JPH0556789B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention improves adhesive strength by providing _two layers of SiO on the adhesive surface in advance when manufacturing optical elements by bonding them together using Si-alcoholate as an adhesive. Regarding how to improve. [Prior Art] Conventionally, balsam, epoxy, and ultraviolet curing adhesives have been used to bond optical elements used in transmission optical systems, such as lenses and prisms. However, the refractive index of these adhesives does not match that of the adhesive substrate (optical element), the thickness of the adhesive layer becomes too thick, and the transmittance in the ultraviolet region is low, making optical design difficult. However, there were drawbacks such as restrictions on the selection of adhesive substrates. [Problems to be Solved by the Invention] Therefore, in order to eliminate the above-mentioned drawbacks, the present inventor first bonded optical components together using a hydrolysis product of Si-alcoholate as an adhesive. A method for manufacturing optical elements was introduced in June 1986.
The proposal was made on the 18th of May. However, even with this invention, when an optical element is formed by bonding, for example, an optical element whose main component is SiO ₂ and an optical element whose surface is coated with a thin film of metal or dielectric, However, due to differences in the types of constituent components of the thin film serving as the adhesive surface and the surface roughness of the adhesive surface, it was sometimes not possible to obtain a sufficiently high adhesive force. The present invention was made to improve these points, and when using Si-alcoholate as an adhesive in manufacturing optical elements, a layer of SiO ₂ is applied to at least one of the pair of adhesive surfaces. By providing this, the purpose is to significantly improve the adhesive strength of Si-alcoholate without affecting the optical properties of the optical element, regardless of the surface condition of the adhesive surface. [Means for Solving the Problems] The above object is to provide a method for manufacturing an optical element that includes a step of bonding an optical element by bonding it together using a hydrolysis product of silicon alcoholate. This is achieved by forming a silicon oxide film on the surface in advance. [Example] Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic diagram showing a prism-type polarizing beam splitter for a KrF excimer laser. This polarizing beam splitter is formed by adhering a prism 1 on which a multilayered polarizing beam splitter film 3 is formed and another prism 2 with an adhesive. The polarizing beam splitter film 3 has a layer configuration as shown in Table 1, that is, ZrO ₂ as a high refractive index material and SiO ₂ as a low refractive index material are alternately deposited,
In the case of a layer structure in which the outermost layer is ZrO ₂ , the prism 1 provided with the polarizing beam splitter film 3 and the other prism 2 may be bonded together using a hydrolysis product of Si-alcoholate. , its adhesive strength cannot be said to be sufficiently high. However, when the method of the present invention uses SiO ₂ as the outermost layer of the polarizing beam splitter film 3 to form a layer structure as shown in Table 2, the prisms are formed by the hydrolysis product of Si-alcolate. The adhesion strength is significantly improved. Although various Si-alcoholates can be used, for example, ethyl silicate Si ₅ O ₄
(OC ₂ H ₅ ) ₁₂ etc. should be selected. However, there are other silicon tetraethoxides such as Si (OC ₂ H ₅ ) _{4 .}
Si _o O _o-1 (OR) _2o+2 represented by O _o-1 (OC ₂ H ₅ ) _2o+2
(R is a substituted or unsubstituted hydrocarbon group, n is 1 or more)
Si alcoholates such as R _o Si (OR) _4-o and the like can be used. All of these can provide high adhesive strength. The reason why the adhesive strength is improved by the method of the present invention is considered to be as follows. Hydrolyzed Si-alcoholate, which is an adhesive, is dehydrated and polymerized to transform into an amorphous SiO ₂ film, which exerts adhesive strength. The components constituting the adhesive surface of the prism 2 made of synthetic quartz have almost the same components and composition as this amorphous film. On the other hand, a prism 1 provided with a polarizing beam splitter film 3
The adhesive surface is ZrO ₂ in the layer configuration shown in Table 1,
Although it is the same oxide as the adhesive layer, it has a weak affinity because it is a different substance. In particular, if the surface of ZrO ₂ is rough, the affinity weakens and the adhesive strength decreases considerably. However, in the layer structure shown in Table 2 to which the present invention is applied, the outermost layer of the prism 1 provided with the splitter film 3 is made of SiO ₂ , so the affinity with the adhesive layer is significantly improved. As a result, high adhesive strength can be maintained even if the surface roughness of the adhesive surface becomes somewhat rough. Note that polarized beams with the layer configurations shown in Tables 1 and 2
The spectral characteristics of the splitter are shown in FIGS. 2 and 3 in order. In the figure, 5 is a curve representing the S component of the reflectance, and 6 is a curve representing the P component of the reflectance. From the figure, the spectral characteristics do not change even when SiO ₂ is added, and the S-polarized light and P-polarized light in KrF (input = 248) are completely separated. In the method of the present invention, the SiO ₂ layer may be formed by a film forming method such as vacuum evaporation, sputtering, or ion plating. The thickness of this SiO ₂ layer is
Considering the optical characteristics of the optical element to be formed, m/2 (m=1,
2, 3,...) times. In the method of the present invention, the Si-alcoholate is used after being hydrolyzed, but the hydrolysis conditions and catalyst are not particularly limited, and the hydrolysis may be carried out according to a conventional method. After hydrolysis, the solvent alcohol or ester remains, but low boiling point alcohols and esters (for example, ethyl alcohol, sulfuric ester, etc.) are effective after adhesion. If you want to remove it more aggressively, you can use heat or vacuum. Also, when adhering, dust and dirt may be left on the adhesive surface.
The presence of foreign matter and impurities such as dust can reduce adhesive strength and cause laser damage. Therefore, when bonding, thoroughly clean the bonding surface and use the adhesive by mouth-filling to remove impurities. Removal is necessary. A clean room is particularly suitable as a work environment. In the present invention, in order to coat the surface to be bonded with the hydrolyzed product of Si-alcoholate, general methods such as dripping or coating on the surface to be bonded can be used; The following method is suitable for thinning the layer to about 1 μm. That is, the objects to be bonded are joined together, and a hydrolyzed product of Si alcoholate is injected into the gap using a syringe, etc., and the hydrolyzed product is spread over the entire joint surface of both lenses by capillary action. This is a way to spread the word. In this method, the Si-alcoholate is successfully spread on the joint surface and
In addition, in order to control the film thickness and film formation rate, it is necessary to adjust the Si-alcoholate so that it has an appropriate viscosity. This can be achieved by dissolving the metal alcoholate in an appropriately selected solution. As this solution, for example, a high boiling point alcohol such as butyl alcohol or an ester can be used. In general, by heating Si-alcoholate after hydrolysis, dehydration and polymerization proceed, making it more similar to the material of optical elements. However, the present invention
Particularly in this example, even without heating, the adhesive layer exhibits the same optical properties as those with heating and exhibits practically sufficient adhesion ability, so heating is usually not necessary. The present invention is not limited to the above-mentioned embodiments, but as long as the functions of the manufactured product are kept within a range that does not impede practical use, the present invention is not limited to the above embodiments.
It can be applied to the production of various optical elements formed by bonding together arbitrary optical elements that perform functions such as reflection, refraction, and interference. For example, optical elements that have a metal film formed on their surface, such as a metal half mirror, or optical elements that have no dielectric or metal film formed on their surface (for example, optical elements that are mainly made of oxides other than SiO ₂ ). It is an optical element formed using optical elements such as lenses and prisms. In addition, in the present invention, the SiO ₂ layer may be provided on both of the pair of bonding surfaces, if necessary.

