Method for manufacturing stretch film

Abstract

This invention reduces relaxation and / or wrinkles in films resulting from oblique stretching. The invention relates to a method for manufacturing a stretch film, comprising the steps of: clamping the left and right ends of an elongated film in the width direction using left and right clamps respectively; obliquely stretching the film by moving the left and right clamps, and then releasing the film from the left and right clamps; and roller conveying the film using a planar spreading roller having: a pair of ring members arranged facing each other at an angle of more than 0° relative to the film conveying direction and rotatable in the circumferential direction; and a plurality of stretchable elastic bands installed between the ring members at predetermined intervals in the circumferential direction.

Description

Technical Field

[0001] This invention relates to a method for manufacturing stretch films and a method for manufacturing optical laminates. Background Technology

[0002] Circular polarizers are used in image display devices such as liquid crystal displays (LCDs) and organic light-emitting diode (OLEDs) to improve display characteristics and prevent reflections. A circular polarizer is typically made by stacking a polarizer and a retardation film (typically a λ / 4 plate) at a 45° angle between the absorption axis of the polarizer and the slow axis of the retardation film. Conventionally, retardation films are typically fabricated by uniaxial or biaxial stretching in the longitudinal and / or transverse directions; therefore, their slow axis often lies along the transverse (width direction) or longitudinal (length direction) of the strip-shaped film preform. As a result, to fabricate a circular polarizer, the retardation film needs to be cut at a 45° angle relative to the width or length direction and then laminated piece by piece.

[0003] In addition, to ensure the wide bandwidth of the circular polarizer, sometimes two retardation films, a λ / 4 plate and a λ / 2 plate, are stacked. In this case, the λ / 2 plate needs to be stacked at a 75° angle relative to the absorption axis of the polarizer, and the λ / 4 plate needs to be stacked at a 15° angle relative to the absorption axis of the polarizer. In this case, when fabricating the circular polarizer, the retardation films also need to be cut at 15° and 75° angles relative to the width or length direction, respectively, and then laminated piece by piece.

[0004] In another embodiment, to prevent light from a laptop PC from reflecting onto the keyboard, etc., and to rotate the orientation of the linearly polarized light emitted from the polarizer by 90°, a λ / 2 plate is sometimes used on the visible side of the polarizer. In this case, the retardation film also needs to be cut at a 45° angle relative to the width or length direction and laminated piece by piece.

[0005] To address this problem, a technique has been proposed whereby a strip-shaped membrane is clamped at its left and right ends in the width direction by left and right clamps of a variable-pitch type with varying clamp spacing in the longitudinal direction. The clamp spacing of at least one of the left and right clamps is varied, causing stretching in an oblique direction relative to the length direction (hereinafter also referred to as "oblique stretching"), thereby causing the slow axis of the phase retardation membrane to exhibit an oblique orientation (e.g., Patent Document 1). However, obliquely stretched membranes obtained using this technique sometimes exhibit slack (sagging) and wrinkles.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent No. 4845619 Summary of the Invention

[0009] The problem that the invention aims to solve

[0010] The present invention was made to solve the above-mentioned problems, and its main purpose is to reduce the relaxation and / or wrinkles that occur in the membrane after oblique stretching.

[0011] means for solving problems

[0012] According to one aspect of the present invention, a method for manufacturing a stretch film is provided, comprising the steps of: clamping the left and right ends of an elongated film in the width direction by left and right clamps respectively; moving the left and right clamps to obliquely stretch the film, and then releasing the film from the left and right clamps; and roller conveying the film using a planar spreading roller having: a pair of ring members arranged facing each other with an angle of more than 0° relative to the conveying direction of the film, and rotatable in the circumferential direction; and a plurality of retractable elastic bands installed between the ring members at predetermined intervals in the circumferential direction.

[0013] In one embodiment, the angle is greater than 0° and less than 4.0°.

[0014] In one embodiment, the Rockwell hardness of the above-mentioned membrane is R100 to M120.

[0015] In one embodiment, in addition to the aforementioned planar spreading roller, concave rollers and / or curved rollers are used to roll-feed the film.

[0016] In one embodiment, the clamp is a variable-pitch type clamp with a longitudinally varying clamp spacing. It moves while varying the clamp spacing of at least one of the left clamp holding the left end of the membrane and the right clamp holding the right end, thereby stretching the membrane obliquely.

[0017] In one embodiment, the oblique stretching includes: (i) increasing the clamp spacing of one of the clamps in the left and right clamps from P1 to P2 while decreasing the clamp spacing of the other clamp from P1 to P3; and (ii) changing the clamp spacing of each clamp in such a way that the reduced clamp spacing and the increased clamp spacing become a predetermined equal spacing.

[0018] In one embodiment, P2 / P1 is 1.25 to 1.75, and P3 / P1 is 0.50 or more but less than 1.

[0019] In one embodiment, the membrane is obliquely stretched by changing the transport direction of the membrane midway through the process while moving the left clamp holding the left end of the membrane and the right clamp holding the right end at the same speed.

[0020] According to another aspect of the present invention, a method for manufacturing an optical laminate is provided, comprising: obtaining an elongated stretch film by the above-described manufacturing method; and continuously laminating the elongated optical film and the elongated stretch film by aligning their length directions while conveying them.

[0021] In one embodiment, the optical film is a polarizer, and the stretched film is a λ / 4 plate or a λ / 2 plate.

[0022] Invention Effects

[0023] In the method for manufacturing the stretch film of the present invention, a flat spreading roller is used to roll-feed an obliquely stretched elongated film. This results in an elongated obliquely stretched film with reduced relaxation and / or wrinkles. Attached Figure Description

[0024] Figure 1 This is a top view schematic diagram illustrating the overall configuration of an example of a stretching apparatus that can be used in the method for manufacturing a stretch film according to the present invention.

[0025] Figure 2 It is used for in Figure 1 A top view schematic diagram illustrating the main part of the connecting mechanism that changes the clamp spacing in the tensioning device.

[0026] Figure 3 It is used for in Figure 1 A top view schematic diagram illustrating the main part of the connecting mechanism that changes the clamp spacing in the tensioning device.

[0027] Figure 4 This is a top view schematic diagram illustrating the overall configuration of another example of a stretching apparatus that can be used in the method for manufacturing the stretch film of the present invention.

[0028] Figure 5A This is a schematic diagram showing the distribution of clamp spacing in one embodiment of oblique stretching.

[0029] Figure 5B This is a schematic diagram showing the distribution of clamp spacing in one embodiment of oblique stretching.

[0030] Figure 6 (a) and (b) are top and side views, respectively, illustrating an example of a roller conveyor.

[0031] Figure 7This is a top view schematic diagram illustrating the planar spreading roller preferably used in an embodiment of the present invention.

[0032] Figure 8 This is a top view schematic diagram illustrating the concave roller preferably used in an embodiment of the present invention.

[0033] Figure 9 This is a top view schematic diagram illustrating the preferred use of the bending roller in an embodiment of the present invention.

[0034] Figure 10 This is a cross-sectional schematic diagram of a circular polarizer using a phase difference film obtained by the manufacturing method of the present invention.

[0035] Figure 11 This is a schematic diagram illustrating the method for measuring relaxation.

[0036] Symbol Explanation

[0037] 1. Stretch film

[0038] 10L Annular Ring

[0039] 10R Annular Ring

[0040] 20 Fixtures

[0041] 51 Planar Extending Roller

[0042] 60. Volume Taking Section

[0043] 100 Tensioning device

[0044] 200 Circular Polarizer

[0045] 300 Ultrasonic Displacement Sensor Detailed Implementation

[0046] The preferred embodiments of the present invention will be described below, but the present invention is not limited to these embodiments. Furthermore, in this specification, "longitudinal clamp spacing" refers to the center-to-center distance between adjacent clamps in the longitudinal direction of travel. Additionally, unless otherwise specified, the left-right relationship of the elongated membrane in the width direction refers to its left-right relationship towards the conveying direction of the membrane.

[0047] A. Manufacturing method of stretch film

[0048] The method for manufacturing a stretch film according to an embodiment of the present invention includes the following steps: clamping the left and right ends of an elongated film in the width direction with left and right clamps respectively; moving the left and right clamps to obliquely stretch the film, then releasing the film from the left and right clamps; and roller conveying the film using a planar spreading roller. In this embodiment, the planar spreading roller has: a pair of ring members arranged facing each other with an angle of more than 0° relative to the film conveying direction and rotatable in the circumferential direction; and a plurality of retractable elastic bands installed between the ring members at predetermined intervals in the circumferential direction. Typically, the method for manufacturing a stretch film according to this embodiment further includes a preheating step. Specifically, the film clamped by the left and right clamps is preheated and then subjected to oblique stretching.

