Electroluminescent display device

An electroluminescent display device mounted on a vehicle and powered by an on-board battery comprising:

• an electroluminescent panel having electroluminescent elements;
• driver means for selectively activating the electroluminescent elements to emit light therefrom;
• a power source circuit for supplying electric power to the driver means;
• switching means for controlling power supply from the battery to power source circuit, operation of the switching means being triggered by a key switch of the vehicle;
• and
• a controller for controlling operation of the driver means and the switching means, wherein:
• the driver means continues to apply termination of a display operation, for at least one period of the electroluminescent panel, a voltage having a value in a vicinity of a threshold voltage used to activate the electroluminescent elements on at least all of the electroluminescent elements which were activated in a previous display operation, whereby the applied voltage eliminates residual charges stored in the electroluminescent elements in the previous display operation, which cause a momentary image display upon re-starting the display operation;
• and wherein
• the switching means shuts off the power supply from the battery to the power source circuit after the application of the voltage to eliminate residual charge.

An electroluminescent display device powered by a DC power source comprising:

• an electroluminescent panel including a plurality of scanning electrodes, a plurality of data electrodes, and an electroluminescent layer interposed between the scanning and data electrodes, the scanning and data electrodes constituting a matrix, each intersection of the scanning and data electrodes and the electroluminescent layer constituting a plurality of pixels;
• a scanning electrode driving circuit for sequentially applying scanning voltages on the scanning electrodes, polarities of the scanning voltages being alternately switched every positive and negative field;
• a data electrode driving circuit for applying data voltages on the data electrodes;
• a power source circuit for supplying voltages to the scanning and data electrode driving circuits;
• a switching circuit for allowing and shutting off power from the DC power source to the power source circuit;
• and
• a control circuit for controlling the scanning electrode driving circuit to apply a voltage to eliminate residual charges and has a value in a vicinity of a threshold voltage used to activate the pixels on the scanning electrodes for a period at least covering one field after a termination of display on the panel, the control circuit controlling the data electrode driving circuit to apply a data voltage which inactivates the pixels so that the pixels do not emit light on the data electrodes for the same period in which the scanning voltage is applied on the scanning electrodes after termination of display on the panel, and for controlling the switching circuit to shut off the voltage supply from the DC power source to the power source circuit.

An electroluminescent display device comprising:

• an electroluminescent panel having electroluminescent elements;
• driver means for selectively activate the electroluminescent elements to emit light therefrom;
• power source means for supplying electric power to the driver means;
• and
• a controller for controlling operation of the driver means and the power source means, wherein:
• substantially all the electroluminescent elements are activated to emit light causing an image due to residual charges to be invisible, and displaying an initial display on the panel, upon turning on the electroluminescent display device.

A method of driving an electroluminescent display panel having picture elements, the method comprising steps of:

• displaying images on the electroluminescent panel by applying to the picture elements scanning voltages and data voltages in synchronized relation;
• discontinuing image display by changing the data voltages to a voltage level which displays no image while continuing to supply the scanning voltages for a period sufficient to scan all the picture elements at least one time, thereby eliminating electric charges stored in the picture elements, which cause a momentary image upon re-starting the image display;
• and
• shutting off power for driving the electroluminescent display panel.

A method of driving an electroluminescent display panel having picture elements, the method comprising steps of:

• starting a power supply for driving the electroluminescent display panel;
• activating substantially all the picture elements so that the picture elements emit light at least one time, thereby making residual images invisible, which are momentarily displayed upon starting the power supply;
• and
• displaying images on the electroluminescent display panel by imposing scanning voltages and data voltages on the picture elements.