JPH01287501A - Reflection reducing coating - Google Patents

Abstract

PURPOSE:To improve adhesion and durability of a reflection reducing coating by constituting the coating in such constitution that a first layer counted from the surface of an optical glass element is constituted of SiO2. CONSTITUTION:The title reflection reducing coating is constituted by laminating a dielectric material on an optical glass element 1 prepd. by press-forming a glass base material, wherein a first layer 2 counted from the surface of the optical glass element comprises a layer of SiO2. By this constitution, adverse influence caused by a degenerated layer on the surface of the optical glass element 1 can be avoided, and a reflection reducing coating having high adhesion and high durability is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an antireflection film formed by laminating a dielectric material on the surface of an optical glass element made by press-molding a glass material.

BACKGROUND OF THE INVENTION In recent years, optical glass elements such as optical glass lenses are becoming more aspherical in order to simultaneously achieve simplification and weight reduction of the lens structure of optical equipment, as well as improved optical characteristics. When manufacturing this aspherical glass, the conventional manufacturing method, the polishing method, is difficult to process and mass-produce, so press molding is seen as a promising alternative manufacturing method. It has been put to practical use in disc pickup lenses, etc.

In addition, no matter which manufacturing method the optical glass element is made in, in order to improve the optical properties, it is not possible to layer a dielectric material on the surface of the optical glass element using a vacuum evaporation method or the like to form an anti-reflection film. This is known as a general technology. (For example, "Optical Technology Handbook" by Kubota et al.) Hereinafter, a conventional antireflection film for an optical glass element will be explained with reference to the drawings. Figure 5 shows the refractive index (
Fig. 6(C) is a diagram showing a structure in which an antireflection film made of magnesium fluoride (MgF2) is formed on the surface of an optical glass element having a refractive index of 1.63.
is the optical thickness λ of the antireflection coating. /4(λ.-830nm
) is a diagram showing spectral reflection characteristics when formed to a thickness of . In FIG. 5, 1 is an optical glass element, and 5 is an antireflection film made of magnesium fluoride (MgF2).

The antireflection film 5 is generally formed by a vacuum deposition method.

Problems to be Solved by the Invention In manufacturing the above-mentioned optical glass elements, the image forming performance of the optical glass elements must be superior to that of optical glass elements produced by the conventional polishing method, and extremely high surface precision must be achieved. and surface roughness are required.

For example, in the case of a high-precision camera lens, the surface accuracy is within 5 Newton rings, and the surface roughness is 0.02μ within 1 Ayu.
m or less is required. Furthermore, with the miniaturization of optical equipment, it is desired to make optical components smaller and lighter, and conventional polishing methods cannot produce compact optical components in large quantities and at low cost.

The press method is attracting attention as a method for manufacturing highly precise optical glass elements. Among the press methods, the reheat press method is particularly suitable for manufacturing highly precise optical glass elements. The reheat press method involves creating a glass material with a surface shape similar to the desired optical glass element, and then heating the glass material in a mold.

This method involves applying pressure, cooling, and taking out the molded optical glass element. In this reheat press method, the shape and weight of the glass material and product quality are important, and these have a great influence on the characteristics of the molded optical glass element. A common method is to grind and then polish the surface to make it smooth. However, because an altered layer is formed on the surface of an optical glass element formed by this method due to the thermal influence during press molding,
When a conventional antireflection film is formed on an optical glass element, the problem is that the antireflection film has poor adhesion to the optical glass element and has low durability.

In view of the above problems, the present invention provides an antireflection film with excellent adhesion and durability for an optical glass element made by press-molding a glass material.

Means for Solving the Problems In order to solve the above problems, the present invention provides an anti-reflection film formed by laminating a dielectric material on an optical glass element, comprising:
The anti-reflection film is characterized in that the first N-th layer from the surface side of the optical glass element is a layer made of silicon dioxide (S i 02 ).

Function: As mentioned above, the pressing method is attracting attention as a method for producing high-precision optical glass elements in large quantities and at low cost.

Among these, the reheat press method is said to be suitable for producing optical glass elements with even higher precision.

The present invention provides an anti-reflection film formed by laminating a dielectric material on an optical glass element made by press-molding a glass material, wherein the first N of the anti-reflection film from the surface side of the optical glass element is oxidized. By using silicon (SiO□), it is possible to obtain an antireflection film with excellent adhesion and durability while avoiding the adverse effects of a deteriorated layer on the surface of an optical glass element.

EXAMPLE Hereinafter, an antireflection film according to an example of the present invention will be described with reference to the drawings.

FIG. 2 is a diagram showing the glass material used in the example,
The glass material used had a refractive index of 1.63. In Fig. 2, 10.11 indicates the surface of the glass material to be pressed, r, , r2 are the radius of curvature of each surface, and 1
is the total length of the glass material, and d is the diameter of the glass material. In this example, 1=2.6ms+, r2-3.4m
m, 1=5.1a, d=4.95. This glass material was press-molded using a pair of mirror-finished molds, one with a radius of curvature of 3.4 mm and the other with a radius of 6.08 mm. The molding conditions were a mold temperature of 520 degrees Celsius, a molding pressure of 10 kg/C12, and a molding time of 2 minutes.

Silicon dioxide is applied to the press-molded optical glass element by vacuum deposition to an optical thickness λ. /4(λ.-830nm
) thickness. FIG. 1 is a diagram showing the structure of an antireflection film in a first embodiment of the present invention, and FIG. 6(a)
indicates its spectral reflection characteristics. In FIG. 1, 2 is a layer made of silicon dioxide.

