KR20220136224A - Method for producing stretched film - Google Patents

Abstract

The purpose of the present invention is to reduce sagging and/or wrinkles generated in an obliquely stretched film. The present invention relates to a manufacturing method of a stretched film which comprises: a step of holding the left and right ends in a width direction of an elongated film by left and right clips, respectively; a step of running the left and right clips to obliquely stretch the film and then opening the same from the left and right clips; and a step of roll conveying the film using a curved roll, wherein the film is roll conveyed by shifting the center of a width direction of the film and the center of a width direction of the curved roll such that the end of a non-sagging side of the film is closer to the center of the width direction of the curved roll than the end of a sagging side.

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 direction and/or transverse direction, so that the slow axis thereof is in many cases the transverse direction (width direction) of the elongated film original. ) or in the longitudinal direction (longitudinal direction). As a result, in order to produce a circularly polarizing plate, it was necessary to cut retardation film so that it may make the angle of 45 degrees with respect to the width direction or the elongate 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, in order to avoid the light from the note PC from being reflected on the keyboard or the like, 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°. 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 held by left and right clips of a variable pitch type in which the clip pitch in the longitudinal direction is changed, respectively, and the clip pitch of at least one 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 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 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 generated 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 gripped by the clips on the left and right, respectively, the clips on the left and right are run to move the film to obliquely stretch, and then, the clips on the right and left A method for producing a stretched film, comprising opening the film from the side and roll conveying the film using a curved roll, wherein the edge of the film on the non-sagging side is at the center of the width direction of the curved roll rather than the edge on the side where it is drooping. The manufacturing method of the stretched film which shifts the width direction center of this film and the width direction center of this curved roll so that it may become close, and roll conveys this film is provided.

In one embodiment, the amount of curvature of the curved roll is between 5 mm and 15 mm.

In one embodiment, the distance between the width direction center of the said film at the time of passing through the said curved roll and the width direction center of the said curved roll is 10 mm - 40 mm.

In one embodiment, the distance between the width direction center of the said film at the time of passing through the said curved roll and the width direction center of the said curved roll is 40 mm - 120 mm.

In one embodiment, in addition to the curved roll, a flat expander roll and/or a concave roll is used to roll convey the film.

In one embodiment, the clip is a variable pitch type clip in which the clip pitch in the longitudinal direction changes, and at least one clip pitch of a left clip gripping the left end of the film and a right clip gripping the right end of the film. It is made to travel while changing, and the said film is diagonally stretched.

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 1.25-1.75 and P ₃ /P ₁ is 0.50 or greater 1 is less than

In one embodiment, the film is diagonally stretched by changing the conveyance direction of the film on the way while traveling and moving the left clip holding the left end and the right clip holding the right end of the film at a constant speed.

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 curved roll is made to pass the long film diagonally stretched in the state which mutually shifted the center of the width direction. Specifically, the width direction center of the film and the width direction center of the curved roll are shifted so that the end of the film on the non-sagging side is closer to the center in the width direction of the curved roll than at the end on the side where the film does not hang. As a result of this, a larger tension is applied to the non-sagging side of the film than to the sagging side, and a long obliquely stretched film in which sagging and/or wrinkles are reduced 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.
FIG. 2 : 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 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 plan view explaining the whole structure of another example of the extending|stretching apparatus which can be used for 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 diagonal stretch.
It is a schematic diagram which shows the profile of the clip pitch in one Embodiment of diagonal stretch.
6(a) and 6(b) are a schematic plan view and a schematic side view each illustrating an example of roll conveyance.
7 : is the schematic which expanded the curved roll part in roll conveyance.
8 is a schematic plan view illustrating a flat expander roll preferably used in the embodiment of the present invention.
It is a schematic plan view explaining the concave roll used suitably by embodiment of this invention.
10 is a schematic cross-sectional view of a circularly polarizing plate using the retardation film obtained by the manufacturing method of the present invention.
It 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

In the method for manufacturing a stretched film according to an embodiment of the present invention, the left and right ends of the elongated film in the width direction are respectively gripped by the left and right clips, the left and right clips are moved to run and the film is diagonally stretched, and then , and roll conveying the film using a curved roll and opening from the clips on the left and right. In the manufacturing method of the said stretched film, the width direction center of the said film and the width direction center of the said curved roll are shifted so that the edge part of the said film on the non-sagging side may be closer to the width direction center of the said curved roll than the edge part on the drooping side. and roll conveyed the film. Typically, the method for manufacturing a stretched film according to an embodiment of the present invention further includes a preheating process. Specifically, the film held by the left and right clips is preheated and then subjected to diagonal stretching.

