Extended film manufacturing method

Abstract

The present invention reduces slack and / or corrugations created in diagonally extending films. A method for manufacturing an extended film according to the present invention includes: gripping left and right ends of a long film in a width direction by left and right jigs, respectively; moving the left and right clamps to obliquely extend the film, and then releasing the film from the left and right clamps; a concave roller is used for carrying the film in a rolling mode; the concave roller has a central portion and end portions located on both end sides thereof, and each end portion has a cylindrical shape having a radius larger than that of the central portion.

Description

[0001] This application is a divisional application of the invention patent application with Chinese national application number 202210313115.0 filed on March 28, 2022, and invention name “Method for manufacturing stretched film”. Technical Field

[0002] The present invention relates to a method for producing a stretched film and a method for producing an optical layered body. Background Art

[0003] In image display devices such as liquid crystal display devices (LCDs) and organic electroluminescent display devices (OLEDs), circular polarizers are used to improve display characteristics or prevent reflection. Circular polarizers typically stack polarizers and phase difference films (typically λ / 4 plates) in a manner such that the absorption axis of the polarizer forms a 45° angle with the slow axis of the phase difference film. Phase difference films have been typically made by uniaxial stretching or biaxial stretching in the longitudinal and / or transverse directions, so their slow axes are mostly presented in the transverse direction (width direction) or longitudinal direction (length direction) of the long strip of film raw material. As a result, when making a circular polarizer, it is necessary to cut the phase difference film at a 45° angle relative to the width direction or the length direction and stick them together one by one.

[0004] In addition, in order to ensure the wide band of the circular polarizer, there is also a case where two phase difference films of a λ / 4 plate and a λ / 2 plate are stacked. In this case, it is necessary to stack the λ / 2 plate at an angle of 75° relative to the absorption axis of the polarizer, and to stack the λ / 4 plate at an angle of 15° relative to the absorption axis of the polarizer. In this case, when making a circular polarizer, it is necessary to cut the phase difference film at an angle of 15° and 75° relative to the width direction or the length direction, and stick them one by one.

[0005] Furthermore, in other embodiments, in order to prevent the light from the laptop from being reflected into the keyboard, etc., a λ / 2 plate is sometimes used on the visible side of the polarizer for the purpose of rotating the direction of the linear polarized light from the polarizer by 90°. In this case, it is necessary to cut the phase difference film at an angle of 45° with respect to the width direction or the length direction and laminate them one by one.

[0006] In order to solve this problem, a technique has been proposed in which the left and right ends of the long strip film in the width direction are held by using left and right clamps of a variable spacing type in which the clamp spacing in the longitudinal direction is changed, and the clamp spacing of at least one of the left and right clamps is changed, and the slow axis of the phase difference film is presented in the oblique direction by stretching in the oblique direction relative to the longitudinal direction (hereinafter also referred to as "oblique stretching") (for example, Patent Document 1). However, the obliquely stretched film obtained by this technique sometimes sags (droops) or wrinkles.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent No. 4845619 Summary of the invention

[0010] Technical problem to be solved by the invention

[0011] The present invention has been made to solve the above-mentioned technical problems, and its main object is to reduce the sag and / or wrinkles generated in the obliquely stretched film.

[0012] Means for solving technical problems

[0013] According to one aspect of the present invention, there is provided a manufacturing method, which is a manufacturing method for a stretched film, comprising: respectively holding the left and right ends of a long strip of film in the width direction using left and right clamps; moving the left and right clamps, obliquely stretching the film, and then releasing it from the left and right clamps; and rolling the film using a concave roller, the concave roller having a central portion and end portions located at both ends thereof, the end portions being cylindrical in shape with a radius greater than the central portion.

[0014] In one embodiment, the concave roller further includes a diameter-enlarged portion whose diameter is enlarged from both ends of the central portion toward the end portions.

[0015] In one embodiment, the difference between the radius of the center portion and the radius of the end portions of the concave roller is 0.2 mm to 2.0 mm.

[0016] In one embodiment, the width of the end portion of the concave roller is 30 mm to 180 mm.

[0017] In one embodiment, the film is rolled and conveyed using an expansion roll and / or a bending roll in addition to the concave roll.

[0018] In one embodiment, the clamp is a variable-pitch clamp in which the clamp pitch in the longitudinal direction changes. The film is stretched obliquely by moving at least one of the left clamp holding the left end of the film and the right clamp holding the right end while changing the clamp pitch.

[0019] In one embodiment, the oblique extension includes: (i) increasing the clamp spacing of one of the left and right clamps from P1 to P2, while reducing the clamp spacing of the other clamp from P1 to P3; and (ii) changing the clamp spacing of each clamp in such a manner that the reduced clamp spacing and the increased clamp spacing become a specified equal spacing.

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

[0021] In one embodiment, the film is stretched obliquely by changing the conveying direction of the film midway while moving a left clamp holding the left end of the film and a right clamp holding the right end of the film at a constant speed.

[0022] According to another aspect of the present invention, there is provided a method for producing an optical laminate, comprising: obtaining a long-shaped stretched film by the above-mentioned production method; and continuously bonding the long-shaped optical film and the long-shaped stretched film while conveying them in the same longitudinal direction.

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

[0024] Effects of the Invention

[0025] In the method for producing a stretched film of the present invention, a long obliquely stretched film is passed through a concave roll having a predetermined shape, thereby obtaining a long obliquely stretched film with reduced sag and / or wrinkles. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic plan view for explaining the overall structure of an example of a stretching device that can be used in the method for producing a stretched film of the present invention.

[0027] Figure 2 For the purpose of explaining Figure 1 A schematic top view of the main parts of the linkage mechanism for changing the distance between the clamps in the extension device.

[0028] Figure 3 For the purpose of explaining Figure 1 A schematic top view of the main parts of the linkage mechanism for changing the distance between the clamps in the extension device.

[0029] Figure 4 This is a schematic plan view for explaining the overall structure of another example of a stretching device that can be used in the method for producing a stretched film of the present invention.

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

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

[0032] Figure 6 (a) and (b) are respectively a schematic top view and a schematic side view for explaining an example of roll conveyance.

[0033] Figure 7 This is a schematic plan view for explaining an example of a concave roller having an expanded diameter portion.

[0034] Figure 8 This is a schematic plan view of an expansion roll preferably used in explaining an embodiment of the present invention.

[0035] Fig. 9 This is a schematic plan view of a bending roll preferably used in explaining an embodiment of the present invention.

[0036] Fig.10 This is a schematic cross-sectional view of a circularly polarizing plate using a retardation film obtained by the production method of the present invention.

[0037] Fig.11 This is a schematic diagram for explaining the method of measuring the relaxation amount.

[0038] Explanation of symbols

[0039] 1. Stretch film

[0040] 10L Endless Ring

[0041] 10R Endless Ring

[0042] 20 Clamp

[0043] 50 Transport roller

[0044] 51 Concave roller

[0045] 60 Coiling Department

[0046] 100 Extension device

[0047] 200 Circular Polarizer

[0048] 300 Ultrasonic displacement sensor DETAILED DESCRIPTION

[0049] The preferred embodiments of the present invention are described below, but the present invention is not limited to these embodiments. In addition, in this specification, "the clamp spacing in the longitudinal direction" refers to the distance between the centers of adjacent clamps in the longitudinal direction in the travel direction. In addition, the left-right relationship in the width direction of the long film refers to the left-right relationship facing the conveying direction of the film unless otherwise specified.

[0050] A. Method for producing stretched film

[0051] The method for manufacturing a stretched film according to an embodiment of the present invention comprises: holding the left and right ends of a long film in the width direction with left and right clamps respectively; moving the left and right clamps to obliquely stretch the film, and then releasing it from the left and right clamps; and rolling the film with a concave roller. The concave roller used in this embodiment has a central portion and ends located at both ends thereof, and the ends are cylindrical in shape with a radius greater than that of the central portion. In one embodiment, the concave roller has an expanded diameter portion and ends that exist in sequence from the central portion and its two ends toward the outside, and the ends are cylindrical in shape. Representatively, the method for manufacturing a stretched film according to an embodiment of the present invention further comprises a preheating step. Specifically, the film held by the left and right clamps is preheated and then provided for oblique stretching.

