JPH07137157A - Manufacture of optical thin film - Google Patents

Abstract

PURPOSE:To form an optical thin film which hardly causes discoloration of glass and absorption of light by a method wherein, even in the case of a lead- containing glass base, reduction of PbO present in the vicinity of the surface of the glass base due to the ions bombardment is suppressed. CONSTITUTION:In forming an optical thin film on a surface of a lead-containing glass base containing 20wt.% or more of at least lead oxide (PbO) by a sputtering method, a film is formed at film-forming speed as slow as 0.1nm/sec or less until at least a physical film thickness of the optical thin film becomes 10nm or more, or a film is formed by introducing gas containing at least oxygen (O) molecules.

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 optical thin film such as an antireflection film or a half mirror on the surface of an optical glass containing lead oxide (PbO).

[0002]

2. Description of the Related Art Conventionally, in the case of forming an optical thin film such as an antireflection film or a half mirror on the surface of a glass substrate, a vacuum deposition method in which a film forming material is heated by resistance heating or electron beam to adhere to the surface of the glass substrate Has been mainly used. However, in recent years, as disclosed in, for example, Japanese Patent Application Laid-Open No. 62-73202, excellent film adhesion can be obtained without heating the substrate, and automation and mass production are easy as compared with vacuum evaporation. Due to such advantages, a technique for forming an optical thin film by a sputtering method has been studied.

Here, the sputtering method is that the inside of the film forming apparatus is decompressed and an inert gas such as Ar is introduced, and then a high frequency voltage or the like is applied to generate plasma, and a target material is knocked out by Ar ions or the like. This is a technique for forming a thin film on the substrate surface by (sputtering).

[0004]

Generally, there are not a few so-called lead-containing glasses that contain lead oxide (PbO) for adjusting the refractive index in optical glasses. When an optical thin film is simply formed on such a lead-containing glass substrate by the sputtering method as in the conventional technique, the substrate surface is hit by Ar ions in the plasma or sputtered ions, and the ion bombardment thereof is performed. As a result, O of PbO existing near the substrate surface is knocked out and reduced to Pb. Therefore, the lead-containing glass absorbs light, which causes a serious problem of discoloration to yellow.

Therefore, the present invention was developed in view of the above problems in the prior art. Even if an optical thin film is formed on a lead-containing glass substrate by a sputtering method, the glass is discolored or light is absorbed. It is an object of the present invention to provide a method for producing an optical thin film that does not cause

[0006]

According to the present invention, in forming an optical thin film on a surface of a lead-containing glass substrate containing at least 20% by weight of lead oxide (PbO) by a sputtering method, at least a physical layer of the optical thin film is formed. Film thickness is 10n
This is a method of forming a film at a slow film forming rate of 0.1 nm / sec or less until the m or more, or introducing a gas containing at least oxygen (O) molecules.

Here, the optical thin film referred to in the present invention includes, for example, an antireflection film, a reflection increasing film, a half mirror, a polarization beam splitter, a bandpass filter and a cut filter, and the materials constituting them are oxide and Derivatives such as fluorides and metals can be used and are not particularly limited. Further, the sputtering method in the present invention includes, for example, magnetron sputtering, bipolar sputtering, tripolar or quadrupolar sputtering, high frequency sputtering, DC sputtering,
There are bias sputtering, ion beam sputtering, ECR sputtering, facing target sputtering, and the like, and there is no particular limitation. Furthermore, the gas containing O molecules of the present invention means oxygen (O ₂ ), ozone (O ₃ ), water (H
₂ O), carbon monoxide (CO), carbon dioxide (CO ₂ ),
There are nitric oxide (NO) and nitrogen dioxide (NO ₂ ), which are not particularly limited.

At least lead oxide (PbO) is added to 20
The lead-containing glass substrate containing not less than 20% by weight of the lead-containing glass contains 20% by weight or more of lead oxide (PbO) when the optical thin film is formed by the sputtering method as described in the problems of the prior art. However, especially the discoloration of glass and the absorption of light are remarkable, and the action of the present invention is sufficiently exerted,
This is because the effect is great. Further, when forming an optical thin film by a sputtering method, lead oxide (Pb
The lead-containing glass containing 20% by weight or more of O) causes discoloration and absorption of light because the surface of the lead-containing glass is hit by Ar ions in the plasma or sputtered ions in the early stage of film formation. Therefore, at least until the physical film thickness of the optical thin film becomes 10 nm or more and the substrate surface is uniformly protected by the optical thin film, the film is formed at a slow film forming rate of 0.1 nm / sec or less, or At least oxygen (O)
It is desirable to introduce a gas containing molecules to form a film.

[0009]

In the present invention, Ar ions in plasma can be formed by forming the film at a slow film forming rate of 0.1 nm / sec or less by reducing the input power until at least the physical film thickness of the optical thin film becomes 10 nm or more. In addition to reducing the number of sputtered ions and the energy of such ions, the reduction of PbO due to ion bombardment can be suppressed.
Also, when a gas containing O molecules is introduced to form a film until at least the physical film thickness of the optical thin film is 10 nm or more, the oxidation of Pb reduced by the supply of O molecules is promoted. As a result, reduction is suppressed.