As a method of diagonally stretching the film by the traveling movement of the left and right clips, any suitable method capable of stretching the left and right ends of the film at different draw ratios (as a result, it is possible to stretch the film diagonally with respect to the long direction) is used. can be For example, a method of oblique stretching by moving a clip holding the left end of the film and a clip holding the right end of the film at different speeds. The method of carrying out a traveling movement and carrying out diagonal stretch is mentioned. In one embodiment of the former diagonal stretching, at least one of a left clip gripping the left end of the film and a right clip gripping the right end of the film using a variable-pitch clip in which the clip pitch in the longitudinal direction changes is used. By moving the clip while changing the clip pitch, the film can be stretched in an oblique direction. In one embodiment of the latter oblique stretching, the conveying direction of the film is changed halfway while the left clip holding the left end of the film and the right clip holding the right end of the film are driven and moved at a constant speed (as a result, conveying of the left and right ends) different path lengths), the film can be stretched in the oblique direction. Moreover, in the diagonally stretched film obtained by the said diagonal stretch, there exists a tendency for a sagging and wrinkles to easily produce on the side with a small draw ratio. Therefore, in one embodiment, in the diagonally stretched film, the side with a small draw ratio at the time of diagonal stretch may be a drooping side. The diagonally stretched film is preferably a λ/4 plate or a λ/2 plate.

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 said former diagonal stretch. The stretching apparatus 100a 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, from the entrance side to the exit side of the sheet, a holding zone A, a preheating zone B, a stretching zone C, and an open zone D are provided in this order. 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. 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. In addition, although not shown in figure similarly, the said extending|stretching apparatus is a heating apparatus (for example, a hot air type, a near-infrared type, a far infrared ray type) for making each zone from the preheating zone B to the open zone D a heating environment typically. Various ovens such as meals) are provided. In one embodiment, the preheating, oblique stretching and opening from the clip may each be performed in an oven set to a predetermined temperature.

In the holding zone A and the preheating zone B of the stretching apparatus 100a, 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 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 (not shown) of the driving roller (not shown) engaged with these driving 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 as they move. 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. For example, in Patent Document 1, Japanese Patent Application Laid-Open No. 2008-44339, etc., a tenter-type simultaneous biaxial stretching apparatus using a pantograph-type link mechanism is described in detail. Hereinafter, the link mechanism (pantograph mechanism) is demonstrated as an example.

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 carrying 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.

Fig. 4 is a schematic plan view for explaining the overall configuration of an example of a stretching apparatus that can be used for the latter diagonal stretching. The stretching apparatus 100b includes, in a plan view, an endless loop 10L and an endless loop 10R in a loop including a plurality of clips 20 for holding films on both left and right sides. The clips 20 of the left and right endless loops 10L and 10R are guided by the reference rail 40, respectively, and cyclically move on the loop (in the example shown, a part of the endless loops 10L and 10R is omitted ). 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, from the entrance side to the exit side of the sheet, a holding zone (A), a preheating zone (B), a stretching zone (C), and an open zone (D) are provided in this order. 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. In addition, it should be noted that the ratio of the length of each zone in the stretching apparatus of Fig. 4 is different from the ratio of the actual length.

In FIG. 4, although it is not shown in figure, between the extending|stretching zone C and the open zone D, the zone for performing arbitrary appropriate processes as needed may be provided. As such a process, a transverse shrinkage process, such as a transverse stretching process, is mentioned. In addition, although not shown in figure similarly, the said extending|stretching apparatus is a heating apparatus (for example, a hot air type, a near-infrared type, a far infrared ray type) for making each zone from the preheating zone B to the open zone D a heating environment typically. Various ovens such as meals) are provided. In one embodiment, preheating, oblique stretching, and opening from the clip may each be performed in an oven set to a predetermined temperature.

In the holding zone A and the preheating zone B of the stretching apparatus 100b, 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, the left endless loop 10L and the right endless loop 10R are stretched in the left-right asymmetrical direction, so that the conveying direction of the film changes and the preheating zone B As it goes from the side to the open zone D, it has a structure which expands gradually until the separation distance of the endless loops 10L, 10R on either side corresponds to the width|variety after extending|stretching of the said film. 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.

