JPH0195444A - Cathode-ray tube - Google Patents

Abstract

PURPOSE:To make convergence condition of an electron beam optionally variable by arranging a capacitance element to be connected within a tube on at least one of other electrodes not supplied with a dynamic potential. CONSTITUTION:Incorporating a capacitance element 300 in a tube, one end of said element 300 is connected to any electrode other than electrodes 30, 50 to which a dynamic potential VD is applied, with the other end connected to a ground potential or a DC power source. Namely, if said other end of the capacitance element 300 is connected to the ground potential or the DC power source, overlapping AC component is bypassed through the capacitance element 300 to the ground potential. As a result, little AC components of the overlapping dynamic potential remain in the electrode connected to the capacitance element 300, and an electron lens works normally. This makes it possible to vary the convergence condition of the electron lens as required and to obtain a cathode- ray tube having a high resolution over the entire area of the screen.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) The present invention supplies a dynamic potential corresponding to the amount of deflection of an electron beam to an electrode of an electron gun, thereby controlling the focused state of the electron beam. The present invention relates to a cathode ray tube equipped with a means for changing the direction of the cathode ray tube.

(Prior art) Generally, as shown in Fig. 5, a cathode ray tube is provided with a screen surface (■) on the inside front of the envelope (■), a deflection yoke (■) on the cone part, and a deflection yoke (■) on the inside of the neck (■). An electron gun (4) that emits an electron beam is provided, and the electron beam is deflected and scanned by a deflection yoke to display a desired image.

The electron gun (a) consists of a cathode that generates an electron beam, an electrode that is sequentially arranged in the direction of the screen surface with respect to the cathode, and to which a low voltage is applied to control the generation of the electron beam from the cathode, and a An electron lens is formed with a plurality of electrodes, including electrodes that focus and accelerate the emitted electron beam.

Generally, a high anode voltage is applied to the accelerating electrode from an anode terminal 0 provided on the side surface of the envelope via an internal conductive film 0 and the like. Especially for color picture tubes, 20~
A high voltage of about 30 kV is applied.

Also in this case, the focusing electrode is divided, and one side has 5 to 8 k
On the other hand, a DC potential of about V was applied, and the DC potential was synchronized with the deflection scanning of the electron beam. A dynamic potential obtained by superimposing an AC potential of several hundred to several thousand volts is supplied through the stem bottle located in the stem section that seals the neck end, and changes the focusing state of the electron lens to create a screen. For example, a method for improving the resolution over the entire surface is disclosed in Japanese Patent Application Laid-Open No. 1986-
It is shown in Japanese Patent No. 39346.

In this way, when a dynamic potential containing an alternating current component synchronized with the electron beam is supplied to the focusing electrodes, between each electrode,
Because of the stray capacitance, a phenomenon occurs in which an alternating current component synchronized with the electron beam is superimposed on a desired potential due to electrostatic induction in electrodes other than the focusing electrode that supplies the dynamic potential. An alternating current component synchronized with the electron beam is superimposed on one of the focusing electrodes that forms the electron lens, facing the focusing electrode that supplies the dynamic potential, and the relative potential difference between the other focusing electrodes changes over time. Since the dynamic potential does not consist only of alternating current components, it becomes difficult to increase the resolution over the entire surface of the screen in this dynamic focused state of the electron beam.

To widen the range of intensity variation of the electron lens, increasing the potential of the AC component of the dynamic potential can be solved to some extent, but this is not an effective method because the AC component superimposed on other electrodes also increases. The withstand voltage characteristics of the stem pin, which electrically connects the inside of the tube and the outside of the tube to supply dynamic potential from outside the tube, poses a practical problem.

Furthermore, Japanese Patent Laid-Open No. 58-161233 discloses a method in which a voltage dividing resistor is placed inside the tube, and a capacitive element for time constant correction is built in to obtain a divided voltage that follows fluctuations in the high voltage supplied to the resistor. A cathode ray tube is shown.

The high voltage in this case corresponds to the screen voltage.

However, the purpose of this technology is to suppress fluctuations in convergence, and it merely provides a resistance-divided potential to the convergence electrode and incorporates a balancing capacitive element to balance the ripple of this potential. When a dynamic potential is applied to the focus electrode, it is not possible to suppress the dynamic voltage induced in other electrodes due to stray capacitance or the like.

Furthermore, in this technique, the resistor must be connected to a high voltage, and the time constant correction capacitive element must also be directly connected to a high potential in a DC manner.

(Problems to be Solved by the Invention) As described above, in the conventional technology, in order to dynamically vary the focusing state of an electron beam, the dynamic potential applied to the focusing electrode changes from the potential of other electrodes. Due to the superposition, it becomes difficult to dynamically vary the focusing state of the electron beam as desired.

