JPH06300917A - Production of phase difference plate - Google Patents

Abstract

PURPOSE:To provide a method capable of easily producing the phase difference plate which is uniform over approximately the entire area of the film and has excellent phase difference compensation performance and visual field angle characteristic. CONSTITUTION:This process for production of the phase difference plate consists in transversely uniaxially stretching a thermoplastic resin film, then overfeeding this transversely uniaxially stretched thermoplastic film having 25 to 150mum thickness, puncturing both ends in the transverse direction of the film with needle clips 10 having plural needles for clamping the film arranged respectively in a longitudinal direction, thereby clamping the film in the state of generating the loose parts of the film, then subjecting the film to a heat treatment to thermally shrink the thermoplastic resin film in its longitudinal direction. The length in the longitudinal direction of the film is <=100mm and the inter-clip spacings of the adjacent needle clips are 5 to 40mm. The overfeed rate F in the overfeed is specified to 0<F<=(1-1/sq. rt. A)X100 (%) when the stretching magnification is defined as A.

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 is suitably used for, for example, a liquid crystal display plate, and particularly to a retardation film having excellent viewing angle characteristics. The present invention relates to a method for manufacturing a plate.

[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). This is to eliminate the phase difference generated in the liquid crystal of the liquid crystal display plate (called phase difference compensation).

As such a retardation plate, a cellulosic resin (see JP-A-63-167363), a vinyl chloride resin (JP-B-45-34477, JP-A-5-34473).
6-125702), polycarbonate resin (JP-B-41-12190, JP-A-56-13).
0703), acrylonitrile resin (see JP-A-56-130702), styrene resin (see JP-A-56-125703), 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 simultaneous biaxial stretching (Japanese Patent Application Laid-Open No. 3-23405) 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 plate does not have a uniform refractive index (nx, ny, nz) in the three-dimensional direction and is represented by a refractive index ellipsoid. And the relationship of the refractive index in each direction is
For example, in the uniaxially stretched film p shown in FIG. 5, x is a stretching axis, y is an axis orthogonal to the stretching direction in the film plane, and z is
Is the normal direction of the film, there is a relationship of nx> ny ≧ nz in the film having a positive intrinsic refractive index, and a relationship of nx <ny ≦ nz in the film having a negative intrinsic refractive index. 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
(View angle) Birefringence [Δnxz
(Θ)] and the retardation value [Rxz (θ)] are represented by the following formulas (Electronic Materials February 1991 No. 4).
(See page 0).

[0008]

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

FIG. 6 shows the result calculated based on the above equations (1) and (2).

In the graph of FIG. 6, 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.
A value Rxz (θ) / Rxz obtained by dividing xz (θ) by the retardation value Rxz (0) at a viewing angle of 0 (when viewed from the normal direction z).
(0), and the rate of change in retardation R is [1-R
xz (θ) / Rxz (0)] is represented by an absolute value. Further, in FIG. 6, α represents a completely uniaxially stretched film of nz = ny, and β
Indicates a completely uniaxially stretched film with nz <ny.

Here, the viewing angle is wider as the rate of change of the retardation R, that is, the absolute value of [1-Rxz (θ) / Rxz (0)] is smaller. From FIG. 6, the complete uniaxial stretching (nz = ny) has a smaller change in retardation value and a wider viewing angle, while the molecular orientation has biaxiality (nz <ny). It can be confirmed that the change in the foundation value is large and the viewing angle is very narrow.

FIG. 7 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. 7, γ represents a completely uniaxially stretched film of nz = ny,
λ indicates a completely uniaxially stretched film of nz <ny.

Also from this result, if the molecular orientation is biaxial, the rate of change of the retardation value, that is, [1
-Ryz (φ) / Ryz (0)] has a large absolute value and a narrow viewing angle, while the higher the uniaxial orientation of the molecule, the higher the rate of change in retardation value, that is, [1-Ryz (φ) / Ryz
(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. 6 and 7 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 have occurred in the stretching in the direction perpendicular to the stretching direction.

In Japanese Patent Laid-Open No. 2-191904, this reduction ratio is also 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 (1-1 / square root of draw ratio) × 100 (%) to (1-1 / third root of draw ratio).
It is disclosed that a retardation plate having excellent viewing angle characteristics can be manufactured by setting the ratio to × 100 (%). As a concrete method, the distance between the drawing rolls is set to 5
A method (longitudinal uniaxial free width stretching method) of stretching in the machine direction while allowing free shrinkage in the width direction by setting the width to more than twice is disclosed.

