GB1585645A

GB1585645A - Gas discharge-electron display device

Info

Publication number: GB1585645A
Application number: GB5188277A
Authority: GB
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 1976-12-14
Filing date: 1977-12-13
Publication date: 1981-03-11
Also published as: FR2374736A1; DE2656621A1; DE2656621C3; NL7712287A; JPS5375757A; FR2374736B1; DE2656621B2

Description

(54) GAS DISCHARGE ELECTRON DISPLAY DEVICE (71) We, SIEMENS AKTIENGESELLSCHAFT, a German company of Berlin and Munich, Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a gas discharge electron display device, sometimes called a plasma-electron display device.

British Patent Specification No. 1,496,442 discloses a luminous discharge device containing a matrix of gas discharge cells with which there are coordinated an auxiliary anode electrode structure for controlling the discharge line by line, and a control electrode structure for controlling the brightness in columns perpendicular to the lines. In the interior of the gas-tight envelope of this device, there is a gas discharge path between a cathode and the auxiliary anode electrode structure and an electron acceleration path between the control electrode structure and an anode.The matrix of gas discharge cells in the form of a perforated plate of insulating material divides the interior of the envelope into a relatively long auxiliary discharge chamber within which a gas discharge may be induced between the cathode and the auxiliary anode electrode structure with a relatively low voltage, and a relatively short electron acceleration chamber for accelerating electrons towards the anode with a relatively high voltage. The perforated insulating plate acts as carrier for the auxiliary anode electrode structure and the control electrode structure, the latter being disposed on the opposite face of the plate to the former. The cathode and anode are designed with large surface areas.A glow discharge may be induced in the gas discharge chamber by applying a suitable potential difference between the cathode and the auxiliary anode structure, which discharge is controllable line by line by that structure. The free electrons formed in such a discharge move towards the auxiliary anode structure. The discharge thorough the perforated plate is controlled point by point by the control electrode structure and the electrodes are accelerated by the high electric field within the electron acceleration chamber towards the anode which is in the form of a continuous phosphor screen. The electrons impinging on the screen are represented as defined image points of light.With the modulation of one line of the auxiliary anode structure a discharge burns uniformly along the entire line, whilst the negative glow light covers an area, the surface area of which is determined by the known dependence of current density on the cathode material and the gas pressure.

In this known form of gas discharge device the gas discharge chamber is not sealed off from the electron acceleration chamber. Thus the gas pressure in the two chambers will be substantially the same and the gas pressure and the cathode material must be selected such as, on one hand, to render possible optimum glow discharge in the gas discharge chamber with, in particular, the highest possible current density, and, on the other hand, to avoid the ignition of an automatic discharge which is also called a dielectric breakdown and prevents an electron stream from being produced. The value of the acceleration voltage is therefore limited by the choice and pressure of the gas to a predetermined maximum value and the luminous density of the image on the phosphor screen is also limited.

According to the present invention, there is provided a gas discharge electron display device having a gas-tight envelope and including, within the envelope: a. a partition permeable to radiation of a pre determined wavelength and dividing the space within the envelope into a gas dis charge chamber and an electron acceleration chamber in gas-tight manner; b. a gas in the gas discharge chamber; c. discharge means in the gas discharge chamber for inducing a discharge within the gas to cause radiation of the predetermined wave length to pass through the partition; d. photoelectric means in the electron accelera tion chamber for emitting electrons when acted upon by radiation of the predetermined wavelength from the gas discharge chamber; e. display means in the electron acceleration chamber for emitting light when acted upon by electrons from the photoelectric means; f. a first set of control electrodes for contin uous line switching; and g. a second set of control electrodes, disposed perpendicular to the first set of control elec trodes, for brightness control.

In order that the present invention may be more fully understood, reference will now be made, by way of example, to the accompanying drawing, in which the single figure diagrammatically shows a section through a gas discharge-electron display device in accordance with the present invention.

The device shown diagrammatically in the figure is a part of a television receiver. The device has a gas-tight envelope 2 made, for example, of glass, the interior of which is divided by a partition 3 permeable to radiation of a predetermined wavelength into two chambers 4 and 5, in gas-tight manner. The partition can be designed as a large surface area plane glass window. One of these chambers 4 is designed as a gas discharge chamber and discharge means in the form of an anode 6 intended to be maintained at a prescribed potential of 200 V and spaced from the partition 3, and, opposite the anode 6, on the partition 3 a cathode 7 constituted by a screen electrode permeable to radiation of the predetermined wavelength. The gas discharge chamber 4 is filled with a gas, whose basic component is, for example, neon, at a pressure of a few torr.Small amounts of a supplementary component, such as mercury vapour, may be added to this gas. Sputtering of the cathode, in particular, can thereby be reduced.

