JP2009119774A - Method for manufacturing obliquely stretched optical film, and stretching apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing an obliquely stretched optical film having less restrictions on stretching magnification, causing neither creases of film nor rupture at the end and formed to incline a molecule orientation axis uniformly to the longitudinal direction of the film, and a stretching apparatus for manufacturing the optical film. <P>SOLUTION: An angle θa1 defined by a conveying direction and a straight line connecting a stretch start position P1 and a stretch stop position P2 of one grip means and an angle θb1 defined by the conveying direction and a straight line connecting a stretch start position S1 and a stretch stop position S2 of another grip means in an stretching region, and an angle θa2 defined by the conveying direction and a straight line connecting a relaxation start position P3 and a relaxation stop position P4 of one grip means and an angle θb2 defined by the conveying direction and a straight line connecting a relaxation start position S3 and a relaxation stop position S4 of another grip means in a relaxation region, satisfy four conditional expressions: θa1≥θb1, θa1≤16.0°, θb2>θa2 and θa2≤0.30°. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a manufacturing method and a stretching apparatus for an obliquely stretched optical film whose orientation angle is tilted with respect to the longitudinal direction of the film.

  2. Description of the Related Art Conventionally, in an image display device such as a liquid crystal display device or an organic EL display device, a retardation film is used for optical compensation such as coloring prevention, viewing angle expansion, and prevention of reflection of external light. In some cases, the retardation film and the polarizing plate are arranged so that the slow axis and the transmission axis of the polarizing plate are at a predetermined angle and bonded together as a film for optical compensation.

  Conventionally, as a method for producing this retardation film, after forming a long transparent resin film, it is stretched in the longitudinal direction or the transverse direction of the film. Therefore, the orientation axis of the resin film is also the longitudinal direction or the lateral direction, and as a result, the slow axis of the retardation film is also substantially the direction perpendicular to the stretching direction or the stretching direction. Therefore, in order to adjust the angle between the slow axis of the retardation film and the transmission axis of the polarizing plate to an angle other than parallel or orthogonal, after cutting the retardation film of a necessary area one by one, the polarizing plate The method of adjusting and adhering to the transmission axis was taken. However, such a method has a problem that a lot of cutting loss occurs, the yield decreases, and the waste increases.

  As a method for solving such a problem, the slow axis direction of the retardation film is set to the longitudinal direction or the width direction so that the retardation film and the polarizing film can be continuously laminated by a roll-to-roll method. A method has been proposed in which the orientation axis of the resin film is inclined so as to have a predetermined angle in the longitudinal direction, which is different from the direction.

  For example, in Patent Document 1, the roll-shaped cellulose ester film is stretched in a direction substantially 45 degrees with respect to the longitudinal direction so that the angle between the longitudinal direction and the slow axis is substantially 45 degrees. A method for producing a quarter-wave plate of a roll film has been proposed. Specifically, in the tenter type stretching apparatus in which the speeds of the grip portions at both ends are different, this can be achieved by making the thickness of the film before stretching different in the width direction in advance. However, since the film is stretched with a thickness deviation in the width direction of the film, it becomes a film having thickness unevenness not only in the width direction but also in the longitudinal direction, and uniform stretching is difficult.

  Further, in Patent Document 2, in a method of extending obliquely using a tenter type stretching device having endless chains on the left and right sides, a rail part that drives the endless chain is divided into an entrance rail part, a bent rail part, and an exit rail part, Each rail part is positioned by width direction positioning means independent on the left and right. By doing in this way, it is supposed that the film of arbitrary draw ratios can be obtained with arbitrary orientation angles.

  Moreover, in patent document 3, in the method of extending | stretching diagonally using the tenter type | formula extending | stretching apparatus which has an endless chain on either side, it is set as the structure which has a meandering part so that only one chain may bulge outside, and it extends diagonally A method has been proposed.

  However, in both Patent Documents 2 and 3, if the force for stretching the film generated when bending or meandering the chain is applied non-uniformly or the stretching direction is not changed gradually and smoothly, the grip portion such as a clip In many cases, excessive force is applied to the film, causing wrinkles (partial sagging), slipping (partial pulling) and damage of the film.

In addition, as a method of solving the wrinkles and breakage of the film as described above, an arm is attached to a continuous left and right endless chain, the arm has a clip for gripping the end of the film, and the arm is transported on the chain. Patent Documents 4 and 5 propose a method of sliding obliquely with respect to the direction. However, even in such a method, when the draw ratio becomes high or the drawing at high temperature is necessary, the deformation amount of the film end portion becomes large, the breakage occurs around the clip, and the draw ratio is restricted. The problem that came out occurred.
JP 2002-22944 A JP 2003-276082 A JP 2003-207625 A JP 2005-349698 A JP 2007-30466 A

  As described above, in any of the conventional stretching methods, it is possible to obtain a film that has uniform optical quality and is free from wrinkles and breaks, even though the orientation axis can be inclined in the oblique direction with respect to the film longitudinal direction. It was difficult.

  An object of the present invention is a method for producing an obliquely stretched optical film in which the stretching ratio is uniform, the molecular orientation axis is uniformly inclined with respect to the film longitudinal direction, and there is no wrinkle or breakage at the end of the film. It is providing the extending | stretching apparatus which manufactures a film.

  The above object of the present invention is achieved by the following configurations.

