JP2003195048A - Method for regenerating cellulose triacetate film and thereby manufactured cellulose triacetate film, polarizing plate and picture display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for efficiently manufacturing a TAC (cellulose triacetate) film from a used polarizing plate using a TAC film as a transparent protective film. <P>SOLUTION: The method for regenerating the TAC film is characterized by having a step to subject the polarizing plate using the TAC film as the transparent protective film on at least a surface of a polarizer to solvent treatment and to dissolve the TAC film in the solvent and manufacturing the film from the TAC solution obtained in the previous step. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a regenerated TAC film from a polarizing plate using a cellulose triacetate (hereinafter, cellulose triacetate is also referred to as TAC) film as a transparent protective film. The present invention also relates to a regenerated TAC film obtained by the manufacturing method, a polarizing plate using the regenerated TAC film, and a liquid crystal display device, an organic EL display device, an image display device such as a PDP using the polarizing plate. .

[0002]

2. Description of the Related Art Polarizing plates are used in image display devices such as liquid crystal display devices. As the polarizing plate, one in which a TAC film is stuck as a transparent protective film on one or both sides of a polarizer such as a polyvinyl alcohol-based resin film dyed with a dichroic dye such as iodine is often used. Since such a polarizing plate is used for a liquid crystal display device or the like by cutting the absorption axis in a predetermined direction, it has a problem that the area yield is poor and a large amount of industrial waste is generated.

To address such a problem, Japanese Patent Laid-Open No. 2001-1
Japanese Patent No. 81400 proposes a method of recovering cellulose ester by treating a polarizing plate with water. However, in this method, even plasticizers, ultraviolet absorbers, lubricants, and other additives contained in the cellulose ester cannot be dissolved, and it is necessary to add a separate additive when regenerating cellulose as a transparent protective film. There is. Moreover, in this method, it takes time to recover the cellulose ester, and the recovery rate is not sufficient.

[0004]

An object of the present invention is to provide a method for efficiently producing a recycled TAC film from a polarizing plate using a TAC film as a transparent protective film.

Further, as the polarizing plate, an adhesive type polarizing plate having a pressure sensitive adhesive layer on the surface thereof, or one having an antiglare layer or a hard coat layer are used. When such a polarizing plate is used, there is a problem that a large amount of foreign matter is generated in the recycled TAC film. An object of the present invention is to provide a method for producing a recycled TAC film in which the generation of foreign matter is suppressed even when an adhesive polarizing plate or the like is used.

Another object of the present invention is to provide a regenerated TAC film obtained by the above manufacturing method, a polarizing plate using the regenerated TAC film, and an image display device using the polarizing plate.

[0007]

As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that the above-mentioned object can be achieved by the following manufacturing method, and completed the present invention.

That is, the present invention is obtained by the steps of treating a polarizing plate using a cellulose triacetate film as a transparent protective film on at least one surface of a polarizer with a solvent to dissolve the cellulose triacetate film in the solvent, and then by the steps described above. The present invention relates to a method for producing a regenerated cellulose triacetate film, which comprises producing a film from a cellulose triacetate solution.

According to the method for producing a recycled TAC film of the present invention, the polarizer portion of the polarizing plate does not dissolve,
The TAC used as the transparent protective film can be dissolved and reused. As a result, industrial waste can be reduced and the industrial utility value is great. See also T
The solution in which the AC film is dissolved contains additives such as a plasticizer, an ultraviolet absorber, and a lubricant in addition to TAC, and a film is produced using the obtained solution to obtain a plasticizer, an ultraviolet absorber, and a lubricant. It is possible to obtain a recycled TAC film containing additives such as.

The method for producing the recycled TAC film is suitable when the polarizing plate is an adhesive type polarizing plate having an adhesive layer on at least one side of the polarizing plate and the gel fraction of the adhesive is 70% or more. Available. The gel fraction is preferably 75% or more, more preferably 80% or more.

When the polarizing plate is an adhesive type polarizing plate, when the gel fraction of the adhesive is 70% or more, the amount of the adhesive component dissolved in the solvent is reduced, and the foreign matter from the solution does not pose a practical problem. A TAC film is obtained. In addition, the gel fraction is the measured value of the initial weight of the pressure-sensitive adhesive, and this is put into ethyl acetate, left at room temperature for 1 week or more, then only the insoluble matter is taken out, and the solvent contained in the insoluble matter is dried. From the weighed value of the insoluble content after removal, the following formula: gel fraction (%) =
(Weight of insoluble matter / initial weight) × 100.

Further, in the method for producing the recycled TAC film, the polarizing plate is a polarizing plate having an antiglare layer and / or a hard coat layer on the surface of the polarizing plate, and the antiglare layer and / or
Alternatively, it can be suitably used when the curing rate of the hard coat layer is 70% or more. Curing rate is 75% or more, and even 8
It is preferably 0% or more.

