CARRIER SUBSTRATE

Abstract: The invention relates to a carrier substrate (1) for carrying objects subjected to elevated temperatures, in particular for annealing processes as used in the manufacture of shadow masks for a cathode ray tube. By constructing the carrier substrate (1) with interengaging connection portions (5,6), no additional connection methods are required. This leads to a carrier substrate (1) with a shape which remains unchanged after many temperature cycles. The lifetime of the carrier substrate (1) can be further increased by constructing it from materials selected from the group of materials molybdenum, tungsten, austenitic steel, ceramics or alloys of nickel and iron.

Description: Carrier substrate. The invention relates to a carrier substrate for carrying objects subjected to elevated temperatures, the carrier substrate comprising at least a grid part and a border part. The invention also relates to a method of manufacturing a selection electrode for a color cathode ray tube, said selection electrode comprising a shadow mask blank having a pattern of apertures, the method comprising the steps of providing patterns of apertures in a steel foil, cutting mask blanks from the steel foil, and annealing a stack of mask blanks at an elevated temperature, in which annealing step a carrier substrate of the above-mentioned type is used. A carrier substrate for carrying objects subjected to elevated temperatures is known. In US 4,427,396 a carrier substrate is described for use during an annealing step of mask blanks. Several manufacturing steps transform the mask blanks finally into selection electrodes for color Cathode Ray Tubes. To facilitate the subsequent deep drawing and obtain a grain size for good magnetic screening by the shadow mask, an annealing process is carried out on the blanks. To this end, a stack of blanks is placed on a carrier substrate and subjected to temperatures in the range of 600 to 880 °C. It appears that the lifetime of such carrier substrates is limited due to permanent deformation of the carriers occurring after several temperature cycles. It is an object of the invention to provide a carrier substrate that has an improved lifetime. A first aspect of the invention is characterized in that the carrier substrate comprises elements that are interconnected solely by interengaging connection portions. Carrier substrates according to the state of the art comprise parts that are often connected to each other by welding or a similar connection technique. At elevated temperatures, the connection points appear to be sensitive to internal thermal stress, which leads to permanent deformation of the carrier substrate. The inventors have realized that internal stresses may be reduced by creating a connection without any additional connection means. An advantageous embodiment of the invention is defined by claim 2. This way of connecting elements to each other has proved to result in a rigid frame, which has as an additional advantage that the separate elements are easily replaced in case the frame needs to be repaired. A further advantageous embodiment of the invention is defined by claim 3. This embodiment has the advantage that a rigid frame is obtained in which repair may easily take place. A further embodiment of the carrier substrate according to the invention is defined by claim 5. This construction further improves the rigidity of the frame. An embodiment of the invention further provides a proper selection of materials, which have a high yield strength, if the carrier substrate comprises a material selected from the group of materials molybdenum, tungsten, austenitic steel, ceramics or alloys of nickel and iron. Good results were obtained. A second aspect of the invention provides a method of manufacturing a selection electrode for a color cathode ray tube, said selection electrode comprising a shadow mask blank having a pattern of apertures, the method comprising the steps of providing patterns of apertures in a steel foil, cutting shadow mask blanks from the steel foil, and annealing a stack of shadow mask blanks at an elevated temperature, in which annealing step a carrier substrate is used for carrying the shadow mask blanks, said carrier substrate comprising at least a grid part and a border part, characterized in that said carrier substrate comprises elements that are interconnected solely by interengaging connection portions. These and other aspects of the invention are apparent from and will be elucidated with reference to the embodiments described hereinafter. In the drawings: Figurel is an elevational view of a substrate carrier according to the invention; Figure 2 is a side view of a grid element according to the invention; and Figure 3 is an elevational cross-section of a border part of the carrier substrate according to the invention. In general, like reference numerals identify like elements. Figure 1 shows a carrier substrate 1 according to the invention, comprising a grid part 2 and a border part 3, which are interconnected solely by interengaging connection portions 5,6. The grid part 2 comprises grid elements 7, which are interconnected via interengaging connection portions of a first type 5. In this way, no additional connection methods, such as welding, are required for constructing the grid part 2 and it results in a carrier substrate 1 with a shape which remains unchanged after many temperature cycles. The lifetime of the carrier substrate 1 is further increased by constructing it from materials having a high yield strength. Good results were obtained with materials selected from the group of materials molybdenum, tungsten, austenitic steel, ceramics or alloys of nickel and iron. Figure 1 further shows an embodiment of the invention in which also the border part 3 comprises border elements 9 which are interconnected via sleeves 10. It is also possible to construct the border part 3 from a single piece. The carrier substrate 1 is designed in such a way that the substrates 1 may be stacked very easily. The border part 3 is provided with metal wires 22, which extend between two different sides to give the carrier substrate 1 additional rigidity. Figure 2 is a side view of a grid element 7 according to the invention. It comprises interengaging connection portions 5 of a first type consisting of sleeves 5. The grid elements 7 are interconnected solely by cooperation of the sleeves 5. The grid element 7 has a longitudinal direction and a widthwise direction. The grid element 7 comprises end portions 12 extending in the longitudinal direction, which are provided with holes 14 perpendicular to the longitudinal direction and the widthwise direction. Figure 3 is an elevational cross-section of a border part 3 of the carrier substrate 1 comprising interengaging connection portions 6 of a second type. End portions 12 of the grid elements 7 extend partly through sleeves 16 which are provided in the border part 3. Metal wires 18 extending through the holes 14 comprise bended end portions 20 for fixing the wires 18 to the carrier substrate 1. In summary, the invention relates to a carrier substrate 1 for carrying objects subjected to elevated temperatures, in particular for annealing processes as used in the manufacture of shadow masks for a cathode ray tube. By constructing the carrier substrate 1 with interengaging connection portions 5,6, no additional connection methods are required. This leads to a carrier substrate 1 with a shape which remains unchanged after many temperature cycles. The lifetime of the carrier substrate 1 can be further increased by constructing it from materials selected from the group of materials molybdenum, tungsten, austenitic steel, ceramics or alloys of nickel and iron. It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word "comprising" does not exclude the presence of elements or steps other than those listed in a claim.

