JP2000147251A - Production of polarizing film and polarizing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To develop a method for producing a polarizing film by a wet method by which a polarizing film of good quality can be efficiently produced in a high production yield without causing wrinkles, bending or flaws. SOLUTION: A hydrophilic polymer film 1 is impregnated with a dichroic substance and dipped and transported in a soln. 4 while the film is stretched to produce a polarizing film. In this process, the liquid in the bath 3 is sprayed 5 to the hydrophilic polymer film during the film is being dipped and transported so as to maintain the stretched state of the film. Then a transparent protective layer is formed on one or both surfaces of the polarizing film to obtain the polarizing plate. By this method, even when the film is locally loosened due to the difference in the swelling rate caused by absorption of the soln., the stretched state of the hydrophilic polymer film while being dipped and transported can be maintained by spraying the soln., and the polarizing film of high quality can be efficiently produced in a high yield.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for efficiently producing a polarizing film having stable quality by a wet method and a polarizing plate using the polarizing film.

[0002]

BACKGROUND OF THE INVENTION Conventionally, as a method of manufacturing a polarizing film by a wet method, as shown in a thick arrow, a hydrophilic film is provided via guide rolls 2, 8, 6, 7 disposed inside and outside a bath 3 as shown in FIG. The polymer film 1 is impregnated with a dichroic substance to form a bath solution 4
There has been known a method of performing a stretching treatment while immersing and transporting the inside.

However, when immersed and conveyed through the guide rolls 8 and 6 arranged in the bath liquid, the hydrophilic polymer film that has absorbed the bath liquid and swelled may partially loosen due to a difference in swelling speed. For this reason, there is a problem that wrinkles, bends, and scratches occur. Currently, wrinkles and the like are prevented by adjusting the bath temperature and stretching ratio, but it takes time to find conditions for adjusting the conditions, and it is generally difficult to efficiently produce good quality polarizing films with good yields. Met.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to develop a method for producing a polarizing film by a wet method, which can efficiently obtain a good-quality polarizing film with good yield without wrinkles, bending or scratches.

[0005]

According to the present invention, a hydrophilic polymer film is impregnated with a dichroic substance and stretched while being immersed and conveyed in a bath solution to produce a polarizing film. A method for producing a polarizing film, which comprises maintaining a stretched state of the film by spraying a bath liquid in a bath on a molecular film, and comprising providing a transparent protective layer on one or both sides of the polarizing film. To provide a polarizing plate.

[0006]

According to the present invention, it is possible to maintain the stretched state of the hydrophilic polymer film under immersion and conveyance through spraying of the bath liquid even if partial slackening or the like occurs due to a difference in swelling speed due to bath liquid absorption. As a result, the film can be prevented from wrinkling, bending, and scratching, and a polarizing film of good quality can be efficiently produced with high yield.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The manufacturing method according to the present invention is characterized in that a hydrophilic polymer film is impregnated with a dichroic substance and stretched while being immersed and conveyed in a bath liquid to produce a polarizing film. A bath solution in a bath is sprayed on the hydrophilic polymer film of (1) to obtain a polarizing film by a wet method in which the stretched state of the film is maintained. An example is shown in FIG. 1 is a hydrophilic polymer film, 2 and 7 are guide rolls disposed outside the bath, 3 is a bath, 4 is a bath liquid, 5 is a liquid spray tube, and 6 is a guide roll disposed in the bath liquid.

In the illustrated example, as shown by the thick arrow, the liquid blowing tube 5 and the guide roll, which are placed in the bath liquid, while the hydrophilic polymer film 1 is introduced into the bath via the guide roll 2 which is placed outside the bath. 6, the liquid is held in the bath liquid, and then guided out of the bath via a guide roll 7 arranged outside the bath.

In the above description, the liquid spraying tube 5 is arranged so as to spray the bath liquid from above the hydrophilic polymer film 1 toward the bath bottom as indicated by the thick arrow, and the hydrophilic liquid flows through the bath liquid flow. While maintaining the polymer film confined in the bath liquid and enabling its immersion conveyance, the stretched state is formed and maintained through the flow pressure of the bath liquid to prevent the film from being wrinkled, bent or damaged. Has become.

In the present invention, there is no particular limitation on the means for spraying the bath solution in the bath onto the immersion-conveying hydrophilic polymer film, and the immersion-conveying hydrophilic polymer film is stretched through the flow pressure of the spraying bath solution. Any suitable one can be used. In particular, a system using a liquid spray tube as shown in the above-mentioned example is preferable from the viewpoint of simplification of the apparatus.

As the above-mentioned liquid spray pipe, an appropriate pipe which can be disposed in the bath liquid and blow out the bath liquid through a circulation system using a pump or the like can be used. In particular, rather than preventing wrinkles, bends or scratches from being generated in the hydrophilic polymer film under immersion transportation, the central portion in the width direction of the hydrophilic polymer film as indicated by an arrow in FIG. It is preferable that the spray pressure of the liquid is reduced toward both ends.

