JP3992969B2 - Homeotropic alignment liquid crystal film, brightness enhancement film, and optical film - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a homeotropic alignment liquid crystal film. The homeotropic alignment liquid crystal film of the present invention can be used as an optical film such as a retardation plate, a viewing angle compensation film, an optical compensation film, an elliptically polarizing film, and a brightness enhancement film alone or in combination with other optical films. In particular, a film in which the homeotropic alignment liquid crystal film of the present invention is disposed between a cholesteric liquid crystal film and a quarter-wave plate is useful as a brightness enhancement film or the like. Furthermore, the present invention relates to an image display device such as a liquid crystal display device, an organic EL display device, or a PDP using an optical film such as a homeotropic alignment liquid crystal film or a brightness enhancement film.
[0002]
[Prior art]
Homeotropic alignment of liquid crystal molecules is that the long-axis molecular direction of the liquid crystal is aligned in a direction substantially perpendicular to the substrate. It is well known that homeotropic alignment can be obtained by applying an electric field by putting liquid crystal in two glass substrates like a liquid crystal display, but it is very difficult to make this alignment state into a film. difficult.
[0003]
US Pat. No. 5,731,886 describes that a reflective polarizing plate with improved viewing angle characteristics can be obtained by using a brightness enhancement film in which a homeotropically aligned liquid crystal layer is disposed between a cholesteric liquid crystal layer and a quarter-wave plate. Has been. However, it is difficult to control the alignment state of the homeotropic alignment liquid crystal layer, and the alignment state varies. Therefore, if the alignment state is not controlled well, unevenness in the viewing angle characteristic is confirmed. Yes.
[0004]
[Problems to be solved by the invention]
An object of this invention is to provide the homeotropic alignment liquid crystal film which improved the brightness improvement characteristic at the time of applying to a brightness improvement film, and improved the nonuniformity in a viewing angle characteristic. Furthermore, it aims at providing the image display apparatus using optical films, such as a brightness improvement film and an optical film using the said homeotropic alignment liquid crystal film, and also the said homeotropic alignment liquid crystal film.
[0005]
[Means for solving problems]
As a result of intensive studies to solve the above problems, the present inventors have found that the object can be achieved by the homeotropic alignment liquid crystal film shown below, and have completed the present invention.
[0006]
That is, the present invention has a thickness d (nm), the main in-plane refractive index as n _x, n _y, and a refractive index in the thickness direction and n _z, and when the n _x> n _y, a front retardation : △ average value of _{n xy (n x -n y)} × d is not less 10nm or less, a thickness direction _{retardation: △ n zx (n z -n} x) is the average value of × d is 50 to 400 nm, and Thickness direction retardation: Δn _zx × d, the value obtained by the formula: {(maximum value−minimum value) / average value} × 100 (%) is 10 or less, and the average value of haze is 3% A homeotropic alignment liquid crystal film, which is:
The homeotropic alignment liquid crystal film has a general formula (a) as a monomer unit (a) containing a liquid crystalline fragment side chain:
[Chemical 1B]
(Wherein R ¹ represents a hydrogen atom or a methyl group, a represents a positive integer of 1 to 6, X ¹ represents a —CO ₂ — group or —OCO— group, R ² represents a cyano group, and has 1 to 6 carbon atoms. An alkoxy group, a fluoro group, or an alkyl group having 1 to 6 carbon atoms, b and c each represent an integer of 1 or 2, and a monomer unit having a side chain having nematic liquid crystallinity,
As the monomer unit (b) containing a non-liquid crystalline fragment side chain, the general formula (b):
[Chemical 2B]
(However, R ³ is a hydrogen atom or a methyl group, R ⁴ is an alkyl group having 7 to 22 carbon atoms, a fluoroalkyl group having 1 to 22 carbon atoms, or the general formula (c):
[Chemical 3B]
However, d is a positive integer from 1 to 6, R ⁵ represents an alkyl group having 1 to 6 carbon atoms. It is related with the homeotropic alignment liquid crystal film characterized by containing the side chain type liquid crystal polymer containing the monomer unit which has a linear side chain represented by this.
[0007]
When applying a homeotropic alignment liquid crystal film to the brightness enhancement film, if the front phase difference of the homeotropic alignment liquid crystal film itself is large, it will affect the phase difference of the quarter-wave plate, resulting in a liquid crystal. Therefore, the homeotropic alignment liquid crystal film of the present invention has a controlled average value of the front phase difference of 10 nm or less. Used. The average value of the front phase difference is preferably as small as possible, and is preferably 5 nm or less, more preferably 3 nm or less.
[0008]
Further, the thickness direction retardation is preferably adjusted to a suitable phase difference by matching with a cholesteric liquid crystal, and the average thickness direction retardation is controlled to 50 to 400 nm, preferably 100 to 400 nm. Is. Moreover, the thickness direction retardation is a value obtained by dividing the difference between the maximum value and the minimum value by the average value, that is, a value obtained by the formula: {(maximum value−minimum value) / average value} × 100 (%). Is 10 or less, and variation in the alignment state is controlled to be small and the alignment state is stable. The formula value is preferably 8 or less, more preferably 5 or less.
[0009]
Moreover, since the transmitted light is diffused by increasing the haze and the front luminance is lowered, the average value of the haze is controlled to 3% or less. The average value of haze is preferably 2% or less, more preferably 1% or less.
[0010]
As described above, the homeotropic alignment liquid crystal film of the present invention improves the luminance by controlling the front phase difference, the thickness direction phase difference, and the haze variation to stabilize the alignment state and uniformly align in the plane. It has improved brightness enhancement characteristics when applied to a film, and has improved unevenness in viewing angle characteristics.
[0011]
In the homeotropic alignment liquid crystal film, the difference between the maximum value and the minimum value of front phase difference: Δn _xy × d is preferably 5 nm or less, and the difference between the maximum value and the minimum value of haze is preferably 2% or less.
[0012]
The smaller the difference between the maximum value and minimum value of the front phase difference and the maximum value and minimum value of haze, the more stable the orientation state, and when applied to a brightness enhancement film, the brightness enhancement characteristics and viewing angle characteristics It is preferable for improving unevenness. The difference between the maximum value and the minimum value of the front phase difference is preferably 3 nm or less, and more preferably 2 nm or less. The difference between the maximum value and the minimum value of haze is preferably 1% or less, and more preferably 0.5%.
[0013]
The present invention also relates to a brightness enhancement film, wherein the homeotropic alignment liquid crystal film is disposed between a cholesteric liquid crystal film and a quarter-wave plate.
[0014]
The present invention also relates to an optical film, wherein at least one optical film is further laminated on the homeotropic alignment liquid crystal film or the brightness enhancement film.
