JP2011235610A - Oriented film, method for manufacturing oriented film, and phase difference plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an oriented film capable of variously changing an inclination angle of an orientation axis and improving laminate efficiency with a polarizing plate by simple equipment.SOLUTION: In the method for manufacturing the oriented film which is obtained by stretching a thermoplastic resin film and whose optical axis is not parallel nor perpendicular to a flow direction of the film, the method for producing the oriented film includes adjusting the inclination angle of the orientation axis by shrinking the oriented film oriented in an angle direction slightly oblique to a width direction in the width direction beforehand while heating. The oriented film manufactured by this method whose inclination angle of the orientation axis to the width direction is 20 to 70 degrees is provided.

Description

  The present invention relates to a stretched film and a method for producing a stretched film, and in particular, a stretched film having a molecular orientation axis that is inclined with respect to any side of the film and having excellent optical properties, and a method for producing the stretched film It is about. Moreover, this invention relates to the phase difference plate formed with such a stretched film.

  In recent years, liquid crystal display devices typified by monitors (displays) for personal computers and television receivers have been widely used as various display means. In these liquid crystal display devices, a technique for improving display visibility by arranging polarizers on both sides of a liquid crystal cell and further providing a retardation film between the liquid crystal cell and the polarizer is known.

Here, the retardation film is formed into a rectangular shape in accordance with the shape of the liquid crystal display device. Moreover, as a property of the retardation film used in the liquid crystal display device, it may be required that the molecules are oriented in an oblique direction with respect to each side of the rectangle.
Such a film which is molecularly oriented in an oblique direction with respect to each side of the rectangle has been conventionally manufactured by the following process.
That is, in the prior art, first, a polymer film is uniaxially stretched in the longitudinal direction or a direction perpendicular to the longitudinal direction (hereinafter referred to as the width direction) to produce a stretched film in which molecular orientation is caused. In the stretched film produced by this process, the molecular orientation axis is parallel to one side of the film and perpendicular to the other side.

Then, as the next step, each side of the film is cut obliquely to form a rectangular film.
More specifically, a stretched film that has been uniaxially stretched to cause molecular orientation is punched obliquely to make a small rectangular film. This rectangular film apparently has an orientation axis inclined with respect to each side.

However, in this method, since the polymer film is punched at an inclination with respect to the longitudinal direction, a large amount of unusable portions are generated at the end portions in the width direction of the polymer film, and the yield of the film is poor.
Therefore, there has been a demand for a method for producing a stretched film having a high yield that can be used up to the vicinity of the end in the width direction by molecularly orienting in the oblique direction at the stage of stretching the polymer film. Examples of such methods include the inventions disclosed in Patent Documents 1 to 4. First, Patent Document 1 will be described.

FIG. 6 is a reproduction of the drawing disclosed in Patent Document 1. However, the text is added for ease of explanation.
In the invention disclosed in Patent Document 1, when both ends of a film (polymer film) are held and advanced in the longitudinal direction, the distance L2 from the holding start point 108 at one end to the holding release point 109 is set at the other end. This is longer than the distance L1 from the holding start point to the holding release point. As a result, when the film is advanced in the longitudinal direction, the holding position at both ends having the same position in the longitudinal direction (traveling direction) at the start, the holding position at one end is in the traveling direction relative to the holding position at the other end It will shift to the rear side. Therefore, the holding position of the other end is pulled to the rear side in the traveling direction, and the film can be stretched in an oblique direction.

In the invention disclosed in Patent Document 1, in order to increase the difference between the distance L1 from the holding start point at one end to the holding release point and the distance L2 from the holding start point at the other end to the holding release point, FIG. Like this, one of the tenter's roads is largely detoured.
More specifically, the tenter shown in FIG. 6 has a pair of rails 100 and 101, to which clips (not shown) are respectively fixed. And the edge part of a film is hold | maintained with the said clip, and a clip is moved to a running direction with the run of a rail.

Here, in a general tenter, the total length of the pair of rails 100 and 101 is the same, but in Patent Document 1, the total length of the rails 100 and 101 is different. That is, as shown in FIG. 6, a large detour portion 103 is provided on one rail 101, and this detour portion 103 provides a large difference between the distances L <b> 1 and L <b> 2.
More specifically, in the introduction part of the tenter, as shown in FIG. 6, the traveling paths of the rails 100 and 101 are both straight, and the rails 100 and 101 are parallel.
After passing through the introduction part, one rail 100 continues to travel linearly, while the other rail 101 largely detours in a curve. This area functions as an extension area.
When the rail 101 passes the detour 103, the rail 101 travels in a straight line direction and travels in parallel with one rail 100.
When the film is stretched by the tenter shown in FIG. 6, the film is stretched in an oblique direction in the stretching area where the detour portion 103 is provided.
After passing the detour portion 103, the stretching does not proceed any further and the orientation direction is stabilized. That is, according to Patent Document 1, only the bypass portion 103 tilts the orientation axis of the film, and the tilt angle of the orientation axis does not change after the bypass portion 103. Thus, in the invention disclosed in Patent Document 1, the orientation axis of the film is inclined only by the action of stretching the film in an oblique direction.

However, there may be a case where the retardation film has an inclination angle of the orientation axis of about 45 degrees with respect to the width direction. In order to obtain such a large orientation angle, it is necessary to enlarge the bypass portion 103 to provide a large difference between the distances L1 and L2 and to stretch the retardation film obliquely in the direction of substantially 45 degrees at the bypass portion 103. .
However, there is a problem that wrinkles occur in the film when the bypass portion 103 is enlarged to an extent that the film is substantially obliquely stretched in the 45-degree direction and the distances L1 and L2 are increased.
Therefore, in the invention disclosed in Patent Document 1, the film is impregnated with a solvent in advance, and in this state, the film is stretched in an oblique direction in the stretching area having the bypass 103, and then the solvent is volatilized to volatilize the film. I'm going to take firewood.
That is, as described above, the tenter has an introduction portion where the rails 100 and 101 travel in parallel, an extension area where one rail 101 bypasses, and a volatile evaporation area where the rails 100 and 101 travel again in parallel. ing. In the invention disclosed in Patent Document 1, the film is stretched obliquely in the stretching area having the bypass 103 to provide an inclination angle of the orientation axis, and the film is heated to travel the solvent in the volatile component evaporation area. Volatilizes and stretches the film.
That is, the orientation axis of the film is tilted to a desired angle in the stretching area having the detour 103, and the subsequent volatile component evaporation area simply takes a wrinkle, and the tilt angle of the orientation axis of the film does not change.
Thus, in the invention disclosed in Patent Document 1, the orientation axis is inclined only by stretching the film in an oblique direction.

  In addition, the invention disclosed in Patent Document 2 is uniaxially stretching the film in the transverse or longitudinal direction, and by stretching the film in the longitudinal or transverse direction different from the stretching direction at different speeds on the left and right of the stretching direction, The orientation axis is inclined with respect to the uniaxial stretching direction.

  Furthermore, the invention disclosed in Patent Document 3 grips both ends in the width direction of the film by the gripping means, makes the travel distance of the gripping means different at both ends in the width direction, and changes the traveling direction of the film in the middle. The orientation axis of the film is inclined with respect to the width direction.

  The invention disclosed in Patent Document 4 changes the expansion / contraction ratio by regulating stretching or shrinking in the tilting direction (longitudinal direction) after regulating stretching or shrinking of the film in the transport direction (or tilting direction). Thus, the direction in which the film expands and contracts is changed to adjust the orientation angle of the film.

JP 2002-086554 A JP 2000-009912 A JP 2007-090532 A JP 2007-030466 A

However, according to the method of Patent Document 1, a large burden is applied to the film when passing through the detour path 103, and stress may be applied to the film in a direction other than the desired stretching direction. Therefore, the quality of the manufactured film may vary, or the film may be partially stretched in a direction other than the desired direction.
That is, in the invention disclosed in Patent Document 1, the film is stretched in an oblique direction exclusively in the stretching area having the bypass 103, and the orientation axis is inclined to a desired angle only by the action of stretching in the oblique direction. For this reason, a strong force acts on the film during stretching, and stress in the shrinking direction acts on the film in the direction perpendicular to the stretching direction. For example, the quality of the film varies or the film is partially stretched in a direction other than the desired direction. There is a case.

Further, as pointed out in Patent Document 1, if the film is stretched strongly in an oblique direction, wrinkles are generated in the film. Although the wrinkle is somewhat improved by the measure of Patent Document 1, the measure of Patent Document 1 is merely to extend the wrinkle once generated, and it cannot be denied that the quality is deteriorated due to the occurrence of the wrinkle.
In addition, since the method disclosed in Patent Document 1 contains a large amount of volatile components, a large amount of equipment is required such as a dipping tank in which water or a solvent is immersed.
Furthermore, since the method disclosed in Patent Document 1 requires a step of evaporating the solvent, an exhaust facility for exhausting the solvent and a protective measure for preventing solvent poisoning are necessary.

  In the method of Patent Document 2, there is a problem that a desired inclination angle (for example, 45 degrees) of the orientation axis cannot be obtained due to the occurrence of a wrinkle or a film shift on the film due to the difference in the conveyance speed between the left and right. .

  Further, according to the method of Patent Document 3, there is a problem that the equipment becomes large in order to change the film traveling direction, and the equipment cost increases.

And according to the method of patent document 4, when the produced stretched film is used as a phase difference film, there exists a problem that biaxiality will become very high. That is, the refractive index nx in the slow axis direction in the plane of the stretched film, the refractive index ny in the direction perpendicular to the slow axis in the plane, and the refractive index nz in the thickness direction are required for a general retardation plate as follows. Formula (1):
0.5 ≦ (nx−nz) / (nx−ny) ≦ 2 (1)
There is a problem that the relationship cannot be satisfied.

  Therefore, the present invention pays attention to the above-mentioned problems of the prior art, and the tilt angle of the orientation axis of the molecules of the stretched film can be changed variously, can be produced with simple equipment, and can produce a stretched film with more stable quality. It is an object to provide a method.

  The invention according to claim 1 for solving the above-mentioned problems is a long film, and is a pre-stretched film pre-stretched so that the inclination angle of the orientation axis is not less than 5 degrees and less than 20 degrees with respect to the width direction. This is a method for producing a stretched film, characterized in that both ends in the width direction are held, and the pre-stretched film is heated and thermally contracted to gradually narrow the holding interval between the both ends.

The present invention includes a pre-stretching step of inclining the orientation axis at a gentler angle before tilting the orientation axis to the target angle by heat shrinkage.
As a result, it is possible to share the burden on the polymer film when changing the orientation axis. Therefore, the orientation axis can be tilted to a larger angle than when the polymer film orientation axis is rapidly tilted at once. In addition, since the properties of the polymer film can be changed in stages, it is easy to make the quality of the produced stretched film uniform.
Furthermore, in the present invention, the polymer film is thermally contracted to make the inclination angle of the orientation axis steep.
Hereinafter, this principle will be described.
For example, a film 105 that is stretched in the width direction as shown in FIG. 4 and has no tilt angle in the orientation axis (arrow) is used, and this width W is changed from FIG. 4 (a) to FIG. 4 (b). ), The inclination angle of the molecular orientation axis does not change at all as shown in FIG.
However, a film 106 stretched in the width direction as shown in FIG. 5 and having an orientation axis (arrow) slightly inclined is used, and the width W of this film 106 is determined from FIG. Assuming the case of contraction as shown in FIG. 5B, the inclination angle A of the orientation axis becomes a steep angle as shown in FIG.
That is, the initial inclination direction of the film 106 is a direction illustrated by arrows ab, cd, ef... In FIG.
For example, when the points a, b, c, d,... In FIG. 5A are held and the width W of the film 106 is reduced, the points a, b, c in FIG. Since the position in the longitudinal direction of points d,... Does not change, the direction of the orientation axis becomes a lying direction and the inclination angle A becomes steep as shown in FIG.
Therefore, holding the both ends in the width direction of the pre-stretched film pre-stretched at a small inclination angle, and gradually shrinking the holding interval between the both ends while heating and pre-shrinking the pre-stretched film, the inclination of the orientation axis The angle changes to a steep slope. And the stretched film in which the orientation axis inclined to a desired inclination angle can be obtained by adjusting the holding interval at both ends of the film.