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, similarly to the stretching apparatus shown in FIG. 1 , the drive sprocket 11 of the left endless loop 10L is rotationally driven in the counterclockwise direction by the electric motor 13, and the right endless loop 10R is driven The sprocket 11 for use is rotationally driven by an electric motor 13 in a clockwise direction. Typically, the clip 20 on the left and the clip 20 on the right move at a constant speed, and the clip pitch in the longitudinal direction may be kept constant. In addition, when the difference in the traveling speed of the pair of left and right clips is 1% or less, the traveling speed of both can be said to be constant speed, and the difference in the traveling speed is preferably 0.5% or less, more preferably 0.1% or less.

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. Hereinafter, each process of the manufacturing method of the said stretched film is demonstrated in detail.

A-1. Gripping of film by clip

In the holding zone A (the entrance of the film blowing in the stretching apparatus 100a or 100b), both ends of the film to be stretched are the same and constant with the clips 20 of the left and right endless loops 10L and 10R. They are gripped at clip pitches, or 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).

A-2. Preheat

In the preheating zone B, the left and right endless loops 10L and 10R are configured to be substantially parallel to each other with a separation distance corresponding to the initial width of the film to be stretched as described above, so basically, transverse stretching 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 extended.

In preheating, the film is heated to a temperature T1 (°C). The temperature T1 is preferably equal to or higher than the glass transition temperature (Tg) of the film, more preferably 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 stretching

A-3-1. Oblique stretching using variable-pitch clips

In the extending|stretching zone C of the extending|stretching apparatus 100a, the clip 20 on either side is made to travel, changing the clip pitch of the at least one longitudinal direction, and a film is diagonally stretched. More specifically, by increasing or decreasing the clip pitch of the left and right clips at different positions, changing (increasing and/or reducing) the clip pitch of the right and left clips at different changing rates, respectively, is obliquely 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 among the pair of left and right clips that have shifted to the stretching zone at the same time to reach the end of the stretching zone. 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.

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

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, 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, and sets the clip pitch of _one clip in P1. up to P ₂ while increasing the clip pitch of the other clip at P ₁ up to P ₃ By decreasing, oblique stretching of the film (first oblique stretching) and increasing the distance between the left and right clips, keep the clip pitch of the one clip at P ₂ or up to P ₄ so that the clip pitch of the left and right clips becomes the same 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 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, the clip pitches on either side are all 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 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 / the 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, in the first oblique stretching, the product of the rate of change of the clip pitch of the first clip and the rate of change of the clip pitch of the second clip is preferably 0.7 to 1.5, more preferably 0.8 to 1.45, still more preferably 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 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 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 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. 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 - 4.0 times, more preferably 1.4 times - 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 with respect to the glass transition temperature (Tg) of the film, more preferably Tg-10°C to Tg+20°C, particularly preferably about Tg. . 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 of Unexamined-Japanese-Patent No. 2014-194483 - 0032 can be referred.

A-3-2. Oblique stretching using clips of constant pitch type

In the stretching zone C of the stretching apparatus 100b, as a result of the left endless loop 10L and the right endless loop 10R extending in an asymmetric direction, the conveying direction of the film changes (specifically, preheating) It is configured such that the transport direction of the film in the zone B (the direction in which the arrow B stretches) and the transport direction of the film in the release zone D (the direction in which the arrow D stretches) become non-parallel have. Due to such a configuration, the lengths of the right and left endless loops 10L and R in the diagonal stretching zone C (in other words, the travel distances of the right and left clips in the diagonal stretching zone C) are different. As a result, as for a pair of left and right clips traveling and moving at a constant speed, the clip with the shorter travel distance runs preceding (in FIG. 4, the clip on the left travels ahead), and the film is stretched in the oblique direction. . About the diagonal stretch of the said embodiment, description of Unexamined-Japanese-Patent No. 2004-226686, WO2007/111313, etc. can be referred, for example.

Oblique stretching may be typically performed at a temperature T2. The temperature T2 is preferably Tg-20°C to Tg+30°C with respect to the glass transition temperature (Tg) of the film, more preferably Tg-10°C to Tg+20°C, particularly preferably about Tg. . 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 of Unexamined-Japanese-Patent No. 2014-194483 - 0032 can be referred.

