TW202237377A - Method for manufacturing diagonally stretched film including a diagonally stretching process, a trimming process and a film receiving process - Google Patents

Abstract

The issue of the present invention is a thin film that does not break during and after the trimming process. The thin film has excellent cut surface quality, high productivity and stable production, and is capable of suppressing uneven display. The solution is a method for manufacturing a diagonally stretched film, which includes: a diagonally stretching process, which uses a pair of grippers to grip two ends of the film in the width direction, such that one of the grippers moves first and the other gripper moves relatively late to transport the film and diagonally stretch the film in the width direction; a trimming process, which trims the end portion of the diagonally stretched film after stretched by the stretching process; and a film receiving process, which receives the trimmed leading-side end portion on the leading-side, the trimmed delay-side end portion on the delay-side, and a non-trimmed area. The manufacturing method is characterized in that the receiving tension of the leading-side end portion is set as T IN, the receiving tension of the non-trimmed area is set as T C, the width of the film end at the leading side end portion is set as width IN, and the film width of the non-trimmed area is set as width C, the following formula (1) is satisfied: [T C/width C] < [T IN/width IN].

Description

Method for producing diagonally stretched film

The present invention relates to a method for producing a diagonally stretched film, and particularly relates to a film that does not break during and after the trimming process, has excellent cut surface quality of the film, is highly productive and can be produced stably, and A method for producing a diagonally stretched film that suppresses the occurrence of display unevenness.

As an optical film that is required for use in organic electroluminescent display devices and polarized sunglasses, it is required to develop a film that tilts the in-plane slow axis of the film at a desired angle with respect to the transmission axis of the polarizing layer. In addition, with the recent evolution of lightweight and flexible devices, the demand for reducing the thickness of the above-mentioned optical film has greatly increased. Here, as a method of producing a film in which the in-plane slow axis is inclined at a desired angle, a method of obliquely stretching is known. After oblique stretching, a trimming process (also known as "cutting process", "cutting process" or "trimming process") that removes unnecessary parts clamped during stretching is used as an optical film. Coiled and manufactured. Here, the difficulty in trimming of a diagonally stretched film to be a film is particularly remarkable. This is because if it is a film, the mechanical strength is low, so disturbances in the state of the film slitting knife and the state of conveyance are likely to cause problems, and there is a problem in continuous productivity. In addition, there are process contaminations that bring cutting slag to the next process due to poor end faces of the film, uneven stress when the film is cut, etc., so that when the film is installed on a display device, there will be display unevenness. problems arising.

In addition, for example, in Patent Document 1, a method of clamping both sides of the film is proposed, but if the film tension of a very thin film is weak, the film cannot resist the push of the film cutting knife, resulting in the film being applied to the film. In the case of breaking due to such a load as cracking, there is a problem that the cut surface is deformed even if it is not broken. If coiling is carried out with the cut surface deformed and sent out repeatedly in the next process, stress concentration will be caused by the strained part, and breakage will occur when sending out continuously, and the strained part will be deformed, causing the part to be bent during transportation. A problem such as breakage occurs. Also, in the trimming process, there is disclosed a technology in which trimming width (cutting width) is different on the inner peripheral side and outer peripheral side of the obliquely stretched film (for example, refer to Patent Documents 2 and 3), however, There is no disclosure about the receiving tension of the trimmed film. [Prior Art Literature] [Patent Document]

[Patent Document 1] Japanese Unexamined Patent Publication No. 2015-3368 [Patent Document 2] International Publication No. 2013/118187 [Patent Document 3] International Publication No. 2013/125195

[Problem to be solved by the invention]

The present invention has been developed in view of the above-mentioned problems and circumstances, and its purpose is to provide a film that does not break during and after the trimming process, has an excellent quality of the cut surface of the film, and can be stably produced with high productivity. A method for producing a diagonally stretched film that suppresses the occurrence of unevenness. [Technical means to solve the problem]

In order to solve the aforementioned problems, the inventors of the present invention discovered the following during the process of examining the causes of the aforementioned problems, that is, when trimming the ends of the diagonally stretched film, by The receiving tension in the width direction of the film, that is, the receiving tension at the leading edge and the non-trimming area is set within a specific range, so that no breakage occurs during and after the trimming process, and the quality of the cut surface of the film is excellent. Improvement in productivity can be achieved, and occurrence of display unevenness can be suppressed. That is, the aforementioned problems of the present invention can be solved by the following means.

1. A method of manufacturing a diagonally stretched film, comprising: a diagonal stretching process, which is to hold both ends of the width direction of the film with a pair of grippers on one side, and move one of the grippers relatively first. , and the other side of the gripper is relatively delayed to move the aforementioned film, whereby the aforementioned film is stretched in the direction of the oblique direction in the width direction; the trimming process is to stretch the oblique direction of the aforementioned film by the aforementioned stretching process trimming toward the end of the stretched film; and a film receiving process for receiving the trimmed end of the preceding obliquely stretched film, that is, the leading end and the trimmed oblique The end portion of the stretched film, that is, the end portion on the retarding side, and the non-trimmed region of the obliquely stretched film are characterized in that when the receiving tension of the leading-side end portion is T _IN , the receiving tension of the non-trimmed region is When the tension is T _C , the film edge width of the leading edge is width _IN , and the film width of the non-trimming region is width c, the following expression (1) is satisfied. Formula (1): [T _C /width _C ]<[T _IN /width _IN ].

2. The method for producing a diagonally stretched film according to item 1, wherein when the receiving tension at the end of the delay side is T _OUT and the width of the film end at the end of the delay side is width _OUT , It satisfies the following formula (2). Formula (2): 0.8<[T _C /width _C ]/[T _OUT /width _OUT ]<[T _IN /width _IN ]/[T _C /width _C ]<4.0.

3. The method for producing a diagonally stretched film according to item 1 or 2, wherein, in the trimming process, the trimming start position of the leading side end of the diagonally stretched film and the delay side end are The distance difference between the trimming start position is within the range of ±200mm.

4. The method for producing a diagonally stretched film according to any one of items 1 to 3, wherein, in the trimming process, the leading edge and the retarding edge of the diagonally stretched film are simultaneously or Trim within ±3 seconds.

5. The method for producing a diagonally stretched film according to any one of items 1 to 4, wherein, in the trimming process, the edges of the leading edge, the retarding edge, and the non-trimming region to be trimmed are The respective widths satisfy the following formula (3) or formula (4). Formula (3): 15%<(width _IN /width _C )×100(%)<40%, formula (4): 15%<(width _OUT /width _C )×100(%)<40%.

6. The method for producing a diagonally stretched film according to any one of items 1 to 5, wherein, in the trimming process, when the diagonally stretched film is brought into contact with the support supporting the diagonally stretched film When the width is defined as the contact width A, the following expression (5) is satisfied. Formula (5): 0%<A/(width _IN + width _C + width _OUT )×100(%)<10%.

7. The method for producing a diagonally stretched film according to any one of items 1 to 6, wherein the thickness of the diagonally stretched film is 25 μm or less.

8. The method for producing a diagonally stretched film according to any one of items 1 to 7, wherein the NZ coefficient of the diagonally stretched film is less than 1.3. [Invention effect]

By means of the aforementioned means of the present invention, it is possible to provide a film that does not break during and after the trimming process, has an excellent quality of the cut surface of the film, has high productivity and can be produced stably, and can suppress the occurrence of display unevenness. A method for producing a diagonally stretched film. Although the generation mechanism or operation mechanism of the effect of this invention is not clear, it can guess as follows. In the conventional film thickness, although it did not cause a big problem, the strength of the film was reduced due to thinning of the film. When the receiving is performed at the receiving tension T1, breaks are likely to occur in the non _- trimming region C starting from the leading edge IN of the film during and after the trimming process. It is presumed that this is because the tension T2 immediately after trimming acts in a direction different from the orientation direction H of the film (a direction approximately perpendicular to the orientation direction H ₎ at the leading edge IN of the film, so that the film becomes Because it is easy to break (for example, refer to Figure 1(a)). Furthermore, at the retardation side end OUT of the film, the tension T3 immediately after trimming acts strongly in the same direction as the orientation direction H _of the film (a direction approximately parallel to the orientation direction H), thereby preventing the film from breaking. . Therefore, in the present invention, in the trimming process, the receiving tension of the leading side end portion of the obliquely stretched film and the non-trimming region is controlled to conform to the aforementioned formula (1). That is, by trimming so that the receiving tension T IN of the leading edge _IN is higher than the receiving tension T _c of the non-trimming region C, it is possible to prevent a fault at the leading edge IN of the film as a starting point. Cracks are generated in the trimmed region C, and the quality of the cut surface of the film is also good and the productivity is improved (for example, refer to FIG. 1( b )).

The manufacturing method of the obliquely stretched film of the present invention includes: oblique stretching process, which is to hold both ends of the width direction of the film with a pair of grippers, and move one of the grippers relatively first. , and the other side of the gripper is relatively delayed to move the aforementioned film, whereby the aforementioned film is stretched in a diagonal direction in the width direction; the trimming process is to stretch the oblique direction of the aforementioned film by the aforementioned stretching process trimming toward the end of the stretched film; and a film receiving process for receiving the trimmed end of the preceding obliquely stretched film, that is, the leading end and the trimmed oblique The end portion of the stretched film, that is, the end portion on the retarding side, and the non-trimmed region of the obliquely stretched film are characterized in that the receiving tension of the leading-side end portion is set to T _IN , and the non-trimmed region is When the tension is T _C , the film edge width of the leading edge is width _IN , and the film width of the non-trimming region is width c, the following expression (1) is satisfied. Formula (1): [T _C /width _C ]<[T _IN /width _IN ]. This feature is a common or corresponding technical feature in each of the following embodiments.

As an embodiment of the present invention, when the take-up tension at the end of the retardation side is T _OUT , and the width of the film end at the end of the retardation side is width _OUT , the above expression (2) is satisfied, It is excellent in that uneven stress at the time of film cutting can be prevented.

In the trimming process, it is preferable that the distance difference between the trimming start position of the leading edge of the diagonally stretched film and the trimming start position of the retarding edge be within the range of ±200 mm. The space of the equipment can be reduced by setting the difference in the distance between the trimming start positions of the leading end and the delaying end within the range of ±200 mm. In addition, the transportability of the film at the end of the film clamped by clips is in a state where the restraining force at the end is high (the film is thicker because the end is an unstretched part), so if it is carried out in two stages In the case of trimming, after trimming in the first stage, the film tends to incline toward the side opposite to the trimmed part. Therefore, there will be a problem that the conveyance stability of the trimmed cut portion becomes unstable in the second stage. However, as described above, by setting the If the distance difference is within the range of ±200 mm, the aforementioned problems will not occur. In particular, setting the distance difference between the trimming start positions within the aforementioned range is particularly effective for a thin film. In addition, in the trimming process, the preceding edge and the retarding edge of the obliquely stretched film are trimmed at the same time or within ±3 seconds, so that the distance difference can be within the range of ±200 mm. Excellent.

In the aforementioned trimming process, the respective widths of the aforementioned leading-side end portion, the aforementioned delay-side end portion, and the aforementioned non-trimming region to be trimmed conform to the aforementioned formula (3) or formula (4), which can make The stability of the end of the film is good, and the production stability of the diagonally stretched film is also improved.

In the aforementioned trimming process, when the contact width between the aforementioned obliquely stretched film and the support supporting the obliquely stretched film is set as the contact width A, it is preferable to satisfy the aforementioned formula (5). In the trimming process, when tension is applied to the diagonally stretched film, if the contact between the film and the support that supports the film is large, the support will exert a restrictive force, so it becomes difficult to trim the diagonally stretched film. The internal propagation conforms to the tension of the aforementioned formula (1). Therefore, in the trimming process, the tension can be stably propagated to the trimming portion by making the film and the support conform to the above formula (5), that is, reducing the contact between the film and the support.

Moreover, the fact that the thickness of the above-mentioned diagonally stretched film is 25 μm or less is excellent in that it can cope with weight reduction and flexibility of the device. In addition, the fact that the NZ coefficient of the above-mentioned diagonally stretched film is less than 1.3 is excellent in terms of a viewing angle improvement.

Hereinafter, the present invention, its constituent requirements, and forms and aspects for carrying out the present invention will be described. In addition, in this specification, [~] is used in the meaning which includes the numerical value described before and after it as a lower limit and an upper limit.