【table】

【table】

〔Effect of the invention〕

As explained in detail above, by the method of the present invention in which _two layers of SiO are provided on the surface of the optical element that will serve as the adhesive surface, and Si-alcoholate is used as the adhesive to manufacture the optical element, the components can be bonded together. Optical elements with significantly improved adhesive strength can be manufactured.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of a polarizing beam splitter, FIG. 2 is a diagram showing the spectral characteristics of a conventional polarizing beam splitter having the layer structure shown in Table 1, and FIG. 2 is a diagram showing the spectral characteristics of a polarizing beam splitter having the layer structure shown in Table 2. FIG. 1 and 2 are prisms, 3 is a polarizing beam splitter film formed on prism 1, 4 is a Si-alcoholate adhesive layer, 5 is an S component of reflectance, and 6
is the P component.

Claims (1)

[Claims] 1. A method for manufacturing an optical element, which includes a step of bonding an optical element together using a hydrolysis product of silicon alcoholate, in which a silicon oxide film is preliminarily applied to the adhesive surface of the optical element. A method for manufacturing an optical element, characterized by forming a film. 2. The method of manufacturing an optical element according to claim 1, wherein a dielectric film or a metal film is formed on the surface of the optical element. 3. The optical system according to claim 1 or 2, wherein the thickness of the silicon oxide film is m/2 times (m=1, 2, 3, . . . ) the design reference wavelength of the optical element. Device manufacturing method.