KR20230046220A - Method for producing stretched film, method for producing optical laminate and device for stretching film - Google Patents

Abstract

The purpose of the present invention is to obtain a long obliquely stretched film with reduced deviation in orientation angle with high production efficiency. The present invention relates to a method for producing the stretched film by using a film stretching device which is provided with a gripping zone, a preheating zone, a stretching zone, and an opening zone in this order from an entrance side of the film to an exit side thereof and comprises: left and right reference rails of endless shape passing through these zones; and a plurality of variable pitch type left and right clips guided by the left and right reference rails and moving in a circular motion passing through the gripping zone, the preheating zone, the stretching zone, and the opening zone in this order. The method for producing the stretched film comprises: gripping the left and right ends of the long film in a width direction by the left and right clips, respectively; preheating the film; running the left and right clips while changing a clip pitch of at least one clip to obliquely stretch the film; and opening the film from the left and right clips. Provided is the method for producing the stretched film in which the temperature of the left and right clips on the way back from the open zone to the gripping zone is adjusted such that the temperature of the left and right clips when gripping the film is below Tg-90℃ of the film. According to the present invention, the effective width can be widened by gripping the film with a clip of a predetermined temperature such that manufacturing efficiency can be improved.

Description

Stretched film manufacturing method, optical laminate manufacturing method, and film stretching device

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

BACKGROUND ART In image display devices such as liquid crystal displays (LCDs) and organic electroluminescent displays (OLEDs), circularly polarizing plates are used for the purpose of improving display characteristics or preventing reflection. In the circular polarizing plate, typically, a polarizer and a retardation film (typically a λ/4 plate) are laminated so that the absorption axis of the polarizer and the slow axis of the retardation film form an angle of 45°. Conventionally, since the retardation film is typically produced by uniaxial stretching or biaxial stretching in the machine direction and/or transverse direction, the slow axis thereof is, in many cases, the transverse direction ( width direction) or longitudinal direction (long direction). As a result, in order to produce a circular polarizing plate, it was necessary to cut the retardation film so as to form an angle of 45° with respect to the width direction or the elongated direction, and bond it one by one.

Further, in order to secure the broadband property of the circular polarizing plate, there are cases in which two retardation films, a λ/4 plate and a λ/2 plate, are laminated. In that case, the λ/2 plate needs to be laminated at an angle of 75° with respect to the absorption axis of the polarizer, and the λ/4 plate needs to be laminated at an angle of 15° with respect to the absorption axis of the polarizer. Also in this case, when producing a circular polarizing plate, it was necessary to cut the retardation film so as to form angles of 15° and 75° with respect to the width direction or the elongated direction, and bond them one by one.

In another embodiment, a λ/2 plate is used on the viewing side of the polarizing plate for the purpose of rotating the direction of linearly polarized light emitted from the polarizing plate by 90° in order to avoid light from a note PC from being reflected on a keyboard or the like. . Also in this case, it was necessary to cut the retardation film so as to form an angle of 45° with respect to the width direction or the elongated direction, and bond it one by one.

In order to solve such a problem, the left and right ends of a long film in the width direction are respectively held by left and right clips of a variable pitch type in which the clip pitch in the longitudinal direction changes, and at least one of the left and right clips is fixed with a clip pitch. A technique for developing the slow axis of the retardation film in an oblique direction by stretching the film in an oblique direction with respect to the elongate direction (hereinafter also referred to as "oblique stretching") has been proposed (for example, Patent Document 1). However, in the obliquely stretched film obtained by such a technique, the orientation angle may vary. Moreover, further improvement of productivity is also calculated|required.

Japanese Patent No. 4845619

This invention was made in order to solve the said subject, The main objective is to obtain the obliquely stretched film of the shape of a long picture in which the dispersion|variation of orientation angle was reduced with high manufacturing efficiency.

According to one aspect of the present invention, a holding zone, a preheating zone, a drawing zone, and an open zone are provided in this order from the inlet side of the film toward the exit side, and the left and right standards of the endless shape passing through these zones A film stretching device including a rail and a plurality of variable-pitch type left and right clips guided by the left and right reference rails and passing through the holding zone, the preheating zone, the stretching zone, and the opening zone in this order and moving in a circular motion. A method for producing a stretched film using a film, wherein the left and right ends of a long film in the width direction are respectively held by the left and right clips, the film is preheated, and the left and right clips are clipped with at least one clip. The film is obliquely stretched by traveling while changing the pitch, and the film is opened from the left and right clips, while monitoring the temperature of the left and right clips when holding the film. A method for producing a stretched film in which the temperature of the clips on the left and right while returning from the open zone to the gripping zone is adjusted so that the temperature of the clips on the left and right when holding the film is equal to or less than Tg-90°C of the film. is provided.

In one embodiment, the fluctuation range of the temperature of the left and right clips at the time of gripping the film is adjusted to within 6°C.

In one embodiment, the temperature of the left and right clips when gripping the film is 20°C to 50°C.

In one embodiment, the temperature of the left and right clips is adjusted by blowing cooling air to the left and right clips on the way back from the open zone to the holding zone.

In one embodiment, the film is a resin film containing at least one selected from polycarbonate-based resins, cellulose ester-based resins, polyester-based resins, polyester carbonate-based resins, and cycloolefin-based resins.

According to another aspect of the present invention, obtaining a long stretched film by the above manufacturing method, and conveying the long optical film and the long picture-shaped stretched film, aligning the direction of the long picture and continuously bonding them together Optical A method for manufacturing a laminate is provided.

In one embodiment, the optical film is a polarizing plate, and the stretched film is a λ/4 plate or a λ/2 plate.

According to another aspect of the present invention, an endless reference rail on the left and right, including a holding zone, a preheating zone, a drawing zone, and an open zone in this order from the inlet side to the exit side of the film, and provided to pass through these zones, A plurality of left and right clips of the variable pitch type that are guided by the left and right reference rails and pass through the corresponding holding zone, the corresponding preheating zone, the corresponding stretching zone, and the corresponding opening zone in this order, and the left and right clips of the variable pitch type, and the corresponding clip before entering the corresponding gripping zone A film stretching device comprising means for monitoring the temperature of the left and right clips, and means for adjusting the temperature of the left and right clips on the way back from the opening zone to the holding zone.

In the method for producing a stretched film of the present invention, while monitoring the temperature of the left and right clips when holding the film, return from the open zone to the holding zone so that the temperature of the left and right clips when holding the film reaches a predetermined temperature. Adjust the temperature of the left and right clips on the way. Thereby, the temperature of the clip at the time of gripping a film can be controlled with high precision, and the dispersion|variation of the orientation angle in the width direction can be reduced. Further, when the film is gripped with a high-temperature clip, elongation occurs in the gripped portion, and as a result, the effective width of the resulting film is reduced. In contrast, by gripping the film with a clip at a predetermined temperature, the effective width can be widened and the manufacturing efficiency can be improved.

