JPH0254837A - Color cathode-ray tube - Google Patents

Abstract

PURPOSE:To obtain a clear image by making the shape of an electron beam passing hole an elliptic shape with the Y-axis direction diameter made smaller than the X-axis direction diameter as it is separated in the X-axis direction of rectangular coordinate axes and correcting the projection into a circle. CONSTITUTION:A shadow mask 6 is symmetrical against the horizontal axis X and vertical axis Y. The shape of a hole 7 of beam passing holes is made an elliptic shape extended in the Y-axis direction while the hole diameter B1 in the X-axis direction is made constant and the hole diameter B2 is set to B1-KX<2> (K is a constant). On the other hand, the size, shape and relative positional relationship of phosphor dots on a fluorescent screen 5 are independent from the projected shape and size of the beam passing hole, thus the cross sectional shape of a projected beam 3 and a phosphor dot can be matched by changing the hole diameter of the hole 7 and correcting the projected shape into a circle. The deterioration of purity characteristic is prevented, and a clear color image is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a shadow mask in particular for a color cathode ray tube used in, for example, a vision receiver or a computer terminal display device.

[Prior Art] This type of shadow mask type color cathode ray tube utilizes the fact that the electron gun is arranged in-line to distribute the horizontal deflection magnetic field of the deflection yoke in a binction-like manner, and to distribute the vertical deflection magnetic field in a barrel-like manner. The circuit is designed to achieve so-called convergence free, which does not require convergence correction, by distorting the convergence.

By the way, the focus characteristics of the color cathode ray tube are not necessarily at a satisfactory level, and in particular, when used in a computer terminal display device, deterioration of the focus characteristics at the periphery of the screen is a problem.

-What are the causes of the deterioration of the focus characteristics mentioned above?

One example of this is that the horizontal deflection magnetic field, which is an essential condition for achieving convergence-free, is distorted in a vinctusion shape. In other words, even if a circular electron beam is emitted from the electron gun, the electron beam will be deflected horizontally, and due to the influence of the deflection magnetic field of the water distribution plate, the electron beam will be subjected to a force that will cause it to converge in the vertical axis direction. The focus state in the axial direction becomes a bundled state, resulting in a so-called halo, resulting in deterioration of the focus state.

In order to prevent deterioration of J-2 focus characteristics, conventionally, for example, rsID 86 DIGEST 327.
” 1B, 3: Dynamic Beam Shap
ing or In-1,ine Co1or CRT
sby Quadrupolar 1. cnscs-
It has been proposed to use quadrupole electrodes, as disclosed in J.

As shown in Fig. 4, the quadrupolar electrode is composed of a pair of horizontal electrode pieces (+1. By applying a higher convergence voltage than the vertical electrode piece f21.[2) to the electron beam (3), the electron beam (3) receives an attractive force in the vertical axis Y direction, and after passing through the two quadrupole electrodes (4), the electron beam ( The cross-sectional shape of 3) is an ellipse that is elongated in the vertical direction.

When the above-mentioned quadrupole electrode (4) is used in a color cathode ray tube, a voltage that changes over time in synchronization with the deflection is applied to the quadrupole electrode (4).
11, (2), the beam diameter is circular near the center of the screen where the deflection angle is small, and vertically elongated near the periphery of the screen where the deflection angle is large.

This vertically elongated electron beam (3) is shown in Figure 5.

Under the action of convergence in the vertical axis Y direction and divergence in the horizontal axis X direction by the horizontal deflection magnetic field A of the binction type,
The beam diameter changes from a vertically elongated shape to a circular shape, which corrects the deflection aberration of the electron beam (3) at the periphery of one screen.
Focus characteristics are modified.

In addition, - the horizontal axis X is set in a direction perpendicular to the tube axis and parallel to the in-line arrangement direction of the electron gun; It is assumed that the direction is perpendicular to the axis X.

[Problems to be Solved by the Invention] However, in a color cathode ray tube using a quadrupole electrode as described above, the electron beam (
Even if the deflection aberration (3) is corrected, the spot diameter of the electron beam at the periphery of the screen does not become circular.

