Patent Publication Number: US-2012043562-A1

Title: Organic electroluminescence display device and manufacturing method therefor

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an organic electro luminescence (EL) display device including multiple organic EL elements each having organic compound layers containing an emission layer between electrodes, and to a manufacturing method therefor. 
     2. Description of the Related Art 
     In recent years, as a flat panel display, an organic EL display device that is a self-emission device has attracted attention and has been developed actively. 
     On a substrate of such an organic EL display device, multiple first electrodes are arranged in matrix, and organic compound layers expressing different light emission colors are respectively formed on the first electrodes by a vacuum deposition method. In this case, a vapor deposition mask having multiple pixel apertures is brought into contact with the surface of an insulating layer having a protruding shape, so as to expose the first electrodes corresponding to pixels. 
     Here, the insulating layer, which has an element separating function and a width corresponding to an interval between pixels, is disposed so as to surround the perimeter of each pixel. Therefore, a contact area between the insulating layer and the vapor deposition mask is increased. As a result, when the vapor deposition mask is pressed to contact with the surface of the insulating layer, an attached matter such as a foreign substance adhered to the vapor deposition mask is easily transferred to the surface of the insulating layer. Accordingly, when a tension is applied to the vapor deposition mask, the surface of the insulating layer may be damaged due to a scratch by rubbing. If the insulating layer is damaged, moisture may easily enter through the damaged part, and hence the emission life may be shortened. In addition, if the attached matter on the vapor deposition mask enters a light emitting part in the pixel aperture, the organic compound layer formed inside is easily disconnected in a vicinity of the foreign substance, resulting in an emission defect caused by a short-circuit between electrodes. 
     As a measure for eliminating such a trouble, for example, there is proposed a structure in which a part of the insulating layer is protruded upward so as to form a rib so that the vapor deposition mask contacts with the rib, thereby reducing a contact area with the vapor deposition mask (Japanese Patent Application Laid-Open No. 2005-322564). 
     By the way, it is necessary for forming the rib protruding on the insulating layer to perform a pattern exposure for partially controlling an exposure amount in a step of forming the insulating layer and to perform two photolithography steps. In order to partially control the exposure amount, for example, a method of using two photomasks and a method of using a halftone mask are employed, each of which, however, causes an increase in the number of steps and an increase in manufacturing cost due to increasing cost of the photomask. Thus, there has been a problem in productivity. 
     SUMMARY OF THE INVENTION 
     Therefore, an object of the present invention is to provide an organic EL display device and a manufacturing method therefor, which are capable of reducing a contact area between a vapor deposition mask and an insulating layer arranged around each pixel so as to prevent transfer of an attached matter from the vapor deposition mask to the insulating layer, without increasing the number of steps or manufacturing cost. 
     The following is a structure of the present invention for achieving the above-mentioned object. 
     That is, an organic EL display device according to the present invention includes a first insulating layer formed on a substrate, multiple first electrodes disposed on the first insulating layer, one of a first opening and a first recess formed in the first insulating layer at a periphery of each of the multiple first electrodes, a second insulating layer that covers the one of the first opening and the first recess, and has second openings corresponding to the multiple first electrodes, an organic compound layer disposed on the each of the multiple first electrodes and a second electrode formed on the organic compound layer, in which a material forming the each of the multiple first electrodes is absent in the one of the first opening and the first recess and the second insulating layer has a second recess formed in a surface thereof, corresponding to the one of the first opening and the first recess of the first insulating layer. 
     Further, a method of manufacturing an organic EL display device according to the present invention includes forming a first insulating layer on a substrate, forming one of a first opening and a first recess in the first insulating layer, forming multiple first electrodes on the first insulating layer, forming a second insulating layer having second openings corresponding to the multiple first electrodes in regions overlapping with the one of the first opening and the first recess, forming an organic compound layer for covering the multiple first electrodes by bringing a vapor deposition mask into contact with a surface of the second insulating layer and forming a second electrode on the organic compound layer, in which the forming multiple first electrodes is performed so that a material forming each of the multiple first electrodes is absent in the one of the first opening and the first recess of the first insulating layer and the forming a second insulating layer includes forming the second insulating layer corresponding to the first opening of the first insulating layer, and forming a second recess in the surface of the second insulating layer. 
     According to the present invention, the contact area between the vapor deposition mask and the insulating layer arranged around each pixel can be reduced so as to prevent transfer of an attached matter from the vapor deposition mask to the insulating layer, without increasing the number of steps or manufacturing cost. Therefore, it is possible to obtain an excellent effect that the surface of the insulating layer is hardly damaged by abrasion or scratch due to transfer of an attached matter from the vapor deposition mask, to thereby prevent entrance of moisture so that the risk of a short-circuit between electrodes can be reduced. 
     Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A and 1B  are schematic diagrams illustrating a cross-sectional structure in a manufacturing process of an organic EL display device according to an embodiment of the present invention. 
         FIG. 2  is a schematic diagram illustrating a plane structure in the manufacturing process of the organic EL display device according to the embodiment of the present invention. 
         FIGS. 3A ,  3 B,  3 C,  3 D and  3 E are schematic diagrams illustrating a cross sectional structure in a manufacturing process of an organic EL display device, taken along the line A-A of  FIG. 2 . 
         FIG. 4  is a schematic diagram illustrating another example of the cross sectional structure taken along the line A-A of  FIG. 2 . 
         FIG. 5  is an explanatory diagram illustrating a plane state in which a vapor deposition mask is brought into contact with a second insulating layer in a manufacturing method for the organic EL display device according to the embodiment of the present invention. 
         FIG. 6  is a circuit diagram illustrating an example of an equivalent circuit of the organic EL display device according to the embodiment of the present invention. 
         FIG. 7  is a schematic diagram illustrating a state in which a force is applied to the backside of a substrate so that the surface of the second insulating layer on the substrate is pressed to the surface of the vapor deposition mask in the manufacturing process for the organic EL display device according to the embodiment of the present invention. 
         FIGS. 8A ,  8 B and  8 C are schematic diagrams illustrating plane structures of recesses in the second insulating layer and openings in a first insulating layer in the organic EL display device according to the embodiment of the present invention. 
     
    
    
     DESCRIPTION OF THE EMBODIMENT 
     Preferred embodiments of the present invention will now be described in detail in accordance with the accompanying drawings, but the present invention is not limited to this embodiment. Note that, for convenience sake of description, each layer is illustrated in a recognizable size in the drawings, and the scale of the drawings is different from an actual one. In addition, as to matters that are not particularly described in this specification or not particularly illustrated in the drawings, well-known or publicly-known technologies shall be applied. 
     In this embodiment, a top emission organic EL display device of an active matrix drive type is exemplified, and a detailed structure of each layer is described according to a procedure of a manufacturing method therefor.  FIGS. 1A and 1B  are schematic diagrams illustrating a cross-sectional structure in a manufacturing process of the organic EL display device according to the embodiment of the present invention.  FIG. 2  is a schematic diagram illustrating a plane structure in the manufacturing process of the organic EL display device according to this embodiment. 
     As illustrated in  FIGS. 1A ,  1 B and  2 , multiple first electrodes  13  are arranged in matrix on a substrate  10  of the organic EL display device according to this embodiment. Each of the first electrodes  13  is surrounded by a second insulating layer  12 , and an organic compound layer including an emission layer is disposed on the first electrode  13  in a pixel aperture formed in the second insulating layer  12 . Further, a second electrode (not shown) is disposed on the organic compound layers so as to be opposed to the first electrodes  13 . Between the electrodes, multiple organic EL elements having the organic compound layers are disposed on the substrate  10 . Note that, in the top emission organic EL display device of this embodiment, the first electrode  13  has a reflective property while the second electrode has a transparent property. 
     Here,  FIG. 6  is a circuit diagram illustrating an example of an equivalent circuit of the organic EL display device according to this embodiment. As illustrated in  FIG. 6 , on the substrate  10 , scanning lines  60  and signal lines  50  that are electrically separated from each other are disposed at positions orthogonal to each other. The scanning line  60  and the signal line  50  are connected via a transistor (Tr). A source electrode of a first transistor  43  is connected to a capacitor  44  and a gate electrode of a second transistor  42 . A source electrode of the second transistor  42  is connected to a power supply (Vcc) and the capacitor  44 . In addition, a drain electrode of the second transistor  42  is connected to the first electrode  13  of an organic EL element  41 . In the organic EL display device of the active matrix drive type according to this embodiment, circuit units K enclosed by the dot lines as illustrated in  FIG. 6  are formed corresponding to the individual organic EL elements and are integrated in the number of the organic EL elements. Multiple light emission pixels are formed and arranged in matrix. 
     Next, with reference to  FIGS. 1A to 6 , a manufacturing method for the organic EL display device according to this embodiment is described according to manufacturing steps.  FIGS. 3A to 3E  and  4  are schematic diagrams illustrating a cross sectional structure in a manufacturing process of an organic EL display device, taken along the line A-A of  FIG. 2 . 
