Electroluminescent device with improved cathode

Claim 2

An electroluminescent device comprising in sequence, an anode, an organic hole transporting zone, an organic electron transporting zone, and a cathode, characterized in that said cathode is comprised of a layer con­sisting essentially of a plurality of metals other than alkali metals, at least one of said metals hav­ing a work function of less than 4 eV.

Claim 3

An electroluminescent device according to claim 1 further characterized in that said metal having a work function of less than 4 eV includes at least one alkaline earth or rare earth metal.

Claim 4

An electroluminescent device according to claim 2 further characterized in that at least one metal other than an alkaline earth or rare earth metal is present having a work function of less than 4 eV.

Claim 5

An electroluminescent device according to claim 3 further characterized in that said one other metal is a Group III metal.

Claim 6

An electroluminescent device according to any one of claims 1 to 4 further characterized in that said cathode includes at least one metal having a work function greater than 4 eV.

Claim 7

An electroluminescent device according to claim 5 further characterized in that at least one metal having a work function greater than 4 eV is present chosen from the group consisting of Group III, Ib, IV, V and VIII metals.

Claim 8

An electroluminescent device according to any one of claims 1 to 6 further characterized in that said cathode is light transmissive.

Claim 9

An electroluminescent device according to any of claims 1 to 7 further characterized in that said cathode is less than 250 Angstroms in thickness.

Claim 10

An electroluminescent device according to any one of claims 1 to 8 further characterized in that said organic electron transporting zone is formed of a stilbene or chelated oxinoid compound.

Claim 11

An electroluminescent device according to any one of claims 1 to 9 further characterized in that at least one of said metals is magnesium and at least one other of said metals is chosen from the group consisting of aluminum, copper, silver, gold, tin, lead, bismuth, tellurium, indium, and antimony.

Claim 12

An electroluminescent device according to any one of claims 1 to 10 further characterized in that said cathode is a light transmissive layer having a thickness of less than 250 Angstroms and a sheet resistance of less than 100 ohms per square consisting essentially of at least two metals other than alkali metals, one of said metals being an alkaline earth or rare earth metal having a work function of less than 4 eV and at least one other of said metals having a higher work function than said one metal and being present in a concentration of from 0.1 to 50 percent of total metal atoms present.

Claim 13

An electroluminescent device according to any one of claims 1 to 11 further characterized in that said electron transporting layer is comprised of a vacuum vapor deposited stilbene or chelated oxinoid layer and said cathode is a layer vacuum deposited on said electron transporting layer.

Claim 14

An electroluminescent device according to any one of claims 1 through 12 further character­ized in that said electron transporting layer is com­prised of an chelated oxinoid compound of the formula: wherein Me represents a metal; n is an integer of from 1 to 3; and Z independently in each occurrence represents the atoms completing a nucleus having at least two fused aromatic rings.

Claim 15

An electroluminescent device according to any one claims 1 through 13 further characterized in that said device comprises in sequence, an opaque anode comprised of a metal having a work function greater than 4 eV, an organic luminescent medium consisting of an organic hole transporting zone and a chelated oxinoid electron transporting zone, and a light transmissive cathode consisting essentially of a vacuum vapor deposited layer having a thickness of from 50 to 250 Angstroms and a sheet resistance of less than 100 ohms per square consist­ing essentially of magnesium and silver, said silver being present in a concentration of from 0.1 to 50 percent, based on total magnesium and silver atoms present.

Claim 16

An electroluminescent device according to claim 14 further characterized in that said silver is present in said cathode layer in a concentration of from 1 to 20 percent of the total metal atoms present.

Claim 17

An electroluminescent device according to any one of claims 1 to 15 further characterized in that said organic luminescent medium has a thickness of less than 1 micrometer.

Claim 18

An electroluminescent device according to any one of claims 12 to 16 further characterized in that said chelated oxinoid compound is aluminum trisoxine.