JP2000009935A - Production of phase different plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a producing method of phase difference film by which a phase difference film having uniform retardation all over the film can be stably produced with high productivity in the production process of the phase difference film including a stretching process even when the thermoplastic resin film before stretching has large difference in thickness. SOLUTION: The producing device of a phase difference film used is equipped with a heating zone 2, cooling zone 3 and stretching zone 4 in this order. In the heating zone 1, the thermoplastic resin film is heated to a specified temp. between the glass transition temp. (Tg) of the film and (Tg+60 deg.C). Then the film is cooled to a temp. lower by 10 to 30 deg.C than the film temp. above described for 1 to 20 sec in the cooling zone 3. Further, in the stretching zone 4, the film is stretched in such a manner that stretching of the film is started while the film is cooled for 1 to 20 sec to a temp. lower by 10 to 30 deg.C than the temp. of the thermoplastic resin film in the cooling zone and that the temp. of the film is controlled to (Tg-30 deg.C) to (Tg+20 deg.C) when stretching is completed.

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 a retardation film, and more particularly to a method for manufacturing a retardation film for compensating a retardation of a liquid crystal display device or the like.

[0002]

2. Description of the Related Art Conventionally, twisted nematic (TN)
Liquid crystal display and super twisted nematic (ST
N) Liquid crystal display devices are used for display devices of various OA devices. However, the above-mentioned liquid crystal display device has a disadvantage that the display screen is colored in blue, yellow or the like due to a phase difference generated in the liquid crystal cell. Therefore, a method of eliminating these colorings by using a retardation film has been adopted.

[0003] Usually, the above retardation film is obtained by, for example, stretching a thermoplastic resin film longitudinally or uniaxially as shown in JP-A-2-191904 or JP-A-2-42406. . The coloring compensation for eliminating the coloring has an optimum value in a very narrow range of retardation of the uniaxially stretched thermoplastic resin film. Regarding the above color compensation, the retardation characteristic represented by the retardation value is anisotropy of the refractive index of the thermoplastic resin film, that is, when the birefringence is Δn and the thickness of the thermoplastic resin film is d, Since it is represented by Δnxd, in order to eliminate color unevenness and contrast unevenness over the entire surface of the liquid crystal display device, a film showing a uniform retardation value over the entire surface of the uniaxially stretched thermoplastic resin film. Is required.

Conventionally, in order to obtain a retardation film having a uniform retardation value, a thermoplastic resin film produced by a solution casting method and having excellent thickness accuracy and surface uniformity has been used as a raw stretched film. Further, Japanese Unexamined Patent Publication No.
Japanese Patent Application Laid-Open No. 122526 discloses a method using a stretched raw material having a solvent content of 0.5 to 7% by weight on a solid basis.

However, according to the method disclosed in Japanese Patent Application Laid-Open No. 8-122526, if the thickness of a thermoplastic resin film used as a stretched raw material has a large variation, a large retardation value proportional to the thickness variation is obtained. The liquid crystal display devices using these retardation films have color unevenness that can be easily discriminated visually.
Further, since the thermoplastic resin film is produced by a solution casting method, productivity is low.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above facts, and its object is to
Even if there is a large variation in thickness of the thermoplastic resin film before stretching, in the production process of the retardation film including the stretching process, the retardation film having a uniform retardation value over the entire surface is stable and high. An object of the present invention is to provide a method for producing a retardation film that can be produced with high productivity.

[0007]

According to a first aspect of the present invention, there is provided a method for manufacturing a retardation film, comprising a heating apparatus, a cooling zone, and a stretching zone in the above-described order. In the zone, the thermoplastic resin film has a glass transition temperature (Tg) to (Tg +
60 ° C.), and then, in a cooling zone, the thermoplastic resin film is cooled by a cooling means that generates a temperature difference between minute portions corresponding to the thickness, and stretched. In the zone, the thermoplastic resin film is further stretched while being cooled, and the temperature of the thermoplastic resin film at the end of stretching is (Tg−30 ° C.)
To (Tg + 20 ° C.).

