JPH1195029A - Manufacture of phase difference film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To uniform the retardation so as to prevent the color unevenness of a liquid crystal display device by drawing a thermoplastic resin film in an area where temperature continuously rises at a specific temperature gradient from the temperature lower than the glass transition temperature (Tg) of thermoplastic resin to the temperature of Tg or higher. SOLUTION: A phase difference film is manufactured by drawing a thermoplastic resin film in an area where temperature continuously rises at the temperature gradient of 5-40 deg.C/m from the temperature lower than Tg of thermoplastic resin to the temperature of Tg or higher. That is, at the time of applying constant tension to the traveling film to perform longitudinal uniaxial free width drawing, drawing is performed in the area where the temperature rises continuously and slowly. The cast film is thus drawn in a longitudinal uniaxial zone drawing furnace where temperature continuously rises. This zone drawing furnace is provided with an intermediate furnace 5 between a first furnace 4 and a second furnace 6 and is formed in such structure that hot air is blasted to an exhausted from the intermediate furnace 5 from the furnaces 4, 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a retardation film suitable for compensating for a retardation in a liquid crystal display device or the like.

[0002]

2. Description of the Related Art Conventionally, TN (twisted nematic) liquid crystal display devices and STN (super twisted nematic) liquid crystal display devices have been used for various OA devices and display parts. However, the above-described liquid crystal display device has a disadvantage that a display screen is colored by a phase difference generated in a liquid crystal cell. Therefore, a method of eliminating the above-mentioned coloring using a retardation film is used.

A retardation film can be obtained by uniaxially stretching a thermoplastic resin film. However, when the film is mounted on a liquid crystal display device, color retardation does not occur on the entire screen. It needs to be uniform. Conventionally, as a method for obtaining a retardation film having a uniform retardation value, there is a method of providing a heat relaxation region in a stretching zone in longitudinal uniaxial stretching as described in JP-A-3-235902. .

[0004]

However, in the method for producing a retardation film by the above method,
It could not be said that the factor that makes the retardation value non-uniform was completely removed.

The inventors of the present invention have pursued factors that make the retardation value of the retardation film non-uniform, and as a result, the retardation value in the film depends on the shape of the film at the time of neck-in in the longitudinal uniaxial free width stretching. Revealed that it will change. That is, when the stretching is started and the film width changes due to neck-in, the film is deformed into a corrugated sheet, causing a local tension difference or a temperature difference, whereby the phase difference of the film becomes partially different. .
In particular, when the distribution of the retardation in the direction perpendicular to the stretching axis direction of the film is measured, the retardation value tends to increase in a portion where the corrugated deformation is remarkable.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and a retardation film having a uniform retardation value over the entire surface of the film and having excellent retardation compensation performance which does not cause color unevenness in a liquid crystal display device. It is an object of the present invention to provide a method for stably producing.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a thermoplastic resin having a glass transition temperature (Tg).
5 to 40 ° C./m from a temperature lower than
The present invention provides a method for producing a retardation film, characterized in that the thermoplastic resin film is stretched in a region where the temperature is continuously increased by the temperature gradient.

That is, when a certain tension is applied to the running film to stretch the film in the longitudinal and uniaxial free width, the film is stretched continuously and gradually in a region where the temperature rises, so that the film width shrinks, that is, the neck width is reduced. It is possible to suppress the occurrence of gradual inflow and the formation of a corrugated film. As a result, a local tension difference or temperature difference of the film does not occur, and the retardation value is made uniform.

The temperature gradient in the region where the temperature is continuously raised where the stretching is performed is 40 ° C./m or less, preferably 3 ° C./m or less.
0 ° C./m or less. When the temperature gradient is larger than 40 ° C./m, neck-in due to stretching tends to occur rapidly, and corrugated flare tends to occur in the film. Further, a state where the temperature gradient is less than 5 ° C./m is difficult to create with equipment and is not practical.

The length of the stretched region is preferably at least one third of the width of the film to be stretched. If the length of the stretched region with the temperature gradient is less than one third of the film width, the effect of suppressing the occurrence of flare against neck-in becomes insufficient.

As the thermoplastic resin used in the present invention, an appropriate resin exhibiting birefringence depending on orientation can be used. For example, a cellulose resin, a vinyl chloride resin, a polycarbonate resin, an acrylonitrile resin, an olefin resin Resins, polymethyl methacrylate resins, polysulfone resins, polyarylate resins, polyethersulfone resins, polynorbornene resins, and the like.

The method for producing the thermoplastic resin film is not particularly limited, and a known solution casting method,
A film produced by a method such as a melt casting method or a melt extrusion method is used.

