JP2005195811A - Laminated birefringent film, liquid crystal panel using it, and liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laminated birefringent film which is excellent in appearance such as in transparency and can realize excellent optical characteristics, especially excellent transparency and a large phase difference in the thickness direction. <P>SOLUTION: This laminated birefringent film is composed of three layers, namely a transparent high polymer film, a barrier layer formed directly on this transparent film, and a birefringent layer formed on the above barrier layer. For the material of the above birefringent layer, polyamide, polymide etc. can be used. As to the material of the above barrier layer, polyurethane resin, epoxy resin etc. can be used. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a laminated birefringent film, a liquid crystal panel using the same, and a liquid crystal display device.

Conventionally, in a liquid crystal display device, various retardation films have been used in order to compensate the viewing angle of the display screen and improve display characteristics. In recent years, for example, a retardation film formed from a non-liquid crystalline polymer such as polyamide, polyimide, or polyester has been put into practical use (see, for example, Patent Document 1). Such a non-liquid crystalline polymer, due to the properties of the polymer itself, generates a retardation in the thickness direction simply by coating on a substrate or the like, so it is much thinner than conventional retardation films and it is easy to adjust optical characteristics. It has excellent properties. However, such a retardation film has the following problems. That is, the retardation film is usually formed into a film by coating a non-liquid crystalline polymer dissolved in a solvent on a substrate made of an inorganic compound such as a SUS belt, a copper thin plate, glass, or a Si wafer. The negative birefringent layer is formed by, and the birefringent layer is peeled off from the substrate and transferred to another substrate that does not interfere with the optical characteristics of the birefringent layer (for example, Patent Document 2). , Patent Literature 3, Patent Literature 4, and Patent Literature 5). As described above, since transfer is necessary in the conventional manufacturing method, the number of work steps increases, and accordingly, various problems such as a decrease in yield and deterioration in appearance uniformity occur.
JP 2000-190385 A US Pat. No. 5,344,916 US Pat. No. 5,395,918 US Pat. No. 5,480,964 US Pat. No. 5,580,950

  In order to avoid the above-mentioned problems, a polyimide dissolved in a solvent is directly applied to a substrate such as a transparent polymer film, a birefringent layer is directly formed on the substrate, and this laminate is directly laminated birefringent. A new method for use as a film has been found (separately pending). However, the laminated birefringent film in which the birefringent layer is directly formed on the substrate in this way is, for example, the deterioration of the transparent polymer film due to cracking, breaking, etc., the variation in the size and weight of the film, and the like. There is a possibility that the film becomes clouded or the transmittance is lowered.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a laminated birefringent film that is excellent in appearance such as transparency and can realize optical characteristics, particularly excellent transmittance and large retardation in the thickness direction, and a method for producing the same.

To achieve the above object, the laminated birefringent film of the present invention is a laminated birefringent film comprising a transparent polymer film and a birefringent layer,
The birefringent layer comprises at least one polymer selected from the group consisting of polyamide, polyimide, polyester, polyetherketone, polyamide-imide and polyesterimide;
A barrier layer is directly formed on the transparent polymer film, and the birefringent layer is directly formed on the barrier layer.

The method for producing a laminated birefringent film of the present invention is a method for producing a laminated birefringent film comprising a transparent polymer film and a birefringent layer,
The birefringent material comprises at least one selected from the group consisting of polyamide, polyimide, polyester, polyetherketone, polyamide-imide and polyesterimide;
A step of forming a barrier layer on the transparent polymer film by directly coating and fixing a coating liquid containing a barrier layer forming material on the transparent polymer film, and further on the barrier layer It is a manufacturing method including a step of forming the birefringent layer on the barrier layer by directly applying and fixing a solution obtained by dissolving the birefringent material in a solvent.

  In order to achieve the above object, the present inventors first conducted a series of studies to elucidate the cause of problems such as white turbidity of the transparent polymer film and a decrease in transmittance. As a result, as described above, when a solution such as polyimide is directly applied to the transparent polymer film, the solvent in the solution erodes from the surface of the transparent polymer film, and the transparent polymer film is partially dissolved or Swelling was found. And, for this reason, the interface between the transparent polymer film and the birefringent layer is roughened, and it has been found that the transparent polymer film becomes white turbid, a decrease in transmittance, etc. did. That is, if a barrier layer is formed on the transparent polymer film as in the present invention, the solvent in the solution does not erode on the transparent polymer film, so that the transparency, etc. Thus, a laminated birefringent film can be obtained which is excellent in appearance and can realize optical characteristics, particularly excellent transmittance. For this reason, if the laminated birefringent film of the present invention is applied to various image display devices, excellent display characteristics can be realized. Such a laminated birefringent film can be easily manufactured, for example, by the manufacturing method of the present invention.

The laminated birefringent film of the present invention is a laminated birefringent film including a transparent polymer film and a birefringent layer as described above,
The birefringent layer comprises at least one polymer selected from the group consisting of polyamide, polyimide, polyester, polyetherketone, polyamide-imide and polyesterimide;
A barrier layer is directly formed on the transparent polymer film, and the birefringent layer is directly formed on the barrier layer.

  The laminated birefringent film of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing a laminated birefringent film of the present invention. As shown in FIG. 1, the laminated birefringent film 1 is a laminated birefringent film having a three-layer structure in which a birefringent layer 11 is directly formed on the transparent polymer film 13 via a barrier layer 12.

  The barrier layer forming material is not particularly limited as long as it is a polymer that is difficult to dissolve in various solvents, and examples thereof include polyurethane resins, epoxy resins, polyacrylic resins, polyethyleneimine resins, and polyester resins. Among these, polyurethane resins are preferable, and specific examples include polyester-based urethane resins, polyether-based urethane resins, and polycarbonate-based urethane resins, and more preferable are polyester-based urethane resins. As described above, the barrier layer formed from such a material not only prevents erosion of the solvent in which the birefringent material is dissolved into the transparent polymer film, but also the transparent polymer film, the barrier layer, and the barrier. Excellent adhesion between the layer and the birefringent layer can also be realized. These forming materials may be one kind or a combination of two or more kinds.

  The thickness of the barrier layer is, for example, in the range of 0.05 to 10 μm, preferably 0.1 to 5 μm, and more preferably 0.5 to 3 μm.

  Next, the material for forming the transparent polymer film is not particularly limited, but can be used as an optical film as it is, that is, even when it is included as a component of a laminated birefringent film as in the present invention. As long as the optical characteristics of the birefringent layer are not practically affected. As such a material, a material excellent in transparency is preferable. For example, cellulose resin such as triacetyl cellulose (TAC), polyester resin, polycarbonate resin, polyamide resin, polyimide resin, polyethersulfone resin, polysulfone resin, Examples thereof include polystyrene resins, norbornene resins, polyolefin resins, acrylic resins, acetate resins, polymethyl methacrylate resins, and the like. As the transparent polymer film made of the norbornene resin, for example, trade name Arton (manufactured by JSR), trade name ZEONOR (manufactured by Nippon Zeon Co., Ltd.) and the like can be used.

  Further, as a material of the transparent polymer film, for example, a thermoplastic having a substituted imide group or an unsubstituted imide group in a side chain as described in JP-A-2001-343529 (WO 01/37007). The construction of the present invention is particularly useful when a film formed from a mixture of a resin and a thermoplastic resin having a substituted or unsubstituted phenyl group and a nitrile group in the side chain is used. Specific examples include a resin composition having an alternating copolymer composed of isobutene and N-methylmaleimide and an acrylonitrile-styrene copolymer. Among these forming materials, for example, a material capable of setting the birefringence when a transparent polymer film is formed to be relatively lower is preferable. Specifically, a substituted imide group or an unsubstituted imide in the aforementioned side chain is preferable. A mixture of a thermoplastic resin having a group and a thermoplastic resin having a substituted phenyl group or an unsubstituted phenyl group and a nitrile group in the side chain is preferred. Further, these transparent polymer films may contain an aromatic compound having at least two aromatic rings as a retardation adjusting agent as described in European Patent 0911656A2, for example.

  The thickness of the transparent polymer film is, for example, in the range of 5 to 200 μm, preferably 10 to 150 μm, and more preferably 20 to 100 μm.

