JPH09272204A - Ink jet recording device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an on-demand type ink jet recording device which can be easily driven at a high speed. SOLUTION: This ink jet recording device controls the application of a pressure to be applied to ink chamber 7 and also the application of an electric field for giving electrostatic power which attracts the ink to the ink to be discharged from a nozzle 6, in accordance with image information. In addition, this device is equipped with an elastically deformable diaphragm 3a with a second electrode 4 formed opposite to a second electrode on an insulating substrate 1. Further, a third electrode 9 is arranged across the second electrode 4 and the ink chamber 7 in the ink discharge direction. (A) shows a standby state and (B) shows an ink discharge state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an on-demand type ink jet recording apparatus for selectively ejecting ink from an ink ejecting element in accordance with image information, and for output printing of an office or personal computer. It is used.

[0002]

2. Description of the Related Art As an on-demand type ink jet recording apparatus, various methods have been proposed. As typical ones, there are a method of drawing out ink by electrostatic force and a method of applying pressure to the ink. There is a method of ejecting ink by force.

A device for drawing out and ejecting ink by electrostatic force is disclosed in, for example, Gen Oda, "IS &T's".
Eighth International Congres
sson Advances in Non-Inpa
ct Printing Technologies ”,
(1992), p. 343-345.
This device is composed of an electrode on the back surface of the recording paper, a bias electrode near the nozzle opening, and a signal electrode located on the head substrate side from the nozzle tip, and applies a positive DC bias voltage to the back electrode and the bias electrode. A negative pulse voltage is applied to the signal electrode and the ink is sucked and ejected by electrostatic force. However, a large potential difference is required to fly the ink. Further, there is a problem that the response of the ink to the electrostatic force is poor and the printing speed is slow.

On the other hand, a device for applying pressure to ink to eject the ink is described in, for example, Japanese Patent Laid-Open No. 6-340069. In this device, an electrode is formed on an elastically deformable movable plate, the movable plate is deformed by an electrostatic force with an opposing electrode, and the pressure due to the restoring force of the movable plate is applied to the ink to eject the ink. Further, by controlling the amount of deformation of the pressure generating member such as the movable plate to control the amount of pressure and the amount of change in volume of the ink chamber, the dot size can be modulated. However, when performing dot size modulation, if the ink droplets are made smaller, the ejection pressure also becomes smaller, so that minute ink droplets cannot be ejected, and dot size modulation of several tens of gradations or more is difficult. Have the problem of being.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an on-demand type ink jet recording apparatus which can be easily driven at high speed and is low in cost. It is a thing. It is possible to drive at a low voltage, and in the case of providing gradation, dot size modulation of several tens of gradations or more is possible.

[0006]

According to a first aspect of the present invention, in an ink jet recording apparatus for ejecting ink in an ink chamber from a nozzle on demand, pressure is applied to the ink in the ink chamber. It has a pressure applying means and an electric field applying means for applying an electrostatic force to the ink ejected from the nozzle to attract the ink, and the pressure applying means and the electric field applying means are controlled according to an input signal. It is a feature.

According to a second aspect of the invention, in the ink jet recording apparatus according to the first aspect, the pressure applying means has an elastically deformable diaphragm and first and second electrodes, and the diaphragm is the The second electrode is formed on the diaphragm, forms a part of the side wall of the ink chamber, the first electrode is formed on the substrate so as to face the second electrode, and the electric field applying unit is formed of at least one third electrode. And the third electrode is arranged in the ink ejection direction with the second electrode and the ink chamber separated from each other.

According to a third aspect of the invention, in the ink jet recording apparatus according to the second aspect, the third
At least one of the electrodes is disposed in the vicinity of the nozzle, and the electrode area is smaller than the electrode area of the second electrode.

According to a fourth aspect of the invention, in the ink jet recording apparatus according to the second or third aspect,
Applying a predetermined voltage between the first electrode and the third electrode,
It is characterized in that the discharge standby state and the discharge state are switched by controlling the voltage applied to the second electrode.

According to a fifth aspect of the present invention, in the ink jet recording apparatus according to the fourth aspect, the plurality of nozzles are provided, and the first electrode and the third electrode are common electrodes for the plurality of nozzles. The second electrode is an individual electrode for each nozzle.