According to the present invention, a retardation film having a uniform retardation value in a film plane and having no unevenness in retardation compensation performance can be manufactured. When this retardation film is applied to a liquid crystal display cell, uniform and high-quality display can be obtained over substantially the entire display cell surface.

[0014]

Next, examples of the present invention will be described.

Example 1 A polysulfone resin ("Udel P-3500" manufactured by Teijin Amoko Engineering Plastics) was dissolved in anisole to prepare a 35% by weight solution. This solution was cast on a chromium-plated steel belt, peeled off while heating and drying in a hot air oven at 210 ° C., and was 1050 mm in width and 70 μm in average thickness
Of polysulfone was prepared.

The Tg (glass transition temperature) of the produced cast film was measured using a thermogravimetric differential calorimeter (“TG / DTA 320” manufactured by Seiko Instruments Inc.).
80 ° C.

This cast film was stretched by 135% in a longitudinal uniaxial zone stretching furnace in which the temperature was continuously raised from 175 ° C. to 185 ° C. in a region of about 50 cm in length. As shown in FIG.
The intermediate furnace 5 is provided between the first furnace 4 at 185 ° C. and the second furnace 6 at 185 ° C., and has a structure in which hot air is blown into and exhausted from the 185 ° C. furnace and the 175 ° C. furnace. The cast film 1 is guided by the primary-side nip rolls 2 and 2 ′ and enters a zone stretching furnace, is stretched by passing through the first furnace 4, the intermediate furnace 5, and the second furnace 6 in order, and is secondary-nip rolls 3 and 3. 'Sent out guided by.

Comparative Example 1 The polysulfone cast film used in Example 1 was stretched 135% in a longitudinal uniaxial zone stretching furnace in which the temperature was changed from 175 ° C. to 185 ° C. in a region of about 20 cm.

Example 2 3% by weight of diethyl phthalate was added as a plasticizer to a polysulfone resin ("Udel P-3500" manufactured by Teijin Amoko Engineering Plastics Co., Ltd.) and dissolved in anisole to form a 35% by weight solution. This solution was cast on a chromium-plated steel belt, and peeled off while heating and drying at 210 ° C. in a hot-air oven to produce a cast film of polysulfone having a width of 1050 mm and an average thickness of 70 μm. It was 157 degreeC when the Tg of the produced cast film was measured.

The cast film was stretched by 135% in a longitudinal uniaxial zone stretching furnace in which the temperature was continuously raised from 150 ° C. to 160 ° C. in a region of about 50 cm in length.

Comparative Example 2 The polysulfone cast film used in Example 2 was stretched by 135% in a longitudinal uniaxial zone stretching furnace in which the temperature was changed from 150 ° C. to 160 ° C. in a region of about 20 cm.

Example 3 A polycarbonate resin ("Panlite C1400" manufactured by Teijin Limited) was dissolved in methylene chloride to prepare a 20% by weight solution. The solution was cast on a chrome-plated steel belt and heated in a hot air oven at 170 ° C.
Peeled off while heating and drying until 1050 mm in width,
A cast film of polycarbonate having an average thickness of 70 μm was prepared. The Tg of the produced cast film was 149 ° C. when measured.

This cast film was stretched 125% in a longitudinal uniaxial zone stretching furnace in which the temperature was continuously raised from 145 ° C. to 155 ° C. in a region of about 50 cm in length.

Comparative Example 3 The polycarbonate film used in Example 3 was stretched 125% in a longitudinal uniaxial zone stretching furnace in which the temperature was changed from 145 ° C. to 155 ° C. in a region of about 20 cm.

Table 1 shows the properties of the retardation films obtained in Examples 1 to 3 and Comparative Examples 1 to 3.

[0026]

[Table 1]

[0027]

As described above, according to the present invention, a retardation film having a uniform retardation value over the entire surface of the film and having excellent retardation compensation performance which does not cause color unevenness in a liquid crystal display device can be stably obtained. Can be manufactured.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a zone stretching furnace used in an example.

[Explanation of symbols]

 1: Cast film 2, 2 ': Primary nip roll 3, 3': Secondary nip roll 4: First furnace 5: Intermediate furnace 6: Second furnace

Claims (1)

[Claims] 1. A method for producing a retardation film obtained by stretching a thermoplastic resin film, the method comprising:
(Phase difference) wherein the thermoplastic resin film is stretched in a region where the temperature is continuously increased at a temperature gradient of 5 to 40 ° C./m from a temperature lower than (glass transition temperature) to a temperature equal to or higher than Tg. Film production method.