[Summary of the manufacturing method of the obliquely stretched film] The manufacturing method of the obliquely stretched film of the present invention includes: a diagonally stretching process, which is to hold both ends of the width direction of the film by a pair of grippers on one side On the one hand, one of the grippers is moved relatively first, and the other gripper is relatively delayed to move the aforementioned film, thereby stretching the aforementioned film in the width direction in an oblique direction, and trimming the process, which will be carried out by Trimming the end of the diagonally stretched film stretched by the stretching process; and a film receiving process for receiving the trimmed end of the diagonally stretched film on the leading side, that is, the leading side The end portion, the end portion of the retarded side of the diagonally stretched film that has been trimmed, that is, the retarded side end portion, and the non-trimmed region of the aforementioned diagonally stretched film are characterized in that: When the receiving tension is T _IN , the receiving tension in the non-trimming area is T _C , the width of the film end at the leading edge is the width _IN , and the film width in the non-trimming area is c, the following conditions are met: The formula (1). Formula (1): [T _C /width _C ]<[T _IN /width _IN ].

In addition, the method for producing a diagonally stretched film according to the present invention satisfies the following formula when the take-up tension at the end of the retardation side is T _OUT and the width of the film end at the end of the retardation side is width _OUT . The point (2) is excellent in that it can prevent uneven stress when the film is cut. Formula (2): 0.8<[T _C /width _C ]/[T _OUT /width _OUT ]<[T _IN /width _IN ]/[T _C /width _C ]<4.0. More preferably, it is a relationship satisfying the following formula (2-1). Formula (2-1): 1.0<[T _C /width _C ]/[T _OUT /width _OUT ]<[T _IN /width _IN ]/[T _C /width _C ]<3.0.

The above-mentioned "leading side end IN" refers to the end of the shorter running distance of the gripper described later, that is, the inner part of the film, among both ends in the width direction of the film. The aforementioned "retardation-side end portion OUT" refers to the end portion at which the travel distance of the gripper described later is longer among both ends in the width direction of the film, that is, the outer portion of the film. The aforementioned "untrimmed region C" refers to an untrimmed film region that does not contain the aforementioned leading-side end IN and the aforementioned delay-side end OUT.

Here, Fig. 4 is a schematic diagram showing the track pattern of the oblique stretch tenter. Walk on the asymmetric track Ri and Ro connected by the position (B position in Fig. 4). The track pattern in FIG. 4 is a case of turning to the right, so the inner peripheral side is the track Ri side, and the outer peripheral side is the Ro side. Also, when the track pattern turns to the left, the aforementioned Ri and Ro are reversed.

In addition, the aforementioned "receiving tension (T _IN ) of the leading edge" refers to the tension when receiving the trimmed leading edge in the film receiving process after the trimming process. In addition, the aforementioned "receiving tension (T _C ) of the non-trimming area" refers to the tension when the aforementioned non-trimming area is received in the film receiving process after the trimming process. In addition, the aforementioned "receiving tension (T _OUT ) of the delay-side end" refers to the tension when receiving the delay-side end in the film receiving process after the trimming process.

As a method of measuring the above-mentioned receiving tensions (T _IN , T _C , T _OUT ), for example, there is a method of measuring the load applied to the roller. A method of measuring the load applied to the roller, that is, the tension of the film. As the load cell, known ones such as tension dies and compression dies can be used. In addition, various well-known measurement methods can also be applied.

The aforementioned "film end width (width _IN ) of the leading-side end" refers to the film width of the leading-side end that has been trimmed in the trimming process. That is, it refers to the distance from the most distal end in the width direction of the trimmed leading end to the trimmed position. Furthermore, the "width direction" refers to the short-side direction of the film to be trimmed, that is, the direction from the lateral end of the film toward the end. The aforementioned "film edge width of the retardation side edge (width _OUT )" refers to the film width of the retardation edge edge that has been trimmed in the aforementioned trimming process. In other words, it refers to the distance from the top end in the width direction of the trimmed retard side end to the cut position. The aforementioned "film width (width _C ) of the non-trimming area" refers to the film width of the non-trimming area that has been trimmed in the aforementioned trimming process. That is, it refers to the distance from the most end portions in the width direction of the trimmed non-trimmed area.

Also, in the aforementioned trimming process of the present invention, the respective widths (width _IN , width _C , and width _OUT ) of the aforementioned leading-side end portion, the aforementioned delay-side end portion, and the aforementioned non-trimming region to be trimmed conform to the following formula ( 3) or formula (4) is excellent in that the stability of the film end immediately after trimming can be improved, and the production stability of the diagonally stretched film can also be improved. Formula (3): 15%<(width _IN /width _C )×100(%)<40%, formula (4): 15%<(width _OUT /width _C )×100(%)<40%.

[Diagonal stretching device] 2 and 3 are diagrams schematically showing a diagonal stretching device used in each process of the method for producing a diagonally stretched film according to an embodiment of the present invention. However, this is only an example, and the present invention is not limited to this embodiment.

In FIGS. 2 and 3 , symbols indicate the following members, devices, and the like. 1: Oblique stretching device, 2: Diagonal stretching tenter, 3: Continuous film feeding device, 4a: Film receiving device at the end of the leading side, 4b: Film receiving device in the non-trimming area, 4c: Delayed side Film receiver at the end, 5 and 8: Conveying rollers, 6: Inner guide rail, 7: Outer guide rail, 9a: Leading side cutter, 9b: Delayed side cutter, 11 and 12: Guide rail start position, 13 and 14: rail end position, 15: strip-shaped film (raw film) or diagonally stretched film.

＜Film production process＞ The method for producing the obliquely stretched film of the present invention preferably has a process of forming a long film containing resin (hereinafter also referred to as "raw film") before the aforementioned obliquely stretching process. The film forming process is performed by various means depending on the type of resin and the like, and details thereof will be described later. In the present invention, "elongated" refers to those having a length of at least about 5 times the width of the film, ideally 10 times or more, specifically, a film having a length that is wound into a roll shape. The length for storage or transportation (film roll).

＜Diagonal stretching process＞ The oblique stretching process in the production method of the present invention is to continuously send out the film from the film continuous sending device in a specific direction different from the receiving direction of the stretched film, and to separate the two ends of the aforementioned raw film in the width direction Gripping and conveying with the gripper of the oblique stretching tenter, and stretching the raw material film obliquely, whereby the film is applied at any angle exceeding 0° and less than 90° in the width direction of the film. The in-plane slow axis process. Here, the angle with respect to the width direction of a film means the angle in the plane of a film. Since the slow axis generally occurs in the stretching direction or in a direction at right angles to the stretching direction, in the production method of the present invention, the direction perpendicular to the conveying direction of the film is at an angle of more than 0° and less than 90°. , arbitrarily set and stretched at a desired angle, thereby producing a diagonally stretched film having the slow axis.

(constant delivery device) As shown in Figures 2 and 3, the continuous film delivery device 3 is preferably able to slide and rotate in order to send the film at a predetermined angle to the entrance of the oblique stretching tenter. In addition, it is preferable that the film continuous sending device 3 is slidable, and the film can be sent out toward the entrance of the diagonally stretching tenter by means of the conveying direction changing device. By configuring the above-mentioned film continuous feeding device 3 and the conveying direction changing device in such a structure, the continuous feeding position and angle of the film can be finely controlled, and a diagonally stretched film with small distribution of film thickness and optical value can be obtained. In addition, by making the aforementioned film continuous feeding device 3 and the conveying direction changing device movable, it is possible to effectively prevent the gripper from biting into the film. The film that is fed out continuously can be continuously connected with the above-mentioned film production process, but it is preferable to continuously feed out the film produced by winding into a roll in the film production process. By making the film forming process and the diagonal stretching process independently, the device can be compacted. Also, when the rolled roll is continuously sent out, a high degree of productivity can be ensured by continuously connecting the old film with the new film. Conventional means can be used as the means for connecting the films, such as bonding tape, thermal welding, ultrasonic welding, laser welding, etc., but joining by thermal welding is preferred.

(transfer roller) The conveying roller 5 is a roller for conveying the film continuously sent out from the above-mentioned continuous feeding device 3 to the guide rail starting positions 11 and 12 . The number of the aforementioned conveyance rollers 5 is not particularly limited. In addition, a static elimination device for removing static electricity from the thin film may be provided before and after the arrangement of the conveyance rollers and between a plurality of conveyance rollers. As the above-mentioned static elimination device, the same device as that used in the trimming process described later can be used.

(Diagonal Stretcher) In the production method of this embodiment, a diagonal stretch tenter is used to impart orientation in a diagonal direction to a raw film. The oblique stretch tenter used in this embodiment is preferably a film stretching device that can freely set the orientation angle of the film by changing the track pattern variously. In addition, a film stretching device that can orient the orientation axis of the film uniformly across the width direction of the film with high precision, and that can control the film thickness, phase difference, etc. with high precision, is preferable.

Fig. 4 is a schematic view schematically showing an example of a track pattern of a diagonal stretch tenter used in the method for producing a diagonally stretched film according to an embodiment of the present invention. However, this is only an example, and the present invention is not limited to this embodiment. The feed-out direction D1 of the raw material film is different from the take-up direction D2 of the stretched obliquely stretched film, and is formed at a feed-out angle θi. The continuous feeding angle θi can be arbitrarily set to a desired angle within a range exceeding 0° and less than 90°. The raw material film is attached to the entrance of the oblique stretch tenter (position A in Fig. 4), both ends of which are held by the left and right grippers, and travels along with the movement of the grippers. The left and right grippers are at the entrance of the oblique stretch tenter (position A in FIG. 4 ), which are opposite to the left and right grippers Ci and Co in a direction approximately perpendicular to the direction of travel of the film (continuous feeding direction D1), The system runs on the left-right asymmetrical rails Ri and Ro, and releases the film held at the position (position B in FIG. 4 ) at the end of stretching. At this time, the left and right grippers facing the entrance of the diagonal stretch tenter (position A in FIG. 4 ) travel on the left-right asymmetrical rails Ri and Ro, and form a gripper Ci that travels on the Ri side. The positional relationship of the movement of the gripper Co traveling on the Ro side. That is to say, at the entrance of the oblique stretching tenter (by the holding start position of the holding device of the film) A, the holding devices Ci and Co facing each other in a direction slightly perpendicular to the continuous feeding direction D1 of the film are located at the pulling position of the film. In the state of the position B at the end of stretching, the straight line connecting the grippers Ci and Co is inclined at an angle θL to a direction approximately perpendicular to the take-up direction D2 of the film. As described above, the film is stretched obliquely in the direction of θL. Here, the slightly vertical system means that it is in the range of 90±1°.

The aforementioned diagonal stretch tenter can heat the raw material film to an arbitrary temperature at which stretching can be performed. The aforementioned oblique stretching tenter is equipped with: a heating area; a pair of left and right rails for the grips used to transport the film to run; and a plurality of grips running on the rails. Both ends of the film supplied sequentially to the entrance of the tenter are held by the grippers, the film is guided into the heating zone, and the film is released from the grippers at the exit of the tenter. The film released from the gripper is received in the receiving process. The pair of rails each have an endless continuous rail, and the gripper that releases the grip of the film at the exit of the tenter travels outside and returns to the entrance in sequence.

Furthermore, the orbital pattern of the tenter is formed in an asymmetrical shape on the left and right, and the orbital pattern can be adjusted manually or automatically according to the orientation angle θ and stretching ratio of the obliquely stretched film to be manufactured. . In the oblique stretch tenter used in the manufacturing method of the embodiment of the present invention, it is preferable that the position of each track portion and the track connecting portion can be freely set, and the track pattern can be arbitrarily changed. In the embodiment of the present invention, the holding device of the tenter is kept at a constant distance from the front and rear holding devices, and then travels at a constant speed.

The running speed of the aforementioned grip can be appropriately selected, but generally falls within the range of 1 to 100 m/min. Under high-speed production conditions, the inclination of the orientation angle on the inner peripheral side becomes larger, so problems such as scratches and dents during film slitting become more prominent. Therefore, be the scope of 4～75m/ minute in walking speed, if implementing the present invention, then can make effect of the present invention promote further, if aforementioned walking speed is implemented in the scope of 10～50m/ minute, can make effect of the present invention more further improvement.

The difference in running speed between the left and right pair of grips is usually 1% or less, preferably 0.5% or less, and more preferably 0.1% or less. This is because if there is a speed difference between the left and right sides of the film at the exit of the stretching process, wrinkles and wrinkles will occur at the exit of the stretching process. Therefore, the speed difference between the left and right grippers is required to be substantially the same speed. In a general tenter device, etc., depending on the period of the teeth of the sprocket driving the chain, the frequency of the driving motor, etc., there will be speed unevenness on the order of seconds or less, and usually a few percent unevenness occurs, but these None of them correspond to the speed difference described in the embodiment of the present invention.