1 is a schematic plan view illustrating the entire configuration of an example of a film stretching device according to an embodiment of the present invention.
Fig. 2 is a schematic plan view of main parts for explaining a link mechanism for changing a clip pitch in the stretching device of Fig. 1;
Fig. 3 is a schematic plan view of main parts for explaining a link mechanism for changing a clip pitch in the stretching device of Fig. 1;
Fig. 4A is a schematic diagram showing a clip pitch profile in one embodiment of oblique stretching.
4B is a schematic diagram showing a clip pitch profile in one embodiment of oblique stretching.
5 is a schematic cross-sectional view of a circular polarizing plate using the retardation film obtained by the manufacturing method of the present invention.

Preferred embodiments of the present invention will be described below, but the present invention is not limited to these embodiments. In addition, in the present specification, 'clip pitch in the longitudinal direction' means a distance between centers in the running direction of clips adjacent to the longitudinal direction. In addition, the left-right relationship in the width direction of a long film-shaped film means the left-right relationship toward the conveyance direction of the said film, unless there is a special description.

A. Manufacturing method of stretched film

In the method for producing a stretched film according to an embodiment of the present invention, a holding zone, a preheating zone, a stretching zone, and an open zone are provided in this order from the inlet side to the outlet side of the film, and the left and right sides of the endless shape passing through these zones A film including a plurality of variable-pitch type left and right clips guided by the reference rail and the left and right reference rails and moving in a circular motion through the holding zone, the preheating zone, the stretching zone, and the opening zone in this order. A stretched film is manufactured using a stretching device.

In the manufacturing method of the stretched film of the embodiment, the left and right ends of the long film in the width direction are respectively held by the left and right clips (holding step),

Preheating the film (preheating process);

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

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

While monitoring the temperature of the left and right clips when holding the film, move the film from the open zone to the holding zone so that the temperature of the left and right clips when holding the film is equal to or less than the Tg-90°C of the film. Adjust the temperature of the corresponding left and right clips on the way back.

A-1. film stretching device

The method for manufacturing a stretched film according to an embodiment of the present invention has, for example, a gripping zone, a preheating zone, a stretching zone, and an open zone in this order from the inlet side to the exit side of the film, and an endless shape provided so as to pass through these zones. A plurality of variable pitch type left and right clips that are guided by the left and right reference rails and the left and right reference rails and pass through the holding zone, the preheating zone, the stretching zone, and the opening zone in this order to move in a circuit, Using a film stretching device including means for monitoring the temperature of the left and right clips before entering the gripping zone, and means for adjusting the temperature of the left and right clips on the way back from the open zone to the gripping zone can lose The film stretching device is configured to obliquely stretch the film by moving the left and right clips in the stretching zone while changing the clip pitch of at least one clip.

1 is a schematic plan view illustrating the overall configuration of an example of a film stretching apparatus that can be used in a method for producing a stretched film according to an embodiment of the present invention. The stretching device 100 includes, in plan view, endless loops 10L and endless loops 10R including a plurality of clips 20 for gripping the film on both left and right sides symmetrically. In addition, in this specification, the left endless loop viewed from the entry side of the film is referred to as the left endless loop 10L, and the right endless loop is referred to as the right endless loop 10R. The clips 20 of the left and right endless loops 10L and 10R are respectively guided by the left and right reference rails 70 of the endless shape, and are circularly moved in a loop shape. The clip (left clip) 20 of the left endless loop 10L rotates counterclockwise, and the clip (right clip) 20 of the right endless loop 10R rotates clockwise. . In the stretching device, a holding zone (A), a preheating zone (B), a stretching zone (C), and an open zone (D) are provided in this order from the inlet side to the outlet side of the sheet. Each of these zones means a zone in which the film to be stretched is substantially gripped, preheated, obliquely stretched, and opened, and does not mean a mechanically or structurally independent section. In addition, it should be noted that the ratio of the length of each zone in the stretching device of FIG. 1 is different from the ratio of the actual length.

In FIG. 1, although not shown, the zone for performing arbitrary appropriate processing may be provided between the drawing zone C and the opening zone D as needed. Examples of such a treatment include a transverse shrinkage treatment and the like. Also, although not shown, the stretching device is typically a heating device (for example, a hot air type, a near infrared ray type, a far infrared ray type) for setting each zone from the preheating zone B to the open zone D to a heating environment. Various types of ovens such as food) are provided. In one embodiment, preheating, oblique stretching, and opening from a clip may each be performed in an oven set to a predetermined temperature.

In the holding zone A and the preheating zone B of the stretching device 100, the left and right endless loops 10L and 10R are substantially parallel to each other with a separation distance corresponding to the initial width of the film to be stretched. Consists of. In the stretching zone (C), from the side of the preheating zone (B) toward the open zone (D), the distance between the left and right endless loops 10L and 10R gradually expands until the distance corresponding to the width after stretching of the film. is composed of In the open zone D, the left and right endless loops 10L and 10R are configured to be substantially parallel to each other with a separation distance corresponding to the width of the film after stretching. However, the configuration of the left and right endless loops 10L and 10R is not limited to the example shown above. For example, the left and right endless loops 10L and 10R may be configured to be substantially parallel to each other with a separation distance corresponding to the initial width of the film to be stretched from the holding zone A to the open zone D.

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

The clip (left clip) 20 of the left endless loop 10L and the clip (right clip) 20 of the right endless loop 10R are each variable pitch type. That is, the left and right clips 20 and 20 can each independently change the clip pitch in the vertical direction according to the movement. The configuration of the variable pitch type can be realized by employing a driving method such as a pantograph method, a linear motor method, or a motor/chain method. For example, Patent Document 1 and Japanese Unexamined Patent Publication No. 2008-44339 describe in detail a tenter type simultaneous biaxial stretching device using a pantograph type link mechanism. Hereinafter, as an example, a link mechanism (pantograph mechanism) will be described.

2 and 3 are respectively schematic plan views of main parts for explaining a link mechanism for changing the clip pitch in the stretching device of FIG. 1, FIG. 2 shows a state where the clip pitch is minimum, and FIG. 3 shows a state where the clip pitch is maximum. indicate state.

