# US 7,609,004 B2 · Eliminating silver migration in EL lamps

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- Number: US 7,609,004 B2
- Document ID: US7609004B2
- Status: Granted
- Kind: B2
- Application number: 11/784,077
- Filed: 2007-04-05
- Published: 2008-10-09
- Granted: 2009-10-27
- Earliest claimed: 2007-04-05
- Assignees: World Properties, Inc.
- Inventors: Sujatha Narayan; Aniruddha J. Shere
- Web page: https://patentgrep.com/patent/US7609004B2

## CPC

- H05B 44/00: Circuit arrangements for operating electroluminescent light sources (for operating light emitting diodes H05B45/00)
- Y02B 20/30: Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]
- H05B: ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- Y02B: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS

## Abstract

A net negative charge is used to eliminate silver migration in an EL lamp. An electrode containing silver, either the entire electrode, a bus bar on the electrode, or a contact area on the electrode, receives a net negative charge while the EL lamp is being driven with alternating current. The net negative charge can be provided by the driver itself or by a current source, such as a battery or a charged capacitor; or by asymmetric current means in the current path of the EL lamp, including the lamp itself.

## Claims

### Claim 1

A lighting system including an EL lamp having a first electrode, a second electrode, a dielectric layer and a phosphor layer between the first electrode and the second electrode, and a driver supplying alternating current to the lamp, characterized in that the first electrode contains silver particles, the second electrode does not contain silver particles, and the driver includes a bias circuit that produces a net negative charge on the first electrode.

### Claim 2 (depends on 1)

The lighting system as set forth in claim 1 wherein said bias circuit is an source of direct current.

### Claim 3 (depends on 1)

The lighting system as set forth in claim 1 wherein said bias circuit is an asymmetric conducting means in series with said EL lamp.

### Claim 4 (depends on 1)

The lighting system as set forth in claim 1 wherein substantially the entire first electrode includes silver particles and is reflective.

### Claim 5

A lighting system including an EL lamp having a first electrode, a second electrode, a dielectric layer and a phosphor layer between the first electrode and the second electrode, and a driver supplying alternating current to the lamp, characterized in that the first electrode includes a bus bar and the bus bar contains silver particles, the second electrode does not contain silver particles, and the driver includes a bias circuit that charges the EL lamp with net negative charge on the first electrode.

### Claim 6 (depends on 5)

The lighting system as set forth in claim 5 wherein said bias circuit includes a source of direct current.

### Claim 7 (depends on 5)

The lighting system as set forth in claim 5 wherein said bias circuit includes asymmetric conducting means in series with said EL lamp.

### Claim 8

A lighting system including an EL lamp having a first electrode, a second electrode, a dielectric layer and a phosphor layer between the first electrode and the second electrode, and a driver supplying alternating current to the lamp, characterized in that the first electrode includes a contact area and the contact area contains silver particles, the second electrode does not contain silver particles, and the driver includes a bias circuit that charges the EL lamp with net negative charge on the first electrode.

### Claim 9 (depends on 8)

The lighting system as set forth in claim 8 wherein said bias circuit includes a source of direct current.

### Claim 10 (depends on 8)

The lighting system as set forth in claim 8 wherein said bias circuit includes asymmetric conducting means in series with said EL lamp.

### Claim 11

A method for eliminating silver migration in an EL lamp having an electrode containing silver particles, said method comprising the steps of:
supplying alternating current to the EL lamp during operation; and providing a DC offset to the alternating current, thereby generating a net negative charge on the electrode.

### Claim 12 (depends on 11)

The method as set forth in claim 11 wherein said providing step includes the step of:
coupling an asymmetric current means in series with the EL lamp.

### Claim 13 (depends on 11)

The method as set forth in claim 11 wherein said providing step includes the step of:
adding direct current to the alternating current.