KR100425326B1 - Inkjet printing head - Google Patents

Abstract

The disclosed inkjet printing head includes a chamber filled with ink supplied from an ink reservoir through a flow path, a chamber heater for generating a discharge pressure by heating the ink filled in the chamber to generate bubbles, and ink communicating with the chamber. A nozzle plate having a nozzle discharged therein; a flow path resistor for increasing flow resistance of ink passing through the flow path by reducing the cross-sectional area of the flow path; a flow path heater for heating the flow path; and a current in the chamber heater and the flow path heater. It is characterized by having a current supply line for supplying the flow path is opened and closed depending on whether or not the current is supplied to the flow path heater. According to this configuration, since the flow path can be selectively opened and closed by using the viscosity of the ink according to the temperature, it is possible to implement an inkjet printing head which prevents pressure loss and crosstalk phenomenon through the flow path and enables stable printing.

Description

Inkjet printing head {Inkjet printing head}

BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to inkjet printing heads, in particular improved inkjet printing to prevent the loss of discharge pressure generated in the chamber and to eliminate crosstalk phenomena affecting other adjacent chambers. It's about the head.

In general, an inkjet printing head refers to a device that converts electrical energy into thermal energy to generate bubbles, and discharges ink at a pressure due to expansion of the bubbles.

FIG. 1 schematically illustrates a structure of a conventional inkjet printing head, and FIG. 2 is a cross-sectional view taken along line AA ′ of FIG. 1.

1 and 2, the substrate 10 is filled with a chamber 12 filled with ink, an oil passage 14 connecting the ink reservoir (not shown) and the chamber 12, and filled in the chamber 12. A chamber heater 13 for heating ink and a metal wiring 15 for supplying electrical energy to the chamber heater 13 are provided. The nozzle plate 11 provided on the substrate 10 is provided with a nozzle 11a in communication with the chamber 12.

According to the ink ejection principle of the above structure, when the ink filled in the chamber 12 is heated by supplying electrical energy to the chamber heater 13 through the metal wiring 15, the temperature of the ink adjacent to the chamber heater 13 is increased. Bubble 16 rises locally. At this time, as the bubble 16 expands, the pressure in the chamber 12 rises and the ink droplet 17 is pushed out of the chamber 12 through the nozzle 11a by this pressure. Then, when the heat generation of the chamber heater 13 stops, the bubble 16 contracts and the ink droplet 17 is disconnected from the ink in the chamber 12. Then, the ink droplets 17 are transferred from the nozzle 11a to an ink receptor (not shown) such as paper and printed. When the bubble 16 expands and contracts, ink is supplied from the ink reservoir (not shown) to the chamber 12 through the flow passage 14 by the negative pressure generated in the chamber 12, thereby completing the next ink ejection preparation. .

However, in this configuration, since the flow passage 14 connected to the chamber 12 is always open, the pressure due to the expansion of the bubble leaks into the ink reservoir (not shown) through the flow passage 14. Therefore, in order to obtain an appropriate ink discharge pressure, it is necessary to generate a high pressure in consideration of such a pressure loss, thereby increasing the amount of heat generated by the chamber heater 13. In addition, a cross-talk phenomenon in which the leaked pressure affects the adjacent chamber 13 also occurs, which adversely affects stabilization of the tip of the nozzle 11a after the ink droplets are ejected.

In order to solve this problem, it is necessary to install a valve in the flow path to shut off the flow path when ink is discharged and open the flow path when filling the ink, but it is practically difficult to install the valve in the space within the fine flow path.

Therefore, in some cases, as shown in FIG. 3, the flow path heater 20 is installed in the flow path 14 to serve as a valve.

According to the configuration shown in FIG. 3, the bubble 21 is heated by heating the ink in the flow path 14 with the flow path heater 20 simultaneously with or slightly before the bubble 16 grows to eject the ink from the chamber 12. To form. Then, since the flow passage 14 is blocked by the bubble 21, the pressure generated in the chamber 12 does not leak toward the ink reservoir (not shown).

However, in such a configuration, there is a problem that the pressure change due to the generation and depression of bubbles in the flow passage 14 affects the adjacent chamber 12 so that the crosstalk phenomenon becomes more severe. This is because the flow passage 14 is closer to the other adjacent chamber 12 than the chamber 12. Further, after the ink is discharged, new ink must be filled into the chamber 12 through the flow passage 14. If bubbles generated in the flow passage 14 are not completely recessed at the same time as the discharge of the ink, the flow passage 14 is consequently. Since the cross sectional area of the ink is narrowed, it may interfere with refilling of the ink. Therefore, the time required for filling the ink is long, so that the maximum discharge frequency of the inkjet printing head is lowered.

