KR20170104367A - Optical film manufacturing method - Google Patents

Abstract

The present invention relates to a method of manufacturing an optical film using a tenter stretching apparatus having a plurality of clips as gripping means. In this method, the both side edges of a long-length resin film are gripped at the clip interval L1 in the transport direction by the clip (gripping step). While the resin film is transported in the longitudinal direction, the clip interval in the width direction is changed from W1 to W2 And the resin film is loosened in the width direction (relaxation step), the clip interval in the carrying direction is increased to L2 while the resin film loosened in the width direction is conveyed in the longitudinal direction, Followed by stretching (stretching step).

Description

[0001] OPTICAL FILM MANUFACTURING METHOD [0002]

The present invention relates to a process for producing an optical film.

BACKGROUND ART Conventionally, there has been known a technique of gripping and transporting a long film by a tenter clip and widening the distance in the transport direction of the tenter clip, thereby stretching the film to produce an optical film (see, for example, Patent Document 1 7). In such a stretching technique, wrinkling or folding may occur in the side edge portion of the film at the initial stage of stretching, and as a result, the side edge portion of the film does not reach the clip at the time of clip chucking, (Hereinafter referred to as " clip miss ") occurs, leading to a decrease in productivity.

Japanese Patent Application Laid-Open No. 2008-26881

The main object of the present invention is to provide an optical film production method comprising stretching a long-length resin film in a carrying direction by using a tenter stretching device, And to provide a method capable of suppressing a clip miss.

The present invention provides a method of manufacturing an optical film using a tenter stretching apparatus having a plurality of clips as gripping means. In this method, the both side edges of a long-length resin film are gripped at the clip interval L1 in the transport direction by the clip (gripping step). While the resin film is transported in the longitudinal direction, the clip interval in the width direction is changed from W1 to W2 (Loosening step) in which the resin film is loosened in the transverse direction (loosening step), and the resin film stretched in the transverse direction is transported in the longitudinal direction, the distance between the clips in the transport direction is increased to L2, (Stretching step).

In one embodiment, the total draw ratio A (A = L2 / L1) in the longitudinal direction is 2.0 or more.

In one embodiment, the reduction magnification B (B = W2 / W1) of the clip interval in the width direction is 0.60 to 0.99.

In one embodiment, the relaxation step includes stretching the resin film in the longitudinal direction by reducing the clip interval in the width direction, enlarging the clip interval in the carrying direction to L1 ', and stretching the resin film in the longitudinal direction And the reduction magnification B (B = W2 / W1) of the clip interval in the width direction satisfy the relation of B < 1 /? A.

In one embodiment, the thickness of the optical film to be produced is 110 占 퐉 or less.

In one embodiment, the optical film to be produced is a polarizing film.

In the production method of the present invention, the resin film is relaxed in the width direction before stretching in the longitudinal direction. As a result, it is possible to form a relaxed region in which the resin film is relaxed in the width direction in the region before stretching in the longitudinal direction, so that the wrinkle or folding occurring in the stretching region in the longitudinal direction can be prevented from reaching the entrance of the tenter. As a result, occurrence of a clip mist can be suppressed, and it becomes possible to manufacture an optical film without lowering productivity.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a schematic plan view illustrating an overall configuration of an example of a drawing apparatus that can be used in the manufacturing method of the present invention. FIG.
2 is a schematic diagram for explaining one embodiment of the present invention.
3 is a schematic diagram for explaining another embodiment of the present invention.

A. Manufacturing Method of Optical Film

In the method for producing an optical film of the present invention, a tenter stretching apparatus having a plurality of clips is used as a holding means of a film. The manufacturing method of the present invention is characterized in that both side edges of a long-length resin film are gripped by the clip at a clip interval L1 in the transport direction (gripping step), while a clip interval in the width direction is W1 (Loosening process) of the resin film in the width direction, and the distance between the clips in the carrying direction is increased to L2 while the resin film loosened in the width direction is transported in the longitudinal direction, (Stretching step) in the longitudinal direction. In the tenter stretching apparatus for gripping a film with a clip, the end of the resin film is gripped with a clip in a state where no tensile force is applied before stretching, and then the tension is applied to the resin film by heating or stretching As a result, stress is applied to the resin film in accordance with the in-plane deviation of the heating temperature and the accuracy of conveying each clip. As a result, it is considered that large wrinkles or folds are generated in the resin film in the initial stretching region, leading to a clip miss. On the other hand, in the present invention, the resin film is relaxed in the width direction before stretching in the longitudinal direction. Thereby, a relaxed region in which the resin film is relaxed in the width direction in the region before stretching in the longitudinal direction is formed, and excessive tension can be prevented from being generated in the resin film in the tenter entrance region where the resin film is gripped, The occurrence of clip miss can be suppressed.