[0049] As a method for obliquely stretching the membrane by the movement of the aforementioned left and right clamps, any suitable method can be used that can stretch the left and right ends of the membrane at different stretching ratios (resulting in stretching in an oblique direction relative to the length direction). Examples include: a method of oblique stretching by moving the clamp holding the left end of the membrane and the clamp holding the right end at different speeds; and a method of oblique stretching by moving the clamp holding the left end of the membrane and the clamp holding the right end by moving different distances. In one embodiment of the former oblique stretching, the clamps are moved while the clamp spacing of at least one of the left clamp holding the left end of the membrane and the right clamp holding the right end is varied using a variable-pitch clamp with a longitudinally varying clamp spacing, thereby enabling the membrane to be stretched in an oblique direction. In one embodiment of the latter oblique stretching, while the left clamp holding the left end of the membrane and the right clamp holding the right end move at the same speed, the membrane's transport direction is changed midway (resulting in different transport path lengths for the left and right ends), thereby enabling the membrane to be stretched in the oblique direction. Furthermore, in the obliquely stretched membrane obtained by the above-described oblique stretching, the side with the smaller stretch ratio tends to become loose and wrinkled. Therefore, in one embodiment, the side with the smaller stretch ratio during oblique stretching can be the loose side. Additionally, the above-described obliquely stretched membrane is preferably a λ / 4 plate or a λ / 2 plate.

[0050] Figure 1This is a top view schematic diagram illustrating the overall configuration of an example of a stretching device that can be used for the aforementioned oblique stretching. The stretching device 100a, viewed from above, has annular rings 10L and 10R symmetrically arranged on the left and right sides, each annular ring 10L and 10R having multiple clamps 20 for membrane clamping. Furthermore, in this specification, the annular ring on the left when viewed from the membrane inlet side is referred to as the left annular ring 10L, and the annular ring on the right when viewed from the membrane inlet side is referred to as the right annular ring 10R. The clamps 20 of the left and right annular rings 10L and 10R are guided by reference tracks 70 and move in a circular loop. The clamps 20 of the left annular ring 10L move counterclockwise, and the clamps 20 of the right annular ring 10R move clockwise. In the stretching device, from the inlet side of the sheet to the outlet side, a clamping area A, a preheating area B, a stretching area C, and a release area D are sequentially arranged. The aforementioned regions refer to the areas where the membrane, which is to be stretched, is clamped, preheated, obliquely stretched, and released; they do not refer to mechanically or structurally independent blocks. Additionally, it should be noted that... Figure 1 The ratio of the length of each region in the stretching device is different from the ratio of the actual length.

[0051] exist Figure 1 Although not shown in the diagram, a region for performing any appropriate processing can be provided between the stretching region C and the release region D as needed. Examples of such processing include lateral shrinkage. Furthermore, similarly, although not shown, the stretching device typically includes a heating device (e.g., various ovens such as hot air, near-infrared, and far-infrared ovens) for setting the heating environment for each region from the preheating region B to the release region D. In one embodiment, preheating, oblique stretching, and release from the clamp can be performed separately in an oven set to a predetermined temperature.

[0052] In the clamping region A and preheating region B of the stretching device 100a described above, the left and right annular rings 10L and 10R are configured to be approximately parallel to each other at intervals corresponding to the initial width of the film to be stretched. In the stretching region C, the intervals between the left and right annular rings 10L and 10R gradually increase from the side of the preheating region B toward the release region D until they correspond to the stretched width of the film. In the release region D, the left and right annular rings 10L and 10R are configured to be approximately parallel to each other at intervals corresponding to the stretched width of the film. However, the configuration of the left and right annular rings 10L and 10R is not limited to the example shown in the figure above. For example, the left and right annular rings 10L and 10R may also be configured to be approximately parallel to each other at intervals corresponding to the initial width of the film to be stretched from the clamping region A to the release region D.

[0053] The clamps 20 of the left annular ring 10L (left clamp) and the clamps 20 of the right annular ring 10R (right clamp) can move independently in a cyclic motion. For example, the drive sprockets 11 and 12 of the left annular ring 10L can be driven to rotate counterclockwise by electric motors 13 and 14, and the drive sprockets 11 and 12 of the right annular ring 10R can be driven to rotate clockwise by electric motors 13 and 14. As a result, a traveling force can be applied to the clamp-bearing components (not shown) of the drive rollers (not shown) that engage with these drive sprockets 11 and 12. Thus, the left annular ring 10L moves counterclockwise in a cyclic motion, and the right annular ring 10R moves clockwise in a cyclic motion. By driving the left and right electric motors independently, the left annular ring 10L and the right annular ring 10R can move independently in a cyclic motion.

[0054] Furthermore, the clamps 20 of the left annular ring 10L (left clamp) and the clamps 20 of the right annular ring 10R (right clamp) are both variable-pitch types. That is, the clamps 20 on the left and right sides can independently change the longitudinal clamp spacing as they move. The variable-pitch type can be achieved by using a telescopic mechanism, a linear motor mechanism, a motor chain mechanism, or other drive methods. For example, Patent Document 1 and Japanese Patent Application Publication No. 2008-44339 describe in detail a tensioning synchronous biaxial tensioning device using a telescopic connection mechanism. Hereinafter, the connection mechanism (telescopic mechanism) will be described as an example.

[0055] Figure 2 and Figure 3 These are used for in Figure 1 A top view schematic diagram illustrating the main part of the connecting mechanism that changes the clamp spacing in the tensioning device. Figure 2 This shows the state where the clamp spacing is at its minimum. Figure 3 This shows the state with the largest clamp spacing.

[0056] like Figure 2 and Figure 3 As illustrated, a slender rectangular clamp-supporting component 30, viewed from above, is provided to support each clamp 20. Although not shown, the clamp-supporting component 30 is a robust frame structure with a closed cross-section formed by an upper beam, a lower beam, a front wall (the wall on the clamp side), and a rear wall (the wall on the side opposite to the clamp). The clamp-supporting component 30 is configured to rotate on the travel surfaces 81 and 82 via travel wheels 38 at both ends. Furthermore, in Figure 2 and Figure 3The travel wheels on the front wall side (travel wheels rotating on the travel surface 81) are not shown in the figure. The travel surfaces 81 and 82 run parallel to the reference track 70 throughout the entire area. On the rear side of the upper and lower beams of the clamp support member 30 (the opposite side of the clamp side (hereinafter referred to as the anti-clamp side)), an elongated hole 31 is formed along the length direction of the clamp support member, and the slider 32 is engaged in a manner that allows it to slide along the length direction of the elongated hole 31. Near the clamp 20 side end of the clamp support member 30, a first shaft member 33 is provided vertically through the upper and lower beams. On the other hand, a second shaft member 34 is provided vertically through the slider 32 of the clamp support member 30. One end of the main connecting member 35 is pivotally connected to the first shaft member 33 of each clamp support member 30. The other end of the main connecting member 35 is pivotally connected to the second shaft member 34 of the adjacent clamp support member 30. On the first shaft member 33 of each clamping support member 30, in addition to the main connecting member 35, one end of a secondary connecting member 36 is pivotally connected. The other end of the secondary connecting member 36 is pivotally connected to the middle portion of the main connecting member 35 via a pivot 37. By utilizing the connection mechanism of the main connecting member 35 and the secondary connecting member 36, such as... Figure 2 As shown, the further the slider 32 moves towards the rear (anti-clamping side) of the clamping support component 30, the smaller the longitudinal distance between the clamping support components 30 (resulting in clamping distance), such as... Figure 3 As shown, the closer slider 32 moves to the front (clamp side) of the clamping support component 30, the greater the longitudinal spacing between the clamping support components 30 (resulting in clamp spacing). The positioning of slider 32 is achieved via the spacing setting track 90. Figure 2 and Figure 3 As shown, the smaller the distance between the reference track 70 and the spacing setting track 90, the larger the clamp spacing.

[0057] Figure 4This is a top view schematic diagram illustrating the overall configuration of an example of a stretching device that can be used for the latter type of oblique stretching described above. In top view, the stretching device 100b has annular rings 10L and 10R on the left and right sides, each with multiple clamps 20 for film clamping. The clamps 20 of the left and right annular rings 10L and 10R are guided by reference tracks 40 and move in a circular, cyclical motion (in the example shown, a portion of the annular rings 10L and 10R is omitted). The clamp 20 of the left annular ring 10L moves counterclockwise, and the clamp 20 of the right annular ring 10R moves clockwise. In the stretching device, from the inlet side to the outlet side of the sheet, a clamping area A, a preheating area B, a stretching area C, and a release area D are arranged sequentially. These individual regions refer to the areas where the membrane, which is to be stretched, is actually clamped, preheated, obliquely stretched, and released; they do not refer to mechanically or structurally independent blocks. Additionally, it should be noted that... Figure 4 The ratio of the length of each region in the stretching device is different from the ratio of the actual length.

[0058] exist Figure 4 Although not shown in the diagram, a region for performing any appropriate processing can be provided between the stretching region C and the release region D as needed. Examples of such processing include lateral stretching and lateral contraction. Furthermore, similarly, although not shown, the stretching device typically includes a heating device (e.g., various ovens such as hot air, near-infrared, and far-infrared ovens) for setting the heating environment for each region from the preheating region B to the release region D. In one embodiment, preheating, oblique stretching, and release from the clamp can be performed separately in an oven set to a predetermined temperature.

