CN115782147A - Method for producing stretched film and method for producing optical laminate - Google Patents
Method for producing stretched film and method for producing optical laminate Download PDFInfo
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- CN115782147A CN115782147A CN202211103114.XA CN202211103114A CN115782147A CN 115782147 A CN115782147 A CN 115782147A CN 202211103114 A CN202211103114 A CN 202211103114A CN 115782147 A CN115782147 A CN 115782147A
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Abstract
The invention provides a long obliquely-stretched film with reduced in-plane retardation and/or variation in orientation angle. Also provided is a method for producing a stretched film, comprising: clamping the left and right ends of the long film in the width direction by a variable-pitch left and right jig with a vertical jig pitch varying; moving the left and right clamps while changing the clamp pitch of at least one of the left and right clamps, thereby obliquely stretching the film; heat fixing the film; releasing the film from the left and right clamps; and measuring variations in-plane retardation and/or variations in orientation angle in the width direction of the film, wherein, when the variations in-plane retardation and/or orientation angle exceed a predetermined reference, the distance between the left and right jigs and/or the jig pitch of the left and right jigs at the time of the heat-setting are corrected.
Description
Technical Field
The present invention relates to a method for producing a stretched film and a method for producing an optical laminate.
Background
In image display devices such as liquid crystal display devices (LCDs) and organic electroluminescent display devices (OLEDs), circularly polarizing plates are used for improving display characteristics and preventing reflection. Typically, a circularly polarizing plate is formed by laminating a polarizer and a retardation film (typically, a λ/4 plate) so that the absorption axis of the polarizer and the slow axis of the retardation film form an angle of 45 °. Conventionally, since a retardation film is typically produced by uniaxial stretching or biaxial stretching in the longitudinal direction and/or the transverse direction, the slow axis thereof appears in the transverse direction (width direction) or the longitudinal direction (length direction) of a long film blank in many cases. As a result, in the production of the circularly polarizing plate, the retardation film must be cut at an angle of 45 ° to the width direction or the longitudinal direction and bonded one by one.
In order to secure broadband characteristics of the circularly polarizing plate, two retardation films, i.e., a λ/4 plate and a λ/2 plate, may be laminated. In this case, the λ/2 plates need to be stacked at an angle of 75 ° to the absorption axis of the polarizer, and the λ/4 plates need to be stacked at an angle of 15 ° to the absorption axis of the polarizer. Even in this case, when the circularly polarizing plate is manufactured, the retardation film needs to be cut out at angles of 15 ° and 75 ° to the width direction or the longitudinal direction and bonded one by one.
In another embodiment, in order to rotate the direction of the linearly polarized light from the polarizing plate by 90 ° to avoid the light from the notebook PC from being reflected on the keyboard or the like, a λ/2 plate is sometimes used on the viewing side of the polarizing plate. Even in this case, the retardation film needs to be cut at an angle of 45 ° to the width direction or the longitudinal direction and bonded one by one.
In order to solve the above problems, the following techniques are proposed: the slow axis of the retardation film appears in an oblique direction by holding the left and right ends of the long film in the width direction with a variable-pitch type left and right jig having a vertically-varied jig pitch, varying the jig pitch of at least one of the left and right jigs, and stretching the film in an oblique direction with respect to the longitudinal direction (hereinafter, also referred to as "oblique stretching") (for example, patent document 1). However, in the obliquely stretched film obtained by the above-described technique, variations may occur in the in-plane retardation and/or the orientation angle.
Documents of the prior art
Patent document
Patent document 1: japanese patent No. 4845619
Disclosure of Invention
Problems to be solved by the invention
The present invention has been made to solve the above problems, and a main object thereof is to provide a long obliquely stretched film in which variations in-plane retardation and/or orientation angle are reduced.
Means for solving the problems
According to 1 aspect of the present invention, there is provided a method for producing a stretched film, comprising: the left and right ends of the long film in the width direction are respectively clamped by a variable-pitch left and right clamp with the longitudinal clamp pitch changing; moving the left and right clamps while changing the clamp pitch of at least one of the left and right clamps, thereby stretching the film in an oblique direction; heat fixing the film; releasing the film from the left and right clamps; and measuring variations in-plane retardation and/or variations in orientation angle in the width direction of the film, wherein, when the variations in-plane retardation and/or orientation angle exceed a predetermined reference, the distance between the left and right jigs and/or the jig pitch of the left and right jigs at the time of the heat-setting are corrected.
In one embodiment, the left and right ends of the film released from the left and right jigs are cut and removed, and then the variation in-plane retardation and/or orientation angle in the width direction is measured.
In one embodiment, the correction of the jig pitch of the left and right jigs is performed by a correction rate defined by the following equation (1) of 0.5% to 4.0%, respectively.
Correction rate (%) = (jig pitch at the end of thermal fixation after correction-jig pitch at the end of thermal fixation before correction)/(jig pitch at the end of thermal fixation before correction) × 100 formula (1)
In one embodiment, the correction of the distance between the left and right jigs is performed at a correction rate defined by the following formula (2) of 0.5% to 3.0%.
Correction rate (%) = (distance between left and right jigs at the end of thermal fixation after correction-distance between left and right jigs at the end of thermal fixation before correction)/(distance between left and right jigs at the end of thermal fixation before correction) × 100 formula (2)
In one embodiment, the bias stretching comprises: (i) While the distance between the left and right clamps is from P 1 Increase to P 2 While making the distance between the clamps of the other clamp from P 1 Is reduced to P 3 (ii) a And (ii) changing the jig pitch of each jig so that the reduced jig pitch and the increased jig pitch are equal to each other.
In one embodiment, P 2 /P 1 Is 1.25 to 1.75 of P 3 /P 1 Is 0.50 or more and less than 1.
According to another aspect of the present invention, there is provided a method of manufacturing an optical stack, comprising: a long stretched film obtained by the above production method; and continuously laminating the optical film and the stretched film while aligning the optical film and the stretched film in the longitudinal direction.
In one embodiment, the optical film is a polarizer and the stretched film is a λ/4 plate or a λ/2 plate.
Effects of the invention
In the method for producing a stretched film of the present invention, after oblique stretching and heat-setting, the in-plane retardation and/or the variation in orientation angle in the width direction of the film released from the jig are measured, and when the in-plane retardation and/or the variation in orientation angle exceeding a predetermined reference occurs, the distance between the left and right jigs and/or the jig pitch of the left and right jigs in the heat-setting step downstream of the production line are corrected. This makes it possible to obtain a long obliquely stretched film with reduced variations in-plane retardation and/or orientation angle in the width direction. The reason why the above-described effects are obtained is presumably that: in the heat fixation, relaxation of the residual stress by the oblique stretching can be performed more favorably, and as a result, the bending can be suppressed, but the reason is not at all limited to the present invention.
Drawings
Fig. 1 is a schematic view illustrating an example of the method for producing a stretched film of the present invention.
Fig. 2 is a schematic plan view illustrating an overall configuration of an example of a stretching apparatus that can be used in the method for producing a stretched film of the present invention.
Fig. 3 is a schematic plan view of essential parts of a link mechanism for explaining the change of the clamp pitch in the stretching apparatus of fig. 2.
Fig. 4 is a schematic plan view of essential parts of a link mechanism for explaining a change in the clamp pitch in the stretching apparatus of fig. 2.
