JPH09155951A - Manufacture of polysulphone resin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacture of a resin film having an optical quality being preferable as the raw material for a phase differential plate of a liquid crystal display in use of polysulphone resin by an extrusion molding method. SOLUTION: By the use of an extrusion machine, polysulphone resin is melted and extruded into a film from the T-die at an extrusion resin temperature of 330-400 deg.C, and the resin film extruded is introduced to a cooling roll 4 or belt 6 at an air gap of 50-250mm to subsequently be pinch compresed between the roll and the roll, the roll and the belt, and the belt and the belt under the conditions of a cooling roll 4 or belt temperature of 120-220 deg.C and a pinch- compression force of 50-500kg/cm.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a polysulfone resin film (including a sheet) by an extrusion molding method, and more particularly, it is excellent in optical quality suitable as a raw material for a retardation plate of a liquid crystal display. The present invention relates to a method for producing a resin film by using an extrusion molding method using a polysulfone resin.

[0002]

2. Description of the Related Art There are TN (twisted nematic) type and STN (super twisted nematic) type as display modes of commonly used liquid crystal displays. The TN type is
The twist angle of liquid crystal molecules is 90 degrees, and it has been used for clocks, calculators, etc. for a long time. The STN type is a display mode improved from the TN type and has a twist angle of liquid crystal molecules of 180 degrees or more (usually 210 degrees to 270 degrees). As a result, the response of the liquid crystal molecules becomes sharp, and it is possible to increase the screen size and display capacity, which were difficult for the TN type.

However, the STN type display is
The conventional TN type has a drawback that it cannot display black and white, which is possible. For example, yellow and black (yellow mode),
A coloring phenomenon of blue and white (blue mode) appears. This occurs because the amount of light transmitted through the liquid crystal varies depending on the wavelength of light (wavelength dispersibility of the liquid crystal). Since the STN type display has such a hue, it is impossible to obtain a color display or a clear black and white display.

Therefore, in order to eliminate the coloring phenomenon of the STN type display (color compensation), a retardation plate is used. Conventionally, as the retardation plate, one obtained by uniaxially stretching a polycarbonate resin film and imparting a certain retardation is usually used. The retardation plate is lighter than other methods such as the two-layer STN method and the liquid crystal polymer layer because the coloring phenomenon can be eliminated simply by disposing it between the liquid crystal cell (STN panel) and the polarizing plate. It is thin and has excellent cost performance.

However, the retardation plate made of a polycarbonate resin cannot completely compensate for the wavelength dispersion of the liquid crystal, and it is used by stacking two liquid crystals or compensating the response speed and contrast of the liquid crystal for color compensation. . On the other hand, if polysulfone resin is used for the retardation plate, the wavelength dispersion of the resin will be relatively close to that of liquid crystal, and the wavelength range of color compensation will be wide, and better color compensation will be possible compared to polycarbonate resin. Becomes

Such a retardation plate is disclosed in JP-A-2-2560.
No. 03 is disclosed. That is, the publication discloses a method for continuously producing an optical film in which optical unevenness is hardly observed by a solvent casting method using a polycarbonate resin or the like. The optical film obtained by this method is said to be suitable as a retardation plate for liquid crystal displays. However, the solvent casting method requires high equipment costs, high running costs, residual solvent components in the molded product, which deteriorates the performance of the molded product. It has drawbacks such as being harmful to.

If the resin film is manufactured by the extrusion molding method, the above-mentioned drawbacks of the solvent casting method can be solved. However, in the extrusion molding method, unevenness in thickness, die lines, gear marks, unevenness in phase difference and the like are generated in the produced film, so that only a film unsuitable for optical applications such as liquid crystal display members can be obtained.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a resin film excellent in optical quality, which is suitable as a raw material for a retardation plate of a liquid crystal display by an extrusion molding method using a polysulfone resin. To do. The present inventors, as a result of earnest research to solve the problems of the prior art, when producing a film from a polysulfone resin by a melt extrusion method, under specific conditions, by sandwiching the molten resin film, It was found that a film having no unevenness in thickness, excellent uniformity over the entire surface, and excellent optical performance can be obtained. The present invention has been completed based on these findings.

