JPH0854504A - Infrared mirror - Google Patents

Abstract

PURPOSE:To obtain stable and high reflectance without influences of contamination and scratches of a gold film and to produce a mirror at a low cost by forming a chromium film on a glass base body and controlling the thickness of the film to a specified range. CONSTITUTION:This IR mirror is obtd. by forming a chromium film 11 of 10-50Angstrom thickness on a glass base body and forming a gold film 12 o on the chromium film. Since the chromium film 11 is formed to <=50Angstrom thickness, it is possible to allow light beams to enter not the gold film 12 but the glass base body and to transmit through the chromium film 11 to be reflected by the gold film 12. When the chromium film 11 is formed to <=50Angstrom thickness, most of light entering the glass base body transmits through spaces among chromium particles in the chromium film 11, and then the light is reflected by the gold film 12. Thus, higher reflectance is obtd. However, it is not preferable to form the chromium film 11 to <=10Angstrom thickness because the adhesion strength with the base body decreases and the film is easily peeled. Therefore, preferable thickness of the chromium film is 15 to 25Angstrom .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an infrared mirror applicable as an optical component such as a hemispherical lens or a prism.

[0002]

2. Description of the Related Art Gold, which has a very high reflectance in the infrared region, has been used as a reflective material for infrared mirrors.

However, a film made of gold (hereinafter referred to as a gold film)
Has a very weak adhesion to a substrate made of a dielectric such as glass, and is easily peeled off even when it is formed into a film on the substrate.
Therefore, when depositing this on a substrate, a method of first depositing a chromium film having strong adhesion to a dielectric on the surface of the substrate and then depositing a gold film on it is adopted. .

[0004]

An infrared mirror having a chromium film and a gold film formed on a substrate as described above makes light incident from the gold film side and reflects it at the gold film. Even if the film is contaminated by dust or dew, the gold film is extremely susceptible to scratches, so the cleaning method was limited to blowing air or an organic solvent. In addition, if the gold film were to be scratched, the reflection characteristics would be impaired, making it unusable.

Therefore, it has been attempted to form a dielectric film on the gold film to prevent the gold film from being soiled or scratched. Will rise significantly.

The present invention has been made in view of the above circumstances. Since glass is used as the base material and light is incident from the side of the base, it is stable without being affected by dirt or scratches on the gold film. It is an object of the present invention to provide an infrared mirror which can obtain high reflectance and can be manufactured at low cost.

[0007]

The infrared mirror of the present invention is an infrared mirror in which a chromium film is formed on a glass substrate and a gold film is further formed thereon, and the thickness of the chromium film is 10 to 10. It is characterized by being 50Å.

[0008]

In the infrared mirror of the present invention, the thickness of the chrome film is
Since it is 50 Å or less, it becomes possible to allow light to enter from the glass substrate side, not the gold film side, and reflect the light through the chromium film at the gold film.

That is, in the conventional infrared mirror,
When forming a chrome film on a substrate, only the workability of the film formation is taken into consideration. Therefore, a chrome film having a thickness of about 100 to 1000 Å is generally used. However, very little light passes between the chrome particles.

Therefore, an infrared mirror in which transparent glass is used as the material of the substrate, a chromium film having a thickness of about 100 to 1000 Å is formed on this substrate, and a gold film is further formed thereon Even if light is made incident from the side of the base material, the chromium film tends to reflect the light and makes it difficult for the light to reach the gold film, so that a high reflectance cannot be obtained.

However, when the thickness of the chromium film is 50 Å or less as in the infrared mirror of the present invention, most of the light incident from the glass substrate side passes through between the chromium particles of the chromium film, and they are the gold film. Is reflected at
High reflectance. However, when the thickness of the chrome film is 10 Å or less, the adhesion to the substrate is lowered and the film peeling easily occurs, which is not preferable. In the present invention, the more preferable thickness of the chromium film is 15 to 25Å.