Fig. 5 is a schematic diagram illustrating the distance between the left and right jigs and the jig pitch.
Fig. 6A is a schematic view showing a contour of a clip pitch in one embodiment of oblique stretching.
Fig. 6B is a schematic view showing a profile of a clip pitch in one embodiment of the oblique stretching.
Fig. 7 is a schematic diagram illustrating a method of measuring an in-plane retardation and/or an orientation angle.
Fig. 8 is a schematic cross-sectional view of a circularly polarizing plate using a retardation film obtained by the production method of the present invention.
Description of the symbols
1. Stretched film
10L Ring
10R cyclic ring
20. Clamp apparatus
100. Stretching device
500. Circular polarizing film
Detailed Description
Preferred embodiments of the present invention will be described below, but the present invention is not limited to these embodiments. In the present specification, the left-right relationship in the width direction of the long film means a left-right relationship in the film transport direction unless otherwise specified.
A. Method for producing stretched film
The method for producing a stretched film according to an embodiment of the present invention includes:
clamping the left and right ends of the long film in the width direction by a variable-pitch left and right clamp with a clamp pitch that varies in the longitudinal direction (clamping step);
moving the left and right clamps while changing the clamp pitch of at least one of the left and right clamps, thereby obliquely stretching the film (oblique stretching step);
heat-fixing the film (heat-fixing step);
releasing the film from the left and right clamps (releasing step); and
measuring the variation of the in-plane retardation and/or the orientation angle in the width direction of the film (variation measuring step),
wherein, when the variation of the in-plane retardation and/or the orientation angle exceeds a predetermined reference, the method includes: the distance between the left and right jigs and/or the jig pitch of the left and right jigs during the heat setting are corrected (correction step). Typically, the method for producing a stretched film according to the embodiment of the present invention further includes a preheating step. Specifically, the film sandwiched by the left and right clamps is preheated and then subjected to oblique stretching.
Fig. 1 is a schematic view illustrating an example of the method for producing a stretched film of the present invention. The long obliquely-stretched film 1, which is obliquely stretched in the stretching device 100 and then released from the jig, is sent out from the outlet of the stretching device 100, is roll-conveyed using conveying rollers 200a, 200b, 200c, and 200d, and is wound by the winding section 300. When the film 1 is conveyed by a roll, a variation in-plane retardation and/or a variation in orientation angle in the film width direction (hereinafter, sometimes referred to as a "variation in-plane retardation or the like") is measured, and when the variation exceeds a predetermined reference, the distance between the left and right jigs and/or the jig pitch of the left and right jigs in the heat curing is corrected by tracing back to the upstream of the production line. By performing the correction as described above, a long obliquely stretched film with reduced variations such as in-plane retardation in the width direction can be obtained.
The above-described sandwiching of the film by the clips, preheating, oblique stretching, heat fixing, and releasing from the clips may be performed, for example, using a tenter set simultaneous biaxial stretching apparatus having left and right clips capable of moving at different speeds while sandwiching the left and right ends in the width direction of the long film.
Fig. 2 is a schematic plan view illustrating an overall configuration of an example of a stretching apparatus that can be used in the method for producing a stretched film of the present invention. The stretching device 100 has an annular ring 10L and an annular ring 10R symmetrically left and right on both sides in a plan view, and the annular ring 10L and the annular ring 10R have a large number of clamps 20 for film clamping. In the present specification, the left annular ring is referred to as a left annular ring 10L and the right annular ring is referred to as a right annular ring 10R, when viewed from the inlet side of the membrane. The jigs 20 of the left and right annular rings 10L, 10R are guided by the reference rail 70 and circularly move in an annular shape. The gripper 20 of the left annular ring 10L moves in a counterclockwise direction, and the gripper 20 of the right annular ring 10R moves in a clockwise direction. In the stretching apparatus, from the inlet side toward the outlet side of the film, a nip zone a, a preheating zone B, a stretching zone C, a heat-fixing zone D, and a releasing zone E are disposed in this order. These respective regions are regions where the film to be stretched is substantially sandwiched, preheated, obliquely stretched, thermally fixed, and released, and do not mean mechanically and structurally independent partitions. In addition, it is to be noted that the ratio of the lengths of the respective zones in the stretching apparatus of fig. 2 is different from the ratio of the actual lengths.
Although not illustrated in fig. 2, the stretching apparatus typically includes a heating device (for example, various ovens such as a hot air oven, a near infrared oven, and a far infrared oven) for setting the temperature from the preheating zone B to the heat fixing zone D or the release zone E as a heating environment.
In fig. 2, in the nip zone a and the preheating zone B of the stretching apparatus 100, the left and right endless rings 10L and 10R are configured such that: are substantially parallel to each other at a spacing distance corresponding to the initial width of the film to be stretched. In the stretching zone C, the following composition is set: the distance between the left and right annular rings 10L, 10R gradually increases from the preheating zone B toward the heat fixing zone D until the distance corresponds to the stretched width of the film. In the heat-fixing zone D and the releasing zone E, the left and right annular rings 10L, 10R are configured such that: substantially parallel to each other at a spacing distance corresponding to the stretched width of the film.
On the other hand, the left and right annular rings 10L and 10R are configured to be able to freely change the distance between them. Therefore, the configuration (reference track pattern) of the left and right annular rings 10L and 10R can be arbitrarily changed according to the purpose and the like. For example, when performing a correction to reduce the distance between the left and right jigs during thermal fixing, the thermal fixing area D may be configured as follows: the distance separating the left and right endless loops 10L, 10R gradually decreases from the stretch zone C toward the release zone E. For example, the left and right annular rings 10L, 10R may be configured such that: are substantially parallel to each other at a spacing distance corresponding to the initial width of the film to be stretched. The configuration in which the distance between the left and right annular rings 10L and 10R (the track pattern of the left and right reference tracks) can be changed is not particularly limited, and any appropriate configuration that is generally used in the simultaneous biaxial stretching machine can be adopted.
The jig (left jig) 20 of the left annular ring 10L and the jig (right jig) 20 of the right annular ring 10R can be independently moved cyclically. For example, the driving sprockets 11 and 12 of the left annular ring 10L are rotationally driven counterclockwise by the motors 13 and 14, and the driving sprockets 11 and 12 of the right annular ring 10R are rotationally driven clockwise by the motors 13 and 14. As a result, a traveling force is applied to the jig holding member of the driving roller (not shown) engaged with the driving sprockets 11 and 12. Thereby, the left jig is circularly moved counterclockwise, and the right jig is circularly moved clockwise. The left and right clamps can be independently moved in a circulating manner by independently driving the left and right electric motors.
The jig (left jig) 20 of the left annular ring 10L and the jig (right jig) 20 of the right annular ring 10R are of variable pitch type. That is, the left and right jigs 20, 20 can change the jig pitch in the longitudinal direction independently of each other. The variable pitch type configuration can be realized by adopting a drive system such as a pantograph system, a linear motor system, and a motor chain system. Hereinafter, a link mechanism (a pantograph mechanism) will be described as an example.
Fig. 3 and 4 are schematic plan views of essential parts for explaining a link mechanism for changing the clamp pitch in the stretching apparatus of fig. 2, in which fig. 3 shows a state where the clamp pitch is minimum, and fig. 4 shows a state where the clamp pitch is maximum.
