Abstract:
An opposing substrate which is subjected to desiccant application, baking, UV cleaning, UV sealant application, or the like and an element substrate having EL elements formed thereon are affixed together by applying a sealing liquid such as silicon oil in a vacuum. Subsequently, when exposed to a normal atmosphere, the opposing substrate and the element substrate are adsorbed to each other while a predetermined gap is maintained in between. In this state, the UV sealant is cured with UV irradiation. It is thus possible to enclose the sealing liquid between the opposing substrate and the element substrate using a simple manufacturing method.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a method of manufacturing an organic EL panel, in which an EL (electroluminescence) element substrate having a plurality of EL elements formed thereon and an opposing substrate facing the EL element substrate are laminated together to form an organic EL panel. 
   2. Description of Related Art 
   Conventionally, organic EL (ElectroLuminescence) panels, one type of flat display device, have attracted attention as self-emissive display panels. An organic EL panel is produced by first forming a large number of EL elements on a glass substrate (an element substrate) by evaporation of various materials and then laminating an opposing substrate (cap glass, sealing substrate) onto an element forming surface of the element substrate. In such an organic EL panel, moisture must be excluded because the organic EL elements will significantly deteriorate if exposed to moisture. Further, in order to protect the organic EL elements from external damage, after formation of the EL elements, the opposing substrate is laminated onto the element substrate such that the EL elements are covered with the opposing substrate. 
   A method of manufacturing an organic EL panel according to the related art will be described with reference to  FIGS. 1 ,  2 A to  2 D,  3 A and  3 B. First, an opposing substrate (cap glass) is prepared and a desiccant is applied to the opposing substrate (S 1 ). More specifically, as shown in  FIG. 2A , a desiccant  42  is applied to an etching pocket  64  formed on a panel region of the glass substrate  60  by etching. Then, the whole system is baked in an oven (S 2 ). As a consequence, a solvent or the like evaporates from the desiccant  42  and the desiccant  42  is activated. Then, after cleaning a surface of the substrate  60  by UV irradiation (S 3 ), a UV sealant is applied on the surface to form a UV sealing member  66  on planar portions surrounding the etching pocket  64 , as shown in  FIG. 2B . A region surrounded by this UV sealing member  66  corresponds to the panel region. 
   Next, as shown in  FIG. 2C , an element substrate  10  is laminated on the cap glass  60  with a gap maintained between these two layers, while UV radiation is applied under pressure (S 5 ). This lamination is carried out in a dry nitrogen gas (N 2 ) atmosphere so that dry N 2  is enclosed in a space surrounded by the UV sealing member  66  (a sealed space). At this point, EL elements are formed on the element substrate  10 . More specifically, each organic EL element comprises an anode  12 , an emissive element layer  20  having at least an emissive layer, and a cathode  14 , which may be accumulated, for example, in that order, on the element substrate  10  made of glass or the like. The organic EL element has a passive matrix configuration in which the anodes  12  and the cathodes  14  are disposed in respective, orthogonal striped patterns with the emissive element layer  20  interposed therein between, or an active matrix pattern in which a thin film transistor or the like is provided for each pixel (not shown), and the anode  12  is individually formed for each pixel whereas the cathode  14  is formed as a common electrode for all the pixels. 
   While a region corresponding to only a single organic EL panel is shown in  FIGS. 2A to 2D , when a plurality of panels are formed from a single large-size substrate, each of the cap substrate  60  and the element substrate  10  includes a plurality of panel regions which are partitioned from each other by a plurality of sealing members  66 . Therefore, the cap glass  60  and the element substrate  10  which have been bonded together are cut into individual panels (S 6 ) to thereby form the individual organic EL panels. 
   More specifically, as shown in  FIG. 3A , a plurality of etching pockets  64 , each corresponding to one of the individual organic EL panels, are formed in the cap glass (substrate)  60 . Further, as shown in  FIG. 3B , the thickness of the cap glass  60  is set to approximately 700 μm and the depth of the etching pocket  64  is set to approximately 300 μm. 
