KR20230043712A - Method for producing stretched film and method for producing optical laminate - Google Patents

Abstract

An object of the present invention is to reduce deviations in an in-plane retardation and/or an orientation angle which may occur over time in continuous production of a long tilted stretched film. The present invention provides a method for producing a stretched film using a film stretching device which includes left and right reference rails each having an endless shape, left and right pitch setting rails provided along the left and right reference rails, respectively, a plurality of left and right clip supporting members traveling while being guided to the left and right reference rails, respectively; left and right clips supported on the left and right clip supporting members, respectively; and a link mechanism configured to enable adjustment of a pitch between the clip supporting members by a distance between the reference rails and the pitch setting rails, wherein the method comprises the steps of: traveling the left and right clips while changing a clip pitch of at least one clip so as to tilt and stretch the film; opening the film from the left and right clips; and measuring deviations in an in-plane retardation and/or an orientation angle in a width direction of the film, wherein the method further includes traveling speed of the left and right clips when gripping the film is changed, when the deviations in the in-plane retardation and/or the orientation angle exceed a predetermined reference.

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, in the continuous production of the obliquely stretched film obtained by such a technique, variations may occur in the in-plane retardation and/or orientation angle of the obtained obliquely stretched film over time.

Japanese Patent No. 4845619

The present invention has been made to solve the above problems, and its main object is to reduce the in-plane retardation and/or orientation angle deviation that may occur over time in the continuous production of long obliquely stretched films.

According to one aspect of the present invention, left and right reference rails of an endless shape, left and right pitch setting rails provided along the left and right reference rails, and a plurality of left and right clips that are guided by the left and right reference rails and are supported by clips. A film stretching device comprising: a member, left and right clips supported on the left and right clip-bearing members, and a link mechanism configured to be able to adjust a pitch between the clip-bearing members by a separation distance between the reference rail and the pitch setting rail. A method for producing a stretched film using a method, wherein the left and right ends of a long film in the width direction are respectively held by the left and right clips, and the left and right clips are moved while changing the clip pitch of at least one clip. obliquely stretching the film, opening the film from the left and right clips, and measuring the in-plane retardation and/or deviation of the orientation angle in the width direction of the film, wherein the in-plane retardation and/or A method for producing a stretched film is provided, which includes changing the traveling speed of the left and right clips when gripping the film when the deviation of the orientation angle exceeds a predetermined criterion.

In one embodiment, after cutting and removing the left and right ends of the film opened from the left and right clips, the in-plane retardation and/or orientation angle deviation in the width direction is measured.

In one embodiment, with respect to the traveling speed of the left and right clips when gripping the film, the change rate of the traveling speed of the clip defined by the following equation (1) is -10% to -1% or 1% to 10 %am.

Change rate (%) of traveling speed of clip when holding film = (traveling speed of clip after change - traveling speed of clip before change)/traveling speed of clip before change × 100 (1)

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, when a long obliquely stretched film is continuously produced using a predetermined stretching device, over time, in the case of deviation in in-plane retardation and / or orientation angle, The traveling speed of the left and right clips when gripping the film is changed. In this way, an obliquely stretched film in which in-plane retardation and/or orientation angle variation that may occur over time are reduced without changing obliquely stretched conditions such as clip pitch profile or heating temperature can be obtained. The reason for such an effect can be guessed as follows, although it does not limit the present invention in any way. That is, due to the unintentional change in the separation distance between the reference rail and the pitch setting rail due to the stress acting on the clip holding member during oblique stretching, the clip pitch also changes from the set value, and as a result, the in-plane phase difference and Or, a deviation may occur in the orientation angle. In contrast, by reducing the stress by changing the line speed, an unintended change in the separation distance between the reference rail and the pitch setting rail (as a result, an unintended change in clip pitch) is suppressed, and the in-plane phase difference of the obliquely stretched film is suppressed. And/or it is possible to prevent deviations from occurring in the orientation angle.

