JPH11170537A - Ink jet recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet recorder in which a very small quantity of ink can be jetted stably even when a colloidal liquid ink produced by dispersing a coloring component uniformly into a high resistance solvent using a surfactant is employed. SOLUTION: A DC bias voltage having a specified magnitude and a jet signal 11 comprising positive and negative continuous pulses of specified width corresponding to an input image signal are generated. The jet signal 11 is superposed on the bias voltage to produce a drive signal 12 having lower voltage than the bias voltage immediately after falling of the jet signal 11. The drive signal 12 is then applied, as an applying jet voltage, to a jet electrode arranged in an ink channel thus jetting ink toward a recording medium.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink-jet recording apparatus, and more particularly to an ink-jet recording apparatus using a colloidal liquid ink in which a coloring material component is uniformly dispersed using a surfactant in a high-resistance solvent. The present invention relates to an ink jet recording apparatus that performs recording by discharging ink onto a recording medium.

[0002]

2. Description of the Related Art There have been many proposals for an ink jet recording method in an ink jet printer. Among them, the following two methods are typical ones. One is a method in which ink vapor is generated by the heat of a heating element and an ink droplet is caused to fly by the pressure, and the other is a method in which a mechanical pressure pulse is generated by a piezoelectric element to generate an ink droplet. This is a method of flying.

As a recording head used in these ink jet printers, for example, a serial scanning head has been put to practical use. In the serial scanning type head, a recording head mounted on a carriage moves in a direction (called a main scanning direction) orthogonal to a conveying direction of a recording medium such as paper (called a sub-scanning direction). This is for recording. As described above, an inkjet printer using this recording head performs recording while mechanically moving the recording head in the main scanning direction, so that it is difficult to increase the recording speed.

Therefore, in order to increase the recording speed, a method of using a recording head called a line scanning type head having the same size as the width of the recording medium and eliminating a mechanically movable part in the main scanning direction during recording. There is. However, the above-described ink jet recording method has a problem in that the nozzles of the recording head are clogged and a problem in processing because the structure of the recording head itself is complicated. With technical difficulties.

In order to realize a line scanning type head that solves these problems, a configuration that does not require a nozzle for each individual dot or a configuration that does not require a partition of an ink flow path for each individual dot is provided. It is desirable that the recording head be easy to manufacture. As a specific method, there has been proposed a method in which a voltage is applied to a thin-film electrode array, and a coloring material component in the ink liquid surface is caused to fly from the ink liquid surface using electrostatic force.

For example, Japanese Patent Application Laid-Open No. 8-207307 describes an "ink-jet recording apparatus" using this method. In this method, an ink obtained by dispersing a charged or chargeable color material component in an insulating liquid is used.
By circulating through the ink flow path and applying a high voltage having the same polarity as the charged color material component to the discharge electrode formed in the ink flow path, the charged color material component and the discharge electrode The repelling force mainly causes the color material components to fly.

Here, as a prior art, Japanese Patent Laid-Open No.
The structure and operation of the recording head disclosed in 207307 will be described. FIG. 9 schematically shows a cross section near an ink ejection position of a conventional ink jet recording head.

In the recording head 28 shown in FIG. 1, a plurality of discharge auxiliary electrodes 30 are formed on a first insulating base material 32 having a gradually decreasing shape. 2
The insulating base material 31 is provided so as to be spaced apart, and a slope portion 35 is formed at the tip of the second insulating base material 31.

A plurality of discharge electrodes 29 are provided on the upper surface 31a of the second insulating base 31 at an acute angle with the inclined surface 35. The tips of the plurality of ejection electrodes 29 are extended to near the tips of the upper surface portion 31a, and the tips project forward from the ejection auxiliary electrodes 30.

The first and second insulating substrates 32,
An ink flow path 36 is formed between the bases 31, and an ink recovery path 37 as ink recovery means is formed below the second insulating base material 31. In addition, a porous member 33 as an ink suction means is provided on the slope portion 35 of the second insulating base material 31, and the porous member 33 is arranged in a direction in which the ejection electrodes 29 are arranged. Is formed with a width dimension wider than the formation width of. Note that the ejection electrode 29 and the ejection auxiliary electrode 30 have a one-to-one correspondence.

First and second insulating substrates 32, 31
Is positioned with a space of about 1 mm,
At this interval, the surface having the ejection electrode 29 and the ejection auxiliary electrode 30
, And the tip of the ejection electrode 29 projects 1 mm from the tip of the ejection auxiliary electrode 30 so that the ejection electrode 29 and the ejection auxiliary electrode 30 face each other.

