TWI551894B - Method of manufacturing polarizing film - Google Patents

Description

Polarized film manufacturing method Field of invention

The present invention relates to a method for producing a polarizing film which is obtained by moving a belt-shaped polyvinyl alcohol-based resin film while extending in a longitudinal direction of the moving path.

Background of the invention

Conventionally, an optical film including a polarizing film or the like can be used for an image display device such as a liquid crystal display device.

In the method for producing such a polarizing film, a polyvinyl alcohol-based resin film (raw material roll film) can be fed by using a raw material roll in which a strip-shaped polyvinyl alcohol-based resin (PVA) film which is a raw material is wound into a roll shape. This method is extended by providing a device which restricts the movement path of the raw material roll film and simultaneously guides a plurality of roll shafts of the raw material roll film and various chemical liquid baths. For example, a method in which the raw material roll film is moved in the longitudinal direction and continuously immersed in a swelling bath or a dye bath, and the raw material roll film is sandwiched by the roll shaft at the front and rear positions, and tension is applied therebetween to carry out the stretching.

Incidentally, in the method for producing such a polarizing film, it is very complicated and time consuming to install a new material roll film around a reel or the like every time the material roll is replaced. Therefore, the end portion of the raw material roll film of the front end is joined to the front end portion of the raw material roll film fed from the raw material roll described below, and the raw material roll film is continuously supplied to the apparatus in this order.

Such a joining method can be carried out by a conventional bonding method such as an adhesive tape or an adhesive, a sewing method by a rivet or a thread, or a heat welding method by a heat sealer or the like.

However, among the methods as described above, there are problems as described below.

‧ Problems in bonding by adhesive tape or adhesive

In the step of immersing the raw material roll film in a swelling bath, a dye bath, or the like, the components of the adhesive are eluted into the chemical solution, thereby contaminating the chemical liquid, which may cause foreign matter to adhere to the product. In addition, the adhesive is dissolved in the chemical solution or swollen by the components of the chemical solution, resulting in a decrease in the joint strength, and during the stretching step, the joint portion may be broken before the desired stretch ratio is reached.

‧ Problems in stitching by rivets or wires

In this method, a hole for passing the rivet or the wire through the raw material roll film is provided. Therefore, when tension is applied to the joint portion, there is a fear that the hole is broken as a starting point.

If the number of holes is reduced or the interval between the holes is increased in order to prevent such a phenomenon, wrinkles are likely to occur when tension is applied, and there is a concern that unevenness may occur.

‧ Problems in heating fusion by heat sealing machine, etc.

A method of joining the problems in the bonding or the stitching as described above is known, and a method of joining by a heat sealing machine as disclosed in Patent Documents 1, 2, and 3 below is known.

In this method, the concern of the contaminated liquid is lower than that of the bonding, and there is no need The holes are to be sewn together.

However, in the case of a heat sealer, the welded region and its periphery tend to be denatured by heat during welding, and tend to be harder than a normal portion.

Therefore, if the welding zone is clamped and stretched when the extension is applied, the boundary between the hardened portion and the normal state tends to concentrate stress locally, and the region will be concentrated until the entire stretch ratio is desired. There are extreme extension concerns.

Therefore, if elongation is to be performed at a high stretching ratio, there is a concern that the raw material roll film of the joint portion is broken.

Prior technical literature Patent literature

Patent Document 1: Japanese Laid-Open Patent Publication No. 2007-171897

Patent Document 2: Japanese Laid-Open Patent Publication No. 2010-8509

Patent Document 3: Japanese Patent Laid-Open Publication No. 2004-160665

Summary of invention

In order to impart a high polarizing function to the polarizing film, it is generally required to apply an extension of 5.25 times or more. However, when the raw material roll film made of the polyvinyl alcohol-based resin is connected by the conventional connection method as described above, the connection portion cannot withstand an extension load of 5.25 times or more, and there is a fear that cracking may occur. Therefore, there is a countermeasure for changing the stretching ratio when the connecting portion is passed to less than 5.25 times to avoid cracking.

However, when the countermeasure for avoiding as described above is selected, the stretching ratio before and after the connecting portion cannot be a desired magnification (5.25 times or more), so that it cannot be used as a product, and the material is lost.

It is difficult to carry out the continuous transfer of the raw material roll film made of the polyvinyl alcohol-based resin which is connected in this manner with a stretching ratio of 5.25 times or more with respect to the raw material roll film, and it is difficult to carry out the continuous transfer. The connection method for extension and handling has not been proposed so far.

In other words, in the conventional method for producing a polarizing film, there is a problem that it is difficult to efficiently produce a polarizing film having a high polarizing function.

The present invention has been made in view of the above problems, and an object thereof is to provide a method for producing a polarizing film, which can efficiently produce a polarizing film having a high polarizing function.

The present invention for solving the above problems is a method for producing a polarizing film in which a polarizing film is continuously produced by using a plurality of strip-shaped polyvinyl alcohol-based resin films, and is characterized in that the first step is to sequentially The polyvinyl alcohol-based resin film is fed into the movement path from the distal end side and extends in the longitudinal direction in the movement path; and the second step is to terminate the distal end portion of the first polyvinyl alcohol-based resin film before the first step. The tip end portions of the two polyvinyl alcohol-based resin films are overlapped and joined by welding, and in the second step, the initial elastic modulus of the joined portion can be 65% or more with respect to the initial elastic modulus of the non-joined portion. The bonding is performed in a manner of 100% or less.

In the present invention, the initial elastic modulus of the joint portion means that the joint portion is cut out (the length of the polyvinyl alcohol-based resin film in the longitudinal direction is 1.5 mm) × (the length of the polyvinyl alcohol-based resin film in the width direction is 20 mm) In the region of the joint portion of the cut joint portion, the stress obtained by the tensile test was performed under the condition of an initial inter-clamp distance of 10 mm and a tensile speed of 0.1 mm/min in an environment of room temperature of 20 ° C - The tangent slope at a stress of 1 N/mm ² in the deformation curve.

In addition, the initial elastic modulus of the non-joining portion means a region cut in the non-joining portion (the length in the longitudinal direction of 3.0 mm) × (the length in the width direction is 20 mm), and the non-joining portion of the cut non-joining portion is sliced. The tangential slope at a stress of 1 N/mm ² in a stress-deformation curve obtained by tensile test under the conditions of an initial inter-clamp distance of 10 mm and a tensile speed of 0.1 mm/min in an environment of room temperature of 20 °C.

Further, when the width of the joint portion is less than 1.5 mm, the length that can be taken is set as the length in the longitudinal direction of the joint portion, and the length of the length is twice as long as the long side in the non-joining portion. The direction length was cut out and evaluated in the same manner as described above, whereby the initial elastic modulus of the joint portion and the non-joining portion was obtained.

In the two or more strip-shaped polyvinyl alcohol-based resin films which are stretched by the above-described production method, the terminal portion of the first strip-shaped polyvinyl alcohol-based resin film and the second strip-shaped polyvinyl alcohol connected thereto can be obtained. The front end portion of the resin film is joined so that the initial elastic modulus of the joined portion of the welded portion is equal to the initial elastic modulus of the non-joined portion so as to satisfy the above relationship. Thereby, the hardness of the joint portion can be made close enough to the hardness of the non-joining portion, and thus the length is When the joint portion is extended in the side direction, stress concentration due to the extension of the boundary portion between the joint portion and the non-joining portion can be alleviated. Therefore, even if it is extended at an extension ratio of, for example, 5.25 times or more, the occurrence of cracking in the above-described boundary can be avoided. Thereby, even when the joint portion passes, the extension can be continuously performed without changing the extension condition. Therefore, the effect of improving work efficiency, improving productivity, increasing productivity, and reducing material loss can be obtained.

Further, in the method for producing a polarizing film of the present invention, it is preferable that the second step is carried out by bonding and connecting the distal end portion and the distal end portion by laser welding.

