DE2363566A1 - CATHODE TUBE WITH SHADOW MASK - Google Patents

Description

US Serial No. 319 375
Convention Sate:
December 29, 1972

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

Cathode ray tube with shadow mask

The present invention relates to a cathode ray tube having an evacuated piston which is a Includes electron gun and an image window has, on the inside of which is a screen made of a mosaic of different fluorescent areas Emission colors is arranged, and with a shadow mask arranged in the bulb near the screen, which has two opposite major surfaces and has an array of perforations, one of which Go through the main surface to the other and are aligned with the Leuchtoffbereiehe.

Shadow mask cathode ray tubes of the above type are known and used as a television picture tube. The fluorescent areas of the mosaic are generally round spots ("dots ¹ *) and the electron gun generally supplies three electron beams which excite the fluorescent areas of the mosaic to emit also those that are luminous

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Contains areas of fabric of a different shape (e.g. stripes). The shadow mask has essentially the same shape like the usually spherically curved picture window. the The shadow mask is mounted on a heavier frame, which in turn is secured by springs attached to it Piston is supported.

When operating a shadow mask cathode ray tube, the electron beams scan a grid that is practically constant in shape and size. When the grid is scanned, parts of the slectron beams are intercepted by the mask, while other parts, which are to be referred to here as "small bundles", penetrate the openings of the mask and excite the desired phosphor areas. The energy of the intercepted parts of the electron beams heats the mask and causes the mask material to expand. At the beginning of the warm-up. period warms up the middle part "of the mask faster than both άβτ stalks ale also the edge parts of the mask. Bieg has SVX sequence _g that the mask bulges and their center part moves Aich toward the screen ^ while the distance of the edge of If the mask is heated unevenly ₉ SoB ₉ when reproducing a test image or another unchangeable image _{9 the} mask would become deformed have an unfavorable influence, so that misregistration occurs, ie some or all of the bundles

miss the fluorescent areas assigned to them * \

Part of the mask's warmth is caused by radiation

delivered to a black coating on the cone of the tubular piston. The screen generally contains a highly reflective thin® layer of metal, usually aluminum. The heat that is radiated forward from the Mask® in the direction of the screen

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reflected by the metal layer and the mask can therefore only transmit relatively little heat through radiation Hand over the screen. The insufficient heat dissipation through radiation to the screen can, as it is from the US-PS 3,392,297 is known, can be increased by the fact that the entire reflective layer is by vapor deposition and vacuum deposition with a top layer of a heat absorbing material such as lithium nitride, Boron carbide or nickel oxide coated. This top layer is intended to increase the speed of the radiation caused by the radiation Heat transfer between the mask and the screen can be increased. It is from US Pat. No. 3,703,401 known for the same purpose to spray a coating of coal particles on the entire screen. Farther it is known to use a temperature-compensating holder for the mask, the bimetallic elements or contains other devices to mask the assembly and move the frame towards the screen. However, such a bracket is only available during later stages the heating period is effective when the frame supporting the mask or the holder of the frame is heated will.

The present invention is based on the problem outlined above, caused by the Heating of the mask should be avoided, in particular protrusions and deformations of the mask and thus register errors to avoid.

This object is achieved by the in claim 1 characterized invention solved.

The subclaims relate to further developments and advantageous configurations of the subject matter of the patent claim 1.

In one embodiment of the invention, at least one of the major surfaces of the mask include and

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the inner surface of the screen areas that are selectively reflective, and areas that are are selectively absorptive to infrared radiation to allow faster heat transfer by radiation from the middle part of the mask than from the edge parts of the mask.

In certain embodiments of the invention one or more major surfaces of the mask and the phosphor screen each have dee to the heat transfer to improve a mean surface area which is colored dark and rough textured by radiation. The middle surface area is partially or completely surrounded by peripheral areas that are brightly colored or textured metallic and smooth in order to reduce the heat transfer through radiation.

