A multicolor liquid crystal display

Claim 1

A multicolor liquid crystal display device (300) having an output panel (330), comprising: a liquid crystal cell (320) including two transparent, insulating substrates arranged in parallel and each with a confronting surface bearing at least one transparent electrode (73), a layer of nematic liquid crystal material having liquid crystal molecules parallel to the substrates, said layer being contained between the insulating substrates with said liquid crystal molecules being gradually twisted between the substrates, the cell being capable of transmitting light therethrough in the vicinity of the electrodes upon the application of an electric field across the layer when a potential difference of appropriate magnitude is applied between the electrodes; a light source (314) for directing light towards one of the insulating surfaces; means for applying a potential difference between said electrodes and producing an electric field across said cell to align the liquid crystal molecules substantially parallel with the direction of the electric field; a high extinction ratio polarizer (324, 326) located on each insulating substrate surface opposite the ones with the electrodes for polarizing the light received from the light source, the polarizers having dark fields and polarizing axes which are parallel or orthogonal to the direction of the liquid crystal molecules adjacent the insulating surface nearer to the light source, said polarizers enabling full contrast and density capability from the liquid crystal cell during passage of the main vector component of polarized light; a relatively small amount of dichroic dye admixed with the liquid crystal material to form a guest-host mixture therewith, molecules of the dichroic dye being the guest molecules and being added for the purpose of absorbing and thus preventing the buildup and subsequent passage of an orthogonal vector component of polarized light created by imperfect rotation of the polarized light by the orientation of the twisted nematic liquid crystal molecules when no electric field is present; and a luminance-balanced color mask (318) located between the light source and the liquid crystal cell, the mask containing a plurality of color patches (319) with the rest of the mask (317) being gray, the color patches being luminance balanced with each other and the gray surround in order that each different patch and the gray surround have substantially equal luminance transmission, so that the output panel appears as a uniformly dark, dead-front output panel to an observer, when a potential difference is not applied to the cell electrodes.

Claim 10

A method of providing a multicolor liquid crystal display device selectively capable of being in the on-state or off-state condition and having a uniformly dark, dead-front output panel when in the off-state condition, said method comprising the steps of: providing a liquid crystal cell having a pair of parallel, transparent glass substrates with transparent electrodes on their confronting surfaces, and a twisted nematic liquid crystal material contained between the substrates; attaching high extinction ratio polarizers on each of the substrate surfaces opposite the confronting ones, the polarizing axes of both polarizers being either parallel or orthogonal with the direction of molecules of the liquid crystal material adjacent the substrate surface selected as the input substrate which is to receive light from a light source; admixing a relatively small amount of dichroic dye with the liquid crystal material to form a guest-host mixture of liquid crystal and dye molecules; directing light from a light source toward said polarizer on the input substrate so that the light received by the input substrate is polarized; applying an alternating voltage across the electrodes to change the orientation of the molecules of the mixture and enable the passage of light when the passage of light is desired; and inserting a luminance-balanced color mask between said light source and said polarizer on the input substrate of the liquid crystal cell, so that the liquid crystal cell with the dichroic dye and two high extinction ratio polarizers in combination with the luminance-balanced color mask cause said output panel to appear uniformly dark to an observer when said multicolor liquid crystal display device is in the off-state condition.

Claim 11

A method of providing a multicolor liquid crystal display device selectively capable of being in the on-state or off-state condition and having a uniformly dark, dead-front output panel when in the off-state condition, said method comprising the steps of: providing a liquid crystal cell having a pair of parallel, transparent glass substrates with transparent electrodes on their confronting surfaces, and a twisted nematic liquid crystal material contained between the substrates; attaching high extinction ratio polarizers on each of the substrate surfaces opposite the confronting ones, the polarizing axes of both polarizers being either parallel or orthogonal with the direction of molecules of the liquid crystal material adjacent the substrate surface selected as the input substrate which is to receive light from a light source; admixing a relatively small amount of dichroic dye with the liquid crystal material to form a guest-host mixture of liquid crystal and dye molecules; directing light from a light source toward said polarizer on the input substrate so that the light received by the input substrate is polarized; applying an alternating voltage across the electrodes to change the orientation of the molecules of the mixture and enable the passage of light when the passage of light is desired; and inserting a luminance-balanced color mask between said light source and said polarizer on the input substrate of the liquid crystal cell, so that the liquid crystal cell with the dichroic dye and two high extinction ratio polarizers in combination with the luminance-balanced color mask cause said output panel to appear uniformly dark to an observer when said multicolor liquid crystal display device is in the off-state condition.