JP7020942B2 - Film stretching device and method for manufacturing retardation film - Google Patents

Description

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

In image display devices such as liquid crystal displays (LCDs) and organic electroluminescence display devices (OLEDs), circular polarizing plates are used for the purpose of improving display characteristics and preventing reflection. In a circular polarizing plate, typically, a polarizing element and a retardation film (typically a λ / 4 plate) form an angle of 45 ° between the absorption axis of the substituent and the slow axis of the retardation film. It is laminated in this way. Conventionally, retardation films are typically produced by uniaxial or biaxial stretching in the longitudinal and / or lateral directions, so that the slow axis is often lateral to the original film. It appears in the direction (width direction) or the vertical direction (long direction). As a result, in order to produce a circular polarizing plate, it was necessary to cut the retardation film at an angle of 45 ° with respect to the width direction or the length direction and bond them one by one.

In order to solve such a problem, the left and right ends (width direction ends) of the long film are gripped by variable pitch type left and right clips whose vertical clip pitch changes, respectively, and the left and right ends. A technique has been proposed in which the slow axis of a retardation film is expressed in an oblique direction by changing the clip pitch of at least one of the clips and stretching the clip in an oblique direction (for example, Patent Document 1). However, according to such an oblique stretching technique, the stretched film may be caught by the clip and the clip may not be released smoothly.

Patent No. 4845619

The present invention has been made to solve the above problems, and an object of the present invention is to smoothly open a clip that grips a film after the completion of diagonal stretching.

According to one aspect of the present invention, a variable pitch type that grips the left and right ends of the film to be stretched and runs through the stretch zone, and at least one of the clip pitches in the vertical direction changes with the passing run. A clip-type film stretching device having left and right clips is provided. In the clip-type film stretching device, the clip has an upper gripping member and a lower gripping member that sandwich and grip the end portion of the film, and at least the inner corner portion of the upper gripping member in the film width direction is formed. The chamfered portion has a chamfered dimension of more than 0 mm and 20 mm or less.
In one embodiment, the inner corners of the upper gripping member and the lower gripping member in the film width direction are chamfered portions having a chamfering dimension of more than 0 mm and 20 mm or less.
In one embodiment, in one of the left and right clips, the chamfered portion is formed only at the corner portion of the upper gripping member and the lower gripping member inward in the film width direction and downstream in the traveling direction. In the other clip, the chamfered portion is formed only at the corner portion of the upper gripping member and the lower gripping member inward in the film width direction and upstream in the traveling direction.
In one embodiment, the clip grips a position at a distance of 20 mm or more from the left and right edges 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 upper 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 upper surface of the lower gripping member in the traveling direction of the clip is 30 mm or more.
According to another aspect of the present invention, the left and right ends of the film to be stretched are gripped by the variable pitch type left and right clips whose vertical clip pitch changes, respectively, and the film is preheated. A method for producing a retardation film is provided, which comprises varying the clip pitch of at least one of the left and right clips to diagonally stretch the film and opening the clip holding the film. In the method for manufacturing the retardation film, the clip has an upper gripping member and a lower gripping member that sandwich and grip the end portion of the film, and at least the inner corner portion of the upper gripping member in the film width direction. However, the chamfered portion has a chamfered dimension of more than 0 mm and 20 mm or less.
In one embodiment, the method for producing a retardation film is performed using the clip-type film stretching apparatus.
In one embodiment, the method for manufacturing the retardation film is performed by using the clip-type film stretching device, and the corners of the upper gripping member and the lower gripping member are inward in the film width direction and downstream in the traveling direction. A clip having only a chamfered portion travels in advance, and a clip having only a corner portion of the upper gripping member and the lower gripping member inward in the film width direction and upstream in the traveling direction has a chamfered portion is rearward. The film is stretched diagonally by changing the clip pitch of at least one of the left and right clips so as to run in a row.
In one embodiment, the diagonal stretching comprises transverse stretching.

According to the film stretching apparatus and the method for manufacturing a retardation film of the present invention, by diagonally stretching using a clip having a chamfered portion, the film is suppressed from being caught in the clip, so that the clip can be smoothly released. be able to.

It is a schematic plan view explaining the whole structure of the stretching apparatus by one Embodiment of this invention. FIG. 3 is a schematic plan view of a main part for explaining a link mechanism for changing the clip pitch in the stretching device of FIG. 1, and shows a state where the clip pitch is the minimum. FIG. 3 is a schematic plan view of a main part for explaining a link mechanism for changing the clip pitch in the stretching device of FIG. 1, and shows a state in which the clip pitch is maximum. It is a schematic side view of the main part explaining the structure and the open state of a clip. It is a schematic side view of the main part explaining the structure and the closed state of a clip. It is a schematic diagram which shows the plan view shape of the upper gripping member or the lower gripping member which can be used in this invention. It is a schematic diagram explaining the gripping allowance and gripping length of the film gripping surface, the clip position, and the clip pitch. It is a schematic diagram explaining the manufacturing method of the retardation film in one Embodiment of this invention. It is a schematic diagram explaining an example of diagonal stretching. It is a graph which shows the relationship between each process of diagonal stretching shown in FIG. 9 and a clip pitch. It is a schematic diagram explaining the relationship between an example of diagonal stretching and the formula (1). It is a schematic diagram explaining the clip moving speed and the formula (1) of each of the left and right in an example of diagonal stretching. It is a schematic diagram explaining the clip moving speed and the equation (1) respectively on the left and right in another example of diagonal stretching. It is a schematic plan view of the main part which enlarged the end part of the stretched film in order to explain the method of measuring the neck-in amount. It is the schematic which looked at the holding state of the film edge by a clip from the horizontal direction.

A. Film Stretching Device According to one aspect of the present invention, the left and right ends (edges in the width direction) of the film to be stretched are gripped and traveled through the stretching zone, and at least one of the vertical ends is traveled along with the traveling. A clip-type film stretching apparatus is provided which has variable pitch type left and right clips in which the clip pitch in a direction is changed. Hereinafter, one embodiment of the film stretching apparatus of the present invention will be described, but the present invention is not limited to these embodiments.

An embodiment of the film stretching apparatus of the present invention will be described with reference to FIGS. 1 to 5. FIG. 1 is a schematic plan view illustrating an overall configuration of an example of the film stretching apparatus of the present invention. 2 and 3 are schematic plan views of a main part for explaining a link mechanism for changing the clip pitch in the stretching device of FIG. 1, respectively, FIG. 2 shows a state where the clip pitch is the minimum, and FIG. 3 shows a state where the clip pitch is the minimum. Indicates the maximum clip pitch. 4 and 5 are schematic side views of a main part for explaining a clip configuration and an open / closed state.