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.

[0018]

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, since the film is stretched in the longitudinal direction of the film while allowing the film to freely shrink in the width direction between the stretching rolls arranged at intervals, the film in the vicinity of the stretching roll is treated. 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 was bad.

On the other hand, in the method disclosed in Japanese Patent Laid-Open No. 3-23405, a pantograph type tenter stretching machine having a complicated mechanism and an expensive mechanism is used, so that the obtained retardation plate is also expensive. There was a problem.

On the other hand, in the transverse uniaxial tenter stretching as disclosed in JP-A-2-42406, the temperature control in the heating zone is relatively easy and the stretching with few defective portions is possible. Reduction rate (neck-in rate) is almost 0
Therefore, stress remains in the vertical direction, biaxiality occurs in the molecular orientation, and the viewing angle becomes narrow.

The present invention has been made by paying attention to such a problem, and its object is to obtain 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 an object of the present invention to provide a method capable of easily and inexpensively manufacturing a plate.

[0023]

That is, the invention according to claim 1 is that after a thermoplastic resin film is uniaxially stretched,
The laterally uniaxially stretched thermoplastic resin film having a thickness of 25 to 150 μm is over-fed, and both lateral ends of the film are pierced by needle clips each having a plurality of film-holding needles arranged in the longitudinal direction. A method for producing a retardation plate in which a slack portion of a film is gripped while being produced, and thereafter, heat treatment is performed to thermally shrink the longitudinal direction of the thermoplastic resin film, which is the longitudinal direction of the needle clip. The length is 100 mm or less, the clip interval between the adjacent needle clips is 5 to 40 mm, and the overfeed rate F in the overfeed is 0 <F ≤ (1-1 / √A when the draw ratio is A. ) × 100 (%).

In order to produce a retardation plate having a wide viewing angle, 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 reduce). In other words, only the amount of reduction generated by stretching in the direction perpendicular to the stretching direction,
It may be reduced during or after the stretching.

Therefore, in the present invention, the thermoplastic resin film is uniaxially stretched in the lateral direction, and then a slack state is created in the longitudinal direction of the film, and the slackness is heat-shrinked to enhance the uniaxiality of the molecular orientation. .

The slackened state in the longitudinal direction of the thermoplastic resin film is realized by overfeeding the thermoplastic resin film after the tenter stretching and supplying it excessively, and piercing and holding the needle clip.

As the method of this overfeed, for example, with respect to the traveling speed (line speed) of the needle clip,
A method of feeding the thermoplastic film after tenter stretching (transverse uniaxial stretching) along a roll rotating faster than this so as not to slip and supplying excessively is considered.

In the present invention, both lateral ends of the over-fed film are pierced and held by needle clips. This makes it possible to easily hold the film. By the way, if another method is used, for example, if both ends of the film over-fed by the tenter clip are to be held, folding or the like occurs, so that the film cannot be held stably.

FIG. 1 shows an example of the needle clip according to the present invention. In this example, the needle clip 10 has a base plate 11 and a plurality of needles 12 mounted so as to project above the base plate 11. The diameter of the needle, the length of the needle, the pitch of the needle, the arrangement of the needle, etc. are not particularly limited, and may be appropriately selected and used in consideration of the specifications of the film to be held.

FIG. 2 shows a diagram in which a plurality (three in the present drawing) of such needle clips 10 are arranged at a clip interval S (interval between adjacent needle clips). In this figure, L indicates the length of the needle clip 10.

The length L of the needle clip 10 in the present invention
Is preferably 100 mm or less, and particularly preferably 10 to 50 mm. When the length L of the needle clip exceeds 100 mm, the slack cannot be received only between the needle clips when holding the over-fed film. For example, as shown in FIG. There is an inconvenience of being folded and held in a gather shape. When heat shrinking is performed in this state, streak unevenness occurs and a uniform retardation film cannot be obtained.

The length L of the needle clip is, for example, 10 m.
If it is less than m, restrictions on the device such as the strength of the holding portion of the clip may occur.

The clip interval S in the present invention is 5-4.
It is 0 mm, more preferably 10 to 30 mm. When the clip interval S is less than 5 mm, the slack of the over-fed film cannot be received only between the clips, and for example, as shown in FIG. 3B, the needle clip portion is folded and held in a gather shape. There is an inconvenience that When heat shrinking is performed in this state, streak unevenness occurs and a uniform retardation film cannot be obtained. On the other hand, if the clip interval S exceeds 40 mm, neck-in occurs between the clips during heat shrinkage, resulting in significant edge unevenness and poor yield.