The resin film used in the production method of the present invention may be a laminate having a thermoplastic resin base material and a resin layer formed on one side of the thermoplastic resin base material, or may be a single layer film composed of a single film. The optical film to be produced may be any suitable optical film as long as it can be produced by a manufacturing method including the above-mentioned grasping process, relaxation process and stretching process. The thickness of the optical film is preferably 110 占 퐉 or less, preferably 80 占 퐉 or less, more preferably 70 占 퐉 or less, further preferably 60 占 퐉 or less. On the other hand, the thickness of the optical film is preferably 10 占 퐉 or more, and more preferably 20 占 퐉 or more.

As specific examples of the optical film to be produced, a polarizing film, an optical compensation film and the like can be preferably exemplified.

The tenter stretching device used in the production method of the present invention includes, for example, a pair of rails having a tapered portion in which a distance between rails continuously decreases and a straight portion having a constant distance between rails, A stretching device having a plurality of clips which can be traveled while being changed can be used. According to such a stretching apparatus, by changing the clip interval (distance between clips on the same rail) in the carrying direction and the clip interval in the width direction (distance between clips on different rails) while holding both side edges of the resin film with clips (MD stretching) in the longitudinal direction and relaxation (TD relaxation) in the width direction of the resin film.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a schematic plan view illustrating an overall configuration of an example of a drawing apparatus that can be used in the manufacturing method of the present invention. FIG. Referring to Fig. 1, a drawing apparatus usable in the manufacturing method of the present invention will be described. The elongating device 100 has an endless rail 10L and an endless rail 10R symmetrically on both left and right sides when viewed in plan. In this specification, the left endless rail is referred to as an endless rail 10L and the right endless rail is referred to as a right endless rail 10R as viewed from the entrance side of the resin film. On the left and right endless rails 10L and 10R, a plurality of clips 20 for holding a resin film are disposed. The clip 20 is guided by the respective rails and circulated in the loop. The clip 20 on the left endless rail 10L is moved in the counterclockwise direction while the clip 20 on the right endless rail 10R is moved in the clockwise direction. In the stretching apparatus, a ripple zone (A), a TD relax zone (B), a MD stretching zone (C), and a release zone (D) are formed in this order from the carry side to the carry side. Further, each of these zones means a zone in which the resin film is substantially grasped, TD relaxed (or TD relaxed and MD stretched), MD stretched and released, and does not mean mechanically and structurally independent segments. It should be noted that the ratio of the length of each zone in the stretching apparatus of Fig. 1 is different from the ratio of the actual length.

In the grip zone A, the left and right endless rails 10R and 10L are linear portions having a constant distance between rails. Typically, the left and right endless rails 10R, 10L are configured to be substantially parallel to each other at a rail-to-rail distance corresponding to the initial width of the resin film to be processed. In the TD relaxation zone B, the left and right endless rails 10R and 10L are tapered portions in which the distance between the rails is continuously reduced. Typically, the left and right endless rails 10R, 10L gradually decrease from the ridge A side toward the MD stretching zone C side until the distance between the rails corresponds to the width after relaxation of the resin film . In the MD stretching zone C and the release zone D, the left and right endless rails 10R and 10L are linear portions having a constant distance between rails. Typically, And are configured to be approximately parallel to each other at a distance of one day.

The clips (left clip) 20 on the left stepless rail 10L and the clips (right clip) 20 on the right stepless rail 10R can independently travel through each other. For example, the driving sprockets 30a and 30b of the left endless rail 10L are rotationally driven in the counterclockwise direction by the electric motors 40a and 40b, and the driving sprockets 30a and 30b of the right- (30a, 30b) are rotationally driven in the clockwise direction by the electric motors (40a, 40b). As a result, a driving force is applied to a clip supporting member (not shown) of a driving roller (not shown) engaged with the driving sprockets 30a and 30b. As a result, the left clip 20 moves in the counterclockwise direction while the right clip 20 moves in the clockwise direction. The left clip 20 and the right clip 20 can be independently traversed by independently driving the left electric motor and the right electric motor.

