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

Abstract

To provide a phase difference compensation element and the like that can substantially reduce an arrangement space, have excellent durability, and respond to variations in a pretilt angle of liquid crystal.SOLUTION: A phase difference compensation element includes: a transparent substrate; a first optically anisotropic layer that is composed of an inorganic material and has a C-plate phase difference characteristic; and a second optically anisotropic layer that is composed of an inorganic material and is an orthorhombic vapor deposition film not having an O-plate phase difference characteristic. The phase difference compensation element, in which the first optically anisotropic layer and the second optically anisotropic layer are combined, has a phase difference characteristic like an O plate.SELECTED DRAWING: Figure 4

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 technology]

[0002] In recent years, optical compensation techniques using retardation compensation elements have been used in liquid crystal display devices to improve contrast and viewing angle characteristics. For example, compensation for black luminance floating in vertically aligned liquid crystals can be mentioned. In addition, in order to compensate for the phase difference due to the pretilt angle of the liquid crystal and the phase difference due to birefringence caused by obliquely incident light, a method of optical compensation in which a retardation compensation element such as quartz is arranged parallel to the main surface of the liquid crystal panel, and a method of optical compensation in which an organic material having birefringence such as a polymer film is arranged parallel to the main surface of the liquid crystal panel have been proposed (for example, see Patent Documents 1 to 3).

[0003] However, when a method of processing a single crystal is used as a retardation compensation element, especially when compensation is to be made while taking into consideration the pretilt angle of the liquid crystal, it is necessary to cut out the crystal at a specified angle to the crystal axis, and extremely high precision is required for cutting and polishing the material, resulting in high costs. Moreover, it is not easy to control the crystal axis in a stretched film, etc. For this reason, a method has been proposed in which the phase difference compensation element itself is arranged at an angle with respect to the main surface of the liquid crystal panel (see, for example, Patent Documents 4 and 5).

[0004] However, as projectors become smaller, there is a concern that there will not be enough space inside to place the retardation compensation element at an angle with respect to the main surface of the liquid crystal panel.Furthermore, the retardation compensation element is susceptible to deterioration due to heat and high-brightness, high-output light, and there is an issue with durability. Furthermore, there is variation in the pretilt angle of liquid crystal, and a retardation compensation element that can deal with this variation has been desired.

[0005] Therefore, there is a demand for a retardation compensation element that can reduce the space required for installation significantly, has excellent durability, and can deal with variations in the pretilt angle of the liquid crystal. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2005-172984 A [Patent Document 2] Patent No. 4661510 [Patent Document 3] Patent No. 4566275 [Patent Document 4] JP 2006-11298 A [Patent Document 5] JP 2009-229804 A Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention aims to solve the above-mentioned problems in the prior art and to achieve the following objects: That is, the present invention aims to provide a retardation compensation element that can significantly reduce the arrangement space and has excellent durability and can accommodate variations in the pretilt angle of liquid crystal, a liquid crystal display device using the retardation compensation element, and a projection type image display device using the liquid crystal display device. [Means for solving the problem]

[0008] The means for solving the above problems are as follows. <1> A transparent substrate; a first optically anisotropic layer made of an inorganic material and having a retardation characteristic of a C plate; a second optically anisotropic layer which is an obliquely evaporated film made of an inorganic material and does not have the phase difference characteristic of an O-plate; Equipped with The retardation compensation element, which is a combination of the first optically anisotropic layer and the second optically anisotropic layer, is characterized in that it has retardation characteristics similar to those of an O-plate. <2> a first optically anisotropic layer having a retardation characteristic of a C plate is a birefringent body having an optical axis perpendicular to a substrate surface; the phase difference characteristic of the O plate is such that, in the inclination angle dependence of the phase difference in the optical axis direction of a uniaxial or biaxial birefringent body whose optical axis is inclined from the direction perpendicular to the substrate surface, the phase difference is 0 at an inclination angle θ that is the optical axis, and the phase difference increases as the inclination angle deviates from the inclination angle θ within a range of inclination angles of ±45° from the inclination angle θ, The O-plate-like phase difference characteristic is a phase difference characteristic in which, in the tilt angle dependence of the phase difference in the direction showing the oblique anisotropy, the minimum value of the phase difference is not 0, and the phase difference increases as the tilt angle deviates from the tilt angle φ in the range of tilt angles ±45° from the tilt angle φ at which the phase difference is minimum. The above <1> 2. The phase difference compensation element according to claim 1, <3> The second optically anisotropic layer, which does not have the retardation characteristic of an O-plate, is an optically anisotropic layer in which the optical axis is inclined from a direction perpendicular to the substrate surface, and the sign of the retardation changes depending on the inclination angle in the inclination angle dependency of the retardation in the optical axis direction. <1> and <2> 10. The phase difference compensation element according to claim 9, <4> The inorganic material in the second optically anisotropic layer is an oxide containing at least one of Si, Nb, Zr, Ti, La, Ta, Al, Hf, and Ce. <1> from <3> 10. The phase difference compensation element according to claim 9, <5> The first optically anisotropic layer is an antireflection layer formed by laminating two or more types of inorganic oxide films having different refractive indices. <1> from <4> 13. The phase difference compensation element according to claim 12, wherein <6> The present invention relates to a matching layer having two or more inorganic oxide films having different refractive indices laminated between the transparent substrate and the second optically anisotropic layer. <1> from <5> 13. The phase difference compensation element according to claim 12, wherein <7> At least one of the inorganic oxide films in the antireflection layer is an oxide film containing at least one of Ti, Si, Ta, Al, Ce, Zr, Nb, and Hf. <5> 2. The phase difference compensation element according to claim 1, <8> At least one of the inorganic oxide films in the matching layer is an oxide film containing at least one of Ti, Si, Ta, Al, Ce, Zr, Nb, and Hf. <6> 2. The phase difference compensation element according to claim 1, <9> The optically anisotropic film according to claim 1, further comprising a protective layer made of a dielectric film on the second optically anisotropic layer. <1> from <8> 13. The phase difference compensation element according to claim 12, wherein <10> The transparent substrate is any one of glass, quartz, crystal, and sapphire. <1> from <9> 13. The phase difference compensation element according to claim 12, wherein <11> Liquid crystal panel and <1> from <10> and a phase difference compensation element according to any one of claims 1 to 5. <12> The liquid crystal panel and the phase difference compensation element are arranged such that a main surface of the liquid crystal panel and a main surface of the phase difference compensation element are parallel to each other, and an inclination between the main surface of the liquid crystal panel and the main surface of the phase difference compensation element is within 2°. <10> 2. The liquid crystal display device according to claim 1 . <13> A light source that emits light; a projection optical system that projects the modulated light; The projection optical system is disposed on the optical path between the light source and the projection optical system. <12> and the liquid crystal display device according to claim 1. Effect of the Invention

