KR20220133108A - Method for producing stretched film - Google Patents

Abstract

The present invention relates to a manufacturing method of a stretched film which reduces sagging and/or wrinkles generated in an obliquely stretched film. The manufacturing method of a stretched film comprises the steps of: holding the left and right ends of the width direction of an elongated film by the left and right clips of a variable pitch in which the clip pitch of the longitudinal direction changes, respectively; moving the left and right clips while changing the clip pitch of at least one clip to obliquely stretch the film; opening the film from the left and right clips; detecting the amount of sagging and/or the presence or absence of wrinkles in a central unit of the width direction of the film in; and performing clip pitch correction to increase the clip pitch of the left and right clips at the end of the oblique stretching based on a detection result.

Description

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

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

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. A 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 transverse directions, so their slow axis is, in most cases, the transverse direction (width direction) or longitudinal direction of the elongated film original. Expressed in the direction (long 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 left and right clips of a 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 is adjusted. A technique of expressing the slow axis of the retardation film in an oblique direction by changing it and extending it in an oblique direction with respect to the elongate 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 and wrinkles may arise.

Japanese Patent No. 4845619

The present invention has been made in order to solve the above problems, and its main object is to reduce sagging and/or wrinkles occurring in the diagonally stretched film.

According to one aspect of the present invention, the left and right ends of the long film in the width direction are respectively gripped by the right and left clips of the variable pitch type in which the clip pitch in the longitudinal direction changes, and the left and right clips are at least one clip. oblique stretching of the film by moving while changing the clip pitch of There is provided a method for manufacturing a stretched film, including performing a clip pitch correction for increasing the clip pitch of the clips on the left and right at the end of the diagonal stretching based on the detection result.

In one embodiment, after cutting and removing the left and right ends of the film opened from the left and right clips, the amount of sagging and/or the presence or absence of wrinkles is detected.

In one embodiment, the clip pitch correction rate defined by the following equation (1) with respect to the left and right clips is each independently 3% to 40%:

[Equation 1]

Clip pitch correction rate (%) = (Clip pitch at completion of increase - Clip pitch at end of oblique elongation before clip pitch correction) / Clip pitch at end of oblique elongation before clip pitch correction x 100.

In one embodiment, the oblique stretching before the clip pitch correction is performed by (i) changing the clip pitch of one of the left and right clips from 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 method for producing the substrate, and conveying the long optical film and the elongated stretched film while aligning the direction of the long picture and continuously bonding them , a method for manufacturing an optical 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 method for producing a stretched film of the present invention, the amount of sagging and/or the presence or absence of wrinkles generated in the center portion in the width direction of the diagonally stretched film is detected, and based on the detection result, the clip pitch of the left and right clips in the diagonal stretch Clip pitch correction to increase . Thereby, a long obliquely stretched film in which sagging and/or wrinkles are eliminated or reduced as a result of applying tension to the entire film can be obtained.

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

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 of the elongated film in the width direction 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 the clip pitch of at least one clip to diagonally stretch the film (oblique stretching process);

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

Detecting the amount of sagging and/or the presence or absence of wrinkles in the central portion in the width direction of the film (detecting step of the amount of sagging and/or the presence or absence of wrinkles), and

Based on the detection result, performing clip pitch correction for increasing the clip pitch of the left and right clips at the end of the diagonal stretching (clip pitch correction process)

includes

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

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram explaining an example of the manufacturing method of the stretched film of this invention. The elongate diagonally stretched film 1 diagonally stretched by the extending|stretching apparatus 100, and then opened from the clip is sent out from the exit of the extending|stretching apparatus 100, and conveyance rolls 200a, 200b, 200c, and 200d are used. The roll is conveyed and wound in the winding unit 300 . When the film 1 is roll conveyed, the amount of sagging is detected between the conveying rolls, and, based on the detection result, a clip pitch correction is performed to increase the clip pitch of the left and right clips at the end of oblique stretching upstream of the conveyance line. do Although not shown, as another example of the manufacturing method of the stretched film of this invention, instead of or in addition to the detection of the amount of sagging, the presence or absence of a wrinkle is detected, and based on the detection result, a conveyance line upstream Clip pitch correction may be performed to increase the clip pitch of the left and right clips at the end of diagonal stretching. By the clip pitch correction, as a result of applying tension to the entire film, a long obliquely stretched film with reduced sagging and/or wrinkles can be obtained.