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.
Fig. 5 is a schematic diagram explaining a method for measuring an in-plane retardation and/or an orientation angle.
6 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 manufacturing a stretched film according to an embodiment of the present invention includes an endless left and right reference rail, left and right pitch setting rails provided along the left and right reference rails, and a plurality of running movements guided by the left and right reference rails. A link mechanism configured to be able to adjust the pitch between the left and right clip carrying members, the left and right clips supported on the left and right clip carrying members, and the distance between the reference rail and the corresponding pitch setting rail to adjust the pitch between the clip carrying members. It is performed using a film stretching device.

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

Holding the left and right ends of the elongated film in the width direction, respectively, with the left and right clips (gripping step),

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

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

Including measuring in-plane retardation and/or orientation angle deviation in the width direction of the film (in-plane retardation and/or orientation angle deviation measurement process),

When the deviation of the in-plane retardation and/or orientation angle exceeds a predetermined criterion, changing the traveling speed of the left and right clips when holding the film (line speed change step).

Typically, the manufacturing method of the present embodiment further includes a preheating step. Specifically, the film held by the left and right clips is preheated and then subjected to oblique stretching.

A-1. stretching device

A stretching device used in a method for manufacturing a stretched film according to an embodiment of the present invention is guided by endless left and right reference rails, left and right pitch setting rails provided along the left and right reference rails, and the left and right reference rails. The pitch between the clip carrying members can be adjusted by the separation distance between the plurality of left and right clip carrying members that travel and move, the left and right clips supported on the left and right clip carrying members, and the reference rail and the pitch setting rail. Including the configured link mechanism.

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, a holding zone A, a preheating zone B, a stretching zone C, and an opening zone D are provided in this order from the inlet side to the outlet side of the film. Each of these zones means a zone in which the film to be stretched is substantially gripped, preheated, obliquely stretched, 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 open 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, various ovens such as hot air type, near infrared type, and far infrared type) for setting a heating environment from the preheating zone B to the open zone D. ) is 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 guided to the left reference rail 10L (as a result, the clip (left clip) 40 supported on the clip carrying member) is circularly moved in the counterclockwise rotation direction, and the right reference rail The clip carrying member guided to the 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, from the side of the preheating zone B to the open zone D, the distance between the left and right reference rails 10L and 10R gradually expands until it corresponds to the width of the film after stretching. is composed of In the open zone D, 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 D.

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 the main link member 35 is pivotally coupled to the first shaft member 33 of each clip holding member 30 . 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.

According to the stretching device, when the clip pitch is kept constant, the running speed of the clip is also kept constant, and when the clip pitch is changed (increased or decreased), the clip is moved at a change rate substantially corresponding to the change rate of the clip pitch. The driving speed also changes. Therefore, the basic traveling speed of the clip is the traveling speed of the clip (traveling speed of the clip holding member) when a traveling force is applied from the driving means, and then the clip is clipped by adjusting the separation distance between the reference rail and the pitch setting rail. The pitch (and consequently, the running speed of the clip) can be arbitrarily changed. Therefore, by keeping the distance between the reference rail and the pitch setting rail from the installation point of the driving means to the gripping zone A constant, the clip can enter the gripping zone A while substantially maintaining the basic traveling speed. . In addition, in this specification, the running speed of the left and right clips at the time of gripping a film may be called "line speed."

By performing oblique stretching of the film using the stretching apparatus as described above, an obliquely stretched film, for example, a retardation film having a slow axis in an oblique direction can be produced. In addition, about the specific embodiment of the above stretching apparatus, it describes, for example in Unexamined-Japanese-Patent No. 2008-44339, and the whole is used here as a reference. In addition, the stretching apparatus applicable to the manufacturing method of the stretched film according to the embodiment of the present invention is not limited to the illustrated example. For example, various stretching devices equipped with a link mechanism as described in Japanese Unexamined Patent Publication No. 2003-71921, Japanese Unexamined Patent Publication No. 2017-113890 and the like can be applied.

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, both ends of the film to be stretched are at the same constant clip pitch with the clips 40 on either side, and at the same timing. is gripped by 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).

The running speed of the left and right clips when gripping the film can be appropriately set in consideration of production efficiency, oblique stretching conditions (eg, rate of change of clip pitch, timing, heating temperature), and the like. The traveling speed of the left and right clips is, for example, 5 m/min to 30 m/min, preferably 10 m/min to 25 m/min, and more preferably 15 m/min to 25 m/min.

