JP2007256761A - Elliptical polarizing plate, manufacturing method thereof, and liquid crystal display device using the same - Google Patents

Abstract

An elliptically polarizing plate having a thin film and good heat-and-moisture resistance and a method for producing the same are provided.
Furthermore, since it can bond in a long film form also in the bonding process with a polarizing element, there exists an advantage which can rationalize a bonding process from the conventional method.
An elliptically polarizing plate in which a polarizing element is sandwiched between an optically anisotropic element composed of a liquid crystal layer aligned on an optically isotropic substrate and a translucent protective film, the optically anisotropic element comprising: An elliptically polarizing plate comprising: a homeotropic alignment liquid crystal layer in which a liquid crystal composition in which the element has at least positive uniaxial property is homeotropically aligned in a liquid crystal state and then the alignment is fixed.
[Selection] Figure 1

Description

  The present invention relates to an elliptically polarizing plate composed of a liquid crystal layer having a homeotropic alignment structure fixed, and a method for producing the same, and further relates to a liquid crystal display device using the elliptically polarizing plate.

The retardation film plays an important industrial role such as being used to improve the image quality of a liquid crystal display device. Retardation 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 using 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, a main-chain polymer liquid crystal is homeotropically aligned, and then a film is obtained by glass fixation (Patent Documents 1 to 3). However, in homeotropic alignment, it is surmised that there is a problem that cracks are likely to occur in the in-plane direction because the polymers are aligned in the film thickness direction, but in these reports, measures such as strengthening the material by crosslinking are taken. Absent. In Patent Document 4, the homeotropic alignment of the side chain type liquid crystal is fixed by vitrification, but it is considered that there is a problem in strength as compared with the main chain type polymer liquid crystal.

  On the other hand, there are reports of adding polymerizable low-molecular liquid crystals to side-chain liquid crystals (Patent Documents 5 to 6), but low-molecular liquid crystals polymerize alone, so there is a limit to reinforcing the strength of side-chain liquid crystals. is there. 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 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.

  In addition, the retardation film is used in a liquid crystal display device as an elliptically polarizing plate bonded with a polarizing element. However, when the retardation film and the polarizing element are bonded with an adhesive / adhesive layer, the thickness of the adhesive film is equal to the adhesive / adhesive layer. In addition, when winding on a roll in the manufacturing process of the elliptically polarizing plate, there are problems that the amount of winding per roll is reduced and productivity is deteriorated, and the thickness of the liquid crystal panel of the final product is increased. In addition, since it is composed of a plurality of different types of layers, there may be a problem such as peeling of the interface between the polarizing plate and the retardation film due to the difference in expansion and contraction behavior of each layer with respect to heat and humidity.

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 purpose of the present invention is to reduce the thickness by simplifying the layer structure of the elliptically polarizing plate, without causing problems such as peeling even under high temperature and high humidity conditions, and fixing the homeotropic alignment structure. It is an object to provide an elliptically polarizing plate capable of continuously laminating an optically anisotropic element and a polarizing element comprising a liquid crystal layer, from a long film form, a manufacturing method thereof, and a liquid crystal display device using the same And

  That is, a first aspect of the present invention is an elliptically polarizing plate in which a polarizing element is sandwiched between an optically anisotropic element composed of a liquid crystal layer aligned on an optically isotropic substrate and a translucent protective film. An elliptically polarizing plate comprising: a homeotropic alignment liquid crystal layer in which the alignment is fixed after homeotropic alignment of a liquid crystalline composition in which the optical anisotropic element exhibits at least positive uniaxiality in a liquid crystal state , Regarding.

  According to a second aspect of the present invention, the elliptically polarizing plate according to the first aspect of the present invention, wherein the elliptically polarizing plate is obtained from an optically anisotropic element in the form of a long film, a translucent protective film, and a polarizing element, About.

  According to a third aspect of the present invention, the optically anisotropic element comprises a liquid crystalline composition containing a side chain type liquid crystalline polymer compound having an oxetanyl group, and homeotropically aligns the oxetanyl group in a liquid crystal state. The elliptically polarizing plate according to the first aspect of the present invention, which is a homeotropic alignment liquid crystal layer in which the homeotropic alignment is fixed by reacting.

A fourth aspect of the present invention relates to the elliptically polarizing plate according to the first aspect of the present invention, wherein the optically anisotropic element comprises a homeotropic alignment liquid crystal layer satisfying the following [1] and [2]: .
[1] 0 ≦ Re ≦ 200
[2] −500 ≦ Rth ≦ −30
(Here, Re means an in-plane retardation value of the liquid crystal layer, and Rth means a retardation value in the thickness direction of the liquid crystal layer. Re and Rth are respectively Re = (Nx−Ny) × d [nm], Rth = (Nx−Nz) × d [nm] where d is the thickness of the liquid crystal film, Nx and Ny are the main refractive index in the liquid crystal layer surface, and Nz is the main refraction in the thickness direction. (Nz> Nx ≧ Ny)

A fifth aspect of the present invention relates to the elliptically polarizing plate according to the first aspect of the present invention, wherein the optically isotropic substrate is triacetyl cellulose.
A sixth aspect of the present invention relates to the elliptically polarizing plate according to the first aspect of the present invention, wherein the optically isotropic substrate is a cycloolefin polymer.
A seventh aspect of the present invention relates to the elliptically polarizing plate according to any one of the first to sixth aspects, wherein an optically anisotropic element is surface-treated.
An eighth aspect of the present invention relates to the elliptically polarizing plate according to the seventh aspect of the present invention, wherein the surface treatment is a saponification treatment.
A ninth aspect of the present invention relates to the elliptically polarizing plate according to the seventh aspect of the present invention, wherein the surface treatment is a corona discharge treatment.
A tenth aspect of the present invention relates to the elliptically polarizing plate according to any one of the first to ninth aspects, wherein the elliptically polarizing plate has a thickness of 250 μm or less.
The eleventh aspect of the present invention relates to the elliptically polarizing plate according to any one of the first to tenth aspects of the present invention, wherein a translucent overcoat layer is provided on the surface of the liquid crystal layer.