Claims: CLAIMS: 1. A carrier substrate (1) for carrying objects subjected to elevated temperatures, said carrier substrate (1) comprising at least a grid part (2) and a border part (3), characterized in that the carrier substrate comprises elements (3,7) that are interconnected solely by interengaging connection portions (5,6). 2. A carrier substrate (1) according to claim 1, wherein the grid part (2) has grid elements (7) having interengaging connection portions (5) comprising sleeves (5) for connecting the grid elements (7) to each other solely by cooperation of the sleeves (5). 3. A carrier substrate (1) according to claim 1, wherein the grid part (2) has grid elements (7) having end portions (12) provided with holes (14), said end portions (12) partly extending outside the border part (3) via sleeves (16) in the border part (3), and said grid elements (7) and said border part (3) being interconnected by interengaging connection portions (6) comprising said end portions (12) and metal wires (18) extending through the holes (14). 4. A carrier substrate (1) according to claim 3, wherein said metal wires (18) comprise bended end portions (20) for fixing the wires (18) to the carrier substrate (1). 5. A carrier substrate (1) according to claim 3, characterized in that the border part (3), having sides, is provided with metal wires (22), each wire (22) extending between two different sides. 6. A carrier substrate (1) according to claim 1, wherein the carrier substrate (1) comprises a material selected from the group of materials molybdenum, tungsten, austenitic steel, ceramics or alloys of nickel and iron. 7. A method of manufacturing a selection electrode for a color cathode ray tube, said selection electrode comprising a shadow mask blank having a pattern of apertures, the method comprising the steps of : providing patterns of apertures in a steel foil, cutting shadow mask blanks from the steel foil, and annealing a stack of shadow mask blanks at an elevated temperature, in which annealing step a carrier substrate (1) is used for carrying the shadow mask blanks, said carrier substrate (1) comprising at least a grid part (2) and a border part (3), characterized in that said carrier substrate (1) comprises elements (3,7) that are interconnected solely by interengaging connection portions (5,6).

Inventors: MEIJER JAN P, VAN DER LINDEN PETRUS J C C, MEIJER, JAN, P., VAN DER LINDEN, PETRUS, J., C., C.
Applicants: KONINKL PHILIPS ELECTRONICS NV, KONINKLIJKE PHILIPS ELECTRONICS N.V.
Application year: 1999
Main classification: C21D9
IPC codes: C21D1, C21D9, F27D3, F27D5, H01J9