JPH02165101A - Optical antireflection film - Google Patents

Abstract

PURPOSE:To improve durability by mixing yttria powder and zirconia powder at the compsn. ratio of the solid soln. range of the yttria and zirconia and forming a yttria-stabilized zirconia layer by sputtering on the light transparent body of an optical device with the sintered body of the yttria-stabilized zirconia formed by sintering the above-mentioned mixture as a pole. CONSTITUTION:The yttria powder and the zirconia powder are mixed in the solid soln. range of the yttria and the zirconia so that the content of the Y2O3 is in the range of 0.1 to 40mol% of the zirconia powder. The ZrO2 powder and the Y2O3 powder are precisely mixed in this compsn. and the body obtd. by sintering this molding is used as one pole of sputtering. The yttria-stabilized zirconia layer is formed by sputtering on the light transparent body of the optical device. Since the films are stuck by the sputtering method, the distance between the target and the one pole of sputtering is short and the respective films stick strongly. There are no differences in the film structure between the central part and peripheral part of the films. An important contribution is thus made to the improvement in the durability and the reduction of the compsn. to the metal is obviated by the reduced pressure inert atmosphere. The formation of the designed films is thus possible.

Description

[Detailed description of the invention] C) Industrial application field) The present invention relates to optical antireflection coatings.

[Conventional technology]

In order to prevent light reflection on the surfaces of camera lenses, glasses, cathode ray tubes, etc., the surfaces are coated with optical anti-reflection films.

Such an optical antireflection film is disclosed in, for example, Japanese Patent Application Laid-Open No. 55-2
2704, JP 56-59202, JP 60-29701, JP 61-189501
JP-A No. 62-272202, etc.

All of these optical antireflection films are formed by a vapor deposition method.

In the invention described in Japanese Patent Application Laid-open No. 55-22704,
It was difficult to deposit the anti-reflection film by the conventional vapor deposition method so as to obtain the optical properties as calculated.
l By using a mixture of thallium oxide and zirconia as part of the deposited film, an anti-reflection film with high strength, uniformity, and no temperature dependence is obtained.

In the invention described in JP-A-56-59202,
The air-side outermost layer of conventional optical antireflection films was made of silica, but the durability was poor, so an improved version was obtained by providing an alumina layer under the silica layer.

In the invention described in JP-A-60-29701,
It is explained in detail that even if there is a magnesium fluoride layer on the alumina layer, the alumina film has poor alkali resistance, and in order to improve this, the thickness of the outermost layer of magnesium fluoride is specified, and each layer It has been described that an excellent optical antireflection coating can be obtained by oblique vacuum deposition.

Furthermore, in the invention described in JP-A-61-189501, different from the above-mentioned invention, when forming a zirconia layer by vapor deposition, as the vapor deposition time elapses, air is removed from the substrate side. The refractive index decreases toward the layer side, and in order to improve this problem, a solution is described in which titania is mixed with zirconia and deposited by vapor deposition.

Japanese Unexamined Patent Publication No. 62-272202 discloses that when a mixture of zirconia and yttriya is used for vapor deposition, the object to be vaporized is
It is described that when deposited on a substrate with poor acid resistance such as Ki6 or LaK7, a light scattering phenomenon called clouding occurs.

[Problem to be solved by the invention]

The methods for forming an antireflection film described in each of the above-mentioned publications are all methods of forming the antireflection film by a vapor deposition method.

When attempting to form an antireflection film by a vapor deposition method, it is difficult to deposit the antireflection film in such a way that optical properties as calculated are obtained, as described in Japanese Patent Application Laid-Open No. 55-22704.

On the other hand, the durability of the deposited film depends on the composition of the layers, the structure of the layers in the case of multilayers, and the like. The alumina layer has low durability, so even if it is protected with a silica layer, the durability will often be low depending on the thickness and structure of the film.If the film thickness is increased to improve durability, the optical properties will be disrupted. This creates a contradiction.

Therefore, in order to improve the durability of the surface layer, magnesium fluoride, which has good durability, was vapor-deposited.
As explained in Japanese Patent No. 9701, a material film having an intermediate refractive index in the range of 1.66 to 1.76 is required due to the relationship of refractive index, and alumina is selected as the film material.