As shown in FIG. 1, the stretching device 100 has an endless loop 10L and an endless loop 10R having a large number of clips 20 for film gripping on both left and right sides symmetrically in a plan view. In the present specification, the endless loop on the left side when viewed from the inlet side of the film is referred to as the endless loop 10L on the left side, and the endless loop on the right side is referred to as the endless loop 10R on the right side. The clips 20 of the left and right endless loops 10L and 10R are guided by the reference rail 70 and circulate in a loop shape, respectively. The endless loop 10L on the left side circulates in the counterclockwise direction, and the endless loop 10R on the right side circulates in the clockwise direction. In the stretching device, a gripping zone A, a preheating zone B, a stretching zone C, and an open zone D are provided in order from the inlet side to the outlet side of the sheet. It should be noted that each of these zones means a zone in which the film to be stretched is substantially released from gripping, preheating, stretching, and clipping, and does not mean a mechanically and structurally independent section. .. Also note that the length ratio of each zone is different from the actual length ratio. Further, although not shown, a zone may be provided between the stretching zone C and the open zone D, if necessary, for performing arbitrary appropriate treatment. Examples of such a treatment include a longitudinal shrinkage treatment, a transverse stretching treatment, and the like.

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 stretched zone C, the distance between the left and right endless loops 10L and 10R gradually increases from the side of the preheating zone B toward the open zone D until the distance between the left and right endless loops 10L and 10R corresponds to the stretched width 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 stretched width of the film.

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

Further, the clip (clip on the left side) of the endless loop 10L on the left side and the clip (clip on the right side) 20 of the endless loop 10R on the right side 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 with movement. The variable pitch type configuration can be realized by adopting a known drive system such as a pantograph system, a linear motor system, or a motor chain system. Hereinafter, the link mechanism (pantograph mechanism) will be described as an example.

As shown in FIGS. 2 and 3, a clip supporting member 30 having an elongated rectangular shape in the horizontal direction in a plan view is provided to individually support the clips 20. Although not shown, the clip-supporting member 30 is formed into a strong frame structure having a closed cross section by an upper beam, a lower beam, a front wall (a wall on the clip side), and a rear wall (a wall on the opposite side of the clip). The clip-supporting 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. In addition, in FIGS. 2 and 3, the traveling wheel on the front wall side (the traveling wheel rolling on the traveling road surface 81) is 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 on the rear side (opposite side of the clip) of the upper beam and the lower beam of the clip supporting member 30 along the longitudinal direction of the clip supporting member, and the slider 32 can slide in the longitudinal direction of the elongated hole 31. Is engaged in. In the vicinity of the clip 20 side end of the clip supporting member 30, one first shaft member 33 is vertically provided so as to penetrate the upper beam and the lower beam. On the other hand, the slider 32 of the clip-supporting member 30 is provided with a second shaft member 34 vertically penetrating. One end of the main link member 35 is pivotally connected to the first shaft member 33 of each clip-supporting member 30. The other end of the main link member 35 is pivotally connected to the second shaft member 34 of the adjacent clip-supporting member 30. 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-supporting member 30. The other end of the sub-link member 36 is pivotally connected to the intermediate portion of the main link member 35 by a pivot 37. As shown in FIG. 2, the slider 32 moves to the rear side (opposite side of the clip side) of the clip supporting member 30 due to the link mechanism by the main link member 35 and the sub link member 36, and is vertically adjacent to each other. The pitch between the clip-supporting members 30 (as a result, the pitch between the supported clips) becomes smaller, and as shown in FIG. 3, the slider 32 moves to the front side (clip side) of the clip-supporting member 30. , 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, the smaller the separation distance between the reference rail 70 and the pitch setting rail 90. Since the link mechanism is well known in the art, a more detailed description thereof will be omitted.

The clip 20 grips the film 200 in a detachable manner. In the embodiment illustrated in FIGS. 4 and 5, the clip 20 includes a clip main body 21 having a substantially U-shaped vertical cross-sectional shape, and a substantially rectangular flat plate-shaped lower grip member 22 attached to the clip main body 21. It is provided with an elevating lever 24 rotatably attached to the clip main body 21 by the attachment shaft member 23, and a substantially rectangular flat plate-shaped holding portion 26a rotatably attached to the lower end of the elevating lever 24 by the attachment shaft member 25. It has an upper gripping member 26 and.

The lower gripping member 22 is fixed to the clip body 21 by any fixing method such as screw mounting, adhesion, and welding.

The upper grip member 26 moves up and down with the rotation of the elevating lever 24. Specifically, the upper gripping member 26 is lifted diagonally outward in the width direction of the film as the elevating lever 24 stands up 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 diagonally about the mounting shaft member 23, the upper gripping member 26 also descends diagonally inward in the film width direction, and the holding portion 26a and the lower gripping member 22 The end portion of the film 200 is sandwiched and gripped with (FIG. 5). Note that FIGS. 4 and 5 show a clip that grips the film by a so-called slide-in method, but unlike the illustrated example, even if the upper gripping member descends in the vertical direction to grip the film. good. Further, the upper gripping member 26 does not have to be a member separate from the elevating lever, and may be integrally formed at the lower end of the elevating lever.

In the present invention, at least the inner corner portion of the upper gripping member 26 (specifically, the pressing portion 26a) in the film width direction is the chamfered portion 26b. Preferably, as illustrated in FIGS. 4 and 5, the inner corners of the upper gripping member 26 (specifically, the holding portion 26a) and the lower gripping member 22 in the film width direction are chamfered portions 26b and 22b. It is said that. By forming the chamfered portions 26b and 22b, it is possible to prevent the film from being caught in the clip when the clip is opened. The reason why the effect is exhibited is not clear, but it is presumed as follows, for example. That is, during diagonal stretching, stress is generally likely to be concentrated on the corners of the clip (specifically, the upper gripping member and the lower gripping member), and at the inner corners in the film width direction, the film is generally stretched. Biting, deformation, etc. occur, which causes the film to flutter or get caught in the clip when the clip is opened. On the other hand, by chamfering the corners, even if the film is deformed, the clip does not bite into the film. As a result, it is considered that the film is prevented from fluttering and being caught by the clip when the clip is opened.

6 (a) to 6 (f) are schematic views showing a plan view shape of the upper gripping member or the lower gripping member that can be used in the present invention (the upper side of the drawing is inward in the film width direction). As shown in FIGS. 6A to 6F, the upper gripping member or the lower gripping member has a substantially rectangular shape in which at least one corner portion in the film width direction is chamfered portions 26b and 22b in a plan view. Has. Specifically, in the embodiment shown in FIGS. 6 (a), 6 (d) and (f), the chamfered portion is formed only at one corner in the width direction, whereas the chamfered portion is formed in the figure. In the embodiment illustrated in 6 (b) and 6 (e), chamfered portions are formed at both corners inward in the width direction. Further, a chamfered portion may be formed not only at the inner corner portion in the width direction but also at one or both corner portions outside the width direction. For example, in the embodiment shown in FIG. 6 (c), all four corners are chamfered portions.

The chamfered portions 26b and 22b may be formed linearly or curvedly. In the present specification, even when chamfering in multiple stages with a plurality of straight lines, it is assumed that the chamfer is linear. For example, the chamfered portions 26b and 22b are curved so-called R chamfered portions in the embodiments shown in FIGS. 6 (a) to 6 (c), and are shown in FIGS. 6 (d) and 6 (e). In the embodiment, it is a linear so-called C chamfered portion, and in the embodiment shown in FIG. 6 (f), it is linearly chamfered in three stages. The present invention is not limited to the above illustrated example. For example, a linear chamfered portion and a curved chamfered portion may be provided in combination. Further, one gripping member may be provided with two or more chamfered portions having different chamfer dimensions.

