DE2331535A1 - METHOD OF MANUFACTURING A SHADOW MASK FOR A CATHODE BEAM TUBE - Google Patents

Description

7Γο5 - To Ks / 80

HCA Ö4, ιΟ4

U.S. Serial No: 264.833

Filed: June 21, 1972

RGA Corporation
New York, NY, V. St. A.

Method of manufacturing a shadow mask for a cathode ray tube

The invention relates to a method for producing a shadow mask for a cathode ray tube.

Cathode ray tubes for color television purposes usually contain
a screen with red, green and blue emitting fluorescent lines
or - points, an electron beam system to excite the screen and a shadow mask between the beam system and the screen. the
Shadow mask is a thin sheet of metal which is placed in precise alignment near the screen so that the mask openings follow the fluorescent lines or points
Are assigned to the system.

The port development of color television tubes has so far mostly related to improvements of a type of tube in which the shadow mask
Contains round openings and the screen has fluorescent dots. As development progressed, however, various limits were reached beyond which such a "shadow mask tube"
Can hardly be improved any further. For example, if you have chosen the optimal size for the round openings in the mask in order to achieve a desired tube brightness with given tolerances of the screen, then the transmittance of the mask for the electron

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beam already set, and further improvements to the tube brightness were only possible by improving the fluorescent material, the beam system, the deflection yoke and the optical devices for printing the screen.

Recently, attention has been paid to a type of tube in which the shield has a line pattern and the shadow mask has its has flutes in the form of slits. Such "slot mask tubes" can have increased electron beam transmission and therefore bring a greater brightness than is currently possible with shadow masks with round openings. However, if you can then forms a slit mask in the same manner as is currently known for forming masks with round openings In the case of shadow masks with round openings, some problems, which are not to be taken seriously, gain so much weight that they can no longer be found can pass. For example, the edges of each slot opening must be much sharper than required for a round opening will. The reason for this is the electron scattering on the Rändex ^ n of the openings that are suppressed in a slit mask must be because with a slot the ratio of the edge length to the area is greater than with a round opening. Because of this different ratios lead to poorly formed edges of the openings in a slit mask tube rather to deterioration the image contrast than with a shadow mask tube with round mask openings. To reduce electron scattering in the case of slit mask tubes Keeping it low and thereby improving the image contrast is therefore the choice of a mask production process important, in which openings with sharp knife edges and very precise dimensions can be formed.

In the case of a slit mask, the slits are usually longitudinal and are arranged as rows or columns. Slits that are adjacent in the longitudinal direction are separated from one another by transverse webs separated, which hold the mask together. In order to get the maximum benefit from the slit mask, the area of this must

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Crossbars are kept small, so that the part of the electrons caught by the crossbars is small. For the normal For tube operation, the crossbars only need to be strong enough so that the mask is self-supporting. In the prior art, however, it is It is common to bring the mask into its final shape after the slots ofer openings have been formed. Therefore the transverse webs in the known masks had to be made sufficiently thick to withstand the loads during this shaping to withstand. The thick transverse webs of the known slot mask tubes, however, impaired the tube brightness and threw visible shadows on the screen.

The present invention is now a method of manufacture a shadow mask for a cathode ray tube, in which a relief pattern is embossed in a metal sheet to produce on the Sheet metal areas of lesser thickness compared to other parts of the sheet metal, whereupon these areas of lesser thickness are removed, to form openings in the sheet metal.

The invention is explained below using exemplary embodiments with reference to drawings.

Figure 1 is a side view of a color picture tube according to one Embodiment of the invention;

Figure 2 is a cross-sectional view along line 2-2 of Figure 1 and shows, partially broken away, the mask assembly the tube;

Figures 3-9 are cross-sectional views of tools and workpieces Figures 13 and 15 illustrate the step-by-step manufacture of a shadow mask in accordance with an embodiment of the invention;

FIG. 10 shows, on an enlarged scale, the bottom view of part of a first driving or embossing form according to a? other ex

design of the invention;

FIG. 11 shows, likewise enlarged, a partial side view of the form shown in FIG. 10;

