Color cathode ray tube

Abstract: A color cathode ray tube comprises a vacuum envelope including a substantially rectangular faceplate having a first axis and a second axis perpendicular to the first axis and a plurality of necks opposing the faceplate. A plurality of electron gun assemblies are located in the necks, respectively. A phosphor screen is formed on the inner surface of the faceplate and includes a plurality of continuous segment regions scanned with electron beams emitted from corresponding ones of the assemblies. A mask member is located in the vacuum envelope and has a plurality of effective regions through which the electron beams pass. A plurality of effective regions are formed into a plurality of groups.

Description: The present invention relates to a color cathode ray tube, and more particularly to a color cathode ray tube of multineck structure. A color cathode ray tube has been used as a typical display device, in which a fluorescent screen in a vacuum envelope is scanned by electron beams and an image is displayed on the screen, for a high definition broadcasting device or computer terminal high resolution graphic display device. For these applications, increased resolution has been an issue. High resolution in a color cathode ray tube can be achieved by minimising an electron beam spot on its screen. In conventional tubes, there have been improvements of the structure of the electrode of the electron gun assembly, which is the electron beam generating source, enlarging the diameter of the electron gun assembly itself and elongation thereof, but they are not completely satisfactory. The main reason lies in that the distance between the electron gun assembly and the screen becomes longer as the diameter of the tube, i.e., screen size, becomes large, so that magnification of the electron lens becomes too large. In other words, in order to achieve high resolution, it is important to shorten the distance between the electron gun assembly and the screen. For this purpose, the tube is designed as a wide angle deflection tube. However, in such a tube, the magnification at the center region of the screen differs from that at the peripheral region thereof. In order to solve the above problem, Japanese Patent Disclosure JP-A-48090428 describes a multi-tube structure display device having a plurality of small or medium cathode ray tubes arranged in the horizontal or vertical direction to display an image on a large screen with high resolution. A conventional display device of the multi-tube structure can be effectively used outdoors to display an image on a very large screen divided into blocks. However, the display device is not suitable for a medium screen size, i.e., about 1 m (40 inches), since the joint of the divided blocks of the screen stand out and result in a poor image. In particular, when this display device is used as a computer-aided design graphic terminal, the presence of joints becomes a device shortcoming. In addition, United States Patent No. US-A-3071706, Japanese Utility Model Publication JP-A-39254641, and Japanese patent publications JP-A-42004928 and JP-A-50017167 describe multi-tube structures in which a plurality of independent tubes are integrated into a screen. However, in such a tube, when a screen is dividedly scanned into a plurality of segment regions, rasters in the adjacent segment regions overlap each other at their boundary or have a blank therebetween and result in a poor image. In order to solve the above problem, EP-A-201098 describes a color cathode ray tube having a multineck structure according to the prior art portion of claim 1. As shown in Figure 1 of the accompanying drawings, the color cathode ray tube comprises a vacuum envelope having a single faceplate 1, on which a phosphor screen 2 is formed, and a plurality of necks 3a, ...3d. A plurality of electron gun assemblies 4a, ...4d are respectively received in necks 3a, ...3d. Phosphor screen 2 is defined by a plurality of continuous segment regions each of which is scanned with electron beams 5R, 5G, and 5B from a corresponding electron gun assembly,. A shadow mask 6 is located in the panel and faces the screen 2. The shadow mask 6 has a plurality of effective row and column regions 7 corresponding to the segment regions and a non-effective region 8 for surrounding and partitioning the respective segment regions. A plurality of deflection units 9a, ... 9d, generating deflection magnetic fields, are respectively mounted in the vicinity of the electron gun assemblies 4a, ... 