Patent Publication Number: US-9853093-B2

Title: Organic light emitting diode device

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a Continuation of U.S. patent application Ser. No. 14/736,733, filed on Jun. 11, 2015, now issued as U.S. Pat. No. 9,627,654, and claims priority from and the benefit of Korean Patent Application No. 10-2014-0124806, filed on Sep. 19, 2014, which is hereby incorporated by reference for all purposes as if fully set forth herein. 
    
    
     BACKGROUND 
     Field 
     Exemplary embodiments of the present invention relate to an organic light emitting diode display having improved viewing angle and light efficiency. 
     Discussion of the Background 
     An organic light emitting diode (OLED) display device is a self-emission-type display device that displays an image with an OLED that emits light. Unlike a traditional liquid crystal display (LCD), the OLED display may not require a separate light source, and thus, may have a reduced thickness and weight when compared to the traditional LCD. Further, the OLED display may exhibit properties such as low power consumption, high luminance, and high response speed. For these reasons, and others, the OLED has drawn attention as a next generation display device. 
     The OLED may generally include a hole injection electrode, an organic light emitting layer, and an electron injection electrode. A hole injected from the hole injection electrode and an electron injected from the electron injection electrode are combined to form an exciton, and the OLED may emit light by energy generated when the exciton falls from an excited state to a ground state. 
     It is to be understood that this background of the technology section is intended to provide useful background for understanding the technology and as such disclosed herein, the technology background section may include ideas, concepts or recognitions that were not part of what was known or appreciated by those skilled in the pertinent art prior to a corresponding effective filing date of subject matter disclosed herein. 
     The above information disclosed in this Background section is only for enhancement of understanding of the background of the inventive concept, and, therefore, it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art. 
     SUMMARY 
     Exemplary embodiments provide an OLED display having an improved viewing angle and light efficiency. 
     Additional aspects will be set forth in the detailed description which follows, and, in part, will be apparent from the disclosure, or may be learned by practice of the inventive concept. 
     An exemplary embodiment of the present invention discloses an OLED display, including a first substrate, a first electrode on the first substrate, a pixel defining layer having a first aperture exposing the first electrode, an organic light emitting layer on the first electrode, a second electrode on the organic light emitting layer, a second substrate disposed to face the first substrate, a black matrix disposed on the second substrate and having a second aperture, and a lens disposed to cover at least a part of the second aperture and protruding toward the first substrate. 
     An exemplary embodiment of the present invention also discloses an OLED display, including a first substrate, a first electrode on the first substrate, a pixel defining layer having a first aperture exposing the first electrode, an organic light emitting layer on the first electrode, a second electrode on the organic light emitting layer, a second substrate disposed to face the first substrate, a black matrix disposed on the second substrate and having a second aperture, a first lens disposed to cover at least a part of the first aperture and protruding toward the second substrate, and a second lens disposed to cover at least a part of the second aperture and protruding toward the first substrate. 
     Exemplary embodiments of the present invention provide an OLED display may have an improved viewing angle and light efficiency, and decreased color distortion. 
     Exemplary embodiments of present invention also provide an OLED display having reduced ambient light reflection without using a separate polarizer. 
     The foregoing is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description. 
     The foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the claimed subject matter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the inventive concept, and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the inventive concept, and, together with the description, serve to explain principles of the inventive concept. 
         FIG. 1  is a plan view illustrating an OLED display according to an exemplary embodiment of the present invention. 
         FIG. 2  is a first cross-sectional view taken along line I-I′ of  FIG. 1  according to an exemplary embodiment of the present invention. 
         FIG. 3  is a second cross-sectional view taken along line I-I′ of  FIG. 1  according to an exemplary embodiment of the present invention. 
         FIG. 4  is a third cross-sectional view taken along line I-I′ of  FIG. 1  according to an exemplary embodiment of the present invention. 
         FIG. 5  is a first cross-sectional view taken along line I-I′ of  FIG. 1  according to another exemplary embodiment of the present invention. 
         FIG. 6  is a second cross-sectional view taken along line I-I′ of  FIG. 1  according to another exemplary embodiment of the present invention. 
         FIG. 7  is a third cross-sectional view taken along line I-I′ of  FIG. 1  according to another exemplary embodiment of the present invention. 
