TWI551897B - Method for manufacturing polarizing film - Google Patents

Description

Polarized film manufacturing method Field of invention

The present invention relates to a method of joining a polyvinyl alcohol-based resin film in which the surface of a polyvinyl alcohol-based resin film is superposed on the surface of another polyvinyl alcohol-based resin film and the interface is laser-welded, and a bonding method is used. A method for producing a polarizing film for producing a polarizing film from a raw material film of two or more polyvinyl alcohol-based resin films.

Background of the invention

Conventionally, a polyvinyl alcohol-based resin (PVA) film is known as a resin film which exhibits relatively high water absorbability, and the polyvinyl alcohol-based resin film is used for a material of a polarizing film or the like.

In a video display device such as a liquid crystal display device, a high-quality polarizing film is used, and in the method for producing such a polarizing film, a polyvinyl alcohol-based resin film is immersed in a swelling bath or a dye bath, and is stretched in an extension bath. Various processing such as processing.

For example, a polyvinyl alcohol-based resin film (raw material film) is fed from a raw material roll-shaped polyvinyl alcohol-based resin film in a roll shape, and a raw material film is conveyed in the longitudinal direction thereof and continuously immersed in a swelling bath or After the dyeing bath, the raw material film was held by the above-mentioned rolls in the front and rear of the stretching bath, and the polarizing film was produced by applying a tension to the raw material film by applying a difference in the sending speed.

However, in such a manufacturing method, the raw material rolls are re-exchanged each time. Moreover, it is very troublesome and time consuming to install a new raw material film on a roll or the like and set it on the apparatus. Therefore, the raw material film which is joined to the end portion of the raw material film fed from the next raw material roll at the end portion of the preceding raw material film is continuously supplied to the above apparatus in order.

Conventionally, the joining method at this time is a joining and joining method such as a tape or an adhesive, a stitching joining method such as a rivet or a thread, a heat fusion bonding method such as a heat sealer, or the like.

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

. Adhesive bonding of tapes and adhesives, etc.

In the step of immersing the raw material film in a swelling bath, a dye bath, or the like, the components of the adhesive agent and the like are eluted into the chemical liquid, thereby contaminating the chemical liquid and causing foreign matter to adhere to the product. Further, since the adhesive is dissolved in the chemical solution or swelled by the components of the chemical liquid, the joint strength is lowered, and there is a fear that the joint portion is broken before reaching the desired stretch ratio in the stretching step.

. The problem of stitching by rivets and wires

In this method, since the raw material film is passed through a hole such as a rivet or a wire, when a tension is applied to the joint portion, a fracture originating from the hole may occur.

In order to prevent such a situation, the number of holes is reduced to ensure the interval between the holes, and when tension is applied, wrinkles are likely to occur, which is a cause of trouble during transportation.

. Heat fusion bonding by heat sealer or the like

The joining method of the heat sealer shown in the following Patent Documents 1 and 2 and the like is used as a joint which can solve the problems of the subsequent joining and the seam joining as described above. The method is known.

This method directly joins the joined members to each other, and thus can be joined in the case where the possibility of fouling the chemical liquid is low as compared with the subsequent joining. Further, the joint portion can be made homogeneous in comparison with the stitch joint, so that formation of wrinkles or the like can be prevented.

By performing the joining by the heat sealer in this manner, it is possible to suppress the stain generated by the chemical solution or the like during the immersion treatment as compared with the subsequent joining and the stitching.

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

Summary of invention

However, in the joining by the heat sealer, the joint portion of the welded portion and the periphery thereof are denatured by heat during welding, and tend to be hardened as compared with the unheated region. Therefore, when the polarizing film as described above is used, the raw material film composed of the polyvinyl alcohol-based resin film is joined by a heat sealer, and the stretching process is continuously performed at a stretching ratio of 5.25 times or more in order to impart a high polarizing function. Stress is concentrated on the boundary portion between the hardened region and the uncured region, and cracks are generated.

Therefore, conventionally, it has been considered to use a bonding using laser welding such as joining of resin members to each other instead of the heat sealer as described above.

In conventional laser welding, laser light having a wavelength in the infrared or near-infrared region is utilized. Moreover, the interface between the two films to be joined includes an indigo-based pigment or the like. The light absorber is superposed and overlapped, and the aforementioned laser light is irradiated at the overlap.

Since such a laser welding selectively heats a very small portion of the interface portion, the bonding of the joint portion and the periphery thereof as described above can be suppressed, and therefore, a joint body which can withstand the elongation treatment with a high stretch ratio can be formed.

However, there is a fear that the light absorber remaining around the welded portion will contaminate the chemical solution or the like.

In other words, in the conventional joining method, it is difficult to form a joined body having a bonding portion suitable for the treatment in the chemical solution or the like, and which is resistant to the stretching of the polyvinyl alcohol-based resin film having a high stretching ratio.

In view of the above problems, an object of the present invention is to provide a joint of a polyvinyl alcohol-based resin film which can form a joint portion suitable for the treatment in a chemical solution or the like and which can withstand a high stretch ratio. A method of joining a vinyl alcohol resin film and a method of producing a polarizing film using the bonded body of the polyvinyl alcohol resin film.

In the present invention, the present invention is a polyvinyl alcohol-based resin film in which the surface of the first polyvinyl alcohol-based resin film and the surface of the second polyvinyl alcohol-based resin film are superposed and bonded to each other. In the bonding method, at least one of the first and second polyvinyl alcohol-based resin films is made to absorb water at the interface side of the region where the polyvinyl alcohol-based resin film overlaps, so as to be in a state of being dry relative to the dry state. The thickness of the region is such that the thickness of the region after water absorption is 101% or more and 110% or less. After the water absorption, the first and second polyvinyl alcohol-based resin films are superposed on each other. Laser light having a peak wavelength in a range of 1.9 μm to 2.2 μm is irradiated onto the water absorbing region, and water existing in the water absorbing region absorbs the laser light, and the interface laser of the overlapping portion is laser welded.

Here, the thickness of the aforementioned region in the dry state means the thickness of the aforementioned region when it is left in an environment of 83 ° C for 1 hour and the weight is in an equilibrium state. Further, the thickness after water absorption refers to the thickness of the region when the thickness of the region is balanced after the region where the overlapping portion is absorbed.

Moreover, the method for producing a polarizing film of the present invention is a method for producing a polarizing film of a polarizing film by immersing a chemical liquid and extending a raw material film of a polyvinyl alcohol resin film of 2 or more, and the above-mentioned connection of the raw material film This is carried out by a joining method of a polyvinyl alcohol-based resin film as in the first aspect of the patent application.