As shown in FIGS. 2 and 3 , there is provided a clip holding member 30 having an elongated rectangular shape in the transverse direction in plan view for individually holding the clips 20 . Although not shown, the clip holding member 30 is formed into a rigid frame structure with a cross section closed by an upper crossbeam, a lower crossbeam, a front wall (a wall on the clip side), and a rear wall (a wall on the opposite side to the clip). The clip holding member 30 is provided so as to roll over the running road surfaces 81 and 82 by the running wheels 38 at both ends thereof. 2 and 3, running wheels on the front wall side (traveling wheels that roll on the running road surface 81) are not shown. The running road surfaces 81 and 82 run parallel to the reference rail 70 throughout. A long hole 31 is formed along the longitudinal direction of the clip holding member 30 on the rear side of the upper and lower cross beams of the clip holding member 30 (the side opposite to the clip side (hereinafter, the opposite clip side)), and the slider 32 ) is slidably engaged in the longitudinal direction of the long hole 31 . In the vicinity of the end of the clip 20 side of the clip holding member 30, one first shaft member 33 is vertically provided through the upper crossbeam and the lower crossbeam. On the other hand, one second shaft member 34 is provided vertically penetrating the slider 32 of the clip holding member 30. One end of a main link member 35 is coupled to the first shaft member 33 of each clip holding member 30 by driving. The main link member 35 is pivotally coupled to the second shaft member 34 of the clip holding member 30 adjacent to the other end. In addition to the main link member 35, one end of the sub link member 36 is coupled to the first shaft member 33 of each clip holding member 30 by driving. The other end of the sub link member 36 is coupled to the intermediate portion of the main link member 35 by a pivot 37. As shown in FIG. 2 by the link mechanism of the main link member 35 and the auxiliary link member 36, the slider 32 is moved to the rear side (half clip side) of the clip holding member 30, When the pitch of the clip holding members 30 in the longitudinal direction (as a result, the clip pitch) becomes small and the slider 32 moves to the front side (clip side) of the clip holding member 30 as shown in FIG. As a result, the pitch of the clip holding members 30 in the longitudinal direction (as a result, the clip pitch) increases. Positioning of the slider 32 is performed by the pitch setting rail 90 . As shown in Figs. 2 and 3, the clip pitch increases as the separation distance between the reference rail 70 and the pitch setting rail 90 decreases.

The stretching device 100 includes means 40L and 40R for monitoring the temperature of the clip at the inlet of the film. As the clip temperature monitoring means 40L, 40R, a radiation thermometer such as a spot radiation thermometer, a scanning radiation thermometer, or a thermography camera is preferably used. Among them, a thermography camera is preferable. The position where the clip temperature monitoring means 40L, 40R is disposed is not limited to the entrance of the film, and may be any position where the temperature when the clip holds the film can be measured substantially. In addition, in this specification, the temperature of a clip or a clip temperature means the temperature of the upper and lower gripping part which contact|connects the film when a clip grips a film.

The stretching device 100 also includes means 50L and 50R for adjusting the temperature of the clip on the way from the open zone D of the left and right endless loops 10L and 10R to the holding zone A. The clip temperature adjusting means 50L, 50R is, for example, a cooling fan, and blows cooling air at a predetermined temperature into the clip according to setting or input.

The stretching device 100 changes the output (temperature, wind volume, wind speed, etc.) of the clip temperature adjusting means 50L, 50R based on the set temperature of the clip and the monitoring result sent from the clip temperature monitoring means 40L, 40R. The controllers 60L and 60R may be further provided. The controllers 60L and 60R compare the monitoring result (the actual measured value of the clip temperature when holding the film) with the set temperature of the clip temperature when holding the film, and offset (cancel) the difference to hold the film. A signal such that the clip temperature at the time of processing approaches the set value is output to the clip temperature adjusting means 50L, 50R (as a result, the output of the clip temperature adjusting means 50L, 50R is changed). Thus, clip temperature can be controlled with high precision by controller 60L, 60R feeding back the monitoring result to clip temperature adjusting means 50L, 50R. In general, without providing the controllers 60L and 60R in the stretching device 100, the operator compares the monitoring result and the set temperature of the clip temperature when holding the film, and the clip temperature adjusting means so that the difference is offset. The output settings of (50L, 50R) may be manually changed.

As needed, in the stretching device 100, from the viewpoint that the cooling air blown from the clip temperature adjusting means 50L, 50R does not affect the stretching of the film, cooling air enters the heating environment from the preheating zone to the open zone. A cover (not shown) for preventing this may be additionally provided.

Hereinafter, each process is demonstrated in detail.

A-2. holding process

In the gripping zone A (entrance for taking in the film of the stretching device 100), by the clips 20 of the left and right endless loops 10L and 10R, the left and right ends of the film to be stretched are at the same constant clip pitch. are gripped at the same time as At this time, the line connecting the centers of the left and right clips is approximately orthogonal (for example, 90 ° ± 3 °, preferably 90 ° ± 1 °, more preferably 90 ° ± 0.5 °, and more preferably 90 ° ± 0.5 °) with respect to the transport direction of the film. preferably 90°). The clip pitch of the left and right clips during gripping is, for example, 100 mm to 200 mm, preferably 125 mm to 175 mm, and more preferably 140 mm to 160 mm.

The temperature of the clip when gripping the film is typically Tg - 90°C or less of the film, for example, Tg - 100°C or less, and may be, for example, 20°C to Tg - 110°C. In one embodiment, the temperature of the clip when gripping the film is, for example, 50°C or lower, preferably 20°C to 50°C, more preferably 20°C to 40°C. In addition, the fluctuation range of the temperature of the clip at the time of gripping the film during continuous production of a long stretched film is preferably within the range of 6°C, more preferably 4°C. By setting the temperature of the clip when holding the film to the Tg of the film - 90 DEG C or less, a stretched film with excellent uniformity of the orientation angle in the width direction and a wide effective width can be obtained. In addition, by narrowly controlling the fluctuation range, the effect can be obtained stably. In addition, the film temperature at the time of gripping with a clip is typically room temperature.

By the movement of the clip 20 of the left and right endless loops 10L and 10R (actually, the movement of each clip holding member guided by the reference rail), the film is sent to the preheating zone B.

A-3. preheating process

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

In the preheating step, the film is heated to a temperature T1 (° C.). The temperature T1 is preferably equal to or higher than the glass transition temperature (Tg) of the film, more preferably equal to or higher than Tg+2°C, and still more preferably equal to or higher than Tg+5°C. On the other hand, the heating temperature T1 is preferably Tg+40°C or lower, more preferably Tg+30°C or lower. Although different depending on the film used, the temperature T1 is, for example, 70°C to 190°C, preferably 80°C to 180°C.

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

A-4. oblique stretching process

In the stretching zone C, the clips 20 on either side are run and moved while changing the clip pitch in the longitudinal direction of at least one of the clips, thereby obliquely stretching the film. More specifically, by moving the left and right clips while increasing or reducing the clip pitch at different positions, by changing (increasing and/or reducing) the clip pitch at different changing speeds, etc. The film is obliquely stretched. As a result of running the left and right clips while changing the clip pitch in this way, among a pair of left and right clips that have simultaneously moved to the stretching zone, one clip precedes the other and reaches the end of the stretching zone. According to such oblique stretching, the end of the preceding clip is stretched at a higher draw ratio than the end of the following clip, and as a result, the elongated film is stretched in a desired direction (e.g., 45° with respect to the longitudinal direction). direction) can express the slow axis.

