JPH0820126A - Electrostatic image making apparatus - Google Patents

Abstract

PURPOSE:To provide an electrostatic image making apparatus in which a charge generation control element is made by utilizing a principle of electron discharge from the surface of a ferroelectric substance the to constitute a control element for charge generation and driving voltage can be reduced remarkably. CONSTITUTION:A charge generation control element is composed of a line electrode 2 formed on an insulating substrate 1, the first insulating film 3 formed on part of the surface of the line electrode 2, ferroelectric films 4 formed on part of the line electrode 2 and on the surface of the first insulating film 3, a finger electrode 5 which is formed on the surface of the ferroelectric film 4 and has a finger hole 5a in the middle, the second insulating film 6 which is formed on the surface of the finger electrode 5 and has a hole part 6a in the middle, and a screen electrode 7 which is formed on the surface of the insulating film 6 and has a screen hole 7a in the middle. An electrostatic image making apparatus is composed with the use of the charge generation control element.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic image forming apparatus used for electrostatic printing and a manufacturing method thereof.

[0002]

2. Description of the Related Art Conventionally, as a method of forming a latent image by electrostatic charges on a dielectric recording body by the principle of transferring charges directly onto the dielectric recording body and depositing it, a method utilizing corona discharge is particularly fair. No. 2-62862. FIG. 10 is a diagram showing a cross section of a part of the charge generator of the electrostatic image forming apparatus disclosed in the above publication. In the figure,
Reference numeral 100 denotes one charge generation control element of the charge generator. The charge generator is configured by arranging a large number of charge generation control elements 100 one-dimensionally or two-dimensionally. The charge generation control element 100 includes a line electrode 101 made of metal, a dielectric film 103, and the line electrode 10 via the dielectric film 103.
A finger electrode 105 made of metal, which is partially opposed to 1; an insulating film 107; and a screen electrode 109 made of metal, which is arranged so as to face the finger electrode 105 via a space. It is composed of.

Next, the operation of the charge generation control element 100 thus constructed will be described. In FIG.
By applying an AC voltage from the power supply 102 between the line electrode 101 and the finger electrode 105 arranged with the dielectric film 103 sandwiched between them, electric charges are generated in the surface region 104 of the dielectric film 103 by a corona discharge phenomenon. . Negative charges having high mobility in this charge group are used for latent image formation. When a positive potential higher than the potential applied to the finger electrode 105 is applied to the screen electrode 109 facing the finger electrode 105 with the insulating film 107 interposed, the negative charge generated by the corona discharge passes through the channel 106. It is extracted through the screen hole 108 formed in the screen electrode 109. The negative charge extracted from the screen hole 108 is accelerated toward the drum 110, which is a dielectric recording medium, and the drum 11
Deposit to 0 to form a latent charge image. On the contrary, when a negative potential is applied to the screen electrode 109 with respect to the finger electrode 105, extraction of negative charges from the screen hole 108 is blocked, and a latent image is not formed on the drum 110.

[0004]

By the way, since the principle of corona discharge is expressed by Paschen's law, first, Paschen's law will be briefly described. FIG. 11 shows a capacitor composed of parallel plate electrodes. 121 is an upper electrode to which a voltage V is applied, and 122 is a lower electrode which is grounded. Reference numeral 123 denotes a gap between electrodes, in which a gas such as air exists, and the distance between the electrodes is represented by L.

In the capacitor having such a structure, when the applied voltage V exceeds a certain voltage V _S , a corona discharge phenomenon occurs in the gap 123. FIG. 12 is a graph showing the relationship between the voltage V _S at which corona discharge starts and the p · L product. Here, p represents the pressure of the gas in the gap 123 of the capacitor, and L represents the distance between the electrodes 121 and 122. In FIG. 12, the types of gas (air, H ₂ , A,
Ne) is shown as a parameter. When the gas is air, the value of p · L product that minimizes V _S is 0.57. That is, under atmospheric pressure (760 torr) conditions, when L is about 7.5 microns, the minimum discharge start voltage (V _smin ) is about 330 V. Under the atmospheric pressure condition, when L is smaller than this value, the charge traveling distance becomes short and the discharge starting voltage rises. Also, when L is larger than this value, the electric field becomes weak and the discharge starting voltage rises.

Table 1 shows a summary of the minimum discharge inception voltage V _smin and the value of p · L product when various gases and various electrode materials are used. Even when the same electrode material is used, the gas It can be seen that the discharge start voltage is increased or decreased by changing the type.

[0007]

[Table 1]

As described above, in the charge generation control element using the corona discharge having the conventional structure shown in FIG. 10, the drive voltage of at least the minimum discharge start voltage V _{smin is required for the} charge generation by the corona discharge. It turns out that is necessary. Furthermore, according to Paschen's law, the driving voltage for this corona discharge is about 330 V or more under the normal operating atmosphere, where the gas is air and atmospheric pressure operation, and high withstand voltage characteristics are required for driving corona discharge. There is a problem that a special drive circuit is required, and the drive circuit eventually becomes expensive.

The present invention solves the above-mentioned problems in an electrostatic image forming apparatus which forms a charge latent image by electrostatic charges on a dielectric recording body by utilizing the conventional corona discharge. Provided is an electrostatic image forming apparatus using a charge generation control element based on a new charge generation principle, which can drastically reduce a driving voltage for charge generation as compared with a conventional method using corona discharge. The purpose is to

[0010]

In order to solve the above problems, the invention according to claim 1 of the present application provides a line electrode formed on an insulator, and a solid ferroelectric substance formed on the surface of the line electrode. A film, a finger electrode formed on the surface of the solid ferroelectric film and having a hole for charge generation in the center, and a solid insulator having a hole in the center of the finger electrode for allowing charges to pass therethrough. The electrostatic image forming apparatus is configured by using a charge generation control element including a screen electrode having a hole for charge control in the central portion formed through a film.

The invention according to claim 2 is characterized in that a plurality of hole portions of the finger electrodes of the charge generation control element in the electrostatic image forming apparatus according to claim 1 are formed.

The invention according to claim 3 is characterized in that a plurality of hole portions of the screen electrode of the charge generation control element in the electrostatic image forming apparatus according to claim 1 or 2 are formed.

The invention according to claim 4 is the same as claims 1 to 3.
2. The electrostatic image forming apparatus according to any one of 1 to 3, wherein a second screen electrode having a hole portion for allowing charges to pass through in a central portion is provided between the finger electrode of the charge generation control element and the screen electrode. It is characterized by.

According to a fifth aspect of the present invention, in the electrostatic image forming apparatus according to the fourth aspect, the second screen electrode of the charge generation control element has a plurality of holes. It is a thing.

According to a sixth aspect of the present invention, a line electrode formed on an insulator, a solid ferroelectric film formed on the surface of the line electrode, and a solid ferroelectric film formed on the surface of the solid ferroelectric film,
A finger electrode having a hole for electric charge generation in the center,
A charge generation control element comprising a screen electrode having a hole for charge control in the center, which is formed on the surface of the finger electrode through a solid insulator film having a hole for allowing the charge to pass through in the center, A plurality of two-dimensionally arranged charge generation control elements arranged in the row direction are commonly connected to the line electrodes, and respective charge generation control elements arranged in the column direction are commonly connected to the finger electrodes. An electrostatic image forming apparatus is configured using the charge generation unit.

According to a seventh aspect of the present invention, a line electrode formed on an insulator, a solid ferroelectric film formed on the surface of the line electrode, and a solid ferroelectric film formed on the surface of the solid ferroelectric film,
A finger electrode having a hole for electric charge generation in the center,
A first screen electrode having a hole for charge control in the center formed on a surface of the finger electrode via a solid insulator film having a hole for allowing the charge to pass therethrough;
A second hole provided between the finger electrode and the first screen electrode, the hole having a hole for allowing charges to pass therethrough
A plurality of charge generation control elements each including a screen electrode are arranged two-dimensionally, and the line electrodes and finger electrodes of the charge generation control elements arranged in the row direction are connected in common and arranged in the column direction. The electrostatic image forming apparatus is configured by using the charge generation unit formed by commonly connecting the second screen electrodes of the respective charge generation control elements.

According to an eighth aspect of the present invention, in the electrostatic image forming apparatus according to the sixth or seventh aspect, a peripheral circuit for driving the charge generating section is provided, and the thin film transistor group constituting the peripheral circuit is the thin film transistor group. It is characterized in that it is formed on the same substrate as the charge generating portion.

Other features of the present invention are listed below. (1) In the electrostatic image forming apparatus according to any one of claims 1 to 3, the charge generation control element includes a finger electrode and a line other than a hole for charge generation of the finger electrode and a region in the vicinity thereof. An insulating film is provided between the electrodes. (2) In the electrostatic image forming apparatus according to any one of claims 1 to 5, the solid ferroelectric film of the charge generation control element is formed of PZT, PLZT, or Y1. Is characterized by. (3) In the above item (2), the thickness of the solid ferroelectric film is in the range of 1 to 10 μm. (4) In the electrostatic image forming apparatus according to any one of claims 1 to 5, the line electrode of the charge generation control element is
It is characterized by being composed of a single-layer film formed of platinum, gold, gold-palladium, silver, or a palladium-based metal. (5) In the electrostatic image forming apparatus according to any one of claims 1 to 5, the line electrode of the charge generation control element is
It is characterized in that it is composed of a multi-layered film composed of an upper film formed of platinum, gold, gold-palladium, silver, or a palladium-based metal and a lower film formed of aluminum. (6) In the electrostatic image forming device according to any one of claims 1 to 5, the finger electrodes of the charge generation control element are made of platinum, gold, gold-palladium, silver, or a palladium-based metal. It is characterized in that it is composed of a single layer film formed in. (7) In the electrostatic image forming apparatus according to any one of claims 1 to 5, the finger electrodes of the charge generation control element are platinum, gold, gold-palladium, silver, or a palladium-based metal. It is characterized in that it is composed of a multi-layered film composed of a lower film formed in 1 above and an upper film formed of any of aluminum, molybdenum, and titanium. (8) In the above items (4) to (7), the film thickness of the finger electrodes or line electrodes is about 1 micron. (9) In the above item (1), the insulating film is formed of silicon oxide or silicon nitride. (10) In the above item (9), the thickness of the insulating film is about 2 μm. (11) In the electrostatic image forming apparatus according to any one of claims 1 to 5, the solid insulator film of the charge generation control element is formed of an organic material made of polyimide or resist. And (12) In the above item (11), the thickness of the solid insulator film is about
Characterized by a range of 10 to 100 microns. (13) In the electrostatic image forming apparatus according to any one of claims 1 to 5, the screen electrode or the first screen electrode of the charge generation control element is formed of molybdenum or titanium. Characterize. (14) In the electrostatic image forming apparatus according to claim 4 or 5, the second screen electrode of the charge generation control element is made of molybdenum or titanium. (15) In the above items (13) and (14), the film thickness of the screen electrode or the first screen electrode and the second screen electrode is about 1 micron. (16) In the electrostatic image forming apparatus according to claim 6, the line electrodes and the finger electrodes of the charge generation control element are AC.
It is characterized in that the screen electrode is driven to operate at a constant potential. (17) In the electrostatic image forming apparatus according to claim 7, the line electrode and the second screen electrode of the charge generation control element are AC-driven, and the first screen electrode and the finger electrode are set to a constant potential to operate. It is characterized by (18) In the electrostatic image forming apparatus according to claim 7, the finger electrodes of the charge generation control element and the second screen electrode are AC-driven, and the first screen electrode and the line electrode are set to a constant potential to operate. It is characterized by (19) In the electrostatic image forming apparatus according to the sixth or seventh aspect, the atmosphere is kept constant at least during operation. (20) In the above item (19), the atmosphere is N ₂ gas or a mixed gas of argon and carbon dioxide. (21) In the electrostatic image forming apparatus according to any one of claims 1 to 5, the hole formed in the solid insulator film of the charge generation control element is formed after the screen electrode is formed. Is characterized by. (22) In the electrostatic image forming apparatus according to the eighth aspect, the charge generation control element is formed after the thin film transistor group forming the peripheral circuit is formed.

[0019]

[Operation] The present invention uses the charge generation control element based on the principle of electron emission from the ferroelectric substance constructed as described above. First, the principle of operation will be described.
IEICE Technical Report [technical report of IEICE ED
93-146 (1993-12) pp. 81-88], in the title of "field electron emission from ferroelectric PZT ceramics", it is meant that electron emission into a vacuum is performed using a ferroelectric substance. Has been reported. FIG. 13A is a sectional structure of the device shown in this paper. 201 is an upper electrode having a grid-like planar shape, which is formed of platinum (P
t), and the electrode thickness t is 2000Å. 202 is P
It is a ferroelectric ceramic film made of ZT and its thickness is
60 microns. 203 is a lower electrode and 20 is an upper electrode.
It is made of platinum (Pt) like 1 and its thickness t is 2000
It is Å. Reference numeral 204 denotes a current probe for detecting an electron current, which is located about 10 mm above the upper electrode 201. FIG. 13B shows a drive waveform applied to each electrode. The lower electrode 203 is always grounded and has a ground potential. The upper electrode 201 is normally applied with a positive potential of about 100 V, but it is pulsed from −30 to −300 V.
A degree of negative potential is applied. In a device having such a structure, “in a nitrogen (N ₂ ) residual gas atmosphere,
Under a pressure condition of 0.5 torr or less, the emission electron current density value per pulse obtained a constant good current value of about 13.1 A / cm ² regardless of pressure. ” There is.

The principle of electron emission from the ferroelectric substance is that "electrons existing on the surface of the ferroelectric substance in the state where the upper electrode is at a positive potential undergoes polarization reversal by application of a negative pulse voltage. As a result, a large electric field is induced on the surface by the uncompensated polarization charge, and electrons are emitted from the metal of the electrode and the ferroelectric surface of the edge into the vacuum. ” ing. Further, as the material of the ferroelectric substance, PZT (lead zirconate titanate),
PLZT in which lanthanum (La) is added to PZT and the like are listed, and as the electrode material, in addition to platinum, gold, gold-palladium, silver and the like are listed. Furthermore, in the Nikkei Microdevice May 1994 issue pp.80-81, it was experimentally revealed that an iridium-based metal is desirable as a ferroelectric electrode material in terms of the reliability and durability of the ferroelectric. Has been reported.

By the way, in the charge generation control element of the conventional electrostatic image forming apparatus shown in FIG. 10, the distance from the surface of the screen electrode to the drum is about 200 microns. In the above paper, no electrons were detected at a pressure of 0.5 torr or more, but if the distance from the upper electrode to the current probe is closer than 10 mm to about 200 microns, it is possible to detect electrons even at atmospheric pressure. In addition, the work function difference for electrons emitted from the ferroelectric surface into space in vacuum and in air is the same, and the electric field inside the ferroelectric is inversely proportional to the thickness. If the ferroelectric film thickness of 60 μm of the existing device is reduced to, for example, 6 μm, the driving voltage for electron emission can be reduced to several tens of volts or less. On the basis of the above findings, the invention described in each claim of the present application constitutes the charge generation control element in the electrostatic image forming apparatus by utilizing the ferroelectric thin film as described above.

As described above, by adopting the charge generation control element using the ferroelectric thin film, compared with the conventional charge generation control element capable of generating the charge at the minimum discharge start voltage or higher predicted by Paschen's law. As a result, it is possible to exert an excellent action such as generation of electric charges with a drastically reduced driving voltage.

[0023]

EXAMPLES Next, examples will be described. FIG. 1 is a diagram showing a device cross-sectional structure of a charge generation control element of a first embodiment of an electrostatic image forming apparatus according to the present invention. In FIG. 1, 1 is an insulating substrate made of quartz (glass), and 2 is a line electrode made of metal formed on the substrate 1. Three
Is a first insulating film composed of a silicon oxide film or the like,
Reference numeral 4 is a ferroelectric thin film formed on a part of the line electrode 2 and on the first insulating film 3. Reference numeral 5 is a finger electrode made of metal, and a finger hole 5a serving as a charge generating portion is formed in the central portion.
It has. Reference numeral 6 is a second insulating film made of polyimide or the like, and has a hole 6a for passing charges in the center. Reference numeral 7 denotes a screen electrode made of metal, which has a screen hole 7a for controlling charge in the central portion. The first insulating film 3
Is formed between the finger electrode 5 and the line electrode 2 other than the finger hole 5a which is the charge generation portion and the vicinity thereof, and electrically maintains insulation between both electrodes or reduces capacitance between both electrodes. It plays a role such as. In this embodiment, the first insulating film 3 is formed directly above the line electrode 2, but the first insulating film 3 may of course be formed directly below the finger electrode 5. Parameters such as specific materials or film thicknesses for forming each insulating film, ferroelectric thin film, and each electrode will be described in detail in the next second embodiment.

FIG. 2 is a diagram showing a planar structure of a charge generation section of an electrostatic image forming apparatus in which a plurality of charge generation control elements having the structure shown in FIG. 1 are two-dimensionally arranged. Line electrodes are linearly connected in the row (horizontal) direction to form line electrode lines 2 _i and 2 _{i + 1} formed in parallel. On the other hand, the finger electrodes of each charge generation control element are linearly connected in the column (vertical) direction, and the line electrode wires 2 _i ,
The finger electrode lines 5 _j-1 , 5 _j , and 5 _{j + 1} are formed in parallel with each other so as to obliquely intersect with 2 _{i + 1} . The screen electrode 7 located at the top of the cross-sectional structure is formed over the entire surface in common for each charge generation control element. Then, the screen hole 7a has the line electrode wires 2 _i , 2
_It is formed at the intersection of _{i + 1} and the finger electrode wires 5 _j-1 , 5 _j , 5 _{j + 1} , and a finger hole 5a is formed below the screen hole 7a.

FIG. 3 is a diagram showing drive waveforms of respective parts for driving the electrostatic image forming apparatus shown in FIGS. 1 and 2.
First, with respect to the potential V _{D of the} drum on which the electrostatic image is formed,
The screen electrode potential V _S is a constant negative potential in terms of DC. On the other hand, the finger electrodes have two different levels.
Two potentials V _FH and V _FL are applied AC-wise or pulse-wise. When electric charges are to be generated, two potentials V _LH and V _LL having different levels are applied to the line electrode in an AC or pulse manner, and when electric charges are not to be generated, As shown, a DC potential is applied. The relationship between the level of each potential is
In the order of more positive potential, V _D , V _FH , V _LH , V _FL , V
_{It is LL} . In addition, there is a high-low relation with respect to the potential of V _FH > V _S > V _FL .

Next, the operation of the charge generator shown in FIG. 2 will be described. First, when the line electrode of the charge generation control element in the i-th row enters the operating state, the AC potential shown in FIG. 3 is applied to the i-th line electrode wire 2 _i , and the other line electrode wires V _LL indicated in 3
Is applied or a floating state is applied. By applying such a potential, electrons are generated in the finger holes 5a of each line electrode 2 on the line electrode line 2 _i .

Then, the finger electrodes are sequentially selected while the line electrodes 2 on the i-th line electrode line 2 _i are in the operating state. That is, when it is desired to extract electrons from the j-th screen hole 7a on the i-th line electrode line 2 _i , a potential V _FL lower than the screen electrode potential V _S is applied to the corresponding j-th finger electrode line 5 _j. Apply. By applying this potential V _FL , the electrons generated in the finger holes 5 a move toward the screen electrode 7 to which a positive potential is applied from the finger electrodes 5 and are extracted from the screen holes 7 a.

On the contrary, when it is not desired to extract the electrons from the screen hole 7a, the corresponding finger electrode wire has the potential V
_It suffices to maintain the same state as that of the other finger electrode wires to which _FH is applied.

The operation of the charge generation control element is usually performed in the atmosphere, but the atmosphere can be controlled at least during the operation of the element to improve the reliability or durability of the element. It will be possible. Suitable atmospheres include, for example, 100% nitrogen (N ₂ ) or argon (90%) + carbon dioxide (10%).

Further, in the above embodiment, the finger holes formed in the finger electrode are shown as a single hole as shown in FIG. 4A, but the finger hole is shown in FIG. As shown in B) and (C), a multi-hole structure including a plurality of holes can be used. By forming the finger holes in such a multi-hole structure, the amount of generated charges can be improved.

Next, a second embodiment and its manufacturing method will be described with reference to FIG.
This will be described with reference to the manufacturing process chart of FIG. In order to manufacture the charge generation control element in the second embodiment, first, as shown in FIG. 5A, an insulating substrate 11 made of quartz (glass) or the like is prepared, and the line electrode 12 is provided on the substrate 11. Patterning is formed. As the material of the line electrode 12, gold, gold-palladium, silver, a palladium-based metal, or the like is used in addition to platinum. The line electrode 12 has a multi-layer metal film structure in which a lower layer is a low resistance metal film such as aluminum, and a metal film such as platinum, gold, gold-palladium, silver, or a palladium-based metal is formed on the lower layer. You may comprise.
The line electrode 12 is formed with a thickness of about 1 micron by a manufacturing process such as a sputtering method or a vacuum deposition method.

After the line electrode 12 is formed and patterned as described above, the first insulating film 13 made of a silicon oxide film or a silicon nitride film is formed by plasma CVD.
(Plasma Chemical Vapor Deposition) and other manufacturing processes. The thickness of the first insulating film 13 is about 2 μm from the viewpoint of electrical breakdown voltage. First
After the insulating film 13 is formed, a resist film 14 is patterned by photolithography in order to remove the first insulating film 13 in the portion where the finger holes are formed.

Next, the first insulating film 13 is selectively removed by using the resist film 14 as a mask, and then the resist film 14 is removed. Then, as shown in FIG. The film 15 is formed. As the material of the ferroelectric film, PZT (lead zirconate titanate), PLZT obtained by adding lanthanum (La) to PZT, or what is called Y1 is used. This ferroelectric film is metalorganic CVD (MOCVD)
Film is formed by a process such as a method, and its film thickness is set to 1 in order to reduce the driving voltage for charge generation to several tens of volts or less.
A thin film is formed to about 10 microns.

Next, the finger electrode film 16 is formed on the ferroelectric film 15. As a material of the finger electrode film 16,
In addition to platinum, gold, gold-palladium, silver, or palladium-based metal is used. Further, the finger electrode film 16 is made of a low resistance metal film such as aluminum, molybdenum or titanium as the upper layer, and platinum, gold,
A multi-layer metal film structure in which a metal film of gold-palladium, silver, or a palladium-based metal is formed may be used. The finger electrode film 16 is formed by a manufacturing process such as a sputtering method or a vacuum evaporation method, and has a film thickness of 1
It is around micron.

After the finger electrode film 16 is formed as described above, the resist film 17 is patterned by photolithography as shown in FIG. 5C for patterning the finger electrode. And
Using the resist film 17 as a mask, unnecessary portions of the finger electrode film 16 are selectively removed by dry etching or wet etching to form finger electrodes 16a.

Next, after removing the resist film 17, as shown in FIG. 5D, a second insulating film 18 is formed on the finger electrodes 16a by a coating method such as a spin coating method. Polyimide, resist, or the like is suitable as the material of the second insulating film 18, and the film thickness is 10 to 100.
The micron range is desirable. After that, a single-layer metal film such as molybdenum, titanium, titanium nitride, or aluminum, or a multi-layer metal film made of these materials is formed on the second insulating film 18 by using a sputtering method or a vacuum deposition method. Form a film. Then, a resist pattern 20 for patterning the screen electrode is formed in a desired region by a photolithography method, and then a screen electrode 19a is patterned by a dry etching method or a wet etching method. The film thickness of the screen electrode 19a is about 1 micron.

Then, as shown in FIG. 5E, only the second insulating film 18 is formed by a dry etching method using oxygen plasma or a wet etching method in a chemical solution using the screen electrode 19a as a mask. Selectively remove,
A space 18a for passing charges is formed below the screen hole 19b. As a result, the charge generation control element of the second embodiment is obtained.

In the second embodiment, both the finger electrodes 16a and the screen electrodes 19a have a multi-hole structure, so that the amount of generated charges can be improved and the screen electrodes can be improved. By adopting a multi-hole structure, the diameter of each hole of the multi-hole structure becomes smaller than the diameter of the hole of the single-hole structure, so that the control voltage for controlling the amount of charges discharged in the drum direction can be lowered. It will be possible.

Next, a third embodiment will be described. In the above-mentioned first and second embodiments, the screen electrode has a cross-sectional structure in which one layer is provided. However, due to the cross-sectional structure, the charge generation control having the second screen electrode between the screen electrode and the finger electrode is performed. The structure according to the present invention can be applied to an element. The charge generation control element having the second screen electrode is also called a double screen structure element, and is a charge generation control element capable of controlling on / off of the emitted charge by a potential applied between the two screen electrodes. In this device, charge generation is turned on and off by the line electrodes and finger electrodes.

In the third embodiment, the structure according to the present invention is applied to the charge generation control element having the second screen electrode as described above, and FIG. 6 shows the charge generation control element of the third embodiment. FIG. 3 is a diagram showing a cross-sectional structure, the same or corresponding members as those of the charge generation control element of the first embodiment shown in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted. The charge generation control element of this embodiment is different from that of the first embodiment in that a second screen electrode 8 is provided between the first screen electrode 7 and the finger electrode 5, and this second screen electrode is different. As the plane structure of No. 8, a single-hole structure is shown, but it is of course possible to use a multi-hole structure. The constituent material and the film thickness of the second screen electrode 8 are the same as the constituent material and the film thickness of the first screen electrode 7.

FIG. 7 shows a planar structure of the charge generation portion of the third embodiment, which is formed by arranging the charge generation control elements shown in FIG. 6 two-dimensionally. The line electrodes of the charge generation control elements and the finger electrodes formed on the charge generation control elements are linearly connected in the row (horizontal) direction in an overlapping form, and the line electrode lines 2 _i and 2 are formed in parallel. _{i + 1} and finger electrode lines 5 _i and 5 _{i + 1} are formed. On the other hand, the second screen electrode of each charge generation control element is linearly connected in the column (vertical) direction, and is connected to the line electrode lines 2 _i and 2 _{i + 1} and the finger electrode lines 5 _i and 5 _{i + 1} . Second screen electrode lines 8 _j-1 , which are formed in parallel in a diagonally intersecting form,
8 _j and 8 _{j + 1} are formed. The first screen electrode 7 located at the top in the sectional structure is formed over the entire surface in common for each charge generation control element. Then, the first screen hole 7a has the finger electrode wires 5 _i , 5 _{i + 1.}
And second screen electrode wires 8 _j-1 , 8 _j , 8 _{j + 1} are formed at the intersections, and finger holes 5a and second screen holes 8a are formed below the first screen hole 7a. ing.

FIG. 8 is a diagram showing drive waveforms of respective parts for driving the electrostatic image forming apparatus of the third embodiment shown in FIGS. 6 and 7. First, the potential V of the drum on which the electrostatic image is formed
_In contrast to _D , the first screen electrode potential V _S is a constant negative potential in terms of DC. A constant DC potential V _L is also applied to the line electrode. On the other hand, two potentials V _SH and V _SL having different levels are applied to the second screen electrode.
It is applied AC or pulsed. If you want to generate an electric charge in the finger electrodes, as shown in,
When two electric potentials V _FH and V _FL having different levels are applied AC-wise or in a pulse-like manner and charge is not generated, a DC-like potential is applied as indicated by. The relation of the level of each potential is V _D , V _SH , V _S , and V _SL , in the order of more positive potential, and V
There is also a height relationship for the potentials _SL > V _FH > V _L > V _FL .

Next, the operation of the charge generator shown in FIG. 7 will be described. First, when the finger electrode of the charge generation control element in the i-th row enters the operating state, A indicated by A in FIG.
The C potential is applied to the i-th finger electrode line 5 _i, and the constant potential of V _FH shown in FIG. 8 is applied to the other finger electrode lines 5 _i , or the finger electrode lines 5 _i are floated. By applying such a potential, electrons are generated in the finger holes 5a of each finger electrode 5 on the finger electrode wire 5 _i.

Then, while the finger electrodes 5 on the i-th finger electrode line 5 _i are in the operating state, the respective second screen electrodes are sequentially selected. That is, when it is desired to extract electrons from the j-th first screen hole 7a on the i-th finger electrode line 5 _i , the corresponding j-th second screen electrode line 8 _j is set to the first screen electrode. Potential V
_A potential V _SL lower than _S is applied. By applying this potential V _SL , the electrons generated in the finger holes 5a move toward the first screen electrode 7 to which a positive potential is applied from the second screen electrode 8, and then from the first screen hole 7a. To be extracted.

On the contrary, when it is not desired to extract electrons from the first screen hole 7a, the corresponding second screen electrode line is the same as the other second screen electrode line to which the potential V _SH is applied. You just need to keep the state.

In the above description of the operation, the line electrode is set to a constant potential and the finger electrode is AC driven. However, instead of the finger electrode, the line electrode is AC driven and the finger electrode is set to a constant potential. Of course, it can be operated.

By constructing an electrostatic image forming apparatus using the charge generation control element according to the present invention, the drive voltage required for charge generation and the control voltage required for charge control are both several tens. It is possible to reduce the voltage to V or less, which is achieved by a thin film transistor (TFT) based on thin film amorphous silicon or polycrystalline silicon formed on a glass (quartz) substrate. It means that a peripheral drive circuit for driving the can be configured. Therefore, as a fourth embodiment, an electrostatic image forming apparatus constituted by forming a charge generating section including a large number of charge generation control elements and a peripheral drive circuit on the same substrate will be described with reference to FIG.

In FIG. 9, reference numeral 51 denotes a charge generation portion which is formed by arranging a large number of charge generation control elements shown in the first to third embodiments in a one-dimensional or two-dimensional form. 53 is a TFT for driving the electrode lines arranged in the row (long side) direction
The drive circuit is configured by, and is connected to the charge generation unit 51 by the wiring 55. This drive circuit 53 is a driver of the line electrode line in the case of the charge generation section according to the first embodiment, while it is a driver of the finger electrode line or the line electrode line in the case of the charge generation section according to the third embodiment. I'm a driver. Reference numeral 58 denotes a pad portion for operating the drive circuit 53, which is connected to the drive circuit 53 by a wiring 56.

On the other hand, reference numeral 52 denotes a drive circuit composed of TFTs for driving the electrode lines arranged in the column (short side) direction, which is connected to the charge generation section 51 by the wiring 54. The drive circuit 52 is a driver of the finger electrode line in the case of the charge generating portion according to the first embodiment, while it is a driver of the second screen electrode line in the case of the charge generating portion according to the third embodiment. Has become. Reference numeral 59 denotes a pad portion for operating the drive circuit 52, which is connected to the drive circuit 52 by a wiring 57. All of these constituent elements 51 to 59 are formed on the same substrate 50.

In this embodiment, the drive circuits 52 and 53 are
Although the structure is shown in which the charge generators 51 are arranged on both sides of the charge generator 51, of course, each drive circuit or one drive circuit may be arranged only on one side of the charge generator 51. Is. That is, for example, the drive circuits 53 for the electrode lines in the row direction are arranged on both sides of the charge generation section 51, while the drive circuits 52 for the electrode lines in the column direction are arranged on the charge generation section 51.
It is possible to adopt a configuration in which it is arranged on only one side of.

In the manufacturing process of the electrostatic image forming apparatus thus constructed, the driving circuits 52 and 53 are first formed by the well-known TFT manufacturing process, and then the manufacturing process as described in the second embodiment is performed. A manufacturing process for forming the charge generating portion 51 is used.

With the above structure, it is possible to realize an electrostatic image forming apparatus which can be driven at a lower voltage, has a high resolution, and is excellent in uniformity as compared with the conventional one.

[0053]

As described above on the basis of the embodiments,
According to the present invention, since the electrostatic image forming apparatus is configured using the charge generation control element configured by utilizing the principle of electron emission from the ferroelectric surface, the conventional charge generation using corona discharge is performed. As compared with the one using the control element, the electric charge can be generated with a remarkably small driving voltage, so that the driving voltage can be significantly reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing a sectional structure of a single charge generation control element of a first embodiment of an electrostatic image forming apparatus according to the present invention.

FIG. 2 is a schematic view showing a planar structure of a charge generation section formed by arranging a plurality of charge generation control elements shown in FIG. 1 in a two-dimensional manner.