  Invention of Claim 2 formed the process of forming a pre-stretched film by extending | stretching the inclination-angle of an orientation axis to 5 to 20 degree | times with respect to a longitudinal direction with respect to a elongate film. The method for producing a stretched film according to claim 1, wherein the prestretched film is heated and thermally contracted, and the step of gradually narrowing the holding interval at both ends is continuously performed. .

  The present invention heat shrinks immediately after forming a pre-stretched film. If it does in this way, since the time concerning stretched film manufacture can be shortened, efficiency improvement of a manufacturing operation can be aimed at.

  The invention according to claim 3 is characterized in that the both ends of the pre-stretched film are evenly moved with respect to the center line in the width direction when the holding interval between the both ends is gradually narrowed while being thermally contracted. Item 3. A method for producing a stretched film according to Item 1 or 2.

  In the present invention, variation in various characteristics in the width direction of the stretched film can be reduced by causing heat shrinkage evenly with respect to the center line in the width direction.

  Invention of Claim 4 makes the inclination with respect to the width direction of the molecular orientation axis | shaft of a pre-stretched film 20 degrees or more and less than 70 degrees by heating and heat-shrinking a pre-stretched film. It is a manufacturing method of the stretched film in any one of thru | or 3.

  According to the present invention, a stretched film having a molecular orientation axis greatly inclined with respect to the width direction can be produced.

  The invention according to claim 5 is a stretched film according to any one of claims 1 to 4, wherein the prestretched film is heated and thermally contracted by a tenter type stretching machine capable of adjusting expansion and contraction in the width direction. It is a manufacturing method.

  In this invention, even if it uses the tenter-type extending | stretching machine in which the expansion / contraction adjustment of the width direction is possible, it can implement suitably.

  Invention of Claim 6 is a stretched film manufactured by the manufacturing method of the stretched film in any one of Claims 1 thru | or 5, Comprising: The inclination-angle of the orientation axis with respect to the width direction of a stretched film is from 20 degree | times. It is a stretched film characterized by being larger than 70 degrees.

The invention according to claim 7 is a stretched film produced by the method for producing a stretched film according to any one of claims 1 to 5, wherein the refractive index nx in the slow axis direction in the plane of the stretched film. The refractive index ny in the direction perpendicular to the in-plane slow axis and the refractive index nz in the thickness direction are expressed by the following formula (1):
0.5 ≦ (nx−nz) / (nx−ny) ≦ 2 (1)
It is a stretched film characterized by satisfying

  The stretched film of this invention is formed by the manufacturing method of the stretched film in any one of Claims 1 thru | or 5. Therefore, a stretched film having an orientation axis greatly inclined with respect to the width direction and a stretched film having excellent optical properties can be provided.

  The invention according to claim 8 is a retardation plate characterized by being formed by including at least one stretched film according to claim 6 or 7.

  The stretched film produced according to the present invention can be used as a phase difference plate by being overlaid.

  The present invention has an effect that the tilt angle of the orientation axis can be changed without imposing an excessive burden on the polymer film. Therefore, there is an effect that the inclination angle of the alignment axis can be increased. In addition, there is an effect that it is easy to make the quality of the produced stretched film uniform.

It is a top view which shows an example of the film extending machine which can be used for the manufacturing method of the phase difference film of this invention. It is a top view which shows an example of the film extending machine which can be used for the manufacturing method of the retardation film of this invention different from FIG. It is a top view which shows an example of the film extending machine which can be used for the manufacturing method of the retardation film of this invention different from FIG. 1, FIG. It is explanatory drawing which shows the change of the orientation axis at the time of shrinking | stretching the polymer film uniaxially stretched in the width direction, (a) shows the polymer film before shrinkage | contraction, (b) shows the polymer film after shrinkage | contraction. . It is explanatory drawing which shows the change of the orientation axis at the time of shrinking | stretching the polymer film extended in the direction inclined in the width direction, (a) shows the polymer film before shrinkage | contraction, (b) is the polymer after shrinkage | contraction. The film is shown. It is a schematic plan view which shows the conventional extending | stretching machine. 10 is a plan view showing an example of a film stretching machine that can be used in Comparative Example 3. FIG. It is a top view which shows an example of the state at the time of the trial run of the extending | stretching machine of FIG.

  Hereinafter, although embodiment of this invention is described in detail, this invention is not limited to these examples.

  In the present invention, the polymer film (thermoplastic resin film) that is a material of the stretched film is not particularly limited to the raw material resin, and a film made of an appropriate thermoplastic resin is appropriately selected according to the purpose. Specific examples include cellulose acetate, polyester, polysulfone, polyethersulfone, polystyrene, polyvinyl alcohol, polyvinyl chloride, polymethyl methacrylate, polyarylate and polyamide. More preferably, it is preferable to use a polycarbonate and a cyclic olefin resin.

The method for producing a stretched film according to the first embodiment of the present invention basically conveys a long polymer film f that is continuously supplied while holding (holding) the film, and conveys the polymer film f. It is the method of extending | stretching in the direction which inclines with respect to the conveyance direction. The following three steps are included as characteristic steps.
(1) A step (hereinafter referred to as a pre-stretching step) in which a tilt angle (5 degrees or more and less than 20 degrees) is more gently inclined than an inclination angle of the target orientation axis (20 degrees or more and less than 70 degrees, for example, 45 degrees).
(2) A step of winding a stretched film (pre-stretched film) whose orientation axis is gently inclined through a pre-stretching step (hereinafter referred to as a temporary winding step).
(3) A step of performing heat shrinkage treatment for angle adjustment on the wound stretched film (hereinafter referred to as angle adjustment step).
The example which manufactures a stretched film using the stretched film manufacturing apparatus 1 of FIG. 1 about the 1st Embodiment of this invention is demonstrated below. However, as a matter of course, it is not essential to use the stretched film manufacturing apparatus 1 of FIG. 1 in the present invention.

  The stretched film manufacturing apparatus 1 in FIG. 1A is roughly composed of a pre-stretching stretching machine 2 and an angle adjusting heat shrinking machine 3.

The pre-drawing drawing machine 2 is a conventionally known drawing machine, and substantially the same drawing machine as disclosed in Patent Document 1 can be used. In addition, a substantially similar one to the oblique stretching machine disclosed in Patent Document 4 can be used. Note that the pre-stretching stretcher 2 used in this embodiment has a smaller difference in distance from the holding start point at both ends to the holding release point than the stretching device disclosed in Patent Document 1, and the angle at which the film is stretched Was small.
Specifically, the pre-drawing drawing machine 2 includes at least a gripping member 6, a drawing roll 8, a winding roll 9, and a rail 10. Then, the polymer film f attached to the drawer roll 8 is pulled out, the both ends of the film f are gripped by the gripping members 6 and run toward the winding roll 9, and the polymer film is in front of the winding roll 9. f is opened and wound up by a winding roll 9.

Here, the gripping member 6 travels on the rail 10 integrally with a chain (not shown) while gripping both ends of the polymer film f pulled out from the pulling roll 8. Here, the rail 10 is composed of a pair of rails 10a and 10b, and the gripping members 6 travel on the rails 10a and 10b, respectively.
And the path | route which the grip member 6 which hold | gripped the one-side edge part travels is longer than the path | route which the grip member 6 which hold | gripped the other end part travels. That is, the rail 10b takes a detour path with respect to the rail 10a on one side. The speed at which the gripping member 6 travels on the rail is substantially the same at both ends.

That is, the pre-drawing drawing machine 2 is divided into three continuous areas A, B, and C from the drawing roll 8 side to the winding roll 9 side as shown in FIG. The width of the rail 10 is different in each area.
In area A, the widths of the rails 10a and 10b are equally spaced. In area B, the rail on one side (rail 10b) detours, and in area C, the rails 10a travel again at equal intervals. In both areas A and C, the rails are equally spaced, but the rail 10 in area C is wider than area A.
In addition, the pre-drawing drawing machine 2 may have a configuration in which a heating furnace is provided. In that case, the heating furnace is preferably installed from the A area to the B area.

The angle adjusting heat shrinking machine 3 includes at least a gripping member 11, a drawing roll 12, a winding roll 13 rail 14, and a heating furnace 15. Then, the polymer film f attached to the drawer roll 12 is pulled out, and both ends of the polymer film f are gripped by the gripping member 11, and then run toward the winding roll 13 and wound up by the winding roll 13. It is.
Here, the gripping member 11 travels on the rail 14 and travels by gripping both ends of the polymer film f drawn from the pulling roll 12. Here, the rail 14 is composed of a pair of rails 14a and 14b, and the gripping members 11 travel on the rails 14a and 14b, respectively.
The gripping members 11 at both ends of the polymer film f are moved closer to each other as they approach the take-up roll 13, thereby approaching the distance in the width direction. That is, the distance between the rail 14 a and the rail 14 b is narrowed from the pulling roll 12 side toward the winding roll 13.

More specifically, the angle adjusting heat shrinking machine 3 is divided into three continuous areas D, E, and F from the drawing roll 12 side toward the winding roll 13 side. And the width of a rail differs in each area. That is, first, in the area D, the widths of the rails 14 are equally spaced. Next, in the area E, the rail 14a and the rail 14b gradually incline toward the center in the width direction as the traveling direction proceeds, and the width of the rail becomes narrower. In the area F, the widths of the rails 14 are again equally spaced.
Here, the widths of the rails 14 in the areas D and F are equally spaced, but the width of the rails 14 in the area F is narrower than that in the area D. In addition, in the area E, the rails 14 at both ends are inclined toward the center in the width direction, but the inclination start point and the inclination end point in the traveling direction, and the inclination angle with respect to the traveling direction are the same. . Therefore, the rails 14 are arranged symmetrically in the width direction along the traveling direction.

  The heating furnace 15 is provided across the areas D to F, and heats the polymer film f with hot air.

Next, the example which manufactures a stretched film using the above-mentioned stretching machine 1 is demonstrated.
First, a long polymer film f is attached to the drawer roll 8 in a roll shape. Then, in the area A, the polymer film f is caused to travel toward the take-up roll 9 using a transport device such as a roll (not shown).
When the polymer film f is caused to travel a certain distance to the winding roll 9 side, the polymer film f is gripped by the gripping members 6 at both ends in the width direction. Then, the polymer film f is continuously run toward the winding roll 9 side.

