JP2748066B2 - Reflector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflector used in various optical systems, and more particularly to a silver reflector having a plurality of protective layers on a silver layer.

[0002]

2. Description of the Related Art A silver reflector formed by depositing a silver layer on a substrate is known as a reflector used in various optical systems.

[0003] Silver reflecting mirrors have attracted attention because they have higher reflectance in the visible light region and higher spectral reflection characteristics than aluminum reflecting mirrors.

[0004] While a silver reflecting mirror has such an advantage, it has a problem in strength such as durability, so that a mirror provided with a protective layer on a silver layer is known.

[0005] As a protective layer of a silver reflector, a layer formed by laminating aluminum oxide, zirconium oxide and silicon dioxide in this order is known, thereby improving abrasion resistance while maintaining good reflection characteristics. be able to.

[0006]

By the way, the quality of the polarization characteristics of the silver reflecting mirror is judged by the difference between the P-polarized light reflectance and the S-polarized light reflectance. Since the reflectance greatly changes, it is preferable that the difference in the reflectance be within about 1% especially in the visible region.

However, when the above-mentioned protective layer is laminated on the silver layer, the difference in the reflectivity may be larger than about 1%.

The present invention has been made in view of such circumstances, and provides a reflector having a three-layered protective film capable of making the difference in reflectance between P-polarized light and S-polarized light within the visible region within about 1%. The purpose is to do so.

[0009]

According to the present invention, there is provided a reflector comprising a silver layer, an aluminum oxide layer, a zirconium oxide layer and a silicon dioxide layer laminated on a substrate in this order. The thickness of the zirconium oxide layer is set to a thickness of 37 nm to 77 nm, and the thickness of the silicon dioxide layer is set to a thickness of 60 nm to 100 nm. It is.

Note that the above configuration does not mean that other layers are not provided between the substrate and the silver layer and between the silver layer and the aluminum oxide layer.

[0011]

According to the above structure, an aluminum oxide layer having a thickness of not less than 49 nm and not more than 89 nm is used as a protective layer of the silver reflecting mirror.
Zirconium oxide layer with a thickness of not less than nm and not more than 77 nm and thickness of 60 nm
A silicon dioxide layer having a thickness of 100 nm or less is laminated in this order.

In the above three-layer thickness range, polarization characteristics are good for incident light in the visible region. That is, according to the experimental results of the present inventors, if the thickness of the three layers is set in the above range, the difference between the reflectances of the P-polarized light and the S-polarized light in the visible region can be made within about 1%. Therefore, according to the reflecting mirror of the present invention, it is possible to prevent the polarization characteristics from being deteriorated due to the provision of the protective layer.

[0013]

Embodiments of the present invention will be described below.

FIG. 1 is a schematic diagram showing a layer configuration of a reflecting mirror according to an embodiment of the present invention. This reflecting mirror comprises a Cr layer 2 having a thickness of 5 to 15 nm, a Cu layer 3 having a thickness of 10 to 40 nm,
m thick Ag layer 4,49nm~89nm thickness of Al ₂ O ₃ ZrO ₂ (zirconium oxide, refractive index 1.98) of (aluminum oxide) layer 5,37nm~77nm thick layer 6 and 60nm~100nm thick Si
An O ₂ (silicon dioxide) layer 7 is laminated in this order.

The Cr layer 2 and the Cu layer 3 function as an adhesion strengthening layer for enhancing the adhesion between the glass substrate 1 and the Ag layer 4. The Ag layer 4 is a layer for reflecting incident light. The above Al ₂ O ₃ layer 5 is the Ag layer 4
Is a protective layer for improving the durability of the film. Also, Zr
The O ₂ layer 6 is a protective layer for improving the durability of the Ag layer 4 and a high refractive index dielectric layer for improving the reflection characteristics. Further, the uppermost SiO ₂ layer 7 is a protective layer for improving abrasion resistance.

Next, a method of manufacturing the reflecting mirror having the layer structure shown in FIG. 1 will be described.

First, the cleaned glass substrate 1 is mounted on a holder, which is inserted into a vacuum chamber and fixed. The inside of the vacuum chamber is evacuated without heating to about 1 × 10 ⁻⁶ Torr.

Thereafter, a Cr layer 2 having a thickness of 5 to 15 nm is formed on the glass substrate 1 by using an electron beam evaporation method. Next, 10 to 40 nm thick C is deposited on the Cr layer 2 by using a resistance heating evaporation method.
The u layer 3 is formed.