When the polarizing plate is a polarizing plate having an antiglare layer or a hard coat layer, the curing rate of the antiglare layer or the hard coat layer is 7
By setting the content to 0% or more, the amount of components that dissolve in the solvent decreases, and foreign matter from the solution does not pose a practical problem.
A C film is obtained. Since the forming agent for the antiglare layer or the hard coat layer is usually a curable resin such as an ultraviolet curable resin, it has a functional group of the forming agent before curing and a functional group of the forming agent after curing. From the value quantified by IR or NMR, the following formula: Curing rate (%) = {(amount of functional group before curing)-(amount of functional group after curing) / (amount of functional group before curing)}
It can be determined by × 100. When the forming agent is an ultraviolet curable resin, the quantitative value can be, for example, a quantitative value of carbon-carbon double bond.

The present invention also relates to a recycled TAC film obtained by the above manufacturing method. The present invention also relates to a polarizing plate using the recycled TAC film as a transparent protective film on at least one surface of a polarizer. Furthermore, an image display device using at least one of the polarizing plates,
Regarding

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention relates to a polarizing plate using a TAC film as a transparent protective film on at least one surface of a polarizer, and uses these as industrial wastes to produce a recycled TAC film. To do.

The polarizer is not particularly limited and various kinds can be used. Examples of the polarizer include a hydrophilic polymer film such as a polyvinyl alcohol film, a partially formalized polyvinyl alcohol film, and an ethylene / vinyl acetate copolymer partially saponified film, and a dichroic dye such as iodine or a dichroic dye. Examples include polyene oriented films, such as those obtained by adsorbing a volatile substance and uniaxially stretched, polyvinyl alcohol dehydration products, polyvinyl chloride dehydrochlorination products, and the like. Among these, a polarizer made of a polyvinyl alcohol film and a dichroic substance such as iodine is preferable. The thickness of these polarizers is not particularly limited,
Generally, it is about 5 to 80 μm.

A polarizer in which a polyvinyl alcohol film is dyed with iodine and uniaxially stretched is produced by, for example, immersing polyvinyl alcohol in an aqueous solution of iodine, dyeing it, and stretching it to 3 to 7 times its original length. You can If necessary, it can be immersed in an aqueous solution of potassium iodide, which may contain boric acid, zinc sulfate, zinc chloride or the like. If necessary, the polyvinyl alcohol film may be immersed in water and washed with water before dyeing. By washing the polyvinyl alcohol-based film with water, it is possible to wash the stains and anti-blocking agents on the surface of the polyvinyl alcohol-based film, and by swelling the polyvinyl alcohol-based film, the effect of preventing unevenness such as uneven dyeing is also obtained. is there. Stretching may be performed after dyeing with iodine, stretching while dyeing, or stretching and then dyeing with iodine. It can be stretched in an aqueous solution of boric acid or potassium iodide, or in a water bath.

The thickness of the TAC film provided on at least one surface of the polarizer is not particularly limited, but is generally 500 μm or less, preferably 1 to 300 μm. In particular, the thickness is preferably 5 to 200 μm. In the TAC film, a plasticizer such as triphenyl phosphate, a salicylic acid ester compound, a benzophenol compound, a benzotriazole compound, a cyanoacrylate compound, an ultraviolet absorber such as a nickel complex salt compound, a lubricant such as silica particles, etc. It may contain additives such as.

The adhesion treatment between the polarizer and the TAC film is not particularly limited, but examples thereof include isocyanate adhesives, polyvinyl alcohol adhesives, gelatin adhesives, vinyl latex adhesives, water-based polyesters and the like. Is used. The polyvinyl alcohol-based adhesive or the like may contain a water-soluble crosslinking agent such as boric acid, borax, glutaraldehyde, melamine, or oxalic acid. Such an adhesive layer can be formed as a coating / drying layer of an aqueous solution, but other additives and a catalyst such as an acid can be blended as necessary when preparing the aqueous solution.

An adhesive layer may be provided on one side or both sides of the polarizing plate. As described above, the pressure-sensitive adhesive layer is preferably formed using a pressure-sensitive adhesive having a gel fraction of 70% or more. The gel fraction is preferably 75% or more, more preferably 80% or more. The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer is not particularly limited, but for example, an acrylic polymer, a silicone-based polymer, polyester, polyurethane, polyamide, polyether, or a polymer having a fluorine-based or rubber-based polymer as a base polymer is appropriately used. It can be selected and used. In particular, it is preferable to use an acrylic adhesive, which has excellent optical transparency, shows appropriate wettability, cohesiveness and adhesiveness, and has excellent weather resistance and heat resistance.

In addition to the above, prevention of foaming phenomenon and peeling phenomenon due to moisture absorption, deterioration of optical characteristics due to thermal expansion difference and the like, prevention of warpage of liquid crystal cells, and further formation of a liquid crystal display device having high quality and excellent durability, etc. From this point of view, a pressure-sensitive adhesive layer having a low moisture absorption rate and excellent heat resistance is preferable.

The pressure-sensitive adhesive layer is, for example, a natural or synthetic resin, in particular, a tackifying resin, a filler, a pigment, a colorant made of glass fiber, glass beads, metal powder, or other inorganic powder. It may contain an additive such as an antioxidant that is added to the pressure-sensitive adhesive layer. Further, it may be a pressure-sensitive adhesive layer containing fine particles and exhibiting light diffusion property.

The pressure-sensitive adhesive layer may be provided on one side or both sides of the polarizing plate as a superposed layer of different compositions or types. When it is provided on both surfaces, the pressure-sensitive adhesive layers having different compositions, types and thicknesses may be provided on the front and back of the polarizing plate. Although the thickness of the pressure-sensitive adhesive layer varies depending on the purpose of use and the adhesive strength, it is generally 1 to 500 μm, and 5 to 200
μm is preferable, and 10 to 100 μm is particularly preferable.

