CN1241228C - Colour cathode-ray tube - Google Patents

Abstract

The present invention discloses a color cathode ray tube combined with a linear arrangement type electron gun assembly and a dot type fluorescent screen, wherein the outer surface of a glass screen is basically flat, and the inner surface of the glass screen has a bending surface; a shadow mask is provided with a plurality of circular holes, and the bending surface of the shadow mask is provided with a bulge protruding toward the glass screen. A picture tube is characterized in that a shadow mask hole has a horizontal hole pitch Ph and a vertical hole pitch Pv; the value of the horizontal hole pitch Ph on the end of the short axis of the shadow mask is basically 5% larger than the value of the hole pitch of the center of the shadow mask, and the Ph/Pv value of the end of the short axis of the shadow mask is larger than the Ph/Pv value of the center of the shadow mask. The configuration of the present invention possibly improves the mechanical strength of a part close to the short axis of the shadow mask.

Description

Color cathode ray tube

Technical field

The present invention is directed to a kind of so specific color cathode ray tube (color picture tube), it has is flat glass screen outer surface basically, and simultaneously, glass screen inner surface and shadow mask have certain curvature.

Background technology

The graduation of the outer glass screen surfaces of color cathode ray tube makes might improve visuality visual on the screen., in the Braun of shadow mask type pipe, require the active surface of shadow mask is partly bent to the curvature of regulation, so that make this shadow mask keep desired mechanical strength.For this reason, a scheme of knowing is in glass screen outer surface graduation, makes the glass screen inner surface facing to shadow mask that certain curvature be arranged.When the thickness of glass at glass screen periphery place shields the thickness of core greater than glass, following problem will occur: at the peripheral part of display screen, effectively brightness or luminous intensity can descend (1), and/or the manufacturability of (2) glass screen can reduce.Therefore under the situation of glass screen outer surface graduation, no longer allow to increase significantly the curvature of glass screen inner surface.In this case, just can not or be difficult at least make shadow mask that enough curvature be arranged, this will cause that this is undesirable about the problem of the mechanical strength decline of shadow mask.

A known arrangement that has earlier of improving small curve (promptly having than larger radius of curvature) shadow mask intensity is to adopt such technology, promptly in the active surface zone of this shadow mask, form small bead (bead) or irregular bending/arch section, as U.S. Patent No. 5,506,466 is described such.The shortcoming that this prior art proposal is such, promptly the small bead of shadow mask (bead) and/or irregular arc/sweep show nocuously and cause visible tangible projection on fluorescence coating or relative phosphor screens, thereby characteristic is degenerated.

U.S. Patent No. 4,136,300 disclose a kind of glass screen structure, and it has flat surfaces externally and internally, and it utilizes and a kind ofly makes shadow mask that the technology of certain curvature be arranged by the pitch-row that changes this shadow mask., this United States Patent (USP) does not comprise about containing the elaboration of linear array formula electron gun and the fluoroscopic display screen structure of point type.In addition, though this document has proposed a kind of method therein, be used for making shadow mask that certain curvature be arranged having line of rabbet joint type shadow mask, simultaneously glass screen inner surface being made under the situation on plane, but it does not comprise the elaboration of the problem that is taken place when putting into practice, without any the details of its layout yet.

In international display seminar (IDW) among the collected works pp.413-416 a kind of technology was disclosed in 1998, be used for changing electron beam spacing (in the professional and technical personnel, being called " S size "), so that make the curvature of the curvature of this shadow mask greater than glass screen inner surface by changing deflection angle.This technology as set forth, must use more than an electromagnetism quadrapole S size is changed with the change of deflection angle.

U.S. Patent No. 5,479,068 discloses a kind of band linear array formula electron gun structure and the fluoroscopic Braun pipe of point type, and it adopts a kind of technology to increase vertical pitch-row value of shadow mask hole, thereby improves color purity allowance, and has improved the electron beam percent of pass simultaneously.Regrettably, U.S. Patent No. 5,479,068 does not mention the structure of arc shadow mask fully, does not mention the method for relevant therewith maintenance intensity yet.

