Abstract:
An organic light emitting diode (OLED) display is disclosed. In one embodiment, the display includes i) a substrate, ii) a driving circuit formed on the substrate, iii) an organic light emitting diode formed on the substrate and electrically connected to the driving circuit, iv) an encapsulation thin film formed on the driving circuit and organic light emitting diode and v) a spacer formed on the substrate and surrounding the encapsulation thin film.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims priority to and the benefit of Korean Patent Application No. 10-2010-0050488 filed in the Korean Intellectual Property Office on May 28, 2010, the entire contents of which are incorporated herein by reference. 
       BACKGROUND 
       [0002]    1. Field 
         [0003]    The described technology generally relates to an organic light emitting diode (OLED) display, and more particularly, to an OLED display that has an encapsulation thin film and a manufacturing method thereof. 
         [0004]    2. Description of the Related Technology 
         [0005]    OLED displays are generally lightweight and have a thin profile. In addition, they are self-emissive and thus they do not require a separate light source. Furthermore, since the displays have characteristics of low power consumption, high luminance and high reaction speed, they have received much attention as the next generation display. 
         [0006]    An OLED display includes a substrate on which an organic light emitting diode is formed. If moisture and oxygen penetrates into the organic light emitting diode that is made of an organic material, its performance degrades. Accordingly, an encapsulation method is generally used in order to prevent penetration of moisture and oxygen into OLED displays. 
       SUMMARY 
       [0007]    One inventive aspect is an organic light emitting diode (OLED) display that suppresses performance degradation of an organic light emitting diode by internal penetration of moisture and oxygen. 
         [0008]    Another aspect is a method for manufacturing an organic light emitting diode (OLED) display that suppresses the occurrence of particles. 
         [0009]    Another aspect is an organic light emitting diode (OLED) display which includes: a substrate; a driving circuit and organic light emitting diode that is formed on the substrate; an encapsulation thin film that is formed on the driving circuit and organic light emitting diode; and a spacer that surrounds the encapsulation thin film on the substrate. 
         [0010]    The height of the spacer may be higher than the height of the layered structure of the driving circuit and the organic light emitting diode. 
         [0011]    The height of the spacer may be higher than the height of the layered structure of the driving circuit and the organic light emitting diode and the encapsulation thin film. 
         [0012]    The height of the spacer may be 3 μm to 5 μm. 
         [0013]    The spacer may include any one of acryl, urethane and polyimide (PI). 
         [0014]    The spacer may be directly contacted with the encapsulation thin film along the circumference of the encapsulation thin film. 
         [0015]    The encapsulation thin film may include at least a pair of inorganic film and organic film, and may be formed by alternately layering the inorganic film and the organic film. 
         [0016]    Another aspect is a method for manufacturing an organic light emitting diode (OLED) display, which includes: preparing a substrate; forming a spacer on the substrate along an edge of the substrate; forming a driving circuit and organic light emitting diode on the substrate in an internal area that is partitioned by the spacer; and forming an encapsulation thin film so as to cover the driving circuit and the organic light emitting diode. The mask that is used in the forming of the driving circuit and the organic light emitting diode may be disposed on the spacer. 
         [0017]    The height of the spacer may be higher than the height of the layered structure of the driving circuit and the organic light emitting diode. 
         [0018]    The height of the spacer may be higher than the height of the layered structure of the driving circuit and the organic light emitting diode and the encapsulation thin film. 
         [0019]    The height of the spacer may be 3 μm to 5 μm. 
         [0020]    The spacer may be formed by including any one of acryl, urethane and polyimide (PI). 
         [0021]    The encapsulation thin film may be contacted with the spacer in the internal area. 
         [0022]    The encapsulation thin film may be formed by alternately layering at least a pair of inorganic film and organic film. Another aspect is an organic light emitting diode (OLED) display, comprising: a substrate; a driving circuit formed on the substrate; an organic light emitting diode formed on the substrate and electrically connected to the driving circuit; an encapsulation thin film formed on the driving circuit and organic light emitting diode; and a spacer formed on the substrate and surrounding the encapsulation thin film. 