The heating zone, cooling zone and stretching zone in the retardation film manufacturing apparatus used in the present invention are such that the thermoplastic resin film transferred therein is continuously heated, cooled, and further cooled. This means that each step of stretching is performed, and it is inevitable that some intermediate temperature region exists at the boundary of these zones. Means for reducing these intermediate temperature regions as much as possible are not particularly limited.For example, a narrow slit-like passage through which the thermoplastic resin film is transferred between the respective zones may be used. Other than the method, a method of shielding heat with a heat insulating partition, a method of shielding heat with an air curtain, a method of combining these, and the like can be given.

The thermoplastic resin film used in the present invention is not particularly limited as long as it is a thermoplastic resin film which exhibits birefringence by stretching.
For example, cellulose resin, vinyl chloride resin, polycarbonate resin, polystyrene resin, acrylonitrile resin, olefin resin, polymethyl methacrylate resin, polysulfone resin, polyarylate resin, polyether sulfone resin, A film made of a thermoplastic resin such as a polynorbornene-based resin may be used.

In the present invention, the thermoplastic resin film is first heated in a heating zone so that the thermoplastic resin film has a constant temperature of Tg to (Tg + 60 ° C.). In addition, the temperature of the thermoplastic resin film in the present invention indicates the surface of the thermoplastic resin film (the same applies hereinafter). By keeping the temperature of the thermoplastic resin film at the outlet of the heating zone at the above-mentioned constant temperature of Tg to (Tg + 60 ° C.), the dispersion of the viscosity of the thermoplastic resin film is reduced, and the thermoplastic resin stretched while being cooled, which will be described later. Variations in the thickness of the resin film are reduced.

If the temperature of the thermoplastic resin film at the outlet of the heating zone is lower than Tg, the shear stress generated in the thermoplastic resin film at the time of stretching in the stretching zone described later becomes larger than the strength of the thermoplastic resin film. Brittle fracture may occur, and the thermoplastic resin film being stretched may be broken. If the temperature is higher than (Tg + 60 ° C.), the viscosity of the thermoplastic resin film becomes low, and the thermoplastic resin film to be conveyed hangs to cause trouble. Or the stretching effect may not be obtained in the stretching zone described later.

The heating means in the heating zone is not particularly limited, but includes, for example, hot air, a combination of hot air and cold air, electromagnetic heaters such as microwaves and far-infrared rays, temperature-controlled heating rolls, heat pipe rolls. And a heated metal belt whose temperature has been adjusted.

Next, the thermoplastic resin film kept at a constant temperature of Tg to (Tg + 60 ° C.) is cooled by a cooling means that generates a temperature difference between minute portions corresponding to the thickness. The thermoplastic resin film, due to the difference in heat capacity between minute parts according to the thickness of the thickness,
The thick part is relatively hard to cool, and the thin part is relatively easy to cool, so that the cooling causes the temperature between the minute parts corresponding to the thickness of the thermoplastic resin film to be reduced. Differences can be made.

The means for cooling the thermoplastic resin film includes:
If cooled too rapidly, the temperature may become lower than the appropriate temperature for stretching before reaching the next stretching step, and if cooled too slowly, the temperature difference between minute portions corresponding to the thickness is small. Therefore, a cooling rate and a cooling temperature that do not cause such a state are selected, and cooling is performed by a cooling unit that generates a temperature difference between minute portions corresponding to the thickness.

The cooling means in the cooling zone is not particularly limited. For example, hot air, a combination of hot air and cold air, electromagnetic heaters such as microwaves and far infrared rays,
A temperature-controlled heating roll, a heat pipe roll, a temperature-controlled heating metal belt, and the like are included.

In the stretching zone of the third step, stretching of the thermoplastic resin film is further started while being cooled, and the temperature of the thermoplastic resin film at the end of stretching is (Tg).
The film is stretched so as to have a temperature of −30 ° C. to (Tg + 20 ° C.).

In the stretching zone, the thermoplastic resin film is further cooled. The purpose of the cooling is to make the thermoplastic resin film in the cooling zone have relatively thick and thin portions. Is to maintain the temperature difference generated between them and to try to start stretching in this state. The means for cooling is not particularly limited as long as it can achieve the above-mentioned purpose.
A method of cooling to a temperature lower by 10 to 30 ° C. than the temperature of the thermoplastic resin film in the cooling zone in 20 to 20 seconds is adopted.