  On the other hand, as described above, the birefringent material may contain at least one polymer selected from the group consisting of polyamide, polyimide, polyester, polyetherketone, polyamideimide, and polyesterimide. These polymers are excellent in heat resistance, chemical resistance and transparency, have high rigidity, and are suitable for optical applications. Among these, polyimide is particularly preferable because of its high transparency, high orientation, and high stretchability.

  Examples of the polyimide include polyimides disclosed in US Pat. No. 5,071,997, JP-A-8-511812, JP-A-10-508048, and in particular, the following general formulas (1) and (2) The polyimide composed only of the repeating unit is preferable, and more preferably, the polyimide is composed of only the repeating unit of the following general formula (2) because a large thickness direction retardation can be realized with a thin thickness. Moreover, as said polyether ketone, what has an ether group and a ketone group in a repeating unit, and these are connected by the aryl group is preferable. In addition, any one kind of the polymer may be used alone, or may be used as a mixture of two or more kinds having different functional groups such as a mixture of polyaryletherketone and polyamide. Good.

  Although the molecular weight of the polymer is not particularly limited, for example, the weight average molecular weight (Mw) is preferably 10,000 to 400,000. Among them, 30,000 to 400,000 is preferable because the birefringence in the thickness direction of the birefringent layer is increased, and further, 50,000 to 200,000 is preferable because the viscosity becomes appropriate upon coating. Is particularly preferred.

  The thickness of the birefringent layer is, for example, in the range of 0.5 to 30 μm, preferably 0.5 to 20 μm, and more preferably 1 to 10 μm.

  The optical characteristics of the birefringent layer are not particularly limited, and may be optically uniaxial or optically biaxial, but optically biaxial because it is optically superior. Is preferable.

  The thickness direction birefringence (Δna) of the birefringent layer is preferably 0.0005 to 0.5, for example, because the control of the phase difference is extremely easy and the thickness can be further reduced. Furthermore, since it is possible to obtain a thin laminated birefringent film with more excellent productivity, it is more preferably 0.005 to 0.15, and particularly preferably 0.02 to 0.1. The Δna is represented by {(nx + ny) / 2} −nz, where nx, ny and nz are the refractive indexes in the X-axis, Y-axis and Z-axis directions in the birefringent layer, respectively, and the X-axis direction Is an axial direction showing the maximum refractive index in the plane of the birefringent layer, the Y-axis direction is an axial direction perpendicular to the X-axis in the same plane, and the Z-axis is A thickness direction perpendicular to the X axis and the Y axis is shown.

  Regardless of optical uniaxiality or optical biaxiality, the thickness direction retardation (Rth) of the birefringent layer is, for example, 10 to 1000 nm, preferably 50 to 800 nm, more preferably 100 to 100 nm. 700 nm. The Rth is represented by [{(nx + ny) / 2} -nz] × d, where nx, ny and nz are as described above, and d is the thickness of the birefringent layer.

  In the case of optical biaxiality, the in-plane retardation (Δnd) of the birefringent layer is, for example, 5 to 200 nm, preferably 5 to 150 nm, and more preferably 10 to 100 nm. In the case of optical uniaxiality, the in-plane retardation is practically not developed and is generally about 0 to 3 nm. The Δnd is represented by (nx−ny) × d, and nx, ny, and d are as described above.

The laminated birefringent film of the present invention preferably satisfies at least one of the conditions of the following formulas (I) to (III).
Δna> Δnb × 10 (I)
1 <(nx-nz) / (nx-ny) (II)
0.0005 ≦ Δna ≦ 0.5 (III)
In the formula (I) to the formula (III), Δna, nx, ny and nz are as described above, and in the formula (I), Δnb is the birefringence of the transparent polymer film, In the following formula, n′x, n′y, and n′z are refractive indexes in the X-axis, Y-axis, and Z-axis directions of the transparent polymer film, respectively, and the X-axis direction Is an axial direction showing the maximum refractive index in the plane of the transparent polymer film, and the Y-axis direction is an axial direction perpendicular to the X-axis in the same plane, and the Z-axis direction. Indicates a thickness direction perpendicular to the X-axis and the Y-axis.
Δnb = {(n′x + n′y) / 2} −n′z
Above all, the formula (II) is a formula showing optical biaxiality, preferably satisfying at least this condition, and more preferably satisfying all of the formulas (I) to (III). Further, the formula (III) represents the range of the thickness direction birefringence (Δna) of the birefringent layer, as described above. Further, as shown in the formula (I), if the birefringence layer thickness direction birefringence (Δna) is larger than 10 times the transparent polymer film thickness direction birefringence (Δnb), viewing angle compensation and display It becomes a laminated birefringent film having more excellent characteristics, and preferably Δna> Δnb × 15, more preferably Δna> Δnb × 20.

  In addition, the birefringent layer in the present invention is not limited to those exhibiting optical uniaxiality and optical biaxiality as described above, and may be an inclined birefringent layer. The tilted birefringent layer is, for example, the material (polymer) of the birefringent layer is tilted and oriented, the normal of the birefringent layer is 0 °, and the angle between the normal and the measurement axis is measured. In the case of an angle (including 0 °), the phase difference value measured from the measurement axis direction is the phase difference value between the + side and the − side with respect to the phase difference value at 0 °. This is a birefringent layer in which the change of is asymmetric. Among such tilted birefringent layers, when the measurement angle is −50 ° to + 50 °, one having a maximum or minimum phase difference value in the range of −50 ° to −2 ° or + 2 ° to + 50 °. preferable.

Next, the method for producing a laminated birefringent film of the present invention is a method for producing a laminated birefringent film including a transparent polymer film and a birefringent layer as described above,
The birefringent material comprises at least one selected from the group consisting of polyamide, polyimide, polyester, polyetherketone, polyamide-imide and polyesterimide;
A step of forming a barrier layer on the transparent polymer film by directly coating and fixing a coating liquid containing a barrier layer forming material on the transparent polymer film, and further on the barrier layer It is a manufacturing method including a step of forming the birefringent layer on the barrier layer by directly applying and fixing a solution obtained by dissolving the birefringent material in a solvent.

  Below, although an example of the manufacturing method of the laminated birefringent film of this invention is explained in full detail, this invention is not limited to this.

  First, a transparent polymer film as described above is prepared, and a coating liquid containing the barrier layer forming material is directly applied to this surface, followed by drying treatment to form a barrier layer. The coating liquid can be prepared by suspending, dispersing, or dissolving the barrier layer forming material as described above in a solvent, for example, or a commercially available product can be used. The type of the solvent can be appropriately determined according to, for example, the type of the barrier layer forming material to be used, the form of the coating liquid to be prepared, etc. For example, water, isopropyl alcohol, NMP (N-methylpyrrolidone), ethanol, Examples include methanol, butanol, methyl ethyl ketone, toluene, acetone, and ethyl acetate. In addition, one kind of the solvent may be used, or two or more kinds may be used in combination. When two or more types are used in combination, the selection of the type and the mixing ratio can be appropriately determined depending on the resin to be dissolved. The transparent polymer film includes a mixture of a thermoplastic resin having a substituted and / or unsubstituted imide group in the side chain and a thermoplastic resin having a substituted and / or unsubstituted phenyl group and a nitrile group in the side chain. In this case, it is preferable to use three kinds of mixed solvents composed of water / isopropyl alcohol / N-methylpyrrolidone, and the ratio of N-methylpyrrolidone is preferably 5 to 50%. Further, ethanol, methanol, and butanol may be used alone. When the transparent polymer film is a triacetyl cellulose film, it is preferable to use three kinds of mixed solvents composed of water / isopropyl alcohol / N-methylpyrrolidone, and the ratio of N-methylpyrrolidone is 10 to 50. % Is preferred. Ethanol, methanol, butanol, methyl ethyl ketone, toluene, acetone, and ethyl acetate may be used alone.

  The form of the coating liquid is not particularly limited, and examples thereof include an aqueous solution, an emulsion liquid, and a dispersion liquid.

  As a specific example of the combination of the barrier layer forming material and the solvent, when the forming material is a polyester urethane, it is preferable to use a solvent such as water, isopropyl alcohol, or N-methylpyrrolidone.

  The ratio of the barrier layer forming material in the coating solution is, for example, 3 to 80% by weight, preferably 5 to 70% by weight, and more preferably 10 to 50% by weight.

