JPH05249914A - Driving circuit for fluorescent character display device - Google Patents

Abstract

PURPOSE:To reduce electric power consumption to the possible minimum level while being driven and while staying in standby, and make a low cost low voltage logic IC usable by enabling a driving circuit for a fluorescent character display device formed by using an electric field electron emitting element as an electron source to be driven by means of a battery. CONSTITUTION:A driving circuit for a fluorescent character display device formed by using an electric field electron emitting element 6 as an electron source is composed of a high voltage electric power supply circuit 20 and a low voltage driving circuit 25, and is characterized in that the high voltage electric power supply circuit 20 outputs bipolar constant voltage in the same level between positive and negative to an earthing level by using a battery 21 as an electric power supply, and the low voltage driving circuit 25 outputs driving voltage to carry out a display operation of the fluorescent display device to inputted signal voltage by using the bipolar constant voltage as an electric power supply, and positive constant voltage is inputted to an anode of the fluorescent display device, and negative constant voltage is inputted to a cathode, and respective driving voltages are inputted to a gate electrode group, respectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting type character display used for displaying, for example, watches, in-vehicle instruments, OA equipment and other various information display devices, or a small matrix display used for a viewfinder of a camcorder. And the like, and particularly to a drive circuit for a fluorescent display device using a field electron emission element as an electron source.

[0002]

2. Description of the Related Art Recently, as a fluorescent display device as described above, it has been proposed to use a field electron emission element as an electron source and irradiate electrons from the field electron emission element to a fluorescent layer for display. For example, EURODISPLAY'90 (September 25
-27, 1990) or Technical Digest of IVMC 91). FIG. 13 shows an example of the specific configuration.
A conductive cathode electrode 102 is formed on an element substrate 101 made of glass or the like, and a gate electrode 104 is formed on the cathode electrode 102 with an insulating layer 103 interposed therebetween.
A substantially conical field electron emission device (microchip) 105 is provided on the cathode electrode 102 in the opening formed in the insulating layer 103 and the gate electrode 104. In addition, IT is provided on the lower surface of the element substrate 106 made of glass or the like arranged above the element substrate 106.
An anode electrode 107 made of O or the like is formed, and the fluorescent layer 10 is provided on the lower surface side above the field electron emission device 105.
8 is provided. The field electron emission device 1
05 and the fluorescent layer 108 are evacuated, and the cathode electrode 102, the gate electrode 104 and the anode electrode 10 are evacuated.
By applying a predetermined voltage to 7 and 7, electrons are emitted from the tip of the conical field electron emission device 105, and the fluorescent layer 108 is irradiated with the desired display.

[0003]

However, since the conventional device is driven by a commercial power source of 100 V, there is a problem that it cannot be applied to portable devices such as wristwatches and amusement devices which are premised on battery operation. there were.

The present invention has been proposed in view of the above problems, and enables the fluorescent display device as described above to be driven by a battery to reduce power consumption during driving and standby as much as possible, and at a low cost. The purpose is to enable the use of voltage logic ICs.

[0005]

In order to achieve the above object, the driving circuit of the fluorescent display device according to the present invention has the following configuration. That is, a drive circuit of a fluorescent display device using a field electron emission device as an electron source is composed of a high voltage power supply circuit and a low voltage drive circuit, and the high voltage power supply circuit uses a battery as a power source and has a positive / negative same level with respect to a ground level. The bipolar constant voltage is output, and the low voltage drive circuit outputs the drive voltage for performing the display operation of the fluorescent display device with respect to the input signal voltage using the bipolar constant voltage as a power source, and the positive constant voltage is applied to the anode of the fluorescent display device. A negative constant voltage is input to the cathode, and each driving voltage is input to the gate electrode group.

[0006]

By configuring the drive circuit of the fluorescent display device as described above, it becomes possible to drive the battery, and it is possible to reduce power consumption during drive and standby as much as possible. Further, it becomes possible to use an inexpensive constant voltage logic IC.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A driving circuit for a fluorescent display device according to the present invention will be specifically described below with reference to the embodiments shown in the drawings. Figure 1
Is a plan view showing an example of a fluorescent display device to which the present invention is applied,
2, 3 and 4 are respectively AA and B- in FIG.
It is a sectional view taken along the line B-C-C, and the fluorescent display device of this example exemplifies a character display for displaying a clock.