FIG. 12 shows part of a shadow mask in a plan view, which is formed with the shape of Figures 10 and 11;

FIG. 13 shows, on an enlarged scale, part of that shown in FIG Mask from the side;

FIG. 14 shows an enlarged view of a part of a second Embossing form in a different configuration;

FIG. 15 shows, on an enlarged scale, part of that shown in FIG Embossing form from the side;

FIG. 16 shows an enlarged plan view of part of a shadow mask which has the shape according to FIGS 15 is formed;

FIG. 17 is an enlarged side view of that shown in FIG Mask part;

FIG. 18 shows, on an enlarged scale, the bottom view of part of a third Embossing mold according to a further embodiment of the invention;

FIG. 19 is an enlarged side view of that shown in FIG Part of the embossing mold;

FIG. 20 shows an enlarged plan view of two parts of a shadow mask as they are in the course of production by means of the shapes shown in Figures 18 and 19 appear at different times;

Figure 21 is a cross-section through the mask portions shown in Figure 20;

FIG. 22 shows, on an enlarged scale, the bottom view of part of a fourth embossing mold according to another embodiment of FIG Invention;

FIG. 23 is an enlarged side view of that shown in FIG Molded parts;

Figure 24 shows an enlarged plan view of two parts of a Shadow mask as it means there at different times of manufacture? shown in Figs Embossing shape look;

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FIG. 25 is a cross section through that shown in FIG Mask parts;

FIG. 26 shows an enlarged view from below of part of a fifth embossing form according to a further embodiment the invention;

FIG. 27 shows an enlarged side view of that shown in FIG Molding;

Figure 28 shows a plan increased eight to two parts S _o had mask, as they appear at different times of the manufacture by means of the embodiment shown in Figures 26 and 27 form;

FIG. 29 is a cross section through that shown in FIG Mask parts;

FIG. 30 shows an exploded view and in a perspective illustration a metal sheet used in mask manufacture;

FIG. 31 shows the sheet metal shown in FIG. 30 in perspective together with an embossing form;

Figures 32 and 33 show from the side and from the front that in the Figures 30 and 31 shown sheet metal during the Embossing process;

Figure 34 shows an enlarged plan view of a sheet metal shadow mask formed in FIGS. 30 and 31;

Figures 35 to 39 are enlarged cross-sectional views for illustrative purposes the step-by-step production of a perforated mask;

FIG. 40 is an enlarged perspective view of a part of the mask produced in accordance with FIGS. 35 to 39;

Figures 41 to 46 are enlarged partial views from above and from the top the side to illustrate the step-by-step production of the embossing form shown in FIGS. 14 and 15 ;

Figures 47 to 5I are enlarged partial top and front views the side illustrating the stages of another Production method of the embossing form according to Figures 14 and 15

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The color picture tube 4 ^Ü shown in Figure 1 consists of an evacuated piston 42, which has three parts: a funnel-shaped part 44, a neck part 46 and an end cap 48 'The end cap 48 contains a Fraabplatte 50, which is made on the inside with a screen 52 is coated in different colors emitting phosphors. An electron beam system 54 is arranged in the tube neck 46 and can send at least one, but preferably three electron beams through a magnetic deflection yoke 56 to the screen 52. The deflection yoke 56 can be acted upon in such a way that it deflects the electron beams for scanning the screen 52 in a rectangular grid.

The screen 52, which is shown in more detail in Figure 2, consists of a plurality of parallel fluorescent strips or lines 58. These Lines 58 can be arranged in such a way that glowing red, green-glowing and blue-glowing fluorescent strips on top of each other and this sequence is repeated cyclically. Preferred embodiments of the invention are set out below in connection described with such a line screen, but the invention also relates to embodiments with screens on which the phosphors individual points bildao.

To enable the color selection, a shadow mask is arranged within the end cap 48 at a close distance from the screen 52. This mask is therefore in the path of the one emanating from the beam system 54- Electron beams. The screen 52 is only hit by those parts of the electron beams that pass through the openings in the Mask 60 arrive. The dashed lines 62 indicate the maximum vertical deflection of the electron beams for that shown in FIG 90 ° v-rectangular tube.