1.
A method for producing an obliquely stretched optical film comprising a stretching step of gripping both ends in the width direction of a long film by gripping means and stretching the film so that the transport direction after stretching of the film and the direction of the orientation axis of the film are tilted In
The stretching step includes
A stretching region for stretching the film to the maximum stretching width;
After the stretching region, having a relaxation region that relaxes to a relaxation width that is narrower than the maximum stretching width,
In the stretching region,
A gripping means for gripping one end of the film,
P1 is the position where the film starts to be stretched,
The position where the stretching of the film is stopped is P2,
A gripping means for gripping the other end of the film,
S1 is the position to start stretching the film,
S2 is a position where the stretching of the film is stopped.
And when
An angle θa1 between a straight line connecting P1 and P2 and the transport direction;
The angle θb1 between the straight line connecting S1 and S2 and the transport direction satisfies the following conditional expressions (1) and (2):
In the relaxation region,
A gripping means for gripping one end of the film,
The position where relaxation of the film starts is P3,
The position where the relaxation of the film is stopped is P4,
A gripping means for gripping the other end of the film,
The position where relaxation of the film starts is S3,
The position where the relaxation of the film stops is S4,
And when
An angle θa2 between a straight line connecting P3 and P4 and the transport direction;
A method for producing an obliquely stretched optical film, characterized in that the straight line connecting S3 and S4 and the angle θb2 between the conveying direction satisfy the following conditional expressions (3) and (4).

θa1 ≧ θb1 (1)
θa1 ≦ 16.0 ° (2)
θb2> θa2 (3)
θa2 ≦ 0.30 ° (4)
2.
2. The method for producing an obliquely stretched optical film according to 1, wherein the θb1 and the θb2 satisfy the following conditional expression (5).

θb1> θb2 (5)
3.
Two chains on both sides of the film transport path;
A number of bases provided in the chain;
An arm that is slidably mounted on the base and protrudes toward the film;
A clip provided at one end of the arm on the film side and capable of gripping both side edges of the film;
In a stretching apparatus for gripping both side edges of the film with the clip and stretching the film by sliding the arm while transporting,
The stretching apparatus, wherein the clip is rotatable at least in a predetermined angle range with respect to a traveling direction of the chain.

4).
Two chains on both sides of the film transport path;
A number of bases provided in the chain;
An arm that is slidably mounted on the base and protrudes toward the film;
A clip provided at one end of the arm on the film side and capable of gripping both side edges of the film;
In a stretching apparatus for gripping both side edges of the film with the clip and stretching the film by sliding the arm while transporting,
The stretching apparatus, wherein the arm is curved.

5).
Two chains on both sides of the film transport path;
A number of bases provided in the chain;
An arm that is slidably mounted on the base and protrudes toward the film;
A clip provided at one end of the arm on the film side and capable of gripping both side edges of the film;
In a stretching apparatus for gripping both side edges of the film with the clip and stretching the film by sliding the arm while transporting,
A stretching apparatus, wherein a plurality of the arms are attached to the clip.

6).
Two chains on both sides of the film transport path;
A number of bases provided in the chain;
Connecting a base provided in one chain and a base provided in the other chain, and an arm attached to each base;
A pair of clips provided slidably on the arm and capable of gripping both side edges of the film;
A stretching apparatus characterized by gripping both side edges of the film with the clip and stretching the film by sliding the clip while being conveyed.

7).
7. The method for producing an obliquely stretched optical film according to 1, wherein the stretching apparatus according to any one of 3 to 6 is used.

  In the manufacturing method of the obliquely stretched optical film of the present invention, the stretched film has a stretched region for stretching the film to the maximum stretched width, and a relaxed region that is narrower than the maximum stretched width and relaxed to the relaxed width after the stretched region. In the region, an angle θa1 between a straight line connecting a position P1 at which one gripping means starts stretching of the film and a position P2 at which stretching is stopped and the transport direction, and a position at which the other gripping means starts stretching the film. An angle θb1 between the straight line connecting S1 and the position S2 at which stretching stops and the conveyance direction, and a straight line connecting the position P3 at which one gripping means starts relaxation of the film and the position P4 at which relaxation is stopped in the relaxation region When the angle θa2 between the conveyance direction and the angle θb2 between the straight line connecting the position S3 where the other gripping means starts relaxation of the film and the position S4 where the relaxation stops and the conveyance direction θa1 ≧ θb1, θa1 ≦ 16.0 °, θb2> θa2, so that satisfy the four conditions expressions θa2 ≦ 0.30 °. By satisfying such conditions, there are few restrictions on the draw ratio, there is no film wrinkle or break at the end, and a method for producing an obliquely stretched optical film in which the molecular orientation axis is uniformly inclined with respect to the film longitudinal direction. And the extending | stretching apparatus which manufactures this optical film can be provided.

  The best mode for carrying out the present invention will be described in detail below, but the present invention is not limited thereto.

  The obliquely stretched optical film obtained in the present invention is obtained by stretching a thermoplastic resin film so that the molecular orientation axis is inclined with respect to the longitudinal direction. Examples of the thermoplastic resin include appropriate thermoplastics such as maleimide, polycarbonate, polysulfone, polyethersulfone, polystyrene, polyolefin, polyvinyl alcohol, polyvinylidene fluoride, poly (meth) acrylate, polyethylene terephthalate, cellulose ester, and polynorbornene. Resin can be used. In addition, additives, such as a plasticizer and an ultraviolet absorber, may be appropriately added to the thermoplastic resin.

  The method for producing the thermoplastic resin film used is not particularly limited. For example, the thermoplastic resin film can be used by various general film forming methods such as melt extrusion molding, melt casting molding, calendar method, and solution casting method.

  The thickness of the thermoplastic resin film before stretching is preferably in the range of about 30 to 200 μm. If it is 30 μm or less, the thickness becomes thin after stretching, and the film strength may be insufficient or the waist may become weak and handling may be difficult. If it exceeds 200 μm, it is difficult to obtain an orientation axis uniformly in the thickness direction. Become.