1‧‧‧Polyvinyl alcohol resin film film

1a‧‧‧End

1b‧‧‧ front end

1ba‧‧‧Swelling part; water absorption area

3‧‧‧Material film supply department

4‧‧‧dipping bath

4a‧‧‧Swelling bath

4b‧‧‧dye bath

4c‧‧‧crossing bath

4d‧‧‧Extension bath

4f‧‧‧washing bath

9‧‧‧ Rolls

9a‧‧‧ roll extension; clamping roll

10‧‧‧Winding Department

11‧‧‧Drying device; dryer

12‧‧‧Layer film

20‧‧‧Water absorption department

30‧‧‧Blackened; welded joint

40‧‧‧ pedestal

50‧‧‧ Pressurized components

D1‧‧‧ thickness

R‧‧‧Laser light

Fig. 1 is a schematic perspective view showing an apparatus for manufacturing a polarizing film of an embodiment.

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

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

Fig. 4 is a schematic side sectional view showing a state in which a raw material film is made to absorb water.

Form for implementing the invention

Hereinafter, an embodiment of a method for producing a polyvinyl alcohol-based resin film according to the present invention will be described with reference to an example of a method for producing a polarizing film.

More specifically, a case where the belt-shaped polyvinyl alcohol-based resin film is bonded to each other and the belt-shaped polyvinyl alcohol-based resin film is continuously supplied to the stretching device to produce a polarizing film will be described.

First, a preferred stretching device for carrying out the method for producing a polarizing film of the present embodiment will be described with reference to the drawings.

The stretching device of the present embodiment includes a raw material film of a raw material roll 1 which is wound into a roll shape by a belt-shaped polyvinyl alcohol-based resin film (hereinafter also referred to as "raw material film" or simply "film"). a supply unit 3; a plurality of dip baths 4 for immersing the raw material film 1 to be dispensed in a predetermined chemical solution; restricting a movement path of the material film 1 so that the material film 1 passes through a plurality of rolls 9 in the dip bath 4; The extending portion of the raw material film 1 is stretched in the path; and the polarizing film winding portion 10 is formed by winding a film which is immersed in the plurality of immersion baths 4 as a polarizing film and wound up in a roll shape.

1 and 2 are schematic perspective views showing one aspect of a preferred extension device.

As shown in Fig. 1, five kinds of immersion baths 4 are provided as a plurality of immersion baths 4 in the extension device from the upstream side in the flow direction of the film, that is, a swelling bath in which the swelling liquid for swelling the polyvinyl alcohol-based resin film is stored. 4a, a dyeing bath 4b storing a dyeing solution for dyeing a swollen film, a cross-linking bath 4c storing a cross-linking agent liquid for crosslinking a molecular chain of a resin constituting the film, and an extension bath for extending the film in the bath 4d, and, in addition, a washing bath 4f for washing the washing liquid which has passed through the film of the stretching bath 4d is stored.

Further, the stretching device of the present aspect has a film attached to the film 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. The drying device 11 for drying the washing liquid, specifically, a drying oven.

Further, in the stretching apparatus of the present aspect, a surface protective film (for example, a triacetyl cellulose film, a cycloolefin polymer film, or the like) wound in a roll shape is disposed on both sides of the film dried by the drying device 11 described above. The film 12 for lamination is used. Further, there is a laminating device (not shown) for laminating the laminated film 12 on both surfaces of the dried film.

The aforementioned extension portion employs a so-called roll extension portion 9a. In other words, in the moving path, the plurality of arrays are arranged such that the pair of nip rolls 9a are formed by sandwiching the film therebetween and are sent to the downstream side in the flow direction, and the circumferential speed of the group on the downstream side in the flow direction is higher than that on the upstream side. Construction.

Further, the present stretching apparatus has, as shown in Fig. 2, before the end portion 1a of the raw material film 1 passes the restricted moving path, specifically, before the immersion bath 4, the end of the raw material film 1 is joined by laser welding. The portion 1a and the connecting means (not shown in Fig. 2) of the front end portion 1b of the new raw material film 1 in the moving path after the raw material film 1 are passed.

Further, in Fig. 2, the blackened portion 30 is used to display the portion joined by the laser irradiation.

Next, a preferred coupling device will be described with reference to Fig. 3 .

FIG. 3 is a schematic structural view showing a connecting device in which the raw material films are bonded to each other by laser welding.

Fig. 3 is a front elevational view showing the joining device of the old and new raw material films which are joined by the side faces in the TD direction (width direction).

As shown in FIG. 3, the connecting device includes a pedestal 40 having a flat upper surface; a pressing member 50 disposed above the pedestal 40 and arranged to be movable in the vertical direction; and being disposed above the pressing member 50 Laser source (not shown). Further, the connecting device is configured such that the end portion 1a of the leading raw material film (first polyvinyl alcohol-based resin film) 1 and the front end portion 1b of the new raw material film 1 (second polyvinyl alcohol-based resin film) connected thereto are The pedestal 40 is vertically overlapped, and the overlapping portion is pressed by the pressing member 50, and the laser beam is irradiated with the laser light R, whereby the interface between the distal end portion 1a and the distal end portion 1b can be made. Heated and melted and welded. The pressing member 50 is formed of a transparent member having excellent laser light R permeability.

Further, the connecting device is provided with a water absorbing portion for absorbing moisture in advance on any one surface (or both surfaces) of the end portion 1a or the front end portion 1b that is in contact with the interface portion, so as to raise the end portion 1a and the front end portion. The light absorption of the laser light R at the interface portion of 1b can be performed more efficiently.

The water absorbing portion is used to join the film in comparison with a water absorbing portion for absorbing water under the upper side film (the front material portion (end portion 1a) in FIG. 3) for transmitting the laser light to the interface. The water absorbing portion 20 (see FIG. 4) which absorbs the upper surface of the lower raw material film (front end portion 1b) is particularly preferable.

Further, the water absorbing portion may be constituted by a general device for coating water, and may be, for example, a dispenser, an inkjet printer, a screen printing machine, a 2-fluid type, a 1-fluid or an ultrasonic atomizer, a printer, and a coating. A device or the like is used as the coating device.

For example, when using an ultrasonic atomizer, the amount of water absorption (water absorption) can be adjusted by appropriately setting the spot (mmΦ), the amount of spray (mL/min), the scanning speed (mm/sec), and the number of scans (times). .

