JP2013099901A - Ion flow type electrostatic drawing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ion flow type electrostatic drawing device capable of drawing a high-resolution electrostatic latent image by preventing mechanical damage of an electron emitter due to contact and by suppressing ion diffusion.SOLUTION: An electron emitter 11 emitting an electron toward a photoreceptor is provided in a recess 2a of a glass substrate 2 in which the recess 2a opposed to the photoreceptor is formed, and two floating electrodes 24 are stacked on sidewall parts 2ab of the recess 2a so as to face the electron emitter 11. The two floating electrodes 24 are provided so as to be inclined relative to a bottom surface of the recess 2a, respectively.

Description

  The present invention relates to an ion flow type electrostatic drawing apparatus.

  An element structure that enables electron emission in the atmosphere without causing a discharge phenomenon is disclosed in Patent Document 1, for example. This electron-emitting device has an electron accelerating layer including a conductive fine particle having a strong anti-oxidation effect between electrodes and an insulator material larger than the size of the conductive fine particle. Enables long-term operation in the atmosphere.

  Since electrons emitted from the electron-emitting device generate an ion flow in the atmosphere, the electron-emitting device is used in a recording apparatus that obtains an image using an electrostatic latent image. In such a usage form, compared to a corona charger generally used in the charging process of an electrophotographic process, there is no generation of ozone harmful to the human body, and the amount of active substance generated in the atmosphere is extremely small, so the photoconductor. Further, there are merits such as that the deterioration of the developer can be suppressed. In addition, the electron emission portion of the electron emission element can be formed into a large number of fine dots, and an independent electrode can be arranged on each dot for multi-channel driving, whereby an electrostatic latent image can be formed on the photoreceptor. Can be made an ion flow type electrostatic drawing apparatus that directly draws.

  Since such an electron-emitting device is composed of a thin film laminate, it has a significantly low mechanical strength and is easily broken as compared with a substrate material made of glass or aluminum. Therefore, mechanical damage easily occurs when the thin film stack is touched with a finger or collided with a hard object.

  Therefore, in order to handle the electron-emitting device, it is necessary to provide some structure for protecting the electron-emitting device. Patent Document 2 discloses a method for preventing mechanical damage of a semiconductor element or the like due to external contact and handling failure. In the method of Patent Document 2, a semiconductor element to be protected is embedded in a fine recess formed on the surface of an insulating support substrate by molding with an insulator such as a resin, thereby causing external contact and handling deficiencies. Mechanical damage of semiconductor elements and the like is prevented.

JP 2009-146891 A JP 2008-192413 A

  If the electron-emitting device is arranged at the bottom of a fine recess formed in the substrate as in the method of Patent Document 2, the electron-emitting device can be protected. However, when the electron-emitting device is used in an ion flow type electrostatic drawing apparatus, the following problem occurs in the simple configuration in which the electron-emitting device is disposed in the concave portion of the substrate.

  The step formed by the concave portion makes the distance between the electron-emitting device and the member to be charged (photosensitive member) longer than that when there is no concave portion. As a result, the distance over which the ion current flies is increased, and the ion diffusion effect due to the repulsive force between the ions appears greatly. As a result, the ion landing area on the photoconductor is larger than the electron emission area in the electron-emitting device. Will become bigger. In addition, since the electron-emitting device is disposed in the concave portion of the insulating substrate, the surface of the concave portion is charged, the trajectory of the ion flow is changed by the charged charge, and the landing position of the ions is shifted. As described above, when the landing area of ions increases or the landing position shifts, the electrostatic latent image becomes blurred and it becomes impossible to draw a high-resolution latent image.

  The present invention is for solving the above-described problems, and prevents mechanical damage to the electron-emitting device due to contact, and suppresses ion diffusion to enable drawing of a high-resolution electrostatic latent image. An object is to provide an ion flow type electrostatic drawing apparatus.

The present invention includes a substrate on which a recess opening toward the electrostatic latent image carrier is formed;
A plurality of first electrodes arranged side by side, a second electrode provided opposite to the first electrode, and the first electrode, the electron-emitting devices installed on the bottom surface of the recess An insulating layer provided between the second electrode and having an opening corresponding to the first electrode on a one-to-one basis, and a fine particle including an insulating fine particle and a conductive fine particle and filling the opening An electron-emitting device that emits electrons in a direction from the bottom toward the electrostatic latent image carrier when a voltage is applied between the first electrode and the second electrode.
A floating electrode provided on each of the two side walls of the recess, the floating electrodes provided to be inclined with respect to the surface of the bottom so as to move away from each other toward the charged body side from the bottom side; An ion flow type electrostatic drawing apparatus comprising:

  In addition, the present invention is characterized in that the inclination angle of the floating electrode with respect to the surface of the bottom is selected within a range of 15 ° to 75 °.

  In addition, the present invention is characterized by comprising a third electrode laminated on the second electrode and formed to be narrower than the second electrode.

  According to the present invention, since the electron-emitting device is provided in the recess formed in the substrate, mechanical damage to the electron-emitting device due to contact can be prevented. Furthermore, since the electric field for causing ions generated by the electrons emitted from the electron-emitting device to fly toward the electrostatic latent image carrier is distorted by the floating electrode, ion diffusion is suppressed. Therefore, mechanical damage to the electron-emitting device due to contact can be prevented, and ion diffusion can be suppressed, and a high-resolution electrostatic latent image can be drawn.

