KR20060022367A - Droplet jetting method and device using electrostatic field - Google Patents

Abstract

The present invention relates to an ink injection method and an ink injection device using an electrostatic field,

A method of forming and spraying ink droplets by supplying ink or ink containing charged particles to a nozzle in a state in which an electric field direction is set toward the discharge port of the nozzle, and a laminate in which electrode layers and insulating layers are laminated in the nozzle direction. Since the part relates to the ink jetting device installed

Ink spraying is easily obtained even without a heater device, a diaphragm vibrating device, or the like, and ink spraying is performed using an electrostatic field, so that the ink has a low impact and excellent printing quality.

Description

Ink jetting method using electrostatic field and ink jetting device {DROPLET JETTING METHOD AND DEVICE USING ELECTROSTATIC FIELD}

1 is a front sectional view showing the structure of an ink ejecting apparatus using the electrostatic field according to the present invention.

2 is a conceptual diagram showing the principle of causing an electric charge to a particle.

3 is a diagram showing an electric field applied near the oil surface according to one embodiment of the present invention.

4 is a conceptual diagram illustrating the principle of the formation of an electrostatic field in accordance with the present invention.

Fig. 5 is a conceptual diagram showing the principle of adjusting the voltage applied to the nozzle of the ink ejection apparatus according to the present invention.

Fig. 6 is a view showing the coating and ink spraying states of the nozzle inner surface of Fig. 1, (a) before voltage supply, and (b) after voltage supply.

7 is a conceptual diagram for calculating and estimating the minimum allowable time of the adjustment period when adjusting the voltage applied to the nozzle of the ink jetting apparatus according to the present invention.

Fig. 8 is a time-phase situation diagram for adjusting the voltage applied to the nozzle of the ink ejection apparatus in order to induce ink ejection according to the present invention.

※ Explanation of Major Drawings

110 ... chamber

200 ... print head

210 ... Nozzle

220. Electrode layer

230 ... insulation layer

300 ... ink particles

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink ejection method and an ink ejection apparatus using an electrostatic field, and more particularly, to an ink ejection method and an ink ejection apparatus for ejecting ink by generating a specific electric field on an ink surface near a nozzle.

The ink jetting device used in a conventional ink jet printer or the like has a structure in which ink is ejected by using a heater device or a diaphragm vibrator provided in the ink jet head.

An example of an inkjet printer using a heater is briefly described as follows.

First, when an electric current flows through the electrode provided with a heater part, heat generate | occur | produces in a heater part, and this heat | fever is in turn conducted to the protective layer by which the ink was wet. When the ink is heated by the conducted heat, a bubble is formed, and the bubble is pushed through the opening formed in the nozzle plate because a volume change occurs in the ink of the upper layer portion.

Accordingly, the ink that is expanded and discharged out of the opening of the nozzle plate is sprayed on paper or the like in the form of droplets by the surface tension.

However, such a conventional ink spraying device has a problem in that a thermal change may occur in the ink due to a heating action for bubble generation and the like, and the print quality is deteriorated due to the shocking volume inside.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an ink spraying method and an ink spraying device capable of improving print quality by enabling flow control of a new concept using an electrostatic field.

In order to achieve the above object, the ink injection method using the electrostatic field according to the present invention,

In the state where the electric field direction is set toward the discharge port of the nozzle, ink droplets are formed and sprayed by supplying ink or ink containing charged particles to the nozzle.

In addition, the ink injection value including the nozzle according to the present invention,

It is characterized in that a lamination part in which an electrode layer and an insulating layer are laminated in the nozzle direction is provided.

At this time, it is preferable that each of the stacked electrode layers is connected to an independent power source for controlling the direction of the electric field.

It is also desirable to control the formation of droplets through a coating in which the hydrophilic and hydrophobic materials are continuously configured inside the nozzle.

In addition, it is possible to control the formation and ejection of ink droplets by adjusting the magnitude of the voltage applied to each independent power source over time.

On the other hand, another ink injection method using the electrostatic field according to the present invention, by setting the independent electric field direction in each of the plurality of nozzles by supplying ink or ink containing charged particles to the plurality of nozzles Independent ink droplets are formed and sprayed.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 shows an ink injection apparatus using an electrostatic field according to the present embodiment.

As shown in FIG. 1, an ink jetting device using an electrostatic field according to the present embodiment includes a print 110 including a chamber 110 for storing ink 300 and a nozzle 210 formed in the chamber 110. It consists of a head.

