Patent Publication Number: US-2021165262-A1

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

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to Japanese application No. 2019-215093, filed on Nov. 28, 2019 and incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a phase difference compensation element, liquid crystal display device, and a projection image display device. 
     Description of the Related Art 
     Recently, optical compensation techniques using phase difference compensation elements have been used for improving contrast and view angles of liquid crystal display devices. Example of such techniques include compensation of black level reduction in vertically aligned liquid crystal molecules. Moreover, proposed are an optical compensation method where a phase difference compensation element, such as crystal, is disposed to be parallel to a main plane of a liquid crystal panel to compensate a retardance due to pretilt angles of liquid crystal molecules, or retardance due to birefringence caused by oblique angle incident light, and a method where an organic material having birefringence, such as a polymer film, is disposed to be parallel to a main plane of a liquid crystal panel to perform optical compensation (see, for example, Japanese Patent Application Laid-Open (JP-A) No. 2005-172984, and Japanese Patent (JP-B) Nos. 4661510 and 4566275). 
     In a case where a method for processing monocrystal as a phase difference compensation element, in order to perform optical compensation considering particularly pretilt angles of liquid crystal molecules, it is necessary to cut the monocrystal out with a predetermined angle relative to a crystal axis thereof, and extremely high accuracy in cut-out of the material or polishing is important. 
     Therefore, a cost of such a phase difference compensation element is high. Moreover, it is not easy to control a crystal axis in a stretched film. 
     Therefore, proposed is a method where a phase difference compensation element itself is arranged to be tilted with respect to a main plane of a liquid crystal panel (see, for example, JP-A Nos. 2006-11298 and 2009-229804). 
     SUMMARY OF THE INVENTION 
     
         
         &lt;1&gt; A phase difference compensation element, including: a transparent substrate; 
         a first optical anisotropic layer that is a birefringent body including an inorganic material, where an optic axis of the birefringent body is orthogonal to the transparent substrate; and 
         a second optical anisotropic layer that is a birefringent layer obtained by depositing an inorganic material, where an angle formed between a direction along which the inorganic material is deposited in the birefringent layer and a surface of the transparent substrate is other than 90°, 
         wherein the phase difference compensation element is disposed to face a liquid crystal panel, and is configured to compensate a residual retardance of the liquid crystal panel, and 
         wherein the phase difference compensation element satisfies the following formula (1): 
       
    
       0.5 &lt;A/B&lt; 1.5   Formula (1)
     where A is an average retardance of the phase difference compensation element with incident light tilted by ±5° towards a pretilt direction of liquid crystal molecules of the liquid crystal panel disposed to face the phase difference compensation element, when a direction orthogonal to a main plane of the phase difference compensation element is determined as 0°, and B is an average retardance of the liquid crystal panel with incident light tilted by ±5° towards the pretilt direction of the liquid crystal molecules of the liquid crystal panel, when a direction orthogonal to a main plane of the liquid crystal panel is determined as 0°.   &lt;2&gt; The phase difference compensation element according to &lt;1&gt;, wherein the birefringent layer includes an oblique angle vapor deposition film of the inorganic material.   &lt;3&gt; The phase difference compensation element according to any one of &lt;1&gt; to &lt;2&gt;,   wherein the inorganic material included in the second optical anisotropic layer is an oxide including at least one selected from the group consisting of Si, Nb, Zr, Ti, La, Ta, Al, Hf, and Ce.   &lt;4&gt; The phase difference compensation element according to any one of &lt;1&gt; to &lt;3&gt;,   wherein the first optical anisotropic layer is an antireflection layer, in which two or more inorganic oxide films having mutually different refractive indexes are laminated.   &lt;5&gt; The phase difference compensation element according to any one of &lt;1&gt; to &lt;4&gt;, further including:   a matching layer in which two or more inorganic oxide films having mutually different refractive indexes are laminated, where the matching layer is disposed between the transparent substrate and the second optical anisotropic layer.   &lt;6&gt; The phase difference compensation element according to &lt;4&gt;,   wherein at least one of the inorganic oxide films in the antireflection layer is an oxide film including at least one selected from the group consisting of Ti, Si, Ta, Al, Ce, Zr, Nb, and Hf.   &lt;6&gt; The phase difference compensation element according to &lt;5&gt;,   wherein at least one of the inorganic oxide films in the matching layer is an oxide film including at least one selected from the group consisting of Ti, Si, Ta, Al, Ce, Zr, Nb, and Hf.   &lt;8&gt; The phase difference compensation element according to any one of &lt;1&gt; &lt;7&gt;, further including:   a protective layer that is a dielectric film, and is disposed on or above the second optical anisotropic layer.   &lt;9&gt; The phase difference compensation element according to any one of &lt;1&gt; to &lt;8&gt;,   wherein the transparent substrate is glass, quartz, crystal, or sapphire.   &lt;10&gt; A liquid crystal display device, including:   a liquid crystal panel; and   a phase difference compensation element that is disposed to face the liquid crystal panel and is configured to compensate a residual retardance of the liquid crystal panel,   wherein the phase difference compensation element includes:   a transparent substrate;   a first optical anisotropic layer that is a birefringent body including an inorganic material, where an optic axis of the birefringent body is orthogonal to the transparent substrate; and   a second optical anisotropic layer that is a birefringent layer obtained by depositing an inorganic material, where an angle formed between a direction along which the inorganic material is deposited in the birefringent layer and a surface of the transparent substrate is other than 90°,   wherein the phase difference compensation element satisfies the following formula (1):   

