Organic el device and liquid crystal display

Abstract: A liquid crystal display including a liquid crystal panel and an organic EL device, which functions as a backlight. The organic EL device includes a Peltier element, which functions as a substrate, and an organic EL element formed on the Peltier element. The organic EL element includes an organic EL layer and first and second electrodes, which sandwich the organic EL layer. The first electrode is shared with a metal layer, which is a heat absorbing electrode of the Peltier element. The second electrode is formed from ITO, which transmits visible light. Light emitted from the organic EL element exits from the second electrode. As a result, the organic EL device is thin and has a superior cooling effect. (end of abstract)

Agent: Morgan & Finnegan, L.L.P. - New York, NY, US
Inventors: Yoshifumi Kato, Tadahiro Ohmi, Shigetoshi Sugawa, Akihiro Morimoto
USPTO Applicaton #: #20070188082 - Class: 313504000 (USPTO)

Organic el device and liquid crystal display description/claims

The Patent Description & Claims data below is from USPTO Patent Application 20070188082, Organic el device and liquid crystal display.

Brief Patent Description - Full Patent Description - Patent Application Claims

[0001] This application is a divisional of co-pending U.S. application Ser. No. 10/809,755 filed on Mar. 25, 2004, herein incorporated by reference.

[0002] The present invention relates to an organic electroluminescence (EL) device and a liquid crystal display using the organic EL device as a backlight.

[0003] A liquid crystal display is extensively used as a display in, for example, portable devices. With an increasing demand for smaller, lighter, and less power consuming portable devices, thinner liquid crystal displays having low power consumption are becoming necessary.

[0004] Reflection type liquid crystal displays are being used to reduce the power consumption, but the image quality thereof is not sufficient. A transmissive (including semi-transmissive) liquid crystal display using a backlight excels in achieving a sufficient image quality. Recently, the use of a light-emitting element, such as an organic EL element, for a backlight has been proposed and has been put into actual application.

[0005] Furthermore, organic EL elements have gained attention as being the elements for the next generation of displays following liquid crystal displays. In general, an organic EL element is configured by forming a transparent electrode (anode) made of indium-tin-oxide (ITO) on a glass substrate, forming organic layers including a light-emitting layer on the transparent electrode, and then superimposing an opaque cathode on the organic layer. Such an organic EL element has a bottom-emission structure in which light emitted from the light-emitting layer exits from the glass substrate side.

[0006] The organic EL element performs carrier injection type light emission. Thus, the electric energy that is not converted to EL light emission is converted to Joule heat. The Joule heat increases the temperature of the device. This results in problems such as decomposition of the organic compounds constituting the organic EL element, decrease in brightness, and shortening of lifetime. If the organic EL has a light-emission efficiency of 100%, the generation of the Joule heat would be zero. However, such situation is impossible in reality. Thus, an organic EL element that effectively dissipates the heat generated during light-emission of the organic EL element has been proposed in the prior art. Such an organic EL element is disclosed in for example, Japanese Laid-Open Patent Publication No. 4-129194, Japanese Laid-Open Patent Publication No. 8-124679, and Japanese Laid-Open Patent Publication No. 2002-117973.

[0007] Japanese Laid-Open Patent Publication No. 4-129194 proposes forming the organic EL element on a substrate having high thermal conductivity. Further, to employ the organic EL element in a display, a configuration is proposed for arranging the organic EL element in contact with a substrate having high thermal conductivity between thin electrical insulation layers.

[0008] Japanese Laid-Open Patent Publication No. 8-124679 proposes arranging an organic EL device on a metal substrate with a metal thin film arranged therebetween. The metal thin film has high thermal conductivity.

[0009] In Japanese Laid-Open Patent Publication No. 2002-117973, an element region is formed by superimposing a first electrode, an organic compound layer including a light-emitting layer, and a second electrode layer on a glass substrate. Further, a protective film composed of heterocyclic compound polymer is formed thereon so as to cover the entire element region of the substrate. The protective film has sufficient heat resistance for an organic EL element, and has relatively high thermal conductivity. Thus, the Joule heat generated by driving the organic EL element is dissipated to the protective film and radiated from the surface of the protective film. Furthermore, the above publication also states that the use of a forced cooling means, such as Peltier cooling or fan cooling, together with the protective film facilitates the radiation of heat from the surface of the protective film.

[0010] In the configurations described in Japanese Laid-Open Patent Publication No. 4-129194 and Japanese Laid-Open Patent Publication No. 8-124679, heat radiation is enhanced by arranging an organic EL element or an organic EL device directly or by way of a thin film on a substrate having high thermal conductivity. Hence, the organic EL element or organic EL device cannot be cooled to a temperature lower than ambient temperature. Furthermore, Japanese Laid-Open Patent Publication No. 2002-117973 discloses the use of a forced cooling means, such as Peltier cooling, under the assumption that an organic EL element is formed on a glass substrate. However, when the forced cooling means is used, the characteristic of the organic EL device, which is a device that is thin, is sacrificed.

SUMMARY OF THE INVENTION

[0011] It is an object of the present invention to provide a thin organic EL device having a superior cooling effect, and a liquid crystal display using such an organic EL device as a backlight.

[0012] To achieve the above object, the present invention provides an organic electroluminescence device including a semiconductor substrate. At least part of the semiconductor substrate forms a Peltier element including a heat absorbing portion and a heat radiating portion. An organic electroluminescence element is arranged on or above the semiconductor substrate. The organic electroluminescence element is arranged so that heat resistance between the organic electroluminescence element and the heat absorbing portion is less than heat resistance between the organic electroluminescence element and the heat radiating portion. Light emitted from the organic electroluminescence element exits from a side facing away from the semiconductor substrate.

[0013] A further aspect of the present invention is an organic electroluminescence device including a substrate having a semiconductor region. A Peltier element is formed in at least part of the semiconductor region. The Peltier element includes a heat absorbing electrode and a heat radiating electrode. An organic electroluminescence element is arranged on or above the heat absorbing electrode. Light emitted from the organic electroluminescence element exists from a side facing away from the substrate.

[0014] A further aspect of the present invention is an organic electroluminescence device including a substrate having a semiconductor region. A Peltier element is formed in at least part of the semiconductor region. The Peltier element includes a heat absorbing portion and a heat radiating portion. An organic electroluminescence element is arranged on or above the substrate. The organic electroluminescence element is arranged so that heat resistance between the organic electroluminescence element and the heat absorbing portion is less than heat resistance between the organic electroluminescence element and the heat radiating portion. Light emitted from the organic electroluminescence element exits from the substrate.

[0015] The present invention further provides a liquid crystal display having the organic electroluminescence device described above and a liquid crystal panel. The organic electroluminescence device functions as a backlight for the liquid crystal panel.

[0016] Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The invention, together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiment together with the accompanying drawings in which:

[0018] FIG. 1 is a cross sectional view schematically showing a liquid crystal display according to a first embodiment of the present invention;

[0019] FIG. 2 is a cross sectional view schematically showing an organic EL device according to a second embodiment of the present invention;

[0020] FIG. 3 is a cross sectional view schematically showing an organic EL device according to a third embodiment of the present invention;

[0021] FIG. 4 is an enlarged cross sectional view showing one pixel of the organic EL device in FIG. 3;

[0022] FIG. 5 is a plan view showing an organic EL element, a heat absorbing electrode, and a scanning line;

Brief Patent Description - Full Patent Description - Patent Application Claims
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Organic electroluminescent device and method of manufacturing the same
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Industry Class:
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