For producing the shadow mask 60 according to the present invention a relief pattern is embossed in a metal sheet in order to reduce areas at the points provided for the mask openings Form thickness. The metal sheet is then treated, for example by etching, in such a way that the sheet metal material at the points

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reduced thickness disappears and openings or holes in the Sheet metal emerge. One of the advantages of this procedure is that that the metal sheet can be bent or otherwise shaped to the prescribed external shape of the mask before the metal material is removed at the points of reduced thickness. If the mask is deformed before the material is removed into the Areas of reduced thickness can in fact serve these areas to provide a certain mechanical strength during the deformation maintain. Since the crossbars have to absorb all the forces during deformation, they can be made thinner , whereby you can achieve maximum tube brightness.

A manufacturing method for a shadow mask is in the figures Illustrates $ through 9. According to. Figure 3 is a thin sheet of metal 70 placed on the flat surface 72 of an anvil 7 ^. Immediately above the metal sheet 70, an embossing form 76 is shown. The die 76 offered a plurality of raised portions 78 the places provided for the mask openings. The areas 80 between the raised parts 78 are recessed to form furrows to the To keep compression of the metal sheet 70 in these areas low and to create a possibility that the metal from the can flow away from the area 78 compressed zones. Everyone Raised area 78 is longitudinally of adjacent areas separated by small grooves 81. These grooves 81 serve to form the transverse webs in the mask, which make the mask self-supporting do.

Figure 4- illustrates the embossing process where the embossing die is has moved to uilen in order to emboss its pattern in the metal sheet 70. After the end of the stamping process, the mold 76 is raised again, and the embossed metal sheet 70 is removed. As shown in Figure 5, each raised area leaves 78 of the die 76 a recess 82 in the metal sheet 70. Below these recesses 82 are the regions 84 of minimal thickness of the sheet metal 70. The embossed sheet metal is then edged or machined to a

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To leave the pattern all around the edge, whereupon the sheet metal 70 into the desired mask shape is bent, as can be seen in Figure 6. · After bending, the embossed side of the sheet metal 70 can be completely be coated with a material in order to protect them during the subsequent etching processes, as for example in Figure 7 is shown with layer 86. This layer can be a protective lacquer (stop-off laquer) made from a suitably treated Irish glue be. The uncoated side of the sheet metal 70 is then uniformly etched until the regions 84 of the smallest thickness are complete have disappeared, as shown in Figure 8. The protective layer 86 is then removed so that the finished mask 70 'remains, where the depressions 82 have become the mask openings which are separated from one another in the longitudinal direction by transverse webs 83 are.

FIGS. 10 and 11 show part of an embossing mold 90 from below and from the side. As with the side view according to FIG. 11 can be seen, the pattern of the embossing die looks similar to one trimmed sawtooth shaft. The flattened vertices of the whales form raised areas 92, which lead to the later openings Form depressions in the sheet metal. Each raised area 92 is provided with slots 94- at longitudinally spaced locations, which represent the areas of the embossing pattern leading to the formation of the transverse webs.

A mask 96, which is made with the embossing form 90 according to FIGS 11 using the method described above is shown in Figure 12 in a plan view and in Figure 13 in a side view. The mask includes openings 98 at those locations which correspond to the locations of the raised areas 92 the embossing form 90, as well as transverse webs 100, which have been formed by the slots 94-.

Another embossing die 102 is shown in FIGS. 14 and 15. B _e i of this mold 102, the raised portions 104 that serve to form the grooves for the later openings on pedestals

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arranged, which form shoulders 108 running around the raised areas. The shadow mask 110 produced with such a mold 102 using the method described above is shown in FIGS. It can be seen that the shoulders 108 of the embossing mold form sections 112 of low material thickness all around the openings 114 of the shadow mask 110. B _e i of this particular embodiment of the mask are formed, the openings with straight vertical sides. The etching 2 bit is therefore much less critical for this mask 110 than for the mask according to FIGS. 12 and 13, because the width of the openings in the mask 110 remains constant over a longer etching period after the openings 114 have appeared once.

