Display discharge tubes

Abstract: A discharge tube for a display device includes a pair of memory elements (Ma, Mb) having memory electrodes (3a, 3b) formed of conductive layers with a plurality of apertures (5a, 5b) arranged in an XY matrix form, and in which the entire surfaces of the memory electrodes (3a, 3b) are covered with insulating layers (4a, 4b) and laminated such that corresponding apertures (5a, 5b) covered with the insulating layers (4a, 4b) communicate with each other thereby forming discharge cells, all of which are sealed into a tube body (1, 6) in which a discharging gas is enclosed. An AC voltage (10) necessary for maintaining a discharge is applied between the memory electrodes (3a, 3b) of the pair of memory elements (Ma, Mb).

Description: The present invention relates to discharge tubes for use in display devices. Previously-proposed discharge tubes for use with display devices will be described with reference to FIGS. 1 to 3 of the accompanying drawings. FIG. 1 shows a known DC-plasma display panel (PDP). As shown in FIG. 1, a plurality of parallel striped cathodes 7 are deposited on a rear glass panel 6 by a thick film technique such as screen printing or the like. On a front glass panel 1 which forms a tube together with the rear glass panel 6, there are deposited a plurality of parallel striped transparent anodes 2 (which may be made of indium tin oxide (ITO)) at a right angle to the cathodes 7. Barrier ribs 12 that prevent discharge from being spread are deposited on the front glass panel 1 or on the rear glass panel 6 so as to be located at each spacing between the adjacent anodes 2 by the thick film technique. A discharge gas is sealed into the tube composed of the front glass panel 1 and the rear glass panel 6. FIG. 2 shows a known AC-PDP, the same reference numerals being used for parts common to FIG. 1. As shown in FIG. 2, a plurality of parallel striped Y electrodes 14 are deposited on the rear glass panel 6 by a thick film technique such as screen printing or a thin film technique such as vapour deposition, etching or the like. On the front glass panel 1 that forms the tube together with the rear glass panel 6, there are deposited a plurality of parallel striped X electrodes 13 at a right angle to the Y electrodes 14 by the thick film technique such as screen printing or the thin film technique such as vapour deposition, etching or the like. The Y electrodes 14 and the X electrodes 13 are respectively covered with insulating layers 15b, 15a, and protecting layers 16b, 16a are respectively deposited on the insulating layers 15b, 15a. The AC-type PDP does not need barrier ribs because it is not susceptible to diffused discharge. FIG. 3 shows a known hybrid-PDP (see WO-A-81/00026 or EP-A-0023082). As shown in FIG. 3, two sets of address electrodes 22, 23, each having a self-scanning function based on DC discharge, are formed on the rear glass panel 6 so as to intersect at a right angle with each other. A semi-AC memory unit comprises a transparent full electrode 17 disposed on the front glass panel 1 and which establishes discharge spaces between it and the address electrodes 22, 23 of the rear glass panel 6 through a plurality of apertures and a metal electrode plate 20 having corresponding apertures opposed to the transparent full electrode 17. Insulating substrates 24 are disposed on each spacing between adjacent address electrodes 22, and the transparent full electrode 17 is covered with a transparent insulating layer 18. Barriers 19, 21 are respectively disposed between the apertured metal electrode plate 20 and the transparent insulating layer 18, and between the apertured metal electrode plate 20 and the insulating substrate 24. The above elements arranged as described are sealed into a tube formed of the rear glass panel 6 and the front glass panel 1, the tube containing a suitable discharge gas. In this hybrid-PDP, electrons, generated due to discharge between the address electrodes 22, 23, are supplied to the semi-AC memory unit by a voltage applied to the apertured metal electrode plate 20 so that AC-discharge is maintained between the transparent full electrode 17 covered by the transparent insulating layer 18 on the front glass panel 1 and the apertured metal electrode plate 20. The hybrid-PDP can simplify associated circuitry owing to its self-scanning function, and can increase the display brightness owing to its memory function. The DC-PDP shown in FIG. 1 is simple in structure and is driven to display an image by simultaneously applying a signal to the anodes 2 and by sequentially applying a ground potential to the cathodes 7 in a so-called line sequential driving fashion. Therefore, the driving technique of the DC-PDP can be relatively simple. However, the above DC-PDP has no memory function so that, if the number of the anodes 2 and the cathodes 7 is increased in order to improve resolution, the luminous brightness will be lowered. Moreover, the electrodes have a relatively short service life because a sputtering phenomenon occurs on the electrodes due to direct ion bombardment. The AC-PDP shown in FIG. 2 has a memory function based on wall charge caused by the fact that electric charges are accumulated in the insulating layers that cover the electrodes so that, even if the number of X electrodes and Y electrodes is increased in order to improve resolution, the brightness will not necessarily be lowered. On the other hand, a complex signal must be applied between the X and Y electrodes in order to write, memorize and erase a signal. Consequently, the driving circuit for the AC-PDP needs to be complicated, and the manufacturing process for the PDP also becomes complicated because the operation range must be widened. The hybrid-PDP shown in FIG. 