Method for manufacturing an extended film

Abstract

The present invention reduces slack and / or wrinkles generated in oblique stretching of a film. The manufacturing method of the present invention is a manufacturing method of a stretched film, which includes: holding left and right end portions in a width direction of a long film by left and right grippers, respectively; moving the left and right grippers in a walking manner, stretching the film obliquely, and then releasing the film from the left and right grippers; and performing roll conveying of the film using a concave roll having a central portion and end portions on both end sides thereof, the end portions having a cylindrical shape with a radius larger than that of the central portion.

Description

[0001] This application is a divisional application of the application patent application with Chinese National Application No. 202210313115.0, filed on March 28, 2022, and the title of “Manufacturing Method of Extended Film”. TECHNICAL FIELD

[0002] The present application relates to a manufacturing method of an extended film and a manufacturing method of an optical laminate. BACKGROUND

[0003] In image display devices such as liquid crystal display devices (LCDs), organic electroluminescent display devices (OLEDs), and the like, a circularly polarizing plate is used in order to improve display characteristics or prevent reflection. The circularly polarizing plate is typically a laminate of a polarizer and a phase difference film (typically, a λ / 4 plate) in such a manner that the absorption axis of the polarizer and the slow axis of the phase difference film are at an angle of 45°. Hitherto, the phase difference film has been typically produced by uniaxial stretching or biaxial stretching in the longitudinal direction and / or the lateral direction, and thus the slow axis thereof is often exhibited in the lateral direction (width direction) or the longitudinal direction (length direction) of the long film material. As a result, in the production of the circularly polarizing plate, it is necessary to cut the phase difference film in such a manner that the angle with respect to the width direction or the length direction is 45°, and to attach the pieces one by one.

[0004] In addition, in order to ensure the broadband property of the circularly polarizing plate, there is also a case where two phase difference films of a λ / 4 plate and a λ / 2 plate are laminated. In this case, it is necessary that the λ / 2 plate is laminated in such a manner that the angle with respect to the absorption axis of the polarizer is 75°, and the λ / 4 plate is laminated in such a manner that the angle with respect to the absorption axis of the polarizer is 15°. In this case, in the production of the circularly polarizing plate, it is necessary to cut the phase difference film in such a manner that the angle with respect to the width direction or the length direction is 15° and 75°, and to attach the pieces one by one.

[0005] Further, in other embodiments, in order to avoid the reflection of light from a notebook computer into a keyboard or the like, a λ / 2 plate is sometimes used on the viewable side of the polarizing plate with the aim of rotating the orientation of linearly polarized light from the polarizing plate by 90°. In this case, it is necessary to cut the phase difference film in such a manner that the angle with respect to the width direction or the length direction is 45°, and to attach the pieces one by one.

[0006] In order to solve such a problem, a technique has been proposed in which the left and right ends of a long film in the width direction are held by left and right clamps of a variable pitch type in which the pitch of the clamps in the longitudinal direction is varied, the pitch of at least one of the clamps of the left and right clamps is varied, and the slow axis of the phase difference film is exhibited in the oblique direction by stretching in the oblique direction with respect to the length direction (hereinafter also referred to as “oblique stretching”) (for example, Patent Document 1). However, in the obliquely stretched film obtained by this technique, relaxation (sagging) or wrinkles sometimes occur.

[0007] Prior Art Documents

[0008] Patent Documents

[0009] Patent Document 1: Japanese Patent No. 4845619 SUMMARY

[0010] PROBLEMS TO BE SOLVED BY THE INVENTION

[0011] The present invention has been achieved in order to solve the above-described problems, and its main object is to reduce slack and / or wrinkles generated in a film that is extended obliquely.

[0012] MEANS FOR SOLVING THE PROBLEMS

[0013] According to one aspect of the present invention, there is provided a manufacturing method, which is a manufacturing method of an extended film, comprising: holding left and right end portions in a width direction of a long film by left and right grippers, respectively; moving the left and right grippers while extending the film obliquely, and then releasing the film from the left and right grippers; and performing roll conveying of the film using a concave roll having a central portion and end portions on both end sides thereof, the end portions having a cylindrical shape with a radius larger than that of the central portion.

[0014] In one embodiment, the above-described concave roll further has a diameter expansion portion that expands in diameter from both ends of the above-described central portion to the above-described end portions.

[0015] In one embodiment, the difference between the radius of the central portion and the radius of the end portion of the above-described concave roll is 0.2 mm to 2.0 mm.

[0016] In one embodiment, the width of the end portion of the above-described concave roll is 30 mm to 180 mm.

[0017] In one embodiment, in addition to the above-described concave roll, an expansion roll and / or a bending roll are used to perform roll conveying of the film.

[0018] In one embodiment, the above-described grippers are variable pitch type grippers in which the gripper pitch in the longitudinal direction is changed, and the film is extended obliquely while at least one of the left gripper that holds the left end portion of the film and the right gripper that holds the right end portion is moved while changing the gripper pitch thereof.

[0019] In one embodiment, the above-described oblique extension includes: (i) increasing the gripper pitch of one of the above-described left and right grippers from P1 to P2, while decreasing the gripper pitch of the other gripper from P1 to P3; and (ii) changing the gripper pitch of each gripper in such a manner that the decreased gripper pitch and the increased gripper pitch become a prescribed equal pitch.

[0020] In one implementation, P2 / P1 is 1.25 to 1.75, and P3 / P1 is 0.50 or more but less than 1.

[0021] In one embodiment, the membrane is extended obliquely by moving the left clamp holding the left end of the membrane and the right clamp holding the right end at the same speed while changing the transport direction of the membrane midway.

[0022] According to another aspect of the present invention, a method for manufacturing an optical laminate is provided, comprising: obtaining an elongated extended film by the above-described manufacturing method; and continuously bonding the elongated optical film and the elongated extended film together while unifying their length direction.

[0023] In one embodiment, the optical film is a polarizer, and the extended film is a λ / 4 plate or a λ / 2 plate.

[0024] Invention Effects

[0025] In the method for manufacturing the extended film of the present invention, an obliquely extended strip of film is passed through a concave roller having a predetermined shape. This results in an obliquely extended strip of film with reduced slack and / or wrinkles. Attached Figure Description

[0026] Figure 1 A schematic top view illustrating the overall configuration of an example of an extension apparatus that can be used in the method for manufacturing the extension film of the present invention.

[0027] Figure 2 For the purpose of illustration Figure 1 A top view of the main components of the linkage mechanism that changes the clamp spacing in the extension device.

[0028] Figure 3 For the purpose of illustration Figure 1 A top view of the main components of the linkage mechanism that changes the clamp spacing in the extension device.

[0029] Figure 4 A schematic top view illustrating the overall configuration of another example of an extension apparatus that can be used in the method for manufacturing the extension film of the present invention.

[0030] Figure 5A A schematic diagram showing the outline of the clamp spacing in one embodiment of the oblique extension.

[0031] Figure 5B A schematic diagram showing the outline of the clamp spacing in one embodiment of the oblique extension.

[0032] Figure 6 (a) and (b) are schematic top view and schematic side view, respectively, illustrating an example of roll handling.

[0033] Figure 7 FIG. 1 is a schematic plan view for explaining one example of a concave roll having a diameter expansion portion.

[0034] Figure 8 FIG. 2 is a schematic plan view for explaining an extension roll preferably used in an embodiment of the present application.

[0035] Figure 9 FIG. 3 is a schematic plan view for explaining a bending roll preferably used in an embodiment of the present application.

[0036] Figure 10 FIG. 4 is a schematic sectional view of a circularly polarizing plate using a phase difference film obtained by the production method of the present application.

[0037] Figure 11 FIG. 5 is a schematic view for explaining a method of measuring a relaxation amount.

[0038] Explanation of symbols

[0039] 1 Stretched film

[0040] 10L Endless loop

[0041] 10R Endless loop

[0042] 20 Clamp

[0043] 50 Carrying roll

[0044] 51 Concave roll

[0045] 60 Winding section

[0046] 100 Stretching device

[0047] 200 Circularly polarizing plate

[0048] 300 Ultrasonic wave displacement sensor DETAILED DESCRIPTION

[0049] The preferred embodiments of the present application will be described below, but the present application is not limited to these embodiments. In addition, in this specification, the "clamper pitch in the longitudinal direction" means the distance between the centers of the adjacent clamps in the traveling direction in the longitudinal direction. Further, the left-right relationship in the width direction of the long film means the left-right relationship facing the carrying direction of the film, unless otherwise specified.

[0050] A. Method of producing stretched film

[0051] The method for manufacturing the extended film according to the embodiment of the present application includes: holding the left and right end portions of the long film in left and right grips, respectively; moving the left and right grips to extend the film obliquely, and then releasing the film from the left and right grips; and transporting the film by a nip roll using a concave roll. The concave roll used in the embodiment has a central portion and end portions on both end sides thereof, and the end portions have a cylindrical shape with a larger radius than the central portion. In one embodiment, the concave roll has a diameter expanding portion and an end portion in order from the central portion and both ends thereof toward the outside, and the end portion has a cylindrical shape. Typically, the method for manufacturing the extended film according to the embodiment of the present application further includes a preheating step. Specifically, the film held by the left and right grips is preheated and then supplied to the oblique extension.

