Backlighting for electro-optical passive displays and transflective layer useful therewith

Claim 2

An electroluminescent lamp (14) comprising a phosphor layer (60) disposed between corresponding lamp electrodes (46, 112) that are adapted to apply an excitation potential to cause said phosphor layer to emit light, the front lamp electrode being light-transmissive to radiation from said phosphor layer, characterized in that said front lamp electrode (46) comprises a thin layer of light-transmissive binder (48) containing a distribution of discrete particles (50) that are characteristically light-reflective and electrically conductive, said particles providing aggregate diffuse outward reflectance sufficient to serve as a reflector behind an LCD display (12) for ambient light that falls upon said LCD display to illuminate said LCD display under light ambient conditions, said particles in said layer being in sufficient electrical continuity to at least assist in applying excitation to said phosphor layer, and said particles having sufficient spaces (51) between them to provide outward escape paths for light from said excited phosphor layer to back-illuminate said LCD display under dark ambient conditions.

Claim 3

The electroluminescent lamp of claim 1 characterized in that said electrical continuity is achieved by physical contact between said light-reflective particles in said front lamp electrode layer.

Claim 4

The electroluminescent lamp of claim 1 characterized in that said particles in said front lamp electrode have diameters of the order of about 10 microns in the direction of the plane of the layer in which they reside.

Claim 5

The electroluminescent lamp of claim 1 characterized in that said particles in said front lamp electrode have the form of metal flakes, said particles being generally aligned with the plane of the layer in which they reside.

Claim 6

The electroluminescent lamp of any of the claims 1, 2, 3 or 4 characterized in that said binder is a polymer consisting essentially of polyvinylidene fluoride (PVDF).

Claim 7

The electroluminescent lamp of claim 1 characterized in that said particle distribution in said front lamp electrode provides a reflectance of about 80 percent to ambient light incident upon the front of said electrode.

Claim 8

The electroluminescent lamp of claim 1 characterized in that said lamp is adapted to emit radiation through said front lamp electrode of brightness of at least one foot-lambert.

Claim 9

The electroluminescent lamp of claim 1 in combination with a display (12) comprising an array of a large number of discrete LCD picture elements activatable selectively to form desired characters, characterized in that said front lamp electrode (46) is arranged to serve as a rear reflective surface for said LCD display under light ambient conditions, and said lamp is adapted to provide light through said front lamp electrode to back-illuminate said display under dark ambient conditions.

Claim 10

The device of claim 8 characterized in that the average surface area of a said particle in said front lamp electrode has a surface area less than about one percent of the surface area of a said picture element.

Claim 11

The device of claim 8 characterized in that said device is capable of providing, for all ambient conditions, a display contrast ratio of at least about 2:1.

Claim 12

An electro-optical display device (10) comprising an electroluminescent lamp (14) having a phosphor layer (60) disposed between corresponding lamp electrodes (46, 112) that are adapted to apply an excitation potential to cause said phosphor layer to emit light, the front lamp electrode (46) being light-transmissive to radiation from said phosphor layer, and, positioned in front of said front electrode, a passive LCD device (12) having a display defined by an array of a large number of discrete picture elements activatable selectively to form desired characters, characterized in that said front lamp electrode (46) comprises at least in part a thin layer of light-transmissive binder (48) containing a uniform distribution of particles (50) that are characteristically light-reflective and electrically conductive, said particles providing aggregate diffuse reflectance sufficient to serve as a reflector behind said LCD display for ambient light to illuminate said LCD display under light ambient conditions, said particles in said layer being in sufficient electrical continuity to at least assist in applying excitation to said phosphor layer, and said particles having sufficient spaces (51) between them to provide outward escape paths for light from said excited phosphor layer through said front lamp electrode to back-illuminate said LCD display under dark ambient conditions, whereby said front lamp electrode is adapted to serve as a rear reflective surface for said LCD under light ambient conditions, and said lamp is adapted to provide light through said front lamp electrode to back-illuminate said display under dark ambient conditions.

Claim 13

An electro-optical display device (10) comprising an electroluminescent lamp (14) having a phosphor layer (60) disposed between corresponding lamp electrodes (46, 112) that are adapted to apply an excitation potential to cause said phosphor layer to emit light, the front lamp electrode (46) being light-transmissive to radiation from said phosphor layer, and, positioned in front of said front electrode, a passive LCD device (12) having a display defined by an array of a large number of discrete picture elements activatable selectively to form desired characters, characterized in that said front lamp electrode (46) comprises at least in part a thin layer of light-transmissive binder (48) containing a uniform distribution of particles (50) that are characteristically light-reflective and electrically conductive, said particles providing aggregate diffuse reflectance sufficient to serve as a reflector behind said LCD display for ambient light to illuminate said LCD display under light ambient conditions, said particles in said layer being in sufficient electrical continuity to at least assist in applying excitation to said phosphor layer, and said particles having sufficient spaces (51) between them to provide outward escape paths for light from said excited phosphor layer through said front lamp electrode to back-illuminate said LCD display under dark ambient conditions, whereby said front lamp electrode is adapted to serve as a rear reflective surface for said LCD under light ambient conditions, and said lamp is adapted to provide light through said front lamp electrode to back-illuminate said display under dark ambient conditions.

Claim 14

The electro-optical device of claim 11 characterized in that said electrical continuity is achieved by physical contact between said light-reflective particles in said front lamp electrode layer.

Claim 15

The electro-optical device of claim 11 characterized in that the average surface area of a said particle in said front lamp electrode has a surface area less than about one percent of the surface area of a said picture element.

Claim 16

The electro-optical device of claim 11 characterized in that said device is capable of providing, for all ambient conditions, a display contrast ratio of at least about 2:1.

Claim 21

The method of claim 16 adapted to form a front electrode (46) for an electroluminescent lamp (14) characterized in that said particles are electrically conductive.

Claim 22

The method of claim 17 characterized in that the layer forming said front electrode (46) is deposited by shear transfer upon a fused first layer comprising said polymer solid, and said heating causes said layers to fuse continuously throughout and between said layers to form a monolithic unit.

Claim 23

The method of claim 16, 17 or 18 characterized in that said layer is deposited by silk screen printing or doctor blade coating.

Claim 24

The method of claim 16, 17 or 18 characterized in that said discrete particles (50) have the form of flakes and during the drying of said electrode layer a large multiplicity of said particles are caused to align themselves generally with the extent of the plane of said thin layer.

Claim 25

The method of claim 16, 17 or 18 characterized in that said polymeric binder consists essentially of polyvinylidene fluoride (PVDF).

Claim 26

A transflector (46) characterized in that said transflector comprises a thin layer of light-transmissive polymer binder (48) consisting essentially of polyvinylidene fluoride (PVDF) containing a distribution of discrete particles (50) that are characteristically light reflective, said particles in said layer providing aggregate diffuse reflectance.

Claim 27

A transflector (46) characterized in that said transflector comprises a thin layer of light-transmissive polymer binder (48) consisting essentially of polyvinylidene fluoride (PVDF) containing a distribution of discrete particles (50) that are characteristically light reflective, said particles in said layer providing aggregate diffuse reflectance.

Claim 28

The transflector of claim 22 characterized in that at least some of said particles are electrically conductive and serve to conduct electricity through said layer.

Claim 29

The transflector of claim 23 in combination with an electroluminescent lamp (14) comprising a phosphor layer (60) disposed between corresponding lamp electrodes (46, 112) that are adapted to apply excitation potential to cause said phosphor layer to emit light, characterized in that said transflector layer (46) is disposed over said phosphor layer and serves at least in part as the front electrode of said lamp.