[0009]

According to the present invention, an extruder is used to melt extrude a polysulfone resin into a film at a resin temperature of 330 to 400 ° C. at the time of discharging from a T-die, and extrude the extruded resin film with air. Gap 50-250m
m to a cooling roll or belt, between rolls, between rolls, or between belts, cooling roll or belt temperature 120-220
There is provided a method for producing a polysulfone resin film, which comprises clamping at a temperature of 50 ° C. and a clamping pressure of 50 to 500 kg / cm.

The resin temperature at the time of discharge is the temperature of the molten resin discharged from the tip of the T die lip of the extruder. The air gap is the distance from the tip of the T die lip of the extruder to the portion where the molten resin (resin film) first contacts the cooling roll or belt. The narrow pressure is applied by narrowing the molten resin (resin film) between the rolls, between the rolls and the belt, or between the belts. The narrow pressure is defined by the following equation. (Narrow pressure) = (force at narrow pressure) / (resin width)

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The details of the present invention will be described below. As the extruder, a generally used single-screw or twin-screw or more screw type extruder can be used. It is preferable to dispose a gear pump between the extruder and the T die for discharging, because the discharge amount becomes stable. The T die is not particularly limited as long as it is a die for forming a film, but is generally used straight manifold type,
A coat hanger type is sufficient. The molten resin melt-extruded (cast) into a film form from the T-die is a take-up having a function of being able to strongly press the molten resin between rolls, between rolls and between belts, or between belts. Picked up by the machine. The film collected is
Usually, it is wound up by a winder.

The resin temperature at the time of discharge is the temperature of the molten resin discharged from the tip of the T die lip of the extruder. The resin temperature may be measured by using a thermocouple or the like while holding each part of the extruder at a predetermined temperature and discharging the resin at a predetermined screw rotation speed before the extruder and the take-up machine are coupled.
Further, if an infrared radiation thermometer, an optical fiber thermometer, etc. are set to suit the environment, it is possible to measure the resin temperature in-line.

As shown in FIG. 1, the air gap is a distance 7 from the tip of the lip of the T die 2 of the extruder 1 to the portion where the molten resin 3 first contacts the cooling roll 4 or the belt.
It is. The T-die may be attached to the extruder at an angle to the extruder extrusion direction to achieve the desired air gap. In the apparatus shown in FIG. 1, the driving temperature adjusting roll 5 drives the belt 6 so that the molten resin is sandwiched between the belt 6 and the cooling roll 4. The resin film 3 that has been pressed and cooled is guided by the guide rolls 8,
It is taken up via 9 in the direction 10 of the winder.

The temperature of the cooling roll or belt is adjusted within a predetermined range by making the cooling roll 4 and the driving temperature control roll 5 capable of heating from the inside. A heating medium or the like may be used to heat the roll from the inside. As shown in FIG. 2, the belt used is an endless belt, and its temperature is adjusted by bringing it into contact with the temperature control roll 11 and the drive temperature control roll 12. Further, in order to make the belt temperature more uniform, in addition to heating with a temperature control roll, a temperature controlled air stream may be blown from the inside of the belt, or heating may be performed with a lamp, a heating wire or the like.

The surface roughness (JIS B0601) of the contact surface between the cooling roll and the resin of the belt is usually 0.5 S or less, preferably 0.2 S or less. These surface roughness influences the surface condition of the molded film, and if the contact surface is rough, the optical properties are deteriorated. The material of the cooling roll and the belt is preferably a metal having good thermal conductivity, and examples thereof include stainless steel, carbon steel, aluminum, copper, and titanium alloy, and peeling during heating should not occur due to the difference in thermal expansion coefficient. For example, it may be plated with hard chrome. As the most suitable for processing and performance (rust, strength, surface finish), the cooling roll is preferably made of polished hard chromium-plated carbon copper, and the belt is particularly preferably made of stainless steel. As shown in FIG. 2, the belt 6 is an endless belt and is supported by two or more temperature control rolls 11 and 12. The belt is driven by rotating one or more of the temperature control rolls used inside as the drive temperature control roll 12 and rotating the drive temperature control roll. According to the roll rotation direction 13, the belt 6 moves in the belt driving direction 1
It is driven in the direction of 4. The surface of the temperature control roll may be coated with a polymer material such as a silicone resin so that the belt does not slip.