[0052] As the method for extending the film obliquely by moving the left and right grips, any appropriate method can be used, which can extend the left and right end portions of the film at different extension ratios from each other (as a result, can extend in the oblique direction with respect to the longitudinal direction). For example, a method in which the left grip holding the left end portion of the film and the right grip holding the right end portion are moved at different speeds, and a method in which the left grip holding the left end portion of the film and the right grip holding the right end portion are moved by different distances from each other can be mentioned. In one embodiment of the former oblique extension, the film can be extended in the oblique direction by changing the grip interval of at least one of the left grip holding the left end portion of the film and the right grip holding the right end portion of the film while moving the grips obliquely by using a variable interval type grip in which the grip interval in the longitudinal direction is changed. In one embodiment of the latter oblique extension, the film can be extended in the oblique direction by moving the left grip holding the left end portion of the film and the right grip holding the right end portion at a constant speed while changing the transport direction of the film (as a result, making the transport path lengths of the left and right end portions different) halfway. Furthermore, in the obliquely extended film obtained by the above oblique extension, there is a tendency that slack or wrinkles are easily generated on the side with a smaller extension ratio. Therefore, in one embodiment, the side with a smaller extension ratio at the time of oblique extension can be the slack side in the obliquely extended film. In addition, the above obliquely extended film is preferably a λ / 4 plate or a λ / 2 plate.

[0053] Figure 1Fig. 1 is a schematic plan view of the entire configuration of an example of an extension device that can be used in the oblique extension of the former. The extension device 100a has endless loops 10L and 10R with a plurality of clamps 20 for holding the film on both the left and right sides in a left-right symmetrical manner in plan view. In this specification, the endless loop on the left side is referred to as the left endless loop 10L and the endless loop on the right side is referred to as the right endless loop 10R when viewed from the inlet side of the film. The clamps 20 of the left and right endless loops 10L and 10R are respectively guided to the standard rails 70 to move in a loop. The clamps 20 of the left endless loop 10L move in a counterclockwise direction and the clamps 20 of the right endless loop 10R move in a clockwise direction. In the extension device, the holding area A, the preheating area B, the extension area C, and the release area D are provided in this order from the inlet side of the sheet toward the outlet side. These areas are areas in which the film that is the extension target is substantially held, preheated, obliquely extended, and released, and are not mechanically and structurally independent divisions. Note that, Figure 1 The length ratio of each area in the extension device of the above-described former is different from the ratio of the actual length.

[0054] Figure 1 Although not shown in the above-described embodiment, an area for performing an arbitrary appropriate process can be provided as needed between the extension area C and the release area D. As such a process, a transverse shrinkage process or the like can be given. Also, although not shown, the above-described extension device is typically provided with a heating device (for example, various ovens such as a hot air type, a near-infrared type, and a far-infrared type) for creating a heating environment in each area from the preheating area B to the release area D. In one embodiment, the preheating, the oblique extension, and the release from the clamps can be performed in ovens set to a predetermined temperature, respectively.

[0055] In the holding area A and the preheating area B of the above-described extension device 100a, the left and right endless loops 10L and 10R are configured to be substantially parallel to each other at an interval distance corresponding to the initial width of the film that is the extension target. The extension area C is configured such that the interval distance between the left and right endless loops 10L and 10R gradually expands toward the release area D from one side of the preheating area B to an interval distance corresponding to the width of the film after the extension. In the release area D, the left and right endless loops 10L and 10R are configured to be substantially parallel to each other at an interval distance corresponding to the width of the film after the extension. However, the configuration of the left and right endless loops 10L and 10R is not limited to the example shown above. For example, the left and right endless loops 10L and 10R can be configured to be substantially parallel to each other at an interval distance corresponding to the initial width of the film that is the extension target from the holding area A to the release area D.

[0056] The clamps 20 of the left endless ring 10L (left clamp) and the clamps 20 of the right endless ring 10R (right clamp) can each move independently in a cyclic motion. For example, the drive chain teeth 11 and 12 of the left endless ring 10L are driven counterclockwise by motors 13 and 14, and the drive chain teeth 11 and 12 of the right endless ring 10R are driven clockwise by motors 13 and 14. As a result, the clamp holding members (not shown) of the drive rollers (not shown) meshing with these drive chain teeth 11 and 12 are given a traveling force. Thus, the left endless ring 10L moves in a cyclic motion in the counterclockwise direction, and the right endless ring 10R moves in a cyclic motion in the clockwise direction. By independently driving the left and right motors, the left endless ring 10L and the right endless ring 10R can each move independently in a cyclic motion.

[0057] Furthermore, the clamps 20 of the left endless ring 10L (left clamp) and the clamps 20 of the right endless ring 10R (right clamp) are both variable-pitch types. That is, the left and right clamps 20 are independent, and the clamp spacing in the longitudinal direction can change as the device moves. The variable-pitch type can be achieved by using a pantograph, a linear motor, a motor chain, or other drive methods. For example, Patent Document 1 and Japanese Patent Application Publication No. 2008-44339 describe in detail a fabric tensioning machine type simultaneous dual-axis extension device using a pantograph linkage mechanism. Hereinafter, the linkage mechanism (pantograph mechanism) will be described as an example.

[0058] Figure 2 and Figure 3 These are for explanation Figure 1 A top view of the main components of the linkage mechanism for changing the clamp spacing in the extension device. Figure 2 This indicates the state where the clamp spacing is at its minimum. Figure 3 This indicates that the clamp spacing is at its maximum.

[0059] like Figure 2 and Figure 3 As shown in the diagram, slender rectangular clamping members 30 are provided in the transverse direction of each clamping fixture 20 in plan view. Although not shown, the clamping member 30 is enclosed by an upper beam, a lower beam, a front wall (the wall on the side of the clamp), and a rear wall (the wall on the opposite side of the clamp), forming a robust frame structure. The clamping member 30 is arranged to rotate and travel on the road surfaces 81 and 82 using the traveling wheels 38 at both ends. Furthermore, Figure 2 and Figure 3The traveling wheels (rotating on the traveling surface 81) on the front wall side are not shown. The traveling surfaces 81, 82 run in parallel with the standard rails 70 over the entire area. On the rear side of the upper and lower beams of the jig carrying members 30 (the opposite side of the jig side (hereinafter, the reverse jig side)), long holes 31 are formed along the length direction of the jig carrying members, and the sliders 32 are slidably engaged in the length direction of the long holes 31. In the vicinity of the jig 20 side end of the jig carrying members 30, a first shaft member 33 is vertically provided through the upper and lower beams. On the other hand, a second shaft member 34 is vertically provided through the sliders 32 of the jig carrying members 30. One end of a main link member 35 is pivotally connected to the first shaft member 33 of each jig carrying member 30. The main link member 35 is pivotally connected to the second shaft member 34 of the other jig carrying member 30 adjacent thereto. One end of a sub link member 36 is pivotally connected to the first shaft member 33 of each jig carrying member 30 in addition to the main link member 35. The other end of the sub link member 36 is pivotally connected to the middle portion of the main link member 35 by a pivot 37. By the link mechanism obtained by the main link member 35 and the sub link member 36, as shown in FIG. 6, the more the slider 32 moves toward the rear side (the reverse jig side) of the jig carrying member 30, the smaller the distance in the longitudinal direction between the jig carrying members 30 (the result is the jig pitch) becomes, as shown in FIG. 7. As shown in FIG. 8, the more the slider 32 moves toward the front side (the jig side) of the jig carrying member 30, the larger the distance in the longitudinal direction between the jig carrying members 30 (the result is the jig pitch) becomes. The positioning of the slider 32 is performed by a pitch setting rail 90. As shown in FIG. 9 and FIG. 10, the smaller the distance between the standard rail 70 and the pitch setting rail 90, the larger the jig pitch becomes. Figure 2 Figure 3 Figure 2 Figure 3

[0060] Figure 4 FIG. 6 is a schematic plan view showing the entire configuration of an example of an extension device which can be used in the oblique extension of the latter. The extension device 100b has, in plan view, a ring-shaped endless loop 10L and an endless loop 10R on the left and right sides, each of which has a plurality of jigs 20 for holding a film. The jigs 20 of the left and right endless loops 10L, 10R are guided to the standard rails 40 to move in a circular manner (in the illustrated example, a part of the endless loops 10L, 10R is omitted). The jigs 20 of the left endless loop 10L move in a counterclockwise direction, and the jigs 20 of the right endless loop 10R move in a clockwise direction. In the extension device, from the inlet side to the outlet side of the film, a holding region A, a preheating region B, an extension region C, and a release region D are provided in this order. These regions are regions in which a film to be extended is actually held, preheated, obliquely extended, and released, and are not independent regions in terms of mechanism and structure. Note that, Figure 4 ​​​​The length ratio of each region in the stretching device is different from the ratio of the actual length.

[0061] Figure 4 Although not shown, a region for performing any appropriate processing as needed can be provided between the stretching region C and the release region D. As such processing, a transverse stretching process or a transverse shrinkage process can be cited. Also, although not shown, the above-mentioned stretching device is typically provided with a heating device (for example, various ovens such as a hot air type, a near-infrared type, a far-infrared type, and the like) for making each region from the preheating region B to the release region D a heating environment. In one embodiment, the preheating, the oblique stretching, and the release from the gripper can be performed in ovens set to a prescribed temperature, respectively.

