JPH0246640A - Color cathode-ray tube - Google Patents

Abstract

PURPOSE:To improve the tolerance of the color purity of a cathode-ray tube by making the vertical pitch of electron through holes in the shadow mask larger and larger as the horizontal distance from the central vertical axis of the fluorescent screen and providing the phosphor dots on the screen at positions facing to the electron through holes respectively. CONSTITUTION:The arrangement of electron through holes 11 on the shadow mask is made so as that the vertical pitches PVS of the said holes are larger and larger as the horizontal distances from the central vertical axis of the fluorescent screen 10 and the vertical pitches of the phosphor dots 2 are also larger and larger corresponding to the vertical pitches of the through holes. Thereby even when the shape of the electron beams spot 3 is an ellips longer in vertical direction, the deterioration of the tolerance of the color purity can be compensated most effectively.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a shadow mask type color cathode ray tube.

[Prior Art] A shadow mask type color cathode ray tube, which is currently widely used in TVs, computer terminal display devices, etc., has an electron gun arranged in-line. The deflection yoke takes advantage of the in-line arrangement of the color cathode ray tube's electron gun and appropriately distorts the distribution of its deflection magnetic field, eliminating the need for convergence correction in terms of circuitry.
It is designed to achieve so-called convergence free.

However, the focus characteristics of color cathode ray tubes designed as such are not necessarily at a satisfactory level. This is particularly problematic when used in computer terminal display devices. This is because uniformity of focus characteristics on the display screen is particularly required.

This deterioration of focus characteristics is explained as follows. This is because the horizontal deflection magnetic field that deflects the electron beam in the horizontal direction, which is an essential condition for achieving convergence-free, is distorted into a binction magnetic field, which causes the electron beam to receive a force that converges in the vertical direction. The focus state becomes a hyperacid flux state, resulting in a so-called halo, resulting in deterioration of the focus state.

In order to compensate for this deterioration of focus characteristics and obtain good focus characteristics, for example, SID'86 DIGES
A quadrupole lens like the one seen in the T is being considered. The gist of this quadrupole lens is to make the electron beam emitted from the electron gun into a vertically elongated shape so as to cancel the convergence force exerted in the vertical direction due to the horizontal deflection magnetic field. Therefore, the electron gun is equipped with electrodes that can apply electric fields independently in the horizontal and vertical directions, and when using such a color cathode ray tube,
A time varying voltage synchronized with the deflection is applied to the electrodes.

According to experiments conducted by the present inventor, the electron beam spot diameter at the periphery of the screen was improved by about 30 to 40%.

[Problems to be Solved by the Invention] However, it has been found that the color cathode ray tube using such an electron gun has some disadvantages.

This phenomenon is caused by the deterioration of the purity characteristics when an external magnetic field such as the earth's magnetism is applied to the color cathode ray tube.As a result of investigation, it was found that the shape of the electron beam is an ellipse that becomes larger in the vertical direction when it exits the electron gun. It was found that this was caused by the shape.

The inventor's experimental results for a 20 inch dot type color cathode ray tube with a 90° deflection are as shown in FIG.

This figure shows the shape and size of the electron beam spot (3) projected by the electron beam onto the phosphor screen through the electron beam passage hole of the shadow mask. Three electron beams for blue are provided, and the average value of these is shown here. Furthermore, since the projected shape is symmetrical with respect to the horizontal and vertical axes of the screen, only the portion corresponding to the first quadrant of the fluorescent screen is shown. According to this result, the projected shape of the electron beam spot (3) has a vertical width larger by about 20 μm at the diagonal and horizontal ends, and the proportion is 1
It has become larger by a few percent. On the other hand, the horizontal width does not differ much at any position.

The size, shape and relative position of the phosphor dots are
Since the shadow mask by the electron beam is independent of the projected shape and size of the electron beam passage hole, the above result reduces the privacy margin.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to obtain a color cathode ray tube with good focus characteristics and a large visibility margin.

[Means for Solving the Problems] A color cathode ray tube according to the present invention includes an in-line electron gun having a quadrupole lens, and a vertical pitch of circular electron beam passing holes passing through the center point of a phosphor screen. A point comprising a shadow mask formed at a pitch that gradually increases with increasing distance from the axis in the horizontal direction, and a phosphor screen in which phosphor dots are formed at positions facing each electron beam passage hole of this shadow mask. It is characterized by

[Function] The quadrupole lens has the effect of transforming the transmitted circular electron beam into an oval shape that becomes vertically elongated on the phosphor screen as the distance from the center of deflection in the horizontal direction increases. The vertical pitch of the beam transmission holes is
The vertical pitch increases as the distance from the center of the phosphor screen increases in the horizontal direction, and the phosphor dots on the phosphor screen are arranged in positions that face each electron beam passage hole accordingly, increasing the ubiquity margin. growing.