         FIG. 8  is a fourth cross-sectional view taken along line I-I′ of  FIG. 1  according to another exemplary embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS 
     In the following description, for the purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of various exemplary embodiments. It is apparent, however, that various exemplary embodiments may be practiced without these specific details or with one or more equivalent arrangements. In other instances, well-known structures and devices are shown in block diagram form in order to avoid unnecessarily obscuring various exemplary embodiments. 
     In the accompanying figures, the size and relative sizes of layers, films, panels, regions, etc., may be exaggerated for clarity and descriptive purposes. Also, like reference numerals denote like elements. 
     When an element or layer is referred to as being “on,” “connected to,” or “coupled to” another element or layer, it may be directly on, connected to, or coupled to the other element or layer or intervening elements or layers may be present. When, however, an element or layer is referred to as being “directly on,” “directly connected to,” or “directly coupled to” another element or layer, there are no intervening elements or layers present. For the purposes of this disclosure, “at least one of X, Y, and Z” and “at least one selected from the group consisting of X, Y, and Z” may be construed as X only, Y only, Z only, or any combination of two or more of X, Y, and Z, such as, for instance, XYZ, XYY, YZ, and ZZ. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
     Although the terms first, second, etc. may be used herein to describe various elements, components, regions, layers, and/or sections, these elements, components, regions, layers, and/or sections should not be limited by these terms. These terms are used to distinguish one element, component, region, layer, and/or section from another element, component, region, layer, and/or section. Thus, a first element, component, region, layer, and/or section discussed below could be termed a second element, component, region, layer, and/or section without departing from the teachings of the present disclosure. 
     Spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper,” and the like, may be used herein for descriptive purposes, and, thereby, to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the drawings. Spatially relative terms are intended to encompass different orientations of an apparatus in use, operation, and/or manufacture in addition to the orientation depicted in the drawings. For example, if the apparatus in the drawings is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the exemplary term “below” can encompass both an orientation of above and below. Furthermore, the apparatus may be otherwise oriented (e.g., rotated 90 degrees or at other orientations), and, as such, the spatially relative descriptors used herein interpreted accordingly. 
     The terminology used herein is for the purpose of describing particular embodiments and is not intended to be limiting. As used herein, the singular forms, “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. Moreover, the terms “comprises,” comprising,” “includes,” and/or “including,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, components, and/or groups thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
     Various exemplary embodiments are described herein with reference to sectional illustrations that are schematic illustrations of idealized exemplary embodiments and/or intermediate structures. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, exemplary embodiments disclosed herein should not be construed as limited to the particular illustrated shapes of regions, but are to include deviations in shapes that result from, for instance, manufacturing. For example, an implanted region illustrated as a rectangle will, typically, have rounded or curved features and/or a gradient of implant concentration at its edges rather than a binary change from implanted to non-implanted region. Likewise, a buried region formed by implantation may result in some implantation in the region between the buried region and the surface through which the implantation takes place. Thus, the regions illustrated in the drawings are schematic in nature and their shapes are not intended to illustrate the actual shape of a region of a device and are not intended to be limiting. 
     Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure is a part. Terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense, unless expressly so defined herein. 
     Referring to  FIG. 1 , in the OLED display according to an exemplary embodiment of the present invention, a plurality of pixel regions are each defined by a gate line  101  disposed along one direction and data and common power lines  102  and  103 , respectively, insulated from and intersecting the gate line  101 . One pixel may be disposed in each pixel region, but is not limited thereto. In some embodiments, each pixel region may be defined by the pixel defining layer described below and a plurality of pixels may be disposed in each pixel region. 
     In the OLED display according to an exemplary embodiment of the present invention, a pixel may have a 2TFT-1Cap structure, including two thin film transistors (TFTs): switching TFT  104  and driving TFT  105 ; and a capacitor (CAP)  106 , but exemplary embodiments of the present invention are not limited thereto. In some embodiments, one pixel may include three or more TFTs and/or two or more capacitors. 
     The switching TFT  104  may select a pixel to emit light. The switching TFT  104  may include a switching gate electrode  104   a  connected to the gate line  101 , a switching source electrode  104   b  connected to the data line  102 , a switching drain electrode  104   c  connected to the first capacitor plate  106   a , and a switching semiconductor layer  104   d.    
     The driving TFT  105  may provide a driving power, which allows an organic light emitting layer  130  in a pixel selected by the switching TFT  104  to emit light. The driving TFT  105  may include a driving gate electrode  105   a  connected to the first capacitor plate  106   a , a driving source electrode  105   b  connected to the common power line  103 , a driving drain electrode  105   c  connected to the first electrode  110 , and a driving semiconductor layer  105   d.    
