KR20220134456A - Method for producing stretched film - Google Patents

Abstract

The purpose of the present invention is to reduce the sagging generated in an obliquely stretched film. The present invention relates to a manufacturing method of a stretched film which comprises: a step of gripping the left and right ends of a width direction of a continuously conveyed elongated film with variable pitch type left and right clips in which the clip pitch in a longitudinal direction changes, respectively; a step of moving the left and right clips while changing at least one clip pitch to obliquely stretch the film; and a step of opening the film from the left and right clips. In addition, the present invention relates to the manufacturing method of a stretched film in which a conveying direction of the film before being gripped by the left and right clips is obliquely inclined with respect to the conveying direction of the film during the oblique stretching, and a line connecting the left and right clips when gripping the film is obliquely inclined with respect to the conveying direction of the film during the oblique stretching.

Description

The manufacturing method of a stretched film {METHOD FOR PRODUCING STRETCHED FILM}

This invention relates to the manufacturing method of a stretched film, and the manufacturing method of an optical laminated body.

DESCRIPTION OF RELATED ART In image display apparatuses, such as a liquid crystal display device (LCD) and an organic electroluminescent display device (OLED), a circularly polarizing plate is used for the purpose of the improvement of a display characteristic, and reflection prevention. The circularly polarizing plate is typically laminated with a polarizer and a retardation film (typically a λ/4 plate) so that the absorption axis of the polarizer and the slow axis of the retardation film form an angle of 45°. Conventionally, retardation films are typically produced by uniaxially stretching or biaxially stretching in the longitudinal and/or lateral directions, so that their slow axis is, in many cases, in the transverse direction ( width direction) or longitudinal direction (long picture direction). As a result, in order to produce a circularly polarizing plate, it was necessary to cut|disconnect retardation film so that it may make an angle of 45 degrees with respect to the width direction or a long direction, and to bond together one by one.

Moreover, in order to ensure the broadband property of a circularly polarizing plate, the retardation film of 2 sheets of a λ/4 plate and a λ/2 plate may be laminated. In that case, it is necessary to laminate the λ/2 plates so as to form an angle of 75° with respect to the absorption axis of the polarizer, and the λ/4 plates so as to form an angle of 15° with respect to the absorption axis of the polarizer. Also in this case, when producing a circularly polarizing plate, it was necessary to cut retardation film so that it may make the angle of 15 degrees and 75 degrees with respect to the width direction or a long direction, and to bond together one by one.

In another embodiment, a λ/2 plate may 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 the light from the note PC from being reflected on the keyboard or the like. . Also in this case, it was necessary to cut|disconnect retardation film so that it might make an angle of 45 degrees with respect to the width direction or a long direction, and to bond together one by one.

In order to solve such a problem, the left and right ends of the long film in the width direction are respectively gripped by the right and left clips of the variable pitch type in which the clip pitch in the longitudinal direction changes, and at least one clip pitch of the left and right clips. A technique of expressing the slow axis of the retardation film in an oblique direction by changing the direction and extending in an oblique direction with respect to the long direction (hereinafter also referred to as 'diagonal stretching') has been proposed (eg, Patent Document 1). However, in the diagonally stretched film obtained by such a technique, sagging may arise.

Japanese Patent No. 4845619

MEANS TO SOLVE THE PROBLEM This invention was made|formed in order to solve the said subject, The main objective is to reduce the sagging which arose in the diagonally stretched film.

According to one aspect of the present invention, the left and right ends of the continuously conveyed long film in the width direction are respectively gripped by the right and left clips of the variable pitch type in which the clip pitch in the longitudinal direction changes, the left and right clips A method for producing a stretched film, comprising: moving the film while changing at least one clip pitch, obliquely stretching the film, and opening the film from the left and right clips, wherein the right and left clips The conveyance direction of the said film before is obliquely inclined with respect to the conveyance direction of the said film at the time of the said diagonal stretch, and the line which connected the said left and right clips when holding the said film is that of the said film at the time of diagonal stretching. A method for producing a stretched film, which is inclined with respect to a conveying direction, is provided.

In one embodiment, the conveying direction of the film before gripping with the left and right clips is inclined with respect to the conveying direction of the film at the time of the diagonal stretching so that the end of the film on the non-sagging side becomes the concave side. .

In one embodiment, the conveyance direction of the said film before holding by the said right and left clips makes an angle of 10-40 degrees with respect to the conveyance direction of the said film at the time of the said diagonal stretch.

In one embodiment, the diagonal stretching comprises: (i) a clip pitch of one of the left and right clips at P ₁ . Increase the clip pitch of the other clip from P ₁ while increasing to P ₂ . reducing to P ₃ , and (ii) varying the clip pitch of each clip such that the reduced clip pitch and the increased clip pitch are a predetermined equal pitch.

In one embodiment, P ₂ /P ₁ is between 1.25 and 1.75 and P ₃ /P ₁ is at least 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 elongated stretched film while aligning the direction of the long picture and continuously bonding the optical, including A method of making 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.

In the manufacturing method of the stretched film of this invention, the conveyance direction of the film before hold|gripping with a clip is set so that it may incline with respect to the conveyance direction of the film at the time of diagonal stretch. Thus, by conveying a film from the diagonal direction with respect to the conveyance direction at the time of diagonal stretching, the travel path length (path length) of the left and right end parts from a film feeding out from a roll to opening from a clip can be made different. As a result, tension is applied to the slack side of the film and the overall flatness is achieved, so that an elongate stretched film with reduced sagging can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic plan view explaining the whole structure of an example of the extending|stretching apparatus which can be used for the manufacturing method of the stretched film of this invention.
It is a principal part schematic plan view for demonstrating the link mechanism which changes a clip pitch in the extending apparatus of FIG.
It is a principal part schematic plan view for demonstrating the link mechanism which changes a clip pitch in the extending|stretching apparatus of FIG.
4 : is a schematic plan view explaining a holding|gripping process.
It is a schematic diagram which shows the profile of the clip pitch in one Embodiment of diagonal stretch.
It is a schematic diagram which shows the profile of the clip pitch in one Embodiment of diagonal stretch.
6 is a schematic cross-sectional view of a circularly polarizing plate using the retardation film obtained by the manufacturing method of the present invention.
7 : is a schematic diagram explaining the measuring method of the amount of sagging.

