Color LCD including transistors having layer thicknesses selected for small photocurrents
First Claim
1. An active matrix liquid crystal display device comprising a multiplicity of liquid crystal display elements, each controlled by a thin film transistor, (TFT) having a gate layer, a semiconductor layer providing a channel region insulated from the gate layer by a gate insulation layer, and means for illuminating the display elements, the display elements comprising groups providing outputs of respective different colors, characterised in that the thickness of at least one of said layers of the TFTs differ from one group to another group and is selected in accordance with the color of light within which each group operates such that interference effects results in a small amount of absorption of said colored light in the semiconductor layer.
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Abstract
A color display device has groups of liquid crystal display elements controlled by respective TFTs, the groups providing respective different color outputs, e.g. red, green and blue, and being either interspersed in a single panel with individual elements associated with color filter elements or in respective separate panels illuminated by differently colored light. The TFTs are of multilayer structure having semiconductor, gate insulator and gate layers. At least one layer thickness of the TFTs is different from group to group and is selected in accordance with the color light to which they are subjected so as to reduce absorption of that light, and consequently photo-induced currents in their semiconductor layers. Significantly reduced absorption is achievable by appropriate choice for example of semiconductor and insulator layer thicknesses based on optical interference considerations. The device can be used as a projection display device.
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Citations
30 Claims
- 1. An active matrix liquid crystal display device comprising a multiplicity of liquid crystal display elements, each controlled by a thin film transistor, (TFT) having a gate layer, a semiconductor layer providing a channel region insulated from the gate layer by a gate insulation layer, and means for illuminating the display elements, the display elements comprising groups providing outputs of respective different colors, characterised in that the thickness of at least one of said layers of the TFTs differ from one group to another group and is selected in accordance with the color of light within which each group operates such that interference effects results in a small amount of absorption of said colored light in the semiconductor layer.
Specification