  According to the present invention, since the floating electrode is installed at an inclination angle of 15 ° to 75 ° with respect to the surface of the bottom of the recess, the effect of distorting the electric field and suppressing the diffusion of ions is reliably exhibited. can do.

  According to the present invention, the third electrode having a width smaller than that of the second electrode is laminated on the second electrode. Therefore, by applying a voltage to the third electrode, the potential distribution in the surface direction of the second electrode is increased. Uniform voltage application without bias is possible. Thereby, electrons can be uniformly emitted at each electron emission point of the electron-emitting device, and as a result, the electrostatic latent image carrier can be uniformly irradiated with ions.

1 is a cross-sectional view illustrating a configuration of an electrostatic latent image recording mechanism 10 including an ion flow type electrostatic drawing apparatus 1. 3 is an enlarged cross-sectional view showing an electron-emitting device 11 of the ion flow type electrostatic drawing apparatus 1. FIG. 1 is a perspective view of an ion flow type electrostatic drawing apparatus 1. FIG. FIG. 6 is a diagram for explaining the operation of the floating electrode 24. It is a figure which expands and shows the part 9 of FIG.

  FIG. 1 is a cross-sectional view showing a configuration of an electrostatic latent image recording mechanism 10 including an ion flow type electrostatic drawing apparatus 1 according to an embodiment of the present invention. FIG. 2 is an enlarged sectional view showing the electron-emitting device 11 of the ion flow type electrostatic drawing apparatus 1. FIG. 3 is a perspective view of the ion flow type electrostatic drawing apparatus 1.

  The electrostatic latent image recording mechanism 10 includes an ion flow type electrostatic drawing apparatus 1 and a photosensitive member 25 that is an electrostatic latent image carrier. The ion flow type electrostatic drawing apparatus 1 is configured by arranging an electron-emitting device 11 on the surface of a bottom 2aa of a groove (recess 2a) formed in a glass substrate 2. The electron-emitting device 11 includes, in order from the glass substrate 2 side, an insulating layer having a plurality of first electrodes (lower electrodes 3) that correspond one-to-one with the electron emission point and an opening (through hole 8) that serves as the electron emission point. 4, the fine particle layer 5 that fills the through-hole 8 and is formed on the insulating layer 4, the second electrode (upper electrode 6) serving as a common electrode for the plurality of lower electrodes 3, and the third electrode (bus wiring 7) ) Is a laminated structure.

  The electron-emitting device 11 is formed such that the uppermost bus wiring 7 does not exceed the height of the recess 2a. With this structure, even if something comes into contact with the ion flow type electrostatic drawing apparatus 1, the two side walls 2ab sandwiching the bottom 2aa of the recess 2a function as a bumper, and the surface of the bottom 2aa It is possible to prevent mechanical damage from occurring in the arranged electron-emitting device 11.

  The bottom 2aa of the recess 2a formed in the glass substrate 2 has a length of 215 mm and a width of 500 μm, for example. The through hole 8 of the insulating layer 4 serving as an electron emission point is formed at the same height along the longitudinal direction of the recess 2a at the center in the width direction of the recess 2a of the glass substrate 2. Further, the lower electrode 3 is drawn out of the recess 2a from the bottom 2aa of the recess 2a of the glass substrate 2 and connected to a drive driver mounted on the surface of the glass substrate 2. In FIG. 1, the pulse power supply 21 is illustrated instead of the drive driver, and the operation of the electrostatic latent image recording mechanism 10 will be described. A DC power source 22 is connected to the bus wiring 7 to apply a voltage to the upper electrode 6.

  The two side wall portions 2ab of the concave portion 2a of the glass substrate 2 are inclined surfaces whose surfaces are inclined so that the degree of opening becomes smaller as the surface approaches the bottom portion 2aa. On this inclined surface, two floating electrodes 24 are respectively installed through the insulating layer 4 in a range where electron emission points exist along the longitudinal direction of the recess 2a. Accordingly, the two floating electrodes 24 are inclined with respect to the surface of the bottom 2aa of the recess 2a so as to move away from each other toward the upper electrode 6 side from the bottom 2aa side of the recess 2a.

  In order to operate such an ion flow type electrostatic drawing apparatus 1, a voltage may be applied between the lower electrode 3 and the upper electrode 6 so that the upper electrode 6 becomes a positive electrode. For example, if a potential difference is formed by applying a voltage of +15 V to the lower electrode 3 and +15 V to the upper electrode 6 and then reducing the voltage of the lower electrode 3 to 0 V, electrons can travel from the lower electrode 3 to the upper electrode 6. At this time, each through-hole 8 of the insulating layer 4 becomes each electron emission point, and the emitted electron goes to the upper electrode 6 side.

  A voltage waveform applied to the lower electrode 3 is, for example, 10 kHz to 100 kHz, and is a rectangular wave having a pulse duty that indicates a ratio of ON time during which electrons are emitted from the upper electrode 6 to 50% or less. The reason why the pulse-like rectangular wave is used is to prevent an abnormal discharge between the electron-emitting device 11 and the photosensitive member 25 due to the electron emission from the electron-emitting device 11. For this reason, the rectangular wave is preferably as high frequency as possible. However, due to the impedance of the electron-emitting device 11, the waveform becomes deformed (rounded) as the frequency becomes high, and it becomes difficult to apply a precise voltage. The upper frequency limit of 100 kHz is a practical control range confirmed by experiments. The lower frequency limit of 10 kHz is determined as follows.