As shown in fig. 3 and 4, jig carrying members 30 each carrying the jig 20 are provided, the jig carrying members being elongated and rectangular in a transverse direction in plan view. Although not shown, the jig carrier member 30 is formed as a firm frame structure of a closed section by an upper beam, a lower beam, a front wall (a wall on the jig side), and a rear wall (a wall on the opposite side from the jig). The jig carrier member 30 is arranged to roll on the travel surfaces 81, 82 by the travel wheels 38 at both ends thereof. In fig. 3 and 4, the travel wheels on the front wall side (the travel wheels that roll on the travel surface 81) are not shown. The travel surfaces 81, 82 are parallel to the reference rail 70 over the entire area. On the rear sides of the upper and lower beams of the jig carrying member 30 (the sides opposite to the jig side (hereinafter referred to as opposite sides to the jig)), long holes 31 are formed along the longitudinal direction of the jig carrying member, and the sliders 32 are slidably engaged in the longitudinal direction of the long holes 31. One 1 st shaft member 33 is provided vertically through the upper and lower beams in the vicinity of the end of the jig 20 side of the jig carrier 30. On the other hand, a single 2 nd shaft member 34 is provided to penetrate vertically through the slider 32 of the jig carrier member 30. One end of a main link member 35 is pivotally connected to the 1 st shaft member 33 of each jig carrier member 30. The other end of the main link member 35 is pivotally connected to the 2 nd shaft member 34 of the adjacent jig carrier member 30. One end of a sub link member 36 is pivotally connected to the 1 st shaft member 33 of each jig carrier member 30 in addition to the main link member 35. The other end of the sub link member 36 is pivotally connected to the intermediate portion of the main link member 35 via a pivot shaft 37. With the link mechanism formed of the main link member 35 and the sub link member 36, as shown in fig. 3, the longitudinal distance between the jig carrier members 30 (as a result, the jig distance) becomes smaller as the slider 32 moves to the rear side (the opposite side to the jig) of the jig carrier member 30, and as shown in fig. 4, the longitudinal distance between the jig carrier members 30 (as a result, the jig distance) becomes larger as the slider 32 moves to the front side (the jig side) of the jig carrier member 30. The positioning of the slider 32 is performed by the pitch setting rail 90. As shown in fig. 3 and 4, the smaller the spacing distance between the reference rail 70 and the pitch setting rail 90, the larger the jig pitch becomes.
By obliquely stretching the film using the stretching apparatus as described above, an obliquely stretched film, for example, a retardation film having a slow axis in an oblique direction can be produced. A specific embodiment of the stretching apparatus as described above is described in, for example, japanese patent application laid-open No. 2008-44339, and the entire description is incorporated by reference. Hereinafter, each step will be described in detail.
A-1. Clamping procedure
In the clamping zone a (the entrance of the stretching apparatus 100 into which the film enters), typically, the left and right ends of the film to be stretched are clamped simultaneously at a constant clamp pitch equal to each other by the clamps 20 of the left and right annular rings 10L, 10R. In this case, a line connecting the centers of the left and right jigs is preferably substantially orthogonal to the film conveying direction (for example, 90 ° ± 3 °, preferably 90 ° ± 1 °, more preferably 90 ° ± 0.5 °, and even more preferably 90 °). The distance between the left and right clamps at the time of clamping is, for example, 100mm to 200mm, preferably 125mm to 175mm, and more preferably 140mm to 160mm.
In the present specification, the "vertical jig pitch" or the "jig pitch" refers to an inter-center distance P in the traveling direction of the vertically adjacent jigs 20, and the "left-right jig distance" refers to a distance L between inner ends of the left and right jigs 20 arranged so that a line connecting the centers is substantially orthogonal to the transport direction of the film 1, and may correspond to the distance between the left and right annular rings 10L, 10R (see fig. 5).
The film is conveyed to the preheating zone B by the movement of the jigs 20 of the left and right annular rings 10L, 10R (substantially, the movement of the respective jig carrying members guided by the reference rails 70).
A-2 preheating step
In the preheating zone B, the left and right annular rings 10L and 10R are configured to be substantially parallel to each other at the interval distance corresponding to the initial width of the film to be stretched as described above, and therefore the film is heated without substantially performing the transverse stretching and the longitudinal stretching. However, in order to avoid troubles such as deflection of the film due to preheating and contact with the nozzle in the oven, the distance between the left and right jigs (distance in the width direction) may be slightly increased.
In the preheating step, the film is heated to a temperature T1 (. Degree. C.). The temperature T1 is preferably not less than the glass transition temperature (Tg) of the film, more preferably not less than Tg +2 ℃, and still more preferably not less than Tg +5 ℃. On the other hand, the heating temperature T1 is preferably Tg +40 ℃ or less, more preferably Tg +30 ℃ or less. The temperature T1 varies depending on the film used, and is, for example, 70 to 190 ℃ and preferably 80 to 180 ℃.
The temperature rise time to the temperature T1 and the holding time at the temperature T1 may be appropriately set depending on the constituent material of the film and the production 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 jig 20, the length of the preheating zone, the temperature of the preheating zone, and the like.
A-3. Oblique stretching Process
In the stretching zone C, the film is obliquely stretched by moving the left and right clamps 20 while changing the clamp pitch in the longitudinal direction of at least one of the left and right clamps 20. More specifically, the film is obliquely stretched by the following steps: moving the left and right clamps while increasing or decreasing the clamp pitch at different positions; moving the left and right jigs while changing (increasing and/or decreasing) the jig pitch at different changing speeds; and so on. As a result of moving the left and right clamps while changing the clamp pitch in this manner, the left and right clamps are simultaneously moved into the pair of left and right clamps in the stretching zone, and one clamp reaches the end of the stretching zone before the other clamp. According to the above-described oblique stretching, the leading jig-side end portion is stretched at a higher stretching ratio than the trailing jig-side end portion, and as a result, the slow axis can be expressed in a desired direction of the long film (for example, a direction of 45 ° with respect to the longitudinal direction).
The oblique stretching may also include transverse stretching. In this case, the diagonal drawing can be performed while increasing the distance between the left and right jigs (the distance in the width direction), as shown in the illustrated example. Alternatively, the oblique stretching may be performed in a state where the distance between the left and right jigs is maintained without including the lateral stretching, unlike the illustrated example.
In the case where the oblique stretching includes transverse stretching, the stretching ratio in the Transverse Direction (TD) (width W of the film after the oblique stretching) final Relative to the initial width W of the film initial Ratio of (W) final /W initial ) ) is preferably 1.05 to 6.00, more preferably 1.10 to 5.00.
In one embodiment, the diagonal stretching may be performed by: the jig pitch of each of the left and right jigs is increased or decreased to a predetermined interval in a state where a position where the jig pitch of one of the jigs starts to increase or decrease and a position where the jig pitch of the other jig starts to increase or decrease are set to different positions in the vertical direction. For the oblique stretching in this embodiment, for example, refer to the disclosure of patent document 1 and japanese patent application laid-open No. 2014-238524.
In another embodiment, the diagonal stretching may be performed by the steps of: while the jig pitch of one of the left and right jigs is fixed, the jig pitch of the other jig is increased or decreased to a predetermined pitch, and then returned to the original jig pitch. For the oblique stretching in this embodiment, for example, the contents described in japanese patent laid-open nos. 2013-54338 and 2014-194482 can be referred to.
