JPH0634814A - Production of phase difference plate - Google Patents

Abstract

PURPOSE:To provide the method which can easily produce the phase difference plate having the phase difference compensation performance and visual field angle characteristic which are uniform and excellent over approximately the entire area of a film. CONSTITUTION:The phase difference plate is produced by supplying the transversely uniaxially stretched film (p) to a film transporting means 1, which is constituted of plural jig 10 groups and is set at <=100mm length (a) of the gripping parts thereof, <=50mm spacings (b) between the respective jigs and 1/2 to 10 a/b, at a speed higher than the transporting speed, assumed to be 100, of the above-mentioned transporting means, and lower than 130, and successively gripping both transverse ends of the film (p) by means of the gripping parts while slackening the film (p) to a waveform, then by subjecting the film (p) to a heating treatment under control in such a manner that the variations in the reduction rate at every inter-jig 10 spacing are kept within a + or -25% range, thereby thermally shrinking the longitudinal of the film (p). The partial shrinkage (neck-in) in the transverse direction of the film (p) does not arise in this method and since the variations in the reduction rate are controlled within the + or -25% range, the unevenness of the phase difference values is lessened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a retardation plate which is composed of a uniaxially stretched thermoplastic resin film and which is suitably used in, for example, a liquid crystal display panel, and particularly, it has excellent viewing angle characteristics and retardation. The present invention relates to a method of manufacturing a retardation plate having less unevenness in value.

[0002]

2. Description of the Related Art A retardation film (film) utilizes the birefringence of a stretched polymer film (generated due to the difference in refractive index between the stretching direction and the direction orthogonal thereto due to the molecular orientation due to stretching). It is intended to eliminate the phase difference generated in the liquid crystal of the liquid crystal display plate (referred to as phase difference compensation). Conventionally, as this type of phase difference plate (film), a cellulose resin (see JP-A-63-167363), Vinyl chloride resin (JP-B-45-34477, JP-A-56-)
125702), polycarbonate resin (Japanese Patent Publication No. 41190/41, JP 56-130).
No. 703), an acrylonitrile resin (see JP-A-56-130702), a styrene resin (see JP-A-56-125703), an olefin resin (see JP-A-60-24502). Etc. are known, and as a uniaxial stretching method, longitudinal uniaxial stretching (see Japanese Patent Application Laid-Open No. 2-191904), transverse uniaxial stretching (see Japanese Patent Application Laid-Open No. 2-42406), and the like have been proposed.

The retardation compensation performance of the retardation film (film) is called a retardation value, and is represented by Δn × d. Here, Δn is the anisotropy of the refractive index, and d is the thickness of the film.

By the way, when the angle formed by the incident light and the normal to the film surface increases, the retardation value changes (in the case of rotating about the stretching direction and in the case of rotating about the axis perpendicular to the stretching direction). (The increase and decrease are different depending on the). Coloring of the liquid crystal display occurs.

An optical anisotropic body such as a retardation film (film) does not have a uniform three-dimensional refractive index (nx, ny, nz) and is represented by a refractive index ellipsoid. The relationship between the refractive indices in the respective directions is, for example, in the uniaxially stretched film p shown in FIG. 3, where x is the stretching axis, y is the axis orthogonal to the stretching direction in the film plane, and z is the normal direction of the film. , A film having a positive intrinsic refractive index has a relationship of nx> ny ≧ nz,
A film having a negative intrinsic refractive index has a relationship of nx <ny ≦ nz. Further, in a completely uniaxially stretched film, the refractive index ny in the direction y orthogonal to the stretching direction in the film plane and the refractive index nz in the normal direction z of the film are equal, and ny = nz is established.

In the following, as an example, θ from the z axis in the xz plane
(Viewing angle) Birefringence [Δn
_xz (θ)] and the retardation value [R _xz (θ)] are represented by the following formulas (see Electronic Material, February 1991, p. 40).

[0007]

[Equation 1] However, in the formula, d is the thickness of the film, and n is the average refractive index.

FIG. 4 shows the result of calculation based on the above equations (1) and (2).

In the graph of FIG. 4, the horizontal axis is the viewing angle θ,
The vertical axis represents the retardation value R at the viewing angle θ in the xz plane.
_xz retardation value R _xz (0) divided by the value R _xz of (θ) the viewing angle 0 (when viewed from the normal direction z) (θ) / R
_xz (0), and the rate of change in retardation R is [1-
It is represented by the absolute value of R _xz (θ) / R _xz (0)]. Also,
In FIG. 4, a represents a completely uniaxially stretched film of nz = ny,
b shows the perfect uniaxially stretched film of nz <ny.

