JP2003195818A - Fluorescent display tube and its driving method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fluorescent display tube which can control luminance spots and its driving method. <P>SOLUTION: According to the relative positions of a filament and a fluorescent material layer, specifically, whether the fluorescent material layer is positioned right below the filament or between filaments, a driving pulse to a filament at a relatively short distance is made long and a driving pulse to a filament at a relatively long distance is made short. Consequently, the time of incidence of electrons on the filament positioned at the short distance which tends to relatively decrease in luminance is made long to increase the quantity of incidence, thereby its luminance is relatively increased. The time of incidence of electrons on the filament at the long distance which tends to relatively increase in luminance is made short to decrease the quantity of incidence, thereby the luminance is relatively lowered. The difference in luminance due to the difference in the distance from the filament and then luminance spots are suitably reduced, so uniform luminance can be obtained over the entire display surface. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a fluorescent display tube and its driving method.

[0002]

2. Description of the Related Art Phosphor layers are fixed on a plurality of anodes provided on a display surface of a substrate, and thermoelectrons generated from a filament cathode erected above the anodes in a vacuum space are generated in the phosphor layers. Control electrode provided between the cathode and the cathode
2. Description of the Related Art There is known a fluorescent display tube of a type in which a phosphor layer is excited and emits light by being controlled by a (grid electrode) and selectively entering the phosphor layer. In such a fluorescent display tube, since a phosphor layer against which thermoelectrons generated from the cathode collide is provided in the vicinity of the cathode, the operating voltage is clearly displayed at a low level, and a plurality of types of emission colors different from each other are provided. There is a feature that color display can be performed by preparing the above-mentioned phosphor. Therefore, it is widely used as a display component such as an audio device and a display panel of an automobile or an aircraft. In particular, in the fluorescent display tube having a rib-grid structure in which the grid electrode is composed of a conductive film fixed to the top of the rib-shaped wall protruding higher than that around the phosphor layer,
Since the mesh-shaped grid electrode that covers the phosphor layer is not used, display defects such as uneven brightness and short circuits due to thermal deformation of the grid electrode when the display pattern of the phosphor layer is increased are eliminated. At the same time, there is an advantage in that the decrease in the brightness of the fluorescent display tube associated with the aperture ratio of the grid electrode is eliminated.

[0003]

By the way, in the conventional fluorescent display tube, as the cumulative driving time becomes longer,
As the brightness decreases, brightness unevenness tends to occur along the filamentary cathodes with the lowest brightness immediately below and the highest brightness in the middle. Such a brightness unevenness is hardly noticeable in a character display pattern such as a 7-segment 8-shaped display, because the phosphor layers emit light with a relatively large mutual spacing and a fixed shape. In a graphic display pattern in which a plurality of phosphor layers for forming dot-shaped pixels are arranged in two directions, for example, in the vertical and horizontal directions, the phosphor layers are closely arranged over a wide area and have an arbitrary pattern. Since it emits light, it has a non-negligible effect on the impression of the displayed image. Therefore, there is a problem that the display quality deteriorates when the cumulative driving time becomes long. On the other hand, if the brightness of the phosphor layer can be partially raised or lowered according to the use, that is, the brightness unevenness can be intentionally generated, it is considered that the expression ability can be dramatically improved. However, conventionally,
Although the whole brightness was adjusted according to whether it is day or night, partial brightness adjustment was not considered.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a fluorescent display tube capable of controlling luminance unevenness and a driving method thereof.

As a result of intensive studies to solve the above problems, the present inventor came to consider that the distribution of the amount of electrons reaching the phosphor layer is the main cause of the brightness unevenness, as shown in FIG. It was That is, the electrons jumping from the entire circumference of the filament cathode 8 toward the outer circumference in the radial direction are directed to the phosphor layer along the electric field formed by the grid electrode. At this time, during a short cumulative driving time, since the electrons jumping upward have a relatively long flight distance, a sufficient amount of electrons also reach immediately below the adjacent filamentary cathode 8, so that the electrons immediately below the cathode 8 can be immediately below. The amount of arriving electrons becomes substantially uniform at the position of and the position between the filamentary cathodes 8. However, as the cumulative driving time becomes longer, the flight distance of the electrons becomes shorter due to the deterioration of the emission characteristics of the filamentary cathode 8, so that the amount of electrons reaching directly below the adjacent filamentary cathode 8 becomes smaller, and finally, Since the electrons do not reach, the amount of electrons reaching each filament cathode 8 tends to be relatively larger than the position immediately below. Therefore, the brightness of the phosphor, which becomes higher as the amount of incident electrons increases because it is made to emit light by electronic excitation, is substantially uniform as shown in FIG. 1 (a) at first, but as the driving time becomes longer, As shown in FIG. 1 (b), a luminance distribution according to the distribution of the amount of arriving electrons comes to be generated, and in the latter half of the life, the filament 8 as shown in FIG. 1 (c) is generated.
It is considered that the luminance distribution according to the distribution of the amount of reaching electrons which is the smallest is generated just below.

[0006]

The first aspect of the present invention has been made based on such findings, and the gist of the driving method of a fluorescent display tube according to the first aspect of the present invention is the display surface of a substrate. A phosphor layer fixed to each of the plurality of anodes, and a plurality of control electrodes arranged above the phosphor layer, and arranged above the control electrode in a vacuum space. A method for driving a fluorescent display tube in which electrons generated from a filament cathode are controlled by its control electrode to selectively enter the phosphor layer to cause the phosphor layer to emit light. ) Adjusting at least one of a pulse width and a voltage of a drive pulse applied to at least one of the plurality of anodes and the plurality of control electrodes in relation to a distance from the filamentary cathode to the anode. .

[0007]

According to this structure, at least one of the pulse width and the voltage of the driving pulse applied to at least one of the plurality of anodes and the plurality of control electrodes is set to the distance from the filament cathode to the anode. It is possible to control the luminance unevenness by changing the distribution of the amount of arriving electrons due to the difference in the distance. That is, as the pulse width becomes longer, the time for the electrons to travel to the phosphor layer becomes longer, so that the amount of arriving electrons increases, and conversely, when the pulse width becomes shorter, the amount of arriving electrons decreases. Also, as the driving voltage becomes higher, it becomes easier to attract electrons, so the number of arriving electrons increases,
On the contrary, the lower the number, the smaller the amount of arriving electrons. for that reason,
If these are adjusted in relation to the distance from the filamentary cathode, the effect caused by the difference in the distance can be mitigated or emphasized to obtain a desired distribution of the amount of arriving electrons,
It becomes possible to control the brightness unevenness of the phosphor layer, that is, to mitigate the brightness unevenness or to intentionally or temporarily provide an intentional level of brightness.

