JPH0418663B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an improvement in a shadow mask for preventing color shift occurring during operation of a color picture tube.

[Prior art]

It has been known that in a shadow mask type color picture tube, the temperature of the shadow mask increases due to the impact of an electron beam, causing thermal deformation. Since this thermal deformation causes color misregistration, which is generally referred to as misregistration, it has been desired to take appropriate measures for each cause.

One of these thermal deformations is called doming. This is because only a part of the image reproduction screen (generally a relatively compact part having a size of a fraction to several tenths of the total effective screen area) during operation of a color picture tube is larger than other parts. This is a phenomenon in which when an extremely bright and almost static image continues for a long time, the shadow mask corresponding to this bright area is locally thermally deformed. This will be explained in detail below using FIG.

Figure 1 is a schematic diagram showing the relationship between the image reproduced on the color picture tube screen and the doming of the shadow mask. In Figure 1a, 1 is the picture tube panel whose inner surface is coated with phosphor, and 2 is the shadow mask. It is. Note that accessory parts such as a holding mechanism for the shadow mask 2 and an electron gun are omitted. On the other hand, Fig. 1b
In a drawing showing a color picture tube image, 10 shows a part that is significantly brighter than other parts, such as a white cloud in the blue sky, and this state remains almost stationary for a little while (more than 5 seconds). If it continues,
The part corresponding to image 10 of shadow mask 2 is
Since the amount of electron beam impact is larger than in other parts, the temperature locally increases, and what should originally be the shape of the broken line 21 is deformed as shown by the solid line 22. For this reason, the hole 3 for passing the electron beam in the shadow mask 2 cannot be maintained in a fixed position, causing unevenness in the amount of irradiation of the phosphor dots, resulting in color shift. In a general shadow mask, this deformation occurs in a direction in which the portion corresponding to the bright screen bulges toward the fluorescent surface side. This phenomenon becomes more noticeable as the deflection angle becomes larger, and becomes a very serious problem in color picture tubes that have recently become wider in angle, such as 110° deflection.

Such a doming phenomenon occurs because, as shown in FIG. 1, when a portion of the shadow mask 2 is locally heated and expands due to the impact of the electron beam, the impact of the surrounding electron beam causes This is because the parts without 2 do not expand. If the amount of doming is expressed by the amount W that the heated part moves perpendicularly to the surface of the shadow mask 2 when the heated part is circular, then W is approximately proportional to the local radius R of the spherical surface. That is, the following equation is obtained.

W=αR The derivation of the above equation is described in some detail in, for example, the magazine Television, Vol. 31, No. 6 (1977), pages 49-50.

It should be noted that although the coefficient of thermal expansion of the shadow mask material is included in the proportionality constant α in the above equation, constants such as the material's elastic modulus and strength against deformation are not included in an explicit form. There is no such thing. This is because, as mentioned above, deformation occurs due to the force relationship between the heated part and its surrounding parts.If the part of the shadow mask in question is made of the same material, This is thought to be because the stronger the heated part, the stronger the surrounding area (in other words, a material that is strong against deformation has a strong force forcing it to deform from its surroundings), and the doming deformation caused by surrounding pressure will eventually be the same. .

Now, doming occurs in proportion to the radius of the spherical surface of the shadow mask 2, but the reciprocal of the local radius R is 1/
If we call R the curvature K, the curvature K (originally,
Although the local curvature should be K, since the entire description below is local, it can be said that it is inversely proportional to the local curvature (the word "local" is omitted). Furthermore, the larger the curvature K is, the more doming can be reduced.

By the way, the curvature of the mask surface and the strength of the material of the shadow mask 2 are generally not isotropic. A typical example of this is a color picture tube shadow mask having a striped phosphor surface. In such a shadow mask, the holes provided in the mask surface are elongated and continuous in one direction, and are arranged at intervals in a direction perpendicular to this. However, the shape of the mask surface is not necessarily spherical. In order to discuss such cases, coordinate axes are established as follows. In other words, as shown in Fig. 2, a normal line is set at an arbitrary point A on the curved surface of the shadow mask 2, which is the Z-axis, and an X-axis and a Y-axis that are perpendicular to this Z-axis and perpendicular to each other. Define the axis. The directions of the X and Y axes are as described below.
It is assumed that it is practical to determine it in relation to the arrangement of the holes 3 of the shadow mask 2. Therefore, when the mask of shadow mask 2 is cut on the XZ plane,
A curved line appears at the cut. Let the curvature of this curve near the above point A be _K
Let the nearby curvature be K _Y.

