Composite substrate material and process for producing the same

Abstract

A functional film, which has photo-catalytic effects, is overlaid on a surface of each of at least two substrate materials. The functional film, which has been overlaid on the surface of each of the substrate materials, is exposed to light having a wavelength falling within an absorption wavelength range of the functional film. The substrate materials are then bonded to each other with the functional films, which have been exposed to the light, intervening between the substrate materials. The functional film may be a film containing TiO2, and the light irradiated to the functional film may be ultraviolet light. In cases where a film other than the functional film is also overlaid on the surface of each of the substrate materials, the functional film is formed as a top layer.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] This invention relates to a composite substrate material comprising at least two substrates which are bonded to each other. This invention also relates to a process for producing the composite substrate material. [0003] 2. Description of the Related Art [0004] Composite materials have heretofore been formed by bonding optical crystals, such as laser crystals, optical wavelength converting crystals, and quartz glass mirrors, to each other or by bonding optical substrates to each other. As techniques for the bonding, techniques, wherein the optical crystals or the optical substrates are adhered to each other by optical adhesive agents, or techniques, wherein the optical crystals or the optical substrates are fusion bonded under heat, have heretofore been used widely. [0005] However, the techniques, wherein the optical crystals or the optical substrates are adhered to each other by optical adhesive agents, have the pro...

AI Technical Summary

Benefits of technology

The present invention provides a process for producing a composite substrate material with high bond strength, high long-term reliability, and good environmental temperature resistance characteristics. The process involves overlaying a functional film, which has photo-catalytic effects, on a surface of each of at least two substrate materials, and then exposing the functional film to light having a wavelength falling within the absorption wavelength range of the functional film. The functional film acts as an anti-reflection film and also decomposes organic substances on the substrate materials, resulting in a super-hydrophilic state on the surface of each substrate material. The substrate materials are then combined with each other, and a load and heat are applied to bond them together. The process is wet processing-free, and the resulting composite substrate material has low reflectivity and scattering loss. It can be used for various applications such as solid lasers and optical devices.

Problems solved by technology

However, the techniques, wherein the optical crystals or the optical substrates are adhered to each other by optical adhesive agents, have the problems in that optical scattering and reflection loss are caused to occur and long-term reliability of the adhered areas is low.

Particularly, as for optical members to be located within laser resonators, the problems described above arise markedly.

The techniques, wherein the optical crystals or the optical substrates are fusion bonded under heat, have the problems in that the techniques are applicable only to limited combinations of materials and can be utilized only in limited applications.

However, the wafer bonding techniques have the problems in that wet processing must be performed for cleaning the substrates and therefore production steps cannot be kept simple.

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