JP2001277497A - Method for driving ink jet head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a driving method in which an ink drop can be ejected stably by removing residual charges between a diaphragm and an electrode. SOLUTION: An ink jet head comprises a nozzle 104, an ink channel 106 communicating with the nozzle, a diaphragm 105 disposed at a part of the channel, and an electrode 109 disposed oppositely to the diaphragm wherein recording is performed by deforming the diaphragm 105 to eject an ink drop from the nozzle 104. The diaphragm 105 is deformed by applying a voltage, in a driving form comprising a combination of a voltage having a first polarity and a voltage having a second different polarity, between the diaphragm 105 and the electrode 109.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for driving an ink-jet head, and more particularly to a method for driving an ink-jet head of a type in which ink droplets are ejected by deforming a diaphragm using electrostatic force. Further, the present invention relates to a method of driving an ink jet head capable of always performing a good ink droplet discharging operation by eliminating the influence of residual charges remaining on a diaphragm.

[0002]

2. Description of the Related Art Japanese Patent Application Laid-Open No. 7-81088 (a method for driving an ink-jet head, a driving apparatus for the same, and a printing apparatus using the same) discloses a method for preventing a residual charge from being generated between a diaphragm and an electrode. Has proposed the following method of driving an ink jet head. That is, as a drive signal applied between the diaphragm and the electrode, a first voltage for performing normal recording by deforming the diaphragm by electrostatic force;
By adopting a second voltage different from the first voltage and applying a second voltage between the diaphragm and the electrode at regular intervals, residual charges between the diaphragm and the electrode are removed, and The amount of displacement can be kept constant. According to the method described in this patent publication, the first voltage is used exclusively for discharging ink droplets,
That is, the second voltage is used only for the printing drive, and the second voltage is used only for removing the residual charges. For this reason, measures are taken, such as lowering the value of the second voltage, so as to prevent the ink droplet from being ejected in an incomplete state when the second voltage is applied.

In Japanese Patent Application Laid-Open No. 9-136413 (ink jet driving method), a nozzle, an ink flow passage communicating with the nozzle, a diaphragm provided in a part of the ink flow passage, An electrode provided to face the plate, wherein the diaphragm is deformed using electrostatic force to discharge ink droplets from the nozzles to perform recording, and wherein the diaphragm is And deforming the diaphragm in a first driving mode in which a voltage of a first polarity is applied between the electrodes to cause the nozzles to eject ink droplets, and at least one
A second driving mode in which a voltage of a second polarity opposite to the first polarity is applied between the diaphragm and the electrode every time the ink droplet is ejected by the first driving mode. Then, the vibration plate is deformed so that ink droplets are ejected from the nozzles.

[0004]

SUMMARY OF THE INVENTION The above-mentioned Japanese Patent Application Laid-Open
In the invention of JP-A-81088, as a driving signal applied between the diaphragm and the electrode, a first voltage for performing normal recording by deforming the diaphragm by electrostatic force and the first voltage are used.
A second voltage different from the voltage of the diaphragm is adopted, and a second voltage is applied between the diaphragm and the electrode at regular intervals to remove residual charges therebetween and to reduce the displacement of the diaphragm. It keeps it constant. However, when a second voltage different from the first voltage is applied, the ink droplets are erroneously ejected in an incomplete state, causing the recording paper to become dirty. Therefore, measures such as lowering the value of the second voltage are taken, but in this case, if the voltage is too low, it may not be possible to remove the residual charges.

In the invention disclosed in Japanese Patent Application Laid-Open No. Hei 9-136413, a voltage of a first polarity is applied between a diaphragm and an electrode to cause ink droplets to be ejected from a nozzle, A voltage having a second polarity opposite to the first polarity is applied between the first electrode and the electrode to cause the nozzle to eject ink droplets. However, in an on-demand type ink jet printer, an electric pulse to be applied is determined by a pattern to be printed, so that a difference occurs in how a voltage of the first polarity and a voltage of the second polarity are applied to the ink jet head. As a result, the state of accumulation of the residual charges changes and it is difficult to stabilize.

Accordingly, an object of the present invention is to provide an ink-jet head which discharges ink droplets by using an electrostatic force, similarly to the invention described in the above-mentioned patent publication, and which is provided between a diaphragm and an electrode. An object of the present invention is to propose a driving method capable of performing a stable ink droplet ejection operation by removing residual charges. More specifically, the present invention proposes a method of driving an inkjet head that can reliably discharge any print pattern while reliably removing residual charges.

