JP2002083554A - Cathode-ray tube and manufacturing method of its cathode structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To automatize a welding process by eliminating cracks in an insulating coating (and a black coating) formed on an end of a heater when welded to a heater support. SOLUTION: A heating core is coiled around a mandrel into a helical structure and then the mandrel is dissolved and removed. The heating core forms the heater 25 built in an indirectly-heated cathode structure constituting an electron beam generating part of an electron gun. The heater support 33 for holding the heating core with its respective end parts welded thereto comprises components made by pressing a high-melting point metallic material undissolved by a dissolving liquid for dissolving/removing the mandrel in the manufacturing process of the heating core.

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 provided with an electron gun having an indirectly heated cathode, and more particularly to a method for welding an insulated coated heater, which is a heating element of an indirectly heated cathode, to a heater support. The present invention relates to a cathode ray tube having improved reliability by avoiding cracks in insulation coating and deformation of a heater, and a method for manufacturing the cathode assembly.

[0002]

2. Description of the Related Art A cathode ray tube used for a television picture tube, a display tube or the like has a fine image reproducibility, and is therefore widely used as a display means of various information processing devices.

[0003] This type of cathode ray tube has a panel section having a phosphor screen formed by applying a phosphor on the inner surface thereof, and an electron beam generated by an electron beam generating section comprising an indirectly heated cathode structure, a control electrode and an accelerating electrode. A neck portion accommodating an electron gun having a main lens portion for emitting light toward the phosphor screen, and a deflection for connecting the panel portion and the neck portion to scan an electron beam emitted from the electron gun on the phosphor screen. It consists of a vacuum envelope made up of a funnel with a yoke.

FIG. 7 is a schematic cross-sectional view for explaining a schematic structure of a shadow mask type color cathode ray tube as an example of a cathode ray tube, wherein 1 is a panel portion, 2 is a funnel portion, 3 is a neck portion, and 4 is a panel portion. A phosphor screen formed by applying a phosphor on the inner surface of the hologram, 5 is a shadow mask as a color selection electrode, 6 is a magnetic shield for shielding an external magnetic field (geomagnetism), and prevents the trajectory of the electron beam from being changed by terrestrial magnetism. I do. Reference numeral 7 denotes a deflection yoke, 8 denotes a correction magnetic device for correcting mismatch between the electron gun and the phosphor due to a slight axis shift or rotation shift between the electron gun and the panel / funnel / shadow mask, and 9 denotes three electron beams. Gun with an indirectly heated cathode structure that emits light, 10 is one of three electron beams
The book is shown as a representative.

[0005] Three electron beams 10 from the electron gun 9 are modulated by video signals from an external signal processing circuit (not shown).
The light is emitted toward the fluorescent screen 4. The electron beam 10 is scanned two-dimensionally on the phosphor screen 4 by passing through horizontal and vertical deflection magnetic fields generated by a deflection yoke 7 provided in a transition region between the neck portion 3 and the funnel portion. The shadow mask 5 passes through a large number of apertures formed in the plane.
Each of the electron beams of the book is selected for each color to excite the corresponding phosphor on the phosphor screen to reproduce a required image.

FIG. 8 is a side view illustrating a configuration example of an electron gun used in the cathode ray tube shown in FIG. This electron gun has a control electrode (first grid electrode: G1) 11, an acceleration electrode (second grid electrode: G2) 12, a focusing electrode (third grid electrode: G3, a fourth grid electrode: G4, a fifth grid electrode). : G5) 13, 14, 15; anodes (sixth grid electrode: G6) 16; and shield cups 17 are arranged at predetermined intervals and in a positional relationship in the tube axis direction. A tab or a lead wire provided on each electrode is welded to the stem pin 18a erected on the base 18.

In this electron gun, an indirectly heated cathode structure 21 is disposed in the vicinity of the stem 18 of the control electrode 11, and the indirectly heated cathode structure 21 has a built-in heater for heating the electron emission portion. ing.