In yet another embodiment, the diagonal stretching may be performed by: (i) While making at the same timeThe clamp pitch of one of the left and right clamps is from P 1 Increase to P 2 While making the distance between the clamps of the other clamp from P 1 Is reduced to P 3 (ii) a And (ii) changing the jig pitch of each jig so that the reduced jig pitch and the increased jig pitch are equal to each other. As for the oblique stretching in this embodiment, for example, refer to the description of japanese patent application laid-open No. 2014-194484 and the like. The bias stretching of this embodiment may include: the distance between the left and right clamps is enlarged, and the clamp pitch of one clamp is increased from P 1 Increase to P 2 While simultaneously making the clamp pitch of the other clamp from P 1 Is reduced to P 3 Thereby subjecting the film to oblique stretching (oblique stretching No. 1); and maintaining the clamp pitch of the one clamp at P so that the clamp pitches of the left and right clamps are equal while the distance between the left and right clamps is increased 2 Or reduced to P 4 And increasing the clamp pitch of the other clamp to P 2 Or P 4 Thereby subjecting the film to oblique stretching (2 nd oblique stretching).
In the above-described first oblique stretching, the slow axis can be developed with high uniaxiality and in-plane orientation in a desired direction (for example, a direction of 45 ° with respect to the longitudinal direction) by performing the oblique stretching while extending one end portion of the film in the longitudinal direction and contracting the other end portion in the longitudinal direction. In addition, in the 2 nd diagonal stretching, the diagonal stretching is performed while reducing the difference between the left and right jig pitches, so that the additional stress can be relaxed and the stretching can be sufficiently performed in the diagonal direction.
In the oblique stretching of the three embodiments described above, since the film can be released from the left and right clamps in a state where the moving speeds of the clamps become equal, a variation in the film transport speed or the like is less likely to occur when the left and right clamps are released, and the subsequent winding of the film can be appropriately performed.
Fig. 6A and 6B are schematic diagrams showing an example of the profile of the jig pitch in the oblique stretching including the 1 st oblique stretching and the 2 nd oblique stretching. The followingThe 1 st oblique stretching will be specifically described with reference to these drawings. In addition, in fig. 6A and 6B, the horizontal axis corresponds to the travel distance of the jig. At the start of the 1 st oblique stretching, the left and right jig pitches are set to P 1 。P 1 Typically the clip pitch when gripping the film. At the same time as the 1 st oblique stretching starts, the grip pitch of one grip (hereinafter sometimes referred to as the 1 st grip) starts to be increased, and the grip pitch of the other grip (hereinafter sometimes referred to as the 2 nd grip) starts to be decreased. In the 1 st oblique stretching, the clamp pitch of the 1 st clamp is increased to P 2 Reducing the clamp pitch of the 2 nd clamp to P 3 . Therefore, it is set as: at the end of the 1 st oblique stretching (at the start of the 2 nd oblique stretching), the 2 nd jig is at a jig pitch P 3 Moving, 1 st gripper with gripper pitch P 2 And (4) moving. In addition, the ratio of the gripper pitches may substantially correspond to the ratio of the moving speeds of the grippers.
In fig. 6A and 6B, both the timing to start increasing the jig pitch of the 1 st jig and the timing to start decreasing the jig pitch of the 2 nd jig are set to the timing to start the 1 st oblique stretching, but unlike the illustrated example, the jig pitch of the 2 nd jig may be started to decrease after the jig pitch of the 1 st jig is started to increase, or the jig pitch of the 1 st jig may be started to increase after the jig pitch of the 2 nd jig is started to decrease. In a preferred embodiment, the gripper pitch of the 2 nd gripper starts to decrease after the gripper pitch of the 1 st gripper starts to increase. According to the above embodiment, since the film is already stretched in the width direction to some extent (preferably about 1.2 to 2.0 times), wrinkles are less likely to occur even if the clip pitch of the 2 nd clip is greatly reduced. Therefore, it is possible to perform more acute oblique stretching, and a retardation film having high uniaxiality and in-plane orientation can be preferably obtained.
Similarly, in fig. 6A and 6B, the increase in the jig pitch of the 1 st jig and the decrease in the jig pitch of the 2 nd jig are both continued until the 1 st oblique stretching is finished (the 2 nd oblique stretching is started), but unlike the illustrated example, either the increase or decrease in the jig pitch may be finished earlier than the other, and the jig pitch may be maintained until the other is finished (until the 1 st oblique stretching is finished).
Rate of change of grip spacing (P) of 1 st grip 2 /P 1 ) Preferably 1.25 to 1.75, more preferably 1.30 to 1.70, and still more preferably 1.35 to 1.65. In addition, the rate of change of the chuck pitch (P) of the 2 nd chuck 3 /P 1 ) For example, the content is 0.50 or more and less than 1, preferably 0.50 to 0.95, more preferably 0.55 to 0.90, and still more preferably 0.55 to 0.85. If the rate of change of the clip pitch is within the above range, the slow axis can be expressed 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 distance between the jigs can be adjusted by adjusting the distance between the distance setting rail of the stretching device and the reference rail to position the slider.
The stretching ratio in the width direction of the film in the 1 st oblique stretching (film width at the end of the 1 st oblique stretching/film width before the 1 st oblique stretching) is preferably 1.1 to 3.0 times, more preferably 1.2 to 2.5 times, and further preferably 1.25 to 2.0 times. If the draw ratio is less than 1.1 times, white iron skin-like wrinkles may occur at the end portions on the contraction side. If the stretching ratio exceeds 3.0 times, the resulting retardation film will have high biaxial properties, and when the retardation film is applied to a circularly polarizing plate or the like, the viewing angle characteristics may be degraded.
In one embodiment, the 1 st oblique stretching is performed such that the product of the rate of change of the clip pitch of the 1 st clip and the rate of change of the clip pitch of the 2 nd clip is preferably 0.7 to 1.5, more preferably 0.8 to 1.45, and still more preferably 0.85 to 1.40. When the product of the change rates is within the above range, a retardation film having high uniaxiality and in-plane orientation can be obtained.
Next, an embodiment of the 2 nd oblique stretching will be specifically described with reference to fig. 6A. In the 2 nd oblique drawing of the present embodiment, the clip pitch of the 2 nd clip is set from P 3 Increase to P 2 . On the other hand, during the 2 nd diagonal drawing, the jig pitch of the 1 st jig is maintained at P 2 And is not changed. Thus, in the first place2 at the end of the diagonal drawing, both the left and right jigs are set to have a jig pitch P 2 The movement is performed.
The rate of change (P) of the clip pitch of the 2 nd clip in the 2 nd oblique stretching of the embodiment shown in FIG. 6A 2 /P 3 ) Without limitation so long as the effects of the present invention are not impaired. The rate of change (P) 2 /P 3 ) For example, 1.3 to 4.0, preferably 1.5 to 3.0.
Another embodiment of the 2 nd oblique stretching will be specifically described with reference to fig. 6B. In the 2 nd oblique stretching of the present embodiment, the jig pitch of the 1 st jig is decreased and the jig pitch of the 2 nd jig is increased. Specifically, the clamp pitch of the 1 st clamp is set to be P 2 Decrease to P 4 Making the distance between the 2 nd clamps from P 3 Increase to P 4 . Therefore, at the end of the 2 nd diagonal drawing, both the left and right jigs are set at the jig pitch P 4 The movement is performed. In the illustrated example, the 1 st jig and the 2 nd jig start decreasing the jig pitch and increasing the jig pitch at the same time as the 2 nd diagonal drawing starts, but they may start at different timings. Similarly, the decrease in the jig pitch of the 1 st jig and the increase in the jig pitch of the 2 nd jig may be finished at different timings.
