JPS5947420B2 - cathode ray tube - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cathode ray tube having a flat face plate and a built-in perforated shadow mask, in particular to a phenomenon in which the shadow mask bulges into a spherical shape during warm-up of the tube.
The present invention relates to a configuration of a shadow mask capable of reducing misalignment (hereinafter referred to as positional deviation) between a phosphor element of a tube screen and an electron beam caused by doming (hereinafter referred to as doming).

In a shadow mask type cathode ray tube for producing color images, a color selection shadow mask with a large number of holes is used to produce color images.
Multiple focused electron beams are projected onto a mosaic of fluorescent screens.

The beams are directed through the mask so that each beam impinges upon or excites only one type of color-forming phosphor on the screen.

Generally, the shadow mask is mounted on a rigid frame that is supported within the picture tube envelope.

During operation of a color cathode ray tube, the shadow mask receives electron bombardment and generates heat.

The periphery of the shadow mask is attached to a somewhat heavy frame, and this frame acts as a heat sink, creating a certain temperature difference between the center and peripheral parts of the mask.

This temperature difference causes the periphery, center, and frame of the mask to expand at different rates.

Due to this difference in expansion degree, some parts of the mask
Doming occurs towards the screen.

This doming is due to the fact that in the central part of the screen, changes in the spacing between the mask and the screen do not affect the linear progression of the beam to the phosphor element. It has little effect on the positional overlap between the electron beam and the phosphor element.

Further, since the peripheral portion of the mask is fixed to the frame, doming does not occur in this portion.

Therefore, the maximum positional deviation due to doming appears near the center between the center of the mask and the periphery of the mask.

Here, "misregister J" is
It is defined as the amount by which an electron beam is eccentric from its corresponding phosphor element.

Because of the above-mentioned doming, the electron beam passing through the mask is misaligned with the phosphor elements of the screen.

This misalignment due to doming reaches its peak within 3 to 5 minutes after the tube starts operating, but it also reaches its peak within 10 to 1 minute.
The 5 minute period affects tube performance, albeit attenuated.

Once the tube reaches a stable temperature condition, the electron beam misalignment caused by the expansion of the mask is compensated for by the temperature sensitive frame support means which moves the mask and frame assembly as a whole towards the screen.

Such temperature-compensated support means are suitable for morel (IVitrr
U.S. Pat. No. 3,803,436 to John E.

Another problem that has some bearing on doming is partial warping of the mask, like a blister.

This "blister" is caused by localized heating of a portion of the mask during operation of the tube by a video slam, such as a persistent white spot in a TV picture.

The cathode ray tube of this invention has a flat face plate,
Additionally, a perforated shadow mask is utilized to align the electron beam onto the phosphor elements of the screen.

The cathode ray tube of the present invention is configured such that the polarity of the rate of change in the distance between the mask and the screen changes at least once between the center of the mask and the periphery of the mask; The change in the distance from the screen is configured to include a change proportional to the change in the distance between adjacent holes of the mask.

With this invention, mask doming and "blister"
phenomena are reduced, and the misalignment of the electron beam due to these problems is also reduced.

FIG. 1 shows a conventional color picture tube with a rectangular picture surface, including a rectangular panel or cap 22 and a tubular neck part 24 connected thereto via a funnel part 26.
and an evacuated glass envelope 20 consisting of.

Panel 22 has a faceplate 28 and a surrounding flange or sidewall 30 by which it is sealed to funnel portion 26 .

A screen 32 made of mosaic-shaped phosphors of three colors is provided on the inner surface of the face plate 28.

The screen 32 is a line screen, ie, an array of parallel phosphor lines or stripes of phosphor lines substantially parallel to the vertical axis of the screen of the tube.

The space between adjacent phosphor lines is filled with light-absorbing material.

A color selection electrode plate, that is, a shadow mask 34 having a large number of holes formed therein at a predetermined distance from the screen 32.
is removably attached.

An in-line electron gun 36 is provided within the neck 24.

The electron gun 36 has three
generating book electron beams 38B, 38R and 38G;
These electron beams are directed through a mask 34 to a screen 32 along a coplanar focused path.

When a suitable voltage is applied to the yoke 40, these three beams 38B, 38R and 38G, under the influence of vertical and horizontal magnetic fields, span the entire surface of the screen 32.
Perform horizontal and vertical scanning to create a rectangular mask.

In FIG. 1, for the sake of simplicity, the actual curve of the path of the deflected beam in the deflection region is not shown.