The narrow pressure is applied by sandwiching the molten resin between rolls, rolls, rolls and belts, and belts (FIGS. 3, 4, and 5). In the apparatus shown in FIG. 3, the molten resin (resin film) 3 melt-extruded from the T die is
A pressure is applied between the cooling roll 4 and the other cooling roll 15 in the two arrow A directions. The resin film is taken out in the extrusion direction 10 via the cooling roll groups 16 and 17.

In the apparatus shown in FIG. 4, the molten resin (resin film) 3 melt-extruded from the T die is sandwiched between the cooling roll 4 and the belt 20 in the two arrow A directions.
The belt 20 includes a driving temperature control roll 5 and two temperature control rolls 1.
It is supported by 8 and 19. According to the rotation direction 21 of the drive temperature control roll, the belt is driven in that direction. After that, the resin film passes through the guide roll group 22, the tremming device 23, and the pinch roll group 24, and then the extrusion direction 10
Is taken in the direction of.

In the apparatus shown in FIG. 5, the molten resin (resin film) 3 melt-extruded from the T die is sandwiched between the belt 29 and another belt 31 in the two arrow A directions. The belt 29 includes the driving temperature control roll 5 and the temperature control roll 26.
And is driven in the direction of roll rotation 28. The belt 31 is supported by two temperature control rolls 27 and 30. The pressed resin film is taken out in the extrusion direction 10.

Narrow pressure is defined by linear pressure. For example, as shown in FIG. 4, when the resin film is squeezed by the roll and the belt, the cooling roll 4 is pushed up by the hydraulic cylinder 25, the screw jack or the like and squeezed in the two arrow A directions. The narrow pressure is determined by the force that pushes up the cooling roll and the resin width as shown in the following formula. (Narrow pressure) = (Force pushing up the cooling roll) / (Resin width) When a high load is applied to the roll or belt due to the narrow pressure and there is a risk of damage, the roll to which the narrow pressure is applied is used as a buffer. At least one may be coated with a polymer resin such as a resin. Polysulfone resin has a sulfone group (-S
It is an aromatic polymer having O ₂ −) in the molecule. The raw material resin is mass-produced by Teijin Amoco Engineering Plastics Co., Ltd. (trade name: Udel), for example. A transparent grade is used as the polysulfone resin.
This is because it is a liquid crystal member and is preferably transparent.

When a belt is used, that is, when a narrow pressure is applied to the molten resin (resin film) by the belt and the roll or the belt and the belt, the tension applied in the extrusion direction becomes relatively small, so that the phase difference in the extrusion direction becomes small. Become. When sandwiched between the rolls, the molten resin that has been cast is tensioned and wound up before being cooled by the rolls on the rear side, so that the phase difference becomes large. However, when a belt is used, it is sufficiently cooled and then wound by a rear pinch roll or the like, so that tension is not applied to the molten resin during cooling. This is because during cooling, the belt and the roll or the belt and the belt are conveyed while being suppressed to some extent. Therefore, when a belt is used, the molecular orientation of the film molded product is random (free), and it is easy to give a predetermined orientation, that is, a retardation when processing (stretching) the retardation plate. It means that the molecules can be rearranged freely.
Also, the stretching direction is not limited.