Here, the viewing angle is wider as the rate of change of the retardation R, that is, the absolute value of [1-R _xz (θ) / R _xz (0)] is smaller. As shown in FIG. 4, perfect uniaxial stretching (nz = ny) has a smaller change in retardation value and a wider viewing angle, while biaxiality exists in the molecular orientation (nz <ny). It can be confirmed that the change in the foundation value is large and the viewing angle is very narrow.

FIG. 5 shows the calculation result when a viewing angle φ tilted from the z axis in the yz plane is used instead of θ.
In FIG. 5, c indicates a completely uniaxially stretched film of nz = ny,
d indicates a completely uniaxially stretched film of nz <ny.

Also from this result, if the molecular orientation is biaxial, the rate of change in retardation value, that is, [1
The absolute value of −R _yz (φ) / R _yz (0)] is large and the viewing angle is narrow, while the higher the uniaxial orientation of the molecule, the rate of change in retardation value, that is, [1-R _yz (φ)] / R
_yz (0)] has a small absolute value and a wide viewing angle. Further, it can be seen that the viewing angle is widest in the case of perfect uniaxial stretching of nz = ny.

Therefore, it can be seen from these results shown in FIGS. 4 and 5 that the higher the uniaxial orientation of the molecules, the smaller the rate of change in retardation value and the wider viewing angle.

By the way, in order to enhance the uniaxiality of the molecular orientation, it is necessary to minimize the stress generated in the direction perpendicular to the stretching direction (residual stress to be reduced). In other words, it is sufficient to reduce in the direction perpendicular to the stretching direction by the amount of reduction considered to occur in the stretching in the direction perpendicular to the stretching direction.

In Japanese Patent Application Laid-Open No. 2-191904, this reduction ratio is referred to as "neck-in ratio (refers to the rate of change in the length of the film in the direction orthogonal to the stretching direction before and after stretching). That is, neck-in rate = (B−A) / B × 100; where A is the length in the direction orthogonal to the stretching direction after annealing, and B is the length in the direction orthogonal to the stretching direction of the film before stretching. ], And the neck-in ratio is set to (1-1 / square root of draw ratio) × 100 (%) to (1-1 / third root of draw ratio) × 100 (%) It is disclosed that an excellent retardation plate (film) can be manufactured. As this specific method, there is disclosed a method (longitudinal uniaxial free width stretching method) in which the distance between the stretching rolls is set to 5 times or more of the film width and the film is stretched in the longitudinal direction while allowing free shrinkage in the width direction. .

Further, in Japanese Patent Laid-Open No. 3-23405,
Applying a pantograph-type simultaneous biaxial tenter stretching machine, both ends of the film in the width direction are partially held by tenter clips and simultaneously stretched in both the longitudinal direction and the width direction.
A method for producing a retardation plate having a neck-in rate of (1-1 / square root of draw ratio) is disclosed.

[0017]

However, Japanese Patent Laid-Open No. 2-1.
In the method disclosed in Japanese Patent No. 91904, since the distance between the stretching rolls is set to 5 times or more the film width as described above, it is possible to uniformly control the heating temperature during stretching over the entire area between the rolls. There was a difficult problem.

Further, in this method, the film is stretched in the longitudinal direction of the film while allowing the film to shrink freely in the width direction between the drawing rolls arranged at intervals, so that the film in the vicinity of the drawing roll is stretched. The shrinkage amount in the width direction of the film in the vicinity of the central portion between the stretching rolls becomes larger than the shrinkage amount in the width direction, and due to the difference in the shrinkage ratio, the direction of the stretching axis (stretching main axis) at both ends of the film in the width direction There is a defect that the direction of the stretching axis in the central portion of the film does not match. Therefore, since the phase difference compensation performance and the viewing angle characteristics are different between the widthwise both ends and the central portion of the stretched film, the widthwise both ends of the film must be discarded as a large quantity as a defective product, and the yield There was a problem that it was bad.

On the other hand, in the method disclosed in Japanese Patent Application Laid-Open No. 3-23405, both ends of the film in the width direction are held partially by the tenter clips and stretched. Neck-in occurred in a portion that was not held, and there was a problem in the retardation compensation performance of the manufactured retardation plate and the uniformity of viewing angle characteristics.