[0052] As a method of obliquely stretching the film by moving the left and right clamps, any appropriate method that can stretch the left and right ends of the film at different stretching ratios (as a result, the film can be extended in an oblique direction relative to the length direction) can be used. For example, there can be cited a method of moving the clamp holding the left end of the film and the clamp holding the right end at different speeds to perform oblique stretching; and a method of moving the clamp holding the left end of the film and the clamp holding the right end to different distances to perform oblique stretching. In one embodiment of the former oblique stretching, the film can be extended in an oblique direction by using a variable spacing type clamp that changes the clamp spacing in the longitudinal direction, changing the clamp spacing of at least one of the left clamp holding the left end of the film and the right clamp holding the right end, while moving the clamps. In one embodiment of the latter oblique stretching, the film can be stretched in an oblique direction by moving the left clamp holding the left end of the film and the right clamp holding the right end at a constant speed while changing the conveying direction of the film midway (as a result, making the conveying path lengths of the left and right ends different). In addition, the obliquely stretched film obtained by the above oblique stretching has a tendency to be loose or wrinkled on the side with a small stretching ratio. Therefore, in one embodiment, in the obliquely stretched film, the side with a small stretching ratio during oblique stretching can be a relaxed side. In addition, the above obliquely stretched film is preferably a λ / 4 plate or a λ / 2 plate.

[0053] Figure 1This is a schematic top view of the overall structure of an example of a stretching device that can be used in the above-mentioned former oblique stretching. In a top view, the stretching device 100a has an endless ring 10L and an endless ring 10R with multiple clamps 20 for holding the film on the left and right sides, which are symmetrical on the left and right. In addition, in this specification, when observing from the inlet side of the film, the endless ring on the left is called the endless ring 10L on the left, and the endless ring on the right is called the endless ring 10R on the right. The clamps 20 of the endless rings 10L and 10R on the left and right are respectively led to the standard track 70 and move in a circular manner. The clamps 20 of the endless ring 10L on the left are moved in a counterclockwise direction, and the clamps 20 of the endless ring 10R on the right are moved in a clockwise direction. In the stretching device, a holding area A, a preheating area B, a stretching area C and a release area D are sequentially arranged from the inlet side of the sheet to the outlet side. These areas refer to the areas where the film to be stretched is actually held, preheated, stretched obliquely, and released, and do not refer to mechanically or structurally independent partitions. Figure 1 The ratio of the lengths of the various regions in the extension device is different from the ratio of the actual lengths.

[0054] Figure 1 Although not shown in the figure, an area for performing any appropriate treatment may be provided between the stretching area C and the release area D as required. Such treatment may include a lateral shrinkage treatment. In addition, although not shown in the figure, the stretching device typically includes a heating device (e.g., various ovens such as hot air type, near infrared type, and far infrared type) for making each area from the preheating area B to the release area D a heating environment. In one embodiment, preheating, oblique stretching, and release from the fixture may be performed in an oven set to a specified temperature.

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

[0056] The clamp (clamp on the left side) 20 of the endless ring 10L on the left side and the clamp (clamp on the right side) 20 of the endless ring 10R on the right side can be moved in a circular motion independently. For example, the driving sprockets 11 and 12 of the endless ring 10L on the left side are driven to rotate in the counterclockwise direction by the motors 13 and 14, and the driving sprockets 11 and 12 of the endless ring 10R on the right side are driven to rotate in the clockwise direction by the motors 13 and 14. As a result, the clamp holding member (not shown) of the driving roller (not shown) meshing with these driving sprockets 11 and 12 is given a walking force. As a result, the endless ring 10L on the left side is moved in a circular motion in the counterclockwise direction, and the endless ring 10R on the right side is moved in a circular motion in the clockwise direction. By driving the left motor and the right motor independently, the endless ring 10L on the left side and the endless ring 10R on the right side can be moved in a circular motion independently.

[0057] Furthermore, the clamp 20 of the left endless ring 10L (the clamp on the left) and the clamp 20 of the right endless ring 10R (the clamp on the right) are of variable spacing type. That is, the left and right clamps 20, 20 are independent of each other, and the clamp spacing in the longitudinal direction can be changed as they move. The variable spacing type structure can be realized by adopting a driving method such as a pantograph method, a linear motor method, and a motor chain method. For example, Patent Document 1, Japanese Patent Publication No. 2008-44339, etc. describe in detail a cloth-stretching machine-type simultaneous dual-axis stretching device using a pantograph-type connecting rod mechanism. Below, the connecting rod mechanism (pantograph mechanism) is described as an example.

[0058] Figure 2 and Figure 3 For illustration Figure 1 A schematic top view of the main part of the link mechanism for changing the distance between the clamps in the extension device. Figure 2 Indicates that the distance between the fixtures is the smallest. Figure 3 Indicates the state where the distance between the fixtures is at the maximum.

[0059] like Figure 2 and Figure 3 As shown in the figure, a slender rectangular clamp holding member 30 is provided in the horizontal direction of each holding clamp 20 when viewed from above. Although not shown in the figure, the clamp holding member 30 is closed by an upper beam, a lower beam, a front wall (the wall on the clamp side) and a rear wall (the wall on the opposite side of the clamp), forming a frame structure with a strong cross section. The clamp holding member 30 is arranged in such a way that it rotates on the running surfaces 81 and 82 using the running wheels 38 at both ends. In addition, Figure 2 and Figure 3In the figure, the running wheels on the front wall side (the running wheels on the rotating running surface 81) are not shown. The running surfaces 81 and 82 are parallel to the standard track 70 in the entire area. On the rear side of the upper beam and the lower beam of the clamp holding member 30 (the opposite side of the clamp side (hereinafter referred to as the anti-clamp side)), a long hole 31 is formed along the length direction of the clamp holding member, and the slider 32 can be slidably engaged in the length direction of the long hole 31. Near the end of the clamp 20 side of the clamp holding member 30, a first shaft member 33 is vertically provided through the upper beam and the lower beam. On the other hand, a second shaft member 34 is vertically provided on the slider 32 of the clamp holding member 30. One end of the main connecting rod member 35 is pivotally connected to the first shaft member 33 of each clamp holding member 30. The main connecting rod member 35 is pivotally connected to the second shaft member 34 of the clamp holding member 30 at the other adjacent end. In addition to the main link member 35, one end of a secondary link member 36 is also pivotally connected to the first shaft member 33 of each clamp holding member 30. The other end of the secondary link member 36 is pivotally connected to the middle part of the main link member 35 through a pivot 37. The link mechanism obtained by the main link member 35 and the secondary link member 36 is as follows: Figure 2 As shown in FIG. 1 , the more the slider 32 moves toward the rear side (anti-clamp side) of the clamp holding member 30, the smaller the longitudinal distance between the clamp holding members 30 (resulting in the clamp distance) becomes. Figure 3 As shown in FIG. 1 , the more the slider 32 moves toward the front side (the clamp side) of the clamp holding member 30, the larger the longitudinal distance between the clamp holding members 30 (resulting in the clamp distance). The slider 32 is positioned by the distance setting rail 90. Figure 2 and Figure 3 As shown, the smaller the spacing distance between the standard rail 70 and the spacing setting rail 90 is, the larger the clamp spacing becomes.