  FIG. 1 is a schematic plan view for explaining an example of the method for producing the obliquely stretched optical film of the present invention. When producing an obliquely stretched optical film by the method for producing an obliquely stretched optical film of the present invention, a stretched optical film production apparatus 1 schematically shown in FIG. 1 is used. The manufacturing apparatus 1 includes an unwinding process 2 for unwinding a thermoplastic resin film from a roll, an extending process 3 for performing a stretching process, and a winding process 4 for winding the roll on a roll. In the stretching step 3, a heating device for heating the film is arranged, stretched while being heated, and then cooled to obtain an obliquely stretched optical film in which the orientation axis is fixed. The means used for the heating device is not particularly limited as long as the thermoplastic resin film can be uniformly heated, and examples thereof include a heating device such as a hot air type, a panel heater, a halogen heater, etc. A hot air type that can be accurately performed is preferable. Further, if necessary, a preheating device for preheating the unrolled thermoplastic resin film is provided between the unwinding step 2 and the stretching step 3, or between the stretching step 3 and the winding step 4. A cooling device may be provided. Moreover, let the direction which unwinds a thermoplastic resin film be an unwinding direction, and let the direction wound around a roll be a conveyance direction.

  Moreover, in the extending | stretching process 3, it has the extending | stretching area | region 31 which extends | stretches a thermoplastic resin film to the maximum extending | stretching width W1, and the relaxation area | region 32 which relaxes to the relaxation width W2 narrower than a maximum extending | stretching width. The stretching device may be any device that can be stretched obliquely, but it is preferable to use a tenter that grips both ends in the width direction of the film with a number of gripping means and stretches obliquely. In the manufacturing apparatus of FIG. 1, a tenter is used for the stretching apparatus. Moreover, in this invention, the direction of the orientation axis of a film inclines in the manufacturing method of a diagonally stretched optical film that the direction of the orientation axis of a film inclines 20-70 degree | times with respect to the film conveyance direction after extending | stretching. Point to.

  The long thermoplastic resin film having the width W0 is unwound by the unwinding roll 21, and is gripped at the grip start positions P0 and S0 by the left and right clips 51 and 52 as gripping means at both ends in the film width direction. . While being gripped by the left and right clips 51, 52, a predetermined distance is conveyed in the unwinding direction with a width W 0. Next, the left clip 51 starts stretching in the diagonally outward direction at the stretching start position P1 moved from the grip start position P0 by the distance L1. Further, the right clip 52 starts to extend obliquely outward at the extension start position S1 moved by the distance L2 from the grip start position S0. The left clip 51 stops extending in the diagonally outward direction at the extension stop position P2, and the right clip 52 extends in the diagonally outward direction at the extension stop position S2 that is separated from the extension stop position P2 by a distance of L3. Stop. In this manner, the thermoplastic resin film is stretched obliquely in the stretching region 31 of the stretching step 3 up to the maximum stretching width W1. Next, a predetermined distance is conveyed in the state of the maximum stretching width W1, and when the left clip 51 reaches the relaxation start position P3, it moves in an oblique inward direction opposite to the direction in which the film is stretched and starts relaxation. To do. Further, when the right clip 52 reaches the relaxation start position S3, the clip 52 moves diagonally inward and starts relaxation. When the left and right clips 51 and 52 reach the relaxation stop positions P4 and S4, respectively, the movement in the relaxation direction is stopped, and the width of the film becomes a relaxation width W2 narrower than the maximum stretch width W1. Then, it conveys in the state of the relaxation width W2 to the grip cancellation | release position of P5 and S5, and the clips 51 and 52 are cancelled | released. The obliquely stretched film released from the clips 51 and 52 is wound on the winding roll 41 in the winding process 4. In this way, an obliquely stretched optical film having an orientation axis inclined with respect to the transport direction is produced by the method for producing an obliquely stretched optical film of the present invention.

  Thus, in the manufacturing method of the diagonally stretched optical film of the present invention, the stretching step 3 includes a stretching region 31 that stretches the film to the maximum stretching width W1, and a relaxation width that is narrower than the maximum stretching width W1 after the stretching region. A relaxation region 32 that relaxes to W2, and the gripping means is opened after passing through the relaxation region 32.

  By providing such a relaxation region 32, there is an advantage that non-uniform residual stress can be made uniform in the width of the film generated in the stretching region 31, and there is no film thickness unevenness or breakage. An obliquely stretched optical film in which the orientation axis is uniformly inclined in the direction can be obtained.

  In the stretching region 31, the angle θa1 between the straight line connecting P1 and P2 and the transport direction, and the angle θb1 between the straight line connecting S1 and S2 and the transport direction are the following conditional expressions (1) and (2): In the relaxation region 32, an angle θa2 between the straight line connecting P3 and P4 and the transport direction, and an angle θb2 between the straight line connecting S3 and S4 and the transport direction are the following conditional expressions (3) and (3): 4) is satisfied. The angles θa1, θb1, θa2, and θb2 are expressed as absolute values. Θa2 and θb2 are angles toward the center side (inward direction) of the film as shown in FIG.

θa1 ≧ θb1 (1)
θa1 ≦ 16.0 ° (2)
θb2> θa2 (3)
θa2 ≦ 0.30 ° (4)
By satisfying the formulas (1) to (4) in this way, an obliquely stretched optical film in which the orientation axis is uniformly inclined in the transport direction without any film thickness unevenness or breakage can be obtained. When θa1 exceeds 16.0 °, a clip or arm arranged in the front and back interferes with each other, so that a complicated mechanism is required, and stable stretching is difficult. Further, when θa1 ≧ θb1, when θb2 ≦ θa2, if the stress remains nonuniformly in the width direction of the film, the orientation axis becomes nonuniform. Similarly, when θa1 <θb1, when θb2> θa2, the stress remains non-uniformly in the width direction of the film, resulting in non-uniform orientation axes. If θa2 and θb2 are inclined outwardly from the center in the width direction of the film, the film is broken, which is not preferable. On the other hand, when [theta] a2 exceeds 0.3 [deg.], Slippage occurs in the film transport direction, resulting in a flatness failure.

  Further, it is preferable that θb1 and θb2 satisfy the following conditional expression (5).

θb1> θb2 (5)
Thus, by satisfy | filling Formula (5), the diagonally stretched optical film in which the orientation axis | shaft inclined more uniformly in the conveyance direction more without a nonuniformity and fracture | rupture can be obtained.

