GB1411600A - Electroluminescent display devices - Google Patents

Abstract

1411600 Electroluminescence WESTERN ELECTRIC CO Inc 28 Dec 1972 [30 Dec 1971] 59769/72 Heading C4S [Also in Division G5] An electroluminescent display device comprises a substrate having at least one EL element 14 thereon and around the EL elements, a light reflective region in which the light reflective regions are covered with a photoresist material 13 baked at a temperature sufficient to darken the resist so as to inhibit reflections. The resist may be darkened from light brown to deep brown or black and the heating step may be that used to bond LEDs and Si chips to the substrate. Films may be 0À1 to 10 Á and applied by spinning, spraying, dipping or roll casting. Ceramic substrate 10 may be high density alumina, beryllia, or other stable refractory oxide or mixtures of oxides, or carbides for example; usually formed by compressed powder or glass forming techniques. In Figs. 2a-2f, metal layer 11 (Fig. 2a) is masked by photoresist mask 12 (Fig. 2b), and etched (Fig. 2c). After all photolithographic and etching steps having been completed and circuitry tested, Figs. 2d-2f steps follow and are described in detail, including pretreatment of the substrate and particular photoresists and solvent film 13 (Fig. 2d) may be 8 Á thick, and regions subsequently exposed may include those between bar segments to detract from delineation between same. Following removal of exposed film, the substrate is thermally cycled in air to 350‹ C. starting at 150‹ C. with a 50‹ C./5 min. slope. LEDs 14 (e.g. GaP, GaAsP) and IC chips are subsequently bonded to the exposed pads 11a and (11b), (Fig. 2f, and Fig. 1 (not shown)). The darkening step may be that used to bond the final elements, and temperatures in excess of 200‹ C. or 300‹ C. are instanced. Fig. 1 (not shown) is a seven bar array and in which metallization may be Au, Si, W, Mo or Al. Reference is made to alphanumeric displays with LEDs, and Si chips on a ceramic substrate supporting active components and metallization interconnecting LEDs and logic circuitry on the Si chip. Also disclosed is a filter transmitting only the display wavelength and blackening of the ceramic, e.g. by painting.