In addition, a lamination part in which the electrode layer 220 and the insulating layer 230 are alternately stacked in the extending direction is provided around the nozzle 210. The material of the electrode layer 220 may be made of aluminum (Al), and the insulating layer 230 may be formed of Si ₃ N _4, or the like.

In addition, the electrode layers 220 are connected to independent power sources, respectively, the size of the electrode layers 220 may be set according to a predetermined control signal, and the electric field direction around the nozzle 210 may be adjusted to a predetermined value. Consists of.

In addition, as shown in FIG. 6, the inner surface of the nozzle 210 may be coated with a coating 211 in which a hydrophilic material and a hydrophobic material are continuously formed. As the hydrophilic material, a material such as SiO ₂ may be used, and as the hydrophobic material, Teflon or silicon may be used. Accordingly, droplet formation can be controlled using instability when transitioning from hydrophilic to hydrophobic. In this unstable state, an external electric field exerts a repulsive force on the meniscus (the concave surface of the ink surface) to tear off the droplets.

On the other hand, as shown in FIG. 4, each of the stacked electrode layers 220 is connected to a voltage gradually increasing toward the discharge port of the nozzle 210.

Hereinafter, the operation and principle of the present invention will be described.

Briefly, the present invention is characterized in that the fluid is naturally discharged by applying different voltages to electrodes stacked around the nozzle in a state in which a nanofluid having general ink or electric charge is contained in the chamber.

In particular, when the nanofluid in the chamber has a charge, it may be configured by a triboelectric charging method or a contact charging method, as shown in Figure 2, briefly described as follows.

(1) triboelectric charging (FIG. 2 (a))

When electrically neutral insulators with different electrostatic properties come into contact, they transfer charge from plane to plane in order to reach thermodynamic equilibrium (ie, to reduce chemical potential differences). At this time, if the surface is quickly separated, such as slippage or friction, excess charge remains on the surface. The particles are filled by collision with a rotary stirrer which is used to disperse the powder. Therefore, the triboelectric charging in liquid nitrogen has the advantage that the filling process and the dispersion of the powder can be performed together using a high shear agitating system.

(2) contact charging (FIG. 2 (b))

Suspensions are blown out through a lattice-shaped metal electrode connected to a high voltage supply, and due to the potential difference, charges are transferred from the electrode to the particles.

Through research, triboelectric charging was more effective at charging more surface charge per particle than contact charging.

Next, with reference to Figures 3 and 4 will be described the principle that the actual ink is ejected from the nozzle.

The electric field formed by the nozzle part depends on the arrangement of the driving electrodes and the magnitude of the voltage. The magnitude and direction of the electrostatic force also varies depending on the position of the fluid and the shape of the oil surface. The appropriate model was chosen.

In this model, the bottom of the chamber at the bottom is the reference potential, and three electrodes of the nozzle circumference are stacked at regular intervals to adjust the voltage of each electrode. At this time, the magnitude and direction of the electric field are determined at the central portion of the nozzle inlet in accordance with the voltage applied to the electrode. As shown in FIG. 3, assuming that the charging aspect of the nanoparticles distributed in the fluid is in the form of a cathode, the direction of the electric field is entirely located below the nozzle inlet to induce the transport of the particles out of the nozzle. The electrode must be higher toward the top because it must be formed inside the chamber.

Here, the main area for moving the fluid is below the oil level, due to the fluid medium characteristics, the electric field is smaller than the air area outside the nozzle. In particular, the large electric field outside the oil surface shown in the drawing does not play a significant role in fluid movement.

Fig. 4 shows an aspect of the electric field applied to the fluid when various voltages are applied to the electrode around the nozzle inlet.

Fig. 4 (a) is a typical voltage condition which causes the fluid to flow from the inside of the chamber to the outlet, and in particular, the strength of the electric field at the nozzle outlet is increased so that the fluid receives a greater force.

Fig. 4 (b) shows a case where all three electrodes are connected with a negative voltage to change the direction of the electric field by 180 degrees. Here, the negative voltage was made smaller toward the upper layer of the electrode, so that a small portion of the fluid pulled up to the discharge port surface was separated so as to be discharged into the air.

If the representative two types of electrode operation is a basic control process, ink droplet formation and discharge are naturally induced.

5, 7 and 8 illustrate the principle of controlling the formation and injection of ink droplets by adjusting the magnitude of the voltage applied to each independent power source over time. This is briefly described below.