FIG. 3 is a diagram showing drive waveforms of each unit for driving the charge generation unit shown in FIGS. 1 and 2.

FIG. 4 is a diagram showing an example of a planar shape of finger electrodes.

FIG. 5 is a diagram showing a manufacturing process for explaining the charge generation control device according to the second embodiment of the present invention and the manufacturing method thereof.

FIG. 6 is a diagram showing a cross-sectional structure of a charge generation control element according to a third embodiment of the present invention.

FIG. 7 is a schematic diagram showing a planar structure of a charge generation section formed by arranging a plurality of charge generation control elements shown in FIG. 6 in a two-dimensional array.

FIG. 8 is a diagram showing drive waveforms of each unit for driving the charge generation unit shown in FIGS. 6 and 7.

FIG. 9 is a schematic perspective view showing a fourth embodiment of the present invention.

FIG. 10 is a diagram showing a configuration example of a charge generation control element of a conventional electrostatic image forming apparatus.

FIG. 11 is an explanatory diagram for explaining Paschen's law.

FIG. 12 is a diagram showing a relationship between a discharge start voltage V _S and a p · L product.

FIG. 13 is a diagram showing a device for causing electrons to be emitted from a ferroelectric surface and a drive waveform thereof.

[Explanation of symbols]

1 Insulating Substrate 2 Line Electrode 2 _i , 2 _{i + 1} Line Electrode Wire 3 First Insulating Film 4 Ferroelectric Film 5 Finger Electrode 5a Finger Hole 5 _j-1 , 5 _j , 5 _{j + 1} Finger Electrode Wire 6th 2 Insulating film 7 Screen electrode 7a Screen hole 8 Second screen electrode 11 Insulating substrate 12 Line electrode 13 First insulating film 14 Resist film 15 Ferroelectric film 16 Finger electrode film 16a Finger electrode 17 Resist film 18 Second Insulating film 18a Space 19a Screen electrode 19b Screen hole 20 Resist pattern 50 Substrate 51 Charge generator 52 Drive circuit 53 Drive circuit 54, 55, 56, 57 Wiring 58, 59 Pad

Claims (8)

[Claims] 1. A line electrode formed on an insulator, a solid ferroelectric film formed on the surface of the line electrode, and a charge generating film formed on the surface of the solid ferroelectric film at the center. And a screen electrode having a hole for charge control in the center formed on a surface of the finger electrode through a solid insulator film having a hole for allowing charges to pass through in the center of the finger electrode. An electrostatic image forming apparatus including a charge generation control element including 2. The finger electrode of the charge generation control element has a plurality of holes.
The electrostatic image forming apparatus described. 3. The screen electrode of the charge generation control element has a plurality of holes.
Or the electrostatic image forming apparatus according to 2. 4. The charge generation control element is provided with a second screen electrode having a hole portion for allowing a charge to pass therethrough in a central portion between a finger electrode and the screen electrode. The electrostatic image forming apparatus according to any one of 3 above. 5. The electrostatic image forming apparatus according to claim 4, wherein the second screen electrode of the charge generation control element has a plurality of holes. 6. A line electrode formed on an insulator, a solid ferroelectric film formed on the surface of the line electrode, and a charge generating layer formed on the surface of the solid ferroelectric film at the center. And a screen electrode having a hole for charge control in the center formed on a surface of the finger electrode through a solid insulator film having a hole for allowing charges to pass through in the center of the finger electrode. A charge generation control element consisting of
A plurality of two-dimensionally arranged charge generation control elements arranged in the row direction are commonly connected to the line electrodes, and respective charge generation control elements arranged in the column direction are commonly connected to the finger electrodes. An electrostatic image forming apparatus including a charge generation unit. 7. A line electrode formed on an insulator, a solid ferroelectric film formed on the surface of the line electrode, and a charge generating film formed on the surface of the solid ferroelectric film at the center. A finger electrode having a hole portion and a solid insulator film having a hole portion for allowing a charge to pass through at the center portion on the surface of the finger electrode, and having a charge controlling hole portion at the center portion; A two-dimensional charge generation control element comprising: a screen electrode; and a second screen electrode provided between the finger electrode and the first screen electrode and having a hole for allowing charges to pass through in the center thereof. Array many,
Charge generation by commonly connecting the line electrodes and finger electrodes of the charge generation control elements arranged in the row direction and commonly connecting the second screen electrodes of the charge generation control elements arranged in the column direction Image forming apparatus having a section. 8. The electrostatic image forming apparatus according to claim 6, further comprising a peripheral circuit for driving the charge generating section, wherein a thin film transistor group forming the peripheral circuit is on the same substrate as the charge generating section. An electrostatic image forming device formed on the above.