JP4570022B2 - Optical element comprising liquid crystal layer and liquid crystal display device using the same - Google Patents

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 is used to mean a layer composed of molecules having optically liquid crystal properties, and the state of the layer is in a fixed solid state composed of oligomers or polymers. Say something.

  The type of retardation layer is classified by the direction of the optical axis (optical axis) and the magnitude of the refractive index in the optical axis direction relative to the refractive index in the direction orthogonal to the optical axis. A plate in which the direction of the optical axis is along the layer surface, A plate in which the direction of the optical axis is in the normal direction perpendicular to the layer, and C plate in which the direction of the optical axis is inclined from the normal direction It is called an O plate. A plate with a refractive index in the direction of the optical axis larger than the refractive index in the direction perpendicular to the optical axis is a positive plate, and a refractive index in the direction of the optical axis smaller than the refractive index in the direction perpendicular to the optical axis is negative. Say the plate. Therefore, 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 including a liquid crystal layer, a polarization separation element, a polarizing plate, a color filter, and the like including a liquid crystal layer having a cholesteric phase structure (cholesteric liquid crystal layer) have been proposed. In addition, a retardation plate or the like including 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 liquid crystal display elements by combining various retardation plates, half-wave plates, quarter-wave plates, circularly polarized light separating elements, etc. (Patent Literature) 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 2002-55342 A Special table 2002-506532 gazette JP 2002-72209 A JP 2002-107541 A 2002 Japanese Liquid Crystal Society Summer School Text pp69-77

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

  However, Patent Document 6 discloses that a circularly polarized light separating element made of a cholesteric liquid crystal layer is directly formed on a quarter-wave layer made of a nematic liquid crystal layer. Since the liquid crystal layer has the ability to align the upper cholesteric liquid crystal layer, both layers can be formed directly. In the general case where a plurality of liquid crystal layers are integrated, the alignment film is used as a liquid crystal layer. Must be deposited.

  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 combined with a retardation plate, a circularly polarized light separating element, or the like is used in a liquid crystal cell. In-cell arrangement inside (between transparent substrates) was difficult.

  Further, in the case where a retardation plate or the like is integrated with a liquid crystal layer, a transfer method must be used to stack a plurality of layers, or an alignment film must be disposed between the liquid crystal layers.

  The present invention has been made to solve such problems of the prior art, and its purpose is to provide a liquid crystal molecule axis between adjacent liquid crystal layers when a plurality of liquid crystal layers are stacked to form an optical element. By interposing a liquid crystal molecular axis conversion layer that continuously connects the directions of each other, an adhesive film, an alignment film, and the like can be integrated without being arranged.

  In the optical element comprising the liquid crystal layer of the present invention that achieves the above object, 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 certain direction, and further on the first liquid crystal layer. A second liquid crystal layer having a liquid crystal molecular axis direction 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 composed of chiral nematic liquid crystal or cholesteric liquid crystal.

  In the optical element composed of the liquid crystal layer of the present invention, the first liquid crystal layer and the second liquid crystal layer can be composed of, for example, nematic liquid crystal.

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

  The liquid crystal molecular axis conversion layer desirably has a helical structure with a pitch of 1 pitch or less.

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

  In the optical element comprising the liquid crystal layer of the present invention, either the first liquid crystal layer or the second liquid crystal layer constitutes a quarter wavelength retardation layer, and the other half wavelength. The phase difference layer can be constituted.

  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.

  In the optical element comprising 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 desirable that the liquid crystal molecular axes are aligned in a specific angle direction, and the angle of the liquid crystal molecular axes between the two 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 having an angle substantially equal to the specific angle with respect to the film surface. It can have.

  The optical element comprising another liquid crystal layer of the present invention comprises a liquid crystal molecular axis conversion layer on a first liquid crystal layer comprising chiral nematic liquid crystal or cholesteric liquid crystal having a helical axis substantially perpendicular to the film surface. Is directly laminated, and a second liquid crystal layer having a liquid crystal molecular axis direction aligned in a certain direction is directly laminated thereon.

  In this case, the liquid crystal molecular axis conversion layer has liquid crystal molecular axes aligned in a certain direction along the interface at the interface with the first liquid crystal layer, and in the direction of a specific angle intersecting the interface at the other interface. It is desirable that they have uniform liquid crystal molecular axes, and the angle of the liquid crystal molecular axes between the two 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 further the liquid crystal molecular axis direction aligned in a direction different from the liquid crystal molecular axis direction of the second liquid crystal layer. 3 liquid crystal layers can be directly laminated.