The rate of change (P) of the chuck pitch of the 1 st chuck in the 2 nd diagonal drawing of the embodiment shown in FIG. 6B 4 /P 2 ) And rate of change of grip spacing (P) of 2 nd grip 4 /P 3 ) There is no limitation as long as the effects of the present invention are not impaired. Rate of change (P) 4 /P 2 ) For example, 0.4 or more and less than 1.0, preferably 0.6 to 0.95. In addition, the rate of change (P) 4 /P 3 ) For example, it is more than 1.0 and 2.0 or less, preferably 1.2 to 1.8. Preferably P 4 Is P 1 The above. If P 4 <P 1 Then, the following problems may occur: wrinkles occur at the end portions, and biaxial deformation is high.
The stretching ratio of the film in the width direction at the time of the 2 nd oblique stretching (film width at the end of the 2 nd oblique stretching/film width at the end of the 1 st oblique stretching) is preferably 1.1 to 3.0 times, more preferably 1.2 to 2.5 times, and still more preferably 1.25 to 2.0 times. If the draw ratio is less than 1.1 times, a white iron skin-like wrinkle may occur at the end portion on the contracted side. If the stretching ratio exceeds 3.0 times, the resulting retardation film has high biaxial properties, and when the retardation film is applied to a circularly polarizing plate or the like, the viewing angle characteristics may be degraded. From the same viewpoint as described above, the stretching ratio in the width direction in the 1 st oblique stretching and the 2 nd oblique stretching (the film width at the end of the 2 nd oblique stretching/the film width before the 1 st oblique stretching) is preferably 1.2 times to 4.0 times, and more preferably 1.4 times to 3.0 times.
The oblique stretching may be typically performed at a temperature T2. The temperature T2 is preferably from Tg-20 ℃ to Tg +30 ℃, more preferably from Tg-10 ℃ to Tg +20 ℃, and particularly preferably around Tg, relative to the glass transition temperature (Tg) of the film. The temperature T2 varies depending on the film used, and is, for example, 70 ℃ to 180 ℃, preferably 80 ℃ to 170 ℃. The difference (T1-T2) between the temperature T1 and the temperature T2 is preferably. + -. 2 ℃ or more, more preferably. + -. 5 ℃ or more. In one embodiment, T1> T2, whereby a film heated to temperature T1 in a pre-heating zone can be cooled to temperature T2.
As described above, the transverse contraction treatment may be performed after the oblique stretching. Regarding this treatment after the oblique stretching, reference can be made to paragraphs 0029 to 0032 of japanese patent laid-open No. 2014-194483.
The film is transported from the stretching zone to the heat-fixing zone by the movement of the left and right clamps. At this time, typically the left and right clamps are simultaneously transferred to the heat fixing zone. In other words, the film is transferred to the thermal fixing zone in a state where a line connecting the centers of the left and right clamps that clamp the film is substantially orthogonal to the film conveyance direction.
A-4. Heat fixation Process
In the heat-fixing zone D, the obliquely stretched film is subjected to heat treatment. In the heat fixation region D before the later-described correction is applied, the distance between the left and right jigs is maintained during the heat treatment. As the jig pitch in the longitudinal direction, the jig pitch at the end of the oblique stretching can be maintained, but may be gradually decreased as necessary to relax the stress. In this case, the reduction rate of the jig pitch of the left and right jigs [ (jig pitch at the start of thermal fixing-jig pitch at the end of thermal fixing)/jig pitch at the start of thermal fixing × 100] is, for example, 0.5% to 5%, preferably 1% to 3%.
The heat treatment may typically be performed at a temperature T3. The temperature T3 may vary depending on the film to be stretched, and T2. Gtoreq.T 3 may be used, or T2< T3 may be used. Generally, T2 ≧ T3 is used for the film as an amorphous material, and T2< T3 is used for the film as a crystalline material to perform the crystallization treatment. When T2. Gtoreq.T 3, the difference between the temperatures T2 and T3 (T2-T3) is preferably 0 ℃ to 50 ℃. The heat treatment time is typically 10 seconds to 10 minutes.
A-5 Release Process
At any position of the release zone E, the film is released from the jig. In the releasing zone E, generally, the film after the heat-fixing is not stretched in the transverse direction nor in the longitudinal direction, but the film is cooled to a desired temperature, followed by releasing the film from the jig.
The film temperature when released from the jig is, for example, 150 ℃ or lower, preferably 70 to 140 ℃, and more preferably 80 to 130 ℃.
The stretched film released from the jig is sent out from the outlet of the stretching device and is supplied to the measurement of the in-plane retardation and the like.
A-6. Measuring Process for variation in-plane retardation and/or orientation Angle
In one embodiment, the film fed out from the outlet of the stretching device is conveyed by rollers, and the in-plane retardation and the like at a plurality of locations in the width direction are measured on line. The difference between the maximum value and the minimum value of the in-plane retardation or the like measured at a plurality of locations in the width direction is calculated as the deviation of the in-plane retardation or the like in the width direction.
For example, in the embodiment shown in fig. 7, the measuring device 400 is provided above the center and the right and left ends of the film 1 in the width direction on the transport line, and the in-plane retardation and the like of the transported film are measured at fixed points at 3 locations in the width direction. The measurement site may be different from the illustrated example, and may be set to 2 sites in total, or 2 sites in total only at the left and right end portions, or 2 sites, 3 sites, 4 sites, 5 sites, or more at equal intervals in the width direction of the film, for example. Preferably, in-plane retardation or the like is measured at 2 or more locations including the left and right end portions (for example, within 25mm from the left and right end edges).
The in-plane retardation and the like may be measured continuously or at predetermined intervals. For example, the in-plane retardation and the like can be measured at intervals of 0.1 to 1 second, preferably 0.1 to 0.5 second.
The measurement wavelength of the in-plane retardation and the like can be appropriately set according to the purpose. For example, the measurement wavelength of the in-plane retardation or the like may be in the range of 500nm to 600 nm. In the present specification, re (λ) is an in-plane retardation of the film measured at 23 ℃ with light having a wavelength of λ nm. Thus, re (550) is the in-plane retardation of the film measured at 23 ℃ with light having a wavelength of 550 nm. When the thickness of the film is set to d (nm), re (λ) can be represented by the formula: re (λ) = (nx-ny) × d. Here, nx is a refractive index in a direction in which the in-plane refractive index reaches a maximum (i.e., the slow axis direction), and ny is a refractive index in a direction orthogonal to the slow axis (i.e., the fast axis direction) in the plane.
The in-plane retardation and the like may be measured by cutting and removing the left and right ends in the width direction of the stretched film released from the jig. By measuring the in-plane retardation or the like in a state where both end portions are removed, more accurate measurement results can be obtained.
The width of the cut and removed end portions is, for example, 20mm to 600mm, preferably 100mm to 500mm, independently of each other. The end portions can be cut and removed by a usual slitting process.
