JP2003177242A - Homeotropically aligned liquid crystal film, brightness heightening film and optical film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a homeotropically aligned liquid crystal film which improves brightness heightening characteristics when applied to a brightness heightening film and which improves unevenness in viewing angle characteristics. <P>SOLUTION: When thickness, in-plane principal refractive indexes and a refractive index in a thickness direction are represented by d (nm), n<SB>x</SB>, n<SB>y</SB>and n<SB>z</SB>respectively and an inequality n<SB>x</SB>>n<SB>y</SB>holds, the homeotropically aligned liquid crystal film is characterized by having a mean value of in-plane retardation Δn<SB>xy</SB>(n<SB>x</SB>-n<SB>y</SB>)×d to be 10 nm or less, a mean value of retardation in the thickness direction Δn<SB>zx</SB>(n<SB>z</SB>-n<SB>x</SB>)×d to be 30-500 nm and a value calculated with a formula ä(the maximum value - the minimum value)/the mean value}×100 (%) for the retardation in the thickness direction Δn<SB>zx</SB>×d to be 10 or less and further a mean value of haze to be 3% or less. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a homeotropically aligned liquid crystal film. The homeotropic alignment liquid crystal film of the present invention can be used alone or in combination with other optical films as an optical film such as a retardation film, a viewing angle compensation film, an optical compensation film, an elliptically polarizing film and a brightness enhancement film. In particular, the homeotropic alignment liquid crystal film of the present invention provided between the cholesteric liquid crystal film and the 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, a PDP or the like using the optical film such as the homeotropic alignment liquid crystal film or the brightness enhancement film.

[0002]

2. Description of the Related Art Homeotropic alignment of liquid crystal molecules is that the major axis of the liquid crystal molecules is aligned substantially perpendicular to the substrate. It is well known that homeotropic alignment can be obtained by putting liquid crystal in two glass substrates and applying an electric field like a liquid crystal display, but it is very difficult to make this alignment state into a film. difficult.

In US Pat. No. 5,731,886, a reflective polarizing plate having improved viewing angle characteristics can be obtained by using a brightness enhancement film in which a homeotropically aligned liquid crystal layer is arranged between a cholesteric liquid crystal layer and a quarter wavelength plate. Is described. However, it is difficult to control the alignment state of the homeotropic alignment liquid crystal layer, and variations occur in the alignment state.Therefore, if the alignment state is not well controlled, unevenness in the viewing angle characteristics will be confirmed. There is.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a homeotropic alignment liquid crystal film which has improved brightness enhancement characteristics and unevenness in viewing angle characteristics when applied to a brightness enhancement film. It is another object of the present invention to provide a brightness enhancement film or an optical film using the homeotropic alignment liquid crystal film, and an image display device using the optical film such as the homeotropic alignment liquid crystal film or the brightness enhancement film.

[0005]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that the above-mentioned object can be achieved by the homeotropically aligned liquid crystal film shown below, and have completed the present invention. I arrived.

That is, according to the present invention, the thickness d (nm), the surface
The main refractive index inside is n_x , N_y And the refractive index in the thickness direction is n
_z And n_x > N_y , The front phase difference: Δn
_xy(N_x -N_y ) × d has an average value of 10 nm or less,
Thickness direction retardation: △ n_zx(N _z -N_x ) × d average value
30 to 500 nm and thickness direction retardation: Δn _zx
For xd, the formula: {(maximum value−minimum value) / average value} ×
The value obtained by 100 (%) is 10 or less,
Moreover, homeo characterized by haze of 3% or less
A tropic alignment liquid crystal film.

When a homeotropic alignment liquid crystal film is applied 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 wavelength plate, and Since it becomes difficult to convert the circularly polarized light obtained in step 1 into linearly polarized light and it becomes impossible to sufficiently exhibit the brightness improving characteristics, the homeotropic aligned liquid crystal film of the present invention is controlled to have an average front phase difference of 10 nm or less. I am using The smaller the average value of the front phase difference is, the more preferable it is.
Further, those having a thickness of 3 nm or less are preferable.

Further, the retardation in the thickness direction is preferably adjusted to an appropriate retardation by matching with a cholesteric liquid crystal, and the average value of the retardation in the thickness direction is 3.
It is controlled to 0 to 500 nm, preferably 50 to 400 nm, and more preferably 100 to 400 nm. 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, the formula: {(maximum value-minimum value) / average value} × 100 (%) Is 10 or less, the variation of the alignment state is controlled to be small, and the alignment state is stable. The expression value is preferably 8 or less, more preferably 5 or less.

Moreover, since the transmitted light is diffused as the haze increases and the front luminance is lowered, the average value of the haze is controlled to 3% or less. The average haze value is preferably 2% or less, more preferably 1% or less.

As described above, in the homeotropic alignment liquid crystal film of the present invention, the alignment state is stabilized and uniform alignment is achieved in the plane by controlling the variations of the front retardation, the thickness direction retardation and the haze. In addition, it has improved brightness enhancement characteristics when applied to a brightness enhancement film, and also improves unevenness in viewing angle characteristics.

In the homeotropic alignment liquid crystal film, the difference between the maximum value and the minimum value of the front phase difference: Δn _xy × d is 5 nm or less, and the difference between the maximum value and the minimum value of the haze is 2.
% Or less is preferable.

As for the difference between the maximum and minimum values of the front phase difference and the difference between the maximum and minimum values of the haze, the smaller the orientation, the more stable the alignment state, and when applied to the brightness enhancement film, the brightness enhancement characteristics, It is preferable in terms of improving unevenness in viewing angle characteristics. The difference between the maximum value and the minimum value of the front phase difference is 3 nm or less,
Further, it is preferably 2 nm or less. Further, the difference between the maximum value and the minimum value of haze is preferably 1% or less, and more preferably 0.5%.

