JPS61110902A - Multilayer film reflecting mirror - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a multilayer film reflecting mirror used for floodlights and the like, and particularly to a modification of a multilayer film reflecting mirror having a cold light mirror as its base.

[Technical background of the invention and its problems]

Multilayer reflective mirrors, which are based on cold-light mirrors, are often used as light sources for projectors, store lighting, medical lighting, etc., but they reflect as much visible light as possible and transmit long wavelength infrared light.
It is characterized by reducing the heating of the illuminated object by the heat rays, and by preventing the substrate from being heated by absorption when the heat rays from the light source pass through the multilayer film. Generally, the larger the value, the higher the reflectance and the wider the reflection band. The following table shows the combinations of materials used in cold light mirrors and their refractive index ratios.

table Na: refractive index of substance a, Nb: refractive index of substance a.

From the table above, it can be seen that it is advantageous to use ZnS-MgFt alternating layers to obtain high reflectance, but ZnS
When the MgFt alternating layer is applied to a light source that generates high heat, such as a halogen lamp, the film peels off due to heating and the ZnS layer on the film surface becomes oxidized and becomes cloudy. Normally, the lamp becomes unusable after 30 hours at a temperature of 350° C. or 100 hours at a temperature of 300° C. when the lamp is lit. Z again
n5ll'l is hygroscopic, so the temperature is 50℃ and the humidity is 90℃.
% atmosphere for 50 hours, the film peels off, resulting in poor durability.

Alternating layers of Ti0z-5ift have excellent durability, but in a multilayer reflector made of these alternating layers, Zn
In order to maintain optical properties comparable to those of the S-MgFt alternating layers, it is necessary to increase the number of film layers by 50%, which increases the cost and poses a problem in practicality from an economical point of view. For this reason, it is desired to enhance the durability of a multilayer reflector made of alternating layers of ZnS-MgF'.

[Purpose of the invention]

The present invention was made in view of the above-mentioned circumstances, and includes a 5-ift film between the substrate surface of the reflecting mirror and the ZnS-MgF2 alternating layers.
It is an object of the present invention to provide a multilayer film reflecting mirror that does not peel off even when applied to a light source that generates high heat and has excellent durability by interposing a thin film of the invention.

[Summary of the invention]

In the cold light mirror that serves as the base of the multilayer reflective mirror of the present invention, '
If a high refractive index material consisting of ln8 is (I()) and a low refractive index material consisting of MgF□ is (Ll), this ()(l and tLl are alternately measured m times on the glass substrate surface to form m layers. It is known that the highest reflectance can be obtained by adding one layer of ZnS-MgFt to a total of (2+++) layers.In this film configuration, the adhesion between the glass substrate and the alternating ZnS-MgFt layers This is because the adhesion of the 7 and n8 thin films to the glass substrate is much weaker than that of fluoride or oxide thin films.

The present inventor focused on the fact that the reflective mirror substrate is made of hard glass, and by interposing a thin film of 8102 between the glass substrate and the ZnS-MgF2 alternating layers, the combination of the glass substrate and the ZnS-MgFz alternating layers It was found that the adhesion was strengthened. That is, in the present invention, S10. In order to deposit a thin film of ZnS and thin films of Mg/F2 on the upper surface thereof, and to prevent the final layer of ZnS from being oxidized,
This is a multilayer film reflecting mirror in which a protective film, such as a thin film of Sioi, is deposited on the upper surface and then fired at a temperature of 350° C. or higher. The reason why this reflective mirror was baked at a temperature of 350°C or higher to harden the coating is because the heat load when the light source lamp is turned on is usually 350°C or higher, and the film cured at less than 350°C is not affected by the heat load. This is because they cannot endure it.

Figure 3 shows the relationship between the adhesion strength between a thin film of SiO2 or M g F 2 and a glass substrate and the coefficient of linear expansion of the glass substrate. It can be seen that the strength is more than twice as strong.

[Embodiments of the invention]

Next, an embodiment of the present invention will be described with reference to FIGS. 1 and 2. Reflector substrate for floodlights made of hard glass (1)
A thin film (2) of 5I02 is deposited on the top surface of the 5I02 film with a thickness of 70~+3OA, and 1g of ZnS is deposited on the top surface of this 5iOz film (2).
F2 15 to 23 layers of this thin film are deposited alternately to form ZnSh
1 g F2 alternating layers (3) are formed. Furthermore, ZnS-Mg
A protective film (4) of 5iOz is placed on the top surface of the F2 alternating layer (3).
After evaporating to a film thickness of 0 to 260A, 400' was deposited in an electric furnace.
Firing was performed at a temperature of C for 1 hour. (5) is a halogen lamp as a light source. The multilayer reflector thus obtained can be used for more than 100 hours at a temperature of 350°C with a heat load during lamp lighting, and in the above embodiment, the reflector for floodlighting can be used at a temperature of 50°C and a humidity of 90°C. However, the multilayer film structure according to the present invention can also be applied to color filter glass for studio lighting used as a light source that emits high heat to improve the heat insulation effect.

〔Effect of the invention〕

As described above, the present invention has a structure in which 8102 layers are formed between the substrate surface of a reflecting mirror made of hard glass and the ZnS-MgFz alternating layers.
This is a multilayer reflector with a thin film interposed between them, and it can be used for more than 100 hours in combination with a light source that emits high heat, such as a halogen lamp.However, it does not cause peeling of the film, which was a drawback in the past, and has excellent durability. It's also excellent. Furthermore, it can be used even under adverse conditions of high temperature and humidity, and has excellent practical effects.

・11 Figure 11 Simple explanation Figure 1 is a longitudinal side view showing an embodiment of the present invention, Figure 2 is an enlarged sectional view of section A, and Figure 3 is the attachment of a 5if2, MgF2 thin film and a glass substrate. It is a curve diagram showing the relationship between strength and linear expansion coefficient of a glass substrate.

1 substrate, 2:5iOt(7) thin film, 3: ZnS
- MgFz alternating layers, 4: protective film.

Patent applicant: Toshiba Glass Corporation Figure 1 4 Protective film Linear expansion coefficient (×IO complete)

Claims (1)

[Claims] A thin film of SiO_2 was deposited on the substrate surface of a reflector made of hard glass, thin films of ZnS and MgF_2 were alternately laminated on the top surface, and a protective film was further deposited on the top surface of the alternating layers of ZnS-MgF_2. After that, the multilayer film reflector is fired at a temperature of 350°C or higher.