In one embodiment, in one of the left and right clips, only the corner portion of the upper gripping member (specifically, the holding portion) and the lower gripping member inward in the film width direction and downstream in the traveling direction. A chamfered portion is formed in the other clip, and a chamfered portion is formed only in the inner corner portion in the film width direction and the upstream side in the traveling direction of the upper gripping member (specifically, the holding portion) and the lower gripping member. To. By providing the chamfered portion asymmetrically in this way, it is possible to suitably prevent the film from fluttering and getting caught in the clip when the clip is opened, and the clip (specifically, the upper gripping member and the lower gripping member) can be prevented. ) Spontaneously exerts the effect of preventing deformation of the film, and can suppress breakage of the film due to neck-in or stretching. The effect of the clip on preventing deformation of the film will be described later.

The chamfered portions 26b and 22b are formed so that the chamfered dimensions (the length of the side cut off from the tip of the corner portion) x and y are both more than 0 mm and 20 mm or less. The chamfer dimensions x and y may be equal to or different from each other. Preferably, they are set equally to each other. When the chamfer size is large, the effect of preventing the film from being deformed by the clip is impaired, the neck-in amount tends to increase, and the film tends to break easily during stretching. Therefore, it is preferable that the chamfer size is small as long as the effect of the present invention can be obtained. For example, the chamfer dimensions x and y can be preferably 1 mm or more and 15 mm or less, more preferably 3 mm or more and 10 mm or less, and further preferably about 5 mm.

The chamfered portion is typically formed by chamfering (cutting) a target corner portion, but the forming method is not limited as long as the corner portion is a chamfered portion, for example, gold. It may be formed using a mold or a mold.

When the film is gripped, the holding portion 26a of the upper gripping member and the lower gripping member 22 may have completely overlapping outer peripheral shapes in a plan view, or may have a portion that does not overlap. When there is a non-overlapping portion, from the viewpoint of preferably obtaining the effect of the present invention, the pressing portion 26a and the lower gripping member 22 are formed on the inner end side in the film width direction and the chamfered portions at both ends thereof (corners if present). It is preferable that the outer circumferences of the portions) overlap each other so as to be at the same position in a plan view.

When gripping the film, the clips (specifically, the upper gripping member and the lower gripping member) grip the positions at a distance of preferably 20 mm or more, more preferably 25 mm or more from the left and right edges of the film. More specifically, with reference to FIG. 7, the distance D from the end edge of the film 200 to the innermost part of the film gripping surface 28 in the film width direction (hereinafter, also referred to as “clip position”) is preferably 20 mm or more. Grasp the film. By gripping such a position with a clip, breakage of the film is suppressed. Further, as a result of suppressing neck-in, a uniformly stretched region is expanded, so that the effect of widening the effective area can be obtained. The upper limit of the distance from the edge of the film to the clip position can be, for example, 60 mm. In the present specification, the film gripping surface means a film surface sandwiched between the upper gripping member 26 (specifically, the holding portion 26a) and the lower gripping member 22, and is the upper side when the film is gripped. It is defined by the overlap between the bottom surface of the gripping member 26 and the upper surface of the lower gripping member 22. The clip position can be controlled, for example, by adjusting the distance between the reference rails.

As shown in FIG. 7, the length of the film gripping surface 28 in the traveling direction of the clip (the direction in which the reference rail extends) is defined as the gripping length (L), and the length of the film gripping surface 28 in the direction orthogonal to the traveling direction of the clip. When the gripping allowance (W) is taken as a gripping allowance (W), the gripping allowance (W) is preferably 15 mm or more, more preferably 20 mm or more, still more preferably 25 mm or more. The gripping allowance (W) can be, for example, 60 mm or less. On the other hand, 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. The grip length (L) can be, for example, 80 mm or less. By setting the gripping allowance or gripping length in such a range, the film gripping surface becomes a wide surface, so that stress concentration on the clip peripheral edge is relaxed and breakage of the film is suppressed. Further, the clip (specifically, the upper gripping member and the lower gripping member) acts like a wall that prevents the film from being deformed, and can suppress neck-in.

Further, the gripping ratio represented by the following formula is preferably 50% or more. The grip ratio is more preferably 70% or more, still more preferably 80% or more, and even more preferably 90% or more. When the gripping ratio is within such a range, breakage and neck-in of the film can be suppressed. Further, it is possible to prevent the film from being caught by the clip and deformed or broken when the clip is opened.
Gripping ratio (%) = Gripping allowance / distance from film edge to clip position x 100

B. Method for manufacturing a retardation film According to another aspect of the present invention, the left and right ends of the film to be stretched are gripped by the variable pitch type left and right clips whose clip pitches in the vertical direction change (grasping step). ), Preheating the film (preheating step), changing the clip pitch of at least one of the left and right clips to diagonally stretch the film (diagonal stretching step), and opening the clip holding the film. A method of manufacturing a retardation film is provided, including the process of doing (opening step). In the method for manufacturing the retardation film, a clip having an upper gripping member and a lower gripping member that sandwiches and grips the end portion of the film is used, and at least the inner corner portion of the upper gripping member in the film width direction is formed. The chamfered portion has a chamfered dimension of more than 0 mm and 20 mm or less. Preferably, the inner corner portion of the upper gripping member and the lower gripping member in the film width direction is the chamfered portion. The chamfer size may be preferably 1 mm or more and 15 mm or less, more preferably 3 mm or more and 10 mm or less, and further preferably about 5 mm. According to the method for manufacturing a retardation film, the film is suppressed from being caught in the clip when the clip is opened, so that the retardation having a slow axis in an oblique direction (for example, a direction of 45 ° with respect to the vertical direction). The film can be produced efficiently.

The method for producing the retardation film is preferably performed by using the stretching apparatus according to the above item A. Hereinafter, each step will be described in detail by taking the embodiment using the stretching device according to the above item A as a specific example. In the present specification, the "longitudinal clip pitch" (sometimes referred to simply as "clip pitch") is the distance between the centers in the traveling direction of vertically adjacent clips (more specifically, the distance between the centers in the traveling direction). It means the distance between the centers in the traveling direction of the film gripping surface), and is the distance represented by P in FIG. 7.

[B-1. Gripping process]
First, in the gripping zone A (the entrance of the film take-in of the stretching device 100), the films to be stretched are clipped at both ends of the left and right endless loops 10L and 10R by clips 20 having the same constant clip pitch or each other. It is gripped at different clip pitches. The clip pitches of the left and right clips in the gripping process can be appropriately set according to a desired phase difference, axial angle, and the like. The clip pitch can be, for example, 50 mm to 180 mm. In the present specification, the edge of the film means a region of 10% of the entire width of the film from the edge of the film.

The clip position in the gripping 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 (edges in the width direction) of the long film. 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 suppressed. Further, as a result of suppressing neck-in, a uniformly stretched region is expanded, so that the effect of widening the effective area can be obtained.

Further, it is preferable that the film gripping surface is a wide surface. By making the film gripping surface wide, stress concentration on the clip is relaxed and breakage of the film is suppressed. In addition, the clip acts like a wall that prevents deformation of the film, and neck-in can be suppressed. Specifically, as described in the above item A, the gripping allowance (W) by the clip is preferably 15 mm or more, more preferably 20 mm or more, still more preferably 25 mm or more, and can be, for example, 60 mm or less. The grip length (L) can be, 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 for example, 80 mm or less.

