KR102531094B1 - Method for producing stretched film and method for producing optical laminate - Google Patents

Abstract

An object of the present invention is to suppress the deviation of the orientation angle and the deviation of the in-plane retardation that may occur over time in the continuous production of a long obliquely stretched film.
In the present invention, the left and right ends of a long film in the width direction are respectively gripped with variable-pitch left and right clips in which the clip pitch in the longitudinal direction changes (gripping step), and the film is preheated (preheating step). , moving the left and right clips while changing the clip pitch of at least one clip, obliquely stretching the film (oblique stretching step), heat fixing the film (heat setting step), and Including opening from the left and right clips (opening step), the constant speed rotation sprocket is engaged with the link mechanism that changes the clip pitch between the film being gripped by the left and right clips and the heat fixing being completed. of the stretched film, which limits the moving speed of the clip to a predetermined speed, monitors the rotational phase of the constant speed rotation sprocket, and adjusts the rotational phase so as to approach the set phase based on the monitoring result. manufacturing method.

Description

Stretched film manufacturing method and optical laminate manufacturing method {METHOD FOR PRODUCING STRETCHED FILM AND METHOD FOR PRODUCING OPTICAL LAMINATE}

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

BACKGROUND ART In image display devices such as liquid crystal displays (LCDs) and organic electroluminescent displays (OLEDs), circularly polarizing plates are used for the purpose of improving display characteristics or preventing reflection. A circularly polarizing plate typically has a polarizer and a retardation film (typically a λ/4 plate) laminated so that the absorption axis of the polarizer and the slow axis of the retardation film form an angle of 45°. Conventionally, since retardation films are typically produced by uniaxial stretching or biaxial stretching in the machine direction and/or transverse direction, the slow axis thereof is, in many cases, in the transverse direction (width direction) of a long film master. ) or longitudinally (longitudinal direction). As a result, in order to produce a circular 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 elongated direction, and bond it one by one.

Further, in order to secure the broadband property of the circular polarizing plate, there are cases in which two retardation films, a λ/4 plate and a λ/2 plate, are laminated. In that case, the λ/2 plate needs to be laminated to form an angle of 75° with respect to the absorption axis of the polarizer, and the λ/4 plate needs to be laminated to form an angle of 15° with respect to the absorption axis of the polarizer. Also in this case, when producing a circular polarizing plate, it was necessary to cut the retardation film so as to form angles of 15° and 75° with respect to the width direction or the elongated direction, and bond them one by one.

In another embodiment, a λ/2 plate can be used on the viewing side of the polarizing plate for the purpose of rotating the direction of linearly polarized light emitted from the polarizing plate by 90° in order to avoid light from a note PC from shining onto a keyboard or the like. Also 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 elongated direction, and bond it one by one.

In order to solve such a problem, the left and right ends of a long film in the width direction are respectively held by left and right clips of a variable pitch type in which the clip pitch in the longitudinal direction changes, and at least one of the left and right clips is fixed with a clip pitch. A technique has been proposed in which the slow axis of the retardation film is expressed in an oblique direction by changing and stretching in an oblique direction with respect to the elongate direction (hereinafter also referred to as 'oblique stretching') (eg, Patent Document 1). However, when an obliquely stretched film is continuously produced by such a technique, the direction of the slow axis may shift from the set value over time. In contrast, a technique for controlling the direction of the slow axis by applying a load to a link mechanism that changes the clip pitch and limiting the moving speed of the clip to a predetermined speed has been proposed (Patent Document 2).

Japanese Patent Publication No. 4845619 Japanese Unexamined Patent Publication No. 2015-206994

According to the technique of Patent Literature 2, shift in the orientation angle (direction of the slow axis) that may occur over time in continuous production of a long obliquely stretched film, for example, shift in the orientation angle at the center in the width direction can be suppressed, but the width Regarding the deviation of the in-plane retardation in the direction, there is room for further improvement.

The present invention has been made to solve the above problems, and its object is to suppress deviations in orientation angles and deviations in in-plane retardation that may occur over time in the continuous production of long obliquely stretched films.

According to one aspect of the present invention, the left and right ends of a long film in the width direction are respectively held by left and right clips of a variable pitch type in which the clip pitch in the longitudinal direction changes (gripping step), and the film is preheated. (preheating process), moving the left and right clips while changing the clip pitch of at least one clip, and obliquely stretching the film (oblique stretching process), heat fixing the film (heat setting process), and opening the film from the left and right clips (opening process), and changing the clip pitch between the time when the film is held by the left and right clips and the end of the heat fixation. By engaging the constant speed rotation sprocket, the moving speed of the clip is limited to a predetermined speed, the rotation phase of the constant rotation sprocket is monitored, and the rotation phase is adjusted so as to approach the set phase based on the monitoring result. A method for producing a stretched film is provided.

In one embodiment, in at least one process selected from the preheating process, the oblique stretching process, and the heat setting process, the moving speed of the clip is limited to a predetermined speed.

In one embodiment, the rotational phase difference of the constant speed rotation sprocket is adjusted to -1 mm to +1 mm.

In one embodiment, the oblique stretching, (i) the clip pitch of one of the left and right clips at P ₁ Increase the clip pitch of the other clip at P ₁ by increasing it to P ₂ . P ₃ , and (ii) changing the clip pitch of each clip so that the corresponding reduced clip pitch and the corresponding increased clip pitch are the same predetermined pitch.

In one embodiment, P ₂ /P ₁ is between 1.25 and 1.75 and P ₃ /P ₁ is greater than or equal to 0.50 1 is less than

According to another aspect of the present invention, obtaining a long stretched film by the above manufacturing method, and conveying the long optical film and the long picture-shaped stretched film, aligning the direction of the long picture and continuously bonding them together Optical A method for manufacturing a laminate is provided.

