Patent Publication Number: US-10333097-B2

Title: OLED display device

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This is a divisional application of U.S. patent application Ser. No. 14/781,591, filed on Oct. 1, 2015, which is a national stage of PCT application number PCT/CN2015/079380, filed on May 20, 2015, claiming foreign priority of Chinese patent application number 201510222560.6, filed on May 4, 2015. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to the field of flat panel displays, and in particular to an organic light emitting diode (OLED) display device. 
     2. The Related Arts 
     Active matrix flat panel display devices have various advantages, such as thin device body, low power consumption, and being free of radiation, and are thus widely used. Among them, an OLED (Organic Light Emitting Diode) is a flat panel displaying technique of extremely prosperous future and it shows excellent displaying performance and particularly possesses various advantages, such as being self-luminous, simple structure, being ultra thin, fast response, wide view angle, low power consumption, and being capable of achieving flexible displaying and is thus regarded as a “dream display”. This, in combination with the factor that the facility expenditure is far less than that of thin-film transistor liquid crystal displays (TFT-LCDs), has attracted the attention of major display manufacturers and becomes the mainstream of the third-generation display devices of the field of displaying technology. It is now the time that mass production of the OLEDs is about to come true and advanced researches cause new techniques increasingly emerging. There will surely be a breakthrough process of the OLED displays. 
     As shown in  FIG. 1 , a conventional OLED display device comprises an upper substrate  200 , a lower substrate  400 , an enclosure resin frame  600  hermetically connecting between the upper substrate  200  and the lower substrate  400 . 
     The lower substrate  400  comprises a first electrode  450  and a second electrode  480  that is located above the first electrode  450  and at a top of the lower substrate  400 . The upper substrate  200  provides a sole function of serving as a package lid for isolation of moisture. The first electrodes  450  only functions as a pixel electrode (anode). The second electrode  480  (cathode) is generally thinner. Particularly, for a top-emitting OLED, the second electrode  450  must be made transparent and thus it must be even thinner to provide better light transparency. The thinner the second electrode  450  is, the greater the electrical resistance thereof would be. Thus, for a large-sized OLED display device, it is possible that there exists non-uniform in-plane voltage, affecting the homogeneity of displaying and causing undesired issues, such as non-uniform brightness and mura (which refers to a phenomenon of various tracing on a display due to inhomogeneous brightness). 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide an organic light emitting diode (OLED) display device, which reduces the resistance of a second electrode, increases homogeneity of in-plane voltage, and improves issues of non-uniform panel brightness and mura. 
     To achieve the above objects, the present invention provides an OLED display device, which comprises an upper substrate, a lower substrate, and an enclosure resin frame hermetically connecting between the upper substrate and the lower substrate; 
     the upper substrate comprising a first base plate and an assisting conductive layer arranged on the first base plate; 
     the lower substrate comprising a second base plate, a thin-film transistor (TFT) layer arranged on the second base plate, a first insulation layer arranged on the TFT layer, a second insulation layer arranged on the first insulation layer, a first electrode arranged on the second insulation layer, a pixel definition layer arranged on the second insulation layer and the first electrode, an OLED light emission layer arranged on the first electrode, and a second electrode arranged on the pixel definition layer and the OLED light emission layer; and 
     the upper substrate being arranged above the lower substrate, a side of the upper substrate on which the assisting conductive layer is formed is arranged to face a side of the lower substrate on which the second electrode is formed, the assisting conductive layer and the second electrode being in direct contact with and electrically connected to each other. 
     The upper substrate further comprises a first photo spacer arranged on the first base plate, the assisting conductive layer being arranged on the first photo spacer and the first base plate and covering the first photo spacer, wherein a portion of the assisting conductive layer that covers the first photo spacer is in direct contact with the second electrode that is arranged on a top surface of the lower substrate so that electrical connection between the second electrode and the assisting conductive layer is established. 