While the film is held by the clip, the left and right endless loops 10L and 10R move (substantially, the movement of each clip-carrying member guided by the reference rail 70) without lateral stretching or vertical stretching. ) Sends to the preheating zone B.

[B-2. Preheating process]
In 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 as described above, and thus are basically laterally stretched. 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 the film bending due to preheating and contact with the nozzle in the oven.

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

The temperature raising time up to the temperature T1 and the holding time at the temperature T1 can be appropriately set according to the constituent materials of the film and the manufacturing conditions (for example, the transport speed of the film). These temperature rise 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.

[Diagonal stretching process]
In the stretching zone C, the film is stretched diagonally by changing the clip pitch in the vertical direction of at least one of the left and right clips 20. More specifically, by changing the clip pitch in the vertical direction of at least one of the left and right clips 20 while traveling through the extension zone C, one clip is driven ahead and the other clip is run backward. The film is stretched diagonally. Typically, the end portion of the stretching zone C, that is, the rate of change in the clip pitches of the left and right clips at the end of diagonal stretching (clip pitch at the end of diagonal stretching / clip pitch before diagonal stretching) is substantially equal to each other.

In one embodiment, as shown in FIG. 8, a clip having a chamfered portion formed only at a corner portion of the upper gripping member and the lower gripping member inward in the film width direction and downstream in the traveling direction (left clip in the illustrated example). ) Leads, and a clip (right clip in the illustrated example) having a chamfered portion formed only at the corners of the upper gripping member and the lower gripping member inward in the film width direction and upstream in the traveling direction is run backward. By forming chamfered portions at these corners where the stress concentration is higher than that of the other corners, not only the effect of the present invention is suitably obtained, but also the other corners are maintained, and as a result, the film is formed. The deformation preventing effect is also maintained, and breakage of the film due to neck-in or stretching can be suitably suppressed.

Diagonal stretching may or may not include transverse stretching. For example, as shown in the illustrated example, it may be performed while increasing the distance between the left and right clips (distance in the width direction), or unlike the illustrated example, it is performed while maintaining the distance between the left and right clips. You may. Preferably, the diagonal stretch comprises a transverse stretch.

When the oblique stretching includes lateral stretching, the ratio of the lateral (TD) stretching ratio (the ratio of the width W _final of the film after diagonal stretching to the initial width W _initial of the film (W _final / W _initial ) is preferably 1.05. It is about 6.00, more preferably 1.10 to 5.00.

In one embodiment, the oblique stretching differs 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. This can be done by increasing or decreasing the clip pitch of each clip to a predetermined pitch while in position. For the diagonal stretching of the embodiment, for example, the description of Patent Document 1, Japanese Patent Application Laid-Open No. 2014-238524, etc. can be referred to.

In another embodiment, oblique stretching increases or decreases the clip pitch of the other clip to a predetermined pitch while keeping the clip pitch of one of the left and right clips fixed, and then increases or decreases the original clip pitch. Can be done by returning to. For the diagonal stretching of the embodiment, for example, the description of JP-A-2013-54338, JP-A-2014-194482, etc. can be referred to.

In yet another embodiment, oblique stretching (i) increases the clip pitch of one of the left and right clips while decreasing the clip pitch of the other clip, and (ii) the decrease. This can be done by changing the clip pitch of each clip so that the clip pitch and the expanded clip pitch have a predetermined equal pitch. For the diagonal stretching of the embodiment, for example, the description in JP-A-2014-194484 can be referred to. In the oblique stretching of the embodiment, the film is stretched diagonally by increasing the clip pitch of one clip and decreasing the clip pitch of the other clip while increasing the distance between the left and right clips (the first). 1), and while increasing the distance between the left and right clips, the clip pitch of one clip is maintained or reduced so that the clip pitches of the left and right clips are equal, and the clip pitch of the other clip is maintained or reduced. Increasing the clip pitch of the clip may include diagonally stretching the film (second diagonal stretching step).

In the first diagonal stretching step, the film is stretched diagonally while stretching one side edge portion in the longitudinal direction and contracting the other side edge portion in the longitudinal direction, thereby performing diagonal stretching in a desired direction (for example,). It is possible to develop a slow axis with high uniaxiality and in-plane orientation (in the direction of 45 ° with respect to the longitudinal direction). Further, in the second diagonal stretching step, by performing diagonal stretching while reducing the difference between the left and right clip pitches, it is possible to sufficiently stretch in the diagonal direction while alleviating excess stress. Further, since the film can be subjected to the opening process in a state where the moving speeds of the left and right clips are equal, the film transport speed and the like are less likely to vary when the left and right clips are opened, and the subsequent winding of the film is preferable. Can be done in.

Hereinafter, an example of diagonal stretching of the embodiment will be specifically described with reference to FIGS. 9 and 10. _First , in the preheating zone B, the left and right clip pitches are both set to P1. P ₁ is typically a clip pitch when the film is gripped. Next, as soon as the film enters the first diagonally stretched zone C1, the clip pitch of one clip (on the right side in the illustrated example) starts to increase, and the clip pitch of the other clip (on the left side in the illustrated example) begins to increase. Start decreasing. _In the _first diagonally stretched zone C1, the clip pitch of the right clip is increased to P2 and the clip pitch of the left clip is decreased to P3. Therefore, at the end of the first diagonally stretched zone C1 (the start of the _second diagonally stretched zone C2), the left clip moves at the clip pitch _P3 and the right clip moves at the clip pitch P2. ing. The clip pitch ratio can roughly correspond to the clip moving speed ratio. Therefore, the ratio of the clip pitches of the left and right clips can roughly correspond to the ratio of the stretching ratios of the right side edge portion and the left side edge portion of the film in the vertical direction (MD direction).

In FIGS. 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 set as the start portions of the first diagonally stretched zone C1, but unlike the illustrated example, they are different from the illustrated examples. The clip pitch of the left clip may begin to decrease after the clip pitch of the right clip begins to increase, or 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, the clip pitch of the clip on one side begins to increase and then 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, even if the clip pitch on the other side is greatly reduced. Wrinkles are less likely to occur. Therefore, it is possible to stretch diagonally at an acute angle, and a retardation film having high uniaxial and in-plane orientation can be preferably 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 decrease until the end of the first oblique extension zone C1 (the start of the second oblique extension zone C2). However, unlike the illustrated example, either the increase or decrease of the clip pitch ends before the end of the first diagonally stretched zone C1 and clips to the end of the first diagonally stretched zone C1. The pitch may be maintained as it is.

The rate of change in the increased clip pitch (P ₂ / P ₁ ) is preferably 1.05 to 1.75, more preferably 1.10 to 1.70, and even more preferably 1.15 to 1.65. .. The rate of change in clip pitch (P ₃ / P ₁ ) that decreases 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. It is 0.55 to 0.90. When the rate of change of the clip pitch is within such a range, the slow axis can be developed with high uniaxial and in-plane orientation in the direction of approximately 45 degrees with respect to the longitudinal direction of the film.

