Patent Application
20110279425
The present invention relates to a vacuum fluorescent display with a driver IC, and particularly relates to a filament support structure of the vacuum fluorescent display.
Vacuum fluorescent displays with a driver IC (also referred to below as CIG-VFDs) can have a driver IC mounted inside the vacuum fluorescent display, and are therefore capable of a reduced package size, as well as high density and display capacity.
A filament support provided to a metal cover of an IC shield is known in the prior art as an example of a filament support structure of a CIG-VFD (Unexamined Utility Model Application Publication No. 1-46948). Examples (Patent Reference 2, Patent Reference 3) are also known in which the filament support is provided separately from the metal IC shield to an end part of a metal frame whereon a metal IC shield for shielding the driver IC is mounted (Unexamined Utility Model Application Publication No. 5-36741, Japanese Laid-open Patent Application Publication No. 6-51335).
There has been demand in recent years for a higher-definition dot pitch in full-dot-type graphic CIG-VFDs. The graphic CIG-VFDs generally employ a dynamic scan drive as a drive method. However, when a high definition is reached wherein the pixel pitch of the display unit is at a level of 0.325 mm, the grid cut-off voltage effect increases, and light and dark parts become markedly more noticeable in comparison with a roughly pixilated display at a pixel pitch level of 0.65 mm. It is known that the distance between a grid and an anode substrate can be reduced in order to solve this problem, but a problem has been encountered in the prior art in that reducing this distance leads to a decrease in display luminance and a loss of display quality.
Accordingly, in order to prevent a decrease in display luminance, an arrangement has been considered wherein the distance between a filamentary cathode and a phosphor on the anode substrate is reduced by setting the distance between the filamentary cathode and the grid to be shorter than in a conventional product.
However, there is a problem in that the distance between the filamentary cathode and the grid in a CIG-VFD cannot be reduced.
The filamentary cathode and the filament support are usually subjected to a cut-off bias voltage in the driving of a CIG-VFD.
Also, the bonding wire on the driver IC serves as an anode, grid, logic+, or logic GND and must be prevented from coming into contact with the filament support.
Accordingly, the filament support must be maintained at a constant distance from the surface of the anode substrate so as to prevent the bonding wire of the driver IC mounted underneath the filament support from coming into contact with the filament support.
The problem is that a certain constant luminance or greater cannot be obtained because the minimum distance between the filamentary cathode and a phosphor is determined by the factors described above, even when an attempt is made to reduce the distance between the filamentary cathode and the phosphor and to achieve increased luminance.
An object of the present invention, which was devised in order to address such problems, is to provide a high-definition graphic CIG-VFD in which the distance between the filamentary cathode and the phosphor on the anode substrate can be reduced and high luminance obtained without a loss of display quality by shortening the distance between the filamentary cathode and the grid.
The present invention provides a CIG-VFD comprising a display unit provided with a phosphor layer on an anode substrate, a plurality of filamentary cathodes installed above the display unit, a grid disposed between the filamentary cathodes and the display unit, an IC (also referred to below as a “driver IC”) mounted on the anode substrate within an end cooling area of the filamentary cathodes and adapted to drive the display unit, and a filament support for shielding the driver IC from electrons generated by the cathodes and supporting an end part of the filamentary cathodes; wherein the phosphor layer is excited and caused to emit light by irradiating the phosphor layer with electrons generated from the filamentary cathodes; characterized in that the end part of the filamentary cathodes is fixed to one short side of the vacuum fluorescent display at a long side of the filament support; a depression is provided to a surface of the filament support disposed below the end cooling area of the filamentary cathodes, or a slit is provided to the filament support; the filamentary cathodes and the surface of the filament support are prevented from making contact; and the distance between the filamentary cathodes and the phosphor layer is reduced.
In particular, the present invention is characterized in that the depression or slit formed on a surface of the filament support is provided in a plural number in parallel to each of the plurality of filamentary cathodes.
The present invention is also characterized in that one end of the filamentary cathodes fixed to the filament support is fixed to a surface of the filament support.
The present invention is also characterized in that an end part of the filament support to which one end of the filamentary cathodes is fixed forms an opening relative to the anode substrate of the vacuum fluorescent display.
Since depressions are provided to the surface of the filament support to which one end of the filamentary cathodes is fixed, or slits are provided to the filament support, the distance between the filamentary cathodes and the phosphor can be reduced. Therefore, the vacuum fluorescent display with a driver IC according to the present invention can produce high luminance without loss of display quality, even in high-definition graphic CIG-VFDs.
Also, because one end of the filamentary cathodes is fixed to the surface of the filament support, the press-shape of the filament support itself can be more simplified compared with the conventional product. The press-shape is accordingly stable, and the die used for press becomes less expensive than the conventional product.
The CIG-VFD of the present invention will now be described with reference to
A CIG-VFD 1 comprises a display unit 3 comprising at least an aluminum or other wiring (not shown) on an anode substrate 2, and an anode that is formed in a matrix pattern in a predetermined area of the wires and that has a phosphor layer 3a adhered thereto, and also comprises a plurality of grids 4 provided substantially parallel to each other above the display unit 3 so as to cover the display unit 3, and a plurality of filamentary cathodes 5 installed above the grids 4, as shown in
The CIG-VFD 1 is constructed of an external peripheral device in which a front glass (not shown) at least partially having permeability and a spacer glass 9 are bonded together using fritted glass to form a vacuum vessel.
