Phase difference compensation element, liquid crystal display device, and projection type image display device

Abstract

【Problem】The present invention provides a retardation compensation element and the like that can significantly reduce the mounting space, have excellent durability, and correspond to the deviation of the pretilt angle of liquid crystal. 【Solution】The retardation compensation element includes: a transparent substrate; a first optically anisotropic layer made of an inorganic material and acting as a C-plate; and a second optically anisotropic layer made of an inorganic material and being an oblique evaporation film that does not act as an O-plate, and the retardation characteristics after combining the first optically anisotropic layer and the second optically anisotropic layer act as an approximate O-plate.

Description

Technical Field

[0001] The present invention relates to a phase difference compensation element, a liquid crystal display device, and a projection type image display device. Background Art

[0002] In recent years, in liquid crystal display devices, in order to improve contrast characteristics and viewing angle characteristics, an optical compensation technique using a phase difference compensation element has been used. For example, compensation for black luminance fluctuations in vertically aligned liquid crystals can be cited. In addition, in order to compensate for the phase difference caused by the pretilt angle of the liquid crystal and the phase difference caused by birefringence due to obliquely incident light, a method of optically compensating by arranging a phase difference compensation element such as quartz parallel to the main surface of the liquid crystal panel, or a method of optically compensating by arranging an organic material having birefringence such as a polymer film parallel to the main surface of the liquid crystal panel has been proposed (for example, refer to Patent Documents 1 to 3).

[0003] However, in the case of a method using a processed single crystal as a phase difference compensation element, especially when it is desired to perform compensation considering the pretilt angle of the liquid crystal as well, it is necessary to cut out at a predetermined angle with respect to the crystal axis, and very high precision is required for material cutting, grinding, etc., resulting in high costs. In addition, it is not easy to control the crystal axis for extended films and the like.

[0004] Therefore, a method of arranging the phase difference compensation element itself inclined with respect to the main surface of the liquid crystal panel has been proposed (for example, refer to Patent Documents 4 and 5).

[0005] However, there is a concern that there is insufficient space for arranging the phase difference compensation element inclined with respect to the main surface of the liquid crystal panel inside a miniaturized projector. Furthermore, it is prone to aging for heat or high-brightness and high-output light beams, and there are problems in durability.

[0006] In addition, there are deviations in the pretilt angle of the liquid crystal, and a corresponding phase difference compensation element is desired.

[0007] Therefore, at present, there is a demand for providing a phase difference compensation element that can significantly reduce the arrangement space, has excellent durability, and corresponds to the deviation of the pretilt angle of the liquid crystal.

[0008] [Prior Art Documents]

[0009] [Patent Documents]

[0010] [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2005-172984;

[0011] [Patent Document 2] Japanese Patent No. 4661510;

[0012] [Patent Document 3] Japanese Patent No. 4566275;

[0013]

Patent Document 4

[0014]

Patent Document 5

[0015]

Problems to be Solved by the Invention

[0016] The present invention aims to solve the above-described various problems and achieve the following object. That is, an object of the present invention is to provide a retardation compensation element, a liquid crystal display device using the retardation compensation element, and a projection type image display device using the liquid crystal display device, the retardation compensation element being capable of significantly reducing the mounting space, having excellent durability, and corresponding to the deviation of the pretilt angle of the liquid crystal.

[0017]

Means for Solving the Problems

[0018] As means for solving the above-described problems, as follows. That is,

[0019] <1> A retardation compensation element, comprising:

[0020] A transparent substrate;

[0021] A first optically anisotropic layer made of an inorganic material and functioning as a C-plate; and

[0022] A second optically anisotropic layer made of an inorganic material and being an inclined angle evaporation film that does not function as an O-plate,

[0023] The retardation characteristics after combining the first optically anisotropic layer and the second optically anisotropic layer function as an approximate O-plate.

[0024] <2> The retardation compensation element according to <1> above, wherein the inorganic material in the second optically anisotropic layer is an oxide containing at least any one of Si, Nb, Zr, Ti, La, Ta, Al, Hf, and Ce.

[0025] <3> The retardation compensation element according to any one of <1> to <2> above, wherein the first optically anisotropic layer is an antireflection layer formed by laminating two or more inorganic oxide films having different refractive indexes.

[0026] <4> The retardation compensation element according to any one of <1> to <3> above, wherein a matching layer formed by laminating two or more inorganic oxide films having different refractive indexes is provided between the transparent substrate and the second optically anisotropic layer.

[0027] <5> The retardation compensation element according to <4>, wherein,

[0028] at least one of the inorganic oxide films in the antireflection layer is an oxide film containing at least any one of Ti, Si, Ta, Al, Ce, Zr, Nb, and Hf,

[0029] at least one of the inorganic oxide films in the matching layer is an oxide film containing at least any one of Ti, Si, Ta, Al, Ce, Zr, Nb, and Hf.

[0030] <6> The retardation compensation element according to any one of <1> to <5>, wherein a protective layer made of a dielectric film is provided on the second optically anisotropic layer.

[0031] <7> The retardation compensation element according to any one of <1> to <6>, wherein the transparent substrate is any one of glass, quartz, crystal, and sapphire.

[0032] <8> A liquid crystal display device, characterized by comprising a liquid crystal panel and the retardation compensation element according to any one of <1> to <7>.

