WO2019188010A1

WO2019188010A1 - Optical element, polarization conversion element, image display device, and method for manufacturing optical element

Info

Publication number: WO2019188010A1
Application number: PCT/JP2019/008349
Authority: WO
Inventors: 元米澤; 昇平阿部; 高橋　祐一
Original assignee: ソニー株式会社
Priority date: 2018-03-30
Filing date: 2019-03-04
Publication date: 2019-10-03
Also published as: JPWO2019188010A1; JP7322873B2; JP2023153170A

Abstract

An optical element according to one embodiment of the present technique is provided with a first glass substrate, a second glass substrate, an optical functional film and an inorganic bonding layer. The first glass substrate has a first bonding surface. The second glass substrate has a second bonding surface. The optical functional film covers the first bonding surface. The inorganic bonding layer is arranged between the optical functional film and the second bonding surface, and comprises a silicon compound bonded to the second bonding surface through direct bonding.

Description

Optical element, polarization conversion element, image display apparatus, and optical element manufacturing method

The present technology relates to an optical element having an optical functional film, a polarization conversion element, an image display apparatus including the same, and a method for manufacturing the optical element.

In the projection type image display device (projector), a polarization conversion element is used in order to increase the light use efficiency. As this type of polarization conversion element, for example, in Patent Document 1, a first base material and a second base material made of optical glass such as BK7 are disposed between the first base material and the second base material. A polarization conversion element having a polarization separation film and a bonding layer made of an organic film such as polyorganosiloxane disposed between the polarization separation film and a second base material is disclosed.

JP 2010-113056 A

In recent years, in a projection-type image display device, in order to achieve high brightness of an image, higher output of a light source or higher density of light energy has been promoted. For this reason, the polarization separation element is required to further improve heat resistance, light resistance and light transmittance. However, since a conventional polarization separation element uses an organic adhesive at the joint between the glass substrate and the polarization separation film, heat resistance is low, and deterioration due to light is inevitable. Furthermore, light transmission loss is likely to occur due to a difference in refractive index at the bonding interface.

In view of the circumstances as described above, an object of the present technology is to provide an optical element excellent in heat resistance, light resistance and light transmittance, a polarization conversion element, an image display apparatus including the same, and a method for manufacturing the optical element. There is.

An optical element according to an embodiment of the present technology includes a first glass substrate, a second glass substrate, an optical functional film, and an inorganic bonding layer.
The first glass substrate has a first bonding surface.
The second glass substrate has a second bonding surface.
The optical functional film covers the first bonding surface.
The inorganic bonding layer is formed of a silicon compound that is provided between the optical function film and the second bonding surface and bonded to the second bonding surface by direct bonding.

The optical element is excellent in heat resistance and light resistance because the bonding portion between the optical functional film and the second bonding surface is composed of an inorganic bonding layer made of a silicon compound. Furthermore, since the bonding layer is directly bonded to the second bonding surface, the refractive index difference at the interface is reduced, and thus the transmittance can be improved.

The silicon compound may be a silicon oxide.

The direct bonding may be plasma bonding.

In this case, the surface roughness (Ra) of the inorganic bonding layer and the second bonding surface can be 2 nm or less.

The thickness of the inorganic bonding layer can be 200 nm or more and 1000 nm or less.

The optical functional film is an optical multilayer film in which a first dielectric having a first refractive index and a second dielectric having a second refractive index different from the first refractive index are alternately stacked. It may be.

The optical multilayer film can be a polarization separation film.

Each of the first glass substrate and the second glass substrate may have a refractive index (n _d ) of 1.6 or more and 1.8 or less.

A polarization conversion element according to an embodiment of the present technology includes a polarization separation element, an inorganic wavelength plate, and a support.
The polarization separation element includes: a first glass substrate having a first bonding surface; a second glass substrate having a second bonding surface; and an optical functional film provided on the first bonding surface; And an inorganic bonding layer made of a silicon compound that is provided between the optical functional film and the second bonding surface and bonded to the second bonding surface by direct bonding.
The inorganic wave plate converts the first polarized light transmitted through the inorganic bonding layer into a second polarized light orthogonal to the first polarized light.
The support supports the polarization separation element and the inorganic wavelength plate in common so that the inorganic wavelength plate faces the polarization separation element with a gap therebetween.

An image display device according to an embodiment of the present technology includes a polarization conversion element.
The polarization conversion element includes a polarization separation element, an inorganic wavelength plate, and a support.
The polarization separation element includes: a first glass substrate having a first bonding surface; a second glass substrate having a second bonding surface; and an optical functional film provided on the first bonding surface; And an inorganic bonding layer made of a silicon compound that is provided between the optical functional film and the second bonding surface and bonded to the second bonding surface by direct bonding.
The inorganic wave plate converts the first polarized light transmitted through the inorganic bonding layer into a second polarized light orthogonal to the first polarized light.
The support supports the polarization separation element and the inorganic wavelength plate in common so that the inorganic wavelength plate faces the polarization separation element with a gap therebetween.

