JPH05205653A - Cathode-ray tube - Google Patents

Abstract

PURPOSE:To eliminate the dispersion of cutoff voltage. CONSTITUTION:An electron gun is so constructed that a plurality of electrodes provided with electron beam apertures are arranged at, a certain spacing one after another on cathodes Ka, Kb, Kc and the plate thickness of the electrode G1 adjacent to cathode in its part around the aperture is made smaller than the plate thickness of the other areas. That part of the electrode adjacent to cathode which has smaller plate thickness is protruded a certain height to the cathode side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cathode ray tube such as a color picture tube, and more particularly to a cathode ray tube capable of obtaining a stable cutoff voltage.

[0002]

2. Description of the Related Art Generally, cathode ray tubes such as color picture tubes are
The electron beam emitted from the electron gun arranged in the envelope evacuated to a high vacuum is deflected by the magnetic field generated by the deflection yoke, and the front surface of the envelope (or face plate) of the envelope is formed. The phosphor screen formed on the inner surface is horizontally and vertically scanned to form an image on the phosphor screen.

The electron gun usually has a cathode, a heater for heating the cathode, and a plurality of electrodes which are sequentially arranged on the cathode in the direction of the phosphor screen at predetermined intervals, and these electrodes are integrated by an insulating support. It is formed in a structure fixed to. Each of the electrodes is provided with an electron beam passage hole through which the electron beam from the cathode passes.

FIG. 5 shows a structure near the cathode of a conventional electron gun. This electron gun is an in-line type three-electron gun that emits three electron beams that pass through the same plane used in ordinary color picture tubes and color display tubes. In the drawing, three cathodes Ka are arranged in a row. , Kb, Kc, three heaters H for separately heating the cathodes Ka, Kb, Kc, a first grid G1 (control electrode) arranged on the cathodes Ka, Kb, Kc at a predetermined interval and this 1st grid G1
The second grid G2 (acceleration electrode) arranged at a predetermined distance is shown above. The first and second grid G
Each of 1 and G2 is composed of a plate-shaped electrode having a common structure common to three electron guns, and three electron beam passage holes are arranged in a row on the plate surface corresponding to the three cathodes Ka, Kb, and Kc. Has been formed.

In FIG. 5, G3 is the second grid G2.
Third grid G3, KHa arranged above by a predetermined distance
, KHb, KHc are cathode support parts that respectively support the three cathodes Ka, Kb, Kc, and 1 is a pair of insulating supports.

Generally, in a color picture tube, in order to obtain a good white screen, it is important to keep the cutoff voltage of each electron gun emitting three electron beams constant. The cutoff voltage EK is generally Ec2 which is the applied voltage of the second grid, φ is the electron beam passage hole diameter of the first grid, and a distance (G1 / K gap) between the cathode and the first grid is a,
When the distance between the first grid and the second grid is f and the plate thickness around the electron beam passage holes of the first grid is t,

## EQU1 ## EK = φ ³ Ec2 / aftt, and the distance a between the cathode and the first grid is an important factor that determines the cutoff voltage EK.

By the way, the electron gun of the color picture tube is
The electron gun assembling jig has three cathode supporting portions for individually supporting the cathode and a heater supporting portion for supporting the heater, and a plurality of electrodes are arranged via spacers for controlling the spacing between them, and these are arranged as cathode supporting portions. After assembling a bead mount by implanting a heater support part and a plurality of electrodes in an insulating support made of bead glass that has been heated and melted, a predetermined distance a from the first grid is attached to the cathode support part of the bead mount. And the heater is attached to the heater support by welding.

Various methods are known for attaching the cathode to the cathode supporting portion. Generally, an air micro device, an electric micro device, or the like is used to remove compressed air blown from the air nozzle. The setting method using the back pressure characteristic is widely used.

FIG. 6 shows a method of setting the distance between the cathode and the first grid by an air micro device. In this method, as shown in (a) of the above, air micros are provided in the electron beam passage holes (only the first grid G1 and the second grid G2 are shown in the figure) of the respective electrodes of the bead mount integrally assembled as described above. Insert the air nozzle 3 of the device and
The compressed air of a predetermined pressure is blown from 3 and the reference surface 6 of the dami gauge 5 in which the concave hole 4 having a depth equal to the distance between the cathode and the first grid is formed is formed in the electron beam passage hole 7 of the first grid G1. It is brought into contact with the surface of the surrounding portion on the cathode side. At this time, the distance from the tip of the air nozzle 3 to the bottom of the concave hole 4 of the dami gauge 5 is measured, and the measured value is stored and displayed in the storage display unit (not shown) of the air micro device. Next, as shown in (b), the dummy gauge is removed without changing the positional relationship between the first grid G1 and the air nozzle 3, and instead of this dummy gauge, the cathode K is replaced based on the memory display of the memory display section. It is assembled by positioning it at the same position as the bottom of the recess of the Dami gauge and welding it to the cathode support.

