JP7092630B2 - Optical element and projection type image display device - Google Patents

Description

The present art relates to an optical element having an orthorhombic vapor film and a projection type image display device.

Conventionally, an optical element in which an oblique vapor deposition film of a dielectric material is formed on the surface of a transparent substrate is known. Diagonal thin-film deposition is a method of forming a film by inclining the surface of the substrate with respect to the direction of arrival of the vapor-deposited material. It is observed as a columnar structure. The density of this column is in-plane anisotropy, and the refractive index is in-plane anisotropy, resulting in a birefringence phenomenon in the oblique film. The oblique vapor deposition film is used for optical elements such as a 1/4 wavelength wave plate and a 1/2 wave plate due to its birefringence phenomenon. For example, Patent Document 1 describes a retardation element having an orthorhombic vapor-filmed film containing tantalum pentoxide (Ta ₂ O ₅ ) as a main component.

Japanese Unexamined Patent Publication No. 2012-256024

In recent years, as a light source used in a projector, a laser light source that can obtain high-luminance and high-output light has attracted attention. However, the above-mentioned orthorhombic vapor deposition film containing tantalum pentoxide as a main component may be damaged by high-intensity and high-power light from a laser light source.

This technique has been proposed in view of such circumstances, and an object thereof is to provide an optical element and a projection type image display device capable of obtaining excellent resistance to high-luminance and high-output light. And.

Further, the projection type image display device according to the present technology includes the above-mentioned optical element, an optical modulation device, a light source for emitting light, and a projection optical system for projecting modulated light, and the optical modulation device and the above-mentioned optical modulation device. The optical element is arranged on an optical path between the light source and the projection optical system.

In order to solve the above-mentioned problems, the method for manufacturing an optical element according to the present technology comprises laminating two or more types of dielectric films having different refractive coefficients on a substrate that is transparent to light in the frequency band used. A matching layer is formed, and a vapor deposition source containing hafnium oxide as a main component is placed at a position inclined with respect to the normal of the vapor deposition target surface of the matching layer. Is 180 degrees, and oblique vapor deposition is alternately performed, and the first oblique vapor deposition film having a first inclination direction such that the inclination angle of the substrate with respect to the normal is 60 ° or more and 80 ° or less, and the substrate surface. The second oblique vapor-filmed film having a second inclination direction which is opposite to the first inclination direction and has an inclination angle of 60 ° or more and 80 ° or less with respect to the normal of the substrate alternates with each other. At least two or more kinds of dielectric films having different refractive folds are laminated by forming a film-formed double-filmed double-reflecting layer and performing an annealing treatment at a temperature of 300 ° C. or higher and 600 ° C. or lower after forming the double-filming layer. It is characterized by forming one antireflection layer.

According to this technique, since the orthorhombic vapor-film film is formed mainly of hafnium oxide, excellent resistance to high-luminance and high-output light can be obtained.

FIG. 1 is a cross-sectional view showing a configuration example of a retardation element. FIG. 2 is a schematic perspective view of the oblique vapor deposition film. FIG. 3 is a schematic diagram for explaining an orthorhombic vapor deposition method for forming an orthorhombic vapor deposition film. FIG. 4 is a schematic diagram showing the direction in which the vapor deposition direction from the vapor deposition source is projected onto the vapor deposition target surface. FIG. 5 is a schematic cross-sectional view of the antireflection layer. FIG. 6 is a flowchart showing a method of manufacturing a retardation element.

Hereinafter, embodiments of the present technology will be described in detail in the following order with reference to the drawings.
1. 1. Optical element 2. Manufacturing method of optical element 3. Projection type image display device 4. Example

<1. Optical element>
The optical element according to the present embodiment includes a substrate that is transparent to light in the wavelength band used, and a birefringent layer made of an oblique vapor-deposited film containing hafnium oxide as a main component. This makes it possible to obtain excellent resistance to high-intensity and high-output light from a laser light source or the like. It is considered that this is because hafnium oxide having a high melting point prevents thermal decay of the columnar structure of the orthorhombic vapor-film film.

In the birefringent layer, a first oblique vapor deposition film having a first inclination direction with respect to the normal of the substrate and a second oblique vapor deposition film having a second inclination direction are alternately formed. May be good. When the birefringent layer is a film in which the first oblique-deposited film and the second oblique-deposited film are alternately formed, the filling rate of the columnar structure becomes large, so that the light has high brightness and high output. The effect of resistance becomes remarkable.