     The capacitor  106  may include first and second capacitor plates  106   a  and  106   b . The first capacitor plate  106   a  may be connected to the switching drain electrode  104   c  and the driving gate electrode  105   a . The second capacitor plate  106   b  may be connected to the common power line  103 . Capacitance of the capacitor  106  may be determined by electric charges stored in the capacitor  106  and a voltage across the first and second capacitor plates  106   a  and  106   b.    
     Voltage equivalent to a difference between a data voltage applied from the switching TFT  104  and a common voltage applied from the common power line  103  to the driving TFT  105  may be stored in the capacitor  106 . Current corresponding to the voltage stored in the capacitor  106  may flow to the organic light emitting layer  130  through the driving TFT  105 , so that the organic light emitting layer  130  may emit light. 
     Referring to  FIG. 2 , an OLED display according to an exemplary embodiment of the present invention may include a first substrate  100 , a first electrode  110  disposed on the first substrate  100 , a pixel defining layer  120  including a first aperture  122  that exposes the first electrode  110 , organic light emitting layer  130  disposed on the first electrode  110 , a second electrode  140  disposed on the organic light emitting layer  130 , a second substrate  200  facing the first substrate  100 , black matrix  210  disposed on the second substrate  200  and including a second aperture  212 , and a lens  300  covering at least a part of the second aperture  212  and protruding toward the first substrate  100 . 
     The first substrate  100  may be made of an insulating material selected from a group of glass, quartz, ceramic, plastic and the like, but is not limited thereto. For example, the first substrate  100  may be made of a metal material such as stainless steel, etc. 
     A buffer layer  107  may include an organic or inorganic layer and may be disposed on the first substrate  100 . The buffer layer  107  may reduce or prevent infiltration of detrimental elements such as impurities or moisture and may planarize a surface of the first substrate  100 . Further, a gate insulating layer  108  may be disposed on the first substrate  100  between the gate electrodes  104   a  and  105   a  and semiconductor layers  104   d  and  105   d , and between the first and second capacitor plates  106   a  and  106   b . An interlayer insulating layer  109  may be disposed between the thin film transistor and the first electrode  110 . 
     The first electrode  110 , the organic light emitting layer  130 , and the second electrode  140  may be sequentially laminated on the first substrate  100 . The first electrode  110  may be an anode that may facilitate hole injection, and the second electrode  140  may be a cathode that may facilitate electron injection. However, exemplary embodiments of the present invention are not limited thereto. For example, the first electrode may be a cathode and the second electrode may be an anode. 
     At least one of a hole injection layer (not illustrated) and a hole transporting layer (not illustrated) may be disposed between the first electrode  110  and the organic light emitting layer  130 . At least one of an electron transporting layer (not illustrated) and an electron injection layer (not illustrated) may be disposed between the second electrode  140  and the organic light emitting layer  130 . A thin film encapsulation layer (not illustrated) may be further disposed on the second electrode  140  and may have a structure in which at least one organic layer and at least one inorganic layer may be alternately disposed. 
     The pixel defining layer  120  may have a first aperture  122  and the first electrode  110  may be exposed by the first aperture  122 . That is, the first electrode  110 , the organic light emitting layer  130 , and the second electrode  140  may be sequentially laminated in the first aperture  122  of the pixel defining layer  120 . The organic light emitting layer  130  and the second electrode  140  may be disposed on the pixel defining layer  120 . 
     According to an exemplary embodiment of the present invention, the organic light emitting display device may be a top emission type. That is, the first electrode  110  may be formed of a reflective material and the second electrode  140  may be formed of a transflective material. Light generated from the organic light emitting layer  130  may be emitted on the second substrate  200  through the second electrode  140 . 
     The reflective layer and the transflective layer may include one or more metal, such as magnesium (Mg), silver (Ag), gold (Au), calcium (Ca), lithium (Li), chromium (Cr), and aluminum (Al), or metal alloys thereof. Whether an electrode is a transflective type or a reflective type depends on the thickness of the layer. That is, the transflective electrode has a thickness of about 200 nm or less. 
     The first electrode  110  may further include a transparent conductive layer formed of a transparent conductive material. The transparent conductive material may include, for example, transparent conductive oxides (TCO) such as indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO) and indium oxide (In 2 O 3 ), but is not limited thereto. 
