Abstract:
Providing a technology capable of coping with the problem in accuracy of the electrode pattern forming caused by high density formation of an electrode and the like, according to higher definition of a PDP. A plurality of address electrodes, which are formed, for example, on a front face of a back glass substrate, have an electrode terminal in a peripheral portion of a PDP. The back glass substrate on the peripheral portion has a conduction hole, passing between the front face and a back face, provided therein. On the peripheral portion, a first group of the electrodes terminals of the plurality of address electrodes are formed and disposed as front electrodes on the front face, and a second group of electrodes terminals are formed and disposed as back electrodes so as to extend up from the front face to the back face through the conduction hole and a conduction electrode.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present application claims priority from Japanese patent application No. JP 2006-205574 filed on Jul. 28, 2006, the content of which is hereby incorporated by reference into this application. 
       TECHNICAL FIELD OF THE INVENTION 
       [0002]    The present invention relates to a technology of a plasma display panel (PDP) and a display apparatus including the same, particularly to a structure of an electrode terminal portion formed on a panel. 
       BACKGROUND OF THE INVENTION 
       [0003]    In conventional PDPs, a terminal of an electrode (a terminal portion) is formed and disposed on one face side (in particular, an inner face of a panel on which an element or a structure is formed) of a substrate (glass substrate), in both a front substrate and a back substrate. In general, conventional methods for forming an electrode terminal portion in a PDP and structures of such a terminal portion are largely classified into two kinds. One method (a first method) is a method in which a metal material (which in many cases has a three-layer structure of Cr (chromium), Cu (copper), and Cr) composing an electrode structure (electrode pattern) including a terminal portion, is formed on a glass substrate by photolithography. The other method (a second method) is a method in which a structure composed of a metal glass paste (a paste material mainly composed of Ag (silver) and including glass) is formed on a glass substrate by pattern printing or by photosensitive paste printing plus photolithography. 
         [0004]    As a PDP has a higher definition in recent years, the pitch of formation and disposition of an electrode including a terminal portion, of a PDP has tended to be narrower. 
         [0005]    As a PDP has a higher definition, the second method that uses a metal glass paste as mentioned above is preferable as a method for forming an electrode including a terminal portion in a PDP, in securing electrical connectivity. However, the second method has a problem in securing accuracy of the electrode pattern forming. Besides, a problem of migration (ionic migration) specific to an Ag material, particularly to one used as a metal glass paste, has become more serous. Specifically, a short circuit between electrode terminal portions caused by migration would cause a malfunction in the apparatus. 
         [0006]    Some manufacturers use Au (gold) paste printing to form an electrode terminal portion in order to avoid the above-mentioned migration. However, in such an Au paste printing, using pattern printing, which is a low cost, causes a problem in accuracy of the electrode pattern forming. 
         [0007]    Therefore, it is desirable to form the electrode pattern on a substrate by the second method as a method for manufacturing a PDP, preferably using an AG or Au material as a metal glass paste, as well as to secure accuracy of the electrode pattern forming. 
       SUMMARY OF THE INVENTION 
       [0008]    In view of the foregoing, it is an object of the present invention to provide a technology capable of coping with the problem in accuracy of the electrode pattern forming caused by high density formation/disposition of an electrode according to higher definition of a PDP, more specifically, reduced pitches between electrode terminal portions, migration, and the like, without dependence on selection of an electrode material. 
         [0009]    An outline of typical elements of the invention disclosed in this application is described briefly as follows. To achieve the above-mentioned object, the invention is a PDP technology and includes technological means and structures to be discussed later. 
         [0010]    To cope with above-mentioned problem, in a PDP according to the invention, devises in a panel structure, specifically, in forming and disposing an electrode terminal portion are performed. More specifically, in the PDP according to the invention, an electrode terminal portion is formed and disposed on both front and back faces of a main plate portion (typically, glass substrate) of at least one of a front substrate structure and a back substrate structure, on which an electrode pattern is formed and disposed. In conventional PDPs, the electrode terminal portion has been formed and disposed on either of front or back face of the substrate. By using the structure of the invention, addressing a higher definition PDP is achieved. Simply put, by forming and disposing an electrode terminal portion using both front and back faces of the substrate, it is made possible to cope with twice the degree of definition of a conventional PDP structure. 