Further, the method of absorbing water in the region to be the overlapping portion may be employed in addition to the method of absorbing water by applying water as described above. A method of adjusting the humidity environment in a room where laser welding is performed, and causing the entire surface of the raw material film to absorb water, thereby absorbing water at the interface side between the end portion 1a or the tip end portion 1b. Thus, the water for absorbing the superposed portion may be water vapor.

Further, the laser light used in the connection device is absorbed by water absorbed in the middle (interface) of the overlapping portion of the old and new raw material films, and has a function of generating heat. Further, the laser light to be used preferably has a wavelength which is highly sensitive to water absorption. From this point of view, laser light having a peak wavelength in the range of 1.9 μm to 2.2 μm can be employed. The type of laser light source is one that produces such a laser light, and is not particularly limited. For example, a laser used to illuminate such laser light can use an erbium doped fiber laser, an erbium doped YAG laser, and an InGaAs semiconductor laser.

From the viewpoint of avoiding the decomposition of the raw material film and promoting the melting of the raw material film, the CW laser of the continuous wave is better than the pulse laser of the high energy input instantaneously.

The optical characteristics such as the water absorption state and the light absorptivity of the target polyvinyl alcohol resin film and the polymerization of the constituent raw material film, such as the output (power) of the laser beam, the beam size and shape, the number of irradiations, and the scanning speed. The difference in thermal characteristics such as the melting point of the substance and the glass transition temperature (Tg) may be appropriately optimized. For example, the laser irradiation part in order to manipulation of polyvinyl alcohol resin fluidizing efficiently obtaining the bonding strong, the power density within the range of the laser beam is irradiated based on 200W / cm ² to 10,000W / cm ² as the good, in the range of / cm ² of 300W / cm ² more preferably to 5,000W, and the scope / cm ² in the Bennett good 1,000W / cm ² to 3,500W.

In addition, total amount of irradiation of the laser beam based preferably, in the range of 10J / cm ² to 300J / cm ² more preferably in the range of 5J / cm ² to 400J / cm ² of, and at 30J / cm ² to 150J / Excellent within the range of cm ² .

Therefore, it is preferable to use a laser that satisfies these conditions in the joining device.

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

When the spot diameter (irradiation width) satisfies the power of the irradiation laser density, it is preferably 1/10 or more and 3 times or less of the overlap width of the old and new raw material films.

When it is less than 1/10 of the overlap width, the unjoined portion of the overlapping portion is large, and the film is shaken during conveyance after joining, which may hinder the good handling property of the film.

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.

Preferably, the spot diameter is 1/5 or more and 2 times or less of the overlap width.

Further, the overlap width of the new and old raw material films is preferably 0.1 mm or more and less than 50 mm, and more preferably 0.5 mm or more and less than 30 mm.

This is because when the overlap width is less than 0.1 mm, it is difficult to overlap the raw material film having a large width with a high overlap precision, and when the overlap width is 50 mm or more, the unjoined area becomes large, and there is a fear that film shake occurs during conveyance after bonding.

Further, in the overlapping portion of the old and new raw material films, a sufficient region of the front end portion of each of the raw material films is joined, whereby the both front end portions are not shaken during conveyance, and it is preferable in terms of achieving good conveyance of the film. In consideration of this point of view, the width of the unjoined portion in the overlapping portion of the new and old raw material films is preferably 5 mm or less, more preferably 2 mm or less, and more preferably 0 mm (full joint of the overlapping portions).

Further, the shape of the laser beam may be circular, and may be linear from the viewpoint of obtaining higher power density.

In the present embodiment, the coupling means is preferably configured to perform laser welding along the overlapping portions of the coincident new and old raw material films so that a linear welded portion can be formed. For example, the aforementioned connecting device preferably has a light collecting lens to collect the light into a light. A mechanism for scanning a beam of light at a desired beam size along a coincident portion; a mechanism for shaping a linear laser beam and illuminating a coincident portion of a raw material film by using an optical member such as a cylindrical lens and a diffractive optical element And further arrange a plurality of laser light sources along the overlapping portion, and irradiate the entire batch of molten heat bonding mechanisms without scanning.

The pressing member 50 of the above-mentioned new and old raw material film (the end portion 1a of the old raw material film and the front end portion 1b of the new raw material film) which is superposed on the pedestal when irradiated with such laser light can be used to exhibit high transparency to the used laser light. Glass components.

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

Therefore, the pressing member 50 preferably used in the above-described joining device may be any member that can be pressurized with such strength, and the shape of the glass member is not particularly limited, and may be used, for example, a flat plate, a cylinder, or a ball. Shape.

The thickness of the glass member is not particularly limited, but when it is too thin, it may not be well pressurized due to strain, and when the thickness is too thick, the utilization efficiency of the laser light is lowered, so the thickness of the laser light transmitting direction is preferably 3 mm or more and less than 30 mm, and More preferably 5 mm or more and less than 20 mm.

The material of the pressurizing member 50 may, for example, be quartz glass, alkali-free glass, TMEPAX, PYREX (registered trademark), vycol refractory glass (vycol), D263, OA10, AF45 or the like.

In order to improve the utilization efficiency of the laser light R, the glass member used as the pressing member should have high transparency to the wavelength of the laser light to be used, and preferably have a light transmittance of 50% or more, and have a light transmittance of 70% or more. Better.

Moreover, when the pressurizing member 50 is configured using the glass member as described above, A buffer layer which is more excellent in cushioning properties than the above-described glass member is formed in a portion to be bonded to the polyvinyl alcohol-based resin film, so that a wider area can be more uniformly pressed, and good bonding can be performed in the entire region.

In other words, a pressurizing member 50 including a rubber sheet having good light transmittance and a transparent resin sheet having good cushioning properties can be used. For example, it can be formed of a glass member on the back side and connected to a polyvinyl alcohol resin film. The pressing member 50 is formed of a transparent rubber sheet on the front side.

In order to form the buffer layer, for example, a rubber-based material such as ruthenium rubber or urethane rubber, a resin material such as polyethylene, or the like can be used.

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

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

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.

The material of the pedestal 40 in which the overlapping portion of the pressure-sensitive material film is bonded to the above-mentioned pressing member is not particularly limited. However, for example, a person who forms the upper surface thereof with metal, glass, rubber, ceramics or the like can be used.

However, when laminating (joining) a raw material film having a large width, it is preferable to use a rubber-based or resin-based resin which has a relatively low hardness and has a cushioning property in order to uniformly pressurize the inside of the film to achieve a good bonding in the entire region. The material forms the upper face.

