Patent Issued for Organic Electroluminescent Display

According to news reporting originating from Alexandria, Virginia, by VerticalNews journalists, a patent by the inventors Hamaguchi, Atsushi (Yokohama, JP);Mizuno, Nobutaka (Mobara, JP), filed on July 19, 2011, was published online on December 31, 2013.

The assignee for this patent, patent number 8618559, is Canon Kabushiki Kaisha (Tokyo, JP).

Reporters obtained the following quote from the background information supplied by the inventors: "The present invention relates to organic electroluminescent (EL) displays having a plurality of organic EL devices, each including electrodes and an organic compound layer including a light-emitting layer therebetween, and particularly to an organic EL display having a resonator structure.

"Organic EL displays are displays having a plurality of organic EL devices arranged, for example, in a matrix. Organic EL devices, also called organic light-emitting devices, have a layered structure in which an organic compound layer including a light-emitting layer is held between an anode and a cathode. As a current flows through the organic compound layer, electrons and holes are injected from the electrodes to generate excitons. The organic EL devices are based on the property of the excitons emitting light as they return to the ground state.

"Organic EL displays, which have high contrast and are thin because they are self-emitting, have recently attracted attention as a promising flat-panel display and have been developed extensively. In addition, organic EL displays are suitable for video display because they have significantly higher response speeds than liquid crystal displays.

"For organic EL displays and organic EL devices, various techniques have been proposed in which the optical thickness between the anode and the cathode is controlled to improve light output efficiency and color purity by optical interference.

"Japanese Patent Laid-Open No. 2000-323277 proposes a technique for providing an organic EL display having high light output efficiency by setting a different thickness to each color of light emitted for any of the functional layers in the organic compound material layer.

"In addition, U.S. Pat. No. 6,469,438 proposes an organic EL device having the color robustness thereof improved using an extremum of chromaticity and a method for producing the organic EL device.

"In the technique disclosed in Japanese Patent Laid-Open No. 2000-323277, however, the total amount of current through all subpixels during display of white color is not necessarily minimized even if the luminous efficiency (current-luminance efficiency) of subpixels of one color is maximized. For display of white color, red ®, green (G), and blue (B) subpixels are turned on in a predetermined proportion; the amount of current required for display of a white color with the desired chromaticity varies with the chromaticities that the organic EL devices of the subpixels show frontward. For example, in the case of blue devices having a higher luminous efficiency and a lighter chromaticity (higher CIEy) and blue devices having a lower luminous efficiency and a deeper chromaticity (lower CIEy), the former ones may require a larger amount of current for display of white color despite their higher luminous efficiency. Thus, the amount of current required is not necessarily determined only by the luminous efficiency.

"According to the technique disclosed in U.S. Pat. No. 6,469,438, on the other hand, a display with a smaller color shift can be produced by setting the color of organic EL devices of subpixels to an extremum of chromaticity, although the display has a higher power consumption."

In addition to obtaining background information on this patent, VerticalNews editors also obtained the inventors' summary information for this patent: "An organic EL display according to an aspect of the present invention includes a plurality of organic EL devices for red, green, and blue subpixels, each including a first electrode on a light output side, a second electrode opposite the first electrode, and an organic compound layer including a light-emitting layer therebetween. The organic EL devices have a resonator structure configured to resonate light emitted from the light-emitting layer between a first reflective surface closer to the first electrode than the organic compound layer and a second reflective surface closer to the second electrode than the organic compound layer. A predetermined white color is displayed by mixing the three colors such that an optical distance of the organic EL devices of each color between an emission position in the light-emitting layer and the second reflective surface is set within .+-.10% from an optical distance corresponding to an nth-order minimum of a curve of required current density against at least the optical distance.

"Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings."

Source: 4-Traders (http://goo.gl/jLYXwY)