According to a sixth aspect of the invention, in the ink jet recording apparatus according to the fourth or fifth aspect,
It is characterized in that the potential of the second electrode in the ejection standby state is controlled and the potential maintenance time of the second electrode in the ejection state is controlled.

[0012]

FIG. 1 is a sectional view for explaining a first embodiment of an ink jet recording apparatus of the present invention. FIG. 1 (A) shows a standby state of an element, and FIG. ) Indicates the ejection state of the element. In the figure, 1 is an insulating substrate, 2 is a first electrode, 3 is a pressure generating member, 3a is a diaphragm, 3b is a gap, 4 is a second electrode, 5 is a nozzle forming member, 6 is a nozzle, and 7 is an ink chamber. , 8 is a recording paper, and 9 is a third electrode.

This embodiment is an ink jet recording apparatus for ejecting ink from a nozzle on demand in accordance with image information, and applies pressure to the ink in an ink chamber 7 and at the same time ejects the ink ejected from the nozzle 6. On the other hand, an electric field that gives an electrostatic force for attracting this ink is applied, and the application of this pressure and the application of the electric field are controlled according to the image information. The pressure applying means has, for example, an elastically deformable diaphragm 3a, and the diaphragm 3a has a second
The electrode 4 is formed, and the first electrode 2 is formed on the insulating substrate 1 so as to face the second electrode. Further, the electric field applying means has a third electrode 9, and the third electrode 9
The second electrode 4 and the ink chamber 7 are separated from each other in the ink ejection direction.

In the standby state shown in FIG. 1 (A),
The diaphragm 3a is deformed toward the insulating substrate 1 side by the voltage applied between the first and second electrodes 2 and 4. FIG.
In the discharge state shown in (B), the diaphragm 3a
Deforms in the direction opposite to the standby state, a voltage is applied between the second and third electrodes 4 and 9, and an electric field is applied in a direction parallel to the ink ejection direction.

Again, the details of the structure will be described with reference to FIG. The insulating substrate 1 is made of ceramic, glass, or the like, and the first electrode 2 is formed in the central portion and the pressure generating member 3 is placed on the upper surface thereof.
A movable plate portion, for example, a diaphragm 3a is formed on a central upper surface portion of the pressure generating member 3. When the pressure generating member 3 is made of silicon by a semiconductor process, the central upper surface thereof is processed into a sufficiently thin film by a method such as anisotropic etching to form the diaphragm 3a. The diaphragm 3a is circular as an example, and a gap 3b is formed between the diaphragm 3a and the upper surface of the insulating substrate 1, and the gap 3b of the diaphragm 3a is formed.
The second electrode 4 is formed on the side surface. This second
The peripheral portion of the pressure generating member 3 is bonded onto the insulating substrate 1 so that the electrode 4 of the pressure generating member 3 faces the first electrode 2.

The diaphragm 3a has the above-mentioned Japanese Patent Laid-Open No. 6-
Like the movable plate portion of the prior art described in Japanese Patent No. 340069, the entire circumference is connected to the periphery of the pressure generating member 3, or a cantilever structure in which three pieces are separated by a cut groove is provided, and the cut groove is formed. A thin film having low rigidity such as closing may be covered from the ink chamber 7 side or the gap 3b side. Even when it is covered with a thin film as described above, the diaphragm 3a substantially forms a part of the side wall of the ink chamber 7.

The second electrode 4 is used as the above-mentioned JP-A-6-34.
Similar to the conventional technique described in Japanese Patent Laid-Open No. 0069, it can be formed by adhering aluminum to the diaphragm 3a by vacuum vapor deposition or sputtering, or by doping impurities when it is manufactured by a semiconductor process. Further, the second electrode 4 may be formed on the surface of the diaphragm 3a on the ink chamber 7 side. The second electrode 12 is typically circular and has the same outer diameter as the first electrode 2.

A nozzle forming member 5 is mounted on the pressure generating member 3. An ink chamber 7 is formed by the upper surface of the pressure generating member 3 and the nozzle forming member 5, and the diaphragm 3a is one side wall of the ink chamber 7. The ink chamber 7 has a nozzle 6 for ejecting ink at the center upper part,
Further, an ink supply path (not shown) is also provided, and the inside is filled with ink.

