JP3320148B2 - Manufacturing method of metal mirror - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a metal mirror used for an optical machine such as a camera, a copying machine, a printer and the like.

[0002]

2. Description of the Related Art Conventionally, a metal mirror used for an optical machine such as a camera, a copying machine, a printer or the like is made of a metal having a high reflectance such as Al, Cu, Au, Ag or the like on a surface of a base made of plastic or the like. In general, a reflection film is formed, and a protective film of a dielectric material and a reflection-enhancing film are provided thereon. In particular, a reflective film made of a metal that easily corrodes, such as Al, is used in order to compensate for the property that the reflectance decreases with time (hereinafter referred to as “deterioration characteristic”) and the low film strength and chemical resistance. Formation of oxide layer by oxidation treatment or SiO ₂
For example, the following examples are known, such as laminating a protective film of SiO2 or SiO.

1) A reflective film of Al, Au, Ag, Ni, Cr or the like is deposited on the surface of a plastic substrate by vacuum deposition or the like, and a protective film of SiO having a thickness of 3 to 8 nm is provided thereon. No. 56-110904).

2) A reflective film of Al is formed on the surface of the transparent substrate, and a reflection-enhancing film composed of a SiO ₂ film and a TiO ₂ film is laminated without heating, and then heated in the air to form an Al reflection film.
Oxidizes the surface of the reflective film (see JP-A-58-43402).
Reference).

3) A reflective film of Al is formed on the surface of the substrate,
After oxidizing the surface of the Al reflection film in an atmosphere of oxygen gas, an enhanced reflection film composed of a SiO ₂ film and a TiO ₂ film is provided (see Japanese Patent Application Laid-Open No. 58-55901).

4) Oxidizing the surface of the Al reflection film to reduce
to form an Al ₂ O ₃ layer having a thickness of
An O ₂ protective film is provided (see Japanese Patent Application Laid-Open No. 58-72106).

[0007] 5) After depositing a reflective film of Al on the surface of the substrate, the optical film thickness 0.03λ ₀ ~0.15λ ₀ (λ ₀ is a protective film of silicon oxide or magnesium fluoride design wavelength) (See JP-A-2-50104).

6) A protective film of SiO is provided on the surface of a synthetic resin substrate, a reflective film is deposited thereon, and then a protective film of SiO having a thickness of 0.05 to 1.0 μm is provided. -235502).

7) In the back reflector of synthetic resin, a protective film of silicon oxide, an Al reflective film, and a film thickness of 10 to 10 from the substrate side.
A protective layer of 0 nm SiO ₂ is laminated (Japanese Patent Laid-Open No.
No. 0802).

[0010]

However, according to the above-mentioned prior art, since the transmission of moisture cannot be completely prevented only by the protective film mainly composed of SiO ₂ or SiO, the deterioration of the reflective film with the passage of time. The improvement of characteristics is not enough. In addition, the method of oxidizing the surface of the reflective film has the disadvantage that the oxidizing step is complicated and the reflectance of the reflective film is low from the beginning. That is, since the method 1) merely provides the protective film of SiO, the time-dependent deterioration characteristics of the Al reflection film due to the permeation of moisture cannot be sufficiently modified, and the methods 2) to 4) require By forming an Al oxide film having high impermeability to moisture on the surface of the Al reflective film, the deterioration characteristics with the passage of time are improved, but in order to oxidize the surface of the Al reflective film, Heating or plasma treatment is required, or a step of depressurizing the film formation chamber again for forming a protective film after introducing oxygen to oxidize the surface of the Al reflective film is required, and productivity is reduced. In addition to being low, the material of the base is limited, and there is a risk of damage or contamination due to the plasma treatment. The method 5) is to form an Al oxide film on the interface with the Al reflection film by reducing the thickness of the protective film of silicon oxide or magnesium fluoride. The methods 2) to 4) Similarly to the above, the modification of the deterioration characteristics with time is sufficient, but the thickness of the protective film is changed to the design wavelength (650 nm).
m) is 13 to 65 nm, which has a drawback that the reflectance is low from the beginning. In the methods 6) and 7), the silicon oxide protective film alone does not have sufficient impermeability to moisture.
Corrosion of the reflective film proceeds, and the reflectance decreases.

The present invention has been made in view of the above-mentioned problems of the prior art, has an extremely high reflectance, does not cause the reflectance to decrease with time, and has a simple manufacturing process. it is an object to provide a method for producing a metal mirror is in inexpensive.

