Electro-optic passive display cell
AssigneeEbauches S.A.
InventorFereydoun Gharadjedaghi
Life of this patent
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Abstract
An electro-optic passive display device comprising a pair of plates having, as an active component between the plates, a mixture comprising a nematic liquid crystal possessing negative dielectric anisotropy, dichroic molecules and a chiralic compound capable of providing a helical structure to the active component, the chiralic compound concentration being selected to produce a pitch of the helix between 0.9d and 3d, "d" being the distance between plates, critical to ensure the formation of a helical structure only under the effect of an electric field and to provide a high contrast display.
Claims6
An electro-optic passive display cell comprising:
- two substantially parallel spaced plates;
- a frame sealed between said plates and defining a tight chamber therebetween;
- control electrodes arranged on the inner facing surfaces of said plates for providing an electric field therebetween;
- a coating of homeotropic alignment material covering said inner surfaces and said electrodes, an active component disposed in said chamber, said active component comprising a mixture of a nematic liquid crystal having a negative dielectric anisotropy, dichroic molecules and a chiralic compound capable of providing a helical structure to the said active component when an electric field is applied and a homeotropic structure in the absence of an applied electric field, the concentration of the said chiralic compound being selected to provide a pitch of the helical structure having a value substantially comprised between 0.9 and 3 times the distance between plates whereby satisfactory readable contrast is provided between areas under effect of an electric field and areas where such electric field effect is absent.
An electro-optic passive display cell comprising:
- two substantially parallel spaced plates;
- a frame sealed between said plates and defining a tight chamber therebetween,
- control electrodes arranged on the inner facing surfaces of said plates for providing an electric field therebetween;
- and
- a coating of homeotropic alignment material covering said inner surfaces and the said electrodes,
- an active component disposed in said chamber, said component comprising a mixture of a nematic liquid crystal having a negative dielectric anisotropy, dichroic molecules and a chiralic compound capable of providing a helical structure to the said active component when an electric field is applied, the concentration of said chiralic compound selected to provide a pitch of the said helical structure having a value substantially comprised between 0.9 and 3 times the distance between plates whereby to be compatible with the spontaneous formation of a homeotropic structure in the absence of an electric field.
Dependencies are inferred from the claim text.