The fact that surface areas are provided through which the heat from the central part of the mask more quickly As dissipated from the peripheral parts of the mask, it becomes the bulge or bulge of the mask decreased during the start of the warm-up period. By changing the shape and thickness of these areas accordingly dimensioned, the bulging and distortion of the mask and thus misregistration between the electron bundles can and the phosphor areas are very largely eliminated.

In the following, exemplary embodiments of the invention are explained in more detail with reference to the drawing; show it:

Figure 1 is a partially broken away longitudinal sectional view of a three-beam, three-color cathode ray tube with a shadow mask and a point grid fluorescent screen according to an embodiment of the invention;

FIG. 2 shows a diagrammatic plan view of the Sohatten, drawn on a smaller scale than FIG.

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mask of the drill according to Figure 1 seen from the screen side, wherein the location of surface areas can be seen that have a relatively greater absorption capacity and have a relatively greater reflectivity for infrared radiation;

Pigur 3 a scaled-down, dated beam generation system seen from plan view of the screen of the tube according to Pigur 1, the position of surface areas with relatively greater absorption capacity for infrared radiation and surface areas with relatively greater reflectivity for infrared radiation can be seen;

FIGS. 4 to 7 are plan views of various patterns of infrared absorbent and infrared emissive Areas for each of the surfaces of the mask, the screen and / or a funnel-shaped part of the Cathode ray tube can be used;

Figure 8 is a diagram with a family of curves showing the temperature changes over a 90 minute period shows continuous warm-up period at various points of a tube corresponding to FIG. 1, but in which all Surfaces of the mask and the screen are blackened evenly;

FIG. 9 shows a diagram in which the same family of curves as in FIG. 8, but with a different time scale and shown for the first five minutes of warming is;

FIG. 10 shows a diagram with two sets of curves, from which the mean displacements of the electron impact areas, calculated in the radial direction, with respect to the associated phosphor areas excited by them during the first time after the start-up of a stirrer according to the invention can be seen .

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example 1

In this exemplary embodiment, the invention is implemented in a right ok color television picture tube shown in FIGS. 1 and 2, which has an evacuated glass bulb 11 with a funnel-shaped part 13 and a front panel panel 15 , which consists entirely of a heat-absorbing material ₉ such as graphite particles in a silicone binder. The one end © of the funnel-shaped portion 13 merges into a IColbenhals 19 üb © r _p in the check beam generating system assembly 23 is ^ the three electron beams allows generate su, which are directed to a © BildscMrmanordnung on the opposite Since © dee glass bulb 11 = The Bildechirmaaord - ~ voltage contains © inen Istraineszenzsehim disposed on a glass-made display window 27 25p constituting an N- part d © s Prontplatteapanels 15 »the Lumineesenzsehim 25 consists essentially of a Yielsahl of red-emitting _p green-emitting and blue-emitting Leuchtetoffber @ ichen C "fluorescent -> ^{dots 89} ) E, B hmu G- ₅ - di © on the inner surface 29

essentially round and arranged in a regular, repeating pattern of triads or tripela consisting of three Isemehtstoffverbindungen§ - each triple contains a point ^ © d ©! ¹ Color emission characteristics On the arrangement of the outer fluorescent lamps there is a reflective layer 31 made of aluminum. The reflective layer 51 carries in its middle

33, as will be explained in more detail below. On the one facing the ray suction system Since the picture window 27 is aafei © m distance from the @aa © in © made of metal b © ei