  Although the effect of suppressing abnormal discharge appears even at a frequency of 10 kHz or less, the time for drawing an electrostatic latent image is limited in the image forming process, and a low-frequency rectangular wave cannot be used. That is, when a dot-like electrostatic latent image is drawn by the electron-emitting device 11, the time that the electrostatic latent image recording mechanism 10 can draw the latent image is the image forming process of the recording apparatus that obtains an image using the electrostatic latent image. (In general, the photosensitive member 25 is movable, and a latent image must be drawn in accordance with the moving speed) and the resolution of the latent image. For example, if the process speed for drawing a latent image is 145 mm / sec and the resolution of the latent image is 600 dpi, the time allowed to draw a one-dot latent image is 290 μsec, which is 3.4 kHz in terms of frequency. Become. This frequency will be referred to as the pixel frequency. When the driving frequency of the ion flow type electrostatic drawing apparatus 1 is lower than the pixel frequency, the same voltage application conditions as when the ion flow type electrostatic drawing apparatus 1 is driven with a DC voltage when the latent images are drawn continuously. End up. In this case, since the meaning of the rectangular wave for suppressing the abnormal discharge is lost, the driving frequency of the ion flow type electrostatic drawing apparatus 1 must be a value sufficiently higher than the pixel frequency. Thus, the lower limit value of the drive frequency is a value limited by the process speed and resolution, and is set to 10 kHz as a sufficient condition when the above conditions are assumed.

The pulse power supply 21 operates by constant voltage control in which the peak value is 16V _0-p . At this time, the DC power source 22 applies the same DC voltage as the peak value of the pulse power source 21. From the voltage-current characteristics of the ion flow type electrostatic drawing apparatus 1, it is necessary to raise and lower the peak value of the pulse power supply 21 due to environmental fluctuations, deterioration with time, etc., but the output value of the DC power supply 22 is always Link with high price.

  By driving the ion flow type electrostatic drawing apparatus 1 under such conditions, electrons from the lower electrode 3 toward the upper electrode 6 are emitted, and ions are formed in the air by the emitted electrons. The photoconductor 25 is installed at a position facing the upper electrode 6 of the electron emitter 11 so that the ions can land. Ions generated by the ion flow type electrostatic drawing apparatus 1 land on the surface of the photoreceptor 25, and as a result, an electrostatic latent image is formed.

  The photoconductor 25 includes a metal electrode 25a on the back surface to form an electrostatic field (collection electric field) for collecting ions, and a DC power source 23 is connected to the metal electrode 25a. The DC power source 23 causes the metal electrode 25a to generate a positive voltage that is larger than the output value of the DC power source 22, for example, a voltage of + 600V. In this way, when a voltage is applied to the photoconductor 25 by the DC power source 23, a gap between the photoconductor 25 and the ion flow type electrostatic drawing apparatus 1 is obtained from the photoconductor 25 for collecting negative ions. An electrostatic field (recovery field) toward the electron-emitting device 11 is formed.

  In an ion generation mechanism using a general discharge, since the atmospheric ionization region = strong electric field region, the generated ions have a large initial velocity immediately after the generation. However, since the electrons emitted by the electron-emitting device 11 repeatedly collide with oxygen molecules in the atmosphere, and oxygen ions are thereby generated, the initial velocity of oxygen ions at the time of generation is considered to be almost zero. . Therefore, the ions are caused to fly toward the photoconductor 25 by the recovery electric field as described above.

  Since ions generated by electrons as described above have the same polarity (negative polarity), they repel each other and have a property of diffusing. Since the initial velocity of ions at the time of generation is considered to be almost zero, the traveling time of ions by the electron-emitting device 11 becomes longer than that in the case of using a general discharge. Further, since the electron-emitting device 11 is provided in the recess 2a, the travel distance is increased by the level difference of the recess 2a. Therefore, the ion flow from the electron emitter 11 toward the photoconductor 25 is easily diffused. When the ion flow is diffused, the landing area of ions on the photoconductor 25 becomes larger than the electron emission area of the electron-emitting device 11, and the electrostatic latent image on the photoconductor 25 becomes a blurred image. End up. Therefore, in the present invention, the floating electrode 24 is provided to suppress ion diffusion. More specifically, the recovery electric field is distorted by providing the floating electrode 24 inclined with respect to the surface of the bottom 2aa of the recess 2a so as to sandwich the electron-emitting device 11 disposed in the recess 2a. Ion diffusion is suppressed, and a high-resolution latent image can be formed. The cause of distorting the recovery electric field is a physical phenomenon in which the electric field is generated only in the vertical direction from the conductor surface, as will be described below.

  The operation of the floating electrode 24 will be described with reference to FIG. FIG. 4A shows electric lines of force corresponding to the recovery electric field when the two floating electrodes 24 are respectively installed at an inclination of 45 ° with respect to the surface of the bottom 2aa of the recess 2a. In the case where the floating electrode 24 is not provided, the electric lines of force extend straight from the surface of the paper toward the electron-emitting device 11 from the photosensitive member 25. However, by providing the floating electrode 24, the electric lines of force are They are bent away from each other in the width direction of the recess 2a. This is because the floating electrode 24, which is a conductor, is placed in an electrostatic field from the photoconductor 25 to the electron-emitting device 11, so that negative induced charges are formed on the surface of the floating electrode 24 on the photoconductor 25 side. This is because. The cause of the induction charge is that when a conductor is placed in an electrostatic field, free electrons in the conductor move so as to cancel the electric field inside the conductor. When negative ions are generated in a state where the electric lines of force are bent as shown in FIG. 4A, that is, in a state where the recovery electric field is distorted, the negative ions proceed in the opposite direction along the electric lines of force. In the width direction of the recess 2a, the process advances toward each other, and as a result, ion diffusion is suppressed.