4d to deflect the electron beams 5R, 5G and 5B. Generally, in a color cathode ray tube with a shadow mask, only 30% or less of the electron beams originally emitted by the electron guns pass through the apertures formed in the shadow mask. The remaining 70% or more of the beams impinge on the shadow mask, which is, in some cases, heated. As a result, the shadow mask thermally expands and deforms. When it deforms, landing error occurs and color purity is degraded. In conventional color cathode ray tubes with one phosphor screen and one electron gun assembly, deformation of the shadow mask is symmetric about the center of the phosphor screen corresponding to the center of the shadow mask. In order to correct landing error, there has been used means for adjusting the distance between the mask and screen in response to the temperature of the shadow mask and the mask frame. In the color cathode ray tube of multineck structure, as mentioned above, deformation is symmetric about the center of the shadow mask, similar to conventional tubes. As a result, the direction of deformation of each effective region against the corresponding segment region is different in accordance with its position in the shadow mask. Therefore, compensation of landing error as used in the conventional tube is not useful in this type of tube. It is an object of the present invention to provide a color cathode ray tube having a multineck structure and having advanced characteristics to prevent landing error. According to the present invention a color cathode ray tube comprises a vacuum envelope including a faceplate having an inner surface and a first axis and a second axis perpendicular to the first axis, and a plurality of necks opposing the faceplate; a plurality of electron gun assemblies located one in each of the necks, a phosphor screen formed on the inner surface of the faceplate and including a plurality of continuous segment regions each being a region scanned by an electron beam emitted from a corresponding one of the electron gun assemblies; and a mask structure located in the vacuum envelope and facing the phosphor screen, said mask structure having a plurality of effective regions corresponding to said segment regions and through which the electron beams pass; characterised in that the mask structure is divided into a plurality of zones each including a plurality of said effective regions each of which is surrounded by a non-effective region for the non-passage of electron beams and in each zone, the number of effective regions in the direction of the first axis is equal to, or less than, the number of the effective regions in the direction of the second axis. In order that the invention may be more readily understood, it will now be described, by way of example only, with reference to the accompanying drawings, in which:- Figure 1 is a sectional view of a color cathode ray tube having a multineck structure according to the prior art. Figure 2 is a perspective view of a color cathode ray tube having a multineck structure according to a first embodiment of the present invention. Figure 3 is a cross sectional view of the color cathode ray tube in Fig.2 taken along the line X-X thereof. Figure 4 is a cross sectional view of the color cathode ray tube in Fig.2 taken along the line Y-Y thereof. Figure 5 is a plan view of mask member according to the present invention. Figure 6 is a perspective view of a color cathode ray tube having a multineck structure according to a second embodiment of the present invention. Figure 7 is a cross sectional view of the color cathode ray tube in Fig.6 taken along the line Y-Y thereof. Figure 8 is a plan view of another structure of a mask member according to the present invention. Figure 9 is a partial sectional view of the color cathode ray tube having the mask member in Fig.8. Figure 10 is a partial sectional view of another structure of a mask member according to the present invention. Figure 11 is a plan view of another structure of a mask member and shielding means according to the present invention. Figure 12 is a partial sectional view of the color cathode ray tube having the mask member and shielding means in Fig.11. Figure 13 is a plan view of another structure of a mask means according to the present invention. An embodiment of the present invention will be explained with reference to the drawings. Referring to Figs. 2 to 5, there is illustrated a first embodiment of a color cathode ray tube having a multineck structure according to the present invention. Fig. 2 is a perspective view showing the entire structure and Figs. 3 and 4 are cross sectional views of Fig.2. A color cathode ray tube comprises a vacuum envelope including a panel 10 having a sustantially rectangular faceplate 10-1 and skirt 10-2 extending along the edge of faceplate 10-1, and funnel 11 hermetically coupled to skirt 10-2 of panel 10. A plurality of necks 12-1,...12-12 are hermetically coupled to funnel 11. Faceplate 10-1 is substantially rectangular, which has a first axis and a second axis perpendicular to the first axis. In this embodiment, the first axis is X-X axis and the second axis is Y-Y axis. According to this embodiment, the number of necks is four in the horizontal direction (X-X axis) and three in the vertical direction (Y-Y axis) and twelve in total. A phosphor screen 13 is formed on the inner surface