Patent Publication Number: US-2015069364-A1

Title: Organic light-emitting diode display and method of manufacturing the same

Description:
BACKGROUND OF THE INVENTION 
     This Application claims priority of China Patent Application No. CN 201310409844.7, filed on Sep. 9, 2013, and the entirety of which is incorporated by reference herein. 
     1. Field of the Invention 
     The present invention generally relates to a display, and more particularly, to an organic light-emitting diode (OLED) display and method of manufacturing the same. 
     2. Description of the Prior Art 
     The organic light-emitting diode (OLED) display is always considered as being among the most competitive technology in next display generation, with the advantages of self-luminous (does not need a backlight unit), fast response, and low operating voltage. 
     A standard OLED display is self-luminous with an organic material layer formed of organic materials. When a current is applied on the organic material layer, the organic material in the organic material layer emits light. With different organic materials, the OLED display may emit light with different colors, to fulfill the requirement of full color display. 
     Currently, an evaporation tool is utilized to form the organic material layer with red(R), green(G) and blue(B) colors in the manufacture of the OLED displays. The evaporation tool has a tension mask with openings to define pixel areas on the organic material layer. During the evaporation process, the organic material with one of the R, G, B colors is first deposited on a pixel area through the openings of the tension mask. The tension mask is then moved to other pixel area and forms the organic materials with other color (ex. G and B) through the same openings. Since the organic material would leave residue on the tension mask near the openings during the evaporation process, the weight of the organic materials would cause the deformation of the tension mask and change the original shape of the openings on the tension mask, so that the openings of the tension mask can&#39;t be precisely aligned in the process and results in mixed color regions on the organic material layer. That is, a pixel area is formed with stacked different colors, thereby causing the color deviation issue. 
     BRIEF SUMMARY OF THE DISCLOURE 
     In view of the above-mentioned issue, an approach of disposing a color deviation protective layer in the organic light-emitting diode (OLED) display is utilized in the present invention to prevent the mixed color regions of the organic light-emitting layer from emitting light, thereby solving the conventional color deviation issue. 
     An OLED display is provided in the present invention, including an anode layer and a cathode layer opposite to and spaced apart from each other, an organic light-emitting layer disposed between the anode layer and the cathode layer, wherein the organic light-emitting layer includes primary color regions and mixed color regions, and a color deviation protective layer disposed between the anode layer and the organic light-emitting layer or between the organic light-emitting layer and the cathode layer, and the color deviation protective layer is provided with insulating patterns corresponding to the mixed color regions, wherein the insulating patterns is used to prevent the corresponding mixed color regions from emitting light. 
     A method of manufacturing an OLED display is provided in the present invention, including the steps of disposing an anode layer and a cathode layer opposite to and spaced apart from each other, disposing an organic light-emitting layer between the cathode layer and the anode layer, wherein the organic light-emitting layer includes primary color regions and mixed color regions, and disposing an color deviation protective layer between the anode layer and the organic light-emitting layer or between the organic light-emitting layer and the cathode layer, and the color deviation protective layer is provided with insulating patterns corresponding to the mixed color regions, wherein the insulating pattern is used to prevent the mixing color regions from emitting light. 
     The approach of disposing a color deviation protective layer in the OLED display is utilized in the present invention to prevent the mixed color regions of the organic light-emitting layer from emitting light, thereby solving the conventional color deviation issue and significantly increase the production yield. 
     These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1-4  are cross-sectional views schematically showing a process flow of an OLED display in accordance with one preferred embodiment of the present invention; and 
         FIGS. 5-9  are cross-sectional views schematically showing a variety of types of the OLED display of the present invention. 
     
    
    
     It should be noted that all the figures are diagrammatic. Relative dimensions and proportions of parts of the drawings have been shown exaggerated or reduced in size, for the sake of clarity and convenience in the drawings. The same reference signs are generally used to refer to corresponding or similar features in modified and different embodiments. 
     Description of the Exemplary Embodiments 
     In the following detailed description of the present invention, reference is made to the accompanying drawings which form a part hereof and is shown by way of illustration and specific embodiments in which the invention may be practiced. These embodiments are described in sufficient details to enable those skilled in the art to practice the invention. Other embodiments may be utilized and structural, logical, and electrical changes may be made without departing from the scope of the present invention. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims. Besides, the terms “on” or “under” (“above” or “below”) referred in the following embodiments are used to describe relative positions between components rather than limiting the scope of the present invention. 