  On the other hand, FIG. 4B shows a recovery electric field when the floating electrode 24 is installed at an inclination of 0 ° with respect to the surface of the bottom 2aa of the recess 2a, that is, in parallel with the bottom 2aa. The corresponding electric field lines are shown. When installed in this way, the direction of the electric lines of force does not change at all, so the effect of suppressing ion diffusion is not exhibited. FIG. 4C shows the electric field corresponding to the recovery electric field when the floating electrode 24 is installed at an inclination of 90 ° with respect to the surface of the bottom 2aa of the recess 2a, that is, perpendicular to the bottom 2aa. The field lines are shown. When installed in this manner, negative charge is generated at the upper end of the floating electrode 24, and the lower end of the floating electrode 24 becomes positive. As a result, the negative ions generated by the electron-emitting device 11 are attracted to the lower end of the floating electrode 24, so that the ions are more diffused.

  The floating electrodes 24 are preferably installed in different directions and with an inclination of 45 ° with respect to the surface of the bottom 2aa of the recess 2a. Table 1 below shows the installation angle of the floating electrode 24 confirmed in the experiment and the ion diffusion suppression effect corresponding to the installation angle. The latent image to be evaluated was an isolated dot of 600 dpi 1 by 1 (an image formed by 40 μm dots at intervals of 40 μm). In Table 1, ◎ indicates that an isolated dot of 600 dpi was clearly produced, ○ indicates that the image diffusion of the isolated dot is within 20%, and Δ indicates the image diffusion of the isolated dot. Indicates that it is within 50%. Further, x indicates that the image is blurred to the extent that it is difficult to recognize an isolated dot of 600 dpi.

  As shown in Table 1, the installation angle of the floating electrode 24 can be set within a range of 15 ° to 75 °. Since the through hole 8 of the insulating layer 4 serving as an electron emission point is formed at the same height along the longitudinal direction of the recess 2a at the center in the width direction of the recess 2a, both the installation angles of the floating electrodes 24 are 45 °. It is preferable to make it. As shown in Table 1, when the installation angles are both 45 °, the ion diffusion suppressing effect is most apparent.

  Next, the detail of each member which comprises the ion flow type electrostatic drawing apparatus 1 is demonstrated. The minute recess 2a formed in the glass substrate 2 has a width of the bottom 2aa of, for example, 300 μm and an opening width of, for example, 500 μm so that the degree of opening increases as the distance from the bottom 2aa increases. Moreover, the height of the recessed part 2a is 100 micrometers, for example. The recess 2a can be formed by a general wet etching method using photolithography or a dicing process using a dicer.

  FIG. 5 shows an enlarged portion 9 of FIG. As shown in FIG. 3 and FIG. 5, the plurality of lower electrodes 3, with 400 lines as a group, extend from the position in the recess 2 a facing each electron emission point formed in a dot shape to the outside of the recess 2 a. And is connected to each drive driver 21A which is an IC (Integrated Circuit) chip mounted on the left and right of the recess 2a in the glass substrate 2. In FIG. 1, for convenience of explanation, the pulse power source 21 is shown instead of the drive driver 21 </ b> A, but the actual configuration of the electron-emitting device 11 is the configuration of FIG. 3 in which each drive driver 21 </ b> A is mounted on the glass substrate 2. It becomes.

  As will be described later, since the electron-emitting device 11 generates an electric current in the fine particle layer 5 and emits electrons, the lower electrode 3 is preferably composed of a metal having a small resistance, and is particularly a few hundred nm or more. It is preferable to use copper having a film thickness. In order to suppress the movement of copper atoms when driving the electron-emitting device 11, it is preferable to stack a thin film of a refractory metal such as chromium or molybdenum. More specifically, a laminated film formed by sandwiching copper having a thickness of several hundreds nm or more with a thin film of titanium, chromium, and molybdenum is preferable. For example, a metal thin film in which titanium is formed to a thickness of 200 nm on the surface of the glass substrate 2, copper is formed to a thickness of 1000 nm, and titanium is again formed to a thickness of 50 nm is useful. Also useful is a metal thin film in which a chromium film of 150 nm is formed on the surface of the glass substrate 2, a copper film of 300 nm is formed thereon, and a chromium film of 50 nm is formed thereon again.

  The insulating layer 4 formed on the lower electrode 3 has a through hole 8 serving as an electron emission point. As described above, the lower electrodes 3 are respectively formed below the through holes 8 of the insulating layer 4. The insulating layer 4 is formed to extend from a position in the recess 2a to the outside of the recess 2a.

  The size of the through-hole 8 serving as an electron emission point is a parameter that determines the resolution of the electrostatic latent image. Considering ion diffusion after irradiation, the aperture diameter is preferably 30 μm in order to obtain a resolution of 600 dpi.

  The insulating layer 4 is preferably formed from an acrylic resin in view of electrical insulation performance, heat resistance, surface hardness, and ease of arbitrary pattern formation processing. The acrylic resin is, for example, a photosensitive acrylic resin. The base polymer of the photosensitive acrylic resin is a polymer of methacrylic acid and glycidyl methacrylate, and includes a naphthoxydiazide positive photosensitive agent as the photosensitive agent. The thickness of the insulating layer 4 formed from acrylic resin is about 1 μm. The film thickness of the insulating layer 4 is set to about twice the film thickness of the fine particle layer 5 in consideration of the ease of forming the fine particle layer 5. For example, when the thickness of the insulating layer 4 made of acrylic resin is larger than 1 μm, a problem occurs when trying to form the fine particle layer 5 having a thickness of about 500 μm by the spin coating method. In addition, when the film thickness of the insulating layer 4 formed from the acrylic resin is smaller than 1 μm, the insulating property of the insulating layer 4 is deteriorated, which causes a problem in the electric withstand voltage of the electron-emitting device 11.

