TWI780395B - Manufacturing method of stretched film - Google Patents

Abstract

The object of the present invention is to reduce the slack generated in the obliquely stretched film. The solution is a method for manufacturing a stretched film. The method includes the following steps: using left and right clamps to respectively hold the left and right ends of the strip-shaped film in the width direction. ; while changing the grip distance of at least one of the left and right grippers, it is moved to extend the film obliquely; the film is released from the left and right grippers; the film is transported by rollers, and the film is detected The amount of slack between the conveying rollers and the location where the slack occurs; and, performing correction based on the detection result, the correction is to change the gripper pitch of at least one of the left and right grippers located upstream of the conveying line.

Description

Manufacturing method of stretched film

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

In image display devices such as liquid crystal display devices (LCD) and organic electroluminescent display devices (OLED), circular polarizing plates are used for the purpose of improving display characteristics and anti-reflection. Typically, a circular polarizer has a polarizer and a retardation film (typically a λ/4 plate) laminated so that the absorption axis of the polarizer forms an angle of 45° with the slow axis of the retardation film. In the past, retardation films were typically produced by uniaxial stretching or biaxial stretching in the longitudinal and/or transverse directions, so the slow axis was mostly in the transverse direction (width direction) or Appears vertically (lengthwise). As a result, when producing a circular polarizing plate, the retardation film must be cut so as to form an angle of 45° with respect to the width direction or the longitudinal direction, and bonded to the polarizing plate (polarizer) one by one.

In addition, in order to ensure the broadband performance of the circular polarizing plate, two retardation films, the λ/4 plate and the λ/2 plate, may be laminated. In this case, it is necessary to laminate the λ/2 plate so as to form an angle of 75° with respect to the absorption axis of the polarizer, and to laminate the λ/4 plate so as to form an angle of 15° with respect to the absorption axis of the polarizer. In this case, when making a circular polarizing plate, it is also necessary to cut out the retardation film so that an angle of 15° and an angle of 75° are formed with respect to the width direction or the longitudinal direction, and attach the polarizing plate (polarizer) one by one. pieces) fit.

Furthermore, in another embodiment, in order to prevent the light from the notebook PC from being reflected on the keyboard, etc., for the purpose of rotating the direction of the linearly polarized light emitted from the polarizer by 90°, λ is used on the viewing side of the polarizer. /2 plates. In this case, too, the retardation film must be cut so as to form an angle of 45° with respect to the width direction or the longitudinal direction, and bonded to the polarizing plate (polarizer) one by one.

In order to solve such a problem, the following technology has been proposed: use variable-pitch left and right clamps whose vertical clamp pitch can be changed, respectively hold the left and right ends of the elongated film in the width direction, and make at least one of the left and right clamps The clip pitch is changed to extend in an oblique direction (hereinafter also referred to as "inclined extension"), whereby the slow axis of the retardation film appears in an oblique direction (for example, Patent Document 1). However, in an obliquely stretched film obtained by such a technique, slack (sagging) may occur at the ends in the width direction. When such a slack-generated film is wound, wrinkles and scratches may occur in the obtained film roll. In addition, if the slack film is bonded to other optical films, uneven application of adhesives and adhesives or uncoated parts may occur, or wrinkles and scratches may occur in the obtained optical layered product. Condition.

prior art literature patent documents Patent Document 1: Japanese Patent No. 4845619

The problem to be solved by the invention The present invention was made to solve the above-mentioned problems, and its main purpose is to reduce slack generated in a film stretched obliquely.

(上述式中，d表示檢測出的鬆弛量(單位：mm)，W表示上述薄膜每m的質量(單位：g)，g表示重力加速度，S表示上述輸送輥間的距離(單位：mm)，H表示對產生從式(1)計算之鬆弛的端部側施加的張力(單位：N/m))。 在一實施形態中，上述使夾具間距變化的校正係在上述傾斜延伸中進行，此時的氣體環境溫度為上述薄膜的Tg～Tg+20℃。 根據本發明的另一態樣，提供一種光學積層體之製造方法，該製造方法包含以下步驟：利用上述延伸薄膜之製造方法獲得長條狀延伸薄膜；及，一邊輸送長條狀光學薄膜與該長條狀延伸薄膜，一邊使其長邊方向對齊來連續貼合。 在一實施形態中，上述光學薄膜為偏光板，上述延伸薄膜為λ/4板或λ/2板。MEANS FOR SOLVING THE PROBLEMS According to an aspect of the present invention, there is provided a method of manufacturing a stretched film. The manufacturing method includes the steps of: holding the left and right ends of the elongated film in the width direction with left and right jigs, the left and right jigs are a variable-pitch clamp in which the longitudinal clamp pitch can be changed; at least one of the left and right clamps is moved while changing the clamp pitch to extend the film obliquely; the film is released from the left and right clamps; Carrying out the roller conveying of the film, and detecting the amount of slack of the film between the conveying rollers and the position where the slack occurs; The fixture spacing changes. In one embodiment, after the left and right ends of the film released from the left and right clamps are cut and removed, the amount of slack and the site where slack occurs are detected. In one embodiment, the above-mentioned correction of changing the jig pitch includes the step of increasing the jig pitch of the jig for holding the end portion that is far from the portion where the slack has occurred. In one embodiment, the correction for changing the distance between the grippers is performed during the period from when the preceding gripper passes a position of 1/2 to 9/10 of the inclined traveling section to when the film During the period from when the above-mentioned left and right clamps are released. In one embodiment, the above-mentioned correction for changing the distance between the grippers is performed with a correction amount greater than the difference L' (unit: mm) in length between the left and right ends of the film between the above-mentioned conveying rollers, but L' is carried out by Calculated by substituting the length L (unit: mm) of the above-mentioned film between the above-mentioned conveying rollers calculated based on the following formula (1) and formula (2) into the following formula (3);

(In the above formula, d represents the detected slack (unit: mm), W represents the mass of the above-mentioned film per m (unit: g), g represents the acceleration of gravity, and S represents the distance between the above-mentioned conveying rollers (unit: mm) , H represents the tension (unit: N/m) applied to the end side that causes the slack calculated from the formula (1). In one embodiment, the above-mentioned correction for changing the distance between clips is performed during the above-mentioned oblique stretching, and the ambient temperature of the gas at this time is Tg to Tg+20° C. of the above-mentioned thin film. According to another aspect of the present invention, there is provided a method for manufacturing an optical laminate, the method comprising the steps of: obtaining a long stretched film by using the above method for manufacturing a stretched film; and, while conveying the long optical film and the Long stretched films are laminated continuously while aligning their long sides. In one embodiment, the optical film is a polarizing plate, and the stretched film is a λ/4 plate or a λ/2 plate.