3 is complicated in structure and hence cannot readily be mass-produced. Moreover, this hybrid-PDP suffers from the following further shortcomings and disadvantages. The diameter of the apertures through which the discharge spaces of the address electrode side and the memory unit side are coupled must be increased to make the coupling between the two discharge spaces strong so that the hybrid-PDP can be operated reliably. If the aperture diameter is increased too much, then the two discharge spaces cannot be separated reliably. When the memory discharge is erased, the wall electric charge accumulated on the insulating layer formed on the transparent electrode of the front glass panel must be erased. In this case, if the aperture diameter of the metal electrode plate is small, then it becomes impossible to control the wall electric charge by the address electrode on the rear glass panel side. Further, if the aperture diameter is large, then stable addressing and the self-scanning function are degraded by the influences of memory discharge. Furthermore, the apertured metal electrode plate that isolates the address side and the display side of the display panel must be exposed to the gas in order to extract the electrons from the addressing discharge at the scanning section even though a part of the metal electrode plate is covered with the insulating layer or the metal layer is formed on an insulating body instead of on the metal plate. Accordingly, due to the insulation of the apertured metal electrode plate from the DC-scanning section and the requirement for safe operation, the elements must be separated with high accuracy during construction, which makes the manufacturing process of the hybrid-PDP more difficult. In addition, since the hybrid-PDP operates in a semi-AC fashion, the wall electric charge that contributes to the memory function accumulates only on the address side. Therefore, the memory function is not powerful so that the hybrid-PDP needs a high voltage to maintain the memory function. European Patent Application No. EP-A-0 123 496 discloses a display discharge tube in which a base plate carries arrays of anodes and cathodes transverse to each other, insulating strips on the face plate spacing the cathodes from a first apertured plate electrode. A second apertured electrode, whose apertures form display cells, is disposed over the first plate electrode. The insulating strips, the first apertured plate electrode and the second apertured electrode are formed by coating the apertured plate electrode on both sides with insulating material and photoetchable material. The assembly is exposed and developed, and then etched so as to leave the desired pattern. According to a first aspect of the present invention, there is provided a display discharge tube comprising: a pair of memory electrodes each formed of a conductive layer having a plurality of apertures arranged in an XY matrix form and in which the whole surface of each memory electrode is covered with an insulating layer, the memory electrodes being laminated together such that corresponding apertures covered with the insulating layers communicate together to form an array of discharge cells; a plurality of first parallel and second parallel address electrode strips disposed at predetermined intervals so as to cross each other, the memory electrodes laminated together being disposed between the first and second address electrode strips such that respective crossing points of the first and second address electrode strips correspond to the respective discharge cells; and a tube body in which the first and second address electrode strips and the memory electrodes are sealed and in which a discharging gas is sealed, wherein when a predetermined voltage is applied between selected ones of the first and second address electrode strips a discharge is caused to occur in the discharge cell located at the crossing point thereof, and when a predetermined AC voltage is applied between the memory electrodes the discharge is maintained. According to a second aspect of the present invention there is provided a display discharge tube comprising: a front memory electrode having a plurality of apertures arranged in an XY matrix form serving as discharge cells, the surface of the front memory electrode being covered with an insulating layer; a rear memory electrode the surface of which is formed of a conductive layer and is covered with an insulating layer, the front memory electrode and the rear memory electrode being disposed in an opposing relation; a plurality of first parallel and second parallel address electrode strips being disposed so as to cross each other, the front memory electrode being disposed between the first and second address electrode strips such that respective crossing points of the first and second address electrode strips correspond to respective discharge cells; and a tube body in which a discharging gas is sealed and in which the second address electrode strips are sealed such that they are disposed between the front and rear memory electrodes, wherein when a predetermined voltage is applied between selected ones of the first and second address electrodes a discharge is caused to occur in the discharge cell located at the crossing point of the selected first and second address electrode strips and when a predetermined AC voltage is applied between the front and rear memory electrodes the discharge is maintained. According to a third aspect of the present invention there is provided a display discharge tube comprising: a front memory electrode the surface of which is formed of a transparent conductive layer, the surface of the front memory electrode being covered with a transparent insulating layer; a rear memory electrode