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.

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, in a plan view, 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 symmetrically. 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, 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. Each of these zones means a zone in which the film to be stretched is substantially gripped, preheated, diagonally stretched, and opened, and does not mean a mechanically or structurally independent compartment. Also, note that the ratio of the length of each zone in the stretching apparatus of FIG. 2 is different from the ratio of the actual length.

Although not shown in FIG. 2, 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. In addition, although not shown in figure similarly, the said extending|stretching apparatus is a heating apparatus (for example, various ovens, such as a hot air type, a near-infrared type, a far-infrared type, etc., for making a heating environment typically from the preheating zone B to the open zone D). ) is provided.

In the holding zone A and the preheating zone B of the stretching apparatus 100, the left and right endless loops 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) 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, 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 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 circulate. 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 circulated 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 left and right clips 20 and 20 may 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.

3 and 4 are, respectively, a schematic plan view of main parts for explaining the link mechanism for changing the clip pitch in the stretching apparatus of FIG. 2, FIG. 3 shows a state in which the clip pitch is the minimum, and FIG. indicates the status.

As shown in FIGS. 3 and 4 , a clip supporting member 30 having a narrow and long rectangular shape in the lateral direction in plan view is provided for individually supporting 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.3 and FIG.4, 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). As shown in FIG. 3 by the link mechanism by the main link member 35 and the sub link member 36, 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. 4 , 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.3 and FIG.4, 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 diagonally stretching the film using the stretching apparatus as described above, a diagonally stretched film, for example, a retardation film having a slow axis in the diagonal 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

In the holding zone A (the inlet of the film blowing in the stretching apparatus 100), the both ends of the film to be stretched are at the same constant clip pitch by the clips 20 of the left and right endless loops 10L and 10R. , or with different clip pitches. The film is sent to the preheating zone B by the movement of the clip 20 of the left and right endless loops 10L and 10R (actually, movement of each clip carrying member guided by the reference rail 70). .

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, so basically, lateral stretching is performed. Neither longitudinal stretching is performed, but a 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 increased.

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, and 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 used, the temperature T1 is, for example, 70 degreeC - 190 degreeC, 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 temperature increase 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 of the clips, 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 left and right clips while changing the clip pitch in this way, one of the pair of left and right clips that have simultaneously shifted to the stretching zone arrives at the end of the stretching zone prior to the other clip. According to such oblique stretching, the preceding 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 (eg, 45° with respect to the longitudinal direction). direction) to express the slow axis.

The diagonal stretching may include transverse 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, the oblique stretching refers to 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 to a different position in the longitudinal direction. In one 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 can 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. . 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, the oblique stretching comprises (i) the clip pitch of one of the left and right clips at P ₁ . decreasing the clip pitch of the other clip from P ₁ to P ₃ while increasing to P ₂ ; This can be done by changing the 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 of the clip, and sets the clip pitch of _one clip from P1. up to P ₂ while increasing the clip pitch of the other clip at P ₁ up 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, and also up to 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 pitch 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 a clip pitch when a film is gripped. 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 are continued until the end of the first diagonal stretching (at the start of the second diagonal stretching), but unlike the example shown in FIG. 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 may be adjusted by positioning the slider by adjusting the 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 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 elongation is preferably a 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 from 0.7 to 1.5, more preferably from 0.8 to 1.45, even more preferably It is performed so that it may become 0.85-1.40. 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 set from 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 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 the second diagonal stretching will be specifically described with reference to 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 determined from P ₂ . Decrease to P ₄ and the clip pitch of the second clip from 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 . Also, although the illustrated example discloses the reduction of the clip pitch of the first clip and the increase of 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. Further, similarly, the reduction of the clip pitch of the first clip and the increase of the clip pitch of the second clip may be finished at different timings.