  Moreover, in the above, it is laminated | stacked on a support base material, it is patterned within a film surface, and shall have the exposed part of a support base material.

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

  In addition, it is preferable that the first liquid crystal layer, the liquid crystal molecular axis conversion layer, and the second liquid crystal layer are formed using a material mainly containing the same liquid crystal molecules.

  The present invention includes a liquid crystal display device using an optical element composed of the above liquid crystal layer, and the optical element can be disposed 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 directly laminated thereon, so that an adhesive film, an alignment film, etc. are arranged. The optical element can be formed integrally. In addition, by using the same material or a material related thereto, interface reflection can be suppressed, and an optical element such as a retardation plate that is resistant to thermal environment changes such as thermal expansion can be obtained. In-cell arrangement is possible. Further, since the liquid crystal molecular axis conversion layer also serves as an alignment film for the first liquid crystal layer or the second liquid crystal layer directly stacked thereon, the liquid crystal molecular axis conversion layer can be formed without rubbing, and there is no risk of contamination due to foreign matters. In addition, there is no problem of disturbance of the interface or mixing of bubbles due to the bonding of the first liquid crystal layer and the second liquid crystal layer.

  The principle and examples of the optical element comprising the liquid crystal layer of the present invention and the liquid crystal display device using the same will be described below.

  For example, in order to construct a circular polarizer with a wide wavelength band (broadband circular polarizer), one or two λ / 2 plates (half-wave plates) and λ / 4 plates (quarter-wave plates) ) Obtained by combining one sheet (for example, Non-Patent Document 1). A λ / 2 plate or a λ / 4 plate can be composed of a positive A plate. For example, the positive A plate is formed by planarly aligning nematic polymerizable liquid crystal molecules having a positive refractive index anisotropy in a layer plane. can do. When forming a broadband circularly polarizing plate, the slow axis (optical axis) of the λ / 2 plate and the slow axis (optical axis) of the λ / 4 plate are shifted by a predetermined angle and overlapped. Similarly, various optical elements are configured by overlapping a plurality of A plates.

  In this way, when a plurality of A plates are stacked and integrated to constitute various optical elements, and when these A plates are constituted by planar alignment of polymerizable liquid crystal molecules, the optical axis between the A plates is In order to make the alignment direction of the upper liquid crystal layer laminated in order to shift from each other into a predetermined direction, generally, a transfer method or an alignment film must be disposed between the liquid crystal layers.

  In such a case, according to the present invention, the liquid crystal molecular axis conversion layer composed of the liquid crystal layer is interposed between the liquid crystal layers to be stacked, and the directions of the axis of the liquid crystal molecules between the liquid crystal layers to be stacked are continuously connected. It 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 orientation of liquid crystal molecular axes at the interface of each layer in FIG. It is.

1 includes a first liquid crystal layer 3, a liquid crystal molecular axis conversion layer 4, and a second liquid crystal layer 5 laminated integrally from the substrate 2 side. The axis of the liquid crystal molecule 3 ′ at the interface on the molecular axis conversion layer 4 side is oriented in a specific direction indicated by a double arrow along the interface, and the interface on the liquid crystal molecular axis conversion layer 4 side of the second liquid crystal layer 5. The axis of the liquid crystal molecule 5 ′ is aligned in another specific direction indicated by a double arrow along the interface, and the axis of the liquid crystal molecule 4 ′ in the liquid crystal molecular axis conversion layer 4 is the first liquid crystal layer 3 The liquid crystal molecules 4 ₁ ′ are aligned in such a manner that they are continuously connected by drawing a spiral from the side to the second liquid crystal layer 5 side, and the interface of the liquid crystal molecular axis conversion layer 4 on the first liquid crystal layer 3 side is The first liquid crystal layer 3 is aligned in the same direction as the axis of the liquid crystal molecule 3 ′ at the interface on the liquid crystal molecular axis conversion layer 4 side, and the liquid crystal molecule 4 at the interface on the second liquid crystal layer 5 side of the liquid crystal molecular axis conversion layer 4. 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 liquid crystal molecule axes of the first liquid crystal layer 3 and the liquid crystal molecular axis conversion layer 4 and the liquid crystal molecular axis conversion layer 4 and the second liquid crystal layer 5 the same at each interface, 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 a similar structure may be used. Thus, if the characteristics of the liquid crystal molecules of the adjacent liquid crystal layer are not greatly changed, the orientation of the axis of the liquid crystal molecules on the surface of the liquid crystal layer previously formed is aligned at the interface of the liquid crystal layer formed thereon. In order to regulate the alignment in the same direction (to act as an alignment film), the direction of the axis of the liquid crystal molecules at the interface of the liquid crystal layer to be formed later is the liquid crystal molecule at the interface of the liquid crystal layer formed first. The direction of the axis is the same.

