MXPA99001244A - Shadow mask for colour picture tubes - Google Patents

Abstract

The invention relates to a shadow mask for colour picture tubes. The aim of the invention is to avoid to a large extent doming of the shadow mask, which is caused by the effect of electron beams. Inexpensive steel is to be used as the mask material. The shadow mask of the invention is characterized in that its cathode-side surface is provided with at least one heat insulating layer and with at least one heavy metal-containing covering layer, the heat insulating layer being arranged between the shadow mask and the covering layer and made of temperature resistant porous solid matters, and in that said layers contain a binding agent.

Description

SHADOW MASK FOR CATHODE RAYS TUBES FOR COLOR IMAGES DESCRIPTION OF THE INVENTION The invention relates to a shadow mask for a cathode ray tube for color images according to the preamble of claim 1. In a cathode ray tube For color images that have a shadow mask, the mask is placed in direct proximity to the inner surface of the screen. Because it is produced on the inner surface of the screen, the geometry of the shadow mask is required to conform to the luminescent segments when the cathode ray tube for color images is in operation. The maximum impact accuracy of the electronee rays in the luminescent segments is achieved when the aperture geometry of the shadow mask matches the distribution of the luminescent segments on the inner surface of the screen at the operating temperature. However since only a small portion of the emitted electrons passes the mask and collide with the mask directly, the mask as a result of this is heated to 80 ° C, increasing the change in the geometry of the mask which gives as a result the Accompanied in the form of dome of the marcara (effect doming). The geometry of the holes in the shadow mask no longer matches the model of the luminescence segments, REF .: 29384 resulting in an increase in inaccurate electron shocks. Losing quality in the reproduction of the colors of the screen. With a high contrast image, different areas of the mask will heat up at different levels, causing partial masking of the mask (local doming) which also results in image faults when the tolerance is exceeded. Various attempts have been made to limit or prevent such unfavorable thermal behavior of the shadow mask. Thus several measures have been suggested to limit the excessive heating of the mask. The U.S. patent 3,887,828 suggests placing a porous layer of manganese dioxide and a thin layer of metallic aluminum on top of the perforated metal mask. The aluminum layer has contact with the shadow mask only at the opening edge. It must have properties of electrical conduction and absorption of electrons. Placed as a coating on the top of the aluminum layer is another layer of graph, nickel oxide or nickel-plated iron. The porosity of the manganese oxide layer proposed herein is said to be eubstantially originating from the individually arranged particles, the layer being formed in a sandwich structure with the thin layer of aluminum.

Due to this layered structure, it is intended to keep away the heat generated by the impact of electrons, from the perforated metal mask and emit them in the opposite direction. This solution has several disadvantages. It has been shown that keeping heat away from the perforated mask has not been tested since most of the heat is not generated inside the aluminum layer and the euperior layer of graphite but in the perforated mask. The properties of reflection and electron ablation and heat emission of the aluminum layer are too low. The heat-insulating sandwich structure placed on top of the perforated mask now results in the opposite effect: Heat can be emitted only with difficulty. Patent document DE 3,125,075 C2 describes an electron reflecting layer coated directly on the shadow mask. This layer contains heavy metals, particularly in its carbides, sulphides or oxides. During the impact of the electron beam, up to 30% of the electronee can be reflected, which means that the shadow mask is heated menoe. However, most of the beam of electronee still reaches the shadow mask, increasing the undesirable generation in it and thus the general and local phenomenon of shading of the shadow mask. The U.S. patent 4, 671,776 suggests coating the shade marker with borate glass. The glass powder is sprayed onto the mask and subsequently deposited by fusion. In the operating conditions the effect of settling is reduced due to some thermal insulator but most of the forces are inside the mask that result from the different coefficients of expansion of the layer and the metal of the metal mask. With such a coating, hardly any reflective effects of electrons can be observed, so that a greater part of the energy of the beam of electronee that makes an impact is still transferred to the mask, increasing the deepening effect on it. In addition, the rigid fixing of the mask by means of a stable layer of glass can no longer meet the high requirements with respect to the quality of the color image in the age of multimedia. Other means of significantly limiting the phenomenon is the phenomenon of the use of high-quality ethalic alloys such as Invar for the shadow mask, because this alloy has a particularly favorable thermal expansion coefficient. However, this material is very expensive with respect to the cost. However, since the percentage of the cost of the shadow mask with respect to the total cost of a cathode ray of color images is already relatively high, the use of metal alloys will result in an additional increase in the number of coats.

