JP3603471B2 - Field emission display device and driving method thereof - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a field emission display device known as a display device having a cold cathode, and an improvement in a driving method.
[0002]
[Prior art]
When the electric field applied to the surface of the metal or semiconductor is set to about 10 ⁹ [V / m], electrons pass through the barrier and emit electrons in a vacuum even at room temperature due to the tunnel effect. This is called field emission, and a cathode that emits electrons based on such a principle is called a field emission cathode (hereinafter, referred to as FEC).
[0003]
In recent years, it has become possible to produce micron-sized FEC by making full use of semiconductor integration technology. As one example, an FEC called a Spindt type is known. When this FEC is manufactured by using a semiconductor microfabrication technique, a conical emitter, that is, a distance between the emitter cone and the gate electrode can be made submicron, so that a voltage of several tens of volts is applied between the emitter cone and the gate electrode. , Electrons can be emitted from the emitter cone.
Further, since the pitch between the emitter cones can be manufactured to be 5 μm to 10 μm, tens of thousands to hundreds of thousands of FECs can be provided on one substrate.
As described above, it is possible to manufacture a surface emission type FEC, and it has been proposed that this FEC be applied as a field emission type electron source for a fluorescent display device, a CRT, an electron microscope, and an electron beam device. .
[0004]
FIG. 5 shows a schematic structure of a Spindt-type FEC, in which a conductive cathode electrode 101 is formed in a thin film on a glass substrate 100, a resistance layer 102 is further formed on the cathode electrode 101, and An insulating layer 103 made of silicon dioxide or the like is formed. A thin-film gate electrode 104 is formed on the insulating layer 103, and a number of openings penetrating the gate electrode 104 and the insulating layer 103 are provided.
The resistive layer 102 is exposed in the opening, and a conical emitter cone 105 is formed on the resistive layer 102.
[0005]
The reason why the resistive layer 102 is provided between the emitter cone 105 and the cathode electrode 101 in the FEC thus configured is as follows.
In a general FEC, the distance between the tip of the emitter cone and the gate is an extremely short distance of submicron, and tens to hundreds of thousands of emitter cones are provided on one substrate. During the manufacturing process, the emitter cone and the gate may be short-circuited due to dust or the like. In this way, if any one of the gates and the emitter cone is short-circuited, it means that the cathode and the gate are short-circuited, so that no voltage is applied to all the emitter cones and the inoperable field emission electron source turn into.
[0006]
In addition, local degassing occurs during the initial operation of the field emission electron source, and this gas may cause a discharge between the emitter cone and the gate or the anode, so that a large current flows to the cathode and the cathode is blown. Had to be done.
Furthermore, since there is an emitter cone from which electrons are likely to be emitted among a large number of emitter cones, an abnormally bright spot may be generated on a screen due to the electrons emitted from the emitter cone in a concentrated manner.
[0007]
Therefore, as shown in FIG. 5, a resistive layer 102 is formed between the cathode electrode 101 and the emitter cone 105, and when one of the emitter cones 105 starts emitting abnormally many electrons due to the non-uniform shape. In addition, a voltage drop occurs between the gate electrode 104 and the cathode electrode 101 due to the resistance layer 102. Due to this voltage drop, the applied voltage of the emitter cone 105 that intends to emit an abnormally large current is reduced in accordance with the emission current, so that electron emission is suppressed, and each emitter cone 105 performs stable electron emission. Become. For this reason, the fusing of the cathode electrode 101 can be prevented.
[0008]
That is, when the Vg (gate voltage) -Ie (emission current) characteristics are different as shown in FIG. 6, this voltage drop results in a different emission current Ie determined by the intersection of the Vg-Ie curve and the load line. In the emitter cone 105 having the Vg-Ie characteristic, a difference in a voltage drop of ΔV _drop shown in the drawing occurs.
Therefore, by providing the resistance layer 102, it is possible to improve the production yield of the FEC and to ensure the stable operation of the FEC.
[0009]
[Problems to be solved by the invention]
Incidentally, the resistance layer 102 can be formed using an amorphous silicon (α-Si) material. However, the α-Si material is a semiconductor, and a certain amount of impurities must be introduced in order to control the resistance value of the resistance layer 102. By doing so, the resistivity is controlled. Thereby, fluctuation of electrons emitted from the emitter cone 105 can be suppressed.