According to the present invention, the homeotropic alignment liquid crystal film comprises a cholesteric liquid crystal film,
It relates to a brightness enhancement film, which is arranged between a four-wave plate and a four-wave plate.

The present invention also relates to an optical film characterized in that at least one optical film is further laminated on the homeotropically aligned liquid crystal film or the brightness enhancement film.

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]

BEST MODE FOR CARRYING OUT THE INVENTION As the homeotropic alignment liquid crystal film of the present invention, those having the characteristics relating to the above-mentioned front phase difference, thickness direction phase difference and haze can be used without particular limitation, but the homeotropic alignment liquid crystal film of the present invention can be used. Is, for example, a side chain type liquid crystal polymer having a positive refractive index anisotropy and containing a monomer unit (a) containing a liquid crystal fragment side chain and a monomer unit (b) containing a non-liquid crystal fragment side chain. Can be formed by.

The side chain type 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 crystal fragment side chain having an alkyl chain or the like in addition to the monomer unit (a) containing a liquid crystal fragment side chain which a normal side chain type liquid crystal polymer has. By virtue of the action of the monomer unit (b) having (b) and containing a non-liquid crystal fragment side chain, a nematic liquid crystal phase is brought into a liquid crystal state by, for example, heat treatment and a nematic liquid crystal phase is exhibited by using a homeoalignment film, thereby producing homeo It is inferred that the tropic orientation was exhibited.

The monomer unit (a) has a side chain having nematic liquid crystallinity, and is represented by, for example, the general formula (a):

[Chemical 1] (However, R ¹ is a hydrogen atom or a methyl group, and a is 1 to
6 positive integer of, X ¹ is -CO ₂ - group or a -OCO-
R ² is a cyano group, an alkoxy group having 1 to 6 carbon atoms,
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. ) A monomer unit represented by

The monomer unit (b) has a linear side chain, and has, for example, the general formula (b):

[Chemical 2] (However, R ³ is a hydrogen atom or a methyl group, R ⁴ is an alkyl group having 1 to 22 carbon atoms, a fluoroalkyl group having 1 to 22 carbon atoms, or general formula (b1):

[Chemical 3] However, d is a positive integer of 1 to 6, and R ⁵ is a carbon number of 1 to 6.
Is an alkyl group. ) A monomer unit represented by

Further, the ratio of the monomer unit (a) and the monomer unit (b) is not particularly limited and varies depending on the kind of the monomer unit, but when the ratio of the monomer unit (b) increases, the side chain type Since the liquid crystal polymer no longer exhibits liquid crystal monodomain alignment,
It is preferable that (b) / {(a) + (b)} = 0.01 to 0.8 (molar ratio). In particular, it is more preferably 0.1 to 0.5.

As the liquid crystal polymer capable of forming a homeotropic alignment liquid crystal film, the monomer unit (a) containing a liquid crystal fragment side chain and the monomer unit containing a liquid crystal fragment side chain having an alicyclic ring structure are mentioned. An example is a side chain type liquid crystal polymer containing (c).

According to the side chain type liquid crystal polymer, homeotropic alignment of the liquid crystal polymer can be realized without using a vertical alignment film. The side chain type liquid crystal polymer is
In addition to a monomer unit (a) containing a liquid crystal fragment side chain that a normal side chain type liquid crystal polymer has, a monomer unit (c) containing a liquid crystal fragment side chain having an alicyclic ring structure is included. Therefore, it is presumed that, due to the action of the monomer unit (c), a nematic liquid crystal phase is brought into a liquid crystal state by, for example, heat treatment and a homeotropic alignment is exhibited even without using a vertical alignment film.

The monomer unit (c) has a side chain having nematic liquid crystallinity, and is represented by, for example, the general formula (c):

[Chemical 4] (However, R ⁶ hydrogen atom or methyl group, h is 1 to 6
, A positive integer of X ^2, a —CO ₂ — group or a —OCO— group, e and g are integers of 1 or 2, f is an integer of 0 to 2, R ⁷ is a cyano group, and has 1 carbon atom. ~ 12 alkyl groups are shown. ) A monomer unit represented by

The ratio of the monomer unit (a) to the monomer unit (c) is not particularly limited and varies depending on the kind of the monomer unit, but as the ratio of the monomer unit (c) increases, the side chain type Since the liquid crystal polymer no longer exhibits liquid crystal monodomain alignment,
It is preferable that (c) / {(a) + (c)} = 0.01 to 0.8 (molar ratio). In particular, it is more preferably 0.1 to 0.6.

The liquid crystal polymer capable of forming the homeotropic alignment liquid crystal layer is not limited to the one having the above-exemplified monomer unit, and the above-mentioned monomer units can be appropriately combined.

The weight average molecular weight of the side chain type liquid crystal polymer is preferably 2,000 to 100,000. The performance as a liquid crystal polymer is exhibited by adjusting the weight average molecular weight within such a range. If 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 2.5 thousand 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 tends to be difficult to form a uniform alignment state. Therefore, the weight average molecular weight is more preferably 50,000 or less.

The above-mentioned side chain type liquid crystal polymer is
It can be prepared by copolymerizing an acrylic monomer or a methacrylic monomer corresponding to the monomer unit (a), the monomer unit (b) and the monomer unit (c). The monomers corresponding to the monomer unit (a), the monomer unit (b) and the monomer unit (c) can be synthesized by a known method. The copolymer can be prepared according to a conventional polymerization method of acrylic monomers such as a radical polymerization method, a cationic polymerization method, and an anionic polymerization method. When the radical polymerization method is applied, various polymerization initiators can be used, but among them, the decomposition temperature of azobisisobutyronitrile, benzoyl peroxide, etc. is neither high nor low and decomposes at an intermediate temperature. Those are preferably used.

