KR20010053992A - Structures and manufacture methode for impregnated cathode of Cathode Ray Tube - Google Patents

Abstract

PURPOSE: An impregnated cathode structure for a cathode ray tube and a fabrication method of the same are provided to be capable of increasing the heat transfer speed as well as reducing heat loss from a heat to a pellet by coating a nitride coating layer on a bottom surface of the pellet, thereby enhancing the power-saving performance of the impregnated cathode. CONSTITUTION: A sputtering film(11) is deposited on and an electron emission layer is impregnated into a pellet(12). A coating layer(13) of a predetermined thickness is coated on a bottom surface of the pellet(12). A sleeve(14) is directly coupled to the pellet(12) having the coating layer(13) formed. A heater(15) generates heat from the interior of the sleeve(14). The coating layer(13) consists of aluminum nitride and is coated by a CVD(Chemical Vapor Deposition).

Description

Impregnated cathode structure for cathode ray tube and its manufacturing method {Structures and manufacture methode for impregnated cathode of Cathode Ray Tube}

The present invention relates to an impregnated cathode structure for a cathode ray tube and a method for manufacturing the same, and in particular, to form a coating layer on the bottom of the pellet impregnated with the electrospinning material to improve the heat transfer rate from the heater to the pellet and to reduce the heat loss. An impregnated cathode structure for a CRT and a method of manufacturing the same.

As the conventional CRT impregnated cathode structure is shown in Figure 1,

Pellets 1 impregnated with an electrospinning material, a cup CUP 1 containing the pellets 1, and a cylindrical sleeve 3 into which the cup 1 is inserted and welded. And a heater 5 that generates heat inside the sleeve 3, and a ribbon 5 connecting the lower end of the sleeve 3 to the holder 6.

Hereinafter, a description will be given of a conventional cathode impregnated cathode structure with reference to the accompanying drawings.

First, referring to the process for manufacturing an impregnated cathode (Cathode), the pellet 1 is impregnated with electron emitting materials (BaO, CaO, Al ₂ O _3, etc.) to increase the electron emission efficiency on the surface In order to make a thin film (not shown) is formed of a metal or a metal oxide or a composite compound thereof.

In addition, the contact surface is welded by placing the pellet 1 in a cup 2 made of molybdenum (Mo) or tantalum (Ta) having a predetermined thickness (several tens of micrometers).

To this end, there are several welding methods for the pellet 1 and the cup 2, one of which is a solder (eg, copper, molybdenum, ruthenium, etc.) inserted between the pellet and the cup. ) Is a method of scanning by welding to the bottom of the cup, and the second method is to insert the pellet into the cup in a clamped manner to weld directly.

When welding of the pellet 1 and the cup 2 is completed in this way, the cup 2 is inserted into the cylindrical sleeve 3 again, and in this state, the inner periphery of the sleeve 3 and the outside of the cup 2 are contacted. The periphery is welded on the outside of the sleeve 3.

Then, by connecting the lower end of the sleeve 3 and the holder 6 with a ribbon 5, the impregnation type consisting of the cup 2 containing the pellet 1, the sleeve 3, the ribbon 5 and the holder 6 Obtain the negative electrode.

The heater 4 is inserted into the completed cathode sleeve 3 to assemble electrodes (not shown) such as the first grid electrode G1, the second grid electrode G2, and the third grid electrode G3. To complete the electron gun.

Looking at the operation of the impregnated cathode of such a structure,

First, when a rated voltage (approximately 6.3 V) is applied to the heater 4 inserted into the sleeve 1, the heat generated from the heater 4 is transferred to the pellet 1 through the sleeve 3 and the cup 2. Delivered.

At this time, an electron-emitting material, that is, an oxide such as barium oxide (BaO), is reduced with a metal such as tungsten by using heat transferred to the pellet 1 to generate a barium (Ba) atom to form an electron generating source. The produced barium atoms absorb this heat to emit electrons.

To this end, the heat generated from the heater 4 is transmitted to the pellet 1 through two paths, the first of which radiant heat from the heater 4 is transferred to the bottom of the cup 2, the heat conduction mechanism The heat is transferred to the contact surface of the pellet 1 and the cup 2 through the cup (2).

In the second path, radiant heat is transferred from the heater 4 to the sleeve 3, part of which causes radiant heat loss to the outer surface of the sleeve 3, and the other part of the cup 2 and sleeve (through the heat conduction mechanism). After 3), heat is transferred to the contact surface of the cup 2 and the pellet 1.

