JP3460707B2 - Electron emission device and driving method thereof - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron emission device and a driving method thereof, and more particularly to an electron emission device having improved emission spreading characteristics and a driving method thereof.

[0002]

2. Description of the Related Art An electron emission device captures electrons emitted from an emitter by an anode electrode and recognizes them as an electric signal.
Alternatively, it has a function of causing a phosphor coated on the anode electrode to emit light by electron excitation when capturing electrons, and recognizing it as an optical signal. Examples of applications as a device for recognizing an electric signal include an amplifier and an oscillator generally called a vacuum tube. On the other hand, examples of applications as a device for recognizing an optical signal include a cathode ray tube, a fluorescent display tube, and a field emission display (FED).
There is a flat display (field emission type image display device) called n Display.

An FED will be described as a conventional example of an electron emitting device. FIG. 23 is a cross-sectional view schematically illustrating one picture element of a conventional FED, showing a structure in which electrons are emitted to excite a red phosphor to emit light. Here, the picture element means the minimum unit when the image displayed by the FED is spatially divided. In an FED that displays a color picture by a three-primary-color display method of R (red), G (green), and B (blue) light, one of the colors, for example, R (red) is called a picture element.

As shown in FIG. 23, a SiO 2 film having a thickness of about 1 μm is deposited as an insulating film 2 on the substrate 1 by sputtering, and an aluminum film having a thickness of about 200 nm is formed on the insulating film 2 as the gate electrode 3. A cylindrical gate hole 4 that is deposited as a through hole and penetrates through the gate electrode 3 and the insulating film 2, respectively.
Is formed. At the bottom of the gate hole 4, a cathode material is deposited on the substrate 1 to form an emitter 5. Further, the anode electrode 6 is arranged at a position apart from the substrate 1 by about 5 mm above. A phosphor 7 having a red fluorescence characteristic is applied to a portion of the anode electrode 6 located immediately above the gate hole 4.

The anode 6 and the phosphor 7 have 5.1 k
A voltage of about V is applied. A voltage of about 0 V is applied to the emitter 5 made of the cathode material, and a voltage of about 100 V is applied to the gate electrode 3. In this way, the equipotential surface 8 is formed by applying a voltage to each part. Here, the distance between the anode electrode 6 and the gate electrode 3 is 5 mm, and the voltage is 50
Since it is 00 V, the electric field between both electrodes 6 and 3 is 5000/5 [V / mm] = 1 [kV / mm].

On the other hand, since the distance between the gate electrode 3 and the emitter 5 is 1 μm (1E-3 [mm]) and the voltage is 100 V, the electric field between the gate and the emitter between both electrodes 3 and 5 is 100. / 1E-3 = 100 [kV / mm]. Since the value of the electric field between the gate and the emitter is 100 times the value of the electric field between the gate and the anode between the anode electrode 6 and the gate electrode 3, the inside of the gate hole 4 and its vicinity are the same as those of the gate hole 4 on the equipotential surface 8. The central part floats up and functions as a circular hole lens. In this circular hole lens, it can be said that the electric field applied to the emitter 5 becomes weak near the central axis of the gate hole 4. In other words, the circular hole lens has the power to diverge electrons, and the electrons emitted from the emitter 5 located off the central axis (convergence axis) move in the direction away from the axis (spreading direction). The track is bent. Here, the “power” of the circular hole lens represents the energy of the equipotential surface 8 forming the circular hole lens to diverge or converge the electrons.

Next, the phenomenon that the electron emission trajectory is bent by the circular hole lens effect will be described in detail. In FIG. 23, the emitter 5 is divided into smaller regions, and the trajectories of electrons emitted from the respective regions are shown. Since the gate hole 4 has an axially symmetric shape, the emitter 5 deposited on the bottom of the gate hole 4 is
Divide into three areas from the area near the axis toward the periphery. The area separated by concentric circles in the shape of a bow and arrow from the center side a, b,
It is called c. The area a is an area including the axis. 9 is area a
, Electrons emitted from the region b, and electrons emitted from the region c. Each of the electrons 9, 10, 11 spreads outward in the order of regions a, b, c.

[0008]

The above-mentioned conventional electron-emitting device has a problem that emitted electrons 9 to 11 spread in a direction away from the axis before reaching the anode electrode 6. In the FED, since the picture elements are finely divided and arranged, when the electrons spread, there is a problem that the electrons jump into the phosphor 7 of the adjacent picture element instead of the phosphor 7 of the own picture element. When an electron jumps into a phosphor 7 of a picture element of another color, a different color actually occurs, and when an electron jumps into the phosphor 7 of an adjacent picture element of the same color, a poor spatial resolution occurs.

FIG. 24 is a graph showing operating characteristics of the conventional electron-emitting device shown in FIG. FIG. 24 shows the relationship between the electric field applied to the cathode and the amount of emission current. The cathode applied electric field shown in the graph is applied to the emitter 5 deposited on the bottom of the gate hole 4. Here, the value of the electric field at the intermediate height of the gate hole (0.5 μm height in the insulating film structure of 1 μm) is used as the value of the cathode applied electric field.

When the electric field applied to the cathode is gradually increased,
An electric field (threshold electric field) where the emission current starts to flow appears. The maximum value of the required emission amount is called the maximum current amount, and the cathode applied electric field required to obtain the current amount is called the maximum electric field. In order to display an image in an analog manner in the FED, it is necessary to apply an arbitrary electric field between the threshold electric field and the maximum electric field in accordance with an input signal to obtain fluorescence of a desired brightness. is there. In the pulse width driving method, fluorescent light having a desired brightness can be obtained by adjusting the time for applying a constant electric field, for example, the maximum electric field.

If there is no limit to the emission (emission electron) spread characteristic, the electron emission device may be driven in accordance with the emission characteristic shown in FIG. 24. In reality, however, the effect of the circular hole lens causes the emission to exceed the limit. spread. The larger the electric field difference at the gate hole opening (phenomenon),
Further, as the electrons emitted from the cathode electrode at the off-axis position (phenomenon), the phenomenon in which the electrons spread due to the circular hole lens effect becomes more prominent.

FIG. 25 is a graph for explaining the phenomenon when the electric field difference at the gate hole opening is large. When the cathode applied electric field is increased while the voltage of the anode electrode 6 is constant, phenomena such as (1) distortion of the equipotential surface increase and (2) increase in speed at the gate hole opening occur. Due to the phenomena (1) and (2), the emission spread range when reaching the anode electrode 6 becomes wider.

"Length D" of FIG. 25 showing the above-mentioned spread range
The range indicated by the arrow D shown in FIG. To increase the cathode applied electric field, the gate electrode potential is increased. When an inconvenience occurs that electrons jump into the adjacent phosphor, the spread range “D” has already exceeded the limit. Strictly speaking, electrons that jump into an ineffective region such as a black matrix do not excite the phosphor, so that the generation of electrons that do not jump into a predetermined phosphor has already exceeded the limit of spread. Although the marginal spread varies depending on the situation, it is certain that there is a certain limit. This spread range "D" is called the limit spread length, and the cathode applied electric field that gives the characteristic is called the limit electric field.

In the electron emission device used for FED and other applications, it is not possible to use a cathode applied electric field above the limit electric field, so the maximum electric field required to obtain the maximum amount of current must be below the limit electric field. . In the conventional electron-emitting device having the gate hole structure, the driving is performed so that the electric field in the gate hole is stronger than that in the outside, so that the electron spread by the circular hole lens is always affected. In particular, it is not preferable that the degree of spread increases as it approaches the maximum current amount. In such a tendency, when a very small proportion of the emitted electrons jump into an area outside the standard, the electron parameter is large, and as a result, a sufficient amount of electrons are notable, or a considerable amount of noise cannot be ignored. You will jump outside.