The clip size is preferably 12 mm to 40 mm, and more preferably 15 mm to 35 mm. When the clip size is less than 12 mm, the stretching tension can not be maintained and may be broken, or a driving problem may occur due to a lack of strength of the clip conveying portion. If the clip size exceeds 40 mm, a region that is not stretched in the vicinity of the clip becomes large to cause irregularity of the end portion, or cracks may be generated on the surface of the resin film by locally stretching the non-peeling portion. The clip size means the width of the grip area.

The left clip 20 and right clip 20 are each of a variable pitch type. That is, the left and right clips 20 and 20 can change the clip interval (clip pitch) in the carrying direction with independent movement. The variable-pitch type clip can be realized by any suitable structure such as a pantograph mechanism (for example, the structure disclosed in Japanese Patent Application Laid-Open No. 2008-23775).

When a stretching device as shown in Fig. 1 is used, the production method of the present invention is characterized in that both side edges of the resin film in the rubbing zone A are gripped by a clip at a clip interval L1 in the transport direction ), The resin film is passed through the tapered portion to reduce the clip interval in the width direction from W1 to W2, thereby loosening the resin film in the width direction (loosening step), and passing the resin film through the straight portion, To the length L2, and stretching the resin film in the longitudinal direction (MD stretching step). If necessary, the clip for gripping the resin film may be released (release step). Figs. 2 and 3 are schematic views for explaining an example of the manufacturing method of the present invention including these steps, respectively. Hereinafter, each step will be described in more detail with reference to these drawings.

First, in the gripping process (grip zone A), the side edges of the resin film 50 introduced into the stretching device are grasped at a fixed gripping interval L1 (clip interval) L1 by the left and right clips 20, The resin film 50 is transported to the TD relaxation zone B by the movement of each clip 20 guided by the endless rails of the TD. The gripping intervals (clip intervals) of the side edges in the grip zone A are typically equal to each other. L1 may be, for example, 30 mm to 200 mm. The clip interval is a distance between centers of neighboring clips.

As the resin film held by the clip, any suitable film may be selected depending on the use of the optical film to be produced and the like. When the optical film to be produced is a polarizing film, for example, a laminate having a thermoplastic resin base material and a PVA-based resin layer formed on one side of the thermoplastic resin base material is held as a resin film. Hereinafter, characteristics, conditions and the like peculiar to the laminate will be described, and the steps after the relaxation process will be described. Regarding the process after the relaxation process, the same operation, conditions, and the like can be applied irrespective of whether it is laminated or a conventional resin film (single film).

The laminate is produced by forming a PVA resin layer on a long-form thermoplastic resin base material. The thermoplastic resin substrate may have any suitable structure as long as it can support the PVA resin layer (polarizing film obtained) from one side.

Examples of the material for forming the thermoplastic resin base material include, for example, ester-based resins such as polyethylene terephthalate resins, cycloolefin resins, olefin resins such as polypropylene, polyamide resins, polycarbonate resins, And a binder resin. Of these, cycloolefin resins (for example, norbornene resins) and amorphous polyethylene terephthalate resins are preferable. Specific examples of the amorphous polyethylene terephthalate resin include a copolymer further containing isophthalic acid as the dicarboxylic acid and a copolymer further containing cyclohexanedimethanol as the glycol.

The stretching temperature of the thermoplastic resin base material can be set to any appropriate value depending on the forming material of the thermoplastic resin base material, the stretching method and the like. The stretching temperature is typically at least the glass transition temperature (Tg) of the thermoplastic resin base, preferably at least Tg + 10 占 폚, more preferably from Tg + 15 占 폚 to Tg + 30 占 폚. When a dry stretching method or a wet stretching method is used as the stretching method and an amorphous polyethylene terephthalate resin is used as the material for forming the thermoplastic resin base material, the stretching temperature is set to a glass transition temperature (for example, 60 DEG C ~ 100 < 0 > C).

The surface of the thermoplastic resin base material may be subjected to surface modification treatment (for example, corona treatment or the like) in advance, or an easy adhesion layer may be formed on the thermoplastic resin base material. By performing such a treatment, the adhesion between the thermoplastic resin base material and the PVA-based resin layer can be improved. In addition, the surface modification treatment and / or the formation of the adhesion-facilitating layer may be carried out before the stretching or after the stretching.

