JP6988013B1 - Method for manufacturing stretched film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce slack and / or wrinkles generated in a diagonally stretched film. SOLUTION: The left and right ends of a long film in the width direction are gripped by left and right clips, respectively, the left and right clips are traveled and moved to diagonally stretch the film, and then from the left and right clips. A method of making a stretched film, comprising opening and rolling the film, comprising passing the film through a tilted guide roll, wherein the tilted guide roll is: A method for producing a stretched film, wherein the stretched film is arranged so as to be inclined with respect to a horizontal plane so that the transport path length of the end portion on the loose side of the film is longer than the transport path length of the end portion on the non-slack side. [Selection diagram] Fig. 3

Description

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

In image display devices such as liquid crystal displays (LCDs) and organic electroluminescence display devices (OLEDs), circular polarizing plates are used for the purpose of improving display characteristics and preventing reflection. In a circular polarizing plate, typically, a polarizing element and a retardation film (typically a λ / 4 plate) form an angle of 45 ° between the absorption axis of the polarizing element and the slow axis of the retardation film. It is laminated in this way. Traditionally, retardation films are typically made by uniaxial or biaxial stretching in the longitudinal and / or lateral directions, so that the slow axis is often a long film. It appears in the horizontal direction (width direction) or vertical direction (long direction) of the original fabric. As a result, in order to produce a circularly polarizing plate, it was necessary to cut the retardation film at an angle of 45 ° with respect to the width direction or the length direction and bond them one by one.

Further, in order to secure the wide band of the circularly polarizing plate, two retardation films, a λ / 4 plate and a λ / 2 plate, may be laminated. In that case, the λ / 2 plates are laminated so as to form an angle of 75 ° with respect to the absorber absorption axis, and the λ / 4 plates are laminated so as to form an angle of 15 ° with respect to the absorber absorption axis. There is a need. Even in this case, when producing the circularly polarizing plate, it was necessary to cut the retardation film so as to form an angle of 15 ° and 75 ° with respect to the width direction or the length direction, and to bond them one by one. ..

In yet another embodiment, in order to prevent the light from the notebook PC from being reflected on the keyboard or the like, the direction of the linearly polarized light emitted from the polarizing plate is rotated by 90 ° on the visual side of the polarizing plate. A λ / 2 plate may be used. Even in this case, it was necessary to cut the retardation film at an angle of 45 ° with respect to the width direction or the length direction and bond the films one by one.

In order to solve such a problem, the left and right ends of the long film in the width direction are gripped by the left and right clips of the variable pitch type in which the clip pitch in the vertical direction changes, respectively, and at least the left and right clips are held. A technique has been proposed in which the slow axis of the retardation film is expressed in the diagonal direction by changing one of the clip pitches and stretching in the diagonal direction with respect to the long direction (hereinafter, also referred to as "diagonal stretching"). (For example, Patent Document 1). However, the diagonally stretched film obtained by such a technique may have slack or wrinkles.

Patent No. 4845619

The present invention has been made to solve the above problems, and a main object thereof is to reduce slack and / or wrinkles caused in a diagonally stretched film.

According to one aspect of the present invention, the left and right ends of the elongated film in the width direction are gripped by the left and right clips, respectively, and the left and right clips are moved to run and the film is stretched diagonally, and then the film is stretched diagonally. A method for producing a stretched film, comprising releasing from the left and right clips and rolling the film, the roll transport comprising passing an inclined guide roll through the film. The stretched film is arranged so as to be inclined with respect to the horizontal plane so that the transport path length of the end of the film on the loose side is longer than the transport path length of the end of the film on the non-slack side. Manufacturing method is provided.
In one embodiment, the film passes through the tilted guide roll within 120 seconds after being released from the clip.
In one embodiment, roll transport comprises passing a guide roll X and a guide roll Y provided in this order on the film continuously toward the downstream in the transport direction, and the guide roll Y is the guide roll Y. It is arranged below the roll X, and the guide roll X is the inclined guide roll, and is inclined so that the end portion of the film on the non-sagging side is located 2 mm to 80 mm below the end portion on the loosening side. Is arranged.
In one embodiment, the roll transport comprises passing a guide roll X and a guide roll Y provided in this order continuously through the film toward the downstream in the transport direction, and the guide roll Y is the guide roll Y. It is arranged above the guide roll X, and the guide roll X is the inclined guide roll, and is inclined so that the end portion of the film on the non-sagging side is located 2 mm to 80 mm above the end portion on the loosening side. And are arranged.
In one embodiment, the transport path lengths of the left and right ends of the film from the opening point of the clip to the inclined guide roll are the same.
In one embodiment, the tilted guide rolls are arranged so that their rotation axis directions are substantially orthogonal to the transport direction of the film.
In one embodiment, the clip is a variable pitch type clip in which the clip pitch in the vertical direction changes, and the clip pitch of at least one of the clip that grips the left end portion of the film and the clip that grips the right end portion. The film is stretched in an oblique direction by traveling and moving while changing the above.
In one embodiment, the film is tilted in an oblique direction by changing the transport direction of the film in the middle while moving the clip that grips the left end portion of the film and the clip that grips the right end portion at a constant speed. Stretch.
According to another aspect of the present invention, the elongated stretched film is obtained by the above-mentioned manufacturing method, and the elongated optical film and the elongated stretched film are conveyed in the elongated direction thereof. A method for manufacturing an optical laminate is provided, which comprises aligning and continuously laminating the two.
In one embodiment, the optical film is a polarizing plate and the stretched film is a λ / 4 plate or a λ / 2 plate.

In the method for producing a stretched film of the present invention, when the diagonally stretched film is transported by a roll, a guide roll arranged at an angle with respect to a horizontal plane is passed through the roll. As a result, as a result of adjusting the transport path length (path length) at the left and right ends in the width direction of the film, a long diagonally stretched film with reduced slack and / or wrinkles can be obtained.

It is a schematic plan view explaining the whole structure of the example of the stretching apparatus which can be used in the manufacturing method of the stretched film of this invention. It is a schematic plan view explaining the whole structure of another example of the stretching apparatus which can be used in the manufacturing method of the stretched film of this invention. (A) and (b) are schematic plan views and schematic side views explaining an example of roll transport, respectively. (A) is a schematic diagram for explaining the arrangement of the guide rolls in the conventional roll transport, and (b) explains the inclination of the inclined guide rolls when viewed from the arrow III side shown in FIG. 2 (b). It is a schematic diagram. It is a schematic side view explaining another example of a roll transfer. It is a schematic diagram explaining the holding angle between a film and an inclined guide roll. It is the schematic sectional drawing of the circular polarizing plate using the retardation film obtained by the manufacturing method of this invention. It is a schematic diagram explaining the method of measuring a slack amount.

Hereinafter, preferred embodiments of the present invention will be described, but the present invention is not limited to these embodiments. In addition, in this specification, "the clip pitch in the vertical direction" means the distance between the centers in the traveling direction of the clip adjacent in the vertical direction. Further, the left-right relationship in the width direction of the long film means the left-right relationship in the transport direction of the film unless otherwise specified.

