JP2006337575A - Homeotropically oriented liquid-crystal film, and device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a homeotropically oriented film stably produced without a complicated step such as light irradiation in an inert gas atmosphere, and excellent in orientation retention after liquid-crystalline orientation fixing and in mechanical strength. <P>SOLUTION: On an alignment substrate, a liquid-crystalline substance comprising as a constituent ingredient a side-chain type liquid-crystalline polymer having an oxetanyl group is homeotropically oriented in a liquid-crystalline state. Thereafter, the oxetanyl group is reacted to fix the homeotropic orientation. In the liquid crystal film, the requirements of the following [1] and [2] are satisfied: [1] 0 nm≤Re≤200 nm, and [2] -500 nm≤Rth≤-30 nm; wherein, Re represents a retardation value in the plane of the liquid crystal film; Rth represents a retardation value in the thickness direction of the liquid crystal film; and the Re and Rth satisfy Re=(Nx-Ny)×d, and Rth=(Nx-Nz)×d, respectively. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  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. Furthermore, the present invention relates to a liquid crystal display device using at least the homeotropic alignment liquid crystal film, an organic EL display device, an image display device such as a PDP, and the like.

  An optical film having a refractive index anisotropy plays an important industrial role such as being used for improving the image quality of a liquid crystal display device. Refractive index anisotropic films can be broadly classified into those obtained by stretching a plastic film and those obtained by aligning liquid crystals. The latter is more remarkable because it has the potential to realize various refractive index structures.

  For example, a film having a larger refractive index in the film thickness direction is considered to be effective for improving the viewing angle of a liquid crystal display device, but such a film is considered to be a shortcut to use the homeotropic alignment (vertical alignment) of the liquid crystal. It is done. 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 as in a liquid crystal display device, but it is very difficult to make this alignment state into a film. However, there are problems with the methods reported in the past.

  For example, in Patent Documents 1 to 3, a film is obtained by glass-fixing after the main-chain polymer liquid crystal is homeotropically aligned. However, in homeotropic alignment, it is assumed that there is a problem that cracks are likely to occur in the in-plane direction because the polymer compounds are aligned in the film thickness direction, but in these reports, measures such as strengthening the material by crosslinking are taken. Not. In Patent Document 4, although the homeotropic alignment of the side chain type polymer liquid crystal is fixed by vitrification, it is considered that there is a problem in strength as compared with the main chain type polymer liquid crystal. In Patent Documents 5 to 6, a polymerizable low-molecular liquid crystal is added to the side-chain polymer liquid crystal. However, since the low-molecular liquid crystal polymerizes alone, there is a limit to reinforcing the strength of the side-chain polymer liquid crystal.

  In Patent Document 7, a material in which a radical polymerizable group or a cationic polymerizable group such as vinyl ether or epoxy is introduced into a side chain type polymer liquid crystal is used. However, since radical polymerization is generally subjected to oxygen inhibition, there is a risk that polymerization may be insufficient, and if equipment is used to remove oxygen, the apparatus becomes large. Vinyl ether groups and epoxy groups are advantageous in this respect because they are not affected by oxygen inhibition, but the ether bond of vinyl ether groups is unstable and easily cleaved, and epoxy groups are complicated to introduce into liquid crystal materials. In addition, it is difficult to obtain a high degree of polymerization when the crosslinking treatment is performed. Furthermore, in order to obtain homeotropic alignment, a large amount of non-liquid crystalline structural units are introduced into the liquid crystal material, and there is a question about the stable liquid crystallinity. As described above, problems remain in the production of conventional homeotropic alignment films.

Japanese Patent No. 2853064 Japanese Patent No. 3018120 Japanese Patent No. 3078948 JP 2002-174725 A JP 2002-333524 A JP 2002-333642 A JP 2003-2927 A

  The present invention is capable of stable production without requiring a complicated process such as light irradiation under an inert gas atmosphere, and is excellent in alignment retention ability and mechanical strength after liquid crystal alignment fixation. It aims at providing the homeotropic alignment film which has the retardation value of. Furthermore, it aims at providing the liquid crystal display device using optical films, such as an optical film using the said homeotropic alignment liquid crystal film, a brightness improvement film, and also the said homeotropic alignment liquid crystal film, a brightness improvement film.

  The present invention has been made in view of the above problems, and uses an oxetanyl group as a reactive group having excellent reactivity when fixing a liquid crystal alignment structure.

That is, the present invention provides a liquid crystal material containing a side chain type liquid crystalline polymer substance having an oxetanyl group as a constituent component, homeotropically aligned in a liquid crystal state on an alignment substrate, and then reacted with the oxetanyl group to react with the homeophilic group. The present invention relates to a homeotropic alignment liquid crystal film, which is a liquid crystal film obtained by fixing a tropic alignment and has the following requirements [1] and [2].
[1] 0 nm ≦ Re ≦ 200 nm
[2] −500 nm ≦ Rth ≦ −30 nm
(Here, Re means an in-plane retardation value of the liquid crystal film, and Rth means a retardation value in the thickness direction of the liquid crystal film. Re and Rth are respectively Re = (Nx−Ny) × d, Rth = (Nx−Nz) × d, where d is the thickness [nm] of the liquid crystal film, Nx and Ny are the main refractive index in the liquid crystal film plane, and Nz is the main refractive index in the thickness direction. Yes, Nz> Nx ≧ Ny.)

The present invention also relates to the homeotropic alignment liquid crystal film as described above, wherein the alignment substrate comprises at least an organic substance having a long-chain alkyl group.
The present invention also relates to the homeotropic alignment liquid crystal film as described above, wherein the alignment substrate comprises at least polyvinyl alcohol having a long-chain alkyl group.
The present invention also relates to an optical film characterized in that at least one optical film is further laminated on the homeotropic alignment liquid crystal film described above.
The present invention also relates to a liquid crystal display device, an organic EL display device or an image display device using the liquid crystal film or optical film described above.

