JPH06102401A - Method of forming antireflection film - Google Patents

Abstract

(57) [Summary] [Object] The present invention relates to a method for forming an antireflection film for use in optical parts and the like.
It is an object of the present invention to provide a gF ₂ ) film which has high adhesion and durability without the conventional substrate heating and has an effect of preventing crack generation. [Configuration] Magnesium fluoride (Mg
It has a structure of forming an antireflection film made of F ₂ ), and its forming method is to form an MgF ₂ evaporated film while irradiating an electron beam to the evaporated part while the optical component serving as the substrate is not heated. A method for forming a characteristic antireflection film.

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 a thin film such as an antireflection film used for optical parts.

[0002]

_2. Description of the Related Art Conventionally, MgF ₂ is transparent in the visible to near-infrared region, has a low refractive index in the visible region, and can be easily deposited, so that it is useful as an optical thin film, particularly as an antireflection film. Is one of the optical materials used in. In addition, MgF ₂ has a substrate temperature of 300 to 4 in vacuum.
The MgF ₂ film was hardened and made durable by using a hot coating method in which vapor deposition was performed at a high temperature of 00 ° C. A conventional MgF ₂ antireflection film and a method for forming the same will be described below with reference to the drawings, using an MgF ₂ single-layer antireflection film as an example.

[0003] Figure 4 anti-reflection film 7 of MgF ₂ on the surface of the glass substrate _{8 nd = λ 0/4 (} nd: optical thickness, lambda _0:
It is sectional drawing when it forms in the center wavelength of an antireflection wavelength range. The antireflection film 7 of MgF ₂ is usually formed by a vacuum vapor deposition method, which is shown in FIG. MgF ₂ and a substrate are prepared in an evaporation source 2 and a substrate holder 3 in a vacuum deposition tank 1 kept in a vacuum, respectively. Here, the MgF ₂ film deposited on the substrate side at room temperature (without heating) is soft and easily scratched. To avoid this, use heater 5
Vapor deposition is performed while heating at 00 to 400 ° C. By this method, a MgF ₂ film which is strong and hardly scratched was obtained.

However, although inorganic glass has been often used for optical components such as lenses, in recent years, plastics, which are lightweight, easy to process, and excellent in mass productivity, are used as optical components. It's coming.
Along with this, recently, in order to improve the adhesion and durability of the antireflection film on the surface of the plastic substrate, a method of heating the plastic substrate to 60 ° C. to 80 ° C. for vacuum deposition and a method of RF ion plating have been used. A method of forming an antireflection film using the same has been performed. Further, by accelerating the inert gas ions generated by the ion source to several hundreds to several kV and irradiating the film being formed (hereinafter referred to as ion beam assist), relaxation of internal stress of the film and adhesion A method of obtaining effects such as improvement is also proposed.

[0005]

When a plastic substrate is used, the conventional method for forming an antireflection film made of magnesium fluoride using a glass substrate by the vacuum deposition method is not suitable for the plastic flow temperature and thermal deformation. Since the temperature is low and there is a problem of gas released from the inside of plastic, it is impossible to heat the substrate (300 ° C to 400 ° C) when forming a vapor deposition film on a glass substrate, and to obtain a strong vapor deposition film. However, since the antireflection film is formed on the plastic substrate at a low temperature of 60 ° C. to 80 ° C. or less, the adhesion of the film is poor and the durability is low. Also, as described above, the plastic substrate is heated to 60 ° C to 80 ° C, or the RF
The antireflection film formed by using the ion plating method is apt to be cracked, and it is difficult to keep the conditions of formation constant and to keep the plastic surface constant, which is not suitable for mass production. Furthermore, even with the ion beam assisted method, MgF ₂ is decomposed into magnesium and fluorine, the fluorine is dissipated as a gas, and the formed film contains a large amount of magnesium. As a result, it has a drawback that it becomes a film having a large amount of absorption and cannot be used as an optical thin film.

In view of the above problems, the present invention has an object of providing a method of forming an MgF ₂ film which is strongly scratch-resistant, suppresses the occurrence of cracks, and improves the adhesion.

