Method for producing stretched film

Abstract

The present invention provides a method for manufacturing a stretched film, which can sufficiently change the pitch of a plurality of first jigs in a stretching step and can stably manufacture a stretched film in which the deviation of the orientation angle is suppressed. A method for producing a stretched film according to one embodiment of the present invention includes a clamping step, a stretching step, and a releasing step in this order. In the clamping step, a first end portion of the film is clamped by a plurality of first clamps, and a second end portion of the film is clamped by a plurality of second clamps. In the stretching step, the plurality of first jigs and the plurality of second jigs are moved while the pitch between the plurality of first jigs is changed, and the film is stretched in the inclined direction. In the release step, the film is released from the first jig and the second jig. In this method for manufacturing a stretched film, the pitch between the plurality of first jigs and the pitch between the plurality of second jigs are substantially consistent before the nip step.

Description

Technical Field

[0001] The present invention relates to a method for producing a stretched film. Background Art

[0002] For the purpose of improving display characteristics and preventing reflection, circular polarizers are used in image display devices such as liquid crystal display devices (LCDs) and organic electroluminescent display devices (OLEDs). Circular polarizers are typically stacked by placing a polarizer and a phase difference film (representatively a λ / 4 plate) so that the absorption axis of the polarizer and the slow axis of the phase difference film are at an angle of 45°. In the past, phase difference films were typically made by uniaxial stretching or biaxial stretching in the longitudinal and / or transverse directions, and therefore, their slow axis was in many cases expressed in the transverse (width direction) or longitudinal (length direction) direction of the long film blank. As a result, in order to make a circular polarizer, it is necessary to cut the phase difference film at an angle of 45° relative to the width direction or the length direction and laminate it one by one.

[0003] Therefore, it is desirable to manufacture a phase difference film having a slow axis extending in a direction oblique to the longitudinal direction. A representative method for manufacturing such a phase difference film is to clamp the left and right ends of a long film in the width direction with left and right clamps of a variable-pitch type in which the longitudinal clamp spacing varies, respectively. One of the left and right clamps is set as the advancing side, and the other as the slow-moving side. The clamp spacing on the advancing side is changed so as to become larger than the clamp spacing on the slow-moving side, and the film is stretched in a direction oblique to the longitudinal direction (hereinafter also referred to as "oblique stretching").

[0004] However, if a stretched film is produced by oblique stretching, the clamp on the slow side is pulled by the clamp on the advancing side through the film, and the relative positional relationship between the clamp on the advancing side and the clamp on the slow side is offset. As a result, there is a risk that the orientation angle of the produced stretched film deviates from the desired value.

[0005] Therefore, for example, the following method for manufacturing a stretched film has been proposed: when the deviation of the orientation angle relative to the set value exceeds a prescribed reference, the phase of at least one of the left and right clamps is shifted during the period from clamping the film with the left and right clamps to releasing the film (for example, refer to patent document 1).

[0006] In the method for producing a stretched film described in Patent Document 1, a constant-speed rotating sprocket is engaged with a link mechanism that changes the distance between clips, thereby adjusting the distance between clips holding a film.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application Laid-Open No. 2023-46840 Summary of the Invention

[0010] Problems to be solved by the invention

[0011] However, in the stretched film manufacturing method described in Patent Document 1, the clamp spacing is adjusted while the clamps are holding the film. This adjustment of the clamp spacing may affect the variability of the clamp spacing during the stretching process. Therefore, there is room for improvement in achieving both variability of the clamp spacing during the stretching process and suppressing deviations in the orientation angle of the stretched film.

[0012] A main object of the present invention is to provide a method for producing a stretched film, which can sufficiently change the pitch between a plurality of first clips during the stretching step and stably produce a stretched film with suppressed deviation in orientation angle.

[0013] Means used to solve problems

[0014] [1] A method for manufacturing a stretched film according to one embodiment of the present invention includes, in sequence, a clamping step, a stretching step, and a releasing step. In the clamping step, a first end portion of a long film in the width direction is clamped by a plurality of first clamps arranged along the length direction of the film, and a second end portion of the film in the width direction is clamped by a plurality of second clamps arranged along the length direction. In the stretching step, the plurality of first clamps and the plurality of second clamps are moved in the length direction while changing the spacing between the plurality of first clamps, thereby stretching the film in an oblique direction intersecting both the length direction and the width direction. In the releasing step, the first end portion of the film is released from the plurality of first clamps, and the second end portion of the film is released from the plurality of second clamps. Such a method for manufacturing a stretched film also includes a first spacing adjustment step. In the first spacing adjustment step, before the clamping step, the spacing between the plurality of first clamps and the spacing between the plurality of second clamps are made substantially consistent.

[0015] [2] The method for producing a stretched film described in [1] may further include a second spacing adjustment step. In the second spacing adjustment step, after the release step, the spacing between the plurality of first clamps and the spacing between the plurality of second clamps are adjusted.

[0016] [3] In the method for manufacturing a stretched film described in [1] or [2] above, the in-plane birefringence Δn(550) of the film may be 0.002 to 0.009. The temperature in the stretching step may be 180°C or lower. The clamping area of ​​the film of each of the plurality of first clamps may be substantially the same as the clamping area of ​​the film of each of the plurality of second clamps. The clamping area of ​​the film of each of the plurality of first clamps may be 10 cm2 ~300cm 2 .

[0017] Effects of the Invention

[0018] According to the embodiment of the present invention, the intervals between the plurality of first jigs can be sufficiently varied during the stretching step, and a stretched film with suppressed deviation in orientation angle can be stably manufactured. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram showing the configuration of an example of a stretching apparatus capable of carrying out the method for producing a stretched film according to one embodiment of the present invention.