     The lower substrate further comprises a second photo spacer arranged on the pixel definition layer, the second electrode being arranged on the second photo spacer, the pixel definition layer, and the OLED light emission layer and covering the second photo spacer, wherein a portion of the second electrode that covers the second photo spacer is in direct contact with the assisting conductive layer that is arranged on a bottom surface of the upper substrate so that electrical connection between the second electrode and the assisting conductive layer is established. 
     The upper substrate further comprises a first photo spacer arranged on the first base plate, the assisting conductive layer being arranged on the first photo spacer and the first base plate and covering the first photo spacer; the lower substrate further comprises a second photo spacer arranged on the pixel definition layer, the second electrode being arranged on the second photo spacer, the pixel definition layer, and the OLED light emission layer and covering the second photo spacer, wherein the first photo spacer of the upper substrate and the second photo spacer of the lower substrate are arranged to correspond to each other and a portion of the assisting conductive layer that covers the first photo spacer is in direct contact with a portion of the second electrode that covers the second photo spacer so that electrical connection between the second electrode and the assisting conductive layer is established. 
     The assisting conductive layer has a structure of an entire surface. 
     The assisting conductive layer has a continuous grating structure. 
     The assisting conductive layer is composed of multiple non-continuous parts. 
     The assisting conductive layer is a transparent conductive layer or an opaque conductive layer. 
     The assisting conductive layer is made of a material of indium tin oxide, indium gallium zinc oxide, tin oxide, copper, aluminum, chromium, titanium, or molybdenum. 
     In the lower substrate, the first insulation layer and the second insulation layer comprise a first via formed therein to correspond to the TFT layer, the first electrode being connected through the first via to the TFT layer; and the pixel definition layer comprises a second via formed therein to correspond to the first electrode, the OLED light emission layer being arranged in the second via. 
     The present invention also provides an OLED display device, which comprises an upper substrate, a lower substrate, and an enclosure resin frame hermetically connecting between the upper substrate and the lower substrate; 
     the upper substrate comprising a first base plate and an assisting conductive layer arranged on the first base plate; 
     the lower substrate comprising a second base plate, a TFT layer arranged on the second base plate, a first insulation layer arranged on the TFT layer, a second insulation layer arranged on the first insulation layer, a first electrode arranged on the second insulation layer, a pixel definition layer arranged on the second insulation layer and the first electrode, an OLED light emission layer arranged on the first electrode, and a second electrode arranged on the pixel definition layer and the OLED light emission layer; and 
     the upper substrate being arranged above the lower substrate, a side of the upper substrate on which the assisting conductive layer is formed is arranged to face a side of the lower substrate on which the second electrode is formed, the assisting conductive layer and the second electrode being in direct contact with and electrically connected to each other; 
     wherein the upper substrate further comprises a first photo spacer arranged on the first base plate, the assisting conductive layer being arranged on the first photo spacer and the first base plate and covering the first photo spacer, wherein a portion of the assisting conductive layer that covers the first photo spacer is in direct contact with the second electrode that is arranged on a top surface of the lower substrate so that electrical connection between the second electrode and the assisting conductive layer is established; 
     wherein the assisting conductive layer has a structure of an entire surface; and 
     wherein in the lower substrate, the first insulation layer and the second insulation layer comprise a first via formed therein to correspond to the TFT layer, the first electrode being connected through the first via to the TFT layer; and the pixel definition layer comprises a second via formed therein to correspond to the first electrode, the OLED light emission layer being arranged in the second via. 
     The efficacy of the present invention is that the present invention provides an OLED display device, which comprises an assisting conductive layer formed on a bottom surface of an upper substrate in such a way that the assisting conductive layer is in direct contact with and electrically connected to a second electrode that is located on a top surface of a lower substrate so that electrical conduction capability of the second electrode is enhanced and the electrical resistance of the second electrode is reduced to thereby make in-plane voltage homogenous, improve consistency of displaying, and alleviate the issues of non-uniform panel brightness and mura and also help reduce the thickness of the second electrode for saving material of the second electrode and increase light transparency of the second electrode. 