[0060] Figure 4 This is a schematic top view of the overall structure of an example of a stretching device that can be used in the latter oblique stretching described above. In a top view, the stretching device 100b has an annular endless ring 10L and an endless ring 10R with a plurality of clamps 20 for holding the film on the left and right sides. The clamps 20 of the left and right endless rings 10L and 10R are respectively guided to the standard track 40 and move in a circular manner (in the example shown in the figure, a part of the endless rings 10L and 10R are omitted). The clamp 20 of the left endless ring 10L moves in a counterclockwise direction, and the clamp 20 of the right endless ring 10R moves in a clockwise direction. In the stretching device, a holding area A, a preheating area B, a stretching area C and a release area D are sequentially arranged from the entrance side of the sheet to the exit side. These respective areas refer to areas where the film to be stretched is actually held, preheated, obliquely stretched and released, and do not refer to mechanically and structurally independent partitions. It should also be noted that Figure 4The ratio of the lengths of the various regions in the extension device is different from the ratio of the actual lengths.

[0061] Figure 4 Although not shown in the figure, an area for performing any appropriate treatment may be provided between the stretching area C and the release area D as required. Such treatments include lateral stretching treatment and lateral shrinkage treatment. In addition, although not shown in the figure, the stretching device typically includes a heating device (e.g., various ovens such as hot air type, near infrared type, and far infrared type) for making each area from the preheating area B to the release area D a heating environment. In one embodiment, preheating, oblique stretching, and release from the fixture may be performed in an oven set to a specified temperature.

[0062] In the holding area A and the preheating area B of the stretching device 100b, the left and right endless loops 10L and 10R are constructed in a manner that they are approximately parallel to each other at a distance corresponding to the initial width of the film to be stretched. In the stretching area C, the left endless loop 10L and the right endless loop 10R are stretched in a left-right asymmetric direction, thereby, as the conveying direction of the film changes, the distance between the left and right endless loops 10L and 10R gradually expands to a width corresponding to the stretched width of the film from one side of the preheating area B toward the release area D. In the release area D, the left and right endless loops 10L and 10R are constructed in a manner that they are approximately parallel to each other at a distance corresponding to the width of the film after stretching. However, the structure of the left and right endless loops 10L and 10R is not limited to the above-mentioned example.

[0063] The clamp 20 of the left endless loop 10L (the clamp on the left) and the clamp 20 of the right endless loop 10R (the clamp on the right) can move independently. Figure 1 Similarly, in the stretching device shown, the driving sprocket 11 of the left endless ring 10L is driven by the motor 13 in the counterclockwise direction, and the driving sprocket 11 of the right endless ring 10R is driven by the motor 13 in the clockwise direction. Representatively, the left clamp 20 and the right clamp 20 travel at a constant speed, and the clamp spacing in the longitudinal direction can be kept constant. In addition, when the difference in travel speed between a pair of left and right clamps is 1% or less, it can be said that the travel speeds of the two are constant, and the difference in travel speed is preferably 0.5% or less, and more preferably 0.1% or less.

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

[0065] A-1. Holding the membrane with a clamp

[0066] In the holding area A (film receiving entrance of the stretching device 100a or 100b), the two ends of the film to be stretched are held by the clamps 20 of the left and right endless loops 10L and 10R at a constant clamp pitch equal to each other or at different clamp pitches. The film is sent to the preheating area B by the movement of the clamps 20 of the left and right endless loops 10L and 10R (substantially, the movement of each clamp holding member guided to the standard track).

[0067] A-2. Preheating

[0068] In the preheating area B, the left and right endless rings 10L and 10R are configured as described above to be approximately parallel to each other at a distance corresponding to the initial width of the film to be stretched, so that the film is heated without being stretched horizontally or vertically. However, since the preheating may cause the film to bend, in order to avoid contact with the nozzle in the oven, etc., the distance between the left and right clamps (the distance in the width direction) may be slightly widened.

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

[0070] The heating time to reach the temperature T1 and the holding time at the temperature T1 can be appropriately set according to the constituent material of the film or the manufacturing conditions (e.g., the conveying speed of the film). The heating time and the holding time can be controlled by adjusting the moving speed of the clamp 20, the length of the preheating zone, the temperature of the preheating zone, etc.

[0071] A-3. Oblique extension

[0072] A-3-1. Oblique extension using variable pitch clamps

[0073] In the stretching area C of the stretching device 100a, the film is stretched obliquely while the longitudinal clamp spacing of at least one of them is changed and the left and right clamps 20 are moved. More specifically, the film is stretched obliquely by increasing or decreasing the clamp spacing of the left and right clamps at different positions, changing (increasing and / or decreasing) the clamp spacing of the left and right clamps at different changing speeds, etc.

[0074] The oblique extension may also include lateral extension. Figure 1As shown in the structure, it can be carried out while increasing the distance between the left and right clamps (the distance in the width direction). Figure 1 Unlike the structure shown, this can be done while maintaining the distance between the left and right clamps.

[0075] When the oblique stretching includes the transverse stretching, the stretching ratio in the transverse direction (TD) (the width W of the film after the oblique stretching) final The initial width W of the film initial The ratio (W final / W initial )) is preferably 1.05 to 6.00, more preferably 1.10 to 5.00.

[0076] In one embodiment, the oblique extension can be performed by increasing or decreasing the clamp spacing of each clamp to a predetermined spacing while making the position where the clamp spacing of one of the left and right clamps starts to increase or decrease different from the position where the clamp spacing of the other clamp starts to increase or decrease in the longitudinal direction. For the oblique extension of this embodiment, for example, the description of Patent Document 1, Japanese Patent Application Publication No. 2014-238524, etc. can be referred to.

[0077] In other embodiments, the oblique extension can be performed by increasing or decreasing the clamp spacing of the other clamp to a predetermined spacing while fixing the clamp spacing of one of the left and right clamps, and then returning to the initial clamp spacing. For the oblique extension of this embodiment, for example, reference can be made to the records of Japanese Patent Publication No. 2013-54338, Japanese Patent Publication No. 2014-194482, etc.

[0078] In other embodiments, the oblique extension can be performed by: (i) increasing the clamp spacing of one of the left and right clamps from P1 to P2, while reducing 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. For the oblique extension of this embodiment, for example, reference can be made to the records of Japanese Patent Publication No. 2014-194484. The oblique extension of this embodiment may also include: extending the distance between the left and right clamps while increasing the clamp spacing of one clamp from P1 to P2 and reducing the clamp spacing of the other clamp from P1 to P3, thereby extending the film obliquely (first oblique extension); and extending the distance between the left and right clamps while maintaining the clamp spacing of one clamp at P2 or reducing it to P4 in a manner that the clamp spacings of the left and right clamps become equal, and increasing the clamp spacing of the other clamp to P2 or P4, thereby extending the film obliquely (second oblique extension).

[0079] In the first oblique stretching, by stretching one end of the film in the longitudinal direction and shrinking the other end in the longitudinal direction while performing oblique stretching, a slow axis can be presented in a desired direction (for example, a direction at 45° relative to the longitudinal direction) with high uniaxiality and in-plane orientation. In addition, in the second oblique stretching, by narrowing the difference in the gap between the left and right clamps while performing oblique stretching, it is possible to fully stretch in the oblique direction while relieving excess stress.

[0080] In the oblique stretching of the above three embodiments, since the film can be released from the clamps while the moving speeds of the left and right clamps become equal, it is difficult for unevenness in the film conveying speed to occur when the left and right clamps are released, and the subsequent film winding can also be carried out appropriately.

[0081] Figure 5A and Figure 5B 1 and 2 are schematic diagrams showing an example of the outline of the clamp spacing in the oblique extension including the first oblique extension and the second oblique extension. The first oblique extension will be described in detail below with reference to these diagrams. Figure 5A and Figure 5B In the figure, the horizontal axis corresponds to the travel distance of the clamp. At the beginning of the first oblique extension, the distance between the left and right clamps is P1. P1 is representatively the distance between the clamps when holding the film. At the beginning of the first oblique extension, the clamp distance of one clamp (hereinafter sometimes referred to as the first clamp) begins to increase and the clamp distance of another clamp (hereinafter sometimes referred to as the second clamp) begins to decrease. In the first oblique extension, the clamp distance of the first clamp is increased to P2, and the clamp distance of the second clamp is reduced to P3. Therefore, at the end of the first oblique extension (when the second oblique extension begins), the second clamp moves with a clamp distance P3, and the first clamp moves with a clamp distance P2. In addition, the ratio of the clamp distances can roughly correspond to the ratio of the moving speeds of the clamps.