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 method for producing a stretched film according to an embodiment of the present invention, deviations in orientation angles and deviations in in-plane retardation that may occur over time in continuous production of long obliquely stretched films can be suppressed. The reason for such an effect is estimated as follows, although the present invention is not limited in any way. That is, in the conventional method for producing a stretched film, as the constant-speed rotation sprocket repeats engagement with the link mechanism that changes the clip pitch, the rotational phase is gradually shifted, and the rotational phase of the left and right constant-speed rotation sprockets is shifted. As a result, The relative positional relationship of the left and right clips deviates from the original positional relationship, leading to a shift in orientation angle and a deviation in in-plane phase difference. On the other hand, according to the present invention, the rotational phase of the constant speed rotation sprocket is monitored, and the rotational phase is adjusted so as to approach the set phase, thereby maintaining the relative positional relationship of the left and right clips and increasing the movement speed to a predetermined level. can be limited to the speed of , and as a result, shift over time in the orientation angle of the resulting stretched film and variation in in-plane retardation can be suitably prevented.

1 is a schematic plan view illustrating the overall configuration of an example of a stretching apparatus that can be used in the method for producing a stretched film of the present invention.
Fig. 2 is a schematic plan view of main parts 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 main parts for explaining a link mechanism for changing a clip pitch in the stretching device of Fig. 1;
Fig. 4A is a schematic diagram showing a clip pitch profile in one embodiment of oblique stretching.
4B is a schematic diagram showing a clip pitch profile in one embodiment of oblique stretching.
5 is a schematic cross-sectional view of a circular polarizing plate using the retardation film obtained by the manufacturing method of the present invention.

Preferred embodiments of the present invention will be described below, but the present invention is not limited to these embodiments. In addition, in the present specification, 'clip pitch in the longitudinal direction' means the distance between centers in the running direction of clips adjacent to the longitudinal direction. In addition, the left-right relationship in the width direction of a long film-shaped film means the left-right relationship toward the conveyance direction of the said film unless there is a special description.

A. Manufacturing method of stretched film

A method for producing a stretched film according to an embodiment of the present invention,

Grasping the left and right ends of the elongated film in the width direction, respectively, with variable pitch type left and right clips in which the clip pitch in the longitudinal direction changes (gripping step);

Preheating the film (preheating process);

Moving the left and right clips while changing the clip pitch of at least one clip, and obliquely stretching the film (oblique stretching step);

heat setting the film (heat setting process), and

Including opening the film from the left and right clips (opening process),

Limiting the moving speed of the clip to a predetermined speed by engaging the constant-speed rotation sprocket with a link mechanism that changes the clip pitch between holding the film with the left and right clips and ending the thermal fixing,

The rotational phase of the constant speed rotation sprocket is monitored, and the rotational phase is adjusted so as to approach the set phase based on the monitoring result.

A-1. stretching device

In the method for manufacturing a stretched film according to an embodiment of the present invention, for example, while holding the left and right ends of a film to be stretched and passing through a preheating zone, a stretching zone, and a heat setting zone in this order, the longitudinal direction It includes left and right clips of a variable pitch type whose clip pitch changes, and in the stretching zone, the left and right clips are run while changing the clip pitch of at least one clip, and the film is obliquely stretched. A constant speed rotation sprocket for limiting the movement speed of the left and right clips to a predetermined speed between the film gripping zone and the corresponding heat fixing zone, a monitoring device for monitoring the rotation phase of the constant speed rotation sprocket, and monitoring This can be done using a film stretching device having a correction device for correcting the phase of rotation of the constant speed rotation sprocket based on the result.

As the stretching device, for example, an endless left and right reference rail passing through a preheating zone, a stretching zone, and a heat setting zone in this order, left and right pitch setting rails provided on the inner circumferential side of the left and right reference rails, and the left and right A plurality of left and right clip holding members guided by the reference rail and traveling, and left and right clips supported on the left and right clip holding members and respectively gripping left and right ends of the elongated film to be stretched, and driving force on the clip holding members and a link mechanism configured to be able to adjust the pitch between the clip-bearing members by the distance between the reference rail and the pitch setting rail, and engaged with the link mechanism to move the left and right clips. A constant speed rotation sprocket for limiting to a predetermined speed, a monitoring device for monitoring the rotation phase of the constant speed rotation sprocket, and a correction device for correcting the rotation phase of the constant speed rotation sprocket based on the monitoring result Further comprising, A film stretching apparatus is mentioned.

1 is a schematic plan view illustrating the overall configuration of an example of a stretching device that can be used in the manufacturing method of the present invention. In the stretching apparatus 100, the holding zone (A), the preheating zone (B), the stretching zone (C), the heat setting zone (D), and the opening zone (E) are arranged in this order from the inlet side to the outlet side of the film. are prepared as Each of these zones means a zone in which the film to be stretched is substantially gripped, preheated, obliquely stretched, heat-set, and opened, and does not mean a mechanically or structurally independent section. Also, it should be noted that the ratio of the lengths of each zone in the stretching device of Fig. 1 is different from the ratio of the actual lengths.

Although not shown in Fig. 1, a zone for performing any appropriate treatment may be provided between the drawing zone C and the heat setting zone D as needed. Examples of such a treatment include a transverse shrinkage treatment and the like. Also, although not shown, the stretching device is typically a heating device (for example, a hot air type, a near infrared ray type) for setting a heating environment from the preheating zone B to the heat setting zone D or the open zone E. , various types of ovens such as far-infrared rays) are provided.

The stretching device 100 includes left and right reference rails 10L and 10R of endless shape on both left and right sides symmetrically in a planar view. The stretching device 100 also supports the pitch setting rails 20L and 20R provided on the inner circumferential side of the left and right reference rails 10L and 10R, and the clip 40, and is guided to the left and right reference rails 10L and 10R, A plurality of left and right clip holding members 30L and 30R traveling and driving means (drive sprockets in the illustrated example) 50L and 50R for imparting a running force to the left and right clip holding members 30L and 30R are further included. do. In addition, in this specification, the reference rail on the left side when viewed from the entrance side of a film is called the left reference rail 10L, and the right reference rail is called the right reference rail 10R. The clip holding members 30L and 30R carrying the clip 40 are guided to the standard rails 10L and 10R and move circularly in a loop shape. Specifically, the clip carrying member 30L guided to the reference rail 10L on the left (as a result, the clip (left clip) 40 supported on the clip carrying member) is circularly moved in a counterclockwise rotation direction, The clip carrying member 30R guided to the right standard rail 10R (as a result, the clip (right clip) 40 supported on the clip carrying member) is circularly moved in the clockwise direction.