After making the above preparations, consider the equivalent curvature K ₀ of the shadow mask 2. In other words, if there is anisotropy in the material or the shape of the surface of the shadow mask 2, the doming is inversely proportional to the equivalent curvature.
The idea is to consider K ₀ , judge the magnitude of doming based on this magnitude, and try to find the structure of small doming.

First, it is assumed that the material of the shadow mask 2 is isotropic and only the curvature matters. If the shadow mask 2 is spherical, K _X =K _Y , and this should be considered to be directly equal to the equivalent curvature K ₀ . When K _X ≠K _Y , the average curvature K ₁ between the two
Considering that _it should be _, at _least approximately, it should be K ₁ =K Note that the normal shadow mask 2 has a curved surface that is convex toward the panel 1 side, and K _X and K _Y have the same sign.

Next, consider a case where the material of the shadow mask 2 has anisotropy in its strength characteristics. The strength properties mentioned here are related to Young's modulus, bending rigidity, etc., but for now I will only describe them qualitatively. When both ends of the material are held upright in a testing machine and pressure is applied from both ends, it is thought that the main force is the pressure required for the center of the material to shift by a certain amount, and this is called σ. call.

Now, since the material has anisotropy, this strength property can be determined by moving the elongated test material from the problematic part of Shadow Mask 2 parallel to the axial direction of _K Possible cases include a case in which it is cut out into a long thin line and a case in which it is cut out in a long and thin line parallel to the Y-axis direction. These two are respectively σ _X ,
Let's call it σ _Y.

_Here , when _σ occurs in inverse proportion to the average curvature K ₁ . Assuming that the value of σ takes a maximum or minimum in either the X-axis direction or the Y-axis direction (it does not reach a maximum or minimum in an oblique direction other than the It is natural to expect that it will be observed as a kind of average of the phenomena in both Y-axis directions, so if σ _X ≠
Even _{if σ Y ,} if _K (A material that is strong against deformation also has strong pressure from its surroundings to force deformation.) Therefore, it can be expected that the amount of doming is unrelated to the strength characteristic σ of the material. σ _X ≠σ _Y
However, if K _X ≠ K _Y, the situation becomes different.
i.e. in this case K _X or K _Y to the equivalent curvature K ₀
The degree of contribution of σ increases as σ increases.
Considering that the relationships described so far, including the equations, must be expressed naturally, we arrive at the following equation as the equivalent curvature K ₀ .

K _{0 =} 2σ _X /σ _X + _{σ Y} K _X +2σ _X /σ _X +σ _Y K _Y /2 =σ _{X / σ X} +σ _{Y K} is a simple experiment or a previously published literature such as “A Newly
Designed Shadow Mask for Color Picture
Tube (SID Japan Display 1983 Report No.
1, 4), etc., it can be fully inferred.

The shadow mask 2 of a color picture tube having a striped phosphor surface, which is the subject of this invention, usually has a third
It has the shape shown in the figure. That is, the shadow mask 2 has countless rectangular holes 3 arranged substantially in parallel, and when considering any point on the shadow mask, assuming that the longitudinal direction of this rectangle is the Y-axis direction, the holes 3 are arranged close to each other in the Y-axis direction via a narrow bridge 23 whose width is indicated by W, and in the X-axis direction is an They are arranged in parallel with each other via a band-shaped shadow portion 24 having a width that is more than twice the width of No. 3. Normally, the bridge 23 is a part provided to maintain the shape of the shadow mask 2 itself, and is an unnecessary part in terms of the operating principle of color selection. It is said to be good. Because this part is thin, the shadow mask 2 has σ _X , which is the strength characteristic of the material mentioned above, which is much smaller than σ _Y , and those used for televisions generally have σ _X <σ _{Y. σX} : _σY
= 3: It is seen as 7th place. σ in directions other than the X and Y axes takes a value intermediate between σ _X and σ _Y. On the other hand, the curvatures (K _X and K _Y ) of each part of shadow mask 2 are
It is determined by the inner surface shape of the hole 3, the spacing between the holes 3, and the spacing between the electron guns (not shown), which generally consist of a plurality of electron guns (not shown).