[0007]

According to a first aspect of the present invention, a nozzle, an ink flow path communicating with the nozzle, a vibrating plate provided in a part of the flow path, and a vibrating plate facing the vibrating plate are provided. And an actuator comprising an electrode provided, in a driving method of a printing apparatus that deforms the diaphragm, ejects ink droplets from the nozzles, and performs recording, the method includes: Applying a voltage in a driving mode consisting of a combination of a voltage having a first polarity and a voltage having a second polarity different from the polarity to deform the diaphragm to eject ink droplets from the nozzles. It was done.

According to a second aspect of the present invention, in the first aspect of the present invention, the voltage having the second polarity, which is different in polarity from the voltage having the first polarity, is equal to or higher than a voltage value at which the diaphragm contacts the electrode. It is characterized by having a size of.

According to a third aspect of the present invention, in the first or second aspect of the invention, when the voltage having the first polarity is applied to deform the diaphragm, no ink droplet is ejected. When a voltage having a second polarity is applied to deform the diaphragm, ink droplets are ejected from the nozzles.

According to a fourth aspect of the present invention, in the third aspect of the present invention, the polarity of the driving voltage is switched before the diaphragm moves away from the electrode.

According to a fifth aspect of the present invention, in the third aspect of the present invention, the polarity of the driving voltage is switched after the pressure oscillation in the ink flow path communicating with the nozzle becomes positive. It is what it was.

According to a sixth aspect of the present invention, in the fifth aspect of the invention, after the pressure oscillation in the ink flow path communicating with the nozzle becomes a negative pressure, the ink droplet is ejected from the nozzle. It is a characteristic.

According to a seventh aspect of the present invention, in the third aspect of the present invention, the time T12 required for switching the polarity of the drive voltage is set to T12.
(The time from the voltage Vp1 having the first polarity to the voltage Vp2 having the second polarity) is shorter than half of the ink pressure oscillation cycle of the ink discharge chamber communicating with the nozzle. Things.

According to an eighth aspect of the present invention, in the third aspect of the present invention, the time T12 required to switch the polarity of the drive voltage is set.
(Time from Vp1 to Vp2) is T12 ≦ 5
0 (microseconds).

According to a ninth aspect of the present invention, in the first or second aspect of the present invention, the voltage having the first polarity is applied to deform the vibrating plate, and the ink droplets discharged from the nozzles and A voltage having a second polarity different from the first polarity is applied to deform the vibrating plate, and ink droplets ejected from the nozzles are united before reaching the recording medium, and one dot printing is performed on the recording medium. It is characterized by being formed on top.

According to a tenth aspect of the present invention, in the ninth aspect of the present invention, the voltage having the first polarity (Vp1) and the voltage having the second polarity (Vp2) having a different polarity are Vp
It is characterized by satisfying the relationship of 1 <Vp2.

According to an eleventh aspect of the present invention, in any one of the first to tenth aspects, the absolute value of the time integral of the voltage having the first polarity and a second polarity different from the first polarity And the absolute value of the time integral of the voltage having

According to a twelfth aspect of the present invention, in any one of the first to ninth aspects or the eleventh aspect of the present invention, the voltage having the first polarity (Vp1) and a second voltage different from the first polarity are used. Voltage (Vp2) is Vp1 = Vp
It is characterized by satisfying the relationship of 2.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a normal operation of an electrostatic ink jet head, when a voltage having a first polarity is applied to a diaphragm of an ink jet head, for example, a forward voltage pulse is applied between the diaphragm and an electrode, A suction force is generated between them by an electrostatic force, and the diaphragm is deformed by the electrostatic force. Next, when the voltage pulse is released, the ink droplets are ejected from the nozzles by the elastic restoring force of the diaphragm.
In an electrostatic inkjet head, an insulating layer is generally formed between the diaphragm and an individual electrode in order to prevent a short circuit. However, in this case, even if the forward voltage pulse is released, charges remain in the insulating layer, and due to the electric field generated by the remaining charges, the diaphragm does not completely recover and includes residual deflection. become. In such a state, the amount of relative displacement between the diaphragm and the electrode is reduced, and stable ink droplet ejection cannot be performed.