  In FIG. 1, P0 to P5 are set on the left side of the drawing and S1 to S5 are set on the right side. However, the P side (P0 to P5) and the S side ( What is necessary is just to determine S1-S5).

  Moreover, in the extending process 3, it is preferable to heat and stretch a thermoplastic resin film with a heating means. In particular, it is more preferable that the temperature of the film in the relaxation region is lower than the temperature of the film in the stretching region 31 in the stretching step 3. By doing so, it is possible to obtain an obliquely stretched optical film in which the orientation axis is uniformly inclined in the transport direction without any film thickness unevenness or breakage.

  When the stretching start positions P1 and S1 of the left and right clips 51 and 52 are shifted by L2-L1 as shown in FIG. 1, the stretching start of the clip 52 on the downstream side is started as shown in FIG. The position S1 is preferably set to the position of S12 on the center side of the film. That is, if the trajectory of the clip 51 is P1-P2, it is preferable to set the stretching angles θa1 and θb0 to be the same so that the clip 52 draws the trajectory of S11-S22 so as to be parallel to P1-P2. By doing in this way, the stress of an edge part is relieve | moderated more and the diagonally stretched optical film with a uniform orientation axis | shaft can be obtained.

  Further, the shift amount L3 between the positions P2 and S2 at which the left and right clips 51 and 52 shown in FIG. 1 stop extending is preferably in the relationship of the following expression (6) with the maximum extending width W1.

L3 × 0.35 ≦ W1 ≦ L3 × 3.0 (6)
Such a relationship is preferable because there is no need to increase the size of the facility and the stretching in the oblique direction can be efficiently realized.

  In addition, a holding region 33 that holds the maximum stretching width W <b> 1 exists between the stretching region 31 and the relaxation region 32. In the holding region 33, if the stretching stop positions P2 and S2 of the left and right clips 51 and 52 are shifted, the substantial holding time may be different. In such a case, it is preferable to set the temperature in the width direction of the film in the holding region 33 to be different. By setting the temperature in the width direction of the film to be different, the stress at the end is further relaxed, and an obliquely stretched optical film having a uniform orientation axis can be obtained, which is preferable. As a means of varying the temperature in the film width direction, a plurality of hot air outlets may be installed in the width direction to control the hot air temperature from each outlet, and the distance between the outlet and the film surface may be controlled. The temperature may be adjusted, and furthermore, a plurality of planar heaters, halogen lamps, and the like may be installed in the width direction to adjust each temperature.

  Further, it is preferable to install a longitudinal stretching machine on the upstream side of the tenter which is the oblique stretching apparatus in FIG. 1 in order to adjust the angle of the orientation axis with high accuracy. In this case, the film that has passed through the longitudinal stretching machine may cause a difference in film thickness between the film width direction end and the central part, and the film thickness at the end may become thick. In that case, the film is stretched by the longitudinal stretching machine. It is sometimes preferable to adjust the film so that the film has a uniform thickness by adding a temperature difference in the width direction. Moreover, a uniform film thickness can be obtained in the width direction after stretching by increasing the thickness of the film before longitudinal stretching at the center. In addition, the film stretched by a longitudinal stretching machine has a large residual stress in the film moving direction, and therefore breaks in the stretching process in the tenter, which is a subsequent process, and fine cracks (craze) occur on the film surface. There is. In order to relieve the residual stress due to the longitudinal stretching machine, it is preferable to put a relaxation step between the longitudinal stretching machine and the tenter. As a method of longitudinal relaxation in the relaxation step, contraction by two rolls having a difference in peripheral speed may be used, or a general relaxation process can be used.

  In addition, when an oblique stretching device is installed at the subsequent stage of a film production apparatus of a solution casting method in which a thermoplastic resin is dissolved in a solvent and cast on a metal body to produce a film, and the film peeled off from the metal body is stretched The film containing a large amount of volatile solvent is stretched. When stretching a film containing such a volatile solvent, it is preferable to appropriately adjust the temperature used in the tenter and the boiling point of the volatile solvent from the viewpoint of eliminating unevenness of the stretching axis in the film width direction. In addition, by adjusting the content of the high boiling point solvent of the film before stretching, or by adjusting the volatilization amount of the volatile solvent with the atmosphere inside the tenter as the volatile solvent atmosphere, it has a more uniform orientation axis. An obliquely stretched optical film can be produced.

  In addition, as an explanatory view of the manufacturing method of the obliquely stretched optical film of the present invention described above, the film unwinding direction and the transport direction are substantially the same as shown in FIG. The present invention is also applied to the case shown in FIG. 3 in which the direction has a constant angle. In the case of FIG. 3 as well, the reference direction of the angle is the transport direction in which the film is wound with a roll. Although the symbols and numbers corresponding to FIG. 1 are also given in FIG. 3, the same symbols and numbers are used in the same meaning as in FIG.

  Next, a preferred stretching apparatus for use in the method for producing the obliquely stretched optical film of the present invention will be described with reference to FIGS.

  4 and 5 show a cross-section and a plane of a film stretching apparatus (stretching apparatus) 401 that is an embodiment of the present invention. The film stretching apparatus 401 includes a supply apparatus 403 that supplies the film 402, a longitudinal stretching furnace 404 that heats the film, and a longitudinal stretching section (longitudinal stretching section) 406 that includes an intermediate transport apparatus 405 that transports the film 402 downstream. An oblique stretching machine 407 that stretches in a direction inclined with respect to the transport direction while transporting the film 402, and an oblique stretching furnace 408 that is provided so as to cover the center of the oblique stretching machine 407 and heats the film 402. And a winding device 410 that winds up the film 402.

