JP2000304926A - Production of long-length optical compensation sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a method of producing a long-length optical compensation sheet to easily produce an optical compensation sheet of a large area which increases the viewing angle and has no display defects when the sheet is used for a liquid crystal display device. SOLUTION: This invention provides a method of producing a long-length flexible sheet with alignment film forming material layer by which an aq. soln. prepared by dissolving an alignment film forming material filtering through a porous filter having 0.2 to 3 μm average pore diameter is applied on the surface of a long-length flexible sheet 4b while travelling, and then dried. Moreover, the invention provides a method of producing a long-length optical compensation sheet by which an org. solvent soln. prepared by dissolving a liquid crystalline discotic compd. filtering through a porous filter having 0.1 to 3 μm average pore diameter is applied on the alignment film face of the long- length flexible sheet with an alignment film while travelling, and then dried and heated to form a liquid crystalline discotic nematic phase.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an optical compensatory sheet, and more particularly to a method for manufacturing an optical compensatory sheet effective for improving display contrast and display color viewing angle characteristics.

[0002]

2. Description of the Related Art CRT as a cathode ray tube type image display device
On the other hand, a liquid crystal display device having great advantages such as thinness, light weight, and low power consumption is generally used as a display device of a portable word processor or a personal computer. Currently popular liquid crystal display devices (hereinafter referred to as L
Most of the CDs use a twisted nematic liquid crystal. Such a liquid crystal display element generally comprises a liquid crystal cell and polarizing plates provided on both sides thereof. A display method using such a liquid crystal can be roughly classified into two methods, a birefringence mode and an optical rotation mode.

A super-twisted nematic liquid crystal display device utilizing a birefringence mode (hereinafter referred to as ST)
The N-LCD uses a super twisted nematic liquid crystal having a twist angle exceeding 90 degrees and steep electro-optical characteristics. Therefore, such STN
-The LCD can display a large amount of data by time division driving. However, practical mode contrast can be obtained in STN-LCD in the yellow mode (yellow-green / dark blue) and blue mode (blue / light yellow). To obtain the black-and-white mode, a retardation plate (uniaxially stretched polymer film) is required. And a compensating liquid crystal cell).

In the optical rotation mode, which is a display mode of the TN-LCD, high-speed response (tens of milliseconds) and high contrast are obtained. Thus, the optical rotation mode has many advantages over the birefringence mode and other modes. However, since the TN-LCD does not include a retardation plate unlike the STN-LCD, there is a problem that the display color and the display contrast easily change depending on the angle when viewing the liquid crystal display device (viewing angle characteristics). .

In order to improve the viewing angle characteristics of the TN-LCD (ie, to increase the viewing angle), a retardation plate (hereinafter also referred to as an optical compensation sheet) is provided between a pair of polarizing plates and the liquid crystal cell. It is known to provide. This optical compensatory sheet has a phase difference of almost 0 in the vertical direction with respect to the liquid crystal cell.
Has no optical effect from the front,
When tilted, a phase difference appears, and this action compensates for the phase difference generated in the liquid crystal cell.

An optical compensatory sheet having negative birefringence and an inclined optical axis is also known. This sheet
Manufactured by stretching a polymer, such as polycarbonate or polyester, and has a direction of principal refractive index that is tilted from the sheet normal. However, in order to produce such a sheet by a stretching process, an extremely complicated stretching process is required, so that it is extremely difficult to produce a large-area optical compensation sheet by a generally known method.

On the other hand, an optical compensation sheet using a liquid crystal polymer is also known. For example, an optical compensation sheet obtained by applying a polymer having liquid crystallinity to the surface of an alignment film on a support film, or an optical compensation sheet comprising a support and a polymerizable rod-like compound having liquid crystallinity and positive birefringence (birefringence) Board) is known. Furthermore, as an optical compensation sheet with an expanded omnidirectional viewing angle by a simple manufacturing method, an alignment film is formed on a long flexible sheet, and a liquid crystal discotic compound layer is formed on the alignment film. Sheets are also known (EP 0 646 829 A1 published specification).