Invention effect In the method for producing a stretched film of the present invention, the amount of slack and the location of the slack in the obliquely stretched film are detected, and the gripper pitch of at least one of the left and right grippers located upstream of the conveying line is corrected based on the detection results. This reduces the difference in length between the left and right ends of the film, and as a result, a long obliquely stretched film with reduced slack can be obtained.

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, "longitudinal clip pitch" means the center-to-center distance along the traveling direction of the clips adjacent to the vertical direction. In addition, the left-right relationship in the width direction of the elongated film refers to the left-right relationship in the conveying direction of the film, unless otherwise specified.

A. Manufacturing method of stretched film The manufacturing method of the stretched film of the present invention comprises the following steps: use the left and right clamps to hold the left and right ends of the strip film in the width direction respectively, and the left and right clamps are variable-pitch clamps whose vertical clamp spacing can be changed; At least one of the grippers is moved while changing the distance between the grippers, whereby the film is stretched obliquely; the film is released from the left and right grippers; the film is conveyed by rollers, and the slack of the film is detected between the conveying rollers amount and the location where the slack occurs; and, performing correction based on the detection result, the correction is to change the grip distance of at least one of the left and right grippers located upstream of the conveying line. Typically, the film held by the jig is preheated and then subjected to oblique stretching.

Fig. 1 is a schematic diagram illustrating an example of a method for producing a stretched film of the present invention. The obliquely stretched film 1 that has been stretched obliquely in the stretching device 100 and then released from the clamp is sent out from the exit of the stretching device 100, and after being rolled by conveying rollers 200a, 200b, 200c, and 200d, it is wound up in the take-up section 300. coiled. When the film 1 is conveyed by rollers, the amount of slack is detected between the conveying rollers, and correction is performed based on the detection results. The correction is to change the gripper pitch of at least one of the left and right grippers located upstream of the conveying line. In this regard, the difference in length between the left and right ends of the stretched film obtained after correction is reduced, and as a result, a long obliquely stretched film with reduced slack can be obtained.

The gripping, preheating, oblique stretching and releasing of the film by the aforementioned clamps can be performed, for example, using a tenter-type simultaneous biaxial stretching device equipped with left and right clamps capable of holding the long film in the width direction. The left and right ends move at different speeds.

Fig. 2 is a schematic plan view illustrating an overall configuration of an example of a stretching device that can be used in the manufacturing method of the present invention. The stretching device 100 has an endless loop 10L and an endless loop 10R symmetrically arranged on the left and right sides in a plan view, and the endless loop 10L and the endless loop 10R have a plurality of jigs 20 for holding the film. In addition, in this specification, when viewed from the entrance side of the film, the endless loop on the left is called a left endless loop 10L, and the endless loop on the right is called a right endless loop 10R. The jigs 20 of the left and right endless loops 10L, 10R are respectively guided by the reference rail 70 to move around in a circle. The jig 20 of the left endless loop 10L moves around in the counterclockwise direction, and the jig 20 of the right endless loop 10R moves around in the clockwise direction. In the stretching device, a gripping area A, a preheating area B, an oblique stretching area C, and a release area D are provided in this order from the inlet side of the sheet toward the outlet side. These regions refer to regions where the film to be stretched is substantially gripped, preheated, obliquely stretched, and released, and do not mean mechanically and structurally independent regions. In addition, it should be noted that the ratio of the length of each region in the stretching device in FIG. 1 is different from the ratio of the actual length.

Although not shown in FIG. 2 , a region for performing any appropriate processing may be provided between the obliquely extending region C and the release region D as necessary. Examples of such treatment include lateral shrinkage treatment and the like. Also, not shown in the figure, the above stretching device typically includes a heating device (for example, various ovens such as hot air type, near-infrared type, and far-infrared type) to make the heating environment from the preheating area B to the release area D .

In the grasping area A and the preheating area B of the stretching apparatus 100 described above, the left and right endless loops 10L, 10R are configured so that the spacing distance corresponding to the initial width of the film to be stretched is substantially parallel to each other. In the inclined stretching region C, the distance between the left and right endless loops 10L, 10R is gradually increased to correspond to the stretched width of the film as it goes from the preheating region B side to the releasing region D. In the released region D, the left and right endless loops 10L, 10R are configured so that the spacing distance corresponding to the stretched width of the film is substantially parallel to each other. However, the configuration of the left and right endless loops 10L, 10R is not limited to the above-mentioned illustrated examples. For example, the left and right endless loops 10L, 10R may be formed so that the spacing distance corresponding to the initial width of the film to be stretched is substantially parallel to each other from the gripping region A to the releasing region D.

The jig (the left jig) 20 of the left endless loop 10L and the jig (the right jig) 20 of the right endless loop 10R are independently movable in a revolving manner. For example, the driving sprockets 11 and 12 of the left endless loop 10L are driven by the electric motors 13 and 14 to rotate in the counterclockwise direction, and the driving sprockets 11 and 12 of the right endless loop 10R are driven by the electric motors 13 and 14. Rotate clockwise. As a result, a traveling force is applied to the jig carrying member of the driving roller (not shown) engaged with the driving sprockets 11 and 12 . Thereby, the left endless loop 10L moves counterclockwise, and the right endless loop 10R moves clockwise. By independently driving the electric motor on the left side and the electric motor on the right side, the endless loop 10L on the left side and the endless loop 10R on the right side can be independently moved around.

Furthermore, the jig (left jig) 20 of the left endless loop 10L and the jig (right jig) 20 of the right endless loop 10R are variable-pitch types, respectively. That is, the left and right jigs 20 , 20 can change the jig pitch in the vertical direction with movement, respectively, independently. The configuration of the variable pitch type can be realized by using a pantograph type, a linear motor type, a motor-chain type, and other driving methods. Hereinafter, a link mechanism (pantograph mechanism) will be described as an example.

3 and 4 are schematic plan views of main parts for explaining the link mechanism for changing the distance between clamps in the stretching device of FIG. 1 .