     First, as illustrated in  FIG. 3A , gate lines  25  of the transistors, a gate insulating layer  26 , and a passivation layer (insulating layer)  27  are formed on the substrate  10 . The substrate surface after forming the transistors is uneven due to a wiring structure, and hence there is formed a first insulating layer (flattening layer)  11  having a flattening function for flattening the unevenness. The first insulating layer  11  is formed by applying a positive photosensitive resist by a spin coating method and irradiating the positive photosensitive resist with light such as ultraviolet rays in a predetermined region to remove, such as openings  15  to be described later. 
     Note that, the first insulating layer  11  is formed to have a thickness of approximately 2 μm in the case where the unevenness of the substrate surface after the transistors are formed is approximately 1 μm, for example. In addition, as the positive photosensitive resist, for example, an insulating material that has photosensitivity and contains polyimide, polybenzoxazole, or the like, but the material should not be interpreted as a limitation. 
     Next, exposure is performed so as to form at least contact holes  16  for connecting the first electrode  13  and the drain electrode of the transistor, which are to be connected electrically, and linear openings  15  corresponding to the regions between the first electrodes. Next, development is performed using a puddle development apparatus, and then baking is performed in a clean bake furnace to cure the resist. Thus, the contact holes  16  that can electrically connect the first electrode  13  to the drain electrode are formed in the first insulating layer  11  as illustrated in  FIG. 2 . Further, as illustrated in  FIG. 3B , the linear openings  15  are formed in the first insulating layer  11  along the arrangement of the first electrodes  13  in regions where the transistor between the first electrodes  13  and  13  cannot electrically contact with the first electrode  13 . 
     Next, as illustrated in  FIG. 3C , the first electrodes  13  are formed on the entire surface of the first insulating layer  11  having the contact holes  16  and the openings  15 . Then, the material forming the first electrode  13  is deposited not only on the first insulating layer  11  but also in the contact holes  16  and the openings  15 . The first electrode  13  in this embodiment is formed to have a three-layer structure (ITO/Ag/ITO) in which a reflective metal layer made of a silver alloy is sandwiched between transparent conductive layers made of ITO, but the material to be used and a thickness thereof are not limited. For instance, the reflective metal layer may be made of an aluminum alloy or silver, and the transparent conductive layer may be made of other material such as an indium zinc oxide (IZO). 
     After forming the first electrode  13 , as illustrated in  FIG. 3D , for example, etching using a mask that is a resist pattern formed by photolithography is performed to form and pattern the first electrode  13  in which the reflective metal layer made of the silver alloy is sandwiched between the transparent conductive layers made of ITO. In other words, in this embodiment, the material forming the first electrode  13  is deposited also in the opening  15 , and then the material forming the first electrode  13  in the opening  15  is removed by etching using the photolithography technology. Without limiting to this method, it is also possible to form and pattern the first electrode  13  using a vapor deposition mask, for example, so as to prevent the material forming the first electrode  13  from being deposited in the opening  15 . 
     After that, in order to form the second insulating layer  12 , the positive photosensitive resist is applied onto the substrate on which the first electrodes  13  are formed in matrix by the spin coating method, and the predetermined region to remove is irradiated with light. Here, the exposure is performed so that at least a part of the first electrode  13  is exposed to form the opening corresponding to a light emission region of the organic EL element. Next, after being developed by the puddle development apparatus, baking is performed in the clean bake furnace so that the resist is cured. Thus, as illustrated in  FIG. 3E , the second insulating layer  12  having a function of partitioning the light emission regions of the organic EL elements is formed so as to surround the peripheries of the first electrodes  13 . The second insulating layer  12  includes linear recesses  17  reflecting the openings  15  formed in the first insulating layer  11 , between neighboring first electrodes  13 . In other words, in the organic EL display device of this embodiment, the openings  15  are positively formed in the first insulating layer  11 , which is to be flat. Thus, the recesses  17  reflecting the openings  15  are formed in the surface of the second insulating layer  12  formed in the regions overlapping with the openings  15 . 
     Here, the first meaning of absence of the material forming the first electrode  13  in the opening  15  is to easily obtain sufficient depth and width of the recess  17  in the second insulating layer  12 . Thus, it is possible to reduce a contact area between the second insulating layer  12  and a vapor deposition mask  19  to be described later. If the material forming the first electrode  13  exists in the opening  15 , the depth and width of the recess  17  are reduced due to the material forming the first electrode  13 . Particularly in a high definition display, because the interval between the first electrodes  13  and  13  is set to be small, the width of the formed opening  15  is also small. Therefore, if the material forming the first electrode  13  exists in the opening  15 , a problem comes to the surface. In addition, if the material forming the first electrode  13  exists in the opening  15  and if the interval between the first electrodes  13  and  13  is set to be small, it is also worried that there is a risk of reducing yield due to a defective pattern between electrodes in the opening  15 . 