     For better understanding of the features and technical contents of the present invention, reference will be made to the following detailed description of the present invention and the attached drawings. However, the drawings are provided for the purposes of reference and illustration and are not intended to impose limitations to the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The technical solution, as well as other beneficial advantages, of the present invention will become apparent from the following detailed description of an embodiment of the present invention, with reference to the attached drawings. 
       In the drawings: 
         FIG. 1  is a schematic view showing a conventional OLED display device; 
         FIG. 2  is a schematic view illustrating an OLED display device according to a first embodiment of the present invention; 
         FIG. 3  is a schematic view illustrating an OLED display device according to a second embodiment of the present invention; 
         FIG. 4  is a schematic view illustrating an OLED display device according to a third embodiment of the present invention; 
         FIG. 5  is a schematic view illustrating a structure of an assisting conductive layer of the OLED display device according to the present invention; 
         FIG. 6  is a schematic view illustrating another structure of an assisting conductive layer of the OLED display device according to the present invention; and 
         FIG. 7  is a schematic view illustrating a further structure of an assisting conductive layer of the OLED display device according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     To further expound the technical solution adopted in the present invention and the advantages thereof, a detailed description is given to a preferred embodiment of the present invention and the attached drawings. 
     Referring to  FIGS. 2-4 , the present invention provides an organic light-emitting diode (OLED) display device, which comprises an upper substrate  20 , a lower substrate  40 , and an enclosure resin frame  60  hermetically connecting between the upper substrate  20  and the lower substrate  40 . 
     The upper substrate  20  comprises a first base plate  21  and an assisting conductive layer  23  arranged on the first base plate  21 . 
     The lower substrate  40  comprises a second base plate  41 , a thin-film transistor (TFT) layer  42  arranged on the second base plate  41 , a first insulation layer  43  arranged on the TFT layer  42 , a second insulation layer  44  arranged on the first insulation layer  43 , a first electrode  45  arranged on the second insulation layer  44 , a pixel definition layer  46  arranged on the second insulation layer  44  and the first electrode  45 , an OLED light emission layer  47  arranged on the first electrode  45 , and a second electrode  48  arranged on the pixel definition layer  46  and the OLED light emission layer  47 . 
     In the lower substrate  40 , the first insulation layer  43  and the second insulation layer  44  comprise a first via  434  formed therein to correspond to the TFT layer  42 . The first electrode  45  is connected, through the first via  434 , to the TFT layer  42 . The pixel definition layer  46  comprises a second via  465  formed therein to correspond to the first electrode  45  and the OLED light emission layer  47  is located in the second via  465 . 
     The upper substrate  20  is arranged above the lower substrate  40 . The side of the upper substrate  20  on which the assisting conductive layer  23  is formed is arranged to face the side of the lower substrate  40  on which the second electrode  48  is formed; and the assisting conductive layer  23  and the second electrode  48  are in direct contact with and electrically connected to each other. 
     Specifically, the first base plate  21  and the second base plate  41  can each be a glass plate, a plastic plate, or an aluminum plate. The first base plate  21  and the second base plate  41  can be of materials that are the same or different. 
     At least one of the first base plate  21  and the second base plate  41  is transparent. 
     Preferably, the first base plate  21  and the second base plate  41  are both glass plates. 
     The enclosure resin frame  60  comprises an ultraviolet (UV) curable resin. 
     Referring to  FIG. 2 , a first embodiment of the OLED display device according to the present invention is shown. In the instant embodiment, the upper substrate  20  further comprises a first photo spacer  25  arranged on the first base plate  21 . The first photo spacer  25  is a protrusion formed on the first base plate  21  and is not electrically conductive. The assisting conductive layer  23  is arranged on the first photo spacer  25  and the first base plate  21  and covers the first photo spacer  25 , wherein a portion of the assisting conductive layer  23  that covers the first photo spacer  25  is set in direct contact with the second electrode  48  that is arranged on a top surface of the lower substrate  40  so that electrical connection between the second electrode  48  and the assisting conductive layer  23  is achieved. 