       0.5 &lt;A/B&lt; 1.5   Formula (1)
     where A is an average retardance of the phase difference compensation element with incident light tilted by ±5° towards a pretilt direction of liquid crystal molecules of the liquid crystal panel disposed to face the phase difference compensation element, when a direction orthogonal to a main plane of the phase difference compensation element is determined as 0°, and B is an average retardance of the liquid crystal panel with incident light tilted by ±5° towards the pretilt direction of the liquid crystal molecules of the liquid crystal panel, when a direction orthogonal to a main plane of the liquid crystal panel is determined as 0°.   &lt;11&gt; The liquid crystal display device according to &lt;10&gt;,   wherein the liquid crystal panel and the phase difference compensation element are disposed in a manner that a main plane of the liquid crystal panel is parallel to a main plane of the phase difference compensation element, or the main plane of the liquid crystal panel is tilted by 2° or less with respect to the main plane of the phase difference compensation element.   &lt;12&gt; A projection image display device, including:   a light source configured to emit light;   a projection optical system configured to project modulated light; and   a liquid crystal display device disposed on an optical path between the light source and the projection optical system,   wherein the liquid crystal display device includes:   a liquid crystal panel; and   a phase difference compensation element that is disposed to face the liquid crystal panel and is configured to compensate a residual retardance of the liquid crystal panel,   wherein the phase difference compensation element includes:   a transparent substrate;   

     a first optical anisotropic layer that is a birefringent body including an inorganic material, where an optic axis of the birefringent body is orthogonal to the transparent substrate; and
     a second optical anisotropic layer that is a birefringent layer obtained by depositing an inorganic material, where an angle formed between a direction along which the inorganic material is deposited in the birefringent layer and a surface of the transparent substrate is other than 90°,   wherein the phase difference compensation element satisfies the following formula (1):   

       0.5 &lt;A/B&lt; 1.5   Formula (1)
     where A is an average retardance of the phase difference compensation element with incident light tilted by ±5° towards a pretilt direction of liquid crystal molecules of the liquid crystal panel disposed to face the phase difference compensation element, when a direction orthogonal to a main plane of the phase difference compensation element is determined as 0°, and B is an average retardance of the liquid crystal panel with incident light tilted by ±5° towards the pretilt direction of the liquid crystal molecules of the liquid crystal panel, when a direction orthogonal to a main plane of the liquid crystal panel is determined as 0°.   

    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view illustrating a structural example of a phase difference compensation element; 
         FIG. 2  is a cross-sectional view illustrating an antireflection layer; 
         FIG. 3  is a perspective schematic view of an oblique angle vapor deposition film; 
         FIG. 4  is a schematic view illustrating one example of an oblique angle vapor deposition for forming an oblique angle vapor deposition film; 
         FIG. 5  is a schematic view illustrating one example of a direction in which a deposition direction from a deposition source is projected towards a deposition target surface; 
         FIG. 6  is a flowchart illustrating a production method of a phase difference compensation element; 
         FIG. 7  is a schematic view illustrating one example of a structure of a liquid crystal display device; 
         FIG. 8  is a schematic view illustrating one example of a structure of a projection image display device; and 
         FIG. 9  is a graph depicting results of Examples 1 and 2. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Embodiments of the present technology will be described in details according to the following order with reference to drawings.
     1. Phase difference compensation element   2. Liquid crystal display device   3. Projection image display device   4. Examples   

     The prior art of phase difference compensation elements is as described earlier. However, there is a concern that an internal space of a projector, which has been downsizing, may not be sufficient to arrange a phase difference compensation element to be tilted with respect to a main plane of a liquid crystal panel. Moreover, the phase difference compensation element tends to be deteriorated by heat or light of high brightness and high output, and therefore there is a problem in durability of the phase difference compensation element. 
     Accordingly, there is currently a need for a phase difference compensation element that can significantly reduce a space to be disposed, and has excellent durability. 
     The present invention aims to solve the above-described various problems existing in the art, and to achieve the following object. Specifically, the present invention has an object to provide a phase difference compensation element, which can significantly reduce a space to be disposed, and has excellent durability, a liquid crystal display device using the phase difference compensation element, and a projection image display device using the liquid crystal display device. 
     The present invention can solve the above-described various problems existing in the art, and can provide a phase difference compensation element, which can significantly reduce a space to be disposed, and has excellent durability, a liquid crystal display device using the phase difference compensation element, and a projection image display device using the liquid crystal display device. 
     (Phase Difference Compensation Element) 
     The phase difference compensation element according to the present embodiment is a phase difference compensation element configured to compensate a residual retardance of a liquid crystal panel. 
     The phase difference compensation element includes a transparent substrate, a first optical anisotropic layer, and a second optical anisotropic layer. 