A-4. opening of the clip

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 normally 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. . 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 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.

In one embodiment, the width of the film opened from the clip (and consequently the width of the film provided for roll conveyance using a curved roll described below) is, for example, 1500 mm to 3000 mm, preferably 1800 mm to 2700 mm. and more preferably 2000 mm to 2400 mm.

A-5. roll conveyance

The film open|released from the said clip is roll conveyed using a curved roll. At this time, the film is roll conveyed by shifting the width direction center of the film and the width direction center of a curved roll so that the edge part on the side where the film does not hang may become closer to the width direction center of a curved roll than the edge part on the side which hangs. In addition, in this specification, the cylindrical conveyance roll used for normal roll conveyance may be called a straight roll.

6(a) and 6(b) are a schematic plan view and a schematic side view illustrating an example of roll conveyance using the above-mentioned curved roll, respectively, and FIG. 7 is an enlarged schematic view of a curved roll portion in roll conveyance. to be. In roll conveyance of the example of illustration, the film 1 sent out from the extending|stretching apparatus 100 is conveyed through seven rolls (curved roll 51, 1st - 6th straight rolls 52-57), and is wound, It is wound by the attachment (60).

As shown in FIG. 7, the curved roll 51 is curved symmetrically centering on the width direction center (center line C1) so that it may become convex toward a conveyance direction. When the film 1 opened from the clip passes over such a curved roll 51, it receives a frictional force so as to expand outward in the width direction. At this time, the film 1 is curved roll ( 51), a greater tension is applied to the non-sagging side of the film than to the sagging side. As a result, a long obliquely stretched film with reduced sagging and/or wrinkles can be obtained.

The curved roll 51 has, for example, a structure in which a plurality of radial ball bearings (not shown) are attached around the curved shaft 51a, and the surface layer thereof is covered with a barrel containing an elastically deformable elastic material such as rubber, , the cylinder is configured to be rotatable around the curved shaft 51b. In addition, although there exist a thing in which the curvature degree was fixed and a variable thing in a curved roll, you may use either.

The curvature amount D (mm) and the overall width Wa (mm) of the curved roll 51 can be set to appropriate values depending on the desired amount of sagging reduction, the film width, and the like, respectively. The amount of curvature D may be, for example, 5 mm to 15 mm, preferably 8 mm to 13 mm. The curvature (D/Wa×100) of the curved roll 51 may be, for example, 0.1% to 1.5%, preferably 0.2% to 0.7%. When the amount of curvature and/or the curvature is within the range, a long stretched film having reduced sagging and/or wrinkles while substantially maintaining the desired axial angle and in-plane retardation can be suitably obtained. Further, the total width Wa of the curved roll 51 may be, for example, 105% to 170%, preferably 110% to 155% of the width of the film 1 .

The distance between the width direction center of the film 1 and the width direction center of the curved roll 51 when passing through the curved roll 51 (the center line C2 of the film 1 and the center line C1 of the curved roll) distance) (L) can be set to any value as long as the effect of the present invention is obtained.

In one embodiment, the distance L is, for example, between 10 mm and 40 mm, preferably between 15 mm and 30 mm. When the distance L is within the range, a long stretched film with reduced wrinkles can be suitably obtained while substantially maintaining the desired axial angle and in-plane retardation.

In one embodiment, the distance L is, for example, between 40 mm and 120 mm, preferably between 45 mm and 110 mm, more preferably between 50 mm and 100 mm. When the distance L is within the range, a long stretched film with reduced sagging can be suitably obtained while substantially maintaining the desired axial angle and in-plane retardation.

The enveloping angle when the film passes through the curved roll is, for example, 45° to 135°, preferably 70° to 100°. When the enveloping angle is within such a range, the effects of the present invention can be suitably obtained.

As shown in the illustrated example, roll conveyance can be performed using a plurality of rolls including curved rolls. In roll conveyance, the total number of rolls (including curved rolls) through which the film passes may be, for example, 1 to 12, preferably 2 to 10, more preferably 3 to 8. In that case, the order in particular in which a film passes through a curved roll among all the rolls is not restrict|limited, A curved roll can be arrange|positioned at arbitrary positions.