[0062] In the holding region A and the preheating region B of the above-mentioned stretching device 100b, the left endless loop 10L and the right endless loop 10R are configured so as to be substantially parallel to each other at an interval distance corresponding to the initial width of the film to be stretched. In the stretching region C, the left endless loop 10L and the right endless loop 10R are stretched in a direction that is not symmetrical between left and right, whereby the interval distance between the left endless loop 10L and the right endless loop 10R gradually expands to correspond to the width of the film after stretching as the film moves from one side of the preheating region B toward the release region D. In the release region D, the left endless loop 10L and the right endless loop 10R are configured so as to be substantially parallel to each other at an interval distance corresponding to the width of the film after stretching. However, the configuration of the left endless loop 10L and the right endless loop 10R is not limited to the example shown above.

[0063] The grippers (left grippers) 20 of the left endless loop 10L and the grippers (right grippers) 20 of the right endless loop 10R can be independently moved in a tour, respectively. For example, the grippers 20 of the left endless loop 10L and the grippers 20 of the right endless loop 10R are moved in a tour at a constant speed, and the interval distance between the grippers 20 of the left endless loop 10L and the grippers 20 of the right endless loop 10R can be kept constant. Figure 1 As with the above-mentioned stretching device, the drive sprocket 11 of the left endless loop 10L is rotationally driven in the counterclockwise direction by the motor 13, and the drive sprocket 11 of the right endless loop 10R is rotationally driven in the clockwise direction by the motor 13. Typically, the left grippers 20 and the right grippers 20 are moved in a tour at a constant speed, and the interval distance between the grippers 20 in the vertical direction can be kept constant. Further, when the difference between the walking speeds of the pair of left and right grippers is 1% or less, the walking speeds of the two can be said to be constant, and the difference between the walking speeds is preferably 0.5% or less, and more preferably 0.1% or less.

[0064] By using the above-mentioned stretching device to stretch a film obliquely, an obliquely stretched film, for example, a phase difference film having a slow axis in the oblique direction, can be produced. Hereinafter, each process of the method for producing the above-mentioned stretched film will be described in detail.

[0065] A-1. Holding of the film by the grippers

[0066] In the holding area A (film acquisition inlet of the stretching device 100a or 100b), the two end portions of the film to be stretched are held by the grips 20 of the endless loops 10L, 10R on the left and right at a grip interval distance equal to each other or different from each other. The film is sent to the preheating area B by the movement of the grips 20 of the endless loops 10L, 10R (substantially the movement of the grip holding members guided to the standard rails).

[0067] A-2. Preheating

[0068] In the preheating area B, the endless loops 10L, 10R on the left and right are configured in a manner substantially parallel to each other at an interval distance corresponding to the initial width of the film to be stretched as described above, and thus the film is heated without being stretched in the transverse direction or in the longitudinal direction. However, the film can be slightly widened in the distance (width direction) between the grips on the left and right to avoid problems such as contact with the nozzles in the oven due to the preheating.

[0069] In the preheating, the film is heated to a temperature T1 (°C). The temperature T1 is preferably equal to or higher than the glass transition temperature (Tg) of the film, more preferably equal to or higher than Tg + 2°C, and further preferably equal to or higher than Tg + 5°C. On the other hand, the heating temperature T1 is preferably equal to or lower than Tg + 40°C, and more preferably equal to or lower than Tg + 30°C. The temperature T1 is, for example, 70°C to 190°C, and preferably 80°C to 180°C, depending on the film to be used.

[0070] The temperature increase time to reach the above-mentioned temperature T1 and the holding time at the temperature T1 can be appropriately set depending on the constituent material of the film or the manufacturing conditions (for example, the film conveying speed). The temperature increase time and the holding time can be controlled by adjusting the moving speed of the grips 20, the length of the preheating area, the temperature of the preheating area, and the like.

[0071] A-3. Oblique stretching

[0072] A-3-1. Oblique stretching using a variable interval type grip

[0073] In the stretching area C of the stretching device 100a, the film is obliquely stretched by moving the grips 20 on the left and right while changing the longitudinal direction grip interval distance of at least one of them. More specifically, the film is obliquely stretched by increasing or decreasing the grip interval distance of the grips on the left and right at different positions, respectively, changing (increasing and / or decreasing) the grip interval distance of the grips on the left and right at different changing speeds, and the like.

[0074] The oblique stretching can also include transverse stretching. At this time, the oblique stretching is, for example, as described above. Figure 1The oblique stretching can be performed while widening the distance between the left and right clamps (the distance in the width direction). Alternatively, the oblique stretching can be performed while maintaining the distance between the left and right clamps. Figure 1 The oblique stretching can be performed while maintaining the distance between the left and right clamps.

[0075] The oblique stretching can be performed while maintaining the distance between the left and right clamps. final The ratio of the initial width W initial of the film to the width W final of the film after the oblique stretching (W initial / W initial ) is preferably 1.05 to 6.00, more preferably 1.10 to 5.00.

[0076] In one embodiment, the oblique stretching can be performed by increasing or decreasing the clamp distance of each of the left and right clamps to a prescribed distance in a state where the position at which the clamp distance of one of the left and right clamps starts to increase or decrease and the position at which the clamp distance of the other clamp starts to increase or decrease are different in the longitudinal direction. For the oblique stretching of this embodiment, for example, reference can be made to the description in Patent Document 1, Japanese Patent Application Publication No. 2014-238524, and the like.

[0077] In another embodiment, the oblique stretching can be performed by, after increasing or decreasing the clamp distance of one of the left and right clamps to a prescribed distance in a state where the clamp distance of the other clamp is fixed, returning to the initial clamp distance. For the oblique stretching of this embodiment, for example, reference can be made to the description in Japanese Patent Application Publication No. 2013-54338, Japanese Patent Application Publication No. 2014-194482, and the like.

[0078] In another embodiment, the oblique stretching can be performed by (i) increasing the clamp distance of one of the left and right clamps from PI to P2 while decreasing the clamp distance of the other clamp from PI to P3, and (ii) changing the clamp distance of each of the clamps in such a manner that the decreased clamp distance and the increased clamp distance become a prescribed equal distance. For the oblique stretching of this embodiment, for example, reference can be made to the description in Japanese Patent Application Publication No. 2014-194484, and the like. The oblique stretching of this embodiment can further include obliquely stretching the film while widening the distance between the left and right clamps, increasing the clamp distance of one of the clamps from PI to P2 while decreasing the clamp distance of the other clamp from PI to P3 (first oblique stretching), and obliquely stretching the film while widening the distance between the left and right clamps, maintaining the clamp distance of the one clamp at P2 or decreasing it to P4 and increasing the clamp distance of the other clamp to P2 or P4 in such a manner that the clamp distance of the left and right clamps becomes equal (second oblique stretching).

[0079] In the first oblique extension described above, by elongating one end of the membrane in the length direction while simultaneously contracting the other end in the length direction during oblique extension, a slow axis can be achieved with high uniaxiality and in-plane orientation in the desired direction (e.g., a direction at 45° relative to the length direction). Furthermore, in the second oblique extension, by reducing the difference in the distance between the left and right clamps while performing oblique extension, excess stress can be alleviated while sufficient extension is achieved in the oblique direction.

[0080] In the oblique extension of the above three embodiments, since the film can be released from the clamps when the moving speeds of the left and right clamps become equal, it is difficult for uneven film transport speed to occur when the left and right clamps are released, and subsequent film winding can also be performed appropriately.

[0081] Figure 5A and Figure 5B This is a schematic diagram illustrating one example of the outline of the clamp spacing in the oblique extensions including the first and second oblique extensions described above. Hereinafter, the first oblique extension will be described in detail with reference to these diagrams. Furthermore, in Figure 5A and Figure 5B In the diagram, the horizontal axis corresponds to the travel distance of the clamps. At the start of the first oblique extension, the clamp spacing on both sides is P1. P1 is representative of the clamp spacing when holding the film. Simultaneously with the start of the first oblique extension, the clamp spacing of one clamp (hereinafter sometimes referred to as the first clamp) begins to increase while the clamp spacing of the other clamp (hereinafter sometimes referred to as the second clamp) begins to decrease. During the first oblique extension, the clamp spacing of the first clamp is increased to P2, and the clamp spacing of the second clamp is decreased to P3. Therefore, at the end of the first oblique extension (and at the start of the second oblique extension), the second clamp moves with a clamp spacing of P3, and the first clamp moves with a clamp spacing of P2. Furthermore, the ratio of the clamp spacings can be approximated by the ratio of the clamp movement speeds.

[0082] Figure 5A and Figure 5BIn the first inclined stretching, the timing at which the clamping distance of the first clamp starts to increase and the timing at which the clamping distance of the second clamp starts to decrease can be after the clamping distance of the first clamp starts to increase, and the clamping distance of the second clamp can start to decrease after the clamping distance of the first clamp starts to increase. In one preferred embodiment, the clamping distance of the second clamp can start to decrease after the clamping distance of the first clamp starts to increase. According to this embodiment, since the film has already been stretched in the width direction to some extent (preferably, about 1.2 to 2.0 times), even if the clamping distance of the second clamp is greatly decreased, it is difficult for wrinkles to occur. Therefore, more acute inclined stretching can be performed, and a phase difference film having high uniaxiality and in-plane orientation can be preferably obtained.

