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Publication numberUS3800186 A
Publication typeGrant
Publication dateMar 26, 1974
Filing dateFeb 15, 1973
Priority dateFeb 16, 1972
Also published asDE2307487A1, DE2307487B2, DE2307487C3
Publication numberUS 3800186 A, US 3800186A, US-A-3800186, US3800186 A, US3800186A
InventorsKaji T, Miyashita T, Mizushima M, Murayama S, Seko T, Shinada S, Yamane M
Original AssigneeHitachi Ltd
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Display device
US 3800186 A
Abstract
A display device comprising means having a plurality of pairs of discharge electrodes and defining a discharge space for producing electrons by discharge, a plurality of first control grids disposed in parallel with one another for controlling the electron beam emanating from the discharge space, a plurality of second control grids disposed in parallel with one another in perpendicularly crossing relation with the first control grids, means for accelerating the electron beam controlled by these first and second control grids, a phosphor luminescing in response to the impingement of the accelerated electron beam thereagainst, voltage supplying means for supplying a discharge voltage to the discharge electrodes for causing intermittent discharge in the discharge space, and means for applying a scanning pulse voltage and a pulse modulated signal to the first and second control grids respectively upon cessation of the discharge.
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Description  (OCR text may contain errors)

nited States Patent [1 1 Yamane et al.

[ DISPLAY DEVICE 73 Assignee: Hitachi, Ltd., TokyoJJapan 22 Filed: Feb. 15,1973

21 Appl.No.:332,590

[30] Foreign Application Priority Data Feb. 16, 1972 Japan 47-15561 [52] US. Cl..... 315/169 TV, l78/7.3 D, 313/108 B, 313/109.5, 315/169 R [51] Int. Cl H04n 3/16, l-lOSb 37/00 [58] Field of Search l78/7.3 D, 7.5 D; 315/169 R, 169 TV; 313/108 B, 109.5

[56] References Cited UNITED STATES PATENTS 3,176,184 3/1965 Hopkins 315/169 R X 3,579,015 5/1971 Gregory l78/7.5 D

3,753,041 8/1973 Lustig 315/169 R Primary Examiner-Herman Karl Saalbach Assistant ExaminerLawrence J. Dab] Attorney, Agent, or Firm-Craig and Antonelli [5 7] ABSTRACT A display device comprising means having a plurality of pairs of discharge electrodes and defining a discharge space for producing electrons by discharge, a plurality of first control grids disposed in parallel with one another for controlling the electron beam emanating from the discharge space, a plurality of second control grids disposed in parallel with one another in perpendicularly crossing relation with the first control grids, means for accelerating the electron beam controlled by these first and second control grids, a phosphor luminescing in response to the impingement of the accelerated electron beam thereagainst, voltage supplying means for supplying a discharge voltage to the discharge electrodes for causing intermittent discharge in the discharge space, and means for applying a scanning pulse voltage and a pulse modulated signal to the first and second control grids respectively upon cessation of the discharge.

6 Claims, 10 Drawing Figures PATENTED R26 I974 SHEET 01 HF 10 FIG.

HIGH V 28 DISCHARGE VOLTAGE SIIEET 02 0F 10 mDOKO mmzmo FIG. 2

m2] ZPZONEOI mmzzddm m2: ZFZONEOI PATENTEII "I828 I874 VERTICAL LINE DRIVER GROUP PULSE WIDTH MODULATOR GROUP GATE GROUP 7 DELAY LINE VOLTAGE APPLIES TO GRID PAI'ENIEII IIIRZS I974 sum 03 0F 10 VERTICAL I SYNCHRONIZING SIGNAL HORIZONTAL I I I SYNCHRONIZING 1 SIGNAL VOLTAGE AGRGG I" ELECTRODES. d I? AND I8 :H*

VOLTAGE APPLIED TO GRID 0 SJ:

VOLTAGE APPLE?) TO GRID -Ec2 VOLTAGE APPUED T o GRID I I I I I I TIME PAIENTEWR26 m4 3.800.186

saw an or 10 saw usor.1o

FIG. 5

MODULATOR GROUP VERTICAL LINE DRIVER .GROUP PULSE WIDTH GATE GROUP DELAY LINE PATENTEDIARZG I974 PAIENIEUIIIII2G I974 I 3,800,186

SHEET '08 0F 10 FIG. 6

VERTICAL SYNCHRONIZING E'IITC'EFISIIZHNG SIGNAL I I I] [I VOLTAGE AcROss ELEcTRODEs Vd IT-I AND I8-I O VOLTAGE AcRoss -Td ELECTRODES Vd I7-2 AND l8-2 VOLTAGE APPLIED I TO GRID 4-I r" I I I I 6.- i T F I I I I I VOLTAGE APPLIED I I TO GRID 4-2 I D I I L J I I I I VOLTAGEAPPLIED I I TO GRID 7-l I in VOLTAGE APPLIED I TO GRID 7-2 PATENTED M26 1974 FIG. 7