As a method of forming the PVA resin layer, any appropriate method can be adopted. Preferably, the PVA resin layer is formed by applying a coating liquid containing a PVA-based resin onto the thermoplastic resin substrate subjected to the stretching treatment and drying the coating liquid.

As the PVA resin, any suitable resin can be used. For example, polyvinyl alcohol and ethylene-vinyl alcohol copolymer. Polyvinyl alcohol is obtained by saponifying polyvinyl acetate. The ethylene-vinyl alcohol copolymer is obtained by saponifying an ethylene-vinyl acetate copolymer. The degree of saponification of the PVA resin is usually from 85 mol% to 100 mol%, preferably from 95.0 mol% to 99.95 mol%, and more preferably from 99.0 mol% to 99.93 mol%. The saponification degree can be obtained according to JIS K 6726-1994. By using such a saponification degree PVA resin, a polarizing film having excellent durability can be obtained. When the degree of saponification is excessively high, the coating liquid tends to gel and it may be difficult to form a uniform coating film.

The average degree of polymerization of the PVA resin can be appropriately selected depending on the purpose. The average degree of polymerization is usually from 1000 to 10000, preferably from 1200 to 4500, and more preferably from 1500 to 4300. The average polymerization degree can be obtained according to JIS K 6726-1994.

The coating liquid is typically a solution in which the PVA resin is dissolved in a solvent. Examples of the solvent include water, dimethylsulfoxide, dimethylformamide, dimethylacetamide N-methylpyrrolidone, various glycols, polyhydric alcohols such as trimethylolpropane, ethylenediamine, diethylenetriamine and the like Amines. These may be used alone or in combination of two or more. Of these, water is preferable. The concentration of the PVA resin in the solution is preferably 3 parts by weight to 20 parts by weight based on 100 parts by weight of the solvent. With such a resin concentration, a uniform coating film adhered to the thermoplastic resin substrate can be formed.

An additive may be added to the coating liquid. Examples of the additive include plasticizers, surfactants, and the like. Examples of the plasticizer include polyhydric alcohols such as ethylene glycol and glycerin. The surfactant includes, for example, nonionic surfactants. These can be used for further improving the uniformity, dyeability and stretchability of the resulting PVA-based resin layer.

As a coating method of the coating liquid, any appropriate method can be adopted. Examples of the coating method include a roll coating method, a spin coating method, a wire bar coating method, a dip coating method, a die coating method, a curtain coating method, a spray coating method, and a knife coating method (comma coating method).

The drying temperature is preferably not higher than the glass transition temperature (Tg) of the thermoplastic resin-based material, more preferably not higher than Tg-20 ° C. By drying at such a temperature, it is possible to prevent the thermoplastic resin base from being deformed before forming the PVA-based resin layer, and to prevent the orientation property of the obtained PVA-based resin layer from deteriorating. In this way, the thermoplastic resin base material can be well deformed together with the PVA resin layer, so that the later-described laminate can be relaxed and stretched well. As a result, it is possible to obtain a polarizing film having favorable optical properties and good orientation property to the PVA resin layer. Here, " orientation property " means orientation of the molecular chains of the PVA resin layer.

Then, in the relaxation process (TD relaxation zone B), the resin film 50 gripped by the left and right clips 20 is conveyed in the longitudinal direction and relaxed in the width direction. In the TD relaxation zone B, since the left and right endless rails 10R and 10L are tapered portions in which the rail-to-rail distance is continuously reduced, the clip interval in the width direction decreases from W1 to W2, Thereby, the resin film 50 is relaxed in the width direction. The amount of relaxation can be controlled by adjusting the amount of change in the distance between rails. Concretely, at the exit of the TD relaxation zone B (the end portion on the MD stretching zone C side) with respect to the rail-to-rail distance at the entrance of the TD relaxation zone B The smaller the ratio of the rail-to-rail distance is, the larger the amount of relaxation is obtained. In this specification, " loosening the resin film in the width direction " means forming a region loosened in the width direction (in other words, tension is not applied) to the resin film, and in one embodiment In this case, the resin film may be shrunk in the width direction.

