JPH08234004A - Metal mirror and production thereof - Google Patents

Abstract

PURPOSE: To obtain a metal mirror having high reflectance which does not deteriorate with the lapse of time. CONSTITUTION: This mirror is produced by forming a SiO base layer 2 on the surface of a substrate 1 and further forming a first Cr film 3, an Ag reflection film 4, a second Cr film 5 and a protective layer 6 compopsed of an Al2 O3 film 6a and a SiO2 film 6b. The first Cr film 3 increase the adhesion property between the under coating layer 2 and the reflection film 4 and is effective to form the reflection film 4 having no defect. The second Cr film 5 has an effect to smoothen the surface of the reflection film 4 and to make the film of the protective layer 6 dense.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Conventionally, a metal mirror used in an optical machine such as a camera, a copying machine or a printer has Al
In general, a reflective film of a metal having a high reflectance such as Cu, Au, and Ag is formed, and a protective film of a dielectric material and a reflection increasing film are provided thereon. In particular, a reflective film made of a metal such as Ag that easily corrodes has a property that the reflectance decreases with time (deterioration property over time), and generally, the film strength and the solvent resistance are low, so these are supplemented. Various ideas have been made for this.

The following examples are known as metal mirrors using a reflective film of Ag.

1) A silver mirror in which a Ni—Cr alloy film and a SiO ₂ film are formed as protective films on a silver film (Ag film) (see Japanese Patent Laid-Open No. 61-284703).

2) A layer in which a silver layer (Ag layer), an aluminum oxide layer and a high refractive index dielectric layer are laminated in this order on a substrate (see Japanese Patent Application Laid-Open No. 5-127004).

[0006]

However, according to the above-mentioned conventional technique, especially when the Ag film is used as the reflective film, the reflectance is not deteriorated and the coloring is avoided when the film is left in a high temperature and high humidity environment for a long time. I can't.

Generally, Ag has a property of being difficult to oxidize, but it is difficult to avoid deterioration in a high temperature and high humidity environment because even a trace amount of sulfur component in the atmosphere causes corrosion due to a sulfurization reaction. It is known that this tendency is particularly remarkable when the packing density of the Ag film is low or when the surface of the Ag film is rough.

Among the above known examples, N is formed on the surface of the Ag film.
i-Cr alloy film and that a protective layer of SiO ₂ film, a back side mirror has a drawback of low reflectance from the beginning to the Ni-Cr alloy film, also, Ag on the substrate
A laminate of a film, an aluminum oxide layer, and a high-refractive-index dielectric layer requires the use of a glass substrate because the substrate needs to be heated to a high temperature in the film forming process, and thus a plastic substrate cannot be used. Is not suitable.

Further, it has been proposed that the above-mentioned protective layer is provided on a metal reflection film such as an Ag film, and then a coating film of a resin is applied or a resin film is attached to prevent corrosion of the reflection film. The process of applying a resin coating film and laminating the resin film are
Since a new device or jig is required in addition to the device used for forming the reflective film or the protective layer, there is a possibility that the manufacturing process of the metal mirror may be complicated and the manufacturing device may be expensive, which is not preferable.

The present invention has been made in view of the above problems of the prior art, and has an extremely high reflectance,
In addition to the possibility that the reflectance will decrease with time,
It is an object of the present invention to provide a metal mirror which is suitable for a plastic optical component because a substrate can be formed without heating and a manufacturing process is simple and inexpensive, and a manufacturing method thereof.

[0011]

In order to achieve the above object, the metal mirror of the present invention comprises a metal reflection film formed on the surface of a substrate through an undercoat, and a metal reflection film laminated on the reflection film. An overcoat, and each of the undercoat and the overcoat has a film thickness of 0.1 to 10 nm
Of the Cr film, which are in contact with the reflection film.

The metal reflection film is preferably an Ag film.

The overcoat may have a single or multiple protective layers of dielectric material.

The method of manufacturing a metal mirror of the present invention is
A step of forming a first Cr film on a substrate, and a first formed film
The step of depositing a metal reflection film on the Cr film and the step of laminating an overcoat having a second Cr film on the deposited metal reflection film. It is characterized by no heating.

[0015]

The undercoat Cr film strengthens the bonding force (adhesiveness) of the reflective film to the substrate and is very useful for forming a defect-free reflective film, which results in extremely excellent optical characteristics. It is possible to obtain a reflective film having

The lowermost layer of the overcoat, Cr
The film functions to fill the irregularities on the surface of the reflective film to smooth it, strengthen the bonding force of the dielectric material formed on the reflective layer with the protective layer, and to make the quality of the protective layer dense. To do. As a result, while further improving the optical characteristics of the reflective film, the amount of water and sulfur components that penetrate the protective layer and penetrate into the reflective film is greatly reduced, and the reflective film is left in a high temperature and high humidity environment for a long time. In addition, it is possible to obtain a metal mirror that has no significant decrease in reflectance or coloring.