In the figure, 1 is an element substrate, and in this embodiment, an n-type single crystal silicon substrate having a (100) plane orientation is used. Above the element substrate 1, counter substrates 2 are arranged substantially parallel to each other with a constant space therebetween, and a sandwiching body 3 interposed in the peripheral portion between the both substrates 1 and 2 tightly and tightly bonds them. A space S is formed between the substrates 1 and 2 surrounded by the holding body 3. As a material of the counter substrate 2, the element substrate 1 having the thermal expansion coefficient described above is used.
It is desirable to use a transparent glass substrate made of borosilicate glass (# 7740 manufactured by Corning Incorporated) in this embodiment.

Further, the material of the sandwiching body 3 is preferably one having a thermal expansion coefficient close to that of the both substrates 1 and 2 in order to reduce the stress after the both substrates 1 and 2 are bonded.
Particularly, an intermediate value thereof is desirable. In this example, the working point was 450 ° C. and the coefficient of thermal expansion was 53 × 10 ⁻⁷ /
A low melting point powdered glass of ℃ is used.

Further, it is desirable to mix spacers or the like in the holding body 3 in order to hold both substrates 1 and 2 in parallel. In that case, it is necessary to select a spacer or the like that does not soften when the sandwiching body 3 is heated and melted and softened to seal the two substrates 1 and 2, and in this embodiment, the softening point is the above-mentioned. A spherical glass spacer having a sealing temperature or higher is used. Further, it is necessary to use a spacer having a particle size larger than at least the thickness of the phosphor layer 8, and in this example, the spacer having a particle size of 60 μm is used.
・ 2 are arranged in parallel facing each other at intervals of about 60 μm.

1 and 4, reference numeral 2a denotes both substrates 1.
An exhaust port for exhausting the air in the space S surrounded by 2 and the sandwiching body 3 to create a vacuum, and for example, housing both substrates 1 and 2 in a sealed state in a vacuum chamber or the like. Thus, the air in the space S is evacuated to form a vacuum, and then sealed by the sealing member 9 or the like. Further, in FIGS. 1 and 2, 10 is a getter material for adsorbing the gas remaining in the space S, and in the present embodiment, B is used.
aAl ₄ or the like is used, which is previously provided on the inner surface of the counter substrate 2 by vapor deposition or the like, and the space S is evacuated, and then the getter material 1 is used.
By irradiating 0 with a laser or the like to evaporate the space S,
The gas that remains inside is adsorbed.

On the surface in the space S of the element substrate 1, a plurality of segment electrodes 5 arranged for time display are provided.
Each segment electrode 5 is provided with a plurality of field electron emission devices 6 which are electron emission sources, as shown in FIGS. 5 and 6. 5a is a segment terminal 5a for connecting each segment electrode 5 to an external circuit,
The terminals 5a are provided on the surface of the insulating substrate 1 outside the space S, and are connected to the segment electrodes 5 via the segment wirings 5b.

As shown in FIG. 7, the field electron emission device 6 is a device substrate 1 except for a substantially conical protrusion 6a processed by anisotropic etching or the like and the vicinity of the protrusion 6a.
An insulating layer 6b made of a silicon dioxide thin film or the like formed on the surface of, and a molybdenum thin film or a tantalum thin film formed on the surface of the insulating layer 6b and having a substantially circular opening in the vicinity of the upper portion of the protrusion 6a. It is composed of a segment electrode (gate electrode) 5.

On the other hand, on the surface of the counter substrate 2 in the space S, an anode electrode 7 common to all the segments on the element substrate 1 is formed. An ITO thin film is used for the anode electrode 7 in this embodiment, and the thickness thereof is 200
It is formed to 0 angstrom. In the figure, 7a is an anode terminal for connecting the anode electrode 7 to an external circuit. In this embodiment, a Cr thin film is formed on the anode electrode 7 protruding outside the space S. An external circuit can be directly connected to the anode electrode 7 protruding outside S.

