JPS60127250A - Forming of antireflection film - Google Patents

Abstract

PURPOSE:To form an antireflection layer having low reflectance to the surface of an optical part, etc., by coating a substrate with a partially polycondensed sol solution containing an organometallic compound, and treating the coating layer with a specific aqueous solution of an acidic salt. CONSTITUTION:One or more organometallic compounds e.g. a metal alkoxide such as Si(OC2H5)4, etc. are dissolved in an organic solvent such as alcohol, and stirred to effect the hydrolysis. The product is then subjected to the partial polycondensation reaction at normal temperature. The obtained sol solution is applied to the surface of an optical part such as glass substrate plate, and heat- treated to form an amorphous film. The amorphous film is treated with an aqueous solution obtained by adding <=0.01mol/l of polyvalent ion such as Al<3+>, Si<4+>, etc. to an aqueous solution containing 0.01-1mol/l of an acidic salt exhibiting weakly alkaline nature in aqueous solution, e.g. Na2HAsO4, etc. An antireflection film having low reflectance can be formed by only a chemical treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming an antireflection film on the surface of an optical component such as glass or ceramics.

It has been known that an antireflection film can be formed on the surface of glass by chemically treating it with hydrofluoric acid, an acidic ammonium fluoride aqueous solution, or a weakly alkaline solution such as disodium arsenate.

However, glasses that can be subjected to surface reflection prevention treatment using such a weakly alkaline solution are limited to those within a certain composition range. To put it simply, it is impossible to form an antireflection film on quartz glass from the glass substrate itself by such surface treatment.

This invention was made by focusing on such conventional problems, and even optical components such as glass substrates on which an anti-reflection film cannot be directly formed on the surface by chemical treatment, can be coated on the surface of the optical component. The object of the present invention is to provide a method in which an antireflection film can be formed by chemical treatment by forming an amorphous film in advance.

This invention was completed as a result of the following research. First, the present inventors used some method to form an amorphous film on the glass surface whose composition would reduce the reflectance when treated with a weakly alkaline solution as described above. Regardless of the composition of the substrate glass, an amorphous film on the surface can be formed by hydrolyzing an alcoholic solution of a metal alkoxide, causing a partial polycondensation reaction, and then coating the glass surface. It can be formed by applying appropriate heat treatment. At this time, by changing the solution concentration, degree of partial condensation polymerization, heat treatment conditions, etc., membranes with different structures, i.e., porosity, pore diameter, and bonding strength, can be obtained. It was predicted that treatment with an alkaline solution would transform the film into a film with low reflectance.

Based on such predictions, the present inventors coated a glass or ceramic substrate with a partial condensation polymerization sol solution containing one or more types of organometallic compounds such as metal alkoxides, and then heat-treated this to form a For example, if the composition of the amorphous film is the same as that of quartz glass, Si02
It has been found that even when the film is composed of a single component, if it is treated with an aqueous solution of disodium arsenate by appropriately controlling the heat treatment conditions, etc., a film can be obtained that can reduce the reflectance. In addition, when the composition of the amorphous film formed on the glass substrate as described above is the same as that of the substrate glass, and the substrate glass itself is treated with an aqueous solution of arsenic acid, etc. It has been found that when an anti-reflection film is formed on an amorphous film, the amorphous film can also be turned into an anti-reflection film by a similar aqueous solution treatment.

Therefore, this invention provides a sol solution obtained by hydrolyzing one or more metal alkoxides and other organometallic compounds dissolved in alcohol or other organic solvent, and subjecting the resultant to a partial condensation polymerization reaction. is coated on the surface of an optical component and heat-treated to form an amorphous film, and this amorphous film is coated with an acid salt that exhibits weak alkalinity in an aqueous solution at a concentration of 0.01 to 1 mol/l. It is characterized in that it is treated with a solution in which the following polyvalent ions are added in an amount of 0.01 mol/ml to an aqueous acidic salt solution containing .

