JP2023046840A - Method for producing stretched film and method for producing optical laminate - Google Patents

Abstract

To provide a technique for reducing deviation of an orientation angle that can occur over time in continuous production of a long diagonally stretched film.SOLUTION: There is provided a method for producing a stretched film which comprises: gripping right and left side edges in a width direction of a long film with each of right and left variable-pitch type clips, in which a clip pitch in a longitudinal direction varies; preheating the film; obliquely stretching the film by running and moving the right and left clips while changing the clip pitch of at least one of the right and left clips; thermally fixing the film; releasing the film from the left and right clips; and measuring the orientation angle of the film, wherein when the deviation of the orientation angle from the set value exceeds a predetermined criterion, the method comprises shifting the phase of at least one of the left and right clips during from the time the film is gripped with the left and right clips to the time the film is released.SELECTED DRAWING: Figure 1

Description

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

BACKGROUND ART In image display devices such as liquid crystal display devices (LCD) and organic electroluminescence display devices (OLED), circularly polarizing plates are used for the purpose of improving display characteristics and preventing reflection. A circularly polarizing plate is typically a polarizer and a retardation film (typically a λ/4 plate), and the absorption axis of the polarizer and the slow axis of the retardation film form an angle of 45°. It is layered in this way. Conventionally, a retardation film is typically produced by uniaxial stretching or biaxial stretching in the machine direction and / or the transverse direction, so the slow axis is often a long film It develops in the horizontal direction (width direction) or the vertical direction (lengthwise direction) of the raw fabric. As a result, in order to produce a circularly polarizing plate, it was necessary to cut the retardation film so as to form an angle of 45° with respect to the width direction or the longitudinal direction, and to bond the films one by one.

Moreover, in order to secure the broadband property 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 plate is laminated so as to form an angle of 75° with respect to the absorption axis of the polarizer, and the λ/4 plate is laminated so as to form an angle of 15° with respect to the absorption axis of the polarizer. There is a need. Even in this case, when producing a circularly 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 longitudinal direction, and to laminate one by one. .

In still another embodiment, in order to prevent light from a notebook PC from being reflected on a keyboard or the like, a A λ/2 plate may be used. Even in this case, it was necessary to cut the retardation film so as to form an angle of 45° with respect to the width direction or the longitudinal direction, and to bond the films one by one.

In order to solve such a problem, the left and right ends in the width direction of the long film are respectively gripped by left and right variable-pitch clips with variable clip pitches in the vertical direction. A technique has been proposed in which the slow axis of the retardation film is expressed in an oblique direction by changing one clip pitch and stretching in an oblique direction with respect to the longitudinal direction (hereinafter also referred to as "diagonal stretching"). (for example, Patent Document 1). However, continuous production of obliquely stretched films by such a technique may cause the orientation angle to deviate from the desired value over time.

On the other hand, Japanese Patent Laid-Open No. 2002-200002 proposes a technique for preventing the deviation of the orientation angle over time in the continuous production by controlling the movement speed of the left and right clips to be constant. On the other hand, there is still a need for alternative techniques that can solve the problem of orientation angle shift over time.

Japanese Patent No. 4845619 JP 2015-206994 A

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

According to one aspect of the present invention, the left and right ends in the width direction of a long film are respectively held by left and right variable-pitch clips with varying clip pitches in the vertical direction, and the film is preheated. running and moving the left and right clips while changing the clip pitch of at least one of the clips to obliquely stretch the film; heat 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 from the set value exceeds a predetermined standard, the period from gripping the film with the left and right clips to releasing it and shifting the phase of at least one of the left and right clips.
According to one embodiment, the phase of at least one of the left and right clips is shifted by engaging a constant speed rotating sprocket with the link mechanism that changes the clip pitch.
According to one embodiment, at least one of the left and right clips is out of phase in the thermal fixation.
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 diagonal 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 to _P2 . and (ii) varying the clip pitch of each clip such that the reduced clip pitch and the increased clip pitch are equal to a predetermined pitch _.
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 advanced. delay the phase of
According to one embodiment, when the orientation angle deviates longitudinally beyond the predetermined criterion, the phase of the clip on one side is retarded and/or the clip on the other side is Advance the phase of the clip.
According to another aspect of the present invention, a long stretched film is obtained by the above-described production method, and the long optical film and the long stretched film are transported in the longitudinal direction. A method for manufacturing an optical laminate is provided, comprising aligning and successively laminating the layers.
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 an embodiment of the present invention, in the continuous production of a long obliquely stretched film, when the orientation angle deviation exceeds a predetermined standard over time, the left and right clips that hold the film upstream of the production line to change the phase of at least one of This makes it possible to change the relative positional relationship between the left and right clips without changing the oblique stretching conditions such as the clip pitch profile, rail pattern, and heating temperature. It is possible to continuously produce a long obliquely stretched film.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic plan view explaining the whole structure of an example of the stretching apparatus which can be used for 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; FIG. 10 is a schematic diagram showing a profile of clip pitch in one embodiment of diagonal stretching. FIG. 10 is a schematic diagram showing a profile of clip pitch in one embodiment of diagonal stretching. It is the schematic explaining the measuring method of an orientation angle. FIG. 4 is a schematic diagram illustrating a method of shifting the phase of a clip; 1 is a schematic cross-sectional view of a circularly polarizing plate using a retardation film obtained by the manufacturing method of the present invention; FIG.