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

The stretching ratio (W ₂ / W ₁ ) in the width direction of the film in the first diagonal stretching step is preferably 1.05 to 3.0 times, more preferably 1.1 times to 2.5 times, still more preferable. Is 1.15 to 2.0 times. If the draw ratio is less than 1.05 times, galvanized iron-like wrinkles may occur on the side edge portion on the contracted side. Further, if the draw ratio exceeds 3.0 times, the biaxiality of the obtained retardation film becomes high, and the viewing angle characteristics may deteriorate when applied to a circular polarizing plate or the like.

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

Subsequently, as soon as the film enters the second diagonally stretched zone C2, it begins to increase the clip pitch of the left clip. In the _second diagonally stretched zone C2, the clip pitch of the left clip is increased to P2. On the other hand, the clip pitch of the right clip is maintained at P2 in the _second diagonally stretched zone C2. Therefore, at the end of the second diagonally stretched zone C2 (the start of the open zone D), _both the left clip and the right clip are supposed to move at the clip pitch P2.

The rate of change in the clip pitch (P ₂ / P ₃ ) that increases is not limited as long as the effect of the present invention is 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, in the first diagonal stretching and the second diagonal stretching, the diagonal stretching ratio S obtained from the following formula (1) is, for example, 1.5 or more, preferably 2.0 or more, more preferably 2.0 or more. It is carried out so as to be 2.0 to 4.0, more preferably 2.5 to 3.5. If the diagonal draw ratio is less than 1.5, the biaxiality may be high or the in-plane orientation may be low.

（式中、
Ｗ_１は、第１の斜め延伸前のフィルム幅、
Ｗ_３は、第２の斜め延伸後のフィルム幅、
ｖ３’は、第１の斜め延伸工程でクリップピッチを増大させる方のクリップに関して、該クリップのクリップピッチが第２の斜め延伸工程で所定のクリップピッチに変化した際のクリップ移動速度、
t３は、第１の斜め延伸工程でクリップピッチを減少させる方のクリップが、予熱ゾーンに入ってから、第２の斜め延伸工程が終了するまでの時間、
t３’は、第１の斜め延伸工程でクリップピッチを増大させる方のクリップが、予熱ゾーンに入ってから、第２の斜め延伸工程が終了するまでの時間
を表す。）

(During the ceremony,
W ₁ is the film width before the first diagonal stretching,
W ₃ is the film width after the second diagonal stretching,
v3'is the clip moving speed when the clip pitch of the clip is changed to a predetermined clip pitch in the second diagonal stretching step with respect to the clip whose clip pitch is increased in the first diagonal stretching step.
t3 is the time from when the clip whose clip pitch is reduced in the first diagonal stretching step enters the preheating zone to the end of the second diagonal stretching step.
t3'represents the time from when the clip whose clip pitch is increased in the first diagonal stretching step enters the preheating zone to the end of the second diagonal stretching step. )

With respect to the above v3', the predetermined clip pitch is the clip pitch when the clip pitch whose increase is completed in the first diagonal stretching step is maintained in the second diagonal stretching step (described with reference to FIGS. 9 and 10). It means the clip pitch after (corresponding to P ₂ in) or decreased. Further, regarding the clip whose clip pitch is increased in the first diagonal stretching step, the clip pitch of the clip becomes a predetermined clip pitch in the _first diagonal stretching step (P2 in the description using FIGS. 9 and 10). If the moving speed of the clip when changed to (corresponding) is v2',
When v2'= v3', the above t3 is expressed by the following equation (2), and the above t'3 is expressed by the following equation (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, equations (2) to (5) will be described. In the explanation of each symbol in the formula, FIGS. 11 to 13 can be referred to. The asterisk mark (*) in the equations (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.

（式中、
ａ１＝（ｖ２－ｖ３）／（Ｌ２－Ｌ３）、
ｂ１＝ｖ３－ａ１＊Ｌ３、
ａ＝（ｖ１－ｖ２）／（Ｌ１－Ｌ２）、
ｂ＝ｖ２－ａ＊Ｌ２であり、
ｖ１は、第１の斜め延伸工程でクリップピッチを減少させる方のクリップが予熱ゾーンを通過する際のクリップ移動速度、
ｖ２は、第１の斜め延伸工程でクリップピッチを減少させる方のクリップに関して、該クリップのクリップピッチが第１の斜め延伸工程で所定のクリップピッチ（図９および図１０を用いた説明におけるＰ_３に対応する）に減少した際のクリップ移動速度、
ｖ３は、第１の斜め延伸工程でクリップピッチを減少させる方のクリップに関して、該クリップのクリップピッチが第２の斜め延伸工程で所定のクリップピッチ（図９および図１０を用いた説明におけるＰ_２に対応する）に増大した際のクリップ移動速度であり、
Ｌ１は、予熱ゾーン入口から、第１の斜め延伸工程でクリップピッチを減少させる方のクリップがクリップピッチを減少し始めるまでの距離（１つの実施形態においては、予熱ゾーン入口から予熱ゾーン出口までの距離）、
Ｌ２は、予熱ゾーン入口から、第１の斜め延伸工程でクリップピッチを減少させる方のクリップがクリップピッチを増大し始める箇所までの距離（１つの実施形態においては、予熱ゾーン入口から第１の斜め延伸ゾーン出口までの距離）、
Ｌ３は、予熱ゾーン入口から、第１の斜め延伸工程でクリップピッチを減少させる方のクリップがクリップピッチを増大し終わる箇所までの距離（１つの実施形態においては、予熱ゾーン入口から第２の斜め延伸ゾーン出口までの距離）
である。）

(During the ceremony,
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 diagonal stretching step passes through the preheating zone.
In v2, regarding the clip whose clip pitch is reduced in the first diagonal stretching step, the clip pitch of the clip is a predetermined clip pitch in the first diagonal stretching step (P3 in the description using FIGS. ₉ and 10). (Corresponding to)) Clip movement speed when reduced,
In v3, regarding the clip whose clip pitch is reduced in the first diagonal stretching step, the clip pitch of the clip is a predetermined clip pitch in the _second diagonal stretching step (P2 in the description using FIGS. 9 and 10). Corresponds to), which is the clip movement speed when increased.
L1 is the distance from the preheating zone inlet to the clip whose clip pitch is reduced in the first diagonal stretching step starts to reduce the clip pitch (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 reduces the clip pitch in the first diagonal stretching step begins to increase the clip pitch (in one embodiment, the first diagonal from the preheating zone inlet). Distance to the extension zone exit),
L3 is the distance from the preheating zone inlet to the point where the clip that reduces the clip pitch in the first diagonal stretching step finishes increasing the clip pitch (in one embodiment, the second diagonal from the preheating zone inlet). Distance to the extension zone exit)
Is. )