The method of manufacturing an optical element according to an aspect of the present technology is as follows.
Forming an optical functional film on the surface of the first glass substrate;
Forming an inorganic bonding layer made of a silicon compound on the optical functional film;
A second glass substrate is bonded to the inorganic bonding layer by plasma bonding.

In the method for manufacturing the optical element, after the inorganic bonding layer is formed, the bonding surface of the inorganic bonding layer and the second glass substrate may be polished before bonding the second glass substrate. Good.

Alternatively, before the optical functional film is formed, the method for manufacturing the optical element comprises polishing the surface of the first glass substrate and bonding the second glass substrate to the inorganic bonding layer. The bonding surface of the second glass substrate may be polished.

The optical functional film may be formed by ion beam sputtering or bias sputtering.

As described above, according to the present technology, an optical element having excellent heat resistance, light resistance, and light transmittance can be obtained.
Note that the effects described here are not necessarily limited, and may be any of the effects described in the present disclosure.

It is an exploded perspective view showing the composition of the polarization conversion element concerning one embodiment of this art. It is a schematic sectional drawing of the principal part which shows the structure of the said polarization conversion element. It is a schematic sectional drawing of the principal part which shows the structure of the polarization separation element in the said polarization conversion element. It is a figure explaining the preparation methods of the said polarization splitting element. It is a figure explaining the preparation methods of the said polarization splitting element. It is a schematic process drawing which shows an example of the manufacturing method of the said polarization splitting element. It is a schematic diagram which shows an example of the layer structure of the polarization separation film in the said polarization separation element. It is a schematic process drawing which shows another example of the manufacturing method of the said polarization splitting element. It is a figure which shows an example of the optical characteristic of the said polarization splitting element. It is a schematic structure figure showing an image display device concerning one embodiment of this art.

Hereinafter, embodiments of the present technology will be described with reference to the drawings.

<First Embodiment>
FIG. 1 is an exploded perspective view illustrating a configuration of a polarization conversion element 100 according to an embodiment of the present technology, and FIG. 2 is a schematic cross-sectional view of a main part of the polarization element 100. The polarization conversion element 100 includes a polarization separation element 10, an inorganic wavelength plate 20, and a support 30 that supports them. The polarization conversion element 100 is an optical element that converts non-polarized incident light L into predetermined polarized light (P-polarized light in this example).

[Polarized light separation element]
The polarization separation element 10 has a light incident surface 101 and a light emitting surface 102. The polarization separation element 10 is an optical element (polarization beam splitter) that transmits or reflects the incident light L depending on the polarization direction of the incident light L.

The polarization separation element 10 is configured, for example, by bonding a plurality of parallelepiped prisms in the Z-axis direction. In the present embodiment, the plurality of prisms includes a first glass substrate 11 and a second glass substrate 12. Between the first glass substrate 11 and the second glass substrate 12, the S-polarized light is reflected, the polarization separation layer 13 that transmits the P-polarized light, and the S-polarized light reflected by the polarization separation layer 13 is reflected again. The reflective layers 14 are alternately arranged.

FIG. 3 is a schematic cross-sectional view of the main part showing the configuration of the polarization separation element 10. As shown in the figure, the polarization separation layer 13 is composed of a laminate of a polarization separation film 131 and an inorganic bonding layer 132.

The polarization separation film 131 is an optical functional film that reflects the S-polarized light Ls and transmits the P-polarized light Lp, and is a dielectric that covers the bonding surface 11 a (first bonding surface) of the first glass substrate 11. It consists of a multilayer film. The angle formed by the joint surface 11a and the incident surface 101 is typically 45 °. The polarization separation film 131 is an optical multilayer film in which a first dielectric having a first refractive index and a second dielectric having a second refractive index different from the first refractive index are alternately stacked. is there.

The first dielectric is made of a material having a refractive index (nd) smaller than that of the second dielectric. The refractive index of each of the first dielectric and the second dielectric is selected according to the refractive indices of the first and

second glass substrates

11 and 12. For example, when the refractive index (nd) of the first and

second glass substrates

11 and 12 is 1.6 to 1.8, the first dielectric is SiO ₂ (nd: 1.46), The dielectric is Ta ₂ O ₅ (nd: 2.16). Examples of the glass material having a refractive index (nd) of 1.6 to 1.8 include OHARA glass material S-TIH (nd: 1.72).

The inorganic bonding layer 132 is provided between the polarization separation film 131 and the bonding surface 12a (second bonding surface) of the second glass substrate 12. The joint surface 12a is a plane parallel to the joint surface 11a. The inorganic bonding layer 132 is made of a silicon compound and bonded to the bonding surface 12a of the second glass substrate 12 by direct bonding. The surface of the inorganic bonding layer 132 facing the bonding surface 12a forms a bonding interface that is directly bonded to the second glass substrate 12. That is, the inorganic bonding layer 132 functions as a buffer layer for forming the bonding interface. The buffer layer constitutes a part of the polarization separation layer 13 and is laminated on the polarization separation film 131 to achieve a predetermined polarization separation function.

