JP2001108827A - Polarizing film and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To develop a polarizing film comprising a polarizing layer and an optical retardation layer respectively placed on the front and rear sides of the same film adjacently and integrally, being excellently thin, having excellent transmittance and degree of polarization and little variance of them, and a method of efficiently manufacturing the polarizing film. SOLUTION: The polarizing film comprises the polarizing layer and the optical retardation layer on the front and rear side of the same film respectively. Its average transmittance is >=40% with <=0.1 standard deviation and its average degree of polarization is >=99.0% with <=0.015 standard deviation. Furthermore, the method for manufacturing the polarizing film forming the polarizing layer and the optical retardation layer on the front and rear side of the same film respectively comprises introducing a hydrophilic polymer film 1 into a dyeing bath 5 bringing only one side of the film into contact with a dyeing liquid 4 containing a dichroic substance and stretch treating the film while dye treating only its one surface (3, 2). Consequently, the dyeing liquid is uniformly and efficiently permeated with a concurrent treatment of dyeing and stretching so as to stably manufacture the polarizing film integrated with the optical retardation layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin polarizing film in which a polarizing layer and a retardation layer are integrated adjacently on the front and back of the same film and have excellent light transmittance and degree of polarization and small variations, and an efficient method for producing the same. .

[0002]

BACKGROUND OF THE INVENTION Conventionally, a method for producing a polarizing film in which a polarizing layer and a retardation layer are adjacently integrated on the front and back of the same film is performed by coating or printing an iodine-containing solution on one surface of polyvinyl alcohol and printing on one surface of the film. A method of subjecting only a dyeing treatment to a stretching treatment has been known. However, simultaneous processing of dyeing and stretching is difficult and production efficiency is poor,
In addition, there is a problem that streak-like unevenness is easily generated, and it is difficult to perform a uniform dyeing treatment, and a large variation occurs in the light transmittance and the degree of polarization of the obtained polarizing film.

On the other hand, there is also known an immersion method in which polyvinyl alcohol is successively conveyed through a guide roll or the like, immersed in an iodine bath, and stretched while being dyed from the front and back of the film to continuously produce a polarizing film. However,
In the polarizing film by such an immersion method, when the whole film becomes a polarizing layer and a retardation layer integrated type is obtained, it is necessary to bond and laminate a separate retardation film, and the production efficiency is still poor. In addition, there is a problem that the bulk becomes thick.

[0004]

The present invention relates to a polarizing film, in which a polarizing layer and a retardation layer are adjacently integrated on the front and back of the same film to be excellent in thickness, and excellent in light transmittance and degree of polarization and small in variation. Another object of the present invention is to develop a method for efficiently manufacturing such a polarizing film.

[0005]

According to the present invention, the same film has a polarizing layer on the front side and a retardation layer on the back side, and has an average light transmittance of 40% or more and a standard deviation of 0%. 0.1 or less, and an average of the degree of polarization is 99.0% or more and its standard deviation is 0.015 or less.

The present invention also provides a method wherein a hydrophilic polymer film is introduced into a dye bath in such a manner that only one side of the film comes into contact with a dye solution containing a dichroic substance, and the film is dyed only on one side. It is intended to provide a method for producing a polarizing film, wherein a polarizing layer is formed on the front side and a retardation layer is formed on the back side of the same film while stretching.

[0007]

According to the method of the present invention, the dyeing solution can be efficiently and uniformly penetrated by simultaneous treatment of dyeing and stretching, and has excellent light transmittance and degree of polarization, and its dispersion is small.
A polarizing layer and a retardation layer are adjacently integrated on the front and back of the same film, and a polarizing film having excellent thickness can be obtained stably with high production efficiency.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The polarizing film according to the present invention has a polarizing layer on the front side of the same film and a retardation layer on the back side, and has an average light transmittance of 40% or more. The standard deviation is 0.1 or less and the average degree of polarization is 9
It is composed of not less than 9.0% and its standard deviation is not more than 0.015.

The above-mentioned polarizing film is prepared, for example, by introducing a hydrophilic polymer film into a dye bath so that only one side of the film is in contact with a dye solution containing a dichroic substance, and dyeing the film only on one side thereof. The film can be obtained by a wet-type production method in which a polarizing layer is formed on the front side of the same film, and a retardation layer is formed on the back side of the same film.

