Patent Publication Number: US-7902735-B2

Title: Gas discharge tube, and display device having gas discharge tube arrays

Description:
CROSS-RELATED APPLICATION 
     This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2008-118661, filed on Apr. 30, 2008, the entire contents of which are incorporated herein by reference. 
     FIELD OF THE INVENTION 
     The present invention relates generally to a gas discharge tube for a display device and, more particularly, to such a gas discharge tube in which reduction of light-emission at end portions thereof is improved. 
     BACKGROUND OF THE INVENTION 
     In a known plasma display panel (PDP), plasma discharge is generated in closed discharge spaces of a large number of small cells arranged in length and width directions of the panel, and phosphor materials are excited by ultraviolet light of 147 nm emitted from the discharged plasma, to thereby emit light. The cell spaces are formed between two planar glass plates disposed one on the other. On the other hand, in a known plasma tube array (PTA), as disclosed in Japanese Patent Application Publication No. 2003-92085-A, a phosphor layer is formed within a thin, elongated glass tube in which a large number of cell spaces are formed. A large-sized display screen of 6 m×3 m, for example, can be provided by arranging a number of such plasma tubes side by side. 
     Japanese Patent Application Publication No. 2006-164635-A (which corresponds to US Patent Application Publication No. 2006/119247 A1) describes a method of manufacturing a gas discharge tube for a display device. In this method, an opening of a glass tube is closed by forming a glass layer with outer peripheral shape identical to the outer peripheral shape of the glass tube on an end face of the glass tube. An open end face of the glass tube is pressure-welded to a dry film containing a low-melting-point glass powder and a binder resin. The glass tube is then lifted up to transfer the dry film portion to the end face of the glass tube, to thereby close the opening of the glass tube. A phosphor support member is inserted into the glass tube through an opening on a side opposite to the end face and then an end of the phosphor support member is adhered to the dry film portion. The binder resin is burnt off, and the dry film is vitrified to produce a low-melting-point glass layer. 
     Japanese Patent Application Publication No. 2006-140075-A describes a method of manufacturing a gas discharge tube and a display device. The gas discharge tube includes a thin tube having a discharge space therein and an electron emissive coating formed within the thin tube. The thin tube has a display surface on which a pair of display electrodes is adapted to be disposed, and has a rear surface on which a signal electrode is adapted to be disposed. A surface portion facing toward the display surface is formed within the thin tube at a location nearer to the display surface from the midway between the display and rear surfaces. An electron emissive coating is formed on the surface portion. Thus the gas discharge tube can reduce its firing voltage. 
     SUMMARY OF THE INVENTION 
     In accordance with an aspect of an embodiment, a gas discharge tube includes: an elongated tube within which an electron-emissive film and a phosphor layer are formed, and which is filled with a discharge gas and sealed; a plurality of pairs of display electrodes disposed on a display side of the elongated tube; a signal electrode disposed on a rear side of the elongated tube; and an elongated support member inserted into the elongated tube and extending in the length direction of the elongated tube. The support member has a curved shape so that a curved inner surface thereof forms a discharge space, has longitudinally extending opposite edges, and has a phosphor layer formed on the inner surface of the support member. The support member further has an end wall at each of longitudinally opposite ends thereof. The end walls and the curved inner surface form an elongated depression in the support member. 
     In accordance with another aspect of the embodiment, a display device includes a plurality of such gas discharge tubes as above-described. 