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

When the oblique stretching includes transverse stretching, the draw ratio in the transverse direction (TD) (the ratio of the width of the film after oblique stretching (W _final ) to the initial width of the film (W _initial ) (W _final /W _initial )) Silver is preferably 1.05 to 6.00, more preferably 1.10 to 5.00.

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

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

In another embodiment, the oblique stretching is (i) the clip pitch of one of the left and right clips is P_Onein P₂increase the clip pitch of the other clip to P_Onein P₃and (ii) changing the clip pitch of each clip so that the corresponding reduced clip pitch and the corresponding increased clip pitch are the same predetermined pitch. Regarding the oblique stretching of the embodiment, descriptions such as Unexamined-Japanese-Patent No. 2014-194484 can be referred, for example. In the oblique stretching of the embodiment, the clip pitch of one clip is set to P while the distance between the left and right clips is increased._Onein P₂increase the clip pitch of the other clip to P_Oneat P₃until decrease, obliquely stretching the film (first oblique stretching), and while enlarging the distance between the left and right clips, the clip pitch of the one clip is set to P so that the clip pitches of the left and right clips become the same.₂keep as or P₄until decrease, and also set the clip pitch of the corresponding other clip to P₂ or P₄until It may include stretching the film obliquely by increasing it (second oblique stretching).

In the first oblique stretching, oblique stretching is performed while one end of the film is stretched in the direction of a long picture and the other end is contracted in the direction of a long picture, so that the film is stretched in a desired direction (for example, in a direction at 45° with respect to the direction of a long picture). A slow axis can be developed with uniaxial and in-plane orientation. In addition, in the second oblique stretch, by performing the oblique stretch while reducing the difference between the left and right clip pitches, the film can be sufficiently stretched in an oblique direction while relieving excess stress.

In the oblique stretching of the above three embodiments, since the film can be released from the clips in a state where the moving speeds of the left and right clips are the same, variation in the transport speed of the film and the like is unlikely to occur when the clips on the left and right are released. Winding of the later film can be suitably performed.

4A and 4B are schematic diagrams showing an example of a clip pitch profile in oblique stretching including the first oblique stretching and the second oblique stretching, respectively. Hereinafter, 1st oblique stretch is demonstrated concretely, referring these drawings. Also, in Figs. 4A and 4B, the horizontal axis corresponds to the traveling distance of the clip. No. 1 At the start of oblique stretching, both the left and right clip pitches are P ₁ . P ₁ is typically a clip pitch when the film is gripped. Simultaneously with the start of the first oblique stretching, the increase in the clip pitch of one clip (hereinafter sometimes referred to as a first clip) is started, and the other clip (hereinafter sometimes referred to as a second clip) Initiates a decrease in clip pitch. In the first oblique stretching, the clip pitch of the first clip is set to P ₂ increase, and the clip pitch of the second clip up to P ₃ Decrease. Therefore, at the end of the first oblique stretch (start of the second oblique stretch), the second clip moves at the clip pitch P ₃ and the first clip moves at the clip pitch P ₂ . Further, the ratio of the clip pitches may correspond substantially to the ratio of the moving speeds of the clips.

In FIGS. 4A and 4B, the timing at which the clip pitch of the first clip starts to increase and the timing at which the clip pitch of the second clip starts to decrease are both taken as the start of the first oblique stretch, but different from the illustrated example. , You may start decreasing the clip pitch of the second clip after starting to increase the clip pitch of the first clip, or you may start increasing the clip pitch of the first clip after starting to decrease the clip pitch of the second clip. . In one preferred embodiment, after starting to increase the clip pitch of the first clip, start decreasing the clip pitch of the second clip. According to this embodiment, since the film is already stretched to a certain extent in the width direction (preferably, about 1.2 to 2.0 times), wrinkles are unlikely to occur even if the clip pitch of the second clip is greatly reduced. Therefore, oblique stretching at a more acute angle becomes possible, and a retardation film having high uniaxial property and high in-plane orientation can be suitably obtained.

Similarly, in FIGS. 4A and 4B, the clip pitch of the first clip continues to increase and the clip pitch of the second clip continues to decrease until the end of the first oblique stretch (the start of the second oblique stretch). Unlike , either of the increase or decrease of the clip pitch ends earlier than the other, and the clip pitch may be maintained as it is until the other ends (until the end of the first oblique stretch).

The rate of change of the clip pitch of the first clip (P ₂ /P ₁ ) is preferably 1.25 to 1.75, more preferably 1.30 to 1.70, still more preferably 1.35 to 1.65. The rate of change of the clip pitch of the second clip (P ₃ /P ₁ ) is, for example, 0.50 or more and less than 1, preferably 0.50 to 0.95, more preferably 0.55 to 0.90, still more preferably 0.55 to 0.85. When the rate of change of the clip pitch is within this range, a slow axis can be developed with high uniaxiality and in-plane orientation in a direction of approximately 45 degrees with respect to the longitudinal direction of the film.

As described above, the clip pitch can be adjusted by positioning the slider by adjusting the separation distance between the pitch setting rail of the stretching device and the reference rail.

The draw ratio in the width direction of the film in the first oblique stretch (film width at the end of the first oblique stretch/film width before the first oblique stretch) is preferably 1.1 to 3.0 times, more preferably 1.2 to 1.2 times. 2.5 times, more preferably 1.25 times to 2.0 times. When the draw ratio is less than 1.1 times, tin-like wrinkles may be formed at the end portion on the contracted side. Moreover, when the said draw ratio exceeds 3.0 times, the biaxiality of the retardation film obtained will become high, and when applied to a circular polarizing plate etc., the viewing angle characteristic may fall.

In one embodiment, in the first oblique stretching, the product of the rate of change of the clip pitch of the first clip and the rate of change of the clip pitch of the second clip is preferably 0.7 to 1.5, more preferably 0.8 to 1.45, still more preferably. It is performed so that it is 0.85 to 1.40. When the product of change rates is within this range, a retardation film having high uniaxiality and high in-plane orientation can be obtained.

Next, one Embodiment of 2nd diagonal stretch is concretely demonstrated, referring FIG. 4A. In the second oblique stretching of the present embodiment, the clip pitch of the second clip is set at P ₃ up to _P2 increase On the other hand, the clip pitch of the first clip remains P ₂ during the second oblique stretching. maintain. Therefore, at the end of the second oblique stretch, both the left and right clips move at the clip pitch P ₂ .

The change rate (P ₂ /P ₃ ) of the clip pitch of the second clip in the second oblique stretch in the embodiment shown in FIG. 4A is not limited as long as the effect of the present invention is not impaired. The rate of change (P ₂ /P ₃ ) is, for example, 1.3 to 4.0, preferably 1.5 to 3.0.