Generally, the resistance value of a semiconductor has a negative temperature coefficient, and the resistance value tends to decrease with increasing temperature. The same applies to the α-Si material, and the resistance value R decreases logarithmically with respect to the temperature change T as shown in FIG. The vertical axis in FIG. 7 is a logarithmic scale. Therefore, the resistance value of the resistance layer 102, that is, the emitter resistance value fluctuates with the change of the ambient temperature, and the amount of voltage drop at the emitter resistance portion changes.
[0010]
Then, the gate-emitter voltage V _GE applied to the emitter substantially fluctuates. As a result, the emission current emitted from the emitter cone 105 fluctuates rapidly due to the temperature fluctuation. FIG. 8 shows this state. Curves a to g show IV characteristics when a is the lowest temperature and g is the highest temperature, and rises exponentially with temperature. The anode current Ia sharply rises with the temperature rise. Therefore, there is a problem that the light emission luminance fluctuates with the fluctuation of the ambient temperature.
Further, when the emission current fluctuates depending on the temperature, the anode current Ia at a high temperature becomes a current value several times or more than the rated current. There was also a problem that power supply costs increased.
[0011]
Accordingly, it is an object of the present invention to provide a field emission display element in which the light emission luminance does not fluctuate even when the ambient temperature rises, and a driving method thereof.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, a field emission display device according to the present invention comprises a cathode substrate having a field emission part and an anode substrate having a light emitting part opposed to the cathode substrate, which operates in a vacuum atmosphere. In the type display device, the field emission unit has a resistance layer formed between a cathode electrode and an emitter for emitting electrons, and a heater resistance layer for heating the resistance layer is provided below the cathode electrode. Is formed.
[0013]
A method of driving a field emission display device according to the present invention is directed to a field emission display device operating in a vacuum atmosphere comprising a cathode substrate having a field emission portion, and an anode substrate having a light emission portion opposed to the cathode substrate. Wherein the field emission unit has a heater resistance layer for heating a resistance layer formed between a cathode electrode and an emitter for emitting electrons, and the heater resistance layer at a low temperature. The temperature of the resistive layer is raised by applying a current to the light-emitting section, and the light emission luminance of the light-emitting section is not changed by controlling the power of the light-emitting section at normal temperature and high temperature.
[0014]
Further, in the driving method of the field emission display device of the present invention, at a low temperature, the heater voltage applied to the heater resistance layer is controlled so that the resistance value of the resistance layer becomes a substantially constant resistance value. I have.
Furthermore, the heater voltage is controlled by detecting the resistance value of the resistance layer by detecting the resistance value of the heater resistance layer.
[0015]
According to the present invention, the light emitting unit is controlled at a constant power when the ambient temperature is the normal temperature or the high temperature. Therefore, even when the ambient temperature changes, the fluctuation of the emission luminance can be suppressed.
In addition, if the light emitting unit is controlled at a constant power when the ambient temperature is low, a high anode voltage is required. Therefore, by supplying a current to the heater resistance layer for heating the resistance layer, the resistance value of the resistance layer is almost constant. It is controlled to be a value. Furthermore, since the resistance value of the resistance layer is detected from the resistance value of the heater resistance layer, the resistance value of the resistance layer can be controlled with a simple configuration, and the field emission display element can be operated even when the ambient temperature changes. Can be prevented from changing.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
A method for driving a field emission display device according to an embodiment of the present invention will be described. In the method for driving a field emission display device according to the present invention, when the ambient temperature is normal temperature and high temperature, and when the ambient temperature is low, And different driving are performed.
FIGS. 1 and 2 show the configuration of the embodiment of the field emission display device of the present invention which performs the driving method of the field emission display device of the invention.
In FIG. 1, a conductive comb-shaped heater electrode pattern 2 is formed on a cathode substrate 1 made of glass or the like, and a heater resistance layer 3 is formed on the heater electrode pattern 2 using an α-Si material or the like. Formed over the entire surface. The perspective view shown in FIG. 2 shows a state in which the heater electrode pattern 2 and the heater resistance layer 3 are formed on the cathode substrate 1 as described above.
[0017]
Further, an insulating film 4 made of a passivation film is formed on the heater resistance layer 3, and a conductive cathode electrode 5 is laminated thereon. Furthermore, a resistance layer 6 is formed on the cathode electrode 5 using an α-Si material or the like, and an insulating layer 7 made of silicon dioxide or the like is laminated thereon. A thin-film gate electrode 8 is formed on the insulating layer 7, and the gate electrode 8 and the insulating layer 7 are provided with a large number of openings penetrating therethrough.