Therefore, in the present invention, a voltage having a first polarity (in this case, a forward voltage pulse) and a voltage having a second polarity different from the first polarity (in this case, in one driving mode) Are applied between the diaphragm and the electrode to perform an ink droplet ejection operation. In this way, generation of residual charges is avoided by applying a bipolar voltage pulse to the insulating layer. As a result, the relative displacement between the diaphragm and the electrode can be kept constant, and a stable ink droplet ejection operation can be maintained. Here, the same effect can be obtained by using a voltage having the first polarity as a reverse voltage pulse and a voltage having a second polarity having a different polarity as a forward voltage pulse.

Further, the voltage having the second polarity, which is different from the voltage having the first polarity, is set to a magnitude equal to or higher than a voltage value (hereinafter referred to as a contact voltage) at which the diaphragm contacts the electrode. The displacement of the diaphragm is the distance between the diaphragm and the electrode, and can be kept constant for all bits. Therefore, variations in the vibration characteristics due to variations in the process such as variations in the thickness of the diaphragm do not matter, and the productivity of the inkjet head can be improved by improving the yield of the inkjet head. In addition, when a voltage having a first polarity greater than the contact voltage is applied, the residual charge cannot be removed by a voltage having a second polarity having a polarity less than the contact voltage, but the magnitude of the contact is small. The use of a voltage having a second polarity having a polarity equal to or larger than the voltage can be quickly and reliably removed.

When a voltage having a first polarity is applied to deform the diaphragm, ink droplets are not ejected,
A voltage having a second polarity is applied to deform the diaphragm, and eject ink droplets from the nozzles. According to this driving method, since a bipolar voltage pulse is applied in one driving mode, no residual charge is generated in the insulating layer between the diaphragm and the electrode, and one driving mode is applied. , Ink ejection is performed once, so that any print pattern can always be stably printed in an on-demand type ink jet printer.

In the method of driving an ink-jet head according to the present invention, a voltage having a first polarity is applied in a single driving mode to deform the diaphragm and cause ink droplets to be discharged from the nozzles. A voltage having a second polarity different from the first polarity is applied to deform the vibrating plate, and the ink droplets ejected from the nozzles are united before reaching the recording medium, and one dot printing is performed on the recording medium. Formed on top. According to the driving method of the present invention, since the bipolar voltage pulse is applied in one driving mode, no residual charge is generated in the insulating layer between the diaphragm and the electrode, and Since one dot printing is formed in one driving mode, any printing pattern can always be stably printed in an on-demand type ink jet printer (claim 9).

Embodiment 1 (Claims 3 and 4) FIG. 1 is a sectional view of a main part of an ink jet head according to the present invention. In FIG. 1, an inkjet head 1
00 is an edge eject type in which ink droplets are ejected from a nozzle hole provided at an end of the substrate, but may be a face eject type in which ink droplets are ejected from a nozzle hole provided on the upper surface of the substrate.

Referring to FIG. 1, the structure of the ink jet head 100 according to the present invention will be described. In FIG. 1, an inkjet head 100 includes three substrates 101, 10
It has a laminated structure in which 2, 103 are overlapped. The intermediate substrate 102 is, for example, a silicon substrate, and includes a plurality of nozzle grooves formed at equal intervals in parallel from one end on the surface of the substrate 102 so as to form the plurality of nozzle holes 104. And a concave portion whose bottom wall constitutes a discharge chamber 106 functioning as a diaphragm 105;
A narrow groove for an ink inlet, which forms an orifice 107 provided at the rear of the recess, and an ink common liquid chamber 108 for supplying ink to each discharge chamber 106
And a concave portion that constitutes the above.

A lower portion of the vibration plate 105 is provided with a silicon insulating film 119 which constitutes a vibration chamber 110 for mounting an electrode 109 described later, for example, a concave portion formed of a silicon oxide film. I have. On the other hand, a common electrode 111 is formed on the upper surface of the intermediate substrate 102.
Upper substrate 101 bonded to the upper surface of intermediate substrate 102
Is made of, for example, glass or plastic, and the upper substrate 101 is joined to form the nozzle hole 104, the discharge port 106, the orifice 107, and the ink common liquid chamber 1.
08 is configured. The upper substrate 101 has an ink common liquid chamber 1
08 is formed.
The ink supply port 112 is connected to an ink tank (not shown) via a connection pipe 113 and a tube 114.