Another embodiment of the second oblique stretch will be specifically described with reference to Fig. 4B. In the second oblique stretching of the present embodiment, while reducing the clip pitch of the first clip, the clip pitch of the second clip is increased. Specifically, the clip pitch of the first clip is set at P ₂ Decrease to P ₄ , and increase the clip pitch of the second clip from P ₃ to P ₄ . Therefore, the second At the end of oblique stretching, both the left and right clips move at the clip pitch P ₄ . In the illustrated example, the reduction of the clip pitch of the first clip and the increase of the pitch of the second clip are disclosed simultaneously with the start of the second oblique stretch, but these may be started at different timings. Similarly, the reduction of the clip pitch of the first clip and the increase of the clip pitch of the second clip may end at different timings.

The rate of change of the clip pitch of the first clip (P ₄ /P ₂ ) and the rate of change of the clip pitch of the second clip (P ₄ /P ₃ ) in the second oblique stretch of the embodiment shown in FIG. 4B are the effects of the present invention. There is no limit as long as it does not harm the The rate of change (P ₄ /P ₂ ) is, for example, 0.4 It is more than 1.0 and less than 1.0, Preferably it is 0.6-0.95. In addition, the rate of change (P ₄ /P ₃ ) is, for example, more than 1.0 and 2.0 or less, preferably 1.2 to 1.8. Preferably, P ₄ is greater than or equal to P ₁ . If P ₄ < P ₁ , problems such as wrinkles at the end and increased biaxiality may occur.

The draw ratio in the width direction of the film in the second oblique stretch (film width at the end of the second oblique stretch/film width at the end of the first oblique stretch) is preferably 1.1 times to 3.0 times, more preferably 1.2 times. times - 2.5 times, more preferably 1.25 times - 2.0 times. When the draw ratio is less than 1.1 times, tin-like wrinkles may be formed at the end portion on the contracted side. Moreover, when the said draw ratio exceeds 3.0 times, the biaxiality of the retardation film obtained will become high, and when applied to a circular polarizing plate etc., the viewing angle characteristic may fall. In addition, the draw ratio in the width direction in the first oblique stretch and the second oblique stretch (film width at the end of the second oblique stretch/film width before the first oblique stretch) is preferably 1.2 from the viewpoint similar to the above. times - 4.0 times, more preferably 1.4 times - 3.0 times.

The oblique stretch may be typically performed at a temperature T2. Regarding the glass transition temperature (Tg) of the film, the temperature T2 is preferably Tg-20°C to Tg+30°C, more preferably Tg-10°C to Tg+20°C, and particularly preferably about Tg. . Although different depending on the film used, the temperature T2 is, for example, 70°C to 180°C, preferably 80°C to 170°C. The difference (T1-T2) between the temperature T1 and the temperature T2 is preferably ±2°C or more, more preferably ±5°C or more. In one embodiment, T1 > T2, therefore, a film heated to temperature T1 in the preheating zone can be cooled to temperature T2.

As described above, transverse shrinkage treatment may be performed after oblique stretching. Regarding the treatment after oblique stretching, paragraphs 0029 to 0032 of Unexamined-Japanese-Patent No. 2014-194483 can be referred.

A-5. open process

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

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

A-6. Adjustment of clip temperature

The temperature of the clip when opening the film is, for example, 100°C to 140°C. After opening the film in the opening zone, the clip moves toward the gripping zone, and in the meantime is cooled to a set temperature by the clip temperature adjusting means, while the clip temperature monitoring means provided near the entrance of the film can grip the film. When the clip temperature is monitored.

The clip returns to the gripping zone and grips the film again at a clip temperature equal to or lower than the Tg of the film - 90°C. At that time, the clip temperature is monitored by a clip temperature monitoring means provided near the inlet of the film, and the desired temperature is controlled by the controller (i.e., the clip temperature described in A-2 and its fluctuations, e.g., 50 ° C. or less The output of the clip temperature adjusting means can be appropriately changed so that the clip temperature and the variation of the clip temperature within 6° C., preferably within 3° C.) are achieved. Specifically, the controller changes the output of the clip temperature adjusting means so that the actual measured value of the clip temperature obtained by monitoring approaches the set value.

B. Film to be stretched

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

As the polycarbonate-based resin, any suitable polycarbonate-based resin is used. For example, a polycarbonate-based resin containing a structural unit derived from a dihydroxy compound is preferred. As a specific example of a dihydroxy compound, 9,9-bis (4-hydroxyphenyl) fluorene, 9,9-bis (4-hydroxy-3-methylphenyl) fluorene, 9,9-bis (4-hydroxyl) Roxy-3-ethylphenyl)fluorene, 9,9-bis(4-hydroxy-3-n-propylphenyl)fluorene, 9,9-bis(4-hydroxy-3-isopropylphenyl)fluorene , 9,9-bis (4-hydroxy-3-n-butylphenyl) fluorene, 9,9-bis (4-hydroxy-3-sec-butylphenyl) fluorene, 9,9-bis (4 -Hydroxy-3-tert-butylphenyl)fluorene, 9,9-bis(4-hydroxy-3-cyclohexylphenyl)fluorene, 9,9-bis(4-hydroxy-3-phenylphenyl) Fluorene, 9,9-bis (4- (2-hydroxyethoxy) phenyl) fluorene, 9,9-bis (4- (2-hydroxyethoxy) -3-methylphenyl) fluorene, 9, 9-bis(4-(2-hydroxyethoxy)-3-isopropylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-isobutylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-tert-butylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-cyclohexylphenyl) Fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-phenylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3,5-dimethyl Phenyl) fluorene, 9,9-bis (4- (2-hydroxyethoxy) -3-tert-butyl-6-methylphenyl) fluorene, 9,9-bis (4- (3-hydroxy-2 , 2-dimethylpropoxy) phenyl) fluorene and the like. Polycarbonate resins, in addition to structural units derived from the above dihydroxy compounds, are isosorbide, isomannide, isoidet, spiroglycol, dioxane glycol, diethylene glycol (DEG), triethylene glycol (TEG), polyethylene Structural units derived from dihydroxy compounds such as glycol (PEG), cyclohexanedimethanol (CHDM), tricyclodecane dimethanol (TCDDM), and bisphenols may be included.

Details of the above polycarbonate-based resins are described in, for example, Japanese Unexamined Patent Publication No. 2012-67300 and Japanese Patent No. 3325560. Description of the said patent document is used as a reference in this specification.

The glass transition temperature of the polycarbonate-based resin is preferably 110°C or higher and 250°C or lower, more preferably 120°C or higher and 230°C or lower. If the glass transition temperature is excessively low, the heat resistance tends to deteriorate, and there is a possibility of causing dimensional change after forming the film. If the glass transition temperature is excessively high, the molding stability during film molding may deteriorate, and the transparency of the film may also be impaired. In addition, the glass transition temperature can be obtained according to JIS K 7121 (1987).