EMBODIMENT OF THE INVENTION Hereinafter, although preferred embodiment of this invention is described, this invention is not limited to these embodiment. In addition, in this specification, the "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 of the width direction of a long film means the left-right relationship toward the conveyance direction of this 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,

Holding the left and right ends in the width direction of the continuously conveyed long film by the right and left clips of the variable pitch type in which the clip pitch in the longitudinal direction changes, respectively (holding step);

moving the clips on the left and right while changing at least one clip pitch to diagonally stretch the film (diagonal stretching step), and opening the film from the right and left clips (opening step);

includes

In the manufacturing method of embodiment of this invention, the conveyance direction of the said film before gripping with the said right and left clips is inclined with respect to the conveyance direction of the said film at the time of the said diagonal stretch, When holding the said film, The line which connected the clip on either side is inclined with respect to the conveyance direction of the said film at the time of the said diagonal stretch. Typically, the method for producing a stretched film according to an embodiment of the present invention further includes a preheating step. Specifically, the film gripped by the left and right clips is preheated and then subjected to diagonal stretching.

The gripping, preheating, diagonal stretching and opening from the clip of the film by the clip are, for example, a tenter type having left and right clips that can travel and move at different speeds while gripping the left and right ends of a long film in the width direction, respectively. It can be done using a simultaneous biaxial stretching device.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic plan view explaining the whole structure of an example of the extending|stretching apparatus which can be used for the manufacturing method of this invention. The stretching apparatus 100 includes an endless loop 10L and an endless loop 10R including a large number of clips 20 for holding films on both left and right sides in a plan view. In addition, in this specification, as seen from the entrance side of a film, the left endless loop is called the left endless loop 10L, and the right endless loop is called the right endless loop 10R. The clips 20 of the left and right endless loops 10L and 10R are guided by the reference rail 70, respectively, and circulated on the roof. The clip 20 of the endless loop 10L on the left cyclically moves counterclockwise, and the clip 20 of the right endless loop 10R cyclically moves clockwise. In the stretching apparatus 100, the holding zone A, the preheating zone B, the stretching zone C, and the opening zone D are provided in this order from the entrance side to the exit side of the film, and a preheating zone is provided in this order. From (B) to the open zone (D), the conveyance direction of the film does not change, and in the meantime, the film is conveyed linearly. In addition, each of these zones means a zone in which a film to be stretched is substantially gripped, preheated, diagonally stretched, and opened, and does not mean a mechanically or structurally independent section. In addition, it should be noted that the ratio of the length of each zone in the stretching apparatus of Fig. 1 is different from the ratio of the actual length.

Although not shown in FIG. 1, the zone for performing arbitrary appropriate processes may be provided between the extending|stretching zone C and the open zone D as needed. A transverse shrinkage process etc. are mentioned as such a process. Although not shown in the same way, the stretching device is typically a heating device (eg, hot air type, near-infrared type, far-infrared type, etc.) for making the heating environment from the preheating zone B to the open zone D. various ovens).

In the holding zone A of the stretching apparatus 100, the left endless loop 10L is configured to be longer than the right endless loop 10R, and the distance between the left and right endless loops 10L and 10R is the stretching target. It is maintained at a distance corresponding to the initial width of the film. From the stretching zone B to the open zone D, the left and right endless loops 10L and 10R are configured symmetrically in plan view. Specifically, in the preheating zone B, the left and right endless loops 10L and 10R are configured to be substantially parallel to each other at a separation distance corresponding to the initial width of the film to be stretched. In the stretching zone (C), from the side of the preheating zone (B) toward the open zone (D), the distance between the left and right endless loops (10L, 10R) is gradually expanded until it corresponds to the width after stretching of the film. is made up of In the open zone D, the left and right endless loops 10L and 10R are configured to be substantially parallel to each other at a separation distance corresponding to the width after stretching of the film. However, the configuration of the left and right endless loops 10L and 10R is not limited to the example illustrated above. For example, the left and right endless loops 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 preheating zone B to the open zone D. Moreover, regarding the gripping zone A, in the example of illustration, although the left endless loop 10L is comprised so that it may become longer than the right endless loop 10R, either of the left and right endless loops depends on the site|part where sagging occurs. You may configure it to be long.

The clip (left clip) 20 of the left endless loop 10L and the clip (right clip) 20 of the right endless loop 10R can each independently circulately move. For example, the driving sprockets 11 and 12 of the left endless loop 10L are rotationally driven in the counterclockwise direction by the electric motors 13 and 14, and the driving sprockets 11 of the right endless loop 10R are driven. 12) is rotationally driven in a clockwise direction by electric motors 13 and 14. As a result, a running force is applied to the clip bearing member of the drive roller (not shown) engaged with these drive sprockets 11 and 12 . Thereby, the endless loop 10L on the left cyclically moves counterclockwise, and the endless loop 10R of the right cyclically moves clockwise. By driving the left electric motor and the right electric motor independently, respectively, the left endless loop 10L and the right endless loop 10R can be cyclically moved independently, respectively.

Moreover, the clip (left clip) 20 of the left endless loop 10L and the clip (right clip) 20 of the right endless loop 10R are each variable pitch type. That is, the clips 20 and 20 on the left and right can each independently change the clip pitch in the longitudinal direction according to movement. The configuration of the variable pitch type can be realized by adopting a driving method such as a pantograph method, a linear motor method, or a motor chain method. Hereinafter, as an example, the link mechanism (pantograph mechanism) is demonstrated.

2 and 3 are, respectively, a schematic plan view of a main part for explaining a link mechanism for changing a clip pitch in the stretching apparatus of FIG. 1, FIG. 2 shows a state in which the clip pitch is the minimum, and FIG. indicates the status.

