JPS593721B2 - anti-reflection film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an anti-reflection film having an optical thickness structure of iλ01λo.
- Concerning a three-layer antireflection film with a 1λ0.

It has long been known that in order to fully demonstrate the performance of optical glass such as eyeglass lenses and camera lenses, it has been known to apply an anti-reflection coating to the surface of the glass, which can prevent the reflection of light. A three-layer antireflection film with an optical film thickness structure of iλO−nλo·1λo has been developed as a high-performance antireflection film that can suppress the residual reflectance of light to approximately 1% or less.

However, the film material constituting the above-mentioned preventive film must be easily made into a thin film, have stable and durable physicochemical properties, and have good adhesion 10 between the base glass or each layer so that it does not peel off. Due to the fact that various properties are required, such as having an appropriate refractive index depending on the underlying glass, known three-layer anti-reflection coatings are only made with MgF2 in the top layer.
ZrO2, CEO2, TiO2, etc. are used for the second layer, and 15CeF3, Al2O3, etc. are used for the third layer in contact with the base glass. However, the known antireflection coatings using these coating materials still have problems with their mechanical strength and chemical durability, and in particular, as a result of a durability test using a 5% saline water boiling test, the coating itself showed significant corrosion. Moreover, it has serious disadvantages in terms of practical improvement in the surface hardness test using Micropi 20 Tsukaas hardness tester and the practical durability test using sand eraser. In view of the above-mentioned current situation, the present inventors have discovered that it is possible to suppress the residual reflectance of light rays with wavelengths in the visible region, particularly wavelengths of about 4,000 to 6,000 A, to about 1% or less, and to have excellent mechanical strength and chemical durability. Various studies have been carried out with the aim of obtaining a new three-layer anti-reflection film that has excellent properties and is extremely useful in practice.

As a result, SiO2-x (x indicates 0 to 0.7) was used as the film material constituting the top layer, which has not been known to be used in this kind of anti-reflection film, let alone its possibility. and has a specific refractive index in the third layer, M9
When selectively using Al2O4 spinane compounds,
It has been found that a three-layer antireflection coating can be provided that meets the above objectives. The present invention was completed based on this new knowledge.

That is, in the present invention, the optical film thickness structure is T2o, λo・4・
In a three-layer anti-reflection film with λo, the top layer is SiO2
-x (x represents O to 0.7), and the third layer in contact with the base glass is an M9Al2O4 spinel compound having a refractive index in the range of 1.75 to 1.88. Pertains to membranes.

The anti-reflection film of the present invention is M9F2-
It exhibits an excellent antireflection effect equal to or superior to that of ZrO2-CeF3, and has excellent mechanical strength and chemical durability not found in known three-layer antireflection films.

In particular, the microvitkers hardness of the antireflection film of the present invention is 13.
00Hν, and as shown in the surface hardness test using sand eraser described later, it is better than the known M9F2-ZrO
While scratches were observed on the surface of the 2-Al2O3 film after only 10 scratches, virtually no scratches were observed even after 20 scratches. Further, the antireflection film of the present invention shows no corrosion in the 5% saline boiling test, and has excellent chemical durability. Therefore, this product is used not only for eyeglass lenses that are directly exposed to external environment and often rubbed by fingers, but also for wristwatch cover glasses, camera lenses, telescopes, window glasses, automobile glass, television cathode ray tubes, and various measurement instruments. It can be used extremely effectively for preventing reflection in optical glasses such as dexterous cover glasses. In the present invention, SiO2 (x represents 0 to 0.7) is used as the uppermost layer.

This layer is easily formed by vacuum evaporating ordinary SO2 using an electron beam, resistance heating, or the like according to a conventional method.
The value of x changes depending on the degree of vacuum during the vapor deposition, and the refractive index itself of the formed film also changes depending on the value of X. The above degree of vacuum is within the range used in normal vapor deposition, for example 10-
It may be about 3 to 10-6 Torr, and within this range, the value of X can be set to an appropriate value in the range of 0 to 0.7. When the value of x is O, that is, SiO2 has a refractive index of 1.
．． 46, and when the value of x is 0.7, that is, SiOl.
3, its refractive index is approximately 1.52. The value of X above is 0
．． If it exceeds 7, the refractive index of the top layer becomes too large, making it difficult to form a film having the desired antireflection ability. In the present invention, various known materials such as CeO2, zrO2, stabilized zirconia, etc. can be used as the second layer.