Between the anode 6 and the cathode 7, which lies at zero potential in use, may be generated a glow discharge, the glow light of which is of said predetermined wavelength and is indicated by a front 8 shown in broken lines in the figure. Provision of mercury vapour in the gas enables the W-quota of the glow light to be raised. The glow light adjacent the partition 3 and denoted 9 in the figure is designated as "negative glow light" and is formed along a sharp front adjacent the cathode 7 and the partition 3.The photons emitted can penetrate the partition 3 which is made of material which is permeable to radiation of the predetermined wavelength and is incident on photoelectric means in the form of a photocathode 11 attached to the face of the partition 3 which delimits the chamber 5 which is designed as an electron acceleration chambers. By appropriate selection of a spectral type of photocathode, it can be adapted to the spectrum produced by the glow discharge. Since the gas discharge chamber is sealed off from the electron acceleration chamber by the partition 3, a high vacuum at a pressure of less than 10-6 torr may prevail in the electron acceleration chamber.

There are virtually no reactive effects between the two chambers. Since there is a high vacuum prevailing in the electron acceleration chamber, high acceleration voltages can be provided without there being a risk of dielectric breakdown.

Electrons are released from the photo cathode 11 by the impinging photons. Disposed on the side of the electron acceleration chamber 5 facing the photo cathode 11 is display means in the form of a screen 12 comprising a layer of luminescent phosphor 13 on the wall 15 of the envelope 2, the phosphor layer 13 being masked from the electron acceleration chamber 5 by a thin aluminium coating 14. The device is so disposed in the television receiver that the screen 12 faces the viewer (not shown in the figure). Between the photocathode 11 and the aluminium coating 14 which are separated by only a few millimetres is applied a high voltage of approximately 10 to 20 kV. The electrons emitted by the photocathode 11 are accelerated by this high voltage and penetrate the aluminium coating so that they impinge on the phosphor layer 13 where they produce light.

With high acceleration voltages a relatively high image amplification and good image sharpness (proximity focus) is obtainable. Furthermore, the aluminium coating is penetrated relatively easily by the eletrons without differences in brightness occurring because of differing aluminium coating thicknesses. Further, in the highly evacuated electron acceleration chamber, the risk of electrons being scattered by gas molecules is virtually nil. This also helps in obtaining a high degree of sharpness of the image.

The auxiliary electrode structure required for continuous line switching and the further auxiliary electrode structure required for brightness control are not drawn in detail in the figure for the sake of clarity. The auxiliary electrode structure is constituted by a first set of substantially rectilinear, mutually parallel control electrodes and the further auxiliary electrode structure is constituted by a second set of substantially rectilinear, mutually parallel control electrodes, the electrodes of the first set being substantially perpendicular to the electrodes of the second set. Both sets of electrodes may be disposed in the gas discharge chamber 4 or in the electron acceleration chamber 5, or either the first set or the second set may be disposed in the gas discharge chamber 4 and the other set may be disposed in the electron acceleration chamber 5. The cathode 7 mas be one of the sets of electrodes and the photocathode 11 may be the other set of electrodes.

Since it is virtually impossible for ion formation to take place in the electron acceleration chamber, brightness control may be carried out with relatively low control power.

If necessary, a gauze-like grid 17 can be provided in the electron acceleration chamber 5, with the aid of which grid secondary electrons can be generated to amplify the electron stream emerging from the photocathode 11. A further increase in the brightness of the light emitted by the phosphor layer 13 can thereby be achieved. A potential difference of approximately 200 V may be provided, between the grid 17 and the photocathode 11. It is possible to have good adaptation of the glow discharge to the particular photocathode used, for instance by appropriately selecting the gas required for the glow discharge. Further adaptation may also be effected by adding a suitable supplementary component to the basic component of the gas. A further parameter for adaptation is the gas pressure.

The envelope 2 of the device may be substantially flat and may have a substantially square section of large area, thus rendering the device particularly suitable for use in a television receiver. The device can be used for producing multicolour images in a colour television.