     In the present invention, the following formula (1) is satisfied: 
       0.5 &lt;A/B&lt; 1.5   Formula (1)
 
     In the formula above, A is an average retardance of the phase difference compensation element with incident light tilted within the range of 5° towards a pretilt direction of liquid crystal molecules, i.e., an average retardance of the phase difference compensation element of incident light tilted by ±5° towards a pretilt direction of liquid crystal molecules of the liquid crystal panel disposed to face the phase difference compensation element, when a direction orthogonal to a main plane of the phase difference compensation element is determined as 0°; and B is an average retardance of the liquid crystal panel with incident light tilted within the range of 5° towards the pretilt direction of the liquid crystal molecules of the liquid crystal panel, i.e., an average retardance of the liquid crystal panel with incident light tilted by ±5° towards the pretilt direction of liquid crystal molecules of the liquid crystal panel, when a direction orthogonal to a main plane of the liquid crystal panel is determined as 0°. 
     Since the formula (1) is satisfied, a residual retardance of the liquid crystal panel can be compensated without tilting the phase difference compensation element with respect to the liquid crystal panel. Therefore, a space in which the phase difference compensation element is disposed can be significantly reduced. 
     In the present specification, the phrase “pretilt direction of liquid crystal molecules” means a direction along which liquid crystal molecules are pretilted in the liquid crystal panel disposed to face the phase difference compensation element (i.e. the direction for aligning the liquid crystal molecules). Moreover, the phrase “pretilt direction of liquid crystal molecules” with respect to the phase difference compensation element means the pretilt direction of the liquid crystal molecules in the liquid crystal panel to which the phase difference compensation element is disposed to face. For example, the pretilt direction of the liquid crystal molecules can be represented as the direction indicated with the symbol L in  FIG. 5 , as a direction projected onto the main plane of the phase difference compensation element. 
     Note that, the average retardance is an average value of retardance values obtained by measuring with incident light tilted within the range of 5° towards the pretilt direction of the liquid crystal molecules per 1° (i.e., tilted by −5°, −4°, −3°, −2°, −1°, 0°, 1°, 2°, 3°, 4°, and 5°. 
     Moreover, the retardance can be measured by a retardation measuring device RETS-100, available from Otsuka Electronic Co., Ltd. 
     The average retardance of the phase difference compensation element with incident light tilted within the range of 5  20   towards the pretilt direction of the liquid crystal molecules of the liquid crystal panel may be appropriately selected depending on the average retardance of the liquid crystal panel. For example, the average retardance of the phase difference compensation element is 1 nm or greater but 10 nm or less. 
     The average retardance of the liquid crystal panel with incident light tilted in the range of 5° towards the pretilt direction of the liquid crystal molecules therein is not particularly limited and may be appropriately selected depending on the intended purpose. For example, the average retardance of the liquid crystal panel is 1 nm or greater but 10 nm or less. 
     The first optical anisotropic layer includes an inorganic material. 
     The second optical anisotropic layer is a birefringent layer obtained by depositing an inorganic material. 
     Since the phase difference compensation element includes inorganic materials as constitutional materials, the phase difference compensation element has excellent durability. 
       FIG. 1  is a cross-sectional view illustrating a structural example of the phase difference compensation element. As illustrated in  FIG. 1 , the phase difference compensation element  10  includes a transparent substrate  11 , a matching layer  12  disposed on the transparent substrate  11 , a second optical anisotropic layer  13  formed of an oblique angle vapor deposition film disposed on the matching layer  12 , and a protective layer  14  formed of a dielectric film disposed on the second optical anisotropic layer  13 . In the matching layer  12 , high refractive index films and low refractive index films are alternately disposed, and a thickness of each film is equal to or less than a wavelength for use. Moreover, a first optical anisotropic layer  15  A is disposed at the side of the transparent substrate  11 , and the antireflection layer  15 B is disposed at the side of the protective layer  14 . 
     &lt;Transparent Substrate&gt; 
     The transparent substrate  11  is transparent to light of a wavelength range for use. The transparent substrate  11  has a high transmittance to light of a wavelength range for use. For example, a material of the transparent substrate  11  is an inorganic material. Examples of the inorganic material include glass, quartz, crystal, and sapphire. A shape of the transparent substrate  11  is typically a square, but the shape thereof is appropriately selected depending on the intended purpose. For example, a thickness of the transparent substrate  11  is preferably 0.1 mm or greater but 3.0 mm or less. 
     &lt;First Optical Anisotropic Layer and Antireflection Layer&gt; 
     For example, the first optical anisotropic layer  15 A is disposed to be in contact with a plane of the transparent substrate  11  opposite to the side of the second optical anisotropic layer  13 . 
     The first optical anisotropic layer  15 A includes an inorganic material. 
     The first optical anisotropic layer  15 A functions as a C plate. 
     In the present specification, the C-plate is a birefringent body an optic axis of which is orthogonal to a plane of the transparent substrate. The optic axis is a direction along which birefringence does not occur, and a direction with which a phase difference (retardance) is 0. 
     For example, the antireflection layer  15 B is optionally disposed to be in contact with a plane of the protective layer  14  opposite to the side of the second optical anisotropic layer  13 . 
