DE1958534A1 - Shadow mask, especially for cathode ray tubes - Google Patents

Description

It

. Corporati on3 Tokyo / Japan

Shadow mask, in particular for cathode ray tubes

The invention relates to a shadow mask and a color cathode ray tube, in which by means of such a shadow mask an exact impingement of an electron beam on a Parb point of the tube is achieved.

Known parb cathode ray tubes contain an electron gun for emitting an electron beam, and also one Color screen and a shadow mask or an opening grille for beam selection; those in this mask or in this grid provided openings correspond exactly to the individual color points, so that the beam exactly on the predetermined Color points to reproduce a color image hits. Sus For various reasons, which will be explained in more detail below, there is generally no exact impingement of the beam. This error is particularly noticeable in the outer areas of the screen.

The invention is therefore based on the object of developing an improved shadow mask which ensures that an electron beam hits a specified color point exactly. One equipped with the shadow mask according to the invention Parbkat> odenstrahlröhre should thus be free from the mentioned color errors and an increased brightness of the picture guarantee.

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The shadow mask according to the invention is essentially thereby characterized in that the bores are arranged at least in the outer part of the shadow mask along curved lines.

According to a further embodiment, the invention Shadow mask used on a color cathode ray tube that uses an electron gun to produce electron beams lie in a line (plane).

With the invention, a parb cathode ray tube can also be designed so that the colored dots on the screen lie close together in the outer part.

Some embodiments of the invention are illustrated in the drawing. Show it

Fig. 1 is a partially sectioned perspective view of a cathode ray tube j

Fig. 2 is a diagram of a conventional shadow mask used in a known color cathode ray tube;

3A and 3B are schematic representations for explaining the relative position of images on the screen perpendicular to the central axis of a cathode ray tube, using that shown in Fig. 2, known shadow mask j

4 shows a diagram of the relative arrangement of the picture elements on a spherical screen when using a shadow mask according to FIG. 2;

FIGS. 5A and 5B are enlarged diagrams for explanation the relative position of the picture elements on the screen;

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6 shows a schematic representation of an exemplary embodiment of a shadow mask according to the invention for a color cathode ray tube;

7 shows a basic illustration of the relative position of the picture elements on a spherical screen Use of a shadow mask according to the invention,

8 shows a basic illustration of a further exemplary embodiment a shadow mask according to the invention.

For a better understanding of the invention, a shadow mask color cathode ray tube 11 illustrated in FIG. 1 will first be explained. It is designed so that red, green and blue electron beams 12, 13, 14, which run in a common horizontal plane 15, are deflected horizontally and vertically in a common plane 16 running perpendicular to the central axis of the tube by deflection devices (not illustrated) whereby an outwardly curved spherical screen 18 is scanned through a shadow mask. In this case, the ratio or the relationship between the openings 19 of the shadow mask 17 and the phosphor sites on the screen 18 is of primary importance, which is explained in more detail below with reference to the drawing .

A description will first be given in connection with a conventional shadow mask 1, as illustrated in FIG. 2. When viewed from the direction of the z-axis, the shadow mask 1 shows horizontal and vertical lines Xj, X ₂ > X ₁ S X ₀ * ^X 1 '» ^X 2'» ^X 3 '' * * * ^and ... Y ,, Y ₂ , Y ₁ , Y ₀ , Y ₁ ¹ , Y ₂ ' ³ Υ,' ··. «. The shadow mask 1 has openings 2 at the intersections of straight

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BATH ORIGINAL

Numerous horizontal and vertical lines ... Xg, X _Q , Xp 'and ... Y ₂ , Y _Q , Yp' ···· * also at the intersections of odd horizontal and vertical lines ... X-, ₃ X ₁ , X - * '... and ... Y-, Y _±) Y' ...