[0015]
Furthermore, the present invention relates to an image display device to which the homeotropic alignment liquid crystal film, the brightness enhancement film, or the optical film is applied.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Homeotropic alignment liquid crystal film of the present invention, the front retardation, thickness direction retardation, Ru der having a characteristic related to haze. The homeotropic alignment liquid crystal film of the present invention includes, for example, a monomer unit (a) having a positive refractive index anisotropy and containing a liquid crystalline fragment side chain and a monomer unit (b) containing a non-liquid crystalline fragment side chain. It can be formed by a side chain type liquid crystal polymer containing
[0017]
The side-chain liquid crystal polymer can realize homeotropic alignment of the liquid crystal polymer without using a vertical alignment film. The side chain type liquid crystal polymer is a monomer unit containing a non-liquid crystalline fragment side chain having an alkyl chain in addition to the monomer unit (a) containing a liquid crystalline fragment side chain of a normal side chain type liquid crystal polymer. (B), the monomer unit (b) containing a non-liquid crystalline fragment side chain allows the nematic liquid crystal phase to be expressed by a heat treatment, for example, without the use of a vertical alignment film, thereby producing a homeo It is presumed that the tropic orientation has been exhibited.
[0018]
The monomer unit (a) has a side chain having nematic liquid crystallinity, for example, the general formula (a):
[Chemical 1]
(Wherein R ¹ represents a hydrogen atom or a methyl group, a represents a positive integer of 1 to 6, X ¹ represents a —CO ₂ — group or —OCO— group, R ² represents a cyano group, and has 1 to 6 carbon atoms. An alkoxy group, a fluoro group, or an alkyl group having 1 to 6 carbon atoms, and b and c each represent an integer of 1 or 2.).
[0019]
The monomer unit (b) has a linear side chain. For example, the monomer unit (b) has the general formula (b):
[Chemical 2]
(However, the R ³ is a hydrogen atom or a methyl group, R ⁴ is an alkyl group having 1 to 22 carbon atoms, fluoroalkyl group having 1 to 22 carbon atoms, or the general formula, (b1):
[Chemical 3]
However, d is a positive integer from 1 to 6, R ⁵ represents an alkyl group having 1 to 6 carbon atoms. ) Monomer units.
[0020]
Further, the ratio of the monomer unit (a) to the monomer unit (b) is not particularly limited and varies depending on the type of the monomer unit. However, when the ratio of the monomer unit (b) is increased, the side chain type liquid crystal polymer is changed. In order to stop showing liquid crystal monodomain orientation, it is preferable to set it as (b) / {(a) + (b)} = 0.01-0.8 (molar ratio). In particular, 0.1 to 0.5 is more preferable.
[0026]
The side chain type liquid crystal polymer preferably has a weight average molecular weight of 2,000 to 100,000. By adjusting the weight average molecular weight to such a range, performance as a liquid crystal polymer is exhibited. When the weight average molecular weight of the side chain type liquid crystal polymer is too small, the film forming property of the alignment layer tends to be poor. Therefore, the weight average molecular weight is more preferably 2.5000 or more. On the other hand, if the weight average molecular weight is excessive, the orientation as a liquid crystal tends to be poor and it becomes difficult to form a uniform alignment state. Therefore, the weight average molecular weight is more preferably 50,000 or less.
[0027]
Incidentally, the illustration of the side chain type liquid crystal polymers can be prepared by copolymerizing the monomer units (a), acrylic monomers or methacrylic monomers corresponding to the monomer unit (b). Incidentally, the monomers corresponding to the monomer unit (a), the monomer unit (b) can be synthesized by known methods. The copolymer can be prepared, for example, according to a polymerization method such as a conventional acrylic monomer such as a radical polymerization method, a cationic polymerization method, and an anionic polymerization method. When applying the radical polymerization method, various polymerization initiators can be used. Among them, decomposition temperatures such as azobisisobutyronitrile and benzoyl peroxide are not high and are not low. Those are preferably used.
[0028]
The side-chain liquid crystal polymer can be used as a liquid crystal composition by blending a photopolymerizable liquid crystal compound. Since the side chain type liquid crystal polymer can form a film on a substrate without using a vertical alignment film, the Tg of the liquid crystal film is designed to be low. In order to improve the durability that can be used for applications such as a liquid crystal display for these liquid crystal films, it is preferable to use a homeotropic alignment liquid crystal composition containing a photopolymerizable liquid crystal compound. The homeotropic alignment liquid crystalline composition is aligned and then irradiated with light such as ultraviolet rays.
[0029]
The photopolymerizable liquid crystal compound is a liquid crystal compound having at least one unsaturated double bond such as an acryloyl group or a methacryloyl group as a photopolymerizable functional group, and a nematic liquid crystal compound is awarded. Examples of such photopolymerizable liquid crystal compounds include acrylates and methacrylates that serve as the monomer unit (a). As the photopolymerizable liquid crystal compound, those having two or more photopolymerizable functional groups are preferable for improving durability. As such a photopolymerizable liquid crystal compound, for example,
[Chemical formula 5]
(In the formula, R is a hydrogen atom or a methyl group, A and D are each independently 1,4-phenylene group or 1,4-cyclohexylene group, and X is each independently a —COO— group or —OCO group. -Group or -O- group, B is 1,4-phenylene group, 1,4-cyclohexylene group, 4,4'-biphenylene group or 4,4'-bicyclohexylene group, and m and n are each And a cross-linked nematic liquid crystal monomer represented by the following formula: Examples of the photopolymerizable liquid crystal compound include compounds in which the terminal “H ₂ C═CR—CO ₂ —” in Chemical Formula 5 is substituted with a vinyl ether group or an epoxy group, “— (CH ₂ ) _m —” and / Or “— (CH ₂ ) _n —” is replaced with “— (CH ₂ ) ₃ —C ^* H (CH ₃ ) — (CH ₂ ) ₂ —” or “— (CH ₂ ) ₂ —C ^* H (CH ₃ )-(CH ₂ ) ₃ — ”.
[0030]
The photopolymerizable liquid crystal compound can be converted into a liquid crystal state by heat treatment, for example, by developing a nematic liquid crystal layer and homeotropically aligning with the side chain type liquid crystal polymer, and then polymerizing or crosslinking the photopolymerizable liquid crystal compound. As a result, the durability of the homeotropic alignment liquid crystal film can be improved.
[0031]
The ratio of the photopolymerizable liquid crystal compound and the side chain type liquid crystal polymer in the liquid crystal composition is not particularly limited and is appropriately determined in consideration of the durability of the obtained homeotropic alignment liquid crystal film. Photopolymerizable liquid crystal compound: side chain type liquid crystal polymer (weight ratio) = about 0.1: 1 to 30: 1 is preferable, 0.5: 1 to 20: 1 is particularly preferable, and 1: 1 to 10: is more preferable. 1 is preferred.
[0032]
The liquid crystalline composition usually contains a photopolymerization initiator. Various photopolymerization initiators can be used without particular limitation. Examples of the photopolymerization initiator include Irgacure 907, 184, 651, and 369 manufactured by Ciba Specialty Chemicals. The addition amount of the photopolymerization initiator is added to such an extent that the homeotropic orientation of the liquid crystalline composition is not disturbed in consideration of the type of the photopolymerized liquid crystal compound, the blending ratio of the liquid crystalline composition, and the like. Usually, about 0.5-30 weight part is preferable with respect to 100 weight part of photopolymerizable liquid crystal compounds. Particularly preferred is 3 parts by weight or more.