The recording drive IC 39 shown in FIG. 9 individually drives the ejection electrodes 29 in accordance with image information and is connected to a signal voltage power supply 40 as a voltage applying means for applying a potential to the electrodes. The ejection auxiliary electrode 30 is also connected to a bias power supply (not shown). A backing 38 is provided on the surface of the second insulative base material 31 opposite to the surface on which the ejection electrodes are formed so as to be spaced apart from each other. is there.

Next, the operation of the conventional ink jet recording head having the above configuration will be described. The ink 34 in the ink flow path 36 is supplied by an ink supply device (not shown) in a direction indicated by an arrow B1 in FIG.
Of the porous member 33 and the ink recovery path 3
After 7 is collected.

The ink 34 is obtained by dispersing toner particles containing a coloring material pigment such as carbon black, a dispersant, and a charge control agent in a binder mainly composed of a resin in an insulating liquid. Used. The toner particles are charged to have the same polarity as the potential applied to the discharge electrode 29 and the discharge auxiliary electrode 30, or are charged.

FIGS. 10 and 11 are views for explaining the state of the ink 34 near the tip of the discharge electrode shown in FIG. That is, FIG. 10 shows a state at the time of non-printing. In a state where the flow of the ink 34 is stopped, the ink 34 stays at the tip of the discharge electrode 29 at the tip of the printing head due to its surface tension.

Next, when recording is started and the supply of the ink 34 is started by operating the ink supply device, as shown in FIG. 11, at the boundary between the discharge electrode 29 and the second insulating base material 31,
An ink retaining section 34B is generated. However, the porous member 33
Is provided close to the ejection electrode 29, the ink stagnation portion is absorbed by the porous member 33 before expansion, and the ink stagnation portion does not expand and grow in the vicinity of the tip of the ejection electrode. A thick ink flow is obtained.

At this time, when a drive voltage according to image information is applied to the discharge electrode 29 from the signal voltage power supply 40 of FIG. 9 via the recording drive IC 39, the charged toner particles located at the tip of the discharge electrode are charged. When the repulsive force (repulsive force) is generated between the ink and the ejection electrode 29, and the repulsion overcomes the surface tension of the ink, the toner particles fly as ink droplets from the tip of the ejection electrode.

As described above, a configuration in which a nozzle is not required for each individual dot and a partition of an ink flow path for each individual dot is not required, and a color material component is mainly ejected as an ink droplet. Can be. However, in practice, the charging characteristics of the coloring material components in the ink vary, and even when a constant electric field is applied between the discharge electrode and the recording medium, the charge amount is different. The size varies.

Further, in such an ink, the coloring material component, which is fine particles, easily aggregates in the insulating liquid to form a lump of the coloring material component of a certain size. There are individual variations. Therefore, when such a lump is ejected, a large ink droplet is formed.

Therefore, as a method of solving such a variation in ejection, there is a method of using a colloidal ink in which a coloring material component is uniformly dispersed using a surfactant in a solvent having a high resistance. When this type of ink is used, the entire ink including the solvent receives a repulsive force and can discharge ink droplets having the same density as the supplied ink.
Therefore, there is no variation in the charging characteristics of the color material components as described above, and no variation in discharge due to aggregation of the color material components.

[0021]

However, when this colloidal ink is used, the ejection amount becomes larger than that of the ink in which the coloring material component is dispersed in the above-mentioned insulating liquid. In addition, when the ejection interval is long, ejection failure occurs.

FIG. 12 shows an example of a driving waveform of a conventional ink jet recording head. That is, the bias voltage V
to b, the pulse width t _01, was obtained by superimposing an ejection signal of the peak value V _01, by applying a discharging drive signal voltage V ₀₂ to the ejection electrodes to eject ink. At this time, as shown in the drawing, if the interval t ₀₂ between the drive signals S ₀₁ and S ₀₂ is long in time, a phenomenon appears that the ink becomes difficult to be ejected when the ejection signal S ₀₂ is applied.

As described above, in the conventional ink jet recording apparatus, when an ink in which a coloring material component is uniformly dispersed using a surfactant in a high-resistance solvent is used, the ink ejection amount is large. For example, there is a problem that minute recording dots cannot be obtained. In addition, there is also a problem that a discharge failure is likely to occur in the next discharge in which a certain discharge is performed and a time interval is long after that.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to use an ink in which a coloring material component is uniformly dispersed using a surfactant in a high-resistance solvent. It is an object of the present invention to provide an ink jet recording apparatus capable of ejecting a small amount of ink even when the ink jet recording is performed, and capable of stably ejecting ink even when an ejection interval is long.