Preferred embodiments of the present invention will be described below, but the present invention is not limited to these embodiments. In this specification, the term "vertical clip pitch" means the center-to-center distance in the running direction of vertically adjacent clips. Further, the lateral relationship in the width direction of a long film means the lateral 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 an embodiment of the present invention comprises:
gripping the left and right ends in the width direction of the elongated film with left and right variable-pitch clips in which the clip pitch in the vertical direction changes (gripping step);
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 setting the film (heat setting step);
releasing the film from the left and right clips (release step); and
Measuring the orientation angle of the film (orientation angle measurement step),
When the deviation of the orientation angle from the set value exceeds a predetermined standard, the phase of at least one of the left and right clips is shifted (phase shifting step).

A-1. Stretching Apparatus In the method for producing a stretched film according to an embodiment of the present invention, for example, the left and right ends of a film to be stretched are held and passed through a preheating zone, a stretching zone, and a heat setting zone in this order, and each It has variable-pitch type left and right clips with which the clip pitch in the vertical direction changes accordingly, and in the stretching zone, the left and right clips are moved while changing the clip pitch of at least one clip to stretch the film. Using a film stretching device configured to stretch diagonally and comprising at least one means for changing the phase of at least one of the left and right clips between a zone for gripping the film and the heat setting zone can be done.

The drawing apparatus includes, for example, endless left and right reference rails passing through a preheating zone, a drawing zone and a heat setting zone in this order, left and right pitch setting rails provided along the left and right reference rails, and the A plurality of left and right clip carrying members that travel while being guided by left and right reference rails, and left and right clips that are carried by the left and right clip carrying members and hold the left and right ends of the elongated film to be stretched, respectively. a drive means for imparting a running force to the clip carrying members; and a link mechanism capable of adjusting the pitch between the clip carrying members according to the separation distance between the reference rail and the pitch setting rail; The film stretching apparatus further includes a constant speed rotating sprocket engaging at least one of the left and right clip carrying members as a means for varying the phase.

FIG. 1 is a schematic plan view illustrating the overall configuration of an example of a stretching apparatus that can be used in the manufacturing method of the present invention. In the stretching apparatus 100, a gripping zone A, a preheating zone B, a stretching zone C, a heat setting zone D and an opening zone E are provided in this order from the film entrance side to the exit side. These respective zones mean zones in which the film to be stretched is substantially gripped, preheated, obliquely stretched, heat set and released, and do not mean mechanically and structurally independent compartments. Also note that the length ratios of the respective zones in the drawing apparatus of FIG. 1 differ from the actual length ratios.

Although not shown in FIG. 1, between the drawing zone C and the heat setting zone D, a zone for any suitable treatment may be provided as required. Examples of such processing include lateral contraction processing and the like. Also, although not shown, the stretching apparatus typically includes a heating apparatus (e.g., hot air type, near-infrared Equipped with various types of ovens such as external and far-infrared ovens).

The stretching device 100 has left and right endless reference rails 10L and 10R symmetrically on both left and right sides in plan view. The stretching device 100 further carries pitch setting rails 20L and 20R provided on the inner peripheral side of the left and right reference rails 10L and 10R and a clip 40, and travels while being guided by the left and right reference rails 10L and 10R. It further has a plurality of left and right clip carrying members 30L, 30R, and drive means (in the illustrated example, drive sprockets) 50L, 50R that apply running force to the left and right clip carrying members 30L, 30R. In this specification, the reference rail on the left side as viewed from the entrance side of the film is called the left reference rail 10L, and the reference rail on the right side is called the right reference rail 10R. The clip carrying members 30L, 30R carrying the clips 40 are guided by the reference rails 10L, 10R and circulate in a loop. Specifically, the clip carrying member 30L (resultingly, the clip (left clip) 40 carried by the clip carrying member) guided by the left reference rail 10L circulates in the counterclockwise direction, A clip carrying member 30R guided by the rail 10R (and consequently a clip (right clip) 40 carried by the clip carrying member) circulates clockwise.

In the gripping zone A and the preheating zone B of the stretching apparatus 100, the left and right reference rails 10L and 10R are configured to be substantially parallel to each other with 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 preheating zone B toward the heat setting zone D until it corresponds to the width of the film after stretching. In the heat setting zone D and the release zone E, the left and right reference rails 10L, 10R are configured to be substantially parallel to each other with a separation distance corresponding to the width of the film after stretching. However, the configuration of the left and right reference rails 10L and 10R is not limited to the example illustrated above. For example, the left and right reference rails 10L, 10R may be configured to be substantially parallel to each other from the grip zone A to the release zone E with a separation distance corresponding to the initial width of the film to be stretched.

The left clip 40 and the right clip 40 are configured so as to be independently rotatable. Specifically, the clip carrying members 30L and 30R are provided with drive rollers 39 selectively engageable with the drive sprockets 50L and 50R, and the drive rollers 39 are rotationally driven by electric motors 60L and 60R. Selective engagement with 50L, 50R imparts running force to clip carrier members 30L, 30R. Therefore, by rotating the driving sprocket 50L for the left reference rail 10L counterclockwise and rotating the driving sprocket 50R for the right reference rail 10R clockwise, the left clip is rotated counterclockwise. The right clip rotates clockwise. By adjusting the output of the electric motor to change the running force transmitted from the drive sprocket to the clip carrying member, the running speeds of the left and right clip carrying members (as a result, the running speed of the left and right clips) can be controlled independently. can be controlled to an arbitrary value. Clip position adjusting sprockets 52L and 52R are arranged on the film entrance side for synchronizing the left and right film gripping timings of the clips, and these sprockets are driven to rotate by electric motors 62L and 62R, respectively. does not affect the running speed of the clip. In addition, unlike the illustrated example, a driving sprocket may be arranged on the film entrance side.