（式中、
ａ’＝（ｖ１’－ｖ２’）／（Ｌ１’－Ｌ２’）、
ｂ’＝ｖ３’－ａ’＊Ｌ２’であり、
ｖ１’は、第１の斜め延伸工程でクリップピッチを増大させる方のクリップが予熱ゾーンを通過する際のクリップ移動速度、
ｖ２’は、第１の斜め延伸工程でクリップピッチを増大させる方のクリップに関して、該クリップのクリップピッチが第１の斜め延伸工程で所定のクリップピッチ（図９および図１０を用いた説明におけるＰ_２に対応する）に増大した際のクリップ移動速度、
ｖ３’は、第１の斜め延伸工程でクリップピッチを増大させる方のクリップに関して、該クリップが第２の斜め延伸ゾーンを通過する際のクリップ移動速度であり、
Ｌ１’は、予熱ゾーン入口から、第１の斜め延伸工程でクリップピッチを増大させる方のクリップがクリップピッチを増大し始めるまでの距離（１つの実施形態においては、予熱ゾーン入口から予熱ゾーン出口までの距離）、
Ｌ２’は、予熱ゾーン入口から、第１の斜め延伸工程でクリップピッチを増大させる方のクリップがクリップピッチを増大し終わる箇所までの距離（１つの実施形態においては、予熱ゾーン入口から第１の斜め延伸ゾーン出口までの距離）、
Ｌ３’は、予熱ゾーン入口から、第２の斜め延伸ゾーン出口までの距離
である。）

(During the ceremony,
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 diagonal stretching step passes through the preheating zone.
In v2', with respect to the clip whose clip pitch is increased in the first diagonal stretching step, the clip pitch of the clip is a predetermined clip pitch in the first diagonal 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 diagonal stretching zone with respect to the clip whose clip pitch is increased in the first diagonal stretching step.
L1'is the distance from the preheating zone inlet to the clip whose clip pitch is increased in the first diagonal stretching step starts to increase the clip pitch (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 diagonal stretching step finishes increasing the clip pitch (in one embodiment, the first from the preheating zone inlet). Distance to the diagonal extension zone exit),
L3'is the distance from the entrance of the preheating zone to the exit of the second diagonal extension zone. )

（式中、ａ１、ｂ１、ａ、ｂ、ｖ１、ｖ２、ｖ３、Ｌ１、Ｌ２およびＬ３は、式（２）に関して定義したとおりである。）

(In the formula, a1, b1, a, b, v1, v2, v3, L1, L2 and L3 are as defined with respect to the formula (2).)

（式中、
ａ’＝（ｖ１’－ｖ２’）／（Ｌ１’－Ｌ２’）、
ｂ’＝ｖ２’－ａ’＊Ｌ２’、
ａ’’＝（ｖ２’－ｖ３’）／（Ｌ２’－Ｌ３’）、
ｂ’’＝ｖ３’－ａ’’＊Ｌ３’であり、
ｖ１’は、第１の斜め延伸工程でクリップピッチを増大させる方のクリップが予熱ゾーンを通過する際のクリップ移動速度、
ｖ２’は、第１の斜め延伸工程でクリップピッチを増大させる方のクリップに関して、該クリップのクリップピッチが第１の斜め延伸工程で所定のクリップピッチ（図９および図１０を用いた説明におけるＰ_２に対応する）に増大した際のクリップ移動速度、
ｖ３’は、第１の斜め延伸工程でクリップピッチを増大させる方のクリップに関して、該クリップのクリップピッチが第２の斜め延伸工程で所定のクリップピッチに減少した際のクリップ移動速度であり、
Ｌ１’は、予熱ゾーン入口から、第１の斜め延伸工程でクリップピッチを増大させる方のクリップがクリップピッチを増大し始める箇所までの距離（１つの実施形態においては、予熱ゾーン入口から予熱ゾーン出口までの距離）、
Ｌ２’は、予熱ゾーン入口から、第１の斜め延伸工程でクリップピッチを増大させる方のクリップがクリップピッチを増大し終わる箇所までの距離（１つの実施形態においては、予熱ゾーン入口から第１の斜め延伸ゾーン出口までの距離）、
Ｌ３’は、予熱ゾーン入口から、第１の斜め延伸工程でクリップピッチを増大させる方のクリップが第２の斜め延伸工程でクリップピッチを所定のクリップピッチに減少し終わる箇所までの距離（１つの実施形態においては、予熱ゾーン入口から第２の斜め延伸ゾーン出口までの距離）である。）

(During the ceremony,
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 diagonal stretching step passes through the preheating zone.
In v2', with respect to the clip whose clip pitch is increased in the first diagonal stretching step, the clip pitch of the clip is a predetermined clip pitch in the first diagonal 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 a predetermined clip pitch in the second diagonal stretching step with respect to the clip whose clip pitch is increased in the first diagonal stretching step.
L1'is the distance from the preheating zone inlet to the point where the clip that increases the clip pitch in the first diagonal stretching step starts to increase the clip pitch (in one embodiment, from the preheating zone inlet to the preheating zone outlet). Distance to),
L2'is the distance from the preheating zone inlet to the point where the clip that increases the clip pitch in the first diagonal stretching step finishes increasing the clip pitch (in one embodiment, the first from the preheating zone inlet). Distance to the diagonal extension zone exit),
L3'is the distance from the inlet of the preheating zone to the point where the clip that increases the clip pitch in the first diagonal stretching step finishes reducing the clip pitch to a predetermined clip pitch in the second diagonal stretching step (one). In the embodiment, it is the distance from the entrance of the preheating zone to the exit of the second diagonal extension zone). )

Diagonal stretching can typically be done 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 about Tg, with respect to the glass transition temperature (Tg) of the resin film. Although it depends on the resin 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 temperature T1 and the temperature T2 is preferably ± 2 ° C. or higher, more preferably ± 5 ° C. or higher. In one embodiment, T1> T2, so the film heated to temperature T1 in the preheating zone can be cooled to temperature T2.

The longitudinal shrinkage treatment and the transverse stretching treatment are performed after diagonal stretching. For these treatments after diagonal stretching, paragraphs 0029 to 0032 of JP-A-2014-194483 can be referred to.

[Opening process]
Finally, the clip that grips the film is opened to obtain a retardation film. Usually, the clip is released after cooling the film to Tg or less. If necessary, the film is heat treated to fix the stretched state, cooled and then the clip is released.

The heat treatment can typically be performed at temperature T3. The temperature T3 depends on the film to be stretched, and may be T2 ≧ T3 or T2 <T3. Generally, 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. When T2 ≧ T3, the difference between the temperatures T2 and T3 (T2-T3) is preferably 0 ° C to 50 ° C. The heat treatment time is typically 10 seconds to 10 minutes.

After opening the clip, the film can be rolled up by cutting the clip gripping portions at both ends.

C. A film to be stretched and a retardation film obtained by stretching Examples of a film preferably used in the production method of the present invention include any suitable elongated film that can be used as a retardation film. The width of the film to be stretched is, 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. Examples include based resins. Preferably, it is a polycarbonate resin, a polyvinyl acetal resin, a cellulose ester resin, a polyester resin, or a polyester carbonate resin. This is because with these resins, a retardation film showing so-called reverse dispersion wavelength dependence can be obtained. These resins may be used alone or in combination according to desired characteristics.

As the polycarbonate-based resin, any suitable polycarbonate-based resin is used. 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, and 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-hydroxyethoxy) -3-methylphenyl) fluorene, 9,9-bis (4- (2-hydroxyethoxy) -3-isopropylphenyl) fluorene, 9,9-bis ( 4- (2-Hydroxyethoxy) -3-isobutylphenyl) fluorene, 9,9-bis (4- (2-hydroxyethoxy) -3-tert-butylphenyl) fluorene, 9,9-bis (4- (2) -Hydroxyethoxy) -3-cyclohexylphenyl) fluorene, 9,9-bis (4- (2-hydroxyethoxy) -3-phenylphenyl) fluorene, 9,9-bis (4- (2-hydroxyethoxy) -3 , 5-Dimethylphenyl) fluorene, 9,9-bis (4- (2-hydroxyethoxy) -3-tert-butyl-6-methylphenyl) fluorene, 9,9-bis (4- (3-hydroxy-2) , 2-Dimethylpropoxy) phenyl) fluorene and the like. In addition to the structural units derived from the above dihydroxy compounds, 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. You may be.