Therefore, as shown in FIG. 3 (A), the over-fed film is pierced and held by a needle clip having a clip interval S of 5 to 40 mm and a clip length L of less than 100 as in the present invention. It becomes possible to hold the film that has been over-fed with the film so as to slacken evenly between the clips, and by heat-shrinking, it is possible to manufacture a retardation film with few defects and a wide viewing angle.

The overfeed rate F in the overfeed of the present invention is, as shown in FIG. 4, the distance between the same proximal end sides of the adjacent needle clips is a, and the slack of the film at this a distance is also taken into consideration. When the inserted film length is b, it is given by [(b−a) / b] × 100 (%). The overfeed rate F is the stretch ratio A
Then, the operation is performed so as to be within the range of 0 <F ≦ (1-1 / √A) × 100 (%). Here, the draw ratio A
Is the stretching ratio when the thermoplastic resin film is uniaxially stretched in the lateral direction, and usually takes a value of more than 1.

If the overfeed rate F is (1-1 / √)
If it exceeds A) × 100 (%), the slack cannot be completely contracted. The overfeed rate F is appropriately set within the above range in accordance with the stretching ratio of the film, the stretching temperature, the stretching time, etc. in order to obtain the optimum viewing angle.

The heat treatment conditions for heat-shrinking the thermoplastic resin film in the longitudinal direction, that is, the treatment temperature, time, etc., are appropriately selected in order to obtain the desired retardation value after the heat-shrink treatment. is there.

In the present invention, the film is transversely uniaxially stretched before such a heat-shrinking treatment in the machine direction, but the thickness of the thermoplastic resin film after the transverse uniaxial stretching in the present invention is performed. 25-150 μm,
The thickness is more preferably 50 to 100 μm. This value is 2
When the thickness is less than 5 μm, the rigidity of the film is weak, so that gather-shaped folding is likely to occur at the needle clip portion, and when heat-shrinking is performed, streak unevenness occurs and a uniform retardation film cannot be obtained. On the other hand, if this value exceeds 150 μm,
If the film floats or comes off, it becomes impossible to hold the film stably.

Further, in such technical means, the stretching of the thermoplastic resin film in the lateral uniaxial direction can be carried out by a lateral uniaxial tenter stretching machine. Also, its stretching temperature,
Stretching ratio, stretching speed, heat setting (heat treatment after stretching)
Various conditions such as temperature and heat setting time can be appropriately set according to a desired phase difference value.
The control is extremely easy as compared with the manufacturing method disclosed in Japanese Patent Publication No. 904.

Further, a defective portion of neck-in (axis misalignment) which is a problem of free width stretching according to Japanese Patent Laid-Open No. 2-191904.
Occurs because the stretching axis (optical principal axis of the retardation plate) is largely deviated between the center and both ends because it is not constrained in the stretching orthogonal direction. On the other hand, in the manufacturing method according to the present invention, the film is held by the film-holding needle in the direction orthogonal to the stretching, the restraining force is exerted, and when the clip interval S is set to 40 mm or less, a defective portion is generated. It can be suppressed as much as possible.

As an actual facility, it is conceivable to improve the device used for tentering of the cloth, and the above-mentioned Japanese Patent Laid-Open No. 2-1.
It is easier to control the temperature as compared with the one disclosed in Japanese Patent No. 91904, and is cheaper and simpler than the one disclosed in Japanese Patent Laid-Open No. 3-23405.

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.

The film may be produced by any of the solvent casting method, calendering method and extrusion method.

[0044]

According to the invention of claim 1, the thermoplastic resin film is laterally uniaxially stretched, and then the laterally uniaxially stretched thickness 2
A slack portion of the film is generated by overfeeding a thermoplastic resin film of 5 to 150 μm and piercing both lateral ends of the film with needle clips each having a plurality of film-holding needles arranged in the longitudinal direction. A method of manufacturing a retardation plate in which the longitudinal direction of the thermoplastic resin film is thermally shrunk by performing a heat treatment, and the needle clip has a longitudinal length of 100 mm or less, The clip interval of the matching needle clips is 5 to 40 mm, and the overfeed rate F in the above overfeed is 0 <F ≤ (1-1 / √A) x 100 (%) when the draw ratio is A. While holding the slack under the film, hold the film with the needle clip, and then heat it to adjust the longitudinal direction of the thermoplastic resin film. It is made to contraction.