As described above, a single nozzle element having the nozzle 6 is formed by the laminated structure of the insulating substrate 1, the pressure generating member 3 and the nozzle forming member 5. In the drawing, the nozzle element is arranged so that the nozzle 6 faces vertically upward, but it may be arranged so that the nozzle 6 faces the horizontal direction. In this case, the surface of the ink at the opening of the nozzle 6 is also possible. Ink does not leak due to tension. A recording paper 8 is arranged so as to face the nozzles 6, and a third electrode 9 is provided on the back surface of the recording paper 8. Ink ejection is performed by controlling the respective potentials V ₁ , V ₂ , V ₃ of the first to third electrodes ₂ , ₄ , 9 by a controller (not shown).

The first to third electrodes 2, 4 and 9 may be protected by an insulating film of silicon oxide or the like to prevent a short circuit between the electrodes, and as long as the driving principle of the present invention can be realized, Can be variously changed.

The principle of operation will be described while comparing FIG. 1 (A) and FIG. 1 (B). When a positive potential difference (V ₁ −V ₂ ) is applied to the first electrode 2 and the second electrode 4, the standby state shown in FIG. The diaphragm 3a is in a deformed state in which it is deformed in the direction of the first electrode 2 and protrudes toward the gap 3b, and the restoring force is retained. According to the image signal, the positive potential difference (V ₁ -V ₂ ) between the first electrode 2 and the second electrode 4 is selectively opened, and at the same time, the second electrode 4 and the third electrode 9 are released.
And a positive potential difference (V ₂ −V ₃ ) between them. As a result, the diaphragm 3a generates a discharge pressure on the ink in the ink chamber 7 by the restoring force from the deformed state in the standby state, as shown in FIG. 1 (B).

In addition, the electrostatic meniscus is charged by the electrostatic field generated by the positive potential difference (V ₂ -V ₃ ) between the second electrode 4 and the third electrode 9, and the coulomb with the third electrode 9 is charged. The force causes the action of sucking the ink. FIG.
At the initial stage when the standby state shown in (A) is changed to the discharge state shown in FIG. 1 (B), the pressure due to the restoring force of the diaphragm 3a and the Coulomb force described above act simultaneously,
It is possible to shorten the ejection start time from the time of applying an electric field and realize low voltage driving. Therefore, high-speed printing can be efficiently realized as compared with the conventional electrostatic suction method. Further, the second electrode 4
While the positive potential difference (V ₂ −V ₃ ) between the third electrode 9 and the third electrode 9 maintains the ink suction voltage, the ink is continuously sucked to the recording paper, so that the application time of the ink suction voltage is changed. By controlling, gradation expression by dot size modulation can be easily performed. As the ink, the ink for the electrostatic ink jet recording apparatus may be used as in the case of the paper cited as the prior art.

FIG. 2 is a sectional view for explaining the second embodiment of the ink jet recording apparatus of the present invention. In the figure, the same parts as those in FIG. Reference numeral 11 is an electrode supporting member, 12 is a third electrode, and 13 is an opening. In this embodiment, the third electrode 12 is formed on the electrode support member 11, so that the third electrode is not provided on the back surface of the recording paper 8 as shown in FIG. It is arranged inside.

The electrode supporting member 11 is attached to the upper surface across the center of the nozzle forming member 5 and has an opening 13 in the extending direction of the nozzle 6. The opening 13 is
The nozzle 6 has the same shape and is designed to have substantially the same size or slightly larger size, but is not necessarily limited thereto. Electrode support member 1
The upper surface of No. 1 is at a predetermined distance from the upper surface of the nozzle forming member 5, a third electrode 12 is formed adjacent to the opening 13, and the third electrode 12 is arranged near the nozzle 6. The third electrode 12 is typically ring-shaped, and its outer shape has the same diameter as the second electrode 4. Although illustration is omitted, the recording paper is arranged so as to face the nozzles 6 and the openings 13 as in the first embodiment described with reference to FIG. The potential of the third electrode 12 does not necessarily have to be the same potential as the potential of the third electrode 9 shown in FIG. 1, but may be any potential that generates a force for sucking ink.

The ink ejection control and the ink ejection state are the same as those in the first embodiment described with reference to FIG. 1, but according to this embodiment, all the electrodes are provided in the print head. It is possible to reduce the distance between the third electrode 12 and the second electrode 4 as compared with the case where it is arranged on the back surface of the recording paper 8 as well as the structure is simplified. It is possible to further lower the applied voltage.