Summary of the invention

The objective of the invention is to improve the mechanical strength of minor axis place or near its minor axis by increasing particularly curvature at the shadow mask of near its minor axis.

In order to reach this purpose, adopt the color cathode ray tube of the principle of the invention to comprise: to have the flat glass screen outer surface and the glass screen of inner surface with the convex surface that protrudes to described outer surface; Linear array formula electron gun structure; The point type phosphor screen that on glass screen inner surface, forms; And shadow mask, described shadow mask is facing to described glass screen inner surface setting and have the convex surface that shields projection to described glass, the effective coverage of described shadow mask have a large amount of circles, be used to the hole that allows electron beam pass, the hole of described a large amount of circles has horizontal direction pitch-row Ph and vertical direction pitch-row Pv, it is characterized in that: the Ph value than place, shadow mask centre is big by 5% at least in the value of the Ph of the end of shadow mask minor axis, stipulates in the shadow mask center $\mathrm{Ph}<\sqrt{3}\mathrm{Pv},$ The value of the Ph/Pv at the place, upper and lower end of shadow mask minor axis is greater than the value of the Ph/Pv of shadow mask center, and the horizontal direction pitch-row Ph at place, the end of shadow mask major axis is greater than the lateral aperture distance of described shadow mask center; Near the equivalent radius of curvature of the short-axis direction of the part place shadow mask display short-axis is less than the equivalent radius of curvature of the short-axis direction of described glass screen inner surface.

Wherein, shield the equivalent radius of curvature of outer surface more than or equal to 10,000 millimeters (mm) at the above glass of short-axis direction.

Preferably, more than the horizontal direction pitch-row value big 10% or 10% of described horizontal direction pitch-row value than shadow mask core of shadow mask minor axis end.

In the described color cathode ray tube, vertically elongated in the shape of the shadow mask hole in display screen centre.

The shape of the shadow mask hole of upper and lower end is vertically elongated near display short-axis.

With regard to entire display screen, vertical direction pitch-row Pv is less than or equal to 0.27mm.

In the display screen centre, the pass of lateral aperture apart from Ph and upright opening apart from Pv is $\mathrm{Ph}\&le;0.93\sqrt{3}$ Pv。Preferably, in the display screen centre, the pass of lateral aperture apart from Ph and upright opening apart from Pv is $\mathrm{Ph}\&le;0.85\sqrt{3}\mathrm{Pv}.$

The horizontal direction pitch-row Ph at contiguous minor axis position is can be according to the distance of leaving the shadow mask center, according to the quadratic surface variation.

Preferably, the Ph numerical value on the circumference that with the shadow mask center is the center of circle is identical.

Wherein, in the equivalent radius of curvature of the above glass of short-axis direction screen outer surface more than or equal to 10,000mm.

For whole shadow mask, it is constant that vertical direction pitch-row Pv keeps.

For whole shadow mask, vertical direction pitch-row Pv is less than or equal to 0.27mm.

In the shadow mask centre, lateral aperture apart from Ph to upright opening apart from the pass of Pv is $\mathrm{Ph}\&le;0.93\sqrt{3}\mathrm{Pv}.$ Preferably, in the shadow mask centre, lateral aperture apart from Ph to upright opening apart from the pass of Pv is $\mathrm{Ph}\&le;0.85\sqrt{3}$ Pv。

At the diagonal angle of shadow mask periphery place, lateral aperture apart from Ph to upright opening apart from the pass of Pv is $\mathrm{Ph}\&cong;\sqrt{3}$ Pv。

In the shadow mask center, the shape of shadow mask hole is vertically elongated.

In the minor axis end parts of shadow mask, the shape of shadow mask hole is vertically elongated.

Description of drawings

Fig. 1 is the schematic diagram that schematically shows color cathode ray tube of the present invention.

Fig. 2 is the sectional view of glass screen.

Fig. 3 has described the layout of shadow mask hole.

Fig. 4 is illustrated in an example of the shadow mask hole layout patterns at shadow mask center and its periphery place.