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 of the clip pitch of the clip (P ₄ /P ₃ ) 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 used, the 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), neither transverse stretching nor longitudinal stretching is usually performed, and if necessary, the film is heat treated to fix the stretched state (heat set) and/or cool to Tg or less, and then the film is opened from the clip. do. In addition, when heat-setting, the clip pitch in the longitudinal direction may be decreased to relieve stress by this.

The heat treatment may be typically performed at a temperature T3. The temperature T3 differs 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 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, and provided for detection of the amount of sagging and/or the presence or absence of wrinkles.

A-5. Detection of the amount of sagging and/or the presence or absence of wrinkles

A-5-1. 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 the difference between the position (conveyance height) of the width direction edge portion of the film and the position (conveyance height) of the central portion at the midpoint between the conveyance rolls.

6 is a schematic diagram illustrating an example of a method for detecting the amount of sagging. As shown in FIG. 6, in the midpoint of two adjacent conveyance rolls 200b, 200c, the ultrasonic displacement sensor 400 is arrange|positioned below the center part of the width direction of the stretched film 1, and an edge part, and an ultrasonic displacement Measuring the distance from the sensor 400 to the stretched film 1, the difference (L ₂ -L ₁ ) between the distance (L ₁ ) at the center part in the width direction and the average (L ₂ ) of the distances at the left and right ends It can be set as the amount of sagging of the central part in the width direction. In addition, as the cause of sagging in the central portion in the width direction of the diagonally stretched film, the central portion in the width direction sags due to the weight of the film during preheating, and the influence of the change due to the weight of the film is greater than the stress during stretching. and the like. In addition, unlike the illustrated example, the distance (L ₀ ) from the ultrasonic displacement sensor to the film is measured by conveying the film without sagging in advance, and the distance (L ₁ ) between the central portion in the width direction and the ultrasonic displacement sensor and The difference with L ₀ can also be made into the amount of sagging. In addition, although the ultrasonic displacement sensor has been described as an example of the sagging detection means, the sagging is determined by any suitable detection means (eg, using a laser dropper velocimeter to obtain the film passing speed of the cylindrical portion and the sagging portion, and calculating the difference in length therefrom, etc. ) can be detected using

Although the distance D between 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 it may become difficult to detect sagging. On the other hand, when the transport tension is excessively 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 opened 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 each end to be cut and removed may be each independently, for example, 20 mm to 600 mm, preferably 100 mm to 500 mm. Cutting and removal of the ends can be performed by ordinary slitting.

A-5-2. Detection of the presence or absence of wrinkles

The presence or absence of wrinkles can be performed, for example, by observing the film surface while irradiating light as needed. Observation of the film surface may be performed visually, and may be performed mechanically using a sensor etc. Moreover, the presence or absence of a wrinkle may be detected after cutting and removing the left and right ends of the width direction of the stretched film open|released from a clip similarly to the detection of a sagging amount.

A-6. Clip pitch correction process

Clip pitch correction is performed by increasing the clip pitch of the clips on either side at the time of the diagonal stretch completion|finish in the diagonal stretch process upstream of a conveyance line based on the said detection result. For example, when an amount of sagging more than a predetermined value is detected and/or when wrinkles are detected, clip pitch correction is performed, and when the amount of sagging is less than a predetermined value or when no wrinkles are detected, clip pitch correction is not performed, The diagonal stretching conditions so far can be maintained. Specifically, the clip pitch correction can be performed when the amount of sagging detected at a distance between rolls of 1000 mm is, for example, 3 mm or more, 5 mm or more, 10 mm or more, or 15 mm or more.

