CN1694812A - Electrostatic attraction fluid ejection device - Google Patents

Abstract

An electrostatic suction type fluid jetting device, comprising a nozzle (4) formed in a shape corresponding to a meniscus equal to a tailor cone-shaped tip part formed in a conventional electrostatic suction process of ink (2) as a fluid, wherein the diameter of the ink discharge hole (4b) of the nozzle (4) is set to a diameter generally equal to the diameter of the tip part of the meniscus (14) immediately before the jetting of the ink and equal to or lower than the diameter of the droplet of the ink (2) immediately after the jetting, whereby both an increase in resolution and safety can be assured and a highly versatile recording device can be commercialized.

Description

Electrostatic attraction fluid ejection device

technical field

The present invention relates to an electrostatic attraction type fluid ejection device that discharges the fluid toward a target object by charging a fluid such as ink and electrostatically attracting it.

Background technique

In general, there are various types of fluid ejection methods for discharging fluid such as ink onto a target object (recording medium). Here, an ink ejection method using ink as a fluid will be described.

As the on-demand (Japanese: Ondemand) inkjet method, the piezoelectric method using the piezoelectric phenomenon, the thermal method using the ink film boiling phenomenon, and the electrostatic attraction method using the electrostatic phenomenon have been developed. Especially in recent years, High-resolution inkjet methods are urgently needed. In order to realize high-resolution inkjet recording, miniaturization of discharged ink droplets is indispensable.

Here, the motion of ink droplets discharged from the nozzles until they are ejected onto the recording medium can be expressed by the motion equation (1).

ρink·(4/3·π·d ³ )·dv/dt＝-Cd·(1/2·ρair·v ² )·(π·d ^2/4 ) …(1)

Above-mentioned ρink is the volume density of ink, V is droplet volume, v is droplet velocity, Cd is drag coefficient, ρair is air density, d is ink droplet radius, Cd is represented by formula (2).

Cd＝24/Re·(1+3/16·Re ^0.62 ) …(2)

Above-mentioned Re is Reynolds number, and η is the viscosity of air, and then Re can be represented by formula (3).

Re = 2 · D · kink · V/η ... (3)

The influence of the droplet radius on the kinetic energy of the ink droplet on the left side of the above formula (1) is greater than the influence of the droplet radius on the air viscous resistance. Therefore, in the case of the same speed, the smaller the droplet, the faster the droplet velocity decelerates, or it cannot reach the recording medium at a predetermined distance, and even if it does, the accuracy of the ejection landing point is poor.

In order to prevent such a situation, it is necessary to increase the discharge initial velocity of liquid droplets, that is, to increase the discharge energy per unit volume.

However, conventional piezoelectric and thermal inkjet heads have the following problems when the discharged liquid droplets are miniaturized, that is, the discharge energy per unit volume of the discharged liquid droplets is increased. In particular, it is difficult to make the amount of discharged liquid droplets 1P1 or less, that is, it is difficult to make the diameter of the droplet (hereinafter referred to as the droplet diameter) φ10 μm or less.

The existing problems are:

Problem (A): The discharge energy of the piezoelectric inkjet head is related to the displacement and pressure of the driven piezoelectric element. The displacement amount of the piezoelectric element is closely related to the ink discharge amount, that is, the ink droplet size. To reduce the droplet size, the displacement amount needs to be reduced, and it is difficult to increase the discharge energy per unit volume of the discharged liquid droplet.

Problem (B): The thermal inkjet head uses the film boiling phenomenon of ink, so the pressure when forming bubbles is physically limited, and the discharge energy is roughly determined by the area of the heating element. The area of the heating element is approximately proportional to the volume of the generated air bubbles, that is, the amount of ink discharged. Therefore, if the size of the ink droplet is reduced, the volume of the generated air bubbles decreases and the discharge energy decreases, so it is difficult to increase the discharge energy per unit volume of the ink discharge droplet.

Problem (C): Since the driving amount of the driving (heating) element of the piezoelectric method and the thermal method is closely related to the discharge amount, it is extremely difficult to suppress the deviation especially when discharging micro-sized liquid droplets.

Therefore, as means to solve the various problems described above, a method of discharging fine liquid droplets by electrostatic attraction is being developed.

In the electrostatic attraction method, the equation of motion of the ink droplets discharged from the nozzles is represented by the following equation (4).

ρink·(4/3·π·d ³ )·dv/dt＝q·E-Cd·(1/2·ρair·v ² )·(π·d ^2/4 ) …(4)

where q is the charge amount of the droplet and E is the surrounding electric field strength.

It can be seen from the above formula (4) that in the electrostatic attraction method, in addition to the discharge energy, the discharged liquid droplets are also subjected to electrostatic force during flight, so the discharge energy per unit volume can be reduced, and it can be applied to the discharge of tiny liquid droplets.

As an ink ejection device of this type of electrostatic attraction method (hereinafter referred to as an electrostatic attraction type ink ejection device), for example, in Patent Document 1 (Japanese Laid-Open Patent Publication: Japanese Unexamined Patent Publication No. Hei 8-238774 (publication date: September 17, 1996) Japan)) discloses an ink jetting device in which electrodes for applying voltage are provided inside the nozzles. In addition, in Patent Document 2 (Japanese Laid-Open Patent Publication: JP-A No. 2000-127410 (publication date: May 9, 2000)), it is disclosed that the nozzle is made into a groove, and a needle electrode protruding from the nozzle is provided. An inkjet device that ejects ink including fine particles.

The ink ejecting device disclosed in the above-mentioned Patent Document 1 will be described below with reference to FIG. 17 . Fig. 17 is a schematic sectional view of an ink ejecting device.

In Fig. 17, 101 is an ink ejection chamber, 102 is ink, 103 is an ink chamber, 104 is a nozzle hole, 105 is an ink tank, 106 is an ink supply path, 107 is a rotating drum, 108 is a recording medium, and 110 is a control element. Part, 111 is a process control part.

In addition, 114 is an electrode part for applying an electrostatic field arranged on the side of the ink chamber 103 of the ink ejection chamber 101, 115 is a metal drum provided on the rotary drum 107, that is, a counter electrode part, and 116 is a counter electrode part 116 for applying an electrostatic field to the counter electrode part 115. volts of negative voltage for the bias power section. 117 is a high-voltage power supply unit that supplies a high voltage of several hundred volts to the electrode unit 114 for applying an electrostatic field, and 118 is a grounding unit.

Here, between the electrode section 114 for applying an electrostatic field and the counter electrode section 115, the bias power supply section 116 for applying a negative voltage of several thousand volts to the counter electrode section 115 and the high voltage voltage of the high voltage power supply section 117 of several hundreds of volts are superimposed, An overlapping electric field is formed, and discharge of the ink 102 from the nozzle hole 104 is controlled by the overlapping electric field.

In addition, 119 is a convex meniscus formed in the nozzle hole 104 by applying a bias voltage of several thousand volts to the counter electrode portion 115 .

The operation of the electrostatic attraction type inkjet device having the above configuration will be described below.

First, the ink 102 is transferred to the nozzle hole 104 from which the ink 102 is discharged through the ink supply channel 106 by capillary action. At this time, the counter electrode portion 115 on which the recording medium 108 is mounted is provided facing the nozzle hole 104 .

The ink 102 reaching the nozzle hole 104 forms a convex ink meniscus 119 by applying a bias voltage of several thousand volts to the counter electrode portion 115 . By applying a signal voltage from the high-voltage power supply unit 117 of several hundred volts to the electrode unit 114 for applying an electrostatic field provided in the ink chamber 103, and superimposed on the voltage from the bias power supply unit 116 applied to the counter electrode unit 115, the ink 102 A printed image is formed by superimposing the electric field to the recording medium 108 .

18( a ) to FIG. 18( c ) will describe how the meniscus varies before the droplet flies in the ink jet device disclosed in Patent Document 1 above.

Before the driving voltage is applied, as shown in FIG. 18( a ), the electrostatic force caused by the bias voltage applied to the ink is balanced with the surface tension of the ink to form a bulging meniscus 119 a on the ink surface.

When the drive voltage is applied in the above state, as shown in Figure 18(b), the meniscus 119b, the charge generated on the liquid surface begins to approach the center of the bulge of the liquid surface, thus forming the center of the bulge of the liquid surface to increase The meniscus 119b.

Thereafter, continue to apply the drive voltage, as shown in Figure 18(c), the charge generated on the liquid surface is further concentrated in the center to form a half-moon meniscus 119c called a Taylor cone, which is concentrated in the Taylor cone In the stage where the electrostatic force due to the amount of charge on the top is greater than the surface tension of the ink, the droplets are separated and discharged.

The ink ejecting device disclosed in the above-mentioned Patent Document 2 will be described below with reference to FIG. 19 . Fig. 19 is a schematic configuration diagram of an ink ejecting device.

As shown in Figure 19, inside the frame body of this ink jetting device is housed: as an ink jetting head, a bar-shaped (Japanese: ライン) recording head 211 formed of a low-electrolyte material (acrylic resin, ceramics, etc.); The opposite electrode 210 made of metal or high electrolyte that the ink discharge port of 211 is arranged relatively; The ink tank 212 that is used to store the ink that is dispersed with charged pigment particle in the non-conductive ink medium in advance; Ink circulation system (pumps 214a, 214b; tubes 215a, 215b) that circulates between the heads 211; a pulse voltage that is applied to each of the discharge electrodes 211a to attract the ink droplets that form one pixel of the recorded image Device 213; Drive circuit (not shown) that pulse voltage generating device 213 is controlled according to image data; Make recording medium A pass through the recording medium conveying mechanism (not shown) that is located at the gap between recording head 211 and opposite electrode 210 ); the overall controller (not shown) of the control device, etc.

The above ink circulation system includes: two pipes 215a, 215b connecting the recording head 211 and the ink tank 212, and two pumps 214a, 214b driven by the controller.

The ink circulation system described above is divided into an ink supply system for supplying ink to the recording head 211 and an ink recovery system for recovering ink from the recording head 211 .

In the ink supply system, the ink is sucked up from the ink tank 212 by the pump 214a, and the ink is pressure-fed to the ink supply part of the recording head 211 through the tube 215a. On the other hand, in the ink recovery system, ink is sucked from the ink recovery part of the recording head 211 by the pump 215b, and the ink is forcibly recovered to the ink tank 212 through the tube 215b.

As shown in FIG. 20 , the above-mentioned recording head 211 is provided with: an ink supply part 220a that spreads the ink sent from the pipe 215a of the ink supply system to the width of the stripe; The channel 221; the ink recovery part 220b connecting the ink flow channel 221 and the pipe 215b of the ink recovery system; the groove-shaped ink row with an appropriate width (about 0.2mm) opening the top of the ink flow channel 221 toward the opposite electrode 210 side Outlet 222; a plurality of discharge electrodes 211a arranged in the discharge port 222 at a predetermined pitch (about 0.2mm); low-electrolyte (for example, ceramic) partition walls 223 arranged on both sides and the upper surface of each discharge electrode 211a .

Each of the discharge electrodes 211a is made of metal such as copper and nickel, and a low-electrolyte film (such as a polyimide film) for preventing pigment adhesion with good wettability is formed on the surface. In addition, the tip of each discharge electrode 211 a is formed in a triangular pyramid shape, and protrudes from the ink discharge port 222 toward the counter electrode 210 with an appropriate length (70 μm to 80 μm).

When the driving circuit not shown above applies the control signal to the pulse voltage generating device 213 within the time corresponding to the grayscale data contained in the image data according to the control of the controller, the pulse voltage generating device 213 will The pulse Vp at the top of the pulse of different types is output as a high-voltage signal superimposed on the bias voltage Vb and the bias voltage Vb.

When the image data is transmitted, the controller drives the two pumps 214a, 214b of the ink circulation system. Thus, as the ink is pressure-fed from the ink supply part 220, the ink recovery part 220b becomes negative pressure, and the ink flowing in the ink flow path 221 rises in the gaps between the partition walls 223 by capillary action, and the wetted part is expanded to each part. The tip of the electrode 211a is discharged. At this time, negative pressure acts on the ink liquid surface near the tip of each discharge electrode 211a, so that an ink meniscus is formed at the tip of each discharge electrode 211a.

The recording medium conveying mechanism is controlled by the controller to convey the recording medium A in a predetermined direction, and the above-mentioned high voltage signal is applied to and from the discharge electrode 211a by controlling the drive circuit.

The fluctuation of the meniscus before the flight of the liquid droplet in the ink jet device disclosed in Patent Document 2 will be described below with reference to FIGS. 21 to 24 .

As shown in FIG. 21, when the pulse voltage from the pulse voltage generator 213 is applied to the discharge electrode 211a in the recording head 211, an electric field is generated from the discharge electrode 211a side toward the counter electrode 210 side. Here, since the discharge electrode 211a with a sharp tip is used, the strongest electric field is generated near the tip.

As shown in FIG. 22, when such an electric field is generated, each charged pigment particle 201a in the ink solvent receives a force fE (FIG. 23) from the electric field and moves toward the ink liquid surface. As a result, the pigment concentration near the ink liquid surface is concentrated.

As shown in FIG. 23, when the pigment concentration is thus concentrated, a plurality of charged pigment particles 201a near the ink liquid surface approach the opposite side of the electrode and start to aggregate. When the pigment aggregate 201 near the ink liquid surface starts to grow into a spherical shape, each charged pigment particle 201a starts to receive the electrostatic reaction force fcon from the pigment aggregate 201 respectively. That is, the resultant force ftotal of the electrostatic reaction force fcon from the pigment aggregate 201 and the force fE of the electric field E caused by the pulse voltage acts on each charged pigment particle 201a.