[0008]

[Other Aspects of the First Aspect of the Invention] Here, it is preferable that the distance from the filament cathode is set so that the amount of electrons incident on each of the plurality of phosphor layers is uniform on the display surface. The closer the position, the longer the pulse width or the higher the voltage. By doing so, when the phosphor at a position close to the filamentary cathode, which has a relatively low brightness, is caused to emit light, the pulse width is lengthened or the driving voltage is increased to increase the amount of arriving electrons. The brightness is increased. Therefore, since the amount of incident electrons in one lighting in one cycle is adjusted in relation to the distance from the filamentary cathode so as to be uniform over the entire display surface, the distance from the filamentary cathode may be different. It is possible to suitably alleviate the luminance unevenness caused by it.

Further, in the aspect in which the amount of incident electrons is uniformly controlled on the display surface, it is preferable that the drive pulse and the applied voltage are related to the cumulative drive time of the fluorescent display tube.
The longer the cumulative driving time, the larger the adjustment amount of the pulse width and the voltage related to the distance from the filamentary cathode. By doing so, the emission characteristics of the filamentous cathode deteriorate as the cumulative driving time becomes longer, and even when the luminance immediately below that is lower than in the initial stage, the reduction causes the adjustment amount of the pulse width or the voltage. It is compensated by making it larger. Therefore, the conspicuous brightness unevenness is preferably alleviated as the cumulative use time becomes longer. The drive accumulated time is counted by, for example, a non-volatile memory provided in the fluorescent display tube. More preferably, when the pulse width is adjusted, the adjustment is performed by changing the distribution while maintaining the length of one display cycle.

[0010]

A second aspect of the present invention for attaining the above-mentioned object is to provide a fluorescent display tube having a plurality of anodes provided on the display surface of a substrate. It has a fixed phosphor layer and a plurality of control electrodes arranged above the phosphor layer, and controls electrons generated from a filament cathode erected above the control electrode in a vacuum space. In a fluorescent display tube of a type in which the phosphor layer is controlled to be selectively incident on the phosphor layer to cause the phosphor layer to emit light, (a) the control electrode, each in the longitudinal direction of the filamentary cathode. A plurality of them are arranged side by side in a direction perpendicular to the longitudinal direction so as to extend along them.

[0011]

According to this structure, since the plurality of control electrodes are provided along the longitudinal direction of the filamentary cathode, the phosphor layer for emitting light is arranged along the longitudinal direction of the filamentous cathode. One row or a plurality of rows are selected as a group in units. Therefore, since the phosphor layer can be made to emit light in row units at the same distance from the filamentary cathode, the pulse width or voltage of the drive pulse applied to at least one of the anode and the control electrode can be changed from the filamentary cathode to the anode. Since the distance can be easily adjusted in relation to the distance, by applying the driving method of the first invention, it is possible to preferably control the luminance unevenness generated along the longitudinal direction of the filamentary cathode. Moreover, since the display surface of the fluorescent display tube is generally formed in a rectangular shape having a long dimension in the longitudinal direction of the filamentary cathode, a grid electrode extending along the direction perpendicular to the longitudinal direction is provided in the above manner. The number of grid electrodes can be reduced as compared with the case where it is used. Therefore, if the drive duty is maintained at the same level as the conventional one, the brightness is increased, and conversely, if there is no need to particularly increase the brightness, there is an advantage that the drive duty can be decreased within a range where flicker does not occur.

That is, in the driving method according to the first aspect of the present invention, preferably, the control electrode disposed above the phosphor layer is
The present invention is applied to a fluorescent display tube in which a plurality of filamentous cathodes are arranged side by side in a direction perpendicular to the longitudinal direction of the filamentous cathode so as to extend along the longitudinal direction thereof.

[0013]

According to another aspect of the second aspect of the present invention, preferably, the control electrode is a rib / grid electrode provided on the top of a rib-shaped wall projecting on the display surface so as to surround the phosphor layer. Is. In this way, the rib / grid electrode provided on the top of the rib-shaped wall projecting on the display surface does not bend like the mesh-shaped grid electrode supported by the legs provided at both ends. Since it cannot occur, no matter how long the length of the display surface in the longitudinal direction of the filamentary cathode becomes, the grid electrode can be provided with the length required accordingly.

Further, preferably, the phosphor layers are provided at predetermined center intervals along two directions in which each of the phosphor layers forms a dot shape and intersects with each other, and the filament cathodes are integers of the center intervals. It is provided with a double center interval.
That is, in the vacuum space, a plurality of filament cathodes are provided in parallel with each other and at the above-mentioned uniform mutual intervals. By doing so, in the fluorescent display tube for graphic display in which a plurality of phosphor layers for forming the dot-shaped pixels are arranged side by side in two directions intersecting with each other, the filament cathode is used for the fluorescent display. Since the distance between the filament cathode and the phosphor layer is simplified because the distance between the center of the body layer is an integral multiple of the center distance, the pulse width or the type of applied voltage to be set is reduced,
There is an advantage that the driving is simple. Moreover, since a driving method of simultaneously emitting light from a plurality of rows of phosphor layers having a similar arrival electron amount can be easily applied, the pulse width and the driving voltage are the same for the phosphor layers to emit light at the same time. The brightness unevenness can be suitably mitigated by adjusting to. For graphic display applications, it is usually preferable to employ a driving method in which phosphor layers in a plurality of rows or a plurality of columns simultaneously emit light in order to suppress a decrease in drive duty due to an increase in the number of pixels. Further, the effect of the present invention can be enjoyed even if the number of filamentary cathodes provided in the vacuum space is one, but it is preferable to provide a plurality of filamentous cathodes in order to reduce the brightness unevenness as much as possible. It is preferable that the plurality of filamentary cathodes are provided in parallel with each other.