   It is also possible to inject silicon oil rather than enclosing dry N 2  in the individual panels. When this is done, as in the case of a liquid crystal display, an injection opening  68  is formed in part of the UV sealing member  66  of an individual organic EL panel as shown in  FIG. 2D , and the silicon oil is injected through the injection opening  68  into the interior space of the individual panel which has been cut (S 7 ). After injection of silicon oil, the injection opening  68  is sealed (S 8 ), and the organic EL panel is thus completed. 
   However, with the above-described configuration in which dry nitrogen is enclosed between the opposing substrate  60  and the element substrate  10 , it is difficult to maintain a gap between the substrates in the sealed space where nitrogen only exists, and this may cause the opposing substrate  60  to come in contact with the elements and damage them when the opposing substrate  60  is deformed due to external pressure or the like. These problems are likely to occur as the panel size increases. 
   When silicon oil is injected, on the other hand, it is necessary to seal the injection opening formed in part of the UV sealing member  66  after injection, which complicates the assembly and manufacturing procedures. 
   Further, when dry nitrogen is enclosed between the opposing substrate  60  and the element substrate  10  according to the above-described manufacturing method, there is a possibility that an excessive amount of nitrogen gas may be enclosed in the sealed space, for example, due to misalignment in bonding the two substrates. Enclosure of excessive nitrogen would increase the pressure in the sealed space of the panel, leading to a problem that the opposing substrate  60  is likely to be unstuck from the element substrate. 
   SUMMARY OF THE INVENTION 
   The present invention is made in view of the foregoing disadvantages and aims to provide a simple manufacturing method capable of securing a sealed space for reliably protecting the organic EL elements or the like between an element substrate and an opposing substrate. 
   In accordance with one aspect of the present invention, there is provided a method of manufacturing an electroluminescence panel in which an opposing substrate is laminated on an element substrate on which a plurality of electroluminescence elements are formed, to thereby form an electroluminescence panel, the method comprising the steps of forming a sealing member which defines a periphery of one electroluminescence panel region on either one of the element substrate or the opposing substrate, applying a drop of sealing liquid to fill the panel region bounded by the sealing member in a vacuum, and affixing the element substrate and the opposing substrate together with the sealing member. 
   In accordance with another aspect of the present invention, in the above method, after the element substrate and the opposing substrate are brought into contact with each other via the sealing member in a vacuum, the element substrate and the opposing substrate having the sealing member in between are exposed to atmospheric pressure and then the sealing member is cured. 
   In accordance with another aspect of the present invention, there is provided a method of manufacturing an electroluminescence panel in which an opposing substrate is laminated on an element substrate on which a plurality of electroluminescence elements are formed, to thereby form an electroluminescence panel, the method comprising the steps of forming a sealing member which defines a periphery of one electroluminescence panel region in a jointless manner on either one of the element substrate or the opposing substrate, applying a drop of sealing liquid to fill the panel region bounded by the sealing member in a vacuum, and adhering the element substrate and the opposing substrate together with the sealing member. 
   In accordance with a further aspect of the present invention, there is provided an electroluminescence panel comprising an element substrate on which a plurality of electroluminescence elements are formed, and an opposing substrate laminated onto the element substrate, wherein a sealing member for bonding the element substrate and the opposing substrate together defines a periphery of one electroluminescence panel region in a jointless manner, and the panel region which is bounded by the sealing member and sealed is filled with a sealing liquid. 
   In this manner, in a vacuum, a drop of sealing liquid such as silicon oil is applied onto the panel region and the element substrate and the opposing substrate are adhered together with a sealing member. Therefore, the necessity of forming an injection opening in the sealing member can be eliminated. The sealing member is formed in a jointless manner and therefore requires no sealing operation of the injection opening. Further, because the substrates are bonded together in a vacuum, even when some space is formed between the substrates and the sealing liquid, such a space would disappear when the substrates are returned to a normal atmosphere. Accordingly, an organic EL panel can be manufactured using a very effective lamination operation. 
   In accordance with another aspect of the present invention, in the above manufacturing method, it is preferable that the sealing member is formed on the opposing substrate and injection of a sealing liquid and affixing of the opposing substrate and the element substrate is performed in a vacuum, with the opposing substrate disposed in substantially the horizontal direction such that the sealing member is located on top of the opposing substrate. 