That is, there are two paths of heat transfer: heater → cup → pellet heat transfer and heater → sleeve → cup → pellet heat transfer. Both paths allow the heat of the heater 4 to be transferred to the pellet 1 via a heat resistant layer, such as the cup 2 or the sleeve 3.

In addition, the energy conservation equation for the cup, which will be described later in order to obtain the heat transfer rate and heat loss in the cup 2, uses Equation 1.

Where temperature T is a function of time and location, Is the density of the cup, Cp is the specific heat of the cup, and k is the thermal conductivity of the cup. On the right side [ Cp ∂T / ∂t] is the rate of change of the thermal energy of the cup over time, and the second [-∇ (k∇T)] is the difference between the heat entering and leaving the cup.

In Equation 1 above, k∇T is the heat transfer rate per unit area and per unit time, and multiplying the inner and outer surfaces of the cup not only calculates the heat entering and leaving the cup per hour, but also inside the cup. Heat transfer rates can also be obtained. Of course, the heat transfer rate is obtained by multiplying the specific heat of the cup by the mass and the temperature change from the computer simulation.

That is, the first [ Cp ∂T / ∂t] is a term representing the heat loss caused by the cup. In order to reduce the heat loss caused by the cup 2, the thickness is made thin to reduce the mass or use a low specific heat material. However, there is a limit to changing the material to a thin metal or high thermal conductivity of the cup (2). If the thickness of the cup is too thin, there is a difficulty in welding the sleeve 3 and the cup 2, the cup 2 and the pellet 1.

Therefore, even if the material of the sleeve 3 is used as a material having excellent thermal conductivity or a blackening layer is formed on the inner surface to increase the radiation efficiency, the heat transfer from the heater 4 to the pellet 1 is performed by the medium of the cup 2. The heater 4 is designed in consideration of some heat loss. That is, since the heat transfer efficiency from the heater 4 to the pellet 1 is reduced, the heat lost in the heater 4 design should be taken into account.

However, in the related art, heat is transferred to the pellet 1 through the intermediate medium of the cup 2 as described above, so that the heat transfer rate is slowed and heat loss occurs in the cup 2 itself.

In addition, since the cup 2 itself is a thermal resistor and has a heat capacity with respect to the mass it basically has, it is difficult to minimize heat loss, and the cup 2 and the sleeve 3 are welded. There is also a resistance to increase the heat transfer rate is also limited.

In addition, since there is a medium of the cup 2, there is a problem of assembling the impregnated cathode, that is, inserting the pellet 1 into the cup 2, and welding the pellet 1 and the cup 2. .

The present invention has been made to solve the above-mentioned conventional problems, by coating a coating layer having a horizontal monolayer of aluminum nitride on the bottom of the pellet so that the heat transferred from the heater to the pellet can be transferred more quickly, from the heater To provide a CRT type impregnated cathode structure and a method of manufacturing the same, which can improve the speed and power saving of the impregnated cathode by increasing the heat transfer rate to the pellet as well as reducing the heat loss. The purpose is.

1 is a cross-sectional view showing a conventional CRT impregnated cathode structure.

Figure 2 is a cross-sectional view showing an impregnated cathode structure for CRT according to the present invention.

Figure 3 is a view showing the impregnated cathode manufacturing method for CRT according to the present invention.

Figure 4 is a table showing a comparison of the electron emission time according to the thickness of the coating film and the conventional cup of the present invention.

Figure 5 is a table showing a comparison of the heater current and power consumption according to the coating film thickness and conventional cup thickness of the present invention.

<Description of Symbols for Main Parts of Drawings>

1,12 ... pellet 2 ..... cup

3,14 ... sleeve 4,15 ... heater

5,16 ... ribbon 6,17 ... holder

11 ... sputtering film 13 .... coating layer

The impregnated cathode structure for a CRT according to the present invention,

Pellets impregnated with an electron radiating material,

Forming a coating layer on the bottom of the pellet,

It is characterized in that the pellet formed with the coating layer is directly bonded to the sleeve.

Here, the coating layer is characterized in that it comprises an aluminum nitride material.

Method for producing an impregnated cathode for CRT according to the present invention,

Coating a heat transfer medium on the bottom of the pellet containing the electrospinning material;

Inserting the coated pellets directly into the sleeve;

Welding the pellet and the sleeve at the side of the sleeve into which the pellet is inserted.