In the driving method according to the first aspect of the present invention, in a mode in which a plurality of rows of phosphor layers are made to emit light at the same time, it is preferable that the center interval of the filament cathodes is the center interval of the phosphor layers as described above. The combination of rows of phosphor layers is set to be an integral multiple and the rows of phosphor layers to be simultaneously emitted are arranged so as to be symmetrically positioned with the filamentary cathode interposed therebetween. In this way, the shape of the grid electrode in the case of simultaneously emitting light from a plurality of rows is, for example, a row direction portion passing between the rows of the phosphor layer and a plurality of rows passing vertically between the columns of the phosphor layer. And the column direction part. In one aspect, the row-direction portion is provided with two on one grid electrode, and the column-direction portion each intersects one of the two row-direction portions and forms a T-shape with the other one. As described above, the length of the phosphor layer is approximately twice the center interval in the column direction. Further, in another aspect, one row electrode is provided for one grid electrode, and the column direction portion has a substantially central spacing in the column direction of the phosphor layer so as to intersect the row direction portion at a midpoint thereof. It is provided with a double length dimension.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 2 shows a fluorescent display tube 1 according to an embodiment of the present invention.
FIG. 3 is a perspective view showing the entire 0, with a part thereof cut away.
In the figure, a fluorescent display tube 10 includes, for example, a substrate 14 made of an insulating material such as glass, ceramics, enamel, etc., provided with a large number of dot-shaped pattern phosphor layers 12 on one surface, and a glass formed in a frame shape. Spacer 16, a transparent cover glass plate 18, and a plurality of anode terminals 20 _P ,
A grid terminal 20 _G and a cathode terminal 20 _K are provided, and the substrate 14, the spacer 16, and the cover glass plate 18 are glass-sealed to each other,
A vacuum space surrounded by these members is formed.

The one surface 22 of the substrate 14 covered with the vacuum space functions as a display surface of the fluorescent display tube 10. The large number of dot-shaped phosphor layers 12 on the display surface 22 have polygonal shapes similar to each other, for example, each side along the longitudinal direction of the substrate 14 and the width direction substantially orthogonal thereto is 400. It has a square shape of about (μm) and is provided with a constant center interval in the two directions. Further, a plurality of grid electrodes 24, which have a lattice shape as a whole and have the same shape as each other, are provided on the display surface 22, and each of the phosphor layers 12 has its grid electrode substantially all around. It is surrounded by 24. Each of the plurality of grid electrodes 24 has a longitudinal shape extending along the long side direction of the substrate 14, and passes between the plurality of phosphor layers 12 arranged along the longitudinal direction of the substrate 14. Is.
That is, the grid electrode 24 is provided between rows of the plurality of phosphor layers 12 arranged along the long side direction of the substrate 14. In this embodiment, the grid electrode 24 corresponds to the control electrode.

A pair of filament support frames 26 having the cathode terminals 20 _K are provided at both ends of the substrate 14 (only one of them is located on the right side in the figure).
Are fixedly provided, and between the filament support frames 26, a plurality of fine filaments (filament.
The cathode) 28 is stretched so as to be parallel to the longitudinal direction of the substrate 14 and at a predetermined height position separated from the display surface 22. The grid electrode 24 is provided so that its longitudinal direction coincides with the longitudinal direction of the filament 28, and the direction perpendicular to the longitudinal direction, that is, the substrate 14
Is divided into a plurality of pieces in the short side direction. The fluorescent display tube 10 is provided with an exhaust hole for evacuating and sealing the inside of the vacuum container, a getter for maintaining the internal vacuum degree after the sealing, and the like in FIG. Omitted.

FIG. 3 is an enlarged perspective view showing a part of the display surface 22 of the substrate 14 described above. As shown in the figure,
On the display surface 22, a rib-shaped wall 3 that forms a lattice shape as a whole
0 is provided so as to be in contact with and surround the outer peripheral edge of the phosphor layer 12. That is, it is erected in the direction away from the substrate 12, that is, in the direction toward the filament 28 side. The rib-shaped wall 30 is made of, for example, an insulating material such as low-melting glass containing an inorganic filler such as alumina particles, and has a width dimension of, for example, about 60 to 150 (μm) and the phosphor layer 12. Higher than the surface of, for example, 150-300 (μm)
It is formed to a height dimension of the order of magnitude. The grid electrode 24 is made of particulate graphite, silver, palladium, copper,
A thick film conductor containing a particulate conductive material such as aluminum or nickel as a main component.
The thickness is about 50 (μm), for example, about 20 (μm). That is, in this embodiment, the control electrode is provided in a rib-grid structure in which the grid electrode 24 is provided on the top of the rib-shaped wall 30. Therefore, the grid electrode 24 has the rib-shaped wall 30 so that the phosphor layer 1 is
It is insulated from 2.

Further, as shown in FIG. 3 and FIG. 4 showing a plan view of the main part of the display surface 22, all of the plurality of grid electrodes 24 extend along the longitudinal direction of the substrate 14 and are mutually adjacent. Two parallel longitudinal parts (row direction parts) 24a,
A plurality of branch portions which are orthogonal to one of the two longitudinal portions 24a in the intermediate portion, form a T shape with the other at one end portion, and extend in parallel directions along the short side direction of the substrate 14 ( Row direction portion) 24b. The plurality of branch portions 24b are provided at a plurality of locations having a constant center interval in the longitudinal direction of the longitudinal portion 24a, and one branch portion 24a from which one of the intersecting longitudinal portions 24a extends to both sides in the width direction. The protruding length dimension is almost the same. In addition, the center distance df of the filament 28 is the phosphor layer 12
Is an integral multiple of the center interval of, for example, four times. This center interval df is also twice as large as the center interval of the grid electrode 24. The branch portions 24b are provided at the same position in the longitudinal direction of the substrate 14 in any of the grid electrodes 24, and the center interval in the width direction thereof is the same as the center interval of the phosphor layer 12. However, there is a small gap of, for example, about 100 (μm) between the adjacent grid electrodes 24 and the tips of the branch portions 24b protruding toward them. The electrical independence between the grid electrodes 24, 24 is ensured by the gap.

Therefore, each of the phosphor layers 12 is formed on the substrate 1
1 or 2 located on both sides in the longitudinal direction of 4
The two grid electrodes 24, more specifically, the longitudinal portions 24a and the branch portions 24b surround the substantially entire circumference thereof. However, in the portion sandwiched by the two grid electrodes 24, their mutual mutual relation is eliminated. The enclosing method is incomplete at the position between them. Since the phosphor layer 12 is provided in the region surrounded by the grid electrode 24 in close contact with the inner peripheral edge of the grid electrode 24, the mutual spacing between the phosphor layers 12 is determined by the longitudinal portions 24a of the grid electrode 24 and It is equal to the width dimension of the branch portion 24b and is, for example, about 60 to 150 (μm). Also,
The planar shape of the rib-shaped wall 30 is the same as the planar shape of the grid electrode 24 as shown in FIG.
It is composed of a and a branch portion 30b.

