 minute at a rate of 10 l / m ² · min and washed.
In addition, although it implemented by any said coating saponification method, the result similar to the immersion saponification method was shown.

(2) Production of Polarizing Layer According to Example 1 of Japanese Patent Laid-Open No. 2001-141926, a peripheral speed difference was given between two pairs of nip rolls, and the polarizing layer was produced by stretching in the longitudinal direction.

(3) Bonding The polarizing layer obtained in this manner, the saponified unstretched, stretched cellulose acylate film, and the saponified Fujitac (unstretched triacetate film) were combined with PVA (manufactured by Kuraray Co., Ltd., PVA). -117H) 3% aqueous solution was used as an adhesive, and the laminate was bonded in the following combination so that the longitudinal direction of the polarizing axis and the cellulose acylate film was 45 °.
Polarizing plate A: Stretched cellulose acylate film / polarizing layer / unstretched cellulose acylate film Polarizing plate B: Stretched cellulose acylate film / polarizing layer / Fujitack Polarizing plate C: Stretched cellulose acylate film / deflection layer / stretched cellulose acylate the film

3. Production of Optical Compensation Film / Liquid Crystal Display Device The retardation plate A or B was used in place of a 15-inch display VL-1530S (VA method) polarizing plate manufactured by Fujitsu Limited. The amount of light leakage of the liquid crystal display device thus obtained was measured according to the following method.
(Light leakage evaluation method)
The liquid crystal display device had a black display on the entire surface and was placed in a completely dark room. The brightness of the screen at this time was measured with a photometer. The amount of light was divided by the value when the entire surface was displayed in white, and the amount expressed as a percentage was defined as “light leakage amount”. The results are shown in Table 1.
What used the retardation polarizing plate using the stretched cellulose acylate film of this invention had little light leakage, and was able to produce the favorable optical compensation film. On the other hand, light leakage was remarkable in the case outside the scope of the present invention. In particular, the light leakage of the sample (Comparative Example 1 in Table 1) according to Sample 11 in the examples of JP-A No. 2000-352620 was remarkable. On the other hand, Examples 1-9 which implemented this invention on the conditions similar to the comparative example 1 showed the favorable result.
Furthermore, even when the stretched cellulose acylate film of the present invention was used in place of the cellulose acetate film coated with the liquid crystal layer of Example 1 of JP-A-11-316378, a good optical compensation film could be produced.
Further, in place of the cellulose acetate film coated with the liquid crystal layer of Example 1 of JP-A-7-333433, even if an optical compensation filter film is produced by changing to the stretched cellulose acylate film of the present invention, good optical properties can be obtained. A compensation film could be produced.
Further, the polarizing plate and the retardation polarizing plate in the present invention are 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. An optically anisotropic layer containing an alignment film, 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 FIG. 10 of JP-A-2000-154261 When the 20-inch OCB type liquid crystal display device described in -15 is used in the IPS type liquid crystal display device shown in FIG. 11 of Japanese Patent Application Laid-Open No. 2004-12731, a good liquid crystal display device free from light leakage was obtained. .

4). Production of Low Reflective Film A low reflective film was produced using the stretched cellulose acylate film of the present invention in accordance with Example 47 of the Japan Society for Invention and Innovation (public technical number 2001-1745), and good optical performance was obtained. It was.
Furthermore, the low-reflection film obtained from the above is used as a liquid crystal display device described in Example 1 of Japanese Patent Laid-Open No. 10-48420, and a 20-inch VA liquid crystal display described in FIGS. When an evaluation was made on the outermost layer of the device, a 20-inch OCB type liquid crystal display device described in FIGS. 10 to 15 of JP 2000-154261 A, a good liquid crystal display device was obtained.

  According to the present invention, a cellulose acylate film formed by melt casting, which can reduce the occurrence of display failure during black display when incorporated in a liquid crystal display device, and A manufacturing method thereof and a liquid crystal display device using the same can be provided. Therefore, the present invention has high industrial applicability.

Claims (4)

The acylate group is formed by melt casting a cellulose acylate resin satisfying the substitution degree represented by the following formulas (1) and (2), and the density is 1.240 g / cm ^{2 to} 1.350 g / cm ^3. And a retardation in the thickness direction (Rth) of 100 nm to 800 nm.
2.5 ≦ A + B ≦ 3.0 Formula (1)
1.25 ≦ B ≦ 3.0 (2)
[In formula, A shows the substitution degree of an acetyl group. B shows the sum total of the substitution degree of a propionyl group, a butyryl group, a pentanoyl group, and a hexanoyl group. ] The cellulose acylate film according to claim 1, wherein the in-plane retardation (Re) and the retardation in the thickness direction (Rth) satisfy all of the following formulas (3) to (5). .
Rth ≧ Re Formula (3)
300 ≧ Re ≧ 0 Formula (4)
500 ≧ Rth ≧ 100 Formula (5) A film forming step of forming a molten cellulose acylate resin in which the acylate group satisfies the substitution degree represented by the following formulas (1) and (2) to a predetermined thickness on a support; and A density comprising: a stretching step of stretching the formed cellulose acylate resin; and a cooling step of cooling the cellulose acylate resin stretched in the stretching step at a rate of 10 to 60 ° C./min. Is a method for producing a cellulose acylate film having a thickness direction retardation (Rth) of 100 nm to 800 nm with a thickness of 1.240 g / cm ^{2 to} 1.350 g / cm ³ .
2.5 ≦ A + B ≦ 3.0 Formula (1)
1.25 ≦ B ≦ 3.0 (2)
[In formula, A shows the substitution degree of an acetyl group. B shows the sum total of the substitution degree of a propionyl group, a butyryl group, a pentanoyl group, and a hexanoyl group. ] A liquid crystal display device comprising the cellulose acylate film according to claim 1 .