As shown in Figs. 2 and 3 , there is provided a clip supporting member 30 having a rectangular shape elongated in the lateral direction in plan view, which individually supports the clips 20 . Although not shown, the clip holding member 30 is formed in a rigid frame structure with a cross-section closed by an upper cross-beam, a lower cross-beam, a front wall (a wall on the clip side), and a rear wall (a wall on the opposite side to the clip). The clip carrying member 30 is provided so as to roll over the traveling road surfaces 81 and 82 by the traveling wheels 38 at both ends thereof. In addition, in FIG.2 and FIG.3, the traveling wheel (driving wheel which rolls on the traveling road surface 81) on the side of a front wall is not shown. The running road surfaces 81 and 82 are parallel to the reference rail 70 over the entire area. In the rear side (opposite side of the clip side (hereinafter, semi-clip side)) of the upper and lower crossbeams of the clip carrying member 30, an elongated hole 31 is formed along the longitudinal direction of the clip carrying member, and the slider 32 ) is slidably engaged in the longitudinal direction of the long hole 31 . In the vicinity of the clip 20 side end of the clip holding member 30, the one 1st shaft member 33 is provided vertically through an upper cross-beam and a lower cross-beam. On the other hand, the slider 32 of the clip carrying member 30 is provided with one second shaft member 34 penetrating vertically. One end of the main link member 35 is driven and connected to the first shaft member 33 of each clip holding member 30 . The main link member 35 is driven and connected to the second shaft member 34 of the clip holding member 30 adjacent to the other end thereof. In addition to the main link member 35, one end of the sub link member 36 is driven and driven to the first shaft member 33 of each clip holding member 30 . The other end of the sub-link member (36) is connected to the intermediate portion of the main link member (35) by a shaft (37). By the link mechanism by the main link member 35 and the sub-link member 36, as shown in FIG. 2, as much as the slider 32 is moved to the rear side (half clip side) of the clip holding member 30, , the pitch of the clip bearing members 30 in the longitudinal direction (as a result, the clip pitch) becomes small, and as shown in FIG. 3 , the slider 32 moves to the front side (the clip side) of the clip bearing member 30 . As a result, the pitch of the clip bearing members 30 in the longitudinal direction (as a result, the clip pitch) increases. The positioning of the slider 32 is performed by the pitch setting rail 90 . As shown in FIG.2 and FIG.3, the clip pitch becomes large, so that the clearance gap between the reference|standard rail 70 and the pitch setting rail 90 is small.

By performing diagonal 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 specific embodiment of the above extending|stretching apparatus, it describes in Unexamined-Japanese-Patent No. 2008-44339, for example, The whole is taken in in this specification as a reference. Hereinafter, each process is demonstrated in detail.

A-1. Gripping process

The gripping of the film may be performed at the inlet of the film blowing of the stretching apparatus. Hereinafter, the holding process will be described in detail with reference to FIG. 4 . The film 1 before being held by the clips 20 on the left and right is the conveyance direction of the film 1 at the time of diagonal stretching (in other words, the conveyance direction of the film 1 in the stretching apparatus 100) (X) It is being conveyed at an angle to the Specifically, the conveyance direction Y of the film 1 before holding inclines so that it may make angle (theta) with respect to the conveyance direction X of the film 1 at the time of diagonal stretch. The film 1 conveyed from the diagonal direction in this way is the holding zone A of the extending|stretching apparatus 100 typically in the same timing by the clip 20 of the left and right by the right and left ends, and mutually It is gripped with the same and constant clip pitch. As described above, in the stretching apparatus 100, one endless loop in the holding zone (in the example shown, the left endless loop 10L) is higher than the other endless loop (in the example, the right endless loop 10R). It is designed to be long. According to such a stretching apparatus 100, the line which connected the clips 20 on either side (more specifically, the line which connected the conveyance direction centers of the clips 20 on the left and right) Z at the time of diagonal stretching The film 1 can be gripped so that it may incline with respect to the conveyance direction X of the film 1, and the conveyance direction after that can be changed to the direction X. As a result, the conveyance path|route length of the film 1 between holding by the clip 20 until it opens can be made into the distance different from the left and right ends. In one embodiment, the line Z connecting the centers of the clips 20 on the left and right at the time of gripping may be substantially orthogonal to the conveyance direction Y of the film 1 before gripping. Also, in this specification, substantially orthogonal includes the range of 87.0° to 93.0°, for example, 89.0° to 91.0°, preferably 89.7° to 90.3°, more preferably 89.9° to 90.1°. and more preferably 90.0°.

Preferably, the film 1 before being gripped by the clips on the left and right is inclined with respect to the conveying direction X so that the end (right end in the example shown) on the non-sagging side after diagonal stretching becomes the concave side (inner side). is returned By bending the conveying direction of the film so that the end portion on the non-sagging side becomes the concave side, the travel path length (path length) from when the film is drawn out from the roll until it is released from the clip is determined by the end portion on the drooping side (illustration example). At the left end), it is longer than the end on the non-sagging side. As a result, tension is added to the end of the sagging side to flatten the entire film, so that sagging can be suitably reduced. In addition, in a stretched film obtained by diagonal stretching, the stretching process (timing, number, sequence, heat history, etc. of stretching or contraction) of the left and right ends of the film at the time of diagonal stretching differs from each other, resulting in residual stress after clip opening. Since the amount of deformation at both ends to be used becomes non-uniform, sagging may occur at either end. In one embodiment, in the diagonally stretched film in which the left and right ends were stretched at different draw ratios, the side with the low draw ratio at the time of diagonal stretch is the sagging side, and the film before holding is the side with the high draw ratio (the non-sagging side) ) is conveyed at an inclination with respect to the conveyance direction X so that the edge part of it may become a concave side.

The angle θ may be any suitable value as long as the effect of the present invention is obtained. The angle θ is, for example, 5° to 50°, preferably 7° to 45°, and more preferably 10° to 40°. When the angle θ is within this range, the effect of reducing sagging can be suitably obtained while maintaining the desired in-plane retardation and axial angle. In addition, the angle θ can be determined by changing the shape of the left and right endless loops 10L and 10R, changing the conveying direction Y by applying various techniques capable of changing the conveying direction of the web, and the like. value can be adjusted. Techniques capable of changing the conveying direction of the web are described, for example, in JP-A-2000-351506 and JP-A-2009-046285.

In the gripping zone, the clip pitch can be adjusted so that sagging or wrinkles do not occur at the edge of the concave side due to the change in the conveying direction of the film. In one embodiment, generation|occurrence|production of a sagging or a wrinkle is prevented by slightly increasing the clip pitch of the clip which grips the edge part on the concave side. At this time, it is preferable to also adjust the clip pitch of the clip which grips the edge part of a convex side together. By adjusting the clip pitch of both clips, a pair of left and right clips can be transferred to the preheating zone at the same clip pitch and at the same timing while preventing sagging or wrinkling at the end of the concave side. Further, the pair of left and right clips that transition to the preheating zone at the same timing may be a different combination from the pair of left and right clips that grip the film at the same timing.

The film 1 held by the left and right clips 20 is preheated by the movement of the left and right clips 20 as described above (actually, movement of each clip carrying member guided by the reference rail 70). sent to zone B.

A-2. preheating process

In the preheating zone B, the left and right endless loops 10L and 10R are configured to be substantially parallel to each other at a separation distance corresponding to the initial width of the film to be stretched as described above, Neither stretching nor longitudinal stretching is performed, and the film is heated. However, in order to avoid problems such as warping of the film due to preheating and contact with the nozzle in the oven, the distance between the left and right clips (distance in the width direction) may be slightly extended.