A-7 correction Process
In the above measurement, when the variation in-plane phase difference or the like exceeds a predetermined reference, the distance between the left and right jigs and/or the jig pitch of the left and right jigs in the thermal fixing step are corrected by tracing the upstream of the production line. More specifically, the correction is performed so that the distance between the left and right jigs and/or the jig pitch of the left and right jigs are different before and after the correction and at the time of completion of the thermal fixing. Preferably, the correction is performed so that the distance between the left and right jigs and the jig pitch of the left and right jigs are different before and after the correction and at the time of completion of the thermal fixing. On the other hand, when the deviation is equal to or less than the predetermined reference, the production of the stretched film may be continued under the same conditions as before without performing the above correction.
In one embodiment, the above correction can be performed when the variation of the in-plane retardation Re (550) is, for example, 8nm or more, 7nm or more, or 6nm or more.
In one embodiment, the correction may be performed when the deviation of the orientation angle is, for example, 6 ° or more, 5 ° or more, or 4 ° or more.
When the jig pitch of the left and right jigs is corrected, the correction rate can be appropriately set according to the degree of variation in-plane phase difference or the like. The correction of the jig pitch may be performed at a correction rate defined by the following formula (1), for example, of 0.5% to 4.0%, preferably 1.0% to 3.5%, and more preferably 1.5% to 3.0%. Further, the same or different correction rates may be applied to the left and right jigs as long as the effects of the present invention are obtained, but it is preferable to apply the same correction rate. By making the jig pitch correction rates of the left and right jigs the same, it is possible to preferably reduce variations in-plane phase difference and the like, and at the same time, the timing of releasing the left and right jigs is matched with the traveling speed at that time, and therefore, there is an advantage that it is possible to preferably perform conveyance and winding.
Correction rate (%) = (jig pitch at the end of thermal fixation after correction-jig pitch at the end of thermal fixation before correction)/(jig pitch at the end of thermal fixation before correction) × 100 formula (1)
When the distance between the left and right jigs is to be corrected, the correction rate can be appropriately set according to the degree of variation such as in-plane phase difference. The distance between the left and right jigs may be corrected at a correction rate defined by the following formula (2), for example, of 0.5% to 3.0%, preferably 1.0% to 2.5%, and more preferably 1.0% to 2.0%. By correcting the distance between the left and right jigs, an effect of making the shrinkage behavior of the film uniform can be obtained. The correction rate of the distance between the left and right clips may substantially correspond to the rate of transverse stretching or transverse contraction of the film.
Correction rate (%) = (distance between left and right jigs at the end of thermal fixation after correction-distance between left and right jigs at the end of thermal fixation before correction)/(distance between left and right jigs at the end of thermal fixation before correction) × 100 formula (2)
The above correction may be made at any timing in the heat setting. In one embodiment, the above correction is performed gradually from the beginning to the end of the heat-fixing zone (i.e., throughout the heat-fixing process). In another embodiment, the above-described correction is completed from the beginning of the thermal fixing zone to the middle thereof, and the heat treatment is continued in a corrected state until the end of the thermal fixing zone. In yet another embodiment, the above correction is made from part way through the thermal fixation area to the terminal.
If necessary, the stretched film obtained by the correction in the heat-setting may be subjected to measurement of variation such as in-plane retardation, and the correction may be performed each time the variation exceeds a predetermined reference. In one embodiment, the variation such as in-plane retardation can be continuously measured during the production of the stretched film, and the correction step can be performed every time the variation exceeds a predetermined reference.
b. Film for stretching object
In the production method of the present invention, any appropriate film may be used. For example, a resin film to which a retardation film can be applied is given. Examples of the material constituting such a film include polycarbonate-based resins, polyvinyl acetal-based resins, cycloolefin-based resins, acrylic-based resins, cellulose ester-based resins, cellulose-based resins, polyester carbonate-based resins, olefin-based resins, polyurethane-based resins, and the like. Preferred are polycarbonate-based resins, cellulose ester-based resins, polyester carbonate-based resins, and cycloolefin-based resins. This is because a retardation film exhibiting wavelength dependence of so-called reverse dispersion can be obtained by using these resins. These resins may be used alone or in combination according to desired characteristics.
As the polycarbonate-based resin, any appropriate polycarbonate-based resin can be used. For example, a polycarbonate-based resin containing a structural unit derived from a dihydroxy compound is preferable. As specific examples of the dihydroxy compound, there may be mentioned, examples thereof include 9,9-bis (4-hydroxyphenyl) fluorene, 9,9-bis (4-hydroxy-3-methylphenyl) fluorene, 9,9-bis (4-hydroxy-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-hydroxyethoxy) -3-isobutylphenyl) fluorene, 9,9-bis (4-hydroxyethoxy) -3-isopropylphenyl) fluorene, 9-bis (4- (2-hydroxyethoxy) -3-isobutylphenyl) fluorene, 9,9-bis (4-hydroxyethoxy) -fluorene, 9-hydroxyethoxy) -fluorene, 9,9-2-isobutene, 9-2-hydroxyethoxy) -fluorene, 9-3-bis (4-hydroxyethoxy) fluorene, and 9-3-isobutene, 9-3-2-isobutene, 9-bis (4-hydroxyethoxy) fluorene 9, 9-bis (4- (2-hydroxyethoxy) -3-cyclohexylphenyl) fluorene, 9-bis (4- (2-hydroxyethoxy) -3-phenylphenyl) fluorene, 9-bis (4- (2-hydroxyethoxy) -3, 5-dimethylphenyl) fluorene, 9-bis (4- (2-hydroxyethoxy) -3-tert-butyl-6-methylphenyl) fluorene, 9-bis (4- (3-hydroxy-2, 2-dimethylpropoxy) phenyl) fluorene and the like. The polycarbonate resin may contain, in addition to the structural unit derived from the above dihydroxy compound, a structural unit derived from a dihydroxy compound such as isosorbide, isomannide, 1,4, 6-dianhydro-L-iditol (isoidide), spiroglycol, dioxane glycol, diethylene glycol (DEG), triethylene glycol (TEG), polyethylene glycol (PEG), cyclohexanedimethanol (CHDM), tricyclodecanedimethanol (TCDDM), or a bisphenol.
Details of the polycarbonate-based resin as described above are described in, for example, japanese unexamined patent publication No. 2012-67300 and japanese patent No. 3325560. The contents of the patent document are incorporated herein by reference.
The glass transition temperature of the polycarbonate resin is preferably 110 to 250 ℃ and more preferably 120 to 230 ℃. If the glass transition temperature is too low, the heat resistance tends to be poor, and dimensional change may occur after film formation. If the glass transition temperature is too high, the molding stability during film molding may be deteriorated, and the transparency of the film may be impaired. The glass transition temperature was determined in accordance with JIS K7121 (1987).
As the polyvinyl acetal resin, any suitable polyvinyl acetal resin can be used. Typically, the polyvinyl acetal resin can be obtained by condensation reaction of at least two aldehyde compounds and/or ketone compounds with a polyvinyl alcohol resin. Specific examples of polyvinyl acetal resins and detailed production methods are described in, for example, jp 2007-161994 a. The contents of this description are incorporated herein by reference.
The stretched film (retardation film) obtained by stretching the film to be stretched is preferably one having a refractive index characteristic showing a relationship of nx > ny. In one embodiment, the retardation film may preferably function as a λ/4 plate. In the present embodiment, the in-plane retardation Re (550) of the retardation film (. Lamda./4 plate) is preferably 100 to 180nm, more preferably 135 to 155nm. In another embodiment, the retardation film may preferably function as a λ/2 plate. In the present embodiment, the in-plane retardation Re (550) of the retardation film (. Lamda./2 plate) is preferably 230 to 310nm, more preferably 250 to 290nm.
