JP7079364B1 - Method for manufacturing stretched film and method for manufacturing optical laminate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique for reducing a deviation of an orientation angle which may occur over time in continuous production of a long diagonally stretched film. SOLUTION: The left and right ends of a long film in the width direction are gripped by left and right clips of a variable pitch type in which the clip pitch in the vertical direction is changed, the film is preheated, and the left and right clips are used. To stretch the film diagonally, heat-fix the film, release the film from the left and right clips, and to move the film while changing the clip pitch of at least one of the clips. Including measuring the orientation angle, when the deviation of the orientation angle from the set value exceeds a predetermined reference, the left and right clips are held between the time when the film is gripped by the left and right clips and the time when the film is released. A method for producing a stretched film, which comprises shifting the phase of at least one of the films. [Selection diagram] Fig. 1

Description

The present invention relates to a method for producing a stretched film and a method for producing an optical laminate.

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. Traditionally, retardation films are typically made by uniaxial or biaxial stretching in the longitudinal and / or lateral directions, so that the slow axis is often a long film. It appears in the horizontal direction (width direction) or vertical direction (long direction) of the original fabric. 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.

Further, in order to secure the wide bandwidth of the circularly polarizing plate, two retardation films, a λ / 4 plate and a λ / 2 plate, may be laminated. In that case, the λ / 2 plates are laminated so as to form an angle of 75 ° with respect to the absorber absorption axis, and the λ / 4 plates are laminated so as to form an angle of 15 ° with respect to the absorber absorption axis. There is a need. Even in this case, when producing the circular polarizing plate, it was necessary to cut the retardation film so as to form an angle of 15 ° and 75 ° with respect to the width direction or the length direction and bond them one by one. ..

In yet another embodiment, in order to prevent the light from the notebook PC from being reflected on the keyboard or the like, the direction of the linear polarization emitted from the polarizing plate is rotated by 90 ° on the visual side of the polarizing plate. A λ / 2 plate may be used. Even in this case, 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 the films one by one.

In order to solve such a problem, the left and right ends of the long film in the width direction are gripped by the left and right clips of the variable pitch type in which the clip pitch in the vertical direction changes, respectively, and at least the left and right clips are held. A technique has been proposed in which the slow axis of the retardation film is expressed in the diagonal direction by changing one of the clip pitches and stretching in the diagonal direction with respect to the long direction (hereinafter, also referred to as "diagonal stretching"). (For example, Patent Document 1). However, when the diagonally stretched film is continuously produced by such a technique, the orientation angle may deviate from a desired value over time.

On the other hand, Patent Document 2 proposes a technique for preventing the deviation of the orientation angle with time in the continuous production by braking the moving speeds of the left and right clips and controlling them to be constant. On the other hand, there is still a demand for an alternative technique that can solve the problem of the deviation of the orientation angle over time.

Japanese Patent No. 4845619 JP-A-2015-206994

A main object of the present invention is to provide a technique for preventing the deviation of the orientation angle that may occur over time in the continuous production of a long diagonally stretched film.

According to one aspect of the present invention, the left and right ends of the long film in the width direction are gripped by the left and right clips of the variable pitch type in which the clip pitch in the vertical direction changes, respectively, to preheat the film. That, moving the left and right clips while changing the clip pitch of at least one of the clips to stretch the film diagonally, thermally fixing the film, and releasing the film from the left and right clips. , And measuring the orientation angle of the film, and when the deviation of the orientation angle with respect to the set value exceeds a predetermined reference, from gripping the film with the left and right clips to opening. Provided is a method for producing a stretched film, which comprises shifting the phase of at least one of the left and right clips.
According to one embodiment, the constant speed rotating sprocket is engaged with the link mechanism that changes the clip pitch to shift the phase of at least one of the left and right clips.
According to one embodiment, in the thermal fixation, at least one of the left and right clips is out of phase.
According to one embodiment, the amount of phase shift when shifting the phase is 0.1 mm to 3.0 mm.
According to _one embodiment, the oblique stretching (i) increases the clip pitch of _one of the left and right clips from P1 to P2 while increasing the clip pitch of the _other clip from P1. It involves reducing to P3 and ₍ ii) changing the clip pitch of each clip so that the reduced clip pitch and the increased clip pitch are at predetermined equal pitches.
According to one embodiment, P ₂ / P ₁ is 1.25 to 1.75 and P ₃ / P ₁ is 0.50 or more and less than 1.
According to one embodiment, when the orientation angle deviates in the width direction beyond the predetermined reference, the phase of the clip on one side is advanced and / or the clip on the other side is shifted. Delays the phase of.
According to one embodiment, if the orientation angle deviates in the longitudinal direction beyond the predetermined reference, the clip on one side is phased out and / or the other side. Advance the phase of the clip.
According to another aspect of the present invention, the elongated stretched film is obtained by the above-mentioned manufacturing method, and the elongated optical film and the elongated stretched film are conveyed in the elongated direction thereof. A method for manufacturing an optical laminate is provided, which comprises aligning and continuously laminating the two.
In one embodiment, the optical film is a polarizing plate and the stretched film is a λ / 4 plate or a λ / 2 plate.

According to the embodiment of the present invention, in the continuous production of a long diagonally stretched film, the left and right clips that grip the film upstream of the production line when the orientation angle shifts beyond a predetermined reference over time. Change the phase of at least one of them. As a result, the relative positional relationship between the left and right clips can be changed without changing the diagonal stretching conditions such as the clip pitch profile, rail pattern, and heating temperature, and as a result, the deviation of the orientation angle is prevented. However, it is possible to continuously produce a long diagonally stretched film.