In view of the above, it is an object of the present invention to provide an electron emission device capable of suppressing the emission spread and improving the spread characteristic at the maximum emission amount, and a driving method thereof.

[0016]

In order to achieve the above object, an electron-emitting device of the present invention includes a substrate, a gate electrode having an opening and arranged on the substrate, and formed in the opening. In the electron emission device including the emitter and the anode electrode arranged at a predetermined distance from the emitter, the emitter described later is adopted. The present invention
In a desirable mode, the gate potential is applied such that the spread range of the electrons emitted from the emitter when reaching the anode electrode is within a predetermined limit value.

In the electron emission device of the present invention, the converging electric field is
Since it functions as a lens (circular lens) that converges the electrons emitted from the cathode electrode, it is possible to suppress the emission spread without widening the electron emission trajectory and maintain a good electron arrival state to the anode electrode. it can. When the electrons bent by the focusing effect of the lens are in an overfocus state where they intersect each other before the anode electrode,
The electrons reach the anode electrode with a spread distribution.
However, the spread characteristic at the time of overfocus becomes significantly narrower than in the case of the conventional electron emitting device in which the lens of the divergence system functions due to the distortion of the equipotential surface. This is for the following reason. That is, when the electric field applied between the gate electrode and the emitter is lower than the electric field applied between the anode electrode and the gate electrode, the highest electric field and the largest amount of field emission are near the axial center of the lens. And the amount of emission decreases as it goes off axis. Due to the influence of the spherical aberration of the lens, the diverging power is greater toward the edge (off-axis position) of the lens, and the electron emission amount has the largest electron emission amount at the axial center and the electron emission amount distribution that decreases as it deviates from the axial center. These suppress the phenomenon that electrons spread.
On the other hand, in the divergent lens of the conventional electron emission device, the electric field acting on the emitter near the center of the axis is the weakest, the number of electrons passing around the lens is the largest, and the spread of the electrons is promoted. When the spreading phenomenon due to overfocus in the present invention and the spreading phenomenon due to the lens of the divergence system in the conventional electron-emitting device are compared,
It is self-evident that overfocus has less spread as long as the lenses have the same power.

In the electron emission device of the present invention, a substrate, a gate electrode having an opening portion and arranged on the substrate, an emitter formed in the opening portion, and arranged at a predetermined distance from the emitter. In an electron emission device provided with an anode electrode provided, a converging electric field for converging electrons emitted from the emitter toward the anode electrode side is formed, and the converging electric field is present between the gate electrode and the emitter. A gate-emitter electric field applied is applied between the anode electrode and the gate electrode.
It is formed by being set to a value smaller than the electric field between the anodes. According to the electron-emitting device of the present invention, it is possible to suppress emission spread and easily obtain an electric field having an electron converging action.

Further, in addition to the magnitude relationship between the gate-emitter electric field and the gate-anode electric field, when the gate-emitter electric field is set to a value larger than the gate-anode electric field. It is preferable that electrons are emitted from the emitter toward the anode electrode and the inclination of the equipotential surface in the converging electric field becomes larger as it approaches the anode electrode.

In this case, the condition of the desired spread characteristic can be utilized to the maximum. If it is assumed that the electrons emitted from the emitter do not originally have a lateral velocity or are negligibly small, the state where there is no lens effect due to distortion of the equipotential surface has the best straightness of emission electrons, The spread of electrons reaching the anode electrode is small. The state in which there is no lens effect means that there is no change in the electric field strength near the gate electrode. This state can be created by making the electric field between the gate and the emitter and the electric field between the gate and the anode equal to each other. When the electric field between the gate and the emitter is set to be stronger than that in this state, a diverging system lens effect slightly occurs, and the amount of field emission increases due to the increase in the electric field applied to the emitter. Even in the state of having a slight divergence effect, it may fall within the allowable range of the desired spread characteristic. Therefore, when the electron emission device is operated including this range, a larger amount of electrons emitted from the emitter is secured. be able to.

As a reference example of the present invention, it is preferable that the emitter in the opening of the gate electrode is formed in a mortar shape such that the inner peripheral surface side of the opening projects toward the gate electrode. In this case, the converging electric field can be favorably formed by the mortar-shaped recessed emitter shape.

Further, as a reference example of the present invention , the emitter is formed smaller than the inner circumference of the opening. here
In the present invention, the mode in which the emitter is formed in an annular shape
Is disclosed. Electrons emitted from the cathode electrode at the bottom of the opening are out of the orbital range to the desired anode electrode, which may limit the application of a further electric field. However, according to this configuration, since the portion of the opening bottom portion close to the inner peripheral surface or the emitter on the center side of the opening portion is removed, the above restriction can be removed and a higher electric field can be applied to the opening bottom portion. Can be applied to.

More preferably, the emitter is composed of a plurality of types of cathode materials having mutually different emission characteristics. In this case, for example, a cathode material having a normal emission characteristic and a cathode material having a high emission threshold electric field and a low emission level even when an electric field above the threshold value is applied are mixed. In this case, the selection range for selecting desired emission characteristics and spreading characteristics is wider than when only one type of cathode material is used.

Further, it is preferable that a plurality of the openings are formed in a line in the gate electrode, and the emitters in the openings are aligned with each other. As a result, it is possible to avoid a phenomenon in which the emission unnecessarily spreads to the left and right.

More preferably, the opening is formed as a substantially rectangular hole, and the emitter is formed in a strip shape along the longitudinal direction of the substantially rectangular hole. In this case, the openings corresponding to the respective picture elements can be arranged adjacent to each other, and the phosphors corresponding to the respective picture elements can be separated from each other in the direction orthogonal to the longitudinal direction of the openings.

Preferably, one set of picture elements composed of the emitter and the gate electrode are arranged adjacent to each other in three sets, and the first picture element located in the central portion of the three sets of picture elements. In the second picture element located on one side of the three sets of picture elements, the emitter extending in the central portion of the substantially rectangular hole in the second picture element. Of the third picture element which is located on the other side of the three sets of picture elements and which has a substantially rectangular hole. The side close to the first picture element extends along the longitudinal direction.

In this case, in the structure in which the phosphors corresponding to the respective picture elements are separated from each other, for example, the emitted electrons from the emitter of the green picture element have an emission spread range immediately above, and the emitter of the red picture element is provided. It is possible to give the emission electron from the emission spread range to the upper left direction and to give the emission electron from the blue pixel emitter to the emission spread range to the upper right.

Further, the gate electrode is formed in a substantially rectangular shape, the opening is formed in each of the central portion and each corner of the gate electrode, and the emitter is formed in the opening located at the central portion. It is preferable that an intermediate portion in the opening extends along the longitudinal direction of the gate electrode, and in the opening located at each corner, the emitter is formed closer to the outer side in the opening. . In this case, the emission spread range can be set satisfactorily.

In the electron emission device of the present invention, a substrate, a gate electrode having an opening and arranged on the substrate, an emitter formed in the opening, and a predetermined interval from the emitter are arranged. In an electron emission device provided with an anode electrode provided, a converging electric field for converging electrons emitted from the emitter toward the anode electrode side is formed, and an equipotential surface in the converging electric field has a lens shape having a converging axis. The lens-shaped equipotential surface makes the electrons emitted from the emitter reach the anode electrode in a just focus state intersecting the convergence axis and then in an overfocus state intersecting the convergence axis. Is characterized by.