In the oblique stretch tenter used in the manufacturing method of the embodiment of the present invention, especially in the portion where the conveyance of the film becomes oblique, a large curvature is usually required for the track that regulates the track of the gripper. For the purpose of avoiding interference between grippers due to sharp bending or local stress concentration, it is preferable to draw a curve as the trajectory of the gripper at the bent portion.

In the embodiment of the present invention, the raw material film is at the entrance of the oblique stretch tenter (position A in FIG. 4 ), and its two ends are sequentially held by the left and right grippers, and travels along with the travel of the grippers. At the entrance of the oblique stretching tenter (position A in Fig. 4), the left and right grippers are opposite to the film traveling direction D1 in a direction slightly perpendicular to the left and right asymmetrical tracks. Heating zone for zone, stretch zone and heat fix zone.

The preheating zone refers to the section where the grippers held at both ends are kept at a certain distance from each other at the entrance of the heating zone. In addition, the stretching region refers to a region in which the gap between the grippers gripped at both ends is opened until a predetermined gap is reached. At this time, the above-mentioned oblique stretching is performed, but if necessary, stretching may be performed in the lateral direction before and after the diagonal stretching. The heat fixation zone refers to a zone where the grippers at both ends run while maintaining parallel to each other while the distance between the grippers becomes constant again after the stretching region. After passing through the heat-fixing zone, the temperature in the passing zone may be set to a zone (cooling zone) equal to or lower than the glass transition temperature Tg°C of the thermoplastic resin constituting the film. At this time, considering the shrinkage of the film due to cooling, it is also possible to create a track pattern in which the distance between the opposing grippers is narrowed in advance.

For the temperature of each zone, for the glass transition temperature Tg of thermoplastic resin, the temperature in the preheating zone is set to Tg~Tg+30°C, the temperature in the stretching zone (stretch temperature) is set to Tg~Tg+50°C, and the heat setting It is better to set the temperature of the zone as Tg-40~Tg+50℃, and the temperature of the cooling zone as Tg-80~Tg℃. Furthermore, in order to control thickness unevenness in the width direction, a temperature difference may be given in the width direction in the stretched region. In order to provide a temperature difference in the width direction in the stretching area, it is possible to adjust the opening of the nozzle that sends warm air into the thermostatic chamber to give a difference in the width direction. Arrange heaters and hot air generators in the A known method of heating control etc. in the width direction. The length of the preheating zone, stretching zone, heat fixing zone and cooling zone can be selected appropriately. For the length of the stretching zone, the length of the preheating zone is generally 25~150%, and the length of the heat fixing zone is generally 50~200%. , The length of the cooling area is generally 25~150%.

The stretching ratio (W/W0) of the aforementioned oblique stretching process is preferably in the range of 1.1-3.0, more preferably in the range of 1.5-2.8. If the stretching ratio is within this range, it is very preferable since the uneven thickness in the width direction becomes small. In the stretching region of the diagonal stretch tenter, if a difference in stretching temperature is provided in the width direction, the thickness unevenness in the width direction can be further made to a favorable level. In addition, W0 represents the width of the raw material film before stretching, and W represents the width of the diagonally stretched film after stretching.

<Trimming Process> The trimming process of the production method of the present invention is a process of trimming (cutting) both ends of the diagonally stretched film after the aforementioned diagonal stretching process with a trimming device. Since the two ends of the obliquely stretched film will be deformed by the holding tool during the oblique stretching process, it is necessary to cut off the two ends with unstable shapes. In addition, in the trimming process of the present invention, when the receiving tension of the preceding end portion of the film receiving process described later is T _IN , the receiving tension of the non-trimming area is T _C , and the film at the preceding end portion is When the end portion width is defined as the width _IN and the film width of the non-trimmed region is defined as the width _C , the following expression (1) is satisfied. Formula (1): [T _C /width _C ]<[T _IN /width _IN ].

5 is a schematic diagram of a trimming device used to illustrate the trimming process of the present invention. FIG. 5(a) is a front view viewed from the conveying direction, and FIG. 5(b) is a perspective view. The trimming device of this embodiment is a device that trims both ends of the obliquely stretched film 15 in a direction along the conveyance direction (arrow F direction in FIG. 5( b )). In addition, the trimming apparatus is not limited to the trimming apparatus 90 shown in FIG. 5, What is necessary is just what can trim the both ends of a diagonally stretched film to a conveyance direction. Specifically, shear cut, leather cut, slitting (score cut), thermal cutting, ultrasonic cutting, laser cutting, etc. are mentioned.

As shown in FIG. 5, the structure of the trimming device 90 is arranged on the extension line of the inner guide rail 6 and the outer guide rail 7 of the oblique stretch tenter 2 (refer to FIGS. 2 and 3), and a leading side cutter is arranged. 9a and a retardation side cutter 9b; and a support body 10 for supporting the diagonally stretched film 15 from the lower side. The leading side cutter 9 a is arranged on the inner side and upper side of the diagonally stretched film 15 , and the retarding side cutter 9 b is arranged on the outer side and upper side of the diagonally stretched film 15 .

The leading side cutter 9a and the delaying side cutter 9b are preferably circular blades that are rotatably pivoted. Here, the leading side cutter 9a and the delaying side cutter 9b are rotatably pivoted so as to passively rotate according to the conveyance of the obliquely stretched film 15, and the support body 10 described later is driven by an unillustrated The motor is rotationally driven by conveyance of the diagonally stretched film 15 so as to match the conveyance speed of the diagonally stretched film 15 .

Moreover, both the leading side cutter 9a, the retarding side cutter 9b, and the support body 10 may be rotationally driven so as to substantially match the conveyance speed of the diagonally stretched film 15. In addition, one or both of the leading cutter 9a, the retarding cutter 9b, and the support 10 may be driven in reverse rotation.

As the leading side cutter 9a and the delaying side cutter 9b, any one of a so-called disc-shaped blade, a bowl-shaped blade, and a circular blade of other shapes may be used, but here the leading side cutter 9a and the delaying side The cutter 9b serves as a disc-shaped blade.

The material of the leading cutter 9a and the retarding cutter 9b may be made of metal or ceramics, but it is preferable to use cemented carbide or high-speed steel. From the viewpoint of the amount of dross generated and the smoothness of the cut surface, it is desirable to use a cemented carbide blade made of cemented carbide. The diameter of the leading side cutter 9a and the delaying side cutter 9b is preferably in the range of 90 to 150 mm, and the thickness is preferably in the range of 1 to 5 mm. The laser-type cutting device is ideally a device capable of irradiating laser light with a circular cross-sectional shape in a direction perpendicular to the irradiation direction of laser light. Also, it is also desirable to use a device in which a focal point is provided in front of the irradiation direction of laser light, and the diameter of the aforementioned circle is reduced toward the focal point to irradiate laser light. The means for reducing the circular diameter of the laser beam is not particularly limited, and examples thereof include generally used means such as lenses, prisms, and mirrors. It does not specifically limit as said laser light, A well-known thing can be used. For example, _CO2 laser, YAG laser, UV laser etc. are mentioned. When irradiating the above-mentioned laser light, the laser light irradiation time, irradiation intensity, and spot diameter are not particularly limited, and the laser irradiation conditions can be appropriately selected as the aforementioned irradiation means within the range where the irradiated part will not dissolve or deform when the film is heated. , heating may be performed by one irradiation, or heating may be performed by plural irradiations. The output of the aforementioned laser irradiation is, for example, irradiated in the range of 1W to 300W, preferably in the range of 5W to 50W.

The above-mentioned support body 10 is a member that supports the diagonally stretched film 15 from the lower side, and is preferably in the form of a roller, for example. The support body 10 is rotationally driven by the drive motor so that it may match the conveyance speed of the diagonally stretched film 15 as mentioned above. Also, the support body 10 shown in FIG. 5 is formed in an elongated shape along the width direction of the obliquely stretched film 15, and the support body 10 is at a position corresponding to the leading side cutter 9a and the retarding side cutter 9b. A groove portion 10c and a groove portion 10d into which the leading side cutter 9a and the retarding side cutter 9b are inserted are respectively formed. Grooves 10c and 10d.

In addition, in the present invention, when the contact width between the diagonally stretched film 15 and the support body 10 supporting the diagonally stretched film 15 is defined as the contact width A, it is preferable to satisfy the following formula (5). Formula (5): 0%<A/(width _IN +width _C +width _OUT )×100(%)<10%. More preferably, it is a relationship satisfying the following formula (5-1). Formula (5-1): 1%<A/(width _IN +width _C +width _OUT )×100(%)<5%.

Here, the aforementioned [contact width A] refers to the width (length) when the support body 10 is in contact with the diagonally stretched film 15, and the width indicated by symbol A in FIG. 5( a ).

Since it is desirable to satisfy the formula (5) as mentioned above, it is more preferable to adopt the form as shown in FIG. 6 as a support body, for example. Fig. 6 is a schematic view illustrating another embodiment of the trimming device of the present invention, Fig. 6(a) is a front view viewed from the conveying direction, and Fig. 6(b) is a perspective view. In the trimming device 90 shown in Figure 6, when A/(width _IN +width _C +width _OUT )*100 represented by the aforementioned formula (5) is 10%, in the trimming device shown in Figure 5 90, when A/(width _IN +width _C +width _OUT )×100 represented by the aforementioned formula (5) is 100%.

In the trimming device 90 shown in FIG. 6, the inner support body 10a is provided at a position corresponding to the leading side cutter 9a so that the width direction of the obliquely stretched film 15 is parallel, and the outer support body 10b is provided at a position corresponding to the leading side cutter 9a. At the position corresponding to the delay side cutter 9b. In addition, the contact width A in which the two supports 10a and 10b contact the diagonally stretched film 15 satisfies the aforementioned expression (5).

As a material of the said support body 10 (inner support body 10a and outer support body 10b), metal, rubber, etc. are preferable, and metal is especially preferable. Moreover, when the support bodies 10, 10a, and 10b are metal, it is preferable to perform mirror finishing, groove|grooving, or matte processing on the surface, and it is more preferable to perform mirror finishing on the surface. In this case, the surfaces of the supports 10, 10a, and 10b preferably have an Ra (arithmetic mean roughness) of 10 nm or less and no pinholes, protrusions, etc. exist.

Also, in the present invention, in the trimming process, it is preferable that the distance difference between the trimming start position of the leading edge of the obliquely stretched film and the trimming starting position of the retarding edge be within the range of ±200 mm.

Fig. 6(b) is a diagram showing the case where the distance difference between the trimming start position of the leading edge and the trimming start position of the retarding edge is 0 mm, and Fig. 7 shows the trimming starting position of the leading edge and the retarding edge The diagram for the case where the distance difference between the trimming start positions at the top is less than +200mm.

Here, the trimming start position of the leading end refers to the vertex in the height direction perpendicular to the axial direction of the inner support body 10a provided at the leading end as shown in Fig. 6(b) and Fig. 7 X. Also, the trimming start position of the end portion of the delay side refers to the vertex Y in the height direction perpendicular to the axial direction on the outer support body 10b provided at the end portion of the delay side as shown in FIG. 6(b) and FIG. . Therefore, the "distance difference between the trimming start position of the leading edge and the trimming start position of the lagging edge" refers to the shortest distance m along the conveyance direction F between the apex X and the apex Y. Also, "within a distance difference of ±200 mm" refers to the positive (+) side defined as the opposite direction to the conveying direction F of the film based on the trimming start position (i.e., apex X) of the leading end. , the conveying direction F of the film is defined as the negative (-) side, from the position of 200 mm in the opposite direction from the apex X to the film conveying direction F to the range of 200 mm in the film conveying direction F. The diagonally stretched film is preferably trimmed on the leading side and the retarding side at the same time or within ±3 seconds. Thereby, the aforementioned distance difference can be set within the range of ±200 mm.

In FIG. 6( b ), the shortest distance between the vertex X and the vertex Y along the conveyance direction F is 0 mm, and the inner support body 10 a and the outer support body 10 b are arranged at the same position in the conveyance direction.

In addition, in FIG. 7 , the shortest distance m between the apex X and the apex Y along the conveyance direction F is less than +200 mm, and the inner support body 10 a and the outer support body 10 b are arranged at offset positions in the conveyance direction F.

In addition, in the present invention, the respective widths (width _IN , width _C , width _OUT ) of the preceding-side end, the delay-side end, and the non-trimming region to be trimmed conform to the following formula (3) or formula (4), the stability of the end of the film just after trimming can be improved, and the production stability of the obliquely stretched film is also improved. Formula (3): 15%<(width _IN /width _C )×100(%)<40%, formula (4): 15%<(width _OUT /width _C )×100(%)<40%.