Further, the left clip carrying member (resulting in the left clip) and the right clip carrying member (resulting in the right clip) are each of the variable pitch type. That is, the left and right clip carrying members (resultingly, the left and right clips) can independently change the clip pitch in the vertical direction as they move. A variable pitch configuration can be achieved by employing a linkage that is configured to adjust the pitch between the clip carrying members by the distance between the reference rail and the pitch setting rail. An example of the link mechanism (pantograph mechanism) will be described below.

2 and 3 are respectively schematic plan views of essential parts for explaining the link mechanism for changing the clip pitch in the drawing device of FIG. Indicates the maximum pitch.

As shown in FIGS. 2 and 3, the clip carrying member 30 has an elongated rectangular shape in the horizontal direction in plan view, and individually carries a clip 40 at one end in the longitudinal direction. Although not shown, the clip carrying member 30 is formed into a rigid frame structure with a closed cross section by an upper beam, a lower beam, a front wall (the wall on the clip side), and a rear wall (the wall on the side opposite to the clip). The clip carrier member 30 is mounted to roll on the running surfaces 81, 82 by running wheels 38 at both ends thereof. 2 and 3, the running wheels on the front wall side (running wheels that roll on the running road surface 81) are not shown. The running road surfaces 81 and 82 are parallel to the reference rail 10 over the entire area. Long holes 31 are formed along the longitudinal direction of the clip carrier member 30 on the rear side of the upper and lower beams of the clip carrier member 30 (on the side opposite to the clip side (hereinafter referred to as the anti-clip side)), and the slider 32 is elongated. It is slidably engaged in the longitudinal direction of hole 31 . A single first shaft member 33 is provided vertically through the upper and lower beams in the vicinity of the clip 40 side end of the clip support member 30 . 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 groove provided on the reference rail 10 . A driving roller 39 is rotatably provided at the upper end of the first shaft member 33 . On the other hand, a single second shaft member 34 is provided vertically through the slider 32 of the clip carrier member 30 . 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 groove provided in the pitch setting rail 20 . One end of a main link member 35 is pivotally connected to the first shaft member 33 of each clip carrier member 30 . The main link member 35 is pivotally connected at its other end to the second shaft member 34 of the adjacent clip carrier member 30 . In addition to the main link member 35 , one end of a secondary link member 36 is pivotally connected to the first shaft member 33 of each clip carrier member 30 . The secondary link member 36 has its other end pivotally connected to the intermediate portion of the main link member 35 by a pivot 37 . As shown in FIG. 2, the link mechanism of the main link member 35 and the sub-link member 36 causes the clip support members 30 to move vertically toward each other as the slider 32 moves to the rear side (anti-clip side) of the clip support members 30 . The pitch in the direction (resultingly, the clip pitch) becomes smaller, and as shown in FIG. The pitch (resulting in 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 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 apparatus 100 has means 54L, 54R (in the illustrated example, electric motors 64L, 64R) for changing the phase of the left and right clips 40 at the same position in the conveying direction. (high-speed rotating sprocket). The constant-speed rotation sprocket 54L on the left side and the constant-speed rotation sprocket 54R on the right side are each configured to be able to arbitrarily change the phase of rotation (the phase of the teeth of the sprockets), and a link mechanism that changes the clip pitch. (in the example shown, by engaging the clip carrier, more specifically the drive roller of the clip carrier) by engaging the clip with the phase of rotation. Therefore, for example, while aligning the phase of rotation of the left constant-speed rotation sprocket 54L and the phase of the clip support member 30L (resultingly, the left clip), the phase of rotation of the right constant-speed rotation sprocket 54R and the clip support member 30R (and consequently the right clip) allows the right clip to be out of phase without changing the phase of the left clip after engagement of each sprocket with the clip carrier. Further, for example, by shifting the rotation phase of the left constant-speed rotation sprocket 54L and the left clip phase, and the rotation phase of the right constant-speed rotation sprocket 54R and the right clip phase by different amounts, The phases of the left and right clips after engagement can be shifted independently.

Unlike the illustrated example, means for changing the phase of the clip may be provided only for either the right clip or the left clip. Also, the location where the means for changing the phase of the clip is provided is not limited to the preheat zone. At least one means for changing the phase of the clip is provided in at least one zone selected from a preheating zone, a stretching zone and a heat setting zone. Means for changing the phase of two or more clips may be provided in one zone, or may be provided in two or more zones, one for each. Preferably the means for changing the phase of the clip are provided in the heat setting zone.

Each step will be described in detail below.

A-2. Gripping Step In the gripping zone A (entrance of the film taking-in of the stretching device 100), the left and right ends of the film to be stretched are typically held at a predetermined clip pitch by the clips 40 of the left and right endless loops 10L and 10R. They are gripped simultaneously in phase, that is, with constant clip pitches that are 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 between the left and right clips when held 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 movement of the left and right clips (substantially movement of each clip carrying member guided by the left and right reference rails 10L, 10R).