     Several embodiments are provided hereinafter accompanying the figures to describe the skill of the present invention, wherein  FIGS. 1-4  are cross-sectional views schematically showing a process flow of manufacturing an OLED display according to one preferred embodiment of the present invention, and  FIGS. 5-9  are cross-sectional views schematically showing a variety of types of the OLED display of the present invention. 
     The method of manufacturing an OLED display in the present invention includes the steps of disposing an anode layer and a cathode layer opposite to and spaced apart from each other, disposing an organic light-emitting layer between the cathode layer and the anode layer, wherein the organic light-emitting layer includes primary color regions and mixed color regions, and disposing a color deviation protective layer between the anode layer and the organic light-emitting layer or between the organic light-emitting layer and the cathode layer, and the color deviation protective layer is provided with insulating patterns corresponding to the mixed color regions to prevent light generation from the mixed color regions. 
     In one embodiment, an upper substrate and a lower substrate are further provided before the organic light-emitting layer is disposed, and the anode layer and the cathode layer are disposed between the upper substrate and the lower substrate. 
     The flow of manufacturing the OLED display will be explained in detail in the following embodiments with reference to the accompanying figures. 
     Please note that, in this embodiment, the OLED display is top-emitting display, which means the light of the OLED display is emitted out from the upper substrate. In other embodiments, the OLED display can be bottom-emitting display, in other words, the light of OLED display is emitted out from the lower substrate. 
     Please refer to  FIG. 1 . In the beginning, a lower substrate  100  is provided as a base for all components, for example, the lower substrate  100  may be a transparent glass plate or plastic plate or other material which may support the components, in addition, the lower substrate  100  may be a reinforced plate. An anode layer  101  is then formed above or on the upper surface of the lower substrate  100  by evaporation or sputtering process. The material of the anode layer  101  may be transparent conducting oxide (TCO), such as indium tin oxide (ITO), zinc oxide (ZnO), Al:ZnO (AZO), or opaque metals, such as Ni, Au, Mo, or Pt, etc. 
     After the anode layer  101  is formed, an organic light-emitting layer (EML)  102  is formed on the anode layer  101 . The organic light-emitting layer  102  includes primary color regions  1021 , for example, red primary color regions  1021   a,  green primary color regions  1021   b  and blue primary color regions  1021   c.  The material of primary color regions  1021  of the organic light-emitting layer  102  may be different depending on the colors of the primary color regions  1021 , for example, uses red dyes of DCM(4-(Dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran),DCM-2, or DCJTB(4-(Dicyanomethylene)-2-tert-butyl-6-(1,1,7,7-tetra methyljulolidin-4-yl-vinyl)-4H-pyran) for red primary color region  1021   a,  uses green dyes of Alq((8-hydroxyquinoline)aluminum), Alq3(tris-(8-hydroxyquinoline)aluminum), or DMQA(N,N′-Dimethyl-quinacridone) for green primary color regions, and uses anthracene, Alq2, BCzVBi(4,4″-bis(9-ethyl-3-carbazovinylene)-1,1″-biphenyl), Perylene, OXD(oxadiazole), DPVB(Bis(2,2-diphenylvinyl)benzene) for blue primary color regions. The organic light-emitting layer  102  may be formed by using a conventional evaporation tool and corresponding tension mask to deposit red, green and blue color emitting materials to respectively form red primary color regions  1021   a,  green primary color regions  1021   b  and blue primary color regions  1021   c.  Since the organic material would leave residue on the tension mask near the openings during the evaporation process, the weight of the organic materials would cause the deformation of the tension mask and change the original shape of the openings on the tension mask, so that the openings of the tension mask can&#39;t be precisely aligned in the process and results in mixed color regions  1022  on the organic material layer  102 . 
     Please refer to  FIG. 2 , a mask  103  is disposed above or below (disposed above in this embodiment) the organic light-emitting layer  102  after the organic light-emitting layer  102  is formed. An evaporation process or sputtering process is then performed through the mask  103  to form color deviation protective layer  104  on the organic light-emitting layer  102 , wherein the color deviation protective layer  104  is provided with insulating patterns  104   a  corresponding to the mixed color regions  1022 . The material of the insulating pattern  104   a  may be silicon dioxide or photoresist. 
     If the material of the insulating pattern  104   a  is photoresist, a photoresist layer is first coated and the photolithographic process and etching process (including the steps of UV exposure and development, etc) are then performed to pattern the photoresist layer and form the insulating patterns  104   a.  Alternatively, the photoresist layer may be formed first by sputtering process on the organic light-emitting layer  102 , then the photolithographic and etching processes are performed to pattern the photoresist layer and form the insulating patterns  104   a.    