         [0011]    The structure of the PDP is, for example, as follows. Basically, in the PDP, a first (front face) and a second (back face) substrates (substrate structure) both composed essentially of glass and the like are opposed and combined. A plurality of electrodes (X/Y electrodes, address electrode, etc.) of at least one type are formed and disposed on at least one face of at least one of the first and second substrates. An image is displayed by applying a voltage from an external drive circuit to the electrodes to utilize a discharge of gas sealed in a discharge space between the substrates. 
         [0012]    In the invention, terminals of the plurality of electrodes on the first face of the substrate of the PDP are disposed in a peripheral portion of the PDP so as to be electrically connected to an external circuit side. The terminal portions of the plurality of electrodes in the peripheral portion are formed and disposed on both the first and second faces separately using a hole portion and the like provided in the substrate. In groups of the terminal portions of the electrodes, one group (first group) is disposed on a front face (first face) and the other group (second group) is disposed on a back face (second face). By disposing the electrode terminal portions on the first and second faces separately, intervals between the electrode terminal portions become larger on one face. To establish conduction of an electrode from the first face to the second face, a hole portion (via hole, contact hole) is provided in a prescribed position of the substrate. An electrode portion (conduction electrode) is also formed in the hole portion using a conductive material. 
         [0013]    A method for manufacturing the PDP is, for example, as follows. 
         [0014]    (1) Hole portion forming step: The above-mentioned hole portion is formed in a prescribed position of the substrate composing the PDP, such as glass substrate, or a substrate structure including such a substrate, by machining using a drill, waterjet (ultra high water pressure) or the like. 
         [0015]    (2) Continuity electrode forming step: The conduction electrode for electrically connecting the electrode portion on the first face to the electrode portion on the second face is formed by embedding a conductive material in the hole portion of the substrate or filling the hole portion with the material, using either one or some of the second method, offset printing, inkjet, dispenser, die coat, or the like. 
         [0016]    (3) Front electrode forming step: A terminal portion (front electrode) is formed on the first face of the substrate using, for example, a similar method to that shown in the step (2). 
         [0017]    (4) Back electrode forming step: A terminal portion (back electrode) is formed on the second face of the substrate using, for example, a similar method to that shown in the step (3). 
         [0018]    (5) Electrode calcining step: After the steps (1) to (4) are performed, all the electrode portions are calcined. By this step, manufacturing the PDP is completed. As a matter of course, the electrode parts, such as the terminal portions on the first and second faces and the conduction electrodes portions, must be electrically connected, and insulated from adjacent electrodes. The order of the steps (2) to (4), associated with formation of the entire electrode pattern, may be changed. Alternatively, some of the steps may be combined or one step may be divided into some steps. 
         [0019]    An advantageous effect obtained by typical elements of the invention disclosed in this application is described briefly as follows. According to the invention, it is possible to cope with the difficulty with electrode pattern forming accuracy caused by high density formation/disposition of an electrode according to a higher definition of a PDP, more specifically, reduced pitches between electrode terminal portions, migration, and the like, without depending on selection of an electrode material. 
         [0020]    In particular, it is possible to cope with the migration problem that is attributed to a material, such as silver (silver glass paste), used as a material of an electrode including an electrode terminal portion, and thus to secure product reliability. Further, as with conventional PDPs, it is possible to use pattern printing, which is low cost, in forming an electrode, and thus to reduce the cost. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]      FIG. 1  is a drawing showing a configuration of a PDP according to an embodiment of the present invention, seen from a front side of the PDP. 