of faceplate 10-1 of panel 10, which screen includes a large number of groups each consisting of red, green and blue phosphor stripe layer. Each phosphor stripe extends continuously along the vertical direction (Y-Y axis).A mask structure 14 is mounted on the inner surface of skirt 10-2 of panel 10 so as to face screen 13. Electron gun assemblies 15-1,...15-12 each emitting substantially three different electron beams 16-R, 16-G, and 16-B toward the screen 13 are respectively received in necks 12-1,...12-12. Therefore, the color cathode ray tube, in the present invention, includes electron beam generating means having a plurality of electron gun assemblies 15-1,...15-12, for example, twelve electron gun assemblies as shown in Figs. 2 to 4. A plurality of deflection units 17-1,...17-12, generating deflection magnetic fields, are respectively mounted on the outer surface of the funnels to deflect the electron beams 16-R, 16-G, and 16-B emitted from electron gun assemblies 15-1,...15-12. Beams 16-R, 16-G, and 16-B are deflected by corresponding deflection units 17-1,...17-12. A single screen is defined as a set of segment regions 18-1,.. .18-12, divided with dashed lines 19, as drawn and respectively corresponding to electron gun assemblies 15-1,...15-12. Segment regions 18-1,...18-12 are scanned with the respective set of deflected beams 16-R, 16-G, and 16-B. These segment regions 18-1,...18-12 are traversed by a signal applied to electron gun assemblies 15-1,...15-12 and deflection units 17-1,...17-12, and one large image is reproduced on the entire screen. As shown in Fig. 5, maskstructure 14 includes a plurality of effective regions 20-1,...20-12, respectively corresponding to segment regions 18-1,...18-12 and each having a large number of apertures for passing electron beams, and non-effective regions 21 surrounding the effective regions 20-1,...20-12. Effective regions 20-1, ...20-12 are connected through non-effective regions 21 in the vertical direction parallel to the longitudial axis of the phosphor stripes, and are separated into several parts in the horizontal direction perpendicular to the longitudial axis of the phosphor stripes, to constitue a plurality of individual masks 22-1,...22-4, as drawn. Therefore, mask member is comprised as a plurality of groups each of which has at least one effective region. The width of the non-effective regions, at where effective regions are divided in the horizontal direction, is about 10 % of the horizontal width of the effective regions. And individual masks 22-1,..,22-4 are received at predetermined interval in the horizontal direction to provide gaps or isolation opening 23-1,... 23-4 between adjacent individual masks 22-1,...22-4. Moreover, each of individual masks 22-1,...22-4 includes a shadow mask, which is made of a single iron plate and which has a plurality of effective regions and non-effective regions, and mask frame 24 for supporting shadow mask. Therefore, longitudinal axes of individual mask 22-1,...22-4 are parallel to vertical direction (Y-Y axis) which is the direction of phosphor stripes. The operation of the present invention will be described below. In the above structure, that is, a color cathode ray tube having a single phosphor screen, formed substantially continuous with a large number of groups, each consisting of different colors of phosphor stripes extending continuously along the vertical direction, a plurality of electron gun assemblies, and mask member, having a plurality of effective regions and being separated in the horizontal direction into individual masks, electron beams impinge on the masks as in a conventional tube. As a result, the individual masks are thermally expanded and deform. In the present invention, the magnitude of the electron beam displacement caused by deformation of the mask may be made small in proportion to separating number of mask member, i.e., the number of individual masks. For example, in a case where the mask member is separated into four individual masks, as drawn, the magnitude of deformation is 1/4 of the conventional type, in which the mask member is not separated. Furthermore, deformation is substantially symmetric about the center of each individual mask. Landing error will occur in the vertical direction as well as in the horizontal direction. However, since each of the phosphor stripes extends continuously along the vertical axis, emitting of rays of different color and landing electron beams on areas other than phosphor stripes are prevented. Therefore, degradation of color purity caused by vertical landing error can be prevented according to the present invention. Deformation of the mask member, caused by thermal expansion, is insignificant in terms of color purity, as mentioned above. However, the relationship between each segment region 18-1,...18-12 of screen 13 and effective regions 20-1,...20-12 of the mask member may change. As a result, a non-light-emitting area