[0059] In the clamping region A and preheating region B of the stretching device 100b described above, the left and right annular rings 10L and 10R are configured such that their spacing is approximately parallel to the initial width of the film to be stretched. In the stretching region C, the left annular ring 10L and the right annular ring 10R are configured to extend in asymmetrical directions. Thus, as the film transport direction changes, the spacing between the left and right annular rings 10L and 10R gradually increases from the preheating region B towards the release region D until it corresponds to the stretched width of the film. In the release region D, the left and right annular rings 10L and 10R are configured such that their spacing is approximately parallel to the stretched width of the film. However, the configuration of the left and right annular rings 10L and 10R is not limited to the example shown in the figure above.

[0060] The clamps 20 of the left annular ring 10L (left clamp) and the clamps 20 of the right annular ring 10R (right clamp) can move independently in a cyclic motion. For example, with Figure 1Similarly, the stretching device shown also drives the drive sprocket 11 of the left annular ring 10L to rotate counterclockwise via an electric motor 13, and drives the drive sprocket 11 of the right annular ring 10R to rotate clockwise via an electric motor 13. Typically, the left and right clamps 20 move at equal speeds, and the longitudinal clamp spacing can be kept constant. Furthermore, when the difference in the travel speed of a pair of left and right clamps is less than 1%, their travel speeds can be considered equal; this difference is preferably less than 0.5%, more preferably less than 0.1%.

[0061] By using the stretching device described above to perform oblique stretching of the membrane, it is possible to produce obliquely stretched membranes, such as phase difference membranes having a slow axis in the oblique direction. Hereinafter, each step of the above-described method for manufacturing the stretched membrane will be described in detail.

[0062] A-1. Using clamps to hold the membrane

[0063] In clamping area A (the membrane inlet of stretching device 100a or 100b), the membrane to be stretched is clamped at both ends by clamps 20 of left and right annular rings 10L and 10R with equal and constant clamp spacing or different clamp spacing. The membrane is fed to preheating area B by the movement of clamps 20 of left and right annular rings 10L and 10R (essentially the movement of each clamp-bearing component guided by the reference track).

[0064] A-2. Preheating

[0065] In preheating zone B, as described above, the left and right annular rings 10L and 10R are configured to be approximately parallel to each other in terms of the spacing between them, corresponding to the initial width of the film to be stretched. Therefore, the film is heated without substantially performing lateral or longitudinal stretching. However, to avoid adverse conditions such as film deflection or contact with nozzles in the oven caused by preheating, the distance between the left and right clamps (distance in the width direction) can be slightly widened.

[0066] During preheating, the film is heated to a temperature T1 (°C). Temperature T1 is preferably above the glass transition temperature (Tg) of the film, more preferably above Tg+2°C, and even more preferably above Tg+5°C. On the other hand, the heating temperature T1 is preferably below Tg+40°C, more preferably below Tg+30°C. Although it varies depending on the film used, temperature T1 is, for example, 70°C to 190°C, preferably 80°C to 180°C.

[0067] The heating time up to the aforementioned temperature T1 and the holding time at temperature T1 can be appropriately set according to the membrane's constituent materials and manufacturing conditions (e.g., membrane conveying speed). Their heating and holding times can be controlled by adjusting the moving speed of the clamp 20, the length of the preheating zone, and the temperature of the preheating zone.

[0068] A-3. Oblique stretching

[0069] A-3-1. Inclined stretching using a variable-pitch clamp.

[0070] In the stretching region C of the stretching apparatus 100a, the membrane is obliquely stretched by moving the left and right clamps 20 while changing the clamp spacing of at least one of the left and right clamps 20 in the longitudinal direction. More specifically, the membrane is obliquely stretched by increasing or decreasing the clamp spacing of the left and right clamps at different positions, or by changing the clamp spacing of the left and right clamps at different rates of change (increasing and / or decreasing).

[0071] Diagonal stretching can include transverse stretching. In this case, for example, diagonal stretching... Figure 1 As shown in the diagram, this can be achieved by simultaneously increasing the distance (width direction) between the left and right clamps. Alternatively, it can be combined with... Figure 1 The configuration shown is different, and the operation is carried out directly while maintaining the distance between the left and right clamps.

[0072] In the case of oblique stretching including transverse stretching, the transverse (TD) stretching ratio (the width W of the film after oblique stretching) final With the initial width W of the membrane initial The ratio (W) final / W initial The preferred value is 1.05 to 6.00, and more preferably 1.10 to 5.00.

[0073] In one embodiment, the oblique stretching can be performed as follows: the position where the clamping distance of one of the left and right clamps begins to increase or decrease is set to be different in the longitudinal direction from the position where the clamping distance of the other clamp begins to increase or decrease. In this state, the clamping distance of each clamp is increased or decreased to a predetermined distance. Regarding the oblique stretching of this embodiment, for example, refer to the description in Patent Document 1, Japanese Patent Application Publication No. 2014-238524, etc.

[0074] In another embodiment, the oblique stretching can be performed as follows: with the clamping distance of one of the clamps in the left and right clamps fixed, the clamping distance of the other clamp is increased or decreased to a predetermined distance, and then restored to the initial clamping distance. For details regarding the oblique stretching in this embodiment, please refer to, for example, Japanese Patent Application Publication No. 2013-54338 and Japanese Patent Application Publication No. 2014-194482.

[0075] In another embodiment, the oblique stretching can be performed as follows: (i) while increasing the clamp spacing of one of the left and right clamps from P1 to P2, the clamp spacing of the other clamp is decreased from P1 to P3; and (ii) the clamp spacing of each clamp is varied in such a way that the reduced clamp spacing and the increased clamp spacing become a predetermined equal spacing. For details regarding the oblique stretching of this embodiment, please refer to, for example, the description in Japanese Patent Application Publication No. 2014-194484, etc. The oblique stretching of this embodiment may include: increasing the distance between the left and right clamps while increasing the clamp spacing of one clamp from P1 to P2 and decreasing the clamp spacing of the other clamp from P1 to P3 to perform oblique stretching of the membrane (first oblique stretching); and increasing the distance between the left and right clamps while maintaining the clamp spacing of one clamp at P2 or decreasing it to P4 such that the clamp spacing of the left and right clamps becomes equal, and increasing the clamp spacing of the other clamp to P2 or P4 to perform oblique stretching of the membrane (second oblique stretching).

[0076] In the first oblique stretching described above, by simultaneously stretching one end of the membrane in the length direction and contracting the other end in the length direction while performing oblique stretching, the slow axis can exhibit 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 stretching, by performing oblique stretching while reducing the difference in the spacing between the left and right clamps, excess stress can be mitigated while sufficient stretching is achieved in the oblique direction.

[0077] In the oblique stretching of the above three embodiments, the film can be released from the clamps when the moving speeds of the left and right clamps become equal. Therefore, when the left and right clamps are released, deviations in the film conveying speed, etc., are less likely to occur, and subsequent film winding can be carried out appropriately.

[0078] Figure 5A and Figure 5B These are schematic diagrams illustrating an example of the distribution of clamp spacing in an oblique stretch including the first and second oblique stretches described above. The first oblique stretch will be specifically described below with reference to these diagrams. Furthermore, in Figure 5A and Figure 5BIn this diagram, the horizontal axis corresponds to the travel distance of the clamps. At the start of the first oblique stretch, the clamp spacing on both sides is set to P1. P1 is representative of the clamp spacing when holding the film. Simultaneously with the start of the first oblique stretch, the clamp spacing of one clamp (hereinafter sometimes referred to as the first clamp) begins to increase, and the clamp spacing of the other clamp (hereinafter sometimes referred to as the second clamp) begins to decrease. During the first oblique stretch, 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 stretch (and at the start of the second oblique stretch), the second clamp moves with clamp spacing P3, and the first clamp moves with clamp spacing P2. Furthermore, the ratio of clamp spacings can approximately correspond to the ratio of clamp travel speeds.

[0079] exist Figure 5A and Figure 5B In this embodiment, the moment when the clamp spacing of the first clamp begins to increase and the moment when the clamp spacing of the second clamp begins to decrease are both defined as the start of the first oblique stretching. However, unlike the example shown, the clamp spacing of the second clamp may begin to decrease after the clamp spacing of the first clamp begins to increase, or vice versa. In a preferred embodiment, the clamp spacing of the second clamp begins to decrease after the clamp spacing of the first clamp begins to increase. According to this embodiment, the film has already been stretched to a certain extent (preferably about 1.2 to 2.0 times) in the width direction, so even if the clamp spacing of the second clamp is significantly reduced, wrinkles are less likely to occur. Thus, more acute-angle oblique stretching can be achieved, and a phase reversal film with high uniaxiality and in-plane orientation can be appropriately obtained.