Further, it is preferable that the optical element includes at least one antireflection layer in which two or more kinds of dielectric films having different refractive indexes are laminated. This can reduce reflections and increase transmittance.

Examples of the optical element having such a configuration include a phase difference element that gives a phase difference to the incident light, a phase difference compensating polarizing element, and the like. Hereinafter, the phase difference element will be described as an example of the optical element.

FIG. 1 is a cross-sectional view showing a configuration example of a retardation element. As shown in FIG. 1, in the retardation element 10, the transparent substrate 11 and the high refractive index film and the low refractive index film are alternately laminated on the transparent substrate 11, and the thickness of each layer is equal to or less than the used wavelength. The layer 12 includes a birefringent layer 13 made of an oblique vapor deposition film formed on the matching layer 12, and a protective layer 14 made of a dielectric film formed on the birefringent layer 13. Further, the transparent substrate 11 side is provided with the first antireflection layer 15A, and the protective layer 14 side is provided with the second antireflection layer 15B.

The transparent substrate 11 is transparent to light in the wavelength band used and has a high transmittance for light in the wavelength band used. Examples of the material of the transparent substrate 11 include glass, quartz, crystal, and sapphire. The shape of the transparent substrate 11 is generally a quadrangle, but a shape suitable for the purpose is appropriately selected. The thickness of the transparent substrate 11 is preferably 0.1 to 3.0 mm, for example.

The matching layer 12 is a multilayer film in which a dielectric film is laminated, and is provided between the transparent substrate 11 and the birefringent layer 13 as needed. The matching layer 12 is designed so as to reverse the phases of the surface reflected light and the interfacial reflected light and cancel each other out, thereby preventing reflection at the interface between the transparent substrate 11 and the birefringent layer 14.

The matching layer 12 is composed of two or more kinds of dielectric films selected from TiO ₂ , SiO ₂ , Ta ₂ O ₅ , Al ₂ 0 ₃ , CeO ₂ , ZrO ₂ , ZrO, Nb ₂ O ₅ , and HfO ₂ . be able to. Further, the dielectric film in contact with the birefringence layer 13 of the matching layer 12 is preferably SiO ₂ having excellent adhesion to hafnium oxide. This makes it possible to further improve the light resistance to a laser light source or the like.

The birefringent layer 13 is made of an orthorhombic vapor-filmed film containing hafnium oxide (HfO ₂ ) as a main component. Here, the main component means the component having the largest proportion in the columnar structure of the orthorhombic vapor-film film. Further, the birefringent layer 13 may be a single-layer film of an oblique-deposited film or a film in which the oblique-deposited films are alternately formed. Further, the thickness of each orthorhombic vapor-film deposition film is preferably equal to or less than the wavelength used.

FIG. 2 is a schematic perspective view of the oblique vapor deposition film. As shown in FIG. 2, the oblique vapor deposition film is formed by depositing a vapor deposition material in a direction inclined with respect to the normal line S of the vapor deposition target surface 21. The inclination angle of the vapor deposition target surface 21 with respect to the normal line S is preferably 60 ° or more and 80 ° or less.

The oblique vapor deposition film has a diagonal columnar structure in which columnar bundles containing hafnium oxide as a main component are formed diagonally with respect to the normal of the vapor deposition target surface. This diagonal columnar structure has a columnar portion in which fine particles containing hafnium oxide as a main component are deposited, and a void portion which is an air layer between the columnar portions.

FIG. 3 is a schematic diagram for explaining an oblique vapor deposition method for forming an oblique vapor deposition film, and FIG. 4 is a direction in which the direction of arrival of the vapor deposition material from the vapor deposition source is projected onto the vapor deposition target surface (vapor deposition direction). ) Is a schematic diagram. As shown in FIGS. 3 and 4, the films in which the oblique vapor deposition films are alternately formed are formed by thin-film deposition from the first thin-film deposition direction 31 and film formation by thin-film deposition from the second thin-film deposition direction 32. And are formed by repeating alternately. Specifically, after film formation by vapor deposition from the first vapor deposition direction 31, the second vapor deposition target surface is rotated by 180 ° around the center line passing through the center of the vapor deposition target surface perpendicular to the vapor deposition target surface. A film is formed by vapor deposition from the vapor deposition direction 32. Then, by repeating this, the first oblique vapor deposition film having the first inclined direction with respect to the normal of the vapor deposition target surface and the second oblique vapor deposition film having the second inclined direction are alternately arranged. A film formed is obtained.