As shown in FIG. 3 and FIG. 4 , there are provided jig holding members 30 for respectively holding the jigs 20 and having a long and thin rectangular shape in the lateral direction when viewed from above. Although not shown, the jig carrying member 30 is formed into a solid frame structure with a closed cross section by an upper beam, a lower beam, a front wall (a wall on the side of the jig) and a rear wall (a wall on the side opposite to the jig). The jig carrying member 30 is provided so as to roll on the traveling road surfaces 81 and 82 by the traveling wheels 38 at both ends thereof. In addition, in FIG. 3 and FIG. 4 , the traveling wheels on the front wall side (traveling wheels rolling on the traveling road surface 81 ) are not shown. The travel surfaces 81, 82 run parallel to the reference track 70 across the entire area. On the rear side of the upper beam and the lower beam of the jig carrying member 30 (the side opposite to the jig side (hereinafter, referred to as the opposite side of the jig)), a long hole 31 is formed along the longitudinal direction of the jig carrying member, and can be The slider 32 is engaged to slide along the longitudinal direction of the elongated hole 31 . One first shaft member 33 is vertically provided near the end portion of the jig carrying member 30 on the side of the jig 20 so as to penetrate the upper beam and the lower beam. On the other hand, a second shaft member 34 is vertically penetrated through the slider 32 of the jig carrying member 30 . One end of the main link member 35 is pivotally connected to the first shaft member 33 of each jig carrying member 30 . The other end of the main link member 35 is pivotally connected to the second shaft member 34 of the adjacent jig carrying member 30 . To the first shaft member 33 of each jig carrying member 30 , in addition to the end to which the main link member 35 is pivotally connected, one end of the sub-link member 36 is also pivotally connected. The other end of the secondary link member 36 is pivotally connected to the middle portion of the main link member 35 via a pivot 37 . Utilize the link mechanism that is made up of main link member 35, auxiliary link member 36, as shown in Figure 3, slide block 32 moves toward the rear side (the opposite side of clamp) of clip carrying member 30, and clip carrying member 30 The smaller the vertical distance between each other (result is the clamp distance), and as shown in FIG. The result is a larger clamp spacing). The positioning of the slide block 32 is carried out by means of the pitch setting rail 90 . As shown in FIGS. 3 and 4 , the smaller the distance between the reference rail 70 and the pitch setting rail 90 , the larger the gap between the clamps.

By performing oblique stretching of the film using the stretching apparatus described above, it is possible to produce an obliquely stretched film, for example, a retardation film having a slow axis in the oblique direction. In addition, a specific embodiment of the stretching device as described above is described in, for example, Japanese Patent Application Laid-Open No. 2008-44339, and this specification uses the entirety thereof as a reference. Hereinafter, each step will be described in detail.

A-1. Gripper holding film In the gripping area A (entrance for taking in the film of the stretching apparatus 100), the grippers 20 of the left and right endless loops 10L, 10R grip the film to be stretched at a constant gripper pitch that is equal to each other or at a gripper pitch that is different from each other. side edges. This film is conveyed to the preheating zone B by movement of the grippers 20 of the left and right endless loops 10L, 10R (essentially, movement of each gripper carrying member guided by the reference rail 30 ).

A-2. Preheating In the preheating zone B, since the left and right endless loops 10L, 10R are configured so that the spacing distance corresponding to the initial width of the film to be stretched is substantially parallel to each other as described above, basically neither horizontal stretching nor longitudinal stretching is performed. while heating the film. However, the distance between the left and right clamps (distance in the width direction) may be slightly increased in order to avoid problems such as deflection of the film due to preheating and contact with nozzles in the oven.

In preheating, the film is heated to temperature T1 (° C.). The temperature T1 is preferably not less than the glass transition temperature (Tg) of the film, more preferably not less than Tg+2°C, and still more preferably not less than Tg+5°C. On the other hand, the heating temperature T1 is preferably Tg+40°C or lower, more preferably Tg+30°C or lower. The temperature T1 varies depending on the film to be used, but is, for example, 70°C to 190°C, preferably 80°C to 180°C.

The heating time up to the above-mentioned temperature T1 and the holding time at the temperature T1 can be appropriately set according to the constituent materials of the film or production conditions (for example, the transport speed of the film). The heating time and the 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. Inclined extension In the oblique extension area C, at least one of the right and left clips 20 is advanced while changing the longitudinal clip pitch, and the film is extended obliquely by advancing one of the clips ahead of the other. More specifically, the distance between the clamps of the left and right clamps is increased or decreased at different positions, the distance between the clamps of the left and right clamps is changed (increased and/or reduced) at different changing speeds, etc., and either The gripper travels ahead of the other gripper, thereby stretching the film obliquely.

The oblique extension may also include lateral extension. In this case, for example, as shown in the illustration, the oblique stretching may be performed while increasing the distance between the left and right jigs (distance in the width direction). Alternatively, unlike the illustrated example, it may be performed while maintaining the distance between the left and right jigs.

When the oblique extension includes lateral extension, the extension ratio in the lateral direction (TD) (the ratio of the width W _final of the oblique stretched film to the initial width W _initial of the film (W _final /W _initial )) is preferably 1.05 to 6.00, More preferably, it is 1.10 to 5.00.

In one embodiment, the oblique extension may be different in the longitudinal direction at the position where the distance between the clamps of one of the left and right clamps starts to increase or decrease and the position where the distance between the other clamps starts to increase or decrease. In the state of the position, it is carried out by increasing or decreasing the distance between the grippers of each gripper to a predetermined distance. Regarding the oblique extension in this embodiment, for example, the descriptions in Patent Document 1, JP-A-2014-238524 and the like can be referred to.

In another embodiment, the inclined extension can be made by increasing or decreasing the distance between the clamps of one of the left and right clamps to a predetermined distance after the distance between the clamps of one of the above-mentioned left and right clamps is fixed. The fixture spacing is carried out. Regarding the oblique extension in this embodiment, for example, descriptions in JP-A-2013-54338, JP-A-2014-194482, etc. can be referred to.

Moreover, in yet another embodiment, the oblique extension can be performed by (i) increasing the clamp pitch of one of the above-mentioned left and right clamps and decreasing the clamp pitch of the other clamp; and (ii) The clip pitches of the respective clips are changed so that the reduced clip pitch and the increased clip pitch become predetermined equal pitches. Regarding the oblique extension in this embodiment, for example, descriptions in JP-A-2014-194484 and the like can be referred to. The oblique stretching in this embodiment may include the step of extending the film obliquely by increasing the distance between the left and right clamps while increasing the distance between the clamps of one clamp and decreasing the distance between the clamps of the other clamp (first oblique stretching). step); and, while expanding the distance between the left and right jigs, maintain or reduce the jig spacing of the one jig so that the jig spacings of the left and right jigs are equal, and increase the jig spacing of the other jig, so that the The film is obliquely stretched (second oblique stretching step).

Inclined extension can be performed at temperature T2. The temperature T2 is preferably Tg-20°C to Tg+30°C relative to the glass transition temperature (Tg) of the film, more preferably Tg-10°C to Tg+20°C, particularly preferably about Tg. Depending on the film used, the temperature T2 is, for example, 70°C to 180°C, preferably 80°C to 170°C. The difference (T1-T2) between the temperature T1 and the temperature T2 is preferably at least ±2°C, more preferably at least ±5°C. In one embodiment, T1>T2, so the film heated to the temperature T1 in the preheating zone can be cooled to the temperature T2.

The above-mentioned lateral shrinkage treatment is performed after the oblique stretching. Regarding the processing after the oblique stretching, paragraphs 0029 to 0032 of JP-A-2014-194483 can be referred to.