The fine particle layer 5 is filled in the through hole 8 of the insulating layer 4 and is laminated on the insulating layer 4 on the bottom 2aa of the recess 2a. The fine particle layer 5 includes insulating fine particles and conductive fine particles, both of which are nano-sized fine particles. The insulating fine particles are, for example, silica fine particles formed from silicon dioxide (abbreviated as “silica”, hereinafter referred to as “SiO ₂ ”). However, the material of the insulating fine particles is not limited to this, and may be any material having an insulating property and an appropriate surface level functioning as an electron trap. In addition to SiO ₂ , aluminum oxide (hereinafter “ A material selected from “Al ₂ O ₃ ” and titanium dioxide (hereinafter referred to as “TiO ₂ ”) may be a main component. If the material has high insulating properties such as SiO ₂ , Al ₂ O ₃ , and TiO ₂ , it is easy to adjust the resistance value of the fine particle layer 5 to a desired value. In addition, by using these oxides, it is possible to realize the electron-emitting device 11 that is less likely to be oxidized, and to prevent the ion flow type electrostatic drawing apparatus 1 from being deteriorated.

  It is considered that the electron trap by the insulating fine particles becomes an energy barrier and becomes a seed of field electron emission. Therefore, an amorphous structure is dominant as a material for the insulating fine particles. Therefore, it is preferable to use amorphous insulating fine particles such as fumed silica C413 manufactured by Cabot Corporation.

  The average particle diameter of the insulating fine particles is, for example, 50 nm. Here, the average particle diameter is an arithmetic average value of equivalent circle diameters of a predetermined number of particles taken with an electron microscope. The insulating fine particles preferably have an average particle diameter of 10 nm to 1000 nm, and more preferably 10 nm to 200 nm. Insulating fine particles may have a broad dispersion relative to the average particle size. For example, fine particles having an average particle size of 50 nm may have a problem even if the particle size is widely distributed in the range of 20 nm to 100 nm. Even in such a dispersed state, it is only necessary that the particle diameter of the insulating fine particles satisfies the above-described range of the average particle diameter.

  When the average particle size is smaller than 10 nm, the force acting between the particles is strong, so that the particles are likely to aggregate and dispersion in the fine particle layer 5 becomes difficult. If the average particle diameter is larger than 1000 nm, the dispersibility is good, but the voids of the fine particle layer 5 formed in the thin film become large, and it becomes difficult to adjust the resistance of the fine particle layer 5. Therefore, the average particle diameter is preferably the above-described average particle diameter.

  The unevenness of the surface of the fine particle layer 5 causes nonuniformity in the electric field strength formed in the fine particle layer 5. In particular, since the concave portion on the surface of the fine particle layer 5 forms a portion of a local strong electric field, the conductive path tends to concentrate. When this state is remarkable, the electron emission points are concentrated in the concave portion, and the electron emission cannot be maintained in a planar shape. Therefore, in order to alleviate this phenomenon, the average particle size of the insulating fine particles is preferably smaller than 200 nm.

  The conductive fine particles are made of, for example, silver. However, the conductive fine particles are preferably formed using a noble metal in order to prevent the electron-emitting device 11 from being oxidized and deteriorated in the atmosphere. For example, the conductive fine particles are preferably formed from a metal material containing gold, platinum, palladium, or nickel as a main component in addition to silver. Conductive fine particles can be formed using a known fine particle production technique such as sputtering or spray heating, and commercially available metal fine particle powders such as silver nanoparticles produced and sold by Applied Nano Laboratory can be used. .

  The average particle diameter of the conductive fine particles is, for example, 10 nm. As the conductive fine particles, those having an average particle size smaller than the average particle size of the insulating fine particles are used in order to control the conductivity of the fine particle layer 5. Therefore, the average particle diameter of the conductive fine particles is preferably 3 nm to 20 nm. By making the average particle size of the conductive fine particles smaller than the average particle size of the insulating fine particles, a conductive path is not formed by the conductive fine particles in the fine particle layer 5, and dielectric breakdown occurs in the fine particle layer 5. It becomes difficult. When the average particle size is 3 nm or less, the cohesive force is too strong, so that the particle size cannot be maintained. In addition, the upper limit of the average particle diameter is set to 20 nm is a limitation from the manufacturing process of the ion flow type electrostatic drawing apparatus 1. Specifically, if the particle size of the conductive fine particles is too large, the conductive fine particles may settle during film formation due to a mass difference from the silica fine particles that are insulating fine particles, and the conductive fine particles may be maintained in a dispersed state. It becomes difficult.

  In the fine particle layer 5, insulating fine particles and conductive fine particles are fixed with a silicone resin as a binder. Since the silicone resin has a water repellent function in addition to the improvement of the mechanical strength of the fine particle layer 5, the adhesion of water molecules to the fine particle layer 5 is suppressed. For this reason, the electrical resistance of the fine particle layer 5 in the atmosphere is stabilized. Therefore, it is possible to realize the ion flow type electrostatic drawing apparatus 1 that operates stably even in the atmosphere with humidity fluctuation. As this silicone resin, for example, room temperature / humidity curing type SR2411 silicone resin manufactured by Toray Dow Corning Silicon Co., Ltd. is useful.