The present invention is described in detail below.
In the present invention, selection of a liquid crystal material and an alignment substrate is extremely important for obtaining a liquid crystal film in which homeotropic alignment is fixed.

First, the liquid crystal material will be described.
The liquid crystal material used in the present invention is a liquid crystal material containing at least a side chain type liquid crystalline polymer substance having an oxetanyl group as a constituent component. Specifically, it contains a side chain type liquid crystalline polymer such as poly (meth) acrylate or polysiloxane as a main constituent, and the terminal of the side chain type liquid crystal polymer has a polymerizable oxetanyl group. More specifically, the side chain obtained by homopolymerizing the (meth) acrylic moiety of the (meth) acrylic compound having an oxetanyl group represented by the formula (1) or copolymerizing with another (meth) acrylic compound. A preferred example is a liquid crystalline polymer material.

In the above formula (1), R ₁ represents hydrogen or a methyl group, R ₂ represents hydrogen, a methyl group or an ethyl group, and L ₁ and L ₂ each independently represents a single bond, —O—, —O. It represents either —CO— or —CO—O—, M represents any one of formulas (2) to (4), and n and m each independently represent an integer of 0 to 10.
-P ₁ -L ₃ -P ₂ -L ₄ -P _3- (2)
-P ₁ -L ₃ -P _3- (3)
-P _3- (4)

In Formulas (2) to (4), P ₁ and P ₂ each independently represent a group selected from Formula (5), P ₃ represents a group selected from Formula (6), and L ₃ and L ₄ each independently represents a single bond, —CH═CH—, —C≡C—, —O—, —O—CO— or —CO—O—.

  The method for synthesizing the (meth) acrylic compound having an oxetanyl group represented by the formula (1) is not particularly limited, and can be synthesized by applying a method used in a general organic chemical synthesis method. For example, by combining a site having an oxetanyl group and a site having a (meth) acrylic group by means such as Williamson's ether synthesis or ester synthesis using a condensing agent, oxetanyl group and (meth) acrylic group 2 A (meth) acrylic compound having an oxetanyl group having two reactive functional groups can be synthesized.

  It is represented by the following formula (7) by homopolymerizing the (meth) acrylic group of the (meth) acrylic compound having an oxetanyl group represented by the formula (1) or copolymerizing with another (meth) acrylic compound. A side-chain liquid crystalline polymer substance containing units can be obtained. The polymerization conditions are not particularly limited, and normal radical polymerization or anionic polymerization conditions can be employed.

  As an example of radical polymerization, a (meth) acrylic compound is dissolved in a solvent such as dimethylformamide (DMF), and 2,2′-azobisisobutyronitrile (AIBN), benzoyl peroxide (BPO), or the like is used as an initiator. The method of making it react at 60-120 degreeC for several hours is mentioned. Moreover, in order to make the liquid crystal phase appear stably, copper bromide (I) / 2,2′-bipyridyl series, 2,2,6,6-tetramethylpiperidinooxy free radical (TEMPO) series, etc. are used. A method of controlling the molecular weight distribution by conducting living radical polymerization as an initiator is also effective. These radical polymerizations are preferably performed under deoxygenation conditions.

  Examples of anionic polymerization include a method in which a (meth) acrylic compound is dissolved in a solvent such as tetrahydrofuran (THF) and reacted with a strong base such as an organic lithium compound, an organic sodium compound, or a Grignard reagent as an initiator. In addition, the molecular weight distribution can be controlled by optimizing the initiator and the reaction temperature for living anionic polymerization. These anionic polymerizations must be performed strictly under dehydration and deoxygenation conditions.

  In addition, the (meth) acryl compound to be copolymerized at this time is not particularly limited and may be anything as long as the synthesized polymer substance exhibits liquid crystallinity, but in order to increase the liquid crystallinity of the synthesized polymer substance, A (meth) acrylic compound having a mesogenic group is preferred. For example, a (meth) acrylic compound represented by the following formula can be exemplified as a preferred compound.

  Here, R represents hydrogen, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, or a cyano group.

  The side chain type liquid crystalline polymer substance having an oxetanyl group used as a liquid crystal material in the present invention preferably contains 5 to 100 mol% of the unit represented by the formula (7), and particularly contains 10 to 100 mol%. preferable. The side chain type liquid crystalline polymer substance preferably has a weight average molecular weight of 2,000 to 100,000, particularly preferably 5,000 to 50,000.

  The liquid crystal material used in the present invention may contain various compounds that can be mixed without impairing liquid crystallinity, in addition to the side-chain liquid crystalline polymer substance. Examples of compounds that can be contained include compounds having a cationic polymerizable functional group such as an oxetanyl group, an epoxy group, and a vinyl ether group, various polymer substances having film-forming ability, and various low-molecular liquid crystal compounds exhibiting liquid crystallinity. And polymer liquid crystalline compounds. When the side chain liquid crystalline polymer substance is used as a composition, the proportion of the side chain liquid crystalline polymer substance in the entire composition is 10% by mass or more, preferably 30% by mass or more, and more preferably. Is 50 mass% or more. If the content of the side chain type liquid crystalline polymer substance is less than 10% by mass, the concentration of the polymerizable group in the composition becomes low, and the mechanical strength after polymerization becomes insufficient.

  In addition, since the liquid crystal material is subjected to an alignment treatment, the oxetanyl group is cationically polymerized and crosslinked to cross-link the liquid crystal state. Therefore, the liquid crystal material is subjected to cation by external stimulation such as light or heat. It is preferable to contain a photo cation generator and / or a thermal cation generator which generate If necessary, various sensitizers may be used in combination.