[0008]

An optical compensatory sheet which is partially defective cannot be used for a liquid crystal display device and is discarded. In particular, in the case of an optical compensation sheet having a large area, if a partial defect occurs, the area of the optical compensation sheet to be discarded also increases, so that an alignment film or a liquid crystal discotic compound is formed on the large area sheet. Must be formed with almost no defects. However, as described in the above-mentioned EP 0 646 829 A1 published specification and JP-A-9-166784, an aqueous solution in which an alignment film forming material is dissolved is applied to a transparent sheet and dried to form an alignment film forming material layer. Rubbing the film forming material layer to an alignment film, applying an organic solvent solution in which a liquid crystalline discotic compound is dissolved on the alignment film, drying and heating to form a liquid crystal discotic compound layer, In the manufacturing method, there is a problem that it is difficult to manufacture an optical compensatory sheet having no defect. In particular, trace amounts of foreign matter and insoluble impurities in an aqueous solution in which an alignment film forming material is dissolved or an organic solvent solution in which a liquid crystalline discotic compound is dissolved cause defects.

Accordingly, an object of the present invention is to provide a method for producing a long optical compensation sheet which can easily produce an optical compensation sheet having a large viewing angle and a large area without display defects when used in a liquid crystal display device. To provide.

[0010]

According to the present invention, an organic solvent solution in which a liquid crystalline discotic compound is dissolved is applied to an alignment film surface of a long flexible sheet with an alignment film under conveyance,
In the method for producing a long optical compensation sheet which forms a liquid crystalline discotic nematic phase by drying and heating, before applying the liquid crystalline discotic compound organic solvent solution, the liquid crystalline discotic compound organic solvent solution is coated with the liquid crystalline discotic compound organic solvent solution. The present invention provides a method for producing a long optical compensation sheet, which comprises a step of filtering with a porous filter having an average pore size of 0.1 to 3 μm.

The method for producing the long optical compensation sheet is as follows.
A long flexible sheet with an alignment film is formed on a surface of the long flexible sheet being conveyed by filtration through a porous filter in which holes having an average pore size of 0.2 to 3 μm are formed. It is preferable that the alignment film forming material layer is formed by applying an aqueous solution in which the material is dissolved and drying to form an alignment film forming material layer, and then rubbing the alignment film forming material layer.

According to the present invention, an aqueous solution in which an alignment film forming material is dissolved is applied to the surface of a long flexible sheet being conveyed,
In the method for producing a long flexible sheet provided with an alignment film forming material layer that is dried to form an alignment film forming material layer, before applying the aqueous solution of the alignment film forming material, the aqueous solution of the alignment film forming material may have an average pore diameter. There is also a method for producing a long flexible sheet provided with an alignment film forming material layer, which includes a step of filtering with a 0.2 to 3 μm porous filter.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The method for producing the above-mentioned long optical compensation sheet is carried out, for example, by the following steps. 1) a sending step of sending out a long flexible sheet; 2) a coating step of applying an aqueous solution in which an alignment film forming material is dissolved on the surface of the long flexible sheet; 3) an alignment film forming material for drying a coating liquid layer Layer forming step; 4) A rubbing treatment is performed on the surface of the resin layer on a long flexible sheet having a resin layer for forming an alignment film formed on the surface to form an alignment film on the long flexible sheet. Rubbing step; 5) Step of applying a liquid crystal discotic compound in which an organic solvent solution in which a liquid crystal discotic compound is dissolved is applied on an alignment film; 6) Drying of the coating liquid layer to evaporate the solvent in the organic solvent solution 7) a liquid crystal discotic compound is heated to a discotic nematic phase formation temperature to form a liquid crystal layer of a discotic nematic phase; and 8) a liquid crystal layer is solidified ( That is, a step of solidifying by quenching after the formation of the liquid crystal layer, or, when a liquid crystalline discotic compound having a crosslinkable functional group is used, crosslinking the liquid crystal layer by light irradiation (or heating)); 9) Alignment film And a winding step of winding the long flexible sheet on which the liquid crystal layer is formed.

