News Column

Patent Issued for Display Pixels with Alternating Colors

August 27, 2014

By a News Reporter-Staff News Editor at Journal of Engineering -- According to news reporting originating from Alexandria, Virginia, by VerticalNews journalists, a patent by the inventor Cok, Ronald Steven (Rochester, NY), filed on March 7, 2012, was published online on August 12, 2014.

The assignee for this patent, patent number 8803929, is Eastman Kodak Company (Rochester, NY).

Reporters obtained the following quote from the background information supplied by the inventors: "Display devices that render image, graphic, and textual information are widespread. Such devices are found in handheld, portable, and fixed-location electronic devices such as mobile smart-phones, laptop computers, computer monitors, and televisions. Such displays typically include an array of light-emitting (or light-reflecting) elements formed on a substrate to represent information controlled by an electronic controller. Color displays include light-emitting elements organized into multi-color pixels. Each multi-color pixel includes multiple, single-color sub-pixels that each emit or reflect a different color of light. A typical pixel in a multi-color emissive display has a red light-emitting sub-pixel, a green light-emitting sub-pixel, and a blue light-emitting sub-pixel. The pixels are usually arranged in a two-dimensional array. The three colors define a full-color gamut for the color display.

"Referring to prior-art FIG. 10, a flat-panel color display system 1 includes a controller 41 receiving an image signal 42 that is rendered by the controller 41 into an output display signal 45 for controlling a display 5 formed on a substrate 8. An array of pixels 11, each having a red light-emitting sub-pixel 50, a green light-emitting sub-pixel 52, and a blue light-emitting sub-pixel 54 is formed on the substrate 8. Thin-film transistor circuits 9 control the sub-pixels 50, 52, 54 in response to the display signal 45 from the controller 41. A variety of flat-panel light-emitting color displays 5 are known in the art, for example liquid crystal displays (LCDs), inorganic light-emitting diodes (LEDs), organic light-emitting diode displays (OLEDs), and plasma displays. Reflective displays are also known, for example reflective LCDs, and electro-phoretic displays, as are projected displays.

"Display characteristics include brightness, resolution, a high fill factor, and color gamut. The brightness of a light-emitting display is limited in part by the amount of power that is converted to emitted light. The resolution of a light-emitting display is limited by the size of the light-emitting elements on the substrate. The fill factor specifies the percentage of the substrate area that is used to emit or reflect light and can influence the efficiency and life-time of the display. The color gamut is determined by the saturation of the emitted colors. A desirable light-emitting flat-panel display has high brightness, high resolution, high efficiency, a large fill factor, and a large color gamut. For low-resolution displays, a large fill factor is desirable to avoid perceptible dark areas in the display. Therefore, color displays with a large fill factor and small pixels capable of efficiently transforming electrical power into highly saturated colors are desirable.

"In order to increase the color gamut of a color display, pixels with more than three colors of light-emitting sub-pixels have been proposed. For example, as shown in FIG. 11, an extended-color-gamut pixel 18 includes a red light-emitting sub-pixel 50, a green light-emitting sub-pixel 52, a blue light-emitting sub-pixel 54, a yellow light-emitting sub-pixel 56, and a cyan light-emitting sub-pixel 58. As illustrated in FIG. 12, U.S. Pat. No. 7,483,095 entitled 'Multi-Primary Liquid Crystal Display' discloses a display with pixels that each include eight sub-pixels emitting light of five different colors. Three of the colors are repeated twice. Referring to FIG. 12, the extended-color-gamut pixel 18 includes red light-emitting sub-pixels 50, green light-emitting sub-pixels 52, blue light-emitting sub-pixel 54, yellow light-emitting sub-pixels 56, and cyan light-emitting sub-pixel 58.

"Furthermore, because the human vision system perceives luminance signals at a higher spatial resolution than color signals, some color light-emitting sub-pixels can be present at a lower spatial resolution. For example, U.S. Pat. No. 7,495,722 entitled 'Multi-Color Liquid Crystal Display' discloses a display with four-color light-emitting pixels emitting red, green, blue, and yellow light alternating with four-color light-emitting pixels emitting cyan, red, green, and blue light, as illustrated in FIG. 13. Referring to FIG. 13, a first extended-color-gamut pixel 18A includes a red light-emitting sub-pixel 50, a green light-emitting sub-pixel 52, a blue light-emitting sub-pixel 54, and a yellow light-emitting sub-pixel 56. A second extended-color-gamut pixel 18B includes a red light-emitting sub-pixel 50, a green light-emitting sub-pixel 52, a blue light-emitting sub-pixel 54, and a cyan light-emitting sub-pixel 58.

"Each sub-pixel 50, 52, 54, 56, 58 and associated thin-film transistor circuits 9 (FIG. 10) occupy some portion of the substrate 8. Thus, such extended-color-gamut pixels 18 require a larger substrate area. This increase in area reduces the resolution of the display. Alternatively, the light-emitting area (fill factor) of the sub-pixels is reduced, consequently reducing the lifetime or brightness of the display. (For example the lifetime of OLED materials varies inversely with the emitting area of the materials for a given light output.) The efficiency of the light emitters can also be reduced when the area of a light-emitter is reduced at a given brightness because the power density is increased.

"There is a need, therefore, for an improved color display device that improves efficiency, color gamut, and resolution."

In addition to obtaining background information on this patent, VerticalNews editors also obtained the inventor's summary information for this patent: "In accordance with the present invention, a display, comprises:

"a substrate;

"a plurality of pixels located on the substrate, each pixel including only three light-emitting sub-pixels that each emit light of a different non-white color, the plurality of pixels including a first sub-set of first pixels and a second sub-set of second pixels, the second pixels having locations alternating with the first pixels, each of the first and second pixels including at least one first sub-pixel emitting light of a common first color, and the second pixels including at least one different sub-pixel emitting light of a different color that is not emitted by any sub-pixel of the first pixels; and

"wherein the light emitted by the sub-pixels of the first pixels define a full-color gamut, and the light emitted by the sub-pixels of the second pixels define less than a full-color gamut.

"The present invention provides an improved display device that improves efficiency, color gamut, and resolution. The present invention further enables these attributes without increasing manufacturing costs.

"These, and other, attributes of the present invention will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following description, although indicating embodiments of the present invention and numerous specific details thereof, is given by way of illustration and not of limitation. For example, the summary descriptions above are not meant to describe individual separate embodiments whose elements are not interchangeable. Many of the elements described as related to a particular embodiment can be used together with, and interchanged with, elements of other described embodiments. The figures below are not intended to be drawn to any precise scale with respect to relative size, angular relationship, or relative position or to any combinational relationship with respect to interchangeability, substitution, or representation of an actual implementation."

For more information, see this patent: Cok, Ronald Steven. Display Pixels with Alternating Colors. U.S. Patent Number 8803929, filed March 7, 2012, and published online on August 12, 2014. Patent URL:

Keywords for this news article include: Eastman Kodak Company.

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Source: Journal of Engineering

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