KR100327255B1 - Inkjet printhead - Google Patents

Abstract

The present invention relates to an inkjet printhead which makes it possible to easily eject ink even with a lower operating voltage by lowering the viscosity of ink ejected at the time of ejecting ink from a head using a piezoelectric driving method. In order to achieve the present invention, in the inkjet printhead configuration in which ink is forcibly ejected by deforming the piezoelectric body by a power input from the outside to change the volume in the chamber, the ink is introduced into the chamber by driving the piezoelectric body. The heating means is integrally provided in the flow path for outflowing the ink to the outside so that the ink can be heated up to the temperature required by the ink in the chamber immediately before the ejection of the ink by the piezoelectric body. The print quality can be improved. There is a characteristic to make it.

Description

Inkjet printheads {Inkjet printhead}

The present invention is to reduce the viscosity of the ink by the instantaneous heating during printing in the head using the piezoelectric drive method to minimize the spread of the ink on the paper immediately after the ejection speed and ejected to improve the print quality It relates to an inkjet printhead.

In general, inkjet printers are largely classified into thermal / bubble jet type and piezoelectric type according to the driving method.

The thermal and bubble jet method electrically heats the chamber so that ink in the chamber is injected through the nozzle by thermal expansion, and the piezoelectric method drives the diaphragm by deformation of the piezoelectric body, and the ink in the chamber is driven by the vibration force through the nozzle. To be injected.

On the other hand, the ink used in the printhead has a high viscosity in terms of evaporation during storage, spreadability in the paper immediately after discharge, and meniscus stability in the nozzle immediately after the discharge. It is more advantageous that the viscosity of the ink is low.

In other words, the ink stored in the head has a high viscosity to reduce the evaporation into the air, and also reduces the spread absorbed by the paper when it is discharged and touches the paper. The meniscus can be stabilized quickly after the droplets are ejected from the nozzle.

On the contrary, when the droplets are ejected, the lower the viscosity of the ink, the better the speed of the droplets, and the lower the output power is expected to discharge the ink, so that the operating voltage that drives the piezoelectric body can be maintained at a lower level. There is a number.

1 is a partially enlarged cross-sectional view showing an example of a printhead driven by the piezoelectric method, wherein reference numeral 1 denotes a micro actuator, and the micro actuator 1 has electrodes on the top, top, and bottom of the piezoelectric body, respectively. This is a substantial driving part in the print head which causes the driving force by deforming the piezoelectric body by energizing between the electrodes while stacking them.

The bottom of the micro-actuator 1 is provided with a flow path plate 2 which combines a plurality of thin plates to each other, but the flow path plate 2 has a reservoir 2a and a restrictor 2b for storing or guiding ink therein. ), The chamber 2c, and the nozzle 2d are formed.

Therefore, the ink stored in the reservoir 2a receives a certain amount of ink through the restrictor 2b due to the pressure change that expands the volume in the chamber 2c by the deformation restoring force of the diaphragm driven by the micro actuator 1. The ink flowed into the chamber 2c, and the ink flowed into the chamber 2c is again caused by the pressure change which reduces the volume in the chamber 2c by the bending deformation of the diaphragm driven by the micro actuator 1. It has a flow path to be discharged to the outside through).

However, in the piezoelectric printhead as described above, ink having a relatively high viscosity is used to increase the ejection speed, that is, the ejection operation frequency, which is the number of droplets ejected per predetermined time. Although the ejection speed of the droplets is high, there is a problem that the droplet speed, which reaches the printing paper from the nozzle 2d, becomes slow.

This drop can be solved by supplying a higher operating voltage or by using a lower viscosity ink. When using a lower viscosity ink, ink evaporation at the nozzle 2d and paper contact as described above can be solved. Since the spread of the maniscus has an unstable problem, a method of increasing the speed of droplets by changing the operating voltage according to the ink temperature has been proposed.

In other words, as shown in Fig. 2, the ink is ejected by checking the current temperature of the ink in the head at the time of ejection command so that an appropriate operating voltage is supplied thereto.

On the other hand, while the printer is being used while the solid ink is used, some of the methods are applied in such a manner that the ink is formed as a state having an appropriate viscosity by heating the head and the cartridge to a predetermined temperature or more.