         [0023]    In the above display, the height of the spacer is greater than the height of the layered structure of the driving circuit and the organic light emitting diode. In the above display, the height of the spacer is greater than the height of the layered structure of i) the driving circuit, ii) the organic light emitting diode and iii) the encapsulation thin film. In the above display, the height of the spacer is about 3 μm to about 5 μm. 
         [0024]    In the above display, the spacer is formed at least partially of acryl, urethane and polyimide (PI). In the above display, the spacer directly contacts the encapsulation thin film along the circumference of the encapsulation thin film. In the above display, the encapsulation thin film includes at least a pair of an inorganic film and an organic film which are alternately formed. 
         [0025]    Another aspect is a method of manufacturing an organic light emitting diode (OLED) display, comprising: preparing a substrate; forming a spacer on the substrate along an edge of the substrate; forming a driving circuit and an organic light emitting diode on the substrate to be surrounded by the spacer; and forming an encapsulation thin film so as to substantially cover the driving circuit and the organic light emitting diode, wherein the mask that is used in the forming of the driving circuit and the organic light emitting diode is supported by and contacts the spacer. 
         [0026]    In the above method, the height of the spacer is greater than the height of the layered structure of the driving circuit and the organic light emitting diode. In the above method, the height of the spacer is greater than the height of the layered structure of i) the driving circuit, ii) the organic light emitting diode and iii) the encapsulation thin film. In the above method, the height of the spacer is about 3 μm to about 5 μm. In the above method, the spacer is formed at least partially of acryl, urethane and polyimide (PI). 
         [0027]    In the above method, the encapsulation thin film contacts the spacer. In the above method, the encapsulation thin film is formed by alternately layering at least a pair of an inorganic film and an organic film. In the above method, the spacer substantially completely surrounds the encapsulation thin film in a selected plane: 
         [0028]    Another aspect is an organic light emitting diode (OLED) display, comprising: a substrate; an organic light emitting diode formed on a surface of the substrate; an encapsulation layer covering the organic light emitting diode, wherein at least part of the encapsulation layer contacts the surface of the substrate; and a spacer formed on the surface of the substrate and surrounding the encapsulation layer. 
         [0029]    In the above display, the spacer contacts the encapsulation layer: In the above display, the spacer substantially completely surrounds the encapsulation layer in a selected plane: In the above display, the spacer is greater in height than the encapsulation layer, and wherein the height is defined from the surface of the substrate. In the above display, the height of the spacer is about 3 μm to about 5 μm. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0030]      FIG. 1  is a top plan view of an organic light emitting diode (OLED) display according to an embodiment. 
           [0031]      FIG. 2  is a cross-sectional view of an organic light emitting diode (OLED) display according to an embodiment, which is taken along the line II-II of  FIG. 1 . 
           [0032]      FIG. 3  is a plan layout view of a pixel of an organic light emitting diode (OLED) display according to an embodiment. 
           [0033]      FIG. 4  is a cross-sectional view of a pixel of an organic light emitting diode 
           [0034]    (OLED) display according to an embodiment, which is taken along the line IV-IV of  FIG. 3 . 
           [0035]      FIG. 5  is a view that illustrates a contact of an organic light emitting diode (OLED) display and a mask according to an embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0036]    In general, the substrate for an OLED display is encapsulated by using metal or glass. However, if glass is used, there is a lower limit as to by how much the thickness of the entire display device can be reduced. In addition, flexible OLED displays are possible, and in view of the hardness of metal and glass, they are not suitable for such designs. 
         [0037]    In manufacturing OLED displays, a mask is generally used to pattern OLED elements such as an organic light emitting diode and a driving circuit for supplying electrical signals to it. The mask may contact the substrate in the patterning process and particles may be introduced by the contact. The particles penetrate into the OLED display in conjunction with moisture and oxygen causing a deleterious effect to the organic light emitting diode, such that the life-span of the OLED display is reduced. 