However, as mentioned above, alumina film has low durability, and when it is deposited by evaporation method, it cannot be used under conditions where the angle between the flying direction of the evaporated atoms during evaporation and the substrate, that is, the angle of incidence, is 30° or more. When an optical anti-reflection film is deposited obliquely, the alkali resistance of the alumina film and the film on it decreases due to changes in the structure of the deposited film due to the oblique deposition, resulting in the problem that the elution of the alumina film by alkali cannot be suppressed. be.

For these reasons, if a protective film is provided to increase durability, a layer is required to adjust the overall reflectance, and if such a layer is provided, the durability will change depending on the layer structure. The problem is that the layer thickness has to be adjusted, and the layer thickness also affects durability, resulting in a complicated relationship.

Further, if the base material has poor acid resistance, there is a problem in that a light scattering phenomenon called clouding occurs.

[Means to solve the problem]

The present invention was invented in order to solve the above-mentioned problems, and it is made by mixing Yttriya powder and zirconia powder in a composition ratio within the solid solution range of Yttria and zirconia, and sintering the mixture to produce an Yttriya-stabilized zirconia powder. This is an optical antireflection film characterized in that an yttria-stabilized zirconia layer is formed by sputtering on a transparent body of an optical element using a sintered body of the present invention as a pole.

The solid solution range in the above invention is as follows:
S, 5TtlBICAN, R, C, 1IINK, S
, P, RAY] S+ - Nar of the American
Ceramic Society [J, Amer, Ceram,
Soc,] 62 p17 (1878), as shown in the table, Y2O, is 0.1 to 40 for ZrO□.
The mo is in the range of 1%.

ZrO2 powder and Y2O3 powder are finely mixed within this composition range, and the molded product is sintered to form a single pole of suba-tsutering.

[For production]

Since the film is attached to the transparent body of the optical element by the sputtering method, the distance between the target and the sputtering pole is short, and each film has the effect of firmly adhering.

Since the sputtering source is larger than the object to be sputtered, it has the effect of eliminating the difference in film thickness between the center and peripheral parts of the deposited film.

If it is just a mixture of Zr0z powder and Y2O3 powder, some of the components may be reduced during sputtering or vapor deposition, but the raw materials are mixed finely and sintered to become Ittria-stabilized zirconia. Therefore, during sputtering, it flies in a stable form and adheres to the transparent body of the optical element, so it does not cause abnormalities in the refractive index or the like.

Ittriya-stabilized zirconia and alumina have similar coefficients of thermal expansion in bulk, and assuming that the coefficient of thermal expansion of the thin film also takes the value of that of the bulk, the coefficients of thermal expansion are similar, so it is possible to peel it off. It's hard to do. In particular, when a rutile crystal is used as a transparent material for an optical element, this effect becomes remarkable since the coefficient of thermal expansion is similar to that of the rutile crystal.

In addition, since Yttria-stabilized zirconia does not have abnormal expansion regions that are unique to zirconia crystals, the strength of adhesion to optical element transparent bodies, alumina layers, and magnesium fluoride layers increases.

The refractive index of Ittria stabilized zirconia is α=2.13
Also, since the refractive index of zirconia is also equivalent to α=2.13, it becomes the same as that in which a zirconia film was conventionally used.

Examples will be described below.

[Example] Example 1 A sputtering gas pressure of 8 x 1 Torr, Argon gas flow rate of 5 cc/win, The transmittance of the rutile single crystal, which was sputtered with a sputtering power of 300 W to form an optical anti-reflection coating of a Yttriya-stabilized zirconia layer to a thickness of λ/4 (λ = 1550 nn+), is as shown in the graph of Figure 1. Ta.

This material was exposed to a steam-saturated pressure vessel at a temperature of 120° C. and a pressure of 2 atm for 8 hours. As a result, there was no change in the film before and after the test.

Also, O-! : Soak in water at O~5°C for 15 seconds, then in a vortex at 100°C±O~5'C within 3 seconds.15
Hold for 1 second, and within 3 seconds return to 1°C in water at 0±0~5°C.
There was no change in the film before and after the test in a cold/heat test in which the 5-second dipping cycle was repeated 10 times.

