JPS6015604A - Reflection mirror for automobile - Google Patents

Abstract

PURPOSE:To obtain a desired color tone at a low cost and to prevent the driver's fatigue owing to the dazzle by forming transparent thin dielectric films having different refractive indexes on base glass then forming a metallic film thereon. CONSTITUTION:The 1st transparent thin dielectric film 2 (refractive index n=2.3) consisting of MgF2 having a low refractive index is deposited by vacuum evaporation on base glass 1 (n=1.53). The 2nd transparent thin dielectric film 3 (n=2.3) consisting of TiO2 having the refractive index higher than the refractive index of the glass 1 is deposited by vacuum evaporation on the surface of the film 2. A metallic film 4 consisting of a nickel-chromium alloy to serve as a reflecting surface of light is deposited by vacuum evaporation at a desired film thickness on the surface of the film 3. When light is made incident to such reflection mirror from the direction of an arrow L, the light of the quantity determined by the difference in the refractive indexes is reflected at the boundary between the glass 1 and the film 2 and the boundary between the film 2 and the film 3. The reflected light and the light reflected on the surface of the film 4 interfere with each other, by which the spectral characteristic of the reflected light is not made flat and the effect of coloring and preventing the dazzle is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a reflecting mirror for automobiles, and is effective for use in, for example, a rearview mirror or a fender mirror of an automobile.

Conventional automotive reflectors are made by vapor-depositing aluminum on a glass substrate, have a high reflectance of 80 to 90%, and have spectral characteristics of Furan I. For this reason, if you have your back to the sun or are illuminated by a trailing light at night,
The glare causes fatigue. In order to prevent this, there are some that use optical interference to reduce the luminous reflectance to about 50% and use a blue mirror. However, this has a structure of 3 to 5 layers plus a black coating, and the manufacturing cost is high.

Furthermore, if another color tone (for example, bronze color) is attempted, there is a problem in that the luminous reflectance is extremely reduced and the automobile standards cannot be satisfied.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, it is an object of the present invention to provide a reflector for an automobile that can be made into any color tone at a fixed cost and that prevents driver fatigue due to glare.

In order to achieve this objective, the present invention takes the following measures. That is, a first transparent dielectric thin film having a lower refractive index than the substrate glass is formed on a substrate glass, a second transparent dielectric thin film having a higher refractive index than the substrate glass is formed on the first transparent dielectric thin film, and A metal film was formed on this second transparent dielectric thin film.

Next, embodiments of the present invention will be described based on the drawings.

As shown in FIG. 1, a first transparent dielectric thin film 2 (made of magnesium fluoride (MgF2)) having a refractive index lower than that of the substrate glass 1 (refractive index 1.53) is formed on one surface of the substrate glass 1. A refractive index of 1.38) is vacuum deposited. This first
On the surface of the transparent dielectric thin film 2, a second transparent dielectric 111A3 (refractive index 2.3) made of titanium oxide (1" i 02 ) having a higher refractive index than the substrate glass 1 is vacuum deposited. Further, on the surface of the second transparent dielectric thin film 3, a metal film 4 made of a nickel-chromium alloy and serving as a light reflecting surface is vacuum-deposited to a desired thickness.

Note that the first and second transparent dielectric thin films M2 and 3 and the metal film 4 are not limited to the vacuum deposition method, but may be formed by a sputtering method.

The light enters from the direction of the arrow in Fig. 1, and the light enters the substrate glass 1.
It passes through the first and second transparent dielectric IM films 2.3 and is reflected on the surface of the metal film 4, and then passes through the first and second transparent dielectric thin films 2 and 3.
The light then passes through the substrate glass 1 and returns to the direction of incidence. At this time, an amount of light determined by the difference in refractive index is also reflected at the interface between the substrate glass 1 and the first transparent dielectric thin film 2 and the interface between the first transparent dielectric thin film 2 and the second transparent dielectric thin film 3. Ru. When this reflected light and the light reflected on the surface of the metal film 4 interfere with each other, the spectral characteristics of the reflected light are no longer flat, and the coloring and anti-glare effects can be improved. The color tone and reflectance at this time will be described below.

FIG. 2 shows the relationship between the thickness of the second transparent dielectric film 3 and the color tone.
The color tone of the reflected light when the standard light C defined by C is perpendicularly incident is expressed by chromaticity coordinates. Here, the thickness of the first transparent dielectric thin film 2 is constant for 1000 people. In Figure 2, the chromaticity coordinates are: X is the red component, Y is the green component, 1-(X
-1-Y) represents the blue component; roughly speaking, the area G surrounded by the dotted line in Figure 2 is green, the area Y is yellow, and the area R
is red, area (3) is purple, area B is blue, and the area between each area is an intermediate color. Further, the relationship between film thickness and hue is as follows: chromaticity for each 400 persons is indicated by ○, and chromaticity for each 40 persons is indicated by .

FIG. 3 shows the relationship between the film thickness and color tone of the second transparent dielectric thin film 3 when there is no first transparent dielectric thin film 2, that is, when there is only one layer of the second transparent dielectric thin film 3. It shows.