The cooling means in the stretching zone is not particularly limited, but includes, for example, hot air used in the previous step, a combination of hot air and cold air, electromagnetic heaters such as microwaves and far infrared rays, and temperature control. Similarly, a heating roll, a heat pipe roll, a temperature-controlled heating metal belt, and the like can also be used.

As described above, the thermoplastic resin film stretched while being cooled in two stages is subjected to cooling conditions in the stretching zone such that the temperature of the film at the time of completion of stretching is (Tg−30 ° C.) to (Tg + 20 ° C.). Is set.

When the temperature of the film at the end of stretching is (Tg-3)
If the temperature is lower than (Tg + 20 ° C.), the thermoplastic resin film in the stretching process may have a partial stress concentration and may be unevenly stretched. The effect is diminished, and the desired retardation value may not be obtained.

The temperature of the film immediately after the completion of stretching is preferably within 1 second, more preferably within 0.5 seconds, and even more preferably within 0.25 seconds.
(−20 ° C.) to freeze the molecular orientation of the thermoplastic resin film. As described above, the thermoplastic resin film immediately after the completion of the stretching is rapidly cooled to suppress the excessive relaxation of the stretching stress due to the annealing, so that a desired retardation value with less variation can be obtained stably.

The means for quenching the thermoplastic resin film immediately after the completion of stretching is not particularly limited. For example, it may be selected from the cooling means in the above-mentioned stretching zone. A provided cooling roll may be additionally used.

The stretching means in the stretching zone is not particularly limited, and examples thereof include a longitudinal uniaxial stretching method using a roll, a horizontal uniaxial stretching method using a tenter, and a biaxial stretching method combining these. The stretching ratio in the stretching means is determined depending on the use of the obtained retardation film and is not particularly limited. For example, in the case of a retardation film for a liquid crystal display device, preferably 1. It is about 1-2 times.

According to a second aspect of the present invention, in the method for manufacturing a retardation film according to the first aspect, the cooling means in the cooling zone comprises one of:
In about 20 seconds, the temperature of the thermoplastic resin film is 10
The cooling means in the stretching zone further cools the thermoplastic resin film in the cooling zone by 1 to 20 seconds for 1 to 20 seconds.
Stretching is started while cooling to a temperature lower by 30 ° C.

FIG. 1 shows the cooling means 1 to 20 of the present invention.
In seconds, the temperature of the thermoplastic resin film is 10 to 30
2C shows a cooling rate for cooling to a temperature lower than the cooling rate of 35 ° C./sec which is sharper than that shown in FIG. 2 and a cooling rate of 0.3 ° C./sec which is slower. The temperature curve drawn with the vertical axis representing the temperature difference between the relatively thick and thin portions of the film and the horizontal axis representing the time is shown.

The above heated thermoplastic resin film is
When the cooling is performed at a slow cooling rate of less than 0.5 ° C./sec, as shown in FIG. 2, there is almost no difference in temperature between relatively thick and thin portions of the thermoplastic resin film.
Further, when the cooling is performed at an extremely rapid cooling rate exceeding 30 ° C./sec, the temperature of each part of the thermoplastic resin film is uniformly cooled in a short time as apparent from FIG. There is no temperature difference between relatively thick and thin portions of the film. The stretched raw material, which has a relatively large variation in thickness and has almost no temperature difference between the relatively thick and thin portions of the thermoplastic resin film as described above, can be cooled at a slow cooling rate, At any cooling speed, the retardation film having a relatively large variation in retardation value in the next step of stretching while being cooled will have a relatively large variation proportional to the thickness variation.

The cooling rate in the above-mentioned stretching zone is 1 to 20 for the same reason as in the above-mentioned cooling zone.
In a second, the stretching is started while being cooled to a temperature lower by 10 to 30 ° C. than the temperature of the thermoplastic resin film in the cooling zone. In the thermoplastic resin film stretched while being cooled in two stages in this way, the cooling conditions in the stretching zone are set such that the temperature of the film at the time of completion of stretching is (Tg−30 ° C.) to (Tg + 20 ° C.). .

According to a third aspect of the present invention, there is provided a method for producing a retardation film, comprising the steps of:
(−20 ° C.) or less.