This can be as follows. In other words, when the end portion and the tip end portion are integrally heated in the thickness direction by heat sealing or the like, the region where the joint portion as the welded portion is hardened becomes large. On the other hand, in the laser welding, only the interface between the tip end portion and the tip end portion or a region in the vicinity thereof can be locally heated and welded, so that the region where the joint portion is hardened can be made small. Therefore, in the case where the stretching is performed, the joint portion is formed by laser welding, and the joint portion is formed by heat sealing or the like, and the hardness of the joint portion is more likely to be close to the hardness of the non-joining portion. Therefore, it is easy to join so that the initial elastic modulus of the joint portion is 65% or more and 100% or less with respect to the initial elastic modulus of the non-joining portion.

Further, in the method for producing a polarizing film of the present invention, it is preferable that a light absorbing agent is disposed at an interface portion between the end portion and the tip end portion to perform the laser welding.

Thereby, the light absorption property of the laser light in the interface part of the front-end part and the terminal part improves, and it can fuse|melt the both with the high efficiency.

Further, in the method for producing a polarizing film of the present invention, the laser welding is preferably performed by an infrared laser having a wavelength of 800 nm or more and 11,000 nm or less.

Thereby, the end portion and the tip end portion can be efficiently melted, so that the first and second polyvinyl alcohol-based resin films can be joined and joined efficiently.

Further, in the method for producing a polarizing film of the present invention, the stretching ratio of each of the non-joining portion and the joint portion of the first polyvinyl alcohol-based resin film and the second polyvinyl alcohol-based resin film is preferably 5.25 times or more.

Thereby, the quality as a polarizing film can be improved.

As described above, according to the present invention, a polarizing film having a high polarizing function can be efficiently produced.

Simple illustration

Fig. 1 is a schematic perspective view showing an apparatus used in a method of producing a polarizing film according to an embodiment.

Fig. 2 is a schematic perspective view showing a state in which a raw material roll film is connected and supplied to a manufacturing apparatus of a polarizing film.

Fig. 3 is a schematic front view showing a mechanism for connecting a main part of a joining device of a raw material roll film.

Fig. 4 is a view showing a joint portion and a non-joining portion. Fig. 4(a) is a schematic side view, and Fig. 4(b) is a schematic plan view.

Fig. 5 is a view showing a section of a joint portion and a section of a non-joining portion, Fig. 5(a) In the schematic plan view of the joint portion, FIG. 5(b) is a schematic plan view of the non-joining portion.

Fig. 6 is a schematic plan view showing a joint portion or a non-joined portion slice before and during stretching.

Fig. 7 is a view showing an example of a stress-deformation curve and a tangent line in a stress of 1 N/mm ² .

Fig. 8 is a graph showing the ratio of the initial elastic modulus of the examples and the comparative examples.

Form for implementing the invention

Hereinafter, embodiments of the present invention will be described.

First, an extension device suitable for the method for producing the polarizing film of the present embodiment will be described with reference to the drawings.

The extension device of the present embodiment is provided with a raw material roll in which a strip-shaped polyvinyl alcohol-based resin film (hereinafter also referred to as "raw material roll film" or simply "film") is wound into a roll shape, and the raw material is fed. The raw material roll film supply unit 3 of the roll film 1; the plurality of immersion baths 4 for immersing the supplied material roll film 1 in a predetermined chemical solution; and the raw material roll film 1 passing through the immersion bath 4 to restrict the raw materials a plurality of roller shafts 9 for moving the film 1; an extending portion for extending the material roll film 1 in the moving path; and immersing in the plurality of immersion baths 4 and winding the stretched film as a polarizing film into a roll shape The polarizing film winding portion 10.

Figures 1 and 2 are schematic perspective views showing one form of a suitable extension device.

As shown in Fig. 1, the extension device is provided with a plurality of dip baths 4; The swelling bath 4a in which the swelling liquid which swells the polyvinyl alcohol-type resin film is stored, the dyeing bath 4b which preserves the dyeing liquid which dyed the film after swelling, and the storage of the dyeing liquid 4b of the dyeing liquid which swelled the film| a cross-linking bath 4c of a cross-linking agent liquid of a molecular chain of a resin of a film, an extension bath 4d for extending a film in a bath, and a washing liquid for storing a film to be washed through the stretching bath 4d. Wash bath 4f these 5 kinds of dip bath 4.

Further, in the extension device of the present embodiment, the drying device 11 for drying the film, specifically, the drying oven, is provided on the downstream side of the washing bath 4f in the moving path of the film and on the upstream side of the winding portion 10.

Further, in the stretching device of the present embodiment, the film for laminated film 12 which is wound into a roll-shaped surface protective film (for example, a triethylenesulfonated cellulose film or a cycloolefin polymer film) is disposed on the above-mentioned On both sides of the film after drying of the drying device 11, a layering device for laminating the film for lamination 12 on both surfaces of the dried film is provided.

The aforementioned extension portion may employ a so-called roller shaft extension portion 9a. In other words, a pair of nip rollers 9a formed by arranging a plurality of sets in the moving path to sandwich the film therebetween and feeding the downstream side in the flow direction may be employed, and the configuration is set to be downstream of the flow direction. The rotational speed of the roller group on the side is higher than that on the upstream side.

Further, the stretching apparatus is configured such that two or more raw material roll films can be continuously extended, and the end portion of the first raw material roll film in the two or more raw material roll films is provided A device for joining two raw material film films. That is, as shown in Fig. 2, the present stretching apparatus is provided with a moving path for restricting the end portion 1a of the first raw material roll film 1 passing through the front end, specifically, before the immersion bath 4 the first A connecting device (not shown) in which the tip end portion 1a of the material roll film 1 and the front end portion 1b of the new material roll film (second material roll film) in the moving path after passing through the material roll film 1 are joined by laser welding (not shown) In Figure 2).

Further, in the second drawing, a portion (welded portion) joined by laser irradiation is indicated by the blackened portion 30.

Next, reference is made to Fig. 3 and a description will be made for a suitable joining device.

This third drawing shows a schematic configuration of a connecting device in which raw material roll films are joined to each other by laser welding.

Fig. 3 is a front view showing a connecting device in which the material roll film to be joined is viewed from the side surface in the TD direction (width direction).

As shown in FIG. 3, the connecting device has a pedestal 40 having a flat upper surface, a pressing member 50 disposed above the pedestal 40 and movable in the vertical direction, and a pressing member 50 disposed on the pedestal 40. A laser light source (not shown) above the pressing member 50. Further, the distal end portion 1a of the first raw material roll film 1 at the front and the front end portion 1b of the new second raw material roll film 1 connected thereto are vertically overlapped on the pedestal 40, and the pressurizing member 50 overlaps the front end portion 1b. When the laser light is partially pressurized and the laser light R is irradiated by the laser light source, the interface between the distal end portion 1a and the distal end portion 1b can be heated and melted and welded. Further, the pressurizing member 50 is composed of a transparent member having excellent light transmittance of the laser light R.

Further, in the above-described connection device, the light absorption property of the laser beam R in the interface portion between the end portion 1a and the tip end portion 1b can be improved, and the interface can be provided in a more efficient manner. In the portion, the coating device of the light absorbing agent is applied in advance to any of the surfaces (or both surfaces) of the end portion 1a or the front end portion 1b where the surfaces are in contact with each other.

Further, the light absorbing agent used herein is not particularly limited as long as it absorbs the laser light R to generate heat, and carbon black, a pigment, a dye, water, or the like can be used.

For example, an anthraquinone-based absorbent, a naphthoquinone-based absorbent, a polymethine-based absorbent, a diphenylmethane-based absorbent, a triphenylmethane-based absorbent, an anthraquinone-based absorbent, an azo-based absorbent, or the like may be used. Diammonium salt and the like.