Reference numeral 19 denotes a valve spacer contact, which has a function of resiliently contacting the inner wall of the neck portion so that the central axis of the electron gun coincides with the tube axis, and also includes a funnel and an internal conductive film applied to the inner wall of the neck. It has the function of introducing anode voltage to the gun.

The control electrode 11, the accelerating electrode 12, and the indirectly heated cathode assembly 21 constitute an electron beam generator (three-pole part). The focusing electrodes 13 to 15 accelerate and focus the electron beam emitted from the electron beam generator, converge to a predetermined electron beam diameter by a main lens formed between the focusing electrode 15 and the anode 16, and move toward the fluorescent screen. Be oriented.

The stem 18 is welded to the open end of the neck portion of the vacuum envelope to transmit an external signal or voltage to the stem pin 1.
A signal / voltage input terminal to be applied to each electrode via 8a.

The heater 25 constituting the indirectly heated cathode assembly 21 is made of alumina (Al ₂ O ₃ ) except for an end welded to a heater support for holding and holding a tungsten (W) core wire heater wound in a spiral coil. ) Is applied, and a black coating is applied on the surface of the insulating coating, preferably using a solvent in which alumina and tungsten fine powder are dispersed. For the above-mentioned insulating coating and black coating, an electrodeposition method such as an electrophoresis method is used. The purpose of the blackening process is to increase the efficiency of radiation of radiant heat from the heater, lower the temperature of the heater, and improve the reliability.

FIG. 9 is a process chart for explaining a method of manufacturing a heater subassembly constituting a conventional cathode assembly. This step includes sub-steps P-10 to P-80. Less than,
FIG. 9 will be described in the order of the sub-steps.

The sub-step P-10 is a primary coil winding step, in which a core wire 25A preferably made of molybdenum and a heating core wire 25B made of tungsten (hereinafter also referred to as a heater core wire or simply a core wire) 25B are formed into a spiral structure. Wind the coil. In the coil winding of the heater core wire 25B, the main part (heater main part) of the heater is a single coil winding part SC, and the part (end) to be welded to the heater support shown in FIG. And The multi-coil winding part (multi-spiral structure part) MC is double or more. Here, it is a triple winding.

In the sub-step P-20, the sub-step P-
The primary coil formed in step 10 is twisted and wound with the central portion as the top of the heater to form a secondary coil having a spiral structure.

In the sub-step P-30, both ends of the secondary coil are shaped to form a heater as a whole. At this time, the multiple coil winding part MC becomes a part (weld end) to be welded to the heater support.

Next, in a sub-process P-40, an insulating coating CV is applied to a portion except for a heater main portion of the secondary coil and a welded end portion continuous with the heater main portion.

Subsequently, a black coating CB is applied to cover the insulating coating CV in a sub-process P-50. At this time, the insulating coating CV on the welding end side is slightly exposed.

In the sub-step P-60, the coated insulating coating CV and black coating CB are sintered and solidified.

Thereafter, in a sub-step P-70, a mixed acid (nitric acid:
The secondary coil is immersed in sulfuric acid = about 47: about 53), and the core wire 25A is dissolved and removed. Thereby, the tungsten core wire having a hollow coil winding shape having the insulating coating CV and the black coating CB other than the welded portion remains in the heater.

Finally, in a sub-step P-80, the two legs 33A, 33B of the heater support 33 prepared in advance and having a shape in which two substantially parallel legs 33A, 33B are connected by beams. Each end 3 bent in the opposite direction in the same direction
4A and 34B are welded to both ends 25 of the secondary coil.

In the heater subassembly thus manufactured, after inserting the cathode main portion into a cathode sleeve structure (cathode assembly) constituting a cathode assembly, the two legs 33A and 33B of the heater support 33 are connected to a heater lead (not shown). To weld. Then, the beam is cut to separate the two legs.

Tungsten core wire for heater (heating core wire)
Is extremely thin, usually has a diameter of 20 to 50 μm, and the mechanical strength of the coiled structure is weak, and the work of welding and fixing the structure to the heater support requires a high degree of skill. Improving the weldability of the heater, disconnection of the heater due to sparks and disconnection due to overcurrent when the switch is turned on,
It is suppressed by the triple winding specification described above.