[0082] Figure 5A and Figure 5BIn the embodiment, the timing of starting to increase the clamp spacing of the first clamp and the timing of starting to reduce the clamp spacing of the second clamp are both at the beginning of the first oblique extension. Unlike the illustrated example, the clamp spacing of the second clamp can be reduced after the clamp spacing of the first clamp is increased, and the clamp spacing of the first clamp can be increased after the clamp spacing of the second clamp is reduced. In a preferred embodiment, the clamp spacing of the second clamp can be reduced after the clamp spacing of the first clamp is increased. According to this embodiment, since the film has been extended to a certain extent (preferably about 1.2 times to 2.0 times) in the width direction, wrinkles are difficult to occur even if the clamp spacing of the second clamp is greatly reduced. Therefore, a more acute oblique extension can be performed, and a phase difference film with high uniaxiality and in-plane orientation can be preferably obtained.

[0083] Likewise, in Figure 5A and Figure 5B In the figure, the increase in the clamp spacing of the first clamp and the decrease in the clamp spacing of the second clamp continue until the end of the first oblique extension (the beginning of the second oblique extension), but unlike the illustrated example, either the increase or the decrease in the clamp spacing may end earlier than the other, and the clamp spacing may remain the same until the other ends (until the end of the first oblique extension).

[0084] 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 further preferably 1.35 to 1.65. In addition, the rate of change of the clamp spacing of the second clamp (P3 / P1) is, for example, greater than 0.50 and less than 1, preferably 0.50 to 0.95, more preferably 0.55 to 0.90, and further preferably 0.55 to 0.85. When the rate of change of the clamp spacing is within this range, a slow axis can be presented with high uniaxiality and in-plane orientation in a direction of approximately 45 degrees relative to the length direction of the film.

[0085] As described above, the distance between the fixtures can be adjusted by adjusting the spacing between the extension device, setting the distance between the track and the standard track, and positioning the slider.

[0086] The stretch ratio in the width direction of the film in 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 times to 3.0 times, more preferably 1.2 times to 2.5 times, and further preferably 1.25 times to 2.0 times. When the stretch ratio is less than 1.1 times, tinplate-like wrinkles sometimes occur at the end of the contracted side. In addition, when the stretch ratio exceeds 3.0 times, the biaxiality of the obtained phase difference film becomes high, and when it is applied to a circular polarizer, the viewing angle characteristics are sometimes reduced.

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

[0088] Next, while referring to Figure 5A One embodiment of the second diagonal extension will be specifically described. In the second diagonal extension of this embodiment, the clamp pitch of the second clamp is increased from P3 to P2. On the other hand, the clamp pitch of the first clamp is maintained at P2 during the second diagonal extension. Therefore, at the end of the second diagonal extension, both the left and right clamps move with a clamp pitch of P2.

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

[0090] While referring to Figure 5B Another embodiment of the second diagonal extension will be specifically described. In the second diagonal extension of this embodiment, while reducing the clamp pitch of the first clamp, the clamp pitch of the second clamp is increased. Specifically, the clamp pitch of the first clamp is reduced from P2 to P4, and the clamp pitch of the second clamp is increased from P3 to P4. Therefore, at the end of the second diagonal extension, both the left and right clamps move with a clamp pitch of P4. In addition, in the illustrated example, the reduction of the clamp pitch of the first clamp and the increase of the clamp pitch of the second clamp start simultaneously at the start of the second diagonal extension, but these can start at different timings. Similarly, the reduction of the clamp pitch of the first clamp and the increase of the clamp pitch of the second clamp can also end at different timings.

[0091] Figure 5B The rate of change (P4 / P2) of the clamp pitch of the first clamp and the rate of change (P4 / P3) of the clamp pitch of the second clamp in the second diagonal extension of the illustrated embodiment are not limited as long as the effects of the present invention are not impaired. The rate of change (P4 / P2) is, for example, 0.4 or more and less than 1.0, preferably 0.6 to 0.95. In addition, the rate of change (P4 / P3) is, for example, more than 1.0 and 2.0 or less, preferably 1.2 to 1.8. It is preferred that P4 is equal to or greater than P1. When P4 < P1, problems such as wrinkles occurring at the ends and an increase in biaxiality may sometimes occur.

[0092] The stretch ratio in the width direction of the film in 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 times to 3.0 times, more preferably 1.2 times to 2.5 times, and more preferably 1.25 times to 2.0 times. When the stretch ratio is less than 1.1 times, the end of the contracted side sometimes produces tinplate-like wrinkles. In addition, when the stretch ratio exceeds 3.0 times, the biaxiality of the obtained phase difference film will become higher, and when it is suitable for circular polarizers, there is a situation where the viewing angle characteristics are reduced. In addition, the stretch ratio in the width direction in the first oblique stretching and the second oblique stretching (film width at the end of the second oblique stretching / film width before the first oblique stretching) is preferably 1.2 times to 4.0 times, more preferably 1.4 times to 3.0 times from the same viewpoint as above.

[0093] The oblique stretching can be typically carried out at a temperature T2. The temperature T2 is preferably Tg-20°C to Tg+30°C, more preferably Tg-10°C to Tg+20°C, and particularly preferably around Tg, relative to the glass transition temperature (Tg) of the film. 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 (T1-T2) between the above-mentioned temperature T1 and the temperature T2 is preferably ±2°C or more, more preferably ±5°C or more. In one embodiment, T1>T2, so the film heated to the temperature T1 in the preheating zone can be cooled to the temperature T2.

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

[0095] A-3-2. Oblique extension using a fixture with a fixed pitch

[0096] In the stretching area C of the stretching device 100b, the left endless loop 10L and the right endless loop 10R are stretched in an asymmetric direction, resulting in a change in the conveying direction of the film (specifically, the conveying direction of the film in the preheating area B (the stretching direction of the arrow B) and the conveying direction of the film in the release area D (the stretching direction of the arrow D) become non-parallel). Due to this structure, the lengths of the left and right endless loops 10L and R in the oblique stretching area C (in other words, the travel distances of the left and right clamps in the oblique stretching area C) are different. As a result, the pair of left and right clamps that travel at the same speed becomes the clamp with the shorter travel distance that travels first ( Figure 4 In the embodiment, the left clamp moves first), and the film is stretched in an oblique direction. For the oblique stretching of this embodiment, for example, reference can be made to the records of Japanese Patent Publication No. 2004-226686, WO2007 / 111313, etc.

[0097] The diagonal extension can be carried out at temperature T2. The temperature T2 is preferably Tg - 20°C to Tg + 30°C, more preferably Tg - 10°C to Tg + 20°C, and particularly preferably around Tg, relative to the glass transition temperature (Tg) of the film. 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 temperature T1 and temperature T2 (T1 - T2) is preferably ±2°C or more, more preferably ±5°C or more. In one embodiment, T1 > T2, so the film heated to temperature T1 in the preheating region can be cooled to temperature T2.

[0098] As described above, a lateral shrinkage treatment can be performed after the diagonal extension. For this treatment after the diagonal extension, reference can be made to paragraphs 0029 to 0032 of Japanese Patent Laid-Open No. 2014-194483.

[0099] A-4. Release of the clamp

[0100] At any position in the release region D, the above-mentioned film is released from the clamp. In the release region D, generally neither lateral extension nor longitudinal extension is performed. The film is heat-treated as needed to fix the extended state (thermal fixation), and / or cooled below Tg, and then the film is released from the clamp. In addition, when performing thermal fixation, the clamp pitch in the longitudinal direction can also be reduced to relieve stress.

