WO2000063872A1

WO2000063872A1 - Gradient light effect for electroluminescent lamp

Info

Publication number: WO2000063872A1
Application number: PCT/US2000/005100
Authority: WO
Inventors: Bryan D. Haynes
Original assignee: Add Vision Inc
Current assignee: Add Vision Inc
Priority date: 1999-04-15
Filing date: 2000-02-24
Publication date: 2000-10-26
Anticipated expiration: 2001-10-15

Abstract

An electroluminescent lamp (100, 400) is provided. The electroluminescent lamp (100, 400) uses a rear electrode layer (110) having a conductive pattern (112) and a bus bar (404). The conductive pattern (112) is applied so that electrical resistivity of the rear electrode layer (110) increases in areas adjacent to the bus bar (404). An excitation voltage is applied to the bus bar (404). This causes a phosphor layer (106) adjacent to the rear electrode layer (110) to illuminate. The illumination starts in areas adjacent to the bus bar and spreads to additional areas as the applied voltage is increased. In this way, the present invention provides an electroluminescent lamp having a sweepable area of illumination.

Description

Gradient Light Effect for Eiectroluminescent Lamp

Field Of The Invention The present invention is generally related to the design and fabrication of electroluminescent lamps. More specifically, the present invention includes an electroluminescent lamp having an illuminated region that may be progressively moved or extended.

Background Of The Invention

Electroluminescent lamps (also known as EL lamps) are electric lamps that produce light using phosphorescent materials. A typical EL lamp is constructed by sandwiching a phosphor layer between a positive and a negative electrode layer. The electrodes allow an excitation voltage to be applied across the phosphor layer causing the phosphor layer to emit light. One or both of the electrode layers is formed using a transparent or translucent material. This makes the light emitting phosphor visible, making the entire assembly act as a lamp.

The basic structure of EL lamps is relatively old, dating back to the invention of EL lamps in 1936. Surprisingly, these lamps have only recently started to see widespread commercial application. This is attributable, in part to recent advances in manufacturing technology that have made EL lamps increasingly practical.

The improvement in manufacturing technology has greatly increased the number of applications where EL lamps may be deployed. This is especially true for non-traditional lamp applications such as clothing, promotional displays or other consumer and non-consumer products. EL lamps may be printed on these products to serve both decorative and utilitarian purposes. Uses like these have fueled the desire to produce EL lamps that are visually creative or appealing. These same uses also contribute to the need to produce EL lamps that have novel functional elements.

For these and other reasons, there is a continual need to develop EL lamps that are visually interesting, creative or appealing. There is also a continual need to develop EL lamps that have novel and interesting functional elements. These needs are particularly important where EL lamps are employed in non-traditional roles. The same needs are also important for the manufacture of more mainstream EL lamps. EL lamps of these types should be practical to produce and to operate.

Summary Of The invention

Embodiments of the present invention provide an EL lamp and a method for its manufacture. The EL lamp is constructed as a sandwiched series of layers. In order, these layers are a protective substrate, a front electrode layer, a phosphor layer, a dielectric layer and a rear electrode layer.

A conductive pattern is printed or otherwise applied to the rear electrode. The conductive pattern forms a matrix or pattern of dots, grids or other designs. These dots or grids are closely spaced in areas where the conductive pattern is intended to have low electrical resistance. The dots or grids are closely widely in areas where the conductive pattern is intended to have higher electrical resistance.

The front electrode is also printed (or otherwise fabricated) with a conductive pattern. Unlike the pattern applied to the rear electrode, the front electrode pattern preferably forms a regular pattern. This gives the front electrode uniform electrical resistance at all points.

The EL lamp also includes one or more primary bus bars and may include one or more secondary bus bars. The primary bus bars are positioned to be adjacent to those areas that are intended to illuminate at low power levels. The secondary bus bars are placed wherever there is a need for increased conductivity within the EL lamp.

For a typical embodiment, the primary bus bars, secondary bus bars and the conductive pattern of the rear electrode layer are configured to create an initially illuminated region. The initially illuminated region becomes active when power is applied to the lamp. As the applied power increases, additional lamp regions gradually and smoothly illuminate. The order in which these areas illuminate is also determined by the configuration of the primary bus bars, secondary bus bars and the conductive pattern of the rear electrode layer. The progressive illumination of different lamp regions can be used to create different visual effects. For one of these effects, the initially illuminated region appears to sweep into the non-illuminated region. For another effect, the initially illuminated region appears to travel. The configuration of the conductive pattern of the rear electrode layer also creates a visually pleasing diffused or gradient appearance to the edges between the initially illuminated region and non-illuminated lamp regions.