PATENTED M26 I974 saw uaIII' I0 FIG. 8

' "z 1 LL] I I 32 POWER 9 SOURCE 7-3 2 26 27 I8. 3| 5 5% tlB-Z E I g 4+ 3' l-LLI 4 2 22 I 4-3 @5 E1?" $3 [5% IB-L E/ I I 4-M VERTICAL LINE -25 DRIVER GROUP PULSE WIDTH -24 MODULATOR GROUP 20 GATE GROUP 23 I I I 2 DELAY. LINE 22 PATENTEBHARZB 19m VERTICAL SYNCHRONIZ I NG SIGNAL 9" HORIZONTAL SYNCHRONIZING SIGNAL FIG. 9

VOLTAGE Amos ELECTRODES I7- I AND l8- l \OLTAGE ACROSS ELECTRODES Vd I7-2 AND I8-2 I I I VOLTAGE ACROSS PL ATE S l i I l 9 AND 30 VOLTAGE APPLIED) T0 GRID 4-| VOLTAGE APPLIED TO GRID 4'2 VOLTAGE APPLIEB T0 GRID 7-| Ec2 VOLTAGE APPLIED TO GRID 7-2 TIME DISPLAY DEVICE This invention relates to devices for displaying images and the like and more particularly to a display device having an electron source for producing electrons by electric discharge.

One of known devices for displaying images and the like comprises generally a grid conductor group, a phosphor and a thermionic emission cathode disposed within an evacuated envelope. However, such a display device has not yet been put into practical use chiefly for the reason that a cathode capable of efficiently and uniformly emitting electrons over a wide area is difficult to obtain.

It is an object of the present invention to provide a display device having an electron source for producing electrons by discharge in a gaseous atmosphere.

Another object of the present invention is to provide a display device which can display an image with substantially uniform brightness and with which electrons can be utilized with high efficiency.

A further object of the present invention is to provide a display device having the following features: Firstly, discharge occurs intermittently and voltage for causing this discharge and voltage for controlling electron beams are applied at different times so as to draw out electrons from a discharge space within the period of time in which the discharge is ceased; secondly, a plurality of discharge electrode pairs constituting a discharge electrode group are successively and periodically caused to discharge; and thirdly, an electric field is established in the direction in which the electrons are drawn out from the discharge space after the interruption of discharge so as to utilize any remaining electrons for display.

According to the present invention there is provided a display device comprising a first insulating member having a plurality of pairs of discharge electrodes and defining a discharge space for producing electrons by discharge in a gaseous atmosphere, a sealing member for sealing said discharge space gas-tight against the exterior, a conductive member formed with a plurality of perforations for allowing passage of the electron beam emerging from said discharge space, a second insulating member defining an acceleration space for accelerating the electron beam passed through said perforations in said conductive member, a transparent insulating member for sealing said acceleration space gastight against the exterior, a plurality of first and second control grid conductors disposed between said conductive member and said second insulating member and crossing with each other on said perforations in said conductive member so as to control the entrance of said electron beam into said acceleration space, a pair of spaced insulating separators having a plurality of aligned perforations formed at positions corresponding to the positions of said perforations in said conductive member so as to hold said first and second control grid conductors in the crossing relation with a predetermined spacing therebetween, a transparent electrode sandwiched between a phosphor layer and said transparent insulating member for causing said electron beam accelerated in said acceleration space to impinge against said phosphor layer formed on said transparent insulating member, a power source for generating a discharge voltage periodically in synchronism with a predetermined external signal, means for applying the discharge voltage from said power source to said discharge electrodes, means for generating a control voltage for successively and periodically applying said control voltage to said second control grids one after another in synchronism with the application of said discharge voltage to said discharge electrodes, means for applying to said first control grids a signal obtained by pulse width modulation of a predetermined display signal depending on the level thereof, and means for applying an accelerating voltage to said transparent electrode for accelerating said electron beam in said acceleration space, said electron beam being drawn out toward said second control grids during the period of time in which the discharge occurs in said discharge space.

The above the other objects, features and advantages of the present invention will be apparent from the following detailed description taken in conjunction with the accompanying drawing, in which:

FIG. 1 is a diagrammatic view showing the structure of a display device according to the present invention;

FIG. 2 is a block diagram showing the structure of a system used in the display device of the present invention adapted for displaying a television picture;

FIG. 3 shows voltage waveforms appearing at various parts of the system shown in FIG. 2;

FIG. 4 is a schematic view showing the arrangment of elements in the embodiment of the present invention;

FIG. 5 is a block diagram showing the structure of a system used in the display device of the present invention adapted for displaying a television picture;

FIG. 6 shows voltage waveforms appearing at various parts of the system shown in FIG. 5;

FIGS. 7 and 10 are diagrammatic views showing other forms of the display device according to the present invention;

FIG. 8 is a block diagram showing the structure of a system used in the display device of the present invention adapted for displaying a television picture; and

FIG. 9 shows voltage waveforms appearing at various parts of the system shown in FIG. 8.