A photopolymerizable liquid crystal compound may be blended with the side chain type liquid crystal polymer to be used as a liquid crystal composition. Since the side chain type liquid crystal polymer can form a film on a substrate without using a vertical alignment film, the liquid crystal film is designed to have a low Tg. In order to improve the durability of these liquid crystal films that can be used for applications such as liquid crystal displays, it is preferable to use a homeotropically aligned liquid crystal composition containing a photopolymerizable liquid crystal compound. After the homeotropic alignment liquid crystalline composition is aligned, it is irradiated with light such as ultraviolet rays.

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 a prize. To be done. Examples of the photopolymerizable liquid crystal compound include acrylate and methacrylate that serve as the monomer unit (a). As the photopolymerizable liquid crystal compound, those having two or more photopolymerizable functional groups are preferable in order to improve durability. As such a photopolymerizable liquid crystal compound, for example,
The following formula 5:

[Chemical 5] (In the formula, R is a hydrogen atom or a methyl group, and A and D are each independently a 1,4-phenylene group or a 1,4-phenylene group.
The cyclohexylene group and X are each independently -COO.
-Group, -OCO- group or -O- group, B is 1,4-phenylene group, 1,4-cyclohexylene group, 4,4'-
A biphenylene group or a 4,4′-bicyclohexylene group, and m and n each independently represent an integer of 2 to 6. The cross-linked nematic liquid crystal monomer represented by the formula () can be exemplified. Further, as the photopolymerizable liquid crystal compound, a compound in which the terminal “H ₂ C═CR—CO ₂ —” in Chemical formula 5 above is substituted with a vinyl ether group or an epoxy group,
"- (CH _{2) m} -" and / or "- (CH _{2) n}
- "and" ^{_{- (CH 2) 3 -C *}} H (CH 3) - (C
H _{2) 2} - "or" ^{_{- (CH 2) 2 -C *}} H (CH
_{3) - (CH 2) 3} - The compound was replaced with "can be exemplified.

The above-mentioned photopolymerizable liquid crystal compound can be brought into a liquid crystal state by heat treatment, for example, by causing a nematic liquid crystal layer to be developed and homeotropically aligned with a side chain type liquid crystal polymer, and then the photopolymerizable liquid crystal compound is polymerized or By crosslinking, the durability of the homeotropically aligned liquid crystal film can be improved.

The ratio of the photopolymerizable liquid crystal compound to the side chain type liquid crystal polymer in the liquid crystal composition is not particularly limited and may be appropriately determined in consideration of the durability of the homeotropically aligned liquid crystal film obtained. Usually, a photopolymerizable liquid crystal compound: side chain type liquid crystal polymer (weight ratio) is preferably about 0.1: 1 to 30: 1, particularly preferably 0.5: 1 to 20: 1,
Furthermore, 1: 1-10: 1 is preferable.

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 (IrCure manufactured by Ciba Specialty Chemicals).
gacure) 907, ibid 184, ibid 651, ibid 369
Can be exemplified. The addition amount of the photopolymerization initiator is determined in consideration of the type of the photopolymerization liquid crystal compound, the compounding ratio of the liquid crystal composition, and the like.
It is added to such an extent that the homeotropic alignment of the liquid crystal composition is not disturbed. Usually, about 0.5 to 30 parts by weight is preferable with respect to 100 parts by weight of the photopolymerizable liquid crystal compound. Especially 3
It is preferably at least part by weight.

The homeotropically aligned liquid crystal film is produced by coating a substrate with a side chain type liquid crystal polymer having homeotropic alignment, then subjecting the side chain type liquid crystal polymer to homeotropic alignment in the liquid crystal state, and then changing the alignment state. It is carried out by immobilizing it while maintaining it. When a homeotropic alignment liquid crystalline composition containing the side chain type liquid crystal polymer and a photopolymerizable liquid crystal compound is used,
After applying this to a substrate, the liquid crystalline composition is then homeotropically aligned in the liquid crystal state, and light irradiation is carried out while maintaining the aligned 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, the treatment time, the coating method, and the like.

The substrate on which the side chain type liquid crystal polymer or the liquid crystalline composition is applied may be in the form 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.

The plastic film is not particularly limited as long as it does not change at the orientation temperature, and examples thereof include polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, diacetyl cellulose,
Examples of the film include a transparent polymer such as a cellulose-based polymer such as triacetyl cellulose, a polycarbonate-based polymer, and an acrylic-based polymer such as polymethylmethacrylate. Further, polystyrene, styrene-based polymers such as acrylonitrile-styrene copolymer, polyethylene, polypropylene, polyolefin having a cyclic or norbornene structure, olefin-based polymers such as ethylene-propylene copolymer, vinyl chloride-based polymer,
There is also a film made of a transparent polymer such as an amide polymer such as nylon or aromatic polyamide. 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 A film made of a transparent polymer such as a polymer, an epoxy-based polymer or a blend of the above-mentioned polymers can also be used. Among these, plastic films such as triacetyl cellulose, polycarbonate, norbornene polyolefin and the like, which have a high hydrogen bonding property and are used as optical films, are preferred.

As the metal film, for example, the film formed of aluminum or the like can be used.

As the plastic film, ZEONOR (trade name, manufactured by ZEON Corporation), ZEONEX (trade name, manufactured by ZEON Corporation), ARTON (trade name,
A plastic film made of a polymer material having a norbornene structure, such as JSR Corporation, has excellent optical properties.

An anchor coat layer may 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 ensure good homeotropic alignment.

As the anchor coat material, a metal alkoxide, particularly a metal silicon alkoxide sol is used. The metal alkoxide is usually used as an alcohol-based solution. Since the anchor coat layer needs to have a uniform and flexible film, the thickness of the anchor coat layer is preferably about 0.04 to 2 μm, and 0.05 to 0.2 μm.
About m is more preferable.