Further, in the case of using a laser light source that emits laser light R having a wavelength of 800 nm to 1200 nm, for example, a light absorbing agent commercially available under the trade name "Clearweld (registered trademark)" manufactured by Gentex Corporation of the United States can be used.

These absorbents can be diluted with an organic solvent or the like and applied by the aforementioned coating device. The coating device may be a general coating device such as a spreader, an ink jet printer, a screen printer, a 2-fluid, a 1-fluid or ultrasonic spray, a printer, a coater or the like.

Further, among the connection devices, the type of the laser light source to be used is not particularly limited. The laser light system used has a light absorbing agent disposed at the interface of the new and old material roll film at the interface of the new and old material roll film, and is applied to the surface of one or both of the material roll films. It has a function of heating, and it is preferable to have absorption sensitivity at a high wavelength for the light absorbing agent to be used.

Specifically, the types of the laser light include a semiconductor laser having a wavelength in the visible light region or the infrared region, a fiber laser, a femtosecond laser, a picosecond laser, a YAG laser, a solid laser, and a CO ₂ laser. Wait for a gas laser.

Among them, a semiconductor laser or a fiber laser which is easy to obtain an inexpensive and in-plane uniform laser beam is preferable.

Further, in order to avoid decomposition of the raw material roll film and to promote melting, it is preferable to use a continuous wave CW laser as compared with a pulse laser which instantaneously inputs high energy.

The output (power) of the laser light, the size and shape of the beam, the number of times of irradiation, and even the scanning speed, etc., are as long as the optical characteristics of the material roll film and the light absorbing agent of the object, or the melting point of the polymer constituting the film of the material roll, The difference in thermal characteristics such as the glass transition point (Tg) can be optimized. In the laser irradiated part, in order to efficiently flow the polyvinyl alcohol-based resin to give a robust bond, the irradiation power density of a laser beam system in the range of ^{200W / cm 2 ~ 10,000W / cm} 2 is preferred, at 300W / cm ² ~ 5,000W / cm ² is within the range of more preferably, in the range of ^{1,000W / cm 2 ~ 3,000W / cm} 2 is particularly preferred.

In addition, the laser irradiation conditions are not particularly limited as long as the initial elastic modulus of the joint portion is 65% or more and 100% or less with respect to the initial elastic modulus of the non-joining portion. .

Further, among the connecting devices, it is preferable that the laser light source used is irradiated with laser light at a spot diameter (irradiation width) of a predetermined size at the interface between the new and old material roll films.

The irradiation spot diameter (irradiation width) is a power that satisfies the above-described irradiation laser power density, and preferably 1/10 or more and 3 times or less of the overlap width of the old and new material roll films.

When the overlap width is less than 1/10, the unjoined portion of the overlapping portion is large, and there is a concern that the conveyance after the joining is disturbed and the good handling property is hindered.

Further, when the laser light is irradiated with a width of more than three times, the bonding and the extension characteristics are not affected, but it is not preferable from the viewpoint of energy utilization efficiency.

It is preferably 1/5 or more and 2 times or less of the overlap width.

In addition, when the overlapping width of the new and old material roll films is small, there is a concern that it is difficult to repeat and the wide-width material roll film is superposed with high precision. When the film thickness is increased, the unjoined area becomes large. There is a concern that the film becomes messy when transported after joining. Therefore, the overlapping width of the film of the new and old material rolls can be appropriately set, for example, from such a viewpoint.

In addition, the beam shape of the laser light may be circular, and may be linear from the viewpoint of obtaining a higher power density.

In addition, cumulative laser beam irradiation amount in the range of lines ^{5J / cm 2 ~ 400J / cm} 2 is preferred, and the range of ^{10J / cm 2 ~ 300J / cm} 2 is more ^{preferably, 30J / cm 2 ~ 150J /} cm The range of ² is particularly good.

Therefore, it is preferable to use a laser light source that satisfies these conditions for the connection device.

In the laser light irradiation, the pressurizing member 50 that presses the overlapped new and old material roll film (the end portion 1a of the old material roll film and the front end portion 1b of the new material roll film) on the pedestal can be used. A glass member exhibiting high transparency to the laser light used is used.

The pressing strength at the time of laser light irradiation is preferably in the range of 0.5 to 100 kgf/cm ² , more preferably in the range of 10 to 70 kgf/cm ² .

Therefore, among the aforementioned connecting devices, it is suitable as a pressurized structure. The member 50 is not particularly limited as long as it can be pressed at such strength, and for example, a flat plate, a cylinder, or a spherical shape can be used.

The thickness of the glass member is not particularly limited. However, if it is too thin, the pressure cannot be favorably pressurized due to deformation, and if it is too thick, the utilization efficiency of the laser light is lowered. Therefore, the thickness of the laser light in the light transmitting direction is preferably 3 mm or more and less than 30 mm, more preferably 5 mm or more and less than 20 mm.

Examples of the material of the pressing member 50 include quartz glass, alkali-free glass, TEMPAX, PYREX (registered trademark), BAYCOL, D263, OA10, AF45, ZERODUR, and the like.

In order to improve the utilization efficiency of the laser light R, the glass member used as the pressing member 50 preferably has high transparency with respect to the wavelength of the laser light to be used, and has a light transmittance of 50% or more and 70%. The above light transmittance is more preferable.

In addition, when the pressurizing member 50 is formed using the glass member as described above, it is also possible to pressurize the large area relatively uniformly, and it is possible to form the pressurizing member in a good manner over the entire region, and to be in a form of polyvinyl alcohol. The portion where the resin film is in contact with each other forms a buffer layer which is more excellent in cushioning properties than the above-described glass member.

In other words, a pressurizing member 50 having a rubber sheet having good light transmittance or a transparent resin sheet having a cushioning property may be used. For example, a pressurizing member 50 made of a transparent rubber sheet on the back side of the polyvinyl alcohol-based resin film may be used.

For the formation of the buffer layer, for example, a rubber-based material such as ruthenium rubber or urethane rubber or a resin material such as polyethylene can be used.

The thickness of the buffer layer is preferably 50 μm or more and less than 5 mm, more preferably 1 mm or more and less than 3 mm.

When the thickness is less than 50 μm, the cushioning property is lacking. When the thickness is 5 mm or more, the buffer layer absorbs or scatters the laser light, and the laser light energy reaching the contact interface portion between the distal end portion 1a and the distal end portion 1b is lowered. concern.

The buffer layer preferably has a light transmittance of 30% or more for the wavelength of the laser light to be used, and more preferably 50% or more.

Further, a buffer layer similar to the buffer layer may be disposed on the upper surface of the pedestal 40. In the case of being disposed on the pedestal 40, it is not limited to the optical characteristics of the material for forming the buffer layer, that is, the light transmittance is particularly limited, and in addition to the use of the ruthenium rubber or the like as described above, for example, polycarbonate may be used. Polyethylene terephthalate, norbornene resin, cycloolefin polymer, polymethyl methacrylate, polyimide, triethyl fluorene cellulose, and the like.

In the method for producing a polarizing film of the present embodiment, it is preferable to form the above-described connecting means so that the linear welding portion can be formed by performing laser welding along the overlapping portion of the superposed old and new material roll films. a mechanism for, for example, scanning a point beam that is condensed to a desired beam size by a collecting lens along an overlapping portion; linear laser beam by using an optical member such as a lenticular lens or a diffractive optical element Further, a mechanism for shaping and irradiating the overlapping portion of the raw material roll film; more preferably, a plurality of laser light sources are disposed along the overlapping portion, and irradiation is performed simultaneously without scanning, whereby a mechanism for performing fusion heat bonding at a time is preferable.

In addition, although not described in detail herein, the connecting device as described above may be a general laser welding device and a peripheral device thereof. Various institutions utilized.

Next, a method of manufacturing a polarizing film by using an extension device having such a connecting device will be described.