[0083] Also, in the first inclined stretching, Figure 5A and Figure 5B In the first inclined stretching, the increase in the clamping distance of the first clamp and the decrease in the clamping distance of the second clamp can continue until the end of the first inclined stretching (at the start of the second inclined stretching), but unlike the illustrated example, either one of the increase or the decrease in the clamping distance can end earlier than the other, and until the other ends (until the end of the first inclined stretching), the clamping distance can be maintained as it is.

[0084] The rate of change in the clamping distance of the first clamp (P2 / P1) is preferably 1.25 to 1.75, more preferably 1.30 to 1.70, and further preferably 1.35 to 1.65. In addition, the rate of change in the clamping distance of the second clamp (P3 / P1) is, for example, 0.50 or more and less than 1, preferably 0.50 to 0.95, more preferably 0.55 to 0.90, and further preferably 0.55 to 0.85. When the rate of change in the clamping distance is within this range, in a direction of about 45 degrees with respect to the longitudinal direction of the film, a slow axis can be exhibited with high uniaxiality and in-plane orientation.

[0085] The clamping distance can be adjusted as described above by adjusting the interval distance between the pitch setting rail and the standard rail of the stretching device and the position of the slide.

[0086] The stretching ratio in the width direction of the film in the first inclined stretching (the film width at the end of the first inclined stretching / the film width before the first inclined stretching) is preferably 1.1 to 3.0, more preferably 1.2 to 2.5, and further preferably 1.25 to 2.0. When the stretching ratio is less than 1.1, tinny wrinkles can sometimes occur at the end of the side that is shrunk. In addition, when the stretching ratio exceeds 3.0, the biaxiality of the obtained phase difference film becomes high, and in the case of being applied to a circular polarizing plate or the like, the viewing angle characteristics can sometimes be reduced.

[0087] In one embodiment, the first oblique extension is performed in such a manner that the product of the rate of change of the nip pitch of the first clamp and the rate of change of the nip pitch of the second clamp is preferably 0.7 to 1.5, more preferably 0.8 to 1.45, and further preferably 0.85 to 1.40. When the product of the rates of change is within this range, a phase difference film having high uniaxiality and in-plane orientation can be obtained.

[0088] Next, one embodiment of the second oblique extension will be described specifically while referring to Figure 5A Next, one embodiment of the second oblique extension will be described specifically while referring to

[0089] Figure 5A The rate of change of the nip pitch of the second clamp (P2 / P3) in the second oblique extension of the illustrated embodiment is not limited as long as the effect of the present application is not impaired. The rate of change (P2 / P3) is, for example, 1.3 to 4.0, and preferably 1.5 to 3.0.

[0090] Next, one embodiment of the second oblique extension will be described specifically while referring to Figure 5B Next, one embodiment of the second oblique extension will be described specifically while referring to

[0091] Figure 5B The rate of change of the nip pitch of the first clamp (P4 / P2) and the rate of change of the nip pitch of the second clamp (P4 / P3) in the second oblique extension of the illustrated embodiment are not limited as long as the effect of the present application is not impaired. The rate of change (P4 / P2) is, for example, 0.4 or more and less than 1.0, and preferably 0.6 to 0.95. In addition, the rate of change (P4 / P3) is, for example, more than 1.0 and 2.0 or less, and preferably 1.2 to 1.8. It is preferable that P4 be P1 or more. When P4 < P1, problems such as generation of wrinkles at the end portion and deterioration of biaxiality can occur.

[0092] The extension ratio in the width direction of the film in the second oblique stretching (the film width at the end of the second oblique stretching / the film width at the end of the first oblique stretching) is preferably 1.1 to 3.0 times, more preferably 1.2 to 2.5 times, and further preferably 1.25 to 2.0 times. When the extension ratio is less than 1.1 times, a white-iron-like wrinkle can sometimes occur at the end of the side that shrinks. In addition, when the extension ratio exceeds 3.0 times, the biaxiality of the resulting phase difference film can become high, and in the case of being applied to a circularly polarizing plate or the like, there can be a case where the viewing angle characteristics are reduced. In addition, the extension ratio in the width direction in the first and second oblique stretching (the film width at the end of the second oblique stretching / the film width before the first oblique stretching) is preferably 1.2 to 4.0 times, and more preferably 1.4 to 3.0 times, from the same viewpoint as described above.

[0093] The oblique stretching can be typically performed at a temperature T2. The temperature T2 is preferably Tg - 20°C to Tg + 30°C, further preferably Tg - 10°C to Tg + 20°C, and particularly preferably around Tg, with respect to the glass transition temperature (Tg) of the film. The temperature T2 is, for example, 70°C to 180°C, and preferably 80°C to 170°C, depending on the film to be used. The difference (T1 - T2) between the above-mentioned temperature T1 and the temperature T2 is preferably ±2°C or more, and more preferably ±5°C or more. In one embodiment, T1 > T2, and thus the film heated to the temperature T1 in the preheating zone can be cooled to the temperature T2.

[0094] As described above, the transverse shrinkage treatment can also be performed after the oblique stretching. For this treatment after the oblique stretching, reference can be made to paragraphs 0029 to 0032 of Japanese Patent Application Publication No. 2014-194483.

[0095] A-3-2. Oblique stretching using a jig of a fixed distance type

[0096] In the stretching zone C of the stretching device 100b, the constitution is such that the left endless loop 10L and the right endless loop 10R are stretched in asymmetric directions, and as a result, the direction of conveyance of the film is changed (specifically, the direction of conveyance of the film in the preheating zone B (the direction of extension of the arrow B) and the direction of conveyance of the film in the release zone D (the direction of extension of the arrow D) become non-parallel). Due to this constitution, the lengths of the left and right endless loops 10L, R in the oblique stretching zone C (in other words, the walking distances of the left and right jigs in the oblique stretching zone C) are different. As a result, the pair of left and right jigs that walk at a constant speed become the jig of the above-mentioned walking distance that is shorter to walk first (in this embodiment, the left jig walks first), and the film is stretched in the oblique direction. For the oblique stretching of this embodiment, reference can be made to the description of Japanese Patent Application Publication No. 2004-226686, WO2007 / 111313, and the like. Figure 4 ​

[0097] The oblique stretching is preferably performed at a temperature T2. The temperature T2 is preferably Tg - 20°C to Tg + 30°C, further preferably Tg - 10°C to Tg + 20°C, and particularly preferably around Tg, with respect to the glass transition temperature (Tg) of the film. The temperature T2 varies depending on the film to be used, but is, for example, 70°C to 180°C, and preferably 80°C to 170°C. The difference (T1 - T2) between the above-mentioned temperature T1 and the temperature T2 is preferably ±2°C or more, and more preferably ±5°C or more. In one embodiment, T1 > T2, and thus the film heated to the temperature T1 in the preheating zone can be cooled to the temperature T2.

[0098] As described above, the transverse shrinkage treatment can be performed after the oblique stretching. For this treatment after the oblique stretching, reference can be made to paragraphs 0029 to 0032 of Japanese Patent Application Publication No. 2014-194483.

[0099] A-4. Release from the grippers

[0100] The film is released from the grippers at any position in the release zone D. In the release zone D, neither the transverse stretching nor the longitudinal stretching is generally performed, and the film is heat-treated as necessary, fixed (heat-fixed) in the stretched state, and / or cooled to below Tg, and then released from the grippers. In addition, when heat-fixed, the pitch between the grippers in the longitudinal direction can be reduced, and thus the stress can be relaxed.

[0101] The heat treatment is preferably performed at a temperature T3. The temperature T3 varies depending on the film to be stretched, and can be either T2 ≥ T3 or T2 < T3. In general, when the film is an amorphous material, there is a case where the crystallization treatment is performed at T2 ≥ T3, and when the film is a crystalline material, there is a case where the crystallization treatment is performed at T2 < T3. When T2 ≥ T3, the difference (T2 - T3) between the temperatures T2 and T3 is preferably 0°C to 50°C. The heat treatment time is typically 10 seconds to 10 minutes.

[0102] In one embodiment, the width of the film released from the grippers (resulting in the width of the film supplied to the roll-to-roll transport using a concave roll described later) is, for example, 1500 mm to 3000 mm, preferably 1800 mm to 2700 mm, and more preferably 2000 mm to 2400 mm.

[0103] A-5. Roll-to-roll transport

[0104] The film released from the jig described above is subjected to roll transport using a concave roll. The concave roll has a structure in which the diameter of the end portion is larger than that of the central portion, and the difference in circumferential speed between the central portion and the end portion can function to expand the film. The concave roll used in the embodiments of the present application has a cylindrical shape in which the central portion and the end portions on both end sides thereof have radii larger than that of the central portion. In one embodiment, a concave roll having a central portion and end portions on both end sides thereof, the end portions having a cylindrical shape with radii larger than that of the central portion, can be preferably used. In addition, in the present specification, a cylindrical transport roll used in general roll transport is sometimes referred to as a flat roll.

[0105] Figure 6 (a) and Figure 6 (b) are schematic plan and side views, respectively, illustrating one example of roll transport using the concave roll described above, Figure 7 is a schematic plan view of one example of a concave roll having a diameter expansion portion. In the roll transport illustrated in the example, the film 1 fed out from the stretching device 100 is transported through seven rolls (the concave roll 51 and the first to sixth flat rolls 52 to 57), and is wound up at the winding section 60.