The correction amount (increase amount) of the clip pitch of the left and right clips in the clip pitch correction can be appropriately set according to the detected amount of sagging or the like. The clip pitch correction may be performed such that the clip pitch correction rate defined by the following equation (1) is, for example, 3% to 40%, preferably 5% to 30%. When the clip pitch correction rate is within the range, an elongated stretched film with reduced sagging and/or wrinkles can be obtained while substantially maintaining the axial angle and in-plane retardation before clip pitch correction. In addition, the clip pitch correction rate may be mutually the same in the right and left clips, and may differ from each other. When the clip pitch correction rates of the right and left clips are the same, tension can be uniformly applied to the entire film, and as a result, there is an advantage that the influence on the axial angle and the in-plane retardation can be suppressed.

[Equation 1]

Clip pitch correction rate (%) = (Clip pitch at completion of increase - Clip pitch at end of oblique elongation before clip pitch correction) / Clip pitch at end of oblique elongation before clip pitch correction x 100.

In one embodiment, the clip pitch correction rate is preferably 3% to 10%, more preferably 5% to 10%. When the clip pitch correction rate is within this range, the sagging reduction effect can be suitably obtained while substantially maintaining the axial angle and the in-plane phase difference before the clip pitch correction.

In one embodiment, the clip pitch correction rate is preferably 10% to 30%, more preferably 10% to 20%. When the clip pitch correction rate is within the range, the wrinkle reduction effect can be suitably obtained while substantially maintaining the axial angle and the in-plane retardation before the clip pitch correction.

The clip pitch correction can be started at any timing during the oblique stretching as long as the clip pitches of the left and right clips at the end of the oblique stretching (that is, the end of the oblique stretching zone) are higher than before the correction. In one embodiment, at any timing after the preceding clip passes the midpoint of the traveling section of the stretching zone, preferably the preceding traveling clip passes 1/2 to 9/10 of the traveling section of the stretching zone From a point in time, more preferably, an increase in the clip pitch is started from a point in time when the clip traveling ahead has passed 3/4 to 9/10 of the traveling section of the stretching zone. The increase in the clip pitch may be completed at the end of the diagonal stretching, or the increase in the clip pitch may be continued after the completion of the diagonal stretching to complete the increase in the clip pitch in the open zone. In the latter half of diagonal stretching, especially in the final half, at least one clip pitch is kept constant or remains at a change at a small change rate, so by starting the clip pitch correction at the said timing, the effect of the present invention can be suitably obtained. As a specific example, when the diagonal stretching includes the first diagonal stretching and the second diagonal stretching, it is preferable that the clip pitch correction is performed in the second diagonal stretching. For example, the clip pitch correction can be started at the same time as starting the second diagonal stretching, or when the clip traveling ahead has passed one-third or one-half of the travel distance in the second diagonal stretching. have.

Clip pitch correction may be typically performed at a temperature T4. The temperature T4 is preferably Tg°C+Tg20°C, more preferably Tg+3°C to Tg10°C, still more preferably Tg+4°C to +Tg8°C. By performing the clip pitch correction at a temperature equal to or slightly higher than Tg (in other words, oblique stretching is performed with a clip pitch increased from the initial setting), the effect of the present invention can be suitably obtained.

In one embodiment, a film passing through the stretching zone while undergoing clip pitch correction at temperature T4 and transitioning to the open zone is opened from the clip after heat treatment, followed by cooling, while maintaining the amount of correction made in the stretching zone. do. With respect to the film which has shifted to an open zone, you may apply a clip pitch correction also during heat processing. The heat treatment and cooling are as described in Section A-4.