[0080] Similarly, in Figure 5A and Figure 5B In this case, the increase in the clamping distance of the first clamp and the decrease in the clamping distance of the second clamp continue until the end of the first oblique stretch (when the second oblique stretch begins). However, unlike the example in the figure, either the increase or decrease in the clamping distance can end earlier than the other, and its clamping distance can be maintained until the other ends (until the end of the first oblique stretch).

[0081] The rate of change of the clamp spacing of the first clamp (P2 / P1) is preferably 1.25 to 1.75, more preferably 1.30 to 1.70, and even more preferably 1.35 to 1.65. Furthermore, the rate of change of the clamp spacing 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 even more preferably 0.55 to 0.85. If the rate of change of the clamp spacing is within such a range, the slow axis can exhibit high uniaxiality and in-plane orientation in a direction approximately 45 degrees relative to the length direction of the membrane.

[0082] As described above, the slider can be positioned by adjusting the spacing of the tensioning device to set the distance between the track and the reference track, and the clamp spacing can be adjusted.

[0083] The stretching ratio of the film in the width direction during the first oblique stretching (film width at the end of the first oblique stretching / film width before the first oblique stretching) is preferably 1.1 to 3.0 times, more preferably 1.2 to 2.5 times, and even more preferably 1.25 to 2.0 times. When the stretching ratio is less than 1.1 times, there is a possibility that galvanized iron-like wrinkles may form at the end on the shrinking side. In addition, when the stretching ratio exceeds 3.0 times, the biaxiality of the obtained phase retardation film becomes higher, and the viewing angle characteristics decrease when applied to circular polarizers, etc.

[0084] In one embodiment, for the first oblique stretching, the product of the rate of change of the clamp spacing of the first clamp and the rate of change of the clamp spacing of the second clamp is preferably 0.7 to 1.5, more preferably 0.8 to 1.45, and even more preferably 0.85 to 1.40. If the product of the rates of change is within such a range, a retardation film with high uniaxiality and in-plane orientation can be obtained.

[0085] Next, refer to Figure 5A One embodiment of the second oblique stretching will be specifically described. In the second oblique stretching of this embodiment, the clamping distance of the second clamp is increased from P3 to P2. On the other hand, the clamping distance of the first clamp is maintained at P2 during the second oblique stretching. Therefore, at the end of the second oblique stretching, both the left and right clamps are moved by the clamping distance P2.

[0086] Figure 5A The rate of change (P2 / P3) of the clamp spacing of the second clamp in the second oblique stretching of the illustrated embodiment is not limited as long as it does not impair the effects of the invention. This rate of change (P2 / P3) is, for example, 1.3 to 4.0, preferably 1.5 to 3.0.

[0087] Reference Figure 5BAnother embodiment of the second oblique stretching will be specifically described. In the second oblique stretching of this embodiment, the clamping distance of the first clamp is decreased while the clamping distance of the second clamp is increased. Specifically, the clamping distance of the first clamp is decreased from P2 to P4, and the clamping distance of the second clamp is increased from P3 to P4. Therefore, at the end of the second oblique stretching, both the left and right clamps move by the clamping distance P4. Furthermore, in the example shown, the decrease in the clamping distance of the first clamp and the increase in the clamping distance of the second clamp begin simultaneously with the start of the second oblique stretching, but they may also begin at different times. Similarly, the decrease in the clamping distance of the first clamp and the increase in the clamping distance of the second clamp may also end at different times.

[0088] Figure 5B The rate of change of the clamp spacing of the first clamp (P4 / P2) and the rate of change of the clamp spacing of the second clamp (P4 / P3) in the second oblique stretching of the illustrated embodiment are not limited as long as they do not impair the effects of the present invention. The rate of change (P4 / P2) is, for example, 0.4 or more and less than 1.0, preferably 0.6 to 0.95. Furthermore, the rate of change (P4 / P3) is, for example, more than 1.0 and less than 2.0, preferably 1.2 to 1.8. P4 is preferably P1 or more. If P4 < P1, problems such as wrinkles at the ends and increased biaxiality may occur.

[0089] The stretching ratio in the width direction of the film during the second oblique stretching (film width at the end of the second oblique stretching / 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 even more preferably 1.25 to 2.0 times. When the stretching ratio is less than 1.1 times, there is a possibility of galvanized iron-like wrinkles forming at the ends on the shrinkage side. In addition, when the stretching ratio exceeds 3.0 times, the biaxiality of the obtained phase retardation film increases, and the viewing angle characteristics decrease when applied to circular polarizers, etc. Furthermore, from the same viewpoint as above, the stretching ratio in the width direction during the first and second oblique stretching (film width at the end of the second oblique stretching / film width before the first oblique stretching) is preferably 1.2 to 4.0 times, more preferably 1.4 to 3.0 times.

[0090] The oblique stretching can typically be performed at a temperature T2. The temperature T2 relative to the glass transition temperature (Tg) of the film is preferably Tg-20°C to Tg+30°C, more preferably Tg-10°C to Tg+20°C, and particularly preferably around Tg. Although it varies depending on the film used, the temperature T2 is, for example, 70°C to 180°C, preferably 80°C to 170°C. The difference between the above-mentioned temperatures T1 and T2 (T1-T2) is preferably ±2°C or more, more preferably ±5°C or more. In one embodiment, T1 > T2; therefore, in the preheating zone, the film heated to temperature T1 can be cooled to temperature T2.

[0091] As described above, a transverse shrinkage treatment can be performed after oblique stretching. For details regarding this treatment after oblique stretching, please refer to paragraphs 0029 to 0032 of Japanese Patent Application Publication No. 2014-194483.

[0092] A-3-2. Oblique stretching using a clamp with constant spacing.

[0093] In the stretching region C of the stretching device 100b, the left annular ring 10L and the right annular ring 10R extend in asymmetrical directions. This results in a configuration that alters the membrane transport direction (specifically, the membrane transport direction in the preheating region B (the direction of extension of arrow B) is not parallel to the membrane transport direction in the release region D (the direction of extension of arrow D)). Due to this configuration, the lengths of the left and right annular rings 10L and R in the oblique stretching region C (in other words, the travel distance of the left and right clamps in the oblique stretching region C) are different. As a result, for a pair of left and right clamps moving at equal speeds, the clamp with the shorter travel distance travels first (in... Figure 4 In the middle (with the left clamp moving first), the membrane is stretched in an inclined direction. Regarding the inclined stretching in this embodiment, for example, refer to the descriptions in Japanese Patent Application Publication No. 2004-226686, WO2007 / 111313, etc.

[0094] The oblique stretching can typically be performed at a temperature T2. The temperature T2 relative to the glass transition temperature (Tg) of the film is preferably Tg-20°C to Tg+30°C, more preferably Tg-10°C to Tg+20°C, and particularly preferably around Tg. Although it varies depending on the film used, the temperature T2 is, for example, 70°C to 180°C, preferably 80°C to 170°C. The difference between the above-mentioned temperatures T1 and T2 (T1-T2) is preferably ±2°C or more, more preferably ±5°C or more. In one embodiment, T1 > T2; therefore, in the preheating zone, the film heated to temperature T1 can be cooled to temperature T2.

[0095] As described above, a transverse shrinkage treatment can be performed after oblique stretching. For details regarding this treatment after oblique stretching, please refer to paragraphs 0029 to 0032 of Japanese Patent Application Publication No. 2014-194483.

[0096] A-4. Release of the clamp

[0097] The membrane is released from the clamp at any location in the release region D. In the release region D, neither lateral nor longitudinal stretching is typically performed. Instead, the membrane is heat-treated as needed to fix the stretched state (heat-fixing), and / or cooled below Tg, after which the membrane is released from the clamp. Furthermore, during heat-fixing, the longitudinal clamp spacing can be reduced, thereby mitigating stress.

[0098] Heat treatment can typically be performed at temperature T3. The temperature T3 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 temperature difference between T2 and T3 (T2 - T3) is preferably 0°C to 50°C. The heat treatment time is typically 10 seconds to 10 minutes.

[0099] In one embodiment, the width of the film released from the clamp (which results in the width of the film supplied to the rollers using the planar extension rollers described later) is, for example, 1500 mm to 3000 mm, preferably 1800 mm to 2700 mm, and more preferably 2000 mm to 2400 mm.

[0100] A-5. Roller Conveyor

[0101] The membrane released from the clamp is conveyed using a planar extension roller. Figure 6 (a) and Figure 6 (b) are a top view and a side view illustrating an example of a roller conveyor using the aforementioned planar extended rollers. Figure 7 This is a top view schematic diagram of a planar spreading roller that can be used in embodiments of the present invention. In the roller conveying illustrated in the figure, the film 1 fed from the stretching device 100 is conveyed through seven rollers (planar spreading roller 51, first to sixth planar rollers 52 to 57) and wound up by the winding unit 60. Furthermore, in this specification, a planar roller refers to a cylindrical conveying roller used in conventional roller conveying.