Any appropriate polyvinyl acetal-based resin can be used as the polyvinyl acetal-based resin. Typically, polyvinyl acetal-based resin can be obtained by subjecting at least two types of aldehyde compounds and/or ketone compounds to a condensation reaction of polyvinyl alcohol-based resin. The specific example and detailed manufacturing method of polyvinyl acetal-type resin are described, for example in Unexamined-Japanese-Patent No. 2007-161994. The description is incorporated herein by reference.

The cycloolefin-based resin is a generic term for resins polymerized using cycloolefin as a polymerized unit, and is described in, for example, Japanese Unexamined Patent Publication Nos. Resin described in 122137 etc. is mentioned. Specific examples include ring-opening (co)polymers of cycloolefins, addition polymers of cycloolefins, copolymers of cycloolefins and α-olefins such as ethylene and propylene (typically random copolymers), and unsaturated carboxylic acids and derivatives thereof and graft modified products modified with , and hydrides thereof. Specific examples of the cycloolefin include norbornene-based monomers.

Examples of the norbornene monomer include norbornene and alkyl and/or alkylidene substituents thereof such as 5-methyl-2-norbornene, 5-dimethyl-2-norbornene, 5-ethyl-2-norbornene, 5-butyl-2-norbornene, 5-ethylidene-2-norbornene, etc., these halogen-substituted polar groups; dicyclopentadiene, 2,3-dihydrodicyclopentadiene and the like; Dimethanooctahydronaphthalene, its alkyl and/or alkylidene substituents, and polar substituents such as halogen, such as 6-methyl-1,4:5,8-dimethano-1,4,4a,5,6 ,7,8,8a-octahydronaphthalene, 6-ethyl-1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene, 6-ethyl Iden-1,4:5,8-dimethano-1,4, 4a,5,6,7,8,8a-octahydronaphthalene, 6-chloro-1,4:5,8-dimethano- 1,4,4a,5,6,7,8,8a-octahydronaphthalene, 6-cyano-1,4:5,8-dimethano-1,4,4a,5,6,7,8 ,8a-octahydronaphthalene, 6-pyridyl-1,4:5,8-dimethano-1, 4,4a,5,6,7,8,8a-octahydronaphthalene, 6-methoxycarbonyl -1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene, etc.; Tri-tetramers of cyclopentadiene, such as 4,9:5,8-dimethano-3a,4,4a,5,8,8a,9,9a-octahydro-1H-benzoindene, 4, 11:5,10:6,9-trimethano-3a,4,4a,5,5a,6,9,9a,10,10a,11,11a-dodecahydro-1H-cyclopentaanthracene, etc. can

As said polyester-type resin, the polyester-type resin which contains polyester obtained by polycondensing dicarboxylic acid and diol as a main component is typically used.

Examples of the dicarboxylic acids constituting the polyester include phthalic acid, isophthalic acid, terephthalic acid, 5-sulfoisophthalic acid, 4,4'-diphenyl dicarboxylic acid, 4,4'-diphenyl ether dicarboxylic acid, and 4,4 aromatic dicarboxylic acids such as '-diphenyl ketone dicarboxylic acid, 4,4'-diphenoxyethane dicarboxylic acid, 4,4'-diphenylsulfone dicarboxylic acid, and 2,6-naphthalenedicarboxylic acid; alicyclic dicarboxylic acids such as 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, and 1,4-cyclohexanedicarboxylic acid; aliphatic dicarboxylic acids such as malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, and dodecanoic acid; unsaturated dicarboxylic acids such as maleic acid, maleic anhydride, and fumaric acid; Derivatives thereof (for example, lower alkyl esters of dicarboxylic acids such as terephthalic acid, etc.); and the like. These can be used individually by 1 type or in combination of 2 or more types. Especially, from viewpoints of heat resistance etc., aromatic dicarboxylic acid is preferable and terephthalic acid is more preferable. The proportion of terephthalic acid in the dicarboxylic acid constituting the polyester is preferably 50% by weight or more (for example, 80% by weight or more, typically 95% by weight or more), even if the dicarboxylic acid is substantially composed of only terephthalic acid. do.

Examples of the diol constituting the polyester include ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, 1,3-propanediol, 1,5-pentanediol, neopentyl glycol, and 1,4-propanediol. aliphatic diols such as butanediol, 1,6-hexanediol, 1,8-octanediol, and polyoxytetramethylene glycol; Alicyclic diols such as 1,2-cyclohexanediol, 1,4-cyclohexanediol, 1,1-cyclohexanedimethylol and 1,4-cyclohexanedimethylol, xylylene glycol, 4,4'-di aromatic diols such as hydroxybiphenyl, 2,2-bis(4'-hydroxyphenyl)propane, and bis(4-hydroxyphenyl)sulfone; etc. can be mentioned. These can be used individually by 1 type or in combination of 2 or more types. Among them, aliphatic diols are preferable from the viewpoint of suitably realizing desired physical properties (eg, probe drop stress, elongation at break, tensile strength, etc.), and 1,4-butanediol, 1,6-hexanediol, 1, 8-octanediol and polyoxytetramethylene glycol are more preferred, and 1,4-butanediol and polyoxytetramethylene glycol are particularly preferred. The proportion of the aliphatic diol (preferably 1,4-butanediol and/or polyoxytetramethylene glycol) in the diol constituting the polyester is 50% by weight or more (for example, 80% by weight or more, typically 95% by weight) above) is preferred, and the diol may be substantially constituted only of aliphatic diols (1,4-butanediol and/or polyoxytetramethylene glycol).

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

The in-plane retardation Re (550) of the retardation film can be set to a desired range by appropriately setting the oblique stretching conditions. For example, a method for producing a retardation film having an in-plane retardation Re (550) of 100 nm to 180 nm by oblique stretching is disclosed in Japanese Unexamined Patent Publication No. 2013-54338, Japanese Unexamined Patent Publication No. 2014-194482, Japanese Unexamined Patent Publication Patent Publication No. 2014-238524, Japanese Unexamined Patent Publication No. 2014-194484 and the like are disclosed in detail. Therefore, those skilled in the art can set appropriate oblique stretching conditions based on the said disclosure.

When a circular polarizing plate is manufactured using one sheet of retardation film, or when the direction of linearly polarized light is rotated by 90° using one sheet of retardation film, the direction of the slow axis of the retardation film used is the length of the film. With respect to the direction, preferably 30 ° to 60 ° or 120 ° to 150 °, more preferably 38 ° to 52 ° or 128 ° to 142 °, more preferably 43 ° to 47 ° or 133 ° to 137 °, Particularly preferably, it is about 45° or 135°.

