Electroluminescent lamps and phosphors

• US 4,855,189 A
• Filed: 11/24/1987
• Issued: 08/08/1989
• Est. Priority Date: 11/24/1987
• Status: Expired due to Fees

• Current Assignee: Menasha Corporation
• Original Assignee: Lumel, Inc.
• Inventors: Simopoulos, George N., Simopoulos, Nicholas T.
• Primary Examiner(s): Swisher, Nancy A. B.
• Application Number:
  US07/124,808
• Time in Patent Office: 623 Days
• Field of Search: 428/690, 428/691, 313/503
• US Class Current: 428/690
• CPC Class Codes: C09K 11/025 non-luminescent particle coatings or suspension media
• CPC Class Codes: H05B 33/10 Apparatus or processes specially adapted to the manufacture of electroluminescent light sources
• CPC Class Codes: H05B 33/20 characterised by the chemical or physical composition or the arrangement of the material in which the electroluminescent material is embedded

Abstract

Electroluminescent phosphors, electroluminescent panels and lamps made with such phosphors, and a process and apparatus for treating phosphors are disclosed in which the phosphor particles are coated with a very thin coating of SiO₂, to protect the phosphor particles from aging due to moisture intrusion. The phosphor particles are coated in a cold wall reactor by the pyrolytic decomposition of silane in the presence of heat and oxygen to a coating thickness of approximately between 0.1 and 3.0 microns. The apparatus and method of coating includes the placement of a quantity of phosphor in a cup-shaped heated reactor bowl and subjecting the particles to a temperature of about 490° C. and an atmosphere of silane and oxygen, while continuously mechanically agitating the particles with a blade arrangement in which the particles are continuously rotated and turned so as to expose the surfaces of the heated particles to the reaction atmosphere. Panels and lamps made from such phosphors may be die cut and trimmed, have an increased life as compared to panels and lamps made with untreated phosphors, and exhibit a minimum of color shift during the lifetime of the panel.

Claims

1. An improved long-life, flexible electroluminescent lamp which may be die cut or served by cutting or trimming through all of the active layers, including the phosphor layer, and which maintains its brightness up to a cut or severed edge substantially for the life of the lamp, and which exhibits a minimum of color shift during use, comprising:

a base formed of temperature stabilized, flexible film material,

a transparent electrode on said base, a phosphor layer on said transparent electrode, said phosphor layer including phosphor particles in a size range in which about 90% of the particles are between about 14 and 62 microns in size,

each of said particles being coated with an encapsulating layer of silicon dioxide formed thereon as the product of pyrolytic decomposition of silane in the presence of oxygen at the surface of a heated particle,

said containing on each said particle being of substantially uniform thickness in the order of approximately between 0.1 and 3.0 microns,

said coated phosphor particles being dispersed in a resin carrier,

a dielectric layer applied to said phosphor layer, and

a back electrode applied to said dielectric layer.

2. The electroluminescent lamp of claim 1 in which said silicon dioxide layer is formed as a homogeneous single thickness conforming to the shape of the associated phosphor particle.

3. The lamp of claim 1 in which said coating is between 0.4 and 1.0 micron in thickness.

4. An improved flexible electroluminescent lamp, comprising:

a based formed of temperature stabilized flexible film, a transparent electrode on one surface of said base,

a phosphor layer on said transparent electrode,

said phosphor layer having discrete particles of phosphor in a cured resin binder,

each of said particles including a discrete encapsulating coating of clear silicon dioxide, each said coating having a substantially uniform thickness, and each said particle having a coating of substantially the same thickness as the other particles in the order of 0.1 to 3.0 microns, said coating being formed on said particles as the product of pyrolytic decomposition of silane in the presence of oxygen at the surface of a heated particle,

a dielectric layer on said phosphor layer, and a back electrode layer on said dielectric layer.

5. The lamp of claim 4 in which said coating is between 0.4 and 1.0 micron in thickness.

6. The flexible electroluminescent lamp of claim 4 in which said phosphor particles have a size distribution such that about 90% thereof are between 14 and 62 microns in size.