JPS61159602A - Multi-layered antireflection film - Google Patents

Abstract

PURPOSE:To improve the reflection preventive effect in the entire region of visible wavelengths by forming multi-layered antireflection films on a substrate, incorporating a specific high refractive index material and low refractive index material therein and forming the 2nd layer to a specific layer thickness. CONSTITUTION:The multi-layered films into which the high refractive index material selected from ZrO2, TiO2, Nd2O3, CeO2, TaO2, InO2 and HfO2 and the low refractive index material selected from MgF2, SiO2, cyrolite and LiF are incorporated are laminated on the substrate to form the antireflection films. The conditions expressed by the formula are required to be satisfied where the film thickness of the 2nd layer from the substrate side is designated as N2d2 and lambda as the wavelength of light. The satisfactory reflection preventive effect is provided in the entire region of visible wavelengths for various kinds of substrate glass having a wide range of refractive indices by forming such multi-layered antireflection films.

Description

[Detailed description of the invention] Technical field The present invention relates to an antireflection coating consisting of a multilayer thin film.

BACKGROUND OF THE INVENTION Many single-layer or multi-layer antireflection films deposited on the surface of optical glass have been proposed.

For example, an antireflection film consisting of seven thin films described in Japanese Patent Publication No. 53-10861 can be mentioned.

The anti-reflection coating consists of seven layers of thin film salt, high refractive index materials such as zirconium oxide (ZrO2) and titanium oxide (TiO2).
).

Neodymium oxide (Ndgos) - cerium oxide (CeO
2) Tantalum oxide (Tag3), indium oxide (
Ink, ), is composed of magnesium fluoride (MgF2), silicon oxide (SiO2), cryolite, and lithium fluoride (LiF) as low refractive index materials, and the optical thin film of each layer is adjusted to the refractive index of the substrate glass. It is to be changed appropriately depending on the situation. Furthermore, the optical thickness of the second high refractive index layer, counting from the air side, is λ/2 or more.

However, in a multilayer anti-reflection film having the above structure, the optical thickness of each layer must be changed according to the refractive index of the substrate glass, and there are many points to control the film thickness in actual production. It was difficult to maintain stable reproducibility of characteristics.

The multilayer antireflection coatings shown in the first to tenth examples shown in Table 1 above are composed of seven thin layers, and the layer numbers are such that the first layer is on the air side, and the layers are sequentially numbered toward the substrate side. 2
layer to seventh layer, the first of the first layer to seventh layer
．． Third. Fifth. each seventh layer has a refractive index of 1.38;
Magnesium fluoride (MgF2), which has stable optical properties and excellent wear resistance and moisture resistance, is used; 4th.
Zircon oxide (ZrO2) having a refractive index of 2.00 and stable optical properties is used for each of the sixth layers, and the refractive index of the substrate glass is varied over a wide range,
Accordingly, the optical thickness of the sixth layer (ie, the second layer counted from the substrate) is set so as to obtain a sufficient antireflection effect over the entire visible wavelength range.

As is clear from the diagrams in FIGS. 1 to 10 showing the spectral reflection characteristics obtained by each of the antireflection films constructed in the first to tenth embodiments, the antireflection films of each of the examples have visible wavelengths. It has a sufficient anti-reflection effect over the entire area.

Further, the optical thickness of each layer in each example is as shown in Table 1, and the design wavelength is 500 nm.

The materials constituting each layer of the first to tenth examples shown in Table 1 are merely illustrative, and are not limited to these materials. Examples of high refractive index materials include zirconium oxide (Z
r02) plus titanium oxide (T'i0.).

Neodymium oxide (Nd, O2), cerium oxide (CeO
2).

Tantalum oxide (TaO5) l (Tag,) to indium oxide (Ink,).

Hafnium oxide (Hfo2) and the like can be mentioned, as well as mixtures of selected plurality of these.

In addition, as a low refractive index substance, magnesium fluoride (M
gFz) plus silicon oxide (Sif2), cryolite.

Examples include lithium fluoride (LiF).

Furthermore, although Table 1 shows only the antireflective coating consisting of seven thin layers, the number of layers is not limited to this, and the same effect can be obtained with a multilayer antireflective coating consisting of the required number of layers. It can be implemented while

Effects of the invention By changing only the thickness of the second layer from the substrate among the thin films of the multilayer antireflection coating, sufficient antireflection can be achieved over the entire visible wavelength range for various substrate glasses with a wide range of refractive index. An effective antireflection film can be obtained.

Furthermore, from the viewpoint of industrial productivity, the reproducibility is good, and the yield of this type of multilayer antireflection film can be improved.

[Brief explanation of drawings]

1 to 10 are diagrams showing the spectral reflection characteristics of each antireflection film obtained by the first to tenth embodiments of the present invention. Figure 1 ρ Wavelength Figure 2 Wavelength Figure 3 Figure 4 Wavelength Figure 5 Wavelength Figure 8 Wavelength Figure 7 Figure 8 R-t, + Wavelength Figure 9 Wavelength Figure 10 Wavelength long

Claims (3)

[Claims] (1) In a multilayer antireflection film, zirconium oxide (ZrO_2) and titanium oxide (T) are used as high refractive index substances.
iO_2), neodymium oxide (Nd_2O_3), cerium oxide (CeO_2), tantalum oxide (TaO_3)
, indium oxide (InO_2), hafnium oxide (H
fO_2) or a selected mixture thereof as a low refractive index substance, magnesium fluoride (MgF_2),
Silicon oxide (SiO_2), cryolite, lithium fluoride (
LiF) was used, and the thickness of the second layer counted from the substrate was 0.07λ≦N_2d_2≦0.15λ, where the optical thickness of the second layer was N_2d_2 and λ was the wavelength of light. A multilayer anti-reflection film characterized by being composed of (2) The multilayer antireflection film is composed of seven antireflection films, and each of the first, third, fifth, and seventh layers counted from the substrate is made of magnesium fluoride (MgF_2). A multilayer antireflection film according to claim 1. (3) The multilayer anti-reflection coating consists of seven anti-reflection coatings, and the second, fourth, and sixth layers counting from the substrate are zirconium oxide (ZrO_2), hafnium oxide (HfO_2), and hafnium oxide (HfO_2).
_2), tantalum oxide (TaO_5) or a mixture of zirconium oxide (ZrO_2) and titanium oxide (TiO_2), or zirconium oxide (ZrO_2)
2) and tantalum oxide (TaO_5).