  The fine particle layer 5 has a film thickness of 300 nm to 500 nm. This film thickness is limited by the amount of power required for energization processing for forming a current path in the fine particle layer 5, ie, so-called forming preprocessing.

  The fine particle layer 5 that originally behaves as an insulator generates a current when a voltage is applied at a slow pressure increase rate in an atmosphere having a temperature of 25 ° C. and a relative humidity of 20 to 60%. This is a process called forming, and the electron-emitting device 11 that has completed this process can emit electrons by applying a necessary voltage. The voltage value and the current value required for forming differ depending on the film thickness of the fine particle layer 5, and a low voltage may be used when it is thin, and a high voltage needs to be applied when it is thick. As will be described later, since the electron emission mechanism is considered to be thermal field emission, in order to perform the forming process so as to perform constant electron emission, when the fine particle layer 5 is thin, electron emission by field emission is strengthened. When the fine particle layer 5 is thick, the influence of a decrease in energy barrier due to heat (heat assist) is strengthened. Therefore, when the fine particle layer 5 is thick, the role played by heat is increased, and the amount of power consumed by the entire electron-emitting device 11 is increased during forming. When the total power consumption increases, the power consumed by the glass substrate 2 increases accordingly, which causes the lower electrode 3 formed on the surface of the glass substrate 2 to be destroyed. That is, as the power consumption increases, Joule heat is generated in the refractory metal film (the electric resistance is large in the metal) that is a component of the lower electrode 3, and the current path of the glass substrate 2 and the lower electrode 3. The part that hits will be warmed intensively. As a result, the difference between the thermal expansion coefficient of the glass substrate 2 and the thermal expansion coefficient of the lower electrode 3 is triggered, and the lower electrode 3 is damaged. In order to prevent this phenomenon, when the fine particle layer 5 is thick, it is necessary to control so that the voltage is not increased so much, but in this case, the voltage required for electron emission cannot be applied. The upper limit value of the film thickness 500 nm of the fine particle layer 5 is a value confirmed by forming characteristic evaluation for each film thickness. If the film thickness of the fine particle layer 5 is 500 nm or less, the above phenomenon does not occur and electron emission is not caused. The required voltage can be applied.

  The lower limit value of the film thickness of 300 nm is the lower limit value by the current spin coating method. It is considered that further improvement in performance can be expected by making the fine particle layer 5 thinner.

  On the fine particle layer 5, an upper electrode 6 is laminated. The lower electrode 3 is an electrode patterned according to the electron emission point, whereas the upper electrode 6 is a solid film common to each lower electrode 3 and each electron emission point. The upper electrode 6 is provided so as to face all the electron emission points along the longitudinal direction of the recess 2a, and has a width of, for example, 100 μm to 280 μm. The upper electrode 6 may be a material having a function as an electrode and a function of suppressing oxidation in the atmosphere. For example, a metal film made of gold and palladium is preferable.

  The film thickness of the upper electrode 6 is an important parameter as a condition for efficiently emitting electrons from each electron emission point to the outside, and is preferably in the range of 15 nm to 100 nm. If the thickness of the upper electrode 6 is smaller than 15 nm, the conductivity cannot be maintained. Presumably, the irregularities on the surface of the fine particle layer 5 far exceed 15 nm. Moreover, when the film thickness of the upper electrode 6 exceeds 100 nm, the amount of electron emission is extremely reduced. The decrease in the amount of electron emission is considered to be due to the electron emission efficiency being reduced by the upper electrode 6 absorbing or reflecting electrons.

  The bus wiring 7 is formed on the upper electrode 6 and is provided over the entire upper electrode 6 in the longitudinal direction of the recess 2a. The width of the bus wiring 7 is smaller than the width of the upper electrode 6 and is, for example, 10 μm to 50 μm. The film thickness of the bus wiring 7 is, for example, 500 nm to 1000 nm. The reason why the bus wiring 7 is provided is that when the uppermost electrode 6 is the uppermost electrode of the electron-emitting device 11, a uniform voltage cannot be applied due to a potential drop generated in the upper electrode 6. That is, although the upper electrode 6 that needs to be formed of a thin film of 100 nm or less is made of a conductive material, the resistance value becomes high, so that a potential drop occurs in proportion to the increase in the amount of current. End up. In addition, since the electron emission element 11 has a structure in which the respective electron emission points are aligned long in one direction, a potential drop is likely to occur in the longitudinal direction of the electron emission element 11. Therefore, a sufficient voltage is not applied at a portion far from the electricity supply point to the upper electrode 6, resulting in a decrease (variation) in the amount of electron emission. In order to prevent this, bus wiring 7 is provided.

  The bus wiring 7 is a metal layer provided so as to overlap the upper electrode 6 at a position other than on the electron emission point over the longitudinal direction of the electron emission element 11. Since the bus wiring 7 has a sufficient film thickness that electrical resistance does not become a problem, it is possible to apply a uniform voltage without biasing the potential distribution in the surface direction of the upper electrode 6. As a result, electrons can be uniformly emitted at each electron emission point of the electron-emitting device 11, and as a result, the photosensitive member 25 can be irradiated with ions uniformly.