In the holding zone A and the preheating zone B of the stretching device 100, the left and right reference rails 10L and 10R are substantially parallel to each other at a separation distance corresponding to the initial width of the film to be stretched. Consists of. In the stretching zone C, the separation distance between the left and right reference rails 10L and 10R gradually expands from the preheating zone B side toward the heat setting zone D until the distance corresponding to the width of the film after stretching is reached. It is composed of In the heat setting 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 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 shown above. 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 holding zone A to the open zone E.

The left clip 40 and the right clip 40 are configured to be independently circulating. Specifically, drive rollers 39 that can be selectively engaged with drive sprockets 50L and 50R are provided on clip holding members 30L and 30R, and drive rollers 39 are connected to electric motors 60L and 60R. By selectively engaging with the driving sprockets 50L and 50R that are rotationally driven by the driving force, a traveling force is imparted to the clip holding members 30L and 30R. Therefore, by rotationally driving the driving sprocket 50L for the reference rail 10L on the left side in a counterclockwise direction, and rotationally driving the driving sprocket 50R for the reference rail 10R on the right side in a clockwise direction, , The left clip rotates in the counterclockwise direction, and the right clip rotates in the clockwise direction. By adjusting the output of the electric motor to change the traveling force transmitted from the driving sprocket to the clip holding member, the traveling speed of the left and right clip holding members (as a result, the traveling speed of the left and right clips) is independently controlled to an arbitrary value. can do. Further, on the film inlet side, sprockets 52L and 52R for adjusting clip position are disposed for simultaneous left and right timing of gripping the film by the clip, and are rotationally driven by electric motors 62L and 62R, respectively. These sprockets are clipped. does not affect the driving speed of Also, unlike the illustrated example, a driving sprocket may be disposed on the film inlet side.

Further, the left clip-bearing member (result, left clip) and the right-side clip-bearing member (result, right clip) are each of a variable pitch type. That is, the left and right clip holding members (as a result, the left and right clips) can each independently change the clip pitch in the longitudinal direction according to the movement. The configuration of the variable pitch type can be realized by adopting a link mechanism configured to be able to adjust the pitch between the clip carrying members by the separation 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 main parts 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 minimum, and FIG. 3 shows a state where the clip pitch is maximum. indicate state.

As shown in FIGS. 2 and 3 , the clip holding member 30 is provided in an elongated rectangular shape in the transverse direction in plan view, and clips 40 are individually supported at one end in the longitudinal direction. Although not shown, the clip holding member 30 is formed of a rigid frame structure with a cross section closed by an upper crossbeam, a lower crossbeam, a front wall (wall on the clip side) and a rear wall (wall on the opposite side to the clip). The clip holding member 30 is provided so as to roll over the running road surfaces 81 and 82 by the running wheels 38 at both ends thereof. 2 and 3, running wheels on the front wall side (traveling wheels that roll on the running road surface 81) are not shown. The running road surfaces 81 and 82 run parallel to the reference rail 10 over the entire area. A long hole 31 is formed along the longitudinal direction of the clip holding member 30 on the rear side of the upper and lower cross beams of the clip holding member 30 (opposite to the clip side (hereinafter, the half clip side)), and the slider 32 ) is slidably engaged in the longitudinal direction of the long hole 31 . In the vicinity of the end of the clip 40 side of the clip holding member 30, one first shaft member 33 is vertically provided through the upper crossbeam and the lower crossbeam. 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. In addition, a driving 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 holding member 30 is provided with one second shaft member 34 penetrating vertically. 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 a main link member 35 is coupled to the first shaft member 33 of each clip holding member 30 by driving. The main link member 35 is pivotally coupled to the second shaft member 34 of the clip holding member 30 adjacent to the other end. In addition to the main link member 35, one end of the sub link member 36 is coupled to the first shaft member 33 of each clip holding member 30 by driving. The other end of the sub link member 36 is coupled to the intermediate portion of the main link member 35 by a pivot 37. As shown in FIG. 2 , by the link mechanism of the main link member 35 and the auxiliary link member 36, the slider 32 is moved to the rear side of the clip holding member 30 (half clip side). , the pitch of the clip holding members 30 in the longitudinal direction (as a result, the clip pitch) decreases, and as shown in FIG. 3 , the slider 32 moves to the front side (clip side) of the clip holding member 30. The pitch of the clip carrying members 30 in the longitudinal direction (as a result, the clip pitch) increases as much as it is. Positioning of the slider 32 is performed by the pitch setting rail 20 . As shown in Figs. 2 and 3, the clip pitch increases as the separation distance between the reference rail 10 and the pitch setting rail 20 decreases.

The stretching device 100 further includes left and right constant-speed rotation sprockets 54L and 54R arranged at the same position in the conveying direction of the preheating zone B, and a monitoring device for monitoring the rotational phase of the constant-speed rotation sprockets 54L and 54R. 70L and 70R, and correction devices 80L and 80R for correcting the phase of rotation of the constant speed rotation sprocket based on the monitoring result.

The left and right constant speed rotation sprockets 54L and 54R are driven at constant speed rotation by electric motors 64L and 64R, respectively. By engaging the left and right constant-speed rotation sprockets 54L and 54R rotating at a predetermined rotational speed with a link mechanism (more specifically, a clip holding member) that changes the clip pitch, the travel speed of the clip is limited to a predetermined speed can do. Also, the phase of rotation of the constant speed rotation sprocket can be arbitrarily adjusted by changing the output pattern of the electric motor according to the input from the correction devices 80L and 80R. As an electric motor capable of arbitrarily adjusting the rotational phase of the constant-speed rotation sprocket, a stepping motor can be used, for example.

Unlike the illustrated example, the left and right constant-speed rotation sprockets may be disposed at positions in which the conveying directions are different from each other. In addition, only either one of left and right constant-speed rotation sprockets may be provided.

The place where the constant speed rotation sprocket is provided is not limited to the preheating zone. The constant speed rotation sprocket is provided in at least one zone selected from a holding zone (but after holding the film with a clip), a preheating zone, a stretching zone and a heat setting zone, preferably at least one selected from the preheating zone and the stretching zone. It can be provided in one zone. As long as the effect of the present invention is obtained, two or more constant speed rotation sprockets may be provided in one zone, and one or more constant speed rotation sprockets may be provided in each of two or more zones.