Advantages of the invention will be set forth, in part, in the description that follows and, in part, will be understood by those skilled in the art from the description herein. The advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims and equivalents.

Brief Description Of The Drawings The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate several embodiments of the invention and, together with the description, serve to explain the principles of the invention.

Figure 1 is a cross-sectional view of an EL lamp shown as an embodiment of the present invention.

Figure 2 shows the electrical resistivity of a rear electrode layer as used by an embodiment of the present invention.

Figure 3 is a top view of a rear electrode layer as used by an embodiment of the present invention. Figure 4 is a cross-sectional view of a second EL lamp shown as an embodiment of the present invention. Detailed Description Of The Preferred Embodiments

Reference will now by made in detail to preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings.

Wherever convenient, the same reference numbers will be used throughout the drawings to refer to the same of like parts.

Embodiments of the present invention provide an EL lamp and a method for its manufacture. An example of the EL lamp of the present invention is designated 100 in Figure 1. EL lamp 100 is fabricated as a series of layers. The layers include protective substrate 102, front electrode layer 104, phosphor layer 106, dielectric layer 108 and rear electrode layer 110.

The following description provides details describing each of these layers.

Additional details may be found in a co-pending US Patent Application Serial

No. 08/910,724 for an invention entitled "Electroluminescent Lamp Designs".

The disclosure of that application is incorporated in this document by reference.

Protective substrate 102 shields EL lamp 100 from environmental conditions and provides a degree of electrical insulation. Protective substrate

102 is an optional element and may not be included in all embodiments.

When used, protective substrate 102 is formed from a transparent or translucent material, allowing light to be emitted from EL lamp 100 along the direction indicated in Figure 1.

Front electrode layer 104 is printed (or otherwise fabricated) with a conductive pattern. The conductive pattern is formed as a regular grid or matrix that includes a series of openings. The openings allow light to pass through front electrode layer 104 along the direction indicated in Figure 1. The regularity of the grid or matrix means that front electrode 104 has relatively uniform electrical resistance at all points.

Phosphor layer 106 is the light-emitting element in EL lamp 100.

Phosphor layer 106 is generally formed as a mixture of electroluminescent particles suspended in a binder. For many embodiments, these particles emit light in the visible portion of the optical spectrum. For other embodiments, electroluminescent particles that emit light in the ultra-violet or infrared portions of the spectrum may be used.

Dielectric layer 108 is intended to provide a degree of electrical insulation to phosphor layer 106. Dielectric layer 108 is an optional element and may not be used in all embodiments of the present invention.

Rear electrode layer 110 is printed (or otherwise fabricated) with a conductive pattern 112. Conductive pattern 112 is made up of dots, grids or any other shape or combination of shapes. Portions of conductive pattern 112 are closely spaced or dense. Other portions are more open or sparse. As a result, some portions of the rear electrode layer 110 (i.e., the dense portions of the conductive pattern 112) have lower electrical resistance. Other portions of the rear electrode layer 110 (i.e., the sparse portions of conductive pattern 112) have higher electrical resistance. This can be seen in Figure 2, where the resistance of rear electrode layer 110 is shown graphically. As may be seen, resistance is lowest at the right side of the figure. This corresponds to areas where conductive pattern 112 is most densely distributed. Conversely, resistance is highest at the right side of the figure. This corresponds to areas where conductive pattern 112 is most sparse.

Front electrode layer 104 includes a front electrode trace 114. Front electrode trace 104 functions as a conduit through which electrical energy can be supplied to front electrode layer 104.

Front electrode layer 104 and rear electrode layer 110 include front primary bus bar 116 and rear primary bus bar 118, respectively. Front primary bus bar 116 and rear primary bus bar 118 are metal or otherwise conductive traces that have been printed or otherwise applied to front electrode layer 104 and rear electrode layer 110. Front primary bus bar 116 and rear primary bus bar 118 serve to locally enhance the conductivity of portions of front electrode layer 104 and rear electrode layer 110. This enhanced conductivity is used to determine which areas of EL lamp 100 will illuminate first. During operation of EL lamp 100, an excitation voltage is applied to front electrode layer 104 and rear electrode layer 110. At low voltage levels, only the area of EL lamp 100 that is adjacent to front primary bus bar 116 and rear primary bus bar 118 illuminates. Increasing the voltage causes the size of the illuminated region to expand. In effect, the edge of the illuminated region sweeps to the right, moving farther and farther from front primary bus bar 116 and rear primary bus bar 118. At some maximum voltage level, EL lamp 100 becomes fully illuminated. The change in resistance, between the left and right sides of rear electrode layer 110 acts to help the edge of the illuminated region to sweep to the right and lowers the voltage that must be applied to fully illuminate EL lamp 100.