[0009] According to the present invention, it is possible to provide a retardation compensation element which can solve the above-mentioned conventional problems, can greatly reduce the arrangement space, and has excellent durability and can accommodate variations in the pretilt angle of liquid crystal, a liquid crystal display device using the retardation compensation element, and a projection type image display device using the liquid crystal display device. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a graph showing the tilt angle dependence of the phase difference of a C-plate. [Diagram 2] FIG. 2 is a graph showing the tilt angle dependence of the phase difference of an O-plate. [Diagram 3] FIG. 3 is a graph showing the tilt angle dependence of the O-plate-like phase difference. [Figure 4] FIG. 4 is a cross-sectional view showing an example of the configuration of a phase difference compensation element. [Diagram 5] FIG. 5 is a schematic cross-sectional view of the antireflection layer. [Figure 6] FIG. 6 is a schematic perspective view of an obliquely evaporated film. [Figure 7] FIG. 7 is a schematic diagram for explaining an example of an oblique deposition method for forming an obliquely deposited film. [Figure 8] FIG. 8 is a schematic diagram showing an example of the direction of deposition from a deposition source projected onto a deposition target surface. [Figure 9] FIG. 9 is a flowchart showing a method for manufacturing a phase difference compensation element. [Figure 10] FIG. 10 is a schematic diagram showing an example of the configuration of a liquid crystal display device. [Figure 11] FIG. 11 is a schematic diagram showing an example of the configuration of a projection type image display device. [Figure 12] FIG. 12 is a graph showing the tilt angle dependence of the retardation of the first optically anisotropic layer in Example 1. [Figure 13] FIG. 13 is a graph showing the tilt angle dependence of the retardation of the second optically anisotropic layer in Example 1. [Figure 14] FIG. 14 is a graph showing the tilt angle dependence of the combined retardation of the first optically anisotropic layer and the second optically anisotropic layer in Example 1. In FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, embodiments of the present technology will be described in detail with reference to the drawings in the following order. 1. Phase difference compensation element 2.Liquid crystal display device 3.Projection type image display device 4. Working Example

[0012] (Retardation compensation element) The phase difference compensation element according to the present embodiment has a transparent substrate, a first optically anisotropic layer, and a second optically anisotropic layer. The first optically anisotropic layer acts as a C plate, i.e., has the phase difference characteristics of a C plate. The second optically anisotropic layer does not act as an O-plate, i.e., it does not have the phase difference property of an O-plate. The second optically anisotropic layer is an obliquely evaporated film. The combined retardation properties of the first and second optically anisotropic layers act as an O-plate, that is, have an O-plate-like retardation property.