     For example, the first optical anisotropic layer  15 A has an antireflection function in a desired wavelength range for use. 
     For example, the antireflection layer  15 B has an antireflection function in a desired wavelength range for use. 
       FIG. 2  is a schematic cross-sectional view of the first optical anisotropic layer. As illustrated in  FIG. 2 , the first optical anisotropic layer  15 A is an antireflection layer in which two or more inorganic oxide films having mutually different refractive indexes are laminated. For example, the first optical anisotropic layer  15 A is a multiple layer, in which first oxide films  151  and second oxide films  152  are alternately laminated, where the first oxide film  151  and the second oxide film  152  have mutually different refractive indexes. The number of layers in the antireflection layer is appropriately determined, and is preferably from about 5 layers to about 40 layers in view of the productivity. Note that, the antireflection layer  15 B also has the same structure as the first optical anisotropic layer  15 A. 
     The larger difference between the refractive index of the first oxide film  151  and the refractive index of the second oxide film  152  is more preferable. In view of availability of materials and film formability, the difference is preferably 0.5 or greater but 1.0 or less. The refractive index is, for example, a refractive index at a wavelength of 550 nm. 
     For example, the inorganic oxide films of the first antireflection layer  15 A and the inorganic oxide films of the second antireflection layer  15 B are each an oxide film including at least one selected from the group consisting of Ti, Si, Ta, Al, Ce, Zr, Nb, and Hf. 
     For example, the first optical anisotropic layer  15 A and the antireflection layer  15 B are each a multiple film where first oxide films  151  formed of niobium oxide (refractive index at wavelength of 550 nm: 2.3) having a relatively high refractive index, and second oxide films  152  formed of silicon oxide (refractive index at wavelength of 550 nm: 1.5) having a relatively low refractive index are alternately laminated. 
     Note that, the oxides constituting the first optical anisotropic layer  15 A or the antireflection layer  15 B may be nonstoichiometric. Specifically, an atomic ratio of constitutional elements of the oxide is not necessarily a simple whole number ratio. When an oxide film is formed by sputtering etc., the formed oxide is often nonstoichiometric. Moreover, an elemental ratio of the oxide of the formed film cannot be easily measured stably, thus it is difficult to determine an elemental ratio of the oxide. 
     Considering the oxide being nonstoichiometric, for example, the oxide including Nb is represented by the following formula. 
       NbO X  (0&lt;X≤2.5)
 
     For example, the oxide including Si is represented by the following formula. 
       SiO Y  (0&lt;Y&lt;2) 
     A thickness of the first optical anisotropic layer  15 A and a thickness of the antireflection layer  15 B are not particularly limited and may be appropriately selected depending on the intended purpose. For example, the thickness thereof is 250 nm or greater but 2,300 nm or less. In the present specification, a thickness of a layer (film thickness) means an average film thickness. 
     &lt;Matching Layer&gt; 
     The matching layer  12  is, for example, a multiple layer film where two or more inorganic oxide films having mutually different refractive indexes are laminated. The matching layer  12  is disposed between the transparent substrate  11  and the second optical anisotropic layer  13 . The matching layer  12  is designed to cancel interface reflection light by interference, to thereby prevent reflection at an interface between the transparent substrate  11  and the second optical anisotropic layer  13 . Specifically, the matching layer  12  is designed to cancel out reflected light at an interface between the transparent substrate  11  and the matching layer  12  and reflected light at an interference between the matching layer  12  and the second optical anisotropic layer  13 . 
     For example, the matching layer  12  is formed of an oxide film including at least one selected from the group consisting of Ti, Si, Ta, Al, Ce, Zr, Nb, and Hf. 
     Note that, the oxides constituting the matching layer  12  may be nonstoichiometric. Specifically, an atomic ratio of constitutional elements of the oxide is not necessarily a simple whole number ratio. When an oxide film is formed by sputtering etc., the formed oxide is often nonstoichiometric. 
     A thickness of the matching layer  12  is not particularly limited and may be appropriately selected depending on the intended purpose. For example, the thickness of the matching layer  12  is 140 nm or greater but 240 nm or less. 
     &lt;Second Optical Anisotropic Layer&gt; 
     The second optical anisotropic layer  13  is a birefringent layer obtained by depositing an inorganic material. 
     An angle formed between a direction along which the inorganic material is deposited in the birefringent layer and a surface of the transparent substrate is other than 90°. 
     For example, the birefringent layer includes an oblique angle vapor deposition film. 
     In the phase difference compensation element  10  illustrated in  FIG. 1 , the second optical anisotropic layer  13  is disposed between the matching layer  12  and the protective layer  14 . 
     The birefringent layer includes, for example, a plurality of birefringent films each formed of an inorganic material. The inorganic material is preferably a dielectric material. Examples of the inorganic material include an oxide including at least one selected from the group consisting of Si, Nb, Zr, Ti, La, Ta, Al, Hf, and Ce. 
     The inorganic material is preferably tantalum oxide (e.g., Ta 2 O 5 ). 
     For example, the plurality of birefringent films constituting the birefringent layer may be formed of the same material or composition. 
     A retardance of each of the birefringent films is not particularly limited and may be appropriately selected depending on a liquid crystal panel for use. 