  In addition to the barrier layer forming material as described above, the coating liquid is, for example, a blending material such as a crosslinking agent, a curing agent, a grafting agent to the main chain of the barrier layer forming material, polyvinyl alcohol, a coupling agent, etc. A variety of compounds may be blended.

  The coating method of the coating liquid is not particularly limited, and for example, spin coating method, roll coating method, flow coating method, printing method, dip coating method, casting film forming method, barcode method, gravure printing method, etc. Can be given. In addition, the coating amount of the coating liquid can be appropriately determined according to, for example, the content of the forming material, the thickness of the desired barrier layer, and the like.

  Before applying the coating liquid to the transparent polymer film, for example, the transparent polymer film is subjected to various surface treatments such as dry treatment such as corona treatment and ozone treatment, and wet treatment such as alkali treatment. Thereby, the adhesiveness of the said transparent polymer film and a barrier layer can be improved further.

  The conditions for the drying treatment are not particularly limited, and examples include natural drying and heat treatment (for example, 40 ° C. to 350 ° C.).

  Next, a birefringent layer is directly formed on the barrier layer. In this method, a birefringent material as described above is dissolved in a solvent to prepare a coating solution, which is directly coated on the barrier layer and dried to fix the coated film. Can be formed.

  The solvent is not particularly limited as long as it can dissolve the birefringent material as described above. For example, halogenated chloroform, dichloromethane, carbon tetrachloride, dichloroethane, tetrachloroethane, trichloroethylene, tetrachloroethylene, chlorobenzene, orthodichlorobenzene, etc. Hydrocarbons; phenols such as phenol and parachlorophenol; aromatic hydrocarbons such as benzene, toluene, xylene, methoxybenzene and 1,2-dimethoxybenzene; acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone and cyclopentanone , Ketone solvents such as 2-pyrrolidone and N-methyl-2-pyrrolidone, ester solvents such as ethyl acetate and butyl acetate; t-butyl alcohol, glycerin, ethylene glycol, triethyl Alcohol solvents such as ethylene glycol monoethylene ether, diethylene glycol dimethyl ether, propylene glycol, dipropylene glycol, 2-methyl-2,4-pentanediol; amide solvents such as dimethylformamide, dimethylacetamide; acetonitrile, butyronitrile, etc. Nitrile solvents; ether solvents such as diethyl ether, dibutyl ether, and tetrahydrofuran; carbon disulfide, ethyl cellosolve, butyl cellosolve, and the like. Among these, ketone solvents such as methyl ethyl ketone, acetone, methyl isobutyl ketone, cyclopentanone, and cyclohexanone are preferable. In addition, any one kind of these solvents may be used, or two or more kinds may be used in combination.

  In the present invention, the reason that the type of the solvent is not limited as long as the birefringent material can be dissolved in this way is that a barrier layer is previously formed on the transparent polymer film as described above. That is, if the barrier layer is not formed, there arises a problem that the solvent erodes from the surface of the transparent polymer film. For this reason, the solvent which can be used is limited or a transparent polymer film will be limited. However, since the barrier layer is formed in advance on the transparent polymer film, the influence of the kind of the solvent, that is, the dissolving power of the solvent is avoided.

  Since the dissolution ratio of the birefringent material in the solution is more excellent in coatability, it is, for example, 5 to 50 parts by weight, and preferably 10 to 40 parts by weight with respect to 100 parts by weight of the solvent. Moreover, the coating amount of the said solution can be suitably determined according to the birefringent material content in the said solution, the thickness of the desired birefringent layer, etc., for example.

  In addition, the coating method and the drying treatment of the solution are the same as in the case of forming the barrier layer, and before applying the solution, as in the case of the transparent polymer film described above, In order to further improve the adhesion to the birefringent layer, the surface treatment as described above may be performed on the surface of the barrier layer in advance.

  According to such a manufacturing method, since the birefringent layer is continuously formed on the transparent polymer film through the barrier layer, the transparent polymer film is not colored, clouded, cracked, etc. However, it is possible to obtain the laminated birefringent film of the present invention that is maintained in an extremely excellent state. Since such a laminated birefringent film is excellent in appearance, it suppresses a decrease in optical characteristics due to poor appearance, and can realize extremely excellent display characteristics when used in an image display device such as a liquid crystal display device. Of course, since it is not a laminated birefringent film in which a transparent polymer film and a birefringent layer are separately formed and laminated, manufacturing is easy and there is no problem such as a decrease in yield due to peeling from the substrate.

  The laminated birefringent film produced as described above is further subjected to a stretching process or a shrinking process after the step of forming the birefringent layer by drying the formed coating film. May be. By performing the stretching treatment or the shrinking treatment in this way, the optical characteristics of the birefringent layer directly formed on the surface of the barrier layer can be further changed. Specifically, the birefringent layer of the laminated birefringent film produced as described above usually exhibits optical uniaxiality (nx> nz, ny> nz) only by forming into a film due to the properties of the forming material. Further, optical biaxiality (nx> ny> nz) is further exhibited by performing a stretching process or a shrinking process. It is preferable to further control the in-plane birefringence (nx−ny), the in-plane retardation (Δnd), and the like of the birefringent layer by the stretching process and the shrinking process.

  First, the stretching process will be described. The stretching method of the birefringent layer is not particularly limited. For example, free end longitudinal stretching that is uniaxially stretched in the longitudinal direction, fixed end lateral stretching that is uniaxially stretched in the width direction with the longitudinal direction of the film fixed, longitudinal direction and width Examples of the method include sequential or simultaneous biaxial stretching in which stretching is performed in both directions.

  The stretching process of the birefringent layer may be performed by, for example, pulling together the three layers of the transparent polymer film, the barrier layer, and the birefringent layer. It is preferable to stretch only the molecular film. When only the transparent polymer film is stretched, the barrier layer on the transparent polymer film is indirectly stretched by the tension generated in the transparent polymer film by this stretching treatment, and further generated in the barrier layer. The birefringent layer on the barrier layer is indirectly stretched by the tension applied. And, since stretching a single layer body is usually a uniform stretching rather than stretching a laminate, if only a transparent polymer film is uniformly stretched as described above, the transparent The barrier layer on the polymer film and the birefringent layer thereon can also be stretched uniformly.

  In addition, in order to perform the stretching treatment and the shrinking treatment in this way, the barrier layer before the stretching treatment or the shrinking treatment has an elongation percentage of, for example, 50% or more, preferably 50% to 500%, More preferably, it is 70% to 400%. With such an elongation rate, for example, it can sufficiently withstand the tensile strength of the stretching treatment, and the birefringent layer can be sufficiently contracted with the contraction of the transparent polymer film.

In addition, the said elongation rate is represented by a following formula, for example, can be measured with the following method. That is, using Tensilon (tensile tester), both ends of the barrier layer in the longitudinal direction are fixed, and both ends are pulled in both directions in the longitudinal direction under the condition of 300 mm / min, and the process is continued until it breaks. And the longitudinal direction full length [L (a)] of the barrier layer at the time of a fracture | rupture is measured, The longitudinal direction full length [L (b)] of the barrier layer before the tension | pulling previously measured and said L (a) are set to a following formula. The elongation is calculated by substitution. The elongation percentage of the barrier layer can be measured as described above even when, for example, a barrier layer that is separately formed on a substrate (for example, a glass plate) and peeled off under the same conditions is used.
Elongation rate (%) = [{L (a) −L (b)} / L (b)] × 100
Next, the contraction process will be described. In the case of performing the shrinkage treatment, for example, the transparent polymer film having a shrinkage property is used, and after forming a barrier layer and a birefringent layer on the transparent polymer film, the transparent polymer film It may be contracted. As the transparent polymer film shrinks, the barrier layer and the birefringent layer on the transparent polymer film can be shrunk. As a result, the optical characteristics of the birefringent layer can be optically reduced as described above. It can be converted to axiality. The barrier layer also preferably has shrinkability, and the birefringent layer may be contracted as the barrier layer itself contracts.

  The shrinkage of the transparent polymer film and the barrier layer can be performed, for example, by subjecting them to a heat treatment. The conditions for the heat treatment are not particularly limited, and can be appropriately determined depending on, for example, the type of material for forming the transparent polymer film or the barrier layer. For example, the heating temperature is in the range of 60 to 180 ° C., preferably Is 80-150 degreeC, More preferably, it is 100-120 degreeC.