This will be described in detail with reference to the drawings. FIG.
FIG. 1 shows a schematic view of a method for producing an optical compensation sheet of the present invention.
The long flexible sheet 4b sent out from the long flexible sheet roll (sheet roll) 4a by the feeder 1 is conveyed by a drive roller, and is dust-removed by the surface dust remover 2, and then by the coating machine 3. A coating solution in which the alignment film forming material is dissolved is applied and dried in the drying zone 5 to form an alignment film forming material layer on the surface of the long flexible sheet (1) to above).
Step 3)). The long flexible sheet obtained here may be once wound up.

Elongated flexible sheet 4 with alignment film forming material layer
c is subjected to a rubbing process by a rubbing device including a rubbing roller 8, a guide roller 6 fixed to a roller stage by a spring, and a dust remover 7 provided on the rubbing roller, and the surface of the formed alignment film is rubbed. The dust is removed by the surface dust remover 9 provided adjacent to the apparatus (step 4). As the rubbing device, a known device other than the above may be used.

The long flexible sheet 4d with an alignment film is conveyed by a driving roller, and an organic solvent solution in which a liquid crystalline discotic compound is dissolved is applied on the alignment film by a coating machine 10 (step 5). ) Then, after evaporating the solvent (step (6) above), in the heating zone 11,
The liquid crystalline discotic compound is heated to a discotic nematic phase formation temperature (the residual solvent in the coating layer also evaporates) to form a discotic nematic phase liquid crystal layer (Step 7).

Next, the liquid crystal layer is irradiated with ultraviolet rays from an ultraviolet (UV) lamp 12 to crosslink the liquid crystal layer (step 8). In order to crosslink, it is necessary to use a liquid crystalline discotic compound having a crosslinkable functional group as the liquid crystalline discotic compound. When a liquid crystalline discotic compound having no crosslinkable functional group is used, the step of irradiating ultraviolet rays is omitted, and cooling is performed immediately. In this case, the cooling needs to be performed rapidly so that the discotic nematic phase is not destroyed during the cooling.

With respect to the long flexible sheet on which the alignment film and the liquid crystal layer are formed, the optical characteristics of the surface of the long flexible sheet are measured by the inspection device 13 and an inspection is performed for any abnormality. Next, the protective film 14 is laminated on the surface of the liquid crystal layer by a laminating machine 15 and wound up by a winding device (step 9).

In the method for producing an optical compensatory sheet of the present invention, the average pore diameter is preferably 0.2 to 3 μm (preferably 0.2 to 3 μm) before applying an aqueous solution in which an alignment film forming material is dissolved to the sheet.
2 μm, more preferably 0.2 to 1 μm), and before applying the organic solvent solution in which the liquid crystalline discotic compound is dissolved to the sheet, the average pore diameter is 0.1 to 3 μm (preferably, 0.2 to 1 μm). , 0.1 to 2 μm, more preferably 0.1 to 1 μm). The method for applying a coating liquid in the present invention will be described with reference to the drawings.

FIG. 2 shows an example of an apparatus for applying an aqueous solution in which an alignment film forming material is dissolved, which can be used in the manufacturing method of the present invention. The aqueous solution in which the alignment film forming material is dissolved in the coating liquid tank 20 is supplied to the porous filter 3 by the pump 21a.
Then, it is fed into the extrusion die 24 having the decompression chamber 23 and applied onto the long flexible sheet 4b conveyed while being supported by the backup roller 25. The distance between the extrusion die 24 and the long flexible sheet 4 is generally 100 to 300 μm, and the application speed is preferably 0.1 to 1.0 m / sec. The viscosity of the aqueous solution is preferably 1 to 20 mPa · s (25 ° C.), and the coating amount is preferably 10 to 50 g / m. The coating can be performed in the same manner using a wire bar described later, in addition to the extrusion die.

