JPH097497A - heater - Google Patents

Abstract

(57) [Summary] [Structure] A metal wire 1 made of a conductive material having heat resistance is formed into a coiled coil shape, and a heater having an inorganic porous insulating film 2 covering the metal wire 1 is insulated from the metal wire 1. A heater in which a protective layer 6 is provided between the films 2 and the protective layer 6 is made of a material having a higher electrical resistivity than the metal wire 1. [Effect] The mechanical strength of the insulating film is high, and a heater with high reliability and long life can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a product having an insulating film, and more particularly to a high performance heater having a high filling rate of the insulating film in the step of forming the insulating film of a heater for heating a cathode ray tube.

[0002]

2. Description of the Related Art Conventionally, cathode ray tubes and impregnated cathode ray tubes have a heater for heating a cathode. FIG. 2 shows the appearance of the heater. After winding the metal wire 1 in a coil shape and further winding it in a coil shape, an insulating film 2 is formed, and a dark layer 3 is formed outside the insulating film 2. The heater is located in a cylindrical metal cover called a sleeve 4. In the impregnated cathode heater, the impregnated cathode 5 is arranged on the top of the heater. The metal wire is a conductive material having heat resistance, such as tungsten (W) or rhenium-tungsten alloy (Re-).
W) is used. Since the surface of the metal wire is cleaned through processes such as heating in a hydrogen atmosphere, the material itself is exposed. The insulating film is formed on the surface of the metal wire by a method such as an electrophoretic coating method, a spraying method, or a dipping method with an insulator such as alumina. Since the heater energizes the metal wire to perform heating, the heater operates in an environment in which a high temperature of about 1200 ° C. when energized and a room temperature when stopped are repeatedly applied as the cathode ray tube is turned on and off. In an environment of high temperature and intermittent energization, sintering causes grain growth of insulating particles constituting the insulating film and contraction of the insulating film. As a result, peeling or cracking of the insulating film occurs, or the metal wires come into contact with each other, resulting in short-time insulation failure. Moreover, disconnection failure of the metal wire has occurred. As means for improving them, JP-A-3-379
In the 88 publication, an electrolyte is selected according to the purpose in the electrophoretic method to form an insulating film having a uniform film filling rate, and the strength and insulating properties are improved, cracks in the insulating film are prevented, and a long-life heater is obtained. ing.

[0003]

In order to prevent contact between metal wires and to improve insulating film characteristics, it was considered necessary to form a sufficient insulating film in the space between the metal wires. In the conventional technology, the electrolyte in the electrophoretic method is selected according to the purpose to form an insulating film having a uniform film filling rate, and the strength and insulating properties of the insulating film are improved to prevent cracks in the insulating film. . However, problems such as an increase in the number of steps and difficulty in maintaining heater manufacturing accuracy have occurred.

[0004]

The present invention provides a high-reliability and long-life heater by forming a high-performance insulating film by providing a protective layer between a metal wire and an insulating film. An explanatory view of the insulating film structure is shown in FIG. A protective layer 6 is provided between the metal wire 1 and the insulating film 2, and a dark layer 3 is formed on the outer periphery of the insulating film 2.

By coating the surface of the metal wire with a substance having a high electric resistivity when forming a film by the electrophoretic method, an insulating film is selectively formed between the metal wires to prevent contact between the metal wires. At the same time, it was thought that the filling rate of the insulating film could be increased to improve the strength and insulating properties. FIG. 3 shows an explanatory view of a heater portion when a film is formed by the electrophoretic method. The metal wire 1 is wound around the metal core wire 7 to form a coil. The counter electrode 8 is arranged opposite to this. These are immersed in the dispersion liquid 9 and a power supply 10 is used to supply electricity. The insulating particles 11 charged by the electrolyte migrate to the coil, which is an electrode, to form an insulating film. At the time of film formation, the metal wire 1 is wound around the metal core wire 7 which is the support material, and the metal core wire and the metal wire are in contact with each other, so that they have the same potential. Therefore, insulating particles do not easily migrate between the metal wires and the insulating film is likely to be insufficiently formed. At this time, when the surface of the metal wire is covered with the protective layer 6 having a high electric resistivity, the metal core wire 7 has a higher potential than the metal wire 1, so that the insulating particles 11 migrate toward the metal core wire 7. As a result, insulating particles 11 are formed between the metal wires.
Can be selectively filled to prevent the metal wires from contacting each other, and the insulating film filling rate can be increased to improve strength and insulating characteristics. FIG. 4 shows a schematic diagram of film formation of the present invention and the conventional method. In the conventional method, since film formation proceeds simultaneously on the metal wire and on the metal core wire, it is difficult to fill the insulating particles between the metal wires. In the present invention, since the metal wire is covered with the protective layer having a higher electric resistance than the metal wire, the potential of the metal core wire is higher than that of the metal wire. Therefore, the insulating particles are formed from the surface of the metal core wire having a high potential, and as a result, an insulating film having a high filling between the metal wires can be obtained.