The above-described CIG-VFD 1 is a display in which the phosphor layer 3a is excited and caused to emit light by irradiation of the phosphor layer 3a via the grids 4 with electrons generated from the filamentary cathodes 5.
The filamentary cathodes 5 are fixed to an end part 7a of the filament support 7. In the end part 7a, the end cooling area 5a of the filamentary cathodes 5 is fixed to the end part 7a by welding or the like so as to be positioned above the filament support 7.
Depressions 7b are provided to the surface of the filament support 7 positioned underneath the end cooling area 5a of the filamentary cathodes 5, as shown in
Providing the surface with the depressions 7b allows the filamentary cathodes 5 to be fixed to the surface of the filament support 7. Providing the depressions 7b and fixing the cathodes to the surface of the filament support 7 allows the filament height t1, which is the distance between the filamentary cathodes 5 and the phosphor layer 3a, to be markedly reduced by about 20% in comparison with a conventional example in which the depressions 7b are not provided. It should be noted that slits 7c may be provided in place of the depressions 7b.
The distance t2 between the upper surface of the driver IC 6 and the filament support 7 is determined by the thickness t3 of the driver IC 6 and the shape of the bonding wire 6a, and therefore is a distance that cannot be changed in terms of the design of the filament support 7.
The thickness t4 of the filament support 7 is determined by the size of the vacuum fluorescent display 1.
Taking as an example a case in which the size of the vacuum fluorescent display 1 is such that the length of the short side in the planar view of
The depressions 7b or slits 7c formed on the surface of the filament support 7 are provided in parallel to the lower surfaces of the plurality of filamentary cathodes 5 in a corresponding manner. Forming the depressions or slits in the lower surfaces of the filamentary cathodes 5 allows contact between the filamentary cathodes 5 and the filament support 7 to be avoided.
The depressions 7b or slits 7c can be readily formed by half-etching, press working, or the like.
The width t6 of the depressions 7b and the slits 7c must be such that the filamentary cathodes 5 are prevented from making contact with the filament support 7 by vibration from the exterior when the vacuum fluorescent display is operated. The width may, for example, be in the range of 0.2 to 0.6 mm in the case of a vacuum fluorescent display in which the length of the short side is 35 mm and the length of the long side is 96 mm.
The width t6 of the depressions 7b may be increased in a case in which the mechanical strength can be maintained. Alternatively, the width may be such that the fan-shaped depressions open toward the center of the vacuum fluorescent display relative to the filamentary cathodes 5.
Furthermore, the step in the conventional example can be reduced and the depressions 7b or slits 7c provided.
The filamentary cathodes 5 are prevented from making contact with the filament support 7 under the action of vibration from the exterior by setting the width t6 of the depressions 7b and slits 7c to within the range described above, and the depth t5 of the depressions 7b to within the range described below. The filament support 7 also has a tabular shape, which improves ease of processing when the filamentary cathodes 5 are welded to the filament support 7.
A state in which the filamentary cathodes 5 are brought into contact with the filament support 7 by vibration is illustrated by
In
Following is a calculation of the distance tx in an arrangement in which the filamentary cathodes 5 are fixed at point “a” of the filament support 7, and the filamentary cathodes 5 are in contact with point “b.” Determining the radius R of the arc described by the vibrating filamentary cathodes 5 gives R=1841 mm. Based on this value, the maximum oscillation width H of the filamentary cathodes 5 is 0.5 mm, and tx is 0.125 mm; the depth t5 of the depressions 7b can be assumed to be 0.13 mm if solely the vibration of the filamentary cathodes 5 is taken into account. Similarly, the width t6 of the depressions 7b can be assumed to be 0.13 mm.
As a comparative example, results are described with reference to
In
Table 1 shows a comparison with the configuration of the CIG-VFD according to the present invention as shown in
As shown in Table 1, structuring the filament support in accordance with the present invention brings the height t1 of the filamentary cathodes 5 to 1.05 mm in the case of the present invention, and 1.3 mm in the case of the conventional structure. The height in the case of the present invention is markedly lowered by about 20% in comparison with the conventional structure.
Grid height: 0.5 mm
Anode voltage: 30 V
Grid voltage: 30 V
Cut-off voltage: 1 V
Duty: 1/20
The luminance is 679 Cd/m2 in a case in which the height t1 of the filamentary cathodes having the conventional structure is 1.3 mm, but the luminance is 1200 Cd/m2 or greater in the case of the present invention where the height t1 is 1.05 mm, as shown in
The CIG-VFD of the present invention can obtain higher luminance without loss of display quality, even in high-definition graphic CIG-VFDs, and therefore can be applied to all CIG-VFDs in the future.
| Number | Date | Country | Kind |
|---|---|---|---|
| P2010-113584 | May 2010 | JP | national |