Fig. 5 represents a layout patterns as example of shadow mask hole, and the isosceles triangle form has been departed from a hole on it on the position.

Fig. 6 represents an example, and vertical pitch-row of its shadow mask hole on those aspects on the concentric circles of shadow mask (shadow) is all identical.

Fig. 7 is the curve chart of gradual change of the lateral aperture distance of expression shadow mask hole.Fig. 8 represents the shadow mask active surface shape as example.

Embodiment

With reference now to Fig. 1,, represented cross section on it according to the 20V type color cathode ray tube (color picture tube) of a most preferred embodiment of the present invention.The outer surface of glass screen 1 is made flat, and inner surface is made curved surface.Neck part 2 is being held a linear array formula electron gun within it, and is connected with the glass screen by a funnel.On phosphor screen 4, form the point type fluorescent material layer.Shadow mask 5 has the hole of a large amount of circles, and is installed on the glass screen 1 with spring 8, firmly is supported framework 6 simultaneously and supports.The active zone of shadow mask has a large amount of holes that allows electron beam pass therethrough.Inner magnetic screen 7 is installed on the supporting frame 6.For the electron beam deflecting provides deflecting coil 10, make magnetic assembly 11 carry out the convergence and the colorimetric purity control/adjustment of electron beam simultaneously.Reinforce or " tension force " with 12 implosions that are used for preventing the glass bulb chance.Making glass screen outer surface graduation and allow glass screen inner surface that certain curvature is arranged simultaneously, is in order to allow shadow mask that certain curvature is arranged equally.Because the existence of the curvature difference between glass screen inner surface and the glass screen outer surface, the interior plate thickness of the glass screen of heart part is 12 millimeters (mm) therein, and numerically shields the thickness of center greater than glass in the sheet thickness of the periphery of glass screen.At glass screen diagonal effective diameter is under the situation of 508mm, and the definite equation Zo of glass screen outer surface is:

Zo(x，y)＝R _x-{(R _x-R _y+(R ² _y-y ²) ^1/2-x ²)} ^1/2

R wherein _x=50,000mm, and R _y=80,000mm.In addition, the definite equation Zi of glass screen inner surface is:

Zi(x，y)＝R _x-{(R _x-R _y+(R ² _y-y ²) ^1/2-x ²)} ^1/2

R wherein _x=1,990mm, and R _y=1,870mm.For the glass screen of such arrangement, the radius of curvature value is different with diverse location.

Therefore, as shown in Figure 2, utilize the equivalent radius of curvature R of slippage (drop-down amount) definition as follows:

R＝(D ²+Z ²)/(2Z)

Wherein D is half length of effective diameter, and Z is the difference in height of screen center and active surface marginal portion.Described equivalent radius of curvature can define with major axis, minor axis and diagonal axis.As discussed above with the R value defined like that, be 62 in the equivalent radius of curvature on the angular direction of glass screen, 500mm, and the equivalent radius of curvature on short-axis direction is 77,000mm.

Usually, if the equivalent radius of curvature of glass screen outer surface is 10,000mm or more than, then formed surperficial human eye looks like flat.

Under the situation of the glass screen of this flat outer surface, the mechanical strength of the shadow mask that is produced, particularly the intensity at some position of contiguous minor axis is problematic, the consideration of therefore this being careful.Increase glass and shield the thickness of the glass screen board at peripheral position,, just might make shadow mask have similar flexure plane so that make glass screen inner surface become flexure plane.In the glass screen of above-mentioned equation definition, be 1 along the equivalent radius of curvature of the inner surface of minor axis, 866mm.If the center is remarkable with the sheet thickness difference of periphery, then to pay following cost: center and peripheral luminance difference thereby increase; And because the influence of the flexure plane of glass screen inner surface, the display screen of formation is flat inadequately.In this case, center and be 6.04mm along the plate thickness difference between the peripheral 150mm surface region, and the ratio of the relative center of this thickness difference sheet thickness is approximately 50.3 percent (%).

To provide the example of corresponding aperture mask curved surface Z below.

