JPH0945219A - Image forming device - Google Patents

Abstract

(57) Abstract: Dispersion of voltage applied to each electron-emitting device is compensated by voltage drop caused by wiring resistance between electron-emitting devices, and the amount of electron beam emitted from each electron-emitting device is made uniform. Thus, an image forming apparatus capable of obtaining a high quality image is obtained. In an image forming apparatus using an electron source in which a plurality of electron-emitting devices each having a carbonaceous film formed on a conductive film including an electron-emitting portion provided between electrodes are electrically connected to each other, The thickness of the carbonaceous coating of the emitting element is varied depending on the wiring position of the element.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus using an electron source in which a plurality of electron-emitting devices are electrically connected, and more specifically, an image forming apparatus applicable to a flat panel CRT, a fluorescent display tube or the like. The present invention relates to technology for improving the quality of equipment.

[0002]

2. Description of the Related Art Conventionally, two types of electron-emitting devices are known, which are a thermoelectron-emitting device and a cold cathode electron-emitting device. Field emission type (hereinafter, referred to as "FE")
Type ". ), Metal / insulating layer / metal type (hereinafter referred to as “MI
It is called "M type". ) And surface conduction electron-emitting devices.

As an example of the surface conduction electron-emitting device,
M. I. Elinson, Radio Eng.
Electron Phys. , 10, 1290 (1
965) and the like.

The surface conduction electron-emitting device utilizes the phenomenon that electron emission occurs when a current is passed through a thin film of a small area formed on a substrate in parallel with the film surface. Examples of the surface conduction electron-emitting device include a device using an SnO ₂ thin film by Elinson et al. And a device using an Au thin film [G. Dittmer: "Thin Solid
Films ", 9,317 (1972)] , In 2 O
₃ / SnO ₂ thin film [M. Hartwell
and C.I. G. FIG. Fonstad: "IEEE Tr
ans. ED Conf. , 519 (197
5)], using a carbon thin film [Hisashi Araki et al .: Vacuum,
26, No. 1, p. 22 (1983)].

A typical device configuration of these surface conduction electron-emitting devices is schematically shown in FIG. In the figure, 1 is a substrate, 4 and 5 are electrodes for obtaining electrical connection, 3 is a conductive film made of an electron emitting material, and 2 is an electron emitting portion. Conventionally, in these surface conduction electron-emitting devices, it is general that the electron-emitting portion 2 is formed on the conductive film 3 by an energization process called energization forming before the electron emission. That is, when a voltage is applied between the electrodes 4 and 5, the conductive film 3 is energized to locally destroy, deform or alter the conductive film 3 so that the electron emission becomes an electrically high resistance state. The electron emission function is obtained by forming the portion 2. Conventionally, in the surface conduction electron-emitting device, a voltage is applied to the above-mentioned conductive film 3 by the electrodes 4 and 5, and a current is caused to flow on the device surface, so that electrons are emitted from the electron-emitting portion 2.

Further, the applicant of the present invention has filed Japanese Patent Application Laid-Open No. 1-200533.
In Japanese Patent Laid-Open No. 2 and Japanese Patent Laid-Open No. 2-56822, a technology of a novel surface conduction electron-emitting device in which fine particles for emitting electrons are dispersedly arranged between electrodes is disclosed. This electron-emitting device has (1) high electron emission efficiency. (2) Since the structure is simple, manufacturing is easy. (3) A large number of elements can be arrayed and formed on the same substrate. It is an element having advantages such as. A typical device configuration of these surface conduction electron-emitting devices is shown in FIG. In FIG. 12, 1 is an insulating substrate, 4 and 5 are electrodes for obtaining electrical connection, 11
Is an electron emitting portion in which fine particles for emitting electrons are dispersedly arranged.

The applicant of the present invention has also filed Japanese Patent Application Laid-Open No. 1-30924.
In Japanese Patent Laid-Open No. 2 (1994), a surface conduction electron-emitting device and an image forming apparatus in which a carbonaceous film is formed on an electron-emitting portion are disclosed. This electron-emitting device has the effect of reducing variations in characteristics. Further, this image forming apparatus has advantages such as high definition and high image quality. A typical configuration diagram of this electron-emitting device is shown in FIG. In FIG. 13, 1 is an insulating substrate, 4 and 5 are electrodes for obtaining electrical connection, 1
Reference numeral 1 is an electron emitting portion in which fine particles for emitting electrons are dispersed, and 12 is a carbonaceous film.

Since the surface conduction electron-emitting device as described above has a simple structure and is easy to manufacture, there is an advantage that many arrays can be formed over a large area. Therefore, various applications for utilizing this feature are being researched. For example, it can be used for an image forming apparatus such as a display device.

Conventionally, as an example in which a large number of surface-conduction type electron-emitting devices are formed in an array, the surface-conduction type electron-emitting devices are arranged in parallel, and both ends (both device electrodes) of each surface-conduction type electron-emitting device are wired. An electron source in which a large number of rows connected to each other (also referred to as common wiring) is arranged (also referred to as a ladder arrangement) (Japanese Patent Laid-Open No. 64-31332 and 1-283).
749, and 2-257552). Further, particularly in the case of a display device, a large number of surface conduction electron-emitting devices can be used as a self-luminous display device that can be a flat panel display device similar to a display device using liquid crystal and does not require a backlight. A display device has been proposed in which an arranged electron source is combined with a phosphor that emits visible light when irradiated with an electron beam from the electron source (US Pat. No. 506).
No. 6883).

[0010]

When these electron-emitting devices are applied to an image forming apparatus, in general,
A large number of electron-emitting devices were arranged on the substrate, and thin film or thick film electrodes were used to electrically connect between the devices to use as a multi-electron beam source. There is a phenomenon in which the applied voltage varies from time to time. As a result, the amount of current of the electron beam emitted from each electron-emitting device varies, which causes a problem that density unevenness occurs in the formed image.

14 and 15 are views for explaining this problem in more detail. In both figures, (a) is an equivalent circuit diagram including an electron-emitting device, wiring resistance and a power source, and (b) is each electron-emitting device. FIG. 7 is a diagram showing the potentials of the positive electrode and the negative electrode of the device, and (c) is a diagram showing the voltage applied between the positive and negative electrodes of each electron-emitting device.

FIG. 14A shows a circuit in which _N surface-conduction electron-emitting devices D _{1 to} D _N connected in parallel and a power supply V _E are connected. The positive electrode of the power supply and the electron-emitting device D are shown. The positive electrode ₁ is connected to the negative electrode of the power source and the negative electrode of the electron-emitting device D _N. Further, the common wiring connecting the electron-emitting devices in parallel has a resistance component of r between the adjacent electron-emitting devices as shown in the figure (in the image forming apparatus,
Pixels that are targets of electron beams are usually arranged at equal pitches. Therefore, the electron-emitting devices are also arranged at equal intervals in space, and the wiring connecting them has the same resistance between the electron-emitting devices unless the width and the film thickness vary in manufacturing. ).

The electron-emitting devices D _{1 to} D _N are assumed to have substantially the same resistance value Rd.

In the circuit of FIG. 14 (a), FIG. 14 (b) shows the potentials of the positive and negative electrodes of each electron-emitting device. The horizontal axis of the figure shows the element numbers D _{1 to DN} , and the vertical axis shows the potential. The ● mark represents the positive electrode potential of each electron-emitting device, and the ■ mark represents the negative electrode potential, and the ● mark (■ mark) is connected with a solid line for the sake of convenience in order to make the tendency of the potential distribution easy to see.

As is clear from this figure, the voltage drop due to the wiring resistance r does not occur uniformly, and is steeper as it is closer to the electron-emitting device D ₁ on the positive electrode side, and conversely on the negative electrode side. The closer it is to D _N , the steeper it is. This is because on the positive electrode side, the current flowing through the wiring resistance r increases as it approaches D ₁ ,
On the negative electrode side, conversely, a larger current flows as it approaches D _N.

FIG. 14C shows the voltage applied between the positive and negative electrodes of each electron-emitting device. The vertical axis represents the applied voltage, and the circles are connected by a solid line for the sake of convenience in order to make it easier to see the same tendency as in FIG.

As is clear from this figure, in the case of the circuit as shown in FIG. 14A, the larger voltage is applied to the electron-emitting devices (D ₁ and D _N ) on both ends, and the larger voltage is applied to the vicinity of the central portion. The applied voltage is small in the electron-emitting device. Therefore, the electron beam emitted from each electron-emitting device has a larger emission current as the electron-emitting devices at both ends have a great inconvenience when applied to an image forming apparatus (for example, an image near the both ends has a dark density). Is dark, and the density near the center becomes lighter.)

On the other hand, FIG. 15 shows the case where the positive and negative electrodes of the power source are connected to one surface (the electron-emitting device D ₁ side in this figure) of the device rows connected in parallel. In the case of such a circuit, the potential on the positive electrode side and the potential on the negative electrode side are as shown in FIG. Therefore, the voltage applied to each electron-emitting device becomes larger as it approaches D ₁ as shown in FIG. 7C, which is extremely inconvenient for application as an image forming apparatus.

The degree of variation in the applied voltage for each electron-emitting device as shown in the above two examples is determined by the total number N of electron-emitting devices connected in parallel and the ratio of the device resistance Rd to the wiring resistance r (= Rd / r) and / or the connection position of the power source, but in general, the larger N is and the smaller Rd / r is, the more remarkable the variation is, and the connection method of FIG. 15 applies to the electron-emitting device more than that of FIG. The variation of the applied voltage is large.

For example, according to the connection method of FIG. 14, the element resistance Rd
= 1 kΩ, r = 10 mΩ, and N = 100,
Comparing the electron-emitting device having the largest applied voltage and the electron-emitting device having the smallest applied voltage, Vmax: Vmin = 102: 1
However, if N = 1000, Vmax:
Vmin = 472: 100, and the ratio of variation becomes large.

Further, N = 1000, Rd = 1 kΩ, r =
In the case of 1 mΩ, Vmax: Vmin = 127: 10
Although it is about 0, in the case of a wiring resistance of r = 10 mΩ,
The degree of variation becomes large as Vmax: Vmin = 472: 100.

As described above, when a plurality of electron-emitting devices having the same characteristics are connected in parallel, a voltage drop caused by the wiring resistance causes the voltage effectively applied to each electron-emitting device to emit electrons. This varies from element to element, resulting in non-uniform electron beam emission, which is inconvenient when applied as an image forming apparatus.

In particular, when attempting to realize a large-capacity display device having a large number of pixels (that is, a large N), the ratio of the above-mentioned variation becomes remarkable, and uneven density of the image becomes a serious problem.

According to the present invention, even if the voltage applied to each electron-emitting device varies due to the voltage drop caused by the wiring resistance between the electron-emitting devices, the amount of electron beams emitted from each electron-emitting device is made uniform. An object of the present invention is to obtain an image forming apparatus capable of obtaining a high quality image.

[0025]

The constitution of the present invention made to achieve the above object is as follows.

That is, according to the present invention, an image forming apparatus is provided with an electron source in which a plurality of electron-emitting devices each having a carbonaceous film formed on a conductive film including an electron-emitting portion provided between electrodes are electrically connected. 2. In the image forming apparatus, the carbonaceous film formed on the plurality of electron-emitting devices has at least two different film thicknesses.

In the present invention described above, the thickness of each carbonaceous film formed on each of the plurality of electron-emitting devices is set specifically by taking out, for example, the positive electrode side of the electron-emitting device rows connected in parallel. When the electrode is arranged at one end of the positive electrode of the element row and the negative side take-out electrode is arranged at the other end of the negative electrode of the element row, electron emission located at the end of the element row The thickness of the carbonaceous coating of the device is made larger than the thickness of the carbonaceous coating of the electron-emitting device located in the center of the device row. Further, when the positive electrode side and the negative electrode side extraction electrodes of the electron-emitting device rows connected in parallel are arranged on the positive electrode side electrode and the negative electrode side electrode at the same end of the device row, respectively, The thickness of the carbonaceous film of the electron-emitting device is made smaller as the distance from the extraction electrode increases.

According to the present invention, the thickness of the carbonaceous film formed on the electron-emitting devices connected in parallel is changed for each device, and the electron-emitting characteristics of each electron-emitting device are changed, whereby each device is changed. Even if the applied voltage to the device varies, the emission current of each device can be corrected so as to be constant.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION As described above, the present invention relates to a novel structure of an image forming apparatus using an electron source having a plurality of electron-emitting devices, which will be further described below.

The electron-emitting device according to the present invention is called a surface conduction electron-emitting device as described above.
The structure of this surface conduction electron-emitting device will be described.

1 (a) and 1 (b) are views showing the basic structure of a surface conduction electron-emitting device according to the present invention. In the drawings, 1 is a substrate, 2 is an electron emitting portion, and 3 is Conductive film, 4 and 5
Is an electrode (element electrode), and 6 is a carbonaceous film.

The substrate 1 is, for example, quartz glass or Na.
And glass having reduced impurity content such as glass, blue plate glass, a laminate obtained by laminating SiO ₂ on a blue plate glass by a sputtering method or the like, and ceramics such as alumina.

As the material of the device electrodes 4 and 5 facing each other,
Common conductor materials are used, such as Ni, Cr, Au,
Metals or alloys such as Mo, W, Pt, Ti, Al, Cu, Pd, and Pd, Ag, Au, RuO ₂ , Pd-Ag
Printed conductors composed of metals or metal oxides and glass and the like, transparent conductors such as In ₂ O ₃ —SnO ₂ , and semiconductor conductor materials such as polysilicon are appropriately selected.

The element electrode spacing L, the element electrode length W, the shape of the conductive film 3 and the like are designed according to the applied form.

The element electrode spacing L is preferably several hundred angstroms to several hundred micrometers, and more preferably several micrometers to several tens of micrometers depending on the voltage applied between the device electrodes 4 and 5. .

The device electrode length W is preferably several micrometers to several hundreds of micrometers in consideration of the electrode resistance value and electron emission characteristics, and the device electrode thickness d is
Hundreds of Angstroms to a few micrometers.

In the electron-emitting device shown in FIG. 1, the device electrodes 4, 5 and the conductive film 3 are laminated in this order on the substrate 1, but the conductive film is formed on the substrate 1. 3, the device electrodes 4 and 5 may be laminated in this order.

In order to obtain good electron emission characteristics, the conductive film 3 is particularly preferably a fine particle film composed of fine particles, and the thickness of the conductive film 3 depends on the step coverage of the device electrodes 4 and 5 and the device. It is appropriately selected depending on the resistance value between the electrodes 4 and 5 and the forming conditions described later. The thickness of the conductive film 3 is preferably several angstroms to several thousand angstroms, particularly preferably 10 angstroms to 500 angstroms, and its resistance value is 10 3 to 10 7 ohm / □ sheet. It is the resistance value.

The fine particle film is a film in which a plurality of fine particles are aggregated, and as a fine structure thereof, not only the fine particles are individually dispersed and arranged but also the fine particles are adjacent to each other or overlap each other (some fine particles). Also includes the case where they are aggregated to form an island-like structure as a whole).

In the present specification, the term “fine particles” is frequently used, and the meaning will be described.

Small particles are called "fine particles", and smaller ones are called "ultra fine particles". It is widely known that particles smaller than "ultrafine particles" and having a number of atoms of about several hundreds or less are called "clusters".

However, each boundary is not strict, and changes depending on what kind of property is focused on. Further, “fine particles” and “ultrafine particles” may be collectively referred to as “fine particles”, and the description in this specification is in line with this.

For example, in “Experimental Physics Course 14: Surfaces and Particles” (edited by Kinoshita Yoshio, published by Kyoritsu Shuppan, September 1, 1986), “particles in this paper have a diameter of about 2-3 μm to 10 nm. And especially when it is referred to as ultrafine particles, the particle size is about 10 nm to 2-3 n.
It means up to about m. It is not exactly strict because both are collectively written as fine particles, but it is a rough guide. When the number of atoms constituting a particle is from 2 to several tens to several hundreds, it is called a cluster. (Page 195, lines 22 to 26).

In addition, the definition of “ultrafine particles” in the “Hayashi / Ultrafine Particle Project” of the New Technology Development Corporation has the following lower limit of the particle size, and is as follows.

In the "Ultrafine particle project" (1981-1986) of the Creative Science and Technology Promotion System, particles having a particle size (diameter) in the range of about 1 to 100 nm are called "ultrafine particles". Then, one ultrafine particle is an aggregate of about 100 to 10 ⁸ atoms. From the atomic scale, the ultrafine particles are large to huge particles. "(" Ultrafine particles- Creative Science and Technology "Takashi Hayashi, Ryoji Ueda, Akira Tasaki ed .; Mita Publishing 198
8 years, page 2, lines 1 to 4) / "Even smaller than ultrafine particles, that is, composed of several to several hundred atoms 1
Individual particles are usually called clusters "(ibid., Page 2, lines 12-13).

Based on the above general term,
In the present specification, “fine particles” are an aggregate of a large number of atoms and molecules, and the lower limit of the particle size is several Å to 10 Å, and the upper limit is several μm.
I will refer to something of a degree.

As the material forming the conductive film 3, for example, Pd, Pt, Ru, Ag, Au, Ti, In, Cu,
Metals such as Cr, Fe, Zn, Sn, Ta, W, and Pb;
oxides such as dO, SnO ₂ , In ₂ O ₃ , PbO, Sb ₂ O ₃ , HfB ₂ , ZrB ₂ , LaB ₆ , CeB ₆ , Y
Borides such as B ₄ and GdB ₄ , TiC, ZrC, HfC,
Carbides such as TaC, SiC and WC, TiN, ZrN,
Examples include nitrides such as HfN, semiconductors such as Si and Ge, and carbon.

The electron emitting portion 2 is, for example, a crack formed in a part of the conductive film 3, and the electron emission is performed from the vicinity of this crack. This crack is formed depending on the film thickness of the conductive film 3, the film quality, the material, the energization forming conditions described later, and other manufacturing methods. Therefore, the position and shape of the electron-emitting portion 2 are not limited to the position and shape as shown in FIG.

Inside the cracks, there may be conductive fine particles having a particle size of several angstroms to several hundred angstroms. The conductive fine particles are similar to some or all of the elements of the material constituting the conductive film 3. In addition, the electron emitting portion 2 including a crack and the conductive film 3 in the vicinity thereof
Has a film containing carbon as a main component.

Various methods are conceivable as a method of manufacturing the surface conduction electron-emitting device, one example of which will be described with reference to FIGS. 2 to 4. In FIG. 2, the same reference numerals as those in FIG. 1 denote the same members.

1) After the substrate 1 is thoroughly washed with a detergent, pure water and an organic solvent, an element electrode material is deposited by a vacuum evaporation method, a sputtering method or the like, and then an element is formed on the surface of the substrate 1 by a photolithography technique. The electrodes 4 and 5 are formed (FIG. 2A).

2) The element electrode 4 is formed by applying an organometallic solution on the substrate 1 on which the element electrodes 4 and 5 are provided and leaving it to stand.
And the element electrode 5 are connected to each other to form an organic metal film. still,
The organic metal solution is a solution of an organic compound whose main element is a metal of the constituent material of the conductive film 3 described above. After that, the organic metal film is heated and baked to form the conductive film 3 patterned by lift-off, etching or the like (FIG. 2).
(B)).

Although the method of coating the organic metal solution has been described here, the method is not limited to this, and examples thereof include a vacuum vapor deposition method, a sputtering method, a chemical vapor deposition method, a dispersion coating method, a dipping method and a spinner method. It is also possible to form an organic metal film.

3) Subsequently, an energization process called forming is performed. When electricity is applied between the device electrodes 4 and 5 from a power source (not shown), the electron emitting portion 2 having a changed structure is formed at the site of the conductive film 3 (FIG. 2C). By this energization treatment, the conductive film 3 is locally destroyed, deformed or denatured, and the site where the structure is changed is the electron emitting portion 2.

FIG. 3 shows an example of the voltage waveform of forming.

The voltage waveform is particularly preferably a pulse waveform,
There are a case where a voltage pulse whose pulse peak value is a constant voltage is continuously applied (FIG. 3A), and a case where a voltage pulse is applied while increasing the pulse peak value (FIG. 3B).

First, the case where the pulse peak value is a constant voltage will be described with reference to FIG.

In FIG. 3A, T1 and T2 are the pulse width and pulse interval of the voltage waveform. For example, T1 is 1 microsecond to 10 milliseconds and T2 is 10 microseconds to 100.
It is set to millisecond, and the peak value (peak voltage during forming) is appropriately selected according to the form of the surface conduction electron-emitting device described above, and applied for several seconds to several tens of minutes in a vacuum atmosphere with an appropriate degree of vacuum. The voltage waveform to be applied is not limited to the illustrated triangular wave, and a desired waveform such as a rectangular wave can be used.

Next, the case where the voltage pulse is applied while the pulse crest value is increased will be described with reference to FIG.

T1 and T2 in FIG. 3B are shown in FIG.
As in (a), the peak value (peak voltage at the time of forming) is increased by, for example, about 0.1 V steps,
Application is performed in an appropriate vacuum atmosphere similar to the description of FIG.

During the pulse interval T2, the element current is measured at a voltage that does not locally damage, deform or alter the conductive film 3, for example, a voltage of about 0.1 V to obtain a resistance value. Forming is preferably terminated when the resistance is equal to or higher than ohms.

The steps from the forming step onward can be performed in a measurement and evaluation system as shown in FIG. This measurement evaluation system will be described.

4, the same reference numerals as those in FIG. 1 indicate the same members. Further, 51 is a power supply for applying a device voltage Vf to the device, 50 is an ammeter for measuring a device current If flowing through the conductive film 3 between the device electrodes 4 and 5, and 54 is an electron emitting portion 2. An anode electrode for trapping the emission current Ie generated, 53 is a high-voltage power supply for applying a voltage to the anode electrode 54, 52 is an ammeter for measuring the emission current Ie emitted from the electron emission portion 2, 55 Is a vacuum device,
56 is an exhaust pump.

The electron-emitting device, the anode electrode 54 and the like are installed in a vacuum device 55, and this vacuum device 55 is equipped with necessary equipment such as a vacuum gauge (not shown) so that the electron-emitting device can be operated under a desired vacuum. It is possible to measure and evaluate.

The exhaust pump 56 is composed of a normal high vacuum system such as a turbo pump and a rotary pump, and an ultra high vacuum system such as an ion pump.
The entire vacuum device 55 and the substrate 1 of the electron-emitting device are
The heater can heat up to about 200 ° C. This measurement and evaluation system configures the display panel and its inside as the vacuum device 55 and its inside at the stage of assembling the display panel as will be described later, so that the measurement and evaluation in the forming step and the subsequent steps described later are performed. It is applied to processing.

4) Next, a carbonaceous film 6 is formed on the region including the electron emitting portion 2 by a vacuum vapor deposition method or the like.

5) It is preferable that the electron-emitting device manufactured as described above is subjected to a stabilizing process in which the electron-emitting device is operated and driven in a vacuum atmosphere having a vacuum degree higher than that in the forming step. More preferably, in a vacuum atmosphere having a high degree of vacuum, after heating at 80 to 150 ° C., the operation is driven.

A vacuum atmosphere having a vacuum degree higher than that in the forming step means, for example, about 10 −6 torr.
A vacuum atmosphere having the above-mentioned degree of vacuum is preferable, and an ultrahigh vacuum system is more preferable.

That is, by encapsulating the electron-emitting device in the above-mentioned vacuum atmosphere, it is possible to suppress further deposition of the carbonaceous film, thereby stabilizing the device current If and the emission current Ie.

The basic characteristics of the surface conduction electron-emitting device obtained as described above will be described below.

The basic characteristics of the surface conduction electron-emitting device described below are that the voltage of the anode electrode 54 of the measurement / evaluation system of FIG. 4 is 1 kV to 10 kV, and the distance H between the anode electrode 54 and the surface conduction electron-emitting device is 2 Usually, the measurement is performed by setting the width to 8 mm.

Here, in order to explain the operation of controlling the film thickness of the carbonaceous film, which is the most characteristic feature of the present invention, first, the emission current Ie and the device in the electron-emitting device in which the carbonaceous film is not formed are described. An example of the relationship with the voltage Vf is shown in FIG.
Shown in

As is apparent from FIG. 5, the surface conduction electron-emitting device has the following three characteristic characteristics with respect to the emission current Ie.

First, in the surface conduction electron-emitting device, when a device voltage Vf exceeding a certain voltage (called a threshold voltage: about 8 V in FIG. 5) is applied, the emission current Ie rapidly increases, while Below the threshold voltage, the emission current Ie
Is hardly detected. That is, it is a non-linear element having a clear threshold voltage with respect to the emission current Ie.

Secondly, since the emission current Ie has a characteristic of monotonically increasing with respect to the element voltage Vf (called MI characteristic), the emission current Ie can be controlled by the element voltage Vf.

Thirdly, the emitted charges captured by the anode electrode 54 (see FIG. 4) depend on the time for applying the device voltage Vf. That is, the amount of charges captured by the anode electrode 54 can be controlled by the time for which the device voltage Vf is applied.

Next, the relationship between the emission current Ie and the device voltage Vf when the carbonaceous film is formed on the electron-emitting device of the above example,
6 and changes in the stability of the emission current are shown in FIG.

As shown in FIG. 6, the emission current is changed by forming a carbonaceous film on the region including the electron emitting portion of the electron emitting device. Then, the emission current amount can be controlled by changing the film thickness of the carbonaceous film.

Therefore, when a plurality of electron-emitting devices are electrically connected in parallel as shown in FIGS. 14 and 15 and the voltage applied to each device varies due to the voltage drop of the wiring electrode, this application is performed. By setting the film thickness of the carbonaceous film of each element so as to compensate for the variation in voltage, the amount of emission current from each element can be made uniform.

Specifically, the emission current decreases as the carbonaceous film is formed thicker. Therefore, for example, as shown in FIG. 14, if the element applied voltage is higher in the element closer to the extraction electrode side, By reducing the film thickness of the carbonaceous film as the distance from the extraction electrode side increases, the variation in the amount of electron emission can be reduced. Further, as shown in FIG. 15, if the element applied voltage at the central portion is low and is high at both ends,
By making the thickness of the carbonaceous coating smaller toward the central portion and increasing toward the both ends, it is possible to reduce variations in the amount of electron emission.

In the present invention, the thickness of the above carbonaceous film,
The material is not particularly limited as long as it is a combination that can compensate the variation in the emission current of each element due to the voltage drop due to the wiring electrode. For example, when the material is carbon or metal carbide, the film thickness is It is preferably 300 Å or less, particularly 10 to 200 Å, and in the case of organic carbon, the film thickness is 200 Å or less, particularly 50 to 100 Å. According to the combination of the material and the film thickness, there is no inconvenience that the coating thickness is too large and the emission current amount and efficiency are impaired, and conversely, the coating thickness is too small to obtain the coating effect. On the other hand, there is an effect that the fluctuation of the emission current amount is reduced (stability is increased).

Next, an example of an electron source in which a plurality of the surface conduction electron-emitting devices are arranged and an image forming apparatus of the present invention using the electron source will be described with reference to FIGS. 7 and 8.

In FIG. 7, 1 is a substrate, 104 is a surface conduction electron-emitting device, 304 is a surface conduction electron-emitting device 1.
There are 10 common wirings for connecting 04, each having external terminals D1 to D10.

The surface conduction electron-emitting device 104 is the substrate 1
A plurality of them are arranged in parallel on the top. This is called an element array. As described above, the carbonaceous coating formed on each element in the element array is set so as to compensate the variation in the emission current of each element due to the voltage drop due to the wiring electrode. A plurality of rows of the element columns are arranged to form an electron source.

Each element row can be independently driven by applying an appropriate drive voltage between the common wiring 304 of each element column (for example, the common wiring 304 of the external terminals D1 and D2). That is, a voltage higher than the threshold voltage may be applied to the element array in which the electron beam is desired to be emitted, and a voltage lower than the threshold voltage may be applied to the element array in which the electron beam is not desired to be emitted. The application of such a driving voltage is performed on the common wirings D2 to D9 located between the respective element columns by adjoining the common wirings 304 adjacent to each other, that is, the external terminals D2 and D3, D4 and D5, D6 and D7, respectively. The common wiring 304 for D8 and D9 can also be formed as an integrated single wiring.

FIG. 8 shows a display panel 3 provided with the above electron source.
It is a figure which shows the structure of 01.

In FIG. 8, 302 is a grid electrode, 303 is an opening through which electrons pass, D1 to Dm are external terminals for applying a voltage to each surface conduction electron-emitting device, and G1 to G are shown.
n is an external terminal connected to the grid electrode 302.
Further, the common wiring 304 between each element row is formed on the substrate 1 as an integral same wiring.

In FIG. 8, 111 is a rear plate and 1
Reference numeral 12 is a support frame, 116 is a face plate, and 118 is an envelope.

A grid electrode 302 is provided between the substrate 1 and the face plate 116. The grid electrode 302 is capable of modulating the electron beam emitted from the surface conduction electron-emitting device 104, and the electron beam is applied to a stripe-shaped electrode that is orthogonal to the ladder-shaped arrangement of the device rows. A circular opening 303 corresponding to each surface-conduction type electron-emitting device 104 is formed in order to allow passage.
Is provided.

The shape and position of the grid electrode 302 are
It does not necessarily have to be as shown in FIG. 8, and a large number of openings 303 may be provided in a mesh shape, and the grid electrode 302 may be provided, for example, around or near the surface conduction electron-emitting device 104. Good.

The external terminals D1 to Dm and G1 to Gn are connected to a drive circuit (not shown). Then, by applying a modulation signal for one image line to the column of the grid electrode 302 in synchronization with sequentially driving (scanning) the element rows one by one, each electron beam is irradiated on the fluorescent film 114. And images can be displayed line by line.

As described above, the image forming apparatus of the present invention sets the thickness of the carbonaceous film of each element so as to compensate the applied voltage to each element caused by the voltage drop of the wiring electrode. The amount of emitted electron beams becomes uniform, and high-quality image display can be obtained.

Further, the image forming apparatus of the present invention is not limited to a display device for television broadcasting, but also a video conference system,
It is suitable as a display device such as a computer,
Furthermore, the present invention can be used as an exposure device of an optical printer including a photosensitive drum.

[0094]

The present invention will be described in more detail with reference to the following examples.

[Embodiment 1] In this embodiment, FIG.
An example in which an image forming apparatus is configured using an electron source having a plurality of element rows in which a plurality of electron-emitting devices are connected in parallel as shown in the equivalent circuit diagram of FIG. In FIG. 15A, D ₁ , D ₂ , D ₃ , ..., D _n are electron-emitting devices,
r indicates wiring resistance.

First, before actually manufacturing an electron-emitting device, based on the characteristics of a typical surface conduction electron-emitting device,
When the voltage drop due to the wiring resistance when 1000 elements were connected in parallel was estimated, the wiring resistance r = 1 mΩ and the element resistance Rd were all 1000Ω, and the voltage applied to the actual element was the maximum Vf _{max at} both ends and the central portion. Is the minimum Vf
_min (see FIG. 15C), the ratio Vf _max :
Vf _min ≈121: 100. This indicates that when a drive voltage of 17.5V is applied from both ends of both the positive and negative electrodes, the applied voltage is effectively about 14V to the central element. Further, when an emission current of about 1.5 μA is required for each element as an image forming apparatus, in order to obtain an emission current of about 1.5 μA for all the elements, a central portion at a driving voltage of 17.5 V is required. In the element of 1), Ie = 1.5 μA when the applied voltage is 14 V, and in the elements at both ends, Ie = 1.5 μA when the applied voltage is 17.5 V. That is, a carbonaceous film whose film thickness is controlled so as to exhibit the electron emission characteristics may be formed on the conductive film 3 (see FIG. 1) including the electron emission portion of each element.

The manufacturing procedure will be described below. The electron-emitting device manufactured in this example has the form shown in FIG. 1, and 1000 devices are connected in parallel to each device row.

1) A quartz substrate is used as the insulating substrate 1,
After thoroughly washing this with an organic solvent, electrodes 4 and 5 were formed on the surface of the substrate 1. Ni metal was used as the material of the electrodes, the electrode interval L was 2 μm, the electrode width W was 300 μm, and the thickness thereof was 1000 Å.

2) Next, Al (ρ≈3) is applied to the wiring electrode 304.
× using 10 ^-8 Ωm), and a width 600 .mu.m, a thickness of 50 [mu] m. The wiring resistance r at this time was about 1 mΩ.

3) Next, an organic solvent containing an organopalladium compound (Catapaste CCP, manufactured by Okuno Chemical Industries Co., Ltd.) was spin-coated on the substrate 1 by a spinner, and the solution was dried in air at 25
Firing was performed at 0 ° C. for 10 minutes to form a conductive fine particle film containing PdO as a main component. Then, this fine particle film is patterned by using a normal photolithography technique to form a plurality of conductive films 3, and then each conductive film is subjected to an energization process (forming) to form a crack to form an electron. The discharge part was used.

4) Next, carbon was deposited by a vacuum vapor deposition method to form a carbonaceous coating 6 which gradually decreased from the film thickness of 100 Å of the element at both ends to the film thickness of 10 Å of the element in the central portion. Position of each element of the present embodiment (from the positive electrode side of the power source to D
FIG. 9 is a plot of the relationship between ₁ , D ₂ , D ₃ , ..., D _n = D ₁₀₀₀ ) and the film thickness of the carbonaceous film 6 produced here.

5) Next, a glass spacer having a thickness of 5 mm is provided on the substrate 1, and a phosphor substrate in which the phosphor is uniformly applied is provided on the substrate 1, and then the whole is housed in the measurement / evaluation system of FIG. Then, the degree of vacuum was maintained at about 1 × 10 −6 torr, and the electron emission characteristics were confirmed at a driving voltage of 17.5 V and an acceleration voltage of 1 kV.

As a result, bright spots corresponding to each electron emitting portion were observed, and the brightness of each bright spot was visually almost uniform. Moreover, when the variation of each luminance was measured using a spot luminance meter, the variation was within 5%. Further, there was an effect of reducing the fluctuation amount of the emission current.

[Embodiment 2] In the present embodiment, FIG.
An example in which an image forming apparatus is configured using an electron source having a plurality of element rows in which a plurality of electron-emitting devices are connected in parallel as shown in the equivalent circuit diagram of FIG. In FIG. 14A, D ₁ , D ₂ , D ₃ , ..., D _n are electron-emitting devices,
r indicates wiring resistance. The electron-emitting device manufactured in this example also has the form shown in FIG. 1, and 1000 devices are connected in parallel to each device row.

The manufacturing method of this embodiment is the same as that of the first embodiment, and the thickness of the carbonaceous film formed on each element is different from that of the first embodiment. In this example, the film thickness of the carbonaceous film of the device D ₁ was set to 200Å, and the film thickness was successively reduced to 10Å the carbonaceous film of the device D ₁₀₀₀ . Position of each element in the present embodiment (from the positive electrode side of the power source, D ₁ , D ₂ , D ₃ , ..., D _n
= D ₁₀₀₀ ) and the thickness of the carbonaceous film 6 are plotted in FIG.

When the electron emission characteristics were observed in the same manner as in Example 1, bright spots corresponding to each electron emission portion were observed,
The brightness of each bright spot was visually almost uniform. In addition, when the variation of each luminance was measured using a spot luminance meter,
The variation was within 5%. Further, there was an effect of reducing the fluctuation amount of the emission current.

[Embodiment 3] A plurality of rows of surface conduction electron-emitting devices connected in parallel were formed on the same substrate as in Embodiment 2, and an electron source substrate as shown in FIG. 7 was obtained.

An image forming apparatus panel as shown in FIG. 8 was produced using this electron source substrate. The inside of the envelope 118 is evacuated to about 1 × 10 ⁻⁶ torr.

Among the external terminals D1 to Dm of this panel, odd-numbered terminals (D1, D3, which are drawn out from the positive electrode).
...) is connected to the positive electrode side of the power supply, and the even-numbered terminals (D2, D4, ...) Pulled out from the negative electrode are connected to the ground, and the panel is operated at a power supply voltage of 17.5 V and an acceleration voltage of 1 kV. When driven, bright spots corresponding to each electron emitting portion were observed, and the brightness of each bright spot was visually almost uniform. Also,
The variation in each luminance was within 5%.

[Embodiment 4] FIG. 16 is provided to a display panel (see FIG. 8) using the above-mentioned surface conduction electron-emitting device as an electron source from various image information sources such as television broadcasting. FIG. 6 is a diagram showing an example of the image forming apparatus of the present invention configured to display the image information to be displayed.

In the figure, 201 is a display panel, 100
1 is a display panel drive circuit, 1002 is a display controller, 1003 is a multiplexer, 10
04 is a decoder, 1005 is an input / output interface circuit, 1006 is a CPU, 1007 is an image generation circuit, 10
08, 1009 and 1010 are image memory interface circuits, 1011 is an image input interface circuit, 1012 and 1013 are TV signal receiving circuits, 101
Reference numeral 4 is an input unit.

Incidentally, when the image forming apparatus receives a signal containing both video information and audio information, such as a television signal, it naturally reproduces audio at the same time as displaying video. Descriptions of circuits, speakers, and the like relating to reception, separation, reproduction, processing, storage, and the like of audio information that are not directly related to the features of the present invention will be omitted.

The functions of the respective parts will be described below along the flow of image signals.

First, the TV signal receiving circuit 1013 is a circuit for receiving a TV signal transmitted using a wireless transmission system such as radio waves or spatial optical communication.

The TV signal system to be received is not particularly limited. For example, NTSC system, PAL system, SEC.
Any method such as AM method may be used. Further, a TV signal comprising a larger number of scanning lines than these, for example, a so-called high-definition TV including the MUSE system is a signal suitable for taking advantage of the display panel suitable for a large area and a large number of pixels. Source.

T received by the TV signal receiving circuit 1013
The V signal is output to the decoder 1004.

The TV signal receiving circuit 1012 is a circuit for receiving a TV signal transmitted using a wire transmission system such as a coaxial cable or an optical fiber. Similar to the TV signal receiving circuit 1013, the system of the TV signal to be received is not particularly limited, and the TV signal received by this circuit is also output to the decoder 1004.

Image input interface circuit 1011
Is a circuit for capturing an image signal supplied from an image input device such as a TV camera or an image reading scanner. The captured image signal is output to the decoder 1004.

Image memory interface circuit 101
Reference numeral 0 is a circuit for capturing an image signal stored in a video tape recorder (hereinafter abbreviated as VTR), and the captured image signal is output to the decoder 1004.

Image memory interface circuit 100
Reference numeral 9 denotes a circuit for capturing an image signal stored in the video disk.
004 is output.

Image memory interface circuit 100
Reference numeral 8 denotes a circuit for capturing an image signal from a device that stores still image data, such as a still image disk, and the captured still image data is input to the decoder 1004.

The input / output interface circuit 1005 is
A circuit for connecting the display device to an external computer, a computer network, or an output device such as a printer. It is of course possible to input / output image data and character / graphic information, and in some cases, input / output control signals and numerical data between the CPU 1006 of the image forming apparatus and the outside. .

The image generation circuit 1007 receives image data, character / graphic information, or CPU 100 externally input through the input / output interface circuit 1005.
6 is a circuit for generating display image data based on the image data and character / graphic information output from 6. Inside this circuit, for example, a rewritable memory for storing image data and character / graphic information, a read-only memory storing an image pattern corresponding to a character code, a processor for performing image processing, etc. And other circuits necessary for generating an image.

The display image data generated by this circuit is output to the decoder 1004, but in some cases, it can be output to an external computer network or printer via the input / output interface circuit 1005.

The CPU 1006 mainly performs operations related to operation control of the display device and generation, selection and editing of a display image.

For example, a control signal is output to the multiplexer 1003 to appropriately select or combine image signals to be displayed on the display panel. At that time, the display panel controller 1 is operated according to the image signal to be displayed.
A control signal is generated for 002 to appropriately control the operation of the display device such as the screen display frequency, the scanning method (for example, interlaced or non-interlaced), and the number of scanning lines on one screen. Further, the image data or the character / graphic information is directly output to the image generation circuit 1007, or the external computer or memory is accessed through the input / output interface circuit 1005 to display the image data or the character / graphic information. input.

It should be noted that the CPU 1006 may also be involved in work for other purposes. For example, it may directly relate to a function of generating and processing information, such as a personal computer or a word processor. Alternatively, as described above, the input / output interface circuit 1005
The computer may be connected to an external computer network via a computer, and work such as numerical calculation may be performed in cooperation with an external device.

The input unit 1014 is used by the user to input commands, programs, data, etc. to the CPU 1006. For example, a keyboard, a mouse, a joystick, a bar code reader, a voice recognition device, and the like can be used. An input device can be used.

The decoder 1004 converts various image signals input from the above 1007 to 1013 into three primary color signals,
Alternatively, it is a circuit for inversely converting the luminance signal into the I signal and the Q signal. In addition, as shown by a dotted line in the figure, the decoder 100
4 preferably has an image memory inside. This is for handling a television signal that requires an image memory when performing inverse conversion, such as the MUSE method.

By providing the image memory, it is easy to display a still image. Alternatively, the image generation circuit 1007
And the CPU 1006 in cooperation with the image thinning, interpolation,
There is an advantage that image processing and editing including enlargement, reduction, and composition become easy.

The multiplexer 1003 corresponds to the CPU 1
The display image is appropriately selected based on the control signal input from 006. That is, the multiplexer 1003
Selects a desired image signal from the inversely converted image signals input from the decoder 1004, and drives the drive circuit 1001.
Output to In that case, by switching and selecting an image signal within one screen display time, it is also possible to divide one screen into a plurality of areas and display different images depending on the areas, as in a so-called multi-screen television. .

Display panel controller 1002
Is a circuit for controlling the operation of the drive circuit 1001 based on a control signal input from the CPU 1006.

As a signal related to the basic operation of the display panel, for example, a signal for controlling the operation sequence of a power source (not shown) for driving the display panel is output to the drive circuit 1001. A signal for controlling a screen display frequency and a scanning method (for example, interlace or non-interlace) is output to the drive circuit 1001 as a method related to the display panel drive method. In some cases, a control signal relating to image quality adjustment such as luminance, contrast, color tone, and sharpness of a display image may be output to the driving circuit 1001.

The drive circuit 1001 is a circuit for generating a drive signal to be applied to the display panel 201, and based on the image signal input from the multiplexer 1003 and the control signal input from the display panel controller 1002. It works.

Although the functions of the respective parts have been described above, the image information input from various image information sources can be displayed on the display panel 201 in the present image forming apparatus with the configuration illustrated in FIG. . That is, various image signals including television broadcasting are transmitted to the decoder 10.
After being inversely converted in 04, it is appropriately selected in the multiplexer 1003 and input to the drive circuit 1001.
On the other hand, the display controller 1002 generates a control signal for controlling the operation of the drive circuit 1001 according to an image signal to be displayed. The drive circuit 1001 uses the image signal and the control signal to display the display panel 201.
Is applied with a drive signal. Thus, an image is displayed on the display panel 201. These series of operations are totally controlled by the CPU 1006.