A-3. Preheating Step In the preheating zone B, the left and right reference rails 10L and 10R are configured to be substantially parallel to each other with a separation distance corresponding to the initial width of the film to be stretched as described above. The film is heated without lateral stretching 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 coming into contact with the nozzles in the oven.

In the preheating step, the film is heated to temperature T1 (°C). The temperature T1 is preferably the glass transition temperature (Tg) of the film or higher, 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. Depending on the film used, the temperature T1 is, for example, 70°C to 190°C, preferably 80°C to 180°C.

The heating time 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 manufacturing conditions (for example, transport speed of the film). These heating 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 moved while changing the vertical clip pitch of at least one clip to diagonally stretch the film. More specifically, the left and right clips are moved while increasing or decreasing the clip pitch at different positions, or are moved while changing (increasing and/or decreasing) the clip pitch at different changing speeds. etc., to obliquely stretch the film. As a result of moving the left and right clips while changing the clip pitch in this manner, one of the pair of left and right clips simultaneously transferred to the stretching zone reaches the end of the stretching zone ahead of the other clip. . According to such oblique stretching, the leading clip-side end is stretched at a higher draw ratio than the trailing clip-side end, and as a result, the desired direction of the long film A slow axis can be developed in (for example, a direction at 45° to the longitudinal direction).

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

When the diagonal stretching includes lateral stretching, the stretching ratio in the transverse direction (TD) (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. ~6.00, more preferably 1.10 to 5.00.

In one embodiment, the diagonal stretching is such that 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 are different in the vertical direction. This can be done by increasing or decreasing the clip pitch of each clip to a predetermined pitch while in position. For the oblique stretching in this embodiment, for example, reference can be made to the descriptions in Patent Document 1, JP-A-2014-238524, and the like.

In another embodiment, the diagonal stretching is performed by increasing or decreasing the clip pitch of one of the left and right clips while fixing the clip pitch of the other clip to a predetermined pitch, followed by can be done by returning to For the diagonal stretching of the embodiment, for example, reference can be made to the descriptions of JP-A-2013-54338, JP-A-2014-194482, and the like.

In yet another embodiment, diagonal 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 to _P3. and (ii) varying the clip pitch of each clip such that the reduced clip pitch and the increased clip pitch are equal to a predetermined pitch. For the oblique stretching of the embodiment, for example, the description of JP-A-2014-194484 can be referred to. The diagonal stretching of this embodiment increases the clip pitch of one clip from _P1 to _P2 while increasing the distance between the left and right clips, while decreasing the clip pitch of the other clip from _P1 to _P3 . to stretch the film diagonally (first diagonal stretching), and while increasing the distance between the left and right clips, the clip pitch of the one clip is set to P so that the clip pitches of the left and right clips are equal. ₂ or reduced to _P4 and increasing the clip pitch of the other clip to _P2 or _P4 to diagonally stretch the film (second diagonal stretch).

In the first diagonal stretching, one end of the film is stretched in the longitudinal direction and the other end is shrunk in the longitudinal direction while diagonally stretching to obtain a desired direction (e.g., longitudinal A slow axis can be expressed with high uniaxiality and in-plane orientation in the direction of 45° to the slender direction. Further, in the second diagonal stretching, the diagonal stretching is performed while reducing the difference between the left and right clip pitches, thereby allowing sufficient stretching in the diagonal direction while relieving excess stress.

In the diagonal stretching of the above three embodiments, the film can be released from the clips with the left and right clips moving at the same speed. Subsequent winding of the film can be suitably performed.

FIGS. 4A and 4B are schematic diagrams showing examples of clip pitch profiles in diagonal stretching including the first diagonal stretching and the second diagonal stretching, respectively. Hereinafter, the first oblique stretching will be specifically described with reference to these figures. 4A and 4B, the horizontal axis corresponds to the travel distance of the clip. At the start of the first diagonal stretching, both left and right clip pitches are set to _P1 . _P1 is typically the clip pitch when the film is gripped. At the same time as the first diagonal stretching starts, one clip (hereinafter sometimes referred to as the first clip) starts increasing the clip pitch, and the other clip (hereinafter referred to as the second clip) start reducing the clip pitch of the 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 start of the second diagonal stretching), the second clip moves at clip pitch _P3 , and the first clip moves at clip pitch _P2 . ing. Note that 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 at the start of the first oblique stretching, but the illustrated example is different. Alternatively, the clip pitch of the second clip may begin to decrease after the clip pitch of the first clip begins to increase, and the clip pitch of the first clip may begin to decrease after the clip pitch of the second clip begins to decrease. You can start increasing it. In one preferred embodiment, the clip pitch of the second clip begins to decrease after the clip pitch of the first clip begins to increase. According to such an embodiment, since the film has already been stretched in the width direction to a certain degree (preferably about 1.2 to 2.0 times), even if the clip pitch of the second clip is greatly reduced, Wrinkles are less likely to occur. Therefore, more acute-angle oblique stretching becomes possible, and a retardation film with high uniaxiality and in-plane orientation can be suitably 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 decreases until the end of the first diagonal stretching (the start 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

The clip pitch change rate (P ₂ /P ₁ ) of the first clip is preferably 1.25 to 1.75, more preferably 1.30 to 1.70, still more preferably 1.35 to 1.65. is. Further, the clip pitch change rate (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, more preferably 0.55 to 0.90, It is more preferably 0.55 to 0.85. If the change rate of the clip pitch is within such a range, the slow axis can be expressed with high uniaxiality and in-plane orientation in a direction approximately 45 degrees to the longitudinal direction of the film.