The photo cation generator means a compound capable of generating a cation by irradiating with light having an appropriate wavelength, and examples thereof include organic sulfonium salt systems, iodonium salt systems, and phosphonium salt systems. Antimonates, phosphates, borates and the like are preferably used as counter ions of these compounds. Specific examples of the compound include Ar ₃ S ⁺ SbF ₆ ⁻ , Ar ₃ P ⁺ BF ₄ ⁻ and Ar ₂ I ⁺ PF ₆ ⁻ (wherein Ar represents a phenyl group or a substituted phenyl group). In addition, sulfonate esters, triazines, diazomethanes, β-ketosulfone, iminosulfonate, benzoinsulfonate, and the like can also be used.

  The thermal cation generator is a compound capable of generating a cation when heated to an appropriate temperature, for example, benzylsulfonium salts, benzylammonium salts, benzylpyridinium salts, benzylphosphonium salts, hydrazinium salts, carboxylic acid esters Examples thereof include sulfonic acid esters, amine imides, antimony pentachloride-acetyl chloride complexes, diaryliodonium salts-dibenzyloxycopper, and boron halide-tertiary amine adducts.

  The amount of these cation generators added to the liquid crystal material varies depending on the structure of the mesogenic part and spacer part, the oxetanyl group equivalent, the alignment condition of the liquid crystal, etc. constituting the side chain type liquid crystalline polymer material to be used. Although it cannot be said, it is usually 100 mass ppm to 20 mass%, preferably 1000 mass ppm to 10 mass%, more preferably 0.2 mass% to 7 mass%, most preferably based on the side chain type liquid crystalline polymer substance. Is in the range of 0.5% to 5% by weight. If the amount is less than 100 mass ppm, the amount of cations generated may not be sufficient and polymerization may not proceed. If the amount is more than 20 mass%, the remaining cation generator remains in the liquid crystal film. It is not preferable because there is a risk that the light resistance and the like may deteriorate due to an increase in the number of objects.

Next, the alignment substrate will be described.
As the alignment substrate, a substrate having a smooth plane is preferable, and examples thereof include a film or sheet made of an organic polymer material, a glass plate, and a metal plate. From the viewpoint of cost and continuous productivity, it is preferable to use a material made of an organic polymer compound. Examples of organic polymer materials include polyvinyl alcohol, polyimide, polyphenylene sulfide, polyphenylene oxide, polyether ketone, polyether ether ketone, polyether sulfone, polyethylene naphthalate, polyethylene terephthalate, polyarylate, and triacetyl cellulose. .

  In order to stably obtain homeotropic alignment using the liquid crystal material described above, the material constituting these substrates has a long-chain (usually 4 or more carbon atoms, preferably 8 or more) alkyl group. Is more preferable. Of these, polyvinyl alcohol having a long-chain alkyl group is most preferred. These organic polymer materials may be used alone as a substrate, or may be formed as a thin film on another substrate.

  In the field of liquid crystal, it is common to rub the substrate with a cloth or the like, but the homeotropic alignment film of the present invention is an alignment in which in-plane anisotropy does not basically occur. Because of the structure, rubbing is not necessarily required. However, it is more preferable to apply a weak rubbing treatment from the viewpoint of suppressing repelling when a liquid crystal material is applied. An important setting value that defines the rubbing condition is a peripheral speed ratio. This represents a ratio between the movement speed of the cloth and the movement speed of the substrate when the rubbing cloth is wound around a roll and rubbed while being rubbed. In the present invention, the weak rubbing treatment usually has a peripheral speed ratio of 50 or less, more preferably 25 or less, and particularly preferably 10 or less. When the peripheral speed ratio is greater than 50, the effect of rubbing is too strong, and the liquid crystal material cannot be completely aligned vertically, and there is a possibility that the alignment is tilted in the in-plane direction from the vertical direction.

Next, the manufacturing method of the liquid crystal film of this invention is demonstrated. Although the method for producing the liquid crystal film is not limited to these, the above-mentioned liquid crystal material is spread on the above-mentioned alignment substrate, and after aligning the liquid crystal material, light irradiation and / or heat treatment is performed. It can manufacture by fixing the said orientation state.
The liquid crystal material is spread on the alignment substrate to form the liquid crystal material layer. The liquid crystal material is applied directly on the alignment substrate in a molten state, or the liquid crystal material solution is applied on the alignment substrate, and then the coating film is applied. And drying the solvent to distill off the solvent.

  The solvent used for preparing the solution is not particularly limited as long as it can dissolve the liquid crystal material of the present invention and can be distilled off under appropriate conditions. Generally, ketones such as acetone, methyl ethyl ketone, isophorone, and cyclohexanone, butoxy Ether alcohols such as ethyl alcohol, hexyloxyethyl alcohol, methoxy-2-propanol, glycol ethers such as ethylene glycol dimethyl ether and diethylene glycol dimethyl ether, esters such as ethyl acetate and ethyl lactate, phenols such as phenol and chlorophenol, Amides such as N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone, halogens such as chloroform, tetrachloroethane, dichlorobenzene, etc. Mixed system is preferably used. Moreover, in order to form a uniform coating film on the alignment substrate, a surfactant, an antifoaming agent, a leveling agent, or the like may be added to the solution.

Regardless of the method of directly applying the liquid crystal material or the method of applying the solution, the application method is not particularly limited as long as the uniformity of the coating film is ensured, and a known method may be adopted. it can. Examples thereof include spin coating, die coating, curtain coating, dip coating, and roll coating.
In the method of applying a liquid crystal material solution, it is preferable to include a drying step for removing the solvent after the application. As long as the uniformity of a coating film is maintained, this drying process can employ | adopt a well-known method, without being specifically limited. For example, a method such as a heater (furnace) or hot air blowing may be used.