In addition, in the trimming process of the present invention, trimming is preferably carried out under the condition that the temperature of the diagonally stretched film is higher than room temperature. That is, before the slitting knife comes into contact with the film, by heating the position of the film where the slitting knife is to contact, the trimming of the obliquely stretched film can be carried out under high temperature conditions, so that the film fragments and slag become It is not easy to attach to the film cutter.

The adjustment of the aforementioned temperature is preferably carried out by heating the _CO2 laser light irradiation device and the heat generating device before cutting off. The above-mentioned heat generating device is not particularly limited if it is a device capable of heating the resin film to be conveyed to a predetermined temperature. For example, an infrared heater may be used, or heated air at a certain temperature may be circulated to obtain a predetermined temperature.

It is preferable that the trimming device has a follow-up mechanism that follows the extending direction of the obliquely stretched film. In the aforementioned diagonal stretch tenter, the stretching direction and the winding direction can be arbitrarily set in order to obtain a diagonally stretched film having an orientation axis inclined to the width direction of the film as needed. Therefore, for the trimming device of the present invention, it is also required to have a mechanism that can follow and move along with the conveyance in the aforementioned extending direction and winding direction. In this way, since the trimming device has the following mechanism, it is possible to easily cut both ends of the diagonally stretched film. Especially in the present invention, when changing the trimming tension according to the width of the leading end and the delaying end, when changing the inclination angle of the stretching direction and the receiving direction, it becomes unnecessary to remove the trimming device or Since it is reconstructed, it is excellent in productivity.

As a specific example of the above-mentioned follow-up mechanism, for example, it can be fixed to move from the end positions 13 and 14 of the guide rail including the conveying roller 8 and the leading side cutter 9a and the delaying side cutter 9b to the film receiving device 4a. , 4b and 4c on the plate, or a movable unit fixed on a movable guide rail. That is, there is a method of moving together from the end positions of the guide rails 13 and 14 to the film receivers 4a, 4b, and 4c, but it is not particularly limited.

In addition, it is preferable that the trimming device has a confirming mechanism capable of confirming the position of the angle between the extending direction of the diagonally stretched film and the advancing direction of the slitting knife. By having such a confirmation mechanism, it is possible to more easily operate the trimming device accompanying the conveyance in the extending direction. As a specific example of the aforementioned confirmation mechanism, a light source is provided on the leading side cutter 9a and the delaying side cutter 9b, so that the sensors installed on the film receiving devices 4a, 4b, and 4c, or the heating area 2, etc., detect the light from the light source. Mechanism to confirm position by light. As the light source, a commercially available device such as a laser may be used, and it is not particularly limited.

In addition, the above-mentioned trimming device may be installed between the conveying rollers 8 as shown in FIGS. 2 and 3 , and may be installed at any position between the conveying rollers 8 . The number of the aforementioned conveying rollers 8 is not particularly limited, and a process of affixing a protective sheet for protecting the obliquely stretched film may also be provided during the disposition of the conveying rollers. Also, before winding the film, the following process may be set, that is, the left and right ends of the film are knurled by an embossing ring and a back roll (back roll), and an embossing portion is applied to the end of the film ( not shown) process.

In addition, a film thickness gauge, an optical value measuring machine, etc. capable of on-line measurement may be arranged during the arrangement of the conveying rollers. In addition, before and after the arrangement of the conveying rollers, and between a plurality of conveying rollers, a static eliminating device for eliminating static electricity of the diagonally stretched film may be provided.

The static elimination device can be implemented in such a way that the charging potential of the original coil is kept below ±2kV when it is sent out again, and the reverse potential is applied by the static removal device or the forced charging device when coiling, but it can also be made as The following structure, that is, eliminates static electricity with a static eliminator whose forced electrification potential is 1~150 Hz and alternates between positive and negative. In addition, static eliminators and static eliminators that generate ion wind can also be used to replace the aforementioned eliminators. Here, the static eliminator eliminates static by blowing ion wind onto the film wound up from the embossing device via the conveyance roller. Ionic wind is generated by static eliminator. As the eliminator, known eliminators can be used without limitation.

＜Film receiving process＞ The film receiving process of the manufacturing method of the present invention (hereinafter simply referred to as "receiving process" refers to the process of receiving the obliquely stretched film after the aforementioned trimming process, specifically, one of the obliquely stretched films after the trimming process is The trimmed leading-side edge, delay-side edge, and non-trimmed region each receive a winding process independently. Hereinafter, the receiving device used in the film receiving process will be described.

(receiving device) As shown in Figures 2 and 3, the film at the leading end, the non-trimming area, and the delaying side end that have been trimmed in the trimming process are respectively received by the film receiving device 4a at the leading end and the film at the non-trimming area. The device 4b and the film receiving device 4c at the end of the delay side receive each independently. The receiving devices 4a, 4b, and 4c can finely control the receiving position and angle of the film by forming the film at a predetermined angle to the exit of the oblique stretching tenter, and can obtain a film with a small deviation in film thickness and optical value. Stretch film diagonally. Therefore, generation of wrinkles on the film can be effectively prevented.

The film receiving device 4b is preferably a roller that can take up the film. Each of the film receiving devices 4a and 4c may be a roll capable of winding up a film, or may be a device for receiving only, and is not particularly limited.

Here, in the receiving process of the present invention, when the receiving tension of the trimmed leading end is T _IN , the receiving tension of the non-trimmed area is T _C , and the film end of the preceding leading end is When the portion width is width _IN and the film width of the non-trimming region is width _C , each of the leading side edge, the delay side edge, and the non-trimming region is received in such a manner as to satisfy the following expression (1). film. Formula (1): [T _C /width _C ]<[T _IN /width _IN ].

Furthermore, when the reception tension at the retardation side end is T _OUT and the width of the film end at the retardation side end is width _OUT , it is more preferable that the reception conforms to the following formula (2). . Formula (2): 0.8<[T _C /width _C ]/[T _OUT /width _OUT ]<[T _IN /width _IN ]/[T _C /width _C ]<4.0.

Specifically, the receiving tension T _C of the non-trimming region is in the range of 0.01-0.2 N/mm, more preferably 0.02-0.15 N/mm, and particularly preferably 0.03-0.1 N/mm. In addition, about the said numerical value, it can change suitably according to the thickness and resin to be used.

As a method of controlling the receiving tension T _IN , receiving tension T _C , and receiving tension T _OUT within the aforementioned ranges, for example, it is possible to measure the load applied to the rollers, that is, the tension of the film, and make the values within the aforementioned ranges. The method within is a method of controlling the rotational speed of the receiving roller by the general PID control method. As a method of measuring the above-mentioned load, there is a method of attaching a load cell to the bearing portion of the roller and measuring the load applied to the roller, that is, the tension of the film. As the load cell, known ones such as tension dies and compression dies can be used.

The obliquely stretched film after stretching is opened by the holding device, discharged from the outlet of the tenter, trimmed at both ends (both sides) of the film, and divided into trimmed leading side ends , the end of the delay side and the non-trimming area are respectively independently and sequentially received by the receiving device. The non-trimming area can be wound up sequentially and can be made into a roll body. The untrimmed area of the film wound up in this way is used as a diagonally stretched film for various products such as polarizing plates and organic EL display devices.

In addition, before winding up, for the purpose of preventing the blocking of the films, the masking film can be overlapped and rolled up at the same time, and it is also possible to stick a tape or the like to at least one, preferably both, ends of the diagonally stretched film. Do coiling. The masking film is not particularly limited as long as it can protect the film, and examples thereof include polyethylene terephthalate films, polyethylene films, and polypropylene films. The static elimination method and static elimination device described in the film slitting process can also be used for the static elimination during film production and winding.

＜Resin used for raw film＞ The raw material film of the present invention is not particularly limited, and any film made of a thermoplastic resin is applicable. For example, when the stretched film is used for optical applications, it is desirable to have transparency to a desired wavelength. Thin films made of resins with different properties. Examples of such resins include polycarbonate-based resins (PC), polyester-based resins, olefin polymer-based resins having an alicyclic structure (cycloolefin-based resins, COP), polyether-based resins, polyparaphenylene resins, Ethylene glycol diformate resin, polyimide resin, polymethyl methacrylate resin, polyethylene resin, polyarylate resin, polyethylene resin, polyvinyl chloride resin, cellulose ester Department of resin, etc.

Polycarbonate-based resins refer to polyesters of carbonic acid and ethylene glycol or divalent phenols, and polymers with carbonate bonds of -O-CO-O-, and the most practical ones are bisphenols and carbonates. Molecules, such as (Panlite® (registered trademark) and Pure-Ace® (registered trademark)) sold by Teijin Co., Ltd., (Elmec® (registered trademark)) of Kaneka Corporation, Mitsubishi Engineering Plastic Co., Ltd. (Iupilon® (registered trademark)), etc. Of course, since a polymer copolymerized with a monomer having a fluorenyl group (for example, refer to Japanese Patent Application Laid-Open No. 2005-189632 ) exhibits reverse wavelength dispersion of a phase difference, such a polycarbonate can also be ideal depending on the application. ground use.

Examples of polyester-based resins include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), etc. Such a polymer system exhibits retardation inverse wavelength dispersion, so such a polyester can also be ideally used depending on the application.

As the polyethylene naphthalate-based resin, for example, polyethylene naphthalate produced by polycondensing a lower alkyl ester of naphthalene dicarboxylic acid and ethylene glycol can be preferably used. As a commercially available product, Teonex® (manufactured by Teijin Corporation) or the like can be preferably used.

The cycloolefin-based resin is not particularly limited as long as it is a resin having a unit of a monomer consisting of a cyclic olefin (cycloolefin). The cycloolefin-based resin may be either a cycloolefin polymer (COP) or a cycloolefin copolymer (COC). The cyclic olefin copolymerization system refers to a copolymer of a cyclic olefin and an olefin such as ethylene, that is, a non-crystalline cyclic olefin resin.

As the aforementioned cyclic olefin, there are polycyclic cyclic olefins and monocyclic cyclic olefins. Examples of such polycyclic cyclic olefins include norcamphene, methylnorcamphene, dimethylnorcamphene, ethylnorcamphene, ethylidene norcamphene, and butylnorcamphene. , Dicyclopentadiene, Dihydrodicyclopentadiene, Methyldicyclopentadiene, Dimethyldicyclopentadiene, Tetracyclododecene, Methyltetracyclododecene, Dimethyl Cyclotetradecene, tricyclopentadiene, tetracyclopentadiene, etc. Moreover, examples of monocyclic cyclic olefins include cyclobutene, cyclopentene, cyclooctene, cyclooctadiene, cyclooctatriene, cyclododecatriene, and the like.

Cycloolefin-based resins can be purchased as commercial products, and examples thereof include "ZEONOR" manufactured by ZEON Corporation, "ARTON" manufactured by JSR Corporation, "TOPAS" manufactured by Polyplastics, and "TOPAS" manufactured by Mitsui Chemicals Corporation. APEL" and so on.

In addition, as the resin constituting the raw material film, the resin composition described in JP-A-2006-45369 and the alkoxycinnamate-based polymer described in JP-A-2016-108544 can also be used. In the cycloolefin resin, as long as the effect of the present invention is not impaired, for example, specific hydrocarbon-based resins described in Japanese Patent Application Laid-Open No. 9-221577, Japanese Patent Laid-Open No. 10-287732, or conventional Known thermoplastic resins, thermoplastic elastomers, rubbery polymers, organic microparticles, inorganic microparticles, etc., may also contain specific wavelength dispersants, sugar ester compounds, oxidation inhibitors, peeling accelerators, rubber particles, plasticizers, Additives such as UV absorbers.

＜Film production method of raw material film＞ As the film forming method of the raw material film, there are solution casting film forming method and melt casting film forming method as shown below. Each film forming method will be described below.

(solution casting method) In the solution casting method, the following processes are carried out, that is, the process of dissolving the resin and additives in the solvent to adjust the dopant; the process of casting the dopant on a strip-shaped or roller-shaped metal support; A process of drying the salivated dopant as a salivating film (mesh); a process of peeling the mesh from a metal support; a process of stretching or maintaining the width of the mesh; a process of further drying the mesh; And the process of winding the finished film.

The metal support of the drool process is ideal for the surface to be mirror-finished, and it is ideal to use a roller with a stainless steel strip or a casting whose surface is plated. The surface temperature of the metal support is set from -50°C to below the temperature at which the solvent does not boil and foam. Since the higher the temperature of the support body, the faster the drying speed of the mesh material is, it is ideal, but if it is too high, the mesh material may foam or the planarity may deteriorate.