A-4. Unclamp release At an arbitrary position in the release area D, the above-mentioned film is released from the jig. In the release zone D, generally neither transverse stretching nor longitudinal stretching is performed, but the film is heat-treated to fix the stretched state (heat fixation) as necessary, and/or cooled to below Tg, and then the film is released from the jig. open. In addition, when heat fixing is performed, the longitudinal clamp pitch can be reduced, thereby relieving stress.

The heat treatment can typically be carried out at temperature T3. The temperature T3 varies depending on the film to be stretched, and may be the case of T2≥T3, or may be the case of T2<T3. Generally speaking, there are cases where the crystallization treatment is carried out by setting T2≧T3 when the thin film is an amorphous material, and by setting T2<T3 when the thin film is a crystalline material. When T2≥T3, the temperature difference between T2 and T3 (T2-T3) is preferably 0°C-50°C. The heat treatment time is typically 10 seconds to 10 minutes.

The stretched film released from the clips is sent out from the exit of the stretching device, and is conveyed by rollers described later.

A-5. Roller conveying In roller feeding, the amount of slack in the stretched film between the feeding rollers and the location where the slack occurs are detected.

In one embodiment, after cutting and removing the left and right end portions in the width direction of the stretched film released from the clips, detection of the amount of slack and the location where slack occurs is performed. More accurate detection results can be obtained by performing the detection of the above-mentioned amount of slack and the portion where the slack occurs in a state where both ends are removed.

The widths of the cut and removed ends are independent, and may be, for example, 20 mm to 600 mm, preferably 100 mm to 500 mm. Cutting and removal of the end portion can be performed by normal slit processing.

In one embodiment, the detection of the slack amount and the slack location can be performed by detecting the difference between the original traveling position of the film and the actual traveling position of the film during roller conveyance. For example, this detection can be performed by detecting the difference of the position (transportation height) of the width direction of a film at the intermediate point between conveyance rollers.

5 is a schematic diagram illustrating an example of a detection method for detecting the amount of slack and the location where the sag occurs. As shown in FIG. 5 , an ultrasonic displacement sensor 400 is arranged at the midway point between two adjacent conveying rollers 200b and 200c, below the central portion and the left and right ends of the stretched film 1 in the width direction, to measure the displacement from the ultrasonic wave. The distance between the acoustic displacement sensor 400 and the stretched film 1, and the difference (L _MAX -L _MIN ) between the maximum distance (L _MAX ) and the minimum distance (L _MIN ) can be set as the slack. The portion where the minimum distance occurs is detected as the portion where slack occurs. In addition, the reason for the slack in the obliquely stretched film can be cited that the stretching results (time points, times, sequence, thermal history, etc.) of the left and right ends of the film during the oblique stretching of the film are different from each other, leading to The amount of deformation at both ends is uneven, so the part where slack occurs is usually one of the ends. Therefore, only the left and right end portions in the width direction of the stretched film 1 may be used as the slack detection locations. In this case, the film without slack can be transported in advance and the distance (L ₀ ) from the ultrasonic displacement sensor to the film can be measured in advance, and the distance between the left and right ends and the ultrasonic displacement sensor and L ₀ The difference is set as the amount of slack. In addition, an ultrasonic displacement sensor has been described as an example of the slack detection device, but any suitable detection device may be used for the slack (for example, using a laser Doppler velocimeter to obtain the film passing speed between the normal part and the slack part , thus calculating the difference in length, etc.) to detect.

The distance (D) between the conveying rollers during the above detection is not particularly limited, for example, it may be 500 mm to 2000 mm, preferably 700 mm to 1500 mm.

The film tension during the above detection is not particularly limited, for example, it may be 50N/m-400N/m, preferably 100N/m-200N/m. If the conveying tension is too high, the film being conveyed will elastically deform, making it difficult to detect slack. On the other hand, if the conveying tension is too low, the tension itself becomes unstable, and the measured value of slack may become unstable.

The above-mentioned roller conveyance can be carried out in a non-heated environment. The air ambient temperature at the time of roller conveyance is, for example, about 15°C to 40°C, and may be, for example, about 20°C to 30°C.

A-6. Correction to change the distance between jigs The correction to change the distance between the grippers is the so-called feedback correction, which is based on the detection results of the above-mentioned slack and the location where the slack occurs, so that at least one of the left and right grippers located upstream of the conveying line is adjusted to reduce the slack. Fixture spacing changes are made. For example, when the detected slack is equal to or greater than a predetermined value, correction is performed to change the chuck pitch, and when the detected slack is smaller than a predetermined value, the oblique stretching may be continued without correction. Specifically, when the amount of slack detected at a distance between rollers of 1000 mm is, for example, 3 mm or more, 5 mm or more, 10 mm or more, or 15 mm or more, the above correction can be performed.

The above-mentioned correction for changing the jig pitch (hereinafter also simply referred to as "feedback correction") may be performed by any appropriate method as long as the effect of the present invention can be obtained. For example, feedback correction can be performed by increasing the distance between the clamps for holding the end that is remote from the slack site; decreasing the clamp for holding the end near the slack site fixture spacing; or a combination of these. However, even if the distance between the clips is reduced, the film may still be loose without shrinking. Therefore, it is preferable to increase the distance between the clips for holding the end that is far from the part where the slack occurs. Make feedback corrections. More specifically, when the slack occurs at any one of the left and right ends of the stretched film, feedback correction can be appropriately performed by increasing the clip pitch of the clips for holding the other end.

In the feedback correction described above, there is no particular limitation on the timing of changing the jig pitch as long as the effect of the present invention can be obtained. In one embodiment, it is possible to change to the corrected clamp pitch at any point in time after the film upstream of the conveying line is transferred to the inclined extension region and released from the clamps. Preferably, the corrected gripper pitch is applied during the period from any point in time after the gripper traveling ahead upstream of the conveying line passes through the middle of the travel section of the inclined extension region until the film is released from the gripper, more preferably The corrected clip pitch is applied from the time point when the preceding clip passes through 1/2 to 9/10 of the travel section of the inclined extension region until the film is released from the clip. More specifically, at any point in time after the preceding jig passing through the middle of the travel section of the inclined extension region upstream of the conveying line, it is preferably 1/3 of the travel interval of the inclined extension region from the preceding jig. At the timing of 2 to 9/10, the above-mentioned feedback correction is started to be applied, and the jig pitch is changed so that the desired correction amount is obtained at the end point of the inclined extension region. In addition, it is preferable that the correction amount is maintained even after the film is released from the clamp after the transition from the inclined stretching region to the releasing region. In the second half of the oblique extension, especially in the final stage, at least one of the gripper distances is maintained constant or limited to changes with a small rate of change, so by correcting the gripper distance at this time point, the present invention can be suitably obtained. Effect.