In the method for producing a polarizing film of the present embodiment, a plurality of strip-shaped polyvinyl alcohol-based resin films are used, and each of the polyvinyl alcohol-based resin films is fed into the moving path from the distal end side, and is elongated in the moving path. a first step of extending in the lateral direction; and a second step of overlapping the distal end portion of the first polyvinyl alcohol-based resin film of the front end with the distal end portion of the second polyvinyl alcohol-based resin film described below, and being joined by fusion bonding; A polarizing film is continuously produced.

In addition, in the second step, the initial elastic modulus of the joint portion is joined to the initial elastic modulus of the non-joining portion so as to be 65% or more and 100% or less.

Specifically, in the method for producing a polarizing film of the present embodiment, the first step is performed; the swelling step of immersing the raw material roll film in the swelling bath 4a to swell; and the swelled film is immersed in the dyeing bath. a dyeing step of dyeing 4b; a crosslinking step of immersing the dyed film in the crosslinking bath 4c to crosslink the molecular chain of the resin constituting the film; and extending the film after the crosslinking step in the stretching bath 4d Extension step.

In other words, in the method for producing a polarizing film of the present embodiment, the respective stretching ratios of the swelling bath 4a to the stretching bath 4d are extended so as to finally achieve the target stretching ratio.

Further, in the method for producing a polarizing film of the present embodiment, a washing step of washing the film after the stretching step, a drying step of drying the cleaned film by the drying device 11, and a drying step are performed. After drying A lamination step of a thin film laminated surface protective film.

In the method for producing a polarizing film of the present embodiment, the raw material roll film supply unit 3 continuously feeds the raw material roll film by the raw material roll film supply unit 3, and the moving material path is carried out. The above-described steps are completed by performing a winding step in which a product (polarizing film) that has finally completed the lamination step is wound into a roll in the polarizing film winding portion 10. Further, a plurality of raw material rolls are prepared, and before the first raw material rolls are used up, the raw material roll film is sent out by the new second raw material roll, so that the front end portion 1b of the new raw material roll film and the front portion are The joining step of joining the end portions 1a of one raw material roll and connecting them can be carried out separately as the second step.

Then, the raw material roll film is supplied to the stretching device by the new material roll, and the first step is performed to continuously manufacture the polarizing film. Further, the polarizing film can be continuously produced by repeating the first step and the second step in this order.

Further, the raw material roll film (belt-shaped polyvinyl alcohol-based resin film) supplied to such a step can be a film as described below.

A film composed of a polyvinyl alcohol-based polymer resin material used as a raw material of the polarizing film can be used as the material roll film used in the method for producing a polarizing film of the present embodiment. Specifically, for example, a polyvinyl alcohol film, a partially saponified polyvinyl alcohol film, or a dehydrated film of polyvinyl alcohol can be used.

Usually, these raw material roll films are used in a state in which they are wound into a roll of a raw material roll in the above manner.

Polymerization of a polymer forming a material of the above polyvinyl alcohol-based resin film The degree is generally in the range of 500 to 10,000, preferably in the range of 1,000 to 6,000, and preferably in the range of 1,400 to 4,000.

Further, in the case of a partially saponified polyvinyl alcohol film, for example, from the viewpoint of solubility in water, the degree of saponification is preferably 75 mol% or more, preferably 98 mol% or more, and 98.3 to 99.8 mol. The range of ear % is better.

In the polyvinyl alcohol-based resin film, a stock solution obtained by dissolving in water or an organic solvent can be suitably used, and the stock solution can be formed by any method such as a casting method, a casting method, or an extrusion method. film.

The phase difference of the raw material roll film is preferably 5 nm to 100 nm.

Further, in order to obtain a uniform polarizing film in the plane, the phase difference variation in the surface of the polyvinyl alcohol resin film is preferably as small as possible. The in-plane phase difference variation of the polyvinyl alcohol-based resin film as the raw material roll film is preferably 10 nm or less at the measurement wavelength of 1000 nm, more preferably 5 nm or less.

Further, the water absorption state at the time of joining by laser welding is preferably 2% by mass to 15% by mass, and more preferably 4% by mass to 10% by mass.

When the raw material roll film to be joined has a water absorption ratio of more than 15% by mass, foaming due to evaporation of moisture in the heating and melting portion during laser welding tends to occur, and there is a concern that bonding failure may occur.

On the other hand, when the water absorption rate is less than 2% by mass, the fluidity of the resin in the portion where the raw material roll film is heated by the laser is insufficient, and there is a concern that the joining efficiency is lowered.

From this point of view, the water absorption rate of the raw material roll film used at the time of joining is preferably within the above range.

Further, the water absorption rate can be obtained by comparing the masses before and after drying. For example, the polyvinyl alcohol-based resin film can be heated at 83 ° C for 1 hour, and the heating mass loss is divided by the polyvinyl alcohol before heating. The quality of the resin film is obtained.

Next, each step of processing the polarizing film for extending the above-mentioned material roll film by the above-described stretching device will be described.

(swelling step)

In this step, for example, the moving speed of the material roll film fed from the material roll film supply unit 3 is kept constant while being guided to the swelling bath 4a filled with water, and the raw material roll film is immersed in the roll shaft 9 In the water.

By this, the raw material roll film is washed with water, and the dirt or the anti-blocking agent on the surface of the raw material roll film can be washed, and the raw material roll film is swollen with water. Therefore, an effect of preventing unevenness in dyeing unevenness can be expected.

In addition to water, the swelling liquid in the swelling bath 4a may be appropriately added with glycerin, potassium iodide or the like. In the case where these are added, the concentration is preferably 5% by mass or less, and the case of potassium iodide is preferably 10% by mass or less.

The temperature of the swelling liquid is preferably in the range of 20 to 45 ° C, and more preferably in the range of 25 to 40 ° C.

The immersion time of the raw material roll film immersed in the swelling liquid is preferably 2 to 180 seconds, more preferably 10 to 150 seconds, and particularly preferably 30 to 120 seconds.

Further, in the swell bath, the polyvinyl alcohol-based resin film may be extended in the longitudinal direction, and at this time, the stretching ratio is caused by swelling. It is preferably 1.1 to 3.5 times inclusive.

(staining step)

The film which has passed through the swelling step is subjected to a dyeing step by immersing in the dyeing liquid stored in the dyeing bath 4b by the roll shaft 9 in the same manner as the swelling step.

The dyeing step may be carried out by immersing the polyvinyl alcohol-based resin film subjected to the swelling step in a dyeing liquid containing a dichroic substance such as iodine, thereby adsorbing the dichroic substance on the film.

As the dichroic substance, a conventionally known substance can be used, and examples thereof include iodine or an organic dye.

For the organic dye, for example, red BR, red LR, red R, pink LB, royal red BL, wine red GS, sky blue LG, lemon yellow, blue BR, blue 2R, navy RY, green LG, purple LB, purple B, Black H, Black B, Black GSP, Yellow 3G, Yellow R, Orange LR, Orange 3R, Scarlet GL, Scarlet KGL, Congo Red, Bright Purple BK, Turquoise Blue G, Turquoise GL, Green Orange GL, Direct Sky Blue, Direct fast orange S, fast black, etc.

These dichroic substances may be used alone or in combination of two or more.

In the case of using the above organic dye, for example, in order to achieve neutralization of the visible light region, it is preferred to combine two or more kinds.

Specific examples include a combination of Congo Red and Turquoise Blue G, Green Orange GL, and Direct Sky Blue, or a combination of direct sky blue and fast black.

As the dyeing liquid of the dye bath, a solution obtained by dissolving the above-mentioned dichroic substance in a solvent can be used.

As the solvent, water may be generally used, and an organic solvent having water-melting property may be further added.

The concentration of the dichroic substance in the dyeing liquid is preferably in the range of 0.010 to 10% by mass, preferably in the range of 0.020 to 7% by mass, and particularly preferably in the range of 0.025 to 5% by mass.