With such an arrangement, when the phosphor screen 3 is a plane perpendicular to the central axis of the tube and when the red, green and blue phosphor sites D ^ ₃ D _Q and D _ß on the screen 3 by a conventional light or electron beam printing method using If a light or electron beam are produced which passes through the center of the horizontal and vertical beam deflection, the phosphor points Dn ₁ D _Q and D _ß with the diameter 6, which represent groups of three picture elements for each opening 2 of the mask 1, are successively on the horizontal Lines ... Xz, Xp, X ₁ , Xq j ^X j * »Xp '» ^X 3' ··· arranged in the form of horizontal rows of groups of three, as shown in FIGS. 3A and 3B. Because of the need for closely spaced hexagonal arrangements of the phosphorus points D ", D _ß and D _ß on the phosphor screen 3, the distance Lx between neighboring vertical columns from openings of the shadow mask 3 is chosen so that it has V J times the value Ly of neighboring horizontal rows of openings .

In the case of a shadow mask tube 11 (FIG. 1) containing a so-called "in-line" gun, the point of impact of the rays of a group of three 10 passing through individual openings 19 is rotated against the original, aligned position of these three rays (cf. Fig. ^2J) j this phenomenon is referred to as rotation of the impact point of the "inline" -Strahldreiergruppe. This twisting phenomenon is explained as a purely geometric effect through the combination of a linear alignment of the three rays and a spherical screen. If the coordinate system shown in FIG. 1 is considered, the three rays 12, 13, I ¹ J, which pass through the opening 19 of the shadow mask 17, form

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pass through the plane 16 which runs parallel to the x-axis of the tube and which forms an angle θ _ν (angle of vertical deflection) with the xz-plane. This plane 16 intersects the spherical screen 18, the center O of which lies on the z-axis. The point of impact of the group of three rays 10 aligned on a line is on a line of intersection C, which when viewed from the direction of the z-axis is an elliptical arc and can be expressed by the following equation:

(1) x ² + (1 + ~ -) y ² +> ^{2 (R} " ^L) y + L ² - 2RL = 0

tan Qy tanQ

Here, R is the radius of curvature of the spherical screen 18 and L is the distance between the beam deflection center and the screen center.

This is the reason for the twisting of the point of incidence of a group of three rays lying in a line; the mathematical The expression for the twist angle is obtained by differentiating equation (1) and using the relationship

tan9 _y = y / (I / r ² - x ² - y ² - R + L).

From this it follows

(2) tanO = ^d | = SL

R ² - x ² - (RL) ^ R ² - x ² - y ²

where θ is that measured counterclockwise from the positive x-axis Twist angle is.

An approximate form of equation (2) is (3) tanQ = ~ ^ J

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If, however, in an arrangement explained above, the diameter of the phosphor sites D _RJ, D _Q and D _ß on the phosphor screen is selected so that it corresponds to the value έ previously described with reference to FIG , so the phosphor sites D _R , D _ß and D _ß overlap corresponding to one of the horizontal rows of the openings 2 the phosphor sites of the adjacent horizontal rows of openings because of the fixed relative arrangements of adjacent openings (see. Pig. 5A). To avoid this, the diameter of the openings of the shadow mask in accordance with the angle θ made small _t the diameter of the phosphor ύ locations on the screen 3 is selected accordingly. In the case of a conventional shadow mask with an "in-line" gun (ie an electron impregnation device in which the various electron beams lie on a single line), the impact tolerance is reduced considerably because of the twisting phenomenon at the points of impact of a group of three beams (FIG. 5A ). The aim of the new shadow mask is to fully compensate for this twisting phenomenon. The basic principle of the new shadow mask according to the invention consists in adapting the orientation of the openings to the geometrical rotation of the points of impact of a group of three beams. This means that a horizontal row of the aligned openings in the spherically curved shadow mask and the line which runs through the centers of deflection of the three electron beams must lie in a single, flat surface. If one takes into account the fact that the radius of the spherically curved shadow mask is approximately equal to the radius R of the inner screen surface and one neglects the length of the gap between the shadow mask and the inner screen surface (compared to the value L), the horizontal alignment lines of the openings be the arcs of the ellipses given by equation (1); this equation is the solution to the differential equation of geometric rotation. A transformation of the

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Integration constants θ _ν in equation (1) leads to the following expression:

₂ R ² + (RL) ² - 2 (RL)

(RL) ² - (RL) ^ R ² - y ²
_2 ~ y + IT - 2RL = 0

^y o

where y-C 0 at yQ

y ₀ is a parameter that represents the portion of the curve cut off from the curve by the y-axis.

