EP0198753B1 - Elektronenstrahlerzeuger für Kathodenstrahlröhre, insbesondere für das Farbfernsehen - Google Patents
Elektronenstrahlerzeuger für Kathodenstrahlröhre, insbesondere für das Farbfernsehen Download PDFInfo
- Publication number
- EP0198753B1 EP0198753B1 EP19860400661 EP86400661A EP0198753B1 EP 0198753 B1 EP0198753 B1 EP 0198753B1 EP 19860400661 EP19860400661 EP 19860400661 EP 86400661 A EP86400661 A EP 86400661A EP 0198753 B1 EP0198753 B1 EP 0198753B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- electrode
- cathode
- potential
- gun
- electron gun
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
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Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
- H01J29/46—Arrangements of electrodes and associated parts for generating or controlling the ray or beam, e.g. electron-optical arrangement
- H01J29/48—Electron guns
- H01J29/50—Electron guns two or more guns in a single vacuum space, e.g. for plural-ray tube
- H01J29/503—Three or more guns, the axes of which lay in a common plane
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
- H01J29/46—Arrangements of electrodes and associated parts for generating or controlling the ray or beam, e.g. electron-optical arrangement
- H01J29/48—Electron guns
- H01J29/488—Schematic arrangements of the electrodes for beam forming; Place and form of the elecrodes
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J2229/00—Details of cathode ray tubes or electron beam tubes
- H01J2229/48—Electron guns
- H01J2229/4844—Electron guns characterised by beam passing apertures or combinations
- H01J2229/4848—Aperture shape as viewed along beam axis
- H01J2229/4872—Aperture shape as viewed along beam axis circular
Definitions
- the invention relates to an electron gun for cathode ray tube, in particular for color television.
- a cathode ray tube is constituted by a vacuum glass vial having at its front part a screen slab the internal face of which is covered with cathodoluminescent materials (called phosphors) emitting a radiation of visible light when they are excited by a electron beam produced by one (or more) electron gun.
- the screen is generally made up of triplets of phosphors, one for each fundamental color, usually red, green and blue.
- three electron guns are provided, each intended to excite a particular color, the perforated mask placed in front of the screen allowing the electron beam intended for a color to excite only phosphors of this color.
- An electron gun is formed, on the one hand, of a cathode with surface emitting electrons when it is heated by a filament and, on the other hand, of electrodes or grids denoted generally Gi, G 2 , Gs etc the index representing the position relative to the cathode, this index increasing with the distance from the cathode -of which the first two G 1 and G 2 perform a prefocusing of the electron beam and the following G s , G 4 , etc ... form electrostatic lenses for focusing and concentrating the electron beam.
- the modulation of the electron beam as a function of the intensity of the point to be projected on the screen is obtained by modulating the potential of the cathode or by modulating the potential of the first grid G i (Wehnelt).
- the electrodes of electrostatic lenses are usually brought to very high potentials, most often of the order of several kilovolts.
- the invention relates more particularly to a tube of which at least one grid of the electrostatic lenses is, in normal operation, brought to a very high potential, of the order of 25 Kilovolts for example, and which retains a potential of the same order of greatness for a significant time after the power supply to this tube has been cut off.
- the glass bulb has an internal conductive coating to which said grid is connected as well as an external conductive coating brought to ground potential; the glass bulb thus constitutes, with its coatings, a large capacity capacitor which retains its charge for a long period even after it has been disconnected from its power source; therefore the internal coating and the electrode connected to it retain the high potential.
- the invention according to claim 1 makes it possible to suppress at low cost the phenomenon of cathode glow appearing when the tube supply is cut off.
- the opening of this end wall closest to the cathode has a rim or flange, advantageously turned towards the inside of this elongated grid.
- Another embodiment of the intermediate grid is as in claim 10. It has been found that good results are obtained when the ratio between these diameters is at most 0.92.
- the example which will be described in relation to the figures relates to an electron gun for color television tube of the mask type, the three beams produced by the (triple) gun being said to be in line, that is to say - say coplanar.
- Such an electron gun comprises, on the one hand, three cathodes K each having an emissive surface 10 perpendicular to the axis 11 of the tube and heated by a filament (not shown) and, on the other hand, a set of electrodes G 1 , G 2 , Gs, G 4 , Gs and Ge of which the first two, G 1 and G 2 , ef carry out the prefocusing and the following, G 3 to Gs, constitute electrostatic lenses for focusing and concentrating the electron beams.