[0101] The heat treatment can be carried out at temperature T3. The temperature T3 varies depending on the extended film. There may be a case where T2 ≥ T3, or a case where T2 < T3. Generally speaking, when the film is an amorphous material, there is a case of performing a crystallization treatment at T2 ≥ T3; when it is a crystalline material, there is a case of performing a crystallization treatment at T2 < T3. When T2 ≥ T3, the difference between temperature T2 and T3 (T2 - T3) is preferably 0°C to 50°C. The heat treatment time is typically 10 seconds to 10 minutes.

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

[0103] A-5. Roll handling

[0104] The film released from the above-mentioned clamp is rolled and conveyed using a concave roller. The concave roller has a structure in which the diameter of the end portion is larger than that of the central portion, and the circumferential speed difference generated between the central portion and the end portion can play a role in expanding the film. The concave roller used in the embodiment of the present invention is a cylindrical shape having a central portion and end portions located at both ends thereof, and the end portions have a radius larger than that of the central portion. In one embodiment, a concave roller can be preferably used, which has a central portion and an expanded diameter portion and an end portion that exist in sequence from both ends toward the outside, and the end portion is cylindrical. In addition, in this specification, a cylindrical conveying roller used in conventional roll conveying is sometimes referred to as a flat roller.

[0105] Figure 6 (a) and Figure 6 (b) are a schematic top view and a schematic side view respectively illustrating an example of roll conveyance using the above-mentioned concave rolls, Figure 7 In the roller conveyance of the illustrated example, the film 1 fed from the stretching device 100 is conveyed by seven rollers (a concave roller 51 and first to sixth flat rollers 52 to 57 ) and then wound up in the winding section 60 .

[0106] Figure 7 The concave roller 51 shown has a central portion 51a and an expanded diameter portion 51b and an end portion 51c which exist in sequence from both ends thereof toward the outside. The central portion 51a and the end portion 51c are cylindrical in shape, and the concave roller 51 has a point symmetrical shape with the center of the rotation axis A as the symmetry center. It is predicted that when the concave roller 51 is arranged in a manner that the center in the width direction overlaps with the film 1, due to its shape, it will exert its expandability symmetrically with respect to the center in the width direction of the film. However, when it is applied to an obliquely stretched film having slack and / or wrinkles caused by the slack on one side, it can obtain an excellent effect of reducing slack and / or wrinkles while substantially maintaining the intended axis angle and in-plane phase difference. Although the reason for obtaining such an effect is uncertain, it is speculated that when there is slack and / or wrinkles, they will be improved by a slight stretching effect, and since uniform tension is applied in the width direction of the film at this time, the uniformity of the surface can be maintained.

[0107] The difference X between the radius of the central portion 51a and the radius of the end portion 51c can be, for example, 0.2 mm to 2.0 mm. In addition, the width W4 of the end portion 51c can be, for example, 20 mm to 200 mm, preferably 30 mm to 180 mm. When the difference X and / or the width W4 are within this range, a relaxation and / or wrinkle reduction effect can be preferably obtained. In addition, in the example shown in the figure, the central portion 51a has a width W2 and is cylindrical, but the width W2 of the central portion 51a 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 (center line C1) to both ends.

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

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

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

[0111] The diameter expansion ratio (X / W3×100) of the diameter expansion portion 51b is, for example, 0.1% to 6.0%, preferably 0.2% to 5.0%, and more preferably 1.0% to 4.5%. When the diameter expansion ratio is within this range, the effect of reducing slack and / or wrinkles can be obtained while substantially maintaining the target axial angle and in-plane phase difference. In addition, in the example shown in the figure, the diameter expansion portion is linearly expanded, but the diameter expansion portion may also be concave.

[0112] Unlike the example shown in the figure, a concave roller without an expanded diameter portion (i.e., a concave roller whose ends stand vertically from both ends of the central portion) may be used. The same description as that of the concave roller with an expanded diameter portion as described above may be applied to the difference X between the radius of the central portion 51a and the radius of the end portion 51c and the width W4 of the end portion 51c in such a concave roller.

[0113] The total width W1 of the concave roller 51 and the width W2 of the central portion 51a can be appropriately set according to the film width when the roller passes, the width W4 of the end portion, the diameter expansion rate, the difference X, etc. The total width W1 of the concave roller 51 can be designed, for example, so that the left and right ends 51c overlap the film passing over the roller by, for example, 5 mm to 195 mm, for example, 10 mm to 190 mm.

[0114] The material for forming the concave roller is not particularly limited as long as the effects of the present invention are obtained, and examples thereof include rubber and metal.

[0115] The embrace angle when the film passes through the concave roll is, for example, 45° to 135°, and preferably 70° to 100°. When the embrace angle is within such a range, the effects of the present invention can be preferably obtained.

[0116] As shown in the example of the figure, the roller conveying can be performed by a plurality of rollers including a concave roller. In the roller conveying, the total number of rollers (including the concave rollers) through which the film passes 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 film passes through the concave rollers among all the rollers is not particularly limited, and the concave rollers can be arranged at any position.

[0117] In one embodiment, in addition to the concave roller, an expansion roller and / or a bending roller may be used for roller conveying. By using them together, the effect of reducing slack can be more preferably obtained. The configuration positions of the expansion roller and the bending roller are not particularly limited. These rollers can be respectively configured at any position upstream or downstream of the concave roller in the conveying direction.

[0118] Figure 8 This is a schematic plan view for explaining an expansion roller preferably used in the above-mentioned embodiment. Figure 8 The expansion roller 58 shown is a linear roller. The expansion roller 58 has a long handle 58a, a pair of support base plates 58b mounted at both ends of the long handle 58a, a pair of ring members 58c mounted on the inner side of the support base plate 58b and arranged opposite to each other in a manner of expanding at an angle θ relative to the conveying direction of the film, and a plurality of elastic pads (representatively rubber pads) 58d that are installed in the circumferential direction at a predetermined interval between the pair of ring members 58c. The ring member 58c is configured to have a bearing, and the inner side of the ring member 58c can rotate in the circumferential direction together with the elastic pad 58d under the friction force between the elastic pad 58d and the conveyed film. In addition, the ring member 58c is configured in a manner that the angle θ relative to the conveying direction of the film can be arbitrarily changed. In the example shown in the figure, the angle θ is configured to be changed by the insertion amount of the four adjustment bolts 58e, but the angle θ can also be changed by other configurations. The larger the angle θ of the expansion roller is, the greater the expansion property can be exerted.

[0119] The inclination angle θ of the ring member may be, for example, greater than 0° and less than 4.0°, preferably 0.1° to 3.5°. By using the expansion roll at such an inclination angle, a long stretched film with reduced sag can be obtained while substantially maintaining the target axis angle and in-plane phase difference.

[0120] Fig. 9 This is a schematic plan view for explaining a bending roll preferably used in the above-mentioned embodiment. Fig. 9The bending roller 59 shown is bent symmetrically with the center in the width direction (center line C3) in a manner that it is convex toward the conveying direction. When using the bending roller, it is preferred to convey the film 1 by rolling the film 1 with the center in the width direction (center line C2) and the center in the width direction (center line C3) of the bending roller offset so that the end of the unrelaxed side of the film 1 is closer to the center in the width direction of the bending roller than the end of the relaxed side. By conveying in this way, since a greater tension is applied to the unrelaxed side of the film than to the relaxed side, it is helpful to reduce relaxation.

[0121] The bending roller 59 has a structure in which, for example, a plurality of radial ball bearings (not shown) are mounted around a bending long handle 59a, and the surface of the handle is covered with a tube made of elastic material such as rubber that can be elastically deformed, and the tube is configured so as to be rotatable around the bending axis 59b. In addition, there are bending rollers with a fixed bending degree and a variable bending degree, and either type can be used.