In the case of producing a circular polarizing plate using two retardation films (specifically, a λ/2 plate and a λ/4 plate), the direction of the slow axis of the retardation film (λ/2 plate) used is It is preferably about 60° to 90°, more preferably about 65° to 85°, and particularly preferably about 75° with respect to the elongated direction of . Further, the direction of the slow axis of the retardation film (λ/4 plate) is preferably 0° to 30°, more preferably 5° to 25°, and particularly preferably about 15° with respect to the long direction of the film. .

The retardation film preferably exhibits so-called reverse dispersion wavelength dependence. Specifically, the in-plane phase difference satisfies the relationship of Re(450)<Re(550)<Re(650). Re(450)/Re(550) is preferably 0.8 or more and less than 1.0, more preferably 0.8 to 0.95. Re(550)/Re(650) is preferably 0.8 or more and less than 1.0, more preferably 0.8 to 0.97.

The retardation film has an absolute value of its photoelastic coefficient, preferably 2 × 10 ^-12 (m 2 /N) to 100 × 10 ^-12 (m 2 /N), more preferably 5 × 10 ^-12 (m 2 /N) to 50 × 10 ^-12 (m 2 /N).

C. Optical laminates and methods of manufacturing the optical laminates

The stretched film obtained by the production method of the present invention can be bonded together with other optical films to be used as an optical laminate. For example, the retardation film obtained by the manufacturing method of the present invention can be bonded to a polarizing plate and suitably used as a circular polarizing plate.

5 is a schematic cross-sectional view of an example of such a circular polarizing plate. The illustrated circular polarizing plate 500 includes a polarizer 510, a first protective film 520 disposed on one side of the polarizer 510, a second protective film 530 disposed on the other side of the polarizer 510, A retardation film 540 disposed outside the second protective film 530 is included. The retardation film 540 is a stretched film (eg, λ/4 plate) obtained by the manufacturing method described in section A. The second protective film 530 may be omitted. In that case, the retardation film 540 may function as a protective film for the polarizer. The angle between the absorption axis of the polarizer 510 and the slow axis of the retardation film 540 is preferably 30° to 60°, more preferably 38° to 52°, still more preferably 43° to 47°, Particularly preferably, it is about 45°.

The retardation film obtained by the production method of the present invention is long and has a slow axis in an oblique direction (for example, a direction of 45° with respect to the long direction). In many cases, a long picture-like polarizer has an absorption axis in the direction of a long picture or in the width direction. Therefore, if the retardation film obtained by the production method of the present invention is used, so-called roll-to-roll can be used, and a circular polarizing plate can be produced with extremely excellent production efficiency. In addition, roll-to-roll refers to the method of continuously bonding the elongated films together while the elongated films are conveyed by roll.

In one embodiment, the manufacturing method of the optical laminated body of this invention obtains a long stretched film by the manufacturing method of the stretched film of item A, and conveying the long optical film and this long stretched film, , including continuously bonding together in the direction of the long picture.

[Example]

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited by these examples. In addition, the measurement and evaluation methods in Examples are as follows.

(1) Thickness

It was measured using a dial gauge (manufactured by PEACOCK, product name 'DG-205 type pds-2').

(2) Phase difference value

The in-plane retardation Re(550) at a wavelength of 550 nm was measured using a retardometer (manufactured by Oji Instruments, KOBRA series). In the case of in-line measurement, measurements were performed at intervals of 0.5 seconds using an in-line retardation meter.

(3) Orientation angle (direction of development of slow axis)

The orientation angle (θ) was measured at a wavelength of 550 nm using a retardometer (manufactured by Oji Instruments, KOBRA series). In the case of in-line measurement, measurements were performed at intervals of 0.5 seconds using an in-line retardation meter.

(4) Glass transition temperature (Tg)

It was measured according to JIS K 7121.

<Example 1>

(Production of polyester carbonate resin film)

Polymerization was carried out using a batch polymerization apparatus including two vertical reactors equipped with stirring blades and a reflux condenser controlled at 100°C. Bis [9- (2-phenoxycarbonylethyl) fluoren-9-yl] methane 29.60 parts by mass (0.046 mol), ISB 29.21 parts by mass (0.200 mol), SPG 42.28 parts by mass (0.139 mol), DPC 63.77 parts by mass part (0.298 mol) and 1.19 × 10 ^-2 mass parts (6.78 × 10 ^-5 mol) of calcium acetate monohydrate as a catalyst. After replacing the inside of the reactor with reduced pressure nitrogen, heating was performed with a heating medium, and stirring was started when the internal temperature reached 100°C. The internal temperature reached 220°C 40 minutes after the start of the temperature rise, and while controlling to maintain this temperature, the pressure reduction was started, and after reaching 220°C, it was set to 13.3 kPa in 90 minutes. Phenol vapor produced as a by-product of the polymerization reaction was directed to a reflux condenser at 100°C, a small amount of monomer components contained in the phenol vapor was returned to the reactor, and uncondensed phenol vapor was directed to a condenser at 45°C for recovery. After nitrogen was introduced into the first reactor to once restore the pressure to atmospheric pressure, the oligomerized reaction solution in the first reactor was transferred to the second reactor. Then, the temperature increase and pressure reduction in the 2nd reactor were started, and it set the internal temperature to 240 degreeC and the pressure to 0.2 kPa in 50 minutes. Thereafter, polymerization was allowed to proceed until a predetermined agitation power was reached. When the predetermined power was reached, nitrogen was introduced into the reactor to restore pressure, and the resulting polyester carbonate was extruded into water, and the strands were cut to obtain pellets. Tg of the obtained polyester carbonate resin was 140 degreeC.

After vacuum drying the obtained polyester carbonate resin at 80 ° C. for 5 hours, a single screw extruder (manufactured by Toshiba Machinery Co., Ltd., cylinder set temperature: 250 ° C.), T die (width 1500 mm, set temperature: 250 ° C.), chilled roll ( A resin film having a thickness of 135 μm was produced using a film forming apparatus equipped with set temperature: 120 to 130° C.) and a winding machine.

(Production of stretched film)

For the polyester carbonate resin film obtained as described above, a film stretching device as shown in FIG. 1, specifically, a thermograph for monitoring the temperature of the left and right clips is provided at the entrance of the film, and the left and right endless rails On the way from the open zone to the gripping zone, a film having a cooling fan that blows cooling air at a predetermined temperature into the clip according to a setting or input, and a controller that changes the output of the cooling fan based on the set temperature of the clip temperature and the monitoring result. It was obliquely stretched using a stretching device to obtain a retardation film.

Specifically, at the entrance of the film of the stretching device, the right and left ends of the polyester carbonate resin film were held at the same timing and the same clip pitch with the right and left clips. Connecting the center of the left and right clips when holding the film The line was orthogonal to the transport direction of the film, and the clip pitch P ₁ of the left and right clips was 125 mm.