[Embodiment of the Invention] FIG. 1 shows the first shadow mask of an embodiment of the invention.
It is a diagram showing a quadrant part. In the figure, (1) is a shadow mask, and (11) is a circular electron beam passage hole made in the shadow mask (1). Although not shown, an electron gun equipped with a quadrupole lens is arranged in-line along the horizontal axis.

Next, the operation of this embodiment will be explained using FIG. 2.

Figure 2 shows a fluorescent screen (1
This is an enlarged view of a part of the peripheral area of 0). Here, the solid line circle is the phosphor dot (2), and the broken line ellipse is the electron beam spot (3). .

Considering the purity margin (Δ) in the diagonal direction shown by the dashed-dotted line in Figure 2, it is for the case where PV and PH are usually determined very close to this regular triangular array. - It does not lose its film properties.

Also, pvx 0.31mm, pH=f, H0,3
1 mm (PH: horizontal spacing between phosphor dots of the same color, Pv: vertical spacing, DP
: Diameter of phosphor dot, D! l: diameter of the electron beam spot in the oblique direction). Then, if pH=Ji'''・Pv, a Δ
δ Δ δ(PJ”δ(P・), and the contribution rate of PV and PM to the privacy margin Δ is p′
It can be seen that V is larger. This idea is based on the fact that the arrangement of phosphor dots (2) of the same color is a regular triangle (PH = Ji”pv).
It can be seen that the privacy margin Δ is sensitive to changes in Pv.

From the above, in this embodiment, the shadow mask (1
), the shape of the electron beam passage hole (11) of the fluorescent screen (10
) The vertical pitch P of the electron beam passage holes (11) increases as the distance from the vertical axis passing through the center point 0 of
V11 is gradually increased, and the vertical pitch of the phosphor dots (2) is also increased accordingly. Therefore,
Even if the shape of the electron beam spot (3) is an ellipse long in the vertical direction, the deterioration of the purity margin Δ can be most effectively compensated for.

Incidentally, a periodic correction voltage is applied to the quadrupole lens of the electron gun at the horizontal and vertical periods of raster scanning, but in many cases, an approximately parapolitan waveform is sufficient. Therefore, the extent to which the vertical pitch pvs of the shadow mask in this embodiment is increased as the distance from the vertical axis passing through the center point O in the horizontal direction increases is the square of the distance X in the horizontal direction from the vertical axis passing through the center point O. A function of Pvs = PVO + a X2 (where Pvo: vertical pitch on the vertical axis, α
; constant) is preferably expressed by the following formula.

[Effects of the Invention] In the color cathode ray tube according to the present invention, the vertical arrangement pitch of the electron beam passing holes of the shadow mask is gradually increased as the distance from the vertical axis passing through the center of the phosphor screen in the horizontal direction increases. At the same time, since the phosphor dots on the phosphor screen were formed at positions facing each electron beam passage hole,
Found in color cathode ray tubes of the convergence-free type that have an in-line array electron gun with a pole lens. The phenomenon in which the projected shape of the electron beam passage hole is expanded in the vertical direction and the purity margin deteriorates is effectively compensated for, making it possible to obtain a color cathode ray tube with good focus characteristics and a large purity margin. be.

[Brief explanation of the drawing]

FIG. 1 is a front view showing a portion corresponding to the first quadrant of a shadow mask according to an embodiment of the present invention, FIG. 2 is an enlarged view of a portion thereof, and is a diagram for explaining the purity tolerance, and FIG. 3 is an enlarged view of a portion thereof. 4
FIG. 3 is a diagram showing a projected shape of an electron beam passage hole on a phosphor screen by a polar lens. (1)...shadow mask, (2)...phosphor dots, (3)...projection shape of the electron beam passing hole on the fluorescent screen by the electron beam, (10)...phosphor screen, ( 11)・
...Electron beam passage hole. In each figure, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] (1) An in-line electron gun equipped with a quadrupole lens whose vertical and horizontal focus characteristics can be varied independently of each other, and a vertical pitch of circular electron beam passing holes that passes through the center point of the phosphor screen. A collar comprising a shadow mask formed at a pitch that gradually increases as it moves away from the axis in the horizontal direction, and a phosphor screen on which phosphor dots are formed at positions facing each electron beam passage hole of the shadow mask. cathode ray tube.