As shown in the partial cross-sectional structure of FIG. 3, a plurality of anodes 32 each having a substantially rectangular shape are provided below the phosphor layer 12 on the display surface 22. There is. The anode 32 is composed of a graphite layer having a thickness of, for example, about 30 to 40 (μm). The plurality of phosphor layers 12 are fixed on the anode 32, respectively, and the length dimension of each side of the anode 32 is about 400 (μm), that is, the same dimension as the phosphor layer 12 and It has a shape. The rib-shaped walls 30 are provided so as to protrude between the anodes 32, and the anodes 32 are divided into the rib-shaped walls 30 on the substrate 14 so that they are independent of each other, that is, electrically connected to each other. Insulated state.

The phosphor layer 12 is provided with one or several kinds of phosphors corresponding to a desired emission color for each anode 32, and the thickness dimension thereof is determined for each emission color. For example, it is about 30 (μm). When a plurality of types of phosphors are used, for example, in a color display using three colors of RGB, for example, RG is sequentially arranged for each row along the longitudinal direction of the substrate 14.
Phosphor layers 12 corresponding to the three colors of B are provided to form a stripe arrangement, or 4 rows of 2 columns × 2 columns adjacent to each other.
The phosphor layers 12 corresponding to the four colors of RGGB are provided in an individual unit to form a quartet arrangement. One pixel of the fluorescent display tube 10 has three or four different emission colors arranged adjacent to each other in a stripe shape or a rectangular shape (however, in the case of four, two of them have the same emission color). It is composed of the phosphor layer 12.

FIG. 5 is a view for explaining the electrode structure on the substrate 14 in a cross section parallel to the longitudinal direction of the grid electrode 24. On the display surface 22 of the substrate 14, a thick film conductor paste is printed by a screen printing method or the like in a thickness of about 15 (μm) and baked, or by vapor deposition and etching treatment of an aluminum thin film or the like, a plurality of anode strips 34 are formed so as to be connected to the anode terminal 20 _P. On this anode wiring 34, an insulator layer 38 is fixedly formed so as to cover substantially the entire surface of the display surface 22 and has a through hole 36 penetrating in the thickness direction. The insulator layer 38 is formed, for example, by applying a thick film insulating paste composed of a low melting point glass and a coloring pigment to a thickness of about 30 to 40 (μm) by a screen printing method and baking the paste. .

The anode 32 is provided on the insulating layer 38 at a position electrically connected to the anode wiring 34 through the through hole 36. The anode 32 is formed by printing a thick film printing paste containing graphite as a main component in a predetermined dot pattern and firing the paste. The phosphor layer 12 is the anode 32.
It is formed by printing a thick film phosphor paste on top. Further, the rib-shaped wall 30 is formed by printing a thick film insulating paste around the phosphor layer 12 and the anode 32. That is,
It is erected on the insulating layer 38, not directly on the substrate 14. The rib-shaped wall 30 is formed by laminating a thick-film insulating paste made of an insulating material such as low-melting glass or inorganic filler in a predetermined pattern having a line width of 120 to 150 (μm) repeatedly. The height of the phosphor layer 1 is about 200 (μm) from the surface of the insulator layer 38.
2 has a height of about 100 to 120 (μm) from the surface.
The grid electrode 24 is provided on the top of the rib-shaped wall 30.
10 to 50 thick film conductor paste containing particulate conductive material such as silver, palladium, aluminum, nickel, carbon, etc.
It is fixedly formed by printing with a thickness of about (μm).

The plurality of anode wirings 34 are provided, for example, along the short side direction of the substrate 14, that is, along the direction perpendicular to the longitudinal direction of the grid electrode 24. 32, that is, each of the phosphor layers 12 is connected to different anode wirings 34 in a column unit along the short side direction so that those arranged in the longitudinal direction of the substrate 14 are electrically independent from each other. Figure 4 above
The connection relationship of the k-th column of the anode 32 (phosphor layer 12) located on the rightmost side in the figure is shown in FIG. In FIG. 4, the anode wiring 34 includes four lines a to d which are independent from each other in each column of the anode 32, for example, 34ka, 3 for the kth column.
4 kb, 34 kc, and 34 kd are provided, and the plurality of anodes 32 in each column are connected to the common one of the four anode wirings 34 at intervals of three. That is,
In this embodiment, the substrate 14 is constructed in an anode quadruple wiring structure, and the anodes 32 connected to any of the four anode wirings 34 are arranged at regular intervals in the short side direction of the substrate 14. Lined up. Other anodes 3 not shown
The connection state with the anode wiring 34 is the same for any of the two columns. Note that, in FIG. 4, for convenience of illustration, the anode 32 and the grid electrode 24 are drawn so as not to be in contact with each other. In addition, in the cross section shown in FIG. 5, the anode wiring 34 that is connected to the six anodes 32 before and after the anode 32 in the illustrated row and is not connected to the anode 32 in the cross section shown in the drawing is actually a rib-shaped wall. Although there are three between 24b, only one is shown for convenience of illustration.

When the fluorescent display tube 10 constructed as described above is driven, for example, two grid electrodes adjacent to each other are fed while a predetermined heating current is constantly applied to the plurality of filaments 28. 24 as a set, for example, for that zero (V) filament 28, for example 2
A relatively positive accelerating voltage of about 0 (V) is sequentially applied, and scanning is performed in the downward direction in FIG. 4, for example, while changing the combination one by one (that is, shifting one by one). Then, in synchronization with the scanning timing, a drive voltage of about 20 (V), which is the same as the above acceleration voltage and is positive with respect to the cathode potential, is applied to a predetermined anode wiring 34 corresponding to the input data. As a result, the thermoelectrons emitted from the filament 28 are accelerated by the grid electrode 24 to which a positive voltage is applied, so that the phosphor layer 12 surrounded by the anode 32 also has the anode 32.
When a positive voltage is applied through the phosphor layer 12
Electrons are incident on and excite them to emit light. However, even if a positive voltage is applied to the phosphor layer 12, the grid electrode 24 surrounding the phosphor layer 12 has several
When a negative cutoff bias of about (V) is applied, thermoelectrons do not reach the phosphor layer 12 and the phosphor layer 12 does not emit light. Therefore, in the state where the thermoelectrons are emitted by the current flowing through the filament 28, the desired one of the phosphor layers 12 is selected in synchronization with the timing when the acceleration voltage is sequentially applied to the grid electrode 24. Also, when a positive voltage is applied, so-called dynamic driving causes light emission display in a desired pattern.