A twelfth aspect of the present invention relates to the elliptically polarizing plate according to the eleventh aspect of the present invention, wherein the translucent overcoat layer is made of an acrylic resin.
A thirteenth aspect of the present invention relates to an elliptically polarizing plate, wherein the elliptically polarizing plate according to any one of the first to twelfth aspects of the present invention is further laminated with at least one optical film.
According to the fourteenth aspect of the present invention, after forming a liquid crystal layer on an optically isotropic substrate, an optically anisotropic element is produced by providing a translucent overcoat layer on the surface of the liquid crystal layer, An elliptically polarizing plate characterized in that an optically anisotropic element is subjected to a surface treatment, and then the polarizing element is bonded so as to be sandwiched between the optically anisotropic element and a light-transmitting protective film via an adhesive / adhesive layer. The manufacturing method.
A fifteenth aspect of the present invention relates to a liquid crystal display device in which the elliptically polarizing plate according to any one of the first to thirteenth aspects of the present invention is disposed on at least one surface of a liquid crystal cell.

  In the present invention, an elliptically polarizing plate is produced by using an optically anisotropic element as a protective film for a polarizing element. By doing so, a layer number can be reduced rather than the elliptical polarizing plate which bonded the optically anisotropic element to the polarizing plate by which the both sides of the polarizing element were protected by the triacetyl cellulose film like the past. As a result, the influence of shrinkage strain of each layer due to heat or humidity is reduced, and problems such as peeling at the bonded interface can be eliminated.

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

First, the liquid crystal composition will be described.
The liquid crystalline composition used in the present invention preferably contains at least a side chain type liquid crystalline polymer such as poly (meth) acrylate or polysiloxane as a main constituent component. Particularly preferred are those having a polymerizable oxetanyl group at the end of the side chain type liquid crystalline polymer. 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 liquid crystalline polymer substance is preferably used.

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 represent a single bond, —O—, —O—CO. -Represents either-or -CO-O-, M represents formula (2), (3) or formula (4), and n and m each represents 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), (3) and (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 these (meth) acrylic compounds having an oxetanyl group is not particularly limited, and can be synthesized by applying a method used in an ordinary 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.

  A unit represented by the following formula (7) by homopolymerizing or copolymerizing with a (meth) acryl group of a (meth) acrylic compound having an oxetanyl group represented by the formula (1) A side chain liquid crystalline polymer containing 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) acrylic compound to be copolymerized at this time is not particularly limited and may be anything as long as the synthesized polymer compound exhibits liquid crystallinity, but in order to increase the liquid crystallinity of the synthesized polymer compound, 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 CN group.

  The side chain type liquid crystalline polymer compound preferably contains 5 to 100 mol% of the unit represented by the formula (7), and particularly preferably contains 10 to 100 mol%. The side chain type liquid crystalline polymer compound preferably has a weight average molecular weight of 2,000 to 100,000, and particularly preferably 5,000 to 50,000.

  In the liquid crystalline composition used in the present invention, various compounds that can be mixed without impairing liquid crystallinity can be contained in addition to the side chain liquid crystalline polymer compound. 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 crystal polymer compound is used as a composition, the proportion of the side chain liquid crystal polymer compound 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 compound 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, which is not preferable.

  In addition, since the liquid crystalline composition is subjected to an alignment treatment, the oxetanyl group is cationically polymerized and crosslinked, thereby taking a step of fixing the liquid crystal state. Therefore, in the liquid crystalline composition, light, heat, etc. It is preferable to contain a photo cation generator and / or a thermal cation generator that generate cations by external stimulation. 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 composition varies depending on the structure of the mesogen portion or spacer portion constituting the side chain type liquid crystal polymer compound used, the oxetanyl group equivalent, the liquid crystal alignment conditions, and the like. Although it cannot be generally stated, it is usually 100 mass ppm to 20 mass%, preferably 1000 mass ppm to 10 mass%, more preferably 0.2 mass% to 7 mass% than the compound, with respect to the side chain liquid crystalline polymer. Most preferably, it is the range of 0.5 mass%-5 mass%. 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 residual cation generator remaining in the liquid crystal layer may remain decomposed. 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, a film or sheet made of an organic polymer is preferable. Examples of organic polymer materials constituting the film or sheet include polyvinyl alcohol, polyimide, polyphenylene sulfide, polyphenylene oxide, polyether ketone, polyether ether ketone, polyether sulfone, polyethylene naphthalate, polyethylene terephthalate, polyarylate, Examples include triacetyl cellulose and cycloolefin polymers. In order to obtain homeotropic alignment stably using the liquid crystalline composition described above, the materials constituting these substrates have long-chain (usually 4 or more carbon atoms, preferably 8 or more) alkyl groups. Or those in which a compound layer having the alkyl group is formed on the surface of the film or sheet. The compound having a long chain alkyl group is preferably polyvinyl alcohol having a long chain alkyl group.

  In the field of liquid crystal, rubbing treatment with a cloth or the like is generally performed on a substrate, but the homeotropic alignment liquid crystal layer of the present invention is an alignment in which in-plane anisotropy basically does not occur. Because of the structure, rubbing is not necessarily required. However, it is more preferable to perform a weak rubbing treatment from the viewpoint of suppressing repelling when the liquid crystalline composition is applied. An important setting value that defines the rubbing condition is a peripheral speed ratio. This represents the 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 the substrate is 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 larger than 50, the effect of rubbing is too strong, and the liquid crystalline composition cannot be completely aligned vertically, and there is a fear that the alignment is tilted in the in-plane direction from the vertical direction.

Next, the manufacturing process of the optical anisotropic element used in the present invention will be described.
The manufacturing method of the optically anisotropic element is not limited to these, but the above-mentioned liquid crystalline composition is spread on the above-mentioned alignment substrate, and the liquid crystalline composition is aligned, and then light irradiation and / or Or it can manufacture by fixing the said orientation state by heat-processing.
As a method for forming a liquid crystalline composition layer by spreading the liquid crystalline composition on an alignment substrate, a method in which the liquid crystalline composition is directly applied on the alignment substrate in a molten state, or a solution of the liquid crystalline composition is aligned. The method of drying a coating film and distilling a solvent after apply | coating on a board | substrate is mentioned.