[0033]
Preparation of homeotropic alignment liquid crystal film is a state in which a homeotropic alignment side chain type liquid crystal polymer is coated on a substrate, and then the side chain type liquid crystal polymer is homeotropically aligned in a liquid crystal state and the alignment state is maintained. This is done by immobilizing with. When a homeotropic alignment liquid crystalline composition comprising the side chain liquid crystal polymer and the photopolymerizable liquid crystal compound is used, this is applied to a substrate, and then the liquid crystalline composition is homeomorphized in a liquid crystal state. A tropic alignment is performed, and light irradiation is performed while maintaining the alignment state. In producing the homeotropic alignment liquid crystal film, the front phase difference, the thickness direction phase difference, and the haze can be adjusted within the above ranges by appropriately changing the alignment temperature, treatment time, coating method, and the like.
[0034]
The substrate on which the side chain type liquid crystal polymer or liquid crystalline composition is applied may have any shape of a glass substrate, a metal foil, a plastic sheet, or a plastic film. The vertical alignment film may not be provided on the substrate. The thickness of the substrate is usually about 10 to 1000 μm.
[0035]
The plastic film is not particularly limited as long as it does not change with the orientation temperature. For example, polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, cellulose polymers such as diacetyl cellulose and triacetyl cellulose, polycarbonate polymers, polymethyl Examples thereof include a film made of a transparent polymer such as an acrylic polymer such as methacrylate. Styrene polymers such as polystyrene and acrylonitrile / styrene copolymers, polyethylene, polypropylene, polyolefins having a cyclic or norbornene structure, olefin polymers such as ethylene / propylene copolymers, vinyl chloride polymers, nylon and aromatic polyamides, etc. Examples thereof include films made of transparent polymers such as amide polymers. Furthermore, imide polymers, sulfone polymers, polyether sulfone polymers, polyether ether ketone polymers, polyphenylene sulfide polymers, vinyl alcohol polymers, vinylidene chloride polymers, vinyl butyral polymers, arylate polymers, polyoxymethylene polymers Examples thereof include a film made of a transparent polymer such as a polymer, an epoxy-based polymer, and a blend of the aforementioned polymers. Among these, the hydrogen bonding property is high, and plastic films such as triacetyl cellulose, polycarbonate, norbornene polyolefin and the like used as an optical film are awarded.
[0036]
Moreover, as a metal film, the said film formed from aluminum etc. is mentioned, for example.
[0037]
As plastic films, polymers having a norbornene structure such as ZEONOR (trade name, manufactured by ZEON CORPORATION), ZEONEX (trade name, manufactured by ZEON CORPORATION), Arton (trade name, manufactured by JSR Corporation), etc. A plastic film made of a substance has excellent optical properties.
[0038]
An anchor coat layer can be formed on the substrate on which the vertical alignment film is not provided. The anchor coat layer can improve the strength of the substrate, and can ensure good homeotropic orientation.
[0039]
As the anchor coat material, a metal alkoxide, particularly a metal silicon alkoxide sol is used. Metal alkoxides are usually used as alcoholic solutions. Since the anchor coat layer requires a uniform and flexible film, the thickness of the anchor coat layer is preferably about 0.04 to 2 μm, and more preferably about 0.05 to 0.2 μm.
[0040]
As a method for coating the anchor coating material on the substrate, for example, a roll coating method, a gravure coating method, a spin coating method, a bar coating method, or the like can be employed. After the coating, the solvent is removed, and the sol-gel reaction is accelerated by heating to form a transparent vitreous polymer film. A metal silicon alkoxide gel layer is formed from the metal silicon alkoxide sol. As a method for promoting solvent removal and reaction, drying at room temperature, drying in a drying furnace, heating on a hot plate, and the like are usually used.
[0041]
When the substrate has an anchor coat layer, a binder layer is provided between the substrate and the anchor coat layer, or a material that enhances adhesion to the substrate is contained in the anchor coat layer. The adhesion of the coat layer can be improved. Due to the improved adhesion between the substrate and the anchor coat layer, peeling easily occurs at the interface between the anchor coat layer and the liquid crystal film, and only the liquid crystal film can be easily peeled off.
[0042]
As the binder material used for forming the binder layer, a material capable of improving the adhesion between the substrate (particularly the polymer substance) and the anchor coat layer (transparent glassy polymer film) can be used without particular limitation. Examples of the binder material include a coupling agent. The coupling agent has a functional group that easily binds to both the substrate (particularly the polymer substance) and the anchor coat layer (transparent glassy polymer film). For example, the silane coupling agent, titanium coupling agent, zirconium A coupling agent etc. can be illustrated. Among these, the silane coupling agent has a great effect of improving adhesion. As a material that reinforces adhesion to the substrate, the above coupling agent can be used. A silane coupling agent is also suitable as the coupling agent.
[0043]
The binder material is appropriately diluted with a solvent and applied onto the substrate. As the coating method, for example, a roll coating method, a gravure coating method, a spin coating method, a bar coating method, or the like can be employed. As a method for removing the solvent after coating and promoting the reaction by heating, drying at room temperature, drying in a drying furnace, heating on a hot plate, or the like is usually used.
[0044]
The method of applying the side chain type liquid crystal polymer or liquid crystalline composition to the substrate (or the anchor coat layer of the substrate) is a solution coating using a solution in which the side chain type liquid crystal polymer or liquid crystalline composition is dissolved in a solvent. And a method of melting and coating the liquid crystal polymer or liquid crystalline composition. Among them, a solution of a side-chain liquid crystal polymer or liquid crystalline composition is applied onto a support substrate by a solution coating method. The method of working is preferred.
[0045]
The solvent used in preparing the solution varies depending on the type of the side chain type liquid crystal polymer, photopolymerizable liquid crystal compound and substrate, and cannot generally be said, but usually chloroform, dichloromethane, dichloroethane, tetrachloroethane, trichloroethylene, Halogenated hydrocarbons such as tetrachloroethylene and chlorobenzene, phenols such as phenol and parachlorophenol, aromatic hydrocarbons such as benzene, toluene, xylene, methoxybenzene, and 1,2-dimethoxybenzene, other acetone, acetic acid Ethyl, tert-butyl alcohol, glycerin, ethylene glycol, triethylene glycol, ethylene bricol monomethyl ether, diethylene glycol dimethyl ether, ethyl cellosolve, butyl cellosolve, 2-pyro Don, N- methyl-2-pyrrolidone, pyridine, triethylamine, tetrahydrofuran, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, can be used acetonitrile, butyronitrile, carbon disulfide, cyclohexanone and the like. Since the concentration of the solution depends on the solubility of the side chain type liquid crystal polymer or liquid crystalline composition to be used and the film thickness of the finally oriented liquid crystal layer, it cannot be generally stated, but usually 3 to 50% by weight, Preferably it is the range of 7-30 weight%.
[0046]
The thickness of the coated homeotropic alignment liquid crystal film made of the side chain liquid crystal polymer or liquid crystalline composition is preferably about 1 to 10 μm. In particular, when it is necessary to precisely control the film thickness of the homeotropic alignment liquid crystal film, the film thickness is almost determined at the stage of coating on the substrate, so control of the solution concentration, the film thickness of the coating film, etc. Need to pay special attention.