When applying the above-mentioned feedback correction in the inclined extension region, it is preferable to heat the thin film of the object to Tg ℃ ~ Tg + 20 ℃, more preferably Tg + 3 ℃ ~ Tg + 10 ℃, further preferably Tg + 4 ℃ ~ Tg + 8 ℃ . The effects of the present invention can be suitably obtained by applying feedback correction at a temperature equal to or slightly higher than Tg. In one embodiment, the film transferred to the release region through the oblique stretch region while receiving feedback correction at the above temperature is heat-treated while maintaining the correction amount performed in the oblique stretch region, then cooled, and then is released from the fixture. The heat treatment and cooling are as described in A-4.

Fig. 6A is a schematic diagram showing a curve of a clip pitch in one embodiment of the method for producing a stretched film of the present invention. In the example shown in the figure, the fixture spacing of the left and right fixtures X and Y in the preheating area B is set to P ₁ , and in the initial inclined extension before feedback correction, when entering the inclined extension area C, it starts to increase by one fixture clamp spacing of X, and start reducing the clamp spacing of another clamp Y, after increasing the clamp spacing of clamp X to _P2 and reducing the clamp spacing of clamp Y to _P3 , maintaining the clamp spacing of clamp X _Be the state of P2 and increase the clamp spacing of clamp Y to _P2 . The left and right clamps X and Y move to the release area D with the clamp distance P ₂ and release the film. Thereafter, as a result of feedback correction based on the amount of slack of the film at the time of roller conveyance, etc., in the inclined stretching region C, the clip pitch of the clip X is gradually increased from _P2 to _P2 '. In addition, as will be described later, in the released region, the gripper pitches of the grippers X and Y are maintained at P ₂ ′ and P ₂ , respectively, and the correction amount (P ₂ ′−P ₂ ) at the end point of the inclined extension region is maintained.

Fig. 6B is a schematic diagram showing a curve of a clip pitch in another embodiment of the method for producing a stretched film of the present invention. In the embodiment shown in the figure, the oblique extension is carried out in the same manner as the embodiment shown in FIG. 6A , and the clamp distance between the left and right clamps X and Y is reduced from _P2 at the time of heat fixing in the released region D. Release the film after _P3 . Then, as a result of feedback correction based on the amount of slack of the film when it is conveyed by rollers, etc., in the inclined extension region C, the gripper pitch of the _gripper X is gradually increased from P2 to _P2 ′, and in the release region, the gripper X _The clamp pitch of X is reduced from P2' to _P3 ', while the clamp pitch _of clamp Y is reduced from P2 to _P3 . In addition, as will be described later, in the release region, the distance between the grippers X and Y is reduced in such a way that the correction amount (P ₂ ′-P ₂ ) at the end point of the inclined extension region is maintained, and P ₃ ′- The relationship of P ₃ =P ₂ ′-P ₂ .

In the above-mentioned oblique extension region, the change to the corrected clamp spacing (the change to P ₂ ') should be from the point where the feedback correction is applied to the end point (in Fig. 6A and Fig. 6B, from 2 through the oblique extension region /3 time point to the end point) and proceed slowly. Also, it is preferable to maintain the correction amount at the end time of the inclination stretch during the period from the end point of the inclination extension region to the release of the clamps (｜clamp distance before correction at the end time of inclination stretch-between the end time point of inclination stretch Corrected fixture spacing |). For example, in the curves shown in FIGS. 6A and 6B , during the period from the end of the inclined extension region to the release of the clamps, the difference between the clamp spacing of clamp X and the clamp spacing of clamp Y remains constant (that is, P _2' - _P2 ). The effects of the present invention can be suitably obtained by changing the jig pitch as described above.

The above-mentioned change of the clamp pitch can be performed by adjusting the distance between the reference track and the pitch setting track, etc. as mentioned above. These adjustments can be made without temporarily stopping or stopping the transmission line.

In the above-mentioned feedback correction, the correction amount of the clamp pitch at the end time of inclination stretching (|the clamp pitch before correction at the end time of inclination stretching-the corrected clamp pitch at the end time of inclination stretch|) can be appropriately set according to the amount of slack, etc. . The amount of correction of the distance between the clamps is preferably a correction amount greater than the difference in length between the left and right ends of the stretched film between the above-mentioned conveying rollers, more preferably 1.4 times to 5.0 times the difference in length, and more preferably the difference in length The correction amount is 1.6 to 4.0 times of the length difference, and more preferably 1.8 to 3.0 times of the length difference. If the amount of correction of the clip pitch is less than or equal to the difference in length between the left and right ends, the amount of reduction in slack may not be sufficient.

(上述式中，d表示檢測出的鬆弛量(單位：mm)，W表示上述薄膜每m的質量(單位：g)，g表示重力加速度，S表示上述輸送輥間的距離(單位：mm)，H表示對產生從式(1)計算之鬆弛的端部側施加的張力(單位：N/m))。The length difference L' (unit: mm) between the left and right ends of the stretched film between the conveying rollers can be obtained by calculating the stretched film between the conveying rollers based on the following equations (1) and (2). The length L (unit: mm) is substituted into the following formula (3) and calculated. [mathematical formula 2]

(In the above formula, d represents the detected slack (unit: mm), W represents the mass of the above-mentioned film per m (unit: g), g represents the acceleration of gravity, and S represents the distance between the above-mentioned conveying rollers (unit: mm) , H represents the tension (unit: N/m) applied to the end side that causes the slack calculated from the formula (1).

In one embodiment, the amount of slack reduced by the feedback correction (the amount of slack of the stretched film obtained before the feedback correction - the amount of slack of the stretched film obtained after the feedback correction: however, is measured with a distance between the conveying rollers of 1000mm The amount of slack) may be, for example, 3 mm or more, preferably 5 mm or more, more preferably 8 mm or more, and further preferably 10 mm or more. And the slack of the stretched film obtained after feedback correction may be, for example, less than 15 mm, preferably less than 10 mm, more preferably less than 8 mm, more preferably less than 5 mm, and still more preferably less than 3 mm.

B. Stretch the film of the object In the production method of the present invention, any appropriate film can be used. For example, a resin film applicable as a retardation film is mentioned. Examples of materials constituting the film include polycarbonate resins, polyvinyl acetal resins, cycloolefin resins, acrylic resins, cellulose ester resins, cellulose resins, polyester resins, Polyester carbonate resin, olefin resin, polyurethane resin, etc. Preferred are polycarbonate-based resins, cellulose ester-based resins, polyester-based resins, polyester carbonate-based resins, and cycloolefin-based resins. This is because, as long as these resins are used, a retardation film exhibiting wavelength dependence of so-called inverse dispersion can be obtained. These resins may be used alone or in combination according to desired properties.