FIG. 3 shows another example of the step of applying an organic solvent solution in which the liquid crystalline discotic compound of the present invention is dissolved. The organic solvent solution in which the liquid crystalline discotic compound dissolved in the porous filter 22 is dissolved is sent from the supply port 30, and the primary-side liquid reservoir 31 and the connection pipe 32
Is filled in the secondary-side liquid reservoir 33. Primary pool 3
The liquid levels of the first and second liquid reservoirs 33 are regulated by a liquid level regulating plate 34, and the overflowed liquid is discharged from an outlet 36 through an overflow liquid reservoir 35. The discharged coating liquid is adjusted to an appropriate viscosity by adding a coating liquid sent from the coating liquid layer 20 by a pump 21b in a viscosity adjusting chamber 37, and adding a solvent as necessary, and being sent by a pump 21c. After being filtered again by the filter 22, it is sent to the supply port 69A. A densitometer 38 is arranged in front of the filter 22, and the viscosity is adjusted based on this information.

The coating is performed on a long flexible sheet 4d with an alignment film.
Then, a wire bar 39 is contacted or brought into contact via an organic solvent solution. Wire bar 39
Is generally a rod having a diameter of 5 to 20 mm and a diameter of 20 to 15 mm.
A wire having a thickness of 0 μm is densely wound, and the wire is rotated in the same direction as the transport direction of the long flexible sheet 4 and at substantially the same speed as the transport speed. The coating is performed by bringing the solvent solution into contact with the long flexible sheet 4.

The organic solvent solution has a solid concentration of 15 to 50.
% By weight (particularly in the range of 15 to 40% by weight), and the viscosity of the organic solvent solution is preferably in the range of 1 to 20 mPa · s (particularly in the range of 1 to 15 mPa · s). In order to suppress the generation of streaks due to coating, it is preferable that the residence time of the organic solvent solution in the primary-side liquid pool be 10 seconds or less. The residence time (T) of the organic solvent solution is defined by the following equation. T = V ₁ / Q In the above equation, V ₁ represents the volume of the primary sump (cm ³ ), and Q represents the circulation flow rate (cm ³ / sec). In addition, it is preferable that the wire bar 39 is floated by 20 μm or more from the position of the core of the bar when the application is not performed by using the force of the application liquid to come into contact with the long flexible sheet during the application. For application, an extrusion die, a roll coater or the like can be used in addition to the wire bar.

In the step of filtering the aqueous solution in which the alignment film forming material is dissolved and the organic solvent solution in which the liquid crystalline discotic compound is dissolved, 0.05 to 2 kgf / cm
The pressure loss of the aqueous solution in which the alignment film forming material is supplied from the pump to the porous filter at the pressure of ² and the organic solvent solution in which the liquid crystalline discotic compound is dissolved are 0.
It is preferably from 0.01 to 1.0 kgf / cm ² ,
More preferably, it is 0.01 to 0.5 kgf / cm ² .

The material of the porous filter 22 is at least one of polymethyl methacrylate resin, polyacrylonitrile resin, polyamide resin, epoxy resin, polysulfone resin, fluorine resin and glass fiber impregnated resin. It is preferable that the resin be made of a resin containing, particularly, a polyamide resin, an epoxy resin, a polysulfone resin, a fluorine resin, and a glass fiber impregnated resin. Specifically, a polyamide resin, a polytetrafluoroethylene resin (PTFE), and a polysulfone resin are particularly preferable.

As the material for the long flexible sheet, any material can be used as long as it is transparent. A material having a light transmittance of 80% or more is preferable, and a material having optical isotropy when viewed from the front is particularly preferable. Therefore, the long flexible sheet is preferably manufactured from a material having a small intrinsic birefringence. Examples of such materials include cellulose triacetate, a commercial product,
ZEONEX (manufactured by Nippon Zeon Co., Ltd.), ARTON (manufactured by Nippon Synthetic Rubber Co., Ltd.) and FUJITAC (manufactured by Fuji Photo Film Co., Ltd.) can be used. Furthermore, even for materials with a large intrinsic birefringence such as polycarbonate, polyarylate, polysulfone, and polyethersulfone, conditions such as solution casting and melt extrusion, as well as stretching in the longitudinal and transverse directions are appropriately set. By doing so, it can be obtained. Further, in order to increase the adhesive strength with the alignment film forming material layer applied to the long flexible sheet, it is preferable to provide the undercoat layer on a transparent long sheet. Examples of the material for the undercoat layer include gelatin.