The surface of the polarizing plate of the present invention may have a hard coat layer or an antiglare layer. As described above, the antiglare layer and the hard coat layer preferably have a curing rate of 70% or more. The curing rate is preferably 75% or more, more preferably 80% or more.

The hard coat layer is provided for the purpose of preventing scratches on the surface of the polarizing plate.
It can be formed by a method of adding a cured film excellent in hardness, sliding properties and the like made of an appropriate ultraviolet curable resin such as a silicone-based resin to the surface of the TAC film.

The antiglare layer is provided for the purpose of preventing external light from being reflected on the surface of the polarizing plate and obstructing visual recognition of light transmitted through the polarizing plate. For example, a sandblast method or an embossing method is used. It can be formed by imparting a fine concavo-convex structure to the surface of the TAC film by an appropriate method such as a surface roughening method or a method of blending transparent fine particles. The fine particles contained in the formation of the surface fine uneven structure,
For example, silica, alumina, titania, zirconia, tin oxide, indium oxide having an average particle size of 0.5 to 50 μm,
Transparent fine particles such as inorganic fine particles which may be conductive, such as cadmium oxide and antimony oxide, and organic fine particles which are crosslinked or uncrosslinked polymers, etc. are used. When forming the surface fine uneven structure, the amount of the fine particles used is generally about 2 to 50 parts by weight, preferably 5 to 25 parts by weight, based on 100 parts by weight of the transparent resin forming the surface fine uneven structure. The antiglare layer may also serve as a diffusion layer for diffusing the light transmitted through the polarizing plate and expanding the viewing angle (viewing angle expanding function, etc.). The antiglare layer may be provided on the TAC film itself, or may be provided separately from the TAC film.

In the manufacturing method of the present invention, first, the polarizing plate is treated with a solvent to dissolve TAC in the solvent. As the solvent, a solvent that dissolves TAC but does not dissolve the polarizer can be preferably used. Examples of such a solvent include methylene chloride, 1,2-dichloroethane, chloroform, methyl acetate, fluoroalcohol and the like. By treating with the solvent, a TAC solution in which a TAC film which is a transparent protective film for a polarizing plate is dissolved can be obtained. If the transparent protective film contains additives such as a plasticizer, an ultraviolet absorber and a lubricant, the resulting TAC solution can also be dissolved. The treatment with the solvent is not particularly limited as long as it is a method by which a TAC solution can be obtained. For example, it can be performed by a method of immersing the polarizing plate in a solvent, a method of spraying the solvent on the polarizing plate, or the like. The polarizing plate is immersed in a solvent at 0 to 50 ° C., preferably 10 to 40 ° C. for 10 to 300 minutes, preferably 20 to 240 minutes. Even at room temperature, the immersion treatment of the polarizing plate in the solvent can be performed in a relatively short time of 30 to 120 minutes.

The obtained TAC solution is separated from the polarizer and then used for producing a regenerated TAC film. Reproduction TA
In producing the C film, an operation such as filtration is usually performed to appropriately remove the undissolved material including the polarizer. Further, when producing a recycled TAC film, additives such as a plasticizer, an ultraviolet absorber and a lubricant may be added to the TAC solution. Also, a solvent such as alcohol may be added.

The method of forming a film from the TAC solution is not particularly limited, but generally a casting method can be adopted. The casting method is, for example, regenerated TA by spreading the TAC solution on a mirror-polished endless belt or drum and drying it.
Make a C film. The drying can be carried out by predrying on an endless belt or a drum, then peeling the film and further drying to obtain a regenerated TAC film with less residual solvent.

The regenerated TAC film thus obtained can be applied to various uses. For example, it can be reused as a transparent protective film for a polarizer according to a conventional method. The polarizer is
Similar to the above example, on at least one side thereof,
A polarizing plate to which a recycled TAC film is applied is formed by the same adhesive treatment as described above.

When the recycled TAC film is used as a transparent protective film on both sides of the polarizer, another transparent protective layer can be formed on the other side if at least one side thereof is a recycled TAC film. . The other transparent protective layer can be provided as a coating layer made of a polymer or as a laminated layer of a film. As the transparent polymer or film material for forming the transparent protective layer, an appropriate transparent material can be used, but a material having excellent transparency, mechanical strength, thermal stability, moisture barrier property and the like is preferably used. Examples of the material for forming the transparent protective layer include polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, cellulose polymers such as diacetyl cellulose and triacetyl cellulose, acrylic polymers such as polymethyl methacrylate, polystyrene and acrylonitrile styrene. Copolymer (AS
Examples thereof include styrene-based polymers such as resins) and polycarbonate-based polymers. Also, polyethylene, polypropylene, polyolefins having a cyclo or norbornene structure, polyolefin polymers such as ethylene / propylene copolymers, vinyl chloride polymers, amide polymers such as nylon and aromatic polyamides, imide polymers, sulfone polymers. , Polyether sulfone-based polymer, polyether ether ketone-based polymer, polyphenylene sulfide-based polymer, vinyl alcohol-based polymer, vinylidene chloride-based polymer, vinyl butyral-based polymer, arylate-based polymer, polyoxymethylene-based polymer, epoxy-based polymer, or the above Blends of polymers and the like are also examples of the polymer forming the transparent protective layer.