  The supply device 403 is loaded with an original reel 411 around which a film 402 is wound, and the film 402 is sandwiched between a reference roll 412 and a nip roll 413 and sent out at a predetermined transport speed. The longitudinal stretching furnace 404 is a box made of a heat insulating material having hot air ducts (heating means) 414 for blowing hot air alternately on the film 402 from above and below. The intermediate transport device 405 sandwiches and transports the film 402 between the ratio roll 415 and the nip roll 416 and stretches it in the E1 direction parallel to the transport direction. The oblique stretching machine 407 stretches the film 402 in the E2 direction inclined by an angle α with respect to the transport direction while transporting the film 402 by the stretch chains 417 disposed on both sides of the film 402, and details will be described later. The oblique stretching furnace 408 is a box made of a heat insulating material having a hot air duct 418 that blows hot air on the film 402 from above and below. The winding device 410 winds the film 402 around the product reel 420 while adjusting the tension with the tension roll 419.

  FIG. 6 shows the configuration of the oblique stretching machine 407. The oblique stretching machine 407 includes two parallel stretching chains 417, a large number of bases 421 provided on the stretching chain 417 at regular intervals, and arms 422 attached to the respective bases 421 so as to be slidable in a certain direction. , And a clip 423 provided at the tip of each arm 422. The clip 423 can grip both side edges of the film 402, and the stretching chain 417 is looped around a sprocket 424 perpendicular to the surface of the film 402.

  FIG. 7 shows a more detailed structure of the oblique stretching machine 407. A base 421 is fixed to the extending chain 417 every other frame. The base 421 is provided with two sliding shafts 425 inclined by 45 ° (angle α in FIG. 5) with respect to the extending chain 417, and the arms 422 are slidable along the respective sliding shafts 425. ing. A positioning member 426 made of a bearing is provided on the upper portion of the arm 422, and the arm 422 is projected and retracted by guiding the positioning member 426 with a guide 427. The clip 423 provided at the tip of the arm 422 is a known film gripping mechanism, and is opened and closed by the guide 428 (the film 402 is gripped or released).

  The oblique stretching machine 407 causes the arms 422 to protrude from the base 421 of the stretching chain 417, grips both side edges of the film 402 with the clip 423, and transports the film 402 as the stretching chain 417 advances. During this time, the arm 422 is retracted while holding the film 402 with the clip 423, whereby the film 402 is stretched and widened in the sliding direction of the arm 422 (direction E2 in FIG. 5). After the film 402 is widened, the clip 423 opens the film 402. The arm 422 then retracts further, preventing the clip 423 from contacting the film 402 when the stretch chain 417 is folded along the sprocket 424.

  Next, stretching of the film 402 in the film stretching apparatus 401 having the above configuration will be described.

  In the longitudinal stretching unit 406, when the film 402 is sent out at a predetermined speed by the reference roll 412 and is transported at a speed faster than the reference roll 412 by the ratio roll 415, the heated part in the longitudinal stretching furnace 404 is transported. The film is stretched in the direction (E1 direction) at the same ratio as the ratio of the conveyance speed of the ratio roll 415 to the reference roll 412. By this stretching in the longitudinal direction, the molecules of the film 402 are aligned in the transport direction, and an orientation angle in the longitudinal direction is given.

  Further, in the oblique stretching section 409, the film 402 is stretched in the E2 direction in a downwardly inclined direction by an angle α with respect to the transport direction. At this time, as shown in FIG. 1, the positions P1, S1, P2, and S2 at which stretching is started and the relaxation is started so that the angle formed with the conveyance direction satisfies the above-described formulas (1) to (4). Stop positions P3, S3, P4, and S4 are set. By doing in this way, in the stretching region, the film 402 is stretched in the inclined direction, and the film 402 is subjected to the tensile force in the E2 direction and the stress against the deformation of the film 402, and is larger in the transport direction than in the E2 direction. Stretching force that attempts to align molecules at an angle works to provide an orientation angle in the tilt direction. In the relaxation region, part of the stress generated in the stretching region can be relaxed.

  As a result, the film 402 can be obtained as an obliquely stretched optical film excellent in optical quality that has no uniform wrinkles, creases, and breakage at the ends and has a uniform orientation axis.

  In the film stretching apparatus 401 of this embodiment, it is preferable that the clip 423 is rotatable at least in a predetermined angle range with respect to the traveling direction of the stretching chain 417.

  As shown in FIG. 8, the clip 423 is rotatable in a predetermined range with respect to the traveling direction of the stretching chain 417, so that a tensile stress is uniformly applied to the film, so that the optical system has a more uniform orientation axis. A high quality obliquely stretched optical film can be obtained. Specifically, it is effective to simply attach the clip 423 attached to the tip of the arm 422 in a rotatable manner. However, the clips facing each other are parallel to each other in accordance with the movement of the arm 422, and the running direction of the film end portion It is preferable to control the angle of the clip 423 so as to face the direction. Although a specific example is shown in FIG. 9, the present invention is not limited to this, and any structure may be used as long as the clip 423 can rotate and be controlled within a predetermined angle range with respect to the traveling direction of the extension chain 417. FIG. 9 is a plan view schematically showing one specific example showing a mechanism for changing the angle of the clip 423. One of the clips 423 rotatably provided at the tip of the arm 422 is urged by a compression spring 501 and the other is controlled by a motor 502 with a drive shaft 503 being taken in and out. The rotation angle can be adjusted by controlling the rotation of the motor by a rotation angle control device (not shown) according to the movement of the arm.

  Moreover, in the film stretching apparatus 401 of this embodiment, it is preferable that the arm 422 is curved.

  Since the arm 422 is curved as shown in FIG. 10, the angle of the clip 423 changes smoothly in conjunction with the sliding of the arm 422 on the base 421, and the film is subjected to a uniform tensile stress. Thus, an obliquely stretched optical film having a more uniform orientation axis and good optical quality can be obtained. FIG. 11 schematically shows a configuration diagram for explaining how the arm 422 curved on the base 421 slides.