It is a schematic plan view explaining the whole structure of the example of the stretching apparatus which can be used in the manufacturing method of the stretched film of this invention. FIG. 3 is a schematic plan view of a main part for explaining a link mechanism for changing a clip pitch in the stretching device of FIG. 1. FIG. 3 is a schematic plan view of a main part for explaining a link mechanism for changing a clip pitch in the stretching device of FIG. 1. It is a schematic diagram which shows the profile of the clip pitch in one embodiment of diagonal stretching. It is a schematic diagram which shows the profile of the clip pitch in one embodiment of diagonal stretching. It is a schematic diagram explaining the method of measuring an orientation angle. It is a schematic diagram explaining the method of shifting the phase of a clip. It is the schematic sectional drawing of the circular polarizing plate using the retardation film obtained by the manufacturing method of this invention.

Hereinafter, preferred embodiments of the present invention will be described, but the present invention is not limited to these embodiments. In addition, in this specification, "the clip pitch in the vertical direction" means the distance between the centers in the traveling direction of the clip adjacent in the vertical direction. Further, the left-right relationship in the width direction of the long film means the left-right relationship in the transport direction of the film unless otherwise specified.

A. Method for Producing Stretched Film The method for producing a stretched film according to the embodiment of the present invention is as follows.
Gripping the left and right edges of the long film in the width direction with variable-pitch type left and right clips that change the clip pitch in the vertical direction (grip process).
Preheating the film (preheating step),
Running and moving the left and right clips while changing the clip pitch of at least one clip to diagonally stretch the film (diagonal stretching step).
Heat fixing the film (heat fixing step),
Releasing the film from the left and right clips (opening step), and
Including measuring the orientation angle of the film (alignment angle measuring step).
When the deviation of the orientation angle with respect to the set value exceeds a predetermined reference, the phase of at least one of the left and right clips is shifted between the time when the film is gripped by the left and right clips and the time when the film is released (phase). Shifting process), including.

A-1. Stretching device In the method for producing a stretched film according to the embodiment of the present invention, for example, the left and right ends of the film to be stretched are gripped and passed through a preheating zone, a stretching zone, and a heat fixing zone in this order, and each of them moves in a traveling manner. It has variable pitch type left and right clips whose vertical clip pitch changes accordingly, and in the stretch zone, the left and right clips are moved while changing the clip pitch of at least one clip to move the film. Using a film stretching device that is configured to stretch diagonally and comprises at least one means of changing the phase of at least one of the left and right clips between the zone that grips the film and the heat-fixing zone. Can be done.

Examples of the stretching device include endless left and right reference rails that pass through the preheating zone, stretching zone, and heat fixing zone in this order, left and right pitch setting rails provided along the left and right reference rails, and the like. A plurality of left and right clip-supporting members that are guided by the left and right reference rails and travel, and left and right clips that are supported by the left and right clip-supporting members and grip the left and right ends of the elongated film to be stretched, respectively. It has a driving means for applying a traveling force to the clip-supporting member, and a link mechanism configured so that the pitch between the clip-supporting members can be adjusted by the separation distance between the reference rail and the pitch setting rail. Examples thereof include a film stretching apparatus having a constant speed rotating sprocket that engages with at least one of the left and right clip-supporting members as a means for changing the phase.

FIG. 1 is a schematic plan view illustrating an overall configuration of an example of a stretching device that can be used in the manufacturing method of the present invention. In the stretching device 100, a gripping zone A, a preheating zone B, a stretching zone C, a heat fixing zone D, and an opening zone E are provided in this order from the inlet side to the outlet side of the film. Each of these zones means a zone in which the film to be stretched is substantially gripped, preheated, diagonally stretched, heat-fixed and opened, and does not mean a mechanically or structurally independent section. Also note that the length ratio of each zone in the stretching device of FIG. 1 is different from the actual length ratio.

Although not shown in FIG. 1, a zone for performing arbitrary appropriate treatment may be provided between the stretching zone C and the heat fixing zone D, if necessary. Examples of such treatment include lateral shrinkage treatment and the like. Similarly, although not shown, the stretching device is typically a heating device for setting a heating environment from the preheating zone B to the heat fixing zone D or the open zone E (for example, hot air type, near red). It is equipped with various ovens such as external type and far infrared type.

The stretching device 100 has endless left and right reference rails 10L and 10R symmetrically on both the left and right sides in a plan view. The stretching device 100 further carries the pitch setting rails 20L and 20R provided on the inner peripheral side of the left and right reference rails 10L and 10R, and the clip 40, and is guided by the left and right reference rails 10L and 10R to move. It further includes a plurality of left and right clip-supporting members 30L and 30R, and driving means (driving sprocket in the illustrated example) 50L and 50R for applying running force to the left and right clip-supporting members 30L and 30R. In the present specification, the reference rail on the left side when viewed from the entrance side of the film is referred to as the reference rail 10L on the left side, and the reference rail on the right side is referred to as the reference rail 10R on the right side. The clip-supporting members 30L and 30R that support the clip 40 are guided by the reference rails 10L and 10R and circulate in a loop. Specifically, the clip-supporting member 30L guided by the left reference rail 10L (as a result, the clip (left clip) 40 supported by the clip-supporting member) circulates in the counterclockwise direction, and the right reference. The clip-supporting member 30R guided by the rail 10R (as a result, the clip (right clip) 40 supported by the clip-supporting member) circulates in the clockwise direction.

In the gripping zone A and the preheating zone B of the stretching device 100, the left and right reference rails 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 separation distance between the left and right reference rails 10L and 10R gradually increases from the side of the preheating zone B toward the heat fixing zone D until the distance between the left and right reference rails 10L and 10R corresponds to the stretched width of the film. In the heat fixing zone D and the open zone E, the left and right reference rails 10L and 10R are configured to be substantially parallel to each other at a separation distance corresponding to the stretched width of the film. However, the configurations of the left and right reference rails 10L and 10R are not limited to the above illustrated example. For example, the left and right reference rails 10L and 10R may be configured to be substantially parallel to each other at a separation distance corresponding to the initial width of the film to be stretched from the grip zone A to the open zone E.