In the embodiment shown in Fig. 2, only the relaxation in the width direction of the resin film 50 is performed in the relaxation step. In this case, the resin film 50 is passed through the TD relaxation zone B while maintaining the clip interval L1 in the conveying direction. On the other hand, in the embodiment shown in Fig. 3, in the relaxation step, the resin film 50 is relaxed in the width direction and stretched in the longitudinal direction. In this case, while moving the resin film 50 through the TD relaxation zone B, the moving speed of the clip 20 in the carrying direction is gradually increased to enlarge the clip interval in the carrying direction from L1 to L1 '. By performing MD stretching in multiple steps in the relaxation process and the stretching process, the final stretch ratio can be increased. In addition, since relaxation in the width direction and stretching in the length direction can be performed at the same time, excessive relaxation can be avoided, so that the effect of suppressing the generation of wrinkles caused by relaxation can be obtained.

The reduction ratio B (B = W2 / W1) of the clip interval in the width direction can be set to any appropriate value depending on the MD stretching magnification or the like. The reduction magnification B is preferably 0.60 to 0.99, more preferably 0.65 to 0.90, and still more preferably 0.70 to 0.80. With such a reduction magnification, the relaxed region can be preferably formed in the width direction of the resin film. Further, in the production of the polarizing film, more excellent optical characteristics can be obtained. The clip interval in the width direction can correspond to the width of the resin film held in the right and left clips.

In the embodiment in which the relaxation process includes MD stretching (the embodiment exemplified in Fig. 3), in the case of uniaxially stretching in the longitudinal direction at the free end, the shrinkage ratio in the width direction is set to be larger than the shrinkage rate in the width direction, It is preferable to reduce the interval. Concretely, it is preferable that the stretching magnification a (a = L1 '/ L1) in the longitudinal direction and the decreasing magnification B of the clip interval in the width direction satisfy the relation of B < 1 / When such a relationship is satisfied, a relaxed region can be preferably formed in the width direction of the resin film irrespective of stretching in the longitudinal direction. The stretching magnification a in the longitudinal direction may preferably be 1.0 to 5.5 times, more preferably 1.1 to 4.0 times.

The temperature (relaxation temperature) of the resin film in the relaxation process can be set to any appropriate value depending on the material for forming the resin film and the like. The relaxation temperature of the laminate in the case of producing the polarizing film is typically at least the glass transition temperature (Tg) of the thermoplastic resin base, preferably at least the glass transition temperature (Tg) of the thermoplastic resin base is at least 10 ° C Preferably at least Tg + 15 占 폚. On the other hand, the relaxation temperature of the laminate is preferably 170 占 폚 or less.

Then, in the stretching step (MD stretching zone C), the resin film 50 held by the left and right clips 20 is stretched in the longitudinal direction while being transported in the longitudinal direction. The stretching of the resin film 50 is performed by gradually increasing the moving speed of the clip 20 in the carrying direction and enlarging the clip interval in the carrying direction to L2. By adjusting the clip interval (L1 or L1 ') in the conveying direction at the entrance of the MD stretching zone (C) and the clip interval (L2) in the conveying direction at the exit of the MD stretching zone (C) L2 / L1 when the process does not include MD stretching, and L2 / L1 'when the process includes MD stretching). In the stretching step, the shrinkage in the width direction may be simultaneously carried out. When the shrinkage in the width direction is simultaneously performed in the stretching process, a tapered portion in which the distance between the rails of the left and right endless rails 10R, 10L is continuously decreased in the MD stretching zone C may be formed. By adjusting the amount of decrease in the distance between the left and right rails, the shrinkage ratio in the width direction can be controlled.

The total stretching ratio (the product of the stretch ratio in the stretching process and the stretch ratio in the relaxation process, L2 / L1) of the resin film after the stretching process is preferably 2.0 times or more , More preferably from 2.0 times to 6.5 times.

The stretching temperature can be set to any appropriate value depending on the material for forming the resin film and the like. The stretching temperature in the case of producing the polarizing film is typically at least the glass transition temperature (Tg) of the thermoplastic resin base, preferably at least the glass transition temperature (Tg) of the thermoplastic resin base is at least 10 ° C, Tg + 15 ℃ or higher. On the other hand, the stretching temperature is preferably 170 占 폚 or less. By stretching at such a temperature, the crystallization of the PVA-based resin can be inhibited from proceeding rapidly, and the problems caused by the crystallization can be suppressed (for example, the orientation of the PVA-based resin layer by stretching is prevented).

Finally, in the release process (release zone D), the clip 20 holding the resin film 50 is released. In the liberation process, typically, the distance between clips and the interval between clips are constant. If necessary, the resin film 50 is cooled to a desired temperature (preferably, a glass transition temperature (Tg) or lower), and then the clip is released.

