JPH0714498A - Cathode structure of electron gun for cathode-ray tube - Google Patents

Abstract

PURPOSE: To suppress a transient current at the time of starting, by coupling a sleeve and an external holder for fixing the sleeve with each other via an internal holder having a large thermal expansion coefficient. CONSTITUTION: A sleeve 33 composed of a Cr 20% Ni 80% alloy incorporates a heater 36 and is equipped with a cap 32 to which an electron emitting material layer 31 is applied. An upper end of an internal holder 34 is joined to an external holder 35 composed of Ni, and an lower end thereof supports the sleeve 33 while is joinned to an lower part 33-1 of the sleeve 33, whereby the electron emitting material layer 31 is positioned so as to stand opposite to a first grid electrode 20 leaving a fixed space between them. The internal holder 34 is composed of an alloy containing Fe of 39% or more, Cr of 19 to 23%, and Ni of 25 to 32%, and its coefficient of thermal expansion is larger than those of the sleeve 33 and the external holder 35. That is to say, when the heater is heated, thermal expansion of the sleeve 33 and of the external holder 35 is compensated and a space between the first grid electrode 20 and the electron emitting material layer 31 is kept constant.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cathode structure of an electron gun for a cathode ray tube for suppressing a transient phenomenon of the cathode current of the electron gun, and more particularly to an improved holder capable of buffering thermal expansion of a sleeve. And a cathode structure having the same.

[0002]

2. Description of the Related Art Generally, an electron gun is provided with a cathode structure and a large number of grid electrodes which are arranged side by side along the axis of the cathode structure at a predetermined interval. In such an electron gun, the cathode current (Ik) can be determined according to the distance between the cathode structure and the first grid electrode. Therefore, the distance between the cathode structure and the first grid electrode must be accurately maintained in order to maintain a uniform cathode current (Ik). Therefore, the cathode structure and the first grid electrode are installed in the structure of the electron gun so as to maintain a predetermined distance during manufacture.
However, when the cathode structure is activated, the cathode structure rapidly expands to reduce the distance between the cathode structure and the first grid electrode, causing a transient phenomenon in which the cathode current (Ik) rapidly increases. The increase in the cathode current (Ik) makes the operating characteristics of the screen of the cathode ray tube unstable. The problem will be described below with reference to FIG.

Referring to FIG. 1, a first grid electrode (20)
There is shown a cathode structure (10) installed under a predetermined distance. The cathode structure (10) includes a sleeve (13) for incorporating a heater (15) and a cap (12) welded to an upper portion of the sleeve (13). Above Cap (12)
Is made of a nickel alloy containing 95% or more of nickel so that it is not deformed by the heat generated by the heater 15. Then, the cathode structure (10) is the cap (1
A holder (14) having an upper part welded to a lower part of the sleeve (13) is provided to support the electron emitting material layer (11) applied on the upper surface of the second part (2) and the sleeve (13). Electron emitting material
(11) is composed of carbonate in which Ba, Ca, Sr, etc. are mixed in an appropriate ratio.

In the cathode structure, the holder (1
4), when the sleeve 13 and the cap 12 are activated, that is, when the heater 15 starts to be heated to about 700 to 1200 ° C., the first grid electrode 20 is thermally expanded to emit the electron. The distance between the material layer 11 and the first grid electrode 20 is reduced, and the cathode current Ik of the electron gun is rapidly increased as shown in FIG.

The amount of increase in the cathode current (Ik) at the time of starting is extremely large, about 150 to 230%, and the change is so great that the screen characteristics of the cathode ray tube become unstable. And
The heat loss due to the sleeve 13 delays the electron emission of the electron emitting material layer.

Further, the time (Tsc) required from the time when the cathode current (Ik) starts to be activated to the time when it is stabilized.
Is about 20 minutes long.

[0007]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a cathode structure capable of accurately maintaining a predetermined distance from the first grid electrode and preventing a transient phenomenon of the cathode current at the time of starting. is there.

[0008]

To achieve the above object, the cathode structure of the present invention comprises a sleeve for containing a heater, an outer holder for supporting the sleeve, and a thermal expansion amount of the sleeve. In order to compensate, an inner holder is provided that extends downward inward from the upper end of the outer holder and supports the lower end of the sleeve.