The protective layer may be made of any material as long as it can withstand a high vacuum (10 ^-7 Pa) and a high temperature (up to 1200 ° C), which is an environment when the heater is operated, and that satisfies the above electrical resistance. The protective layer has a melting point>
The characteristics of stable at 1200 ° C in vacuum and low vapor pressure are desirable. The electrical resistance of the protective layer must be> 5.2 × 10 ⁶ (Ω · cm) when the metal wire is molybdenum (Mo), and> 5.5 × 10 ⁶ (Ω · cm) when it is W. is there. In the present invention, the expression that the electric resistance of the protective layer is higher than that of the metal wire is used, but the same meaning is given even if the electric conductivity of the protective layer is lower than that of the metal wire. Oxides, borides according to claims 3 to 7,
Nitride, silicide or their composite material satisfies all the properties required for the protective layer.

If the thickness of the protective layer is thinner than 0.5 μm, the characteristics of the protective layer cannot be utilized, and the diameter of the metal wire is 1/1
If it is thicker than 0, the characteristics of the metal wire as a heating element will be impaired.

The protective layer may be formed by any of a vapor phase method, a solid phase method and a liquid phase method as long as it can form a film having the above characteristics.

[0009]

Function: A high-performance insulating film is formed by providing a protective layer between a metal wire and an insulating film, and a highly reliable and long-life heater is manufactured. When a material with high electrical resistance is used for the protective layer, an insulating film with a high filling rate can be formed between the metal wires during the film formation by the electrophoretic method, so that the metal wires are prevented from contacting each other, and the strength and insulating property of the insulating film are improved. Can be improved. As a result, a heater with high reliability and long life can be obtained.

[0010]

EXAMPLES The present invention will be described below with reference to examples.

(Example 1) 3% Re-W having a diameter of 30 μm
The metal wire was heated in an electric furnace filled with a hydrocarbon-based gas and carbonized to form a tungsten carbide protective layer having a thickness of 1 μm on the surface. The metal wire was wound around a Mo metal core wire having a diameter of 110 μm to form a heater coil. The dispersion liquid was prepared by dissolving Al (NO ₃ ) ₃ and Mg (NO ₃ ) ₂ .6H ₂ O as electrolyte components in 8 liters of an aqueous ethanol solution, and used as an inorganic insulating particle having a purity of 99.9% or more and having an average particle diameter of 4 μm. Al
9 kg of ₂ O ₃ ) particles were blended.

Using this dispersion, a heater coil was connected to a negative electrode and an aluminum electrode was connected to a positive electrode, and a voltage was applied at 80 V for 3 seconds to form a film.

Thereafter, the average particle size is 1 μm and the purity is 99.9%.
A liquid in which the above-mentioned tungsten particles were dispersed and suspended was applied by dip coating to form a dark layer.

Next, this was baked in a hydrogen atmosphere at 1600 ° C. for 5 minutes. The insulating film thickness including the dark layer after firing was 110 μm.

After completion of firing, the Mo metal core wire was dissolved and removed by a mixed solution of nitric acid and sulfuric acid, washed with water and dried to prepare a heater.

FIG. 5 shows the heater current and the leak current when the heaters of this example and the comparative example were subjected to the life test. The comparative example is a heater having a conventional structure using a 3% Re-W wire having a diameter of 30 μm. In the life test, a cycle in which a voltage higher than the heater operating voltage is applied for 5 minutes and a rest for 15 minutes is repeated. If the insulation film deteriorates or cracks occur, the leak current increases, and the heater current decreases. In the comparative example, when the life test time exceeds 4000 hours, an increase in leak current and a decrease in heater current are observed, whereas in Example 1, 6
No change until 000 hours.

(Example 2) 3% Re-W having a diameter of 30 μm
The metal wire was heated in an electric furnace filled with nitrogen gas for nitriding treatment to form a tungsten nitride protective layer having a thickness of 1 μm on the surface. Thereafter, a heater was prepared in the same process as in Example 1, and a life test was performed. As a result, the same result as in Example 1 was obtained.

