JPH076697A - Method and device for manufacturing projection type cathode-ray tube - Google Patents

Abstract

PURPOSE:To provide a method and a device for manufacturing a projection type cathode-ray tube for removing contamination due to an electron emitting substance sticking to the second grid electrode, and preventing worsening a voltage break down characteristic between electron gun electrodes and an image display characteristic. CONSTITUTION:A process 11, for igniting a heater for heating a cathode to emit an electron flow from the cathode and making this electron flow collide against the second grid electrode system to heat it, is inserted in the intermediate between a reinforcing process 10 and a before stock knocking process 12. A maximum temperature at heating time is set to 600 deg.C or more and 650 deg.C or less, and an electron emitting substance stuck to the second grid electrode system is removed while avoiding fluctuation of cut off voltage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention eliminates the pollution caused by the electron emission material from the cathode attached to the second grid electrode of the electron gun and prevents the deterioration of the withstand voltage characteristic and the image display characteristic between the electron gun electrodes. The present invention relates to a method of manufacturing a projection cathode ray tube and a manufacturing apparatus thereof.

[0002]

2. Description of the Related Art A projection-type image device for enlarging and projecting an image displayed on the fluorescent surface of a cathode ray tube onto a screen through an optical system is improved in the brightness and resolution of the projected image. In recent years, the image quality has been widely used as the image quality has improved to the extent that it can sufficiently counter the image of the direct-view cathode ray tube.

However, in order to improve the above characteristics, the projection type cathode ray tube has a larger maximum current value of the electron beam and a higher maximum applied voltage in comparison with the direct-viewing type cathode ray tube, and moreover, the electrode of the electron gun. Since the distance between them is small, the electric field between the electrodes is very strong.

FIG. 6 is a side view of a unipotential focus type electron gun used in a projection cathode ray tube.
Reference numeral 21 is a first grid electrode, 22 is a second grid electrode (abbreviated as G ₂ ), 23 is a third grid electrode, 24 is a fourth grid electrode, 25 is a fifth grid electrode, and 25a is integrally connected to a fifth grid electrode. The shield cup 26 is provided with an electron emission surface very close to an electron beam passage hole formed in the cylindrical bottom surface of the cylindrical first grid, and is actually a support portion from the outside. Only the cathode that can be seen, 27 is a heater that is inserted into the inside of the cylinder to heat the cathode formed on the outside of the bottom surface of the cylindrical body, and only the power feeding part is visible from the outside, and 28 supports the electron gun composed of the above electrodes. The stem sealed at the end of the neck tube of the glass bulb, which is the vacuum envelope of the cathode ray tube, and the bead glass 29, which insulates and supports the above electrodes while accurately maintaining their relative positions.

At the time of manufacturing a cathode ray tube, the electron gun is assembled in a clean environment as much as possible. There is inevitably the possibility of dust adhering to it, and the metal surfaces forming each electrode should have been smoothed for some time, but in reality, fine irregularities and protrusions remain, and they remain as they are. In such a state, under the high electric field as described above, the electric field is particularly strongly concentrated on the ends of the linear dust and the projections on the electrode surface, which causes the discharge.
For example, by the method disclosed in Japanese Patent Application Laid-Open No. 55-154034, spot knocking processing for applying a high voltage pulse from the third grid electrode to the fifth grid electrode is performed to remove the cause of the electric field concentration. However, the withstand voltage characteristic is maintained. Such knocking treatment has been performed not only once but also after aging in order to remove the electron emitting substance (mainly barium) attached to the second grid electrode.

[0006]

As described above, the electrode spacing of the electron gun of the projection cathode ray tube has generally become narrower in order to improve the focus characteristics, but in order to improve the definition, First, the electron beam diameter generated in the vicinity of the second grid electrode due to the electric field between the first grid electrode and the second grid electrode must be reduced so that the diameter of the crossover portion where the electron beam is most narrowed in the entire flight path of the electron beam. The electrode system after the third grid electrode has a function of forming the image point on the fluorescent surface by using the crossover as an object point. Therefore, in order to reduce the diameter of the crossover, the diameter of the electron beam passage hole of the first grid electrode is reduced, and at the same time, the distance between the cathode surface and the first grid and the distance between the first grid and the second grid are reduced.
The grid spacing should be small.