[0023]

In recent years, it has become difficult to perform skilled work such as the above-described heater welding work. Although the conventional technology described above certainly improves the weldability of the heater, the following points are considered when performing the heater welding process by an unskilled person and when performing automation by a machine instead of an unskilled person. Was in short supply.

That is, in the sub-step P-80 of welding the heater to the cathode support, the coated insulating coating CV (and the black coating CB) tends to crack. Such cracks cause the coating to fall off, causing foreign matter to be generated in the pipe.

As a countermeasure against such cracking of the insulating coating,
It is known that a single coil winding portion for buffering is formed between a multiple coil winding portion at both ends where a heater is welded to a heater support and an insulating coating portion (Japanese Patent Laid-Open No. 7-25 / 1995)
No. 4352).

However, the above-mentioned prior art has the following problems. That is, in the formation of an insulating coating by an electrodeposition method such as an electrophoresis method, the surface of the solvent in which the insulating coating material or the black coating material is dispersed vibrates to control the coating forming region of the insulating coating (and the black coating). It is difficult, and the exposed dimension of the single coil winding portion varies, which causes cracks in the insulating coating (and the black coating) during welding.

Although the secondary coil can be shaped with high accuracy, the opening width at both ends thereof varies after the step of melting the molybdenum wire used as the core metal wire. further,
The exposed portion of the single-coil winding is low in rigidity and deformed even by minute vibration, so that the welding position between the heater support and the heater varies, and it is difficult to automate the welding process to the heater support.

According to the present invention, there is provided an insulating coating (and a black coating) formed on a heater end when welding to a heater support.
It is an object of the present invention to provide a cathode ray tube equipped with an electron gun having an indirectly heated cathode structure that eliminates cracks and enables automation of a welding process.

[0029]

In order to achieve the above object, a typical configuration of the present invention provides a heater support using a high melting point metal material which is insoluble in a mixed acid which dissolves a core wire for winding a coil of a heater. Is formed, and both ends of the secondary coil are welded to predetermined positions on the heater support before forming the insulating coating and the black coating. The heater support has a shape in which two substantially parallel legs for welding both ends of the heater are joined by a beam, and is incorporated in a sleeve of a cathode assembly to fix the heater support to the electron gun. Was cut.

That is, according to the present invention, the heater built in the indirectly heated cathode structure constituting the electron beam generating portion of the electron gun is wound around the core wire in a spiral structure, and then the core wire is melted and removed. The heater support, which consists of a heating core wire and holds each end of the heating core wire by welding, is composed of pressed parts of a high melting point metal material that is insoluble in the solution of the core metal wire that is melted and removed in the manufacturing process of the heating core wire. did.

The core wire is preferably made of molybdenum, and the refractory metal material constituting the heating core wire is preferably tungsten or a tungsten alloy containing a small amount of rhenium or lanthanum.

It should be noted that the present invention is not limited to the above-described structure, and various modifications can be made without departing from the spirit of the present invention described in the appended claims.

[0033]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a sectional view of a main part of a three-pole part for explaining the structure of an indirectly heated cathode structure for explaining an embodiment of a cathode ray tube according to the present invention.

In the figure, reference numeral 20 denotes a pair of multi-form glass (bead glass).
During the period of 0, each electrode and the cathode structure constituting the electron gun are fixed.

The triode comprises a cathode structure, a first electrode 11 and a second electrode 12. The cathode assembly is a heater 2 inserted inside a sleeve 28 suspended on a cylinder 23.
5, a heater support 33 for welding and holding the legs of the heater 25, respectively, a leg 33A of the heater support 33,
Heater leads 31A and 31B for welding 33B, and ceramic disk 3 for mounting heater leads 31A and 31B
2. An eyelet 35 holding the ceramic 32 and welding one end to the end of the first grid. 26 denotes an electron emitting portion.

The heater 2 of the heater support 33
One ends (heater welds) 34A, 34B of the legs 33A, 33B to which the fifth leg is welded are bent inward from the legs 33A, 33B.