may be present at the top and bottom of a raster. This phenomenon, that is electron beam scanning of a non-light-emitting area, is prevented by designing the vertical length of the effective region to be larger than or equal to the size required to form a continuous large raster on the screen when thermal expansion does not occur. Furthermore, the above structure is also effective in terms of location of the mask member against the faceplate, to ease required precision in the vertical direction. Furthermore, compensation of the landing error without correction means is also applicable. For example, in the case where a phosphor screen which has the size of 406.4 mm in the horizontal axis and 304.8 mm in the vertical axis is divided into twelve segment regions of 101.6 mm x 101.6 mm size, and that mask member is made of Al-killed steel, the magnitude of deformation of the mask member is about 10µm. In general, such a extent of deformation does not need landing error correcting means. In the case that each segment region is larger than that of above mentioned embodiment or in the case that the size and pitch of apertures formed on the effective regions of the mask member are smaller, as used in a high resolution color cathode ray tube, landing error may be compensated with conventional landing error correcting means. Moreover, landing error correcting means is not needed if the mask member is formed of a material of low thermal expansion coefficient, such as invar alloy. It will be appreciated that modification may be made in the present invention. In the above mentioned embodiment, the mask member is separated into several parts in the direction perpendicular to phosphor stripes and to constitute several individual masks. The number of individual masks is determined in accordance with the deformation caused by thermal expansion. In case the thermal expansion coefficient or deformation of the mask member is small, or in the case that each effective region is small in response to the size of the phosphor screen, all effective regions are not necessarily separated between the adjacent effective regions in the horizontal direction. Moreover, in the above structure, the effective regions of the mask member are divided in the horizontal direction to constitute several individual masks, and each individual mask includes a plurality of effective regions continuous through non-effective regions in the vertical direction, effective regions of each individual mask are also divided in the vertical direction into several parts. For example, providing a slit or projecting portion for absorbing the deformation between vertically adjacent effective regions is applicable. As a result, deformation of each mask is reduced compared with the above mentioned embodiment. Moreover, a mask member without a mask frame is also applicable. A second embodiment of the present invention will be explained with reference to the drawings. Figs. 6 to 9 show a second embodiment of a color cathode ray tube according to the present invention. Fig. 6 is a perspective view showing the entire structure, and Fig. 7 is a cross sectional view of Fig. 6. A color cathode ray tube 50 comprises a vacuum envelope including a flat faceplate 51, a side wall 52, which is provided around the faceplate 51 and extends in a direction which is substantially perpendicular to the faceplate 51, a rearplate 53 opposing to the faceplate 51, a plurality of funnels 54 and a plurality of necks 55, which are continuous to the rearplate 53. The faceplate 51 is formed of glass. The rearplate 53 is also formed of glass, and openings are formed at predetermined positions. The funnels 54 are bonded to the rearplate 53 around the openings. Between the faceplate 51 and rearplate 53 and in the vicinity of the openings, there are fixed support members ( not shown ), for supporting the faceplate 51 against atmospheric pressure. A phosphor screen 57 is formed on the inner surface of the faceplate 51, which includes a large number of groups each consisting of red, green and blue phosphor stripe layers. Each phosphor stripe extends continuously along the vertical direction ( Y-Y axis ). In each neck 55, there is enclosed an electron gun assembly 56 generating substantially red, green and blue electron beams. In the vicinity of the electron gun assembly 56, there is arranged a deflection unit ( not shown ). Similar to the first embodiment, the electron beams emitted from each electron gun assembly are deflected and scan the phosphor screen 57 so that light rays are emitted from the phosphor screen 57. Then, rasters R1,... R20, which correspond to small segment regions each having the same size, are drawn. These small raster regions are traversed by a signal applied to the electron gun assemblies 56 and deflection units, and one large raster is formed on the entire screen. In this embodiment, mask member 58 is provided on the rearplate 53 with support girder 61, mounted on