This inventor used a 20-inch 90° deflection dot type color cathode ray tube, and the electron beam (3) that passed through the electron lens (15) in FIG. 6 was deflected at the center plane of deflection (16). Through the electron beam passage hole (6a) of the shadow mask (6), the fluorescent screen (5) 17. An examination of the projected shape (17) by the electron beam when irradiated with
When set to m, as shown in FIG. 7, the projected diameter v1 of the projected shape (10) in the vertical axis Y direction of the fluorescent screen (5) in the vertical axis Y direction was about 160 μm.
The projected shape (Ill, +121
The projected diameter V,,v, in the vertical axis Y direction is approximately 180 to 190
It was μm. As a result, it was found that the projected shape at the periphery of the screen was about 20 μm more crowded in the vertical axis Y direction than at the center of the screen, or about 10% more crowded.

As a result, there is a disadvantage in that the purity characteristic deteriorates in the periphery of the screen, similar to when an external magnetic field such as the earth's magnetism is applied to a color cathode ray tube.

This invention was made in view of the above-mentioned conventional problems.
One object of the present invention is to provide a color cathode ray tube that can prevent deterioration of the purity characteristics in the peripheral area of the screen.

[Means for Solving the Problem] After extensive research, the inventor discovered that the reason why the projected shape of the electron beam passage hole by the electron beam is not circular in the peripheral area of the screen is because the vertical axis of the electron beam exits from the electron gun. It was found that this was caused by the elliptical shape that became larger in the direction.

In other words, the projected shape of the electron beam passage hole becomes larger as the deflection angle of the electron beam becomes larger, and the projected shape inevitably becomes larger in the periphery of the screen where the deflection angle is large. Therefore, if the cross-sectional shape of the electron beam is an ellipse that is large in the vertical axis direction when it exits the electron gun, the projected shape will be larger in the vertical axis direction in comparison to when a circular beam exits the electron gun. However, the phosphor dots do not match perfectly circular phosphor dots, resulting in deterioration of the beauty characteristics.

Therefore, in addition to correcting the deflection aberration of the electron beam using a quadrupole electrode, we also changed the shape of the electron beam passage hole of the shadow mask corresponding to the peripheral area of one screen so that the diameter in the vertical axis direction was changed to the diameter in the horizontal and vertical directions. If you set it to an ellipse smaller than
The present invention was completed based on the discovery that the projected shape of the electron beam passage hole at the periphery of the screen becomes circular, thereby preventing deterioration of the utility characteristics.

In the color cathode ray tube according to the present invention, the shape of the electron beam passage hole of the shadow mask is circular on the horizontal axis, and the diameter in the vertical axis direction becomes smaller than the diameter in the horizontal axis direction as the distance from the vertical axis increases in the horizontal axis direction. It is also characterized by having an oval shape that gradually becomes smaller.

[Function] According to the present invention, the shape of the electron beam passage hole of the shadow mask becomes an ellipse in which the diameter in the vertical axis direction becomes gradually smaller than the diameter in the horizontal axis direction as the distance from the vertical axis increases in the horizontal axis direction. Because of this setting, the beam diameter of the electron beam passing through the electron beam passing hole corresponding to the peripheral area of one screen becomes shorter in the vertical axis direction. Therefore, even if the electron beam has a long cross-sectional shape in the vertical axis direction when emitted from the electron gun, by passing through the electron beam passage hole, the projected shape of the electron beam passage hole by the electron beam becomes circular. Therefore, it can be matched with the phosphor dot.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a front view showing a part of the shadow mask according to the present invention. In FIG. 1, the shape of the electron beam passing hole (7) of the shadow mask (6) is set to be circular on the vertical axis Y. , the diameter B in the vertical axis Y direction as the water NV-axis extends from the vertical axis Y in the X-axis direction.

is set to have an elliptical shape that gradually becomes smaller than the diameter B1 in the horizontal axis X direction.

In this embodiment, the projected shape of the fluorescent screen (5) in FIG. 2 at the screen periphery is +211. (22)'s projected diameter in the east vertical axis Y direction V , , V , , and the projected diameter v11 in the vertical axis Y direction of the projected shape (20) at the center of the screen
The electron beam passing hole (7) of the shadow mask (6) in FIG.
The pore diameter is set.

That is, the hole diameter B in the horizontal axis X direction of the electron beam passing hole (7) of the entire screen A/dough mask (6) is set to a uniform value, for example, 125 μm, and the hole diameter in the hair vertical axis Y direction is set to a uniform value of 13. The relationship is set as follows.

13! =13. -KX'' Here, K is 3.9X 10-', [6 represents the distance (mm) in the horizontal axis X direction between the vertical axis Y and the electron beam passage hole (7).