The protective layer 14 is made of a dielectric film and is arranged in contact with the oblique vapor deposition film of the birefringent layer 13. This makes it possible to prevent the retardation element 10 from warping and improve the moisture resistance of the oblique vapor deposition film.

The dielectric material of the protective layer 14 is not particularly limited as long as the stress applied to the retardation element 10 can be adjusted and is effective in improving the moisture resistance, and can be appropriately selected depending on the intended purpose. .. Examples of such a dielectric material include SiO ₂ , Ta ₂ O ₅ , TiO ₂ , Al ₂ O ₃ , Nb ₂ O ₅ , LaO, MgF ₂ , and the like, which are particularly excellent in adhesion to hafnium oxide. It is preferably SiO ₂ . Thereby, the moisture resistance can be further improved.

The first antireflection layer 15A is provided in contact with the surface of the transparent substrate 11 facing the birefringence layer 13 side, and the second antireflection layer 15B faces the birefringence layer 13 side of the protective layer 14. It is provided as needed in contact with the surface to be used. The first antireflection layer 15A and the second antireflection layer 15B have an antireflection function in a desired wavelength band used.

FIG. 5 is a schematic cross-sectional view of the first antireflection layer. As shown in FIG. 5, the first antireflection layer 15A is an optical multilayer film in which two or more kinds of dielectric films having different refractive indexes are laminated. For example, the first dielectric film 151 having different refractive indexes. And the second dielectric film 152 are alternately laminated to form a multilayer film. The number of antireflection layers is appropriately determined as needed, and about 5 to 40 layers is preferable from the viewpoint of productivity. The second antireflection layer 15B is also configured in the same manner as the first antireflection layer 15A.

The first antireflection layer 15A and the second antireflection layer 15B are from TiO ₂ , SiO ₂ , Ta ₂ O ₅ , Al ₂ 0 ₃ , CeO ₂ , ZrO ₂ , ZrO, Nb ₂ O ₅ , and HfO ₂ , respectively. It is composed of two or more types of selected dielectric films. For example, the antireflection layer includes a first dielectric film 151 made of Nb ₂₀₅ having a relatively high refractive index and a _{second dielectric film 152 made of SiO 2 having} a relatively low refractive index. Can be a multilayer film in which is alternately laminated.

According to the phase difference element having such a configuration, it is possible to obtain excellent resistance to high-intensity and high-output light from a laser light source or the like.

<2. Manufacturing method of optical element>
Next, a method for manufacturing an optical element according to the present embodiment will be described. In the method for manufacturing an optical element according to the present embodiment, a vapor deposition material containing hafnium oxide as a main component is deposited in a direction inclined with respect to the normal of the surface to be vapor-deposited, and a diagonal vapor deposition film containing hafnium oxide as a main component is used. Form a birefringent layer. Further, in the method for manufacturing an optical element according to the present embodiment, a vapor deposition material containing hafnium oxide as a main component is deposited in a first direction inclined with respect to the normal of the vapor deposition target surface, and a first oblique vapor deposition film is deposited. And a step of depositing a vapor deposition material containing hafnium oxide as a main component in a second direction inclined with respect to the normal of the vapor deposition target surface to form a second oblique vapor deposition film. Repeatedly, a double-deflected layer composed of films in which diagonally-deposited films are alternately formed is formed. This makes it possible to obtain an optical element having excellent resistance to high-intensity and high-output light from a laser light source or the like.

Hereinafter, as a specific example of the manufacturing method of the optical element, the manufacturing method of the phase difference element of the configuration example shown in FIG. 1 will be described. FIG. 6 is a flowchart showing a method of manufacturing a retardation element.

First, in step S1, the transparent substrate 11 is prepared. Next, in step S2, in order to prevent reflection at the interface between the birefringence layer 13 and the transparent substrate 11, a matching layer 12 in which a dielectric film is laminated on the transparent substrate 11 is formed. Next, in step S3, the first antireflection layer 15A (back surface AR layer) is formed on the opposite surface of the substrate 21 on which the matching layer 12 is not formed.