In one embodiment, in addition to a curved roll, you may roll conveyance using a flat expander roll and/or a concave roll together. By using these together, the effect of reducing sagging can be more suitably obtained. There is no restriction|limiting in particular in the arrangement|positioning location of a flat expander roll and a cone cave roll. These rolls can each be arrange|positioned at arbitrary locations upstream or downstream of a conveyance direction rather than a curved roll.

Fig. 8 is a schematic plan view illustrating a flat expander roll preferably used in the above embodiment. The flat expander roll 58 shown in FIG. 8 is a linear roll. The flat expander roll 58 includes a shaft 58a, a pair of support substrates 58b attached to both ends of the shaft 58a, and a support substrate 58b attached to the inside of the support substrate 58b in the transport direction of the film. A plurality of elastic bands ( Typically, a rubber band (58d) is included. The ring member 58c is provided with a bearing, and receives the frictional force of the elastic band 58d and the film conveyed, and is comprised so that the inner side is rotatable in the circumferential direction together with the elastic band 58d. Moreover, the ring member 58c is comprised so that angle (theta) with respect to the conveyance direction of a film can be changed arbitrarily. In the example of illustration, although it is comprised so that the angle (theta) can be changed according to the insertion amount of the four adjustment bolts 58e, the angle (theta) may be changed by another structure. The flat expander roll can exhibit a large expandability, so that the angle (theta) is large.

The inclination angle θ of the ring member may be, for example, greater than 0°, 4.0° or less, and preferably 0.1° to 3.5°. By using the flat expander roll together at such an inclination angle, a long stretched film with reduced sagging can be more suitably obtained while substantially maintaining the desired axial angle and in-plane retardation.

9 : is a schematic plan view explaining the concave roll preferably used by the said embodiment. The cone cave roll 59 includes a central portion 59a and an enlarged diameter portion 59b and an end portion 59c positioned in this order from both ends thereof toward the outside. Each of the central portion 59a and the end portion 59c has a cylindrical shape, and the concave roll 59 has a point-symmetric shape with the center C of the rotation shaft A as the center of symmetry.

The difference X between the radius of the central portion 59a and the radius of the end portion 59c may be, for example, 0.2 mm to 2.0 mm, preferably 0.3 mm to 1.8 mm. Further, the width W4 of the end portion 59c may be, for example, 20 mm to 200 mm, preferably 30 mm to 180 mm. When the difference X and/or the width W4 are within this range, the effect of reducing the sagging can be suitably obtained. In the illustrated example, the central portion 59a includes the width W2 and has a cylindrical shape, but the width W2 of the central portion 59a may be 0 mm. It has a structure that expands toward both ends from the

The diameter expansion ratio (X/W3×100) of the diameter expansion portion 59b is, for example, 0.1% to 6.0%, preferably 0.2% to 5.0%, more preferably 1.0% to 4.5%. When the diameter expansion rate is within the range, the effect of reducing the sagging can be suitably obtained while substantially maintaining the desired axial angle and in-plane retardation. In addition, in the example of illustration, although the diameter expansion part is linearly expanded, the diameter expansion part may be curved concavely.

Contrary to the illustrated example, a concave roll that does not include an enlarged diameter portion (that is, a concave roll whose ends are vertically erected from both ends of the central portion) may be used. Regarding the difference (X) between the radius of the central portion and the radius of the end portion and the width (W4) of the end portion in such a concave roll, the same explanation as for the concave roll including the expanded diameter portion is applicable.

The total width W1 of the concave roll 59 and the width W2 of the central portion 59a may be appropriately set according to the film width at the time of passing the roll, the width W4 of the end portion, the diameter expansion rate, the difference (X), and the like. can The overall width W1 of the concave roll 59 is, for example, to be designed such that the left and right ends 51c overlap, for example, 5 mm to 195 mm, and also, for example, 10 mm to 190 mm, respectively, with the film passing over the roll. can

The material for forming the cone cave roll is not particularly limited as long as the effect of the present invention is obtained, and examples thereof include rubber or metal.

It is preferable to perform the said roll conveyance, providing tension|tensile_strength to the film after opening|closing from a clip. By providing tension to the entire film in addition to correction of sagging using a curved roll, sagging and/or wrinkles can be more effectively reduced. The tension applied to the film is, for example, 100 N/m or more, preferably 200 N/m or more, and more preferably 250 N/m to 500 N/m. The application of the tension can be performed, for example, by measuring the tension applied to the film between the conveying rolls or the like, and controlling the rotational speed of the conveying roll or the like so that the tension becomes a desired value.