[0025]

In order to achieve the above object, an ink jet recording apparatus according to a first aspect of the present invention supplies ink to an ink flow path from an ink supply section and is arranged in the ink flow path. A predetermined ejection voltage is applied to the ejection electrode to apply an electrostatic force to the ink, and the ink to which the electrostatic force is applied is ejected toward the recording medium from an ejection port arranged to face the recording medium. In the ink jet recording apparatus, means for generating a bias voltage having a predetermined DC voltage, means for generating an ejection signal in which both positive and negative pulses of a predetermined width are continuous according to an input image signal, and Means for superimposing the ejection signal, generating a drive signal having a voltage lower than the bias voltage immediately after the fall of the ejection signal, and setting the drive signal as the ejection voltage. And a discharge voltage applying unit that applies to the discharge electrode.

In an ink jet recording apparatus according to a second aspect of the present invention, ink is supplied from an ink supply unit to an ink flow path, and a predetermined discharge voltage is applied to a discharge electrode disposed in the ink flow path to apply the ink to the ink flow path. A bias voltage having a predetermined cycle is generated in an ink jet recording apparatus that applies an electrostatic force and ejects the ink to which the electrostatic force is applied toward the recording medium from an ejection port arranged opposite to the recording medium. Means for generating an ejection signal composed of pulse trains each having a predetermined width and separated by a predetermined time interval in accordance with the input image signal, and synchronizing with the cycle of the bias voltage, Means for generating a drive signal in which the ejection signal is superimposed during a high level period, and ejection voltage applying means for applying the drive signal to the ejection electrode as the ejection voltage. Provided.

In the ink jet recording apparatus according to the third aspect of the invention, ink is supplied from an ink supply unit to an ink flow path, and a predetermined discharge voltage is applied to a discharge electrode arranged in the ink flow path. A bias voltage having a predetermined cycle is applied to an ink jet recording apparatus that applies an electrostatic force to ink and ejects the ink to which the electrostatic force is applied toward the recording medium from an ejection port arranged opposite to the recording medium. Means for generating an ejection signal in which both positive and negative pulses of a predetermined width are continuous according to the input image signal, and synchronizing with the cycle of the bias voltage, the high-level period of the bias voltage Means for generating a drive signal in which the ejection signal is superimposed such that a positive pulse of the ejection signal corresponds and a negative pulse of the ejection signal corresponds to a low level period of the bias voltage; And a discharge voltage applying unit that applies to the discharge electrode driving signal as the discharge voltage.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 Hereinafter, Embodiment 1 according to the present invention will be described with reference to the drawings. FIG. 1 shows a cross section near an ink ejection position of a recording head constituting an ink jet recording apparatus according to Embodiment 1 of the present invention and a peripheral portion thereof. The recording head 1 shown in FIG.
The ink supply flow path 5 is formed by an insulative base material 2 and a second insulative base material 3 which is provided opposite to the first insulative base material 2 and whose one end has a gradually decreasing shape. Has formed. One or a plurality of ejection electrodes 4 as individual electrodes are formed on the surface of the second insulating substrate 3 on the ink supply channel 5 side.

The tip of the discharge electrode 4 is extended to the vicinity of the tip of the first insulating substrate 2, and the tip projects forward from the first insulating substrate 2. .
In addition, a driving unit 8 is connected to the ejection electrode 4 as ejection voltage application means for individually driving the ejection electrode 4 in accordance with image information input via the terminal 51. The drive unit 8 includes a signal generation circuit 9 for generating an ejection signal 11 for ink ejection in accordance with the image information, and a drive signal obtained by amplifying the ejection signal 11 and superimposing it on a constant bias voltage. And a drive circuit 10 for outputting the signal 12.

The supply pump 7 is connected to the ink supply passage 5 described above.
And functions as an ink supply means for supplying the ink 6 at a constant pressure. Further, the present inkjet recording apparatus is provided with a counter electrode 13, and the recording medium 14 is located on the surface of the counter electrode 13. The counter electrode 13 is provided on a recording medium 14.
It is intended to stabilize the electric field between the electrode and the discharge electrode 4 and is therefore grounded.

Next, the operation of the recording head of the ink jet recording apparatus according to the first embodiment will be described. FIG.
Are supplied from the supply pump 7 as described above, and the ink 6 flows through the ink supply flow path 5 of the recording head 1. The supply pump 7 uses the pressure to
Is pushed out in the direction of arrow A1 to feed the ink 6 to the tip of the recording head 1.