FIG. 2 is an explanatory view of an assembled state of the cathode structure shown in FIG. The cathode assembly consists of a cathode assembly and a heater subassembly. The cathode assembly is performed by the cylinder 2 holding the sleeve 28 described in FIG.
3, an eyelet 35, a ceramic disk 32, and heater leads 31A and 31B. The heater sub-assembly comprises a heater 25 and a heater support 33,
The heater 25 welded to the heater support 33 is inserted into the sleeve 28 of the cathode assembly to form a cathode assembly.

In the heater sub-assembly, the heater 25
Are both ends 33A, 33B of the heater support 33.
Is welded to one end 34A, 34B bent inside. The legs 33A and 33B of the heater support 33 are connected to each other by a beam 33C at the intermediate portion. This beam 33C
Incorporates the cathode assembly into the electron gun and connects the legs 33A and 33B of the heater support 33 to the heater leads 31.
A and 31B are fixed by welding, and then cut and separated by an appropriate means such as a laser beam.

Next, the manufacturing process of the heater sub-assembly constituting the cathode assembly according to the present invention will be described.

FIG. 3 is a process chart for explaining a method of manufacturing a heater sub-assembly constituting the cathode assembly according to the present invention. This step includes sub-steps P-1 to P-8. FIG. 3 will be described below in the order of sub-steps. In the figure, the contents of the process are shown on the left, and the plan view of the heater and heater support manufactured in the process is shown on the right.

As in the description of FIG. 9, first, a tungsten heating core wire 25B is wound around a molybdenum core metal wire 25A to form a primary coil. At this time, the central portion serving as the main portion of the heater has a single-coil winding SC, and both ends serving as the welded portions are coil-wound (here, triple) (primary coil winding process)... Sub-process (P- 1).

A secondary coil having a helical structure is formed by twisting and winding the central portion of the primary coil as the top of the heater to form a heater main portion (secondary coil winding process)... Sub-process (P-2) .

Both ends of the secondary coil are shaped to form a heater as a whole. (Heater leg shaping step) ... sub-step (P-3).

Next, the two substantially parallel legs 33A, 33
Both ends of the secondary coil are welded to respective ends in the same direction of two legs 33A and 33B of the heater support 33 prepared in advance and having a shape in which the space between B and B is joined by a beam 33C.
As the heater support 33, a pressed product of a high melting point metal material (tungsten or a tungsten alloy containing a small amount of rhenium or lanthanum) that is insoluble in a mixed acid is used. The portions of the heater support 33 where the two ends of the secondary coil are welded are bent inward to each other, and the heater weld portions (34A, 3A) are welded.
4B) (heater welding step) ... sub-step (P-4).

An insulating coating CV of alumina fine powder is applied to the spiral structure of the secondary coil and a part of the both ends except for a portion to be welded to the heater support 33 continuously to the spiral structure part ( Insulation coating step) Sub-step (P-5).

Substrate (P-6): Black coating CB of alumina and tungsten fine powder is applied to substantially the entire surface including the top of insulating coating CV (black coating step).

The insulating coating CV and the black coating CB are sintered and solidified (sintering step)... Sub-step (P-7).

The core wire 25A existing inside the secondary coil welded to the heater support 33 is dissolved and removed by immersion in a mixed acid (nitric acid: sulfuric acid = about 47: about 53), and the coiled heating core wire 25B is removed. Let it survive. At this time, the heater support 33 is also immersed in the mixed acid, but the heater support 33 is formed of a pressed product of a high melting point metal material (tungsten or a tungsten alloy containing a small amount of rhenium or lanthanum) which is not dissolved in the mixed acid. Therefore, it is not melted (core wire melting step): Sub-step (8).

The heater subassembly thus manufactured is assembled into the electron gun, and then assembled into the heater support 33.
The beam 3C is cut by a laser or the like, and the two legs 33A, 3
Separate 3B.