[0047]
Examples of the method for applying a solution of a side chain type liquid crystal polymer or liquid crystal composition adjusted to a desired concentration using the above-mentioned solvent on a substrate include a roll coating method, a gravure coating method, a spin coating method, A bar coat method or the like can be employed. After coating, the solvent is removed, and a liquid crystal polymer layer or a liquid crystal composition layer is formed on the substrate. The conditions for removing the solvent are not particularly limited, as long as the solvent can be generally removed and the liquid crystal polymer layer or the liquid crystal composition layer does not flow or even flow down. Usually, the solvent is removed by drying at room temperature, drying in a drying oven, heating on a hot plate, or the like. Among these coating methods, the gravure coating method is preferably used in the present invention because it is easy to uniformly coat a large area.
[0048]
Next, the side chain type liquid crystal polymer layer or liquid crystal composition layer formed on the supporting substrate is brought into a liquid crystal state and homeotropically aligned. For example, heat treatment is performed so that the side chain type liquid crystal polymer or the liquid crystalline composition is in the liquid crystal temperature range, and homeotropic alignment is performed in the liquid crystal state. The heat treatment can be performed by the same method as the above drying method. The heat treatment temperature varies depending on the type of the side chain type liquid crystal polymer or liquid crystalline composition to be used and the support substrate, and cannot be generally stated, but is usually in the range of 60 to 300 ° C, preferably 70 to 200 ° C. The heat treatment time varies depending on the heat treatment temperature and the type of the side chain type liquid crystal polymer or liquid crystal composition or substrate used, but cannot be generally stated, but is usually in the range of 10 seconds to 2 hours, preferably 20 seconds to 30 minutes. Selected. If it is shorter than 10 seconds, homeotropic alignment formation may not proceed sufficiently. Among these orientation temperatures and treatment times, in the present invention, it is preferable from the viewpoint of workability and mass productivity that the treatment time is about 30 seconds to 10 minutes at an orientation temperature of 80 to 150 ° C.
[0049]
After the heat treatment is completed, a cooling operation is performed. As the cooling operation, the homeotropic alignment liquid crystal film after the heat treatment can be performed by taking it out from the heating atmosphere in the heat treatment operation to room temperature. Moreover, you may perform forced cooling, such as air cooling and water cooling. The orientation of the homeotropic alignment layer of the side chain type liquid crystal polymer is fixed by cooling to the glass transition temperature or lower of the side chain type liquid crystal polymer.
[0050]
In the case of a liquid crystalline composition, the homeotropic liquid crystal alignment layer thus fixed is irradiated with light to polymerize or crosslink the photopolymerizable liquid crystal compound to fix the photopolymerizable liquid crystal compound, A homeotropic alignment liquid crystal layer with improved durability is obtained. Light irradiation is performed by, for example, ultraviolet irradiation. The ultraviolet irradiation conditions are preferably in an inert gas atmosphere in order to sufficiently promote the reaction. Usually, a high-pressure mercury ultraviolet lamp having an illuminance of about 80 to 160 mW / cm ² is typically used. Different types of lamps such as metahalide UV lamps and incandescent tubes can also be used. It should be noted that the liquid crystal layer surface temperature at the time of ultraviolet irradiation is appropriately adjusted by, for example, a cold mirror, water cooling or other cooling treatment, or by increasing the line speed.
[0051]
In this way, a thin film of a side chain type liquid crystal polymer or a liquid crystalline composition is produced, and a homeotropically aligned aligned liquid crystal layer is obtained by fixing while maintaining the alignment. The alignment liquid crystal layer has molecules aligned in the same direction. Therefore, it is well known that the alignment vector of this alignment liquid crystal layer can be frozen or stabilized and its anisotropic properties can be preserved. Such thin films have been confirmed for their optical properties and can be used in various applications. Is done. The alignment liquid crystal layer is a thin film having a uniaxial positive birefringence.
[0052]
The orientation of the homeotropic alignment liquid crystal layer obtained as described above can be quantified by measuring the optical phase difference of the liquid crystal layer at an angle inclined from normal incidence. In the case of homeotropic alignment liquid crystal layers, this retardation value is symmetric with respect to normal incidence. Several methods can be used to measure the optical phase difference. For example, an automatic birefringence measuring device (manufactured by Oak) and a polarizing microscope (manufactured by Olympus) can be used. This homeotropic alignment liquid crystal layer appears black between the crossed Nicol polarizers. Thus, homeotropic orientation was evaluated.
[0053]
Homeotropic alignment liquid crystal film thus obtained, the thickness d (nm), the main in-plane refractive index as n _x, n _y, and a refractive index in the thickness direction and n _z, and was n _x> n _y The average value of the front phase difference d, the average value of the thickness direction phase difference, the formula value (%) of the thickness direction phase difference, and the average value of haze are satisfied. In addition, when the thickness d (nm) of the homeotropic alignment liquid crystal film is about 1000 to 10000, nx = 1.45 to 1.70, ny = 1.45 to 1.65, nz = 1.50. ~ 1.75.
[0054]
The homeotropic alignment liquid crystal film is disposed between a cholesteric liquid crystal film and a quarter wave plate to form a brightness enhancement film. As the cholesteric liquid crystal film and the quarter-wave plate, various types used for the brightness enhancement film can be used without particular limitation.
[0055]
A cholesteric liquid crystal film is a characteristic that reflects either left-handed or right-handed circularly polarized light and transmits other light, such as an oriented film of a cholesteric liquid-crystal polymer or a film substrate on which the oriented liquid-crystal layer is supported. And the like showing. As the cholesteric liquid crystal film, for example, a film exhibiting circular dichroism in at least a partial band of visible light or a film exhibiting circular dichroism in a band of 200 nm or more of visible light is used. The cholesteric liquid crystal film can be formed of a cholesteric liquid crystal polymer containing an optically active group-containing monomer as a monomer unit. Since the pitch of the cholesteric liquid crystal changes based on the content of the monomer unit containing the optically active group, the circular dichroism can be controlled by the content of the monomer unit. The thickness of the cholesteric liquid crystal film is usually preferably 1 to 30 μm, and particularly preferably 2 to 15 μm. The cholesteric liquid crystal film may be blended with one or more additives such as polymers other than the liquid crystal polymer, stabilizers, inorganic compounds such as plasticizers, organic compounds, metals and compounds thereof, as necessary.
[0056]
A cholesteric liquid crystal film can be obtained by reflecting circularly polarized light in a wide wavelength range such as a visible light region by combining two or more layers with different reflection wavelengths in combination. Based on this, transmitted circularly polarized light in a wide wavelength range can be obtained.
[0057]
In the case of a brightness enhancement film that transmits circularly polarized light such as a cholesteric liquid crystal layer, it can be directly incident on a polarizer, but from the point of suppressing absorption loss, the circularly polarized light is linearly polarized through a retardation plate to obtain a polarizing plate. It is preferable to make it enter into. By using a quarter wave plate as the retardation plate, circularly polarized light can be converted into linearly polarized light.
[0058]
As the quarter wavelength plate, an appropriate retardation plate is used according to the purpose of use. The quarter wavelength plate can control two or more kinds of retardation plates to control optical characteristics such as retardation. As the retardation plate, a birefringent film formed by stretching a film made of an appropriate polymer such as polycarbonate, norbornene resin, polyvinyl alcohol, polystyrene, polymethyl methacrylate, polypropylene, other polyolefins, polyarylate, polyamide, Examples thereof include an alignment film made of a liquid crystal material such as a liquid crystal polymer, and an alignment layer of the liquid crystal material supported by the film. The thickness of the quarter-wave plate is usually preferably 0.5 to 200 μm, particularly preferably 1 to 100 μm.