Further, a buffer layer similar to the above buffer layer may be disposed on the pedestal 40. When disposed on the pedestal 40, the optical properties of the material used to form the buffer layer, ie, light The permeability and the like are not particularly limited, and in addition to the above-mentioned rubber, for example, polycarbonate, polyethylene terephthalate, norbornene resin, cycloolefin polymer, polymethyl methacrylate may be used. , polyimine, triethyl cellulose, and the like.

Further, although not described in detail herein, the above-described connecting device may employ a general laser welding device and various mechanisms utilized in the peripheral devices thereof.

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

In the method for producing a polarizing film of the present embodiment, a swelling step of immersing the raw material film in the swelling bath 4a to swell is performed, and the swollen film is immersed in a dyeing step in the dyeing bath 4b to dye the dyed film. The film is immersed in the crosslinking bath 4c to crosslink the molecular chain of the resin constituting the film, and the stretching step of the film after the crosslinking step is extended in the stretching bath 4d, and the stretching is washed by the washing bath 4f. The step of washing the film after the step, the drying step of drying the washed film in the drying device 11, and the step of laminating the surface protective film on the dried film.

Further, in the method for producing a polarizing film of the present embodiment, a raw material film is placed on the raw material film supply unit 3, and the raw material film is continuously fed from the raw material film supply unit 3, and is carried out in the moving path. The above-described steps are carried out by performing a winding step of winding the product of the final lamination step in a roll shape in the polarizing film winding unit 10, and additionally, before the end of the raw material roll, the raw material film is discharged from the new raw material roll, and The connection step of the new raw material film front end portion 1b to the end portion 1a of the preceding material roll is continued, whereby the raw material film is continuously supplied from the new material roll to the stretching device, and the polarizing film is continuously produced.

In addition, the following may be employed as a raw material supplied to such a step Film (belt-shaped polyvinyl alcohol-based resin film).

The raw material film used in the method for producing a polarizing film of the present embodiment is a resin film which is swollen by absorbing water, and a film made of a polyvinyl alcohol-based polymer resin material used as a material of the polarizing film can be used. 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 films are used in the state which wound up the roll of the raw material of the roll as mentioned above.

The degree of polymerization of the polymer forming the material of the polyvinyl alcohol-based resin film is usually from 500 to 10,000, and preferably from 1,000 to 6,000, and more preferably from 1,400 to 4,000.

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

The polyvinyl alcohol-based resin film can be suitably formed by any method such as a casting method in which a stock solution dissolved in water or an organic solvent is cast into a film, a casting method, or an extrusion method.

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

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

Further, the thickness of the polyvinyl alcohol-based resin film is preferably from 20 to 100 μm. Since the thickness is 20 to 100 μm, the polyvinyl alcohol-based resin can be more reliably bonded Membranes each other.

Usually, the water content of the polyvinyl alcohol-based resin film is mostly 0.6% by mass. In other words, the water content of the polyvinyl alcohol-based resin film is usually 0.6% by mass or less before the water absorption described later. Further, the water absorption state of the polyvinyl alcohol-based resin film at the time of laser welding will be described below.

Next, the steps of extending the above-mentioned raw material film to process the polarizing film by the above-described stretching device will be described.

(swelling step)

In this step, for example, the raw material film fed from the raw material film supply unit 3 is guided to the swelling bath 4a filled with water while maintaining a constant moving speed by the above-described roll 9, and the raw material film is immersed in water.

Thereby, the raw material film can be washed, and the dirt and clogging preventing agent on the surface of the raw material film can be washed, and the effect of unevenness in dyeing unevenness can be prevented by swelling the raw material film with water.

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

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

The immersion time of the raw material 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 swelling bath, the polyvinyl alcohol-based resin film may be extended in the longitudinal direction, and the stretching ratio at this time also includes stretching due to swelling and is preferably about 1.1 to 3.5 times.

(staining step)

The film which has passed through the swelling step is immersed in the dyeing liquid stored in the dyeing bath 4b by the roll 9 in the same manner as the swelling step, and the dyeing step is carried out.

For example, the dyeing step may be carried out by immersing the polyvinyl alcohol-based resin film which has been 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 material, conventionally known ones can be used, and examples thereof include iodine and an organic dye.

Organic dyes can be used, for example, red BR, red LR, red R, pink LB, jade red BL, jujube GS, sky blue LG, lemon yellow, blue BR, blue 2R, navy blue, sky blue LG, purple LB, purple B, Black H, Black B, Black GSP, Yellow 3G, Yellow R, Orange LR, Orange 3R, Blush KGL, Congo Red, Bright Purple BK, Super Blue (Supra Blue) G, Super Blue GL, Super Orange GL, Direct (direct ) Sky blue, direct fast orange S, light fast black, etc.

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

When the organic dye is used, for example, it is preferable to combine two or more kinds in view of the neutralization of the visible light region.

Specific examples may be a combination of Congo Red and Super Blue G, Super Orange GL and Direct Sky Blue, or a combination of direct sky blue and light fast black.

As the dyeing liquid of the dye bath, a solution in which the above-mentioned dichromatic substance is dissolved in a solvent can be used.

As the solvent, water may be generally used, and an organic solvent having water-miscibility 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, more preferably in the range of 0.020 to 7% by mass, and in the range of 0.025 to 5% by mass. good.

Further, when iodine is used as the dichroic substance, the dyeing efficiency can be further improved, so that iodide is preferably added.

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 is preferably from 0.010 to 10% by mass in the dye bath described above, and more preferably from 0.10 to 5% by mass.

Among these iodides, potassium iodide is particularly preferable, and the ratio (mass ratio) of iodine to potassium iodide is preferably in the range of 1:5 to 1:100, more preferably in the range of 1:6 to 1:80, and 1:7. The range to 1:70 is particularly good.

The immersion time of the film in the dye bath described above is not particularly limited, but is preferably in the range of 0.5 to 20 minutes, and more preferably in the range of 1 to 10 parts. Further, the temperature of the dyeing bath is preferably in the range of 5 to 42 ° C, and more 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 cumulative total stretching ratio at this time is preferably about 1.1 to 4.0 times.

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

Further, in the present invention, a film formed by preliminarily mixing a polymer material of a dichroic substance without using a dyeing step may be used.

(cross-linking step)

Next, the film subjected to the dyeing step is introduced into the crosslinking bath 4c storing the crosslinking agent liquid, 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, glyoxal, glutaraldehyde or the like 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 desirable, and the addition ratio (mol ratio) is preferably in the range of 4:6 to 9:1, and preferably in the range of 5.5:4.5 to 7:3. And 6:4 is the best.

The crosslinking agent liquid of the crosslinking bath can be used by dissolving the above crosslinking agent in a solvent.