However, when the cathode K is attached by the above method, there are the following problems.

That is, in order to mount the cathode K so that the distance between the cathode K and the first grid G1 is exactly a predetermined distance by the above-mentioned method, the electron beam passage hole of the first grid G1 in contact with the dami gauge 5 is installed. The flatness of the surface around 7 on the cathode side is important. Regarding this flatness, the first grid G1 of the color picture tube has conventionally been formed in a coin shape in which the plate thickness around the electron beam passage hole is thinner than the plate thickness of other parts. As the tubes become finer, especially in high-definition tubes such as color display tubes, the electron beam passage hole of the first grid G1 is smaller and the plate thickness around the electron beam passage hole is also extremely thin. Has been formed. For example, a material having a plate thickness of 0.175 to 0.25 mm is pressed to reduce the plate thickness of the portion around the electron beam passage hole to 0.06.
~ 0.10mm. When the thickness of the portion around the electron beam passage hole is reduced by pressing in this manner, as shown in FIG.
As shown in (a) and (b), the electron beam passage hole 7
The thin part 8 (coin-shaped part) around is concave 9a
Alternatively, it is deformed into a convex shape 9b, and it is difficult to obtain flatness.

When the thin plate portion 8 around the electron beam passage hole 7 is deformed indefinitely in this way, the Dami gauge is attached to the cathode side of the portion around the electron beam passage hole of the first grid G1 when the cathode is attached. Even if the cathode mounting position is set with high accuracy by contacting the surface of the cathode, the actual mounting position of the cathode is relative to the electron beam passage hole 7 of the first grid G1 and the thin portion 8 around it. Therefore, it does not have a predetermined interval and varies. For example, as shown by the broken line in FIG. 8, the thin plate portion 8 around the electron beam passage hole 7 is deformed into the concave shape 9a, and the position of the electron beam passage hole 7 is in a normal position (around the electron beam passage hole). The first grid G1 is displaced by α
Assuming that the distance between the cathode and the cathode K is a1, the thin plate portion 8 around the electron beam passage hole 7 changes to a convex shape 9b, as shown by the dashed line in the figure, and the electron beam passage hole 7
The distance between the first grid G1 and the cathode K whose position is displaced α from the normal position is a1 + 2α, and α =
In the case of 0.01 mm, it is converted to a cutoff voltage of 10 to 10.
A variation of 15V will occur. As a result, in the three-electron gun of the color picture tube having the three cathodes Ka, Kb, and Kc, the cutoff voltage of each electron gun varies, and a good white screen cannot be obtained.

[0013]

As described above, in the electron gun of the color picture tube, the bead mount is assembled by implanting the cathode supporting portion, the heater supporting portion, and the plurality of electrodes in the heat-melted insulating supporting body. After that, the cathode is mounted on the cathode supporting portion of the bead mount at a predetermined distance from the first grid, and the heater is mounted on the heater supporting portion by welding to assemble. The cathode is attached by inserting the air nozzle of the air micro device into the electron beam passage hole of each electrode of the bead mount, blowing out compressed air of a predetermined pressure from this air nozzle, and equal to the distance between the cathode and the first grid. The Dami-Gauge with the deep recess is contacted with the cathode side surface of the part around the electron beam passage hole of the first grid, and the distance from the tip of the air nozzle to the bottom of the Dami-Gauge recess is measured. Then, based on the measured value, position the cathode so that it is at the same position as the bottom of the Dami gauge recess,
This is done by welding to the cathode support.

However, when the cathode is attached by the above method, the first grid of the color picture tube is formed in a coin shape in which the thickness of the portion around the electron beam passage hole is thinner than the thickness of other portions, and particularly In a high-definition tube such as a color display tube, the plate thickness around the electron beam passage hole of the first grid is formed to be extremely thin. Therefore, at the time of molding, the thin plate portion around the electron beam passage hole is thin. Deforms into a concave or convex shape indefinitely. Therefore, even if the mounting position of the cathode is set with high accuracy using the air nozzle and the dami gauge, the distance between the actually mounted cathode and the electron beam passage hole of the first grid and the thin portion around it is It will not be a predetermined interval,
It causes variations in cutoff voltage. As a result, a color picture tube has a problem that a good white screen cannot be obtained.

The present invention has been made to solve the above problems, and an object thereof is to make the cutoff voltage of the cathode ray tube constant by eliminating the variation in the interval between the cathode and the first grid. ..