As a method of applying the above anchor coating material on a substrate, for example, a roll coating method, a gravure coating method, a spin coating method, a bar coating method or the like can be adopted. The solution, after coating, remove the solvent,
A transparent glassy polymer film is formed by accelerating the sol-gel reaction by heating. A metal silicon alkoxide gel layer is formed from the metal silicon alkoxide sol. As a method for accelerating the solvent removal and reaction, drying at room temperature, drying in a drying oven, heating on a hot plate, etc. are usually used.

When the substrate has an anchor coat layer, a binder layer may be provided between the substrate and the anchor coat layer, or the anchor coat layer may contain a material that enhances adhesion to the substrate. The adhesion between the substrate and the anchor coat layer can be improved. By improving the adhesiveness 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 easily peel the substrate.

As the binder material used for forming the binder layer, any binder material that can improve the adhesion between the substrate (particularly polymer substance) and the anchor coat layer (transparent glassy polymer film) can be used without particular limitation. Examples of the binder material include coupling agents.
The coupling agent has a functional group that is easily bonded to both the substrate (particularly a polymer substance) and the anchor coat layer (transparent glassy polymer film), and examples thereof include a silane coupling agent, a titanium coupling agent, and zirconium. A coupling agent etc. can be illustrated. Among these, the silane coupling agent has a great effect of improving the adhesiveness. The coupling agent can be used as a material that enhances the adhesion to the substrate. A silane coupling agent is also suitable as the coupling agent.

The binder material, which is appropriately diluted with a solvent, is applied onto the substrate. As the coating method, for example, roll coating method, gravure coating method, spin coating method,
The bar coat method or the like can be adopted. As a method of removing the solvent after coating and accelerating the reaction by heating, drying at room temperature, drying in a drying oven, heating on a hot plate, etc. are usually used.

As a method of applying the side chain type liquid crystal polymer or the liquid crystalline composition to the substrate (or the anchor coat layer of the substrate), a solution obtained by dissolving the side chain type liquid crystalline polymer or the liquid crystalline composition in a solvent is used. A solution coating method or a method of melting and coating the liquid crystal polymer or the liquid crystalline composition by melting the liquid crystal polymer or the liquid crystalline composition can be mentioned. A method of applying a solution is preferable.

The solvent used when preparing the above-mentioned solution varies depending on the side chain type liquid crystal polymer, the photopolymerizable liquid crystal compound and the kind of the substrate and cannot be said unconditionally, but it is usually chloroform, dichloromethane, dichloroethane or tetrachloroethane. Halogenated hydrocarbons such as trichloroethylene, tetrachloroethylene and chlorobenzene, phenols such as phenol and parachlorophenol, benzene, toluene, xylene, methoxybenzene, 1,
Aromatic hydrocarbons such as 2-dimethobenzene, others, acetone, ethyl acetate, tert-butyl alcohol, glycerin, ethylene glycol, triethylene glycol, ethylene bricol monomethyl ether, diethylene glycol dimethyl ether, ethyl cellosolve, butyl cellosolve , 2-pyrrolidone, N-methyl-
2-Pyrrolidone, pyridine, triethylamine, tetrahydrofuran, dimethylformamide, dimethylacetamide, dimethylsulfoxide, acetonitrile, butyronitrile, carbon disulfide, cyclohexanone and the like can be used. The concentration of the solution depends on the solubility of the side chain type liquid crystal polymer or the liquid crystalline composition to be used and the final thickness of the target alignment liquid crystal layer, but cannot be generally stated.
It is usually in the range of 3 to 50% by weight, preferably 7 to 30% by weight.

The thickness of the homeotropically aligned liquid crystal film made of the coated side chain type liquid crystal polymer or the liquid crystalline composition is preferably about 1 to 10 μm. Especially when it is necessary to precisely control the film thickness of the homeotropic alignment liquid crystal film, the film thickness is almost decided at the stage of coating on the substrate. Needs special attention.

As a method for coating a solution of a side chain type liquid crystal polymer or a liquid crystalline composition adjusted to a desired concentration with the above solvent on a substrate, for example, a roll coating method,
A gravure coating method, a spin coating method, a bar coating method or the like can be adopted. 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 off. Usually, the solvent is removed by using 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 adopted in the present invention.
It is preferable because it is easy to coat a large area uniformly.

Next, the side chain type liquid crystal polymer layer or the liquid crystalline 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 method may be the same as the above-mentioned drying method. The heat treatment temperature cannot be generally stated because it varies depending on the type of the side chain type liquid crystal polymer or liquid crystal composition used and the supporting substrate, but is usually 60 to 300.
C., preferably in the range of 70 to 200.degree. The heat treatment time cannot be generally stated because it varies depending on the heat treatment temperature and the type of side chain type liquid crystal polymer or liquid crystalline composition used or the substrate, but is usually 10 seconds to 2 hours, preferably 20 seconds to 30 minutes. Selected in. If it is shorter than 10 seconds, the formation of homeotropic alignment may not proceed sufficiently. In the present invention, it is preferable that the orientation temperature is 80 to 150 ° C. and the treatment time is about 30 seconds to 10 minutes in view of workability and mass productivity.

After completion of the heat treatment, cooling operation is performed. The cooling operation can be performed by exposing the homeotropically aligned liquid crystal film after the heat treatment to the room temperature from the heating atmosphere in the heat treatment operation. Alternatively, forced cooling such as air cooling or water cooling may be performed. In the homeotropic alignment layer of the side chain type liquid crystal polymer, the orientation is fixed by cooling to the glass transition temperature of the side chain type liquid crystal polymer or lower.