the surface of which is formed of a conductive layer, the surface of the rear memory electrode being covered with an insulating layer, the front memory electrode and the rear memory electrode being disposed in an opposing relation; a plurality of first parallel and second parallel address electrode strips being disposed between the front and rear memory electrodes so as to cross each other; an insulating barrier having a plurality of apertures serving as discharging cells corresponding to respective crossing points of the first and second address electrode strips and being disposed therebetween; and a tube body in which a discharging gas is sealed and in which the memory electrodes, the address electrode strips and the insulating barrier are sealed, wherein when a predetermined voltage is applied between selected ones of the first and second address electrode strips a discharge is caused to occur in the discharge cell located at the crossing point of the selected first and second address electrode strips, and when a predetermined AC voltage is applied between the memory electrodes the discharge is maintained. According to a fourth aspect of the present invention there is provided a display discharge tube comprising: a rear memory element including a plurality of first and second memory electrodes arranged alternately, the surfaces of the first and second memory electrodes being covered with an insulating layer; a plurality of first parallel and second parallel address electrode strips being opposed to the rear memory element so as to cross each other; an insulating barrier having a plurality of apertures serving as discharge cells corresponding to respective crossing points of the first and second address electrode strips and being disposed therebetween; and a tube body in which a discharging gas is sealed and in which the rear memory element, the address electrode strips and the insulating barrier are sealed, wherein when a predetermined voltage is applied between selected ones of the first and second address electrode strips a discharge is caused to occur in the discharge cell located at the crossing point of the selected first and second address electrode strips, and when a predetermined AC voltage is applied between the memory electrodes the discharge is maintained. Embodiments of the present invention provide improved discharge tubes for use with display devices in which the shortcomings and disadvantages of the previous proposals can be overcome or at least alleviated. The preferred discharge tubes are relatively simple in structure, can be mass-produced satisfactorily, can have improved resolution, and can readily be made large in size. The preferred discharge tubes can also be driven with ease, as a result of which their driving circuits can be simplified. Thus the discharge tubes can be made relatively inexpensively. The invention will now be described by way of example with reference to the accompanying drawings, throughout which like parts are referred to by like references, and in which: FIG. 1 is a perspective view showing an example of a previously-proposed DC-type plasma display panel (PDP); FIG. 2 is a perspective view showing an example of a previously-proposed AC-PDP; FIG. 3 is a diagrammatic sectional view showing an example of a previously-proposed hybrid-type PDP; FIG. 4 is an exploded perspective view showing a discharge tube for use with a display device, according to a first embodiment of the present invention; FIG. 5 is a diagrammatic sectional view of the first embodiment; FIG. 6 is a perspective view showing a first example of a memory element used in the first embodiment; FIG. 7 is a circuit diagram in the context of a writing operation of the first embodiment; FIG. 8 is a circuit diagram in the context of a memorizing operation of the first embodiment; FIG. 9 is a circuit diagram in the context of an erasing operation of the first embodiment; FIG. 10 is a timing chart indicating the operation of the first embodiment; FIG. 11 is a perspective view showing a second example of the memory element used in the first embodiment; FIG. 12 is a diagrammatic sectional view of a second embodiment of the present invention; FIG. 13 is a diagrammatic sectional view of a third embodiment of the present invention; FIG. 14 is a circuit diagram showing a fourth embodiment of the present invention; FIG. 15 is a diagrammatic sectional view of a fifth embodiment of the present invention. FIG. 16 is an exploded perspective view showing a sixth embodiment of the present invention; FIG. 17 is a diagrammatic sectional view of the sixth embodiment of the present invention; FIG. 18 is a timing chart indicating the operation of the sixth embodiment; FIG. 19 is a circuit diagram showing a seventh embodiment of the present invention; and FIG. 20 is a diagrammatic sectional view of an eighth embodiment of the present invention. Referring to the drawings in detail, and initially to FIGS. 4, 5 and 6, a first embodiment of the present invention will now be described. FIG. 4 of the accompanying drawings shows an exploded perspective view of the discharge tube for use with a display device according to the first embodiment of the present invention. FIG. 5 of the accompanying drawings shows a diagrammatic view of a section thereof and FIG. 6 of the accompanying drawings shows a perspective view of a memory element used in the discharge tube according to the first embodiment of the present invention. In FIGS. 4 to 6, like parts identical to those of FIGS. 1 to 3 are marked with the same references and therefore need not be described in detail. As illustrated, the discharge tube for display includes a tube body. This tube body comprises the front glass panel 1 and the rear glass panel 6 whose