Further, in the case where iodine is used as the dichroic material, it is preferable to further add iodide from the viewpoint of further improving the dyeing efficiency.

Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, cesium iodide, calcium iodide, tin iodide, and titanium iodide.

The addition ratio of the iodide in the dye bath is preferably from 0.010 to 10% by mass, preferably from 0.10 to 5% by mass.

Among them, potassium iodide is preferred, and the ratio (mass ratio) of iodine to potassium iodide is preferably in the range of 1:5 to 1:100, and is preferably in the range of 1:6 to 1:80. Good, it is especially good in the range of 1:7~1:70.

The immersion time of the film immersed in the dye bath is not particularly limited, and is preferably in the range of 0.5 to 20 minutes, and more preferably in the range of 1 to 10 minutes. Further, the temperature of the dyeing bath is preferably in the range of 5 to 42 ° C, and preferably in the range of 10 to 35 ° C.

Further, in the dyeing bath, the film may be extended in the longitudinal direction, and the total stretching ratio accumulated at this time is preferably about 1.1 to 4.0 times.

Further, in addition to the method of immersing in the dye bath as described above, a dyeing step may be carried out, for example, by applying or spraying an aqueous solution containing a dichroic substance to the polymer film.

Further, in the present invention, it is also possible to use a film formed by a polymer raw material in which a dichroic substance is mixed in advance, without using a dyeing step. Raw material roll film.

(cross-linking step)

Next, the film is introduced into the crosslinking bath 4c in which the crosslinking agent liquid is stored, and the film is immersed in the crosslinking agent liquid to carry out a crosslinking step.

As the crosslinking agent, a conventionally known one can be used.

For example, a boron compound such as boric acid or borax, or glyoxal or glutaraldehyde can be used.

These may be used alone or in combination of two or more.

When two or more types are used in combination, for example, a combination of boric acid and borax is preferable, and the addition ratio (mole ratio) is preferably in the range of 4:6 to 9:1, and is set at 5.5:4.5. The range of 7:3 is better, and it is best to set it to 6:4.

As the crosslinking agent liquid of the crosslinking bath, a solution obtained by dissolving the above crosslinking agent in a solvent can be used.

As the solvent, for example, water may be used, and an organic solvent which is fused to water may be further used in combination. The concentration of the crosslinking agent in the crosslinking agent liquid is not particularly limited, but is preferably in the range of 1 to 10% by mass, preferably 2 to 6% by mass.

A compound capable of imparting uniform characteristics to the surface of the polarizing film may be added to the crosslinking agent liquid in the crosslinking bath.

Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, cesium iodide, calcium iodide, tin iodide, and titanium iodide. The content of the iodide in these cases is preferably from 0.05 to 15% by mass, more preferably from 0.5 to 8% by mass.

The combination of a crosslinking agent and an iodide is a combination of boric acid and potassium iodide. Preferably, the ratio (mass ratio) of boric acid to potassium iodide is preferably in the range of 1:0.1 to 1:3.5, and more preferably in the range of 1:0.5 to 1:2.5.

The temperature of the crosslinking agent liquid in the crosslinking bath is usually in the range of 20 to 70 ° C, and the immersion time of the polyvinyl alcohol resin film is usually set to any time in the range of 1 second to 15 minutes. It is better to set it as 5 seconds to 10 minutes.

In the crosslinking step, the film may be extended in the longitudinal direction in the crosslinking bath, and the total stretching ratio accumulated at this time is preferably about 1.1 to 5.0 times.

Further, the crosslinking step may be carried out by a method of coating or spraying a solution containing a crosslinking agent in the same manner as the dyeing step, instead of the treatment method of immersing in the crosslinking agent liquid.

(extension step)

In the above-mentioned stretching step, the polyvinyl alcohol-based resin film which has been dyed and crosslinked is extended in the longitudinal direction so as to have a cumulative total stretch ratio of about 5.25 to 8 times, as will be described later. In the wet stretching method, stretching is performed by applying tension in the longitudinal direction while immersing the film in a solution stored in the stretching bath.

The solution stored in the stretching bath is not particularly limited, and a solution in which, for example, a compound of various metal salts, iodine, boron or zinc is added can be used.

The solvent of this solution may suitably use water, ethanol or various organic solvents.

Among them, a solution in which boric acid and/or potassium iodide are added in an amount of about 2 to 18% by mass is preferably used.

When the boric acid and potassium iodide are used at the same time, the ratio (mass ratio) is about 1:0.1 to 1:4, preferably about 1:0.5 to 1:3. The ratio is better to use.

The temperature of the solution in the stretching bath is preferably in the range of, for example, 40 to 67 ° C, preferably 50 to 62 ° C.

(washing step)

This washing step is a step of washing away the unnecessary residue of boric acid or the like adhered to the previous treatment by passing the film through a washing bath in which a washing liquid such as water is stored.

Preferably, the iodide is added to the aforementioned water, and for example, sodium iodide or potassium iodide is preferably added.

When potassium iodide is added to the water of the washing bath, the concentration thereof is usually 0.1 to 10% by mass, preferably 3 to 8% by mass.

Further, the temperature of the cleaning liquid is preferably set at 10 to 60 ° C, preferably 15 to 40 ° C.

Further, the number of times of the washing treatment, that is, the number of repetitions of the washing liquid after immersion in the washing liquid is not particularly limited, and may be set to be plural times or may be stored in a plurality of washing baths. Water having a different type or concentration of the additive is subjected to a washing step by passing the film through.

Further, when the film is pulled up from the immersion bath in each step, in order to prevent the occurrence of the dripping phenomenon, a drain roller such as a conventionally known nip roll or a method of cutting the liquid by an air knife may be used. Thereby removing residual moisture.

(drying step)

In the washing step, the film to be cleaned can be subjected to the drying step by being introduced into the dryer 11, naturally dried, air-dried, heated and dried, and the like by drying in an optimum manner.

In the case where the drying step by heat drying is carried out, the heating and drying conditions are preferably such that the heating temperature is about 20 to 80 ° C and the drying time is about 1 to 10 minutes.

Further, the drying temperature is not related to the above method, and it is preferable to prevent the deterioration of the film to be as low as possible.

It is preferably 60 ° C or less, and it is particularly preferable to set it to 45 ° C or less.

(layering step) and (winding step)

In the present embodiment, a polarizing film wound in a roll shape can be obtained by performing a winding step of winding a film which has been subjected to the above-described steps onto a winding roll.

Further, in the present embodiment, the step of laminating the surface protective film or the like may be carried out after the step of laminating the surface protective sheet or the both sides of the polarizing film after drying in the drying step.

The final total stretch ratio of the polarizing film produced in this manner is preferably in the range of 5.25 to 8.0 times with respect to the raw material roll film, and is preferably in the range of 5.5 to 7.0 times. Any stretching ratio is preferred.

The stretching ratio as described above is suitable because when the final total stretching ratio is less than 5.25 times, it is difficult to obtain a polarizing film having high polarizing characteristics, and if it exceeds 8.0 times, there is a concern that the film is broken. .

Further, the final total stretch ratio of the polarizing film is preferably any extension in the range of 5.25 to 8.0 times in the non-joining portion (that is, the material roll film), and any extension in the range of 5.5 to 7.0 times. The magnification is better.

(linking step)

As described above, in the present embodiment, one raw material roll is supplied to Before the extension device is completely supplied, the polyvinyl alcohol-based resin film (raw material roll film) is sent out from the raw material roll described below, and the front end portion 1b of the new material roll film and the steps of the extension device are performed. A connecting step (the second step) in which the distal end portions 1a of the raw material reels are joined and joined in an overlapping state. In addition, in the connection step, the distal end portion 1b is overlapped with the distal end portion 1a, and the initial elastic modulus of the joined portion is joined to the initial elastic modulus of the non-joining portion to be 65% or more and 100% or less.