FIG. 3 is a sectional view for explaining the third embodiment of the ink jet recording apparatus of the present invention. In the figure, the same parts as those in FIGS. 1 and 2 are denoted by the same reference numerals, and description thereof is omitted. In this embodiment, the third electrode 12 as shown in FIG. 2 is formed on the electrode supporting member 11, and the third electrode 9 is arranged also on the back surface of the recording paper 8 as shown in FIG. By doing so, a plurality of third electrodes are arranged. As a result, it becomes possible to further improve the speed and directionality of the ejected ink. In addition,
The electric potentials of the third electrode 9 and the third electrode 12 are appropriately adjusted.

FIG. 4 is a constitutional view of second and third electrodes for explaining the fourth embodiment of the ink jet recording apparatus of the present invention. In the figure, the same parts as those in FIGS. 1 and 2 are denoted by the same reference numerals, and description thereof is omitted. Reference numeral 14 is a line of electric force, but only the line of electric force in the front outer peripheral portion is shown. In this embodiment, the electric field distribution between the second electrode 4 and the third electrode 12 in FIG. 2 or 3 is devised. Second electrode 4 and electrode supporting member 1 arranged on diaphragm 3a
When the area of the second electrode 4 is S ₂ and the area of the third electrode is S ₃ with respect to the third electrode 13 formed on 1,
Make sure that S ₂ > S ₃ .

When a voltage is applied between the second electrode 4 and the third electrode 12, the lines of electric force 14 are directed toward the vicinity of the nozzle 6 (FIGS. 2 and 3) adjacent to the opening 13. It's dense. That is, a larger electric field gradient is formed toward the nozzle 6. Since the ink is drawn toward the stronger electric field, an ink flow toward the nozzle 6 is generated. By defining the electrode area as described above, when ink is ejected,
In addition to the pressure due to the diaphragm 3a and the ink suction force due to the Coulomb force, the ink flow due to the electric field gradient causes
More efficient ink ejection can be realized.

Further explaining, by forming the area S ₃ of the third electrode 12 smaller than the area S ₂ of the second electrode 4, it is formed by a pair of the second and third electrodes 4, 12. The strength of the electric field has a gradient such that it becomes larger in the vicinity of the nozzle 6. In general, the force exerted by an electric field on a fluid per unit volume is the Coulomb force acting on an electric charge per unit volume, the force exerted by the spatial change of the dielectric constant, and the force exerted by the spatial change of the electric field strength. Will be the sum of the people.

In other words, the latter two are the forces acting on the polarization of the fluid. In other words, the amount of charge generated by the polarization of the dielectric substance is zero when the positive and negative are added together, but when the force acting on each polarized charge is integrated, a stronger force acts on the polarized charge generated in the place where the electric field is strong. Therefore, the fluid particles are attracted in the direction of strong electric field. Therefore, when a large electric field is formed in the vicinity of the nozzle 6, an ink flow toward the nozzle 6 is generated and plays a part of the ink ejection force. Although the circular electrode is illustrated as the second electrode 4 and the ring-shaped electrode is illustrated as the third electrode 13, the electrode shape is not limited to this.

In the above description, the nozzle element having a single nozzle is assumed. By arranging a plurality of such nozzle elements in a line, it is possible to configure one multi-nozzle head having a plurality of nozzles. 1 to 3, if the first electrode 2 and the third electrode 12 of each nozzle element are used as a common electrode and a common voltage is applied, the third electrode 4 of each nozzle element can be applied.
Can be individually applied as control signals. Of course, the second electrode 9 becomes a common electrode.

Further, since the sectional structure shown in FIGS. 1 to 3 is a layered structure, it is possible to easily form a head in which a plurality of nozzles are arranged adjacent to each other in a line. For example, in FIG. 2, the insulating substrate 1, the pressure generating member 3, the nozzle forming member 5, the ink chamber 7, and the electrode supporting member 11 are formed in a long shape extending in a direction perpendicular to the plane of the drawing, and the pressure generating member 3 is A plurality of diaphragms 3a are formed in the longitudinal direction, a plurality of nozzles 6 are formed correspondingly in the nozzle forming member 5, a plurality of openings 13 are formed in the electrode supporting member 11, and a second electrode is formed in each diaphragm 3a. 4 for each electrode support member 11
Then, the third electrode 4 may be formed. A common voltage can be applied to the first electrode 2 and the third electrode 12, and the electrodes themselves can be shaped to extend in the longitudinal direction. The second electrode 4 applies a control voltage for each nozzle as an individual control electrode.