Therefore, in the range where the electrostatic reaction force between the charged pigment particles does not exceed the mutual cohesion force, when the electric field has a resultant force ftotal towards the pigment aggregate 201, the charged pigment particle 201a (at the front end connected to the discharge electrode 211a and the pigment aggregate) When the force fE exerted by the charged pigment particles 201a) on the straight line at the center of the body 201 is greater than the electrostatic reaction force fcon from the pigment aggregate 201 (fE≧fcon), the charged pigment particle 201a grows into the pigment aggregate 201.

The pigment aggregate 201 formed by n charged pigment particles 201a receives the electrostatic reaction force FE from the electric field E caused by the pulse voltage, and also receives the confining force Fesc from the ink solvent. When the electrostatic reaction force FE and the restraining force Fesc are balanced, the pigment aggregate 201 is stabilized in a state in which it protrudes slightly from the ink liquid surface.

When the pigment aggregates 201 grow further and the electrostatic reaction force FE is greater than the limiting force Fesc, the pigment aggregates 201 come out from the ink liquid surface 200 a as shown in FIGS. 24( a ) to 24 ( c ).

However, according to the principle of the conventional electrostatic attraction method, charges are concentrated at the center of the meniscus to generate swelling of the meniscus. The radius of curvature of the front end of the raised Taylor cone is determined by the concentration of charges. When the electrostatic force caused by the concentration of charges and electric field strength is greater than the surface tension of the meniscus at this time, the droplets begin to separate.

Since the maximum charge of the meniscus is determined by the physical properties of the ink and the radius of curvature of the meniscus, the minimum droplet size is determined by the physical properties of the ink (especially the surface tension) and the strength of the electric field formed on the meniscus .

In general, the surface tension of a liquid containing a solvent tends to be lower than that of a solvent alone. Actually, ink also contains various solvents, so it is difficult to increase the surface tension. Therefore, conventionally, a method of reducing the droplet size by considering the surface tension of the ink to be constant and increasing the electric field intensity has been employed.

Therefore, in the inkjet devices disclosed in the above-mentioned Patent Documents 1 and 2, as the discharge principle of both, a strong electric field intensity is formed in the meniscus region having an area much larger than the projected area of the discharged liquid droplet. In the area of the meniscus, charges are concentrated in the center of the meniscus, and the electrostatic force formed by the concentrated charges and the formed electric field strength is used to discharge, so it is necessary to apply a very high voltage close to 2000 volts. Therefore, drive control is difficult, and there is also a problem in terms of safety when operating the ink ejection device.

Especially when a strong electric field strength is formed in a large area, it needs to be set below the discharge destruction strength (for example, the discharge destruction strength of air between parallel plates is 3×10 ⁶ V/m), so the tiny droplet size that can be formed There are also limits in principle.

In addition, since the charge moves toward the center of the meniscus, the time of charge movement affects the discharge responsiveness, and there is a problem in improving the printing speed.

As a method of solving these problems, the method of reducing the driving voltage by applying a bias voltage lower than the discharge voltage in advance in the above-mentioned Patent Documents 1 and 2, or the method of protruding the electrode from the nozzle part as in Patent Document 2 structure to facilitate charge concentration. In addition, as in Patent Document 1, there is also a method of applying a positive voltage to the ink and swelling the meniscus in advance.

However, none of the methods disclosed in Patent Documents 1 and 2 can fundamentally solve this problem. Especially when a bias voltage is applied, the drive voltage cannot always be applied to only one of the positive and negative sides. When the recording medium is an insulating material, the surface potential caused by the adhesion of the charged discharged droplets will continue to accumulate, so the accuracy of the ejection point will decrease. , it is necessary to take countermeasures such as eliminating static electricity on the surface of the recording medium during printing.

In addition, because an electric field with strong electric field intensity is formed in a large range of meniscus region, it is necessary to arrange the opposite electrode with high precision, and at the same time, the dielectric constant and thickness of the recording medium affect the arrangement of the opposite electrode, so it is necessary to use The degree of freedom is small. Especially when the recording medium is thick, the counter electrode has to be arranged at a position away from the electrode of the nozzle portion accordingly. Therefore, a larger voltage has to be applied, and there are many cases of recording media that are difficult to use in practice.

Therefore, in the conventional electrostatic attraction type ink ejection device (electrostatic attraction type fluid ejection device), there is a problem that it is not possible to realize both high resolution and safety and high versatility into practical use.

Contents of the invention

In view of the above, it is an object of the present invention to provide an electrostatic attraction type fluid ejection device that can realize both high resolution and safety, and can be used as a versatile recording device.

As shown in FIG. 16 , in the conventional method, the inventors of the present application have used a nozzle 23 of a constricted shape on the side of the fluid discharge hole to make the meniscus of the fluid in the Taylor cone shape formed in the electrostatic attraction process. The tip curvature 24 before the droplet discharge of 22 is approximately the same size as the nozzle diameter, and it was found that the electric field that needs to be formed in a large area can be formed in a small area, and the amount of charge movement on the meniscus 22 of the fluid can be reduced.

Utilizing the above principles, the inventors of the present application further set the diameter of the fluid discharge hole at the tip of the nozzle to be equal to or less than the droplet diameter of the fluid immediately after discharge, and found that the charge concentration area can be made approximately the same as the meniscus area.

Therefore, in order to solve the above-mentioned problems, the electrostatic attraction type fluid ejection device of the present invention discharges the fluid charged by the application of voltage in the state of liquid droplets from the fluid discharge hole of the nozzle made of insulating material under electrostatic attraction, and is characterized in that The diameter of the fluid discharge hole of the nozzle is set to be equal to or less than the diameter of the fluid droplet immediately after discharge.

With the above structure, in the present invention, the diameter of the nozzle is set to be the diameter of the front end portion of the Taylor cone shape formed in order to discharge a fluid having a droplet diameter smaller than the diameter of the fluid discharge hole of the conventional nozzle. It is roughly the same, so the electric field that needs to be formed in a large area can be formed in a small area in the conventional electrostatic attraction process of fluid.

Furthermore, by setting the diameter of the fluid discharge hole of the nozzle to be equal to or less than the droplet diameter of the fluid immediately after discharge, the charge concentration region and the meniscus region of the fluid can be made approximately the same size.

Accordingly, it is possible to significantly reduce the voltage required for transferring electric charges, that is, the voltage required for imparting the amount of charge required to electrostatically attract the fluid to the fluid in the state of a droplet having a desired droplet diameter. This eliminates the need for a conventional high voltage of 2000 volts, thereby improving the safety when using the fluid ejection device.

In addition, as described above, by narrowing the electric field, a strong electric field can be formed in the narrow region, and as a result, the droplet that can be formed can be miniaturized. As a result, when liquid droplets are used as ink, it is possible to make a high-resolution printed image.

Furthermore, as described above, since the concentration area of the charge is substantially the same size as the meniscus area of the fluid, the movement time of the charge in the meniscus area does not affect the discharge responsiveness, and the droplet discharge can be improved. Speed (printing speed when the droplet is ink).

In addition, since the charge concentration region is substantially the same size as the meniscus region of the fluid, it is not necessary to form a strong electric field in a wide meniscus region. Therefore, it is not necessary to arrange the counter electrode with high precision in order to form a strong electric field in a wide meniscus region as in the past, and the dielectric constant and thickness of the recording medium do not affect the arrangement of the counter electrode.

Therefore, in the electrostatic attraction type fluid ejection device, the degree of freedom in the arrangement of the opposing electrodes increases. That is, the degree of freedom in design of the electrostatic attraction type fluid ejection device increases. As a result, it is possible to print on a recording medium that has been difficult to use without being affected by the dielectric constant and thickness, and a fluid ejection device with good versatility can be realized.

Therefore, by using the electrostatic attraction type fluid ejection device having the above structure, it is possible to realize a device that satisfies both high resolution and safety and has good versatility.

Here, as the above-mentioned fluid, in addition to simple water, oil, etc., colored liquid ink containing dye or pigment as fine particles, or ink containing a wiring material (conductive fine particles such as silver or copper) that forms a circuit board can also be used. solution etc.

For example, when ink is used as the fluid, high-definition printing is possible, and when a solution containing a wiring material for forming a circuit board is used as the fluid, an ultra-high-definition circuit can be formed with extremely narrow wiring.

In addition, the electrostatic attraction type fluid ejection device of the present invention, in order to solve the above-mentioned problems, discharges the fluid charged by the application of voltage in the state of liquid droplets from the fluid discharge hole of the nozzle made of insulating material under electrostatic attraction, and is characterized in that , The diameter of the fluid discharge hole of the nozzle is set at φ8μm or less.

With the above structure, in the present invention, the diameter of the nozzle is set to be the diameter of the front end portion of the Taylor cone shape formed in order to discharge a fluid having a droplet diameter smaller than the diameter of the fluid discharge hole of the conventional nozzle. It is roughly the same, so the electric field that needs to be formed in a large area can be formed in a small area in the conventional electrostatic attraction process of fluid.

Thereby, the voltage required for moving electric charges, that is, the voltage required for imparting a charge amount required for electrostatic attraction to the fluid can be significantly reduced. As a result, since a conventional high voltage of 2000 volts is unnecessary, the safety when using the fluid ejection device can be improved.

Moreover, the diameter of the fluid discharge hole of the nozzle is set below φ8 μm, so that the electric field intensity distribution can be concentrated near the discharge surface of the fluid discharge hole, and the distance variation from the opposite electrode to the fluid protrusion hole of the nozzle will not affect the electric field. intensity distribution.

As a result, stable fluid discharge can be performed without being affected by the positional accuracy of the counter electrode, or the material property variation and thickness variation of the recording medium.

In addition, as described above, the electric field can be made small, and a strong electric field can be formed in a small area, and as a result, the droplet that can be formed can be miniaturized. As a result, when liquid droplets are used as ink, it is possible to make a high-resolution printed image.

Furthermore, as described above, since the concentration area of the charge is substantially the same size as the meniscus area of the fluid, the movement time of the charge in the meniscus area does not affect the discharge responsiveness, and the droplet discharge can be improved. Speed (printing speed when the droplet is ink).

In addition, since the charge concentration region is substantially the same size as the meniscus region of the fluid, it is not necessary to form a strong electric field in a wide meniscus region. Therefore, it is not necessary to arrange the counter electrode with high precision in order to form a strong electric field in a wide meniscus region as in the past, and the dielectric constant and thickness of the recording medium do not affect the arrangement of the counter electrode.

Therefore, in the electrostatic attraction type fluid ejection device, the degree of freedom in the arrangement of the opposing electrodes increases. That is, the degree of freedom in design of the electrostatic attraction type fluid ejection device increases. As a result, it is possible to print on a recording medium that has been difficult to use without being affected by the dielectric constant and thickness, and a fluid ejection device with good versatility can be realized.

Therefore, by using the electrostatic attraction type fluid ejection device having the above structure, it is possible to realize a device that satisfies both high resolution and safety and has good versatility.

Here, as the above-mentioned fluid, in addition to simple water, oil, etc., colored liquid ink containing dye or pigment as fine particles, or ink containing a wiring material (conductive fine particles such as silver or copper) that forms a circuit board can also be used. solution etc.

For example, when ink is used as the fluid, high-definition printing is possible, and when a solution containing wiring materials for circuit boards is used as the fluid, ultra-high-definition circuits can be formed with extremely narrow wiring. , can make the fluid discharge stably.

In addition, the electrostatic attraction type fluid ejection device of the present invention, in order to solve the above-mentioned problems, discharges the fluid charged by the application of voltage in the state of liquid droplets from the fluid discharge hole of the nozzle made of insulating material under electrostatic attraction, and is characterized in that , having an applied voltage control unit that controls the voltage applied to the fluid in the nozzle, the diameter of the fluid discharge hole of the nozzle is set to φ8 μm or less, and the applied voltage control unit controls the voltage applied to the fluid Control is performed so that the charge amount induced in the fluid droplet immediately after being discharged from the fluid discharge hole becomes 90% or less of the charge amount corresponding to the Rayleigh limit of the droplet.

With the above structure, in the present invention, the diameter of the nozzle is set to be the diameter of the front end portion of the Taylor cone shape formed in order to discharge a fluid having a droplet diameter smaller than the diameter of the fluid discharge hole of the conventional nozzle. It is roughly the same, so the electric field that needs to be formed in a large area can be formed in a small area in the conventional electrostatic attraction process of fluid.

Thereby, the voltage required for moving electric charges, that is, the voltage required for imparting a charge amount required for electrostatic attraction to the fluid can be significantly reduced. This eliminates the need for a conventional high voltage of 2,000 volts, thereby improving safety when using the fluid ejection device.

Moreover, since the diameter of the fluid discharge hole of the nozzle is set below φ8 μm, the electric field intensity distribution can be concentrated near the discharge surface of the fluid discharge hole, and the distance variation from the opposite electrode to the fluid protrusion hole of the nozzle will not affect Electric field strength distribution.

As a result, stable fluid discharge can be performed without being affected by the positional accuracy of the counter electrode, or the material property variation and thickness variation of the recording medium.

In addition, as described above, the electric field can be made small, and a strong electric field can be formed in a small area, and as a result, the droplet that can be formed can be miniaturized. As a result, when liquid droplets are used as ink, it is possible to make a high-resolution printed image.

Furthermore, as described above, since the concentration area of the charge is substantially the same size as the meniscus area of the fluid, the movement time of the charge in the meniscus area does not affect the discharge responsiveness, and the droplet discharge can be improved. Speed (printing speed when the droplet is ink).

In addition, since the charge concentration region is substantially the same size as the meniscus region of the fluid, it is not necessary to form a strong electric field in a wide meniscus region. Therefore, it is not necessary to arrange the counter electrode with high precision in order to form a strong electric field in a wide meniscus region as in the past, and the dielectric constant and thickness of the recording medium do not affect the arrangement of the counter electrode.