On the surface of the transparent protective film on which the polarizer is not adhered (the surface on which the coating layer is not provided), a hard coat layer and an antiglare layer similar to the above can be provided. Further, it may be subjected to an antireflection treatment, a sticking prevention treatment, or a treatment for the purpose of diffusion.

In practical use, the polarizing plate can be used as an optical film laminated with another optical layer. Although the optical layer is not particularly limited, for example, for forming a liquid crystal display device such as a reflection plate, a semi-transmission plate, a retardation plate (including a wavelength plate such as 1/2 or 1/4), and a viewing angle compensation film. One or two or more optical layers that may be used can be used. In particular, a reflective polarizing plate or a semi-transmissive polarizing plate in which a reflective plate or a semi-transmissive reflective plate is further laminated on the polarizing plate,
An elliptical polarizing plate or a circular polarizing plate in which a retardation plate is further stacked on a polarizing plate, a wide viewing angle polarizing plate in which a viewing angle compensation film is further stacked in a polarizing plate, or a brightness enhancement film is further stacked in a polarizing plate. A polarizing plate consisting of

The reflective polarizing plate is a polarizing plate provided with a reflective layer, and is for forming a liquid crystal display device of the type that reflects incident light from the viewing side (display side) to display. Further, there is an advantage that it is possible to omit the incorporation of a light source such as a backlight and to easily reduce the thickness of the liquid crystal display device. The reflective polarizing plate can be formed by an appropriate method such as a method in which a reflective layer made of metal or the like is attached to one surface of the polarizing plate via a transparent protective layer or the like, if necessary.

Specific examples of the reflection-type polarizing plate include a transparent protective film which is mat-treated as necessary, and one side of which is provided with a foil or a vapor deposition film made of a reflective metal such as aluminum to form a reflective layer. can give. Further, by incorporating fine particles into the transparent protective film to form a surface fine uneven structure,
There is also one having a reflective layer having a fine concavo-convex structure thereon. The reflective layer having the fine concavo-convex structure has the advantage that diffused incident light is diffused to prevent directivity and glare, and uneven brightness can be suppressed. Further, the transparent protective film containing fine particles also has an advantage that incident light and reflected light thereof are diffused when they pass therethrough to further suppress uneven brightness. The reflective layer having a fine concavo-convex structure reflecting the surface fine concavo-convex structure of the transparent protective film is formed by, for example, a vacuum deposition method, an ion plating method,
It can be performed by a method of directly attaching a metal to the surface of the transparent protective layer by an appropriate method such as a vapor deposition method such as a sputtering method or a plating method.

The reflection plate may be used as a reflection sheet in which a reflection layer is provided on an appropriate film according to the transparent film, instead of the method of directly applying to the transparent protective film of the polarizing plate. Since the reflective layer is usually made of a metal, the use form in which the reflective surface is covered with a transparent protective film, a polarizing plate, or the like prevents the reduction of the reflectance due to oxidation, and thus the long-lasting initial reflectance. It is more preferable from the viewpoint of avoiding the additional provision of the protective layer.

A semi-transmissive polarizing plate can be obtained by using a semi-transmissive reflective layer such as a half mirror which reflects and transmits light in the reflective layer. The semi-transmissive polarizing plate is usually provided on the back side of the liquid crystal cell, and when the liquid crystal display device is used in a relatively bright atmosphere,
An image is displayed by reflecting incident light from the viewing side (display side), and in a relatively dark atmosphere, an image is displayed using a built-in light source such as a backlight built into the back side of the semi-transmissive polarizing plate. It is possible to form a liquid crystal display device of the type that displays That is, the semi-transmissive polarizing plate is useful for forming a liquid crystal display device of a type that can save energy for using a light source such as a backlight in a bright atmosphere and can be used with a built-in light source in a relatively dark atmosphere. Is.

An elliptically polarizing plate or a circularly polarizing plate in which a retardation plate is further laminated on a polarizing plate will be described. A phase difference plate or the like is used when changing linearly polarized light to elliptically polarized light or circularly polarized light, changing elliptically polarized light or circularly polarized light to linearly polarized light, or changing the polarization direction of linearly polarized light. In particular, a so-called ¼ wavelength plate (also called a λ / 4 plate) is used as a retardation plate that changes linearly polarized light into circularly polarized light or changes circularly polarized light into linearly polarized light. A half-wave plate (also called a λ / 2 plate) is usually used to change the polarization direction of linearly polarized light.

