JP2646979B2 - Method for forming alumina film on glass substrate - 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 for forming an alumina film on a glass substrate surface.

[0002]

2. Description of the Related Art Glass substrates that require properties such as wear resistance and corrosion resistance, such as watch lenses and view windows of vacuum equipment, are known as:
The mechanical properties of the glass substrate itself are improved by a heat treatment method or the like. In the heat treatment method, after heating to or near the softening temperature, it is uniformly cooled to generate large internal stress on the entire surface of the glass substrate to improve the mechanical properties. It has been difficult to uniformly cool the entire material and to obtain desired mechanical properties. Therefore, it is conceivable to coat the glass substrate with a coating having abrasion resistance and corrosion resistance, but there was a problem in coating in terms of transparency and adhesion.

An alumina film is used on a metal substrate as a colorless and transparent wear-resistant and corrosion-resistant protective film. As a method of coating an alumina film on a metal surface, for example, Japanese Patent Application Laid-Open No.
As disclosed in Japanese Patent No. 3178, a reactive ion plating method of evaporating metallic aluminum into oxygen and a high-frequency ion plating method of evaporating sintered alumina as disclosed in Japanese Patent Application Laid-Open No. 63-62868 are known. Have been. However, in these methods, even if the film forming conditions deviate even a little, the color changes and the transparency of the base material is not obtained, and the color of the base material is impaired. It cannot be coated on a substrate.

[0004]

When an alumina film is coated on a glass substrate by an ion plating method using alumina as an evaporating material, the thermal expansion coefficient of the alumina film is 8.6 × 10 ^-6 K ^-1 : 1000 ° C.) compared to a glass substrate (example: quartz glass = 0.54 × 10 ⁻⁶ K ⁻¹ : 1000)
C.) is smaller, and the internal stress in the alumina film is high, so that the alumina film is easily peeled off, and the adhesion is low.

Conventional techniques for improving the adhesion between a metal substrate and an alumina film include a method of performing ion bombard cleaning before coating and a method of applying a voltage to the substrate during coating. However, when the above-described ion bombard cleaning or substrate voltage is applied when the alumina film is coated on the glass substrate, dielectric breakdown occurs because the glass substrate and the alumina film have insulating properties. On the other hand, no voltage is applied to the substrate because the coating becomes difficult.

Accordingly, an object of the present invention is to provide a method for forming an alumina film having excellent adhesion to a glass substrate surface and having colorless transparency on the glass substrate surface.

[0007]

According to the present invention, a glass substrate is subjected to a cleaning treatment with pure water, and then a dissolved alumina produced by melting is used as an evaporation material, and a third layer is formed on the glass substrate as a first layer.
The first alumina film is coated at a temperature of less than 1 × 10 ⁻⁴ Torr by heating and holding at 50 to 600 ° C., and a second layer is formed thereon as a second layer.
1 × 10 ⁻⁴ Torr to 1 × 10 ⁻³ To at 50 to 350 ° C.
It is characterized in that the second alumina film is coated in a state where oxygen gas is introduced so as to attain rr, and the total thickness of the first and second alumina films is set to 15 μm or less.

[0008]

The glass substrate includes silicate glass such as quartz glass and soda-lime glass, borosilicate glass used for scientific glass, and phosphate glass such as optical glass. The size and shape of the glass substrate are not particularly limited as long as they can be set in the vacuum reaction tank.

The adhesion and transparency of the alumina film on the glass substrate depend on the pure water washing treatment and the film forming conditions. When degreasing and washing with an organic solvent or an alkaline solution is performed as a pretreatment of the glass substrate, a detergent or the like remains, causing stains and the like, which causes a decrease in adhesion of a film to be formed thereafter. Therefore,
After degreasing, the glass substrate may be washed with pure water. Pure water is supplied by an ion exchange resin or filter, etc.
Purity 1μS after removing residual chlorine and impurities below 1μm
(Micro Siemens) It is desirable to use the following materials heated to 60 to 80 ° C. It is more effective to use physical forces such as ultrasonic waves and rocking together. After washing with pure water, draining and drying are performed.