  The shrinkability of the transparent polymer film can be imparted, for example, by subjecting the transparent polymer film to a heat treatment or the like in advance. Moreover, in order to give shrinkage | contraction property to one direction within the surface of the said transparent polymer film, it is preferable to extend | stretch in any one direction within a surface, for example. In this way, since a contraction force is generated in the direction opposite to the stretching direction by stretching in advance, the surface of the birefringent material (polymer) is utilized by utilizing the in-plane contraction difference of the transparent polymer film. Internal birefringence is imparted.

  In addition to this, for example, a birefringent layer is contracted by forming a coating film on the opposite surface on which the barrier layer of the transparent polymer film is formed, fixing the film to a metal frame, and heating. It is possible.

  The optical film of the present invention is characterized by including the laminated birefringent film of the present invention as described above, and the structure and configuration are not limited at all except for including the laminated birefringent film.

  Examples of the optical film of the present invention include a laminated polarizing plate further containing a polarizer. Although the structure of such a polarizing plate is not specifically limited, For example, what is shown in FIG. 2 or FIG. 3 can be illustrated. 2 and 3 are cross-sectional views showing examples of the laminated polarizing plate of the present invention, and the same reference numerals are given to the same parts in both figures. In addition, the polarizing plate of this invention is not limited to the following structures, Furthermore, the other optical member etc. may be included.

  A laminated polarizing plate 20 shown in FIG. 2 has a laminate 1 of the above-described transparent polymer film, barrier layer and birefringent layer, a polarizer 2 and two transparent protective layers 3, and is transparent on both sides of the polarizer 2. The protective layers 3 are respectively laminated, and the laminated body 1 is further laminated on one transparent protective layer 3. In addition, since the laminated body 1 is laminated with the transparent polymer film, the barrier layer, and the birefringent layer as described above, any surface of the laminated body 1 may face the transparent protective layer 3. However, the polarizer 2 is preferably laminated on the birefringent layer of the laminate 1 with the transparent protective layer 3 interposed therebetween.

  The said transparent protective layer may be laminated | stacked on both surfaces of a polarizer as shown in the figure, and may be laminated | stacked only on either one surface. Moreover, when laminating | stacking on both surfaces, the same kind of transparent protective layer may be used, for example, or a different kind of transparent protective layer may be used.

  On the other hand, the laminated polarizing plate 30 shown in FIG. 3 has the laminate 1, the polarizer 2, and the transparent protective layer 3, and the laminate 1 and the transparent protective layer 3 are provided on both sides of the polarizer 2. Each is laminated.

  And in the said laminated body 1, since the transparent polymer film, the barrier layer, and the birefringent layer are laminated | stacked as mentioned above, any surface may face a polarizer, For example, as follows For this reason, the polarizer 2 is preferably disposed on the transparent polymer film side of the laminate 1. This is because with such a configuration, the transparent polymer film of the laminate 1 can also be used as a transparent protective layer for the polarizer. That is, instead of laminating a transparent protective layer on both sides of the polarizer, the laminate is arranged such that a transparent protective layer is disposed on one surface of the polarizer and a transparent polymer film faces the other surface. The transparent polymer film also serves as the other transparent protective layer of the polarizer. For this reason, the polarizing plate made still thinner can be obtained.

  The polarizer is not particularly limited, and for example, by dying dichroic substances such as iodine and dichroic dyes on various films by using a conventionally known method, dyeing, crosslinking, stretching, and drying. The prepared one can be used. Among these, a film that transmits linearly polarized light when natural light is incident is preferable, and a film that is excellent in light transmittance and degree of polarization is preferable. Examples of the various films that adsorb the dichroic substance include high hydrophilicity such as polyvinyl alcohol (PVA) film, partially formalized PVA film, ethylene / vinyl acetate copolymer partially saponified film, and cellulose film. In addition to these, for example, polyene oriented films such as PVA dehydrated products and polyvinyl chloride dehydrochlorinated products can be used. Among these, PVA film is preferable. Moreover, although the thickness of the said polarizer is 1-80 micrometers normally, it is not limited to this.

The transparent protective layer is not particularly limited, and a conventionally known transparent film can be used. For example, a layer having excellent transparency, mechanical strength, thermal stability, moisture barrier property, isotropy, and the like is preferable. As a specific example of the material of such a transparent protective layer, the same material as the transparent polymer film can be used. Moreover, it is preferable that the said transparent protective layer does not have coloring, for example. Specifically, the thickness direction retardation value (Rth ″) of the transparent protective film represented by the following formula is preferably in the range of −90 nm to +75 nm, more preferably −80 nm to +60 nm. Particularly preferred is -70 nm to +45 nm. When the retardation value is in the range of −90 nm to +75 nm, the coloring (optical coloring) of the polarizing plate caused by the protective film can be sufficiently eliminated. In the following formula, n ″ x, n ″ y, and n ″ z represent refractive indexes in the X-axis, Y-axis, and Z-axis directions of the protective film, and d ″ represents the thickness thereof.
Rth ″ = [{(n ″ x + n ″ y) / 2} −n ″ z] × d ″
The transparent protective layer may further have an optical compensation function. As described above, the transparent protective layer having an optical compensation function is intended to prevent coloring or increase the viewing angle for good viewing caused by a change in viewing angle based on a phase difference in a liquid crystal cell, for example. A well-known thing can be used. Specific examples include various stretched films obtained by uniaxially or biaxially stretching the above-described transparent resin, alignment films such as liquid crystal polymers, and laminates in which alignment layers such as liquid crystal polymers are disposed on a transparent substrate. Among these, the alignment film of the liquid crystal polymer is preferable because it can achieve a wide viewing angle with good visual recognition, and in particular, the optical compensation layer composed of the tilted alignment layer of the discotic or nematic liquid crystal polymer is the above-mentioned. An optical compensation retardation plate supported by a triacetyl cellulose film or the like is preferable. As such an optical compensation phase difference plate, for example, a commercial product such as a trade name “WV film” manufactured by Fuji Photo Film Co., Ltd. can be mentioned. The optical compensation retardation plate may be one in which optical properties such as retardation are controlled by laminating two or more film supports such as the retardation film and triacetyl cellulose film.

The thickness of the transparent protective layer is not particularly limited, and can be appropriately determined according to, for example, the phase difference or the protective strength, but is usually 500 μm or less, preferably 5 to 300 μm, more preferably 5 to 150 μm. .
The transparent protective layer is appropriately formed by a conventionally known method such as a method of applying the various transparent resins to a polarizing film, a method of laminating the transparent resin film, the optical compensation retardation plate, or the like on the polarizing film. Or a commercially available product may be used.

  The transparent protective layer may be further subjected to, for example, a hard coat treatment, an antireflection treatment, a treatment for preventing sticking or diffusion, antiglare, and the like. The hard coat treatment is for the purpose of preventing scratches on the surface of the polarizing plate, for example, a treatment for forming a cured film having excellent hardness and slipperiness composed of a curable resin on the surface of the transparent protective layer. It is. As the curable resin, for example, a silicone-based, urethane-based, acrylic-based, or epoxy-based ultraviolet curable resin can be used, and the treatment can be performed by a conventionally known method. The purpose of preventing sticking is to prevent adhesion between adjacent layers. The antireflection treatment is intended to prevent reflection of external light on the surface of the polarizing plate, and can be performed by forming a conventionally known antireflection layer or the like.

  The anti-glare treatment is intended to prevent visual interference of the light transmitted through the polarizing plate due to reflection of external light on the surface of the polarizing plate, for example, on the surface of the transparent protective layer by a conventionally known method, This can be done by forming a fine uneven structure. Examples of a method for forming such a concavo-convex structure include a roughening method by sandblasting or embossing, a method of forming the transparent protective layer by blending transparent fine particles in the transparent resin as described above, and the like. It is done.

  Examples of the transparent fine particles include silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, antimony oxide, and the like. In addition, conductive inorganic fine particles, crosslinked or uncrosslinked Organic fine particles composed of polymer particles and the like can also be used. The average particle size of the transparent fine particles is not particularly limited, but is, for example, in the range of 0.5 to 20 μm. Moreover, the blending ratio of the transparent fine particles is not particularly limited, but is generally preferably 2 to 70 parts by mass, more preferably 5 to 50 parts by mass per 100 parts by mass of the transparent resin as described above.