[Structure of the invention]

(Means for Solving the Problems) The present invention incorporates a capacitive element in a tube, connects one end of this capacitive element to an electrode other than the electrode to which a dynamic potential is applied,
By connecting the other end to ground potential or direct current, or by applying a dynamic potential of opposite polarity synchronized with this dynamic potential to the other end of the capacitive element, a cathode ray tube with high resolution over the entire screen is provided. can do.

(Function) In the present invention, when the other end of the capacitive element is grounded or connected to a DC power source, the superimposed AC component is bypassed to the ground potential through the capacitive element. Therefore, there is almost no alternating current component of the dynamic potential superimposed on the electrode to which the capacitive element is connected, and the electron lens operates normally.

Furthermore, even if a dynamic potential of opposite polarity synchronized with the dynamic potential is applied to the other end of the capacitive element to cancel the actively induced alternating current component, the electron lens will operate normally.

As described above, by implementing the present invention, it is possible to eliminate the induced alternating current component, apply a dynamic potential, and change the focusing state of the electron lens as desired, thereby achieving high resolution over the entire screen. This makes it possible to provide a cathode ray tube with

(Example) Next, one embodiment of the present invention will be described in detail using the drawings.

FIG. 1 is a schematic sectional view of an electron gun section of a cathode ray tube showing an embodiment of the present invention.

In FIGS. 1(a) and (b), a heater (not shown)
- three cathodes (KR) arranged in a straight line;

(KG), (KB), first electrode (10), second electrode (
20), third electrode (30), fourth electrode (40), fifth electrode
An electrode (SO), a plurality of intermediate molds m (7o), (80) and a sixth electrode (6o), and a convergence cup (90) are arranged in this order, and are supported and supported by an insulating support rod (200).
Fixed.

A resistor (100) is installed near the electron gun, and the negative end (
11G) is connected to the sixth electrode (60), and the other end (120
) is grounded, and intermediate points (130) and (140) are connected to predetermined intermediate electrodes (70) and (80), respectively.

The first electrode (10) is a thin plate-shaped electrode, and three electron beam passage holes of small diameter are bored therein. Second electrode (20)
The electrode is also a thin plate-shaped electrode, and three small-diameter electron beam passage holes are bored therein.

The third electrode (30) is two cup-shaped electrodes (31).

The open ends of (32) are butted against each other, and on the second electrode side,
Three electron beam passing holes having a diameter slightly larger than the electron beam passing hole formed in the second electrode (20) are formed.

Three large-diameter openings are bored on the fourth electrode side. The fourth electrode (40) is two cup-shaped electrodes (41).

The open ends of (42) are butted against each other, and each
Three large diameter holes are drilled.

The fifth electrode (50) is a plurality of cup-shaped electrodes (51).

Consisting of (52), (53), and (54),
Each has three large diameter apertures.

The intermediate electrodes (70) and (80) have three large-diameter holes formed in a thick plate electrode. The sixth electrode (60) is 2
Consisting of cup-shaped electrodes (61) and (62),
Each has three apertures drilled therein. A convergence cup (90) is fixed to the bottom of the cup-shaped electrode (62). Note that all rjN holes are circular holes from the first electrode to the sixth electrode.

A DC voltage of, for example, about 150 V and a modulation signal corresponding to one image are applied to the cathodes (KR), (KG), and (KB) D.

The first electrode (10) is grounded, and the second electrode (20) has a
0v is applied. Cathode (KR), (KG), (K
B), the first electrode (10), and the second electrode (20) form a bipolar part, emit an electron beam, and form a crossover. The third electrode (30) and the fifth electrode (
50) is connected inside the tube, and approximately 7 KV is applied to provide a focusing voltage.

The fourth electrode (40) is connected to the second electrode (20) inside the tube, and the tail, bottom, and sixth electrodes (60) are connected to 25KV~
A final acceleration voltage of about 30 KV is applied.

The second electrode (20) and the third electrode (30) form a prefocus lens to prefocus the electron beam emitted from the bipolar portion. The third electrode (30), the fourth electrode (40), and the fifth electrode (50) form an auxiliary lens to further pre-focus the electron beam 4.

A voltage of approximately 40% of the final acceleration voltage is supplied to the intermediate electrode (70) by the resistor (100), and a voltage of approximately 40% of the final acceleration voltage is supplied to the intermediate electrode (80).
) are supplied with a voltage of about 65〆 of the final acceleration voltage, the fifth electrode (50), the intermediate electrode (70), (80), and the sixth electrode
A main lens is formed with the electrode (60), and the electron beam is
finally converge on the screen. Since the main lens area of such a main lens is expanded by the intermediate electrodes (70) and (8o), it is called an extended electric field lens and can be made into a long focal length lens.