The left clip 40 and the right clip 40 are configured to be able to patrol independently. Specifically, the clip supporting members 30L and 30R are provided with drive rollers 39 that can be selectively engaged with the drive sprockets 50L and 50R, and the drive rollers 39 are rotationally driven by the electric motors 60L and 60R. By selectively engaging with the 50L and 50R, a running force is given to the clip supporting members 30L and 30R. Therefore, the drive sprocket 50L for the left reference rail 10L is rotationally driven in the counterclockwise direction, and the drive sprocket 50R for the right reference rail 10R is rotationally driven in the clockwise direction, so that the left clip is counterclockwise. It patrolls in the clockwise direction, and the right clip patrolls in the clockwise direction. By adjusting the output of the electric motor to change the traveling force transmitted from the drive sprocket to the clip-supporting member, the traveling speed of the left and right clip-supporting members (as a result, the traveling speed of the left and right clips) becomes independent. Can be controlled to any value. Further, on the film inlet side, clip position adjusting sprockets 52L and 52R for simultaneously adjusting the timing of film gripping by the clips are arranged, and are rotationally driven by the electric motors 62L and 62R, respectively. Does not affect the running speed of the clip. Note that, unlike the illustrated example, the drive sprocket may be arranged on the film inlet side.

Further, the left clip-supporting member (resulting in the left clip) and the right clip-supporting member (resulting in the right clip) are of variable pitch type, respectively. That is, the left and right clip-carrying members (as a result, the left and right clips) can independently change the clip pitch in the vertical direction with movement. The variable pitch type configuration can be realized by adopting a link mechanism configured so that the pitch between the clip-supporting members can be adjusted by the separation distance between the reference rail and the pitch setting rail. Hereinafter, an example of the link mechanism (pantograph mechanism) will be described.

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, FIG. 2 shows a state where the clip pitch is the minimum, and FIG. 3 shows a clip. Indicates the maximum pitch.

As shown in FIGS. 2 and 3, the clip supporting member 30 is provided in an elongated rectangular shape in the horizontal direction in a plan view, and the clips 40 are individually supported at one end in the longitudinal direction. 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 10 over the entire area. A long hole 31 is formed along the longitudinal direction of the clip-supporting member on the rear side of the upper beam and the lower beam of the clip-supporting member 30 (the opposite side of the clip side (hereinafter referred to as the anti-clip side)), and the slider 32 is long. It is slidably engaged in the longitudinal direction of the hole 31. In the vicinity of the clip 40 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. Although not shown, a guide roller is rotatably provided at the lower end of the first shaft member 33, and the guide roller is engaged with a concave groove provided in the reference rail 10. Further, a drive roller 39 is rotatably provided at the upper end of the first shaft member 33. On the other hand, the slider 32 of the clip-supporting member 30 is provided with a second shaft member 34 vertically penetrating. Although not shown, a pitch setting roller is rotatably provided at the lower end of the second shaft member 34, and the pitch setting roller is engaged with a concave groove provided in the pitch setting rail 20. 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, as the slider 32 moves to the rear side (anti-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, the clip-supporting members 30 are vertically aligned with each other. The pitch in the direction (as a result, the clip pitch) becomes smaller, and as shown in FIG. 3, the more the slider 32 moves to the front side (clip side) of the clip supporting member 30, the more the clip supporting members 30 are in the vertical direction. The pitch (as a result, the clip pitch) increases. Positioning of the slider 32 is performed by the pitch setting rail 20. As shown in FIGS. 2 and 3, the smaller the separation distance between the reference rail 10 and the pitch setting rail 20, the larger the clip pitch.

Further, in the preheating zone B, the stretching device 100 is driven by constant speed rotation drive by means 54L, 54R (in the illustrated example, electric motors 64L, 64R) for changing the phases of the left and right clips 40 at the same position in the transport direction. Has a fast-rotating sprocket). The constant-speed rotary sprocket 54L on the left side and the constant-speed rotary sprocket 54R on the right side are each configured to be able to arbitrarily change the phase of rotation (phase of the teeth of the sprocket), and are linked mechanisms that change the clip pitch. By engaging with (in the illustrated example, by engaging with a clip-bearing member, more specifically, a drive roller of the clip-bearing member), the phase of the clip can be aligned with the phase of rotation. Therefore, for example, while the phase of rotation of the left constant speed rotating sprocket 54L and the phase of the clip supporting member 30L (resulting in the left clip) are aligned, the phase of rotation of the right constant speed rotating sprocket 54R and the clip supporting member 30R are aligned. By shifting the phase of (as a result, the right clip), the phase of the right clip can be shifted without changing the phase of the left clip after the engagement between each sprocket and the clip supporting member. Further, for example, the phase of rotation of the left constant-speed rotating sprocket 54L and the phase of the left clip, and the phase of rotation of the right constant-speed rotating sprocket 54R and the phase of the right clip are shifted by different amounts. The phases of the left and right clips after engagement can be shifted independently.

Unlike the illustrated example, the means for changing the phase of the clip may be provided only for either the right clip or the left clip. Further, the place where the means for changing the phase of the clip is provided is not limited to the preheating zone. At least one means for changing the phase of the clip is provided in at least one zone selected from the preheating zone, the stretching zone and the heat fixing zone. A means for changing the phase of two or more clips may be provided in one zone, or one may be provided in each of two or more zones. Preferably, the means for changing the phase of the clip is provided in the heat-fixed zone.