         [0038]    Hereinafter, embodiments will be described more fully hereinafter with reference to the accompanying drawings. 
         [0039]    The drawings and description are to be regarded as illustrative in nature and not restrictive, and the size and thickness of each component shown in the drawings are arbitrarily shown for understanding and ease of description. In addition, it will be understood that when an element such as a layer, film is referred to as being “on” another element, it can be directly on the other element or intervening elements may also be present. 
         [0040]    Referring to  FIGS. 1 and 2 , an OLED display includes a display substrate  110 , an encapsulation thin film  210  and spacer  300 . 
         [0041]    The display substrate  110  is configured to display an image, a driving circuit (DC) is formed on the display substrate  110 , an organic light emitting diode  70  is formed on the driving circuit (DC), thus implementing the image through it. The organic light emitting diode  70  includes the organic emission layer that is made of an organic material, and is driven by a driving circuit (DC) that includes a thin film transistor and a capacitor, thus emitting light. 
         [0042]    The encapsulation thin film  210  is formed on the organic light emitting diode  70 , thus sealing the organic light emitting diode  70 . The encapsulation thin film  210  is formed so that the organic film and the inorganic film are alternately layered on the organic light emitting diode  70  to cover the organic light emitting diode  70  and driving circuit (DC). 
         [0043]    In one embodiment, the OLED display requires a low water vapor transmission rate (WVTR) in order to ensure a sufficient life-span. In one embodiment, by sealing the organic light emitting diode  70  using the encapsulation thin film  210 , it suppresses the penetration of moisture and oxygen into the organic light emitting diode  70  and driving circuit (DC), thereby implementing the low water vapor transmission rate of about 10 −6  g/m 2 /day or less. 
         [0044]    In one embodiment, the spacer  300  surrounds the circumference of the encapsulation thin film  210  on the display substrate  110 . The spacer  300  is configured to support the mask in order to form the driving circuit (DC) and organic light emitting diode  70 , and will be described later. 
         [0045]    In one embodiment, the plane shape of the spacer  300  is determined according to the plane shape of the organic light emitting diode  70  and the encapsulation thin film  210 . In one embodiment, since the plane shape of the organic light emitting diode  70  and the encapsulation thin film  210  is a substantially rectangular shape, the spacer  300  that surrounds the encapsulation thin film  210  has a substantially rectangular band plane shape. In one embodiment, the encapsulation thin film  210  contacts the spacer  300 . That is, the encapsulation thin film  210  contacts the spacer  300 , and is formed in substantially the entire area on the display substrate  110  that is partitioned by the spacer  300 . 
         [0046]    In one embodiment, the height of the spacer  300  is greater than the height of the layered structure of the driving circuit (DC) and the organic light emitting diode  70 . The height of the spacer  300  may be greater than the height of the layered structure of driving circuit (DC), organic light emitting diode  70  and encapsulation thin film  210 . The height of the spacer may be about 3 μm to about 5 μm, but in the case of when the height of the encapsulation thin film  210  is lower than about 3 μm, the height of the spacer may be lower than about 3 μm. 
         [0047]    The spacer  300  may be formed of the same material as the pixel definition film that will be described later. For example, the spacer  300  may be formed of an organic material such as acryl, urethane, and polyimide (PI). As described above, in the case of when the spacer  300  is formed of the same material as the pixel definition film, while the pixel definition film is formed, the spacer  300  is formed at the same time, such that a whole process may be simplified. However, the material of the above spacer is illustrated, various modifications may be possible by those who are skilled in the art. 
         [0048]    As described above, it is possible to more efficiently suppress the penetration of moisture and oxygen into by forming the spacer  300  that surrounds the circumference of the encapsulation thin film  210 . In addition, in the manufacturing process, it is possible to lower the occurrence of defects and prolong a life-span of the OLED display by suppressing the occurrence of particles, and this will be described later. 