The present invention has been made by paying attention to such a problem, and an object thereof is to provide a phase difference having uniform and excellent phase difference compensation performance and viewing angle characteristics over substantially the entire area of the film. It is to provide a method for easily manufacturing a plate.

[0021]

That is, the invention according to claim 1 is that after a thermoplastic resin film is uniaxially stretched,
Based on the method of manufacturing a retardation plate by heat-shrinking the thermoplastic resin film in the longitudinal direction, the length a of the gripping portion of the jig for gripping both ends of the thermoplastic resin film in the horizontal direction is a.
Is 100 mm or less, the distance b between the jigs is 50 mm or less,
Further, when the film conveying means is constituted by a plurality of jig groups in which a / b is set to 1/2 to 10 and the conveying speed is 100 with respect to this film conveying means, it is faster than 130 Excessive supply of the thermoplastic resin film stretched laterally uniaxially at a slow speed, and slackening the film between the jigs in a corrugated manner, sequentially gripping both lateral ends of the thermoplastic resin film with each gripping part of the jig group. After that, the heat treatment is performed while controlling the variation of the reduction ratio between the jigs to be within the range of ± 25% to heat-shrink the thermoplastic resin film in the longitudinal direction. is there.

In order to manufacture a retardation plate having a wide viewing angle by such technical means, it is necessary to enhance uniaxiality of molecular orientation. For that purpose, it is necessary to minimize the stress generated in the direction perpendicular to the stretching direction (stress to be reduced) as described above. In other words, it suffices to reduce the amount during or after the stretching by a reduction amount corresponding to the stress generated by the stretching in the direction perpendicular to the stretching direction. And
In the invention according to claim 1, the laterally uniaxially stretched film is excessively supplied by overfeeding,
Both ends in the lateral direction of the film are sequentially gripped by the gripping portions of the jig group and subjected to a heat treatment while being loosened in a waveform to enhance the uniaxiality of the retardation plate.

The reduction ratio of the film in the longitudinal direction at this time is
When the film is slackened in a wave shape and gripped (b'-b)
/ (A + b) (see FIG. 1A, where a is the length of the gripping portion of the jig that grips both ends of the film, b is the distance between the jigs, and b ′ is the distance between the jigs that are slack in the waveform. The length of the film is shown), and the overfeed amount of the film (the speed of supplying the film to the film conveying means) is adjusted with respect to the conveying speed of the film conveying means constituted by a jig group for grasping the film. By doing so, it is possible to control to a desired value.

In the invention according to claim 1, 1
It is necessary to perform the heat treatment while controlling the variation of the reduction rate for each pitch, that is, for each jig (the interval b is 1 pitch in FIG. 1A) within a range of ± 25%.

[0025] The variation here reduction ratio per one pitch, the reduction rate of each pitch measured in the range of 1 m, the obtained _{(X max -X av) / X} av, and, (X _min - X _av )
/ X _av (where X _av is the average reduction rate, X _max is the maximum reduction rate, and X _min is the minimum reduction rate). In the present invention, this value is ± 25%. It is necessary to be within the range. If the above reduction rate exceeds ± 25%,
The difference between the maximum value and the minimum value is 10 nm or more (350 mm ×
This is because unevenness of the retardation value of 350 mm □ occurs, and it becomes difficult to manufacture a retardation plate having uniform retardation characteristics. The means for controlling the variation in the reduction ratio for each pitch to be within the range of ± 25% is as follows. When the lateral both ends of the transversely uniaxially stretched thermoplastic resin film are gripped and thermally contracted, There is a method of uniformly holding both lateral ends of the film so that the heat shrinkage in the longitudinal direction of the film does not vary.

Next, regarding the film conveying means for grasping and conveying both ends of the thermoplastic resin film in the lateral direction, when the length of the grasped portion of the jig group is a and the interval between the jigs is b , A is 100 mm or less, b is 50 mm or less, and a / b is required to be set to 1/2 to 10. a
If it exceeds 100 mm, color unevenness will occur during the heat treatment, and a uniform retardation plate cannot be obtained, and b will be 50 mm.
If it exceeds, the neck-in in the non-grasping portion (non-grasping portion) of the film becomes large, and the color unevenness at the end becomes remarkable, and there is a risk of breakage in some cases.
Further, when a / b is less than 1/2, color unevenness at the film edge becomes remarkable, and when a / b is greater than 10, streak unevenness occurs in the film along the stretching direction. is there.