At 9, these beams are shown as being bent abruptly at the plane of deflection P--P.

Here, this invention will be explained with reference to a line screen type cathode ray tube with an inline type electron gun, but generally speaking, the idea of this invention is to use a dot phosphor screen type cathode ray tube with an electron gun in a delta arrangement It should be understood that cathode ray tubes or other types of cathode ray tubes are also applicable.

In order to fully understand this invention, it is desirable to know what "misalignment" of an electron beam is.

2, 3, and 4, electron beam 38G is shown impinging on a portion of screen 32. FIG.

Each phosphor line (42R142G and 42B) is separated from its neighbor, and the gap is filled with light absorbing material 44.

The width of beam 38G is slightly wider than the width of its corresponding phosphor line 42G.

Such a configuration is commonly referred to as a negative tolerance matrix and is the preferred screen configuration for practicing this invention.

However, the invention is equally applicable to IJ tubes (in which the width of the phosphor lines separated by light-absorbing material is wider than the corresponding beam width) and matrix-less tubes. It is.

In FIG. 2, the electron beam 38G has a corresponding phosphor line 42.
The center is exactly aligned with G.

This is the desired beam position for accurate color output.

As the tube begins to warm up, doming of the shadow mask appears, causing the central portion of the mask to move toward the screen, causing the misalignment of beam 38G and phosphor line 42G, as shown in FIG. It begins.

In this example, the green phosphor line is no longer sufficiently excited and the intensity of the green output is reduced.

FIG. 4 shows a more extreme case, in which the electron beam 38G is misaligned to the extent that it strikes the adjacent phosphor line 42B, causing a problem with color purity.

As previously pointed out, the doming phenomenon is caused by non-uniform heating of the shadow mask structure.

The graph in FIG. 5 shows the displacement of the electron beam as a function of time for a phosphor line intermediate the center and periphery of the screen.

The solid curve 50 represents the displacement for a conventional tube, and the broken dashed curve represents the displacement for a tube utilizing one embodiment of the present invention.

The peaks of curves 50 and 52 both appear 3 to 5 minutes after the tube is energized.

Thereafter, as the mask continues to warm up, the positional deviation decreases.

It should be noted that doming is a phenomenon in which a portion of the mask moves toward the screen when the peripheral edge of the mask is held stationary.

The effect of this movement is depicted in Figure 6.

The shadow mask is shown in two positions, one at 34 where it is unheated and therefore not doming, and the other at 34' where it is heated and doming occurs.

The boundary of a beam 38G passing through one of the holes in the unheated mask 34 is shown by a dashed line 39, and the boundary of a beam passing through the same hole in the mask 34' which is doming is shown by a dashed line 39'. There is.

The distance \\X" in FIG. 6 represents the amount of positional deviation c that appears due to doming.

The result of misalignment due to doming appears as a movement of the beam arrival position on the screen toward the center of the screen 32.

As the mask warms up, the doming effect also decreases because the temperature distribution within the mask decreases.

Additionally, heating the mask causes the mask to expand and expand, thereby moving the aperture positions in the mask laterally and outwardly from their original positions (ie, parallel to the screen).

This outward movement creates a new displacement away from the center of the screen.

This reduction in doming, in combination with heating the mask, then causes the mask holes to be oriented back into alignment with the corresponding phosphor lines.

However, the expansion of the mask at the periphery of the screen
This causes a more serious problem of misalignment.

In order to correct this misalignment at the periphery of the screen, the mask/frame assembly is supported on a heat-sensing support, and the mask/frame assembly is moved toward the screen to eliminate misalignment due to mask expansion. It is common practice to increase or at least reduce

Since the compensation obtained in this way is only correct if there is no temperature distribution between the parts of the mask in the support, at intermediate points there will be some residual deviation, as shown by the curve in Figure 5. exists.

Also, since the mask is shaped with a large heat sink at its periphery or frame, there is always some heat transfer and temperature change across the mask during operation of the tube, and therefore there is always some doming. exist.

The geometrical relationships of the parts of the shadow mask tube in FIG. 7 are shown.

The line P--P represents the deflection plane (in zero orientation) as in FIG.

The distance between the plane PP and the screen 32 is NL〃, and the distance between the shadow mask 34 and the screen 32 (
(measured parallel to axis A-A) is designated SS q//.