FIG. 1 shows the structure of a display device according to the present invention in which discharge in a gaseous atmosphere is utilized for obtaining electrons.

Referring to FIG. 1, a transparent conductive film 2 such as a Nesa (a trade-mark) film is formed on one surface of a transparent insulating plate 1 of material such as glass and a phosphor layer 3 is coated on the transparent conductive film 2. A plurality oof equally parallelly spaced first control grids 4-1, 4-2, 4-3 and 4-4 constituting a first control grid group 4 are disposed in a plane which is substantially parallel with the phosphor layer 3, and a first insulating frame member 5 is interposed between the phosphor layer 3 and the first control grid group 4 for defining an acceleration space 6. A plurality of equally parallelly spaced second control grids 7-1, 7-2, 7-3 and 7-4 constituting a second control grid group 7 are disposed in perpendicularly crossing relation with respect to the first control grid group 4, and a first insulating separator 8 is interposed between the first and second control grid groups 4 and 7. A second insulating separator 10 is interposed between the second control grid group 7 and a conductive shielding plate 9. A second insulating frame member 11 defining a discharge space 12 is disposed in parallel with the conductive shielding plate 9 and is sealed at the outer end opening thereof gas-tight with an insulating plate 13. The first and second insulating separators 8 and 10 and conductive shielding plate 9 are provided with a plurality of perforations 14, and 16 respectively at positions registering with the intersections of the first and second control grids 4 and 7. A plurality of pairs of electrodes 17 and 18 are disposed in the discharge space 12 for causing discharge in the discharge space 12. The acceleration space 6 and discharge space 12 are sealed gas-tight from the exterior by the transparent insulating plate 1 and insulating plate 13 respectively, and a rare gas or mercury vapor or a mixture of the rare gas and mercury vapor is enclosed within the acceleration space 6 and discharge space 12.

In operation, voltage is applied across the discharge electrode groups 17 and 18 for causing discharge in the discharge space 12. Electrons produced by the discharge diffuse toward the first and second control grids 4 and 7 through the perforations 16 formed in the conductive shielding plate 9. Normally, a voltage negative relative to the conductive shielding plate 9 is applied to the first and second control grids 4 and 7, and thus, the electrons cannot pass by these control grids 4 and 7. When now a plurality of predetermined grids are selected from the first and second control grids 4 and 7 and a voltage which is zero or positive (hereinafter referred to as a control voltage) is applied to these selected control grids, the electrons pass solely through the perforations lying at the intersections of the selected first and second control grids 4 and 7 to be guided toward the acceleration space 6. The electrons entering the acceleration space 6 are accelerated by a high d.c. voltage applied to the conductive film 2 thereby Causing luminescence of the phosphor 3. In displaying, for example, a television picture, a horizontal synchronizing signal is applied to the second control grids 7-l, 7-2, 7-3 and 7-4 and a signal obtained by modulating a pulse signal depending on the level of a video signal, for example, a pulse width modulated signal is applied to the first control grids 4-1, 4-2, 4-3 and 44.

It will thus be understood that utilization of discharge is advantageous in that electrons can be uniformly derived over a wide area, hence a large current can be derived, compared with a prior art arrangement in which the cathode is used as an electron source and the thermionic emission from the cathode is utilized. Further, the response time can be greatly improved due to the utilization of discharge.

In the display device of the type abovedescribed, there is the possibility of appearance of a space charge on the surface ofthe conductive shielding plate 9 opposite to the discharge space 12 in the state in which the discharge voltage is applied to the discharge electrodes 17 and 18. Further, due to the fact that the quantity of the space charge that may appear in the above situation differs depending on the position on the shielding plate 9, different numbers of electrons may pass through the perforations l6-l 16-2, 16-3, thereby giving rise to non-uniformity of the brightness. Further, due to the fact that only a portion of the electrons produced by the discharge can pass through the perforations 16 by diffusion, the electrons may not be utilized with good efficiency. However, the present invention can provide a system which is free from the non-uniform brightness above-described and can utilize the electrons with high efficiency. Such a system'will now be described.

FIG. 2 is a block diagram of a system used in the display device of the present invention which is adapted for displaying, by way of example, a television picture and in which means are provided so that discharge occurs intermittently and voltage for causing this discharge and voltage for controlling the electron beam are applied at different times in order to draw out the electrons from the discharge space within the period of time in which the discharge is interrupted. In the present invention, line sequential scanning is employed as it is advantageous in respect of the brightness of the picture and effective utilization of the electron source. In the present invention, further, the width of the pulse waveform applied to the first control gride 4 is varied depending on the level of the video signal, hence, socalled pulse width modulation is employed for obtaining the gray scale of the picture.