Next, when the polymer film f enters the area B, the “pre-stretching step” is started. Specifically, the gripping member 6 gripping one end portion moves in a direction away from the gripping member 6 gripping the other end portion. That is, one gripping member 6 advances straight to the winding roll 9 side, and the other gripping member 6 advances to the winding roll 9 side while increasing the width of the polymer film f. In other words, one gripping member 6 is skewed with respect to the traveling direction.
As a result, the stretching direction of the polymer film f that has been stretched perpendicular to the running direction is inclined from the perpendicular to the running direction, so that the polymer film f has a gentle orientation angle. That is, the orientation axis of the polymer film f is inclined with respect to the width direction more gently (5 degrees or more and less than 20 degrees) than the intended inclination angle (20 degrees or more and less than 70 degrees, for example, 45 degrees). .
Further, as the distance between the gripping members 6 at the opposite ends in the area A (the width direction of the polymer film f is equal) increases, the force for stretching the polymer film f also increases. It gets bigger. Then, the force for stretching the polymer film f increases and the retardation value increases. Then, the “pre-stretching step” ends.

  Here, in the present embodiment, the tilt angle of the alignment axis is set to a gentler angle than the target tilt angle of the alignment axis by the “pre-stretching step” in area B. Then, in the “angle adjustment step” described later, the tilt angle of the alignment axis is set as the target tilt angle of the alignment axis. Thus, by providing a step that makes the orientation axis a gentler angle than the target angle before tilting the orientation axis to the target tilt angle, compared to the stretching method that makes the target tilt angle at one time, The tilt angle of the orientation axis can be tilted without sharply tilting the orientation axis of the polymer film f. As a result, there is an advantage that problems such as slipping (streaky unevenness resulting from uneven tensile stress), wrinkles, and film deviation (local thickness unevenness) are unlikely to occur.

  Finally, the polymer film f enters the area C, travels toward the take-up roll 9 without changing the length in the width direction, and is taken up by the take-up roll 9. This completes the “temporary winding process”.

Next, the pre-stretched polymer film f (taken up by the take-up roll 9) is attached to the drawer roll 12 of the angle adjusting heat shrink machine 3.
In the area D, the polymer film f is caused to travel toward the take-up roll 13 using a transport device such as a roll (not shown).
When the polymer film f is caused to travel a certain distance toward the winding roll 13, the polymer film f is gripped by the gripping members 11 at both ends in the width direction. Then, the polymer film f continues to run toward the winding roll 13 side.

Next, when the polymer film f enters the area E, the gripping members 6 gripping both end portions move in a direction approaching each other. At this time, the polymer film f is thermally shrunk by performing a heat treatment. In other words, the polymer film f is heated by the heating furnace 15 to be thermally contracted, and the polymer film f is oriented by narrowing the interval from both sides in accordance with the shrinkage of the heat shrink toward the center in the width direction. The angle of the shaft is adjusted.
This completes the “angle adjustment process”.

  Finally, the polymer film f enters the area F. In the area F, the polymer film f travels toward the take-up roll 13 without changing the length in the width direction, and is taken up by the take-up roll 13. With this, all the steps of tilting the orientation axis with respect to the polymer film f are completed, and the production of the stretched film is completed. In addition, the stretched film wound up is sent to the next step (for example, a step such as cutting).

In the above-described embodiment, the pre-stretching machine 2 is used to perform pre-stretching (stretching in which the polymer film is previously oriented in an angle direction slightly oblique to the width direction). The stretching machine is not limited to this. The method and stretching machine used for pre-stretching are not particularly limited as long as the orientation axis is inclined by 5 degrees or more with respect to the width direction of the film, and known methods and stretching machines can be adopted.
When the tilt angle of the orientation axis of the film before heat shrinkage is less than 5 degrees, when the tilt angle of the orientation axis is adjusted to a range of 20 to 70 degrees, significant shrinkage is required in the width direction. In the present invention, it is not preferable in the present invention.

Next, a second embodiment of the present invention will be described. The method for producing the stretched film of the second embodiment of the present invention includes the “pre-stretching step” and the “angle adjusting step” performed in the first embodiment, and these are continuously performed. It is.
Hereinafter, an example of producing a stretched film using the stretching machine 21 of FIG. 2 will be described for the second embodiment of the present invention. However, as a matter of course, it is not essential to use the stretching machine 21 of FIG. 2 in the present invention.

  The drawing machine 21 in FIG. 2 includes at least a gripping member 26, a drawing roll 27, a winding roll 28, a rail 29, and a heating furnace 30. Then, the polymer film f attached to the drawer roll 27 is pulled out, both ends of the polymer film f are gripped by the gripping members 26 and run toward the winding roll 28, and the polymer film is discharged at the outlet of the heating furnace 30. f is opened, and it is wound up by the winding roll 28.

  Here, the gripping member 26 travels integrally with a chain (not shown) on the rail 29, grips both ends of the polymer film f drawn from the pulling roll 27, and travels both ends at the same speed. . The rail 29 is composed of a pair of rails 29a and 29b, and the gripping members 26 travel on the rails 29a and 29b, respectively. Further, the path along which the gripping member 26 that grips both ends of the polymer film f travels is different between the first half and the second half of the stretching machine 21.

If it demonstrates in detail, the extending | stretching machine 21 can be divided roughly and can divide into the pre-stretching implementation part 22 (area A of FIG. 2) of the first half part, and the heat contraction implementation part 23 (area B of FIG. 2) of the latter half part.
First, in the pre-stretching unit 22, the rails 29a and 29b on which the gripping member 26 travels first advance from the drawing roll 27 side to the winding roll 28 side at equal intervals. After that, the rail 29a at one end is moved straight as it is, and the rail 29b at the other end is away from the moving rail 29a, and proceeds from the pulling roll 27 to the winding roll 28. That is, only one rail 29b is skewed with respect to the traveling direction.

Next, in the heat shrinking unit 23, first, the rails 29a and 29b on which the gripping member 26 travels are gradually inclined from both end sides toward the center in the width direction, and the widths of the rails 29a and 29b are narrowed. Go. In other words, the rails 29a and 29b at both ends are gently inclined toward each other as the polymer film f proceeds in the traveling direction. Then, the rail 29 advances toward the take-up roll 28 while maintaining an equal interval in a state where the width is narrowed.
At this time, from the start point of the heat shrinking unit 23 (the point where the rails 29a and 29b start to be inclined toward each other) to the point where the inclination in the width direction of each rail ends, that is, at both ends. A sufficiently long distance is secured in the traveling direction in the portions where the rails 29a and 29b are inclined.
The heat shrinking unit 23 is provided with a heating furnace 30, and the heating furnace 30 heats the polymer film f with hot air.

Next, the example which manufactures a stretched film using the above-mentioned stretching machine 21 is demonstrated.
First, a long polymer film f is attached to the drawer roll 27 in a roll shape. Then, the pre-stretching unit 22 causes the polymer film f to travel toward the take-up roll 28 using a transport device such as a roll (not shown).
The polymer film f is gripped by the gripping members 26 at both ends in the width direction when the polymer film f is moved a certain distance to the winding roll 28 side. Then, the polymer film f continues to run toward the winding roll 28 side.

When the polymer film f gripped at both ends by the gripping member 26 travels a certain distance toward the take-up roll 28 side, the gripping member 26 gripping the one side end grips the other end. It moves in the direction away from the holding member 26.
As a result, the stretching direction of the polymer film f that has been stretched perpendicular to the running direction is inclined from the perpendicular to the running direction. The orientation axis of the polymer film f is gently inclined (5 degrees or more and less than 20 degrees) with respect to the width direction.
In addition, among the gripping members 26 at both ends that have been initially maintained at equal intervals in the width direction of the polymer film f, the gripping member 26 at one end is skewed (the other end is gripped). To move away from the gripping member 26), the force for stretching the polymer film f increases and the retardation value increases. Then, the “pre-stretching step” ends.

  Subsequently, the polymer film f travels through the heat shrinking unit 23. Here, the thermal contraction execution unit 23 performs an “angle adjustment process” after pre-stretching.

  That is, in the heat shrinking execution part 23, the heat shrinking process for angle adjustment is performed on the polymer film f stretched in the direction inclined with respect to the traveling direction in the pre-stretching execution part 22 (the pre-stretching is completed). Is to do. As a result, the orientation of the polymer film f is set to the intended inclination angle of the orientation axis (20 degrees or more and less than 70 degrees, for example, 45 degrees with respect to the width direction).

  Specifically, the polymer film f is first heated and contracted by the heating furnace 30. At this time, the gripping members 26 gripping both end portions are moved toward each other, and the interval is narrowed from both sides toward the center in the width direction in accordance with the amount of thermal shrinkage of the polymer film f. Thus, the angle is adjusted so that the orientation axis of the polymer film f is an inclination angle of the intended orientation axis (20 degrees or more and less than 70 degrees, for example, 45 degrees).

  When the orientation axis of the polymer film f reaches the target inclination angle, the gripping members 26 gripping both end portions finish moving in the direction approaching each other. The gripping member 26 travels to the winding roll 28 side while maintaining the distance in the width direction of the polymer film f.

  Subsequently, the gripping member 26 opens the polymer film f before the winding roll 28. And the process of inclining the orientation axis | shaft of the polymer film f is complete | finished when the roll 28 for winding winds up the open | released polymer film f. That is, the production of the stretched film is completed. In addition, the stretched film wound up is sent to the next step (for example, a step such as cutting).

  Here, when the “pre-stretching step” and the “angle adjusting step” are continuously performed as in the second embodiment, it is necessary to confirm in advance whether the orientation angle becomes a predetermined angle in the “pre-stretching step”. There is. That is, unlike the first embodiment, since there is no step of collecting the polymer film f after the “pre-stretching step”, the pre-stretching step has a predetermined orientation angle during the trial operation of the stretching machine. It is necessary to manufacture a stretched film after confirming whether it becomes.

As a method of confirming the orientation angle in the “pre-stretching step”, for example, a method of using a tenter stretching machine capable of changing the rail width can be considered. If it demonstrates concretely, first, the extending | stretching machine 21 of FIG. 2 will be made into FIG. 8 at the time of a test run. That is, the rails 29 in the thermal contraction execution unit 23 of the stretching machine 21 are set at equal intervals. Then, only a “pre-stretching step” is performed on the polymer film f by performing a trial run with the stretching machine 21. At this time, the orientation angle of the “pre-stretching step” is confirmed by conveying the polymer film f to the outside of the stretching machine 21 and measuring the orientation angle.
When it is confirmed that the predetermined orientation angle is obtained in the “pre-stretching step”, the rails 29a and 29b are gradually inclined from the both end sides toward the center side in the width direction in the front portion of the heat shrinking portion 23. Let That is, the same state as that of the stretching machine 21 in FIG. And the stretched film of 2nd Embodiment mentioned above is manufactured. According to this method, the stretched film can be produced after confirming the angle of the “pre-stretching step”.

  As another method, a method of temporarily stopping the stretching machine is also conceivable. That is, the stretching machine 21 of FIG. 2 is temporarily stopped, and the polymer film f is cut out at the front portion (the portion from the pre-stretching execution portion 22) of the heat shrinking execution portion 23 to confirm the orientation angle.

  Each stretching machine used in each of the above-described embodiments is not particularly limited, and an appropriate stretching machine such as a tenter type, a pantograph type, or a linear motor type can be used.

  In the “pre-stretching step” in each of the embodiments described above, the volatile content of the film is preferably less than 5% (percent), more preferably less than 3% (percent).