The lower substrate 103 bonded to the lower surface of the intermediate substrate 102 is made of, for example, a silicon substrate. The vibration chamber 110 is formed by bonding the lower substrate 103, and the vibration plate 110 is mounted on the upper surface of the lower substrate 103. An individual electrode 109 is formed at each position corresponding to 105. Individual electrode 1
09 has a terminal portion 115. Further, the whole of the electrode 109 except for the terminal portion 115 is covered with an insulating film 116.
A lead wire 117 is bonded to each terminal 115. Reference numeral 122 denotes a sealant for sealing a gas layer in the vibration chamber 110, and an epoxy adhesive or the like is used.

As described above, in the ink jet head 100 formed by overlapping the substrates, a driver 118 is further connected between the common electrode 111 formed on the intermediate substrate 102 and the terminal 115 of each individual electrode 109. You. The ink is supplied from the ink tank to the inside of the intermediate substrate through the ink supply port 112, and fills the ink common liquid chamber 108, the discharge chamber 106, and the like. In FIG. 1, reference numeral 120 denotes an ink droplet ejected from the nozzle hole 104, and reference numeral 121 denotes a recording medium such as a recording paper.

The driver 118 is connected to the individual electrodes 109.
Thus, for example, a positive voltage pulse is applied to
Is charged to a positive potential, the corresponding diaphragm 105
Is charged to a negative potential. Therefore, diaphragm 10
5 is attracted by the electrostatic force and bends downward. Next, when the voltage pulse applied to the electrode 109 is turned off, the diaphragm 105 returns to the original position. Due to this return operation, the internal pressure of the discharge chamber 106 sharply increases, and the nozzle hole 1
04 ejects ink droplets 120 toward the recording paper 121. When the diaphragm 105 bends downward,
Ink is supplied from the common ink chamber 108 to the ejection chamber 106 via the orifice 107.

FIG. 2 shows a drive signal according to the present invention.
Symbols a to j added to the drive signal are shown in FIG.
(J) to (J). FIG. 3 is a view taken along line III-III in FIG. 1 and shows the movement of the diaphragm with respect to the drive signal. The numerals 101 to 119 in FIG. 3 are the same as those described above, and the arrow 200 indicates the direction in which the diaphragm is displaced.

First, the drive signal is changed as shown in FIG. 2A (drive signal Vp>
0V), as shown in FIG. 3 (A), the diaphragm starts to be displaced to the electrode side due to the electrostatic force at the timing when the voltage starts to be applied between the diaphragm and the electrode, and FIG. 2B (drive signal Vp =
In the case of 0 to Vp1), as shown in FIG. 3 (B), the electrode starts to contact the electrode from the center of the diaphragm in the middle of reaching Vp1. Further, in FIG. 2C (drive signal Vp = Vp1), FIG.
As shown in (C), the width direction of the diaphragm starts to contact the electrodes with time.

FIG. 2D (drive signal Vp <Vp1)
Immediately after this, as shown in FIG. 3 (D), the diaphragm starts to move away from the peripheral portion where the elastic restoring force is strong, and then gradually moves toward the central portion. Then, FIG. 2e (driving signal V
3E, the diaphragm comes into contact with the electrode due to resistance to displacement of the diaphragm due to ink pressure fluctuations and internal flow of ink due to the inflow of ink from the common liquid chamber, as shown in FIG. 3E. 2F (driving signal Vp = 0V to -Vp2) in this state, as shown in FIG. 3F, the diaphragm is again moved to the electrode side by the electrostatic force. The ink is not ejected by being pulled (claim 4).

Thereafter, FIG. 2g (driving signal Vp = -Vp
As shown in FIG. 3G in FIG. 3G, the center portion and the width direction of the diaphragm are brought into contact with the electrode again, and FIG. 2H (drive signal Vp>
-Vp2), FIG. 2i (drive signal Vp = 0V to -Vp2)
3 (H) and FIG. 3 (I), the ink is ejected as shown in FIG. 3 (J) for the first time in FIG. 2j (drive signal Vp = 0 V) (Claim 3).