Hereinafter, each step will be described in detail.

A-2. Gripping step In the gripping zone A (the entrance of the film take-in of the stretching device 100), typically, the left and right end portions of the film to be stretched are clipped at a predetermined clip pitch by the clips 40 of the left and right endless loops 10L and 10R. Grasp them in phase, that is, at a constant clip pitch equal to each other. At this time, the line connecting the centers of the left and right clips is typically substantially orthogonal to the film transport direction (for example, 90 ° ± 3 °, preferably 90 ° ± 1 °, more preferably 90 ° ±). 0.5 °, even more preferably 90 °). The clip pitch of the left and right clips at the time of gripping is, for example, 100 mm to 200 mm, preferably 125 mm to 175 mm, and more preferably 140 mm to 160 mm.

The film is fed to the preheating zone B by the movement of the left and right clips (substantially, the movement of each clip supporting member guided by the left and right reference rails 10L and 10R).

A-3. Preheating step In the preheating zone B, the left and right reference rails 10L and 10R are basically 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. The film is heated without lateral or 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 the preheating step, 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 raising time and holding time can be controlled by adjusting the moving speed of the clip 40, the length of the preheating zone, the temperature of the preheating zone, and the like.

A-4. Diagonal stretching step In the stretching zone C, the left and right clips 40 are run and moved while changing the clip pitch in the vertical direction of at least one of the clips, and the film is diagonally stretched. More specifically, moving the left and right clips while increasing or decreasing the clip pitch at different positions, or moving the left and right clips while changing (increasing and / or decreasing) the clip pitch at different speeds of change. The film is stretched diagonally by such means. As a result of running and moving the left and right clips while changing the clip pitch in this way, one of the pair of left and right clips simultaneously transferred to the stretching zone reaches the end of the stretching zone prior to the other clip. .. According to such diagonal stretching, the leading end of the clip side is stretched at a higher stretching ratio than the trailing end of the clip side, and as a result, the desired direction of the long film is obtained. The slow axis can be expressed (for example, in the direction of 45 ° with respect to the longitudinal direction).

Diagonal stretching may include transverse stretching. In this case, the diagonal stretching can be performed while increasing the distance between the left and right clips (distance in the width direction), for example, as shown in FIG. Alternatively, unlike the configuration shown in FIG. 1, it can be performed while maintaining the distance between the left and right clips.

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 W initial 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 from P ₁ to P ₂ , while increasing the clip pitch of the other clip from P ₁ to P ₃ . It can be done by reducing to, and (ii) changing the clip pitch of each clip so that the reduced clip pitch and the increased clip pitch are at predetermined equal pitches. For the diagonal stretching of the embodiment, for example, the description in JP-A-2014-194484 can be referred to. Diagonal stretching of the embodiment increases the clip pitch of one clip from P ₁ to P ₂ while increasing the distance between the left and right clips, while reducing the clip pitch of the other clip from P ₁ to P ₃ . Then, while stretching the film diagonally (first diagonal stretching) and increasing the distance between the left and right clips, the clip pitch of one of the clips is set to P so that the clip pitches of the left and right clips are equal. It may include diagonally stretching the film _{( second} diagonal stretching) by maintaining at ₂ or reducing to P4 and increasing the clip pitch of the other clip to P2 or _P4 .

In the first diagonal stretching, the film is stretched in a desired direction (for example, length) by stretching one end of the film in the elongated direction and contracting the other end in the elongated direction. It is possible to develop a slow axis with high uniaxiality and in-plane orientation (in the direction of 45 ° with respect to the shaku direction). Further, in the second diagonal stretching, by performing the diagonal stretching while reducing the difference between the left and right clip pitches, it is possible to sufficiently stretch in the diagonal direction while relaxing the extra stress.

In the diagonal stretching of the above three embodiments, the film can be released from the clips in a state where the moving speeds of the left and right clips are equal, so that the film transport speed and the like are less likely to vary when the left and right clips are opened. Subsequent winding of the film can be preferably performed.

4A and 4B are schematic views showing an example of the clip pitch profile in the diagonal stretching including the first diagonal stretching and the second diagonal stretching, respectively. Hereinafter, the first diagonal stretching will be specifically described with reference to these figures. In FIGS. 4A and 4B, the horizontal axis corresponds to the mileage of the clip. At the start of the _first diagonal stretching, the left and right clip pitches are both P1. P ₁ is typically a clip pitch when the film is gripped. At the same time as the first diagonal stretching is started, the clip pitch of one clip (hereinafter, may be referred to as the first clip) is started to be increased, and the other clip (hereinafter, the second clip) is started. (Sometimes referred to as) begins to reduce the clip pitch. In the first diagonal stretching, the clip pitch of the _first clip is increased to P2 and the clip pitch of the _second clip is decreased to P3. Therefore, at the end of the first diagonal stretching (at the beginning of the second diagonal stretching), the _second clip moves at the clip pitch P3 and the _first clip moves at the clip pitch P2. ing. The clip pitch ratio can roughly correspond to the clip moving speed ratio.

In FIGS. 4A and 4B, the timing at which the clip pitch of the first clip starts to increase and the timing at which the clip pitch of the second clip starts to decrease are both set as the start of the first diagonal stretching. Unlike, the clip pitch of the second clip may start to decrease after starting to increase the clip pitch of the first clip, and the clip pitch of the first clip may start to decrease after starting to decrease the clip pitch of the second clip. You may start increasing. In one preferred embodiment, the clip pitch of the first clip is started to be increased and then the clip pitch of the second clip is started to be decreased. 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 of the second clip 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. 4A and 4B, the clip pitch of the first clip continues to increase and the clip pitch of the second clip continues to decrease until the end of the first diagonal stretching (at the beginning of the second diagonal stretching). However, unlike the illustrated example, either the increase or decrease of the clip pitch ends earlier than the other, and the clip pitch is maintained as it is until the other ends (until the end of the first diagonal stretching). May be done.