  The arm 422 is fixed and transported to the base 421 by pinion gears 504 and 505. When the pinion gears 504 and 505 are rotated, the rack gear formed on the side surface of the arm 422 engaged with the pinion gears 504 and 505 is driven, and the curved arm 422 is moved along the curved shape. As the position changes from a to b and c in FIG. 10, the clip 423 fixedly disposed at the tip moves while gradually changing the angle. This change in angle can be controlled by defining the curved shape of the arm 422, so that a tensile stress is uniformly applied to the film, and an obliquely stretched optical film having a more uniform orientation axis and good optical quality is obtained. be able to.

  Moreover, in the film stretching apparatus 401 of this embodiment, it is preferable that the two arms 422 are attached to the clip 423.

  As shown in FIG. 12, by attaching two arms 422 to the clip 423 and sliding each arm 422 independently on the base 421, the angle of the clip 423 can be adjusted arbitrarily, and more By applying a tensile stress uniformly, an obliquely stretched optical film having a more uniform orientation axis and good optical quality can be obtained.

  Further, in the film stretching apparatus 401 of this embodiment, as shown in FIG. 13, the base 421 provided in one chain 417 and the base 421 provided in the other chain 417 are connected and attached to each base 421. It is preferable that the arm 422 and a pair of clips provided so as to be slidable on the arm and gripping both side edges of the film are slid while being transported to stretch the film.

  By adopting such a configuration, errors in the stretching direction due to thermal expansion in the stretching process of the arm 422 can be reduced, and a uniform tensile axis is applied to the film, resulting in an optical quality with a more uniform orientation axis. A good obliquely stretched optical film can be obtained. In addition, there is a possibility that the arm 422 crosses the lower part of the film to cause uneven film heating in the stretching process. In such a case, for example, the hot air supply angle is adjusted or the hot air port is conveyed. A more uniform film temperature can be obtained by arranging them in a zigzag pattern above and below the film.

  Moreover, in the film stretching apparatus 401 of this embodiment, it is preferable that the width of the clip 423 is wider than the width of the arm 422. By making the width of the clip 423 wider than the arm 422, it is possible to reduce the angular unevenness of the orientation axis with respect to the transport direction in the vicinity of the end in the width direction of the film.

  Moreover, it is preferable that the pitch of arrangement | positioning of the clip 423 is 20 mm or less. By setting it to 20 mm or less, the end in the film width direction can be pulled more uniformly, and an obliquely stretched optical film having a more uniform orientation axis and good optical quality can be obtained.

  In the film stretching apparatus 401 of this embodiment, the arm 422 is preferably made of a metal material having a small thermal expansion coefficient. Further, from the viewpoint of weight reduction, a carbon fiber material such as carbon fiber may be used. By using such a material, the thermal expansion of the arm 422 is reduced in the stretching process for heating the film, which is effective in securing the film transport stability and the stretching accuracy. It is also preferable to apply cold air for temperature suppression to the arm 422 in order to suppress thermal expansion.

  Further, the film stretching apparatus 401 of the present embodiment preferably has a clip gripping mechanism interlocked with the sliding of the arm 422 so that the clip 423 starts gripping at both ends of the film at the grip start positions P0 and S0.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

(Examples 1-12, Comparative Examples 1-6)
In this example, the thermoplastic resin film was stretched using the stretching apparatus 1 shown in FIG. 4 to produce an obliquely stretched optical film. As a thermoplastic resin film, norbornene resin pellets (ZEONOR1420, manufactured by Nippon Zeon Co., Ltd.) are dried at 100 ° C. for 5 hours, supplied to an extruder, passed through a polymer pipe and a polymer filter, and formed into a sheet on a casting drum from a T die. And cooled to obtain a long unstretched film (0) having a thickness of 160 μm. The unstretched film (0) was wound up on a roll.

  Next, the unstretched film (0) is pulled out from the roll and set to a pattern having a clip locus as shown in FIG. 1 using the stretching apparatus 1 shown in FIG. A long obliquely stretched optical film having an axis angle of 45 (°) was obtained. At this time, the stretching ratio in the E1 direction in the longitudinal stretching portion was 1, and stretching in the longitudinal direction was not performed. Moreover, the width W2 of the obtained film was 10 mm narrower than the maximum stretched width W1. Each position corresponding to FIG. 1 of the oblique stretching machine 407, that is, stretching start positions P1, S1, stretching stop positions P2, S2, relaxation start positions P3, P3, relaxation stop positions P4, S4 are changed, and θa1, As shown in Table 2, θa2, θb1, and θb2 were stretched under the setting conditions of Examples 1 to 12 and Comparative Examples 1 to 6, and wound on a roll.

  About the obtained obliquely stretched optical film, an automatic birefringence meter (manufactured by Oji Scientific Instruments Co., Ltd.) at a total of 5 points including 2 points 50 mm from the width direction center and both ends in the width direction, and 2 points of the intermediate part in the width direction. The angle of the orientation axis with respect to the conveying direction was measured by the product name “KOBRA-21ADH”). The variation in the angle of the orientation axis was defined as the difference between the maximum value and the minimum value among the values measured at the above five points. Table 2 shows the variation of the orientation axis with respect to the obtained conveyance direction.

(Example 13)
In Example 1, using the rotation mechanism of FIG. 9 so that the clip can rotate at a predetermined angle with respect to the traveling direction of the chain, the gripping direction of the film end is smooth according to the traveling direction of the fill end. Controlled to change. Otherwise, an obliquely stretched optical film was produced in the same manner as in Example 1. The angle of the orientation axis with respect to the transport direction of the produced film was measured in the same manner as in Example 1, and the measurement results are shown in Table 2.

(Example 14)
In Example 1, an obliquely stretched optical film was prepared in the same manner as in Example 1 except that the curved arm of FIG. 11 was used as the arm. The angle of the orientation axis with respect to the transport direction of the produced film was measured in the same manner as in Example 1, and the measurement results are shown in Table 2.

(Example 15)
An obliquely stretched optical film was produced in the same manner as in Example 1, except that in Example 1, two arms were attached to the clip and each arm was controlled, the configuration shown in FIG. 12 was used. The angle of the orientation axis with respect to the transport direction of the produced film was measured in the same manner as in Example 1, and the measurement results are shown in Table 2.