Embodiment 2 (Claims 5 and 6) Next, when a voltage having a first polarity is applied, an ink droplet is not ejected, and a voltage having a second polarity having a different polarity is applied. Another method of ejecting ink droplets to the printer will be described. First, there is a method in which an ink droplet is not ejected when a voltage having a first polarity is applied.
(A)-(a1) shows a state in which a voltage having the first polarity is applied (when the voltage is kept constant without decreasing);
4 (A) to 4 (a2) below the graph show a temporal change of the meniscus position according to the drive signal. And Figure 4 below
(A)-(a3) shows a time change of the ink pressure in the ejection liquid chamber.

Here, when the drive signal shown in FIGS. 4A to 4A is applied between the diaphragm and the electrode, the diaphragm is pulled toward the electrode by electrostatic force, and the volume of the ink discharge chamber expands. The meniscus is drawn from the steady state (0 position) to the ink discharge chamber side. Thereafter, the meniscus attempts to return to a steady state (position 0) while performing a vibration in which the pressure fluctuation of the ink itself having a relatively short cycle (cycle: Tm) and the inflow of ink from the common liquid chamber have a relatively long cycle. On the other hand, looking at the time change of the ink pressure in the ejection liquid chamber, positive and negative ink pressures appear alternately at the boundary of the oscillation center of the pressure fluctuation of the ink itself in a relatively short cycle.

Therefore, as shown in FIG. 5A, when the voltage having the first polarity is released while the ink pressure in the discharge liquid chamber is positive, the diaphragm is moved from the electrode by its elastic restoring force. The positive pressure direction (arrow 202) of the ink pressure becomes a resistance to the direction in which the diaphragm is to be separated (arrow 201), and the diaphragm hardly separates from the electrode. In this state, if a voltage having a second polarity, which is different in polarity, is applied, the diaphragm will be pulled to the electrode side again by the electrostatic force and ink will not be ejected (claim 5).

Next, a method for ejecting ink droplets when a voltage having a second polarity having a different polarity is applied will be described. First, FIGS. 4 (B)-(b1) and FIGS. 4 (B)-(b)
2) and FIGS. 4 (B)-(b3) show FIGS. 4 (A)-(a1) and FIG. 4 respectively when a voltage having the second polarity is applied.
(A)-(a2) and FIG. 4 (A)-(a3). Therefore, when the voltage having the second polarity is released when the ink pressure in the discharge liquid chamber is negative as shown in FIG. 5B, the diaphragm tends to separate from the electrode by its elastic restoring force. Since the direction (arrow 201) and the negative direction of the ink pressure (arrow 202) are in the same direction, the diaphragm quickly separates from the electrodes, and ink is easily ejected (claim 6).

Embodiment 3 (Claims 7 and 8) As a method for preventing ink droplets from being ejected when a voltage having the first polarity is applied, a second polarity having a different polarity from the voltage having the first polarity is used. There is a method of adjusting the time for applying a voltage having the following. First, FIG. 6A shows a driving signal of the present invention, FIG. 6B shows a time change of the meniscus position with respect to the driving signal, and FIG. 6C shows FIG.
FIG. 6D shows (A)-(a1), and FIG.
2) and FIG. 6 (e) correspond to FIGS. 4 (A) to (a3). T12 in FIG. 6A is a time (pulse delay time) from a voltage having a first polarity to a voltage having a second polarity having a different polarity, and is shown in FIGS. 6D and 6E.
The middle Tm indicates a relatively short cycle of the ink pressure fluctuation. Therefore, as shown in FIG. 6D, while the ink pressure in the ejection liquid chamber is positive pressure (the cycle is half of Tm), the voltage having the second polarity is different from the voltage having the first polarity. By setting the voltage, the diaphragm can be pulled to the electrode side again by the electrostatic force from the state where the diaphragm is hard to separate from the electrode. Therefore, it is possible to prevent the ink from being ejected (claim 7).

The short side length of the diaphragm is 150 μm and the long side length (b) is 1,000, 4000 μm, 10,000 μm,
FIG. 7 shows the result of measuring the speed of ink droplets ejected at a voltage having the first polarity using T12 as a parameter when the height of the ink ejection chamber is 90 μm. According to this, if T12 is set to 50 (microseconds) or more, ink is reliably ejected at a voltage having the first polarity. Conversely, it can be seen that by setting T12 to 50 (microseconds) or less, ink is not ejected in a range where the long side length (b) is a realistic value (claim 8). In order to enable high-speed printing, it is preferable that T12 is set to 20 (microseconds) or less.

