News Column

Patent Issued for Organic Electroluminescent Display Device

July 23, 2014



By a News Reporter-Staff News Editor at Electronics Newsweekly -- From Alexandria, Virginia, VerticalNews journalists report that a patent by the inventors Yamazaki, Shunpei (Setagaya, JP); Arai, Yasuyuki (Kanagawa, JP), filed on April 22, 2013, was published online on July 8, 2014.

The patent's assignee for patent number 8772766 is Semiconductor Energy Laboratory Co., Ltd. (Atsugi-shi, Kanagawa-ken, JP).

News editors obtained the following quote from the background information supplied by the inventors: "The present invention relates to a semiconductor device having a circuit based on insulated-gate field effect transistors in which a single-crystal semiconductor is used for an active layer, and a method of fabricating the semiconductor device. More particularly, the present invention is well suited for applications to an electrooptic device which is typified by an organic electroluminescent display device wherein the same substrate is overlaid with a pixel unit and driver circuits disposed around the pixel unit, and to an electronic apparatus in which the electrooptic device is installed. Incidentally, here in this specification, the expression 'semiconductor device' is intended to signify general devices which function by utilizing semiconductor properties, and it shall cover within its category the electrooptic device and the electronic equipment including this electrooptic device.

"In the field of flat display devices (flat panel displays) typified by liquid-crystal display devices, organic EL (electroluminescent) display devices, etc., there has been known technology wherein a display device of active matrix type is fabricated by employing insulated-gate field effect transistors (hereinbelow, the 'field effect transistors' shall be abbreviated to 'FETs') formed on a single-crystal semiconductor substrate. Unlike in a case where a display device of active matrix type is fabricated by forming thin-film transistors (hereinbelow, abbreviated to 'TFTs') on a glass substrate or a quartz substrate, the technology has had the advantage that techniques fostered in the field of large-scale integrated circuits (LSIs) are applicable as they are, and that the FETs of high performance which are capable of low-voltage drive at high speed can be integrated and formed at a high density on the substrate. On the other hand, however, it has been considered the disadvantage of the technology that the display device is restricted to one of reflection type or spontaneous luminescence type because the substrate is opaque to visible light, or that the single-crystal semiconductor substrate is restricted to sizes available on the market.

"In the technological trends toward higher image quality and full digitization in the field of the display devices, the enhancements of performances required of the active matrix type display device have inevitably heightened. The active matrix type display device is so constructed that transistors (such as TFTs or FETs) in the number of several tens to several millions are arranged in a pixel unit for displaying an image, and that pixel electrodes are respectively connected to the transistors. In operation, the image is displayed in such a way that voltages to be applied to respective pixels are controlled by the switching functions of the corresponding transistors, whereby some of EL elements are caused to luminesce. In the organic EL display device, when the switching transistors disposed in the respective pixels are turned ON, currents are caused to flow through current controlling transistors by signals generated in accordance with image data, whereby the EL elements luminesce spontaneously.

"However, an organic EL layer which serves as the basic portion of the organic EL display device is very liable to oxidize, and it easily deteriorates in the presence of a slight amount of oxygen. Besides, it has a low resistance to heat, and this also is a factor promoting oxidation. The liability to oxidize is the cause of a short lifetime of the organic EL element, and has formed a serious obstacle in putting this element into practical use."

As a supplement to the background information on this patent, VerticalNews correspondents also obtained the inventors' summary information for this patent: "The object of the present invention is to overcome the problem as stated above, and to provide an organic EL display device of high reliability.

"Another object of the present invention is to provide an electron device whose display unit is highly reliable, by adopting such an organic EL display device for the display unit.

"The construction of the present invention for accomplishing the objects consists in an organic EL display device of active matrix type wherein insulated-gate field effect transistors formed on a single-crystal semiconductor substrate are overlaid with an organic EL layer; characterized in that the single-crystal semiconductor substrate is held in a vacant space which is defined by a bed plate and a cover plate formed of an insulating material and a packing material for bonding the bed and cover plates; and that the vacant space is filled with an inert gas and a drying agent.

"Also, the construction of the present invention consists in an organic EL display device of active matrix type having a pixel unit wherein insulated-gate field effect transistors formed on a single-crystal semiconductor substrate are overlaid with an organic EL layer; characterized in that the single-crystal semiconductor substrate is held in a vacant space which is defined by a bed plate and a cover plate formed of an insulating material, and a packing material for bonding the bed and cover plates; that the cover plate is formed of a transparent member in its area which lies over the pixel unit; and that the vacant space is filled with an inert gas and a drying agent.

"A single-crystal silicon substrate can be favorably employed as the single-crystal semiconductor substrate. Besides, the vacant space should preferably be filled with an inert gas selected from the group consisting of helium, argon, krypton, xenon and nitrogen, and a drying agent selected from the group consisting of barium oxide and silica gel."

For additional information on this patent, see: Yamazaki, Shunpei; Arai, Yasuyuki. Organic Electroluminescent Display Device. U.S. Patent Number 8772766, filed April 22, 2013, and published online on July 8, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=8772766.PN.&OS=PN/8772766RS=PN/8772766

Keywords for this news article include: Electronics, Semiconductor, Semiconductor Energy Laboratory Co., Semiconductor Energy Laboratory Co. Ltd., Technology.

Our reports deliver fact-based news of research and discoveries from around the world. Copyright 2014, NewsRx LLC


For more stories covering the world of technology, please see HispanicBusiness' Tech Channel



Source: Electronics Newsweekly


Story Tools






HispanicBusiness.com Facebook Linkedin Twitter RSS Feed Email Alerts & Newsletters