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. To obtain a homeotropic alignment liquid crystal layer having improved durability. Light irradiation is performed by, for example, ultraviolet irradiation. The ultraviolet irradiation conditions are preferably 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. Other types of lamps such as meta-halide UV lamps and incandescent tubes can also be used. It should be noted that the temperature of the liquid crystal layer surface upon irradiation with ultraviolet rays is appropriately adjusted by using a cold mirror, water cooling or other cooling treatment or increasing the line speed so that the liquid crystal layer surface temperature falls within the liquid crystal temperature range.

In this way, a thin film of the side chain type liquid crystal polymer or the liquid crystalline composition is produced and fixed while maintaining the orientation, whereby a homeotropically oriented oriented liquid crystal layer is obtained. The oriented liquid crystal layer has molecules oriented in the same direction. Therefore, it is well known that freezing or stabilization of the alignment vector of this alignment liquid crystal layer and preservation of its anisotropic physical properties are achieved, and such thin films have been confirmed for their optical properties and used in various applications. To be done.
The oriented liquid crystal layer is a thin film having a uniaxial positive birefringence.

The alignment 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 tilted from the normal incidence. In the case of homeotropically aligned liquid crystal layers, this retardation value is symmetrical about normal incidence. Several methods can be used to measure the optical phase difference, and for example, an automatic birefringence measuring device (manufactured by Oak) and a polarization microscope (manufactured by Olympus) can be used. This homeotropic alignment liquid crystal layer appears black between the crossed Nicols polarizers. In this way, homeotropic alignment was evaluated.

The homeotropic alignment liquid crystal film thus obtained has a thickness d (nm) and an in-plane main refractive index of n.
_x and n _y , the refractive index in the thickness direction is n _z , and n _x
> When the n _y, the average value of the front retardation d, the average value of the thickness direction retardation, the formula value in the thickness direction retardation (%),
It satisfies the average haze value. The thickness d (nm) of the homeotropically aligned liquid crystal film = 1000
In the case of about 10,000, nx = 1.45
1.70, ny = 1.45 to 1.65, nz = 1.50
˜1.75.

The homeotropic alignment liquid crystal film is disposed between the cholesteric liquid crystal film and the quarter wavelength plate to form a brightness enhancement film. As the cholesteric liquid crystal film and the quarter-wave plate, various materials used for the brightness enhancement film can be used without particular limitation.

The cholesteric liquid crystal film reflects either left-handed or right-handed circularly polarized light and reflects other light, such as an oriented film of a cholesteric liquid crystal polymer or an oriented liquid crystal layer supported on a film substrate. Some examples are those that show the property of transmitting light. As the cholesteric liquid crystal film, for example, a film exhibiting circular dichroism in at least a part of a visible light band or a visible light dichroic film is used.
Those exhibiting circular dichroism in the band of 00 nm or more are 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 an 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 2 to
It is preferably 15 μm. If necessary, the cholesteric liquid crystal film may be blended with one or more additives such as polymers other than the above liquid crystal polymer, stabilizers, inorganic compounds such as plasticizers, organic compounds, metals and their compounds.

The cholesteric liquid crystal film has a structure in which two or three or more layers are laminated by combining those having different reflection wavelengths to obtain a film which reflects circularly polarized light in a wide wavelength range such as a visible light region. It is possible to obtain transmitted circularly polarized light in a wide wavelength range based on the above.

In a brightness enhancement film of a type that transmits circularly polarized light such as a cholesteric liquid crystal layer, it is possible to directly enter the polarizer, but from the viewpoint of suppressing absorption loss, the circularly polarized light is linearly polarized through a retardation plate. It is preferable that the light is incident on the polarizing plate. Circularly polarized light can be converted into linearly polarized light by using a ¼ wavelength plate as the retardation plate.

As the quarter-wave plate, an appropriate retardation plate according to the purpose of use is used. The quarter-wave plate can control optical characteristics such as retardation by laminating two or more kinds of retardation plates. As the retardation plate, polycarbonate, norbornene-based resin, polyvinyl alcohol, polystyrene,
An alignment film made of a liquid crystal material such as a birefringent film or a liquid crystal polymer obtained by stretching a film made of an appropriate polymer such as polymethylmethacrylate, polypropylene or other polyolefin, polyarylate, or polyamide, and an alignment layer of the liquid crystal material Some examples are those supported by a film. The thickness of the quarter-wave plate is usually preferably 0.5 to 200 μm, and particularly 1 to 1
It is preferably 00 μm.

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

The brightness enhancement film is produced, for example, by preparing a homeotropically aligned liquid crystal film using a 1/4 wavelength plate as a substrate, and further laminating a cholesteric liquid crystal film to the homeotropically aligned liquid crystal film via an adhesive layer. can do. In addition, the homeotropic alignment liquid crystal film produced on the substrate is coated with a cholesteric liquid crystal film or 1 /
After being transferred to a four-wave plate, a quarter-wave plate or a cholesteric liquid crystal film which is not used for the transfer may be further attached to this via a pressure-sensitive adhesive layer.

The pressure-sensitive adhesive for forming the pressure-sensitive adhesive layer is not particularly limited, but, for example, those having a base polymer of acrylic polymer, silicone polymer, polyester, polyurethane, polyamide, polyether, fluorine-based or rubber-based polymer. Can be appropriately selected and used.
In particular, an acrylic pressure-sensitive adhesive, which has excellent optical transparency, exhibits appropriate wettability, cohesiveness and adhesiveness, and has excellent weather resistance and heat resistance, can be preferably used.

The pressure-sensitive adhesive layer can be formed by an appropriate method. As an example, the base polymer or its composition is dissolved or dispersed in a solvent composed of a single solvent or a mixture of appropriate solvents such as toluene and ethyl acetate.
Prepare a pressure-sensitive adhesive solution of about 0 to 40% by weight and apply it directly onto the substrate or the liquid crystal film by an appropriate development method such as a casting method or a coating method, or adhere to the separator according to the above method. Examples include a method of forming an agent layer and transferring it to the liquid crystal layer. Also, the adhesive layer,
For example, in natural or synthetic resins, in particular, tackifying resins, fillers made of glass fibers, glass beads, metal powder, other inorganic powders, etc., adhesive layers such as colorants, antioxidants, etc. It may contain additives to be added. Further, it may be a pressure-sensitive adhesive layer containing fine particles and exhibiting light diffusion property.

