JP2019136883A - Film drawing apparatus and method for producing retardation film - Google Patents

Abstract

To provide the film drawing apparatus capable of suppressing breakage of a film starting from a clip peripheral part.SOLUTION: A clip type film drawing apparatus comprises variable-pitch type left and right clips that grip left and right ends of the film to be drawn and travel through a drawing zone, and change a clip pitch in at least one vertical direction as they pass, wherein the clip has an upper gripping member and a lower gripping member that sandwich and grip an end of the film, and a bottom surface of the upper gripping member and an upper surface of the lower gripping member are configured to be rotatable around an axis perpendicular to a principal surface of the film.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a film stretching apparatus and a method for producing a retardation film.

  In an image display device such as a liquid crystal display device (LCD) or an organic electroluminescence display device (OLED), a circularly polarizing plate is used for the purpose of improving display characteristics and preventing reflection. In a circularly polarizing plate, typically, a polarizer and a retardation film (typically λ / 4 plate) form an angle of 45 ° between an absorption axis of the polarizer and a slow axis of the retardation film. Thus, they are laminated. Conventionally, a retardation film is typically produced by uniaxially or biaxially stretching in the machine direction and / or the transverse direction, so that the slow axis is often the transverse direction of the original film. Appears in the direction (width direction) or longitudinal direction (long direction). As a result, in order to produce a circularly polarizing plate, it was necessary to cut the retardation film so as to form an angle of 45 ° with respect to the width direction or the long direction and to bond them one by one.

  In order to solve such a problem, the left and right end portions (width direction end portions) of the long film are respectively held by variable-pitch left and right clips whose longitudinal clip pitches change, A technique has been proposed in which the slow axis of the retardation film is expressed in an oblique direction by changing the clip pitch of at least one of the clips and stretching in an oblique direction (for example, Patent Document 1). However, in such an oblique stretching technique, the film may be broken starting from the peripheral edge of the clip that holds the film as the stretching ratio increases.

Japanese Patent No. 4845619

  This invention is made | formed in order to solve the said subject, The place made into the objective is to suppress the fracture | rupture of the film from the clip peripheral part.

According to one aspect of the present invention, a variable pitch mold that grips the left and right ends of a film to be stretched and travels through a stretching zone, and at least one of the longitudinal clip pitches changes with the travel. A clip-type film stretching apparatus having left and right clips is provided. In the clip-type film stretching apparatus, the clip has an upper gripping member and a lower gripping member that sandwich and grip the end portion of the film, and the bottom surface of the upper gripping member and the upper surface of the lower gripping member are , And is configured to be rotatable about an axis perpendicular to the main surface of the film.
In one embodiment, the clip is held at a location separated by 20 mm or more from the edge of the film.
In one embodiment, the length of the film gripping surface defined by the overlap between the bottom surface of the upper gripping member and the top surface of the lower gripping member in a direction orthogonal to the traveling direction of the clip is 15 mm or more.
In one embodiment, the length of the film gripping surface defined by the overlap between the bottom surface of the upper gripping member and the top surface of the lower gripping member in the running direction of the clip is 20 mm or more.
In one embodiment, the shape of the bottom of the upper gripping member and the top surface of the lower gripping member is circular.
According to another aspect of the present invention, the left and right end portions of the film to be stretched are respectively held by variable pitch type left and right clips whose longitudinal clip pitch changes, the film is preheated, There is provided a method for producing a retardation film, comprising changing a clip pitch of at least one of left and right clips to obliquely stretch the film and releasing a clip that holds the film. In the manufacturing method, the clip includes an upper gripping member and a lower gripping member that sandwich and grip an end portion of the film, and the bottom surface of the upper gripping member and the lower gripping member are The upper surface is rotated so as to follow the stretching direction.
In one embodiment, the manufacturing method is performed using the clip-type film stretching apparatus.
In one embodiment, the diagonal stretching includes lateral stretching.
According to another aspect of the present invention, there is provided a clip body, and an upper grip member and a lower grip member that are attached to the clip body and grip a film to be gripped from above and below, respectively. A clip is provided in which the bottom surface of the gripping member and the top surface of the lower gripping member are each configured to be rotatable about an axis perpendicular to the main surface of the film.

  In the film stretching apparatus or the retardation film manufacturing method of the present invention, a clip having an upper gripping member and a lower gripping member is used as a clip for gripping the film, and the bottom surface of the upper gripping member and the lower gripping member are used. Is configured to be rotatable about an axis perpendicular to the main surface of the film. Thereby, since it can rotate so that a clip may follow the extending | stretching direction in the case of diagonal extending | stretching, the stress concentration in a clip peripheral part can be reduced. As a result, it is considered that the film breakage starting from the peripheral edge of the clip is suppressed.

It is a schematic plan view explaining the whole structure of the extending | stretching apparatus by one Embodiment of this invention. It is a principal part schematic plan view for demonstrating the link mechanism which changes a clip pitch in the extending | stretching apparatus of FIG. 1, and shows the state where a clip pitch is the minimum. It is a principal part schematic plan view for demonstrating the link mechanism which changes a clip pitch in the extending | stretching apparatus of FIG. 1, and shows a state with the largest clip pitch. It is a principal part schematic side view explaining the structure and open state of a clip. It is a principal part schematic side view explaining the structure and closed state of a clip. (A) is a schematic sectional drawing of an upper side holding member, (b) is a schematic sectional drawing of a lower side holding member. (A) and (b) are the results of simulating the occurrence of stress at the film edge when obliquely stretched under the same conditions using the conventional clip-type film stretching apparatus and the clip-type film stretching apparatus of the present invention, respectively. FIG. It is the schematic explaining the grip margin and grip length of a film holding surface, a clip position, and a clip pitch. It is a schematic diagram explaining an example of diagonal stretch. It is a graph which shows the relationship between each process of diagonal stretch shown in FIG. 9, and a clip pitch. It is the schematic explaining the relationship between an example of diagonal stretch, and Formula (1). It is the schematic explaining clip movement speed and Formula (1) of each right and left in an example of diagonal stretch. It is the schematic explaining the clip moving speed of right and left each in another example of diagonal stretch, and Formula (1).

[A. Film stretcher]
According to one aspect of the present invention, the right and left end portions (width direction end portions) of the film to be stretched are gripped and traveled through the stretching zone, and at least one longitudinal clip accompanying the passing travel. There is provided a clip-type film stretching apparatus having variable pitch type left and right clips with varying pitches. Hereinafter, although one embodiment of the film stretching apparatus of the present invention is described, the present invention is not limited to these embodiments.

  With reference to FIGS. 1-5, one embodiment of the film extending apparatus of this invention is described. FIG. 1 is a schematic plan view illustrating the overall configuration of an example of the film stretching apparatus of the present invention. 2 and 3 are schematic plan views of main parts for explaining a link mechanism for changing the clip pitch in the stretching apparatus of FIG. 1, respectively, FIG. 2 shows a state in which the clip pitch is minimum, and FIG. Indicates the maximum clip pitch. 4 and 5 are schematic side views of the main part for explaining the configuration and open / close state of the clip.