In FIG. 3, the horizontal axis represents the time from the stretching step to the annealing step, the vertical axis represents the stress applied to the thermoplastic resin film, and the fine portion corresponding to the thickness of the thermoplastic resin film is shown in FIG. The schematic profile of the thermoplastic resin film stress profile is shown in two graphs, “thick” and “thin”. In general, immediately after stretching, the “thin” portion has a larger stress than the “thick” portion. However, in the annealing step, the stress relaxation rate increases, and the difference in stress tends to be smaller than immediately after stretching.

According to the method for producing a retardation film of the present invention, the stretched thermoplastic resin film is rapidly cooled to a temperature of (Tg-20 ° C.) or less, so that the thickness of the thermoplastic resin film can be reduced. The stress difference immediately after the stretching between the various parts is frozen, the reduction in the stress difference due to annealing is suppressed, and the birefringence index Δn difference generated in proportion to the stress is maintained. Further, the birefringence index Δn generated in proportion to the stress
Is inversely proportional to the stretching temperature, there is a thickness difference between the minute portions, and the thermoplastic resin film having a temperature difference between the minute portions according to the thickness difference is Δn
The retardation value represented by xd can be made more uniform.

According to a fourth aspect of the present invention, in the method for producing a retardation film according to the first, second or third aspect, the thermoplastic resin film is a polysulfone resin film.

In the method for producing a retardation film according to the first aspect of the present invention, as described above, in the heating zone, the thermoplastic resin film heated to a constant temperature of Tg to (Tg + 60 ° C.) is used. Then, cooling is performed in two stages in a cooling zone and a stretching zone, and stretching is started while cooling as described above, so that the temperature of the thermoplastic resin film at the end of stretching becomes (Tg−30 ° C.) to (Tg + 20 ° C.). Therefore, there is a temperature difference between a relatively thick portion and a thin portion of the thermoplastic resin film at the time of stretching. In the thick portion, Δn is relatively small, and the thickness is small. In a thin portion, Δn becomes relatively large, the retardation value represented by Δn × d is leveled as a whole, and a retardation film showing uniform retardation characteristics with little variation can be obtained. It is constant.

Therefore, the thermoplastic resin film used in the present invention is not limited to a thermoplastic resin film prepared by a solution casting method and having a relatively small variation in thickness, but may be formed by a melt casting method such as a T-die method. Even with the thermoplastic resin film prepared in the above, it is possible to obtain a retardation film showing uniform retardation characteristics with little variation as described above, and brittle fracture occurs due to excessive shear stress during stretching, and during stretching. The thermoplastic resin film breaks or, conversely, the viscosity of the thermoplastic resin film drops and does not hang down during transport, causing trouble,
A retardation film can be stably produced with high productivity.

As described above, the method for producing a retardation film according to the second aspect of the present invention is the method for producing a retardation film according to the first aspect, wherein the cooling method in the cooling zone is performed for 1 to 20 seconds. And the above film temperature is 10
It is cooled to a temperature lower by ３０30 ° C., and the cooling method in the stretching zone is further performed for 1 to 20 seconds, and the cooling method in the cooling zone is more than 10 ° C.
Since stretching is started while cooling to a temperature lower by 30 ° C., in the cooling zone and the stretching zone, relatively thick portions of the thermoplastic resin film are kept at a high temperature, and thin portions are cooled quickly. It is cooled to a low temperature, and is cooled so as to generate a temperature difference between the thick portion and the thin portion, and the stretching is started while cooling as described above. As in the method for producing a retardation film of the invention according to Item 1, the productivity is high, and
A retardation film can be stably produced.

According to the method for producing a retardation film of the invention according to claim 3, as described above, the stretched thermoplastic resin film in the method for producing a retardation film according to claim 1 or 2 is subjected to the method (Tg-20 ° C.). ) By quenching to the following temperature, the stress difference immediately after the stretching between the minute portions according to the thickness of the thermoplastic resin film is frozen, and the reduction of the stress difference due to stress relaxation is suppressed. Since the birefringence Δn difference generated in proportion to the stress is maintained, the retardation value represented by Δnxd of the thermoplastic resin film can be made more uniform.

That is, the retardation value is such that the birefringence Δn generated in proportion to the stretching stress is inversely proportional to the stretching temperature. If the minute portion has a temperature difference corresponding to the thickness, the Δn of the relatively thick portion appears small, and the Δn of the relatively thin portion increases. Appear, and even if there is a thickness difference between the minute portions of the stretched thermoplastic resin film, as a result, Δn
It is presumed that the retardation value represented by xd is further uniformed.

