JP2004258623A - Optical element consisting of liquid crystal layer and liquid crystal display device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To integrally constitute an optical element without arranging tacky adhesive films, alignment layers, etc., by interposing a liquid crystal molecular axis conversion layer so as to continuously connect the directions of the axes of the liquid crystal molecules between adjacent liquid crystal layers when constituting the optical element by laminating a plurality of the liquid crystal layers. <P>SOLUTION: The optical element 1 is constituted by directly laminating the liquid crystal molecular axis conversion layer 4 on the first liquid crystal layer 3 unified in the liquid crystal molecular axis directions to a specified direction and further directly laminating the second liquid crystal layer 5 unified in the liquid crystal molecular axis directions to the direction different from the liquid crystal molecular axis direction of the first liquid crystal layer 3 thereon. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to an optical element composed of a liquid crystal layer and a liquid crystal display device using the same, and more particularly, to an optical element composed of a plurality of liquid crystal layers and integrally formed and a liquid crystal display device using the same. It is.

  First, the term “liquid crystal layer” used in the present invention means a layer composed of molecules having optically liquid crystal properties, and the state of the layer is a fixed solid state composed of oligomer or polymer. Say something.

  The types of the retardation layers are classified according to the direction of the optical axis (optical axis) and the magnitude of the refractive index in the direction of the optical axis with respect to the refractive index in the direction perpendicular to the optical axis. A plate whose optical axis direction is along the layer plane, C plate whose optical axis direction is normal to the layer perpendicular to the layer, and C plate whose optical axis direction is inclined from the normal direction. An O plate is called a positive plate when the refractive index in the direction of the optical axis is larger than the refractive index in the direction perpendicular to the optical axis, and a plate when the refractive index in the direction of the optical axis is smaller than the refractive index in the direction perpendicular to the optical axis. Say the plate. Thus, there is a distinction between a positive A plate, a negative A plate, a positive C plate, a negative C plate, a positive O plate, and a negative O plate.

  Conventionally, as an optical element having a liquid crystal layer, a polarization separation element, a polarizing plate, a color filter, and the like having a liquid crystal layer having a cholesteric phase structure (cholesteric liquid crystal layer) have been proposed. Further, a retardation plate provided with a liquid crystal layer having a nematic phase structure, a smectic phase structure, or the like has been proposed.

On the other hand, many proposals have been made to improve the viewing angle characteristics of a liquid crystal display element by combining various retardation plates, a half-wave plate, a quarter-wave plate, a circularly polarized light separating element, and the like (Patent Documents). 1-12).
JP-A-8-271837 JP-A-9-189811 JP 2001-147321 A JP 2001-147323 A JP 2001-183643 A JP 2001-249225 A JP 2001-337225 A JP 2001-350022 A JP-A-2002-55342 JP 2002-506532 A JP-A-2002-72209 JP-A-2002-107541 2002 Japanese Liquid Crystal Society Summer School text pp69-77

  In these conventional examples, in order to integrate different layers, lamination by an adhesive layer, lamination by thermocompression bonding, and the like are used, and a retardation film made of a stretched film is used for the retardation layer. There were many things. Further, a conventional retardation layer is used by being adhered outside a liquid crystal cell.

  However, Patent Document 6 discloses that a circularly-polarized light separating element composed of a cholesteric liquid crystal layer is formed directly on a quarter-wavelength layer composed of a nematic liquid crystal layer. Since the liquid crystal layer has the ability to orient the upper cholesteric liquid crystal layer, both layers can be formed directly, and in the general case where multiple liquid crystal layers are integrated, the alignment film is Must be formed.

  As described above, conventionally, since an adhesive layer is used to integrate different layers, thermocompression bonding, or a stretched film is used, an optical element combining a retardation plate and a circularly polarized light separating element is used as a liquid crystal cell. It was difficult to form an in-cell arrangement inside (between transparent substrates).

  Further, when a retardation plate or the like is integrated with a liquid crystal layer, a transfer method has to be used for laminating a plurality of layers, or an alignment film has to be arranged between the liquid crystal layers.

  The present invention has been made to solve such a problem of the prior art, and an object of the present invention is to provide an optical element by stacking a plurality of liquid crystal layers, and to form an axis of liquid crystal molecules between adjacent liquid crystal layers. In this case, a liquid crystal molecular axis conversion layer that allows the directions of the liquid crystal molecules to be continuously connected is interposed so that the liquid crystal molecules can be integrally formed without disposing an adhesive film, an alignment film, and the like.

  In the optical element comprising the liquid crystal layer of the present invention that achieves the above object, a liquid crystal molecular axis conversion layer is directly laminated on a first liquid crystal layer in which liquid crystal molecular axis directions are aligned in a fixed direction, and further thereon. A second liquid crystal layer in which the liquid crystal molecular axis direction is aligned in a direction different from the liquid crystal molecular axis direction of the first liquid crystal layer is directly laminated.

  In this case, the liquid crystal molecular axis conversion layer can be made of a chiral nematic liquid crystal or a cholesteric liquid crystal.

  In the above-mentioned optical element comprising a liquid crystal layer of the present invention, the first liquid crystal layer and the second liquid crystal layer may be composed of, for example, a nematic liquid crystal.

  In this case, the first liquid crystal layer and the second liquid crystal layer can have a liquid crystal molecular axis substantially parallel to the film surface.

  Further, it is desirable that the liquid crystal molecular axis conversion layer has a helical structure of one pitch or less.

  In this case, it is desirable that the pitch of the helical structure be a pitch length having a selective reflection wavelength in the ultraviolet region.

  In the above-mentioned optical element comprising the liquid crystal layer of the present invention, one of the first liquid crystal layer and the second liquid crystal layer constitutes a quarter-wave retardation layer, and the other one-half wavelength retardation layer. It may constitute a retardation layer.

  In this case, a cholesteric liquid crystal layer having selective reflection may be directly laminated on the first liquid crystal layer side or the second liquid crystal layer side.

