JP2000147252A - Production of polarizing film and polarizing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To develop a method for producing a polarizing film which can be used for a wet method while preventing fracture, impressions or the like by making use of spiral rubber rolls which hardly caused wrinkles or bending of a hydrophilic polymer film during transport. SOLUTION: In this method, a hydrophilic polymer film 1 is impregnated with a dichromatic substance and dipped and transported in a soln. 4 by plural guide rolls 2, 5, 6, 7 disposed outside and inside the bath while the film is stretched to obtain a polarizing film. In this process, a spiral rubber roll having spiral grooves symmetric with respect to the central part and having <=100 rubber hardness is used for at least one of the guide rolls 2, 5, 6, 7. Then a transparent protective layer is formed on one or both surfaces of the polarizing film. By this method, the swollen hydrophilic polymer film hardly suffers fracture or the like and the wet method can be used favorably. Production of wrinkles can be prevented by the spiral effect and a polarizing film of good 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 illustrated in FIG. 1, a dichroic substance is applied to a hydrophilic polymer film 1 through a plurality of guide rolls 2, 5, 6, 7 disposed inside and outside a bath 3 as indicated by an arrow. As a method for producing a polarizing film by a wet method in which the film is impregnated and stretched while being immersed and conveyed in the bath liquid 4, a method using a guide roll having a surface as smooth as possible has been known.

[0003] However, there has been a problem that wrinkles and bending are likely to occur in the hydrophilic polymer film due to swelling during immersion transport in the bath liquid. When a conventional spiral rubber roll having a spiral groove formed on its surface for the purpose of removing wrinkles, the hydrophilic polymer film whose strength has been reduced due to swelling is broken and the wet method cannot be applied, or the resulting polarized light cannot be used. A large number of scratches such as rubber roll pressing marks remained on the film, and it was still difficult to apply the wet method.

[0004]

SUMMARY OF THE INVENTION The present invention is directed to the application of a wet method to prevent the occurrence of breaks and push marks while taking advantage of the advantage of a spiral rubber roll in which wrinkles and bending are unlikely to occur in a transported hydrophilic polymer film. It is an object of the present invention to develop a method for manufacturing a polarizing film capable of performing the above-described steps.

[0005]

According to the present invention, a hydrophilic polymer film is impregnated with a dichroic substance through a plurality of guide rolls arranged outside a bath and in a bath liquid, and stretched while being immersed and conveyed in the bath liquid. A polarizing film having at least one of the guide rolls, a spiral groove having a symmetrical spiral groove with respect to a central portion, and a rubber hardness of 100 or less. And a polarizing plate provided with a transparent protective layer on one or both sides of the polarizing film.

[0006]

According to the present invention, the use of the spiral rubber roll having the above-mentioned features allows the swollen hydrophilic polymer film to be broken or pressed by scratches even when the bath is immersed and conveyed in the bath liquid. It is possible to apply the wet method satisfactorily, and to prevent the occurrence of wrinkles and bending due to the spiral effect, and to efficiently produce a polarizing film of good quality with good yield.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The production method according to the present invention is a method in which a hydrophilic polymer film is impregnated with a dichroic substance through a plurality of guide rolls disposed outside a bath and inside a bath liquid, and immersed and conveyed in the bath liquid. In producing a polarizing film by stretching while stretching, at least one of the guide rolls has a spiral groove which is symmetrical with respect to the center part and has a rubber hardness of 1
A polarizing film is obtained by a wet method using a spiral rubber roll of 00 or less.

FIG. 1 shows an example of the manufacturing method. 1 is a hydrophilic polymer film, 3 is a bath, 2, 5, 6, 7
Is a guide roll arranged outside or in the bath liquid, and 4 is a bath liquid. In the example shown in the figure, two guide rolls are arranged outside the bath and inside the bath solution, but the number of the rolls is not particularly limited in the present invention. Can be arranged at an appropriate position.

FIG. 2 shows a spiral rubber roll.
As shown in (a), a rubber layer 8 having a spiral groove symmetrical with respect to the center of the rubber layer and having a rubber hardness of 100 or less is used. By providing the spiral groove symmetrically with respect to the center part, the hydrophilic polymer film can be conveyed in a rotational direction in which the spiral groove becomes divergent, so that functions such as wrinkle removal and bending prevention can be exerted.

[0010] The spiral rubber roll can be formed, for example, by providing spiral grooves in a rubber layer by an appropriate method. In this case, the acting force such as the wrinkle removal described above depends on the width, pitch and number of spiral grooves, rubber, and the like. It can be controlled by the material of the layer and the peripheral speed of the roll.

[0011] In the above, the spiral groove which is preferable from the viewpoint of wrinkle removal and the prevention of the occurrence of a scar due to pressing is preferably such that the portion in contact with the hydrophilic polymer film is 1 mm or more, especially 3 mm, as shown in FIG.
It is formed so as to have a radius of curvature of not less than mm, especially 5 mm to infinity (flat), and has a spiral groove width of 50 mm or less, particularly 1 to 30 mm, particularly 5 to 20 mm.

The sectional shape of the spiral groove is not particularly limited. For example, a groove 81 having a semicircular cross section is formed on a flat surface as shown in FIG. 2B, and a triangular waveform as shown in FIG. 2C. 82, those having a semicircular cross section as illustrated in (d), and those 84 having a rectangular cross section as illustrated in (e). In this case, it is preferable that the portion in contact with the hydrophilic polymer film, particularly the edge portion, is formed to have a predetermined radius of curvature as described above, as shown in the figure.