In the above driving, the voltage waveform applied to the grid electrode 24 and the phosphor layer 12 is, for example, as shown in FIG.
As shown in. Hereinafter, the driving method will be described in more detail with reference to FIG. 4 and the driving waveforms. In addition, in FIG. 6, “... Gp, Gq, to Gu
"..." represents the grid electrodes 24 sequentially arranged in the column direction, and "... Aka, Akb, ~ Alb ..."
.., k columns, l columns, ..., Four anode wires 34a, 34b, 34c, 34d are provided. The voltage is applied to the phosphor layer 12 through the anode wiring 34, and as described above, every three phosphor layers 12 in each row are connected to the common anode wiring 34. 6 shows the drive waveform of the anode wiring 34.

At time ti shown in FIG. 6, first, Gp shown in the uppermost position in FIG.
An acceleration voltage is applied to the two Gq lines, and the anode wiring 3
4 out of 4, Akb, Akc, Alb, Alc, etc., ie 4 in each column
A positive voltage is applied to two of the books whose subscripts are b and c. Therefore, the electrons generated from the filament 28 are
The phosphor layer 12 is attracted to the grid electrodes Gp and Gq to which the acceleration voltage is applied, but is surrounded or in contact with them.
Among the predetermined ones in the b and c rows located in the center, that is, the anode wirings 34b in the b and c rows of the phosphor layer 12 to be made to emit light in one cycle of the light emission currently being performed, Since a positive voltage is applied via 34c, the attracted electrons are directed to the predetermined phosphor layer 12, and the injected electrons excite the phosphor to emit light. On the other hand, the grid electrode G
The other four lines surrounded by or in contact with p and Gq, that is, a,
Since a positive voltage is not applied to one row (not shown) above the rows d, e, and a, electrons are not directed to the phosphor layer 12 and light is not emitted. At this time, the grid electrode 24 and the anode wiring 34 (Akb, Akc, Alb, etc.)
The pulse width w ₁ of the drive pulse applied to
(μs).

At time tj, a cutoff bias is applied to the grid electrode Gp, an acceleration voltage is applied to the grid electrode Gr, and the anode wirings Aka, Aka
A positive voltage is applied to kd, Ala, etc., that is, two of the four in each column with the subscripts a and d. Therefore, among the six rows b to g of the phosphor layers 12 surrounded by or in contact with the grid electrodes Gq and Gr to which the acceleration voltage is applied, the input data in the two rows of d and e located in the center of them is determined. A certain object is made to emit light. At this time, the pulse width w ₂ of the drive pulse applied to the grid electrode 24 and the anode wiring 34 (Aka, Akd, Ala, etc.) is, for example, about 325 (μs).
That is, the pulse width at the time of emitting light from the rows d and e is made longer than that at the time of emitting light from the rows b and c.

The above-mentioned FIG. 6 shows a drive waveform after the cumulative drive time has passed, for example, 2000 hours. The drive waveform of the fluorescent display tube 10 at the beginning of use is the same as that in FIG. 6, but the drive pulse width is, for example, w ₁ =
w ₂ = 300 (μs) and the same value is set. However, if the cumulative drive time exceeds 2000 hours, for example,
Due to deterioration of the emission characteristics of the filament 28 and the like, the area immediately below the filament 28 and the filament 28
The difference in the amount of electrons reaching each other in the vicinity of the center becomes noticeable to the extent that it cannot be ignored, and the difference in the luminance, that is, the luminance unevenness, is observed. Therefore, while the accumulated drive time is short, the pulse widths w ₁ and w ₂ are similar to each other as described above, but when the time exceeds 2000 hours, for example, the drive pulse as shown in FIG. 6 is applied. Will be required.

When driven by the driving pulse as shown in FIG. 6, the grid electrode 24 and the anode are emitted at the time of emission of the rows b and c located at the center between the filaments 28 adjacent to each other as shown in FIG. Pulse width w applied to 32
_{When 1} is shortened, the amount of electrons reaching the phosphor layer 12 becomes relatively small. On the other hand, at the time of emitting light in the rows d and e located immediately below the filament 28, the pulse width w ₂ thereof is lengthened, so that the phosphor layer 12 is formed.
The amount of electrons that reach is relatively large. Since the brightness of the phosphor layer 12 increases as the amount of electrons reaching the phosphor layer increases,
By providing the difference between the pulse widths w ₁ and w ₂ , the brightness of the rows b and c, which should be relatively low when the accumulated driving time is long and the distance is short from the filament 28, is increased, while the long distance is increased. However, since the luminances of the rows d and e, which are supposed to have relatively high luminance when the accumulated driving time becomes long, are lowered, the luminances become substantially the same. It should be noted that the center spacing of the filaments 28 and the relative position to the grid electrode 24 are set such that the filaments
The filament 28 is placed on one of the elongated portions 24a of the grid electrode 24 adjacent to another grid electrode 24 so that the two rows located in the center between them or the two rows located immediately below the filament 28 can be selected. It is defined to be located. Since the two rows that emit light at the same time are at the same distance from the filament 28 in any of the combinations described above, the same drive pulse width results in mutually similar brightness.

At time tk, similarly to the case at time ti, the acceleration voltage is applied to the grid electrodes Gr, Gs, and at the same time, the anode wirings Akb, Akc, Alb, etc., that is, of the four electrodes in each column, are selected. By applying a positive voltage again to the two subscripts b and c, the phosphor layers 1 of two rows f and g are applied.
2 is made to emit light. At the subsequent time tl, the acceleration voltage is applied to the grid electrodes Gs and Gt, and the anode wiring A
A positive voltage is applied to ka, Akd, Ala, etc., and the phosphor layers 12 in two rows h and i are caused to emit light. Even at these times, the pulse width w ₁ is set to a relatively short value of about 275 (μs) when the f and g rows located in the center between the filaments 28 are made to emit light, while the filament 28 When the h and i rows located immediately below are made to emit light, the pulse width w ₂ is set to a relatively long value of about 325 (μs). Therefore, as in the case of times ti and tj, as compared with the case of normal driving in which a driving voltage is applied with a constant pulse width,
Since the brightness of the phosphor layer 12 located in the center between the filaments 28 is reduced and the brightness of the phosphor layer 12 immediately below the filaments 28 is increased, the difference in brightness is reduced.