[0010] The glass substrate thus cleaned is set in a vacuum reactor, evacuated to 1 × 10 ^-5 Torr,
Heat to 350-600 ° C and keep that state,
By coating at less than 1 × 10 ⁻⁴ Torr without introducing oxygen, a film free of cracks and peeling can be obtained. 350
When heated and coated at less than ℃, cracks and peeling occur due to the effect of thermal expansion coefficient and internal stress, and conversely, heating over 600 ℃,
When coated, the first alumina film is crystallized, so that cracks and peeling also occur. Also, 1 × 10 ^-4 Torr
When oxygen is introduced and coated as described above, the mean free path of the evaporating particles is shortened because the probability of collision of the evaporating particles is increased, and as a result, the collision energy to the glass substrate is reduced, and This is undesirable because the adhesion of the alumina film is reduced.

Subsequently, as a second layer on the first alumina film, the film forming temperature is lowered to 250 to 350 ° C.
9% or more of oxygen gas is introduced, and 1 × 10 ⁻⁴ Torr to 1
The second alumina film is formed while maintaining the pressure in the range of × 10 ^-3 Torr. If the film is formed at a temperature lower than 250 ° C., the adhesion to the first alumina film is undesirably reduced. Further, if the oxygen pressure exceeds 1 × 10 ⁻³ Torr, the tungsten filament of the electron gun used for dissolving the evaporation material and the substrate heater are rapidly deteriorated, which is not desirable. In addition, even if the oxygen pressure fluctuates in the above-mentioned pressure range during the film formation, the obtained film characteristics do not change.

The thickness of the alumina film is maintained at 15 μm or less through the first and second layers. If the film thickness exceeds 15 μm, the color changes to white and the mechanical strength decreases, which is not desirable. Further, it is desirable that 30 to 70% of the total thickness of the alumina film is the thickness of the first layer. If the thickness of the alumina film of the first layer is less than 30%, sufficient adhesion cannot be obtained, and
If it exceeds 70%, a high hardness coating cannot be obtained. The film thickness can be controlled by the film forming time.

Alumina as an evaporating material includes sintered alumina produced by sintering and dissolved alumina produced by melting. If sintered alumina is used, a gas is generated from the inside of the alumina during film formation, so bumping is likely to occur, and alumina particles adhere to the surface of the glass substrate, causing a problem that the surface becomes rough. If dissolved alumina is used, bumping can be suppressed considerably because gas generation from alumina is small, and a smooth coated surface can be obtained. However, even if dissolved alumina is used, if the film forming speed is too high, bumping becomes a problem, so the film forming speed needs to be 10 μm / hr or less. The particle size of the dissolved alumina is not particularly limited, but is preferably about 1 to 5 mm.

As the ion plating method used in the present invention, any method may be used as long as the method involves melting of the evaporation material such as resistance heating and electron gun heating.
As a method for ionizing the coating material, any method such as arc discharge, glow discharge, and high-frequency discharge may be used.

[0015] The first alumina film coated under the above conditions lacks oxygen in the alumina film due to decomposition of alumina as an evaporation material, and becomes a film deviated from the chemical composition.
Since the coating is performed at a high temperature, the internal stress is also reduced, so that the hardness is low. Therefore, oxygen is applied to the first alumina film at a concentration of 1 × 10
If the second alumina film is coated in a state where it is introduced so as to be ^-4 Torr to 1 × 10 ^-3 Torr, the insufficient oxygen can be supplemented, and the film formation temperature can be increased to 250 to 350 Torr.
C., the internal stress in the film increases, and Hv 70
A coating with high hardness of about 0 to Hv1100 is obtained.