The second layer preferably has a refractive index of about 2.0 to 2.2. Further, stabilized zirconia is, for example, Zr
A suitable amount of stabilizers such as CaO, M9O, Y2O, etc. are added to O2 to form a substitutional solid matrix, which is a transition from monoclinic to tetragonal system that occurs at about 1000 to 1100°C. It can be advantageously used as a membrane material because it can prevent rapid volume changes due to metastasis.

The amount of stabilizer added is arbitrary, but usually CaO is added in an amount of 8 to 2
5 mol%, Mf! It is preferable to add 14 to 23 mol% of 0 and about 10 mol% of Σρ3, thereby increasing the refractive index of about 2,
0 stabilized zirconia》 can be obtained. The second layer may be formed by a conventional method, for example, by vapor deposition using electron beam heating, resistance heating, etc. under a vacuum of about 10 -3 to 10 -6 Torr. In addition, in the present invention, the third layer in contact with the base glass has a refractive index of 1.75 to 1.
．． It is important to use a M9Al2O3 spinel compound in the range of 88.

In particular, the refractive index of this third layer, in conjunction with the topmost layer of SiO2X, has a significant effect on the antireflection properties of the resulting antireflection film, and if it is outside the above range, the refractive index will be lower throughout the visible region. It becomes difficult to uniformly and effectively prevent reflection of light having a wide range of wavelengths. The material for forming the third layer was selected taking into consideration not only its physicochemical stability but also its adhesion to the underlying glass.
9A! 204 spinel (refractive index 1.75), a solid solution of the spinel and M9O, and TiO2znO, snO to lower the sintering temperature during the formation of the spinel and the solid solution.
2, B2O3, caO, and other additives are included. The refractive index of the M9Al2O4-M9O solid body increases as the amount of M9O added (solid solution amount) increases, and MflA! Usually about 8 M9O per 2041 moles
A solid solution added up to a molar amount can be suitably used as the third layer of the present invention. Furthermore, the use of additives such as TiO2 and SnO2 has the advantage of lowering the sintering temperature of the spinel or solid solution, providing a dense material with a high degree of sintering and low volumetric expansion suitable for use as a vapor deposition material. The refractive index of the material can be adjusted by adding . These additives can usually be added in an amount of 0.1 mole or less per mole of spinel or solid solution, and within this range a desired vapor deposition material with a refractive index of 1.75 to 1.88 can be provided. In addition, when using A'203-Al2O4-Al2O3 solid solution as the material for the third layer, the antireflection effect is greatly reduced, so in the present invention, materials other than the above cannot be used. . The method for manufacturing the material for the third layer and the formation of the film can be performed in accordance with conventional methods.

For example, predetermined amounts of aluminum hydroxide as an Al source and basic magnesium carbonate as an MI source, or desired amounts of each of the above additives, are weighed, wet mixed, and calcined at about 1000°C for 2 to 3 hours, resulting in a powder. It is press-molded using a tablet molding machine under a molding pressure of about 1 ton/pu, baked at a temperature of about 1300 to 1500°C for about 10 hours, and finally heated to about 1700°C for 5-6 hours.
The material can be manufactured by main firing for a period of time. The third layer is formed by electronically heating the material obtained as described above according to a conventional method under a vacuum of about 10-3 to 10-6 Torr at a temperature below the heat-resistant temperature of the underlying glass, usually below 350°C. This can be easily accomplished by vacuum deposition using a beam. The antireflection film of the present invention can be deposited easily, stably, and with good reproducibility on various types of optical glasses, such as eyeglass glasses.

There are no particular restrictions on the material of the base glass, but it usually has a refractive index of 1.
．． It is preferable to use various types of optical glass having a diameter of about 5 to 1.7. Furthermore, the thickness of each layer constituting the antireflection film of the present invention is as follows:
For example, using a photoelectric film thickness meter, it is easy to calculate iλo−iλ0−.
- Tλ0 can be adjusted, and the adhesion between each film and with the underlying glass is extremely good, and there is no risk of peeling. Examples will be given below to explain the present invention in more detail.