Z(x，y)＝A1x ²+A2x ⁴+B1y ²+B2x ⁴+C1x ²y ²+C2x ⁴y ²+C3x ²y ⁴+C4x ⁴y ⁴

At this, the value of each coefficient from A1 to C4 is as shown in table 1 below.

Table 1

Coefficient	Value	Coefficient	Value
				?A1	?0.3177×10 -3	?A2	?0.7237×10 -9
?B1	?0.2176×10 -3	?B2	?0.5224×10 -9
				?C1	?-0.4310×10 -9	?C2	?-0.1219×10 -13
?C3	?0.1951×10 -13	?C4	?-0.3501×10 -18

When the horizontal direction pitch-row of shadow mask keeps steady state value 0.41mm basically on minor axis, just can obtain the represented curved surface of table 1.In this case, the curvature on the shadow mask minor axis can be used coefficient B 1, and B2 represents.And the effective radius of curvature on minor axis is 2,190mm.

The definition of the hole pitch-row value of shadow mask is shown in Fig. 3.Ph is the horizontal direction pitch-row; Pv is the vertical direction pitch-row.According to the low such fact of the intensity of shadow mask at some position of contiguous minor axis, should require to reduce the value of the radius of curvature of near its minor axis, so that increase the intensity at these positions.Aspect the combining of shadow mask and glass screen, on the position of the decentre 145mm of an appointment, " q " is of a size of 10mm.To point out at this, the q-size is the distance between glass screen and the shadow mask, under the situation of linear arranged type electron beam layout, this value can add that the horizontal direction pitch-row of shadow mask hole determines according to the spacing between the deflection center place adjacent electron beam and the distance between deflection center and the phosphor screen.

On the assigned address that leaves center 145mm on the minor axis, when shadow mask horizontal direction pitch-row increases by 5% and when reaching 0.431mm, the q-size also increases about 5% and reach 10.5mm.In this case, the locational slippage of shadow mask minor axis 145mm increases 0.5mm; Like this, the radius of curvature of gained becomes 1,984mm, and this value be gained when the horizontal direction pitch-row numerically keeps constant radius of curvature about 91%.In addition, when horizontal direction pitch-row Ph increases by 10% and when reaching 0.451mm, equivalent radius of curvature becomes 1,813mm, this value be gained when the horizontal direction pitch-row keeps constant radius of curvature about 83%.

Increase reducing of the radius of curvature cause owing to horizontal direction pitch-row Ph, make and might so and improve the mechanical strength of shadow mask.Otherwise, under the situation that the shadow mask radius of curvature needn't change, might make peripheral sheet thickness less.Because the glass panel glass thickness difference between center and the periphery is reduced, thereby might suppress any brightness scrambling that may occur of the display image screen between glass screen center and the periphery or it is reduced to minimum, this brightness scrambling is that the difference owing to the optical transmittance of glass forms originally, by selecting the high glass material of optical absorptivity for use, include but not limited to select for use what is called " tone (tint) " or " low key tone " material, just might improve the contrast of this display image.In addition, the transmitance of the glass plate of the tone glass material that 10.16mm is thick is 57%, and the transmissivity of the glass plate of low key tone glass material is 46%.

Though the horizontal direction pitch-row Ph of shadow mask major axis edge can determine with the method that horizontal direction pitch-row Ph a kind of and the major axis edge has nothing to do, but the horizontal direction pitch-row Ph that the horizontal direction pitch-row Ph at major axis edge numerically preferably is equal to or greater than in the center.

When making fluorophor that compact texture (dense structure) be arranged, a kind of typical known method that obtains and keep needed electron beam screen tolerance or nargin is, the layout of design shadow mask hole makes it be made up of the set of triangle pattern shown in Figure 3 basically.In this case, the relation of horizontal direction pitch-row Ph and vertical direction pitch-row Pv is provided by Ph=√ 3 Pv.In order to keep desired fluorophor compact texture, the upright opening that makes display screen top is apart from also thinking effectively apart from the way that increases with lateral aperture; , this has caused Moire fringe (moire) control difficulty.Owing to having the periodic interference of the electron beam percent of pass of substantial connection the Mohr diagram picture to occur with electron beam scanning line and the vertical pitch-row of shadow mask hole.Therefore, if between center and effective upper and lower position of screen area, the vertical pitch-row of shadow mask hole is numerically different, and then the Moire fringe control procedure just becomes difficult on the entire display screen zone.