The group of elliptical arcs (equation 4) forms a "barrel-shaped" group of curves ... X ^, X «, X ₁ , X _Q , X. ¹ , X ₂ ¹ * X, ', ..., as in Fig Figure 6 illustrates. The vertical alignment lines of the openings must be given the shape shown in the drawing, so that they run perpendicular to the horizontal alignment lines over the entire surface of the shadow mask.

The vertical alignment lines can be obtained by solving the following differential equation, which is the reverse of that with Represents the signed reciprocal of equation (2) for the geometric rotation:

5) dy_ _s R ² - x ² - (R - L) fe ² - x ² - y ² dx "xy

The solution to this equation (5) results; II ² - (H - «Λ? ~ - x" ²

• exp]

(H-L

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where X _{0 is} a parameter representing the piece of curve cut off from the χ axis.

The curves thus obtained (equation 6) form right angles with the group of curves (equation 4) over the whole Area of the shadow mask. However, equation (6) has the following approximation form, that of squareness has an error of -1 ° or less between the horizontal and vertical alignment lines:

where Xq ^ L 0.

This is the group of arcs illustrated in FIG. 6 ... Y ₃ , Y ₂ , Y ₁ , Y ₀ , Y ₁ ', Y ₂ ', Y ₃ ',

The equations (* O, (6) and (7) were based on of the discussions on the spherically curved shadow mask. These equations express the alignment lines of the openings on the spherically curved shadow mask when viewed from the direction of the z-axis. Considered one, however, the experimental result, according to which if a flat shadow mask becomes an approximately spherical surface is deformed by pressing, the shift of the opening position mainly only takes place in the z-direction, while the displacement in the x-y-plane is negligibly small, see above these equations can also be interpreted in such a way that they represent the alignment lines of the openings on the flat (prestressed) Express shadow mask.

The above description has been made for the case that the phosphor screen 3 is spherical; however, the same is also true

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in the event that the screen is a cylindrical surface extending in the vertical direction. In this case, however, the relationship for the inclination angle of the horizontal row of a group of three of the phosphor sites D _R , Dg and Dg for each opening 2 of the mask 1 to the horizontal line is as follows;

(8) tanO =

R ² _ χ ² _ (R - I) / r ² _ χ ²

according to equation (2).

The horizontal alignment lines of the openings are accordingly again barrel-shaped and the vertical alignment lines of the openings run like a pen pad perpendicular to the horizontal alignment lines over the entire surface of the Shadow mask openings are at the intersections of the horizontal and vertical alignment lines are provided. The curve of the horizontal alignment lines is obtained by dissolving the differential equation (8) resulting in an equation corresponding to the equation (Ii), and by satisfying the resulting one Equation. The curve of the vertical alignment lines is obtained by solving the following differential equation, which represents the reciprocal of equation (8) provided with the opposite sign;

(9) dy_ _a R ² - χ ² - (R - g) / r ² - χ

d "

y_ _a - g) / r - χ ²

dx "xy

From this one obtains an equation corresponding to equation (4), which must then be fulfilled. In this way you can achieve the same results as mentioned above.

The invention was explained above on the basis of the case in which the electrons corresponding to the colors red, green and blue

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electron beams in one on a common horizontal plane aligned position enter the area of the horizontal and vertical deflectors. The invention is however, equally applicable in the case in which the electron beams enter the area of the deflection devices are aligned on a common vertical plane. In this case, of course, you have to use a shadow mask use their openings at the intersections of barrel-shaped running vertical alignment lines with correspondingly perpendicular, pin cushion-like horizontal alignment lines are provided; so it becomes the curves for the horizontal and vertical alignment lines reversed.

The invention has also been explained on the basis of cases in which the screen 3 is spherical or cylindrical is; however, the invention is also applicable when the screen is curved outward in any other way is.