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arranges the a plurality of substantially round openings 37 in a regular cyclical arrangement has one opening for each Fluorescent triplet. The size of the openings is graduated} the largest are located in the central part of the shadow mask 35 and the smallest in the edge areas of the Shadow mask 35. The shadow mask 35 is spot welded at various points along its edge connected to a frame 43. With that of the beam generating system arrangement facing side of the frame 43 is a magnetic shield 44 in the form of a hollow Welded truncated pyramid. The frame 43 »the magnetic shield 44 and that of the beam generation system assembly facing rear side 39 of shadow mask 35 are blackened. The one facing the luminescent screen 25 Front side 40 of shadow mask 35 is blackened and has a peripheral coating 41 made of vapor-deposited Aluminum metal delimiting a rectangular infrared emissive area in the central part of the mask, as will be explained in more detail below. The frame 43 is mounted on pins 45 by four springs, connected to the front panel. The perforated shadow mask 35 is so between Arranged beam generating system arrangement 23 and the image window 27, which during operation of the tube through each through Refraction 37 of the shadow mask 35 a bundle of each of the three electron beams or another angle passes through, so that the three bundles each have a different one of the three phosphor areas of a tripod of the luminescent screen 25 excite. One electron beam can therefore all emit red Stimulate fluorescent areas to emit light, the second electron beam excites all green-emitting fluorescent areas and the third electron beam all the blue emitting phosphor areas. The blue emitting Phosphor areas preferably consist essentially of silver-activated zinc sulfide phosphor.

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The green-emitting phosphor ranges are preferably made essentially of a zinc cadmium sulfide phosphor activated with copper and aluminum and the red-emitting phosphor areas preferably consist essentially of one activated with europium Iftbrium oxysulfide phosphor. Of course Instead of the phosphors mentioned, other phosphor compositions can also be used.

In the present example, the shadow mask 35 », which is made of cold rolled steel, is on both the the front side 40 facing the luminescent screen and blackened on the rear side 39, for example by controlled Oxidation of their surfaces. The infrared reflective Coating 31 of aluminum metal is applied to all peripheral surfaces of the front 40 of the Shadow mask applied, as shown in Figure 2, so that an infrared radiation is reflective Area results which surrounds a rectangular, infrared radiation absorbing area 47. In this embodiment, the luminescent screen carries the usual light (and infrared radiation) reflective layer 31 made of aluminum metal. A medium rectangular area the light-reflecting layer 31 has a coating in the form of the layer 33 of carbon particles, as in FIG Figure 3 is shown, so that an infrared absorbent layer formed by the layer 33 rich and an infrared-reflective peripheral region 49 surrounding the edge thereof remains. the the two infrared-absorbent areas, so the areas 47 and the layer 33 have approximately the same size and shape and they are close to each other. With a 63cm picture tube with a deflection angle of 110 ° the screen is about 38 cm high and 51 cm wide. The infrared absorbent layer 33 the luminescent screen 25 is about 25 cm high and about 38 cm wide, so that an edge about 6.5 cm wide

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Infrared reflective aluminum metal remains. The infrared absorbent area 47 on the dem The front side 40 of the shadow mask 35 facing the luminescent screen is also approximately 25 cm high and approximately 38 cm wide. Since the shadow mask 35 is somewhat smaller than the luminescent screen 25 », that is due to the coating 41 formed edge of infrared reflective material somewhat narrower. When the picture tube is switched on is, the electron beams heat the shadow mask 35, as was explained above by infrared radiation from the central area of the shadow mask 35 by the radiation from the warmer black central area 47 on the mask 35 to the colder black central area formed by the layer 33 dissipated on the luminescent screen 25. The coating 41 on the edge of the shadow mask 35 and the peripheral areas 49 of the luminescent screen 25, on the other hand, have a relatively high reflectivity and thus a relatively low emissivity for infrared radiation, so that there the heat transfer takes place more slowly. in the In comparison to the known "tubes", the edge areas of the shadow mask are heated here and the middle one Area of the shadow mask cooled. The shadow mask expands due to its coefficient of thermal expansion accordingly in the edge areas, whereby the center of the shadow mask is pulled in one direction, which is opposite to the bulging (i.e. away from the luminescent screen). Measurements have shown that the Migration of the shadow mask 35 in the direction of the luminescent screen 25 by up to 50 lim and the displacement the electron beam (measured at a distance between about 15 and 20 cm from the center of the screen) around up to. could be decreased about 50yum.