A. Method for manufacturing stretched film In the method for manufacturing stretched film according to the embodiment of the present invention, the left and right ends of the long film in the width direction are gripped by the left and right clips, respectively, and the left and right clips are moved by running. The film includes obliquely stretching and then releasing from the left and right clips and rolling the film, the roll transport comprising passing the film through an inclined guide roll. The inclined guide roll is arranged so as to be inclined with respect to the horizontal plane so that the transport path length of the end portion of the film on the loose side is longer than the transport path length of the end portion on the non-slack side. Typically, the method for producing a stretched film according to the embodiment of the present invention further includes a preheating step. Specifically, the film gripped by the left and right clips is preheated and then subjected to diagonal stretching.

As a method of diagonally stretching the film by the traveling movement of the left and right clips, any arbitrary method capable of stretching the left and right ends of the film at different stretching ratios (as a result, stretching in the diagonal direction with respect to the elongated direction). Appropriate methods can be used. For example, a method in which a clip for gripping the left end of a film and a clip for gripping the right end are moved and diagonally stretched at different speeds, and a clip for gripping the left end of the film and a clip for gripping the right end of the film are used for each other. Examples thereof include a method of traveling a different distance and stretching diagonally. In one embodiment of the former diagonal stretching, at least one of a left clip for gripping the left end of the film and a right clip for gripping the right end is used with a variable pitch type clip in which the clip pitch in the vertical direction changes. By moving the clip while changing the clip pitch, the film can be stretched in an oblique direction. In one embodiment of the latter diagonal stretching, the film transport direction is changed in the middle while the left clip that grips the left end portion of the film and the right clip that grips the right end portion are moved at a constant speed (result). As a result, the film can be stretched in an oblique direction (by making the transport path lengths of the left and right ends different). In the stretched film obtained by the diagonal stretching, the stretching processes (stretching or shrinking timing, number of times, order, thermal history, etc.) of the left and right ends of the film are different from each other at the time of diagonal stretching, and as a result, the residual stress after opening the clip. Since the amount of deformation at both ends is non-uniform due to the above, slack may occur at either end. In one embodiment, in the diagonally stretched film, the side having a small draw ratio at the time of diagonal stretch may be the slack side. The diagonally stretched film is preferably a λ / 4 plate or a λ / 2 plate.

FIG. 1A is a schematic plan view illustrating an overall configuration of an example of a stretching device that can be used for the former diagonal stretching. The stretching device 100a has an endless loop 10L having a large number of clips 20 for gripping the film and an endless loop 10R symmetrically on the left and right sides in a plan view. In the present specification, the endless loop on the left side when viewed from the inlet side of the film is referred to as the endless loop 10L on the left side, and the endless loop on the right side is referred to as the endless loop 10R on the right side. The clips 20 of the left and right endless loops 10L and 10R are guided by the reference rail 30 and circulate in a loop shape, respectively. The clip 20 of the endless loop 10L on the left side circulates in the counterclockwise direction, and the clip 20 of the endless loop 10R on the right side circulates in the clockwise direction. In the stretching device, a gripping 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, diagonally stretched, and opened, and does not mean a mechanically or structurally independent section. Also note that the length ratio of each zone in the stretching device of FIG. 1A differs from the actual length ratio.

Although not shown in FIG. 1A, a zone may be provided between the stretch zone C and the open zone D to perform any appropriate treatment, if necessary. Examples of such treatment include lateral shrinkage treatment and the like. Similarly, although not shown, the stretching device is typically a heating device (for example, a hot air type or a near infrared type) for setting each zone from the preheating zone B to the open zone D as a heating environment. , Various ovens such as far-infrared type). In one embodiment, preheating, diagonal stretching and opening from the clip can each be done in an oven set to a predetermined temperature.

In the gripping zone A and the preheating zone B of the stretching device 100a, the left and right endless loops 10L and 10R are configured to be substantially parallel to each other at a separation distance corresponding to the initial width of the film to be stretched. In the stretched zone C, the distance between the left and right endless loops 10L and 10R gradually increases from the preheating zone B side toward the open zone D until the distance between the left and right endless loops 10L and 10R corresponds to the stretched width of the film. In the open zone D, the left and right endless loops 10L and 10R are configured to be substantially parallel to each other at a separation distance corresponding to the stretched width of the film. However, the configuration of the left and right endless loops 10L and 10R is not limited to the above illustrated example. For example, the left and right endless loops 10L and 10R may be configured to be substantially parallel to each other at a separation distance corresponding to the initial width of the film to be stretched from the grip zone A to the open zone D.

The clip (clip on the left side) 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 be cyclically moved independently. For example, the drive sprockets 11 and 12 of the endless loop 10L on the left side are rotationally driven in the counterclockwise direction by the electric motors 13 and 14, and the drive sprockets 11 and 12 of the endless loop 10R on the right side are clocked by the electric motors 13 and 14. It is driven to rotate in the clockwise direction. As a result, a running force is applied to the clip-supporting member (not shown) of the drive roller (not shown) engaged with the drive sprockets 11 and 12. As a result, the endless loop 10L on the left side circulates in the counterclockwise direction, and the endless loop 10R on the right side circulates in the clockwise direction. By driving the electric motor on the left side and the electric motor on the right side independently, the endless loop 10L on the left side and the endless loop 10R on the right side can be patrolled independently.

Further, the clip (clip on the left side) 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 are each of a variable pitch type. That is, the left and right clips 20 and 20 can independently change the clip pitch in the vertical direction with movement. The variable pitch type configuration can be realized by adopting a drive system such as a pantograph system, a linear motor system, or a motor chain system. For example, Patent Document 1, Japanese Patent Application Laid-Open No. 2008-44339 and the like describe in detail a tenter type simultaneous biaxial stretching device using a pantograph type link mechanism.

FIG. 1B is a schematic plan view illustrating an overall configuration of an example of a stretching device that can be used for the latter diagonal stretching. The stretching device 100b has a loop-shaped endless loop 10L and an endless loop 10R having a large number of clips 20 for gripping the film on both the left and right sides in a plan view. The clips 20 of the left and right endless loops 10L and 10R are guided by the reference rail 40 and circulate in a loop shape, respectively (in the illustrated example, a part of the endless loops 10L and 10R is omitted). The clip 20 of the endless loop 10L on the left side circulates in the counterclockwise direction, and the clip 20 of the endless loop 10R on the right side circulates in the clockwise direction. In the stretching device, a gripping 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 seat. Each of these zones means a zone in which the film to be stretched is substantially gripped, preheated, diagonally stretched, and opened, and does not mean a mechanically or structurally independent section. Also note that the length ratio of each zone in the stretching device of FIG. 1B is different from the actual length ratio.

Although not shown in FIG. 1B, a zone may be provided between the stretch zone C and the open zone D to perform any appropriate treatment, if necessary. Examples of such a treatment include a transverse shrinkage treatment such as a transverse stretching treatment. Similarly, although not shown, the stretching device is typically a heating device (for example, a hot air type or a near infrared type) for setting each zone from the preheating zone B to the open zone D as a heating environment. , Various ovens such as far-infrared type). In one embodiment, preheating, diagonal stretching and opening from the clip can each be done in an oven set to a predetermined temperature.