     Additional objects and advantages of the embodiment will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The object and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates an example of a schematic structure of part of an array of plasma tubes or gas discharge tubes of a color display device; 
         FIG. 2A  illustrates a front support plate with a plurality of pairs of transparent display electrodes formed thereon, and  FIG. 2B  illustrates a rear support plate with a plurality of signal electrodes formed thereon; 
         FIG. 3  illustrates a cross-sectional view of the structure of the array of plasma tubes of the display device in a plane perpendicular to the longitudinal direction; 
         FIG. 4  illustrates a display device of a plasma tube array type, which includes a plasma tube array (PTA) unit, an address (A-) electrode driver unit, an X-electrode driver unit, and a Y-electrode driver unit; 
         FIG. 5  illustrates two of plasma tube array (PTA) units assembled into a display device; 
         FIG. 6  is a bottom view of an array of plasma tubes (PTA), in accordance with an embodiment of the present invention; 
         FIG. 7A  is a cross-sectional view of part of one of plasma tube or gas discharge tubes of  FIG. 6  along a line VIIA-VIIA in  FIG. 6 , and  FIG. 7B  is a cross-sectional view of the plasma tube along a line VIIB-VIIB in  FIG. 7A ; 
         FIG. 8A  illustrates a modification of the plasma tube of  FIGS. 7A and 7B , and is a cross-sectional view of part of a modification of a plasma tube along a line VIIIA-VIIIA in  FIG. 8B , in accordance with another embodiment of the invention, and  FIG. 8B  is a cross-sectional view of the plasma tube of  FIG. 8A  along a line VIIIB-VIIIB in  FIG. 8A ; 
         FIG. 9A  illustrates another modification of the plasma tube of  FIGS. 7A and 7B , and is a cross-sectional view of part of a plasma tube of  FIG. 9B  in accordance with a further embodiment of the invention along a line IXA-IXA in  FIG. 9B , and  FIG. 9B  is a cross-sectional view of the plasma tube of  FIG. 9A  along a line IXB-IXB in  FIG. 9A ; and 
         FIG. 10A  illustrates a modification of the plasma tube of  FIGS. 8A and 8B  and  FIGS. 9A and 9B , and is a cross-sectional view of part of a plasma tube of  FIG. 10B , in accordance with a still further embodiment of the invention along a line XA-XA in  FIG. 10B , and  FIG. 10B  is a cross-sectional view of the plasma tube of  FIG. 10A  along a line XB-XB in  FIG. 10A ; and 
         FIG. 11A  is a schematic plan view of part of an array of plasma tubes or gas discharge tubes, in accordance with a further embodiment of the invention, and  FIG. 11B  is a cross-sectional view the array of the plasma tubes or gas discharge tubes of  FIG. 11A  along a line XIB-XIB. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The invention will be described in connection with non-limiting embodiments with reference to the accompanying drawings. Throughout the drawings, similar symbols and numerals indicate similar items and functions. 
     It is not practical to manufacture a large-sized plasma display device by the use of a single, large-sized array of plasma tubes arranged between front and rear support plates. A large-sized display device may be advantageously manufactured relatively easily by arranging, side by side, a plurality of separate or divided plasma tube array units or modules and by assembling the plasma tube array units. 
     The inventors have recognized that brightness or luminosity of a displayed image is lowered at end portions of plasma or gas discharge tubes near the seams or joints between adjacent arrays of plasma tubes. 
     An object of the present invention is to suppress the lowering of luminosity in the vicinity of end portions of gas discharge tubes. 
     According to the invention, the lowering of luminosity in the vicinity of end portions of gas discharge tubes can be suppressed. 
       FIG. 1  illustrates an example of a schematic structure of part of an array of plasma tubes or gas discharge tubes  11 R,  11 G and  11 B of a color display device  10 . In  FIG. 1 , the display device  10  includes an array of thin, elongated transparent color plasma tubes  11 R,  11 G,  11 B, . . . , disposed in parallel with each other, a front support plate  31  composed of a transparent front support sheet or thin plate, a rear support plate  32  composed of a transparent or opaque rear support sheet or thin plate. The display device  10  further includes a plurality of pairs of display or main electrodes  2 , and a plurality of signal or address electrodes  3 . In  FIG. 1 , a letter X represents a sustain or X electrode of the display electrodes  2 , and a letter Y represents a scan or Y electrode of the display electrodes  2 . Letters R, G and B represent red, green and blue, which are colors of light emitted by the phosphors. The front and rear support plates  31  and  32  are made of, for example, flexible or elastic PET or glass films or sheets. 
     A thin elongated tube  20  for the thin elongated plasma tubes  11 R,  11 G and  11 B is formed of a transparent, insulating material, e.g. borosilicate glass, Pyrex®, soda-lime glass, silica glass, or Zerodur. Typically, the tube  20  has cross-section dimensions of a tube diameter of 2 mm or smaller, for example a 0.55 mm high and 1 mm wide cross section, and a tube length of 300 mm or larger, and a tube wall thickness of about 0.1 mm. 