The elliptically polarizing plate compensates (prevents) coloring (blue or yellow) caused by the birefringence of the liquid crystal layer of a super twisted nematic (STN) type liquid crystal display device, and is used for black and white display without the coloring. Used effectively. Further, the one in which the three-dimensional refractive index is controlled is preferable because it can also compensate (prevent) coloring that occurs when the screen of the liquid crystal display device is viewed obliquely. The circularly polarizing plate is effectively used, for example, when adjusting the color tone of an image of a reflective liquid crystal display device in which an image is displayed in color, and also has a function of preventing reflection. Specific examples of the retardation plate described above include polycarbonate, polyvinyl alcohol, polystyrene, polymethylmethacrylate, polypropylene and other polyolefins, polyarylate, and a birefringent film obtained by subjecting a film made of a suitable polymer such as polyamide to a stretching treatment. And a liquid crystal polymer oriented film, a liquid crystal polymer oriented layer supported by a film, and the like. The retardation plate may be one having an appropriate retardation according to the purpose of use, such as various wavelength plates or one for the purpose of compensating for the viewing angle and the like due to birefringence of the liquid crystal layer, and may be two or more kinds. It may be one in which retardation plates are laminated to control optical properties such as retardation.

The elliptically polarizing plate and the reflection type elliptically polarizing plate are obtained by laminating the polarizing plate or the reflection type polarizing plate and the retardation plate in an appropriate combination. Such an elliptically polarizing plate or the like can be formed by sequentially stacking them separately in the manufacturing process of a liquid crystal display device so as to form a combination of a (reflection type) polarizing plate and a retardation plate. An optical film such as a polarizing plate is excellent in stability of quality, workability of lamination, and the like, and has an advantage that manufacturing efficiency of a liquid crystal display device can be improved.

The viewing angle compensation film is a film for widening the viewing angle so that the image can be seen relatively clearly even when the screen of the liquid crystal display device is viewed from a slightly oblique direction, not perpendicular to the screen. Such a viewing angle compensating retardation plate includes, for example, a retardation film, an orientation film of a liquid crystal polymer or the like, or a transparent substrate on which an orientation layer of a liquid crystal polymer or the like is supported. The ordinary retardation film is a birefringent polymer film uniaxially stretched in the plane direction, whereas the retardation plate used as the viewing angle compensation film is biaxially stretched in the plane direction. A polymer film having birefringence, or a bidirectionally stretched film such as a polymer or a tilt-oriented film having a birefringence in which the refractive index in the thickness direction stretched uniaxially in the plane direction and also stretched in the thickness direction is controlled. Used. Examples of the tilted oriented film include those obtained by adhering a heat-shrinkable film to a polymer film and subjecting the polymer film to stretching treatment and / or shrinking treatment under the action of the shrinkage force caused by heating, and those obtained by obliquely orienting a liquid crystal polymer. Can be mentioned. The raw material polymer of the retardation plate is the same as the polymer explained in the previous retardation plate, which prevents coloration due to the change of the viewing angle due to the phase difference due to the liquid crystal cell and enlarges the viewing angle for good viewing. An appropriate one can be used for the purpose such as.

From the viewpoint of achieving a wide viewing angle with good visibility, an optically anisotropic layer composed of an alignment layer of a liquid crystal polymer, particularly an inclined alignment layer of a discotic liquid crystal polymer, is supported by a triacetyl cellulose film. A compensation retardation plate can be preferably used.

The polarizing plate in which the polarizing plate and the brightness enhancement film are bonded together is usually used by being provided on the back side of the liquid crystal cell. The brightness enhancement film has a property of reflecting linearly polarized light of a predetermined polarization axis or circularly polarized light of a predetermined direction when natural light is incident due to reflection from a backlight of a liquid crystal display device or the back side, and transmits other light. A polarizing plate in which a brightness enhancement film is laminated with a polarizing plate allows light from a light source such as a backlight to enter and obtain transmitted light in a predetermined polarization state, and light other than the predetermined polarization state is reflected without being transmitted. It The light reflected by the surface of the brightness enhancement film is inverted through a reflection layer or the like provided on the rear side of the brightness enhancement film to be re-incident on the brightness enhancement film, and part or all of the light is transmitted as light in a predetermined polarization state to achieve brightness. The brightness can be improved by increasing the amount of light transmitted through the improvement film and by supplying polarized light that is difficult to be absorbed by the polarizer to increase the amount of light that can be used for liquid crystal display image display and the like. That is,
When light is input from the back side of the liquid crystal cell through a polarizer without using a brightness enhancement film, almost all light with a polarization direction that does not match the polarization axis of the polarizer is reflected by the polarizer. It is absorbed and does not pass through the polarizer. That is, although depending on the characteristics of the polarizer used, about 50% of light is absorbed by the polarizer, and the amount of light that can be used for liquid crystal image display and the like is reduced accordingly, and the image becomes dark. The brightness enhancement film allows light having a polarization direction that is absorbed by the polarizer to be reflected once by the brightness enhancement film without being incident on the polarizer, and then inverted through a reflection layer or the like provided behind it. The light-increasing film transmits only the polarized light whose polarization direction is such that the light reflected and inverted between the two can pass through the polarizer. Since the light is supplied to the polarizer, light from a backlight or the like can be efficiently used for displaying an image on the liquid crystal display device, and the screen can be brightened.

The brightness enhancement film is, for example, a multilayer thin film of a dielectric or a multilayer laminate of thin films having different refractive index anisotropies, transmits linearly polarized light having a predetermined polarization axis and reflects other light. Characteristic of reflecting circularly polarized light of either left-handed or right-handed and transmitting other light, such as those exhibiting characteristics, such as an oriented film of cholesteric liquid crystal polymer or an oriented liquid crystal layer supported on a film substrate. An appropriate thing such as a thing showing can be used.