[0012]

[0013]

SUMMARY OF THE INVENTION The manufacture of the metal mirror of the present invention .
The fabrication method includes the steps of forming a metal reflective film on the surface of the substrate in a reduced-pressure film forming chamber;
A process of forming a protective film having a thickness in the range of 0 nm and a predetermined packing density, and a process of oxidizing the surface of the reflective film by introducing oxygen into the film forming chamber after forming the protective film. It is characterized by becoming.

[0014]

In the metal mirror manufactured by the above method, since the surface of the reflection film is oxidized to form an oxide layer that does not transmit moisture, corrosion of the reflection film can be prevented. Further, since the thickness of the protective film is in the range of 0.1 to 10 nm, it is sufficient to improve the surface hardness of the reflective film, and there is no possibility that the reflectance of the reflective film is significantly impaired by the protective film. . When the thickness of the protective film is less than 0.1 nm, the strength is insufficient, and when the thickness of the protective film is more than 10 nm, the reflectance is reduced. Further, since the thickness of the protective film is thin, the surface of the reflective film can be quickly oxidized by oxygen passing through the protective film, and therefore, it is possible to prevent moisture from entering the reflective film before the oxide layer is formed. be able to. As a result, there is no possibility that moisture may enter before the oxide film is formed, and the corrosion of the reflection film may proceed. In addition, after the protective film is formed, oxygen can be introduced into the film forming chamber to oxidize the surface of the reflective film and then be directly exposed to the atmosphere, so that the manufacturing process is simple.

According to the above method, the deposition rate is controlled so that the packing density becomes a predetermined value during the formation of the protective film, and oxygen is introduced into the film forming chamber after the formation of the protective film. By controlling the packing density to 0.6 to 0.9, the surface of the reflection film can be oxidized very quickly. Thereafter, the film formation chamber is released to the atmosphere as it is, and the product can be taken out.

[0016]

An embodiment of the present invention will be described with reference to the drawings.

First Embodiment FIG. 1 shows a vapor deposition apparatus used in the first embodiment. The vapor deposition apparatus is a vacuum chamber 1 which is a film forming chamber having an exhaust port 1a.
And a reaction gas introduction line 1b for introducing a reaction gas such as oxygen gas into this, an umbrella-shaped substrate holder 2 rotated by a rotating device (not shown) in the vacuum chamber 1, and a substrate held by this. It has first and second evaporation sources 3 and 4 for generating vapor toward a certain substrate W, respectively, and a film thickness monitor 5 composed of a quartz sensor for monitoring the deposition rate of a thin film deposited on the substrate W. The first evaporation source 3
Is heated by an electron gun to generate Al vapor,
Of the silicon oxide S is heated by resistance heating.
iO _x (1 <x <2) (hereinafter referred to as “unsaturated silicon oxide”) is generated. The exhaust port 1a is alternately connected to a vacuum pump (not shown) and an atmosphere introduction line 1c.

The metal mirror of the first embodiment is manufactured as follows.

[0019] After the vacuum chamber was evacuated 1 to a pressure below 1 × 10 ^-3 Pa wearing the polycarbonate substrate W to the substrate holder 2, by introducing oxygen gas from the reaction gas inlet line 1b 1 × 10 ^- The pressure is adjusted to ² Pa, and the second evaporation source 4 is heated at this degree of vacuum to form an undercoat of unsaturated silicon oxide with a thickness of 85 nm, and then 1 × 10 ⁻³ Pa
The first evaporation source 3 is heated at a degree of vacuum to form an Al reflective film having a thickness of 100 nm, and then an oxygen gas is introduced in the same manner as described above to introduce a degree of vacuum of 1.5 × 10 ⁻² Pa. The second evaporation source 4 was heated at this degree of vacuum to deposit a 5 nm-thick protective film of unsaturated silicon oxide. The deposition of the undercoat, the reflective film, and the protective film are all performed continuously without heating the substrate W. The deposition rate of the protective film is monitored by the film thickness monitor 5 and is controlled to approximately 0.5 nm / sec. Was.
After the formation of the protective film, oxygen gas was introduced from the reaction gas introduction line 1b, the pressure in the vacuum chamber 1 was increased to about 100 Pa, and the atmosphere introduction line 1c was opened to introduce air. The packing density of the protective film formed at the above-mentioned deposition rate is 0.88 or less, and the refractive index is 400
It was approximately 1.48 at the wavelength of nm.