         [0049]    Referring to  FIG. 3  and  FIG. 4 , an active matrix (AM) type organic light emitting diode (OLED) display that has a 2Tr-1 Cap structure which includes two thin film transistors (TFT), and one capacitor for one pixel is shown, but is not considered limiting. For example, the OLED display may be provided with three or more thin film transistors and two or more capacitors for one pixel, and a disposition of the wire may be changed to provide various structures. Here, the pixel means a minimum unit that displays an image, and the OLED display displays an image through a plurality of pixels. 
         [0050]    The display substrate  110  includes a switching thin film transistor  10 , a driving thin film transistor  20 , a capacitor  80  and an organic light emitting diode (OLED)  70  for each one pixel. In addition, the display substrate  110  further includes a gate line  151  that is disposed along a predetermined direction, and a data line  171  and a common electric power line  172  that insulately cross the gate line  151 . 
         [0051]    The organic light emitting diode  70  includes the first electrode  710 , the organic emission layer  720  that is formed on the first electrode  710 , and the second electrode  730  that is formed on the first organic emission layer  720 . In one embodiment, the pixel electrode  710  is an anode that is a hole injection electrode and the common electrode  730  is a cathode that is an electron injection electrode. The holes and electrons are injected from the pixel electrode  710  and common electrode  730  to the organic emission layer  720 , and when the exciton that is combined with the injected hole and electron falls from the exited state to the bottom state, light emission is implemented. 
         [0052]    The capacitor  80  includes the first capacitor plate  158  and the second capacitor plate  178  that are disposed between gate insulating layers  140  that act as a dielectric material. The capacitor capacitance is determined by the charge that is accumulated in the capacitor  80  and the voltage between both capacitor plates  158  and  178 . 
         [0053]    The switching thin film transistor  10  includes a switching semiconductor layer  131 , switching gate electrode  152 , a switching source electrode  173  and a switching drain electrode  174 . The driving thin film transistor  20  includes a driving semiconductor layer  132 , a driving gate electrode  155 , a driving source electrode  176  and a driving drain electrode  177 . The switching thin film transistor  10  is a switching element that selects the pixel that emits light. The switching gate electrode  152  is electrically connected to the gate line  151 , the switching source electrode  173  is electrically connected to the data line  171 , and the switching drain electrode  174  is separated from the switching source electrode  173  and connected to the first capacitor plate  158 . 
         [0054]    The driving thin film transistor  20  applies a driving power for emitting light of the organic emission layer  720  of the organic light emitting diode  70  to the pixel electrode  710  in the selected pixel. The driving gate electrode  155  is electrically connected to the first capacitor plate  158 , the source electrode  176  and the second capacitor plate  178  are electrically connected to the common power line  172 , and the driving drain electrode  177  is electrically connected to the pixel electrode  710  of the organic light emitting diode  70  through a contact hole  182 . 
         [0055]    By the above structure, the switching thin film transistor  10  is operated by the gate voltage that is applied to the gate line  151  and transfers the data voltage that is applied to the data line  171  to the driving thin film transistor  20 . The voltage that corresponds to a difference in the common voltage that is applied from the common power line  172  to the driving thin film transistor  20  and the data voltage that is transferred from the switching thin film transistor  10  is stored in the capacitor  80 . Further, the current that corresponds to the voltage that is stored in the capacitor  80  flows through the driving thin film transistor  20  to the organic light emitting diode  70  to allow the organic light emitting diode  70  to emit light. 
         [0056]    Referring to  FIG. 4 , a method of manufacturing an OLED display according to one embodiment will be described. 
         [0057]    In one embodiment, the substrate member  111  of the display substrate  110  is formed of an insulating substrate such as glass and the like, and the buffer layer  120  is formed on the first substrate member  111 . The buffer layer  120  may be formed of silicon nitride (SiNx), silicon oxide (SiOx), silicon nitroxide (SiOxNy) and the like, and the buffer layer  120  may be omitted according to the kind of substrate member  111  and the process condition. The driving semiconductor layer  132  is formed on the buffer layer  120 . The driving semiconductor layer  132  includes a channel region  135  in which an impurity is not doped, and a source region  136  and a drain region  137  that are p+ doped to both ends of the channel region  135 . In one embodiment, the doped ion material is a P type impurity such as boron (B). 
