DE1437855A1 - Cathode ray tubes and methods of making the same - Google Patents

Description

Patent application

Applicant: Radio Corporation of America, New York, N. Y., V.St.A.

Cathode ray tube and method of manufacture

the same.

The invention relates generally to a cathode ray tube screen phosphor screen and, more particularly, but not exclusively, a rectangular shadow mask color cathode ray tube and a method for manufacturing the same.

The usual shadow mask color cathode ray tubes have a tubular envelope which consists of a faceplate and a funnel, which has a frit seal are connected to each other. On the faceplate panel is a perforated mask made of sheet metal attached with many openings. Wears on the inside the faceplate a screen, which consists of mosaic-like arranged luminous point surfaces. Several electron beam generators are arranged in the funnel neck in such a way that their electron beams pass through the shadow mask are directed at the luminous dot areas. The illuminated dot areas are carefully aligned with the öff-6266 - 65

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The openings of the high mask electrode and the electron gun are designed to achieve the desired selective excitation of the luminous areas is achieved by the electron beams.

The luminous surfaces can, for example, have the shape of essentially circular points or elongated strips. Since phosphor dots are more common, the invention is explained below with reference to such luminous dots.

According to the usual manufacturing process for such tubes, the phosphor dots are made by a photographic process applied to the faceplate using the shadow mask electrode as a photographic negative. The faceplate is then connected to the funnel via a frit seal, which becomes the beam generator group built tightly into the neck of the funnel and then the finished tubular flask is evacuated.

Due to the external pressure load that occurs here, the faceplate is pushed slightly inwards and the Side walls of the faceplate panel bent slightly outwards. This characteristic deformation of the faceplate panel is referred to below as the "faceplate indentation" designated. The faceplate indentation destroys the required exact alignment that you had previously

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-between the fluorescent dots, the shadow mask openings and the beam generators. In the case of a tube with a rectangular faceplate, the indentation is axially asymmetrical to the central tube axis and therefore requires an axially asymmetrical compensation, which has been the case up to now is still unknown.

The term "axially asymmetrical" used describes one

Shape that extends along a circular path, based on the '

Axis, changes unevenly. This means that the shape or

Size does not have j60 ° (circle) symmetry.

No other size, which is also axially asymmetrical Compensation required consists in the relocation of the electron beam deflection centers along the central tube axis.

To operate a cathode ray tube, a> magnetic deflection yoke placed around the tube. The yoke comprises two pairs of coils, each of which carries the electron beams ^ orthogonally Deflecting directions that are opposite to one another.

For simplicity and for example, these two are orthogonal Directions in the following, according to their days in use, are assumed to be horizontal and vertical.

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The horizontal and vertical deflection coils can be constructed in various ways and will of course be understood excited by deflection signals of different frequencies. As a result of these differences, especially when the Rays with an angle greater than about 55 ° from the central tube axis (commonly referred to as a 70 ° deflection), the axial displacement of the center of the deflection of the horizontal coils not coincident with the axial displacement of the center of deflection of the vertical coils. In order to achieve an optimal compensation for the displacement of the deflection centers, an axially asymmetrical compensation is required required, which was not previously known for this purpose either. Such a non-coincidence of the horizontal and vertical centers of deflection is independent of the shape of the faceplate, that is, regardless of whether this is rectangular or circular.

The invention is based on the object of an improved To create a grid screen made of fluorescent dots, in which the indentation of a rectangular screen carrier and / or the non-coincidence of the horizontal and vertical center of deflection are compensated, and further the invention is intended specify a new method of manufacturing such a screen.

According to the invention, the grid screen of a shadow mask

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Parb cathode tube set in an arrangement that has a predetermined axially asymmetrical distortion has opposite the arrangement of the openings of the shadow mask electrode. If the tube is subsequently evacuated, then causes the axially asymmetrical indentation of the faceplate a relative displacement of the phosphor dots with respect to the openings of the perforated mask, such that the The required fluorescent points after evacuation of the tube have critical alignment with respect to the shadow mask openings and the electron guns.