Examples of the silicon compound constituting the inorganic bonding layer 132 include silicon oxide (SiO ₂ , SiO), silicon nitride (SiN), silicon oxynitride (SiON), silicon oxycarbide (SiOC), and the like. Since the inorganic bonding layer 132 is directly bonded to the bonding surface 12a of the second glass substrate 12, the inorganic bonding layer 132 is bonded integrally to the bonding surface 12a without interposing an adhesive at the interface. Can do.

Examples of direct bonding include plasma bonding. In the plasma bonding, the inorganic bonding layer 132 is firmly fixed to the bonding surface 12a by forming a silicon-oxygen covalent bond or a silicon-silicon covalent bond between the inorganic bonding layer 132 and the bonding surface 12a. The direct bonding may employ a solid phase bonding method such as diffusion bonding in addition to plasma bonding.

In the present embodiment, the inorganic bonding layer 132 is made of silicon oxide, particularly silicon dioxide. As a result, a refractive index close to that of a glass material containing SiO ₂ as a main component is obtained. Therefore, although there is a difference in refractive index at the bonding interface between the inorganic bonding layer 132 and the second glass substrate 12, the thickness of the bonding interface is small. Since it is sufficiently smaller than the wavelength of 1 nm or less, reflection caused by the difference in refractive index can be eliminated.

The surface roughness (Ra) of the inorganic bonding layer 132 and the bonding surface 12a is 2 nm or less. Thereby, the direct joining process by the plasma joining of the inorganic joining layer 132 with respect to the 2nd glass base material 12 can be performed stably. The surface roughness (Ra) of the inorganic bonding layer 132 and the bonding surface 12a is preferably 1 nm or less, and more preferably 0.5 nm or less.

The thickness of the inorganic bonding layer 132 may be sufficient to form the bonding interface, and is, for example, 200 nm or more and 1000 nm or less. Thereby, since the joining thickness between the 1st and 2nd

glass base materials

11 and 12 can be made small, while being able to achieve size reduction of the polarization separation element 10 and the polarization conversion element 100, it is 2nd glass. The amount of gas generated by heating at the time of joining to the substrate 12 can be suppressed. By setting the thickness of the inorganic bonding layer 132 to 200 nm or more, the inorganic bonding layer 132 can function as a part of the polarization separation layer 13 (low refractive index material layer). Note that the thickness of the inorganic bonding layer 132 may be less than 200 nm, and is not particularly limited as long as a bonding interface can be formed.

On the other hand, the reflection layer 14 is an optical functional film that reflects the S-polarized light Ls reflected by the polarization separation layer 13 again toward the light exit surface 102, and includes the first glass substrate 11 and the second glass substrate. 12 is arranged in parallel with the polarization separation layer 13. The reflective layer 14 is composed of, for example, a dielectric multilayer film. Examples of the dielectric multilayer film include a multilayer film in which silicon oxide and titanium oxide are alternately laminated. The reflective layer 14 may be composed of a dielectric multilayer film.

After the dielectric multilayer film is formed on the surface of the first glass substrate 11 (surface opposite to the bonding surface 11a), the reflective layer 14 is formed on the surface of the second glass substrate 12 (bonding surface 12a). To the opposite surface). The bonding method is not particularly limited, and may be direct bonding or bonding using an adhesive. In the case of direct bonding, a silicon dioxide film is formed on the surface of the dielectric multilayer film, and the silicon oxide film is bonded to the first glass substrate 11 by plasma bonding.

For example, as shown in FIG. 4, the polarization separation element 10 is an element set in which a second glass substrate 12 is bonded to both surfaces of a first glass substrate 11 on which a polarization separation layer 13 and a reflection layer 14 are formed. The body 10M is formed by cutting along the cutting line C. As shown in FIGS. 5A to 5C, each polarization separating element 10p separated into pieces is lapped at both ends in the longitudinal direction, and

antireflection films

101m and 102m are formed on the light incident surface 101 and the light emitting surface 102, respectively. After that, both ends are joined in the longitudinal direction.

[Inorganic wave plate]
The inorganic wavelength plate 20 is an optical element (half wavelength plate) that converts the S-polarized light Ls reflected by the reflective layer 14 into P-polarized light Lp. The inorganic wavelength plate 20 is typically formed of a rectangular crystal plate that is long in the X-axis direction, and is disposed at a predetermined interval on the light emitting surface 102 of the polarization separation element 10.

An antireflection film 21 is formed on each surface of the inorganic wave plate 20 on the light incident side and the light emitting side. The antireflection film 21 is a dielectric multilayer film, and is composed of a dielectric multilayer film such as magnesium fluoride (MgF ₂ ), silicon dioxide (SiO ₂ ), TiO ₂ , Ta ₂ O _{5, for} example.

The inorganic wave plate 20 has a long strip shape in the X-axis direction, and a plurality of inorganic wave plates 20 are arranged at intervals on the optical path of the reflected light (S-polarized light Ls) from the reflective layer 14 as shown in FIG. . Each inorganic wave plate 20 is supported in common by the second support frame 120.