The production method of the optical film of the present invention may include other processes besides the above. Other processes in the case of producing the polarizing film as the optical film include, for example, an insolubilization process, a dyeing process, a crosslinking process, a stretching process different from the stretching process, a cleaning process, a drying process . Other processes can be carried out at any appropriate timing.

The dyeing step is typically a step of dyeing the PVA resin layer with a dichroic substance. Preferably, this is carried out by adsorbing a dichroic substance on the PVA-based resin layer. Examples of the adsorption method include a method of immersing a PVA resin layer (laminate) in a dyeing solution containing a dichroic substance, a method of applying a dyeing solution to a PVA resin layer, a method of dyeing a PVA resin layer And a method of spraying the liquid. Preferably, the laminate is immersed in a dyeing solution containing a dichroic substance. This is because the dichroic material can be adsorbed well. Both sides of the laminate may be immersed in the dyeing solution, or only one side may be immersed. In the dyeing step and / or the crosslinking step to be described later, drawing may be performed at the same time.

Examples of the dichroic material include iodine and organic dyes. These may be used alone or in combination of two or more. The dichroic substance is preferably iodine. When iodine is used as the dichroic substance, the dyeing solution is preferably an iodine aqueous solution. The blending amount of iodine is preferably 0.1 part by weight to 1.0 part by weight with respect to 100 parts by weight of water. In order to increase the solubility of iodine in water, it is preferable to add an iodide salt to an aqueous solution of iodine. Examples of the iodide salt include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, titanium iodide and the like. Of these, potassium iodide and sodium iodide are preferable. The compounding amount of the iodide salt is preferably 0.3 part by weight to 15 parts by weight based on 100 parts by weight of water.

The liquid temperature at the time of dyeing the staining solution is preferably 20 ° C to 40 ° C. When the PVA resin layer is immersed in the dyeing solution, the immersing time is preferably 5 to 300 seconds. Under such conditions, the dichroic substance can be sufficiently adsorbed to the PVA-based resin layer.

The insolubilization step and the crosslinking step are typically carried out by immersing a PVA-based resin layer in an aqueous solution of boric acid. The cleaning step is typically performed by immersing the PVA resin layer in an aqueous solution of potassium iodide. The drying temperature in the drying step is preferably 30 ° C to 100 ° C.

B. Polarizing film

The polarizing film produced by the above production method is substantially a PVA-based resin film in which a dichroic substance is adsorbed and oriented. The polarizing film preferably exhibits absorption dichroism at a wavelength of 380 nm to 780 nm.

As for the method of using the polarizing film, any suitable method can be employed. Specifically, it may be used in a state of being integrated with the thermoplastic resin base material, or may be transferred from the thermoplastic resin base material to another member (by peeling the thermoplastic resin base material).

The polarizing film produced by the above production method can exhibit small shrinkage stress and excellent dimensional stability even under a high temperature environment. The degree of polarization at a unit transmittance of 42% is preferably 99.99% or more. Thus, the optical characteristics can be excellent.

Example

Hereinafter, the present invention will be described concretely with reference to examples, but the present invention is not limited to these examples.

[Example 1]

≪ Preparation of laminate >

As a thermoplastic resin substrate, an amorphous PET substrate (100 탆 thick) was prepared, and an aqueous solution of PVA was applied to the amorphous PET substrate and dried at a temperature of 50 캜 to 60 캜. Thus, a PVA layer having a thickness of 14 탆 was formed on the amorphous PET substrate to prepare a laminate.

≪ TD relaxation and MD stretching >

The resultant laminate was relaxed in the width direction using a stretching device as shown in Fig. 1, and then stretched in the longitudinal direction. Concretely, in the ridge zone A, both side edges of the laminate were gripped at a clip interval L1 of 40 mm and conveyed in the longitudinal direction. In TD relaxation zone B, Was reduced from 800 mm (W1) to 680 mm (W2) to shrink the laminate in the width direction (clip spacing L1 'at the exit of the TD relaxation zone (B): 40 mm). Then, in the MD stretching zone C, the laminate was air-stretched three times in the longitudinal direction at 120 占 폚 (the clip interval L2 at the exit of the MD stretching zone C: 120 mm, the clip interval W3 in the width direction : 680 mm). Thereafter, in the release zone D, the clip holding the laminate was released.

The stretching magnification a (a = L1 '/ L1) in the longitudinal direction in the TD relaxation is 1, the magnification B (B = W2 / W1) of the clip interval in the width direction is 0.85 and B <1 / Respectively.