peripheral edges are sealed with frit glass and in which the following elements are accommodated. After the tube body was evacuated, discharge gas such as helium, neon, argon, xenon and so on or mixed gas thereof is sealed into the tube body. A pair of sheet-like memory elements Ma, Mb respectively include conductive layers having a plurality of square apertures 5a, 5b arranged in a two-dimensional fashion or in an XY matrix fashion, i.e., memory electrodes 3a, 3b formed of mesh-shaped metal plates that are formed by the metal plate etching process. The entire surfaces of the memory electrodes 3a, 3b other than the apertures 5a, 5b are covered with insulating layers 4a, 4b, respectively. The shape of the apertures 5a, 5b is not limited to a square and other shapes such as a circle or the like may be used. The memory electrodes 3a, 3b are each made of metal such as stainless steel, aluminum, nickel, etc., or alloy of metals. The insulating layers 4a, 4b are each formed by sintering at high temperature a paste of glass powder after being coated on the memory electrodes 3a, 3b according to some suitable process such as spraying, immersion or the like. When the insulating layers 4a,4b are made of glass, it is preferable that the memory electrodes 3a, 3b may have substantially the same thermal expansion coefficient as that of glass. The insulating layers 4a, 4b may be formed by oxidizing metal or alloy constructing the memory electrodes 3a, 3b. Furthermore, protecting layers such as magnesium oxide or the like may be formed on the insulating layers 4a, 4b similarly to the AC-PDP. The pair of memory elements Ma, Mb of the same shape and size are laminated each other so that the respective corresponding apertures 5a, 5b covered with the insulating layers 4a, 4b communicate to form discharge cells. Then, an AC voltage whose amplitude is sufficient to the extent that the discharge within the discharge cells can be maintained is applied across the pair of memory electrodes 3a, 3b from a memory power supply 10. Memory operation by the pair of memory elements Ma, Mb will be described below. When a discharge is excited within the discharge cell due to the writing of a signal by the discharge between the anodes 2 and the cathodes 7 which will be described later on, electric charge particles such as ions, electrons or the like within the tube body are attracted into the apertures 5a, 5b in response to the polarity of the memory electrodes 3a, 3b by the AC voltage applied thereacross and accumulated on the surfaces of the insulating layers 4a, 4b formed on the inner surfaces of the apertures 5a, 5b to thereby form a wall electric charge. Then, if the polarity of the memory electrodes 3a, 3b is inverted by the AC voltage applied thereacross, then a potential difference between the memory electrodes 3a, 3b is increased because a voltage based on the wall electric charge is superimposed upon the applied AC voltage, resulting in a discharge between the apertures 5a and 5b. This phenomenon is repeated, whereby a discharge within the discharge cell composed of the apertures 5a, 5b when the discharge is excited within the discharge cell due to the writing of the signal is maintained. When the discharge cell is widened, it is enough to laminate three memory elements or more. Apertures of memory elements more than two or three must be made coincident but they are not always the same in shape. A plurality of parallel striped first and second address electrodes, i.e., the anodes 2 and the cathodes 7 are disposed at a predetermined interval so as to cross each other, i.e., at a right angle. Between the anodes 2 and the cathodes 7, there are located the pair of memory elements Ma, Mb which are laminated such that respective crossing points of the anodes 2 and the cathodes 7 are opposed to respective discharge cells constructed by the respective apertures 5a, 5b. Each of the plurality of striped anodes 2 is formed of a transparent conductive layer such as ITO layer or the like. The striped anodes 2 are deposited on the front glass panel 1 with the equal width and at the equal interval. These anodes 2 are commonly connected to a positive voltage source +B through the collectors and emitters of PNP transistors 8 which are supplied at their bases with signals. The plurality of striped cathodes 7 are deposited on the rear glass panel 6 according to the screen printing and the sintering process of the conductive paste such as nickel or the like. These cathodes 7 are grounded via the collectors and emitters of NPN transistors 9 which are turned on when an operation pulse is sequentially supplied to the bases thereof. Since it is sufficient that the trigger-like discharge is excited between the anodes 2 and the cathodes 7, either or both of the anodes 2 and the cathodes 7 may be covered in the insulating layer. The barrier rib is not always needed. If necessary, the barrier rib may be disposed on the front glass panel 1 or on the rear glass panel 6. Alternatively, the barrier rib may be unitarily formed on a part of the insulating layer of the sheet-like memory element. A means for exciting the discharge within each aperture of the pair of memory elements is not limited to the anodes 2 and the cathodes 7 and other suitable means may be used. Operation of the above discharge tube for display device will be described with reference to FIGS. 7 to 10. As shown in FIG. 7, when a discharge is not yet excited within the tube body even by the application of pulse voltages of opposite polarity to the pair of memory electrodes 3a, 3b as shown in FIG. 10 while the AC voltage having an amplitude sufficient to maintain the discharge is applied between the pair of memory electrodes 3a, 3b and the wall electric charge is not generated within the