The present invention was created to solve the above-described problems, by using the viscosity of the ink according to the temperature to selectively open and close the flow path to prevent pressure loss and crosstalk phenomenon through the flow path inkjet printing capable of stable printing The purpose is to provide a head.

1 is a view schematically showing an example of a conventional inkjet printing head.

2 is a cross-sectional view taken along line AA ′ of FIG. 1.

Figure 3 schematically shows another example of a conventional inkjet printing head.

4 illustrates an embodiment of an inkjet printing head according to the present invention.

5 is a cross-sectional view taken along line B-B 'of FIG.

FIG. 6 is a diagram showing another example of the flow path resistor of FIG. 4; FIG.

7 is a view showing another example of the flow heater of FIG.

8A to 8C are views sequentially showing an ink ejection operation by the inkjet printing head according to the present invention shown in FIG.

9 is a graph showing the timing of supplying electrical energy to the chamber heater and the flow path heater.

10 illustrates another embodiment of an inkjet printing head according to the present invention.

<Description of the symbols for the main parts of the drawings>

10,100 ...... substrate 11,110 ...... nozzle plate

12,120 ...... Chamber 13,130,230 ..... Chamber Heater

14,140 ...... Euro 15 ...... Metal wiring

150 ...... first current supply line 160 ...... second current supply line

20,170 ...... Euro Heater 180 ...... Bottleneck

190 ... isolated part

The inkjet printing head of the present invention for achieving the above object, the chamber is filled with ink supplied through the flow path from the ink reservoir; A chamber heater which forms a discharge pressure by heating the ink filled in the chamber to generate bubbles; A nozzle plate in communication with the chamber, the nozzle plate having a nozzle configured to discharge ink; A flow path resistor for increasing the flow resistance of the ink passing through the flow path by reducing the cross-sectional area of the flow path; A flow path heater for heating the flow path; And a current supply line for supplying current to the chamber heater and the flow path heater, wherein the flow path is opened and closed according to whether current is supplied to the flow path heater.

The flow path resistor includes a bottleneck portion extending from the wall forming the flow path to the inside of the flow path to narrow the cross-sectional area of the flow path, and may be an isolation portion for dividing the flow of ink passing through the flow path.

The flow path heater is formed to extend out of the flow path toward the ink reservoir so that ink flowing into the flow path can be preheated. In addition, the flow path heater may be formed by being divided into a plurality in the longitudinal direction of the flow path from the ink reservoir toward the chamber, wherein the flow path heater located in the ink reservoir side of the flow path heater formed by dividing into a plurality It is preferably formed extending out of the flow path toward the ink reservoir.

The current supply line includes a first current supply line for supplying current to the chamber heater, and a second current supply line for supplying current to the flow path heater.

The chamber heater may be formed of a material, for example, tungsten silicide, in which resistance increases as temperature increases. In this case, it is preferable that the current supply line sequentially heats the chamber and the flow path by connecting the chamber heater and the flow path heater in parallel with one current supply line.

According to the inkjet printing head according to the present invention, it is possible to obtain the same effect that the flow path is always closed by the flow path resistor, and when the current is supplied to the flow path heater, the viscosity of the ink in the flow path becomes low due to the heating action, so that the flow path resistor becomes In spite of this, the same effect can be obtained as the flow path is opened.

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

FIG. 4 illustrates an embodiment of an inkjet printing head according to the present invention, and FIG. 5 is a cross-sectional view taken along line BB ′ of FIG. 4.

As shown in FIGS. 4 and 5, an ink reservoir (not shown) and a chamber 120 are connected through a flow path 140, and a chamber heater (heater) for heating filled ink is provided on the bottom surface of the chamber 120. 130). The nozzle plate 110 is formed on the substrate 100 on which the chamber 120 and the flow path 140 are formed, and the nozzle 110a is formed in communication with the chamber 120 to discharge ink. The nozzle plate 110 serves as a top cover of the flow path 140 and the chamber 120.