Thereafter, the Cu film is formed by resistance heating evaporation.
An Ag layer 4 having a thickness of 500 nm is formed on the layer 3. Next, a 49 nm to 89 nm thick A is deposited on the Ag layer 4 by using an electron beam evaporation method.
An l ₂ O ₃ layer 5 is formed.

Thereafter, the vacuum chamber is connected to the glass substrate 1.
Is heated to a temperature of 300 ° C. By this heat treatment, the ZrO ₂ layer 6 and SiO ₂
The strength of the layer 7 can be increased.

If the heat treatment is performed at a stage earlier than this, the metal layers such as the Ag layer 4 and the Cu layer 3 are crystallized, and a clouding phenomenon (white turbidity) occurs, and the light reflectance is undesirably reduced.

Thereafter, the above A
A ZrO ₂ layer 6 having a thickness of 37 nm to 77 nm is formed on the l ₂ O ₃ layer 5.

Finally, this Z
An SiO ₂ layer 7 having a thickness of 60 nm to 100 nm is formed on the rO ₂ layer 6.

The reflecting mirror according to the present invention is not limited to the above-described embodiment.

For example, the glass substrate 1 can be replaced with a metal substrate or a plastic substrate.

Further, the Cr layer 2 and the Cu layer 3 can be omitted as appropriate.

Further, the vapor deposition method for forming each layer is not limited to the above-described method. For example, in the above description, when a layer is formed by using an electron beam vapor deposition method, resistance heating is used instead. An evaporation method may be used,
For those using the resistance heating evaporation method, an electron beam evaporation method may be used instead.

By the way, the polarizing characteristics of the silver reflecting mirror tend to be deteriorated by providing a protective layer. In the above embodiment, the thickness of the Al ₂ O ₃ layer 5 is set to 49 nm to 89 nm, and
Since the thickness of the O ₂ layer 6 is set to 37 nm to 77 nm and the thickness of the SiO ₂ layer 7 is set to 60 nm to 100 nm, the difference in reflectance between the P-polarized light and the S-polarized light can be kept within about 1%.

Next, the thickness of the Al ₂ O ₃ layer 5 is set to 69 nm.
The thickness of the ZrO ₂ layer 6 was set to 57 nm,
FIGS. 2 to 10 show the respective spectral reflectance characteristics when the thickness of the O ₂ layer 7 is set every 10 nm from 40 nm to 120 nm.

That is, FIG. 2 shows the case where the thickness of the SiO ₂ layer 7 is 40 nm, FIG. 3 shows the case where the thickness is 50 nm, FIG. 4 shows the case where the thickness is 60 nm, and FIG. 6, FIG. 7 shows the case of 90 nm, FIG. 8 shows the case of 100 nm, FIG. 9 shows the case of 110 nm, and FIG. 10 shows the case of 120 nm.

2 to 10 show spectral reflection characteristics.
The curves are represented. The curve with the symbol S indicates the reflectance of the S-polarized component, the curve with the symbol P indicates the reflectance of the P-polarized component, and the curve located between the two curves will be the S-polarized component and the P-polarized component. It is a curve showing the average value of the reflectance of both components. In addition, all drawings have an incident angle of 45 °
The case where it is set to is shown.

According to FIGS. 2 to 10, the long-wavelength contact point (or intersection point) of the curves S and P moves to the short-wavelength side as the thickness of the SiO ₂ layer 7 increases, and The difference in polarization reflectance in the wavelength region between the points is reduced.
However, when the SiO ₂ layer 7 has a thickness of 100 nm or more, a portion where the difference between the curves S and P becomes larger on the long wavelength side from the contact (or intersection) on the long wavelength side becomes a visible region, so that good polarization characteristics can be obtained. Becomes difficult.

That is, when the SiO ₂ layer 7 has a thickness in the range of 60 nm to 100 nm, the polarization characteristics are good (the reflectance difference between S-polarized light and P-polarized light is within about 1%).

Next, the thickness of the Al ₂ O ₃ layer 5 is set to 49 nm, 69 n
m, 89 nm, and the thickness of the ZrO ₂ layer 6 is 37 nm, 5 nm.
In each case changed to 7 nm and 77 nm, SiO ₂
The thickness difference of the layer 7 was changed to 60 nm, 80 nm, and 100 nm, and the difference between the reflectances of the two polarized lights was measured.
3 is shown.