Example 2 Sputtering gas pressure 2 Xl0-3 Torr, oxygen gas flow rate 1 using as a pole a Yttria-stabilized zirconia sintered body made by adding 8 molχ Y2O3 powder to ZrO□ powder and sintering it.
The transmittance of the rutile single crystal was sputtered at 0 cc/min with a sputtering power of 500 W to form an optical anti-reflection coating of a Ytturia-stabilized zirconia layer to a thickness of λ/4 (λ = 1550 nm) as in Example 1. It was the same.

This material was exposed to a steam-saturated pressure vessel at a temperature of 120° C. and a pressure of 2 atm for 8 hours. As a result, there was no change in the film before and after the test.

In addition, it was immersed in water at 0 ± 0 to 5°C for 15 seconds, then immersed in water at 100°C ± 0 to 5°C for 15 seconds, and again within 3 seconds at O ± 0 to 5°C. There was no change in the film before and after the test in a cold/heat test in which the film was immersed in water at °C for 15 seconds and repeated 10 times.

Example 3 Sputtering gas pressure IX 10-'Torr, argon gas flow rate 2cc/win, oxygen gas flow rate 5cc/win, using as a pole a Yttriya-stabilized zirconia sintered body made by adding 8 molχ Y2O3 powder to ZrO□ powder and sintering it. ll1i
n, sputtering with a sputtering power of 300W, λ/4
The transmittance of the rutile single crystal in which the optical anti-reflection coating of the Yttriya-stabilized zirconia layer was formed with a thickness of (λ=1550 nm) was the same as in Example 1.

This material was exposed to a steam-saturated pressure vessel at a temperature of 120° C. and a pressure of 2 atm for 8 hours. As a result, there was no change in the film before and after the test.

In addition, it was immersed in water at 0 ± 0 to 5 °C for 15 seconds, then within 3 seconds it was immersed in a vortex at ioo'c ± 0 to 5 °C for 15 seconds, and again within 3 seconds at O ± 0 to 5 °C. There was no change in the film before and after the test in a cold/hot test in which the cycle of immersing the film in C water for 15 seconds was repeated 10 times.

Example 4 A sputtering gas pressure of IX 10-'' Torr, an argon gas flow rate of 4 cc/min, an oxygen gas flow rate of 1 cc using as a pole an Yttoria-stabilized zirconia sintered body obtained by adding 8 molχ of Y2O3 powder to ZrO□ powder and sintering it. /lll
1n, sputtering with a sputtering power of 300W, λ/
The transmittance of the rutile single crystal in which the optical anti-reflection coating of the Yttriya-stabilized zirconia layer was formed with a thickness of 4 (λ=1550 nm) was the same as in Example 1.

This material was exposed to a steam-saturated pressure vessel at a temperature of 120° C. and a pressure of 2 atm for 8 hours. As a result, there was no change in the film before and after the test.

In addition, it was immersed in water at 0±0~5°C for 15 seconds, then immersed in water at 00°C±0~5°C for 15 seconds, and again within 3 seconds. There was no change in the film before and after the test in a cold/heat test in which the cycle of immersing the film in water at 5°C for 15 seconds was repeated 10 times.

〔Effect of the invention〕

As explained in detail above, since the optical antireflection film of the present invention is formed by sputtering, unlike a film deposited by vapor deposition, the film has a structure in the center and periphery of the formed film. There is no difference in zirconium, which greatly contributes to improved durability.Also, although it is common to the vapor deposition method and the sputtering method, instead of simply flying a mixture of ittria and zirconia, it is sintered as ittriya-stabilized zirconia. The advantage is that the composition is decomposed when it is flown to the surface of the adherend, and the composition is not reduced to metal by the reduced pressure inert atmosphere, allowing the film to be formed as designed. There is.

When rutile crystal is used in the optical element's transparent material, the thermal expansion coefficients of the rutile crystal and the optical anti-reflection film are similar, so it does not deteriorate or peel off due to thermal cycles, resulting in increased durability. Becomes excellent.

As described above, the present invention has many excellent advantages and greatly contributes to the development of industry.

[Brief explanation of the drawing]

FIG. 1 is a graph of transmittance of an example of the present invention.

Claims (1)

[Claims] A sintered body of yttria stabilized zirconia is formed by mixing yttria powder and zirconia powder in a composition ratio within the solid solution range of yttria and zirconia, and sintering the mixture.A sintered body of yttria stabilized zirconia is used as a pole, and a yttria stabilized zirconia layer is formed on the transparent body of the optical element. An optical antireflection film formed by sputtering.