As the solvent, for example, water may be used, but an organic solvent having water compatibility may be 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, and more preferably 2 to 6% by mass.

Iodide may also be added to the crosslinking agent liquid of the crosslinking bath to impart in-plane uniformity characteristics to the polarizing film.

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 iodide content when the iodide is added is preferably from 0.05 to 15% by mass, and more preferably from 0.5 to 8% by mass.

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

Usually, the temperature of the crosslinking agent liquid in the aforementioned crosslinking bath is preferably in the range of 20 to 70 °C. In general, the impregnation of the polyvinyl alcohol-based resin film may be any one of a range of from 1 second to 15 minutes, and is preferably from 5 seconds to 10 minutes.

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

Further, the crosslinking step may be carried out by a method of applying or spraying a solution containing a crosslinking agent in place of the treatment method of immersing in the crosslinking agent liquid, similarly to the dyeing step.

(extension step)

The stretching step is a step of stretching the dyed and crosslinked film in the longitudinal direction thereof, for example, a cumulative total stretching ratio of about 2 to 8 times. In the wet stretching method, the film is immersed in the storage. The stretching is carried out by applying tension in the longitudinal direction thereof in the state in the solution in the extension bath.

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

As the solvent of the solution, water, ethanol or various organic solvents can be suitably used.

It is particularly preferable to use a solution in which boric acid and/or potassium iodide are added in an amount of about 2 to 18% by mass.

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

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

(washing step)

In the washing step, for example, the raw material film is passed through a washing bath in which a washing liquid such as water is stored, thereby washing away the unnecessary washing residue such as boric acid adhered thereto.

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

When an aqueous solution of potassium iodide added to water is used as the washing bath, the concentration thereof is usually from 0.1 to 10% by mass, and preferably from 3 to 8% by mass.

Further, the temperature of the washing liquid is preferably from 10 to 60 ° C, and more preferably from 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 many times, and the types of the additives may be stored in a plurality of washing baths. A washing solution is carried out by passing different aqueous solutions of different concentrations and passing the film through the aqueous solutions.

Further, when the film is lifted from the immersion bath in each step, in order to prevent the liquid from falling, the liquid cutting roller such as a conventional nip roll or a liquid knife may be used to remove the liquid, thereby removing the film. Excess water.

(drying step)

The film which has been washed in the washing step can be introduced into the drying device 11, and dried by a suitable optimum method such as natural drying, air drying, or heat drying to carry out the drying step.

Wherein, if the drying step by heating and drying is carried out, the heating and drying conditions are preferably about 20 to 80 ° C for the heating temperature and about 1 to 10 minutes for the drying time.

Further, the drying temperature is intended to prevent deterioration of the film regardless of the above method and is preferably as low as possible.

More preferably, it is 60 ° C or less, and is preferably 45 ° C or less.

(layering step) and (rolling step)

In the present embodiment, the winding step of winding up the raw material film by the above-described step by the polarizing film winding unit 10 is performed, whereby a polarizing film wound in a roll shape can be obtained.

In addition, in the present embodiment, it is also possible to perform drying in the drying step. After the lamination step of laminating a suitable surface protective film or the like on one side or both sides of the surface of the polarizing film, a winding step is performed.

The final total stretch ratio of the polarizing film thus produced is preferably any stretching ratio in the range of 5.25 to 8.0 times with respect to the raw material film, and any stretching ratio in the range of 6.0 to 7.0 times is more preferable.

When the above-described stretching ratio is desirable because the final total stretching ratio is less than 5.25 times, it is difficult to obtain a polarizing film having high polarizing characteristics, and when it exceeds 8.0 times, there is a fear that cracking occurs on the film.

(linking step)

By performing the above steps over the entire length of the raw material roll, the polarizing film can be continuously produced more efficiently. Further, in the present embodiment, before the entire material roll is supplied to the stretching device, the polyvinyl alcohol resin film (raw material film) is discharged from the next material roll, and the end portion 1b and the extension are joined before the new material film is joined. The apparatus performs a joining step of the end portion 1a of the raw material roll of each step.

The interface side of the region where the end portion 1a and the distal end portion 1b are at least one end portion of the distal end portion 1b absorbs water, and the laser light is irradiated onto the region swollen by the water absorption, and the water present in the water absorption region absorbs the aforementioned The joining step is carried out by laser light and laser welding. Therefore, the above-mentioned water-absorbing region can be heated and the molecular motion in the region can be made active, and the interface phase fusion can be caused, and the overlapping portion can be welded.

Further, the laser light irradiates the laser light having a peak wavelength in the range of 1.9 μm to 2.2 μm on the water absorption region, and the water present in the water absorption region absorbs the laser light and performs the above-described laser welding.

Further, at the time of the water absorption, at least the distal end portion 1a and the distal end portion 1b are made The interface side of the region at which the one end portion is overlapped absorbs water so that the thickness (D1) of the region after the water absorption is 101% or more and 110% or less with respect to the thickness (D2) of the region in the dry state.

The thickness D2 in the dry state is the thickness of the above region when it is left in an environment of 83 ° C for 1 hour and the weight is in an equilibrium state, and the thickness D1 after the water absorption is the region where the overlapping portion is absorbed, the thickness of the region is balanced. The thickness of the area in the state.

The thickness D2 in the dry state and the thickness D1 (see Fig. 4) after water absorption can be measured by the method described in the examples. Moreover, in FIGS. 3 and 4, an example (symbol 1ba) of a portion which is swollen by water absorption on the interface side of the distal end portion 1b is schematically shown.

The interface side of the region which becomes the overlapping portion is made to absorb water so that the thickness D1 after the water absorption relative to the dry state is less than 101%, and the amount of laser light absorbed by the water absorption region, that is, the water in the swelling region exists. There will be too little. Therefore, sufficient heat for welding the interface of the overlapping portion cannot be generated, and there is a fear that the two raw material films cannot be sufficiently welded. Further, there is a fear that the absorption efficiency of the laser light is lowered and the manufacturing efficiency is also lowered.

On the other hand, when the thickness D1 after water absorption is 101% or more with respect to the thickness D2 in the dry state by water absorption, the amount of laser light absorbed by the water in the region which is the overlapping portion can be sufficiently large. Therefore, sufficient heat for welding the interface of the coincident portion can be generated, and the two regions can be sufficiently welded. Moreover, therefore, the absorption efficiency of the laser light can be improved. In view of these points, it is preferable to absorb water so as to have a thickness D1 with respect to the dry state, the thickness D1 after water absorption is 103% or more, and the water absorption is preferably 105% or more.

Moreover, the thickness D2 of the relatively dry state by water absorption, the thickness after water absorption When D1 is more than 110%, the amount of laser light absorbed by the water having the above-mentioned water absorption region is excessive. Therefore, excessive heat is generated. Therefore, in the distal end portion 1b or the distal end portion 1a, the region which is amorphized by the heat is excessively enlarged from the interface in the thickness direction, so that the mechanical strength of the joint portion may be lowered. When the mechanical strength of the joint portion is lowered as described above, when the joint portion is stretched at a draw ratio of 5.25 times or more in the above-described stretching device, cracking may occur and the polarizing film may not be continuously produced. Further, since the distal end portion 1a or the distal end portion 1b is excessively swollen in the thickness direction, when the end portion 1b or the distal end portion 1a is overlapped with the opposite side, there is a fear that the position of both ends is likely to vary and positioning is difficult.

When the thickness D1 after water absorption is 101% or more and 110% or less with respect to the thickness D2 in the dry state, the water content of the water absorption region is preferably 3% by mass or more and 40% by mass or less, and 5% by mass. The above and 20% by mass or less are more preferable. When the water content is less than 3% by mass, it is difficult to sufficiently absorb the laser light with respect to the water having the water absorbing region, and the absorption efficiency of the laser light and the welding efficiency of the laser welding are lowered. On the other hand, when the water absorption region is excessively swollen and the end portion 1a is overlapped with the tip end portion 1b, the positional deviation becomes large.

The connection method as described above can be specifically carried out as follows. For example, in the end portion 1a of the preceding film and the front end portion 1b of the new film, it is disposed on the surface of the lower front end portion 1b, and water is applied by the water absorbing portion 20 having the ultrasonic atomizer to absorb water. At this time, the surface is made to absorb water so that the thickness of the end portion 1b (see FIG. 4) before swelling is 101% or more and 110% or less with respect to the thickness of the end portion 1b before the dry state. Then, a new raw material film is placed vertically on the pedestal 40 so that the width of the overlapping portion between the end portion 1a and the front end portion 1b is 0.1 mm. Up and less than 50.0mm. Further, while the overlapping portion is pressed by the pressing member 50, laser light having a peak wavelength in a range of 1.9 μm to 2.2 μm is irradiated onto the water absorbing region, and water existing in the region is absorbed. Therefore, as described above, the resins are mutually fused at the film interface and the welded portion 30 is formed. In this way, the raw material film can be joined.

Conventional laser fusion is a conventional practice of using a pigment of a cordier system and a pigment of naphthoquinone, and irradiating laser light having a peak wavelength in the range of 800 nm to 1200 nm. However, in the present embodiment, as described above, the laser light having a peak wavelength in the range of 1.9 μm to 2.2 μm is used and the pigment as described above is replaced with water as an absorbent.

Therefore, it is possible to carry out the joining of the polyvinyl alcohol-based resin film without using a high-priced light absorbing agent such as a phthalocyanine pigment or a naphthoquinone-based pigment, or to reduce the amount of use thereof as much as possible. Therefore, the cost of raw materials can be reduced. Further, when the light absorbing agent is not used, the equipment for carrying out the coating step of the light absorbing agent or the engineering management burden due to the application of the coating step can be eliminated, so that the engineering cost can be reduced.

Further, since the use of the light absorbing agent can be suppressed as described above, it is possible to provide a raw material film which is less likely to be contaminated with the chemical liquid as the polarizing film. Further, since the possibility of staining the chemical liquid is low, it is possible to reduce the labor required for purifying the chemical liquid, and it is possible to prevent the pigment from adhering to the portion other than the connecting portion which is used as the polarizing film, thereby reducing the yield.

Further, in the case of performing laser welding in the present embodiment, it is advantageous in terms of the stretch ratio as compared with the fusion by the heat sealer.

The details are as follows. For example, it will be connected by a heat sealer. The raw material film of the joint portion and the large hardened region at the periphery thereof is supplied to the above-mentioned stretching device, and when the total stretching ratio is extended to about 5.25 times, the stress is concentrated on the boundary portion between the hardened region and the non-hardened portion. As a result, in the boundary portion, breakage of the raw material film occurs at the time of stretching.

On the other hand, in the present embodiment, since the laser welding is performed as described above, in the overlapping portion of the new and old raw material films, only the interface and its vicinity are selectively (locally) heated and heated, because it is a local portion. Therefore, it can be quenched, so that the joint and its periphery can be prevented from hardening. Thereby, the hardening of the region affected by the heat of fusion can be suppressed, and the region affected by the heat can be approximated to the stretchability of the region not affected by the heat, so that the fracture of the raw material film can be suppressed and the elongation of the high stretch ratio can be performed.

In the connection step of the present embodiment, the polyvinyl alcohol-based resin film joined body having a low possibility of breaking can be formed even if it is extended at a high stretch ratio of 5.25 times or more required for imparting a high polarizing function. Further, even if it is stretched at a high stretching ratio, the fracture can be suppressed. Therefore, even when the joint portion and the periphery thereof are extended, the raw material film of 2 or more can be continuously extended without changing the stretching conditions. Therefore, when a polarizing film is manufactured, the effect of improving work efficiency, improving productivity, improving productivity, and reducing material loss can be obtained.

As described above, in the embodiment, the joint portion which is suitable for the treatment of the chemical liquid or the like is formed, and the joint of the polyvinyl alcohol-based resin film which can withstand the elongation of the high stretch ratio can be formed. Further, the polarizing film can be efficiently produced.

Further, the thickness of the polarizing film produced by the production method exemplified in the embodiment is not particularly limited, but is preferably 5 to 40 μm.

If the thickness is 5 μm or more, the mechanical strength does not decrease, and if the thickness is 40 μm In the following, the optical characteristics are not lowered, and the thickness can be reduced even when used in an image display device.

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

Further, in actual use, various optical layer layers may be used as an optical film on both surfaces or one surface of the polarizing film, or various surface treatments may be applied, and 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, but for example, in addition to a transparent protective layer for the purpose of protecting a polarizing film, an alignment liquid crystal layer for visual compensation is used for laminating other films. In addition to the layer, a polarizing conversion element, a reflection plate, a semi-transmissive plate, a phase difference plate (including 1/2 and 1/4 wavelength plates (λ plates), a visual compensation film, a brightness enhancement film, etc. may be used. A film such as an image display device.

The surface treatment may be exemplified by a surface treatment of a hard coat treatment, a reflection prevention treatment, and prevention of sticking or diffusion or anti-glare.