  In the second embodiment described above, both ends of the polymer film f were uniformly shrunk in the width direction during the “angle adjustment step”. However, if the holding interval at both ends can be reduced, the shrinking method can be reduced to this. It is not limited. For example, it may be contracted only from one end side as shown in FIG. However, it is preferable to shrink both ends evenly from the viewpoint of reducing the characteristic variation in the width direction of the polymer film f.

In each of the embodiments described above, the angle adjustment by the heat shrinkage process (“angle adjustment process”) is performed by controlling the shrinkage rate when shrinking in the width direction, temperature change, time for performing the shrinkage process, and the like. . Accordingly, these are appropriately changed according to the inclination angle of the target orientation axis.
However, if the polymer film is stretched in the longitudinal direction (longitudinal stretching) when heat shrinking in the width direction, the stretched film to be produced will exhibit high biaxiality. preferable.

  In addition, the thickness of the polymer film f of each embodiment described above is not particularly limited. The thickness of the polymer film f can be appropriately determined according to the purpose of use of the stretched film to be produced. However, from the viewpoint of stabilizing the heat shrinkage treatment and producing a stretched film of uniform quality, it is preferably 3 mm or less, more preferably 1 μm to 1 mm, and even more preferably 5 μm to 500 μm.

The stretched film produced by the present invention is not particularly limited, and may be, for example, a plastic film.
Moreover, the length in the longitudinal direction and the length of the width of the stretched film produced according to the present invention are not particularly limited, and may be an appropriate length.
For example, a long plastic film may be continuously stretched with the appropriate stretching machine described above for the purpose of improving production efficiency and efficiently bonding to a long polarizing plate or the like.

The use of the stretched film manufactured by this invention is not specifically limited, It can be used for an appropriate use. However, it can be suitably used for a retardation plate or the like from the viewpoint that the orientation axis is inclined in an oblique direction. More specifically, the tilt angle of the orientation axis is 20 to 70 degrees, and the following formula (1):
0.5 ≦ (nx−nz) / (nx−ny) ≦ 2 (1)
[Nx indicates the refractive index in the slow axis direction of the retardation film, where the slow axis direction indicates the direction in which the refractive index in the retardation film surface is maximized, and ny indicates the phase advance of the retardation film. The refractive index in the axial direction is shown, and nz is the refractive index in the thickness direction of the retardation film. ]
It is preferable to produce a stretched film that satisfies the above relationship and use it as a retardation plate.
Further, the retardation plate preferably has a retardation value measured at a wavelength of 590 nm satisfying 10 to 1000 nm, more preferably 100 to 170 nm or 220 to 290 nm.

  Such a retardation plate can be used for various purposes such as adjustment of birefringence characteristics in a liquid crystal display device, prevention of coloring due to a change in viewing angle, and expansion of a viewing angle. It can also be used to form various optical materials such as an elliptically polarizing plate and a circularly polarizing plate by bonding with a polarizing plate.

Moreover, when using the stretched film manufactured by this invention for a phase difference plate, it is possible to use the superimposition body of the stretched film which piled up the some stretched film as a phase difference plate.
In this case, the number of stretched films to be superimposed is arbitrary, but 2 to 5 is preferable from the viewpoint of light transmittance and the like.
Moreover, the combination of the stretched films to be superposed can be appropriately changed, and the tilt angle, the raw material, the phase difference, etc. of the superposed stretched films may be the same or different. These may be changed as appropriate.

  When the stretched film of the present invention is used as a retardation plate, a stretched film having excellent transparency such as polyolefin such as polycarbonate and cyclic olefin, polysulfone, cellulose acetate, polyvinyl chloride, polymethyl methacrylate, etc. is used. It is preferable. The thickness of the retardation plate may be arbitrarily determined depending on the phase difference according to the purpose of use, but is preferably 1 mm or less, more preferably 1 μm to 500 μm, and even more preferably 5 μm to 300 μm. It is desirable that the thickness be

In the case where a superposed body is formed by overlapping stretched films as described above, or when a retardation plate (stretched film) and a polarizing plate are bonded, suppression of reflection by adjusting the refractive index between layers and prevention of deviation of the optical system, From the viewpoint of preventing entry of foreign matter such as dust, it is preferable that the stretched film or between the retardation plate and the polarizing plate is fixed.
In addition, the adhesive material used for the fixing process is not particularly limited, and for example, a transparent adhesive material can be suitably used. Moreover, a pressure-sensitive adhesive can be suitably used from the viewpoint of preventing changes in optical properties.

  Furthermore, the stretched film (retardation plate) manufactured by the present invention is treated with an ultraviolet absorber such as a salicylic acid ester compound, a benzophenol compound, a benzotriazole compound, a cyanoacrylate compound, or a nickel complex compound. It may be provided with an ultraviolet absorbing ability such as those made.

The present invention will be specifically described with reference to examples and comparative examples, but the present invention is not limited to the examples.
In addition, the measurement methods of various physical properties and optical properties employed in this example are as follows.

(1) Measurement of retardation, Nz coefficient, and tilt angle of orientation axis Using a retardation film inspection apparatus RETS manufactured by Otsuka Electronics, the width direction was measured at a measurement wavelength of 590 nm at intervals of 5 cm. Moreover, the inclination angle at the time of Nz measurement was measured at 45 °. Re, Nz, and the tilt angle of the alignment axis were average values.
Nz = (nx-nz) / (nx-ny)
[Nx indicates the refractive index in the slow axis direction of the retardation film, where the slow axis direction indicates the direction in which the refractive index in the retardation film surface is maximized, and ny indicates the phase advance of the retardation film. The refractive index in the axial direction is shown, and nz is the refractive index in the thickness direction of the retardation film. ]

(2) Thickness Anritsu Co., Ltd. stylus type thickness gauge KG601A was used, and the thickness in the width direction was measured at 1 mm intervals. The average value obtained was taken as the thickness.

[Example 1]
A polycarbonate film (Elmec R-film non-stretched product manufactured by Kaneka Corporation) was introduced into a stretching machine according to the pre-stretching machine 2 in FIG. 1, the retardation measured at a wavelength of 590 nm was 570 nm, and the orientation axis was in the width direction. A polycarbonate film having a thickness of 40 μm and a width of 1000 mm inclined by 6 degrees was obtained. Then, the polycarbonate film is introduced into a tenter stretching machine according to the angle-adjusting heat shrinking machine 3 of FIG. 1 and heated to 160 ° C. to uniformly narrow the widthwise distance between the grippers at both ends. The film was subjected to 40% shrinkage treatment to obtain a stretched film. Next, the properties of the stretched film were measured using a retardation film inspection apparatus RETS manufactured by Otsuka Electronics. As a result, the retardation measured at a wavelength of 590 nm was 69 to 71 nm, and the tilt angle of the alignment axis with respect to the width direction was 44 to 46 degrees. (Nx−nz) / (nx−ny) where the refractive index nx in the in-plane slow axis direction, the refractive index ny in the direction perpendicular to the in-plane slow axis, and the refractive index nz in the thickness direction Was 1.0 to 1.1.

[Example 2]
A polycarbonate film whose orientation axis is tilted by 6 degrees with respect to the width direction is heated to 160 ° C., and the width direction distance between the grippers at both ends is uniformly narrowed to perform a shrinkage treatment of 35% in the width direction. A film was obtained. That is, a stretched film was obtained according to Example 1 except that the shrinkage rate was 35%. As a result of measuring the stretched film characteristics, the retardation measured at a wavelength of 590 nm was 119 to 122 nm, the tilt angle of the orientation axis with respect to the width direction was 26 to 29 degrees, the in-plane slow axis direction refractive index nx, and in-plane The refractive index ny in the direction perpendicular to the slow axis and the refractive index nz in the thickness direction were (nx−nz) / (nx−ny) of 1.4 to 1.5.

Example 3
A polycarbonate film whose orientation axis is tilted by 6 degrees with respect to the width direction is heated to 160 ° C., and the width direction distance between the grippers at both ends is narrowed only on one side, so that a 40% contraction treatment is applied in the width direction. A film was obtained. That is, a stretched film was obtained in the same manner as in Example 1 except that the distance in the width direction between the grips at both ends was narrowed only on one side. As a result of measuring the stretched film characteristics, the retardation measured at a wavelength of 590 nm was 67 to 74 nm, the tilt angle of the orientation axis with respect to the width direction was 42 to 47 degrees, the in-plane slow axis direction refractive index nx, and the in-plane The refractive index ny in the direction perpendicular to the slow axis and the refractive index nz in the thickness direction were (nx−nz) / (nx−ny) of 0.9 to 1.1.

[Comparative Example 1]
A stretched film was obtained according to Example 1 except that the shrinkage rate was 0%. As a result of measuring the stretched film characteristics, the retardation measured at a wavelength of 590 nm was 540 to 550 nm, the tilt angle of the orientation axis with respect to the width direction was 6 degrees, the refractive index nx in the in-plane slow axis direction, the in-plane slow phase The refractive index ny in the direction perpendicular to the axis and the refractive index nz in the thickness direction were (nx−nz) / (nx−ny) was 1.5.

[Comparative Example 2]
A stretched film was obtained according to Example 1 except that a polycarbonate film having an orientation axis not inclined with respect to the width direction, that is, an orientation axis of 0 degree was used. As a result of measuring the stretched film characteristics, the retardation measured at a wavelength of 590 nm was 88 to 92 nm, the tilt angle of the orientation axis with respect to the width direction was 0 to 1 degree, the in-plane slow axis direction refractive index nx, and the in-plane When the refractive index ny in the direction perpendicular to the slow axis and the refractive index nz in the thickness direction were (nx−nz) / (nx−ny) was 1.1.

[Comparative Example 3]
By using a stretching machine 40 shown in FIG. 7, a polycarbonate film having a thickness of 40 μm and a width of 1000 mm with a retardation measured at a wavelength of 590 nm of 570 nm and an orientation axis inclined by 6 degrees with respect to the width direction was obtained. And the polycarbonate film was heated at 150 degreeC, and it introduced into the longitudinal stretch machine 41 by the roll peripheral speed difference, and stretched 5% in the longitudinal direction, and obtained the stretched film. As a result of measuring the characteristics of this stretched film, the retardation measured at a wavelength of 590 nm was 57 to 71 nm, the inclination angle of the orientation axis with respect to the width direction was 44 to 46 degrees, the in-plane slow axis direction refractive index nx, and in-plane (Nx−nz) / (nx−ny) was 7.0 to 7.3 when the refractive index ny in the direction perpendicular to the slow axis and the refractive index nz in the thickness direction were taken.

DESCRIPTION OF SYMBOLS 1 Stretching machine 2 Pre-stretching stretching machine 3 Angle adjustment heat shrink machine 4 Angle adjustment heat shrink machine 6 Gripping member 8 Pull-out roll 9 Winding roll f Polymer film

  The present invention relates to a stretched film and a method for producing a stretched film, and in particular, a stretched film having a molecular orientation axis that is inclined with respect to any side of the film and having excellent optical properties, and a method for producing the stretched film It is about. Moreover, this invention relates to the phase difference plate formed with such a stretched film.

  In recent years, liquid crystal display devices typified by monitors (displays) for personal computers and television receivers have been widely used as various display means. In these liquid crystal display devices, a technique for improving display visibility by arranging polarizers on both sides of a liquid crystal cell and further providing a retardation film between the liquid crystal cell and the polarizer is known.