Here, the coating layer is characterized in that the coating of the material of aluminum nitride by the vapor deposition method.

Hereinafter, with reference to the accompanying drawings as follows. 2 is a cross-sectional view showing an impregnated cathode structure for a CRT, and FIG. 3 is a view illustrating a method of manufacturing an impregnated cathode for a CRT.

2 and 3, the sputtering film 11 is deposited on the upper surface and the pellet 12 impregnated with the electrospinning material, the coating layer 13 coated with a predetermined thickness on the bottom of the pellet 12 and In addition, the coating layer 13 is formed of a sleeve 12 to which the pellets 12 are directly coupled, and a heater 15 that generates heat inside the sleeve 14.

The coating layer 13 is characterized by using a nitride compound and coating it by chemical vapor deposition (CVD).

Reference numeral 16 is a ribbon, 17 is a holder.

The impregnated cathode structure for a CRT and a method of manufacturing the same according to the present invention configured as described above will be described with reference to the accompanying drawings.

First, the sputtering film thin film 11 is deposited by sputtering in order to impregnate the pellet 12 with the electron emitting material Bao, CaO, Al ₂ O ₃ and to increase the electron emission efficiency on the surface thereof (FIG. 3). a).

Then, the coating layer 13 is coated on the bottom of the pellet 12. To this end, the coating layer 13 is positioned between the heater 15 and the pellet 12 in the sleeve 13 to use a material having a high work function to effectively transfer heat, and the electrons generated in the pellet 12 are heated by the heater ( Use chemically stable elements to avoid release to side 15).

In addition, even if the work function is high due to the heat transferred from the heater 15 to the coating layer 13 on the bottom surface of the pellet 12, when the temperature reaches a certain level (about 1500 ° C. or more), electrons are emitted toward the heater, so that the characteristics of the CRT It must be refractory to withstand high temperature to prevent it.

As a material that satisfies these conditions, aluminum nitride (AlN) is a refractory material having a high melting point and a high thermal radiation rate, not a metal, and is a material having high thermal conductivity and strong thermal shock.

Here, there are two methods for forming an aluminum nitride coating film of the coating layer 13, such as chemical vapor deposition (CVD) and spin coating method which is widely used for coating a refractory material.

Chemical Vapor Deposition (CVD) is performed by heating aluminum metal while introducing nitrogen gas (N ₂ ) into the reactor to form steam, and depositing and reacting the vapor on the underside of the target pellet 11 to form an aluminum nitride film. It is formed.

That is, when nitrogen gas flows into the chamber and heats the aluminum metal Al as a source to form nitrogen gas N ₂ and aluminum vapor at a low pressure (about 10 ⁻² torr), the target pellet 12 After being adsorbed on the underside, it diffuses and reacts to form aluminum nitride. This is represented by the formula (1).

Al (s) + Heat = Al (v)

2Al (v) + N ₂ = 2 AlN

Here, (v) means a vapor state, and (s) means a solid state.

The aluminum nitride coating film is coated with a predetermined thickness (several μm) to completely cover the pores of the pellet 13 and the electrospinning material to prevent evaporation of barium gas (Ba) from the pellet 13 toward the heater and to prevent the heater ( The heat of 15) is not directly applied to the impregnating material or pores.

At this time, since the melting point is low and the deposition rate is high when the target is heated, aluminum and nitrogen do not need to be heated to a high temperature because the activation energy is not high.

Such a chemical vapor deposition method has a characteristic that the deposition rate is faster than the sputtering method, the ion beam deposition method, or the like, which is a physical vapor deposition method, and is advantageous for forming a film having a predetermined thickness (a few m).

Second, the spin coating method is the most common method for coating non-oxide refractory materials, which requires a sintering process of several hundred degrees or more, and heating pellets impregnated with electron emitting materials to a high temperature may adversely affect the properties of the pellets. Given.

As described above, the present invention forms an aluminum nitride film, which is a material of the coating layer 13, on the bottom surface of the pellet 12 by chemical vapor deposition to a predetermined thickness as described above (b in Fig. 3).

Subsequently, in order to insert the pellet 12 having the coating layer directly into the sleeve 14, the pellet 12 is placed on one side of the sleeve 14, and then pressed by a press or the like, and then the sleeve is in this state. (14) From the outside, the inner edge of the sleeve, the pellet 12, and the outer circumference of the coating layer 13 are directly welded using a laser or the like (Fig. 3 (c)).