  Subsequently, the liquid crystal material layer formed on the alignment substrate is liquid crystal aligned by a method such as heat treatment, and is cured and fixed by light irradiation and / or heat treatment. In the first heat treatment, the liquid crystal is aligned by the self-alignment ability inherent in the liquid crystal material by heating to the liquid crystal phase expression temperature range of the used liquid crystal material. As the conditions for the heat treatment, the optimum conditions and limit values differ depending on the liquid crystal phase behavior temperature (transition temperature) of the liquid crystal material to be used, but it cannot be generally stated, but is usually in the range of 10 ° C to 250 ° C, preferably 30 ° C to 160 ° C. It is preferable to perform heat treatment at a temperature equal to or higher than Tg of the liquid crystal material, and more preferably at a temperature higher by 10 ° C. than Tg. If the temperature is too low, the liquid crystal alignment may not proceed sufficiently, and if the temperature is high, the cationic polymerizable reactive group in the liquid crystal material and the alignment substrate may be adversely affected. Moreover, about heat processing time, it is 3 seconds-30 minutes normally, Preferably it is the range of 10 seconds-10 minutes. If the heat treatment time is shorter than 3 seconds, the liquid crystal alignment may not be completed sufficiently, and if the heat treatment time exceeds 30 minutes, the productivity is deteriorated.

  After the liquid crystal material is formed into a liquid crystal alignment by a method such as heat treatment, the liquid crystal material is cured by polymerizing oxetanyl groups in the liquid crystal material. The curing step is aimed at fixing the liquid crystal alignment state of the completed liquid crystal alignment by a curing (crosslinking) reaction and modifying it into a stronger film.

  Since the liquid crystal material used in the present invention has a polymerizable oxetanyl group, it is preferable to use a cationic polymerization initiator (cation generator) for polymerization (crosslinking) of the reactive group as described above. As the polymerization initiator, it is preferable to use a photo cation generator rather than a thermal cation generator.

  When a photo cation generator is used, the liquid crystal material can be obtained by adding the photo cation generator to the heat treatment for aligning the liquid crystal under dark conditions (light blocking conditions that do not cause the photo cation generator to dissociate). The liquid crystal can be aligned with sufficient fluidity without curing until the alignment stage. Thereafter, the liquid crystal material is cured by generating cations by irradiating light from a light source that emits light of an appropriate wavelength.

As a light irradiation method, a photocation is generated by irradiating light from a light source such as a metal halide lamp, a high pressure mercury lamp, a low pressure mercury lamp, a xenon lamp, an arc lamp, or a laser having a spectrum in the absorption wavelength region of the photocation generator used. Cleave the generator. The dose per square centimeter is usually in the range of 1 to 2000 mJ, preferably 10 to 1000 mJ as the cumulative dose. However, this is not the case when the absorption region of the photocation generator and the spectrum of the light source are remarkably different, or when the liquid crystal material itself has the ability to absorb the light source wavelength. In these cases, it is possible to adopt a method such as using a suitable photosensitizer or a mixture of two or more photocation generators having different absorption wavelengths.
The temperature at the time of light irradiation needs to be within a temperature range in which the liquid crystal material takes liquid crystal alignment. In order to sufficiently improve the curing effect, it is preferable to perform light irradiation at a temperature equal to or higher than Tg of the liquid crystal material.

  The liquid crystal film manufactured by the above method is a sufficiently strong film. Specifically, the mesogens are three-dimensionally bonded by the curing reaction, and not only the heat resistance (the upper limit temperature for maintaining the liquid crystal alignment) is improved as compared to before curing, but also scratch resistance, abrasion resistance, crack resistance. The mechanical strength such as property is also greatly improved.

  As the alignment substrate, it is not optically isotropic, or the liquid crystal film to be obtained is finally opaque in the intended use wavelength region, or the alignment substrate is too thick, resulting in problems in actual use. If there is a problem such as, the film formed on the alignment substrate is optically isotropic, or the obtained liquid crystal film is finally transparent in the intended use wavelength region, or the liquid crystal film is a liquid crystal cell. It is also possible to use a form transferred to a film for temporary support until it is bonded to the film.

As a transfer method, a known method can be adopted. For example, as described in JP-A-4-57017 and JP-A-5-333313, a liquid crystal film layer is laminated on a substrate different from the alignment substrate via an adhesive or an adhesive, and then if necessary. Examples thereof include a method of transferring only a liquid crystal film by performing a surface curing treatment using an adhesive or an adhesive and peeling the alignment substrate from the laminate. As the transfer destination substrate, for example, a triacetyl cellulose film such as Fujitac (product of Fuji Photo Film), Konicatak (product of Konica), TPX film (product of Mitsui Chemicals), Arton film (product of JSR), ZEONEX Examples thereof include a transparent film such as a film (product of Nippon Zeon Co., Ltd.) and an acrylprene film (product of Mitsubishi Rayon Co., Ltd.), a polyethylene terephthalate film which has been subjected to silicon treatment or provided with an easy peeling layer on the surface. If necessary, it can be directly transferred to a polarizing film.
The pressure-sensitive adhesive or adhesive used for transfer is not particularly limited as long as it is of optical grade, and generally used ones such as acrylic, epoxy, and urethane can be used.

  In the homeotropic alignment liquid crystal film of the present invention, the thickness of the liquid crystal film is d [nm], the main refractive index in the liquid crystal film surface is Nx and Ny, the main refractive index in the thickness direction is Nz, and Nx ≧ Ny. In this case, the in-plane retardation value (Re = (Nx−Ny) × d) is 0 to 200 nm, and the retardation value in the thickness direction (Rth = (Nx−Nz) × d) is −500 to −30 nm. It is characterized by being.