In the aging process, in order to improve and stabilize the electron emission characteristics, a voltage higher than the rated voltage is applied to the heater, for example, a maximum of 10.5 V when the rated voltage is 6.3 V. At that time, the cathode temperature rises. The electron-emitting substance (metal barium or the like generated by reduction from the oxide) evaporates and adheres to the cathode surface side of the second grid electrode in a considerably large amount due to the short distance between the electrodes as described above. Since the electron beam passage hole diameter of the second grid electrode is small, a considerable number of electrons collide with the portion other than the hole of this electrode, and the temperature rises to a considerably high temperature even in the normal operating state.

When the electron emitting substance adheres to the second grid electrode, the temperature of this electrode rises, so that electrons are emitted from this electrode, which causes the start of discharge and causes a gap between the electrodes. Deterioration of withstand voltage characteristics, and even after the power supply of the television device is cut off, the electrode temperature decreases relatively slowly, so the above electron emission continues, and it is also observed as stray emission on the fluorescent surface of the cathode ray tube. .
In order to remove such a phenomenon, it has been attempted to remove the above-mentioned electron-emitting substance that is excessively attached by knocking before and after aging and knocking before warehousing, but it has not been sufficient. In addition, the second grid electrode system is heated by an exhaust process or high frequency induction heating using a so-called bomber,
When trying to remove the electron-emitting substance attached thereto by evaporation, the total amount of heat given to the electrode system is large, and if the maximum temperature at that time becomes excessive, the second grid electrode system is deformed and the cut-off voltage is increased. Another problem is that it will change.

The present invention eliminates the inconvenience caused by the excessive adhesion of the electron emission material to the above-mentioned conventional second grid electrode system,
An object of the present invention is to provide a manufacturing method and a manufacturing apparatus of a projection type cathode ray tube that can improve withstand voltage characteristics with a high yield.

[0010]

In order to solve the above problems, according to the present invention, the second grid electrode of the electron gun is further provided between the reinforcing process and the knocking process before warehousing in the conventional manufacturing process of the projection cathode ray tube. A step of heating the system was inserted and installed to remove the electron emission material attached to the electrode system. Specifically, as a method of heating the second grid electrode system of the electron gun, a heater for heating the cathode is ignited to emit an electron flow from the cathode, and the electron flow is collided with the second grid electrode system to generate a second electron beam. The grid electrode system is heated, and the maximum temperature during heating is set to 600 ° C. or higher and 650 ° C. or lower, and the heating process of the second grid electrode system of the electron gun is carried while the product is placed on a frame and conveyed. In the automatic manufacturing apparatus that advances the process, a power supply line for applying a predetermined DC voltage to the second grid electrode system and a power supply line for applying a predetermined DC voltage for ignition of the cathode heater are extended in the carrying direction. It was decided to carry out by a manufacturing apparatus which is installed while being attached and applies the above voltage to the cathode ray tube mounted on the pedestal through a brush provided on the transportation pedestal.

[0011]