  The antiglare layer containing the transparent fine particles can be used as, for example, the transparent protective layer itself, or may be formed as a coating layer on the surface of the transparent protective layer. Further, the antiglare layer may also serve as a diffusion layer (viewing angle compensation function or the like) for diffusing the light transmitted through the polarizing plate to expand the viewing angle.

  The antireflection layer, anti-sticking layer, diffusion layer, anti-glare layer, etc. are laminated on the polarizing plate as an optical layer composed of, for example, a sheet provided with these layers, separately from the transparent protective layer. May be.

  The optical film of the present invention preferably further has at least one of an adhesive layer and a pressure-sensitive adhesive layer. This is because adhesion between the optical film of the present invention and other members such as other optical layers and liquid crystal cells can be facilitated, and peeling of the optical film of the present invention can be prevented. Therefore, the adhesive layer and the pressure-sensitive adhesive layer are preferably laminated on the outermost layer of the optical film, and may be one outermost layer of the optical film or may be laminated on both outermost layers.

  The material of the adhesive layer is not particularly limited. For example, a pressure sensitive adhesive made of a polymer such as acrylic, vinyl alcohol, silicone, polyester, polyurethane, or polyether, or a rubber pressure sensitive adhesive. Etc. can be used. Alternatively, these materials may contain fine particles to form a layer exhibiting light diffusibility. Among these, for example, a material excellent in hygroscopicity and heat resistance is preferable. With such a property, for example, when used in a liquid crystal display device, it can prevent foaming and peeling due to moisture absorption, deterioration of optical characteristics due to a difference in thermal expansion, warpage of the liquid crystal cell, etc., and high quality and durability. The display device is also excellent.

  The method for laminating the components (polarizer, transparent protective layer, etc.) is not particularly limited, and can be performed by a conventionally known method. In general, the same pressure-sensitive adhesives and adhesives as described above can be used, and the type thereof can be appropriately determined depending on the material of each component. Examples of the adhesive include polymer adhesives such as acrylic, vinyl alcohol, silicone, polyester, polyurethane, and polyether, and rubber adhesives. Further, an adhesive composed of a water-soluble crosslinking agent of vinyl alcohol polymers such as glutaraldehyde, melamine and oxalic acid can be used. The pressure-sensitive adhesives and adhesives as described above are hardly peeled off due to, for example, the influence of humidity and heat, and are excellent in light transmittance and degree of polarization. Specifically, when the polarizer is a PVA-based film, for example, a PVA-based adhesive is preferable from the viewpoint of the stability of the adhesion treatment. These adhesives and pressure-sensitive adhesives may be applied to the surface of the polarizer or the transparent protective layer as they are, for example, or a layer such as a tape or sheet composed of the adhesive or pressure-sensitive adhesive is disposed on the surface. May be. For example, when prepared as an aqueous solution, other additives and catalysts such as acids may be blended as necessary. In addition, when apply | coating the said adhesive agent, you may mix | blend another additive and catalysts, such as an acid, with the said adhesive agent aqueous solution, for example. The thickness of such an adhesive layer is not particularly limited, but is, for example, 1 nm to 500 nm, preferably 10 nm to 300 nm, and more preferably 20 nm to 100 nm. The method is not particularly limited, and for example, a conventionally known method using an adhesive such as an acrylic polymer or a vinyl alcohol polymer can be employed. In addition, an adhesive containing a water-soluble cross-linking agent of PVA polymer such as glutaraldehyde, melamine, oxalic acid and the like can be obtained because it can form a polarizing plate that is hardly peeled off by humidity, heat, etc. and has excellent light transmittance and polarization degree. preferable. These adhesives can be used by, for example, applying the aqueous solution to the surface of each component and drying. In the aqueous solution, for example, other additives and a catalyst such as an acid can be blended as necessary. Among these, as the adhesive, a PVA adhesive is preferable from the viewpoint of excellent adhesiveness with a PVA film.

  In addition to the polarizer as described above, the optical film of the present invention can be used in combination with conventionally known optical members such as various retardation plates, diffusion control films, brightness enhancement films, and the like. Examples of the retardation plate include a uniaxially or biaxially stretched polymer film, a Z-axis aligned treatment, a liquid crystalline polymer coating film, and the like. Examples of the diffusion control film include films utilizing diffusion, scattering, and refraction, and these can be used for, for example, control of viewing angle, glare related to resolution, and control of scattered light. As the brightness enhancement film, for example, a brightness enhancement film using selective reflection of a cholesteric liquid crystal and a quarter wavelength plate (λ / 4 plate), a scattering film using anisotropic scattering by the polarization direction, or the like is used. it can. Moreover, the said optical film can also be combined with a wire grid type polarizer, for example.

  In practical use, the laminated polarizing plate of the present invention may further contain other optical layers in addition to the optical film of the present invention. Examples of the optical layer include various conventionally known optical layers used for forming a polarizing plate, a reflecting plate, a transflective plate, a brightness enhancement film, a liquid crystal display device and the like as shown below. One kind of these optical layers may be used, two or more kinds may be used in combination, one layer may be used, or two or more layers may be laminated. The laminated polarizing plate further including such an optical layer is preferably used as an integrated polarizing plate having an optical compensation function, for example, and is suitable for use in various image display devices such as being disposed on the surface of a liquid crystal cell. ing.

  Hereinafter, such an integrated polarizing plate will be described.

  First, an example of a reflective polarizing plate or a transflective polarizing plate will be described. The reflective polarizing plate further includes a reflective plate on the laminated polarizing plate of the present invention, and the transflective polarizing plate further includes a semi-transmissive reflective plate stacked on the laminated polarizing plate of the present invention.

  The reflective polarizing plate is usually disposed on the back side of a liquid crystal cell, and can be used for a liquid crystal display device (reflective liquid crystal display device) of a type that reflects incident light from the viewing side (display side). Such a reflective polarizing plate, for example, has an advantage that the liquid crystal display device can be thinned because the built-in light source such as a backlight can be omitted.

  The reflective polarizing plate can be produced by a conventionally known method such as a method of forming a reflective plate made of metal or the like on one surface of a polarizing plate exhibiting the elastic modulus. Specifically, for example, one surface (exposed surface) of the transparent protective layer in the polarizing plate is matted as necessary, and a metal foil or a vapor deposition film made of a reflective metal such as aluminum is formed on the surface as a reflection plate. And a reflective polarizing plate.

  In addition, as described above, a reflective polarizing plate or the like in which a reflecting plate reflecting the fine uneven structure is formed on a transparent protective layer containing fine particles in various transparent resins and having a fine uneven structure on the surface. It is done. A reflector having a fine concavo-convex structure on its surface has an advantage that, for example, incident light can be diffused by irregular reflection to prevent directivity and glaring appearance and to suppress uneven brightness. Such a reflector is, for example, directly on the uneven surface of the transparent protective layer by a conventionally known method such as a vacuum deposition method, an ion plating method, a sputtering method, or a plating method. It can form as a metal vapor deposition film.

  In addition, instead of the method of directly forming the reflective plate on the transparent protective layer of the polarizing plate as described above, a reflective sheet having a reflective layer provided on a suitable film such as the transparent protective film is used as the reflective plate. May be. Since the reflective layer in the reflective plate is usually composed of metal, for example, from the viewpoint of preventing the decrease in reflectance due to oxidation, and thus the long-term persistence of the initial reflectance, and the separate formation of a transparent protective layer, etc. The usage form is preferably a state in which the reflective surface of the reflective layer is covered with the film, a polarizing plate or the like.

  On the other hand, the transflective polarizing plate has a transflective reflective plate instead of the reflective plate in the reflective polarizing plate. Examples of the transflective reflector include a half mirror that reflects light through a reflective layer and transmits light.

  The transflective polarizing plate is usually provided on the back side of a liquid crystal cell. When a liquid crystal display device or the like is used in a relatively bright atmosphere, the incident light from the viewing side (display side) is reflected to display an image. In a relatively dark atmosphere, it can be used for a liquid crystal display device of a type that displays an image using a built-in light source such as a backlight built in the back side of the transflective polarizing plate. That is, the transflective polarizing plate can save the energy of using a light source such as a backlight in a bright atmosphere, and can be used with the built-in light source in a relatively dark atmosphere. It is useful for the formation of etc.