As an ideal support body temperature, it is suitably determined in the range of 0-100 degreeC, More preferably, it is 5-30 degreeC. Alternatively, the method of peeling off from the roller is also ideal in a state where the net material is gelled by cooling and contains a large amount of residual solvent. The method of controlling the temperature of the metal support is not particularly limited, but there are methods of blowing warm or cold air, and methods of bringing warm water into contact with the back side of the metal support. The use of warm water is preferable because heat can be efficiently transferred and the time until the temperature of the metal support becomes constant can be shortened.

In the case of using warm air, considering the decrease in temperature of the net material due to the latent heat of evaporation of the solvent, warm air above the boiling point of the solvent may be used, and in order to prevent foaming, a higher temperature than the intended temperature may be used. .

In particular, it is preferable to change the temperature of the support and the temperature of the drying air during the period from drooling to peeling to efficiently dry.

In order for the formed resin film to exhibit good planarity, it is preferable that the amount of residual solvent when the mesh material is peeled off from the metal support is within a desired range. Here, the residual solvent amount is defined by the following formula. Residual solvent amount (mass % or %)={(M-N)/N}×100. In addition, M is the mass (g) of the sample taken at arbitrary time points during or after manufacture of a mesh material or a film, and N is the mass (g) after heating M at 115 degreeC for 1 hour.

In the film drying process, the roller drying method (the method of drying the mesh material alternately through a plurality of rollers arranged up and down) and the method of drying the mesh material while being transported by the tenter method are adopted.

(melt casting method) The melt casting method is a method in which a resin composition containing additives such as a resin and a plasticizer is heated to a fluidity temperature and melted, and then the fluid melt is cast to produce a film. The method of forming by melt casting can be classified into melt extrusion (forming) method, stamping forming method, inflation method, injection molding method, blow molding method, stretching forming method, etc. Among these methods, the melt-extrusion method in which a film having excellent mechanical strength, surface precision, etc. can be obtained is preferable. Also, it is generally better to mix and granulate the plurality of raw materials used in the melt extrusion method in advance.

The granulation can be performed by a known method. For example, dry resin, plasticizer, other additives, etc. are supplied to the extruder with a feeder, mixed with a 1-axis or 2-axis extruder, extruded from a die into a strand, and then water-cooled Or air-cooled and cut, thereby enabling granulation.

The additives may be pre-mixed with the resin before being supplied to the extruder, or the additives and the resin may be supplied to the extruder by separate feeders. In addition, small amounts of additives such as particles and anti-oxidation agents are preferably mixed with the resin in advance in order to mix them uniformly.

The extruder suppresses the shearing force so that the resin can be pelletized without deterioration of the resin (molecular weight reduction, coloring, gel formation, etc.), and it is better to process at a low temperature as much as possible. For example, in the case of a 2-axis extruder, it is better to use deep-groove screws that rotate in the same direction. From the viewpoint of the uniformity of kneading, the meshing type is preferable.

Using the pellets obtained as described above, thin film formation was performed. Of course, without granulation, the powder of the raw material may be directly supplied to the extruder by a feeder, and film formation may be performed in this state.

When extruding the above-mentioned pellets with a 1-axis or 2-axis extruder, the melting temperature is set at about 200~300°C, and the foreign matter is removed by filtering with a leaf disc filter, etc., and then cast into a film from a T-die shape, and then clamp the film with cooling rollers and elastic contact rollers, and then solidify on the cooling rollers.

When introducing the above-mentioned pellets from a supply hopper to an extruder, it is preferable to do so under vacuum, under reduced pressure, or under an inert gas atmosphere to prevent oxidative decomposition and the like from occurring.

It is better to stably carry out the extrusion flow rate by introducing a gear pump, etc. Also, as a filter for foreign matter removal, a stainless fiber sintered filter can be ideally used. The stainless steel fiber sintered filter is made by entangled stainless steel fiber complexly and compressed, and then the contact part is sintered to integrate. The density can be changed by the thickness of the fiber and the amount of compression, and can be adjusted. Filtration accuracy.

Additives such as plasticizers and granules can be pre-mixed with the resin, or mixed in during the extruder. In order to add uniformly, it is preferable to use a mixing device such as a static mixer.

When the film is clamped by the cooling roller and the elastic contact roller, the temperature of the film on the contact roller side is preferably above the Tg (glass transition temperature) of the film and below Tg+110°C. As the roller having an elastic body surface used for such purpose, known rollers can be used.

Elastic contact rollers can also be called clamping rotating bodies. Commercially available rollers can also be used as elastic contact rollers.

When peeling the film from the cooling roll, it is preferable to control the tension to prevent deformation of the film.

Furthermore, the raw material film for film production by the above-mentioned film production methods can be a single layer or a laminated film of more than two layers. , coating method and other known methods to obtain. Among these methods, the co-extrusion molding method and the co-saliva molding method are preferable.

＜Specifications of Raw Film＞ The thickness of the raw material film before stretching of the present invention is preferably in the range of 10 to 200 μm, more preferably in the range of 20 to 100 μm. In addition, in this embodiment, from the viewpoint of keeping the receiving tension of the film at the entrance of the oblique stretching tenter described later constant, and stabilizing the optical characteristics of the orientation angle and retardation value, it is supplied to the stretching film described later. The thickness unevenness σm of the material film in the region in the flow direction (transportation direction) is less than 0.30 μm, preferably less than 0.25 μm, more preferably less than 0.20 μm. When the thickness unevenness σm in the flow direction of the raw material film is 0.30 μm or more, variations in optical properties such as retardation values and orientation angles of the obliquely stretched film may deteriorate.

Moreover, as a raw material film, the film which has the thickness gradient of the width direction can also be supplied. The thickness gradient of the raw material film is obtained empirically by experimentally changing the film thickness gradient to various film stretches in order to make the film thickness at the position where the stretching in the subsequent process ends the most uniform. . The thickness gradient of the raw material film can be adjusted so that, for example, the thickness of the end portion on the thicker side becomes thicker by about 0.5 to 3% than the end portion on the thinner side.

The width of the raw material film is not particularly limited, but may be 600 to 2500 mm, preferably within the range of 800 to 2000 mm.

The ideal modulus of elasticity at the stretching temperature of the raw material film when stretched diagonally is not less than 0.01 MPa and not more than 5000 MPa, more preferably not less than 0.1 MPa and not more than 500 MPa, in terms of Young's modulus. If the modulus of elasticity is too low, the shrinkage rate during stretching and after stretching will be low, making wrinkles difficult to disappear. Also, if the modulus of elasticity is too high, the tension applied during stretching will increase, and it will be necessary to increase the strength of the portion holding both side edges of the film, and the load on the tenter in the subsequent process will increase.

As the raw film, one without orientation may be used, or a film having orientation in the longitudinal direction or the transverse direction may be supplied in advance. Also, the distribution in the width direction of the orientation of the raw material film can be made into a so-called bowing shape as needed. That is, the orientation state of the raw material film can be adjusted so that the orientation of the film at the position where stretching in the subsequent process is completed can be made a desired orientation.

＜Specifications of Diagonally Stretched Film＞ The obliquely stretched film obtained by the production method of the present invention (that is, the film in the non-trimmed region) preferably has a thickness of 25 μm or less, more preferably In the range of 1~20μm.

Moreover, although the width|variety of the diagonally stretched film of this invention is not specifically limited, Usually, it is 1500-3000 mm, Preferably it exists in the range of 1700-2400 mm.

In addition, the fact that the NZ coefficient of the diagonally stretched film of the present invention is less than 1.3 is excellent in that the effect of improving the viewing angle can be obtained. In this case, [NZ coefficient] refers to the maximum (slow axis direction) refractive index in the plane of the retardation film, the refractive index in the direction perpendicular to the slow axis (fast axis direction) in the plane of the retardation film, When the refractive index of the retardation film in the thickness direction is nx, ny, and nz, respectively, the value defined by NZ coefficient=(nx-nz)/(nx-ny). That is, the value of the ratio of Ro to Rt (Rt/Ro+0.5).

Means for adjusting the NZ coefficient to fall within the aforementioned range include adding additives or changing the compounding ratio of materials, and changing the film-forming method of the film (drool casting method, stretching temperature, magnification, film-forming speed, etc.).

In addition, in the obliquely stretched film obtained by the production method of the present invention, the orientation angle θ is inclined in the range of, for example, greater than 0° and less than 90° with respect to the take-up direction, and the width of at least 1300 mm, the width direction surface It is preferable that the variation of the internal retardation value Ro is 3 nm or less, and the variation of the orientation angle θ is less than 0.6°.

That is, in the obliquely stretched film, the change in the in-plane retardation value Ro is at least 1300 mm in the width direction, and is 3 nm or less, preferably 1 nm or less. By making the variation of the in-plane retardation value Ro within the aforementioned range, the obliquely stretched film and the polarizing layer can be pasted to form a circular polarizing plate, and when this plate is applied to an organic EL display device, it is possible to suppress black Color spots caused by leakage of reflected light from external light during display. Moreover, when using a diagonally stretched film as a retardation film for liquid crystal display devices, for example, display quality can also be made favorable.

In addition, in the aforementioned obliquely stretched film, the change in the orientation angle θ is preferably less than 0.6°, preferably less than 0.4°, at least 1300 mm in the width direction. If the change of the orientation angle θ is 0.6° or more, the elongated obliquely stretched film is bonded to the polarizing layer to make a circular polarizing plate, and then it is installed in an image display device such as an organic EL display device. Light leakage occurs, reducing the contrast between light and dark.

In addition, the in-plane retardation value Ro of the above-mentioned obliquely stretched film can be selected from an optimal value according to the design of the display device used. Furthermore, the aforementioned Ro is the value of the difference between the refractive index nx in the direction of the slow axis in the plane and the refractive index ny in the direction perpendicular to the slow axis in the plane multiplied by the average thickness d of the film (Ro=(nx-ny) × d).

＜Polarizer＞ FIG. 8 is an exploded perspective view showing a schematic structure of a polarizing plate 50 according to this embodiment. The polarizing plate 50 is formed by laminating a polarizing plate protective film 51 , a polarizing layer (only referred to as “polarizer”) 52 , and a retardation film 53 in this order. The polarizer protective film 51 is made of, for example, a cellulose ester film, and may also be made of other transparent resin films (such as cycloolefin-based resin). In addition, the polarizing plate protective film 51 may also be composed of an optical compensation film that compensates for optical properties such as widening of the viewing angle.

As the polarizing layer 52 , one obtained by stretching polyvinyl alcohol doped with iodine or a dichroic dye can be used. The layer thickness of the polarizing layer is 5 to 40 μm, preferably 5 to 30 μm, particularly preferably 5 to 20 μm.

The phase difference film 53 is comprised from the diagonally stretched film obtained by the manufacturing method of this invention. The slow axis of the retardation film 53 is in the film plane, inclined 10-80° to one side (for example, side 53a) of the rectangular film outer shape. In addition, the said side 53a corresponds to the side of the width direction of the elongated obliquely stretched film. In the film plane, the desired range of the inclination angle of the slow axis of the opposite side 53a is 30° to 60°, more preferably 45°. Also, the angle formed by the slow axis of the retardation film 53 and the absorption axis (or transmission axis) of the polarizing layer 52 is, for example, 10-80°, preferably 15-75°, more preferably 30-60°, most preferably Ideally 45°.

On the surface of the retardation film 53 opposite to the polarizing layer 52, other layers (such as a hard coat layer, a low-refractive index layer, an anti-reflection layer, liquid crystal (positive C-type plate)) can be appropriately provided according to the application. In addition, an easy-adhesive layer may be provided on the surface of the retardation film 53 on the polarizing layer 52 side.

The polarizing plate 50 of the present embodiment can be a strip-shaped polarizing plate protective film 51, a strip-shaped polarizing layer 52, and a strip-shaped retardation film 53 (strip-shaped obliquely stretched film). The elongated polarizing plates laminated sequentially may be sheet-shaped polarizing plates obtained by cutting the elongated polarizing plate 50 along the width direction perpendicular to the longitudinal direction.

The polarizing plate 50 can be produced by a general method. For example, the polarizing plate 50 can be produced by bonding the polarizing layer 52 and the retardation film 53 with an ultraviolet curable adhesive (UV adhesive). In addition, the retardation film 53 subjected to alkaline saponification treatment can also use a fully saponified polyvinyl alcohol aqueous solution (water glue), and the polyvinyl alcohol-based film is pasted on one side of the polarizing layer 52 made by dipping and stretching in an iodine solution. face. In addition, for bonding the polarizing layer 52 and the polarizing plate protective film 51 , an ultraviolet curable adhesive or water glue can be used.