FIG. 1 shows an example of a manufacturing process according to the above method. In this example, the long hydrophilic polymer film 1 is sequentially conveyed in the direction of the arrow through pinch type guide rolls 21, 22, 31, 32 also serving as the stretching rolls 2, 3.
The ink is continuously introduced into the dyeing bath 5 so as to be as close as possible to the level of the dichroic substance-containing dyeing liquid 4 while being controlled to be as horizontal as possible by the adjusting rolls 23 and 33.

In the bath of the dyeing bath 5, the dyeing solution 4 is supplied to the stirrer 5.
It is always in an overflow state while being stirred at 1, 52, and the hydrophilic polymer film 1 introduced horizontally is controlled so as not to come into contact with the edge of the bathtub. Contacting with only one side of the film through the intermediary, proceeding while maintaining contact with only one side of the film, and dyeing only one side of the film, and the feeding speed difference between the stretching rolls 2 and 3 while the dyeing is being performed. The film is stretched through.

As described above, a polarizing layer is formed on the front side of the same-body film 1 by a dyeing and stretching treatment, and a retardation layer is formed on the back side by a stretching treatment in an undyed state.
The desired polarizing film is continuously manufactured. The dye solution 4 overflowing from the bath of the dye bath 5 is used for the dye bath 5.
And is returned to the dyeing bath 5 via a circulating pump 71 and a circulation piping system 7 connecting the baths 5 and 6 as shown by arrows, and reused.

In the method of the present invention, there is no particular limitation except that only one side of the hydrophilic polymer film is dyed with a dye solution containing a dichroic substance and the film is stretched as described above. There is no. Therefore, as for the hydrophilic polymer film and the dyeing solution containing a dichroic substance, an appropriate one according to the conventional method can be used, and a method of dyeing only one side with a dichroic substance or a method of stretching treatment As for the method, an appropriate method according to the conventional wet method can be applied.

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 thereof include iodine and / or a dichroic dye. The thickness of the hydrophilic polymer film can be appropriately determined, but is generally from 10 to 200 μm, preferably from 20 to 200 μm for the purpose of obtaining a polarizing film having a thickness of about 5 to 80 μm.
The thickness is 150 μm.

A method in which a hydrophilic polymer film is introduced into a state where only one side of the film is in contact with a dye solution and only one side of the film is dyed with a dichroic substance is described in, for example, the above-mentioned surface tension. Or a protective cover layer is provided on the non-stained side of the hydrophilic polymer film, or a pair of hydrophilic polymer films is sealed inside so that the stain does not penetrate inside and immersed in the stain. An appropriate method such as a method can be adopted.

In the above-described paired lamination of hydrophilic polymer films, two films can be processed simultaneously by dyeing the front and back outer surfaces of the laminate, which is efficient. Lamination of the hydrophilic polymer film can be performed by bonding the entire surface or the end of the film via an adhesive layer or the like as necessary. In the case of the entire surface bonding, it is necessary to use a separable bonding means such as an adhesive layer. In addition, in the case of end bonding, the part can be removed by post-cutting as non-separable bonding, and after performing a predetermined treatment, it is separated into films and used as one polarizing film. The contact time between the film and the dyeing solution in the dyeing treatment can be appropriately determined according to the permeation time and the like, based on the fact that the dyeing solution penetrates to a depth of about half the film thickness.

Further, regarding the stretching treatment to be carried out together with the dyeing treatment in the dyeing bath, for example, a method in which a stretching force is applied to the continuous hydrophilic long polymer film by a peripheral speed difference using the above-mentioned stretching roll also serving as a guide roll, An appropriate method such as a method of performing a one-sided dyeing treatment and a stretching treatment by a stretching machine in a batch system can be adopted.

There is no particular limitation on the stretching magnification given in the stretching treatment performed together with the above-mentioned dyeing treatment, and the stretching magnification can be set to an appropriate stretching magnification. The entire stretching ratio to be given can be applied, or a part thereof can be applied. The stretching ratio given in the stretching treatment performed together with the dyeing treatment is preferably 5 times or less, more preferably 1.01 to 4.5 times, and particularly preferably 1.1 to 4 times from the viewpoint of uniform dyeing treatment due to improvement in water absorption. .

The stretching ratio by the stretching treatment applied to the hydrophilic polymer film to obtain a polarizing film is appropriately determined depending on the molecular orientation state of the hydrophilic polymer film to be used. 10 times or less based on the initial state of the film, especially 2 to 8 times, especially 3 to
7 times.

In the method of the present invention, the hydrophilic polymer film to be subjected to the one-sided dyeing treatment (stretching treatment) may be subjected to a swelling treatment or a stretching treatment prior to the one-sided dyeing treatment. The swelling treatment aims at improving the dyeing efficiency, the stretching treatment aims at improving the strength, and the stretching treatment is usually performed at a stretching ratio of about 4 times or less in order to leave a margin for the stretching treatment performed in the single-sided dyeing treatment step described above. You.