[0033] <9> A projection type image display device, characterized by comprising: a light source that emits light; a projection optical system that projects the modulated light; and the liquid crystal display device according to <8> disposed on the optical path between the light source and the projection optical system.

[0034]

Advantages of the Invention

[0035] According to the present invention, it is possible to provide a retardation compensation element, a liquid crystal display device using the retardation compensation element, and a projection type image display device using the liquid crystal display device. The retardation compensation element can solve the existing many problems, can greatly reduce the layout space, and further has excellent durability and can correspond to the deviation of the pretilt angle of the liquid crystal. Description of the Drawings

[0036] Figure 1 It is a graph showing the tilt angle dependence of the retardation of the C-plate.

[0037] Figure 2 It is a graph showing the tilt angle dependence of the retardation of the O-plate.

[0038] Figure 3 It is a graph showing the tilt angle dependence of the retardation of the approximate O-plate.

[0039] Figure 4 It is a cross-sectional view showing a structural example of the retardation compensation element.

[0040] Figure 5 It is a cross-sectional schematic view of an antireflection layer.

[0041] Figure 6 It is an oblique view of an oblique-angle evaporation film.

[0042] Figure 7 It is a schematic view showing an example of an oblique-angle evaporation method for forming an oblique-angle evaporation film.

[0043] Figure 8 It is a schematic view showing an example of the orientation in which the evaporation direction from the evaporation source is projected onto the evaporation target surface.

[0044] Figure 9 It is a flowchart showing a manufacturing method of a retardation compensation element.

[0045] Figure 10 It is a schematic diagram showing an example of the structure of a liquid crystal display device.

[0046] Figure 11 It is a schematic diagram showing an example of the structure of a projection type image display device.

[0047] Figure 12 It is a graph showing the tilt angle dependence of the retardation of the first optically anisotropic layer of Example 1.

[0048] Figure 13 It is a graph showing the tilt angle dependence of the retardation of the second optically anisotropic layer of Example 1.

[0049] Figure 14 It is a graph showing the tilt angle dependence of the retardation after combining the first optically anisotropic layer and the second optically anisotropic layer of Example 1. Detailed Description of the Invention

[0050] Hereinafter, with reference to the accompanying drawings, the embodiments of the present technology will be described in detail in the following order.

[0051] 1. Retardation Compensation Element

[0052] 2. Liquid Crystal Display Device

[0053] 3. Projection Type Image Display Device

[0054] 4. Examples

[0055] (Retardation Compensation Element)

[0056] The retardation compensation element according to the present embodiment includes a transparent substrate, a first optically anisotropic layer, and a second optically anisotropic layer.

[0057] The first optical anisotropic layer functions as a C-plate.

[0058] The second optical anisotropic layer does not function as an O-plate.

[0059] The second optical anisotropic layer is an inclined angle evaporation film.

[0060] The retardation characteristics after combining the first optical anisotropic layer and the second optical anisotropic layer function as an approximate O-plate.

[0061] Here, a C-plate refers to a birefringent body whose optical axis is perpendicular to the substrate surface. The optical axis refers to the direction that does not cause birefringence, meaning the direction in which the retardation becomes 0. Figure 1 It is a graph showing the inclination angle dependence of the retardation of the C-plate. The inclination angle of 0° is the direction perpendicular to the substrate surface, where the retardation becomes 0, so it can be known that the optical axis is perpendicular to the substrate surface.

[0062] An O-plate refers to a uniaxial or biaxial birefringent body whose optical axis is inclined from the direction perpendicular to the substrate surface. Figure 2 It is a graph showing the inclination angle dependence of the retardation in the optical axis direction of the O-plate. The retardation becomes 0 at the inclination angle θ1, so it can be known that the optical axis is inclined from the direction perpendicular to the substrate surface. However, even if the optical axis is inclined from the direction perpendicular to the substrate surface, when the inclination angle dependence of the retardation in the optical axis direction is different from that of the Figure 2 O-plate shown, it is not an O-plate.

[0063] In the present invention, an "approximate O-plate" refers to having substantially the same inclination angle dependence of the retardation as an O-plate in the inclination angle dependence of the retardation in the direction showing tilt anisotropy (the direction corresponding to the optical axis of the O-plate), but the minimum value of the retardation is not 0. Figure 3 It is a graph showing the inclination angle dependence of the retardation in the direction showing tilt anisotropy of the approximate O-plate.

[0064] In addition, the retardation can be measured using a RETARDATION measuring device RETS-100 manufactured by Otsuka Electronics Co., Ltd.

[0065] The retardation characteristics after combining the first optical anisotropic layer and the second optical anisotropic layer function as an approximate O-plate, so that it is not necessary to tilt the retardation compensation element with respect to the liquid crystal panel, and the residual retardation of the liquid crystal panel can be compensated. Therefore, the layout space can be significantly reduced. Furthermore, the residual retardation of the liquid crystal panel can be appropriately compensated, so the contrast can be improved.

[0066] Each pre-tilted liquid crystal molecule functions as an O-plate. However, when there is a deviation in the pre-tilt angle, the retardation characteristics of the liquid crystal panel become the retardation characteristics after adding these liquid crystal molecules. In this case, the retardation characteristics of the liquid crystal panel become an approximate O-plate. Therefore, a retardation compensation plate having the retardation characteristics of an approximate O-plate can more appropriately compensate for the residual retardation of the liquid crystal panel and improve the contrast ratio.