In a preheating process, a film is heated to temperature T1 (degreeC). The temperature T1 is preferably equal to or higher than the glass transition temperature (Tg) of the film, more preferably Tg+2°C or higher, still more preferably Tg+5°C or higher. On the other hand, heating temperature T1 becomes like this. Preferably it is Tg+40 degreeC or less, More preferably, it is Tg+30 degreeC or less. Although it changes with the film to be used, temperature T1 is 70 degreeC - 190 degreeC, for example, Preferably it is 80 degreeC - 180 degreeC.

The heating time up to the temperature T1 and the holding time at the temperature T1 may be appropriately set according to the constituent materials of the film or the manufacturing conditions (eg, the conveying speed of the film). These heating time and holding time can be controlled by adjusting the moving speed of the clip 20, the length of the preheating zone, the temperature of the preheating zone, and the like.

A-3. oblique drawing process

In the stretching zone C, the clips 20 on the left and right are moved while changing the clip pitch in the longitudinal direction of at least one clip, and the film is diagonally stretched. More specifically, by moving the left and right clips while increasing or decreasing the clip pitch at different positions, respectively, by traveling and moving while changing (increasing and/or reducing) the clip pitch at different changing rates, etc. The film is diagonally stretched. As a result of moving the clips on the left and right while changing the clip pitch in this way, one clip precedes the other clip and reaches the end of the stretching zone in the pair of left and right clips that have shifted to the stretching zone at the same time. According to such oblique stretching, the leading end of the clip is drawn at a higher draw ratio than the following end of the clip, and as a result, the elongated film is drawn in a desired direction (for example, at 45° with respect to the longitudinal direction). direction) to express the slow axis.

Oblique stretching may include lateral stretching. In this case, diagonal stretching can be performed, for example, while increasing the distance (distance in the width direction) between the clips on the left and right as in the illustrated example. Alternatively, unlike the illustrated example, the diagonal stretching may be performed while maintaining the distance between the left and right clips without lateral stretching.

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

In one embodiment, in the oblique stretching, a position where the clip pitch of one of the left and right clips starts to increase or decrease and a position where the clip pitch of the other clip starts to increase or decrease are different positions in the longitudinal direction. In this state, this can be done by increasing or decreasing the clip pitch of each clip to a predetermined pitch. About the diagonal stretch of the said embodiment, description, such as patent document 1 and Unexamined-Japanese-Patent No. 2014-238524, can be referred, for example.

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

In another embodiment, oblique stretching comprises: (i) increasing the clip pitch of one of the left and right clips from P ₁ to P ₂ while decreasing the clip pitch of the other clip from P ₁ to P ₃ ; and (ii) varying the clip pitch of each clip such that the corresponding reduced clip pitch and the corresponding increased clip pitch are the same predetermined pitch. About the diagonal stretch of the said embodiment, description of Unexamined-Japanese-Patent No. 2014-194484 etc. can be referred, for example. The diagonal stretching of the said embodiment enlarges the distance between the clips on either side, and changes the clip pitch _{of one} clip from P1 to P2. while increasing the clip pitch of the other clip from P ₁ to P ₃ reducing, oblique stretching of the film (first oblique stretching), and maintaining the clip pitch of one clip at P ₂ or P ₄ so that the clip pitch of the left and right clips becomes the same while increasing the distance between the left and right clips Until Reduce the clip pitch of the corresponding other clip to P ₂ or P ₄ and stretching the film diagonally (second diagonal stretching).

In the first diagonal stretching, by performing diagonal stretching while extending one end of the film in the long direction and contracting the other end in the long direction, high A slow axis can be expressed by uniaxiality and in-plane orientation. Moreover, in 2nd diagonal stretching, by performing diagonal stretching while reducing the difference of the clip pitches on either side, it can fully extend|stretch in the diagonal direction, relieving excess stress.

In the oblique stretching of the above three embodiments, since the film can be opened from the clip in a state where the moving speed of the left and right clips becomes the same, it is difficult to cause variation in the conveying speed of the film when the left and right clips are opened, Thereafter, winding of the film may be suitably performed.

5A and 5B are schematic views each showing an example of a profile of a clip pitch in the diagonal stretching including the first diagonal stretching and the second diagonal stretching. Hereinafter, 1st diagonal stretch is demonstrated concretely, referring these drawings. Further, in Figs. 5A and 5B, the horizontal axis corresponds to the travel distance of the clip. first At the start of diagonal stretching, both the right and left clip pitches are set to P ₁ . P ₁ is typically the clip pitch in the preheating step. Simultaneously with the start of the first diagonal stretching, an increase in the clip pitch of one clip (hereinafter, may be referred to as a first clip) is started, and further, the clip pitch of the other clip (hereinafter, may be referred to as a second clip) is started. Initiate a reduction in clip pitch. In the first oblique stretching, the clip pitch of the first clip is increased to P ₂ . and increase the clip pitch of the second clip to P ₃ Reduce. Accordingly, at the end of the first diagonal stretching (at the start of the second diagonal stretching), the second clip moves at the clip pitch P ₃ , and the first clip moves at the clip pitch P ₂ . Also, the ratio of the clip pitches may generally correspond to the ratio of the moving speeds of the clips.

In FIGS. 5A and 5B, the timing at which the clip pitch of the first clip starts to increase and the timing at which the clip pitch of the second clip starts to decrease are both set at the start of the first diagonal stretching, but unlike the illustrated example, You may start to decrease the clip pitch of the second clip after starting to increase the clip pitch of the first clip, or start increasing the clip pitch of the first clip after starting decreasing the clip pitch of the second clip. In one preferred embodiment, starting to increase the clip pitch of the first clip, then starting to decrease the clip pitch of the second clip. According to such an embodiment, since the film has already been stretched to a certain extent (preferably about 1.2 to 2.0 times) in the width direction, even if the clip pitch of the second clip is greatly reduced, wrinkles are unlikely to occur. Therefore, a more acute angle diagonal stretch becomes possible, and retardation film with high uniaxial property and in-plane orientation can be obtained suitably.

Similarly, in FIGS. 5A and 5B, an increase in the clip pitch of the first clip and a decrease in the clip pitch of the second clip continue until the end of the first diagonal stretching (at the start of the second diagonal stretching). Alternatively, the clip pitch may be maintained until either 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 diagonal stretching).

The rate of change (P ₂ /P ₁ ) of the clip pitch of the first clip is preferably 1.25 to 1.75, more preferably 1.30 to 1.70, still more preferably 1.35 to 1.65. In addition, the rate of change (P ₃ /P ₁ ) of the clip pitch of the second clip is, for example, 0.50 or more and 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 change rate of the clip pitch is in such a range, a slow axis can be expressed by high uniaxial property and in-plane orientation in the direction of about 45 degrees with respect to the longitudinal direction of a film.