Further, according to the method for manufacturing a metal mirror of the present invention, since it is not necessary to heat the substrate in all film forming steps, it is suitable for manufacturing a metal mirror whose substrate is made of plastic.

Further, since the step of heating and cooling the substrate is unnecessary, the manufacturing process is simple and there is no fear of complicating the apparatus. As a result, it is possible to realize a metal mirror which has an extremely high reflectance, is not likely to be significantly deteriorated with time, and is lightweight and inexpensive.

[0019]

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

FIG. 1 is a schematic sectional view showing a metal mirror according to an embodiment. In this method, a base layer 2 made of a SiO film is formed on a surface of a polycarbonate substrate 1, a first Cr film 3 is formed thereon, and an Ag reflection film 4 is formed thereon.
Is laminated, a second Cr film 5 is formed thereon, and an Al ₂ O ₃ film 6a and Si which form an overcoat together with the second Cr film 5 are formed.
The protective layer 6 composed of the O ₂ film 6b is provided.

The substrate is not limited to a polycarbonate substrate, but may be a plastic substrate such as acrylic resin or polyolefin, or a glass substrate such as BK7. The base layer 2 made of a SiO film has a function of improving the adhesive force (coupling force) between the polycarbonate substrate 1 and the Ag reflection film 4 and relaxes the deformation of the substrate 1 due to thermal expansion or hygroscopic expansion. The film is formed by controlling the internal stress of. The internal stress of the SiO film or the SiO ₂ film, which is a silicon oxide film, is a compressive stress and greatly depends on the pressure of the film forming chamber. Therefore, the internal stress is prevented from increasing by adjusting the degree of vacuum in the film forming chamber to 1 × 10 ^-2 Pa. Such control can be omitted for a glass substrate or the like in which the deformation of the substrate is small.

The first Cr film 3 is composed of the SiO underlayer 2 and Ag.
Has a function of increasing the adhesiveness of the reflective film 4 and forming the reflective film 4 with few defects, and the film thickness is 0.1 to 10 nm.
Is preferred. If the film thickness is 0.1 nm or less, the effect is small, and as the film thickness increases, the internal stress tends to increase and the adhesive force tends to decrease.

When used as a highly reflective metal mirror, the Ag reflective film 4 preferably has a film thickness in the range of 100 to 200 nm. A film having a film thickness of 50 nm or less is used as a half mirror having a reflectance corresponding to the film thickness.

The second Cr film 5 is for smoothing the surface of the Ag reflection film 4 to enhance the adhesion with the upper protective layer 6 and to improve the quality of the protective layer 6, and the film thickness is 0. .1
The range of 10 nm is preferable. When the film thickness is 0.1 nm or less, the effect is small, and there is an effect of decreasing the reflectance of the reflective film 4 as the film thickness increases. Therefore, it is desirable to control the film thickness with extremely high accuracy by using both the optical film thickness meter and the crystal film thickness meter.

The protective layer 6 consisting of the Al ₂ O ₃ film 6a and the SiO ₂ film 6b functions to prevent the corrosion of the Ag reflection film 4 and to increase the reflectance and improve the film strength and solvent resistance. . The protective layer 6 includes SiO, SiO ₂ , MgF.
_{It is} advisable to use a thin film of a dielectric material appropriately selected from ₂ , Al ₂ O ₃ , ZrO ₂ , TiO ₂ , Ta ₂ O ₅ and mixtures thereof in a single layer or a plurality of laminated layers.

All of the above thin film layers are formed by the vacuum vapor deposition method without heating the substrate and can be taken out of the vacuum chamber immediately after the film formation. That is,
Since the waiting time for heating and cooling is not required, the manufacturing cycle is short and the manufacturing process is extremely simple.

The base layer 2 made of a SiO film may be omitted depending on the situation. It goes without saying that a reflective film of other metal such as Cu may be used instead of the reflective film 4 of Ag.

According to the present embodiment, the first Cr is provided between the metal reflection film and the surface of the substrate or the underlayer deposited on the surface.
By interposing the film, the adhesion between the reflective film and the substrate can be greatly improved. That is, a reflective film of Ag or the like tends to be a thin film with many cavity defects depending on the surface condition of the substrate and the like.
When the r film is interposed, this tendency is significantly reduced, and it is possible to obtain a reflective film having few packing defects and a high packing density.