As described above, the method for producing a retardation film according to the fourth aspect of the present invention is the method for producing a retardation film according to the first, second, or third aspect, wherein the thermoplastic resin film is a polysulfone-based resin. Since it is made of a resin film, it is possible to stably produce a retardation film with high productivity, similarly to the method for producing a retardation film according to the first or second aspect of the present invention.

[0038]

FIG. 4 is a conceptual diagram showing an example of an apparatus for manufacturing a retardation film for carrying out the present invention.
In the film-forming zone indicated by the arrow 1, 11 is cooled by a cooling device composed of a T-die, a rubber roll 12 and a metal roll 13 connected to the tip of the extruder, and a thermoplastic resin film (before stretching) 14 is formed. In the heating zone indicated by the arrow 2, the thermoplastic resin film 14 is heated by the hot air supply device 22 while being transferred between the plurality of guide rolls 21, 21,. The surface temperature of the thermoplastic resin film 14 is measured by a temperature measuring device (not shown) and is fed back to the hot air supply device 22 via a control device. The surface temperature of the thermoplastic resin film 14 at the exit of the heating zone is uniformly heated to a set temperature of Tg to (Tg + 60 ° C.) of the thermoplastic resin film 14.

FIG. 4 shows an embodiment in which the thermoplastic resin film 14 supplied to the heating zone 2 is supplied by directly connecting the thermoplastic resin film 14 formed in the film forming zone 1. The present invention is not limited to this, and may be, for example, a wound and long body of a thermoplastic resin film formed in advance by a solution casting method.

In the cooling zone indicated by the arrow 3, in the heating zone 2, the thermoplastic resin film 14 uniformly heated to the set temperature of Tg to (Tg + 60 ° C.) is cooled by the cool air device 31. FIG. 4 shows an example in which the thermoplastic resin film 14 to be cooled is cooled by the upper and lower cold air devices 31 without being supported in the cooling zone. However, the present invention is not limited to this. As in the heating zone 2, the cooling may be performed during the transfer between the plurality of rolls.

The surface temperature of the thermoplastic resin film 14 at the outlet of the cooling zone 3 depends on the temperature of the thermoplastic resin film 14.
The temperature is lowered by 10 to 30 ° C. in 1 to 20 seconds from the set temperature of Tg to (Tg + 60 ° C.). Whether the cooling rate is too fast or too slow, as detailed above with reference to FIG.
The thermoplastic resin film 14 is completely cooled and fixed so that there is no temperature difference between a relatively thick portion and a relatively thin portion, or a slow temperature where there is almost no temperature difference. Since the cooling rate is lowered, cooling is performed at the above cooling rate.

In the stretching zone indicated by the arrow 4, the thermoplastic resin film 14 cooled in the cooling zone 3 is
While being cooled by the cool air device 31, the stretching is performed between the pair of gripping rolls 42 and 43 and the pair of pulling rolls 44 and 45. As in the cooling zone 3, the cooling rate in the stretching zone 4 is lower than the temperature of the thermoplastic resin film 14 at the outlet of the cooling zone 3 by 10 to 30 ° C. for 1 to 20 seconds, and when the film is stretched at such a temperature, The surface temperature of the thermoplastic resin film (after stretching) 46 immediately after leaving the tension rolls 44 and 45 is (Tg−30 ° C.) to (Tg
+ 20 ° C).

FIG. 5 shows another example of an apparatus for producing a retardation film for carrying out the present invention.
The cooling zone indicated by
Stretched thermoplastic resin film 4 immediately after leaving between 45 and 45
6 is a zone for cooling the surface temperature to a temperature lower than Tg, and is for preventing the stretched thermoplastic resin film 46 from shrinking after cooling. Note that arrows 1 to
4 are the same as those in FIG. 4, the same reference numerals are used for the respective parts. In FIG. 5, 51
Is a cool air device. When fixed by quenching, the stretched thermoplastic resin film 46 immediately after leaving between the tension rolls 44 and 45 in the stretching zone 4 has an equal surface by a take-off roll (not shown) so that the stretching stress is maintained. Speed, between which the stretched thermoplastic resin film 4
6 is cooled to a temperature below Tg.