Referring now to FIG. 2, a delay line 22 is connected to a video signal input terminal 21. The delay time of the delay line 22 is equal to the horizontal scanning period and the number of output terminals of the delay line 22 is equal to the total number M of the first control grids 4-1, 4-2, 4-M. In the period of time equal to the horizontal scanning period after the application of the video signal to the terminal 21, the video signal corresponding to one horizontal scanning period is distributed over the delay line 22. A discharge voltage generator 28 and a gate group 23 are connected to a horizontal synchronizing signal input terminal 20. Thus, in response to the application of the horizontal synchronizing signal to the terminal 20, the horizontal synchronizing signal is applied, on one hand, to the discharge voltage generator 28 so that the generator 28 generates a pulse in synchronism with the horizontal synchronizing signal, andon the other hand, to the gate group 23 so that the individual gates are turned ON to apply the signals appearing at the output terminals of the delay line 22 to respective input terminals of a pulse width modulator group 24. Each pulse width modulator is composed of, for example, a holding circuit for holding an input signal, a saw-tooth waveform generator for generating a saw-tooth waveform, a comparator for comparing the output of the holding circuit with the output of the saw-tooth waveform generator, an an amplitude limiter for limiting the amplitude of the output of the comparator to a predetermined level. Therefore, in order to start the pulse width modulation after the generation of a pulse from the generator 28, the saw-tooth waveform generator is triggered by the falling edge portion of the pulse for obtaining a sawtooth waveform voltage. The comparator delivers its output when the saw-tooth waveform voltage level conincides with the level of the input signal applied to the holding circuit, and thus the output of the comparator is a pulse voltage which is proportional to the input signal level. The amplitude of this pulse voltage is limited to a predetermined level of, for example, E volts by the amplitude limiter. In this manner, the M signals applied to the pulse width modulator group 24 are converted into M pulses which have different widths depending on the original level thereof and which have the same predetermimed level of E volts. These pulses are amplified by a vertical line driver group 25, for example, an amplifier group and are then applied to the first control grids 4-1, 4-2, 4-M.

A horizontal line scanner 26 is connected to the horizontal synchronizing signal input terminal and to a vertical synchronizing signal input terminal 19. The

horizontal line scanner 26 is provided with a plurality of output terminals the number of which is equal to the total number N of the second control grids 7-1, 7-2, 7-N. Thus, in response to the application of the vertical synchronizing signal and horizontal synchronizing signal to the horizontal line scanner 26 through the respective terminals 19 and 20, N scanning pulses having a pulse interval substantially equal to the horizontal scanning period and having an amplitude of E volts appear successively from the output terminals of the horizontal line scanner 26. The horizontal line scanner 26 is composed of, for example, a shift register which is set and reset by the horizontal synchronizing signal and vertical synchronizing signal respectively and which consists of stages whose number is equal to the number of the second control grids, a pulse generator for generating a pulse of phase opposite to that of the pulse voltage generated by the discharge voltage generator 28, and a plurality of AND gates to which the outputs of the respective stages of the shift register are applied as one of the two inputs thereto and the output of the pulse generator is applied as the other and common input thereto. Therefore, each time the horizontal synchronizing signal is applied to the shift register, output pulses appear successively from the respective stages of the shift register and are applied to the corresponding AND gates as one of the inputs to the AND gates, but no outputs appear from the these AND gates due to the fact that the pulse of phase opposite to that of the discharge voltage pulse is generated by the pulse generator and is applied to the AND gates as the other and common input thereto, After the generation of the discharge voltage, the pulse generated by the pulse generator is applied to the AND gates as the other and common input thereto, and thus, the scanning pulses appear successively from the AND gates after the disappearance of the discharge voltage. These scanning pulses are amplified by a horizontal line driver group 27, for example, an amplifier group to be successively applied to the second control grids 7-1, 7-2, 7-N. Further, in response -to the application of the horizontal synchronizing signal, the discharge voltage generator 28 generates a discharge voltage pulse in synchronism with the horizontal synchronizing signal as described hereinbefore. This discharge voltage pulse is applied across the discharge electrodes 17-1, 17-2, 17-L and 18-1, 18-2, 18-L.

The signals appearing at various parts in FIG. 2 vary relative to time as shown in FIG. 3. More precisely, FIG. 3 shows voltage waveforms of the vertical synchronizing signal 19', horizontal synchronizing signal 20', discharge voltage pulse signal having an amplitude Vd applied across the discharge electrodes 17 and 18, pulse width modulated signal applied to the first control grids 4-1, 4-2, 4-M, and scanning pulses applied to the second control grids 7-1, 7-2, 7-N. The horizontal scanning period is Th.