Here, an insulated support rod (
A capacitive element (300) is arranged on one side of the insulating support rod (200), and a resistor (100) is arranged on one side of the insulating support rod (200). (not shown), one end of the capacitive element (300) is connected to the intermediate electrode (70), and the other end is connected to ground potential. Figure 2 shows this using an AC equivalent circuit. (C2) and (C3) are the sixth electrode (60) and the intermediate electrode (80), the intermediate electrodes (70) and (80), and the intermediate electrode (70) and the fifth electrode (50), respectively. In this example, both values are about 1 pF.R□eR29R2 is the resistance value of the built-in resistor in the tube, and R1=787MΩ, R,=
563MΩ, R, = 90ONΩ.

Here, the center frequency of the dynamic voltage is approximately 15KHz.
Then, considering AC impedance, c) C3 - d
If L-=0.5PF, the AC component at the connection point (130) with the intermediate electrode (70) is grounded through the capacitive element (300), so
The AC component at the connection point (130) is reduced to approximately C,/C;
C3 (C) Most of the alternating current component is at the intermediate electrode (70
), and at the same time the intermediate electrode (80
) is cut.

In this embodiment, the capacitance of the capacitive element is approximately 30PF. Therefore, when no capacitive element is connected, a peak-to-peak IKV dynamic potential of about 273 670 V is superimposed on the intermediate electrode (70), but when a capacitive element is connected, the peak-to-peak IKV dynamic potential is reduced to about 20 V. We were able to improve this to a level that poses no practical problems.

Here, the equipotential distribution formed in the main lens section of the electron gun section of the cathode ray tube of this embodiment will be described in detail with reference to FIG. FIG. 6(a) is a horizontal sectional view of the electron gun section, and FIG. 6(b) is a horizontal sectional view of the electron gun section.
) is a vertical cross-sectional view. (SO) is the fifth electrode,
In (70) and (80), the intermediate electrode (60) is the sixth electrode, and the resistor is not shown.

First, in the horizontal cross-sectional view shown in FIG. 6(a), the focused electric field penetrating into the fifth electrode (50)
) 1 The equipotential lines corresponding to the holes (541) and (543) on both sides are common. On the other hand, in the vertical direction shown in FIG. 6(b), the curvature of one equipotential line is smaller than in the horizontal direction due to the influence of the side wall (55) of the electrode. In other words, the focusing effect in the vertical direction is relatively stronger than in the horizontal direction.

Similarly, the diverging electric field penetrating into the sixth electrode (60) is relatively stronger in the vertical direction than in the horizontal direction.

Based on the above concept, the focusing action of the main lens is such that the focusing electric field and the single diverging electric field are separate and independent, and the focusing electric field is relatively strong in the vertical direction, and the diverging electric field is relatively strong in the vertical direction. It is a lens.

When the electron beam is located at the center of one screen without being deflected, a predetermined focusing voltage is applied to the fifth electrode (50), and the asymmetric focusing electric field and the asymmetric divergent electric field are in an equilibrium state. As a result, the electron beam is focused into a substantially perfect circle.

Next, when the electron beam is deflected to the periphery of the screen, the focusing voltage is increased above a predetermined value. At this time, since the focusing voltage approaches the value applied to the intermediate electrode (70), the focusing electric field becomes weak. - On the other hand, since the divergent electric field does not change, the single divergent electric field becomes relatively strong for the main lens as a whole. In other words, it is under-focused in the vertical direction and is receiving the deflection magnetic field. It is possible to eliminate the overfocus state.

Next, with reference to FIG. 7, a dynamic potential synchronized with the deflection of the electron beam and the amount of deflection applied to the focusing electrode will be explained. FIG. 7(a) is a diagram showing the relationship between deflection current and time for deflecting an electron beam. FIG. 7(b) shows the relationship between the dynamic voltage superimposed on the focusing voltage in synchronization with the deflection and time.

When the deflection current is zero, that is, when the electron beam is at the center of the screen, the dynamic voltage is also zero.

As the electron beam is deflected toward the periphery of the screen, the dynamic voltage also increases parabolically. As a result, the focusing voltage rises in synchronization with the deflection toward the periphery of one screen, so as mentioned above, the desired dynamic operation is performed in which only the vertical direction of the electron beam is underfocused, thereby increasing the resolution. However, the intermediate electrodes (70) and (80) facing the fifth electrode (50) in FIG. 1(b) to which the dynamic voltage is applied,
The stray capacitance existing between each electrode induces an alternating current component of the dynamic voltage, which adversely affects the electron lens. However, in the present invention, the induced alternating current component passes through the capacitive element (300) and returns to the ground potential. Bypassed. Therefore, the AC component of the dynamic potential superimposed on the electrode connected to the capacitive element is only 4, and the electron lens always operates normally.