FIG. 2 shows an incident angle 45 of the metal mirror of this embodiment.
9 is a graph showing spectral reflectance in degrees. As can be seen from this figure, the reflectance (hereinafter, referred to as “initial reflectance”) immediately after the manufacture of the metal mirror of this embodiment is extremely high at a wavelength of 400 nm and uniform over a wide wavelength range. In addition, a quality evaluation test immediately after production described below (hereinafter,
"Initial evaluation test". As a result, the metal mirror of this example has good external appearance, chemical resistance, and environmental resistance in a state immediately after production, and a quality evaluation test (evaluating the change over time in appearance and reflectance). Less than,
This is called "aging evaluation test." As a result, it was found that there was no possibility that both the appearance and the reflectance would change significantly.

The packing density is represented by the ratio of the mass per unit volume of a thin film formed in a vacuum chamber to the mass of the thin film when taken out into the atmosphere. In general, the relationship between the deposition rate and the packing density is checked by a film thickness monitor in a vacuum chamber, and the packing density is generally controlled to a predetermined value by controlling the deposition rate during film formation as described above. .

Next, according to an experiment, the thickness of the protective film was 0.1%.
If the packing density is from 0.6 to 0.9 in the range from 10 to 10 nm, the penetration of oxygen takes place very quickly, and before the residual moisture in the vacuum chamber reaches the surface of the reflective film through the protective film, It has been found that the surface is oxidized to form an oxide layer impermeable to moisture. Also, if the protective film is made of silicon oxide, nitride or carbide, these have good affinity for water, so they absorb water and prevent water from reaching the surface of the reflective film. Help. If these are unsaturated compounds, the affinity with water is further increased. Further, it is desirable that the formation of the undercoat, the reflective film, and the protective film is all performed without heating the substrate. The reason is that the residual water in the vacuum chamber is activated by the heating and is easily bonded to the reflection film.

Next, the following metal mirror was manufactured for comparison.

COMPARATIVE EXAMPLE 1 The same method as in the first embodiment was adopted except that the thickness of the protective film was set to approximately 15 nm, and the air introduction line 1c was opened and air was introduced immediately after the protective film was formed. An undercoat, a reflective film, and a protective film were formed. As a result of the initial evaluation test, the initial reflectance was slightly inferior, and in addition, as a result of the aging evaluation test, deterioration of the external appearance was observed, such as a significant decrease in the reflectance and spots of about several μ due to corrosion of the reflective film. .

Second Comparative Example The thickness of the protective film was set to approximately 5 nm, and the pressure in the vacuum chamber was reduced to 1 × 1 without introducing oxygen gas during the film formation.
A metal mirror was manufactured in the same manner as in the first embodiment except that the pressure was adjusted to 0 ⁻³ Pa and air was introduced immediately after the film formation. The refractive index of the protective film was approximately 1.8, and the packing density was approximately 0.96. Although the results of the initial evaluation test were good, the results of the time evaluation test revealed that spot-like clouding was generated due to corrosion of the Al reflection film, and that the appearance and the reflectance were significantly deteriorated. The reason is presumed to be that oxidation of the reflective film was slow due to the high packing density of the protective film, and that moisture entered.

Third Comparative Example The material of the protective film was SiO ₂ , the film thickness was about 5 nm, and the pressure in the vacuum chamber was adjusted to 1 × 10 ⁻³ Pa without introducing oxygen gas during the film formation. A metal mirror was manufactured in the same manner as in the first embodiment except that air was introduced immediately after the film formation. The refractive index of the protective film was approximately 1.45, and the packing density was approximately 0.94. Although the results of the initial evaluation test were good, the temporal evaluation test revealed that clouding occurred due to corrosion of the Al reflection film, and that the appearance and the reflectance were significantly deteriorated. It is considered that the reason for this is that the material of the protective film is a saturated oxide, SiO ₂ , and the packing density is high, so that the oxidation of the reflective film is slow and water has entered.

Fourth Comparative Example During the deposition of the protective film, the pressure in the vacuum chamber was set to 1 × 10 ^-2 Pa.
A metal mirror was manufactured in the same manner as in the first embodiment except that the adjustment was made as follows. The refractive index of the protective film was about 1.55 at a wavelength of 400 nm, and the packing density was 0.88 or less. Although the results of the initial evaluation test and the aging evaluation test were almost the same as those of the first embodiment, there was a disadvantage that the aging of the reflectance was slightly large. This is considered to be caused by the refractive index of the protective film exceeding 1.50.