[0020] Figure 2 To illustrate the Figure 1 A schematic top view of the clamping process performed by the stretching device.

[0021] Figure 3 To illustrate the Figure 1 A schematic cross-sectional view of the clamping process performed by the stretching device.

[0022] Figure 4 To express the passage Figure 1 A schematic diagram showing the distribution of the distance between the clamps in the stretching process performed by the stretching device.

[0023] Figure 5 For illustration purposes Figure 1 A schematic top view of a link mechanism of a stretching device.

[0024] Figure 6 For illustration purposes Figure 5 A schematic top view of the operation of the link mechanism.

[0025] Figure 7 for Figure 1 A schematic top view of an upstream spacing control wheel of a stretching device.

[0026] Description of Reference Numerals

[0027] 1 film

[0028] 40R First Clamp

[0029] 40L Second Clamp

[0030] 60 Upstream side spacing control wheel

[0031] 70 Downstream side spacing control wheel DETAILED DESCRIPTION

[0032] The following describes embodiments of the present invention, but the present invention is not limited to these embodiments. It should be noted that the drawings are schematically or conceptually depicted for ease of viewing and understanding, and the lengths, widths, shapes, sizes, ratios, directions, numbers, etc. may differ from the actual ones and may not correspond to each other in the drawings.

[0033] (Definition of Terms and Symbols)

[0034] The definitions of terms and symbols in this specification are as follows.

[0035] (1) Refractive index (nx, ny, nz)

[0036] “nx” is the refractive index in the direction where the in-plane refractive index is maximum (ie, the slow axis direction), “ny” is the refractive index in the direction orthogonal to the slow axis (ie, the fast axis direction), and “nz” is the refractive index in the thickness direction.

[0037] (2) In-plane birefringence (Δn)

[0038] "Δn(λ)" is the in-plane birefringence measured at 23°C with light of wavelength λnm. For example, "Δn(550)" is the in-plane birefringence measured at 23°C with light of wavelength 550nm. The in-plane birefringence (Δn) is calculated by the formula: Δn = nx - ny.

[0039] (3) Substantially parallel or orthogonal

[0040] The expressions "substantially orthogonal" and "approximately orthogonal" include situations where the angle formed by two directions is 90°±10°, preferably 90°±7°, and more preferably 90°±5°. The expressions "substantially parallel" and "approximately parallel" include situations where the angle formed by two directions is 0°±10°, preferably 0°±7°, and more preferably 0°±5°. Furthermore, the abbreviations "orthogonal" or "parallel" in this specification may include situations where they are substantially orthogonal or substantially parallel.

[0041] A. Overview of the method for producing stretched films

[0042] Figure 1 A schematic diagram showing an example of a stretching apparatus capable of implementing a method for producing a stretched film according to an embodiment of the present invention; Figure 2 To illustrate the Figure 1 A schematic top view of the clamping process performed by the stretching device; Figure 3 For illustration purposes Figure 1 A schematic cross-sectional view of a clamping process performed by a stretching device; Figure 4 It means using Figure 1 A schematic diagram showing the distribution of the distance between the clamps in the stretching process performed by the stretching device.

[0043] A method for producing a stretched film according to one embodiment of the present invention includes a clamping step, a stretching step, and a releasing step in this order.

[0044] like Figure 2 and Figure 3 As shown, during the clamping step, a plurality of first clamps 40R clamp a first end 1R of the film 1, and a plurality of second clamps 40L clamp a second end 1L of the film 1. The film 1 has an elongated shape. The first end 1R is located at one end of the film 1 in the width direction (a direction perpendicular to the longitudinal direction). The second end 1L is located at the other end of the film 1 in the width direction (a direction perpendicular to the longitudinal direction) opposite to the first end 1R. During the clamping step, the plurality of first clamps 40R are arranged along the longitudinal direction of the film 1, and the plurality of second clamps 40L are arranged along the longitudinal direction of the film 1.

[0045] like Figure 4 As shown, during the stretching step, the first clamps 40R and the second clamps 40L are moved along the longitudinal direction of the film 1 while varying the spacing between the first clamps 40R. In one embodiment, the spacing between the first clamps 40R is greater than the spacing between the second clamps 40L. This allows the film 1 to be stretched in an oblique direction that intersects both the longitudinal and width directions.

[0046] In the releasing process, the first end portion 1R of the film 1 is released from the plurality of first clamps 40R, and the second end portion 1L of the film 1 is released from the plurality of second clamps 40L (see FIG. 1 ). Figure 3 ).

[0047] like Figure 1 As shown, such a method for producing a stretched film further includes a first gap adjustment step in addition to the above-mentioned clamping step, stretching step, and releasing step.

[0048] The inventors have discovered that even if the spacing between the plurality of first clamps and the spacing between the plurality of second clamps are adjusted before the film is clamped by the plurality of first clamps and the plurality of second clamps, the first clamps and the second clamps can be maintained in a desired relative positional relationship during the stretching process. Specifically, in the first spacing adjustment process, the spacing between the plurality of first clamps 40R and the spacing between the plurality of second clamps 40L are substantially aligned before the clamping process. Thus, during the stretching process, even if the spacing between the plurality of first clamps 40R is changed, the first clamps 40R and the second clamps 40L can be fully maintained in a desired relative positional relationship. In addition, since the spacing between the plurality of first clamps 40R and the spacing between the plurality of second clamps 40L are adjusted before the film 1 is clamped, the effect of the spacing adjustment on the variability of the spacing between the plurality of first clamps 40R during the stretching process can be suppressed, and the first clamps 40R and the second clamps 40L can stably clamp the film 1 during the clamping process. As a result, the pitch between the plurality of first jigs 40R can be sufficiently and smoothly changed during the stretching step, and a stretched film with suppressed deviation in orientation angle can be stably manufactured.