Therefore, in the brightness enhancement film of the type which transmits the linearly polarized light of the above-mentioned predetermined polarization axis, the transmitted light is directly incident on the polarizing plate with the polarization axis aligned, thereby suppressing the absorption loss by the polarizing plate. It can be efficiently transmitted. On the other hand, in a brightness enhancement film of a type that transmits circularly polarized light like a cholesteric liquid crystal layer, it can be directly incident on a polarizer, but from the viewpoint of suppressing absorption loss, the circularly polarized light is linearly polarized through a retardation plate. It is preferable that the light is incident on the polarizing plate. By using a ¼ wavelength plate as the retardation plate, circularly polarized light can be converted into linearly polarized light.

The retardation plate functioning as a quarter-wave plate in a wide wavelength range such as a visible light region is, for example, a retardation layer functioning as a quarter-wave plate and another retardation film for light color light having a wavelength of 550 nm. It can be obtained by a method of superposing a retardation layer exhibiting characteristics, for example, a retardation layer functioning as a half-wave plate. Therefore, the retardation plate disposed between the polarizing plate and the brightness enhancement film may be composed of one layer or two or more retardation layers.

As for the cholesteric liquid crystal layer,
Two layers or three layers with different reflection wavelengths
By arranging the layers so as to overlap each other, it is possible to obtain an element that reflects circularly polarized light in a wide wavelength range such as a visible light region, and based on that, it is possible to obtain transmitted circularly polarized light in a wide wavelength range.

Further, the polarizing plate may be formed by laminating a polarizing plate and two or three or more optical layers, like the above-mentioned polarization separation type polarizing plate. Therefore, it may be a reflective elliptical polarizing plate or a semi-transmissive elliptical polarizing plate in which the above reflective polarizing plate or semi-transmissive polarizing plate is combined with a retardation plate.

The optical film in which the optical layer is laminated on the polarizing plate can be formed by a method of sequentially laminating separately in the manufacturing process of a liquid crystal display device or the like. Has an advantage that it is excellent in quality stability and assembling work and can improve the manufacturing process of a liquid crystal display device or the like. Appropriate adhesion means such as an adhesive layer may be used for lamination. In adhering the above-mentioned polarizing plate and other optical films, the optical axes thereof can be set at an appropriate arrangement angle according to the intended retardation characteristics and the like.

At least one polarizing plate or at least one polarizing plate is used.
A pressure-sensitive adhesive layer for adhering to another member such as a liquid crystal cell may be provided on the laminated optical film. As the pressure-sensitive adhesive layer, the same ones as those exemplified above can be applied.

The adhesive layer may be attached to one side or both sides of the polarizing plate by an appropriate method. For example,
For example, a base polymer or its composition is dissolved or dispersed in a solvent consisting of a single solvent or a mixture of appropriate solvents such as toluene and ethyl acetate to prepare an adhesive solution of about 10 to 40% by weight, which is cast. And a method of directly attaching on the polarizing plate by an appropriate developing method such as a coating method, or a method of forming an adhesive layer on the separator and transferring it onto the polarizing plate or the optical film according to the above. can give.

The exposed surface of the pressure-sensitive adhesive layer is temporarily covered with a separator for the purpose of preventing its contamination until it is put into practical use. This can prevent contact with the pressure-sensitive adhesive layer in the usual handling state. As the separator, excluding the above thickness conditions, for example, a suitable thin sheet such as a plastic film, a rubber sheet, paper, cloth, non-woven fabric, net, a foamed sheet or a metal foil, or a laminate thereof,
If necessary, a silicone-based or long-chain alkyl-based, fluorine-based, molybdenum sulfide, or other suitable release agent-coated material is used.

The polarizing plate or optical film of the present invention can be preferably used for forming various devices such as liquid crystal display devices. The liquid crystal display device can be formed in a conventional manner. That is, a liquid crystal display device is generally formed by appropriately assembling a liquid crystal cell, a polarizing plate or an optical film, and if necessary, components such as an illumination system and incorporating a drive circuit. There is no particular limitation except that the polarizing plate or the optical film according to the invention is used, and the conventional method can be applied. The liquid crystal cell may be of any type such as TN type, STN type, and π type.

It is possible to form a suitable liquid crystal display device such as a liquid crystal display device in which a polarizing plate or an optical film is arranged on one side or both sides of a liquid crystal cell, or a device using a backlight or a reflector in an illumination system. In that case, the polarizing plate or the optical film according to the present invention can be installed on one side or both sides of the liquid crystal cell. When a polarizing plate or an optical film is provided on both sides, they may be the same or different. Further, when forming the liquid crystal display device, for example, a diffusion plate, an anti-glare layer, an antireflection film, a protective plate, a prism array, a lens array sheet, a light diffusion plate, a backlight, and other appropriate components are provided at appropriate positions in a single layer or Two or more layers can be arranged.

Next, an organic electroluminescence device (organic EL display device) will be described. Generally, in an organic EL display device, a transparent electrode, an organic light emitting layer, and a metal electrode are sequentially laminated on a transparent substrate to form a light emitting body (organic electroluminescent light emitting body). Here, the organic light emitting layer is a laminate of various organic thin films, for example, a laminate of a hole injection layer made of a triphenylamine derivative or the like and a light emitting layer made of a fluorescent organic solid such as anthracene, Alternatively, a structure having various combinations such as a laminated body of such a light emitting layer and an electron injection layer formed of a perylene derivative, or a laminated body of these hole injection layer, light emitting layer, and electron injection layer is known. Has been.