The thickness of the heater support is set to 0.05 to 0.05 in consideration of the cutting of the beam after being incorporated into the electron gun.
It is preferable that the thickness is about 0.15 mm. In addition, when the heating core wire is an ultrafine wire having a wire diameter of 0.05 mm or less, the cathode temperature varies due to slight misalignment of the welding assembly dimensions of the heater. It is possible to obtain a highly accurate cathode assembly without causing temperature variations.

According to this embodiment, cracking of the insulating coating (black coating) when welding the heater to the heater support can be avoided, and heater welding can be automated.

In the above embodiment, the vicinity of the end of the heater to the heater support (welded portion) is formed by multiple coil winding, but the present invention is not limited to this. Hereinafter, another embodiment of the present invention will be described.

FIG. 4 is an explanatory view of a heater subassembly of another embodiment of an indirectly heated cathode structure for explaining an embodiment of a cathode ray tube according to the present invention. In the present embodiment, the end portion (welded portion) of the heater core wire is formed as a single coil, and the welded portion is formed as a single coil and welded to the heater support 33 to form an insulating coating CV and a black coating CB. . afterwards,
The core metal wire 25A is melted to make a heater sub-assembly. This manufacturing method is the same as that of FIG. 9 except for the coil winding of the heating core wire.

As described above, even when the end of the heater core wire is wound by a single coil, welding with the heater support can be performed with high accuracy.

If the thickness of the heater support is reduced, the insulation coating (and black coating) of the heater may be cracked due to deformation of the heater support itself when welding the heater. In order to avoid this, the heater support has the following structure.

FIG. 5 is an explanatory view of a heater sub-assembly of still another embodiment of the indirectly heated cathode structure for explaining the embodiment of the cathode ray tube according to the present invention. In the present embodiment, in the case of a heater support having low rigidity, the heater support 33
The beam portions 33C and 33C 'are provided at the two locations to prevent deformation of the heater support itself when welding the heater and to avoid cracking of the insulating coating (black coating).

FIG. 6 is an explanatory view of a heater sub-assembly of still another embodiment of the indirectly heated cathode structure for explaining an embodiment of the cathode ray tube according to the present invention. This embodiment is shown in FIG.
The heater support of FIG. 5 is applied to a single core wound end portion (welded portion) of the heater core wire described in (1).

According to this embodiment, the heater wound in a single coil is securely welded to the heater support, and even when a heater support having low rigidity is used, the deformation of the heater support itself when welding the heater is prevented. In addition, cracks in the insulating coating and the black coating can be avoided.

[0060]

As described above, according to the typical structure of the present invention, the core metal wire is present when welding the heater constituting the cathode assembly of the electron gun used for the cathode ray tube with the heater support. As a result, it becomes possible to place the welding jig without any gap by applying a slightly larger pressure to the heater core wire,
The dimensional accuracy of the welding assembly can be improved.

Further, since the heater support portion can be transported while being held after the insulating coating or the black coating is formed, no crack is caused in the insulating coating or the black coating at the time of transportation or loading in the manufacturing process. .

As described above, according to the representative configuration of the present invention, the accuracy of assembling the heater of the cathode assembly constituting the electron gun is improved, the variation in the supply voltage of the cathode is reduced, and the variation in the operating temperature of the cathode is reduced. Can be suppressed and the generation of foreign matter in the tube can be avoided, so that a highly reliable cathode ray tube can be provided.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a main part of a triode illustrating a structure of an indirectly heated cathode structure for explaining an embodiment of a cathode ray tube according to the present invention.

FIG. 2 is an explanatory diagram of an assembled state of the cathode structure shown in FIG.

FIG. 3 is a process diagram illustrating a method of manufacturing a heater sub-assembly constituting a cathode structure according to the present invention.

FIG. 4 is an explanatory view of a heater subassembly of another embodiment of the indirectly heated cathode structure for explaining an embodiment of the cathode ray tube according to the present invention.

FIG. 5 is an explanatory view of a heater subassembly of still another embodiment of the indirectly heated cathode structure for explaining the embodiment of the cathode ray tube according to the present invention.

FIG. 6 is an explanatory view of a heater sub-assembly of still another embodiment of the indirectly heated cathode structure for explaining the embodiment of the cathode ray tube according to the present invention.