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

The draw 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 to 2.5 times, more preferably 1.25 to 2.0 times. If the draw ratio is less than 1.1 times, corrugated iron-like wrinkles may occur at the ends on the contracted side. On the other hand, if the draw ratio exceeds 3.0 times, the biaxiality of the obtained retardation film becomes high, and viewing angle characteristics may deteriorate when the film is applied to a circularly polarizing plate or the like.

In one embodiment, in the first diagonal stretching, the product of the clip pitch change rate of the first clip and the clip pitch change rate of the second clip is preferably 0.7 to 1.5, more It is preferably 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 with high uniaxiality and in-plane orientation can be obtained.

Next, one embodiment of the second oblique stretching will be specifically described with reference to FIG. 4A. In the second diagonal stretching of this embodiment, the clip pitch of the second clip is increased from _P3 to _P2 . Meanwhile, the clip pitch of the first clip remains at _P2 during the second diagonal stretch. Therefore, at the end of the second oblique stretching, both the left and right clips are supposed to move at a clip pitch of _P2 .

The rate of change (P ₂ /P ₃ ) of the clip pitch of the second clip in the second oblique stretching of the embodiment shown in FIG. 4A is not limited as long as it does not impair the effects of the present invention. 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 is specifically described with reference to FIG. 4B. In the second diagonal stretching of this 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 _P2 to _P4 , and the clip pitch of the second clip is increased from _P3 to _P4 . Therefore, both the left and right clips are supposed to move at a clip pitch of _P4 at the end of the second oblique stretching. In the illustrated example, the decrease in the clip pitch of the first clip and the increase in the clip pitch of the second clip are started simultaneously with the start of the second oblique stretching, but these can be started at different timings. . Similarly, the clip pitch decrease of the first clip and the clip pitch increase of the second clip may end at different timings.

The clip pitch change rate (P ₄ /P ₂ ) of the first clip and the clip pitch change rate (P ₄ /P ₃ ) of the second clip in the second diagonal stretching of the embodiment shown in FIG. 4B are There is no limitation as long as it does not impair the effects of the present invention. 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. Also, 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, _P4 is greater than or equal to _P1 . If P ₄ <P ₁ , problems such as wrinkles at the ends and increased biaxiality may occur.

The draw 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, 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, corrugated iron-like wrinkles may occur at the ends on the contracted side. On the other hand, if the draw ratio exceeds 3.0 times, the biaxiality of the obtained retardation film becomes high, and viewing angle characteristics may deteriorate when the film is applied to a circularly polarizing plate or the like. Further, the stretch 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, from the same viewpoint as above, It is preferably 1.2 to 4.0 times, more preferably 1.4 to 3.0 times.

Diagonal stretching can typically be performed at temperature T2. The temperature T2 is preferably Tg−20° C. to Tg+30° C., more preferably Tg−10° C. to Tg+20° C., particularly preferably about Tg relative to the glass transition temperature (Tg) of the film. Depending on the film used, the temperature T2 is, for example, 70°C to 180°C, preferably 80°C to 170°C. The difference (T1-T2) between the temperature T1 and the temperature T2 is preferably ±2° C. or more, more preferably ±5° C. or more. In one embodiment, T1>T2, so the film heated to temperature T1 in the preheat zone can be cooled to temperature T2.

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

A-5. Heat-setting process In the heat-setting zone D, the obliquely stretched film is heat-treated. In the heat setting 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 varies depending on the film to be stretched, and may be T2≧T3 or T2<T3. In general, if the film is an amorphous material, T2≧T3, and if the film is a crystalline material, the crystallization treatment may be performed by setting T2<T3. If T2≧T3, the difference between temperatures T2 and T3 (T2-T3) is preferably between 0.degree. C. and 50.degree. 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 speed of the film.

A-6. Release Step At any position in the release zone E, the film is released from the clip. In release zone E, the film is usually cooled to a desired temperature without laterally stretching or longitudinally stretching the heat-set film, and then the film is released from the clips. The film temperature when released from the clip is, for example, 150°C or less, preferably 70°C to 140°C, more preferably 80°C to 130°C.

The stretched film released from the clip is sent out from the exit of the stretching device and subjected to orientation angle measurement.

A-7. Step of Measuring Orientation Angle In one embodiment, the orientation angle (angle with respect to the longitudinal direction) is measured in-line while the film sent out from the outlet of the stretching device is conveyed by rolls. At this time, the difference between the measured orientation angle and the target orientation angle (|measured orientation angle−target orientation angle|) is defined as the orientation angle deviation. The deviation of the orientation angle is measured, for example, at the central portion in the width direction of the film. Moreover, the difference between the maximum value and the minimum value of the orientation angles measured at a plurality of locations in the width direction can be used as the orientation angle variation.

For example, in the embodiment shown in FIG. 5, measuring devices 2 are provided above the width direction central portion and left and right end portions of the film 1 on the transport line, and the orientation angle of the transported film is measured at three fixed points in the width direction. are measuring. The measurement points may be different from the illustrated example, for example, a total of two points at the center in the width direction of the film and either one of the left and right ends, or a total of two points at only the left and right ends, or a width There can be 2, 3, 4, 5 or more evenly spaced along the direction. Preferably, the orientation angle is measured at two or more points including at least one of the width direction central portion and the left and right ends (for example, the distance from the left and right sides is within 25 mm).

