| Light emitting device and electronic device -> Monitor Keywords |
|
|
  Light emitting device and electronic deviceUSPTO Application #: 20070205418Title: Light emitting device and electronic device Abstract: To improve light extraction efficiency of light emitting elements such as electroluminescent elements. A first electrode 101, a light emitting layer 102, and a second electrode 103 are formed over a substrate 100, which partially constitute a light emitting element. Light produced in the light emitting layer 102 is emitted out through the second electrode 103. A plurality of three-dimensional bodies 104 are provided in contact with a surface of the second electrode 103. With the provision of the bodies 104, light totally reflected between the second electrode 103 and the air enters the bodies 104 and can be emitted through faces of the bodies 104 that are not parallel to the interface between the bodies and the second electrode 103. (end of abstract) Agent: Cook, Alex, Mcfarron, Manzo, Cummings & Mehler, Ltd. - Chicago, IL, US Inventor: Masahiro Takahashi USPTO Applicaton #: 20070205418 - Class: 257 79 (USPTO) The Patent Description & Claims data below is from USPTO Patent Application 20070205418. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001]1. Field of the Invention [0002]The present invention relates to a device from which light transmitted through an electrode can be obtained. For example, the invention relates to a light emitting device provided with a light emitting element or a liquid crystal display device. [0003]2. Description of the Related Art [0004]Flat panel displays such as a liquid crystal panel have been improved so as to achieve higher definition images, lower power consumption, and longer life. To put into practical use an electroluminescent panel (hereinafter also referred to as an EL panel) using an electroluminescent element (hereinafter also referred to as an EL element) in a pixel, it is required to realize crisper and brighter display at lower power, utilizing the characteristics of a self light emitting panel. In order to achieve the objective, power efficiency such as current-luminance characteristics of a material used in an EL element has also been improved. However, there are also limitations on the improvements in power efficiency. [0005]The percentage of light produced in a light emitting layer of an EL element that is obtained from a panel (light extraction efficiency) is only approximately 20%. The cause of such low light extraction efficiency is due to that when light produced in a light emitting layer reaches an interface between films having different refractive indices, the light is totally reflected, and the totally reflected light is attenuated while propagating inside the EL element, or the totally reflected light is emitted from a side surface of the light emitting element, for example, an end face of a glass substrate. [0006]Reference 1 (Japanese Published Patent Application No. 2002-278477) discloses an EL element of which light extraction efficiency is increased by reducing the light quantity which is totally reflected. In Reference 1, a low refractive index layer having a refractive index close to that of the air is provided on a surface of a transparent conductive layer on the side from which light is obtained, thereby increasing light extraction efficiency. SUMMARY OF THE INVENTION [0007]However, in Reference 1, although the light quantity which is totally reflected between the transparent conductive layer and an air layer can be improved, there is a fear that the light quantity which is totally reflected may increase at the interface between the transparent conductive layer and the low refractive index layer. It is an object of the present invention to reduce the light quantity which is totally reflected after being transmitted through an electrode, thereby improving light extraction efficiency. [0008]A light emitting element provided in a light emitting device of the present invention includes, for example, an organic EL element in which an organic material is used as a light emitting material, an inorganic EL element in which an inorganic material is used as a light emitting material, a light emitting diode using a semiconductor such as a compound semiconductor, or the like. A light emitting element of the invention is formed by sequentially stacking a first electrode, a light emitting layer, and a second electrode over a substrate. Light produced in the light emitting layer is emitted through a second electrode opposing the first electrode. The light emitting device includes at least one light emitting element. Alternatively, the light emitting device includes at least one light emitting region (a region where light can be taken out from the second electrode). [0009]The first electrode is an electrode which can reflect light from the light emitting layer. Alternatively, the first electrode may be an electrode which can transmit light from the light emitting layer. The second electrode is an electrode which can transmit light from the light emitting layer. [0010]At least one light emitting layer is provided between the first electrode and the second electrode. A plurality of light emitting layers may be provided between the electrodes. In the case where the light emitting element is an organic EL element, layers of an electron injection layer, an electron transporting layer, a hole blocking layer, a hole transporting layer, a hole injection layer, and the like may be provided in addition to the light emitting layer as appropriate. In the case of an inorganic EL element, an insulating layer may be provided between the light emitting layer and the first electrode and between the light emitting layer and