  Next, an example of a polarizing plate in which a brightness enhancement film is further laminated on the laminated polarizing plate of the present invention will be described.

  The brightness enhancement film is not particularly limited, and for example, a linear multi-layer thin film of dielectric material or a multi-layer laminate of thin film films having different refractive index anisotropy transmits linearly polarized light having a predetermined polarization axis, Other light can be used that reflects light. As such a brightness enhancement film, for example, trade name “D-BEF” manufactured by 3M Co., Ltd. may be mentioned. Also, a cholesteric liquid crystal layer, in particular an oriented film of a cholesteric liquid crystal polymer, or a film in which the oriented liquid crystal layer is supported on a film substrate can be used. These reflect the right and left circularly polarized light and transmit the other light. For example, the product name “PCF350” manufactured by Nitto Denko Corporation, the product name “Transmax” manufactured by Merck, etc. can give.

  The various polarizing plates of the present invention as described above may be, for example, optical members obtained by stacking the laminated polarizing plate of the present invention and two or more optical layers.

  An optical member in which two or more optical layers are laminated in this manner can be formed by a method of sequentially laminating separately, for example, in the manufacturing process of a liquid crystal display device or the like. There are advantages such as excellent quality stability and assembly workability, and improvement in manufacturing efficiency of liquid crystal display devices and the like. For the lamination, various adhesive means such as an adhesive layer can be used as described above.

  The various polarizing plates as described above preferably have a pressure-sensitive adhesive layer or an adhesive layer because they can be easily laminated on other members such as a liquid crystal cell. It can be placed on one or both sides of the plate. The material of the adhesive layer is not particularly limited, and a conventionally known material such as an acrylic polymer can be used. In particular, foaming and peeling due to moisture absorption are prevented, optical characteristics are deteriorated due to a difference in thermal expansion, and a liquid crystal cell is warped. For example, it is preferable to form a pressure-sensitive adhesive layer having a low moisture absorption rate and excellent heat resistance, for example, from the viewpoints of prevention, and hence formability of a liquid crystal display device having high quality and excellent durability. Moreover, the adhesion layer etc. which contain microparticles | fine-particles and show light diffusibility may be sufficient. The pressure-sensitive adhesive layer is formed on the surface of the polarizing plate by, for example, adding a solution or a melt of various pressure-sensitive adhesive materials directly to a predetermined surface of the polarizing plate by a developing method such as casting or coating. In the same manner, a pressure-sensitive adhesive layer is formed on a separator, which will be described later, and transferred to a predetermined surface of the polarizing plate. Such a layer may be formed on any surface of the polarizing plate, for example, on the exposed surface of the retardation plate in the polarizing plate.

  As described above, when the surface of the pressure-sensitive adhesive layer or the like provided on the polarizing plate is exposed, it is preferable to cover the surface with a separator for the purpose of preventing contamination until the pressure-sensitive adhesive layer is put to practical use. This separator is formed on a suitable film such as the above-mentioned transparent protective film by a method of providing one or more release coats with a release agent such as silicone, long chain alkyl, fluorine, molybdenum sulfide, etc., if necessary. it can.

  For example, the pressure-sensitive adhesive layer may be a single layer or a laminate. As the laminate, for example, a laminate in which different compositions and different types of single layers are combined can be used. Moreover, when arrange | positioning on the both surfaces of the said polarizing plate, the same adhesive layer may respectively be sufficient, for example, a different composition and a different kind of adhesive layer may be sufficient.

  The thickness of the pressure-sensitive adhesive layer can be appropriately determined according to, for example, the configuration of the polarizing plate, and is generally 1 to 500 μm.

  As the pressure-sensitive adhesive that forms the pressure-sensitive adhesive layer, for example, one that is excellent in optical transparency and exhibits appropriate wettability, cohesiveness, and adhesive pressure-sensitive adhesive properties is preferable. Specific examples include pressure-sensitive adhesives prepared by appropriately using polymers such as acrylic polymers, silicone polymers, polyesters, polyurethanes, polyethers, and synthetic rubbers as base polymers.

  Control of the adhesive property of the pressure-sensitive adhesive layer is, for example, the degree of cross-linking depending on the composition and molecular weight of the base polymer forming the pressure-sensitive adhesive layer, the crosslinking method, the content ratio of the crosslinkable functional group, the blending ratio of the crosslinking agent, and the like. It can be suitably carried out by a conventionally known method such as adjusting the molecular weight.

  The optical film and polarizing plate of the present invention as described above, and various layers such as a polarizing film, a transparent protective layer, an optical layer, and a pressure-sensitive adhesive layer forming various optical members (various polarizing plates laminated with optical layers) are, for example, salicylic acid. It may have an ultraviolet absorbing ability by appropriately treating with an ultraviolet absorber such as an ester compound, a benzophenone compound, a benzotriazole compound, a cyanoacrylate compound, or a nickel complex salt compound.

  As described above, the optical film or polarizing plate of the present invention is preferably used for forming various devices such as a liquid crystal display device. For example, the optical film or polarizing plate of the present invention is disposed on one side or both sides of a liquid crystal cell. Thus, a liquid crystal panel can be used for a liquid crystal display device such as a reflective type, a transflective type, or a transmissive / reflective type.

  The type of the liquid crystal cell forming the liquid crystal display device can be arbitrarily selected. For example, it is represented by an active matrix driving type represented by a thin film transistor type, a twisted nematic (TN) type, or a super twisted nematic (STN) type. Various types of liquid crystal cells such as simple matrix drive type can be used. Among these, the TN cell, the VA (Vertical Alignment) cell, and the OCB (Optically Aligned Birefringence) cell are particularly excellent in optical compensation, so that the optical film of the present invention is suitable for a liquid crystal display device including these liquid crystal cells. Very useful.

  In addition, the liquid crystal cell has a structure in which liquid crystal is usually injected into a gap between opposing liquid crystal cell substrates, and the liquid crystal cell substrate is not particularly limited, and for example, a glass substrate or a plastic substrate can be used. The material of the plastic substrate is not particularly limited, and a conventionally known material can be used.

  Moreover, when providing a polarizing plate and an optical member on both surfaces of a liquid crystal cell, they may be the same kind and may differ. Furthermore, when forming the liquid crystal display device, for example, appropriate components such as a prism array sheet, a lens array sheet, a light diffusing plate, and a backlight can be arranged in one or more layers at appropriate positions.

  Furthermore, the liquid crystal display device of the present invention includes a liquid crystal panel, and is not particularly limited except that the liquid crystal panel of the present invention is used as the liquid crystal panel. In the case of including a light source, the light source is not particularly limited. However, for example, a plane light source that emits polarized light is preferable because the energy of light can be used effectively.

  FIG. 4 is a cross-sectional view showing an example of the liquid crystal panel of the present invention. As illustrated, the liquid crystal panel 40 includes a liquid crystal cell 21, a laminate 1 of a transparent polymer film, a barrier layer, and a birefringent layer, a polarizer 2, and a transparent protective layer 3. A liquid crystal cell 21 is disposed on one surface, and the polarizer 2 and the transparent protective layer 3 are stacked in this order on the other surface of the stacked body 1. The liquid crystal cell 21 has a configuration in which liquid crystal is held between two liquid crystal cell substrates (not shown). The laminate 1 is formed by laminating a transparent polymer film, a barrier layer, and a birefringent layer as described above, the birefringent layer side facing the liquid crystal cell 21, and the transparent polymer film side facing the liquid crystal cell 21. Facing the polarizer 2.

  In the liquid crystal display device of the present invention, for example, a diffusion plate, an antiglare layer, an antireflection film, a protective layer and a protective plate are further disposed on the optical film (polarizing plate) on the viewing side, or the liquid crystal in the liquid crystal panel. A compensation retardation plate or the like can be appropriately disposed between the cell and the polarizing plate.

  In addition, the optical film and polarizing plate of this invention are not limited to the above liquid crystal display devices, For example, it can be used also for self-luminous display devices, such as an organic electroluminescence (EL) display, PDP, and FED. When used in a self-luminous flat display, for example, circular polarization can be obtained by setting the in-plane retardation value Δnd of the birefringent optical film of the present invention to λ / 4. Available.