  The Re and Rth values, which are optical parameters of the homeotropic alignment liquid crystal film, may vary depending on the application, such as when used as a brightness enhancement film, or as a viewing angle improvement film for a liquid crystal display device, and the viewing angle improvement film. Even if it is used in a liquid crystal display, it depends on the type of liquid crystal display device and various optical parameters. However, for a monochromatic light of 550 nm, the retardation value (Re) in the homeotropic alignment liquid crystal film plane Is usually in the range of 0 nm to 200 nm, preferably in the range of 0 nm to 100 nm, more preferably in the range of 0 nm to 50 nm, and the retardation value (Rth) in the thickness direction is usually in the range of −500 nm to −30 nm. Preferably -400 nm to -50 nm, more preferably Those that are controlled in the range of 400 nm to-100 nm.

  By setting the Re value and the Rth value in the above ranges, the viewing angle improving film of the liquid crystal display device can widen the viewing angle while correcting the color tone of the liquid crystal display. A brightness improvement effect can be obtained. When the Re value is larger than 200 nm, the front characteristics of the liquid crystal display element may be deteriorated due to the influence of a large front phase difference value. When the Rth value is larger than −30 nm or smaller than −500 nm, a sufficient viewing angle improvement effect cannot be obtained, or unnecessary coloring may occur when viewed from an oblique direction.

  Although the film thickness of the liquid crystal film depends on the type of the liquid crystal display device and various optical parameters, it cannot be generally stated, but is usually 0.2 μm to 10 μm, preferably 0.3 μm to 5 μm, more preferably 0.5 μm to 2 μm. When the film thickness is thinner than 0.2 μm, there is a possibility that a sufficient viewing angle improvement effect or luminance improvement effect cannot be obtained. If it exceeds 10 μm, the liquid crystal display device may be unnecessarily colored.

  The homeotropic alignment liquid crystal film obtained as described above can be quantified by measuring the optical phase difference of the liquid crystal film at an angle inclined from normal incidence. In the case of homeotropic alignment liquid crystal films, this retardation value is symmetric with respect to normal incidence. Several methods can be used for measuring the optical phase difference. For example, an automatic birefringence measuring apparatus (manufactured by Oji Scientific Instruments) and a polarizing microscope can be used. This homeotropic alignment liquid crystal film appears black between the crossed Nicol polarizers. Thus, homeotropic orientation was evaluated.

The homeotropic alignment liquid crystal film of the present invention can form an optical film by laminating it with at least one other optical film.
For example, the homeotropic alignment liquid crystal film is disposed between a cholesteric liquid crystal film and a quarter wavelength plate to form a brightness enhancement film. As the cholesteric liquid crystal film and the quarter-wave plate, various kinds of materials usually used for the brightness enhancement film can be used without any particular limitation.

  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. The thing which shows is mentioned. 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.

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.
A brightness enhancement film of a type that transmits circularly polarized light, such as a cholesteric liquid crystal film, can be incident on a polarizer as it is, but from the viewpoint 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.

  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 types 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 wavelength plate is usually preferably from 0.5 to 200 μm, particularly preferably from 1 to 100 μm.

  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. A phase difference layer, for example, a phase difference layer that functions as a half-wave plate, can be used to superimpose. Accordingly, the retardation plate disposed between the polarizing plate and the brightness enhancement film may be composed of one or more retardation layers.

  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.

  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.

  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 additives, such as antioxidant. Moreover, the adhesive layer etc. which contain microparticles | fine-particles and show light diffusibility may be sufficient.

  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.

A polarizing plate is used for an optical film applied to an image display device such as a liquid crystal display device. The homeotropic alignment liquid crystal film and brightness enhancement film of the present invention are used by laminating optical films such as polarizing plates.
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 reversed through a reflective layer or the like provided on the rear side thereof and re-entered on the brightness enhancement film, and a 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 or the like is reduced accordingly, resulting in a dark image. 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.

  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. Examples thereof include polyene-based oriented films such as those obtained by adsorbing volatile substances 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.

  A polarizer obtained by dyeing a polyvinyl alcohol film with iodine and uniaxially stretching can be prepared by, for example, dyeing polyvinyl alcohol by immersing it in an aqueous solution of iodine and stretching it 3 to 7 times the original length. it can. 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.

  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 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, acrylonitrile / styrene copolymers, and the like. Examples thereof include styrene polymers such as (AS resin), polycarbonate polymers, and the like. Also, polyethylene, polypropylene, polyolefins having cycloolefin or norbornene structures, polyolefin polymers such as ethylene / propylene copolymers, vinyl chloride polymers, amide polymers such as nylon and aromatic polyamide, imide polymers, sulfones Polymer, 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 Examples of the polymer that forms the protective film include blends of the aforementioned polymers. 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.

  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 on 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.

As the protective film, a film subjected to a hard coat treatment, an antireflection treatment, an antisticking treatment, or a treatment for diffusion or antiglare can be used.
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.

  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. Alternatively, 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 method of blending transparent fine 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 usually 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.

  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.

  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.

  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.

  As the retardation plate, for example, various wavelength plates and those for the purpose of compensating for coloring or viewing angle due to birefringence of the liquid crystal layer can be used, and 2 having an appropriate retardation according to the purpose of use. It is possible to control optical characteristics such as retardation by laminating more than one kind of retardation plate. 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.

  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.

  As such a viewing angle compensation phase difference plate, a birefringent film such as a uniaxial or biaxial stretching treatment or a biaxial stretching treatment, a bi-directional stretched film such as a tilted orientation film, etc. are used. It is done. 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, and 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 expanding a viewing angle with good viewing.

