CROSS REFERENCE TO RELATED APPLICATIONS

This application relates to and claims priority on prior U.S. Provisional Application Serial No. 60/073,032, filed on Jan. 29, 1998.

FIELD OF THE INVENTION

The embodiment of the present invention relates to organic light emitting display devices. In particular, the present invention relates to a system and method for removing heat from the organic light emitting display device.

BACKGROUND OF THE INVENTION

Organic light emitting diodes can potentially generate efficient high brightness displays. However, heat generated during the operation of the display in the high brightness mode can limit the lifetime of the display. It is generally believed that the heat that is generated decreases the quantum efficiency and disintegrates the organic layers leading to the formation of shorts from the cathode layer to the anode layer. The display catastrophically fails at this point. This is especially true for large continuous emitting areas since the heat dissipation is not very efficient.

OBJECT OF THE INVENTION

It is an object of the present invention to provide a device for removing heat from an organic light emitting display device.

It is another object of the present invention to provide a device for removing heat from an organic light emitting display device to allow high brightness.

It is another object of the present invention to provide a device for removing heat from an organic light emitting display device to obtain long life expectancy.

It is another object of the present invention to provide a device for removing heat from the organic layers and conductor layers of the organic light emitting display device.

It is another object of the present invention to provide a method of removing heat from an organic light emitting display device.

It is another object of the present invention to provide a method of removing heat from the organic layers and conductor layers of the organic light emitting display device.

It is another object of the present invention to provide an assembly for transferring heat from the organic light emitting display device to a cooling assembly.

It is another object of the present invention to provide an assembly for dissipating heat away from the organic light emitting display device.

It is another object of the present invention to use a thermal conducting material to transfer heat from the organic light emitting display device.

It is another object of the present invention to use a hydrophobic thermal paste to transfer heat from the organic light emitting display device and to absorb moisture.

SUMMARY OF THE INVENTION

An organic light emitting display device is disclosed. The organic light emitting display device may be either a downwardly light emitting display or an upwardly light emitting display. The organic light emitting device has at least one organic layer and a cathode layer. The improvement in the organic light emitting device includes a heat removal assembly for removing heat from the organic light emitting display device. The heat removal assembly removes heat from one of the at least one organic layer and the cathode layer.

The heat removal assembly may include a heat dissipating assembly for dissipating heat from the organic light emitting device and a heat transfer assembly for transferring heat from one of the at least one organic layer and the cathode layer to the heat dissipating assembly. The incorporation of a heat removal system may significantly improve the performance and brightness of the display.

The heat dissipating assembly may include a heat sink.

The heat transfer assembly may include at least one thermally conducting layer.

The heat removal assembly may further include a cooling assembly for cooling the organic light emitting display device. The cooling assembly may include one of a thermoelectric cooler and a recirculating assembly for recirculating a cooling material. When a recirculating assembly is used, the cooling material may be selected from the group consisting of a cooling liquid and a cooling gas. The cooling assembly may also include an air removal system for removing heat.

The cooling assembly may be positioned between the heat dissipating assembly and the heat transfer assembly.

An organic light emitting display device is disclosed. The device may include a substrate, a first conductor layer located on the substrate, at least one organic layer located on the substrate, a second conductor layer, and heat removal assembly for removing heat from the organic light emitting display device.

The heat removal assembly may include a heat dissipating assembly for dissipating heat from the organic light emitting device, and heat transfer assembly for transferring heat from the organic light emitting device to the heat dissipating assembly. The heat removal assembly may further include a cooling assembly for cooling the organic light emitting display device.

The device may further include a plate positioned between the second conductor layer and the heat removal assembly. The device may further include a heat transferring assembly located between the second conductor layer and the plate for transferring heat from the organic light emitting device to the plate. The heat transferring assembly may include at least one thermally conducting layer.

The organic light emitting display device that includes the above-described heat removal assembly has an increased life expectancy at high brightness.