The discharge voltage pulse is generated upon application of the horizontal synchronizing signal to the discharge voltage generator 28, and after lasting for a period of time of 1, seconds for attaining the discharge, it is restored to the zero potential level again. After the restoration oof the discharge voltage pulse to the zero potential level, the scanning pulses are applied to the second control grids 7-1, 7-2, 7-N and the signal obtained by the pulse width modulation by the video signal is applied to the first control grids 4-1, 4-2, 4-M. In response to the application of these signals to the first and second control grids 4 and 7, the electrons remaining in the discharge space 12 diffuse through the perforations 16 bored in the conductive shielding plate 9. The electrons passing through the perforations 15 and 14 bored in the respective insulating separators 10 and 8 enter the acceleration space 6 and are accelerated by the high DC. voltage applied to the conductive film 2 by the high voltage source 31 to impinge against the phosphor layer 3 thereby producing luminescence.

In the case of the display device in which electrons are obtained by discharge, the plasma produced by the discharge has a potential distribution in the direction of the discharge electrodes, and as a result, the space charge may accumulate with a non-uniform density on the surface of the conductive shielding plate 9 opposite to the discharge space 12, as pointed out previously. This is undesirable in that the density of the electrons emerging from the perforations 16 of the conductive shielding plate 9 varies depending on the position relative to the direction of the discharge electrodes. This disadvantage can be eliminated by the novel arrangement employed in the present invention. According to the present invention, the discharge occurs intermittently and the negative voltages -E,, and E, are applied to the first control grids 4 and second control grids 7 respectively during the discharge so as to prevent flow-out of the electrons from the discharge space 12, the potentials of the first and second control grids 4 and 7 being then raised to the zero level, hence the potential level of the conductive shielding plate 9, immediately after the interruption of the discharge so as to allow flow-out of the electrons from the discharge space 12. Due to the fact that the discharge voltage Vd is zero in this latter period of time, the abovementioned potential distribution of the plasma remaining in the discharge space 12 can be eliminated and the electrons can be drawn out with a uniform density.

The voltage and current values employed in the device are enumerated by way of example as follows:

Accelerating voltage applied to anode or conductive film 2: 5 kV Voltage value -E applied to first control grids 4:

Voltage value E applied to second control grids 7:

Amplitude Vd of discharge voltage pulse: V

Width 7, of discharge voltage pulse: 10 us Discharge current: -10 mA Electron current drawn out from each perforation of conductive shielding plate 9: 10 A The accelerating voltage, voltage E applied to the first control grids 4 and voltage applied to the second control grids 7 above-described represent the values relative to the potential of the conductive shielding plate 9. It will be understood therefore that the values of the accelerating voltage, voltage E,, and voltage E should be suitably varied when the potential of the conductive shielding plate 9 is varied.

In the above description, all the discharge electrodes are simultaneously energized for obtaining an electron beam for utilizing the same for display. However, the

present invention is in no way limited to such arrangement and the discharge electrodes constituting the discharge electrode pairs in the discharge space may be successively and periodically energized for saving the power requirement necessary for obtaining the electron beam used for display.

FIG. 4 shows in more detail the positions of the first and second control grids 4 and 7 and the position of the perforations 16 of the conductive shielding plate 9 relative to the position of the discharge electrode pairs 17-1, 18-1; 17-2, 18-2; 17-L, 18-L. In FIG. 4, the discharge electrode pairs 17-1, 18-1; 17-2, 18-2; 17-L, 18-L are associated with the second control grids 7-1, 7-2, 7-N (L N) respectively. Thus, the electrons obtained from the plasma produced by the discharge across, for example, the electrodes 17-1 and 18-1 constituting one of the electrode pairs appear mainly in the vicinity of the second control grid 7-1. Although a portion of these electrons appear also in the vicinity of the second control grids 7-2, 7-3, the quantity of such electrons is not so large. Similarly, the electrons produced by the discharge across the electrodes 17-2, and 18-2 appear in the vicinity of the second control grid 7-2, and the electrons produced by the discharge across the electrodes l7-3 and 18-3 appear in the vicinity of the second control grid 7-3. The use of the flat display panel having such a structure in the television picture display means and application of line sequential scanning is advantageous in that the electrons emanating from the discharge space 12 and passing through the perforations 16 of the conductive shielding plate 9 can be substantially entirely utilized for display.

FIG. is a block diagram showing the structure of a system preferably used in the present invention which utilizes such an electron beam. In FIG. 5, like reference numberals are used to denote like parts appearing in FIG. 2 and the structure of circuits connnected to first and second control grids 4 and 7, signals appearing therefrom and operation thereof are the same as those shown in FIG. 2. In the case of the system shown in FIG. 2, the individual electrode pairs are connected in parallel with one another so that they operate substantially as a single discharge electrode pair. In the case of the system shown in FIG. 5, however, the electrodes 17-1, 17-2, l7-L in the electrode pairs are connected independently of one another to output terminals of a discharge voltage generator 29 by respective leads 1 1 whereas the opposite electrodes 18-1, 18-2, l8-L in the electrode pairs are connected to the discharge voltage generator 29 by a single lead I, so that the individual discharge electrode pairs are energized independently of one another. Thus, the discharge voltage generated by the discharge voltage generator 29 is successively and periodically applied to the discharge electrodes 17-1, 17-2, 17-L by the respective leads l I and these leads control the application of the discharge voltage to the discharge electrodes.