Embodiment 4 (Claims 9 and 10) In the method of driving an ink jet head according to the present invention, the diaphragm is deformed by applying a voltage having a first polarity in one driving mode. Applying a voltage having a second polarity different from the polarity of the ink droplets ejected from the nozzles and deforming the diaphragm to combine the ink droplets ejected from the nozzles before reaching the recording medium, One dot printing is formed on the recording medium. With this driving method, a voltage pulse having both polarities is applied in one driving mode, so that no residual charge is generated in the insulating layer between the diaphragm and the electrode, and the driving method is performed in one driving mode. Since one-dot printing is performed, in an on-demand type inkjet printer, any printing pattern can be always printed stably (claim 9).

As means for achieving this, as shown in FIG. 8, a voltage having a first polarity is Vp1, a voltage having a second polarity having a different polarity is Vp2, and a voltage having a first polarity is Vp1. Assuming that the time (pulse delay time) until the voltage having the second polarity having a different polarity from T2 is T12, as described above, adjusting T12 causes the ink droplets to be ejected. As shown in FIG. 9, when Vp1 <Vp2 with respect to the magnitude of the applied voltage, the respective ink droplet velocities Vj1 and Vj2 become Vj1 <V.
j2 (FIG. 10). Therefore, by adjusting Vp1 and Vp2, Vp1 is adjusted before the ink droplet reaches the recording paper.
The ink droplets ejected at Vp2 can catch up with the ink droplets ejected at the time and unite. As a result, one dot printing becomes possible by substantially one drive.
0).

Fifth Embodiment (Claim 11) Next, there is one method for removing residual charges remaining on the insulating film, in particular, residual polarization in the insulating film. In this case, when a voltage having the first polarity is applied, the amount of residual charges remaining on the insulating film is determined by the time during which the diaphragm is in contact with the electrode (that is, the time integrated value of the driving voltage, the hatched portion in FIG. 11). ), And the time integral value of the drive voltage when a voltage having a second polarity is applied is the same as the time integral value of the drive voltage when a voltage having a first polarity is applied. By doing so, the residual charges remaining on the insulating film could be reliably removed. Further, there is no residual residual charge caused by applying a voltage having a second polarity having a further different polarity (claim 11).

Embodiment 6 (Claim 12) Next, residual charges remaining on the insulating film, particularly residual charges caused by charge discharge due to a high electric field generated between the diaphragm and the electrodes when the electrodes contact each other. There is one method for the removal of In this case, the amount of residual charge remaining on the insulating film when a voltage having the first polarity is applied is proportional to the area where the diaphragm is in contact with the electrode (hereinafter, contact area).
This contact area is proportional to the voltage value. Therefore, by making the voltage (Vp2) having the second polarity and the voltage (Vp1) having the first polarity different from each other the same, the contact area at the time of application can be made the same. According to this method, when an experiment is conducted, residual charges remaining on the insulating film can be reliably removed, and unnecessary residual charges due to application of a voltage having a second polarity having a different polarity are not left ( Claim 12).

[0044]

According to the first aspect of the invention, there is provided a nozzle, an ink flow path communicating with the nozzle, a vibration plate provided in a part of the flow path, and a vibration plate provided to face the vibration plate. And an actuator comprising a driven electrode, wherein the diaphragm is deformed, ink droplets are ejected from the nozzles, and a printing apparatus driving method for performing recording, wherein a diaphragm is provided between the diaphragm and the electrode. A method of driving an ink-jet head, comprising: deforming the diaphragm in a driving mode including a combination of a voltage having one polarity and a voltage having a second polarity having a different polarity to discharge ink droplets from the nozzles. In this case, since a voltage pulse of both polarities is applied, no residual charge is generated, and as a result, the relative displacement between the diaphragm and the electrode can be kept constant, and a stable ink droplet ejection operation can be performed. Maintain Can be

The voltage having the first polarity and the voltage having the second polarity different from the first polarity are a voltage value at which the diaphragm comes into contact with the electrode (hereinafter referred to as a voltage). In the method of driving an ink jet head, the residual charge is higher than the contact voltage when the voltage having the first polarity is applied. It cannot be removed with the following voltage having the second polarity having a different polarity, but can be quickly and reliably removed with a voltage having a second polarity having a polarity different from that of the contact voltage.