[0044]

Hereinafter, embodiments of the present invention will be described.
The present invention is not limited to these examples. (Example 1) Polysulfone resin (trade name "UDEL P3500", manufactured by Acomo, glass transition point 190 ° C)
Was melt-extruded at a mold temperature of 340 ° C. by a single screw type extruder equipped with a T-die shown in FIG. 4, and cooled while being nipped by a pair of cooling rolls controlled at a surface temperature of 165 ° C. A polysulfone resin film having a thickness of 75 μm ± 2.0 μm was prepared.

The obtained polysulfone resin film was
A heating zone consisting of an oven controlled at 35 ° C. is transferred between the guide rolls 21, 21,.
To a cooling zone consisting of an oven controlled at 215 ° C., passing through the oven controlled at 215 ° C. for 3 seconds, and raising the temperature of the polysulfone resin film at the outlet of the cooling zone to 220 ° C. Cool.

The polysulfone resin film that has exited the cooling zone is then guided to a stretching zone consisting of an oven controlled at 190 ° C., and a vertical uniaxial stretching machine including gripping rolls 42 and 43 and pulling rolls 44 and 45. The film was stretched 1.3 times in the length direction. The polysulfone resin film passed for 3 seconds from the gripping roll of the longitudinal uniaxial stretching machine in the stretching zone to the pulling roll, and the temperature of the polysulfone resin stretched film immediately after leaving the pulling roll was 20.
8 ° C. The stretched polysulfone resin film was further allowed to cool in an environment of 20 ° C. during constant-velocity transfer, cooled to a temperature of Tg or less, and wound around a core as a retardation film.

Example 2 Using a device shown in FIG. 5, a polycarbonate resin (trade name “Panlite”, manufactured by Teijin Chemicals Ltd., glass transition point 150 ° C.) was molded at a mold temperature of 25 ° C.
At 0 ° C., melt extruded, cooled while nipping with a pair of cooling rolls controlled to a surface temperature of 130 ° C., and having a thickness of 75 μm
A polysulfone resin film of ± 2.0 μm was produced.

The obtained polycarbonate resin film was transferred to a heating zone consisting of an oven controlled at 200 ° C. between guide rolls, heated to 200 ° C., and then moved to a cooling zone consisting of an oven controlled at 175 ° C. Induction and passing through the oven for 3 seconds cooled the polycarbonate resin film at the outlet of the cooling zone to 187 ° C.

The polycarbonate resin film exiting the cooling zone was then guided to a stretching zone consisting of an oven controlled at 155 ° C., and stretched 1.3 times in the longitudinal direction by a vertical uniaxial stretching machine. Between the gripping roll and the tension roll of the longitudinal uniaxial stretching machine in the stretching zone, the polycarbonate resin film passed for 3 seconds, and the temperature of the polycarbonate resin stretched film immediately after leaving the tension roll was 176 ° C. . The stretched polycarbonate resin film was further quenched to a temperature of Tg or less with cold air during constant-velocity transport, and wound around a core as a retardation film. The obtained stretched polycarbonate resin film has a thickness of 67
μm ± 2.5 μm.

(Embodiment 3) In the same manner as in Embodiment 2,
A polysulfone resin film having a thickness of 3 μm ± 2.0 μm was formed, stretched in the same manner as in Example 2, and further quenched to a temperature of Tg or less with cold air during constant-velocity transfer to obtain a thickness of 73 μm ±
A 2.5 μm stretched polysulfone resin film was prepared.

(Embodiment 4) In the same manner as in Embodiment 2,
A polysulfone resin film of 3 μm ± 2.0 μm was formed. 240 g of the obtained polysulfone resin film
A heating zone consisting of an oven controlled at 0 ° C. was transferred between guide rolls and heated to 240 ° C.
It was guided to a cooling zone consisting of an oven controlled at 0 ° C., passed through the oven for 3 seconds, and the temperature of the polysulfone resin film at the outlet of the cooling zone was increased to 228 ° C.
And cooled.