The object of the invention is now to largely avoid the setting of the shadow mask caused by the action of electron beams, where low-cost steel is used as a mask material. The solution to this problem is obtained with the characterizing part of the claim. According to the invention, the cathode side surface of a perforated mask is provided with a heat insulating layer and in that layer a reflective and electrically absorbing layer is applied, as a top heat emitting layer. Some of the electrons are reflected while others are absorbed in the upper layer and transformed into heat, without the heat acting directly on the perforated mask, but being emitted into the cathode ray tube due to the arrangement of the layer heat insulator according to the invention. The local temperature differences also decrease so that it can promote the partial adjustment of the perforated mask. Esae differentiate from local temperature, particularly with high contrast images. The insulating layer of heat consists of temperature-resistant porous solids trapped in an adhesive agent. According to the invention, materials based on oxides, sulfides, silicon and / or aluminophosphates or mixtures of these materials are provided. Among others, silicic acid, zirconium dioxide and titanium dioxide are suitable as porous oxide materials. In particular, porous silicic materials include the vast group of zeolites. Particularly suitable are molecular sieves such as the natural molecular sieves chabazite, mordenite, erionite, faujasite and clmoptilol ta, as well as eolithic zeolites A, X, Y, L, ß and / or those of the ZSM type. There is such a wide variety of zeolite structures that all types can not be mentioned here. Surprisingly, it was found that the effective thermal insulation of the perforated mask can be obtained even with the application of thin layers on the mask. In the same way, advantageous results are obtained when using base solids and porous proteins such as the so-called aluminophosphates, silicoalummofoefates and metallic alummophosphates which can be produced by means of sintes e and ee classified by small, medium and large pore types. Other suitable porous solids are intercalated clay minerals, layered phosphates and silica gel as well as a variety of alummosilicates in the known ones. More specifically, the reflecting and electrically absorbing upper layer and heat emitter combined with the thermal insulating layer includes heavy metal compounds; here, particularly advantageous use can be made of the bismuth oxide and bismuth sulfide as well as lead oxide and lead sulfide, and oxide, tantalum, cerium oxide and barium titanate.

In particular, crystalline and vitreous silicates, phosphates and borates are provided as an adhesive for the upper layer and the heat insulating layer, the water glass and the low melting glass such as welder glass and metal phosphates being useful. The aforementioned adhesives are notable for their high adhesiveness properties both on the surface of the mask and between the layer, giving a coating with an extraordinary mechanical stability which gives as a result an additional dimensional stability of the perforated mask. The application of the layers is carried out in accordance with known methods of application, such as, for example, spraying on the surface of the mask and can therefore be carried out at favorable costs. The insulating layer of heat has a thickness of between and 50 μm with an average particle size of between l and 10 μm, while the chalcogenide layer of heavy metals is regularly used with a thickness of 1.5 to 4.5 μm. Below the heat insulating layer, the perforated mask can have a known blackening for example of Fe304. The advantages of the invention can be found in the marked improvement of the trend towards the setting of iron masks, making it possible in many cases to abandon the use of Invar costus for masks. The invention will now be illustrated in more detail with reference to the figures and various modalities. Figure 1: shows a cathode ray tube for color images in sectional view; Figure 2: shows a shadow mask in top vieta; Figure 3: shows a shadow mask in sectional view; Figure 4: shows a sectional view of a layer formation according to the invention; Figure 1 shows a cathode ray tube for color images consisting of a kinescope l with a screen 2 and a line of radiation 7 placed on the neck of the cathode ray tube 5 as the main components. The inner side 3 of the screen 2 has a structured luminescent which, as is known, generates an image as a result of the impact of an electron beam. A cone 4 of the kinescope l forms the union in a funnel shape between the screen 2 and the neck of the tube 5.

The neck of the tube 5 ends in a sleeve 6. The radiation system 7 includes multiple cathodes and other electrodes to generate and control the electron radiation. By means of a mask frame not shown in the figure, a shadow mask 8 is placed inside the interior 3 of the display 2. The high voltage (operating voltage 25-30 kV) is fed through an anode contact 9 . Figure 2 shows a part of the shadow mask 8 in top view, here referred to as a perforated mask 22.