[0049] In this specification, the term "pitch" refers to the length of an imaginary line segment connecting the centers of adjacent components among a plurality of components (clamps, clamp support members, etc.).

[0050] In the releasing step, the plurality of first clamps 40R typically release the clamping of the first end portion 1R of the film 1 while moving in the longitudinal direction of the film 1 (see Figure 3 ). In addition, in the release process, the plurality of second clamps 40L typically release the clamping of the second end portion 1L of the film 1 while moving in the longitudinal direction of the film 1 (see Figure 3 ).

[0051] During the stretching process, if the spacing between the multiple first clamps is larger than the spacing between the multiple second clamps, the second clamps on the slow side may be pulled by the first clamps on the fast side through the film. In this case, during the release process, the spacing between the multiple second clamps becomes too narrow, causing obstruction and potentially hindering the smooth movement of the multiple second clamps.

[0052] In contrast, in one embodiment, the stretch film manufacturing method further includes a second spacing adjustment step. In this second spacing adjustment step, after the aforementioned release step, the spacing between the plurality of first jigs 40R and the spacing between the plurality of second jigs 40L are adjusted. This prevents the plurality of second jigs from becoming blocked during the release step, allowing for smooth movement of the plurality of second jigs.

[0053] In one embodiment, the method for producing a stretched film further includes a preheating step and a heat setting step.

[0054] The preheating step is performed between the clamping step and the stretching step. In the preheating step, the film 1 is preheated to any appropriate temperature.

[0055] The heat setting step is performed between the stretching step and the releasing step. In the heat setting step, the film 1 is heat-set at any appropriate temperature.

[0056] B.Stretching device

[0057] Next, refer to Figure 1 , a stretching device 100 capable of continuously implementing the above-mentioned method for producing a stretched film will be described.

[0058] The stretching apparatus 100 includes a first stretching unit 101R including a plurality of first clamps 40R and a second stretching unit 101L including a plurality of second clamps 40L.

[0059] The first stretching unit 101R and the second stretching unit 101L are arranged at intervals from each other in a first direction perpendicular to the up-down direction (representatively, the vertical direction). In the stretching device 100, a clamping area A for implementing the above-mentioned clamping process, a preheating area B for implementing the above-mentioned preheating process, a stretching area C for implementing the above-mentioned stretching process, a heat-fixing area D for implementing the above-mentioned heat-fixing process, and a release area E for implementing the above-mentioned release process are sequentially provided between the first stretching unit 101R and the second stretching unit 101L. It should be noted that these areas do not mean mechanically and structurally independent partitions. In addition, sometimes Figure 1 The ratio of the lengths of the respective regions in the stretching device is different from the actual length ratio.

[0060] Furthermore, between the stretching zone C and the heat setting zone D, an area for performing any appropriate treatment may be provided as needed. Examples of such treatments include transverse shrinkage. Furthermore, the stretching apparatus typically includes a heating device (e.g., a hot air, near infrared, or far infrared oven) for creating a heated environment from the preheating zone B to the heat setting zone D or release zone E.

[0061] The first stretching unit 101R has a configuration capable of changing the pitch between the plurality of first clamps 40R (variable pitch type).

[0062] In one embodiment, the first stretching unit 101R includes a reference rail 10, a spacing setting rail 20, a plurality of clamp support members 30, a link mechanism 80 (see Figure 5 ), multiple first clamps 40R, driving means 50, upstream side spacing control wheel 60 and downstream side spacing control wheel 70.

[0063] B-1. Reference track

[0064] The reference rail 10 typically has an endless shape and includes a first curved portion 10a, a second curved portion 10b, a third curved portion 10c, and a fourth curved portion 10d.

[0065] The first curved portion 10a and the second curved portion 10b are located at positions separated in a second direction perpendicular to the vertical direction and the first direction. The first curved portion 10a is located on the side opposite to the stretching region C relative to the clamping region A in the second direction. The second curved portion 10b is located on the side opposite to the stretching region C relative to the release region E in the second direction.

[0066] The third bent portion 10c is located at a position separated from the second bent portion 10b in the first direction. The fourth bent portion 10d is separated from the third bent portion 10c in the second direction and separated from the first bent portion 10a in the first direction.

[0067] The central angle of each of the first curved portion 10 a , the second curved portion 10 b , the third curved portion 10 c , and the fourth curved portion 10 d is typically 90°.

[0068] In the illustrated example, the portion of the reference rail 10 corresponding to the clamping region A and the preheating region B extends along the second direction. Furthermore, the portion of the reference rail 10 corresponding to the stretching region C extends in a direction intersecting the second direction, moving away from the second stretching unit 101L as it approaches the thermal fixation region D from the preheating region B. Furthermore, the portion of the reference rail 10 corresponding to the thermal fixation region D and the release region E extends along the second direction.

[0069] It should be noted that the configuration of the reference rail 10 is not limited to the example shown in the above figures. For example, the portion of the reference rail 10 corresponding to the clamping area A to the release area E may also extend linearly along the second direction.

[0070] B-2. Pitch setting track

[0071] The pitch setting rails 20 are typically arranged at predetermined intervals inside the reference rail 10. The pitch setting rails 20 are movable relative to the reference rail 10. In the illustrated example, the pitch setting rails 20 have an endless shape along the reference rail 10.

[0072] B-3. ​​Jig support parts

[0073] like Figure 5 and Figure 6As shown, in one embodiment, a plurality of jig support members 30 are disposed above the reference rail 10 and the spacing setting rail 20. The plurality of jig support members 30 are typically arranged along the reference rail 10 and are capable of circular movement guided by the reference rail 10. The plurality of jig support members 30 typically extend in a direction perpendicular to the reference rail 10.