The orientation angle may be measured continuously or at predetermined intervals. Orientation angle measurements may be taken, for example, 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 orientation angle measurement wavelength can be in the range of 500 nm to 600 nm.

The orientation angle may be measured 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 width of the cut off edges may independently be, for example, 20 mm to 600 mm, preferably 100 mm to 500 mm. Cutting off the ends can be done by normal slitting.

A-8. Phase Shifting Step In the above measurement, if the deviation of the measured orientation angle from the target orientation angle (set value) exceeds a predetermined standard, the phase of at least one of the left and right clips is shifted. By shifting the phase of at least one of the left and right clips, the relative positional relationship between 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, it is possible to easily suppress the deviation of the orientation angle by shifting the phase of the clip without changing the rail pattern of the pitch setting rail one by one. In addition, when the deviation of the orientation angle is equal to or less than a predetermined standard, the production of the stretched film can be continued 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 misalignment angle is, for example, 6° or more, 5° or more, or 4° or more.

The timing for shifting the phase may be arbitrary timing from the time when the film is gripped by the left and right clips to the time when the film is released. In one embodiment, it is preferable to shift the phase at least once from the preheating step to the heat setting step, and more preferable to shift the phase during the heat setting step from the viewpoint of shrinkage uniformity of the film. In one embodiment, it is preferable to shift the phase in the first half of the heat setting process, and more preferable to shift the phase immediately after the start.

In the phase shift step, the phase of at least one of the left and right clips may be shifted. As long as the effects of the present invention can be obtained, there is no limitation as to how the phase of which clip is shifted (that is, whether it is advanced or retarded). 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. The phase of the left clip 40 may be delayed without changing the phase, or as shown in FIG. 6C, the phase of the left clip 40 may be delayed and the phase of the right clip 40 may be advanced. In the drawing, an arrow indicates the transport direction of the film 1, and a clip 40' indicated by a 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 orientation angle shift or variation. 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, more preferably 0.5 mm to 2.0 mm. When the phases of the left and right clips are shifted in opposite directions (for example, FIG. 6(c)), the amount of phase shift is the sum of the phase shift amounts of the respective clips. The amount of phase shift when shifted in the direction is the difference in the amount of phase shift for each clip.

For example, when the measured orientation angle deviates in the width direction beyond a predetermined standard, the phase of the clip on the leading side in the stretching zone is advanced, the phase of the clip on the trailing side is retarded, or both. , the phases of the left and right clips can be shifted. Further, for example, when 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 retarded, the phase of the clip on the trailing side is advanced, or , the combination of these can shift the phases of the left and right clips.

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

In one embodiment, the orientation angle is continuously measured during the production of the stretched film, and each time the orientation angle deviation exceeds a predetermined standard, the phases of the left and right clips are shifted to measure the orientation angle deviation. can be suppressed.

B. Film to be Stretched Any appropriate film can be used in the production method of the present invention. For example, a resin film applicable as a retardation film is mentioned. Examples of materials constituting such films include polycarbonate resins, polyvinyl acetal resins, cycloolefin resins, acrylic resins, cellulose ester resins, cellulose resins, polyester resins, polyester carbonate resins, and olefin resins. resins, polyurethane resins, and the like. Preferred are polycarbonate-based resins, cellulose ester-based resins, polyester-based resins, polyester carbonate-based resins, and cycloolefin-based resins. This is because, with these resins, it is possible to obtain a retardation film exhibiting so-called inverse wavelength dependence of dispersion. These resins may be used alone or in combination depending on the desired properties.

Any appropriate polycarbonate-based resin is used as the polycarbonate-based resin. For example, a polycarbonate-based resin containing a structural unit derived from a dihydroxy compound is preferred. Specific examples of dihydroxy compounds include 9,9-bis(4-hydroxyphenyl)fluorene, 9,9-bis(4-hydroxy-3-methylphenyl)fluorene, 9,9-bis(4-hydroxy-3- ethylphenyl)fluorene, 9,9-bis(4-hydroxy-3-n-propylphenyl)fluorene, 9,9-bis(4-hydroxy-3-isopropylphenyl)fluorene, 9,9-bis(4-hydroxy -3-n-butylphenyl)fluorene, 9,9-bis(4-hydroxy-3-sec-butylphenyl)fluorene, 9,9-bis(4-hydroxy-3-tert-butylphenyl)fluorene, 9, 9-bis(4-hydroxy-3-cyclohexylphenyl)fluorene, 9,9-bis(4-hydroxy-3-phenylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)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. Polycarbonate resin, in addition to structural units derived from the dihydroxy compound, isosorbide, isomannide, isoidet, spiroglycol, dioxane glycol, diethylene glycol (DEG), triethylene glycol (TEG), polyethylene glycol (PEG), cyclohexanedimethanol ( CHDM), tricyclodecanedimethanol (TCDDM), and structural units derived from dihydroxy compounds such as bisphenols.

Details of the above polycarbonate resins are described, for example, in JP-A-2012-67300 and JP-A-3325560. The description of the patent document is incorporated herein by reference.

The glass transition temperature of the polycarbonate-based 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 be poor, and there is a possibility that dimensional change will occur after film formation. If the glass transition temperature is excessively high, the molding stability during film molding may deteriorate, and the transparency of the film may be impaired. The glass transition temperature is obtained according to JIS K 7121 (1987).