In the gripping zone A and the preheating zone B of the stretching device 100b, the left and right endless loops 10L and 10R are configured to be substantially parallel to each other at a separation distance corresponding to the initial width of the film to be stretched. In the stretch zone C, the left endless loop 10L and the right endless loop 10R extend in asymmetrical directions, whereby the film transport direction changes and the film is directed from the preheating zone B side toward the open zone D. Therefore, the distance between the left and right endless loops 10L and 10R is gradually expanded until it corresponds to the width of the film after stretching. In the open zone D, the left and right endless loops 10L and 10R are configured to be substantially parallel to each other at a separation distance corresponding to the stretched width of the film. However, the configuration of the left and right endless loops 10L and 10R is not limited to the above illustrated example.

The clip (clip on the left side) 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 be cyclically moved independently. For example, similarly to the stretching device shown in FIG. 1A, the drive sprocket 11 of the endless loop 10L on the left side is rotationally driven in the counterclockwise direction by the electric motor 13, and the drive sprocket 11 of the endless loop 10R on the right side is driven by the electric motor 13. Is driven to rotate clockwise. Typically, the clip 20 on the left side and the clip 20 on the right side travel at a constant speed, and the clip pitch in the vertical direction can be kept constant. When the difference between the traveling speeds of the pair of left and right clips is 1% or less, it can be said that the traveling speeds of the two are constant, and the difference between the traveling speeds is preferably 0.5% or less. It is preferably 0.1% or less.

By diagonally stretching the film using the stretching device as described above, a diagonally stretched film, for example, a retardation film having a slow phase axis in the diagonal direction can be produced. Hereinafter, each step of the method for producing the stretched film will be described in detail.

A-1. Clipping the film with clips In the gripping zone A (the entrance of the film capture of the stretching device 100a or 100b), the clips 20 of the left and right endless loops 10L and 10R allow both ends of the film to be stretched to have a constant clip pitch equal to each other. , Or they are gripped at different clip pitches. The film is fed to the preheating zone B by the movement of the clips 20 of the left and right endless loops 10L and 10R (substantially, the movement of each clip-carrying member guided by the reference rail).

A-2. Preheating In the preheating zone B, the left and right endless loops 10L and 10R are basically configured to be substantially parallel to each other at a separation distance corresponding to the initial width of the film to be stretched as described above. The film is heated without stretching or longitudinal stretching. 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 the film bending due to preheating and contact with the nozzle in the oven.

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

The temperature raising time up to the temperature T1 and the holding time at the temperature T1 can be appropriately set according to the constituent materials of the film and the manufacturing conditions (for example, the transport speed of the film). These temperature rise time and holding time can be controlled by adjusting the moving speed of the clip 20, the length of the preheating zone, the temperature of the preheating zone, and the like.

A-3. Diagonal stretching A-3-1. Diagonal stretching using variable pitch type clips In the stretching zone C of the stretching device 100a, the left and right clips 20 are moved in a traveling manner while changing the clip pitch in at least one of them in the vertical direction to diagonally stretch the film. More specifically, by increasing or decreasing the clip pitch of the left and right clips at different positions, changing (increasing and / or reducing) the clip pitch of the left and right clips at different speeds of change, and the like. Stretch the film diagonally. As a result of running and moving the left and right clips while changing the clip pitch in this way, one of the pair of left and right clips simultaneously transferred to the stretching zone reaches the end of the stretching zone prior to the other clip. .. According to such diagonal stretching, the leading end of the clip side is stretched at a higher stretching ratio than the trailing end of the clip side, and as a result, the desired direction of the long film is obtained. The slow axis can be expressed (for example, in the direction of 45 ° with respect to the longitudinal direction).

Diagonal stretching may include transverse stretching. In this case, the diagonal stretching can be performed while increasing the distance between the left and right clips (distance in the width direction), for example, as shown in FIG. 1A. Alternatively, unlike the configuration shown in FIG. 1A, it can be performed while maintaining the distance between the left and right clips.

When the oblique stretching includes lateral stretching, the ratio of the lateral (TD) stretching ratio (the ratio _{of the width W final} of the film after diagonal stretching to _{the initial width W initial of the film (W final} / W _initial ) is preferably 1.05. It is ~ 6.00, more preferably 1.10 to 5.00.

In one embodiment, the oblique stretching differs in the vertical direction from 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. This can be done by increasing or decreasing the clip pitch of each clip to a predetermined pitch while in position. For the diagonal stretching of the embodiment, for example, the description of Patent Document 1, Japanese Patent Application Laid-Open No. 2014-238524, etc. can be referred to.

In another embodiment, oblique stretching increases or decreases the clip pitch of the other clip to a predetermined pitch while keeping the clip pitch of one of the left and right clips fixed, and then increases or decreases the original clip pitch. Can be done by returning to. For the diagonal stretching of the embodiment, for example, the description of JP-A-2013-54338, JP-A-2014-194482, etc. can be referred to.

In yet another embodiment, oblique stretching (i) increases the clip pitch of one of the left and right clips while decreasing the clip pitch of the other clip, and (ii) the decrease. This can be done by changing the clip pitch of each clip so that the clip pitch and the increased clip pitch have a predetermined equal pitch. For the diagonal stretching of the embodiment, for example, the description in JP-A-2014-194484 can be referred to. In the oblique stretching of the embodiment, the film is stretched diagonally by increasing the clip pitch of one clip and decreasing the clip pitch of the other clip while increasing the distance between the left and right clips (the first). 1), and while increasing the distance between the left and right clips, the clip pitch of one clip is maintained or reduced so that the clip pitches of the left and right clips are equal, and the clip pitch of the other clip is maintained or reduced. Increasing the clip pitch of the clip may include diagonally stretching the film (second diagonal stretching step).

In the first diagonal stretching step, one end of the film is stretched in the elongated direction and the other end is contracted in the elongated direction while the film is stretched diagonally in a desired direction (for example,). It is possible to develop a slow axis with high uniaxiality and in-plane orientation (in the direction of 45 ° with respect to the longitudinal direction). Further, in the second diagonal stretching step, by performing diagonal stretching while reducing the difference between the left and right clip pitches, it is possible to sufficiently stretch in the diagonal direction while alleviating excess stress.

In the diagonal stretching of the above three embodiments, the film can be released from the clips in a state where the moving speeds of the left and right clips are equal, so that the film transport speed and the like are less likely to vary when the left and right clips are opened. Subsequent winding of the film can be preferably performed.