apertures 5a, 5b covered with the insulating layers 4a, 4b of the pair of memory elements Ma, Mb, as shown in FIG. 7, if a switch SW1 is turned on for the first time and a voltage of 200 V to 250 V is applied to the anodes 2 through an internal resistance, then a switch SW2 is turned on and the cathodes 7 are grounded so that a discharge current flows between the anode 2 and the cathode 7. Consequently, as shown in FIG. 8, the wall electric charge is generated in the apertures 5a, 5b covered with the insulating layers 4a, 4b and the discharge is maintained, thereby a written display being memorized. At that time, the switches SW1, SW2 are both turned off so that a bias voltage, which does not affect the display, is applied to the cathodes 7. Also, the anode 2 is supplied with a voltage that does not affect the discharge of the anode to which other signal is being written. Operation in which the maintained discharge is stopped, i.e., the memory is erased, will be described with reference to FIG. 9. At the timing in which the negative electric charge is accumulated in the aperture 5b close to the cathode 7, or when the positive voltage is applied to the memory electrode 3b, as shown in FIG. 9, the switch SW2 is turned on to apply a negative erasing pulse to the cathode 7. This negative erasing pulse inhibits the wall electric charge to be accumulated in the inner wall of the aperture 5b from being formed. At the next timing, the discharge is therefore stopped and the memory is erased. Another example of the memory element will be described with reference to FIG. 11. In this example, memory electrodes 3Aa (3Ab) and 3Ba (3Bb) are deposited on both surfaces of a glass layer 4Ca (4Cb) having a plurality of apertures 5a, 5b arrayed in an XY matrix fashion according to the screen printing process of the metal plate and the following sintering process thereof. Thereafter, insulating layers 4Aa (4Ab) and 4Ba (4Bb) are deposited on the entire surfaces of the memory electrodes 3Aa (3Ab) and 3Ba (3Bb) by the spraying process or immersion process of the glass paste, thereby obtaining the memory elements Ma, Mb. A second embodiment of the discharge tube for display according to the present invention will be described with reference to FIG. 12. In the second embodiment of the present invention, instead of the sheet-like memory elements Ma, Mb of the first embodiment shown in FIGS. 4 to 6, the memory electrodes 3a, 3b and the insulating layers 4a, 4b of the memory elements Ma, Mb are formed together with the anode 2 and the cathode 7 according to the thick film technique. There is then the advantage that the memory elements Ma, Mb and the anode 2, the cathode 7 can be aligned in relative position easily and accurately. A third embodiment of the discharge tube for display device will be described with reference to FIG. 13. In accordance with the third embodiment of the present invention, the diameter of the aperture 5a in the memory element Ma is made larger than that of the aperture 5b in the memory element Mb unlike the second embodiment of FIG. 12. A fourth embodiment of the discharge tube for display according to the present invention will be described hereinafter with reference to FIG. 14. The fourth embodiment of the present invention is different from the first embodiment of the discharge tube for display shown in FIGS. 4 to 6 such that as shown in FIG. 14, for example, the rear side memory electrode 3b is separated to provide a plurality of rectangular electrodes 3b1, 3b2, ... parallel to a plurality of cathodes 7, the plurality of cathodes 7 are separated into groups in association with a plurality of rectangular electrodes 3b1, 3b2, ... and the electrodes of the same position at every group of the plurality of cathodes 7 are connected commonly. As illustrated in FIG. 14, when eight cathodes 7 are separated into two groups, each having four cathodes 7 and the memory electrode 3b is separated into two memory electrodes 3b1, 3b2, it is to be understood that nine connecting wires for the cathodes 7 and the memory electrodes 3b1, 3b2 are reduced to six connecting wires. A series circuit of the memory power supply 10 and switches Sa, Sb which are connected in parallel to each other and which are alternately turned on and off is connected between the memory electrode 3a and the memory electrodes 3b1, 3b2. Generally, when n cathodes 7 are separated, the number of the connecting wires of the separated memory electrodes 3b1, 3b2, ... and the n cathodes 7 can be reduced to 2 x n and therefore the driver circuits can be reduced considerably. A fifth embodiment of the discharge tube for display according to the present invention will be described with reference to FIG. 15. Operation of the fifth embodiment is similar to that of the first embodiment shown in FIGS. 4 to 6 The front side memory element Ma including the front side memory electrode 3a formed of the conductive layer having a plurality of apertures 5a arranged in an XY matrix form and in which the entire surface of the front side memory electrode 3a is covered with the insulating layer 4a and the rear side memory element Mb including the rear side memory electrode 3b the whole surface of which is formed of a conductive layer and deposited on the rear surface glass plate 6 and the whole surface of the rear side memory electrode 3b is covered with the insulating layer 4b are disposed in an opposing relation to each other. A plurality of anodes 2 deposited on the front glass panel 1 in parallel to each other and a plurality of cathodes 7 deposited on the insulating layer 4b of the memory element Mb in parallel to one another are disposed so as to cross each other. The front side memory element Ma is disposed between the plurality of anodes 2 and cathodes 