  Hereinafter, an electroluminescence (EL) display device including the optical film of the present invention will be described. The EL display device of the present invention is a display device having the optical film of the present invention, and this EL device may be either organic EL or inorganic EL.

  In recent years, it has been proposed to use, for example, an optical film such as a polarizer or a polarizing plate together with a λ / 4 plate in an EL display device as an antireflection from an electrode in a black state. The polarizer and the optical film of the present invention are oblique even when the EL layer emits linearly polarized light, circularly polarized light, or elliptically polarized light, or emits natural light in the front direction. This is very useful when the emitted light in the direction is partially polarized.

  First, a general organic EL display device will be described here. The organic EL display device generally has a light emitter (organic EL light emitter) in which a transparent electrode, an organic light emitting layer, and a metal electrode are laminated in this order on a transparent substrate. 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, or the like. Various combinations such as a laminate of a light-emitting layer and an electron injection layer made of a perylene derivative, or a laminate of the hole injection layer, the light-emitting layer, and the electron injection layer can be given.

  Such an organic EL display device is produced by injecting holes and electrons into the organic light emitting layer by applying a voltage to the anode and the cathode, and recombining the holes and electrons. Energy emits light on the principle that it excites the phosphor and emits light when the excited phosphor returns to the ground state. The mechanism of recombination of holes and electrons is the same as that of a general diode, and current and emission intensity show strong nonlinearity with rectification with respect to applied voltage.

  In the organic EL display device, in order to extract light emitted from the organic light emitting layer, at least one of the electrodes needs to be transparent. Therefore, the organic EL display device is usually formed of a transparent conductor such as indium tin oxide (ITO). A transparent electrode is used as the anode. On the other hand, in order to facilitate electron injection and increase luminous efficiency, it is important to use a material having a small work function for the cathode, and usually metal electrodes such as Mg—Ag and Al—Li are used.

  In the organic EL display device having such a configuration, the organic light emitting layer is preferably formed of an extremely thin film having a thickness of about 10 nm, for example. This is because the organic light-emitting layer transmits light almost completely as in the transparent electrode. As a result, at the time of non-light emission, the light incident from the surface of the transparent substrate, transmitted through the transparent electrode and the organic light emitting layer, and reflected by the metal electrode again returns to the surface side of the transparent substrate. For this reason, when viewed from the outside, the display surface of the organic EL display device looks like a mirror surface.

  The organic EL display device of the present invention is, for example, an organic EL display device including the organic EL light emitting device including a transparent electrode on a front surface side of the organic light emitting layer and a metal electrode on a back surface side of the organic light emitting layer. The optical film (polarizing plate or the like) of the present invention is preferably disposed on the surface of the transparent electrode, and a λ / 4 plate is preferably disposed between the polarizing plate and the EL element. Thus, by arranging the optical film of the present invention, it becomes an organic EL display device that has the effect of suppressing reflection from the outside and improving the visibility. Moreover, it is preferable that a phase difference plate is further disposed between the transparent electrode and the optical film.

  For example, the retardation film and the optical film (polarizing plate, etc.) have a function of polarizing the light incident from the outside and reflected by the metal electrode, so that the mirror surface of the metal electrode is visually recognized from the outside by the polarization action. There is an effect of not letting it. In particular, if a quarter-wave plate is used as a retardation plate and the angle formed by the polarization direction of the polarizing plate and the retardation plate is adjusted to π / 4, the mirror surface of the metal electrode is completely shielded. can do. That is, only the linearly polarized component of the external light incident on the organic EL display device is transmitted by the polarizing plate. The linearly polarized light becomes generally elliptically polarized light by the retardation plate, but becomes circularly polarized light particularly when the retardation plate is a quarter wavelength plate and the angle is π / 4.

  For example, this circularly polarized light is transmitted through the transparent substrate, the transparent electrode, and the organic thin film, reflected by the metal electrode, again transmitted through the organic thin film, the transparent electrode, and the transparent substrate, and again by the retardation plate. Become. And since this linearly polarized light is orthogonal to the polarization direction of the polarizing plate, it cannot pass through the polarizing plate, and as a result, the mirror surface of the metal electrode can be completely shielded as described above. .

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples. In addition, the characteristic of the optical film was evaluated by the following method.

(Determination of chemical structural formula)
A sample was prepared by dissolving 50 mg of a polyimide sample in 0.6 ml of deuterated dimethyl sulfoxide (DMSO) and measured using a trade name LA400 (manufactured by JEOL Ltd.) which is ¹ H-NMR of 400 MHz.

(Measurement of molecular weight)
A polyimide sample was dissolved in DMF (N, N-dimethylformamide) so as to be 0.1% by weight, and this solution was filtered through a 0.45 μm membrane filter, and then the product name HLC-8120GPC (manufactured by Tosoh Corporation) was used. The molecular weight of the polyimide was measured with a polyethylene oxide standard sample.

(Measurement of refractive index)
The refractive index of the obtained optical film was measured using an Abbe refractometer (trade name NAR-1T type: manufactured by Atago Co., Ltd.).

(Measurement of phase difference and birefringence)
The refractive index at a wavelength of 590 nm was measured using an automatic birefringence meter (trade name KOBRA-21ADH: manufactured by Oji Scientific Instruments). In addition, the thickness direction retardation (Rth) measured the value with respect to the incident light from the direction inclined 0-40 degrees from the normal line of the optical film.

(Transmittance measurement)
The transmittance in the normal direction was measured using SPECTROTOPOMETER (trade name DOT-3C: manufactured by MURAKAMI COLOR RESERCH).

(Film thickness measurement)
The film thickness of the birefringent layer was measured using an instantaneous multi-photometry system (trade name MCPD-2000; manufactured by Otsuka Electronics Co., Ltd.).

(Elongation measurement)
The elongation percentage of the barrier layer was measured separately by forming the barrier layer on a PET substrate under the same conditions as in Examples and peeling off the barrier layer from the substrate.

Tensilon (tensile tester) is used to fix both ends of the barrier layer (length 50 mm × width 10 mm, thickness 0.2 mm) in the longitudinal direction, and the barrier layer is moved in the longitudinal direction under the condition of a tensile speed of 300 mm / min. Pull in both directions until it breaks. And the longitudinal direction full length [L (a)] of the barrier layer at the time of a fracture | rupture is measured, The longitudinal direction full length [L (b)] of the barrier layer before the tension | pulling previously measured and said L (a) are set to a following formula. The percent elongation was calculated by substitution.
Elongation rate (%) = [{L (a) −L (b)} / L (b)] × 100

  First, a transparent polymer film was produced. 65 parts by weight of an alternating copolymer containing isobutene and N-methylmaleimide (N-maleimide content 50 mol%) and 35 parts by weight of an acrylonitrile-styrene copolymer (acrylonitrile content 27 mol%) Was dissolved in methylene chloride to prepare a solution having a solid concentration of 15% by weight. Next, the solution was cast on the surface of a polyethylene terephthalate film placed on a glass plate, and allowed to stand at room temperature for 60 minutes to form a film. Then, the film formed on the polyethylene terephthalate film was peeled off. The peeled film was further fixed by drying at 100 ° C. for 10 minutes, 140 ° C. for 10 minutes, and 160 ° C. for 30 minutes. The obtained transparent polymer film had a thickness of 50 μm, an in-plane retardation (Δnd) of 4 nm, and a thickness direction retardation (Rth) of 4 nm.

  Next, a barrier layer was formed on the transparent polymer film as follows. The transparent polymer film prepared in advance is subjected to corona treatment so that its pure water contact angle is 50 °. On the other hand, a water-dispersed polyester urethane (trade name Adekabon) is added to a mixed solution of water and isopropyl alcohol. (Titer HUX320: manufactured by Asahi Denka Kogyo Co., Ltd.) was dissolved so as to be 20% by weight to prepare a barrier layer solution. And this solution was directly coated on the transparent polymer film after the said process, and the barrier layer was formed on the said transparent polymer film by performing a heat processing at 100 degreeC for 10 minute (s). The barrier layer was a completely transparent and smooth film having a thickness of about 3 μm and an elongation of 200%.