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

The draw ratio in the width direction of the film in the first diagonal stretching (film width at the end of the first diagonal stretching/film width before the first diagonal stretching) is preferably 1.1 times to 3.0 times, more preferably 1.2 times to It is 2.5 times, More preferably, it is 1.25 times - 2.0 times. When the draw ratio is less than 1.1 times, a tin-shaped wrinkle may occur at the end of 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 it applies to a circularly-polarizing plate etc., a viewing angle characteristic may fall.

In one embodiment, the first oblique stretching is 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, preferably 0.7 to 1.5, more preferably 0.8 to 1.45, still more preferably It is carried out so as to be 0.85 to 1.40. When the product of the rate of change is within such a range, a retardation film having high uniaxiality and high in-plane orientation can be obtained.

Next, one Embodiment of 2nd diagonal stretch is demonstrated concretely, referring FIG. 5A. In the second oblique stretching of the present embodiment, the clip pitch of the second clip is P ₃ . increase 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 time of completion|finish of _2nd diagonal extending|stretching, both the right and left clips are supposed to move at the clip pitch P2.

As long as the effect of this invention is not impaired, the change rate (P2/P3) of the clip pitch of the _2nd clip in _2nd diagonal stretch of embodiment shown to FIG. 5A is not restrict|limited. 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 2nd diagonal stretch is demonstrated concretely, referring FIG. 5B. In the 2nd diagonal stretch of this embodiment, while reducing the clip pitch of a 1st clip, the clip pitch of a 2nd clip is increased. Specifically, the clip pitch of the first clip is set at P ₂ . Decrease to P ₄ and the clip pitch of the second clip at P ₃ up to P ₄ increase Therefore, the second At the end of oblique stretching, both the left and right clips move at the clip pitch P ₄ . Further, although the illustrated example discloses a decrease in the clip pitch of the first clip and an increase in the clip pitch of the second clip at the same time as the start of the second diagonal stretching, these may be started at different timings. In addition, similarly, the reduction|decrease of the clip pitch of a 1st clip and increase of the clip pitch of a 2nd clip may end at different timing.

Rate of change (P ₄ /P ₂ ) of the clip pitch of the first clip in the second diagonal stretching of the embodiment shown in FIG. 5B . and second The rate of change (P ₄ /P ₃ ) of the clip pitch of the clip is not limited as long as the effects of the present invention are not impaired. The rate of change (P ₄ /P ₂ ) is _, for example, 0.4 or more 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 at least P ₁ . When P ₄ <P ₁ , problems such as wrinkles and increased biaxiality may occur at the edges.

The draw ratio in the width direction of the film in the second diagonal stretching (film width at the end of the second diagonal stretching/the film width at the end of the first diagonal stretching) is preferably 1.1 to 3.0 times, more preferably 1.2 times to 2.5 times, more preferably from 1.25 times to 2.0 times. When the draw ratio is less than 1.1 times, a tin-shaped wrinkle may occur at the end of 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 it applies to a circularly-polarizing plate etc., a viewing angle characteristic may fall. In addition, the stretch ratio in the width direction in the first diagonal stretching and the second diagonal stretching (the film width at the end of the second diagonal stretching / the film width before the first diagonal stretching) is preferably 1.2 from the viewpoint similar to the above. times to 4.0 times, more preferably from 1.4 times to 3.0 times.

Oblique stretching may be typically performed at a temperature T2. The temperature T2 is preferably Tg-20°C to Tg+30°C, more preferably Tg-10°C to Tg+20°C, particularly preferably about Tg with respect to the glass transition temperature (Tg) of the film. . Although it changes with the film to be used, temperature T2 is 70 degreeC - 180 degreeC, for example, Preferably it is 80 degreeC - 170 degreeC. The difference (T1-T2) between the temperature T1 and the temperature T2 is preferably ±2°C or higher, and more preferably ±5°C or higher. 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, the transverse shrinkage treatment may be performed after the diagonal stretching. About the said process after diagonal stretch, Paragraph 0029-0032 of Unexamined-Japanese-Patent No. 2014-194483 can be referred.

A-4. open process

At any position in the open zone D, the film is opened from the clip. In the open zone (D), normally neither transverse stretching nor longitudinal stretching is performed, and if necessary, the film is heat treated to fix the stretched state (heat set) and/or cooled to Tg or less, and then the film is clipped open from In addition, in the case of heat fixing, the clip pitch in the longitudinal direction may be decreased to thereby relieve stress.

The heat treatment may be typically performed at a temperature T3. The temperature T3 varies depending on the stretched film, and may be T2≥T3 or T2<T3. In general, when the film is an amorphous material, T2≥T3, and in the case of a crystalline material, the crystallization treatment is sometimes performed by setting T2<T3. In the case of T2≥T3, the difference (T2-T3) between the temperatures T2 and T3 is preferably 0°C to 50°C. The heat treatment time is typically 10 seconds to 10 minutes.

The stretched film opened from the clip is sent out from the outlet of the stretching device. The film sent out from the extending|stretching apparatus can be roll conveyed, it can be wound up by the winding-up apparatus, and can form a film roll. Alternatively, the film sent out from the stretching apparatus is not wound, and conveying with another long optical film, it can match the direction of the long picture, and can bond continuously, and can comprise an optical laminated body.

In one embodiment, with respect to the film sent out from a stretching apparatus, sagging is detected. Based on the detected amount of sagging and the site|part in which sagging has arisen, the angle (theta) which the conveyance direction Y of the film before holding|grinding and the conveyance direction X of the film at the time of diagonal stretch make|form can be adjusted.

A-5. detection of sagging

The amount of sagging can be detected, for example, between the conveying rolls. Specifically, the amount of sagging can be detected as a difference in position (conveyance height) in the width direction of the film at an intermediate point between the conveying rolls.

Although the distance between the conveyance rolls at the time of the said detection is not specifically limited, For example, it is 500 mm - 2000 mm, Preferably it is 700 mm - 1500 mm.

Although the film tension|tensile_strength at the time of the said detection is not specifically limited, For example, it is 50 N/m - 400 N/m, Preferably it is 100 N/m - 200 N/m. When the conveyance tension is too high, the film in conveyance may elastically deform, and sagging may become difficult to detect. On the other hand, when the conveyance tension is too low, the tension itself may not be stable, and the measured value of sagging may not be stable.

The detection may be performed under a non-heating environment. The atmospheric temperature at the time of detecting the amount of sagging may be, for example, about 15°C to 40°C, and for example, about 20°C to 30°C.