[0013] Here, a C-plate refers to a birefringent body whose optical axis is perpendicular to the substrate surface. The optical axis is the direction in which no birefringence occurs, and refers to the direction in which the phase difference (retardation) is zero. Figure 1 is a graph showing the tilt angle dependency of the phase difference of a C-plate, and shows the phase difference characteristics of a C-plate. The tilt angle of 0° is the direction perpendicular to the substrate surface, and since the phase difference here is zero, it can be seen that the optical axis is perpendicular to the substrate surface. An O-plate is a uniaxial or biaxial birefringent body whose optical axis is inclined from the direction perpendicular to the substrate surface. FIG. 2 is a graph showing the inclination angle dependency of the phase difference in the optical axis direction of an O-plate, showing the phase difference characteristics of the O-plate. Since the phase difference is 0 at the inclination angle θ1, it can be seen that the optical axis is inclined from the direction perpendicular to the substrate surface. That is, in the graph showing the inclination angle dependency of the phase difference in the optical axis direction of an O-plate, the phase difference is a minimum value and is 0 at the inclination angle θ1 which is the optical axis, and in the range of inclination angles of ±45° from the inclination angle θ1 at which the phase difference is minimum, the phase difference increases as the inclination angle moves away from θ1 (the sign of the phase difference does not invert). Even if the optical axis is inclined from the direction perpendicular to the substrate surface, if the inclination angle dependency of the phase difference in the optical axis direction is different from that of the O-plate shown in FIG. 2, that is, if the phase difference does not take the minimum value as shown in FIG. 2 at the inclination angle θ1 which is the optical axis direction, and the sign of the phase difference is inverted, the plate is not an O-plate. In the present invention, "O-plate-like" refers to a material that has almost the same tilt angle dependence of phase difference as an O-plate in the tilt angle dependence of phase difference in a direction exhibiting oblique anisotropy (a direction corresponding to the optical axis of the O-plate), but the minimum value of phase difference does not become 0. FIG. 3 is a graph showing the tilt angle dependence of phase difference in a direction exhibiting O-plate-like oblique anisotropy, and shows the phase difference characteristics of "O-plate-like". That is, in the graph showing the tilt angle dependence of phase difference in a direction exhibiting "O-plate-like" oblique anisotropy, the minimum value of phase difference does not become 0, and in the range of tilt angles ±45° from the tilt angle θ at which this phase difference becomes minimum, the phase difference increases as the tilt angle becomes farther from θ. The phase difference (retardation) can be measured by a retardation measuring device RETS-100 manufactured by Otsuka Electronics Co., Ltd.

[0014] The combined retardation characteristics of the first optically anisotropic layer and the second optically anisotropic layer act as an O-plate, so that the residual retardation of the liquid crystal panel can be compensated for without tilting the retardation compensation element relative to the liquid crystal panel. This allows for a significant reduction in the space required for placement. Furthermore, the residual retardation of the liquid crystal panel can be appropriately compensated for, improving the contrast. Each pretilted liquid crystal molecule acts as an O-plate, but if there is variation in the pretilt angle, the retardation characteristics of the liquid crystal panel will be the sum of the retardation characteristics of these liquid crystal molecules. In this case, the retardation characteristics of the liquid crystal panel will be like that of an O-plate, so a retardation compensator with O-plate-like retardation characteristics can more appropriately compensate for the residual retardation of the liquid crystal panel, improving contrast.

[0015] The first optically anisotropic layer is made of an inorganic material. The second optically anisotropic layer is made of an inorganic material. Such a phase difference compensation element is excellent in durability since it is made of inorganic materials.

[0016] Fig. 4 is a cross-sectional view showing a configuration example of a phase difference compensation element. As shown in Fig. 4, the phase difference compensation element 10 includes a transparent substrate 11, a matching layer 12 in which high-refractive index films and low-refractive index films are alternately laminated on the transparent substrate 11, and the thickness of each layer is equal to or less than the wavelength used, a second optically anisotropic layer 13 made of an obliquely evaporated film formed on the matching layer 12, and a protective layer 14 made of a dielectric film formed 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.

[0017] <Transparent substrate> The transparent substrate 11 is transparent to light in the wavelength band used. The transparent substrate 11 has high transmittance to light in the wavelength band used. The material of the transparent substrate 11 is, for example, an inorganic material. Examples of inorganic materials include glass, quartz, crystal, and sapphire. The shape of the transparent substrate 11 is generally rectangular, but a shape may be appropriately selected depending on the purpose. The thickness of the transparent substrate 11 is preferably, for example, 0.1 mm or more and 3.0 mm or less.

[0018] <First Optically Anisotropic Layer and Antireflection Layer> The first optically anisotropic layer 15A is provided, for example, in contact with the surface of the transparent substrate 11 facing the second optically anisotropic layer 13 side. The first optically anisotropic layer 15A is made of an inorganic material. The first optically anisotropic layer 15A acts as a C-plate.

[0019] The antireflection layer 15B is provided, for example, in contact with the surface of the protective layer 14 facing the second optically anisotropic layer 13, if necessary.

[0020] The first optically anisotropic layer 15A has, for example, an anti-reflection function in a desired wavelength band to be used. The antireflection layer 15B has an antireflection function in a desired wavelength band to be used.

[0021] Fig. 5 is a cross-sectional schematic diagram of the first optically anisotropic layer. As shown in Fig. 5, the first optically anisotropic layer 15A is an antireflection layer formed by laminating two or more types of inorganic oxide films having different refractive indices, and is formed, for example, of a multilayer film in which a first oxide film 151 and a second oxide film 152 having different refractive indices are alternately laminated. The number of layers in the antireflection layer is appropriately determined as necessary, and is preferably about 5 to 40 layers from the viewpoint of productivity. The antireflection layer 15B is also configured in the same manner as the first optically anisotropic layer 15A.

[0022] The larger the difference in refractive index between the first oxide film 151 and the second oxide film 152, the more preferable, but considering the ease of obtaining materials, film formation, etc., the difference is preferably 0.5 or more and 1.0 or less. The refractive index is, for example, the refractive index at a wavelength of 550 nm.

[0023] Each of the inorganic oxide film of the first optically anisotropic layer 15A and the inorganic oxide film of the antireflection layer 15B is made of an oxide film containing at least one of Ti, Si, Ta, Al, Ce, Zr, Nb, and Hf, for example.