By joining the tip end portion of the first raw material roll film to the front end portion of the raw material roll film described below in this manner, it is possible to produce a high stretch ratio necessary for imparting a high polarizing function, for example, an extension of 5.25 times or more. The magnification does not break the link. Thereby, even if the joining portion passes, the step of stretching the second raw material roll film (the first step) can be transferred without changing the stretching conditions, and the polarizing film can be efficiently produced.

That is, the first raw material roll film and the second raw material roll film can be continuously fed to the stretching device without changing the stretching conditions, whereby the effects of improving work efficiency, improving productivity, improving productivity, and reducing material loss can be obtained.

Further, this joining step is not necessarily performed after the step of stretching the first material roll film (the first step) is completed, and may be carried out in parallel with the first step, for example, after the first step.

For example, a stretching device having an accumulation groove between the coupling device and the swelling bath 4a is used, and the first raw material roll is supplied to the swelling bath 4a through the accumulation groove, and the portion where the first raw material roll is wound is temporarily The end portion is brought into a stopped state, and the raw material roll film accumulated in the accumulation tank is also supplied to the swelling bath 4a side, and the extension of the first raw material roll film is performed. (Step 1 described above) At the same time, a joining step of connecting the front end portion of the new material roll to the end portion by laser welding can be performed.

In addition, after the connection step of connecting the two strip-shaped polyvinyl alcohol-based resin films is carried out in advance, the stretching of one polyvinyl alcohol-based resin film in the band-shaped polyvinyl alcohol-based resin film to be joined is started (the aforementioned Step 1).

In the connecting step, the end portion of the first polyvinyl alcohol resin film and the front end portion of the second strip-shaped polyvinyl alcohol resin film are overlapped, and the end portion and the front end which are overlapped in this manner are overlapped The interface of the part is laser welded for implementation. Specifically, the light absorbing agent can be applied to the surface of either or both of the tip end portion 1a of the film at the front and the front end portion 1b of the new film to form a film of the old and new material on the pedestal 40. The overlapping portion is placed in the upper and lower portions, and the overlapping portion is pressurized by the pressing member 50, and the overlapping portion is irradiated with the laser light, and the resin is fused to form the welded portion 30 in the film interface.

In this case, the power density or the cumulative irradiation amount of the above-described laser light is appropriately set so that the initial elastic modulus of the joint portion is 65% or more and 100% or less with respect to the initial elastic modulus of the non-joining portion. Under the conditions of the above, the overlapping portion is irradiated with the laser light under the set conditions.

In this manner, in the present embodiment, by superimposing the laser light, the overlapping portion of the new and old material roll film can be heated selectively (locally) only at the interface or in the vicinity thereof, so that the joint portion becomes Easy to soften. By this, it is easy to perform joining so that the initial elastic modulus of the joint portion is 65% or more and 100% or less with respect to the initial elastic modulus of the non-joining portion.

When the initial elastic modulus of the joint portion is joined to the initial elastic modulus of the non-joining portion to be less than 65%, the joint portion is too soft with respect to the non-joining portion, and therefore, in the extending step, When the stretch ratio is set to 5.25 times or more, and the polyvinyl alcohol-based resin film is continuously stretched, the boundary portion between the joint portion and the non-joining portion is easily broken. In particular, if the joint portion is too soft, the joint portion is easily broken.

On the other hand, when the initial elastic modulus of the joint portion is 65% or more of the initial elastic modulus of the non-joining portion, the joint portion is not excessively soft, and the hardness of the joint portion is close enough to the hardness of the non-joining portion. Therefore, the stress concentration at the above-mentioned boundary portion can be sufficiently alleviated. Therefore, the stretching ratio can be set to 5.25 times or more, and the polyvinyl alcohol-based resin film can be continuously extended.

In addition, it is preferable that the initial elastic modulus of the joint portion is 70% or more with respect to the initial elastic modulus of the non-joining portion, from the viewpoint of sufficiently alleviating the stress concentration.

On the other hand, when the initial elastic modulus of the joint portion is joined to the initial elastic modulus of the non-joining portion by more than 100%, the joint portion is excessively hard with respect to the non-joining portion, and therefore the step of stretching is performed. In the above-mentioned boundary portion, stress tends to concentrate, and thus cracking easily occurs.

On the other hand, when the initial elastic modulus of the joint portion is 100% or less with respect to the initial elastic modulus of the non-joining portion, the joint portion is not excessively bonded to the non-joining portion, and the joint portion is not joined. The hardness of the portion is close enough to the hardness of the non-joining portion, so that the stress concentration at the boundary portion can be alleviated. Therefore, the extension ratio can be set to 5.25 times or more while The polyvinyl alcohol-based resin film can be continuously stretched.

In addition, it is preferable that the initial elastic modulus of the joint portion is 90% or less with respect to the initial elastic modulus of the non-joining portion, from the viewpoint of sufficiently alleviating the stress concentration.

Here, the initial elastic modulus of the joint portion can be measured as described below (see FIGS. 4 to 6).

In other words, a region 33 (the length of the polyvinyl alcohol-based resin film in the longitudinal direction of 1.5 mm) × (the length of the polyvinyl alcohol-based resin film in the width direction of 20 mm) is cut out at the joint portion 31. Next, using a tensile test device (not shown) having a fixing portion jig 37 and a movable jig 38, the joint portion 35 of the cut joint portion is placed in an environment at room temperature of 20 ° C, and the distance between the initial jigs is 10 mm. The tensile speed was 0.1 mm/min, and the tensile direction was measured by stretching in the longitudinal direction (that is, the width direction, the TD direction of FIG. 6), and the stress and deformation were measured for the joint portion 35 to obtain stress-deformation. curve. Then, in the obtained stress-deformation curve, the tangent slope at a stress of 1 N/mm ² was calculated (refer to Fig. 7). The tangent slope calculated in this way is the initial elastic modulus of the joint.

Further, a region 34 (the length in the longitudinal direction of 3.0 mm) × (the length in the width direction of 20 mm) is cut out in the non-joining portion 32. Next, a tensile tester (not shown) having the fixing portion jig 37 and the movable jig 38 is used in the same manner as described above, and the non-joining portion slice 36 of the cut non-joining portion is placed in an environment at room temperature of 20 ° C. The tensile test was performed by stretching the initial inter-clamp distance of 10 mm and the tensile speed of 0.1 mm/min in the longitudinal direction (that is, the width direction, the TD direction of FIG. 6), and the stress was measured for the non-joined section 36. With deformation, a stress-deformation curve is obtained. Then, the tangent slope at a stress of 1 N/mm ² was calculated from the obtained stress-deformation curve. The tangent slope calculated in this way is the initial elastic modulus of the non-joining portion.

Further, as the tensile tester, a thermal analysis measuring device (TMA, SII NanoTechnology, EXSTAR TMA/SS6200) can be used.

In addition, the length of the short-side direction of the non-joining section is set to be twice as long as 1.5 mm in the short-side direction of the joint section because the two polyvinyl alcohol-based resin films are overlapped and joined to each other. When the thickness is twice as large as the thickness of the non-joining portion, the cross-sectional area of the joint portion and the non-joined portion is made equal.

As described above, by bonding the initial elastic modulus of the joined portion to the initial elastic modulus of the non-joining portion of 65% or more and 100% or less, the boundary portion between the joined portion and the non-joined portion can be alleviated. The stress concentration caused by the extension. Thereby, even if it is extended by the extending magnification of 5.25 times or more, the occurrence of the crack in the above-mentioned boundary can be avoided, and even if the joining portion passes, the stretching can be continuously performed without changing the stretching condition. Therefore, the effect of improving work efficiency, improving productivity, increasing productivity, and reducing material loss can be obtained.

Further, since the bonding is performed by laser welding, the interface between the end portion and the tip end portion and the vicinity thereof can be locally heated, and the region where the joint portion is hardened can be reduced. Therefore, the initial elastic modulus of the joint portion is likely to be relatively low. The joint portion is joined by 65% or more and 100% or less.

On the other hand, when the joint is joined by the heat sealer, for example, the end portion and the joint portion are heated in the entire thickness direction. Therefore, the hardened region in the joint portion is increased, so that it is difficult to be the initial portion of the joint portion. The modulus of elasticity tends to be 6% or more and 100% or less with respect to the initial elastic modulus of the non-joining portion.

Therefore, as in the present embodiment, the case of bonding by laser welding is more suitable than the case of bonding by a heat sealing machine. However, as long as the initial elastic modulus of the joined portion is 65% or more and 100% or less with respect to the initial elastic modulus of the non-joining portion, it may be joined by a heat sealer, and other materials may be used. The joining method is joined.

Further, the thickness of the polarizing film produced by the production method of the present embodiment is not particularly limited, but the thickness of the non-joining portion is preferably 5 μm to 40 μm.

When the thickness of the non-joining portion is 5 μm or more, the mechanical strength is not lowered, and if it is 40 μm or less, the optical characteristics are not lowered, and the thickness can be reduced even when applied to an image display device.

The polarizing film produced in the present embodiment can be used as a liquid crystal display device or the like as a polarizing film laminated on a liquid crystal cell substrate. Further, in addition to the liquid crystal display device, a polarizing film in various image display devices such as an electroluminescence display device, a plasma display, and an electric field discharge display can be used.

Further, in actual use, an optical film may be formed on each of two or a single-layer optical layer, or various surface treatments may be performed, and it may be used in an image display device such as a liquid crystal display device.

The optical layer is not particularly limited as long as it satisfies the required optical characteristics, and an alignment liquid crystal layer such as a transparent protective layer for protecting a polarizing film, a visual compensation for use, and the like for laminating other films may be used. In addition to the adhesive layer, a polarizing conversion element, a reflecting plate, a semi-transparent plate, a phase difference plate (including a 1/2 or 1/4 wavelength plate (λ plate)), a visual compensation film, and a brightness-increasing film may be used. A film used for forming an image display device or the like is formed.

Further, the surface treatment may be a hard coat treatment, an anti-reflection treatment, or a surface treatment for preventing adhesion or diffusion or anti-glare.

The method for producing a polarizing film of the present embodiment is as described above, and the present invention is not limited to the embodiment, and the design can be appropriately changed within the scope of the present invention. Further, the effects of the method for producing a polarizing film to which the present invention is related are not limited by the above-described effects.

Example

The invention is further illustrated in the following examples, but the invention is not limited thereto.

(evaluation case) (Basic conditions)

‧ Raw material film: Polyvinyl alcohol resin (PVA) film (manufactured by Kuraray Co., Ltd., thickness 75 μm, width 50 mm, water absorption 6%)

‧ overlap width: 1.5mm width

‧heat welding part: laser

‧Laser: Semiconductor laser (wavelength 940nm, power 95W, spot diameter 2mmΦ, power density 3024W/cm ² , scanning speed 55mm/sec, cumulative exposure 110J/cm ² , top hat beam)

‧Light absorbing agent: The product name "Clearweld (registered trademark) LD120C" (manufactured by Gentex, USA, solvent acetone), coated on the lower side of the raw material roll film at a width of 2.0 mm and 10 nL/mm ²

‧ Pressurized component: quartz glass plate (10mm thick)

‧ Pressurization conditions: Pressing the overlapping portion of the material roll film at a pressure of 50 kgf/cm ²

(evaluation conditions)

‧ Tensile test: Thermomechanical analysis device (TMA, SII NanoTechnology, EXS TAR TMA/SS6200), initial clamp distance 10mm, tensile speed 0.1mm/min

(Example 1)

Under the above-mentioned basic conditions, the two raw material roll films were joined, and a region (the length of the raw material roll film in the longitudinal direction of 1.5 mm) × (the length of the raw material roll film in the width direction of 20 mm) was cut out at the joint portion, and a rectangular joint portion was taken. Further, in the non-joining portion, a region (the length in the longitudinal direction of 3.0 mm) × (the length in the width direction of 20 mm) was cut out, and a rectangular non-joining portion was taken. The joint portion and the non-joined portion were subjected to tensile test under the above-described evaluation conditions to obtain a stress-distortion curve. From the obtained curve, the tangential slope at a stress of 1 N/mm ² was calculated, and the initial elastic modulus was calculated. . As a result, the initial elastic modulus of the joined portion was 0.21 GPa, the initial elastic modulus of the non-joined portion was 0.30 GPa, and the initial elastic modulus of the joined portion was 70.0% with respect to the initial elastic modulus of the non-joined portion. The results are disclosed in Tables 1 and 8.

In addition, the two raw material roll films were joined under the same conditions as the above conditions, and the joint portion was cut back and forth to a length of about 50 mm, and an extension device as shown in Fig. 1 was used, and the total stretch ratio was 2.6 in the swelling bath. The polarizing film was produced in batches by 3.4 times in the dyeing bath, 3.6 times in the crosslinking bath, and 6.0 times in the stretching bath, and then passed through a washing bath. its As a result, no crack was observed even if it was extended to 6.0 times the total stretching ratio.

(Example 2)

In addition to changing the laser power to 100 W, the two raw material roll films were joined by the above-described basic conditions, and the joint portion was taken in the same manner as in Example 1, and the initial elastic modulus of the joint portion taken was measured. As a result, the initial elastic modulus of the joined portion was 0.22 GPa. Moreover, the initial elastic modulus of the non-joining portion was calculated using 0.30 GPa of Example 1, and the initial elastic modulus of the joined portion with respect to the initial elastic modulus of the non-joined portion was calculated. As a result, the initial elastic modulus of the joined portion was 73.3% with respect to the initial elastic modulus of the non-joined portion. The results are disclosed in Tables 1 and 8.

Further, two raw material roll films were joined under the same conditions as in the above conditions, and a polarizing film was batch-produced in the same manner as in Example 1. As a result, no crack was observed even if it extended to the total extension magnification 6.0 times.

(Example 3)

In addition to changing the scanning speed to 30 mm/sec, the two raw material roll films were joined by the above-described basic conditions, and the joint portion was taken in the same manner as in Example 1, and the initial elastic modulus of the joint portion taken was measured. As a result, the initial elastic modulus of the joined portion was 0.28 GPa. Moreover, the initial elastic modulus of the non-joining portion was calculated using 0.30 GPa of Example 1, and the initial elastic modulus of the joined portion with respect to the initial elastic modulus of the non-joined portion was calculated. As a result, the initial elastic modulus of the joined portion was 93.3% with respect to the initial elastic modulus of the non-joined portion. The results are disclosed in Tables 1 and 8.

In addition, the two raw material roll films were joined under the same conditions as the above conditions except that the total stretch ratio in the extension bath was set to 5.5, and Example 1 The polarizing film was produced in batches in the same manner. As a result, no crack was observed even if it extended to the total extension magnification 5.5 times.

(Example 4)

In addition to changing the width of the material roll film to 2600 mm, the old and new material roll films were joined by the above-mentioned basic conditions, and the extension device as shown in Fig. 1 was used to obtain a total stretch ratio of 2.6 times in the swelling bath. A polarizing film was produced in a manner of 3.4 times in the bath, 3.6 times in the crosslinking bath, and 6.0 times in the stretching bath. As a result, in the same manner as in Example 1, even if it was extended to 6.0 times the total stretching ratio, it was not broken and continuous feeding was possible. Further, since the difference in the width of the material roll film does not affect the initial elastic modulus of the joint portion and the non-joining portion, the initial elastic modulus of the joint portion with respect to the non-joining portion in the fourth embodiment is the same as that of the first embodiment. The same can be set to 70.0%.