Therefore, in the electrostatic attraction type fluid ejection device, the degree of freedom in the arrangement of the opposing electrodes increases. That is, the degree of freedom in design of the electrostatic attraction type fluid ejection device increases. As a result, it is possible to print on a recording medium that has been difficult to use without being affected by the dielectric constant and thickness, and a fluid ejection device with good versatility can be realized.

Therefore, by using the electrostatic attraction type fluid ejection device having the above structure, it is possible to realize a device that satisfies both high resolution and safety and has good versatility.

Here, as the above-mentioned fluid, in addition to simple water, oil, etc., colored liquid ink containing dye or pigment as fine particles, or ink containing a wiring material (conductive fine particles such as silver or copper) that forms a circuit board can also be used. solution etc.

For example, when ink is used as the fluid, high-definition printing is possible, and when a solution containing wiring materials for circuit boards is used as the fluid, ultra-high-definition circuits can be formed with extremely narrow wiring. , can make the fluid discharge stably.

Furthermore, the applied voltage control unit controls the voltage applied to the fluid so that the amount of charge induced in a droplet of the fluid immediately after being discharged from the fluid discharge hole becomes equivalent to the Rayleigh value of the droplet. 90% of the limit charge amount, thus preventing the discharge caused by the reduction of the surface area of the droplets due to the drying of the discharged droplets, and at the same time preventing the decrease of the vapor pressure caused by the electrification of the droplets.

This reduces the drying time of the discharged liquid droplets (the time until the solvent of the liquid droplets evaporates completely), and eliminates the variation in the size of the dot diameter of the ejected liquid droplets.

In addition, since the drying time of the discharged liquid droplets becomes longer, it is possible to reduce the change in the diameter of the liquid droplets before they are ejected, that is, the amount of liquid droplets. As a result, since the environmental conditions such as air resistance and ambient humidity experienced by the flying droplets are uniform for each droplet, the accuracy of the landing point of the droplet can be improved, and the deviation of the droplet at the time of landing can be suppressed.

Furthermore, since the drying time of the discharged liquid droplets is prolonged, even if the diameter of the discharged liquid droplets is as small as φ5 μm, the liquid droplets can reach without being dried.

Therefore, by using the electrostatic attraction type fluid ejection device having the above-mentioned structure, it is possible to stably eject fine liquid droplets and reach them with high precision.

In order to reduce the amount of charge induced in a fluid droplet immediately after being discharged from the fluid discharge hole to 90% or less of the charge amount corresponding to the Rayleigh limit of the droplet, the following method can be considered.

That is, the electrostatic attraction type fluid ejection device of the present invention, in order to solve the above-mentioned problems, the fluid charged by the application of voltage is discharged from the fluid discharge hole of the nozzle made of insulating material in the state of liquid droplets under electrostatic attraction, and is characterized in that , having an applied voltage control unit for controlling the voltage applied to the fluid in the nozzle, and setting the diameter of the fluid discharge hole of the nozzle to be equal to or less than the droplet diameter of the fluid immediately after discharge, the applied voltage The control unit controls the voltage applied to the fluid so that the amount of charge induced in the fluid droplet immediately after being discharged from the fluid discharge hole becomes equivalent to that of the fluid caused by the maximum electric field strength of the meniscus. The amount of charge at the Rayleigh limit at the droplet diameter immediately after discharge is less than or equal to that of Rayleigh limit.

In addition, the electrostatic attraction type fluid ejection device of the present invention, in order to solve the above-mentioned problems, the fluid charged by the application of a voltage is electrostatically attracted from the fluid discharge hole of the nozzle made of an insulating material in the state of a liquid droplet in accordance with the applied voltage. The corresponding speed is discharged to the recording medium, and it is characterized in that it has an applied voltage control part that controls the voltage applied to the fluid in the nozzle, and the diameter of the fluid discharge hole of the nozzle is set at φ8μm or less, and the The applied voltage control unit controls the voltage applied to the fluid so that an average discharge speed from when the fluid is discharged to when it reaches the recording medium is 10 m/s or more and 40 m/s or less.

With the above structure, in the present invention, the diameter of the nozzle is set to be different from that of the front end portion of the Taylor cone-shaped charge concentration formed in order to discharge fluid having a droplet diameter smaller than the diameter of the fluid discharge hole of the nozzle in the past. The diameters are approximately the same, so the electric field that needs to be formed in a large area can be formed in a small area in the conventional electrostatic attraction process of fluids.

Thereby, the voltage required for moving electric charges, that is, the voltage required for imparting a charge amount required for electrostatic attraction to the fluid can be significantly reduced. This eliminates the need for a conventional high voltage of 2000 volts, and improves the safety when using the fluid ejection device.

Moreover, the diameter of the fluid discharge hole of the nozzle is set below φ8 μm, so that the electric field intensity distribution can be concentrated near the discharge surface of the fluid discharge hole, and the distance variation from the opposite electrode to the fluid protrusion hole of the nozzle will not affect the electric field. intensity distribution.

As a result, stable fluid discharge can be performed without being affected by the positional accuracy of the counter electrode, or the material property variation and thickness variation of the recording medium.

In addition, as described above, the electric field can be made small, and a strong electric field can be formed in a small area, and as a result, the droplet that can be formed can be miniaturized. As a result, when liquid droplets are used as ink, it is possible to make a high-resolution printed image.

Furthermore, as described above, since the concentration area of the charge is substantially the same size as the meniscus area of the fluid, the movement time of the charge in the meniscus area does not affect the discharge responsiveness, and the droplet discharge can be improved. Speed (printing speed when the droplet is ink).

In addition, since the charge concentration region is substantially the same size as the meniscus region of the fluid, it is not necessary to form a strong electric field in a wide meniscus region. Therefore, it is not necessary to arrange the counter electrode with high precision in order to form a strong electric field in a wide meniscus region as in the past, and the dielectric constant and thickness of the recording medium do not affect the arrangement of the counter electrode.

Therefore, in the electrostatic attraction type fluid ejection device, the degree of freedom in the arrangement of the opposing electrodes increases. That is, the degree of freedom in design of the electrostatic attraction type fluid ejection device increases. As a result, it is possible to print on a recording medium that has been difficult to use without being affected by the dielectric constant and thickness, and a fluid ejection device with good versatility can be realized.

Therefore, by using the electrostatic attraction type fluid ejection device having the above structure, it is possible to realize a device that satisfies both high resolution and safety and has good versatility.

Here, as the above-mentioned fluid, in addition to simple water, oil, etc., colored liquid ink containing dye or pigment as fine particles, or ink containing a wiring material (conductive fine particles such as silver or copper) that forms a circuit board can also be used. solution etc.

For example, when ink is used as the fluid, high-definition printing is possible, and when a solution containing wiring materials for circuit boards is used as the fluid, ultra-high-definition circuits can be formed with extremely narrow wiring. , can make the fluid discharge stably.

Moreover, the voltage applied to the fluid is controlled by the applied voltage control unit so that the average discharge speed during the period from when the fluid is discharged to when it reaches the recording medium is 10 m/s or more and 40 m/s or less. Due to the influence of drying during the flight of the fluid, as a result, the accuracy of the droplet landing on the recording medium can be improved, and the deviation of the diameter of the droplet landing point can be suppressed, and the electric field intensity at the meniscus can be prevented. Occurrence of atomization of the discharged liquid droplets caused by the impact can be stably discharged.

Here, if the average discharge speed of the fluid reaches the recording medium is less than 10m/s, the landing accuracy is poor, and the discharge stability is also poor, so the diameter of the droplet's landing spot varies. In addition, if the average discharge velocity during the period when the fluid reaches the recording medium is greater than 40m/s, a high voltage is required, so the electric field strength at the meniscus surface becomes very strong, and the discharged droplets are frequently atomized, making it impossible to discharge the liquid stably. drop.

Therefore, like the electrostatic attraction type fluid ejection device of the above-mentioned structure, by making the average discharge velocity during the period from the fluid discharge to the recording medium to be 10 m/s or more and 40 m/s or less, the liquid droplets can be stably flew, and as a result , can improve the accuracy of droplet landing point ejection, and can suppress the deviation of the diameter of the droplet landing point.

In addition, the electrostatic attraction type fluid ejection device configured as described above can also be realized by the following configuration.

That is, in the electrostatic attraction type fluid ejection device of the present invention, the fluid charged by the application of a voltage is electrostatically attracted from the fluid discharge hole of the nozzle made of an insulating material to the object at a speed corresponding to the applied voltage in the state of droplets. The recording medium discharge is characterized in that it has an applied voltage control unit that controls the voltage applied to the fluid in the nozzle, and the diameter of the fluid discharge hole of the nozzle is set to be equal to the droplet diameter of the fluid immediately after discharge. On the other hand, the applied voltage control unit controls the voltage applied to the fluid so that an average discharge speed from when the fluid is discharged to when it reaches the recording medium is 10 m/s or more and 40 m/s or less.

In addition, the electrostatic attraction type fluid ejection device of the present invention, in order to solve the above-mentioned problem, discharges the fluid containing fine particles and charged by applying a voltage in the state of liquid droplets from the fluid discharge hole of the nozzle made of insulating material under electrostatic attraction, It is characterized in that the diameter of the fluid discharge hole of the nozzle is set below φ8μm, and the particle diameter of the microparticles contained in the fluid is below φ30nm.

With the above structure, in the present invention, the diameter of the nozzle is set to be the diameter of the front end portion of the Taylor cone shape formed in order to discharge a fluid having a droplet diameter smaller than the diameter of the fluid discharge hole of the conventional nozzle. It is roughly the same, so the electric field that needs to be formed in a large area can be formed in a small area in the conventional electrostatic attraction process of fluid.

Thereby, the voltage required for moving electric charges, that is, the voltage required for imparting a charge amount required for electrostatic attraction to the fluid can be significantly reduced. This eliminates the need for a conventional high voltage of 2000 volts, and improves the safety when using the fluid ejection device.

Moreover, the diameter of the fluid discharge hole of the nozzle is set below φ8 μm, so that the electric field intensity distribution can be concentrated near the discharge surface of the fluid discharge hole, and the distance variation from the opposite electrode to the fluid protrusion hole of the nozzle will not affect the electric field. intensity distribution.

As a result, stable fluid discharge can be performed without being affected by the positional accuracy of the counter electrode, or the material property variation and thickness variation of the recording medium.

In addition, as described above, since the electric field can be made small, a strong electric field can be formed in a small area, and as a result, the formed liquid droplets can be miniaturized. As a result, when liquid droplets are used as ink, it is possible to make a high-resolution printed image.

Furthermore, as described above, since the concentration area of the charge is substantially the same size as the meniscus area of the fluid, the movement time of the charge in the meniscus area does not affect the discharge responsiveness, and the droplet discharge can be improved. Speed (printing speed when the droplet is ink).

In addition, since the charge concentration region is approximately the same size as the meniscus region of the fluid, it is not necessary to form a strong electric field in a wide meniscus region. Therefore, it is not necessary to arrange the counter electrode with high precision in order to form a strong electric field in a wide meniscus region as in the past, and the dielectric constant and thickness of the recording medium do not affect the arrangement of the counter electrode.

Therefore, in the electrostatic attraction type fluid ejection device, the degree of freedom in the arrangement of the opposing electrodes increases. That is, the degree of freedom in design of the electrostatic attraction type fluid ejection device increases. As a result, it is possible to print on a recording medium that has been difficult to use without being affected by the dielectric constant and thickness, and a fluid ejection device with good versatility can be realized.

Therefore, by using the electrostatic attraction type fluid ejection device having the above structure, it is possible to realize a device that satisfies both high resolution and safety and has good versatility.

Here, as the above-mentioned fluid, in addition to simple water, oil, etc., colored liquid ink containing dye or pigment as fine particles, or ink containing a wiring material (conductive fine particles such as silver or copper) that forms a circuit board can also be used. solution etc.

For example, when ink is used as the fluid, high-definition printing is possible, and when a solution containing wiring materials for circuit boards is used as the fluid, ultra-high-definition circuits can be formed with extremely narrow wiring. , can make the fluid discharge stably.

Furthermore, since the particle size of the fine particles contained in the above-mentioned fluid is φ30nm or less, the influence of the charging of the fine particles themselves can be reduced, and stable discharge can be performed even if the liquid droplets contain fine particles.

In addition, since the influence of the charging of the fine particles themselves can be reduced, the movement of the fine particles with small particle diameters does not slow down as in the conventional case of discharging fluid by using the charging of the fine particles. Therefore, a fluid containing fine particles, even ink, does not lower the recording speed.

In addition, the electrostatic attraction type fluid ejection device configured as described above can also be realized by the following configuration.

That is, the electrostatic attraction type fluid ejection device of the present invention discharges a fluid containing fine particles and charged by applying a voltage in the state of liquid droplets from the fluid discharge hole of a nozzle made of an insulating material under electrostatic attraction, and is characterized in that The diameter of the fluid discharge hole of the nozzle is set to be equal to or less than the droplet diameter of the fluid immediately after discharge, and the particle diameter of the fine particles contained in the fluid is φ30nm or less.

Other objects, features, and advantages of the present invention can be fully understood from the following description. In addition, the advantages of the present invention can be understood by the following description with reference to the accompanying drawings.

A brief description of the drawings

Fig. 1 is a cross-sectional view showing a schematic configuration of an ink ejecting device according to an embodiment of the present invention.

2( a ) to 2( c ) are diagrams illustrating fluctuations in the ink meniscus of the ink ejection device shown in FIG. 1 .

FIG. 3( a ) is a graph showing the relationship between the distance to the nozzle center and the distance to the counter electrode when the distance between the nozzle and the counter electrode is 2000 μm.

FIG. 3( b ) is a graph showing the relationship between the distance to the center of the nozzle and the distance to the counter electrode when the distance between the nozzle and the counter electrode is 100 μm.