As the ink 6, an ink in which a coloring material pigment is uniformly dispersed using a surfactant in a solvent having a high electric resistivity is used. In this case, the electrical resistivity of the ink as a whole is desirably 10 ⁸ Ωcm or more. The ink 6 supplied to the ink supply channel 5 stays at the tip of the ejection electrode 4 and forms a liquid surface 6 a between the first insulating base material 2 and the ejection electrode 4.

FIG. 2 is a diagram for explaining the movement of ink at the tip of the recording head 1. FIG. 2 (a)
The state of ink at the tip of the recording head 1 when only the supply pump 7 described above is operated is shown. In this state, the ink 6 flows between the ejection electrode 4 and the first insulating substrate 2 due to the surface tension of the ink.
a is formed and is in a balanced state. Therefore, the supply force for flowing ink in the direction of arrow A1 in FIG. 1 must be adjusted to such an extent that the ink level 6a can be maintained.

Next, a bias voltage Vb is applied to the ejection electrode 4 from the drive unit 8. FIG. 2B shows the state of the ink at the tip of the recording head 1 at this time. That is, the electric field is concentrated by sharpening the respective tips of the ejection electrodes 4, and the ink 6 receives an electrostatic force corresponding to the electric field by the bias voltage in the vicinity of the tips of the ejection electrodes 4,
The ink level 6a moves forward and a new ink level 6
b is formed. At this time, at the tip of the discharge electrode 4,
Since the ink 6 protrudes in the direction of the recording medium 14, the tip of the discharge electrode 4 is well wetted, and the ink is easily discharged.

The bias voltage Vb applied here is:
The voltage value must be such that the ink does not fly out of the recording head.

When image information is input to the drive unit 8 from the terminal 51, the drive unit 8 generates a discharge voltage described later in accordance with the image information, and superimposes the discharge voltage on the bias voltage Vb to discharge. Applied to the electrode 4. FIG. 2C shows the state of the ink at the tip of the recording head 1 at this time.

That is, at the tip end of the discharge electrode 4, a larger force is generated by the discharge voltage, and the ink is stretched in a thread shape toward the recording medium to form a liquid thread 6c. The grown liquid thread 6 c is eventually broken, and as a result, ink is ejected toward the recording medium 14.

Next, the ejection voltage applied to the ejection electrode 4 from the drive unit 8 will be described. As described above, when image information is input from the terminal 51 to the inkjet recording apparatus according to the present embodiment, the signal generation circuit 9 in FIG. FIG. 3 shows the signal waveform, and the signal generation circuit 9 outputs the voltage values V ₁ ,
And the rectangular wave of the pulse width t _1, generates a signal waveform and the rectangular wave is continuous at its trailing minus voltage V ₂ continues for a time t _2. At this time, the condition is t ₂
<T ₁ .

The ejection signal 11 having the above-mentioned waveform is input to the drive circuit 10. The drive circuit 10 amplifies the ejection signal 11 at a fixed magnification, and superimposes it on the bias voltage Vb. Output. FIG. 4 shows the signal waveform. That is, the signal waveform S2 in FIG. 4 is obtained by amplifying the ejection signal 11 and superimposing it on the bias voltage Vb.

[0040] In the discharge electrode 4 as described above, the ink 6 is raised toward the recording medium by the bias voltage Vb, the voltage value V ₃ is applied to the ejection electrode 4, the ink toward a recording medium To discharge. And the voltage value V
₃ is applied for a time t ₁ , the drive signal 12 changes its voltage value to the bias voltage V according to the waveform of the ejection signal shown in FIG.
become low V ₄ than b. At this time, a force that pulls back the raised ink acts on the ink at the tip of the ejection electrode 4, that is, the voltage value V ₄ indicates that the ink is ejected to the ejection electrode 4 more than necessary. Acts to suppress.

As described above, according to the present embodiment, when a signal waveform obtained by superimposing a discharge signal corresponding to an image signal on a constant bias voltage is applied to the discharge electrode,
By applying a voltage lower than the bias voltage to the ejection electrode at the fall of the ejection signal, a force acts to pull back the ink raised at the tip of the ejection electrode. Even when using an ink in which the color material components are evenly dispersed using the above, it is possible to prevent the ejection of the ink more than necessary at the time of applying the ejection voltage,
By discharging a small amount of ink, it is possible to stably output minute recording dots.