The monitoring devices 70L and 70R monitor the phase of rotation of the constant speed rotation sprockets 54L and 54R. The monitoring method is not limited. For example, the phase of rotation can be monitored by detecting passage of teeth of a constant-speed rotating sprocket using a displacement sensor that measures the amount of displacement or an optical sensor that measures reflected light as a monitoring device.

Correction devices 80L and 80R specify a shift between the rotation phase of the constant speed rotation sprocket input from the monitoring device and the desired rotation phase (that is, the rotation phase as a set value), and cancel (cancel) the shift. Thus, a signal for bringing the rotational phase of the constant speed rotation sprocket closer to the rotational phase as set is output to the control unit of the electric motor. In addition, as long as the effect of the present invention is obtained, the operator calculates a correction amount (amount of phase shift) for approaching the rotation phase as set based on the monitoring result without providing a correction device, and sends the control unit of the electric motor A correction amount may be input.

Hereinafter, each process is demonstrated in detail.

A-2. holding process

In the gripping zone A (entrance for taking in the film of the stretching device 100), typically, the left and right ends of the film to be stretched are fixed by the clips 40 of the left and right reference rails 10L and 10R. Phases are matched with the clip pitch, that is, they are gripped at the same constant clip pitch as each other. At this time, the line connecting the centers of the left and right clips is typically approximately orthogonal to the transport direction of the film (for example, 90 ° ± 3 °, preferably 90 ° ± 1 °, more preferably 90 ° ± 0.5 °, more preferably 90°). The clip pitch of the left and right clips during 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 sent to the preheating zone B by the left and right movement of the clip (actually, the movement of each clip holding member guided by the left and right reference rails 10L and 10R).

A-3. preheating process

In the preheating zone B, since 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 as described above, basically transverse stretching The film is heated without performing either longitudinal 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 warping of the film due to preheating and contact with nozzles in the oven.

In the preheating step, the film is heated to a temperature T1 (° C.). The temperature T1 is preferably equal to or higher than the glass transition temperature (Tg) of the film, more preferably equal to or higher than Tg+2°C, still more preferably equal to or higher than Tg+5°C. On the other hand, the heating temperature T1 is preferably Tg+40°C or lower, more preferably Tg+30°C or lower. Although different 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 up to the temperature T1 and the holding time at the temperature T1 may be appropriately set depending on the constituent materials of the film or manufacturing conditions (eg, film conveyance speed). These heating times and holding times 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. oblique stretching process

In the stretching zone C, the left and right clips 40 are run and moved while changing the clip pitch in the longitudinal direction of at least one of the clips, and the film is stretched obliquely. More specifically, by moving the left and right clips while increasing or decreasing the clip pitch at different positions, by changing (increasing and/or reducing) the clip pitch at different rates, respectively, is obliquely stretched. As a result of running the left and right clips while changing the clip pitch in this way, among a pair of left and right clips that have simultaneously moved to the stretching zone, one clip precedes the other and reaches the end of the stretching zone. According to such oblique stretching, the edge of the preceding clip is stretched at a higher draw ratio than the edge of the following clip, and as a result, the elongated film is stretched in a desired direction (for example, a direction of 45° with respect to the longitudinal direction). ) to express the slow axis.

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

When oblique stretching includes transverse stretching, the draw ratio in the transverse direction (TD) (the ratio of the width of the film after oblique stretching (W _final ) to the initial width of the film (W _initial ) (W _final /W _initial )) is , preferably 1.05 to 6.00, more preferably 1.10 to 5.00.

In one embodiment, the oblique stretching moves 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 to different positions in the longitudinal direction. In one state, it can be done by increasing or decreasing the clip pitch of each clip to a predetermined pitch. Regarding the oblique stretching of the embodiment, descriptions such as Patent Document 1 and Unexamined-Japanese-Patent No. 2014-238524 can be referred, for example.

In another embodiment, oblique stretching can be performed by increasing or decreasing the clip pitch of one of the left and right clips to a predetermined pitch while fixing the clip pitch of the other clip, and then returning it to the original clip pitch. . Regarding the oblique stretching of the embodiment, descriptions such as Unexamined-Japanese-Patent No. 2013-54338 and Unexamined-Japanese-Patent No. 2014-194482 can be referred to, for example.

In another embodiment, oblique stretching is (i) the clip pitch of one of the left and right clips at P ₁ reducing the clip pitch of the other clip from P ₁ to P ₃ while increasing it to P ₂ , and (ii) the clip of each clip such that the corresponding reduced clip pitch and the corresponding increased clip pitch are the same predetermined pitch. This can be done by changing the pitch. Regarding the oblique stretching of the embodiment, descriptions such as Unexamined-Japanese-Patent No. 2014-194484 can be referred, for example. In the oblique stretching of the embodiment, the clip pitch of one clip is increased from P ₁ while the distance between the left and right clips is increased. up to _P2 while increasing the clip pitch of the other clip at P ₁ up to _P3 to obliquely stretch the film (first oblique stretching), and while increasing the distance between the left and right clips, the clip pitch of the left and right clips is maintained at P ₂ or P ₄ so that the clip pitches of the left and right clips are the same. until decrease, and also set the clip pitch of the corresponding other clip to P ₂ or up to _P4 It may include stretching the film obliquely by increasing it (second oblique stretching).

In the first oblique stretching, oblique stretching is performed while one end of the film is stretched in the direction of a long picture and the other end is contracted in the direction of a long picture, so that the film is stretched in a desired direction (for example, in a direction at 45° with respect to the direction of a long picture). A slow axis can be expressed with uniaxiality and in-plane orientation. Further, in the second oblique stretch, by performing the oblique stretch while reducing the difference between the left and right clip pitches, the film can be sufficiently stretched in an oblique direction while relieving excess stress.

In the oblique stretching of the above three embodiments, since the film can be released from the clips in a state where the moving speeds of the left and right clips are the same, deviation in the transport speed of the film or the like is difficult to occur when the clips on the left and right are released, Winding of the film thereafter can be suitably performed.