FIG. 5 is a waveform diagram for explaining the first specific example of the method for driving the ink jet recording apparatus of the present invention. FIG. 5 (A) shows the potential V ₃ of the third electrode, FIG. B) is the potential V ₂ of the second electrode, and FIG. 5C is the potential V ₁ of the first electrode. In the figure, the horizontal axis represents time and the vertical axis represents the potential of each electrode. 21 is a discharge standby time. In this specific example, a predetermined voltage is applied to the first electrode 2 and the third electrodes 9 and 12, and the voltage applied to the second electrode 4 is controlled in a pulsed manner to achieve the discharge standby state and the discharge And the second electrode 4 in the discharge state.
The discharge amount is controlled by the ink suction time by controlling the potential maintenance time.

In the illustrated example, as shown in the periods A to D, the control is performed at equal intervals, but at the start of each period A to D, the discharge standby time 21 of a predetermined length is set, and the discharge standby time is set. When 21 is passed, the ejection is started, and the ejection start time becomes equal intervals. At least one of the nozzle head and the recording paper 8 moves according to the elapse of the periods A to D, and the relative positional relationship between the two changes, and an image signal input to the second electrode 4 is recorded on the recording paper 8. The corresponding dot is recorded.

First electrode 2 and third electrode 9 or 12
A potential difference corresponding to the total drive voltage is given in advance so that the potential V ₁ of the _first electrode 2 is higher than the potential V ₃ of the third electrode 9 or 12. The electric potential V ₂ of the second electrode 4 is controlled to be equal to the electric potential V _{3 of} the third electrode 9 or 12 in the standby state and during the ejection standby time 21, and in the ejection state, the electric potential V ₂ of the first electrode 2 is controlled. Switching to a value equal to the potential V ₁ .

The period A is a period in a standby state in which ink is not ejected according to the image signal. The potential V of the second electrode 4
₂ is always equal to the potential V ₃ of the third electrodes 9, 12 during the period. The diaphragm 3a shown in FIGS. 1 to 3 remains deformed by the electrostatic force between the first electrode 2 and the second electrode 4, and no electric field is applied to the ink, so that no ink is ejected.

Periods B, C and D are periods in which ink is ejected according to the image signal. After the ejection standby time 21 has elapsed at the beginning of each period, the potential V ₂ of the _second electrode 4 is switched to the potential V ₁ of the first electrode 2 so that the potential between the first electrode 2 and the second electrode 4 is changed. At the same time as the electrostatic force disappears, an electrostatic field is generated between the second electrode 4 and the third electrodes 9 and 12. As a result, the diaphragm 3a is displaced in the direction of the nozzle 6 from the initial deformation to generate pressure on the ink in the ink chamber 7, and as described with reference to FIG. 4, the Coulomb force and electric field gradient acting on the ink meniscus. The ink flow due to the above action acts simultaneously to eject the ink.

As shown in the periods B, C and D, the potential V ₂ of the _second electrode 4 is set to the first electrode according to the gradation data of the image to be recorded on the recording paper 8 shown in FIG. 2 potential V ₁
By controlling the time to be maintained at, the amount of ink sucked onto the recording paper 8 can be changed to modulate the dot size and express gradation. In the illustrated example, the holding time is sequentially lengthened, and thus the dot size is sequentially increased.

It should be noted that the discharge standby time 21 gives a recovery time for the diaphragm 3a in the discharge state shown in FIG. 1 (B) to return to the initial deformed state shown in FIG. 1 (A). Second electrode 4
The potential V ₂ of the third electrode 9 does not necessarily have to be equal to the potential V ₃ of the third electrodes 9 and 12 in the standby state and the ejection standby time 21, and it is sufficient if ink is not ejected.
By controlling this potential, it is possible to control the initial deformation amount of the diaphragm 3a shown in FIG.