FIG. 4( a ) is a graph showing the relationship between the distance to the center of the nozzle and the distance to the counter electrode when the distance between the nozzle and the counter electrode is 2000 μm.

FIG. 4( b ) is a graph showing the relationship between the distance to the center of the nozzle and the distance to the counter electrode when the distance between the nozzle and the counter electrode is 100 μm.

FIG. 5( a ) is a graph showing the relationship between the distance to the nozzle center and the distance to the counter electrode when the distance between the nozzle and the counter electrode is 2000 μm.

FIG. 5( b ) is a graph showing the relationship between the distance to the center of the nozzle and the distance to the counter electrode when the distance between the nozzle and the counter electrode is 100 μm.

FIG. 6( a ) is a graph showing the relationship between the distance to the nozzle center and the distance to the counter electrode when the distance between the nozzle and the counter electrode is 2000 μm.

FIG. 6( b ) is a graph showing the relationship between the distance to the nozzle center and the distance to the counter electrode when the distance between the nozzle and the counter electrode is 100 μm.

FIG. 7( a ) is a graph showing the relationship between the distance to the center of the nozzle and the distance to the counter electrode when the distance between the nozzle and the counter electrode is 2000 μm.

FIG. 7( b ) is a graph showing the relationship between the distance to the center of the nozzle and the distance to the counter electrode when the distance between the nozzle and the counter electrode is 100 μm.

FIG. 8( a ) is a graph showing the relationship between the distance to the center of the nozzle and the distance to the counter electrode when the distance between the nozzle and the counter electrode is 2000 μm.

FIG. 8( b ) is a graph showing the relationship between the distance to the center of the nozzle and the distance to the counter electrode when the distance between the nozzle and the counter electrode is 100 μm.

Fig. 9 is a graph showing the relationship between nozzle diameter and maximum electric field intensity.

Fig. 10 is a graph showing the relationship between nozzle diameter and various voltages.

Fig. 11 is a graph showing the relationship between the nozzle diameter and the strong electric field region.

Fig. 12 is a graph showing the relationship between the applied voltage and the charged charge amount.

Fig. 13 is a graph showing the relationship between the initial discharge droplet diameter and drying time.

Fig. 14 is a graph showing the relationship between ambient humidity and drying time.

Fig. 15 is a cross-sectional view showing a schematic configuration of an ink ejecting device according to another embodiment of the present invention.

Fig. 16 is a diagram illustrating the principle of the present invention.

Fig. 17 is a cross-sectional view showing a schematic configuration of a conventional electrostatic attraction type fluid ejection device.

18( a ) to 18 ( c ) are diagrams illustrating fluctuations in the ink meniscus of the ink ejection device shown in FIG. 17 .

Fig. 19 is a schematic configuration diagram showing another conventional electrostatic attraction type fluid ejection device.

20 is a schematic cross-sectional perspective view showing a nozzle portion of the ink ejecting device shown in FIG. 19 .

FIG. 21 is a diagram explaining the principle of ink discharge by the ink ejection device shown in FIG. 19 .

FIG. 22 is an explanatory view showing the state of fine particles when a voltage is applied to the nozzle portion of the ink ejecting device shown in FIG. 19 .

FIG. 23 is a diagram illustrating the principle of formation of fine particles in the nozzle portion of the ink ejection device shown in FIG. 19 .

24( a ) to 24 ( c ) are diagrams illustrating fluctuations of the ink meniscus in the ink ejection device shown in FIG. 19 .

Detailed ways

[implementation form]

The best mode for carrying out the present invention (hereinafter referred to as embodiment) will be described below. In this embodiment, an electrostatic attraction type fluid ejection device using ink as a fluid will be described.

Fig. 1 is a block diagram showing an ink ejecting device according to an embodiment of the present invention.

As shown in FIG. 1 , the above-mentioned ink jetting device has nozzles 4 for discharging ink 2 which is a fluid stored in an ink chamber 1 . The nozzle 4 is connected to the ink chamber 1 through a gasket 5 . Thereby, the ink 2 in the ink chamber 1 is sealed so that it does not leak to the outside from the connecting portion between the nozzle 4 and the ink chamber 1 .

In addition, the nozzle 4 has a constricted shape in which the inner diameter decreases toward the side opposite to the connection portion with the ink chamber 1 , that is, toward the tip portion 4 a on the ink discharge side. The inner diameter (diameter) of the ink discharge hole 4b at the tip portion 4a of the nozzle 4 is set in relation to the particle diameter of the ink 2 immediately after discharge.

In order to distinguish the ink 2 discharged from the nozzle 4 from the ink 2 stored in the ink chamber 1 , the ink 2 discharged from the nozzle 4 will be referred to as a droplet 3 in the following description. The details of the relationship between the diameter of the ink discharge hole 4 b and the droplet diameter of the liquid droplet 3 immediately after discharge will be described later.

Furthermore, an electrostatic field applying electrode 9 for applying an electrostatic field to the ink 2 is provided inside the nozzle 4 . The electrode 9 for applying an electrostatic field is connected to a process control unit 10 , and the intensity of an electric field generated by an applied voltage from a drive circuit (not shown) is controlled by the process control unit 10 . By controlling the intensity of the electric field, the droplet diameter of the liquid droplet 3 discharged from the nozzle 4 is adjusted. That is, the flow control unit 10 functions as an applied voltage control device that controls the voltage applied to the ink 2 via the electrode 9 for applying an electrostatic field.

The counter electrode 7 is disposed at a position separated by a predetermined distance from the ink discharge hole 4 b of the nozzle 4 . The counter electrode 7 is used to charge the surface of the recording medium 8 conveyed between the nozzle 4 and the counter electrode 7 to a polarity opposite to that of the charged potential of the liquid droplets 3 discharged from the ink discharge holes 4 b of the nozzle 4 . potential. As a result, the liquid droplets 3 discharged from the ink discharge holes 4 b of the nozzles 4 reach the surface of the recording medium 8 stably.

In this way, since the droplets 3 need to be charged, it is preferable that at least the ink discharge surface of the front end 4a of the nozzle 4 is formed by an insulating member, and it is necessary to form a fine nozzle diameter (the inner diameter of the ink discharge hole 4b), so in this embodiment, A glass capillary is used as the nozzle 4 .

Therefore, the above-mentioned nozzle 4 is formed as a meniscus of ink with a Taylor cone shape formed in order to discharge liquid droplets having a diameter smaller than the diameter of the ink discharge hole of the nozzle during the electrostatic attraction of the ink 2 as the fluid. Equivalent shape, while setting the diameter of the ink discharge hole 4b of the nozzle 4 to be approximately the same as the diameter of the front end of the ink of the above-mentioned meniscus that is about to be discharged, and set to the diameter of the droplet 3 immediately after discharge. equal or below.

In the ink jetting device having the above configuration, the voltage applied to the ink 2 is controlled by the flow control unit 10 through the electrode 9 for applying an electrostatic field so that the droplet volume of the discharged ink 2 is 1 pl or less.

In addition, the ink chamber 1 is connected to an ink supply channel 6 for supplying the ink 2 from an ink tank (not shown) in addition to the nozzle 4 . Here, in the ink chamber 1 and the nozzle 4, since the ink 2 is kept filled, a negative pressure acts on the ink 2 .

Next, changes in the meniscus surface (meniscus region) 14 formed near the ink discharge hole 4b when the ink 2 is discharged from the nozzle 4 as the droplet 3 will be described. 2( a ) to 2( c ) are model diagrams showing movement of the meniscus portion 14 in the vicinity of the ink discharge hole 4 b.

First, in the state before the ink 2 is discharged, as shown in FIG. concave shape.

Next, in order to discharge the ink 2, the voltage applied to the ink 2 is controlled by the process control unit 10 through the electrode 9 for applying an electrostatic field, and when a predetermined voltage is applied to the ink 2, the ink 2 in the nozzle 4 Charge is induced on the surface, and the ink 2, as shown in FIG. ) of the meniscus 14b. At this time, since the diameter of the nozzle 4 is small, the meniscus 14b stretches outward while forming a Taylor cone shape from the beginning.

Next, the meniscus 14b stretched outward, as shown in FIG. The force of the charge on the surface of the meniscus 14c and the electric field (electric field strength) formed in the nozzle 4 is greater than the surface tension of the ink 2, thereby forming discharged liquid droplets.

Here, the inner diameter of the ink discharge hole 4b of the nozzle 4 used in this embodiment (hereinafter referred to as the nozzle diameter) is made φ5 μm. In this way, when the nozzle diameter of the nozzle 4 is small, the radius of curvature of the tip of the meniscus does not gradually decrease due to the concentration of surface charges as in the past, but can be regarded as substantially constant.

Therefore, if the physical property value of the ink is constant, the surface tension when the droplet is separated is approximately constant in the discharge state generated by the applied voltage, and the amount of surface charge that can be concentrated is also a value exceeding the surface tension of the ink, that is, due to the Rayleigh Below the split value, the maximum amount can be uniquely defined.

In addition, because the diameter of the nozzle is small, the electric field intensity is extremely strong only at the extreme edge of the meniscus, and because the discharge destruction intensity of the strong electric field in such a small area is extremely large, it is not necessary to will be a problem.

As the ink used in the inkjet device according to this embodiment, dye-based inks containing pure water and inks containing fine particles can be used. Here, as the ink containing fine particles, the nozzle part has been extremely small in the past, so the particle size of the contained fine particles also needs to be small. Generally speaking, clogging is less likely to occur if it is about 1/20 to 1/100 of the nozzle.

Therefore, when the nozzle diameter of the nozzle 4 used in this embodiment is 5 μm as described above, the particle diameter of ink particles corresponding to the nozzle diameter is 50 nm or less. At this time, as in the principle of discharging ink containing fine particles shown in Patent Document 2, in the method of concentrating the charges on the meniscus surface by the movement caused by charging of the fine particles, and discharging by the electrostatic reaction force between the concentrated fine particles, Since it is smaller than the minimum particle diameter φ100nm used in the past, the movement speed of the charged particles in the ink is reduced, and the response speed of discharge and the recording speed are slowed down.

In contrast, in the present invention, instead of using the electrostatic reaction force between charged fine particles, discharge is performed using the charges on the surface of the meniscus as in the case of ink not containing fine particles. In this case, in order to eliminate the discharge instability caused by the influence of the charge of the fine particles in the ink on the charge on the surface of the meniscus, it is preferable to form the amount of charge of the fine particles in the ink to be equal to the charge on the surface of the meniscus. The shape for much smaller values.

In this way, if the charge per unit mass of the particles in the ink is below 10 μC/g, the electrostatic reaction force and response speed between the particles will be reduced, and by reducing the mass of the ink particles, that is, reducing the diameter of the ink particles , can reduce the total charge of the particles in the ink.

Table 1 below shows the discharge stability when the average particle diameter in the ink is φ3 nm to φ50 nm.

Table 1 particle diameter Nozzle diameter φ0.4μm φ1μm φ4μm φ8μm φ50nm x △ △ △ φ30nm ○ ○ ○ ○ φ10nm ○ ○ ○ ○ φ3nm ○ ○ ○ ○

The symbols in Table 1 indicate the discharge stability of each nozzle, ×: There is a case where the discharge is not performed due to clogging, etc., △: There is discharge instability during continuous discharge, ○: Stable discharge

As can be seen from Table 1, the diameter of fine particles is preferably φ30nm or less. Especially when the particle diameter is less than φ10nm, the influence of the charged amount of one particle in the ink as the charge in the ink discharge is roughly negligible, and the movement speed caused by the charge is also extremely slow, and the particle will not move toward the center of the meniscus. concentrated. In addition, when the nozzle diameter is less than φ3μm, the maximum electric field intensity is extremely increased due to the concentration of the electric field on the meniscus, and the electrostatic force of each particle is also increased. Therefore, it is best to use ink containing particles of φ10nm or less. However, when the diameter of the fine particles is less than φ1nm, the aggregation of the fine particles and the unevenness of the concentration increase, so the fine particle diameter is preferably in the range of φ1nm to φ10nm.

In this embodiment, a slurry containing fine particles of silver having an average particle diameter of φ3 nm to φ7 nm is used, and a coating for preventing aggregation is applied to the fine particles.

Next, the relationship between the nozzle diameter of the nozzle 4 and the electric field intensity will be described with reference to FIGS. Figure 3(a), (b) to Figure 8(a), (b) show the electric field strength when the nozzle diameter is φ0.2, 0.4, 1, 8, 20μm and the nozzle diameter φ50μm used as a reference distributed.

Here, in each figure, the nozzle center position refers to the center position of the ink discharge surface of the ink discharge hole 4 b of the nozzle 4 . In addition, (a) of each figure shows the electric field intensity distribution when the distance between the nozzle and the counter electrode is set to 2000 μm, and figure (b) shows the electric field intensity distribution when the distance between the nozzle and the counter electrode is set to 100 μm. The applied voltage was set to a constant 200 volts under each condition. The distribution line in the figure indicates the electric field intensity ranges from 1×10 ⁶ V/m to 1×10 ⁷ V/m.

Table 2 below shows the maximum electric field strength under each condition.

Table 2 Nozzle diameter (μm) Gap (μm) Rate of change (%) 100 2000 0.2 2.001×10 ⁹ 2.00005×10 ⁹ 0.05 0.4 1.001×10 ⁹ 1.00005×10 ⁹ 0.09 1 0.401002×10 ⁹ 0.40005×10 ⁹ 0.24 8 0.0510196×10 ⁹ 0.05005×10 ⁹ 1.94 20 0.0210476×10 ⁹ 0.0200501×10 ⁹ 4.98 50 0.00911111×10 ⁹ 0.00805×10 ⁹ 13.18

From Figure 3(a), (b) to Figure 8(a), (b), it can be seen that when the nozzle diameter is above φ20μm (Figure 7(a), (b)), the electric field intensity distribution spreads into a large area. In addition, it can be seen from Table 2 that the distance between the nozzle and the opposite electrode has an influence on the electric field intensity.