The thickness of the perforated mask 22 is generally in the range between 0.130 to 0.280 mm within an etched tolerance. The models of the desired holes are engraved by chemical means. The formation of the shadow mask 8, which is required for the operation of the cathode ray tube, is carried out by deep drawing. To evaluate cathode ray tubes under bombardment of electron beams during the operation, the impact of electron radiation is examined. For this purpose, the affected areas of the perforated mask 22 are eroded, which is represented by the four measurement points 25 and the measuring points 24, 26 and 27. The drift due to the impact of the radiation caused by the heating of the mask under the bombardment of electronee ee a measure of the quality of the cathodic ray tube and finally a measure of the success of any measurement made to avoid the cathodic cathode tube assembly. The configuration of the perforated mask 22 is shown in Figures 3 and 4. The perforated mask 22 provided with engraved holes 33 has a blackened layer with Fe304 36. On the cathode side, the layer is coated with a heat insulating layer 32. The heat-insulating layer 32 is covered with an upper layer 34 of the metalee peeadoe chalcogenuroe. Due to the constructive design of the shadow mask 8 only a part of the electrons passes through the perforated mask 22 and reaches the luminescent layer. Most of the radiation of eiectronee strikes against the perforated mask 22. Due to the metal pee atoms preened in the upper layer 34, a minor part 40 of the reflected electron beams (approximately 30%), and the others They lose their energy in the upper layer, heating it. The heat insulating layer 32 prevents the heat from being transferred to the perforated steel mask 22, and the heat is emitted to the rear side, this being in the direction of the seventh of beams 7. The main component of the upper layer 34 is a Heavy metal caleogenide with a grain size below i μm. The caicogenuroe grains are fixed to the insulating layer of the lower heat 32 by means of conventional adhesive. According to the invention, the heat-treating layer 32 contains porous eolids, the porous material consisting in this case eubstantially of synthetic zeolite M: -O.AljOjXSiO; . and H: 0, which is a lauminium silicate containing an alkaline substance (M = metal ion). For example, zeolites with structural type A have a modulus value of x = 2 and aei contain 2 parts of SiO. to the part of A1203. In zeolite 4A the pore size is 0.4 nm and the pore volume is about 23%. A zeslite sold by the company Degussa under the trade name of WESSALITH P was used successfully. The grain size of the zeolite powder was between 0.5 and 9 μm with an average particle size D5C of 3.5 μm. The particle size was further reduced by means of a grinding process. The solidoe poroeoe were fixed to the base using water glass. By using water glass as an adhesive, good adhesion of the heat insulating layer 32 to the upper layer 34 can be obtained, and by using additives such as surfactants and water, the required wetting capacity of the sole can be compared with the application of the coating. A spray procedure proved to be a useful method for applying the heat insulating layer 32 and for applying the upper layer 34. The measurements of the operating life of the cathode ray tubes produced according to the invention showed a behavior comparable to those of the cathode ray tube without A / D shell. A comparison of the purity drift of ioe cathode ray tubes with an uncoated iron mask and the cathode ray tubes eo etides to the coating according to the invention, resulted in a substantially reduced purity drift for the coated masks. Thus, the purity drift was reduced to 50% of the value of uncoated mascarae. This is also a significant improvement over the purity drift of the masks coated only with B-Oj (30%).