  In addition, the liquid crystal polymer alignment layer, especially the optically anisotropic layer composed of the tilted alignment layer made of discotic liquid crystal polymer or rod-like liquid crystal polymer, is made of triacetyl cellulose film in order to achieve a wide viewing angle with good visibility. A supported optical compensation phase difference plate can be preferably used.

  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 an elliptical polarizing plate or a circular polarizing plate is further laminated with a reflective plate or a semi-transmissive reflective plate can be used.

  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.

  Specific examples of the reflective polarizing plate include those in which a reflective layer is formed by attaching a foil or a vapor-deposited film made of a reflective metal such as aluminum on one side of a protective film matted as necessary. Moreover, what has microparticles | fine-particles contained in the said protective film to make a surface fine concavo-convex structure, and has the reflection layer of a fine concavo-convex structure on it is mentioned. 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.

  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.

  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.

Further, the polarizing plate may be formed by laminating a polarizing plate and two or more optical layers as in 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 semi-transmissive polarizing plate and a retardation plate are combined may be used.
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 (reflection type) 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.

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.
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 film and a transfer substrate can be illustrated. Moreover, it can provide by the same system.

  The pressure-sensitive adhesive layer can also 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 adhesive layers, such as a different composition, a kind, and thickness, 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, and particularly preferably 10 to 100 μm.

  A separator is temporarily attached to the exposed surface of the pressure-sensitive adhesive layer for the purpose of preventing contamination until it is put into practical use. Thereby, it can prevent contacting an adhesive layer in the usual handling state. As the separator, for example, a suitable thin leaf body such as a plastic film, rubber sheet, paper, cloth, nonwoven fabric, net, foamed sheet, metal foil, laminate thereof, or the like, silicone-based or long-chain alkyl-based, fluorine-based An appropriate material according to the prior art, such as a material coated with an appropriate release agent such as molybdenum sulfide or molybdenum sulfide, can be used.

  In the present invention, the polarizer, transparent protective film, optical film, or pressure-sensitive adhesive layer that forms the polarizing plate described above is, for example, a salicylic acid ester compound, a benzophenol compound, a benzotriazole compound, a cyanoacrylate compound, By treating with an ultraviolet absorber such as a nickel complex compound, these films and layers can be provided with an ultraviolet absorbing ability.

  The optical film of the present invention can be preferably used for forming various devices such as a liquid crystal display device. In particular, it is preferably used as a viewing angle improving film for liquid crystal display devices. The liquid crystal display device can be formed according to a known method. 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 necessary, and incorporating a drive circuit. There is no limitation in particular except the point which uses a film, and it can carry out according to the conventional method. Although there is no restriction | limiting in particular as a liquid crystal display device, Various liquid crystal display devices of a transmissive type, a reflective type, and a semi-transmissive type can be mentioned.

  Examples of modes by liquid crystal alignment in a liquid crystal cell include TN type, STN type, VA (vertical alignment) type, MVA (multi-domain vertical alignment) type, OCB (optically compensated bend) type, ECB (electrically controlled biriefringence). Type, HAN (hybrid-aligned nematic) type, IPS (in-plane switching) type, bistable nematic type, ASM (Axially Symmetric Aligned Microcell) type, halftone grayscale type, ferroelectric liquid crystal A display method using ferroelectric liquid crystal can be used.

  The liquid crystal alignment may have a single direction in the plane of the cell, or may be used for a liquid crystal display device in which the alignment is divided. In terms of a method of applying a voltage to the liquid crystal cell, for example, a liquid crystal display device driven by a passive method using an ITO electrode or the like, an active method using a TFT (thin film transistor) electrode or a TFD (thin film diode) electrode, etc. Can do.

  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.

  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.

  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.

  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.

  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.

  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.

  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. .

  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. .

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.
The polarizing plate using the optical film of the present invention can be suitably used for an organic EL display device.

  Using a liquid crystal material containing a side chain type liquid crystalline polymer obtained by polymerizing a (meth) acrylic compound having a novel oxetanyl group, it has excellent heat resistance by fixing the alignment state of the liquid crystal material, A homeotropic alignment film having high hardness and excellent mechanical strength can be obtained, and is useful as an optical film for various liquid crystal display devices, organic EL display devices, image display devices such as PDPs.

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.
In addition, each analysis method used in the Example is as follows.
⁽¹⁾ Measurement compound of 1 H-NMR was dissolved in deuterated chloroform and measured by ¹ H-NMR of 400 MHz (Variant Co. INOVA-400).
(2) Measurement of GPC The number average molecular weight (Mn) and weight average molecular weight (Mw) of the liquid crystalline polymer were determined by dissolving the compound in tetrahydrofuran and using TSK-GEL SuperH1000, SuperH2000, SuperH3000, and SuperH4000 with Tosoh 8020GPC system. They were connected in series and measured using tetrahydrofuran as an eluent. Polystyrene standards were used for molecular weight calibration.
(3) Microscope observation The alignment state of the liquid crystal was observed with an Olympus BH2 polarizing microscope.
(4) Parameter measurement of liquid crystal film Obi Scientific Instruments Co., Ltd. automatic birefringence meter KOBRA21ADH was used.

[Example 1]
A liquid crystalline polymer of the following formula (8) was synthesized by radical polymerization. The molecular weight was Mn = 8000 and Mw = 15000 in terms of polystyrene. In addition, the description in Formula (8) represents the structural ratio of a monomer, and does not mean a block polymer (The following formulas (9) to (12) have the same meaning).
After dissolving 1.0 g of the polymer of the formula (8) in 9 ml of cyclohexanone and adding 0.1 g of a triallylsulfonium hexafluoroantimonate 50% propylene carbonate solution (manufactured by Aldrich) in the dark, A solution of liquid crystal material was prepared by filtering insoluble matter with a 0.45 μm polytetrafluoroethylene filter.