     The first electrode  110  may include a reflective layer, a double-layer structure including a reflective layer and a transparent conductive layer, or a triple-layer structure where a transparent conductive layer, a reflective layer, and a transparent conductive layer are sequentially laminated, but is not limited thereto. For example, the first electrode may have a structure including a transparent conductive layer. 
     The second electrode  140  may include a transparent conductive layer. When the second electrode  140  includes a transparent conductive layer, the second electrode  140  may be an anode to facilitate hole injection and the first electrode  110  may be a cathode formed of a reflective material. 
     The second substrate  200  may be formed of the same material as the first substrate  100  and the black matrix  210  including a second aperture  212  may be disposed on the second substrate  200 . 
     The black matrix  210  may include metal oxides, such as CrO and CrOx, or a black resin, and may absorb ambient light incident on the black matrix  210  through the second substrate  200 , thereby reducing ambient light reflection. Thus, the OLED display according to an exemplary embodiment of the present invention may reduce ambient light reflection without using a separate polarizer. 
     The second aperture  212  may be formed facing the first aperture  122  and light emitted from the organic light emitting layer  130  may radiate on the second substrate  200  through the second aperture  212 . The second aperture  212  may be smaller than the first aperture  122 . Thus, the second aperture  212  may be about 0.5% to 50% of the size of the first aperture  122 . 
     The lens  300  may be configured to collect light emitted from the organic light emitting layer  130  to the second aperture  212 . Both end portions of the lens  300  may overlap the black matrix  210  so that the lens  300  may completely cover the second aperture  212 , but the structure is not limited thereto. For example, the lens  300  may be disposed to only partly cover the second aperture  212  and/or may be provided in plural. 
     The lens  300  may have a refractive index of about 1.4 to 2.0. The lens may be an acrylic lens including acrylic derivatives or a high refractive index lens including high refractive index nanoparticles. However, exemplary embodiments of the present invention are not limited thereto, and thus the lens may be properly modified to include a variety of materials having a refractive index of about 1.4 to 2.0. 
     The lens  300  may include variety of materials and structures according to a refractive index of a layer disposed in a space between the first and second substrates  100  and  200 . Further, a curvature of the lens  300  may vary according to a distance from the organic light emitting layer  130 , a size of the organic light emitting layer  130 , and other factors. 
     A distance W 1  between the lens  300  and the organic light emitting layer  130  may be about 1 μm to about 50 μm, considering light collecting efficiency. Further, a width W 2  of the lens  300  may be smaller than a width of the first aperture  122 . 
     The OLED display illustrated in  FIG. 2  may include an air layer  400  in the space between the first and second substrates  100  and  200 . The air layer  400  may have a lower refractive index than the lens  300 . Therefore, the lens  300  may have a convex structure extending toward the first substrate  100 . 
     Referring to  FIG. 3 , an OLED display according to an exemplary embodiment of the present invention may have substantially the same configuration as the OLED display illustrated in  FIG. 2 , except that a lens  300  has a different structure and a filler  500  is disposed in a space between the first and second substrates  100  and  200 . The repeated description will not be provided for sake of brevity. 
     The filler  500  may include an organic or inorganic material having a refractive index of about 1.1 to about 1.6. The organic material may include acrylics, polyimides, polyamides, poly(methyl methacrylate) (PMMA), and combinations thereof, but is not limited thereto. For example, the filler  500  may include various kinds of organic or inorganic materials having a refractive index of about 1.1 to about 1.6. 
     The OLED display illustrated in  FIG. 3  may include a filler  500  having a refractive index of about 1.4 to about 1.6 disposed in a space between the first and second substrates  100  and  200 . The filler  500  may have a higher refractive index than the lens  300 . Therefore, the lens  300  may have a concave structure extending towards the first substrate  100 , but is not limited thereto. For example, in a case when the filler  500  has a refractive index of about 1.1 to 1.4, the lens  300  may have a convex form extending toward the first substrate  100 . 
     Referring to  FIG. 4 , the OLED display according to an exemplary embodiment of the present invention may have substantially the same configuration as the OLED display illustrated in  FIG. 2 , except for a color filter  220 . Thus, the repeated description will not be provided for sake of brevity. 