[0067] The first optically anisotropic layer is made of an inorganic material.

[0068] The second optically anisotropic layer is made of an inorganic material.

[0069] Since this retardation compensation element uses an inorganic material as a constituent material, its durability is excellent.

[0070] Figure 4 It is a cross-sectional view showing a structural example of the retardation compensation element. As Figure 4 shown, the retardation compensation element 10 includes: a transparent substrate 11; a matching layer 12 in which a high refractive index film and a low refractive index film are alternately laminated on the transparent substrate 11 and the thickness of each layer is below the use wavelength; a second optically anisotropic layer 13 formed of an oblique angle evaporation film on the matching layer 12; and a protective layer 14 formed of a dielectric film on the second optically anisotropic layer 13. In addition, a first optically anisotropic layer 15A is provided on the transparent substrate 11 side, and an antireflection layer 15B is provided on the protective layer 14 side.

[0071] <Transparent Substrate>

[0072] The transparent substrate 11 is transparent to light in the use wavelength band. The transparent substrate 11 has a high transmittance for light in the use wavelength band. As the material of the transparent substrate 11, for example, an inorganic material is used. As the inorganic material, glass, quartz, crystal, sapphire, etc. can be cited. The shape of the transparent substrate 11 is generally square, but a shape corresponding to the purpose can be appropriately selected. The thickness of the transparent substrate 11 is preferably, for example, 0.1 mm or more and 3.0 mm or less.

[0073] <First Optically Anisotropic Layer and Antireflection Layer>

[0074] The first optically anisotropic layer 15A is provided, for example, in contact with the surface of the transparent substrate 11 opposite to the second optically anisotropic layer 13 side.

[0075] The first optically anisotropic layer 15A is made of an inorganic material.

[0076] The first optically anisotropic layer 15A functions as a C-plate.

[0077] The antireflection layer 15B can be provided, for example, in contact with the surface of the protective layer 14 opposite to the second optically anisotropic layer 13 as needed.

[0078] The first optically anisotropic layer 15A has an antireflection function, for example, in a desired wavelength band of use.

[0079] The antireflection layer 15B has an antireflection function in a desired wavelength band of use.

[0080] Figure 5 is a schematic cross-sectional view of the first optically anisotropic layer. As Figure 5 shown, the first optically anisotropic layer 15A is an antireflection layer formed by laminating two or more inorganic oxide films having different refractive indexes. For example, it is formed by a multilayer film in which a first oxide film 151 and a second oxide film 152 having different refractive indexes are alternately laminated. The number of layers of the antireflection layer can be appropriately determined as needed, and about 5 to 40 layers are preferably considered from the aspect of productivity. In addition, the antireflection layer 15B is also configured in the same manner as the first optically anisotropic layer 15A.

[0081] As the refractive index difference between the first oxide film 151 and the second oxide film 152, the larger the better. However, considering the ease of obtaining materials, film formability, etc., it is preferably 0.5 or more and 1.0 or less. In addition, the refractive index is, for example, the refractive index at a wavelength of 550 nm.

[0082] The inorganic oxide film of the first optically anisotropic layer 15A and the inorganic oxide film of the antireflection layer 15B are each composed of an oxide film containing at least any one of Ti, Si, Ta, Al, Ce, Zr, Nb, and Hf, for example.

[0083] For example, the first optically anisotropic layer 15A and the antireflection layer 15B can be set as a multilayer film in which a first oxide film 151 composed of niobium oxide (refractive index of 2.3 at a wavelength of 550 nm) having a relatively high refractive index and a second oxide film 152 composed of silicon oxide (refractive index of 1.5 at a wavelength of 550 nm) having a relatively low refractive index are alternately laminated.

[0084] In addition, the oxides constituting the first optically anisotropic layer 15A and the antireflection layer 15B can also be non-stoichiometric substances. That is, the atomic ratio of the constituent elements of the oxide may not be a simple integer ratio. This is because when forming an oxide film by a sputtering method or the like, the oxide often becomes non-stoichiometric. In addition, it is difficult to stably measure the element ratio in the oxide film after film formation, so it is difficult to determine the element ratio in the oxide.

[0085] In view of the case where the oxide is non-stoichiometric, for example, the oxide containing Nb can be represented by the following formula.

[0086]

[0087] For example, the oxide containing Si can be represented by the following formula.

[0088]

[0089] There is no particular limitation on the thicknesses of the first optically anisotropic layer 15A and the antireflection layer 15B, and they can be appropriately selected according to the purpose. For example, 250 nm or more and 2,300 nm or less can be cited. In addition, in this specification, the thickness (film thickness) of a layer means the average film thickness.

[0090] <Match layer>

[0091] The match layer 12 is, for example, a multilayer film in which two or more inorganic oxide films having different refractive indexes are laminated. The match layer 12 is provided between the transparent substrate 11 and the second optically anisotropic layer 13. The match layer 12 is designed to eliminate the interface reflected light by interference and prevent the reflection on the interface between the transparent substrate 11 and the second optically anisotropic layer 13. That is, the match layer 12 is designed to eliminate the interface reflected light between the transparent substrate 11 and the match layer 12 and the interface reflected light between the match layer 12 and the second optically anisotropic layer 13.