  The solvent used for preparing the solution is not particularly limited as long as it can dissolve the liquid crystalline composition of the present invention and can be distilled off under appropriate conditions. Generally, ketones such as acetone, methyl ethyl ketone, isophorone, cyclohexanone, Ether alcohols such as butoxyethyl alcohol, hexyloxyethyl alcohol, methoxy-2-propanol, glycol ethers such as ethylene glycol dimethyl ether and diethylene glycol dimethyl ether, esters such as ethyl acetate, ethyl lactate and γ-butyrolactone, phenol, chlorophenol Phenols such as N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone and other amides, chloroform, tetrachloroethane, dichlorobenzene, etc. Halogen-like or mixtures of these systems are preferably used. Further, 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.

There is no particular limitation on the application method, either a method of directly applying a liquid crystalline composition or a method of applying a solution, as long as the uniformity of the coating film is ensured, and a known method is adopted. be able to. Examples thereof include spin coating, die coating, curtain coating, dip coating, and roll coating.
In the method of applying the liquid crystal composition 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 crystalline composition layer formed on the alignment substrate is formed into a liquid crystal alignment by a method such as heat treatment, and cured by light irradiation and / or heat treatment to fix the alignment. In the first heat treatment, the liquid crystal is aligned by the self-alignment ability inherent in the liquid crystal composition by heating to the liquid crystal phase expression temperature range of the liquid crystal composition used. 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 composition to be used, but it cannot be generally stated, but is usually 10 to 250 ° C., preferably 30 to 160 ° C. It is preferable that the heat treatment be performed at a temperature not lower than the glass transition point (Tg) of the liquid crystalline composition, more preferably not lower than 10 ° C. higher 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 crystalline composition 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 composition layer is formed into a liquid crystal alignment by a method such as heat treatment, the liquid crystal composition is cured by a polymerization reaction of an oxetanyl group in the composition while maintaining the liquid crystal alignment state. 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 crystalline composition of the present invention has a polymerizable oxetanyl group, it is preferable to use a cationic polymerization initiator (photo cation generator and / or thermal cation generator) for polymerization (crosslinking) of the reactive group. This is 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 crystalline composition can be obtained if the steps from the addition of the photo cation generator to the heat treatment for liquid crystal alignment are performed under dark conditions (light blocking conditions that do not cause the photo cation generator to dissociate). The product can be liquid crystal aligned with sufficient fluidity without being cured until the alignment stage. Thereafter, the liquid crystal composition layer 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 significantly different, or when the liquid crystalline polymer constituting the liquid crystalline composition 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 in a temperature range in which the liquid crystalline composition takes liquid crystal alignment. In order to sufficiently enhance the curing effect, it is preferable to perform light irradiation at a temperature equal to or higher than Tg of the liquid crystalline composition.

  The liquid crystalline composition layer of the optical anisotropic element manufactured by the above process 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.

  Note that the alignment substrate is not optically isotropic, or the optically anisotropic element to be obtained is finally opaque in the intended use wavelength region, or the alignment substrate is too thick, which hinders actual use. In the case where there is a problem such as the formation of an optically anisotropic element from the form formed on the alignment substrate, or the optical anisotropic element obtained is finally transparent in the intended use wavelength region, or optical A form transferred to a film for temporarily supporting the anisotropic element until it is bonded to a liquid crystal cell or the like can also be used. 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 layer is laminated with an optically isotropic substrate different from the alignment substrate via an adhesive or an adhesive. Then, if necessary, a method of transferring only the liquid crystal layer by subjecting the surface to a curing treatment using an adhesive or an adhesive and peeling the alignment substrate from the laminate can be exemplified.

The optically isotropic substrate used in the present invention has an in-plane retardation value (Re1) of 10 nm or less, preferably 0 to 5 nm.
The retardation value (Rth1) in the thickness direction is 60 nm or less, preferably 0 to 10 nm.
Outside this range, the performance of the obtained elliptically polarizing plate may be adversely affected, which is not preferable. Re1 is a value represented by Re1 = (nx−ny) × d, where nx and ny (nx ≧ ny) are the main refractive indices in the plane of the substrate and d [nm] is the film thickness. is there. Rth1 is a value represented by Rth1 = (nx−nz) × d where the refractive index in the thickness direction of the substrate is nz and the film thickness is d [nm].
Moreover, a film thickness can also be selected suitably and it is 5-100 micrometers normally, Preferably it is 10-50 micrometers.

  Examples of optically isotropic substrates include triacetyl cellulose films such as Fujitac (product of Fuji Photo Film) and Konicatak (product of Konica), Arton film (product of JSR), ZEONOR film, ZEONEX film ( Cycloolefin polymers such as Nippon Zeon Co., Ltd.), TPX film (Mitsui Chemicals Co., Ltd.), acrylprene film (Mitsubishi Rayon Co., Ltd.), etc. Triacetyl cellulose and cycloolefin polymers are preferred. In addition, when using the film for temporarily supporting, it is not always necessary to be concerned with the value of Re1, for example, a polyethylene terephthalate film having a silicone treatment or an easily peelable layer provided on the surface. Can be mentioned.

  As a material for forming the overcoat layer provided on the liquid crystal layer of the optical anisotropic element, the material has sufficient adhesion to the liquid crystal layer and the isotropic substrate and does not impair the optical characteristics of the liquid crystal layer. If there is no particular limitation, for example, acrylic resin-based, methacrylic resin-based, epoxy resin-based, ethylene-vinyl acetate copolymer system, rubber system, urethane system, polyvinyl ether system and mixtures thereof, thermosetting type and And / or various reactive types such as a photo-curing type and an electron beam-curing type. These overcoat layers include those having the function of a transparent protective layer for protecting the liquid crystal layer. An adhesive or a pressure sensitive adhesive can also be used as the overcoat layer.