           [0022]      FIG. 2  is a drawing showing a configuration of a cross sectional view of the PDP according to an embodiment of the present invention. 
           [0023]      FIG. 3  is a drawing showing a configuration of an electrode terminal portion, and the like on front and back faces of a substrate in a part of a peripheral portion of the PDP according to an embodiment of the present invention. 
           [0024]      FIG. 4A  is a drawing showing a configuration of an electrode terminal portion and the like in a cross sectional view of the substrate at a position of the electrode terminal portion of the PDP according to a embodiment of the present invention. 
           [0025]      FIG. 4B  is a drawing showing a configuration of an electrode terminal portion and the like in a cross sectional view of the substrate at a position of a conduction hole of the PDP according to a embodiment of the present invention. 
           [0026]      FIG. 5  is a drawing showing a configuration of a electrical connection portion to an external circuit portion in a cross sectional view of the substrate in a part of a peripheral portion of the PDP according to a embodiment of the present invention. 
           [0027]      FIG. 6A  is a drawing showing a configuration of an electrode terminal portion and the like on a face of a substrate of a PDP according to a premised technique of the present invention. 
           [0028]      FIG. 6B  is a drawing showing a cross sectional view at a position of the electrode terminal portion to show a configuration of an electrode terminal portion and the like of a PDP according to a premised technique of the present invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0029]    An embodiment of the invention will be described in details with reference to the accompanying drawings. In the drawings, identical elements are basically denoted by the same reference symbols respectively and will not be described repeatedly.  FIGS. 6A and 6B  show a configuration of a premised technique of the invention to facilitate understanding of the invention. 
         [0030]    With reference to  FIGS. 1 to 5 , a three electrode surface discharge type PDP  10  according to the embodiment of the invention is described. In this embodiment, electrode terminal portions of address electrodes on a back substrate are formed alternately on front and back faces of a glass substrate. 
         [0031]    (Front Face of PDP) 
         [0032]    In  FIG. 1 , a configuration of the PDP  10  seen from a front face (display window) side is shown. The surface discharge type PDP  10  is mostly configured by combining a front substrate (front structure)  201  and a back substrate (back structure)  202 , both are composed mainly of a glass substrate. Discharge space between the front substrate  201  and the back substrate  202  is sealed by a sealing area (or sealing object, PDP sealing part)  203  and vacuum-hold. 
         [0033]    A display area  110  inside the sealing area  203  is an area in which an image, which corresponds to a matrix of cells composed of groups of various kinds of electrodes and the like, is displayed. Outside the sealing area  203 , there are provided extra areas that are used for electrical connection to an external drive circuit or other purposes. The front substrate  201  has an area  23   a  on both sides of  FIG. 1 , and the back substrate  202  has an area  23   b  at a top and a bottom of  FIG. 1 . An exhaust hole  125  is used when discharge gas is sealed in. 
         [0034]    Further, the PDP  10  is fixed and held on a chassis that is disposed on a back of the PDP  10 . A circuit portion, such as a drive circuit, disposed on the back of the chassis is electrically connected to the terminal portions of the electrodes of the PDP  10 . In this way, the PDP apparatus (PDP module) is configured. 
         [0035]    (Cross Section of PDP) 
         [0036]    Next, a configuration of a cross section of the PDP  10  will be described with reference to  FIG. 2 .  FIG. 2  illustrates a cross section of the PDP  10  in a transverse (row) direction. A cross section in a vertical (column) direction should be understood similarly. 
         [0037]    Discharge space  19  between the front substrate  201  and the back substrate  202  is sealed by the sealing area  203 , which is formed and disposed in a second area  22  of a peripheral portion (frame)  120  of the PDP  10 . 