Comparing Figure 2 and Figure 3, we find that the chromaticity curve in Figure 2 traces a trajectory farther from the light source color point C than the chromaticity curve in Figure 3. Recognize. In other words, the embodiment of the present invention can express darker colors. This is because the difference in refractive index between the second transparent dielectric thin film 3 and the first transparent dielectric thin film 2 is larger than the difference in refractive index between the second transparent dielectric thin film 3 and the substrate glass 1. This is because more light is reflected at the boundary layer between the dielectric thin film 2 and the second transparent dielectric thin film 3, and the light interference becomes stronger and the color becomes darker.

FIG. 4 shows the relationship between the film thickness and brightness (human visual reflectance) of the second transparent dielectric thin film 3.

The wave in the luminous reflectance as shown in this figure is due to the fact that the sensitivity of the human eye is maximum at a wavelength of approximately 5,550, and decreases as the distance from this wavelength increases. That is, the human eye perceives green light as the brightest and perceives red and blue light of the same intensity as dark, so if the material does not exhibit red or blue and is thin, the luminous reflectance will decrease.

By the way, the automobile standard value of reflectance is 38% or more, and as shown in FIG.
If it is within the range of 50 people, it satisfies the automobile standard value. If we look at the color tones at this film thickness from FIG. 2, we can see that the color tones cover almost all the tones. In other words, any color tone can be expressed while meeting automotive standards. In addition, the luminous reflectance is always below 60%, and is 80-90%.
It has a sufficient anti-glare effect compared to an aluminum vapor-deposited mirror with a reflectance of .

Next, FIG. 5 shows the change in color tone when the thickness of the first transparent dielectric thin film 2 is changed while keeping the thickness of the second transparent dielectric thin film 3 constant for 800 people.

The shade of color changes depending on the film thickness, but since the thickness of the second transparent dielectric thin film 3 is set to a film thickness that indicates blue (800 layers), the hue is blue in all cases and does not change much.

This shows that the hue is determined by the optical thickness of the second transparent dielectric thin film 3 and is hardly influenced by the first transparent dielectric thin film 2. In this case, the hue is blue, so if the wavelength of light that represents blue is λ, the product of the film thickness and refractive index of the first transparent dielectric thin strip 2 (optical film thickness nXd) is λ/4 Alternatively, a deep color can be obtained with a film thickness approximately equal to 3·λ/4. Therefore, it is desirable to form the first transparent dielectric thin film 2 with such a film thickness.

In addition, the thickness of the second transparent dielectric thin film 3 was kept constant for 800 people, and lithium fluoride (LiF) was added to the first transparent dielectric thin film 2.
), chromaticity coordinates when using silicon oxide (Sin2) are shown in FIG. In this case as well, as in the case of FIG. 5, the thickness of the second transparent dielectric thin film 3 is set to a film thickness that indicates blue, so the hue is blue in all cases, but a material with a smaller refractive index is used. You can see that it is possible to express darker colors.

The second transparent dielectric thin film 3 is not limited to titanium oxide (Ti02), but may also be made of a material having a higher refractive index than the substrate glass 1, such as cerium oxide (Ce02), zirconium oxide (Zr02), or tungsten oxide (W03). It's fine.

Furthermore, if the metal film 4 is not limited to nickel-chromium alloy, but also titanium, chromium, nickel-cobalt alloy, etc., the reflectance of which is approximately 50 to 70% when formed into a thin film can be used.
A colored mirror with high anti-glare effect can be obtained.

As explained above, by using the automotive reflector of the present invention, it can be manufactured at low cost, and can have any color tone or density, thereby preventing driver fatigue due to glare.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view showing an embodiment of the present invention, Figure 2 is a diagram showing the relationship between the film thickness and color tone of the second transparent dielectric thin film, and Figure 3 is a diagram showing the relationship between the thickness and color tone of the second transparent dielectric thin film. Figure 4 is a diagram showing the relationship between the thickness of the second transparent dielectric thin film and color tone. Figure 4 is a diagram showing the relationship between the thickness of the second transparent dielectric 'Ws film and human visual reflectance. Figure 5 is FIG. 6 is a diagram showing the relationship between the thickness of the first transparent dielectric thin film and the chromaticity coordinates, and FIG. 6 is a diagram showing the relationship between the material of the first transparent dielectric thin film and the chromaticity coordinates. DESCRIPTION OF SYMBOLS 1... Substrate glass, 2... First transparent dielectric thin film, 3
... second transparent dielectric thin film, 4... metal film. Representative patent attorney Takashi Okabe Figure 1 Figure 2 Figure 3 Figure 4 PIL team (entered) Figure 5 Figure 6

Claims (1)

[Claims] a first transparent dielectric thin film formed on the substrate glass and having a smaller curvature than the substrate glass; and a first transparent dielectric thin film formed on the first transparent dielectric thin film and having a larger curvature than the substrate glass. A reflective mirror for an automobile comprising a second transparent dielectric thin film having a second transparent dielectric thin film and a metal film formed on the second transparent dielectric thin film.