Most portable electronic devices include displays for displaying various types of images. Examples of such displays include electrowetting displays (EWDs), liquid crystal displays (LCDs), electrophoretic displays (EPDs), light emitting diode displays (LED displays), etc. Electrowetting displays include oil that covers a pixel (or sub-pixel) region of the display when the display is in an off-state. In an on-state, the oil is retracted and thus, does not cover the pixel region. To switch the pixel region into the on-state, a voltage is applied across the oil via an electrically conductive fluid that is substantially immiscible with the oil. To switch the pixel region into the off-state, the voltage is switched off and the oil once again covers the pixel region. Light, either from a backlight source or a frontlight source, is generally passed through the pixel regions in order to illuminate the electrowetting display. In various embodiments, the oil is black, i.e. appears black to an observer and thus, when a pixel region is in the on-state, the light passes through the pixel region and thus, the pixel region provides a white pixel (or sub-pixel). Alternatively, a color filter may be provided with the pixel region and thus, the light during the on-state would be colored based upon the color of the color filter. Alternatively, when the pixel region is in the off-state, light may pass through the oil, which may be colored, and thus, the pixel region may produce a colored pixel (or sub-pixel) based upon the color of the oil. If the oil is black, then during the off-state, the pixel region will produce a black pixel (or sub-pixel).
The oil is given a black appearance using a mixture of multiple colored dyes. Likewise, the oil may be colored a single color by providing a single colored dye within the oil. The color of the dyes may however fade over a period of time due to prolonged exposure of the dyes to components of the light produced by the backlight source or the frontlight source within a spectrum of short wavelengths, i.e. high energy wavelengths, and/or the ultraviolet light spectrum. This is often referred to as photo-bleaching, which may affect the lifetime of the display.
USPTO Backgrounds
USPTO Backgrounds