[0007]

In order to achieve the above object, the present invention provides a method of forming an antireflection film by depositing a vapor deposition film of MgF _{2 on} the surface of an optical material by vacuum vapor deposition to an arbitrary thickness. It is provided with a manufacturing process in which the film is irradiated with an electron beam when it is formed.

[0008]

According to the present invention, the MgF ₂ film, which is an antireflection film, maintains the durability by the above-described structure and forming method, and at the same time, the occurrence of cracks is suppressed by relaxing the internal stress and the adhesion is improved.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An antireflection film according to an embodiment of the present invention and a method for forming the same will be described below with reference to the drawings.

FIG. 2 is a sectional view of an antireflection film according to an embodiment of the present invention. Although the structure is the same as the conventional one,
In this example, the substrate is plastic.

FIG. 1 shows how the antireflection film is formed.
The conditions for forming the MgF ₂ film are as follows. Vacuum deposition container 1
After exhausting the inside of the chamber to 2.0 × 10 ^-5 Torr, the unheated glass substrate mounted on the substrate holder 3 is irradiated with an electron beam by the electron gun 4 and evaporated from the evaporation source 2 MgF ₂ optical and on a glass substrate film thickness nd = λ _0/4
At (λ ₀ = 520 nm), the vapor deposition rate is about 8 to 11Å / sec.
Formed by.

By irradiating the MgF ₂ being formed with an electron beam, the effect of improving durability can be obtained by hardening the vapor deposition film obtained when vapor deposition is performed while heating the substrate. Further, similar to the ion beam assist, the internal stress is relaxed, the generation of cracks is suppressed, and the adhesion is improved. However, the drawback of ion beam assist was Mg.
There is no such thing as decomposing F ₂ .

The tests carried out to confirm the adhesion and durability of the antireflection film of the above-mentioned examples were as follows: (1) Adhesive tape peeling test (temperature 40 ° C., relative humidity 85% in high temperature and high humidity atmosphere) After being left for 1000 hours, the adhesive tape is brought into close contact with the surface of the optical component and peeled off.), (2) Moisture resistance test (temperature 4
1000 in a high temperature and high humidity atmosphere at 0 ° C and 95% relative humidity
(3) Thermal shock test (Temperature -40 ℃, 120 ℃)
Leave it in the low and high temperature atmosphere for 30 minutes alternately for about 1
00 hours).

[0014]

[Table 1]

As can be seen from Table 1, the antireflection film of this example has excellent adhesion and durability. Further, conventionally, cracks were observed in some cases when the antireflection film was formed, but in this example, it was always stable.

[0016]

As is apparent from the above description, the antireflection film of the optical component of the present invention has MgF _{2 on} the surface of the optical material.
When a vapor-deposited film made of is vapor-deposited and formed to a desired thickness by electron beam irradiation, the film can be highly durable without heating the substrate, and cracks can be prevented. It is also possible to improve adhesion.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a vapor deposition method according to an embodiment of the present invention.

FIG. 2 is a sectional view of an optical component and an antireflection film according to an embodiment of the present invention.

FIG. 3 is a diagram illustrating a conventional vapor deposition method.

FIG. 4 is a sectional view of a conventional optical component and an antireflection film.

[Explanation of symbols]

1 Vacuum Deposition Tank 2 Evaporation Source 3 Substrate Holder 4 Electron Gun 5 Heater 6 Plastic Substrate 7 Magnesium Fluoride (MgF ₂ ) Film 8 Glass Substrate

Claims (2)

[Claims] 1. When forming an antireflection film made of magnesium fluoride (MgF ₂ ) on the surface of an optical component substrate,
While irradiating the surface of the optical component substrate with an electron beam, MgF
_2. A method for forming an antireflection film for vapor deposition of ₂ . In forming the wherein the MgF ₂ film, optic substrate on which is deposited antireflection film according to claim 1, wherein the particular performing remains MgF ₂ deposition was maintained at 100 ° C. or less without heating Forming method.