Second Example A metal mirror having a 5 nm-thick unsaturated silicon nitride SiN _x protective film was manufactured in place of the 5 nm-thick unsaturated silicon oxide protective film of the first embodiment. The method of forming the undercoat and the reflection film is the same as that of the first embodiment.
Oxygen gas is introduced into the vacuum chamber to adjust the degree of vacuum to 1.5 × 10 ^-2 Pa, and the evaporation material is heated and vaporized by an electron gun to form a film. 1
After the pressure was increased to 0 ² Pa, the atmosphere was released. The refractive index of the protective film was about 2.05 at a wavelength of 400 nm, and the packing density was 0.86 or less. The results of the initial evaluation test and the aging evaluation test were all good as in the first example.

Third Example A metal mirror having a 5 nm-thick protective film of unsaturated silicon carbide SiC was manufactured in place of the 5 nm-thick unsaturated silicon oxide protective film of the first example. The method of forming the undercoat and the reflective film is the same as in the first embodiment. The protective film is adjusted to a vacuum of 1.5 × 10 ⁻² Pa by introducing oxygen gas into the vacuum chamber, Was heated and vaporized by an electron gun to form a film. Thereafter, the pressure was increased to 10 ² Pa by introducing oxygen gas, and then the atmosphere was released. The refractive index of the protective film is 40
About 2.07 at 0 nm wavelength, packing density is 0.85
It was below. The results of the initial evaluation test and the aging evaluation test were good.

Next, B is replaced with a polycarbonate substrate.
Using the K7 optical glass substrate, the acrylic resin substrate, and the polyolefin resin substrate, metal mirrors similar to those of the first example were manufactured, and an initial evaluation test and a time evaluation test were performed on each of them. A metal mirror using a BK7 optical glass substrate as a fourth embodiment, a fifth embodiment using an acrylic resin substrate as a fifth embodiment, and a sixth embodiment using a polyolefin resin substrate as a first to a fifth embodiment. Table 1 shows the results of the initial evaluation test and the aging evaluation test performed on the metal mirror of Example 6 and the metal mirrors of the first to fourth comparative examples.

[0031]

[Table 1] The appearance was evaluated by visually inspecting for abnormalities such as clouding, film cracking, film peeling, etc., and the chemical resistance was measured at 500 g / cm ² using silbon paper immersed in a mixed solution of alcohol and Freonsolve. The results were obtained by examining the external appearance abnormality after 10 reciprocations with a load of 3.
This is to examine abnormalities in appearance when the temperature change from 0 degrees to 60 degrees is repeated for 10 consecutive steps. The aging evaluation test was conducted to examine abnormalities in appearance and reflectance after 500 hours in an environment at a temperature of 60 ° C. and a humidity of 90%.

[0032]

Since the present invention is configured as described above, the following effects can be obtained.

It is possible to realize a metal mirror which has an extremely high reflectivity, does not have the possibility that the reflectivity decreases with time, and has a simple manufacturing process and is inexpensive.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram for explaining a vapor deposition apparatus for manufacturing a metal mirror of a first embodiment.

FIG. 2 is a graph showing the reflectance characteristics of the metal mirror of the first embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vacuum tank 1b Reaction gas introduction line 2 Substrate holder 3 First evaporation source 4 Second evaporation source 5 Film thickness monitor

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G02B 5/08

Claims (6)

(57) [Claims] 1. A step of forming a metal reflective film on a surface of a substrate in a reduced-pressure film forming chamber, and having a film thickness in the range of 0.1 to 10 nm and a predetermined packing density on the surface of the reflective film. A method for manufacturing a metal mirror, comprising: forming a protective film; and introducing oxygen into the film forming chamber to oxidize the surface of the reflective film after the formation of the protective film . 2. A method for producing a metal mirror of claim 1, wherein the packing density of the protective layer is 0.9 to 0.6 to. 3. A process according to claim 1 or 2 method for producing a metal mirror according to wherein all steps are performed continuously without heating the substrate. 4. A method according to claim 1, wherein said reflection film is formed of Al.
The metal mirror according to any one of claims 1 to 3, characterized in that:
Manufacturing method. 5. The method according to claim 1, wherein said protective film is made of an unsaturated silicon oxide,
Any one of Japanese silicon nitride and unsaturated silicon carbide
5. The method according to claim 1, wherein the first member is formed from
The method for producing a metal mirror according to claim 1. 6. The protective film according to claim 1, wherein said protective film is adapted for light having a wavelength of 400 nm.
Formed from unsaturated silicon oxide having a refractive index of 1.48
The method according to any one of claims 1 to 4, wherein
Manufacturing method of metal mirror.