[0122] The bending amount D (mm) and the total width W5 (mm) of the bending roller 59 can be set to appropriate values ​​corresponding to the desired relaxation reduction amount, film width, etc. The bending amount D can be, for example, 5mm to 15mm, and preferably 8mm to 13mm. The curvature (D / W5×100) of the bending roller 59 can be, for example, 0.1% to 1.5%, and preferably 0.2% to 0.7%. When the bending amount and / or curvature is within this range, while substantially maintaining the target axis angle and in-plane phase difference, a long strip of stretched film with reduced relaxation can be preferably obtained. In addition, the total width W5 of the bending roller 59 can be, for example, 105% to 170% of the width of the film 1, and preferably 110% to 155%.

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

[0124] The above-mentioned roller conveying is preferably carried out while applying tension to the film after it is released from the clamp. By applying tension to the entire film in addition to the correction of slack using the concave roller, slack and / or wrinkles can be more effectively reduced. The tension applied to the film is, for example, 100 N / m or more, preferably 200 N / m or more, and more preferably 250 N / m to 500 N / m. The application of tension can be carried out, for example, by measuring the tension applied to the film between the conveying rollers, and controlling the rotation speed of the conveying rollers in such a way that the tension reaches the desired value.

[0125] The application of tension may be performed during the period from the release of the clamps to the time when the roller reaches any conveying roller (for example, during the period from the release of the clamps to the time when the roller reaches the roller downstream of the concave roller).

[0126] The time for applying tension can be appropriately set according to the film forming material, relaxation amount, etc. The time can be, for example, 5 seconds to 60 seconds.

[0127] Roll conveying can be performed in a heated environment or in a non-heated environment. It is preferred that roll conveying be performed in a non-heated environment. By passing the concave rollers in a non-heated environment, the generation of scratches can be prevented and the slack and / or wrinkles can be reduced. The atmosphere temperature of the non-heated environment can be, for example, about 15°C to 40°C, for example, about 20°C to 30°C. In addition, the atmosphere temperature of the heated environment can be, for example, the same as the atmosphere temperature in the release area of ​​the above-mentioned stretching device.

[0128] The film 1 conveyed by the rollers is wound up to form a film roll in the winding unit 60. Alternatively, unlike the example shown in the figure, the film may not be wound up, but may be continuously bonded to other long optical films while conveying them in the same longitudinal direction to form an optical laminate.

[0129] In one embodiment, a stretched film released from a clamp and fed out of a stretching device is rolled and conveyed using only flat rollers while its slack is measured. When a slack exceeding a specified amount is detected, the slack of the stretched film obtained later can be reduced by replacing at least one flat roller with a concave roller for roll conveyance.

[0130] A-6. Detection of relaxation

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

[0132] The distance between the conveying rollers during the above detection is not particularly limited, and may be, for example, 500 mm to 2000 mm, and preferably 700 mm to 1500 mm.

[0133] The film tension during the above detection is not particularly limited, and may be, for example, 50 N / m to 400 N / m, preferably 100 N / m to 200 N / m. When the transport tension is too high, the film during transport may undergo elastic deformation, and relaxation may become difficult to detect. On the other hand, when the transport tension is too low, the tension itself may be unstable, and the measured value of relaxation may become unstable.

[0134] The above detection can be performed in a non-heating environment. The ambient temperature when detecting the relaxation amount is, for example, about 15°C to 40°C, and can also be, for example, about 20°C to 30°C.

[0135] In one embodiment, the slack amount is detected after the left and right ends in the width direction of the stretched film released from the clamp are cut off and removed. By detecting the slack amount in a state where both ends are removed, a more accurate detection result can be obtained.

[0136] The width of the end portions to be cut and removed is independent of each other, and may be, for example, 20 mm to 600 mm, and preferably 100 mm to 500 mm. The end portions may be cut and removed by ordinary slit processing.

[0137] The amount of slack reduction obtained by the method for producing a stretched film of the present invention (slack of the film conveyed by rollers without using concave rollers - slack of the film conveyed by rollers using concave rollers: slack 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. In addition, the amount of slack that can remain in the film after roller conveyance using the concave 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.

[0138] B. Extending the membrane of an object

[0139] In the manufacturing method of the present invention, any appropriate film can be used. For example, a resin film that can be used as a phase difference film can be cited. As the material constituting this film, for example, polycarbonate resins, polyvinyl acetal resins, cycloolefin resins, acrylic resins, cellulose ester resins, cellulose resins, polyester resins, polyester carbonate resins, olefin resins, polyurethane resins, etc. can be cited. Preferred are polycarbonate resins, cellulose ester resins, polyester resins, polyester carbonate resins, and cycloolefin resins. The reason is that if these resins are used, a so-called wavelength-dependent phase difference film showing reverse dispersion can be obtained. These resins can be used alone or in combination with the desired properties.

[0140] As the polycarbonate resin, any appropriate polycarbonate resin may be used, and for example, a polycarbonate resin including a structural unit derived from a dihydroxy compound is preferred. 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-(2 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, etc. 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, spiroethylene glycol, dioxane glycol, diethylene glycol (DEG), triethylene glycol (TEG), polyethylene glycol (PEG), cyclohexanedimethanol (CHDM), tricyclodecanedimethanol (TCDDM), and bisphenols.

[0141] The details of the polycarbonate-based resin are described in, for example, Japanese Patent Application Laid-Open No. 2012-67300 and Japanese Patent No. 3325560. The descriptions of these patent documents are incorporated herein by reference.

[0142] The glass transition temperature of the polycarbonate resin is preferably 110°C to 250°C, more preferably 120°C to 230°C. When the glass transition temperature is too low, the heat resistance tends to deteriorate, and dimensional changes may occur after film molding. When the glass transition temperature is too high, the molding stability during film molding may deteriorate, and the transparency of the film may be impaired. In addition, the glass transition temperature is obtained according to JIS K 7121 (1987).

[0143] As the above-mentioned polyvinyl acetal resin, any appropriate polyvinyl acetal resin can be used. Representatively, the polyvinyl acetal resin can be obtained by condensing at least two aldehyde compounds and / or ketone compounds with a polyvinyl alcohol resin. Specific examples of polyvinyl acetal resins and detailed production methods are described in, for example, Japanese Patent Publication No. 2007-161994. This description is cited in this specification as a reference.

[0144] The stretched film (phase difference film) obtained by stretching the film of the above-mentioned stretching object preferably shows a refractive index characteristic of nx>ny. In one embodiment, the phase difference film can preferably function as a λ / 4 plate. In the present embodiment, the in-plane phase difference Re(550) of the phase difference film (λ / 4 plate) is preferably 100nm~180nm, more preferably 135nm~155nm. In other embodiments, the phase difference film can preferably function as a λ / 2 plate. In the present embodiment, the in-plane phase difference Re(550) of the phase difference film (λ / 2 plate) is preferably 230nm~310nm, more preferably 250nm~290nm. In addition, in this specification, nx is the refractive index in the direction where the in-plane refractive index reaches the 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. In addition, Re(λ) is the in-plane phase difference of the film measured at 23°C with light of a wavelength of λnm. Therefore, Re(550) is the in-plane retardation of the film measured with light of a wavelength of 550 nm at 23° C. Re(λ) is a value obtained by the formula: Re(λ)=(nx-ny)×d when the thickness of the film is d (nm).

[0145] The in-plane phase difference Re (550) of the phase difference film can be set to a desired range by appropriately setting the oblique stretching conditions. For example, the method of manufacturing a phase difference film having an in-plane phase difference Re (550) of 100 nm to 180 nm by oblique stretching is disclosed in detail in Japanese Patent Publication No. 2013-54338, Japanese Patent Publication No. 2014-194482, Japanese Patent Publication No. 2014-238524, Japanese Patent Publication No. 2014-194484, etc. Therefore, those skilled in the art can set appropriate oblique stretching conditions according to the disclosure.

[0146] When a circular polarizing plate is prepared using a single retardation film, or when the direction of linear polarized light is rotated 90° using a single retardation film, the slow axis direction of the retardation film used 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°, further preferably 43° to 47° or 133° to 137°, and particularly preferably about 45° or 135°.