[0102] Figure 7The planar expanding roller 51 shown is a straight roller. The planar expanding roller 51 includes: a shaft 51a; a pair of support substrates 51b mounted at both ends of the shaft 51a; a pair of ring members 51c mounted inside the support substrates 51b and arranged facing each other with an angle θ relative to the film conveying direction; and a plurality of elastic belts (typically rubber belts) 51d, which are installed between the pair of ring members 51c at predetermined intervals in the circumferential direction of the planar expanding roller 51 and are telescopic. The ring members 51c have bearings and are configured such that their inner sides can rotate circumferentially together with the elastic belts 51d due to the frictional force between the elastic belts 51d and the conveyed film. Furthermore, the ring members 51c are configured to allow arbitrary changes in the angle θ relative to the film conveying direction. In the example shown, the angle θ can be changed by the insertion amount of four adjusting bolts 51e, but other configurations can also be used to change the angle θ. For the planar expanding roller, a larger angle θ results in greater expansion capability.

[0103] The angle θ can be appropriately set within a range exceeding 0° depending on the amount of relaxation and the degree of wrinkling in the stretched film. Furthermore, when the angle θ is 0°, the planar spreading roller cannot perform its expanding function, functioning the same as the planar roller. Additionally, when the planar spreading roller is arranged to overlap the film with its width direction center, it can be predicted that due to its shape, it will perform expanding symmetrically with respect to the width direction center of the film. However, when applied to obliquely stretched films that have relaxation and / or wrinkles on one side, it can achieve excellent results in substantially maintaining the target axial angle and in-plane phase difference, and reducing relaxation and / or wrinkles. While the reason for achieving such results is not yet determined, it is speculated that in the presence of relaxation and / or wrinkles, a slight stretching effect can improve relaxation and / or wrinkles; furthermore, since uniform tension is applied in the film width direction at this time, surface uniformity can be maintained.

[0104] In one embodiment, the angle θ can be, for example, greater than 0° and less than 4.0°, preferably 2.0° to 3.5°. By using a planar spreading roller at such an angle, it is possible to obtain a long strip of stretched film that substantially maintains the target axial angle and in-plane phase difference and has reduced relaxation.

[0105] In one embodiment, the angle θ can be, for example, 0.1° to 3°, preferably 0.5° to 2.5°. By using a planar spreading roller at such an angle, it is possible to obtain a long, strip-shaped stretch film that substantially maintains the target axial angle and in-plane phase difference and reduces wrinkles.

[0106] In one embodiment, the angle θ can be, for example, 1.5° to 3.5°, preferably 2.0° to 3.0°. By using a planar spreading roller at such an angle, it is possible to obtain a long, strip-shaped stretch film that substantially maintains the target axial angle and in-plane phase difference, and has reduced relaxation and wrinkles.

[0107] The wrap angle of the membrane as it passes through the planar spreading roller is, for example, 45° to 135°, preferably 70° to 100°. If the wrap angle is within this range, the effects of the present invention can be appropriately obtained.

[0108] As shown in the example, roller conveying can be performed using multiple rollers, including planar extension rollers. In roller conveying, the total number of rollers through which the membrane passes (including the planar extension rollers) can be, for example, 1 to 12, preferably 2 to 10, and more preferably 3 to 8. In this case, the order in which the membrane passes through the planar extension rollers is not particularly limited, and the planar extension rollers can be positioned arbitrarily.

[0109] In one embodiment, in addition to the planar extended rollers, concave rollers and / or curved rollers can also be used for roller conveying. By using these rollers together, a more appropriate reduction in slack can be achieved. There are no particular limitations on the placement of the concave rollers and curved rollers. These rollers can be positioned at any location upstream or downstream of the planar extended rollers in the conveying direction.

[0110] Figure 8 This is a top view schematic diagram illustrating the concave roller preferably used in the above embodiment. The concave roller 58 has a central portion 58a, and an expanded diameter portion 58b and an end portion 58c arranged sequentially from both ends of the central portion 58a outwards. The central portion 58a and the end portion 58c are both cylindrical in shape, and the concave roller 58 has a point-symmetric shape with the center C of the rotation axis A as the center of symmetry.

[0111] The difference X between the radius of the central portion 58a and the radius of the end portion 58c can be, for example, 0.2 mm to 2.0 mm, preferably 0.3 mm to 1.8 mm. Additionally, the width W4 of the end portion 58c can be, for example, 20 mm to 200 mm, preferably 30 mm to 180 mm. If the difference X and / or the width W4 are within this range, a relaxation reduction effect can be appropriately obtained. Furthermore, in the example shown, the central portion 58a has a width W2 and is cylindrical; however, the width W2 of the central portion 58a can also be 0 mm. In this case, the concave roller has a structure that expands in diameter from the center in the width direction towards both ends.

[0112] The diameter expansion ratio (X / W3×100) of the diameter expansion section 58b is, for example, 0.1% to 6.0%, preferably 0.2% to 5.0%, and more preferably 1.0% to 4.5%. If the diameter expansion ratio is within this range, the target axial angle and in-plane phase difference can be substantially maintained, and the relaxation reduction effect can be appropriately obtained. Furthermore, in the example shown, the diameter expansion section is expanded in a straight line, but the diameter expansion section may also be concave.

[0113] Unlike the example shown in the figure, a concave roller without an expanded diameter section can also be used (i.e., a concave roller whose ends rise vertically from both ends of the central section). For the difference X between the radius of the central section and the radius of the end section, and the width W4 of the end section in such a concave roller, the same explanation as that for the concave roller with an expanded diameter section described above can be applied.

[0114] The total width W1 of the concave roller 58 and the width W2 of the central portion 58a can be appropriately set according to the film width when the roller passes through, the end width W4, the expansion ratio, the difference X, etc. For example, the total width W1 of the concave roller 58 can be designed such that the left and right ends 58c overlap with the film passing through the roller by, for example, 5mm to 195mm, or by, for example, 10mm to 190mm.

[0115] There are no particular limitations on the material used to form the concave roller, as long as it achieves the effects of the present invention; for example, rubber or metal can be used.

[0116] Figure 9 This is a top view schematic diagram illustrating the bending roller preferably used in the above embodiments. Figure 9 The bending roller 59 shown is symmetrically bent about the center (centerline C1) in the width direction, protruding in the conveying direction. When using the bending roller, it is preferable to roll the film 1 such that the unrelaxed end of the film 1 is closer to the center in the width direction of the bending roller than the relaxed end, thus offsetting the center (centerline C2) in the width direction of the film 1 from the center (centerline C1) of the bending roller. By conveying the film as described above, a greater tension is applied to the unrelaxed side of the film than to the relaxed side, which is beneficial for reducing relaxation.

[0117] The bending roller 59, for example, has a structure in which multiple radial ball bearings (not shown) are mounted around the bending shaft 59a, and its surface is covered by a cylinder made of an elastic material such as rubber that can be elastically deformed, and the cylinder is configured to rotate about the bending shaft 59b. In addition, there are bending rollers with a fixed degree of bending and bending rollers with a variable degree of bending, and any of the bending rollers can be used.

[0118] The bending amount D (mm) and total width W5 (mm) of the bending roller 59 can be set to appropriate values ​​according to the desired relaxation reduction, film width, etc. The bending amount D can be, for example, 5mm to 15mm, preferably 8mm to 13mm. The bending rate (D / W5×100) of the bending roller 59 can be, for example, 0.1% to 1.5%, preferably 0.2% to 0.7%. If the bending amount and / or bending rate are set within this range, a long strip-shaped stretched film that substantially maintains the target axial angle and in-plane phase difference, and exhibits relaxation reduction, can be appropriately obtained. Furthermore, the total width W5 of the bending roller 59 can be, for example, 105% to 170% of the width of the film 1, preferably 110% to 155%.

[0119] The distance L between the center of the membrane 1 in the width direction and the center of the bending roller 59 in the width direction (the distance between the center line C2 of the membrane 1 and the center line C1 of the bending roller) 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.

[0120] The aforementioned roller conveying is preferably performed while tension is applied to the film after it is released from the clamp. In addition to correcting slack using the planar spreading roller, tension is applied to the entire film, thereby more effectively reducing slack and / or wrinkles. 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. Tension can be applied, for example, by measuring the tension applied to the film between the conveying rollers and controlling the rotational speed of the conveying rollers in a manner that ensures the tension reaches a desired value.

[0121] Tension can be applied from the moment the clamp is released until any of the conveyor rollers (e.g., from the moment the clamp is released until a roller downstream of the planar extension roller).

[0122] The time for applying tension can be appropriately set according to the membrane forming material, relaxation amount, etc. This time can be, for example, 5 seconds to 60 seconds.

[0123] Roller conveying can be performed in a heated or unheated environment. Preferably, roller conveying is performed in an unheated environment. By allowing the flat spreading rollers to pass through in an unheated environment, scratches can be prevented, and slack and / or wrinkles can be reduced. The ambient temperature of the unheated environment can be, for example, around 15°C to 40°C, or, for example, around 20°C to 30°C. Alternatively, the ambient temperature of the heated environment can be set to, for example, the same level as the ambient temperature in the release zone of the aforementioned stretching device.

