JPH0685004B2 - High durability infrared reflector - Google Patents

Description

TECHNICAL FIELD The present invention relates to a reflector in the infrared wavelength range.

[Prior Art] Conventionally, as a reflecting mirror in the infrared region, a substrate made of glass or the like and provided with a thin film of a metal such as aluminum, gold, silver or copper is used. However, each of these metal film reflecting mirrors has the drawbacks of low wear resistance and low chemical stability except for the gold film reflecting mirror.

Therefore, in order to compensate for this drawback, a protective film such as MgF ₂ or SiO which is transparent in the infrared region is provided on the metal film. However, in providing such a protective film, a thin film is insufficient, and unless a considerably thick film is applied, durability such as abrasion resistance and chemical stability will not be sufficient. For this reason, there is no choice but to provide a relatively thick film,
When the film thickness of the protective film is increased, not only the spectral reflectance is decreased but also the internal stress of the film is increased to deform the substrate and the optical performance such as surface accuracy is deteriorated.

[Object of the Invention] The present invention has been made in view of the above-mentioned conventional techniques, and an object thereof is to provide an infrared reflecting mirror having sufficient durability and good optical performance.

[Summary of the Invention] According to the present invention, the above object is to provide Cr, Ti,
First consisting of one of Co and Ni or mixtures thereof
A film of the first layer is formed, and TiN is formed on the film of the first layer.
A second-layer film is formed, and 1 ≦ the film thickness d ₁ of the first-layer film and the second film thickness d ₂ of the second-layer film.
(D ₁ / d ₂ ) ≦ 10, thereby preventing the reduction of the surface accuracy of the reflecting surface due to the film stress, which is achieved by a highly durable infrared reflecting mirror.

[Examples of the Invention] Specific examples of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a schematic sectional view of a highly durable infrared reflecting mirror according to the present invention. In the figure, 1 is a glass substrate and 2 is a first
A third layer is a TiN film, and a third layer is a TiN film. In this example, Ti was used as the material of the first layer film. The second film thickness of the first layer was 0.8 μm, and the film thickness of the second layer was 0.3 μm.

The film formation of the first layer is performed by an ordinary vacuum deposition method. After evacuation to a vacuum degree of 1 × 10 ^-6 Torr, the substrate temperature is set to about 300.
The film thickness of metallic Ti is 0.8 by the electron gun evaporation source while keeping it at ℃.
μm vapor deposited. The second layer is a TiN film formed by introducing nitrogen gas as a reaction gas up to 4 × 10 ^-4 Torr, evaporating metallic Ti with an electron gun evaporation source and performing ion plating while being activated by plasma discharge. A film thickness of 0.3 μm was formed.

FIG. 2 is a graph of the spectral characteristics of the reflecting mirror of this embodiment. From this, it can be seen that the reflecting mirror of this embodiment exhibits a good reflectance of about 90% in the infrared region, and the reflectance becomes higher as the wavelength becomes longer.

Similarly, as the material of the first layer film, Cr and C other than Ti are used.
Using a mixture of metals such as o and Ni and these metals including Ti, the film thickness is 0.8 μm, and the film thickness of the second TiN film is
When the reflecting mirror was made to have a size of 0.3 μm, both were second
The spectral characteristics similar to those in the figure were exhibited, and a good reflectance of about 90% could be obtained in the infrared region.

Since the TiN film 3 of the second layer has excellent chemical stability and abrasion resistance, the reflecting mirror of the present invention can be used even under severe conditions.

In the reflecting mirror of the present invention, a tensile stress is present in the first metal film when formed by the vacuum deposition method, while a compressive force is created in the second TiN film when formed by ion plating or sputtering. Since the stress exists, the internal stress of the entire film can be reduced by appropriately setting the film thickness of the first layer film and the film thickness of the second layer film. It has the effect of preventing a decrease in surface accuracy. To this end, considering that the internal stress of the TiN film is several times as large as the internal stress of the metal film, in the reflecting mirror of the present invention, the film thickness of the first layer film and the second layer There is a relationship of 1 ≦ (d ₁ / d ₂ ) ≦ 10 with the film thickness of the eye film.

[Effect of the Invention] According to the present invention as described above, an infrared reflecting mirror having good durability such as abrasion resistance and chemical stability and good optical performance is provided.

[Brief description of drawings]

FIG. 1 is a sectional view of an infrared reflecting mirror of the present invention, and FIG. 2 is a graph of its spectral characteristics. 1 ... Substrate, 2 ... First layer film, 3 ... Second layer Ti
N film

Claims (1)

[Claims] 1. A first layer film made of one of Cr, Ti, Co and Ni or a mixture thereof is formed on a substrate, and TiN is formed on the first layer film. A second layer film is formed, and the film thickness d ₁ of the first layer film and the second film
High durability characterized by preventing deterioration of surface accuracy of the reflecting surface due to film stress by establishing a relationship of 1 ≦ (d ₁ / d ₂ ) ≦ 10 with the film thickness d ₂ of the _second layer Infrared reflector.