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

[0148] The retardation film preferably exhibits a so-called inverse dispersion wavelength dependence. Specifically, the in-plane retardation satisfies the relationship of 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.

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

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

[0151] 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 preferably used as a circular polarizer.

[0152] Fig.10 is a schematic cross-sectional view of an example of such a circular polarizer. The illustrated circular polarizer 200 has a polarizer 210, a first protective film 220 disposed on one side of the polarizer 210, a second protective film 230 disposed on the other side of the polarizer 210, and a 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 item A. The second protective film 230 can also be omitted. In this case, the retardation film 240 can function as a protective film for the polarizer. The angle formed by the absorption axis of the polarizer 210 and the slow axis of the retardation film 240 is preferably 30° to 60°, more preferably 38° to 52°, further preferably 43° to 47°, and particularly preferably about 45°.

[0153] The phase difference film obtained by the manufacturing method of the present invention is long and has a slow axis in an oblique direction (for example, a direction of 45° relative to the length direction). In addition, in most cases, the long polarizer has an absorption axis in the length direction or the width direction. Therefore, if the phase difference film obtained by the manufacturing method of the present invention is used, the circular polarizer can be made with extremely excellent manufacturing efficiency using the so-called roll-to-roll method. In addition, roll-to-roll refers to a method in which long strips of film are rolled and transported to each other while their length directions are uniformly and continuously bonded.

[0154] In one embodiment, the method for producing an optical layered body of the present invention comprises: obtaining a long stretched film by the method for producing a stretched film described in Section A; and continuously laminating the long optical film and the long stretched film together in a uniform longitudinal direction while conveying the long optical film and the long stretched film.

[0155] [Example]

[0156] The present invention will be specifically described below by way of examples, but the present invention is not limited to these examples. In addition, the measurement and evaluation methods of the examples are as follows.

[0157] (1) Thickness

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

[0159] (2) Phase difference

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

[0161] (3) Orientation angle (direction of the slow axis)

[0162] The central portion of the film to be measured was cut into a square shape of 50 mm in width and 50 mm in length so that one side was parallel to the width direction of the film to prepare a sample. The sample was measured using Axoscan manufactured by Axometrics to measure the orientation angle θ at a wavelength of 590 nm.

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

[0164] Measured according to JIS K7121.

[0165] (5) Relaxation

[0166] like Fig.11As shown in the figure, an ultrasonic displacement sensor 300 is arranged below the conveying path of the film 1 at the middle point between the conveying rollers 50a and 50b (distance between rollers: 912 mm), and the distance from the ultrasonic displacement sensor to the stretched film is measured at the center and end portions in the width direction when conveying at a conveying tension of 150 N / m, and the maximum distance (L MAX ) and the minimum distance (L MIN ) difference (L MAX -L MIN ) as the slack amount (mm). In addition, the above-mentioned slack amount was measured by cutting off the tension applied to correct the slack using a suction roll or the like, and then conveying the roll at a conveying tension of 150 N / m.

[0167] (6) Tension

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

[0169] <Example 1>

[0170] (Production of polyester carbonate resin film)

[0171] The polymerization was carried out using a batch polymerization apparatus consisting of two vertical reactors equipped with stirring blades and a reflux cooler controlled at 100° C. 29.60 parts by mass (0.046 mol) of bis[9-(2-phenoxycarbonylethyl)fluoren-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 mol of calcium acetate monohydrate as a catalyst were added. -2 Mass parts (6.78×10 -5mol). After the reactor was replaced with nitrogen under reduced pressure, it was heated by a heat medium and stirring was started when the internal temperature reached 100°C. After 40 minutes from the start of heating, the internal temperature reached 220°C, and the temperature was kept under control while the pressure was reduced. After reaching 220°C, it reached 13.3 kPa in 90 minutes. The phenol vapor produced as a by-product during the polymerization reaction was introduced into a 100°C reflux cooler, and a certain amount of monomer components contained in the phenol vapor was returned to the reactor. The uncondensed phenol vapor was introduced into a 45°C condenser for recovery. Nitrogen was introduced into the first reactor, and after temporarily restoring the pressure to atmospheric pressure, the oligomerized reaction liquid in the first reactor was transferred to the second reactor. Next, the temperature and pressure reduction in the second reactor were started, and the internal temperature reached 240°C and the pressure reached 0.2 kPa in 50 minutes. After that, polymerization was carried out until the specified stirring power was reached. When the specified power was reached, nitrogen was introduced into the reactor for restoring the pressure, the generated polyester carbonate was extruded into water, and the strands were cut to obtain pellets. The Tg of the obtained polyester carbonate resin was 140°C.

[0172] After the obtained polyester carbonate resin was vacuum dried at 80°C for 5 hours, a resin film with a thickness of 135 μm was prepared using a film-making device having a uniaxial extruder (manufactured by Toshiba Machine Co., Ltd., cylinder setting temperature: 250°C), a T-die (width 200 mm, setting temperature: 250°C), a chilled roll (setting temperature: 120-130°C) and a winder.

[0173] (Production of stretched film)

[0174] use Figures 1 to 3 The stretching device shown in the figure obliquely stretches the polyester carbonate resin film obtained as above to obtain a phase difference film.

[0175] Specifically, the left and right ends of the polyester carbonate resin film were gripped by left and right clamps at the entrance of the stretching device and preheated to 145° C. in the preheating zone B. In the preheating zone, the clamp pitch ( P1 ) between the left and right clamps was 125 mm.

[0176] Next, as the film enters the stretching region C, the clamp spacing of the right clamp begins to increase and the clamp spacing of the left clamp begins to decrease. While the clamp spacing of the right clamp is increased to P2, the clamp spacing of the left clamp is reduced to P3 (first oblique extension). At this time, the clamp spacing change rate (P2 / P1) of the right clamp is 1.42, the clamp spacing change rate (P3 / P1) of the left clamp is 0.78, and the lateral stretch ratio relative to the original width of the film is 1.45 times. Next, while maintaining the clamp spacing of the right clamp at P2, the clamp spacing of the left clamp begins to increase from P3 to P2 (second oblique extension). During this period, the rate of change (P2 / P3) of the clamp spacing of the left clamp is 1.82, and the lateral stretch ratio relative to the original width of the film is 1.9 times. In addition, the stretching region C is set to Tg+3.2°C (143.2°C).

[0177] Next, the film was held at 125° C. for 60 seconds for thermal fixation in the release zone D. After the thermally fixed film was cooled to 100° C., the left and right clamps were released and the film was sent out from the outlet of the stretching device.

[0178] (Relaxation Detection)

[0179] As mentioned above, at room temperature, Figure 6 (a) and Figure 6 (b) The film (width 2050mm) delivered from the outlet of the stretching device is transported in the transport line of 7 transport rollers, and the slack is detected between the transport rollers. During the roller transport, by adjusting the torque of the roller most downstream in the transport direction, a tension of 300N / m is applied to the film from the clamp release point to the most downstream roller in the transport direction for 180 seconds. In addition, all the rollers set in the transport line are flat rollers. The test results show that in the film delivered from the outlet of the stretching device, slack occurs at the left end in the width direction, and the slack is 18mm.

[0180] (Roller handling)

[0181] During the roller conveyance, the roller through which the film sent out from the stretching device outlet initially passes is replaced with a concave roller, and the roller conveyance is continued. At this time, the roller conveyance is performed in such a manner that the center of the width direction of the concave roller (center line C1) overlaps the center of the width direction of the film (center line C2). The total width W1 of the concave roller used is 2100 mm, the width W2 of the center is 1800 mm, the width W4 of the end is 100 mm, and the difference X between the radius of the center and the radius of the end is 0.9 mm.

[0182] The phase difference Re (590) of the obtained stretched film was 147 nm, and the angle between the slow axis direction and the longitudinal direction was 45°.