     Phosphor support members having respective red, green and blue (R, G, B) phosphor layers  4  formed or deposited thereon are inserted into the interior rear spaces of the plasma tubes  11 R,  11 G and  11 B, respectively. Discharge gas is introduced into the interior space of each plasma tube, and the plasma tube is sealed at its opposite ends. An electron emissive film  5  of MgO is formed on the inner surface of the plasma tube  11 R,  11 G,  11 B. The phosphor layers R, G and B typically have a thickness within a range of from about 10 μm to about 30 μm. 
     The support member  6  has generally a shape of a trough or boat having a generally U-shaped or C-shaped transverse cross-section. Similarly to the plasma tubes  11 R,  11 G and  11 B, the support member  6  is formed of a insulating material, e.g. borosilicate glass, Pyrex®, silica glass, soda-lime glass, or lead glass, and has the phosphor layer  4  formed thereon. The support member  6  can be disposed within the glass tube by applying a paste of phosphor over the support member  6  outside the glass tube and then baking the phosphor paste to form the phosphor layer  4  on the support member  6 , and then inserting the support member  6  into the glass tube. As the phosphor paste, a desired one of various phosphor pastes known in this technical field may be employed. 
     The electron emissive film  5  emits charged particles, when it is bombarded with the discharge gas. When a voltage is applied between the pair of display electrodes  2 , the discharge gas contained in the tube is excited. The phosphor layer  4  emits visible light by converting thereinto vacuum ultraviolet radiation generated in the de-excitation process of the excited rare gas atoms. 
       FIG. 2A  illustrates the front support plate  31  with the plurality of pairs of transparent display electrodes  2  formed thereon.  FIG. 2B  illustrates the rear support plate  32  with the plurality of signal electrodes  3  formed thereon. 
     The signal electrodes  3  are formed on the front-side surface, or inner surface, of the rear support plate  32 , and extend along the longitudinal direction of the plasma tubes  11 R,  11 G and  11 B. The pitch, between adjacent ones of the signal electrodes  3 , is equal to the width of each of the plasma tubes  11 R,  11 G and  11 B, which may be, for example, 1 mm. The pairs of display electrodes  2  are formed on the rear-side surface, or inner surface, of the front support plate  31  in a well-known manner, and are disposed so as to extend perpendicularly to the signal electrodes  3 . The width of the display electrode  2  may be, for example, 0.75 mm, and the distance between the edges of the display electrodes  2  in each pair may be, for example, 0.4 mm. A distance providing a non-discharging region, or non-discharging gap, is secured between one display electrode pair  2  and the adjacent display electrode pairs  2 , and the distance may be, for example, 1.1 mm. 
     The signal electrodes  3  and the pairs of display electrodes  2  are brought into intimately contact respectively with the lower and upper peripheral surface portions of the plasma tubes  11 R,  11 G and  11 B, when the display device  10  is assembled. In order to provide better contact, an electrically conductive adhesive may be placed between the display electrodes and the plasma tube surface portions. 
     In plan view of the display device  10  seen from the front side, the intersections of the signal electrodes  3  and the pairs of display electrodes  2  provide unit light-emitting regions. Display is provided by using either one electrode of each pair of display electrodes  2  as a scan electrode, generating a selection discharge at the intersection of the scan electrode with the signal electrode  3  to thereby select a light-emitting region, and generating a display discharge between the pair of display electrodes  2  using the wall charge formed by the selection discharge on the region of the inner tube surface at the selected region, which, in turn, causes the associated phosphor layer to emit light. The selection discharge is an opposed discharge generated within each plasma tube  11 R,  11 G,  11 B between the vertically opposite scan electrode and signal electrode  3 . The display discharge is a surface discharge generated within each plasma tube  11 R,  11 G and  11 B between the two display electrodes of each pair of display electrodes disposed in parallel in a plane. 