The alignment substrate was prepared as follows.
A 38 μm-thick polyethylene naphthalate film (manufactured by Teijin DuPont Films Co., Ltd.) was cut into a 15 cm square, and a 5 wt% solution of alkyl-modified polyvinyl alcohol (PVA, Kuraray Co., Ltd., MP-203) (the solvent was water). And a mixture solvent of isopropyl alcohol in a weight ratio of 1: 1) was applied by spin coating, dried on a hot plate at 50 ° C. for 30 minutes, and then heated in an oven at 120 ° C. for 10 minutes. Subsequently, it was rubbed with a rayon rubbing cloth. The film thickness of the obtained PVA layer was 1.2 μm. The peripheral speed ratio during rubbing (moving speed of rubbing cloth / moving speed of substrate film) was 4.

The liquid crystal solution described above was applied to the alignment substrate thus obtained by spin coating. Next, it was dried on a hot plate at 60 ° C. for 10 minutes and heat-treated in an oven at 150 ° C. for 2 minutes to align the liquid crystal material. Next, the sample is placed in close contact with an aluminum plate heated to 60 ° C., and then a 600 mJ / cm ² ultraviolet light (however, measured at 365 nm) is irradiated with a high-pressure mercury lamp lamp to cure the liquid crystal material. It was.

Since the polyethylene naphthalate film used as the substrate has a large birefringence and is not preferable as an optical film, the obtained liquid crystal film on the alignment substrate is converted into a triacetyl cellulose (TAC) film via an ultraviolet curable adhesive. Transcribed. That is, on the cured liquid crystal material layer on the polyethylene naphthalate film, an adhesive is applied to a thickness of 5 μm, laminated with a TAC film, and irradiated with ultraviolet rays from the TAC film side to cure the adhesive. After that, the polyethylene naphthalate film was peeled off.
When the obtained optical film (PVA layer / liquid crystal layer / adhesive layer / TAC film) is observed under a polarizing microscope, there is no disclination and the monodomain has a uniform orientation. It was found that the homeotropic orientation has a structure. The retardation (Re) in the in-plane direction of the TAC film and the liquid crystal layer measured using KOBRA21ADH was 0.5 nm, and the retardation (Rth) in the thickness direction was −150 nm. Since the TAC film alone was negative uniaxial, the in-plane retardation was -0.5 nm, and the retardation in the thickness direction was +40 nm, the retardation of the liquid crystal layer alone was Re 0 nm, Rth Was estimated to be -190 nm.
Furthermore, only the liquid crystal material portion of the optical film was scraped, and the glass transition point was measured using DSC. The Tg was 100 ° C. Moreover, the pencil hardness of the liquid crystal material layer surface of the film was about 2H, and a sufficiently strong film was obtained.

[Example 2]
A liquid crystalline polymer of the following formula (9) was synthesized by radical polymerization. The molecular weight was Mn = 6000 and Mw = 12000 in terms of polystyrene. In addition, a low molecular liquid crystal having an oxetanyl group represented by the following formula (10) was synthesized. 0.8 g of the material of the formula (9) and 0.2 g of the material of the formula (10) are dissolved in 9 ml of diethylene glycol dimethyl ether, and in the dark, triallylsulfonium hexafluoroantimonate 50% propylene carbonate solution (manufactured by Aldrich, Reagent) After adding 0.1 g of a small amount of a fluorosurfactant, the insoluble matter was filtered through a polytetrafluoroethylene filter having a pore size of 0.45 μm to prepare a liquid crystal material solution.

The alignment substrate was prepared as follows.
A 50 μm-thick polyethylene naphthalate film (manufactured by Teijin DuPont Films Co., Ltd.) was cut into a 15 cm square, and a 5 wt% solution of alkyl-modified polyvinyl alcohol (PVA, Kuraray Co., Ltd., MP-102) (the solvent was water). And a mixture solvent of isopropyl alcohol in a weight ratio of 1: 1) was applied by spin coating, dried on a hot plate at 50 ° C. for 30 minutes, and then heated in an oven at 150 ° C. for 5 minutes. Subsequently, it was rubbed with a rayon rubbing cloth. The film thickness of the obtained PVA layer was 0.8 μm. The peripheral speed ratio during rubbing (moving speed of rubbing cloth / moving speed of substrate film) was 10.

The liquid crystal solution described above was applied to the alignment substrate thus obtained by spin coating. Next, it was dried on a hot plate at 60 ° C. for 10 minutes and heat-treated in an oven at 150 ° C. for 2 minutes to align the liquid crystal material. Next, the sample is placed in close contact with an aluminum plate heated to 60 ° C., and then the liquid crystal material is cured by irradiating 400 mJ / cm ² ultraviolet light (however, measured at 365 nm) with a high-pressure mercury lamp lamp. I let you.

Since the polyethylene naphthalate film used as the substrate has a large birefringence and is not preferable as an optical film, the obtained liquid crystal film on the alignment substrate is subjected to a retardation of 140 nm in the in-plane direction via an ultraviolet curable adhesive. It was transferred to a polycarbonate film. That is, on the cured liquid crystal material layer on the polyethylene naphthalate film, an adhesive is applied, laminated with a polycarbonate film, and irradiated with ultraviolet light of 400 mJ / cm ² from the polycarbonate film side to cure the adhesive. After that, the PVA layer and the polyethylene naphthalate film were peeled off.