In TD relaxation and MD stretching, chucking miss did not occur.

<Dyeing treatment>

Subsequently, the laminate was immersed in an aqueous iodine solution (iodine concentration: 0.5 wt%, potassium iodide concentration: 10 wt%) at 25 캜 for 30 seconds.

<Crosslinking Treatment>

The laminate after dyeing was immersed in a boric acid aqueous solution (boric acid concentration: 5% by weight, potassium iodide concentration: 5% by weight) at 60 캜 for 60 seconds and stretched 1.6 times in the MD direction (total draw magnification: 5 times).

<Cleaning Treatment>

After the crosslinking treatment, the laminate was immersed in an aqueous potassium iodide solution (potassium iodide concentration: 5 wt%) at 25 캜 for 5 seconds.

Thus, a polarizing film having a thickness of 3.5 탆 was formed on the thermoplastic resin substrate.

[Example 2]

A polarizing film having a thickness of 3.5 탆 was formed on the thermoplastic resin substrate in the same manner as in Example 1, except that TD relaxation and MD stretching were carried out as follows.

&Lt; TD relaxation and MD stretching &gt;

The resultant laminate was relaxed in the width direction using a stretching device as shown in Fig. 1, and then stretched in the longitudinal direction. Concretely, in the ridge zone A, both side edges of the laminate were gripped at a clip interval L1 of 40 mm and conveyed in the longitudinal direction. In TD relaxation zone B, Was reduced from 800 mm (W1) to 680 mm (W2) to shrink the laminate in the width direction. At the same time, in the TD relaxation zone B, the clip interval was increased to L1 ': 45 mm and stretched in the longitudinal direction. Then, in the MD stretching zone C, the laminate was air-stretched three times in the longitudinal direction at 120 占 폚 (the clip interval L2 at the exit of the MD stretching zone C: 120 mm, the clip interval W3 in the width direction : 680 mm). Thereafter, in the release zone D, the clip holding the laminate was released. That is, TD relaxation and MD stretching were carried out in the same manner as in Example 1, except that MD stretching was performed simultaneously in the TD relax zone (B).

1 /? A is 0.943, and the reduction magnification B (B = W2 / W1) of the clip interval in the width direction is? 0.85, and the relation of B &lt; 1 /? A was satisfied.

In TD relaxation and MD stretching, chucking miss did not occur.

[Example 3]

A polarizing film having a thickness of 3.5 탆 was formed on the thermoplastic resin substrate in the same manner as in Example 1, except that TD relaxation and MD stretching were carried out as follows.

&Lt; TD relaxation and MD stretching &gt;

The resultant laminate was relaxed in the width direction using a stretching device as shown in Fig. 1, and then stretched in the longitudinal direction. Concretely, in the ridge zone A, both side edges of the laminate were gripped at a clip interval L1 of 40 mm and conveyed in the longitudinal direction. In TD relaxation zone B, Was reduced from 800 mm (W1) to 680 mm (W2) to shrink the laminate in the width direction. At the same time, in the TD relaxation zone B, the clip interval was increased to L1 ': 45 mm and stretched in the longitudinal direction. Then, in the MD stretching zone C, the laminate was air-stretched three times in the longitudinal direction at 120 占 폚 (clip interval L2 at the exit of the MD stretching zone C: 120 mm). At the same time, in the MD stretching zone C, the interval between the clips in the width direction was reduced from 680 mm (W2) to 560 mm (W3) to shrink the laminate in the width direction. Thereafter, in the release zone D, the clip holding the laminate was released. That is, TD stretching and MD stretching were performed in the same manner as in Example 1, except that the MD stretching was simultaneously performed in the TD relaxation zone (B) and the width stretching was simultaneously performed in the MD stretching zone (C) Respectively.

1 /? A is 0.943, and the reduction magnification B (B = W2 / W1) of the clip interval in the width direction is? 0.85, and the relation of B &lt; 1 /? A was satisfied.

In TD relaxation and MD stretching, chucking miss did not occur.

[Example 4]

A polarizing film having a thickness of 3.5 탆 was formed on the thermoplastic resin substrate in the same manner as in Example 1, except that TD relaxation and MD stretching were carried out as follows.