[0124] The film 1, which has been conveyed by rollers, can be wound up by the winding section 60 to form a film roll. Alternatively, unlike the example shown in the figure, the film may not be wound up, but may be conveyed along with other long strip optical films while being continuously laminated with them aligned in their length directions, thereby forming an optical laminate.

[0125] In one embodiment, when a slack amount exceeding a predetermined amount is detected while the stretch film released from the clamp and delivered from the stretching device is being roller-fed using only a flat roller, the slack amount of the subsequently obtained stretch film can be reduced by changing at least one flat roller to a flat extended roller for roller-fed feeding.

[0126] A-6. Detection of relaxation amount

[0127] The amount of relaxation can be detected, for example, between the conveyor rollers. Specifically, the amount of relaxation can be detected as the difference between the midpoint between the conveyor rollers and the position (conveyor height) in the width direction of the film.

[0128] The distance between the conveyor rollers during the above-mentioned testing is not particularly limited. For example, it can be set to 500mm to 2000mm, and preferably 700mm to 1500mm.

[0129] The membrane tension used in the above-mentioned test is not particularly limited; for example, it can be set to 50 N / m to 400 N / m, preferably 100 N / m to 200 N / m. If the transport tension is too high, the membrane may undergo elastic deformation during transport, making it difficult to detect slack. On the other hand, if the transport tension is too low, the tension itself may be unstable, resulting in unstable measured values ​​for slack.

[0130] The above tests can be performed in a non-heated environment. The ambient temperature for testing relaxation can be, for example, around 15℃ to 40℃, or around 20℃ to 30℃.

[0131] In one embodiment, the stretch membrane released from the clamp is cut off at its left and right ends in the width direction, and then the relaxation amount is measured. By measuring the relaxation amount after removing both ends, more accurate measurement results can be obtained.

[0132] The width of the ends to be cut off can be, for example, 20 mm to 600 mm, preferably 100 mm to 500 mm. The cutting off of the ends can be performed by conventional slitting.

[0133] The relaxation reduction amount obtained by the stretch film manufacturing method of the present invention (relaxation amount of film transported by rollers without using planar expansion rollers - relaxation amount of film transported by rollers using planar expansion rollers: wherein the relaxation amount is measured with a roller distance of 1000 mm) can be, for example, 3 mm or more, preferably 5 mm or more, more preferably 8 mm or more, and even more preferably 10 mm or more. Furthermore, the relaxation amount that may remain in the film after roller transport using the aforementioned planar expansion rollers can be, for example, less than 15 mm, preferably less than 10 mm, more preferably less than 8 mm, even more preferably less than 5 mm, and even more preferably less than 3 mm.

[0134] B. The membrane as the object of stretching

[0135] In the manufacturing method of the present invention, any suitable membrane can be used. For example, resin membranes that can be used as retardation membranes can be cited. Examples of materials constituting such membranes include: polycarbonate resins, polyvinyl acetal resins, cycloolefin resins, acrylic resins, cellulose ester resins, cellulose resins, polyester resins, polyester carbonate resins, olefin resins, polyurethane resins, etc. Polycarbonate resins, cellulose ester resins, polyester resins, polyester carbonate resins, and cycloolefin resins are preferred. This is because, with these resins, a retardation membrane exhibiting wavelength-dependent so-called reverse dispersion can be obtained. These resins can be used alone or in combination according to desired properties.

[0136] As the aforementioned polycarbonate-based resin, any suitable polycarbonate-based resin can be used. For example, a polycarbonate resin containing structural units derived from dihydroxy compounds is preferred. Specific examples of dihydroxy compounds 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) ... 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-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-dimethylpropoxy)phenyl)fluorene, etc. In addition to the structural units derived from dihydroxy compounds mentioned above, polycarbonate resins may also contain structural units derived from dihydroxy compounds such as isosorbide, isomannitol, isoidide, spirodiol, dioxaneglycol, diethylene glycol (DEG), triethylene glycol (TEG), polyethylene glycol (PEG), cyclohexanediethanol (CHDM), tricyclodecanediethanol (TCDDM), and bisphenols.

[0137] Details of the polycarbonate resins described above are described, for example, in Japanese Patent Application Publication No. 2012-67300 and Japanese Patent No. 3325560. The contents of these patent documents are incorporated herein by reference.

[0138] The glass transition temperature of the polycarbonate resin is preferably 110°C to 250°C, more preferably 120°C to 230°C. If the glass transition temperature is too low, the heat resistance tends to deteriorate, and dimensional changes may occur after film formation. If the glass transition temperature is too high, the forming stability during film formation deteriorates, and the transparency of the film may also be impaired. Furthermore, the glass transition temperature is determined according to JIS K 7121 (1987).

[0139] As the aforementioned polyvinyl acetal resin, any suitable polyvinyl acetal resin can be used. Typically, polyvinyl acetal resins can be obtained by reacting at least two aldehyde compounds and / or ketone compounds with a polyvinyl acetal resin. Specific examples and detailed manufacturing methods of polyvinyl acetal resins are described, for example, in Japanese Patent Application Publication No. 2007-161994. This description is incorporated herein by reference.

[0140] The Rockwell hardness of the aforementioned membrane is preferably R100 to M120, more preferably R120 to M110, and even more preferably M70 to M100. In roller conveying using planar extension rollers, scratches may sometimes occur in the membrane due to the indentation strength. However, by keeping the membrane hardness within this range, the formation of these scratches can be prevented. Furthermore, a reduction in slack or wrinkles can be more appropriately achieved.

[0141] The stretched film (phase reversal film) obtained by stretching the film described above preferably exhibits a refractive index characteristic showing a relationship of nx > ny. In one embodiment, the phase reversal film preferably functions as a λ / 4 plate. In this embodiment, the in-plane phase difference Re(550) of the phase reversal film (λ / 4 plate) is preferably 100 nm to 180 nm, more preferably 135 nm to 155 nm. In another embodiment, the phase reversal film preferably functions as a λ / 2 plate. In this embodiment, the in-plane phase difference Re(550) of the phase reversal film (λ / 2 plate) is preferably 230 nm to 310 nm, more preferably 250 nm to 290 nm. Furthermore, in this specification, nx is the refractive index in the direction of maximum in-plane refractive index (i.e., the slow axis direction), ny is the refractive index in the direction orthogonal to the slow axis (i.e., the fast axis direction), and nz is the refractive index in the thickness direction. In addition, Re(λ) is the in-plane phase difference of the film measured with light at a wavelength of λ nm at 23°C. Therefore, Re(550) is the in-plane phase difference of the film measured with light at a wavelength of 550 nm at 23 °C. Re(λ) is calculated using the formula: Re(λ)=(nx-ny)×d when the thickness of the film is set to d (nm).

[0142] The in-plane phase difference Re(550) of the retardation film can be set to a desired range by appropriately setting the oblique stretching conditions. For example, a method for manufacturing a retardation film with an in-plane phase difference 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, and 2014-194484, etc. Therefore, those skilled in the art can set appropriate oblique stretching conditions based on these disclosures.

[0143] When using a phase retardation film to fabricate a circular polarizer, or when using a phase retardation film to rotate the orientation of linearly polarized light by 90°, the slow axis direction of the phase retardation film is preferably 30° to 60° or 120° to 150° relative to the length direction of the film, more preferably 38° to 52° or 128° to 142°, even more preferably 43° to 47° or 133° to 137°, and particularly preferably around 45° or 135°.

[0144] Furthermore, when using two retardation films (specifically, a λ / 2 plate and a λ / 4 plate) to fabricate a circular polarizer, the slow axis direction of the retardation film (λ / 2 plate) relative to its length direction is preferably 60° to 90°, more preferably 65° to 85°, and particularly preferably around 75°. Conversely, the slow axis direction of the retardation film (λ / 4 plate) relative to its length direction is preferably 0° to 30°, more preferably 5° to 25°, and particularly preferably around 15°.

[0145] The retardation film preferably exhibits a wavelength dependence of so-called reverse dispersion. Specifically, its in-plane phase difference satisfies the relationship Re(450) < Re(550) < Re(650). Re(450) / Re(550) is preferably 0.8 or more and less than 1.0, more preferably 0.8 to 0.95. Re(550) / Re(650) is preferably 0.8 or more and less than 1.0, more preferably 0.8 to 0.97.

[0146] The absolute value of the photoelastic coefficient of the phase retardation film is preferably 2 × 10⁻⁶. -12 (m 2 / N)~100×10 -12 (m 2 / N), more preferably 5×10 -12 (m 2 / N)~50×10 -12 (m 2 / N).

[0147] C. Optical laminate and method for manufacturing the optical laminate

[0148] The stretched film obtained by the manufacturing method of the present invention can be laminated with other optical films and used as an optical laminate. For example, the retardation film obtained by the manufacturing method of the present invention can be laminated with a polarizer and suitably used as a circular polarizer.