[0106] Figure 7 The concave roll 51 illustrated has a central portion 51a and a diameter expansion portion 51b and an end portion 51c present in this order toward the outside from both ends thereof. The central portion 51a and the end portion 51c each have a cylindrical shape, and the concave roll 51 has a point-symmetrical shape with the center of the rotation axis A as the center of symmetry. When the concave roll 51 is arranged so that the central portion thereof overlaps the film 1 in the width direction thereof, the concave roll 51 is expected to function to expand the film symmetrically with respect to the central portion and the left and right of the film in the width direction thereof due to its shape, but when it is applied to a diagonal stretching film having slack and / or wrinkles due to the slack on one side thereof, an excellent effect of reducing the slack and / or wrinkles while substantially maintaining the target axial angle and in-plane retardation can be obtained. The reason for obtaining this effect is not certain, but it is presumed that when there is slack and / or wrinkles, they are improved by a slight stretching effect, and in addition, since uniform tension is applied to the film in the width direction thereof at this time, the characteristics of the film can be maintained uniformly.

[0107] The difference X between the radius of the central portion 51a and the radius of the end portion 51c can be, for example, 0.2 mm to 2.0 mm. In addition, the width W4 of the end portion 51c can be, for example, 20 mm to 200 mm, and preferably 30 mm to 180 mm. When the difference X and / or the width W4 are within this range, the effect of reducing the slack and / or wrinkles can be preferably obtained. In addition, in the illustrated example, the central portion 51a has a width W2 and has a cylindrical shape, but the width W2 of the central portion 51a can be 0 mm, in which case the concave roll has a structure in which the diameter is expanded from the central portion (the center line Cl) toward both end portions in the width direction.

[0108] In one embodiment, the difference X between the radius of the central portion 51a and the radius of the end portion 51c is preferably 0.6 mm to 1.8 mm, more preferably 0.8 mm to 1.5 mm. In addition, the width W4 of the end portion 51c can be preferably 30 mm to 180 mm, more preferably 30 mm to 160 mm. When the difference X and / or the width W4 is in this range, a relaxation reduction effect can be more preferably obtained.

[0109] In one embodiment, the difference X between the radius of the central portion 51a and the radius of the end portion 51c is preferably 0.3 mm to 1.8 mm, more preferably 0.4 mm to 1.5 mm. In addition, the width W4 of the end portion 51c can be preferably 30 mm to 130 mm, more preferably 30 mm to 120 mm. When the difference X and / or the width W4 is in this range, a wrinkle reduction effect can be more preferably obtained.

[0110] In one embodiment, the difference X between the radius of the central portion 51a and the radius of the end portion 51c is preferably 0.6 mm to 1.8 mm, more preferably 0.8 mm to 1.5 mm. In addition, the width W4 of the end portion 51c can be preferably 30 mm to 130 mm, more preferably 30 mm to 120 mm. When the difference X and / or the width W4 is in this range, a relaxation and wrinkle reduction effect can be more preferably obtained.

[0111] The diameter expansion rate (X / W3 x 100) of the diameter expansion portion 51b is, for example, 0.1% to 6.0%, preferably 0.2% to 5.0%, more preferably 1.0% to 4.5%. When the diameter expansion rate is in this range, a relaxation and / or a wrinkle reduction effect can be obtained while substantially maintaining the intended axial angle and in-plane retardation. In the illustrated example, the diameter expansion portion expands linearly, but the diameter expansion portion can be concave.

[0112] Instead of the illustrated example, a concave roll without a diameter expansion portion (i.e., a concave roll in which the end portions are vertically erected from both ends of the central portion) can also be used. For the difference X between the radius of the central portion 51a and the radius of the end portion 51c and the width W4 of the end portion 51c in such a concave roll, the same description as the above-described concave roll with a diameter expansion portion can be applied.

[0113] The total width Wl of the concave roll 51 and the width W2 of the central portion 51a can be appropriately set in accordance with the film width at the time of roll passage, the width W4 of the end portion, the diameter expansion rate, the difference X, and the like. The total width Wl of the concave roll 51 can be designed, for example, so that the left and right end portions 51c each overlap the film on the roll passage by, for example, 5 mm to 195 mm, for example, 10 mm to 190 mm.

[0114] The forming material of the concave roll is not particularly limited as long as the effect of the present application is obtained, and for example, rubber or metal can be given.

[0115] The angle of contact of the film as it passes through the concave roll is, for example, 45° to 135°, preferably 70° to 100°. When the angle of contact is within this range, the effects of the present application can be preferably obtained.

[0116] As shown in the illustrated example, the roll conveying can be performed by a plurality of rolls including the concave roll. In the roll conveying, the total number of rolls (including the concave roll) through which the film passes can be, for example, 1 to 12, preferably 2 to 10, more preferably 3 to 8. At this time, the order in which the film passes through the concave roll among all the rolls is not particularly limited, and the concave roll can be disposed at any position.

[0117] In one embodiment, in addition to the concave roll, an expansion roll and / or a bending roll can be used in combination for the roll conveying. By using them in combination, the relaxation reduction effect can be more preferably obtained. The disposition position of the expansion roll and the bending roll is not particularly limited. These rolls can be disposed at any position upstream or downstream of the concave roll in the conveying direction.

[0118] Figure 8 is a schematic plan view illustrating the expansion roll preferably used in the above-described embodiment. Figure 8 The expansion roll 58 shown is a linear roll. The expansion roll 58 has a long shaft 58a, a pair of support substrates 58b attached to both ends of the long shaft 58a, a pair of ring members 58c attached to the inner sides of the support substrates 58b and disposed facing each other in a manner to expand at an angle θ with respect to the conveying direction of the film, and a plurality of elastic pads (typically, rubber pads) 58d provided at a predetermined interval in the circumferential direction between the pair of ring members 58c. The ring member 58c is configured to have a bearing and to be rotatable in the circumferential direction with the elastic pad 58d and the film being conveyed by the frictional force of the elastic pad 58d. In addition, the ring member 58c is configured in a manner that the angle θ with respect to the conveying direction of the film can be arbitrarily changed. In the illustrated example, the angle θ is configured to be changeable by the insertion amount of four adjustment bolts 58e, but the angle θ can be changed by other configurations. The larger the angle θ of the expansion roll, the greater the expansibility.

[0119] The inclination angle θ of the ring member can be, for example, more than 0° and 4.0° or less, preferably 0.1° to 3.5°. By using the expansion roll at this inclination angle, a long-stretch film with reduced relaxation can be more preferably obtained while substantially maintaining the target axial angle and in-plane phase difference.

[0120] Figure 9 is a schematic plan view illustrating the bending roll preferably used in the above-described embodiment. Figure 9The illustrated bending roller 59 bends the widthwise center (center line C3) symmetrically about the center in a manner that protrudes toward the conveyance direction. When using a bending roller, it is preferable to perform nip conveyance of the widthwise center (center line C2) of the film 1 and the widthwise center (center line C3) of the bending roller in a manner that the end portion of the film 1 on the side of the unrelaxed side is closer to the widthwise center of the bending roller than the end portion on the relaxed side. By performing conveyance in this manner, since a greater tension is applied to the side of the film that is unrelaxed than the relaxed side, it is advantageous to reduce the relaxation.

[0121] The bending roller 59 has, for example, a structure in which a plurality of radial ball bearings (not shown) are attached around the bending shaft 59a, and a cylinder formed of an elastic material that can elastically deform, such as rubber, covers the surface of the cylinder in a manner that the cylinder can rotate about the bending shaft 59b. Furthermore, the bending roller can be either fixed in terms of the degree of bending or variable in terms of the degree of bending, and either can be used.

[0122] The bending amount D (mm) and the total width W5 (mm) of the bending roller 59 can be set to appropriate values corresponding to the desired amount of relaxation reduction, the film width, and the like. The bending amount D can be, for example, 5 mm to 15 mm, and preferably 8 mm to 13 mm. The bending ratio (D / W5 x 100) of the bending roller 59 can be, for example, 0.1% to 1.5%, and preferably 0.2% to 0.7%. When the bending amount and / or the bending ratio are within this range, a long-stretch film in which the relaxation is reduced can be preferably obtained while substantially maintaining the intended axis angle and in-plane phase difference. Furthermore, the total width W5 of the bending roller 59 can be, for example, 105% to 170% of the width of the film 1, and preferably 110% to 155%.

[0123] The distance between the widthwise center of the film 1 and the widthwise center of the bending roller 59 (the distance between the center line C2 of the film 1 and the center line C3 of the bending roller) L when passing through the bending roller 59 is, for example, 40 mm to 120 mm, preferably 45 mm to 110 mm, and more preferably 50 mm to 100 mm.

[0124] The above-described nip conveyance is preferably performed while applying a tension to the film after being released from the jig. By applying a tension to the entire film in addition to the relaxation correction using the concave roller, the relaxation and / or the wrinkles can be more effectively reduced. The tension applied to the film is, for example, 100 N / m or more, preferably 200 N / m or more, and more preferably 250 N / m to 500 N / m. The application of the tension can be performed, for example, by measuring the tension applied to the film between the conveyance rollers and the like, and controlling the rotation speed of the conveyance rollers in a manner that the tension reaches a desired value.

[0125] The tension application can be performed from the time after the release from the grippers to the time when the conveyance rollers are reached (for example, from the time after the release from the grippers to the time when the nip rollers downstream of the concave rollers are reached).