There remains the problem of determining the values of the parameter XQS and y _Q s, ie the determination of the pitch over the entire surface of the shadow mask. In the corner areas of the shadow mask area, the horizontal pitch is increased by the pillow-like nature of the vertical alignment lines, while the vertical pitch is decreased by the barrel shape of the horizontal alignment lines. Therefore, if x _Q s and y _Q s are simply chosen to be linear, ie x _Q = mx ₀₀ and y _Qn = ny ₀₀ under the condition x _Q0 = \ ß y _Q0 , the face-centered arrangement of the is not in the corner area of the shadow mask openings in the form of equilateral hexagons available,

However, one can have such a face-centered arrangement of the openings in the form of equilateral hexagons over the whole

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BATH ORIGINAL

Achieve the area of the shadow mask. For this purpose, the horizontal distances are reduced quadratically along the x-axis towards the outside and the vertical distances are increased quadratically along the y-axis towards the outside. In mathematical terms, x _Q s and y _Q s are chosen as follows:

^x 0m ^{= mx} 00

^{= ny}

00

where Oi = x _oo ² / 6RL = y _OQ ² / 2RL
β = y _oo ² / 6RL

y _Q0 is the standard division between the openings (ie the division in the center of the shadow mask).

For this choice of the values of x _Q s and y _Q s, the distances on both edges of the x-axis are reduced by about 10 $ compared to the distance in the center, while the distances on both edges of the y-axis are reduced by about 6% the center can be enlarged. The same distances are provided from the center to the four diagonal areas of the shadow mask as in the center. The desired change in the spacing thus results in an almost complete, face-centered arrangement of the openings in the form of equilateral hexagons over the entire surface of the shadow mask, it being sufficient to use round openings. The shadow mask produced in this way is illustrated in FIG.

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Claims (12)

Claims ) Shadow mask for use in cathode ray tubes, consisting of a metal plate with a large number of holes, characterized in that the bores at least in the outer part of the shadow mask are arranged along curved lines. 2.) shadow mask according to claim 1, characterized in that the holes - with the exception of the central area of the Shadow mask - are arranged lengthwise in the horizontal direction, curved lines. 3.) shadow mask according to claim 1, characterized in that the holes in the outer part of the shadow mask at the points of intersection horizontal and vertical curved lines are arranged. 4.) shadow mask according to claim 1, characterized in that the metal plate is curved. 5.) shadow mask according to claim 3 »characterized in that the horizontal and vertical curved lines, at the points of intersection of which the bores are provided, roughly correspond to one another cross at right angles » 6.) Shadow mask according to claim 5, characterized in that the vertical curved lines are pillow-shaped. 7.) Shadow mask according to claim 5, characterized in that the horizontal curved lines are barrel-shaped. 8.) shadow mask according to claim 5 »characterized in that the distance of the horizontal curved lines in the outer part of the shadow mask is different from the distance in the central area is. 009840/1155 BATH ORIGINAL 9.) shadow mask according to claim 5, characterized in that the distance between the vertical curved lines in the outer part of the shadow mask differs from the distance in the middle area is. 10.) shadow mask according to claim 5, characterized in that As the outer circumference of the shadow mask is approached, the distance between the horizontal curved lines increases and that of the vertical curved lines is reduced. 11.) Cathode ray tube with a shadow mask with a curved surface, furthermore with a spaced apart from the shadow _{mask t} and provided with applied phosphorus points f Phosphorschirni, furthermore with a production facility a number of electron beams, the shadow mask having a plurality of bores or openings, characterized in that the openings are arranged in the outer part of the shadow mask along curved lines, so that the electron beams exactly on the Strike phosphorus points of the phosphor screen. 12.) Kathodenetrahlröhre with a curved screen, which has a number of applied phosphor sites, further comprising means for generating a number of electron beams, the deflection centers are aligned etc. to a common plane, further comprising a shadow mask between the screen and the beam generating means wherein the The shadow mask has a number of bores or openings, characterized in that the openings are arranged along curved lines when viewed from the central axial direction of the cathode ray tube. 009840/1155 Blank page