JPH04143702A - Reflection preventive film - Google Patents

Abstract

PURPOSE:To obtain a superior spectral reflection characteristic over a wide wavelength range, to have superior durability, and to maintain stable performance by laminating layers made of specific materials in specific order. CONSTITUTION:The optical film thicknesses of the 1st, 2nd, and 3rd layers which are laminated in order on the surface of an optical component are denoted as n1d1 - n3d3 within ranges shown by expressions I - III. Here, lambda is the wavelength of applied light, n1, n2, and n3 are the refractive indexes of the 1st, 2nd, and 3rd layers to the light with the wavelength lambda, and d1, d2, and d3 are the thicknesses of the 1st, 2nd, and 3rd layers. Consequently, reflection prevention effect is superior over a wide wavelength range and the sufficient durability is obtained.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an anti-reflection coating applied to optical components constituting optical application equipment such as office automation equipment, optical communication, optical information processing, and cameras. .

[Conventional technology]

Conventionally, optical components such as lenses and prisms have been provided with antireflection layers in order to reduce harmful surface reflections.

Reducing surface reflection is particularly important for optical components used in laser application equipment, and antireflection layers that meet this purpose generally have a single-layer structure made of a low refractive index material.
Alternatively, a multilayer structure in which a high refractive index material layer and a low refractive index material layer are combined is often used.

[Problem to be solved by the invention]

However, such a conventional antireflection film has a reflectance of 1.3% or more in a single layer structure, for example, and does not have sufficient antireflection performance. In addition, in the case of a two-layer membrane,
Although it is possible to reduce the reflectance in the central wavelength range to 0.2% or less, there is a problem that the reflectance increases rapidly in wavelength ranges far from this, so it is not satisfactory as an anti-reflection coating for optical components. It wasn't.

Furthermore, these antireflection films are formed by vacuum deposition on the surface of optical components, but there is also a problem that their durability is not good.

The present invention was made in view of the above circumstances, and an object of the present invention is to provide an antireflection film for optical components that has an excellent antireflection effect over a wide wavelength range and has sufficient durability.

[Means for Solving the Problems] An object of the present invention is to provide a first layer made of silicon dioxide, a second layer made of cerium oxide or tantalum pentoxide, and a third layer made of silicon dioxide on the surface of an optical component. The optical film thicknesses of the first layer, the second layer and the third layer are each expressed by the following formula: % formula % where λ is the wavelength of the applied light, nl, nl and n3 is the refractive index of the first layer, second layer, and third layer, respectively, with respect to light of wavelength λ, and d, d, and d are the film thicknesses of the first layer, second layer, and third layer, respectively.

nl dl , nz dZ and n within the range expressed by .

d, and a first layer made of silicon dioxide and a second layer made of a mixture of zirconium oxide, titanium oxide and yttrium oxide. A third layer made of silicon dioxide, a fourth layer made of the mixture, and a fifth layer made of silicon dioxide are sequentially laminated on the surface of the optical component, and the first layer, the second layer, and the third layer , the optical thicknesses of the fourth layer and the fifth layer are each expressed by the following formula: % formula % where λ is the wavelength of the applied light, n1tn2.

n 3 y na and n are the refractive indices of the first layer, second layer, third layer, fourth layer, and fifth layer, respectively, for light of wavelength λ, d, , dt , d, , d, and d , are the film thicknesses of the first layer, second layer, third layer, fourth layer, and fifth layer, respectively.

n, dl 9n2 dZ , n within the range expressed by
= d.

This can also be achieved by an antireflection coating for an optical component characterized by having values of , n4d4 and ns d.

In order to form the antireflection film of the present invention on the surface of an optical component, each unit layer constituting the antireflection film is sequentially laminated using a film formation technique such as a vacuum evaporation method or an ion blating method. is used.

[Function] The antireflection film of the present invention formed as described above has excellent optical properties and durability.