When the homeotropic alignment liquid crystal film formed on the substrate is transferred via the pressure-sensitive adhesive layer, the homeotropic alignment liquid crystal film can be surface-treated. The means for surface treatment is not particularly limited, but surface treatment methods such as corona discharge treatment, sputtering treatment, low-pressure UV irradiation, and plasma treatment that can maintain the transparency of the surface of the liquid crystal film can be preferably adopted. Among these surface treatment methods, corona discharge treatment is preferable.

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
It is used by laminating optical films such as polarizing plates.

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

The polarizing plate usually has a protective film on one side or both sides of the polarizer. The polarizer is not particularly limited, and various kinds can be used. As a polarizer,
For example, polyvinyl alcohol film, partially formalized polyvinyl alcohol film, ethylene
Polyvinyl acetate copolymer-based partially saponified hydrophilic polymer film, uniaxially stretched by adsorbing dichroic substances such as iodine and dichroic dye, polyvinyl alcohol dehydration products and polyvinyl chloride Examples include polyene-based oriented films such as dehydrochlorinated products. Among these, those obtained by stretching a polyvinyl alcohol film to adsorb and orient a dichroic material (iodine, dye) are preferably used. The thickness of the polarizer is also not particularly limited, but is 5 to 80 μm.
Degree is general.

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

The protective film provided on one side or both sides of the polarizer is preferably one having excellent transparency, mechanical strength, thermal stability, moisture shielding property, isotropy and the like.
Examples of the material for 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 and acrylonitrile-styrene copolymers. Examples thereof include styrene-based polymers such as (AS resin) and polycarbonate-based polymers. Also, polyethylene, polypropylene,
Polyolefins having 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 polymers , Polyether ether ketone-based polymers, polyphenylene sulfide-based polymers, vinyl alcohol-based polymers, vinylidene chloride-based polymers, vinyl butyral-based polymers, arylate-based polymers, polyoxymethylene-based polymers, epoxy-based polymers, or blends of the aforementioned polymers. It may be mentioned as an example of the polymer forming the protective film. In addition, a film made of a thermosetting or ultraviolet curable resin such as an acrylic or urethane type, an acrylic urethane type, an epoxy type or a silicone type may be used. The thickness of the protective film is generally 500 μm or less, preferably 1 to 300 μm. In particular, the thickness is preferably 5 to 200 μm.

As the protective film, a cellulose-based polymer such as triacetyl cellulose is preferable from the viewpoint of polarization characteristics and durability. A triacetyl cellulose film is particularly suitable. When protective films are provided on both sides of the polarizer, protective films made of the same polymer material may be used on the front and back sides, or protective films made of different polymer materials may be used. The polarizer and the protective film are usually in close contact with each other via an aqueous pressure-sensitive adhesive or the like. Examples of the water-based adhesive include polyvinyl alcohol-based adhesive, gelatin-based adhesive, vinyl-based latex-based, water-based polyurethane, water-based polyester and the like.

As the protective film, a hard coat layer, an antireflection treatment, a sticking prevention treatment, or a treatment for the purpose of diffusion or antiglare can be used.

The hard coat treatment is carried out for the purpose of preventing scratches on the surface of the polarizing plate. For example, a cured film excellent in hardness and sliding characteristics is formed by an appropriate ultraviolet curable resin such as acrylic or silicone. It can be formed by a method of adding to the surface of the protective film. The antireflection treatment is carried out 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 conventional methods. Further, the sticking prevention treatment is performed for the purpose of preventing adhesion with an adjacent layer.

The anti-glare treatment is carried out for the purpose of preventing external light from being reflected on the surface of the polarizing plate and obstructing visual recognition of the light transmitted through the polarizing plate. For example, a sandblasting method or an embossing method is used. 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 surface-rendering method or a method of blending transparent fine particles. As the fine particles to be contained in the formation of the surface fine uneven structure, for example, silica having an average particle diameter of 0.5 to 50 μm,
Transparent fine particles such as inorganic fine particles which may be conductive, such as alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, and antimony oxide, and organic fine particles which are crosslinked or uncrosslinked polymers are used. When the surface fine uneven structure is formed, the amount of the fine particles used is generally about 2 to 50 parts by weight based on 100 parts by weight of the transparent resin forming the surface fine uneven structure.
Parts by weight are preferred. The anti-glare layer may also serve as a diffusion layer (such as a viewing angle enlarging function) for diffusing the light transmitted through the polarizing plate and enlarging the viewing angle.

The antireflection layer, the sticking prevention layer, the diffusion layer, the antiglare layer and the like can be provided on the protective film itself, or can be provided as an optical layer separately from the transparent protective layer. .

The polarizing plate can be used as an elliptical polarizing plate or a circular polarizing plate in which retardation plates are laminated. The elliptically polarizing plate or circularly polarizing plate will be described. These change linearly polarized light into elliptically polarized light or circularly polarized light, change elliptically polarized light or circularly polarized light into linearly polarized light, or change the polarization direction of linearly polarized light by a retardation plate. In particular, a so-called quarter-wave plate is used as a retardation plate that changes linearly polarized light into circularly polarized light or circularly polarized light into linearly polarized light. 1/2
A wave plate is usually used when changing the polarization direction of linearly polarized light.