(Comparative Example 1)

The overlap width of the new and old raw material roll films was set to 3 mm, and a nickel-chromium wire having a width of 3 mm was used, and heat sealing was performed at 250 ° C for 10 seconds to form a linear welded portion. Otherwise, two raw material roll films were joined in the same manner as in the first embodiment. Further, in the same manner as in Example 1, the joint portion was taken, and the initial elastic modulus of the joint portion taken was measured in the same manner as in Example 1. As a result, the initial modulus of elasticity of the joint portion was 0.33 GPa. Moreover, the initial elastic modulus of the non-joining portion was calculated using 0.30 GPa of Example 1, and the initial elastic modulus of the joined portion with respect to the initial elastic modulus of the non-joined portion was calculated. As a result, the initial modulus of elasticity of the joint portion with respect to the initial elastic modulus of the non-joining portion was 110.0%. The results are disclosed in Tables 1 and 8.

Further, two raw material roll films were joined under the same conditions as in the above conditions, and a polarizing film was batch-produced in the same manner as in Example 1 except that the total stretch ratio of the stretching bath was 6.0. As a result, cracking occurred when the total stretching ratio was extended to 4.3 times.

(Comparative Example 2)

The two raw material roll films were joined by the above basic conditions, except that the laser power was changed to 50 W, the power density was changed to 1592 W/cm ² , the scanning speed was changed to 5 mm/sec, and the total irradiation amount was changed to 637 J/cm ² . The joint portion was taken in the same manner as in Example 1, and the initial elastic modulus of the joint portion taken was measured. As a result, the initial modulus of elasticity of the joint portion was 0.31 GPa. Moreover, the initial elastic modulus of the non-joining portion was calculated using 0.30 GPa of Example 1, and the initial elastic modulus of the joined portion with respect to the initial elastic modulus of the non-joined portion was calculated. As a result, the initial modulus of elasticity of the joined portion with respect to the initial elastic modulus of the non-joined portion was 103.3%. The results are disclosed in Tables 1 and 8.

Further, two raw material roll films were joined under the same conditions as in the above conditions, and a polarizing film was batch-produced in the same manner as in Example 1. As a result, cracking occurred when extending to a total stretching ratio of 5.25 times.

(Comparative Example 3)

In addition to the polyimine (PI) film having a thickness of 125 μm interposed between the overlapping portion of the pressing member and the raw material roll film, and between the overlapping portion and the pedestal, two raw material roll films are used under the above basic conditions. Engage. The joint portion was taken in the same manner as in Example 1, and the initial elastic modulus of the joint portion taken was measured. As a result, the initial elastic modulus of the joined portion was 0.19 GPa. In addition, the initial elastic modulus of the non-joining portion was calculated by using 0.30 GPa of Example 1. The initial elastic modulus of the joint portion with respect to the initial elastic modulus of the non-joining portion was calculated. As a result, the initial modulus of elasticity of the joint portion with respect to the initial elastic modulus of the non-joining portion was 63.3%. The results are disclosed in Tables 1 and 8.

Further, two raw material roll films were joined under the same conditions as in the above conditions, and a polarizing film was batch-produced in the same manner as in Example 1. As a result, cracking occurred when extending to a total stretching ratio of 5.8 times.

1‧‧‧ material roll film

1a‧‧‧End

1b‧‧‧ front end

3‧‧‧ Raw material film supply department

4‧‧‧dipping bath

4a‧‧‧Swelling bath

4b‧‧‧dye bath

4c‧‧‧crossing bath

4d‧‧‧Extension bath

4f‧‧‧washing bath

9‧‧‧ Roller

9a‧‧‧Roller extension/nip roller

10‧‧‧(polarized film) winding

11‧‧‧Drying device/machine

12‧‧‧Layer film

30‧‧‧Blackening/welding

31‧‧‧ joints

32‧‧‧ Non-joining

33,34‧‧‧Area

35‧‧‧ Joint section

36‧‧‧ Non-joint section

37‧‧‧Fixed fixture

38‧‧‧ movable clamp

40‧‧‧ pedestal

50‧‧‧ Pressurized components

R‧‧‧Laser light

Fig. 1 is a schematic perspective view showing an apparatus used in a method of producing a polarizing film according to an embodiment.

Fig. 2 is a schematic perspective view showing a state in which a raw material roll film is connected and supplied to a manufacturing apparatus of a polarizing film.

Fig. 3 is a schematic front view showing a mechanism of a main part of a connecting device for connecting a raw material roll film.

Fig. 4 is a view showing a joint portion and a non-joining portion. Fig. 4(a) is a schematic side view, and Fig. 4(b) is a schematic plan view.

Fig. 5 is a view showing a joint portion and a non-joined portion, and Fig. 5(a) is a schematic plan view of the joint portion, and Fig. 5(b) is a schematic plan view of the joint portion.

Fig. 6 is a schematic plan view showing a joint portion or a non-joined portion slice before and during stretching.

Fig. 7 is a view showing an example of a stress-deformation curve and a tangent line in a stress of 1 N/mm2.

Fig. 8 is a graph showing the ratio of the initial elastic modulus of the examples and the comparative examples.

1‧‧‧ material roll film

3‧‧‧ Raw material film supply department

4a‧‧‧Swelling bath

4b‧‧‧dye bath

4c‧‧‧crossing bath

4d‧‧‧Extension bath

4f‧‧‧washing bath

9‧‧‧ Roller

9a‧‧‧Roller extension/nip roller

10‧‧‧(polarized film) winding

11‧‧‧Drying device/machine

12‧‧‧Layer film

Claims (5)

A method for producing a polarizing film, which is characterized in that a polarizing film is continuously produced by using a plurality of belt-shaped polyvinyl alcohol-based resin films, and is characterized in that: in the first step, each polyvinyl alcohol-based resin film is sequentially passed from the front end The side is fed into the movement path and extends in the longitudinal direction in the movement path; and in the second step, the end portion of the first first polyvinyl alcohol-based resin film and the succeeding second polyvinyl alcohol-based resin film are In the second step, the initial elastic modulus of the joint portion is set to be 65% or more and 100% or less with respect to the initial elastic modulus of the non-joining portion, in which the front end portion is overlapped and joined by welding. The initial elastic modulus of the joint portion and the non-joining portion is a value calculated by cutting the joint portion (the length of the polyvinyl alcohol-based resin film in the longitudinal direction of 1.5 mm) × (the aforementioned polyvinyl alcohol system) In the region of the resin film having a length of 20 mm in the width direction, the joint portion was cut, and the non-joining portion (the length of the polyvinyl alcohol-based resin film in the longitudinal direction of 3.0 mm) was cut out × (the aforementioned polyethylene A section of the non-joining portion of the resin film in the width direction of the length of 20 mm), and a section of the joint portion and the non-joined portion were respectively cut at room temperature using a tensile test device having a fixing portion jig and a movable jig. In a 20 ° C environment, stretching was performed at an initial jig distance of 10 mm and a tensile speed of 0.1 mm/min, thereby performing a tensile test to obtain a stress-distortion curve, and a stress of 1 N/mm in the obtained stress-deformation curve. The tangential slope at ² o'clock was used to calculate the initial elastic modulus. The method for producing a polarizing film according to claim 1, wherein the second step is carried out by joining and joining the distal end portion and the distal end portion by laser welding. In the method for producing a polarizing film according to the second aspect of the invention, the light absorbing agent is disposed at an interface portion between the end portion and the tip end portion to perform the laser welding. The method for producing a polarizing film according to claim 2 or 3, wherein the laser welding is performed by an infrared laser having a wavelength of 800 nm or more and 11,000 nm or less. The method for producing a polarizing film according to the first or second aspect of the invention, wherein the non-joining portion and the joint portion of the first polyvinyl alcohol-based resin film and the second polyvinyl alcohol-based resin film each have a stretching ratio of 5.25. More than double.