[0092] The match layer 12 is composed of, for example, an oxide film containing at least any one of Ti, Si, Ta, Al, Ce, Zr, Nb, and Hf.

[0093] In addition, the oxide constituting the match layer 12 may also be a non-stoichiometric substance. That is, the atomic ratio of the constituent elements of the oxide may not be a simple integer ratio. This is because when forming an oxide film by a sputtering method or the like, the oxide often becomes non-stoichiometric.

[0094] There is no particular limitation on the thickness of the match layer 12, and it can be appropriately selected according to the purpose. For example, 140 nm or more and 240 nm or less can be cited.

[0095] <Second optically anisotropic layer>

[0096] The second optically anisotropic layer 13 is made of an inorganic material.

[0097] The second optically anisotropic layer 13 is an inclined evaporation film.

[0098] The second optically anisotropic layer 13 does not function as an O-plate.

[0099] The second optically anisotropic layer 13 is, for example, a birefringent layer on which an inorganic material is deposited.

[0100] The angle formed by the deposition direction of the inorganic material in the birefringent layer and the surface of the transparent substrate is not 90°.

[0101] The second optical anisotropic layer 13 does not function as a C-plate.

[0102] For example, the optical axis of the second optical anisotropic layer 13 is inclined from the direction perpendicular to the substrate surface, and the inclination angle dependence of the phase difference in the optical axis direction is different from that of an O-plate. For example, the optical axis of the second optical anisotropic layer 13 exists within ±45° from the direction perpendicular to the substrate surface.

[0103] In Figure 4 In the phase difference compensating element 10 shown, the second optical anisotropic layer 13 is disposed between the matching layer 12 and the protective layer 14.

[0104] The birefringent layer includes, for example, a birefringent film made of an inorganic material. As the inorganic material, a dielectric material is preferable, and examples thereof include oxides containing at least any one of Si, Nb, Zr, Ti, La, Ta, Al, Hf, and Ce.

[0105] As the inorganic material, tantalum oxide (for example, Ta2O5) is preferable.

[0106] There is no particular limitation on the phase difference of the birefringent film, and it can be appropriately set according to the liquid crystal panel.

[0107] The thickness of the second optical anisotropic layer can be appropriately selected according to the phase difference to be compensated. For example, values such as 50 nm or more and 500 nm or less can be cited.

[0108] Figure 6 It is a schematic diagram of the oblique incidence of an oblique angle evaporation film. As Figure 6 shown, the oblique angle evaporation film 23 constituting the second optical anisotropic layer 13 is formed by depositing the evaporation material along a direction inclined with respect to the surface of the transparent substrate 11, or by depositing the evaporation material along a direction inclined with respect to the direction orthogonal to the evaporation target surface 21, that is, the normal line S. The inclination angle with respect to the normal line S of the evaporation target surface 21 is preferably 60° or more and 80° or less.

[0109] There is also a case where the second optical anisotropic layer 13 has a structure such as a deposited multi-layer birefringent film.

[0110] Each birefringent film is formed by depositing along a direction inclined with respect to the normal line S, and the angle formed by the film formation direction of the inorganic material constituting the birefringent film and the surface of the transparent substrate is not 90°.

[0111] Regarding each birefringent film, as a method of setting the angle formed by the film formation direction of the inorganic material and the surface of the transparent substrate to a state where the angle is not 90°, for example, it is preferable to arrange the evaporation source at a position inclined with respect to the normal line S, and form an oblique angle evaporation film by oblique angle evaporation from the evaporation source. In the case of forming a birefringent layer by multiple oblique angle evaporations, the evaporation angle is changed and the oblique angle evaporation is repeated to obtain the final birefringent layer.

[0112] Figure 7 It is a schematic diagram for explaining an example of the oblique angle evaporation method for forming an oblique angle evaporation film.

[0113] Figure 8 It is a schematic diagram showing an example of the direction (evaporation direction) in which the flying direction of the evaporation material from the evaporation source is projected onto the evaporation target surface.

[0114] As Figure 7 As shown, when forming an oblique angle evaporation film from the evaporation source R toward the transparent substrate 11 in the evaporation direction D, d represents the direction of the line segment obtained by projecting the film formation direction of the birefringent film onto the surface of the transparent substrate.

[0115] As Figure 8 As shown, in the evaporation process P1, when the xy axes are defined on the evaporation surface and the counterclockwise direction from the center is set as "+", the birefringent film is formed by oblique angle evaporation from the 135° direction. In addition, the reference numeral L represents the direction of the line segment obtained by projecting the liquid crystal molecules onto the surface of the transparent substrate.

[0116] <Protective layer>

[0117] The protective layer 14 is composed of a dielectric film and is disposed in contact with the oblique angle evaporation film of the second optically anisotropic layer 13. Thereby, warping of the retardation compensation element 10 can be prevented, and the moisture resistance of the oblique angle evaporation film can be improved.

[0118] As the dielectric material of the protective layer 14, there is no particular limitation as long as it can adjust the stress applied to the retardation compensation element 10 and is effective in improving the moisture resistance, and it can be appropriately selected according to the purpose. As such a dielectric material, for example, oxides containing at least any one of Si, Ta, Ti, Al, Nb, and La, MgF2, etc. can be cited.