烷二醇、二乙二醇(DEG)、三乙二醇(TEG)、聚乙二醇(PEG)、環己烷二甲醇(CHDM)、三環癸烷二甲醇(TCDDM)、雙酚類等二羥基化合物的結構單元。Any appropriate polycarbonate-based resin can be used for the above-mentioned polycarbonate-based resin. For example, a polycarbonate resin containing a structural unit derived from a dihydroxy compound is preferable. Specific examples of dihydroxy compounds 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-secondary butylphenyl) fluorene, 9,9-bis( 4-Hydroxy-3-tertiary 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-isobutylbenzene base) fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-tertiary 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-tertiary butyl-6-methylphenyl)fluorene, 9,9- Bis(4-(3-hydroxy-2,2-dimethylpropoxy)phenyl)fluorene, etc. The polycarbonate resin may also contain alcohol, dehydromannitol, isoidide, spiroglycerin, two

Alkanediol, Diethylene Glycol (DEG), Triethylene Glycol (TEG), Polyethylene Glycol (PEG), Cyclohexane Dimethanol (CHDM), Tricyclodecane Dimethanol (TCDDM), Bisphenols structural units of dihydroxy compounds.

The details of the above-mentioned polycarbonate resin are described in, for example, Japanese Patent Laid-Open No. 2012-67300 and Japanese Patent No. 3325560. The description of this patent document is incorporated by reference in this specification.

The glass transition temperature of the polycarbonate resin is preferably not less than 110°C and not more than 250°C, more preferably not less than 120°C and not more than 230°C. If the glass transition temperature is too low, the heat resistance tends to deteriorate, which may cause dimensional changes after film formation. If the glass transition temperature is too high, the molding stability during film molding may deteriorate, and the transparency of the film may be impaired. In addition, the glass transition temperature was calculated|required based on JISK 7121 (1987).

Any appropriate polyvinyl acetal resin can be used for the polyvinyl acetal resin. Typically, polyvinyl acetal-based resins can be obtained by subjecting at least two types of aldehyde compounds and/or ketone compounds to condensation reactions with polyvinyl alcohol-based resins. Specific examples and detailed production methods of polyvinyl acetal resins are described in, for example, JP-A-2007-161994. This description is incorporated by reference in this specification.

The retardation film obtained by stretching the above stretched film preferably has a refractive index characteristic showing the relationship of nx>ny. In one embodiment, the retardation film preferably functions as a λ/4 plate. In this 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 preferably functions as a λ/2 plate. In this embodiment, the in-plane retardation Re(550) of the retardation film (λ/2 plate) is preferably 230 nm to 310 nm, more preferably 250 nm to 290 nm. In addition, in this specification, nx is the refractive index in the direction in which the in-plane refractive index becomes the largest (that is, the direction of the slow axis), and ny is the refraction in the direction (that is, the direction of the fast axis) that is perpendicular to the slow axis in the plane. rate, nz is the refractive index in the thickness direction. And Re(λ) is the in-plane retardation of the film measured with light of wavelength λnm at 23°C. Accordingly, Re(550) is the in-plane retardation of the film measured at 23° C. with light having a wavelength of 550 nm. When the thickness of the film is d (nm), Re(λ) is obtained from the formula Re(λ)=(nx-ny)×d.

The in-plane retardation Re(550) of the retardation film can be set in a desired range by appropriately setting the oblique stretching conditions. For example, in JP-A-2013-54338 , JP-A-2014-194482 , JP-A-2014-238524 , JP-A-2014-194484 , etc., it is disclosed in detail that the 100 nm The method of retardation film with in-plane retardation Re(550) of ~180nm. Therefore, those skilled in the art can set appropriate tilt extension conditions based on this disclosure.

When using a single retardation film (specifically, a λ/4 plate) to produce a circular polarizing plate, or when using a single retardation film to rotate the orientation of linearly polarized light by 90°, the slow axis of the retardation film used The direction relative to the long side direction of the film should be about 30°～60° or 120°～150°, more preferably about 38°～52° or 128°～142°, further preferably 43°～47° or 133° °～137°, especially about 45° or 135°.

And when using two retardation films (specifically, a λ/2 plate and a λ/4 plate) to make a circular polarizing plate, the direction of the slow axis of the retardation film (λ/2 plate) used is relative to the film The direction of the long side should be about 60°-90°, more preferably about 65°-85°, especially about 75°. In addition, the slow axis direction of the retardation film (λ/4 plate) is preferably about 0°-30°, more preferably about 5°-25°, particularly about 15° relative to the long-side direction of the film.

The retardation film preferably exhibits 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, more preferably 0.8 to 0.95. Re(550)/Re(650) is preferably 0.8 or more and less than 1.0, more preferably 0.8 to 0.97.

The 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), more preferably 5×10 ^-12 (m ² /N) ~50×10 ⁻¹² (m ² /N).

C. Optical layered body and method for manufacturing the optical layered body The stretched film obtained by the production method of the present invention can be laminated with other optical films 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. 7 is a schematic cross-sectional view of an example of the circular polarizing plate. The circular polarizing plate 500 illustrated in the illustration has a polarizer 510, a first protective film 520 disposed on one side of the polarizer 510, a second protective film 530 disposed on the other side of the polarizer 510, and a second protective film disposed on the second protective film. Retardation film 540 on the outside of 530. The retardation film 540 is a stretched film (for example, a λ/4 plate) obtained by the manufacturing method described in item A. The second protective film 530 may be omitted. In this case, the retardation film 540 can function as a protective film of the polarizer. The angle formed by the absorption axis of the polarizer 510 and the slow axis of the retardation film 540 is preferably about 30° to 60°, more preferably about 38° to 52°, further preferably about 43° to 47°, and particularly preferably about Around 45°.

The retardation film obtained by the production method of the present invention is elongated and has a slow axis in an oblique direction (direction at, for example, 45° with respect to the longitudinal direction). In addition, in many cases, the elongated 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 can be used to produce a circularly polarizing plate with extremely excellent production efficiency. In addition, roll-to-roll refers to a method of aligning the longitudinal direction of the long films while conveying them by rolls, and continuously laminating them.

In one embodiment, the method for producing an optical laminate of the present invention includes the steps of: obtaining a long stretched film by using the method for producing a stretched film described in item A; and, while conveying the long optical film and the long Shape stretched film is continuously bonded while aligning its long side direction. Example

Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these Examples. In addition, the measurement and evaluation methods in the Examples are as follows.