Further, after the physical thickness of the optical thin film formed on the lead-containing glass substrate becomes 10 nm or more, the substrate surface is uniformly protected by the optical thin film to prevent ion bombardment. Even if a film is formed at a high film forming rate of 1 nm / sec or more and a gas containing O molecules is not introduced, PbO
No reduction will occur. Therefore, slow down the film formation speed,
The reduction in productivity due to the introduction of the gas containing O molecules is minimized.

[0011]

Embodiment 1 FIGS. 1 and 2 are graphs showing this embodiment. In this embodiment, KzFS1 (P
bO content 38% by weight, refractive index 1.613)
A glass substrate was produced by processing into a shape having a thickness of 30 mm and a thickness of 1 mm. This glass substrate was set in a vacuum chamber of an RF magnetron sputtering device so that the distance from the target was 70 mm. SiO ₂ was used as the target. Next, the inside of the vacuum chamber was evacuated to 1 × 10 ⁻⁴ Pa without heating the substrate. Then, the partial pressure is 1 × 10 ⁻¹ Pa of Ar.
Gas was introduced into the vacuum chamber.

Then, SiO is applied under the condition of a power of 80 W.
₂ was sputtered to form a film with a physical film thickness of 10 nm. The film formation rate at this time was 0.1 nm / sec, which was extremely low. Further increase the input power to 800W, 1n
Film formation was performed at a slow film formation rate of m / sec until the film thickness reached 90 nm. Thus, an antireflection film consisting of one layer of SiO ₂ was obtained. FIG. 1 shows the spectral characteristics of the antireflection film obtained in this example, and FIG. 2 shows the absorption characteristics of the optical components.

According to this embodiment, a good antireflection effect can be obtained with a single layer, and the visible range (400 to 700) of the optical component can be obtained.
(nm) did not absorb light and there was almost no discoloration.

[0014]

Embodiment 2 FIGS. 3 and 4 are graphs showing this embodiment. In this embodiment, LF1 (PbO) is used as the optical glass.
A glass substrate was prepared using a content of 35% by weight and a refractive index of 11.573). This glass substrate was set in the same manner as in Example 1 above. ZrO ₂ and SiO ₂ were used as the target. Next, Example 1 and after venting similarly, partial pressure 5 × 10 ^-2 partial pressure of Ar gas in Pa 5 × 10 ^-2 Pa of O ₂
The mixed gas to which the gas was added was introduced into the vacuum chamber. Subsequently, ZrO ₂ was sputtered under the condition of an applied power of 700 W to form a film until the physical film thickness became 14 nm. The film forming rate at this time was as high as 1 nm / sec.

Next, the introduced gas is subjected to A with a partial pressure of 1 × 10 ⁻¹ Pa.
Switch to r, input power 800 W, film formation rate 1 nm /
SiO ₂ was sputtered under the condition of _second to form a film thickness of 113 nm. Thus, an antireflection film having two layers was obtained. FIG. 3 shows the spectral characteristics of the antireflection film obtained in this example.
FIG. 4 shows the absorption characteristics of the optical components.

According to the present embodiment, the formed antireflection film has a good antireflection effect, does not absorb light in the visible range (400 to 700 nm) of the optical component, and hardly discolors. It was

[0017]

Third Embodiment FIGS. 5 and 6 are graphs showing the present embodiment. In this example, as in Example 2, LF1 was used as the optical glass to manufacture a glass substrate. This glass substrate was set in the same manner as in Example 2. TiO ₂ and SiO ₂ were used as the target. Next, after evacuating the same manner as in Example 1, was introduced a partial pressure 5 × 10 ^-2 Pa Ar gas partial pressure 5 × 10 ^-2 Pa mixed gas obtained by adding CO ₂ gas in the vacuum chamber .

Subsequently, Ti is fed under the condition of an input power of 60 W.
O ₂ was sputtered to form a film with a physical film thickness of 10 nm. The film forming rate at this time was 0.08 nm / sec, which was extremely low. Further, the introduced gas was switched to Ar with a partial pressure of 1 × 10 ⁻¹ Pa, the input power was increased to 900 W, and TiO ₂ was sputtered under the condition of the film forming rate of 1.2 nm / sec to form a film thickness of 76 nm. The first layer was obtained.

Next, input power 800 W, film formation rate 1 nm
SiO ₂ is sputtered under the condition of 1 / second, and the film thickness is 110 nm.
Formed to obtain a second layer. Next, TiO ₂ is sputtered under the conditions of an input power of 900 W and a film forming rate of 1.2 nm / sec.
A film thickness of 76 nm was formed to obtain a third layer. Next, input power 8
SiO ₂ was sputtered under the conditions of 00 W and a film forming rate of 1 nm / sec to form a film having a thickness of 110 nm, thereby obtaining a fourth layer.