FIG. 6 is a waveform diagram for explaining a second specific example of the method for driving the ink jet recording apparatus of the present invention. FIG. 6 (A) shows the potential V ₃ of the third electrode, FIG. B) is the potential V ₂ of the second electrode, and FIG. 6C is the potential V ₁ of the first electrode. In the figure, the horizontal axis represents time and the vertical axis represents the potential of each electrode. Reference numeral 31 is a discharge standby time. In this specific example, compared to the first embodiment described with reference to FIG. 5, the discharge end times are set at equal intervals and are matched with the end times of the periods A to D. Therefore, as shown in FIG. 6B, the ejection standby time 31 from the start of each period A to D until the ejection is variably controlled. However, in order to return the diaphragm 3a in the discharge state shown in FIG. 1B to the initial deformed state shown in FIG.
It is necessary to secure a return time as in the discharge standby time 21 shown in FIG.

As described with reference to FIGS. 5 and 6, the first and second driving methods of the ink jet recording apparatus according to the present invention.
In the specific example, by switching one electrode as a signal electrode, it is possible to simultaneously control a plurality of types of forces acting on the ink. That is, only by inputting an image signal into the second electrode 4 to control the potential V ₂ , and although a plurality of forces are used as the ink ejection force, a complicated control circuit is not required and the cost can be reduced. It is possible to make a printhead. In addition, by controlling the time for maintaining the high potential V ₂ of the second electrode 4 at the time of ejecting the ink and by pulse-width modulating the voltage applied to the signal electrode, the ink electrostatically attracted to the recording paper 8 is obtained. The amount can be adjusted with high accuracy, and dot size modulation of several tens of gradations or more can be easily realized.

[0042] Here, the potential V ₂ of the second electrode 4 is not necessarily the first potential V ₁ of the electrode 2 to be switched to a potential between the potential V ₃ of the third electrode 9, 12. First
The magnitude of the electrostatic force between the electrode 2 and the second electrode 4 of
₁₂ , when the magnitude of the electrostatic force between the second electrode 4 and the third electrode 9 or 12 is F ₂₃ , F ₁₂ > F ₂₃ ≧ 0 in the standby state and 0 ≦ F in the ejection state. ₁₂ <
As long as it is F ₂₃ , the potential V ₂ of the second electrode 4 can be changed including its polarity.

FIG. 7 is an explanatory view schematically showing waveforms and dot sizes for explaining the third embodiment of the method for driving an ink jet recording apparatus of the present invention. In this embodiment, the amount of ink ejection is modulated and gradation is expressed by a combination of the control of the deformation amount of the diaphragm in the ejection standby state and the control of the potential maintenance time of the second electrode in the ejection state. Cases (1) to (9) are shown as an example. The horizontal axis of each graph shows the time elapsed during the ink ejection period, and the vertical axis shows the potential V ₂ of the second electrode 4. The dots shown under each graph schematically represent the size of the dots recorded on the recording paper 8 in each case. The shapes shown as (A) to (C) in the left column of the figure are cases (1) to (3), (4) to (6), (7) shown in the rows next to the shapes.
5A to 5C schematically show the ink flying state in (9).

[0044] In the example shown, in each case, the potential V ₂ of the second electrode 4, first the potential V ₁ of the electrode 2 which is high potential, the third electrode 9, 12 and the low potential The potential is changed between V ₃ . Although not shown in the drawing during the standby period in which ink is not ejected according to the image signal, the second
The electric potential V ₂ of the electrode 4 may be made equal to the electric potential V ₃ of the third electrode 9 or 12. The second described with reference to FIG.
Similar to the embodiment described above, an example will be described in which the discharge end times are set at equal intervals, but the same applies when the discharge start times are set at equal intervals as shown in FIG.

During the discharge standby time 31, the first electrode 2
Potential V₁And the potential V of the second electrode 4 _TwoPotential difference (V₁−
V_Two) Is controlled in three steps. However, the die shown in FIG.
The yaf ram 3a is attracted toward the first electrode 2, and
The area where ink is not ejected due to the electric field applied to the ink
It is controlled by the fence. The initial deformation amount of the diaphragm 3a is the potential
Difference (V₁-V_Two) Becomes larger, the larger
Also, the volume change amount of the ink chamber 7 at the time becomes large. But
As shown in (A), (B), and (C),
It is possible to control the size of the loop portion.