7, and a plurality of cathodes 7 are disposed between the front side and rear side memory elements Ma and Mb. A sixth embodiment of the discharge tube for display according to the present invention will be described below with reference to FIGS. 16 and 17. FIG. 16 is an exploded perspective view of the sixth embodiment and FIG. 17 is a diagrammatic view of a section thereof. As shown in FIGS. 16 and 17, in this discharge tube for display, the following structure is accommodated within the tube body which is formed in such a manner that the peripheral edges of the front and rear glass panels 1 and 6 are sealed by frit glass. The tube body is evacuated and then a discharging gas such as helium, neon, argon, xenon and so on or mixed gas thereof is sealed into the tube body. The front side memory element Ma and the rear side memory element Mb are disposed within the tube body in an opposing relation to each other. The front side memory element Ma includes the front side memory electrode 3a formed of the transparent whole surface conductive layer and the whole surface of the front side memory electrode 3a is covered with the transparent insulating layer 4a. The rear side memory element Mb includes the rear side memory electrode 3b formed of the whole surface conductive layer. The whole surface of the rear side memory electrode 3b is covered with the insulating layer 4b. Between the front side and rear side memory elements Ma, Mb, there are disposed a plurality of parallel striped anodes 2 and a plurality of parallel cathodes 7 in such a manner that they cross each other across an insulating barrier 11 of a grating configuration having apertures 11a of square shape arranged in an XY matrix fashion and corresponding to the crossing points of the anodes 2 and the cathodes 7. The front side memory electrode 3a is formed of a transparent whole surface conductive layer such as an SnO 2 , ITO or the like. The transparent insulating layer 4a is formed by the thick film technique in which the pasted glass powder is printed and baked or by the thin film technique such as vapor deposition, sputtering method or the like. The surface of the transparent insulting layer 4a may be covered with a protecting film such as MgO or the like. The anode 2 is deposited on the insulating layer 4a by the printing and baking of metal pastes such as Ag, Au, Al, Ni or the like according to the thick film method or by Cr according to the thin film method, in addition to the transparent conductive layer. It is preferable that a width of the anode 2 is made as narrow as possible in order to generate much more wall electric charges on the insulating layer 4a that constructs one portion of the discharge cell of the memory element Ma. The memory electrode 3b is formed on the rear glass panel 6 according to the thick film method or thin film method. It is desirable that the cathode 7 is made of a material which has a low work function and an anti-ion impulse property similar to the DC-PDP such as Ni, Lab 6 or the like. Upon address operation, the cathode 7 is operated at a small current as compared with the ordinary DC-PDP so that the material forming the cathode 7 is not limited thereto and a range in which the material is selected for the cathode 7 can be widened. Also, it is preferable that a width of the cathode 7 is made as narrow as possible similarly to the anode 2 in order to generate much more wall electric charges on the insulating layer 4b that constructs one portion of the discharge cell of the memory element Mb. While the barrier 11 serves as a spacer which is used to hold a proper spacing between the front glass panel 1 and the rear glass panel 6 to seal the discharging gas in the tube body, the shape of the barrier 11 is not limited to the grating and may be striped like the DC-PDP. Further, the barrier 11 is not limited to the independent structure and may be formed on the front glass panel 1 or rear glass panel 6 according to the thick film technique. Operation of the sixth embodiment of the discharge tube for display according to the present invention will hereinafter be described with reference to FIG. 18. When the discharge is not yet generated within the tube body and the wall electric charge is not yet generated on the insulating layers 4a, 4b of a pair of memory elements Ma, Mb within the aperture 11a of the barrier 11 under the condition such that the AC voltage having an amplitude necessary for maintaining the discharge is applied to a pair of memory electrodes 3a, 3b by the application of pulse voltages of opposite polarities, a voltage of 200V to 250V is initially applied to the anodes 2 as shown in FIG. 18. Also, when the cathodes 7 are grounded, a discharging current flows between the anode 2 and the cathode 7. Therefore, as shown in FIG. 18, the wall electric charge is generated on the walls of the insulating layers 4a, 4b within the aperture 11a and the discharge is maintained, thereby the written display content being memorized. At that time, a bias voltage that is prevented from affecting the display is applied to the cathode 7 and a voltage that is prevented from affecting the discharge of the anode in which other signal is written is applied to the anode 2. In order to stop the maintained discharge or to erase the memory, the erasing pulse of negative polarity is applied to the cathode 7 at the timing at which a negative electric charge is accumulated on the insulating layer 3b of the cathode 7, or when the positive voltage is applied to the memory electrode 3b. By this erasing pulse, the wall electric charge to be accumulated on the inner wall of the aperture 11a can be prevented from being formed so that the discharge is stopped at the next timing, thereby erasing the memory. When the above discharge