[Support]
The support 30 is constituted by a joined body of the first support frame 110 and the second support frame 120. The first support frame 110 is made of a metal plate having a plurality of apertures 111 and is disposed on the light incident surface 101 side of the polarization separation element 10. The second frame 120 is configured by a frame-shaped metal plate disposed on the light exit surface 102 side of the polarization separation element 10. The first support frame 110 and the second support frame 120 are bonded to each other via the adhesive layer 130 or an appropriate connection mechanism with the polarization separation element 10 and the inorganic wavelength plate 20 interposed therebetween.

The support 30 supports the polarization separation element 10 and the inorganic wavelength plate 20 in common so that the inorganic wavelength plate 20 faces a predetermined position of the light exit surface 102 of the polarization separation element 10. Thereby, the relative positional relationship between the polarization separation element 10 and the inorganic wavelength plate 20 is maintained without mutually bonding the polarization separation element 10 and the inorganic wavelength plate 20 with an adhesive or the like. Accordingly, it is possible to avoid a decrease in heat resistance, light resistance, and translucency due to the presence of the adhesive between the polarization separation element 10 and the inorganic wave plate 20.

The first support frame 110 has a frame shape and is in contact with the light incident surface 101 of the polarization separation element 10. The second support frame 120 has a plate shape in which an opening for supporting the inorganic wave plate 20 is formed in the plane. The first and second support frames 110 and 120 are secured to each other by reinforcing the periphery. The constituent material is not particularly limited, and is typically composed of a metal material. The adhesive layer 130 is made of an organic material such as an ultraviolet curable resin, adheres between the second support frame 120, the inorganic wave plate 20, and the polarization separation element 10, and is disposed in a region where the incident light L is not irradiated. . Thereby, deterioration of the adhesive layer 130 due to light irradiation can be avoided.

[Production Method of Polarization Separation Element]
Then, the manufacturing method of the polarization separation element 10, especially the manufacturing method of the polarization separation layer 13, is demonstrated.

The method for manufacturing the polarization separation element 10 of the present embodiment includes a step of forming the polarization separation film 131 on the surface (bonding surface 11a) of the first glass substrate 11, and an inorganic material made of a silicon compound on the polarization separation film 131. There are a step of forming the bonding layer 132 and a step of bonding the second glass substrate 12 to the inorganic bonding layer 132 by plasma bonding.

(Method 1)
FIG. 6 is a schematic process diagram showing an example of a method for manufacturing the polarization separation element 10. In this example, the polarization separation film 131 and the inorganic bonding layer 132 are formed on the first glass substrate 11 (FIG. 6A), and the surface of the inorganic bonding layer 132 and the bonding surface 12a of the second glass substrate 12 are formed. After planarization by polishing (FIG. 6B), the inorganic bonding layer 132 and the second glass substrate 12 are directly bonded (FIG. 6C). That is, in this example, after forming the inorganic bonding layer 132 and before bonding the second glass substrate 12, the bonding surface 12a of the inorganic bonding layer 132 and the second glass substrate 12 is polished.

A method for forming the polarization separation film 131 and the inorganic bonding layer 132 is not particularly limited, and a sputtering method, an ion beam sputtering method, a vacuum evaporation method, an ion assist evaporation method, or the like is applicable. For example, SiO ₂ can be used as the low refractive index material layer, and Ta ₂ O ₅ can be used as the high refractive index material layer for the dielectric multilayer film constituting the polarization separation film 131. The thickness, the number of layers, etc. of each material layer can be appropriately set according to the required polarization separation characteristics. As an example, as shown in FIG. 7, the polarization separation film 131 is composed of a 12-layer dielectric multilayer film, and a silicon dioxide film constituting the inorganic bonding layer 132 is formed on the upper layer (13th layer).

The bonding surface 12a of the inorganic bonding layer 132 and the second glass substrate 12 is polished so that the surface roughness (Ra) is 1 nm or less, more preferably 0.5 nm or less. The polishing method is not particularly limited, and typically, a high-accuracy polishing method that can adjust the surface roughness on the order of nm is employed. Thereby, desired joining strength can be obtained by plasma joining described later.

By polishing the surface of the inorganic bonding layer 132, the surface roughness necessary for bonding to the second glass substrate 12 can be obtained, and thus the film is formed on the bonding surface 11a of the first glass substrate 11 and on the surface. The surface roughness of the polarization separation film 131 may be 1 nm or more. Thereby, the processing cost of the bonding surface 11a and the film thickness control of the polarization separation film 131 are facilitated. In addition, since the thickness of the inorganic bonding layer 132 is reduced by polishing, the inorganic bonding layer 132 is formed to a thickness of, for example, 5000 nm, and then polished to a thickness of, for example, 2000 nm or less.