Example 1 A glass lens with a refractive index of 1.523 is used as the base glass.

As the third layer, aluminum hydroxide and basic magnesium carbonate (containing M924%) were weighed and wet-mixed so that Mg:Al=1:2 (atomic ratio), and after calcining at 1000°C for 2 hours, a tablet molding machine was used. M9Al2O4 pellets (refractive index 1.7) were press-molded under a pressure of 1 ton/CT7L at
5) is used. First, the base glass is attached to the vapor deposition tank, and the inside of the tank is evacuated.

During the exhaust, the base glass is heated by radiation heating from a micro heater and a halogen lamp. Vacuum level inside the tank is 5 x 10-
When the temperature reached 5 torr and the base glass temperature reached 300°C, vapor deposition of MIAl2O4 adjusted above was started,
Vapor deposition is terminated when the film thickness reaches 1λ0 as measured by a photoelectric film thickness meter. Next, 1λo of CeO2 (refractive index: 2.08) was deposited as the second layer in the same manner, and finally SiO,-x was deposited at T with a leak valve opened and a vacuum level of 5XI0-4 torr.
Deposit λo. The top layer deposited is SiOl. It was 4.5. The deposition of each layer followed an electron beam heating method. In this way, the antireflection film of the present invention is obtained. Comparative Example 1 An Iλo-Iλo-+λ0 three-layer antireflection film in which the first layer is MflF2, the second layer is ZrO2, and the third layer is Al2O3 is prepared in the same manner as in Example 1 above.

The vapor deposition of MIF2 was carried out under a vacuum of 2 x 10-5 Torr by resistance heating, and the deposition of ZrO2 and Al2O3 was carried out under a vacuum of 2 x 10-5 Torr by electron beam heating. Comparative Example 2 Comparative Example 1 except that instead of Al2O3 as the third layer, CeF3 was vapor deposited by resistance heating under a vacuum of 2×10 Torr.
A three-layer antireflection film of MflF2-ZrO2-CeF3 is prepared in the same manner as above.

The following tests were conducted on each of the antireflection films obtained in the above Examples and Comparative Examples.

I Spectral Characteristics Test Each antireflection film was irradiated with light having a wavelength of 3,500 to 7,000 Λ, and its spectral reflectance was measured.

The results are shown in Figure 1. Curves A, B, and C are the results for the antireflection films obtained in Example 1, Comparative Example 1, and Comparative Example 2, respectively. It can be seen from FIG. 1 that the antireflection film of the present invention exhibits an excellent antireflection effect equivalent to or even superior to known antireflection films.

Surface Hardness Test The surface hardness of each antireflection film is measured using a Micro-Vickers hardness meter manufactured by Akashi Seisakusho.

The test was carried out at a load of 1009 and a Vickers hardness reduction of 5 for 15 seconds.
I went around. The average hardness (Hv) of the five tests obtained is shown in Table 1 below. From Table 1 above, it is clear that the antireflection coating of the present invention has extremely superior surface hardness compared to known antireflection coatings.

Durability test The durability of each anti-reflection film was tested using a type sand eraser ((526
61STXEIyrLER-RASOr, GERIVA
NY), each membrane has a width of 5 to 6 meters and a length of 10 to 20 m7.
! After repeatedly rubbing L for a predetermined number of times, the degree of surface scratches is judged with the naked eye and evaluated according to the following criteria.

From Table 2 above, it is clear that the antireflection film of the present invention is extremely superior in durability to known antireflection films.

Examples 2 to 5 As the third layer, aluminum hydroxide and basic magnesium carbonate were mixed with Al2O, :MgO (various M9Al2O4-M9O solid solutions prepared in the same manner as in Example 1 after weighing each so that the molar ratio was a predetermined ratio). Or further TiO2
Using a solid solution prepared by adding 10 mol% of
It was carried out under the condition of 1 × 10-6 Torr (the following specified S
(forming a deposited film containing iO2-X), the antireflection films of Examples 2 to 5 below are obtained in the same manner as in Example 1.