[0059]
A retardation plate that functions as a quarter-wave plate in a wide wavelength range such as a visible light region exhibits, for example, a retardation layer that functions as a quarter-wave plate for light-color light having a wavelength of 550 nm and other retardation characteristics. It can be obtained by a method of superposing a retardation layer, 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 or more retardation layers.
[0060]
The brightness enhancement film can be produced, for example, by producing a homeotropic alignment liquid crystal film using a quarter-wave plate as a substrate, and further bonding a cholesteric liquid crystal film to the homeotropic alignment liquid crystal film via an adhesive layer. it can. In addition, a homeotropic alignment liquid crystal film produced on a substrate is transferred to a cholesteric liquid crystal film or a quarter-wave plate through an adhesive layer, and then a quarter-wave plate or a cholesteric that is not used for the transfer. A liquid crystal film can be produced by further bonding through an adhesive layer.
[0061]
The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer is not particularly limited. For example, an acrylic polymer, a silicone-based polymer, a polyester, a polyurethane, a polyamide, a polyether, a fluorine-based or rubber-based polymer is appropriately used as a base polymer. It can be selected and used. In particular, those having excellent optical transparency such as an acrylic pressure-sensitive adhesive, exhibiting appropriate wettability, cohesiveness, and adhesive pressure-sensitive adhesive properties, and being excellent in weather resistance, heat resistance and the like can be preferably used.
[0062]
The pressure-sensitive adhesive layer can be formed by an appropriate method. For example, a pressure sensitive adhesive solution of about 10 to 40% by weight in which a base polymer or a composition thereof is dissolved or dispersed in a solvent composed of a suitable solvent alone or a mixture such as toluene and ethyl acetate is prepared. A method of attaching it directly on the substrate or liquid crystal film by an appropriate development method such as a casting method or a coating method, or forming an adhesive layer on a separator according to the above and transferring it onto the liquid crystal layer The method to do. The pressure-sensitive adhesive layer includes, for example, natural and synthetic resins, in particular, tackifier resins, fillers and pigments made of glass fibers, glass beads, metal powders, other inorganic powders, colorants, You may contain the additive added to adhesion layers, such as antioxidant. Moreover, the adhesive layer etc. which contain microparticles | fine-particles and show light diffusibility may be sufficient.
[0063]
In addition, when transferring the said homeotropic alignment liquid crystal film formed on the board | substrate through an adhesive layer, a homeotropic alignment liquid crystal film can be surface-treated. The surface treatment means is not particularly limited, and a surface treatment method such as corona discharge treatment, sputtering treatment, low-pressure UV irradiation, or plasma treatment that can maintain the transparency of the liquid crystal film surface can be suitably employed. Among these surface treatment methods, corona discharge treatment is good.
[0064]
A polarizing plate is used for an optical film applied to an image display device such as a liquid crystal display device. The obtained homeotropic alignment liquid crystal film and brightness enhancement film are used by laminating optical films such as polarizing plates.
[0065]
A polarizing plate obtained by bonding a polarizing plate and a brightness enhancement film is usually provided on the back side of a liquid crystal cell. The brightness enhancement film reflects a linearly polarized light with a predetermined polarization axis or a circularly polarized light in a predetermined direction when natural light is incident due to a backlight such as a liquid crystal display device or reflection from the back side, and transmits other light. In addition, 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 to obtain transmitted light in a predetermined polarization state, and reflects light without transmitting the light other than the predetermined polarization state. The The light reflected on the surface of the brightness enhancement film is further inverted through a reflective layer or the like provided behind the brightness enhancement film and re-incident on the brightness enhancement film, and part or all of the light is transmitted as light having a predetermined polarization state. Luminance can be improved by increasing the amount of light transmitted through the enhancement film and increasing the amount of light that can be used for liquid crystal display image display or the like by supplying polarized light that is difficult to be absorbed by the polarizer. That is, when light is incident through the polarizer from the back side of the liquid crystal cell without using a brightness enhancement film, light having a polarization direction that does not coincide with the polarization axis of the polarizer is almost polarized. It is absorbed by the polarizer and does not pass through the polarizer. That is, although depending on the characteristics of the polarizer used, approximately 50% of the light is absorbed by the polarizer, and the amount of light that can be used for liquid crystal image display is reduced, 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 further inverted through a reflective layer provided on the rear side thereof. Repeatedly re-enter the brightness enhancement film, and the brightness enhancement film transmits only polarized light whose polarization direction is such that the polarization direction of light reflected and inverted between the two can pass through the polarizer. Therefore, light such as a backlight can be efficiently used for displaying an image on the liquid crystal display device, and the screen can be brightened.
[0066]
The polarizing plate usually has a protective film on one side or both sides of the polarizer. The polarizer is not particularly limited, and various types can be used. Examples of the polarizer include hydrophilic polymer films such as polyvinyl alcohol film, partially formalized polyvinyl alcohol film, and ethylene / vinyl acetate copolymer partially saponified film, and two colors such as iodine and dichroic dye. And polyene-based oriented films such as those obtained by adsorbing a volatile substance and uniaxially stretched, polyvinyl alcohol dehydrated products and polyvinyl chloride dehydrochlorinated products. Among these, those obtained by stretching a polyvinyl alcohol film and adsorbing and orienting a dichroic material (iodine, dye) are preferably used. The thickness of the polarizer is not particularly limited, but is generally about 5 to 80 μm.
[0067]
A polarizer obtained by dyeing a polyvinyl alcohol film with iodine and uniaxially stretching it can be produced, for example, by dyeing polyvinyl alcohol in an aqueous solution of iodine and stretching it 3 to 7 times the original length. If necessary, it can be immersed in an aqueous solution of boric acid or potassium iodide. Further, if necessary, the polyvinyl alcohol film may be immersed in water and washed before dyeing. In addition to washing the polyvinyl alcohol film surface with dirt and anti-blocking agents by washing the polyvinyl alcohol film with water, it also has the effect of preventing unevenness such as uneven coloring by swelling the polyvinyl alcohol film. is there. Stretching may be performed after dyeing with iodine, may be performed while dyeing, or may be dyed with iodine after stretching. The film can be stretched in an aqueous solution of boric acid or potassium iodide or in a water bath.
[0068]
The protective film provided on one side or both sides of the polarizer preferably has excellent transparency, mechanical strength, thermal stability, moisture shielding properties, isotropic properties, and the like. Examples of the material of the protective film 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, acrylonitrile / styrene copolymers, and the like. Examples thereof include styrene polymers such as (AS resin) and polycarbonate polymers. In addition, 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 polyamide, imide polymers, sulfone polymers , Polyether sulfone polymer, polyether ether ketone polymer, polyphenylene sulfide polymer, vinyl alcohol polymer, vinylidene chloride polymer, vinyl butyral polymer, arylate polymer, polyoxymethylene polymer, epoxy polymer, or the above Examples of polymers that form protective films include polymer blends. Other examples include films made of thermosetting or ultraviolet curable resins such as acrylic, urethane, acrylic urethane, epoxy, and silicone. Generally the thickness of a protective film is 500 micrometers or less, and 1-300 micrometers is preferable. In particular, the thickness is preferably 5 to 200 μm.