A-3-2. Diagonal stretching using a clip with a constant pitch In the stretching zone C of the stretching device 100b, the left endless loop 10L and the right endless loop 10R are stretched in asymmetric directions, so that the film transport direction changes. (Specifically, the transport direction of the film in the preheating zone B (the direction in which the arrow B extends) and the transport direction of the film in the release zone D (the direction in which the arrow D extends) are non-parallel). There is. Due to such a configuration, the lengths of the left and right endless loops 10L and R in the diagonally stretched zone C (in other words, the mileage of the left and right clips in the diagonally stretched zone C) are different. As a result, for the pair of left and right clips that travel at a constant speed, the clip with the shorter mileage travels in advance (in FIG. 1B, the clip on the left travels in advance), and the film runs diagonally. It is stretched. For the diagonal stretching of the embodiment, for example, the description of JP-A-2004-226686, WO2007 / 111313 and the like can be referred to.

Diagonal stretching can typically be done at temperature T2. 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, with respect to the glass transition temperature (Tg) of the film. Although it depends 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 higher, more preferably ± 5 ° C. or higher. In one embodiment, T1> T2, so the film heated to temperature T1 in the preheating zone can be cooled to temperature T2.

As described above, lateral shrinkage treatment may be performed after diagonal stretching. For the treatment after the diagonal stretching, paragraphs 0029 to 0032 of JP-A-2014-194483 can be referred to.

A-4. Clip Opening The film is released from the clip at any position in the open zone D. In the open zone D, neither lateral stretching nor longitudinal stretching is usually performed, and if necessary, the film is heat-treated to fix the stretched state (heat-fixed) and / or cooled to Tg or less, and then the film. Release from the clip. At the time of heat fixing, the clip pitch in the vertical direction may be reduced to relieve the stress.

The heat treatment can typically be performed at temperature T3. The temperature T3 depends on the film to be stretched, and may be T2 ≧ T3 or T2 <T3. Generally, when the film is an amorphous material, T2 ≧ T3, and when the film is a crystalline material, the crystallization treatment may be performed by setting T2 <T3. 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 5 seconds to 10 minutes.

In one embodiment, the open zone D is a heated environment. In this embodiment, the film is released from the clip in a heated environment and held in a heated environment until it passes through the end point of the open zone. If necessary, the clip may be released after the film is heat-treated to fix the stretched state (heat-fixed).

The atmospheric temperature when released from the clip and after that while the stretched film is held (for example, when the clip is released in the oven and thereafter until it is sent out from the oven outlet) is, for example, Tg. It is −20 ° C. to Tg ° C., preferably Tg −15 ° C. to Tg ° C., and more preferably Tg −10 ° C. to Tg-3 ° C. By keeping the film in a heated state at a predetermined atmospheric temperature after being released from the clip, it is possible to preferably reduce the slack by using the inclined roll thereafter.

After opening from the clip, the time for the stretched film to be held in the heating environment (for example, the time from opening the clip in the oven until it is sent out from the oven outlet) is preferably 1 second or longer, more preferably. It is preferably 2 seconds or longer, and more preferably 3 seconds or longer. The upper limit of the time is not particularly limited, but may be, for example, 15 seconds, preferably 10 seconds. By keeping the film in a heated state for a predetermined time or longer after being released from the clip, it is possible to preferably reduce the slack using the inclined roll thereafter.

A-5. Roll transport Roll transport is an angle θ1 with respect to the horizontal plane so that the transport path length of the loosened end of the film is longer than the transport path length of the non-slackened end of the film released from the clip. Includes passing through an inclined guide roll that is arranged to be inclined so as to form a. By passing through the inclined guide rolls arranged at an angle in this way, tension is applied to the slack side of the film and the film is flattened as a whole, so that a stretched film with reduced slack and / or wrinkles can be obtained. Can be. Further, the transport distance can be changed by tilting the guide roll in the horizontal plane, but according to the embodiment of the present invention, the rotation axis direction of the tilted guide roll is substantially orthogonal to the transport direction of the film. Since it can be used, it has an advantage of excellent transport stability. In the present specification, the guide roll is a rotatable roll arranged in contact with the film on the transport path of the film, and may or may not be provided with a drive mechanism. good. The guide roll may be in any form such as a suction roll or a nip roll. In the present specification, substantially orthogonality includes a range of 89.7 ° to 90.3 °, preferably a range of 89.9 ° to 90.1 °, and more preferably 90.0 °. ..

The inclined guide roll can be provided at any position of the roll transport as long as the effect of the present invention can be obtained. In one embodiment, the tilt roll is provided immediately after the outlet of the stretching device. By passing the film immediately after being released from the clip through the inclined guide roll, a slack and / or wrinkle reducing effect can be preferably obtained. Specifically, the time from when the film is released from the clip until it passes through the inclined guide roll is, for example, 120 seconds or less, preferably 5 seconds to 60 seconds.

The inclined guide roll may be arranged in a heated environment or may be arranged in a non-heated environment. Preferably, the inclined guide roll is arranged in a non-heated environment, and the roll transfer is performed in a non-heated environment. By arranging the inclined guide roll in a non-heated environment, the holding angle of the film described later can be easily realized, and slack and / or wrinkles can be reduced while preventing the occurrence of scratches. The atmospheric temperature in the non-heated environment can be, for example, about 15 ° C to 40 ° C, or for example, about 20 ° C to 30 ° C. The atmospheric temperature when arranged in the heating environment can be about the same as the atmospheric temperature in the open zone of the stretching device, and in this case, the inclined guide roll can be arranged in the open zone D.

In one embodiment, roll transport may be performed using a plurality of guide rolls, including tilted guide rolls. In roll transport, the total number of guide rolls through which the film passes (including tilted guide rolls) can be, for example, 1-12, preferably 2-10, more preferably 3-8. Typically, the guide rolls other than the inclined guide rolls are arranged so that the rotation axis direction is horizontal and the rotation axis direction and the film transport direction are substantially orthogonal to each other (hereinafter, inclined guide rolls). Guide rolls other than the above may be referred to as "horizontal guide rolls"). Preferably, in roll transport, the tilted guide roll is the first guide roll through which the film is first delivered from the stretching apparatus. Further, the guide roll arranged next to the inclined guide roll is arranged above or below the inclined guide roll. By arranging the inclined guide roll and the next guide roll at different heights, it is easy to make the transport path length between these two guide rolls different distances at the left and right ends of the film.

The roll transfer is preferably performed while applying tension to the film after being released from the clip. By applying tension to the entire film in addition to correcting slack using an inclined guide roll, slack and / or wrinkles can be reduced more effectively. The tension applied to the film is, for example, 100 N / m or more, preferably 200 N / m or more, and more preferably 250 N / m to 500 N / m. The tension can be applied, for example, by measuring the tension applied to the film between the transport rolls and controlling the rotation speed of the guide rolls so that the tension becomes a desired value.

Tension can be applied between the opening of the clip and any guide roll (eg, between the opening of the clip and the guide roll downstream of the tilted guide roll).

The time for applying tension can be appropriately set according to the film forming material, the amount of slack, and the like. The time can be, for example, 5 to 60 seconds.