The rate of change in the clip pitch (P ₂ / P ₁ ) of the first clip is preferably 1.25 to 1.75, more preferably 1.30 to 1.70, and even more preferably 1.35 to 1.65. Is. The rate of change in the clip pitch (P ₃ / P ₁ ) of the second clip is, for example, 0.50 or more and less than 1, preferably 0.50 to 0.95, and more preferably 0.55 to 0.90. More preferably, it is 0.55 to 0.85. 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 stretch ratio in the width direction of the film in the first diagonal stretching (film width at the end of the first diagonal stretching / film width before the first diagonal stretching) is preferably 1.1 times to 3.0 times, more. It is preferably 1.2 times to 2.5 times, more preferably 1.25 times to 2.0 times. If the draw ratio is less than 1.1 times, galvanized iron-like wrinkles may occur at the end 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 oblique stretching, the product of the rate of change in the clip pitch of the first clip and the rate of change in the clip pitch of the second clip is preferably 0.7 to 1.5. It is preferably 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.

Next, one embodiment of the second diagonal stretching will be specifically described with reference to FIG. 4A. In the _second diagonal stretching of the present embodiment, the clip pitch of the _second clip is increased from P3 to P2. On the other hand, the clip pitch of the first clip is maintained at P2 during the _second diagonal stretching. Therefore, at the end of the _second diagonal stretching, both the left and right clips are supposed to move at the clip pitch P2.

The rate of change in the clip pitch (P ₂ / P ₃ ) of the second clip in the second diagonal stretching of the embodiment shown in FIG. 4A 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, 1.3 to 4.0, preferably 1.5 to 3.0.

Another embodiment of the second diagonal stretching will be specifically described with reference to FIG. 4B. In the second diagonal stretching of the present embodiment, the clip pitch of the first clip is decreased and the clip pitch of the second clip is increased. Specifically, the clip pitch of the first clip is decreased from P ₂ to P ₄ , and the clip pitch of the second clip is increased from P ₃ to P ₄ . Therefore, at the end of the second diagonal stretching, both the left and right clips are supposed to move at the clip pitch _P4 . In the illustrated example, the clip pitch of the first clip is decreased and the clip pitch of the second clip is increased at the same time as the start of the second diagonal stretching, but these can be started at different timings. .. Similarly, the decrease in the clip pitch of the first clip and the increase in the clip pitch of the second clip may end at different timings.

The rate of change in the clip pitch of the first clip (P ₄ / P ₂ ) and the rate of change in the clip pitch of the second clip (P ₄ / P ₃ ) in the second diagonal stretching of the embodiment shown in FIG. 4B are There is no limitation as long as the effect of the present invention is not impaired. The rate of change (P ₄ / P ₂ ) is, for example, 0.4 or more and less than 1.0, preferably 0.6 to 0.95. The rate of change (P ₄ / P ₃ ) is, for example, more than 1.0 and 2.0 or less, preferably 1.2 to 1.8. Preferably, P ₄ is P ₁ or higher. If P ₄ <P ₁ , problems such as wrinkles at the ends and high biaxiality may occur.

The stretching ratio in the width direction of the film in the second diagonal stretching (film width at the end of the second diagonal stretching / film width at the end of the first diagonal stretching) is preferably 1.1 times to 3.0 times. It is more preferably 1.2 times to 2.5 times, still more preferably 1.25 times to 2.0 times. If the draw ratio is less than 1.1 times, galvanized iron-like wrinkles may occur at the end 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. Further, the stretching ratio in the width direction in the first diagonal stretching and the second diagonal stretching (film width at the end of the second diagonal stretching / film width before the first diagonal stretching) is determined from the same viewpoint as above. It is preferably 1.2 times to 4.0 times, and more preferably 1.4 times to 3.0 times.

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 film. Although it depends on the film used, the temperature T2 is, for example, 70 ° C. to 180 ° C., preferably 80 ° C. to 170 ° C. The difference (T1-T2) between the 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.

As described above, lateral shrinkage treatment may be performed after diagonal stretching. For the treatment after the diagonal stretching, paragraphs 0029 to 0032 of JP-A-2014-194483 can be referred to.

A-5. Heat fixing step In the heat fixing zone D, the diagonally stretched film is heat-treated. In the heat-fixing zone D, neither lateral stretching nor longitudinal stretching is normally performed, but if necessary, the clip pitch in the longitudinal direction may be reduced to relieve stress.

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. The heat treatment time can be controlled by adjusting the length of the heat treatment zone and / or the transport rate of the film.

A-6. Opening Step The film is released from the clip at an arbitrary position in the opening zone E. In the open zone E, the film is usually cooled to a desired temperature without performing lateral stretching or longitudinal stretching on the heat-fixed film, and then the film is released from the clip. The film temperature when released from the clip is, for example, 150 ° C. or lower, preferably 70 ° C. to 140 ° C., and more preferably 80 ° C. to 130 ° C.

The stretched film released from the clip is sent out from the outlet of the stretching device and is used for measuring the orientation angle.

A-7. Orientation angle measurement step In one embodiment, the orientation angle (angle with respect to the elongated direction) is measured in-line while the film fed from the outlet of the stretching device is transported by roll. At this time, the difference between the measured orientation angle and the set value as the target orientation angle (| measured orientation angle-target orientation angle |) is defined as the deviation of the orientation angle. The deviation of the orientation angle is measured, for example, at the center of the film in the width direction. Further, the difference between the maximum value and the minimum value of the orientation angle measured at a plurality of points in the width direction can be used as the variation of the orientation angle.