         [0038]    On an inner face (downward face in  FIG. 2 ) of a front glass substrate  1  of the front substrate  201 , an X electrode  11  and a Y electrode  12 , which are both a plurality of display electrodes (sustain electrode) generating surface discharge, are formed so as to extend in a transverse direction, and then covered with a dielectric layer or the like. On an inner face (upward face in  FIG. 2 ) of a back glass substrate  2  of the back substrate  202 , a plurality of address electrodes  13 , which are used for address operation, are formed so as to extend in a vertical direction, and then covered with a dielectric layer or the like. Further, structures such as a partition wall  18  and a fluorescent substance (not shown) are formed on the inner face of the back glass substrate  2  including address electrodes  13 . The terminal portions of the various kinds of electrodes are electrically connected to a drive circuit portion side. 
         [0039]    (Premised Technique) 
         [0040]    Now a configuration of a PDP of a premised technique will be described with reference to  FIGS. 6A and 6B  for comparison. For example,  FIG. 6A  illustrates a structure of terminal portions of address electrodes  13  on a back substrate in a part of a peripheral portion of the PDP as seen from above the back glass substrate  2 . X electrodes and Y electrodes on a front substrate should be understood similarly. 
         [0041]    For convenience, the address electrodes  13  is structurally classified into three parts: an electrode body  131 , which lies in a first area  21  inside the sealing area  203 , a leader  132 , which lies in an second area  22  that partly overlaps the sealing area  203 , and an electrode terminal portion  133 , which lies on a third area  23  near an edge of the PDP. These parts are formed continuously using a conductive material. The electrode body  131  is a part that extends on a display area of the PDP. The electrode terminal portion  133  is a part that is electrically connected to a drive circuit side, and lies outside the sealing area  203  and extends up to a prescribed connecting position to outside near a side face of the PDP. The leader  132  is a part that electrically connects the electrode body  131  to the electrode terminal portion  133 . 
         [0042]      FIG. 6B  shows a cross section of the back glass substrate  2  and the address electrodes  13 , at a position of the electrode terminal portion  133 , of the PDP in  FIG. 6A . A plurality of electrode terminal portions  133  are formed only on a front side (A) of the back glass substrate  2 . For electrical connection to outside, the electrode terminal portions  133  are formed such that a width thereof is larger than that of the electrode body  131 . As the PDP has a higher definition, pitches (DO) between the adjacent electrode terminal portions  133  become increasingly narrower. Further, occurrence of migration in the electrode terminal portion  133  may cause a short circuit between the electrode terminal portions  133 . 
         [0043]    (Electrode Terminal Portion) 
         [0044]    Now a structure of a vicinity of the electrode terminal portion  133  will be described as a distinctive structure of the PDP  10  with reference to  FIG. 3 .  FIG. 3  illustrates structures of the address electrodes  13  on the back substrate  202  of the PDP  10  as seen from both the front side (A) and the back side (B) of the back glass substrate  2  in a part of the peripheral portion  120  of the PDP  10 . This distinctive structure can be also applied to the X electrode  11  and the Y electrode  12  on the front substrate  201 . 
         [0045]    For convenience, the peripheral portion  120  of the PDP  10  is classified into the first area  21  to the third area  23 . The first area  21  is an area near an end of the electrode body  131  in the display area  110 . The third area  23  is an area at an edge of the PDP  10 , in which the electrode terminal portion  133  is disposed. The second area  22  is an area between the first area  21  and the third area  23 , partly overlaps the sealing area  203 , and in which the leader  132  of the address electrodes  13  is disposed. 
         [0046]    The address electrode  13  is structurally classified into four parts: the electrode body  131 , which lies in the first area  21 , the leader portion  132 , which lies in the second area  22 , the electrode terminal portion  133 , which lies in the third area  23 , and the conduction electrode portion  134 , which is formed in the conduction hole  50 . Further, the electrode terminal portion  133  is classified into a front electrode  133 A, which lies on the front face (A) of the back glass substrate  2 , and a back electrode  133 B, which lies on the back face (B) of the back glass substrate  2 . 
         [0047]    As a conductive material to form an electrode pattern including the parts ( 131  to  134 ) of the address electrode  13 , for example, a silver paste is used. Electrical contact between the parts ( 131  to  134 ) of the electrode pattern is secured. 