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 while changing the clip pitch in at least one longitudinal direction thereof, and the film is obliquely stretched. More specifically, by increasing or reducing the clip pitches of the left and right clips at different positions, by changing (increasing and/or reducing) the clip pitches of the left and right clips at different changing speeds, respectively, is obliquely stretched.

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. As described above, according to the oblique stretching including the first oblique stretching and the second oblique stretching, a retardation film exhibiting high uniaxiality and in-plane orientation can be obtained, while a large stress is applied to the clip carrying member during oblique stretching. Since it is applied, the problem of in-plane retardation and/or deviation of the orientation angle tends to occur, but the problem can be appropriately suppressed by applying the method for producing a stretched film of the present invention.

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, variation in the transport speed of the film or the like is difficult to occur when the clips on the left and right are opened, 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 figures. 4A and 4B, the horizontal axis corresponds to the travel distance of the clip. No. 1 At the start of the oblique stretch, both 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 (the 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, unlike the illustrated example. , You may start decreasing the clip pitch of the second clip after starting to increase the clip pitch of the first clip, or you may start increasing the clip pitch of the first clip after starting to decrease 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 (the start of the second oblique stretch). , the clip pitch may be maintained as it is until one of the increase or decrease of the clip pitch ends earlier than the other, and the other ends (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 times to 3.0 times, more preferably 1.2 times to 2.5 times. 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 _P2 . 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, while reducing the clip pitch of the first clip, 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 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 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 times from the viewpoint similar to the above. It is -4.0 times, More preferably, it is 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. open process

At an arbitrary position in the open zone D, the film is released from the clip. In the open zone D, neither transverse nor longitudinal stretching is normally performed, and the film is heat-treated as necessary to fix the stretched state (heat setting), and/or cooled to Tg or less, and then the film is released from the clip do. In addition, when heat fixing, the clip pitch in the longitudinal direction may be reduced, thereby relieving stress.

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. In the case of 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 stretched film released from the clip is sent out from the outlet of the stretching device and subjected to measurement of in-plane retardation and/or orientation angle.

A-6. In-plane retardation and/or orientation angle deviation measurement process

In one embodiment, the in-plane retardation and/or orientation angle (hereinafter referred to as 'in-plane retardation and/or orientation angle') at a plurality of points in the width direction is referred to as 'in-plane retardation' while roll conveying the film sent out from the exit of the stretching device. etc.) is measured in-line. The difference between the maximum value and the minimum value of the in-plane retardation or the like measured at a plurality of locations in the width direction is calculated as a deviation.

For example, in the embodiment shown in FIG. 5 , the measuring device 2 is provided above the central portion and the left and right ends of the film 1 in the width direction on the conveyance line, and the in-plane retardation of the conveyed film is measured at three locations in the width direction. vertices are being measured. The measurement location may be different from the illustrated example, for example, a total of two locations at either the left and right ends or the central portion in the width direction of the film, or a total of two locations only at the left and right ends, or two or three locations at equal intervals in the width direction. , 4 places, 5 places or more. Preferably, the in-plane retardation or the like is measured at two or more locations including the left and right ends (for example, the distance from the left and right short sides is within 25 mm).

Measurement of the in-plane retardation or the like may be performed continuously or at predetermined intervals. For example, measurements of in-plane retardation and the like may be performed at intervals of 0.1 second to 1 second, preferably 0.1 second to 0.5 second.

The measurement wavelength of the in-plane retardation or the like can be appropriately set depending on the purpose. For example, the measurement wavelength of the in-plane retardation or the like may be within a range of 500 nm to 600 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).

Measurement of the in-plane retardation or the like may be performed after cutting and removing the left and right ends in the width direction of the stretched film released from the clip. By measuring the in-plane retardation or the like in a state where both ends are removed, more accurate measurement results can be obtained.

The width of the ends to be cut off may be each independently, for example, 20 mm to 600 mm, preferably 100 mm to 500 mm. Cutting off the ends can be done by conventional slitting.