  The floating electrode 24 is a metal rectangular flat plate that is installed on each of the two side wall portions 2ab of the concave portion 2a via the insulating layer 4. The floating electrode 24 is provided in a range where electron emission points exist along the longitudinal direction of the recess 2a, has a width of, for example, 100 μm to 120 μm, and a film thickness of, for example, 500 nm to 1000 nm. The material of the floating electrode 24 is preferably a noble metal such as gold from the viewpoint of suppressing oxidation of the electrode. The floating electrode 24 can be processed and formed by general photolithography.

  In the electron-emitting device 11 configured as described above, when a voltage is applied between the lower electrode 3 and the upper electrode 6 so that the upper electrode 6 has a positive potential, electrons supplied from the lower electrode 3 are When moving to the upper electrode 6 through the fine particle layer 5, some energy is given to the electrons, and the electrons are emitted from the upper electrode 6 to the external space.

  There are many unclear points about the physical phenomenon that leads to electron emission at the present time, and there is no estimation, but the Joule heat caused by the current flowing through the fine particle layer 5 and the local strong electric field region formed in the fine particle layer 5 Is expected to be involved.

Generally, thermal electron emission, photoelectron emission, field electron emission, secondary electron emission, and the like are known as physical mechanisms by which electrons are emitted from the inside to the outside of the solid. Thermionic emission is performed by applying energy (work function) corresponding to the energy barrier between the Fermi level (level filled with electrons at zero K) and the vacuum level by heat. It is a phenomenon that is released. In addition, field electron emission (cold field electron emission) is achieved by setting the electric field strength formed between the metal surface and the vacuum to about 1 × 10 ⁹ V / m and making the energy barrier very thin, even at about room temperature. This is a phenomenon in which electrons are emitted into vacuum by the tunnel effect. This phenomenon in which thermionic emission and field electron emission are mixed is called thermal field emission, and is considered to be the most appropriate mechanism as the electron emission mechanism of the electron emitter 11. That is, it is considered that electron emission is caused by a combination of a decrease in the apparent work function due to Joule heat, a decrease in the energy barrier due to a strong electric field, and a tunnel phenomenon.

  A method for manufacturing the ion flow type electrostatic drawing apparatus 1 as described above will be described. First, a glass substrate 2 is prepared, and a tapered groove (concave portion 2a) is formed on the surface of the glass substrate 2 by dicing. The width of the bottom 2aa of the recess 2a is, for example, 300 μm, the opening width is, for example, 500 μm, and the height of the recess 2a is, for example, 100 μm. On the surface of the bottom 2aa of the recess 2a, a circular electrode island of φ34 μm is formed at 5000 positions along the longitudinal direction of the recess 2a at the center in the width direction of the recess 2a with a distance between the centers of the circles of 42 μm. Then, taking 400 electrode islands as a group, electrode lines are drawn to the left and right of the recess 2a from each circular electrode island to the outside of the recess 2a through the surface of the side wall 2ab of the recess 2a. The circular electrode island and the electrode line become the lower electrode 3. The electrode line patterning process is performed using a general photolithography process and a sputtering process. The configuration of the electrode line is a laminated structure of a chromium layer 150 nm, a copper layer 300 nm, and a chromium layer 50 nm in order from the glass substrate 2 side.

  Next, the insulating layer 4 having a through hole 8 having a diameter of 30 μm is laminated. At this time, the lamination is performed so that the center line of the circular electrode island and the center line of the through hole 8 coincide. The insulating layer 4 is formed from the inside of the recess 2a to the outside of the recess 2a so as to cover a part of the electrode line drawn out from the recess 2a on the surface of the glass substrate 2. The insulating layer 4 is formed, for example, by applying a solution containing a photosensitive acrylic resin material on the glass substrate 2 by spin coating, followed by pre-baking, pattern exposure of the through-holes 8, alkali development, and pure water cleaning. .

  Specifically, first, a solution containing a photosensitive acrylic resin is applied onto the glass substrate 2 by a spin coat application method so that the film thickness becomes 1 μm after curing. The base polymer of the photosensitive acrylic resin is a polymer of methacrylic acid and glycidyl methacrylate. The glass substrate 2 coated with this polymer is pre-baked, dried with a solvent of a photosensitive acrylic resin, for example, a solvent such as ethyl lactate, and thermally cured again. On the glass substrate 2 to which the acrylic resin is applied, a metal mask pattern for forming the through hole 8 is overlapped and exposed. The acrylic resin exposed with the metal mask pattern superimposed is developed with an alkaline solution after exposure. The exposed portion of the acrylic resin is etched by the alkaline solution, and the through hole 8 is obtained at a desired position. Further, the acrylic resin in which the through holes 8 are formed is heated by a hot plate after the developer remaining on the surface is washed with pure water, and is cured by a crosslinking reaction.

  After the formation of the insulating layer 4, the floating electrode 24 is formed. The floating electrode 24 is processed and formed by general photolithography. The floating electrode 24 is disposed on each of the two side wall portions 2ab of the recess 2a via the insulating layer 4. The floating electrode 24 is provided over a range where the through hole 8 exists along the longitudinal direction of the recess 2a, has a width of, for example, 100 μm, and a film thickness of, for example, 500 nm.