Furthermore, the distance SS S" is the distance in the deflection plane P-P from the center axis A-A to the center 54 of the electron beam located off-axis, and SS a// is the distance between the centers of the two holes in the mask 34. - shall represent the center spacing.

The dimensions described above have a relationship roughly expressed by the following formula.

In the present invention, in order to reduce the effect of doming, the shadow mask 56 is given a greater curvature than that seen in conventional tubes of similar construction, resulting in a greater change in Nq.

At the same time, the value of the curve a" is also changed in proportion to XX q".

This means that the value of SS a'' is uniform throughout the mask, and XX q〃 is equal to SS I, "and SS S
It is possible to change according to the change of // only,
This is different from the conventional screen-type cathode ray tube.

In Figures 8, 8A, 8B and 8C.

A conventional shadow mask with a radius of curvature of 1000 m is shown.

The value of Na'' of this mask and the width of the slit (vertical hole) are expressed in units of tone.

The value of 6a'' at the center 60, periphery 62, and intermediate portion 64 between the center and periphery of the mask is a constant 0.77rr.
It is shown that an.

The slit width is from the center 60 to the periphery 62 of the mask 34.
The dimensions are gradually becoming shorter towards the end.

The radius of curvature is 850 tran as shown in FIGS. 9, 9A, 9B and 9C.
In the shadow mask 56, the distance 6a'' between the centers of the holes (slits in the case of 2) is 0.77 rrrms at the center 66.
0.885m at intermediate point 68, 1.000m at peripheral part 70
The store is gradually getting bigger.

If the same slit width used in conventional mask 34 of FIG. 8 were used in mask 56 of FIG. 9, the transmission of the mask would be reduced to the desired level.

Therefore, in order to maintain the desired transmittance of the mask, this slit width is increased compared to the slit width of conventional masks.

In fact, the value of XXa" is 0.77rr at the center of the mask.
If it can be changed from rm to 1.14m at the periphery,
The slit width may be kept at a constant value of 0.15:rarL over the entire mask in order to obtain a predetermined transmittance.

Increasing the slit width is desirable as it facilitates mask fabrication.

The ratio of the mask-to-screen distance (measured parallel to the major axis of the q-tube) is shown in Table A for two conventional tubes and two tubes related to the present invention.

The first column shows the ratio of q at the edge on the long axis of the mask surface to q at the center of the mask.

The second column also shows the same ratio on the diagonal of the mask surface.

It can be seen that in the tubes associated with this invention, the peripheral to central q-spacing ratio is significantly greater than the same ratio in conventional tubes.

It can also be seen that for the two examples of tubes associated with this invention, the values of the peripheral to center q-spacing ratio are all greater than 1.15.

Change the curvature of the shadow mask from radius 1000wm to radius 8
A larger value of 50 mmt' reduces doming and "blister" distortions, as well as the misalignment caused by these.

Increasing curvature increases strength.

Therefore, it is possible to reduce distortion (warpage) of the mask.

Furthermore, because of the geometric relationships between the parts when the tube is actuated and the mask is heated, for a given mask expansion, one point on the mask with a greater curvature is - less than Compared to a point at a similar position on a mask with curvature,
The distance traveled towards the screen is short.

Regarding the curvature of the mask shown above, doming or nudging of a part of the mask.

The shift toward phosphorus decreases from about 48 microns for a mask with a radius of curvature of 1000 m to about 30 microns for a mask with a radius of curvature of 850 rML.

Increasing Na" allows increasing the misalignment tolerance of the phosphor lines at off-center positions.

Again, as mentioned before, the line spacing on the screen cannot be too large; if it is too large, the roughness of the screen will become noticeable.

The spacing chosen is therefore a compromise between the allowable roughness of the linear phosphor triplet and the possible increased tolerance.

By keeping XX a" to a small value in the center of the screen and increasing SS a" near the periphery, the appearance of the screen appears to be one with a fine pixel arrangement. You will be able to do it.

Table B shows, at a point midway between the center and the periphery of the screen, for a conventional tube and a tube associated with the invention comprising a shadow mask with a radius of 850M vs. 100100O greater than the mask of the conventional tube. Measurements of misalignment due to tolerances and doming are shown.

All these values are per cabinet.

The increased tolerance in the tubes associated with this invention is that the spacing SS a
The decrease in displacement is due to an increase in the curvature of the shadow mask.

Therefore, by increasing the mask curvature and spacing % a", the displacement on the screen where the effects of doming are most pronounced will be significantly reduced (eg, by 0.027 an in Table B).