The discharge voltage generator 29 is driven by the vertical synchronizing signal and horizontal synchronizing signal and generates successively discharge voltage pulses which appear periodically at L output terminals in synchronism with the horizontal synchronizing signal. The signals appearing at various parts of the system shown in FIG. 5 vary relative to time as shown in FIG. 6. In response to the application of the first horizontal synchronizing signal 20" after the application of the vertical synchronizing signal 19'', the discharge voltage generator 20 generates a discharge voltage pulse Vd which is applied across the discharge electrode pair 17-1 and 18-1. The discharge voltage pulse Vd lasts for a period of time rd which does not contribute to the display, and therefore, the pulse width r is desirably sufficiently smaller than the horizontal scanning period T,,. However, this period of time 7,, must be such that discharge can occur sufficiently across the discharge electrodes. Upon interruption of the discharge across the discharge electrodes 17-1 and 18-1, a line scanning pulse having a pulse width 1 is applied to the second control grid 7-1 among the secured control grids which have been kept at a negative potential of E volts and have acted to prevent the passage of electrons. Thus, the potential of the second control grid 7-1 is now raised to the zero level. At the same time, a pulse signal obtained by pulse width modulation by the video signal is applied to the first control grids 4-1, 4-2, 4-M, to raise the potential level from E volts to the zero level, so that the electrons can pass by these first control grids. The electrons entering the acceleration space are accelerated by a high DC. voltage applied to the anode 2 and impinge against the phosphor layer 3. In response to the second horizontal synchronizing signal, discharge occurs across the discharge electrodes 17-2 and 18-2 and the line scanning pulse is applied to the second control grid 7-2. In this manner, discharge occurs across the discharge electrodes 17-K and l8-K in response to the K-th horizontal synchronizing signal counting from the vertical synchronizing signal. The above description has referred to a display device in which one discharge electrode pair is associated with each of the second control grids. However, when the width of the plasma is larger than the spacing between the second control grid conductors, a purality of grid conductors may be associated with one discharge electrode pair. For example, in a display device in which n second control grid conductors are associated with one discharge electrode pair, discharge occurs n times consecutively across one discharge electrode pair and is the transferred to the next discharge electrode pair. In such a display device, the rate of utilization of electrons is about l/n.

in another form of the display device according to the present invention shown in FIG. 7, an electric field is applied to the discharge space after the interruption of the discharge thereby increasing the number of electrons derivable from the discharge space and attaining an improvement in the rate of utilization of electrons. The display device shown in FIG. 7 is a modification of the structure shown in FIG. 1 and a flat metal plate 30 is added to the structure shown in FIG. 1. Referring to FIG. 7, the flat metal plate 30 is disposed opposite to the conductive shielding plate 9 with the discharge space 12 interposed therebetween and the insulating plate 13 is brought into gas-tight sealing engagement with the flat metal plate 30. The insulating plate 13 may be omitted when the flat metal plate 30 is made of a material which can withstand the atmospheric pressure and hermetically seal the insulating frame member 11 against the atmospheric air. In the display device having such a structure, the flat metal plate 30 and conductive shielding plate 9 are kept at the same potential during the period of time in which discharge occurs across the discharge electrodes 17 and 18, but upon interruption of the discharge, a voltage negative relative to the conductive shielding plate 9 is applied tothe flat metal plate 30 so that the electrons in the discharge space 12 are accelerated to migrate toward the conductive shielding plate 9. Although a portion of the electrons are arrested by the conductive shielding plate 9., the remaining portion of the electrons pass through the perforations 16 bored in the conductive shielding plate 9 to reach the second control grids 7.

In the case of the display device which is not provided with the flat metal plate 30, the electrons produced by the discharge are drawn out from the discharge space by diffusion as described previously. When no electric field is present in the discharge space, the electrons produced by the discharge tend to diffuse uniformly toward the conductive shielding plate 9, insulating plate 13 and insulating frame member 11, resulting in a reduction in the quantity of electrons passing through the perforations 16 of the conductive shielding plate 9. Even if the solid angle for the insulating frame member 11 when viewed from the center of the discharge space is extremely smaller than those for the conductive shielding plate 9 and insulating plate 13, the quantity of electrons diffusing toward the conductive shielding plate 9 is less than about one-half of the total quantity. However, in the display device shown in FIG. 7 in which an electric field can be established in a direction in which the electrons can be drawn out from the discharge space, the electrons are accelerated to migrate toward the conductive shielding plate 9 at a velocity higher than the diffusing velocity. Thus, substantially all the electrons migrate toward the conductive shielding plate 9. By suitably selecting the structure of the conductive shielding plate 9, intensity of the electric field, etc., electrons in a large quantity can be passed throuugh the perforations 16 of the conductive shielding plate 9 andd any electrons remaining in the discharge space after interruption of the discharge can be substantially entirely drawn out from the discharge space.