[0024] For example, the first optically anisotropic layer 15A and the antireflection layer 15B can be a multilayer film in which a first oxide film 151 made of niobium oxide, which has a relatively high refractive index (refractive index 2.3 at a wavelength of 550 nm), and a second oxide film 152 made of silicon oxide, which has a relatively low refractive index (refractive index 1.5 at a wavelength of 550 nm), are alternately laminated.

[0025] The oxides constituting the first optically anisotropic layer 15A and the anti-reflection layer 15B may be non-stoichiometric. That is, the atomic ratio of the constituent elements of the oxides does not have to be a simple integer ratio. This is because when an oxide film is formed by a sputtering method or the like, the oxide often becomes non-stoichiometric. In addition, the element ratio in the formed oxide is difficult to measure stably, so it is difficult to specify the element ratio in the oxide.

[0026] Considering that the oxide is non-stoichiometric, for example, an oxide containing Nb is represented by the following formula: NbO X (0 <X≦2.5) For example, an oxide containing Si is represented by the following formula: SiO Y (0 <Y≦2)

[0027] The thickness of the first optically anisotropic layer 15A and the antireflection layer 15B is not particularly limited and can be appropriately selected depending on the purpose, and may be, for example, 250 nm or more and 2,300 nm or less. In this specification, the thickness (film thickness) of a layer means the average film thickness.

[0028] <Matching layer> The matching layer 12 is, for example, a multilayer film in which two or more types of inorganic oxide films having different refractive indices are laminated. The matching layer 12 is provided between the transparent substrate 11 and the second optically anisotropic layer 13. The matching layer 12 is designed to cancel out the interfacial reflected light by interference, and prevents reflection at the interface between the transparent substrate 11 and the second optically anisotropic layer 13. That is, the matching layer 12 is designed to cancel out the interfacial reflected light between the transparent substrate 11 and the matching layer 12 and the interfacial reflected light between the matching layer 12 and the second optically anisotropic layer 13.

[0029] The matching layer 12 is made of, for example, an oxide film containing at least one of Ti, Si, Ta, Al, Ce, Zr, Nb, and Hf.

[0030] The oxide constituting the matching layer 12 may be non-stoichiometric. That is, the atomic ratio of the constituent elements of the oxide does not have to be a simple integer ratio. This is because when an oxide film is formed by a sputtering method or the like, the oxide often becomes non-stoichiometric.

[0031] The thickness of the matching layer 12 is not particularly limited and can be appropriately selected depending on the purpose, and may be, for example, 140 nm or more and 240 nm or less.

[0032] <Second Optically Anisotropic Layer> The second optically anisotropic layer 13 is made of an inorganic material. The second optically anisotropic layer 13 is an obliquely evaporated film. The second optically anisotropic layer 13 does not act as an O-plate. The second optically anisotropic layer 13 is made of, for example, a birefringent layer on which an inorganic material is deposited. The angle between the deposition direction of the inorganic material in the birefringent layer and the surface of the transparent substrate is not 90°.

[0033] The second optically anisotropic layer 13 does not act as a C-plate. The second optically anisotropic layer 13 has, for example, an optical axis that is tilted from a direction perpendicular to the substrate surface, and the tilt angle dependency of the phase difference in the optical axis direction differs from that of an O-plate. The second optically anisotropic layer 13 has an optical axis that is, for example, within ±45° from the direction perpendicular to the substrate surface.

[0034] In the retardation compensation element 10 shown in FIG. 4, the second optically anisotropic layer 13 is disposed between the matching layer 12 and the protective layer 14 .

[0035] The birefringent layer includes, for example, a birefringent film made of an inorganic material. The inorganic material is preferably a dielectric material, such as an oxide containing at least one of Si, Nb, Zr, Ti, La, Ta, Al, Hf, and Ce. The inorganic material is preferably tantalum oxide (eg, Ta2O5).

[0036] The phase difference of the birefringent film is not particularly limited, and is set appropriately depending on the liquid crystal panel.

[0037] The thickness of the second optically anisotropic layer can be appropriately selected depending on the retardation to be compensated, and may be, for example, from 50 nm to 500 nm.

[0038] Fig. 6 is a perspective schematic diagram of an obliquely evaporated film. As shown in Fig. 6, the obliquely evaporated film 23 constituting the second optically anisotropic layer 13 is formed by depositing an evaporation material in a direction inclined with respect to a normal line S, which is a direction perpendicular to the surface of the transparent substrate 11 or the evaporation target surface 21. The inclination angle of the evaporation target surface 21 with respect to the normal line S is preferably 60° or more and 80° or less. The second optically anisotropic layer 13 may have a structure in which a plurality of such birefringent films are stacked, for example.

[0039] Each of the birefringent films is deposited in a direction inclined with respect to the normal line S, and the angle between the deposition direction of the inorganic material constituting the birefringent film and the surface of the transparent substrate is not 90°.

[0040] A preferred method for making the angle between the deposition direction of the inorganic material and the surface of the transparent substrate not 90° for each birefringent film is, for example, to arrange a deposition source at an angle with respect to the normal line S and deposit an obliquely deposited film by oblique deposition from the deposition source. When forming a birefringent layer by multiple oblique depositions, the deposition angle is changed and the oblique deposition is repeated to obtain the final birefringent layer.