In the above description, in order to help the understanding of the invention, a specific example of a pipe related to the invention will be given, and the curvature of the face plate of the pipe will be increased and the interval SS B" will be changed. Although the mask has been described above, the present invention is applied to a flat face plate.

Historically, shadow masks used in conjunction with line screens have been approximately parallel to the faceplate, even though they have not had exactly the same curvature as the faceplate.

A flat faceplate is preferred because it allows for a larger viewing angle without distorting portions of the screen.

FIG. 10 shows a cathode ray tube 72 including a curved shadow mask 74 and a planar face plate 76.

In this tube, the spacing XXq'' increases virtually from the center of the mask to the periphery, and the mask hole spacing SS
a'' has been similarly increased to maintain a satisfactory phosphor line pattern on the screen.

In the cathode ray tube of the present invention, for example, as shown in FIG. 11, a mask 78 used in a cathode ray tube 80 having a flat face plate is given an opposite curvature for the purpose of strengthening the mask. It is configured.

In this case, the interval XXq'' increases once and then decreases as it progresses from the center of the mask to the periphery.

Therefore, the value of %B'' is also changed in proportion to the change in the interval Nq'', and therefore the value of Na'' is also increased once and then decreased as it progresses from the center to the periphery of the mask.

The basic idea of the inventive arrangement lies in the combination of increasing the curvature of the shadow mask and varying the spacing SS B'' as one moves outward from the center of the tube.

In some conventional tubes, the distance between the mask and the screen is Nq“
is larger at the periphery than at the center of the mask.

When applying the present invention to such tubes, a significant change in mask-to-screen spacing is provided.

However, it is also possible to apply the present invention to conventional tube structures in which Nq" at the periphery is smaller than SS q" at the center.

When applying the invention to such tube structures, the spacing SS q'' will be varied more extensively in otherwise conventional tubes.

However, such a change does not actually limit the tube to having a larger ks q at the periphery than at the center; A tube with a periphery with a small Sk q" or a uniform SS q" could also be obtained.

That is, the present invention does not address the relative magnitude of Nq at the periphery of a tube versus SSq at the center, but rather hand,
It concerns the relative size of XXq'' at the center and the periphery and its changes.

Furthermore, the same idea is applied to the expression of the dimension Na'' which is changed in proportion to the change in Nq''.

a Due to the relationship of q=38 shown above, it is possible to correctly incorporate the phosphor elements on the illusion 7 in a mosaic pattern.

Here, “Incorporate in a mosaic pattern (nes-ti■)” means
Represents the relationship between phosphor elements that form a trio,
(within one triplet) or the spacing between lines is different from another triplet.
This refers to making the distance equal to the distance between adjacent dots or lines belonging to a set.

[Brief explanation of the drawing]

Fig. 1 is a plan view of a conventional shadow mask cathode ray tube, with a portion taken in cross section along the main axis, and Figs. 2 to 4 show a portion of the screen with linear phosphor elements. FIG. 5 is an enlarged view showing the electron beam incident thereon, and FIG. 6 is an enlarged view showing the mask and screen in the part indicated by 6 in FIG. 1, FIG. 7 is a diagram showing the geometrical relationship between the electron beam, the mask, and the screen, and FIG. Figures 8A, 8B, and 8C are the partially removed rear views of the faceplate of a tube incorporating a conventional shadow mask; FIG. 9 is an enlarged view of a portion corresponding to the position, and FIG. 9 is a similar view to FIG. 8, FIG. 9A, FIG. 9B, and FIG.
Figure c shows Figures 8A and 8 for the cathode ray tube in Figure 9.
FIG. 10 is a partially removed plan view of a cathode ray tube with a flat face plate; FIG. 11 is an embodiment of the present invention. 1 is a partially cut-away plan view of a cathode ray tube with a flat faceplate; FIG. 32... Screen, 78... Shadow mask, a... Center distance between mask holes, q...
...The distance between the mask and the screen.

Claims (1)

[Claims] 1 A cathode ray tube with a flat faceplate that utilizes a perforated shadow mask to align the electron beam onto the phosphor elements of a screen, the polarity of the rate of change of the spacing between the mask and the screen is configured to change at least once between the center of the mask and the periphery of the mask, and the change in the distance between the mask and the screen is proportional to the change in the distance between adjacent holes in the mask. A cathode ray tube configured to contain changes.