[0126] The time of the tension application can be appropriately set in accordance with the forming material of the film, the amount of relaxation, and the like. The time can be, for example, 5 seconds to 60 seconds.

[0127] The nip conveyance can be performed in a heated environment, and can also be performed in a non-heated environment. The nip conveyance is preferably performed in a non-heated environment. By passing the concave rollers in a non-heated environment, the generation of scratches can be prevented, and the relaxation and / or the wrinkles can be reduced. The atmospheric temperature of the non-heated environment can be, for example, about 15°C to about 40°C, for example, about 20°C to about 30°C. In addition, the atmospheric temperature of the heated environment can be, for example, the same as the atmospheric temperature in the release region of the stretching device described above.

[0128] The film 1 that has been subjected to the nip conveyance is wound in the winding section 60, and a film roll can be formed. Alternatively, instead of winding the film, the film can be continuously joined in the lengthwise direction while being conveyed together with other long optical films, and an optical laminate can be formed.

[0129] In one embodiment, the relaxation amount of the stretched film that is released from the grippers and is sent out from the stretching device while being subjected to the nip conveyance using only the flat rollers is measured, and when a relaxation amount of a predetermined amount or more is detected, the nip conveyance is performed by changing at least one of the flat rollers to the concave rollers, and the relaxation amount of the stretched film that is obtained thereafter can be reduced.

[0130] A-6. Detection of the relaxation amount

[0131] The relaxation amount can be detected, for example, between the conveyance rollers. Specifically, the relaxation amount can be detected at a midpoint between the conveyance rollers as a difference in the position in the widthwise direction of the film (conveyance height).

[0132] The distance between the conveyance rollers at the time of the detection is not particularly limited, and can be, for example, 500 mm to 2000 mm, and is preferably 700 mm to 1500 mm.

[0133] The tension of the film at the time of the detection is not particularly limited, and can be, for example, 50 N / m to 400 N / m, and is preferably 100 N / m to 200 N / m. When the conveyance tension is too high, the film in the conveyance can be elastically deformed, and the relaxation can become difficult to detect. On the other hand, when the conveyance tension is too low, the tension itself can become unstable, and the measured value of the relaxation can become unstable.

[0134] The detection can be performed in a non-heated environment. The atmospheric temperature at the time of the detection of the relaxation amount is, for example, about 15°C to about 40°C, and can also be, for example, about 20°C to about 30°C.

[0135] In one embodiment, the widthwise left and right end portions of the extended film released from the jig are cut off and removed, and then the amount of relaxation is measured. By measuring the amount of relaxation with the two end portions removed, a more accurate measurement result can be obtained.

[0136] The width of the end portions cut off and removed is independent, and for example, can be 20 mm to 600 mm, and preferably can be 100 mm to 500 mm. The cutting and removal of the end portions can be performed by slit processing.

[0137] The amount of relaxation reduction (amount of relaxation of the film subjected to roll transfer without using a concave roll - amount of relaxation of the film subjected to roll transfer using a concave roll: the amount of relaxation measured with a roll gap distance of 1000 mm) obtained by the manufacturing method of the extended film of the present application can be, for example, 3 mm or more, preferably 5 mm or more, more preferably 8 mm or more, and further preferably 10 mm or more. In addition, the amount of relaxation that can remain in the film after the roll transfer using a concave roll described above can be, for example, less than 15 mm, preferably 10 mm or less, more preferably 8 mm or less, further preferably 5 mm or less, and further more preferably less than 3 mm.

[0138] B. Film to be extended

[0139] In the manufacturing method of the present application, any appropriate film can be used. For example, a resin film that can be used as a phase difference film can be mentioned. As a material constituting such a film, for example, polycarbonate-based resins, polyvinyl acetal-based resins, cyclic olefin-based resins, acrylic-based resins, cellulose ester-based resins, cellulose-based resins, polyester-based resins, polyester carbonate-based resins, olefin-based resins, polyurethane-based resins, and the like can be mentioned. Polycarbonate resins, cellulose ester-based resins, polyester-based resins, polyester carbonate-based resins, and cyclic olefin resins are preferred. The reason for this is that if these resins are used, a phase difference film exhibiting so-called reverse dispersion wavelength dependence can be obtained. These resins can be used alone or in combination in accordance with the desired properties.

[0140] As the polycarbonate-based resin described above, any appropriate polycarbonate-based resin can be used. For example, a polycarbonate resin containing a structural unit derived from a dihydroxy compound is preferable. As specific examples of the dihydroxy compound, 9,9-bis(4-hydroxyphenyl)fluorene, 9,9-bis(4-hydroxy-3-methylphenyl)fluorene, 9,9-bis(4-hydroxy-3-ethylphenyl)fluorene, 9,9-bis(4-hydroxy-3-n-propylphenyl)fluorene, 9,9-bis(4-hydroxy-3-isopropylphenyl)fluorene, 9,9-bis(4-hydroxy-3-n-butylphenyl)fluorene, 9,9-bis(4-hydroxy-3-sec-butylphenyl)fluorene, 9,9-bis(4-hydroxy-3-t-butylphenyl)fluorene, 9,9-bis(4-hydroxy-3-cyclohexylphenyl)fluorene, 9,9-bis(4-hydroxy-3-phenylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)phenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-methylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-isopropylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-isobutylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-t-butylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-cyclohexylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-phenylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3,5-dimethylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-t-butyl-6-methylphenyl)fluorene, 9,9-bis(4-(3-hydroxy-2,2-dimethylpropoxy)phenyl)fluorene, and the like can be given. The polycarbonate resin can contain, in addition to the structural unit derived from the dihydroxy compound described above, a structural unit derived from a dihydroxy compound such as isosorbide, isomannide, isoidide, spiroglycol, dioxane glycol, diethylene glycol (DEG), triethylene glycol (TEG), polyethylene glycol (PEG), cyclohexanedimethanol (CHDM), tricyclodecanedimethanol (TCDDM), bisphenols, and the like.

[0141] Details of such a polycarbonate-based resin described above are described, for example, in Japanese Patent Application Publication No. 2012-67300 and Japanese Patent No. 3325560. The description of these patent documents is incorporated herein by reference.

[0142] The polycarbonate-based resin preferably has a glass transition temperature of 110°C to 250°C, more preferably 120°C to 230°C. When the glass transition temperature is too low, there is a tendency that heat resistance becomes poor; and after film formation, dimensional changes can occur. When the glass transition temperature is too high, there are cases where the stability of molding during film formation becomes poor, and in addition, cases where the transparency of the film is impaired. Furthermore, the glass transition temperature is obtained according to JIS K 7121 (1987).

[0143] As the above polyvinyl acetal-based resin, any appropriate polyvinyl acetal-based resin can be used. Typically, the polyvinyl acetal-based resin can be obtained by subjecting at least two aldehyde compounds and / or ketone compounds to a condensation reaction with a polyvinyl alcohol-based resin. Specific examples of the polyvinyl acetal-based resin and detailed production methods are described, for example, in Japanese Patent Application Publication No. 2007-161994. The description is incorporated herein by reference.

[0144] The stretched film (retardation film) obtained by stretching the above film to be stretched preferably exhibits a refractive index characteristic of a relationship of nx>ny. In one embodiment, the retardation film preferably functions as a λ / 4 plate. In the present embodiment, the in-plane retardation Re(550) of the retardation film (λ / 4 plate) is preferably 100 nm to 180 nm, more preferably 135 nm to 155 nm. In another embodiment, the retardation film preferably functions as a λ / 2 plate. In the present embodiment, the in-plane retardation Re(550) of the retardation film (λ / 2 plate) is preferably 230 nm to 310 nm, more preferably 250 nm to 290 nm. In the present specification, nx is the refractive index in the direction in which the in-plane refractive index is the largest (i.e., the slow axis direction), ny is the refractive index in the direction orthogonal to the slow axis in the plane (i.e., the fast axis direction), and nz is the refractive index in the thickness direction. In addition, Re(λ) is the in-plane retardation of the film measured at 23°C with light of wavelength λ nm. Thus, Re(550) is the in-plane retardation of the film measured at 23°C with light of wavelength 550 nm. Re(λ) is a value obtained from the formula: Re(λ) = (nx-ny) x d, when the thickness of the film is d (nm).

[0145] The in-plane retardation Re(550) of the retardation film can be made to be in the desired range by appropriately setting the oblique stretching conditions. For example, a method of producing a retardation film having an in-plane retardation Re(550) of 100 nm to 180 nm by oblique stretching is disclosed in detail in Japanese Patent Application Publication Nos. 2013-54338, 2014-194482, 2014-238524, 2014-194484, and the like. Thus, a person skilled in the art can set appropriate oblique stretching conditions based on the disclosure.

[0146] When a circularly polarizing plate is produced using one retardation film, or the orientation of linearly polarized light is rotated by 90° using one retardation film, the slow axis direction of the retardation film used is preferably 30° to 60° or 120° to 150°, more preferably 38° to 52° or 128° to 142°, further preferably 43° to 47° or 133° to 137°, particularly preferably about 45° or 135°, with respect to the length direction of the film.