As described above, in this embodiment, of the six rows of phosphor layers 12 surrounded by or in contact with the two grid electrodes 24 to which the acceleration voltage is simultaneously applied, the two rows located at the center, that is, the two rows. Of the phosphor layers 12 surrounded by the grid electrodes 24 of the book, two rows located inside are selected as rows that emit light at the same time, and a positive voltage is applied to the phosphor layers 12 that emit light within one cycle in the rows. As a result, the phosphor layer 12 is caused to emit light in two rows. In this case, if the accumulated driving time becomes long, the filament 2
8 and the phosphor layer 12, depending on whether they are located directly below the filament 28 or between the filaments 28, in other words, the filament 28
The drive pulse of the grid electrode 24 and the anode 32 when applying a drive voltage to a relatively short distance is long and the drive pulse to a relatively long distance is short according to the distance from To be extinguished. Therefore, since the electron injection time to an object located at a short distance, where the brightness tends to be relatively low, is increased and the injection amount is increased, the brightness is relatively increased, while the relative brightness is increased. Since the incident time of electrons to those located at a long distance, where the brightness tends to be high, is shortened and the incident amount is reduced, the brightness is relatively lowered. Therefore, even after a certain accumulated drive time has elapsed, the filament 28
Since the difference in brightness due to the difference in the distance from and the unevenness in brightness are suitably alleviated, uniform brightness is obtained over the entire display surface 22. That is, a constant display quality can be secured regardless of the elapsed cumulative driving time.

In this embodiment, the filament 28 is divided into a plurality of pieces in the direction perpendicular to the longitudinal direction,
Since the grid electrode 24 is provided along the longitudinal direction of the filament 28, as described above, the phosphor layers 12 that emit light are selected on a row unit basis including a plurality of phosphor layers 12 arranged in the longitudinal direction. Therefore, since the phosphor layer 12 located at the same distance from the filament 28 is caused to emit light at the same time, the pulse width of the drive pulse applied to the grid electrode 24 and the phosphor layer 12 can be easily adjusted according to the difference in the distance from the filament 28. Can be adjusted to.

The pulse widths w ₁ and w ₂ are constant values determined according to the positional relationship between the filament 28 and the row of the phosphor layer 12 to emit light, and when 2000 hours have passed. Then, they are set to 275 (μs) and 325 (μs), respectively, but the values may be further changed according to, for example, changes in characteristics of the fluorescent display tube 10 over time. That is, the pulse widths w ₁ and w ₂ are 300 (μs) and
A value of about 300 (μs), 275 (μs), 32 after 2000 hours
It is set to a value of about 5 (μs) and then kept at that value,
Alternatively, for example, 250 (μs), 350 after about 5000 hours
It can be changed to a value of about (μs). Further, if necessary, a difference in pulse width may be provided after a certain period of time. By changing the pulse width in multiple stages, it is possible to further alleviate the change in luminance over time. As described above, in order to change the pulse width according to the cumulative drive time, for example, a nonvolatile memory is provided in the fluorescent display tube 10 to count the cumulative drive time, and the time reaches a predetermined constant time. Then, the pulse width may be changed.

Further, in the drive waveform shown in FIG. 6, the pulse widths of the drive pulses applied to the grid electrode 24 and the anode wiring 34 are controlled to have the same value.
Since the electrons can enter the phosphor layer 12 only during the period when the positive voltage is applied to both, it is not essential to set these pulse widths to the same value, and the pulse widths are relatively set. Similar control is possible by changing one of the shorter values. For example, if the pulse width of the grid electrode 24 is 2
One pulse width w _1, is fixed to one value w ₂ of longer one of w _2, a pulse width of the anode wiring 34 may be varied between w _1, w _2. Alternatively, conversely, the pulse width of the anode wiring 34 is fixed to w ₂ , and the pulse widths of the grid electrode 24 are w ₁ and w _2.
May vary between.

In the above description, the driving pulse widths w ₁ and w ₂ were set to the same value at the beginning of use, but the distribution of the amount of arriving electrons according to the distance from the filament 28 is Since it is from the beginning, when the luminance unevenness is observed from the beginning due to the characteristics of the fluorescent display tube 10, or when a higher display quality is desired, the pulse widths w ₁ and w ₂ are set to different values from the beginning, that is, The pulse width w ₂ may be set to a value larger than the pulse width w ₁ . As the initial value of the pulse width in this case, for example, w ₁ = 290 (μs), w ₂
A value of about 310 (μs) is used. As the value of the pulse width after the elapse of the fixed time, for example, the same value as that described above is used. In this case, change the pulse width based on the cumulative drive time at an appropriate time (for example, 2000 hours).
It may be carried out only once when the time has elapsed, twice (for example, after the elapse of 5000 hours for the second time) or more times. Thus, the driving method of the present invention can be applied from the beginning or after a certain driving time has elapsed.

Further, in the drive waveform shown in FIG. 6, the drive pulse width is set to be different depending on the distance from the filament 28, but as shown in FIG.
The potential of the drive pulse may be changed according to the distance. FIG. 7 is a diagram in which drive voltage waveforms to the grid electrodes Gp to Gr at times ti to tk in FIG. 6 are extracted and shown. In this drive waveform, the drive pulse width is kept constant regardless of whether the phosphor layer 12 having a positional relationship with the filament 28 is made to emit light, while the drive pulse potential is, for example, v ₁ = 40 (V ) And v ₂ = 42 (V). A relatively low potential pulse v ₁ was applied when the row of the phosphor layer 12 distant from the filament 28 connected to the anode wirings 34b and 34c was made to emit light, and was connected to the anode wirings 34a and 34d. A pulse v ₂ of relatively high potential is applied when a row of the phosphor layer 12 at a short distance is issued. Although the voltage waveform applied to the anode wiring 34 is omitted, its pulse width is kept constant similarly to the pulse width to the grid electrode 24 described above.

Therefore, since the electrons generated from the filament 28 are accelerated toward the phosphor layer 12 as the voltage applied to the grid electrode 24 is higher, the pulse width is constant, that is, the drive voltage application time is constant. Even
When the acceleration voltage is high, the amount of electrons that reach the phosphor layer 12 is large, and when the acceleration voltage is low, the amount of electrons that arrive is small. Therefore, even in this case, it becomes possible to adjust the reaching electron amount in relation to the distance from the filament 28, for example, to make it uniform on the display surface 22. As described above, the method of adjusting the amount of electrons reaching by voltage has an advantage that the duty ratio cannot be changed as compared with the case of changing the pulse width.