- a cathode K is along the axis 11 of the tube, while the axes of the other two are parallel to the axis 11, in the same plane, and in positions symmetrical with respect to this axis 11.
- the electrodes G 1 , G 2 and G 4 of generally planar shape each have three circular openings centered on the axis of the corresponding cathode to let the electron beam coming from this cathode pass while the elongated electrodes, substantially in the shape of cylinders or parallelepiped, Gs, Gs and Ge have end walls, each of which also includes three circular openings centered on the axis of the corresponding cathode.
- Figure 1 being a section along the axis of the tube shows only the central cathode and the corresponding openings of the electrodes.
- the electrodes or grids G 3 and Gs are connected to a terminal 3 receiving a potential of average value, of the order of 8 Kilovolts, while the electrodes or grids G 4 and Ge are connected to a terminal 4 connected to a source of potential of high value, of the order of 25 Kilovolts.
- the assembly formed by the electrodes or grids Gs, G 4 and Gs constitutes an electrostatic lens of the unipotential type, called Einzel, while the electrodes or grids G 5 and Ge constitute an electrostatic lens called the bipotential.
- Each of the electrodes is metallic and is formed from a sheet of constant thickness.
- the elongated part 12 of the electrode G s has the same thickness as the end walls 13 and 14.
- the openings of the electrode G 4 and of the walls ends of the electrodes G 5 and Gs, as well as the openings in the end wall 15 of the grid G 3 which is furthest from the cathode K all have the same diameter.
- the openings of the grids G 1 and G 2 as well as the openings of the wall 16 of the grid G s which faces the cathode K, have smaller diameters.
- the grid G 3 has, like the grid G s , a generally substantially cylindrical or parallelepipedal shape with the same thickness of the cylindrical wall 17 and of the end walls 15 and 16. But at the wall 16, of the same thickness as the wall 15, is welded, according to an exemplary embodiment of the invention, a plate or insert 18 ( Figures 3 and 4) with openings 19, 20 and 21 corresponding to the openings of the wall 16, that is to say of same diameter and same relative arrangement.
- the plate 18 is welded against the internal face of the wall 16, for example by four welding points in the vicinity of its corners.
- This welding is carried out before the mounting of the electrodes, that is to say before the two cups 22 and 23 constituting the two parts of the electrode Ga are associated with one another.
- the assembly constituted by the walls 16 and 18 has a thickness which is approximately three times greater than the thickness of the wall 15; in other words the insert 18 has a thickness which is approximately twice that of the walls of the original grid G 3 .
- terminal 4 retains a potential of the order of 25 Kilovolts while the potentials of the other electrodes reach zero immediately (ground potential).
- the limit 25 ′ of influence of the potential induced by the gate G 4 is much further from the cathode K, which considerably reduces the proportion of electrons which will reach the central part of the screen and thus there will be practically no stray glow visible in the center of this screen.
- the thickness of the front wall of the grid G 3 is of the order of three times the thickness of its rear wall 15. A satisfactory result of eliminating cathode gleams is still obtained when this thickness of the anterior wall is about twice the thickness of the posterior wall.
- the electrode G 3 is in two parts, the first comprising only the front wall 30 of greater thickness than the rest, 31, of the electrode Gs.
- This second part 31 comprises the elongated part and the other end wall.
- the parts 30 and 31 are associated for example by welding.
- FIG. 6 represents yet another embodiment in which the front wall 16 'of the electrode G s has the same thickness as the other parts of this electrode but the openings of this front wall 16' are all bordered by a flange or rim 32.
- the advantage of this embodiment is that it involves only a slight modification of the known electron gun.
- the holes 19, 20 and 21 of the insert 18 have a diameter greater than the diameter of the corresponding holes of the wall 16. But in this case, it is preferable that the thickness of the insert be greater than that which it presents when the diameters are equal. In other words it is preferable that the thickness of the insert increases with the diameter of its opening.
- the opening of the wall 15 of the grid G 3 has a diameter d 3 less than the diameter d 4 common to the opening of the grid G 4 and to the anterior opening, facing the cathode, of the grid Gs.
- the ratio ds / d 4 is less than 1.