According to the electron-emitting device of the present invention, it is possible to suppress the emission spread and improve the spread characteristic at the maximum emission amount.

Here, it is preferable that the electrons in the overfocus state go to the anode electrode in a range smaller than the opening. In this case, emitted electrons can be narrowed down and irradiated to the anode electrode in a range narrower than the gate opening area. If the phosphor is coated on the anode electrode so as to have the same size as or a larger area than the gate opening area, all the electrons emitted to the anode electrode can be made incident on the phosphor.

The driving method of the electron-emitting device of the present invention is a driving method of driving the electron-emitting device, characterized in that the electric field between the anode electrode and the emitter is set to a threshold value.

According to the driving method of the electron emission device of the present invention, the gate modulation potential can be realized by a positive voltage which is not biased, and when the display composed of a plurality of pixels is used, the threshold electric fields of the pixels are mutually changed. When it is different, the threshold value of the lowest potential can be set. The variation can be stored in an external storage means and reflected in the gate modulation.

The driving method of the electron-emitting device of the present invention is a driving method of driving the electron-emitting device, wherein the electric field between the anode electrode and the emitter is between the threshold electric field and the maximum current amount electric field. It is characterized by being set to an electric field.

According to the method of driving the electron-emitting device of the present invention, the electric field between the anode and the cathode is set to the electric field having the highest application frequency, and the gate electric potential is modulated to both positive and negative polarities so that the gate electric potential is 0. It is possible to increase a certain period of time and reduce driving power consumption. Further, the amplitude of the gate potential modulation can be minimized by setting the anode-cathode electric field to an electric field intermediate between the maximum current amount electric field and the threshold electric field.

The driving method of the electron emitting device of the present invention is a driving method for driving the electron emitting device, characterized in that the electric field between the anode electrode and the emitter is set to a maximum current amount electric field.

According to the driving method of the electron-emitting device of the present invention, since the gate modulation can be performed only with the negative potential,
The configuration of the gate modulation circuit can be simplified. In addition, when the gate modulation circuit fails and only 0 potential is generated, or when the wire is broken and only floating potential is generated, the screen has the maximum brightness, so that there is an advantage that the failure is immediately identified. It can be used as emergency lighting.

[0038]

The present invention will be described in more detail with reference to the drawings. FIG. 1 is a sectional view schematically showing one picture element of an FED as an electron emission device according to the first embodiment of the present invention. An insulating film 2 made of a SiO2 film having a thickness of about 1 μm is deposited on the substrate 1. Aluminum film of about 200 nm is deposited on the insulating film 2 to form the gate electrode 3
Is formed. Cylindrical gate hole 4 with a diameter of 5 μm
Are formed so as to penetrate the gate electrode 3 and the insulating film 2, respectively. At the bottom of the gate hole 4, a cathode material is deposited on the substrate 1 to form an emitter (hereinafter also referred to as a cathode electrode) 5. Here, the emitter 5 can be buried under the insulating film 2 before the gate hole 4 is provided,
After the gate hole 4 is provided, it can be deposited on the bottom of the gate hole 4.

As the cathode material of the emitter 5, carbon nanotube (hereinafter referred to as CNT) can be mentioned. CNT is a form of fullerene, which is a cylindrical crystal having an inner diameter of several nm and has a long crystal having a total length of more than 1 mm. An iron metal film (not shown) on the substrate 1, which was collected from the end of the CNT for a length of about 100 nm.
Is deposited on top of. This metal film is connected to a wiring for applying a cathode potential.

The anode electrode 6 is arranged about 1 mm above the gate electrode 3, and a vacuum state is established between the anode electrode 6 and the gate electrode 3. The degree of vacuum is set so that the emitter 5 can maintain desired characteristics. The residual gas is ionized by the electrons and damages the emitter 5,
Alternatively, there is a problem that the substrate 1 is charged up to cause discharge breakdown. For example, the above problem can be eliminated by setting the vacuum degree to 1 × 10 −4 Pa or less.

A phosphor 7 is applied to a part of the anode electrode 6. The electrons jump into the phosphor 7 and are excited to cause fluorescence. The brightness of fluorescence depends on the amount of electrons and their speed. A vapor deposition film of aluminum having a thickness of about 50 nm is deposited on the surface of the phosphor 7 on which the electrons fly. This aluminum film is provided to protect the surface of the electron jump surface from electron damage and negative ion damage, and to reflect fluorescence on the surface (observation surface) of the phosphor 7 opposite to the aluminum film.

For example, the anode electrode 6 and the phosphor 7 have 3
When kV, 2 V is applied to the gate electrode 3, and 0 V is applied to the emitter 5, an equipotential surface 8 between the anode electrode 6 and the gate electrode 3 and between the anode electrode 6 and the gate hole 4 is obtained.
Has a concave convergent lens shape that is recessed at a position corresponding to the gate hole 4 (FIG. 1). The lines representing the equipotential surface 8 are conceptual and do not necessarily correspond to the actual equipotential surface, but they have a common tendency to be indented.

When the emitter 5 at the bottom of the gate hole 4 is divided into concentric circles into regions a, b, and c, the electrons 9 emitted from the region a go straight up almost directly to the region a.
The electrons 11 emitted from the region b on the outer peripheral side of the are jumped into the phosphor 7 in a slightly overfocused state. The electrons 10 emitted from the region c on the outer peripheral side of the region b jump into the phosphor 7 in an overfocus state in which it is focused on the near side. As a result, all the electrons jump into the range of the phosphor 7. Here, the focus is defined on the assumption that the converging axis of the circular hole lens exists when the equipotential surface 8 near the gate hole 4 is considered as the circular hole lens. in this case,
Since there are three states of under focus, just focus, and over focus, under focus is "state before electrons intersect with the convergence axis", just focus is "state where electrons intersect with the convergence axis", and over focus is "electron". Are further advanced by intersecting the convergence axis. "

The state of FIG. 1 will be described in more detail with reference to FIG. FIG. 2 is a graph showing emission current density characteristics of the electron emission device of FIG. a to c
The gate potential dependence was shown for each of the three regions.

In the region a closest to the convergence axis in FIG. 2, the influence of changing the potential of the gate electrode 3 (gate potential) is the smallest. In a state in which electrons are field-emitted from the emitter 5 toward the anode electrode 6 having a voltage of 3 kV separated by about 1 mm, (A) electron emission is suppressed by changing the voltage applied to the gate electrode 3, (B) electron emission Each control can be switched without affecting (C), promoting electron emission (C).

When the potentials of the anode electrode 6 and the cathode electrode 5 are 0V, the case where a voltage of 3V is applied to the gate electrode 3 corresponds to the state where the influence of (B) is not exerted. In this state, the case where the gate potential exists is called a state of uniform electric field. When the gate potential is less than 3V, it is suppressed, and when it exceeds 3V, it is accelerated. The emission characteristics from the three regions a, b, and c are all equal under the condition of a uniform electric field. The emission current density in this state is called the uniform electric field current density. As shown in FIG. 2, the respective characteristics of the three regions a to c have different threshold values, and the magnitude relation thereof is inverted by the uniform electric field. In the example shown in FIG. 1, the maximum electric field for obtaining the maximum amount of current is set to the gate potential of 2V. The 2V is a case where the electric field between the gate electrode 3 and the emitter 5 is smaller than the uniform electric field.