  Since the reaction (curing) conditions for the reactive substances vary depending on the components constituting the overcoat layer, the viscosity, the reaction temperature, and the like, the conditions suitable for each may be selected. For example, in the case of a photo-curing type, it is preferable to add various known photoinitiators to emit 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, a laser, or a synchrotron radiation light source. Irradiation may be performed to cause the reaction. The amount of irradiation per unit area (one square centimeter) is usually in the range of 1 to 2000 mJ, preferably 10 to 1000 mJ as the integrated irradiation amount. However, this is not the case when the absorption region of the photoinitiator and the spectrum of the light source are significantly different, or when the reactive compound itself has the ability to absorb the light source wavelength. In these cases, an appropriate photosensitizer or a method of using a mixture of two or more photoinitiators having different absorption wavelengths can be used. The acceleration voltage in the case of the electron beam curable type is usually 10 kV to 200 kV, preferably 50 kV to 100 kV.

  Although the thickness of an overcoat layer changes with the components which comprise the said layer as mentioned above, the intensity | strength of the said layer, use temperature, etc., it is 1-50 micrometers normally, Preferably it is 2-30 micrometers, More preferably, it is 3-10 micrometers. Outside this range, it is not preferable because the film thickness of the final product becomes too thick or the intended function is insufficient.

  These overcoat layers can also contain various fine particles and surface modifiers for the purpose of controlling the optical properties or controlling the peelability and erosion properties of the substrate as long as the properties are not impaired.

  Examples of the fine particles include fine particles having a refractive index different from that of the compound constituting the overcoat layer, conductive fine particles for improving antistatic performance without impairing transparency, fine particles for improving wear resistance, and the like. Specific examples include fine silica, fine alumina, ITO (Indium Tin Oxide) fine particles, silver fine particles, and various synthetic resin fine particles.

  The surface modifier is not particularly limited as long as it has good compatibility with the adhesive and does not affect the curability of the adhesive or the optical performance after curing, and is an ionic or nonionic water-soluble interface. Activators, oil-soluble surfactants, polymer surfactants, fluorosurfactants, organometallic surfactants such as silicone, reactive surfactants, and the like can be used. In particular, fluorine-based surfactants such as perfluoroalkyl compounds and perfluoropolyether compounds, and organometallic surfactants such as silicone are particularly desirable because they have a large surface modification effect. The addition amount of the surface modifier is desirably in the range of 0.01 to 10% by mass with respect to the adhesive, more desirably 0.05 to 5% by mass, and further desirably 0.1 to 3% by mass. If the amount added is less than this range, the effect of addition becomes insufficient. On the other hand, if the amount added is too large, there is a risk of adverse effects such as an excessive decrease in adhesive strength. In addition, a surface modifier may be used independently and may use multiple types together as needed.

Furthermore, you may mix | blend various additives, such as antioxidant and a ultraviolet absorber, in the range which does not impair the effect of this invention.
The overcoat layer is more preferably resistant to various surface treatments described later.

  In the liquid crystal layer of the optical element used in the present invention, the thickness of the liquid crystal layer is d, the main refractive index in the liquid crystal layer surface is Nx, Ny, the main refractive index in the thickness direction is Nz, and Nx ≧ Ny. In-plane retardation value (Re) is Re = (Nx−Ny) × d [nm], and retardation value (Rth) in the thickness direction is Rth = (Nx−Nz) × d [nm]. The Re and Rth, which are optical parameters of the liquid crystal layer, are used for a brightness enhancement film or when used as a viewing angle improvement film for a liquid crystal display device. However, since it depends on the method of the liquid crystal display device and various optical parameters, the liquid crystal layer Re is usually 0 nm to 200 nm, preferably 0 nm to 100 n for monochromatic light of 550 nm. m, more preferably in the range of 0 nm to 50 nm, and Rth is usually controlled to be −500 to −30 nm, preferably −400 to −50 nm, more preferably −400 to −100 nm.

  By setting Re and Rth 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. When Re is larger than 200 nm, the front characteristics of the liquid crystal display element may be deteriorated due to the large front phase difference value. On the other hand, when Rth is larger than −30 nm or smaller than −500 nm, a sufficient viewing angle improvement effect may not be obtained, or unnecessary coloring may occur when viewed from an oblique direction.

  The film thickness of the liquid crystal layer depends on the optical anisotropy (birefringence) of the liquid crystal composition to be used, the type of liquid crystal display device and various optical parameters. The thickness is 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 improving effect cannot be obtained. If it exceeds 10 μm, the liquid crystal display device may be unnecessarily colored.

  The liquid crystal layer obtained as described above can be quantified by measuring the optical phase difference of the liquid crystal layer at an angle inclined from normal incidence. In the case of homeotropic alignment liquid crystal layers, this retardation value is symmetric with respect to normal incidence. Several methods can be used 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 layer appears black between the crossed Nicol polarizers. Thus, homeotropic orientation was evaluated.

  The polarizing element that can be used in the present invention is not particularly limited, and various types can be used. Examples of polarizing elements include hydrophilic polymer films such as polyvinyl alcohol films, partially formalized polyvinyl alcohol films, and ethylene / vinyl acetate copolymer partially saponified films, and two colors such as iodine and dichroic dyes. And polyene-based oriented films such as those obtained by adsorbing a functional substance and uniaxially stretched, 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 polarizing element is not particularly limited, but is generally about 5 to 80 μm.

  A polarizing element in which a polyvinyl alcohol film is dyed with iodine and uniaxially stretched can be produced 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. 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 translucent protective film provided on one surface of the polarizing element can be appropriately selected from the above optically isotropic substrates, but the thickness of the translucent protective film is generally 200 μm. 1 to 100 μm is preferable. In particular, the thickness is preferably 5 to 50 μm. In addition, a hard coat layer, an antireflection treatment, an antisticking treatment, or a treatment subjected to diffusion or antiglare treatment can be used.

  Hard coat treatment is performed for the purpose of preventing scratches on the surface of the polarizing plate, for example, a protective film with a cured film excellent in hardness, sliding properties, etc. 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 film. 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. It can be formed by imparting a fine concavo-convex structure to the surface of the protective film by an appropriate method such as a blending method of transparent 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 made of a crosslinked or uncrosslinked polymer, etc. are used. When forming a surface fine uneven structure, the amount of fine particles used is generally about 2 to 50 parts by weight, preferably 5 to 25 parts by weight, based on 100 parts by weight of the transparent resin forming the surface fine uneven structure. The antiglare layer may also serve as a diffusion layer (viewing angle expanding function or the like) for diffusing the light transmitted through the polarizing plate to expand the viewing angle.