  In order to align the liquid crystal molecules 4 ′ in the layer so that the axes of the liquid crystal molecules 4 ′ are continuously connected so as to draw a spiral as in the liquid crystal molecular axis conversion layer 4 of FIG. 1, for example, a cholesteric liquid crystal or a chiral agent is mixed into the spiral. 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 according to the same liquid crystal material. It can be produced by using a material, and the difference in refractive index between liquid crystal layers can be reduced, so that interface reflection can be suppressed, and it is resistant to thermal environmental changes such as thermal expansion. Further, since the alignment between the liquid crystal layers can be controlled by the liquid crystal layer provided on the lower liquid crystal layer, an optical element free from rubbing and contaminated by foreign matters can be configured. In addition, there is no disturbance of the interface due to bonding and no problem of bubbles. Furthermore, since such an optical element 1 is made of a heat-resistant liquid crystal polymer without using an adhesive or the like, in-cell arrangement in a liquid crystal cell is possible.

  Here, the liquid crystal layer having a helical structure of the liquid crystal molecular axis conversion layer 4 in FIG. 1 has the function of continuously connecting the liquid crystal molecule axes between the liquid crystal layer 3 and the liquid crystal layer 5 as its function. A thin pitch of 1 or less is sufficient for the helical structure. Moreover, in order to prevent the liquid crystal molecular axis conversion layer 4 from reflecting the visible light incident on the optical element 1 by the spiral structure, the selective reflection wavelength of the spiral structure (cholesteric liquid crystal) is an ultraviolet light outside the visible light 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. Therefore, it is desirable to select one having a selective reflection wavelength in the ultraviolet region where the helical pitch is relatively short.

By the way, FIG. 1 is for explaining the principle of the present invention in the case where various optical elements are constructed by superposing a plurality of A plates, but the A plate and C plate, cholesteric liquid crystal layer (hereinafter referred to as CLC). Layer) and the C plate, the A plate and the O plate, or the compensation plate that improves the viewing angle characteristics by superimposing the CLC layer and the O plate (Patent Documents 9 and 11, etc.) In such a liquid crystal molecular axis conversion layer 4, the liquid crystal molecule axes between the liquid crystal layer constituting the A plate or the CLC layer and the liquid crystal layer constituting the C plate or the O plate cannot be continuously connected. . 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 is 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 less than 90 ° when the first liquid crystal layer 3 is an O plate). The liquid crystal molecular axis conversion layer of the first liquid crystal layer 3 is aligned with the axis of the liquid crystal molecule 4 ₁ ′ at the interface of the liquid crystal molecular axis conversion layer 4 on the first liquid crystal layer 3 side. Aligned in the same direction as the axis of the liquid crystal molecule 3 ′ at the interface on the 4 side, the axis of the liquid crystal molecule 4 ₂ ′ at the interface on the second liquid crystal layer 5 side of the liquid crystal molecular axis conversion layer 4 is the axis of the second liquid crystal layer 5 The liquid crystal molecule axis conversion layer 4 is aligned in the same direction as the axis of the liquid crystal molecules 5 ′ at the interface.

  Also in this case, in order to make the directions of the liquid crystal molecular axes of the first liquid crystal layer 3 and the liquid crystal molecular axis conversion layer 4 and the liquid crystal molecular axis conversion layer 4 and the second liquid crystal layer 5 the same at each interface, 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 a similar structure may be used. Thus, if the characteristics of the liquid crystal molecules of the adjacent liquid crystal layer are not greatly changed, the orientation of the axis of the liquid crystal molecules on the surface of the liquid crystal layer previously formed is aligned at the interface of the liquid crystal layer formed thereon. In order to regulate the alignment in the same direction (to act as an alignment film), the direction of the axis of the liquid crystal molecules at the interface of the liquid crystal layer to be formed later is the liquid crystal molecule at the interface of the liquid crystal layer formed first. The direction of the axis is the same.