[0119] As the thickness of the protective layer 14, there is no particular limitation, and it can be appropriately selected according to the purpose. For example, 10 nm or more and 100 nm or less can be cited.

[0120] <Manufacturing method of retardation compensation element>

[0121] Next, the manufacturing method of the retardation compensation element according to the present embodiment will be described.

[0122] Hereinafter, as a specific example of a method for manufacturing a phase difference compensation element, the manufacturing method of the phase difference compensation element having the structural example shown in Figure 4 will be described. Figure 9 FIG. is a flowchart showing a method for manufacturing a phase difference compensation element.

[0123] <<S1>>

[0124] First, in step S1, a transparent substrate 11 is prepared.

[0125] <<S2>>

[0126] Next, in step S2, in order to prevent reflection at the interface between the second optically anisotropic layer 13 and the transparent substrate 11, a matching layer 12 formed by laminating an inorganic oxide film is formed on the transparent substrate 11.

[0127] <<S3>>

[0128] Next, in step S3, on the opposite surface of the transparent substrate 11 on which the matching layer 12 is not formed, a first optically anisotropic layer 15A (back surface AR (anti-reflection) layer) is formed.

[0129] <<S4>>

[0130] Next, in step S4, the second optically anisotropic layer 13 is formed on the matching layer 12 by an oblique angle evaporation method. For example, as shown in Figure 7 and Figure 8 , film formation is performed using the evaporation process P1.

[0131] <<S5>>

[0132] Next, in step S5, the second optically anisotropic layer 13 is annealed at a temperature of 200 °C or higher and 600 °C or lower. More preferably, the second optically anisotropic layer 13 is annealed at a temperature of 300 °C or higher and 500 °C or lower, and further preferably at a temperature of 400 °C or higher and 500 °C or lower. Thereby, the characteristics of the second optically anisotropic layer 13 can be stabilized.

[0133] <<S6>>

[0134] Next, in step S6, a protective layer 14 is formed on the second optically anisotropic layer 13. For example, when forming SiO2 as the protective layer 14, it is preferable to use TEOS (tetraethyl orthosilicate) gas and O2 as the material of SiO2, and use a plasma CVD apparatus.

[0135] The SiO2 CVD film formed by a plasma CVD apparatus is characterized by using a vaporized material gas, which is different from physical vapor growth represented by sputtering. Therefore, the TEOS gas can easily penetrate into the voids of the columnar structure, and the adhesion to the second optically anisotropic layer 13 can be further improved.

[0136] <<S7>>

[0137] Next, in step S7, an antireflection layer 15B (surface AR layer) is formed on the protective layer 14.

[0138] <<S8>>

[0139] Finally, in step S8, scribing and cutting are performed in accordance with the specified dimensions.

[0140] Through the above manufacturing method, a retardation compensation element can be obtained.

[0141] (Liquid crystal display device)

[0142] The liquid crystal display device according to the present embodiment includes a liquid crystal panel and the above-described retardation compensation element.

[0143] In the liquid crystal display device, the liquid crystal panel and the retardation compensation element are arranged, for example, such that the main surfaces of the liquid crystal panel and the retardation compensation element are parallel. In this way, compared with the case where the retardation compensation element is arranged obliquely with respect to the liquid crystal panel, the arrangement space can be significantly reduced. Here, parallel does not mean completely parallel, and as long as the arrangement space can be significantly reduced, the main surface of the retardation compensation element may be inclined with respect to the main surface of the liquid crystal panel. For example, the main surface of the retardation compensation element may be inclined with respect to the main surface of the liquid crystal panel within a range of 2°.

[0144] The liquid crystal display device has at least a liquid crystal panel and a retardation compensation element, and may further include other components such as a first polarizing plate and a second polarizing plate as needed.

[0145] <Liquid crystal panel>

[0146] The liquid crystal panel is not particularly limited. For example, it has a substrate and a VA mode liquid crystal layer, and the VA mode liquid crystal layer contains liquid crystal molecules having a pretilt angle in a direction orthogonal to the main surface of the substrate, and modulates the incident light beam. The VA mode (Vertical alignment mode) is a method of using a longitudinal electric field in the vertical direction to move liquid crystal molecules that are vertically (or have a pretilt angle) aligned with respect to the substrate.

[0147] <First polarizing plate and second polarizing plate>

[0148] The first polarizing plate is disposed on the incident side of the liquid crystal panel, and the second polarizing plate is disposed on the exit side of the liquid crystal panel. In consideration of durability, the first polarizing plate and the second polarizing plate are preferably inorganic polarizing plates.

[0149] Use Figure 10 , a typical optical system will be described. In the case of a vertically aligned transmissive liquid crystal panel, in the state where no voltage is applied, the liquid crystal molecules 1 are inclined in a certain direction with respect to the orthogonal direction of the substrate surface by a pretilt angle α and are aligned. At this time, the liquid crystal panel is disposed so as to be sandwiched between a pair of polarizing plates (the transmission axis directions of which are opposed at 90°). In addition, in Figure 10 , reference numeral 2 denotes a glass substrate, reference numeral 3 denotes a glass substrate, reference numeral 4 denotes a retardation compensation element, reference numeral 5 denotes a second polarizing plate, reference numeral 6 denotes a first polarizing plate, reference numeral 7 denotes the exit light, and reference numeral 8 denotes the incident light.