  The anti-reflection layer, anti-sticking layer, diffusion layer, anti-glare layer, etc. can be provided on the optically isotropic substrate itself, and separately provided as a separate optical layer from the transparent protective film layer. You can also.

Next, the optical anisotropic element is bonded to the polarizing element, but it is preferable to subject the optical anisotropic element to surface treatment before bonding.
For the surface treatment, a method suitable for an optically transparent substrate constituting the optical anisotropic element may be used. Examples of such a method include saponification treatment, corona discharge treatment, flame treatment, and the like. Saponification treatment is preferred when acetylcellulose is used, and corona discharge treatment is preferred when a cycloolefin polymer is used.

  The saponification treatment is usually performed by contacting with an alkaline aqueous solution. As the alkaline aqueous solution, potassium hydroxide, sodium hydroxide or the like is used, and the alkali concentration is about 0.1 to 10% by mass, preferably about 0.5 to 5% by mass, more preferably about 1 to 3% by mass. A dilute solution of about% is sufficient. As treatment conditions, mild conditions of 1 to 60 minutes at room temperature, preferably 30 minutes or less, more preferably 15 minutes or less are sufficient. Needless to say, it is necessary to thoroughly wash with water after the treatment. If the overcoat layer is provided on the liquid crystal layer, the liquid crystal layer will not be eroded or damaged in the saponification treatment step.

The corona discharge treatment may be performed under normal conditions, for example, on the isotropic substrate surface in contact with the adhesive layer. The processing conditions vary depending on the type of substrate and corona processing apparatus to be used. For example, the energy density is preferably 1 to 300 W · min / m ² . The surface tension is increased by performing the corona discharge treatment, but it is desirable to increase the surface tension to 40 dyn / cm or more.

  Bonding of the optically anisotropic element and the polarizing element can be performed using an appropriate adhesive / adhesive. Any adhesive / adhesive can be used as long as it is translucent and optically isotropic, and examples thereof include acrylic, epoxy, ethylene-vinyl acetate, and rubber. May have a reactive group such as a photopolymerizable group, in which case it is necessary to perform a curing step suitable for reacting the reactive group after bonding. Among the above-mentioned adhesives / adhesives, acrylic adhesives / adhesives are particularly preferably used.

  The formation of the adhesive / adhesive layer can be performed by a known method, and for example, it may be performed in the same manner as the formation of the liquid crystal layer. Bonding between an optically anisotropic element and a polarizing element is performed using a laminator, a roll, a pressurizer, etc. in order to improve the bonding strength, prevent the generation of bubbles due to the remaining air at the bonding interface, etc. Pressure, heating or the like may be applied. For the bonding, a so-called non-carrier adhesive / adhesive in which the above-mentioned adhesive / adhesive layer is formed on an appropriate substrate provided with an easy peeling treatment such as silicone may be used.

Subsequently, the elliptically polarizing plate of this invention can be obtained by bonding a translucent protective film to the surface on the opposite side to the said bonding surface of the polarizing element with which the optical anisotropic element was bonded.
The translucent protective film may be bonded using the same method and apparatus as those used for bonding the optically anisotropic element and the polarizing element.
Said optically anisotropic element, polarizing element, and translucent protective film can be laminated | stacked by superimposing continuously in the state aligned in MD direction in the form of a long film, respectively.
In addition, even if these three members simultaneously bond the optical anisotropic element and the translucent protective film to both sides of the polarizing element, the optical anisotropic element and the translucent protective film are sequentially applied to the polarizing element, or the translucent You may bond in order of a protective film and an optical anisotropic element.
Furthermore, the elliptically polarizing plate of the present invention may contain one or more antireflection layers, antiglare treatment layers, hard coat layers, adhesive layers, adhesive layers, light diffusing layers, light diffusing adhesive layers and the like.

Next, a liquid crystal display device to which the elliptically polarizing plate of the present invention is applied will be described.
The liquid crystal display device of the present invention has at least the elliptically polarizing plate. When the elliptically polarizing plate of the present invention is disposed in a liquid crystal cell, it is necessary to dispose the liquid crystal polymer layer of the elliptically polarizing plate between the polarizing element layer and the liquid crystal cell.
A liquid crystal display device is generally composed of a polarizing plate, a liquid crystal cell, and a member such as a retardation compensation plate, a reflection layer, a light diffusion layer, a backlight, a front light, a light control film, a light guide plate, and a prism sheet as necessary. Although comprised, in this invention, there is no restriction | limiting in particular except the point which uses the said elliptically polarizing plate. Further, the use position of the elliptically polarizing plate is not particularly limited, and may be one place or a plurality of places.

The polarizing plate used for the liquid crystal display device is not particularly limited, and those obtained from the same polarizing element as those used for the elliptically polarizing plate described above can be used.
The liquid crystal cell is not particularly limited, and a general liquid crystal cell such as a liquid crystal layer sandwiched between a pair of transparent substrates provided with electrodes can be used.
The transparent substrate constituting the liquid crystal cell is not particularly limited as long as the liquid crystal material constituting the liquid crystal layer is aligned in a specific alignment direction. Specifically, a transparent substrate in which the substrate itself has a property of orienting liquid crystals, a transparent substrate in which an alignment film having the property of orienting liquid crystals is provided, but the substrate itself lacks the alignment ability. Either can be used. Moreover, a well-known thing can be used for the electrode of a liquid crystal cell. Usually, it can be provided on the surface of the transparent substrate in contact with the liquid crystal layer, and when a substrate having an alignment film is used, it can be provided between the substrate and the alignment film.

  The material exhibiting liquid crystallinity for forming the liquid crystal layer is not particularly limited, and examples thereof include various ordinary low-molecular liquid crystal substances, polymer liquid crystal substances, and mixtures thereof that can constitute various liquid crystal cells. In addition, a dye, a chiral agent, a non-liquid crystal substance, or the like can be added to these as long as liquid crystallinity is not impaired.