     The color filter  220  may be disposed in the second aperture  212  and may be one of red, green, and blue. The color filter  220  may, along with the black matrix  210 , reduce ambient light reflection. That is, the second substrate  200  may transmit light having a predetermined wavelength range in accordance with each corresponding pixel and may block light having other wavelength range, thereby reducing reflection of ambient light incident on the color filter  220  through the second substrate  200 . Therefore, the OLED display according to an exemplary embodiment of the present invention may reduce ambient light reflection without using a separate polarizer. 
     Referring to  FIG. 5 , the OLED display according to an exemplary embodiment of the present invention may have substantially the same configuration as the OLED display illustrated in  FIG. 2 , except for a plurality of lenses  302  and  304  and a thin film encapsulation layer  600 . Thus, the repeated description will not be provided for sake of brevity. 
     The lens  300  may include a first lens  302  covering at least a part of the first aperture  122  and protruding toward the second substrate  200 , and a second lens  304  covering at least a part of the second aperture  212  and protruding toward the first substrate  100 . 
     The thin film encapsulation layer  600  may be disposed on the second electrode  140  and may protect the organic light emitting layer  130 . The thin film encapsulation layer  600  may include at least one organic layer and at least one inorganic layer alternately disposed. However, exemplary embodiments of the present invention are not limited thereto. Thus, the thin film encapsulation layer  600  may be not be present. 
     In the OLED display illustrated in  FIG. 5 , the first lens  302  may be disposed on the thin film encapsulation layer  600  and may overlap the pixel defining layer  120  at both end portions to completely cover the first aperture  122 . Further, both end portions of the second lens  304  may overlap the black matrix  210  to completely cover the second aperture  212 . 
     In the OLED display illustrated in  FIG. 5 , an air layer  400  may be disposed in a space between the first and second substrates  100  and  200 . The air layer  400  may have a lower refractive index than the first and second lenses  302  and  304 . Thus, the first lens  302  may have a convex structure extending toward the second substrate  200  and the second lens  304  may have a convex structure extending toward the first substrate  100 . 
     Referring to  FIG. 6 , an OLED display according to an exemplary embodiment of the present invention may have substantially the same configuration as the OLED display illustrated in  FIG. 5 , except that the thin film encapsulation layer is not provided, lenses  302  and  304  have a different form, and a filler  500  is disposed in a space between the first and second substrates  100  and  200 . Thus, the repeated description will not be provided for sake of brevity. 
     In the OLED display illustrated in  FIG. 6 , the filler  500  having a refractive index of about 1.4 to about 1.6 may be disposed in a space between the first and second substrates  100  and  200 . The filler  500  may have a higher refractive index than the first and second lenses  302  and  304 . The first lens  302  may have a concave structure extending toward the second substrate  200  and the second lens  304  may have a concave structure extending toward the first substrate  100 . 
     Referring to  FIG. 7 , an OLED display according to an exemplary embodiment of the present invention may have substantially the same configuration as the OLED display illustrated in  FIG. 5 , except that the thin film encapsulation layer is not provided, a first lens  302  has a different form, and a filler  500  is disposed in a space between the first and second substrates  100  and  200 . Thus, the repeated description will not be provided for sake of brevity. 
     In the OLED display illustrated in  FIG. 7 , the filler  500  having a refractive index of about 1.1 to about 1.6 may be disposed in a space between the first and second substrates  100  and  200 . The filler  500  may have a refractive index higher than the first lens  302  and lower than the second lens  304 . Thus, the first lens  302  may have a concave form extending toward the second substrate  200  and the second lens  304  may have a convex form extending toward the first substrate  100 . The second lens  304  may cover at least a part of the second aperture  212 . 
     Referring to  FIG. 8 , an OLED display according to an exemplary embodiment of the present invention may have substantially the same configuration as the OLED display illustrated in  FIG. 5 , except for a second lens  304  provided in a different form and a filler  500  disposed in a space between the first and second substrates  100  and  200 . Thus, the repeated description will not be provided for sake of brevity. 
     In the OLED display illustrated in  FIG. 8 , the filler  500  having a refractive index of about 1.1 to about 1.6 may be disposed between the first and second substrates  100  and  200 . The filler  500  may have a refractive index lower than the first lens  302  and higher than the second lens  304 . Therefore, the first lens  302  may have a convex form extending toward the second substrate  200  and the second lens  304  may have a concave form extending toward the first substrate  100 . 
     Although certain exemplary embodiments and implementations have been described herein, other embodiments and modifications will be apparent from this description. Accordingly, the inventive concept is not limited to such embodiments, but rather to the broader scope of the presented claims and various obvious modifications and equivalent arrangements.