[0074] The plurality of jig support members 30 each support the first jig 40R. More specifically, one end portion of the first support member 30R in the extending direction supports the first jig 40R.

[0075] In the illustrated example, the jig support member 30 includes a frame 31 , a first shaft member 33 , a second shaft member 34 , and a slider 32 .

[0076] The frame 31 extends in a direction perpendicular to the reference rail 10. In one embodiment, the frame 31 has a generally rectangular shape when viewed in the direction of movement of the jig support member 30. The frame 31 has an elongated hole 31a. The elongated hole 31a is formed in the upper beam of the frame 31. The elongated hole 31a extends in the same direction as the upper beam of the frame 31.

[0077] The first shaft member 33 extends in the vertical direction. It penetrates the jig support member 30 between the first jig 40R and the elongated hole 31a. A guide roller (not shown) is rotatably mounted at the lower end of the first shaft member 33. The guide roller fits into a groove (not shown) provided in the reference rail 10.

[0078] The second shaft member 34 extends in the vertical direction. The second shaft member 34 is located on the opposite side of the first jig 40R from the first shaft member 33 and extends through the jig support member 30. A gap setting roller (not shown) is rotatably mounted on the lower end of the second shaft member 34. The gap setting roller fits into a groove (not shown) provided in the gap setting rail 20. In the illustrated example, the upper end of the second shaft member 34 is inserted into the elongated hole 31a.

[0079] The slider 32 is guided by the inner surface of the long hole 31a and is slidable relative to the frame 31. In the illustrated example, the slider 32 is provided at the upper end portion of the second shaft member 34.

[0080] The jig support member 30 may further include a driving roller 39. The driving roller 39 can be engaged with the driving means 50. In the illustrated example, the driving roller 39 is provided at the upper end portion of the first shaft member 33.

[0081] B-4. Linkage Mechanism

[0082] The link mechanism 80 is configured to change the interval between the plurality of jig support members 30 by changing the interval between the reference rail 10 and the interval setting rail 20. In one embodiment, the link mechanism 80 has a pantograph structure.

[0083] like Figure 6 As shown, the link mechanism 80 includes a plurality of main link members 81 and a plurality of sub-link members 82 .

[0084] The plurality of main link members 81 connect the first shaft member 33 provided on one side of the adjacent jig support members 30 to the second shaft member 34 provided on the other side of the adjacent jig support members 30. In the illustrated example, one end of the main link member 81 is connected to the first shaft member 33 so as to be rotatable relative to the first shaft member 33. The other end of the main link member 81 is connected to the second shaft member 34 so as to be rotatable relative to the second shaft member 34.

[0085] The plurality of sub-link members 82 each connect the main link member 81 to the first shaft member 33, which is not connected to the main link member 81. In the illustrated example, one end of the sub-link member 82 is connected to the main link member 81 via a pivot 87 so as to be relatively rotatable. The other end of the sub-link member 82 is connected to the first shaft member 33 so as to be relatively rotatable.

[0086] like Figure 5 As shown, when the distance between the reference rail 10 and the spacing setting rail 20 increases relatively, the slider 32 moves within the elongated hole 31a, moving away from the reference rail 10. This causes the main link member 81 and the sub-link member 82 to tilt, and the adjacent jig support members 30 to move closer together. As a result, the spacing between the plurality of first jigs 40R decreases.

[0087] On the other hand, Figure 6 As shown, when the distance between the reference rail 10 and the spacing setting rail 20 becomes relatively small, the slider 32 moves within the elongated hole 31a toward the reference rail 10. This causes the main link member 81 and the sub-link member 82 to rise, moving the adjacent jig support members 30 apart. As a result, the spacing between the plurality of first jigs 40R increases.

[0088] B-5. Clamp

[0089] The plurality of first jigs 40R are respectively supported by the corresponding jig support members 30. The first jigs 40R are located on the side opposite to the pitch setting rail 20 with respect to the reference rail 10 in a direction perpendicular to the reference rail 10.

[0090] like Figure 3As shown, the first clamp 40R is configured to clamp the first end portion 1R of the film 1. In one embodiment, the first clamp 40R can clamp the first end portion 1R of the film 1 in the thickness direction of the film 1. In the illustrated example, the first clamp 40R includes a base 401 and a pressing portion 402.

[0091] The base 401 is fixed to one end portion of the first support member 30R in the extending direction. The pressing portion 402 is supported at one end portion of the first support member 30R in the extending direction so as to be movable relative to the base 401 in the thickness direction of the film 1 .

[0092] B-6. Driving means

[0093] like Figure 1 As shown, the driving means 50 is configured to impart driving force to the plurality of clamp support members 30. The driving means 50 can be positioned at any appropriate location. In the illustrated example, the driving means 50 is positioned inside the spacing setting rail 20. The driving means 50 is located on the opposite side of the second stretching unit 101L, spaced apart from the downstream spacing control wheel 70 in the first direction.

[0094] In one embodiment, the driving means 50 is a sprocket 50a. The sprocket 50a is rotatable about an axis extending in the vertical direction. The driving force from the motor 90 is input to the sprocket 50a.

[0095] In the illustrated example, when the driving force from the motor 90 is input to the sprocket 50a, the sprocket 50a is driven to rotate and selectively engage with the driving roller 39 provided on the clamp support member 30. As a result, the driving force is sequentially transmitted to the plurality of clamp support members 30, and the plurality of clamp support members 30 move in a circular motion.

[0096] B-7. Upstream side spacing control wheel

[0097] The upstream spacing control wheel 60 is configured to adjust the spacing between the plurality of first clamps 40R. The upstream spacing control wheel 60 is typically located upstream of the clamping region A (i.e., on the opposite side of the stretching region C relative to the clamping region A) in the circumferential direction of the plurality of clamp support members 30. In one embodiment, the upstream spacing control wheel 60 is located between the clamping region A and the fourth curved portion 10d in the circumferential direction of the plurality of clamp support members 30. In the illustrated example, the upstream spacing control wheel 60 is positioned along the first curved portion 10a of the reference rail 10.