The obtained optical film (liquid crystal layer / adhesive layer / polycarbonate film) had an in-plane retardation (Re) of 140 nm and was biaxial. The retardation of the liquid crystal layer alone was estimated to be -120 nm by transferring to a TAC film having no in-plane anisotropy as in Example 1.
Using one liquid crystal film on the polycarbonate film thus obtained, as shown in FIG. 1, the backlight 6, the lower polarizing plate 5, the IPS liquid crystal cell 4, and the upper polarizing plate 1 are arranged in this order. An optical film (homeotropic alignment liquid crystal film 2: polycarbonate film 3) was disposed between the upper polarizing plate 1 and the liquid crystal cell 4 for a commercially available IPS type liquid crystal television. As a result, it was found that the viewing angle was widened compared to the case where the present film was not used, and a good image was obtained even when viewed from an oblique direction.

[Example 3]
A liquid crystalline polymer of the following formula (11) was synthesized. The molecular weight was Mn = 11000 and Mw = 20000 in terms of polystyrene. After dissolving 1.0 g of the polymer of the formula (11) in 9 ml of cyclohexanone and adding 0.05 g of a photoinitiator (SP-172 manufactured by Asahi Denka Co., Ltd.) in the dark, polytetrafluoro having a pore size of 0.45 μm The insoluble matter was filtered with an ethylene filter to prepare a liquid crystal material solution.

The alignment substrate was prepared as follows.
A 5 wt% N-methylpyrrolidone solution of polyamide of the following formula (12) was applied to a borosilicate glass having a thickness of 0.7 mm and a 15 cm square by a spin coat method, dried on a hot plate at 80 ° C. for 30 minutes, and then 120 Heated in an oven at 0 ° C. for 10 minutes.

The liquid crystal solution described above was applied to the alignment substrate thus obtained by spin coating. Next, it was dried on a hot plate at 60 ° C. for 10 minutes and heat-treated in an oven at 140 ° C. for 2 minutes to align the liquid crystal material. Next, the sample is placed in close contact with an aluminum plate heated to 70 ° C., and then the liquid crystal material is cured by irradiating 300 mJ / cm ² of ultraviolet light (however, measured at 365 nm) with a high-pressure mercury lamp lamp. I let you.
When the obtained optical film on the glass substrate was observed under a polarizing microscope, monodomain uniform homeotropic liquid crystal alignment without disclination was observed. The retardation (Rth) measured using KOBRA21ADH was -250 nm.

[Example 4]
Using a TAC film (thickness 80 μm) on which a cholesteric liquid crystal layer (thickness 5 μm) exhibiting circular dichroism in a band of 400 to 700 nm is formed, the liquid crystal layer is obtained in Example 3. A quarter-wave plate made of polycarbonate film (front retardation) obtained by pasting the homeotropic alignment liquid crystal film through an adhesive layer (thickness: 25 μm) formed of an acrylic adhesive, and further stretching it. 130 nm) (thickness 60 μm) was bonded through an adhesive layer (thickness 25 μm) formed of the same acrylic pressure-sensitive adhesive to produce a brightness enhancement film.
As shown in FIG. 2, the brightness enhancement film thus obtained is a backlight of a commercially available liquid crystal display in which the backlight 21, the lower polarizing plate 9, the liquid crystal cell 8, and the upper polarizing plate 7 are arranged in this order. A brightness enhancement film 13 (cholesteric liquid crystal film 12: homeotropic alignment liquid crystal film 11: quarter-wave plate 10) was disposed between 21 and the lower polarizing plate 9. As a result, it was found that a bright image having a luminance improvement rate of 30% was obtained compared to the case where the luminance enhancement film 13 was not used.

6 is a conceptual diagram of a liquid crystal display used in Example 2. FIG. 6 is a conceptual diagram of a liquid crystal display used in Example 4. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Upper polarizing plate 2 Homeotropic alignment liquid crystal film 3 Polycarbonate film 4 IPS type liquid crystal cell 5 Lower polarizing plate 6 Backlight 7 Upper polarizing plate 8 Liquid crystal cell 9 Lower polarizing plate 10 1/4 wavelength plate 11 Homeotropic alignment liquid crystal film 12 Cholesteric Liquid crystal film 13 Brightness enhancement film 14 Diffusion plate 15 Condensing sheet 16 Condensing sheet
17 Diffuser 18 Light guide 19 Reflector 20 Lamp 21 Backlight

Claims (7)

A liquid crystal material containing a side chain type liquid crystalline polymer substance having an oxetanyl group as a constituent component is homeotropically aligned in a liquid crystal state on an alignment substrate, and then the oxetanyl group is reacted to fix the homeotropic alignment. A homeotropic alignment liquid crystal film comprising the following requirements [1] and [2]:
[1] 0 nm ≦ Re ≦ 200 nm
[2] −500 nm ≦ Rth ≦ −30 nm
(Here, Re means an in-plane retardation value of the liquid crystal film, and Rth means a retardation value in the thickness direction of the liquid crystal film. Re and Rth are respectively Re = (Nx−Ny) × d, Rth = (Nx−Nz) × d, where d is the thickness [nm] of the liquid crystal film, Nx and Ny are the main refractive index in the liquid crystal film plane, and Nz is the main refractive index in the thickness direction. Yes, Nz> Nx ≧ Ny.)   The homeotropic alignment liquid crystal film according to claim 1, wherein the alignment substrate is made of at least an organic substance having a long-chain alkyl group.   The homeotropic alignment liquid crystal film according to claim 1, wherein the alignment substrate comprises at least polyvinyl alcohol having a long-chain alkyl group.   An optical film, wherein the homeotropic alignment liquid crystal film according to claim 1 is further laminated with at least one optical film.   The liquid crystal display device using the film in any one of Claims 1-4.   The organic electroluminescence display using the film in any one of Claims 1-4.   The image display apparatus using the film in any one of Claims 1-4.

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