Important notion of the present invention is, makes in the specific region, promptly can not surpass the increase of lateral aperture distance in the upper and lower portion of shadow mask, the increase of upright opening distance.More particularly, as shown in Figure 4, the Pv/Ph value at the upper and lower active surface position by making near its minor axis remains on the value less than the center, just can obtain desired Moire fringe controllability.Though depend on and the relation of essential number of scanning lines that certain uncertainty is arranged, we can say that under the situation of PV value less than 0.27mm on the entire display screen, Moire fringe control becomes easier.Provided in the following Table 2 the center of the effective coverage of shadow mask and in the horizontal direction pitch-row Ph of the upper and lower portion of this shadow mask effective coverage and upright opening value as example apart from Pv.

Table 2

The measuring position	Ph	?Pv
			The center	0.41mm	?0.237mm
On the active surface/following position	0.451mm	?0.237mm

Only the lateral aperture that changes shadow mask on the short-axis direction apart from the time, on some position at shadow mask edge, the layout patterns that three holes are a group deforms from the isosceles triangle of expection, as shown in Figure 5, the result has reduced color purity allowance.In order to prevent this point, lateral aperture is also changed like that on the shadow mask long axis direction in the mode similar in appearance to short-axis direction apart from Ph.After doing like this, this program means that for being in the surf zone of the expansion at the position on the circumference of being concerned about from the center to those, the lateral aperture distance is identical numerically.In other words, on circle shown in Figure 6, form identical lateral aperture distance.In this case, just such problem occurs, promptly at the peripheral position at each diagonal angle of shadow mask, the screen picture resolution on the horizontal direction descends, and this is undesirable.

The present invention can utilize following special technique to avoid this problem.Vertically be elongated at layout patterns near the selected part place shadow mask hole at center.More particularly, establish relation $\mathrm{Ph}<\sqrt{3}\mathrm{Pv},$ And make Ph numerically littler in advance simultaneously.Because it is inappreciable relatively to say so in shadow mask center electron beam miscontacting of screen problem, just can allow to make Ph smaller significantly.Lateral aperture is satisfied the relation of upright opening apart from Pv apart from Ph $\mathrm{Ph}<0.9\sqrt{3}\mathrm{Pv}$ Never difficult.With such arrangement, just might prevent the peripheral position at each diagonal angle of glass screen, the obvious decline of the image resolution ratio on the horizontal direction.Actual numerical example is shown in table 3.In this example, the shadow mask center is defined as $\mathrm{Ph}=0.85\sqrt{3}$ Pv, and be defined as at the periphery place at diagonal angle $\mathrm{Ph}=\sqrt{3}\mathrm{Pv}.$ In this example, on short-axis direction, add 10.6% gradual change, and add 17.7% gradual change in diagonal.Term " minor axis upper and lower " used in the following table refers to one or some positions, and they leave effective edges of regions 3mm on the shadow mask minor axis; And " diagonal angle periphery " is appreciated that for referring to some positions like that, they leave effective edges of regions 5mm on the shadow mask diagonal axis.

Table 3

The position	Ph	?Pv
			The center	0.384mm	?0.261mm
The minor axis upper and lower	0.425mm	?0.261mm
			The diagonal angle periphery	0.452mm	?0.261mm

The method that also has another available design hole arrangement, it is designed to become at periphery place, diagonal angle side direction to hole arrangement and elongates or become " fat " pattern, thereby reaches the balance with the longitudinal length grade (thedegree of longitudinal length..) at center.Below table 4 be illustrated in the shadow mask center and be defined as Ph=0.93 √ 3 Pv, and be defined as at diagonal angle periphery place $\mathrm{Ph}=1.03\sqrt{3}$ ) example of Pv.