[0098] like Figure 7As shown in FIG, the upstream side pitch control wheel 60 is rotatable around an axis extending in the vertical direction. Although not shown, the upstream side pitch control wheel 60 is configured so as to receive a driving force from a motor.

[0099] The outer diameter of the upstream pitch control wheel 60 is, for example, 10 cm to 120 cm, and preferably 30 cm to 100 cm.

[0100] In the illustrated example, a plurality of recesses 61 are provided on the circumferential surface of the upstream pitch control wheel 60. Each of the recesses 61 is typically configured to receive an end portion of the frame 31 on the side opposite the first clamp 40R. The recesses 61 are located at equal intervals along the circumference of the upstream pitch control wheel 60. When viewed from above and below, the recesses 61 each have a generally V-shape, opening radially outward of the upstream pitch control wheel 60.

[0101] There is no particular limitation on the number of the plurality of recesses 61. The number of the plurality of recesses 61 is, for example, 2 to 10, preferably 4 to 6.

[0102] The depth of the plurality of recesses 61 (the dimension in the radial direction of the upstream pitch control wheel 60 ) is, for example, 5 cm to 100 cm, or preferably 20 cm to 80 cm.

[0103] B-8. Downstream side spacing control wheel

[0104] like Figure 1 As shown, the downstream-side spacing control wheel 70 is configured to adjust the spacing between the plurality of first clamps 40R. The downstream-side spacing control wheel 70 is typically located downstream of the release region E (i.e., on the opposite side of the stretching region C relative to the release region E) in the circumferential direction of the plurality of clamp support members 30. In one embodiment, the downstream-side spacing control wheel 70 is located between the release region E and the third curved portion 10c in the circumferential direction of the plurality of clamp support members 30. In the illustrated example, the upstream-side spacing control wheel 60 is positioned along the second curved portion 10b of the reference rail 10.

[0105] like Figure 7 As shown, the downstream side pitch control wheel 70 typically has the same structure as the above-mentioned upstream side pitch control wheel 60. Therefore, a detailed description of the downstream side pitch control wheel 70 is omitted.

[0106] B-9. Second stretching unit

[0107] like Figure 1 As shown, the second stretching unit 101L has a configuration capable of changing the pitch between the plurality of second clamps 40L (variable pitch type).

[0108] The second stretching unit 101L typically has a configuration that is line-symmetrical with the first stretching unit 101R with respect to the second direction. The second stretching unit 101L is described similarly to the first stretching unit 101R, except that it includes a plurality of second clamps 40L instead of a plurality of first clamps 40R. Therefore, the description of the configuration of the second stretching unit 101L is omitted.

[0109] C. Details of the method for producing stretched film

[0110] Next, the implementation of the method for producing a stretched film using the stretching apparatus 100 will be described.

[0111] In one embodiment, in the stretching device 100 , a first gap adjustment step, a clamping step, a preheating step, a stretching step, a heat fixing step, a releasing step, and a second gap adjustment step are sequentially and continuously performed.

[0112] C-1. First gap adjustment step

[0113] In the first pitch adjustment step, the pitch between the plurality of first jigs 40R and the pitch between the plurality of second jigs 40L are made substantially equal by the upstream pitch control wheel 60 .

[0114] More specifically, first, in each of the first stretching unit 101R and the second stretching unit 101L, the driving force from the motor 90 is input to the sprocket 50a. In the illustrated example, the driving force is then transmitted from the sprocket 50a to the multiple clamp support members 30 included in the first stretching unit 101R, causing them to rotate clockwise when viewed from above. Consequently, the multiple first clamps 40R, like the multiple clamp support members 30, rotate clockwise when viewed from above.

[0115] Furthermore, the plurality of clamp support members 30 included in the second stretching unit 101L receive driving force from the sprocket 50a and rotate counterclockwise when viewed from above. Consequently, the plurality of second clamps 40L rotate counterclockwise when viewed from above, similarly to the plurality of clamp support members 30.

[0116] It should be noted that the moving speed of the multiple first clamps 40R in the first stretching unit 101R and the moving speed of the multiple second clamps 40L in the second stretching unit 101L can be independently controlled to any value by adjusting the power of the motor 90 to change the driving force transmitted from the sprocket 50a to the clamp support part 30.

[0117] In addition, in each of the first stretching unit 101R and the second stretching unit 101L, a driving force from a motor (not shown) is input to the upstream pitch control wheel 60 and the downstream pitch control wheel 70 .

[0118] As a result, each of the upstream pitch control wheel 60 and the downstream pitch control wheel 70 included in the first stretching unit 101R rotates clockwise when viewed from above.

[0119] Furthermore, each of the upstream-side pitch control wheel 60 and the downstream-side pitch control wheel 70 included in the second stretching unit 101L rotates counterclockwise when viewed from above.

[0120] Typically, the rotation speed of the upstream pitch control wheel 60 included in the first stretching unit 101R and the rotation speed of the upstream pitch control wheel 60 included in the second stretching unit 101L are substantially the same.

[0121] Furthermore, the rotation speed of the downstream-side pitch control wheel 70 included in the first stretching unit 101R and the rotation speed of the downstream-side pitch control wheel 70 included in the second stretching unit 101L are typically substantially the same.

[0122] In the first pitch adjustment step, in each of the first stretching unit 101R and the second stretching unit 101L, when the upstream pitch control wheel 60 rotates, the ends of the frames 31 of the plurality of clip support members 30 are sequentially fitted into the recesses 61 of the upstream pitch control wheel 60 .