When the molecules are oriented in the extrusion direction, it is easy to further stretch in the extrusion direction (usually referred to as longitudinal uniaxial stretching), and it is easy to impart a predetermined retardation. This is because the molecules of the unstretched raw film are arranged in advance in the extrusion direction to some extent. Therefore, when attempting to stretch against this arrangement, that is, in the transverse direction (direction perpendicular to the extrusion direction), the rearrangement of molecules is not smooth and phase difference unevenness is likely to occur. For this reason, the use of a belt allows the formation of a film having a low retardation, and thus has an advantage that the secondary stretching process is easy. Either longitudinal uniaxial or transverse uniaxial stretching treatment may be performed, and even if biaxial stretching treatment is performed to impart a desired retardation, a retardation plate having uniform retardation and excellent optical quality can be obtained. Further, when a belt is used, since forced cooling can be performed simultaneously on the front and back of the film, the front and back of the film are cooled in the same manner, and there is an advantage that there is no difference in optical quality between the front and back. In the case of pressure between rolls, one side is air cooled. Even if a belt is used, the combination of the belt and the roll is most suitable. Compared to the combination of the belt and the roll, the combination of the belt and the belt has a high equipment cost and a complicated mechanical structure.

By adjusting the resin temperature, the air gap, and the temperature of the cooling roll or the belt to specific conditions, a polysulfone resin film having excellent optical quality can be obtained by the extrusion molding method. By setting the resin temperature to 330 to 400 ° C., shearing in the die can be suppressed at the optimum temperature, so that optical distortion is small. Air gap 50-250mm
By making the distance relatively short, it is possible to suppress neck-in and slack in the central portion and make the molded product uniform in the width direction. There is no optical unevenness due to the cooling difference between the end and the center in the width direction. Since the cooling roll or belt temperature is set to 120 to 220 ° C. and the optimum cooling temperature is set, a film having a uniform retardation can be formed without any bending or distortion of the film formed product due to uneven cooling.

[0023]

EXAMPLES The present invention will be described more specifically below with reference to Examples and Comparative Examples. The performance evaluation method of the molded product is as follows. <Performance evaluation of molded product> Thickness unevenness The thickness unevenness of the film was measured with a micrometer (manufactured by Mitutoyo Corporation) at 20 points at a pitch of 10 mm in the extrusion direction and at 24 points at a pitch of 10 mm in the width direction. ◯: Thickness unevenness of less than 1% with respect to average thickness, ×: Thickness unevenness of 1% or more with respect to average thickness. In-plane retardation The in-plane retardation was measured by the Senarmont method. The extrusion direction was measured at a pitch of 10 mm at 20 points, and the width direction was measured at a pitch of 10 mm at 24 points. ◯: 3 with respect to average phase difference (converted to 100 μm thickness unit)
When the thickness is less than nm, x: When the average retardation is 3 nm or more. Uniformity over the entire surface A molded product film was inserted between polarizing plates in a direct Nicol arrangement and visually observed. ◯: Die line, no gear mark, uniform throughout, ×: Die line, gear mark is recognized.

Example 1 As a polysulfone resin,
Teijin Amoco Engineering Plastics Co., Ltd. product name Udel P-1700 (glass transition temperature 19
0 ° C.). The pellets of polysulfone resin were thoroughly dried in a drying hopper with a dehumidifier for 4 hours at 135 ° C. As the extruder, φ50 mm, L / D = 28, with gear pump, 10.3 cc / REV was used. Since the gear pump stabilizes the extrusion amount, thickness unevenness and phase difference unevenness can be suppressed. The T-die used was a coat hanger type with a width of 500 mm. As shown in FIG. 6, the extruder puts the raw material resin pellets into the main body of the extruder 1 from the hopper 32, and heats and melts the resin pellets in each zone (C1 to C4) of the cylinder section. The molten resin is melt-extruded from the lip of the tip of the T die through the adapter portion 33, the gear pump portion 34, the neck portion 35, and the T die 2.・ Screen mesh: # 80 × 120 × 200 × 12
0 × 80 ・ Discharge rate: 14 kg / hr ・ Extruder, gear pump, T-die temperature conditions are shown in Table 1.