The arrangement of the fluorescent points must also be made such that they are such after evacuation axially asymmetrical distortion that when using a deflection yoke with non-coincident horizontal and vertical deflection center the electron beams that pass through those shadow mask openings, which lie along a direction of beam scan (e.g., vertical) from the central tube axis, as well as the electron beams passing through the perforated mask openings pass through that from the central tube axis along the other direction of the beam scan (e.g. horizontally) hit the correct fluorescent points.

The distortion of the phosphor dot array leading to Compensation for the indentation of a rectangular shield

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as well as the distortion of the phosphor dot arrangement, to compensate for the non-coincidence of The centers of deflection used are axially asymmetrical. Hence can both compensation measures combined if desired and can be embodied in a single part * For example, the axially asymmetrical distortion of the phosphor point arrangement can be created by a photographic process. The exposure rays occur here " through an optical device which, at a given distance from the central tube axis, has a different Refraction of the rays along an azimuth, z. B. the major axis, screen and rays along a different azimuth, e.g. B. the minor axis, of the screen causes.

the major axis of a rectangular faceplate is understood to be the surface axis that goes through the center points of the two short sides of the faceplate } the minor axis is that which goes through the center points of the two long sides.

The term azimuth is used to describe the angular position of a point on a circle around the central tube axis. For example, the 0 ° and 180 ° azimuths can coincide with the vertical or smaller axis and the 90 ° 27Ο ⁰ azimuths with the horizontal or larger axis. -

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- 7 In the drawings show:

1 shows a longitudinal section through a shadow mask cathode ray tube ;

Pig. 2 shows a plan view of the faceplate of the Pig tube. Ij

5 shows a schematic section through the umbrella ™ support plate of the tube according to FIG. 1, which shows the faceplate indentation and its effect illustrated!

Fig. 4 is a graph showing the non-coincidence of the horizontal and vertical center of deflection j

5 shows a schematic representation of a section through the faceplate and shadow mask electrode | the tube of Fig. 1 together with an optical -Device used for photographic printing of fluorescent dots Screen serves j and

Fig. 6 is a plan view of the refractive body according to Fig. 5 and two diametrical sections of this body.

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The one in the Pig. 1 and 2 shown shadow mask cathode ray tube 10 has a rectangular faceplate 12 and a lighter 14, which parts are symmetrical to the central Longitudinal axis AA of the tube lie and by means of a frit. tend seal 15 are connected. The plate 12 includes a Faceplate 16 and a side wall 17. A grid screen made of fluorescent dots is applied to the inner surface of the faceplate 16, and one with numerous openings provided, made of sheet metal, shadow mask electrode 20 with z. B. is essentially equidistant openings arranged next to the plate. A plurality of electron guns 21, 22 and 23 are in the neck portion of the funnel 14- arranged so that they pass electron beams through the openings of the perforated mask 20 on the grid screen 18 can judge.

The tube 10 can be operated using a magnetic deflection yoke 24 which is made up of a pair of horizontal and a pair of vertical deflection coils.

Like from Pig. 2 can be seen, the rectangular Faceplate 16 a larger and smaller surface axis xx and yy that intersect. During normal operation of the tube Jtegen the axes xx and yy - in the following main axis xx and minor axis called yy - each horizontal and vertical; they are perpendicular to each other and to the central Tube axis AA and intersect axis AA.

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In a preferred embodiment of the cathode ray tube 10, the electron guns 21, 22 and 25 are in a triangle arranged symmetrically around the axis AA. Both the openings of the shadow mask 20 and the phosphor dots of the Grid screens 18 are arranged in a repeating hexagonal pattern. Three of each of the fluorescent points (Three) are assigned to each opening of the shadow mask electrode 20. Every threesome contains a green emitting, a red-emitting and a blue-emitting phosphor dot. The fluorescent dots of the grid screen 18 are critical to the openings of the shadow mask electrode 20 and to the electron guns 21, 22 and 23 aligned so that each electron gun Different types of fluorescent points are excited than the remaining Klektron emitters.