Recently, in order to make the appearance of the panel 1 of a color picture tube as flat as possible, the inner surface of the panel 1 has been made into a relatively complicated curved surface. As a result, the curved shape of _the shadow mask 2, which is determined in relation to the inner surface shape of the panel 1, also becomes complicated, and at least partially _K
has come to be used. An example of this is the case where a panel as shown in Japanese Patent Laid-Open No. 55-28269 is used.

The invention described in this publication changes the shape of the inner and outer surfaces of the panel, which have been almost spherical so far, so that the peripheral outer surface radius line 30 of the panel 1 is included in the same plane as shown in FIG. The purpose is to determine the shape of its inner and outer surfaces.

According to the invention described in this publication, representative points P ₀ , X ₀ , Q ₀ ,
If Y ₀ ′, P ₀ ′, X ₀ ′, Q ₀ ′, and Y ₀ are taken, all of them are substantially contained within the same plane. In order to realize this, the inner surface is also made so that all representative points on the virtual line corresponding to the above-mentioned P ₀ to Y ₀ are included in substantially the same plane. As _a result, the contour lines of _the inner surface are arranged as shown at 31 in _Figure 7 (the panel is symmetrical with respect to X ₀ ).

Generally, the curved shape of the shadow mask is determined most strongly by the inner surface shape of the panel. Therefore, FIG. 7 can also be regarded as an enlarged representation of the approximate distribution of contour lines of the shadow mask mounted within this panel.

In the well-known striped phosphor screen, the stripes are parallel to the Y ₀ Y ₀ ' direction. Therefore, the longitudinal direction of the rectangular shadow mask, ie the direction of the rows of holes, is also substantially parallel to Y ₀ Y ₀ '. If this is the case, as is clear from the contour lines in the figure, when FIG. 7 is regarded as a curved surface of a shadow mask, a portion where K _X <K _Y appears in a surface area 33 separated by a boundary 32 of two-dot chain lines. As mentioned above, in such a curved surface part, it is effective to satisfy σ _X <σ _Y to increase the equivalent curvature K ₀ and reduce doming. Therefore, a shadow mask 2 having a rectangular hole 3 as shown in FIG.
In this case, as mentioned before, σ _X <σ _Y , but
Furthermore, if this difference can be made larger, it is possible to more effectively utilize the fact that K _X <K _Y to reduce doming.

[Summary of the invention]

In view of such circumstances, the present invention increases the degree of contribution of K _Y to the equivalent curvature K ₀ by making σ _X smaller relative to σ _Y when K _X <K _Y. More specifically, a groove extending in the Y-axis direction is provided only in the shadow portion of the area where K _X <K _Y on the shadow mask.

[Embodiments of the invention]

Embodiments of the present invention will be described below based on the drawings.

FIG. 4 shows a shadow mask 2 which is an embodiment of the present invention. Since the shadow mask 2 has a plate thickness, the figure is drawn so that this situation can be understood.
In the figure, the arrangement of the holes 3 is the same as in FIG.

In this embodiment, the grooves 25 are formed only in the shadow portion 24 in the area where K _X <K _Y. This groove 2
5 is a shadow portion 24 extending long in the Y-axis direction.
It is a narrow thin walled part located approximately in the center of the window, also in the Y-axis direction, and its width is approximately 2/3 to 1/4 of the width of the shadow part at the opening, and the depth is approximately 2/3 to 1/4 of the width of the shadow part at the opening. It is made about 3/4 to 1/4 of the thickness. When _such a groove 25 is provided, _{both σ X} is proportionally smaller. Conversely, σ _Y becomes larger in proportion. Therefore, as mentioned above, _{the equivalent curvature K 0 in} the area where _K

^Specifically _, ^when _{K _ _} 7, then from the formula, K ₀ = 3/3 + 7 x 0.00056 + 7/3 + 7 x 0.00112 ≒ 0.00095 mm ^-1 .