(1) Thickness was measured using a dial gauge (manufactured by PEACOCK, product name "DG-205 type pds-2"). (2) Retardation value The in-plane retardation Re(550) was measured using Axoscan manufactured by Axometrics. (3) Orientation Angle (Appearance Direction of Slow Axis) The central part of the film to be measured was cut out into a square shape with a width of 50 mm and a length of 50 mm so that one side was parallel to the width direction of the film to prepare a sample. 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) Measured based on JIS K 7121. (5) Amount of slack As shown in FIG. 5 , an ultrasonic displacement sensor is installed at the middle point (distance between rollers: 912 mm) of two adjacent conveying rollers under the conveying path of the stretched film. While conveying the stretched film with a conveying tension of 150N/m, the distance from the ultrasonic displacement sensor to the stretched film was measured at the center and end of the width direction, and the maximum distance (L _MAX ) and the minimum distance (L _MIN ) difference (L _MAX -L _MIN ) was set as the amount of slack (mm). Then, the portion where the minimum distance has occurred is determined as the portion where slack has occurred.

<Example 1> (Production of polyester carbonate resin film) Polymerization was carried out using a batch polymerization device consisting of two vertical reactors equipped with stirring blades and a reflux cooler controlled at 100°C . 29.60 parts by mass (0.046mol) of bis[9-(2-phenoxycarbonylethyl)fluoren-9-yl]methane, 29.21 parts by mass (0.200mol) of ISB, 42.28 parts by mass (0.139mol) of SPG, 63.77 parts by mass (0.298 mol) of DPC, and 1.19×10 ^-2 parts by mass (6.78×10 -5 mol) of calcium acetate monohydrate as a catalyst. After replacing the inside of the reactor with nitrogen under reduced pressure, it was heated with a heat medium, and stirring was started when the internal temperature became 100°C. 40 minutes after the start of temperature rise, the internal temperature was brought to 220° C., and the pressure was started while controlling to maintain the temperature, and it was set to 13.3 kPa over 90 minutes after reaching 220° C. The by-generated phenol vapor along with the polymerization reaction is introduced into a reflux cooler at 100°C, a certain amount of monomer components contained in the phenol vapor is returned to the reactor, and the uncondensed phenol vapor is introduced into a condenser at 45°C for recovery. After introducing nitrogen into the first reactor and returning it to atmospheric pressure once, the reaction liquid in which the oligomers were formed in the first reactor was transferred to the second reactor. Next, temperature rise and pressure reduction in the second reactor were started, and the internal temperature was 240° C. and the pressure was 0.2 kPa within 50 minutes. Thereafter, polymerization is performed until predetermined stirring power is obtained. When the predetermined power was reached, nitrogen was introduced into the reactor to restore the pressure, and the resulting 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 Machinery Co., Ltd., cylinder set temperature: 250° C.) and a T-shaped die (width 200 mm, set temperature: 250° C.) were used. °C), cold rolls (setting temperature: 120 °C to 130 °C), and a film forming device of a coiler to produce a resin film with a thickness of 135 μm.

(Inclined Stretching Before Feedback Correction) The polyester carbonate resin film obtained above was obliquely stretched using the stretching apparatus shown in FIGS. 2 to 4 to obtain a retardation film. Specifically, the polyester carbonate resin film was preheated to 145° C. in the preheating zone of the stretching device. In the preheating zone, the clamp pitch (P ₁ ) of the left and right clamps was 125 mm. Next, at the same time as the film enters the obliquely extending region C, start to increase the gripper pitch of the right gripper and decrease the gripper pitch reduction of the left gripper, increase the gripper pitch of the right gripper to _P2 and decrease the gripper pitch of the left gripper as small as _P3 . At this time, the rate of change of the clamp pitch (P ₂ /P ₁ ) of the right clamp was 1.42, the rate of change of the clamp pitch of the left clamp (P ₃ /P ₁ ) was 0.78, and the lateral stretch ratio relative to the original width of the film was 1.45 times . Next, while maintaining the clip pitch of the right clip at _P2 , the clip pitch of the left clip starts to be increased from _P3 to _P2 . During this period, the rate of change (P ₂ /P ₃ ) of the clip pitch of the left clip was 1.82, and the transverse stretching magnification relative to the original width of the film was 1.9 times. In addition, the oblique extension region C is set to Tg+3.2°C (143.2°C).

Next, in the release zone D, the film was held at 125° C. for 60 seconds to be heat-set. After the heat-fixed film was cooled to 100°C, the left and right clamps were released.

(roller conveying) Both ends of the stretched film released from the above-mentioned clamps and sent out from the stretching device were cut off by 250 mm. The film with both ends cut off is conveyed by rollers, and the amount of slack between the conveying rollers and the location where slack occurs are detected. As a result, slack occurred at the left end, and the amount of slack was 18.0 mm. In addition, the difference L' in the lengths of both ends of the stretched film before correction calculated based on the above formulas (1) to (3) was 0.95 mm.

(Feedback Correction) During the period from the time when 3/4 of the traveling section of the inclined extension region C has passed to reaching the end point, the clip pitch of the right clip is gradually increased to P ₂ ′ (the correction amount of the clip pitch ( P ₂ '-P ₂ ): 0.3mm), and in the same manner as above, heat-fixing (125°C, 60 seconds) and cooling (100°C) and release of the clamps were performed while maintaining the distance between the clamps. Change the curve of the above-mentioned clamp spacing and continue the inclined extension. That is, the clamp pitch when the obliquely stretched film after feedback correction is released from the clamp is: P ₂ ′ on the right side and P ₂ on the left side.

The retardation Re(590) of the obtained stretched film was 147 nm, and the angle formed by the slow axis direction and the long side direction was 45°.

<Example ₂ > Except having set the correction amount (P2' _- P2) of a clip pitch to 0.6 mm, it carried out oblique stretching similarly to Example 1, and obtained the stretched film.

<Example 3> Except having set the correction amount ( _{P2' -} P2) of a clip pitch to 0.95 mm, it carried out oblique stretching similarly to Example 1, and obtained the stretched film.

<Example 4> Except having set the correction amount ( _{P2' -} P2) of a clip pitch to 1.8 mm, it carried out oblique stretching similarly to Example 1, and obtained the stretched film.

<Example 5> Except having set the correction amount ( _{P2' -} P2) of a clip pitch to 2.6 mm, it carried out oblique stretching similarly to Example 1, and obtained the stretched film.

<Example 6> Except that the correction amount (P ₂ ′-P ₂ ) of the clamp pitch is set to 0.6 mm, and the section after 3/4 of the travel section of the inclined extension area C is set to Tg+6.0°C (146.0°C ) except that it was obliquely stretched in the same manner as in Example 1 to obtain a stretched film.

<Example 7> Except that the correction amount (P ₂ ′-P ₂ ) of the clamp pitch is set to 0.95 mm, and the section after 3/4 of the travel section of the inclined extension area C is set to Tg+6.0°C (146.0°C ) except that it was obliquely stretched in the same manner as in Example 1 to obtain a stretched film.

<Example 8> In addition to setting the correction amount (P ₂ ′-P ₂ ) of the clamp pitch to 1.8 mm, and setting 3/4 of the travel range of the inclined extension region C to Tg+6.0°C (146.0°C ) except that it was obliquely stretched in the same manner as in Example 1 to obtain a stretched film.