  Furthermore, a birefringent layer (polyimide layer) was formed on the barrier layer. First, using 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane and 2,2'-bis (trifluoromethyl) -4,4'-diaminobiphenyl (PFMB), the following general formula A polyimide (Mw = 110,000) composed of the repeating unit represented by (3) was synthesized. This polyimide was dissolved in ethyl acetate so as to have a solid content concentration of 15% by weight to prepare a polyimide solution, which was directly coated on the surface of the barrier layer and then dried at 150 ° C. for 10 minutes. Thereby, a laminated birefringent film having a three-layer structure in which a birefringent layer (polyimide layer) was directly laminated on the transparent polymer film via a barrier layer was obtained. This laminated birefringent film was a completely transparent and smooth film and had a transmittance of 97%. The birefringent layer (polyimide layer) in the laminated birefringent film had a thickness of 4 μm, a birefringence of 0.035, and a thickness direction retardation (Rth) of 300 nm.

(Comparative Example 1)
A laminated birefringent film was produced in the same manner as in Example 1 except that a birefringent layer (polyimide layer) was directly formed on the transparent polymer film without forming the barrier layer. In addition, the obtained laminated birefringent film became cloudy and had a transmittance of 83%.

  In the laminated birefringent film of Comparative Example 1, the transparent polymer film became cloudy due to the influence of the solvent used for forming the birefringent layer, and as a result, the transmittance of the laminated birefringent film was as low as 83%. On the other hand, in Example 1, since the transparent polymer film was maintained in a completely transparent state by forming a birefringent layer (polyimide layer) on the transparent polymer film via a barrier layer, The transmissivity of the birefringent film was also very excellent, 97%. It is clear that such a laminated birefringent film realizes excellent display characteristics when applied to a liquid crystal display device or the like.

  As described above, by forming a barrier layer between the transparent polymer film and the birefringent layer, it is possible to avoid white turbidity of the transparent polymer film, excellent appearance such as transparency, and optical properties, A laminated birefringent film capable of realizing particularly excellent transmittance and a large thickness direction retardation can be obtained. For this reason, if the laminated birefringent film of the present invention is used in various image display devices, excellent display characteristics can be realized.

It is sectional drawing which shows an example of the lamination | stacking birefringent film of this invention. It is sectional drawing which shows an example of the optical film of this invention. It is sectional drawing which shows another example of the laminated polarizing plate of this invention. It is sectional drawing which shows an example of the liquid crystal panel of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Birefringent layer 12 Barrier layer 13 Transparent polymer film 1 Laminated birefringent film 2 Polarizer 3 Protective layer 20 Laminated polarizing plate 21 Liquid crystal cell 30 Laminated polarizing plate 40 Liquid crystal panel

Claims (25)

A laminated birefringent film comprising a transparent polymer film and a birefringent layer,
The birefringent layer comprises at least one polymer selected from the group consisting of polyamide, polyimide, polyester, polyetherketone, polyamide-imide and polyesterimide;
A laminated birefringent film, wherein a barrier layer is directly formed on the transparent polymer film, and further, the birefringent layer is directly formed on the barrier layer. The laminated birefringent film according to claim 1, wherein the barrier layer includes at least one selected from the group consisting of a polyurethane resin, an epoxy resin, a polyacrylic resin, and a polyethyleneimine resin. The laminated birefringent film according to claim 1, wherein the barrier layer includes at least one selected from the group consisting of a polyester urethane resin, a polyether urethane resin, and a polycarbonate urethane resin. The transparent polymer film comprises a mixture of a thermoplastic resin having a substituted and / or unsubstituted imide group in the side chain and a thermoplastic resin having a substituted and / or unsubstituted phenyl group and a nitrile group in the side chain. The laminated birefringent film according to any one of claims 1 to 3. The laminated birefringent film according to any one of claims 1 to 4, which satisfies at least one of the conditions of the following formulas (I) to (III).
Δna> Δnb × 10 (I)
1 <(nx-nz) / (nx-ny) (II)
0.0005 ≦ Δna ≦ 0.5 (III)
In the formula (I) and the formula (III), Δna is the birefringence of the birefringent layer, and in the formula (I), Δnb is the birefringence of the transparent polymer film, and the Δna and The Δnb is respectively represented by the following formula, and in the formula (II) and the following formula, nx, ny and nz are refractive indexes in the X-axis, Y-axis and Z-axis directions in the birefringent layer, respectively, n 'x, n'y, and n'z are refractive indexes in the X-axis, Y-axis, and Z-axis directions of the transparent polymer film, respectively, and the X-axis direction is the birefringent layer or the transparent height An axial direction showing the maximum refractive index in the plane of the molecular film, the Y-axis direction is an axial direction perpendicular to the X-axis in the same plane, the Z-axis is the X-axis and the Shows thickness direction perpendicular to Y-axis .
Δna = {(nx + ny) / 2} −nz
Δnb = {(n′x + n′y) / 2} −n′z A method for producing a laminated birefringent film comprising a transparent polymer film and a birefringent layer,
The birefringent material comprises at least one selected from the group consisting of polyamide, polyimide, polyester, polyetherketone, polyamide-imide and polyesterimide;
A step of forming a barrier layer on the transparent polymer film by directly coating and fixing a coating liquid containing a barrier layer forming material on the transparent polymer film, and further on the barrier layer Forming a birefringent layer on the barrier layer by directly applying and fixing a solution obtained by dissolving the birefringent material in a solvent. The production method according to claim 6, wherein the coating liquid is in the form of an aqueous solution, an emulsion liquid or a dispersion liquid. The manufacturing method according to claim 6 or 7, wherein the barrier layer forming material includes at least one selected from the group consisting of a polyurethane resin, an epoxy resin, a polyacrylic resin, and a polyethyleneimine resin. The manufacturing method according to claim 6 or 7, wherein the barrier layer forming material includes at least one selected from the group consisting of a polyester urethane resin, a polyether urethane resin, and a polycarbonate urethane resin. The elongation rate represented by the following formula of the barrier layer is 50% or more, The production method according to any one of claims 6 to 9.
Elongation rate (%) = [{L (a) −L (b)} / L (b)] × 100
In the above formula, L (a) indicates the total length of the barrier layer in the longitudinal direction when the barrier layer is pulled in the longitudinal direction under the condition of 300 mm / min, and L (b) is before tension. The overall length in the longitudinal direction of the barrier layer is shown. The transparent polymer film comprises a mixture of a thermoplastic resin having a substituted and / or unsubstituted imide group in the side chain and a thermoplastic resin having a substituted and / or unsubstituted phenyl group and a nitrile group in the side chain. The manufacturing method as described in any one of Claims 6-10 containing. The manufacturing method according to any one of claims 6 to 11, further comprising a step of stretching or shrinking the birefringent layer after the step of forming the birefringent layer. The manufacturing method according to claim 12, wherein the stretching process is a uniaxial stretching process or a biaxial stretching process. The transparent polymer film and the barrier layer each have shrinkability, and after the step of forming the birefringent layer, further comprising the step of shrinking the birefringent layer in accordance with the shrinkage of the transparent polymer film. The manufacturing method of Claim 12. The manufacturing method according to claim 14, wherein the shrinking step is a step of shrinking the transparent polymer film by heating. The laminated birefringent film manufactured by the manufacturing method as described in any one of Claims 6-15. An optical film comprising the laminated birefringent film according to any one of claims 1 to 5 and claim 16. The optical film according to claim 17, further comprising a polarizer. The optical film according to claim 18, wherein the transparent polymer film also serves as a transparent protective layer of the polarizer. Furthermore, the optical film of Claim 19 containing at least one of a phase difference plate or a reflecting plate. 21. A liquid crystal panel comprising a liquid crystal cell and an optical member, wherein the optical member is disposed on at least one surface of the liquid crystal cell, wherein the optical member is the optical according to any one of claims 17 to 20. A liquid crystal panel that is a film. The liquid crystal panel according to claim 21, wherein the liquid crystal cell is at least one selected from the group consisting of an OCB mode, a VA mode, and a TN mode. The optical film according to any one of claims 17 to 20, wherein the optical compensation layer side of the optical film is arranged to face the liquid crystal cell. LCD panel. 24. A liquid crystal display device including a liquid crystal panel, wherein the liquid crystal panel is a liquid crystal panel according to any one of claims 21 to 23. The image display apparatus containing the optical film as described in any one of Claims 17-20.

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