2 (a) and 2 (b) are schematic plan views and schematic side views for explaining an example of the roll transfer, respectively. Further, FIG. 3A is a schematic diagram illustrating the arrangement of guide rolls in the conventional roll transport, and FIG. 3B is an inclination guide when viewed from the arrow III side shown in FIG. 2B. It is a schematic diagram explaining the inclination of a roll. In the roll transport of the illustrated example, the film 1 fed from the stretching device 100 is subjected to four guide rolls (tilted guide roll 52, first horizontal guide roll 54, second horizontal guide roll 56, third horizontal guide). It is conveyed through the roll 58) and wound up by the winding unit 60.

In the inclined guide roll 52, the first horizontal guide roll 54, the second horizontal guide roll 56, and the third horizontal guide roll 58, the rotation axis directions a1, a2, a3, and a4 are abbreviated as the transport direction X of the film 1, respectively. They are arranged so that they are orthogonal to each other.

As shown in FIG. 3A, in the conventional roll transfer, the guide roll 50 is arranged so that the left and right ends of the film 1 are located at the same height. As a result, the film 1 can be conveyed in a state where the width direction is parallel to the horizontal plane H, and as a result, the transfer path lengths of the left and right ends of the film 1 are the same. On the other hand, in the roll transport shown in FIG. 3B, the inclined guide roll 52 is the end on the loose side of the film 1 (the right end when viewed from the arrow III side in the illustrated example) b1 on the side where the loose side does not loosen. The portion (in the illustrated example, the left end portion when viewed from the arrow III side) is arranged at an angle with respect to the horizontal plane H so as to be located above b2, whereby the transport path length of the end portion b1 on the slackening side is not loosened. Make it longer than the transport path length of the side end b2. The inclination direction is not limited as long as the length of the transport path at the end on the slack side can be made longer than the length of the transport path at the end on the non-slack side. Therefore, for example, as shown in FIG. 4, when the first horizontal guide roll 54 is arranged above the inclined guide roll 52, the inclined guide roll 52 has a loosened end portion of the film 1. It can be tilted so that it is located below the end on the non-side.

In one embodiment, the tilted guide rolls are arranged so that the transport path lengths of the left and right ends of the film from the opening point of the clip to the tilted guide roll are equidistant. Specifically, the inclined guide roll is placed at the center c in the width direction so that the distances D1 and D2 of the left and right ends of the film are equidistant with respect to the horizontal plane (for example, the horizontal plane at the height of the opening points of the left and right clips) H. Tilt around. With such a configuration, the grip force at both ends can be made uniform, and the film does not slip easily on the roll, so that there is an advantage that the transportability is easily stabilized.

The tilt amount of the tilt guide roll can be appropriately set according to the desired reduction amount of slack and the like. For example, in the inclined guide roll 52, the height difference Y between the end portion b1 on the slack side and the end portion b2 on the non-slack side of the film 1 is 2 mm to 80 mm, preferably 2 mm to 70 mm, and more preferably 2 mm to 60 mm. As such, it can be arranged at an angle. By passing the film through the guide roll 52 inclined in this way, the effect of reducing slack can be suitably obtained while maintaining the desired in-plane phase difference and axial angle. In one embodiment, the distance between the horizontal plane (eg, the horizontal plane at the height of the open points of the left and right clips) H and the slack side end b1 or the non-slack side end b2 of the film 1 on the inclined guide roll 52. D1 or D2 can be, for example, 1 mm to 40 mm, preferably 1 mm to 35 mm, and more preferably 1 mm to 30 mm, respectively. Further, in the present embodiment, the inclination angle θ can be, for example, 0.1 ° to 10 °, preferably 0.1 ° to 7 °, and more preferably 0.1 ° to 5 °.

Further, for example, in the inclined guide roll 52, the height difference Y between the end portion b1 on the loose side and the end portion b2 on the loose side of the film 1 is, for example, 2 mm to 40 mm, preferably 2 mm to 35 mm, and more preferably 2 mm to 30 mm. It can be arranged at an angle so as to be. By passing the guide roll 52 inclined in this way, a wrinkle reducing effect can be preferably obtained, and as a result, a stretched film in which both slack and wrinkles are reduced can be obtained. In one embodiment, the distance between the horizontal plane (eg, the horizontal plane at the height of the open points of the left and right clips) H and the non-slack side end b1 or the loose side end b2 of the film 1 on the inclined guide roll 52. D1 or D2 can be, for example, 1 mm to 20 mm, preferably 1 mm to 18 mm, and more preferably 1 mm to 15 mm, respectively. Further, in the present embodiment, the inclination angle θ can be, for example, 0.1 ° to 5 °, preferably 0.1 ° to 3.5 °, and more preferably 0.1 ° to 2.5 °.

The holding angle between the film and the inclined guide roll (angle θ2 in FIG. 5) is preferably 45 ° to 135 °, more preferably 60 ° to 120 °, and even more preferably 70 ° to 100 °. When the hugging angle is within the range, the film is held by the inclined guide roll, and tension can be selectively applied to one side. Further, it is possible to obtain the effect that the film does not slip when tension is applied and it is difficult for scratches to occur.

The roll-conveyed film 1 can be wound by the winding unit 60 to form a film roll. Alternatively, unlike the illustrated example, the film can be continuously bonded in the same length direction while being conveyed with another long optical film without being wound up to form an optical laminate. ..

In one embodiment, the amount of slack is measured while the film released from the clip and sent out from the stretching device is rolled and conveyed using only a horizontal guide roll, and when a slack amount of a predetermined amount or more is detected. The amount of slack can be reduced by inclining at least one horizontal guide roll (preferably the first horizontal guide roll) in the vertical direction and carrying out the roll transfer as the inclined guide roll.

A-6. Detection of slack amount The slack amount can be detected, for example, between transport rolls. Specifically, the amount of slack can be detected as a difference in position (transport height) in the width direction of the film at an intermediate point between the transfer rolls.

The distance between the transport rolls at the time of the above detection is not particularly limited, but may be, for example, 500 mm to 2000 mm, preferably 700 mm to 1500 mm.

The film tension at the time of the above detection is not particularly limited, but can be, for example, 50 N / m to 400 N / m, preferably 100 N / m to 200 N / m. If the transport tension is too high, the film being transported may be elastically deformed, making it difficult to detect slack. On the other hand, if the transport tension is too low, the tension itself may not be stable and the measured value of slack may not be stable.

The above detection can be performed in a non-heated environment. The atmospheric temperature at which the amount of slack is detected may be, for example, about 15 ° C to 40 ° C, or for example, about 20 ° C to 30 ° C.

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

The widths of the edges to be cut and removed can be independently, for example, 20 mm to 600 mm, preferably 100 mm to 500 mm. Cutting and removal of the end portion can be performed by ordinary slit processing.

The amount of slack reduction obtained by the method for producing a stretched film of the present invention (the amount of slack in a film not rolled using a tilted guide roll-the amount of slack in a film transported by a roll using a tilted guide roll: however, between rolls). The amount of slack measured at a distance of 1000 mm) may be, for example, 3 mm or more, preferably 5 mm or more, more preferably 8 mm or more, still more preferably 10 mm or more. The amount of slack that can remain in the film after the roll transfer using the inclined guide roll is, for example, less than 15 mm, preferably 10 mm or less, more preferably 8 mm or less, still more preferably 5 mm or less, still more preferably less than 3 mm. possible.