(Composition of UV curable adhesive) As an ultraviolet curable adhesive composition for polarizing plates, a photoradical polymerizable composition using photoradical polymerization, a photocationic polymerizable composition using photocationic polymerization, and a combination of photoradical polymerization and photocationic polymerization The hybrid composition of is well known.

As the photoradical polymerizable composition, it is described in Japanese Patent Application Laid-Open No. 2008-009329, which contains a radically polymerizable compound containing a polar group such as a hydroxyl group or a carboxyl group and a radically polymerizable compound not containing a polar group in a specific ratio. The composition and so on are well known. In particular, the radically polymerizable compound is preferably a compound having a radically polymerizable ethylenically unsaturated bond. Examples of compounds having an ethylenically unsaturated bond capable of radical polymerization include compounds having a (meth)acryl group. Examples of compounds having a (meth)acryl group include N-substituted (meth)acrylamide compounds, (meth)acrylate compounds, and the like. (Meth)acrylamide means acrylamide or formamide.

In addition, as a photocationic polymerizable composition, as disclosed in JP-A-2011-028234, it is possible to include (α) a cationic polymerizable compound, (β) a photocationic polymerization initiator, and (γ) a compound longer than 380 nm. A photosensitizer that exhibits maximum absorption for light with a wavelength of 100000000000000000000000000000000000000000000000000, and (δ) naphthalene-based photosensitizer, an ultraviolet curable adhesive composition of each component. However, ultraviolet curable adhesives other than this adhesive may also be used.

(1) Pre-treatment process The pre-treatment process is a process for easy bonding of the bonding surface of the retardation film and polarizing plate protective film (here, these films are collectively referred to as "protective film") and the polarizing layer. As easy-adhesive treatment, a corona treatment, a plasma treatment, etc. are mentioned.

(Coating process of UV curable adhesive) As a coating process of the ultraviolet curable adhesive, the aforementioned ultraviolet curable adhesive is applied to the adhesive surface of at least one of the polarizing layer and the protective film. When directly applying the ultraviolet curable adhesive to the surface of the polarizing layer or the protective film, the application method is not particularly limited. Various wet coating methods such as a doctor blade, a wire bar, a die coater, a comma coater, and a gravure coater can be used. Also, a method of applying (drooling) the ultraviolet curable adhesive between the polarizing layer and the protective film, and then applying pressure with a roller or the like to evenly apply the ultraviolet curable adhesive can also be used.

(2) Paste process After applying the UV curable adhesive by the aforementioned method, it is processed in the pasting process. In this pasting process, for example, in the case where an ultraviolet curing adhesive is applied to the surface of the polarizing layer in the previous coating process, a protective film is superimposed there. Moreover, in the case of the system which apply|coats an ultraviolet-curable adhesive agent to the surface of a protective film, a polarizing layer is laminated|stacked at this place. In addition, when the ultraviolet curable adhesive is drooled between the polarizing layer and the protective film, the polarizing layer and the protective film are overlapped in this state. In addition, generally in this state, it is clamped and pressurized by pressure rollers etc. from the protective film side of both surfaces. As the material of the pressure roller, metal, rubber, etc. can be used. The pressure rollers arranged on both sides can be made of the same material or different materials.

(3) hardening process In the curing process, ultraviolet rays are irradiated to the uncured UV-curable adhesive to make cationic polymerizable compounds (such as epoxy compounds, oxetane compounds), radical polymerizable compounds (such as acrylate compounds, acrylic compounds) The ultraviolet curable adhesive layer of amine compound, etc.) is cured, and the polarizing layer and the protective film are bonded through the ultraviolet curable adhesive. In the structure of this embodiment in which a protective film is pasted on both sides of the polarizing layer, the protective film is superimposed on both sides of the polarizing layer through an ultraviolet curing adhesive, and ultraviolet rays are irradiated to simultaneously seal the ultraviolet curing adhesive on both sides. It is better to harden.

As for the irradiation conditions of ultraviolet rays, any correct conditions may be adopted as long as the ultraviolet curing adhesive can be cured. The irradiation amount of ultraviolet rays is preferably in the range of 50~1500mJ/cm ² of accumulated light, more preferably in the range of 100~500mJ/cm ² .

In the case of a continuous production line for the manufacturing process of polarizing plates, although the production line speed will vary due to the curing time of the adhesive, it is ideally in the range of 1~500m/min, and more ideally in the range of 5~300m/min. More ideally, it is in the range of 10~100m/min. If the line speed is 1 m/min or more, productivity can be ensured, damage to the protective film can be suppressed, and a polarizing plate having excellent durability can be produced. Also, if the line speed is 500 m/min or less, the ultraviolet curable adhesive can be sufficiently cured, and a ultraviolet curable adhesive having the desired hardness and excellent adhesiveness can be formed.

＜Organic EL display device＞ FIG. 9 is an exploded cross-sectional view showing a schematic structure of an organic EL display device 100 which is an example of a display device according to this embodiment. Furthermore, the structure of the organic EL display device 100 is not limited thereto.

The organic EL display device 100 is constituted by forming a polarizing plate 301 via an adhesive layer 201 on an organic EL element 101 as a display unit. The organic EL element 101 is structured on a substrate 111 made of glass, polyimide, etc., and has a metal electrode 112, a light emitting layer 113, a transparent electrode (ITO, etc.) 114, and a sealing layer 115 in sequence. Moreover, the metal electrode 112 can also be formed by a reflective electrode and a transparent electrode.

The polarizing plate 301 is formed by sequentially stacking a λ/4 retardation film 311, an adhesive layer 312, a polarizing layer 313, an adhesive layer 314, and a protective film 315 from the organic EL element 101 side. The film 311 and the protective film 315 are sandwiched. The angle formed by the transmission axis (or absorption axis) of the polarizing layer 313 and the slow axis of the λ/4 retardation film 311 made of the obliquely stretched film obtained by the production method of the present invention is about 45° (or 135°) to paste the two together to form a polarizer 301 (circular polarizer). Furthermore, the protective film 315 , polarizing layer 313 , and λ/4 retardation film 311 of the polarizer 301 correspond to the polarizer protective film 51 , polarizing layer 52 , and retardation film 53 of the polarizer 50 in FIG. 8 .

Preferably, a hardened layer is laminated on the aforementioned protective film 315 . The hardened layer has the effect of not only preventing damage to the surface of the organic EL display device but also preventing warpage due to the polarizing plate 301 . In addition, an antireflection layer may be provided on the hardened layer. The organic EL element 101 itself has a thickness of about 1 μm.

In the aforementioned structure, when a voltage is applied to the metal electrode 112 and the transparent electrode 114, electrons are injected from the metal electrode 112 and the transparent electrode 114 as the cathode, and holes are injected from the anode as the electrode of the metal electrode 112 and the transparent electrode 114. These are recombined in the luminescent layer 113, whereby visible ray emission corresponding to the luminescent characteristics of the luminescent layer 113 can be generated. The light generated in the light-emitting layer 113 is taken out to the outside through the transparent electrode 114 and the polarizer 301 directly or after being reflected by the metal electrode 112 .

Generally, in an organic EL display device, a metal electrode, a light-emitting layer, and a transparent electrode are sequentially laminated on a transparent substrate to form an element (organic EL element) as a light emitter. Here, the light-emitting layer is a laminate of various organic thin films, such as a laminate of a hole injection layer made of triphenylamine derivatives and a light-emitting layer made of a fluorescent organic solid such as anthracene. Layers and electron injection layers made of perylene derivatives, etc., laminates of these hole injection layers, light-emitting layers, and electron injection layers, etc., are known in various combinations.

The organic EL display device emits light according to the following principle, that is, by applying a voltage to the transparent electrode and the metal electrode, holes and electrons are injected into the light-emitting layer, and the energy generated by the recombination of these holes and electrons will excite Fluorescent substance, the principle of emitting light when the excited fluorescent substance returns to the ground state. The mechanism of recombination on the way is the same as that of a general diode, and it can be predicted from this that the current and luminous intensity are strongly nonlinear with rectification to the applied voltage.

In an organic EL display device, at least one electrode must be transparent in order to extract light from the light emitting layer, and a transparent electrode formed of a transparent conductor such as indium tin oxide (ITO) is generally used as an anode. In addition, in order to facilitate electron injection and improve luminous efficiency, it is very important to use a substance with a small work function in the cathode, and metal electrodes such as Mg-Ag and Al-Li are generally used.

In the organic EL display device having such a structure, the light-emitting layer is formed as an extremely thin film with a thickness of about 10 nm. Therefore, the light emitting layer can transmit light almost completely similarly to the transparent electrode. As a result, when the light is not emitted, the light incident from the surface of the transparent substrate, transmitted through the transparent electrode and the light-emitting layer, and reflected by the metal electrode appears again toward the surface side of the transparent substrate. Therefore, when it is recognized from the outside, the organic EL The display surface of the display device looks like a mirror.

The circular polarizing plate of this embodiment is suitable for use in such an organic EL display device in which external light reflection is a particular problem.

That is, when the organic EL element 101 is not emitting light, half of the external light incident from the outside of the organic EL element 101 by indoor lighting or the like will be absorbed by the polarizing layer 313 of the polarizing plate 301, and the remaining half will be absorbed as linearly polarized light. penetrates and enters the λ/4 retardation film 311 . The light incident on the λ/4 retardation film 311 crosses at 45° (or 135°) due to the transmission axis of the polarizing layer 313 and the slow axis of the λ/4 retardation film 311, so by passing through the λ/4 4. The phase difference film 311 is converted into circularly polarized light.

When the circularly polarized light emitted from the λ/4 retardation film 311 is mirror-reflected by the metal electrode 112 of the organic EL element 101 , its phase is reversed by 180 degrees, and it is reflected as reversed circularly polarized light. Since the reflected light is converted into linearly polarized light perpendicular to the transmission axis of the polarizing layer 313 (parallel to the absorption axis) by entering the λ/4 retardation film 311, it is all absorbed by the polarizing layer 313 and not emitted. to the outside. That is, the reflection of light outside the organic EL element 101 can be reduced by the polarizing plate 301 .

＜Liquid crystal display device＞ FIG. 10 is an exploded cross-sectional view showing the schematic structure of a liquid crystal display device 400 which is another example of the display device of this embodiment. The liquid crystal display device 400 is configured such that a polarizing plate 402 is disposed on one side of a liquid crystal cell 401 .

The liquid crystal cell 401 is a display cell in which a liquid crystal layer is interposed between a pair of substrates. Furthermore, on the side opposite to the polarizing plate 402 for the liquid crystal unit 401, other polarizing plates arranged in a cross-polarized state with the polarizing plate 402 are provided; and a backlight for illuminating the liquid crystal unit 401 is provided. In 10, respective illustrations are omitted.

In addition, the liquid crystal display device 400 may have a front window 403 on the opposite side of the polarizing plate 402 to the liquid crystal cell 401 . The front window 403 is a member serving as an external cover of the liquid crystal display device 400 , and is made of cover glass, for example. Between the front window 403 and the polarizing plate 402 is filled a filler 404 made of, for example, an ultraviolet curable resin. In the absence of the filling material 404, an air layer is formed between the front window 403 and the polarizer 402. Therefore, there will be light reflection at the interface between the front window 403, the polarizer 402, and the air layer, resulting in a display problem. When the visibility of the image is reduced. However, since no air layer is formed between the front window 403 and the polarizing plate 402 by the filler 404, it is possible to avoid degradation of display image visibility due to light reflection at the interface.

The polarizing plate 402 has a polarizing layer 411 through which predetermined linearly polarized light passes. On one side of the polarizing layer 411 (the side opposite to the liquid crystal cell 401 ), a λ/4 retardation film 413 and a cured layer 414 made of ultraviolet curable resin are laminated in this order via an adhesive layer 412 . In addition, a protective film 416 is pasted on the other surface side (the liquid crystal cell 401 side) of the polarizing layer 411 via an adhesive layer 415 .

The polarizing layer 411 is obtained, for example, by dyeing a polyvinyl alcohol film with a dichroic dye, and then stretching it at a high ratio. After the polarizing layer 411 is subjected to alkali treatment (also called saponification treatment), the λ/4 retardation film 413 is pasted via the adhesive layer 412 on one side, and the protective film 416 is attached via the adhesive layer 415 on the other side. Be pasted. Furthermore, the protective film 416 , polarizing layer 411 , and λ/4 retardation film 413 of the polarizer 402 correspond to the polarizer protective film 51 , polarizing layer 52 , and retardation film 53 of the polarizer 50 in FIG. 8 . The adhesive layers 412 and 415 are layers made of, for example, polyvinyl alcohol adhesives (PVA adhesives, hydrogels), but may also be layers made of ultraviolet-curable adhesives (UV adhesives).