The polysulfone resin film exiting the cooling zone was then guided to a stretching zone comprising an oven controlled at 190 ° C., and stretched 1.3 times in the longitudinal direction by a longitudinal uniaxial stretching machine. The polysulfone resin film passed for 3 seconds from the gripping roll of the longitudinal uniaxial stretching machine in the stretching zone to the pulling roll, and the temperature of the polysulfone resin stretched film immediately after leaving the pulling roll was 2
18 ° C. The stretched polycarbonate resin film was further rapidly cooled to a temperature of Tg or less while being nipped by a pair of cooling rolls controlled at a surface temperature of 165 ° C., and wound around a core as a retardation film. The obtained stretched polycarbonate resin film has a thickness of 73 μm ± 2.5 μm.
Met.

(Comparative Example 1) Thickness 7 in the same manner as in Example 1.
A polysulfone resin film of 5 μm ± 2.0 μm was formed. The obtained polysulfone resin film was 245
The heating zone consisting of an oven controlled at 0 ° C. was transferred between guide rolls and heated to 245 ° C., and then immediately guided to a stretching zone consisting of an oven controlled at 180 ° C., with a vertical uniaxial stretching machine. The film was stretched 1.3 times in the length direction. Between the gripping roll and the pulling roll of the longitudinal uniaxial stretching machine in the drawing zone, the polysulfone resin film passed for 1 second, and the temperature of the polysulfone resin stretched film immediately after leaving the pulling roll was 234 ° C. . The stretched polysulfone resin film was further allowed to cool in an environment of 20 ° C. during constant-velocity transfer, cooled to a temperature of Tg or less, and wound around a core as a retardation film. The obtained stretched polysulfone resin film has a thickness of 67 μm.
m ± 2.5 μm.

(Comparative Example 2)
A polysulfone resin film of 5 μm ± 2.0 μm was formed. The obtained polysulfone resin film was 230
A heating zone consisting of an oven controlled at 0 ° C. was transferred between guide rolls and heated to 230 ° C.
It was guided to a cooling zone consisting of an oven controlled at 0 ° C., passed through the oven for 30 seconds, and the temperature of the polysulfone resin film at the outlet of the cooling zone was increased to 225.
Cooled to ° C.

The polysulfone resin film exiting the cooling zone was then guided to a stretching zone comprising an oven controlled at 205 ° C., and stretched 1.3 times in the longitudinal direction by a longitudinal uniaxial stretching machine. Between the gripping roll and the tension roll of the longitudinal uniaxial stretching machine in the stretching zone, the polysulfone resin film passes for 30 seconds, and the temperature of the polysulfone resin stretched film immediately after leaving the tension roll is:
218 ° C. The stretched polysulfone resin film is further allowed to cool in an environment of 20 ° C. during uniform speed transfer,
g or less, and wound on a core as a retardation film.

(Comparative Example 3) Thickness 8 in the same manner as in Example 1.
A polysulfone resin film of 3 μm ± 2.0 μm was formed. The obtained polysulfone resin film was treated with 210
A heating zone consisting of an oven controlled at 0 ° C. was transferred between guide rolls, heated to 210 ° C., and then immediately led to a stretching zone consisting of an oven controlled at 210 ° C., as in Example 1. The film was stretched 1.3 times in the length direction by a longitudinal uniaxial stretching machine. The stretched polysulfone resin film left from the pulling roll was further allowed to cool in an environment of 20 ° C. during constant-velocity transport, cooled to a temperature of Tg or less, and wound around a core as a retardation film. The obtained stretched polysulfone resin film has a thickness of 73 μm ±
It was 2.5 μm.

(Comparative Example 4)
A polysulfone resin film of 3 μm ± 2.0 μm was formed. 240 g of the obtained polysulfone resin film
A heating zone consisting of an oven controlled at 0 ° C. was transferred between guide rolls and heated to 240 ° C.
The polysulfone resin film was guided to a cooling zone consisting of an oven controlled at 0 ° C. and passed through the oven for 30 seconds to cool the polysulfone resin film to 225 ° C.

The polysulfone resin film exiting the cooling zone was then guided to a stretching zone comprising an oven controlled at 190 ° C., and stretched 1.3 times in the longitudinal direction by a longitudinal uniaxial stretching machine. The stretched polysulfone resin film released from the tension roll of the longitudinal uniaxial stretching machine is further 170
It was guided to a slow cooling zone consisting of an oven controlled at a temperature of ° C., cooled to 170 ° C. in one minute at a constant speed, and wound on a core as a retardation film. The obtained stretched polysulfone resin film has a thickness of 73 μm ± 2.5 μm.
m.