     The pair of display electrodes  2  and the signal electrode  3  can generate discharges in the discharge gas within the tube by applying voltages between them. The electrode structure of the plasma tubes  11 R,  11 G and  11 B illustrated in  FIG. 1  is such that the three electrodes are disposed in one light-emitting region, and that the discharge between the pair of display electrodes generates a discharge for display. However, the electrode structure is not limited to such a structure. A display discharge may be generated between the display electrode  2  and the signal electrode  3 . In other words, an electrode structure of a type employing a single display electrode may be employed instead of each pair of display electrodes  2 , in which the single display electrode  2  is used as a scan electrode so that a selection discharge and a display discharge (opposed discharge) are generated between the single display electrode  2  and the signal electrode  3 . 
       FIG. 3  illustrates the cross-section of the structure of the array of plasma tubes  11  of the display device  10  in a plane perpendicular to the longitudinal direction. In the display device  10 , phosphor layers  4 R,  4 G and  4 B are formed on the inner surface portions of the support members  6 R,  6 G and  6 B in the rear-half spaces of the plasma tubes  11 R,  11 G and  11 B, respectively. The plasma tubes are thin tubes having a tube thickness of 0.1 mm, a width in the cross-section of 1.0 mm, a height in the cross-section of 0.55 mm, and a length of from 1 m to 3 m. For example, the red-emitting phosphor  4 R may be formed of an yttria based material ((Y.Ga)BO 3 :Eu), the green-emitting phosphor  4 G may be formed of a zinc silicate based material (Zn 2 SiO 4 :Mn), and the blue-emitting phosphor  4 B may be formed of a BAM based material (BaMgAl 10 O 17 :Eu). 
     In  FIG. 3 , the rear support plate  32  is bonded or fixed to bottom surfaces of the red-emitting plasma tubes  11 R,  11 G and  11 B. The signal electrodes  3 R,  3 G and  3 B are disposed on the bottom surfaces of the plasma tubes  11 R,  11 G and  11 B and on an upper surface of the rear support plate  32 . 
       FIG. 4  illustrates a display device  100  of a plasma tube array type, which includes a plasma tube array (PTA) unit  300 , an address (A-) electrode driver unit  400 , an X-electrode driver unit  500 , and a Y-electrode driver unit  600 . The PTA unit  300  has n pairs of display electrodes  2 , (X 1 , Y 1 ), . . . , ((Xj, Yj), . . . , (Xn, Yn). X-electrodes of the pairs of display electrodes  2  are connected to a sustain voltage pulse circuit (SST)  50  for the X-electrodes in the X-electrode driver unit  500 . Y-electrodes of the pairs of display electrodes  2  are connected to scan pulse circuits (SCNs)  70  in the Y-electrode driver unit  600 . The PTA unit  300  has also a plurality, m, of signal electrodes  3 , A 1 , . . . , Ai, . . . , Am, which are connected to the A-electrode driver unit  400 . The X-electrode driver unit  500  includes also a reset circuit (RST)  51 . The Y-electrode driver unit  600  includes also a sustain voltage pulse circuit (SST)  60  and a reset circuit (RST)  61 . A driver control circuit (CTRL)  42  is connected to the A-electrode driver unit  400 , the X-electrode driver circuit  500 , and the Y-electrode driver unit  600 . 
     Now, one exemplary method for driving an AC gas discharge display device of the plasma tube array type is described. One picture typically has one frame period. One frame consists of two fields in the interlaced scanning scheme, and one frame consists of one field in the progressive scanning scheme. For displaying a moving picture in a conventional television system, thirty or sixty frames per second must be displayed. In displaying on the display device  10  of this type of AC gas discharge display device, for reproducing colors by the binary control of light emission, one field F is typically divided into or replaced with a set of q subfields SF&#39;s. Often, the number of times of discharging for display for each subfield SF is set by weighting these subfields SF&#39;s with respective weighting factors of 2 0 , 2 1 , 2 2 , . . . , 2 q-1  in this order. N (=1+2 1 +2 2 + . . . +2 q-1 ) steps of brightness can be provided for each color of R, G and B in one field by associating light emission or non-emission with each of the subfields in combination. In accordance with such a field structure, a field period Tf, which represents a cycle of transferring field data, is divided into q subfield periods Tsf&#39;s, and the subfield periods Tsf&#39;s are associated with respective subfields SF&#39;s of data. Furthermore, a subfield period Tsf is divided into a reset period TR for initialization, an address period TA for addressing, and a display or sustain period TS for emitting light. Typically, the lengths of the reset period TR and the address period TA are constant independently of the weighting factors for the brightness, while the number of pulses in the display period TS becomes larger as the weighting factor becomes larger, and the length of the display period TS becomes longer as the weighting factor becomes larger. In this case, the length of the subfield period Tsf becomes longer, as the weighting factor of the corresponding subfield SF becomes larger. 