In the present image forming apparatus, the image memory built in the decoder 1004 and the image generation circuit 100.
7 and information not only selected but also displayed image information such as enlargement, reduction, rotation, movement, edge enhancement, thinning, interpolation, color conversion, image aspect ratio conversion, etc. It is also possible to perform initial image processing and image editing including synthesizing, erasing, connecting, replacing, and fitting. Although not specifically mentioned in the description of the present embodiment, a dedicated circuit for processing and editing audio information may be provided as in the above-described image processing and image editing.

Therefore, the present image forming apparatus includes a display device for television broadcasting, a terminal device for a video conference, an image editing device for handling still images and moving images, a terminal device for a computer,
It is possible to combine the functions of office terminals such as word processors, game machines, etc., with a very wide range of applications for industrial or consumer use.

Note that FIG. 16 shows only an example of the configuration in the case of an image forming apparatus using a display panel having a surface conduction electron-emitting device as an electron beam source, and the image forming apparatus of the present invention is It goes without saying that the present invention is not limited to this.

For example, of the constituent elements shown in FIG. 16, circuits relating to functions unnecessary for the purpose of use may be omitted.
Conversely, additional components may be added depending on the purpose of use. For example, when this display device is applied as a video phone, a TV camera, a voice microphone,
It is preferable to add an illuminator, a transmission / reception circuit including a modem, and the like to the components.

In this image forming apparatus, since the surface conduction electron-emitting device is used as the electron source, the display panel can be easily thinned and the depth of the image forming apparatus can be reduced. In addition, a display panel using a surface conduction electron-emitting device as an electron beam source is easy to enlarge the screen, has high brightness, and has excellent viewing angle characteristics, so that the image forming apparatus is full of a sense of reality and has a powerful image. Can be displayed with good visibility.

[0141]

As described above, according to the present invention,
Since a carbonaceous film having a different film thickness is formed for each element on the region including the electron emitting portion so as to compensate for variations in the applied voltage to each element due to a voltage drop caused by the wiring resistance between the electron emitting elements, The amount of electron beams emitted from each electron-emitting device becomes uniform, and an image forming apparatus capable of high-quality image display can be obtained.

[Brief description of drawings]

FIG. 1 is a plan view and a vertical sectional view schematically showing an example of a surface conduction electron-emitting device according to the present invention.

FIG. 2 is a diagram illustrating a method of manufacturing the surface conduction electron-emitting device of FIG.

FIG. 3 is a diagram showing an example of a forming waveform.

FIG. 4 is a schematic configuration diagram showing an example of a measurement / evaluation system of a surface conduction electron-emitting device.

FIG. 5 is a diagram showing a relationship between an emission current Ie and a device voltage Vf of a surface conduction electron-emitting device.

FIG. 6 is a diagram showing a relationship between a film thickness of a carbonaceous film of a surface conduction electron-emitting device and an emission current Ie.

FIG. 7 is a schematic plan view showing an example of an electron source according to the present invention in which a plurality of electron-emitting devices are connected in parallel in a ladder shape.

8 is a schematic configuration diagram showing an example of a display panel used in the image forming apparatus of the present invention using the electron source of FIG.

FIG. 9 is a diagram showing the thickness of the carbonaceous film of each electron-emitting device in the image forming apparatus of Example 1.

FIG. 10 is a diagram showing the thickness of a carbonaceous film of each electron-emitting device in the image forming apparatus of Example 2.

FIG. 11 is a configuration diagram of a conventional surface conduction electron-emitting device.

FIG. 12 is a configuration diagram of a conventional surface conduction electron-emitting device.

FIG. 13 is a configuration diagram of a conventional surface conduction electron-emitting device.

FIG. 14 is an explanatory diagram showing an equivalent circuit, a potential, and an applied voltage when a plurality of electron-emitting devices are connected in parallel.

FIG. 15 is an explanatory diagram showing an equivalent circuit, a potential, and an applied voltage when a plurality of electron-emitting devices are connected in parallel.

FIG. 16 is a block diagram illustrating an image forming apparatus according to a fourth exemplary embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Electron emission part 3 Conductive film 4,5 Element electrode 6 Carbonaceous film 11 Electron emission part consisting of fine particle film 12 Carbonaceous film 50 Ammeter 51 for measuring device current If 51 Power supply 52 Measured emission current Ie Ammeter 53 for operation High voltage power supply 54 Anode electrode 55 Vacuum device 56 Exhaust pump 301 Display panel 302 Grid electrode 303 Opening 304 Common wiring (wiring electrode) 1001 Driving circuit 1002 Display controller 1003 Multiplexer 1004 Decoder 1005 Input / output interface circuit 1006 CPU 1007 Image generation circuit 1008 Image memory interface circuit 1009 Image memory interface circuit 1010 Image memory interface circuit 1011 Image input interface circuit 1012 T Signal receiving circuit 1013 TV signal receiving circuit 1014 input

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Ichiro Nomura 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Kazuhiro Sandou 3-30-2 Shimomaruko, Ota-ku, Tokyo Kya Non-Incorporated (72) Inventor Hidetoshi Haru 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (3)

[Claims] 1. An image forming apparatus comprising an electron source electrically connected to a plurality of electron-emitting devices each having a carbonaceous coating formed on a conductive film including an electron-emitting portion provided between electrodes. The image forming apparatus, wherein the carbonaceous film formed on the electron-emitting device has at least two different film thicknesses. 2. The plurality of electron-emitting devices are connected in parallel, and the positive electrode side take-out electrode of the electron-emitting device array connected in parallel is arranged at one end of the positive electrode side electrode of the device array, and the negative electrode side. The extraction electrode is arranged at the other end of the negative electrode of the device row, and the thickness of the carbonaceous coating of the electron-emitting device located at the end of the device array is the electron emission located at the center of the device array. The image forming apparatus according to claim 1, wherein the thickness is larger than the thickness of the carbonaceous film of the element. 3. The plurality of electron-emitting devices are connected in parallel, and the extraction electrodes on the positive electrode side and the negative electrode side of the electron-emitting device columns connected in parallel are positive electrode electrodes on the same end of the device column. 2. The carbonaceous coatings of the electron-emitting devices of the device array arranged on the negative electrode and the negative electrode, respectively, and the thickness of the carbonaceous film decreases with distance from the extraction electrode. Image forming apparatus.