Pig »j5 shows how the faceplate is depressed when the tube 10 is evacuated. The shape of the plate 12, the \

this before evacuation is shown in solid lines, while its after evacuation the resulting shape is shown in dashed lines. The change in shape is greatly enlarged here for the sake of clarity shown. The corresponding parts of this figure are provided with the same item numbers, but the index "a" is added for the parts of the evacuated tube. The at the

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External pressure load resulting from evacuation bends the Faceplate 16 inwards «as a result of this indentation the side walls 17 pressed outwards.

A deflected beam 25 of an electron gun, ζ. B. the electron gun 2l _a is shown as if it would extend to the faceplate 16 in its non-depressed state. In practice, this does not occur because the beam is only generated after evacuation, i.e. when the faceplate is pushed in. The hypothetical extension of the beam 25 between the two states of the faceplate is intended to explain the effect of the faceplate indentation »

If there is a fluorescent spot at point 26 before evacuation of the tube 10 is arranged such that it lies in the hypothetical extension of the beam path 25, then this becomes when the tube is evacuated out of the path 25 moved to position 26 a. Such a shift Zp compensate, the fluorescent dots before evacuation of the tube in this way on the faceplate 16 arranged "that they were not at the time of their attachment lie in the hypothetical extension of the ray path. For example, there will be a fluorescent dot on the spot 28 deposited next to the ray path 25; when the tube 10 is evacuated and the faceplate 16

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U37855 - ii -

is pressed, then the point location 28 is now in a new position 28a moved, which is in the real Ray path 25 lies.

Due to the rectangular shape of the cathode ray tube 10 is explained with reference to FIG. 3, to compensate for the Faceplate indentation, used red dot shift not axially symmetrical to axis AA. That is, this Displacement, for example, is not the same along the major axis xx and the minor axis yy. On the azimuths between other values can occur on these axes.

The indentation of the faceplate shows a maximum in Center of the faceplate and a minimum at its edges on. This is true along all azimuths, e.g. B. along the major axis xx and along the minor axis yy; the gradient the indentation is smaller along the main axis xx.

Figure 2 illustrates the axial asymmetry of the faceplate indentation. Lines JO, 3I, J2, 33 and J> k are lines of equal indentation. That is, the faceplate 16 experiences the same degree of indentation at all points of each of these lines 30 to ^ K during evacuation. Lines 30-j54-, each of which forms a closed curve, go from a generally rectangular shape near the edges of the faceplate to a substantially elliptical and then more circular shape in FIG

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Close to the center of the faceplate over. Because of the axial Asymmetry of the faceplate indentation is the required degree of the compensation explained with reference to FIG. 3 in a given distance from the axis AA at an azimuth, z. B. the major axis, larger than on another azimuth, e.g. on the minor axis.

To achieve the required axially asymmetrical compensation for To achieve the faceplate indentation, the phosphors will be used points of the screen 18 applied in a predetermined, axially asymmetrical, radially distorted arrangement Arrangement is made such that the center of a Phosphor point on an azimuth, e.g. B. the main axis XX, for a given distance from the central axis AA, further inward towards the central axis AA. away from the center of the path of its associated electron beam is arranged as the center of a fluorescent point at a different azimuth, ζ. B. the minor axis yy, at the same given distance from the central axis AA away from the center of the trajectory of its associated electron beam.

In the case of a perforated mask tube 10 with three electron beams Each shadow mask opening is a three of different colors assigned to emitting phosphor points.

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The luminous point arrangement is such that the center of a Leuchtpunktdreiers that a shadow mask opening on the Secondary axis xx at a given distance from the central one Axis AA is assigned, at a greater distance from .the central axis AA than the center of a Red dot three, which is a shadow mask opening on the Main axis xx is assigned at the same given distance from the central axis AA «,

The center of a luminous point threesome is understood to mean the center of an inner circle of the triangle at which Corners are the centers of the fluorescent dots of the threesome.