A modification of the embossing form shown in FIGS. 14 and 15g © is shown in FIGS. 18 and 19. This modified embossing die 116 contains base 118 with two steps or shoulders 120 and 124 ·. This pattern of the embossing mold is particularly suitable for the manufacture of color tubes of the known type, where a partial finished mask with initially narrow slits is used to set and print the tube screen, whereupon after finished, position of the screen a larger slot width for the tube to be inserted into the finished tube. Mask is created.

FIGS. 20 and 21 show the shadow mask 128 produced with the embossing die 116 according to FIGS. 18 and 19. Part A of FIG Figures 20 and 21 show the shadow mask 128 after the first step of the etching process, where the tube screen is formed serving narrow slots 130 are present. Part B shows the same mask after a second step of the etching process, where the Slots 132 are formed as used in the finished tube will. It can be seen that the first etch uniformly removes the metal from the uncoated side of the mask and can be terminated at any time after the narrow slots 130 are open but before the furrows forming the wide ones To define slots 132 are reached. The protective varnish is then removed from the mask, and the mask is inserted into the front

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plate of a cathode ray tube used. Then you use the well-known exposure process in the light house, defining the fluorescent screen of the tube. If the Is shielded, the embossed side of the mask is in turn with coated with a protective lacquer, and the mask is subjected to a second etching. This etching process can be ended at any point in time at which the wide slots 132 are reached, but the slot shoulders are etched away. To maximum strength To achieve the mask, it is advantageous to finish the second etch shortly after opening the wide slits.

FIGS. 22 and 23 show another embossing form 134 from below or from the side. This embossing form 134 also supplies a mask openings in polygon shape for use in a cathode ray tube, whose screen has a point-like fluorescent pattern. The pattern of the die 134 · has a plurality of hexagonal Pedestals 136, on each of which a hexagonal raised part 138 is seated. The mask 14-0 formed with this embossing die 134- is shown in Figures 24- and 25. Part A of these figures shows the shadow mask after a first etching process in which the openings used to form the tube screen 14-2 can be created. Part B of the figures shows the same mask after a second etching process in which the openings 14-4- used in the finished tube are created.

An embodiment of the invention relating to cathode ray tubes is used, the screens of which have round fluorescent dots, is illustrated in FIGS. 26 to 29. The pattern of the embossing form 14-5 used here has a large number cylindrical base 14-6, on the £ of which there is a small raised cylindrical part 14-7 is located. The mask 14-8 produced with the embossing form 14-5 can be seen in FIGS. 28 and 29. Part A of FIGS. 28 and 29 shows the shadow mask after a first etching process in which small openings 14-9 are created will. The mask with these small openings is then inserted into the faceplate of a cathode ray tube and is used

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to form a dot screen. Then the mask is back removed from the front plate and etched a second time, resulting in the large openings 14-9 a, as they are in part B of the figures 28 and 29 can be seen. The now equipped with the large openings The mask is then reinserted into the front panel and serves as a finished shadow mask when the cathode ray tube is in operation .

Yet another embodiment of the invention is shown in the figures 30 to 34- illustrated. Figures 30 and 31 show once pulled apart and assembled once a layer arrangement 150 consisting of two metal sheets I52 and 154 · and one Multitude of intervening parallel wires I56. The layer arrangement 150 can be manufactured by a rolling process by wires 156 of suitable diameter between two metal sheets 152 and 154- laying the sheets together, so that the wires are compressed and embedded between the metal sheets when the layer arrangement 150 is rolled thinner.

The panel 150 stacked together in this way is then embossed by means of a mold 158, the pattern of which consists of raised elongated parts 160 and grooves 161 therebetween. Each of these raised parts 160 forming a groove in the panel I50 that may become a S _c hlitz in the finished mask. Figure 31 shows the die 158 in a raised position above the panel 150, and Figures 32 and 33 show two views of the die 158 and 15. of the sheet I50 during the embossing process. Each raised elongate portion 160 is crossed by incisions or grooves 159 which prevent deformation of the embedded wires during the coining process.