As described above, when aluminum nitride (AlN) is coated on the bottom surface of the pellet 12 as the coating layer 12, the heat generated from the heater 15 is transferred to the pellet 12 through the coating layer 13 or the sleeve 14. By directly transmitting to the film, a thinner and smaller mass than a conventionally used cup can bring a small heat capacity as a coating film and a small heat loss.

In addition, the aluminum nitride refractory has a high melting point (2200 ° C. or more), a low thermal expansion rate, and is suitable for an impregnated cathode that is heated to a predetermined temperature or more (1000 ° C.) by being resistant to thermal shock. In addition, the thermal conductivity of aluminum nitride is 100-220W / mK, and the thermal conductivity is high, and the radiation efficiency is high, so that the heat transfer rate from the heater 15 to the pellet 12 is fast.

4 is a view comparing electron emission time (TEW) according to coating thickness and cup thickness, and FIG. 5 is a view comparing heater current (If) and power consumption (Watt) according to coating thickness and cup thickness. .

Tantalum (Ta) having an inner diameter of about 1.20 µm and a thickness of about 30 µm is used, and the inner surface of the sleeve 11 is blackened, the thickness of the pellet is about 0.4 mm, and the molar ratio of the pellet to the electron-emitting material is Barium oxide (BaO), calcium oxide (CaO) and aluminum oxide (Al ₂ O ₃ ) is impregnated with 3: 1: 1, and the surface is coated with osmium / ruthenium (Os / Ru) by sputtering.

In this structure, three samples having a thickness of 5 μm, 10 μm, and 50 μm of aluminum nitride coated film were formed on the bottom of the pellet, and the cup was formed by using a tantalum material having a thickness of 30 μm, 50 μm, or 100 μm. Welded.

Also, the conditions for measuring the electron emission time (TEW) are 4kV for high voltage, 3kV for focus voltage, 200V for acceleration voltage, and 6.3V for heater voltage. Under these conditions, the result of measuring the time (TEW) when the cathode current reaches 450 mA is shown in the table of FIG. 4.

When the aluminum nitride is coated on the bottom surface of the pellet 12 as shown in the table of FIG. 4, the conventional cup is applied to the amount of heat applied to the heater so that the electron emission time (TEW) and the cathode temperature become a constant temperature (about 1000 ° C.). As a result, the electron emission time (TEW) coated with the coating film is faster than the electron emission time using the cup.

That is, when the thickness of the aluminum nitride coating film was 5 μm, 25 μm, and 50 μm, the electron emission time was shown as 3.1, 3.9, and 4.9 sec, while the thickness of the cup was 30 μm, 50 μm, and 100 μm. Since the emission times are 4.7, 5.1, and 7.2 (sec), respectively, the electron emission time of aluminum nitride is faster.

As shown in the table of Fig. 5, the heat applied to the heater so that the temperature of the cathode is 1000 ° C. is coated with aluminum nitride and a cup is used, and the heater current is under the rated voltage (about 6.3 V). ) Was modified, designed and tested. As a result of this experiment, the coating of aluminum nitride on the pellet has more power saving effect, and coating the thickness of the coating film with several μm brings more advantages to speed and power saving.

As described above, in the structure of the impregnated cathode for CRT, the refractory aluminum nitride material is coated on the bottom of the pellet instead of the cup containing the pellet so that the heat transfer rate from the heater to the pellet can be increased and the heat loss can be reduced. In addition, the CRT impregnated cathode for the tube can obtain an advantageous structure than the conventional in the speed and power saving, there is an effect that can simplify the impregnated cathode manufacturing process.

Claims (4)

Pellets impregnated with an electron radiating material, Forming a coating layer on the bottom of the pellet, The impregnated cathode structure for a cathode ray tube, characterized in that the coating layer formed pellets are directly bonded to the sleeve. The method of claim 1, The coating layer is an impregnated cathode structure for a CRT, characterized in that it comprises an aluminum nitride material. Coating a heat transfer medium on the bottom of the pellet containing the electrospinning material; Inserting the coated pellets directly into the sleeve; The impregnated cathode manufacturing method for a CRT comprising the step of welding the pellet and the sleeve on the side of the sleeve is inserted pellet. The method of claim 3, wherein The coating layer is an impregnated cathode manufacturing method for a CRT, characterized in that the coating of aluminum nitride material by the vapor deposition method.