The flow path 140 has a bottleneck portion 180 extending from the wall to the inside of the flow path 140 in order to narrow the cross-sectional area through which the ink passes, and serves as a flow path resistor. 4 and 5 illustrate a case in which the width of the flow path 140 is narrowed. However, the width of the flow path 140 may be narrowed, and the width of the flow path 140 may be narrowed. It is also possible to narrow it down at the same time. The bottleneck 180 may be formed in a part of the length direction of the flow path 140, and may be formed over the whole in the length direction of the flow path 140, thereby consequently narrowing the entire flow path. In addition, as shown in FIG. 6, the flow path resistor may be an isolation part 190 that reduces the cross-sectional area of the flow path 140 while dividing the flow of ink in the flow path 140.

The flow path heater 170 is for heating the ink in the flow path 140, and most preferably provided to surround the flow path 140. However, in this embodiment, since the flow path is difficult to manufacture, the substrate of the flow path 140 100) is provided on the side. In addition, the flow path heater 170 is preferably installed to extend out of the flow path 140 toward the ink reservoir (not shown) as shown in FIG. In addition, as shown in FIG. 7, the first flow path heater 171 and the second flow path heater 172 may be divided and installed in the longitudinal direction of the flow path 140, or may be divided into three or more. At this time, the first flow path heater 171 installed on the ink reservoir (not shown) is preferably installed to extend out of the flow path 140 toward the ink reservoir (not shown).

The first current supply line 150 and the second current supply line 160 supply current to the chamber heater 130 and the flow path heater 170, respectively.

Looking at Figures 8a to 8c now looks at the action by the embodiment shown in FIG.

First, when electrical energy is supplied to the chamber heater 130 through the first supply line 150, bubbles 210 are generated while the ink temperature near the chamber heater 130 increases. As the bubble 210 grows rapidly, the pressure of the ink in the chamber 120 rises. At this time, since the bottleneck portion 180 is formed in the flow path 140, the flow resistance of the ink in the flow path 140 is so large that it is as if the flow path 140 is closed. Therefore, the pressure generated by the bubble 210 is concentrated toward the nozzle 110a without being distributed toward the ink reservoir (not shown) through the flow passage 140. Thus, the ink in the chamber 120 is pushed out of the nozzle 110a to form the ink column 220 (FIG. 8A).

Next, when the supply of electrical energy to the chamber heater 130 is stopped, the bubble 210 begins to shrink as the ink temperature in the chamber 120 decreases due to heat transfer through the substrate 100 and the nozzle plate 110. do. Then, as the ink of the tip of the nozzle 110a is recessed toward the chamber 120, the ink column 221 connecting the ink droplet 221 pushed out of the nozzle 110 and the ink in the chamber 120 is broken, and the ink The droplet 221 is discharged out of the nozzle 110a to an ink receptor (not shown) such as paper (FIG. 8B).

Next, when the electric energy is supplied to the flow path heater 170 through the second supply line 160, the temperature of the ink in the flow path 140 rises. In general, the viscosity of the gas increases with temperature rise, but the viscosity of the fluid decreases with temperature rise. Therefore, the viscosity of the ink decreases as the temperature of the ink rises, and the flowability of the ink also increases. Then, ink flows through the flow path 140 as if the valve that was closed is opened. At this time, since the inside of the chamber 120 is in a negative pressure state due to the shrinking of the bubble 210, ink is supplied from the ink reservoir (not shown) to the chamber 120 through the flow path 140. Then, the tip portion of the nozzle 110a, which has been recessed as the ink is filled in the chamber 120, returns to stability and is ready for the next ejection operation. (FIG. 8C) As shown in FIG. If it extends out of the flow path 140 toward the ink reservoir (not shown), it is possible to raise the temperature of the ink more effectively.

FIG. 9 illustrates a timing chart for supplying electrical energy to the chamber heater 130 and the flow path heater 170. As shown, the chamber heater 130 is supplied with high energy in a short time to generate a strong bubble, and after the supply of electrical energy to the chamber heater 130 is finished, the euro heater (at a slight time interval t). 170 is energized. At this time, low energy is supplied to raise the temperature of the ink without generating bubbles in the flow path 140. The time interval t is determined by experiment as a time required for the ink droplets 221 to be separated from the nozzle 110a.

As described above, in order to discharge the ink, a series of processes such as bubble formation, ink pillar formation, bubble shrinkage, ink drop ejection, ink inflow into the chamber 120, and stabilization of the nozzle 110a tip in the chamber 120 are performed. In this process, the flow path 140 to be opened is only an ink inflow process, and the flow path 140 is preferably closed in other processes.