[0016]

【Example】

(Example 1) As an example of the present invention, an alumina film was coated on a glass substrate by an ion plating method using dissolved alumina (manufactured by Kojundo Chemical Laboratory) as an evaporating material, and the coating hardness was measured by a Vickers hardness meter. Scratch tester (LSRH R
EVETEST) was used to measure the adhesion.

A soda-lime glass substrate was used as a base material. The substrate was subjected to ultrasonic cleaning with ethanol, immersed in pure water heated to 70 ° C. for cleaning, and drained and dried with a drier. After setting in a vacuum reaction tank, the inside of the tank was set to 1 × 10 ⁻⁵ Torr.
Evacuated to r. After reaching the target vacuum degree, 350 ° C
, And the dissolved alumina was heated and melted with an electron beam of 9 kV to 400 mA. When the molten surface of the dissolved alumina became stable, the first layer was coated at less than 1 × 10 ⁻⁴ Torr for 20 minutes without introducing oxygen gas. afterwards,
After the film formation temperature was lowered to 300 ° C., oxygen gas having a purity of 99.99% was introduced, the pressure was set to 1.5 × 10 ⁻⁴ Torr, and the second layer was coated for 40 minutes. No bias voltage is applied to the substrate through the first and second layers. The film forming speed was 5.2 μm / hr. From the film formation under the above conditions, a 5.2 μm alumina film was obtained. The adhesion was 12 N and the hardness was Hv1080. Further, the obtained alumina film was colorless and transparent.

(Embodiment 2) In order to ionize the evaporation material during the formation of the first and second layers, 200 W was applied to the ionization electrode.
An alumina film was formed under the same conditions as in Example 1 except that the high frequency was applied. The obtained film was 4.8 μm, had an adhesion of 15 N, and had a film hardness of Hv1130. Further, the obtained alumina film was colorless and transparent.

Example 3 Example 1 was repeated except that a quartz glass substrate was used as the base material and the film forming temperature of the first layer was 500 ° C.
An alumina film was formed under the same conditions as described above. The obtained coating was 4.5 μm, had an adhesion of 8 N, and had a coating hardness of Hv1050. Further, the obtained alumina film was colorless and transparent.

Example 4 Example 1 was repeated except that a quartz glass substrate was used as the base material and the film forming temperature of the first layer was set to 600 ° C.
An alumina film was formed under the same conditions as described above. The obtained coating film was 5 μm, the adhesion was 7.5 N, and the coating hardness was Hv978. Further, the obtained alumina film was colorless and transparent.

(Comparative Example 1) Example 1 was repeated except that a quartz glass substrate was used as a base material and the film forming temperature of the first layer was set to 300 ° C.
An alumina film was formed under the same conditions as described above. The resulting coating had cracks.

Comparative Example 2 An alumina film was formed in the same manner as in Example 1 except that the thickness of the alumina film was changed to 20 μm through the first layer and the second layer. Adhesion force is 9N, hardness is Hv9
It was 88, but the coating turned white and was not colorless and transparent. In addition, a large number of particles considered to be attached by bumping were observed on the surface.

[0023]

By using the film forming method of the present invention,
An alumina film having excellent adhesion to the glass substrate surface of 8 to 15 N, high Vickers hardness of about Hv 980 to 1100, and colorless and transparent to the glass substrate surface is obtained. Abrasion resistance and corrosion resistance can be improved.

Claims (1)

(57) [Claims] 1. A glass substrate is subjected to a washing treatment with pure water, and then a molten alumina prepared by melting is used as an evaporating material to heat and maintain a first layer on the glass substrate at 350 to 600 ° C. The first alumina film is coated by an ion plating method at less than 10 ^-4 Torr, and a second layer is formed on the first layer at 250 to 350 ° C. at 1 × 10 ^-4 Torr to 1 × 1 as a second layer.
The second alumina film is coated by ion plating in a state where oxygen gas is introduced so as to be 0 ^-3 Torr, and the total thickness of the first and second alumina films is set to 15 μm or less. A method for forming an alumina film on a glass substrate, characterized by comprising: