JPH04307251A - inkjet head - Google Patents

Abstract

PURPOSE:To prevent a signal electrode from deterioration due to melting by a method wherein an energy quantity to be given to conductive ink, when electric potential of the common electrode is higher than electric potential of the signal electrode, is made larger than that when it is lower than the electric potential of the signal electrode. CONSTITUTION:Conductive ink is discharged from a plurality of nozzles 3 provided to a nozzle plate 4. A pressure chamber 7 is formed among a plurality of counter electrodes 10 to be provided according to the nozzle 3. Further, a voltage applicator to the counter electrode 10 and an electrification direction switching device which emits at least 2 or more even pulses for electrification time necessary for forming one dot and controls the voltage applicator so that a direction of electrified voltage is switched for each pulse, are provided. Said electrification direction switching device is equipped with an energy control circuit, and controls the voltage applicator so that an energy quantity to be applied to the conductive ink, when electric potential of the common electrode 10B is higher than that of the other signal electrode 10A, becomes larger than an energy quantity to be given when the electric potential of the common electrode 10B is lower than that of the signal electrode 10A.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention involves passing a current through conductive ink, boiling the conductive ink with the flowing current,
The present invention relates to an inkjet head that uses bubbles generated at that time to fly ink droplets.

0002

2. Description of the Related Art In recent years, demands on printers have been increasing, such as higher speed, lower noise, and color printing, and inkjet printers have been attracting attention in this sense.

[0003] Inkjet printer systems can be roughly divided into continuous types and on-demand types.Furthermore, among the on-demand types, there are Kaiser type, Stemme type, and Gould type that are driven by piezo elements, and those that generate bubbles with heat and change their volume. There is a bubble jet method in which conductive ink is ejected.

There are two methods for generating bubbles: a heating method using a heater and an energizing method in which a current is directly passed through the conductive ink itself to generate heat. The present invention relates to the energizing method.

[0005] The energization method is described in US Pat. No. 3,179,042 (19
Although the concept is shown in 65.4.20), there are some points that are insufficient in terms of response frequency, stability of flight, power consumption, efficiency, etc.

An example of a conventional inkjet head will be described below with reference to FIGS. 3 and 4. FIG. 3 is a partial sectional view of a nozzle of an inkjet head in a conventional example, and FIG. 4 is a sectional view taken along the line A--A in FIG. In the figure, 1 is a base, a heat insulating layer 2 is laminated on the upper surface of this base 1, and a nozzle plate 4 in which a plurality of nozzles 3 (one in FIG. 3) are formed parallel to the base 1 is a nozzle plate 4 on which a plurality of nozzles 3 are formed. are placed at a certain interval.

Furthermore, a signal electrode 5 is provided on the upper surface of the heat insulating layer 2.
A counter electrode 5 consisting of a common electrode 5B and a common electrode 5B is patterned at regular intervals in correspondence with the nozzle 3. A voltage applying device (not shown) is provided to flow a current between the common electrode 5B and the signal electrode 5A. This voltage application device includes an energization direction switching device that emits at least two or more even-numbered pulses within the energization time necessary to form one dot in order to suppress electrode deterioration, and the direction of the energization voltage is switched for each pulse. (not shown) is connected.

A partition 6 made of an insulating material is provided between the heat insulating layer 2 and the nozzle plate 4 to prevent interference between the nozzles 3. A space partitioned by the heat insulating layer 2, the partition part 6, and the nozzle plate 4 is a pressure chamber 7, into which conductive ink flows from an ink channel 8 provided on the signal electrode 5A side. It is configured as follows.

Arrow A indicates the line of electric force passing through the conductive ink between the signal electrode 5A and the common electrode 5B, and the portion indicated by A indicates the distance a between the signal electrode 5A and the common electrode 5B, and the electrode width b. , and a current passage section of conductive ink partitioned by electrode thickness c.

As shown in FIG. 3, the conductive ink in the current passing portion A self-heats due to electric lines of force A from the nozzle 3, causing a pressure change in the pressure chamber 7 due to vapor bubbles generated, and the ink droplets 9 is discharged.

The operation of the inkjet head constructed as described above will be explained below. When a voltage is applied to an arbitrary signal electrode 5A using a voltage application device (not shown), electric lines of force are generated in the current passing portion A of the conductive ink having an arbitrary volume resistivity, as shown in FIGS. 3 and 4. is generated, and a current flows along this line of electric force A. Therefore, the conductive ink in the current passing section A self-heats due to I2R,
Eventually, boiling begins and bubbles (not shown) are generated. As a result, the pressure of the conductive ink in the pressure chamber 7 increases rapidly, and ink droplets 9 fly out from the nozzle 3 and fly to and adhere to recording paper (not shown) to form dots. Of course, the consumed conductive ink is always stored in the ink flow path 8.
Since the ink droplets 9 are replenished from the ink droplets 9, ink droplets 9 are continuously generated according to the signals, and it is possible to form arbitrary continuous dots on the recording paper.