During the coining process, the raised portions 160 of the die I58 press against the metal between the wires I56. Through this some of the metal just below the raised areas 160 is compressed and the excess metal flows in the recessed longitudinal areas 161 of the die. In this State, the table I50 has a large number of elongated

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rich reduced thickness, each of which is longitudinally divided by wires 156. Laterally, the rows or columns "of the areas of reduced thickness are separated by longitudinally extending strips, as the actual body forming the mask.

After the embossing process, the whole board is brought into the correct shape and etched until the areas with the smallest Thickness are removed. The material of the wires 156 is chosen so that it is not attacked by the etchant. The completed mask 162 is shown in FIG. 34-. The mask consists of par all elaa metal strips 164- which are hewn together by transverse parallel tie wires 156. In this embodiment, the transverse binding wires 156 may be thinner than the transverse binding wires the previously described embodiments, if the binding wires 156 are made of a suitably strong material.

Another mask structure is illustrated in FIGS. 35 to 4-0. FIG. 35 shows a metal sheet 170 which has been embossed in such a way that it has a plurality of elongate parts 174 with triangular cross-section, which is reduced by areas I76 Sheet thickness are interconnected. The sheet metal I70 will then formed into the correct shape, i.e. bent into the shape of a mask as shown in Figure 36, and onto the apex a plurality of wires 178 are welded to each of the triangular portions 174- as shown in FIG. Then a protective material 180 is layered over the wires 178 and the embossed side of the sheet 170 (see Figure 38), and the sheet areas 176 of reduced thickness are etched away (see Fig. 39). The resulting mask 182 shown in Figure 4-0 consists of a plurality of parallel triangular strips 184-, which through a plurality of wires I78 welded onto each strip are held together.

With the help of the manufacturing process described above many different forms of mask construction are possible, including some are described below. An important tool

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The embossing mold, which is designed as an embossing roller and together with a smooth roller, is used to form all mask shapes can represent a roller gear in a rolling mill.

A preferred method for producing the in Figures 14- and 15 is illustrated in FIGS. 4-1 to 46. Figures 4-1 and 4-2 show from above and from the Side a steel plate 190 with a multitude of them thereon parallel strip 192 of photoresist (photoresist). The middle of each Strip 192 is arranged to hold together with the intended location of a raised portion of the die. The areas 194 between the photoresist strips 192 are then etched away (See Figure 4-3) to form a plurality of parallel ribs 196. The photoresist pattern 192 is then removed and a different pattern of photoresist strips 198 (see Figures 44 and 4-5) is applied to the top of the ribs 196. As shown, each photoresist strip 198 covers only a central portion of the respective one The rib and each strip 198 has several interruptions 199 · The contour is created on the plate 190 by a second etching process of the embossed pattern, as indicated by the dashed line in Figure 4-6. After removing the photoresist pattern 198 the embossing mold 102 is ready.

Another method for producing the embossing mold 102 shown in FIGS. 14 and 15 is illustrated in FIGS. 4-7 through 5I. This procedure is simply the reverse of the preferred procedure just described. FIGS. 4-7 and 4-8 show, from above and from the side, a steel plate 200 with a first photoresist pattern 202 thereon. The pattern 202 covers those areas 104 - of the steel plate which are later to become the ribs 104 - of the embossing mold 102. After the pattern 202 has been applied, the surface of the plate 200 is lightly etched to form a plurality of sockets 204 and shallow depressions 206 (see FIGS. 4-9). After this first etching, the resist pattern 202 is removed, laundri the surface of the plate 200 is supplied with a

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A plurality of parallel photoresist strips 208 are provided. Each strip 208 completely covers a base 204 and extends slightly beyond the sides of the base. The surface of the plate 200 is then etched a second time, so that between grooves 210 are formed in each of the bases 204. This second manufacturing process for the embossing form 102 is then completed by cutting the second photoresist pattern consisting of the strips 208 removed.