(Example 16)
In Example 1, an obliquely stretched optical film was formed in the same manner as in Example 1 except that the bases corresponding to each other were connected by one arm and two clips arranged on the arm were slid. Produced. The angle of the orientation axis with respect to the transport direction of the produced film was measured in the same manner as in Example 1, and the measurement results are shown in Table 2.

(Example 17)
It produced similarly to Example 1 except having replaced with the thermoplastic resin film in Example 1 and having used the cellulose-ester film produced according to the following.

  The materials used for producing the cellulose ester film are summarized below.

<Fine particle dispersion>
Fine particles 11 parts by weight Ethanol 89 parts by weight The above was stirred and mixed with a dissolver for 50 minutes, and then dispersed with Manton Gorin.

<Fine particle additive solution>
Cellulose ester A was added to a dissolution tank containing methylene chloride and heated to completely dissolve, and this was then added to Azumi filter paper No. 3 manufactured by Azumi Filter Paper Co., Ltd. Filtered using 244. The fine particle dispersion was slowly added thereto while sufficiently stirring the filtered cellulose ester solution. Further, the particles were dispersed by an attritor so that the secondary particles had a predetermined particle size. This was filtered through a Naslon Finepore NF filter manufactured by Nippon Seisen Co., Ltd. to prepare a fine particle addition solution.

Methylene chloride 99 parts by weight Cellulose ester A 4 parts by weight Fine particle dispersion 11 parts by weight A main dope solution having the following composition was prepared. First, methylene chloride and ethanol were added to the pressure dissolution tank. Cellulose ester A was added to a pressurized dissolution tank containing a solvent while stirring. This was heated and stirred to completely dissolve, and a plasticizer and an ultraviolet absorber were further added and dissolved. This was designated as Azumi Filter Paper No. The main dope solution was prepared by filtration using 244.

  In addition to adding 100 parts by mass of the main dope solution and 2 parts by mass of the fine particle additive solution, mix thoroughly with an in-line mixer (Toray static type in-pipe mixer Hi-Mixer, SWJ), and then use a belt casting apparatus to adjust the width. It was cast uniformly on a 2 m stainless steel band support. On the stainless steel band support, the solvent was evaporated until the residual solvent amount became 110%, and the stainless steel band support was peeled off.

<Composition of main dope solution>
Methylene chloride 300 parts by mass Ethanol 57 parts by mass Cellulose ester A 100 parts by mass Plasticizer (A), (B), (C) 5.5 parts by mass of plasticizer (D) 5.5 parts by mass Part UV absorber (A) 0.4 part by weight UV absorber (B) 0.7 part by weight UV absorber (C) 0.6 part by weight The film peeled off from the stainless steel band support was the same as in Example 1. Then, using the stretching apparatus 1 shown in FIG. 4, a long obliquely stretched optical film having an orientation axis angle of 45 (°) with respect to the transport direction was obtained. The angle of the orientation axis with respect to the transport direction of the produced film was measured in the same manner as in Example 1, and the measurement results are shown in Table 2.

  The evaluation is such that the variation value is ◎ if 0.5 ° or less, ○ if 0.5 ° or more and 1.5 ° or less, １．５ if 1.5 ° or more, and 3 ° or less if △ or 3 °. X. If the variation is 3 ° or less, the obliquely stretched optical film can be used for optical compensation of an image display device.

  From the results of Examples 1 to 12 in Table 2, the obliquely stretched optical film in which the variation is 3 ° or less and the molecules are uniformly oriented under the conditions satisfying the above-described formulas (1) to (4). You can see that Moreover, when Examples 1-8 are compared with Examples 9-12, it turns out that having the above-mentioned formula (5) can obtain an obliquely stretched optical film having an orientation axis with less variation. On the other hand, when Examples 1 to 12 and Comparative Example 1 are compared, it can be seen that the variation increases when Expression (4) is out of range under the conditions of Expressions (1) to (4) described above. Further, when Examples 1 to 12 and Comparative Example 2 are compared, it can be seen that the variation increases when Expression (2) is out of the range under the conditions of Expressions (1) to (4) described above. Further, when Examples 1 to 12 and Comparative Examples 3 to 5 are compared, it can be seen that the variation increases when Expression (3) is out of range under the conditions of Expressions (1) to (4) described above. Moreover, when Examples 1-12 are compared with the comparative example 6, when Formula (1) becomes out of the range on the conditions of above-mentioned Formula (1)-(4), it turns out that dispersion | variation becomes large.

  In addition, comparing Example 1 and Example 13, an obliquely stretched optical film with less variation and better optical quality by enabling the clip to rotate at least a predetermined angular range with respect to the traveling direction of the chain. It can be seen that In addition, when Example 1 and Example 14 are compared, it can be seen that an obliquely stretched optical film with less variation and good optical quality can be obtained even if the arm has a curved shape. In addition, when Example 1 and Example 15 are compared, an obliquely stretched optical film with less optical variation and better optical quality can be obtained even when a configuration in which two arms are attached to a clip and each arm is controlled is obtained. I understand that Furthermore, when Example 1 is compared with Example 16, even if the bases corresponding to each other are connected by one arm and two clips arranged on the arm are slid, there is more variation. It can be seen that an obliquely stretched optical film with little optical quality can be obtained.

  In addition, when Example 1 and Example 17 are compared, an oblique stretching apparatus is installed at the subsequent stage of the film production apparatus of the solution casting method in which a thermoplastic resin is dissolved in a solvent and cast on a metal body to produce a film. And even when extending | stretching the film peeled off from the metal body, it turns out that the diagonally stretched optical film with good optical quality can be obtained.