     In one preferred embodiment, the insulating patterns  104   a  may be formed of silicon dioxide. In addition, the insulating patterns  104   a  may be formed by using the same photolithographic and etching processes, and thus is not repeatedly described herein. 
     Please refer to  FIG. 3 , a cathode layer  105  is then formed on the color deviation protective layer  104 . The function of the cathode layer  105  is to generate electrons, thus metal materials with low work function are generally utilized, such as alkali, alkaline earth or lanthanide materials with low work function. Afterward, an upper substrate  106  is provided on the cathode layer  105  to protect the whole components. The upper substrate  106  may be a transparent glass plate, plastic plate or other material which may support the components. The main process of making the structure of the OLED display  10  is therefore completed. 
     As shown in  FIG. 3 , when a current is applied, holes generated from the anode layer  101  and electrons generated from the cathode layer  105  would combine in the organic light-emitting layer  102  to generate photons and emit light from the organic light-emitting layer  102 . However, in the present invention, the holes generated from the anode layer  101  and the electrons generated from the cathode layer  105  can not combine in the mixed color regions  1022  to form photons due to the insulating patterns  104   a  disposed on corresponding mixed color regions  1022 , thereby inhibiting light emitted from the mixed color regions  1022  and preventing the color deviation issue. 
     It should be noted that the direction of light emitted from the OLED display may be different depending on the selected materials of the anode layer  101  and the cathode layer  105 . 
     In one embodiment, the anode layer  101  may be an aluminum layer with a thickness of 150 nm to 200 nm or a gold layer with a thickness of 100 nm to 150 nm, and the cathode layer  105  may be an aluminum layer with a thickness of 0.1 nm to 20 nm, a silver layer with a thickness of 0.1 nm to 20 nm, or an ITO layer or IZO layer with a thickness of 20 nm to 100 nm. In this embodiment, the anode layer  101  is light-reflective type, and the cathode layer  105  is light-transparent type. The light of the OLED display  10  is emitted upward along the direction Al and to the upper substrate  106 . 
     In another embodiment, the anode layer  101  may be ITO layer or IZO layer with a thickness of 50 nm to 300 nm, and the cathode layer  105  may be an aluminum layer with a thickness of 150 μm to 200 μm. In this embodiment, the anode layer  101  is light-transparent type, and the cathode layer  105  is light-reflective type. The light may be emitted downwardly from the OLED display  10  to the lower substrate  100 . 
     In the embodiment above, the color deviation protective layer  104  is disposed between the cathode layer  105  and the organic light-emitting layer  102 . In other embodiments, the color deviation protective layer  104  may be disposed between the anode layer  101  and the organic light-emitting layer  102 . 
     In the above embodiment, other layer structures may be added to the OLED display  10  to improve the emitting efficiency of the OLED display. 
     Please refer to  FIG. 4 . In this embodiment, the anode layer  101  is formed on the lower substrate  100 . A hole injection layer  107  is formed on the anode layer  101 . The hole injection layer  107  may be formed of the material with the highest occupied molecular orbital (HOMO) energy level and the material with work function matching the anode layer  101 , such as CuPc (copper phthalocyanine), TiOPc, m-MTDATA(4,4′,4″-tris(3-methylphenylphenylamino)triphenylamine), 2-TNATA (4,4′A″-tris(2-naphthylphenylamino)triphenylamine) or PEDOT-PSS (poly(3,4-ethylene dioxythiophene)-poly(styrenesulfonate)), etc. The hole injection layer  107  may be formed through the process such as evaporation, spin coating, or blade coating, etc. The function of the hole injection layer  107  is to increase the charge injection so as to increase the emitting efficiency of the OLED display  10 . 
     After the hole injection layer  107  is formed, a hole transport layer (HTL)  108  is formed on the hole injection layer  107  by the process such as evaporation, spin coating or blade coating, etc. The hole transport layer  108  may be formed of thin film materials with high hole mobility and high thermal stability, for example, NPB (naphtha-phenylene benzidine), TPD(N,N′-diphenyl-N,N′-di(3-methylphenyl)-1,1′-biphenyl-4,4′-diamine), or PVK (poly(9-vinyl carbazole)), etc. The function of the hole transport layer  108  is to increase the hole transport rate, so as to increase the emitting efficiency of the OLED display  10 . 