A test was conducted to compare the adhesion and durability of the anti-reflection film of the example of the present invention and a conventional anti-reflection film.
) Adhesive tape peel test (temperature 40"C2 relative humidity 85%
After leaving it in a high temperature / high temperature atmosphere for 1000 hours, stick the adhesive tape to the surface of the optical glass element and peel it off) (2
) Moisture resistance test (temperature 60'C.

The conventional anti-reflection film for comparison was one of the conventional examples, which was a magnesium fluoride anti-reflection film applied to an optical glass element by vacuum coating. Optical film thickness λ by vapor deposition method. /4(
λo-830 nm), and the fifth
It has the structure shown in the figure. The results of the adhesion and durability tests are shown in Table 1.

(Margins below) Table 1 As can be seen from Table 1, the antireflection film of the present invention has silicon dioxide (S i 0 ) as the first layer from the surface side of the optical glass element.
2), which is superior to conventional antireflection films in terms of adhesion and durability.

A second embodiment of the present invention will be described below with reference to the drawings. The optical glass element used in this example is the same as that used in the first example described above.

FIG. 3 is a diagram showing the structure of an antireflection film in a second embodiment of the present invention, and FIG. 6 and others) show its spectral reflection characteristics. In FIG. 3, 2 is silicon dioxide (S i
3 is aluminum oxide (A/
! 20. ) is titanium dioxide (T i
02), 3rd N and 5 are magnesium fluoride (M
gF2), and the optical thickness of each layer is λ. /4, λ. /4. λ. /2. λ. /4(λ
. The anti-reflection film of the second example of the present invention, which has a wavelength of -830 nm), was also subjected to the adhesive tape peel test and moisture resistance test, but no abnormalities were found as in the first example. Further, as can be seen from FIG. 6, the spectral reflection characteristics of this embodiment are superior to those of the conventional example.

A third embodiment of the present invention will be described below with reference to the drawings. The optical glass element used in this example has a refractive index of 1.43 and was formed by the process described above. (Drawings showing swelling and softening are omitted.) FIG. 4 is a diagram showing the structure of an antireflection film in the third embodiment of the present invention, and FIG. 7 Fdl shows its spectral reflection characteristics. For comparison, FIG. 7(e) shows the optical film thickness λ of magnesium fluoride (MgF2) on the optical glass element. /4 (λ0 = 830 nm) and the characteristics when forming an antireflection film with silicon dioxide (SiC2
) optical film thickness λ. 4 shows the characteristics when an antireflection film of /4 (λ.=830 nm) is formed. Figure 7(e),
As can be seen from (f), in the case of a low refractive index glass element with a refractive index of 1.48 or less, a single layer antireflection film has a large residual reflectance, so it is necessary to use a multilayer antireflection film.

The structure of the antireflection film in the third embodiment of the present invention is the same as that in the second embodiment, and in FIG. (Afi208), 4 is a third layer made of titanium dioxide (Ti02), 5 is a fourth layer made of magnesium fluoride (MgF2), and the optical thickness of each layer is λ. /4. λo/4. λ. /2
．． λ. /4 (λ.-830 nm).

The anti-reflection film of this example was also subjected to the adhesive tape 211 release test and moisture resistance test, but as with the first and second examples, no abnormalities were found.

In addition, the above-mentioned 2. The number of layers of the anti-reflection film in the third embodiment, the dielectric material constituting the anti-reflection film, and the optical film thickness of each layer are not particularly limited to those mentioned above, but may vary depending on the desired characteristics, design wavelength, etc. The first layer from the surface side of the optical glass element is silicon dioxide (S I O2).
If the anti-reflection film is formed from the above, it is possible to obtain an anti-reflection film with excellent adhesion and durability.

Effects of the Invention As is clear from the above explanation, the anti-reflection film of the present invention is an anti-reflection film formed by laminating a dielectric material on an optical glass element made by press-molding a glass material.
Silicon dioxide (S
By forming the anti-reflection film from iO□), it is possible to obtain an antireflection film with excellent adhesion and durability, which has great practical value.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the antireflection film in the first embodiment of the present invention, FIG. 2 is a block diagram showing the shape of the glass material used in the first and second embodiments of the present invention, and FIG. is the second aspect of the present invention.
FIG. 4 is a block diagram of an anti-reflection film in the third embodiment of the present invention, FIG. 5 is a block diagram of a conventional anti-reflection film, and FIGS. The figure is a spectral reflection characteristic diagram. 1... Optical glass element, 2... Layer made of silicon dioxide, 3... Layer made of aluminum oxide, 4... Layer made of titanium dioxide, 5.
...layer consisting of magnesium fluoride, 10.11.
... Glass material side to be pressed, (a) ...
...Antireflection film in the first embodiment of the present invention, (b)
...Antireflection film in the second embodiment of the present invention, (C) ...Antireflection film in the conventional example, (d)...
...Antireflection film in the third embodiment of the present invention, (
e)...Single layer anti-reflection film (comparative example), (f)
...Single layer antireflection film (comparative example). Name of agent Patent attorney Toshio Nakao 1 person 1- Optical glass elements Figure 3 Figure 4 Figure 5

Claims (2)

[Claims] (1) An anti-reflection film formed by laminating a dielectric material on an optical glass element made by press-molding a glass material, the anti-reflection film being the first layer from the surface side of the optical glass element.
An antireflection film characterized in that each layer is a layer made of silicon dioxide (SiO_2). (2) The antireflection film according to claim (1), wherein the glass material has a refractive index (n_d) for d-line of 1.48 or less.