A fluorescent layer 8 is provided on the surface of the anode electrode 7, and the fluorescent layer 8 is a fluorescent material such as ZnO: Zn which emits green light in this example, and a low fluorescent material such as frit glass which functions as an adhesive. A material containing a melting point glass is used. As the phosphor, Zn that emits green light as described above is used.
In addition to O: Zn, for example, ZnS: Cl + I that emits blue light
n ₂ O ₃ or ZnS: Ag + In ₂ O ₃ which emits orange light may be used. It is also possible to perform multi-color display or full-color display by using a plurality of types of phosphors having different colors as described above.

The present invention is such that the fluorescent display device as described above is driven by a drive circuit having a high-voltage power supply circuit and a low-voltage drive circuit. FIG. 8 shows driving of the fluorescent display device according to the present invention. It is a block diagram of a schematic structure showing one example of a circuit. In FIG. 8, 20 is a high-voltage power supply circuit, which is composed of a battery 21, an oscillation circuit 22, a smoothing circuit 23, and a stabilizing circuit 24. Reference numeral 25 is a logic circuit as a low voltage drive circuit.

A stabilizing circuit 24 of the high voltage power supply circuit 20.
Outputs positive and negative polar constant voltages + V ₀ and -V ₀ ,
Inputs are made to the element substrate 1 as the anode electrode 7 and the cathode electrode, respectively. The logic circuit 25 as the low voltage drive circuit is driven by the constant voltage from the stabilization circuit 24 as a power source, and applies the drive voltage v to the gate electrode 5 of each segment based on an input signal from the outside. It is a composition. FIG. 9 is a graph showing the relationship between the applied voltage V _GK to the gate electrode 5 and the anode current I _A at that time.

For example, in the fluorescent display device for time display for watches as shown in FIG. 1, when the number of field electron emission devices is 1000 / segment, V ₀ = 100V, -V ₀ = -1.
When the driving voltage V is applied to each segment as shown in Table 1 below, the display operation can be performed when the voltage is set to 00V and the light is not emitted.

[0019]

FIG. 10 is a schematic block diagram showing another embodiment of the drive circuit of the fluorescent display device according to the present invention.
In this embodiment, the stabilization circuit 24 of the high voltage power supply circuit 20
Constant voltage for input to anode and cathode + V ₀ , -V
₀ a constant voltage + V _L for separate logic circuit driving is obtained by taking out the -V _L to drive the logic circuit 25, other configurations are the same as in the previous examples.

In this embodiment, although the output voltage from the stabilizing circuit 24 is of two systems, a constant voltage for driving the logic circuit is separately output, so that a driving voltage of 30 V or less is sufficient as compared with the above embodiment, which is inexpensive and low cost. The voltage IC can be used for the logic circuit, and the drive circuit becomes cheaper.

For example, in the fluorescent display device for time display as shown in FIG. 1, the density of the field electron emission devices is 1 × 10 ⁶ /
In the case of cm ² , V ₀ = 80 V and V _L = 15 V, and a display operation can be performed by applying a driving voltage as shown in Table 2 below to each segment during non-light emission and light emission.

[0023]

Although the above embodiment has been described by taking as an example the case where the present invention is applied to the 7-segment type character display for displaying the time, it can be applied to the matrix type fluorescent display device shown in FIGS. 11 and 12, for example. That is, in the figure, 11 is a matrix element substrate made of a silicon substrate or the like, and the field electron emission element 6 similar to the above is provided on the substrate 11. The field electron emission device is not limited to this, and may be a Spindt type or a lateral type formed on a glass substrate. On the other hand, an ITO thin film 7 of a conductor serving as an anode electrode is formed on the counter substrate 2,
A fluorescent layer 8 that emits a fluorescent color is formed thereon.