In FIG. 1, only a partial structure of an FED (a constituent part of a pixel) is shown as an electron-emitting device, so the overall structure will be briefly described here. The FED display is realized by arranging the picture elements in a two-dimensional matrix.
Although various methods are conceivable for supplying the picture element signals to the picture elements arranged in two dimensions, the case of the simple matrix method is shown as an example. In this example, a plurality of strip-shaped gate electrodes 3 are arranged, and the emitters 5 are arranged in a direction orthogonal to the gate electrodes 3. In the FED, the base material of the anode electrode 6 is a glass material, and I is formed on the lower surface (the surface on the vacuum side) of the glass.
A TO conductive film is deposited. On the ITO surface, a phosphor and an aluminum film are further deposited in this order.

Here, the case where the equipotential surface is concave in a range that cannot be defined only by the electric field relationship based on the gate lower surface potential will be described. For example, in the conventional electron emission device described in FIG. 23, since there is no consideration regarding the equipotential surface and overfocus, the size of the anode electrode target region may be larger than the size of the cathode electrode 5 at the bottom of the gate hole 4. There is.

First, the equipotential surface will be considered. In this case, as shown in FIG.
Assume a triode structure in which the cathode electrode 5 and the gate electrode 3 having the gate hole 4 therebetween are arranged.
Here, the distance between the front surface of the cathode electrode 5 and the back surface of the gate electrode 3 is t (gk), and the distance between the back surface of the anode electrode 6 and the front surface of the cathode electrode 5 is t (ak). Is Va, the potential of the gate electrode 3 is Vg, the film thickness of the gate electrode 3 is t (g), the distance between the back surface of the gate electrode 3 and the surface of the cathode electrode 5 is t (gk), and the anode electrode 6 Let t (ag) be the distance between the back surface of the cathode electrode and the surface of the gate electrode 3, and Vk be the potential of the cathode electrode 5. It should be noted that the following equation is simplified by setting Vk = 0 [V].

In order to form the concave equipotential surface in the vicinity of the gate hole 4 when the gate electrode film thickness t (g)> 0, the following expression Va / t (ak) ≧ Vg / t (gk) ...... (1) must be satisfied. Here, the equation (1) is transformed into Vg ≦ {t (gk) / t (ak)} · Va (2).

On the other hand, in order for the equipotential surface near the gate hole 4 to form a convex shape, the following expression Va / t (ak) ≧ (Va-Vg) / t (ag) (3) must be satisfied. is necessary. When the anode electrode 6 and the emitter 5 are considered upside down, the same situation as the expression (1) can be obtained. Here, by substituting the relational expression of t (ag) = t (ak) -t (g) -t (gk) into the expression (3), the following expression Vg ≧ [{t (g) + t (gk) } / T (ak)] ・ Va …… (4) is obtained.

The areas not defined by the equations (2) and (4) are {t (gk) / t (ak)} · Va <Vg <[{t (g) + t (gk)} / t (ak )] ・ Va …… (5) The equipotential surface in this region has a convex shape from the cathode electrode 5 toward the gate electrode 3, and gradually shifts to a concave shape within the range of the thickness of the gate electrode 3. From the viewpoint of the inclination of the equipotential surface that forms the concave-convex shape, equations (2) and (4)
It can be classified into three regions of the formula and the formula (5).

FIG. 4 is a graph showing the above three regions according to equations (2), (4), and (5). In the graph,
The areas defined by the expressions (2), (4), and (5) are in contact with each other in this order. In the region of the formula (2), the concave type, that is, the electrons emitted from the cathode electrode 5 are acted as a converging lens from the equipotential surface.

Here, in order to facilitate understanding, the situation of Vg = {t (gk) / t (ak)} · Va which is the boundary region will be described.
For example, when the film thickness of the gate electrode 3 is 0, the equipotential surface is formed parallel to the cathode electrode 5 and the anode electrode 6. However, in reality, since the gate electrode 3 has a film thickness, the equipotential surface in the gate hole 4 rises to the upper surface of the gate electrode 4 by an amount corresponding to this film thickness to form a concave equipotential surface.

In the region defined by the equation (2), the cathode electrode 5
Forming a convex equipotential surface when viewed from above, the anode electrode 6
When viewed from above, a concave equipotential surface is formed. That is, it is a case where the situation expressed by the equation (2) is considered upside down.

In the region of the equation (4), an electric field equal to Va / t (ak) (hereinafter referred to as an anode electric field) exists in the gate electrode 3 (gate hole 4) having a film thickness. Since the electric field between the back surface of the gate electrode 3 and the surface of the cathode electrode 5 is stronger than the anode electric field and the equipotential surface is dense, the equipotential surface closer to the cathode electrode than the anode electric field is convex.

FIG. 5 is a diagram showing the result of simulating the lens action of the equipotential surface by the equation (5). In the electron emitted from the cathode electrode 5, the electron 9 emitted from the X coordinate 0.0 of the center of the gate hole 4 advances straight to the anode electrode (not shown) in the upper part of the figure, and the X coordinate slightly outside the center. Due to the converging type lens effect, the electrons 11 emitted from 2.0 pass through the abutting surfaces of both the concave and convex equipotential surfaces and then proceed with a slight inclination toward the central axis. The electron 10 emitted from the X coordinate 4.0, which is closer to the gate electrode 3 side than the electron 11, bends a little away from the central axis up to the mating surfaces of both the concave and convex equipotential surfaces, but the mating When it passes through the surface, the path is bent so as to converge on the central axis side due to the converging lens effect of the concave equipotential surface. In the figure, the potential difference on each equipotential surface is about 0.
It is 1V.

On the other hand, the anode electrode 6 rather than the anode electric field
At the side position, the electric field between the front surface of the gate electrode 3 and the back surface of the anode electrode 6 is stronger than the electric field of the anode and the equipotential surface is dense, so that the equipotential surface is concave. The electrons emitted from the position deviated from the center of the cathode electrode 5 progress toward the central axis along the direction perpendicular to the concave equipotential surface and converge, and when reaching a high position, they are overfocused and diverge outward. move on.

Next, the target region, which is a range where electrons reach the anode electrode 6, will be considered. First, when the circular hole lens functions as a divergent lens, the target region is wider than the emitter region at the bottom of the gate hole 4, but it is not narrowed. On the other hand, when the circular hole lens functions as a converging lens, the target region may be wider than the emitter region, may be narrower than the emitter region, or may be the same as the emitter region. Whether the target area becomes wider or narrower cannot be determined only by the definition of the electric field made in consideration of the equipotential surface. For example, the anode electrode 6 is separated by 1 mm from the cathode electrode 5 and is 1 kV.
Voltage is applied, and 10kV when separated by 10mm
An electric field of 1 kV / mm is obtained when both voltages are applied, but when the distance between the cathode and anode electrodes of the electrons passing through the converging lens system is 1 mm, the target area may appear before or immediately after overfocus. When the distance between the cathode and the anode electrode is 10 mm, the target area may become wider due to sufficient overfocus.

The above is summarized in Table 1.

[0061]

[Table 1]

Next, the second embodiment of the present invention will be described. FIG. 6 is a cross-sectional view showing one picture element of the FED of the electron emission device described in the first embodiment with a slightly different drawing method of emitted electrons. FIG. 7 shows an electric field between the gate electrode and the cathode electrode as an anode. FIG. 7 is a cross-sectional view showing an electron emission trajectory when the electric field between the electrode and the gate electrode is stronger. 6 and 7 show typical states of convergence (suppression) and divergence (promotion), respectively.