  As in the liquid crystal molecular axis conversion layer 4 in FIG. 2, there are several methods for aligning the liquid crystal molecules 4 ′ in the layer so that the axes are continuously connected and changed from one interface to the other interface. is there. This will be described below.

(1) Liquid crystal molecules have the property of being aligned vertically at the air interface, with exceptions. In the case of normal film formation, a surfactant is added to make the film face parallel to the interface so that the surface is modified so that it is not oriented vertically. The type of surfactant to be added and the surfactant 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 second liquid crystal layer 5 side as shown in FIG. 2 is 90 ° or smaller. Then, the liquid crystal molecular axis conversion layer 4 as shown in FIG. 2 is obtained by irradiating with ultraviolet rays or the like to be crosslinked and cured.

  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 limitation in particular in the kind of surfactant, Generally what is marketed can fully respond. Specific examples include cationic surfactants such as imidazoline, quaternary ammonium salts, alkylamine oxides, polyamine derivatives, polyoxyethylene-polyoxypropylene condensates, primary or secondary alcohol ethoxylates, Anionic interfaces such as alkylphenol ethoxylates, polyethylene glycol and esters thereof, sodium lauryl sulfate, ammonium lauryl sulfate, amines of lauryl sulfate, alkyl-substituted aromatic sulfonates, alkylates, aliphatic or aromatic sulfonate formalin condensates Activators, amphoteric surfactants such as laurylamidopropylbetaine, laurylaminoacetic acid betaine, nonionic surfactants such as polyethylene glycol fatty acid esters, polyoxyethylene alkylamine, perf Oroalkyl sulfonate, perfluoroalkyl carboxylate, perfluoroalkyl ethylene oxide adduct, perfluoroalkyltrimethylammonium salt, perfluoroalkyl group / hydrophilic group-containing oligomer, perfluoroalkyl / lipophilic group-containing oligomer perfluoroalkyl Fluorine surfactants such as group-containing urethanes, and acrylic surfactants such as polyacrylic acid, acrylic acid copolymers, methacrylic acid, and methacrylic acid copolymers.

  (2) A vertical alignment film or an alignment film having a pretilt is brought into close contact with a surface (an interface on the second liquid crystal layer 5 side as shown in FIG. 2) on which the liquid crystal molecular axis conversion layer 4 is to be vertically aligned or pretilt aligned at a predetermined angle. The liquid crystal molecular axis conversion layer 4 is irradiated with ultraviolet rays or the like to undergo cross-linking polymerization and cured, and after the curing, the alignment film is peeled off to obtain the liquid crystal molecular axis conversion layer 4 as shown in FIG.

  According to this method, the tilt angle θ is 90 ° or less from the orientation parallel to one interface to the other interface as shown in FIG. The liquid crystal molecular axis conversion layer 4 having a smaller angle can be obtained.

  A vertical alignment film or an alignment film having a pretilt may be a commercially available film.

  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 can be integrated without interposing an adhesive layer or an alignment layer. Optical elements such as compensators, polarization separation elements, and polarizing plates that are laminated to improve various retardation plates and viewing angle characteristics can be configured.

  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 is substantially thermal because the amount of the chiral agent added is smaller than that of the main nematic liquid crystal (generally 0 to 20%). It can be regarded as optically the same physical property. However, as described above, even if the liquid crystal molecules used in each liquid crystal layer are not the same, the molecular characteristics do not change greatly if they have a similar structure, so that an optical element having desired optical characteristics can be obtained.

  When the liquid crystal molecular axis conversion layer 4 is sufficiently thin, discontinuity of the liquid crystal molecular alignment inside the conversion layer when adopting a manufacturing method in which an alignment film is arranged above and below the conversion layer 4 to regulate the alignment. Dots may occur. This occurs when the change in the liquid crystal layer structure cannot follow when the influence of the upper and lower alignment regulating force is strong, but it does not affect the performance as the liquid crystal molecular axis conversion layer 4 and also in terms of optical characteristics. The defect does not appear.

  By the way, from the above description, the liquid crystal molecular axis conversion layer 4 must be optically optically negligible with respect to the wavelength used. An example shows that such a liquid crystal molecular axis conversion layer 4 can be constructed.