     In addition, in the case where a reflective material is used as the material forming the first electrode  13  like this embodiment, because the material forming the first electrode  13  does not exist in the opening  15 , it is possible to prevent ambient light reflection from occurring at the region. 
     Note that, in order to form the recess  17  in the second insulating layer  12 , it is preferred that a width tx of the opening  15  in the first insulating layer  11  be equal to or larger than a depth d of the opening  15  in the first insulating layer  11 , and that the depth d of the opening  15  in the first insulating layer  11  be equal to or larger than the thickness of the second insulating layer  12  as illustrated in  FIG. 1A . 
     In addition, a recess depth g of the second insulating layer  12  formed in the region overlapping with the opening  15  formed in the first insulating layer  11  is set to a value of at least the thickness of the organic compound layer or larger. Because the recess  17  in the second insulating layer  12  is a recess reflecting the opening  15  formed in the first insulating layer  11 , this recess depth g can be adjusted by a combination of the depth d and the width tx of the opening  15  in the first insulating layer  11 . Therefore, in  FIGS. 3A to 3E , the opening  15  passes through the first insulating layer  11 , but not necessarily, and may be a recess. For instance, as illustrated in  FIG. 4  which shows a cross sectional structure, taken along A-A of  FIG. 2 , the depth d of the opening  15  may be set to approximately a half of the first insulating layer  11 . In order to form the opening  15  having a predetermined depth in the first insulating layer  11  using the positive photosensitive resist, for example, there is a method of decreasing an exposure opening space of a photomask  18  so as to reduce the irradiation amount to be relatively smaller than that in the case of forming the opening  15  in a passed-through manner, to thereby adjust the depth that can be soluble in development liquid. 
     It is sufficient that the recess depth g of the second insulating layer  12  is in a range of at least the thickness of the organic compound layer or larger. The reason is described below. 
     In the manufacturing process of the organic EL display device, vapor deposition is performed on multiple substrates successively using the same vapor deposition mask. Therefore, the vapor deposition mask and the surface of the second insulating layer  12  are brought into contact with each other repeatedly. In the organic EL elements that are formed by sequentially stacking multiple organic compound layers, when the vapor deposition mask is used for the second or subsequent layer, an organic compound adhered to the surface of the second insulating layer  12  in the previous vapor deposition step is pressed onto the vapor deposition mask. Therefore, the organic compound at the pressed part may be transferred onto the vapor deposition mask, and hence may become a foreign substance that causes a defect. 
     In this embodiment, the recess depth g of the second insulating layer  12  is set to be larger than the thickness of the organic compound layer. In this way, the transferring of the organic compound on the second insulating layer  12  onto the vapor deposition mask  19  can be reduced, and hence it is possible to prevent the organic compound adhered to the vapor deposition mask  19  from contacting with the second insulating layer  12 . Therefore, it is preferred to set the recess depth g to be at least the thickness of the organic compound layer or larger as described above. 
     In addition, the contact area between the vapor deposition mask  19  and the second insulating layer  12  can be reduced more as the width of the recess  17  in the second insulating layer  12  is larger. The shape of the recess in the second insulating layer  12  can be adjusted by the width and the depth d of the opening  15  formed in the first insulating layer  11 . In addition, in order to avoid a damage to the surface of the first electrode  13  or the organic compound layer formed on the surface of the first electrode  13  due to the foreign substance adhered to the vapor deposition mask  19 , for example, it is preferred to set the thickness of the second insulating layer  12  to be larger than the foreign substance adhered to the vapor deposition mask  19 . Specifically, it is preferred to set the thickness of the second insulating layer  12  to 0.1 μm or larger. 
     Note that, the manufacturing method by the photolithography technology using a photosensitive resist as the second insulating layer  12  is described above, but various organic or inorganic materials can be used as the material of the insulating layer as long as the material is an insulator having a volume resistivity of 1.0×10 8  Ω·cm or larger. More preferably, an insulator having a volume resistivity of 1.0×10 12  Ω·cm or larger is used for the second insulating layer  12 . 
     The description of the process after forming the second insulating layer  12  is further continued. First, a baking process is performed in a vacuum atmosphere, and a pretreatment of the substrate is performed using O 2  plasma. Next, under a state maintaining the vacuum atmosphere, multiple organic compound layers including a hole transport layer, an emission layer, an electron transport layer, and an electron injection layer are deposited sequentially by vapor deposition on the first electrode  13 . 
     A process of forming the emission layers of different colors of red color pixels, green color pixels, and blue color pixels using the vapor deposition mask  19 , in particular, is further described in detail. Here, with reference to  FIG. 5 , a structure of the vapor deposition mask  19  is described, which is used in a state of being in contact onto the second insulating layer  12  when the organic compound layers are deposited on the first electrode  13  by vapor deposition.  FIG. 5  is an explanatory diagram illustrating a plane state in which the vapor deposition mask is brought into contact with the second insulating layer in the manufacturing method of the organic EL display device of this embodiment. 