That is, in the present invention, after the thermoplastic resin film is uniaxially stretched in the transverse direction, a slack state is created in the longitudinal direction of this film, and the slackness is generated by stretching in the direction perpendicular to the stretching direction by heat shrinking treatment. The film is stretched by the amount of reduction to reduce the stress in the direction orthogonal to the stretching, thereby enhancing the uniaxiality of the film. Then, in the state where the thermoplastic resin film is slack in the longitudinal direction, it is possible to form a slack portion by overfeeding the thermoplastic resin film. By piercing and grasping with a needle clip provided with a needle for use, the longitudinal direction of the thermoplastic film is thermally shrunk while maintaining that state.

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

[0047]

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

Example 1 Width 430 mm, Thickness 100 μ
m, glass transition point (Tg) 184 ° C. polysulfone film using a tenter stretching machine, stretching temperature 180 ° C.,
A transversely uniaxially stretched film having a length of 600 mm was produced by transversely uniaxially stretching under conditions of a draw ratio of 1.5 times, a heat setting temperature of 160 ° C., and a heat setting time of 20 sec, and slitting the ears. The thickness of the film thus obtained after transverse uniaxial stretching was 69 μm.

Next, the laterally uniaxially stretched film thus obtained was over-fed so that the overfeed rate was 13% to form a slack portion, and both ends of the film were clipped so as to hold the slack portion. 11 mm
A needle clip having a clip length of 39 mm arranged in step 3 was pierced and fixed in the state shown in FIG. 3 (A). In addition,
The specifications of the needle clip used are a needle length of 8 mm and a needle diameter of 0.8.
mm, needle pitch 6 mm, double row alternating arrangement.

Thereafter, the film thus formed with the slack portion was subjected to heat treatment at an annealing temperature of 180 ° C. for an annealing time of 30 seconds to reduce the dimension in the longitudinal direction. The obtained uniaxially stretched film was evaluated for viewing angle characteristics, R value, and R value uniformity.

The viewing angle characteristics are as follows: the stretching axis of the film and the axis orthogonal to the stretching axis (in the plane of the film)
The absolute value of the difference between the retardation value (590 nm) when rotated by 0 degree and the retardation value when 0 degree is divided by the retardation value (590 nm) at 0 degree to be 1
The one with the larger value (%) multiplied by 00 was used as the substitute characteristic. It can be said that the smaller this value is, the better the viewing angle characteristic is.

The R value is a phase difference value when the measured wavelength and the phase difference value are equal.

The uniformity of the R value was evaluated by the effective width ratio of the R value, with the portion within which the variation of the retardation value in the width direction is within ± 5 nm as the effective width. The effective width ratio of this R value is calculated by the following formula.

Effective width ratio of R value = (effective width / width after stretching)
× 100 (%) The results are shown in Table 1.

Example 2 First, a lateral uniaxially stretched film was obtained under the same conditions as in Example 1 above.

Then, the laterally uniaxially stretched film thus obtained is over-fed to form a slack portion, and both ends of the film are pierced with needle clips so as to hold the slack portion, as shown in FIG. 3 (A). It was fixed in this state and heat-treated to reduce the vertical dimension.

In this film holding and heat treatment, the clip interval S is 25 mm and the clip length L is 90.
Holding and heat treatment were performed under the same conditions as in Example 1 except that mm was used.

Viewing angle characteristics of the obtained uniaxially stretched film,
Table 1 shows the R value and the uniformity of the R value (effective width ratio of the R value).

Example 3 Width 430 mm, Thickness 150 μ
m, glass transition point (Tg) 184 ° C. polysulfone film using a tenter stretching machine, stretching temperature 180 ° C.,
A transversely uniaxially stretched film having a length of 600 mm was produced by transversely uniaxially stretching under conditions of a draw ratio of 1.5 times, a heat setting temperature of 160 ° C., and a heat setting time of 20 sec, and slitting the ears. The thickness of the film thus obtained after lateral uniaxial stretching was 97 μm.

Next, the laterally uniaxially stretched film obtained was over-fed to form a slack portion, and both ends of the film were pierced with needle clips so as to hold the slack portion, as shown in FIG. 3 (A). It was fixed in this state and heat-treated to reduce the vertical dimension.

The film was held and heat-treated under the same conditions as in Example 1 (heat-shrink annealing treatment).