Fig. 4 illustrates a typical example of non-coincidence of the centers of deflection of the horizontal and vertical Deflection coils. The two curves according to FIG. 4 show that with increasing deflection angle of the electron beam the deflection centers of both the horizontal and the vertical deflection coils move towards the fluorescent screen, the displacement of, for example, the vertical center of deflection a lags behind that of the horizontal center of deflection to an ever increasing extent.

The relocation of the two distraction centers can occur in one typical yoke essentially up to an angle of for example 50 to 60 ° coincident and even up to a deflection angle of 70 ° only slightly non-

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be coincident. From a deflection angle of ¹ JO ⁰ £> is to. A deflection angle of 90 °, however, the degree of non-coincidence of the horizontal and vertical deflection centers grows rapidly, as in Pig. Λ is represented by -the two increasingly divergent curves running apart''.;. ; _{; t} - _v /

With some other typical yokes, there may be a non-steadily increasing non-coincidence, and that may be ^. horizontal center of distraction behind the vertical center of distraction. . -...-. _; .- ■ -— .- ■; - / _ -.,.: ./ .; : - _:, -

Since the known ^ shadow masks ^ cathode ray tubes ^ im. generally have no distraction greater than fO »-: become; ^ - ₇ these with essentially coincident deflection centers - ·; .. ^. drove. Therefore, in this one axial ^ ^ ^ syinmetrische -Ko ₁ Bj is pensation for the described displacement of the Ablenkzentren sufficient. Even if such a -symmetrisehe; Compensation even at a few ^ 0 °. Tubes are attached - especially when using a single yoke, with which only one, miKiinaie * _; ,. ■ Non-coincidence of the distraction centers occurs J so ^ required. one ^? optional compensation of the displacement of the ■ deflection centers along the central tube axis, often an a2cLalasymmetrical> radial distortion of the 'luminous point arrangement. tion. - - ^: - "■" - · '>":" ^ - ^; - ^: · ■■■ ... ^ 'v: ... ^: ;.: J. : ■ ...--. ;.: ■ :; - ,: ■ ■ .- .- .- _■: -----

Since the axiaX-asymmetrical · VerÄerrürig ^ the; both for

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Compensation for the indentation of a rectangular faceplate as well as the non-coincidence of the horizontal and vertical Serves deflection center, its nature consists in a radial displacement of the phosphor points, can the compensation in connection with or as a modification of the known, axially symmetrical, radial phosphor point offset be made. Accordingly, the light-refracting device (lens), the axially symmetric Has refractive properties to achieve an axially symmetrical, radial displacement of the phosphor points, modified in a new way or in optical series connection be used with a special new supplementary lens. An example of the first alternative the two embodiments of the invention are described below with reference to FIG.

In the following description of an embodiment of the invention are only the specific peculiarities an indentation of a rectangular screen door, a Non-coincidence of the horizontal and vertical center of deflection and the aforementioned axially symmetric, radial correction taken into account for a substantially axial displacement of the deflection centers. In practice, the Printing of the grid screen usually carried out other types of compensations, e.g. B. a compensation to correct an incorrect grouping of the fluorescent

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points of an individual threesome, caused by the use of dynamic forces of convergence, and the Compensation to correct a character with perspective foreshortening caused by the geometric position of the Electron emitter is caused opposite the central axis of the ears. (Compare e.g. the USA patent 2,885,935 by D. W. Epstein from May 12, 1959). If in the If a fluorescent screen is printed in practice, then the compensation described here is preferably different Compensations combined by either optically combining the desired refractive properties in the same lens or by using a plurality of different lenses in an optical daisy chain.

Fig. 5 shows an embodiment of an optical device, to achieve the desired axially asymmetrical Correction can be used. The optical device comprises a light collimator 36 and a refractor 37 which are optically connected in series.