If the embossing form is produced by means of etching, it is important that the photoresist is completely free of defects. A pore in the Photoresist can, for example, result in the embossing form being etched in the wrong places. A mending such by Pores of defects? is difficult and there is a risk that the repaired area will not be nearly as good in use withstands like the one originally used to manufacture the embossing mold Stole. This problem of durability of mended Spot is especially serious when there is a pore on the edge of a plinth. For this reason an additional one is preferred Testing of the flawlessness of the photoresist pattern carried out. The flawlessness of the photoresist pattern can be checked, for example, by that one tries to apply a metal of a contrasting color such as copper to the workpiece coated with the photoresist plate. If the photoresist has pores, then the metal underneath is exposed in these places, and the metal with the contrasting color precipitates in these open areas, whereby the location of the pores is visibly indicated. The pores localized in this way can then be repaired before the process continues.

The embossing forms according to the invention can also be very precise mechanical processing can be produced. Each embossing form can either be a flat, uniform plate or a cylindrical one Be formed roller.

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Details of two embodiments of the Invention described.

Example I.

A first manufacturing process for a mask begins with a metal sheet of, for example, about 0.15 now being _{pressed in a} rolling mill between a smooth roller and a special embossing roller with a relief pattern on it. The relief pattern can, for example, have the shape shown in FIGS. 18 and 19, an embossed pattern of longitudinal furrows being created in the sheet metal. The bottom of the grooves is quite thin (about 0.038mm thick) because the metal will flow during the coining process.

The embossed sheet is then annealed and then spherically curved. So that the curved sheet a further shape changes Opposes the greatest possible resistance, the glow is preferably carried out only with a minimum intensity that is just sufficient to. to prevent the sheet metal from tearing during the arching process »

After this shaping (arching), the entire embossed side of the sheet is coated with a protective varnish, and the uncoated side of the sheet is etched evenly with a suitable etchant such as chlorine iron. At least 0.038 mm of this uncoated side is removed to avoid the thin Completely remove areas of the metal sheet. After the etching, the protective lacquer is removed, for example by peeling off or washing off with the aid of a suitable solvent, so that the finished mask remains. Further measures, such as blackening the mask. and welding the mask to a frame can then be carried out according to the known methods. If a second etch is necessary, as described above, the convex embossed side of the mask is again provided with a protective lacquer (after the mask has been used to form the screen) and the ^ri aske is etched a second time. This etching is preferably carried out on the mask attached in the frame in order to ensure the correct alignment.

'' ferric chloride ' ¹

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position of the mask to the screen.

Example II

A second method of mask production uses a plurality of wires between two metal sheets (e.g. 0.076 mm thick), and the two sheets are rolled in a rolling process layered together to create a good bond. The wires can have a diameter of 0.05 to 0.1 mm and exist made of a material which is resistant to the etchant used in the subsequent process steps. Using When using chlorine iron as the etchant, the wires are preferably made of titanium or a titanium alloy. The layered together Metal sheets are then embossed with a stamping mold, for example with the shape shown in FIG. 31, in order to make furrows perpendicular to form the embedded wires. Next, the embossed laminated core is spherically arched and then annealed. After that the curved and embossed laminated core is etched with a suitable etchant such as chlorine iron to create the final mask to obtain.

^ aby that an embossing process takes place during the production of the mask, the mask openings get knife edges and exact dimensions. The transverse webs formed have uniform surfaces and can be made as thin as possible, i.e. as the requirement for mechanical strength allows. As the locations of the mask openings are solidified by the embossing process, the mask can be given its final form before the areas of reduced sheet metal thickness are removed Be brought into shape. This means that the metal sheet can be deformed into the final mask shape when the embossed Sheet metal has the greatest strength. This allows a much thinner design of the transverse webs than if these transverse webs would have to absorb the entire mechanical load during the deformation.

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In addition to the increased transmittance and reduced electron scattering the embodiments of a shadow mask described above have still further advantages. For example, the diminished Thickness of the transverse webs contributes to the fact that so-called moiré is low to keep. The moire is an interference pattern that is visible on the television screen in the form of alternating light and dark bands, which often resembles a wood grain. This phenomenon is caused due to fluctuations in the proportion of the Electron beams when the spacing and phase of the scanning lines changes. With the minimum thickness of the horizontally extending The visible moiré therefore remains minimal across webs of a mask.