For example, in the case of the liquid crystal molecular axis conversion layer 4 that converts the axes of liquid crystal molecules parallel to the film surface, for example, by 45 ° to each other like the liquid crystal molecular axis conversion layer 4 in FIG. 1, a chiral nematic liquid crystal that selectively reflects a wavelength of 350 nm ( When n = 1.6 and Δn (value obtained by subtracting the extraordinary refractive index from the ordinary refractive index) = 0.1),
1 pitch of spiral (360 °) = 219nm
1/8 pitch of spiral (45 °) = 27nm
Therefore, the liquid crystal molecular axis conversion layer 4 having a thickness of 27 nm is obtained. The retardation ΔRe of the nematic liquid crystal layer is ΔRe = 2.7 nm (0.1 × 27). Since the incident light is generally linearly polarized light, the action at 45 ° is maximum, but in the case of a chiral nematic liquid crystal layer (liquid crystal molecular axis conversion layer 4), ΔRe <2.7 nm. . Further, the optical rotation of the unit length due to the spiral of liquid crystal molecules is given by −π · Δn ² · (P / 4) · λ ² (P: pitch, λ: wavelength), and light of λ = 550 nm passes through. 6 × 10 ⁻⁶ rad / nm, and when passing through the liquid crystal molecular axis conversion layer 4 having a thickness of 27 nm, the optical rotation is 0.00016 rad = 0.09 °.

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

  By the way, liquid crystal monomer molecules (polymerizable liquid crystal molecules) capable of three-dimensional crosslinking constituting the liquid crystal layers 3 and 5 and the liquid crystal molecular axis conversion layer 4 in the present invention are disclosed in, for example, Patent Document 3 and Patent Document 4. Liquid crystalline monomers and mixtures of such 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 [Chemical Formula 1] to [Chemical Formula 10] compounds is used. be able to. In the case of the liquid crystalline monomer represented by the general chemical formula [Chemical Formula 11], X is preferably 2 to 5 (integer).

  Further, as the chiral agent, for example, a chiral agent represented by the general chemical formulas [Chemical Formula 12] to [Chemical Formula 14] can be used. In the case of the chiral agent represented by the general chemical formulas [Chemical Formula 12] and [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 is 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 add a polymerization initiator to these liquid crystals. When polymerizing liquid crystal monomer molecules by electron beam irradiation, a polymerization initiator may be unnecessary. For example, when polymerizing liquid crystal monomer molecules by ultraviolet irradiation, a polymerization initiator (photopolymerization initiator) is used. It is preferably used for promoting polymerization.

  Examples of the photopolymerization initiator to be added include benzyl (also called bibenzoyl), benzoin isobutyl ether, benzoin isopropyl ether, benzophenone, benzoylbenzoic acid, methyl benzoylbenzoate, 4-benzoyl-4′-methyldiphenyl sulfide, and benzylmethyl. Ketal, dimethylaminomethylbenzoate, 2-n-butoxyethyl-4-dimethylaminobenzoate, isoamyl p-dimethylaminobenzoate, 3,3′-dimethyl-4-methoxybenzophenone, methylobenzoyl formate, 2-methyl- 1- (4- (methylthio) phenyl) -2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butan-1-one, 1- (4 -Dodecylfe ) -2-hydroxy-2-methylpropan-1-one, 1-hydroxycyclohexyl phenyl 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, etc. Can give.

  In addition to the photopolymerization initiator, it is also possible to add a sensitizer as long as the object of the present invention is not impaired.

  The addition amount of such a photopolymerization initiator is generally 0.01 to 20% by weight, preferably 0.1 to 10% by weight, more preferably 0.5% with respect to the polymerizable liquid crystal material. It can be added in the range of ˜5% by weight.

  Next, the optical element 1 as shown in FIG. 1 is a half-wave retardation layer or a quarter-wave retardation layer as the first liquid crystal layer 3 and is divided into four minutes as the second liquid crystal layer 5. FIG. 3 shows an example of use in a liquid crystal display device in the case where a wide-band quarter-wave plate is formed by using the one-wavelength retardation layer or the half-wave retardation layer. 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 the broadband transflective cholesteric disposed thereon. A liquid crystal filter 15 is disposed, and the second broadband quarter-wave plate 16 according to the present invention as described above is disposed on the inner surface of the glass substrate 12 on the opposite side. A liquid crystal layer 13 in a liquid phase is sandwiched between the transflective cholesteric liquid crystal filter 15 and the second broadband quarter-wave plate 16, and the glass substrate 11, 12 is sandwiched between the sealing members 20. The liquid crystal cell 10 is configured by being sealed. Here, the transflective cholesteric liquid crystal filter 15 reflects about 50% of the circularly polarized light of the cholesteric liquid crystal filter 15 (for example, right circularly polarized light) and transmits the remaining 50%, opposite to the reflective characteristics. The circularly polarized light (for example, left circularly polarized light) is a cholesteric liquid crystal filter that transmits without being reflected.