As for the shape of the jig for holding the thermoplastic resin film, any shape can be applied as long as the film does not break or slip.

Further, the reduction ratio in the longitudinal direction of the thermoplastic resin film after the heat treatment needs to be 30% or less. Usually, when a retardation plate is manufactured, a draw ratio of 1.3 to 2.0 is suitable, and if the longitudinal reduction ratio exceeds 30%, the corrugated state remains even after the heat treatment. It becomes difficult for the film surface to become flat, or
This is because even if the film surface becomes flat, streak-like color unevenness is likely to occur in the stretching direction, making uniform heat treatment difficult. Therefore, it is necessary to set the supply speed of the thermoplastic resin film to the film conveying means to a speed higher than 130 and lower than 130 when the conveying speed of the film conveying means is 100.

In the invention according to claim 1, the value of the length a of the holding portion of the jig and the distance b between the jigs, and
By adjusting the value of a / b, the neck-in can be reduced and the phase difference unevenness at the end can be suppressed.
It is possible to eliminate the drawbacks of the manufacturing method disclosed in Japanese Patent No. 3405. Further, in the present invention, both lateral ends of the film are gripped during the heat treatment, and
Since a substantially uniform contraction in the longitudinal direction is possible, the method disclosed in Japanese Patent Application Laid-Open No. 2-19
The adverse effects of the manufacturing method disclosed in Japanese Patent 1904 can be eliminated.

Further, in such technical means, the stretching of the thermoplastic resin film in the lateral uniaxial direction can be carried out by a device obtained by modifying the lateral uniaxial tenter stretching machine. Also,
Various conditions such as the stretching temperature, the stretching ratio, the stretching speed, the heat setting (heat treatment after stretching), and the heat setting time can be appropriately set so as to obtain a desired retardation value. The above-mentioned JP-A-2-191904. The control is extremely easy as compared with the manufacturing method disclosed in.

Next, as the thermoplastic resin film applied in this technical means, for example, cellulose resin, vinyl chloride resin, polycarbonate resin, acrylonitrile resin, olefin resin, polystyrene resin, polymethacryl Examples of the film include a methyl acid resin, a polysulfone resin, a polyarylate resin, and a polyether sulfone resin.

As the method for producing these films, any of solvent casting method, calendering method and extrusion method may be used.

[0033]

According to the first aspect of the present invention, the length a of the holding portion of the jig for holding the both ends of the thermoplastic resin film in the lateral direction is 100 mm or less, the distance b between the jigs is 50 mm or less, and , A / b is set to 1/2 to 10 and the film conveying means is constituted by a plurality of jig groups, and when the conveying speed of the film conveying means is 100, it is faster than this and slower than 130. The thermoplastic resin film laterally uniaxially stretched at a speed is excessively supplied, and while the film is slackened between the jigs, the both ends of the thermoplastic resin film in the lateral direction are sequentially gripped by the gripping portions of the jig group. After
The thermoplastic resin film is thermally shrunk in the longitudinal direction by performing heat treatment while controlling the variation of the reduction ratio between the jigs to be within a range of ± 25%.

As a result, the stress in the direction perpendicular to the stretching direction (stress to reduce) is reduced, and the required uniaxiality of the retardation plate is enhanced, so that a retardation plate with a wide viewing angle can be manufactured. .

Further, the variation of the reduction ratio between the jigs is ± 2.
Since it is controlled within the range of 5%, it becomes possible to manufacture a retardation plate with less unevenness of retardation value.

[0036]

EXAMPLES Examples of the present invention will be described in detail below.

Example 1 Width 430 mm, Thickness 100 μ
m, the glass transition point (Tg) of 190 ℃ polysulfone film using a tenter stretching machine, stretching temperature 190 ℃,
Lateral uniaxial stretching was performed under the conditions of a draw ratio of 1.5 times, a heat setting temperature of 170 ° C., and a heat setting time of 30 seconds.

Next, as shown in FIG. 1 (A) and FIG. 2, the length a of the gripping portion constituted by a plurality of jigs 10 is a = 5.
mm, and the distance between the jigs 10 b = 10 mm (a / b
= 1/2), the film transport means 1 is set to
When the conveying speed of the film conveying means 1 is 100, the transverse uniaxially stretched film p is supplied at a speed higher than 130 and slower than 130, and the transverse uniaxially stretched film p is slackened in a waveform between the jigs 10 ( After being gripped in sequence, the heat treatment was performed at 195 ° C. for 2 minutes to reduce the dimension in the vertical direction (see FIG. 1B).