     A thickness of each birefringent film constituting the birefringent layer may be appropriately selected depending on a retardance to be compensate. 
     A thickness of the whole second optical anisotropic layer including the birefringent films is appropriately selected depending on a retardance to compensate. For example, the thickness of the second optical anisotropic layer is 50 nm or greater but 500 nm or less. 
       FIG. 3  is a perspective schematic view of an oblique angle vapor deposition film. As illustrated in  FIG. 3 , the oblique angle vapor deposition film  23  constituting the second optical anisotropic layer  13  is formed by depositing a deposition material in a direction slanting relative to a normal line S that is a direction perpendicular to a surface of the transparent substrate  11  or the deposition target surface  21 . The slanted angle relative to the normal line S of the deposition target surface  21  is preferably 60° or greater but 80° or less. 
     For example, the second optical anisotropic layer  13  has a structure where a plurality of the above-described birefringent films are deposited. 
     Each birefringent film is formed by depositing in the direction slanting relative to the normal line S, and an angle formed between the film formation direction of an inorganic material constituting the birefringent film and a surface of the transparent substrate is not 90°. 
     A method creating a state where an angle formed between the film formation direction of the inorganic material and the surface of the transparent substrate is not 90° is, for example, preferably a method where a deposition source is arranged in a position slanted relative to the normal line S and an oblique angle vapor deposition film is formed by oblique angle vapor deposition from the deposition source. When a birefringent layer is formed by performing oblique angle vapor deposition multiple times, the oblique angle vapor deposition is repeated with varying the deposition angle to thereby obtain a final birefringent layer. 
       FIG. 4  is a schematic view illustrating one example of an oblique angle vapor deposition for forming the oblique angle vapor deposition film. 
       FIG. 5  is a schematic view illustrating one example of a direction (vapor deposition direction) projecting a flying direction of the deposition material from a vapor deposition source to a vapor deposition target surface. 
     As illustrated in  FIG. 4 , a linear direction for projecting a film formation direction of the birefringent film on a surface of the transparent substrate is represented by d, when an oblique angle vapor deposition film is formed on the transparent substrate  11  in the deposition direction D from the deposition source R. 
     During the deposition process P 1 , as illustrated in  FIG. 5 , oblique angle deposition is performed from the direction of 93° to form a birefringent film (first deposition direction), when the anticlockwise direction with a center defined by x and y axes on a deposition surface is determined as +. During the subsequent deposition process P 2 , oblique angle deposition is performed from the direction of 177° to form a birefringent film (second deposition direction), when the anticlockwise direction with a center defined by x and y axes on a deposition surface is determined as +. In this manner, an optical anisotropic layer including two birefringent films is ultimately obtained, Note that, the sign L denotes a direction of a line component obtained by projecting a liquid crystal molecule onto a surface of the transparent substrate. 
     &lt;Protective Layer&gt; 
     The protective layer  14  is formed of a dielectric film, and is disposed to be in contact with the oblique angle vapor deposition film of the second optical anisotropic layer  13 . The presence of the protective layer  14  can prevent warping of the phase difference compensation element  10 , and can improve humidity resistance of the oblique angle vapor deposition film. 
     The dielectric material of the protective layer  14  is not particularly limited and may be appropriately selected depending on the intended purpose, as long as the dielectric material can adjust stress applied to the phase difference compensation element  10 , and can exhibit an effect of improving humidity resistance. Examples of such a dielectric material include oxide including at least one selected from the group consisting of Si, Ta, Ti, Al, Nb, and La, and MgF 2 . 
     A thickness of the protective layer  14  is not particularly limited and may be appropriately selected depending on the intended purpose. The thickness of the protective layer  14  is, for example, 10 nm or greater but 100 nm or less. 
     &lt;Production Method of Phase Difference Compensation Element&gt; 
     Next, a production method of the phase difference compensation element according to the present embodiment will be described. As a specific example of the production method of the phase difference compensation element, the production method of the phase difference compensation element having the configuration example illustrated in  FIG. 4  will be described hereinafter.  FIG. 9  is a flowchart depicting the production method of the phase difference compensation element. 
     &lt;&lt;S 1 &gt;&gt; 
     First, a transparent substrate  11  is provided in Step S 1 . 
     &lt;&lt;S 2 &gt;&gt; 
     Next, a matching layer  12 , in which inorganic oxide films are laminated, is formed on the transparent substrate in order to prevent reflection at an interface between the second optical anisotropic layer  13  and the transparent substrate  11  in Step S 2 . 
     &lt;&lt;S 3 &gt;&gt; 
     Next, a first optical anisotropic layer  15 A [back antireflection (AR) layer] is formed on a surface of the transparent substrate  11 , on which the matching layer  12  is not formed, in Step S 3 . 
     &lt;−S 4 &gt;&gt; 
     Next, a second optical anisotropic layer  13  is formed on the matching layer  12  by oblique angle vapor deposition in Step S 4 . As illustrated in  FIGS. 4 and 5 , for example, after performing film formation by a vapor deposition process P 1 , the plane of the deposition target is rotated by 84° and a vapor deposition process P 2  is performed to form a second optical anisotropic layer  13 . 