Fig. 7A is a schematic diagram showing a profile of a clip pitch in one embodiment of a method for manufacturing a stretched film of the present invention (in Fig. 7A, the horizontal axis corresponds to the travel distance of the clip). In the illustrated example, in the preheating step, the clip pitches of the first clip and the second clip are set to P ₁ together. In the diagonal stretching step before the clip pitch correction, in the first diagonal stretching, the clip pitch of the first clip is increased from P ₁ to P ₂ , and the clip pitch of the second clip is decreased from P ₁ to P ₃ . Then, in the second oblique stretching, the clip pitch of the second clip is increased from P ₃ to P ₂ while maintaining the clip pitch of the first clip at P ₂ . From the end of the oblique stretching until opening the film (ie, during heat setting), the clip pitches of the first clip and the second clip are respectively maintained at P ₂ , after which the film is opened from the clip. Then, the amount of sagging and/or the presence or absence of a wrinkle in the width direction center part of the said film are detected, and clip pitch correction is applied by the diagonal stretch in the conveyance direction upstream based on the said detection result. Specifically, the clip pitch of the _first clip increases from P2 to P2' between the time point when _1/2 of the travel distance in the second diagonal stretching is passed and the end time of the second diagonal stretching. _{Simultaneously} , the clip pitch _of the _2nd clip which was changing from P3 to P2 is increased so that it may become P2'. In addition, during the period from the end of the diagonal stretching until the film is opened, the clip pitch of the first clip and the second clip are respectively maintained at P ₂ ', and the correction amount of the clip pitch (the amount of increase at the end of the diagonal stretching: P ₂ ) '-P ₂ ) is maintained.

Fig. 7B is a schematic diagram showing a profile of a clip pitch in another embodiment of the method for manufacturing a stretched film of the present invention (in Fig. 7B, the horizontal axis corresponds to the travel distance of the clip). In the illustrated example, in the preheating step, the clip pitches of the first clip and the second clip are set to P ₁ together. In the diagonal stretching step before the clip pitch correction, in the first diagonal stretching, the clip pitch of the first clip is increased from P ₁ to P ₂ , and the clip pitch of the second clip is decreased from P ₁ to P ₃ . Then, in the second oblique stretching, the clip pitch of the second clip is increased from P ₃ to P ₄ while decreasing the clip pitch of the first clip from P ₂ to P ₄ . During the period from the end of the diagonal stretching until the film is opened, the clip pitch of the first clip and the second clip is reduced from P ₄ to P ₅ , and then the film is opened. Then, the amount of sagging and/or the presence or absence of a wrinkle in the width direction center part of the said film are detected, and clip pitch correction is applied by the diagonal stretch in the conveyance direction upstream based on the said detection result. Specifically, the clip pitch of the first clip, which has been changed from P ₂ to P ₄ in the second diagonal stretching, from the time point passing 1/2 of the travel distance to the end time point, P ₄ 'is change as much as possible. Similarly, the clip pitch of the second clip, which has been changed from P ₃ to P ₄ , is changed so as to be P ₄ ′ between the time point passing 1/2 of the travel distance of the second diagonal stretching and the end time point. . Further, during the period from the end of the oblique stretching until the film is opened, the clip pitches of the first clip and the second clip are respectively decreased from P ₄ ′ to P ₅ ′, but even during that time, the correction amount of the clip pitch (end of oblique stretching) increase in the city) is maintained (ie, P ₄ '-P ₄ =P ₅ '-P ₅ ).

Fig. 7C is a schematic diagram showing a profile of a clip pitch in another embodiment of the method for producing a stretched film of the present invention (in Fig. 7C, the horizontal axis corresponds to the travel distance of the clip). The embodiment of the illustrated example is different from the embodiment shown in Fig. 7A in that the increase in the clip pitch continues even during heat setting after the end of diagonal stretching. Specifically, the clip pitch of the _first clip increases from P2 to P2' between the time point when _1/2 of the travel distance in the second diagonal stretching is passed and the end time of the second diagonal stretching. _{Simultaneously} , the clip pitch _of the _2nd clip which was changing from P3 to P2 is increased so that it may become P2'. The increase in the clip pitch continues even after the end of the second diagonal stretching and is completed when the clip pitch becomes P ₆ , and the clip pitch is maintained at P ₆ until the film is opened. The correction amount of the clip pitch in this embodiment is P ₆ -P ₂ .