       FIG. 5  illustrates two ( 300  and  302 ) of plasma tube array (PTA) units assembled into a display device  102 . The PTA units  300  and  302  are arranged such that the lower ends of vertically extending plasma tubes  110  of the PTA unit  300  contact the upper ends of corresponding, vertically extending plasma tubes  112  of the PTA unit  302 . 
     The inventors have discovered that the brightness at the ends of the plasma tubes or gas discharge tubes  11 ,  110 ,  112  tends to be lower. The inventors have recognized that lowering of brightness or image artifacts in the vicinity of the seam or joint between the adjacent PTA units  300  and  302  can be suppressed by preventing the lowering of brightness at the ends of the plasma tubes. 
     The inventors have also discovered that, when plasma tubes or PTA units are being handled during manufacture and/or transportation thereof, part of phosphor layers formed on support members at the ends of the plasma tubes may be peeled off due to contacting with, rubbing against, or impacting on other members. The inventors have further recognized that little or almost no light can be emitted from discharge cells lacking phosphors in end portions of the plasma tubes even when discharge occurs in inner discharge spaces of the plasma tubes. 
     The inventors have further recognized that, in discharge cells lacking part of phosphors at end portions of plasma tubes, discharge conditions, such as charging characteristics and inter-line capacitance, may change, which causes a firing voltage to increase. The inventors have further recognized that discharge cells in end portions of plasma tubes having higher firing voltage than other discharge cells may fail to discharge or, otherwise, emit little light. 
       FIG. 6  is a bottom view of an array of plasma tubes (PTA)  11 , including plasma tubes  11 R,  11 G and  11 B, in accordance with an embodiment of the present invention. The array of plasma tubes  11  illustrated in  FIG. 6  corresponds to the one illustrated in  FIG. 3 . In  FIG. 6 , the array of plasma tubes  11  is illustrated with its outer wall at the bottom end removed for ease of explanation. Each of the plasma tubes  11  in  FIG. 6  is illustrated in its cross-section along a line VI-VI through a plasma tube  11  illustrated in  FIG. 7A and 7B . 
     Generally semicircular or semi-elliptical end walls  602  with respective generally U-shaped or C-shaped edges are secured to longitudinally opposite ends of a support member  6  ( 6 R,  6 G or  6 B) disposed within each plasma tube  11 . 
       FIG. 7A  is a cross-sectional view of part of one of plasma tube or gas discharge tubes  11  ( 11 R,  11 B or  11 G) of  FIG. 6  along a line VIIA-VIIA in  FIG. 6 .  FIG. 7B  is a cross-sectional view of the plasma tube  11  along a line VIIB-VIIB in  FIG. 7A . 
     The support member  6  has a curved surface shape or contour generally conformable to the inner surface of the plasma tube  11  so as to provide a discharge space inside. The curved surface of the support member  6  forms, together with the end walls  602  on the opposite ends of the support member  6 , a trough having an elongated recess, depression or discharge space therein. 
     The plasma tube  11  has outer walls  112  at its longitudinally opposite ends. The thickness of each outer walls  112  is generally the same as that of the thin tube  20  of the plasma tube  11  ( FIG. 1 ) or may be slightly larger. The thickness of the outer wall  112  may be, for example, within a range of from 0.1 mm to 0.15 mm. The thickness Tw of each end wall  602  of the support member  6  is generally the same as the thickness of the remaining portions of the support member  6  or may be slightly larger. The thickness of the end wall  602  may be, for example, within a range of from 0.1 mm to 0.15 mm. 