Typical organometallic compounds used in this invention include metal alkoxides and metal acetylacetonates, and metal elements forming this organometallic compound include metal elements that can form glass. After coating and heat treatment, it forms an amorphous film.

kLsBsNa etc. are used. On the other hand, alcohol and acetylacetone are commonly used as organic solvents. After dissolving one or more of these organometallic compounds in an organic solvent and mixing thoroughly, water for hydrolysis is added.
They are added as they are or diluted with an organic solvent, and are stirred and mixed to cause hydrolysis and polycondensation. At this time, the concentration of the organometallic compound in the solution is adjusted to fall within the range of 0.1 mol/# to 5 mol/#. If it is less than 0.1 mol/#, a film of sufficient thickness will not be formed during coating, and if it is more than 5 mol/#, the rate of the condensation reaction that occurs following hydrolysis will be too high, and the solution will become jelly-like. It solidifies and cannot be used as a coating solution.

The ratio of organometallic compound to water is also an important parameter to properly create a coating solution.

When the amount of water is relatively small, only a small proportion of the alkyl groups in an organometallic compound, such as a metal alkoxide with the molecular formula M(OR)n + M is a metal and R is an alkyl group, are substituted by H and M ( OR) x(OR)y
and changes. Therefore, since the number of crosslinks formed by dehydration condensation as schematically shown in the following formula is small, it is not possible to form a continuously bonded film by coating.

M(OH)x(OR)y +M'(OH)x(OR)y
→(OR) FM-0-M' (OR)V+H20 The preferred amount of water added for hydrolysis varies depending on the type of organometallic compound, but is approximately 1 mol to 5 mol per 1 mol of the organometallic compound. is within the range of If the amount of water is less than this, an extremely long reaction time is required to obtain a coatable partially condensed sol solution, and if the amount of water is more than this, the solution gels quickly and becomes stable. Coating solution is difficult to obtain.

A dipping method or a spinner method is used to coat the surface of a glass substrate with a sol solution that is hydrolyzed with an appropriate amount of water and partially condensed by aging. An amorphous film can be obtained by firing this coating film under appropriate heat treatment conditions. In this case, when this amorphous film is treated with an aqueous solution such as disodium arsenate, the heating rate of heat treatment, holding temperature, Control retention time, etc. In particular, when molten glass having the same composition as the amorphous film is not subjected to antireflection treatment with a solution such as disodium arsenate, for example in a %5i02 single-component system, setting of the heat treatment conditions is extremely important.

Furthermore, as a method for facilitating the formation of an antireflection film by treatment with a solution such as disodium arsenate, it is also effective to add an extender such as glycerin to the coating solution. This glycerin, etc. decomposes and burns during the heat treatment process of the coating film, so the formed amorphous film is thought to have a structure with many local voids when viewed microscopically. A porous antireflection film is more likely to be formed.

The obtained amorphous film is slightly alkaline in an aqueous solution.

Acid salts such as disodium arsenate (Na B H
An aqueous solution containing As04) etc. at a concentration of 0.01 to 1 mol/l is treated with a solution to which 0.01 mol/l of the following polyvalent ions, specifically A3, S14, etc. are added. Accordingly, a porous antireflection film can be formed on the glass surface.

As acid salts that exhibit weak alkalinity in aqueous solution, any of the acid salts conventionally used in the production of antireflection films can be used.
In addition to 04, NaHCO3, Na2HPO4 and Na
Includes C2H30, etc. The acid salt concentration in the treatment solution can also be the same as that of the conventional method, and is selected within the range of 0.01 to 1 mol/l. If this concentration is too low, no antireflective film will be formed, and if this concentration is too high, the antireflective film will be non-uniform.

The above-mentioned erosion of the glass surface by an aqueous solution of acidic salts such as Na2HAsO4 is a leaching process in which a slightly porous so-called blue discoloration layer is formed through ion exchange between alkali ions in the amorphous film and H+ ions in the solution. This is explained by the synergistic effect with the etching process in which the amorphous film dissolves. By appropriately controlling the etching process and the etching process, the amorphous film can be made into a porous antireflection film with a low refractive index. Multivalent ions: /fc 3+ and 84' are added to control the etching process and the etching process, and the concentration of this addition is 0.01 to form a homogeneous antireflection film. mol/ is taken as below. As a result of treating the antireflection film formed according to the present invention with an aqueous acidic salt solution containing multivalent ions as described above, it can be made into an antireflection film with a high laser damage resistance threshold.

Next, an example will be described. However, the invention is not limited to the scope of the following examples.

Example 1 Ethyl silicate 5t (OC2Hs)4 and 0.1N-4 (
No., aqueous solution and ethyl alcohol in a molar ratio of 5i (
OC2Hs) 410 and 1N-HNos-1/2, and the mixture was stirred at room temperature for 1 hour to perform hydrolysis. Thereafter, this solution was allowed to stand at room temperature for two days to undergo a partial condensation polymerization reaction to form a sol solution, thereby preparing a coating solution.