On the other hand, by setting the hardness of the rubber layer provided with the spiral groove to 100 or less, even when the spiral rubber roll is arranged in the bath solution and the swollen hydrophilic polymer film is immersed and conveyed, the same effect can be obtained. It is possible to prevent the film from being broken or pressed and scarred.
The rubber hardness is preferably 90 or less, more preferably 40 to 80, and particularly preferably 60 to 75, from the viewpoint of its prevention effect and abrasion durability. The rubber hardness is based on JIS K6301.

The rubber layer can be formed of an appropriate rubber, and the type of the rubber is not particularly limited. Incidentally, examples thereof include natural rubber (hardness 10 to 100), styrene butadiene rubber (hardness 30 to 100), nitrile rubber (hardness 15 to 100) and chloroprene rubber (hardness 10 to 10).
90), butyl rubber (hardness 25-85), ethylene propylene rubber (hardness 25-85), chlorosulfonated polyethylene rubber (hardness 50-95), silicone rubber (hardness 20-90), fluorine rubber (hardness 55-80) And urethane rubber (hardness 10 to 99).

In the present invention, the spiral rubber roll is used for one or more of the guide rolls arranged outside the bath or in the bath liquid, and may be used for all of the guide rolls. It is preferable to arrange two or more spiral rubber rolls in a combination in which the rubber hardness or the shape of the spiral groove is different from the viewpoints of the wrinkle removing effect and the stable conveyance.

The spiral rubber roll can be placed outside the bath and / or inside the bath liquid as described above, but wrinkles and the like are more likely to be generated by swelling with the bath liquid than from the point of wrinkling of the hydrophilic polymer film. It is preferable to arrange in a bath liquid and use it for immersion conveyance of a hydrophilic polymer film in the bath liquid.

As described above, the present invention is to produce a polarizing film by a wet method in which a hydrophilic polymer film is impregnated with a dichroic substance using a predetermined spiral rubber roll and is stretched while being conveyed. In the present invention, there is no particular limitation except that the above-mentioned spiral rubber roll is used in the production.

Therefore, the hydrophilic polymer film and dichroic substance to be used, the impregnation treatment, the bath solution, the stretching conditions, and the like can be the same as those in the related art. Incidentally, examples of the hydrophilic polymer film include a polyvinyl alcohol-based film, a partially formalized polyvinyl alcohol-based film, an ethylene-vinyl acetate copolymer-based partially saponified film, and the like. Examples of the dichroic substance include iodine and / or Or dichroic dyes.

The impregnating treatment of 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 can be achieved by, for example, a method in which the peripheral speed of the guide roll is made different to apply an extension force to the hydrophilic polymer film, and the stretching magnification is 50%.
Hereinafter, it is generally 1-20%, especially 2-10%. 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 the conventional ones. For example, the hydrophilic polymer film can be swelled before the stretching step. Also in the present invention, it is preferable to prevent wrinkles and the like by using the spiral rubber roll described above.

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. Among them, plastics and the like, which are excellent in transparency, mechanical strength, heat stability and moisture shielding property, 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.

[0026]

EXAMPLE 1 A two-layer spiral groove having a cross-sectional shape shown in FIG. 2E and a groove width of 10 mm was formed on a rubber layer of nitrile butadiene rubber having a rubber hardness of 70 and having a diameter of 70 mm and a surface length of 500 mm. A spiral rubber roll formed under the conditions of a depth of 3 mm, a pitch of 20 mm, and a lead of 40 mm is used as a guide roll denoted by reference numeral 5 in FIG. 1, and flat rubber rolls are used for the other guide rolls 2, 6, and 7 in accordance with FIG. A polyvinyl alcohol film having a width of 400 mm and a thickness of 20 μm was introduced into a bath solution composed of water in which iodine was dissolved at a speed of 2 m / min, immersed and conveyed, and subjected to a 5% stretching treatment. I got The radius of curvature of the protruding portion of the spiral groove was about 1.5 mm.

Example 2 A polarizing film was obtained in the same manner as in Example 1, except that a rubber roll was used which was not squared at the projecting corner of the spiral groove but was kept at a right angle.

Example 3 A polarizing film was obtained in the same manner as in Example 1 except that a rubber roll having a rubber layer hardness of 110 was used.

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.

In the above, in Example 3, remarkable pressing marks and scratches were generated on the obtained polarizing film, but in Example 1, no abnormalities such as pressing marks and scratches were generated, and the polarizing film was good in appearance and good in quality. Was obtained. Further, in Example 2, although not as remarkable as in Example 3, pressing marks were generated on the obtained polarizing film, and scratches were also generated on the high temperature side.

[Brief description of the drawings]

FIG. 1 is an explanatory view of an embodiment.

FIG. 2 is an explanatory view of a spiral rubber roll.

[Explanation of symbols]

1: hydrophilic polymer film 2, 5, 5, 7: guide roll 3: bath 4: bath liquid 8: spiral rubber roll 81, 82, 83, 84: spiral groove

Claims (5)

[Claims] 1. A polarizing film is drawn by impregnating a hydrophilic polymer film with a dichroic substance through a plurality of guide rolls arranged outside a bath and in a bath liquid and immersing and transporting the film in the bath liquid. In manufacturing, a method for manufacturing a polarizing film, wherein at least one of the guide rolls has a spiral groove symmetrical with respect to a central portion and has a rubber hardness of 100 or less. 2. The method according to claim 1, wherein the spiral rubber roll has a groove width of 50 mm or less formed by forming a portion of the spiral groove in contact with the hydrophilic polymer film to have a radius of curvature of 1 mm or more. 3. The method according to claim 1, wherein two or more spiral rubber rolls are used in a combination having different rubber hardness or spiral groove shape. 4. The production method according to claim 1, wherein the spiral rubber roll is disposed in a bath liquid. 5. 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.