On the other hand, as in this embodiment, the shadow part 24
Assuming that the _{ratio of σ} ×0.00112 ≒0.00104mm ^-1 , and if doming is inversely proportional to the equivalent curvature K ₀ , then 0.00095/0.00104≒0.91,
A reduction (improvement) of approximately 9% can be expected.

Note that the groove 25 is connected to the shadow part 2 in the area where K _X ≦K _Y.
4, the equivalent curvature K ₀ becomes smaller than when the groove 25 is not provided, and doming increases on the contrary.

In the embodiment described above, σ _X of the surface area where K _X <K _Y
The cross-sectional shape of the shadow portion ₂₄ is devised so that σ is smaller relative to σ _{Y ,} but the relationship between σ This can also be achieved by providing a shaped thin section. However, Bridge 2
If the width and wall thickness of the shadow mask 3 are made smaller, the bridge 23, which is generally formed as narrow as possible to increase the electron beam transmittance and therefore to the maximum mechanical strength, will be further weakened. There are side effects such as difficulty in forming a curved surface and an increased possibility of deformation of the curved surface during the color picture tube manufacturing process, and also when something like a groove in a thin wall portion touches the side wall 3a of the hole forming the hole 3. In this case, the shape of the hole 3 cannot be made accurately and appears unevenly on the screen. Therefore, in this embodiment, a simple groove 25 is provided in the shadow portion 24 without it covering the side wall 3a of the hole 3. It's not better than that.

In addition, for general shadow masks, the fifth
As shown in the figure, the side wall 3a of the hole 3 is not perpendicular to the surface of the material plate, but has a considerable slope, and the size of the opening on the surface of the material plate is indicated by D and d in the figure. As a result, the cross-sectional shape of the shadow portion 24 in the X-axis direction is approximately trapezoidal. Therefore, it is natural that the groove 25 is formed by etching a material plate, but in this case, the side wall 25a of the groove 25 must also have an inclination so that the width thereof becomes gradually narrower as the depth of the groove increases. Even in such a case, in order _to maximize the effect of _the groove ₂₅ on _σ It is effective to provide it from the side d (in FIG. 5).

In addition, in connection with FIGS. 6 and 7, the surface area 3 in which the groove 25 according to the present invention is provided on the curved surface of the shadow mask
As mentioned above, the distribution _{of K} The shape of the surface area is not limited to that shown in Figure 7, as it changes depending on the design constants, and the inner surface shape of the panel is not limited to that of the cited Japanese Patent Application Laid-Open No. 55-28269. do not have.

〔Effect of the invention〕

According to the invention described above, between the curvatures K _X and K _Y of the shadow mask in the X and Y directions, K _X <
Grooves extending _in the Y-axis direction are provided only in the shadow area of the area where K _Y is concerned _, and σ can get.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of the doming phenomenon in a shadow mask type color picture tube, Fig. 2 is an explanatory diagram of the coordinate axes, Fig. 3 is an explanatory diagram of a shadow mask having a hole long in one direction, which is the subject of this invention, and Fig. 4 is a partial perspective view showing an embodiment of this invention, FIG. 5 is a sectional view showing a more effective embodiment of this invention, and FIGS. FIG. 2 is a diagram for explaining the invention of FIG. 1... Panel, 2... Shadow mask, 3...
Hole, 3a... Side wall, 23... Bridge, 24...
Shadow part, 25... groove, 25a... side wall. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 1 A thin plate is formed by forming a row of approximately rectangular holes extending in the longitudinal direction via a bridge, and the rows of rectangular holes are arranged in parallel at intervals through a shadow part, and a thin plate is formed with a convex shape toward the panel side. In a shadow mask formed on a curved surface, the Z-axis is a normal line erected at an arbitrary point A on the surface of the shadow mask, and the line of rectangular holes passing through the point A and perpendicular to the Z-axis The direction is the Y axis, the direction passing through the point A and perpendicular to the Y axis and the Z axis is the X axis, and the shadow mask surface is aligned with the Z axis and the X axis.
Let K _X be the curvature near the above point A of the curve that appears at the cut end when cutting along the XZ plane that includes the axis, and near the above point A of the curve that appears at the cut end when cutting along the YZ plane that also includes the Z and Y axes. the curvature of
_A shadow mask characterized in that a groove extending parallel to the row _of rectangular holes is provided in the shadow portion only in a surface area where _K