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

The stretched film (retardation film) obtained by stretching the film to be stretched preferably exhibits 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 the in-plane retardation of the film measured with light of wavelength λnm at 23°C. Therefore, Re(550) is the in-plane retardation of the film measured at 23° C. with light having a wavelength of 550 nm. 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 in-plane refractive index is maximized (that is, the slow axis direction), and ny is the in-plane refractive index in the direction perpendicular to the slow axis (that is, the fast axis direction). is the refractive index.

The in-plane retardation Re(550) of the retardation film can be set within a desired range by appropriately setting the diagonal stretching conditions. For example, a method for producing a retardation film having an in-plane retardation Re (550) of 100 nm to 180 nm by diagonal stretching is disclosed in JP-A-2013-54338, JP-A-2014-194482, and JP-A-2014-238524. This is disclosed in detail in publications such as JP-A-2014-194484. Therefore, those skilled in the art can set appropriate diagonal stretching conditions based on the disclosure.

When producing a circularly polarizing plate using one retardation film, or when rotating the direction of linearly polarized light 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 to 137°, particularly preferably about 45° or 135°.

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

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

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), more preferably 5×10 ⁻¹² (m ² /N) to 50×10 ⁻¹² (m ² /N).

C. Optical Laminate and Method for Producing the Optical Laminate The stretched film obtained by the production method of the present invention can be used as an optical laminate by being laminated with another optical film. For example, the retardation film obtained by the production method of the present invention can be suitably used as a circularly polarizing plate by being attached to a polarizing plate.

FIG. 7 is a schematic cross-sectional view of an example of such a circularly polarizing plate. The illustrated circularly polarizing plate 500 includes a polarizer 510, a first protective film 520 arranged on one side of the polarizer 510, a second protective film 530 arranged on the other side of the polarizer 510, and a second protective film 530 arranged on the other side of the polarizer 510. and a retardation film 540 arranged outside the protective film 530 of No. 2. The retardation film 540 is a stretched film (for example, a λ/4 plate) obtained by the manufacturing method described in Section A. The second protective film 530 may be omitted. In that case, the retardation film 540 can function as a protective film for the polarizer. The angle between the absorption axis of the polarizer 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°, particularly preferably It is about 45°.

The retardation film obtained by the production method of the present invention is elongated and has a slow axis in an oblique direction (for example, a direction at 45° to the elongated direction). Also, in many cases, a long polarizer has an absorption axis in the length direction or the width direction. Therefore, by using the retardation film obtained by the production method of the present invention, so-called roll-to-roll can be used, and a circularly polarizing plate can be produced with extremely excellent production efficiency. In addition, roll-to-roll refers to a method in which long films are conveyed in a roll and continuously pasted together with their longitudinal directions aligned.

In one embodiment, the method for producing an optical laminate of the present invention comprises obtaining a long stretched film by the method for producing a stretched film described in Section A, and While transporting the stretched film, the longitudinal direction is aligned and continuously pasted together.

EXAMPLES The present invention will be specifically described below 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) Retardation Value In-plane retardation Re(550) at a wavelength of 550 nm was measured at intervals of 0.5 seconds using an in-line retardation meter (KOBRA series manufactured by Oji Keisoku Kiki Co., Ltd.).
(3) Orientation angle (development direction of slow axis)
The orientation angle θ 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 Scientific Instruments).
(4) Glass transition temperature (Tg)
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 stirring blades and reflux condensers controlled at 100°C. Bis[9-(2-phenoxycarbonylethyl)fluoren-9-yl]methane 29.60 parts by mass (0.046 mol), ISB 29.21 parts by mass (0.200 mol), SPG 42.28 parts by mass (0. 139 mol), 63.77 parts by mass (0.298 mol) of DPC, and 1.19×10 ⁻² parts by mass (6.78×10 ⁻⁵ mol) of calcium acetate monohydrate as a catalyst were charged. After the interior of the reactor was replaced with nitrogen under reduced pressure, heating was performed with a heating medium, and stirring was started when the internal temperature reached 100°C. After 40 minutes from the start of heating, the internal temperature was allowed to reach 220°C, and the pressure was reduced at the same time as controlling to maintain this temperature. Phenol vapor produced as a by-product of the polymerization reaction was led to a reflux condenser at 100°C, a small amount of monomer components contained in the phenol vapor was returned to the reactor, and uncondensed phenol vapor was led to a condenser at 45°C and recovered. After nitrogen was introduced into the first reactor and the pressure was once restored to atmospheric pressure, the oligomerized reaction liquid in the first reactor was transferred to the second reactor. Next, the temperature rise and pressure reduction in the second reactor were started, and the internal temperature was brought to 240° C. and the pressure to 0.2 kPa in 50 minutes. After that, polymerization was allowed to proceed until a predetermined stirring power was obtained. When a predetermined power was reached, nitrogen was introduced into the reactor to restore the pressure, the polyester carbonate produced was extruded into water, and 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., 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 was used to prepare a resin film having a thickness of 135 μm.