FIG. 8 is a block diagram a system for displaying a television picture by the use of the display device having a structure as shown in FIG. 7. In FIG. 8, like reference numerals are used to like parts appearing in FIG. 5. Line sequential scanning is similarly employed and discharge occurs successively and periodically across discharge electrodes for producing electrons. Upon interruption of discharge across one electrode pair, an electron drawing-out power source 32 generates a drawing-out voltage and this voltage is applied to the flat metal plate 30. FIG. 9 shows the signal waveforms appearing at various parts of the system shown in FIG. 8. After the first discharge occurs across the discharge electrode pair 17-1 and 19-1, a negative voltage of V,,, volts is applied from the power source 32 to the flat metal plate 30. As a result, the electrons produced in the discharge space migrate toward the second control grid 7-1, and due to the fact that the potential of the second control grid 7-1 is zero due to the application of a line scanning pulse, the electrons pass by the second control grid 7-1 to migrate further toward the first control grids 4-1, 4-2, 4-M. These first control grids 4-1, 4-2, 4-M are maintained at the zero potential level for a predetermined period of time due to the simultaneous application of a signal obtained by pulse width modulation by the video signal. Thus, the electrons pass by these first control grids and are accelerated by a high DC. voltage applied to the anode 2 thereby impinging against the phosphor layer 3 for causing luminescence.

In the system described with reference to FIG. 8, a voltage of V,,, volts is applied to the flat metal plate 30 for the sole purpose of drawing out the electrons from the discharge space. However, the conductive shielding plate 9 may be replaced by a group of shielding control electrodes so as to eliminate the second control grids. FIG. 10 shows the structure of such a modification. Referring to FIG. 10, the conductive shielding plate 9 shown in FIG. 7 is replaced by a group of conductors 32 serving as shielding grids and an insulating plate 33 which supports the shielding grids 32. This plate 33 is provided with perforations 34 at predetermined positions for allowing passage of electrons therethrough.

In operation, the shielding grids 32 and flat metal plate 30 are maintained at the same potential during the period of time in which discharge occurs in the discharge space. Upon interruption of the discharge, a positive voltage is applied to only one of the shiedling grids 31-1, 32-2, 32-K for drawing out the electrons from the discharge space toward the predetermined poistion. The line sequential scanning can be carried out by successively and periodically applying the voltage to the individual shielding grids.

Further, the shielding control grids shown in FIG. 10 may be disposed in place of the conductive shielding plate 9 in FIG. 7 in such a manner that they cross the second control grids 7. A video signal or a positive pulse signal obtained by pulse width modulation by the video signal may be applied to these grids thereby realizing a display device from which the first control grids 4 are eliminated.

It will be understood from the foregoing description that the present invention which utilizes discharge for producing electrons can provide a display device which shows a quick response, in which a large current can be derived, which operates with high efficiency and which is substantially free from non-uniformity of brightness.

What we claim is:

1. A display device comprising a first insulating member having a plurality of pairs of discharge electrodes and defining a discharge space for producing electrons by discharge in a gaseous atmosphere, a sealing member for sealing said discharge space gas-tight against the exterior, a conductive member formed with a plurality of perforations for allowing passage of the electron beam emerging from said discharge space, a second insulating member defining an acceleration space for accelerating the electron beam passed through said perforations in said conductive member, a transparent insulating member for sealing said acceleration space gastight against the exterior, a plurality of first and second control grid conductors disposed between said conductive member and said second insulating member and crossing with each other on said perforations in said conductive member so as to control the entrance of said electron beam into said acceleration space, a pair of spaced insulating separators having a plurality of aligned perforations formed at positions corresponding to the positions of said perforations in said conductive member so as to hold said first and second control grid conductors in the crossing relation with a predetermined spacing therebetween, a transparent electrode sandwiched between a phosphor layer and said transparent insulating member for causing said electron beam accelerated in said acceleration space to impinge against said phosphor layer formed on said transparent insulating member, a power source for generating a discharge voltage periodically in synchronism with a predetermined external signal, means for applying the discharge voltage from said power source to said discharge electrodes, means for generating a control voltage for successively and periodically applying said control voltage to said second control grids one after another in synchronism with the application of said discharge voltage to said discharge electrodes, means for applying to said first control grids a signal obtained by pulse width modulation of a predetermined display signal depending on the level thereof, and means for applying an accelerating voltage to said transparent electrode for accelerating said electron beam in said acceleration space, said electron beam being drawn out toward said second control grids during the period of time in which the discharge occurs in said discharge space.