[0123] Thus, the pitch of the first jigs 40R in the first stretching unit 101R is substantially the same as the pitch of the second jigs 40L in the second stretching unit 101L. In other words, the phases of the first jigs 40R and the second jigs 40L are aligned at a predetermined pitch.

[0124] At this time, if Figure 4 As shown, the imaginary line segment connecting the center of the first clamp 40R and the center of the second clamp 40L is typically substantially perpendicular to the film conveying direction (second direction). The angle formed by this imaginary line segment and the film conveying direction (second direction) is, for example, 87° to 93°, preferably 89° to 91°, more preferably 89.5° to 90.5°, and even more preferably 90°.

[0125] The pitch of the plurality of first jigs 40R adjusted in the first pitch adjustment step is, for example, 100 mm to 200 mm, preferably 125 mm to 175 mm, and more preferably 140 mm to 160 mm.

[0126] When the pitch of the plurality of first jigs 40R is set to 100%, the pitch of the plurality of second jigs 40L adjusted in the first pitch adjustment step is, for example, 97% to 103%, preferably 99% to 101%, more preferably 99.5% to 100.5%, and further preferably 100%.

[0127] C-2. Clamping process

[0128] like Figure 1 As shown, in the clamping step, typically, the long film 1 is fed along the second direction to the clamping region A located between the first stretching unit 101R and the second stretching unit 101L.

[0129] The film 1 is made of any appropriate resin material. Examples of the resin material include polycarbonate resins, polyvinyl acetal resins, cycloolefin resins, acrylic resins, cellulose ester resins, cellulose resins, polyester resins, polyester carbonate resins, olefin resins, and polyurethane resins. Polycarbonate resins are preferred. The resin materials may be used alone or in combination.

[0130] Preferred examples of the polycarbonate-based resin include polycarbonate-based resins containing a structural unit derived from a dihydroxy compound. Specific examples of the dihydroxy compound include 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-tert-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-( 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-tert-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-tert-butyl-6-methylphenyl)fluorene, 9,9-bis(4-(3-hydroxy-2,2-dimethylpropyloxy)phenyl)fluorene. In addition to the structural units derived from the above-mentioned dihydroxy compounds, the polycarbonate resin may also contain structural units derived from dihydroxy compounds such as isosorbide, isomannide, isoidide, spirodiol, dioxane glycol, diethylene glycol (DEG), triethylene glycol (TEG), polyethylene glycol (PEG), cyclohexanedimethanol (CHDM), tricyclodecanedimethanol (TCDDM), and bisphenols.

[0131] The polycarbonate resin described above is described in detail in, for example, Japanese Patent Application Laid-Open No. 2012-67300 and Japanese Patent No. 3325560. The contents of these patent documents are incorporated herein by reference.

[0132] The glass transition temperature of such a resin material is, for example, 110°C to 250°C, preferably 120°C to 230°C. If the glass transition temperature is too low, there is a tendency for heat resistance to deteriorate, and dimensional changes may occur after film forming. If the glass transition temperature is too high, there is a situation where the molding stability during film forming deteriorates, and there is also a situation where the transparency of the film is impaired. It should be noted that the glass transition temperature is obtained in accordance with JIS K 7121 (1987).

[0133] The in-plane birefringence Δn(550) of such a film 1 is in the range of, for example, 0.002 to 0.009, or preferably 0.003 to 0.005.

[0134] The width of the film 1 is, for example, 500 cm to 2000 cm, and preferably 650 cm to 1500 cm.

[0135] The thickness of the film 1 is, for example, 30 μm to 200 μm, or preferably 60 μm to 150 μm.

[0136] In the illustrated example, in the clamping area A, the reference rail 10 of the first stretching unit 101R and the reference rail 10 of the second stretching unit 101L are stretched along the second direction (the longitudinal direction of the film 1) and are substantially parallel. Therefore, in the clamping area A, the plurality of first clamps 40R, whose pitches are aligned with each other during the first spacing adjustment step, are arranged along the second direction (the longitudinal direction of the film 1), and the plurality of second clamps 40L, whose pitches are aligned with each other during the first spacing adjustment step, are arranged along the second direction (the longitudinal direction of the film 1).

[0137] In one embodiment, the first clamp 40R and the second clamp 40L described above clamp both widthwise ends of the film 1 in the clamping area A. More specifically, the first clamp 40R clamps the first end 1R of the film 1 when it reaches a desired position through movement, and the second clamp 40L clamps the second end 1L of the film 1 when it reaches a desired position through movement. In this case, the timing of clamping by the first clamp 40R and the timing of clamping by the second clamp 40L are preferably simultaneous.

[0138] like Figure 3 As shown, in one embodiment, the clamping area of ​​the film 1 of each of the plurality of first clamps 40R is substantially the same as the clamping area of ​​the film 1 of each of the plurality of second clamps 40L. Specifically, the clamping area of ​​the first clamp 40R is the area of ​​the portion of the film 1 clamped by the base 401 and the pressing portion 402, for example, 10 cm 2 ~300cm 2 , preferably 50cm 2 ~200cm 2 .

[0139] When the clamping area of ​​the first clamp 40R is 100%, the clamping area of ​​the second clamp 40L is, for example, 97% to 103%, preferably 99% to 101%, more preferably 99.5% to 100.5%, and further preferably 100%.

[0140] When the clamping area of ​​the first clamp and the clamping area of ​​the second clamp are within this range, even if the film has the above-mentioned in-plane birefringence Δn(550), stress concentration on the film during the stretching process can be suppressed. As a result, the load applied to the stretching device can be reduced, and for example, bending of the reference rail can be suppressed.

[0141] C-3. Preheating process

[0142] like Figure 1 As shown, the film 1 is sent to the preheating area B as the first clamp 40R and the second clamp 40L move.