[0183] <Example 2>

[0184] A stretched film was obtained in the same manner as in Example 1 except that a concave roll having a total width W1 of 2100 mm, a width W2 of 1800 mm at the center, a width W4 of 50 mm at the end, and a difference X of 1.3 mm was used.

[0185] The phase difference Re (590) of the obtained stretched film was 147 nm, and the angle formed between the slow axis direction and the longitudinal direction was 45°.

[0186] <Example 3>

[0187] A stretched film was obtained in the same manner as in Example 1 except that a concave roll having a total width W1 of 2100 mm, a width W2 of 1800 mm at the center, a width W4 of 100 mm at the end, and a difference X of 1.3 mm was used.

[0188] The phase difference Re (590) of the obtained stretched film was 147 nm, and the angle formed between the slow axis direction and the longitudinal direction was 45°.

[0189] <Example 4>

[0190] A stretched film was obtained in the same manner as in Example 1 except that a concave roll having a total width W1 of 2100 mm, a width W2 of the center portion of 1800 mm, a width W4 of the end portions of 120 mm, and a difference X of 1.3 mm was used.

[0191] The phase difference Re (590) of the obtained stretched film was 147 nm, and the angle formed between the slow axis direction and the longitudinal direction was 45°.

[0192] <Example 5>

[0193] A stretched film was obtained in the same manner as in Example 1 except that a concave roll having a total width W1 of 2100 mm, a width W2 of the center portion of 1800 mm, a width W4 of the end portions of 150 mm, and a difference X of 1.3 mm was used.

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

[0195] <Example 6>

[0196] A stretched film was obtained in the same manner as in Example 1 except that a concave roll having a total width W1 of 2100 mm, a width W2 of 1800 mm at the center, a width W4 of 50 mm at the end, and a difference X of 0.4 mm was used.

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

[0198] <Example 7>

[0199] A stretched film was obtained in the same manner as in Example 1 except that the flat roll through which the film sent out from the outlet of the stretching device initially passed was replaced with a curved roll with a curvature of 10 mm, the center line C2 of the film was arranged so as to be 50 mm to the left of the center line C3 of the curved roll, the third flat roll arranged from the outlet of the stretching device was replaced with a concave roll, and the sixth flat roll arranged was replaced with an expansion roll. In addition, the inclination angle θ of the ring member of the expansion roll was 3.5°. The difference between the radius of the end portion and the radius of the central portion of the concave roll was 0.9 mm, the total width W1 was 2100 mm, the width W2 of the central portion was 1800 mm, the width W4 of each end portion was 100 mm, and each expanded diameter portion W3 was 50 mm.

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

[0201] [Appearance and handling evaluation]

[0202] The stretched films obtained in the above-mentioned examples and comparative examples were laminated to a long strip of masking film (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 masking film was peeled off from the film laminate, an adhesive was applied using a gravure coater, and the film laminate was laminated to a polarizer and irradiated with UV to obtain an optical laminate. The appearance (visual) of the optical laminate and the handling properties of the stretched film were evaluated according to the following criteria.

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

[0204] △: When laminating the masking film, the laminating tension was increased to 300 N / m, so that the masking film could be laminarized without wrinkles. However, when applying the adhesive, the adhesive could not be applied to the slackened portion.

[0205] ×: After the masking film was attached, there were wrinkles and the appearance was deteriorated.

[0206] [Wrinkle evaluation]

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

[0208] ○: No wrinkles were observed even when irradiated with a Purulite lamp (manufactured by Purulite, product number "NP-1").

[0209] △: Even when illuminated by fluorescent light, wrinkles are not visible, but when illuminated by Purui light, wrinkles are visible.

[0210] ×: Wrinkles are visible when illuminated with fluorescent light.

[0211] [Evaluation of transportability]

[0212] The obtained stretched film was visually checked for deformation or folds caused by sag and / or wrinkles, and evaluated based on the following criteria.

[0213] ○: No deformation or crease occurred in the film.

[0214] ×: Deformation and / or creases occurred in the film.

[0215] [Visibility Evaluation]

[0216] The optical laminate prepared in the above appearance and handling evaluation was bonded to the visible side of a reflector or an organic EL panel via an adhesive layer. The obtained optical laminate was visually checked for uneven shape or light leakage due to sag or wrinkles, and evaluated according to the following criteria.

[0217] ○: No unevenness or light leakage was observed in both the reflector and the panel installation.

[0218] △: Unevenness and / or light leakage is visible in the reflector, but not in the panel installation.

[0219] ×: Unevenness and / or light leakage were observed in both the reflector and the panel installation.

[0220] Table 1 shows the relaxation amounts and the evaluation results of the stretched films obtained in the above Examples.

[0221]

[0222] <Evaluation>

[0223] As shown in Table 1, in the production of a long obliquely stretched film, passing a concave roller through the obliquely stretched film can reduce sag and / or wrinkles. Specifically, it was confirmed that sag is effectively reduced by using a concave roller with larger values ​​of X and W4 (i.e., a larger diameter expansion ratio), and wrinkles are effectively reduced by using a concave roller with smaller values ​​of X and W4.

[0224] Industrial Applicability

[0225] The method for producing a stretched film of the present invention is preferably used for producing a phase difference film, and as a result, can contribute to the production of image display devices such as liquid crystal display devices (LCD) and organic electroluminescent display devices (OLED).

Claims

1. A manufacturing method, which is a method for manufacturing a stretched film, comprising: holding the left and right ends of a long film in a width direction by using left and right clamps respectively; moving the left and right clamps to obliquely stretch the film, and then releasing it from the left and right clamps; and rolling the film with a concave roller, The concave roller has a central portion and end portions located at both ends thereof, and the end portions are cylindrical in shape with a radius greater than that of the central portion. The difference between the radius of the central portion and the radius of the end portion of the concave roller is 0.6 mm to 2.0 mm. The film is passed through the concave roller in such a manner that the width center of the concave roller overlaps the width center of the film, and in such a manner that both ends of the concave roller having a cylindrical shape with a radius larger than the center overlap the film by 5 mm to 195 mm respectively.

2. The method for producing a stretched film according to claim 1, wherein: The concave roller further includes a diameter-enlarging portion whose diameter is enlarged from both ends of the central portion toward the end portions.

3. The method for producing a stretched film according to claim 1 or 2, wherein: The difference between the radius of the central portion and the radius of the end portion of the concave roller is 0.6 mm to 1.8 mm.

4. The method for producing a stretched film according to any one of claims 1 to 3, wherein: The width of the end of the concave roller is 30 mm to 180 mm.

5. The method for producing a stretched film according to any one of claims 1 to 4, wherein: In addition to the concave roll, a flat expansion roll and / or a curved roll are used to roll the film.

6. The method for producing a stretched film according to any one of claims 1 to 5, wherein: The clamp is a variable-pitch type clamp in which the clamp pitch in the longitudinal direction varies. The film is stretched obliquely by moving the left clamp holding the left end of the film and the right clamp holding the right end of the film while changing the clamp pitch between the left clamp and the right clamp.

7. The method for producing a stretched film according to claim 6, wherein: The oblique extension includes: (i) increasing the clamp spacing of one of the left and right clamps from P1 to P2, while reducing 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 specified equal spacing.

8. The method for producing a stretched film according to claim 7, wherein: P2 / P1 is 1.25 to 1.75, and P3 / P1 is 0.50 or more and less than 1.

9. The method for producing a stretched film according to any one of claims 1 to 5, wherein: The film is stretched obliquely by changing the conveying direction of the film midway while moving the left clamp holding the left end of the film and the right clamp holding the right end of the film at a constant speed.

10. A method for producing an optical laminate, comprising: obtaining a long-strip stretched film by the production method according to any one of claims 1 to 9; and While conveying the long optical film and the long stretched film, their length directions are aligned and they are continuously bonded together.

11. The method for producing an optical layered body according to claim 10, wherein: The optical film is a polarizing plate, and the stretched film is a λ / 4 plate or a λ / 2 plate.

Images