In addition to the electrode substrate and the liquid crystal layer, the liquid crystal cell may include various components necessary for forming various types of liquid crystal cells described later.
As the liquid crystal cell system, TN (Twisted Nematic) system, STN (Super Twisted Nematic) system, ECB (Electrically Controlled Birefringence) system, IPS (In-Plane Switching) system, VA (Vertical Alignment) system, OCB (Optically Compensated Birefringence (HAN), Hybrid Aligned Nematic (HAN), ASM (Axially Symmetric Aligned Microcell), halftone gray scale, domain division, or display using ferroelectric liquid crystal or anti-ferroelectric liquid crystal There are various methods.

  Also, the liquid crystal cell driving method is not particularly limited, and a passive matrix method used for STN-LCDs, etc., and an active matrix method using active electrodes such as TFT (Thin Film Transistor) electrodes and TFD (Thin Film Diode) electrodes, Any driving method such as a plasma addressing method may be used.

The retardation compensation plate used in the liquid crystal display device is not particularly limited as long as it has excellent transparency and uniformity, but a polymer stretched film or an optical compensation film made of liquid crystal can be preferably used. Examples of the stretched polymer film include a uniaxial or biaxial retardation film made of a cellulose, polycarbonate, polyarylate, polysulfone, polyacryl, polyethersulfone, cycloolefin polymer or the like. it can. Of these, polycarbonate is preferred from the viewpoint of cost and film uniformity.
In addition, the optical compensation film made of liquid crystal as used herein is not particularly limited as long as the film can utilize the optical anisotropy generated by aligning the liquid crystal and resulting from the alignment state. For example, known materials such as various optical functional films using nematic liquid crystal, discotic liquid crystal, smectic liquid crystal and the like can be used.
The phase difference compensator exemplified here may be used alone or in a plurality of sheets when constituting a liquid crystal display device. Further, both a polymer stretched film and an optical compensation film made of liquid crystal can be used.

  The reflective layer is not particularly limited, and is a metal such as aluminum, silver, gold, chromium, or platinum, an alloy containing them, an oxide such as magnesium oxide, a dielectric multilayer film, a liquid crystal exhibiting selective reflection, or these. The combination of these can be illustrated. These reflective layers may be flat or curved. In addition, the reflective layer is processed to have a surface shape such as a concavo-convex shape so as to have diffuse reflectivity, the liquid crystal cell is combined with an electrode on the electrode substrate opposite to the observer side, and the thickness of the reflective layer It may be a semi-transmissive reflective layer in which light is partially transmitted by thinning or forming a hole or the like, or a combination thereof.

  The light diffusion layer is not particularly limited as long as it has a property of diffusing incident light isotropically or anisotropically. For example, it may be composed of two or more regions and have a difference in refractive index between the regions, or a surface shape with irregularities. Examples of the two or more regions having a difference in refractive index between the regions include those in which particles having a refractive index different from that of the matrix are dispersed in the matrix. The diffusion layer itself may have an adhesive property.

The film thickness of the light diffusing layer is not particularly limited, but is usually preferably 10 μm or more and 500 μm or less.
Further, the total light transmittance of the light diffusion layer is preferably 50% or more, and particularly preferably 70% or more. Further, the haze value of the light diffusion layer is usually 10 to 95%, preferably 40 to 90%, and more preferably 60 to 90%.

The backlight, front light, light control film, light guide plate, and prism sheet are not particularly limited, and known ones can be used.
The liquid crystal display device of the present invention can be provided with other constituent members in addition to the constituent members described above. For example, by attaching a color filter to the liquid crystal display device of the present invention, a color liquid crystal display device capable of performing multicolor or full color display with high color purity can be manufactured.

  The elliptically polarizing plate of the present invention uses a liquid crystalline composition containing a side chain liquid crystalline polymer obtained by polymerizing a (meth) acrylic compound having an oxetanyl group, and fixes the alignment state of the liquid crystalline composition. It has excellent heat resistance, high hardness, high mechanical strength, optically anisotropic element composed of at least a homeotropically aligned liquid crystal layer, and excellent adhesion between the optically anisotropic element and the polarizing element, It is useful as an elliptically polarizing plate for a liquid crystal display device having good resistance to moisture and heat and hardly causing damage to the liquid crystal layer in the bonding step. Furthermore, since it can bond in a long film form also in the bonding process with a polarizing element, there exists an advantage which can rationalize a bonding process from the conventional method.

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 of GPC The compound was dissolved in tetrahydrofuran, and TSK-GEL SuperH1000, SuperH2000, SuperH3000, and SuperH4000 were connected in series with a Tosoh 8020GPC system and measured using tetrahydrofuran as an eluent. Polystyrene standards were used for molecular weight calibration.
(2) Microscope observation The alignment state of the liquid crystal was observed with an Olympus BH2 polarizing microscope.
(3) Parameter measurement of liquid crystal film Obi Scientific Instruments Co., Ltd. automatic birefringence meter KOBRA21ADH was used.
(4) Film thickness measurement method SURFACE TEXTURE ANALYSIS SYSTEM Dektak 3030ST made by SLOAN was used. Moreover, the method of calculating | requiring a film thickness from the data of interference wave measurement (The JASCO Corporation UV / visible / near infrared spectrophotometer V-570) and refractive index data was used together.

<Example 1>
(1) Production of Liquid Crystal Layer A A liquid crystalline polymer compound of the following formula (8) was synthesized by radical copolymerization. The molecular weight by GPC was a number average molecular weight Mn = 8000 and a weight average molecular weight Mw = 15000 in terms of polystyrene. In addition, although Formula (8) is described with the structure of a block copolymer, it represents the component ratio of a monomer.
Dissolve 1.0 g of the liquid crystalline polymer compound of the formula (8) in 9 mL of cyclohexanone, and add 0.1 g of triallylsulfonium hexafluoroantimonate 50% propylene carbonate solution (aldrich, reagent) in the dark. Thereafter, the solution was filtered through a polytetrafluoroethylene filter having a pore diameter of 0.45 μm to prepare a liquid crystal composition solution.
The alignment substrate was prepared as follows. A 5 mass% solution of alkyl-modified polyvinyl alcohol (PVA, manufactured by Kuraray Co., Ltd., MP-203) while being transported on a long polyethylene terephthalate film (PET, manufactured by Toray Industries, Inc.) having a width of 650 mm and a thickness of 38 μm. (The solvent was a mixed solvent of water and isopropyl alcohol having a mass ratio of 1: 1) was continuously applied and dried using a die coater, and heat-treated at 130 ° C. to obtain an oriented substrate film.
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.
A liquid crystal polymer solution is continuously applied to the alignment substrate thus obtained using a die coater and dried to form an unaligned liquid crystal polymer layer, followed by heat treatment at 130 ° C. for 10 minutes. The liquid crystal composition was aligned. Next, while adhering to a metal drum heated to 60 ° C., 600 mJ / cm ² of ultraviolet light (however, the amount of light measured at 365 nm) is irradiated from above with a high-pressure mercury lamp lamp to cure the liquid crystalline composition layer. Thus, a liquid crystal layer A was obtained.