  Further, in the optical element including the liquid crystal layer of the present invention, the liquid crystal molecular axis conversion layer has a liquid crystal molecular axis aligned in a certain direction along the interface at one interface, and intersects the interface at the other interface. It is preferable that the liquid crystal molecular axes have a uniform angle in the direction of the specific angle, and the angle of the liquid crystal molecular axis between both interfaces changes continuously or discontinuously from one interface to the other interface.

  In this case, the first liquid crystal layer has a liquid crystal molecular axis substantially parallel to the film surface, and the second liquid crystal layer has a molecular axis at an angle substantially equal to the specific angle with respect to the film surface. Can be provided.

  An optical element comprising another liquid crystal layer of the present invention comprises a first liquid crystal layer comprising a chiral nematic liquid crystal or a cholesteric liquid crystal having a helical axis substantially perpendicular to the film surface, and a liquid crystal molecular axis conversion layer. Are directly laminated, and a second liquid crystal layer in which the liquid crystal molecular axis directions are aligned in a fixed direction is directly laminated thereon.

  In this case, the liquid crystal molecular axis conversion layer has a liquid crystal molecular axis aligned in a certain direction along the interface at the interface with the first liquid crystal layer, and at a specific angle crossing the interface at the other interface. It is desirable that the liquid crystal molecules have a uniform liquid crystal molecular axis and that the angle of the liquid crystal molecular axis between both interfaces changes continuously or discontinuously from one interface to the other interface.

  In the above, another liquid crystal molecular axis conversion layer is directly laminated on the second liquid crystal layer, and the liquid crystal molecular axis direction is aligned on the second liquid crystal layer in a direction different from the liquid crystal molecular axis direction of the second liquid crystal layer. No. 3 liquid crystal layer can be directly laminated.

  Further, in the above, it is possible to have an exposed portion of the support substrate, which is laminated on the support substrate and patterned in the film plane.

  Further, the optical region is divided into a plurality of regions, and an optical effect on light transmitted through the adjacent region can be different between the adjacent regions.

  Further, it is preferable that the first liquid crystal layer, the liquid crystal molecule axis conversion layer, and the second liquid crystal layer are formed using a material containing the same liquid crystal molecule as a main component.

  The present invention includes a liquid crystal display device using an optical element comprising the above liquid crystal layer, and the optical element can be arranged in a liquid crystal cell.

  In the present invention, the liquid crystal molecular axis conversion layer is directly laminated on the first liquid crystal layer, and the second liquid crystal layer is further laminated directly on the first liquid crystal layer. Instead, the optical element can be integrally formed. In addition, by using the same material or a material having a relation similar thereto, interface reflection can be suppressed, and an optical element such as a phase difference plate that is resistant to a change in a thermal environment such as thermal expansion can be obtained. The in-cell arrangement can be performed. Further, since the liquid crystal molecular axis conversion layer also functions as an alignment film of the first liquid crystal layer or the second liquid crystal layer directly laminated thereon, it can be formed without rubbing, and there is no possibility of occurrence of contamination due to foreign matter or the like. In addition, the problem of interface disturbance and air bubble mixing due to the bonding of the first liquid crystal layer and the second liquid crystal layer is eliminated.

  Hereinafter, the principle and examples of an optical element comprising a liquid crystal layer of the present invention and a liquid crystal display device using the same will be described.

  For example, to construct a circularly polarizing plate (broadband circularly polarizing plate) having a wide wavelength band, one λ / 2 plate (a half-wave plate) or two λ / 2 plates (a quarter-wave plate) is used. ) It is obtained by combining one sheet (for example, Non-Patent Document 1). The λ / 2 plate and the λ / 4 plate can be constituted by a positive A plate, and the positive A plate is constituted, for example, by planar alignment of nematic polymerizable liquid crystal molecules having a positive refractive index anisotropy in a layer plane. can do. When a broadband circularly polarizing plate is formed, the slow axis (optical axis) of the λ / 2 plate and the slow axis (optical axis) of the λ / 4 plate are displaced from each other by a predetermined angle. Similarly, various optical elements are configured by stacking a plurality of A plates.

  As described above, in the case where various optical elements are configured by stacking and integrating a plurality of A-plates, and when the A-plates are configured by planarizing polymerizable liquid crystal molecules, the optical axis between the A-plates is changed. In order to make the orientation direction of the upper liquid crystal layer laminated so as to be shifted from each other to a predetermined direction, it is generally necessary to use a transfer method or to arrange an orientation film between the liquid crystal layers.

  In such a case, the present invention interposes a liquid crystal molecule axis conversion layer made of a liquid crystal layer between the liquid crystal layers to be stacked, so that the axes of the liquid crystal molecules between the stacked liquid crystal layers are continuously connected. Is what you want to do.

  This configuration will be described with reference to FIG. FIG. 1A is a cross-sectional view of one embodiment of an optical element comprising a liquid crystal layer according to the present invention, and FIG. 1B is a perspective view showing the direction of the liquid crystal molecular axis at the interface of each layer in FIG. It is.

The optical element 1 shown in FIG. 1 has a structure in which a first liquid crystal layer 3, a liquid crystal molecular axis conversion layer 4, and a second liquid crystal layer 5 are integrally laminated from a substrate 2 side. The axis of the liquid crystal molecules 3 ′ at the interface on the side of the molecular axis conversion layer 4 is oriented in a specific direction indicated by a double arrow along the interface, and the interface of the second liquid crystal layer 5 on the side of the liquid crystal molecule conversion layer 4 is formed. Are oriented in another specific direction indicated by a double arrow along the interface, and the axes of the liquid crystal molecules 4 ′ in the liquid crystal molecule axis conversion layer 4 are aligned with the first liquid crystal layer 3. The liquid crystal molecules 4 ₁ ′ at the interface of the liquid crystal molecule axis conversion layer 4 on the side of the first liquid crystal layer 3 are aligned so as to be continuously connected in a spiral from the side to the second liquid crystal layer 5 side. The first liquid crystal layer 3 is oriented in the same direction as the axis of the liquid crystal molecules 3 ′ at the interface on the liquid crystal molecule axis conversion layer 4 side, and the liquid crystal molecules 4 on the interface of the liquid crystal molecule axis conversion layer 4 on the second liquid crystal layer 5 side. the axis of the ₂ ' It is oriented in the same direction as the axis of the second liquid crystal molecular axis conversion layer 4 side of the liquid crystal molecules at the interface 5 of the liquid crystal layer 5 '.