Next, input power 900 W, film formation rate 1.2.
TiO ₂ is sputtered under the condition of nm / sec, and the film thickness is 76 nm.
Formed to obtain a fifth layer. Finally, SiO ₂ was sputtered under the conditions of an input power of 800 W and a film formation rate of 1 nm / sec to form a film having a thickness of 110 nm, thereby obtaining a sixth layer. Thus, a half mirror having 6 layers was obtained. FIG. 5 shows the spectral characteristic of the half mirror obtained in this example, and FIG. 6 shows the absorption characteristic of the optical component.

According to the present embodiment, the formed half mirror has a wavelength of He--Ne laser (633 nm),
It was a semi-transmissive film with 50% reflection and 50% transmission, and there was no light absorption at 633 nm of the optical component, and there was almost no discoloration.

[0022]

Comparative Example 1 FIGS. 7 and 8 are graphs showing this comparative example. In this comparative example, KzFS1 was used as the optical glass in the same manner as in Example 1, and was set in the vacuum chamber and exhausted as in Example 1. Then, set the partial pressure to 1 x 10
Ar gas of ^-1 Pa was introduced into the vacuum chamber. Then, SiO ₂ was sputtered under the condition of an input power of 800 W to form a film until the physical film thickness became 90 nm. The film forming rate at this time was very high at 1 nm / sec. In this way S
An antireflection film consisting of one layer of iO ₂ was obtained. FIG. 7 shows the spectral characteristic of the antireflection film obtained in this comparative example, and FIG. 8 shows the absorption characteristic of the optical component.

According to this comparative example, although a sufficient antireflection effect was obtained, the optical components were in the visible range (400 to 700n).
In m), absorption of light occurred and the color changed to yellow.

[0024]

Comparative Example 2 FIGS. 9 and 10 are graphs showing this comparative example. In this comparative example, LF1 was used as the optical glass as in the case of Example 2, and was set in the vacuum chamber and exhausted as in Example 2. After that, set the partial pressure to 1 × 10 ^-1
Ar gas of Pa was introduced into the vacuum chamber. Subsequently, ZrO ₂ was sputtered under the condition of an applied power of 700 W to form a film until the physical film thickness became 14 nm. The film forming rate at this time was very high at 1 nm / sec.

Next, with the introduction of Ar as it is, SiO ₂ was sputtered under the conditions of an input power of 800 W and a film formation rate of 1 nm / sec to form a film having a thickness of 113 nm. Thus, an antireflection film having two layers was obtained. FIG. 9 shows the spectral characteristics of the antireflection film obtained in this example, and FIG. 10 shows the absorption characteristics of the optical components.

According to this comparative example, although a sufficient antireflection effect was obtained, the optical components were in the visible range (400 to 700n).
In m), absorption of light occurred and the color changed to yellow.

[0027]

As described above, according to the method for producing an optical thin film by sputtering according to the present invention, at least until the physical thickness of the optical thin film becomes 10 nm or more.
Since a film is formed at a low film formation rate of 0.1 nm / sec or less, or a gas containing at least O molecules is introduced, PbO existing near the surface of the lead-containing glass substrate is present.
The reduction due to ion bombardment is suppressed, and discoloration of glass and absorption of light are less likely to occur.

[Brief description of drawings]

FIG. 1 is a graph showing Example 1.

2 is a graph showing Example 1. FIG.

FIG. 3 is a graph showing Example 2.

FIG. 4 is a graph showing Example 2.

FIG. 5 is a graph showing Example 3.

FIG. 6 is a graph showing Example 3.

FIG. 7 is a graph showing Comparative Example 1.

FIG. 8 is a graph showing Comparative Example 1.

9 is a graph showing Comparative Example 2. FIG.

FIG. 10 is a graph showing Comparative Example 2.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Ken Kawamata 2-43-2 Hatagaya, Shibuya-ku, Tokyo Olympus Optical Co., Ltd. (72) Inventor Nobuyoshi Toyohara 2-43-2 Hatagaya, Shibuya-ku, Tokyo No. Olympus Optical Co., Ltd. (72) Inventor Issei Tokuda 2-43-2 Hatagaya, Shibuya-ku, Tokyo No. 2 Olympus Optical Co., Ltd. (72) Inventor Yoshiki Nitta 2-43 Hatagaya, Shibuya-ku, Tokyo No. 2 Olympus Optical Co., Ltd. (72) Inventor Toshiaki Namasu 2-43-2 Hatagaya, Shibuya-ku, Tokyo Olympus Optical Co., Ltd.

Claims (2)

[Claims] 1. When forming an optical thin film on the surface of a lead-containing glass substrate containing at least 20% by weight of lead oxide by a sputtering method, at least until the physical thickness of the optical thin film becomes 10 nm or more. A method for producing an optical thin film, which comprises forming a film at a slow film forming rate of 1 nm / sec or less. 2. When forming an optical thin film on the surface of a lead-containing glass substrate containing at least 20% by weight of lead oxide by a sputtering method, at least oxygen until at least the physical thickness of the optical thin film becomes 10 nm or more. A method for producing an optical thin film, which comprises forming a film by introducing a gas containing molecules.