  As shown in FIG. 1, the stretching device 100 has an endless loop 10 </ b> L having a large number of clips 20 for gripping films and a endless loop 10 </ b> R symmetrically on the left and right sides in a plan view. In this specification, the left endless loop as viewed from the film entrance side is referred to as the left endless loop 10L, and the right endless loop is referred to as the right endless loop 10R. The clips 20 of the left and right endless loops 10L and 10R are guided by the reference rail 70 and move in a loop. The left endless loop 10L rotates in a counterclockwise direction, and the right endless loop 10R rotates in a clockwise direction. In the stretching apparatus, a gripping zone A, a preheating zone B, a stretching zone C, and an open zone D are provided in this order from the inlet side to the outlet side of the sheet. Each of these zones means a zone where the film to be stretched is substantially gripped, preheated, stretched, and released from the clip, and does not mean a mechanically and structurally independent section. . It should also be noted that the length ratio of each zone is different from the actual length ratio. Furthermore, although not illustrated, a zone for performing any appropriate treatment may be provided between the stretching zone C and the open zone D as necessary. Examples of such treatment include longitudinal shrinkage treatment and transverse stretching treatment.

  In the gripping zone A and the preheating zone B, the left and right endless loops 10L and 10R are configured to be substantially parallel to each other at a separation distance corresponding to the initial width of the film to be stretched. In the stretching zone C, the distance between the left and right endless loops 10L and 10R gradually increases from the preheating zone B side toward the open zone D until it corresponds to the width after stretching of the film. In the open zone D, the left and right endless loops 10L and 10R are configured to be substantially parallel to each other at a separation distance corresponding to the width of the film after stretching.

  The clip 20L on the left endless loop 10L (left clip) and the clip 20R on the right endless loop 10R (right clip) can each move independently. For example, the driving sprockets 11 and 12 of the left endless loop 10L are rotationally driven counterclockwise by the electric motors 13 and 14, and the driving sprockets 11 and 12 of the right endless loop 10R are clocked by the electric motors 13 and 14. It is driven to rotate around. As a result, traveling force is applied to the clip carrying member 30 of the drive roller (not shown) engaged with the drive sprockets 11 and 12. As a result, the left endless loop 10L cyclically moves in the counterclockwise direction, and the right endless loop 10R cyclically moves in the clockwise direction. By driving the left electric motor and the right electric motor independently of each other, the left endless loop 10L and the right endless loop 10R can be cyclically moved independently.

  Further, the clip (left clip) 20 of the left endless loop 10L and the clip (right clip) 20 of the right endless loop 10R are each of a variable pitch type. That is, the left and right clips 20 and 20 can independently change the clip pitch in the vertical direction as they move. The variable pitch type configuration can be realized by adopting a known driving method such as a pantograph method, a linear motor method, a motor chain method or the like. Hereinafter, a link mechanism (pantograph mechanism) will be described as an example.

  As shown in FIGS. 2 and 3, an elongated rectangular clip carrying member 30 is provided in the lateral direction in plan view for carrying the clips 20 individually. Although not shown, the clip carrying member 30 is formed into a solid frame structure with a closed cross section by an upper beam, a lower beam, a front wall (wall on the clip side), and a rear wall (wall on the side opposite to the clip). The clip carrying member 30 is provided so as to roll on the traveling road surfaces 81 and 82 by the traveling wheels 38 at both ends thereof. 2 and 3, the traveling wheels on the front wall (the traveling wheels that roll on the traveling road surface 81) are not shown. The traveling road surfaces 81 and 82 are parallel to the reference rail 70 over the entire area. A long hole 31 is formed along the longitudinal direction of the clip carrying member on the rear side (the side opposite to the clip) of the upper and lower beams of the clip carrying member 30, and the slider 32 can slide in the longitudinal direction of the long hole 31. Is engaged. In the vicinity of the end portion of the clip carrying member 30 on the clip 20 side, a single first shaft member 33 is vertically provided so as to penetrate the upper beam and the lower beam. On the other hand, a single second shaft member 34 is vertically provided through the slider 32 of the clip carrying member 30. One end of a main link member 35 is pivotally connected to the first shaft member 33 of each clip carrying member 30. The main link member 35 is pivotally connected to the second shaft member 34 of the adjacent clip carrier member 30 at the other end. In addition to the main link member 35, one end of the sub link member 36 is pivotally connected to the first shaft member 33 of each clip carrying member 30. The sub link member 36 is pivotally connected at the other end to the intermediate portion of the main link member 35 by a pivot shaft 37. As the slider 32 moves to the rear side of the clip carrying member 30 (opposite side of the clip side) by the link mechanism by the main link member 35 and the sub link member 36, it is adjacent in the vertical direction as shown in FIG. The pitch between the clip carrying members 30 (as a result, the pitch between the carried clips) becomes smaller, and as the slider 32 moves to the front side (clip side) of the clip carrying member 30 as shown in FIG. The pitch becomes large. Positioning of the slider 32 is performed by the pitch setting rail 90. As shown in FIGS. 2 and 3, the larger the pitch is, the smaller the distance between the reference rail 70 and the pitch setting rail 90 is. Since the link mechanism is well known in the art, a more detailed description is omitted.

  The clip 20 grips the film 200 so as to be detachable. In the embodiment illustrated in FIGS. 4 and 5, the clip 20 includes a clip body 21 having a substantially U-shaped vertical cross-sectional shape, a lower gripping member 22 attached to the clip body 21, and an attachment shaft member 23. The lift lever 24 is pivotally attached to the clip main body 21 and the upper gripping member 26 is pivotally attached to the lower end of the lift lever 24 by the attachment shaft member 25.

  The upper gripping member 26 moves up and down as the lifting lever 24 rotates. Specifically, the upper gripping member 26 is lifted obliquely outward in the width direction of the film as the elevating lever 24 rises in the vertical direction. At this time, the clip is open and does not grip the film (FIG. 4). On the other hand, when the elevating lever 24 rotates in the oblique direction about the attachment shaft member 23, the upper gripping member 26 also descends obliquely inward in the film width direction, and the end portion of the film 200 together with the lower gripping member 22 Is sandwiched and held (FIG. 5). 4 and 5 illustrate a clip for gripping the film by a so-called slide-in method, but unlike the illustrated example, the clip may be gripped by the upper gripping member descending in the vertical direction. Good.

  As shown in FIG. 6A, the upper gripping member 26 has a circular shape in plan view, has a through hole penetrating in a vertical direction at a substantially central portion, and has a curved surface shape with a bottom surface protruding downward. The holding portion 26a, a bearing (radial bearing) 26b fixed by press fitting into the through hole of the upper holding portion 26a, a through hole inserted into the bearing 26b and capable of receiving the mounting shaft member 25, and a lower end portion Includes a mounting shaft 26c having a curved surface shape that is continuous with the bottom surface shape of the upper pressing portion 26a, and a bearing (thrust bearing) 26d fitted to the mounting shaft 26c up to the position of the upper surface of the upper pressing portion 26a. According to such a configuration, when the lower gripping pressure is applied to the bearing (thrust bearing) 26d by the upper gripping member 26 descending to the position for gripping the film as the elevating lever 24 rotates, The upper pressing portion 26a (as a result, the bottom surface of the upper gripping member 26) can rotate around an axis perpendicular to the main surface of the film about the mounting shaft 26c. The diameter of the upper pressing portion is not limited as long as the effect of the present invention is obtained, and may be, for example, 15 mm to 50 mm. The diameter of the lower end portion of the mounting shaft is not limited as long as the effect of the present invention is obtained, and may be, for example, 5 mm to 40 mm. The configuration of the upper gripping member is not limited to the above illustrated example. For example, as shown in the illustrated example, only a part of the bottom surface of the upper gripping member may be rotated, more specifically, only the outer edge portion (radially outer portion) may be rotated. May be configured to rotate.

On the other hand, as shown in FIG. 6B, the lower gripping member 22 includes a lower pressing portion 22a having a concave curved upper surface corresponding to the bottom shape of the upper gripping member 26, and a bottom surface of the lower pressing portion 22a. A bearing (thrust bearing) 22b fixed by press-fitting in a recess provided in the clip, a radial bearing 22d fixed by press-fitting in a recess provided in the clip body, and a mounting shaft inserted into the bearings 22b and 22d 22c.
With this configuration, when the lower gripping member 22 is attached to the clip body 21, the lower pressing portion 22a (as a result, the upper surface of the lower gripping member 22) is centered on the mounting shaft 22c. It can rotate around an axis perpendicular to the main surface of the film. The configuration of the lower gripping member is not limited to the above illustrated example. For example, as shown in the illustrated example, the entire upper surface of the lower gripping member may be configured to rotate. Unlike the illustrated example, only a part of the bottom surface, more specifically, the outer edge (the radially outer portion) ) May rotate.

  There is no limitation on the rotation direction and rotation angle of the upper pressing portion 26a of the upper gripping member 26 and the lower pressing portion 22a of the lower gripping member 22, and it is free to exceed 360 ° in either the clockwise direction or the counterclockwise direction. Can be rotated.

  In the illustrated example, the bottom surface of the upper gripping member and the upper surface of the lower gripping member have curved surfaces corresponding to each other. However, unlike the illustrated example, they may be flat. Similarly, the fixing method of the bearing is not limited to press-fitting into the recess, and may be a fixing method using a nut, a bolt, a screw, a retaining ring, an adhesive, or the like. The bearing may be a sliding bearing or a rolling bearing.

  The plan view shapes of the bottom surface of the upper pressing portion 26a and the upper surface of the lower pressing portion 22a can be any appropriate shape as long as the effects of the present invention can be obtained. For example, a circle, an ellipse, and a rectangle are mentioned. When the bottom surface of the upper pressing portion 26a and the upper surface of the lower pressing portion 22a are circular, it is possible to always form a film gripping surface having a constant shape (circular shape) without being affected by the rotation angle. In the present specification, the film gripping surface is sandwiched between the upper gripping member 26 (specifically, the upper pressing portion 26a) and the lower gripping member 22 (specifically, the lower pressing portion 22a). It means the film surface and is defined by the overlap between the bottom surface of the upper pressing portion 26a and the upper surface of the lower pressing portion 22a.

  When the film is gripped, the upper pressing portion 26a of the upper gripping member and the lower pressing portion 22a of the lower gripping member may have the outer peripheral shape completely overlapped in plan view, or may have a portion that does not overlap. Good. When there is a portion that does not overlap, it is preferable that the upper pressing portion 26a and the lower pressing portion 22a overlap so that the inner edges in the film width direction are at the same position in plan view.

  7 (a) and 7 (b), respectively, simulated the state of stress generation at the film edge when obliquely stretched under the same conditions using the conventional clip-type film stretching apparatus and the clip-type film stretching apparatus of the present invention. It is a figure which shows a result. As shown in FIG. 7 (a), according to the conventional clip-type film stretching apparatus, the film as a whole is stretched in an oblique direction, while the clip acts at the periphery of the clip to prevent deformation of the film. The stress is concentrated due to the above, and the stress is concentrated in an imbalance in the upstream region and the downstream region in the traveling direction. On the other hand, as shown in FIG. 7B, according to the clip-type film stretching apparatus of the present invention, the upper pressing portion of the upper holding member and the lower pressing portion of the lower holding member are on the main surface of the film. It can rotate freely around a vertical axis. Therefore, during oblique stretching, these pressing portions can rotate so as to follow the direction in which the film is stretched (that is, the stretching direction), and as a result, the concentration of stress at the clip peripheral portion is suppressed, and the clip peripheral portion is Breaking of the film as a starting point can be suppressed. In the present specification, the upper pressing portion of the upper gripping member and the lower pressing portion of the lower gripping member `` rotate to follow the stretching direction '' means that the clip travels in the oblique stretching zone. In addition to the case where the rotation angle of these pressing portions (based on the film width direction) coincides with the stretching angle (angle formed by the film width direction and the stretching direction), the angle of the pressing portion is within the range where the effect of the present invention is obtained. It may also include the case where the change patterns match. When these pressing portions rotate so as to follow the extending direction, typically, the stress imbalance between the upstream region and the downstream region in the traveling direction is eliminated, and can be substantially equal.

  When gripping the film, the clip (specifically, the upper gripping member and the lower gripping member) is preferably a distance of 20 mm or more, more preferably 25 mm or more from the left and right edges (widthwise edges) of the film. Grab the position. Describing in more detail with reference to FIG. 8, the distance D from the edge of the film 200 to the innermost part in the film width direction of the film gripping surface 28 (hereinafter also referred to as “clip position”) is preferably 20 mm or more. Grip the film. By gripping such a position with a clip, breakage of the film can be further suppressed. The upper limit of the distance from the edge of the film to the clip position can be 60 mm, for example. The clip position can be controlled, for example, by adjusting the separation distance of the reference rail.

  As shown in FIG. 8, the length of the film gripping surface 28 in the clip traveling direction (the direction in which the reference rail extends) is defined as the grip length (L), and the length of the film gripping surface 28 in the direction orthogonal to the clip traveling direction. The gripping allowance (W) is, for example, not less than 15 mm, preferably not less than 20 mm, when the gripping allowance (W) is used. The gripping allowance (W) can be set to 60 mm or less, for example. On the other hand, the grip length (L) is, for example, 20 mm or more, preferably 25 mm or more. The grip length (L) can be set to 80 mm or less, for example. By setting the gripping allowance or gripping length in such a range, the film gripping surface becomes wide, so that the stress concentration on the peripheral edge of the clip is alleviated and the film breakage can be further suppressed.

[B. Method for producing retardation film]
According to another aspect of the present invention, the left and right end portions of the film to be stretched are each gripped by variable-pitch left and right clips that change the longitudinal clip pitch (gripping step), and the film is preheated (Preheating step), changing the clip pitch of at least one of the left and right clips to obliquely stretch the film (diagonal stretching step), and opening the clip that holds the film (opening step) A method for producing a retardation film is provided. In the method for producing the retardation film, a clip having an upper gripping member and a lower gripping member that sandwich and grip an end portion of the film is used, and the bottom surface of the upper gripping member and the lower gripping member are obliquely stretched. The upper surface of the member is rotated so as to follow the stretching direction. Thereby, the stress concentration and the unbalanced concentration of stress at the peripheral edge of the clip can be reduced. As a result, the film breakage starting from the peripheral edge of the clip can be suppressed. Moreover, the manufacturing method of this retardation film is suitably performed by using the extending | stretching apparatus as described in said A term. Hereinafter, each process will be described in detail using the embodiment using the stretching apparatus described in the above section A as a specific example. In this specification, “vertical clip pitch” (sometimes simply referred to as “clip pitch”) is the distance between the centers in the running direction of clips adjacent in the vertical direction (more specifically, The distance between the centers of the film gripping surfaces in the traveling direction) is a distance represented by P in FIG.

[B-1. Gripping process]
First, in the gripping zone A (film entrance of the stretching apparatus 100), the film to be stretched is clipped at the left and right endless loops 10L and 10R, and both ends thereof are equal to each other at a constant clip pitch or mutually mutually. Grasped with different clip pitches. The clip pitch of the left and right clips in the gripping process can be appropriately set according to a desired phase difference, shaft angle, and the like. The clip pitch can be, for example, 50 mm to 180 mm. In addition, in this specification, the edge part of a film means the area | region of 10% of a film full width from a film edge.

  The clip position in the holding step is preferably a position at a distance of 20 mm or more, more preferably 25 mm or more from the left and right edges of the film. The upper limit of the distance from the edge of the film to the clip position can be, for example, 60 mm or less. By gripping such a position with a clip, breakage of the film is further suppressed.

  Moreover, it is preferable that a film holding surface is a wide surface. By making the film gripping surface wide, stress concentration on the clip is alleviated and the film breakage is further suppressed. Specifically, as described in the above section A, the grip allowance (W) by the clip is preferably 15 mm or more, more preferably 20 mm or more, further preferably 25 mm or more, and can be set to 60 mm or less, for example. Further, the grip length (L) is, for example, 20 mm or more, preferably 30 mm or more, more preferably 35 mm or more, still more preferably 40 mm or more, and can be, for example, 80 mm or less.

  When the film is held by the clip, the left and right endless loops 10 </ b> L and 10 </ b> R move (substantially the movement of each clip carrier guided by the reference rail 70) without being stretched horizontally or vertically. ) To the preheating zone B.

  The clip has an upper gripping member and a lower gripping member that sandwich and grip an end portion of the film. As described in the above section A, the upper pressing portion of the upper gripping member (as a result, the bottom surface of the upper gripping member) and the lower pressing portion of the lower gripping member (as a result, the upper surface of the lower gripping member) are It is configured to be rotatable about an axis perpendicular to the main surface of the film.

[B-2. Preheating process]
In the preheating zone B, the left and right endless loops 10L, 10R are basically parallel to each other at a separation distance corresponding to the initial width of the film to be stretched as described above. The film is heated without any longitudinal stretching. However, the distance between the left and right clips (distance in the width direction) may be slightly increased in order to avoid problems such as film deflection due to preheating and contact with the nozzles in the oven.

  In preheating, the film is heated to a temperature T1 (° C.). It is preferable that temperature T1 is more than the glass transition temperature (Tg) of a film, More preferably, it is Tg + 2 degreeC or more, More preferably, it is Tg + 5 degreeC or more. On the other hand, the heating temperature T1 is preferably Tg + 40 ° C. or lower, more preferably Tg + 30 ° C. or lower. Although it changes with films to be used, temperature T1 is 70 to 190 degreeC, for example, Preferably it is 80 to 180 degreeC.

  The temperature raising time to the temperature T1 and the holding time at the temperature T1 can be appropriately set according to the constituent material of the film and the manufacturing conditions (for example, the film conveyance speed). These temperature raising time and holding time can be controlled by adjusting the moving speed of the clip 20, the length of the preheating zone, the temperature of the preheating zone, and the like.

[B-3. Diagonal stretching process]
In the stretching zone C, the film is stretched obliquely by changing the vertical clip pitch of at least one of the left and right clips 20. More specifically, while traveling through the stretching zone C, by changing the clip pitch in the vertical direction of at least one of the left and right clips 20, one clip is advanced and the other clip is driven backward. The film is stretched obliquely. Typically, the terminal zone of the stretching zone C, that is, the rate of change of the clip pitch of the left and right clips at the end of oblique stretching (clip pitch at the end of oblique stretching / clip pitch before oblique stretching) is substantially equal to each other.

  As described above, the upper pressing part of the upper gripping member of the clip (as a result, the bottom surface of the upper gripping member) and the lower pressing part of the lower gripping member (as a result, the upper surface of the lower gripping member) are on the main surface of the film. On the other hand, since it can rotate around a vertical axis, these pressing portions rotate so as to follow the stretching direction during oblique stretching. As a result, the stress concentration and the imbalance in the clip peripheral part are reduced, and the film breakage starting from the clip peripheral part can be suppressed.

  The oblique stretching may or may not include lateral stretching. For example, the distance between the left and right clips (distance in the width direction) may be increased as in the illustrated example, or, unlike the illustrated example, the distance between the left and right clips may be maintained. May be. Preferably, the oblique stretching includes lateral stretching.

When the oblique stretching includes lateral stretching, the stretching ratio in the transverse direction (TD) (ratio of the width W _final of the film after oblique stretching to the initial width W _initial of the film (W _final / W _initial )) is preferably 1. It is 05-6.00, More preferably, it is 1.10-5.00.

  In one embodiment, the oblique stretching is different in the vertical direction from the position where the clip pitch of one of the left and right clips starts to increase or decrease and the position where the clip pitch of the other clip starts to increase or decrease. In position, this can be done by increasing or decreasing the clip pitch of each clip to a predetermined pitch. For the oblique stretching of the embodiment, for example, descriptions in Patent Document 1, Japanese Patent Application Laid-Open No. 2014-238524, and the like can be referred to.

  In another embodiment, the diagonal extension is performed by increasing or decreasing the clip pitch of the other clip to a predetermined pitch while fixing the clip pitch of one of the left and right clips, and then the original clip pitch. Can be done by moving back up. Regarding the oblique stretching of the embodiment, for example, descriptions in JP2013-54338A, JP2014-194482A, and the like can be referred to.

  In yet another embodiment, the oblique stretching comprises: (i) increasing the clip pitch of one of the left and right clips while decreasing the clip pitch of the other clip; and (ii) reducing the clip The clip pitch of each clip can be changed so that the clip pitch and the increased clip pitch are equal to a predetermined equal pitch. Regarding the oblique stretching of the embodiment, for example, the description in JP-A No. 2014-194484 can be referred to. In the oblique stretching of the embodiment, the film is stretched obliquely by increasing the clip pitch of one clip while decreasing the clip pitch of the other clip while increasing the distance between the left and right clips (first step). 1), and while increasing the distance between the left and right clips, the clip pitch of the one clip is maintained or reduced so that the clip pitches of the left and right clips are equal, and the other Increasing the clip pitch of the clip and stretching the film obliquely (second oblique stretching step) may be included.

  In the first oblique stretching step, by stretching one side edge of the film in the longitudinal direction and stretching the other side edge in the longitudinal direction, the film is stretched in a desired direction (for example, The slow axis can be expressed with high uniaxiality and in-plane orientation in a direction of 45 ° with respect to the longitudinal direction. Further, in the second oblique stretching step, by performing oblique stretching while reducing the difference between the left and right clip pitches, it is possible to sufficiently stretch in the oblique direction while alleviating excess stress. Furthermore, since the film can be used in the opening process with the moving speeds of the left and right clips equal, it is difficult for the film transport speed to vary when the left and right clips are opened, and subsequent film winding is preferable. Can be done.

Hereinafter, an example of the oblique stretching of the embodiment will be specifically described with reference to FIGS. 9 and 10. First, in the preheating zone B, the right and left clip pitch are both set to P _1. P ₁ is typically a clip pitch at the time of gripping the film. Next, as soon as the film enters the first oblique stretching zone C1, the clip pitch of one (right side in the illustrated example) starts to increase, and the clip pitch of the other (left side in the illustrated example) Start decreasing. In the first oblique stretching zone C1, it increases the clip pitch of the right clip to the P _2, to reduce the clip pitch of the left clip to the P _3. Therefore, the end portion of the first oblique stretching zone C1 in (beginning of the second oblique stretching zone C2), left clip moves the clip pitch P _3, right clip is a moving clip pitch P ₂ ing. The clip pitch ratio can generally correspond to the clip moving speed ratio. Therefore, the ratio of the clip pitch of the left and right clips can generally correspond to the ratio of the stretching ratio in the longitudinal direction (MD direction) of the right side edge and the left side edge of the film.

  9 and 10, both the position where the clip pitch of the right clip starts to increase and the position where the clip pitch of the left clip starts to decrease are the start portions of the first oblique extension zone C1, but unlike the illustrated example, The clip pitch of the left clip may begin to decrease after the clip pitch of the right clip begins to increase, and the clip pitch of the right clip may begin to increase after the clip pitch of the left clip begins to decrease (not shown) . In one preferred embodiment, after the clip pitch of the clip on one side begins to increase, the clip pitch of the clip on the other side begins to decrease. According to such an embodiment, since the film has already been stretched to a certain extent (preferably about 1.2 to 2.0 times) in the width direction, the clip pitch on the other side can be greatly reduced. Less likely to wrinkle. Accordingly, a more acute oblique stretching is possible, and a retardation film having high uniaxiality and high in-plane orientation can be suitably obtained.

  Similarly, in FIGS. 9 and 10, the clip pitch of the right clip continues to increase and the clip pitch of the left clip continues to the end of the first oblique stretching zone C1 (the start of the second oblique stretching zone C2). However, unlike the illustrated example, either the increase or decrease of the clip pitch ends before the end of the first oblique stretching zone C1, and the clip is clipped to the end of the first oblique stretching zone C1. The pitch may be maintained as it is.

Rate of change of the clip pitch to increase the _(P 2 / _{P 1)} is preferably 1.05 to 1.75, more preferably 1.10 to 1.70, more preferably is 1.15 to 1.65 . Moreover, the rate of change (P ₃ / P ₁ ) of the decreasing clip pitch is, for example, 0.50 or more and less than 1, preferably 0.50 to 0.95, more preferably 0.55 to 0.93, and even more preferably. 0.55 to 0.90. If the change rate of the clip pitch is within such a range, the slow axis can be expressed with high uniaxiality and in-plane orientation in a direction of approximately 45 degrees with respect to the longitudinal direction of the film.

  As described above, the clip pitch can be adjusted by positioning the slider by adjusting the distance between the pitch setting rail of the stretching device and the reference rail.

Stretch ratio in the width direction of the film in the first diagonal drawing step _(W 2 / _{W 1)} is preferably 1.05 to 3.0 times, more preferably 1.1 to 2.5 times, more preferably Is 1.15 times to 2.0 times. If the draw ratio is less than 1.05 times, tin-like wrinkles may occur at the side edge portion on the contracted side. Moreover, when the said draw ratio exceeds 3.0 times, the biaxiality of the obtained retardation film will become high, and when applied to a circularly-polarizing plate etc., a viewing angle characteristic may fall.

  In one embodiment, the first oblique stretching has a product of the rate of change of the clip pitch of one clip and the rate of change of the clip pitch of the other clip, preferably 0.7 to 1.5, more preferably It is carried out so as to be 0.8 to 1.45, more preferably 0.85 to 1.40. When the product of the change rate is within such a range, a retardation film having high uniaxiality and in-plane orientation can be obtained.

Subsequently, as soon as the film enters the second oblique stretching zone C2, the clip pitch of the left clip starts to increase. In the second oblique stretching zone C2, it increases the clip pitch of the left clip to the P _2. On the other hand, the clip pitch of the right clip is maintained at P2 in the _second oblique stretching zone C2. Therefore, the end portion of the second oblique stretching zone C2 in (beginning of the open zone D), left clip and right clips together, there is a moving clip pitch P _2.

The increasing rate (P ₂ / P ₃ ) of the increasing clip pitch is not limited as long as the effects of the present invention are not impaired. The rate of change (P ₂ / P ₃ ) is, for example, 1.1 to 4.0, preferably 1.2 to 3.0.

  In one embodiment, as for 1st diagonal stretch and 2nd diagonal stretch, the diagonal stretch ratio S calculated | required from the following formula | equation (1) is 1.5 or more, for example, Preferably it is 2.0 or more, More preferably It is carried out so as to be 2.0 to 4.0, more preferably 2.5 to 3.5. If the oblique stretching ratio is less than 1.5, biaxiality may be increased or in-plane orientation may be decreased.

(Where
W _1, the first oblique stretching before the film width,
W ₃ being the second oblique stretching after the film width,
v3 ′ is the clip moving speed when the clip pitch of the clip is changed to the predetermined clip pitch in the second oblique stretching step with respect to the clip whose clip pitch is increased in the first oblique stretching step,
t3 is the time from when the clip whose clip pitch is reduced in the first oblique stretching process enters the preheating zone until the second oblique stretching process ends,
t3 ′ represents the time from when the clip whose clip pitch is increased in the first oblique stretching process enters the preheating zone until the second oblique stretching process ends. )

Regarding the above v3 ′, the predetermined clip pitch is the clip pitch when the increase in the first oblique stretching step is completed in the second oblique stretching step (explanation using FIGS. 9 and 10). It means the clip pitch after corresponding) or reduced to P ₂ in. Further, with respect to the clip towards increasing the clip pitch in a first diagonal drawing step, the P ₂ in the description clip pitch of the clips using the first predetermined clip pitch obliquely stretching step (FIGS. 9 and 10 When the moving speed of the clip when changed to (corresponding) is v2 ′,
In the case of v2 ′ = v3 ′, the above t3 is represented by the following formula (2), and the above t′3 is represented by the following formula (3).
In the case of v2 ′> v3 ′, the above t3 is represented by the following formula (4), and the above t′3 is represented by the following formula (5).