When a voltage having a first polarity is applied to deform the diaphragm, ink droplets are not ejected and a voltage having a second polarity is applied. In the case of a method of driving an ink jet head, wherein the diaphragm is deformed to discharge ink droplets from the nozzles, a voltage pulse of both polarities is applied in a single driving mode. Since no residual charge is generated in the insulating layer between the plate and the electrode, and one ink ejection is performed in one driving mode, any print pattern can be obtained in an on-demand type inkjet printer. Printing can always be stabilized.

According to a fourth aspect of the present invention, in the method of driving an ink jet head, the polarity of the driving voltage is switched before the diaphragm moves away from the electrode. When the voltage is applied to deform the diaphragm, ink droplets are not ejected.

An ink jet head characterized in that the polarity of the drive voltage is switched after the pressure oscillation in the ink flow path communicating with the nozzle becomes positive. If the driving method is
When a voltage having a first polarity is applied to deform the diaphragm, no ink droplets are ejected.

An ink jet head wherein the polarity of the drive voltage is switched after the pressure oscillation in the ink flow passage communicating with the nozzle becomes positive. If the driving method is
The diaphragm can be quickly separated from the electrodes, ink can be easily ejected, and the delay time is eliminated, so that the frequency characteristics are improved.

Operation and Effect Corresponding to the Invention of Claim 7 The time T12 (V) required to switch the polarity of the drive voltage
In the method of driving an ink-jet head, the time required for changing from p1 to Vp2) is shorter than half of the natural oscillation period of the ink flow path communicating with the nozzle. When the diaphragm is deformed by applying the voltage, no ink droplet is ejected.

Operation and Effect Corresponding to the Invention of Claim 8 The time T12 (V) required to switch the polarity of the drive voltage
In the method of driving an ink-jet head, the time required for changing from p1 to Vp2) is shorter than 10 (microseconds), when a voltage having a first polarity is applied to deform the diaphragm. Does not eject ink droplets.

According to a ninth aspect of the present invention, a voltage having a second polarity, which is different in polarity from ink droplets ejected from the nozzles by applying a voltage having a first polarity to deform the diaphragm and apply a voltage having a first polarity. Applying the pressure to the recording medium to deform the vibrating plate so that the ink droplets ejected from the nozzles merge with each other before reaching the recording medium to form one-dot printing on the recording medium. According to the method, since a bipolar voltage pulse is applied in one driving mode, no residual charge is generated in the insulating layer between the diaphragm and the electrode, and one dot is formed in one driving mode. Since printing is performed, in an on-demand type inkjet printer, any printing pattern can always be stably printed.

Operation and Effect Corresponding to the Tenth Invention The voltage (Vp1) having the first polarity and the voltage (Vp2) having the second polarity different from the above-mentioned polarity are expressed by V
If the method of driving the ink jet head is characterized in that p1 is smaller than Vp2, one dot printing can be realized by one driving mode.

According to the eleventh aspect, the absolute value of the time integral of the voltage having the first polarity is equal to the absolute value of the time integral of the voltage having the second polarity having a different polarity. The method for driving an ink jet head according to the present invention can reliably remove the remaining residual charges, and does not cause unnecessary residual charges due to application of a voltage having a second polarity having a different polarity.

An ink jet printing apparatus characterized in that the voltage (Vp1) having the first polarity and the voltage (Vp2) having the second polarity different in polarity are equal to each other. According to the head driving method, the remaining residual charges can be reliably removed, and unnecessary residual charges due to application of a voltage having a second polarity having a different polarity do not remain.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a main part of an inkjet head according to the present invention.

FIG. 2 is a diagram for explaining a drive signal in the present invention.

FIG. 3 is a view taken along the line III-III in FIG. 1 and shows the movement of the diaphragm corresponding to the drive signal in FIG. 2;

FIG. 4 is a diagram for explaining a relationship between a driving signal, a position of a meniscus, and a fluctuation in ink pressure in a discharge chamber.

FIG. 5 is a diagram for explaining the relationship between the movement of a diaphragm and the ink pressure in a discharge chamber.

FIG. 6 is a diagram for explaining a relationship between a driving voltage, a meniscus position, and ink pressure fluctuation in a discharge chamber.

FIG. 7 is a diagram illustrating a relationship between a pulse delay time and an ink droplet velocity.

FIG. 8 is a drive signal waveform diagram for explaining an example of a drive signal.