In the measurements, the areas of lOxlOcm2 were swept with an electron beam at 270 μA and 24 kV in the critical regions of the tube; the remaining part of the screen does not succeed with electrode radiation. Embodiment Example 1: A perforated mask consisting predominantly of iron metal and provided on both sides with a layer blackened by Fe304 is coated on the cathode side with an insulating layer of the heat and an upper layer using two successive spray procedures. The first heat insulating layer placed directly on the mask and with a thickness of 20 μm, is produced by spraying a dispersion consisting of 20 partse of zeolite 4A, Na: 2 [A102), 2 (Si02) 12] .12H20 ( average particle size 2 μm), 5 partse of sodium silicate solution (5.8 M, Na / Si = 0.61: 0.1), 30 parts of water and 0.001 parte of a Deepuée eaufactant from the heat insulating layer in a stream of hot air, ee produces an upper layer with a thickness of 3 μ, when spraying in the heat insulating layer a consistent dispersion of 20 partse of bismuth oxide, Bi2o3 (average particle size 0.9 μm), 10 parts of solution of Sodium silicate (5.8M; Na / Si = 0.61: 1.0), 75 parts of water and 0.001 part of a eurfactant. After applying the upper layer spray, the mask is baked at a temperature of 300 ° C. Embodiment example 2: As in the embodiment 1, except that the heat insulating layer is produced by spraying a dispersion of 20 parts of mesoporous zirconium dioxide, Zr02 (average particle size 2.5 μm), 4 parts of tetrapropylate of zirconium, (C3H-0) 4Zr, 4 parts of tetraethoxysilane, (C2H; 0) 4S ?, pre-hydrolyzed with an alkaline substance, 20 parts of propanol, C, H, 0H, and 0.2 parts of water. Embodiment example 3: As in the embodiment 1, except that the heat insulating layer is produced by spraying a diepereión of 20 partse of Cf-zirconium dihydrofoefato, a-Zr (HP04) 2, it was thermally expanded in an eetabie with aluminum oxide A1: 03 and chromium oxide, Cr: 05. 2 parts of 80% foephoric acid, H3P04 and 40 parts of water.

Reference list 1 kinescope perforated mask 2 screen 24 measuring point J inner side 25 measuring point 4 cone 26 measuring point 5 tube neck 27 measuring point 6 cap 32 heat insulating layer 7 radiation radiation 34 upper layer 8 emerald mask 36 blackened layer with Fe304 9 anode contact 38 major part 40 minor part It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is the conventional one for the manufacture of the products to which the refers. Having described the invention as above, the property contained in the following is claimed as property:

Claims (14)

1. CLAIMS l. - A shadow mask for cathode ray tubes for color images, consisting of a perforated mask containing predominantly iron metal, which is fixed to a frame and placed in front of the screen formed, mask characterized by the side surface The anode of the perforated mask has at least one insulating layer of heat and when there is an upper layer containing a peeled metal being placed between the perforated mask and the upper layer and consisting of thermally stable porous solids and because the layers contain an adhesive .
2. 2. The eardrum according to claim 1, characterized in that the porous eolids are solids of oxides and / or silicon and / or foefates or mixtures of solidoe.
3. 3. The eardrum according to claim 1 or 2, characterized in that the oxides-based eolides are porous metal oxides such as titanium dioxide, zirconium dioxide, silicon dioxide, magnesium oxide and aluminum, and other oxides of eeg-group elements.
4. 4. The eardrum according to claim 1, characterized in that the silicon solids are zeolite, expanded clays and / or gel.
5. 5. - The shadow mask according to one of claims 1 to 4, characterized in that the foem solids are aluminum-phosphates, silicoaluminophosphate and metal alum-phosphates and metal phosphates such as zirconium phosphate.
6. 6. - The shade mask according to one of claims 1 to 5, characterized in that the top layer consists of a heavy metal composite and an adhesive.
7. 7. - The mask of eombra according to one of claims 1 to 6, characterized in that the compounds of metals peeadoe eon caleogenuroe, nitruroe and / or metalee peeadoe carbides.
8. 8. The shallow mask according to one of claims 1 to 7, characterized in that the heavier metal heavies of the upper layer are oxides and / or sulfides.
9. 9. The shade mask according to one of claims 1 to 8, characterized in that the heavy metal compounds are composed of black heavy metals or heavy metal mixtures.
10. 10. The eraser mask according to one of claims 1 to 9, characterized in that it is composed of peeadoe negroe and not negroe metals. The shadow mask according to one of claims 1 to 10, characterized in that the surface of the upper layer is blackened. 12. - The mask of eombra according to one of claims 1 to 11, characterized in that the compounds of heavy metal are compueetoe barium, lead, tantalum, biemuto, cerio or tungeteno. 13. - The shadow mask according to one of claims 1 to 12, characterized in that the adhesives are silicon and / or phosphate materials. 14. - The shadow mask according to one of claims 1 to 13, characterized in that the adhesives are crystalline metallic silicates and / or glass silicates, metal phosphates, metal borates and / or glasses.