[0041] FIG. 7 is a schematic diagram for explaining an example of an oblique deposition method for forming an obliquely deposited film. FIG. 8 is a schematic diagram showing an example of the direction (deposition direction) of the deposition material coming from the deposition source projected onto the deposition target surface. As shown in FIG. 7, when an obliquely evaporated film is formed from an evaporation source R toward a transparent substrate 11 in an evaporation direction D, the direction of the line segment projected along the deposition direction of the birefringent film onto the surface of the transparent substrate is indicated by d. 8, in deposition process P1, when the xy axes are defined on the deposition surface and the counterclockwise direction from the center is defined as +, oblique deposition is performed from a direction of 135° to form a birefringent film. Note that the symbol L indicates the direction of the line segment formed by projecting the liquid crystal molecules onto the surface of the transparent substrate.

[0042] <Protective layer> The protective layer 14 is made of a dielectric film and is disposed in contact with the obliquely evaporated film of the second optically anisotropic layer 13. This can prevent warping of the retardation compensation element 10 and improve the moisture resistance of the obliquely evaporated film.

[0043] The dielectric material of the protective layer 14 is not particularly limited as long as it can adjust the stress applied to the phase difference compensation element 10 and is effective in improving moisture resistance, and can be appropriately selected according to the purpose. Examples of such dielectric materials include oxides containing at least one of Si, Ta, Ti, Al, Nb, and La, and MgF2.

[0044] The thickness of the protective layer 14 is not particularly limited and can be appropriately selected depending on the purpose, and may be, for example, from 10 nm to 100 nm.

[0045] <Method of manufacturing phase difference compensation element> Next, a method for manufacturing the phase difference compensation element according to this embodiment will be described. As a specific example of a method for manufacturing a phase difference compensation element, a method for manufacturing a phase difference compensation element having the configuration example shown in Fig. 4 will be described below. Fig. 9 is a flowchart showing a method for manufacturing a phase difference compensation element.

[0046] < <s1>> First, in step S1, the transparent substrate 11 is prepared.

[0047] < <s2>> 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 made of an inorganic oxide film is formed on the transparent substrate 11.

[0048] < <s3>> Next, in step S3, a first optically anisotropic layer 15A (rear surface AR (Anti-reflection) layer) is formed on the opposite surface of the transparent substrate 11 on which the matching layer 12 is not formed.

[0049] < <s4>> Next, in step S4, the second optically anisotropic layer 13 is formed by oblique deposition on the matching layer 12. For example, as shown in Figs. 7 and 8, deposition is performed by a deposition process P1.

[0050] < <s5>> Next, in step S5, the second optically anisotropic layer 13 is annealed at a temperature of 200° C. to 600° C., more preferably at a temperature of 300° C. to 500° C., and further preferably at a temperature of 400° C. to 500° C. This makes it possible to stabilize the characteristics of the second optically anisotropic layer 13.

[0051] < <s6>> Next, in step S6, the protective layer 14 is formed on the second optically anisotropic layer 13. For example, when forming a SiO2 film as the protective layer 14, it is preferable to use TEOS (tetraethoxysilane) gas and O2 as SiO2 materials and to use a plasma CVD apparatus. The SiO2 CVD film formed by a plasma CVD apparatus is characterized by using vaporized material gas, unlike physical vapor phase growth methods such as sputtering, and therefore allows TEOS gas to penetrate relatively easily into the voids in the columnar structure, further improving adhesion to the second optically anisotropic layer 13.

[0052] < <s7>> Next, in step S7, an antireflection layer 15B (front AR layer) is formed on the protective layer 14.

[0053] < <s8>> Finally, in step S8, scribe cutting is performed to a size that meets the specifications.

[0054] By the above manufacturing method, a phase difference compensation element can be obtained.

[0055] (Liquid crystal display device) The liquid crystal display device according to this embodiment includes a liquid crystal panel and the above-mentioned phase difference compensation element.

[0056] In a liquid crystal display device, the liquid crystal panel and the retardation compensation element are arranged so that, for example, the main surface of the liquid crystal panel and the main surface of the retardation compensation element are parallel to each other. This allows the arrangement space to be significantly reduced compared to the case where the retardation compensation element is arranged at an angle to the liquid crystal panel. Here, "parallel" does not mean completely parallel, and the main surface of the retardation compensation element may be inclined to the main surface of the liquid crystal panel as long as the arrangement space can be significantly reduced. For example, the main surface of the retardation compensation element may be inclined to the main surface of the liquid crystal panel within a range of 2°.

[0057] A liquid crystal display device includes at least a liquid crystal panel and a retardation compensation element, and may further include other members such as a first polarizing plate and a second polarizing plate, as necessary.

[0058] <Liquid crystal panel> The liquid crystal panel is not particularly limited, and may, for example, have a substrate and a VA mode liquid crystal layer containing liquid crystal molecules with a pretilt in a direction perpendicular to the main surface of the substrate, and modulate the incident light beam. VA mode (Vertical alignment mode) refers to a method in which liquid crystal molecules aligned perpendicular to the substrate (or with a pretilt) are moved by a vertical electric field in the vertical direction.