         [0048]    The electrode body  131  extends straight in the display area  120  of the PDP  10 . The electrode terminal portion  133  is electrically connected to the drive circuit side, lies outside the sealing area  203  and extends to a prescribed connecting position to outside near a side face of the PDP  10 . The leader portion  132  partly overlaps the sealing area  203  and electrically connects the electrode body  131  to the electrode terminal portion  133 . 
         [0049]      FIG. 3  illustrates first to sixth address electrodes ( 13 - 1  to  13 - 6 ) of the address electrodes  13 , as examples, which are arranged sequentially with the first address electrode located at an end. The seventh and later address electrodes are arranged in the same way. The odd-numbered address electrodes ( 13 - 1 ,  13 - 3 ,  13 - 5 , . . . ) makes up a first group, and even-numbered ones ( 13 - 2 ,  13 - 4 ,  13 - 6 , . . . ) makes up a second group. 
         [0050]    On the back glass substrate  2 , the electrode terminal portions  133  of the first group of the address electrodes  13  are formed as front electrodes  133 A straight from the leader portions  132  up to a prescribed connecting position to outside near a side face of the PDP  10  on the front face (A), as with conventional PDPs. The electrode terminal portions  133  of the second group of the address electrodes  13  are formed as back electrodes  133 B on the back face (B). Therefore, the second group of the address electrodes  13  are disposed so as to extend from the leader portions  132  on the front face (A) through the conduction electrode portion  134  in the conduction hole  50  up to the back face (B), then to be electrically connected to the back electrodes  133 B, and further to extend up to a prescribed connecting position to outside. 
         [0051]      FIG. 4  illustrates cross sections of the back glass substrate  2  and the address electrodes  13  of the PDP  10  as shown in  FIG. 3 , at a position of the electrode terminal portion  133 . As shown in  FIG. 4A , the front electrodes  133 A, which are the first group of electrode terminal portions  133 , are formed at equal intervals on the front face (A) of the back glass substrate  2 , and the back electrodes  133 B, which are the second group of electrode terminal portions  133 , are formed at equal intervals on the back face (B). For electrical connection to outside, the electrode terminal portions  133  are formed such that a width thereof is larger than that of the electrode body  131 . The electrode terminal portions  133  are disposed alternately between the front face (A) and the back face (B), so pitches (D 1 ) between the adjacent electrode terminal portions  133  are sufficiently secured. 
         [0052]    As shown in  FIG. 4B , the conduction electrode portion  134  is formed in the conduction hole  50 , and the leader portion  132  on the front face (A) and the electrode terminal portion  133  on the back face (B) are electrically connected to the conduction electrode portion  134 . Although conduction hole  50  can be a simple cylindrical hole, in this embodiment, the conduction hole  50  has a taper shape portion  51  on both the front face (A) and the back face (B). Hence, electrical connection between the conduction electrode portion  134  and the leader portion  132 , and between the conduction electrode portion  134  and the electrode terminal portion  133  are secured or are made satisfactory. 
         [0053]    According to the above-mentioned configuration, it is possible to cope with reduced pitches between the adjacent electrode terminal portions  133  due to a high definition of the PDP  10 . Even if migration occurs in the electrode terminal portion  133 , it is possible to prevent a short circuit between the electrode terminal portions  133 . 
         [0054]    (Manufacturing Method) 
         [0055]    As a method for manufacturing the PDP  10 , a manufacturing method regarding the configurations as shown in  FIGS. 3 and 4  will be described. 
         [0056]    (1) To begin with, the conduction hole  50  is formed in the back substrate  2 . By machining (for example, lathe type minute hole processing machine), one conduction hole  50  is formed every two electrode terminal portions  133  of the address electrodes  13  to be formed, from an edge of the PDP  10 . In other words, the conduction hole  50  is formed in positions near ends of the leaders  132  outside the sealing area  203 , corresponding to the second group of electrodes in this embodiment, which are even-numbered ones. While the conduction hole  50  is provided near a electrical connection between the leader portion  132  and the electrode terminal portion  133  in this example, it can be provided in another position. 