[0016]

A plurality of electrodes having electron beam passage holes formed on a cathode are sequentially arranged at predetermined intervals, and a plate thickness of a portion of the electrode adjacent to the cathode around the electron beam passage hole. In a cathode ray tube having an electron gun formed thinner than the plate thickness of other portions, the thin plate portion around the electron beam passage hole of the electrode adjacent to the cathode is projected to the cathode side by a certain height. It was

[0017]

As described above, when the thin plate portion around the electron beam passage hole of the electrode adjacent to the cathode is projected to the cathode side by a certain height, the cathode is mounted by using the air micro device and the dami gauge. When setting the position, the reference plane of the Dami gauge can be surely brought into contact with the card-side surface of the portion around the electron beam passage hole, and the cathode and the electrode adjacent to the electron beam passage hole It is possible to reduce variations in the intervals and eliminate variations in the cutoff voltage.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described based on embodiments with reference to the drawings.

FIG. 3 shows a color picture tube which is one of the embodiments. This color picture tube consists of panel 10 and this panel
The panel 10 has an envelope composed of a funnel 11 integrally bonded to the panel 10. A phosphor screen 12 is formed on the inner surface of the panel 10 and is composed of three-color phosphor layers that emit blue, green, and red. A shadow mask 13 having a large number of electron beam passage holes formed therein is arranged so as to face the body screen 12. Also, inside the neck 14 of the funnel 11, a center beam 15G and a pair of side beams 15 that pass on the same plane.
A row of three electron beams consisting of B and 15R 15B and 15G,
A three electron gun 16 that emits 15R is arranged.

Reference numeral 17 is a deflection yoke which generates a magnetic field for deflecting the three electron beams 15B, 15G and 15R emitted from the electron gun 16 in horizontal and vertical directions.

The three-electron gun 16 includes three cathodes arranged in a row, three heaters for heating the cathodes separately, and a plurality of heaters arranged on the cathodes in the direction of the phosphor screen 12 at predetermined intervals. Of electrodes, which are integrally fixed by a pair of insulating supports.

FIG. 1 shows the structure in the vicinity of the cathode, which is the main part of the structure. With respect to the three cathodes Ka, Kb, Kc arranged in a row, the first and second grids G1, G2 sequentially arranged on the cathodes Ka, Kb, Kc at predetermined intervals are arranged,
They are integrally fixed by a pair of insulating supports 19 made of bead glass. Its first and second grid
Each of G1 and G2 is composed of a plate-shaped electrode having a common structure common to the three electron guns 16, and these electrodes have the above-mentioned cathodes Ka, Kb, Kc.
Corresponding to, three electron beam passage holes are formed in a line. Particularly for the first grid G1, as shown in FIG. 2, each electron beam passage hole 20a, 20b, 20c (see FIG.
The portion 21 around 20b is formed into a coin shape having a thinner plate thickness than the other portions, and the portion 21 around the electron beam passage hole 20 having the smaller plate thickness corresponds to The cathodes Ka, Kb, and Kc (only Kb is shown in FIG. 2) are projected. The protrusion height h is 0.01 mm or less.

In FIG. 1, H is each cathode Ka,
A heater for heating Kb and Kc separately, KHa, KHb and KHc are cathode supporting portions for separately supporting each cathode Ka, Kb and Kc,
G3 is a third grid adjacent to the second grid G2.

The above-mentioned first grid G1 is formed by a forming method substantially similar to that of the conventional coin-shaped first grid, but particularly the electron beam passage holes 20a, 20b, 20c.
When press-molding (coining) the thin plate portion 21 around the punch, by using a punch with a tip having an arbitrary convex shape and a die corresponding to this punch, it is possible to select an arbitrary cathode Ka, Kb, Kc side. It can be projected in shape.

The electron gun 15 is assembled by a method similar to that of a conventional electron gun. That is, three cathode supporting portions for individually supporting the cathode and a heater supporting portion for supporting the heater are arranged on the electron gun assembly jig, and a spacer for regulating a plurality of electrodes arranged on the cathode at intervals thereof. And the cathode support portion, the heater support portion, and the plurality of electrodes are planted in a pair of insulating supports made of bead glass that is softened by heating to assemble a bead mount.

Next, as shown only in the vicinity of the cathode in FIG. 4A, an electron beam passage hole of each electrode of the bead mount, for example, an electron beam passage hole (for the first grid G1) that constitutes the central electron gun. Inserts an air nozzle 3 of an air micro device into the electron beam passage hole 20b) to blow out compressed air of a predetermined pressure from the air nozzle 3, and at the same time, a cathode and a first electrode adjacent to the cathode.
A reference surface 6 of a dami gauge 5 having a bottomed concave hole 4 having a depth equal to the distance from the grid G1 is brought into contact with the cathode side surface of the first grid G1 around the electron beam passage hole 20b. In this case, the reference surface 6 of the dami gauge 5 comes into contact with the portion of the first grid G1 that protrudes toward the cathode side around the electron beam passage hole 20b. At this time, the distance from the tip of the air nozzle 3 to the bottom of the concave hole 4 is measured, and the measured value is stored and displayed in the storage display unit of the air micro device. Next, as shown in (b), the dummy gauge was removed without changing the positional relationship between the first grid G1 and the air nozzle 3, and instead of the dummy gauge, the measurement stored in the memory display section of the air micro device was measured. Based on the value, the cathode Kb is positioned so as to be at the same position as the bottom of the recessed hole of the Dami gauge and welded to the cathode support. The electron gun 15 uses this cathode Kb as a mounting method for other cathodes.
It is assembled by repeating Ka and Kc.