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, methods for producing a retardation film having an in-plane retardation Re (550) of 100nm to 180nm by oblique stretching are disclosed in detail in japanese patent application laid-open nos. 2013-54338, 2014-194482, 2014-238524, 2014-194484, and the like. Therefore, those skilled in the art can set appropriate oblique stretching conditions in view of this disclosure.
When a circularly polarizing plate is produced using one retardation film or when the direction of linearly polarized light is rotated by 90 ° using one retardation film, the slow axis direction of the retardation film to be used is preferably 30 ° to 60 ° or 120 ° to 150 °, more preferably 38 ° to 52 ° or 128 ° to 142 °, further preferably 43 ° to 47 ° or 133 ° to 137 °, and particularly preferably about 45 ° or 135 ° with respect to the longitudinal direction of the film.
When a circularly polarizing plate is produced using two retardation films (specifically, a λ/2 plate and a λ/4 plate), the slow axis direction of the retardation film (λ/2 plate) used is preferably 60 ° to 90 °, more preferably 65 ° to 85 °, and particularly preferably about 75 ° with respect to the longitudinal 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 longitudinal direction of the film.
The retardation film preferably exhibits wavelength dependence of so-called reverse dispersion. Specifically, the in-plane retardation 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)～100×10 -12 (m 2 /N), more preferably 5X 10 -12 (m 2 /N)～50×10 -12 (m 2 /N)。
C. Optical laminate and method for producing same
The stretched film obtained by the production method of the present invention can be used as an optical laminate by bonding it to another optical film. For example, the retardation film obtained by the production method of the present invention can be bonded to a polarizing plate and preferably used as a circularly polarizing plate.
Fig. 8 is a schematic cross-sectional view of an example of the circularly polarizing plate as described above. The circularly polarizing plate 500 illustrated in the figure includes a polarizer 510, a 1 st protective film 520 disposed on one side of the polarizer 510, a 2 nd protective film 530 disposed on the other side of the polarizer 510, and a retardation film 540 disposed outside the 2 nd protective film 530. The retardation film 540 is a stretched film (for example, a λ/4 plate) obtained by the production method described in the section a. The 2 nd protective film 530 may also be omitted. In this case, the retardation film 540 may function as a protective film of the polarizer. The angle formed by the absorption axis of polarizer 510 and the slow axis of retardation film 540 is preferably 30 ° to 60 °, more preferably 38 ° to 52 °, still more preferably 43 ° to 47 °, and particularly preferably about 45 °.
The retardation film obtained by the production method of the present invention has a long shape and has a slow axis in an oblique direction (direction of, for example, 45 ° with respect to the longitudinal direction). In many cases, the long polarizer has an absorption axis in the longitudinal direction or the width direction. Therefore, if the retardation film obtained by the production method of the present invention is used, a so-called roll-to-roll (roll-to-roll) can be used to produce a circular polarizing plate with extremely excellent production efficiency. Further, the roll-to-roll method refers to the following method: the long films are continuously laminated while being aligned in the longitudinal direction thereof by being roll-fed.
In one embodiment, a method for manufacturing an optical laminate according to the present invention includes: a long stretched film obtained by the method for producing a stretched film described in item a; and continuously laminating the optical film and the stretched film while aligning the optical film and the stretched film in the longitudinal direction.
Examples
The present invention will be specifically described below 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 of
The measurement was carried out using a dial gauge (product name "DG-205 type pds-2" manufactured by PEACOCK Co., ltd.).
(2) Phase difference value
An in-plane retardation Re (550) at a wavelength of 550nm was measured at 0.5-second intervals using an in-line phase difference meter (KOBRA series, manufactured by prince instruments).
(3) Orientation angle (slow axis display direction)
The orientation angle θ at a wavelength of 550nm was measured at 0.5-second intervals using an on-line phase difference meter (KOBRA series, manufactured by Oji instruments Co., ltd.).
(4) Glass transition temperature (Tg)
Measured according to JIS K7121.
< example 1>
(preparation of a polyester carbonate resin film)
Polymerization was carried out using a batch polymerization apparatus formed of 2 vertical reactors equipped with a stirring paddle and a reflux cooler controlled at 100 ℃. Adding bis [9- (2-phenoxycarbonylethyl) fluoren-9-yl]29.60 parts by mass (0.046 mol) of methane, 29.21 parts by mass (0.200 mol) of ISB, 42.28 parts by mass (0.139 mol) of SPG, 63.77 parts by mass (0.298 mol) of DPC, and 1.19 × 10 of calcium acetate 1 hydrate as a catalyst -2 Mass portion (6.78X 10) -5 Moles). After the inside of the reactor was replaced with nitrogen under reduced pressure, the reactor was heated with a heat medium, and stirring was started when the internal temperature reached 100 ℃.40 minutes after the start of the temperature increase, the internal temperature was set to 220 ℃ and the pressure reduction was started while controlling the temperature to be maintained, and the pressure was set to 13.3kPa for 90 minutes after the temperature reached 220 ℃. Phenol vapor produced as a by-product during the polymerization reaction was introduced into a reflux condenser at 100 ℃ to return a monomer component contained in the phenol vapor in a certain amount to the reactor, and the phenol vapor that was not condensed was introduced into a condenser at 45 ℃ to be recovered. After nitrogen was introduced into the 1 st reactor and the pressure was once returned to atmospheric pressure, the reaction solution in the 1 st reactor, which had been oligomerized, was transferred to the 2 nd reactor. Subsequently, the temperature increase and pressure reduction in the 2 nd reactor were started, and the internal temperature and pressure were set to 240 ℃ and 0.2kPa for 50 minutes. Then, polymerization was carried out until a predetermined stirring power was reached. When the predetermined power was reached, nitrogen was introduced into the reactor to repress the reactor, the produced polyester carbonate was extruded into water, and the strand was cut to obtain pellets. The Tg of the polyester carbonate resin obtained was 140 ℃.
The obtained polyester carbonate resin was vacuum-dried at 80 ℃ for 5 hours, and then a resin film having a thickness of 135 μm was produced using a film-forming apparatus equipped with a single-screw extruder (manufactured by Toshiba machine Co., ltd., cylinder set temperature: 250 ℃), a T-die (width 200mm, set temperature: 250 ℃), chill rolls (set temperature: 120 to 130 ℃) and a winder.
(production of stretched film)
The polyester carbonate resin film obtained as described above was obliquely stretched using a stretching apparatus shown in fig. 2 to 4 to obtain a retardation film.
Specifically, the left and right ends of the polyester carbonate resin film were held at the entrance of the stretching apparatus by the left and right clamps at the same timing and at the same clamp pitch. The line connecting the centers of the left and right clamps when clamping the film is orthogonal to the film conveying direction, and the distance between the clamps and the clamp pitch (P) of the left and right clamps 1 ) 150mm and 125mm respectively. The film was then transferred to preheat zone B, preheated to 145 ℃. In the preheating zone B, the distance between the clamps and the distance between the clamps are maintained.