A quartz glass substrate is immersed in this solution and pulled up to form a film. After drying at room temperature,
The temperature was raised to ℃ to obtain an amorphous film. With a 0.02 mol/l Na2HAs04 aqueous solution containing this 31'+ ion,
By processing at 90° C. for 10 hours, an antireflection film having reflectance characteristics as shown in FIG. 1 was obtained. This antireflection coating was also found to have a λ15100 uniformity at a wavelength of 6328λ.

Example 2 Ethyl silicate S i (OC2H5) 4, methyl borate B (OCH3) 3 and sodium inopropoxide Na0C3H7, 0.1N-HCt aqueous solution and inopropyl alcohol in molar ratio S i (QC2H5)
4/ B (OCH3)s, / Na0Cs H7/
First, ethyl silicate, a portion of 0.1N HCl, and inpropyl alcohol were mixed and hydrolyzed at 40°C. Next, methyl borate diluted with inopropyl alcohol was added, and after stirring at 40°C for 1 hour, sodium impropoxide was added and thoroughly mixed.
Stirred. Thereafter, this solution was allowed to stand at room temperature for one day to undergo a partial condensation polymerization reaction to form a sol solution, thereby preparing a coating solution. A quartz glass substrate was immersed in this solution and pulled up to form a film, dried at room temperature, and then gradually heated to 420° C. to obtain an amorphous film. This film is
l0 'mol/l (o, 0 including D At''+ ion
By treating with a 3 mol/l Na2HAs04 aqueous solution at a temperature of 85 DEG C. for 3 hours, an antireflection film having surface reflectance characteristics as shown in FIG. 2 was obtained.

Example 3 Ethyl silicate s+ (oczus)*, methyl borate B (
OCH3)3, sodium methoxide NaOCH3 and aluminum impropoxide kA(OCsHt)s
, 0.1N-HC1 aqueous solution and inpropyl alcohol in molar ratio, S I (QCzHs)4/B (
OCHs)3/NaOCH3/At(QC3H7
) 3/ H2O = 4/ 110.610.08/8. First, ethyl silicate and O,1NHC1
and isopropyl alcohol were mixed and hydrolyzed at 40°C.

Next, methyl borate diluted with inpropyl alcohol was added, stirred at 40°C for 1 hour, and then left at 70°C for 1 day. Next, sodium methoxide and aluminum impropoxide were added, thoroughly mixed and stirred, and then
The coating solution was left at 0° C. for 2 days to form a coating solution. A glass substrate was immersed in this solution and pulled up to form a film. After drying at room temperature, the temperature was gradually raised to 550° C. to obtain an amorphous film. This film was coated with 0.03”/l Na
An antireflection film with low reflectance was obtained by treatment with a 2HAs04 aqueous solution at 85° C. for 3 hours.

[Brief explanation of the drawing]

Figures 1 and 2 are characteristic diagrams showing the relationship between wavelength and reflectance of the antireflection film produced by the formation method according to the present invention, and Figure 1 shows the amorphous film made of 8102 single-component system. Characteristic diagram of the antireflection film obtained in the example, Figure 2 shows the amorphous film 5i02.
FIG. 3 is a characteristic diagram of an antireflection film obtained in another example using a three-component system of B2O2Na2O.

Claims (1)

[Scope of Claims] 1. Obtained by hydrolyzing a solution of one or more metal alkoxides or other organometallic compounds in alcohol or other organic solvent, and then subjecting this to a partial polycondensation reaction. An amorphous film is formed by coating the surface of an optical component with a sol solution and applying heat treatment to the surface of the optical component. 1. A method for forming an antireflection film, which comprises treating an aqueous acid salt solution containing a concentration of 0.01 mole of the following polyvalent ions. 2. Organometallic compound 1 of St as an organometallic compound
A method for forming an antireflection film according to claim 1, using only seeds. 3. As an organometallic compound, the metal element is 81°B%At
The method for forming an antireflection film according to claim 1, using two or more organometallic compounds consisting of metal elements capable of forming glass, such as Na. 4. As an acid salt? A method for forming an antireflection film according to claim 1, 2, or 3, in which JB2HAs04 is used and kt'' 10 and 4+ are used as multivalent ions.