Before the heat treatment, the reduction rate for each pitch was measured (length: 1 m), and the reduction rate was calculated as X _av = 1.
3.97%, X _min : 13.72%, X _max = 14.3
It is 5%, and if the variation is calculated from these values, ±
It was 1.7%.

The retardation film (retardation film) thus obtained was evaluated for viewing angle characteristics, R value and uniformity of R value.

With respect to the above-mentioned viewing angle characteristics, the stretching axis of the film and the axis orthogonal to the stretching axis (in the plane of the film) are used as axes.
Retardation value when rotated by 45 degrees (590n
m) and the absolute value of the difference between the retardation values at 0 degrees was divided by the retardation value at 0 degrees (590 nm) and multiplied by 100, and the larger value was used as the substitute characteristic. It can be said that the smaller this value is, the better the viewing angle characteristic is.

Next, the R value is the phase difference value when the measured wavelength and the phase difference value are equal.

Regarding the uniformity of the R value, the effective width was evaluated by defining the effective width as a portion within which the variation in the retardation value in the lateral direction of the film was within ± 5 nm.

The effective width ratio of the R value is calculated by the following calculation.

Effective width ratio of R value = (effective width / width after stretching)
× 100 (%) Then, as a result of the evaluation, the viewing angle characteristic is 13.1, and the R value is 5.
The effective width ratio of 81.7 nm and R value was 77%.

Example 2 Width 430 mm, Thickness 100 μ
m, the glass transition point (Tg) of 190 ℃ polysulfone film using a tenter stretching machine, stretching temperature 190 ℃,
Lateral uniaxial stretching was performed under the conditions of a draw ratio of 1.5 times, a heat setting temperature of 170 ° C., and a heat setting time of 30 seconds.

Next, the length a of the grip portion is 50 mm,
Also, the lateral uniaxially stretched film p is supplied to the film conveying means 1 set to the jig interval b = 50 mm (a / b = 1), and the lateral uniaxially stretched film p is slackened in a waveform (setting). (Reduction ratio 14%) 190
Heat treatment was performed at 8 ° C. for 8 minutes to reduce the vertical dimension.

Before the heat treatment, the reduction ratio for each pitch was measured (length: 1 m), and the reduction ratio was calculated, X _av = 1
_{4.08%, X min: 13.87%} , X max = 14.3
It is 9%, and if the variation is calculated from these values, ±
It was 2.2%.

With respect to the retardation film (retardation film) obtained in the same manner as in Example 1, its viewing angle characteristics, R value,
When the uniformity of the R value was evaluated, the viewing angle characteristic was 1
3.2, the R value was 580.5 nm, and the effective width ratio of the R value was 61%.

[Embodiment 3] Width 430 mm, thickness 100 μ
m, the glass transition point (Tg) of 190 ℃ polysulfone film using a tenter stretching machine, stretching temperature 190 ℃,
Lateral uniaxial stretching was performed under the conditions of a draw ratio of 1.5 times, a heat setting temperature of 170 ° C., and a heat setting time of 30 seconds.

Next, the length a of the grip portion is 30 mm,
Also, the lateral uniaxially stretched film p is supplied to the film conveying means 1 set to the jig interval b = 10 mm (a / b = 3), and the lateral uniaxially stretched film p is slackened in a waveform (setting (Reduction ratio 14%) 190
Heat treatment was performed at 8 ° C. for 8 minutes to reduce the vertical dimension.

Before the heat treatment, the reduction ratio for each pitch was measured (length: 1 m), and the reduction ratio was calculated, X _av = 1
_{4.01%, X min: 13.85%} , X max = 14.2
It is 2%, and if the variation is calculated from these values, ±
It was 1.5%.

With respect to the retardation film (retardation film) obtained in the same manner as in Example 1, its viewing angle characteristics, R value,
When the uniformity of the R value was evaluated, the viewing angle characteristic was 1
3.8, the R value was 578.4 nm, and the effective width ratio of the R value was 75%.

Example 4 Width 430 mm, Thickness 100 μ
m, the glass transition point (Tg) of 190 ℃ polysulfone film using a tenter stretching machine, stretching temperature 190 ℃,
Lateral uniaxial stretching was performed under the conditions of a draw ratio of 1.5 times, a heat setting temperature of 170 ° C., and a heat setting time of 30 seconds.