4A and 4B are schematic diagrams showing an example of a clip pitch profile in oblique stretching including the first oblique stretching and the second oblique stretching, respectively. Hereinafter, 1st oblique stretch is demonstrated concretely, referring these drawings. 4A and 4B, the horizontal axis corresponds to the travel distance of the clip. No. 1 At the start of oblique stretching, both the left and right clip pitches are P ₁ . P ₁ is typically a clip pitch when the film is gripped. Simultaneously with the start of the first oblique stretching, the increase in the clip pitch of one clip (hereinafter sometimes referred to as a first clip) is started, and the other clip (hereinafter sometimes referred to as a second clip) Initiates a decrease in clip pitch. In the first oblique stretching, the clip pitch of the first clip is set to P ₂ increase, and the clip pitch of the second clip up to P ₃ Decrease. Therefore, at the end of the first oblique stretch (start of the second oblique stretch), the second clip moves at the clip pitch P ₃ and the first clip moves at the clip pitch P ₂ . Further, the ratio of the clip pitches may correspond substantially to the ratio of the moving speeds of the clips.

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 taken as the start of the first oblique stretch, but unlike the illustrated example, You may start decreasing the clip pitch of the second clip after you start increasing the clip pitch of the first clip, or you may start increasing the clip pitch of the first clip after you start decreasing the clip pitch of the second clip. In one preferred embodiment, after starting to increase the clip pitch of the first clip, start decreasing the clip pitch of the second clip. According to this embodiment, since the film is already stretched to a certain extent (preferably, about 1.2 to 2.0 times) in the width direction, wrinkles are unlikely to occur even if the clip pitch of the second clip is greatly reduced. Therefore, oblique stretching at a more acute angle becomes possible, and a retardation film having high uniaxiality and high in-plane orientation can be obtained suitably.

Similarly, in FIGS. 4A and 4B, the clip pitch of the first clip is increased and the clip pitch of the second clip is decreased until the end of the first oblique stretch (when the second oblique stretch is started). Alternatively, either increase or decrease of the clip pitch may end earlier than the other, and the clip pitch may be maintained as it is until the other end (until the end of the first oblique stretch).

The rate of change of the clip pitch of the first clip (P ₂ /P ₁ ) is preferably 1.25 to 1.75, more preferably 1.30 to 1.70, still more preferably 1.35 to 1.65. Further, the change rate of the clip pitch of the second clip (P ₃ /P ₁ ) is, for example, 0.50 or more 1 less than, preferably 0.50 to 0.95, more preferably 0.55 to 0.90, still more preferably 0.55 to 0.85. If the rate of change of the clip pitch is within this range, a slow axis can be developed with high uniaxiality and in-plane orientation in a direction of approximately 45 degrees with respect to the longitudinal direction of the film.

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

The draw ratio in the width direction of the film in the first oblique stretch (film width at the end of the first oblique stretch/film width before the first oblique stretch) is preferably 1.1 to 3.0 times, more preferably 1.2 to 1.2 times. 2.5 times, more preferably 1.25 times to 2.0 times. When the draw ratio is less than 1.1 times, tin-like wrinkles may be formed at the end portion on the contracted side. Moreover, when the said draw ratio exceeds 3.0 times, the biaxiality of the retardation film obtained will become high, and when applied to a circular polarizing plate etc., viewing angle characteristics may fall.

In one embodiment, in the first oblique stretching, the product of the rate of change of the clip pitch of the first clip and the rate of change of the clip pitch of the second clip is preferably 0.7 to 1.5, more preferably 0.8 to 1.45, still more preferably 0.85. It is done so that it becomes ~1.40. When the product of change rates is within this range, a retardation film having high uniaxiality and high in-plane orientation can be obtained.

Next, one Embodiment of 2nd diagonal stretch is concretely demonstrated, referring FIG. 4A. In the second oblique stretching of the present embodiment, the clip pitch of the second clip is set at P ₃ Increase up to P ₂ . On the other hand, the clip pitch of the first clip remains P ₂ during the second oblique stretching. maintain. Therefore, at the end of the second oblique stretch, both the left and right clips move at the clip pitch P ₂ .

The change rate (P ₂ /P ₃ ) of the clip pitch of the second clip in the second oblique stretch in 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 oblique stretch will be specifically described with reference to FIG. 4B. In the second oblique stretching of the present embodiment, the clip pitch of the first clip is reduced and the clip pitch of the second clip is increased. Specifically, the clip pitch of the first clip is set at P ₂ Decrease the clip pitch of the second clip to P ₄ , and set the clip pitch of the second clip to P ₃ . up to _P4 increase Therefore, the second At the end of the oblique stretching, both the left and right clips move at the clip pitch P ₄ . In the illustrated example, the reduction of the clip pitch of the first clip and the increase of the pitch of the second clip are disclosed simultaneously with the start of the second oblique stretch, but these may be started at different timings. Similarly, the reduction of the clip pitch of the first clip and the increase of the clip pitch of the second clip may end at different timings.

Change rate of clip pitch of the first clip in the second oblique stretch of the embodiment shown in FIG. 4B (P ₄ /P ₂ ) and second The rate of change of the clip pitch of the clip (P ₄ /P ₃ ) is not limited 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 It is more than 1.0 and less than 1.0, Preferably it is 0.6-0.95. In addition, 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 greater than or equal to P ₁ . If P ₄ < P ₁ , problems such as wrinkles at the end and increased biaxiality may occur.

The draw ratio in the width direction of the film in the second oblique stretch (film width at the end of the second oblique stretch/film width at the end of the first oblique stretch) is preferably 1.1 times to 3.0 times, more preferably 1.2 times. times - 2.5 times, more preferably 1.25 times - 2.0 times. When the draw ratio is less than 1.1 times, tin-like wrinkles may be formed at the end portion on the contracted side. Moreover, when the said draw ratio exceeds 3.0 times, the biaxiality of the retardation film obtained will become high, and when applied to a circular polarizing plate etc., viewing angle characteristics may fall. In addition, the draw ratio in the width direction in the first oblique stretch and the second oblique stretch (film width at the end of the second oblique stretch/film width before the first oblique stretch) is preferably 1.2 from the viewpoint similar to the above. times - 4.0 times, more preferably 1.4 times - 3.0 times.