(Production of stretched film)
The polyester carbonate resin film obtained as described above is stretched in the longitudinal direction using a stretching device having a pair of left and right constant-speed rotating sprockets at the same position in the transport direction near the beginning of the heat setting zone D. The retardation film was obtained by obliquely stretching so that the slow axis was developed in the direction of 45° (that is, the target orientation angle was set to the direction of 45° with respect to the longitudinal direction).
Specifically, the left and right ends of the polyester carbonate resin film were held by left and right clips at the entrance of the stretching device, and preheated to 145°C in the preheating zone B. In the preheat zone, the clip pitch (P ₁ ) of the left and right clips was 125 mm.
Next, as the film enters stretching zone C, it begins 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 decreasing the clip pitch of the left clip. reduced to P ₃ (first oblique 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 (P ₃ /P ₁ ) of the left clip is 0.78, and the original width of the film is The transverse draw ratio for the film was 1.45 times. Next, while maintaining the clip pitch of the right clip at _P2 , the clip pitch of the left clip started to increase from _P3 to _P2 (second oblique stretching). The clip pitch change ratio (P ₂ /P ₃ ) of the left clip during this period was 1.82, and the transverse draw ratio to the original width of the film was 1.9 times. The stretching zone C was set at Tg+3.2°C (143.2°C).
Then, in the heat setting zone D, the film was held at 125° C. for 60 seconds for heat setting. After cooling the heat-set film to 100° C., the left and right clips were opened.
During the production of the stretched film, the rotation phases of the left and right constant-speed rotating sprockets were both synchronized with the phases of the left and right clips that had moved to the heat setting zone. Therefore, no phase shift occurred between the left and right clips due to engagement with the left and right constant-speed rotating sprockets.

(Measurement of orientation angle and phase shift)
Left and right ends of the stretched film released from the clip and sent out from the stretcher were cut by 25 mm each. Next, the orientation angle (angle with respect to the longitudinal direction) was measured at a total of three points, 25 mm inward from the center in the width direction and the left and right ends of the film, while being conveyed by rolls. At this time, when the orientation angle of the central portion in the width direction of the film deviates from the angle of 45° to the longitudinal direction by 4° or more (that is, when it becomes 49° or more), the constant speed rotation sprocket on the left side By changing the phase of rotation, the phase of the left clip was retarded by 0.5 mm. As described above, a stretched film (Re(550)=140 nm) was obtained.

<Example 2>
It was diagonally stretched so that the slow axis was expressed in the direction of 46 ° with respect to the longitudinal direction (specifically, the clip pitch of the stretching zone was adjusted), and the width direction of the film in the measurement of the orientation angle Changing the rotation phase of the left constant speed rotation sprocket when the orientation angle of the central portion deviates from the angle of 46° with respect to the longitudinal direction by 4° or more (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 retarded by 1 mm.

<Example 3>
It was diagonally stretched so that the slow axis was expressed in the direction of 47 ° with respect to the longitudinal direction (specifically, the clip pitch of the stretching zone was adjusted), and the width direction of the film in the measurement of the orientation angle When the orientation angle of the central portion deviates from 47° to the longitudinal direction by 4° or more (that is, when it becomes 51° or more), the rotation phase of the left constant speed rotation sprocket is changed. 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 retarded 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 the orientation angle at the central portion in the width direction 5 minutes and 1 hour after the start of production of the stretched film and the variation in the orientation angle in the width direction 1 hour after the start of production.

As shown in Table 1, in the production of a long obliquely stretched film, if there is a deviation in the orientation angle over time, such a deviation can be 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 image display devices such as liquid crystal displays (LCDs) and organic electroluminescence displays (OLEDs). .

Reference Signs List 1 stretched film 10 reference rail 20 pitch setting rail 30 clip carrier 40 clip 54 means for changing phase 100 stretching device 500 circular polarizer

Claims (10)

gripping left and right ends in the width direction of a long film by left and right variable-pitch clips with variable clip pitches in the vertical direction;
preheating the film;
diagonally stretching the film by moving the left and right clips while changing the clip pitch of at least one of the clips;
heat setting the film;
releasing the film from the left and right clips; and measuring an orientation angle of the film;
shifting the phase of at least one of the left and right clips after the film is gripped by the left and right clips until the film is released when the deviation from the set value of the orientation angle exceeds a predetermined standard; A method for producing a stretched film, comprising: 2. The manufacturing method according to claim 1, wherein the phase of at least one of the left and right clips is shifted by engaging a constant-speed rotating sprocket with the link mechanism that changes the clip pitch. 3. The manufacturing method according to claim 1, wherein at least one of said left and right clips is phase-shifted in said thermal fixation. 4. The manufacturing method according to any one of claims 1 to 3, 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 _P1 to _P2 while decreasing the clip pitch of the other clip from _P1 to _P3 ; and , (ii) varying the clip pitch of each clip such that the reduced clip pitch and the increased clip pitch are at a predetermined equal pitch. A method for producing a stretched film. 6. The method for producing a stretched film according to claim 5, 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. 6. The phase of the clip on the one side is advanced and/or the phase of the clip on the other side is retarded when the orientation angle deviates in the width direction beyond the predetermined reference. Or the method for producing a stretched film according to 6. 3. Retarding the phase of the clip on the one side and/or advancing the phase of the clip on the other side when the orientation angle deviates in the longitudinal direction beyond the predetermined reference. 7. The method for producing a stretched film according to any one of 5 and 6. Obtaining a long stretched film by the production method according to any one of claims 1 to 8, and transporting the long optical film and the long stretched film, and A method for producing an optical laminate, comprising aligning and continuously laminating. the optical film is a polarizing plate,
10. The method for producing an optical laminate according to claim 9, wherein the stretched film is a λ/4 plate or a λ/2 plate.

Images