[0025]

[Table 1]

The resin temperature was 340 ° C. when measured with an infrared radiation thermometer (manufactured by Raytec Co., Ltd.). As the take-up machine, one having a belt and roll shown in FIG. The conditions were as follows.・ Narrow pressure: 220 kg / cm ・ Air gap: 180 mm ・ Roll and belt temperature: 170 ° C ・ Line speed: 10 m / min ・ Resin width at narrow pressure: 320 mm Molded product (film) width is 250 m after trimming
m. Table 2 shows the performance of the obtained film. The film original fabric thus formed was longitudinally uniaxially stretched to obtain a retardation plate. When incorporated into a commercially available monochrome display STN type liquid crystal display, good image quality could be obtained.

Comparative Example 1 A film was produced in the same manner as in Example 1 except that each part of the extruder was adjusted so that the resin temperature was 410 ° C.

[Comparative Example 2] Air gap of 300 mm
A film was produced in the same manner as in Example 1 except that

[Comparative Example 3] Roll and belt temperatures were set to 70
A film was produced in the same manner as in Example 1 except that the temperature was changed to ° C.

Comparative Example 4 A film was produced in the same manner as in Example 1 except that the narrow pressure was set to 30 kg / cm.

[0031]

[Table 2]

[0032]

EFFECTS OF THE INVENTION According to the present invention, a polysulfone resin film excellent in optical quality, which is suitable as a raw material for a retardation plate of a liquid crystal display, is provided by an extrusion molding method. More specifically, according to the present invention, the following remarkable effects can be achieved. (1) Since the polysulfone resin film is manufactured by a combination of an extruder and rolls, a roll and a belt, or a belt and a belt, the equipment cost is low,
Running costs will also be low. (2) Since no solvent is used, it is environmentally friendly and safe for the human body. Also, since the solvent component does not remain in the molded product,
A film that is safe in terms of quality and retains the original performance of the resin can be obtained. (3) Since pressure is narrowed between rolls at regular intervals, rolls and belts, and belts and belts, uneven thickness, die line,
It is possible to obtain a film having excellent optical quality without causing gear marks and uneven phase difference. (4) By setting the resin temperature, the air gap, and the temperature of the cooling roll or the belt to specific conditions, a polysulfone resin film having excellent optical quality can be obtained by the extrusion molding method. (5) By using a belt at a narrow pressure, a film having good secondary workability and excellent optical properties can be formed.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view for explaining the manufacturing method of the present invention.

FIG. 2 is a schematic cross-sectional view for explaining a belt used in the manufacturing method of the present invention.

FIG. 3 is a schematic cross-sectional view showing one embodiment of the manufacturing method of the present invention.

FIG. 4 is a schematic cross-sectional view showing one embodiment of the manufacturing method of the present invention.

FIG. 5 is a schematic sectional view showing an embodiment of the manufacturing method of the present invention.

FIG. 6 is a schematic cross-sectional view of an extruder used in the present invention.

[Explanation of symbols]

 1: Extruder, 2: T die, 3: Molten resin film, 4: Cooling roll, 5: Driving temperature adjusting roll, 6: Belt, 7: Air gap, 8: Guide roll, 9: Guide roll, 10: Extrusion Direction: 11: Temperature control roll, 12: Driving temperature control roll, 13: Roll rotation direction, 14: Belt drive direction, 15: Cooling roll, 16: Cooling roll, 17: Cooling roll, 18: Temperature controlling roll, 19: Temperature control roll, 20: Belt, 21: Roll rotation direction, 22: Guide roll, 23: Treming device, 24: Pinch roll, 25: Hydraulic cylinder, 26: Temperature control roll, 27: Cooling roll, 28: Roll rotation direction , 29: belt, 30: temperature control roll, 31: belt, 32: hopper, 33: adapter part, 34: gear pump part, 35: neck part.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location // B29K 81:00 B29L 7:00 11:00

Claims (1)

[Claims] 1. A polysulfone resin is melt-extruded into a film at a resin temperature of 330 to 400 ° C. when discharged from a T-die using an extruder, and the extruded resin film is cooled to a cooling roll or a belt with an air gap of 50 to 250 mm. Guide, between rolls, between rolls and belts, or between belts and belts, cooling roll or belt temperature 120-220 ° C., clamping pressure 50-500 kg / cm
A method for producing a polysulfone resin film, which comprises pressing under the conditions described in 1.