As described above, the joining method of the polyvinyl alcohol-based resin film of the present embodiment is such that the surface of the first polyvinyl alcohol-based resin film 1 and the surface of the second polyvinyl alcohol-based resin film 1 are superposed and bonded to each other. In the bonding method of the resin film, the interface side of the region where at least one of the first and second polyvinyl alcohol-based resin films 1 is a portion of the overlapping portion of the polyvinyl alcohol-based resin film absorbs water so as to be relatively dry. The thickness D2 of the aforementioned region, the thickness D1 of the aforementioned region after water absorption is 101% or more and 110% or less, and after the water absorption, the overlap In addition, the first and second polyvinyl alcohol-based resin films 1 are irradiated with laser light R having a peak wavelength in a range of 1.9 μm to 2.2 μm in the water absorption region (1ba in the present embodiment), and The water in the water absorption region is caused to absorb the laser light R, and the laser is welded to the interface of the overlapping portion.

When the interface side of the region where the overlapping portion is formed in at least one of the first and second polyvinyl alcohol-based resin films 1 is absorbed, the region of the overlapping portion can be swollen. Further, after the water absorption, the first and second polyvinyl alcohol-based resin films 1 are superposed, and the laser light R is irradiated onto the water absorbing region, so that the water in the water absorbing region absorbs the laser light R. The above-mentioned water-absorbing region is heated and the molecular motion in the region is made active, and therefore, the overlapping portion can be welded.

Therefore, the use of the light absorber used for absorbing laser light can be suppressed. Therefore, a resin film assembly having a joint portion suitable for being immersed in a treatment such as a chemical liquid or the like can be formed.

Further, by absorbing and swelling the region which is the overlapping portion, the thickness of the region after the water absorption is 101% or more and 110% or less with respect to the thickness in the dry state, so that the water in the water absorbing region can be absorbed. The amount of laser light is an appropriate amount. Therefore, appropriate heat for welding the interface of the coincident portion can be generated, and the overlapping portion is appropriately welded.

Therefore, the hardening of the joint portion and its periphery can be suppressed.

Further, by using laser light having a peak wavelength in the range of 1.9 μm to 2.2 μm, the absorption sensitivity of the laser light to water can be improved, so that the polyvinyl alcohol-based resin film can efficiently generate heat.

Therefore, it is possible to form a joint having a treatment suitable for immersion in a chemical liquid or the like. And a joint of a polyvinyl alcohol-based resin film which can withstand the elongation of a high stretch ratio.

Moreover, the method for producing a polarizing film of the present embodiment is a method for producing a polarizing film of a polarizing film by impregnating a raw material film of a polyvinyl alcohol-based resin film of two or more with a chemical liquid, and the raw material film is The joining is carried out by a joining method of a polyvinyl alcohol-based resin film as in the first aspect of the patent application.

By using the polyvinyl alcohol-based resin film 1 joined by the above-described joining method as a raw material film and producing a polarizing film, it is possible to suppress the staining of the chemical liquid when immersed in the chemical liquid 4. Further, it is possible to suppress the breakage of the raw material film when the elongation of the high stretch ratio is performed. Further, since the fracture can be suppressed even if the elongation of the high stretching ratio is performed in this way, it is not necessary to reduce the stretching ratio and extend the operation to avoid the trouble of the fracture only when the joint portion and the periphery thereof are extended, so that the polarizing film can be efficiently produced. .

In addition, in the present embodiment, an example in which a raw material film for producing a polarizing film is used and a polyvinyl alcohol-based resin film is bonded is used, but the joining method of the polyvinyl alcohol-based resin film of the present invention is not necessarily limited to A method of joining the raw material film as described above. Further, the method for producing a polarizing film of the present invention is not limited to the production method shown in the above embodiment. Further, the joining method of the polyvinyl alcohol-based resin film of the present invention and the method for producing the polarizing film are not limited to the above-described effects.

Example

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

(Basic conditions) . Raw material film:

Polyvinyl alcohol-based resin (PVA) film (manufactured by KURARAY Co., Ltd., 30 mm, manufactured with a thickness of 75 μm)

. Coincidence width

1.5mm width

(heating and fusion bonding means) . Water coating method:

Ultrasonic sprayer (light spot diameter 5mmΦ, flow rate 0.4mL / min, scanning speed 10mm / sec, coating times 1 time)

. Laser:

Erbium-doped fiber laser (wavelength 2μm, power 100W, spot diameter 2mmΦ, power density 3,183W/cm ² , scanning speed 50mm/sec, coating times 1 times, cumulative exposure 127.3J/cm ² , top hat beam)

. Pressurized component:

Quartz glass plate (10mm thick)

. Pressurization conditions:

Pressing 50kgf/cm ² on the raw material film overlap

(Method for measuring the thickness of raw material film) . Thickness of dry state

The PVA film was cut into a thin rectangular shape of 1 mm wide by 7 mm long to prepare a test piece. A dryer (manufactured by Sanyo Electric Co., Ltd.) was used, and the test piece was placed in an environment of 83 ° C for 1 hour to balance the weight. The test piece was taken out by the dryer and quickly fixed on a fixing jig and impregnated and frozen in liquid nitrogen. Connect The frozen test piece was cut, and a cross-sectional observation was performed using a Cryo FIB SEM (Helios Nano Lab 600, manufactured by FEI Co., Ltd.), and the thickness of the dried state of the test piece (PVA film) was measured. Further, the conditions of the Cryo FIB SEM were an acceleration voltage of 1 kV, and observation magnifications of 500 times and 1000 times.

. Thickness after water absorption

A PVA film similar to that used in the manufacturer was cut into a thin rectangular shape of 1 mm width × 50 mm length to prepare a test piece. The test piece was allowed to absorb water using the same conditions as the above-described water application method and the following conditions. After the test piece was allowed to absorb water, it was fixed on a fixing jig, and immersed in liquid nitrogen 1 minute after the end of the water absorption to freeze the test piece. Next, the test piece was cut, and cross-sectional observation was performed by Cryo FIB SEM under the same conditions as above, and the thickness of the test piece (PVA film) after water absorption was measured.

(Example 1)

Water was applied to the lower raw material film in the raw material film of the two PVA films which were placed in a superposed manner by an ultrasonic atomizer. In other words, water is applied under the above-described basic conditions so as to swell the interface side of the raw material film on the lower side so that the upper side of the lower raw material film becomes a part of the interface of the raw material film.

At this time, the thickness of the dried state in the PVA film was 74 μm, and the thickness after water absorption was 76 μm. From these values, the thickness after water absorption was calculated to be 103% in the thickness of the dry state (thickness after water absorption/thickness in dry state) × 100.