[0059] <First Polarizing Plate and Second Polarizing Plate> 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. From the viewpoint of durability, the first polarizing plate and the second polarizing plate are preferably inorganic polarizing plates.

[0060] A typical optical system will be described with reference to Fig. 10. In the case of a vertically aligned transmissive liquid crystal panel, when no voltage is applied, liquid crystal molecules 1 are aligned at a pretilt angle α in a certain direction relative to the direction perpendicular to the substrate surface. In this case, the liquid crystal panel is disposed so as to be sandwiched between a pair of polarizing plates whose transmission axes face each other at 90°. In Fig. 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 outgoing light, and reference numeral 8 denotes incoming light.

[0061] (Projection type image display device) The projection type image display device according to this embodiment includes a light source that emits light, a projection optical system that projects the modulated light, and the above-mentioned liquid crystal display device. The liquid crystal display device is disposed on the optical path between the light source and the projection optical system.

[0062] The projection type image display device is suitably used for projectors such as liquid crystal projectors and LCOS (Liquid Crystal On Silicon) projectors.

[0063] <Light source> There are no particular limitations on the light source as long as it is a member that emits light, and it can be appropriately selected depending on the purpose. For example, a laser light source that emits high-brightness, high-output light can be used. The wavelength of the laser light source is, for example, 455 nm.

[0064] <Projection optical system> The projection optical system is not particularly limited as long as it is a component that projects modulated light, and can be appropriately selected depending on the purpose. For example, it may be a projection lens that projects the modulated light onto a screen.

[0065] According to a projection type image display device having such a configuration, the space required for arranging the phase difference compensation element can be significantly reduced, so that a small projection type image display device can be constructed.

[0066] Fig. 11 is a schematic diagram showing an example of the configuration of a projection type image display device according to this embodiment. The projection type image display device 115A is a so-called three-panel type liquid crystal projector device that displays color images using three liquid crystal panels for each color of red, green, and blue. As shown in Fig. 11, this projection type image display device 115A includes liquid crystal display devices 101R, 101G, and 101B, a light source 102, dichroic mirrors 103 and 104, a total reflection mirror 105, polarizing beam splitters 106R, 106G, and 106B, a composite prism 108, and a projection lens 109.

[0067] The light source 102 emits source light (white light) L that contains 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.

[0068] The dichroic mirror 103 has a function of separating the light source light L into blue light LB and light of other colors 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 polarizing beam splitter 106B.

[0069] The polarizing beam splitters 106R, 106G, and 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 polarizing beam splitters 106R, 106G, and 106B have polarizing separation surfaces 107R, 107G, and 107B, respectively, and have the function of separating the incident color light into two polarized components that are orthogonal to each other at the polarizing separation surfaces 107R, 107G, and 107B. The polarizing separation surfaces 107R, 107G, and 107B reflect one polarized component (e.g., S polarized component) and transmit the other polarized component (e.g., P polarized component).

[0070] Colored light of a predetermined polarization component (e.g., S-polarized component) separated by polarization separation surfaces 107R, 107G, 107B of polarization beam splitters 106R, 106G, 106B is incident on liquid crystal display devices 101R, 101G, 101B. Liquid crystal display devices 101R, 101G, 101B are driven according to a driving voltage applied based on an image signal, and have the function of modulating the incident light and reflecting the modulated light toward polarization beam splitters 106R, 106G, 106B.

[0071] Between the polarizing beam splitters 106R, 106G, 106B and the liquid crystal panels 111 of the liquid crystal display devices 101R, 101G, 101B, the quarter-wave plates 113R, 113G, 113B and the phase difference compensation element 10 are disposed. The quarter-wave plates 113R, 113G, 113B function as half-wave plates by passing light twice, when it enters the liquid crystal panel and when it leaves the liquid crystal panel. (For example, they convert S-polarized light components into P-polarized light components.) The quarter-wave plates 113R, 113G, 113B have a function of improving the decrease in contrast caused by the angle dependency of the incident light of the polarizing beam splitters 106R, 106G, 106B. The phase difference compensation element 10 has a function of compensating for the residual phase difference of the liquid crystal panels constituting the liquid crystal display devices 101R, 101G, 101B. In one embodiment, the phase difference compensation element 10 is the phase difference compensation element according to the present embodiment.

[0072] The combining prism 108 has a function of combining color lights of predetermined polarization components (e.g., P polarization components) that are emitted from the liquid crystal display devices 101R, 101G, and 101B and pass through the polarizing beam splitters 106R, 106G, and 106B. The projection lens 109 has a function of projecting the combined light emitted from the combining prism 108 onto the screen 110.

[0073] Next, the operation of the projection type image display device 115A configured as above will be described. First, white light L emitted from the light source 102 is separated into blue light LB and other colored light (red light and green light) LRG by the function of the dichroic mirror 103. Of these, the blue light LB is reflected by the function of the total reflection mirror 105 toward the polarizing beam splitter 106B.

[0074] 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 by the function of the dichroic mirror 104. The separated red light LR and green light LG are incident on polarizing beam splitters 106R and 106G, respectively.