According to the known photo-precipitation method, in which such a device is used, can initially a layer of photosensitized gel (e.g. with aaimonium dichromate sensitized polyvinyl alcohol) are sprayed over the surface of the faceplate 16, whereafter this layer is allowed to dry. Fluorescent material (e.g.

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silver-activated zinc sulfide) can be mixed with the gel before it Application to the faceplate can be mixed or applied to this after application of the gel. An ultraviolet -Iiichtquelie (not shown) lies behind the Collimator 36 and generates actinic light rays that from the tip of the collimator through openings in the shadow mask electrode 20 are directed to the photosensitized layer on faceplate 16. The through the openings of the shadow mask electrode 20 defined fluorescent "" Points are therefore printed photographically on the faceplate 16. The non-exposed part of the photosensitive Layer is dated by a suitable piitwicking process Faceplate washed off.

To facilitate the manufacture of the light refraction body yi , the compensation that is to be achieved by means of it can be analytically broken down into various components, as follows. j

The compensation to correct the caused by the shift The error caused by the centers of distraction can be divided into two components. The first component can consist of a relatively large, axially symmetrical, radially outward refraction, For example, to compensate for the shift in the distraction center that lags behind the other.

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143'7δ; 55--

. ■■ '.. ■■ .-. ■. ; - is - - ■. ·. ■■; ..-.- ■

In the example according to FIG. 4, this is the vertical center of deflection. A second component can be in a relatively small, consist of axially asymmetrical, outward refraction, which is the non-coincidence (that is, the difference of the displacements) of the horizontal and vertical center of deflection is compensated. This second refraction component points for a given distance from the central axis AA different values for actinic ones Rays that hit the screen on the major axis xx, and for those actinic rays that hit the screen meet on the minor axis.

The difference between the radially outward Refraction along these two axes usually increases (depending on the particular yoke) constantly with the distance from the central axis AA to and becomes such calculated that they are the non-coincidence of the horizontal and vertical center of deflection corresponds and thus this compensated. ■

Similarly, compensation can be used to correct the impression of the rectangular faceplate analytically can be broken down into two components »The first component can consist of an axially symmetrical, radially inward one Refraction that supports the screen support corrected along the azimuth which requires the least correction, that is, along the minor axis yy.

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f ■

The second component can consist of an axially asymmetrical, radially inward refraction, which is the smallest difference in child displacement along the azimuth Compensation and all other azimuths compensated. This second component is for a given distance from the central axis AA different for the actinic light rays that hit the screen on the main axis xx, and for the actinic rays that hit the screen on the minor axis yy. The difference between the radially inward Refractive index along these two axes depends on the particular faceplate of a cathode ray tube from and is calculated in such a way that the axially asymmetrical screen carrier compression when the tube is evacuated and compensates for this.

These four components of the above-described refraction compensation can be achieved by four separate, series-connected, optical elements can be achieved. Alternatively (these can be combined and with, for example, two or even a single optical element, e.g. B. the element 57 * be achieved.

As the overall result of combining these four refractive components an axially asymmetrical radial refraction is obtained, which is usually directed outwards, since the relatively large outwardly directed refractive

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- 20 -; ;.:. ■ '■' ■■ '. ■■

component that is used to compensate, the main shift in the both distraction centers is required proportionately is great. The refraction pattern, albeit axially asymmetrical, is symmetrical about two different planes, the contain the central axis AA.