[0150] (Projection type image display device)

[0151] The projection type image display device according to the present embodiment includes: a light source that emits light; a projection optical system that projects the modulated light; and the above-described liquid crystal display device.

[0152] The liquid crystal display device is disposed on the optical path between the light source and the projection optical system.

[0153] The projection type image display device is suitable for use in projectors such as liquid crystal projectors and LCOS (Liquid Crystal On Silicon) projectors.

[0154] <Light source>

[0155] As the light source, as long as it is a member that emits light, there is no particular limitation, and it can be appropriately selected according to the purpose. For example, a laser light source that emits high-brightness and high-output light can be used.

[0156] As the wavelength of the laser light source, for example, 455 nm etc. can be cited.

[0157] <Projection optical system>

[0158] As the projection optical system, as long as it is a member that projects the modulated light, there is no particular limitation, and it can be appropriately selected according to the purpose. For example, a projection lens that projects the modulated light onto a screen etc. can be cited.

[0159] According to the projection type image display device configured in this way, the arrangement space of the retardation compensation element can be significantly reduced, and thus a small-sized projection type image display device can be configured.

[0160] Figure 11This is a schematic diagram showing an example of the structure of the projection-type image display device according to the present embodiment. The projection-type image display device 115A is a so-called three-panel liquid crystal projector device that uses three liquid crystal panels for red, green, and blue color image display. As Figure 11 shown, the projection-type image display device 115A includes: liquid crystal display devices 101R, 101G, 101B, a light source 102, dichroic mirrors 103, 104, a total reflection mirror 105, polarization beam splitters 106R, 106G, 106B, a synthesis prism 108, and a projection lens 109.

[0161] The light source 102 emits source light (white light) L including blue light LB, green light LG, and red light LR required for color image display, and includes, for example, a halogen lamp, a metal halide lamp, or a xenon lamp.

[0162] The dichroic mirror 103 has a function of separating the source light L into blue light LB and other color light LRG. The dichroic mirror 104 has a function of separating the light LRG that has passed through the dichroic mirror 103 into red light LR and green light LG. The total reflection mirror 105 reflects the blue light LB separated by the dichroic mirror 103 toward the polarization beam splitter 106B.

[0163] The polarization beam splitters 106R, 106G, 106B are prism-type polarization separation elements provided along the optical paths of the red light LR, the green light LG, and the blue light LB, respectively. These polarization beam splitters 106R, 106G, 106B each have a polarization separation surface 107R, 107G, 107B, and have a function of separating the incident color light into two orthogonal polarization components on the polarization separation surfaces 107R, 107G, 107B. The polarization separation surfaces 107R, 107G, 107B reflect one polarization component (for example, the S polarization component) and transmit the other polarization component (for example, the P polarization component).

[0164] The color light of a predetermined polarization component (for example, the S polarization component) separated by the polarization separation surfaces 107R, 107G, 107B of the polarization beam splitters 106R, 106G, 106B is incident on the liquid crystal display devices 101R, 101G, 101B. The liquid crystal display devices 101R, 101G, 101B are driven in response to a driving voltage provided based on an image signal, and have a function of modulating the incident light and reflecting the modulated light toward the polarization beam splitters 106R, 106G, 106B.

[0165] Between the polarization beam splitters 106R, 106G, 106B and the liquid crystal panels 111 of the liquid crystal display devices 101R, 101G, 101B, quarter-wave plates 113R, 113G, 113B and a retardation compensation element 10 are respectively arranged. Regarding the quarter-wave plates 113R, 113G, 113B, they are transmitted twice, when incident on the liquid crystal panel and when exiting from the liquid crystal panel, so as to function as half-wave plates. (For example, converting the S polarization component into the P polarization component.) In addition, the quarter-wave plates 113R, 113G, 113B have the function of improving the contrast reduction due to the angular dependence of the incident light of the polarization beam splitters 106R, 106G, 106B. The retardation compensation element 10 has the function of compensating for the residual retardation of the liquid crystal panels constituting the liquid crystal display devices 101R, 101G, 101B. In one embodiment, the retardation compensation element 10 is the retardation compensation element according to this embodiment.

[0166] The synthesis prism 108 has the function of synthesizing the color lights of a predetermined polarization component (for example, the P polarization component) that exit from the liquid crystal display devices 101R, 101G, 101B and pass through the polarization beam splitters 106R, 106G, 106B. The projection lens 109 has the function of projecting the synthesized light that exits from the synthesis prism 108 onto the screen 110.

[0167] Next, the operation of the projection type image display device 115A configured as above will be described.

[0168] First, the white light L emitted from the light source 102 is separated into blue light LB and other color lights (red light and green light) LRG due to the function of the dichroic mirror 103. Among them, the blue light LB is reflected toward the polarization beam splitter 106B due to the function of the total reflection mirror 105.

[0169] On the other hand, the other color lights (red light and green light) LRG are further separated into red light LR and green light LG due to the function of the dichroic mirror 104. The separated red light LR and green light LG are respectively incident on the polarization beam splitters 106R, 106G.