Examples of the alignment film forming material include polymethyl methacrylate, acrylic acid / methacrylic acid copolymer,
Styrene / maleimide copolymer, polyvinyl alcohol, poly (N-methylolacrylamide), styrene / vinyltoluene copolymer, chlorosulfonated polyethylene, nitrocellulose, polyvinyl chloride, chlorinated polyolefin, polyester, polyimide, vinyl acetate / Examples include polymers such as vinyl chloride copolymers, ethylene / vinyl acetate copolymers, carboxymethyl cellulose, polyethylene, polypropylene and polycarbonate, and compounds such as silane coupling agents. Preferred examples of the polymer include polyimide, polystyrene, polymers of styrene derivatives, gelatin, polyvinyl alcohol, and modified polyvinyl alcohol having an alkyl group (preferably having 6 or more carbon atoms).

[0028] Among the above polymers, polyvinyl alcohol or modified polyvinyl alcohol is preferred. Examples of the modified polyvinyl alcohol are described in JP-A-9-166.
The one described in Japanese Patent No. 784 is preferable.

The aqueous solution in which the alignment film forming material is dissolved is preferably a mixed solvent of water and an organic solvent such as methanol having a defoaming effect, and the ratio of water to methanol is 1:99 to 99: 1 by weight. Are common, 1: 99-91:
9 is preferable. Thereby, generation of bubbles is suppressed, and defects on the alignment film and further on the surface of the optically anisotropic layer are significantly reduced.

Examples of the above liquid crystalline discotic compound include C.I. Destrade et al., Mo.
l. Cryst. Vol. 71, p. 111 (1981); Destrade
Et al., Mol. Cryst. , 122, 14
1 (1985), Physics lett. ,
A, vol. 78, p. 82 (1990); Research report by Kohne et al., Ang
w. Chem. Vol. 96, p. 70 (1984) and cyclohexane derivatives described in J. Am. M. J. Lehn et al. Chem. Commun. , P. 1794 (1985); Research report by Zhang et al. A
m. Chem. Soc. 116, 2655 (19
1994), azacrown-based and phenylacetylene-based macrocycles.
Liquid crystal discotic (disc-like) compounds generally have a structure in which these are used as the core of the molecular center, and linear alkyl groups, alkoxy groups, substituted benzoyloxy groups, and the like are radially substituted as the linear chains. Yes, they exhibit liquid crystallinity and include those generally called discotic liquid crystals.
However, the present invention is not limited to the above description as long as the molecule itself has negative uniaxiality and can impart a certain orientation. Further, in the present invention, the term "formed from a discotic compound" does not mean that the final product is the above compound, and for example, the low molecular discotic liquid crystal has a group which reacts with heat, light or the like. As a result, those which are polymerized or cross-linked by reaction with heat, light or the like to have a high molecular weight and lose liquid crystallinity are also included. Specific preferred examples of the liquid crystalline discotic compound include those described in JP-A-9-166784.
And those described in Japanese Patent Application Laid-Open Publication No. H10-26095.

The optical compensatory sheet of the present invention is prepared by applying an organic solvent solution in which a discotic compound and other compounds are dissolved in an organic solvent onto an alignment film as described above, drying the film, and then heating the film to a discotic nematic phase forming temperature. Then, it is obtained by cooling while maintaining the orientation state (discotic nematic phase). Alternatively, an organic solvent solution obtained by dissolving a discotic compound and other compounds (for example, a polymerizable monomer and a photopolymerization initiator) in an organic solvent is applied on the alignment film as described above, dried, and then dried in a discnematic phase. It is obtained by heating to the formation temperature, polymerizing (by irradiation with UV light, etc.) and further cooling. The discotic nematic liquid crystal phase-solid phase transition temperature of the liquid crystalline discotic compound used in the present invention is preferably from 70 to 300C, particularly preferably from 70 to 17C.
0 ° C. is preferred.