It is a schematic plan view for demonstrating the manufacturing method of the diagonally stretched optical film of this invention. It is the elements on larger scale for demonstrating the extending | stretching start position of a clip. In the manufacturing method of the diagonally stretched optical film of this invention, it is a typical top view which shows the case where the unwinding direction of a film and a conveyance direction have a fixed angle. It is a figure which shows typically sectional drawing of the film extending apparatus which is one Embodiment of this invention. It is a figure which shows typically the top view of the film extending apparatus which is one Embodiment of this invention. It is a figure which shows typically the structure of an oblique drawing machine. It is a figure which shows typically the more detailed structure of an oblique drawing machine. It is a figure which shows typically that the clip of the extending | stretching apparatus of this invention can rotate in the predetermined range with respect to the running direction of an extending | stretching chain. It is a figure which shows typically the specific example that the clip of the extending | stretching apparatus of this invention can rotate in the predetermined range with respect to the running direction of an extending | stretching chain. It is a figure which shows typically that the arm of the extending | stretching apparatus of this invention is curving. It is a figure which shows typically the block diagram for demonstrating a mode that the arm of the extending | stretching apparatus of this invention slides. It is a figure which shows typically the state which attached two arms to the clip of the extending | stretching apparatus of this invention. In the extending | stretching apparatus of this invention, it is a figure which shows typically the structure which has an arm which connected one base and the other base.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Manufacturing apparatus of stretched optical film 2 Unwinding process 3 Stretching process 4 Winding process W1 Maximum stretched width W2 Relaxed width 31 Stretched area 32 Relaxed area 33 Holding area W0 Width of film before stretching P0, S0 Holding start position 21 Unwinding Roll 51, 51, 423 Clip P1, S1 Stretch start position P2, S2 Stretch stop position P3, S3 Relax start position P4, S4 Relax stop position P5, S5 Grasp release position 41 Winding roll 401 Film stretching device (stretching device)
402 Film 403 Feeder 404 Longitudinal Stretching Furnace 405 Intermediate Conveying Device 406 Longitudinal Stretching Section (Vertical Stretching Section)
407 Oblique Stretching Machine 408 Oblique Stretching Furnace 409 Oblique Stretching Diagram (oblique stretching part)
410 Winding device 411 Material reel 412 Reference roll 413, 416 Nip roll 414, 418 Hot air duct (heating means)
415 Ratio roll 417 Stretch chain 419 Tension roll 420 Product reel 421 Base 422 Arm 424 Sprocket 425 Slide shaft 426 Positioning member 427, 428 Guide 501 Compression spring 502 Motor 503 Drive shaft 504, 505 Pinion gear

Claims (7)

A method for producing an obliquely stretched optical film comprising a stretching step of gripping both ends in the width direction of a long film by gripping means and stretching the film so that the transport direction after stretching of the film and the direction of the orientation axis of the film are tilted In
The stretching step includes
A stretching region for stretching the film to the maximum stretching width;
After the stretching region, having a relaxation region that relaxes to a relaxation width that is narrower than the maximum stretching width,
In the stretching region,
A gripping means for gripping one end of the film,
P1 is the position where the film starts to be stretched,
The position where the stretching of the film is stopped is P2,
A gripping means for gripping the other end of the film,
S1 is the position to start stretching the film,
S2 is a position where the stretching of the film is stopped.
And when
An angle θa1 between a straight line connecting P1 and P2 and the transport direction;
The angle θb1 between the straight line connecting S1 and S2 and the transport direction satisfies the following conditional expressions (1) and (2):
In the relaxation region,
A gripping means for gripping one end of the film,
The position where relaxation of the film starts is P3,
The position where the relaxation of the film is stopped is P4,
A gripping means for gripping the other end of the film,
The position where relaxation of the film starts is S3,
The position where the relaxation of the film stops is S4,
And when
An angle θa2 between a straight line connecting P3 and P4 and the transport direction;
A method for producing an obliquely stretched optical film, characterized in that the straight line connecting S3 and S4 and the angle θb2 between the conveying direction satisfy the following conditional expressions (3) and (4).
θa1 ≧ θb1 (1)
θa1 ≦ 16.0 ° (2)
θb2> θa2 (3)
θa2 ≦ 0.30 ° (4) The method for producing an obliquely stretched optical film according to claim 1, wherein the θb1 and the θb2 satisfy the following conditional expression (5).
θb1> θb2 (5) Two chains on both sides of the film transport path;
A number of bases provided in the chain;
An arm that is slidably mounted on the base and protrudes toward the film;
A clip provided at one end of the arm on the film side and capable of gripping both side edges of the film;
In a stretching apparatus for gripping both side edges of the film with the clip and stretching the film by sliding the arm while transporting,
The stretching apparatus, wherein the clip is rotatable at least in a predetermined angle range with respect to a traveling direction of the chain. Two chains on both sides of the film transport path;
A number of bases provided in the chain;
An arm that is slidably mounted on the base and protrudes toward the film;
A clip provided at one end of the arm on the film side and capable of gripping both side edges of the film;
In a stretching apparatus for gripping both side edges of the film with the clip and stretching the film by sliding the arm while transporting,
The stretching apparatus, wherein the arm is curved. Two chains on both sides of the film transport path;
A number of bases provided in the chain;
An arm that is slidably mounted on the base and protrudes toward the film;
A clip provided at one end of the arm on the film side and capable of gripping both side edges of the film;
In a stretching apparatus for gripping both side edges of the film with the clip and stretching the film by sliding the arm while transporting,
A stretching apparatus, wherein a plurality of the arms are attached to the clip. Two chains on both sides of the film transport path;
A number of bases provided in the chain;
Connecting a base provided in one chain and a base provided in the other chain, and an arm attached to each base;
A pair of clips provided slidably on the arm and capable of gripping both side edges of the film;
A stretching apparatus characterized by gripping both side edges of the film with the clip and stretching the film by sliding the clip while being conveyed. The manufacturing method of the diagonally stretched optical film of Claim 1 using the extending | stretching apparatus of any one of Claim 3 thru | or 6.

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