[0143] In preheating area B, a preheating process is performed, and the film 1 is heated (preheated) while being transported by the first clamp 40R and the second clamp 40L. In preheating area B, the reference track 10 of the first stretching unit 101R and the reference track 10 of the second stretching unit 101L are substantially parallel. Therefore, in the illustrated example, in preheating area B, the film 1 is heated without being stretched transversely or longitudinally. However, in order to avoid undesirable situations such as film deflection caused by preheating and contact with the nozzle in the oven, the distance between the first clamp 40R and the second clamp 40L (the distance in the width direction) may be slightly increased.

[0144] The preheating temperature T1 in the preheating step is, for example, at least the glass transition temperature (Tg) of the film 1, preferably at least Tg + 2°C, and more preferably at least Tg + 5°C. On the other hand, the preheating temperature T1 is, for example, at most Tg + 40°C, preferably at most Tg + 30°C. The preheating temperature T1 can be appropriately adjusted depending on the material of the film 1. The preheating temperature T1 is, for example, 70°C to 190°C, and preferably 80°C to 180°C.

[0145] The heating time to the preheating temperature T1 and the holding time at the preheating temperature T1 can be appropriately set according to the constituent material of the film and the manufacturing conditions (e.g., the film conveying speed). These heating time and holding time can be controlled by adjusting the moving speed of the first clamp 40R and the second clamp 40L, the length of the preheating zone, the temperature of the preheating zone, etc.

[0146] C-4. Stretching process

[0147] Next, the film 1 is sent to the stretching area C as the first clamp 40R and the second clamp 40L move.

[0148] In the stretching zone C, a stretching step is performed to obliquely stretch the film 1. In this way, a stretched film is produced.

[0149] During the stretching process, the first clamps 40R and the second clamps 40L are moved at least in the second direction (the longitudinal direction of the film 1) while the spacing between the first clamps 40R is varied (increased and / or reduced). In the illustrated example, the spacing between the first clamps 40R is greater than the spacing between the second clamps 40L. During the stretching process, the spacing between the second clamps 40L can be varied (increased and / or reduced) or maintained constant.

[0150] Thus, one of the first and second clamps (the first clamp in the example shown) that arrive at the stretching zone simultaneously arrives at the end of the stretching zone first. Due to this oblique stretching, the end of the film 1 on the side of the leading clamp is stretched at a higher stretch ratio than the end on the side of the trailing (slower) clamp. As a result, a slow axis can be formed in a desired direction (for example, a direction at 45 degrees relative to the longitudinal direction) of the film 1.

[0151] The details of the above-mentioned oblique stretching are described in, for example, Japanese Patent Application Laid-Open No. 2023-46840, the contents of which are incorporated herein by reference.

[0152] The stretching process may include transverse stretching. In this case, the stretching process may be, for example, Figure 1 As shown in the structure, the distance (distance in the width direction) between the first jig 40R and the second jig 40L is increased.

[0153] When the stretching step includes transverse stretching, the width W of the film after oblique stretching is final The stretch ratio in the transverse direction (TD) (the initial width of the film W initial ) ratio (W final / W initial ) is, for example, 1.05 to 6.00, preferably 1.10 to 5.00.

[0154] The product of the change rate of the first clamp 40R pitch and the change rate of the second clamp 40L pitch during the stretching step is, for example, 0.7 to 1.5, preferably 0.8 to 1.45, and more preferably 0.85 to 1.40. If the product of the change rates is within this range, a retardation film with high uniaxiality and in-plane orientation can be produced.

[0155] The stretching temperature T2 in the stretching process is, for example, Tg - 20°C to Tg + 30°C with respect to the glass transition temperature (Tg) of the film, preferably Tg - 10°C to Tg + 20°C, and more preferably Tg. The stretching temperature T2 can be appropriately adjusted according to the material of the film 1. The stretching temperature T2 is, for example, 180°C or lower, preferably 160°C or lower, and more preferably 150°C or lower. On the other hand, the stretching temperature T2 is, for example, 130°C or higher, preferably 140°C or higher.

[0156] The difference (T1 - T2) between the preheating temperature T1 and the stretching temperature T2 is, for example, ±2°C or higher, preferably ±5°C or higher. In one embodiment, T1 > T2. Therefore, in the preheating area, the film heated to the preheating temperature T1 can be cooled to the stretching temperature T2.

[0157] C-5. Heat setting process

[0158] Next, the stretched film 1 (stretched film) is sent to the heat setting area D as the first jig 40R and the second jig 40L move.

[0159] In the heat setting area D, a heat setting process is performed, and the stretched film 1 (stretched film) is heat-treated while being carried by the first jig 40R and the second jig 40L. In the heat setting area D, the reference track 10 of the first stretching unit 101R and the reference track 10 of the second stretching unit 101L are substantially parallel. Therefore, in the illustrated example, in the heat setting area D, the film 1 is substantially neither stretched transversely nor longitudinally. However, if necessary, the distance between multiple first jigs 40R can be reduced to relieve stress.

[0160] [[ID=1…]]The heat setting temperature T3 in the heat setting process varies depending on the film to be stretched. Sometimes T2 ≥ T3, and sometimes T2 < T3. Generally, crystallization treatment can also be performed by setting T2 ≥ T3 when the film is an amorphous material and T2 < T3 when the film is a crystalline material>. When T2 ≥ T3, the difference (T2 - T3) between the temperature T2 and T3 is, for example, 0°C to 50°C. The heat setting time is, for example, 10 seconds to 10 minutes. The heat treatment time can be controlled by adjusting the length of the heat treatment area and / or the conveying speed of the film.

[0161] C-6. Release process

[0162] Next, the heat-set stretched film is sent to the release area E as the first jig 40R and the second jig 40L move.