Next, in step S4, the birefringent layer 13 is formed on the matching layer 12 by an orthorhombic vapor deposition method. For example, as shown in FIGS. 3 and 4, after film formation by vapor deposition from the first vapor deposition direction 31, the vapor deposition target surface is rotated 180 ° around the center line passing through the center of the vapor deposition target surface perpendicular to the vapor deposition target surface. By doing so, a film is formed by thin-film deposition from the second thin-film deposition direction 32. Then, by repeating this, the first oblique vapor deposition film having the first inclined direction with respect to the normal of the vapor deposition target surface and the second oblique vapor deposition film having the second inclined direction are alternately arranged. A film formed is obtained.

Next, in step S5, the birefringent layer 13 is annealed at a temperature of 200 ° C. or higher and 600 ° C. or lower. The birefringence layer 13 is annealed at a temperature of 300 ° C. or higher and 500 ° C. or lower, more preferably 400 ° C. or higher and 500 ° C. or lower. Thereby, the characteristics of the birefringent layer 13 can be stabilized.

Next, in step S6, the protective layer 14 is formed on the birefringence layer 13. For example, when forming SiO ₂ as the protective layer 14, it is preferable to use TEOS (tetraethoxysilane) gas and O ₂ as the material of SiO ₂ and use a plasma CVD apparatus.

The SiO ₂ CVD film formed by the plasma CVD apparatus is characterized by using vaporized material gas, unlike physical vapor deposition represented by the sputtering method, and therefore TEOS gas has a columnar structure relatively easily. It is possible to invade the void portion of the above, and the adhesion with the double refractive layer 13 can be further improved.

Next, in step S7, a second antireflection layer 15B (surface AR layer) is formed on the protective layer 14. Finally, in step S8, scribe cutting is performed to a size according to the specifications.

By the above manufacturing method, it is possible to obtain a phase difference element having excellent resistance to high-intensity and high-output light from a laser light source or the like.

<3. Projection type image display device>
Since the above-mentioned optical element has excellent resistance to high-intensity and high-output light, it is a liquid crystal projector, a DLP (registered trademark) (Digital Light Processing) projector, an LCOS (Liquid Crystal On Silicon) projector, and a GLV (registered). Trademark) (Grating Light Valve) Suitable for projector applications such as projectors. That is, the projection type image display device according to the present embodiment includes the above-mentioned optical element, an optical modulation device, a light source that emits light, and a projection optical system that projects modulated light, and is an optical modulation device. And the optical element is arranged on the optical path between the light source and the projection optical system. Examples of the optical modulation device include a liquid crystal display device having a transmissive liquid crystal panel and the like, a micromirror display device having a DMD (Digital Micro-mirror Device) and the like, a reflective liquid crystal display device having a reflective liquid crystal panel and the like, and one-dimensional diffraction. Examples thereof include a one-dimensional diffraction type display device having a type optical modulation element (GLV) and the like.

For example, in a projection type image display device using a liquid crystal display device, the liquid crystal display device has at least a liquid crystal panel, a first polarizing plate, and a second polarizing plate, and further, if necessary, other Has a member of.

The liquid crystal panel is not particularly limited, and has, for example, a substrate and a VA mode liquid crystal layer containing liquid crystal molecules having a pretilt with respect to the direction orthogonal to the main surface of the substrate, and modulates the incident light flux. The VA mode (Vertical alignment mode) means a method of moving liquid crystal molecules arranged vertically (or having a pretilt) on a substrate by using a vertical electric field.

The first polarizing plate is arranged on the incident side of the liquid crystal panel, and the second polarizing plate is arranged on the emitting side of the liquid crystal panel. The first polarizing plate and the second polarizing plate are preferably inorganic polarizing plates from the viewpoint of durability.

The retardation element includes, for example, an oblique vapor deposition film containing hafnium oxide as a main component in the configuration example shown in FIG. 1, and is located at a required position on the optical path constituting the projection type image display device. Be placed.

Further, even in a projection type image display device using a micromirror display device, the phase difference element is provided on the same optical path in combination with a diffuser plate, a polarization beam splitter, or the like.

The light source is not particularly limited as long as it is a member that emits light, and can be appropriately selected according to the purpose. In the present embodiment, since the liquid crystal display device includes an optical element having an oblique vapor deposition film containing hafnium oxide as a main component, a laser light source or the like that emits high-intensity and high-output light can be used.