The ability to selectively control the size of the illuminated portion of EL lamp 100 allows EL lamp to be employed for many novel applications. These applications include histogram type or bar-type indicators. Indicators of this type can be conveniently used to display signal strength or other data such as voltage levels. An example of and rear electrode layer 110 as configured to provide a histogram type indicators is shown in Figure 3. More elaborate effects, such as dancing flames, are also possible.

As a second example, Figure 4 shows a second EL lamp 400. EL lamp 400 shares many of the components previously described with regard to EL lamp 100. It should be noted however, that the distribution of conductive pattern 112 differs. In the case, of EL lamp 400, conductive pattern 112 is densest midway between the right and left edges of EL lamp 400. Density decreases towards either edge. EL lamp 400 also includes front secondary bus bar 402 and rear secondary bus bar 404. Front secondary bus bar 402 and rear secondary bus bar 404 are metal or otherwise conductive traces that have been printed or otherwise applied to front electrode layer 104 and rear electrode layer 110, respectively.

The configuration of EL lamp 400 may be used to produce several novel effects. For one effect, an initial voltage is applied to front primary bus bar 116 and rear primary bus bar 118 and front secondary bus bar 402 and rear secondary bus bar 404. This causes both edges of EL lamp 400 to illuminate. As voltage is increased, the illuminated portions extend towards each other until EL lamp 400 is fully illuminated. For a second effect, and initial voltage is applied to front primary bus bar 116 and rear primary bus bar 118 causing the left edge of EL lamp 400 to illuminate. The voltage applied to primary bus bars 116, 118 is then gradually decreased while a second voltage, applied to front secondary bus bar 402 and rear secondary bus bar 404. This causes the illuminated region of EL lamp 400 to move, or travel, from left to right. This movement may be controlled or reversed by appropriate adjustments to the voltages applied to front primary bus bar 116 and rear primary bus bar 118 and front secondary bus bar 402 and rear secondary bus bar 404.

Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope of the invention being indicated by the following claims and equivalents.

Claims

What Is Claimed Is:

1. An electroluminescent lamp which comprises: a front electrode layer; a phosphor layer;

a rear electrode layer having a rear primary bus bar and a rear conductive pattern, the rear conductive pattern formed so that the electrical resistance of the rear electrode layer increases in areas adjacent to the rear primary bus bar, the rear primary bus bar usable to apply an excitation voltage to the phosphor layer, the excitation voltage causing the phosphor layer to progressively illuminate with the illumination starting in areas adjacent to the rear primary bus bar and spreading to other areas as the excitation voltage is increased.

2. An electroluminescent lamp as recited in claim 1 , which further comprises a front electrode layer having a front primary bus bar and a front conductive pattern, the front conductive formed so that the electrical resistance of the front electrode layer is substantially uniform.

3. An electroluminescent lamp as recited in claim 2, wherein the front electrode layer is transparent to light emitted by the phosphor layer.

4. An electroluminescent lamp as recited in claim 1 , wherein the rear electrode layer further comprises a rear secondary bus bar and wherein the rear conductive pattern is formed so that the electrical resistance of the rear electrode layer increases in areas adjacent to the rear secondary bus bar, the rear secondary bus bar usable to apply an excitation voltage to the phosphor layer, the excitation voltage causing the phosphor layer to progressively illuminate with the illumination starting in areas adjacent to the rear secondary bus bar and spreading to other areas as the excitation voltage is increased.

5. An electroluminescent lamp as recited in claim 4 wherein the rear primary bus bar and the rear secondary bus bar are interconnected in a way that causes the excitation voltage applied to the rear primary bus bar to decrease as the voltage applied to the rear secondary bus bar is increased.

6. An electroluminescent lamp as recited in claim 4 which further comprises a dielectric layer between the phosphor layer and the rear electrode layer.

7. An electroluminescent lamp as recited in claim 4 which further comprises a protective substrate positioned over the front electrode layer.