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, which may cause a dimensional change after film molding. If the glass transition temperature is excessively high, the molding stability during film molding may be deteriorated, and the transparency of the film may be impaired. The glass transition temperature is determined according to JIS K 7121 (1987).

As the polyvinyl acetal resin, any suitable polyvinyl acetal resin can be used. Typically, the polyvinyl acetal resin can be obtained by subjecting at least two kinds of aldehyde compounds and / or ketone compounds to a condensation reaction with a polyvinyl alcohol-based resin. Specific examples and detailed production methods of the polyvinyl acetal resin are described in, for example, Japanese Patent Application Laid-Open No. 2007-161994. This 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 maximized (that is, the slow phase axis direction), and ny is the in-plane direction orthogonal to the slow phase axis (that is, phase advance). It is the refractive index in the axial direction), and nz is the refractive index in the thickness direction. Re (λ) is an in-plane phase difference of the film measured with light having a wavelength of λ nm at 23 ° C. Therefore, Re (550) is the in-plane phase difference of the film measured with light having a wavelength of 550 nm at 23 ° C. Re (λ) is obtained 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 the diagonal stretching conditions. For example, methods for producing a retardation film having an in-plane retardation Re (550) of 100 nm to 180 nm by diagonal stretching are described in JP2013-54338, JP2014-194482, and JP2014-238524. It is disclosed in detail in Japanese Patent Application Laid-Open No. 2014-194484 and the like. Therefore, those skilled in the art can set appropriate diagonal 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 can be suitably used as a circular polarizing plate by being bonded to a polarizing plate. The angle formed by the absorption axis of the splitter 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). Also, in many cases, the elongated polarizing element has an absorption axis in the elongated direction or the width direction. Therefore, if the retardation film obtained by the production method of the present invention is used, so-called roll-to-roll can be used, and a circularly polarizing plate can be produced with extremely excellent production efficiency. Note that roll-to-roll refers to a method of continuously laminating long films by aligning their long directions while transporting them in a roll.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples. The measurement and evaluation methods in the examples are as follows.

(1) Thickness Measured using a dial gauge (manufactured by PEACOCK, product name "DG-205 type pds-2").
(2) Glass transition temperature (Tg)
It was measured according to JIS K 7121.
(3) Neck-in amount As shown in FIG. 14, the distance (mm) from the clip position to the neck-in valley portion was measured at five points on each of the left and right edges, and the average value was taken as the neck-in amount. ..

<Example 1>
(Preparation of polyester carbonate resin film)
Polymerization was carried out using a batch polymerization apparatus consisting of 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 were charged as a catalyst. After substituting nitrogen under reduced pressure in the reactor, heating was performed with a heat medium, and stirring was started when the internal temperature reached 100 ° C. The internal temperature was brought to 220 ° C. 40 minutes after the start of the temperature rise, and the depressurization was started at the same time as controlling to maintain this temperature, and the temperature was 13.3 kPa 90 minutes after reaching 220 ° C. The phenol vapor produced by the polymerization reaction was guided to a reflux condenser at 100 ° C., the monomer component contained in a small amount in the phenol vapor was returned to the reactor, and the non-condensed phenol vapor was guided to a condenser at 45 ° C. for recovery. Nitrogen was introduced into the first reactor and the pressure was once restored to atmospheric pressure, and then the oligomerized reaction solution in the first reactor was transferred to the second reactor. Then, the temperature rise and depressurization in the second reactor were started, and the internal temperature was 240 ° C. and the pressure was 0.2 kPa in 50 minutes. Then, the polymerization was allowed to proceed until the stirring power became a predetermined value. When the predetermined power was reached, nitrogen was introduced into the reactor to repressurize, the produced 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.

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

(Stretching)
The elongated polyester carbonate resin film obtained as described above was obliquely stretched using a clip-type film stretching device as shown in FIGS. 1 to 5. Both the upper gripping member (specifically, the holding portion thereof) and the lower gripping member of the clip attached to the stretching device have an R chamfered portion having a chamfering dimension of 5 mm at two inner corners in the film width direction. It was formed into a rectangular flat plate shape, and had the same plan view shape (planar view shape as shown in FIG. 6B).

The specific stretching method is as follows. First, the polyester carbonate resin film (width: 765 mm) was clipped at the intake port (grip zone) of the stretching device so that the distance (D) from the left and right edges of the film to the clip position was 30 mm. At this time, as shown in FIG. 15A, the film was gripped so that the bottom surface of the upper gripping member and the upper surface of the lower gripping member completely overlapped each other. The clip pitch of the left and right clips at the time of gripping was 150 mm. The gripping allowance of the film gripping surface was 30 mm, and the gripping length was 45 mm.
Next, 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 diagonally stretched zone C1, it started to increase the clip pitch of the right clip and decrease the clip pitch of the left clip. The rate of change in the clip pitch of the right clip (P ₂ / P ₁ ) at the end of the first diagonally stretched zone C1 is 1.42, and the rate of change in the clip pitch of the left clip (P ₃ / P ₁ ) is 0. It was .72. The film width (W ₂ ) after the first diagonal stretching was 1092 mm (TD stretching ratio (W ₂ / W ₁ ) = 1.45 times).
Next, as soon as the film enters the second diagonally stretched zone C2, the clip pitch of the left clip in the _second diagonally stretched zone C2 is clipped in order to start increasing the clip pitch of the left clip and increase from _P3 to P2. The rate of change in pitch (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 diagonally stretched zone C2. Further, the stretching ratio (W ₃ / W ₁ ) in the width direction in the first diagonal stretching step and the second diagonal stretching step was set to 1.9 times.
However, the film broke during the second diagonal stretching step. The state of the film was observed from the outlet of the stretching machine, and the MD magnification and the TD magnification of the fractured portion were specified based on the position where the fracture occurred. When the diagonal stretching ratio at the time of breaking was calculated based on the MD magnification and the TD magnification of the fractured portion and using the above formula (1), it was 2.43 times. Both the first diagonal stretching and the second diagonal stretching were performed at 142 ° C.
Then, in the open zone, the film was held at 125 ° C. for 60 seconds for heat fixation. After cooling the heat-fixed film to 100 ° C., the left and right clips were opened.

Next, the amount of neck-in immediately before fracture was determined as follows.
The right clip in the first diagonal stretching zone C1 so that the diagonal stretching ratio at the end of the diagonal stretching step is 0.01 times smaller than the diagonal stretching ratio at the time of breaking (that is, 2.42 times). Diagonal stretching was performed in the same manner as above except that the clip pitch P ₂ of the left clip in the clip pitch P ₂ and the second diagonal stretching zone C2 was adjusted (that is, P ₁ , P ₃ , and 1). Or, there is no change in the stretching ratio in the width direction in the second diagonal stretching). As a result, a diagonally stretched film was obtained without causing breakage. The obtained diagonally stretched film was used as a film immediately before breaking, and the neck-in amount thereof was measured as the neck-in amount immediately before breaking.