tube for display is formed as a discharge tube for color display device, a fluorescent layer is coated on the inside wall of the apertures 11a of the barrier 11 and the fluorescent layer may be made luminous by ultraviolet rays upon the discharge. A seventh embodiment of the discharge tube for display according to the present invention will be described with reference to FIG. 19. In this embodiment, the rear side memory electrode 3b in the sixth embodiment of FIGS. 16 and 17 is separated to provide a plurality of rectangular electrodes 3b1, 3b2, ... which are parallel to a plurality of cathodes 7. Then, a plurality of cathodes 7 are separated into groups in association with a plurality of rectangular rear side memory electrodes 3b1, 3b2, ... and electrodes of a plurality of the thus grouped cathodes 7 are connected commonly at the same positions of every group. When the eight cathodes 7 are separated into the two groups, each having four cathodes and the memory electrode 3b is separated into two memory electrodes 3b1, 3b2 as shown in FIG. 19, it is clear that nine connecting wires for the cathodes 7 and the memory electrodes 3b1, 3b2 can be reduced to six connecting wires. Generally, when n cathodes 7 are separated, the connecting wires for the separated memory electrodes 3b1, 3b2, ... and the n cathodes 7 can be reduced to 2 x n. An eighth embodiment of the discharge tube for display according to the present invention will be described with reference to FIG. 20. In this embodiment, as shown in FIG. 20, a rear side memory element M including a plurality of first and second alternate memory electrodes 3a, 3b arranged alternately and in which the whole surfaces of a plurality of first and second memory electrodes 3a, 3b are covered with the insulating layer 4b is formed on the rear glass panel 6. In an opposing relation to the rear side memory element M, a plurality of parallel striped anodes 2 and a plurality of cathodes 7 cross each other across the insulating barrier 11 having apertures 11a serving as discharge cells corresponding to respective crossing points between the anodes 2 and the cathodes 7. While a plurality of memory electrodes 3a, 3b are alternately formed on the rear side glass panel 6 in parallel to a plurality of cathodes 7 in this embodiment, the cathodes 7 are commonly connected at each of a plurality of memory electrodes 3a, 3b. Therefore, this discharge tube is operated similarly to the discharge tube in which a plurality of memory electrodes 3a, 3b are disposed in an opposing relation. A plurality of memory electrodes 3a, 3b may be disposed in parallel to a plurality of anodes 2. The apertures 11a of the insulating barrier 11 may be formed as rectangular grooves parallel to a plurality of cathodes 7. When the discharge tube for display according to this embodiment is formed as a discharge tube for color display, the discharge tube is formed as a surface discharge type in which the fluorescent layer can be coated on the front glass panel 1 side. While a capacity coupling based on an electrostatic capacity exists on the insulating layer 4a or 4b formed between a plurality of anodes 2 or cathodes 7 and a plurality of memory electrodes 3a or 3b, if a plurality of insulating layers, each having the same width as that of each of a plurality of anodes 2 or cathodes 7 are disposed between a plurality of anodes 2 or cathodes 7 and the insulating layer 4a or 4b, then the capacity can be reduced and therefore a problem caused by the capacity coupling from a driving standpoint can be solved. According to the first to fourth embodiments of the present invention, since a plurality of anodes and cathodes need not the insulating layer formed on the respective electrodes thereof similarly to those of the conventional DCPDP and the discharge is produced within the apertures provided on the memory elements, the barrier rib is not needed and a driving circuit similar to that of the DCPDP can be utilized. Therefore, the discharge tube is simple in structure, excellent in mass-production, can be increased in resolution and made large in size with ease. The discharge tube can be driven with ease and a driver circuit thereof can be simplified. In addition, the discharge tube for display can be made inexpensive with ease. Further, according to the third embodiment of the present invention, the driver circuit can be simplified more in structure. According to the fifth to seventh embodiments of the present invention, although a plurality of anodes and cathodes needs no insulating layer formed on the respective electrodes thereof similarly to the electrodes of the known DC-PDP and a memory driving circuit requires relatively high electric power, such memory driving circuit may be provided for only one system. Therefore, the discharge tube for display can be simplified in structure, excellent in mass-production, high in resolution and made large in size with ease. Further, the driving circuit can be simplified since its driving technique is simple. In addition, the discharge tube can readily be made inexpensively. Still further, according to the sixth embodiment of the present invention, the driving circuit can be even more simplified. According to the fifth to seventh embodiments of the present invention, since the discharge spaces of the address discharge and the memory discharge are the same and the positive or negative electric charge is generated on the insulating layer on the memory electrode by the address discharge, the discharge tube can be operated reliably and stably. In addition, since the discharge tube for display has a memory function, its luminous brightness is high. There is then no risk that, even when the number of lines is increased, the brightness will be lowered as a result.