The λ/4 retardation film 413 is a layer that imparts an in-plane retardation of about 1/4 of the wavelength to transmitted light, and is composed of a diagonally stretched film obtained by the production method of the present invention. Also, the angle (intersection angle) formed by the slow axis of the λ/4 retardation film 413 and the absorption axis of the polarizing layer 411 is, for example, 30° to 60°, more preferably 45°. Thus, the linearly polarized light from the polarizing layer 411 is converted into circularly polarized light or elliptically polarized light by the λ/4 retardation film 413 .

The hardened layer 414 (also referred to as a hard coat layer) is made of an active energy ray curable resin (such as an ultraviolet curable resin).

The protective film 416 is formed of a resin film made of, for example, cellulose-based resin (cellulose-based polymer), acrylic resin, cyclic polyolefin (COP), or polycarbonate (PC). The protective film 416 is provided only as a film for protecting the back side of the polarizing layer 411, but an optical film may also be provided as a retardation film having a desired optical compensation function.

Furthermore, in the case of a liquid crystal display device, the liquid crystal cell 401 (liquid crystal cell) is disposed on the opposite side of the polarizing plate 402, and the other polarizing plate is formed by interposing the surface of the polarizing layer with two optical films, but As the polarizing layer and the optical film, the same ones as the polarizing layer 411 and the protective film 416 of the polarizing plate 402 can also be used.

Furthermore, on the side of the adhesive layer 412 of the λ/4 retardation film 413 , an easy-adhesive layer for improving the adhesiveness of the λ/4 retardation film 413 may also be provided. The easy-adhesive layer is formed by performing an easy-adhesive treatment on the adhesive layer 412 side of the λ/4 retardation film 413 . The easy-adhesive treatment includes corona (discharge) treatment, plasma treatment, frame treatment, ITRO treatment, glow treatment, ozone treatment, primer coating treatment, etc., and at least one of these treatments may be performed. Among these easy-adhesive treatments, corona treatment and plasma treatment are preferable as easy-adhesive treatments from the viewpoint of productivity.

In this way, in the structure of the liquid crystal display device 400 in which the polarizing plate 402 is located on the viewing side with respect to the liquid crystal cell 401 and the λ/4 retardation film 413 of the polarizing plate 402 is located on the opposite side to the liquid crystal cell 401 with respect to the polarizing layer 411, the light emitted from the liquid crystal cell 401 and The linearly polarized light passing through the polarizing layer 411 on the identification side is converted into circularly polarized light or elliptically polarized light by the λ/4 retardation film 413 . Therefore, when the observer wears polarized sunglasses and observes the displayed image of the liquid crystal display device 400, no matter what angle is formed between the transmission axis of the polarizing layer 411 and the transmission axis of the polarized sunglasses, the transmission axis of the polarized sunglasses can also be adjusted. The light components parallel to the transmission axis are guided to the eyes of the observer to observe the displayed image. [Example]

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples. Furthermore, in the following examples, unless otherwise noted, the operations were carried out at room temperature (25° C.). In addition, unless otherwise noted, [%] and [part] mean [mass %] and [mass part], respectively.

[Manufacture of Diagonally Stretched Film 1] ＜Preparation of Raw Film B1＞ The alicyclic olefin polymer-based resin film (COP film) serving as the raw material film B1 was produced by the following production method (melt casting method).

In a nitrogen atmosphere, in 500 parts by mass of dehydrated cyclohexane, 1.2 parts by mass of 1-hexene, 0.15 parts by mass of dibutyl ether, and 0.30 parts by mass of triisobutylaluminum are placed in the reactor at room temperature After mixing, while maintaining at 45°C, 20 mass parts of tricyclo[4.3.0.12,5]dec-3,7-diene (dicyclopentadiene, hereinafter only described as DCP), 140 mass parts Parts of 1,4-methano-1,4,4a,9a-tetrahydrofluorene (hereinafter only described as MTF), and 40 parts by mass of 8-methyl-tetracyclo[4.4.0.12,5.17,10]-3 - A norbornene-based monomer mixture composed of dodecene (hereinafter referred to as MTD) and 40 parts by mass of tungsten hexachloride (0.7% toluene solution) were continuously added for 2 hours to perform polymerization. 1.06 parts by mass of butyl glycidyl ether and 0.52 parts by mass of isopropyl alcohol were added to the polymerization solution to deactivate the polymerization catalyst and stop the polymerization reaction.

Next, to 100 parts by mass of the reaction solution containing the obtained ring-opening polymer, add 270 parts by mass of cyclohexane, and further add 5 parts by mass of nickel-aluminum catalyst as a hydrogenation catalyst. Co., Ltd.), pressurized to 5 MPa with hydrogen, heated to 200°C while stirring, and reacted for 4 hours to obtain a hydrogenated polymer containing 20% DCP/MTF/MTD ring-opening polymer solution.

After the hydrogenation catalyst was removed by filtration, a soft polymer (manufactured by Kuraray Co., Ltd.; SEPTON®2002) and an oxidation inhibitor (manufactured by Ciba Japan K.K. Co., Ltd.; Irganox®1010) were added to the obtained solution and dissolved (both at 0.1 parts by mass per 100 parts by mass of polymer). Next, using a cylindrical concentration dryer (manufactured by Hitachi, Ltd.), cyclohexane and other volatile components in the solvent were removed from the solution, and the hydrogenated polymer was extruded in a molten state from an extruder in a strand form, Granulated and recovered after cooling. From the residual norbornene composition in the solution after polymerization (according to gas chromatography), the copolymerization ratio of each norbornene monomer in the calculation polymer is known, DCP/MTF/MTD=10/ 70/20, almost equal to prep ingredients. The weight average molecular weight (Mw) of the ring-opened polymer hydrogen additive is 31,000, the molecular weight distribution (Mw/Mn) is 2.5, the hydrogen addition rate is 99.9%, and the glass transition temperature Tg is 134°C.

The obtained pellets of the ring-opening polymer hydrogen additive were dried at 70° C. for 2 hours using a hot air drier that circulated air to remove moisture. Next, using a short-axis extruder (manufactured by Mitsubishi Heavy Industries Co., Ltd.; the diameter of the screw is 90mm, the material of the lip member of the T-die is tungsten carbide, and the peeling strength with molten resin is 44N) with a coat hanger as a T-die. The pellets were melt-extruded to obtain a cycloaliphatic olefin polymer-based resin film (COP film) as a raw material film B1 with a thickness of 50 μm and a residual solvent content of 10 ppm.

＜Diagonal stretching process＞ The raw material film B1 obtained above was stretched by the method shown below using the diagonal stretching apparatus of this invention, and the diagonal stretched film 1 was obtained.

First, the angle (turn angle) formed by the feeding direction of the film and the winding direction was set to 47°. Then, both ends of the raw material film B1 sent from the film continuous feeding device are held by the first clamp (inner peripheral side of the track) and the second clamp (outer peripheral side of the track).

Furthermore, when the raw material film is to be held, the raw material film is held by actuating the clamp bars of the first and second clips with the clip closer. In addition, when holding the clips, both ends of the raw material film are held simultaneously by the first and second clips, and the lines connecting the holding positions of the two ends are held in parallel with respect to an axis parallel to the transverse direction of the film. .

Next, the unstretched raw material film that has been grasped passes through the preheating zone, stretching zone, and heat-fixing zone in the heating zone by the aforementioned first and second clamps, thereby heating and pulling it in the width direction. stretched to obtain a diagonally stretched film. Furthermore, the conveying speed of the film during heating and stretching is set at 15 m/min, and the stretching temperature is appropriately selected and implemented in the range of Tg+10~Tg+30°C in accordance with the thickness.

Moreover, the stretching ratio of the film before and after stretching was set to 2 times, and the thickness of the film after stretching was 25 micrometers, and the width|variety was 1530 mm. The aforementioned thickness of the stretched film refers to the average film thickness measured at 20 mm intervals in the width direction of the film. Also, the average orientation angle of the stretched film measured at a pitch of 50 mm in the film width direction was 45°.

<Trimming process> The diagonally stretched film 1 obtained by the aforementioned diagonal stretching process is sent to a trimming device, and both ends of the diagonally stretched film 1 are trimmed. As the trimming device, the device shown in the aforementioned FIG. 5 is used. The leading side cutter 9a and the delaying side cutter 9b are circular blades pivotally supported in a rotatable manner, and the leading side cutter 9a and the delaying side cutter 9b are The supporting body 10 is freely rotatably pivoted so as to be passively rotated according to the conveyance of the diagonally stretched film, and the supporting body 10 is driven by the motor to match the conveying speed of the diagonally stretched film according to the speed of the diagonally stretched film. The transport is driven by rotation. As the material of the leading side cutter 9a and the delaying side cutter 9b, a super steel material with a diameter of 100 mm was used. In addition, the supporting body (supporting roller) 10 is elongated along the width direction of the film, and the material of the supporting body 10 is made of metal. In addition, the support body used here was not given a mirror finish or a matte finish. Also, when the contact width between the film and the support is defined as the contact width A, the value of A/(width _IN +width _C +width _OUT )×100(%) is set to the value shown in Table 1 below. Using such a trimming device, the respective widths (width _IN , width _c , and width _OUT ) of the leading side end, non-trimming region, and retardation side end of the film and the trimming of the leading side end of the diagonally stretched film 1 are trimmed. The difference in distance between the start position and the trimming start position of the retard side end has the values shown in Table I below.

<Film receiving process> The leading side end, non-trimming area and retarding side end of the obliquely stretched film trimmed in the aforementioned trimming process are respectively received by the film receiving device. Here, the receiving tensions (T _IN , T _c , T _OUT ) of the leading side end, non-trimmed region, and retarding side end of the diagonally stretched film were controlled to be the values shown in Table I below. The film is received by the load applied to the roller.

[Manufacture of Diagonal Stretched Films 2 to 15 and 19 to 21] The aforementioned obliquely stretched film 1 was manufactured in the same manner except that the following points were changed. In the diagonal stretching process, stretching was carried out so that the thickness of the stretched diagonally stretched film and the width of the film became the values shown in Table 1 below. In addition, in the manufacture of the diagonally stretched films 2, 20, and 21, the thicknesses of the raw material film B1 were 30 μm, 90 μm, and 24 μm (that is, twice the thickness of the diagonally stretched film) were used. In the trimming process, each width (width _IN , width _c , width _OUT ) of the leading side end, non-trimming region, and retardation side end of the film is trimmed, and the trimming start position and The distance difference between the trimming start positions at the retard side end has the values shown in Table I below. In the film receiving process, the receiving tensions (T _IN , T _c , T _OUT ) of the leading side end, non-trimming region and retarding side end of the obliquely stretched film become the values shown in Table I below , receiving film.

[Manufacture of Diagonal Stretched Films 16 and 18 ] Manufacturing of the aforementioned diagonally stretched films 2 to 15 and 19 to 21 was carried out in the same manner except for changing the following points. As the supporting body (supporting roller) of the trimming device, a mirror-finished metal roller (referred to as "supporting body A" in Table I below) is used, and when the contact width between the film and the supporting body is set to contact For width A, set the value of A/(width _IN + width _C + width _OUT )×100(%) to be the value shown in Table I below.

[Manufacture of Obliquely Stretched Film 17 ] In the manufacture of the aforementioned obliquely stretched films 2 to 15 and 19 to 21 , it was manufactured in the same manner except that the following points were changed. As the supporting body (supporting roller) of the trimming device, a roller made of metal and subjected to matting processing (referred to as "supporting body B" in Table I below) is used, and when the contact width between the film and the supporting body is set to For width A, set the value of A/(width _IN + width _C + width _OUT )×100(%) to be the value shown in Table I below.

[Manufacture of Obliquely Stretched Film 22 ] The aforementioned obliquely stretched films 2 to 15 and 19 to 21 were manufactured in the same manner except that the following points were changed. In the trimming method of the leading side cutter 9a and the delay side cutter 9b, the thin film was cut using a CO ₂ laser light irradiation device (wavelength 10.6 μm, laser light output 30W).

[Manufacture of obliquely stretched film 23] In the manufacture of the said diagonally stretched film 13, it manufactured in the same manner except having changed the following raw material film B2. ＜Production of Raw Film B2＞ (cycloolefin resin) As the cycloolefin resin, cycloolefin resin COP1 synthesized in the following manner was prepared.