  In order to make the directions of the axes of the liquid crystal molecules of the first liquid crystal layer 3 and the liquid crystal molecule axis conversion layer 4 and the liquid crystal molecule axis conversion layer 4 and the second liquid crystal layer 5 at each interface the same, the respective directions are as follows. As the liquid crystal molecules used for the liquid crystal layers 3, 4, and 5, the same liquid crystal molecules or liquid crystal molecules having similar structures may be used. If the characteristics of the liquid crystal molecules of the adjacent liquid crystal layer do not change significantly, the orientation of the axes of the liquid crystal molecules on the surface of the liquid crystal layer formed earlier will be changed at the interface of the liquid crystal layer formed thereon. In order to regulate the alignment in the same direction (because it acts as an alignment film), the direction of the axis of the liquid crystal molecule at the interface of the liquid crystal layer formed later is the liquid crystal molecule at the interface of the liquid crystal layer formed earlier. Axis direction.

  As in the liquid crystal molecular axis conversion layer 4 in FIG. 1, in order to orient the liquid crystal molecules 4 'in the layer so as to be continuously connected so as to draw a helix, for example, a cholesteric liquid crystal or a chiral agent is mixed to form a helix. A chiral nematic liquid crystal having a structure may be used.

  As described above, in the optical element 1, the liquid crystal layers 3, 4, and 5 are integrally laminated without interposing an adhesive layer or an alignment layer therebetween, and the same liquid crystal material or a liquid crystal having a similar relationship similar thereto. Since it can be manufactured by using a material and the difference in the refractive index between the liquid crystal layers can be reduced, the reflection at the interface can be suppressed, and the material is resistant to a thermal environment change such as thermal expansion. Further, since the orientation between the liquid crystal layers can be controlled by the orientation of the liquid crystal layer provided on the lower liquid crystal layer, an optical element free of rubbing and free from contamination by foreign substances or the like can be constituted. In addition, there is no problem of interface disturbance due to bonding and bubbles. Further, since such an optical element 1 is made of a heat-resistant liquid crystal polymer without using an adhesive or the like, it is possible to arrange the optical element 1 in a liquid crystal cell.

  Here, the liquid crystal layer having a helical structure of the liquid crystal molecule axis conversion layer 4 in FIG. 1 has a function of continuously connecting the axes of the liquid crystal molecules between the liquid crystal layer 3 and the liquid crystal layer 5 because of its function. It is sufficient that the pitch of the spiral structure is 1 or less. In addition, the liquid crystal molecular axis conversion layer 4 needs to have a selective reflection wavelength of the helical structure (cholesteric liquid crystal) outside the visible light range in order to prevent visible light incident on the optical element 1 from being reflected by the helical structure. Or in the infrared region. If the selective reflection wavelength is in the infrared region, the helical pitch becomes longer, and the thickness of the liquid crystal molecular axis conversion layer 4 becomes thicker, and the influence of the refractive index anisotropy increases. Therefore, it is desirable to select a material having a selective reflection wavelength in the ultraviolet region where the helical pitch can be relatively short.

FIG. 1 is for explaining the principle of the present invention in the case where a plurality of A plates are stacked to constitute various optical elements. However, FIG. 1 shows an A plate, a C plate, and a cholesteric liquid crystal layer (hereinafter, CLC). 1) and a C-plate, an A-plate and an O-plate, or a CLC layer and an O-plate are superimposed to constitute a compensator or the like for improving viewing angle characteristics (Patent Documents 9 and 11). In such a liquid crystal molecule axis conversion layer 4, it is not possible to continuously connect the axes of the liquid crystal molecules between the liquid crystal layer forming the A plate or the CLC layer and the liquid crystal layer forming the C plate or the O plate. . In this case, like the liquid crystal molecular axis conversion layer 4 shown in FIG. 2, the axis of the liquid crystal molecules 4 ′ in the liquid crystal molecular axis conversion layer 4 moves from the first liquid crystal layer 3 side to the second liquid crystal layer 5 side. The angle (tilt angle) formed with respect to the film surface is continuously from 0 ° to a predetermined angle (a predetermined angle smaller than 90 ° when the first liquid crystal layer 3 is a C plate and smaller than 90 ° when the first liquid crystal layer 3 is an O plate). And the axes of the liquid crystal molecules 4 ₁ ′ at the interface of the liquid crystal molecule axis conversion layer 4 on the first liquid crystal layer 3 side are aligned with the liquid crystal molecule axis conversion layer of the first liquid crystal layer 3. The liquid crystal molecules are oriented in the same direction as the axes of the liquid crystal molecules 3 ′ at the interface on the side 4, and the axes of the liquid crystal molecules 4 ₂ ′ at the interface on the side of the second liquid crystal layer 5 of the liquid crystal molecule axis conversion layer 4 The liquid crystal molecules are oriented in the same direction as the axis of the liquid crystal molecules 5 ′ at the interface on the liquid crystal molecule axis conversion layer 4 side.

  Also in this case, in order to make the directions of the axes of the liquid crystal molecules of the first liquid crystal layer 3 and the liquid crystal molecule axis conversion layer 4 and the liquid crystal molecule axis conversion layer 4 and the second liquid crystal layer 5 at the respective interfaces the same, respectively. As the liquid crystal molecules used for the liquid crystal layers 3, 4, and 5, the same liquid crystal molecules or liquid crystal molecules having similar structures may be used. If the characteristics of the liquid crystal molecules of the adjacent liquid crystal layer do not change significantly, the orientation of the axes of the liquid crystal molecules on the surface of the liquid crystal layer formed earlier will be changed at the interface of the liquid crystal layer formed thereon. In order to regulate the alignment in the same direction (because it acts as an alignment film), the direction of the axis of the liquid crystal molecule at the interface of the liquid crystal layer formed later is the liquid crystal molecule at the interface of the liquid crystal layer formed earlier. Axis direction.