In one embodiment, after cutting and removing the left and right ends of the width direction of the stretched film open|released from a clip, the amount of sagging is detected. By detecting the amount of sagging with both ends removed, a more accurate detection result can be obtained.

The width of the ends to be cut off may each independently be, for example, 20 mm to 600 mm, preferably 100 mm to 500 mm. The cutting and removal of the end portion can be performed by ordinary slitting.

The amount of sagging reduction obtained by the method for producing a stretched film according to an embodiment of the present invention (the transport direction (Y) of the film before gripping and the transport direction (X) of the film at the time of oblique stretching are parallel to each other) obtained by the stretched film production method The amount of sagging of the film - the amount of sagging of the stretched film obtained by the method for producing a stretched film according to the embodiment of the present invention: provided that the amount of sagging measured at a distance between rolls of 1000 mm) is, for example, 3 mm or more, preferably 5 mm or more, more preferably 8 mm or more, and still more preferably 10 mm or more. In addition, the amount of sagging that can remain in the stretched film obtained by the method for producing a stretched film according to the embodiment of the present invention is, for example, less than 15 mm, preferably 10 mm or less, more preferably 8 mm or less, still more preferably Preferably it may be 5 mm or less, and more preferably less than 3 mm.

B. Film to be stretched

In the manufacturing method of this invention, any suitable film can be used. For example, a resin film applicable as a retardation film is mentioned. As a material constituting such a film, for example, polycarbonate-based resin, polyvinyl acetal-based resin, cycloolefin-based resin, acrylic resin, cellulose ester-based resin, cellulose-based resin, polyester-based resin, polyester carbonate-based resin, Olefin-type resin, polyurethane-type resin, etc. are mentioned. Preferably, they are a polycarbonate resin, a cellulose ester-type resin, a polyester-type resin, a polyester carbonate-type resin, and a cycloolefin resin. This is because, with these resins, a retardation film exhibiting the wavelength dependence of so-called reverse dispersion can be obtained. These resins may be used independently and may be used in combination according to a desired characteristic.

As said polycarbonate-type resin, arbitrary appropriate polycarbonate-type resin is used. For example, a polycarbonate resin containing a structural unit derived from a dihydroxy compound is preferable. Specific examples of the dihydroxy compound include 9,9-bis(4-hydroxyphenyl)fluorene, 9,9-bis(4-hydroxy-3-methylphenyl)fluorene, and 9,9-bis(4-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) and ,2-dimethylpropoxy)phenyl)fluorene. Polycarbonate resin, in addition to the structural unit derived from the dihydroxy compound, 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), tricyclodecanedimethanol (TCDDM), and bisphenols may be included.

Details of the polycarbonate-based resin as described above are described in, for example, Japanese Patent Application Laid-Open No. 2012-67300 and Japanese Patent No. 3325560. The description of the said patent document is taken in here as a reference.

It is preferable that the glass transition temperature of polycarbonate-type resin is 110 degreeC or more and 250 degrees C or less, More preferably, they are 120 degreeC or more and 230 degrees C or less. When the glass transition temperature is excessively low, heat resistance tends to deteriorate, and there is a possibility of causing a dimensional change after film forming. When the glass transition temperature is excessively high, the molding stability at the time of film forming may deteriorate, and the transparency of the film may be impaired. In addition, a glass transition temperature can be calculated|required according to JISK7121 (1987).

Any suitable polyvinyl acetal-type resin can be used as said polyvinyl acetal-type resin. Typically, a polyvinyl acetal-type resin can be obtained by carrying out the condensation reaction of at least 2 types of aldehyde compound and/or a ketone compound, and polyvinyl alcohol-type resin. A specific example and a detailed manufacturing method of a polyvinyl acetal-type resin are described in Unexamined-Japanese-Patent No. 2007-161994, for example. The description is incorporated herein by reference.

As for the stretched film (retardation film) obtained by extending|stretching the film which is the said extending|stretching object, Preferably, a refractive index characteristic shows the relationship of nx>ny. In one embodiment, the retardation film may preferably function as a λ/4 plate. In the present embodiment, the in-plane retardation Re(550) of the retardation film (λ/4 plate) is preferably 100 nm to 180 nm, more preferably 135 nm to 155 nm. In another embodiment, the retardation film may preferably function as a λ/2 plate. In the present embodiment, the in-plane retardation Re(550) of the retardation film (λ/2 plate) is preferably 230 nm to 310 nm, more preferably 250 nm to 290 nm. In addition, in this specification, nx is the refractive index in the direction in which the in-plane refractive index is maximized (ie, the slow axis direction), ny is the refractive index in the direction orthogonal to the slow axis in the plane (ie, the fast axis direction), and nz is It is the refractive index in the thickness direction. In addition, Re(λ) is the in-plane retardation of the film measured with light having a wavelength of λ nm at 23°C. Accordingly, 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 calculated by the formula: Re(λ)=(nx-ny)×d when the thickness of the film is d (nm).

The in-plane retardation Re(550) of the retardation film can be made into a desired range by appropriately setting the diagonal stretching conditions. For example, a method for producing a retardation film having an in-plane retardation Re(550) of 100 nm to 180 nm by diagonal stretching is disclosed in Japanese Patent Application Laid-Open Nos. 2013-54338, 2014-194482, and JP Patent Publication No. 2014-238524, Japanese Patent Application Laid-Open No. 2014-194484, etc. are disclosed in detail. Therefore, a person skilled in the art can set appropriate diagonal stretching conditions based on the said indication.

When a circularly polarizing plate is produced using a single retardation film, or when the direction of linearly polarized light is rotated by 90° using a single retardation film, the slow axis direction of the retardation film used is with respect to the direction 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°, Especially preferably, it is about 45 degrees or 135 degrees.

In addition, when producing a circularly polarizing plate using two retardation films (specifically, a λ/2 plate and a λ/4 plate), the slow axis direction of the retardation film (λ/2 plate) used is the film It is preferably 60° to 90°, more preferably 65° to 85°, particularly preferably about 75° with respect to the long direction of 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 the wavelength dependence of so-called inverse dispersion. Specifically, the in-plane phase difference satisfies the relationship of Re(450)<Re(550)<Re(650). Re(450)/Re(550) becomes like this. Preferably it is 0.8 or more and less than 1.0, More preferably, it is 0.8-0.95. Re(550)/Re(650) becomes like this. Preferably it is 0.8 or more and less than 1.0, More preferably, it is 0.8-0.97.