Plasma bonding is used for bonding the inorganic bonding layer 132 and the second glass substrate 12. In plasma bonding, first, plasma activation treatment is performed on the surface of the inorganic bonding layer 132 on the first glass substrate 11 and the bonding surface 12 a of the second glass substrate 12. As a result, OH groups are generated on the surface of the inorganic bonding layer 132 and the bonding surface 12a so as to be hydrophilized.

As a gas used for the plasma activation treatment, oxygen (O ₂ ), nitrogen (N ₂ ), helium (He), argon (Ar), hydrogen (H ₂ ), or the like can be used. In particular, by using the same kind of gas (oxygen in this example) as that of the constituent elements of the inorganic bonding layer 132 and the bonding surface 12a, alteration of the inorganic bonding layer 132 and the bonding surface 12a can be suppressed.

Subsequently, the inorganic bonding layer 132 and the second glass substrate 12 are bonded together, and a temporary bonding state is obtained by hydrogen bonding between the OH groups. In this state, for example, heat treatment (annealing) is performed at a temperature of 200 ° C. or more, and Si—OH at the interface is subjected to a dehydration condensation reaction to form a silicon-oxygen covalent bond or a silicon-silicon covalent bond, thereby completing plasma bonding. .

(Method 2)
FIG. 8 is a schematic process diagram illustrating another example of the method of manufacturing the polarization separation element 10. In this example, the bonding surface 11a of the first glass substrate 11 and the bonding surface 12a of the second glass substrate 12 are flattened by polishing (FIG. 8A), and polarized on the bonding surface 11a of the first glass substrate. After the separation membrane 131 and the inorganic bonding layer 132 are sequentially formed (FIG. 8B), the inorganic bonding layer 132 and the second glass substrate 12 are directly bonded (FIG. 8C). That is, in this example, before the polarization separation layer 13 is formed, the bonding surface 11a of the first glass substrate is polished, and before the second glass substrate 12 is bonded to the inorganic bonding layer 132, the first The bonding surface 12a of the second glass substrate 12 is polished.

As a method for forming the polarization separation film 131 and the inorganic bonding layer 132, a film forming method with high surface flatness is used in this example. As such a film forming method, for example, a film forming method having a small surface roughness such as ion beam sputtering, bias sputtering or the like can be applied, whereby the surface roughness (Ra) is, for example, A vapor deposition film having a high flatness of 0.5 nm or less can be formed. Since the polarization separation layer 13 is formed by such a film forming method, the surface of the inorganic bonding layer 132 can be formed with a desired flatness without requiring polishing treatment. Can be reduced to about 200 nm, for example.

In the bonding step between the inorganic bonding layer 132 and the second glass substrate 12, a plasma bonding process similar to the method 1 described above is performed. In this example, since the thickness of the inorganic bonding layer 132 can be reduced, there is an advantage that the amount of degassing from the inorganic bonding layer 132 during annealing can be reduced.

In the polarization conversion element 100 of the present embodiment configured as described above, the joint between the polarization separation layer 13 and the joint surface 12a of the second glass substrate 12 is composed of an inorganic joint layer 132 made of a silicon compound. Therefore, improvement in heat resistance and light resistance can be realized. Further, since the inorganic bonding layer 132 is directly bonded to the bonding surface 12a by bonding, there is a difference in refractive index at the bonding interface, but the thickness of the bonding interface is 1 nm or less, which is sufficiently smaller than the wavelength. Thus, the transmittance can be improved by eliminating reflection.

For example, FIG. 9 shows the optical characteristics of the polarization separation element 10 produced by the above-described method 1. FIG. 9 confirms that a high polarization extinction ratio can be obtained in the visible light region. Although not shown, it has been confirmed that the same optical characteristics as in FIG. 9 can be obtained even by the polarization separation element manufactured by the above-described method 2.

Here, generally, when a polarization separation film is formed using a general-purpose glass (white plate glass, blue plate glass, BK7, etc.) having a refractive index (nd) of around 1.5 as a glass substrate, a low refractive index material If MgF ₂ (magnesium fluoride, nd: 1.38) is not used, it is difficult to obtain desired optical characteristics (transmittance). However, since MgF ₂ has a large film stress, it is difficult to form a dielectric multilayer film, and the multilayer film is destroyed when the temperature is raised to 200 ° C. during bonding. For this reason, the polarization separation film cannot be bonded to the glass substrate by direct bonding such as plasma bonding, and it has been necessary to use an organic adhesive such as an ultraviolet curable adhesive.
However, since an organic adhesive is used at the joint between the glass substrate and the polarization separation film, heat resistance is low, and deterioration due to light is inevitable.

On the other hand, according to the polarization separation element 10 of the present embodiment, since no organic adhesive is present at the joint between the glass substrate and the polarization separation film, the heat resistance and light resistance are improved. Therefore, it is possible to sufficiently cope with higher output or higher density of light energy. In addition, since there is no adhesive on the optical path of light, there is a difference in refractive index at the bonding interface, but the thickness of the bonding interface is 1 nm or less, which is sufficiently smaller than the wavelength, so that reflection caused by the difference in refractive index is eliminated. The transmittance can be improved.