  As in the liquid crystal molecule axis conversion layer 4 in FIG. 2, there are several methods for aligning the axes of the liquid crystal molecules 4 ′ in the layer so that the axes change continuously from one interface to the other interface. is there. It is described below.

(1) Liquid crystal molecules have the property of being arranged vertically at the air interface, with exceptions. In the case of normal film formation, a surfactant is added so as to be oriented parallel to the interface so as to modify the surface so as not to be vertically oriented. By optimizing the amount of addition, the tilt angle θ of the axis of the liquid crystal molecules 4 ₂ ′ at the interface on the side of the second liquid crystal layer 5 as shown in FIG. 2 is 90 ° or smaller. Then, the liquid crystal molecular axis conversion layer 4 as shown in FIG.

  In this case, the amount of the surfactant added is generally 0.01 to 0.3% by weight, preferably 0.03 to 0.1% by weight, based on the liquid crystal. There is no particular limitation on the type of surfactant, and generally commercially available surfactants are sufficient. Specific examples include imidazoline, quaternary ammonium salts, alkylamine oxides, cationic surfactants such as polyamine derivatives, polyoxyethylene-polyoxypropylene condensates, primary or secondary alcohol ethoxylates, Anionic interfaces such as alkylphenol ethoxylate, polyethylene glycol and its esters, sodium lauryl sulfate, ammonium lauryl sulfate, lauryl sulfate amines, alkyl-substituted aromatic sulfonates, alkyl phosphates, and condensates of aliphatic or aromatic sulfonic acid formalin Surfactants, amphoteric surfactants such as laurylamidopropylbetaine and betaine laurylaminoacetate; nonionic surfactants such as polyethylene glycol fatty acid esters and polyoxyethylene alkylamine; Oroalkyl sulfonate, perfluoroalkylcarboxylate, perfluoroalkylethylene oxide adduct, perfluoroalkyltrimethylammonium salt, oligomer containing perfluoroalkyl group / hydrophilic group, oligomer containing perfluoroalkyl / lipophilic group perfluoroalkyl Examples include fluorine-based surfactants such as group-containing urethane and acrylic surfactants such as polyacrylic acid, acrylic acid copolymer, methacrylic acid, and methacrylic acid copolymer.

  (2) A vertical alignment film or an alignment film having a pretilt is brought into close contact with the surface of the liquid crystal molecular axis conversion layer 4 where vertical alignment or pretilt alignment at a predetermined angle is desired (an interface on the side of the second liquid crystal layer 5 as shown in FIG. 2). Then, the liquid crystal molecular axis conversion layer 4 as shown in FIG. 2 is obtained by irradiating the liquid crystal molecular axis conversion layer 4 with ultraviolet rays or the like to cause cross-linking polymerization and curing, and then peeling off the alignment film after the curing.

  According to this method, even if the material does not have an orientation such as vertical in the method (1), as shown in FIG. 2, the tilt angle θ is 90 ° or less at the other interface from the orientation parallel to one interface. The liquid crystal molecular axis conversion layer 4 having a smaller angle can be obtained.

  As the vertical alignment film and the alignment film having a pretilt, commercially available ones may be used.

  By interposing one or more liquid crystal molecular axis conversion layers 4 as described above, two or more A plates, C plates, O plates, and CLC layers composed of liquid crystal layers are integrally formed without interposing an adhesive layer or an alignment layer. Optical elements such as various retardation plates, compensating plates for improving viewing angle characteristics, polarizing beam splitters, and polarizing plates can be formed by lamination.

  In this case, it is desirable to use a material mainly composed of the same liquid crystal molecules for each liquid crystal layer. The chiral nematic liquid crystal used for the liquid crystal molecular axis conversion layer 4 in FIG. 1 contains a chiral agent in a smaller amount (generally 0 to 20%) than the nematic liquid crystal as a main component, and is therefore substantially thermally Optically can be regarded as the same physical property. However, as described above, even if the liquid crystal molecules used in each liquid crystal layer are not the same, if the liquid crystal molecules have a similar structure, the molecular characteristics do not largely change, so that an optical element having desired optical characteristics can be obtained.

  When the liquid crystal molecule axis conversion layer 4 is sufficiently thin, when a manufacturing method is employed in which an alignment film or the like is disposed above and below the conversion layer 4 to control the alignment, discontinuity of the liquid crystal molecule alignment inside the conversion layer may occur. Points may occur. This occurs when a change in the structure of the liquid crystal layer cannot be followed when the influence of the upper and lower alignment regulating forces is strong, but does not affect the performance of the liquid crystal molecule axis conversion layer 4 and also has an optical characteristic. No defects appear.

  By the way, from the above description, the liquid crystal molecular axis conversion layer 4 must have an optical effect that can be substantially neglected optically with respect to the used wavelength. An example shows that such a liquid crystal molecular axis conversion layer 4 can be configured.

For example, in the case of a liquid crystal molecular axis conversion layer 4 that converts the axes of liquid crystal molecules parallel to the film surface by, for example, 45 ° with each other as in the liquid crystal molecular axis conversion layer 4 of FIG. When n = 1.6 and Δn (the value obtained by subtracting the ordinary light refractive index from the extraordinary light refractive index) = 0.1),
One spiral pitch (360 °) = 219 nm
1/8 pitch of the helix (45 °) = 27 nm
Therefore, the liquid crystal molecular axis conversion layer 4 has a thickness of 27 nm. The retardation ΔRe of the nematic liquid crystal layer is 2.7 nm (0.1 × 27). Since the incident light is generally linearly polarized light, the effect at 45 ° is the maximum, but in the case of a chiral nematic liquid crystal layer (liquid crystal molecular axis conversion layer 4), ΔRe <2.7 nm. . The optical rotation of a unit length due to the helix of the liquid crystal molecule is given by -π · Δn ² · (P / 4) · λ ² (P: pitch, λ: wavelength), and light of λ = 550 nm passes. , 6 × 10 ⁻⁶ rad / nm, and the optical rotation of 0.00016 rad = 0.09 ° when passing through the liquid crystal molecular axis conversion layer 4 having a thickness of 27 nm.