Example 2

In this embodiment it is a question of a tube, the construction of which is similar to that of the tube of the

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game 1 is the same except that the back 39 the shadow mask is not uniformly infrared • is absorptive, but absorbs infrared radiation and infrared radiation reflecting parts, which represent the mirror image of the figure in Figure 2 th arrangement. This is done by vapor deposition of a strip of aluminum metal on the edge parts of the Reached back of shadow mask. This means that the Beiepi ©! 1 described effects during the first time after Inb @ tri © bm®! »§ the Röhr® reached faster.

Example ?

In this example, the structure of the tube corresponds to the tube according to Example 2, with the exception that the magnetic shield 44 is missing and the inner surfaces of the funnel-shaped part 17 are not uniformly infrared-absorbing. Bonders, wearing a pattern of infrared absorbing and infrared reflecting parts. The projection of this pattern onto the image China is a mirror image of the surveyd illustrated in! Figure 3, when it νίΐτάο viewed in the direction of the longitudinal axis of the tube Man such a pattern can be obtained by that the ^. conductive coating 17 made of graphite replaced with an all-covering conductive coating made of vapor-deposited Aliailaip metal and applied to the middle part © © in © n the desired Pom ",

Allgem a considerations u n d ^ aging ative

The invention can be applied to all cathode ray tubes which contain a shadow mask and a mosaic screen. The mosaic can consist of narrow, continuous stripes or round, oval or rectangular patches ( ⁸⁸ IaBeIn ⁸⁸ ). from round areas or ^ dots ⁸⁸ are distributed in a large umfaag® al® color television picture tubesii

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In all embodiments of the invention, at least one of the surfaces of the tube that emits or receives infrared radiation bears a desired pattern of infrared-absorbing and infrared-reflecting surface areas. These surfaces are the two major surfaces or sides of the mask and the screen surface or side facing the screen side of the mask. The inner surface of the funnel-shaped part, which faces the rear of the mask, can also have such a pattern. For the purposes of the invention, an infrared absorbing surface is a surface that has relatively high emissivity and absorptivity. This results from the fact that by the radiation process made usable, heat is to be transferred by infrared radiation from the mask having the higher temperature to or through the bulb having the lower temperature, which results in a high emissivity for infrared radiation on the mask side and on the Side of the piston requires the presence of a good heat sink by absorbing infrared radiation.

A relatively high reflectivity for infrared radiation has a surface with a mirror finish, which is smooth, shiny and metallic. To a slightly lesser extent, high reflectivity can also be achieved with a Surface can be achieved that is smooth or light colored, preferably both smooth and light colored. in the Vacuum deposited aluminum layers are preferred. However, coatings made of aluminum oxide or titanium oxide can also be used or use magnesium oxide.

Rough and / or matt black surfaces have a relatively high absorption capacity for infrared radiation. Such surfaces also have a high emissivity for infrared radiation. To a somewhat lesser extent , a high absorption capacity for infrared radiation can be achieved with surfaces that are rough or dark-colored.

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big, preferably both rough and dark in color. The optimum absorption results when the thickness of the infrared absorbing material at least 10 # the wavelength of the emission maximum of a black Body is. At 80 ° C, which is above the normal operating temperature of a shadow mask, this wavelength is about 8440 nm. Black particle coatings from materials such as graphite, carbon, nickel oxide and black iron oxide are preferred. Dark colored materials that are brown, gray, blue, green, or purple in color can also be used. One can use vapor-deposition coatings such as those described in US patent mentioned above are described. If the material used allows it, as is the case with a ferrous shadow mask is the pail, the surface can be treated e.g. by controlled oxidation, so that it takes on a dark color. The surface can also be roughened, e.g. by sandblasting or other grinding methods and the like.