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

As the polycarbonate-based resin, any suitable polycarbonate-based resin is used. For example, a polycarbonate resin containing a structural unit derived from a dihydroxy compound is preferable. Specific examples of the dihydroxy compound include 9,9-bis (4-hydroxyphenyl) fluorene, 9,9-bis (4-hydroxy-3-methylphenyl) fluorene, and 9,9-bis (4-hydroxy-3-3). 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-Dimethylphenyl) 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. In addition to the structural units derived from the above dihydroxy compounds, the polycarbonate resin contains isosorbide, isomannide, isoidet, spiroglycol, dioxane glycol, diethylene glycol (DEG), triethylene glycol (TEG), polyethylene glycol (PEG), cyclohexanedimethanol ( It may contain structural units derived from dihydroxy compounds such as CHDM), tricyclodecanedimethanol (TCDDM) and bisphenols.

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

The glass transition temperature of the polycarbonate 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, which may cause a dimensional change after film molding. If the glass transition temperature is excessively high, the molding stability during film molding may be deteriorated, and the transparency of the film may be impaired. The glass transition temperature is determined according to JIS K 7121 (1987).

As the polyvinyl acetal-based resin, any suitable polyvinyl acetal-based resin can be used. Typically, the polyvinyl acetal-based resin can be obtained by subjecting at least two types of aldehyde compounds and / or ketone compounds to a condensation reaction with a polyvinyl alcohol-based resin. Specific examples and detailed production methods of the polyvinyl acetal-based resin are described in, for example, Japanese Patent Application Laid-Open No. 2007-161994. This description is incorporated herein by reference.

The stretched film (phase difference film) obtained by stretching the film to be stretched preferably has a refractive index characteristic of nx> ny. 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 can preferably function as a λ / 2 plate. In the present embodiment, the in-plane retardation Re (550) of the retardation film (λ / 2 plate) is preferably 230 nm to 310 nm, more preferably 250 nm to 290 nm. In the present specification, nx is the refractive index in the direction in which the in-plane refractive index is maximized (that is, the slow phase axis direction), and ny is the in-plane direction orthogonal to the slow phase axis (that is, phase advance). It is the refractive index in the axial direction), and nz is the refractive index in the thickness direction. Re (λ) is an in-plane phase difference of the film measured with light having a wavelength of λ nm at 23 ° C. Therefore, Re (550) is the in-plane phase difference of the film measured with light having a wavelength of 550 nm at 23 ° C. Re (λ) is obtained by the formula: Re (λ) = (nx−ny) × d, where d (nm) is the thickness of the film.

The in-plane retardation Re (550) of the retardation film can be set to a desired range by appropriately setting the diagonal stretching conditions. For example, methods for producing a retardation film having an in-plane retardation Re (550) of 100 nm to 180 nm by diagonal stretching are described in JP2013-54338, JP2014-194482, and JP2014-238524. It is disclosed in detail in Japanese Patent Application Laid-Open No. 2014-194484 and the like. Therefore, those skilled in the art can set appropriate diagonal stretching conditions based on the disclosure.

When making a circularly polarizing plate using one retardation film, or when rotating the direction of linearly polarized light by 90 ° using one retardation film, the slow axis direction of the retardation film used is , Preferably 30 ° to 60 ° or 120 ° to 150 °, more preferably 38 ° to 52 ° or 128 ° to 142 °, still more preferably 43 ° to 47 ° or 133 ° with respect to the longitudinal direction of the film. It is ~ 137 °, particularly preferably about 45 ° or 135 °.

Further, when a circularly polarizing plate is manufactured using two retardation films (specifically, λ / 2 plate and λ / 4 plate), the slow axis of the retardation film (λ / 2 plate) used is used. The direction is preferably 60 ° to 90, more preferably 65 ° to 85, and particularly preferably about 75 ° with respect to the long direction of the film. The slow axis direction 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. be.

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

The absolute value of the photoelastic coefficient of the retardation film is preferably 2 × 10 ^-12 (m ² / N) to 100 × 10 ^-12 (m ² / N), and more preferably 5 × 10 ^-12. It is (m ² / N) to 50 × 10 ^-12 (m ² / N).

C. Optical laminate and method for manufacturing the optical laminate The stretched film obtained by the production method of the present invention can be bonded to another optical film and used as an optical laminate. For example, the retardation film obtained by the production method of the present invention can be suitably used as a circular polarizing plate by being bonded to a polarizing plate.

FIG. 6 is a schematic cross-sectional view of an example of such a circularly polarizing plate. The circular polarizing plate 200 of the illustrated example includes a polarizing element 210, a first protective film 220 arranged on one side of the polarizing element 210, a second protective film 230 arranged on the other side of the polarizing element 210, and a second protective film. It has a retardation film 240 arranged on the outside of the protective film 230 of 2. The retardation film 240 is a stretched film (for example, a λ / 4 plate) obtained by the production method according to Item A. The second protective film 230 may be omitted. In that case, the retardation film 240 can function as a protective film for the stator. The angle formed by the absorption axis of the polarizing element 210 and the slow axis of the retardation film 240 is preferably 30 ° to 60 °, more preferably 38 ° to 52 °, still more preferably 43 ° to 47 °, and 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). Also, in many cases, the elongated polarizing element has an absorption axis in the elongated direction or 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 circularly polarizing plate can be produced with extremely excellent production efficiency. Note that roll-to-roll refers to a method of continuously laminating long films by aligning their long directions while transporting them in a roll.

In one embodiment, in the method for producing an optical laminate of the present invention, a elongated stretched film is obtained by the method for producing a stretched film according to item A, and the elongated optical film and the elongated film are obtained. This includes continuously laminating the stretched film in the shape of a stretched film while aligning its long direction.

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

(1) Thickness Measured using a dial gauge (manufactured by PEACOCK, product name "DG-205 type pds-2").
(2) Phase difference value The in-plane phase difference Re (550) was measured using Axoscan manufactured by Axometrics.
(3) Orientation angle (direction of expression of slow axis)
A sample was prepared by cutting out the central portion of the film to be measured into a square shape having a width of 50 mm and a length of 50 mm so that one side was parallel to the width direction of the film. This sample was measured using Axoscan manufactured by Axometrics, and the orientation angle θ at a wavelength of 590 nm was measured.
(4) Glass transition temperature (Tg)
It was measured according to JIS K 7121.
(5) Loose amount As shown in FIG. 7, the ultrasonic displacement sensor 300 is arranged below the transport path of the film 1 at the midpoint between the guide rolls 50a and 50b (distance between rolls: 912 mm), and the transport tension is 150 N / The distance from the ultrasonic displacement sensor to the stretched film is measured at the center and edges in the width direction when transported at m, and the difference between _{the maximum distance (L MAX} ) and the minimum distance (L _{MIN ) (L MAX-} L). _MIN ) was defined as the amount of slack (mm). The amount of slack was measured by using a suction roll or the like to cut the tension applied to correct the slack, and then carrying the roll at a transport tension of 150 N / m.
(6) Tension The tension applied to the film was measured by a film tension detector installed in the film transport line.