Here, the retardation film is formed into a rectangular shape in accordance with the shape of the liquid crystal display device. Moreover, as a property of the retardation film used in the liquid crystal display device, it may be required that the molecules are oriented in an oblique direction with respect to each side of the rectangle.
Such a film which is molecularly oriented in an oblique direction with respect to each side of the rectangle has been conventionally manufactured by the following process.
That is, in the prior art, first, a polymer film is uniaxially stretched in the longitudinal direction or a direction perpendicular to the longitudinal direction (hereinafter referred to as the width direction) to produce a stretched film in which molecular orientation is caused. In the stretched film produced by this process, the molecular orientation axis is parallel to one side of the film and perpendicular to the other side.

Then, as the next step, each side of the film is cut obliquely to form a rectangular film.
More specifically, a stretched film that has been uniaxially stretched to cause molecular orientation is punched obliquely to make a small rectangular film. This rectangular film apparently has an orientation axis inclined with respect to each side.

However, in this method, since the polymer film is punched at an inclination with respect to the longitudinal direction, a large amount of unusable portions are generated at the end portions in the width direction of the polymer film, and the yield of the film is poor.
Therefore, there has been a demand for a method for producing a stretched film having a high yield that can be used up to the vicinity of the end in the width direction by molecularly orienting in the oblique direction at the stage of stretching the polymer film. Examples of such methods include the inventions disclosed in Patent Documents 1 to 4. First, Patent Document 1 will be described.

FIG. 6 is a reproduction of the drawing disclosed in Patent Document 1. However, the text is added for ease of explanation.
In the invention disclosed in Patent Document 1, when both ends of a film (polymer film) are held and advanced in the longitudinal direction, the distance L2 from the holding start point 108 at one end to the holding release point 109 is set at the other end. This is longer than the distance L1 from the holding start point to the holding release point. As a result, when the film is advanced in the longitudinal direction, the holding position at both ends having the same position in the longitudinal direction (traveling direction) at the start, the holding position at one end is in the traveling direction relative to the holding position at the other end It will shift to the rear side. Therefore, the holding position of the other end is pulled to the rear side in the traveling direction, and the film can be stretched in an oblique direction.

In the invention disclosed in Patent Document 1, in order to increase the difference between the distance L1 from the holding start point at one end to the holding release point and the distance L2 from the holding start point at the other end to the holding release point, FIG. Like this, one of the tenter's roads is largely detoured.
More specifically, the tenter shown in FIG. 6 has a pair of rails 100 and 101, to which clips (not shown) are respectively fixed. And the edge part of a film is hold | maintained with the said clip, and a clip is moved to a running direction with the run of a rail.

Here, in a general tenter, the total length of the pair of rails 100 and 101 is the same, but in Patent Document 1, the total length of the rails 100 and 101 is different. That is, as shown in FIG. 6, a large detour portion 103 is provided on one rail 101, and this detour portion 103 provides a large difference between the distances L <b> 1 and L <b> 2.
More specifically, in the introduction part of the tenter, as shown in FIG. 6, the traveling paths of the rails 100 and 101 are both straight, and the rails 100 and 101 are parallel.
After passing through the introduction part, one rail 100 continues to travel linearly, while the other rail 101 largely detours in a curve. This area functions as an extension area.
When the rail 101 passes the detour 103, the rail 101 travels in a straight line direction and travels in parallel with one rail 100.
When the film is stretched by the tenter shown in FIG. 6, the film is stretched in an oblique direction in the stretching area where the detour portion 103 is provided.
After passing the detour portion 103, the stretching does not proceed any further and the orientation direction is stabilized. That is, according to Patent Document 1, only the bypass portion 103 tilts the orientation axis of the film, and the tilt angle of the orientation axis does not change after the bypass portion 103. Thus, in the invention disclosed in Patent Document 1, the orientation axis of the film is inclined only by the action of stretching the film in an oblique direction.

However, there may be a case where the retardation film has an inclination angle of the orientation axis of about 45 degrees with respect to the width direction. In order to obtain such a large orientation angle, it is necessary to enlarge the bypass portion 103 to provide a large difference between the distances L1 and L2 and to stretch the retardation film obliquely in the direction of substantially 45 degrees at the bypass portion 103. .
However, there is a problem that wrinkles occur in the film when the bypass portion 103 is enlarged to an extent that the film is substantially obliquely stretched in the 45 ° direction and the distances L1 and L2 are increased.
Therefore, in the invention disclosed in Patent Document 1, the film is impregnated with a solvent in advance, and in this state, the film is stretched in an oblique direction in the stretching area having the bypass 103, and then the solvent is volatilized to volatilize the film. I'm going to take firewood.
That is, as described above, the tenter has an introduction portion where the rails 100 and 101 travel in parallel, an extension area where one rail 101 bypasses, and a volatile evaporation area where the rails 100 and 101 travel again in parallel. ing. In the invention disclosed in Patent Document 1, the film is stretched obliquely in the stretching area having the bypass 103 to provide an inclination angle of the orientation axis, and the film is heated to travel the solvent in the volatile component evaporation area. Volatilizes and stretches the film.
That is, the orientation axis of the film is tilted to a desired angle in the stretching area having the detour 103, and the subsequent volatile component evaporation area simply takes a wrinkle, and the tilt angle of the orientation axis of the film does not change.
Thus, in the invention disclosed in Patent Document 1, the orientation axis is inclined only by stretching the film in an oblique direction.

  In addition, the invention disclosed in Patent Document 2 is uniaxially stretching the film in the transverse or longitudinal direction, and by stretching the film in the longitudinal or transverse direction different from the stretching direction at different speeds on the left and right of the stretching direction, The orientation axis is inclined with respect to the uniaxial stretching direction.

  Furthermore, the invention disclosed in Patent Document 3 grips both ends in the width direction of the film by the gripping means, makes the travel distance of the gripping means different at both ends in the width direction, and changes the traveling direction of the film in the middle. The orientation axis of the film is inclined with respect to the width direction.

  The invention disclosed in Patent Document 4 changes the expansion / contraction ratio by regulating stretching or shrinking in the tilting direction (longitudinal direction) after regulating stretching or shrinking of the film in the transport direction (or tilting direction). Thus, the direction in which the film expands and contracts is changed to adjust the orientation angle of the film.

JP 2002-086554 A JP 2000-009912 A JP 2007-090532 A JP 2007-030466 A

However, according to the method of Patent Document 1, a large burden is applied to the film when passing through the detour path 103, and stress may be applied to the film in a direction other than the desired stretching direction. Therefore, the quality of the manufactured film may vary, or the film may be partially stretched in a direction other than the desired direction.
That is, in the invention disclosed in Patent Document 1, the film is stretched in an oblique direction exclusively in the stretching area having the bypass 103, and the orientation axis is inclined to a desired angle only by the action of stretching in the oblique direction. For this reason, a strong force acts on the film during stretching, and stress in the shrinking direction acts on the film in the direction perpendicular to the stretching direction. For example, the quality of the film varies or the film is partially stretched in a direction other than the desired direction. There is a case.

Further, as pointed out in Patent Document 1, if the film is stretched strongly in an oblique direction, wrinkles are generated in the film. Although the wrinkle is somewhat improved by the measure of Patent Document 1, the measure of Patent Document 1 is merely to extend the wrinkle once generated, and it cannot be denied that the quality is deteriorated due to the occurrence of the wrinkle.
In addition, since the method disclosed in Patent Document 1 contains a large amount of volatile components, a large amount of equipment is required such as a dipping tank in which water or a solvent is immersed.
Furthermore, since the method disclosed in Patent Document 1 requires a step of evaporating the solvent, an exhaust facility for exhausting the solvent and a protective measure for preventing solvent poisoning are necessary.

  In the method of Patent Document 2, there is a problem that a desired inclination angle (for example, 45 degrees) of the orientation axis cannot be obtained due to the occurrence of a wrinkle or a film shift on the film due to the difference in the conveyance speed between the left and right. .

  Further, according to the method of Patent Document 3, there is a problem that the equipment becomes large in order to change the film traveling direction, and the equipment cost increases.

And according to the method of patent document 4, when the produced stretched film is used as a phase difference film, there exists a problem that biaxiality will become very high. That is, the refractive index nx in the slow axis direction in the plane of the stretched film, the refractive index ny in the direction perpendicular to the slow axis in the plane, and the refractive index nz in the thickness direction are required for a general retardation plate as follows. Formula (1):
0.5 ≦ (nx−nz) / (nx−ny) ≦ 2 (1)
There is a problem that the relationship cannot be satisfied.

  Therefore, the present invention pays attention to the above-mentioned problems of the prior art, and the tilt angle of the orientation axis of the molecules of the stretched film can be changed variously, can be produced with simple equipment, and can produce a stretched film with more stable quality. It is an object to provide a method.

  The invention according to claim 1 for solving the above-mentioned problems is a long film, and is a pre-stretched film pre-stretched so that the inclination angle of the orientation axis is not less than 5 degrees and less than 20 degrees with respect to the width direction. This is a method for producing a stretched film, characterized in that both ends in the width direction are held, and the pre-stretched film is heated and thermally contracted to gradually narrow the holding interval between the both ends.

The present invention includes a pre-stretching step of inclining the orientation axis at a gentler angle before tilting the orientation axis to the target angle by heat shrinkage.
As a result, it is possible to share the burden on the polymer film when changing the orientation axis. Therefore, the orientation axis can be tilted to a larger angle than when the polymer film orientation axis is rapidly tilted at once. In addition, since the properties of the polymer film can be changed in stages, it is easy to make the quality of the produced stretched film uniform.
Furthermore, in the present invention, the polymer film is thermally contracted to make the inclination angle of the orientation axis steep.
Hereinafter, this principle will be described.
For example, a film 105 that is stretched in the width direction as shown in FIG. 4 and has no tilt angle in the orientation axis (arrow) is used, and this width W is changed from FIG. 4A to FIG. ), The inclination angle of the molecular orientation axis does not change at all as shown in FIG.
However, a film 106 stretched in the width direction as shown in FIG. 5 and having an orientation axis (arrow) slightly inclined is used, and the width W of this film 106 is determined from FIG. Assuming the case of contraction as shown in FIG. 5B, the inclination angle A of the orientation axis becomes a steep angle as shown in FIG.
That is, the initial inclination direction of the film 106 is a direction illustrated by arrows ab, cd, ef... In FIG.
For example, when the points a, b, c, d,... In FIG. 5A are held and the width W of the film 106 is reduced, the points a, b, c in FIG. Since the position in the longitudinal direction of points d,... Does not change, the direction of the orientation axis becomes a lying direction and the inclination angle A becomes steep as shown in FIG.
Therefore, holding the both ends in the width direction of the pre-stretched film pre-stretched at a small tilt angle, and gradually shrinking the holding interval between the both ends while heating and pre-shrinking the pre-stretched film, the tilt of the orientation axis The angle changes to a steep slope. And the stretched film in which the orientation axis inclined to a desired inclination angle can be obtained by adjusting the holding interval at both ends of the film.

  Invention of Claim 2 formed the process of forming a pre-stretched film by extending | stretching the inclination-angle of an orientation axis | shaft to 5 to 20 degree | times with respect to the width direction with respect to a elongate film. The method for producing a stretched film according to claim 1, wherein the prestretched film is heated and thermally contracted, and the step of gradually narrowing the holding interval at both ends is continuously performed. .