   In accordance with a further aspect of the present invention, it is preferable that when a desiccant is provided within a sealed space, the desiccant is fixed to a concave portion formed on the electroluminescence panel region of the opposing substrate and the sealing member is formed on the opposing substrate having the desiccant thus fixed. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other objects of the invention will be explained in the description below, in connection with the accompanying drawings, in which: 
       FIG. 1  is a flowchart showing a manufacturing method of a panel according to a related art; 
       FIGS. 2A ,  2 B,  2 C and  2 D show the manufacturing process of a panel according to a related art; 
       FIGS. 3A and 3B  are diagrams showing a substrate configuration according to a related art; 
       FIG. 4  is a flowchart showing a manufacturing method of a panel according to an embodiment of the present invention; 
       FIGS. 5A ,  5 B,  5 C and  5 D show the manufacturing process of a panel according to the embodiment of the present invention; 
       FIGS. 6A and 6B  are diagrams showing a substrate configuration according to the embodiment of the present invention; and 
       FIGS. 7A ,  7 B, and  7 C show a manufacturing process of a panel according to another embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   A method of manufacturing an organic EL panel according to an embodiment of the present invention will be described with reference to  FIGS. 4 ,  5 A to  5 D,  6 A,  6 B, and  7 A to  7 C. First, an opposing substrate (cap glass: sealing substrate)  40  is prepared and a paste of a desiccant  42  is applied to the substrate  40  (S 11 ). A desiccant paste is a solvent containing a mixture of Ba oxide, Ca oxide or the like. As shown in  FIG. 5A , an etching pocket  44  is formed in the panel region of the cap glass  40  by etching, and the desiccant  42  is applied to this etching pocket  43 . Then, the whole product is baked at about 140° C. or more in an oven (S 12 ). As a result, a solvent or the like evaporates from the desiccant  42  and the desiccant  42  is activated. Next, a surface of the substrate  40  is cleaned with UV irradiation having an energy of 10 mW/cm 2  or greater. Thereafter, a UV sealing member  46  is applied to the substrate  40  such that it projects from a planar surface of the cap glass  40 . More specifically, the UV sealing member  46  is formed on the planar portion of the substrate  40  around the etching pocket  44 . The region surrounded by the UV sealing member  46  corresponds to the panel region (a sealed region). The UV sealing member  46  is made of an epoxy UV resin, for example, and has a height of approximately 30 to 50 μm. 
   Then, in a vacuum (10 −3  Torr or less; 1 Torr≈133 Pa), silicon oil  30  is dropped into the panel region enclosed by the UV sealing member  46  as shown in  FIG. 5C . Because the cap glass  40  is disposed facing upward, the region enclosed by the UV sealing member  46  can be filled with the silicon oil  30  which is dropped. Thereafter, as shown in  FIG. 5D , an element substrate  10  is brought in contact with the cap glass  40  in a vacuum (S 15 ). In this manner, a space between the cap glass whose periphery is enclosed by the UV sealing member  46  and the element substrate  10  is filled with the silicon oil (although some gas may be contained). The element substrate  10  has a passive matrix type or active matrix type configuration which comprises an organic EL element including an anode  12  formed by ITO or the like, an emissive element layer  20  and a cathode  13  formed by Al or the like. The emissive element layer  20  includes, from the anode side, a hole transport layer, an emissive layer, an electron transport layer and an electron injecting layer, for an example. 
   The two substrates which are thus affixed together (temporarily adhered to each other) are then exposed to the atmosphere. Then, due to a difference between the atmospheric pressure and the decompressed pressure within the sealed space, the element substrate  10  and the opposing substrate  40  are firmly affixed to each other with a gap (GAP) thereinbetween determined in accordance with the height and elasticity of the sealing member  46 , an amount of applied silicon oil, or the like. In this state, the UV sealing member  46  is cured by a UV irradiation having an energy of 300 mJ/cm 2  or greater. 
   After the UV sealing member  46  is cured, the cap glass  40  and the element substrate  10  are cut into individual panels (S 17 ) to thereby complete individual organic EL panels. 