  From the above examination, both the retardation and the optical rotation of the liquid crystal molecular axis conversion layer 4 are substantially negligible.

  By the way, in the present invention, liquid crystal monomer molecules (polymerizable liquid crystal molecules) capable of three-dimensional cross-linking constituting the liquid crystal layers 3 and 5 and the liquid crystal molecular axis conversion layer 4 are disclosed in Patent Documents 3 and 4, for example. Liquid crystal monomers and mixtures thereof with chiral compounds. As an example of such a polymerizable liquid crystal material, a compound as included in the following [Chemical formula 11] or a mixture of two or more of the following compounds [Chemical formulas 1 to 10] is used. be able to. In addition, in the case of the liquid crystalline monomer represented by the general chemical formula [Formula 11], X is preferably 2 to 5 (integer).

  Further, as the chiral agent, for example, a chiral agent represented by a general chemical formula [Chemical Formula 12] to [Chemical Formula 14] can be used. In the case of the chiral agent represented by the general chemical formula [Chemical formula 12] or [Chemical formula 13], X is preferably 2 to 12 (integer), and in the case of the chiral agent represented by the general chemical formula [Chemical formula 14] , X are preferably 2 to 5 (integer).

また、これらの液晶には、さらに重合開始剤を添加することが好ましい。電子線の照射により液晶モノマー分子を重合させる際には重合開始剤が不要なる場合もあるが、例えば紫外線の照射により液晶モノマー分子を重合させる際には、重合開始剤（光重合開始剤）が重合促進のために好適に用いられる。

Further, it is preferable to further add a polymerization initiator to these liquid crystals. When polymerizing liquid crystal monomer molecules by irradiation with an electron beam, a polymerization initiator may not be necessary. For example, when polymerizing liquid crystal monomer molecules by irradiation with ultraviolet light, a polymerization initiator (photopolymerization initiator) is used. It is suitably used for promoting polymerization.

  Examples of the added photopolymerization initiator include benzyl (also referred to as bibenzoyl), benzoin isobutyl ether, benzoin isopropyl ether, benzophenone, benzoyl benzoic acid, methyl benzoyl benzoate, 4-benzoyl-4'-methyldiphenyl sulfide, and benzyl methyl. Ketal, dimethylaminomethylbenzoate, 2-n-butoxyethyl-4-dimethylaminobenzoate, isoamyl p-dimethylaminobenzoate, 3,3′-dimethyl-4-methoxybenzophenone, methylobenzoylformate, 2-methyl- 1- (4- (methylthio) phenyl) -2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butan-1-one, 1- (4 -Dodecylfe 1) -2-Hydroxy-2-methylpropan-1-one, 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1- (4-isopropylphenyl) -2 -Hydroxy-2-methylpropan-1-one, 2-chlorothioxanthone, 2,4-diethylthioxanthone, 2,4-diisopropylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 1-chloro-4-propoxythioxanthone and the like Can be given.

  In addition to the photopolymerization initiator, it is also possible to add a sensitizer within a range that does not impair the object of the present invention.

  The amount of the photopolymerization initiator to be added is generally 0.01 to 20% by weight, preferably 0.1 to 10% by weight, more preferably 0.5 to 10% by weight, based on the polymerizable liquid crystal material. It can be added in the range of up to 5% by weight.

  Next, the optical element 1 as shown in FIG. 1 is used as a half-wave retardation layer or a quarter-wave retardation layer as the first liquid crystal layer 3, and as the second liquid crystal layer 5. FIG. 3 shows an example of application to a liquid crystal display device in a case where a single-wavelength phase difference layer or a half-wavelength phase difference layer is used to form a broadband quarter-wave plate. In this example, on the inner surface of the glass substrate 11 on the backlight side, the first broadband quarter-wave plate 14 according to the present invention as described above, and a wide-band semi-transmissive cholesteric disposed thereon. A liquid crystal filter 15 is arranged, and on the opposite inner surface of the glass substrate 12, the above-described second broadband quarter-wave plate 16 according to the present invention is arranged. A liquid crystal layer 13 in a liquid state is sandwiched between the semi-transmissive cholesteric liquid crystal filter 15 and the second broadband quarter-wave plate 16, and the seal member 20 separates the glass substrates 11 and 12. The liquid crystal cell 10 is sealed. Here, the semi-transmissive cholesteric liquid crystal filter 15 means that about 50% of the circularly polarized light having the reflection characteristic (for example, right circularly polarized light) of the cholesteric liquid crystal filter 15 is reflected, and about 50% of the remaining light is transmitted, which is opposite to the reflection characteristic. Is a cholesteric liquid crystal filter of the type that transmits circularly polarized light (for example, left circularly polarized light) without being reflected.

  A first linear polarizing plate 17 is disposed on the incident side of the backlight-side glass substrate 11, and a second linear polarizing plate 18 is disposed on the observation side of the observation-side glass substrate 12. A backlight light source 19 is arranged on the incident side of the first linear polarizing plate 17.

  On the inner surfaces of the glass substrates 11 and 12 of the liquid crystal cell 10, R (red), G (green), and B (blue) color filters and pixel electrodes, counter electrodes, and TFTs aligned with the pixels of the color filters are arranged. (TFD), an alignment film for aligning the liquid crystal layer 13, and the like are provided, but are not shown.