[0147] In addition, when a circularly polarizing plate is produced using two phase difference films (specifically, a λ / 2 plate and a λ / 4 plate), the slow axis direction of the phase difference film (λ / 2 plate) used is preferably 60° to 90°, more preferably 65° to 85°, and particularly preferably about 75°, with respect to the longitudinal direction of the film. In addition, the slow axis direction of the phase difference film (λ / 4 plate) is preferably 0° to 30°, more preferably 5° to 25°, and particularly preferably about 15°, with respect to the longitudinal direction of the film.

[0148] The phase difference film preferably exhibits a so-called reverse dispersion wavelength dependence. Specifically, the in-plane retardation thereof satisfies the relationship Re(450) < Re(550) < Re(650). Re(450) / Re(550) is preferably 0.8 or greater and less than 1.0, and more preferably 0.8 to 0.95. Re(550) / Re(650) is preferably 0.8 or greater and less than 1.0, and more preferably 0.8 to 0.97.

[0149] The absolute value of the photoelastic modulus of the phase difference film is preferably 2 x 10 -12 (m 2 / N) to 100 x 10 -12 (m 2 / N), and more preferably 5 x 10 -12 (m 2 / N) to 50 x 10 -12 (m 2 / N).

[0150] C. Optical laminate and method for manufacturing the optical laminate

[0151] The stretched film obtained by the manufacturing method of the present application can be used as an optical laminate by being laminated with other optical films. For example, a phase difference film obtained by the manufacturing method of the present application can be laminated with a polarizing plate, and preferably used as a circularly polarizing plate.

[0152] Figure 10 is a schematic cross-sectional view of one example of such a circularly polarizing plate. The illustrated circularly polarizing plate 200 has a polarizer 210, a first protective film 220 disposed on one side of the polarizer 210, a second protective film 230 disposed on the other side of the polarizer 210, and a phase difference film 240 disposed outside the second protective film 230. The phase difference film 240 is a stretched film (e.g., a λ / 4 plate) obtained by the manufacturing method described in item A. The second protective film 230 can also be omitted. In this case, the phase difference film 240 can function as a protective film for the polarizer. The angle formed by the absorption axis of the polarizer 210 and the slow axis of the phase difference film 240 is preferably 30° to 60°, more preferably 38° to 52°, further preferably 43° to 47°, and particularly preferably about 45°.

[0153] The phase difference film obtained by the production method of the present application is in a long strip shape and has a slow axis in a diagonal direction (a direction of 45° with respect to the longitudinal direction, for example). In addition, in most cases, a polarizer in a long strip shape has an absorption axis in the longitudinal direction or the width direction. Therefore, if the phase difference film obtained by the production method of the present application is used, a circular polarizing plate can be produced with extremely excellent production efficiency by so-called roll-to-roll. In addition, roll-to-roll means a method in which long strip-shaped films are roll-transported while being aligned with each other, and are continuously laminated with their longitudinal directions unified.

[0154] In one embodiment, the production method of the optical laminate of the present application includes: obtaining a long strip-shaped extended film by the production method of the extended film described in item A; and continuously laminating the long strip-shaped optical film and the long strip-shaped extended film with their longitudinal directions unified while transporting them.

[0155] [Examples]

[0156] The present application is specifically described below by examples, but the present application is not limited by these examples. In addition, the measurement and evaluation methods of the examples are described below.

[0157] (1) Thickness

[0158] The measurement was performed using a dial gauge (manufactured by PEACOCK, product name "DG-205 type pds-2").

[0159] (2) Phase difference value

[0160] The in-plane phase difference Re(550) was measured using Axoscan manufactured by Axometrics.

[0161] (3) Orientation angle (direction in which the slow axis appears)

[0162] The central portion of the film to be measured was cut into a square shape having a width of 50 mm and a length of 50 mm while becoming parallel to the width direction of the film, and a sample was prepared. The sample was measured using Axoscan manufactured by Axometrics, and the orientation angle Θ at a wavelength of 590 nm was measured.

[0163] (4) Glass transition temperature (Tg)

[0164] The measurement was performed in accordance with JIS K 7121.

[0165] (5) Relaxation amount

[0166] As Figure 11As shown, an ultrasonic displacement sensor 300 is installed below the transport path of film 1 at the midpoint between transport rollers 50a and 50b (distance between rollers: 912mm). The distance from the ultrasonic displacement sensor to the stretched film is measured at the center and ends in the width direction when transported at a transport tension of 150N / m. The maximum distance (L) is then measured. MAX ) and minimum distance (L) MIN The difference (L) MAX -L MIN The relaxation amount (mm) is used as the measurement. Furthermore, the relaxation amount is measured by cutting off the tension applied to correct the relaxation using a suction roller or similar device, while the roller is being transported at a transport tension of 150 N / m.

[0167] (6) Tension

[0168] The tension applied to the membrane is measured by a membrane tension detector installed in the membrane transport line.

[0169] <Example 1>

[0170] (Preparation of polyester carbonate resin film)

[0171] Polymerization was carried out using a batch polymerization apparatus consisting of two longitudinal reactors equipped with agitators and reflux coolers controlled at 100°C. 29.60 parts by mass (0.046 mol) of bis[9-(2-phenoxycarbonylethyl)fluorene-9-yl]methane, 29.21 parts by mass (0.200 mol) of ISB, 42.28 parts by mass (0.139 mol) of SPG, 63.77 parts by mass (0.298 mol) of DPC, and 1.19 × 10⁻⁶ mol of calcium acetate monohydrate as a catalyst were added. -2 Parts by weight (6.78 × 10) -5mol) was added. After the inside of the reactor was replaced with nitrogen under reduced pressure, the reactor was warmed with a heating medium, and stirring was started when the inside temperature reached 100°C. Forty minutes after the start of the temperature increase, the inside temperature reached 220°C, and the temperature was controlled at this temperature while reducing the pressure. After the inside temperature reached 220°C, the pressure was reduced to 13.3 kPa in 90 minutes. The phenol vapor generated along with the polymerization was introduced into a reflux cooler at 100°C, and the monomer components contained in the phenol vapor were returned to the reactor. The uncondensed phenol vapor was introduced into a condenser at 45°C and recovered. Nitrogen was introduced into the first reactor, and the oligomerized reaction solution in the first reactor was transferred to the second reactor after the pressure was temporarily returned to atmospheric pressure. Subsequently, the temperature of the second reactor was increased and the pressure was reduced, and the inside temperature reached 240°C and the pressure reached 0.2 kPa in 50 minutes. Thereafter, the polymerization was performed until the prescribed stirring power was reached. When the prescribed power was reached, nitrogen was introduced into the reactor to return the pressure to atmospheric pressure, and the resulting polyester carbonate was extruded into water, and strands were cut to obtain pellets. The Tg of the resulting polyester carbonate resin was 140°C.

[0172] After the resulting polyester carbonate resin was vacuum-dried at 80°C for 5 hours, a resin film having a thickness of 135 μm was produced using a film production apparatus having a single-screw extruder (Toshiba Machine Co., Ltd., cylinder set temperature: 250°C), a T die (width: 200 mm, set temperature: 250°C), a chill roll (set temperature: 120-130°C), and a winder.

[0173] (Production of Stretched Film)

[0174] The polyester carbonate resin film obtained above was stretched obliquely using the stretching apparatus shown in Fig. 1, and a phase difference film was obtained. Figures 1-3

[0175] Specifically, at the inlet of the stretching apparatus, the left and right ends of the polyester carbonate resin film were held by left and right grips, and preheating to 145°C was performed in a preheating zone B. In the preheating zone, the grip pitch (P1) of the left and right grips was 125 mm.

[0176] ​Next, while the membrane enters the extension region C, the clamp spacing of the right clamp is increased and the clamp spacing of the left clamp is decreased. The clamp spacing of the right clamp is increased to P2, while the clamp spacing of the left clamp is decreased to P3 (first oblique extension). At this time, the change rate of the clamp spacing of the right clamp (P2 / P1) is 1.42, the change rate of the clamp spacing of the left clamp (P3 / P1) is 0.78, and the lateral extension ratio relative to the original membrane width is 1.45 times. Then, while maintaining the clamp spacing of the right clamp at P2, the clamp spacing of the left clamp is increased from P3 to P2 (second oblique extension). During this period, the change rate of the clamp spacing of the left clamp (P2 / P3) is 1.82, and the lateral extension ratio relative to the original membrane width is 1.9 times. Furthermore, the extension region C is set to Tg + 3.2℃ (143.2℃).

[0177] Next, in release area D, the membrane is held at 125°C for 60 seconds for heat fixation. After cooling the heat-fixed membrane to 100°C, the left and right clamps are released, and the membrane is sent out from the extension device outlet.

[0178] (Relaxation detection)

[0179] As mentioned above, when used at room temperature Figure 6 (a) and Figure 6 (b) shows a transport line with seven transport rollers. The film (2050 mm wide) delivered from the extension unit outlet is transported, and the slack is measured between the transport rollers. During roller transport, the torque of the downstream roller in the transport direction is adjusted to apply a tension of 300 N / m to the film from the clamp release point to the downstream roller in the transport direction for 180 seconds. Furthermore, all rollers in the transport line are flat rollers. The test results show that slack occurs at the left end of the film delivered from the extension unit outlet in the width direction, with a slack of 18 mm.

