RU2044363C1 - Device for field emission - Google Patents

Abstract

FIELD: radio engineering. SUBSTANCE: device has field cathodes, control electrode and anode which is covered with luminophore. All electrodes are positioned on substrate and have coaxial holes. In addition device has transparent electrode positioned on glass of vacuum housing opposite to anode and cathode. Symmetry axis of cathode is perpendicular to substrate and equals to symmetry axis of hole. Emitting part of cathode is shifted about symmetry axis of hole for movement of electrons towards anode. This shift is greater than rounding radius of emitting part of cathode. Edges of control electrode are at different height with respect to vertex of point of edge of cathode. Film of secondary emission material is applied to glass of vacuum housing which is orthogonal to symmetry axes of cathode and hole. All electrodes (except secondary emission one) is positioned on same substrate. EFFECT: increased service life of screen, facilitated manufacturing, high quality of picture (in terms of brightness, contrast and color). 4 cl, 4 dwg

Description

 The invention relates to devices with field emission, including indicators and flat cathodoluminescent screens.

A device with field emission is known, comprising at least one field electrode cathode made in the form of a tip or blade, a control electrode made in the form of a film with a hole in which the cathode is located on one substrate and the anode is made on another substrate. Moreover, the cathode axis is perpendicular to the planes of the substrates and the control electrode. However, when using this device as a flat color cathodoluminescent screen, when sections of the cathodoluminophore emitting different colors are located on the anode, it is difficult to provide high resolution and color reproduction due to the difficult accurate combination of the pattern of the locations of the phosphors of different colors with the corresponding pattern of the cathode matrix [1]
This disadvantage is eliminated in the closest to the proposed solution device with field emission. In this device, which contains autocathodes, a control electrode and an anode coated with a phosphor, located on the same substrate, in which coaxial windows are made and a transparent electrode is deposited on the glass of the vacuum housing opposite the anode and cathode, the cathode axis being perpendicular to the substrate and coinciding with the window axis [2]
However, this device has a short life. This is due to the fact that the electrodes emitted from the cathode region located near the common axis of symmetry of the cathode and the windows, which make up at least half of all emitted electrons, do not reach the anode, but return towards the cathode. Moreover, these electrons due to impact ionization form significantly more ions of residual gases that bombard the cathode than electrons sent directly to the anode.

 The objective of the invention is to increase the life of the device with field emission.

 This is achieved by the fact that in the device with field emission, containing auto-cathodes, a control electrode and an anode coated with a phosphor, located on the same substrate, in which coaxial windows are made, and a transparent electrode deposited on the glass of the vacuum housing, opposite the anode and cathode, and the axis the cathode is perpendicular to the substrate and coincides with the axis of the window, the field-effect cathode has an emitting edge offset from the axis of symmetry of the window.

The transparent electrode can be made of secondary emission material, the voltage value U _ve (V) on which is selected from the following ratio:
U _anode > U _ve > U _exercise. (1) where U is the _anode. voltage at the anode (phosphor), V;
U _ve voltage at the secondary emission electrode, V;
U _exercise voltage at the control electrode, V.

 The objective of the invention can be achieved by another embodiment. In a device with field emission, containing autocathodes, a control electrode and an anode coated with a phosphor located on the same substrate, in which coaxial windows are made, and a transparent electrode deposited on the glass of the vacuum housing opposite the anode and cathode, the cathode axis being perpendicular to the substrate and coinciding with the axis of the window, the field-effect cathode is blade-shaped, the window is in the form of a slit, and the planes of each control electrode located on both sides of the cathode are located at different levels relative to the top of the cathode.

The transparent electrode can be made of secondary emission material, the voltage value U _ve (V) on which is selected from the following ratio:
U _anode > U _ve > U _exercise. (2) where U is the _anode. voltage at the anode (phosphor), V;
U _ve voltage at the secondary emission electrode, V;
U _exercise voltage at the control electrode, V.

 As the numerical simulation of the trajectories of emitted electrons shows, in the first version of the proposed design, all emitted electrons immediately hit the anode, which significantly reduces the ion bombardment of the cathode and increases the life of the device.

 When a vacuum casing of a material with a secondary electric emission coefficient greater than unity is applied to the glass and the voltages corresponding to relation (2) are applied, the cathode bombardment will be reduced due to that part of the ions that was generated in the area of the movement of electrons from the transparent conducting layer to the anode, because . The ions generated in this area will be neutralized on the secondary emission body, which increases the service life of the device. In addition, when the secondary emission coefficient is greater than unity, the flux density of electrons bombarding the anode (phosphor) increases, which reduces the voltage applied to the electrodes (at the same brightness of the screen glow), reduces the energy of the bombarding ions and, therefore, increases device service life.

