U.S. Philips Corporation

Wilbert J Hartmann

Antonius G Verhulst

Johannes A Van Haaren

Karel E Kuijk

Leonard J Esser

Franciscus Johannes Stommels

Ann M Luyckx-Smolders

Franciscus H Lathouwers

To compensate for the variation of the transmission-voltage characteristic curve due to temperature changes in a ferro-electric display device, the display device is provided with one or more measuring elements (5) for measuring the polarization current. The drive voltages are corrected by means of the polarization current which is used as a feedback parameter.

Ferroelectric display device with temperature compensation

An electro-optic display device with grey scale set by areas of crossing electrodes. In one embodiment, there are 3 strip-shaped sub electrodes with a width relationship of 4:2:1, and two strip shaped column electrodes with a relationship of 8:1. In a second embodiment, there are 4 strip-shaped sub electrodes with a width relationship of 8:4:2:1, and two strip shaped column electrodes with a relationship of 16:1.

Display device with crossing electrodes with specific ratio for gray

An LCD device in which the pixels are divided into sub-pixels composed of one analog adjustable sub-pixel and a plurality of digitally controlled other sub-pixels. By combining a discrete adjustment of the (sub)-transmission levels of the other sub-pixels with an analog adjustment of transmission levels of the one sub-pixel, the total number of light transmission levels is increased considerably. The analog adjustment thus is less critical because the greater part of the ultimate level is defined by the accurate discrete adjustment.

Electro-optic display device with increased number of transmission levels

A liquid crystal device incorporating ferroelectric liquid crystal medium having smectic layers between two supporting plates provided with electrodes, the smectic layers exhibiting a spread of angles with respect to at least one of the supporting plates, whereby a gradual transmission/voltage characteristic is achieved. The spread of angles can be obtained by any of several techniques, such as subjecting the device to a low frequency electric field, or a local thermal, mechanical, chemical or magnetic treatment.

Ferroelectric liquid crystal display having a spread of angles for

In a method of driving a passive ferro-electric display device the selection voltages, 'blanking' voltages and data voltages are given a bipolar character so that the values of the data voltages with respect to the 'blanking' voltage can be chosen to be so low that there is substantially no crosstalk. In a passive display device this provides the possibility of driving large numbers of lines (for example, for LCD-TV) while maintaining the contrast.

Method of driving a passive ferro-electric liquid crystal display device

In the case of active drive of a ferro-electric liquid crystal display device the picture elements within the line selection period are first brought to an extreme state by means of a 'blanking' signal. To obtain grey scales in a reproducible manner (via charge compensation) the data signal is preferably presented during a period which is short with respect to the switching period of the ferro-electric liquid crystal.

Method of driving a ferroelectric to display device to achieve gray

By using an auxiliary signal bringing a ferroelectric liquid crystal to an extreme transmission state in an active matrix it is impossible for successive charge compensation to occur on the pixels. This prevents the growth of regions where transmission occurs or does not occur and provides the possibility of obtaining gray scales in a reproducible manner.

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Eindhoven, Netherlands

Wilbert J Hartmann