ELECTROLUMINESCENT DISPLAYS

摘要

Certain materials are electroluminescent, and this electroluminescent effect has been used in the construction of backlights for displays. Such a backlight commonly consists of a transparent front layer (11) known as the substrate carrying over its rear face a transparent electrically-conductive film (12) forming the backlight's front electrode and covered by a layer of electroluminescent/phosphor material (13) over the rear face of which is a high-dielectric layer (16) bearing on its rear face a conductive film (17) forming the back electrode. The whole is positioned behind a mask (18) that defines whatever characters the display is to show. This use of a mask has some disadvantages, some of which can be overcome by utilising an array of suitably shaped individual electrodes (21) instead of a continuous one; however, this itself has drawbacks, since the lead (22) to each electrode acts as an electrode in its own right, activating the phosphor to show faint but distracting additional illumination. The invention deals with this problem of track-derived tails; it proposes firstly that the electroluminescent material itself be shaped into discrete areas (43) each tightly matching in shape and size the relevant individual shaped back electrode (21), and secondly (or in addition) that there be used a shield layer (71) of electrically-conductive material shaped and sized as a negative of the shaped area back electrode (21) and positioned as an intermediate electrode between and aligned with the shaped area electrode (21) and the electroluminescent material layer (43), and given the same electrical potential as the front electrode (12).