 In another embodiment of the device, where the cathode is made in the form of a blade, and the window in the control electrode is in the form of a gap, and the planes (parts of the control electrode) on both sides of the cathode are located at different levels relative to the top of the cathode, as shown by numerical simulation, all emitted electrons will be fly towards the portion of the control electrode, shifted downward relative to the top of the cathode. Moreover, the cathode region subjected to ion bombardment will be shifted relative to the electron emission region due to the asymmetry of the field in this design. As a result, the life of the cathode and device will be increased.

 The invention is illustrated in the drawing, where Fig. 1 shows a prototype device, Figs. 2-3 show a device according to a first embodiment of the invention, and Fig. 4 according to a second embodiment of the invention.

 Figure 1 presents a device with field emission (prototype), comprising: a substrate 1, a first 2 insulator layer, a control electrode 3, a second 4 insulator layer, anode 5, coated with a phosphor layer 6, autocathode 7, window 8, glass 9 of the vacuum housing , transparent electrode 10.

 2-4, functionally identical elements are indicated by the same numbers. In FIG. 2 shows a device according to a first embodiment of the invention, in which the cathode 7 has a protruding edge 11 offset from the axis of the window 8.

 In FIG. 3 shows a device in which a layer 12 of secondary emission material is placed on the glass.

 Figure 4 shows the device according to the second embodiment of the invention.

 1-4, dashed lines show the electron trajectory obtained by numerical simulation methods.

 PRI me R. A cathode, for example, of silicon, is formed on a conductive substrate, having a vertex with protruding edges displaced relative to the axis of symmetry by an amount greater than the rounding radius of the protruding edge, in particular, a funnel can be formed on the tip. The diameter of the protruding edge formed at the same time at the apex is 0.1 μm. At the top of the cathode there is a control electrode made of a film, for example, niobium, 0.2 μm thick, separated from the substrate by an insulator layer, for example, SiO 42 0, 1 μm thick. The anode is made of a niobium film with a thickness of 0.1 μm, on which a layer of phosphor Zn-O-Zn is applied, a thickness of 0.5 μm, the plane of which is separated from the plane of the control electrode by an insulator layer, for example, SiO 42 0, 2 μm thick. A through window is made in these layers, the axis of which coincides with the axis of the cathode. The diameter of the window in the control electrode is 0.7 μm, and in the anode 1.5 μm. As a secondary emission material, a MgO film 2 μm thick was used.

 Thus, the proposed device has a longer service life by reducing the ion bombardment of the cathode.

Claims (4)

 1. A device with field emission comprising auto-cathodes, a control electrode and an anode coated with a phosphor, located on the same substrate, in which coaxial windows are made, and a transparent electrode deposited on the glass of the vacuum housing opposite the anode and cathode, and the axis of symmetry of the cathode is perpendicular to the substrate and coincides with the axis of symmetry of the window, characterized in that the cathode has an emitting edge offset from the axis of symmetry of the window. 2. The device according to claim 1, characterized in that the transparent electrode is made of secondary emission material, and the voltage on it is selected from the following ratio:
U _{a n o d n .} > U _{in e>} U _{y n p.}
where U _{and n o n d.} voltage at the anode, V;
U _{in e is the} voltage at the transparent electrode, V;
U _{y n p.} voltage at the control electrode, V.  3. A device with field emission containing autocathodes, a control electrode and an anode coated with a phosphor, located on the same substrate, in which coaxial windows are made, and a transparent electrode deposited on the glass of the vacuum housing opposite the anode and cathode, and the axis of symmetry of the cathode is perpendicular to the substrate and coincides with the axis of symmetry of the window, characterized in that the autocathode is made bladed, the window is in the form of a slit, and the planes of the control electrode located on both sides of the autocathode are at different levels relative to The top of the cathode. 4. The device according to claim 3, characterized in that the transparent electrode is made of secondary emission material, and the voltage on it is selected from the following ratio:
U _{a n o d n .} > U _{in e>} U _{y n p.} ,
where U is the voltage at the anode, V;
U _{in e is the} voltage at the transparent electrode, V;
U _{y n p.} voltage at the control electrode, V.

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