Communications: electrical – Land vehicle alarms or indicators – Internal alarm or indicator responsive to a condition of the...
Patent
1983-07-18
1987-01-27
Brigance, Gerald L.
Communications: electrical
Land vehicle alarms or indicators
Internal alarm or indicator responsive to a condition of the...
340713, 350350S, 350351, G09G 336
Patent
active
046397221
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
This invention relates to a liquid crystal display apparatus and more particularly is directed to a liquid crystal display apparatus based on a liquid crystal light emitter actuated by the heat from a laser beam.
2. Background Art
A conventional liquid crystal light emitter actuated by the heat from a laser beam is characterized in that its light scattering center is formed by a laser beam irradiation. The theory thereof will briefly be described with reference to a smectic liquid crystal. The smectic liquid crystal is changed in phase in the following order from a crystal phase, a smectic C phase, a smectic A phase, a nematic phase to an isotropic phase as the temperature thereof rises. Upon use or operation, the temperature of the liquid crystal is set at a temperature between a temperature T.sub.1 at which the phase transition from the smectic C phase to the smectic A phase will occur and a temperature T.sub.2 at which the phase transition from the smectic A phase to the nematic phase will occur, namely, the temperature at which the smectic A phase is retained. In the smectic A phase, the liquid crystal particles exhibit a layer-like structure and each layer is arrayed in the vertical direction. If the surface of a glass substrate is subjected to surface treatment in advance, the liquid crystal particles are arrayed in a layer vertical to the surface of the glass substrate. When a laser beam is focussed and then irradiated on the liquid crystal layer arranged as described above, the heat is generated in the portion thereof on which the laser beam is irradiated and the heat is conducted to the liquid crystal. Then, when the temperature of the liquid crystal exceeds the smectic A-nematic phase transition temperature T.sub.2 and further exceeds the nematic-isotropic phase transition temperature T.sub.3 the isotropic phase results. When the irradiation of the laser beam is stopped at that state, a tendency may appear such that the heated isotropic phase is cooled to restore the smectic A phase again. However, when it is quenched or cooled rapidly the liquid crystal is never returned to the first regular alignment state and the liquid crystal of the disordered orientation direction is kept as it is, thus that portion is recorded therein as a memory. If a voltage is applied to the liquid crystal cell on which the recording was performed as described above and the dielectric constant of the liquid crystal particle in the long axis direction thereof becomes larger than that in the short axis direction, the liquid crystal particles arrayed in the disordered state restore the regular alignment of layers again thereby erasing the recorded information. That is, if on the basis of such operation theory, the laser beam scans the liquid crystal and the intensity of the laser beam is modulated in synchronism therewith, the recording and the subsequent erasing of an image can be performed.
In this case, since the smectic-nematic phase transition or the nematic-isotropic phase transition is the primary phase transition, latent heat is required to cause the phase transition. Thus, the heat energy from the laser beam irradiated upon recording does not contribute to raise the temperature by a sufficient amount, which is then a great obstacle to the increase of the recording speed. Moreover, a sufficient scattering state is necessary to be generated for keeping the recorded display as the memory and for that purpose a quenching is required. Therefore, since the temperature rise upon heating by the laser beam must be as large as possible, it is quite disadvantageous that any loss occurs in the heat energy caused by the irradiation of the laser beam.
If the scattering state is used as the recording state a difficult problem of increasing the contrast is caused. That is, in order to solve the afore-mentioned problem, if the laser absorbing layer such as aluminium or the like is formed on the liquid crystal cell for the purpose of converting the light energy of the irradiated laser beam into heat
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Kojima Shigeru
Urabe Tetsuo
Brigance Gerald L.
Sony Corporation
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