Fig. 6 shows an embodiment of the light refraction body 37, with diametrical ßuerschnitte are shown along the aforementioned two planes at the same time. The cross-section 40 is taken along the diameter 4-1, which corresponds to the main axis xxj the cross-section 42 is taken along the diameter 43, which corresponds to the minor axis yy, each of these cross-sections 40 and 42 is symmetrical to the central axis of the refractive body 37 * but different From the other. The thinnest point 44 of the horizontal cross-section 40 is thinner and is closer to the edge 46 than the thinnest point 48 of the vertical cross-section 42 *. Consequently, the refraction along the major axis xx is different from that along the minor axis yy. Furthermore, the refraction along a radius at each azimuthal angle is essentially the same as the refraction along the radius at the opposite (i.e. offset by 180 °) azimuthal angle. Accordingly came be said ^e 5ie sum of the four components of refraction that in this case the radial refraction of the actinic rays, the screen surfaces on a pair of opposite azimuths

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meet, facing outwards (or inwards) is opposite the radial refraction of actinic rays, the screen surfaces on an angularly offset pair of meet opposite azimuths.

The summary of the four components into a single one Optical element can be achieved by mathematically taking the four necessary to correct the four components Integrated contours and provides a single optical element with this integrated contour.

A suitable way of determining the required contour of the refractive body j57 is to set up and operate a cathode ray tube which has not yet been corrected according to the invention and to check and measure the deviations between the phosphor points and theirs Pathogen rays occur. Such deviation values are determined at points systematically distributed over the screen area. Using usual mathematical calculations, which include the geometry and the optical conditions of the special tube, the deviation values irfc values for the contour of the refractive body yj are converted, so that the desired compensation, i.e. an overlap between the fluorescent points and the electron beams over the entire luminescent screen is achieved away.

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- 22 -. ■■■■■; ■; ■■

In terms of manufacture, the refractive body yj can be implemented with the calculated integrated contour according to the teachings given in U.S. Patent 2,885,852 by JA Briggs dated May 12, 1959.

The absolute size of the deviation values and thus the absolute Contour of the refractive body 37 depend on a Number of factors. Some of these factors are:

(a) -The distance between the luminescent screen 18 and the shadow mask electrode 20 / ^;

(b) the distance between the plane of deflection (i.e. the plane in which the distraction centers lying) and the shadow mask electrode 20,

(c) the distance between the centers of deflection and the central one Axis AA,

(d) the shape, size and structure of the faceplate 16 and

(e) the structure of the deflection yoke.

In one embodiment of the invention, referred to for a shadow mask -Ka thödens tr ahlr eyelets with 9O ⁰ and deflection of a rectangular, 63.5 cm faceplate 25BP22 RCA was as made is the refractive body 37 from

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a circular plate of optical quality glass with a diameter of approximately 25 cm. The thickness along the (vertical) minor axis yy changed in a gentle curve from 0.9525 cm at the center to a minimum thickness of 0.8981 cm at a distance of 8.89 cm from the center and up to a thickness of 0.914- 7 cm at the edge. The thickness along the (horizontal) main axis xx changed in a gentle curve from 0.9525 cm at the center to a minimum thickness of 0.87 ² JO cm at a distance of 10.16 cm from the center and up to a thickness of 0.9451 cm at the edge,

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Claims (12)