(Synthesis of cycloolefin resin COP1) 50 grams of 8-methoxycarbonyl-8-methyltetracyclo[4.4.0.12,5.17,10]-3-dodecene, molecular weight adjustment 2.3 g of 1-hexene and 100 g of toluene were introduced into the nitrogen-substituted reaction vessel and heated to 80°C. And then add 0.09ml of triethylaluminum (0.6 mol/L) toluene solution, 0.29ml of methanol denatured WCl6 toluene solution (0.025 mol/L), react at 80°C for 3 hours, thereby Get aggregates. Next, the obtained ring-opened copolymer solution was placed in an autoclave, and 100 g of toluene was further added. Add 2500ppm of hydrogenation catalyst RuHCl(CO)[P(C ₆ H ₅ )] ₃ to the monomer production amount, and set the hydrogen pressure at 9~10MPa, and carry out the reaction at 160~165°C for 3 hours . After the reaction, the hydrogen addition was obtained by precipitating it in a large amount of methanol solution. The cycloolefin resin COP1, which is the hydrogen additive of the obtained ring-opening polymer, has a glass transition temperature (Tg) = 167°C, a weight average molecular weight (Mw) = 13.5×10 ⁴ , and a molecular weight distribution (Mw/Mn) = 3.06 .

(Preparation of fine particle dispersion) 12 parts by mass of microparticles (AEROSIL R972V; manufactured by NIPPON AEROSIL Co., Ltd.) and 88 parts by mass of ethanol were stirred and mixed with a dissolver for 50 minutes, and then dispersed with a high-pressure emulsifier to prepare a microparticle dispersion. Next, 100 parts by mass of the microparticle dispersion liquid was slowly added to methylene chloride (100 parts by mass) stirred in the dissolution tank. Furthermore, it disperse|distributes with the mixing pulverization apparatus so that the particle diameter of a secondary particle may become a predetermined size. Further, this material was filtered with FINEMET®NF manufactured by Nippon Seisen Co., Ltd. to prepare a fine particle additive solution.

(modulation of main dopant) The main dopant of the following composition was prepared. First, methylene chloride and ethanol were added to the pressurized dissolution tank. The cycloolefin resin COP1 and the microparticle addition liquid were charged into the pressurized dissolution tank to which methylene chloride had been added while stirring. Then, the resin was dissolved while heating and stirring, and this was filtered through Azumi filter paper No. 244 manufactured by Azumi Filter Paper Co., Ltd. to prepare a main dopant. ＜Composition of main dopant＞ Cycloolefin resin COP1 100 parts by mass Dichloromethane 302 parts by mass Ethanol 18 parts by mass Microparticle additive solution 10 parts by mass

<Formation of Raw Film B2> Using the aforementioned dopant, a raw material thin film B2 with a film thickness of 50 μm was produced by a solution casting method. That is, on a support made of SUS316 with a thickness of 2mm driven at a speed of 80m/min, the dopant is salivated from the salivation die, and after the dopant is dried on the support to form a salivation film, the Movement of the Body The conveyed casting film was peeled from the support to obtain the raw material film B2.

[Production of circular polarizing plate 1~23] In the production of the aforementioned obliquely stretched films 1-23, the circular polarizing plates 1-23 were respectively produced in the following manner using the non-trimmed area of the film received in the film receiving process. A polyvinyl alcohol film with a thickness of 120 μm is uniaxially stretched (at a temperature of 110° C. and a stretching ratio of 5 times), and immersed in an aqueous solution composed of 0.075 g of iodine, 5 g of potassium iodide, and 100 g of water for 60 seconds. Next, it was immersed in an aqueous solution at 68° C. consisting of 6 g of potassium iodide, 7.5 g of boric acid, and 100 g of water. The impregnated film was washed with water and dried to obtain a polarizing layer. Next, using a 5% aqueous solution of polyvinyl alcohol as an adhesive, the produced obliquely stretched film 1 was pasted on one side of the aforementioned polarizing layer. At this time, it stuck so that the transmission axis of the polarizing layer and the slow axis of the diagonally stretched film 1 might become the direction of 45 degrees. Also, on the other side of the polarizing layer, Konica Minolta TAC film KC4UAH (manufactured by Konica Minolta Co., Ltd.) subjected to alkaline saponification treatment was similarly pasted to prepare a circular polarizing plate 1 . The circular polarizing plates 2 to 23 were also produced in the same manner using the diagonally stretched films 2 to 22 .

[Production of organic EL display devices 1~23] On a glass substrate, a reflective electrode made of chromium with a thickness of 80 nm was produced by sputtering. Next, on the reflective electrode, ITO (indium tin oxide) as an anode with a thickness of 40 nm was produced by sputtering. Next, on the anode, poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate (PEDOT:PSS) was produced as a hole transport layer with a thickness of 80 nm by sputtering. Then, on the hole transport layer, each light emitting layer of RGB was formed with a film thickness of 100 nm using a shadow mask. Furthermore, calcium was formed into a film with a thickness of 4 nm by a vacuum evaporation method on the light-emitting layer as a first cathode having a low work function capable of efficiently injecting electrons. Then, on the first cathode, aluminum was formed into a film with a thickness of 2 nm to form a second cathode. Here, the aluminum used as the second cathode has the function of preventing chemical deterioration of the calcium used as the first cathode when the transparent electrode to be formed thereon is formed by sputtering. In the manner described above, an organic light-emitting layer was obtained. Next, a transparent conductive film was formed with a thickness of 80 nm on the cathode by a sputtering method. Here, ITO is used as the transparent conductive film. And, on the transparent conductive film, silicon nitride was formed into a film with a thickness of 200 nm by a CVD method (chemical vapor deposition method) to form an insulating film. Thereby, an organic EL element was fabricated. The size of the produced aforementioned organic EL element was 1296 mm x 784 mm. On the insulating film of the aforementioned organic EL element, the circular polarizing plates 1 to 23 manufactured in the above-mentioned manner are fixed with an adhesive in a plurality of sheets at intervals of 100 m, so that the oblique The surface of the stretched film faces the surface of the insulating film of the organic EL element. In this manner, organic EL display devices 1 to 23 were fabricated.

[Evaluation] ＜Frequency of breakage＞ When 100,000 m of film is continuously processed from the continuous feeding process of the aforementioned raw film to the aforementioned film receiving process, the frequency of breakage of the film is evaluated based on the following criteria. Levels 2 to 4 are regarded as a level where there is no practical problem. (baseline) Level 1: Continuous 100,000m, breaking frequency is more than 10 times. Level 2: Continuous 100,000m, breaking frequency is more than 4 times and less than 10 times. Level 3: Continuous 100000m, breaking frequency 1~3 times. Level 4: Continuous 100,000m, breaking frequency is 0 times.

＜Color＞ For each organic EL display device produced above, the color evaluation at the time of black display was performed based on the following reference|standard. Levels 2 to 4 are regarded as a level where there is no practical problem. (baseline) Rank 1: 6 or more of the 10 sheets look slightly different from the color on the screen, or, 1 or more of the 10 sheets look significantly different from the color on the screen. Rank 2: Out of 10 pieces, 3~5 pieces look slightly different from the color on the screen. Rank 3: Out of 10 sheets, 1~2 sheets look slightly different from the color on the screen. Rank 4: Among the 10 sheets, the color on the screen does not appear to be different from that on the screen.

As shown in the above results, it can be seen that the obliquely stretched film obtained by the production method of the present invention has a very low breakage frequency compared with the case of the comparative example, can effectively prevent breakage after the trimming process, and can improve productivity. High and stable production. Moreover, even in the organic EL display device produced using such a diagonally stretched film, it turned out that the quality is excellent.

1: Diagonal stretching device 2: Diagonal stretching stenter 3: Continuous film delivery device 4a: Film receiver at the end of the leading side 4b: Thin film receiver in non-trimmed area 4c: Thin-film receiver at the end of the delay side 5,8: Carrying rollers 6: The inner guide rail 7: Outer rails 9a: Advance side cutter 9b: Delay side cutter 10: Support body 10a: inner support body 10b: Outer support body 10c, 10d: ditch 11,12: rail start position 13,14: end position of guide rail 15: Raw film or diagonally stretched film 90: Dressing device Ci, Co: Grip A: Contact width X: Vertex of the supporting body at the end of the leading side Y: Vertex of the support at the end of the delay side IN: Leading side end C: Non-trimming area OUT: delay side end 50: polarizer 52: Polarizing layer 53: Retardation film (diagonally stretched film) 100: Organic EL display device 101: Organic EL element (display unit) 301: polarizer 311: λ/4 retardation film (diagonally stretched film) 313: Polarizing layer 400: liquid crystal display device 401: LCD unit (display unit) 402: polarizer 411: Polarizing layer 413: λ/4 retardation film (diagonally stretched film)

[ Fig. 1 ] is a schematic diagram for explaining the receiving tension of the leading side end, the non-trimming region and the retarding side end of the film of the present invention, and the orientation direction of the film. [Fig. 2] is a schematic top view of the oblique stretching device. [ Fig. 3 ] is a schematic side view of an oblique stretching device. [ Fig. 4 ] is a schematic diagram of an example of a track pattern of a diagonal stretch tenter. [ Fig. 5 ] A schematic diagram of a trimming device. [ Fig. 6 ] A schematic diagram of a trimming device. [ Fig. 7 ] A schematic diagram of a trimming device. [ Fig. 8 ] is an exploded perspective view showing a schematic structure of a polarizing plate. [ Fig. 9 ] is an exploded cross-sectional view showing a schematic structure of an organic EL display device. [ Fig. 10 ] is a cross-sectional view showing a schematic structure of a liquid crystal display device.

C: Non-trimming area

H: Orientation direction

IN: Leading side end

OUT: delay side end

T ₁ , T ₂ , T ₃ : tension

T _c : receiving tension

T _IN : Receive tension

T _OUT : Receive tension

Claims (8)

A method of manufacturing a diagonally stretched film, comprising: a diagonal stretching process, which is to hold both ends of the film in the width direction with a pair of grippers, and move one of the grippers relatively first, and The other gripper is relatively delayed to move the film, thereby stretching the film in an oblique direction in the width direction; trimming process, which is to stretch the film obliquely after stretching the film by the stretching process The end portion of the stretched film is trimmed; and the film receiving process is to receive the end portion of the aforementioned obliquely stretched film that has been trimmed on the leading side, that is, the end portion of the leading side and the trimmed aforementioned obliquely stretched film on the retarding side. The end portion of the stretched film, that is, the end portion on the retarding side, and the non-trimmed region of the obliquely stretched film are characterized in that: T _IN is the receiving tension of the leading-side end and the receiving tension of the non-trimming region is set When T _C , the film end width of the aforementioned leading side end is set to width _IN , and the film width of the non-trimming region is set to width c, the following formula (1) is met, formula (1): [ T _C /width _C ]<[T _IN /width _IN ]. The method for producing an obliquely stretched film according to claim 1, wherein when the receiving tension at the end of the delay side is T _OUT and the width of the film end at the end of the delay side is width _OUT , the following conditions are met: The above formula (2), formula (2): 0.8<[T _C /width _C ]/[T _OUT /width _OUT ]<[T _IN /width _IN ]/[T _C /width _C ]<4.0. The method for producing a diagonally stretched film according to claim 1 or 2, wherein, in the trimming process, the trimming start position of the leading side end of the diagonally stretched film and the trimming start position of the delay side end of the diagonally stretched film are The distance difference is within the range of ±200mm. The method for producing a diagonally stretched film according to any one of claims 1 to 3, wherein, in the trimming process, the leading side end and the delaying side end of the diagonally stretched film are made to be at the same time or ±3 Repair in seconds. The method for producing a diagonally stretched film according to any one of Claims 1 to 4, wherein, in the trimming process, the respective widths of the leading-side end, the delay-side end, and the non-trimming region to be trimmed It is in accordance with the following formula (3) or formula (4), formula (3): 15% < (width _IN / width _C ) × 100 (%) < 40%, formula (4): 15% ＜(width _OUT / width _C )×100(%)＜40%. The method for producing a diagonally stretched film according to any one of claims 1 to 5, wherein, in the aforementioned trimming process, when the contact width between the aforementioned diagonally stretched film and the support supporting the diagonally stretched film is set When the contact width is A, the following formula (5) is satisfied, formula (5): 0%<A/(width _IN +width _C +width _OUT )×100(%)<10%. The method for producing a diagonally stretched film according to any one of claims 1 to 6, wherein the thickness of the diagonally stretched film is 25 μm or less. The method for producing a diagonally stretched film according to any one of claims 1 to 7, wherein the NZ coefficient of the diagonally stretched film is less than 1.3.

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