A wide variety of patterns of planar areas that are selectively infrared absorbing and infrared reflecting can be used. Pigures 2 and 3 show rectangular surface areas with rounded corners. In Pigur 4, a circular absorbent central region 53 is shown, which is arranged symmetrically in a reflective edge region surrounding it. Pigur 5 shows an absorbent sheet 55, which comprises the middle part as well as the upper and lower edge part of the plane under consideration and has symmetrical indentations for reflective edge areas 57 and 59 on its right and left sides. Pigur 6 shows a panel 61 of relatively high absorption capacity, which has symmetrical indentations on all four sides of the surface area under consideration for relatively good reflective surface areas 63, 65, 67 and 69. Pigur 7 is similar to Pigur 6

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with the exception that the boundaries between relatively good reflective surface areas 71, 72, 75 and 77 and a relatively well absorbing field 79 are formed in a zigzag shape.

Each of the patterns can be on one or more of the tube surfaces of interest here, that is to say in particular the inside of the luminescent screen 25, the Front side 40 of the shadow mask and the rear side 39 of the shadow mask are arranged. The inner surface of the funnel-shaped part 13 can also have such a pattern. If two or more of these surfaces Patterned can have the same or different sizes or same patterns different patterns can also be used. For example, the pattern according to Figure 2 can be used in conjunction with a similar but smaller pattern or in combination with the pattern according to Figure 4 and / or Figure 5 and / or use Figure 6 and / or Figure 7.

Both when used individually or in combination with other patterns, the overall combination in the tube represents the means to achieve a comparatively faster radiant heat transfer from the central part of the heated mask to the cooler surfaces of the screen and the funnel-shaped part and a comparatively slower heat transfer Ensure radiation from the edge parts of the mask. By appropriately shaping the pattern or patterns, it is possible to specifically influence the bulging or deformation that results from the expansion of the mask as a result of temperature changes.

The pattern or patterns used can be formed by having separate, adjacent surface areas or that one makes a complete infrared absorbing surface and then one

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"" ^u "23R3566

or by depositing several areas of infrared-reflecting material that cover the underlying surface, or by making a completely infrared-reflecting surface and then applying one or more areas of infrared-absorbing material that cover the underlying surface can be further modified by fraying, grading or allowing the infrared absorption and / or reflection property of one or more surface areas. This can be achieved through a running thickness of one layer length of the normal limit or through a border with interlocking areas ^ ^ ₀ Bo in a sawtooth or zig-zag shape «,

The pattern on the screen should preferably bring about a substantially uniform weakening of the electron beam is essentially the same for all points of the mosaic " Z ₀ B ₀ can be made thinner than elsewhere in the drilling" according to FIG. 1, the reflective layer 51 below the absorptive layer 33.

In figure, a family of curves shown 8.ist _s ferlauf the temperature in ° G at various points of the shadow mask (corresponding to the shadow mask 35) VB. & A point of the internal magnetic shield 44 during the first 90 minutes of power .for a The tube shows the same as the tube shown in Figure 1 with the exception that all internal parts are blackened evenly. Me curve 81 applies to various stables of the shadow 'mask, which is about 16 _S 5 em from the center are removed waae that Surre -85 applies to various sites of the

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Mask about 11 inches from their center. The curve 87 applies to several places on the inside of the tube inner arranged magnetic shield 44. Measurements were made with thermocouples that are equipped with were in contact with the measuring points. The differences in mean temperatures are transverse from the curves about the mask, the rapid temperature changes during the first five minutes of operation and the fact that even after 90 minutes of operation, no temperature equilibrium has been reached. The temperature differences and the rapid temperature changes cause the mask to temporarily throw itself, whereby a temporary displacement of the openings 37 with respect to the. associated phosphor areas of the luminescent screen 25 entry. Figure 9 shows the same family of curves 81, 83, 85 and 87 for the first five Minutes of operation of the tube.