After the ejection is started, the ink is continuously ejected in the form of filaments by the electric field between the second electrode 4 and the third electrodes 9 and 12. (1) to (3), (4) to (6),
As shown in (7) to (9), the potential V ₂ of the second electrode 4
The ink ejection duration is controlled by modulating the length of time during which the voltage is maintained at the potential V ₁ of the first electrode 4. As a result, it is possible to express a fine gradation that cannot be expressed by the size of the initial drop. In the illustrated example, the potential V ₂ of the second electrode 4 in the ejection standby state is controlled in three steps, and the potential V ₂ of the second electrode 4 in the ejection state is set to the potential V _2.
By controlling the duration to be maintained at ₁ in 3 steps,
10 gradations are expressed including the state in which the ink is not ejected.

In this specific example, by using the pressure control by the diaphragm 3a shown in FIGS. 1 to 3,
The response at the start of discharge is faster and the initial drop amount is 3
The amount of ink ejected in the initial stage is made variable by controlling in stages. Therefore, the ink suction time can be reduced to about one-third as compared with the conventional electrostatic suction method, and the time can be greatly shortened. Moreover, by controlling the ejection amount, which cannot be controlled by the ink pressure control, by the ink suction time, it is possible to express gradation in multiple stages as compared with the conventional pressure method. In addition, the number of control steps of the potential and the number of control steps of the potential maintenance time, the control timing such as the ejection start time, etc.
The present invention is not limited to the above-mentioned examples, and can be modified as long as the present invention can be realized.

In the description of the driving method of the ink jet recording apparatus with reference to FIGS. 5 to 7, the single second electrode 4 is used as the signal electrode to enable simple control.
However, any electrode may be used as a signal electrode and the potentials of a plurality of electrodes may be controlled at the same time as long as the potential relationship enabling the ink ejection operation is maintained.

In the above description, as the pressure applying means for applying pressure to the ink in the ink chamber, a diaphragm which forms a part of the side wall of the ink chamber and is elastically deformable by electrostatic force is used. However, a method other than electrostatic force is used. This diaphragm may be elastically deformed. As long as the pressure is applied to the ink at the start of ejection, it is not limited to the one that maintains the restoring force in the ejection standby state. Also, without using a diaphragm,
As the pressure applying means, it is possible to use a conventionally known means for generating bubbles in the ink by heat generation of the resistor and a means for displacing the piezoelectric vibrating plate.

[0050]

As is apparent from the above description, according to the first aspect of the present invention, the pressure applying means for applying pressure to the ink in the ink chamber and the ink ejected from the nozzle are sucked. Since the pressure application means and the electric field application means are controlled in accordance with the input signal, the pressure application means and the electric field application means for applying electrostatic force are controlled. Therefore, by applying pressure to the ink during the initial deformation of the ink interface, the response of the ejection start is accelerated The effect is that you can. Compared with the conventional electrostatic suction method, the ink suction time can be significantly shortened, and the applied voltage can be lowered, so that high-speed printing can be efficiently realized. Furthermore, since the ink is continuously sucked onto the recording paper by maintaining the electric field for sucking the ink, it is possible to express the gradation by the dot size modulation.

According to the second aspect of the invention, the pressure applying means has the elastically deformable diaphragm and the first and second electrodes, the diaphragm forming a part of the side wall of the ink chamber, and the second side. The electrode is formed on the diaphragm, the first electrode is formed on the substrate so as to face the second electrode, and the electric field applying means has at least one third electrode, and the third electrode is the second electrode. And the ink chamber are separated from each other in the ink ejection direction, the pressure applying means can be easily realized by deforming the diaphragm by the voltage between the first and second electrodes. The voltage between the third electrodes has an effect of easily realizing an electric field applying unit for the ink ejected from the nozzle.

For example, the diaphragm can be deformed toward the substrate side in the standby state by the voltage applied between the first and second electrodes, and can be deformed in the opposite direction to the standby state in the discharge state. The electric field can be applied in a direction parallel to the ink ejection direction by the voltage applied between the second and third electrodes. Further, it is possible to arrange all the first to third electrodes in the print head. In this case, the applied voltage can be further reduced by making the interval between the electrodes narrow.

According to the third aspect of the invention, at least one of the third electrodes is arranged in the vicinity of the nozzle, and the electrode area is smaller than the electrode area of the second electrode. The intensity of the electric field formed by the pair of electrodes forms a gradient, and becomes larger in the vicinity of the nozzle. As a result, there is an effect that an ink flow toward the nozzle is generated and plays a part of the ink ejection force.