Next, the length a of the gripping portion is a = 10 mm,
Also, the lateral uniaxially stretched film p is supplied to the film conveying means 1 set to the jig interval b = 20 mm (a / b = 1/2), and the lateral uniaxially stretched film p is slackened in a wave shape. (Set reduction ratio 14%) After gripping sequentially, 1
The size in the vertical direction was reduced by applying a heat treatment at 90 ° C. for 8 minutes.

Before the heat treatment, the reduction ratio for each pitch was measured (length: 1 m), and the reduction ratio was calculated. X _av = 1
_{4.09%, X min: 13.77%} , X max = 14.6
It is 0%, and if the variation is calculated from these values, ±
It was 3.6%.

With respect to the retardation plate (retardation film) obtained in the same manner as in Example 1, its viewing angle characteristics, R value,
When the uniformity of the R value was evaluated, the viewing angle characteristic was 1
3.7, the R value was 591.9 nm, and the effective width ratio of the R value was 70%.

Comparative Example 1 Width 430 mm, Thickness 100 μ
m, the glass transition point (Tg) of 190 ℃ polysulfone film using a tenter stretching machine, stretching temperature 190 ℃,
The film was laterally uniaxially stretched under the conditions of a stretching ratio of 1.5 times and a heat setting temperature of 170 ° C.

Next, the length a of the grip portion is 50 mm,
Further, the lateral uniaxially stretched film is supplied to the film conveying means set to the jig interval b = 70 mm (a / b = 5/7), and the lateral uniaxially stretched film is slackened in a corrugated shape (setting reduction). 14%), 190
Heat treatment was performed at 8 ° C. for 8 minutes to reduce the vertical dimension.

Before the heat treatment, the reduction rate for each pitch was measured (length: 1 m), and the reduction rate was calculated. X _av = 1
4.15%, X _min : 13.76%, X _max = 14.5
It is 8%, and if the variation is calculated from these values, ±
It was 3.0%.

Then, the viewing angle characteristics, the R value, and the uniformity of the R values of the retardation film (retardation film) obtained in the same manner as in the example were evaluated.
4.3, the R value was 591.3 nm, but the effective width ratio of the R value was 42%, which was inferior to that in the example, because the requirements for the jig interval b = 70 mm and b ≦ 50 mm were lacking.

Comparative Example 2 Width 430 mm, Thickness 100 μ
m, the glass transition point (Tg) of 190 ℃ polysulfone film using a tenter stretching machine, stretching temperature 190 ℃,
The film was laterally uniaxially stretched under the conditions of a stretching ratio of 1.5 times and a heat setting temperature of 170 ° C.

Next, the length a of the gripped portion is a = 120 m.
m and the jig interval b = 50 mm (a / b = 12 /
The lateral uniaxially stretched film is supplied to the film conveying means set in 5), and the laterally uniaxially stretched film is sequentially gripped while slackening in a corrugated shape (set reduction ratio 14%).
The size in the vertical direction was reduced by applying a heat treatment at 90 ° C. for 8 minutes.

Before the heat treatment, the reduction ratio for each pitch was measured (length: 1 m), and the reduction ratio was calculated to be X _av = 1.
_{4.12%, X min: 13.82%} , X max = 14.3
It is 9%, and if the variation is calculated from these values, ±
It was 2.0%.

When the manufactured retardation plate was evaluated, the length of the gripped portion was a = 120 mm and a ≦ 100 m.
Since the requirement of m was lacking, streak-like color unevenness occurred in the stretching direction, and it was difficult to obtain a uniform retardation plate.

Comparative Example 3 Width 430 mm, Thickness 100 μ
m, the glass transition point (Tg) of 190 ℃ polysulfone film using a tenter stretching machine, stretching temperature 190 ℃,
The film was laterally uniaxially stretched under the conditions of a stretching ratio of 1.5 times and a heat setting temperature of 170 ° C.

Next, the length a of the grip portion is 60 mm,
Also, the lateral uniaxially stretched film is supplied to the film conveying means set to the jig interval b = 5 mm (a / b = 12), and the lateral uniaxially stretched film is slackened in a corrugated shape (set reduction ratio 14%). ) After gripping sequentially, 190 ℃, 8
A heat treatment for 1 minute was applied to reduce the vertical dimension.