The retardation film has an absolute value of the photoelastic coefficient, 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 laminate and manufacturing method of the optical laminate

The stretched film obtained by the manufacturing method of this invention can be bonded together with another optical film, and can be used as an optical laminated body. For example, the retardation film obtained by the manufacturing method of this invention is bonded together with a polarizing plate, and can be used suitably as a circularly-polarizing plate.

6 is a schematic cross-sectional view of an example of such a circularly polarizing plate. The circular polarizing plate 500 of the illustrated example 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, a λ/4 plate) obtained by the manufacturing method described in the A section. The second protective film 530 may be omitted. In this case, the retardation film 540 may function as a protective film of 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°, Especially preferably, it is about 45 degrees.

The retardation film obtained by the manufacturing method of this invention is elongate, and has a slow axis in an oblique direction (a direction of 45 degrees with respect to a long direction, for example). Moreover, in many cases, a long polarizer has an absorption axis in a long direction or a width direction. Therefore, when the retardation film obtained by the manufacturing method of this invention is used, what is called a roll-to-roll can be used and a circularly polarizing plate can be produced with extremely excellent manufacturing efficiency. In addition, a roll-to-roll means the method of sticking together continuously, matching the direction of a long picture, roll conveying elongate films.

In one embodiment, the manufacturing method of the optical laminated body of this invention is obtaining an elongate stretched film by the manufacturing method of the stretched film described in item A, and conveying an elongate optical film and the said long stretched film, , including sticking together continuously in the direction of the long picture.

[Example]

Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited by these Examples. In addition, the measurement and evaluation method in an Example 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) was measured using Axoscan manufactured by Axometrics.

(3) orientation angle (direction of slow axis expression)

The center part of the film which is a measurement object was cut out in the square shape of width 50mm and length 50mm, one side becoming parallel to the width direction of the said film, and the sample was created. This sample was measured using Axoscan manufactured by Axometrics, and the orientation angle (θ) at a wavelength of 590 nm was measured.

(4) Glass transition temperature (Tg)

It measured according to JISK7121.

(5) amount of sagging

As shown in FIG. 7, the ultrasonic displacement sensor 300 is arrange|positioned below the conveyance path|route of the film 1 at the midpoint (inter-roll distance: 912 mm) between conveyance rolls 50a, 50b, and conveyance tension The difference between the maximum distance (L _MAX ) and the minimum distance (L _MIN ) by measuring the distance from the ultrasonic displacement sensor to the stretched film at the center and the edge in the width direction when conveyed at 150 N/m (L _MAX -L _MIN ) was taken as the amount of sagging (mm). In addition, the measurement of the said drooping amount was performed, after cutting the tension|tensile_strength provided in order to correct sagging using a suction roll etc., and roll conveying at 150 N/m of conveyance tension|tensile_strength.

<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 mass Parts (0.298 mol) and 1.19×10 ^-2 mass parts (6.78×10 ^-5 mol) of calcium acetate monohydrate as a catalyst were added. 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 was made to reach 220 degreeC 40 minutes after the start of temperature increase, and while controlling so that this temperature might be maintained, pressure reduction was started and it was set to 13.3 kPa in 90 minutes after reaching 220 degreeC. The phenol vapor produced by the polymerization reaction was guided to a reflux condenser at 100° C., the monomer component contained in a small amount in the phenol vapor was returned to the reactor, and the uncondensed phenol vapor was recovered by inducing it to a condenser at 45° C. After nitrogen was introduced into the first reactor and the pressure was returned to atmospheric pressure, the oligomerized reaction solution in the first reactor was transferred to the second reactor. Then, the temperature increase and pressure reduction in the 2nd reactor were started, and it was set as the internal temperature of 240 degreeC and the pressure of 0.2 kPa in 50 minutes. Thereafter, polymerization was allowed to proceed until a predetermined stirring power was reached. When a predetermined power was reached, nitrogen was introduced into the reactor and the pressure was restored, and the produced polyester carbonate was extruded into water, and the strands were 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 200 mm, set temperature: 250 ° C), chilled roll ( Setting temperature: 120-130 degreeC) and the film film forming apparatus provided with the winder were used, and the 135-micrometer-thick resin film was produced.

(Production of stretched film)

The polyester carbonate resin film obtained as mentioned above was diagonally stretched using the extending|stretching apparatus as shown to FIGS. 1-3, and the retardation film was obtained.

Specifically, a stretching apparatus having a configuration in which the left endless loop in the holding zone is longer than the right endless loop was used. The polyester carbonate resin film is continuously supplied from an oblique direction with respect to the conveyance direction of the film in the said stretching apparatus (the conveyance direction (X) of the film at the time of diagonal stretching), and the left and right ends of a film are left and right at the entrance of a stretching apparatus. was simultaneously gripped with the same clip pitch (P ₁ =125 mm) by a clip of Specifically, the film is stretched at an angle so that the conveyance direction Y of the film before gripping with a clip forms an angle of 10° with respect to the conveyance direction X of the film at the time of diagonal stretching, and the right end thereof becomes the concave side. was fed into the apparatus (ie, the conveying direction Y forms an angle of 10° counterclockwise with respect to the conveying direction X). In addition, the angle which the line Z which connected the clips on either side at the time of gripping a film and the conveyance direction Y of the film before gripping with the clips on either side made was 90 degrees. In the holding zone, the conveyance direction of the film was changed from the Y direction to the X direction, and the film was transferred to the preheating zone.

In the preheating zone (B), the film was preheated to 145°C. In the preheating zone, the clip pitch of the left and right clips was P ₁ (125 mm).

Next, as the film enters the stretching zone C, an increase in the clip pitch of the right clip and a decrease in the clip pitch of the left clip are started, and the clip pitch of the right clip is set to P ₂ . With the increase, the clip pitch of the left clip was decreased to P ₃ (first oblique stretching). At this time, the clip pitch change rate of the right clip (P ₂ /P ₁ ) was 1.42, the clip pitch change rate of the left clip (P ₃ /P ₁ ) was 0.78, and the transverse draw ratio of the film with respect to the original width was 1.45 times. Next, while maintaining the clip pitch of the right clip at P ₂ , an increase in the clip pitch of the left clip was started and increased from P ₃ to P ₂ (second oblique stretching). The change rate (P ₂ /P ₃ ) of the clip pitch of the left clip during this period was 1.82, and the transverse stretch ratio of the film with respect to the original width was 1.9 times. In addition, the drawing zone (C) was set to Tg+3.2 degreeC (143.2 degreeC).

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 degreeC, the clips on either side were opened.