[Example 1] Acrylic resin with special alicyclic group (Hitachi Chemical 0Z-1
000, refractive index: 1.49), was precisely cleaned, thoroughly dried, and installed in a vacuum evaporation apparatus under vacuum conditions of 1X10-' to 4X10-5)-1. Optical thickness of 54 nm by electron beam heating
A first layer was formed by depositing a film of silicon dioxide. The thickness of this layer corresponds to 0.069λ when λ is 780 nm.

Next, in the same way, the optical thickness was reduced to 78 nm (0,100
A second layer is formed by vapor depositing a cerium oxide film with an optical thickness of 248 nm.
A third layer was formed by depositing a silicon dioxide film of m (corresponding to 0,318λ) to obtain a three-layer antireflection film.

The results of measuring the spectral reflectance of the antireflection film thus obtained are shown in FIG. 1, and the reflectance was 0.5% or less over the wavelength range from 720 to 840 nm.

[Example 2] On the surface of a plate-shaped optical component molded from polycarbonate resin (Kijin Kasei AD-5503, refractive index: 1.56),
In the same manner as in Example 1, the optical thickness of the first layer was 47.
A film of silicon dioxide with an optical thickness of 93 nm (corresponding to 0,119λ) was formed as a second layer, and then a film of tantalum pentoxide with an optical thickness of 93 nm (corresponding to 0,119λ) was added as a second layer. Optical thickness 242n as 3 layers
m (corresponding to 0.31λ) silicon dioxide films were successively formed to obtain a three-layer antireflection film.

The results of measuring the spectral reflectance of the antireflection film thus obtained are shown in FIG. 2, and the reflectance was 0.5% or less over the wavelength range from 720 to 84 on#l.

[Example 3] Using the same acrylic resin optical parts as used in Example 1, the same vacuum evaporation method as in Example 1 was used to achieve a vacuum degree of 5×10.
Under conditions around -s Toll, the first layer has an optical thickness of 63 nm (if λ is 78 on-, then o, o s iλ
A mixture of zirconium oxide, titanium oxide and yttrium oxide (weight ratio 84:6:14) with an optical thickness of 69n+* (corresponding to 0,088λ) was used as the second layer. The third layer is a silicon dioxide film with an optical thickness of 61 nm (corresponding to 0,078λ), and the fourth layer is a silicon dioxide film with an optical thickness of 197 nm.
A film of the same mixture of zirconium oxide, titanium oxide and yttrium oxide as the second layer (corresponding to 0,252λ), and a fifth layer with an optical thickness of 195 nm...
(corresponding to 0,250λ) were sequentially formed to obtain an antireflection film having a five-layer structure.

The results of measuring the spectral reflectance of the antireflection film thus obtained are shown in FIG. 3, and the reflectance was 0.3% or less over the wavelength range of 700 to 900 nm.

[Example 4] A five-layer antireflection film was formed in the same manner as in Example 3 on the surface of an optical component made of optical glass (BK7, refractive index: 1.51).

This anti-reflection film has an optical thickness of 56 nm as the first layer.
(corresponding to 0.071λ when λ is 780nm), the second layer has an optical thickness of 80nW (
A mixture of zirconium oxide, titanium oxide and yttrium oxide (weight ratio 80:6)
:14) film, with an optical thickness of 55 nm as the third layer (
A film of silicon dioxide with an optical thickness of 194 nm (corresponding to 0,071λ) as the fourth layer, the same mixture of zirconium oxide, titanium oxide and ttrium oxide as the second layer with an optical thickness of 194 nm (corresponding to 0,249λ). A film and a silicon dioxide film having an optical thickness of 195 mm (corresponding to 0°250 λ) were successively formed as a fifth layer.

The results of measuring the spectral reflectance of the antireflection film thus obtained are shown in FIG. 4, and the reflectance was 0.2% or less over the wavelength range from 700 to 900 nm.

[Comparative Example 1] A plate-shaped optical component similar to that used in Example 1 was coated with an optical thickness of 194r+n on the surface by the same method as in Example 1.
A single-layer antireflection film of magnesium fluoride of + (corresponding to 0.249λ when λ is 78On11) was formed.