As the method for forming the chromium film and the gold film in the present invention, a sputtering method, a vacuum vapor deposition method or the like can be used.

[0013]

EXAMPLES The infrared mirror of the present invention will be described in detail below with reference to examples.

Table 1 shows examples of the present invention (Sample Nos. 1 to 1).
4) and Comparative Examples (Sample Nos. 5 to 7).

[0015]

[Table 1]

No. in the table Each sample of 1-6 was produced as follows.

First, a borosilicate glass substrate (5
(0 × 50 × 0.8 mm), a chromium film having the thickness shown in the table was formed thereon by a sputtering method.
Then, a gold film having the thickness shown in the table was formed on this chromium film by a sputtering method.

Further, No. in the table Sample No. 7 was prepared by preparing a borosilicate glass substrate similar to the above and then 270
It is produced by forming a gold film having a thickness of 0Å by a sputtering method.

For each of the samples prepared in this way,
The reflectance at the wavelengths of 1300 nm and 1550 nm was measured, and the peeling test of the gold film was performed. The results are shown in Table 1.

As is clear from Table 1, each of the samples of Examples has a high reflectance of 90.3% or more at a wavelength of 1300 nm and a reflectance of 90.8% or more at a wavelength of 1550 nm. Even in the peeling test, the gold film was not peeled at all.

On the other hand, No. The sample of No. 5 had high reflectance, but peeling occurred in half the area of the gold film. In addition, No. In the sample of No. 6, peeling of the gold film did not occur, but the reflectance was lower than that of each sample of the example. Furthermore, No.
Sample No. 7 had a high reflectance, but the entire gold film was easily peeled off.

The above reflectance was measured by a self-recording spectrophotometer (U-4000 manufactured by Hitachi, Ltd.). In the film peeling test, the gold film of each sample was spaced by about 2 mm with a diamond cutter. After the scratches were made in the shape of a grid and a # 610 Scotch tape (manufactured by 3M Co., Ltd.) was applied over the entire surface, the tape was peeled off right above, and the degree of peeling of the gold film was observed.

FIG. 1 shows a laser diode (LD) using an infrared mirror in which a chrome film (thickness 16Å) 11 is formed on a flat surface of a hemispherical lens 10 and a gold film (thickness 2500Å) 12 is further formed on the chrome film 11. It is sectional drawing which shows a component.

In the figure, a hemispherical lens 10 is made of BK-7 (manufactured by Optical Glass Co., Ltd.), and its spherical surface has Ti.
An antireflection film 13 composed of an O ₂ film layer and a SiO ₂ film layer is formed. A part of the spherical surface of the hemispherical lens 10 is fitted into the metal cap 14, and the metal cap 1
An LD element 15 is attached to the inside of 4.

In such an LD component, the LD element 1
When light rays are emitted from 5, most of the light rays pass through the antireflection film 13 and the chromium film 11, reach the gold film 12, and are reflected at an angle of 90 ° as shown by the arrow.
It is possible to form an optical system by condensing light on a flat plate.

The infrared mirror of the present invention can also be used as a prism to reduce the reflection loss of the amount of light.

[0027]

As described above, the infrared mirror of the present invention is
Since light is incident from the glass substrate side, the reflectance does not decrease even if the surface of the gold film becomes dirty or scratched, and it is necessary to form a dielectric film on the gold film. Since it is not available, it can be produced at low cost and can be expected to have a wide range of uses as an optical component.

[Brief description of drawings]

[Figure 1] LD with a spherical lens fitted in a metal cap
It is sectional drawing which shows a component.

[Explanation of symbols]

 10 hemispherical lens 11 chrome film 12 gold film 13 antireflection film 14 metal cap 15 LD element

Claims (1)

[Claims] 1. An infrared mirror in which a chromium film is formed on a glass substrate, and a gold film is further formed on the chromium film, wherein the thickness of the chromium film is 10 to 50 Å.