IL43290A - Operational method for the display of images with an electro-optical device and electro-optical device for performing said method - Google Patents

Claims (19)

WHAT WE CLAIM IS:

1. A method for displaying optical images using an electro-optical device comprising at least a liquid crystal cell inserted between two polarizers, in which between two supportin members, at least' one of which is transparent and provided with electrode conductive layers, there is inserted a film of a nematic liquid crystal having a negative dielectric anisotropy and a substantially homeotropic alignment, and in which there is applied to the liquid crystal, as a function of the physical properties of the liquid crystal and the thickness of the film, a pulsed energization of suitable waveform, the pulsed energisation being such as not to induce dielectric breakdown and having such a duration and such an RMS amplitude as to give rise, under the conditions of a single applied pulse, to a luminous response of the cell not exceeding 1.3 times that which is necessary to produce a single flash of light of a peak amplitude.

2. A method according to Claim 1, wherein in the case of repetitive energization, the period of repetition of the pulses is such that, under steady state conditions, at the end of the period itself the luminous response of said cell falls irreversibly to a value which" does not exceed one half of its peak value.

3. A method according to claim 2, wherein in the case of repetitive energization, both the RMS amplitude and the duration of the pulses corresponding to the .white level is smaller than, but not smaller than one half of, the values

4. A method according to claim 1, 2 or 3 , wherein the maximum peak electric fields as generated in the liquid -6 crystal by the applied voltage- pulses are greater than 10 V/cm.

5. A method according to claim 4, wherein the maximum peak -4 -6. , electric fields are between 10· / and 10 ; V/cm.

6. A method according to claim 1, 2 or 3 wherein the value of duration and RMS amplitude of the energization pulses are selected as a function of the nature of the liquid crystal arid its thickness and the repetition times are selected, for j a given liquid crystal, as a function of the thickness of i said crystal. . " j I

7. A method according to claim 1,2 or 3, wherein between i the pulses, a voltage is present which voltage is generally non-periodic and insufficient to energize the liquid crystal, and wherein, in the case of single-pulse energization, the duration and/or the RMS amplitude of the pulse are decreased, and in the case of repetitive energization, the duration and/or the RMS amplitude of each pulse, is or are decreased and the period of repetition of the pulses is increased.

8. An electro-optical device for the display of images according to the method according to any one of claims l"~to 7 comprising at least one liquid-crystal cell formed by two supporting members, one at least of which is transparent, and which are provided with electrode conductive layers to v/hich the pulsed energization voltage is applied and .whose surface orientation, between which chere is inserted a film of a nematic liquid crystal having a negative dielectric anisotropy and a substantially homeotropic alignment, said supporting members .being inserted between two polarizers, wherein said liquid crystal film has a thickness not exceeding 10 microns and ε thickness uniformity ranging within + 30% of the desired value.

9. An electro-optical device according to claim 8, wherein Jfor use in displaying television images, the thickness of the liquid crystal is not more than 5 microns and said evenness is. within + 15% of the preselected value.

10. An electro-optical device according to claims 8 or 9, vherein said liquid crystal is N- (p-methoxy-benzylide'ne ) -p~ butyl aniline or mixtures thereof with other nematic liquid crystals of the same class as identified above.

11. An electro-optical device according to claims 8, 9 or 10, wherein the at least one liquid crystal cell is inserted between two linear or nonlinear polarizers, the latter being optically crossed.

12. An electro-optical device according to claim 8, 9 or 10, wherein the at least one liquid crystal cell is inserted between a circular or elliptical polarizer and a reflecting and/or scattering surface so as to give rise, under conditions of .absence of energization electric pulses, to a strong reduction of the transmitted or reflected light as perceived by an observer.

13. An electro-optical device according to any one of'cVaims 8 to 12 wherein the liquid crystal is supplemented with doping substances;.

14. ' An electro-optical device according to claim 13, wherein the doping substanc is water.

15. An electro-optical device according to any one of claims 8 to 14 wherein between the liquid crystal and at least one electrode there is inserted a dielectric layer and/or an electrically nonlinear layer.

16. An electro-optical device for the display of images of the matrix type and comprising at least one liquid crystal cell according to any one of claims 8 to 15 arranged for the display of colored images by additive synthesis, wherein colum elements of the matrix- are subdivided into three parts corresponding to each primary colour with a preselected surfac development as a function of the "weights'* of mono-chromatic light relative to the primaries and of suppressions of possibl chromatic dominants depending upon the polarizers and/or the luminous source.

17. An electro-optical device according to claim 16, wherein parts corresponding to each primary colour are formed. on ribs of the panel supporting member so as to obtain,- by prismatic effect, the superposition of the primary colors on an additional light-scattering screen.

18. A method of displaying images substantially as herei.nbefo r win s.

19. An electro-optical device substantially as hereinbefore described with reference to and as shown by the accompanying drawings.