In FIG. 6, electrons 12 emitted from the outer peripheral side of the cathode electrode 5 deposited on the bottom of the gate hole 4,
Only the electrons 9 emitted from the center side are shown, and the gate electrode 3
The electric field between the cathode electrode 5 and the cathode electrode 5 is set to be smaller than the electric field between the anode electrode 6 and the gate electrode 3. As a result, the electric field formed in and near the gate hole 4 has a lens effect of converging the electrons emitted toward the anode electrode 6. Therefore, the electrons overfocus and jump into the anode electrode 6. This overfocus state does not always occur, but only when the converging lens effect is remarkable. If it is close to the state of the uniform electric field, electrons jump into the anode electrode 6 in the state of underfocus or just focus.

On the other hand, in FIG. 7, the electric field between the gate electrode 3 and the cathode electrode 5 is changed to the anode electrode 6 and the gate electrode 3.
It is set larger than the electric field between and. As a result, the electric field formed in and near the gate hole 4 has a lens effect of diverging the electrons emitted toward the anode electrode 6. Therefore, the electrons 12 emitted from the lens peripheral side reach the anode electrode 6 while spreading outward.

FIG. 8 is a graph showing emission spread characteristics covering each of the convergent and divergent states. In the same figure, the emission spread characteristics when reaching the anode electrode 6 in the regions a, b, and c (see FIG. 1) are shown. The vertical axis of the graph shows the emission spread range when reaching the anode electrode, the horizontal axis shows the potential of the gate electrode, and the length D shows the diameter when the maximum spread range is measured (see FIG. 23).

In the uniform electric field, the electrons emitted from the regions a, b, and c go straight toward the anode electrode 6 without being affected by the lens. The reason that the size of the spread range D is not 0 is that each of the areas a, b, and c has its own size, and the initial velocity is not completely 0. In the graph, the curve changes from a thick line to a thin line with the limit spread range for the target region as a boundary.

When the electric field is less than the uniform electric field, the electron orbit is bent in the converging direction. When the gate potential decreases and the degree of overfocus increases, the spread range D increases. The extent to which the spread range D becomes large depends on the area c near the periphery.
Largest in emissions from. On the other hand, when the gate potential is larger than the uniform electric field, the circular hole lens functions as a divergence system lens, so that the spread range D rapidly increases as the gate potential increases. Above all, area c
Grows most rapidly in.

In FIG. 8, as a result, the spread characteristic is minimal near the uniform electric field. Strictly speaking, when the gate potential is smaller than the uniform electric field, the converging action works properly and becomes the minimum. When the limit spread range is set as shown in FIG. 8, the condition of the gate potential satisfying the condition is determined. Figure 8
Then, a thick line is drawn for the range satisfying the conditions.
If the area of each of a, b, and c is within the range of the thick line, the spread condition at the anode electrode 6 is satisfied. In this embodiment, a good emission spread characteristic is obtained by setting the potential within the range of the thick line that does not exceed the limit spread range.

FIG. 9 is a graph in which the condition range relating to the spread characteristic and the emission current density characteristic are superimposed and drawn. The results of FIG. 8 are shown in the upper area of the graph. The range satisfying the conditions for each of the regions a to c is indicated by double-ended arrows a to c in the uppermost region. The emission current density characteristics with respect to the gate potential are shown in the lower part of the graph.

The condition satisfaction region obtained from FIG. 8 is drawn with a thick line above the graph. In each region, the condition is satisfied in the range equal to or less than the uniform electric field, and in the region larger than the uniform electric field, the potential out of the condition at the lowest gate potential (the condition range of c is shown). The condition up to the right end of the double-ended arrow) is satisfied. In the present embodiment example, the range up to this range is used as the drive region. The total amount of emission current of the three areas a, b, and c is indicated by the label of “total”. In this curve, the current amount was used instead of the current density.

A third embodiment of the present invention will be described. FIG. 10 is a graph showing a spread characteristic that has a minimum value in the vicinity of the uniform electric field as in FIG. In the graph, the limit spread range is set more strictly than in the case of FIG. As a result, the range satisfying the condition indicated by the thick line is narrower than in the case of FIG.

FIG. 11 is a graph in which the condition range regarding the spread characteristic and the emission current density characteristic similar to those in FIG. 9 are drawn on top of each other. In this graph, the lower limit and the upper limit of the total emission current amount are determined, reflecting the strict setting of the limit spread range, so if the gate potential is set so that the current amount is less than this, the spread The characteristics become poor. In the electron emission device having this characteristic, the thickness of the aluminum vapor deposition film covering the electron jumping surface of the phosphor 7 is increased to increase the amount of attenuation of electrons until reaching the phosphor 7, or the fluorescence characteristic is not sensitive. Measures such as using a phosphor 7 having a low threshold value are taken.

Next, a fourth embodiment of the present invention will be described. FIG. 12 shows an example in which the region c in the emitter 5 of the electron emission device shown in FIG. 1 is removed so that the emitter 5 is smaller than the inner circumference of the gate hole 4. The characteristics of the electron emission device of FIG. 12 will be described with reference to the graph of FIG. In the present embodiment example, the region c is deleted, so that the range in which the condition for jumping into the phosphor 7 is satisfied is increased.

Next, a fifth embodiment of the present invention will be described. FIG. 13 is a sectional view showing an example in which the cathode material is deposited only in the region b in FIG. 1 to form the annular emitter 5. FIG. 14 is a graph showing the characteristics when the emitter 5 is deposited only in the region b. Emitter 5 only in region b
Due to the existence of, the maximum emission current density can be secured sufficiently large and the minimum emission current amount can be secured sufficiently small. As a result, gradation display can be widened. Further, by removing the region a, which has low sensitivity to changes in the gate potential,
The change in the emission current density amount with respect to the change in the gate potential becomes sharp. As a result, it is possible to control a wide gradation with a small change in the gate potential.

Next, a sixth embodiment of the present invention will be described with reference to FIG. 12 again. In the present embodiment, as the cathode material of the region a, one having a work function higher than that of the cathode material of the region b is used. As a result, the amount of electrons that excite the central portion of the phosphor 7 decreases, and the electrons irradiate the entire surface of the phosphor 7 relatively uniformly, so that part of the phosphor 7 burns and deteriorates. Can be prevented.

Next, a seventh embodiment of the present invention will be described. FIG. 15 is a diagram when a part of the display portion of the FED is observed in the front from the electron emission direction. One pixel 13 includes a red picture element 14, a green picture element 15 and a blue picture element 16.
It is composed of three color phosphor picture elements. The black matrix 17 fills the gaps between the picture elements 14 to 16. The defective emission spread range 18 and the allowable emission spread range 19 are shown by elliptical ranges, respectively. Spreading range 1 of both
8 and 19 show the spread of emission in the green picture element 15.

In the defective emission spread range 18, conspicuous defects such as red bleeding 20 and blue bleeding 21 occur. In the FED, even if a slight amount of another color is mixed and displayed, it tends to stand out, and therefore it is not acceptable. On the other hand, in the allowable emission spread range 19, only the same color bleeding 22 occurs, so that the spatial resolution is deteriorated, but the color is not impaired and is allowable.