[0009]

With the above structure, the cathode structure of the present invention can accurately maintain a predetermined distance from the first grid electrode when the heater is activated to eliminate the transient phenomenon of the cathode current.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 3, there is shown a cathode structure according to an embodiment of the present invention, which is provided below a first grid electrode 20 at predetermined intervals. The cathode structure (30) includes a sleeve (33) for housing a heater (36) and a cap (32) attached to an upper portion of the sleeve (33). The sleeve (33) has an end (edg) extended outward from the lower end.
e) Has (33-1). An electron emitting material layer (31) is applied to the upper surface of the cap (32). Above Cap (32)
Is made of nickel (Ni), and the sleeve (33) is made of a nickel alloy containing chromium (ie, Cr20%, Ni80).
%). The radiative material layer (31) is made of carbonate.

The cathode structure (30) has an outer holder (35) for supporting the sleeve (33) and a lower end of the sleeve (33) located at an intermediate portion of the outer holder (35). Thus, the inner holder 34 for supporting the sleeve 33 is provided. The outer holder (35) has a joint portion (35-1) formed in a convex shape on the lower end portion of the outer peripheral surface so that it can be joined to the structure of the electron gun, and an end portion (edge) extending inward from the upper end. (35-2) is provided. The inner holder (34) is a first contact portion (34-1) joined to the inner surface of the upper portion of the outer holder (35) and the end portion (35-2), and the outer peripheral surface of the lower portion of the sleeve (33). And a second contact portion (34-2) joined to the end portion (33-1) and the first contact portion (34-1) and extended obliquely downward to the second contact portion (34-2). And an inclined surface portion (34-3). The inner holder 34 is made of a material having a coefficient of thermal expansion higher than that of the sleeve 33 and the outer holder 35.
The material of the inner holder 34 is a nickel alloy containing iron and chromium (that is, Fe39 or more, chromium 19 to 23 and Ni 25 to 32%). The above external holder
(35) is formed of nickel.

4A-4F illustrate the assembly sequence of the cathode structure shown in FIG. 4A and 4B are partial cross-sectional views of the sleeve (33) and the inner holder (34). The inner holder (34) is located on the outer peripheral surface and the end (33-1) of the lower portion of the sleeve (33). After the two contact parts (34-2) are inserted so as to be in contact with each other, they are welded by a laser and combined as shown in FIG. 4C.

FIG. 4C shows the above inner holder at the bottom.
FIG. 4D is a partial cross-sectional view of the sleeve (33) to which the (34) is attached, and FIG. 4D is a partial cross-sectional view of the cap (32). The cap 32 is attached to the upper portion of the sleeve 33 and welded by a laser to assemble as shown in FIG. 4E. 4B, the total length (L1) of the inner holder 34 is 2.
5 to 3.5 mm, the thickness (D) of the upper inner holder (34) is 0.015 mm, the outer diameter (UR1) of the first contact portion (34-1) is 2.60 to 2.70 mm, and the second The outer diameter (DR1) of the joint part (34-2) is 1.56 to 1.60 mm, and the inclined surface part
The width (W) of (34-3) holds about 0.7 mm. FIG. 4F is a partial cross-sectional view showing an outer holder (35) having an end (35-2) extended inward from the upper end. In FIG. 4F, the upper outer diameter (UR2) of the outer holder (35) is 2.65.
~ 2.90mm, lower outer diameter (DR2) is 2.70 ~ 2.9
The length (L2) is 0 mm, the total length (L2) is 8 mm, and the height (H) of the end portion (35-2) is 0.5 mm. Further, the outer holder (35) is coupled to the sleeve (33) so that the first contact portion (34-1) of the inner holder (34) is in contact with the inner peripheral surface and the end portion (35-2). The inner holder (34) is inserted and laser welded. Then, the electron emitting material layer is formed on the upper surface of the cap (32).
(31) is applied.

The cathode structure 30 manufactured as described above is provided with a cap 32 and a sleeve when the heater 36 is heated.
Even if the (33) and the outer holder (35) are thermally expanded, a predetermined distance from the first grid electrode (20) can be maintained, and the transient phenomenon of the cathode current (Ik) of the electron gun can be improved. .