<Example 1>
(Preparation of polyester carbonate resin film)
Polymerization was carried out using a batch polymerization apparatus consisting of two vertical reactors equipped with a stirring blade 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. 139mol), were charged DPC 63.77 parts by weight (0.298 mol) and calcium acetate monohydrate 1.19 × ^{10 -2} parts by weight as a catalyst (6.78 × ¹⁰ -5 mol). After substituting nitrogen under reduced pressure in the reactor, heating was performed with a heat medium, and stirring was started when the internal temperature reached 100 ° C. The internal temperature was brought to 220 ° C. 40 minutes after the start of the temperature rise, and the depressurization was started at the same time as controlling to maintain this temperature, and the temperature was 13.3 kPa 90 minutes after reaching 220 ° C. The phenol vapor produced by the polymerization reaction was guided to a reflux condenser at 100 ° C., the monomer component contained in a small amount in the phenol vapor was returned to the reactor, and the non-condensed phenol vapor was guided to a condenser at 45 ° C. for recovery. Nitrogen was introduced into the first reactor and the pressure was once restored to atmospheric pressure, and then the oligomerized reaction solution in the first reactor was transferred to the second reactor. Then, the temperature rise and depressurization in the second reactor were started, and the internal temperature was 240 ° C. and the pressure was 0.2 kPa in 50 minutes. Then, the polymerization was allowed to proceed until the stirring power became a predetermined value. When the predetermined power was reached, nitrogen was introduced into the reactor to repressurize, the produced polyester carbonate was extruded into water, and the strands were cut to obtain pellets. The Tg of the obtained polyester carbonate resin was 140 ° C.

After vacuum-drying the obtained polyester carbonate resin at 80 ° C. for 5 hours, a single-screw extruder (manufactured by Toshiba Machine Co., Ltd., cylinder set temperature: 250 ° C.), T-die (width 200 mm, set temperature: 250 ° C.), chill roll (Set temperature: 120 to 130 ° C.) and a film forming apparatus equipped with a winder were used to prepare a resin film having a thickness of 135 μm.

(Preparation of stretched film)
The polyester carbonate resin film obtained as described above was obliquely stretched using a stretching device as shown in FIG. 1A to obtain a retardation film.
Specifically, the left and right ends of the polyester carbonate resin film were gripped by the left and right clips at the entrance of the stretching device, and preheated to 145 ° C. in the preheating zone B. In the preheating zone, the clip pitch (P ₁ ) of the left and right clips was 125 mm.
Next, on the film enters the stretching zone C, to start the reduction in the clip pitches increased and left clips clip pitch right clip, clip pitch of the left clip with increasing clip pitch of the right clip to the P ₂ until P ₃ was reduced (first oblique stretching). At this time, the clip pitch change rate (P ₂ / P ₁ ) of the right clip is 1.42, the clip pitch change rate of the left clip (P ₃ / P ₁ ) is 0.78, and the original width of the film is 0.78. The lateral stretching ratio was 1.45 times. Then, while maintaining the clip pitch of the right clip at P ₂ , the clip pitch of the left clip was started to be increased and increased from P _{3 to P 2} (second diagonal extension). During this period, the rate of change in the clip pitch (P ₂ / P ₃ ) of the left clip was 1.82, and the lateral stretching ratio with respect to the original width of the film was 1.9 times. The stretching zone C was set to Tg + 3.2 ° C. (143.2 ° C.).
Then, in the open zone D, the film was held at 125 ° C. for 60 seconds for heat fixation. The heat-fixed film was cooled to 100 ° C., the left and right clips were opened, and the film was fed from the outlet of the stretching device.

(Detection of slack)
As described above, the film delivered from the outlet of the stretching device is transferred to a transport line using four guide rolls as shown in FIGS. 2 (a) and 2 (b) in a room temperature environment (as shown in the figure). , The second guide roll 54 is arranged below the first guide roll 52), and the amount of slack was detected between the transport rolls. As a result, in the obtained stretched film, the left end in the width direction. There was slack in the portion, and the amount of slack was 20 mm. All four guide rolls were horizontal guide rolls arranged so that the transport direction and the rotation axis direction were orthogonal to each other and the positions of the right end and the left end of the film were at the same height. ..

(Roll transfer)
In the roll transfer, the horizontal guide roll (first guide roll 52) arranged at the position closest to the outlet of the stretching device is placed with respect to the horizontal plane so that the position of the right end portion of the film is 60 mm below the position of the left end portion. Tilt it to make a tilted guide roll. At this time, the left and right ends are inclined by equal amounts with the center in the width direction of the horizontal guide roll as the center so that the transport path lengths of the left and right ends of the film from the opening point of the clip to the inclined guide roll are the same length. I let you. Specifically, the horizontal guide roll is tilted so that the left end portion of the film is 30 mm above and the right end portion is 30 mm below the horizontal plane at the height of the opening point of the clip to form an inclined roll. Further, by adjusting the torque of the horizontal guide roll at the most downstream in the transport direction, a tension of 300 N / m was applied to the film from the clip opening point to the horizontal guide roll at the most downstream in the transport direction for 5.85 seconds. The holding angle between the film and the inclined guide roll was 90 °. Further, the inclined guide roll was located immediately after the exit of the stretching device, and the time from the release of the film from the clip to the passage through the inclined guide roll was about 20 seconds.

The phase difference Re (590) of the stretched film that had undergone roll transfer using the inclined guide roll was 147 nm, and the angle between the slow phase axial direction and the elongated direction was 45 °.

<Example 2>
The tilted guide roll was tilted so that the position of the right end of the film was 40 mm below the position of the left end (more specifically, the left end of the film with respect to the horizontal plane at the height of the opening point of the clip). A stretched film was obtained in the same manner as in Example 1 except that the horizontal guide roll was tilted to be 20 mm above and the right end was 20 mm below.

The phase difference Re (590) of the stretched film that had undergone roll transfer using the inclined guide roll was 147 nm, and the angle between the slow phase axial direction and the elongated direction was 45 °.

<Example 3>
The tilted guide roll was tilted so that the position of the right end of the film was 30 mm below the position of the left end (more specifically, the left end of the film with respect to the horizontal plane at the height of the opening point of the clip). A stretched film was obtained in the same manner as in Example 1 except that the horizontal guide roll was tilted so as to be 15 mm above and the right end was 15 mm below.

The phase difference Re (590) of the stretched film that had undergone roll transfer using the inclined guide roll was 147 nm, and the angle between the slow phase axial direction and the elongated direction was 45 °.

<Example 4>
The tilted guide roll was tilted so that the position of the right end of the film was 20 mm below the position of the left end (more specifically, the left end of the film with respect to the horizontal plane at the height of the opening point of the clip). A stretched film was obtained in the same manner as in Example 1 except that the horizontal guide roll was tilted to be 10 mm above and the right end was tilted 10 mm below.

The phase difference Re (590) of the stretched film that had undergone roll transfer using the inclined guide roll was 147 nm, and the angle between the slow phase axial direction and the elongated direction was 45 °.