[0149] Figure 10 This is a cross-sectional schematic diagram of an example of such a circular polarizer. The circular polarizer 200 in the example includes: 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 retardation film 240 disposed outside the second protective film 230. The retardation film 240 is a stretched film (e.g., a λ / 4 plate) obtained by the manufacturing method described in section A. The second protective film 230 can be omitted. In this case, the retardation film 240 can function as a protective film for the polarizer. The angle between the absorption axis of the polarizer 210 and the slow axis of the retardation film 240 is preferably 30° to 60°, more preferably 38° to 52°, further preferably 43° to 47°, and particularly preferably around 45°.

[0150] The retardation film obtained by the manufacturing method of the present invention is elongated and has a slow axis in the tilt direction (for example, 45° relative to the length direction). Furthermore, in most cases, the elongated polarizer has an absorption axis in either the length or width direction. Therefore, if the retardation film obtained by the manufacturing method of the present invention is used, circular polarizers can be manufactured with extremely high manufacturing efficiency using so-called roll-to-roll methods. Furthermore, roll-to-roll refers to a method of continuously laminating elongated films by continuously roller-feeding them while aligning their length directions.

[0151] In one embodiment, the method for manufacturing the optical laminate of the present invention includes: obtaining a strip-shaped stretch film by the stretch film manufacturing method described in paragraph A; and continuously bonding the strip-shaped optical film and the strip-shaped stretch film together while aligning their length directions.

[0152] Example

[0153] The present invention will be specifically described below through examples, but the present invention is not limited to these examples. Furthermore, the measurement and evaluation methods in the examples are described below.

[0154] (1) Thickness

[0155] The measurements were performed using a dial indicator (manufactured by PEACOCK, product name "DG-205type pds-2").

[0156] (2) Phase difference

[0157] The in-plane phase difference Re(550) was measured using an Axoscan manufactured by Axometrics.

[0158] (3) Orientation angle (the direction of the slow axis)

[0159] A sample was prepared by cutting a square with a width of 50 mm and a length of 50 mm from the center of the membrane, with one side parallel to the width direction of the membrane. The sample was measured using an Axoscan instrument manufactured by Axometrics, and the orientation angle θ at a wavelength of 590 nm was measured.

[0160] (4) Glass transition temperature (Tg)

[0161] The measurements were performed according to JIS K 7121.

[0162] (5) Relaxation amount

[0163] like Figure 11 As shown, an ultrasonic displacement sensor 300 is installed below the conveying path of film 1 at the midpoint between conveying rollers 50a and 50b (roller distance: 912mm). The distance from the ultrasonic displacement sensor to the stretched film is measured at the center and end of the width direction when conveying at a conveying tension of 150N / m. The maximum distance (L) is then recorded. MAX ) and minimum distance (L) MIN The difference (L) MAX -L MIN The relaxation amount (mm) is set as follows. Furthermore, after cutting off the tension applied to correct the relaxation using a suction roller or the like, the relaxation amount is measured while the roller is being conveyed at a conveying tension of 150 N / m.

[0164] (6) Tension

[0165] The tension applied to the membrane was measured using a membrane tension detector installed in the membrane delivery line.

[0166] (7) Rockwell hardness

[0167] The measurements were performed using a nanoindentation device (manufactured by Anton-Paar, product name "Nano Indentation-Tester NHT3") and based on ASTM D785.

[0168] <Example 1>

[0169] (Preparation of polyester carbonate resin film)

[0170] Polymerization was carried out in a batch polymerization unit consisting of two vertical reactors equipped with stirring blades 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 calcium acetate monohydrate as a catalyst were added. -2 Parts by weight (6.78 × 10) -5 (mol). The reactor was subjected to depressurization and nitrogen purging, followed by heating with a heating medium. Stirring was initiated when the internal temperature reached 100°C. Forty minutes after the start of heating, the internal temperature was raised to 220°C and maintained at this temperature while depressurization was initiated. After reaching 220°C, the pressure was set to 13.3 kPa over 90 minutes. Phenol vapor, a byproduct of the polymerization reaction, was introduced into a 100°C reflux cooler to return the small amount of monomer components contained in the phenol vapor to the reactor. Uncondensed phenol vapor was recovered by introducing it into a 45°C condenser. Nitrogen was introduced into the first reactor to temporarily restore it to atmospheric pressure, and then the oligomerized reaction liquid in the first reactor was transferred to the second reactor. Next, heating and depressurization were initiated in the second reactor, and the internal temperature was set to 240°C and the pressure to 0.2 kPa over 50 minutes. Polymerization was then carried out until the specified stirring power was achieved. At the point where the specified power was reached, nitrogen was introduced into the reactor to restore the pressure, and the generated polyester carbonate was extruded into water. The filament was then cut to obtain granules. The obtained polyester carbonate resin has a Tg of 140℃.

[0171] The obtained polyester carbonate resin was vacuum dried at 80°C for 5 hours, and then a resin film with a thickness of 135 μm was produced using a film forming apparatus equipped with a single-screw extruder (manufactured by Toshiba Machine Co., Ltd., cylinder set temperature: 250°C), a T-die (width 200 mm, set temperature: 250°C), a cooling roller (set temperature: 120-130°C), and a winding machine. The obtained film had a Rockwell hardness of M78.

[0172] (Fabrication of stretch film)

[0173] Use such as Figures 1-3 The stretching device shown is used to stretch the polyester carbonate resin film obtained as described above at an oblique angle to obtain a phase difference film.

[0174] Specifically, the polyester carbonate resin film is held at the left and right ends by left and right clamps at the inlet of the stretching device, and preheated to 145°C in preheating zone B. In the preheating zone, the clamping distance (P1) between the left and right clamps is 125 mm.

[0175] Next, as the membrane enters the stretching region C, the clamp spacing of the right-side clamps is increased while the clamp spacing of the left-side clamps is decreased, increasing the clamp spacing of the right-side clamps to P2 while decreasing the clamp spacing of the left-side clamps to P3 (first oblique stretching). At this time, the rate of change of the clamp spacing of the right-side clamps (P2 / P1) is 1.42, and the rate of change of the clamp spacing of the left-side clamps (P3 / P1) is 0.78, with a lateral stretching ratio of 1.45 times relative to the original width of the membrane. Then, while maintaining the clamp spacing of the right-side clamps at P2, the clamp spacing of the left-side clamps is increased from P3 to P2 (second oblique stretching). During this period, the rate of change of the clamp spacing of the left-side clamps (P2 / P3) is 1.82, with a lateral stretching ratio of 1.9 times relative to the original width of the membrane. Furthermore, the stretching region C is set to Tg+3.2℃ (143.2℃).

[0176] Next, in release area D, the membrane was heat-fixed by holding it at 125°C for 60 seconds. The heat-fixed membrane was then cooled to 100°C, and the left and right clamps were released, allowing it to be sent out from the stretching device outlet.

[0177] (Relaxation detection)

[0178] As mentioned above, under room temperature conditions, with... Figure 6 (a) and Figure 6 (b) shows a conveyor line using seven conveyor rollers to transport a film (2300 mm wide) exiting the stretching device. Slack was detected between the conveyor rollers. During roller conveying, by adjusting the torque of the downstream roller in the conveying direction, a tension of 300 N / m was applied to the film from the clamp release point to the downstream roller in the conveying direction for 180 seconds. Furthermore, all rollers on the conveyor line were flat rollers. The test results showed that slack occurred at the left end of the film exiting the stretching device in the width direction, with a slack of 23 mm.

[0179] (Roller conveyor)

[0180] In the aforementioned roller conveying process, the roller through which the film initially passes from the stretching device outlet is replaced with a planar expanding roller, and roller conveying continues. At this time, the ring component is configured such that the tilt angle θ relative to the film conveying direction is 2.5°.

[0181] The phase difference Re(590) of the obtained stretched film is 147 nm, and the angle between the slow axis direction and the length direction is 45°.

[0182] <Example 2>

[0183] By setting the angle θ to 2.0°, and otherwise operating in the same manner as in Example 1, a stretched film was obtained.

[0184] The phase difference Re(590) of the obtained stretched film is 147 nm, and the angle between the slow axis direction and the length direction is 45°.

[0185] <Example 3>

[0186] By setting the angle θ to 3.0°, and otherwise operating in the same manner as in Example 1, a stretched film was obtained.

[0187] The phase difference Re(590) of the obtained stretched film is 147 nm, and the angle between the slow axis direction and the length direction is 45°.

[0188] <Example 4>

[0189] By setting the angle θ to 3.5°, and otherwise operating in the same manner as in Example 1, a stretched film was obtained.

[0190] The phase difference Re(590) of the obtained stretched film is 147 nm, and the angle between the slow axis direction and the length direction is 45°.

[0191] <Example 5>

[0192] Polypropylene (PP) resin (manufactured by Nippon Polypropylene Co., Ltd.: EG7F) was vacuum dried at 80°C for 5 hours. Then, a resin film with a thickness of 135 μm was produced using a film-forming apparatus equipped with a single-screw extruder (manufactured by Toshiba Machine Co., Ltd., cylinder set temperature: 220°C), a T-die (width 200 mm, set temperature: 250°C), a cooling roller (set temperature: 120–130°C), and a winding machine. The obtained film had a Rockwell hardness of R90.