The projection optical system is not particularly limited as long as it is a member that projects modulated light, and can be appropriately selected according to the purpose. For example, a projection lens that projects modulated light onto a screen can be mentioned. Be done.

According to the projection type image display device having such a configuration, a high-brightness and high-output image can be displayed by using high-brightness and high-output light from a laser light source or the like.

<4. Example>
Hereinafter, examples of this technique will be described. Here, a retardation element having an orthorhombic thin-film film was prepared and a laser irradiation test was performed. The present technique is not limited to these examples.

[Example 1]
First, a matching layer was formed by laminating three layers of SiO ₂ / Nb ₂ O ₅ / SiO ₂ on one surface of a glass substrate (average thickness 0.7 mm) by a sputtering method.

Next, an antireflection layer was formed by alternately laminating 11 layers by a sputtering method using Nb ₂ O ₅ and SiO ₂ on the other surface of the glass substrate.

Subsequently, using HfO ₂ as a vapor deposition material on the matching layer, the vapor deposition source is placed at a position inclined by 70 degrees with respect to the normal direction of the substrate, and the first vapor deposition direction is 0 degrees and the second vapor deposition direction is 180 degrees. Then, diagonal vapor deposition was performed alternately. After the vapor deposition, an annealing treatment was performed at 450 ° C. to stabilize the characteristics. After the annealing treatment, a SiO ₂ film was formed by a plasma CVD method using TEOS (tetraethoxysilane) gas and _O2 to form a protective layer.

Next, using Nb _{205 and SiO 2 , 7} layers were alternately laminated by a sputtering method to form an antireflection layer. Then, scribe cutting was performed to a size according to the specifications, and a phase difference element was manufactured.

[Comparative Example 1]
A phase difference device was manufactured by the same procedure as in Example 1 except that the vapor deposition material was Ta ₂ O ₅ .

[Laser irradiation test]
Laser irradiation was performed on each of the 30 retardation elements prepared by the methods of Examples and Comparative Examples under the following conditions, and the number of damages was counted. The standard of damage was that the part irradiated with the laser of the transparent retardation element became cloudy, and this was visually confirmed. Table 1 shows the results of the number of damages to the retardation element due to laser irradiation.
Wavelength: 455nm CW (continuous wave) semiconductor laser Laser output: 61W
Power density: 10.2W / mm ²
Irradiation time: 3 minutes

As shown in Table 1, in the comparative example in which the oblique vapor deposition film was Ta ₂ O ₅ , more than half of the damage was caused by the laser irradiation. On the other hand, it was found that no damage occurred in the example in which the oblique vapor deposition film was HfO ₂ , and the durability was excellent against high-luminance and high-output light.

10 Phase difference element, 11 Transparent substrate, 12 Matching layer, 13 Birefringence layer, 14 Protective layer, 15A, 15B Antireflection layer, 21 Deposition target surface, 31 First vapor deposition direction, 32 Second vapor deposition direction, 151st 1 dielectric film, 152 second dielectric film

Claims (3)

A matching layer is formed by laminating two or more types of dielectric films having different refractive indexes on a substrate that is transparent to light in the wavelength band used.
A vapor deposition source containing hafnium oxide as a main component is placed at a position inclined with respect to the normal of the vapor deposition target surface of the matching layer, the first vapor deposition direction is 0 degrees, the second vapor deposition direction is 180 degrees, and alternating. The first oblique vapor deposition film having a first inclination direction such that the inclination angle with respect to the normal of the substrate is 60 ° or more and 80 ° or less, and the first inclination direction on the substrate surface. A plurality of thin-film deposited films having a second inclined direction, which is opposite to the normal direction and has an inclination angle of 60 ° or more and 80 ° or less with respect to the normal of the substrate, are alternately formed. A refractive layer is formed, and after the double refractive layer is formed, annealing treatment is performed at a temperature of 300 ° C. or higher and 600 ° C. or lower.
A method for manufacturing an optical element that forms at least one antireflection layer in which two or more types of dielectric films having different refractive indexes are laminated. The method for manufacturing an optical element according to claim 1 , wherein the substrate is glass. The method for manufacturing an optical element according to claim 1 or 2 , wherein after forming the birefringent layer, annealing treatment is performed at a temperature of 400 ° C. or higher and 600 ° C. or lower.

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