<Example 5>
The tilted guide roll was tilted so that the position of the right end of the film was 10 mm below the position of the left end (more specifically, the left end of the film with respect to the horizontal plane at the height of the opening point of the clip). A stretched film was obtained in the same manner as in Example 1 except that the horizontal guide roll was tilted so as to be 5 mm above and the right end was 5 mm below.

The phase difference Re (590) of the stretched film that had undergone roll transfer using the inclined guide roll was 147 nm, and the angle between the slow phase axial direction and the elongated direction was 45 °.

<Example 6>
The tilted guide roll was tilted so that the position of the right end of the film was 6 mm below the position of the left end (more specifically, the left end of the film with respect to the horizontal plane at the height of the opening point of the clip). A stretched film was obtained in the same manner as in Example 1 except that the horizontal guide roll was tilted so as to be 3 mm above and the right end portion was 3 mm below.

The phase difference Re (590) of the stretched film that had undergone roll transfer using the inclined guide roll was 147 nm, and the angle between the slow phase axial direction and the elongated direction was 45 °.

<Comparative Example 1>
A stretched film was obtained in the same manner as in Example 1 except that the roll was not conveyed using the inclined guide roll. In the obtained stretched film, slack was generated at the left end portion in the width direction, and the amount of slack was 20 mm. The phase difference Re (590) of the stretched film was 147 nm, and the angle formed by the slow phase axial direction and the elongated direction was 45 °.

[Appearance and handleability evaluation]
The stretched films obtained in the above Examples and Comparative Examples were bonded to a long masking film (manufactured by Toray Film Processing Co., Ltd., product name "Tretec 7832C-30") by roll-to-roll to obtain a film laminate. .. Next, the masking film was peeled off from the film laminate, an adhesive was applied with a gravure coater, the film was bonded to the polarizing plate, and UV irradiation was performed to obtain an optical laminate. The appearance (visual) of the optical laminate and the handleability of the stretched film were evaluated based on the following criteria.
〇: After the masking film is bonded (bonding tension 150 N / m), no wrinkles are found and the adhesive can be applied to the entire surface of the film.
Δ: When the masking film was bonded, the bonding could be performed without wrinkles by increasing the bonding tension to 300 N / m, but the adhesive could not be applied to the loosened portion during the adhesive application.
X: After the masking film is attached, there are wrinkles and the appearance is deteriorated.

[Wrinkle evaluation]
The wrinkles of the obtained stretched film were evaluated based on the following criteria.
〇: Wrinkles are not visible even when irradiated with Polarion light (manufactured by Polarion, product number "NP-1").
Δ: Wrinkles are not visible even when irradiated with a fluorescent lamp, but wrinkles are visible when irradiated with a polarion light.
X: Wrinkles are visually recognized when irradiated with a fluorescent lamp.

[Evaluation of transportability]
With respect to the obtained stretched film, it was visually confirmed whether or not the film was distorted or broken due to slack and / or wrinkles, and evaluated based on the following criteria.
〇: The film is not distorted or broken.
X: The film is distorted and / or broken.

[Visibility evaluation]
The optical laminate produced in the above appearance and handleability evaluation was bonded to the visible side of the reflector or the organic EL panel via the adhesive layer. With respect to the obtained optical laminate, the presence or absence of uneven shape or light leakage due to slack or wrinkles was visually confirmed and evaluated based on the following criteria.
〇: Unevenness and light omission are not visible on both the reflector and the panel mounting.
Δ: Unevenness and / or light omission are visible on the reflector, but not on the panel mounting.
X: Unevenness and / or light omission are visually recognized in both the reflector and the panel mounting.

Table 1 shows the amount of slack and the evaluation results of the stretched films obtained in the above Examples and Comparative Examples.

<Evaluation>
As shown in Table 1, in the production of a long diagonally stretched film, the length of the transport path at the end of the film on the loose side is longer than the length of the transport path at the end on the non-slack side. It can be seen that slack and / or wrinkles are reduced by passing the guide rolls arranged at an angle with respect to the guide roll.

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 an image display device such as a liquid crystal display device (LCD) and an organic electroluminescence display device (OLED). ..

1 Stretched film 10L Endless loop 10R Endless loop 20 Clip 50 Guide roll 52 Guide roll 54 Guide roll 56 Guide roll 58 Guide roll 60 Winding part 100 Stretching device 200 Circular polarizing plate 300 Ultrasonic displacement sensor

Claims (10)

To grip the left and right edges of the long film in the width direction with the left and right clips, respectively.
The left and right clips are run and moved to stretch the film diagonally, and then released from the left and right clips, and
A method for producing a stretched film, which comprises rolling and transporting the film.
The roll transfer involves passing an inclined guide roll through the film.
The stretched film is arranged so as to be inclined with respect to a horizontal plane so that the transport path length of the end of the film on the loose side is longer than the transport path length of the end of the film on the non-slack side. Manufacturing method. The method for producing a stretched film according to claim 1, wherein the film passes through the inclined guide roll within 120 seconds after being released from the clip. The roll transfer includes passing the guide roll X and the guide roll Y provided in this order continuously through the film toward the downstream in the transfer direction.
The guide roll Y is arranged below the guide roll X.
The tilted guide roll X is the inclined guide roll, and is arranged so as to be inclined so that the end portion of the film on the non-sagging side is located 2 mm to 80 mm lower than the end portion on the loosening side. Alternatively, the method for producing a stretched film according to 2. The roll transfer includes passing the guide roll X and the guide roll Y provided in this order continuously through the film toward the downstream in the transfer direction.
The guide roll Y is arranged above the guide roll X, and the guide roll Y is arranged above the guide roll X.
The tilted guide roll X is the inclined guide roll, and is arranged so as to be inclined so that the end portion of the film on the non-sagging side is located 2 mm to 80 mm above the end portion on the loosening side. Alternatively, the method for producing a stretched film according to 2. The method for producing a stretched film according to claim 3 or 4, wherein the transport path lengths of the left and right ends of the film from the opening point of the clip to the inclined guide roll are the same. The stretched film according to any one of claims 1 to 5, wherein the inclined guide rolls are arranged so that the rotation axis direction thereof forms an angle of 89.7 ° to 90.3 ° with the transport direction of the film. Manufacturing method. The clip is a variable pitch type clip in which the clip pitch in the vertical direction changes.
Any one of claims 1 to 6, wherein the film is stretched in an oblique direction by traveling and moving while changing the clip pitch of at least one of the clip that grips the left end portion of the film and the clip that grips the right end portion. The method for producing a stretched film according to. 1 The method for producing a stretched film according to any one of 1 to 6. The elongated stretched film is obtained by the production method according to any one of claims 1 to 8, and the elongated optical film and the elongated stretched film are conveyed in the elongated direction. A method for manufacturing an optical laminate, which comprises aligning and continuously laminating. The optical film is a polarizing plate, and the optical film is a polarizing plate.
The method for manufacturing an optical laminate according to claim 9, wherein the stretched film is a λ / 4 plate or a λ / 2 plate.

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