     As illustrated in  FIG. 5 , the vapor deposition mask  19  includes vapor deposition opening portions  20  elongated in the direction in which the same color pixels are arranged, and the vapor deposition opening portions  20  are formed and arranged at a constant pitch in a mask surface.  FIG. 1B  illustrates a cross sectional structure in a state where the vapor deposition mask  19  illustrated in  FIG. 5  is brought into contact with the second insulating layer  12  on the substrate. 
     With reference to  FIGS. 1A and 1B , a case where the vapor deposition mask  19  is used for vapor deposition of the red color emission layer is described. As illustrated in  FIG. 1A , after a hole transport layer  22  is formed, the substrate is transported to a vacuum chamber for forming the red color emission layer, and the vapor deposition mask  19  illustrated in  FIG. 5  is brought into contact with the second insulating layer  12  in a positioned state. Actually, the vapor deposition mask  19  is brought into contact with the hole transport layer  22  on the second insulating layer  12 . In this case, as illustrated in  FIG. 1B , the vapor deposition mask  19  and the second insulating layer  12  are brought into contact with each other only at protrusions of the second insulating layer  12 . In this state, a region corresponding to the first electrode  11  of the red color pixel is exposed, and a red color emission layer  24  is deposited by vapor deposition to be a predetermined thickness. A green color emission layer and a blue color emission layer are also formed in the same manner. Note that, organic compound layers except for the emission layer can be formed as continuous layers common to multiple organic EL elements in each vacuum chamber, or can be formed for each organic EL element in the same manner as the emission layer. 
     In addition,  FIG. 7  is a schematic diagram illustrating a state in which a force is applied to the backside of the substrate so that the surface of the second insulating layer on the substrate is pressed to the vapor deposition mask surface in the manufacturing process of the organic EL display device according to this embodiment. During a period after the vapor deposition mask  19  is positioned with respect to the substrate until the vapor deposition of the emission layer  24  is finished, it is necessary to maintain a relative position and a contact state between the substrate and the vapor deposition mask  19  to be stable. For instance, as illustrated in  FIG. 7 , it is preferred to make a state in which the upper surface of the second insulating layer  12  on the substrate is pressed to the vapor deposition mask surface, by adopting a structure in which the backside of the substrate  10  is pressed by a spring using a spring load structure  30  disposed on the backside of the substrate  10 . 
     Even in the pressed state, in the manufacturing method of the organic EL display device according to this embodiment, because the second insulating layer  12  has the recesses  17 , the contact area between the second insulating layer  12  and the vapor deposition mask  19  can be reduced. Therefore, it is possible to suppress an influence that the second insulating layer  12  is damaged by the foreign substance adhered to the vapor deposition mask  19 . 
     In addition, as another means for maintaining the contact state between the substrate and the vapor deposition mask  19  to be stable, although illustration is omitted, it is possible to use a method of disposing a magnet on the substrate backside so as to attract the vapor deposition mask  19  to the substrate by a magnetic force. In this case, it is necessary to constitute the vapor deposition mask  19  of a ferromagnetic material, and for example, Invar material, Ni, or stainless steel except austenitic stainless steel can be used. 
     Note that, the exemplified shape of the vapor deposition mask  19  does not limit a range to which the present invention is applied, and various known vapor deposition masks can be used. 
     The process after that has the same procedure as the manufacturing method of an ordinary organic EL display device. Although illustration is omitted, for example, a transparent conductive layer made of a translucent Ag alloy thin film and an indium zinc oxide is laminated on the organic compound layer, to thereby form the second electrode. Next, a protection film made of silicon nitride is formed on the transparent conductive layer. Next, a thermosetting resin is applied onto the protection film and a perimeter of the substrate. A substrate made of glass, for example, is adhered onto the resin, so as to seal by heating. 
     According to the manufacturing method described above, it is possible to obtain the top emission organic EL display device, which reflects the light generated in the emission layer of the organic compound layers by the surface of the first electrode  11  including the Ag alloy film, and outputs the light through the second electrode constituted of layers including the translucent Ag alloy thin film. 
     According to the organic EL display device and the manufacturing method therefor according to this embodiment, the opening  15  is formed between neighboring first electrodes in the first insulating layer  11 , and the second insulating layer  12  is formed so as to surround the first electrode  13  in the region overlapping with the opening  15 . Thus, the recess  17  is formed in the vertical direction of the substrate in the surface of the second insulating layer  12  to be brought into contact with the vapor deposition mask  19 , and hence the contact area between the second insulating layer  12  and the vapor deposition mask  19  can be reduced. In other words, without increasing the number of steps and manufacturing cost, in the process of applying different color emission layers using the vapor deposition mask  19 , the second insulating layer  12  hardly suffer from abrasion, scratch, or other damage, and hence it is possible to reduce a risk of a short-circuit or a leakage between electrodes due to moisture invasion. 