- the equipotential line L 2 corresponding to the line 25 in FIG. 2a (or 25 ′ in FIG. 2 b ), intersects the z axis at a point B practically inside the grid Ga. It can be seen that there also, the influence of the high voltage of the gate G 4 is therefore reduced by the reduction in the diameter d a (if we compare with FIG. 2a). It has been found that a d s / d 4 ratio of 0.6875 makes it possible to obtain a good compromise between the quality of the cathode image in image formation and reduction of the parasitic phenomenon of cathode glow when the power supplies.
- the hole in the wall 15 1 of the grid G 3 has, as in FIG. 1, a cylindrical collar which advances inside the cylinder G 3 .
- This flange can be obtained during the manufacture of G 3 by extrusion. Its effect makes it possible to reduce the reduction in the ratio d 3 / d 4 necessary for the invention.
- a ratio d a / d 4 of 0.844 was produced.
- the invention achieves the desired result by limiting the influence of the high level equipotential lines in the beam forming area.
- such an effect can be achieved in particular by increasing the dimensions of the holes of the grids following the very high voltage grid.
- the invention also applies to the case where the grid G 4 is thick, for example made in the form of a cylinder. Its proximity to the filament being unchanged, the problem and the solution of the invention remain.
Landscapes
- Electrodes For Cathode-Ray Tubes (AREA)
Claims (17)
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
AT86400661T ATE49321T1 (de) | 1985-03-29 | 1986-03-27 | Elektronenstrahlerzeuger fuer kathodenstrahlroehre, insbesondere fuer das farbfernsehen. |
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FR8504848 | 1985-03-29 | ||
FR8504848A FR2579823B1 (fr) | 1985-03-29 | 1985-03-29 | Canon a electrons et tube de television utilisant un tel canon |
FR8512419 | 1985-08-14 | ||
FR8512419A FR2586326B1 (fr) | 1985-08-14 | 1985-08-14 | Canon a electrons pour tube a rayons cathodiques, notamment pour la television en couleurs |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0198753A1 EP0198753A1 (de) | 1986-10-22 |
EP0198753B1 true EP0198753B1 (de) | 1990-01-03 |
Family
ID=26224444
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP19860400661 Expired - Lifetime EP0198753B1 (de) | 1985-03-29 | 1986-03-27 | Elektronenstrahlerzeuger für Kathodenstrahlröhre, insbesondere für das Farbfernsehen |
Country Status (6)
Country | Link |
---|---|
EP (1) | EP0198753B1 (de) |
JP (1) | JP2553468B2 (de) |
CA (1) | CA1248576A (de) |
DE (1) | DE3668096D1 (de) |
HK (1) | HK17495A (de) |
SG (1) | SG135292G (de) |
Family Cites Families (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3374379A (en) * | 1964-03-02 | 1968-03-19 | Nippon Columbia | Low second grid voltage electron gun |
US3873879A (en) * | 1972-01-14 | 1975-03-25 | Rca Corp | In-line electron gun |
JPS5816131Y2 (ja) * | 1977-09-16 | 1983-04-01 | 株式会社東芝 | ユニタイズ形電子銃 |
NL8102527A (nl) * | 1981-05-22 | 1982-12-16 | Philips Nv | Kleurenbeeldbuis. |
-
1986
- 1986-03-27 CA CA000505384A patent/CA1248576A/fr not_active Expired
- 1986-03-27 EP EP19860400661 patent/EP0198753B1/de not_active Expired - Lifetime
- 1986-03-27 DE DE8686400661T patent/DE3668096D1/de not_active Expired - Lifetime
- 1986-03-29 JP JP61070611A patent/JP2553468B2/ja not_active Expired - Lifetime
-
1992
- 1992-12-30 SG SG135292A patent/SG135292G/en unknown
-
1995
- 1995-02-09 HK HK17495A patent/HK17495A/xx not_active IP Right Cessation
Also Published As
Publication number | Publication date |
---|---|
SG135292G (en) | 1993-04-16 |
JP2553468B2 (ja) | 1996-11-13 |
CA1248576A (fr) | 1989-01-10 |
JPS61227347A (ja) | 1986-10-09 |
DE3668096D1 (de) | 1990-02-08 |
HK17495A (en) | 1995-02-17 |
EP0198753A1 (de) | 1986-10-22 |
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