5 shows an example of the concept of devices applied for the regulation of the voltage according to the invention.

The basic method of voltage regulation is automatic voltage regulation by computer program. As shown in Fig. 4, the transfer and ejection of ink droplets are performed in a very short time. The experiment and development of a device for controlling the ejection, and the use of a commercial computer for application to an application system and mass production using a small microprocessor Anger is a prerequisite.

First, the entire process is formed by a program in a computer and the voltage of each independent voltage device is set through an external interface. This is implemented digitally through selectors, buffers, and decoders. Through this, after changing the voltage value setting of each voltage device, the voltage is finally applied simultaneously to each of the laminated electrode parts proposed by the present invention.

The above-described process can be carried out collectively in one command function of the main program, and as an optional parameter of this command function, it is possible to change the adjustment and setting time of each independent voltage. In this way, each individual power supply can be freely and actively controlled.

In addition, in order to confirm the operation result according to this and to find a more optimal state setting, an apparatus for photographing the ejection operation state of the nozzle at high speed and feeding the state back to the computer is also applied. In this case, a high speed photographing apparatus may be used in an experiment for development, and when applied to an actual application apparatus, the sensor may be implemented.

At this time, it is necessary to estimate the minimum sustainable time of voltage regulation possible in the nozzle structure proposed in the present invention. This is shown in FIG.

First, the electrodes of the stacked structure can be simulated with the capacitance of the basic circuit device, and are obtained according to a well-known formula for calculating capacitance values. In addition, the approximate resistance according to the conductor structure from the outside of the nozzle to the electrode is obtained according to a known formula, and then the time constant value according to the ratio of the voltage difference applied in the simulation is used to calculate the voltage generated when the voltage difference occurs. Find the rise or fall delay time.

According to the result, it can be predicted that the delay time is approximately 0.285 (microsec), and that the voltage setting holding time is sufficiently larger than this, it does not have a great influence on the voltage regulation.

In addition, the voltage regulation frequency is estimated to be about 3.5 MHz or less, which seems to be a sufficiently large frequency compared with the flow mode of the actual ink liquid.

FIG. 8 illustrates an example of changing a voltage set in an independent power supply device through various steps to vary the direction and magnitude of an electric field to be made in FIG. 4 according to the theoretical and programmatic implementations illustrated in FIGS. 5 and 7. It is.

The stacked electrode of the ink nozzle proposed in the present invention has three layers, and the voltage waveform is set at each step based on the three electrodes. Step 1 obtains the oil level transfer to the inlet, Step 2 separates the droplet into small droplets, and Step 3 and Step 4 are set to restore the momentary discharge and the fluctuated oil level, and return to Step 1 again.

It is shown in FIG. 8 (b) that the distribution of electrostatic force applied to the nozzle inlet center is changed according to each of these steps.

Meanwhile, according to the present invention, an array ink spray method is also possible. For example, a plurality of independent ink droplets may be formed and jetted by supplying ink or ink containing charged particles to the plurality of nozzles by setting electric field directions that are independent of each other in the plurality of nozzles.

According to the present invention having the above-described configuration, there is an advantage that ink injection is easily obtained even without a heater device, a diaphragm vibrator, or the like.                     

In addition, since the ink is sprayed using the electrostatic field, there is an advantage that the ink is less impact and print quality is excellent.

Claims (6)

An ink ejection method using an electrostatic field, wherein ink droplets are formed and ejected by supplying ink or ink containing charged particles to the nozzle while the electric field direction is set toward the discharge port of the nozzle. An ink ejection apparatus comprising a nozzle for ejecting ink, An ink spraying device having a stacking portion in which an electrode layer and an insulating layer are stacked in a nozzle direction. The method of claim 2, Each of the stacked electrode layers is connected to a separate power source for controlling the direction of the electric field, the ink injection device using an electrostatic field. The method of claim 2, An ink spraying device for controlling droplet formation through a coating in which a hydrophilic material and a hydrophobic material are continuously formed in a nozzle.  The method of claim 3, An ink ejection apparatus for controlling the formation and ejection of ink droplets by adjusting the magnitude of the voltage applied to each independent power source over time. An array characterized in that a plurality of independent ink droplets are formed and sprayed by supplying ink or ink containing charged particles to the plurality of nozzles by setting independent electric field directions in the plurality of nozzles. Ink jet method.

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