The present invention relates to color organic light-emitting displays having a tri-color light-emitting pixel pattern.
Tang et al. in U.S. Pat. Nos. 5,294,869 and 5,294,870 recognized the advantages of constructing organic electroluminescent multicolor image display devices by providing integrated shadow masks for the generation of laterally separated pixels capable of emitting light of different hue. Such shadow masks are comprised of walls, pillars, or ribs which are formed on a support or a substrate in a predetermined pattern, and having a height dimension selected to cast a shadow with respect to an obliquely incident vapor stream. These shadow masks separate each color subpixel from an adjacent color subpixel.
Tang et al., U.S. Pat. No. 5,550,066 describes a method of fabricating an active-matrix organic electroluminescent panel based on polysilicon thin-film transistor (TFT) arrays. With an active-matrix TFT array and integrated drivers on the substrate, organic EL displays provide many desirable attributes not commonly found in any one class of conventional displays. These attributes are high resolution, compact display geometry, self luminance, high efficiency, and a wide viewing angle. Other display technologies, in comparison, have certain deficiencies. For instance, the most common active-matrix liquid crystal displays have limited viewing angles and require a back-light for illumination. The plasma displays are self emissive, but are not power efficient. The inorganic thin-film EL displays are rugged and compact, but they require high drive voltage and are not efficient.
Tang et al., U.S. Pat. No. 5,550,066 describes the fabrication processes for an active-matrix array based on polysilicon Tufts and its integration with a monochromatic organic EL device. The integration process for the monochromatic EL device is relatively simple, involving only the deposition of the organic EL medium directly on the substrate pre-patterned with TFT pixels and necessary bus electrodes and drivers. The EL medium refers to the organic layers constituting the EL device. For full-color, active-matrix organic EL display panel providing red, green and blue colors, the EL medium requires patterning into separate and adjacent color pixels in relationship to the active matrix TFT pixels. This patterning procedure can be quite complex depending on the resolution requirements and the configuration of the EL device. This patent describes an organic color EL displays fabricated with an integrated shadow mask on the display which provides a way of patterning the organic EL medium into red, green and blue color pixels.
The present invention provides a full-color active-matrix addressable organic electroluminescent display panel.
Accordingly, it is an object of the present invention to provide a high resolution, full-color, organic electroluminescent display requiring only one level of photolithography in generating a tri-color (RGB) pixel pattern.
In one aspect of the present invention, this object is achieved in an organic electroluminescent color display, comprising:
a) a substrate;
b) a plurality of color pixels formed on the substrate;
c) each color pixel containing three primary color (red, green, and blue) subpixels;
d) an active matrix electrical addressing element associated with each color subpixel;
e) an integrated shadow mask for forming the color subpixels and includes a plurality of pillar structures erected on the substrate;
f) the pillar structures having a geometric arrangement which permits the formation of each color subpixel independent of the formation of the other two color subpixels and wherein the formation of each color subpixel is provided by a line-of-sight vapor deposition for selective patterning the color subpixel; and
g) a common light-transmissive electrode over the plurality of color pixels.
In another aspect of the present invention, this object is achieved in an organic light-emitting color display, comprising:
a) a substrate;
b) a plurality of color pixels formed on the substrate;
c) each color pixel containing three primary color (red, green, and blue) subpixels;
d) an active matrix electrical addressing element associated with each color subpixel;
e) an integrated shadow mask for forming the color subpixels includes a plurality of pillar structures erected on the substrate and wherein the pillar structures having a geometric arrangement which permits the formation of each color subpixel independent of the formation of the other two color subpixels and wherein the formation of each color subpixel is provided by a line-of-sight vapor deposition for selective patterning the color changing medium;
f) each color subpixel having a short wavelength organic electroluminescent (EL) emitter and a fluorescent color conversion layer formed over the EL emitter; and
g) a common light-transmissive electrode over the EL emitter.
In a further aspect of the present invention, this object is achieved in an organic light-emitting color display, comprising:
a) a substrate;
b) a plurality of color pixels formed on the substrate;
c) each color pixel containing three primary color (red, green, and blue) subpixels;
d) an active matrix electrical addressing element associated with each color subpixel;
e) an integrated shadow mask for forming the color subpixels includes a plurality of pillar structures erected on the substrate;
f) the pillar structures having a geometric arrangement which permits the formation of each color subpixel independent of the formation of the other two color subpixels; wherein
g) each color subpixel having an organic electroluminescent (EL) emitter with an emissive layer capable of producing a primary color; wherein
h) the formation of each color subpixel is provided by a line-of-sight vapor deposition for selective patterning the emissive layer of the EL emitter; and
i) a common light-transmissive electrode over the EL emitter.
An advantage of this invention is that the fabrication of a full-color active-matrix organic light-emitting diode (OLED) display panel is simple and economical. The fabrication requires only one additional level of photolithography for the construction of an integrated shadow mask and for the color subpixel patterning scheme.
The integrated shadow mask (also referred to as an in-situ shadow mask) ensures that the deposited fluorescent color conversion layer is self-aligned with respect to a designated color subpixel area. This self-alignment feature is highly precise and therefore it is particularly useful for the fabrication of high-resolution color OLED display panels. Color pixel pitch of less than 10 micrometers can be readily achieved by the pillar structure shadow masks of the invention.
Excellent optical coupling between a short wavelength OLED emitter and a fluorescent color conversion or a fluorescent color changing layer is ensured, since the fluorescent layer is formed within a fraction of a micrometer over the short wavelength light-emitting layer. Thus, efficient color conversion from near ultraviolet or blue to green and from near ultraviolet or blue to red can be accomplished.
Vapor deposition for producing a color conversion fluorescent layer is fully compatible with OLED device fabrication. In particular, the exposure of an ambient-sensitive OLED device to ambient air throughout the entire production cycle is not necessary, thus avoiding the possibility of device degradation due to the elements of air and/or moisture. The color OLED panel fabrication can proceed in a vacuum deposition chamber without a vacuum break, starting with the deposition of the blue emitting OLED array to the deposition of the fluorescent color conversion layers.
The integrated shadow mask structures can also be used to provide full-color display panels having red, green, and blue light-emitting pixels (or subpixels) formed directly from layers of organic electroluminescent (EL) materials.
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