A method of cooling an organic light emitting display device is also disclosed. The method includes the steps of transferring heat generated by the organic light emitting device to a cooling assembly, and dissipating the heat transferred to the cooling assembly.

BRIEF DESCRIPTION OF THE DRAWING

The invention will now be described in conjunction with the following drawings in which like reference numerals designate like elements and wherein:

FIG. 1

is a schematic view of a downwardly emitting display device having a heat removing assembly according to an embodiment of the present invention; and

FIG. 2

is a schematic view of an upwardly emitting display device having a heat removing assembly according to another embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1

illustrates an organic light emitting display device

10

according to an embodiment of the present invention. The OLED device

10

includes a substrate

110

. The substrate

110

may be formed from glass. It, however, is contemplated that other suitable materials may be utilized to form the substrate

110

.

A first conductor layer

120

is formed on the substrate

110

. The first conductor layer

120

may be formed from indium tin oxide (ITO) or other suitable transparent conductor materials. An OLED stack

130

is formed on the first conductor layer

120

. In a preferred embodiment, the OLED stack

130

contains at least one OLED layer. A second conductor layer

140

is formed on the OLED stack

130

. The second conductor layer

140

may be formed from Mg/Ag. Other conductive materials, however, are considered to be well within the scope of the present invention.

The OLED device

10

may be provided with a back plate structure

150

. The back plate structure

150

is preferably formed from a glass material, such as, for example, borosilicate or sodalime. However, other materials having improved thermal conductivity including but not limited to metals and silicon wafers are considered to be within the scope of the present invention. The back plate structure

150

may be secured to the OLED device

10

using a suitable sealant

160

. The OLED device

10

is preferably sealed in an inert environment so that no oxygen or moisture is trapped inside the sealed OLED device

10

.

The OLED device

10

may be further provided with a getter material

180

to remove any trace amounts of moisture. It is contemplated that any suitable moisture absorbing material may be used as a getter material.

During operation of these displays at high current densities, large amounts of heat are generated in the OLED layers

130

as well as the second conductor or cathode metal layers

140

. In a typical sealing process, there is a gap between the display substrate and the back plate structure

150

. This gap makes it difficult for the heat to be transferred from the OLED layers to the cover glass and subsequently to an external heat sink.

According to embodiments of the present invention, an assembly

170

for removing heat from the OLED device

10

will now be described. The heat removing assembly

170

may include a heat transferring assembly

171

. The heat transferring assembly

171

preferably includes an intermediate material located between the second conductor layer

140

and the back plate

150

for efficient heat transfer to the outside environment. The intermediate material forming the heat transferring assembly

171

may be composed of either a metallic or a non-metallic material. A suitable metallic layer is Gallium. Gallium has a very low melting point (approx.

35

C) and, as such, is easy to implement without damaging the OLED stack

130

and the second conductor layer

140

. A suitable non-metallic material is a silicone based thermal paste that includes a silicone grease mixed with a thermally conductive powder such as, for example, zinc oxide. The added advantage of a non-metallic thermal paste is that it is electrically non-conducting and being a paste, it can be conformal to the topography of the OLED device

10

. Moreover, the moisture content of these pastes is negligible. Such pastes are commercially available. Gallium and the silicone-based thermal paste are provided as two suitable examples for the efficient transfer of heat. It is contemplated by the present inventors that the invention is in no way limited to these materials. It is contemplated that numerous other materials having suitable heat transfer properties may be employed.

Once heat is coupled from inside the OLED device

10

to the back plate

150

through the heat removing assembly

171

, it then needs to be transferred from the back plate

150

. The heat removing assembly

171

may also be capable of absorbing moisture such that the getter material

180

may be eliminated. The heat removing assembly

170

may further include a heat transfer assembly

172

. The heat transfer assembly

172

is capable of transferring heat that was transmitted to the back plate

150

through the heat transferring assembly

171

to a heat dissipating assembly

174

. The heat transfer assembly

172

has a structure similar to that described above in connection with the heat transferring assembly

171

.