Further, the second Cr film interposed between the reflective film and the protective layer fills the cavity defects left in the surface layer of the reflective film to smooth the surface of the reflective film and to improve the quality of the protective film. Helps to be precise. Also, the adhesion between the reflective film and the protective layer is significantly improved.

As described above, by interposing the first and second Cr films, the packing density and the surface smoothness of the reflective film such as Ag are improved, and thereby the corrosion resistance of the reflective film itself is greatly enhanced. At the same time, since the second Cr film densifies the quality of the protective layer, the function of preventing entry of moisture and sulfur components in the atmosphere is significantly improved, and even when left in a high temperature and high humidity environment for a long time. It is possible to obtain an excellent metal mirror that does not have a possibility of deteriorating the appearance or being damaged due to deterioration of the reflectance or coloration, film cracks, peeling, or the like.

Further, as described above, since all the thin films constituting the metal mirror can be formed in the same vacuum chamber and the step of heating and cooling the substrate is unnecessary, the manufacturing process is simple and the manufacturing apparatus is inexpensive. Yes, and therefore greatly helps to reduce the manufacturing cost of metal mirrors.

Next, a specific example of this embodiment will be described.

First Example A polycarbonate substrate was placed in a vacuum vapor deposition apparatus, the substrate was evacuated to a pressure of 1 × 10 ⁻³ Pa or less without heating, and then oxygen gas was introduced to introduce a pressure of 1 × 10 ⁻² Pa. The pressure was adjusted to the above condition to form an SiO underlayer with a film thickness of 50 nm.
Then, the oxygen gas is stopped, and the pressure of 1 × 10 ⁻³ Pa or less is applied to the first Cr film to 5 nm, the Ag reflection film to 150 nm, and the second
Each Cr film was formed to a thickness of 2 nm. further,
Introduce oxygen gas and adjust the pressure to 1 × 10 ^-2 Pa,
Al ₂ O ₃ was deposited to a thickness of 100 nm and a SiO ₂ film was deposited to a thickness of 10 nm, and then taken out from the vacuum vapor deposition apparatus.

FIG. 2 shows the incident angle 45 of the metal mirror of this example.
It is a graph which shows the spectral reflectance in degrees. As can be seen from this figure, the reflectance (initial reflectance) immediately after the production of the metal mirror of this example is extremely high at a wavelength of 500 nm and is uniform over a wide wavelength range. As a result of a quality evaluation test (hereinafter referred to as “initial evaluation test”) immediately after manufacturing, which will be described later, the metal mirror of this specific example has good appearance, solvent resistance, and adhesion resistance in a state immediately after manufacturing. In addition, as a result of a quality evaluation test (hereinafter, referred to as “aging evaluation test”) for evaluating changes in appearance and reflectance over time, it was found that neither appearance nor reflectance was significantly changed.

Second Specific Example After forming each layer up to the second Cr film on a polycarbonate substrate in the same manner as in the first specific example, oxygen gas was introduced to adjust the pressure to 1 × 10 ^-2 Pa. Then, set the SiO ₂ film to 1
A film having a thickness of 40 nm was formed, and a metal mirror having a protective layer made of a single dielectric thin film was manufactured. The results of the initial evaluation test and the elapsed evaluation test were as good as those of the first specific example.

Third Specific Example After forming each layer up to the second Cr film on a polycarbonate substrate by the same method as in the first specific example, oxygen gas was introduced to adjust the pressure to 1 × 10 ^-2 Pa. Then, the SiO ₂ film is
A 0 nm thick Al ₂ O ₃ film was formed to a thickness of 60 nm, and a SiO ₂ film was formed to a thickness of 10 nm to form a metal mirror having a protective layer composed of three dielectric thin films. The results of the initial evaluation test and the elapsed evaluation test were as good as those of the first specific example.

Fourth Concrete Example A substrate made of BK glass was first subjected to a pressure of 1 × 10 ⁻³ Pa or less.
Cr film of 5 nm, Cu reflection film of 150 nm, second Cr film of 2 nm, and oxygen gas were introduced to adjust the pressure to 1 × 10 ^-2 Pa. ₂
An O ₃ film was formed to a thickness of 200 nm to manufacture a near-infrared metal mirror having a protective layer made of a single dielectric thin film. The results of the initial evaluation test and the elapsed evaluation test were as good as those of the first specific example.

Next, the following metal mirrors were manufactured for comparison.