Next, the state of thermal expansion of the cathode structure 30 when the heater 36 starts heating will be described. The heater (36) is heated by the driving voltage to 700 to 1200 ° C.
When high heat is generated, the cap (32) and sleeve (3
3) and the outer holder (35) are the joints of the outer holder (35)
(35-1) thermally expands toward the first grid electrode (20) to reduce the distance between the first grid electrode (20) and the electron emitting material layer (31). However, the inner holder (34) is connected to the outer holder (35) from the end portion (35-2) of the outer holder (35) (35-).
The first grid electrode (20) and the electron emitting material layer (31) are expanded by thermal expansion toward the 1) side. As a result, the thermal expansion of the inner holder (34) compensates for the thermal expansion of the cap (32), the sleeve (33) and the outer holder (35). Therefore, the material of the inner holder (34) is
2) It has a sufficient amount of thermal expansion to compensate for the amount of thermal expansion by the sleeve 33 and the outer holder 35. Actually, the thermal expansion amount of the sleeve (33), the cap (32) and the outer holder (35) is about 12 μm / m ° C.
The thermal expansion amount of (34) is 14.4 μm / m ° C.

FIG. 5 shows the characteristics of the cathode current of the electron gun equipped with the cathode structure 30 shown in FIG. In FIG. 5, the time (Tsi) required for the cathode current (Ik) to stabilize after the heater (36) starts heating is about 10 to 15 minutes, which is smaller than the conventional stabilization period of 20 minutes. .

The transient current amount of the cathode current (Ik) by the cathode structure of the present invention is 100 to 1 of the normal current amount.
When it is set to about 10%, it is much less than the transient current amount of the cathode current (Ik) of 150 to 230% by the conventional cathode structure.

[0018]

As described above, according to the present invention, the sleeve is supported by the inner holder that extends obliquely downward from the upper end of the outer holder, and the first holder is provided when the heater is activated.
There is an advantage that a predetermined distance from the grid electrode can be accurately maintained. Due to the above advantages, there is an advantage that the transient phenomenon of the cathode current of the electron gun can be eliminated.

[Brief description of drawings]

FIG. 1 is a sectional view of a main part structure of a conventional cathode structure.

2 is a cathode current characteristic diagram of an electron gun including the cathode structure shown in FIG.

FIG. 3 is a cross-sectional view of a main structure of a cathode structure according to an embodiment of the present invention.

4A to 4F are views illustrating a bonding order of the cathode structure shown in FIG.

5 is a cathode current characteristic diagram of an electron gun including the cathode structure shown in FIG.

[Explanation of symbols]

 30: Cathode structure 31: Electron emitting material layer 32: Cap 33: Sleeve 34: Internal holder 35: External holder 36: Heater

Claims (8)

[Claims] 1. A sleeve for incorporating a heater,
An outer holder for supporting the sleeve, and an inner holder for supporting a lower end of the sleeve by obliquely extending inward from an upper end of the outer holder to compensate for a thermal expansion amount of the sleeve. And a cathode structure of an electron gun for a cathode ray tube. 2. The cathode structure of an electron gun for a cathode ray tube according to claim 1, wherein the inner holder has a larger coefficient of thermal expansion than the sleeve and the outer holder. 3. An electron gun for a cathode ray tube according to claim 2, wherein the inner holder is formed of a nickel alloy containing iron and chromium, and the outer holder and the sleeve are formed of a nickel metal material. Cathode structure. 4. The inner holder has a first contact portion joined to an inner peripheral surface of an upper end of the outer holder, a second contact portion joined to an outer peripheral surface of a lower end of the sleeve, and the first contact. 2. The cathode structure for an electron gun for a cathode ray tube according to claim 1, further comprising an inclined surface portion that extends obliquely downward from the portion to the second contact portion. 5. The length and thickness of the inner holder are 2.5.
.About.3.5 mm and 0.015 mm, and the diameters of the first contact portion and the second contact portion are 2.60 to 2.70 mm and 1.5.
The cathode structure for an electron gun for a cathode ray tube according to claim 4, wherein the width is 6 to 1.60 mm and the width of the inclined surface portion is 0.7 mm. 6. The electron gun for a cathode ray tube according to claim 4, wherein the outer holder further comprises a first end portion extending inward from the upper end to support the upper end of the first contact portion. Cathode structure. 7. The outer holder has an upper diameter, a lower diameter and a total length of 2.65 to 2.90 mm and 2.70 to, respectively.
2.90mm and 8mm, the first end is 0.5mm
The cathode structure of an electron gun for a cathode ray tube according to claim 6, having a width of. 8. The cathode of an electron gun for a cathode ray tube according to claim 4, wherein the sleeve further comprises a second end extending outward from the lower end to support the lower end of the second contact portion. Structure.