In addition, in the present embodiment, since glass materials having a refractive index of 1.6 or more and 1.8 or less are used for the first and second

glass base materials

11 and 12, carbon dioxide is used as the low refractive index material of the polarization separation film 131. Desirable optical characteristics can be ensured by using silicon and a general material such as TiO ₂ and Ta ₂ O ₅ as a high refractive index material.

Furthermore, according to the polarization conversion element 100 of the present embodiment, since the inorganic wavelength plate 20 is supported in common by the support 30 that supports the polarization separation element 10, on the optical path from the polarization separation element 10 to the inorganic wavelength plate 20. The inorganic wave plate 20 can be disposed in a non-contact manner with respect to the light exit surface 102 of the polarization separation element 10 without interposing an organic adhesive on the surface. Thereby, the heat resistance, light resistance, and light transmittance of the polarization conversion element 100 can be improved.

In general, MgF _{2 having} a large film stress in a low refractive index material with respect to quartz having a refractive index (nd) of 1.45 or general-purpose glass of about 1.5 (white plate glass, blue plate glass, BK7, Bolofloat, etc.) The present technology can also be applied when using. In this case, when the temperature is increased at the time of bonding, microcracks may be generated in the multilayer film or the optical characteristics may be deteriorated, but the device can be manufactured.

Similarly, silicon dioxide with a low film stress is used as a low refractive index material for quartz having a refractive index (nd) of 1.45 or general-purpose glass (white glass, blue glass, BK7, Bolofloat, etc.) near 1.5. May be. In this case, the optical characteristics are also inferior, but the device can be manufactured.

<Second Embodiment>
Subsequently, an image display apparatus including an illumination optical system having the polarization conversion element 100 configured as described above will be described. FIG. 10 is a schematic configuration diagram illustrating an image display device 200 according to an embodiment of the present technology.

The image display apparatus 200 according to the present embodiment modulates the illumination optical system 240 that emits polarized light, the spectroscopic optical system 250 that splits the light emitted from the illumination optical system 240, and the light that is split by the spectroscopic optical system 250, respectively.

Liquid crystal panels

63, 68, 73 are provided. The image display apparatus 200 includes a light combining unit 80 that combines the lights modulated by the

liquid crystal panels

63, 68, and 73, and a projection lens 90 that projects the light combined by the light combining unit 80.

In the illumination optical system 240, the white light emitted from the light source 41 such as an ultra-high pressure mercury lamp is reflected by the reflector 42 and transmitted through the explosion-proof glass 43. The UV cut filter 44 removes ultraviolet rays from the light transmitted through the explosion-proof glass 43. The light transmitted through the UV cut filter 44 is reduced in luminance unevenness by the first fly-eye lens 45 and the second fly-eye lens 46 and enters the polarization conversion element 100. The polarization conversion element 100 converts incident light into, for example, P-polarized light. Then, this P-polarized light is emitted from the illumination optical system 240.

The light emitted from the illumination optical system 240 is collimated by the condenser lens 48 and enters the spectroscopic optical system 250. The spectroscopic optical system 250 includes a dichroic mirror 49 that transmits blue light out of white light from the illumination optical system 240 and reflects red light and green light. The spectroscopic optical system 250 includes a dichroic mirror 53 that is disposed on the optical path of the light reflected by the dichroic mirror 49, reflects green light, and transmits red light.

The blue light that has passed through the dichroic mirror 49 passes through the UV absorption filter 51, so that the ultraviolet rays are cut off. The blue light transmitted through the UV absorption filter 51 is reflected by the mirror 52 and enters the condenser lens 61. The blue light condensed by the condenser lens 61 is made to be linearly polarized by the incident side polarizing plate 62 and the polarization direction is aligned, and enters the liquid crystal panel 63. An emission side polarizing plate 64 as an analyzer is disposed at the subsequent stage of the liquid crystal panel 63, and transmits only light having a predetermined polarization direction among the light transmitted through the liquid crystal panel 63.

As the liquid crystal panel 63, for example, a twisted nematic type can be used. In this case, a signal voltage for blue light corresponding to image information is applied to each pixel of the liquid crystal panel 63, and the polarization direction of the blue light transmitted through each pixel is rotated according to this voltage. By transmitting blue light having a different polarization direction for each pixel through the exit-side polarizing plate 64, blue image light having an intensity distribution corresponding to image information is obtained. The blue light that has passed through the exit-side polarizing plate 64 is transmitted through a half-wave film 65 provided on the incident surface of the light combining unit 80 so that the polarization direction is rotated by 90 °, and then the light combining unit 80 such as a combining prism. Is incident on.

The green light reflected by the dichroic mirror 53 enters the condenser lens 66. The green light condensed by the condenser lens 66 becomes linearly polarized light by the incident side polarizing plate 67 and enters the liquid crystal panel 68. The liquid crystal panel 68 rotates the polarization direction of the green light transmitted through each pixel according to the image information. The green light transmitted through the liquid crystal panel 68 is transmitted through the exit side polarizing plate 69, whereby green image light having an intensity distribution corresponding to the image information is obtained. The green light that has passed through the emission-side polarizing plate 69 enters the light combining unit 80.

