US 5,684,365 AGranted

TFT-el display panel using organic electroluminescent media

AssigneeEastman Kodak Company

InventorsChing Wan Tang, Biay Cheng Hseih

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Abstract

A flat panel display comprising thin-film-transistor-electroluminescent (TFT-EL) pixels is described. An addressing scheme incorporating two TFTs and a storage capacitor is used to enable the EL pixels on the panel to operate at a duty factor close to 100%. This TFT-EL device eliminates the need to pattern the EL cathode, thus greatly simplifying the procedure to delineate the EL pixels as well as ensuring high resolution. The TFT-EL panel consumes less power than conventional TFT-LCD panels, especially when the usage factor of the screen is less than unity.

Claims12

Dependent claims

An electroluminescent flat panel display comprising:

a substrate having top and bottom surfaces;
and having disposed on said substrate a plurality of pixels, each of said pixels comprising:
a) a first thin-film-transistor disposed over the top surface of said substrate, wherein said first thin-film-transistor comprises a source electrode, a drain electrode, a gate dielectric, and a gate electrode;
and wherein said gate electrode comprises a portion of a gate bus;
b) a second thin-film-transistor disposed over the top surface of said substrate;
wherein said second thin-film-transistor comprises a source electrode, a drain electrode, a gate dielectric, and a gate electrode;
wherein said gate electrode is electrically connected to said drain electrode of said first thin-film-transistor;
c) a capacitor disposed over the top surface of said substrate;
said capacitor comprising top and bottom electrodes;
d) a display anode layer electrically connected to said drain electrode of said second thin-film-transistor;
e) a dielectric passivation layer overlying said first and second thin-film-transistors and said capacitor;
said dielectric passivation layer having an opening over said anode layer;
and further wherein said passivation layer has a tapered edge at said opening such that the bottom edge of said passivation layer extends further over said anode layer than does the top edge of said passivation layer wherein said tapered edge is tapered at an angle of 10.degree. to 30.degree. with respect to the surface of said anode layer;
f) an organic electroluminescent layer positioned directly on the top surface of said anode layer;
wherein said organic electroluminescent layer is insulated from said first and second thin-film-transistors, and said capacitor, by said passivation layer;
and
g) a cathode layer positioned directly on the top surface of said organic electroluminescent layer;
and further comprising a plurality of column leads connected to the source electrode of said first thin-film-transistor on each pixel and a plurality of row leads connected to the gate electrode of said first thin-film transistor on each pixel and a plurality of ground leads connected to said capacitor of each pixel.

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Dependencies are inferred from the claim text.

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Abstract

An electroluminescent flat panel display comprising:

a substrate having top and bottom surfaces;
and having disposed on said substrate a plurality of pixels, each of said pixels comprising:
a) a first thin-film-transistor disposed over the top surface of said substrate, wherein said first thin-film-transistor comprises a source electrode, a drain electrode, a gate dielectric, and a gate electrode;
and wherein said gate electrode comprises a portion of a gate bus;
b) a second thin-film-transistor disposed over the top surface of said substrate;
wherein said second thin-film-transistor comprises a source electrode, a drain electrode, a gate dielectric, and a gate electrode;
wherein said gate electrode is electrically connected to said drain electrode of said first thin-film-transistor;
c) a capacitor disposed over the top surface of said substrate;
said capacitor comprising top and bottom electrodes;
d) a display anode layer electrically connected to said drain electrode of said second thin-film-transistor;
e) a dielectric passivation layer overlying said first and second thin-film-transistors and said capacitor;
said dielectric passivation layer having an opening over said anode layer;
and further wherein said passivation layer has a tapered edge at said opening such that the bottom edge of said passivation layer extends further over said anode layer than does the top edge of said passivation layer wherein said tapered edge is tapered at an angle of 10.degree. to 30.degree. with respect to the surface of said anode layer;
f) an organic electroluminescent layer positioned directly on the top surface of said anode layer;
wherein said organic electroluminescent layer is insulated from said first and second thin-film-transistors, and said capacitor, by said passivation layer;
and
g) a cathode layer positioned directly on the top surface of said organic electroluminescent layer;
and further comprising a plurality of column leads connected to the source electrode of said first thin-film-transistor on each pixel and a plurality of row leads connected to the gate electrode of said first thin-film transistor on each pixel and a plurality of ground leads connected to said capacitor of each pixel.

15 more elements