         [0058]    In one embodiment, a thin film transistor that has a PMOS structure that uses the P type impurity as the driving thin film transistor  20  is used. Alternatively, a thin film transistor that has an NMOS structure or CMOS structure may be used. In addition, in one embodiment, the driving thin film transistor  20  is a polycrystalline thin film transistor that includes a polysilicon film, but the switching thin film transistor  10  not shown in  FIG. 4  may be a polycrystalline thin film transistor or amorphous thin film transistor that includes an amorphous silicon film. 
         [0059]    In one embodiment, the gate insulating layer  140  that is formed at least partially of silicon nitride or silicon oxide is formed on the driving semiconductor layer  132 . The gate wire that includes the gate electrode  155  is formed on the gate insulating layer  140 , and the gate wire further includes the gate line  151 , the first capacitor plate  158  and the other wires. In addition, the driving gate electrode  155  is formed so as to overlap with at least a portion of the driving semiconductor layer  132 , particularly the channel region  135 . On the gate insulating layer  140 , the interlayer insulating layer  160  that covers the driving gate electrode  155  is formed. The gate insulating layer  140  and the interlayer insulating layer  160  have holes that expose the source region  136  and drain region  137  of the driving semiconductor layer  132 . In one embodiment, the interlayer insulating layer  160  is formed at least partially of silicon nitride, silicon oxide and the like likewise the gate insulating layer  140 . The data wire that includes the driving source electrode  176  and driving drain electrode  177  is formed on the interlayer insulating layer  160 , and the data wire further includes the data line  171 , the common power line  172 , the second capacitor plate  178  and the other wires. In addition, the driving source electrode  176  and driving drain electrode  177  are electrically connected to the source region  136  and drain region  137  of the driving semiconductor layer  132  through the holes that are formed on the interlayer insulating layer  160  and gate insulating layer  140 . 
         [0060]    As described above, the driving semiconductor layer  132 , driving gate electrode  155 , driving source electrode  176  and driving drain electrode  177  are formed, and the configuration of the driving thin film transistor  20  is not limited to the above examples but may be variously modified by those who are skilled in the art. 
         [0061]    A planarization layer  180  that covers a data wire is formed on the interlayer insulating layer  160 , and the contact hole  182  that exposes a portion of the drain electrode  177  is formed on the planarization layer  180 . Meanwhile, any one of the interlayer insulating layer  160  and planarization layer  180  may be omitted. 
         [0062]    The pixel electrode  710  of the organic light emitting diode  70  is formed on the planarization layer  180 , and the pixel electrode  710  is electrically connected through the contact hole  182  to the drain electrode  177 . In addition, a pixel definition film  190  that has a plurality of openings  199  that expose each pixel electrode  710  is formed on the planarization layer  180 . The portion on which the pixel definition film  190  is formed substantially becomes a non-light emitting area and the portion on which the opening  199  of the pixel definition film  190  is formed substantially becomes a light emitting area. The organic emission layer  720  is formed on the pixel electrode  710 , and the common electrode  730  is formed on the organic emission layer  720 , thereby constituting the organic light emitting diode  70 . The organic emission layer  720  is formed of a low molecular organic material or high molecular organic material, and the organic emission layer  720  may be formed of a multilayer that includes one or more of a hole injection layer (HIL), hole transport layer (HTL), electron transport layer (ETL) and electron injection layer (EIL). 
         [0063]    An encapsulation thin film  210  for sealing the organic light emitting diode  70  is formed on the common electrode  730 . The encapsulation thin film  210  includes one pair or more of organic films  211  and  213  and inorganic films  212  and  214 , and is formed by alternately layering the organic films  211  and  213  and inorganic films  212  and  214 . In one embodiment, the encapsulation thin film  210  includes two pairs of organic films  211  and  213  and inorganic films  212  and  214 , but it is not limited thereto. 