For example, in the embodiment shown in FIG. 5, in the transport line, the measuring device 2 is provided above the center portion in the width direction and the left and right end portions of the film 1, and the orientation angles of the transported film are fixed points at three points in the width direction. I'm measuring. The measurement points may be different from those shown in the illustrated example. For example, a total of two points, one of the center portion in the width direction and one of the left and right edges of the film, or a total of two points of only the left and right edges, or the width. It can be 2 places, 3 places, 4 places, 5 places or more at equal intervals in the direction. Preferably, the orientation angle is measured at two or more points including at least one of the central portion in the width direction and the left and right edges (for example, the distance from the left and right edges is within 25 mm).

The orientation angle may be measured continuously or at predetermined intervals. For example, the orientation angle can be measured at intervals of 0.1 seconds to 1.0 seconds, preferably 0.1 seconds to 0.5 seconds.

The measurement wavelength of the orientation angle can be appropriately set according to the purpose. For example, the measurement wavelength of the orientation angle can be in the range of 500 nm to 600 nm.

The measurement of the orientation angle may be performed after cutting and removing the left and right ends in the width direction of the stretched film released from the clip. By measuring the orientation angle with both ends removed, more accurate measurement results can be obtained.

The widths of the edges to be cut and removed can be independently, for example, 20 mm to 600 mm, preferably 100 mm to 500 mm. Cutting and removal of the end portion can be performed by ordinary slit processing.

A-8. Phase shift step In the above measurement, when the deviation of the measured orientation angle with respect to the target orientation angle (set value) exceeds a predetermined reference, at least one of the left and right clips is shifted in phase. By shifting the phase of at least one of the left and right clips, the relative positional relationship of the left and right clips changes from the previous positional relationship, resulting in the same effect as changing the clip pitch of at least one of the left and right clips. Can be obtained. Therefore, according to the manufacturing method according to the embodiment of the present invention, the deviation of the orientation angle can be easily suppressed by shifting the phase of the clip without changing the rail pattern of the pitch setting rail one by one. When the deviation of the orientation angle is equal to or less than a predetermined reference, the stretched film can be continued to be produced under the same conditions as before without changing the phases of the left and right clips.

In one embodiment, the phase of the clip is changed when the deviation of the orientation angle is, for example, 6 ° or more, 5 ° or more, or 4 ° or more.

The timing of shifting the phase may be any timing from gripping the film with the left and right clips to releasing the film. In one embodiment, it is preferable to shift the phase at least once from the preheating step to the heat fixing step, and it is more preferable to shift the phase in the heat fixing step from the viewpoint of film shrinkage uniformity. In one embodiment, it is preferable to shift the phase in the first half of the heat fixing step, and it is more preferable to shift the phase immediately after the start.

In the phase shift step, at least one of the left and right clips may be out of phase. As long as the effect of the present invention is obtained, there is no limitation on how to shift the phase of either clip (that is, whether to advance or delay). Therefore, for example, as shown in FIG. 6A, the phase of the right clip 40 may be advanced without changing the phase of the left clip 40, and as shown in FIG. 6B, the phase of the right clip 40 may be advanced. The phase of the left clip 40 may be delayed without changing the phase, or the phase of the left clip 40 may be delayed and the phase of the right clip 40 may be advanced as shown in FIG. 6 (c). In the figure, the arrow indicates the transport direction of the film 1, and the clip 40'indicated by the dotted line indicates the position of the clip when the phase is not changed.

The amount of phase shift (S) can be appropriately set according to the degree of shift and variation in the orientation angle. The amount of phase shift (S) can be, for example, 0.1 mm to 3.0 mm, preferably 0.3 mm to 2.5 mm, and more preferably 0.5 mm to 2.0 mm. The amount of phase shift when the phases of the left and right clips are shifted in opposite directions (for example, FIG. 6C) is the sum of the amounts of phase shift of each clip, and the phases of the left and right clips are the same as each other. The amount of phase shift when shifted in the direction is the difference in the amount of phase shift of each clip.

For example, if the measured orientation angle is offset in the width direction beyond a predetermined reference, the leading clip in the stretch zone may be out of phase, the trailing clip may be out of phase, or these. Depending on the combination of, the phase of the left and right clips can be shifted. Also, for example, if the measured orientation angle deviates in the longitudinal direction beyond a predetermined reference, the phase of the clip on the leading side in the stretching zone is delayed, the phase of the clip on the trailing side is advanced, or the phase is advanced. , By these combinations, the phase of the left and right clips can be shifted.

The amount of phase shift can be adjusted, for example, by changing the phase of rotation of the constant speed rotating sprocket.

In one embodiment, the orientation angle is continuously measured during the production of the stretched film, and the phase of the left and right clips is shifted each time the deviation of the orientation angle exceeds a predetermined reference. Can be suppressed.

B. Film to be stretched In the production method of the present invention, any suitable film can be used. For example, a resin film applicable as a retardation film can be mentioned. Examples of the material constituting such a film include polycarbonate resin, polyvinyl acetal resin, cycloolefin resin, acrylic resin, cellulose ester resin, cellulose resin, polyester resin, polyester carbonate resin, and olefin. Examples thereof include based resins and polyurethane resins. Preferably, it is a polycarbonate-based resin, a cellulose ester-based resin, a polyester-based resin, a polyester carbonate-based resin, or a cycloolefin-based 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 properties.

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 isosorbide, isomannide, isoidet, spiroglycol, dioxane glycol, diethylene glycol (DEG), triethylene glycol (TEG), polyethylene glycol (PEG), cyclohexanedimethanol ( It may contain structural units derived from dihydroxy compounds such as CHDM), tricyclodecanedimethanol (TCDDM) and bisphenols.