     The upper edge  602   te  of each end wall  602  is generally leveled vertically with the upper edge  6   te  of the support member  6  extending in the length direction of the support member  6 , as illustrated in  FIG. 7A . 
     The presence of the end walls  602  can prevent the phosphor layer  4  from peeling off in the vicinity of the ends of the support member  6 , even when the ends of the support member  6  or its end walls  602  contacts, rubs against or hits against other members, e.g. the interior surface or the outer walls  112  of the plasma tube  11 . Furthermore, the presence of the end walls  602  can prevent or suppress increase of the firing voltage of the discharge cells near the end walls  602 , which may be caused by peeling off of part of the phosphor layer  4 . This can prevent decrease in brightness or luminosity in the vicinity of the ends of the plasma tube  11 , which may be caused by peeling off of the phosphor layer  4  in the end portions of the support member  6 . 
     Each end wall  602  is made of the same material as the support member  6  or of a glass material having a low melting point, and is secured to the support member  6  by fusing a separate glass chip in the shape of the end wall  602 , directly or with a glass material having a low melting point interposed to the inner surface of the associated end of the support member  6 . 
       FIG. 8A  illustrates a modification of the plasma tube  11  of  FIGS. 7A and 7B , and is a cross-sectional view of part of a plasma tube  11  along a line VIIIA-VIIIA in  FIG. 8B , in accordance with another embodiment of the invention.  FIG. 8B  is a cross-sectional view of the plasma tube  11  of  FIG. 8A  along a line VIIIB-VIIIB in  FIG. 8A . 
     An end wall  604  having a generally similar shape to that of the end walls  602  illustrated in  FIGS. 6 ,  7 A and  7 B is disposed at each end of a support member  64  within the plasma tube  11 . The vertical position or level of an upper edge  604   te  of the end wall  604  in  FIG. 8A  is lower by a difference Dd (e.g., 0.1 mm) than the vertical position or level of the upper edge  6   te  of the support member  64 . This arrangement reduces the influence of variations in dimensions of the end walls  604  on the dimensions of the opposite ends of the support member  64 . Since the entire dimensions of the support member  64  are so determined as to conform to the internal dimensions of the plasma tube  11 , it is not desirable, from a view point of the structure of the plasma tube  11 , that the entire or even part of the end walls  604  is larger. In  FIG. 6 , the position of the upper edge  604   te  of the end wall  604  in a bottom view of the array of plasma tubes  11  is illustrated slightly lower by broken lines, as opposed to the upper edge  602   te  of the end wall  602 . The remaining structure and arrangement of the support member  64  are similar to the ones of the support member  6  illustrated in  FIGS. 6 ,  7 A and  7 B. 
     The presence of the end walls  604  can prevent the phosphor layer  4  from peeling off in the vicinity of the ends of the support member  64 , even when the ends of the support member  64  or its end walls  604  contacts, rubs against or hits against other members, e.g. the interior surface or the outer walls  112  of the plasma tube  11 . Furthermore, the presence of the end walls  604  can prevent or suppress increase of the firing voltage of the discharge cells near the end walls  604 , which may be caused by peeling off of part of the phosphor layer  4 . This can prevent decrease in brightness or luminosity in the vicinity of the ends of the plasma tube  11 , which may be caused by peeling off of the phosphor layer  4  in the end portions of the support member  64 . 
       FIG. 9A  illustrates another modification of the plasma tube  11  of  FIGS. 7A and 7B , and is a cross-sectional view of part of a plasma tube  11  along a line IXA-IXA in  FIG. 9B , in accordance with a further embodiment of the invention.  FIG. 9B  is a cross-sectional view of the plasma tube  11  of  FIG. 9A  along a line IXB-IXB in  FIG. 9A . 
     An end wall  602  similar to the one illustrated in  FIGS. 6 ,  7 A and  7 B is disposed at each of the opposite ends of a support member  62  within the plasma tube  11 . A phosphor layer  402  having generally the same thickness as a phosphor layer  402  on the inner surface of the support member  62  is formed on the inner surface of each end wall  602 . The phosphor layer  402  can be formed on the end walls  602  simultaneously with the formation of the phosphor layer  4  on the inner surface of the support member  62 . 