However, the configuration that changes the operating voltage by checking the temperature of the ink at that time in the above manners is very difficult to control, resulting in an increase in manufacturing cost, especially the installation and failure of the component to detect the temperature of the ink. There are a lot of concerns that are not economic.

In the configuration in which the head or the cartridge is heated using the solid ink, the chemical property changes due to the rapid change in the temperature of the ink, and the durability of the head or the cartridge decreases in durability.

The present invention is to compensate for the above-mentioned problems, the present invention is to use the high viscosity ink while ejecting to control the viscosity of the instantaneously low to discharge the most ideal droplet speed and droplet ejection speed even by lower operating voltage Its main purpose is to enable it.

In addition, the present invention has a further object to easily adjust the viscosity of the ink by providing a heating means in the ink flow path of the cell unit, and by heating it at the same time to uniformly control the temperature of the discharged ink.

In addition, the present invention has another object to improve the print quality by forming the ink viscosity at the time of ejection to a level similar to the ink viscosity when it comes in contact with the paper.

1 is a cross-sectional view showing an example of a conventional piezoelectric inkjet printhead;

2 is a characteristic diagram showing a change in viscosity with temperature of ink;

3 is a cross-sectional view showing a first embodiment of an inkjet printhead according to the present invention;

4 is a sectional view showing a second embodiment of an inkjet printhead according to the present invention;

5 is an exemplary view showing a state in which ink is implanted onto paper during printing by the printhead according to the present invention.

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

10 micro actuator 20 euro plate

21: reservoir 23: chamber

24: Euro 25: nozzle

30: heating means

In order to achieve the above object, the present invention, in the inkjet printhead configuration for forcibly ejecting ink by deforming the piezoelectric body by the power input from the outside to change the volume in the chamber, the nozzle is introduced into the chamber by the driving of the piezoelectric body The main feature is that the heating means is integrally provided in the flow path of the ink to be discharged through the ink to be heated to a temperature required for the ink when the piezoelectric element is driven, thereby lowering the viscosity of the ink to be discharged.

That is, by providing a separate heating means in the ink flow space in the head in which the ink is stored or flow, the ink is heated to a predetermined temperature immediately before discharge to lower the viscosity.

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

In general, the piezoelectric inkjet printhead has the same principle of discharging ink by deformation of the piezoelectric body, but the shape and flow of the flow path for introducing ink into or out of the chamber by the deformation of the piezoelectric body. The stacking structure of the laminated plate members forming the furnace is very diverse.

The present invention allows the ink in the flow path to be heated to a predetermined temperature while the heating means is integrally formed in the flow path through which the ink passes in the inkjet printhead formed in various configurations.

3 is an enlarged cross-sectional view of a main part of a first embodiment of a printhead according to the present invention. In this embodiment, a flow path plate 20 is provided at the bottom of the micro actuator 10 in which the piezoelectric body and the electrode are integrally stacked. In this flow path plate 20, a chamber 23 is formed directly under the micro actuator 10, but at one side thereof, a reservoir 21 and a restrictor, which are inflow spaces, allow a predetermined amount of ink to flow into the chamber 23. (22), the other side of the structure is provided with a flow path 24 and a nozzle 25, which is an outflow space, is almost the same as before.

In such a configuration, it is the most prominent feature of this embodiment that the separate heating means 30 is provided in the chamber 23 of the flow path plate 20.

The heating means 30 are each provided in the chamber 23 of each cell consisting of a plurality of cells in the head, and these heating means 30 may be operated at the same time, only the heating means 30 in the cell being driven. It can also be activated selectively.

Most preferably, the temperature of the ink in the chamber 23 heated by the heating means 30 is within about 200 ° C. without generating bubbles.

Referring to the operation of the printhead according to such a configuration as follows.

The ink in the head maintains the relatively high viscosity initially supplied until a print order is issued.

When the print command is issued in such a state, the micro actuator 10 is driven. At this time, the heating means 30 is instantaneously heated to make the ink in the chamber 23 at a predetermined temperature.

Then, the viscosity of the ink is lowered, and thus the ejection rate can be more easily discharged through the nozzle, and the droplet velocity of contact with the printing paper becomes very high.

In this way, the ejected ink is rapidly cooled again by external air before it touches the paper, and is changed to the viscosity before the first heating, and thus has high viscosity at the time of touching the paper, thereby minimizing spreading on the paper.

As described above, in this embodiment, the ink having a relatively high viscosity is heated to a predetermined temperature in the chamber immediately before being discharged to have a lower discharge viscosity, thereby exerting a rapid droplet speed by a given constant operating voltage.

In particular, this embodiment solves the problems of droplet speed and operating voltage at the same time by using a highly viscous ink at the same time to achieve the best printing conditions, and to provide easier control and vastly improved print quality. There is an advantage.

On the other hand, Fig. 4 is an enlarged cross-sectional view of the main portion showing the second embodiment of the printhead according to the present invention. The printhead in this embodiment is almost the same as in the first embodiment.

In this embodiment, however, the most prominent feature is that the heating means 30 for heating the ink is provided in the reservoir 21 for supplying ink to each cell of the head.

In this case, the temperature of the ink heated by the heating means 30 in the reservoir 21 is within about 200 ° C. which does not form a bubble as in the first embodiment.

In particular, since the heating means 30 in the present embodiment cannot be selectively controlled unlike in the first embodiment, the micro actuator 10 in each cell operates unconditionally when driven.

Looking at the operation of the present invention according to the embodiment described above are as follows.

Until the print command is issued, the ink in the head maintains the first high viscosity as in the first embodiment. When the print command is issued, the heating means 30 is operated immediately before the micro actuator 10 is driven. The ink in the reservoir 21 is heated instantaneously, thereby lowering the viscosity of the ink supplied to the chamber 23.

When the heat in the reservoir 21 is transferred to the ink in the chamber 23 while heating the ink in the reservoir 21, the ink in the chamber 23 may have a low viscosity, and thus may be easily discharged by the driving of the micro actuator 10.

In this way, the ejected ink is rapidly cooled again by contact with the outside air before it touches the printing paper and changes to the viscosity before the first heating, as in the first embodiment. Spread is greatly reduced.

On the other hand, the ink discharged by the above embodiments is already low in viscosity from the nozzle 25, and droplets are ejected at a very high speed and implanted onto the paper as shown in FIG. 5, but the amount absorbed by the paper is very weak. Less spread and a greater amount of accumulation on the surface of the paper provide higher resolution image quality.

In addition, in the present invention, since the heating means 30 is momentarily operated only before the driving time of the micro actuator 10, the ink is heated, and once the droplets are discharged, the viscosity of the ink on the nozzle 25 side is rapidly increased by outside air. As a result, the meniscus regains stability at a very high rate and at the same time prevents evaporation.

As such, the present invention allows the viscosity of the inkjet printhead to be lowered only immediately before discharging the ink while using the highly viscous ink, so that the viscosity of the ink is controlled only when the ink is discharged together with the advantage of using the highly viscous ink. This has the advantage of simultaneously accepting the advantages of using low viscosity inks.

Therefore, the present invention simply provides a separate heating means 30 in the flow path through which the ink flows and the action thereof so that the ink immediately after the printhead is not driven and immediately after being ejected through the nozzle is always maintained at high viscosity. In the meantime, the viscosity of the ink is instantaneously lowered only when the ink is discharged by the driving of the micro actuator 10, thereby preventing the evaporation of the ink from the head, reducing the spreading in the printing paper, and stabilizing the meniscus as soon as the liquid is discharged. In addition, it is possible to increase the number of ejection droplets per unit time by using a smaller operating voltage while realizing a faster droplet rate per unit time, thereby greatly improving printing speed and resolution.

Claims (5)

A micro actuator which deforms the piezoelectric body by electric current; A flow path plate configured to communicate the reservoir, the restrictor, the chamber, the flow path, and the nozzles in which ink flows; Heating means provided in the chamber of the flow path plate to immediately heat the ink to be discharged to a predetermined temperature by immediately heating the ink immediately before discharging the ink from the nozzle driven by the micro actuator; Equipped, And the heating means is heated only in a chamber in which the micro actuator is driven. The method of claim 1, wherein the heating means An inkjet printhead, wherein the ink is heated to within 200 ° C. without generating bubbles. Claim 3 has been deleted. Claim 4 has been deleted. Claim 5 has been deleted.