According to the inkjet printing head according to the present invention, the flow path 140 maintains a state similar to that closed by the bottleneck 180, and only draws ink by the flow heater 170 when supplying ink to the chamber 120. Since the state is opened by lowering the viscosity of the ink by heating, the effect as if the valve is present in the flow path 140 can be obtained. In addition, since the loss of pressure generated in the chamber 120 is small, efficient ink discharging is possible with little energy, and at the same time, crosstalk affecting adjacent chambers is also greatly reduced, so that the tip of the nozzle 110a is stabilized after ink discharging. Can also be shortened. Therefore, the maximum discharge frequency of the inkjet printing head can be improved.

10 shows another embodiment of an inkjet printing head according to the present invention. As shown, the chamber heater 230 used in this embodiment is made of a material whose resistance decreases with temperature, for example tungsten silicide. In addition, the chamber heater 230 and the flow path heater 170 are connected in parallel by one current supply line 250.

In this way, the current supplied through the current supply line 250 initially flows into the chamber heater 230 having a small resistance value, thereby raising the temperature of the chamber heater 230. Thus, bubbles grow to eject ink. However, since no current flows toward the flow path heater 170 or only a very small current flows, the ink temperature in the flow path 140 hardly rises. Therefore, the flow path 140 maintains the closed state while discharging the ink.

As the temperature of the chamber heater 230 increases, when the resistance value of the chamber heater 230 increases and becomes larger than the resistance value of the flow path heater 170, the current flows more to the flow path heater 170 so that the flow path 140. The temperature of ink in the inside rises. As a result, the viscosity of the ink is lowered, and the flow path 140 is opened. At this time, since the ink discharge in the chamber 120 is already finished, ink is supplied to the chamber 120 through the flow path 140 by the negative pressure caused by the contraction of the bubble. According to this configuration, it is possible to obtain the effect of supplying electrical energy to the chamber heater 230 and the flow path heater 170 at the timing as shown in FIG. 9 by one current supply line 250.

As described above, according to the inkjet printing head according to the present invention, the following effects can be obtained.

First, the flow path can be maintained in a state similar to that in which the flow path is always closed, but by heating the ink only when supplying ink to the chamber to lower the viscosity so that the flow path is in the same state as the flow path is opened. The effect can be obtained.

Second, since the pressure loss when discharging ink is small, efficient ink discharging is possible with little energy.

Third, since the crosstalk affecting the adjacent chamber is greatly reduced, the time for stabilizing the tip of the nozzle can be shortened, so that the maximum discharge frequency can be improved.

It is to be understood that the invention is not limited to that described above and illustrated in the drawings, and that more modifications and variations are possible within the scope of the following claims.

Claims (10)

A chamber in which ink supplied from the ink reservoir through the flow path is filled; A chamber heater which forms a discharge pressure by heating the ink filled in the chamber to generate bubbles; A nozzle plate in communication with the chamber, the nozzle plate having a nozzle configured to discharge ink; A flow path resistor for increasing the flow resistance of the ink passing through the flow path by reducing the cross-sectional area of the flow path; A flow path heater for heating the flow path; And a current supply line for supplying current to the chamber heater and the flow path heater, wherein the flow path is opened and closed according to whether current is supplied to the flow path heater. The method of claim 1, And the flow path resistor includes a bottleneck portion extending from the wall forming the flow path to the inside of the flow path to narrow the cross-sectional area of the flow path. The method of claim 1, The flow path resistor includes an isolator for dividing a flow of ink passing through the flow path. The method of claim 1, And the flow path heater extends toward the ink reservoir away from the flow path. The method of claim 1, The flow path heater, the inkjet printing head, characterized in that divided into a plurality formed along the longitudinal direction of the flow path. The method of claim 5, The flow path heater positioned in the ink reservoir side of the flow path heater formed by being divided into a plurality of ink jet printing head, characterized in that is formed to extend out of the flow path toward the ink reservoir. The method of claim 1, The current supply line, the first current supply line for supplying a current to the chamber heater; And a second current supply line for supplying current to the flow path heater. The method of claim 1, The chamber heater, the inkjet printing head, characterized in that formed of a material that increases the resistance as the temperature rises. The method of claim 8, The material of the chamber heater is tungsten silicide, the inkjet printing head. The method according to claim 8 or 9, The current supply line, the inkjet printing head, characterized in that for connecting the chamber heater and the flow path heater in parallel.