     As mentioned above, the exemplary embodiment of the present invention is described, but this is an example for describing the present invention. The present invention can be embodied in various forms different from the above-mentioned embodiment in the scope without deviating from the spirit of the present invention. 
     For instance, in the embodiment described above, the opening  15  and the recess  17  are formed in a linear shape as illustrated in the plane structure of  FIG. 2 . The present invention is not limited thereto. The shapes, the lengths, and the widths of the opening  15  and the recess  17  can be selected arbitrary as illustrated in  FIGS. 8A to 8C , as long as the contact area between the vapor deposition mask  19  and the second insulating layer  12  can be reduced. 
       FIGS. 8A to 8C  are schematic diagrams each illustrating plane structures of the recess in the second insulating layer and the opening in the first insulating layer in the organic EL display device of this embodiment. As illustrated in  FIGS. 8A to 8C , for example, the opening  15  as a base of forming the recess  17  may be formed in a plane direction in a broken line shape (see  FIG. 8A ), or in a grating shape (see  FIG. 8B ), or may be disposed as a combination of multiple opening shapes (see  FIG. 8C ). 
     Note that, the opening  15  having a rectangular shape is shown here, but the shape or the layout of the opening in the present invention is not limited to the rectangular shape. For instance, a circular shape, an elliptical shape, or a triangular shape may be adopted. 
     Note that, if the opening  15  having the grating shape as illustrated in  FIG. 8B  is formed, it is possible to form the opening  15  so as to communicate to the contact hole  16  that can electrically connect the first electrode  13  to the drain electrode of the transistor. 
     In addition, in order to reduce ambient light reflection by the recess  17  in the second insulating layer  12 , it is possible to form a layer having a light absorbing function in the region overlapping with the recess  17 . 
     Further, an example of the display device of an active matrix type is described in the embodiment described above, but the present invention can be applied also to a display device of a simple matrix type. 
     Hereinafter, examples are used for describing the organic EL display device and the manufacturing method therefor of the present invention in more detail, but the present invention is not limited to those examples. Note that, as described above, for convenience sake of description, each layer is illustrated in a recognizable size and in an exaggerated manner in the drawings. Therefore, the scale of the drawings does not always correspond to the dimensions exemplified in the following examples. 
     Example 1 
     With reference to  FIGS. 1A and 1B ,  2 , and  3 A to  3 E, a manufacturing method for the organic EL display device according to Example 1 is described.  FIG. 1A  schematically illustrates a cross sectional structure of one pixel region, and illustrates a state where the hole transport layer  22  is formed to have the same thickness in all pixels. When multiple pixels having the cross sectional structure illustrated in  FIG. 1A  are arranged in matrix, a display region of the organic EL display device is constituted. In addition, three sub-pixels including p 1 , p 2  and p 3  are arranged in parallel in one pixel region. Note that, the organic EL display device described here has a pixel pitch of 191 μm and a sub-pixel size of 64 μm×191 μm. 
     As illustrated in  FIGS. 1A and 3A , transistors are formed correspondingly to individual sub-pixels on the substrate  10 . Note that, in  FIGS. 1A and 1B , only gate lines  25  of the transistors, the gate insulating layer  26 , and a passivation layer (insulating layer)  27  are illustrated. In order to flatten unevenness of the substrate  10 , the first insulating layer  11  is first formed on the substrate. Next, as illustrated in  FIG. 3B , the linear openings  15  having a width tx are formed between the first electrodes  13  and  13  of the individual sub-pixels p 1 , p 2  and p 3  in the first insulating layer  11 . Here, the thickness of the first insulating layer  11  is set to 2 μm so that unevenness of the substrate can be sufficiently flattened. The depth d of the opening  15  is set to 2 μm, and the width tx of the opening  15  is set to 20 μm. Note that, the plane structure of the openings  15  formed in the first insulating layer  11  is as illustrated in  FIG. 2 . 
     The first insulating layer  11  described above is formed by applying a positive photosensitive resist containing polyimide using the spin coating method, irradiating regions to remove with exposing light, and performing a developing step and a baking step after that. Here, the regions to remove correspond to the openings  15 , the contact holes  16  for electrically connecting the drain electrodes of the transistors to the first electrodes  13 , and lead-out terminal portions (not shown) outside the display region. 