Then, while the film enters the stretching zone C, the gripper pitch of the right-hand gripper starts to increase and the gripper pitch of the left-hand gripper starts to decrease so that the gripper pitch of the right-hand gripper increases to P 2 While simultaneously reducing the clamp pitch of the left clamp to P 3 (oblique stretching 1 st). At this time, the rate of change of the clamp pitch (P) of the right clamp 2 /P 1 ) 1.42, rate of change of grip pitch (P) of left grip 3 /P 1 ) 0.65, and a transverse stretching magnification of 1.45 times the original width of the film. Then, the clamp pitch of the right clamp is maintained at P 2 In the state of (2), the jig pitch of the left jig is started to be increased from P 3 Increase to P 2 (oblique stretching No. 2). During this time the rate of change of the clamp spacing (P) of the left clamp 2 /P 3 ) The stretching ratio in the transverse direction to the original width of the film was 1.9 times (distance between left and right clamps at the end of the stretching region: 285mm, clamp spacing of the left and right clamps: 177.5 mm). The stretching zone C was set to Tg +3.2 deg.C (143.2 deg.C).
Next, the film is transferred to the heat fixing zone D in such a manner that a pair of left and right clamps holding the film simultaneously enter the heat fixing zone. In the heat-fixing zone D, the film was held at 125 ℃ for 60 seconds and heat-fixed while maintaining the inter-jig distance and the inter-jig distance of the left and right jigs at the terminal end of the stretching zone C.
The film thermally fixed by the operation as described above is cooled to 100 ℃ in the release zone E, and then released from the left and right clamps.
(measurement of in-plane retardation and orientation Angle)
The left and right ends of the stretched film released from the jig and sent out from the stretching apparatus were each cut by 25mm. Subsequently, while carrying out roll conveyance, the in-plane retardation Re (550) and the orientation angle (angle with respect to the longitudinal direction) were measured at fixed points at 3 positions in total inside 25mm from the center and the left and right ends of the film in the width direction. As a result, the in-plane retardation Re (550) and the variation in orientation angle were 16nm and 8 °, respectively.
(correction of inter-jig distance and jig spacing)
In the heat-fixing zone upstream of the production line, the following corrections are made: the distance between the left and right jigs was increased by 2% from the starting end to the ending end, and at the same time, the jig pitch of the left and right jigs was increased by 1.5% (the distance between the left and right jigs at the ending end of the heat-fixing zone: 290.7mm, the jig pitch: 180.2 mm).
The stretched film obtained by the heat fixation after the correction was cut at each of the left and right ends by 25mm in the same manner as described above, and then the in-plane retardation Re (550) and the orientation angle (angle with respect to the longitudinal direction) were measured at fixed points at 3 positions in total in the width direction. The results are shown in Table 1.
< example 2>
In the correction of the inter-jig distance and the jig pitch, the following correction was performed: a stretched film was obtained in the same manner as in example 1, except that the distance between the left and right clips was increased by 2% from the start end to the end of the heat-fixing zone, and the clip pitch of the left and right clips was increased by 2%. The obtained stretched film was cut at each of the left and right ends by 25mm in the same manner as described above, and then the in-plane retardation Re (550) and the orientation angle (angle with respect to the longitudinal direction) were measured at 3 fixed points in total in the width direction. The results are shown in Table 1.
< example 3>
In the correction of the inter-jig distance and the jig pitch, the following correction was performed: a stretched film was obtained in the same manner as in example 1, except that the distance between the left and right clips was increased by 1% from the start end to the end of the heat-fixing zone, and the clip pitch of the left and right clips was increased by 3%. The obtained stretched film was cut at each of the left and right ends by 25mm in the same manner as described above, and then the in-plane retardation Re (550) and the orientation angle (angle with respect to the longitudinal direction) were measured at 3 fixed points in total in the width direction. The results are shown in Table 1.
[ evaluation of appearance and handling ]
With respect to the stretched films obtained in examples and comparative examples (stretched films obtained before the correction step was performed), the appearance and the handling property were evaluated by visual observation according to the following criteria. The results are shown in Table 1.
Good: wrinkles and slacks were not observed in the stretched film during roll conveyance
X: wrinkles and/or slackness can be confirmed on the stretched film during roll conveyance
TABLE 1
As shown in table 1, when a variation in the width direction occurs such as an in-plane retardation in the production of a long obliquely-stretched film, such a variation can be reduced by correcting the distance between the left and right jigs and/or the jig pitch of the left and right jigs in the heat setting.
Industrial applicability
The method for producing a stretched film of the present invention is preferably used for producing a retardation film, and as a result, can contribute to production of an image display device such as a liquid crystal display device (LCD) or an organic electroluminescent display device (OLED).
Claims (8)
1. A method of manufacturing a stretched film, comprising: clamping the left and right ends of the long film in the width direction by a variable-pitch left and right jig with a vertical jig pitch varying;
moving the left and right clamps while changing the clamp pitch of at least one of the left and right clamps, thereby obliquely stretching the film;
heat fixing the film;
releasing the film from the left and right clamps; and
the in-plane retardation and/or the variation of the orientation angle in the width direction of the film were measured,
when the deviation of the in-plane phase difference and/or the orientation angle exceeds a predetermined reference, the distance between the left and right jigs and/or the jig pitch of the left and right jigs during the heat setting are corrected.
2. The method of producing a stretched film according to claim 1, wherein the left and right ends of the film released from the left and right clips are cut and removed, and then the in-plane retardation and/or the variation in orientation angle in the width direction are measured.
3. The method of producing a stretched film according to claim 1 or 2, wherein the correction of the clip pitch of the left and right clips is 0.5% to 4.0% at each correction rate defined by the following formula (1),
correction rate (%) = (jig pitch at the end of thermal fixation after correction-jig pitch at the end of thermal fixation before correction)/(jig pitch at the end of thermal fixation before correction) × 100 formula (1).
4. The method of producing a stretched film according to any one of claims 1 to 3, wherein the correction of the distance between the left and right clips is performed at a correction rate defined by the following formula (2) of 0.5% to 3.0%,
correction rate (%) = (distance between left and right jigs at the end of thermal fixation after correction-distance between left and right jigs at the end of thermal fixation before correction)/(distance between left and right jigs at the end of thermal fixation before correction) × 100 formula (2).
5. The method for producing a stretched film according to any one of claims 1 to 4, wherein the oblique stretching comprises: (i) While making the clamp pitch of one of the left and right clamps from P 1 Increase to P 2 While making the distance between the clamps of the other clamp from P 1 Is reduced to P 3 (ii) a And (ii) changing the jig pitch of each jig so that the reduced jig pitch and the increased jig pitch are equal to each other.
6. The method for producing a stretched film according to claim 5, wherein P 2 /P 1 Is 1.25 to 1.75 of P 3 /P 1 Is 0.50 or more and less than 1.
7. A method of manufacturing an optical laminate, comprising: a long stretched film obtained by the production method according to any one of claims 1 to 6; and
the long optical film and the long stretched film are continuously laminated while being aligned in the longitudinal direction thereof.
8. The method of manufacturing an optical laminate according to claim 7, wherein the optical film is a polarizing plate and the stretched film is a λ/4 plate or a λ/2 plate.
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| CN116252463A (en) * | 2023-05-15 | 2023-06-13 | 龙华相位新材料(绵阳)股份有限公司 | Film stretch forming device and forming method |
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| JP7059429B1 (en) | 2022-04-25 |
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| CN115782147B (en) | 2023-06-23 |
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