For example, the tilt angle at the time of orientation of the discotic compound on the side of the support (transparent long flexible sheet) is generally determined by selecting the material of the discotic compound or the alignment film, or by a rubbing treatment method. Can be adjusted by selecting. In addition, the tilt angle of the discotic unit on the surface side (air side) generally selects a discotic compound or another compound used together with the discotic compound (eg, a plasticizer, a surfactant, a polymerizable monomer and a polymer). Can be adjusted.

The plasticizer, surfactant and polymerizable monomer are compatible with the discotic compound.
Any compound can be used as long as it does not hinder the alignment. Among these, polymerizable monomers (eg,
Compounds having a vinyl group, a vinyloxy group, an acryloyl group and a methacryloyl group) are preferred. The above compounds are generally used in an amount of 1 to 50% by weight, preferably 5 to 30% by weight, based on the discotic compound.

As the polymer, any polymer can be used as long as it has compatibility with the discotic compound and can give a tilt angle to the liquid crystalline discotic compound. Examples of the polymer include a cellulose ester. Preferred examples of the cellulose ester include cellulose acetate, cellulose acetate propionate, hydroxypropylcellulose and cellulose acetate butyrate. The polymer is generally 0.1 to 10% by weight (preferably 0.1 to 8% by weight, particularly 0.1 to 5% by weight) based on the discotic compound so as not to hinder the alignment of the liquid crystalline discotic compound. ).

The organic solvent for dissolving the liquid crystalline discotic compound used in the present invention is not particularly limited as long as it dissolves the liquid crystalline discotic compound and the other compounds described above. Examples of the organic solvent include polar solvents such as N, N-dimethylformamide (DMF), dimethylsulfoxide (DMSO) and pyridine; nonpolar solvents such as benzene and hexane; alkyl halides such as chloroform and dichloromethane; methyl acetate And esters such as butyl acetate; ketones such as acetone and methyl ethyl ketone; and ethers such as tetrahydrofuran and 1,2-dimethoxyethane. Alkyl halides and ketones are preferred. The solvents may be used alone or in combination.

[0036]

EXAMPLES Example 1 One side of a long sheet of triacetylcellulose (manufactured by Fuji Photo Film Co., Ltd.) having a thickness of 120 μm and coated with a gelatin thin film (0.1 μm) was placed directly on one side. FIG. 2 shows a 5% by weight aqueous solution of a chain alkyl-modified polyvinyl alcohol (MP203, manufactured by Kuraray Co., Ltd.).
As shown in Table 2, after filtration using a polysulfone resin porous filter (PSE filter, manufactured by Fuji Photo Film Co., Ltd.) having an average pore diameter of 1 μm, the mixture was applied with an extrusion-die coating machine and heated at 80 ° C. Dry in the wind,
An alignment film forming material layer was formed.

Subsequently, a rubbing treatment was performed on the alignment film forming material layer while conveying the obtained long sheet with the alignment film forming material layer.

1.6 g of a liquid crystal discotic compound of the following chemical formula, 0.4 g of phenoxydiethylene glycol acrylate (M101, manufactured by Toagosei Co., Ltd.), cellulose 0.05 g of acetate butyrate (CAB531-1, manufactured by Eastman Chemical Co., Ltd.) and a photopolymerization initiator (Irgacure-907, manufactured by Ciba Geigy)
As shown in FIG. 3, an organic solvent solution obtained by dissolving 0.01 g in 3.65 g of methyl ethyl ketone was filtered using a PTFE resin porous filter having an average pore size of 3 μm, and then a wire bar coating machine was used. (# 4 bar), affixed to a metal frame and fixed, heated in a high-temperature bath at 120 ° C. for 3 minutes to orient the discotic compound, allowed to cool to room temperature, and A layer (optically anisotropic layer) containing a 0.8 μm discotic compound was formed to produce a long optical compensation sheet.