Before the heat treatment, the reduction ratio for each pitch was measured (length: 1 m), and the reduction ratio was calculated. X _av = 1
4.14%, X _min : 13.88%, X _max = 14.5
It is 5%, and if the variation is calculated from these values, ±
It was 2.4%.

When the manufactured retardation film was evaluated, it was found that the above-mentioned requirements of a / b = 12 and a / b ≦ 10 were lacking, and therefore streak-like color unevenness occurred in the stretching direction and a uniform retardation plate was obtained. Was hard to get.

Comparative Example 4 Width 430 mm, Thickness 100 μ
m, the glass transition point (Tg) of 190 ℃ polysulfone film using a tenter stretching machine, stretching temperature 190 ℃,
The film was laterally uniaxially stretched under the conditions of a stretching ratio of 1.5 times and a heat setting temperature of 170 ° C.

Next, the length a of the grip portion is 10 mm,
Also, the lateral uniaxially stretched film is supplied to the film conveying means set to the jig interval b = 50 mm (a / b = 1/5), and the lateral uniaxially stretched film is slackened in a wavy shape (setting reduction). 14%), 190
Heat treatment was performed at 8 ° C. for 8 minutes to reduce the vertical dimension.

Before the heat treatment, the reduction ratio for each pitch was measured (length: 1 m), and the reduction ratio was calculated, X _av = 1
_{4.11%, X min: 13.80%} , X max = 14.4
6%, and if the variation is calculated from these values, ±
It was 2.5%.

However, a / b = 1/5 and a / b ≧ 1
Since the requirement of / 2 was lacking, it was difficult to obtain the retardation plate because the film was broken during the heat treatment.

[Comparative Example 5] Width 430 mm, thickness 100 μ
m, the glass transition point (Tg) of 190 ℃ polysulfone film using a tenter stretching machine, stretching temperature 190 ℃,
The film was horizontally uniaxially stretched under the conditions of a draw ratio of 2.0 and a heat setting temperature of 170 ° C.

Next, the length a of the gripped portion is 30 mm,
Further, with respect to the film conveying means set to the jig interval b = 20 mm (a / b = 3/2), the lateral uniaxial stretching is performed at a speed higher than 130 when the conveying speed of the film conveying means is 100. A film was supplied, and this laterally uniaxially stretched film was sequentially gripped while being slackened in a corrugated shape (set reduction ratio: 33%), and then heat-treated at 190 ° C. for 8 minutes to reduce the dimension in the longitudinal direction.

Before the heat treatment, the reduction ratio for each pitch was measured (length 1 m), and the reduction ratio was calculated to be X _av = 3
3.11%, X _min : 32.10%, X _max = 34.9
It is 2%, and if the variation is calculated from these values, ±
It was 5.5%.

However, since the feeding rate of the lateral uniaxially stretched film is set higher than 130 and the set reduction ratio is 33% (when the feeding speed of the film feeding means is 100, the feeding speed of the lateral uniaxially stretched film is set to 100%). It is difficult to obtain a flat and uniform retardation plate in which the corrugation remains on the film even after the heat treatment, because the requirement to make the value slower than 130) is lacking.

Comparative Example 6 Width 430 mm, Thickness 100 μ
m, the glass transition point (Tg) of 190 ℃ polysulfone film using a tenter stretching machine, stretching temperature 190 ℃,
The film was horizontally uniaxially stretched under the conditions of a draw ratio of 2.0 and a heat setting temperature of 170 ° C.

Next, the length a of the grip portion is 30 mm.
Also, the lateral uniaxially stretched film is supplied to the film conveying means set to the jig interval b = 20 mm (a / b = 3/2), and the lateral uniaxially stretched film is slackened in a wave shape (setting reduction The rate was 14%, but it was gripped while varying the reduction rate.) After sequentially gripping, heat treatment was performed at 190 ° C. for 8 minutes to reduce the dimension in the vertical direction.

Before the heat treatment, the reduction ratio for each pitch was measured (length: 1 m), and the reduction ratio was calculated. X _av = 1
4.36%, X _min : 10.55%, X _max = 18.3
1%, and if the variation is calculated from these values, ±
It was 27.5%.

When the manufactured retardation film was evaluated, the variation of the reduction ratio for each pitch was ± 27.5%.
Since the requirement within the range of ± 25% was lacking, color unevenness occurred and it was difficult to obtain a uniform retardation plate.