     Referring to  FIG. 3 , a second embodiment of the OLED display device according to the present invention is shown. In the instant embodiment, the lower substrate  40  further comprises a second photo spacer  49  arranged on the pixel definition layer  46 . The second photo spacer  49  is a protrusion formed on the first base plate  21  and is not electrically conductive. The second electrode  48  is arranged on the second photo spacer  49 , the pixel definition layer  46 , and the OLED light emission layer  47  and covers the second photo spacer  49 , wherein a portion of the second electrode  48  that covers the second photo spacer  49  is set in direct contact with the assisting conductive layer  23  that is arranged on a bottom surface of the upper substrate  20  so that electrical connection between the second electrode  48  and the assisting conductive layer  23  is achieved. 
     Referring to  FIG. 4 , a third embodiment of the OLED display device according to the present invention is shown. In the instant embodiment, the upper substrate  20  further comprises a first photo spacer  25  arranged on the first base plate  21  and the assisting conductive layer  23  is arranged on the first photo spacer  25  and the first base plate  21  and covers the first photo spacer  25 ; the lower substrate  40  further comprises a second photo spacer  49  arranged on the pixel definition layer  46  and the second electrode  48  is arranged on the second photo spacer  49 , the pixel definition layer  46 , and the OLED light emission layer  47  and covers the second photo spacer  49 , wherein the first photo spacer  25  of the upper substrate  20  and the second photo spacer  49  of the lower substrate  40  are arranged to correspond to each other and a portion of the assisting conductive layer  23  that covers the first photo spacer  25  is set in direct contact with a portion of the second electrode  48  that covers the second photo spacer  49  so that electrical connection between the second electrode  48  and the assisting conductive layer  23  is achieved. 
     In the above-described first to third embodiments, the first photo spacer  25  and the second photo spacer  49  can both be pillar like structures, such as cylindrical pillars or prismatic pillars. 
     Specifically, the first photo spacer  25  and the second photo spacer  49  are made of materials that can be organic resist or inorganic materials that are not electrically conductive. Preferably, the first photo spacer  25  and the second photo spacer  49  are made of materials that comprise organic resist. Making the first photo spacer  25  and the second photo spacer  49  with organic resist is a mature and easy process, allowing for mass production and requiring only one photolithographic operation, making the cost low. 
     The assisting conductive layer  23  can be a transparent conductive layer or an opaque conductive layer. Preferably, the assisting conductive layer  23  is a transparent conductive layer. 
     The assisting conductive layer  23  can be made of a material of indium tin oxide, indium gallium zinc oxide, tin oxide, copper, aluminum, chromium, titanium, or molybdenum. 
     As shown in  FIGS. 4-6 , the assisting conductive layer  23 / 23 ′/ 23 ″ can be of various shapes. As shown in  FIG. 4 , the assisting conductive layer  23  has a structure of an entire surface; as shown in  FIG. 5 , the assisting conductive layer  23 ′ has a continuous grating structure; and as shown in  FIG. 6 , the assisting conductive layer  23 ″ is composed of multiple non-continuous parts. 
     In summary, the present invention provides an OLED display device, which comprises an assisting conductive layer formed on a bottom surface of an upper substrate in such a way that the assisting conductive layer is in direct contact with and electrically connected to a second electrode that is located on a top surface of a lower substrate so that electrical conduction capability of the second electrode is enhanced and the electrical resistance of the second electrode is reduced to thereby make in-plane voltage homogenous, improve consistency of displaying, and alleviate the issues of non-uniform panel brightness and mura and also help reduce the thickness of the second electrode for saving material of the second electrode and increase light transparency of the second electrode. 
     Based on the description given above, those having ordinary skills of the art may easily contemplate various changes and modifications of the technical solution and technical ideas of the present invention and all these changes and modifications are considered within the protection scope of right for the present invention.