[0069]
As the protective film, a cellulose polymer such as triacetyl cellulose is preferable from the viewpoints of polarization characteristics and durability. A triacetyl cellulose film is particularly preferable. In addition, when providing a protective film in the both sides of a polarizer, the protective film which consists of the same polymer material may be used by the front and back, and the protective film which consists of a different polymer material etc. may be used. The polarizer and the protective film are usually in close contact with each other through an aqueous adhesive or the like. Examples of aqueous adhesives include polyvinyl alcohol adhesives, gelatin adhesives, vinyl latexes, aqueous polyurethanes, aqueous polyesters, and the like.
[0070]
As the protective film, a hard coat layer, an antireflection treatment, an anti-sticking treatment, or a treatment subjected to diffusion or anti-glare treatment can be used.
[0071]
Hard coat treatment is performed for the purpose of preventing scratches on the surface of the polarizing plate. For example, a cured film having excellent hardness and slipping properties with an appropriate ultraviolet curable resin such as acrylic or silicone is applied to the protective film. It can be formed by a method of adding to the surface. The antireflection treatment is performed for the purpose of preventing reflection of external light on the surface of the polarizing plate, and can be achieved by forming an antireflection film or the like according to the conventional art. Further, the anti-sticking treatment is performed for the purpose of preventing adhesion with an adjacent layer.
[0072]
The anti-glare treatment is applied for the purpose of preventing the outside light from being reflected on the surface of the polarizing plate and obstructing the visibility of the light transmitted through the polarizing plate. For example, the surface is roughened by a sandblasting method or an embossing method. It can be formed by imparting a fine concavo-convex structure to the surface of the protective film by an appropriate method such as a blending method of transparent particles. The fine particles to be included in the formation of the surface fine concavo-convex structure are, for example, conductive materials made of silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, antimony oxide or the like having an average particle size of 0.5 to 50 μm. In some cases, transparent fine particles such as inorganic fine particles, organic fine particles composed of a crosslinked or uncrosslinked polymer, and the like are used. When forming a surface fine uneven structure, the amount of 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 (viewing angle expanding function or the like) for diffusing the light transmitted through the polarizing plate to expand the viewing angle.
[0073]
The antireflection layer, antisticking layer, diffusion layer, antiglare layer, and the like can be provided on the protective film itself, or can be provided separately from the transparent protective layer as an optical layer.
[0074]
The polarizing plate can be used as an elliptically polarizing plate or a circularly polarizing plate on which retardation plates are laminated. The elliptically polarizing plate or the circularly polarizing plate will be described. These change the linearly polarized light into elliptically polarized light or circularly polarized light, change the elliptically polarized light or circularly polarized light into linearly polarized light, or change the polarization direction of the linearly polarized light. In particular, a so-called quarter wave plate is used as a retardation plate that changes linearly polarized light to circularly polarized light or changes circularly polarized light to linearly polarized light. The 1/2 wavelength plate is usually used when changing the polarization direction of linearly polarized light.
[0075]
The elliptically polarizing plate is effectively used for black-and-white display without coloring by compensating (preventing) the coloring (blue or yellow) caused by the birefringence of the liquid crystal layer of the Spirsist nematic (STN) type liquid crystal display device. It is done. Further, the one in which the three-dimensional refractive index is controlled is preferable because it can compensate (prevent) coloring that occurs when the screen of the liquid crystal display device is viewed from an oblique direction. 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 an antireflection function.
[0076]
As the phase difference plate, for example, various wavelength plates or those for the purpose of compensating for coloring or viewing angle due to birefringence of the liquid crystal layer can be used, and two types having an appropriate phase difference according to the purpose of use. Optical properties such as retardation can be controlled by laminating the above retardation plates. As such a retardation plate, those exemplified above can be used, and the homeotropic alignment liquid crystal film of the present invention can be used alone or in combination with other films.
[0077]
The retardation plate is laminated on a polarizing plate as a viewing angle compensation film and used as a wide viewing angle polarizing plate. The viewing angle compensation film is a film for widening the viewing angle so that an image can be seen relatively clearly even when the screen of the liquid crystal display device is viewed from a slightly oblique direction rather than perpendicular to the screen.
[0078]
As such a viewing angle compensation retardation plate, a birefringent film that has been biaxially stretched or stretched in two orthogonal directions, a bidirectionally stretched film such as a tilted orientation film, and the like are used. Examples of the inclined alignment film include a film obtained by bonding a heat shrink film to a polymer film and stretching or / and shrinking the polymer film under the action of the contraction force by heating, or a film obtained by obliquely aligning a liquid crystal polymer. Can be mentioned. The viewing angle compensation film can be appropriately combined for the purpose of preventing coloring or the like due to a change in viewing angle based on a phase difference caused by a liquid crystal cell or increasing the viewing angle for good viewing.
[0079]
In addition, from the viewpoint of achieving a wide viewing angle with good visibility, an optical compensation position in which an alignment layer of a liquid crystal polymer, particularly an optically anisotropic layer composed of a tilted alignment layer of a discotic liquid crystal polymer, is supported by a triacetyl cellulose film. A phase difference plate can be preferably used.
[0080]
In addition to the above, the optical layer laminated in practical use is not particularly limited. For example, one or more optical layers that may be used for forming a liquid crystal display device such as a reflective plate or a transflective plate are used. Can do. In particular, a reflective polarizing plate or a semi-transmissive polarizing plate in which a reflecting plate or a semi-transmissive reflecting plate is further laminated on an elliptical polarizing plate or a circular polarizing plate can be given.
[0081]
A reflective polarizing plate is a polarizing plate provided with a reflective layer, and is used to form a liquid crystal display device or the like that reflects incident light from the viewing side (display side). Such a light source can be omitted, and the liquid crystal display device can be easily thinned. 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 as necessary.
[0082]
Specific examples of the reflective polarizing plate include those in which a reflective layer is formed by attaching a foil or vapor-deposited film made of a reflective metal such as aluminum on one surface of a protective film matted as necessary. In addition, the protective film may contain fine particles to form a surface fine concavo-convex structure and a reflective layer having a fine concavo-convex structure thereon. The reflective layer having the fine concavo-convex structure has an advantage that incident light is diffused by irregular reflection to prevent directivity and glaring appearance and to suppress unevenness in brightness and darkness. Moreover, the protective film containing fine particles also has an advantage that incident light and its reflected light are diffused when passing through it and light and dark unevenness can be further suppressed. The reflective layer with a fine concavo-convex structure reflecting the surface fine concavo-convex structure of the protective film is transparently protected by an appropriate method such as a vapor deposition method such as a vacuum deposition method, an ion plating method, a sputtering method, or a plating method. It can be performed by a method of attaching directly to the surface of the layer.
[0083]
The reflective plate can be used as a reflective sheet in which a reflective layer is provided on an appropriate film according to the transparent film, instead of the method of directly imparting to the protective film of the polarizing plate. Since the reflective layer is usually made of metal, the usage form in which the reflective surface is covered with a protective film, a polarizing plate or the like is used to prevent a decrease in reflectance due to oxidation, and thus the long-term sustainability of the initial reflectance. More preferable is the point of avoiding the additional attachment of the protective layer.