It can be seen from the above that when the diameter of the nozzle is φ8μm or less (Figure 6(a), (b)), the electric field intensity is concentrated, and the variation of the distance from the opposite electrode hardly affects the electric field intensity distribution. Therefore, if the nozzle diameter is φ8 μm or less, stable discharge can be performed without being affected by the positional accuracy of the counter electrode, the material property variation and the thickness variation of the recording medium. Here, to discharge the ink 2 with a droplet volume of 1 pl, the nozzle diameter needs to be φ10 μm, so as described above, if the nozzle diameter is φ8 μm or less, the droplet volume can be made 1 pl or less.

Next, FIG. 9 shows the relationship between the nozzle diameter of the nozzle 4 and the maximum electric field intensity of the meniscus 14 and the strong electric field region.

It can be seen from the curve shown in Figure 9 that when the nozzle diameter is below φ4μm, the electric field concentration is extremely increased and the maximum electric field intensity can be increased. As a result, since the initial discharge speed of the ink can be increased, the flight stability of the ink (liquid droplet) can be increased, and the discharge responsiveness can be improved because the movement speed of the charge on the meniscus is increased.

Next, the maximum chargeable charge amount of the discharged liquid droplets 3 of the ink 2 will be described. The chargeable amount of the droplet 3 is expressed by the following formula (5) in consideration of the Rayleigh splitting (Rayleigh limit) of the droplet 3 .

q＝8×π×(ε0×γ×r ³ ) ^1/2 …(5)

where q is the amount of charge that gives the Rayleigh limit, ε0 is the vacuum permittivity, γ is the surface tension of the ink, and r is the radius of the ink droplet.

The closer the charge quantity q obtained by the above formula (5) is to the Rayleigh limit value, the stronger the electrostatic force will be even under the same electric field strength, which can improve the stability of discharge, but if it is too close to the Rayleigh limit value, the opposite will happen. The mist of the ink 2 occurred in the ink discharge hole 4b of the nozzle 4, and the discharge stability was not good.

Here, FIG. 10 shows the nozzle diameter of the nozzle, the discharge start voltage at which the initial discharge droplet starts to fly, and the voltage value at the Rayleigh limit of the initial discharge droplet with a diameter about twice the diameter of the nozzle discharged at the meniscus. And the curve of the relationship between the discharge start voltage and the ratio of the Rayleigh limit voltage value.

From the curve shown in Figure 10, it can be seen that the nozzle diameter is in the range of φ0.2μm to φ4μm, the ratio of the discharge start voltage to the Rayleigh limit voltage value exceeds 0.6, and the charging efficiency of the droplets becomes a good result. Perform stable discharge.

For example, in the graph of the relationship between the nozzle diameter and the region of a strong electric field (1×10 ⁶ V/m or more) at the meniscus shown in FIG. A case of extreme narrowing of the area. This indicates that the discharged liquid droplets cannot receive sufficient energy for acceleration, and the flying stability deteriorates. Therefore, it is necessary to set the nozzle diameter larger than φ0.2 μm.

Next, FIG. 12 shows the meniscus induced by the maximum electric field intensity when the optimum voltage value is changed from the applied voltage when actually driving the ink ejection device with the above-mentioned structure, that is, the voltage above the droplet discharge start voltage. The initial liquid droplet discharged from the face is a graph showing the relationship between the charge amount of the droplet and the Rayleigh limit value derived from the surface tension of the droplet at a certain time.

It can be seen from the curve shown in Figure 12 that point A is the intersection point of the charge amount of the above-mentioned liquid droplet and the Rayleigh limit value from the surface tension of the liquid droplet. A maximum amount of charge approximately close to the Rayleigh limit is formed on the droplet. If the voltage is lower than point A, it means that the amount of charge required for discharge is formed below the Rayleigh limit.

Here, focusing only on the equation of motion of the discharged droplet, the flight is carried out under the optimal conditions of discharge energy with a strong electric field and a maximum amount of charge, so the applied voltage is preferably a voltage higher than that at point A.

However, FIG. 13 is a graph showing the relationship between the initial discharge droplet diameter of ink (here, pure water) and the drying time (time for all the solvent in the droplet to evaporate) when the ambient humidity is 50%. As can be seen from this graph, when the initial droplet diameter is small, the change in the droplet diameter of the ink due to evaporation is very rapid, and the ink dries within a short time while flying.

Therefore, when droplets are formed with the maximum amount of charge at the initial discharge, the droplet diameter decreases due to drying, that is, the surface area of the droplet forming the charge decreases, Rayleigh splitting occurs during the flight of the ink, and when the charge is excessively discharged The charge is released with a part of the droplets, resulting in a decrease in the number of flying droplets above the evaporation.

Therefore, the variation in droplet diameter and landing accuracy at the time of arrival deteriorates, and the mist split in the nozzle and the recording medium floats and contaminates the recording medium. Therefore, in consideration of forming a stable discharge dot, it is necessary to make the charge amount induced in the initially discharged liquid droplet smaller than the charge amount corresponding to the Rayleigh limit to some extent. In this case, if the charge amount is about 95% of the charge amount corresponding to the Rayleigh limit value, the accuracy of the variation in the dot diameter of the landing point cannot be improved, and as a result, it is preferable to make it 90% or less.

As a specific numerical value, the Rayleigh limit of the initial discharge droplet diameter caused by the maximum electric field strength of the meniscus when the nozzle aperture is regarded as the tip shape of the needle electrode is calculated, and by making it a range below the calculated value, it is possible to suppress The deviation of the droplet upon arrival. This is considered to be because the surface area of the discharged droplet before separation is smaller than that of the liquid droplet immediately after discharge, and due to the time lag in the transfer time of the charge, the amount of charge induced in the initially discharged droplet is actually larger than the amount of charge obtained by the above calculation. Small sake.

Under such conditions, Rayleigh splitting during flight can be prevented, and at the same time, stable discharge such as atomization due to a large amount of charge at the time of separation of discharged droplets at the meniscus surface can be reduced.

Charged droplets have reduced vapor pressure and are less likely to evaporate. This can be seen from the following formula (6).

RTρ/M×log(P/P0)＝2γ/dq ² /(8πd ⁴ ) …(6)

Among them, R is the gas constant, M is the molecular weight of the gas, T is the gas temperature, ρ is the gas density, P is the vapor pressure of the tiny droplet, P0 is the vapor pressure of the plane, γ is the surface tension of the ink, and d is the ink droplet of the radius.

As shown in the above formula (6), for a charged droplet, the vapor pressure decreases due to the charge amount of the droplet. Above 60% of the voltage value is the best result. As a result, in the same manner as above, the Rayleigh limit of the diameter of the initial discharge droplet due to the maximum electric field strength of the meniscus when the nozzle aperture is regarded as the shape of the tip of the needle electrode was calculated, and the range representing 0.8 times or more of the calculated value was calculated. The situation is the same.

In particular, as shown in Figure 13, when the diameter of the initial discharge droplet is φ5 μm or less, the drying time is extremely shortened, and it is easily affected by evaporation. It can be seen that the charge amount of the initial discharge droplet is suppressed to be small, and from the viewpoint of suppressing evaporation Look is effective. The ambient humidity when calculating the relationship between the drying time and the initial discharge droplet diameter shown in FIG. 13 was made 50%.

In addition, when considering the drying of discharged liquid droplets, it is necessary to shorten the discharge time of the liquid to the recording medium.

Here, the average flying speed of the discharged liquid droplet from the meniscus is made 5m/s, 10m/s, 20m/s, 30m/s, 40m/s, 50m/s from the nozzle to the recording medium, Table 3 shows the results of comparing the ejection stability with the positional accuracy of the landing point.

table 3 Initial discharge droplet diameter φ0.4μm φ1μm φ3μm Average discharge speed discharge stability Drop point accuracy discharge stability Drop point accuracy discharge stability Drop point accuracy 5m/s ×(not arrived) △ △ ○ △ 10m/s ○ ○ ○ ○ ○ ○ 20m/s ○ ◎ ○ ◎ ○ ◎ 30m/s ○ ◎ ○ ◎ ○ ◎ 40m/s ○ ◎ ○ ◎ ○ ◎ 50m/s × (fog occurs) × (fog occurs) × (fog occurs)

The discharge stability in Table 3 is indicated by a symbol, ×: Almost no discharge, △: There is a case of non-discharge during continuous discharge, ○: There is no case of non-discharge, and the symbol of the accuracy of the landing point is indicated by a symbol, ×: Fall Point offset > drop point diameter, △: drop point offset > drop point diameter × 0.5, ○: drop point offset < drop point diameter × 0.5, ◎: drop point offset < drop point circle Spot diameter × 0.2.

As can be seen from the above Table 3, when the average flying speed is 5m/s, the landing point accuracy is poor, and the discharge stability is also poor. In particular, when the nozzle diameter is φ1 μm or less, when the discharge speed is small, the air resistance factor acting on the droplet increases, and the dot diameter is further reduced by evaporation, which may not reach the droplet. On the contrary, when the average flying speed is 50 m/s, since the applied voltage needs to be increased, the electric field strength on the meniscus surface becomes extremely strong, frequent atomization of discharged liquid droplets occurs, and stable discharge becomes difficult.

As can be seen from the above, it is preferable that the average flying speed of the discharged liquid droplet during the separation from the meniscus to reach the recording medium from the nozzle is between 10 m/s and 40 m/s.

However, Figure 13 shows the relationship between the initial discharge droplet diameter and drying time when the ambient humidity is 50%, and Figure 14 shows that the distance between the nozzle and the recording medium is 0.2 μm when the initial discharge droplet diameter is φ0.5 μm. Ambient humidity in mm versus drying time.

It can be seen from the curve shown in Fig. 14 that when the ambient humidity is below 60%, the value of the drying speed does not change greatly. However, when the ambient humidity exceeds 70%, the evaporation of the ink can be extremely suppressed. When the ambient humidity is 70% or more, the influence of the above conditions and the like is reduced. Especially when the ambient humidity is set to 95% or more, it is found that the By ignoring the influence of drying, the degree of freedom in the design conditions of the ink ejection device of the present invention can be increased and the applicable range can be expanded.

Here, the following Table 4 shows the discharge stability and discharge dot diameter deviation (falling point deviation) when the nozzle diameter is set to φ1 and φ3 μm and the initial discharge droplet diameter is varied. The initial discharge diameter generated from the nozzle can be controlled by changing the applied voltage value, and can also be controlled by adjusting the pulse width of the voltage pulse. Here, in order to eliminate the influence of the electric field intensity under the same nozzle diameter, the initial discharge diameter is adjusted by changing the above pulse width. discharge diameter.

The symbols of the discharge stability in Table 4 are indicated, ×: almost no discharge, △: there was no discharge during 10 minutes of continuous discharge, ○: no non-discharge during 10 minutes of continuous discharge, ◎: Indicates that there is no non-discharge in 30 minutes of continuous discharge, and the symbol of the deviation is indicated, △: the deviation of the landing point > the diameter of the landing point × 0.2, ○: the deviation of the landing point ≤ the diameter of the landing point ×0.2, ◎: The deviation of the landing point ≦the diameter of the landing point×0.1.

Table 4 Initial discharge droplet diameter (μm) Nozzle diameter (μm) φ1 φ3 φ5 deviation discharge stability deviation discharge stability deviation discharge stability φ1 △ ○ x x φ1.5 ◎ ◎ x x φ2 ◎ ◎ x x φ3 ◎ ○ △ △ x φ5 ○ △ ◎ ◎ △ △ φ7 x ◎ ○ ◎ ○ φ10 x △ ○ ◎ ◎ φ15 x △ △ ○ ○ φ20 x x ○ △

It can be seen from Table 4 that when the nozzle diameter is about 1.5 to 3 times the discharge stability is good, especially when the diameter is 1.5 to 2 times, the deviation of the dot diameter of the landing point is extremely suppressed. This is considered to be due to separation of droplets under the condition that the surface area of the liquid column is larger than the surface area of the ball corresponding to the volume of the liquid column when the shape of the ink stretched from the meniscus is regarded as a liquid column. The most stable reason.

With the above-mentioned structure, in the electrostatic attraction type ink ejection device in which the droplet amount of the ink is discharged shortly after the discharge is 1 μl or less, the diameter of the ink discharge hole 4b of the nozzle 4 is made to be short after the discharge of the ink. When the droplet diameter is equal or less, since the electric field for discharge can be concentrated on the meniscus 14 of the nozzle 4, the external voltage required to discharge the ink can be greatly reduced, and the separation and separation of each droplet can be reduced. The diameter of the discharged liquid droplets varies and is discharged stably.

In addition, it is no longer necessary to apply the bias voltage required in the past, and the positive and negative driving voltage can be applied alternately, which can reduce the influence of the increase of the surface potential of the recording medium on the landing accuracy.

In addition, by making the diameter of the nozzle hole within the range of φ8μm or less, the electric field can be concentrated on the meniscus surface of the nozzle, and at the same time, it is not affected by the position accuracy of the counter electrode, the material properties of the recording medium, and the thickness variation. Perform stable discharge.

In particular, by setting the diameter of the ink discharge hole 4b of the nozzle 4 within the range of φ0.2 μm to φ4 μm, the electric field concentration is extremely enhanced. In this way, increasing the maximum electric field intensity increases the initial discharge speed of the ink, so the flying stability is improved, and at the same time, the discharge responsiveness is improved due to the increase of the moving speed of the charge on the meniscus surface, and Rayleigh splitting can be suppressed at the same time. The deviation of the drop point diameter caused by the influence of

Moreover, the stability of discharge can be improved by making the diameter of the droplet immediately after the ink from the nozzle 4 is discharged to be within the range of 1.5 times or more and 3 times or less the diameter of the ink discharge hole 4b of the nozzle 4, especially when the ink is discharged. By setting the droplet diameter immediately after discharge within the range of 1.5 to 2 times the nozzle diameter, variation in the discharge dot diameter can be extremely suppressed.

In this embodiment, as described above, an example in which a negative pressure is applied to the ink in the ink chamber 1 has been described, but a positive pressure may also be applied to the ink. In order to apply a positive pressure to the ink in the ink chamber 1, for example, as shown in FIG. Apply positive pressure. In this case, the flow control unit 13 may control the drive of the pump 12 so as to be driven in accordance with the timing when the ink is discharged from the ink chamber 1 . In this way, when positive pressure is applied to the ink in the ink chamber 1, the trouble of forming the convex shape of the meniscus by electrostatic force can be saved, the applied voltage can be reduced, and the response speed can be improved.

In this embodiment, for the sake of simplification, an ink jet device with a single nozzle has been described, but it is not limited thereto. As long as the design takes into account the influence of the electric field strength of adjacent nozzles, it can also be applied to ink jet devices with multiple nozzles. Ink ejection device with multiple heads of nozzles.

In addition, in this embodiment, as shown in FIG. 1 and FIG. 15 , the ink ejection device in which the counter electrode 7 is always provided has been described. However, as can be seen from Table 2, the distance between the counter electrode 7 and the ink discharge hole 4b of the nozzle 4 is The distance (gap) hardly affects the electric field strength between the recording medium and the nozzle. As long as the distance between the recording medium and the nozzle is short and the surface potential of the recording medium is stable, the opposing electrode is not required.

As described above, the electrostatic attraction type fluid ejection device of the present invention discharges the fluid charged by the application of a voltage in the state of droplets under electrostatic attraction from the fluid discharge hole of the nozzle made of an insulating material, and the fluid discharge hole of the nozzle The diameter is set to be equal to or less than the droplet diameter of the fluid immediately after discharge.

Therefore, the present invention sets the diameter of the nozzle to be approximately the same as the diameter of the front end portion of the Taylor cone-shaped charge concentration formed in order to discharge fluid having a droplet diameter smaller than the diameter of the fluid discharge hole of the nozzle in the prior art. In the conventional process of electrostatic attraction of fluids, an electric field that needs to be formed in a large area can be formed in a small area.

Furthermore, by setting the diameter of the fluid discharge hole of the nozzle to be equal to or less than the droplet diameter of the fluid immediately after discharge, the charge concentration region and the meniscus region of the fluid can be made approximately the same size.

Accordingly, it is possible to significantly reduce the voltage required for transferring electric charges, that is, the voltage required for imparting the amount of charge required to electrostatically attract the fluid to the fluid in the state of a droplet having a desired droplet diameter. This eliminates the need for a conventional high voltage of 2000 volts, and improves the safety when using the fluid ejection device.

In addition, as described above, by narrowing the electric field, a strong electric field can be formed in the narrow region, and as a result, formed droplets can be miniaturized. As a result, when liquid droplets are used as ink, it is possible to make a high-resolution printed image.

Furthermore, as described above, since the concentration area of the charge is substantially the same size as the meniscus area of the fluid, the movement time of the charge in the meniscus area does not affect the discharge responsiveness, and the droplet discharge can be improved. Speed (printing speed when the droplet is ink).

In addition, since the charge concentration region is approximately the same size as the meniscus region of the fluid, it is not necessary to form a strong electric field in a wide meniscus region. Therefore, it is not necessary to arrange the counter electrode with high precision in order to form a strong electric field in a wide meniscus region as in the past, and the dielectric constant and thickness of the recording medium do not affect the arrangement of the counter electrode.

Therefore, in the electrostatic attraction type fluid ejection device, the degree of freedom in the arrangement of the opposing electrodes increases. That is, the degree of freedom in design of the electrostatic attraction type fluid ejection device increases. As a result, it is possible to print on a recording medium that has been difficult to use without being affected by the dielectric constant and thickness, and a fluid ejection device with good versatility can be realized.

Therefore, according to the electrostatic attraction type fluid ejection device having the above structure, it is possible to realize a device that satisfies both high resolution and safety and has good versatility.

In addition, the electrostatic attraction type fluid ejection device of the present invention is configured to discharge the fluid charged by the application of a voltage in the state of liquid droplets from the fluid discharge hole of the nozzle made of an insulating material under electrostatic attraction, and discharge the fluid from the nozzle. The diameter of the hole is set at φ8 μm or less.

Therefore, the present invention sets the diameter of the nozzle to be approximately the same as the diameter of the front end portion of the Taylor cone-shaped charge concentration formed in order to discharge fluid having a droplet diameter smaller than the diameter of the fluid discharge hole of the nozzle in the prior art. In the conventional process of electrostatic attraction of fluids, an electric field that needs to be formed in a large area can be formed in a small area.

Thereby, the voltage required for moving electric charges, that is, the voltage required for imparting a charge amount required for electrostatic attraction to the fluid can be significantly reduced. As a result, since a conventional high voltage of 2000 volts is unnecessary, the safety when using the fluid ejection device can be improved.

Moreover, by setting the diameter of the fluid discharge hole of the nozzle at φ8μm or less, the electric field intensity distribution can be concentrated near the discharge surface of the fluid discharge hole, and the distance variation from the opposite electrode to the fluid protrusion hole of the nozzle will not affect Electric field strength distribution.

As a result, the fluid can be discharged stably without being affected by the positional accuracy of the counter electrode and the variation in material properties and thickness of the recording medium.

In addition, as described above, the electric field can be made small, and a strong electric field can be formed in a small area, and as a result, the droplet that can be formed can be miniaturized. As a result, when liquid droplets are used as ink, it is possible to make a high-resolution printed image.

Furthermore, as described above, since the concentration area of the charge is substantially the same size as the meniscus area of the fluid, the movement time of the charge in the meniscus area does not affect the discharge responsiveness, and the droplet discharge can be improved. Speed (printing speed when the droplet is ink).

In addition, since the charge concentration region is approximately the same size as the meniscus region of the fluid, it is not necessary to form a strong electric field in a wide meniscus region. Therefore, it is not necessary to arrange the counter electrode with high precision in order to form a strong electric field in a wide meniscus region as in the past, and the dielectric constant and thickness of the recording medium do not affect the arrangement of the counter electrode.

Therefore, in the electrostatic attraction type fluid ejection device, the degree of freedom in the arrangement of the opposing electrodes increases. That is, the degree of freedom in design of the electrostatic attraction type fluid ejection device increases. As a result, it is possible to print on a recording medium that has been difficult to use without being affected by the dielectric constant and thickness, and a fluid ejection device with good versatility can be realized.

Therefore, by using the electrostatic attraction type fluid ejection device having the above structure, it is possible to realize a device that satisfies both high resolution and safety and has good versatility.

By controlling the voltage applied to the fluid, the droplet volume (volume and diameter of the droplet) of the discharged fluid can be adjusted. Therefore, an applied voltage control device for controlling the voltage applied to the fluid may be provided so that the droplet volume of the fluid immediately after being discharged from the fluid discharge hole is 1 Pl or less.

In addition, the diameter of the fluid discharge hole of the nozzle may be set to φ0.2 μm or more and φ4 μm or less.

In this case, by setting the diameter of the fluid discharge hole of the nozzle to φ0.2 μm or more and φ4 μm or less, the electric field concentration is extremely enhanced and the maximum electric field intensity can be increased. As a result, fine liquid droplets having a small diameter can be stably discharged.

The voltage applied to the fluid may be controlled by the above-mentioned applied voltage control device so that the diameter of the droplet immediately after being discharged from the above-mentioned fluid discharge hole is 1.5 times or more and 3 times or less the diameter of the fluid discharge hole. Further, the voltage applied to the fluid is controlled so that the diameter of the droplet immediately after being discharged from the fluid discharge hole is 1.5 times or more and 2 times or less the diameter of the fluid discharge hole.

In this case, the stability of fluid discharge can be improved by setting the droplet diameter immediately after discharge from the fluid discharge hole (initial discharge droplet diameter) to 1.5 to 3 times the diameter of the fluid discharge hole. Especially if the diameter of the liquid droplet discharged from the fluid discharge hole is made 1.5 times to 2 times the diameter of the fluid discharge hole, the deviation of the droplet diameter when the fluid is discharged and arrives on the recording medium is extremely reduced. inhibition.

In addition, the electrostatic attraction type fluid ejection device of the present invention discharges the fluid charged by the application of voltage in the state of liquid droplets from the fluid discharge hole of the nozzle made of insulating material under electrostatic attraction, and has The applied voltage control unit that controls the fluid voltage is configured to: set the diameter of the fluid discharge hole of the nozzle to φ8 μm or less, and the applied voltage control unit controls the voltage applied to the fluid so that from the The amount of charge induced in a droplet of the fluid immediately after being discharged from the fluid discharge hole is 90% or less of the amount of charge corresponding to the Rayleigh limit of the droplet.

Therefore, in the present invention, the diameter of the nozzle is set to be approximately the same as the diameter of the front end portion of the Taylor cone shape formed in order to discharge a fluid having a droplet diameter smaller than the diameter of the fluid discharge hole of the nozzle in the prior art. Similarly, the electric field that needs to be formed in a large area can be formed in a small area in the conventional electrostatic attraction process of fluid.

Thereby, the voltage required for moving electric charges, that is, the voltage required for imparting a charge amount required for electrostatic attraction to the fluid can be significantly reduced. This eliminates the need for a conventional high voltage of 2000 volts, and improves the safety when using the fluid ejection device.

Moreover, by setting the diameter of the fluid discharge hole of the nozzle at φ8μm or less, the electric field intensity distribution can be concentrated near the discharge surface of the fluid discharge hole, and the distance variation from the opposite electrode to the fluid protrusion hole of the nozzle will not affect Electric field strength distribution.

As a result, stable fluid discharge can be performed without being affected by the positional accuracy of the counter electrode, or the material property variation and thickness variation of the recording medium.

In addition, as described above, since the electric field can be made small, a strong electric field can be formed in a small area, and as a result, the formed liquid droplets can be miniaturized. As a result, when liquid droplets are used as ink, it is possible to make a high-resolution printed image.

Furthermore, as described above, since the concentration area of the charge is substantially the same size as the meniscus area of the fluid, the movement time of the charge in the meniscus area does not affect the discharge responsiveness, and the droplet discharge can be improved. Speed (printing speed when the droplet is ink).

In addition, since the charge concentration region is substantially the same size as the meniscus region of the fluid, it is not necessary to form a strong electric field in a wide meniscus region. Therefore, it is not necessary to arrange the counter electrode with high precision in order to form a strong electric field in a wide meniscus region as in the past, and the dielectric constant and thickness of the recording medium do not affect the arrangement of the counter electrode.

Therefore, in the electrostatic attraction type fluid ejection device, the degree of freedom in the arrangement of the opposing electrodes increases. That is, the degree of freedom in design of the electrostatic attraction type fluid ejection device increases. As a result, it is possible to print on a recording medium that has been difficult to use without being affected by the dielectric constant and thickness, and a fluid ejection device with good versatility can be realized.

Therefore, by using the electrostatic attraction type fluid ejection device having the above structure, it is possible to realize a device that satisfies both high resolution and safety and has good versatility.

Here, as the above-mentioned fluid, in addition to simple water, oil, etc., colored liquid ink containing dye or pigment as fine particles, or ink containing a wiring material (conductive fine particles such as silver or copper) that forms a circuit board can also be used. solution etc.

For example, when ink is used as the fluid, high-definition printing is possible, and when a solution containing wiring materials for circuit boards is used as the fluid, ultra-high-definition circuits can be formed with extremely narrow wiring. , can make the fluid discharge stably.

Furthermore, since the applied voltage control unit controls the voltage applied to the fluid so that the amount of charge induced in the liquid droplet of the fluid immediately after being discharged from the fluid discharge hole becomes equivalent to that of the liquid droplet. 90% of the limit charge amount, thus preventing the discharge caused by the reduction of the surface area of the droplets due to the drying of the discharged droplets, and at the same time preventing the reduction of the vapor pressure caused by the electrification of the droplets.

This reduces the drying time of the discharged liquid droplets (the time until the solvent of the liquid droplets evaporates completely), and eliminates the variation in the size of the dot diameter of the liquid droplets that reach the landing point.

In addition, since the drying time of the discharged liquid droplets becomes longer, it is possible to reduce the change in the diameter of the liquid droplets before they are ejected, that is, the amount of liquid droplets. As a result, since the environmental conditions such as air resistance and ambient humidity experienced by the flying droplets are uniform for each droplet, the accuracy of the landing of the droplets can be improved, and the variation of the droplets at the time of landing can be suppressed.

Furthermore, since the drying time of the discharged liquid droplets is prolonged, even if the diameter of the discharged liquid droplets is as small as φ5 μm, the liquid droplets can reach the landing point without being dried.

Therefore, by using the electrostatic attraction type fluid ejection device configured as described above, it is possible to stably discharge fine liquid droplets and reach the landing point with high precision.

In order to reduce the amount of charge induced in a fluid droplet immediately after being discharged from the fluid discharge hole to 90% or less of the charge amount corresponding to the Rayleigh limit of the droplet, the following method can be considered.