In addition, prior to the production of the stretched film, except that the film was not supplied from the diagonal direction (specifically, the transport direction (Y) of the film before gripping with a clip is the transport direction (X) of the film at the time of diagonal stretching The film is placed in a stretching apparatus so that the angle formed between the line (Z) connecting the clips on the left and right when the film is gripped and the transport direction (Y) of the film before gripping with the clips on the left and right is 90° so as to be parallel. Except having supplied), although it carried out similarly to Example 1, and obtained the stretched film, sagging had arisen in the left edge part of the width direction, and the slack amount was 16 mm.

<Example 2>

A stretched film was obtained in the same manner as in Example 1, except that the angle between the transport direction (Y) of the film before gripping with a clip and the transport direction (X) of the film at the time of diagonal stretching was set to 20°. In addition, the angle which the line Z which connected the clips on either side at the time of gripping a film, and the conveyance direction Y of the film before gripping with the clips on either side made was 90 degrees.

In addition, prior to the production of the stretched film, except that the film was not supplied from the diagonal direction (specifically, the transport direction (Y) of the film before gripping with a clip is the transport direction (X) of the film at the time of diagonal stretching The film is placed in a stretching apparatus so that the angle formed between the line (Z) connecting the clips on the left and right when the film is gripped and the transport direction (Y) of the film before gripping with the clips on the left and right is 90° so as to be parallel. Except having supplied), although it carried out similarly to Example 2, and obtained the stretched film, sagging had arisen in the left edge part of the width direction, and the slack amount was 17 mm.

<Example 3>

A stretched film was obtained in the same manner as in Example 1 except that the angle between the transport direction (Y) of the film before gripping with a clip and the transport direction (X) of the film at the time of diagonal stretching was set to 40°. In addition, the angle which the line Z which connected the clips on either side at the time of gripping a film, and the conveyance direction Y of the film before gripping with the clips on either side made was 90 degrees.

In addition, prior to the production of the stretched film, except that the film was not supplied from the diagonal direction (specifically, the transport direction (Y) of the film before gripping with a clip is the transport direction (X) of the film at the time of diagonal stretching The film is placed in a stretching apparatus so that the angle formed between the line (Z) connecting the clips on the left and right when the film is gripped and the transport direction (Y) of the film before gripping with the clips on the left and right is 90° so as to be parallel. Except having supplied), although it carried out similarly to Example 3 and obtained the stretched film, sagging had arisen in the left edge part of the width direction, and the slack amount was 17 mm.

<Comparative Example 1>

Except that the film was not supplied from the oblique direction (specifically, the conveying direction (Y) of the film before gripping with a clip is parallel to the conveying direction (X) of the film at the time of diagonal stretching, and the film is gripped Except that the film was fed to the stretching device so that the angle between the line (Z) connecting the left and right clips at the time and the conveying direction (Y) of the film before gripping with the left and right clips was 90°) Similarly, a stretched film was obtained.

[Appearance and handling evaluation]

The stretched films obtained in Examples 1 to 3 and Comparative Example 1 were bonded together with a long masking film (manufactured by Toray Film Processing Co., Ltd., product name 'Tretec 7832C-30') in a roll-to-roll manner to obtain a film laminate. Next, the masking film was peeled from the film laminated body, the adhesive agent was coated with the gravure coater, it bonded together with the polarizing plate, and the optical laminated body was obtained by irradiating UV. The appearance (visual appearance) of the optical laminate and the handleability of the stretched film were evaluated based on the following criteria.

○: After bonding the masking film (bonding tension of 150 N/m), wrinkles are not recognized and the adhesive agent can be coated on the entire surface of the film.

(triangle|delta): At the time of masking film bonding, although it was able to bond without wrinkles by raising bonding tension|tensile_strength to 300 N/m, at the time of adhesive agent coating, an adhesive agent could not be coated to the loosened location.

x: After bonding of the masking film, there is a wrinkle and the external appearance is deteriorated.

Table 1 shows the sagging amount and the evaluation results of the optical laminate.

[Table 1]

<Evaluation>

As shown in Table 1, in diagonal stretching using a tenter-type simultaneous biaxial stretching device, by making the conveyance direction of the film before gripping with a clip oblique with respect to the conveying direction of the film at the time of diagonal stretching, a long picture with reduced sagging An obliquely stretched film can be obtained. Moreover, when the elongate diagonal stretched film in which sagging was reduced is laminated|stacked with the elongate optical film by roll-to-roll, it turns out that generation|occurrence|production of a wrinkle is suppressed.

The method for producing a stretched film of the present invention is suitably used for the production of retardation film, and as a result, it can contribute to the production of image display devices such as a liquid crystal display (LCD) and an organic electroluminescent display (OLED). have.

1: Stretched film
10L: stepless loop
10R: stepless loop
20: clip
50: conveyance roll
100: stretching device
500: circular polarizer

Claims (7)

Holding the left and right ends in the width direction of the continuously conveyed long film by the right and left clips of the variable pitch type in which the clip pitch in the longitudinal direction changes, respectively;
moving the left and right clips while changing at least one clip pitch to obliquely stretch the film; and
A method for producing a stretched film comprising opening the film from the left and right clips,
The conveyance direction of the said film before holding by the said right and left clips is inclined with respect to the conveyance direction of the said film at the time of the said diagonal stretching,
The line which connected the said right and left clips at the time of holding the said film is inclined with respect to the conveyance direction of the said film at the time of the said diagonal stretching, The manufacturing method of a stretched film. According to claim 1,
A method for producing a stretched film, wherein the transport direction of the film before gripping with the right and left clips is inclined with respect to the transport direction of the film at the time of the diagonal stretching so that the end of the film on the non-sagging side becomes the concave side. . 3. The method of claim 1 or 2,
The manufacturing method of a stretched film in which the conveyance direction of the said film before holding by the said right and left clips makes an angle of 10-40 with respect to the conveyance direction of the said film at the time of the said diagonal stretch. 3. The method of claim 1 or 2,
The diagonal stretching is (i) the clip pitch of one of the clips on the left and right at P ₁ Increase the clip pitch of the other clip from P ₁ while increasing to P ₂ . reducing to P ₃ , and (ii) varying the clip pitch of each clip such that the reduced clip pitch and the increased clip pitch are a predetermined equal pitch. 5. The method of claim 4,
P ₂ /P ₁ is 1.25 to 1.75, P ₃ /P ₁ is 0.50 or more 1 Less than, the manufacturing method of a stretched film. obtaining an elongated stretched film by the manufacturing method according to claim 1 or 2, and
The manufacturing method of an optical laminated body including the carrying out of the elongate optical film and the said elongate stretched film, and bonding together continuously the direction of the elongate picture. 7. The method of 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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