the rearplate 53 and serves as a support member, as shown in Figs. 7, and does not include a mask frame which is described in the above embodiment 1. The form of mask member 58 is flat and parallel to the faceplate 51, and tension, parallel to the phosphor stripe, is applied to the mask member 58. Fig. 8 is a plan view of mask member 58 and Fig. 9 is partial sectional view. Therefore, funnels 54, electron gun assemblly 56 and support girder 61 are not shown in Fig. 9. Mask member 58 includes a plurality of effective regions 63-1,...63-20, each of which has a large number of apertures for allowing beam passage, and non-effective region 64 surrounding effective regions 63-1,...63-20, and is separated in the horizontal direction ( X-X axis ), which is perpendicular to the direction of phosphor stripes, into several individual masks 66-1,...66-5. Each of individual masks 66-1,...66-5 includes a plurality of effective regions arranged along the vertical direction, and non-effective regions surrounding the effective regions, and gaps 65-1,...65-4 are provided between adjacent individual mask 66-1,...66-5. Shielding means 62-1,...62-4 are provided at the adjacent edge of individual masks 66-1,...66-5, for shielding the gap 65-1,...65-4, and connect individual masks 66-1,...66-5 structurally. Moreover, each shielding means includes means for absorbing deformation of mask member to divide each individual masks 66-1,...66-5 functionally. In this embodiment, the means for absorbing deformation is a circular arc-like projecting portion 67, which project towards screen 57, of strip-like shielding means 62-1,...62-4. In the color cathode ray tube, which forms continuous rasters on the screen by deflecting and scanning three electron beams from each one of a plurality of electron gun assemblies, in order to prevent the boundary of the rasters from standing out due to change of a circuit constant with the passage of time or due to effect of the earth's magnetic field, the electron beams are deflected by ranges W+d larger than a predetermined effective ranges W. The electron beams deflected to overscanning ranges d are shielded by the non-effective region and do not reach the screen. Therefore, the rasters are smoothly continuous on screen. The amount of overscanning range d is 10% of the effective raster size, similar to the above mentioned embodiment 1. Overscanning of electron beams and shielding the electron beams deflected to overscanning range is necessary to prevent several errors caused by characteristics of the deflection unit or dispersion in mounting precision. In the present embodiment, deformation of the mask member is larger than the above mentioned embodiment 1, for the following reasons. Since mask member 58 is mounted directly on the rearplate 53 with support girder 61, and does not include a mask frame which is mentioned in the above embodiment 1, thermal capacity of mask member 58 without the mask frame is lower than a mask member including the mask frame. Therefore, any increase of temperature due to impingement of electron beams is larger than that of embodiment 1, and deformation of the mask member increases. In addition, when the curvature radius of mask member becomes larger, electron beam displacement due to mask member deformation increases. As a result, the displacement in a flat mask in the present embodiment is conspicuous compared with the curved mask described in the above embodiment 1. Moreover, according to the difference in thermal capacity between the effective regions and the non-effective regions, the edge portions,where the effective regions and the non-effective regions adjoin, deform easily compared with the central portion of the effective region and causes landing error. This phenomenon becomes more conspicuous when the width of the non-effective region becomes wider. Therefore, it is desirable to equalize the thermal capacity between the effective and non-effective regions, by minimizing the width of the non-effective region. To the contrary, as regards shielding overscanning electron beams, a wider non-effective region is desiable. In order to satisfy the above contradictory condition, the mask member in this embodiment includes narrow non-effective region and a shielding means which functions as a non-effective region. Furthermore, low rigidity of the shieding means is desirable in order not to limit deformation of the mask member caused by thermal expansion. In this embodiment, a shielding means is a strip-like member having a projecting portion ( a means for absorbing deformation ), and rigidity of the shielding means reduced by the projecting portion. The thickness of individual masks 66-1,...66-5 is 0.13 mm and the thickness of shielding means 62-1,...62-4 is 0.025 mm, and the radius of curvature of circular arc-like projecting portions 67 is 3 mm. It will be appreciated that modification may be made in the present invention. For example, a triangular or wavy