It should be noted that in all embodiments of the mask the mask parts lying between the rows of openings slope down towards the hands of the openings or are beveled. This ensures that the electric rays in everyone any angle of deflection cannot be deflected away from the mask after it has passed through the mask openings.

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Claims (1)

Claims Method of manufacturing a shadow mask for a cathode ray tube, characterized in that a relief pattern (78) is embossed in a metal sheet (70) in order to be in the metal sheet To form areas of reduced sheet metal thickness (84 ·) compared to other parts of the sheet metal, and that these areas of reduced sheet metal thickness are removed so that openings (82) arise in the sheet metal at these points. 2. The method according to claim 1, that the metal sheet (70 ') is formed into the desired mask shape before the areas are reduced Sheet thickness can be removed. 3. The method according to claim 1, characterized in that the Areas of reduced sheet metal thickness (84) are removed by etching. 4. The method according to claim 1, characterized gekennaeä-chnet that the relief pattern has elongated and arranged in parallel rows depressions (82), the longitudinal directions of which in the direction of the Rows run, and that each well of adjacent wells in the same row is separated by raised webs ($ 8), and that the depressions are the areas of reduced sheet metal thickness represent. 5 · The method according to claim 4, characterized in that each Recess (114) of the relief pattern shoulders (112), which run parallel to and next to the sides of the recess and have substantially the height of the raised webs. 6, method according to claim 1, characterized in that the Relief pattern has first depressions (130), which the loading 309883/1053 represent rich reduced sheet thickness and in parallel. Rows are arranged, in the direction of which they are elongated are J and that the relief pattern has second elongated depressions (132) superimposed on the first depressions and are wider than these and form areas of medium sheet thickness; and that both the heirs and the second depressions are separated from adjacent depressions in the same row by common raised webs. 7. The method according to claim 6, characterized in that the relief pattern has shoulders that are parallel to and adjacent to each Long sides of each of the second depressions (132) run and substantially the same height as the raised Have bridges. 8. The method according to claim 6, characterized in that the metal sheet after removing the areas of reduced sheet thickness at least ao is etched until the areas are medium. rer sheet thickness have been removed and thus enlarged openings have arisen in the sheet metal. 9. The method according to claim 1, characterized in that the Relief pattern an arrangement of essentially -round depressions (149), which represent the areas of reduced sheet metal thickness. 10. The method according to claim 1, characterized in that the Relief pattern an arrangement of polygonal depressions (142) has, which form the areas of reduced sheet thickness. 11. The method according to claim 1, characterized in that the metal sheet (I50) consists of two layers stacked on top of one another (152, 154) consists of metal, between which there are a multitude of spaced parallel wires (156) and that the areas of reduced sheet metal thickness between these wires be shaped. - 3 -309883/1053 2331 - 3 5 12. The method according to claim 11, characterized in that the Relief pattern has depressions which are arranged in parallel rows and the areas of reduced sheet metal thickness form. 13. The method according to claim 11, characterized in that the Relief pattern elongated and the areas of reduced sheet thickness representing depressions in parallel Rows are arranged and, respectively, in the direction of these rows and perpendicular to the wires are elongated, and that adjacent Depressions in, "each row through formed in sheet metal Ridges are separated, which contain the wires. 14. The method according to claim 1, characterized in that the relief pattern is elongated and the areas are reduced Has depressions (176) representing sheet thickness, and that before the removal of these areas of reduced sheet thickness a A plurality of wires (178) is applied to the metal sheet perpendicular to the direction of the elongated depressions. 15. The method according to claim 1, characterized in that the relief pattern has first depressions (I30, 142, 149) which Forming areas of reduced sheet metal thickness with the thinnest sheet metal thickness, and second depressions (132, 144, 149a), which form the first Depressions are superimposed and are wider than these and form areas of medium sheet thickness; and that both the first and also the second wells of adjacent wells in Each of the same row are separated by common raised webs in the sheet metal. 16. Shadow mask for a cathode ray tube, characterized in that that they according to a method according to claims 1 - I5 is made. 309883/1053 44. Blank page