In the organic EL display device, by applying a voltage to the transparent electrode and the metal electrode, holes and electrons are injected into the organic light emitting layer, and the energy generated by the recombination of these holes and electrons is fluorescent. It emits light based on the principle that a substance is excited and the excited fluorescent substance emits light when returning to the ground state. The mechanism of recombination in the middle is similar to that of a general diode, and as can be expected from this, the current and the emission intensity show a strong nonlinearity with rectification with respect to the applied voltage.

In an organic EL display device, at least one of the electrodes must be transparent in order to extract light emitted from the organic light emitting layer.
A transparent electrode formed of a transparent conductor such as O) is used as an anode. On the other hand, it is important to use a substance having a small work function for the cathode in order to facilitate electron injection and increase the luminous efficiency, and a metal electrode such as Mg-Ag or Al-Li is usually used.

In the organic EL display device having such a structure, the organic light emitting layer is formed of an extremely thin film having a thickness of about 10 nm. For this reason, the organic light emitting layer transmits light almost completely like the transparent electrode. As a result, when entering from the surface of the transparent substrate during non-light emission, the light transmitted through the transparent electrode and the organic light emitting layer and reflected by the metal electrode goes out to the surface side of the transparent substrate again, when viewed from the outside, The display surface of the organic EL display device looks like a mirror surface.

In an organic EL display device including an organic electroluminescent light-emitting body having a transparent electrode on the front surface side of an organic light-emitting layer which emits light when a voltage is applied and a metal electrode on the back surface side of the organic light-emitting layer, A polarizing plate can be provided on the surface side of the electrode, and a retardation plate can be provided between the transparent electrode and the polarizing plate.

Since the retardation plate and the polarizing plate have a function of polarizing the light which is incident from the outside and reflected by the metal electrode, there is an effect that the mirror surface of the metal electrode is not visually recognized from the outside by the polarization action. Especially, the phase difference plate is 1/4.
The mirror surface of the metal electrode can be completely shielded by using a wave plate and adjusting the angle between the polarization directions of the polarizing plate and the retardation plate to π / 4.

That is, as for the external light incident on the organic EL display device, only the linearly polarized light component is transmitted by the polarizing plate. This linearly polarized light is generally elliptically polarized by the retardation plate, but it is circularly polarized when the retardation plate is a 1/4 wavelength plate and the polarization direction between the polarizing plate and the retardation plate is π / 4. .

This circularly polarized light passes through the transparent substrate, the transparent electrode, and the organic thin film, is reflected by the metal electrode, passes through the organic thin film, the transparent electrode, and the transparent substrate again, and becomes linearly polarized light again on the retardation plate. . Since this linearly polarized light is orthogonal to the polarization direction of the polarizing plate, it cannot pass through the polarizing plate. as a result,
The mirror surface of the metal electrode can be completely shielded.

[0063]

EXAMPLES Examples and the like specifically showing the constitution and effects of the present invention will be described below.

Example 1 (Production of Polarizing Plate) A polyvinyl alcohol film having a thickness of 80 μm was dyed in an aqueous solution of 0.3% iodine, and then up to 5 times in 4% boric acid and 3% potassium iodide aqueous solution. The film was stretched and dried at 50 ° C. for 4 minutes to obtain a polarizer. A TAC film having a thickness of 80 μm was attached to both sides of this polarizer to obtain a polarizing plate.

(Production of Recycled TAC Film etc.) The polarizing plate obtained above was immersed in methylene chloride at 23 ° C. for 60 minutes to dissolve the TAC film. The obtained TAC solution was filtered to remove the undissolved material containing the polarizer from the TAC solution. Then, using a TAC solution, a casting method was applied on a belt whose surface was mirror-polished to produce a regenerated TAC film. The obtained recycled TAC film was attached again to both sides of the polarizer to obtain a polarizing plate.

Example 2 On one surface of the polarizing plate obtained in Example 1 (production of polarizing plate),
A pressure-sensitive adhesive having a gel fraction of 85% was bonded to obtain a pressure-sensitive adhesive type polarizing plate. Then, a regenerated TAC film was produced in the same manner as in Example 1 (production of regenerated TAC film and the like) except that the adhesive polarizing plate was used instead of the polarizing plate. The obtained recycled TAC film was attached again to both sides of the polarizer to obtain a polarizing plate.

Example 3 An acrylic UV curable resin was applied to one side of a TAC film having a thickness of 80 μm and cured with a high pressure mercury lamp to obtain a TAC film having a hard coat layer with a curing rate of 82%. The curing rate was determined by determining the absorbance of the double bond of the acrylic group by the ATR method of the infrared absorption spectrum of the cured ultraviolet curable resin, and standardizing the absorbance of the double bond of the acrylic group before curing to measure the curing rate. . Then, the hard coat-treated TAC film was attached to one surface of the polarizing plate obtained in Example 1 (Production of Polarizing Plate) so that the hard coat-treated surface was on the outside, and the other surface was thick. 80 μm
The above TAC film was attached to obtain a hard coat-treated polarizing plate.