&Lt; TD relaxation and MD stretching &gt;

The resultant laminate was relaxed in the width direction using a stretching device as shown in Fig. 1, and then stretched in the longitudinal direction. Concretely, in the ridge zone A, both side edges of the laminate were gripped at a clip interval L1 of 40 mm and conveyed in the longitudinal direction. In TD relaxation zone B, Was reduced from 800 mm (W1) to 680 mm (W2) to shrink the laminate in the width direction. At the same time, in the TD relaxation zone B, the clip interval was increased to L1 ': 60 mm and stretched in the longitudinal direction. Then, in the MD stretching zone C, the laminate was air-stretched three times in the longitudinal direction at 120 占 폚 (clip interval L2 at the exit of the MD stretching zone C: 120 mm). At the same time, in the MD stretching zone C, the interval between the clips in the width direction was reduced from 680 mm (W2) to 560 mm (W3) to shrink the laminate in the width direction. Thereafter, in the release zone D, the clip holding the laminate was released. That is, TD relaxation and MD stretching were carried out in the same manner as in Example 3, except that the MD stretching magnification in the TD relaxation zone (B) was 1.5 times.

1 /? A is 0.816, and the reduction magnification B (B = W2 / W1) of the clip interval in the width direction is 1.5? 0.85, and the relation of B &lt; 1 /? A was not satisfied.

In the TD relaxation and MD stretching, although some wrinkles were found in the laminate, chucking miss did not occur, and practical problems did not occur.

[Comparative Example 1]

A polarizing film having a thickness of 3.5 탆 was produced on a thermoplastic resin substrate in the same manner as in Example 1 except that MD stretching and TD shrinkage were carried out as follows.

&Lt; MD stretching and TD shrinkage &gt;

The obtained laminate was first stretched in the longitudinal direction, and then stretched in the longitudinal direction to shrink in the width direction. Concretely, at first, the side edge portions of the laminate were gripped at the clip interval L1: 40 mm and conveyed in the longitudinal direction. Then, while the clip interval in the width direction at 100 DEG C was maintained at 800 mm (W1) ': 70 mm and stretched in the machine direction. Subsequently, the distance between the clips in the width direction at 120 DEG C was reduced from 800 mm (W2 = W1) to 560 mm (W3) to air-stretch the laminate three times in the longitudinal direction while shrinking the laminate in the width direction Clip interval L2: 120 mm). Thereafter, in the release zone D, the clip holding the laminate was released.

In MD stretching and TD shrinkage, a chucking error occurred.

[evaluation]

As is apparent from comparison between Examples 1 to 4 and Comparative Example 1, it is possible to suppress the occurrence of chucking mistakes by loosening the resin film in the width direction before stretching in the longitudinal direction. As is obvious from comparison between Example 3 and Example 4, by controlling the stretching ratio in the longitudinal direction and the decreasing magnification of the clip interval in the width direction in TD relaxation to a predetermined relationship, occurrence of wrinkles or the like is further suppressed As a result, it can be seen that the occurrence of chucking mist can be further suppressed.

Industrial availability

The production method of the present invention is preferably used for producing optical films such as polarizing films and optical compensation films.

10: Rail
20: Clip
50: laminate (resin film)
100: stretching device

Claims (6)

A method of manufacturing an optical film using a tenter stretching apparatus having a plurality of clips as gripping means,
(Gripping step) of grasping both edge portions of the elongated-phase resin film by the clip at the clip interval L1 in the carrying direction,
(The loosening step) of loosening the resin film in the width direction by reducing the clip interval in the width direction from W1 to W2 while conveying the resin film in the longitudinal direction,
(Stretching step) of stretching the resin film in the longitudinal direction by extending the clip interval in the carrying direction to L2 while conveying the resin film relaxed in the width direction in the longitudinal direction. The method according to claim 1,
Wherein the total draw ratio A (A = L2 / L1) in the longitudinal direction is 2.0 or more. The method according to claim 1,
And the reduction ratio B (B = W2 / W1) of the clip interval in the width direction is 0.60 to 0.99. The method according to claim 1,
Wherein the relaxation step includes stretching the resin film in the longitudinal direction by reducing the clip interval in the width direction and enlarging the clip interval in the carrying direction to L1 '
Wherein a ratio of a stretching magnification a in a longitudinal direction (a = L1 '/ L1) and a decreasing magnification B (B = W2 / W1) of a clip interval in a width direction satisfies B <1 / . The method according to claim 1,
Wherein the thickness of the optical film to be produced is 110 占 퐉 or less. The method according to claim 1,
Wherein the optical film to be produced is a polarizing film.

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