That is, the electrostatic attraction type fluid ejection device of the present invention, in order to solve the above-mentioned problems, the fluid charged by the application of voltage is discharged from the fluid discharge hole of the nozzle made of insulating material in the state of liquid droplets under electrostatic attraction, and has the ability to apply The applied voltage control unit that controls the voltage of the fluid in the nozzle sets the diameter of the fluid discharge hole of the nozzle to be equal to or less than the droplet diameter of the fluid immediately after discharge, and the applied voltage control unit applies The voltage on the fluid is controlled so that the amount of charge induced in the liquid droplet of the fluid immediately after being discharged from the fluid discharge hole becomes equivalent to that caused by the maximum electric field strength of the meniscus immediately after the fluid is discharged. The charge amount is below the Rayleigh limit at the droplet diameter.

The applied voltage control unit may control the voltage applied to the fluid so that the amount of charge induced in the fluid droplet immediately after being discharged from the fluid discharge hole becomes equivalent to the Rayleigh value of the droplet. More than 60% of the limit charge.

In general, the vapor pressure of a charged droplet is reduced by the amount of charge (charge amount) charged on the surface of the droplet, and if the charge amount is too small, there is no effect on relaxation of evaporation. Specifically, when the charge amount is less than 60% of the charge amount corresponding to the Rayleigh limit of the droplet, there is no influence on the mitigation of droplet evaporation.

Therefore, it is preferable to set the charge amount induced in the fluid droplet immediately after being discharged from the fluid discharge hole to 60% or more and 90% or less of the charge amount corresponding to the Rayleigh limit of the droplet.

In order to make the charge amount induced in the fluid droplet immediately after being discharged from the fluid discharge hole be 60% or more of the charge amount corresponding to the Rayleigh limit of the droplet, the following method can be considered.

That is, the applied voltage control device controls the voltage applied to the fluid so that the amount of charge induced in the fluid droplet immediately after being discharged from the fluid discharge hole becomes the maximum value corresponding to the meniscus of the fluid. The electric field strength induces a charge amount greater than 0.8 times the Rayleigh limit under the droplet diameter shortly after the fluid is expelled.

The diameter of the fluid discharge hole of the nozzle is preferably set at φ5 μm or less, and more preferably the diameter of the fluid discharge hole of the nozzle is set at φ0.2 μm or more and φ4 μm or less.

In this case, by setting the diameter of the fluid discharge hole of the nozzle to φ5 μm or less, the electric field intensity is concentrated, the electric field concentration is extremely enhanced, and the maximum electric field intensity is increased. As a result, the charging efficiency of droplets can be improved. Furthermore, in order to improve the charging efficiency of the droplets, it is preferable to set the diameter of the fluid discharge hole of the nozzle to φ0.2 μm or more and φ4 μm or less. In this case, the concentration of the electric field is extremely enhanced, and the maximum electric field intensity is increased. As a result, fine liquid droplets having a small diameter can be stably discharged.

In addition, the electrostatic attraction type fluid ejection device of the present invention is configured such that the fluid charged by the application of a voltage is electrostatically attracted in a liquid droplet state from the fluid discharge hole of the nozzle made of an insulating material in accordance with the applied voltage. The speed is discharged to the recording medium, and there is an applied voltage control part that controls the voltage applied to the fluid in the nozzle. The diameter of the fluid discharge hole of the nozzle is set at φ8μm or less. The voltage of the fluid is controlled so that the average discharge velocity from the discharge of the fluid to the recording medium is 10 m/s or more and 40 m/s or less.

Therefore, in the present invention, the diameter of the nozzle is set to be approximately the same as the diameter of the front end portion of the Taylor cone shape formed in order to discharge a fluid having a droplet diameter smaller than the diameter of the fluid discharge hole of the nozzle in the prior art. Similarly, the electric field that needs to be formed in a large area can be formed in a small area in the conventional electrostatic attraction process of fluid.

Thereby, the voltage required for moving electric charges, that is, the voltage required for imparting a charge amount required for electrostatic attraction to the fluid can be significantly reduced. This eliminates the need for a conventional high voltage of 2000 volts, thereby improving the safety when using the fluid ejection device.

Moreover, by setting the diameter of the fluid discharge hole of the nozzle at φ8μm or less, the electric field intensity distribution can be concentrated near the discharge surface of the fluid discharge hole, and the distance variation from the opposite electrode to the fluid protrusion hole of the nozzle will not affect Electric field strength distribution.

As a result, stable fluid discharge can be performed without being affected by the positional accuracy of the counter electrode, or the material property variation and thickness variation of the recording medium.

In addition, as described above, since the electric field can be made small, a strong electric field can be formed in a small area, and as a result, the formed liquid droplets can be miniaturized. As a result, when liquid droplets are used as ink, it is possible to make a high-resolution printed image.

Furthermore, as described above, since the concentration area of the charge is substantially the same size as the meniscus area of the fluid, the movement time of the charge in the meniscus area does not affect the discharge responsiveness, and the droplet discharge can be improved. Speed (printing speed when the droplet is ink).

In addition, since the charge concentration region is approximately the same size as the meniscus region of the fluid, it is not necessary to form a strong electric field in a wide meniscus region. Therefore, it is not necessary to arrange the counter electrode with high precision in order to form a strong electric field in a wide meniscus region as in the past, and the dielectric constant and thickness of the recording medium do not affect the arrangement of the counter electrode.

Therefore, in the electrostatic attraction type fluid ejection device, the degree of freedom in the arrangement of the opposing electrodes increases. That is, the degree of freedom in design of the electrostatic attraction type fluid ejection device increases. As a result, it is possible to print on a recording medium that has been difficult to use without being affected by the dielectric constant and thickness, and a fluid ejection device with good versatility can be realized.

Therefore, by using the electrostatic attraction type fluid ejection device having the above structure, it is possible to realize a device that satisfies both high resolution and safety and has good versatility.

Here, as the above-mentioned fluid, in addition to simple water, oil, etc., colored liquid ink containing dye or pigment as fine particles, or ink containing a wiring material (conductive fine particles such as silver or copper) that forms a circuit board can also be used. solution etc.

For example, when ink is used as the fluid, high-definition printing is possible, and when a solution containing wiring materials for circuit boards is used as the fluid, ultra-high-definition circuits can be formed with extremely narrow wiring. , can make the fluid discharge stably.

Moreover, the voltage applied to the fluid is controlled by the applied voltage control unit so that the average discharge speed during the period from when the fluid is discharged to when it reaches the recording medium is 10 m/s or more and 40 m/s or less. Due to the influence of drying during the flight of the fluid, as a result, the accuracy of the droplet landing on the recording medium can be improved, and the deviation of the diameter of the droplet landing point can be suppressed, and the electric field intensity at the meniscus can be prevented. Occurrence of atomization of the discharged liquid droplets caused by the impact can be stably discharged.

Here, if the average discharge speed of the fluid reaches the recording medium is less than 10m/s, the landing accuracy is poor, and the discharge stability is also poor, so the diameter of the droplet's landing spot varies. In addition, if the average discharge velocity during the period when the fluid reaches the recording medium is greater than 40m/s, a high voltage is required, so the electric field strength at the meniscus becomes very strong, and the discharged droplets are frequently atomized and cannot be discharged stably. droplet.

Therefore, like the electrostatic attraction type fluid ejection device of the above-mentioned structure, by making the average discharge velocity during the period from the fluid discharge to the recording medium to be 10 m/s or more and 40 m/s or less, the liquid droplets can be stably flew, and as a result , can improve the drop point accuracy, and can suppress the deviation of the droplet point diameter deviation.

The diameter of the fluid discharge hole of the nozzle is preferably set at φ5 μm or less, and more preferably the diameter of the fluid discharge hole of the nozzle is set at φ0.2 μm or more and φ4 μm or less.

In this case, by setting the diameter of the fluid discharge hole of the nozzle to φ5 μm or less, the electric field intensity is concentrated, the electric field concentration is extremely enhanced, and the maximum electric field intensity is increased. As a result, the charging efficiency of droplets can be improved. Furthermore, in order to improve the charging efficiency of the droplets, it is preferable to set the diameter of the fluid discharge hole of the nozzle to φ0.2 μm or more and φ4 μm or less. In this case, the concentration of the electric field is extremely enhanced, and the maximum electric field intensity is increased. As a result, fine liquid droplets having a small diameter can be stably discharged.

In addition, the electrostatic attraction type fluid ejection device configured as described above can also be realized by the following configuration.

That is, the electrostatic attraction type fluid ejection device of the present invention is configured such that a fluid charged by application of a voltage is electrostatically attracted in a liquid droplet state from a fluid discharge hole of a nozzle made of an insulating material in accordance with an applied voltage. The speed is discharged to the recording medium, and there is an applied voltage control unit that controls the voltage applied to the fluid in the nozzle, and the diameter of the fluid discharge hole of the nozzle is set to be equal to or less than the droplet diameter of the fluid immediately after discharge. The applied voltage control unit may control the voltage applied to the fluid so that the average discharge speed from the discharge of the fluid to the recording medium is 10 m/s or more and 40 m/s or less.

In addition, the electrostatic attraction type fluid ejection device of the present invention is configured to discharge a fluid containing fine particles and charged by applying a voltage in the state of droplets under electrostatic attraction from a fluid discharge hole of a nozzle made of an insulating material. The diameter of the fluid discharge hole is set below φ8μm, and the particle size of the microparticles contained in the fluid is below φ30nm.

Therefore, in the present invention, the diameter of the nozzle is set to be approximately the same as the diameter of the front end portion of the Taylor cone shape formed in order to discharge a fluid having a droplet diameter smaller than the diameter of the fluid discharge hole of the nozzle in the prior art. Similarly, the electric field that needs to be formed in a large area can be formed in a small area in the conventional electrostatic attraction process of fluid.

Thereby, the voltage required for moving electric charges, that is, the voltage required for imparting a charge amount required for electrostatic attraction to the fluid can be significantly reduced. This eliminates the need for a conventional high voltage of 2000 volts, and improves the safety when using the fluid ejection device.

Moreover, the diameter of the fluid discharge hole of the nozzle is set below φ8 μm, so that the electric field intensity distribution can be concentrated near the discharge surface of the fluid discharge hole, and the distance variation from the opposite electrode to the fluid protrusion hole of the nozzle will not affect the electric field. intensity distribution.

As a result, stable fluid discharge can be performed without being affected by the positional accuracy of the counter electrode, or the material property variation and thickness variation of the recording medium.

In addition, as described above, since the electric field can be made small, a strong electric field can be formed in a small area, and as a result, the formed liquid droplets can be miniaturized. As a result, when liquid droplets are used as ink, it is possible to make a high-resolution printed image.

Furthermore, as described above, since the concentration area of the charge is substantially the same size as the meniscus area of the fluid, the movement time of the charge in the meniscus area does not affect the discharge responsiveness, and the droplet discharge can be improved. Speed (printing speed when the droplet is ink).

In addition, since the charge concentration region is substantially the same size as the meniscus region of the fluid, it is not necessary to form a strong electric field in a wide meniscus region. Therefore, it is not necessary to arrange the counter electrode with high precision in order to form a strong electric field in a wide meniscus region as in the past, and the dielectric constant and thickness of the recording medium do not affect the arrangement of the counter electrode.

Therefore, in the electrostatic attraction type fluid ejection device, the degree of freedom in the arrangement of the opposing electrodes increases. That is, the degree of freedom in design of the electrostatic attraction type fluid ejection device increases. As a result, it is possible to print on a recording medium that has been difficult to use without being affected by the dielectric constant and thickness, and a fluid ejection device with good versatility can be realized.

Therefore, by using the electrostatic attraction type fluid ejection device having the above structure, it is possible to realize a device that satisfies both high resolution and safety and has good versatility.

Here, as the above-mentioned fluid, in addition to simple water, oil, etc., colored liquid ink containing dye or pigment as fine particles, or ink containing a wiring material (conductive fine particles such as silver or copper) that forms a circuit board can also be used. solution etc.

For example, when ink is used as the fluid, high-definition printing is possible, and when a solution containing wiring materials for circuit boards is used as the fluid, ultra-high-definition circuits can be formed with extremely narrow wiring. , can make the fluid discharge stably.

Furthermore, since the particle size of the fine particles contained in the above-mentioned fluid is φ30nm or less, the influence of the charging of the fine particles themselves can be reduced, and stable discharge can be performed even if the liquid droplets contain fine particles.

In addition, since the influence of the charging of the fine particles themselves can be reduced, the movement of the fine particles with small particle diameters does not slow down as in the conventional case of discharging fluid by using the charging of the fine particles. Therefore, even if the fluid containing fine particles is, for example, ink, the recording speed will not decrease.

In addition, the particle size of the fine particles contained in the fluid is preferably not less than φ1 nm and not more than φ10 nm.

In addition, the diameter of the fluid discharge hole of the nozzle may be set to φ0.2 μm or more and φ4 μm or less.

In this case, by setting the diameter of the fluid discharge hole of the nozzle to φ0.2 μm or more and φ4 μm or less, the electric field concentration is extremely enhanced and the maximum electric field intensity is increased. As a result, fine liquid droplets having a small diameter can be stably discharged.

In addition, the electrostatic attraction type fluid ejection device configured as described above can also be realized by the following configuration.

That is, the electrostatic attraction type fluid ejection device of the present invention is configured to discharge a fluid containing fine particles and charged by applying a voltage in the state of liquid droplets from the fluid discharge hole of a nozzle made of an insulating material under electrostatic attraction, and the The diameter of the fluid discharge hole of the nozzle is set to be equal to or less than the droplet diameter of the fluid immediately after discharge, and the particle size of the fine particles contained in the fluid may be φ30nm or less.

The specific implementation forms or examples constituted in the item of the best form for implementing the present invention are only to illustrate the technical content of the present invention, and should not be limited to such specific examples for narrow interpretation, and can be used in the present invention Various modifications can be made within the spirit of the invention and the scope of the claims described below.

