JPH04267038A - Color cathode ray tube - Google Patents

Abstract

PURPOSE: To allow no increase in the number of components, facilitate assembling, and reduce the diameter of an electron beam further, so as to decrease an electron beam amount which collides with the aperture of a shadow mask and is thereby absorbed. CONSTITUTION: The gap between a frame 12 of a shadow mask 10 and an inner shield 16 is insulated, and a voltage, which is higher than a voltage to a frame 12 side, is applied to an inner shield 16 so that a focusing lens is formed inside the inner shield 16.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to the structure of a cathode ray tube.
More specifically, the present invention relates to a color cathode ray tube in which a focusing lens is formed inside an inner shield to improve the utilization efficiency of electron beams emitted from an electron gun.

0002

2. Description of the Related Art A shadow mask and an inner shield are arranged at a predetermined distance inside the face of a color cathode ray tube, particularly a shadow mask type color cathode ray tube. An aperture is formed through which the Usually, the amount of electron beam passing through the aperture of the shadow mask is 1/3 of the total amount of electron beam emitted from the electron gun.
Or known as less than that. On the other hand, the remaining electron beams that do not pass through the aperture will collide with the shadow mask and heat it.
This will induce thermal expansion of the shadow mask, resulting in a decrease in color purity.

[0003] Therefore, in the shadow mask type color cathode ray tube, it is necessary to prevent the shadow mask from being thermally expanded, or to prevent mislanding of the electron beam that causes thermal expansion of the shadow mask. .

[0004] In order to prevent the shadow mask from being thermally expanded, low thermal expansion invar alloy (invar alloy) is used.
lloy) has been put into practical use to some extent as a shadow mask material.

On the other hand, in order to prevent mislanding of the electron beam that causes thermal expansion of the shadow mask, it is necessary to improve the aperture shape of the shadow mask again, or to increase the diameter of the electron beam passing through the aperture. It has been developed by reducing the size.

Here, the method of improving the aperture shape of the shadow mask has the advantage of being easy to implement, but there are limits to obtaining the intended effect.

[0007] Furthermore, as a method for reducing the diameter of the electron beam, as disclosed in Japanese Patent Application Laid-open No. 57-141849 and Japanese Patent Application Laid-Open No. 58-175236, two shadow masks are placed one on top of the other. Methods have been investigated in which a focusing lens is formed by aligning the apertures through an insulator and creating a potential difference between each of these shadow masks.

[0008]

[Problems to be Solved by the Invention] However, when two shadow masks are arranged in a cathode ray tube, the mutually opposing apertures must be aligned with each other with high precision, making assembly difficult. Since the mask becomes a metal having very soft physical properties by annealing, there is a problem in that it is difficult to maintain a constant distance between shadow masks facing each other.

Therefore, an object of the present invention is to form a converging lens between a shadow mask frame possessed by a normal shadow mask type color cathode ray tube and an inner shield connected to the shadow mask frame. The object of the present invention is to provide an improved color cathode ray tube that can improve the efficiency of electron beam utilization regardless of its configuration.

0010

[Means for Solving the Problems] In order to achieve the above-mentioned objects, the present invention provides a frame for supporting a shadow mask disposed in a space inside the face of a shadow mask type color cathode ray tube, and an inner shield attached to the frame. The frame is electrically insulated by an insulator, and different voltages are applied to the frame and the inner shield to form a focusing lens due to a potential difference inside the inner shield. .

More specifically, a shadow mask is disposed in the inner space of a face glass whose inner surface is coated with phosphor, the shadow mask is supported by a frame facing the inner shield, and the center of the shadow mask is A color cathode ray tube in which an electron gun is arranged,
The contact springs are assembled so as to be electrically insulated from each other via an insulator between the frame and the inner shield, each of which is independently connected, and a pair of anode terminals are arranged symmetrically around the outer circumference of the funnel, The contact springs of the frame are brought into electrical contact with conductive films formed on the inner peripheral surface of the funnel so as to have independent electrical paths, and the voltage supplied to the inner shield is controlled. It is characterized in that the voltage is set higher than the voltage supplied to the frame so that a focusing lens is formed inside the inner shield by a potential difference.

0012

[Operation] According to the above configuration, when the electron beam emitted from the electron gun passes through the central space of the inner shield, the beam diameter increases due to the influence of the focusing lens formed by the potential difference between the inner shield and the frame. This reduction in the diameter of the electron beam prevents the electron beam from partially colliding with the shadow mask and being annihilated.
Most of it passes through the aperture and lands on the phosphor. As a result, the utilization rate of the electron beam is improved and the brightness is increased, and the amount of the electron beam that impinges on the shadow mask is greatly reduced, so that almost no thermal expansion of the shadow mask occurs.

[0013] The insulator may be made of ceramic or glass, in which the large diameter part that is held in the through hole of the frame and the small diameter part that is held in the through hole of the inner shield are formed coaxially from the head. This facilitates assembly while maintaining the insulation between the frame and the inner shield.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained in detail below with reference to embodiments shown in the drawings.

As shown in FIG. 1, the funnel 2 is joined to a face glass 6 by a frit 4 to form a conventional bulb 7.

A phosphor 8 is coated on the inner surface of the face glass 6, and an ordinary shadow mask 10 is placed by a frame 12 at a predetermined distance from the phosphor 8.