     After the hole transport layer  108  is formed, the organic light-emitting layer  102  is formed on the hole transport layer  108 . The organic light-emitting layer  102  is provided with primary color regions  1021  and mixed color regions  1022 . A color deviation protective layer  104  (not shown in  FIG. 4 ) is then formed on the organic light-emitting layer  102 , wherein the color deviation protective layer  104  is provided with insulating patterns  104   a  corresponding to the mixed color regions  1022 . An electron transport layer (ETL)  109  may be then formed on the color deviation protective layer  104 . The function of electron transport layer  109  is to facilitate the transportation of the injected electrons from the cathode layer  105  to the organic light-emitting layer  102 , so as to inhibit the transition of the holes to the cathode layer  105 . For this reason, the material of electron transport layer  109  must have high electron mobility with enough barrier level to block the hole, such as the materials of PBD(2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole), OXD, TAZ(3-(biphenyl4-yl)-4-phenyl-5-(4-tert-butylphenyl)-4H-1,2,4-triazole) or Alq3, formed on the color deviation protective layer  104  by evaporation, spin coating or blade coating, etc. 
     An electron injection layer (EIL)  110  is formed on the electron transport layer  109  to facilitate the electron injection, which may be formed of the material with lowest unoccupied molecular orbital (LUMO) energy level and the material with work function matching the cathode layer  105 , such as LiF, LiO 3 , LiBO 2 , etc. A cathode layer  105  is then formed on the electron injection layer  110 , and an upper substrate  106  is finally provided on the cathode layer  105  to protect the whole components, such as a transparent glass plate or plastic or other materials which may support the components. The main process of making the structure of the OLED display  10  is therefore completed. 
     In one embodiment, the main structure of the OLED display  10  is shown in  FIG. 3 . The anode layer  101  of the OLED display is light-reflective type, while the cathode layer  110  is light-transparent type, thus the light emitted from the OLED display  10  would travel upward through the upper substrate  106  along the direction Al. The whole stack structure from bottom up includes the lower substrate  100 , the anode layer  101 , the organic light-emitting layer  102  with primary color regions  1021  and mixed color regions  1022 , the color deviation protective layer  104  with insulating patterns  104   a  corresponding to the mixed color regions  1022 , the cathode layer  105  and the upper substrate  106 . 
     In another embodiment, the main structure of the OLED display  10  is shown like  FIG. 4 . The anode layer  101  of the OLED display is light-reflective type, while the cathode layer  110  is light-transparent type, thus the light emitted from the OLED display  10  would travel upward through the upper substrate  106  along the direction Al. The whole stack structure from bottom up includes the lower substrate  100 , the anode layer  101 , the hole transport layer  108 , the organic light-emitting layer  102  with primary color regions  1021  and mixed color regions  1022 , the color deviation protective layer  104  with insulating patterns  104   a  corresponding to the mixed color regions  1022 , the electron transport layer  109 , the electron injection layer  110 , the cathode layer  105  and the upper substrate  106 . 
     The structure shown in the above embodiment is merely an exemplary configuration of the present invention. In another embodiment, the color deviation protective layer  104  may be disposed in different positions depending on the light-emitting directions of the OLED display  10 , as long as it corresponds to the mixed color regions  1022 . Please refer to  FIGS. 5-9 , which are cross-sectional views schematically showing a variety of types of the OLED display  10  of the present invention. 
     In one embodiment, the color deviation protective layer  104  may be disposed between the electron transport layer  109  and the electron injection layer  110  ( FIG. 5 ), between the electron injection layer  110  and the cathode layer  105  ( FIG. 6 ), between the hole transport layer  108  and the hole injection layer  107  ( FIG. 7 ), between the hole injection layer  107  and the anode layer  101  ( FIG. 8 ), or between the anode layer  101  and the lower substrate  100  ( FIG. 9 ), to achieve the function of inhibiting the combination of holes and electrons in the mixed color regions  1022  and preventing the color deviation issue. 
     In the present invention, the shape of the color deviation protective layer  104  is not limited to squares as shown in the figures. Rhombus, trapezoid, and funnel-shape are within the scope of the present invention, as long as the color deviation protective layer  104  can completely block the mixed color regions  1022 . 
     It should be noted that the light-emitting direction, whether upwardly or downwardly, of the OLED display  10  are not limited in the present invention, and the position of the color deviation protective layer  104  is not limited by the light-emitting direction of the OLED display  10 . The only requirement is the color deviation protective layer  104  being disposed between the anode layer  101  and the cathode layer  105  to inhibit the combination of holes and electrons and the light generation in the mixed color regions  1022  of the organic light-emitting layer  102 , so as to prevent the color deviation issue and significantly increase the production yield. 
     Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.