Adhesives for optical devices

Abstract

Three types of UV-curable adhesives, a room temperature curing sealant and a hot-melt adhesive for the fabrication of optical communications devices were developed. (1) Using new epoxies, acrylates and vinyl sulfide containing fluorine, bromine and sulfur, the refractive indices of UV-curable transparent adhesives can be controlled, in the range 1.41-1.70 within /spl plusmn/0.005 with a high light transmittance of 80-90% at a wavelength of 1.3 /spl mu/m. They possess an excellent refractive index matching that of optical glass and optical fibers. They have high adhesive strength and good durability. (2) The UV-curable precision adhesive has an extremely low volume shrinkage of 1.2% during curing and the cured adhesive has a low thermal expansion coefficient of <2/spl times/10/sup -5///spl deg/C. Therefore, they can be used in the fabrication of optical devices that require sub-micron positioning accuracy. (3) The UV-curable thermal-resistant adhesive exhibits a high glass transition temperature of more than 200/spl deg/C. This adhesive has applications in the assembly of optical components that require higher heat-resistance. (4) The water permeability of the moisture-protected adhesive sealant is an extremely small 8/spl times/10/sup -9/ cc cm/cm/sup 2//cmHg/sec at a high temperature of 75/spl deg/C. The optical excess loss of sealing fiber due to the microbending during curing and temperature cycling (+85/spl deg/C to -40/spl deg/C) is negligibly small (less than 0.01 dB). (5) The water-resistant hot-melt adhesive for reinforcing optical-fiber splices applied to quartz glass by hot-press for 3 minutes at 130/spl deg/C provides excellent adhesion. The peel strength is maintained for over one year after immersion in water of 60/spl deg/C. These qualities of the developed UV-curable adhesives and the new sealants are advantageous for achieving low-cost and high reliability optical devices.