Embodiment 2 Hereinafter, a second embodiment according to the present invention will be described with reference to the drawings. FIG. 5 shows a cross section near an ink ejection position of a print head constituting an ink jet printing apparatus according to Embodiment 2 of the present invention and a peripheral portion thereof. In FIG. 5, the same components as those of the recording head according to the first embodiment shown in FIG. 1 are denoted by the same reference numerals.

In FIG. 5, the discharge electrode 4 has a terminal 61.
A driving unit 15 as an ejection voltage application unit for individually driving the ejection electrodes 4 according to image information input from the camera is connected. The drive unit 15 amplifies the ejection signal 19, a signal generation circuit 16 for generating an ejection signal 19 for ink ejection, a bias generation circuit 17 for generating a bias signal 20, and an ejection signal 19 according to input image information. And a drive circuit 21 for outputting a drive signal 22 obtained by superimposing the bias signal 20 on the bias signal 20. The other parts are the same as those of the ink jet recording apparatus according to the first embodiment, and the description thereof is omitted here.

Next, the operation of the recording head of the ink jet recording apparatus according to the second embodiment will be described. In the case where no voltage is applied to the discharge electrode 4 in FIG. 5, the operation from the supply of the ink 6 from the supply pump 7 to the formation of the liquid surface 6a at the tip of the discharge electrode is described in the first embodiment.
Therefore, the description is omitted.

The bias generation circuit 17 shown in FIG.
A bias signal S3 having a waveform shown in FIG.
Output as a bias signal 20. This bias signal 2
0 is a signal that fluctuates between the voltage values Vb1 and Vb2 in a cycle of 2 × t ₃ , and this cycle is equal to the ejection cycle during continuous ejection of ink.

Therefore, when this bias signal 20 is applied to the ejection electrode 4 through the drive circuit 21, the voltage value Vb
Since the difference between the bias voltages causes a difference in the force acting on the ink 6 between the case of 1 and the voltage value Vb2, the amount of protrusion of the ink at the tip of the ejection electrode 4 is different. Therefore, at the tip of the discharge electrode 4, ink vibration occurs in synchronization with the fluctuation of the bias signal. Note that the voltage value Vb2 at this time needs to be a voltage at which ink is not ejected.

Next, the signal generating circuit 16 of the driving unit 15
When image information is input via the terminal 61, the signal generation circuit 16 outputs a signal S having a waveform shown in FIG.
4, S5 (this is referred to as the ejection signal 19).
As shown in the figure, the discharge signal 19 is a signal having a voltage value (peak value) of V ₆ and a pulse width t ₄ , and two consecutive pulses S 4 and S _{5 have} a time interval of t _5. is there.

When the bias generating circuit 17 outputs the bias signal 20, it outputs a predetermined synchronizing signal 18 synchronized with the bias signal to the signal generating circuit 16. Therefore, the signal generation circuit 16 outputs the ejection signal 19 in synchronization with the synchronization signal.

The drive circuit 21 amplifies the ejection signal 19 input from the signal generation circuit 16 and applies it to the bias signal 2.
It is superimposed on 0 and output as a drive signal 22. FIG.
The signal S6 of (b) is the driving signal 22 obtained as a result of the superposition.
FIG. That is, the drive circuit 21 determines that the peak value of the bias signal 20 (S3) is Vb2,
Superimposing an ejection signal 19 at intervals of the time t ₅ (S4, S5), at the overlapping portion, signal S6 having a voltage value V ₇
Is output.

[0050] In this manner, in response to a voltage value Vb2, when the ink is most raised at the tip of the discharge electrode 4, the discharge voltage V ₇ required ink ejection ejection electrode 4
And ink is ejected. The operation from the application of the ejection voltage to the ejection of the ink is the same as in the first embodiment.

As described above, according to the second embodiment, a bias voltage having an ejection cycle at the time of continuous ejection of ink is applied to the ejection electrodes, and a signal corresponding to an image signal is supplied to the cycle of the bias voltage. By superimposing the bias voltage in synchronization with the bias voltage and applying the obtained voltage to the discharge electrode as a discharge voltage, the ink rises with the bias voltage while vibrating the ink at a fixed period at the tip of the discharge electrode. Since the ejection voltage can be applied at the same timing, even if the ink ejection interval is long due to the image information, there is an effect that the ink can be ejected reliably.