The clip pitch correction may be performed by adjusting the separation distance between the reference rail and the pitch setting rail, as described above. These adjustments can be performed without temporarily stopping the conveyance line or without stopping it.

In one embodiment, the amount of sagging reduced by the clip pitch correction (the amount of sagging of the stretched film obtained before correction - the amount of sagging of the stretched film obtained after correction: provided that the amount of sagging measured at a distance between transport rolls of 1000 mm) is, For example, it may be 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 of the stretched film obtained after the clip pitch correction may be, for example, less than 15 mm, preferably 10 mm or less, more preferably 8 mm or less, still more preferably 5 mm or less, even more preferably less than 3 mm.

In addition, as needed, with respect to the stretched film obtained after the said clip pitch correction, the amount of sagging of the central part in the width direction and/or the presence or absence of a wrinkle may be detected, and a clip pitch correction process may be performed again based on the said detection result. .

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 system resin, polyurethane 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 in this specification as a reference.

It is preferable that the glass transition temperature of a polycarbonate-type resin is 110 degreeC or more and 250 degrees C or less, More preferably, it is 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, the 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. Specific examples and detailed production methods of the polyvinyl acetal-based resin are described in, for example, Japanese Patent Application Laid-Open No. 2007-161994. This description is incorporated herein by reference.

As for the stretched film (retardation film) obtained by extending|stretching the said film to be stretched, Preferably the 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. 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).

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 of manufacturing 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 Japanese Unexamined Patent Publication No. No. 2014-238524, Japanese Patent 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 this disclosure.

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 in the long direction of the film. to 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 usually around 45° or 135°.

In addition, when a circularly polarizing plate is produced 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 direction of the slow axis of the film. With respect to the long direction, it is preferably 60° to 90°, more preferably 65° to 85°, and particularly preferably about 75°. In addition, the direction of the slow axis of the retardation film (λ/4 plate) is preferably 0° to 30°, more preferably 5 to 25°, particularly preferably about 15° with respect to the long direction of the film.

The retardation film preferably exhibits wavelength dependence of the so-called inverse dispersion. Specifically, the in-plane phase difference satisfies the relation 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 preferably has an absolute value of the photoelastic coefficient of 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 can be bonded together with a polarizing plate, and can be used suitably as a circularly polarizing plate.

8 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 (with respect to a long direction, for example, a 45 degree direction). 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 central part of the film to be measured was cut out in a square shape of 50 mm in width and 50 mm in length so that one side might become 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. 6, it is below the conveyance path|route of a stretched film, and the ultrasonic displacement sensor was arrange|positioned at the midpoint (inter-roll distance: 912 mm) of two adjacent conveyance rolls. While conveying the stretched film with a conveying tension of 150 N/m, the distance from the ultrasonic displacement sensor to the stretched film was measured at the center and left and right ends in the width direction, and the average of the distance at the center (L ₁ ) and the distance at the left and right ends ( The difference (L ₂ -L ₁ ) with L ₂ ) was defined as the amount of sagging (mm).

<Example 1-1>

(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. 40 minutes after the start of temperature increase, the internal temperature was reached to 220°C, and while controlling so as to maintain this temperature, the pressure reduction was started, and after reaching 220°C, it was set to 13.3 kPa in 90 minutes. 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 delivered to the condenser at 45° C. and recovered. 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, the resulting 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 (set Temperature: 120-130 degreeC) and the film film forming apparatus provided with the winder was 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 in FIGS. 2-4, and retardation film was obtained.

Specifically, the left and right ends of the polyester carbonate resin film were held by the clips on the left and right at the inlet of the stretching device, 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.

Then, 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 elongation) _. 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 0.65, and the transverse draw ratio of the film with respect to the atomic 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 2.18, 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.