  The present invention heat shrinks immediately after forming a pre-stretched film. If it does in this way, since the time concerning stretched film manufacture can be shortened, efficiency improvement of a manufacturing operation can be aimed at.

  The invention according to claim 3 is characterized in that the both ends of the pre-stretched film are evenly moved with respect to the center line in the width direction when the holding interval between the both ends is gradually narrowed while being thermally contracted. Item 3. A method for producing a stretched film according to Item 1 or 2.

  In the present invention, variation in various characteristics in the width direction of the stretched film can be reduced by causing heat shrinkage evenly with respect to the center line in the width direction.

  Invention of Claim 4 makes the inclination with respect to the width direction of the molecular orientation axis | shaft of a pre-stretched film 20 degrees or more and less than 70 degrees by heating and heat-shrinking a pre-stretched film. It is a manufacturing method of the stretched film in any one of thru | or 3.

  According to the present invention, a stretched film having a molecular orientation axis greatly inclined with respect to the width direction can be produced.

  The invention according to claim 5 is a stretched film according to any one of claims 1 to 4, wherein the prestretched film is heated and thermally contracted by a tenter type stretching machine capable of adjusting expansion and contraction in the width direction. It is a manufacturing method.

  In this invention, even if it uses the tenter-type extending | stretching machine in which the expansion / contraction adjustment of the width direction is possible, it can implement suitably.

  Invention of Claim 6 is a stretched film manufactured by the manufacturing method of the stretched film in any one of Claims 1 thru | or 5, Comprising: The inclination-angle of the orientation axis with respect to the width direction of a stretched film is from 20 degree | times. It is a stretched film characterized by being larger than 70 degrees.

The invention according to claim 7 is a stretched film produced by the method for producing a stretched film according to any one of claims 1 to 5, wherein the refractive index nx in the slow axis direction in the plane of the stretched film. The refractive index ny in the direction perpendicular to the in-plane slow axis and the refractive index nz in the thickness direction are expressed by the following formula (1):
0.5 ≦ (nx−nz) / (nx−ny) ≦ 2 (1)
It is a stretched film characterized by satisfying

  The stretched film of this invention is formed by the manufacturing method of the stretched film in any one of Claims 1 thru | or 5. Therefore, a stretched film having an orientation axis greatly inclined with respect to the width direction and a stretched film having excellent optical properties can be provided.

  The invention according to claim 8 is a retardation plate characterized by being formed by including at least one stretched film according to claim 6 or 7.

  The stretched film produced according to the present invention can be used as a phase difference plate by being overlaid.

  The present invention has an effect that the tilt angle of the orientation axis can be changed without imposing an excessive burden on the polymer film. Therefore, there is an effect that the inclination angle of the alignment axis can be increased. In addition, there is an effect that it is easy to make the quality of the produced stretched film uniform.

It is a top view which shows an example of the film extending machine which can be used for the manufacturing method of the phase difference film of this invention. It is a top view which shows an example of the film extending machine which can be used for the manufacturing method of the retardation film of this invention different from FIG. It is a top view which shows an example of the film extending machine which can be used for the manufacturing method of the retardation film of this invention different from FIG. 1, FIG. It is explanatory drawing which shows the change of the orientation axis at the time of shrinking | stretching the polymer film uniaxially stretched in the width direction, (a) shows the polymer film before shrinkage | contraction, (b) shows the polymer film after shrinkage | contraction. . It is explanatory drawing which shows the change of the orientation axis | shaft at the time of shrinking | stretching the polymer film extended in the direction which inclines in the width direction, (a) shows the polymer film before shrinkage, (b) is the polymer after shrinkage | contraction The film is shown. It is a schematic plan view which shows the conventional extending | stretching machine. 10 is a plan view showing an example of a film stretching machine that can be used in Comparative Example 3. FIG. It is a top view which shows an example of the state at the time of the trial run of the extending | stretching machine of FIG.

  Hereinafter, although embodiment of this invention is described in detail, this invention is not limited to these examples.

  In the present invention, the polymer film (thermoplastic resin film) that is a material of the stretched film is not particularly limited to the raw material resin, and a film made of an appropriate thermoplastic resin is appropriately selected according to the purpose. Specific examples include cellulose acetate, polyester, polysulfone, polyethersulfone, polystyrene, polyvinyl alcohol, polyvinyl chloride, polymethyl methacrylate, polyarylate and polyamide. More preferably, it is preferable to use a polycarbonate and a cyclic olefin resin.

The method for producing a stretched film according to the first embodiment of the present invention basically conveys a long polymer film f that is continuously supplied while holding (holding) the film, and conveys the polymer film f. It is the method of extending | stretching in the direction which inclines with respect to the conveyance direction. The following three steps are included as characteristic steps.
(1) A step (hereinafter referred to as a pre-stretching step) in which a tilt angle (5 degrees or more and less than 20 degrees) is more gently inclined than an inclination angle of the target orientation axis (20 degrees or more and less than 70 degrees, for example, 45 degrees).
(2) A step of winding a stretched film (pre-stretched film) whose orientation axis is gently inclined through a pre-stretching step (hereinafter referred to as a temporary winding step).
(3) A step of performing heat shrinkage treatment for angle adjustment on the wound stretched film (hereinafter referred to as angle adjustment step).
The example which manufactures a stretched film using the stretched film manufacturing apparatus 1 of FIG. 1 about the 1st Embodiment of this invention is demonstrated below. However, as a matter of course, it is not essential to use the stretched film manufacturing apparatus 1 of FIG. 1 in the present invention.

  The stretched film manufacturing apparatus 1 in FIG. 1A is roughly composed of a pre-stretching stretching machine 2 and an angle adjusting heat shrinking machine 3.

The pre-drawing drawing machine 2 is a conventionally known drawing machine, and substantially the same drawing machine as disclosed in Patent Document 1 can be used. In addition, a substantially similar one to the oblique stretching machine disclosed in Patent Document 4 can be used. Note that the pre-stretching stretcher 2 used in this embodiment has a smaller difference in distance from the holding start point at both ends to the holding release point than the stretching device disclosed in Patent Document 1, and the angle at which the film is stretched Was small.
Specifically, the pre-drawing drawing machine 2 includes at least a gripping member 6, a drawing roll 8, a winding roll 9, and a rail 10. Then, the polymer film f attached to the drawer roll 8 is pulled out, the both ends of the film f are gripped by the gripping members 6 and run toward the winding roll 9, and the polymer film is in front of the winding roll 9. f is opened and wound up by a winding roll 9.

Here, the gripping member 6 travels on the rail 10 integrally with a chain (not shown) while gripping both ends of the polymer film f pulled out from the pulling roll 8. Here, the rail 10 is composed of a pair of rails 10a and 10b, and the gripping members 6 travel on the rails 10a and 10b, respectively.
And the path | route which the grip member 6 which hold | gripped the one-side edge part travels is longer than the path | route which the grip member 6 which hold | gripped the other end part travels. That is, the rail 10b takes a detour path with respect to the rail 10a on one side. The speed at which the gripping member 6 travels on the rail is substantially the same at both ends.

That is, the pre-drawing drawing machine 2 is divided into three continuous areas A, B, and C from the drawing roll 8 side to the winding roll 9 side as shown in FIG. The width of the rail 10 is different in each area.
In area A, the widths of the rails 10a and 10b are equally spaced. In area B, the rail on one side (rail 10b) detours, and in area C, the rails 10a travel again at equal intervals. In both areas A and C, the rails are equally spaced, but the rail 10 in area C is wider than area A.
In addition, the pre-drawing drawing machine 2 may have a configuration in which a heating furnace is provided. In that case, the heating furnace is preferably installed from the A area to the B area.

The angle adjusting heat shrinking machine 3 includes at least a gripping member 11, a drawing roll 12, a winding roll 13 rail 14, and a heating furnace 15. Then, the polymer film f attached to the drawer roll 12 is pulled out, and both ends of the polymer film f are gripped by the gripping member 11, and then run toward the winding roll 13 and wound up by the winding roll 13. It is.
Here, the gripping member 11 travels on the rail 14 and travels by gripping both ends of the polymer film f drawn from the pulling roll 12. Here, the rail 14 is composed of a pair of rails 14a and 14b, and the gripping members 11 travel on the rails 14a and 14b, respectively.
The gripping members 11 at both ends of the polymer film f are moved closer to each other as they approach the take-up roll 13, thereby approaching the distance in the width direction. That is, the distance between the rail 14 a and the rail 14 b is narrowed from the pulling roll 12 side toward the winding roll 13.

More specifically, the angle adjusting heat shrinking machine 3 is divided into three continuous areas D, E, and F from the drawing roll 12 side toward the winding roll 13 side. And the width of a rail differs in each area. That is, first, in the area D, the widths of the rails 14 are equally spaced. Next, in the area E, the rail 14a and the rail 14b gradually incline toward the center in the width direction as the traveling direction proceeds, and the width of the rail becomes narrower. In the area F, the widths of the rails 14 are again equally spaced.
Here, the widths of the rails 14 in the areas D and F are equally spaced, but the width of the rails 14 in the area F is narrower than that in the area D. In addition, in the area E, the rails 14 at both ends are inclined toward the center in the width direction, but the inclination start point and the inclination end point in the traveling direction, and the inclination angle with respect to the traveling direction are the same. . Therefore, the rails 14 are arranged symmetrically in the width direction along the traveling direction.

  The heating furnace 15 is provided across the areas D to F, and heats the polymer film f with hot air.

Next, the example which manufactures a stretched film using the above-mentioned stretching machine 1 is demonstrated.
First, a long polymer film f is attached to the drawer roll 8 in a roll shape. Then, in the area A, the polymer film f is caused to travel toward the take-up roll 9 using a transport device such as a roll (not shown).
When the polymer film f is caused to travel a certain distance to the winding roll 9 side, the polymer film f is gripped by the gripping members 6 at both ends in the width direction. Then, the polymer film f is continuously run toward the winding roll 9 side.

Next, when the polymer film f enters the area B, the “pre-stretching step” is started. Specifically, the gripping member 6 gripping one end portion moves in a direction away from the gripping member 6 gripping the other end portion. That is, one gripping member 6 advances straight to the winding roll 9 side, and the other gripping member 6 advances to the winding roll 9 side while increasing the width of the polymer film f. In other words, one gripping member 6 is skewed with respect to the traveling direction.
As a result, the stretching direction of the polymer film f that has been stretched perpendicular to the running direction is inclined from the perpendicular to the running direction, so that the polymer film f has a gentle orientation angle. That is, the orientation axis of the polymer film f is inclined with respect to the width direction more gently (5 degrees or more and less than 20 degrees) than the intended inclination angle (20 degrees or more and less than 70 degrees, for example, 45 degrees). .
Further, as the distance between the gripping members 6 at the opposite ends in the area A (the width direction of the polymer film f is equal) increases, the force for stretching the polymer film f also increases. It gets bigger. Then, the force for stretching the polymer film f increases and the retardation value increases. Then, the “pre-stretching step” ends.

  Here, in the present embodiment, the tilt angle of the alignment axis is set to a gentler angle than the target tilt angle of the alignment axis by the “pre-stretching step” in area B. Then, in the “angle adjustment step” described later, the tilt angle of the alignment axis is set as the target tilt angle of the alignment axis. Thus, by providing a step that makes the orientation axis a gentler angle than the target angle before tilting the orientation axis to the target tilt angle, compared to the stretching method that makes the target tilt angle at one time, The tilt angle of the orientation axis can be tilted without sharply tilting the orientation axis of the polymer film f. As a result, there is an advantage that problems such as slipping (streaky unevenness resulting from uneven tensile stress), wrinkles, and film deviation (local thickness unevenness) are unlikely to occur.