Example 2 Top layer SiOl. 6 (Refractive index 1.5) Vapor deposition conditions: 4X10-5 Torr vacuum Second layer ZrO2 (Refractive index 2.05) Third layer Mf! A22O4-MflO (refractive index 1.8)
Ano,03:M9Ol:9 (molar ratio) Example 3 Top layer SiOl. , (refractive index 1.5) Vapor deposition conditions: 4X10'''5 Torr vacuum 2nd layer Stabilized zirconia (refractive index 2.03) 3rd layer
MlAl2O4 → UO (refractive index 1.79) Al2O3:
M9O=2:8 (molar ratio), and the stabilized zirconia is ZrO
2, calcium carbonate was added in an amount of 8 mol% as CaO to the ZrO2, mixed well, calcined at 1000 to 1300°C for 5 to 10 hours, and formed into pellets at 1 ton/CTl using a tablet molding machine at 1400°C. It was created by firing for 5 to 10 hours.

Example 4 Top layer SlOl. 8 (refractive index 1.48) Vapor deposition conditions: 2
~3×10-4 Torr vacuum Second layer ZrO2 (refractive index 2.05) Third layer M9Al2O4-M9O-TiO2 (refractive index 1
．． 88) Al2O3:M9O:TiO2=1:1:0.
1 molar ratio) Example 5 Top layer SiOl. 8 cap refractive index 1.48) 2-3X10-4 Torr vacuum second layer CeO2 (refractive index 2.08) third layer MlAl2O4-Mf! O (refractive index 1.78)
Al2O3:M9O=3:7 (molar ratio) Each of the above examples 2
The antireflection film obtained in steps 5 to 5 was irradiated with light beams of various wavelengths, and the spectral reflectance (a) was measured. The results are shown in FIG.

Curves D, E, F and G show the results of Examples 2-5, respectively. This is clear from Figure 2. Thus, the obtained antireflection film was an excellent and highly efficient antireflection film. Furthermore, the results of surface hardness, durability, and saline water boiling tests showed that the anti-reflective coating of Example 1 exhibited approximately the same effects as the anti-reflective coating of Example 1, and had extremely superior mechanical strength and durability compared to known anti-reflective coatings. It had a sexual nature. Comparative Example 3 0.2 mol of aluminum hydroxide was added to 1 mol of MgAl2O4 pellets obtained in the same manner as in Example 1, wet-mixed, and after calcining at 1000°C for 2 hours, 1 ton/C was produced using a tablet molding machine.
M9Al2O4-A22O3 solid mass pellets are obtained by press molding under TII pressure, calcining at 1400°C for 10 hours, and then calcining at 1700°C for 5 hours.

The solid body contains Al2O3O. l
It is composed of molar proportions. The thus obtained M9A
l2O4-Al2O3 solid solution pellet (refractive index 1.74
) is the material of the third layer, ZrO2 is the material of the second layer,
Using SiO2 as the material for the uppermost layer, it is sequentially deposited onto a glass lens having a refractive index of 1.523 in the same manner as in Example 1.
The obtained antireflection film was irradiated with a light beam having a wavelength of 3500 to 7000λ, and its spectral reflectance (4) was measured.

The results are shown as curve H in FIG. Incidentally, in FIG. 3, the results of Example 1 are also shown as curve A for comparison. As is clear from the results shown in FIG. 3, Mf! When M9A'204-A,q solid solution { is used instead of Al2O4, the antireflection effect is greatly reduced.

[Brief explanation of the drawing]

FIG. 1, FIG. 2, and FIG. 3 are graphs showing the reflection characteristics of an example product of the present invention and a comparative product.

Claims (1)

[Claims] 1 Optical film thickness structure is (1/4)λ_0・(1/2)λ
In a three-layer antireflection film with _0・(1/4)λ_0, (i) the top layer is SiO_2_-_x (x is 0 to 0.7
), and (ii) the third layer in contact with the base glass is (a) MgAl_2O_4 spinel, (b) a solid solution in which not more than 8 mol of MgO is dissolved in the spinel per 1 mol of MgAl_2O_4, or (c) the spinel is made of MgA
MgO_8 mol or less and TiO for l_2O_41 mol
Mg, which is a solid solution containing 0.1 mol or less of at least one of _2, ZnO, SnO_2, B_2O_3 and CaO, and has a refractive index in the range of 1.75 to 1.88.
An antireflection film characterized by being made of an Al_2O_4 spinel compound.