First Comparative Example Oxygen gas was introduced into a polycarbonate substrate in the same manner as in the first specific example to adjust the pressure to 1 × 10 ⁻² Pa, and the SiO ² underlayer was formed to a thickness of 50 nm. It was formed into a thick film. Then, the oxygen gas is stopped and Ag is applied at a pressure of 1 × 10 ⁻³ Pa or less.
Was formed into a film having a thickness of 150 nm. Then, oxygen gas was introduced to adjust the pressure to 1 × 10 ^-2 Pa, and then Al ₂ O
₃ was deposited to a thickness of 100 nm, and a SiO ₂ film was deposited to a thickness of 10 nm to fabricate a metal mirror without the first and second Cr films. As a result of the initial evaluation test, the adhesiveness of the reflective film was insufficient and the reflective film was peeled off from the substrate.

Second Comparative Example Oxygen gas was introduced into a polycarbonate substrate in the same manner as in the first specific example to adjust the pressure to 1 × 10 ⁻² Pa, and the SiO ² underlayer was formed to a thickness of 50 nm. It was formed into a thick film. Then, the oxygen gas is stopped and the first pressure is set to 1 × 10 ⁻³ Pa or less.
The Cr film of 5 nm and the reflection film of Ag were formed to a film thickness of 150 nm, respectively. Introducing oxygen gas further 1 × 10
Adjust the pressure to ^-2 Pa, and set the protective film of SiO ₂ film to 140n.
A second metal mirror having no Cr film was manufactured by forming a film having a thickness of m. As a result of the aging evaluation test, the appearance and reflectance were abnormal.

Table 1 summarizes the results of the initial evaluation test and the time-dependent evaluation test performed on the metal mirrors of the first to fourth specific examples and the metal mirrors of the first and second comparative examples.

[0042]

[Table 1] ⊚: Good ∘: No problem in practical use Δ: Impractical in practical use The reflectance in the initial evaluation test was at a wavelength of 500 nm (4th
A specific example is at 780 nm), and the appearance is evaluated by visually checking for abnormalities such as spiders, film cracks, and film peeling. For solvent resistance, sillbon paper soaked in a mixed solution of alcohol and freonsolve is used. Using 500
Abnormality in appearance was examined after 10 reciprocations under a load of g / cm ^2. Adhesiveness was obtained by sticking cellophane tape on the reflective film surface, quickly peeling it off, and then checking for film peeling. Is. The aging evaluation test is to examine the abnormal appearance and the reflectance at the wavelength of 500 nm (the fourth specific example is 780 nm) after 500 hours under the environment of the temperature of 60 ° C. and the humidity of 90%.

[0043]

Since the present invention is configured as described above, it has the following effects.

It is possible to realize a metal mirror which has an extremely high reflectance, there is no fear that the reflectance will decrease with time, and which is suitable for a plastic optical component and has a simple and inexpensive manufacturing process.

By using such a metal mirror, it is possible to greatly contribute to the improvement of performance, the improvement of durability and the weight reduction of various optical machines.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a film structure of a metal mirror according to an example.

FIG. 2 is a graph showing the reflection characteristics of the metal mirror according to the first specific example.

[Explanation of symbols]

 1 Substrate 2 Underlayer 3 First Cr film 4 Reflective film 5 Second Cr film 6 Protective layer

Claims (8)

[Claims] 1. A metal reflective film formed on the surface of a substrate through an undercoat, and an overcoat laminated on the reflective film, wherein each of the undercoat and the overcoat is formed by: A metal mirror having a Cr film having a film thickness of 0.1 to 10 nm, which is in contact with the reflection film. 2. The metal mirror according to claim 1, wherein the metal reflection film is an Ag film. 3. The metal mirror according to claim 1, wherein the overcoat has a single layer or a plurality of protective layers made of a dielectric material. 4. The dielectric material is SiO, SiO ₂ , Mg
The metal mirror according to claim 3, wherein the metal mirror is selected from F ₂ , Al ₂ O ₃ , ZrO ₂ , TiO ₂ , Ta ₂ O ₅ or a mixture thereof. 5. The metal mirror according to claim 1, wherein the undercoat has a silicon oxide film. 6. The metal mirror according to claim 1, wherein the substrate is made of plastic. 7. A step of forming a first Cr film on a substrate,
It has a step of forming a metal reflection film on the formed first Cr film and a step of laminating an overcoat having a second Cr film on the formed metal reflection film. A method for manufacturing a metal mirror, wherein the substrate is not heated during each step. 8. A silicon oxide film is provided on a substrate and then the first
By depositing the Cr film, and adjusting the degree of vacuum in the deposition chamber in the step of depositing the silicon oxide film,
The method for manufacturing a metal mirror according to claim 7, wherein the internal stress of the silicon oxide film is controlled.