  Finally, the polymer film f enters the area C, travels toward the take-up roll 9 without changing the length in the width direction, and is taken up by the take-up roll 9. This completes the “temporary winding process”.

Next, the pre-stretched polymer film f (taken up by the take-up roll 9) is attached to the drawer roll 12 of the angle adjusting heat shrink machine 3.
In the area D, the polymer film f is caused to travel toward the take-up roll 13 using a transport device such as a roll (not shown).
When the polymer film f is caused to travel a certain distance toward the winding roll 13, the polymer film f is gripped by the gripping members 11 at both ends in the width direction. Then, the polymer film f continues to run toward the winding roll 13 side.

Next, when the polymer film f enters the area E, the gripping members 6 gripping both end portions move in a direction approaching each other. At this time, the polymer film f is thermally shrunk by performing a heat treatment. In other words, the polymer film f is heated by the heating furnace 15 to be thermally contracted, and the polymer film f is oriented by narrowing the interval from both sides in accordance with the shrinkage of the heat shrink toward the center in the width direction. The angle of the shaft is adjusted.
This completes the “angle adjustment process”.

  Finally, the polymer film f enters the area F. In the area F, the polymer film f travels toward the take-up roll 13 without changing the length in the width direction, and is taken up by the take-up roll 13. With this, all the steps of tilting the orientation axis with respect to the polymer film f are completed, and the production of the stretched film is completed. In addition, the stretched film wound up is sent to the next step (for example, a step such as cutting).

In the above-described embodiment, the pre-stretching machine 2 is used to perform pre-stretching (stretching in which the polymer film is previously oriented in an angle direction slightly oblique to the width direction). The stretching machine is not limited to this. The method and stretching machine used for pre-stretching are not particularly limited as long as the orientation axis is inclined by 5 degrees or more with respect to the width direction of the film, and known methods and stretching machines can be adopted.
When the tilt angle of the orientation axis of the film before heat shrinkage is less than 5 degrees, when the tilt angle of the orientation axis is adjusted to a range of 20 to 70 degrees, significant shrinkage is required in the width direction. In the present invention, it is not preferable in the present invention.

Next, a second embodiment of the present invention will be described. The method for producing the stretched film of the second embodiment of the present invention includes the “pre-stretching step” and the “angle adjusting step” performed in the first embodiment, and these are continuously performed. It is.
Hereinafter, an example of producing a stretched film using the stretching machine 21 of FIG. 2 will be described for the second embodiment of the present invention. However, as a matter of course, it is not essential to use the stretching machine 21 of FIG. 2 in the present invention.

  The drawing machine 21 in FIG. 2 includes at least a gripping member 26, a drawing roll 27, a winding roll 28, a rail 29, and a heating furnace 30. Then, the polymer film f attached to the drawer roll 27 is pulled out, both ends of the polymer film f are gripped by the gripping members 26 and run toward the winding roll 28, and the polymer film is discharged at the outlet of the heating furnace 30. f is opened, and it is wound up by the winding roll 28.

  Here, the gripping member 26 travels integrally with a chain (not shown) on the rail 29, grips both ends of the polymer film f drawn from the pulling roll 27, and travels both ends at the same speed. . The rail 29 is composed of a pair of rails 29a and 29b, and the gripping members 26 travel on the rails 29a and 29b, respectively. Further, the path along which the gripping member 26 that grips both ends of the polymer film f travels is different between the first half and the second half of the stretching machine 21.

If it demonstrates in detail, the extending | stretching machine 21 can be divided roughly and can divide into the pre-stretching implementation part 22 (area A of FIG. 2) of the first half part, and the heat contraction implementation part 23 (area B of FIG. 2) of the latter half part.
First, in the pre-stretching unit 22, the rails 29a and 29b on which the gripping member 26 travels first advance from the drawing roll 27 side to the winding roll 28 side at equal intervals. After that, the rail 29a at one end is moved straight as it is, and the rail 29b at the other end is away from the moving rail 29a, and proceeds from the pulling roll 27 to the winding roll 28. That is, only one rail 29b is skewed with respect to the traveling direction.

Next, in the heat shrinking unit 23, first, the rails 29a and 29b on which the gripping member 26 travels are gradually inclined from both end sides toward the center in the width direction, and the widths of the rails 29a and 29b are narrowed. Go. In other words, the rails 29a and 29b at both ends are gently inclined toward each other as the polymer film f proceeds in the traveling direction. Then, the rail 29 advances toward the take-up roll 28 while maintaining an equal interval in a state where the width is narrowed.
At this time, from the start point of the heat shrinking unit 23 (the point where the rails 29a and 29b start to be inclined toward each other) to the point where the inclination in the width direction of each rail ends, that is, at both ends. A sufficiently long distance is secured in the traveling direction in the portions where the rails 29a and 29b are inclined.
The heat shrinking unit 23 is provided with a heating furnace 30, and the heating furnace 30 heats the polymer film f with hot air.

Next, the example which manufactures a stretched film using the above-mentioned stretching machine 21 is demonstrated.
First, a long polymer film f is attached to the drawer roll 27 in a roll shape. Then, the pre-stretching unit 22 causes the polymer film f to travel toward the take-up roll 28 using a transport device such as a roll (not shown).
The polymer film f is gripped by the gripping members 26 at both ends in the width direction when the polymer film f is moved a certain distance to the winding roll 28 side. Then, the polymer film f continues to run toward the winding roll 28 side.

When the polymer film f gripped at both ends by the gripping member 26 travels a certain distance toward the take-up roll 28 side, the gripping member 26 gripping the one side end grips the other end. It moves in the direction away from the holding member 26.
As a result, the stretching direction of the polymer film f that has been stretched perpendicular to the running direction is inclined from the perpendicular to the running direction. The orientation axis of the polymer film f is gently inclined (5 degrees or more and less than 20 degrees) with respect to the width direction.
In addition, among the gripping members 26 at both ends that have been initially maintained at equal intervals in the width direction of the polymer film f, the gripping member 26 at one end is skewed (the other end is gripped). To move away from the gripping member 26), the force for stretching the polymer film f increases and the retardation value increases. Then, the “pre-stretching step” ends.

  Subsequently, the polymer film f travels through the heat shrinking unit 23. Here, the thermal contraction execution unit 23 performs an “angle adjustment process” after pre-stretching.

  That is, in the heat shrinking execution part 23, the heat shrinking process for angle adjustment is performed on the polymer film f stretched in the direction inclined with respect to the traveling direction in the pre-stretching execution part 22 (the pre-stretching is completed). Is to do. As a result, the orientation of the polymer film f is set to the intended inclination angle of the orientation axis (20 degrees or more and less than 70 degrees, for example, 45 degrees with respect to the width direction).

  Specifically, the polymer film f is first heated and contracted by the heating furnace 30. At this time, the gripping members 26 gripping both end portions are moved toward each other, and the interval is narrowed from both sides toward the center in the width direction in accordance with the amount of thermal shrinkage of the polymer film f. Thus, the angle is adjusted so that the orientation axis of the polymer film f is an inclination angle of the intended orientation axis (20 degrees or more and less than 70 degrees, for example, 45 degrees).

  When the orientation axis of the polymer film f reaches the target inclination angle, the gripping members 26 gripping both end portions finish moving in the direction approaching each other. The gripping member 26 travels to the winding roll 28 side while maintaining the distance in the width direction of the polymer film f.

  Subsequently, the gripping member 26 opens the polymer film f before the winding roll 28. And the process of inclining the orientation axis | shaft of the polymer film f is complete | finished when the roll 28 for winding winds up the open | released polymer film f. That is, the production of the stretched film is completed. In addition, the stretched film wound up is sent to the next step (for example, a step such as cutting).

  Here, when the “pre-stretching step” and the “angle adjusting step” are continuously performed as in the second embodiment, it is necessary to confirm in advance whether the orientation angle becomes a predetermined angle in the “pre-stretching step”. There is. That is, unlike the first embodiment, since there is no step of collecting the polymer film f after the “pre-stretching step”, the pre-stretching step has a predetermined orientation angle during the trial operation of the stretching machine. It is necessary to manufacture a stretched film after confirming whether it becomes.

As a method of confirming the orientation angle in the “pre-stretching step”, for example, a method of using a tenter stretching machine capable of changing the rail width can be considered. If it demonstrates concretely, first, the extending | stretching machine 21 of FIG. 2 will be made into FIG. 8 at the time of a test run. That is, the rails 29 in the thermal contraction execution unit 23 of the stretching machine 21 are set at equal intervals. Then, only a “pre-stretching step” is performed on the polymer film f by performing a trial run with the stretching machine 21. At this time, the orientation angle of the “pre-stretching step” is confirmed by conveying the polymer film f to the outside of the stretching machine 21 and measuring the orientation angle.
When it is confirmed that the predetermined orientation angle is obtained in the “pre-stretching step”, the rails 29a and 29b are gradually inclined from the both end sides toward the center side in the width direction in the front portion of the heat shrinking portion 23. Let That is, the same state as that of the stretching machine 21 in FIG. And the stretched film of 2nd Embodiment mentioned above is manufactured. According to this method, the stretched film can be produced after confirming the angle of the “pre-stretching step”.

  As another method, a method of temporarily stopping the stretching machine is also conceivable. That is, the stretching machine 21 of FIG. 2 is temporarily stopped, and the polymer film f is cut out at the front portion (the portion from the pre-stretching execution portion 22) of the heat shrinking execution portion 23 to confirm the orientation angle.

  Each stretching machine used in each of the above-described embodiments is not particularly limited, and an appropriate stretching machine such as a tenter type, a pantograph type, or a linear motor type can be used.

  In the “pre-stretching step” in each of the embodiments described above, the volatile content of the film is preferably less than 5% (percent), more preferably less than 3% (percent).

  In the second embodiment described above, both ends of the polymer film f were uniformly shrunk in the width direction during the “angle adjustment step”. However, if the holding interval at both ends can be reduced, the shrinking method can be reduced to this. It is not limited. For example, it may be contracted only from one end side as shown in FIG. However, it is preferable to shrink both ends evenly from the viewpoint of reducing the characteristic variation in the width direction of the polymer film f.

In each of the embodiments described above, the angle adjustment by the heat shrinkage process (“angle adjustment process”) is performed by controlling the shrinkage rate when shrinking in the width direction, temperature change, time for performing the shrinkage process, and the like. . Accordingly, these are appropriately changed according to the inclination angle of the target orientation axis.
However, if the polymer film is stretched in the longitudinal direction (longitudinal stretching) when heat shrinking in the width direction, the stretched film to be produced will exhibit high biaxiality. preferable.

  In addition, the thickness of the polymer film f of each embodiment described above is not particularly limited. The thickness of the polymer film f can be appropriately determined according to the purpose of use of the stretched film to be produced. However, from the viewpoint of stabilizing the heat shrinkage treatment and producing a stretched film of uniform quality, it is preferably 3 mm or less, more preferably 1 μm to 1 mm, and even more preferably 5 μm to 500 μm.