On the other hand, the red light transmitted through the dichroic mirror 53 enters the wavelength selection filter 56 via the condenser lens 54 and the mirror 55. The wavelength selection filter 56 is configured by a band pass filter or the like, and transmits only effective red light to the subsequent stage. The red light that has passed through the wavelength selection filter 56 enters the condenser lens 71 via the condenser lens 57 and the mirror 58.

The red light condensed by the condenser lens 71 becomes linearly polarized light by the incident side polarizing plate 72 and enters the liquid crystal panel 73. The liquid crystal panel 73 rotates the polarization direction of the red light transmitted through each pixel according to the image information. The red light transmitted through the liquid crystal panel 73 is transmitted through the exit side polarizing plate 74, whereby red image light having an intensity distribution corresponding to the image information is obtained. The red light that has passed through the exit-side polarizing plate 74 passes through the half-wave film 75 provided on the incident surface of the light combining unit 80, and the polarization direction is rotated by 90 °, and then enters the light combining unit 80.

The light combining unit 80 combines red light, green light, and blue light on the same optical path. The combined light emitted from the combining prism is enlarged and projected onto a screen (not shown) by the projection lens 90.

Here, a transmissive liquid crystal panel is shown as a modulator that modulates light according to image information. However, modulation is performed by a reflective liquid crystal panel or other methods using GLV (Grating Light Valve) or the like. It may be broken.

According to the image display apparatus 200 of the present embodiment, since the illumination optical system 240 includes the polarization conversion element 100 described in the first embodiment, the illumination optical system is excellent in heat resistance, light resistance, and light transmittance. Can be built. In addition, since it is possible to cope with higher output of the light source or higher density of light energy, a high-luminance image can be formed.

As mentioned above, although embodiment of this technique was described, this technique is not limited only to the above-mentioned embodiment, Of course, a various change can be added.

For example, in the above embodiment, the polarization separation film 131 of the polarization separation element 10 is configured by an optical functional film that reflects S-polarized light and transmits P-polarized light. However, the present invention is not limited to this. It may be composed of an optical functional film that transmits light. Alternatively, the inorganic wave plate 20 is not limited to a wave plate that converts S-polarized light into P-polarized light, and a wave plate that converts P-polarized light into S-polarized light may be used.

The number of layers of the polarization separation film 131 is not limited to 12 and may be, for example, 9 to 13 layers. The thickness of each layer can also be set arbitrarily. The total thickness of the polarization separation film 131 is not particularly limited, and can be appropriately set, for example, at 1500 to 2000 nm.

Further, in the above embodiment, the polarization separation element having a polarization separation film is described as an example of the optical element. However, the present invention is not limited to this, and an optical element having an optical function film such as an antireflection film or a wavelength selection film is used. This technique is also applicable.

In addition, this technique can also take the following structures.
(1) a first glass substrate having a first bonding surface;
A second glass substrate having a second bonding surface;
An optical functional film covering the first bonding surface;
An optical element comprising: an inorganic bonding layer made of a silicon compound that is provided between the optical functional film and the second bonding surface and bonded to the second bonding surface by direct bonding.
(2) The optical element according to (1) above,
The optical element is a silicon oxide.
(3) The optical element according to (1) or (2) above,
The direct bonding is a plasma bonding optical element.
(4) The optical element according to any one of (1) to (3) above,
Surface roughness (Ra) of the inorganic bonding layer and the second bonding surface is 2 nm or less.
(5) The optical element according to any one of (1) to (4) above,
The thickness of the said inorganic joining layer is 200 nm or more and 1000 nm or less. Optical element.
(6) The optical element according to any one of (1) to (5) above,
The optical functional film is an optical multilayer film in which a first dielectric having a first refractive index and a second dielectric having a second refractive index different from the first refractive index are alternately stacked. An optical element.
(7) The optical element according to (6) above,
The optical multilayer film is a polarization separation film.
(8) The optical element according to (7) above,
The first glass substrate and the refractive index of the second glass substrate, respectively (n _d), the optical element is 1.6 to 1.8.
(9) a first glass substrate having a first bonding surface, a second glass substrate having a second bonding surface, an optical functional film provided on the first bonding surface, and the optical A polarization beam splitting element having an inorganic bonding layer made of a silicon compound provided between the functional film and the second bonding surface and bonded to the second bonding surface by direct bonding;
An inorganic wave plate that converts the first polarized light transmitted through the inorganic bonding layer into a second polarized light that is orthogonal to the first polarized light, and the inorganic wave plate that faces the polarization separation element with a gap therebetween A polarization conversion element comprising: a support that commonly supports the polarization separation element and the inorganic wavelength plate.
(10) a first glass substrate having a first bonding surface, a second glass substrate having a second bonding surface, an optical functional film provided on the first bonding surface, and the optical A polarization beam splitting element having an inorganic bonding layer made of a silicon compound provided between the functional film and the second bonding surface and bonded to the second bonding surface by direct bonding;
An inorganic wave plate that converts the first polarized light transmitted through the inorganic bonding layer into a second polarized light that is orthogonal to the first polarized light, and the inorganic wave plate that faces the polarization separation element with a gap therebetween Thus, the image display apparatus which comprises the polarization conversion element which has the support body which supports the said polarization separation element and the said inorganic wavelength plate in common.
(11) forming an optical functional film on the surface of the first glass substrate;
Forming an inorganic bonding layer made of a silicon compound on the optical functional film;
A method for manufacturing an optical element, wherein the second glass substrate is bonded to the inorganic bonding layer by plasma bonding.
(12) The method for manufacturing an optical element according to (11), further comprising:
After forming the inorganic bonding layer, the bonding surface of the inorganic bonding layer and the second glass substrate is polished before bonding the second glass substrate.
(13) The method for manufacturing an optical element according to (11), further comprising:
Before forming the optical functional film, the surface of the first glass substrate is polished,
A method for producing an optical element, comprising: polishing a bonding surface of the second glass substrate before bonding the second glass substrate to the inorganic bonding layer.
(14) The method for manufacturing an optical element according to any one of (11) to (13) above,
The inorganic bonding layer is formed by ion beam sputtering or bias sputtering. An optical element manufacturing method.