     &lt;&lt;S 5 &gt;&gt; 
     Next, the second optical anisotropic layer  13  is subjected to annealing at a temperature of 200° C. or higher but 600° C. or lower in Step S 5 . The second optical anisotropic layer  13  is subjected to annealing more preferably at a temperature of 300° C. or higher but 500° C. or lower, further more preferably 400° C. or higher but 500° C. or lower. As a result, properties of the second optical anisotropic layer  13  can be stabilized. 
     &lt;&lt;S 6 &gt;&gt; 
     Next, a protective layer  14  is formed on the second optical anisotropic layer  13  in Step S 6 . When a film of SiO 2  is formed as the protective layer  14 , for example, tetraethoxysilane (TEOS) gas and O 2  are preferably used as a material of SiO 2 , and a plasma CVD device is preferably used. 
     A SiO 2  CVD film formed by a plasma CVD device uses a vaporized material gas for film formation different from physical vapor deposition, such as sputtering. Therefore, TEOS gas is relatively easily penetrated into gaps in the column structure to further improve adhesion of the protective layer  14  to the second optical anisotropic layer  13 . 
     &lt;&lt;S 7 &gt;&gt; 
     Next, a second antireflection layer  15 B (surface AR layer) is formed on the protective layer  14  in Step S 7 . 
     &lt;&lt;S 8 &gt;&gt; 
     Finally, scribe cutting is performed to obtain a size matched to a specification in Step S 8 . 
     According to the production method as described above, an optical element having excellent durability against light of high luminance and high output emitted from a laser light source etc. can be obtained. 
     (Liquid Crystal Display Device) 
     The liquid crystal display device according to the present embodiment includes a liquid crystal panel and the above-described phase difference compensation element. 
     For example, the liquid crystal panel and the phase difference compensation element are disposed in the liquid crystal display device in a manner that a main plane of the liquid crystal panel is parallel to a main plane of the phase difference compensation element. Because of the arrangement as described, a space where the phase difference compensation element is disposed can be significantly reduced compared to a case where the phase difference compensation element is disposed to be oblique to the liquid crystal panel. In the present specification, “being parallel to” does not mean complete parallel, and the main plane of the phase difference compensation element may be tilted from the main plane of the liquid crystal panel as long as the space to be arranged can be significantly reduced. For example, the main plane of the phase difference compensation element may be tilted from the main plane of the liquid crystal panel in the range of 2° or less. 
     The liquid crystal display device includes at least a liquid crystal panel and the phase difference compensation element, and may further include other members, such as a first polarizing plate and a second polarizing plate. 
     &lt;Liquid Crystal Panel&gt; 
     The liquid crystal panel is not particularly limited. For example, the liquid crystal panel includes a substrate, and a VA-mode liquid crystal layer including liquid crystal molecules having pretilt relative to the orthogonal direction to the main surface of the substrate, and modulates the entered luminous flux entered. The VA-mode (vertical alignment mode) means a system where liquid crystal molecules aligned vertical (or with pretilt) to the substrate are moved using a longitudinal electric field in a vertical direction. 
     &lt;&lt;First Polarizing Plate and Second Polarizing Plate&gt;&gt; 
     A first polarizing plate is a polarizing plate disposed at the inlet side of the liquid crystal panel, and a second polarizing plate is a polarizing plate disposed at the outlet side of the liquid crystal panel. The first polarizing plate and the second polarizing plate are preferably inorganic polarizing plates in view of durability. 
     A typical optical system will be described with reference to  FIG. 7 . In case of a vertically aligned transmissive liquid crystal panel, liquid crystal molecules  1  are aligned in a certain direction to be tilted by a pretilt angle a with respect to an orthogonal direction to a plane of the substrate. The liquid crystal panel is disposed to be sandwiched between a pair of polarizing plates arranged in a manner that transmission axes of the polarizing plates are crossed with 90°. Note that, in  FIG. 7 , the numerical sign  2  denotes a glass substrate, the numerical sign  3  denotes a glass substrate, the numerical sign  4  denotes a phase difference compensation element, the numerical sign  5  denotes a second polarizing plate, the numerical sign  6  denotes a first polarizing plate, the numerical sign  7  denotes emitting light, and the numerical sign  8  denotes incident light. 
     (Projection Image Display Device) 
     The projection image display device according to the present embodiment includes a light source configured to emit light, a projection optical system configured to project modulated light, and the above-described liquid crystal display device. 
     The liquid crystal display device is disposed on an optical path between the light source and the projection optical system. The projection image display device is suitably used for projectors, such as a liquid crystal projector, and a liquid crystal on silicon (LCOS) projector. 
     &lt;Light Source&gt; 
     Alight source is not particularly limited and may be appropriately selected depending on the intended purpose, as long as the light source is a member that emits light. For example, a laser light source that emits light of high luminance and high output can be used. 
     The wavelength of the laser light source is, for example, 455 nm. 
     &lt;Projection Optical System&gt; 
     The projection optical system is not particularly limited and may be appropriately selected depending on the intended purpose, as long as the projection optical system is a member for projecting modulated light. Examples of the projection optical system include a projection lens configured to project the modulated light onto a screen. 