The oblique stretching may be typically performed at a temperature T2. Regarding the glass transition temperature (Tg) of the film, 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. . Although different 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 a film heated to temperature T1 in the preheat zone can be cooled to temperature T2.

As described above, transverse shrinkage treatment may be performed after oblique stretching. Regarding the treatment after oblique stretching, paragraphs 0029 to 0032 of Unexamined-Japanese-Patent No. 2014-194483 can be referred.

A-5. heat setting process

In the heat setting zone D, the obliquely stretched film is subjected to heat treatment. In the heat setting zone D, neither transverse stretching nor longitudinal stretching is normally performed, but the clip pitch in the machine direction may be reduced as necessary to relieve stress thereby.

Heat treatment may be typically performed at a temperature T3. The temperature T3 is different depending on the film to be stretched, and may be T2≥T3 or T2<T3. In general, when the film is an amorphous material, T2 ≥ T3, and when the film is a crystalline material, T2 < T3 may be used to perform the crystallization treatment. 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 setting zone and/or the transport speed of the film.

A-6. open process

At any position in the opening zone E, the film is opened from the clip. In the open zone E, neither transverse nor longitudinal stretching is normally performed on the film after heat setting, the film is cooled to a desired temperature, and then the film is released from the clip. The temperature of the film when released from the clip is, for example, 150°C or lower, preferably 70°C to 140°C, more preferably 80°C to 130°C.

A-7. Limitation of clip movement speed and adjustment of rotation phase by constant speed rotation sprocket

In the method for producing a stretched film according to an embodiment of the present invention, between holding the film by the left and right clips and ending the thermal fixation, the clip is moved by engaging a constant-speed rotation sprocket with a link mechanism that changes the clip pitch. Limit the speed to a certain speed. Thereby, in oblique stretching, the orientation angle (angle with respect to the direction of a long picture) of the resulting stretched film, for example, the orientation angle at the center in the width direction, can be prevented from deviating with time from the set value from the beginning to a predetermined period. . More specifically, by precisely controlling the moving speed of the clip by engagement with a constant-speed rotating sprocket, the clip resulting from the force in the oblique direction generated on the film by oblique stretching and the clearance between the bearing supporting the clip and the rail. prevent unwanted movement of As a result of this, the moving speed of the clip is corrected to the set speed, shifting with time of the orientation angle of the resulting stretched film can be prevented.

The movement speed of the clips is limited between holding the film by the left and right clips and ending the heat fixation, preferably between preheating and oblique stretching.

In addition, in the manufacturing method of the stretched film according to the embodiment of the present invention, the rotation phase of the constant speed rotation sprocket is monitored, and the rotation phase is adjusted so as to approach the set phase. In the limitation of the moving speed of the clip, by repeating the engagement with the link mechanism that changes the clip pitch, the rotational phase of the constant speed rotation sprocket gradually shifts, and the relative positional relationship between the left and right clips changes, resulting in a stretched film obtained. Deviations may occur in the in-plane retardation in the width direction. In contrast, by adjusting the rotational phase of the constant speed rotation sprocket to be the set phase, the moving speed of the left and right clips can be limited to a predetermined speed while maintaining the relative positional relationship. As a result, it is possible to suitably prevent the deviation of the orientation angle of the resulting stretched film over time and the deviation of the in-plane retardation in the width direction.

As described above, monitoring of the rotational phase can be performed by detecting passage of teeth of a constant-speed rotating sprocket, for example, by using a displacement sensor that measures the amount of displacement or an optical sensor that measures reflected light as a monitoring device, as described above.

Adjustment of the rotation phase is based on the discrepancy between the rotation phase observed by the monitoring device and the desired rotation phase (ie, the rotation phase as a set value), in order to offset the discrepancy and approach the set phase. This can be done by determining a necessary correction amount (amount of phase shift) and inputting the correction amount to a controller of an electric motor (for example, a stepping motor) that rotationally drives the constant-speed rotation sprocket. For example, when the rotation phase delayed by a predetermined amount from the set phase is monitored, the rotation phase is controlled to increase by a predetermined amount. Further, adjustment of the rotation phase can be performed independently of the left and right constant-speed rotation sprockets.

In one embodiment, the rotation phase difference (the difference between the monitored rotation phase (ie, the measured value of the rotation phase) and the set value of the rotation phase) of the constant speed rotation sprocket is within the range of -1 mm to +1 mm. Adjust the phase of rotation. If the phase difference of rotation is within the said range, the in-plane phase difference and the deviation of an orientation angle can be suitably suppressed.

B. Film to be stretched

In the production method of the present invention, any suitable film can be used. For example, the resin film applicable as retardation film is mentioned. Examples of materials constituting such a film include polycarbonate-based resins, polyvinyl acetal-based resins, cycloolefin-based resins, acrylic resins, cellulose ester-based resins, cellulose-based resins, polyester-based resins, polyester carbonate-based resins, and olefins. system resin, polyurethane type resin, etc. are mentioned. Preferably, they are polycarbonate type resin, cellulose ester type resin, polyester type resin, polyester carbonate type resin, and cycloolefin type resin. This is because, with these resins, a retardation film exhibiting the so-called wavelength dependence of reverse dispersion can be obtained. These resins may be used alone or may be used in combination according to desired properties.

As the polycarbonate-based resin, any suitable polycarbonate-based resin is used. For example, a polycarbonate-based resin containing a structural unit derived from a dihydroxy compound is preferred. As a specific example of a dihydroxy compound, 9,9-bis (4-hydroxyphenyl) fluorene, 9,9-bis (4-hydroxy-3-methylphenyl) fluorene, 9,9-bis (4-hydroxyl) Roxy-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-dimethyl Phenyl) 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 resins, in addition to structural units derived from the above dihydroxy compounds, are isosorbide, isomannide, isoidet, spiroglycol, dioxane glycol, diethylene glycol (DEG), triethylene glycol (TEG), polyethylene Structural units derived from dihydroxy compounds such as glycol (PEG), cyclohexanedimethanol (CHDM), tricyclodecane dimethanol (TCDDM), and bisphenols may be included.

Details of the above polycarbonate-based resins are described in, for example, Japanese Unexamined Patent Publication No. 2012-67300 and Japanese Patent No. 3325560. Description of the said patent document is used as a reference in this specification.