(Example 3) 3% Re-W having a diameter of 30 μm
The metal wire was packed in a container filled with boron, heated in a vacuum, and subjected to a boration treatment to form a tungsten boride protective layer having a thickness of 1 μm on the surface. Thereafter, a heater was prepared in the same process as in Example 1, and a life test was performed. As a result, the same result as in Example 1 was obtained.

(Example 4) 3% Re-W having a diameter of 30 μm
A metal wire is heated in air to be oxidized, and the surface has a thickness of 1 μm.
A tungsten oxide protective layer was formed. Thereafter, a heater was prepared in the same process as in Example 1, and a life test was performed. As a result, the same result as in Example 1 was obtained.

(Embodiment 5) FIG. 6 is a sectional view of a cathode ray tube. The cathode ray tube is a funnel-shaped glass tube, and the electron gun 1
2 and the fluorescent screen 13 are enclosed. The glass bulb is composed of a swollen cone portion and a thin cylindrical neck portion, and a fluorescent substance (a substance that fluoresces when irradiated with an electron gun) is applied to the bottom of the cone portion and is sealed in a high vacuum. Electron gun 12
Is composed of a cathode 15 which emits electrons by the heater 14 for heating the cathode, a cylindrical electrode (grid) 16 for converging the flux of the electrons as an electron beam at a high speed and converging the flux on the phosphor screen. ing. Deflection yoke 1
7, an anode button 18, and a conductive film 19 (aluminum film covering the fluorescent screen 13) is formed on the inner surface of the neck portion and the cone portion.

[0021]

According to the present invention, the filling rate of the insulating film between the metal wires is increased. In particular, a heater for heating a cathode ray tube cathode and a cathode ray tube equipped with the heater have effects of high reliability and long life.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an insulating film structure.

FIG. 2 is a sectional view of a heater.

FIG. 3 is an explanatory view of a heater portion when a film is formed by an electrophoretic method.

FIG. 4 is an explanatory view of a film forming process.

FIG. 5 is a characteristic diagram of changes in the life test time of heater current and leak current.

FIG. 6 is a cross-sectional view of a cathode ray tube.

[Explanation of symbols]

 1 ... Metal wire, 2 ... Insulating film, 3 ... Dark layer, 6 ... Protective layer.

Claims (10)

[Claims] 1. A heater having a porous insulating film of an inorganic material covering a metal wire formed of a heat-resistant conductive material in a coiled coil shape, wherein a protective layer is provided between the metal wire and the insulating film. A heater provided with. 2. The heater according to claim 1, wherein the protective layer is made of a material having a higher electrical resistivity than the metal wire. 3. The protective layer according to claim 1, wherein the protective layer is Al, B.
a, Ca, Cr, Hf, Mg, Mn, Nb, Ni, S
A heater composed of at least one oxide of i, Sr, Th, Ti, W, V, Zn, and Zr. 4. The protective layer according to claim 1, wherein the protective layer is Ba, C.
a, Ce, Cr, Hf, La, Mo, Nb, Sm, S
A heater composed of at least one boride of r, Ta, Th, Ti, W, and Zr. 5. The protective layer according to claim 1, wherein the protective layer is Al,
B, Ba, Be, Ca, Ce, Cr, Fe, Hf, M
n, Mo, Nb, Si, Sr, Ta, Th, Ti, V,
A heater composed of at least one kind of carbide of W and Zr. 6. The protective layer according to claim 1, wherein the protective layer is Al,
B, Be, Hf, Nb, Si, Ta, Th, Ti, V,
A heater composed of at least one nitride of Zr. 7. The protective layer according to claim 1, wherein the protective layer is Cr, M.
A heater composed of at least one kind of silicide of o, Nb, Re, Ta, Th, Ti, V, W and Zr. 8. The heater according to claim 1, wherein the protective layer has a thickness of 0.5 μm or more and 1/10 or less of the wire diameter of the metal wire. 9. A heater for a cathode ray tube, wherein the heater for heating the cathode pellet of the cathode ray tube is the heater according to any one of claims 1, 2, 3, 4, 5, 6, 7 or 8. 10. A phosphor screen, an electron gun provided to face the phosphor screen, the electron gun is a sleeve, a cathode pellet disposed at the tip of the sleeve, and a heater for heating the cathode mounted in the sleeve. A cathode ray heater provided with a heater for heating a cathode coated with an inorganic insulator, wherein the heater for heating the cathode is
A cathode ray tube which is a heater corresponding to any one of 6, 7, and 8.