The elliptically polarizing plate compensates (prevents) coloring (blue or yellow) generated by the birefringence of the liquid crystal layer of a spurts twisted nematic (STN) type liquid crystal display device, and is used for black and white display without the coloring. Used effectively. Further, the one in which the three-dimensional refractive index is controlled is preferable because it can also compensate (prevent) coloring that occurs when the screen of the liquid crystal display device is viewed obliquely. The circularly polarizing plate is effectively used, for example, when adjusting the color tone of an image of a reflective liquid crystal display device in which an image is displayed in color, and also has a function of preventing reflection.

As the retardation plate, for example, various wavelength plates or those for the purpose of compensating for the viewing angle and the like due to birefringence of the liquid crystal layer can be used, and an appropriate retardation according to the purpose of use can be used. By laminating two or more kinds of retardation plates having the same, optical characteristics such as retardation can be controlled. As the 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.

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 a direction perpendicular to the screen.

As such a viewing angle compensating retarder, a birefringent film which has been biaxially stretched or stretched in two orthogonal directions, or a bidirectionally stretched film such as a tilted oriented film is used. To be Examples of the tilted oriented film include those obtained by adhering a heat-shrinkable film to a polymer film and subjecting the polymer film to stretching treatment and / or shrinking treatment under the action of the shrinkage force caused by heating, and those obtained by obliquely orienting a liquid crystal polymer. Can be mentioned. The viewing angle compensation film can be appropriately combined for the purpose of preventing coloring or the like due to a change in viewing angle due to a phase difference due to a liquid crystal cell, and enlarging a viewing angle for good viewing.

From the standpoint of achieving a wide viewing angle for good visibility, an optically anisotropic layer comprising a liquid crystal polymer alignment layer, particularly a discotic liquid crystal polymer tilt alignment layer, was supported by a triacetyl cellulose film. An optical compensation retardation plate can be preferably used.

In addition to the above, the optical layers to be laminated in practical use are not particularly limited, but for example, one or two optical layers that may be used for forming a liquid crystal display device such as a reflecting plate or a semi-transmissive plate. The above can be used. In particular,
A reflection type polarizing plate or a semi-transmission type polarizing plate in which a reflecting plate or a semi-transmissive reflecting plate is further laminated on the elliptically polarizing plate or the circularly polarizing plate is mentioned.

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

Specific examples of the reflection type polarizing plate include a protective film which is mat-treated if necessary, and a foil or vapor deposition film made of a reflective metal such as aluminum attached to one surface to form a reflective layer. To be Further, the protective film may contain fine particles to form a finely textured surface structure, and a reflective layer having a finely textured structure formed on the surface.
The reflective layer having the fine concavo-convex structure has the advantage that diffused incident light is diffused to prevent directivity and glare, and uneven brightness can be suppressed. Further, the protective film containing fine particles also has an advantage that incident light and reflected light thereof are diffused when they pass therethrough to further suppress uneven brightness. The formation of the reflective layer having a fine concavo-convex structure reflecting the surface fine concavo-convex structure of the protective film is carried out by transparently protecting the metal by an appropriate method such as a vapor deposition method such as a vacuum vapor deposition method, an ion plating method, a sputtering method or a plating method It can be carried out by a method such as direct attachment to the surface of the layer.

The reflecting plate may be used as a reflecting sheet in which a reflecting layer is provided on an appropriate film in conformity with the transparent film instead of the method of directly applying to the protective film of the polarizing plate. Since the reflective layer is usually made of a metal, its reflective surface is used in a state of being covered with a protective film, a polarizing plate, etc., to prevent a decrease in reflectance due to oxidation, and in the long term of the initial reflectance. It is more preferable from the standpoint of avoiding the additional provision of the protective layer.

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

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

The above-mentioned elliptically polarizing plate and reflective elliptically polarizing plate are
A polarizing plate or a reflective polarizing plate and a retardation plate are laminated in an appropriate combination. Such elliptically polarizing plates are (reflective type)
A polarizing plate and a retardation plate can be formed by sequentially stacking them separately in the process of manufacturing a liquid crystal display device so as to form a combination, but previously laminated to form an optical film such as an elliptically polarizing plate. Has an advantage that the manufacturing efficiency of a liquid crystal display device and the like can be improved because of excellent quality stability and stacking workability.

An adhesive layer may be provided on the optical film of the present invention. The pressure-sensitive adhesive layer can be used for sticking to a liquid crystal cell and also used for laminating optical layers. When the optical films are adhered, their optical axes may be arranged at appropriate angles depending on the intended retardation characteristics and the like.

The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer is not particularly limited, but the same ones as those used for bonding the homeotropically aligned liquid crystal layer and the translucent film can be exemplified. Further, it can be provided in the same manner.

The pressure-sensitive adhesive layer may be provided on one side or both sides of the polarizing plate or the optical film as a layer in which different compositions or types are laminated. Further, when it is provided on both surfaces, an adhesive layer having different composition, type and thickness may be provided on the front and back of the polarizing plate or the optical film. The thickness of the adhesive layer can be appropriately determined according to the purpose of use, adhesive strength, etc., and is generally 1 to
500 μm, preferably 5 to 200 μm, particularly 1
0 to 100 μm is preferable.

The exposed surface of the adhesive layer is temporarily covered with a separator for the purpose of preventing its contamination or the like until it is put into practical use. As a result, it is possible to prevent contact with the adhesive layer in the usual handling state. As a separator,
Except for the above thickness conditions, for example, a plastic film, a rubber sheet, a paper, a cloth, a non-woven fabric, a net, a foamed sheet or a metal foil, an appropriate thin sheet such as a laminated body thereof, a silicone type or a long mirror alkyl type may be used as necessary. It is possible to use an appropriate one according to the prior art, such as one coated with an appropriate release agent such as fluorine-based or molybdenum sulfide.