The stretched film produced by the present invention is not particularly limited, and may be, for example, a plastic film.
Moreover, the length in the longitudinal direction and the length of the width of the stretched film produced according to the present invention are not particularly limited, and may be an appropriate length.
For example, a long plastic film may be continuously stretched with the appropriate stretching machine described above for the purpose of improving production efficiency and efficiently bonding to a long polarizing plate or the like.

The use of the stretched film manufactured by this invention is not specifically limited, It can be used for an appropriate use. However, it can be suitably used for a retardation plate or the like from the viewpoint that the orientation axis is inclined in an oblique direction. More specifically, the tilt angle of the orientation axis is 20 to 70 degrees, and the following formula (1):
0.5 ≦ (nx−nz) / (nx−ny) ≦ 2 (1)
[Nx indicates the refractive index in the slow axis direction of the retardation film, where the slow axis direction indicates the direction in which the refractive index in the retardation film surface is maximized, and ny indicates the phase advance of the retardation film. The refractive index in the axial direction is shown, and nz is the refractive index in the thickness direction of the retardation film. ]
It is preferable to produce a stretched film that satisfies the above relationship and use it as a retardation plate.
Further, the retardation plate preferably has a retardation value measured at a wavelength of 590 nm satisfying 10 to 1000 nm, more preferably 100 to 170 nm or 220 to 290 nm.

  Such a retardation plate can be used for various purposes such as adjustment of birefringence characteristics in a liquid crystal display device, prevention of coloring due to a change in viewing angle, and expansion of a viewing angle. It can also be used to form various optical materials such as an elliptically polarizing plate and a circularly polarizing plate by bonding with a polarizing plate.

Moreover, when using the stretched film manufactured by this invention for a phase difference plate, it is possible to use the superimposition body of the stretched film which piled up the some stretched film as a phase difference plate.
In this case, the number of stretched films to be superimposed is arbitrary, but 2 to 5 is preferable from the viewpoint of light transmittance and the like.
Moreover, the combination of the stretched films to be superposed can be appropriately changed, and the tilt angle, the raw material, the phase difference, etc. of the superposed stretched films may be the same or different. These may be changed as appropriate.

  When the stretched film of the present invention is used as a retardation plate, a stretched film having excellent transparency such as polyolefin such as polycarbonate and cyclic olefin, polysulfone, cellulose acetate, polyvinyl chloride, polymethyl methacrylate, etc. is used. It is preferable. The thickness of the retardation plate may be arbitrarily determined depending on the phase difference according to the purpose of use, but is preferably 1 mm or less, more preferably 1 μm to 500 μm, and even more preferably 5 μm to 300 μm. It is desirable that the thickness be

In the case where a superposed body is formed by overlapping stretched films as described above, or when a retardation plate (stretched film) and a polarizing plate are bonded, suppression of reflection by adjusting the refractive index between layers and prevention of deviation of the optical system, From the viewpoint of preventing entry of foreign matter such as dust, it is preferable that the stretched film or between the retardation plate and the polarizing plate is fixed.
In addition, the adhesive material used for the fixing process is not particularly limited, and for example, a transparent adhesive material can be suitably used. Moreover, a pressure-sensitive adhesive can be suitably used from the viewpoint of preventing changes in optical properties.

  Furthermore, the stretched film (retardation plate) manufactured by the present invention is treated with an ultraviolet absorber such as a salicylic acid ester compound, a benzophenol compound, a benzotriazole compound, a cyanoacrylate compound, or a nickel complex compound. It may be provided with an ultraviolet absorbing ability such as those made.

The present invention will be specifically described with reference to examples and comparative examples, but the present invention is not limited to the examples.
In addition, the measurement methods of various physical properties and optical properties employed in this example are as follows.

(1) Measurement of retardation, Nz coefficient, and tilt angle of orientation axis Using a retardation film inspection apparatus RETS manufactured by Otsuka Electronics, the width direction was measured at a measurement wavelength of 590 nm at intervals of 5 cm. Moreover, the inclination angle at the time of Nz measurement was measured at 45 °. Re, Nz, and the tilt angle of the alignment axis were average values.
Nz = (nx-nz) / (nx-ny)
[Nx indicates the refractive index in the slow axis direction of the retardation film, where the slow axis direction indicates the direction in which the refractive index in the retardation film surface is maximized, and ny indicates the phase advance of the retardation film. The refractive index in the axial direction is shown, and nz is the refractive index in the thickness direction of the retardation film. ]

(2) Thickness Anritsu Co., Ltd. stylus type thickness gauge KG601A was used, and the thickness in the width direction was measured at 1 mm intervals. The average value obtained was taken as the thickness.

[Example 1]
A polycarbonate film (Elmec R-film non-stretched product manufactured by Kaneka Corporation) was introduced into a stretching machine according to the pre-stretching stretcher 2 of FIG. A polycarbonate film having a thickness of 40 μm and a width of 1000 mm inclined by 6 degrees was obtained. Then, the polycarbonate film is introduced into a tenter stretching machine according to the angle-adjusting heat shrinking machine 3 of FIG. 1 and heated to 160 ° C. to uniformly narrow the widthwise distance between the grippers at both ends. The film was subjected to 40% shrinkage treatment to obtain a stretched film. Next, the properties of the stretched film were measured using a retardation film inspection apparatus RETS manufactured by Otsuka Electronics. As a result, the retardation measured at a wavelength of 590 nm was 69 to 71 nm, and the tilt angle of the alignment axis with respect to the width direction was 44 to 46 degrees. (Nx−nz) / (nx−ny) where the refractive index nx in the in-plane slow axis direction, the refractive index ny in the direction perpendicular to the in-plane slow axis, and the refractive index nz in the thickness direction Was 1.0 to 1.1.

[Example 2]
A polycarbonate film whose orientation axis is tilted by 6 degrees with respect to the width direction is heated to 160 ° C., and the width direction distance between the grippers at both ends is uniformly narrowed to perform a shrinkage treatment of 35% in the width direction. A film was obtained. That is, a stretched film was obtained according to Example 1 except that the shrinkage rate was 35%. As a result of measuring the stretched film characteristics, the retardation measured at a wavelength of 590 nm was 119 to 122 nm, the tilt angle of the orientation axis with respect to the width direction was 26 to 29 degrees, the in-plane slow axis direction refractive index nx, and in-plane The refractive index ny in the direction perpendicular to the slow axis and the refractive index nz in the thickness direction were (nx−nz) / (nx−ny) of 1.4 to 1.5.

Example 3
A polycarbonate film whose orientation axis is tilted by 6 degrees with respect to the width direction is heated to 160 ° C., and the width direction distance between the grippers at both ends is narrowed only on one side, so that a 40% contraction treatment is applied in the width direction. A film was obtained. That is, a stretched film was obtained in the same manner as in Example 1 except that the distance in the width direction between the grips at both ends was narrowed only on one side. As a result of measuring the stretched film characteristics, the retardation measured at a wavelength of 590 nm was 67 to 74 nm, the tilt angle of the orientation axis with respect to the width direction was 42 to 47 degrees, the in-plane slow axis direction refractive index nx, and the in-plane The refractive index ny in the direction perpendicular to the slow axis and the refractive index nz in the thickness direction were (nx−nz) / (nx−ny) of 0.9 to 1.1.

[Comparative Example 1]
A stretched film was obtained according to Example 1 except that the shrinkage rate was 0%. As a result of measuring the stretched film characteristics, the retardation measured at a wavelength of 590 nm was 540 to 550 nm, the tilt angle of the orientation axis with respect to the width direction was 6 degrees, the refractive index nx in the in-plane slow axis direction, the in-plane slow phase The refractive index ny in the direction perpendicular to the axis and the refractive index nz in the thickness direction were (nx−nz) / (nx−ny) was 1.5.

[Comparative Example 2]
A stretched film was obtained according to Example 1 except that a polycarbonate film having an orientation axis not inclined with respect to the width direction, that is, an orientation axis of 0 degree was used. As a result of measuring the stretched film characteristics, the retardation measured at a wavelength of 590 nm was 88 to 92 nm, the tilt angle of the orientation axis with respect to the width direction was 0 to 1 degree, the in-plane slow axis direction refractive index nx, and the in-plane When the refractive index ny in the direction perpendicular to the slow axis and the refractive index nz in the thickness direction were (nx−nz) / (nx−ny) was 1.1.

[Comparative Example 3]
By using a stretching machine 40 shown in FIG. 7, a polycarbonate film having a thickness of 40 μm and a width of 1000 mm with a retardation measured at a wavelength of 590 nm of 570 nm and an orientation axis inclined by 6 degrees with respect to the width direction was obtained. And the polycarbonate film was heated at 150 degreeC, and it introduced into the longitudinal stretch machine 41 by the roll peripheral speed difference, and stretched 5% in the longitudinal direction, and obtained the stretched film. As a result of measuring the characteristics of this stretched film, the retardation measured at a wavelength of 590 nm was 57 to 71 nm, the inclination angle of the orientation axis with respect to the width direction was 44 to 46 degrees, the in-plane slow axis direction refractive index nx, and in-plane (Nx−nz) / (nx−ny) was 7.0 to 7.3 when the refractive index ny in the direction perpendicular to the slow axis and the refractive index nz in the thickness direction were taken.

DESCRIPTION OF SYMBOLS 1 Stretching machine 2 Pre-stretching stretching machine 3 Angle adjustment heat shrink machine 4 Angle adjustment heat shrink machine 6 Gripping member 8 Pull-out roll 9 Winding roll f Polymer film

Claims (8)

  It is a long film, the inclination angle of the orientation axis is held at both ends in the width direction of the prestretched film prestretched to 5 degrees or more and less than 20 degrees with respect to the width direction, and the prestretched film is heated A method for producing a stretched film, characterized in that the holding interval at both ends is gradually narrowed while heat shrinking.   A step of forming a pre-stretched film by stretching the inclination angle of the orientation axis to 5 to 20 degrees with respect to the longitudinal direction with respect to the long film, and heat shrinking by heating the formed pre-stretched film The method for producing a stretched film according to claim 1, wherein the step of gradually reducing the holding interval between the both ends is performed continuously.   The stretched film according to claim 1 or 2, wherein both ends of the prestretched film are moved evenly with respect to the center line in the width direction when the holding interval between the both ends is gradually narrowed while being thermally contracted. Manufacturing method.   The stretching according to any one of claims 1 to 3, wherein the prestretched film is heated and thermally contracted to make the inclination of the molecular orientation axis of the prestretched film with respect to the width direction 20 degrees or more and less than 70 degrees. A method for producing a film.   The method for producing a stretched film according to any one of claims 1 to 4, wherein the prestretched film is heated and contracted by a tenter-type stretching machine capable of adjusting expansion and contraction in the width direction.   A stretched film produced by the method for producing a stretched film according to any one of claims 1 to 5, wherein an inclination angle of an orientation axis with respect to a width direction of the stretched film is larger than 20 degrees and smaller than 70 degrees. Stretched film. A stretched film produced by the stretched film production method according to any one of claims 1 to 5, wherein the refractive index nx in the slow axis direction in the plane of the stretched film is perpendicular to the slow axis in the plane. The refractive index ny in the direction and the refractive index nz in the thickness direction are expressed by the following formula (1):
0.5 ≦ (nx−nz) / (nx−ny) ≦ 2 (1)
A stretched film characterized by satisfying   A retardation film comprising at least one stretched film according to claim 6 or 7.

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