The heat insulating layer 2 is provided to prevent self-heating of the conductive ink from escaping to the substrate 1 and to effectively generate bubbles.

[0013]

[Problems to be Solved by the Invention] However, in the above-mentioned conventional configuration, even if it is attempted to suppress electrode deterioration by using positive and negative currents, changes in the ON resistance of the transistor forming the voltage application device due to aging etc. The resistance value of the conductive ink between the electrodes changes due to the accumulation of conductive substances, etc.
Since the positive and negative current values differ, electrolysis of the electrode is induced and electrode deterioration occurs, so the signal electrode 5A,
A highly corrosion-resistant material such as platinum must be used for the common electrode 5B, and the thickness of the counter electrode 5 cannot be increased because it complicates the manufacturing process and reduces yield. However, there was a problem in that it was not possible to efficiently apply electrical energy to the conductive ink.

The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide an ink jet head in which signal electrodes do not melt and do not deteriorate.

[0015]

[Means for Solving the Problems] An inkjet head of the present invention includes a nozzle plate on which a plurality of nozzles for ejecting conductive ink are formed, a plurality of counter electrodes provided corresponding to the nozzles, and the counter electrode. A pressure chamber provided between a pressure chamber, a voltage applying device for applying a current voltage to the counter electrode, and a voltage applying device that emits at least two or more even pulses within the current flow time required to form one dot, and the direction of the current voltage is adjusted. It is composed of an energization direction switching device that controls the voltage application device so as to switch every pulse, and an energy control circuit that controls the voltage application device so that the amount of energization energy given to the conductive ink differs depending on the direction in which the energization voltage is applied. ing.

[0016]

[Function] The present invention has the above-described structure, by making the energy applied to the conductive ink when the potential of the common electrode is high greater than the energy applied to the conductive ink when the potential of the common electrode is low. It becomes possible to prevent deterioration of the signal electrode, and it becomes possible to efficiently apply electrical energy to the conductive ink.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the inkjet head of the present invention will be described below with reference to FIGS. 1 and 2. FIG. 1 is a sectional view showing an embodiment of an inkjet head of the present invention, and FIG. 2 is a sectional view taken along the line BB in FIG.

In the figure, a base 1, a heat insulating layer 2, a nozzle 3
, the nozzle plate 4, the partition part 6, the pressure chamber 7, the ink flow path 8, etc. are the same as those of the conventional inkjet head, so the drawing numbers are the same and the details are omitted.

In addition, a voltage applying device (not shown) is used to apply the energizing voltage to the counter electrode 10, or an even-numbered pulse of at least two pulses is generated within the energizing time required to form one dot, and the direction of the energizing voltage is adjusted. The energization direction switching device that controls the voltage application device so that the voltage is switched every pulse is also the same as that of the conventional device.

This embodiment differs from conventional embodiments in the following points:
The signal electrode 10A is made of a material such as copper or gold for which processing technology has been established and can be easily formed into a desired shape, and
The common electrode 10B is made of a highly corrosion-resistant material such as platinum or carbon fiber. Note that the common electrode 10B in this embodiment is used in common with the common electrode 10B on the other nozzle side (not shown). However, the common electrode 10B is not limited to one that is commonly used.

Furthermore, in the present invention, the current direction switching device includes an energy control circuit for controlling the voltage application device so that the amount of current energy given to the conductive ink varies depending on the direction of application of the current voltage. That is, this energy control circuit controls the amount of energy given to the conductive ink when the potential of the common electrode 10B is higher than the other signal electrode 10A, and the amount of energy given to the conductive ink when the potential of the opposite common electrode 10B is lower than the potential of the signal electrode 10A. The voltage applying device is controlled so that the amount of energy applied to the liquid ink is greater than the amount of energy given to the liquid ink.

As mentioned above, in order to change the amount of energy given to the conductive ink, the absolute value of the energizing voltage when the potential of the common electrode 10B is higher than the potential of the signal electrode 10A, and vice versa, When the absolute value of the energizing voltage is lower than the potential of the electrode 10A, or when the potential of the common electrode 10B is higher than the potential of the signal electrode 10A, the energizing time is set to be higher than the potential of the signal electrode 10A. The energization time is longer than when the temperature is lower.

In order to change the amount of energy given to the conductive ink in this way, a resistor or a
A circuit (both not shown) is provided to extend or shorten the energization time.