     Next, as illustrated in  FIG. 3C , the material for forming the first electrode  13  is deposited on the entire surface of the first insulating layer  11 . Here, a conductive oxide material containing indium tin oxide (ITO) is deposited by the sputtering method as an adhering layer to have a thickness of approximately 20 nm. On the ITO layer, a silver alloy is deposited by the sputtering method to have a thickness of approximately 100 nm. Further, on the silver alloy film, ITO is deposited by the sputtering method to have a thickness of approximately 10 nm. After that, as illustrated in  FIG. 3D , a pattern of the multiple first electrodes  13  corresponding to individual pixels is formed by etching using the mask that is the resist pattern formed by usual photolithography. 
     After that, in order to form the second insulating layer  12 , the positive photosensitive resist containing polyimide is applied by the spin coating method onto the substrate on which the first electrodes  13  are formed, and the predetermined regions to remove are irradiated with exposing light. Here, the second insulating layer  12  having pixel apertures that exposes the first electrodes  13  and covers ends of the first electrodes  13  is formed. This second insulating layer  12  is formed by the same process as the first insulating layer  11  described above, except for an exposure region. 
     Thus, as illustrated in  FIG. 3E , the second insulating layer  12  formed to enclose the perimeters of the first electrodes  13  includes the linear recesses  17  reflecting the openings  15  formed between neighboring first electrodes  13  and  13  in the first insulating layer  11 . Here, the second insulating layer  12  is formed to have a thickness of 2 μm, a width Wx of 25 μm, a recess width cx of 18 μm, and a recess depth g of approximately 1 μm. Note that, the second insulating layer  12  has a width Wy of 15 μm. Note that, S 1  and S 2  which are formed in the insulating layer  12  and which are regions in which height of the recesses are made high each have a width of 1 μm. 
     As illustrated in  FIG. 1A , the hole transport layer  22  having a thickness of approximately 80 nm is formed on the entire surface of the display region on the substrate  10  described above by the vacuum deposition method. After that, the color emission layers are formed in the sub-pixels of red, green, and blue colors, respectively. As illustrated in  FIG. 1B , when the vapor deposition of the emission layer is performed in the sub-pixel p 2 , the vapor deposition mask  19  having the opening portion for exposing the first electrode  13  of the sub-pixel p 2  is brought into contact with the hole transport layer  22  deposited on the surface (protrusion) of the second insulating layer  12 . 
     Note that, at the recess  17  in the second insulating layer  12 , because the recess  17  has the depth g (1 μm) that is sufficiently larger than the thickness (80 nm) of the hole transport layer  22 , the vapor deposition mask  19  is not brought into contact with the hole transport layer  22 . 
     In this way, an evaporated substance  23  is deposited through the opening portion of the vapor deposition mask  19  so as to cover the first electrode  13  of the sub-pixel p 2 , and hence the emission layer  24  is formed and patterned. Note that, the contact area between the vapor deposition mask  19  and the hole transport layer  22  on the second insulating layer  12  can be reduced by approximately 30% with respect to the case where the recesses  17  are not formed. 
     Other emission layer patterns of the sub-pixels p 1  and p 2  are also formed using the vapor deposition mask  19  in the same manner. After that, the electron transport layer and the electron injection layer are formed as common layers successively in the individual vacuum chambers. 
     The process after that has the same procedure as the manufacturing method of the ordinary organic EL display device. Although illustration is omitted, for example, a transparent conductive layer made of a translucent Ag alloy thin film and IZO is laminated on the organic compound layer, to thereby form the second electrode. Next, a protection film made of silicon nitride is formed on the transparent conductive layer. Next, a thermosetting resin is applied onto the protection film and a perimeter of the substrate. A substrate made of glass, for example, is adhered onto the resin, so as to seal by heating. 
     According to the manufacturing method described above, it is possible to obtain the top emission organic EL display device, which reflects the light generated in the emission layer of the organic compound layers by the surface of the first electrode  11  including the Ag alloy film, and outputs the light through the second electrode  12  constituted of layers including the translucent Ag alloy thin film. 
     According to the organic EL display device and the manufacturing method therefor according to Example 1, the opening  15  having a depth of 2 μm and a width of 20 μm  12  is formed between neighboring first electrodes in the first insulating layer  11 , and the second insulating layer  12  is formed so as to surround the first electrode  13  while including the region overlapping with the opening  15 . Further, the surface of the second insulating layer  12  that is brought into contact with the vapor deposition mask  19  includes the recesses  17  having a depth of 1 μm in the vertical direction of the substrate and a width of 18 μm. Thus, the contact area between the vapor deposition mask  19  and the hole transport layer  22  on the second insulating layer  12  can be reduced by approximately 30% compared with the case where the recesses  17  are not formed. 