In the above waveform diagram, the grid electrode 24
Although the applied voltage to the phosphor layer 12 is changed, the reaching electron amount can be similarly adjusted by changing the applied voltage to the phosphor layer 12. Further, the voltage applied to the grid electrode 24 and the phosphor layer 12 may be changed in only one, but both may be made high or both low. If the voltages applied to both are set to the same potential, there is an advantage that a higher effect can be obtained with a relatively low voltage and the number of prepared potentials is reduced as compared with the case where only one voltage is changed.

Also, in the case of adjusting the brightness by changing the voltage of the drive pulse as described above, it is needless to say that the voltage is constant at the beginning regardless of the distance from the filament 28. The voltage value may be different depending on the distance from.

FIG. 8 corresponds to FIG. 4 for explaining another electrode configuration example to which the present invention is applied. In this configuration example, the plurality of rectangular phosphor layers 12 are arranged vertically and horizontally as in the case of FIG. 4, but the grid electrode 40 passing between them is placed between the phosphor layers 12 and the substrate 14. With one longitudinal portion 40a extending along the longitudinal direction of the phosphor layer 12 and a length dimension substantially the same as or slightly shorter than the length dimension of one side of the phosphor layer 12 at the midpoint thereof. It is composed of a plurality of branch portions 40b intersecting with. Therefore, the phosphor layers 12 in any row are in a positional relationship in which substantially the entire circumference is surrounded by the two grid electrodes 40 located on both sides thereof. In addition, the phosphor layer 12 in each row has two anode wirings 34a, 34 provided in each column.
and b are alternately connected in the column direction. That is, the anode substrate of this example has an anode double matrix structure.

The fluorescent display tube having the substrate 14 constructed as described above is driven, for example, by applying a drive pulse whose voltage waveform is shown in FIG. This drive waveform is for causing the phosphor layer 12 of one row to emit light at a time.
In the figure, first, when a driving pulse having a pulse width w ₁ is applied to the grid electrodes Gr, Gs, in synchronization with this timing, a predetermined one of the anode wirings 34a corresponding to the input data, for example, the anode wiring 34ka or the like is applied. A drive pulse is applied. As a result, the phosphor layer 12 in the c-th row sandwiched between the grid electrodes Gr and Gs is selectively caused to emit light in that period. The pulse width w ₁ is set according to the time of one cycle, the number of rows of the phosphor layer 12, etc., but is set in the same manner as in the embodiment shown in FIG. Is 300 (μs)
Or a value of about 290 (μs), a value of about 275 (μs) after a lapse of about 2000 hours, and a value of about 250 (μs) after a lapse of about 5000 hours. The pulse width of the drive pulse applied to the anode wiring 34 is similar to the drive pulse of the grid electrode 40 in this embodiment.

At the subsequent timing, the drive pulse having the pulse width w ₂ is applied to the grid electrodes Gs and Gt, and at the same time, the drive pulse is applied to a predetermined one of the anode wirings 34b, for example, the anode wiring 34kb. This allows
Fluorescent substance layer 12 in d rows sandwiched between grid electrodes Gs and Gt
Of those, what is to be made to emit light in the cycle is selectively made to emit light. The above pulse width w ₂ is, for example, 300 (μs) in the initial stage as in the case of w ₂ in FIG.
Or a value of about 310 (μs), a value of about 325 (μs) after about 2000 hours, and a value of about 350 (μs) after about 5000 hours. In this way, the driving pulse having the pulse width w ₂ is applied to the grid electrodes Gu and Gu so that the phosphor layer 12 in the e-th row is moved to the grid electrodes Gu and Gv.
By applying a drive pulse having a pulse width w ₁ to the phosphor layers 12 in the fth row in order, and in the same manner, in each of the rows contiguous thereto, a desired image is formed by dynamic driving. Is displayed.

At this time, also in the present embodiment, when a certain cumulative driving time is reached or at the beginning, the rows of the phosphor layer 12 located immediately below the filament 28, for example, a, d, e, h. A drive pulse having a relatively long pulse width of w ₂ is applied to the rows and the like, and rows of the phosphor layer 12 located between the filaments 28, for example, b, c, f, g.
A drive pulse having a relatively short pulse width w ₁ is applied to a row or the like. Therefore, the brightness of the phosphor layer 12 immediately below, which is close to the filament 28 and tends to have low brightness, is increased, and the brightness of the phosphor layer 12 at an intermediate position, which is far from the filament 28 and tends to have high brightness, is decreased. The difference in the luminance of 1 is alleviated, and a display with uniform luminance is obtained on the display surface 22.

In the above description, the driving pulse is applied only to the two grid electrodes 40 located in contact with both sides of the row of the phosphor layer 12 to emit light, but the driving pulse is cut by such a driving method. When a shadow appears due to the influence of a negative electric field formed by the grid electrode 40 in the vicinity where the off bias is applied, a drive pulse is simultaneously applied to a sufficient number of grid electrodes 40 to eliminate the shadow. For example, in FIG. 9, at the timing of causing the phosphor layer 12 in the d-th row to emit light, the acceleration voltage may be simultaneously applied to the grid electrodes Gr and Gu outside the grid electrodes Gs and Gt.

Although one embodiment of the present invention has been described in detail with reference to the drawings, the present invention can be implemented in still another mode.

For example, in the fluorescent display tube 10 of the embodiment, four or two anode wirings 34 are provided in each column. The number of the anode wirings 34 is the number of rows of the phosphor layers 12 that emit light at the same time or the number of rows. Grid electrode 2 for simultaneously applying acceleration voltage
The number can be appropriately changed according to the number of 4 or the like, and can be set to an appropriate number of 3 or 5 or more within a range in which a desired driving method can be realized.

The number of rows of the phosphor layers 12 that emit light at the same time is set to 2 in the example shown in FIGS. 6 and 7, and 1 in the example shown in FIG. 9, but it is made to emit light at each time. The number of rows of the phosphor layer 12 is appropriately set according to the number of anode wirings 34 provided in each column, the required display quality, the grid electrode structure, and the like. For example, in the configuration example shown in FIG. 8, when leak light emission hardly occurs,
By applying an accelerating voltage to three or five grid electrodes 40 at the same time, the central two rows of phosphor layers 12 sandwiched between them may emit light at the same time. However, when a plurality of rows are made to emit light at the same time, the positional relationship between the filament 28 and the grid electrodes 24 and 40, and the grid to which an acceleration voltage is applied at the same time so that those having the same distance from the filament 28 are made to emit light at the same time. Electrodes 24, 40
It is preferable to set the combination of the above in order to simplify the drive waveform.