Incidentally, the liquid spraying pipe 51 illustrated in FIG. 2A is formed so that the blowing pressure of the liquid at the central portion in the width direction is increased by controlling the flow rate by the diameter and density of the outlet 52 provided in the pipe. Have been. Further, in the liquid spraying tube 53 illustrated in FIG. 2B, the liquid spraying pressure from the outlet is constant depending on the distance of the liquid spraying position through the tube with respect to the hydrophilic polymer film under immersion conveyance by bending the tube. It is formed such that the spray pressure of the liquid on the hydrophilic polymer film is increased at the center in the width direction.

As described above, an appropriate method can be adopted as a method of increasing the liquid spray pressure at the center in the width direction via the liquid spray pipe. The material, diameter and length of the liquid spray tube and the shape, diameter and pitch of the outlet can be appropriately determined according to the stretching conditions of the hydrophilic polymer film and are not particularly limited.

Generally, it is 100 A or less, particularly 80 A or less, particularly 6 to 50 made of a suitable material such as a metal tube or a plastic tube such as a stainless steel tube or a polyvinyl chloride tube.
A (JIS standard) pipe with a diameter of 30mm or less, especially 0.
At a pitch of 1 to 20 mm, especially 0.5 to 10 mm, at a pitch of 200 mm or less, preferably 0.5 to 100 mm, particularly 1 to 5 mm, 1/2 of the pipe circumference, preferably 1/3, especially 1/4. 5 or less, especially 1 to 3 articles, etc., are concentrated on the semicircular part of the above.

The length of the liquid spraying tube is generally not more than 5 times the width of the hydrophilic polymer film to be stretched. From the point of prevention of the occurrence of odor, the width of the hydrophilic polymer film is 3 times or less, preferably 0.7 to 2.5 times, particularly 1 to 2 times.
Double is preferred. In the case where the above-described curved tube is used, it is preferable that the tube length is the same. The radius of curvature of the tube in that case is usually at least 100 mm, especially at least 200 mm, especially 250 mm.
mm or more.

One or two or more liquid spray tubes can be arranged at appropriate positions with respect to the hydrophilic polymer film immersed in the bath liquid. From the viewpoint of maintaining the stretched state of the hydrophilic polymer film under immersion conveyance and preventing the occurrence of wrinkles and the like, a preferred method is to apply a liquid spray tube having a different tube shape or a different amount of bath liquid to the hydrophilic polymer film. 2 or 3 at an appropriate position corresponding to the degree of deformation according to the degree of deformation such as a slack state caused by a difference in swelling speed based on the absorption of bath liquid.
This is a method of arranging more than one.

The pressure of the bath solution sprayed on the hydrophilic polymer film under immersion transportation can be appropriately determined according to the stretched state and the like. In general, wrinkles, bends, scratches, and the like in the immersion transportation hydrophilic polymer film are obtained. and fractures of prevention 15 kg / cm ² or less from the point of view of such, especially 0.1 to 10 / cm ^2, are particularly 0.5 to 5 kg / cm ^2.

The bath liquid spraying system according to the present invention is a system in which liquid spraying means is added to the conventional system using a guide roll, that is, before and after the guide rolls 8 and 6 immersed in a bath liquid as shown in FIG. 1 or 2 or more liquid spraying means at appropriate positions such as
As described above, a suitable method such as a method using liquid spraying means instead of one or two or more guide rolls immersed in a conventional bath liquid can be applied. In particular, a system using liquid spraying means instead of the latter conventional guide roll is preferable from the viewpoint of simplification of the apparatus.

Therefore, in the present invention, when a hydrophilic polymer film is impregnated with a dichroic substance and stretched while being immersed and conveyed in a bath solution, the hydrophilic polymer film of the immersion and conveyed film is subjected to a bath treatment. There is no particular limitation except that the bath solution is sprayed to maintain the stretched state of the film.

Therefore, the introduction of the hydrophilic polymer film into the bath, the immersion and transfer in the bath solution, and the removal from the bath are performed in the same manner as in the prior art, and one or two or more guide rolls are appropriately placed inside and outside the bath. The stretching process can be performed in a conventional manner. As the guide roll, a roll having an appropriate form such as a flat roll or a spiral roll can be used.

The hydrophilic polymer film and dichroic substance to be used, the impregnation treatment, bath solution, stretching conditions, and the like are not particularly limited, and may be in accordance with conventional methods. Incidentally, examples of the hydrophilic polymer film include a polyvinyl alcohol-based film and a partially formalized polyvinyl alcohol-based film, an ethylene-vinyl acetate copolymer-based partially saponified film, and the like, and examples of the dichroic substance include iodine and And / or dichroic dyes.