The matrix element substrate 11 and the counter substrate 2 are airtightly adhered to each other by the sandwiching body 3, and the two substrates are held by a spacer 12 produced by a photo process. As the material of the spacer 12, SiO _X or the like formed by spin coating is used. Here, in FIG. 11, the spacer 12 is formed in a columnar shape on the insulating layer 6b where the field electron emission device 6 does not exist and the stripe cathode electrode 14 does not exist. And
On the outer peripheral portion of the matrix element substrate 11, the gate wiring 13 of the stripe gate electrode 13 for connecting an external circuit is formed.
a and the cathode wiring 14a of the stripe cathode electrode 14 are formed. The present invention can be applied to the above-mentioned matrix type fluorescent display device in the same manner as in the above embodiment, and the above matrix type fluorescent display device is used for a color viewfinder of a camcorder or the like.

[0026]

As described above, the drive circuit of the fluorescent display device according to the present invention is composed of the high voltage power supply circuit and the low voltage drive circuit as described above, and the high voltage power supply circuit is grounded using the battery as a power source. The positive and negative positive and negative voltage levels are output, and the low-voltage drive circuit outputs the driving voltage for performing the display operation of the fluorescent display device with respect to the input signal voltage by using the constant bipolar voltage as a power source, and the anode of the fluorescent display device. Since the positive electrode constant voltage is input to the cathode, the negative electrode constant voltage is input to the cathode, and each driving voltage is input to the gate electrode group, an inexpensive general-purpose low-voltage IC can be used as a logic IC with a high degree of integration. . The power consumption of this IC is inevitably small because the voltage it handles is small, and the size of the IC is also small.
This is convenient for small equipment such as watches. Further, as the logic IC, it is possible to use a TTL level input, which is compatible with an external logic which outputs a display signal. Furthermore, the output of the high voltage power supply circuit is a constant voltage output of the same positive and negative levels, which is different from the positive and negative asymmetrical output.
The oscillator circuit and smoothing circuit have a simple structure, and the circuit board can be made compact, which is convenient for downsizing.

[Brief description of drawings]

FIG. 1 is a plan view showing an example of a fluorescent display device to which the present invention is applied.

FIG. 2 is a sectional view taken along the line AA in FIG.

FIG. 3 is a sectional view taken along line BB in FIG.

FIG. 4 is a sectional view taken along the line CC in FIG.

FIG. 5 is an enlarged plan view of one segment portion in the above example.

6 is a cross-sectional view taken along the line AA in FIG.

FIG. 7 is an enlarged cross-sectional view of the field electron emission device in the above example.

FIG. 8 is a schematic block diagram showing an embodiment of a drive circuit for a fluorescent display device according to the present invention.

FIG. 9 is a graph showing the relationship between the gate voltage and the anode current in the above embodiment.

FIG. 10 is a schematic block diagram showing another embodiment of the drive circuit of the fluorescent display device according to the present invention.

FIG. 11 is a plan view of a main part showing another example of the fluorescent display device to which the present invention can be applied.

FIG. 12 is a vertical cross-sectional view of the above example.

FIG. 13 is a vertical cross-sectional view of a conventional fluorescent display device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Element substrate 2 Opposite substrate 3 Clamping body 5 Segment electrode 6 Field electron emission element 7 Anode electrode 8 Fluorescent layer 20 High voltage power supply circuit 22 Oscillation circuit 23 Smoothing circuit 24 Stabilization circuit 25 Low voltage drive circuit (logic circuit)

Claims (1)

[Claims] 1. A drive circuit of a fluorescent display device using a field electron emission device as an electron source is composed of a high-voltage power supply circuit and a low-voltage drive circuit, and the high-voltage power supply circuit uses a battery as a power source and is positive and negative with respect to a ground level. The bipolar constant voltage of the same level is output, and the low voltage drive circuit outputs the drive voltage for performing the display operation of the fluorescent display device with respect to the input signal voltage by using the bipolar constant voltage as a power source, and the positive electrode to the anode of the fluorescent display device. A driving circuit for a fluorescent display device, wherein a constant voltage, a negative constant voltage are input to a cathode, and respective driving voltages are input to a gate electrode group.