     The projection image display device having the above-described structure can significantly reduce a space where the phase difference compensation element is disposed. Therefore, a small projection image display device can be constructed. 
     FIG. 8  is a schematic view illustrating one example of the structure of the projection image display device according to the present embodiment. The projection image display device  115 A is a so-called 3-panel liquid crystal projector, which displays a color image using  3  liquid crystal panels of red, green, and blue. As illustrated in  FIG. 8 , the projection image display device  115 A includes liquid crystal display devices  101 R,  101 G, and  101 B, a light source  102 , dichroic mirrors  103  and  104 , a total reflection mirror  105 , polarization beam splitters  106 R,  106 G, and  106 B, a beam-combining prism  108 , and a projection lens  109 . 
     The light source  102  is configured to emit light-source light (white light) L including blue light LB, green light LG, and red light LR for forming an image display. Examples of the light source  102  include a halogen lamp, a metal halide lamp, and a xenon lamp. 
     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 passed LRG 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  towards the polarization beam splitter  106 B. 
     The polarization beam splitters  106 R,  106 G, and  106 B are prism-type polarized light separators disposed on optical paths of the red light LR, the green light LG, and the blue light LB, respectively. The polarization beam splitters  106 R,  106 G, and  106 B have polarized light splitting surfaces  107 R,  107 G, and  107 B, respectively. The polarization beam splitters  106 R,  106 G, and  106 B have a function of splitting the entered light of each color into two polarized light components orthogonal to each other at the polarized light splitting surfaces  107 R,  107 G, and  107 B, respectively. The polarized light splitting surfaces  107 R,  107 G, and  107 B reflect one polarized light component (e.g., an S-polarized light component) and transmit the other polarized light component (e.g., a P-polarized light component). 
     The color light of the certain polarized light component (e.g., an S-polarized light component) separated by each of the polarized light splitting surfaces  107 R,  107 G, and  107 B of the polarization beam splitters  106 R,  106 G, and  106 B enters each of the liquid crystal display devices  101 R,  101 G, and  101 B. The liquid crystal display devices  101 R,  101 G, and  101 B are driven by driving voltage applied according to an image signal to modulate the incident light, and also have a function of reflecting the modulated light to the polarization beam splitters  106 R,  106 G, and  106 B. 
     The phase difference compensation elements  10  and the 1/4-wave plates  113 R,  113 G, and  113 B are disposed between the polarization beam splitters  106 R,  106 G, and  106 B, and the liquid crystal panels of the liquid crystal display devices  101 R,  101 G, and  101 B, respectively. The 1/4-wave plates  113 R,  113 G, and  113 B each function as a 1/2-wave plate as the 1/4-wave plates  113 R,  113 G, and  113 B allow to pass the light twice, i.e., when the light enters the liquid crystal panel, and when the light is emitted from the liquid crystal panel (for example, converting an S-polarized light component into a P-polarized light component). Moreover, the 1/4-wave plates  113 R,  113 G, and  113 B have a function of suppressing a reduction of the contrast owing to the incident light angle dependency the polarization beam splitters  106 R,  106 G, and  106 B have. The phase difference compensation elements  10  have a function of compensating the residual phase difference of the liquid crystal panels constituting the liquid crystal display devices  101 R,  101 G, and  101 B, respectively. In one aspect, the phase difference compensation element  10  is the phase difference compensation element according to the present embodiment. 
     The beam-combining prism  108  has a function of combining color light of the certain polarized light components (e.g., P-polarized light components) emitted from the liquid crystal display devices  101 R,  101 G, and  101 B and passed through the polarization beam splitter  106 R,  106 G, and  106 B. The projection lens  109  has a function of projecting the synthesized light emitted from the beam-combining prism  108  towards the screen  110 . 
     Next, an operation of the projection image display device  115 A constituted in the above-described manner will be described. 
     First, white light L emitted from the light source  102  is split into blue light LB and other color light (red light and green light) LRB by a function of the dichroic mirror  103 . The blue light LB is reflected to the polarization beam splitter  106 B by a function of the total reflection mirror  105 . 
     Meanwhile, other color light (red light and green light) LRG is further split into red light LR and green light LG by a function of the dichroic mirror  104 . The split red light LR and green light LG enters the polarization beam splitters  106 R and  106 G, respectively. 
     The polarization beam splitters  106 R,  106 G, and  106 B are configured to split the entered color light into two polarized light components orthogonal to each other by the polarized light splitting surfaces  107 R,  107 G, and  107 B, respectively. The polarized light splitting surfaces  107 R,  107 G, and  107 B reflect one polarized light component (e.g., an S-polarized light component) to the liquid crystal display devices  101 R,  101 G, and  101 B. The liquid crystal display devices  101 R,  101 G, and  101 B are driven by driving voltage applied according to an image signal, and modulate color light of the entered certain polarized light by pixel. 
     The liquid crystal display devices  101 R,  101 G, and  101 B reflect the modulated color light to the polarization beam splitters  106 R,  106 G, and  106 B, respectively. The polarization beam splitters  106 R,  106 G, and  106 B only pass through the certain polarized light component (e.g., P-polarized light components) within the reflected light (modulated light) from the liquid crystal display devices  101 R,  101 G, and  101 B, and emit towards the beam-combining prism  108 . 