[0084]
The semi-transmissive polarizing plate can be obtained by using a semi-transmissive reflective layer such as a half mirror that reflects and transmits light with the reflective layer. A transflective polarizing plate is usually provided on the back side of a liquid crystal cell, and displays an image by reflecting incident light from the viewing side (display side) when a liquid crystal display device is used in a relatively bright atmosphere. In a relatively dark atmosphere, a liquid crystal display device or the like that displays an image using a built-in light source such as a backlight built in the back side of the transflective polarizing plate can be formed. In other words, the transflective polarizing plate is useful for forming a liquid crystal display device of a type that can save energy of using a light source such as a backlight in a bright atmosphere and can be used with a built-in light source even in a relatively dark atmosphere. It is.
[0085]
Further, the polarizing plate may be formed by laminating a polarizing plate and two or three or more optical layers like the above-described polarization separation type polarizing plate. Therefore, a reflective elliptical polarizing plate or a semi-transmissive elliptical polarizing plate in which the above-mentioned reflective polarizing plate or transflective polarizing plate and a retardation plate are combined may be used.
[0086]
The elliptically polarizing plate and the reflective elliptical polarizing plate are obtained by laminating a polarizing plate or a reflective polarizing plate and a retardation plate in an appropriate combination. Such an elliptical polarizing plate can be formed by sequentially laminating them in the manufacturing process of the liquid crystal display device so as to be a combination of a (reflective) polarizing plate and a retardation plate. An optical film such as an elliptically polarizing plate is advantageous in that it can improve the production efficiency of a liquid crystal display device and the like because of excellent quality stability and lamination workability.
[0087]
The optical film of the present invention can be provided with an adhesive layer. The pressure-sensitive adhesive layer can be used for adhering to a liquid crystal cell and also used for laminating optical layers. When adhering the optical films, their optical axes can be set at an appropriate arrangement angle in accordance with the target retardation characteristics.
[0088]
Although the adhesive which forms an adhesive layer is not restrict | limited in particular, The thing similar to what was used for bonding of the said homeotropic alignment liquid crystal layer and a translucent film can be illustrated. Moreover, it can provide by the same system.
[0089]
The pressure-sensitive adhesive layer can be provided on one side or both sides of a polarizing plate or an optical film as a superimposed layer of different compositions or types. Moreover, when providing in both surfaces, it can also be set as the adhesion layers of a different composition, a kind, thickness, etc. in the front and back of a polarizing plate or an optical film. The thickness of the pressure-sensitive adhesive layer can be appropriately determined according to the purpose of use and adhesive force, and is generally 1 to 500 μm, preferably 5 to 200 μm, particularly preferably 10 to 100 μm.
[0090]
On the exposed surface of the adhesive layer, a separator is temporarily attached and covered for the purpose of preventing contamination until it is put to practical use. Thereby, it can prevent contacting an adhesion layer in the usual handling state. As the separator, except for the above thickness conditions, for example, a suitable thin leaf body such as a plastic film, rubber sheet, paper, cloth, non-woven fabric, net, foam sheet, metal foil, laminate thereof, and the like, silicone type or Appropriate ones according to the prior art, such as those coated with an appropriate release agent such as a long mirror alkyl type, fluorine type or molybdenum sulfide, can be used.
[0091]
In the present invention, the polarizer, transparent protective film, optical film, and the like that form the polarizing plate described above, and each layer such as an adhesive layer include, for example, salicylic acid ester compounds, benzophenol compounds, benzotriazole compounds, and cyanoacrylates. It may be a compound having an ultraviolet absorbing ability by a method such as a method of treating with an ultraviolet absorber such as a compound based on nickel or a nickel complex salt compound.
[0092]
The optical film of the present invention can be preferably used for forming various devices such as a liquid crystal display device. The liquid crystal display device can be formed according to the conventional method. In other words, a liquid crystal display device is generally formed by appropriately assembling components such as a liquid crystal cell, an optical film, and an illumination system as necessary, and incorporating a drive circuit. There is no limitation in particular except the point which uses a film, and it can apply according to the former. As the liquid crystal cell, any type such as a TN type, an STN type, or a π type can be used.
[0093]
An appropriate liquid crystal display device such as a liquid crystal display device in which a polarizing plate or an optical film is disposed on one side or both sides of a liquid crystal cell, or a backlight or a reflector used in an illumination system can be formed. In that case, the optical film according to the present invention can be installed on one side or both sides of the liquid crystal cell. When providing a polarizing plate and an optical film on both sides, they may be the same or different. Further, when forming a liquid crystal display device, for example, a single layer or a suitable part such as a diffusing plate, an antiglare layer, an antireflection film, a protective plate, a prism array, a lens array sheet, a light diffusing plate, a backlight, etc. Two or more layers can be arranged.
[0094]
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 emitter (organic electroluminescent light emitter). 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 and 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 laminate of such a light emitting layer and an electron injection layer composed of a perylene derivative or the like, or a laminate of these hole injection layer, light emitting layer, and electron injection layer is known. It has been.
[0095]
In organic EL display devices, holes and electrons are injected into the organic light-emitting layer by applying a voltage to the transparent electrode and the metal electrode, and the energy generated by recombination of these holes and electrons excites the phosphor material. Then, light is emitted on the principle that the excited fluorescent material emits light when returning to the ground state. The mechanism of recombination in the middle is the same as that of a general diode, and as can be predicted from this, the current and the emission intensity show strong nonlinearity with rectification with respect to the applied voltage.
[0096]
In an organic EL display device, in order to extract light emitted from the organic light emitting layer, at least one of the electrodes must be transparent, and a transparent electrode usually formed of a transparent conductor such as indium tin oxide (ITO) is used as an anode. It is used as. 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.
[0097]
In the organic EL display device having such a configuration, the organic light emitting layer is formed of a very 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, light that is incident from the surface of the transparent substrate at the time of non-light emission, passes through the transparent electrode and the organic light emitting layer, and is reflected by the metal electrode is again emitted to the surface side of the transparent substrate. The display surface of the organic EL display device looks like a mirror surface.
[0098]
In an organic EL display device comprising an organic electroluminescent light emitting device comprising a transparent electrode on the surface side of an organic light emitting layer that emits light upon application of a voltage and a metal electrode on the back side of the organic light emitting layer, the surface of the transparent electrode While providing a polarizing plate on the side, a retardation plate can be provided between the transparent electrode and the polarizing plate.
[0099]
Since the retardation plate and the polarizing plate have a function of polarizing light 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 by the polarization action. In particular, the mirror surface of the metal electrode can be completely shielded by configuring the retardation plate with a quarter-wave plate and adjusting the angle between the polarization direction of the polarizing plate and the retardation plate to π / 4. .
[0100]
That is, only the linearly polarized light component of the external light incident on the organic EL display device is transmitted by the polarizing plate. This linearly polarized light becomes generally elliptically polarized light by the retardation plate, but becomes circularly polarized light especially when the retardation plate is a quarter-wave plate and the angle between the polarization direction of the polarizing plate and the retardation plate is π / 4. .
