Method for producing buried regions of raised refractive index in a glass member by ion exchange

Claim 1

In a method for producing a buried region of a raised refractive index in a glass member by ion exchange process, said method comprising providing a glass member having one surface provided with a mask of a titanium coating to block the penetration of the ions from a salt melt of refractive-index-raising ions into the glass and said one surface of said glass member having surface areas free of the titanium coating, conducting a first field-assisted ion exchange having an ion for raising the refractive index of the glass coming from a salt melt contacting the exposed surfaces of the glass through the mask to thereby raise the refractive index of the glass immediately beneath the exposed surface portions and thus provide regions of raised refrative index immediately beneath the exposed surface portions, then etching away the titanium coating with an etching solution and then burying the regions of raised refractive index by a second field-assisted ion exchange with another ion contacting the surface of the glass member containing the regions of raised refractive index, said another ion having a neutral effect with regard to the refractive index of the glass, the improvements comprising the step of etching away the titanium coating which has been exposed to a hot salt melt of the first ion exchange being etched away with an ethylene dinitrilo tetraacetic acid (EDTA) disodium etching solution, and then removing any ion barrier on the surface free of the titanium coating by creating a slight material erosion of the surface freed of the titanium coating without deteriorating the regions of the raised refractive index at the surface prior to implementing the second field-assisted ion exchange step.