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

  In addition, on the inner surfaces of the glass substrates 11 and 12 of the liquid crystal cell 10, color filters of R (red), G (green), and B (blue) are aligned with the pixels of the color filter, pixel electrodes, counter electrodes, and TFTs. (TFD), an alignment film for aligning the liquid crystal layer 13, and the like are provided, but illustration is omitted.

  Because of the arrangement as described above, in the case of transmissive display, the naturally polarized illumination light emitted from the backlight light source 19 is transmitted to the first linear polarizing plate 17 and the first broadband quarter-wave plate 14. Thus, only a linearly polarized light component that passes through circularly polarized light (right circularly polarized light) that matches the reflection characteristic (for example, right circularly polarized light) of the semi-transmissive cholesteric liquid crystal filter 15 passes. Right-handed circularly polarized light that has passed through the first linear polarizing plate 17 and the first broadband quarter-wave plate 14 passes through the semi-transmissive cholesteric liquid crystal filter 15 by about 50%, and enters the liquid crystal layer 13. When the pixel display state is white, the right circularly polarized light is converted to left circularly polarized light, and when the pixel display state is black, the second broadband quarter wave plate 16 remains right circularly polarized. And reaches the second linearly polarizing plate 18. The second broadband quarter-wave plate 16 and the second linear polarizing plate 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 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 left circularly polarized light is blocked by the second broadband quarter-wave plate 16 and the second linear polarizing plate 18, and the light from the backlight source 19 is transmitted to the observer. It does not reach and displays a dark state.

  Next, in the case of reflective display using external light, the external light passes through the second linear polarizing plate 18 and the second broadband quarter-wave plate 16 and becomes left-handed circularly polarized light. In the case of white, the left circularly polarized light is converted into right circularly polarized light in the liquid crystal layer 13, and in the case where the display state of the pixel is black, the liquid crystal layer 13 does not convert but remains in the left circularly polarized light and is a semi-transmissive cholesteric The liquid crystal filter 15 is reached.

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

  With such a configuration, an R, G, B absorption color filter is arranged between the transflective cholesteric liquid crystal filter 15 of the liquid crystal cell 10 and the observation-side glass substrate 12, so that the reflection type and the transmission type can be obtained. A liquid crystal display device capable of color display of the mold is obtained. Since the optical element according to the present invention (in the above example, the broadband quarter-wave plates 14 and 16) can be disposed in the liquid crystal cell 10, the interface reflection can be reduced and the liquid crystal display device can be made thin. become. Further, by integrating the optical element according to the present invention with the substrate, pixel patterning can be performed, and further, the panel forming process can be simplified. In particular, as shown in FIG. 3, when sealing between the glass substrates 11 and 12 by the sealing member 20, the broadband 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 is possible, and a liquid crystal display device having excellent durability can be configured.

  Further, for example, the optical element composed of the liquid crystal layer of the present invention is divided into a plurality of regions so as to correspond to R, G, and B pixels, and each region is optimal for the center wavelengths 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 making 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 0.6 μm formed on a glass substrate having a thickness of 500 μm was prepared.

  As a first solution, a xylene solution with a liquid crystal solid content of 30% of a liquid crystal monomer of a polymerization type nematic liquid crystal (n = 1.57, Δn = 0.1 at a wavelength of 550 nm) is prepared, and a photopolymerization initiator is used as the liquid crystal. In contrast, 5% was added. The photopolymerization initiator may be a common material such as Irg907, Irg184, Irg361, Irg651 (all manufactured by Chiba Specialty Chemicals).

  As the second solution, a solution obtained by adding 0.04% of a surfactant Byk390 (by Big 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 having a pretilt angle of 3 ° was prepared.

  As a third solution, a cholesteric liquid crystal toluene solution having a central reflection wavelength at 550 nm (30% cholesteric liquid crystal solid content), 0.06% surfactant Byk352 (manufactured by Big Chemie), and 5% photopolymerization initiator An added one was prepared. The photopolymerization initiator may be a common material such as Irg907, Irg184, Irg361, Irg651 (all manufactured by Chiba Specialty Chemicals).