[0101]
This circularly polarized light is transmitted through the transparent substrate, the transparent electrode, and the organic thin film, is reflected by the metal electrode, is again transmitted through the organic thin film, the transparent electrode, and the transparent substrate, and becomes linearly polarized light again on the retardation plate. And since this linearly polarized light is orthogonal to the polarization direction of a polarizing plate, it cannot permeate | transmit a polarizing plate. As a result, the mirror surface of the metal electrode can be completely shielded.
[0102]
【Example】
Examples of the present invention will be described below with reference to examples, but the present invention is not limited to the examples.
[0103]
Example 1
Ethyl acetate in ethyl acetate and 2% isopropyl alcohol (trade name Colcoat P, Colcoat Co., Ltd.) as a sol solution for anchor coating on a plastic film made of polyethylene terephthalate (made by Toray Industries, Inc., thickness 50 μm) Made by gravure roll coating. Subsequently, it heated at 130 degreeC for 30 second (s), and formed the transparent glassy polymer film (0.08 micrometer) which is an anchor coat layer.
[0104]
[Chemical 6]
5 parts by weight of a side chain type liquid crystal polymer represented by the above chemical formula 6 (the number in the formula represents the mol% of the monomer unit and is expressed in block form for convenience), and a nematic liquid crystal layer. 20 parts by weight of a photopolymerizable liquid crystal compound (BASF, Paliocolor LC242) and 5% by weight of a photopolymerization initiator (Ciba Specialty Chemicals, Irgacure 907) (photopolymerizable liquid crystal compound) were dissolved in 75 parts by weight of cyclohexanone. The solution was applied by bar coating on the anchor coat layer provided on the film substrate. Subsequently, it heated at 80 degreeC for 2 minute (s), the homeotropic alignment liquid crystal film (thickness 1.9 micrometers) was formed by irradiating an ultraviolet-ray with the said liquid crystal layer maintaining homeotropic alignment.
[0105]
Examples 2-3 and Reference Examples 1-3
A homeotropic alignment liquid crystal film was prepared in the same manner as in Example 1 except that the alignment temperature, the treatment time, the solvent of the coating solution, and the thickness of the anchor coat layer were changed as shown in Table 1. Produced.
[0106]
[Table 1]
[0107]
Examples and the homeotropic alignment liquid crystal film obtained in Reference Example, the principal refractive indices n _x in the film plane and the thickness direction, n _y, n _z automatic birefringence measuring apparatus (Oji Scientific Instruments Co., Auto Measured with a birefringence meter KOBRA21ADH), and from the results, the front phase difference (maximum value, minimum value, average value), thickness direction phase difference and formula: {(maximum value-minimum value) / average value} × 100 (% ), And derived the value required. The results are shown in Table 2. Moreover, the haze (maximum value, minimum value, average value) was calculated | required with the haze meter HM-150 made from Murakami Color Research Laboratory. The results are shown in Table 2.
[0108]
(Production of brightness enhancement film)
Using a triacetate film (80 μm) formed with a 5 μm cholesteric liquid crystal layer exhibiting circular dichroism in a band of 400 to 700 nm, the homeotropic alignment obtained in the examples or reference examples is formed on the liquid crystal layer. A liquid crystal film was bonded through an adhesive layer (25 μm) formed of an acrylic adhesive, and a 1/4 wavelength plate (front retardation 130 nm) having a polycarbonate film stretched and oriented thereon was added to the same acrylic film. The film was bonded via an adhesive layer (25 μm) formed of a system adhesive to produce a brightness enhancement film.
[0109]
(Evaluation methods)
As shown in FIG. 1, a brightness enhancement film (cholesteric liquid crystal film: homeotropic alignment liquid crystal film: 1/4 wavelength plate), a polarizing plate, a liquid crystal cell, and a liquid crystal display arranged in this order on the backlight are used. The luminance (cd / m ² ) in the front direction was measured using a luminance meter (BM-7 manufactured by Topcon Corporation). In addition, the presence or absence of unevenness in the oblique viewing angle direction (angle 45 °) was visually evaluated. The results are shown in Table 2. In addition, the example at the time of not using a brightness improvement film as a comparative example 1 is given, and the brightness improvement rate with respect to this is collectively shown in Table 2.
[0110]
[Table 2]

[Brief description of the drawings]
FIG. 1 is a conceptual diagram of a liquid crystal display used in an example.

Claims (7)

The thickness d (nm), the main in-plane refractive index as n _x, n _y, and a refractive index in the thickness direction and n _z, and when the n _x> n _y, front retardation: △ n _xy (n _x -n _y) is the average value of × d is 10nm or less, a thickness direction _{retardation: △ n zx (n z -n} x) average of × d is 50 to 400 nm, and the thickness direction retardation: △ For n _zx × d, the homeotropic orientation is such that the value obtained by the formula: {(maximum value−minimum value) / average value} × 100 (%) is 10 or less and the average value of haze is 3% or less. A liquid crystal film,
The homeotropic alignment liquid crystal film has a general formula (a) as a monomer unit (a) containing a liquid crystalline fragment side chain:
(Wherein R ¹ represents a hydrogen atom or a methyl group, a represents a positive integer of 1 to 6, X ¹ represents a —CO ₂ — group or —OCO— group, R ² represents a cyano group, and has 1 to 6 carbon atoms. An alkoxy group, a fluoro group, or an alkyl group having 1 to 6 carbon atoms, b and c each represent an integer of 1 or 2, and a monomer unit having a side chain having nematic liquid crystallinity,
As the monomer unit (b) containing a non-liquid crystalline fragment side chain, the general formula (b):
(However, R ³ is a hydrogen atom or a methyl group, R ⁴ is an alkyl group having 7 to 22 carbon atoms, a fluoroalkyl group having 1 to 22 carbon atoms, or the general formula (c):
However, d is a positive integer from 1 to 6, R ⁵ represents an alkyl group having 1 to 6 carbon atoms. And a side chain type liquid crystal polymer containing a monomer unit having a linear side chain represented by the formula:   The homeotropic alignment liquid crystal film according to claim 1, wherein the homeotropic alignment liquid crystal film is formed of a homeotropic alignment liquid crystal composition obtained by blending a photopolymerizable liquid crystal compound with the side chain liquid crystal polymer. the film.   The ratio of the monomer unit (a) to the monomer unit (b) in the side chain type liquid crystal polymer is (b) / {(a) + (b)} = 0.01 to 0.8 (molar ratio). The homeotropic alignment liquid crystal film according to claim 1 or 2. The difference between the maximum value and the minimum value of front phase difference: Δn _xy × d is 5 nm or less, and the difference between the maximum value and the minimum value of haze is 2% or less. A homeotropic alignment liquid crystal film according to claim 1.   5. A brightness enhancement film, wherein the homeotropic alignment liquid crystal film according to claim 1 is disposed between a cholesteric liquid crystal film and a quarter-wave plate.   An optical film, wherein at least one optical film is further laminated on the homeotropic alignment liquid crystal film according to any one of claims 1 to 4 or the brightness enhancement film according to claim 5.   An image display device to which the homeotropic alignment liquid crystal film according to claim 1, the brightness enhancement film according to claim 6, or the optical film according to claim 4 is applied.