  With the above arrangement, in the case of the transmissive display, the naturally polarized illumination light emitted from the backlight light source 19 is transmitted to the first linear polarizer 17 and the first broadband quarter-wave plate 14. Therefore, only a linearly polarized light component that becomes circularly polarized light (right circularly polarized light) that matches the reflection characteristics (for example, right circularly polarized light) of the transflective cholesteric liquid crystal filter 15 passes. The right circularly polarized light that has passed through the first linear polarizer 17 and the first broadband quarter-wave plate 14 passes through the semi-transmissive cholesteric liquid crystal filter 15 by approximately 50%, and is transmitted to the liquid crystal layer 13. When the display state of the pixel is white, the right circularly polarized light is converted to left circularly polarized light. When the display state of the pixel is black, the second broadband quarter wave plate 16 is left as the right circularly polarized light. And reaches the second linear polarizing plate 18. The second broadband quarter-wave plate 16 and the second linear polarizer 18 are configured to pass the left circularly polarized light and block the right circularly polarized light. Therefore, when the display state of the pixel is white. Is converted into right-handed circularly polarized light, passes through the second broadband quarter-wave plate 16 and the second linearly polarizing plate 18, and the light from the backlight source 19 reaches the observer to display a bright state. . When the display state of the pixel is black, the light from the backlight source 19 is cut off by the second broadband quarter-wave plate 16 and the second linear polarizer 18 while being left circularly polarized light. Not reach, display dark state.

  Next, in the case of a reflection type display using external light, the external light passes through the second linear polarizer 18 and the second broadband quarter-wave plate 16 to become left circularly polarized light, and the display state of the pixel changes. In the case of white, the left circularly polarized light is converted by the liquid crystal layer 13 into right circularly polarized light. When the display state of the pixel is black, the left circularly polarized light is left unchanged without being converted by the liquid crystal layer 13 and is a transflective cholesteric. The liquid crystal filter 15 is reached.

  Since the transflective cholesteric liquid crystal filter 15 reflects only right circularly polarized light by approximately 50%, the external light converted to right circularly polarized light by the liquid crystal layer 13 remains right circularly polarized by the transflective cholesteric liquid crystal filter 15. Approximately 50% of the light is reflected, converted from right-handed circularly polarized light to left-handed circularly polarized light by the liquid crystal layer 13, reaches the observer via the second broadband quarter-wave plate 16 and the second linearly polarizing plate 18, and reaches a bright state. Display. When the display state of the pixel is black, it reaches the semi-transmissive cholesteric liquid crystal filter 15 with the left-handed circularly polarized light and is not reflected there, so that a dark state is displayed.

  With such a configuration, R, G, and B absorption color filters are arranged between the transflective cholesteric liquid crystal filter 15 of the liquid crystal cell 10 and the glass substrate 12 on the observation side, so that the reflection type and the transmissive color filters are provided. Thus, a liquid crystal display device capable of performing color display of the type is obtained. Further, since the optical element according to the present invention (in the above example, the wide-band quarter-wave plates 14 and 16) can be arranged in the liquid crystal cell 10, interface reflection can be reduced and the liquid crystal display device can be thinned. become. In addition, by integrating the optical element according to the present invention with the substrate, pixel patterning becomes possible, and furthermore, it becomes possible to simplify the paneling process. In particular, as shown in FIG. 3, when sealing between the glass substrates 11 and 12 with the sealing member 20, the wide-band quarter-wave plates 14 and 16 can be patterned and provided only in the effective display area. Since the portion where 20 is provided can be the surface of the glass substrate, reliable sealing can be achieved, and a liquid crystal display device having excellent durability can be configured.

  Furthermore, the optical element comprising the liquid crystal layer of the present invention is divided into a plurality of regions so as to correspond to, for example, R, G, and B pixels, and each region is optimized for the center wavelength of R, G, and B. It is desirable to make the optical action on the light transmitted through the adjacent regions different between the adjacent regions by setting the thickness or the like.

  Next, examples of the optical element comprising the liquid crystal layer of the present invention will be described.

Example 1
As the first substrate, a glass substrate having a thickness of 500 μm and a vertical alignment film of 0.6 μm formed thereon was prepared.

  As a first solution, a xylene solution of a liquid crystal monomer of polymerizable nematic liquid crystal (n = 1.57 at a wavelength of 550 nm, Δn = 0.1) having a liquid crystal solid content of 30% is prepared, and a photopolymerization initiator is added to the liquid crystal. On the other hand, 5% was added. The photopolymerization initiator may be a general material, for example, Irg907, Irg184, Irg361, Irg651 (all manufactured by Chiba Specialty Chemicals).

  As the second solution, a solution prepared by adding 0.04% of a surfactant Byk390 (manufactured by BYK-Chemie) to the first solution was prepared.

  As the second substrate, a glass substrate having a thickness of 500 μm and an alignment film of 0.5 μm with a pretilt angle of 3 ° formed thereon was prepared.

  As a third solution, 0.06% of surfactant Byk352 (manufactured by BYK Chemie) and 5% of photopolymerization initiator were added to a toluene solution of cholesteric liquid crystal having a central reflection wavelength of 550 nm (cholesteric liquid crystal solid content: 30%). What was added was prepared. The photopolymerization initiator may be a general material, for example, Irg907, Irg184, Irg361, Irg651 (all manufactured by Chiba Specialty Chemicals).

  Using such a substrate and a solution, circularly-polarized light separation in which the C-plate and the CLC layer having the layer configuration exemplified above (such as a compensator for improving the viewing angle characteristics by overlapping the CLC layer and the C-plate) is integrated. An element was manufactured. The manufacturing procedure is as follows.

(1) A C plate was formed to a thickness of 2 μm on the first substrate using the first solution. In the film formation method, the first solution was applied with a spinner, dried at 90 ° C., and the solvent was removed to obtain an uncured liquid crystal layer. Thereafter, the film was held at 80 ° C. and irradiated with ultraviolet rays (wavelength 310 nm) at a radiation intensity of 3.6 mW / cm ² for 3 seconds in N ₂ to cure and form a film.

(2) Next, a liquid crystal molecular axis conversion layer having a thickness of 40 nm was formed on the C plate using the second solution. At this time, after the second solution was applied and the solvent was removed, the second substrate was brought into close contact with the applied layer, kept at 80 ° C., and irradiated with N ₂ at an irradiation intensity of 3.6 mW / cm ^2. Irradiation with ultraviolet rays (wavelength 310 nm) for 2 seconds caused ultraviolet curing to form a film.