The hydrophilic polymer film which has been subjected to a one-sided dyeing treatment (stretching treatment) may be subjected to a crosslinking treatment to improve the strength and the like, and a further stretching treatment may be added at the time of the crosslinking treatment. Can also. The swelling treatment and the cross-linking treatment can be performed in a separate bath from the one-sided dyeing treatment (stretching treatment), or can be performed in the same bath.

The swelling treatment is carried out, for example, through a bath with an aqueous medium or a dye bath containing a dichroic substance.
For example, it can be carried out by applying an appropriate method according to a conventional wet method through a bath or the like containing 1 to 10% by weight of boric acid and, if necessary, 10% by weight or less of potassium iodide.
In addition, an appropriate method according to the related art can be applied as a drying method to be performed on the polarizing film obtained after the one-sided dyeing treatment (stretching treatment) or the cross-linking treatment, if necessary.

As described above, the polarizing film according to the present invention has a polarizing layer on the front side and a retardation layer on the back side of the same film. A preferred polarizing film has an average light transmittance of 40% or more, particularly 41% or more, particularly 42% or more, and a standard deviation of 0.1 or less, particularly 0.09 or less, particularly 0.08 or less, The average of the degree of polarization is 99.0% or more, especially 99.5% or more, especially 99.7% or more, and the standard deviation is 0.015 or less, especially 0.013 or less, particularly 0.010 or less. is there.

In practical use of a polarizing film, one or both sides of the polarizing film are provided for the purpose of improving water resistance, strength, handleability, and durability, in which light transmittance and polarization degree are hardly changed even under high temperature and high humidity. A polarizing plate may be provided with a transparent protective layer. For forming the transparent protective layer, an appropriate transparent substance can be used.
Above all, polymers having excellent transparency, mechanical strength, heat stability, moisture shielding property and the like are preferably used.

Incidentally, examples of the polymer include an acetate resin such as triacetyl cellulose, a polyester resin, a polyether sulfone resin, a polycarbonate resin, a polyamide resin, a polyimide resin, and the like.
Examples thereof include a polyolefin resin, an acrylic resin, a thermosetting resin such as an acrylic resin, a urethane resin, an acrylic urethane resin, an epoxy resin, and a silicone resin, or an ultraviolet curable resin.

The transparent protective layer may be formed by an appropriate method such as a method of applying a polymer or a method of forming a film through an adhesive layer, and may have any thickness. Generally 50
The thickness is 0 μm or less, especially 1 to 300 μm, especially 5 to 200 μm. When a transparent protective layer is provided on both sides of the polarizing film, the transparent protective layer may be made of a different polymer or the like on both sides.

The transparent protective layer may have been subjected to a hard coat treatment, an anti-reflection treatment, a treatment for preventing sticking, diffusion or anti-glare, or the like. The hard coat treatment is performed for the purpose of preventing scratches on the surface of the polarizing plate. For example, a hardened film having excellent hardness and slipperiness by the above-described ultraviolet curing resin such as silicone is coated on the surface of the transparent protective layer. Can be formed by a method according to the related art such as a method of adding to the conventional method.

On the other hand, anti-sticking is performed for the purpose of preventing adhesion to an adjacent layer, and anti-glare treatment is performed for the purpose of preventing external light from being reflected on the surface of the polarizing plate and obstructing the visible light transmitted through the polarizing plate. For example, it can be formed by providing a fine uneven structure on the surface of the transparent protective layer by an appropriate method such as a roughening method by a sand blast method or an embossing method or a method of blending transparent fine particles. .

The above-mentioned transparent fine particles may be made of, for example, silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, antimony oxide, or the like having an average particle size of 0.5 to 20 μm. Certain inorganic fine particles, organic fine particles comprising a crosslinked or uncrosslinked polymer or the like are used. The amount of transparent fine particles used is
2 to 50 parts by weight per 100 parts by weight of transparent resin,
25 parts by weight are common.

The antiglare layer containing the transparent fine particles can be provided as the transparent protective layer itself, or as a coating layer on the surface of the transparent protective layer. Note that the anti-glare layer may also serve as a diffusion layer for expanding the viewing angle by diffusing light transmitted through the polarizing plate.