Then, a regenerated TAC film was prepared in the same manner as in Example 1 (manufacturing a regenerated TAC film or the like), except that the hard coat-treated polarizing plate was used instead of the polarizing plate. . The obtained recycled TAC film was attached again to both sides of the polarizer to obtain a polarizing plate.

Reference Example 1 A pressure-sensitive adhesive type polarizing plate was obtained in the same manner as in Example 2 except that the pressure sensitive adhesive having a gel fraction of 60% was used as the pressure sensitive adhesive. Then, in Example 1 (manufacturing of a recycled TAC film or the like), a recycled T film was prepared in the same manner as in Example 1 except that the adhesive polarizing plate was used instead of the polarizing plate.
An AC film was produced. The obtained recycled TAC film was attached again to both sides of the polarizer to obtain a polarizing plate.

Reference Example 2 A hard coat-treated polarizing plate was obtained in the same manner as in Example 3 except that the TAC film treated so that the curing rate of the hard coat layer was 65% was used.
Then, in Example 1 (manufacturing of a recycled TAC film or the like), a recycled TAC film was prepared in the same manner as in Example 1 except that the hard coat-treated polarizing plate was used instead of the polarizing plate.
A film was made. The obtained recycled TAC film was attached again to both sides of the polarizer to obtain a polarizing plate.

Comparative Example 1 The polarizing plate obtained in Example 1 (preparation of polarizing plate) was immersed in warm water at 60 ° C. for 6 hours to dissolve the polarizer, and the TAC film was recovered and dried. Then, the obtained TAC film was immersed in methylene chloride at 23 ° C. for 60 minutes to dissolve the TAC film. The obtained TAC solution was filtered to remove the undissolved material containing the polarizer from the TAC solution. Then, using a TAC solution, a casting method was applied on a belt whose surface was mirror-polished to produce a regenerated TAC film. The obtained recycled TAC film was attached again to both sides of the polarizer to obtain a polarizing plate.

(Evaluation) The number of foreign matters was measured on the polarizing plates prepared in Examples, Reference Examples and Comparative Examples. Foreign matter is detected visually and the size is 2 in the TAC film.
The number of foreign matters of 00 μm or more was counted. The size of the polarizing plate is 1000 mm × 500 mm. The results are shown in Table 1.

[0073]

[Table 1] From the examples and reference examples, it is recognized that a recycled TAC film can be produced from a polarizing plate having a TAC film as a transparent protective film. In addition, the number of appearance defects is reduced by using a gel fraction controlled in the case of an adhesive polarizing plate and a curing rate controlled in the case of a polarizing plate having an antiglare layer and / or a hard coat layer. It is recognized that you can. On the other hand, in the comparative example, the process for obtaining the recycled TAC film is long, and the polarizer is dissolved and recovered TAC.
It takes time to dry the film.

─────────────────────────────────────────────────── ─── Continued Front Page (51) Int.Cl. ⁷ Identification Code FI Theme Coat (Reference) G02F 1/1335 510 B29K 1:00 4F301 // B29K 1:00 B29L 7:00 B29L 7:00 C08L 1: 12 C08L 1:12 G02B 1/10 Z (72) Inventor Tatsumura Nagatsuka 1-2 chome Shimohozumi, Ibaraki City, Osaka Prefecture F-Term (reference) within Nitto Denko Corporation 2H049 BA02 BA27 BB33 BB43 BB52 BB62 BC01 BC22 2H091 FA08X FA08Z FA11X FA11Z FA14Z FA21X FA21Z FA37X FA37Z FA41Y FB04 FC01 FC02 FC03 FC06 GA06 HA07 HA10 KA01 LA11 LA15 LA18 LA19 LA30 2K009 AA15 BB12 CC24 DD02 DD05 4F07A02J02A02A02A02A02A01A02A01A02A01A02A01A02A01A02A01A02A01A02A01A02A01A02A0A0A0A0A0A16A02A0A0A0A0A30AH16BA02A01A02A02 BF32 CA09 CA12 CA72

Claims (6)

[Claims] 1. A step of treating a polarizing plate using a cellulose triacetate film as a transparent protective film on at least one surface of a polarizer with a solvent to dissolve the cellulose triacetate film in the solvent, and then a cellulose triacetate solution obtained in the above step. A method for producing a regenerated cellulose triacetate film, which comprises producing a film from the film. 2. The reproduction according to claim 1, wherein the polarizing plate is a pressure-sensitive adhesive type polarizing plate having a pressure-sensitive adhesive layer on at least one side of the polarizing plate, and the gel fraction of the pressure-sensitive adhesive is 70% or more. Method for producing cellulose triacetate film. 3. A polarizing plate has an antiglare layer and / or
Alternatively, it is a polarizing plate having a hard coat layer, and the curing rate of the antiglare layer and / or the hard coat layer is 70% or more, and the method for producing a regenerated cellulose triacetate film according to claim 1 or 2. 4. A regenerated cellulose triacetate film obtained by the method according to claim 1. 5. A polarizing plate using the regenerated cellulose triacetate film according to claim 4 as a transparent protective film on at least one surface of a polarizer. 6. An image display device using at least one polarizing plate according to claim 5.