According to the invention described in claim 4, by applying a predetermined voltage between the first electrode and the third electrode and controlling the voltage applied to the second electrode, the discharge standby state and the discharge Since the state is switched, the second
The standby state and the discharge state can be switched only by controlling the electric potential of the electrode. As a result, there is an effect that the print head can be manufactured inexpensively without requiring a complicated control circuit.

According to the invention of claim 5, a plurality of nozzles are provided, the first electrode and the third electrode are common electrodes for the plurality of nozzles, and the second electrode is an individual electrode for each nozzle. Therefore, even if the print head has a plurality of nozzles, the same control circuit as that having a single nozzle can be used, and the print head can be manufactured at low cost.

According to the sixth aspect of the present invention, since the potential of the second electrode in the discharge standby state is controlled, the deformation amount of the diaphragm in the discharge standby state can be controlled, and the diaphragm in the discharge state is controlled. It is possible to change the amount of ink to be ejected in the initial stage by controlling the pressure of No. 2 and to control the potential maintenance time of the second electrode in the ejection state. Therefore, the ejection amount that cannot be expressed by pressure control is controlled by the ink suction time. There is an effect that can be done. As a result, the amount of ink that is electrostatically attracted to the recording paper can be adjusted with high precision, so that dot size modulation of several tens of gradations, which is a higher gradation than the inkjet recording device using conventional pressure, can be easily realized. Is.

[Brief description of drawings]

FIG. 1 is a cross-sectional view for explaining a first embodiment of an inkjet recording apparatus of the present invention, FIG. 1 (A) shows a standby state of an element, and FIG. 1 (B) shows a discharge state of the element. To represent.

FIG. 2 is a sectional view for explaining the second embodiment of the inkjet recording apparatus of the present invention.

FIG. 3 is a cross-sectional view for explaining a third embodiment of an inkjet recording device of the present invention.

FIG. 4 is a configuration diagram of second and third electrodes for explaining the third embodiment of the inkjet recording apparatus of the present invention.

FIG. 5 is a waveform diagram for explaining a first specific example of the method for driving the inkjet recording apparatus of the present invention.

FIG. 6 is a waveform diagram for explaining a second specific example of the method for driving the inkjet recording apparatus of the present invention.

FIG. 7 is an explanatory diagram schematically showing waveforms and dot sizes for explaining a third embodiment of a method for driving an inkjet recording apparatus of the present invention.

[Description of Reference Signs] 1 ... Insulating substrate, 2 ... First electrode, 3 ... Pressure generating member, 3
a ... diaphragm, 3b ... gap, 4 ... second electrode, 5 ...
Nozzle forming member, 6 ... Nozzle, 7 ... Ink chamber, 8 ... Recording paper, 9, 12 ... Third electrode, 11 ... Electrode supporting member, 13
... Opening, 14 ... Electric force line, 21,31 ... Discharging standby time.

Claims (6)

[Claims] 1. An ink jet recording apparatus for ejecting ink in an ink chamber from a nozzle on demand, comprising:
The pressure applying means for applying a pressure to the ink in the ink chamber, and the electric field applying means for applying an electrostatic force for attracting the ink to the ink ejected from the nozzle are provided. An inkjet recording apparatus, which is controlled according to an input signal. 2. The pressure applying means has an elastically deformable diaphragm and first and second electrodes, the diaphragm forms a part of a side wall of the ink chamber, and the second electrode is formed on the diaphragm. The first electrode is formed on the substrate so as to face the second electrode, the electric field applying means has at least one third electrode, and the third electrode is the second electrode and the ink chamber. The ink jet recording apparatus according to claim 1, wherein the ink jet recording apparatus is arranged in the ink discharge direction with a space therebetween. 3. The ink jet recording according to claim 2, wherein at least one of the third electrodes is arranged in the vicinity of the nozzle, and the electrode area is smaller than the electrode area of the second electrode. apparatus. 4. A discharge standby state and a discharge state are switched by applying a predetermined voltage between the first electrode and the third electrode and controlling the voltage applied to the second electrode. The ink jet recording apparatus according to claim 2 or 3. 5. A plurality of nozzles are provided, the first electrode and the third electrode are common electrodes for the plurality of nozzles, and the second electrode is an individual electrode for each nozzle. The inkjet recording device according to claim 4. 6. The method according to claim 4, wherein the potential of the second electrode in the ejection standby state is controlled and the potential maintenance time of the second electrode in the ejection state is controlled.
3. The ink jet recording apparatus according to claim 1.