Details of the polycarbonate-based 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-based resin, any suitable polyvinyl acetal-based resin can be used. Typically, the polyvinyl acetal-based resin can be obtained by subjecting at least two types 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-based resin are described in, for example, Japanese Patent Application Laid-Open No. 2007-161994. This description is incorporated herein by reference.

The stretched film (phase difference film) obtained by stretching the film to be stretched preferably has a refractive index characteristic of nx> ny. In one embodiment, the retardation film can preferably function as a λ / 4 plate. In the present embodiment, the in-plane retardation Re (550) of the retardation film (λ / 4 plate) is preferably 100 nm to 180 nm, more preferably 135 nm to 155 nm. In another embodiment, the retardation film can preferably function as a λ / 2 plate. In the present embodiment, the in-plane retardation Re (550) of the retardation film (λ / 2 plate) is preferably 230 nm to 310 nm, more preferably 250 nm to 290 nm. In the present specification, 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. Here, nx is the refractive index in the direction in which the refractive index in the plane is maximized (that is, the slow phase axis direction), and ny is the direction orthogonal to the slow phase axis in the plane (that is, the phase advance axis direction). Refractive index.

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.

When making a circular polarizing plate using one retardation film, or when rotating the direction of linear polarization by 90 ° using one retardation film, the slow axis direction of the retardation film used is , Preferably 30 ° to 60 ° or 120 ° to 150 °, more preferably 38 ° to 52 ° or 128 ° to 142 °, still more preferably 43 ° to 47 ° or 133 ° with respect to the longitudinal direction of the film. It is about 137 °, particularly preferably about 45 ° or 135 °.

Further, when a circular polarizing plate is manufactured using two retardation films (specifically, λ / 2 plate and λ / 4 plate), the slow axis of the retardation film (λ / 2 plate) used is used. The direction is preferably 60 ° to 90, more preferably 65 ° to 85, and particularly preferably about 75 ° with respect to the long direction of the film. The slow axis direction of the retardation film (λ / 4 plate) is preferably 0 ° to 30 °, more preferably 5 to 25 °, and particularly preferably about 15 ° with respect to the long direction of the film. be.

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

The absolute value of the photoelastic coefficient of the retardation film is preferably 2 × 10 ^-12 (m ² / N) to 100 × 10 ^-12 (m ² / N), and more preferably 5 × 10 ^-12 . It is (m ² / N) to 50 × ^10-12 (m ² / N).

C. Optical laminate and method for manufacturing the optical laminate The stretched film obtained by the production method of the present invention 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.

FIG. 7 is a schematic cross-sectional view of an example of such a circular polarizing plate. The circular polarizing plate 500 of the illustrated example includes a polarizing element 510, a first protective film 520 arranged on one side of the polarizing element 510, a second protective film 530 arranged on the other side of the polarizing element 510, and a second protective film. It has a retardation film 540 arranged on the outside of the protective film 530 of 2. The retardation film 540 is a stretched film (for example, a λ / 4 plate) obtained by the production method according to Item A. The second protective film 530 may be omitted. In that case, the retardation film 540 can function as a protective film for the stator. The angle formed by the absorption axis of the splitter 510 and the slow axis of the retardation film 540 is preferably 30 ° to 60 °, more preferably 38 ° to 52 °, still more preferably 43 ° to 47 °, and particularly preferably. It is about 45 °.

The retardation film obtained by the production method of the present invention is elongated and has a slow phase axis in an oblique direction (for example, a direction of 45 ° with respect to the elongated 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.

In one embodiment, in the method for producing an optical laminate of the present invention, a elongated stretched film is obtained by the method for producing a stretched film according to item A, and the elongated optical film and the elongated film are obtained. This includes continuously laminating the stretched film in the shape of a stretched film while aligning its long direction.

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) Phase difference value The in-plane phase difference Re (550) at a wavelength of 550 nm was measured at intervals of 0.5 seconds using an in-line phase difference meter (KOBRA series manufactured by Oji Measuring Instruments Co., Ltd.).
(3) Orientation angle (direction of expression of slow axis)
Using an in-line phase difference meter (KOBRA series manufactured by Oji Measuring Instruments Co., Ltd.), the orientation angle θ at a wavelength of 550 nm was measured at intervals of 0.5 seconds.
(4) Glass transition temperature (Tg)
It was measured according to JIS K 7121.

<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 Machinery Co., Ltd., cylinder set temperature: 250 ° C.), T-die (width 200 mm, set temperature: 250 ° C.), chill roll A resin film having a thickness of 135 μm was produced using a film forming apparatus equipped with (set temperature: 120 to 130 ° C.) and a winder.

(Preparation of stretched film)
The polyester carbonate resin film obtained as described above is stretched in the long direction by using a stretching device having a pair of left and right constant-speed rotating sprocket at the same position in the transport direction near the start end of the heat fixing zone D. A retardation film was obtained by diagonally stretching so that the slow axis was developed in the 45 ° direction (that is, the desired orientation angle was set in the 45 ° direction with respect to the elongated direction).
Specifically, the left and right ends of the polyester carbonate resin film were gripped by the left and right clips at the entrance of the stretching device, and preheated to 145 ° C. in the preheating zone B. In the preheating zone, the clip pitch (P ₁ ) of the left and right clips was 125 mm.
Next, as soon as the film enters the stretch zone _C , it starts increasing the clip pitch of the right clip and decreasing the clip pitch of the left clip, increasing the clip pitch of the right clip to P2 and increasing the clip pitch of the left clip. It was reduced to P3 ₍ first diagonal stretch). At this time, the clip pitch change rate (P ₂ / P ₁ ) of the right clip is 1.42, the clip pitch change rate of the left clip (P ₃ / P ₁ ) is 0.78, and the original width of the film is 0.78. The lateral stretching ratio was 1.45 times. Then, while maintaining the clip pitch of the right clip at P ₂ , the clip pitch of the left clip was started to be increased and increased from P ₃ to P ₂ (second diagonal extension). During this period, the rate of change in the clip pitch (P ₂ / P ₃ ) of the left clip was 1.82, and the lateral stretching ratio with respect to the original width of the film was 1.9 times. The stretching zone C was set to Tg + 3.2 ° C. (143.2 ° C.).
Next, in the heat fixing zone D, the film was held at 125 ° C. for 60 seconds for heat fixing. After cooling the heat-fixed film to 100 ° C., the left and right clips were opened.
During the production of the stretched film, the phases of rotation of the left and right constant-speed rotating sprockets were all synchronized with the phases of the left and right clips that had moved to the heat-fixing zone. Therefore, the phase shift of the left and right clips did not occur due to the engagement with the left and right constant speed rotating sprockets.