[0170] The polarization beam splitters 106R, 106G, 106B separate the incident color lights into two mutually orthogonal polarization components on the polarization separation surfaces 107R, 107G, 107B. At this time, one polarization component (for example, the S polarization component) on the polarization separation surfaces 107R, 107G, 107B is reflected toward the liquid crystal display devices 101R, 101G, 101B. The liquid crystal display devices 101R, 101G, 101B are driven in response to the driving voltage provided based on the image signal, and modulate the color lights of the predetermined polarization component incident thereon in pixel units.

[0171] The liquid crystal display devices 101R, 101G, and 101B reflect the modulated light of each color toward the polarization beam splitters 106R, 106G, and 106B. The polarization beam splitters 106R, 106G, and 106B transmit only a predetermined polarization component (e.g., P polarization component) among the reflected light (modulated light) from the liquid crystal display devices 101R, 101G, and 101B, and emit it toward the combining prism 108.

[0172] The combining prism 108 combines the color light of the predetermined polarization component that has passed through the polarization beam splitters 106R, 106G, and 106B, and emits it toward the projection lens 109. The projection lens 109 projects the combined light emitted from the combining prism 108 onto the screen 110. Thus, an image corresponding to the light modulated by the liquid crystal display devices 101R, 101G, and 101B is projected onto the screen 110, and a desired image display is performed.

[0173] [Embodiment]

[0174] Hereinafter, specific embodiments of the present invention will be described. In addition, the present invention is not limited to these embodiments. For convenience, it is described as an SiO2 film and a Nb2O5 film, but these films are likely to be non-stoichiometric.

[0175] (Embodiment 1)

[0176] <Fabrication of the retardation compensation element>

[0177] Using Nb2O5 and SiO2, a matching layer is formed by alternately laminating 5 layers on one surface of a glass substrate (average thickness 0.7 mm) by sputtering.

[0178] Next, using Nb2O5 and SiO2, a first optically anisotropic layer is formed by alternately laminating 40 layers on the other surface of the glass substrate by sputtering. At this time, a layer structure is set such that the retardation given to obliquely incident light inclined 15° from the normal direction of the glass substrate surface becomes 9 nm. As shown in Reference Example 1, the optical axis of the obtained first optically anisotropic layer is in the direction perpendicular to the substrate surface (tilt angle 0°). That is, the first optically anisotropic layer functions as a C-plate.

[0179] Next, using an evaporation material obtained by adding TiO2 to Ta2O5, an evaporation source is arranged at a position inclined 70° from the substrate normal direction and oblique angle evaporation is performed. As Figure 8As shown, evaporation was performed at an evaporation angle of 135° to form a second optically anisotropic layer with a film thickness of 80 nm. As shown in Reference Example 2, although the optical axis of the obtained second optically anisotropic layer was inclined from the direction perpendicular to the substrate surface, the sign of the phase difference changed at an inclination angle of 35°, which was significantly different from the inclination angle dependence of the phase difference of the O-plate. That is, the second optically anisotropic layer did not function as an O-plate. In addition, it did not function as a C-plate either.

[0180] After evaporation, in order to stabilize the characteristics, annealing treatment was performed at 400 °C. After annealing, SiO2 film was formed by plasma CVD method using TEOS (tetraethyl orthosilicate) gas and O2.

[0181] Next, an antireflection layer was formed by alternately laminating 7 layers of Nb2O5 and SiO2 by sputtering method.

[0182] In the above manner, the phase difference compensation element was completed.

[0183] (Reference Example 1)

[0184] The first optically anisotropic layer shown in Example 1 was fabricated.

[0185] That is, on one surface of a glass substrate (average thickness 0.7 mm), a first optically anisotropic layer was formed by alternately laminating 40 layers of Nb2O5 and SiO2 by sputtering method. At this time, the layer structure was set such that the phase difference given to obliquely incident light inclined 15° from the direction orthogonal to the surface of the glass substrate was 9 nm.

[0186] For the obtained first optically anisotropic layer, the relationship between the inclination angle and the phase difference (Retardation) at a wavelength of 550 nm was obtained using a RETARDATION measuring device RETS-100 manufactured by Otsuka Electronics Co., Ltd. The results are shown in Figure 12 .

[0187] As Figure 12 shown, the optical axis in the first optically anisotropic layer of Example 1 was in the direction perpendicular to the substrate surface (inclination angle 0°). That is, the first optically anisotropic layer of Example 1 functioned as a C-plate.

[0188] (Reference Example 2)

[0189] The second optically anisotropic layer shown in Example 1 was fabricated.

[0190] That is, on one surface of a glass substrate (average thickness 0.7 mm), an evaporation material obtained by adding TiO2 to Ta2O5 was used, and the evaporation source was arranged at a position inclined 70° from the substrate normal direction and oblique angle evaporation was performed. AsFigure 8 As shown, vapor deposition was performed at a vapor deposition angle of 135° to form a second optically anisotropic layer with a film thickness of 80 nm.

[0191] For the obtained second optically anisotropic layer, the relationship between the tilt angle and the retardation at a wavelength of 550 nm was determined using a RETARDATION measuring device RETS-100 manufactured by Otsuka Electronics Co., Ltd. The results are shown in Figure 13 .

[0192] As Figure 13 shown, although the optical axis of the second optically anisotropic layer of Example 1 was tilted from the direction perpendicular to the substrate surface, the sign of the retardation changed at a tilt angle of 35°, which was significantly different from the tilt angle dependence of the retardation of the O-plate. That is, the second optically anisotropic layer of Example 1 did not function as an O-plate. In addition, it did not function as a C-plate either.