         [0064]    As described above, the encapsulation thin film  210  that is obtained by alternately layering the organic films  211  and  213  and the inorganic films  212  and  214  is formed on the organic light emitting diode  70 , such that the contacting of moisture or oxygen to the organic light emitting diode  70  is suppressed to prevent performance degradation. 
         [0065]    Meanwhile, the switching thin film transistor  10 , the driving thin film transistor  20 , the capacitor  80  and the organic light emitting diode  70  are patterned by using the mask. In this patterning process, the mask contacts the display substrate  110  to generate particles. The particles penetrate into the OLED display to deteriorate the performance of the organic light emitting diode, and may be a cause of the occurrence of defects of the OLED display and life-span deterioration thereof. Accordingly, in one embodiment, as described above, the occurrence of defects of the OLED display and the life-span deterioration thereof are suppressed by forming the spacer  300  on the display substrate  110 . 
         [0066]      FIG. 5  is a view that illustrates a contact of an OLED display and a mask according to an embodiment, and a manufacturing method of the OLED display will be described with reference to it. 
         [0067]    In one embodiment, the OLED display is manufactured by preparing a display substrate  110 , forming a spacer  300  along an edge of the display substrate  110 , forming a driving circuit (DC) and organic light emitting diode  70 , and forming an encapsulation thin film  210  to cover the driving circuit (DC) and organic light emitting diode  70 . As shown in  FIG. 5 , the driving circuit (DC) and organic light emitting diode  70  are formed in an internal area of the areas that are partitioned by the spacer  300  on the display substrate  110 , and are formed through deposition and patterning processes using the mask  400 . 
         [0068]    As described above, if the mask  400  contacts the display substrate  110 , the particles are generated and moisture and oxygen may easily penetrate into the OLED device, as a result, the performance of the OLED display may be deteriorated and defects may be generated. However, according to one embodiment, the spacer  300  is formed on the display substrate  110 , the mask  400  is disposed to be supported on the spacer  300 , thereby suppressing the above problems. 
         [0069]    In one embodiment, since the driving circuit (DC) and organic light emitting diode  70  are formed by using the mask  400 , the height of the spacer  300  that supports the mask  400  is greater than the height of the layered structure of the driving circuit (DC) and organic light emitting diode  70 . 
         [0070]    In addition, the height of the spacer  300  may be greater than the height of the layered structure of the driving circuit (DC), organic light emitting diode  70  and encapsulation thin film  210 . In the area that is partitioned by the spacer  300 , the encapsulation thin film  210  is layered to cover the driving circuit (DC) and organic light emitting diode  70 . 1   f  the height of the spacer  300  is greater than the height of the layered structure of the driving circuit (DC), organic light emitting diode  70  and encapsulation thin film  210 , in the area that is partitioned by the spacer  300 , the process for layering the encapsulation thin film  210  may be easily performed. 
         [0071]    In one embodiment, the encapsulation thin film  210  is formed by alternately layering at least a pair of inorganic film and organic film. In addition, since the encapsulation thin film  210  is layered in the area that is partitioned by the spacer  300  on the organic light emitting diode  70 , it may directly contact the spacer  300 . By this process, the organic light emitting diode  70  may be sealed by the encapsulation thin film  210  and an external boundary may be formed by the spacer  300 . Accordingly, it is possible to easily suppress the penetration of moisture and oxygen into the OLED display and to suppress the occurrence of particles in the process. 
         [0072]    According to at least one of the disclosed embodiments, it is possible to prevent performance degradation of an organic light emitting diode (OLED) display by suppressing penetration of moisture and oxygen into the display. 
         [0073]    In addition, in the process of manufacturing the OLED display, it is possible to suppress the occurrence of defects of the display and prolong life-span. 
         [0074]    While this disclosure has been described in connection with certain embodiments, it is to be understood that the disclosed embodiments are not limiting. Thus, the appended claims are intended to cover various modifications and equivalent arrangements.