If necessary, the polarizing film or the transparent protective layer forming the polarizing plate may absorb ultraviolet rays such as a salicylic acid ester compound, a benzophenol compound, a benzotriazole compound, a cyanoacrylate compound, and a nickel complex salt compound. UV absorbing ability can be provided by an appropriate method such as a method of treating with an agent.

[0032]

EXAMPLE 1 Polyvinyl alcohol having a degree of polymerization of 1700 and a thickness of 7
While continuously transporting a 5 μm long film through a guide roll, the film is stretched twice by a free-end uniaxial method in a boric acid aqueous solution, and only one side of the film is dyed with iodine by the method shown in the figure. And then stretched 1.5 times in a boric acid aqueous solution by a free-end uniaxial method.
The film was crosslinked while being stretched 6 times, and dried at 50 ° C. for 7 minutes to continuously obtain a polarizing film having a polarizing layer on the front side of the same film and a retardation layer on the back side.

Comparative Example Thickness 7 made of polyvinyl alcohol having a degree of polymerization of 1700
While continuously transporting a 5 μm long film through a guide roll, the film is stretched four times by a free-end uniaxial method in a boric acid aqueous solution, and one side of the film is coated and impregnated with an iodine aqueous solution by a die coater. Is stretched 1.25 times by a free-end uniaxial method in a boric acid aqueous solution, crosslinked, dried at 50 ° C. for 7 minutes to have a polarizing layer on the front side of the same film, and a retardation layer on the back side. Was continuously obtained.

Evaluation Test Appearance Appearance of the polarizing film obtained in each of Examples and Comparative Examples was observed by observing the appearance on a light table by disposing a separate polarizing film in crossed Nicols. No unevenness was observed, but in the comparative example, several stripe-like unevennesses in dyeing were observed.

Light Transmittance and Degree of Polarization The light transmittance and the degree of polarization in the front (normal) direction were examined at predetermined 10 places of the polarizing films obtained in Examples and Comparative Examples, and the standard deviation was calculated. The results are shown in the following table.

Example 1 Comparative Example Light Transmittance (%) Degree of Polarization (%) Light Transmittance (%) Degree of Polarization (%) 143.2 99.94 43.5 99.92 43.199 .94 43.0 99.93 3 43.2 99.95 43.3 99.95 4 43.2 99.93 43.1 99.90 5 43.3 99.95 43.4 99.89 6 43. 2 99.94 42.9 99.96 7 43.3 99.93 43.2 99.94 8 43.1 99.94 43.0 99.91 9 43.2 99.96 43.2 99.94 10 43.2 99.93 43.5 99.95 Average 43.20 99.94 43.21 99.93 Standard deviation 0.063 0.0094 0.202 0.0221

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an example of a manufacturing process.

[Explanation of symbols]

 1: hydrophilic polymer film 2, 3: stretch roll 4: dye solution containing dichroic substance 5: dye bath

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // C08J 5/18 CER C08J 5/18 CER B29K 29:00 B29K 29:00 B29L 7:00 B29L 7: 00 9:00 9:00 F term (reference) 2H049 BA02 BA06 BA26 BA27 BB03 BB26 BB27 BB36 BB43 BC03 4F070 AA13 AA26 AA28 AB13 AE04 GA09 GB08 GC02 GC06 4F071 AA15 AA28X AA29 AF30 AH19 BB07 BC02 4F0711 EA01 BAB 4F210 AA19 AE10 AG01 AG03 QA03 QC01 QD06 QD09 QG01 QG18 QW33

Claims (5)

[Claims] 1. A polarizing layer is provided on the surface side of the same-body film,
And a retardation layer on the back surface side, the average of the light transmittance is 40% or more and the standard deviation thereof is 0.1 or less,
The average degree of polarization is 99.0% or more and the standard deviation is 0.0
A polarizing film having a size of 15 or less. 2. The polarizing film according to claim 1, wherein a transparent protective layer is provided on one or both sides. 3. A stretching treatment in which a hydrophilic polymer film is introduced into a dye bath so that only one side of the film comes into contact with a dye solution containing a dichroic substance, and the film is dyed only on one side thereof. And a polarizing layer on the surface side of the same film,
A method for producing a polarizing film, comprising forming a retardation layer on the back side. 4. The method according to claim 3, wherein a long hydrophilic polymer film is continuously introduced into a dyeing bath and subjected to a stretching treatment at a stretching ratio of 5 times or less to continuously produce a polarizing film. 5. The method according to claim 3, wherein a cross-linking treatment is performed after the stretching treatment while maintaining contact with one side of the hydrophilic polymer film by the surface tension of the dyeing solution overflowing from the bathtub.