A-7. Line speed change process

In the above measurement, when the deviation of the in-plane retardation or the like exceeds a predetermined criterion, the traveling speed (line speed) of the left and right clips when gripping the film is changed in the upstream process. On the other hand, when the deviation is below the predetermined standard, production of the stretched film can be continued under the same conditions as before without changing the line speed.

In one embodiment, the line speed is changed when the deviation of the in-plane retardation Re(550) is, for example, 10 nm or more, and also, for example, 8 nm or more.

In one embodiment, the line speed is changed when the deviation of the orientation angle is eg 8° or more, and also eg 5° or more.

The change rate of the line speed (change rate (%) of the traveling speed of the clip when gripping the film = (the traveling speed of the clip after the change - the traveling speed of the clip before the change) / the traveling speed of the clip before the change × 100), according to the present invention It is not particularly limited as long as the effect of is obtained. The change rate of the line speed is, for example, -10% to -1% or 1% to 10%, preferably -8% to -1% or 1% to 8%, more preferably -5% to -1% % or 1% to 5%. If the rate of change of the line speed is within this range, an unintentional change in the separation distance between the reference rail and the pitch setting rail caused by stress during oblique stretching can be appropriately suppressed. Needless to say, since the running speed of the left and right clips when holding the film is the same speed, the same rate of change is applied to the left and right clips (in other words, before and after changing the line speed). In this case, the traveling speed of the left clip and the traveling speed of the right clip when gripping the film are the same).

In addition, by changing the line speed at the rate of change, it is possible to optimize the amount of heat applied to the film and obtain a desired in-plane retardation or the like. For example, by increasing the line speed, excessive heat applied to the film can be avoided, and the obtained in-plane retardation or the like can be reduced while suppressing the variation. Further, for example, by lowering the line speed, it is possible to increase the obtained in-plane retardation or the like while suppressing the variation by applying a sufficient amount of heat to the film.

In one embodiment, the line speed after change is, for example, 5.5 m/min to 33 m/min, preferably 5.4 m/min to 32.4 m/min, more preferably 5.25 m/min to 31.5 m/min. When the line speed is within this range, an unintended change in the separation distance between the reference rail and the pitch setting rail caused by stress during oblique stretching can be appropriately suppressed while maintaining practically acceptable production efficiency.

Changing the line speed can be done in any suitable way. For example, the line speed can be reduced by reducing the driving force applied to the clip holding member from the driving means (eg, changing the rotational speed of the driving sprocket), changing the torque of the driving roller, or the like. Further, for example, the line speed can be increased by increasing the running force applied to the clip holding member from the driving means (eg, changing the rotational speed of the driving sprocket), changing the torque of the driving roller, or the like. Preferably, the line speed is changed gradually.

In one embodiment, during continuous production of elongated stretched films, variations such as in-plane retardation are continuously measured, and a line speed change step can be performed whenever the variation exceeds a predetermined standard.

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 characteristics.

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.

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.

6 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 at intervals of 0.5 seconds using an in-line retardation meter (manufactured by Oji Instruments, KOBRA series).

(3) Orientation angle (direction of development 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 (manufactured by Oji Instruments, KOBRA series).

(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 mass parts (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 heating 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 rise, and while controlling to maintain this temperature, pressure reduction was started, and 90 minutes after reaching 220°C, it was set to 13.3 kPa. Phenol vapor produced as a byproduct 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 the pressure to atmospheric pressure, the oligomerized reaction solution in the first reactor was transferred to the second reactor. Subsequently, the temperature increase and pressure reduction in the second reactor were started, and the internal temperature was 240°C and the pressure was 0.2 kPa in 50 minutes. Thereafter, polymerization was allowed to proceed until a predetermined agitation power was reached. When the predetermined power was reached, nitrogen was introduced into the reactor to restore pressure, and the produced 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 by the above was obliquely stretched using the stretching apparatus as shown in FIGS. 1-3, and the retardation film was obtained.

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.

Subsequently, 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 is 0.78, and the transverse stretch magnification with respect to the original width of the film is It 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 open zone (D), heat setting was performed by holding the film at 125°C for 60 seconds. After cooling the heat-set film to 100°C, the left and right clips were opened.