<Example 2>
In the same manner as in Example 1 except that the chamfering dimensions of the upper gripping member and the lower gripping member are set to 10 mm, diagonal stretching is performed until the film breaks to calculate the diagonal stretching ratio at the time of breaking, and at the time of breaking. A film just before the break was prepared based on the diagonal stretch ratio of the above, and the neck-in amount just before the break was obtained.

<Example 3>
The upper gripping member and the lower gripping member of the right clip are provided with R chamfered portions only at the corners inward in the film width direction and downstream in the traveling direction, and the upper gripping member and the lower gripping member of the left clip are provided with the film width direction. In the same manner as in Example 1 except that the R chamfered portion is provided only at the corner portion on the inner side and the upstream side in the traveling direction, the film is diagonally stretched until it breaks, and the diagonal stretch ratio at the time of breaking is calculated. A film immediately before fracture was prepared based on the diagonal stretch ratio at the time of fracture, and the neck-in amount immediately before fracture was determined.

<Example 4>
In the same manner as in Example 1 except that the chamfering dimensions of the upper gripping member and the lower gripping member are set to 15 mm, diagonal stretching is performed until the film breaks to calculate the diagonal stretching ratio at the time of breaking, and at the time of breaking. A film just before the break was prepared based on the diagonal stretch ratio of the above, and the neck-in amount just before the break was obtained.

<Example 5>
In the same manner as in Example 1 except that the chamfering dimensions of the upper gripping member and the lower gripping member are set to 20 mm, diagonal stretching is performed until the film breaks to calculate the diagonal stretching ratio at the time of breaking, and at the time of breaking. A film just before the break was prepared based on the diagonal stretch ratio of the above, and the neck-in amount just before the break was obtained.

<Comparative Example 1>
The film was formed in the same manner as in Example 1 except that the upper gripping member and the lower gripping member were not provided with the R chamfered portion (as a result, the film gripping surface is a rectangle having a gripping length of 45 mm and a gripping allowance of 30 mm). The film was diagonally stretched until it broke to calculate the diagonal stretch ratio at the time of rupture, and a film immediately before the rupture was prepared based on the diagonal stretch ratio at the time of rupture to determine the neck-in amount immediately before the rupture.

<Comparative Example 2>
It does not have an R chamfer and uses upper and lower gripping members of different dimensions (as a result, the film gripping surface is a rectangle with a gripping length of 21.5 mm and a gripping allowance of 2 mm). As shown in FIG. 15B, in the same manner as in Example 1 except that the film is gripped with a clip so that the distance (D) from the edge of the film to the clip position is 15 mm, until the film breaks. Diagonal stretching was performed to calculate the diagonal stretching ratio at the time of breaking, and a film immediately before breaking was prepared based on the diagonal stretching ratio at the time of breaking, and the neck-in amount immediately before breaking was obtained.

≪Evaluation of clip open state≫
In the production of the retardation films of the above Examples and Comparative Examples, the case where 100 or more clips can be continuously opened without being caught by the film is evaluated as "good", and the case where the film is caught by the clips one or more times. Was evaluated as "bad". The results are shown in Table 1 together with the draw ratio and the neck-in amount when the film is broken.

<Evaluation>
As shown in Table 1, in the embodiment in which the chamfered portion is formed at the inner corner portion of the left and right clips in the film width direction, the stretched film could be released without being caught by the clip. Further, it can be seen that the smaller the chamfer size, the more preferably the reduction of the neck-in amount and the realization of a high draw ratio are compatible. Further, a chamfered portion is formed only in the corner portion of the clip traveling in the preceding direction inward in the film width direction and downstream in the traveling direction, and the chamfered portion is formed only in the corner portion of the clip traveling in the trailing direction inward in the film width direction and upstream side in the traveling direction. By forming the portion, it is possible to achieve both a reduction in the amount of neck-in and a high draw ratio at a higher level.

The method for manufacturing a retardation film of the present invention is suitably used for manufacturing a retardation film, and as a result, contributes to the manufacture of an image display device such as a liquid crystal display device (LCD) and an organic electroluminescence display device (OLED). obtain.

10L Endless loop 10R Endless loop 20 Clip 22 Lower gripping member 22b Chamfering part 26 Upper gripping member 26a Holding part 26b Chamfering part 28 Film gripping surface 30 Clip supporting member 70 Reference rail 90 Pitch setting rail 100 Stretching device 200 Film

Claims (6)

A clip-type film having variable-pitch type left and right clips that grips the left and right ends of the film to be stretched and runs through the stretch zone, and at least one of the vertical clip pitches changes with the passing run. It is a stretching device
The clip has an upper gripping member and a lower gripping member that sandwich and grip the end of the film.
The upper gripping member and the lower gripping member have a rectangular shape in a plan view.
In one of the left and right clips, the chamfered portion having a chamfering dimension of more than 0 mm and 20 mm or less is a corner portion of the upper gripping member and the lower gripping member inward in the film width direction and downstream in the traveling direction. In the other clip, the chamfered portion having a chamfering dimension of more than 0 mm and 20 mm or less is a corner portion of the upper gripping member and the lower gripping member inward in the film width direction and upstream in the traveling direction. Is formed only in
When gripping the film with the clip, the inner end side of the upper gripping member and the lower gripping member in the film width direction and the outer periphery of the chamfered portion or the corner portion at both ends thereof are at the same position in a plan view. Clip-type film stretching device that overlaps like this. The clip-type film stretching apparatus according to claim 1 , wherein the clip grips a position at a distance of 20 mm or more from the left and right edges of the film. According to claim 1 or 2 , the length of the film gripping surface defined by the overlap between the bottom surface of the upper gripping member and the upper surface of the lower gripping member in the direction orthogonal to the traveling direction of the clip is 15 mm or more. The clip-type film stretching apparatus according to the above. The invention according to any one of claims 1 to 3 , wherein the length of the film gripping surface defined by the overlap between the bottom surface of the upper gripping member and the upper surface of the lower gripping member in the traveling direction of the clip is 30 mm or more. Clip-type film stretching device. The left and right ends of the film to be stretched are gripped by the variable pitch type left and right clips whose clip pitches change in the vertical direction, respectively, the film is preheated, and at least one of the left and right clips has a clip pitch. A method of making a retardation film, comprising varying and diagonally stretching the film and opening a clip that grips the film.
This is performed using the clip-type film stretching apparatus according to claim 1.
The film with the clip so that the inner end edges of the upper gripping member and the lower gripping member in the film width direction and the outer circumferences of the chamfered portions or corner portions at both ends thereof overlap at the same position in a plan view. Grasp and
A clip having the chamfered portion only at the corner portion of the upper gripping member and the lower gripping member inward in the film width direction and downstream in the traveling direction travels in advance, and the upper gripping member and the lower gripping member The film is stretched diagonally by changing the clip pitch of at least one of the left and right clips so that the clip whose chamfered portion is only the corner portion inward in the film width direction and upstream in the traveling direction travels backward. A method for manufacturing a retardation film. The method for producing a retardation film according to claim 5 , wherein the diagonal stretching includes lateral stretching.

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