On the other hand, the treatment of impregnating the hydrophilic polymer film with the dichroic substance can be carried out in advance in a separate step from the stretching treatment or in the same bath as the stretching treatment.
In that case, the former may be a simple aqueous bath in the former, but in the latter case, an aqueous bath in which a dichroic substance is dissolved is used.

Further, the stretching treatment is carried out, for example, by giving a difference in the peripheral speed of the guide rolls and / or by applying a stretching force in the transport direction to the hydrophilic polymer film through the flow pressure caused by spraying a bath liquid. Can be achieved and the draw ratio is 50
%, Especially 1 to 20%, especially 2 to 10%. The thickness of the polarizing film to be formed is usually 5 to 80 μm, but is not limited thereto.

The other production conditions can be the same as those in the prior art. For example, the hydrophilic polymer film can be swelled before the stretching step. In the present invention, also in this case, wrinkling and the like can be prevented by applying the above-described bath liquid spraying method.

The polarizing film according to the present invention can be preferably used for forming various optical devices such as a liquid crystal display device. In practical use, a polarizing plate having a transparent protective layer provided on one or both sides of the polarizing film is used. Can also. The addition of the transparent protective layer is intended to improve water resistance and handleability.

For the formation of the transparent protective layer, an appropriate transparent substance can be used. In particular, plastics and the like having excellent transparency, mechanical strength, heat stability and moisture shielding properties are preferably used. Examples thereof include polyester resins and acetate resins, polyethersulfone resins and polycarbonate resins, polyamide resins and polyimide resins, polyolefin resins and acrylic resins, or acrylic, urethane and acrylic urethane resins. And thermosetting resins such as epoxy resins and silicone resins, and ultraviolet curing resins.

The transparent protective layer may be formed by an appropriate method such as a plastic coating method or a film-forming lamination method using an adhesive layer, and the thickness is also arbitrary. Generally 500 μm or less, especially 1 to 300 μm, especially 5 to 200 μm
m thickness. The transparent protective layer may have a fine uneven structure on the surface for the purpose of preventing sticking, diffusion or anti-glare.

The formation of the transparent resin layer having the fine surface unevenness structure
For example, transparent fine particles such as silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, antimony oxide, and the like, inorganic fine particles that may be conductive, and organic fine particles such as a crosslinked or uncrosslinked polymer. And a suitable method such as a method in which the surface is ground by sandblasting or matting.

[0029]

EXAMPLE 1 Guide rolls 2, 6, 7 comprising a rubber roll having a nitrile butadiene rubber layer having a diameter of 70 mm and a surface length of 500 mm.
A stainless steel pipe with a radius of curvature of 300 mm and a straight length of 545 mm is provided with a single outlet having a diameter of 2 mm at a pitch of 5 mm outside the stainless steel pipe.
According to a method similar to FIG. 1 using a liquid blowing pipe 5 formed with 0 ports (no-portions at both ends: about 50 mm), polyvinyl alcohol having a width of 400 mm and a thickness of 20 μm was placed in a bath solution of iodine-dissolved water. The film was introduced, and 2 m / cm ² was blown out of the bath with a uniform flow pressure of 1 kg / cm ² through the liquid blowing pipe 5.
The film was immersed and conveyed at a speed of 5 minutes to perform a stretching treatment of 5% to obtain a polarizing film.

Comparative Example A polarizing film was obtained in the same manner as in Example 1 except that the method according to FIG. 3 was used instead of the liquid blowing tube 5 and using the guide roll 8 according to the above.

Evaluation Test The production status of the polarizing film when the bath temperature was set at 20 ° C., 30 ° C. or 40 ° C. was examined. The results are shown in the following table.

As can be seen from the table, in the comparative example, the polarizing film obtained was bent, but in the examples, no abnormalities such as wrinkles, bending and scratches were generated, and a polarizing film having good appearance and good quality was obtained. You can see that.

[Brief description of the drawings]

FIG. 1 is an explanatory view of an embodiment.

FIG. 2 is an explanatory view of a liquid blowing pipe.

FIG. 3 is an explanatory view of a conventional example.

[Explanation of symbols]

1: hydrophilic polymer film 2, 6, 7: guide roll 3: bath 4: bath liquid 5, 51, 53: liquid blow-out tube (52: blow-out port)

Claims (3)

[Claims] When a hydrophilic polymer film is impregnated with a dichroic substance and stretched while being immersed and conveyed in a bath liquid to produce a polarizing film, the immersion-conveyed hydrophilic polymer film is added to a bath. And maintaining the stretched state of the film by spraying the bath solution. 2. The liquid spraying pressure according to claim 1, wherein two or more liquid spraying tubes having different tube shapes or different amounts of bath liquid are used, and the liquid spraying pressure is applied from the center in the width direction of the hydrophilic polymer film to both ends. Manufacturing method to make smaller. 3. A polarizing plate comprising a polarizing film produced by the method according to claim 1 and a transparent protective layer provided on one or both sides of the polarizing film.