In addition, in the above oblique stretching, the rotational speed of the drive sprocket of the stretching device was controlled so that the running speed of the left and right clips (hereinafter referred to as line speed) when holding the film was 15 m/min.

(Measurement of in-plane retardation and orientation angle)

300 mm of each of the left and right ends of the stretched film released from the clip and sent out from the stretching device was cut out. Subsequently, the in-plane retardation Re (550) and the orientation angle (angle in the long direction) were measured at the top of the film at a total of three locations within 25 mm from the center in the width direction and the left and right ends of the film, respectively, while conveying the roll. Table 1 shows the measurement results after about 6 hours and about 24 hours after the start of production of the stretched film.

[Table 1]

(variation of line speed)

The line speed was reduced to 14.55 m/min by lowering the rotational speed of the drive sprocket immediately after the measurement after about 24 hours from the start of the production, and the oblique stretching was continued under the same conditions as above (change rate of line speed: -3%). Further, the clip pitch of the left and right clips slightly decreased due to such a change in line speed.

Table 2 shows Re (550) and the orientation angle measured in the same manner as above after about 30 minutes from the change in the line speed.

<Example 2>

In the change of the line speed, a stretched film was obtained in the same manner as in Example 1 except that the line speed was 14.25 m/min (change rate of the line speed: -5%). Table 2 shows the Re (550) and the orientation angle measured about 30 minutes after the change in line speed.

<Example 3>

In the change of the line speed, a stretched film was obtained in the same manner as in Example 1 except that the line speed was 13.8 m/min (change rate of the line speed: -8%). Table 2 shows the Re (550) and the orientation angle measured about 30 minutes after the change in line speed.

<Example 4>

A stretched film was obtained in the same manner as in Example 1 except that the initial line speed before changing the line speed was 13.5 m/min, and the line speed was 13.9 m/min in line speed change (of line speed rate of change: 3%). Table 2 shows the Re (550) and the orientation angle measured about 30 minutes after the change in line speed.

[Evaluation of appearance and handling]

With regard to the stretched films obtained in Examples 1 to 4 and the stretched films immediately before changing the line speed in Examples 1 and 4 (Comparative Example), the appearance and handleability were visually evaluated based on the following criteria. The results are shown in Table 2.

○: 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 2]

As shown in Tables 1 and 2, in the continuous production of long obliquely stretched films, shifts and variations, such as in-plane retardation, occur in the obliquely stretched films obtained over time, but these variations can be reduced by changing the line speed. can

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.

1: stretched film
10: reference rail
20: pitch setting rail
30: clip holding member
40: clip
50: driving means
100: stretching device
500: circular polarizer

Claims (7)

Endless left and right reference rails, left and right pitch setting rails provided along the left and right reference rails, a plurality of left and right clip holding members guided by the left and right reference rails to travel, and A stretched film is produced using a film stretching device including left and right clips supported on a clip carrying member and 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. As a manufacturing method,
Holding the left and right ends of the elongated film in the width direction with the left and right clips, respectively;
obliquely stretching the film by moving the left and right clips while changing the clip pitch of at least one clip;
opening the film from the left and right clips; and
Including measuring the deviation of the in-plane retardation and / or orientation angle in the width direction of the film,
A method for producing a stretched film comprising changing the travel speed of the left and right clips when holding the film when the in-plane retardation and/or deviation of the orientation angle exceeds a predetermined criterion. According to claim 1,
After cutting and removing the left and right ends of the film opened from the left and right clips, measuring the in-plane retardation and/or orientation angle deviation in the width direction. According to claim 1,
Regarding the traveling speed of the left and right clips when holding the film, the rate of change of the traveling speed of the clip defined by the following equation (1) is -10% to -1% or 1% to 10% of the stretched film Manufacturing method:
Change rate (%) of traveling speed of the clip when holding the film = (traveling speed of the clip after change-traveling speed of the clip before change)/traveling speed of the clip before change x 100 (1). According to claim 1,
The oblique stretching is (i) the clip pitch of one of the left and right clips at P ₁ Increase the clip pitch of the clip on the other side from P ₁ to P ₂ . P ₃ , and (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.

Images