(Measurement of orientation angle and phase shift)
The left and right ends of the stretched film released from the clip and sent out from the stretching device were cut off by 25 mm each. Next, the orientation angle (angle with respect to the elongated direction) was measured at a fixed point at a total of three points 25 mm inward from the center in the width direction and the left and right edges of the film while transporting the roll. At this time, when the orientation angle of the central portion in the width direction of the film deviates by 4 ° or more from the angle of 45 ° with respect to the long direction (that is, when it becomes 49 ° or more), the constant speed rotating sprocket on the left side. The phase of the left clip was delayed by 0.5 mm by changing the phase of rotation. As described above, a stretched film (Re (550) = 140 nm) was obtained.

<Example 2>
It was stretched diagonally so that the slow phase axis appeared in the 46 ° direction with respect to the elongated direction (specifically, the clip pitch of the stretch zone was adjusted), and the width direction of the film when measuring the orientation angle. To change the phase of rotation of the constant speed rotating sprocket on the left side when the orientation angle of the central part deviates by 4 ° or more from the angle of 46 ° with respect to the long direction (that is, when it becomes 50 ° or more). A stretched film (Re (550) = 140 nm) was obtained in the same manner as in Example 1 except that the phase of the left clip was delayed by 1 mm.

<Example 3>
It was stretched diagonally so that the slow phase axis appeared in the 47 ° direction with respect to the elongated direction (specifically, the clip pitch of the stretch zone was adjusted), and the width direction of the film when measuring the orientation angle. To change the phase of rotation of the constant speed rotating sprocket on the left side when the orientation angle of the central part deviates by 4 ° or more from the angle of 47 ° with respect to the long direction (that is, when it becomes 51 ° or more). A stretched film (Re (550) = 140 nm) was obtained in the same manner as in Example 1 except that the phase of the left clip was delayed by 2 mm.

<Comparative Example 1>
A stretched film (Re (550) = 140 nm) was obtained in the same manner as in Example 1 except that the phase of the clip was not changed.

Table 1 shows variations in the orientation angle of the central portion in the width direction 5 minutes and 1 hour after the start of production of the stretched film and the orientation angle in the width direction 1 hour after the start of production.

As shown in Table 1, when the orientation angle shifts over time in the production of a long diagonally stretched film, such shift is reduced by shifting the phases of the left and right clips. Can be done.

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) and an organic electroluminescence display device (OLED). ..

1 Stretched film 10 Reference rail 20 Pitch setting rail 30 Clip supporting member 40 Clip 54 Means for changing the phase 100 Stretching device 500 Circular polarizing plate

Claims (9)

Gripping the left and right edges of the long film in the width direction with variable pitch type left and right clips that change the clip pitch in the vertical direction, respectively.
Preheating the film,
To stretch the film diagonally by moving the left and right clips while changing the clip pitch of at least one of the clips.
To heat-fix the film,
Including releasing the film from the left and right clips and measuring the orientation angle of the film.
When the deviation of the alignment angle with respect to the set value exceeds a predetermined reference, a constant speed rotating sprocket is attached to the link mechanism that changes the clip pitch between the time when the film is gripped by the left and right clips and the time when the film is released. A method of making a stretched film, comprising shifting the phase of at least one of the left and right clips by engaging them . The manufacturing method according to claim 1 , wherein in the heat fixing, at least one of the left and right clips is out of phase. The manufacturing method according to claim 1 or 2 , wherein the amount of phase shift when shifting the phase is 0.1 mm to 3.0 mm. The diagonal stretching (i) increases the clip pitch of one of the left and right clips from P ₁ to P ₂ , while reducing the clip pitch of the other clip from P ₁ to P ₃ . (Ii) The invention according to any one of claims 1 to 3 , wherein the clip pitch of each clip is changed so that the reduced clip pitch and the increased clip pitch have a predetermined equal pitch. A method for producing a stretched film. The method for producing a stretched film according to claim 4 , wherein P ₂ / P ₁ is 1.25 to 1.75, and P ₃ / P ₁ is 0.50 or more and less than 1. 4 Alternatively, the method for producing a stretched film according to 5 . Claimed to delay the phase of the clip on one side and / or advance the phase of the clip on the other side when the orientation angle deviates in the longitudinal direction beyond the predetermined reference. 4. The method for producing a stretched film according to 4 or 5 . The elongated stretched film is obtained by the production method according to any one of claims 1 to 7 , and the elongated optical film and the elongated stretched film are conveyed in the elongated direction. A method for manufacturing an optical laminate, which comprises aligning and continuously laminating. The optical film is a polarizing plate, and the optical film is a polarizing plate.
The method for producing an optical laminate according to claim 8 , wherein the stretched film is a λ / 4 plate or a λ / 2 plate.

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