         [0057]    A diameter of the conduction hole  50  is, for example, 50 μm or more to 500 μm or less. In forming the conduction hole  50 , peripheral portions of the conduction holes  50  are processed to form the taper shape portion  51  in order to strengthen electric contact between the electrode parts to be formed later, or the like. 
         [0058]    (2) Next, the conduction electrode portion  134  is formed in the conduction hole  50  by a method such as embedding a conductive material in the hole. The conduction electrode portion  134  electrically connects the leader portion  132  and the electrode terminal portion  133 . 
         [0059]    (3) Then, as the front electrodes  133 A on the front face (A) and the back electrodes  133 B on the back face (B), the electrode terminal portions  133  are formed by a method such as screen printing or photosensitive printing plus photolithography, using, for example, a silver paste as a conductive material. The electrode body  131  is also formed as have heretofore been formed. 
         [0060]    By carrying out the above-mentioned steps (2) and (3), an electrode pattern with electrical contact between the parts ( 131  to  134 ) for the address electrodes  13  is formed. As a conductive material that makes up the electrode pattern, a single-element metal material, which contains one of silver, gold, aluminum, copper, nickel, platinum, palladium, and chromium, or a multi-element metal material, which contains at least one of the above-mentioned elements, or a metal glass paste material, which contains the above-mentioned metal material and a glass ingredient, is used. 
         [0061]    (4) Subsequently, the electrode pattern is subjected to calcining, and then the structure as shown in  FIG. 3  is completed. 
         [0062]    Note that, in the above-mentioned manufacturing method, formation of the electrode terminal portions  133  ( 133 A and  133 B) or the like and formation of the conduction electrode portions  134  into the conduction holes  50  are carried out in the separate steps, but may be carried out in the same step. For example, after forming the leader portion  132  of the front face (A), the front electrode  133 A, or the like, and the conduction electrode portion  134  in one step, formation of the back electrode  133 B on the back face (B) and electric contact may be carried out in another step. 
         [0063]    (Connecting Portion) 
         [0064]      FIG. 5  illustrates an example of a configuration of a electrically connecting portion between the electrode terminal portions  133  of the address electrodes  13  on the back substrate  202  and the drive circuit portion (address drive circuit) side. The electrode terminal portion  133  is electrically wired and connected to the drive circuit portion on the chassis, using, for example, a flexible substrate (FPCB). The electrode terminal portion  133  is electrically connected to a terminal of the flexible substrate by a connector or by thermocompression bonding. 
         [0065]      FIG. 5  illustrates a configuration in which two separate flexible substrates  60 A and  60 B are electrically connected to the electrode terminal portions ( 133 A and  133 B) on the front and back faces (A, B) of the back glass substrate  2  separately. Alternatively, a configuration in which one flexible substrate pinches the front and the back faces (A, B) is also acceptable. 
         [0066]    Further, for example, as a material of a plate (a part other than structures such as electrode, dielectric layer, and partition wall) mainly constituting a substrate (back substrate  202 ) in which the conduction hole  50  is to be formed, an insulating material composed of any one of a ceramic, a polymeric material, and a metal, which meets panel requirement characteristics (requirements such as electrical insulation, strength, transparency of a display window) may be used. In other words, the substrate may be formed with any material other than a conventional glass, as long as it meets the panel requirement characteristics. In this case, the conduction hole  50  is more easily formed than when a substrate made of glass is used. 
         [0067]    While the invention made by the inventor has been described concretely based the embodiment, the invention is not limited to the embodiment. As a matter of course, various modifications can be made to the invention without departing from the spirit and scope of the invention. 
         [0068]    The present invention is applicable to a PDP including an electrode terminal portion.