[0039]

Embedded image Liquid crystalline discotic compound

(Example 2) In Example 1, a 5% by weight aqueous solution of a linear alkyl-modified polyvinyl alcohol was applied to a polysulfone resin porous filter (PSE filter, Fuji Photo Film Co., Ltd.) having an average pore size of 0.2 μm.
), And the organic solvent solution in which the liquid crystalline discotic compound and the like are dissolved is mixed with a PT having an average pore size of 1 μm.
Except for filtration using a porous filter made of FE resin,
A long optical compensatory sheet was manufactured in the same manner as in Example 1.

Example 3 In Example 1, a 5% by weight aqueous solution of linear alkyl-modified polyvinyl alcohol was mixed with a polysulfone resin porous filter having an average pore size of 1 μm (PSE filter, manufactured by Fuji Photo Film Co., Ltd.). Long optical compensation in the same manner as in Example 1 except that an organic solvent solution in which a liquid crystalline discotic compound or the like was dissolved was filtered using a polyamide resin porous filter having an average pore diameter of 1 μm. A sheet was manufactured.

Example 4 In Example 1, a 5% by weight aqueous solution of linear alkyl-modified polyvinyl alcohol was filtered using a porous filter made of PTFE resin having an average pore size of 1 μm to remove a liquid crystalline discotic compound and the like. Example 1 was repeated except that the dissolved organic solvent solution was filtered using an epoxy resin porous filter having an average pore size of 1 μm.
A long optical compensatory sheet was produced in the same manner as described above.

Example 5 In Example 1, a 5% by weight aqueous solution of a linear alkyl-modified polyvinyl alcohol was filtered using a porous filter made of a glass fiber impregnated resin having an average pore diameter of 1 μm to obtain a liquid crystalline discotic compound. A long optical compensation sheet was produced in the same manner as in Example 1, except that the organic solvent solution in which the above-mentioned components were dissolved was filtered using a PTFE resin porous filter having an average pore diameter of 1 μm.

(Comparative Example 1) In Example 1, a 5% by weight aqueous solution of a linear alkyl-modified polyvinyl alcohol was filtered using a porous filter made of polysulfone resin having an average pore diameter of 5 μm to obtain a liquid crystalline discotic compound or the like. Was dissolved in an organic solvent solution containing PTF having an average pore size of 5 μm.
A long optical compensation sheet was manufactured in the same manner as in Example 1 except that the filtration was performed using a porous filter made of E resin.

(Evaluation and Results) The light reflection state of the optically anisotropic layer of the long optical compensation sheet manufactured in each of Examples 1 to 4 and Comparative Example 1 was visually observed, and abnormality was found in light reflection. The number of parts that were left out was counted. The number of abnormal light reflections per m ^{2 of} the optical compensation sheet was AA when the number was less than 5 and B when 5 to 9 were abnormal.
B: CC which was 10 or more was designated as CC. Table 1 shows the results.

[0046]

[Table 1] Table 1 ────────────────────── Light reflection state ────────────────── ──── Example 1 BB Example 2 AA Example 3 BB Example 4 AA Example 5 BB 比較 Comparative Example 1 CC ──────────────────────

[0047]

According to the optical compensatory sheet obtained by the method for producing an optical compensatory sheet of the present invention, the defects of the alignment film and the liquid crystal layer due to the inclusion of a very small amount of foreign matter and insoluble impurities are reduced. When mounted, not only can the viewing angle be expanded due to the discotic liquid crystal layer, but also there is almost no image unevenness.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example of all steps of a method for producing an optical compensation sheet of the present invention.

FIG. 2 is a view showing an example of a coating apparatus for applying an aqueous solution in which an alignment film forming material is dissolved, which can be used in the manufacturing method of the present invention.