Then, the film was transferred to the preheating zone (B) and preheated to 145°C. In the preheating zone B, the distance and clip pitch between the left and right clips during gripping were maintained.

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

Then, in the open zone (D), heat setting was performed by holding the film at 125°C for 60 seconds. After cooling the heat-set film to 100°C, the left and right clips were opened. The clip temperature when the film was opened was 100°C.

In the production of the stretched film, the temperature of the clip at the time of gripping the film is set to 30°C, a cooling fan is operated, and the result of monitoring the temperature of the clip immediately before gripping the film by thermography (measured temperature) and the set temperature Based on this, the output of the cooling fan was adjusted by the controller so that the measured temperature approached the set temperature. In addition, the temperature of the room where the stretching device was placed was about 23°C.

As will be described later, the effective width of the film released from the clip is specified, and within the effective width, the orientation angle (relative to the elongated direction) is determined at a total of three locations within 25 mm from the center and left and right ends in the width direction of the film. angle) was measured. Table 1 shows the measurement results of the orientation angle after 60 minutes from the start of production. In the table|surface, the deviation of an orientation angle shows the difference of the maximum value and minimum value of the orientation angle measured at three places. In addition, Re (550) measured at the center in the width direction was 145 nm.

<Example 2>

A stretched film was obtained in the same manner as in Example 1 except that the temperature of the clip when holding the film was set to 40°C. About the obtained stretched film, the orientation angle was measured at all three places in the width direction similar to Example 1. Table 1 shows the measurement results of the orientation angle after 60 minutes from the start of production. In addition, Re (550) measured at the center in the width direction was 145 nm.

<Example 3>

A stretched film was obtained in the same manner as in Example 1 except that the temperature of the clip when holding the film was set to 20°C. About the obtained stretched film, the orientation angle was measured at all three places in the width direction similar to Example 1. Table 1 shows the measurement results of the orientation angle after 60 minutes from the start of production. In addition, Re (550) measured at the center in the width direction was 145 nm.

<Example 4>

The temperature of the clip when gripping the film is set to 45°C (the temperature of the cooling air is set to 45°C by adjusting the output of the cooling fan), and the feedback control of the clip temperature based on the set temperature and the monitoring result is not performed. A stretched film was obtained in the same manner as in Example 1 except that it was not (as a result, the cooling fan kept blowing 45°C cooling wind to the clip). About the obtained stretched film, the orientation angle was measured at all three places in the width direction similar to Example 1. Table 1 shows the measurement results of the orientation angle after 60 minutes from the start of production. In addition, Re (550) measured at the center in the width direction was 145 nm.

<Comparative Example 1>

A stretched film was obtained in the same manner as in Example 1 except that the clip was not cooled by the clip temperature adjusting means. About the obtained stretched film, the orientation angle was measured at all three places in the width direction similar to Example 1. Table 1 shows the measurement results of the orientation angle after 60 minutes from the start of production. In addition, Re (550) measured at the center in the width direction was 145 nm.

[effective width]

The orientation angles were measured at a plurality of locations in the width direction of the stretched film, and the effective width was defined as a width in which the orientation angle deviation was within 4°, and the ratio (%) of the effective width to the total width of the film was evaluated. The results are shown in Table 1.

[Evaluation of appearance and handling]

With regard to the stretched films obtained in Examples and Comparative Examples, the appearance and handleability were visually evaluated based on the following criteria. The results are shown in Table 1.

○: Wrinkles and sagging are not observed on the stretched film during roll conveyance

×: Wrinkles and/or slack are observed on the stretched film during roll conveyance

[Table 1]

As shown in Table 1, in the manufacture of a long obliquely stretched film, the uniformity of the orientation angle in the width direction is improved by controlling the temperature of the clip at the time of gripping the film to a predetermined temperature with high precision. , the effective width can be widened.

The method for producing a stretched film of the present invention is suitably used for producing a retardation film, and as a result can contribute to the production of image display devices such as liquid crystal displays (LCDs) and organic electroluminescent displays (OLEDs). there is.

10L: stepless loop
10R: stepless loop
20: clip
40: clip temperature monitoring means
50: clip temperature adjustment means
60: controller
100: stretching device
500: circular polarizer

Claims (8)

A holding zone, a preheating zone, a drawing zone and an opening zone are provided in this order from the inlet side of the film toward the exit side, and the endless reference rails on the left and right passing through these zones and the reference rails on the left and right A method for producing a stretched film using a film stretching device including a plurality of variable pitch left and right clips guided and circularly moved through the gripping zone, the preheating zone, the stretching zone, and the opening zone in this order. As,
Holding the left and right ends of the elongated film in the width direction with the left and right clips, respectively;
preheating the film;
obliquely stretching the film by moving the left and right clips while changing the clip pitch of at least one clip, and
Opening the film from the left and right clips,
While monitoring the temperature of the left and right clips when holding the film, from the open zone to the holding zone so that the temperature of the left and right clips when holding the film is equal to or less than Tg - 90°C of the film. The manufacturing method of the stretched film which adjusts the temperature of the said left and right clip on the way back. According to claim 1,
A method for producing a stretched film, wherein a range of temperature fluctuations of the left and right clips when gripping the film is adjusted to within 6°C. According to claim 1 or 2,
The manufacturing method of the stretched film whose temperature of the said left and right clips at the time of gripping the said film is 20 degreeC - 50 degreeC. According to any one of claims 1 to 3,
A method for producing a stretched film, wherein the temperature of the left and right clips is adjusted by blowing cooling air to the left and right clips on the way back from the open zone to the gripping zone. According to any one of claims 1 to 4,
The manufacturing method of the stretched film whose said film is a resin film containing at least 1 sort(s) chosen from polycarbonate type resin, cellulose ester type resin, polyester type resin, polyester carbonate type resin, and cycloolefin type resin. Obtaining a long stretched film by the manufacturing method according to any one of claims 1 to 5, and
The manufacturing method of the optical laminated body which includes matching the long picture direction and bonding continuously, conveying a long picture-like optical film and the said long picture-like stretched film. According to claim 6,
The optical film is a polarizing plate,
The method for producing an optical laminate wherein the stretched film is a λ/4 plate or a λ/2 plate. including a holding zone, a preheating zone, a drawing zone and an open zone in this order from the inlet side of the film toward the exit side;
Left and right reference rails of endless shape provided to pass through these zones, and a plurality of variables guided by the left and right reference rails and passing through the holding zone, the preheating zone, the drawing zone, and the opening zone in this order and moving in a circular motion. Pitched left and right clips, means for monitoring the temperature of the left and right clips before entering the gripping zone, and means for adjusting the temperature of the left and right clips while returning from the open zone to the gripping zone. , film stretching device.

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