Viewing angle characteristics of the obtained uniaxially stretched film,
Table 1 shows the R value and the uniformity of the R value (effective width ratio of the R value).

Comparative Example 1 First, a lateral uniaxially stretched film was obtained under the same conditions as in Example 1 above.

Then, the laterally uniaxially stretched film obtained was over-fed to form a slack portion, and both ends of the film were pierced with needle clips so as to hold the slack portion, and the film was held and heat-treated. Reduced the vertical dimension.

In the film holding and heat treatment, the clip interval S is 3 mm and the clip length L is 90 m.
Holding and heat treatment (heat shrinkage annealing treatment) were performed under the same conditions as in Example 1 except that m was changed.

As a result, the entire surface of the obtained film was
It was confirmed that streaks in the lateral direction were generated, which was not practical.

Comparative Example 2 First, a lateral uniaxially stretched film was obtained under the same conditions as in Example 1 above.

Next, the laterally uniaxially stretched film obtained was over-fed to form a slack portion, and both ends of the film were pierced with needle clips so as to hold the slack portion, and the film was held and heat treated. Reduced the vertical dimension.

In this film holding and heat treatment, the clip interval S is 50 mm and the clip length L is 39 mm.
Holding and heat treatment (heat-shrink annealing treatment) were performed under the same conditions as in Example 1 except that mm was used.

Viewing angle characteristics of the obtained uniaxially stretched film,
Table 1 shows the R value and the uniformity of the R value (effective width ratio of the R value).

Comparative Example 3 First, a lateral uniaxially stretched film was obtained under the same conditions as in Example 1 above.

Then, the laterally uniaxially stretched film obtained was over-fed to form a slack portion, and both ends of the film were pierced with needle clips so as to hold the slack portion, and the film was held and heat treated. Reduced the vertical dimension.

In this film holding and heat treatment, the clip interval S is 20 mm and the clip length L is 12.
Holding and heat treatment (heat shrinkage annealing treatment) were performed under the same conditions as in Example 1 except that the thickness was changed to 0 mm.

As a result, the entire surface of the obtained film was
It was confirmed that streaks in the lateral direction were generated, which was not practical.

[0075]

[Table 1] "Confirmation" As is clear from the results in Table 1, the retardation plates (stretched films) according to Examples 1 to 3 have a wider viewing angle characteristic and R value effective rate than the retardation plates (stretched films) according to the comparative examples. It has been improved, and it is confirmed that by applying the present invention, a retardation plate having a uniform retardation compensation performance and an excellent viewing angle characteristic can be manufactured with a high yield.

[0076]

According to the invention of claim 1, the stress in the direction perpendicular to the stretching direction (stress to reduce) is reduced, the uniaxiality of the retardation plate is increased, and the retardation plate with a wide viewing angle is manufactured. Is possible.

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. 1 is a perspective view showing an example of a needle clip according to the present invention.

FIG. 2 shows a clip length L and a clip interval S according to the present invention.
FIG.

FIG. 3A is a conceptual diagram showing a good holding state when the film is held by the needle clip, and FIG. 3B is a poor holding state when the film is held by the needle clip, that is, The conceptual diagram which shows the state folded in the shape of a gather.

FIG. 4 is an explanatory diagram for explaining an overfeed rate according to the present invention.

FIG. 5 is a perspective view of a uniaxially stretched film.

FIG. 6 is a graph showing the relationship between the viewing angle θ and Rxz (θ) / Rxz (0) in the xz plane.

FIG. 7 is a graph showing the relationship between the viewing angle φ and Ryz (φ) / Ryz (0) in the yz plane.

[Explanation of symbols]

 10 Needle clip 11 Substrate 12 Needle

Claims (1)

[Claims] 1. A thermoplastic resin film is laterally uniaxially stretched, and then the laterally uniaxially stretched thermoplastic resin film having a thickness of 25 to 150 μm is over-fed, and both lateral ends of the film are respectively longitudinally stretched. By piercing with a needle clip equipped with a plurality of film-holding needles arranged in a state that the slack portion of the film is generated, and then the film is heat-treated to heat-shrink the thermoplastic resin film in the longitudinal direction. A method for manufacturing a retardation plate, wherein the length in the longitudinal direction of the needle clip is 100 mm or less, and the clip interval between the adjacent needle clips is 5 to 40 mm.
And the overfeed rate F in the overfeed
Is 0 <F ≤ (1-1 / √A) x 100 (%), where A is the draw ratio, and is a method for manufacturing a retardation plate.