The retardation values of the retardation films obtained in Examples 1 to 4 and Comparative Examples 1 to 4 were measured, and average values and variations were determined as follows. Table 1 shows the measurement results.

[Sample] Except for the both sides of the retardation film having a width of 1000 mm, the central portion having a width of 500 mm was set to a length of 100 mm.
The sample was cut out at 0 mm to obtain a sample.

[Measurement of Retardation Value] A 630 nm retardation value was measured at 1 cm intervals in the width and length directions of the sample. The measured values were calculated as the average value and the maximum value of the variation, and the difference between the maximum value and the minimum value of the measured values and the maximum value of the variation were calculated as the maximum value of the difference between the measured values of two adjacent points.

[0062]

[Table 1]

[0063]

The method for producing a retardation film of the present invention comprises:
Since it is constituted as described above, it is not limited to a thermoplastic resin film having a relatively small thickness variation prepared by a solution casting method, and a thermoplastic resin film prepared by a melt casting method such as a T-die method. Even if it is a resin film, it is possible to obtain a retardation film showing uniform retardation characteristics with little variation, brittle fracture occurs due to excessive shear stress during stretching, and the thermoplastic resin film breaks during stretching, In addition, the retardation film can be obtained with high productivity and stably without causing the viscosity of the thermoplastic resin film to drop during transportation and causing troubles.

[Brief description of the drawings]

FIG. 1 is an image diagram of a temperature difference generated in a thin portion in a cooling zone and a stretching zone in a method for producing a retardation film of the present invention.

FIG. 2 is an image diagram of a temperature difference generated in a thin portion in a cooling zone and a stretching zone in a cooling method, which is compared with a method for manufacturing a retardation film of the present invention.

FIG. 3 is an image diagram of a stress difference caused by a difference in thickness of a thermoplastic resin film in a stretching step.

FIG. 4 is a conceptual diagram showing an example of a retardation film manufacturing apparatus used in the present invention.

FIG. 5 is a conceptual diagram showing another example of the apparatus for manufacturing a retardation film used in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Film-forming zone 11 T die 12, 13 Cooling roll (rubber roll and metal roll) 14 Thermoplastic resin film 2 Heating zone 21 Guide roll 22 Heating device 3, 5 Cooling zone 31, 41, 51 Cooling device 4 Stretching zone 42, 43 Gripping roll (stretching machine) 44, 45 Pulling roll (stretching machine) 46 Stretched thermoplastic resin film

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // B29K 81:00 B29L 11:00 F term (Reference) 2H049 BA06 BB42 BC03 BC09 BC22 4F071 AA50 AA64 AG28 AG29 AH12 BA01 BB06 BB07 BC01 4F205 AA28 AA34 AG01 AH33 AP11 AR06 GA07 GB02 GW41 4F207 AA28 AA34 AG01 AH33 AP11 AR06 KA01 KA17 KK64 KW41 4F210 AA28 AA34 AG01 AH33 AP11 AR06 QA03 QC01 QG11 QG18 Q

Claims (4)

[Claims] An apparatus for producing a retardation film comprising a heating zone, a cooling zone and a stretching zone in the above order,
First, in the heating zone, the thermoplastic resin film,
The thermoplastic resin film is heated so as to have a constant temperature of the glass transition temperature (Tg) to (Tg + 60 ° C.). Then, in the cooling zone, the temperature difference between the minute portions corresponding to the thickness of the thermoplastic resin film is reduced. In the stretching zone, the thermoplastic resin film is further stretched while being cooled, and the temperature of the thermoplastic resin film at the end of stretching is (Tg−30 ° C.) to (Tg +
20 ° C.). 2. The cooling means in the cooling zone comprises:
In about 20 seconds, the temperature of the thermoplastic resin film is 10
The cooling means in the stretching zone further cools the thermoplastic resin film in the cooling zone by 1 to 20 seconds for 1 to 20 seconds.
The method for producing a retardation film according to claim 1, wherein stretching is started while cooling to a temperature lower by 30 ° C. 3. The rapid stretching of the stretched thermoplastic resin film to a temperature of (Tg-20 ° C.) or less.
A method for producing the retardation film according to the above. 4. The method according to claim 1, wherein the thermoplastic resin film is a polysulfone-based resin film.