The operation of the inkjet head constructed as described above will be explained below. When a voltage applying device generates a potential difference between an arbitrary signal electrode 10A and a common electrode 10B, electric lines of force A are generated in a current passing portion A of conductive ink having an arbitrary volume resistivity, as shown in FIGS. 1 and 2. A current is generated between the signal electrode 10A and the common electrode 10B, and current flows along this electric line of force A. At this time, as described above, the energy applied to the conductive ink when the potential of the common electrode 10B is higher than the potential of the signal electrode 10A is applied to the conductive ink when the potential of the common electrode 10B is lower than the potential of the signal electrode 10A. By increasing the energy applied to the signal electrode 10
On the A side, no metal dissolution occurs and no deterioration occurs.

On the other hand, the common electrode 10B has a large area, so the current density is low, and since it is made of a highly corrosion-resistant material, it hardly deteriorates. Then, the conductive ink in the current passing portion A self-heats due to I2R, and finally boils and generates bubbles (not shown). As a result, the pressure of the conductive ink in the pressure chamber 7 increases rapidly, and ink droplets 9 fly out from the nozzle 3, fly onto the recording paper, and adhere to the recording paper to form dots. Of course, since the consumed conductive ink is always replenished from the ink flow path 8, ink droplets 9 are continuously generated according to the signal, making it possible to form arbitrary continuous dots on the recording paper.

[0026] Depending on the energization method, the ratio of the applied energy amount is suitably 0.95 to 0.999. If the applied energy ratio is less than 0.95, the common electrode 10B will be worn out and its life will be shortened, which is not preferable. In addition, when the applied energy ratio becomes larger than 0.999, the O
It becomes impossible to absorb the change in N resistance, and the signal electrode 10A
This is undesirable as it causes wear and tear.

[0027]

[Effects of the Invention] With the above structure, the inkjet head of the present invention reduces the amount of energizing energy given to the conductive ink when the potential of the common electrode is higher than the potential of the signal electrode. By making the amount of energization energy larger than that given to the conductive ink when it is low, electrode dissolution of the signal electrode does not occur and deterioration does not occur. Therefore, a low-cost and easy-to-process metal can be used for the signal electrode, and the thickness of the electrode can also be increased, so that energy can be efficiently applied to the conductive ink.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an inkjet head in one embodiment of the present invention.

FIG. 2 is a sectional view taken along line BB in FIG. 1;

FIG. 3 is a sectional view of a conventional inkjet head.

FIG. 4 is a sectional view taken along line AA in FIG. 3;

[Explanation of symbols]

3 Nozzle 4 Nozzle plate 7 Pressure chamber 9 Ink droplets 10 Counter electrode 10A Signal electrode 10B Common electrode

Claims (5)

[Claims] 1. A nozzle plate in which a plurality of nozzles for discharging conductive ink are formed, a plurality of counter electrodes provided corresponding to the nozzles, a pressure chamber provided between the counter electrodes, and a pressure chamber provided between the counter electrodes; A voltage applying device that applies an energizing voltage to an electrode, and a voltage applying device that emits at least two or more even numbered pulses within the energizing time required to form one dot and switches the direction of the energizing voltage every pulse. An inkjet head comprising: a current supply direction switching device for controlling the inkjet head; and an energy control circuit for controlling the voltage application device so that the amount of current supply energy applied to the conductive ink differs depending on the direction in which the current supply voltage is applied. 2. The inkjet head according to claim 1, further comprising an energy control circuit having a ratio of 0.95 to 0.999 between energizing energy amounts that differ depending on the application direction. 3. The amount of energy given to the conductive ink when the potential of one common electrode of the opposing electrodes is higher than the other signal electrode, and the amount of energy given to the conductive ink when the potential of the opposite common electrode is lower than the potential of the signal electrode. 2. The inkjet head according to claim 1, further comprising an energy control circuit that controls the voltage application device so that the amount of energy applied to the inkjet head is larger than the amount of energy applied to the inkjet head. [Claim 4] By making the absolute value of the energizing voltage when the potential of the common electrode is higher than the potential of the signal electrode larger than the absolute value of the energizing voltage when the potential of the opposite common electrode is lower than the potential of the signal electrode. The inkjet head according to claim 3, further comprising an energy control circuit that controls the amount of energy given to the conductive ink. [Claim 5] Energy given to the conductive ink by making the energization time when the potential of the common electrode is higher than the potential of the signal electrode longer than the energization time when the potential of the opposite common electrode is lower than the potential of the signal electrode. The inkjet head according to claim 3, further comprising an energy control circuit for controlling the amount.