     The presence of the end walls  602  can prevent the phosphor layer  402  on the inner surface of each end wall  602  and the phosphor layer  4  in the vicinity of the ends of the support member  62  from peeling off, even when the ends of the support member  62  or its end walls  602  contacts, rubs against or hits against other members. Furthermore, the presence of the end walls  602  can prevent or suppress increase of the firing voltage of the discharge cells near the end walls  602 , which may be caused by peeling off of part of the phosphor layer  4 . This can prevent decrease in brightness or luminosity in the vicinity of the ends of the plasma tube  11 , which may be caused by peeling off of the phosphor layer  4  in the end portions of the support member  62 . 
     In the embodiment illustrated in  FIGS. 6 ,  7 A and  7 B, the internal discharge space near each end of the support member  6  in the plasma tube  11  is relatively small due to the presence of the outer wall  112  of the plasma tube  11  and the end wall  602 , and the phosphor layer  4  does not extend beyond the display electrode  2  nearest to the end of the support member  6 . This tends to cause reduction of amount of light emitted by discharging so that the brightness or luminosity decreases near each end of the support member  6 . In contrast, when the support member  62  in the embodiment illustrated in  FIGS. 9A and 9B  are used, the presence of the phosphor layer  402  allows the area of the phosphor layer near each end wall  602  to be increased, whereby sufficient light emission based on discharging in the internal discharge space in the vicinity of the end of the support member  62  can be secured, which can sufficiently suppress and compensate the reduction of the brightness. 
       FIG. 10A  illustrates a modification of the plasma tube  11  of  FIGS. 8A and 8B  and  FIGS. 9A and 9B , and is a cross-sectional view of part of a plasma tube  11  along a line XA-XA in  FIG. 10B , in accordance with a still further embodiment of the invention.  FIG. 10B  is a cross-sectional view of the plasma tube  11  of  FIG. 10A  along a line XB-XB in  FIG. 10A . 
     An end wall  604  having dimensions similar to the ones of the end wall  604  illustrated in  FIGS. 8A and 8B  is provided at each of the opposite ends of a support member  64  within the plasma tube  11 . This arrangement reduces the influence of variations in dimensions of the end walls  604  on the dimensions of the opposite ends of the support member  64 . Similarly to the phosphor layer  402  illustrated in  FIGS. 9A and 9B , a phosphor layer  404  having generally the same thickness as a phosphor layer  4  on the inner surface of the support member  64  is formed on the inner surface of each end wall  604 . The phosphor layer  404  can be formed on the end walls  602  simultaneously with the formation of the phosphor layer  4  on the inner surface of the support member  64 . 
     The presence of the end walls  604  can prevent the phosphor layers  404  on the inner surface of each end wall  604  and the phosphor layer  4  in the vicinity of the ends of the support member  64  from peeling off, even when the ends of the support member  64  or its end walls  604  contacts, rubs against or hits against other members. Furthermore, the presence of the end walls  604  can prevent or suppress increase of the firing voltage of the discharge cells near the end walls  604 , which may be caused by peeling off of part of the phosphor layer  4 . This can prevent decrease in brightness or luminosity in the vicinity of the ends of the plasma tube  11 , which may be caused by peeling off of the phosphor layer  4  in the end portions of the support member  64 . 
     In the embodiment illustrated in  FIGS. 8A and 8B , the internal discharge space near each end of the support member  64  in the plasma tube  11  is relatively small due to the presence of the outer wall  112  of the plasma tube  11  and the end wall  604 , and the phosphor layer  4  does not extend beyond the display electrode  2  nearest to the end of the support member  64 . This tends to cause reduction of amount of light emitted by discharging so that the brightness or luminosity decreases near each end of the support member  64 . In contrast, when the support member  64  in the embodiment illustrated in  FIGS. 10A and 10B  are used, the presence of the phosphor layer  404  allows the area of the phosphor layer near each end wall  604  to be increased, whereby sufficient light emission based on discharging in the internal discharge space in the vicinity of the end of the support member  64  can be secured, which can sufficiently suppress and compensate the reduction of the brightness. 