[0193] Using the membrane prepared as described above as the membrane to be stretched, the same procedure as in Example 1 was followed to obtain a stretched membrane.

[0194] The phase difference Re(590) of the obtained stretched film is 147 nm, and the angle between the slow axis direction and the length direction is 45°.

[0195] <Example 6>

[0196] By setting the angle θ to 1.5°, and otherwise operating in the same manner as in Example 1, a stretched film was obtained.

[0197] The phase difference Re(590) of the obtained stretched film is 147 nm, and the angle between the slow axis direction and the length direction is 45°.

[0198] <Example 7>

[0199] By setting the angle θ to 1.0°, and otherwise operating in the same manner as in Example 1, a stretched film was obtained.

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

[0201] <Example 8>

[0202] Angle θ was set to 1.5°; and the resin film prepared in Example 5 was used as the film to be stretched. Otherwise, the same procedure as in Example 1 was followed to obtain a stretched film.

[0203] The phase difference Re(590) of the obtained stretched film is 147 nm, and the angle between the slow axis direction and the length direction is 45°.

[0204] <Example 9>

[0205] The flat roller through which the film initially passes from the outlet of the stretching device is replaced with a curved roller with a bending amount of 10 mm, arranged such that the center line C2 of the film is 50 mm to the left of the center line C1 of the curved roller. The third flat roller from the outlet of the stretching device is replaced with a concave roller; and the sixth flat roller is replaced with a flat expanding roller. Otherwise, the same procedure as in Example 1 is followed to obtain a stretched film. Furthermore, the inclination angle θ of the ring member of the flat expanding roller is 3.5°. The difference X between the radius of the end and the radius of the center of the concave roller is 0.9 mm, the total width W1 is 2100 mm, the width W2 of the center is 1800 mm, the width W4 of each end is 100 mm, and the diameter expansion W3 of each section is 50 mm.

[0206] The phase difference Re(590) of the obtained stretched film is 147 nm, and the angle between the slow axis direction and the length direction is 45°.

[0207] <Comparative Example 1>

[0208] By setting the angle θ to 0°, and otherwise operating in the same manner as in Example 1, a stretched film was obtained.

[0209] The phase difference Re(590) of the obtained stretched film is 147 nm, and the angle between the slow axis direction and the length direction is 45°.

[0210] [Appearance and operability evaluation]

[0211] The stretched film obtained in the above embodiments and comparative examples was laminated with a strip-shaped mask (manufactured by Toray Film Processing Co., Ltd., product name "TORETEC 7832C-30") in a roll-to-roll manner to obtain a film laminate. Next, the mask was peeled off from the film laminate, an adhesive was applied using a gravure coating machine, and the laminated with a polarizer. UV irradiation was then performed to obtain an optical laminate. The appearance (visual inspection) of the optical laminate and the operability of the stretched film were evaluated based on the following criteria.

[0212] 〇: After the mask was applied (adhesion tension 150 N / m), no wrinkles were observed and the adhesive was able to be applied to the entire surface of the film.

[0213] △: When applying the mask, it is possible to apply it without wrinkles by increasing the bonding tension to 300 N / m. However, when applying the adhesive, it is impossible to apply the adhesive in the loose areas.

[0214] ×: After the mask is applied, wrinkles exist, resulting in a deteriorated appearance.

[0215] [Wrinkle Evaluation]

[0216] The wrinkles of the obtained stretch membrane were evaluated based on the following criteria.

[0217] 〇: Even when illuminated with Polarion light (manufactured by Polarion Corporation, product number "NP-1"), no wrinkles were visually discernible.

[0218] △: The wrinkles were not visually discernible even when illuminated by fluorescent light, but they were visually discernible when illuminated by Polarion light.

[0219] ×: Wrinkles are visually recognizable when illuminated by a fluorescent lamp.

[0220] [Scar Evaluation]

[0221] The scratches on the obtained stretch membrane were evaluated based on the following criteria.

[0222] 0: No damage was detected through visual inspection by the inspector; even if damage was detected, it would be at a level where there would be virtually no practical problems.

[0223] △: The injury was visually identified by the inspector, but it was at a level that was barely acceptable in practical terms.

[0224] ×: Damage that is visually identified by the inspector at a level that is practically unacceptable.

[0225] [Transportability Evaluation]

[0226] Regarding the obtained stretched membrane, it was visually confirmed whether the membrane had undergone strain or bending due to relaxation and / or wrinkles, and evaluated based on the following criteria.

[0227] ○: The membrane did not experience strain or bending.

[0228] ×: The membrane has experienced strain and / or bending.

[0229] [Visual recognition assessment]

[0230] The optical laminates obtained in the above appearance and operability evaluations were bonded to the visible side of a reflector or organic EL panel via an adhesive layer. The obtained optical laminates were visually inspected for any shape inconsistencies or light leakage caused by loosening or wrinkles, and were evaluated based on the following criteria.

[0231] 〇: No unevenness or light leakage was visually detected when installing either the reflector or the panel.

[0232] △: Unevenness and / or light leakage are visually identifiable on the reflector, but not visually identifiable on the panel installation.

[0233] ×: Both the reflector and the panel are visually identifiable as unevenness and / or light leakage.

[0234] Regarding the stretched membranes obtained in the above embodiments, the relaxation amount and the above evaluation results are shown in Table 1.

[0235] Table 1

[0236]

[0237] <Evaluation>

[0238] As shown in Table 1, it can be seen that in the manufacturing of long, obliquely stretched films, relaxation and / or wrinkles are reduced by passing the obliquely stretched film through a planar spreading roller. Specifically, it was confirmed that relaxation is effectively reduced by using a planar spreading roller with a larger tilt angle θ of the ring component, and wrinkles are effectively reduced by using a planar spreading roller with a smaller tilt angle θ.

[0239] Industrial availability

[0240] The method for manufacturing the stretch film of the present invention can be appropriately used for manufacturing phase retardation films, thereby contributing to the manufacture of image display devices such as liquid crystal display devices (LCDs) and organic light-emitting diode (OLEDs).

Claims

1. A method for manufacturing a stretched film, comprising the following steps: a method for manufacturing a phase difference film having a slow axis in an inclined direction and an in-plane phase difference of 100nm to 180nm or 230nm to 310nm with a wavelength of 550nm. The long strip of membrane is held at its left and right ends in the width direction by clamps on the left and right sides respectively. The left and right clamps are moved to stretch the membrane obliquely, and then the membrane is released from the left and right clamps; and The obliquely stretched film is conveyed using a planar expanding roller, which has the following characteristics: A pair of ring components are arranged facing each other at angles of 0.1° to 3.5° relative to the membrane conveying direction, and are capable of rotating circumferentially; and Multiple retractable elastic bands are installed between the ring components at predetermined intervals in the circumferential direction. The planar spreading roller is configured such that the obliquely stretched film overlaps symmetrically with the center of the planar spreading roller in the width direction. The ring component has a bearing and is configured to be subjected to the frictional force between the elastic band and the conveyed membrane, and its inner side is capable of rotating together with the elastic band in the circumferential direction.

2. The method for manufacturing a stretch film according to claim 1, wherein, The Rockwell hardness of the membrane is R100 to M120.

3. The method for manufacturing a stretch film according to claim 1 or 2, wherein, In addition to the planar expansion roller, concave rollers and / or curved rollers are used to roll-feed the film.

4. The method for manufacturing a stretch film according to claim 1 or 2, wherein, The clamp is a variable-spacing clamp with varying clamp spacing in the longitudinal direction. While changing the distance between at least one of the clamps, the left clamp holding the left end of the membrane and the right clamp holding the right end, the membrane is moved to stretch it obliquely.

5. The method for manufacturing a stretch film according to claim 4, wherein, The oblique stretching includes: (i) increasing the clamp spacing of one of the left and right clamps from P1 to P2 while decreasing the clamp spacing of the other clamp from P1 to P3; and (ii) changing the clamp spacing of each clamp in such a way that the reduced clamp spacing and the increased clamp spacing are equal in a predetermined manner.

6. The method for manufacturing a stretch film according to claim 5, wherein, The P2 / P1 ratio is 1.25 to 1.75, and the P3 / P1 ratio is greater than 0.50 and less than 1.

7. The method for manufacturing a stretch film according to claim 1 or 2, wherein, The membrane is stretched 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 conveying direction of the membrane midway.

8. A method for manufacturing an optical laminate, comprising: A long strip-shaped stretched film is obtained by the manufacturing method according to any one of claims 1 to 7; as well as While conveying the long strip-shaped optical film and the long strip-shaped stretch film, they are continuously laminated by aligning their length directions.

9. The method for manufacturing an optical laminate according to claim 8, wherein, The optical film is a polarizer. The stretch membrane is a λ / 4 plate or a λ / 2 plate.

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