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

Any appropriate polyvinyl acetal-based resin can be used as the polyvinyl acetal-based resin. Typically, polyvinyl acetal-based resin can be obtained by subjecting at least two types of aldehyde compounds and/or ketone compounds to a condensation reaction of polyvinyl alcohol-based resin. Specific examples and detailed production methods of polyvinyl acetal-based resins are described, for example, in Japanese Unexamined Patent Publication No. 2007-161994. This description is incorporated herein by reference.

A stretched film (retardation film) obtained by stretching the film to be stretched preferably has a refractive index characteristic of nx > ny. In one embodiment, the retardation film may preferably function as a λ/4 plate. In this 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 may preferably function as a λ/2 plate. In this 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 having a wavelength of λ nm at 23°C. Therefore, Re(550) is the in-plane retardation of the film measured with light having a wavelength of 550 nm at 23°C. Re(λ) can be obtained by the formula: Re(λ)=(nx-ny)×d when the thickness of the film is d(nm). Here, nx is the refractive index in a direction in which the in-plane refractive index is maximized (ie, the slow axis direction), and ny is the refractive index in the in-plane direction perpendicular to the slow axis (ie, the fast axis direction).

The in-plane retardation Re (550) of the retardation film can be set to a desired range by appropriately setting the oblique 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 oblique stretching is disclosed in Japanese Patent Laid-Open No. 2013-54338, Japanese Unexamined Patent Publication No. 2014-194482, and Japanese Unexamined Patent Publication It is disclosed in detail, such as No. 2014-238524 and Unexamined-Japanese-Patent No. 2014-194484. Therefore, those skilled in the art can set appropriate conditions for oblique stretching based on the disclosure.

When a circular polarizing plate is manufactured using one sheet of retardation film, or when the direction of linearly polarized light is rotated by 90° using one sheet of retardation film, the direction of the slow axis of the retardation film used is the same as the long direction of the film. , 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 ° to 137 °, particularly preferably It is about 45° or 135°.

In the case of manufacturing a circular polarizing plate using two retardation films (specifically, a λ/2 plate and a λ/4 plate), the direction of the slow axis of the retardation film (λ/2 plate) used is It is preferably about 60° to 90°, more preferably 65° to 85°, and particularly preferably about 75° with respect to the elongated direction. Further, the direction of the slow axis 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.

The retardation film preferably exhibits so-called reverse dispersion wavelength dependence. Specifically, its 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). ² /N) to 50×10 ^-12 (m ² /N).

C. Optical laminates and methods of manufacturing the optical laminates

The stretched film obtained by the production method of the present invention can be bonded together with other optical films to be used as an optical laminate. For example, the retardation film obtained by the manufacturing method of the present invention can be bonded to a polarizing plate and suitably used as a circular polarizing plate.

5 is a schematic cross-sectional view of an example of such a circular polarizing plate. The illustrated circular polarizing plate 500 includes a polarizer 510, a first protective film 520 disposed on one side of the polarizer 510, and a second protective film 530 disposed on the other side of the polarizer 510. and a retardation film 540 disposed outside the second protective film 530 . The retardation film 540 is a stretched film (eg, 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 may 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 long and has a slow axis in an oblique direction (for example, at an angle of 45° to the long direction). In many cases, a long picture-like polarizer has an absorption axis in the direction of a long picture or in 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 circular polarizing plate can be produced with extremely excellent production efficiency. In addition, a roll-to-roll refers to the method of continuously bonding together the elongate direction while roll-conveying the elongated films.

In one embodiment, the manufacturing method of the optical laminated body of this invention obtains a long stretched film by the manufacturing method of the stretched film of item A, and conveying the long optical film and this long stretched film, , including continuously bonding together in the direction of the long picture.

[Example]

Hereinafter, the present invention will be specifically described by examples, but the present invention is not limited by these examples. In addition, the measurement and evaluation methods in Examples are as follows.

(1) Thickness

It was measured using a dial gauge (manufactured by PEACOCK, product name 'DG-205 type pds-2').

(2) Phase difference value

The in-plane retardation Re(550) at a wavelength of 550 nm was measured using a retardometer (manufactured by Oji Instruments, KOBRA series). In the case of in-line measurement, measurements were performed at intervals of 0.5 seconds using an in-line retardation meter.

(3) Orientation angle (direction of development of slow axis)

The orientation angle (θ) was measured at a wavelength of 550 nm using a retardometer (manufactured by Oji Instruments Co., Ltd., KOBRA series). In the case of in-line measurement, measurements were performed at intervals of 0.5 seconds using an in-line retardation meter.

(4) Glass transition temperature (Tg)

It was measured according to JIS K 7121.

<Example 1>

(Production of polyester carbonate resin film)

Polymerization was carried out using a batch polymerization apparatus including two vertical reactors equipped with stirring blades 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), DPC 63.77 parts by mass part (0.298 mol) and 1.19 × 10 ^-2 parts by mass (6.78 × 10 ^-5 mol) of calcium acetate monohydrate as a catalyst. After replacing the inside of the reactor with reduced pressure nitrogen, heating was performed with a heat medium, and stirring was started when the internal temperature reached 100°C. The internal temperature reached 220°C 40 minutes after the start of the temperature increase, and while controlling to maintain this temperature, the pressure reduction was started, and after reaching 220°C, it was set to 13.3 kPa in 90 minutes. Phenol vapor produced as a by-product of the polymerization reaction was directed 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 directed to a condenser at 45°C for recovery. After nitrogen was introduced into the first reactor to once restore pressure to atmospheric pressure, the oligomerized reaction solution in the first reactor was transferred to the second reactor. Next, the temperature increase and pressure reduction in the second reactor were started, and the internal temperature was 240°C and the pressure was 0.2 kPa in 50 minutes. Thereafter, polymerization was allowed to proceed until a predetermined agitation power was reached. At the time of reaching the predetermined power, nitrogen was introduced into the reactor to restore pressure, the resulting polyester carbonate was extruded into water, and the strand was cut to obtain pellets. Tg of the obtained polyester carbonate resin was 140 degreeC.