[0163] In the release region E, a release process is performed, whereby the first end 1R of the stretched film is released from the first clamp 40R and the second end 1L of the stretched film is released from the second clamp 40L at any position. More specifically, the first end 1R of the film 1 is released when the first clamp 40R reaches a desired position by movement, and the second end 1L of the film 1 is released when the second clamp 40L reaches a desired position by movement.

[0164] In the release region E, the reference rail 10 of the first stretching unit 101R is substantially parallel to the reference rail 10 of the second stretching unit 101L. Therefore, in the illustrated example, in the release region E, the stretched film, after heat setting, is cooled to a desired temperature without undergoing transverse or longitudinal stretching, and then released from the first and second clamps.

[0165] The temperature of the stretched film when released from the first and second clamps is, for example, 150°C or lower, preferably 70°C to 140°C, and more preferably 80°C to 130°C.

[0166] Through the above process, a stretched film is obtained in which the film 1 is stretched. The stretched film will be described in detail later.

[0167] C-7. Second spacing adjustment process

[0168] In the second pitch adjustment step, the downstream pitch control wheel 70 adjusts the pitch of the plurality of first clamps 40R after releasing the first end 1R of the film 1 and the pitch of the plurality of second clamps 40L after releasing the second end 1L of the film 1 .

[0169] More specifically, the plurality of first clamps 40R passing through the release area E reach the downstream pitch control wheel 70 of the first stretching unit 101R. The plurality of second clamps 40L passing through the release area E reach the downstream pitch control wheel 70 of the second stretching unit 101L.

[0170] Then, in each of the first stretching unit 101R and the second stretching unit 101L, the ends of the frames 31 of the plurality of clip support members 30 are sequentially fitted into the recesses 61 of the downstream-side pitch control wheel 70 .

[0171] Thus, the intervals between the first jigs 40R in the first stretching unit 101R and the intervals between the second jigs 40L in the second stretching unit 101L are appropriately adjusted. In one embodiment, the phases of the first jigs 40R and the second jigs 40L are aligned at a predetermined interval.

[0172] In the second pitch adjustment process, the pitch of the plurality of first jigs 40R after adjustment is, for example, 40 mm to 200 mm, preferably 60 mm to 190 mm, and more preferably 80 mm to 180 mm.

[0173] When the pitch of the plurality of first jigs 40R is set to 100%, the pitch of the plurality of second jigs 40L after adjustment in the second pitch adjustment process is, for example, 30% to 100%, preferably 40% to 100%, more preferably 50% to 100%, and further preferably 100%.

[0174] After that, the plurality of first jigs 40R whose pitch has been adjusted in the second pitch adjustment process are moved around along the reference track 10 and are supplied again to the first pitch adjustment process. Further, the plurality of second jigs 40L whose pitch has been adjusted in the second pitch adjustment process are moved around along the reference track 10 and are supplied again to the first pitch adjustment process.

[0175] In such a stretching device 100, it is possible to continuously manufacture a long, obliquely stretched film in which the deviation of the orientation angle is suppressed.

[0176] The stretched film is typically a retardation film. In one embodiment, the refractive indices of the retardation film exhibit the relationship nx > ny. The retardation film preferably functions as a λ / 4 plate. When the retardation film functions as a λ / 4 plate, the in-plane retardation Re(550) of the retardation film (λ / 4 plate) is, for example, 100 nm to 180 nm, preferably 135 nm to 155 nm. In another embodiment, the retardation film can function as a λ / 2 plate. When the retardation film functions as a λ / 2 plate, the in-plane retardation Re(550) of the retardation film (λ / 2 plate) is, for example, 230 nm to 310 nm, preferably 250 nm to 290 nm.

[0177] In addition, the retardation film preferably exhibits a so-called reverse dispersion wavelength dependence. Specifically, its in-plane retardation satisfies the relationship Re(450) < Re(550) < Re(650). Re(450) / Re(550) is, for example, 0.8 or more and less than 1.0, preferably 0.8 to 0.95. Re(550) / Re(650) is, for example, 0.8 or more and less than 1.0, preferably 0.8 to 0.97.

[0178] Industrial applicability

[0179] The method for manufacturing the stretched film of the present invention is suitable for manufacturing a retardation film, and as a result, it can contribute to the manufacture of image display devices such as liquid crystal display devices (LCDs) and organic electroluminescence display devices (OLEDs).

Claims

1. A method for producing a stretched film, wherein: The method comprises, in sequence: a clamping step of clamping a first end portion of the long film in the width direction with a plurality of first clamps arranged along the length direction of the film, and clamping a second end portion of the film in the width direction with a plurality of second clamps arranged along the length direction; a stretching step of moving the plurality of first clamps and the plurality of second clamps in the longitudinal direction while changing the intervals between the plurality of first clamps, thereby stretching the film in an oblique direction intersecting both the longitudinal direction and the width direction; and a releasing step of releasing the first end portion of the film from the plurality of first clamps and releasing the second end portion of the film from the plurality of second clamps; The method further includes a first pitch adjustment step of making the pitches of the plurality of first clamps and the pitches of the plurality of second clamps substantially consistent before the clamping step.

2. The method for producing a stretched film according to claim 1, wherein: The method further includes a second spacing adjustment process of adjusting the spacing between the plurality of first clamps and the spacing between the plurality of second clamps after the releasing process.

3. The method for producing a stretched film according to claim 1 or 2, wherein: The in-plane birefringence Δn(550) of the film is 0.002 to 0.009, the temperature in the stretching step is below 180°C, the film clamping area of ​​each of the plurality of first clamps is substantially the same as the film clamping area of ​​each of the plurality of second clamps, and is 10 cm 2 ~300cm 2 .

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