  (3) Thereafter, the second substrate was separated from the cured liquid crystal molecular axis conversion layer.

(4) A 2 μm thick CLC layer was formed on the liquid crystal molecular axis conversion layer using the third solution. In the film forming method, the third solution was applied with a spinner, dried at 90 ° C., and the solvent was removed to obtain an uncured liquid crystal layer. Thereafter, the film was held at 80 ° C. and irradiated with ultraviolet rays (wavelength 310 nm) at a radiation intensity of 3.6 mW / cm ² for 3 seconds in N ₂ to cure and form a film.

  As described above, a circularly polarized light separating element in which the C plate, the liquid crystal molecular axis conversion layer, and the CLC layer were integrated on the first substrate was obtained.

Example 2
As the substrate, a glass substrate having a thickness of 700 μm and a polyimide alignment film of 0.7 μm formed thereon, or a stretched film or a film base having a PVA alignment film of 1 μm formed thereon is used.

As the first liquid crystal layer, a polymerization type nematic liquid crystal (n = 1.57, Δn = 0.1 at a wavelength of 550 nm) is used, a 35% toluene solution of the nematic liquid crystal monomer is prepared, and a photopolymerization initiator is used. 5% was added to the liquid crystal. The photopolymerization initiator may be a general material, for example, Irg907, Irg184, Irg361, Irg651 (all manufactured by Chiba Specialty Chemicals). As a surfactant, 0.05% of Byk361 (manufactured by BYK-Chemie) was added. The liquid crystal solution adjusted as described above was formed into a film on the substrate on which the alignment treatment was performed. In the film forming method, a liquid crystal solution was applied with a spinner, dried at 90 ° C., and the solvent was removed to obtain an uncured liquid crystal layer. Thereafter, the film was held at 80 ° C. and irradiated with ultraviolet rays (wavelength 310 nm) at a radiation intensity of 3.6 mW / cm ² for 3 seconds in N ₂ to cure and form a film. The thickness was 0.95 μm.

  As the liquid crystal molecular axis conversion layer, a polymerizable chiral nematic liquid crystal (n = 1.57, Δn = 0.1 at a wavelength of 550 nm) was used. A 35% toluene solution of the same nematic liquid crystal monomer as that of the first liquid crystal layer in which a helical structure is obtained by mixing a chiral agent is prepared, and a photopolymerization initiator is added to the corsteric liquid crystal (chiral nematic liquid crystal) in an amount of 5%. did. The photopolymerization initiator may be a general material, for example, Irg907, Irg184, Irg361, Irg651 and the like. The cholesteric liquid crystal solution adjusted as described above was prepared so that the selective reflection wavelength became 350 nm (nematic liquid crystal: chiral agent = 92.5 w%: 7.5 w%). The film formation is similar to that of the first liquid crystal layer. The film thickness was 31 nm (223 nm / (50 ° / 360 °) = 31 nm to convert the axis of liquid crystal molecules by an angle of 50 ° because one pitch is 223 nm).

  The second liquid crystal layer was the same as the first liquid crystal layer and had a thickness of 1.9 μm.

  Thus, an optical element A was obtained in which the half-wave retardation layer and the quarter-wave retardation layer whose optical axes were shifted by 50 ° were laminated.

  The optical element A was attached to a half-wave retardation layer side on a linear polarizing plate. The bonding angle was such that the molecular long axis of the half-wave retardation layer and the absorption axis of the linear polarizer made an angle of 5 °. At this time, the angle formed by the absorption axis of the linear polarizing layer and the molecular long axis of the quarter-wave retardation layer is 55 °.

  As described above, the polarization state of the transmitted light of the white light incident from the linear polarizing plate side on the optical element obtained by bonding the linear polarizing plate and the optical element A was measured.

  As a comparative example, only the above quarter-wave retardation layer (optical element B) and the linear polarizing plate (the angle between the molecular long axis of the quarter-wave retardation layer and the absorption axis of the linear polarizing layer was 45 °) ), An optical element C similar to the optical element A but without the liquid crystal molecular axis conversion layer, and an optical element composed of a linear polarizer were measured (optical without the liquid crystal molecular axis conversion layer). The element C is formed by separately forming a quarter-wave retardation layer and a half-wave retardation layer, transferring the optical axes so that they have a relationship of 31 ° with each other, and bonding them together. did.).

  The results of the comparison are shown in the table below.

Example 3
As in Example 2, the thickness of the liquid crystal molecular axis conversion layer is 37 nm, and the bonding angle is 15 ° (assuming that the absorption axis of the linear polarizing plate is 0 °). Long axis) and 74 ° (the long axis of the quarter-wave retardation layer).

  As a comparative example, an optical element E similar to the optical element D but having no liquid crystal molecular axis conversion layer and an optical element including a linear polarizing plate was measured.

As a result of comparison, the ellipticities of the optical elements A to E at each wavelength were compared. As a result, a circularly polarized element (optical element A) having an ellipticity closer to 1 than the optical element B was obtained. It was found that there was almost no effect of the conversion layer (optical elements A and C, D and E).

Table
│wavelength │optical element A│optical element B│optical element C│optical element D│optical element E│
├───┼─────┼─────┼─────┼─────┼─────┤
│400nm │ 0.50 │ 0.46 │ 0.56 │ 0.69 │ 0.71 │
├───┼─────┼─────┼─────┼─────┼─────┤
│500nm │ 0.86 │ 0.89 │ 0.89 │ 0.94 │ 0.95 │
├───┼─────┼─────┼─────┼─────┼─────┤
│600nm │ 0.89 │ 0.80 │ 0.88 │ 0.96 │ 0.96 │
├───┼─────┼─────┼─────┼─────┼─────┤
│700nm │ 0.76 │ 0.63 │ 0.75 │ 0.73 │ 0.73 │
└───┴─────┴─────┴─────┴─────┴─────┘
.