form of the projecting portion of the shielding means may be used. Moreover, since the function required of the shielding means is not only to limit deformation of the mask member, dividing the shielding means in the vertical direction, or providing the shielding means only where the non-effective region does not have enough width to shield an overscanning electron beam, is also applicable. When the shielding means becomes thinner, the rigidty becomes lower, and in case that shielding means is made of thin plate of 10 µm or less, a shielding means without a projecting portion is available. Moreover, in case that individual masks are made of material with low thermal expansion coefficient, or that the width of the individual mask is made small in order to reduce deformation, the projecting portion, which serves as a means for absorbing deformation, is not always requried. Fig. 10 shows another structure of the shielding means, that is, the shielding means comprise overlapping plate-like members 69-1...69-2, each of which is connected at one side to the individual mask 68 and the other side is free. These absorb deformation by a slipping motion between the two plate-like members 69-1...69-2. Shielding means mentioned above are structurally connected to individual masks. In this invention, structurally separated shielding means is also available. For exaple, as shown in Figs. 11 and 12, shielding means comprises shield plates 70-1,...70-4 provided on the rearplate 53 and extending to the gaps 65-1,...65-4 between individual masks 66-1,...66-5, in a direction which is substantially perpendicular to the rearplate 53 and individual masks 66-1,...66-5. In this structure, tops of shielding plates 70-1,...70-4 are desirably located between the surface of individual masks 66-1,...66-5 and phosphor screen 57. Furthermore, the structure of the mask member, according to the present invention, is not limited to the above mentioned structure, and partially divided and partially connected structure is also available. A third embodiment of the present invention will be explained with reference to Fig.13, which is a plan view of a mask member of this embodiment 3. In this embodiment, the structure of a color cathode ray tube is similar to the above mentioned embodiment except for the mask member. As shown in Fig.13, mask member 80 does not include a shielding member, and is functionally divided without being separated structurally into individual masks. For the reason mentioned above, the width of the non-effective region for shielding an overscanning electron beams is about 10 % of the width of the effective region. Therefore, in order not to use a shielding means and not to limit deformation, the non-effective regions are made wide enough to shield overscanning electron beams, and several slits are formed between adjacent effective regions to divide effective regions in the horizontal direction functionally. As shown in Fig. 13, mask member 80 includes a plurality of effective regions 81-1,...81-20, each of which has a large number of apertures for passing electron beams, non-effective regions 82 surrounding the effective regions 81-1,...81-20, and a plurarity of slits, or isolation openings, 83, formed between horizontally adjacent effective regions. The mask member also include a plurality of groups of effective regions and each of groups has a longitudial axis parallel to the phosphor stripes. Slits 83 are connected through half-etched portions 84 in the vertical direction ( Y-Y axis ), and the vertical length of each slit is longer than that of the effective regions. Since the rigidity of the mask member is reduced at the portion, where slits 83 and half-etchs 84 are provide, compared with the remaining portion, thus, the portion serves as means for absorbing deformation of the member. Furthermore, in order to prevent the mask member deforming due to differences of rigidity between slit portion and half-etched portion, the length of slit 83 is made longer than that of effective region 81-1,...81-20. In this embodiment, the mask member is functionally separated into several parts in the direction, which is perpendicular to the phosphor stripes, between the adjacent effective regions. In the case the thermal expansion coefficient or deformation of the mask member is small, or in the case that each effective region is small in response to the size of the phosphor screen, all effective regions are not necessarily separated between the adjacent effective regions in the horizontal direction. Furthermore, providing slits between vertically adjacent effective regions in addition to slits 83 is also applicable. Moreover, it will be appreciated that modification may be made in the above embodiments of the present invention. For example, a mask member including individual masks, which has longitudinal axis in the horizontal direction, received at predetermined interval in the vertical direction is also applicable.