The application of tension can be performed from after the clip opening to an arbitrary conveying roll (eg, from after opening the clip to a roll downstream of the curved roll).

The time for applying the tension can be appropriately set depending on the material for forming the film, the amount of sagging, and the like. The corresponding time may be, for example, 5 seconds to 60 seconds.

Roll conveyance may be performed in a heating environment, and may be performed in a non-heating environment. Preferably, roll conveyance is performed under a non-heating environment. By passing the curved roll under an unheated environment, sagging and/or wrinkles can be reduced while preventing the occurrence of scratches. The ambient temperature of the non-heating environment may be, for example, about 15°C to 40°C, and for example, about 20°C to 30°C. In addition, the atmospheric temperature of a heating environment can be made into the same grade as the atmospheric temperature in the open zone of the said extending|stretching apparatus, for example.

The roll conveyed film 1 can be wound up by the winding-up part 60, and can form a film roll. Or, unlike an example of illustration, a film is not wound up, and, conveying with another long optical film, it can match the direction of a long picture, and can bond continuously, and can comprise an optical laminated body.

In one embodiment, the stretched film opened from the clip and sent out from the stretching apparatus is roll conveyed using only the straight roll, the amount of sagging thereof is measured, and when the amount of sagging greater than or equal to a predetermined amount is detected, at least one straight roll By changing into a curved roll and performing roll conveyance, the amount of sagging of the stretched film obtained after that can be reduced.

A-6. 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 can be set as 700 mm - 1500 mm.

Although the film tension|tensile_strength at the time of the said detection is although it does not specifically limit, For example, it is 50 N/m - 400 N/m, Preferably it is 100 N/m - 200 N/m. When the conveying tension is too high, the film being conveyed elastically deforms, and sagging may become difficult to detect. On the other hand, when the conveying 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 and removed may be each independently, for example, 20 mm to 600 mm, preferably 100 mm to 500 mm. Cutting and removal of the end can be performed by conventional slitting.

Reduced sag obtained by the method for producing a stretched film of the present invention (sag of a film transported by roll without using a curved roll - sag of a film transported by a roll using a curved roll: provided that measured at a distance between rolls of 1000 mm sag) may be, 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 film after roll conveyance using the curved roll is, for example, less than 15 mm, preferably 10 mm or less, more preferably 8 mm or less, still more preferably 5 mm or less, further more Preferably it may be 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, 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. 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. This 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 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 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 Japanese Patent Application Laid-Open Nos. 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 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 Preferably it is 60 degrees - 90 degrees with respect to the long direction, More preferably, it is 65 degrees - 85 degrees, Especially preferably, it is about 75 degrees. 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 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 its 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.

10 is a schematic cross-sectional view of an example of such a circularly polarizing plate. The circular polarizing plate 200 of the illustrated example includes a polarizer 210 , a first protective film 220 disposed on one side of the polarizer 210 , and a second protective film 230 disposed on the other side of the polarizer 210 . and a retardation film 240 disposed outside the second protective film 230 . The retardation film 240 is a stretched film (eg, λ/4 plate) obtained by the manufacturing method described in the A section. The second protective film 230 may be omitted. In that case, the retardation film 240 may function as a protective film of the polarizer. The angle between the absorption axis of the polarizer 210 and the slow axis of the retardation film 240 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

11, the ultrasonic displacement sensor 300 is arrange|positioned below the conveyance path|route of the film 1 at the intermediate point between conveyance rolls 50a, 50b (inter-roll distance: 912 mm), and conveyance tension 150N Measure the distance from the ultrasonic displacement sensor to the stretched film at the center and end in the width direction when conveyed in /m, and determine the difference (L _MAX -L _MIN ) between the maximum distance (L _MAX ) and the minimum distance (L _MIN ) It was set 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.

(6) tension

The tension applied to the film was measured with the film tension detector installed in the film conveyance line.

<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 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 in FIGS. 1-3, 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 (P ₂ /P ₁ ) of the right clip is 1.42, The clip pitch change rate (P ₃ /P ₁ ) of the left clip was 0.78, and the transverse stretch ratio 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 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 clip on either side was opened, and it sent out from the extending|stretching apparatus exit.