The resistive layer 6 is exposed in the opening, and a conical emitter cone 9 is formed on the resistive layer 6.
[0018]
Although not shown, the anode substrate is opposed to the cathode substrate 1 on which the field emission cathode is formed, at a minute interval (for example, 200 microns). The anode substrate is made of glass or the like. A transparent anode electrode is formed on the anode substrate, and a phosphor that emits light by emitted electrons is provided thereon. In addition, the inside of the container of the field emission display device including the cathode substrate 1 and the anode substrate is set to a high vacuum.
[0019]
The driving method according to the present invention in the field emission display device having the above-described configuration will be described. If temperature compensation is not performed, the resistance value of the resistance layer 6 decreases at normal temperature and high temperature as described above. Emission current increases. Therefore, the anode current flowing through the anode electrode increases. Therefore, when the anode current is controlled according to the resistance value of the resistance layer 6 at normal temperature and high temperature, the light emission luminance can be kept constant.
In the present invention, this is achieved by constant power control of the power consumption at the anode at normal temperature and high temperature. FIG. 3 shows how the temperature T changes with respect to the anode voltage Va and how the temperature T changes with the light emission luminance L at this time.
[0020]
Observing FIG. 3, on the normal temperature / high temperature side, the anode voltage Va is controlled so as to decrease as the temperature rises. As a result, the light emission luminance L becomes substantially constant. The boundary temperature between the normal temperature / high temperature side and the low temperature side is, for example, 20 ° C., and when the constant power control of the anode is performed on the low temperature side, the resistance value of the resistance layer 6 sharply decreases with the temperature drop. As a result, the anode voltage becomes too high. Therefore, at low temperatures, the anode constant power control is not performed, and the anode voltage Va is set to the upper limit constant voltage. At this time, the resistance value of the resistance layer 6 increases as the temperature decreases, so that the emission luminance decreases as the temperature decreases.
[0021]
Therefore, in the present invention, when the temperature is low, the heater resistance layer 3 is heated by supplying electricity to the heater resistance layer 3 via the heater electrode pattern 2, thereby raising the temperature of the resistance layer 6 and keeping the resistance value constant. It is controlled to be a value.
FIG. 4 shows an example of a control unit for controlling the heat generation of the heater resistance layer 3 at this time.
4, reference numeral 3 denotes a heater resistance layer for heating the resistance layer 6, reference numeral 10 denotes a heater voltage source for applying a heater voltage Vh to the heater resistance layer 3, and reference numerals 11-1 and 11-2 denote heaters for the heater resistance layer 3. A switch 12 for controlling the connection of the voltage source 10 is a detection resistor (R) connected in series with the heater resistance layer 3 for detecting the resistance value of the resistance layer 6.
[0022]
Reference numeral 13 denotes a reference voltage source for supplying a reference voltage Vref for setting a detection signal. Reference numeral 14 denotes an OP amplifier that outputs a difference between a voltage between both ends of the detection resistor 12 and the reference voltage Vref as a detection signal. Reference numeral 15 denotes a detection signal. A control circuit for controlling the heater voltage Vh, and a measurement voltage source 16 for applying a measurement voltage Vm to a series circuit of the heater resistance layer 3 and the detection resistor 12.
When the control unit configured as described above determines that the ambient temperature is low, the switches 11-1 and 11-2 are turned on, and the heater voltage source 10 is connected to the heater resistance layer 3 via the heater electrode pattern 2. Connected.
[0023]
As a result, the heater resistance layer 3 generates heat, and the resistance layer 3 is heated and its resistance value decreases. In this case, if the heater resistance layer 3 and the resistance layer 6 are formed using the same material such as the same α-Si material, the resistance of the resistance layer 6 is detected by detecting the resistance value of the heater resistance layer 3. The value can be inferred. That is, a detection resistor 12 is connected in series with the heater resistance layer 3 in order to detect a resistance value, and a voltage signal at both ends of the detection resistor 12 is input to the OP amplifier 14. The resistance value can be detected.
[0024]
The detection signal of the resistance value thus detected is output as a voltage signal from the OP amplifier 14 and input to the control circuit 15. The control circuit 15 controls the heater voltage Vh in accordance with the detection signal so that the resistance value of the heater resistance layer 3 is controlled to be constant. That is, since the resistance value of the resistance layer 6 is controlled to be constant, the emission current becomes substantially constant, and the fluctuation of the emission luminance can be suppressed.
[0025]
Note that the reference voltage Vref is for setting a temperature range to be detected, and is usually set to a different voltage depending on the material of the resistance layer.