[0075] The polarizing beam splitters 106R, 106G, and 106B split the incident color light into two polarized components that are orthogonal to each other on the polarizing separation surfaces 107R, 107G, and 107B. At this time, the polarizing separation surfaces 107R, 107G, and 107B reflect one polarized component (for example, the S polarized component) toward the liquid crystal display devices 101R, 101G, and 101B. The liquid crystal display devices 101R, 101G, and 101B are driven according to a drive voltage applied based on an image signal, and modulate the incident color light of a predetermined polarized component on a pixel-by-pixel basis.

[0076] The liquid crystal display devices 101R, 101G, and 101B reflect the modulated color light toward the polarizing beam splitters 106R, 106G, and 106B. The polarizing beam splitters 106R, 106G, and 106B transmit only a predetermined polarization component (for example, a P polarization component) of the reflected light (modulated light) from the liquid crystal display devices 101R, 101G, and 101B, and emit the light toward the composite prism 108.

[0077] The combining prism 108 combines the color lights of the predetermined polarized components that have passed through the polarizing beam splitters 106R, 106G, and 106B, and emits the combined light toward the projection lens 109. The projection lens 109 projects the combined light emitted from the combining prism 108 toward the screen 110. As a result, 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 is displayed. EXAMPLES

[0078] Specific examples of the present invention will be described below. Note that the present invention is not limited to these examples. Note that for convenience, the SiO2 film and Nb2O5 film are described, but these films are highly likely to be non-stoichiometric.

[0079] Example 1 <Fabrication of phase difference compensation element> A matching layer was formed on one surface of a glass substrate (average thickness 0.7 mm) by alternately laminating five layers of Nb2O5 and SiO2 by sputtering. Next, a first optically anisotropic layer was formed on the other surface of the glass substrate by alternately laminating 40 layers of Nb2O5 and SiO2 by a sputtering method. At this time, the layer structure was such that the phase difference given to the obliquely incident light tilted 15° from the perpendicular direction to the surface of the glass substrate was 9 nm. As shown in Reference Example 1, the optical axis of the obtained first optically anisotropic layer was perpendicular to the substrate surface (tilt angle 0°). That is, the first optically anisotropic layer acts as a C plate.

[0080] Next, an oblique deposition was performed by placing a deposition source at a position inclined by 70° with respect to the normal direction of the substrate using a deposition material of Ta2O5 with TiO2 added. As shown in FIG. 8, deposition was performed so that the deposition direction was 135° and the film thickness was 80 nm, forming a second optically anisotropic layer. As shown in Reference Example 2, the optical axis of the obtained second optically anisotropic layer is inclined from the direction perpendicular to the substrate surface, but the sign of the phase difference changes at the inclination angle of 35°, which is clearly different from the inclination angle dependency of the phase difference of the O-plate. That is, the second optically anisotropic layer does not act as an O-plate. It also does not act as a C-plate.

[0081] After deposition, in order to stabilize the characteristics, annealing was performed at 400°C. After annealing, a SiO2 film was formed by plasma CVD using TEOS (tetraethoxysilane) gas and O2.

[0082] Next, an anti-reflection layer was formed by alternately laminating seven layers of Nb2O5 and SiO2 by a sputtering method.

[0083] In this way, a phase difference compensation element was completed.

[0084] (Reference example 1) The first optically anisotropic layer shown in Example 1 was prepared. That is, a first optically anisotropic layer was formed on one surface of a glass substrate (average thickness 0.7 mm) by alternately laminating 40 layers of Nb2O5 and SiO2 by a sputtering method. At this time, the layer structure was such that the phase difference given to obliquely incident light tilted 15° from the perpendicular direction to the surface of the glass substrate was 9 nm.

[0085] For the obtained first optically anisotropic layer, the relationship between the tilt angle and the phase difference (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 FIG. 12, the first optically anisotropic layer of Example 1 has an optical axis perpendicular to the substrate surface (tilt angle 0°), that is, the first optically anisotropic layer of Example 1 acts as a C plate.

[0086] (Reference example 2) The second optically anisotropic layer shown in Example 1 was prepared. That is, on one surface of a glass substrate (average thickness 0.7 mm), an evaporation source was placed at a position inclined at 70° to the normal direction of the substrate and an oblique evaporation was performed using an evaporation material of Ta2O5 with TiO2 added thereto. As shown in Figure 8, evaporation was performed with the evaporation direction at 135° to a film thickness of 80 nm, forming a second optically anisotropic layer.

[0087] For the obtained second optically anisotropic layer, the relationship between the tilt angle and the phase difference (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 FIG. As shown in Fig. 13, the second optically anisotropic layer of Example 1 has an optical axis tilted from the direction perpendicular to the substrate surface, but the sign of the retardation changes at an inclination angle of 35°, which is clearly different from the inclination angle dependency of the retardation of an O-plate. That is, the second optically anisotropic layer of Example 1 does not function as an O-plate, nor does it function as a C-plate. The sign of the phase difference changes depending on the tilt angle, which means that the direction of the slow axis rotates by 90° depending on the tilt angle and switches places with the fast axis.