According to the above means, it is possible to eject electrons mainly on the cathode side of the second grid electrode system where the electron emitting substance is excessively adhered to surely remove the extra electron emitting substance, and There is no fear of heating other parts unnecessarily to deform them. In addition, since the manufacturing apparatus of the present invention only adds power supply equipment to a relatively short section along the conventional conveyor line, the new equipment cost is minimal and the effect on cost is very good.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a process chart for explaining a method of manufacturing a projection type cathode ray tube according to the present invention. Sealing step 1 for sealing the stem supporting the assembled electron gun to the end of the neck tube of the glass bulb, evacuation step 2 for exhausting the inside of the cathode ray tube where the vacuum envelope is completed, and emission from each member in the tube after exhaustion A getter flash step 3 in which a getter is scattered to absorb a so-called gas to improve the degree of vacuum in the tube, a pre-knocking step 4 in which foreign matter in the electrode system is removed before the aging step, and an electron emission characteristic from the cathode is improved. Aging step 5 for stabilization, post-knocking step 6 for removing electron emission material excessively attached to the electrodes during aging, subsequent primary inspection 7, raster aging 8 performed while drawing a raster, exterior step 9 After the reinforcing step 10 of attaching a reinforcing band to the outside of the panel skirt for preventing implosion, the electron beam heating process for the second grid electrode system according to the present invention is performed. 11,
It consists of knocking before warehousing 12, secondary inspection 13, and warehousing process 14.

In the electron beam heating step 11 of the second grid electrode system according to the present invention, since the second grid electrode system is heated, a gas is newly released from the second grid electrode system and the gas deteriorates the electron emission characteristics of the cathode. However, since the heater is ignited and the temperature of the cathode surface is sufficiently high in this step, the electron emission characteristics are not deteriorated. But the second
When the grid electrode system is heated to a high temperature, there arises a problem that the characteristic of cutting off the electron beam current changes. This is because the surface potential of this electrode is affected by the attachment state of the electron emission material attached to the surface of the second grid electrode.

FIG. 2 is a diagram showing how the withstand voltage characteristic changes depending on the heating temperature when the second grid electrode is heated during the manufacturing process of the projection cathode ray tube according to the present invention.
The horizontal axis shows the heating temperature, and the vertical axis shows the withstand voltage characteristic (actually, the voltage at which stray emission is observed). From this figure, it can be seen that, when the design withstand voltage standard value of 35 kV is determined, almost all of the products are non-defective when the second grid electrode heating temperature is set to 600 ° C. or higher. But,
When the temperature is raised to 680 ° C. or higher, the cut-off voltage fluctuates significantly. Therefore, in the present invention, the maximum heating temperature of the second grid electrode is set to 600 ° C. or higher and 650 ° C. or lower.

FIG. 3 is a diagram showing the relationship between the time from the start of heating and the temperature reached by actually heating the second grid electrode when heating the second grid electrode. The time is plotted on the ordinate, which is the temperature reached by the electrode when heated for that time. The temperature of the second grid electrode is 6
Heating at the above-mentioned maximum setting temperature for 30 seconds or more after reaching 00 ° C is optimal for evaporating and removing the electron-emitting substance excessively attached to the second grid electrode,
It was effective in suppressing the occurrence of defects and improving the yield.

FIG. 4 is a circuit diagram for heating the second grid electrode system according to the present invention. References 21 to 27 refer to the same as those described for the electron gun in FIG. 6, and 30 in this figure is a DC constant voltage power supply (EC ₂ power supply) for attracting and colliding the electron flow with the second grid electrode system. , 31 are DC constant voltage power supplies (Ef power supplies) for heater ignition. That is,
The heater is ignited for 30 seconds in advance, and a predetermined constant voltage is applied to the second grid electrode system to heat this electrode system, thereby removing the electron emitting substance.

FIG. 5 is a perspective view illustrating a manufacturing apparatus according to the present invention (a part of a fully automatic manufacturing apparatus which also serves as a transfer apparatus). In the figure, 32 is a transfer conveyor, 33 is a transfer hanger, and 34 is a drawing. The Ef feeding feeder (feeding line) connected to the heater ignition DC constant voltage power source 31 shown in FIG. 4 is a DC constant voltage power source 30 for attracting and colliding the electron flow with the second grid electrode system 22. A feeder for EC ₂ power supply connected to, 36 is an Ef current collecting brush, 37 is an EC _{2 current} collecting brush,
38 is the conveyor rail, and the arrow is the conveying direction.