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

(1) A C plate was formed to a thickness of 2 μm on the first substrate using the first solution. As a film forming method, the first solution was applied with a spinner, dried at 90 ° C., the solvent was removed, and an uncured liquid crystal layer was obtained. Thereafter, the film was cured at a temperature of 80 ° C. and irradiated with ultraviolet rays (wavelength: 310 nm) for 3 seconds at an irradiation intensity of 3.6 mW / cm ² in N ₂ to 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 applying the second solution and removing the solvent, the second substrate is brought into close contact with the applied layer, maintained at 80 ° C., and irradiated with N ₂ at an irradiation intensity of 3.6 mW / cm ^2. The film was cured with ultraviolet rays by irradiating with ultraviolet rays (wavelength: 310 nm) for 2 seconds.

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

(4) A CLC layer having a thickness of 2 μm was formed on the liquid crystal molecular axis conversion layer using the third solution. As a film forming method, the third solution was applied with a spinner, dried at 90 ° C., the solvent was removed, and an uncured liquid crystal layer was obtained. Thereafter, the film was cured at a temperature of 80 ° C. and irradiated with ultraviolet rays (wavelength: 310 nm) for 3 seconds at an irradiation intensity of 3.6 mW / cm ² in N ₂ to 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 formed with a polyimide alignment film of 0.7 μm, a stretched film, or a film substrate 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 common material such as Irg907, Irg184, Irg361, Irg651 (all manufactured by Chiba Specialty Chemicals). As the surfactant, 0.05% Byk361 (manufactured by Big Chemie) was added. The liquid crystal solution prepared as described above was formed on the substrate subjected to the alignment treatment. As a film forming method, a liquid crystal solution was applied with a spinner, dried at 90 ° C., the solvent was removed, and an uncured liquid crystal layer was obtained. Thereafter, the film was cured at a temperature of 80 ° C. and irradiated with ultraviolet rays (wavelength: 310 nm) for 3 seconds at an irradiation intensity of 3.6 mW / cm ² in N ₂ to form a film. The film thickness was 0.95 μm.

  As the liquid crystal molecular axis conversion layer, a polymerization type chiral nematic liquid crystal (n = 1.57, Δn = 0.1 at a wavelength of 550 nm) was used. Prepare a 35% toluene solution of the same nematic liquid crystal monomer as that of the first liquid crystal layer in which the spiral structure is obtained by mixing the chiral agent, and add 5% of the photopolymerization initiator to this corsteric liquid crystal (chiral nematic liquid crystal). did. The photopolymerization initiator may be a common material such as Irg907, Irg184, Irg361, Irg651, and the like. The cholesteric liquid crystal solution prepared as described above was prepared so that the selective reflection wavelength was 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 (1 pitch is 223 nm, so to convert the axis of liquid crystal molecules by an angle of 50 °, 223 nm / (50 ° / 360 °) = 31 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 with the optical axis shifted by 50 ° were laminated.

  The optical element A was attached to the linearly polarizing plate on the half-wavelength phase difference layer side. The laminating angle was such that the molecular long axis of the half-wave retardation layer and the absorption axis of the linearly polarizing plate formed an angle of 5 °. At this time, the angle formed by the absorption axis of the linearly polarizing layer and the molecular long axis of the quarter-wave retardation layer is 55 °.

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

  As a comparative example, only the above-described quarter-wave retardation layer (optical element B) and a linear polarizing plate (an angle of 45 ° between the molecular long axis of the quarter-wave retardation layer and the absorption axis of the linear polarizing layer). And an optical element that is the same as the optical element A and does not include the liquid crystal molecular axis conversion layer and an optical element that includes the linear polarizing plate (optical without the liquid crystal molecular axis conversion layer). Element C is prepared by forming a quarter-wave retardation layer and a half-wave retardation layer separately, transferring them so that their optical axes are 31 ° to each other, and bonding them together. did.).

  The comparison results are shown in the table below.

Example 3
As in Example 2, when the film thickness of the liquid crystal molecular axis conversion layer is 37 nm and the absorption angle of the linearly polarizing plate is 0 °, the bonding angle is 15 ° (half the wavelength retardation layer). The major axis) is 74 ° (the major axis of the quarter-wave retardation layer).

  As a comparative example, an optical element consisting of an optical element E that is the same as the optical element D and does not have a liquid crystal molecular axis conversion layer and a linearly polarizing plate was measured.