     The number of pixel defects due to abrasion or scratch on the second insulating layer  12  was compared between the case where the recesses were not formed in the second insulating layer  12  as a comparative example and the case where the recesses  17  were formed as Example 1. As a result, the number of pixel defects could be reduced by approximately 20% in Example 1. 
     Example 2 
     With reference to  FIG. 7 , a manufacturing method for an organic EL display device according to Example 2 is described.  FIG. 7  illustrates a process of forming the emission layer in the sub-pixel. Note that, the substrate described in this example has a size of 60 mm×460 mm×0.5 mmt, and 5×5 panel regions are disposed. In each panel region, the structure of the transistor, the first insulating layer  11 , the first electrode  13 , and the second insulating layer  12  formed on the substrate  10  is the same as in Example 1. 
     As illustrated in  FIG. 7 , when the vapor deposition of the emission layer is performed, the vapor deposition mask  19  having the opening that exposes the first electrode  13  in the sub-pixel p 2  is positioned so as to contact with the hole transport layer  22  deposited on the surface of the second insulating layer  12 . Particularly in this example, after positioning the substrate with respect to the vapor deposition mask  19 , the substrate is pressed to the vapor deposition mask  19  by an urging force of the spring load structure  30  disposed on the backside of the substrate, and under this state, the emission layer  24  is formed. Note that, the number of points of the spring load is set to 50 in the substrate surface, and a load at each point is set to 10 g. 
     According to the organic EL display device manufactured by the same method as in Example 1 except for the above description, the contact area between the vapor deposition mask  19  and the hole transport layer  22  on the second insulating layer  12  can be reduced similarly to Example 1. In addition, it is possible to maintain the relative position and the contact state between the substrate and the vapor deposition mask  19  to be stable during the period after the vapor deposition mask  19  is positioned with respect to the substrate until the vapor deposition of the emission layer is finished. 
     The number of pixel defects due to abrasion or scratch on the second insulating layer  12  when the above-mentioned load was applied to the substrate backside was compared between the case where the recesses were not formed in the second insulating layer  12  as a comparative example and the case where the recesses  17  were formed as Example 2. As a result, the number of pixel defects could be reduced by approximately 20% in this example. In addition, good mask vapor deposition accuracy of ±10 μm or smaller could be achieved in all of 5×5 panel regions in the substrate. 
     Example 3 
     With reference to  FIG. 8B , a manufacturing method for an organic EL display device according to Example 3 is described.  FIG. 8B  schematically illustrates a plane structure of a 3×2 sub-pixel region, and multiple sub-pixel regions are disposed in matrix so that the display region of the organic EL display device is constituted. 
     The second insulating layer  12  illustrated in  FIG. 8B  is formed so as to have the recesses  17  reflecting the openings  15  by forming the grating-like openings  15  in the peripheries of the first electrodes  13  in the first insulating layer  11 . The grating-like opening  15  is formed to communicate to the contact hole  16  that can electrically connect the first electrode  13  to the drain electrode of the transistor. 
     The opening  15  having a depth of 2 μm and a width of 20 μm is formed in the first insulating layer  11  between the first electrodes neighboring in an X direction in  FIG. 8B , and the second insulating layer  12  is formed to surround the first electrode  13  while including the region overlapping with the opening  15 . Thus, the surface of the second insulating layer  12  contacting with the vapor deposition mask  19  has the recesses  17  having a depth of 1 μm in the vertical direction of the substrate and a width Cx of 18 μm. In addition, the opening  15  having a depth of 2 μm and a width of 10 μm is formed in the first insulating layer  11  between the first electrodes neighboring in a Y direction in  FIG. 8B , and the second insulating layer  12  is formed to surround the first electrode  13  while including the region overlapping with the opening  15 . Thus, the surface of the second insulating layer  12  contacting with the vapor deposition mask  19  has the recesses  17  having a depth of 1 μm in the vertical direction of the substrate and a width Cy of 12 μm. Note that, the second insulating layer  12  has a thickness of 2 μm. 
     According to the organic EL display device manufactured by the same method as in Example 1 except for the above description, the contact area between the vapor deposition mask  19  and the hole transport layer  22  on the second insulating layer  12  can be reduced by approximately 60% compared with the case where the recesses are not formed. 
     The number of pixel defects due to abrasion or scratch on the second insulating layer  12  was compared between the case where the recesses were not formed in the second insulating layer  12  as a comparative example and the case where the recesses  17  were formed as Example 3. As a result, the number of pixel defects could be reduced by approximately 50% in this example. 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     This application claims the benefit of Japanese Patent Application No. 2010-183874, filed Aug. 19, 2010, which is hereby incorporated by reference herein in its entirety.