       FIG. 11A  is a schematic plan view of part of an array of plasma tubes or gas discharge tubes  11 , in accordance with a further embodiment of the invention.  FIG. 11B  is a cross-sectional view the array of the plasma tubes or gas discharge tubes  11  illustrated in  FIG. 11A  along a line XIB-XIB. 
     An end wall  604  and a phosphor layer  404  having dimensions similar to the ones of the end wall  604  and the phosphor layer  404  illustrated in  FIGS. 10A and 10B  are disposed at each of the opposite ends of the support member  64  in the plasma tube  11 . 
     Alternatively, the plasma tubes illustrated in  FIGS. 7A and 7B ,  8 A and  8 B, or  9 A and  9 B may be used for the plasma tubes  11  in  FIGS. 11A and 11B . 
     The sum of the thickness of the end wall  604  and the thickness of the outer wall  112  is, for example, between 0.2 mm and 0.6 mm. Accordingly, the sum thickness of the two end walls  604  and the two outer walls  112  at the joint of the two adjacent PTA units  300  and  302  of  FIGS. 11A and 11B  in place of those of  FIG. 5  is, for example, between 0.4 mm and 1.2 mm. 
     A region BR (e.g., a distance of BR=0.5 mm) in the vicinity of the outer wall  112  of the plasma tube  11  and the end wall  604  of the support member  64  does not contribute to discharging for display. 
     In order to provide a sufficient discharge space inside the support member  64  to thereby produce a sufficient spatial charge, the outer edge of the display electrode  2  is preferably located inward, in the length direction of the plasma tube  11 , by at least a small distance Dsw (e.g., between about 10 μm and about 50 μm) from the inner surface of the end wall  604  ( 602 ). 
     A width Des of an end non-discharge region, between the outer surface of the outer wall  112  of the plasma tube  11  and the outer edge of the display electrode  2  in the vicinity of the end of the plasma tube  11 , is preferably smaller than a so-called reverse or spacing slit width or non-discharge region width Ds between adjacent pairs of display electrodes  2 , and is, for example, between 0.4 mm and 6 mm. Generally, the width Des of the end non-discharge region is preferably half or slightly smaller than the width Ds (e.g., between 0.9 mm and 1.5 mm) of the non-discharge region. This prevents picture distortion at the joint between the arrays of plasma tubes  11  or between the PTAs  110  and  112  of the adjacent PTA units  300  and  302 . 
     The distance Ds′ between the display electrodes  2  closest to the joint between the two arrays of plasma tubes  11  adjacent in the length direction preferably is substantially equal to the width Ds of the non-discharge region between the adjacent pairs of display electrodes  2  for each plasma tube  11 . This prevents picture distortion at the joint between adjacent PTA units  300  and  302 . 
     When a plurality of plasma tubes or gas discharge tubes  11  like the ones illustrated in  FIGS. 11A and 11B  are used to form the PTA units  300  and  302  similarly to those of  FIG. 5 , the plasma tubes  11  are so arranged that first ends  110   e  of a first group of plasma tubes or gas discharge tubes  110  of one  300  of the adjacent two PTA units  300  and  302  abut second ends  112   e  of a second group of plasma tubes or gas discharge tubes  112  of the other PTA unit  302 . 
     The distance Ds′ between the display electrode  2  closest to the first ends  110   e  of the first group of plasma tubes  110  and the display electrode  2  closest to the second ends  112   e  of the second group of plasma tubes  112  is substantially equal to the distance Ds between adjacent two pairs of display electrodes of each plasma tube  11  of the first or second group of plasma tubes  110  or  112 . 
     The region BR (e.g., a distance of BR=0.5 mm) in the vicinity of the outer wall  11  of the plasma tube  11  and the end wall  604  of the support member  64  does not contribute to discharging for display. However, by virtue of the presence of the phosphor layer  404  on the inner surface of the end wall  604 , a discharge cell Ce in the vicinity of the end wall  604  of the support member  64  can provide generally the same luminosity as other discharge cells Cc. The phosphor layers  402  on the end walls  602  of the support members  62  of  FIGS. 9A and 9B  bring about the same effect. 
     All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the principles of the invention and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority and inferiority of the invention. Although the embodiments of the present invention have been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.