the second electrode, or may be provided either between the light emitting layer and the first electrode or between the light emitting layer and the second electrode. [0011]One or a plurality of bodies are selectively provided in contact with a surface of the second electrode where light is taken out. The refractive index of the body is not limited in particular; however, it may preferably be equal to or more than the refractive index of the light emitting layer. [0012]Selectively providing a body" means providing the body so that there is a region in the light emitting region where the body is not provided over the second electrode. In other words, the surface of the second electrode has a region which is covered with the body and a region which is not covered with the body. When the body is thus disposed, the body has a face which is not parallel to the interface between the second electrode and the body. [0013]Light produced in the light emitting layer enters the second electrode directly or after reflected by the first electrode. Part of light which has reached the interface between the second electrode and the body can be transmitted through the second electrode without being totally reflected. Note that when the refractive index of the body is equal to or more than the refractive index of the light emitting layer, all of the light can enter the interface between the second electrode and the body without being totally reflected. This can be derived from Snell's law of geometrical optics and total reflection conditions. [0014]In accordance with the present invention, the body is provided so as to have a face which is not parallel to the interface between the second electrode and the body, thereby taking out light incident on the body as much as possible. This is because even light incident on a top surface of the body at an incident angle with which the light is totally reflected can be taken outside when it is incident upon the face after totally reflected. That is, in the invention, light having entered the body is totally reflected inside the body, thereby the angle of incidence on the interface between the body and the air can be made smaller than the critical angle; thus, the light quantity taken out from the body increases. In the invention, the light quantity totally reflected on the top surface of the second electrode can be decreased by providing the body, and the incident light can be scattered in the body; thus, light can be efficiently taken out from the body. Therefore, the light extraction efficiency can be improved. As described above, in the invention, a projection is formed on a surface of an electrode where light is taken out so as to scatter light in a light emitting element, thereby taking the light out. The invention is especially suitable for use in a light emitting element having a top emission structure in which light is taken out upward. That is because, in the case of bottom emission, even when irregularities are formed on a surface of a glass, light transmitted through the glass can be taken out; however, light propagating inside the light emitting element cannot be taken out. However, in the case of top emission, all of the light propagates inside the light emitting element; thus, using the invention, probability of extracting light from a light emitting element can be increased. [0015]In the present invention, a protective film may be provided on a surface of the second electrode, and at least one body can be selectively provided thereon. As the protective film, silicon oxide (SiO.sub.y, 0<y.ltoreq.2), silicon nitride (SiN.sub.x, 0<x.ltoreq.4/3), silicon nitride oxide (SiN.sub.xO.sub.y, 0<x<4/3, 0<y<2, 0<3x+2y.ltoreq.4), or the like can be used. [0016]A body of the present invention can be applied without limitation to a light emitting element of self-light emitting type and a light emitting device. For example, the invention can be applied to a transmissive or semi-transmissive liquid crystal display device. A body is provided on a surface of a pixel electrode of a liquid crystal display device, so that light transmitted through the pixel electrode can be taken out efficiently. In the case of a semi-transmissive liquid crystal display device, a body may be selectively provided in a region of a pixel electrode where light passes. [0017]When at least one body is selectively provided over a second electrode, light extraction efficiency of light from the second electrode can be improved. When the light extraction efficiency is improved, a device with lower power consumption can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS [0018]In the accompanying drawings: [0019]FIGS. 1A to 1C show a structure of a light emitting device (Embodiment Mode 1); [0020]FIGS. 2A to 2C show a structure of a light emitting device (Embodiment Mode 2); [0021]FIG. 3 shows a structure of a light emitting device (Embodiment Mode 3); Continue reading... Full patent description for Light emitting device and electronic device Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Light emitting device and electronic device patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Light emitting device and electronic device or other areas of interest. ### Previous Patent Application: Process for making contained layers and devices made with same Next Patent Application: Light emitting element, light emitting device and electronic device Industry Class: Active solid-state devices (e.g., transistors, solid-state diodes) ### FreshPatents.com Support Thank you for viewing the Light emitting device and electronic device patent info. IP-related news and info Results in 0.7359 seconds Other interesting Feshpatents.com categories: Tyco , Unilever , Warner-lambert , 3m |
||