(2) Production of optical anisotropic element B Since the PET film used as a substrate has a large birefringence and is not preferable as an optical film, the liquid crystal layer A on the obtained alignment substrate is bonded via an ultraviolet curable adhesive. And transferred to a triacetyl cellulose (TAC) film (film thickness 40 μm). That is, after the adhesive is applied to the cured liquid crystal layer A on the PET film so as to have a thickness of 5 μm, laminated with the TAC film, and the adhesive is cured by irradiating ultraviolet rays from the TAC film side. The PET film was peeled off to obtain an optical anisotropic element B.
When the obtained optical anisotropic element B (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 value (Re) in the in-plane direction combining the TAC film and the liquid crystal layer measured using KOBRA21ADH was 0.5 nm, and the retardation value (Rth) in the thickness direction was −150 nm. Since the TAC film alone was negative uniaxial and Re was −0.5 nm and Rth was +40 nm, Re of the liquid crystal layer alone was estimated to be 0 nm and Rth was estimated to be −190 nm.
Further, only the liquid crystal layer portion of the optical anisotropic element B was scraped, and the glass transition point was measured using DSC. The Tg was 100 ° C. The pencil hardness on the surface of the liquid crystal layer was about 2H, and a sufficiently strong film was obtained.

(3) Production of elliptically polarizing plate C The optically anisotropic element B was immersed in a 2% by mass aqueous potassium hydroxide solution at room temperature for 5 minutes for saponification treatment, washed in running water and then dried. A saponified optical anisotropic element B was continuously bonded to one surface of a polarizing element in which iodine was adsorbed to stretched polyvinyl alcohol so that the liquid crystal layer was on the outside using an acrylic adhesive.
Next, a saponified TAC film was bonded to the other surface of the polarizing element to produce the elliptically polarizing plate C of the present invention. The total film thickness was about 130 μm, which could be made thinner than a normal one (thickness 160 μm). When this elliptically polarizing plate C was optically inspected, no damage such as spots or scratches was found on the liquid crystal layer. When the optically anisotropic element B side of the elliptically polarizing plate C is attached to a glass plate with an acrylic adhesive, put into a constant temperature and humidity chamber at 60 ° C. and 90% RH, and taken out after 500 hours to observe, peeling off. There were no abnormalities such as bubbles or bubbles.

<Example 2>
(1) Method for Producing Optical Anisotropic Element D The liquid crystal layer on the PET alignment substrate produced in Example 1 was transferred to a ZEONOR film (film thickness: 40 μm, manufactured by Nippon Zeon Co., Ltd.) via an ultraviolet curable adhesive. . That is, on the cured liquid crystal layer on the PET film, an adhesive is applied to a thickness of 5 μm, laminated with a ZEONOR film, and irradiated with ultraviolet rays from the ZEONOR film side to cure the adhesive, The PET film was peeled off to obtain an optical anisotropic element D.
When the obtained optical anisotropic element D (liquid crystal layer / adhesive layer / Zeonor 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 value (Re) in the in-plane direction obtained by combining the ZEONOR film and the liquid crystal layer measured using KOBRA21ADH was 0.1 nm, and the retardation value (Rth) in the thickness direction was −110 nm. Since the ZEONOR film itself was isotropic and had Re of 0.1 nm and Rth of +1 nm, it was estimated that Re in the liquid crystal layer alone was 0 nm and Rth was −110 nm.

(2) Preparation of adhesive As urethane-based adhesive, an isocyanate-based curing agent was added to 100 parts of EL-436A (an aqueous solution having a solid concentration of 35 mass%) manufactured by Toyo Morton Co., Ltd., which is a polyester polyol prepolymer as a main agent. 30 parts of EL-436B (100% active ingredient) manufactured by Toyo Morton Co., Ltd. was added, and further diluted with water to a solid content concentration of 20% by mass. On the other hand, as a polyvinyl alcohol-based adhesive, a carboxyl group-modified polyvinyl alcohol “Kuraray Poval KL318” manufactured by Kuraray Co., Ltd. (a saponification product of a copolymer having a molar ratio of vinyl acetate and sodium itaconate of about 98: 2, saponification degree) A 3 mass% aqueous solution having a molecular weight of 85 to 90 mol% and a molecular weight of about 85,000 was prepared. The obtained urethane-based adhesive and the polyvinyl alcohol-based aqueous solution were mixed at a weight ratio of 1: 1 (20: 3 in terms of solid content weight ratio) to obtain a mixed adhesive.

(3) Production of elliptically polarizing plate E The prepared mixed adhesive was applied to both sides of a polarizing element in which iodine was adsorbed to stretched polyvinyl alcohol within 1 minute after mixing, and one surface was optically anisotropic. The device was subjected to corona treatment on the zeonore surface side of the element D under the condition of 250 W · min / m ² , and was bonded to the corona treatment surface within 30 seconds after the corona treatment.
Next, a saponified TAC film was bonded to the other surface of the polarizing element to produce the elliptically polarizing plate E of the present invention. The total film thickness was about 130 μm, which was thinner than the normal one (160 μm). When this elliptically polarizing plate E was optically inspected, no damage such as spots or scratches was found on the liquid crystal layer. When the optically anisotropic element D side of the elliptically polarizing plate E is attached to a glass plate with an acrylic adhesive, put into a constant temperature and humidity chamber at 60 ° C. and 90% RH, and taken out after 500 hours to observe, peeling off. There were no abnormalities such as bubbles or bubbles.