Table 4

The position	Ph	?Pv
			The center	0.420mm	?0.261mm
The diagonal angle periphery	0.466mm	?0.261mm

At the center, may further make $\mathrm{Ph}<0.85\sqrt{3}\mathrm{Pv}.$ To point out at this, if the shadow mask hole layout departs from the shape of equilateral triangle significantly, then electron beam the screen tolerance reduce, cause feeling as the diameter that need reduce shadow mask hole.In this case, can reduce brightness or luminous intensity.When coming the shape of elongated hole, just might improve the brightness of gained in a kind of mode according to the shape that makes the vertical elongation of hole arrangement distortion becoming.Under the situation of hole arrangement shown in Figure 3, might be vertically elongating at the shadow mask center and in the shape in the hole at some position of the upper and lower portion of minor axis.

There is several different methods to can be used to make lateral aperture apart from the Ph gradual change.Example shown in Fig. 7.In Fig. 7, reference symbol " a " is used for representing a kind of lateral aperture apart from the Ph situation of linear change numerically, and " b " expression lateral aperture is apart from the Ph nonlinear change, for example according to the situation of conic section or index variation.From make the maximized viewpoint of curvature to short-axis direction, can be recommended in the intermediate curve shape between straight line and the conic section.As long as allow to become big in the horizontal direction pitch-row at the position of diagonal angle periphery and those contiguous major axis, any possible curvilinear motion that the value that just can make the horizontal direction pitch-row combines according to biquadratic curve or secondary and conic section.

Fig. 8 represents a kind of shadow mask techniques that has earlier.Design shadow mask effective coverage 51 make its each long limit be barrel-shaped, and each minor face is pincushion like this.This barrel-shaped purposes on each long limit is to make phosphor dot for because the cause of deflecting coil characteristic appears at the gradient of the electron beam of corner edge is identical.Minor face is a pincushion, and this is in order to make fluoroscopic profile rectangular basically.Though shadow mask hole appears at the regulation position of corresponding each vertical cloth exchange line, vertical direction pitch-row Pv also is so in this case, that is, the Pv value on the upper and lower minor face is greater than the value on major axis.But the difference between them is still little of defining Ph _p/ Ph _x=W _p/ W _xDegree, Ph wherein _xBe the horizontal direction pitch-row of the some P1 on the major axis, and Ph _pIt is the horizontal direction pitch-row of the some P2 on the long limit.At this, W _pBe the maximum gauge that nestles up each position horizontal direction on long limit, effective coverage, and W _xIt is major diameter.In 20V type color picture tube as example, W _p=394mm, W _x=391mm.Ph _p/ Ph _xBe 1.0077.When with the pincushion distortion amount (pinamount) among the nearly Fig. 8 of radius of a circle band, the value of gained is 7,077mm.The present invention will extend being parallel to the shadow mask minor axis to alignment on make Ph _p/ Ph _x＞W _p/ W _xIf on the position of near its minor axis, satisfy this relation, then can obtain better result.In addition, the vertical alignment line of each of shadow mask hole of the present invention is such line, and it must have such specific position, and its pincushion distortion is greater than the pincushion distortion at the minor face place of effective coverage 51.In addition, concern Ph _p/ Ph _x＞W _p/ W _xAlso be applicable to W _p＜W _xSituation.

When make the display screen peripheral place or near q size when big, it is more obvious that influence of geomagnetic will become.Particularly in large-sized pipe, this influence of geomagnetic can often cause problem.For fear of this point, can use the coil 13 of the earth magnetism that disappears as shown in Figure 1.This coil can be made of a circle or a few circle lead, and they are to be similar to reinforce belt 12, to be also referred to as the mode of anti-interior ruptured zone around glass screen skirt section.