An example of this embodiment will be described based on the analysis in FIG. FIG. 16 is an example of an electron emission device that realizes the spread characteristic shown by the allowable emission spread range 19 in FIG. 15, and the emitter 5 is observed in the front from the direction in which electrons are emitted. In FIG. 16, three gate holes (openings) 4 are formed in a line in the gate electrode 3, and the emitters 5 formed in each gate hole 4 form a straight line. That is, at the bottom of each of the cylindrical gate holes 4 having a diameter of, for example, 10 μm provided at three locations on the gate electrode 3,
The emitter 5 is applied in a shape similar to a vertically long rectangle. An insulating film (not shown) is provided below the gate electrode 3.

By forming the electrode emitter 5 by applying the cathode material in the shape shown in FIG. 16, the phenomenon in which the emission spreads in the left-right direction in the figure is severely suppressed. On the other hand, the restraint in the vertical direction is loosened. As a result, the allowable emission spread range 19 in FIG.
The same characteristics as those of the emission spread characteristics in the above can be obtained.
In the present embodiment, since the space is spread in the vertical direction, it is possible to prevent the emission from spreading unnecessarily in the left and right due to the space charge effect.

Next, an eighth embodiment of the present invention will be described. FIG. 17 is a diagram showing a main part of the FED having one picture element consisting of three colors of R, G, and B shown in FIG. Figure 1
7, the emitter 5 is observed from the same direction as in FIG.

As shown in FIG. 17, in the FED, for each of the red picture element 14, the green picture element 15 and the blue picture element 16, the gate hole 4 is formed as a substantially rectangular hole, and the emitter 5 is formed.
Are formed in a strip shape along the longitudinal direction of the substantially rectangular hole.
One set of picture elements composed of the emitter 5 and the gate electrode 3 are arranged adjacent to each other in three sets. The emitter 5 in the first picture element located in the central part of the three sets of picture elements extends along the longitudinal direction in the central part of the substantially rectangular gate hole 4. The emitter 5 in the second picture element located on the left side of the three picture elements extends along the longitudinal direction on the side of the gate hole 4 close to the first picture element. In addition, the emitter 5 in the third picture element located on the right side of the three picture elements
Of the gate hole 4 extends along the longitudinal direction on the side close to the first pixel.

The feature of this embodiment is that each of the picture elements 14 to 16 is
That is, the gate holes 4 corresponding to are adjacent to each other, while the phosphors (not shown) of the picture elements 14 to 16 are separated from each other. In order to correspond to this relationship, the emitted electrons from the emitter 5 of the green picture element 15 have an emission spread range 23 immediately above, and the emitted electrons from the emitter 5 of the red picture element 14 have an emission spread range 23 in the upper left direction. The electrons emitted from the emitter 5 of the blue picture element 16 have an emission spread range 23 at the upper right. In order to realize these spread range characteristics, in this embodiment, a vertically long rectangular gate hole 4 with rounded corners and a vertically long rectangular emitter 5 are adopted. At the same time, the emitter 5 corresponding to the red picture element 14 is the gate hole 4
To the right of the center, the emitter 5 corresponding to the green picture element 15
Is arranged in the center of the gate hole 4, and the emitter 5 corresponding to the blue picture element 16 is arranged to the left of the gate hole 4.

Next, a ninth embodiment of the present invention will be described. FIG. 18 is a front view showing an electron emission device corresponding to the green picture element 15 in FIG. In FIG. 18, the gate electrode 3 is formed in a substantially rectangular shape, and the gate hole 4 is formed in each of the central portion and each corner portion of the gate electrode 3. In the gate hole 4 located in the center, the emitter 2
6 extends in the middle of the gate hole 4 along the longitudinal direction of the gate electrode 3, and in the gate hole 4 located at each corner, the emitters 24, 25 are moved outward in the gate hole 4. It is formed. That is, five gate holes 4 are formed in the gate electrode 3, and the cathode material is applied to the bottom of each gate hole 4 to form the emitter 2
4, 25 are formed. In this embodiment, the application position of the cathode material differs depending on the position of the gate hole 4.

In the above structure, in the left-side gate hole 4 which is displaced from the center to the left in the drawing, the cathode material is applied only to the left-side portion. On the contrary, in the right side gate hole 4, the cathode material is applied only to the right side portion. In the central gate hole 4, as in FIG. 13, the cathode material is applied to the central portion. This allows
The emission spread range is set well. Here, for example, even in the gate hole 4 located on the upper right side of the figure among the gate holes 4 on the right side, no consideration is given to the application of the gate material for the arrangement in the upward direction. This is a result of the consideration regarding the allowable emission spread range described with reference to FIG.

As described above, according to the electron-emitting devices of the first to ninth embodiments of the present invention, the emission spread characteristic can be improved while having a simple structure. In the FED, since the parameter is large even at a small ratio, the emission amount itself spreading out of the standard increases, causing serious image quality deterioration such as color fringing. For this reason, the emission spread at the maximum emission amount is treated most severely. First of the present invention
-The ninth embodiment is particularly advantageous for improving the spread characteristic at the maximum emission amount.

Further, when the electron emission device in each of the embodiments is applied to an electron beam application device such as a traveling wave tube amplifier or a cathode ray tube electron beam exposure device, a narrow beam is not necessary for narrowing down by a complicated lens. Therefore, it is unlikely to be affected by various aberrations of the lens, and there is little concern that the lens magnifies the image. Therefore, a thin electron beam can be obtained from the electron extraction portion, and a very thin electron beam can be easily obtained.

Further, in the electron emission device in each of the embodiments, since the method of extracting electrons by the electric field is adopted, it is not necessary to raise the temperature of the emitter made of the cathode material, and the mechanical size shift due to heat and the radiant heat are eliminated. There is no concern that peripheral components will deteriorate due to This allows
A wider range of materials can be selected to form the electron-emitting device, and a fine structure can be adopted.

Here, the driving method of the electron-emitting device of the present invention will be described. In a display in which a phosphor is excited by electrons to emit light, the luminous efficiency of the phosphor is k, the electron current amount is I, the acceleration voltage is V, the light emission time is t, the frame time is T, the light emission area is s, and the whole pixel is When the area is S,
The light emission luminance L is represented by the following equation L = k × I × V × t / T × s / S (6).

FIG. 19 is a schematic diagram showing an analog modulation method. The luminous efficiency k in the equation (6) is the efficiency of converting electron energy into light, and the product of the electron current amount I and the acceleration voltage V is the electron energy. The electron current amount I can be changed by controlling the applied voltage between the gate and the cathode. The acceleration voltage V is the potential difference between the cathode electrode and the anode voltage. The anode voltage is, for example, 2 with respect to the cathode electrode.
It is often used at about kV to 6 kV. In the analog modulation method, the amount of current I is modulated by modulating the gate voltage with respect to the cathode voltage to express the luminance gradation.

FIG. 20 is a schematic diagram showing a pulse width modulation method. The t / T in the equation (6) is an element to be considered when the pulse-shaped electron irradiation is performed within the display period. In the display, light is emitted for a light emission time t within a limited period of a frame which is a constant display period. t
If / T is short, the average luminance in one frame time T decreases. Since the human eye has an afterimage effect, the emission brightness is this average brightness. Most of plasma display panels (PDP) and liquid crystal display devices (LCD) are t /
The brightness gradation is changed by pulse width modulation that changes T.

Although k in equation (6) is treated as constant, there is a saturation phenomenon in the actual phosphor in which the brightness does not increase even when a current of a certain value or more is input. In electron emission, there is a threshold electric field strength that initiates electron emission. Electron emission does not start in an electric field lower than the threshold electric field.