DESCRIPTION OF SYMBOLS 10 ... Polarization separation element 11 ... 1st glass base material 12 ... 2nd glass base material 13 ... Polarization separation layer 14 ... Reflection layer 20 ... Inorganic wavelength plate 30 ... Support body 100 ... Wavelength conversion element 131 ... Polarization separation film 132 ... Inorganic bonding layer 200 ... Image display device

Claims

A first glass substrate having a first bonding surface;
A second glass substrate having a second bonding surface;
An optical functional film covering the first bonding surface;
An optical element comprising: an inorganic bonding layer made of a silicon compound that is provided between the optical functional film and the second bonding surface and bonded to the second bonding surface by direct bonding.
The optical element according to claim 1,
The optical element is a silicon oxide.
The optical element according to claim 1,
The direct bonding is a plasma bonding optical element.
The optical element according to claim 1,
Surface roughness (Ra) of the inorganic bonding layer and the second bonding surface is 2 nm or less.
The optical element according to claim 1,
The thickness of the said inorganic joining layer is 200 nm or more and 1000 nm or less. Optical element.
The optical element according to claim 1,
The optical functional film is an optical multilayer film in which a first dielectric having a first refractive index and a second dielectric having a second refractive index different from the first refractive index are alternately stacked. An optical element.
The optical element according to claim 6,
The optical multilayer film is a polarization separation film.
The optical element according to claim 7,
The first glass substrate and the refractive index of the second glass substrate, respectively (n d), the optical element is 1.6 to 1.8.
A first glass substrate having a first bonding surface; a second glass substrate having a second bonding surface; an optical functional film provided on the first bonding surface; and the optical functional film; A polarization separation element having an inorganic bonding layer made of a silicon compound provided between the second bonding surface and directly bonded to the second bonding surface;
An inorganic wave plate that converts the first polarized light transmitted through the inorganic bonding layer into a second polarized light that is orthogonal to the first polarized light, and the inorganic wave plate that faces the polarization separation element with a gap therebetween A polarization conversion element comprising: a support that commonly supports the polarization separation element and the inorganic wavelength plate.
A first glass substrate having a first bonding surface; a second glass substrate having a second bonding surface; an optical functional film provided on the first bonding surface; and the optical functional film; A polarization separation element having an inorganic bonding layer made of a silicon compound provided between the second bonding surface and directly bonded to the second bonding surface;
An inorganic wave plate that converts the first polarized light transmitted through the inorganic bonding layer into a second polarized light that is orthogonal to the first polarized light, and the inorganic wave plate that faces the polarization separation element with a gap therebetween Thus, the image display apparatus which comprises the polarization conversion element which has the support body which supports the said polarization separation element and the said inorganic wavelength plate in common.
Forming an optical functional film on the surface of the first glass substrate;
Forming an inorganic bonding layer made of a silicon compound on the optical functional film;
A method for manufacturing an optical element, wherein the second glass substrate is bonded to the inorganic bonding layer by plasma bonding.
The method of manufacturing an optical element according to claim 11, further comprising:
After forming the inorganic bonding layer, the bonding surface of the inorganic bonding layer and the second glass substrate is polished before bonding the second glass substrate.
The method of manufacturing an optical element according to claim 11, further comprising:
Before forming the optical functional film, the surface of the first glass substrate is polished,
A method for producing an optical element, comprising: polishing a bonding surface of the second glass substrate before bonding the second glass substrate to the inorganic bonding layer.
It is a manufacturing method of the optical element according to claim 11,
The optical functional film is formed by an ion beam sputtering method or a bias sputtering method.