Claims: A display discharge tube comprising: a pair of memory electrodes (3a, 3b) each formed of a conductive layer having a plurality of apertures (5a, 5b) arranged in an XY matrix form and in which the whole surface of each memory electrode (3a, 3b) is covered with an insulating layer (4a, 4b), the memory electrodes (3a, 3b) being laminated together such that corresponding apertures (5a, 5b) covered with the insulating layers (4a, 4b) communicate together to form an array of discharge cells; a plurality of first parallel and second parallel address electrode strips (2, 7) disposed at predetermined intervals so as to cross each other, the memory electrodes (3a, 3b) laminated together being disposed between the first and second address electrode strips (2, 7) such that respective crossing points of the first and second address electrode strips (2, 7) correspond to the respective discharge cells; and a tube body (1, 6) in which the first and second address electrode strips (2, 7) and the memory electrodes (3a, 3b) are sealed and in which a discharging gas is sealed, wherein when a predetermined voltage (+B) is applied between selected ones of the first and second address electrode strips (2, 7) a discharge is caused to occur in the discharge cell located at the crossing point thereof, and when a predetermined AC voltage (10) is applied between the memory electrodes (3a, 3b) the discharge is maintained. A display discharge tube according to claim 1, wherein the memory electrodes comprise a front memory electrode (3a) and a rear memory electrode (3b), the rear memory electrode (3b) being divided to provide a plurality of rectangular electrodes parallel to the plurality of second address electrode strips (7), the second address electrode strips (7) being separated into groups each of which is associated with one of the plurality of divided rectangular rear memory electrodes (3b), and electrodes disposed within the same group being connected in common. A display discharge tube comprising: a front memory electrode (3a) having a plurality of apertures (5a) arranged in an XY matrix form serving as discharge cells, the surface of the front memory electrode (3a) being covered with an insulating layer (4a); a rear memory electrode (3b) the surface of which is formed of a conductive layer and is covered with an insulating layer (4b), the front memory electrode (3a) and the rear memory electrode (3b) being disposed in an opposing relation; a plurality of first parallel and second parallel address electrode strips (2, 7) being disposed so as to cross each other, the front memory electrode (3a) being disposed between the first and second address electrode strips (2, 7) such that respective crossing points of the first and second address electrode strips (2, 7) correspond to respective discharge cells; and a tube body (1, 6) in which a discharging gas is sealed and in which the second address electrode strips (7) are sealed such that they are disposed between the front and rear memory electrodes (3a, 3b), wherein when a predetermined voltage (+B) is applied between selected ones of the first and second address electrodes (2, 7) a discharge is caused to occur in the discharge cell located at the crossing point of the selected first and second address electrode strips (2, 7) and when a predetermined AC voltage (10) is applied between the front and rear memory electrodes (3a, 3b) the discharge is maintained. A display discharge tube comprising: a front memory electrode (3a) the surface of which is formed of a transparent conductive layer, the surface of the front memory electrode (3a) being covered with a transparent insulating layer (4a); a rear memory electrode (3b) the surface of which is formed of a conductive layer, the surface of the rear memory electrode (3b) being covered with an insulating layer (4b), the front memory electrode (3a) and the rear memory electrode (3b) being disposed in an opposing relation; a plurality of first parallel and second parallel address electrode strips (2, 7) being disposed between the front and rear memory electrodes (3a, 3b) so as to cross each other; an insulating barrier (11) having a plurality of apertures (lla) serving as discharging cells corresponding to respective crossing points of the first and second address electrode strips (2, 7) and being disposed therebetween; and a tube body (1, 6) in which a discharging gas is sealed and in which the memory electrodes (3a, 3b), the address electrode strips (2, 7) and the insulating barrier (11) are sealed, wherein when a predetermined voltage (+B) is applied between selected ones of the first and second address electrode strips (2, 7) a discharge is caused to occur in the discharge cell located at the crossing point of the selected first and second address electrode strips (2, 7), and when a predetermined AC voltage (10) is applied between the memory electrodes (3a, 3b) the discharge is maintained. A display discharge tube according to claim 4, wherein the rear memory electrode (3b) is divided to provide a plurality of rectangular electrodes parallel to the plurality of second address electrode strips (7), the second address electrode strips (7) being separated into groups each of which is associated with one of the plurality of divided rectangular rear memory electrodes (3b), and electrodes disposed within the same group being connected in common. A display discharge tube comprising: a rear memory element (M) including a plurality of first and second memory electrodes (3a, 3b) arranged alternately, the surfaces of the first and second memory electrodes (3a, 3b) being covered with an insulating layer (4b); a plurality of first parallel and second parallel address electrode strips (2, 7) being opposed to the rear memory element (M) so as to cross each other; an insulating barrier (11) having a plurality of apertures (lla) serving as discharge cells corresponding to respective crossing points of the first and second address electrode strips (2, 7) and being disposed therebetween; and a tube body (1, 6) in which a discharging gas is sealed and in which the rear memory element (M), the address electrode strips (2, 7) and the insulating barrier (11) are sealed, wherein when a predetermined voltage is applied between selected ones of the first and second address electrode strips (2, 7) a discharge is caused to occur in the discharge cell located at the crossing point of the selected first and second address electrode strips (2, 7), and when a predetermined AC voltage (10) is applied between the memory electrodes (3a, 3b) the discharge is maintained.

Inventors: AMANO YOSHIFUMI, AMANO, YOSHIFUMI, AMANO, YOSHIFUMI, C/O TECHNOLOGY TRADE AND
Applicants: NORITAKE CO LTD, TECHNOLOGY TRADE AND TRANSFER, NORITAKE CO., LIMITED, TECHNOLOGY TRADE AND TRANSFER CORPORATION
Application year: 1992
Main classification: H01J17
IPC codes: H01J17, H01J11