Here, the shadow mask (6) generally has a hole group consisting of three electron beam passing holes corresponding to a dot group consisting of three red, green, and blue phosphor dots arranged in a triangle. Although a large number of electron beam passing holes are formed, in FIG. 1, the hole group is shown as a representative of one electron beam passing hole for the sake of simplicity. Furthermore, since the shadow mask (6) is symmetrical with respect to the horizontal axis X and vertical axis Y of the screen, the first
In the figure, only 1/4 of both sides are shown.

Note that the electron beam (
3) is the same as the conventional one in that the cross-sectional shape is an ellipse that extends in the vertical axis Y direction at the periphery of the screen.

In the L configuration, as shown in FIG. 1, the electron beam passage hole (7) is formed into an ellipse whose diameter B2 in the vertical axis Y direction gradually becomes smaller than the diameter B in the horizontal axis X direction as the distance from the vertical axis Y increases. Since I set it to be a shape, I added a shadow mask (6
), as shown in Figure 3, in the area corresponding to the periphery of the screen.
The diameter of the electron beam passage hole (7) in the vertical axis Y direction becomes 13 to ls, t<n, and thereby the projected diameter in the vertical axis Y direction becomes V to V, i (<V). Therefore, even if the electron beam (3) has a long cross-sectional shape in the vertical axis Y direction when emitted from the gun, the electron beam (3) passes through the electron beam passage hole (7). The projected shape of the electron beam passage hole (7) according to (3) is corrected from vertically long to circular.

Here, the size, shape and relative positional relationship of the phosphor dots (not shown) deposited on the phosphor screen (5) are as follows: - Projected shape and size of the electron beam passing hole (7) Since the diameter of the electron beam passage hole (7) is changed to correct the projection shape (17) to a circular shape as described above, the spot shape of the electron beam (3) can be changed to a phosphor. This makes it possible to match the dots and prevent deterioration of the utility characteristics.

Moreover, in the center of the screen where the deflection angle of the electron beam (3) is relatively small, the shadow mask (6) is
Since the electron beam passage hole (7) is set in a circular shape,
It goes without saying that the projected shape of the electron beam passage hole (7) at the center of the screen is circular, as in the conventional case.

[Effects of the Invention] As described above, according to the present invention, the diameter of the electron beam passage hole gradually becomes smaller in the vertical axis direction as it moves away from the vertical axis in the water f-axis direction. Since the ellipse is made smaller, the projected shape of the electron beam passage hole by the electron beam can be corrected to a circular shape, thereby preventing the deterioration of the visibility characteristics and making it possible to obtain a clear color image.

[Brief explanation of the drawing]

FIG. 1 is a partially schematic front view showing a shadow mask according to an embodiment of the present invention, FIG. 2 is a partially schematic front view showing the projected shape of an electron beam passage hole by an electron beam of the same embodiment, and FIG. The figure is a vertical sectional view for explaining the relationship between the hole diameter of the electron beam passage hole and the diameter of its projected shape, Figure 4 is a perspective view showing the quadrupole electrode, and Figure 5 is a schematic diagram showing the convergence state of the electron beam. FIG. 6 is a horizontal sectional view showing the deflection state of the electron beam, and FIG. 7 is a partially schematic front view showing the projected shape of a conventional electron beam passage hole. (31-...electron beam, (41-...quadrupole electrode, +
51-...Fluorescent screen, +61-...Shadow mask, (71...Electron beam passing hole, X...Water/r
In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] (1) A fluorescent screen having a large number of dot groups made up of three phosphor dots arranged in a triangle, a shadow mask having electron beam passing holes corresponding to the phosphor dots, and a shadow mask having electron beam passage holes corresponding to the phosphor dots; an electron gun disposed in-line to emit an electron beam; a horizontal axis is set in a direction perpendicular to the tube axis and parallel to the in-line arrangement direction of the electron gun, including the center of the fluorescent screen; When the vertical axis is set perpendicular to the horizontal axis, the electron gun makes the cross-sectional shape of the electron beam at the periphery of the screen an ellipse long in the vertical axis direction, thereby reducing the deflection aberration of the electron beam at the periphery of the screen. In a color cathode ray tube equipped with a quadrupole electrode for correction, the shape of the electron beam passing hole of the shadow mask is circular on the vertical axis, and the diameter in the vertical axis direction becomes horizontal as it moves away from the vertical axis in the horizontal axis direction. A color cathode ray tube characterized by an elliptical shape that gradually becomes smaller than its axial diameter.