The switches 11-1 and 11-2 may be turned on when the control circuit 15 detects that the resistance value of the heater resistance layer 3 has increased. Further, the heater electrode pattern 2 has a comb-like shape so that the heater resistance layer 3 generates heat uniformly, but is not limited to the comb-like shape.
Further, in the above description, the resistance value of the resistance layer 6 is detected also as the heater resistance layer 3, but the resistance value of the resistance layer 6 may be detected by a temperature sensor.
[0026]
As described above, in the driving method of the field emission display device of the present invention, when the ambient temperature is equal to or higher than the normal temperature, the light emission luminance is made substantially constant by controlling the anode at a constant power, When the ambient temperature becomes low, the heater resistance layer 3 formed by applying the cathode forming process to the cathode substrate 1 generates heat so that the light emission luminance becomes substantially constant.
As a material of the resistance layer 6, amorphous silicon or polysilicon doped with impurities is used, and P, Bi, Ga, In, Tl, or the like can be used as impurities to be doped.
[0027]
【The invention's effect】
Since the present invention is configured as described above, when the ambient temperature is normal temperature and high temperature, by controlling the light emitting unit with constant power, it is possible to suppress the fluctuation of the light emission luminance even when the ambient temperature changes.
In addition, if the light emitting unit is controlled at a constant power when the ambient temperature is low, a high anode voltage is required. Therefore, by supplying a current to the heater resistance layer for heating the resistance layer, the resistance value of the resistance layer is almost constant. It is controlled to be a value. In this case, since the heater resistance layer is formed on the cathode substrate by applying the cathode forming process, the cost can be reduced without requiring other circuit components.
[0028]
Furthermore, since the resistance value of the resistance layer is also used as the heater resistance layer and detected from the resistance value, the resistance value of the resistance layer can be controlled with a simple configuration, and even if the ambient temperature fluctuates. It is possible to prevent a change in light emission luminance of the field emission display element at low cost.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a field emission display device of the present invention in which a method of driving a field emission display device according to an embodiment of the present invention is executed.
FIG. 2 is a perspective view showing a characteristic portion of the field emission display device of the present invention.
FIG. 3 is a diagram showing changes in temperature versus anode voltage and changes in temperature versus light emission luminance at room temperature and high temperature when the method of driving a field emission display element according to an embodiment of the present invention is executed. .
FIG. 4 is a circuit diagram showing a configuration of a control circuit of a driving method of the field emission display device according to the embodiment of the present invention.
FIG. 5 is a diagram showing a configuration of a conventional Spindt-type field emission cathode.
FIG. 6 is a diagram showing Vg-Ia characteristics of a conventional Spindt-type field emission cathode.
FIG. 7 is a diagram showing a temperature change of amorphous silicon.
FIG. 8 is a diagram showing IV characteristics of a field emission cathode.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 cathode substrate 2 heater electrode pattern 3 heater resistance layer 4 insulating film 5 cathode electrode 6 resistance layer 7 insulating layer 8 gate electrode 9 emitter cone 10 heater voltage sources 11-1 and 11-2 switch 12 detection resistor 13 reference voltage 14 OP Amplifier 15 Control circuit 16 Voltage source for measurement

Claims (4)

In a field emission display element operating in a vacuum atmosphere comprising a cathode substrate having a field emission portion and an anode substrate having a light emitting portion facing the cathode substrate,
The field emission unit has a resistance layer formed between a cathode electrode and an emitter for emitting electrons, and a heater resistance layer for heating the resistance layer is formed below the cathode electrode. A field emission display device characterized by the above-mentioned. A driving method for driving a field emission display element operating in a vacuum atmosphere including a cathode substrate including a field emission unit and an anode substrate including a light emitting unit opposed to the cathode substrate,
The field emission unit has a heater resistance layer that heats a resistance layer formed between a cathode electrode and an emitter that emits electrons. A method for driving a field emission display element, wherein the temperature is raised and the light emitting unit is controlled at a constant power at normal temperature and high temperature so that the light emission luminance of the light emitting unit does not fluctuate. 3. The driving of the field emission display device according to claim 2, wherein the heater voltage applied to the heater resistance layer is controlled so that the resistance value of the resistance layer becomes substantially constant at a low temperature. Method. 4. The field emission display device according to claim 3, wherein the resistance value of the resistance layer is detected by detecting the resistance value of the heater resistance layer to control the heater voltage. Method.

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