If the above-mentioned alternating current component cannot be controlled as in a conventional cathode ray tube, the potential difference between the electrodes that form the electron lens will differ from the potential difference during normal operation, and as a result, the electron lens will not function as a normal lens. There is a serious problem in that the resolution cannot be improved over the entire area of the cathode ray tube screen.

Next, the capacitive element will be explained.

Figure 4 shows the internal capacitive element (30 mm) used in this example.
(b), which is a schematic diagram of 0), is a cross section of (a).

The capacitive element (300) has electrode plates (302) bonded to both sides of a ceramic plate (301), and an insulator (30
3). This capacitive element (300)
The dimensions are approximately 50 am in length, approximately 8 mm in width, and approximately 1 mm in thickness. Since the ceramic plate used has a dielectric constant of about 9, the capacitance is about 30 pF.

Next, a second embodiment of the present invention will be described with reference to FIG.

In FIG. 3, the other end of the capacitive element (300) is not grounded, and the opposite polarity potential (-V
o) is applied. The rest is the same as the first embodiment. By doing so, the potential superimposed on the intermediate electrode (70) can be actively canceled, and the resolution can be improved over the entire screen.

In the embodiments of the present invention, the basic structure of the electron gun is explained using a composite electron gun called a Fordora potential type, but it can also be applied to other composite electron guns, such as a pi potential type or a unit type electron gun. It can also be applied to potential type electron guns.

Furthermore, although the case where there are two intermediate electrodes has been described, the present invention can also be applied to cases where there is one intermediate electrode or three or more intermediate electrodes.Also, in this embodiment, a structure in which electron beams are arranged in-line has been described. , even if it is a delta type array.
The present invention can be applied.

〔Effect of the invention〕

As described above, one aspect of the present invention is to maintain the focused state of the electron beam as desired without superimposing the induced potential on other electrodes even if a dynamic potential corresponding to the amount of deflection of the electron beam is supplied to the focusing electrode. Can be variable.

It becomes possible to significantly improve the resolution across the entire screen.

[Brief explanation of the drawing]

FIGS. 1(a) and (b) are schematic cross-sectional views of an electron gun section showing a first embodiment of the present invention, FIG. 2 is an equivalent circuit diagram of FIG. 1(b), and FIG. 3 is a diagram of the present invention. 4(a) is a schematic diagram of a capacitive element, FIG. 4(b) is a sectional diagram of FIG. 4(a), and FIG. A schematic cross-sectional view of a conventional cathode ray tube, Figures 6(a) and 6(b) are horizontal and vertical equipotential distribution diagrams of the main lens portion, respectively.
Figures (a) and (b) are characteristic diagrams of deflection current and dynamic voltage, respectively. Agent Patent Attorney Nori Ken Yudo Takehana Kikuo (a) (b) Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

Scope of Claims: (1) At least a screen section, a deflection section, and an electron gun section are provided, and the electron beam emitted from the electron gun section toward the screen section is deflected and scanned by the deflection section to the screen section as desired. A cathode ray tube for displaying an image, the electron gun section comprising an electron beam generating section and at least first, second and third electrodes for controlling, accelerating and focusing the electron beam, each of which an electron lens for supplying a required potential to the electrodes, supplying a dynamic potential corresponding to the deflection scanning to at least one of the electrodes, and dynamically varying the focusing state of the electron beam; A cathode ray tube, characterized in that a capacitive element is connected within the tube to at least one of the other electrodes to which a dynamic potential is not supplied. (2) the capacitive element has at least two terminals,
A patent characterized in that one end is connected to at least one of the other electrodes to which the dynamic potential is not supplied, and at least one of the other ends is connected to a static potential, including ground potential. A cathode ray tube according to claim 1. (3) The capacitive element has at least two terminals, one end of which is connected to at least one of the other electrodes to which the dynamic potential is not supplied.
2. The cathode ray tube according to claim 1, wherein at least one of the other ends is connected to a dynamic potential different from the dynamic potential. (4) A predetermined potential is supplied to the electrode to which the capacitive element is connected by using an anode potential applied to the screen portion by a resistor inside the tube as a resistance dividing potential. The cathode ray tube according to item 1. (5) The capacitive element is arranged on the back side of an insulating support rod that supports a structure in which ceramic is used as a dielectric and electrodes are provided on both sides of the ceramic. The cathode ray tube described.