  Hereinafter, formulas (2) to (5) will be described. 11 to 13 can be referred to in the description of each symbol in the formula. In addition, the asterisk mark (*) in the formulas (1) to (5) is a multiplication symbol. The unit of film width is m, the unit of speed is m / sec, the unit of distance is m, and the unit of time is sec.

(Where
a1 = (v2-v3) / (L2-L3),
b1 = v3-a1 * L3,
a = (v1-v2) / (L1-L2),
b = v2-a * L2,
v1 is the clip moving speed when the clip whose clip pitch is reduced in the first oblique stretching process passes through the preheating zone,
v2 is a clip whose clip pitch is reduced in the first oblique stretching step, and the clip pitch of the clip is a predetermined clip pitch in the first oblique stretching step (P ₃ in the description using FIGS. 9 and 10). Clip movement speed when reduced to
v3 is a clip whose clip pitch is reduced in the first oblique stretching step, the clip pitch of the clip is a predetermined clip pitch in the second oblique stretching step (P ₂ in the description using FIGS. 9 and 10). Is the clip moving speed when increased to
L1 is the distance from the preheating zone inlet to the clip that reduces the clip pitch in the first oblique stretching step (in one embodiment, from the preheating zone inlet to the preheating zone outlet). distance),
L2 is the distance from the preheating zone inlet to the point where the clip whose clip pitch is reduced in the first oblique stretching step begins to increase the clip pitch (in one embodiment, from the preheating zone inlet to the first diagonal Distance to the stretching zone exit),
L3 is the distance from the preheating zone inlet to the point where the clip whose clip pitch is reduced in the first oblique stretching step finishes increasing the clip pitch (in one embodiment, from the preheating zone inlet to the second diagonal Distance to the exit of the drawing zone)
It is. )

(Where
a ′ = (v1′−v2 ′) / (L1′−L2 ′),
b ′ = v3′−a ′ * L2 ′,
v1 ′ is the clip moving speed when the clip that increases the clip pitch in the first oblique stretching process passes through the preheating zone,
v2 ′ indicates a clip whose clip pitch is increased in the first oblique stretching step, the clip pitch of the clip is a predetermined clip pitch in the first oblique stretching step (P in the description using FIGS. 9 and 10). Clip movement speed when increased to (corresponding to ₂ ),
v3 ′ is the clip moving speed when the clip passes through the second oblique stretching zone with respect to the clip that increases the clip pitch in the first oblique stretching step;
L1 ′ is the distance from the preheating zone inlet to the clip that increases the clip pitch in the first oblique stretching step until the clip pitch begins to increase (in one embodiment, from the preheating zone inlet to the preheating zone outlet). Distance)
L2 ′ is the distance from the preheating zone inlet to the point where the clip that increases the clip pitch in the first oblique stretching step finishes increasing the clip pitch (in one embodiment, the first heating zone inlet (Distance to the diagonal stretching zone exit)
L3 ′ is the distance from the preheating zone entrance to the second oblique stretching zone exit. )

(Wherein a1, b1, a, b, v1, v2, v3, L1, L2 and L3 are as defined for formula (2).)

(Where
a ′ = (v1′−v2 ′) / (L1′−L2 ′),
b ′ = v2′−a ′ * L2 ′,
a ″ = (v2′−v3 ′) / (L2′−L3 ′),
b ″ = v3′−a ″ * L3 ′,
v1 ′ is the clip moving speed when the clip that increases the clip pitch in the first oblique stretching process passes through the preheating zone,
v2 ′ indicates a clip whose clip pitch is increased in the first oblique stretching step, the clip pitch of the clip is a predetermined clip pitch in the first oblique stretching step (P in the description using FIGS. 9 and 10). Clip movement speed when increased to (corresponding to ₂ ),
v3 ′ is the clip moving speed when the clip pitch of the clip is reduced to the predetermined clip pitch in the second oblique stretching step with respect to the clip whose clip pitch is increased in the first oblique stretching step,
L1 ′ is the distance from the preheat zone inlet to the point where the clip that increases the clip pitch in the first oblique stretching step begins to increase the clip pitch (in one embodiment, from the preheat zone inlet to the preheat zone outlet Distance)
L2 ′ is the distance from the preheating zone inlet to the point where the clip that increases the clip pitch in the first oblique stretching step finishes increasing the clip pitch (in one embodiment, the first heating zone inlet (Distance to the diagonal stretching zone exit)
L3 ′ is the distance from the entrance of the preheating zone to the point where the clip that increases the clip pitch in the first oblique stretching step finishes decreasing the clip pitch to the predetermined clip pitch in the second oblique stretching step (one In the embodiment, the distance from the preheating zone entrance to the second oblique stretching zone exit). )

  The oblique stretching can typically be performed 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 about Tg with respect to the glass transition temperature (Tg) of the resin film. Although it changes with resin films to be used, the temperature T2 is, for example, 70 ° C to 180 ° C, and preferably 80 ° C to 170 ° C. The difference (T1-T2) between the temperature T1 and the temperature T2 is preferably ± 2 ° C. or more, more preferably ± 5 ° C. or more. In one embodiment, T1> T2, so a film heated to temperature T1 in the preheat zone can be cooled to temperature T2.

  The longitudinal shrinkage treatment and the transverse stretching treatment are performed after oblique stretching. Regarding these treatments after oblique stretching, reference can be made to paragraphs 0029 to 0032 of JP-A No. 2014-194383.

[B-4. Opening process]
Finally, the clip holding the film is released to obtain a retardation film. Usually, the clip is released after the film has cooled to below Tg. If necessary, the film is heat-treated to fix the stretched state, and after cooling, the clip is opened.

  The heat treatment can typically be performed at a temperature T3. The temperature T3 varies depending on the stretched film, and may be T2 ≧ T3 or T2 <T3. In general, when the film is an amorphous material, T2 ≧ T3, and when the film is a crystalline material, the crystallization treatment may be performed by setting T2 <T3. In the case of T2 ≧ T3, the difference (T2−T3) between the temperatures T2 and T3 is preferably 0 ° C. to 50 ° C. The heat treatment time is typically 10 seconds to 10 minutes.

  After releasing the clip, the film can be wound into a roll shape by cutting the clip gripping portions at both ends.

[C. Film to be stretched and retardation film obtained by stretching]
Examples of the film suitably used in the production method of the present invention include any appropriate long film that can be used as a retardation film. The film to be stretched has a width of, for example, 300 mm or more, preferably 500 mm or more, and more preferably 500 mm to 2000 mm.