[possibility of industrial use]

The electrostatic attraction type fluid ejection device of the present invention can be applied to an ink ejection head that discharges ink as a fluid for printing, and if a conductive fluid is used as the fluid, it can also be applied to a circuit board where fine wiring needs to be formed. In addition to wiring applications, it can also be applied to all printing applications, image formation, pattern formation of biological materials such as proteins or DNA, joint chemistry (Japanese: コンビナナトリアルケミストリ 1), etc., and can also be used in Patterning of color filters, organic EL (Electro luminescence: electroluminescence), FED (carbon tube (Japanese: カ一ボンナノチユーブ) patterning), ceramic patterning.

Claims (37)

1. An electrostatic attraction type fluid ejection device that discharges a fluid charged by applying a voltage in the state of liquid droplets from a fluid discharge hole of a nozzle made of an insulating material under electrostatic attraction, characterized in that, The diameter of the fluid discharge hole of the nozzle is set at φ8 μm or less. 2. The electrostatic attraction fluid ejection device of claim 1, wherein: In order to adjust the amount of liquid droplets discharged from the fluid discharge hole, there is an applied voltage control device that controls the voltage applied to the fluid, The applied voltage control device controls the voltage applied to the fluid so that the amount of fluid droplets immediately after being discharged from the fluid discharge hole is 1 Pl or less. 3. The electrostatic attraction type fluid ejection device according to claim 1, wherein the diameter of the fluid discharge hole of the nozzle is set at φ0.2 μm or more and φ4 μm or less. 4. The electrostatic attraction type fluid ejection device according to claim 2, wherein the applied voltage control means controls the voltage applied to the fluid so that the diameter of the liquid droplet immediately after being discharged from the fluid discharge hole becomes The diameter of the fluid discharge hole is not less than 1.5 times and not more than 3 times. 5. The electrostatic attraction type fluid ejection device according to claim 2, wherein the applied voltage control means controls the voltage applied to the fluid so that the diameter of the liquid droplet immediately after being discharged from the fluid discharge hole becomes The diameter of the fluid discharge hole is not less than 1.5 times and not more than 2 times. 6. An electrostatic attraction type fluid ejection device that discharges a fluid charged by applying a voltage in the state of liquid droplets from a fluid discharge hole of a nozzle made of an insulating material under electrostatic attraction, characterized in that, The diameter of the fluid discharge hole of the nozzle is set to be equal to or less than the droplet diameter of the fluid immediately after discharge. 7. The electrostatic attraction fluid ejection device of claim 6, wherein: In order to adjust the amount of liquid droplets discharged from the fluid discharge hole, there is an applied voltage control device that controls the voltage applied to the fluid, The applied voltage control device controls the voltage applied to the fluid so that the droplet amount of the fluid immediately after being discharged from the fluid discharge hole is 1 Pl or less. 8. The electrostatic attraction type fluid ejection device according to claim 6, wherein the diameter of the fluid discharge hole of the nozzle is set to φ0.2 μm or more and φ4 μm or less. 9. The electrostatic attraction type fluid ejection device according to claim 7, wherein the applied voltage control means controls the voltage applied to the fluid so that the diameter of the liquid droplet immediately after being discharged from the fluid discharge hole becomes The diameter of the fluid discharge hole is not less than 1.5 times and not more than 3 times. 10. The electrostatic attraction type fluid ejection device according to claim 7, wherein the applied voltage control means controls the voltage applied to the fluid so that the diameter of the liquid droplet immediately after being discharged from the fluid discharge hole becomes The diameter of the fluid discharge hole is not less than 1.5 times and not more than 2 times. 11. An electrostatic attraction type fluid ejection device that discharges a fluid charged by applying a voltage in the state of liquid droplets from a fluid discharge hole of a nozzle made of an insulating material under electrostatic attraction, characterized in that, having an applied voltage control means for controlling the voltage applied to the fluid in the nozzle, The diameter of the fluid discharge hole of the nozzle is set at φ8μm or less, The applied voltage control means controls the voltage applied to the fluid so that the amount of charge induced in a droplet of the fluid immediately after being discharged from the fluid discharge hole becomes equivalent to the Rayleigh limit charge of the droplet. less than 90% of the amount. 12. The electrostatic attraction type fluid ejection device according to claim 11, wherein the applied voltage control means controls the voltage applied to the fluid so that the fluid immediately after being discharged from the fluid discharge hole The amount of electric charge induced in the droplet becomes 60% or more of the Rayleigh limit charge amount of the droplet. 13. The electrostatic attraction type fluid ejection device according to claim 11, wherein the diameter of the fluid discharge hole of the nozzle is set to φ5 μm or less. 14. The electrostatic attraction type fluid ejection device according to claim 11, wherein the diameter of the fluid discharge hole of the nozzle is set at φ0.2 μm or more and φ4 μm or less. 15. An electrostatic attraction type fluid ejection device, which discharges a fluid charged by applying a voltage in the state of liquid droplets from a fluid discharge hole of a nozzle made of an insulating material under electrostatic attraction, characterized in that, having an applied voltage control means for controlling the voltage applied to the fluid in the nozzle, The diameter of the fluid discharge hole of the nozzle is set to be equal to or less than the droplet diameter of the fluid immediately after discharge, The applied voltage control means controls the voltage applied to the fluid so that the amount of charge induced in the fluid droplet immediately after being discharged from the fluid discharge hole becomes a maximum electric field corresponding to the meniscus. The intensity of the charge induced by the fluid discharge shortly after the droplet diameter falls below the Rayleigh limit. 16. The electrostatic attraction type fluid ejection device according to claim 15, wherein the applied voltage control means controls the voltage applied to the fluid so that the fluid immediately after being discharged from the fluid discharge hole The amount of charge induced in the liquid droplet is 0.8 times or more the Rayleigh limit charge amount corresponding to the droplet diameter immediately after the fluid is discharged due to the maximum electric field strength of the meniscus. 17. The electrostatic attraction type fluid ejection device according to claim 15, wherein the diameter of the fluid discharge hole of the nozzle is set to φ5 μm or less. 18. The electrostatic attraction type fluid ejection device according to claim 15, wherein the diameter of the fluid discharge hole of the nozzle is set to φ0.2 μm or more and φ4 μm or less. 19. An electrostatic attraction type fluid ejection device, in which a fluid charged by applying a voltage is electrostatically attracted to a liquid droplet from a fluid discharge hole of a nozzle made of an insulating material at a speed corresponding to the applied voltage. The recording medium is discharged, characterized in that, having an applied voltage control means for controlling the voltage applied to the fluid in the nozzle, The diameter of the fluid discharge hole of the nozzle is set at φ8μm or less, The applied voltage control device controls the voltage applied to the fluid so that an average discharge speed from when the fluid is discharged to when it reaches the recording medium is 10 m/s or more and 40 m/s or less. 20. The electrostatic attraction type fluid ejection device according to claim 19, wherein the diameter of the fluid discharge hole of the nozzle is set to φ5 μm or less. 21. The electrostatic attraction type fluid ejection device according to claim 19, wherein the diameter of the fluid discharge hole of the nozzle is set to φ0.2 μm or more and φ4 μm or less. 22. An electrostatic attraction type fluid ejection device, in which a fluid charged by applying a voltage is electrostatically attracted to a liquid droplet from a fluid discharge hole of a nozzle made of an insulating material at a speed corresponding to the applied voltage. The recording medium is discharged, characterized in that, having an applied voltage control means for controlling the voltage applied to the fluid in the nozzle, The diameter of the fluid discharge hole of the nozzle is set to be equal to or less than the droplet diameter of the fluid immediately after discharge, The applied voltage control device controls the voltage applied to the fluid so that an average discharge speed from when the fluid is discharged to when it reaches the recording medium is 10 m/s or more and 40 m/s or less. 23. The electrostatic attraction type fluid ejection device according to claim 22, wherein the diameter of the fluid discharge hole of the nozzle is set to φ5 μm or less. 24. The electrostatic attraction type fluid ejection device according to claim 22, wherein the diameter of the fluid discharge hole of the nozzle is set to φ0.2 μm or more and φ4 μm or less. 25. An electrostatic attraction type fluid ejection device, which discharges a fluid containing fine particles and charged by applying a voltage in the state of droplets under electrostatic attraction from a fluid discharge hole of a nozzle made of an insulating material, characterized in that, The diameter of the fluid discharge hole of the nozzle is set below φ8μm, The particle size of the fine particles contained in the fluid is φ30nm or less. 26. The electrostatic attraction type fluid ejection device according to claim 25, wherein the particle size of the fine particles contained in the fluid is not less than φ1 nm and not more than φ10 nm. 27. The electrostatic attraction type fluid ejection device according to claim 25, wherein the diameter of the fluid discharge hole of the nozzle is set at φ0.2 μm or more and φ4 μm or less. 28. An electrostatic attraction type fluid ejection device that discharges a fluid containing fine particles and charged by applying a voltage in the state of droplets under electrostatic attraction from a fluid discharge hole of a nozzle made of an insulating material, characterized in that, The diameter of the fluid discharge hole of the nozzle is set to be equal to or less than the droplet diameter of the fluid immediately after discharge, The particle size of the fine particles contained in the fluid is φ30nm or less. 29. The electrostatic attraction type fluid ejection device according to claim 28, wherein the particle size of the fine particles contained in the fluid is not less than φ1 nm and not more than φ10 nm. 30. The electrostatic attraction fluid ejection device according to claim 28, wherein the diameter of the fluid discharge hole of the nozzle is set at φ0.2 μm or more and φ4 μm or less. 31. An electrostatic attraction type fluid ejection device that discharges a fluid charged by applying a voltage in the state of liquid droplets under electrostatic attraction from a fluid discharge hole of a nozzle made of an insulating material, characterized in that, The diameter of the fluid discharge hole of the nozzle is set to be equal to or less than the droplet diameter of the fluid immediately after discharge, having: electrodes for applying a voltage to the fluid; and a process control section for controlling the voltage applied to the electrodes in order to adjust the amount of liquid droplets discharged from the fluid discharge holes, The flow control unit controls the voltage applied to the electrodes so that the droplet volume of the fluid immediately after being discharged from the fluid discharge hole is 1 Pl or less. 32. An electrostatic attraction type fluid ejection device that discharges a fluid charged by applying a voltage in the state of liquid droplets under electrostatic attraction from a fluid discharge hole of a nozzle made of an insulating material, characterized in that, The diameter of the fluid discharge hole of the nozzle is set to be below φ8μm, with: electrodes for applying a voltage to the fluid; and a process control section for controlling the voltage applied to the electrodes in order to adjust the amount of liquid droplets discharged from the fluid discharge holes, The flow control unit controls the voltage applied to the electrodes so that the droplet volume of the fluid immediately after being discharged from the fluid discharge hole is 1 Pl or less. 33. An electrostatic attraction type fluid ejection device that discharges a fluid charged by applying a voltage in the state of liquid droplets under electrostatic attraction from a fluid discharge hole of a nozzle made of an insulating material, characterized in that, The diameter of the fluid discharge hole of the nozzle is set to be below φ8μm, with: electrodes for applying a voltage to the fluid; and a process control section for controlling the voltage applied to the electrodes in order to adjust the amount of liquid droplets discharged from the fluid discharge holes, The flow control unit controls the voltage applied to the electrodes so that the amount of charge induced in a droplet of the fluid immediately after being discharged from the fluid discharge hole becomes a charge corresponding to the Rayleigh limit of the droplet. less than 90% of the amount. 34. An electrostatic attraction type fluid ejection device that discharges a fluid charged by applying a voltage in the state of liquid droplets under electrostatic attraction from a fluid discharge hole of a nozzle made of an insulating material, characterized in that, The diameter of the fluid discharge hole of the nozzle is set to be equal to or less than the droplet diameter of the fluid immediately after discharge, having: electrodes for applying a voltage to the fluid; and a process control section for controlling the voltage applied to the electrodes in order to adjust the amount of liquid droplets discharged from the fluid discharge holes, The flow control unit controls the voltage applied to the electrodes so that the amount of charges induced in the fluid droplets immediately after being discharged from the fluid discharge hole becomes a maximum electric field intensity corresponding to the meniscus. The amount of charge induced by the fluid discharge shortly after the droplet diameter is below the Rayleigh limit. 35. An electrostatic attraction type fluid ejection device, in which a fluid charged by applying a voltage is electrostatically attracted to a liquid droplet from a fluid discharge hole of a nozzle made of an insulating material at a speed corresponding to the applied voltage. The recording medium is discharged, characterized in that, The diameter of the fluid discharge hole of the nozzle is set below φ8 μm, with: electrodes for applying a voltage to the fluid; and a process control section for controlling the voltage applied to the electrodes in order to adjust the amount of liquid droplets discharged from the fluid discharge holes, The flow control unit controls the voltage applied to the electrodes so that an average discharge speed from when the fluid is discharged to when it reaches the recording medium is 10 m/s or more and 40 m/s or less. 36. An electrostatic attraction type fluid ejection device, in which a fluid charged by applying a voltage is recorded in the state of liquid droplets from a fluid discharge hole of a nozzle made of an insulating material at a speed corresponding to the applied voltage under electrostatic attraction media discharge, characterized by, The diameter of the fluid discharge hole of the nozzle is set to be equal to or less than the droplet diameter of the fluid immediately after discharge, having: electrodes for applying a voltage to the fluid; and a process control section for controlling the voltage applied to the electrodes in order to adjust the amount of liquid droplets discharged from the fluid discharge holes, The flow control unit controls the voltage applied to the electrodes so that an average discharge speed from when the fluid is discharged to when it reaches the recording medium is 10 m/s or more and 40 m/s or less. 37. An electrostatic attraction type ink ejection device that discharges ink charged by applying a voltage in the state of liquid droplets from an ink discharge hole of a nozzle made of an insulating material under electrostatic attraction, characterized in that, The diameter of the ink discharge hole of the nozzle is set to be equal to or less than the diameter of the ink droplet immediately after discharge.

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