<Example 9> Except that the correction amount (P ₂ ′-P ₂ ) of the clamp pitch is set to 2.6 mm, and the section after 3/4 of the travel section of the inclined extension area C is set to Tg+6.0°C (146.0°C ) except that it was obliquely stretched in the same manner as in Example 1 to obtain a stretched film.

＜Comparative example 1＞ A stretched film was obtained by oblique stretching in the same manner as in Example 1 except that no feedback correction was performed.

For the stretched films obtained in the above Examples and Comparative Examples, the amount of sag was measured by the method described above.

In addition, the stretched film obtained in the above-mentioned Examples and Comparative Examples was bonded to a long cover film (manufactured by Toray Film Processing Co., Ltd., product name "Tortec 7832C-30") in a roll-to-roll manner. thin film laminates. Next, the cover film was peeled off from the film laminate, an adhesive was applied using a gravure coater, and then bonded to a polarizing plate, and UV was irradiated to obtain an optical laminate. The appearance (visual observation) of the film laminate and the handleability of the stretched film were evaluated based on the following criteria. ◯: After bonding the cover film (bonding tension: 150 N/m), no wrinkles are observed, and the adhesive can be applied to the entire surface of the film. △: When laminating the cover film, by increasing the lamination tension to 300N/m, it can be bonded without wrinkles, but when applying the adhesive, the adhesive cannot be applied to the slack. x: Wrinkles were present after the cover film was bonded, and the appearance was poor.

Table 1 shows the evaluation results of the above-mentioned sag and the appearance of the thin film laminate together with the production. In Table 1, the "reduction in sag" is the difference from the sag of the stretched film of Comparative Example 1 (the sag of the stretched film obtained in Comparative Example 1−the sag of the stretched film obtained in each Example).

[Table 1]

＜Evaluation＞ As shown in Table 1, it can be seen that the slack of the stretched film obtained later can be reduced by detecting the amount of slack in the obliquely stretched film and appropriately changing the clamp pitch upstream of the conveyance line based on the detection result. Industrial availability

The manufacturing method of the stretched film of the present invention can be suitably used in the manufacture of retardation films, and as a result, can be helpful in the manufacture of image display devices such as liquid crystal display (LCD) and organic electroluminescent display (OLED).

1: Stretched film 10L, 10R: Endless ring 11, 12: Sprocket 13, 14: Electric motor 20: Clamp 30: Clamp holding member 31: Long hole 32: Slider 33: First shaft member 34: Second Shaft member 35: main link member 36: sub-link member 37: pivot 38: traveling wheel 70: reference rail 81, 82: traveling road surface 90: distance setting rail 100: extension device 200a, 200b, 200c, 200d: conveying Roller 300: Take-up section 400: Ultrasonic displacement sensor 500: Circular polarizer 510: Polarizer 520: First protective film 530: Second protective film 540: Retardation film A: Holding area B: Preheating area C : Inclined area D: Release area L _MAX : Maximum distance L _MIN : Minimum distance P ₁ , P ₂ , P ₂ ', P ₃ , P ₃ : Pitch

Fig. 1 is a schematic diagram illustrating an example of a method for producing a stretched film of the present invention. Fig. 2 is a schematic plan view illustrating the overall configuration of an example of a stretching device that can be used in the method for producing a stretched film of the present invention. Fig. 3 is a schematic plan view of main parts for explaining a link mechanism for changing the distance between grippers in the stretching device of Fig. 2 . Fig. 4 is a schematic plan view of main parts for explaining a link mechanism for changing the distance between grippers in the stretching device of Fig. 2 . Fig. 5 is a schematic diagram illustrating a method of measuring the amount of slack. Fig. 6A is a schematic diagram showing a curve of a clip pitch in one embodiment of the method for producing a stretched film of the present invention. Fig. 6B is a schematic diagram showing a curve of a clip pitch in another embodiment of the method for producing a stretched film of the present invention. 7 is a schematic cross-sectional view of a circular polarizing plate using a retardation film obtained by the production method of the present invention.

1: Extended film

100: extension device

200a, 200b, 200c, 200d: conveyor roller

300: coiling department

Claims (8)

A method of manufacturing a stretched film, comprising the following steps: Use the left and right clamps to respectively hold the left and right ends of the strip-shaped film in the width direction. The left and right clamps are variable-pitch clamps whose longitudinal clamp spacing can be changed; at least one of the left and right clamps is moved while changing the clamp distance between them, and one of the clamps advances ahead of the other clamp, thereby extending the film obliquely; releasing the film from the left and right clamps; Roll conveying the film, and detecting the amount of slack of the film between the conveying rollers and the location where the slack occurs; and Correction is performed based on the detection result, the correction is to change the gripper pitch of at least one of the left and right grippers located upstream of the conveying line. The method of manufacturing a stretched film according to claim 1, wherein after cutting and removing the left and right ends of the film released from the left and right clamps, the amount of slack and the location where the slack occurs are detected. The method of manufacturing a stretched film according to claim 1, wherein the correction for changing the distance between the clips includes the step of increasing the distance between the clips for holding the end that is far from the portion where the slack occurs. The method of manufacturing a stretched film according to claim 1, wherein the correction for changing the distance between the clamps is performed during the following period: the preceding clamp passes through a position between 1/2 to 9/10 of the slantedly extending travel range The time point is the period until the film is released from the left and right clamps. The method of manufacturing a stretched film according to claim 1, wherein the correction for changing the gap between the clamps is performed with a correction amount greater than the difference L' (unit: mm) in length between the left and right ends of the film between the conveying rollers, However, L' is calculated by substituting the length L (unit: mm) of the film between the conveying rollers calculated based on the following formula (1) and formula (2) into the following formula (3); Formula 1]

(In the above formula, d represents the detected slack (unit: mm), W represents the mass of the aforementioned film per m (unit: g), g represents the acceleration of gravity, and S represents the distance between the aforementioned conveying rollers (unit: mm) , H represents the tension (unit: N/m) applied to the end side that causes the slack calculated from the formula (1). The method of manufacturing a stretched film according to claim 1, wherein the correction for changing the distance between clamps is performed during the oblique stretching, and The gas ambient temperature at this time is Tg to Tg+20° C. of the aforementioned thin film. A method of manufacturing an optical laminate, comprising the following steps: Obtain a strip-shaped stretched film by using the manufacturing method according to any one of claims 1 to 6; and The elongated optical film and the elongated stretched film were continuously bonded while aligning their longitudinal directions while conveying them. The method of manufacturing an optical laminate as claimed in item 7, wherein the aforementioned optical film is a polarizing plate, The aforementioned stretched film is a λ/4 plate or a λ/2 plate.

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