  Examples of the material constituting the film include polycarbonate resin, polyvinyl acetal resin, cycloolefin resin, acrylic resin, cellulose ester resin, cellulose resin, polyester resin, polyester carbonate resin, olefin resin, and polyurethane. Based resins and the like. Polycarbonate resins, polyvinyl acetal resins, cellulose ester resins, polyester resins, and polyester carbonate resins are preferable. This is because with these resins, a retardation film showing the wavelength dependence of reverse dispersion can be obtained. These resins may be used alone or in combination according to desired properties.

  Any appropriate polycarbonate resin is used as the polycarbonate resin. For example, a polycarbonate resin containing a structural unit derived from a dihydroxy compound is preferable. 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-phenyl) Enyl) fluorene, 9,9-bis (4- (2-hydroxyethoxy) phenyl) fluorene, 9,9-bis (4- (2-hydroxyethoxy) -3-methylphenyl) fluorene, 9,9-bis ( 4- (2-hydroxyethoxy) -3-isopropylphenyl) fluorene, 9,9-bis (4- (2-hydroxyethoxy) -3-isobutylphenyl) fluorene, 9,9-bis (4- (2-hydroxy Ethoxy) -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 and the like. The polycarbonate resin contains structural units derived from dihydroxy compounds such as isosorbide, isomannide, isoidet, spiroglycol, dioxane glycol, diethylene glycol, triethylene glycol, polyethylene glycol, and bisphenols in addition to the structural units derived from the dihydroxy compound. You may go out.

  Details of the polycarbonate resin as described above are described in, for example, Japanese Patent Application Laid-Open No. 2012-67300 and Japanese Patent No. 3325560. The description of the patent document is incorporated herein by reference.

  The glass transition temperature of the polycarbonate resin is preferably 110 ° C. or higher and 250 ° C. or lower, more preferably 120 ° C. or higher and 230 ° C. or lower. If the glass transition temperature is excessively low, the heat resistance tends to deteriorate, and there is a possibility of causing a dimensional change after film formation. If the glass transition temperature is excessively high, the molding stability at the time of film molding may deteriorate, and the transparency of the film may be impaired. The glass transition temperature is determined according to JIS K 7121 (1987).

  Any appropriate polyvinyl acetal resin can be used as the polyvinyl acetal resin. Typically, the polyvinyl acetal resin can be obtained by a condensation reaction of at least two types of aldehyde compounds and / or ketone compounds and a polyvinyl alcohol resin. Specific examples and detailed production methods of the polyvinyl acetal resin are described, for example, in JP-A-2007-161994. The description is incorporated herein by reference.

  The retardation film obtained by stretching the film to be stretched preferably has a refractive index characteristic of nx> ny. Further, the retardation film can preferably function as a λ / 4 plate. The in-plane retardation Re (550) of the retardation film is preferably 100 nm to 180 nm, more preferably 135 nm to 155 nm. In the present specification, nx is the refractive index in the direction in which the in-plane refractive index is maximum (that is, the slow axis direction), and ny is the direction orthogonal to the slow axis in the plane (that is, the fast phase). (Axial direction) and nz is the refractive index in the thickness direction. Re (λ) is an in-plane retardation of the film measured with light having a wavelength of λ nm at 23 ° C. Therefore, Re (550) is the in-plane retardation of the film measured with light having a wavelength of 550 nm at 23 ° C. Re (λ) is determined by the formula: Re (λ) = (nx−ny) × d, where d (nm) is the thickness of the film.

  The in-plane retardation Re (550) of the retardation film can be set to a desired range by appropriately setting oblique stretching conditions. For example, methods for producing a retardation film having an in-plane retardation Re (550) of 100 nm to 180 nm by oblique stretching are disclosed in JP2013-54338A, JP2014-194482A, and JP2014-238524A. This is disclosed in detail in Japanese Patent Laid-Open No. 2004-194484. Therefore, those skilled in the art can set appropriate oblique stretching conditions based on the disclosure.

  The retardation film can be bonded to another optical film and used as an optical laminate. For example, the retardation film obtained by the production method of the present invention is bonded to a polarizing plate and can be suitably used as a circularly polarizing plate. The angle formed by the absorption axis of the polarizer and the slow axis of the retardation film is preferably 30 ° to 60 °, more preferably 38 ° to 52 °, still more preferably 43 ° to 47 °, and particularly preferably 45 °. Degree.

  The retardation film obtained by the production method of the present invention is long and has a slow axis in an oblique direction (for example, a direction of 45 ° with respect to the long direction). In many cases, a long polarizer has an absorption axis in the longitudinal direction or the width direction. Therefore, if the retardation film obtained by the production method of the present invention is used, a so-called roll-to-roll can be used, and a circularly polarizing plate can be produced with extremely excellent production efficiency. The roll-to-roll refers to a method of continuously laminating long films while roll-feeding the long films.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited by these Examples. In addition, the measurement and evaluation method in an Example are as follows.

(1) Thickness It was measured using a dial gauge (manufactured by PEACOCK, product name “DG-205 type pds-2”).
(2) Glass transition temperature (Tg)
It measured according to JIS K7121.

<Example 1>
(Preparation of polyester carbonate resin film)
Polymerization was carried out using a batch polymerization apparatus comprising two vertical reactors equipped with a stirring blade and a reflux condenser controlled at 100 ° C. Bis [9- (2-phenoxycarbonylethyl) fluoren-9-yl] methane 29.60 parts by mass (0.046 mol), ISB 29.21 parts by mass (0.200 mol), SPG 42.28 parts by mass (0. 139 mol), 63.77 parts by mass (0.298 mol) of DPC, and 1.19 × 10 ⁻² parts by mass (6.78 × 10 ⁻⁵ mol) of calcium acetate monohydrate as a catalyst. After the inside of the reactor was purged with nitrogen under reduced pressure, heating was performed with a heating medium, and stirring was started when the internal temperature reached 100 ° C. After 40 minutes from the start of temperature increase, the internal temperature was reached to 220 ° C., and control was performed so as to maintain this temperature. The phenol vapor produced as a by-product with the polymerization reaction was led to a reflux condenser at 100 ° C., and a monomer component contained in a small amount in the phenol vapor was returned to the reactor, and the phenol vapor not condensed was led to a condenser at 45 ° C. and recovered. Nitrogen was introduced into the first reactor and the pressure was once restored to atmospheric pressure, and then the oligomerized reaction liquid in the first reactor was transferred to the second reactor. Subsequently, the temperature increase and pressure reduction in the second reactor were started, and the internal temperature was 240 ° C. and the pressure was 0.2 kPa in 50 minutes. Thereafter, polymerization was allowed to proceed until a predetermined stirring power was obtained. When a predetermined power was reached, nitrogen was introduced into the reactor and the pressure was restored. The produced polyester carbonate was extruded into water, and the strands were cut to obtain pellets. The polyester carbonate resin obtained had a Tg of 140 ° C.

  The obtained polyester carbonate resin was vacuum-dried at 80 ° C. for 5 hours, and then a single-screw extruder (manufactured by Toshiba Machine Co., Ltd., cylinder setting temperature: 250 ° C.), T-die (width 200 mm, setting temperature: 250 ° C.), chill roll (Set temperature: 120 to 130 ° C.) and a film forming apparatus equipped with a winder were used to produce a resin film.