Moreover, the raw material film of the upper side is superposed on the raw material film of the lower side of the water absorption as described above, and the above-mentioned basic conditions are irradiated with the laser light under the above-mentioned basic conditions, and the two raw material films are bonded. As a result, no special light absorber was used, and good bondability was confirmed. Further, the joint portion of the obtained joined body was immersed at 30 ° C In the water for 1 minute, it was confirmed that there was no foreign matter as dissolved by the joint portion.

Further, in the obtained joint portion, the joint portion was cut back and forth by about 50 mm in length, and extended so that the total stretch ratio was 2.6 times in the swelling bath, 3.4 times in the dyeing bath, and 3.6 times in the crosslinking bath. It was 5.5 times in the stretching bath, and further immersed in a washing bath, and a polarizing film was produced in batch. As a result, the polarizing film can be produced without breaking. From this, it is understood that the polarizing film can be continuously produced by using two or more raw material films.

(Example 2)

The water was applied to the raw material film on the lower side under the above basic conditions, except that the flow rate of the ultrasonic atomizer was 0.3 mL/min, and the number of application times (the number of times of scanning) was two. Further, in the same manner as in Example 1, except that the power of the laser light was 80 W, the power density was 2,546 W/cm ² , and the total irradiation amount was 101.9 J/cm ² , the raw material film on the upper side and the raw material film on the lower side were joined. At this time, the thickness of the dried state in the PVA film was 60 μm, and the thickness after water absorption was 63 μm. From these values, the thickness after water absorption was calculated to be 105% by the thickness of the dry state (thickness after water absorption/thickness in dry state) × 100.

As a result of such bonding, a special light absorber was not used, and good bondability was confirmed. Moreover, the joint portion of the obtained joined body was immersed in water in the same manner as in Example 1. As a result, it was confirmed that there was no foreign matter due to the joint portion.

Further, a polarizing film was produced in batches in the same manner as in Example 1 using the obtained joint portion, and as a result, a polarizing film was produced without breaking. From this, it is understood that the polarizing film can be continuously produced by using two or more raw material films.

(Example 3)

In addition to the flow rate of the ultrasonic sprayer of 0.3 mL / min, the above basic Under the conditions, water was applied to the raw material film on the lower side. Further, the raw material film on the upper side and the raw material film on the lower side were joined under the same conditions as in Example 1. At this time, the thickness of the dried state in the PVA film was 75 μm, and the thickness after water absorption was 78 μm. From these values, the thickness after water absorption was calculated to be 104% in the thickness of the dry state (thickness after water absorption/thickness in dry state) × 100.

As a result of such bonding, a special light absorber was not used, and good bondability was confirmed. Moreover, the joint portion of the obtained joined body was immersed in water in the same manner as in Example 1. As a result, it was confirmed that there was no foreign matter due to the joint portion.

Further, a polarizing film was produced in batches in the same manner as in Example 1 using the obtained joint portion, and as a result, a polarizing film was produced without breaking. From this, it is understood that the polarizing film can be continuously produced by using two or more raw material films.

(Example 4)

Water was applied to the raw material film on the lower side under the above basic conditions, except that the number of application times was two. Further, the raw material film on the upper side and the raw material film on the lower side were joined under the same conditions as in Example 1. At this time, the thickness of the dried state in the PVA film was 73 μm, and the thickness after water absorption was 79 μm. From these values, the thickness after water absorption was calculated to be 108% in the thickness of the dry state (thickness after water absorption/thickness in dry state) × 100.

As a result of such bonding, a special light absorber was not used, and good bondability was confirmed. Moreover, the joint portion of the obtained joined body was immersed in water in the same manner as in Example 1. As a result, it was confirmed that there was no foreign matter due to the joint portion.

Further, a polarizing film was produced in batches in the same manner as in Example 1 using the obtained joint portion, and as a result, a polarizing film was produced without breaking. From this, it is understood that the polarizing film can be continuously produced by using two or more raw material films.

(Comparative Example 1)

In the same manner as in Example 1, except that a near-infrared light absorbing agent having a trade name of "Clearweld LD120C" (manufactured by Gentex Co., Ltd., solvent acetone) was used as the light absorbing agent instead of water, and the scanning speed was 200 mm/sec. The raw material film on the upper side and the raw material film on the lower side are joined.

As a result, good bondability was confirmed. However, the joint portion of the obtained joined body was immersed in water in the same manner as in Example 1. As a result, it was visually confirmed that foreign matter due to the light-absorbing agent joint portion was eluted from the joint portion.

As described above, according to the present invention, it is possible to form a bonded body of a polyvinyl alcohol-based resin film which is capable of withstanding a joint having a high stretch ratio and having a joint portion suitable for the treatment in the chemical solution or the like.

Although the embodiments and examples of the present invention have been described above, the features of the respective embodiments and examples are appropriately combined as originally intended. Further, it should be considered that the embodiments and examples disclosed herein are illustrative and not restrictive. The scope of the present invention is defined by the scope of the claims and the scope of the invention is intended to be

1‧‧‧ polyvinyl alcohol resin film; raw material film

3‧‧‧Material film supply department

4a‧‧‧Swelling bath

4b‧‧‧dye bath

4c‧‧‧crossing bath

4d‧‧‧Extension bath

4f‧‧‧washing bath

9‧‧‧ Rolls

9a‧‧‧ roll extension; clamping roll

10‧‧‧Winding Department

11‧‧‧Drying device; dryer

12‧‧‧Layer film

Claims (1)

A method for producing a polarizing film is a method in which a raw material film of a polyvinyl alcohol-based resin film having two or more layers is adhered by a chemical liquid, thereby forming a polarizing film, and the bonding of the raw material film is performed by a polyvinyl alcohol resin. In the method of bonding a film of a polyvinyl alcohol-based resin film, the surface of the first polyvinyl alcohol-based resin film and the surface of the second polyvinyl alcohol-based resin film are superposed and joined, and the bonding method is The interface side of the region where at least one of the first and second polyvinyl alcohol-based resin films is a portion of the overlapping portion of the polyvinyl alcohol-based resin film absorbs water so that the thickness of the region relative to the dry state is absorbed. The thickness of the region is 101% or more and 110% or less; after the water absorption, the first and second polyvinyl alcohol-based resin films are superposed; and the laser light having a peak wavelength in the range of 1.9 μm to 2.2 μm is irradiated. The water in the water absorption region is such that the water in the water absorption region absorbs the laser light, and the interface of the overlapping portion is laser welded.