[0180] (Roller handling)

[0181] In the aforementioned roll handling process, the roll through which the film initially passes after exiting the stretching unit is replaced with a concave roll, and roll handling continues. At this time, roll handling is performed with the center of the concave roll (centerline C1) in the width direction overlapping the center of the film in the width direction (centerline C2). The total width W1 of the concave roll used is 2100 mm, the width W2 of the central portion is 1800 mm, the width W4 of the end portion is 100 mm, and the difference X between the radius of the central portion and the radius of the end portion is 0.9 mm.

[0182] The phase difference Re(590) of the resulting extended film is 147 nm, and the angle between the slow axis and the length direction is 45°.

[0183] <Example 2>

[0184] An extended film was obtained in the same manner as in Example 1, except that a concave roll having a total width Wl of 2100 mm, a width W2 of the central portion of 1800 mm, a width W4 of the end portion of 50 mm, and a difference X of 1.3 mm was used.

[0185] The extended film had a retardation Re(590) of 147 nm, and the angle formed between the slow axis direction and the longitudinal direction was 45°.

[0186] <Example 3>

[0187] An extended film was obtained in the same manner as in Example 1, except that a concave roll having a total width Wl of 2100 mm, a width W2 of the central portion of 1800 mm, a width W4 of the end portion of 100 mm, and a difference X of 1.3 mm was used.

[0188] The extended film had a retardation Re(590) of 147 nm, and the angle formed between the slow axis direction and the longitudinal direction was 45°.

[0189] <Example 4>

[0190] An extended film was obtained in the same manner as in Example 1, except that a concave roll having a total width Wl of 2100 mm, a width W2 of the central portion of 1800 mm, a width W4 of the end portion of 120 mm, and a difference X of 1.3 mm was used.

[0191] The extended film had a retardation Re(590) of 147 nm, and the angle formed between the slow axis direction and the longitudinal direction was 45°.

[0192] <Example 5>

[0193] An extended film was obtained in the same manner as in Example 1, except that a concave roll having a total width Wl of 2100 mm, a width W2 of the central portion of 1800 mm, a width W4 of the end portion of 150 mm, and a difference X of 1.3 mm was used.

[0194] The extended film had a retardation Re(590) of 147 nm, and the angle formed between the slow axis direction and the longitudinal direction was 45°.

[0195] <Example 6>

[0196] An extended film was obtained in the same manner as in Example 1, except that a concave roll having a total width Wl of 2100 mm, a width W2 of the central portion of 1800 mm, a width W4 of the end portion of 50 mm, and a difference X of 0.4 mm was used.

[0197] The extended film had a retardation Re(590) of 147 nm, and the angle formed between the slow axis direction and the longitudinal direction was 45°.

[0198] <Example 7>

[0199] The same stretched film as in Example 1 was obtained, except that the flat roll through which the film initially passed from the outlet of the stretching device was replaced with a curved roll having a curvature of 10 mm, the curved roll was disposed so that the center line C2 of the film was 50 mm to the left of the center line C3 of the curved roll, the third flat roll disposed from the outlet of the stretching device was replaced with a concave roll, and the sixth flat roll was replaced with an expanding roll. In addition, the angle of inclination θ of the ring member of the expanding roll was 3.5°. The difference between the radius of the end portion and the radius of the central portion of the concave roll was 0.9 mm, the total width Wl was 2100 mm, the width W2 of the central portion was 1800 mm, the width W4 of each end portion was 100 mm, and each expanding portion W3 was 50 mm.

[0200] The phase difference Re(590) of the obtained stretched film was 147 nm, and the angle between the slow axis direction and the lengthwise direction was 45°.

[0201] [Appearance and Handleability Evaluation]

[0202] The stretched film obtained in the above examples and comparative examples was laminated with a long mask film (Toray Film Mfg. Co., Ltd., product name "Toretec 7832C-30") in a roll-to-roll manner to obtain a film laminate. Next, the mask film was peeled from the film laminate, an adhesive was applied using a gravure coater, and a polarizing plate was laminated, and an optical laminate was obtained by irradiation with UV. The appearance (visually) of the optical laminate and the handleability of the stretched film were evaluated according to the following criteria.

[0203] O: After lamination of the mask film (laminating tension 150 N / m), no wrinkles were observed, and the adhesive could be applied to the entire surface of the film.

[0204] Δ: When the mask film was laminated, lamination could be performed without wrinkles by increasing the laminating tension to 300 N / m, but when the adhesive was applied, the adhesive could not be applied to the relaxed portions.

[0205] X: After lamination of the mask film, wrinkles were observed, and the appearance was deteriorated.

[0206] [Wrinkle Evaluation]

[0207] The wrinkles of the obtained stretched film were evaluated according to the following criteria.

[0208] O: Wrinkles were not observed even when a Praguer lamp (Praguer Co., Ltd., product serial number "NP-1") was irradiated.

[0209] Δ: Wrinkles were not observed even when a fluorescent lamp was irradiated, but wrinkles were observed when a Praguer lamp was irradiated.

[0210] X: Wrinkles were observed when a fluorescent lamp was irradiated.

[0211] [Carrying property evaluation]

[0212] The resulting stretched film was evaluated by visually confirming whether or not deformation or creases were generated in the film due to relaxation and / or wrinkling, according to the following criteria.

[0213] O: No deformation and creases were generated in the film.

[0214] X: Deformation and / or creases were generated in the film.

[0215] [Visual property evaluation]

[0216] The optical laminate produced in the above appearance and handling property evaluation was attached to the visual side of a reflection plate or an organic EL panel via the adhesive layer. The resulting optical laminate was evaluated by visually confirming unevenness or light leakage of the shape due to relaxation or wrinkling, according to the following criteria.

[0217] O: No unevenness and light leakage were observed in both the reflection plate and the panel mounting.

[0218] Δ: Unevenness and / or light leakage were observed in the reflection plate, but not in the panel mounting.

[0219] X: Unevenness and / or light leakage were observed in both the reflection plate and the panel mounting.

[0220] The relaxation amount and the above evaluation results for the stretched film obtained in the above examples are shown in Table 1.

[0221]

[0222] [evaluation]

[0223] As shown in Table 1, in the production of the obliquely stretched film in a long strip shape, the concave roll was passed through the film after oblique stretching, whereby relaxation and / or wrinkling could be reduced. Specifically, it was confirmed that relaxation was effectively reduced by using a concave roll having a large value of X and W4 (i.e., a large expansion ratio), and that wrinkling was effectively reduced by using a concave roll having a small value of X and W4.

[0224] Industrial applicability

[0225] The production method of the stretched film of the present application is preferably used for the production of a retardation film, and as a result, can contribute to the production of image display devices such as liquid crystal display devices (LCDs), organic electroluminescent display devices (OLEDs), and the like.

Claims

1. A method for manufacturing an extended film, comprising: holding left and right end portions of a long film in a width direction by left and right grippers, respectively; moving the left and right grippers while extending the film obliquely, then releasing the film from the left and right grippers; and transporting the film by a concave roll, the concave roll has a central portion and end portions on both end sides thereof, the end portions have a cylindrical shape with a radius larger than that of the central portion, the difference between the radius of the central portion and the radius of the end portions of the concave roll is 0.6 mm to 2.0 mm, the film passes through the concave roll in a manner that the center in the width direction of the concave roll overlaps the center in the width direction of the film, and in a manner that the two end portions of the concave roll having a cylindrical shape with a radius larger than that of the central portion each overlap the film by 5 mm to 195 mm, the concave roll further has a diameter expansion portion that expands in diameter from both ends of the central portion to the end portions, the diameter expansion rate of the diameter expansion portion is 0.1% to 6.0%.

2. The method of manufacturing an extended film according to claim 1, wherein, the difference between the radius of the central portion and the radius of the end portions of the concave roll is 0.6 mm to 1.8 mm.

3. The method of manufacturing an extended film according to claim 1, wherein, the width of the end portions of the concave roll is 30 mm to 180 mm.

4. The method of manufacturing an extended film according to claim 1, wherein, the film is transported by a flat expansion roll and / or a bending roll in addition to the concave roll.

5. The method of manufacturing an extended film according to claim 1, wherein, the grippers are variable pitch grippers in which the gripper pitch in the longitudinal direction varies, the film is extended obliquely while at least one of the left gripper holding the left end portion of the film and the right gripper holding the right end portion moves while changing the gripper pitch and moving.

6. The method of manufacturing an extended film according to claim 5, wherein, the oblique extension includes (i) increasing the gripper pitch of one of the left and right grippers from PI to P2 while decreasing the gripper pitch of the other gripper from PI to P3, and (ii) changing the gripper pitch of each gripper in a manner that the decreased gripper pitch and the increased gripper pitch become a prescribed equal pitch.

7. The method of manufacturing an extended film according to claim 6, wherein, P2 / PI is 1.25 to 1.75, and P3 / PI is 0.50 or more and less than 1.

8. The method of manufacturing an extended film according to claim 1, wherein, the film is extended obliquely while the left gripper holding the left end portion of the film and the right gripper holding the right end portion move at a constant speed while changing the transport direction of the film midway.

9. A method for manufacturing an optical laminate, comprising: obtaining a long extended film by the method for manufacturing according to any one of claims 1 to 8; and continuously laminating the long optical film and the long extended film while unifying the longitudinal directions thereof while conveying them. 10.The method of manufacturing the optical laminate according to claim 9, wherein the optical film is a polarizing plate, and the extended film is a λ / 4 plate or a λ / 2 plate. the optical film is a polarizing plate, and the extended film is a λ / 4 plate or a λ / 2 plate.

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