Embodiment 3 FIG. Hereinafter, a third embodiment according to the present invention will be described with reference to the drawings. FIG. 7 shows a cross section near an ink ejection position of a print head constituting an ink jet printing apparatus according to Embodiment 3 of the present invention and a peripheral portion thereof. In FIG. 7, the same components as those of the recording head according to the second embodiment shown in FIG. 5 and its peripheral portion are denoted by the same reference numerals.

In FIG. 7, the discharge electrode 4 has a terminal 71.
A drive unit 23 as an ejection voltage application unit for individually driving the ejection electrodes 4 in accordance with image information input from the camera is connected. The drive section 23 amplifies the signal generation circuit 24 for generating the ejection signal 25 for ink ejection, the bias generation circuit 17 for generating the bias signal 20, and the ejection signal 25 according to the image information, and amplifies the signal. The driving circuit 26 outputs a driving signal 27 obtained by being superimposed on the bias signal 20. Other parts are described in the first embodiment or the second embodiment.
Since they are the same as those described above, their description is omitted.

The operation of the recording head of the ink jet recording apparatus according to the third embodiment will be described. In the case where no voltage is applied to the ejection electrode 4, the operation from the supply of the ink 6 from the supply pump 7 to the formation of the liquid surface 6a at the tip of the ejection electrode is the same as that in the first embodiment. Therefore, the description is omitted. Also,
Bias signal 20 generated by bias generation circuit 17
Is applied to the discharge electrode 4 in the same manner as in the second embodiment.

That is, the bias signal 20 generated by the bias generation circuit 17 shown in FIG. 7 is the same as the bias signal S3 shown in FIG. 6A, and is 2 × t ₃ between the voltage values Vb1 and Vb2. It is a signal that fluctuates in a cycle. This cycle is equal to the ejection cycle during continuous ejection of ink.

Next, when image information is input to the drive unit 23 from the terminal 71, the signal generation circuit 24 performs the operations of S7 and S7 in FIG.
An ejection signal 25 having a waveform indicated by 8 is output. The ejection signal 25 includes a pulse signal having a voltage value of V ₉ and a width t6,
At the fall timing, the voltage value becomes −V ₈ ,
The pulse signal having the width t ₇ has a continuous waveform, and the two ejection signals S 7 and S _{8 have} a time interval t ₈ . When outputting the bias signal 20, the bias generation circuit 17 outputs a synchronization signal 18 synchronized with the bias signal 20 to the signal generation circuit 24.

The signal generating circuit 24 is provided with the synchronizing signal 18
The ejection signal 25 is output in synchronism with. Drive circuit 26
Amplifies the input ejection signal 25, superimposes it on the bias signal 20, and outputs the obtained signal as a drive signal 27. S9 in FIG. 8 shows the drive waveform of the drive signal 27.

Here, the timing at which the ejection signal 25 (S7, S8) is superimposed on the bias signal 20 will be described. That is, the drive circuit 26 superimposes the positive pulse of the ejection signal 25 on the bias signal 20 during the period when the bias signal 20 has the voltage value Vb2, and the negative pulse of the ejection signal 25 during the period when the bias signal 20 is at the potential Vb1. It operates so that the pulse is superimposed. That is, the driving circuit 2
6 superimposes the falling of the bias signal 20 and the falling of the ejection signal 25 so as to be synchronized, and outputs the result.

When the signal thus superimposed is applied to the ejection electrode 4, when the voltage of the bias signal is Vb 2, when the ink is most prominent at the tip of the ejection electrode 4, so that the discharge voltage V ₁₁ required ink discharge is applied to the discharge electrode 4. Further, immediately after the ejection voltage V ₁₁ is applied, the drive signal 27, the negative pulse waveform of the discharge signal 25, voltage value becomes the voltage value V ₁₀ is lower than the bias voltage. At this time, a force that pulls back the raised ink acts on the ink at the tip of the discharge electrode 4, and as a result, the ink is suppressed from being discharged more than necessary.

As described above, according to the third embodiment, a bias voltage having a discharge cycle at the time of continuous discharge of ink is applied to the discharge electrode, and a signal obtained by combining positive and negative pulses according to an image signal is output. By superimposing the bias voltage on the ejection electrode in synchronization with the cycle of the bias voltage and applying the obtained voltage to the ejection electrode as an ejection voltage, the ink is vibrated at a constant cycle at the tip of the ejection electrode, and the ejection signal is output. At the falling edge of the voltage, a voltage lower than the bias voltage can be applied to the ejection electrode, so that the ejection voltage can be applied at the timing when the ink is raised by the bias voltage, thereby preventing unnecessary ejection of the ink when the ejection voltage is applied. Not only can a small amount of ink be ejected, but also if ink ejection intervals are long due to image information. In even, there is an effect that it is possible to reliably eject ink.