WHAT WE CLAIM IS: 1. A gas discharge-electron display device having a gas-tight envelope and including, within the envelope: a. a partition permeable to radiation of a pre determined wavelength and dividing the space within the envelope into a gas discharge chamber and an electron acceleration cham ber in gas-tight manner; b. a gas in the gas discharge chamber; c. discharge means in the gas discharge cham ber for inducing a discharge within the gas to cause radiation of the predetermined wavelength to pass through the partition; d. photoelectric means in the electron accelera tion chamber for emitting electrons when acted upon by radiation of the predetermined wavelength from the gas discharge chamber; e. display means in the electron acceleration chamber for emitting light when acted upon by electrons from the photoelectrical means; f. a first set of control electrodes for contin uous line switching; and g. a second set of control electrodes, disposed perpendicular to the first set of control elec trodes, for brightness control.

2. A device according to Claim 1, wherein the display means includes a layer of phosphor.

3. A device according to Claim 1 or 2, wherein the photoelectrical means is in the form of a photocathode on a face of the partition delimiting the electron acceleration chamber.

4. A device according to Claim 1, 2 or 3, wherein first set of control electrodes consists of substantially rectilinear, mutually parallel electrodes and the second set of control electrodes consists of substantially rectilinear, mutually parallel electrodes, and wherein both sets of control electrodes are disposed in the gas discharge chamber or in the electron acceleration chamber.

5. A device according to Claim 1, 2 or 3, wherein the first set of control electrodes consists of substantially rectilinear, mutually parallel electrodes disposed in the gas discharge chamber, and the second set of control electrodes consists of substantially rectilinear, mutually parallel electrodes disposed in the electron acceleration chamber.

6. A device according to any preceding claim, wherein the discharge means comprises an anode spaced from the partition and a cathode permeable to radiation of the predetei mined wavelength disposed between the anode and the partition.

7. A device according to any preceding claim, wherein a grid for inducing secondary electron emission is disposed in the electron acceleration chamber intermediate the photoelectric means and the display means.

8. A device according to any preceding claim, wherein the gas in the gas discharger chamber is constituted by a basic component within which the discharge may be induced an to which a supplementary component has beer added in small quantities.

9. A device according to Claim 8, wherein the supplementary component is mercury.

10. A device according to any preceding claim, wherein the envelope is substantially flat.

11. A device according to any preceding claim adapted to produce multicolour images.

12. A gas discharge-electron display device substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawing.

13. A television receiver incorporating a gas discharge electron display device according to any preceding claim.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. Since it is virtually impossible for ion formation to take place in the electron acceleration chamber, brightness control may be carried out with relatively low control power. If necessary, a gauze-like grid 17 can be provided in the electron acceleration chamber 5, with the aid of which grid secondary electrons can be generated to amplify the electron stream emerging from the photocathode 11. A further increase in the brightness of the light emitted by the phosphor layer 13 can thereby be achieved. A potential difference of approximately 200 V may be provided, between the grid 17 and the photocathode 11. It is possible to have good adaptation of the glow discharge to the particular photocathode used, for instance by appropriately selecting the gas required for the glow discharge. Further adaptation may also be effected by adding a suitable supplementary component to the basic component of the gas. A further parameter for adaptation is the gas pressure. The envelope 2 of the device may be substantially flat and may have a substantially square section of large area, thus rendering the device particularly suitable for use in a television receiver. The device can be used for producing multicolour images in a colour television. WHAT WE CLAIM IS:

1. A gas discharge-electron display device having a gas-tight envelope and including, within the envelope: a. a partition permeable to radiation of a pre determined wavelength and dividing the space within the envelope into a gas discharge chamber and an electron acceleration cham ber in gas-tight manner; b. a gas in the gas discharge chamber; c. discharge means in the gas discharge cham ber for inducing a discharge within the gas to cause radiation of the predetermined wavelength to pass through the partition; d. photoelectric means in the electron accelera tion chamber for emitting electrons when acted upon by radiation of the predetermined wavelength from the gas discharge chamber; e. display means in the electron acceleration chamber for emitting light when acted upon by electrons from the photoelectrical means; f. a first set of control electrodes for contin uous line switching; and g. a second set of control electrodes, disposed perpendicular to the first set of control elec trodes, for brightness control.