(detection of slack amount)

Both ends of the stretched film opened from the clip and sent out from the stretching device were cut off by 250 mm, respectively. Roll conveyance of the film which removed both ends was carried out, and the amount of sagging between conveyance rolls was detected. As a result, the amount of sagging in the center part in the width direction of the stretched film was 17 mm.

(Clip pitch correction)

The clip pitch of the left and right clips is gradually increased from the point in time when 1/2 of the travel distance of the second diagonal stretching (a quarter of the total traveling distance of the diagonal stretching) has been passed, and at the end of the second diagonal stretching. The profile of the clip pitch is adjusted so that the clip pitch is P ₂ ' and the clip is opened by performing heat setting (125 ° C., 60 seconds) and cooling (100 ° C) in the same manner as above while maintaining the clip pitch. It was changed and diagonal stretch was continued (it is a clip pitch profile shown to FIG. 7A). That is, any of the clip pitches when the diagonally stretched film after clip pitch correction|amendment was opened from the clip on either _side was P2'. In addition, the clip pitch correction rate ((P ₂ '-P ₂ )/P ₂ ) was 5%.

The retardation Re (550) of the stretched film obtained before the clip pitch correction was 147 nm, and the angle between the slow axis direction and the long direction was 45°. In addition, retardation Re(550) of the stretched film obtained after clip pitch correction|amendment was 147 nm, and the angle which a slow-axis direction and a long direction make was 45 degrees.

<Example 1-2>

About both the right and left clips, except having made the clip pitch correction rate into 7 %, it carried out similarly to Example 1-1, and obtained the stretched film.

The retardation Re (550) of the stretched film obtained before the clip pitch correction was 147 nm, and the angle between the slow axis direction and the long direction was 45°. In addition, retardation Re(550) of the stretched film obtained after clip pitch correction|amendment was 147 nm, and the angle which a slow-axis direction and a long direction make was 45 degrees.

<Example 1-3>

About both the right and left clips, except having made the clip pitch correction rate into 10 %, it carried out similarly to Example 1-1, and obtained the stretched film.

The retardation Re (550) of the stretched film obtained before the clip pitch correction was 147 nm, and the angle between the slow axis direction and the long direction was 45°. In addition, retardation Re(550) of the stretched film obtained after clip pitch correction|amendment was 147 nm, and the angle which a slow-axis direction and a long direction make was 45 degrees.

<Comparative Example 1>

Except not having performed the clip pitch correction|amendment, it carried out similarly to Example 1-1, and obtained the stretched film.

[Appearance and handling evaluation]

The stretched film obtained in Examples 1-1 to 1-3 and Comparative Example 1 was bonded 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 a gravure coater, and it bonded with a polarizing plate, By irradiating UV, the optical laminated body was obtained. 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 was not able to coat to the drooping 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, when sagging is detected in the width direction central part of a long diagonally stretched film, the extending|stretching obtained after that by increasing the clip pitch of the clip on either side at the time of the diagonal stretch completion|finish of upstream of a conveyance line. It turns out that the said sagging of a film is reduced.

<Example 2-1>

Instead of detecting the amount of sagging between the conveying rolls, it was carried out in the same manner as in Example 1-1 except that the presence or absence of wrinkles was visually confirmed and the clip pitch correction rate was set to 20% for both the right and left clips. A stretched film was obtained. Moreover, wrinkles were confirmed in the stretched film obtained before clip pitch correction|amendment.

The retardation Re (550) of the stretched film obtained before the clip pitch correction was 147 nm, and the angle formed between the slow axis direction and the long direction was 45°. In addition, retardation Re(550) of the stretched film obtained after clip pitch correction|amendment was 147 nm, and the angle which a slow axis direction and a long direction make was 45 degrees.

<Example 2-2>

A stretched film was obtained in the same manner as in Example 2-1 except that the clip pitch correction rate was 10% about both the right and left clips.