  As described above, the optical element including the liquid crystal layer of the present invention and the liquid crystal display device using the same have been described based on the principle and the embodiments. However, the present invention is not limited to these embodiments, and various modifications are possible. .

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view of one embodiment of an optical element comprising a liquid crystal layer of the present invention, and a perspective view showing a direction of a liquid crystal molecular axis at an interface between the layers. It is sectional drawing which shows the direction of the liquid crystal molecular axis of each layer of another form of the optical element which consists of a liquid crystal layer of this invention. FIG. 4 is a cross-sectional view showing an example of using an optical element having a liquid crystal layer of the present invention in a liquid crystal display device.

Explanation of reference numerals

1. Optical element (the present invention)
2, substrate 3, first liquid crystal layer 3 ', liquid crystal molecules 4 at the interface of the first liquid crystal layer on the liquid crystal molecular axis conversion layer side, liquid crystal molecule axis conversion layer 4', liquid crystal molecules 4 in the liquid crystal molecular axis conversion layer. ₁ '... liquid crystal molecules 4 at the interface of the liquid crystal molecular axis conversion layer on the first liquid crystal layer side _{2 2} ' ... liquid crystal molecules 5 at the interface of the liquid crystal molecular axis conversion layer on the second liquid crystal layer side ... second liquid crystal layer 5 ' ... The liquid crystal molecules 10 at the interface of the second liquid crystal layer on the liquid crystal molecular axis conversion layer side; the liquid crystal cell 11; the glass substrate 12 on the backlight side; the glass substrate 13 on the observation side; the liquid crystal layer 14; 1 wavelength plate 15 transflective cholesteric liquid crystal filter 16 2nd broadband quarter wave plate 17 1st linear polarizing plate 18 2nd linear polarizing plate 19 backlight light source 20 seal member

Claims (19)

The liquid crystal molecular axis conversion layer is directly laminated on the first liquid crystal layer in which the liquid crystal molecular axis directions are aligned in a fixed direction, and the liquid crystal molecules are further laid thereon in a direction different from the liquid crystal molecular axis direction of the first liquid crystal layer. An optical element comprising a liquid crystal layer, wherein a second liquid crystal layer having a uniform axial direction is directly laminated. 2. The optical element according to claim 1, wherein the liquid crystal molecular axis conversion layer is made of a chiral nematic liquid crystal. 2. The optical element according to claim 1, wherein the liquid crystal molecular axis conversion layer is made of a cholesteric liquid crystal. 2. The optical element according to claim 1, wherein the first liquid crystal layer and the second liquid crystal layer are made of a nematic liquid crystal. 5. The optical element according to claim 4, wherein the first liquid crystal layer and the second liquid crystal layer have a liquid crystal molecular axis substantially parallel to a film surface. 4. The optical element according to claim 2, wherein the liquid crystal molecular axis conversion layer has a helical structure of one pitch or less. 7. The optical element according to claim 6, wherein the pitch of the helical structure is a pitch length having a selective reflection wavelength in an ultraviolet region. 8. The liquid crystal display device according to claim 1, wherein one of the first liquid crystal layer and the second liquid crystal layer constitutes a quarter-wave retardation layer, and the other is a half-wave retardation layer. An optical element comprising a liquid crystal layer, which constitutes a phase difference layer. The optical element according to claim 7, wherein a cholesteric liquid crystal layer having selective reflection is directly laminated on the first liquid crystal layer side or the second liquid crystal layer side. 2. The liquid crystal according to claim 1, wherein the liquid crystal molecular axis conversion layer has a liquid crystal molecular axis aligned in a certain direction along the interface at one interface and a specific angle direction intersecting the interface at the other interface. An optical element comprising a liquid crystal layer, having a molecular axis, wherein an angle of a liquid crystal molecular axis between both interfaces changes continuously or discontinuously from one interface to the other interface. 11. The device according to claim 10, wherein the first liquid crystal layer has a liquid crystal molecular axis substantially parallel to a film surface, and the second liquid crystal layer is substantially equal to the specific angle with respect to the film surface. An optical element comprising a liquid crystal layer having an angular molecular axis. A liquid crystal molecular axis conversion layer is directly laminated on a first liquid crystal layer made of a chiral nematic liquid crystal or a cholesteric liquid crystal having a helical axis substantially perpendicular to the film surface. An optical element comprising a liquid crystal layer, wherein a second liquid crystal layer aligned in a certain direction is directly laminated. 13. The specific angle according to claim 12, wherein the liquid crystal molecular axis conversion layer has a liquid crystal molecular axis aligned in a certain direction along the interface at the interface with the first liquid crystal layer, and intersects the interface at the other interface. Wherein the angle of the liquid crystal molecular axis between the two interfaces changes continuously or discontinuously from one interface to the other interface. 14. The liquid crystal molecular axis conversion layer according to claim 1, wherein another liquid crystal molecular axis conversion layer is directly laminated on the second liquid crystal layer, and further different from the liquid crystal molecular axis direction of the second liquid crystal layer. An optical element comprising a liquid crystal layer, wherein a third liquid crystal layer in which liquid crystal molecular axis directions are aligned in a direction is directly laminated. 15. An optical element comprising a liquid crystal layer according to claim 1, wherein the optical element is laminated on a support substrate, patterned in a film plane, and has an exposed portion of the support substrate. 16. An optical element comprising a liquid crystal layer according to claim 1, wherein the optical element is divided into a plurality of regions and has different optical effects on light transmitted through the adjacent regions. 17. The liquid crystal display device according to claim 1, wherein the first liquid crystal layer, the liquid crystal molecule axis conversion layer, and the second liquid crystal layer are made of a material mainly composed of the same liquid crystal molecules. An optical element comprising a liquid crystal layer. A liquid crystal display device comprising an optical element comprising the liquid crystal layer according to any one of claims 1 to 17. 19. The liquid crystal display device according to claim 18, wherein an optical element including the liquid crystal layer is disposed in a liquid crystal cell.

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