In the projection type cathode ray tube mounted on the hanger 33, a direct current constant for attracting and colliding the electron flow from the power source 30 to the second grid electrode system via the feeder 35 and the brush 37 is applied to G _2. As the voltage, a constant DC voltage for ignition is supplied to the heater 27 from the power supply 31 via the feeder 34 and the brush 36. Here, for one projection cathode ray tube, EC
₂ power is set to one (only projection type one cathode ray tube for _two power one EC is suppressed an increase in equipment cost so as to be connected). In addition, in order to prepare for the structure in which the temperature of the second grid electrode system becomes high due to the structure of the electron gun, the current value is made variable and G ₂
The electrode temperature can be set within the predetermined maximum temperature.

[0019]

As described above, according to the present invention, it is possible to prevent the deterioration of the withstand voltage characteristic between the electron gun electrodes and the image display characteristic with a relatively small additional equipment cost and an increase in the number of steps.

[Brief description of drawings]

FIG. 1 is a process diagram illustrating a method of manufacturing a projection cathode ray tube according to the present invention.

FIG. 2 shows how the withstand voltage characteristic changes according to the heating temperature when the second grid electrode is heated during the manufacturing process of the projection cathode-ray tube according to the present invention. It is a figure which takes and shows a withstand voltage characteristic (it is actually shown by the voltage at which stray emission is observed).

[Fig. 3] When heating the second grid electrode, the time from the start of heating is plotted on the horizontal axis, and the temperature reached by actually heating the second grid electrode for that time is plotted on the vertical axis, and heating is started. It is a figure which shows the relationship between the time after and the temperature which the 2nd grid electrode reached.

FIG. 4 is a circuit diagram when heating the second grid electrode system according to the present invention.

FIG. 5 is a perspective view illustrating a manufacturing apparatus according to the present invention (a part of a fully automatic manufacturing apparatus that also serves as a conveyor).

FIG. 6 is a side view of a unipotential focus type electron gun used in a projection cathode ray tube.

[Explanation of symbols]

21 ... 1st grid electrode, 22 ... 2nd grid electrode,
23 ... 3rd grid electrode, 24 ... 4th grid electrode, 25 ... 5th grid electrode, 25a ... Shield cup, 26 ... Cathode in which only a supporting part is visible from the outside, 27 ... Only a power feeding part is visible from the outside Heater, 28 ... Stem that supports the electron gun and is sealed at the end of the neck tube, 29 ... Bead glass that insulates and supports while holding the relative position of the electron gun electrode, 30 ... G ₂ and collides by attracting electron flow to G _2. DC constant voltage power supply for operating, 31 ... DC constant voltage power supply for heater ignition, 32 ... Transport conveyor, 3
3 ... Conveyor hanger, 34 ... Ef feeder for feeding,
35 ... EC ₂ feeder, 36 ... Ef current collecting brush, 37 ... EC _{2 current} collecting brush, 38 ... Conveyor rail.

Claims (2)

[Claims] 1. A projection type including steps of sealing a stem for supporting an electron gun, exhausting, getter flash, first knocking, aging, raster aging, reinforcement, second knocking, and (stocking). In the manufacturing process of the cathode ray tube, a process of heating the second grid electrode system of the electron gun is inserted and installed between the reinforcing process and the second knocking process.
A method of manufacturing a projection type cathode ray tube, characterized in that an electron emitting substance attached to the electrode system is removed. 2. A power supply line for applying a predetermined DC voltage to an electron gun second grid electrode system, and a predetermined heater for igniting a cathode heater, in an automatic manufacturing apparatus which advances a process while carrying a product on a gantry. A power supply line for applying a DC voltage is attached so as to extend in the carrying direction, and the above voltage is applied to the cathode ray tube mounted on the gantry via a brush provided on the gantry for carrying the electron gun. An apparatus for manufacturing a projection type cathode ray tube, characterized in that the second grid electrode system is heated.