In the configuration of the ink jet recording apparatus according to the first, second, and third embodiments, the counter electrode is not always a necessary element. Further, when this counter electrode is used, a configuration may be adopted in which a potential having a polarity opposite to that of the discharge electrode is applied thereto. The tip shape of each ejection electrode is not limited to the shape shown in FIG. 1 and the like, and may be any shape as long as high electric field concentration occurs.

Further, when there are a plurality of ejection electrodes, different bias voltages and ejection voltages may be applied to the respective ejection electrodes. Also,
In addition to the above configuration, the discharge electrode 4
It is also possible to arrange a transport electrode facing the printer and apply a constant voltage to the transport electrode to move the ink to the ejection port. This makes it possible to discharge ink more efficiently.

[0063]

As described above, the ink jet recording apparatus according to the first aspect of the present invention generates a bias voltage having a predetermined DC voltage in accordance with an input image signal.
A positive and negative pulse of a predetermined width is superimposed on a continuous ejection signal,
Immediately after the fall of the ejection signal, the ejection electrode is driven by a drive signal having a voltage lower than the bias voltage, so that the color material components are evenly dispersed using a surfactant in a high-resistance solvent. Even when the used ink is used, it is possible to prevent the ink from being unnecessarily ejected at the time of applying the ejection voltage, and it is possible to eject a small amount of ink and stably output minute recording dots.

According to a second aspect of the present invention, there is provided an ink jet recording apparatus comprising: a discharge signal comprising a pulse train, each of which has a predetermined width and is separated by a predetermined time interval, generated according to an input image signal, to a bias voltage having a predetermined cycle; Is superimposed on the high-level period of the bias voltage in synchronization with the cycle of the bias voltage to generate a drive signal and apply it to the ejection electrode, so that the ink is raised by the bias voltage. The ejection voltage can be applied at the timing, and the ink can be ejected reliably even when the ink ejection interval is long due to the image information.

Further, the ink jet recording apparatus according to the third invention is characterized in that a bias voltage having a predetermined cycle and a discharge signal in which both positive and negative pulses of a predetermined width generated according to an input image signal are continuous are applied to the bias voltage. A drive signal is obtained by superimposing the ejection signal so that the positive pulse of the ejection signal corresponds to the high level period of the bias voltage and the negative pulse of the ejection signal corresponds to the low level period in synchronization with the cycle of Is applied to the ejection electrode, so that it is possible to prevent ejection of ink more than necessary at the time of application of an ejection voltage, not only to eject a small amount of ink, but also to eject ink according to image information. Even when the interval is long, ink can be reliably ejected.

An ink jet recording apparatus according to a fourth aspect of the present invention provides a transport electrode which is disposed in an ink flow path so as to face an ejection electrode, and a transport voltage application for applying a voltage having the same polarity as the ejection electrode to the transport electrode. With this configuration, ink can be ejected more efficiently.

In the ink jet recording apparatus according to the fifth aspect of the present invention, since the counter electrode is provided at a position facing the discharge port, the ink can be discharged reliably and efficiently.

Further, in the ink jet recording apparatus according to the sixth aspect of the present invention, the cycle of the bias voltage is made equal to the ejection cycle at the time of continuous ejection of the ink, so that the timing of the rising of the ink by the bias voltage is matched. Reliable and efficient ink ejection is possible.

The ink jet recording apparatus according to the seventh aspect of the invention uses an ink obtained by uniformly dispersing a coloring material component using a surfactant in a high-resistance solvent, so that the ink can reduce the electric field generated by the ejection electrode. Since concentration can be reliably received and unnecessary ink ejection can be prevented, the efficiency of ink ejection can be significantly improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a cross section near an ink ejection position of a recording head constituting an ink jet recording apparatus according to a first embodiment of the present invention and a peripheral portion thereof.

FIG. 2 is a diagram for explaining the movement of ink at the tip of the recording head according to the first embodiment of the present invention.

FIG. 3 is a diagram showing a signal waveform of an ejection signal according to the first embodiment of the present invention.

FIG. 4 is a diagram showing a signal waveform of a drive signal according to the first embodiment of the present invention.

FIG. 5 is a diagram showing a cross section near an ink ejection position of a print head constituting an ink jet printing apparatus according to a second embodiment of the present invention and a peripheral portion thereof.