When the difference in reflectance was within 1% in the entire visible region, the mark was marked with "O", and when the difference was slightly over 1% in a part of the visible region, the mark was marked with "付".

[0036]

[Table 1]

[0037]

[Table 2]

[0038]

[Table 3]

As is clear from the above three tables, Al ₂
In each case where the thickness of the O ₃ layer 5, the thickness of the ZrO ₂ layer 6 and the thickness of the SiO ₂ layer 7 are changed as described above, the reflectance difference between the two polarized lights can be made within about 1%.

The thickness of the SiO ₂ layer 7 is 80 nm and 10 nm.
In the case of 0 nm, the thickness of the Al ₂ O ₃ layer 5 is 89 nm and ZrO
_When the thickness of the _two layers 6 is 77 nm, the reflectance difference becomes larger than about 1%. However, the thickness of the Al ₂ O ₃ layer 5 is slightly reduced or the thickness of the ZrO ₂ layer 6 is slightly reduced. Thereby, it is possible to make the reflectance difference within about 1%.

A film strength test as described below was conducted for the above-described embodiment, but no scratch was generated on the surface of the SiO ₂ layer 7.

That is, in this test method, a clean cheese cloth is pressed against the surface of a reflecting mirror with a force of 1 pound, and reciprocated 25 times on the surface in one direction, and thereafter, the surface of the reflecting mirror is visually inspected for scratches. It is.

[0043]

As described above, according to the reflector of the present invention, by setting the thickness of each of the three protective layers to a predetermined value, the reflectance difference between the P-polarized light and the S-polarized light can be kept within about 1%. The polarization characteristics can be improved while the film strength is enhanced by the protective layer having a three-layer structure.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a layer configuration of a reflecting mirror according to an embodiment of the present invention.

FIG. 2 is a graph showing spectral characteristics when the thicknesses of an Al ₂ O ₃ layer, a ZrO ₂ layer, and a SiO ₂ layer are 69 nm, 57 nm, and 40 nm, respectively.

FIG. 3 is a graph showing spectral characteristics when the thicknesses of an Al ₂ O ₃ layer, a ZrO ₂ layer, and a SiO ₂ layer are 69 nm, 57 nm, and 50 nm, respectively.

FIG. 4 is a graph showing spectral characteristics when the thicknesses of an Al ₂ O ₃ layer, a ZrO ₂ layer, and a SiO ₂ layer are 69 nm, 57 nm, and 60 nm, respectively.

FIG. 5 is a graph showing spectral characteristics when the thicknesses of an Al ₂ O ₃ layer, a ZrO ₂ layer, and a SiO ₂ layer are 69 nm, 57 nm, and 70 nm, respectively.

FIG. 6 is a graph showing spectral characteristics when the thicknesses of an Al ₂ O ₃ layer, a ZrO ₂ layer, and a SiO ₂ layer are 69 nm, 57 nm, and 80 nm, respectively.

FIG. 7 is a graph showing spectral characteristics when the thicknesses of an Al ₂ O ₃ layer, a ZrO ₂ layer, and a SiO ₂ layer are 69 nm, 57 nm, and 90 nm, respectively.

FIG. 8 is a graph showing spectral characteristics when the thicknesses of an Al ₂ O ₃ layer, a ZrO ₂ layer, and a SiO ₂ layer are 69 nm, 57 nm, and 100 nm, respectively.

FIG. 9 is a graph showing spectral characteristics when the thicknesses of an Al ₂ O ₃ layer, a ZrO ₂ layer, and a SiO ₂ layer are 69 nm, 57 nm, and 110 nm, respectively.

FIG. 10 is a graph showing spectral characteristics when the thicknesses of an Al ₂ O ₃ layer, a ZrO ₂ layer, and a SiO ₂ layer are 69 nm, 57 nm, and 120 nm, respectively.

[Explanation of symbols]

1 glass substrate 2 Cr layer 3 Cu layer 4 Ag layer 5 Al ₂ O ₃ layer 6 ZrO ₂ layer 7 SiO ₂ layer

Claims (1)

(57) [Claims] 1. A reflector comprising a silver layer, an aluminum oxide layer, a zirconium oxide layer and a silicon dioxide layer laminated in this order on a substrate, wherein the thickness of the aluminum oxide layer is 49 nm or more and 89 nm or less,
The thickness of the zirconium oxide layer is 37 nm or more and 77 nm or less,
A reflecting mirror, wherein the thickness of the silicon dioxide layer is set to be not less than 60 nm and not more than 100 nm.