     The beam-combining prism  108  synthesize the color light of the certain polarized light components passed through the polarization beam splitters  106 R,  106 G, and  106 B, and emits towards the projection lens  109 . The projection lens  109  projects the synthesized light emitted from the beam-combining prism  108  to the screen  110 . As a result, an image corresponding to the light modulated by the liquid crystal display devices  101 R,  101 G, and  101 B is projected on the screen  110 , and a desired image display is achieved. 
     EXAMPLES 
     Specific example of the present invention will be described hereinafter. However, the present invention is not limited to the example below. Note that, formed films are described as a SiO 2  film and a Nb 2 O 5  film for the matter of convenience, but the films are highly likely nonstoichiometric. 
     Example 1 
     &lt;Production of Phase Difference Compensation Element&gt; 
     On one surface of a glass substrate (average thickness: 0.7 mm), Nb 2 O 5  and SiO 2  were alternately deposited by sputtering to form 5 layers in total, to thereby form a matching layer. 
     On the other surface of the glass substrate, subsequently, Nb 2 O 5  and SiO 2  were alternately deposited by sputtering to form 40 layers in total, to thereby form a first optical anisotropic layer. The layer structure was designed in a manner that retardance given to tilted incident light that was tilted by 15° from the direction orthogonal to the surface of the glass substrate was 15 nm. Moreover, the first optical anisotropic layer was imparted with an antireflection function. An optic axis of the obtained first optical anisotropic layer was orthogonal to the planar direction. Specifically, the first optical anisotropic layer functioned as a C-plate. 
     Subsequently, a deposition source was arranged in a position slanted relative to a normal line of the glass substrate by 70°, and oblique angle vapor deposition was performed using a deposition material prepared by adding TiO 2  to Ta 2 O 5 , to thereby form a second optical anisotropic layer. As illustrated in  FIG. 5 , the vapor deposition direction was set at 93° in the vapor deposition process P 1 , and the vapor deposition direction was set at 177° in the vapor deposition process P 2 . Nine samples were produced in total by adjusting a thickness of the vapor deposition film to thereby give the average retardance thereof of 1 nm, 2 nm, 2.5 nm, 4 nm, 5 nm, 6 nm, 7.5 nm, 8 nm, and 10 nm. The average retardance of each sample was an average retardance of the sample with incident light tilted in the range of 5° towards a pretilt direction (the direction indicated with the symbol L in  FIG. 5 ) of liquid crystal molecules. 
     After the vapor deposition, annealing was performed at 400° C. to stabilize the properties of the second optical anisotropic layer. After the annealing, a SiO 2  film was formed by plasma CVD using tetraethoxysilane (TEOS) gas and O 2 . 
     Subsequently, Nb 2 O 5  and SiO 2  were alternately deposited by sputtering to form 7 layers in total to thereby form an antireflection layer. As described above, a phase difference compensation element was produced. 
     A retardance of each of the produced phase difference compensation elements was measured with incident light tilted per 1° in the range of ±5° towards the pretilt direction of the liquid crystals, and an average values of the measured retardance values was calculated. 
     A liquid crystal panel whose average retardance with incident light tilted within the range of 5° towards a pretilt direction of liquid crystal molecules therein was 5 nm and each of the phase difference compensation elements (9 samples) of Example 1 were mounted in a liquid crystal projector, and contrast thereof was measured. The phase difference compensation element was disposed to be parallel to a main plane of the liquid crystal panel.  FIG. 9  is a graph depicting the contrast value normalized with a contrast value when the average retardance of the phase difference compensation element with incident light tilted within the range of 5° towards the pretilt direction of the liquid crystal molecules is 5 nm (A/B=1). The normalized contrast value was 0.8 or greater in the range of 0.5&lt;A/B&lt;1.5, and excellent contrast was obtained.
     A: an average retardance of the phase difference compensation element with incident light tilted in the range of 5° towards the pretilt direction of the liquid crystal molecules of the liquid crystal panel.   B: an average retardance of the liquid crystal panel with incident light tilted in the range of 5° towards the pretilt direction of the liquid crystal molecules therein.   

     Note that, the contrast is an average value of values obtained by measuring at 9 points by means of an illuminometer T-10 available from KONICA MINOLTA, INC. 
     Example 2 
     A liquid crystal panel whose average retardance with incident light tilted within the range of 5° towards a pretilt direction of liquid crystal molecules therein was 4 nm and each of the phase difference compensation elements (9 samples) of Example 1 were mounted in a liquid crystal projector, and contrast thereof was measured in the same manner as in Example 1.  FIG. 9  is a graph depicting the contrast value normalized with a contrast value when the average retardance of the phase difference compensation element with incident light tilted within the range of 5° towards the pretilt direction of the liquid crystal molecules is 4 nm (A/B=1). The normalized contrast value was 0.8 or greater in the range of 0.5&lt;A/B&lt;1.5, and excellent contrast was obtained. 
     The phase difference compensation element of the present invention can be suitably applied for a small projection image display device, because the phase difference compensation element can significantly reduce a space to be disposed, and has excellent durability.