As a result of comparison, when the ellipticities of the optical elements A to E at the respective wavelengths were compared, a circularly polarizing element (optical element A) having an ellipticity closer to 1 than that of the optical element B was obtained, and the liquid crystal molecular axis It was found that there was almost no influence 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 mentioned above, although the optical element which consists of a liquid-crystal layer of this invention and the liquid crystal display device using the same have been demonstrated based on the principle and Example, this invention is not limited to these Examples, A various deformation | transformation is possible. .

It is sectional drawing of one form of the optical element which consists of a liquid crystal layer of this invention, and a perspective view which shows direction of the liquid crystal molecular axis | shaft of the interface of each layer. It is sectional drawing which shows the direction of the liquid crystal molecular axis | shaft of each layer of another form of the optical element which consists of a liquid crystal layer of this invention. It is sectional drawing which shows the utilization example to the liquid crystal display device of the optical element which consists of a liquid-crystal layer of this invention.

Explanation of symbols

1. Optical element (the present invention)
DESCRIPTION OF SYMBOLS 2 ... Substrate 3 ... 1st liquid crystal layer 3 '... Liquid crystal molecule 4 of liquid crystal molecular axis conversion layer side interface of 1st liquid crystal layer ... Liquid crystal molecular axis conversion layer 4' ... Liquid crystal molecule 4 in 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 ' ... Liquid crystal molecules 5 at the interface of the liquid crystal molecular axis conversion layer on the second liquid crystal layer side ... 2nd liquid crystal layer 5 ' ... Liquid crystal molecules 10 on the interface of the second liquid crystal layer on the liquid crystal molecular axis conversion layer side ... Liquid crystal cell 11 ... Glass substrate 12 on the backlight side ... Glass substrate 13 on the observation side ... Liquid crystal layer 14 ... First broadband 4 minutes 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 ... back light source 20 ... sealing member

Claims (11)

A liquid crystal molecular axis conversion layer is directly laminated on a first liquid crystal layer whose liquid crystal molecular axis directions are aligned in a certain direction, and further liquid crystal molecules in a direction different from the liquid crystal molecular axis direction of the first liquid crystal layer. Ri Na second liquid crystal layer axially aligned are laminated directly,
The liquid crystal molecular axis conversion layer is composed of chiral nematic liquid crystal or cholesteric liquid crystal,
The liquid crystal molecular axis conversion layer has the following helical structure 1 pitch, the optical element comprising a liquid crystal layer the pitch of the helical structure and said pitch length der Rukoto having a selective reflection wavelength in the ultraviolet region. 2. The optical element comprising a liquid crystal layer according to claim 1, wherein the first liquid crystal layer and the second liquid crystal layer are made of a nematic liquid crystal. 3. The optical element comprising a liquid crystal layer according to claim 2 , wherein the first liquid crystal layer and the second liquid crystal layer have a liquid crystal molecular axis substantially parallel to the film surface. In claim 1 of any one of 3, one of the first liquid crystal layer and the second liquid crystal layer form a first-wavelength retardation layer of 4 minutes, the other one wavelength position of 2 minutes An optical element comprising a liquid crystal layer, which constitutes a phase difference layer. 2. The optical element comprising a liquid crystal layer according to claim 1 , 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. Differ in any one of claims 1 to 5, on the second liquid crystal layer, another liquid crystal molecular axis conversion layer is directly laminated, further a liquid crystal molecular axis direction of the second liquid crystal layer thereon An optical element comprising a liquid crystal layer, wherein a third liquid crystal layer having a liquid crystal molecular axis direction aligned in the direction is directly laminated. In any one of claims 1 to 6, is laminated on a supporting substrate, is patterned in a film plane, an optical element comprising a liquid crystal layer, characterized in that has an exposed portion of the supporting substrate. In any one of claims 1 to 7, is divided into a plurality of regions, the optical element comprising a liquid crystal layer, wherein at different inter-area optical action are adjacent with respect to light transmitted through the adjacent areas. Characterized in any one of claims 1 to 8, wherein the first liquid crystal layer of the liquid crystal molecular axis converting layer, said second liquid crystal layer is a material mainly composed of the same liquid crystal molecules An optical element comprising a liquid crystal layer. The liquid crystal display device characterized by using an optical element comprising a liquid crystal layer of any one of claims 1 9. The liquid crystal display device according to claim 10 , wherein an optical element comprising the liquid crystal layer is disposed in a liquid crystal cell.

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