  Next, the fine particle layer 5 is formed. For this purpose, a fine particle dispersion that is a material of the fine particle layer 5 is prepared. The fine particle dispersion is obtained by sequentially adding insulating fine particles and conductive fine particles to a solvent and dispersing them by an ultrasonic disperser. As the dispersion solvent, toluene, benzene, xylene, n-hexane or the like can be used. The dispersion method is not limited to the ultrasonic disperser, but may be dispersed by other methods. Further, a silicone resin is added as a binder for each fine particle. Details and mixing amounts of each material include, for example, 1.5 g of n-hexane as a solvent, 0.05 g of fumed silica C413 having an average particle size of 50 nm manufactured by Cabot, and conductive fine particles. 0.012 g of silver nanoparticles having an alcoholate insulation coating manufactured by Nano Laboratory and having an average particle diameter of 10 nm are 0.44 g of silicone resin and room temperature / moisture-curing SR2411 silicone resin manufactured by Toray Dow Corning. .

  The fine particle dispersion thus prepared has a thickness of, for example, a spin coat method or an inkjet method in the recess 2a of the glass substrate 2 on which the lower electrode 3, the insulating layer 4, and the floating electrode 24 are formed. It is applied so as to be 300 nm to 400 nm. After the fine particle dispersion is applied, the coated material together with the glass substrate 2 is heated at 150 ° C. for 1 minute to evaporate the solvent, thereby forming a layered body containing the fine particles and the silicone resin in the recess 2a. After evaporation of the solvent, the layered body formed on the glass substrate 2 other than on the bottom 2aa of the recess 2a is scraped off using a waste cloth or a scraper. In particular, the use of a scraper is useful for removing the layered body adhering to the surface of the floating electrode 24 on the side wall 2ab of the recess 2a. Then, the layered body together with the glass substrate 2 is heated at 150 ° C. for 1 hour, and further irradiated with vacuum ultraviolet light for 3 minutes to cure the silicone resin as the binder, thereby forming the fine particle layer 5.

  An upper electrode 6 is formed on the fine particle layer 5. The upper electrode 6 is formed so as to face all the circular electrode islands of the lower electrode 3. As the upper electrode 6, for example, a mixed film of gold and platinum is formed to a thickness of 50 nm by using a sputtering method.

  Finally, the bus wiring 7 is formed on the upper electrode 6. The layer thickness of the bus wiring 7 is, for example, 200 nm, and is produced using a vapor deposition method. As described above, the ion flow type electrostatic drawing apparatus 1 is manufactured.

  The bus wiring 7 of the manufactured ion flow type electrostatic drawing apparatus 1 is connected to an electrical contact provided outside the recess 2a. The lower electrode 3 is connected to an output terminal of a drive driver 21A mounted on the surface of the glass substrate 2. The drive driver 21A is, for example, a liquid crystal source driver manufactured by Sharp Corporation. Then, the φ30 mm aluminum drum having the photoconductor 25 is placed on the surface of the glass substrate 2 so that the concave portion 2a of the glass substrate 2 of the ion flow type electrostatic drawing apparatus 1 and the surface of the photoconductor 25 face each other. Set up 0.5mm apart. A voltage of 600 V is applied to the aluminum drum for ion recovery. As described above, the electrostatic latent image recording mechanism 10 including the ion flow type electrostatic drawing apparatus 1 is completed.

  In the electrostatic latent image recording mechanism 10 manufactured as described above, the electron-emitting device 11 is provided in the concave portion 2a formed on the glass substrate 2, so that the electron-emitting device 11 is mechanically damaged by the contact. Can be prevented. Furthermore, since the electric field for causing the ions generated by the electrons emitted from the electron-emitting device 11 to fly toward the photosensitive member 25 is distorted by the floating electrode, the diffusion of ions is suppressed. Therefore, mechanical damage of the electron-emitting device 11 due to contact can be prevented, and ion diffusion can be suppressed, and a high-resolution electrostatic latent image can be drawn.

  Further, in the electrostatic latent image recording mechanism 10, the bus wiring 7 having a narrower width than the upper electrode 6 is formed on the upper electrode 6, so that the potential distribution is uniform in the surface direction of the upper electrode 6. Voltage application is possible. As a result, electrons can be uniformly emitted at each electron emission point of the electron-emitting device 11, and as a result, the photosensitive member 25 can be irradiated with ions uniformly.

DESCRIPTION OF SYMBOLS 1 Ion flow type electrostatic drawing apparatus 2 Glass substrate 2a Recess 3 Lower electrode 4 Insulating layer 5 Fine particle layer 6 Upper electrode 7 Bus wiring 8 Through-hole 10 Electrostatic latent image recording mechanism 11 Electron emitting element 24 Floating electrode

Claims (3)

A substrate on which a recess opening toward the electrostatic latent image carrier is formed;
A plurality of first electrodes arranged side by side, a second electrode provided opposite to the first electrode, and the first electrode, the electron-emitting devices installed on the bottom surface of the recess An insulating layer provided between the second electrode and having an opening corresponding to the first electrode on a one-to-one basis, and a fine particle including an insulating fine particle and a conductive fine particle and filling the opening An electron-emitting device that emits electrons in a direction from the bottom toward the electrostatic latent image carrier when a voltage is applied between the first electrode and the second electrode.
A floating electrode provided on each of the two side walls of the recess, the floating electrodes provided to be inclined with respect to the surface of the bottom so as to move away from each other toward the charged body side from the bottom side; An ion flow type electrostatic drawing apparatus comprising:   2. The ion flow type electrostatic drawing apparatus according to claim 1, wherein an inclination angle of the floating electrode with respect to a surface of the bottom portion is selected within a range of 15 ° to 75 °.   The ion flow type electrostatic drawing apparatus according to claim 1, further comprising a third electrode stacked on the second electrode and formed to be narrower than the second electrode.

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