FIG. 9 is a diagram illustrating a relationship between a driving voltage and an ink droplet speed.

FIG. 10 is a diagram illustrating a relationship between a drive signal and a meniscus position.

FIG. 11 is a diagram for explaining a relationship between a driving voltage and a residual charge amount.

[Explanation of symbols]

100: inkjet head, 101, 102, 10
3 ... substrate, 104 ... nozzle hole, 105 ... diaphragm, 106
.., Discharge port, 107 orifice, 108 common ink chamber, 109 individual electrode, 110 vibration chamber.

Continued on the front page (72) Inventor Shinji Tanaka 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Inventor Hiromichi Komai 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Co., Ltd. F term (reference) 2C057 AF28 AF81 AG12 AG54 AG55 AG85 AM03 AM17 AM18 AM21 AM22 AP02 AP25 AQ01 AQ02 AR04 AR08 BA03 BA15

Claims (12)

[Claims] An actuator comprising a nozzle, an ink flow path communicating with the nozzle, a vibration plate provided in a part of the flow path, and an electrode provided to face the vibration plate. Then, deforming the diaphragm, ejecting ink droplets from the nozzles, in a driving method of a printing apparatus that performs recording,
A voltage is applied in a driving mode consisting of a combination of a voltage having a first polarity and a voltage having a second polarity different from the polarity between the diaphragm and the electrode to deform the diaphragm and form the nozzle from the nozzle. A method for driving an ink jet head, which comprises discharging ink droplets. 2. The method for driving an ink jet head according to claim 1, wherein the voltage having a second polarity different from the voltage having the first polarity is a voltage value at which the diaphragm contacts the electrode. A method for driving an inkjet head, characterized in that the size is as described above. 3. The method of driving an ink jet head according to claim 1, wherein when the voltage having the first polarity is applied to deform the vibration plate, no ink droplet is ejected. An ink droplet is ejected from the nozzle when the diaphragm is deformed by applying a voltage having a second polarity. 4. The method of driving an ink jet head according to claim 3, wherein the polarity of the driving voltage is switched before the diaphragm moves away from the electrode. 5. The method for driving an ink jet head according to claim 3, wherein the polarity of the drive voltage is switched after the pressure vibration in the ink flow path communicating with the nozzle becomes positive. A method for driving an inkjet head, which is characterized by the following. 6. A method for driving an ink jet head according to claim 5, wherein the ink droplets are ejected from the nozzle after the pressure oscillation in the ink flow path communicating with the nozzle becomes negative. A method for driving an ink-jet head, comprising: 7. The method of driving an ink jet head according to claim 3, wherein a time T12 required to switch the polarity of the drive voltage (the voltage Vp1 having the first polarity) is used.
From the time until the voltage Vp2 having the second polarity)
Is a method for driving an ink jet head, wherein the period is shorter than a half of an ink pressure oscillation period of an ink discharge chamber communicating with the nozzle. 8. The method for driving an ink jet head according to claim 3, wherein the time T12 (time from Vp1 to Vp2) required to switch the polarity of the driving voltage is T12 ≦ 50 (microseconds). A method for driving an inkjet head, characterized by satisfying the relationship. 9. The method for driving an ink jet head according to claim 1, wherein a voltage having the first polarity is applied to deform the diaphragm to discharge ink droplets from the nozzles. A voltage having a second polarity different from the first polarity is applied to deform the vibrating plate, and the ink droplets ejected from the nozzles are united before reaching the recording medium to record one dot print. A method for driving an ink jet head, wherein the method is formed on a medium. 10. The method of driving an ink jet head according to claim 9, wherein the voltage having the first polarity (Vp1) and the voltage having a second polarity different from the polarity (Vp2) are Vp1 <Vp2. A method for driving an inkjet head, characterized by satisfying the following relationship: 11. The method for driving an ink jet head according to claim 1, wherein an absolute value of a time integration of the voltage having the first polarity and a second value having a different first polarity are used. A method for driving an ink jet head, wherein the absolute value of the time integral of a voltage having a polarity is equal to the absolute value. 12. The method of driving an ink jet head according to claim 1, wherein the voltage having the first polarity (Vp1) and a voltage different from the first polarity are used. Voltage having two polarities (Vp2)
Is a method for driving an ink-jet head, wherein a relationship of Vp1 = Vp2 is satisfied.