FIG. 10 shows a family of curves 91, 92 and 93 which represent the displacement of the electron beam impact spots with respect to the associated phosphor range excited by them during the initial minutes of operation for a known tube, the one according to FIG except that the entire surfaces of the mask and the screen were blackened evenly was. The tube was operated with a white grid at 25kV and with 1500 microampere beam current. the Curves 91, 92 and 93 indicate the mean values for at least four points each, which are about 15 cm, about 20 cm or about 28 cm from the center of the luminescent screen (12 places in total). The measurements were made optically by viewing the excited phosphor areas through a microscope and the radial displacements of the edge of the excited area were measured with respect to the edge of the phosphor area. A shift from the center of the screen turned out to be positive away and as a negative a shift to

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" ¹⁶ " 7363566

Viewed from the center of the screen. Uneven displacements of the electron impact spots by more than 25 μm towards the center were found, which can be attributed to changes in the shape and position of the perforations 37 in the mask. Curves 95t 96 and 97 apply accordingly to the drill shown in FIG. 1 with the exception that the luminescent screen had a pillow-shaped pattern, as shown in FIG. 6, with the reflective surface areas 63, 65, 67 and 69 at their widest point were about 64 mm wide and the tails of absorbent material separating them were about 50 mm wide in the corners. Curves 95, 96 and 97 show that the selectively absorbing surface areas and selectively reflecting surface areas on the screen significantly reduce the displacement of the electron impact areas with respect to the phosphor areas.

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Claims (9)

" ¹⁷ '" 7363566 Claims (iy cathode ray tube with a one picture window having evacuated flask which contains at least one electron gun and an image window has, on the inside of which is a screen with a mosaic of different fluorescent areas Emission color is arranged, and with a shadow mask arranged in the bulb near the screen, which has two opposite major surfaces and has an array of perforations, one of which go through to the other main surface and are aligned with respect to the phosphor areas, thereby g e k e η η indicates that one and / or the other main side (39, 40) of the shadow mask (35) and / or the inner surface of the screen (25, 31) heat reflecting and heat absorbing surface areas (33, 41, 47, 49 ...) which cause the radiation of heat from the central part of the Shadow mask goes faster than from the edge parts of the shadow mask. 2. Cathode ray tube according to claim 1, characterized in that at least one of the main surfaces (39, 40) of the shadow mask (35) has a central part (47) which is able to selectively absorb infrared radiation, and edge parts (41), which selectively reflect infrared radiation. 3. Cathode ray tube according to claim 1, characterized in that the inner The surface of the screen and the main surface (40) of the shadow mask (35) facing it each have one middle part (33, 47) with a selective or relatively high absorption capacity for infrared radiation and surrounding edge parts (41, 49) with selective or relatively high reflectivity for infrared radiation. 409827/0744 " ¹⁸ " 23R3566 4. A cathode ray tube according to claim 1 _t wherein daß.die inside of the screen and facing this main surface (40) of the shadow mask (35) each having a central region and some marginal regions (55 '61, 79) which have a relatively high absorbance of infrared radiation , and remaining edge areas (57, 59, 63, 65 »71, 73) which have a relatively high reflectivity for infrared radiation. 5. Cathode ray tube according to one of the preceding claims, characterized in that that the infrared radiation absorbing surface parts for. the naked eye has a rough structure and have a dark color and that the infrared radiation reflecting surface parts for the unarmed Eye have a smooth structure and light color. 6. Cathode ray tube according to claim 1, characterized in that the Mosaic of fluorescent areas is completely covered by a reflective metal layer (31) and that at least on the central part of the metal layer Infrared absorbing cover (33) is located. 7 · .Cathode ray tube according to claim 1, characterized in that the two main surfaces (39, 40) of the shadow mask (35) in the are essentially completely blackened and that on the edge area parts of the screen facing Main surface of the mask is a reflective metal layer (41). 8. Cathode ray tube according to claim 1, characterized in that the mosaic BXLjs phosphor areas entirely with a reflect £ 09827/0744 ORfQiNAL INSPECTED - 19 - 7363566 Renden metal layer (31) is covered and that an infrared radiation absorbing black coating is only on the central part and all edge parts of the reflective metal layer located at the corners is located. 9. Cathode ray tube according to claim 1, as through characterized in that the mosaic of fluorescent areas entirely with a reflective Metal layer (31) is coated and that is only on the central part of the reflective layer an infrared radiation absorbing black coating (33) is located. 409827/0744 Blank page