FIG. 3 is a view showing another example of an apparatus for applying an organic solvent solution in which a liquid crystalline discotic compound is dissolved, which can be used in the production method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sending device 2 Surface dust remover 3 Coating machine 4a Film roll 4b Elongated flexible sheet 4c Elongated flexible sheet with alignment film forming material 4d Elongated flexible sheet with alignment film 5 Heat drying zone 6 Guide roller 7 Dust remover 8 Rubbing roller 9 Surface dust remover 10 Coater 11 Heating zone 12 Ultraviolet (UV) lamp 13 Inspection device 14 Protective film 15 Laminator 20 Coating solution tank 21a, 21b, 21c Pump 22 Porous filter 23 Decompression chamber 24 Extrusion Die 25 Backup Roller 30 Supply Port 31 Primary Liquid Pool 32 Connecting Pipe 33 Secondary Liquid Pool 34 Liquid Level Control Plate 35 Overflow Liquid Pool 36 Discharge Liquid Port 37 Viscosity Adjustment Chamber 38 Density Meter 39 Wire Bar

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H049 BA06 BA42 BB43 BC04 BC09 BC22 2H091 FA11X FA11Z FB02 FC22 FC23 GA01 GA06 HA10 LA19 4F073 AA14 AA28 AA32 BA03 BA06 BA07 BA08 BA11 BA13 BA17 BA18 BA19 BA23 BA26 BA31 BB01 BB01 BB01 EA0113

Claims (7)

[Claims] An organic solvent solution in which a liquid crystalline discotic compound is dissolved is applied to the alignment film surface of a long flexible sheet provided with an alignment film under conveyance, and dried and heated to form a liquid crystal discotic nematic phase. In the method for producing a long optically compensatory sheet for forming a liquid crystalline discotic compound organic solvent solution, the liquid crystalline discotic compound organic solvent solution has an average pore size of 0.1 to 3 μm before applying the liquid crystalline discotic compound organic solvent solution.
A method for producing a long optical compensation sheet, comprising a step of filtering with a porous filter. 2. In the step of filtering the liquid crystalline discotic compound organic solvent solution, 0.05 to 2 kgf is used.
/ Cm ² pressure loss of the liquid crystalline discotic compound organic solvent solution supplied to the porous filter at a pressure of:
Elongated optical compensation sheet manufacturing method according to claim 1, characterized in that the 0.01~1.0kgf / cm ^2. 3. The material of the porous filter is at least one of polymethyl methacrylate resin, polyacrylonitrile resin, polyamide resin, epoxy resin, polysulfone resin, fluorine resin, and glass fiber impregnated resin. The method for producing a long optical compensation sheet according to claim 1, wherein the method comprises a resin containing the resin. 4. The method according to claim 1, wherein the long flexible sheet provided with an alignment film has an average pore size of 0.3 mm on the surface of the long flexible sheet being conveyed.
A solution prepared by applying an aqueous solution in which an alignment film forming material filtered through a 2-3 μm porous filter is dissolved, drying and forming an alignment film forming material layer, and then rubbing the alignment film forming material layer. The method for producing a long optical compensation sheet according to any one of claims 1 to 3, wherein: 5. An elongated film with an alignment film forming material layer, in which an aqueous solution in which an alignment film forming material is dissolved is applied to the surface of a long flexible sheet being conveyed and dried to form an alignment film forming material layer. The method for producing a flexible sheet, further comprising a step of filtering the aqueous solution of the alignment film forming material with a porous filter having an average pore size of 0.2 to 3 μm before applying the aqueous solution of the alignment film forming material. Of producing a long flexible sheet with an alignment film forming material layer. 6. In the step of filtering the aqueous solution of the alignment film forming material, the pressure loss of the aqueous solution of the alignment film forming material supplied to the porous filter at a pressure of 0.05 to ² kgf / cm ² is 0.01 to ² kgf / cm ^2. alignment film forming material layer with long flexible sheet manufacturing method according to claim 5, characterized in that a 1.0 kgf / cm ^2. 7. The material of the porous filter is at least one of polymethyl methacrylate resin, polyacrylonitrile resin, polyamide resin, epoxy resin, polysulfone resin, fluorine resin and glass fiber impregnated resin. The method for producing a long flexible sheet with an alignment film forming material layer according to any one of claims 5 to 6, wherein the long flexible sheet is provided with an alignment film forming material layer.