2. A display device comprising a first insulating member having a plurality of pairs of discharge electrodes and defining a discharge space for producing electrons by discharge in a gaseous atmosphere, a sealing member for sealing said discharge space gas-tight against the exterior, a conductive member formed with a plurality of perforations for allowing passage of the electron beam emerging from said discharge space, a second insulating member defining an acceleration space for accelerating the electron beam passed through said perforations in said conductive member, a transparent insulating member for sealing said acceleration space gastight against the exterior, a plurality of first and second control grids disposed between said conductive member and said second insulating member and crossing with each other on said perforations in said conductive member so as to control the entrance of said electron beam into said acceleration space, a pair of spaced insulating separators having a plurality of aligned perforations formed at positions corresponding to the positions of said perforations in said conductive member so as to hold said first and second control grids in the crossing relation with a predetermined spacing therebetween, a transparent electrode sandwiched between a phosphor layer and said transparent insulating member for causing said electron beam accelerated in said acceleration space to impinge against said phosphor layer formed on said transparent insulating member, a power source for generating a discharge voltage periodically in synchronism with a predetermined external signal, means for applying the discharge voltage from said power source to said discharge electrodes, means for applying a control voltage successively to said second control grids one after another after the application of said discharge voltage to said discharge electrodes, means for applying to said first control grids a signal obtained by pulse width modulation of predetermined display signal depending on the level thereof, and means for applying an accelerating voltage to said transparent electrode for accelerating said electron beam in said acceleration space, said electron beam being drawn out toward said second control grids during the period of time in which the discharge is interrupted in said discharge space.

3. A display device as claimed in claim 2, wherein said means for applying said discharge voltage to said discharge electrodes is connected to said discharge electrodes so as to apply said discharge voltage successively and periodically to said discharge electrodes one after another.

4. A display device as claimed in claim 2, wherein another conductive member is disposed between said first insulating member and said sealing member for drawing out the electrons from said discharge space, and means is connected to said conductive member for applying a voltage for drawing out the electrons.

5. A display device as claimed in claim 2, wherein said means for applying said discharge voltage to said discharge electrodes is connected to said discharge electrodes so as to apply said discharge voltage successively and periodically to said discharge electrodes one after another, and another conductive member is disposed between said first insulating member and said sealing member for drawing out the electrons from said discharge space and is connected to means which applies a voltage for drawing out the electrons from said discharge space upon interruption of the discharge in said discharge space.

6. A display device comprising a first insulating member having a plurality of pairs of discharge electrodes and defining a discharge space for producing electrons by discharge in a gaseous atmosphere, a sealing member for sealing said discharge space gas-tight against the exterior, a second insulating member formed with a plurality of perforations for allowing passage of the electron beam emerging from said discharge space, a conductive member interposed between said first insulating member and said sealing member, a third insulating member defining an acceleration space for accelerating the electron beam passed through said perforations in said second insulating member, a transparent insulating member for sealing said acceleration space gas-tight against the exterior, a plurality of first control grids supported by said second insulating member and disposed in parallel with one another so as to control the entrance of said electron beam into said acceleration space from said discharge space, a plurality of second control grids disposed in parallel with one another in such a manner as to perpendicularly cross said frist control grids on said perforations in said second insulating member, an insulating separator having a plurality of perforations formed at positions corresponding to the positions of said perforations in said second insulating member so as to support said second control grids in the crossing relation with said first control grids with a predetermined spacing therebetween, a transparent electrode sandwiched between a phosphor layer and said transparent insulating member for causing said electron beam accelerated in said acceleration space to impinge against said phosphor layer formed on said transparent insulating member, a power source for generating a discharge voltage periodically in synchronism with a predetermined external signal, means for applying the discharge voltage from said discharge source to said discharge electrodes one after another, means for applying a control voltage successively to said second control grids one after another after the application of said discharge voltage to said discharge electrodes, means for applying to said first control grids a signal obtained by pulse width modulation of a predetermined display signal depending on the level thereof, means for beam in said acceleration space, said electron beam being drawn out toward said second control grids during the period of time in which the discharge is interrupted in said discharge space.

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Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3938135 *Nov 27, 1974Feb 10, 1976Zenith Radio CorporationGas discharge display device and an improved cell therefor
US4017893 *Sep 9, 1975Apr 12, 1977Thomson-CsfDisplay device for producing polychromatic luminous images
US4020280 *Feb 20, 1974Apr 26, 1977Ryuichi KanekoPulse width luminance modulation system for a DC gas discharge display panel
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Classifications
U.S. Classification345/65, 313/492, 348/797
International ClassificationG09G3/282, H04N5/66, G09G3/28, H01J17/49, H01J31/15
Cooperative ClassificationH01J17/498
European ClassificationH01J17/49P