FIG. 7 is a schematic sectional view illustrating a schematic structure of a shadow mask type color cathode ray tube as an example of a cathode ray tube.

FIG. 8 is a side view illustrating a configuration example of an electron gun used in the cathode ray tube shown in FIG.

FIG. 9 is a process chart for explaining a method of manufacturing a heater subassembly constituting a conventional cathode assembly.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 20 Multi-form glass (bead glass) 11 1st electrode 12 2nd electrode 23 Cylinder 25 Heater 25A Core wire 25B Core wire 26 Electron emission part 28 Sleeve 31A, 31B Heater lead 32 Ceramic disk 33 Heater support 33A, 33B Heater support leg Portion 34A, 34B One end of the leg portion (heater welding portion) 35 Eyelet.

Claims (4)

[Claims] 1. An electron beam generated by a panel section having a phosphor screen formed by applying a phosphor on an inner surface thereof, and an electron beam generating section having an indirectly heated cathode structure, a control electrode and an acceleration electrode. A neck portion accommodating an electron gun having a main lens portion that emits light toward the outside, and a deflection yoke for connecting the panel portion and the neck portion and scanning an electron beam emitted from the electron gun on a phosphor screen are provided. A cathode ray tube comprising a vacuum envelope constituted by a funnel portion, wherein a heater incorporated in an indirectly heated cathode structure constituting an electron beam generating portion of the electron gun is coil-wound in a helical structure around a core wire. A heating support formed by dissolving and removing the core metal wire later, and holding each end of the heating core wire by welding, is dissolved in a solution of the core metal wire to be melted and removed in the manufacturing process of the heating core wire. Not high Cathode ray tube, characterized by being configured by pressing parts of the point metal material. 2. The cathode ray tube according to claim 1, wherein the refractory metal material constituting the heating core wire is tungsten or a tungsten alloy containing a small amount of rhenium or lanthanum. 3. An electron beam generated by a panel section having a phosphor screen formed by applying a phosphor on an inner surface thereof, and an electron beam generating section having an indirectly heated cathode structure, a control electrode and an acceleration electrode. A neck portion accommodating an electron gun having a main lens portion that emits light toward the outside, and a deflection yoke for connecting the panel portion and the neck portion and scanning an electron beam emitted from the electron gun on a phosphor screen are provided. A method for manufacturing an indirectly heated cathode structure constituting the electron beam generating portion of a cathode ray tube comprising a vacuum envelope constituted by a funnel portion, wherein the indirectly heated cathode structure comprises a heater comprising a heating coil,
And a heater support for welding and holding both ends of the heating winding of the heater. The manufacturing process of the heater assembly includes the following sub-step (1).
To (9) in this order. A primary coil winding step of forming a primary coil by coil-winding a heating core wire around a core metal wire: a sub-process (1). A secondary coil winding step of forming a secondary coil having a helical structure by twisting the central portion of the primary coil as a top of the heater to form a sub-step (2). A heater leg shaping step for shaping both ends of the secondary coil to form a heater shape as a whole—sub-step (3). A heater welding step of welding both ends of the secondary coil to one ends of the two legs of the previously prepared heater support having a shape in which two substantially parallel legs are connected by a beam portion in the same direction;・
..Sub-step (4). An insulating coating step of applying an insulating coating to the helically structured portion of the secondary coil and a part of the both ends except for a portion to be welded to the heater support continuously to the helically structured portion ... Sub-step (5).
A black coating step of applying a black coating to substantially the entirety including the top portion of the insulating coating ... sub-step (6). A sintering step for sintering the insulating coating and the black coating: sub-step (7). A core metal wire melting step of melting and removing the core metal wire present in the secondary coil welded to the heater support to form a heater composed of a heat generating core wire... Sub-step (8). A separating step of cutting the beam portion of the heater support to separate the two legs of the heater support ... a sub-step (9). 4. The method of claim 3, wherein the step of separating the two legs of the heater support is performed after the heater support of the heater assembly is assembled into the electron gun. Cathode ray tube.