[0193] The change in the sign of the retardation according to the tilt angle means that the direction of the slow axis rotates by 90° due to the tilt angle and switches with the fast axis.

[0194] Next, for the retardation compensation element obtained by combining the first optically anisotropic layer and the second optically anisotropic layer in Example 1, the relationship between the tilt angle and the retardation at a wavelength of 550 nm in the direction showing tilt anisotropy ( Figure 8 the direction of the label L) was determined using a RETARDATION measuring device RETS-100 manufactured by Otsuka Electronics Co., Ltd. The results are shown in Figure 14 .

[0195] As Figure 14 shown, the tilt angle dependence of the retardation in the direction showing tilt anisotropy of the retardation compensation element obtained by combining the first optically anisotropic layer and the second optically anisotropic layer in Example 1 had a tilt angle dependence of the retardation substantially the same as that of the O-plate, but the minimum value of the retardation was not 0. That is, the retardation characteristics of the retardation compensation element obtained by combining the first optically anisotropic layer and the second optically anisotropic layer in Example 1 were approximately those of an O-plate.

[0196] <Contrast Evaluation>

[0197] The retardation compensation element of Example 1 was incorporated into a liquid crystal projector, and the contrast was measured. As a result, the average contrast improved to 625.7 compared to 398.8 when there was no retardation compensation element.

[0198] The average contrast is the average value of the contrast measured at nine arbitrary positions.

[0199] The contrast ratio was measured using an illuminometer T-10 manufactured by Konica Minolta Japan, Inc.

[0200]

Industrial Applicability

[0201] The retardation compensation element of the present invention can significantly reduce the mounting space, and further has excellent durability. Therefore, it can be suitably used for a small projection type image display device. In addition, a retardation compensation element corresponding to the deviation of the pretilt angle of the liquid crystal can be provided.

[0202]

Explanation of Reference Numerals

[0203] 1 liquid crystal molecule; 2 glass substrate; 3 glass substrate; 4 retardation compensation element; 5 second polarizing plate; 6 first polarizing plate; 7 outgoing light; 8 incident light; 10 retardation compensation element; 11 transparent substrate; 12 matching layer; 13 second optically anisotropic layer; 14 protective layer; 15A first optically anisotropic layer; 15B antireflection layer; 21 evaporation target surface; 23 oblique angle evaporation film; 31 first evaporation direction; 32 second evaporation direction; 102 light source; 101R, 101G, 101B liquid crystal display device; 109 projection lens; 111 liquid crystal panel; 115A projection type image display device; 151 first oxide film; 152 second oxide film.

Claims

1. A phase difference compensation element, characterized in that, Comprising: A transparent substrate; A first optically anisotropic layer, which is composed of an inorganic material and functions as a C-plate; And A second optically anisotropic layer, which is composed of an inorganic material and is an oblique evaporation film that does not function as an O-plate, The retardation characteristics after combining the first optically anisotropic layer and the second optically anisotropic layer function as an approximate O-plate, The second optically anisotropic layer that does not have the retardation characteristics of an O-plate is the following optically anisotropic layer: the optical axis is inclined from the direction perpendicular to the substrate surface, and the sign of the retardation is changed according to the inclination angle in the inclination angle dependence of the retardation in the optical axis direction, The retardation characteristics of the approximate O-plate are the following retardation characteristics: the minimum value of the retardation is not 0 in the inclination angle dependence of the retardation in the direction showing tilt anisotropy, and the retardation increases as the inclination angle moves away from the inclination angle φ where the retardation becomes minimum in the range from the inclination angle φ to the inclination angles of ±45°.

2. The phase difference compensation element according to claim 1, wherein, The inorganic material in the second optically anisotropic layer is an oxide containing at least any one of Si, Nb, Zr, Ti, La, Ta, Al, Hf, and Ce.

3. The phase difference compensation element according to any one of claims 1 to 2, wherein, The first optically anisotropic layer is an antireflection layer formed by laminating two or more inorganic oxide films having different refractive indices.

4. The phase difference compensation element according to any one of claims 1 to 3, wherein, Between the transparent substrate and the second optically anisotropic layer, there is a matching layer formed by laminating two or more inorganic oxide films having different refractive indices.

5. The retardation compensation element according to claim 4, wherein At least one of the inorganic oxide films in the antireflection layer is an oxide film containing at least any one of Ti, Si, Ta, Al, Ce, Zr, Nb, and Hf, At least one of the inorganic oxide films in the matching layer is an oxide film containing at least any one of Ti, Si, Ta, Al, Ce, Zr, Nb, and Hf.

6. The phase difference compensation element according to any one of claims 1 to 5, wherein, On the second optically anisotropic layer, there is a protective layer composed of a dielectric film.

7. The phase difference compensation element according to any one of claims 1 to 6, wherein, The transparent substrate is any one of glass, quartz, crystal, and sapphire.

8. A liquid crystal display device, characterized in that, Comprising a liquid crystal panel and the retardation compensation element according to any one of claims 1 to 7.

9. A projection type image display device, characterized in that, Comprising: A light source for emitting light; A projection optical system for projecting the modulated light; and The liquid crystal display device according to claim 8 disposed on the optical path between the light source and the projection optical system.

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