The retardation Re (550) of the stretched film obtained before the clip pitch correction was 147 nm, and the angle between the slow axis direction and the long direction was 45°. In addition, retardation Re(550) of the stretched film obtained after clip pitch correction|amendment was 147 nm, and the angle which a slow-axis direction and a long direction make was 45 degrees.

<Example 2-3>

A stretched film was obtained in the same manner as in Example 2-1 except that the clip pitch correction rate was set to 30% about both the right and left clips.

The retardation Re (550) of the stretched film obtained before the clip pitch correction was 147 nm, and the angle between the slow axis direction and the long direction was 45°. In addition, retardation Re(550) of the stretched film obtained after clip pitch correction|amendment was 147 nm, and the angle which a slow-axis direction and a long direction make was 45 degrees.

[Wrinkle evaluation]

Wrinkles of the stretched films obtained in Examples 2-1 to 2-3 and Comparative Example 1 were evaluated based on the following criteria.

○: Wrinkles are not visually recognized even when irradiated with Polarion Light (manufactured by Polarion Corporation, product number 'NP-1').

(triangle|delta): Wrinkles are not visually recognized even if it irradiates a fluorescent lamp, but wrinkles are visually recognized when irradiated with polarion light.

x: When a fluorescent lamp is irradiated, a wrinkle will be visually recognized.

[Evaluation of transportability]

With respect to the obtained stretched film, it was visually confirmed whether or not warping or folding had occurred in the film due to sagging and/or wrinkling, and evaluation was made based on the following criteria.

(circle): Warping and folding did not generate|occur|produce in the film.

x: Warps and/or folds have occurred in the film.

[Visibility evaluation]

The optical laminated body produced by carrying out similarly to the said external appearance and handleability evaluation was bonded together to the visual recognition side of a reflecting plate or organic electroluminescent panel via an adhesive layer. With respect to the obtained optical laminate, the presence or absence of unevenness in shape or light leakage due to sagging or wrinkles was visually confirmed and evaluated based on the following criteria.

(circle): Non-uniformity and light leakage are not visually recognized by both a reflector and panel mounting.

(triangle|delta): Although nonuniformity and/or light leakage are visually recognized by a reflecting plate, it is not visually recognized by panel mounting.

x: Non-uniformity and/or light leakage are visually recognized by both a reflecting plate and panel mounting.

An evaluation result is shown in Table 2.

[Table 2]

<Evaluation>

As shown in Table 2, when a wrinkle is detected in a long diagonally stretched film, the said wrinkle of the stretched film obtained after that by increasing the clip pitch of the right and left clips at the time of the completion|finish of diagonal stretch upstream of a conveyance line. It can be seen that this is reduced.

[Industrial Applicability]

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
100: stretching device
200: conveying roll
300: winding
400: ultrasonic displacement sensor
500: circular polarizer

Claims (7)

Holding the left and right ends of the long film in the width direction by the right and left clips of the variable pitch type in which the longitudinal clip pitch changes, respectively;
moving the left and right clips while changing the clip pitch of at least one clip to obliquely stretch the film;
opening the film from the left and right clips;
Detecting the amount of sagging and / or the presence or absence of wrinkles in the central portion in the width direction of the film, and
The manufacturing method of a stretched film comprising performing clip pitch correction which increases the clip pitch of the said right and left clips at the time of the said diagonal stretch completion|finish based on the said detection result. According to claim 1,
After cutting and removing the left and right ends of the opened film from the left and right clips, the sagging amount and/or the presence or absence of wrinkles are detected. 3. The method of claim 1 or 2,
With respect to the left and right clips, the clip pitch correction rate defined by the following Equation 1 is each independently 3% to 40%, a method for producing a stretched film:
[Equation 1]
Clip pitch correction rate (%) = (Clip pitch at completion of increase - Clip pitch at end of oblique elongation before clip pitch correction) / Clip pitch at end of oblique elongation before clip pitch correction x 100. 3. The method of claim 1 or 2,
The oblique stretching before the clip pitch correction (i) the 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. 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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