(Stretching)
The long polyester carbonate resin film obtained as described above was stretched obliquely using a clip-type film stretching apparatus as shown in FIGS. Each holding part of the upper gripping member and the lower gripping member of the clip attached to the stretching device had the configuration shown in FIGS. 6 (a) and 6 (b). Specifically, each pressing portion is configured to be rotatable around an axis perpendicular to the main surface of the film, and the shape in plan view is circular (φ29 mm). The diameter of the lower end of the mounting shaft was 8 mm.

A specific stretching method is as follows. First, the polyester carbonate resin film (width: 765 mm) was gripped with a clip so that the distance from the left and right edges of the film to the clip position was 30 mm at the take-in port (grip zone) of the stretching apparatus. At this time, the film was gripped so that the bottom surface of the upper gripping member and the upper surface of the lower gripping member were completely overlapped. The clip pitch of the left and right clips during gripping was 150 mm.
Subsequently, the polyester carbonate resin film (thickness 150 μm, width (W ₁ ) 765 mm) was preheated to 145 ° C. in the preheating zone B. In the preheating zone B, the clip pitch (P ₁ ) of the left and right clips was 150 mm. Next, as soon as the film entered the first oblique stretching zone C1, the clip pitch of the right clip and the clip pitch of the left clip started to increase. The rate of change of the clip pitch (P ₂ / P ₁ ) of the right clip at the end of the first oblique stretching zone C1 is 1.42, and the rate of change of the clip pitch of the left clip (P ₃ / P ₁ ) is 0. 72. The film width (W ₂ ) after the first oblique stretching was 1092 mm (TD stretching ratio (W ₂ / W ₁ ) = 1.45 times).
Next, on the film enters the second oblique stretching zone C2, and starts to increase clip pitch of the left clip, in order to increase the P ₃ to P _2, the left clip in the second diagonal drawing zone C2 clip The pitch change rate (P ₂ / P ₃ ) was set to 1.97. On the other hand, the clip pitch of the right clip was maintained at P ₂ in the second oblique stretching zone C2. Moreover, the draw ratio (W ₃ / W ₁ ) in the width direction in the first oblique stretching step and the second oblique stretching step was set to 1.9 times.
However, the film broke during the second oblique stretching process. The state of the film was observed from the exit of the stretching machine, and the MD magnification and TD magnification of the broken portion were specified based on the position where the break occurred. Based on the MD magnification and TD magnification of the broken part, and the oblique stretching ratio at the time of breakage was calculated using the above formula (1). Table 1 shows the draw ratio when the film was broken.

  Both the first oblique stretching and the second oblique stretching were performed at 142 ° C. Moreover, the breakage of the film occurred from the peripheral edge of the clip.

[Comparative Example 1]
A clip having an upper gripping member and a lower gripping member in which each pressing portion is not rotatable around an axis perpendicular to the main surface of the film, and the shape of each plan view is a rectangle (21.5 mm × 2 mm) Except having used the film extending apparatus provided with, it carried out diagonally until the film fractured like Example 1, and calculated the diagonal stretch ratio at the time of a fracture. The shape of the film gripping surface was a rectangle with a grip margin of 2 mm and a grip length of 21.5 mm. Moreover, the breakage of the film occurred from the peripheral edge of the clip. Table 1 shows the draw ratio when the film was broken.

[Comparative Example 2]
Except having used the film extending | stretching apparatus provided with the clip which has an upper holding member and a lower holding member in which each holding | suppressing part cannot rotate around the axis | shaft perpendicular | vertical with respect to the main surface of a film, it carries out similarly to Example 1. The film was stretched diagonally until the film broke, and the diagonal stretch ratio at break was calculated. The shape of the film gripping surface was a circle (φ29 mm). Moreover, the breakage of the film occurred from the peripheral edge of the clip. Table 1 shows the draw ratio when the film was broken.

<Evaluation>
As shown in Table 1, the bottom surface of the upper gripping member and the upper surface of the lower gripping member are obliquely stretched using a clip-type film stretching device configured to be rotatable about an axis perpendicular to the main surface of the film. By performing the above, the film breakage starting from the peripheral edge of the clip is suppressed, and the film can be stretched at a higher stretch ratio.

  The method for producing a stretched film of the present invention is suitably used for producing a retardation film, and as a result, can contribute to the production of an image display device such as a liquid crystal display device (LCD) or an organic electroluminescence display device (OLED). .

10L endless loop 10R endless loop 20 clip 22 lower gripping member 22a lower pressing part 22b bearing 22c mounting shaft 22d bearing 26 upper gripping member 26a upper pressing part 26b bearing 26c mounting shaft 26d bearing 28 film gripping surface 30 clip carrier 70 standard Rail 90 Pitch setting rail 100 Stretching device 200 Film

Claims (9)

A clip-type film having a variable-pitch type left and right clip that grips the left and right ends of a film to be stretched and travels through a stretching zone, and at least one of the longitudinal clip pitches changes with the travel. A stretching device,
The clip has an upper gripping member and a lower gripping member that sandwich and grip the end of the film,
A clip-type film stretching apparatus, wherein a bottom surface of the upper gripping member and an upper surface of the lower gripping member are configured to be rotatable about an axis perpendicular to the main surface of the film.   The clip-type film stretching apparatus according to claim 1, wherein the clip is held at a location separated by 20 mm or more from the edge of the film.   The length in the direction orthogonal to the running direction of the clip of the film gripping surface defined by the overlap between the bottom surface of the upper gripping member and the top surface of the lower gripping member is 15 mm or more. The clip-type film stretching apparatus as described.   The length in the running direction of the clip of the film gripping surface defined by the overlap of the bottom surface of the upper gripping member and the top surface of the lower gripping member is 20 mm or more. Clip type film stretching device.   The clip type film stretching apparatus according to any one of claims 1 to 4, wherein a shape of a bottom surface of the upper gripping member and a top surface of the lower gripping member is circular. The left and right ends of the film to be stretched are respectively held by variable-pitch left and right clips whose longitudinal clip pitch changes, the film is preheated, and the clip pitch of at least one of the left and right clips is set. A method for producing a retardation film, comprising changing the film obliquely and releasing a clip that holds the film,
The clip has an upper gripping member and a lower gripping member that sandwich and grip the end of the film,
A method for producing a retardation film, wherein the bottom surface of the upper gripping member and the top surface of the lower gripping member are rotated so as to follow the stretching direction during the oblique stretching.   The manufacturing method of the retardation film of Claim 6 performed using the clip type film extending | stretching apparatus in any one of Claim 1 to 5.   The method for producing a retardation film according to claim 6, wherein the oblique stretching includes lateral stretching. A clip body, and an upper grip member and a lower grip member that are attached to the clip body and grip the film to be gripped from above and below, respectively.
A clip in which a bottom surface of the upper gripping member and an upper surface of the lower gripping member are each configured to be rotatable about an axis perpendicular to the main surface of the film.