A method of driving the electron emission device will be described based on the above properties. Here, by the analog modulation method, (1) a driving method in which the electric field between the anode and the cathode is set to a threshold value, and (2) the electric field between the anode and the cathode is compared with the threshold electric field and the maximum current amount electric field. The driving method performed by setting the intermediate electric field to (3) and the driving method performed by setting the electric field between the anode and the cathode to the maximum current amount electric field are described below.

According to the driving method (1), there is an advantage that the gate modulation potential can be realized by a positive voltage which is not biased. When a display composed of a plurality of pixels is used and the threshold electric fields of the respective pixels are different from each other, the threshold electric potential is set to the lowest potential. The variation can be stored in an external semiconductor memory and reflected in the gate modulation.

According to the driving method (2), various settings can be made. As a first setting example, the electric field between the anode and the cathode is set to the electric field having the highest application frequency, and the gate potential is modulated to both positive and negative polarities. As a result, the time during which the gate potential is 0 can be increased and drive power consumption can be reduced. As a second setting example, the anode-cathode electric field is set to an electric field intermediate between the maximum current amount electric field and the threshold electric field. As a result, there is an advantage that the gate potential modulation amplitude is minimized.

According to the driving method (3), since the gate modulation can be performed only with the negative potential, the structure of the gate modulation circuit can be simplified. In addition, when the gate modulation circuit fails and only 0 potential is generated, or when the wire is broken and only floating potential is generated, the screen has the maximum brightness, so that there is an advantage that the failure is immediately identified. It can be used as emergency lighting.

With the driving methods (1) to (3), the same can be said for pulse width modulation. For example, when the driving method (2) is performed by the pulse width modulation method, the driving load can be reduced by setting the duty to be 50% in an electric field with a high luminance frequency. With the pulse width modulation method, even if the minimum bit pulse is short and the frequency is high, by keeping multiple bits in the same state continuously, the actual frequency is reduced by that amount, and the drive load (charge / discharge phenomenon) is reduced. It can be reduced. Dut where half of one frame is on and the other is off
The load is smallest when y is 50%.

Next, the driving method of this electron-emitting device will be described from another viewpoint. For example, a method in which a high potential is applied to the anode electrode and a low potential is applied to the gate electrode has been frequently used in the past, and it is preferably used when an electric field higher than the surroundings is applied between the gate and the cathode to extract electrons. To be done. However, contrary to this, the present invention is characterized in that an electric field lower than that of the periphery is applied between the gate and the cathode to suppress electron emission. Based on this feature, the driving method of the present electron emission device will be further described.

In the steady state, the electric field between the anode and the cathode exceeds the threshold value, and therefore it must be suppressed by the gate potential. In this driving method, the application of the gate potential is stopped only when the electric field between the anode and the cathode is equal to or lower than the threshold electric field at the time of starting (applying the device) or ending the application of the voltage.

[0099]

EXAMPLES Next, examples of the driving method of the present electron emitting device will be described.

Example 1 The threshold electric field is 2 V / μm,
When the steady-state anode-cathode electric field is 5 kV / μm, the anode-cathode electric field at startup is 1.9 V / μ
When the value is less than m, the gate is not applied, and when this value is reached, the gate potential is applied so that the electric field between the gate and the cathode becomes 1.9 V / μm. Then, the electric field between the anode and the cathode is increased to 5 kV / μm. At the end, perform the reverse procedure. By performing in such a procedure, when the gate potential is applied, the gate potential is set to 1.9 V / μm with the electric field around the gate electrode being 1.9 V / μm.
Since it can be set to V / μm, no discharge accident occurs and no electron emission occurs.

Next, a method of manufacturing an electron emission substrate using CNT as a cathode material will be described. FIG. 21 is a cross-sectional view showing the structure inside the gate hole, and (a) to (d) show the forming process step by step.

As shown in FIG. 21A, first, a thin film (not shown) made of aluminum metal is formed on the glass substrate 30 and patterned. Then, the polyimide film 31 is applied by a spin coating method so as to have a film thickness of 50 μm. Further, a copper thin film 32 is deposited on the polyimide film 31 by a plating method so as to have a film thickness of 20 μm, a resist film (not shown) is applied and patterned, and the copper thin film 32 is etched to form a gate electrode. Form. Next, the polyimide film 31 is further etched using the copper thin film 32 as a mask to form an insulating film. As a result, the gate hole 34 having a diameter of 50 μm is obtained.

As shown in FIG. 21B, the gate electrode 3
2 μm on the plane between the surface and the bottom of the gate hole 34
The CNT-containing resist film 35 is applied so as to have a certain degree. In the figure, the CNT-containing resist film 35 is drawn so as to be continuous at the end face of the gate hole 34, but it may be stepped at the end face. The coating shape of the CNT-containing resist film 35 on the bottom of the gate hole 34 becomes a mortar shape due to the effect of surface tension when the liquid is applied, as shown in the figure.

As shown in FIG. 21C, the gate electrode 3
The CNT-containing resist film 35 applied to the surface of No. 2 is removed by using the chemical mechanical polishing (CMP) method. In the figure, the CNT-containing resist film 35 applied to the bottom of the gate hole 34 remains without being cut.

As shown in FIG. 21 (d), CN was obtained by performing a heat treatment at about 300 ° C. for 20 minutes in the atmosphere.
The organic substance, which is the main component of the T-containing resist film 35, is vaporized and removed to reduce the volume. As a result, only the CNTs are fixed and remain in the shape of a mortar at the bottom of the gate hole 34.

Next, another method for producing an electron emission substrate using CNT as a cathode material will be described. FIG. 22
FIG. 3A is a cross-sectional view showing the structure inside the gate hole, and
(C) shows the forming process step by step.

As shown in FIG. 22A, first, a thin film (not shown) made of aluminum metal is formed on the glass substrate 30 and patterned. Then, the polyimide film 31 is applied by a spin coating method so as to have a film thickness of 50 μm. Further, a copper thin film 32 is deposited on the polyimide film 31 by a plating method so as to have a film thickness of 20 μm, a resist film (not shown) is applied and patterned, and the copper thin film 32 is etched to form a gate electrode. Form. Next, the polyimide film 31 is further etched using the copper thin film 32 as a mask to form an insulating film. In this case, by over-etching the polyimide film 31, a gate hole 34 having a diameter of 50 μm within the thickness of the gate electrode 32 and a diameter of 100 μm at the bottom is obtained.

As shown in FIG. 22B, the gate electrode 3
2 μm on the plane between the surface and the bottom of the gate hole 34
The CNT films 36 are applied so as to be uniform. In this case, the CNT film 36 is discontinuous at the end face. The coating shape of the CNT film 36 on the bottom portion of the gate hole 34 becomes a mortar shape due to the effect of surface tension when the liquid is applied, as illustrated.

As shown in FIG. 22C, the CNT film 36 applied to the surface of the gate electrode (32) is removed by the CMP method. In the figure, the CNT film 36 applied to the bottom of the gate hole 34 remains without being cut.

As described above with reference to FIGS. 21 and 22, the emitter (cathode electrode) at the bottom of the gate hole 34.
Since the inner peripheral surface side of the gate hole 34 is formed in a mortar shape protruding toward the gate electrode 32 side, a converging electric field can be favorably formed by the mortar-shaped recessed emitter shape.

Although the present invention has been described above based on its preferred embodiments, the electron-emitting device and its driving method of the present invention are not limited to the configurations of the above-mentioned embodiments, and the above-mentioned embodiments are not limited thereto. The electron-emitting device and its driving method which are variously modified and changed from the configuration of the embodiment are also included in the scope of the present invention.