In the present invention, each layer such as a polarizer, a transparent protective film, an optical film, etc. forming the above-mentioned polarizing plate, and each layer such as an adhesive layer may be, for example, a salicylate compound, a benzophenol compound, a benzotriazole compound. Alternatively, it may be one having an ultraviolet absorbing ability by a method such as a method of treating with an ultraviolet absorber such as a cyanoacrylate compound or a nickel complex salt compound.

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

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

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

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

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

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

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

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

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

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

[0102]

EXAMPLES One embodiment of the present invention will be described below with reference to examples, but it goes without saying that the present invention is not limited to the examples.

Example 1 A plastic film made of polyethylene terephthalate as a polymer material (manufactured by Toray Industries, Inc., thickness 50 μm) was used.
As a sol solution for anchor coating, a 2% solution of ethyl silicate in ethyl acetate and isopropyl alcohol (trade name Colcoat P, manufactured by Colcoat Co., Ltd.) was applied by gravure roll coating. Then, it was heated at 130 ° C. for 30 seconds to form a transparent glassy polymer film (0.08 μm) as an anchor coat layer.

[0104]

[Chemical 6] 5 parts by weight of the side chain type liquid crystal polymer represented by the above chemical formula 6 (the numbers in the formula represent mol% of the monomer units, and are represented by blocks for convenience, the weight average molecular weight is 5000) and the nematic liquid crystal layer Photopolymerizable liquid crystal compound (BA
SF solution, Paliocolor LC242) 20 parts by weight, and a photopolymerization initiator (Ciba Specialty Chemicals, Inc., Irgacure 907) 5% by weight (to photopolymerizable liquid crystal compound) dissolved in 75 parts by weight of cyclohexanone was used as a film base material. Coating was performed by bar coating on the provided anchor coat layer. Then, the liquid crystal layer was heated at 80 ° C. for 2 minutes for homeotropic alignment, and irradiated with ultraviolet rays while maintaining the alignment to form a homeotropic aligned liquid crystal film (thickness: 1.9 μm).

Examples 2 to 3 and Reference Examples 1 to 3 In Example 1, except that the orientation temperature, the treatment time, the solvent of the coating liquid, and the film thickness of the anchor coat layer were changed as shown in Table 1. A homeotropic alignment liquid crystal film was prepared in the same manner as in Example 1.

[0106]

[Table 1]

With respect to the homeotropically aligned liquid crystal films obtained in the examples and reference examples, automatic birefringence measuring devices (Oji Scientific Instruments Co., Ltd.) were used to determine the main refractive indices n _x , n _y and _nz in the film plane and in the thickness direction. Made, automatic birefringence meter KOBRA2
1 ADH), and from the results, front phase difference (maximum value, minimum value, average value), thickness direction phase difference and formula: {(maximum value-minimum value) / average value} × 100 (%),
The value obtained by The results are shown in Table 2. Also, haze meter H manufactured by Murakami Color Research Laboratory Co., Ltd.
Haze (maximum value, minimum value, average value) was determined by M-150. The results are shown in Table 2.

(Preparation of brightness enhancement film) A cholesteric liquid crystal layer 5 showing circular dichroism in the band of 400 to 700 nm on a triacetate film (80 μm).
The adhesive layer (25 μm) formed by forming the homeotropic alignment liquid crystal film obtained in Example or Reference Example on the liquid crystal layer with an acrylic adhesive is used.
60 μm of a quarter wave plate (front phase difference 130 nm) in which a polycarbonate film is stretched and oriented, and a polycarbonate film is further laminated thereon, and an adhesive layer (25 μm) formed of the same acrylic adhesive is used. Then, they were bonded together to produce a brightness enhancement film.

(Evaluation method) 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 polarizing plate were arranged in this order on a backlight. Brightness in the front direction (cd / m ² ) using the liquid crystal display placed
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, as Comparative Example 1, an example in which the brightness enhancement film is not used is shown, and the brightness improvement rate for this is also shown in Table 2.

[0110]

[Table 2]

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a liquid crystal display used in an example.

Continued front page    (72) Inventor Shunsuke Sudo             1-2 1-2 Shimohozumi, Ibaraki City, Osaka Prefecture Nitto             Electric Works Co., Ltd. (72) Inventor Sadahiro Nakanishi             1-2 1-2 Shimohozumi, Ibaraki City, Osaka Prefecture Nitto             Electric Works Co., Ltd. F-term (reference) 2H049 BA04 BA06 BA46 BB03 BB43                       BB44 BB45 BB46 BB47 BB49                       BC09 BC22                 2H091 FA08X FA08Z FA11X FA11Z                       FA15X FA37X FA41Z FB02                       FB04 FC03 FC06 GA16 GA17                       HA07 HA10 LA18 LA19

Claims (5)

[Claims] 1. A thickness d (nm) and an in-plane main refractive index n
_x and n _y , the refractive index in the thickness direction is n _z , and n _x
> N _y , front phase difference: Δn _xy (n _x −n _y ).
The average value of xd is 10 nm or less, and the thickness direction retardation:
The average value of Δn _zx ( _nz −n _x ) × d is 30 to 500 nm
And for the thickness direction retardation: Δn _zx × d,
Formula: {(maximum value-minimum value) / average value} × 100 (%),
A homeotropically aligned liquid crystal film having a value of 10 or less and an average haze value of 3% or less. 2. The front phase difference: the difference between the maximum value and the minimum value of 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. The homeotropically aligned liquid crystal film according to 1. 3. A brightness enhancement film, wherein the homeotropically aligned liquid crystal film according to claim 1 or 2 is arranged between a cholesteric liquid crystal film and a quarter-wave plate. 4. An optical film, characterized in that at least one optical film is further laminated on the homeotropically aligned liquid crystal film according to claim 1 or 2, or the brightness enhancement film according to claim 3. 5. An image display device to which the homeotropic alignment liquid crystal film according to claim 1 or 2, the brightness enhancement film according to claim 3, or the optical film according to claim 4 is applied.