(detection of sagging)

As mentioned above, the film (width 2300mm) sent out from the extending|stretching apparatus exit is conveyed by the conveyance line using seven conveyance rolls as shown to Fig.6 (a) and Fig.6 (b) in a room temperature environment. and the amount of sagging between the conveyance rolls was detected. During roll conveyance, the tension|tensile_strength of 300 N/m was provided for 180 second to the film from the clip opening point to the most downstream roll in the conveyance direction by adjusting the torque of the roll at the most downstream in the conveyance direction. In addition, among the rolls provided in the conveyance line, the roll sent out from the extending|stretching apparatus and the film first passed was a curved roll (curvature amount of 10 mm, total width 2400 mm), and all other rolls were straight rolls. Moreover, the film was conveyed so that the center line C2 of a film might overlap with the center line C1 of a curved roll (so that the distance between the center line C1 and the center line C2 might be set to 0 mm). In the obtained stretched film, slack generate|occur|produced in the left edge part of the width direction, and the slack amount was 18 mm.

(Roll conveyance)

In the roll conveyance, the curved roll was moved in parallel with respect to the conveying direction of the film so that the center line C2 of the film was 70 mm to the left of the center line C1 of the curved roll, and the roll conveyance was continued.

The retardation Re (590) of the obtained stretched film was 147 nm, and the angle which the slow axis direction and the long direction make|form was 45 degrees.

<Example 1-2>

A stretched film was obtained in the same manner as in Example 1-1 except that the curved roll was moved in parallel with respect to the transport direction of the film so that the center line C2 of the film was 100 mm left of the center line C1 of the curved roll.

The retardation Re (590) of the obtained stretched film was 147 nm, and the angle which the slow axis direction and the long direction make|form was 45 degrees.

<Example 1-3>

A stretched film was obtained in the same manner as in Example 1-1, except that the curved roll was moved in parallel with respect to the transport direction of the film so that the center line C2 of the film was 50 mm left of the center line C1 of the curved roll.

The retardation Re (590) of the obtained stretched film was 147 nm, and the angle which the slow axis direction and the long direction make|form was 45 degrees.

<Example 1-4>

The curved roll was moved in parallel with respect to the conveying direction of the film so that the center line (C2) of the film was 50 mm to the left of the center line (C1) of the curved roll. Except having replaced one thing and the 6th straight roll with the flat expander roll, it carried out similarly to Example 1-1, and obtained the stretched film. In addition, the inclination angle θ of the ring member of the flat expander roll was 3.5°. The difference (X) between the radius of the end of the concave roll and the radius of the center is 0.9 mm, the total width W1 of the concave roll is 2100 mm, the width W2 of the center is 1800 mm, each The width W4 of the end was 100 mm, and each enlarged diameter W3 was 50 mm.

The retardation Re (590) of the obtained stretched film was 147 nm, and the angle which the slow axis direction and the long direction make|form was 45 degrees.

<Comparative Example 1-1>

A stretched film was obtained in the same manner as in Example 1-1 except that a straight roll was used instead of the curved roll and the center of the width direction overlapped with the center of the film in the width direction.

The retardation Re (590) of the obtained stretched film was 147 nm, and the angle which the slow axis direction and the long direction make|form was 45 degrees.

[Appearance and handling evaluation]

The stretched films obtained in Examples and Comparative Examples were bonded together with a long masking film (manufactured by Toray Film 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.

(circle): A wrinkle is not recognized after masking film bonding (bonding tension|tensile_strength 150 N/m), but an adhesive agent can be coated on the film whole surface.

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

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

Regarding the stretched films obtained in Examples 1-1 to 1-4 and Comparative Example 1-1, the amount of sagging and the evaluation results are shown in Table 1.

[Table 1]

<Example 2-1>

A stretched film was obtained in the same manner as in Example 1-1 except that the curved roll was moved in parallel with respect to the transport direction of the film so that the center line C2 of the film was 40 mm left of the center line C1 of the curved roll.

The retardation Re (590) of the obtained stretched film was 147 nm, and the angle which the slow axis direction and the long direction make|form was 45 degrees.

<Example 2-2>

A stretched film was obtained in the same manner as in Example 1-1 except that the curved roll was moved in parallel with respect to the transport direction of the film so that the center line C2 of the film was 25 mm to the left of the center line C1 of the curved roll.