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 1500 mm, set temperature: 250 ° C.), chilled roll (set Temperature: 120 to 130 ° C.) and a film forming apparatus equipped with a winding machine 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 a film stretching device as shown in Figs. 1 to 3, specifically, a pair of left and right constant-speed rotation sprockets disposed at the same position in the conveying direction of the preheating zone (B), A film stretching device having a monitoring device for monitoring the rotation phase of the constant speed rotation sprocket and a correction device for correcting the rotation phase of the constant speed rotation sprocket based on the monitoring result is used, in a direction of 45° with respect to the long direction. obliquely stretched so that the slow axis is expressed (that is, the target orientation angle is set in the direction of 45° with respect to the long direction) to obtain a retardation film.

Specifically, the left and right ends of the polyester carbonate resin film were held at the inlet of the stretching device by the clips on the left and right, and preheated at 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 stretching zone C, the increase in the clip pitch of the right clip and the decrease in the clip pitch of the left clip are started, and the clip pitch of the right clip is increased to P ₂ . Along with the increase, the clip pitch of the left clip was reduced to P ₃ (first oblique stretching) _. 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 was 0.78, and the transverse stretch ratio to the original width of the film was 1.45 times. Next, while maintaining the clip pitch of the right clip at P ₂ , the increase in the clip pitch of the left clip was started and increased from P ₃ to P ₂ (second oblique stretching). The rate of change of the clip pitch of the left clip between them (P ₂ /P ₃ ) was 1.82, and the transverse stretch ratio to the original width of the film was 1.9 times. In addition, the drawing zone (C) was set to Tg+3.2°C (143.2°C).

Then, in the heat setting zone (D), the film was held at 125°C for 60 seconds to perform heat setting. After the heat-set film was cooled to 100°C in the open zone (E), the left and right clips were opened.

In addition, at the time of starting production of the stretched film, the rotational phases of the left and right constant-speed rotation sprockets were synchronized and set to rotate at the same rotational speed (rotational speed at which the clip travels at a set speed). In addition, a signal for monitoring the rotation phase of each of the left and right constant-speed rotation sprockets with a monitoring device, and canceling the difference between the monitored rotation phase and the set value of the rotation phase to approximate the rotation phase as set. The calibration device was set to output to the controller of the drive motor.

<Comparative Example 1>

A stretched film was obtained in the same manner as in Example 1 using the same film stretching apparatus as the film stretching apparatus used in Example 1 except that the left and right constant-speed rotation sprockets, the monitoring device and the correction device were not provided.

<Comparative Example 2>

A stretched film was obtained in the same manner as in Example 1 except that the phase of rotation of the constant speed rotation sprocket based on the monitoring result was not adjusted.

[Measurement of orientation angle and in-plane phase difference]

The effective width was specified for the stretched film obtained in Example 1 as described below. Within the effective width, the orientation angle (angle with respect to the elongated direction) and the in-plane retardation (Re (550)) were measured in-line at a total of three locations within 25 mm from the center and left and right ends of the film in the width direction, respectively. Table 1 shows the orientation angle in the center of the width direction and the deviation of the in-plane retardation and in-plane retardation (difference between the maximum and minimum values of Re (550) measured at three locations) measured 60 minutes and 24 hours after the start of production of the stretched film. indicate

[effective width]

The overall width of the stretched film obtained 24 hours after the start of production by measuring the in-plane retardation at a plurality of points in the width direction of the stretched film, and setting the width showing the in-plane retardation of ±4 nm with respect to the average in-plane retardation value to the effective width. The ratio (%) of the effective width to was evaluated. The results are shown in Table 1.

[Evaluation of appearance and handling]

With regard to the stretched films obtained in Examples and Comparative Examples, the appearance and handleability were visually evaluated based on the following criteria. The results are shown in Table 1.

○: Wrinkles and sagging are not observed on the stretched film during roll conveyance

×: Wrinkles and/or sagging are observed on the stretched film during roll conveyance

[Table 1]

As shown in Table 1, in the continuous production of a long obliquely stretched film, while limiting the moving speed of the clip to a predetermined speed using a constant speed rotation sprocket, by maintaining the phase of its rotation at the set phase, Shift in the orientation angle of the resulting stretched film over time and variation in in-plane retardation can be suitably prevented.

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 electroluminescent displays (OLEDs). there is.

10: reference rail
20: pitch setting rail
30: clip holding member
40: clip
54: constant speed rotation sprocket
70: monitoring device
80: correction device
100: stretching device
500: circular polarizer

Claims (7)

Holding the left and right ends of the elongated film in the width direction, respectively, with variable pitch type left and right clips in which the clip pitch in the longitudinal direction changes (gripping step),
Preheating the film (preheating process),
Moving the left and right clips while changing the clip pitch of at least one clip to obliquely stretch the film (oblique stretching step);
heat setting the film (heat setting process), and
Including opening the film from the left and right clips (opening step),
Limiting the moving speed of the clip to a predetermined speed by engaging a constant-speed rotation sprocket with a link mechanism that changes the clip pitch between gripping the film with the left and right clips and ending the thermal fixing,
The method of manufacturing a stretched film, wherein the rotation phase of the constant speed rotation sprocket is monitored, and the rotation phase is adjusted so as to approach the set phase based on the monitoring result. According to claim 1,
In at least one step selected from the preheating step, the oblique stretching step, and the heat setting step, the moving speed of the clip is limited to a predetermined speed. According to claim 1,
A manufacturing method in which the phase difference of rotation of the constant speed rotation sprocket is adjusted to -1 mm to +1 mm. According to claim 1,
The oblique stretching (i) sets the clip pitch of one of the left and right clips to P_Oneat P₂increase the clip pitch of the other clip to P_Oneat P₃and (ii) changing the clip pitch of each clip so that the reduced clip pitch and the increased clip pitch become the same predetermined pitch. According to claim 4,
P ₂ /P ₁ is 1.25 to 1.75, and P ₃ /P ₁ is 0.50 or more 1 less than, a method for producing a stretched film. Obtaining a long stretched film by the manufacturing method according to any one of claims 1 to 5, and
The manufacturing method of the optical laminated body which includes matching the long picture direction and bonding continuously, conveying a long picture-like optical film and the said long picture-like stretched film. According to claim 6,
The optical film is a polarizing plate,
The method for producing an optical laminate wherein the stretched film is a λ/4 plate or a λ/2 plate.

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