FIG. 6 is a diagram showing signal waveforms of a bias signal and an ejection signal according to a second embodiment of the present invention.

FIG. 7 is a diagram showing a cross section near an ink ejection position of a recording head constituting an ink jet recording apparatus according to Embodiment 3 of the present invention and a peripheral portion thereof.

FIG. 8 is a diagram showing a signal waveform of a drive signal according to a third embodiment of the present invention.

FIG. 9 is a diagram schematically showing a cross section near an ink ejection position of a conventional inkjet recording head.

FIG. 10 is a view for explaining the state of ink at the time of non-printing in the vicinity of the tip of a discharge electrode of a conventional ink jet print head.

FIG. 11 is a diagram for explaining a state of ink at the time of recording in the vicinity of the tip of a discharge electrode of a conventional ink jet recording head.

FIG. 12 is a diagram illustrating an example of a driving waveform of a conventional inkjet recording head.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Recording head, 2 1st insulating base material, 3 2nd insulating base material, 4 discharge electrode, 5 ink supply flow path, 6 ink, 6b ink liquid level, 7 supply pump, 8, 15,
23 drive unit, 9, 16, 24 signal generation circuit, 10,
21, 26 drive circuit, 11, 19, 25 ejection signal,
12, 22, 27 drive signal, 13 counter electrode, 14
Recording medium, 17 bias generation circuit, 18 synchronization signal,
20 bias signal

Claims (7)

[Claims] An ink supply unit supplies ink to an ink flow path, applies a predetermined discharge voltage to discharge electrodes disposed in the ink flow path, gives an electrostatic force to the ink, and supplies a recording medium with an electrostatic force. Means for generating a bias voltage having a predetermined direct-current voltage in an ink jet recording apparatus that discharges the ink to which the electrostatic force is applied toward the recording medium from discharge ports arranged opposite to each other; Means for generating an ejection signal in which both positive and negative pulses of a predetermined width are continuous in accordance with the signal; and superimposing the ejection signal on the bias voltage, and immediately after the falling of the ejection signal, a voltage lower than the bias voltage. And an ejection voltage applying unit for applying the drive signal as the ejection voltage to the ejection electrode. Recording apparatus. 2. An ink supply section supplies ink to an ink flow path, applies a predetermined discharge voltage to a discharge electrode arranged in the ink flow path, gives an electrostatic force to the ink, and applies a static power to the ink. A means for generating a bias voltage having a predetermined cycle in an ink jet recording apparatus for discharging the ink to which the electrostatic force is applied toward the recording medium from discharge ports arranged opposite to each other; Means for generating an ejection signal composed of pulse trains each having a predetermined width and separated by a predetermined time interval in accordance with the following; and synchronizing with the cycle of the bias voltage, superimposing the ejection signal on a high level period of the bias voltage. And a discharge voltage applying unit for applying the drive signal as the discharge voltage to the discharge electrode. Recording apparatus. 3. An ink supply unit supplies ink to an ink flow path, applies a predetermined discharge voltage to a discharge electrode arranged in the ink flow path, gives an electrostatic force to the ink, and applies a static power to the ink. A means for generating a bias voltage having a predetermined cycle in an ink jet recording apparatus for discharging the ink to which the electrostatic force is applied toward the recording medium from discharge ports arranged opposite to each other; Means for generating an ejection signal in which both positive and negative pulses of a predetermined width are continuous, and the positive pulse of the ejection signal corresponds to a high level period of the bias voltage in synchronization with the cycle of the bias voltage. Means for generating a drive signal in which the ejection signal is superimposed such that a negative pulse of the ejection signal corresponds to a low level period of a bias voltage; and An ink jet recording apparatus characterized by comprising a discharge voltage application means for pressurizing. 4. The image forming apparatus further comprises: a transport electrode disposed in the ink flow path so as to face the discharge electrode; and a transport voltage applying unit configured to apply a voltage having the same polarity as the discharge electrode to the transport electrode. 4. An ink jet recording apparatus according to claim 1, wherein: 5. The recording medium according to claim 1, further comprising a counter electrode at a position facing the discharge port, wherein the recording medium is interposed between the discharge port and the counter electrode. 3. The ink jet recording apparatus according to claim 1. 6. The ink jet recording apparatus according to claim 2, wherein a cycle of the bias voltage is equal to an ejection cycle during continuous ejection of the ink. 7. The ink according to claim 1, wherein the ink is an ink obtained by uniformly dispersing a coloring material component in a high-resistance solvent using a surfactant. Ink jet recording device.