Claims: A color cathode ray tube comprising a vacuum envelope including a faceplate (10-1, 51) having an inner surface and a first axis and a second axis perpendicular to the first axis, and a plurality of necks (12,55) opposing the faceplate (10-1, 51); a plurality of electron gun assemblies (15,56) located one in each of the necks (12,55), a phosphor screen (13,57) formed on the inner surface of the faceplate (10-1, 51) and including a plurality of continuous segment regions (18-1, ...18-12, R1, ...R20) each being a region scanned by an electron beam emitted from a corresponding one of the electron gun assemblies (15, 56); and a mask structure (14, 58, 80) located in the vacuum envelope and facing the phosphor screen (13, 57), said mask structure having a plurality of effective regions (20-1, ...20-12, 63-1, ...63-20, 81-1, ...81-20) corresponding to said segment regions and through which the electron beams pass; characterised in that the mask structure is divided into a plurality of zones each including a plurality of said effective regions (20,63,81) each of which is surrounded by a non-effective region (21,64,82) for the non-passage of electron beams and in each zone, the number of effective regions in the direction of the first axis is equal to, or less than, the number of the effective regions in the direction of the second axis. A color cathode ray tube according to claim 1, characterised in that the zones of the mask structure (14,58,80) are thermally separated by isolation openings or gaps (23-1, ...23-3, 65-1, ...65-4, 83) therebetween. A color cathode ray tube according to claim 2, characterised in that each zone of the mask structure (14, 58) comprises an individual mask (22-1, ...22-4, 66-1, ...66-5). A color cathode ray tube according to claim 3, characterised in that the individual masks (22-1, ...22-4) each comprise a shadow mask (23) and a mask frame (24) for supporting the shadow mask (23). A color cathode ray tube according to claim 3 or 4, characterised in that shielding members (62-1, ...62-4, 69-1, ...69-2, 70-1, ...70-4) are provided between adjacent individual masks (66-1, ... 66-5) for preventing the passage of electron beams. A color cathode ray tube according to claim 5, characterised in that each shielding member (62-1, ... 62-4) includes an absorbing member (67) for absorbing the deformation of the mask member (58) in the direction of the first axis. A color cathode ray tube according to claim 6, characterised in that the absorbing member (67) is a circular arc-like projection of the shielding member (62-1, ...62-4). A color cathode ray tube according to claim 7, characterised in that the absorbing member (67) comprises at least two plate-like members (69), each connected at one side to the adjacent edge portion of the individual masks (68) and the other side being free, the plate-like members (69) overlapping each other. A color cathode ray tube according to claim 5, characterised in that the shielding member (70-1, ...70-4) is separate from the individual masks (66-1, ...66-5). A color cathode ray tube according to claim 3, characterised in that the faceplate (51) and the mask structure (58) are flat. A color cathode ray tube according to claim 10, characterised in that the vacuum envelope further includes a rearplate (53) opposing the faceplate (51), and the mask structure (58) is supported by a support girder (61) located on the rearplate (53). A color cathode ray tube according to claim 10, characterised in that tension is applied to the mask structure (58) in a direction parallel to the second axis. A color cathode ray tube according to claim 1, characterised in that the mask structure (80) comprises a plate having a plurality of zones with slits (83) being provided at predetermined intervals between effective regions (81-1, ...81-20) of adjacent zones in the first axial direction, the slits (83) having their longitudinal axes in the second axial direction. A color cathode ray tube according to claim 13, characterised in that the mask structure (80) includes half-etched portions (84) formed between adjacent slits (83) in the second axial direction. A color cathode ray tube according to claim 13, characterised in that the length of each slit (83) in the second direction is longer than the length of the effective regions (81-1, ...81-20) in the second direction.

Inventors: KAMOHARA EIJI C O INTELLECTUAL, NISHIMURA TAKASHI C O INTELLEC, SEINO KAZUYUKI C O INTELLECTUA, KAMOHARA, EIJI, C/O INTELLECTUAL PROPERTY DIV., NISHIMURA, TAKASHI, C/O INTELLECTUAL PROPERTY DIV., SEINO, KAZUYUKI, C/O INTELLECTUAL PROPERTY DIV.
Applicants: TOSHIBA KK, KABUSHIKI KAISHA TOSHIBA
Application year: 1992
Main classification: H01J31
IPC codes: H01J31