The heat removing assembly

170

may further comprise a cooling assembly

173

. The cooling assembly

173

acts to cool the OLED device

10

. Heat that is generated by the OLED device

10

and transferred by the heat transferring assembly

171

and the heat transfer assembly

172

is reduced by the cooling assembly

173

. The cooling assembly

173

may include a thermoelectric cooler or a recirculating system to reduce the heat. The cooling assembly

173

having a recirculating system may recirculate a cooling liquid, such as, freon or other suitable cooling material. Alternatively, the recirculating system may use air and a fan to reduce the heat.

The heat removing assembly

170

may further include a heat dissipating assembly

174

. The heat dissipating assembly

174

dissipates the heat generated by the OLED device

10

into the environment. The heat dissipating assembly

174

may include a heat sink. The heat dissipating assembly

174

draws the heat from the cooling assembly

173

and dissipates it to the environment. The present invention is not limited to the above-described heat sink; rather other suitable heat dissipating assemblies are considered to be well within the scope of the present invention.

The above-described heat removing assembly

170

removes significant amounts of heat generated by the OLED device

10

to reduce disintegration of the OLED layers

130

. This results in increased brightness and lifetime of the OLED device

10

by reducing the formation of shorts.

The heat removing assembly

170

has been described in connection with a downwardly emitting OLED device

10

. The present invention is not construed to be limited for use in downwardly emitting OLED devices. The heat removing assembly is capable of being used in an upwardly emitting OLED device. An upwardly emitting OLED device

20

is described in connection with FIG.

2

and is substantially similar to the OLED device

10

, described above.

The upwardly emitting OLED device

20

includes a substrate

210

. The substrate

210

is preferably formed from a silicon wafer. However, it is contemplated that other suitable materials may be utilized to form the substrate

210

. A first conductor layer

220

is formed on the substrate

210

. The first conductor layer

220

includes integrated circuitry. An OLED stack

230

is located on the first conductor layer

220

. The OLED stack

230

includes at least one OLED layer. A second conductor layer

240

is located on the OLED stack

230

. The second conductor layer

240

may be formed from indium tin oxide (ITO) or other suitable conductor materials.

The OLED device

20

includes a front plate structure

250

. The front plate structure

250

is preferably formed from glass or other suitable light transmissive material. The front plate structure

250

is secured to the second conductor layer

240

using a suitable sealant structure

260

. The OLED device

20

is preferably sealed in an inert environment so that no oxygen or moisture is trapped inside the sealed OLED device

20

. A getter material

280

may be provided within the sealed OLED device

20

to remove any trace amounts of moisture. As described above, it is contemplated that any suitable moisture absorbing may be used as a getter material.

The OLED device

20

also includes an assembly

270

for removing heat from the OLED device. The heat removing assembly

270

includes a heat transferring assembly

271

. The heat transferring assembly

271

is preferably formed from a material as described above in connection with heat transferring assembly

171

. The heat transferring assembly

271

is located adjacent to the substrate

210

for transferring heat from the OLED device

20

.

The heat removing assembly

270

further includes a cooling assembly

273

. The cooling assembly

273

is similar to the cooling assembly

173

, described above in connection with heat removing assembly

170

. The cooling assembly

273

is located adjacent the heat transferring assembly

271

. The heat removing assembly

270

may further include a heat transfer assembly

272

. The heat transfer assembly

272

has a structure similar to that described above in connection with the heat transferring assembly

171

and heat transfer assembly

172

.

The heat transfer assembly

272

transfers the remaining heat from the cooling assembly

273

to a heat dissipating assembly

274

. The heat dissipating assembly

274

dissipates the heat generated by the OLED device

20

into the environment. The heat dissipating assembly

274

has a structure similar to the heat dissipating assembly

174

.

While this invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, the preferred embodiments of the invention as set forth herein are intended to be illustrative, not limiting. Various changes may be made without departing from the spirit and scope of the invention as defined in the following claims.