[0112]

As described above, according to the electron-emitting device and the driving method thereof of the present invention, it is possible to suppress the emission spread and improve the spread property at the maximum emission amount.

[Brief description of drawings]

FIG. 1 is a cross-sectional view schematically showing one picture element of an FED as an electron emission device according to a first embodiment of the present invention.

FIG. 2 is a graph showing emission current density characteristics of the electron emission device of FIG.

FIG. 3 is a schematic diagram for explaining a case where the equipotential surface is concave in a specific range.

FIG. 4 is a graph showing three regions according to equations (2), (4), and (5).

FIG. 5 is a diagram showing a result of simulating a lens action of an equipotential surface according to equation (5).

FIG. 6 is a cross-sectional view schematically illustrating one picture element of FED as an electron emission device according to a second embodiment of the present invention.

FIG. 7 is a cross-sectional view showing electron emission trajectories when the electric field between the gate electrode and the cathode electrode is stronger than the electric field between the anode electrode and the gate electrode in the second embodiment example.

FIG. 8 is a graph showing emission spread characteristics covering each state of convergence and divergence in the second embodiment example.

FIG. 9 is a graph in which a condition range relating to a spreading characteristic and an emission current density characteristic in the second embodiment are overlaid.

FIG. 10 is a graph showing spread characteristics in the third embodiment of the present invention.

FIG. 11 is a graph in which a condition range related to a spread characteristic and an emission current density characteristic in the third embodiment are overlaid on each other.

FIG. 12 is a cross-sectional view schematically illustrating one pixel of an electron emission device for explaining fourth and sixth embodiments of the present invention.

FIG. 13 is a cross-sectional view schematically illustrating one picture element of the electron emission device according to the fifth embodiment of the present invention.

FIG. 14 is a graph showing characteristics when an emitter is deposited only on a region b in the fifth embodiment example.

FIG. 15 is a front view showing a part of the display portion of the FED in the seventh embodiment of the present invention.

FIG. 16 is an example of an electron-emitting device that realizes the spread characteristic in the seventh embodiment.

FIG. 17 shows R, G, B in the eighth embodiment of the present invention.
It is a figure which shows the principal part of FED which has one picture element which consists of three colors.

FIG. 18 shows R, G, B in the ninth embodiment of the present invention.
It is a figure which shows the principal part of FED which has one picture element which consists of three colors.

FIG. 19 is a schematic diagram showing an analog modulation method.

FIG. 20 is a schematic diagram showing a pulse width modulation method.

FIG. 21 is a cross-sectional view showing the structure inside the gate hole,
(A)-(d) shows a formation process step by step, respectively.

FIG. 22 is a cross-sectional view showing the structure inside the gate hole,
(A)-(c) shows a formation process step by step, respectively.

FIG. 23 is a cross-sectional view schematically illustrating one picture element of a conventional FED.

24 is a graph showing operating characteristics of the conventional electron-emitting device shown in FIG.

FIG. 25 is a graph illustrating phenomenon (1) when the electric field difference at the gate hole opening is large.

[Explanation of symbols]

1: substrate 2: Insulation film 3: Gate electrode 4: Gate hall 5: Emitter 6: Anode electrode 7: Phosphor 8: Equipotential surface 9: Electrons emitted from region a 10: Electrons emitted from region b 11: Electrons emitted from region c 12: Electrons emitted from the periphery 13: Pixel 14: Red picture element 15: Green picture element 16: Blue picture element 17: Black matrix 18: Defective emission spread range 19: Allowable emission spread range 20: Red bleed 21: Blue bleed 22: Bleed with the same color 23: Emission spread range 24: Gate hall to the left 25: Gate hole to the right 26: Central gate hall 30: Glass substrate 31: Polyimide film 32: Copper thin film 34: Gate hall 36: CNT film

Continuation of the front page (56) Reference JP-A-10-125215 (JP, A) JP-A-8-96704 (JP, A) JP-A-6-131996 (JP, A) JP-A-10-149760 (JP , A) JP 10-74473 (JP, A) JP 9-306396 (JP, A) JP 6-310023 (JP, A) JP 8-315721 (JP, A) JP 6-349426 (JP, A) JP 49-79161 (JP, A) JP 2000-268706 (JP, A) JP 2000-156147 (JP, A) Jitsukaihei 3-52944 (JP, U) (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01J 31/12 H01J 29/04

Claims (11)

(57) [Claims] 1. A substrate, a gate electrode having an opening and arranged on the substrate, an emitter formed by forming a cathode material in a thin film on the substrate in the opening, and a predetermined distance from the emitter. And an anode electrode to which a predetermined potential is applied, the emitter is configured such that the cathode material is exposed in the opening.
Formed in an annular shape except for the outer peripheral part and the central part on the protruding substrate
An electron emission device characterized by the above. 2. A substrate and an opening disposed on the substrate.
Gate electrode and cathode material on the substrate in the opening
From an emitter formed of a thin film of material
It is arranged with a predetermined space and a predetermined potential is applied.
In the electron emission device including an anode electrode, the opening is formed as a substantially rectangular hole,
Is formed in a strip shape along the longitudinal direction of the substantially rectangular hole.
An electron emission device characterized in that 3. A set of the emitter and gate electrodes
The three picture elements are arranged adjacent to each other, and
Of the first picture element located in the center of the picture element
The emitter extends along the longitudinal direction in the central portion of the substantially rectangular hole.
Second, which extends and is located on one side of the three sets of picture elements
In the picture element, the emitter has the substantially rectangular hole
The side close to the picture element 1 extends along the longitudinal direction, and
In front of the third picture element located on the other side of the three picture elements
The emitter is close to the first pixel of the substantially rectangular hole.
The side extending along the longitudinal direction.
Item 2. The electron-emitting device according to item 2. 4. A substrate and an opening disposed on the substrate.
Gate electrode and cathode material on the substrate in the opening
From an emitter formed of a thin film of material
It is arranged with a predetermined space and a predetermined potential is applied.
In an electron emission device including an anode electrode, the gate electrode is formed into a substantially rectangular shape, and the opening is formed in the center and corners of the gate electrode.
And the openings formed in the center respectively,
The emitter connects the middle part in the opening to the gate.
In the openings that extend along the longitudinal direction of the electrode and are located at each corner, the emitter is
Characterized by being formed closer to the outside in the opening
And an electron emission device. 5. The electrons emitted from the emitter are annotated.
The spread range when reaching the electrode is within the specified limit value.
A gate voltage is applied so that
The electron emission device according to any one of claims 1 to 4. 6. The electron emission according to claim 1.
In the device , a gate-emitter electric field formed between the gate electrode and the emitter electrode is set to a value smaller than a gate-anode electric field formed between the anode electrode and the gate electrode. And an electron emission device. 7. The electron emission device according to claim 1 , wherein the emitter is composed of a plurality of types of cathode materials having different emission characteristics from each other. 8. The electron emission device according to claim 1 , wherein carbon nanotubes are used as the cathode material. 9. A driving method for driving the electron-emitting device according to claim 1 , wherein the electric field between the anode electrode and the emitter is set to a threshold value. And a method for driving an electron emission device. 10. A driving method for driving the electron-emitting device according to claim 1 , wherein the electric field between the anode electrode and the emitter is a threshold electric field and a maximum current amount. A method for driving an electron-emitting device, characterized by setting an electric field intermediate to the electric field. 11. A driving method for driving the electron-emitting device according to claim 1 , wherein the electric field between the anode electrode and the emitter is set to a maximum current amount electric field. A method for driving an electron-emitting device characterized by the above.