[0082]

According to the invention of claim 1, the length a of the holding portion of the jig for holding both ends of the thermoplastic resin film in the lateral direction is 100 mm or less, and the distance b between the jigs is 50 m.
When the film conveying means is composed of a plurality of jig groups in which m / m and a / b are set to 1/2 to 10 and the conveying speed of the film conveying means is 100, A thermoplastic resin film laterally uniaxially stretched at a speed faster than 130 is excessively supplied, and the both lateral ends of the thermoplastic resin film are gripped by the jig groups while slackening the film between the jigs in a corrugated manner. After being sequentially gripped by, the heat treatment is performed while controlling the variation of the reduction ratio between the jigs within the range of ± 25% to reduce the longitudinal dimension of the thermoplastic resin film. The stress in the direction perpendicular to the stretching direction (stress to reduce) is reduced, and the uniaxiality of the retardation plate obtained is enhanced, and the unevenness of the retardation value is also reduced.

Therefore, there is an effect that a retardation plate having uniform and excellent retardation compensation performance and viewing angle characteristics can be easily manufactured over substantially the entire area of the film.

[Brief description of drawings]

FIG. 1A is an explanatory diagram showing a state before heat treatment of a polysulfone film according to an example, and FIG. 1B is an explanatory diagram showing a state after heat treatment.

FIG. 2 is a schematic plan view of FIG.

FIG. 3 is a perspective view of a uniaxially stretched film.

FIG. 4 is a graph showing the relationship between the viewing angle θ and R _xz (θ) / R _xz (0) in the _xz plane.

FIG. 5 is a graph showing the relationship between the viewing angle φ and R _yz (φ) / R _yz (0) in the _yz plane.

[Explanation of symbols]

 1 film conveying means 10 jig p uniaxially stretched film

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[Procedure amendment]

[Submission date] October 14, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 1

[Correction method] Change

[Correction content]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0021

[Correction method] Change

[Correction content]

That is, the invention according to claim 1 is a method for producing a retardation plate by laterally uniaxially stretching a thermoplastic resin film, and then heat-shrinking the thermoplastic resin film in the longitudinal direction, to produce a retardation plate. The length a of the gripping portion of the jig that grips both lateral ends of the film is 100 mm or less,
The distance b between jigs is 50 mm or less, and a / b is 1 /
When a film conveying means is constituted by a plurality of jig groups set to 2 to 10 and the conveying speed is 70 with respect to the film conveying means, the film is laterally uniaxially stretched at a speed faster than 100 and slower than 100. After the thermoplastic resin film is excessively supplied, the lateral ends of the thermoplastic resin film are sequentially gripped by the gripping portions of the jig group while slackening the film in a wave shape between the jigs. It is characterized in that the thermoplastic resin film is thermally shrunk in the longitudinal direction by performing a heat treatment while controlling the variation of the reduction ratio for each to be within the range of ± 25%.

[Procedure 3]

[Document name to be amended] Statement

[Name of item to be corrected] 0023

[Correction method] Change

[Correction content]

The reduction ratio of the film in the longitudinal direction at this time is
When the film is slackened in a wave shape and gripped (b'-b)
/ (A + b ') (see FIG. 1A, where a is the length of the gripping portion of the jig that grips both ends of the film, b is the distance between the jigs, and b'is the distance between the jigs that are slack in the waveform. The length of the film in Fig. 4) is given as It is possible to control to a desired value by adjusting.

Claims (1)

[Claims] 1. A method for producing a retardation plate by uniaxially stretching a thermoplastic resin film in the transverse direction and then heat-shrinking the thermoplastic resin film in the longitudinal direction, wherein both end portions in the transverse direction of the thermoplastic resin film are gripped. The film conveying means includes a plurality of jig groups in which the length a of the grip portion of the jig is 100 mm or less, the distance b between the jigs is 50 mm or less, and a / b is set to 1/2 to 10 And a transversely uniaxially stretched thermoplastic resin film is excessively supplied at a speed faster than 130 and slower than 130 when the speed of the film is 100, and the film is fed between the jigs. After slackening in a wave shape, the two lateral ends of the thermoplastic resin film are sequentially gripped by each gripping part of the jig group, and then controlled so that the variation in the reduction ratio between the jigs is within ± 25%. Shinaga Method for producing a retardation plate, characterized in that the longitudinal to thermal shrinkage of the thermoplastic resin film is subjected to heat treatment.