By the way, when the portions 21 thinner than the plate thickness around the electron beam passage holes 20a, 20b, 20c of the first grid G1 are made to project to the cathodes Ka, Kb, Kc side by a certain height, respectively, as described above. , When the first nozzle G1 is attached to the bead mount in which the first grid G1 and other electrodes are integrally assembled and the cathodes Ka, Kb, Kc are attached using the dami gauge 5, the reference surface 6 of the dami gauge 5 is It is possible to surely make contact with the surfaces of the one grid G1 around the electron beam passage holes 20a, 20b, 20c protruding toward the cathodes Ka, Kb, Kc. Therefore, by keeping the protruding height h constant, the cathodes Ka, Kb, Kc are attached to the first grid G1, particularly the electron beam passage holes 20a, 20b, 20c and their surroundings at exactly predetermined intervals. Will be able to. As a result, it is possible to eliminate the variation in the cutoff voltage caused by the deformation of the portion around the electron beam passage hole of the first grid in the related art, and improve the white screen of the color picture tube.

The electron beam passage hole of the first grid G1
Cathodes Ka, Kb, Kc around 20a, 20b, 20c
When the protrusion height h to the side becomes large, the electron beam passage hole 20
Not only is the shape of a, 20b, 20c deteriorated and the focus characteristics deteriorated, but the parts around the electron beam passage holes 20a, 20b, 20c are easily deformed when the electron gun is assembled, and the first grid G1 and The potential distribution between the cathodes Ka, Kb, Kc becomes sharp, and the first grid G1 and the cathodes Ka, K
Problems such as deterioration of withstand voltage of b and Kc occur. Therefore, the protrusion height h is preferably 0.01 mm or less.

Although the above embodiment has been described with respect to the color picture tube, the present invention can be applied to a cathode ray tube other than the color picture tube.

[0030]

When the thin plate portion around the electron beam passage hole of the electrode adjacent to the cathode is projected to the cathode side by a certain height, the cathode is mounted by using an air nozzle and a dami gauge of an air micro device, for example. When setting the position, the reference surface of the Dami gauge can be surely brought into contact with the surface on the cathode side of the portion around the electron beam passage hole, and the reference surface of the electrode adjacent to the cathode and the portion around the electron beam passage hole It is possible to reduce variations in the intervals and eliminate variations in the cutoff voltage.

[Brief description of drawings]

FIG. 1 (a) is a sectional front view showing a structure in the vicinity of a cathode of an electron gun of a color picture tube which is an embodiment of the present invention, and FIG. 1 (b) is a side view showing the same. Is.

FIG. 2 is a diagram showing the shape of the first grid.

FIG. 3 is a diagram showing the overall configuration of a color picture tube that is an embodiment of the present invention.

4A and 4B are views for explaining a method of mounting the cathode of the electron gun.

FIG. 5 (a) is a front view showing a cross section of a structure in the vicinity of a cathode of an electron gun of a conventional color picture tube, and FIG. 5 (b) is a side view showing the cross section.

6 (a) and 6 (b) are views for explaining a method of attaching a cathode of a conventional electron gun, respectively.

FIG. 7 (a) and FIG. 7 (b) are each a first conventional example.
It is a figure which shows the deformation | transformation of a grid.

FIG. 8 is a diagram for explaining a change in the distance between the first grid and the cathode due to the modified first grid.

[Explanation of symbols]

 16 ... Electron gun 19 ... Insulating support 20b ... Electron beam passage hole of first grid 21 ... Portion around electron beam passage hole of first grid G1 ... First grid G2 ... Second grid H ... Heaters Ka, Kb, Kc ... Cathode KHa, KHb, KHc ... Cathode support

Claims (1)

[Claims] 1. A plurality of electrodes having electron beam passage holes formed on a cathode are sequentially arranged at predetermined intervals, and the plate thickness of a portion of the electrode adjacent to the cathode around the electron beam passage hole is different. In a cathode ray tube having an electron gun formed to be thinner than the plate thickness of the portion, the thin plate portion around the electron beam passage hole of the electrode adjacent to the cathode protrudes to the cathode side by a certain height. Is a cathode ray tube.