   Each of the cap substrate  40  and the element substrate  10  used in this embodiment includes a plurality of panel regions which are partitioned from each other by a plurality of UV sealing members  46 , as shown in  FIG. 6A . By cutting the substrate along the periphery of each panel, more accurately, between two sealing members disposed between adjacent panel regions, the individual panels can be formed. Further, as shown in  FIG. 6B , a plurality of etching pockets  44  each corresponding to one of the individual organic EL panels, are formed on the cap glass (substrate)  40 . The thickness of the cap glass  40  is set to approximately 700 μm, and the depth of the etching pocket  44  is set to approximately 300 μm. 
   As described above, according to the present embodiment, by enclosing the silicon oil  30  to temporarily adhere the element substrate  10  and the cap substrate  40  to each other in a vacuum and then exposing these substrates to the atmospheric pressure, these substrates are firmly adsorbed to each other to automatically thereby determine a gap between them. Therefore, contrary to the conventional method, there is no need to provide an injection opening or the like in the UV sealing member  46  or to seal such an injection opening, and injection of silicon oil into the sealed space can be completed simultaneously with the gap formation (simultaneously with adhering), enabling simple and reliable sealing operation with less variation in the sealed states. Further, because the silicon oil is enclosed in the sealed space, the opposing substrate  40  is reinforced even when the size of a cell (individual EL panel) is increased. Also, because the elements formed on the element substrate  10  are spaced from the opposing substrate  40  by the silicon oil, the possibility of contact between the opposing substrate  40  and these elements can be reduced. Further, according to the present invention, the two substrates are automatically adsorbed with each other because of the difference in pressures when affixing the substrates together (when forming a gap). As a result, it is not necessary to pressurize the substrates, which eliminates one possible cause for breaking of the cap glass during lamination. In addition, because the substrates are affixed together in a vacuum, even when some space is formed between the substrates and the silicon oil  30 , such a space will disappear when the substrates are returned to the atmosphere, and the lamination operation can be performed very easily. Of course, even when some gas remains within the sealed space, it is unlikely that such a gas will have any significant affect on the elements, because a slight amount of dry nitrogen or the like remains within the vacuum atmosphere. 
     FIGS. 7A to 7C  show another embodiment of the present invention. In this example, no desiccant is provided within the sealed space. Namely, an etching pocket is not formed in a cap glass  50  so that a surface of the cap glass  50  remains flat. According to this embodiment, UV sealing members  46  are provided on the planer surface of the cap glass  50  so as to define the panel regions. Then, in a vacuum, silicon oil is injected and the element substrate  10  is laminated to the cap glass  50 . The substrates are then exposed to the atmospheric pressure, the UV sealing member  46  is cured by UV irradiation, and the glass is cut into individual panels. 
   As described above, even when a desiccant is not used, by injecting silicon oil and affixing the substrates together in a vacuum, it is possible to effectively manufacture an EL panel without intrusion of moisture into the sealed space. Further, because the need of forming a pocket  44  into which a desiccant is provided is eliminated, the cap glass  50  can have an even thickness of 700 μm, for example, over the entire surface, so that the cap glass  50  has higher strength than the glass  50  having an etching pocket  44  formed therein. 
   While silicon oil is enclosed in the sealed space in the above examples, any sealing liquid (fluid) other than silicon oil may be employed as long as it has an insulation property, sufficient chemical stability, moisture-resistant property, and a relatively high boiling point. 
   As described above, because with the present invention silicon oil is enclosed and the substrates are affixed together in a vacuum, there is no need to form an injection opening or the like in the sealing member, which further eliminates the need for sealing of the injection opening. Further, because the substrates are affixed in a vacuum, even when some space is formed between the substrates and the silicon oil  30 , the space will disappear when the substrates are returned to a normal atmosphere. It is therefore possible to manufacture an organic EL panel using a very effective lamination operation. 
   While the preferred embodiments of the present invention have been described using specific terms, such description is for illustrative purposes only, and it is to be understood that changes and variations may be made without departing from the spirit or scope of the appended claims.