1. Evacuated cathode ray tube with a tube bulb approximately rectangular faceplate with main and secondary axis and with a screen of a plurality of phosphor dot triples which triples in a predetermined arrangement on the inner surface of the faceplate are applied; whose perforated mask is provided with numerous openings next to, but at a distance from the grid screen, each opening of the perforated mask being assigned a different threefold; and which has a plurality of electron guns which direct their electron beams through the shadow mask openings onto the phosphor dots, characterized in that the predetermined arrangement of the three is axially asymmetrically radially distorted _β 2. Cathode ray tube according to claim i, characterized in that the predetermined arrangement is such that before Evacuation of the tube (10) the center of a threesome, the an opening of the shadow mask (20) on the IT minor axis (yy) at a given distance from the central tube axis (AA) is assigned at a greater distance from the Axis (AA) lies as the center of a threesome, the one opening of the shadow mask on the main axis (xx) in the same way Distance from the axis (AA) is assigned. 6266-65 Pee / S 8098 11/0288 3 · Tube according to claim. 1, characterized in that the Grid screen (18) is such that before evacuation of the tube (10) the center of a at a given distance from the central tube axis (AA) "located fluorescent point (28) "is at an azimuth further inward from the center of the trajectory (25) of its associated electron beam than the center of an equidistant from the axis (AA) If it is located at a different azimuth away from the center of the orbit, its associated electron beam often lights up is so that when the tube is evacuated, the centers of both fluorescent points closer to the centers of their associated Electron beam paths are brought up by the axially asymmetrical indentation of the faceplate (12) 4-. Cathode ray tube according to Claim 1, characterized in that that the predetermined arrangement is such that before evacuation of the tube (10) the center of one on the major axis (xx) located phosphor point for any given distance from the central tube axis (AA) lies inwardly away from the center of the orbit of its associated ray than the ^ entrum of one on the plane axis (yy) located fluorescent point for the given axis distance away from the center of the path of its associated ray, so that when the tube is evacuated the centers of both Phosphor dots closer to the centers of their associated electron beam paths due to the axially asymmetrical indentation of the faceplate (12) are brought up. 809811/0288 ~ ⁵ ~ _ / * & U37K5 5. Cathode ray tube according to claim. 1, with a deflection yoke which, with increasing deflection angle, has an increasing non-coincidence of the vertical and horizontal deflection centers, characterized in that the shadow mask openings are arranged equidistantly along both intersecting axes (xx, jy) and that the fluorescent material is three-point in with the distance from the central tube axis (AA) increasingly larger distances lie along both axes (sex, yy), the increasing distances along one axis (xx or yy) being greater than the distances along the other axis, namely by Amounts by which the growing non-incidence of distraction centers is compensated. 6 · Cathode ray tube according to claim 1 with a deflection device, the one growing non-coincidence of the vertical and has horizontal centers of deflection with increasing deflection angle1, and with horizontal main and vertical Minor axis, dad-arch marked that the predetermined The arrangement is such that the center of a threesome, which is a shadow mask opening on the main axis (xx) at is associated with any given radius extending from the central axis (AA), at a further distance from the central axis (AA) '"lies as the ^ entrum of a threesome, that of a shadow mask opening on the secondary axis (yy) at the given, vcsn ^ ei * axis (AA) is assigned to the outgoing radius, and that the difference in the 809811/0280 '- M- - Distance to the amount of non-coincidence of the distraction centers "In the case of deflected electron beams" is referred to, so that they pass through the shadow mask openings mentioned "at pass through any given radius. 7 · Method of manufacturing a cathode ray tube according to Any one of the preceding claims, in which a light-sensitive screen is initially used to form the grid screen Layer is applied to the faceplate, which is exposed through the shadow mask, the actinic Exposure rays through a light reflector be broken, characterized in that such Light refraction device (37) is used, which deflects the exposure rays axially asymmetrically radially. 8 »method according to claim 7» characterized in _t that the light refracting means (37) at a given distance from its center, deflects the beam to a diameter line in relation to the beams on a angularly differently situated diameter line inward. 9. The method according to claims 7 and 8, characterized in that that the light refraction device (37) lies in the beam path in front of the shadow mask. 10. The method according to claims 7 to 9 _t characterized thereby- _ SZ __ 811/0288 net that the Lichtbre chungs device (37) so far deflects the rays inwards, thereby causing the outward displacement the faceplate points during evacuation ■ of the tube is compensated, whereby the deflection of the beams, corresponding to the displacement of the faceplate points, along the main axis (xx) greater than along the secondary axis Cyy) is. 11. The method according to claims 7 to 9, characterized in that that the light refraction device (37) deflects the rays so far outwards that this causes the different Shifting the horizontal and vertical Deflection center in the direction of the faceplate during operation of the tube is compensated, the deflection in the direction whose directionally associated deflection. dream is shifted the farthest, is greatest. 12. The method according to claims 7 to 11, characterized in that that a single light refraction body (37) is used, which causes a beam deflection, which at the same time from the faceplate indentation and the different Relocation of the distraction centers compensates for any resulting errors. 8098 1 1/0 288