The frame 12 is suspended by stud fins 14 attached to the face glass 6.

A normal inner shield 16 is attached to the frame 12 facing the shadow mask 10 to shield the inside of the funnel 2.

In the present invention, the inner shield 16 is connected to the frame 12 via an insulator 18 in an insulated manner. Therefore, the frame 12 and the inner shield 16
They are not integrated, at least electrically.

Conductive films F1 and F2 forming different paths are formed on the inner surface of the funnel 2. As shown in FIG.

One conductive film F1 is in electrical contact with a contact spring 20 extending from the frame 12;
Further, the other conductive film F2 is electrically contacted with a contact spring 22 extending from the inner shield 16.

Furthermore, in order to provide a potential difference between the frame 12 and the inner shield 16, one of the conductive films F
1 is a predetermined voltage E through one anode terminal A1.
b1, and a predetermined voltage Eb2 is applied to the other conductive film F2 through the other anode terminal A2.
is supplied.

The levels of the voltages Eb1 and Eb2 are set to have a relationship of Eb1 > Eb2, so that a potential difference is formed. This potential difference is for forming a focusing lens inside the inner shield 16.

Note that the normal electron gun 24 is placed inside the neck 26.

Electron beam 28 emitted from electron gun 24
When the beam passes through the central space of the inner shield 16, the beam diameter is further reduced under the influence of the focusing lens formed by the potential difference between the inner shield 16 and the frame 12.

In this embodiment, due to the aforementioned reduction in the diameter of the electron beam, most of the electron beam passes through the aperture and lands on the phosphor 8 without being partially annihilated by collision with the shadow mask 10.

As a result, the utilization rate of the electron beam is improved and the brightness is increased, and the amount of the electron beam colliding with the shadow mask 10 is greatly reduced, so that almost no thermal expansion of the shadow mask occurs. It becomes like this.

In this embodiment, the insulator 18 interposed between the frame 12 and the inner shield 16 is preferably made of a material that can withstand high heat, such as ceramic or glass.

FIG. 2 is an enlarged cross-sectional view of a portion of FIG. 1 showing a preferred structure of the insulator 18.

The insulator 18 has a large diameter portion 18a inserted into the through hole 12a of the frame 12 and a small diameter portion 18b inserted into the inner shield 16 extending coaxially from the head 18c.

If the large diameter portion 18a of the insulator 18 configured as described above is passed through the through hole 12a of the frame 12 from the shadow mask 10, a small diameter portion 18b formed coaxially with the large diameter portion 18a will be formed. is exposed outside the frame 12.

When the exposed small diameter portion 18b is again aligned with the through hole 16a of the inner shield 16 and penetrated therethrough, the inner shield 16 is supported by the large diameter portion 18a.

Finally, by coating the frit 30 around the small diameter portion 18b and fixing the inner shield 16 and the small diameter portion 18b, the assembly in a non-conducting state between the frame 12 and the inner shield 16 is completed. Ru.

It should be noted that the present invention is not limited to the embodiments described above, and various modifications can be made.

[0035]

Effects of the Invention The present invention described above provides a component for electrically insulating between a frame for fixing a shadow mask, which is included in a normal shadow mask type color cathode ray tube, and an inner shield assembled to the frame. , adding only an anode terminal to supply mutually different voltages to the frame and inner shield, and reducing the diameter of the electron beam so that it can pass through the aperture of the shadow mask with little loss. It has the effect of causing

Furthermore, unlike the conventional method, the number of parts does not increase significantly, and the parts can be easily assembled together, so that an advantage of excellent productivity can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional side view schematically showing an embodiment of a color cathode ray tube of the present invention.

[Fig. 2] A partially enlarged sectional view showing the configuration of the main parts in Fig. 1.

[Explanation of symbols]

2 Funnel 6. Face glass 8. Phosphor 10 Shadow mask 12 Frame 12a Through hole 16 Inner shield 18 Insulator 18a Large diameter part 18b Small diameter part 18c head 20 Contact spring F1, F2 Conductive film A1, A2 Anode terminal Eb1, Eb2 voltage

Claims (5)

[Claims] 1. A shadow mask (10) disposed in the space inside the face of a shadow mask type color cathode ray tube.
a frame (12) that supports this frame (12);
An insulator (18) is used to electrically insulate between the inner shield (16) attached to the frame (1
A color cathode ray tube characterized in that a focusing lens is formed inside the inner shield (16) by applying different voltages to the inner shield (16) and the inner shield (16). 2. The voltage (Eb2) supplied to the inner shield (16) is set to be larger than the voltage (Eb1) supplied to the frame (12), so that the voltage (Eb2) supplied to the inner shield (16) is focused by a potential difference inside the inner shield (16). Claim 1 characterized in that it is configured to form a lens.
Color cathode ray tube as described. 3. The insulator (18) has a large diameter portion (18a) sandwiched between the through hole (12a) of the frame (12).
) and a through hole (16a) of the inner shield (16).
The small diameter part (18b) sandwiched between the head (18c)
Claim 1 characterized in that it is formed coaxially from
Color cathode ray tube as described. 4. A color cathode ray tube according to claim 3, wherein the insulator (18) is made of ceramic. 5. A color cathode ray tube according to claim 3, wherein said insulator (18) is made of glass.