The results of measuring the spectral reflectance of this antireflection film are shown in FIG. 5, and the reflectance was 1.5% or more.

[Comparative Example 2] A plate with an optical thickness of 193 nm (
A first layer of zirconium oxide with a thickness of 196 nm (which corresponds to 0.247 λ if λ is 780 nm) and an optical thickness of 196 nm (
A second layer of cerium fluoride (corresponding to 0.251λ) was sequentially laminated to form a two-layer antireflection film.

The results of measuring the spectral reflectance of this antireflection film are shown in FIG. In this case, the reflectance at the center wavelength of 780 nm is 0.1% or less, but as the wavelength deviates from the center, the reflectance increases rapidly.

[Test Example] The durability of an antireflection film provided on the surface of an optical component was evaluated by the following method.

Humidity test: After being left in a constant temperature and humidity chamber at a temperature of 45° C. and a relative humidity of 95% for 24 hours, it was dried, and changes in the state of the film were observed. No abnormalities were observed in the films of Examples 1.2.3.4 and Comparative Example 2, but peeling and clouding occurred in the film of Comparative Example 1.

Thermal Shock Test After repeating 10 times of leaving the product in an environment of 30'C and 70C for 30 minutes each, the product was returned to room temperature and the surface condition was observed. No changes were observed in the films of Example 1.2.3.4 and Comparative Example 2, but in Comparative Example 1
A crank was growing on the membrane.

[Effects of the Invention] The antireflection film of the present invention is formed by laminating layers made of a specific material in a specific order, and exhibits excellent spectral reflection characteristics in a wide wavelength range from 700 to 900 nm. It has excellent durability and maintains stable performance, making it extremely useful.

[Brief explanation of drawings]

1, 2, 3 and 4 are spectral reflection characteristic diagrams of the antireflection films of Examples 1.2.3 and 4 of the present invention, respectively, and FIG. 5 and 6 are respectively Comparative example 1 and comparative example 2
FIG. 2 is a spectral reflection characteristic diagram of an antireflection film.

Claims (2)

[Claims] (1) A first layer made of silicon dioxide, a second layer made of cerium oxide or tantalum pentoxide, and a third layer made of silicon dioxide.
layers are sequentially laminated on the surface of the optical component, the first layer,
The optical thicknesses of the second layer and the third layer are determined by the following formulas: n_1d_1: 0.06λ to 0.07λ, n_2d_2: 0.10λ to 0.12λ, and n_3d_3: 0.31λ to 0. 32λ However, λ is the wavelength of the applied light, n_1, n_2 and n_3 are the refractive indices of the first layer, second layer and third layer, respectively, for light with wavelength λ, d_1, d_2 and d_3 are the first layer, respectively. This is the film thickness of the second layer and the third layer. An antireflection film for an optical component, characterized in that it has values of n_1d_1, n_2d_2, and n_3d_3 within the range expressed by: (2) a first layer consisting of silicon dioxide and zirconium oxide,
A second layer made of a mixture of titanium oxide and yttrium oxide, a third layer made of silicon dioxide, a fourth layer made of the mixture, and a fifth layer made of silicon dioxide are sequentially laminated on the surface of the optical component. The optical thicknesses of the first layer, the second layer, the third layer, the fourth layer, and the fifth layer are each expressed by the following formula: n_1d_1: 0.07λ to 0.08λ, n_2d_2: 0.08λ ~0.11λ, n_3d_3: 0.07λ to 0.08λ, n_4d_4: 0.24λ to 0.26λ, and n_5d_5: 0.24λ to 0.26λ, where λ is the wavelength of the applied light, n_1, n_2, n3
, n_4 and n_5 are the refractive indexes of the first layer, second layer, third layer, fourth layer and fifth layer, respectively, for light of wavelength λ,
d_1, d_2, d_3, d_4 and d_5 are the film thicknesses of the first layer, second layer, third layer, fourth layer and fifth layer, respectively. n_1d_1, n_2d_ within the range expressed by
2. An antireflection film for an optical component, characterized by having values of n_3d_3, n_4d_4, and n_5d_5.