Claims (18)

1. A color cathode ray tube comprising: a panel having a flat outer panel surface and an inner surface having a convex surface projecting toward said outer surface; Linear array electron gun assembly; a dot phosphor screen formed on the inner surface of the glass screen; and a shadow mask disposed against the inner surface of the glass screen and having a convex surface protruding toward the glass screen, the active area of the shadow mask has a large number of circular holes for passing electron beams , the large number of circular holes have a horizontal hole distance Ph and a vertical hole distance Pv, It is characterized in that the Ph value at the end of the minor axis of the shadow mask is at least 5% greater than the Ph value at the center of the shadow mask, specified at the center of the shadow mask $\mathrm{Ph}<\sqrt{3}\mathrm{PV},$ the value of Ph/Pv at the upper and lower end portions of the minor axis of the shadow mask is greater than the value of Ph/Pv at the center of the shadow mask, and The horizontal hole pitch Ph at the end of the long axis of the shadow mask is equal to or greater than the horizontal hole pitch at the center of the shadow mask; The equivalent radius of curvature of the shadow mask in the direction of the minor axis at the portion near the minor axis of the display screen is smaller than the equivalent radius of curvature of the inner surface of the glass screen in the direction of the minor axis. 2. The color cathode ray tube according to claim 1, characterized in that the equivalent radius of curvature of the outer surface of the glass panel in the minor axis direction is greater than or equal to 10,000 mm. 3. The color cathode ray tube according to claim 1, wherein the horizontal pitch at the end of the minor axis of the shadow mask is 10% or more larger than the horizontal pitch at the central portion of the shadow mask. 4. The color cathode ray tube according to claim 1, wherein the shape of the shadow mask hole at the central portion of the display screen is elongated in the longitudinal direction. 5. A color cathode ray tube according to claim 1, wherein the shapes of the shadow mask holes at upper and lower end portions in the vicinity of the short axis of the display screen are longitudinally elongated. 6. The color cathode ray tube according to claim 1, characterized in that, as far as the entire display screen is concerned, the hole pitch Pv in the vertical direction is less than or equal to 0.27mm. 7. The color cathode ray tube according to claim 1, characterized in that: at the center of the display screen, the relationship between the horizontal pitch Ph and the vertical pitch Pv is: $\mathrm{Ph}\&le;0.93\sqrt{3}\mathrm{PV}.$ 8. The color cathode ray tube according to claim 1, characterized in that: at the center of the display screen, the relationship between the horizontal pitch Ph and the vertical pitch Pv is: $\mathrm{Ph}\&le;0.85\sqrt{3}\mathrm{PV}.$ 9. The color cathode ray tube according to claim 1, characterized in that the horizontal hole pitch Ph near the short axis varies in the form of a quadric surface according to the distance from the center of the shadow mask. 10. The color cathode ray tube according to claim 1, wherein the Ph values are the same on a circle centered on the center of the shadow mask. 11. The color cathode ray tube according to claim 10, wherein the equivalent radius of curvature of the outer surface of the glass panel in the minor axis direction is greater than or equal to 10,000 mm. 12. A color cathode ray tube according to claim 10, characterized in that the vertical hole pitch Pv remains constant for the entire shadow mask. 13. The color cathode ray tube according to claim 10, characterized in that for the entire shadow mask, the vertical hole pitch Pv is less than or equal to 0.27 mm. 14. The color cathode ray tube according to claim 10, characterized in that: at the center of the shadow mask, the relationship between the horizontal hole pitch Ph and the vertical hole pitch Pv is: $\mathrm{Ph}\&le;0.93\sqrt{3}\mathrm{PV}.$ 15. The color cathode ray tube according to claim 10, characterized in that: at the center of the shadow mask, the relationship between the horizontal hole pitch Ph and the vertical hole pitch Pv is: $\mathrm{Ph}\&le;0.85\sqrt{3}\mathrm{PV}.$ 16. The color cathode ray tube according to claim 10, characterized in that: at the diagonal periphery of the shadow mask, the relationship between the horizontal hole pitch Ph and the vertical hole pitch Pv is $\mathrm{Ph}\&cong;\sqrt{3}\mathrm{PV}.$ 17. The color cathode ray tube according to claim 10, wherein the shape of the aperture of the shadow mask is longitudinally elongated at the center of the shadow mask. 18. The color cathode ray tube according to claim 10, wherein the shape of the aperture of the shadow mask is longitudinally elongated at the short-axis end portion of the shadow mask.

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