In the embodiment, the case where the brightness is made uniform on the display surface 22 has been described.
Depending on the arrangement position of 0, purpose of use, display image, etc.,
If you want to increase the brightness partially or lower the brightness,
The drive pulse width may be set long or the drive voltage may be set high when the phosphor layer 12 is desired to have high brightness, and the drive pulse width may be short or the drive voltage may be set low when the phosphor layer 12 is to be low brightness.

In the embodiment, the amount of electrons reaching the phosphor layer 12 and the brightness are adjusted by changing the driving pulse width and the driving voltage of the grid electrodes 24 and 40. The brightness can also be adjusted by similarly changing the driving pulse to the body layer 12. In this way, since the phosphor layers 12 that emit light at the same time are connected to the respective independent anode wirings 34, it is possible to adjust the individual brightness according to the image to be displayed.

Further, in the embodiment, the case where the present invention is applied to the fluorescent display tube 10 for graphic display in which a plurality of rectangular fluorescent material layers 12 for forming dot-shaped pixels are arranged vertically and horizontally will be described. However, a rectangular or hexagonal phosphor layer 12 has a proper angle, for example, a fluorescent display tube for graphic display arranged along two directions intersecting at an angle of 60 degrees, or a 7-segment figure-eight shape. Phosphor layer 1 to represent
The present invention can be similarly applied to a fluorescent display tube or the like in which 2 is provided or the phosphor layer 12 is provided in a character pattern of an appropriate shape. In the character pattern, it is often difficult to adjust the brightness by the method of changing the driving pulse to the grid electrodes 24 and 40, but in such a case, the driving pulse to the phosphor layer 12 is changed exclusively. Any method may be used.

In the embodiment, the grid electrode 2
Although the case where the conductors 4 and 40 are formed on the top of the rib-shaped wall 30 has been described, the present invention is also applicable to the case where the mesh-shaped grid electrode is provided.

Further, in the embodiment, the filament 2
Since 8 are provided at a center interval that is four times as large as the center interval of the phosphor layer 12, the distance between the filament 28 and the phosphor layer 12 becomes two perspectives.
The pulse width or the potential of the seed was changed, but when the above distance is not simplified in this way, each line is changed line by line according to the type of the distance from each filament 28 of the phosphor layer 12. Alternatively, the pulse width and potential may be adjusted individually.

Although not illustrated one by one, the present invention can be variously modified without departing from the spirit thereof.

[Brief description of drawings]

FIG. 1A to FIG. 1C are diagrams for explaining distributions of the amount of electrons that reach a phosphor layer at an early stage, a middle stage, and a late stage of the life of a fluorescent display tube, respectively.

FIG. 2 is a perspective view showing a fluorescent display tube according to an embodiment of the present invention with a part thereof cut away.

FIG. 3 is an enlarged perspective view showing a part of a display surface.

FIG. 4 is a diagram illustrating an electrode connection configuration and the like of the fluorescent display tube of FIG.

FIG. 5 is a diagram illustrating a cross-sectional structure of a main part of an anode substrate of a fluorescent display tube in FIG.

FIG. 6 is a diagram illustrating an example of a drive voltage waveform of the fluorescent display tube of FIG.

FIG. 7 is a diagram illustrating a main part of another example of a drive voltage waveform.

FIG. 8 is a diagram illustrating another example of the electrode configuration of the fluorescent display tube to which the present invention is applied.

9 is a diagram illustrating an example of a drive voltage waveform applied to the electrode configuration of FIG.

[Explanation of symbols] 10: Fluorescent display tube 12: Phosphor layer 24: Grid electrode (control electrode) 22: Display surface 28: Filament 32: Anode 34: Anode wiring

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H01J 31/15 H01J 31/15 BF (72) Inventor Mohri Jun Yasu-cho, Asakura-gun, Fukuoka Prefecture Yatsunami 2160 Noritake Electronics Co., Ltd. Yasu Factory F-term (reference) 5C036 EE02 EE04 EF02 EF06 EG15 EG29 EG30 EG47 EG48 EH26 5C080 AA08 BB05 DD05 EE28 FF12 JJ04 JJ05 JJ06

Claims (6)

[Claims] 1. A vacuum space, comprising: a phosphor layer fixed to each of a plurality of anodes provided on a display surface of a substrate; and a plurality of control electrodes arranged above the phosphor layer. A fluorescent display tube of the type in which electrons generated from a filament cathode erected above the control electrode are controlled by the control electrode to selectively enter the phosphor layer to cause the phosphor layer to emit light. The drive width applied to at least one of the plurality of anodes and the plurality of control electrodes, wherein at least one of the pulse width and voltage of the drive pulse is related to the distance from the filamentary cathode to the anode. A method for driving a fluorescent display tube, which is characterized in that it is adjusted by adjusting. 2. The pulse width is increased or the voltage is increased at a position closer to the filament cathode so that the amount of electrons incident on each of the plurality of phosphor layers is uniform on the display surface. The method for driving a fluorescent display tube according to claim 1, wherein the height is increased. 3. The amount of adjustment of the drive pulse and the applied voltage with respect to the cumulative drive time of the fluorescent display tube, and the pulse width and the voltage related to the distance from the filamentary cathode as the cumulative drive time increases. The method for driving a fluorescent display tube according to claim 2, wherein 4. A vacuum space, comprising: a phosphor layer fixed to each of a plurality of anodes provided on a display surface of a substrate; and a plurality of control electrodes arranged above the phosphor layer. A fluorescent display tube of the type in which electrons generated from a filament cathode erected above the control electrode are controlled by the control electrode to selectively enter the phosphor layer to cause the phosphor layer to emit light. 2. The fluorescent display tube according to claim 1, wherein a plurality of the control electrodes are arranged side by side in a direction perpendicular to the longitudinal direction of the filamentous cathode so as to extend along the longitudinal direction thereof. 5. The fluorescent display tube according to claim 4, wherein the control electrode is a rib grid electrode provided on the top of a rib-shaped wall projecting on the display surface so as to surround the phosphor layer. 6. The phosphor layer is provided at a predetermined center interval along two directions in which each of the phosphor layers forms a dot shape and intersects with each other, and the filament cathode has a center interval that is an integral multiple of the center interval. The fluorescent display tube according to claim 4, wherein the fluorescent display tube is provided.