<Comparative Example 1>
(1) Production of elliptical polarizing plate F A polarizing plate was produced by laminating a saponified TAC film with an acrylic adhesive on both sides of a polarizing element in which iodine was adsorbed to stretched polyvinyl alcohol. The optically anisotropic element B was bonded to the polarizing element via an acrylic adhesive without saponifying the optically anisotropic element B, so that an elliptically polarizing plate F was produced. Since this elliptically polarizing plate F was as thick as about 200 μm and the winding thickness was large, the treatment length in one operation had to be shorter than that of the elliptically polarizing plate of Example 1.
When an acrylic pressure-sensitive adhesive was applied to the optically anisotropic element B side of the elliptically polarizing plate F and adhered to a glass plate, the same test as in Example 1 was performed. After 500 hours had elapsed, 0.5 mm was peeled off at the end. Was recognized.

<Comparative example 2>
(Preparation of elliptical polarizing plate G)
A polarizing plate was prepared by laminating a saponified TAC film with an acrylic adhesive on both sides of a polarizing element in which iodine was adsorbed to stretched polyvinyl alcohol. Without subjecting the optical anisotropic element D to corona treatment, the liquid crystal side was bonded to this polarizing element via an acrylic adhesive to produce an elliptically polarizing plate G. Since this elliptically polarizing plate G was as thick as about 200 μm and the winding thickness was large, the treatment length in one operation had to be shorter than that of the elliptically polarizing plate of Example 2.
When an acrylic pressure-sensitive adhesive was applied to the optically anisotropic element D side of the elliptically polarizing plate G and adhered to a glass plate, the same test as in Example 1 was performed. After 500 hours had elapsed, 0.5 mm was peeled off at the end. Was recognized.

<Example 3>
As shown in FIG. 2, using the elliptically polarizing plate C produced in Example 1, a commercially available IPS type liquid crystal television arranged in the order of a backlight, a lower polarizing plate, an IPS type liquid crystal cell, and an upper polarizing plate is used. Instead of the upper polarizing plate, an elliptical polarizing plate C was disposed. As a result, it was found that the viewing angle was widened compared to the case of using only the polarizing plate, and a good image was obtained even when viewed obliquely.

<Example 4>
Using the elliptically polarizing plate E produced in Example 2, as shown in FIG. 2, a commercially available IPS type liquid crystal television arranged in the order of a backlight, a lower polarizing plate, an IPS type liquid crystal cell, and an upper polarizing plate. Instead of the upper polarizing plate, an elliptical polarizing plate E was disposed. As a result, it was found that the viewing angle was widened compared to the case of using only the polarizing plate, and a good image was obtained even when viewed obliquely.

It is an elevation sectional view showing typically the elliptically polarizing plate of the present invention. 6 is a conceptual diagram of a liquid crystal display used in Example 3. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ellipse polarizing plate 2 Translucent protective film 3 Polarizing element 4 Optically isotropic board | substrate 5 Homeotropic alignment liquid crystal layer 6 IPS liquid crystal panel
7 Polarizing plate 8 Backlight

Claims (15)

  An elliptically polarizing plate in which a polarizing element is sandwiched between an optically anisotropic element composed of a liquid crystal layer aligned on an optically isotropic substrate and a light-transmitting protective film, and the optically anisotropic element is at least An elliptically polarizing plate comprising a homeotropic alignment liquid crystal layer in which a liquid crystal composition exhibiting positive uniaxial property is homeotropically aligned in a liquid crystal state and then the alignment is fixed.   The elliptically polarizing plate according to claim 1, wherein the elliptically polarizing plate is obtained from an optically anisotropic element in the form of a long film, a translucent protective film, and a polarizing element.   The optically anisotropic element comprises a homeotropic alignment of a liquid crystalline composition containing a side chain type liquid crystalline polymer compound having an oxetanyl group in a liquid crystal state, and then reacting the oxetanyl group to form the homeotropic alignment. The elliptically polarizing plate according to claim 1, which is a homeotropic alignment liquid crystal layer in which is fixed. 2. The elliptically polarizing plate according to claim 1, wherein the optically anisotropic element is composed of a homeotropic alignment liquid crystal layer satisfying the following [1] and [2].
[1] 0 ≦ Re ≦ 200
[2] −500 ≦ Rth ≦ −30
(Here, Re means an in-plane retardation value of the liquid crystal layer, and Rth means a retardation value in the thickness direction of the liquid crystal layer. Re and Rth are respectively Re = (Nx−Ny) × d [nm], Rth = (Nx−Nz) × d [nm] where d is the thickness of the liquid crystal film, Nx and Ny are the main refractive index in the liquid crystal layer surface, and Nz is the main refraction in the thickness direction. (Nz> Nx ≧ Ny)   2. The elliptically polarizing plate according to claim 1, wherein the optically isotropic substrate is triacetyl cellulose.   The elliptically polarizing plate according to claim 1, wherein the optically isotropic substrate is a cycloolefin polymer.   The elliptically polarizing plate according to claim 1, wherein the optically anisotropic element is surface-treated.   The elliptically polarizing plate according to claim 7, wherein the surface treatment is a saponification treatment.   The elliptically polarizing plate according to claim 7, wherein the surface treatment is a corona discharge treatment.   The elliptically polarizing plate according to claim 1, wherein the elliptically polarizing plate has a thickness of 250 μm or less.   The elliptically polarizing plate according to claim 1, wherein a translucent overcoat layer is provided on a surface of the liquid crystal layer.   The elliptically polarizing plate according to claim 11, wherein the translucent overcoat layer is made of an acrylic resin.   An elliptically polarizing plate, wherein the elliptically polarizing plate according to claim 1 is further laminated with at least one optical film.   After forming a liquid crystal layer on an optically isotropic substrate, an optical anisotropic element is manufactured by providing a light-transmitting overcoat layer on the surface of the liquid crystal layer, and then surface treatment is performed on the optical anisotropic element. And then bonding the polarizing element so as to be sandwiched between the optically anisotropic element and the translucent protective film via the adhesive / adhesive layer.   The liquid crystal display device which has arrange | positioned the elliptically polarizing plate in any one of Claims 1-13 in the surface of the at least one side of a liquid crystal cell.

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