[0088] Next, for the retardation compensation element in which the first optically anisotropic layer and the second optically anisotropic layer in Example 1 were combined, the relationship between the tilt angle in the direction showing the oblique anisotropy at a wavelength of 550 nm (the direction of the symbol L in FIG. 8) and the retardation (retardation) was obtained using a retardation measuring device RETS-100 manufactured by Otsuka Electronics Co., Ltd. The results are shown in FIG. 14, the retardation compensation element in Example 1, which is a combination of the first and second optically anisotropic layers, has a tilt angle dependency of retardation in a direction exhibiting oblique anisotropy, which is almost the same as that of an O-plate, but the minimum value of retardation does not become 0. That is, the retardation characteristic of the retardation compensation element in Example 1, which is a combination of the first and second optically anisotropic layers, is similar to that of an O-plate.

[0089] <Contrast evaluation> The retardation compensation element of Example 1 was incorporated into a liquid crystal projector, and the contrast was measured. The retardation compensation element was placed parallel to the main surface of the liquid crystal panel. As a result, the average contrast was improved to 625.7, compared with 398.8 when there was no retardation compensation element. The average contrast is the average value of contrast measured at nine random points. The contrast was measured using a Konica Minolta Japan Inc. illuminance meter T-10. [Industrial Applicability]

[0090] The retardation compensation element of the present invention can be suitably used in a small projection type image display device because it can drastically reduce the installation space and has excellent durability. In addition, a retardation compensation element that can deal with the variation in the pretilt angle of the liquid crystal can be provided. [Explanation of symbols]

[0091] 1 Liquid crystal molecules 2. Glass substrate 3. Glass substrate 4 Phase difference compensation element 5 Second polarizing plate 6 First polarizing plate 7. Emitted light 8 Incident light 10 Phase difference compensation element 11 Transparent substrate 12 Matching Layer 13 Second optically anisotropic layer 14 Protective layer 15A First Optically Anisotropic Layer 15B Anti-reflection layer 21 Vacuum deposition target surface 23 Obliquely evaporated film 102 Light source 101R, 101G, 101B LCD 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 transparent substrate; a first optically anisotropic layer made of an inorganic material and having a retardation characteristic of a C plate; a second optically anisotropic layer which is an obliquely evaporated film made of an inorganic material and does not have the phase difference characteristic of an O-plate; Equipped with A phase difference compensation element comprising said first optically anisotropic layer and said second optically anisotropic layer in combination, said phase difference compensation element having phase difference characteristics similar to those of an O-plate.

2. a first optically anisotropic layer having a retardation characteristic of a C plate is a birefringent body having an optical axis perpendicular to a substrate surface; the phase difference characteristic of the O-plate is such that, in the tilt angle dependence of the phase difference in the optical axis direction of a uniaxial or biaxial birefringent body whose optical axis is tilted from a direction perpendicular to the substrate surface, the phase difference is 0 at a tilt angle θ that is the optical axis, and the phase difference increases as the tilt angle deviates from the tilt angle θ within a range of tilt angles of ±45° from the tilt angle θ, The O-plate-like phase difference characteristic is a phase difference characteristic in which, in the tilt angle dependence of the phase difference in the direction exhibiting oblique anisotropy, the minimum value of the phase difference is not 0, and the phase difference increases as the tilt angle deviates from the tilt angle φ in the range of tilt angles ±45° from the tilt angle φ at which the phase difference is minimal.

2. The phase difference compensation element according to claim 1.

3. 3. The phase difference compensation element according to claim 1, wherein the second optically anisotropic layer not having the phase difference characteristic of an O-plate is an optically anisotropic layer whose optical axis is inclined from a direction perpendicular to the substrate surface and whose phase difference in the optical axis direction depends on the inclination angle, and whose sign of the phase difference changes depending on the inclination angle.

4. 4. 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 one of Si, Nb, Zr, Ti, La, Ta, Al, Hf, and Ce.

5. 5. The phase difference compensation element according to claim 1, wherein the first optically anisotropic layer is an antireflection layer formed by laminating two or more types of inorganic oxide films having different refractive indices.

6. 6. The phase difference compensation element according to claim 1, further comprising a matching layer between said transparent substrate and said second optically anisotropic layer, said matching layer being made of two or more inorganic oxide films having different refractive indices laminated thereon.

7. 6. The phase difference compensation element according to claim 5, wherein at least one of the inorganic oxide films in the antireflection layer is an oxide film containing at least one of Ti, Si, Ta, Al, Ce, Zr, Nb, and Hf.

8. 7. The phase difference compensation element according to claim 6, wherein at least one of the inorganic oxide films in the matching layer is an oxide film containing at least one of Ti, Si, Ta, Al, Ce, Zr, Nb, and Hf.

9. 9. The phase difference compensation element according to claim 1, further comprising a protective layer made of a dielectric film on the second optically anisotropic layer.

10. 10. The phase difference compensation element according to claim 1, wherein the transparent substrate is made of any one of glass, quartz, crystal, and sapphire.

11. 11. A liquid crystal display device comprising a liquid crystal panel and the phase difference compensation element according to claim 1.

12. 12. The liquid crystal display device according to claim 11, wherein the liquid crystal panel and the phase difference compensation element are arranged such that a principal surface of the liquid crystal panel and a principal surface of the phase difference compensation element are parallel to each other, and / or an inclination between the principal surface of the liquid crystal panel and the principal surface of the phase difference compensation element is within 2°.

13. A light source that emits light; a projection optical system that projects the modulated light; 13. A projection type image display device comprising: the liquid crystal display device according to claim 12, which is disposed on an optical path between the light source and the projection optical system.

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