The retardation Re (590) of the obtained stretched film was 147 nm, and the angle which the slow axis direction and the long direction make|form was 45 degrees.

<Example 2-3>

A stretched film was obtained in the same manner as in Example 1-1 except that the curved roll was moved in parallel with respect to the transport direction of the film so that the center line C2 of the film was 10 mm left of the center line C1 of the curved roll.

The retardation Re (590) of the obtained stretched film was 147 nm, and the angle which the slow axis direction and the long direction make|form was 45 degrees.

<Comparative Example 2-1>

A stretched film was obtained in the same manner as in Example 1-1, except that the center line (C2) of the film and the center line (C1) of the curved roll overlapped without moving the curved roll in parallel, and roll conveyance was performed.

The retardation Re (590) of the obtained stretched film was 147 nm, and the angle which the slow axis direction and the long direction make|form was 45 degrees.

<Comparative Example 2-2>

A stretched film was obtained in the same manner as in Example 1-1 except that a straight roll was used instead of the curved roll, and the film center line (C2) was arranged to be 25 mm left of the center line (C1) of the straight roll.

The retardation Re (590) of the obtained stretched film was 147 nm, and the angle which the slow axis direction and the long direction make|form was 45 degrees.

[Wrinkle evaluation]

The wrinkles of the obtained stretched film were evaluated based on the following criteria.

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

(triangle|delta): Although a wrinkle is not visually recognized even if it irradiates a fluorescent lamp, a wrinkle is visually recognized when irradiated with a polarion light.

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

[Evaluation of returnability]

With respect to the obtained stretched film, it was visually confirmed whether distortion or fold had occurred in the film due to sagging and/or wrinkling, and evaluation was made based on the following criteria.

(circle): Warp and fold did not arise in a 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.

About the stretched film obtained in said Examples 2-1 to 2-3 and Comparative Examples 2-1 to 2-2, the said evaluation result is shown in Table 2.

[Table 2]

<Evaluation>

As shown in Tables 1 and 2, in the production of a long obliquely stretched film, the film after oblique stretching is passed through a curved roll such that the end of the non-sagging side is close to the center line of the curved roll, thereby reducing sagging and/or wrinkles. is reduced

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
51: curved roll
60: winding unit
100: stretching device
200: circular polarizer
300: ultrasonic displacement sensor

Claims (11)

Gripping the left and right ends of the long film in the width direction with the clips on the left and right,
oblique stretching of the film by moving the clips on the left and right, and then opening them from the clips on the left and right; and
A method for producing a stretched film, comprising roll conveying the film using a curved roll,
Roll conveying the film by shifting the width direction center of the film and the width direction center of the curved roll so that the end of the film on the non-sagging side is closer to the center in the width direction of the curved roll than the end on the side that hangs. A method for producing a stretched film. According to claim 1,
The manufacturing method of the stretched film whose curvature amount of the said curved roll is 5 mm - 15 mm. 3. The method of claim 1 or 2,
The manufacturing method of the stretched film whose distance between the width direction center of the said film at the time of passing the said curved roll and the width direction center of the said curved roll is 10 mm - 40 mm. 3. The method of claim 1 or 2,
The manufacturing method of the stretched film whose distance between the width direction center of the said film at the time of passing the said curved roll and the width direction center of the said curved roll is 40 mm - 120 mm. 3. The method of claim 1 or 2,
In addition to the said curved roll, the manufacturing method of the stretched film which roll conveys the said film using a flat expander roll and/or a concave roll. 3. The method of claim 1 or 2,
The clip is a clip of a variable pitch type in which the clip pitch in the longitudinal direction changes,
A method for producing a stretched film, wherein the film is diagonally stretched by moving while changing the clip pitch of at least one of a left clip for gripping the left end of the film and a right clip for gripping the right end of the film. 7. The method of claim 6,
The oblique stretching,
(i) The clip pitch of one of the clips on the left and right is set 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;
A method for producing a stretched film comprising a. 8. The method of claim 7,
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. 3. The method of claim 1 or 2,
A method for producing a stretched film, wherein the film is diagonally stretched by changing the conveyance direction of the film on the way while traveling and moving the left clip holding the left end of the film and the right clip holding the right end of the film at a constant speed. 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. 11. The method of claim 10,
The optical film is a polarizing plate,
The method for producing an optical laminate, wherein the stretched film is a λ/4 plate or a λ/2 plate.

Images