JP2001277520A - Recording head and image recorder comprising it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a recording head for flying ink using Coulomb force in which low voltage drive is effected without sacrifice of recording speed, a recording head in which the life cycle is prolonged by preventing discharge between recording electrodes and corrosion of the recording electrode, and an image recorder employing it. SOLUTION: An auxiliary electrode for supplying charges to ink is provided in a recording head and an auxiliary electrode drive means for applying a desired voltage to the auxiliary electrode in synchronism with a recording electrode is provided. The recording electrode is covered with an insulating material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printing industry that requires high-speed output of high-quality images, an office, a printer industry based on personal requirements, and a low-cost general-purpose output device that uses various types of recording paper. The present invention relates to a recording head for obtaining an output image on recording paper that can meet a wide range of needs up to the consumer goods industry required, and an image recording apparatus using the recording head.

[0002]

2. Description of the Related Art In a conventional image recording apparatus, in particular, an image recording apparatus using an ink jet system, a recording head using various ink ejection systems, for example, a recording system using a piezoelectric element to apply mechanical vibration or displacement to ink. It has a recording head based on a method in which a head or ink is heated and foamed to utilize the pressure, and the recording head generates and flies small droplets of ink, and a part or all of the recording medium such as paper is used as a recording medium. The recording was performed with the recording medium adhered on the recording medium. However, these recording heads have a structure that requires a piezoelectric element or a heating element, and further, a nozzle is formed to communicate with an ejection port for ejecting ink, and one recording dot corresponds to one recording dot. I was

In addition to the above, as shown in FIGS. 10A and 10B, an ink jet recording system using an electrostatic force (hereinafter, Coulomb force) has been proposed. A single slit-shaped opening 11 composed of the substrate 1 and the insulating upper substrate 7 is filled with ink 9, and the recording electrode 2 and a counter electrode 12 disposed with a small gap from the opening 11. In this method, a Coulomb force is applied to the ink 9 by applying a voltage pulse between the ink and the ink 9 is caused to fly toward the counter electrode 12.

Therefore, the recording head need only be arranged in a pattern of the recording electrodes 2 and there is no need to provide driving elements and integrate them. In addition, since the charged ink 9 flies under the Coulomb force along the lines of electric force of the electric field generated between the recording electrode 2 and the opposing electrode 12, the ink flies.
There is no need to separate 1 by a nozzle.

[0005]

In a conventional image recording apparatus, one nozzle of a recording head for performing recording by discharging and attaching ink droplets to a recording medium corresponds to one recording dot. Since fine nozzles must be formed over the entire width of the recording head and elements for driving each nozzle must be formed,
Not only is a very precise and difficult processing technique required, but also the cost of the recording head is increased.

Further, in the ink jet recording system using Coulomb force, ink can be ejected from an arbitrary position even at the opening of the slit structure, and further, since the drive element is not required, the manufacturing cost can be reduced. Can be.

However, in the above method, the Coulomb force applied to the ink is determined by the electric charge E held by the ink and the electric field E generated by the potential difference applied between both electrodes, as expressed by the formula of F = qE.

However, in a recording head having a conventional structure, electric charge is injected into ink only by a voltage pulse applied to a recording electrode when the ink is caused to fly. Therefore, the higher the voltage value of the voltage pulse, the better the power supply efficiency. However, since the recording electrodes are arranged at a fine pitch, there is a danger of discharge between the electrodes, and the voltage of the drive circuit is high. In view of the withstand voltage, the voltage value is limited to about 300 V, and at this time, a voltage of 2.5 to 3 kV is required for the counter electrode with a voltage value of the opposite polarity to the above voltage. The driving frequency of the recording electrode at this time is 200 Hz to 1
It is about kHz.

There is also a method of increasing the supply amount of charges by lengthening the time of the voltage pulse, but this reduces the driving frequency, that is, decreases the recording speed. Therefore, it has been difficult to satisfy both the reduction of the voltage applied to the recording electrode and the increase of the recording speed.

Further, it is necessary to bring the recording electrode into contact with the ink in order to supply electric charge to the ink. However, the recording electrode generates a potential difference at a position where the ink flies and a position where the ink does not fly. However, there is a problem that a voltage drop occurs due to a current flowing through the ink, the ink does not fly because a desired electric charge is not obtained, and an electrode is easily corroded due to occurrence of electrolysis or oxidation.

[0011]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a recording head for flying ink using Coulomb force to supply a desired charge to ink near the ink opening. Head having a configuration in which an auxiliary electrode for supplying a voltage having the same polarity as the recording electrode to the auxiliary electrode and an auxiliary electrode driving unit are provided, thereby eliminating the need for forming fine nozzles. By applying a voltage to the auxiliary electrode, it is possible to supply a sufficient charge to the ink. Therefore, it is possible to reduce the voltage pulse applied between the recording electrode and the counter electrode without reducing the driving frequency. Voltage can be realized. Conversely, when the voltage value is returned to the conventional value, the charge is supplied to the ink quickly, and the electric field strength between the two electrodes is increased, so that the recording speed can be improved.

Further, by applying a voltage to the auxiliary electrode at a timing earlier than that of the recording electrode or applying a voltage to the counter electrode at the same timing as the auxiliary electrode, the ink can receive a more sufficient charge. Further, it is possible to further reduce the driving voltage or to improve the driving frequency.

Further, in the recording head of the present invention, since the electric charge is supplied by the auxiliary electrode, the recording electrode can fly ink even if the surface thereof is covered with an insulating material. This prevents a discharge between the recording electrodes and a discharge between the opposing electrodes, thereby ensuring safety and stability of ink flying. Further, since the surface of the recording electrode is covered, deterioration of the electrode due to electrolysis, oxidation and the like can be prevented, and the durability and the life of the recording head can be improved.

Further, the recording head according to the present invention, the recording medium is arranged in a minute gap provided between the opening and the counter electrode, and the recording medium is scanned in synchronization with the operation of each recording head. By constituting an image recording apparatus for attaching image pixels on the recording medium by having the means, the size of the apparatus can be reduced by reducing the power supply for driving the recording head, or the recording speed can be reduced by improving the driving frequency. Higher speed can be achieved. Further, the life cycle is long and the stable image output can be realized by the improvement of the durability and the long life of the recording head.

A plurality of recording heads are provided independently and arranged in parallel, means for supplying inks of different colors to the respective head portions are provided, and a minute gap provided between the opening and the counter electrode portion is provided. A recording medium is disposed in the recording medium, and a transport unit for scanning the recording medium in synchronization with the operation of each of the recording heads can easily output images of a plurality of colors on the recording medium.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. (Embodiment 1) FIG. 1 is a perspective view (a) and a side view (b) showing an example of the configuration of a recording head according to the present invention. The recording head shown here is a head unit 8 on the side where ink flies.
And a counter electrode 12 provided to face the head portion 8
It is assumed to be composed of the following two.

First, the configuration of the head section 8 is shown in FIG.
Description will be made based on (b).

Reference numeral 1 denotes a lower substrate serving as a base material of the head section 8. On the upper surface of the lower substrate 1, finely divided recording electrodes 2 are sequentially arranged at a pitch corresponding to recording pixels.

On the lower substrate 1 on which such a pattern is formed, a U-shaped spacer 6 having a uniform thickness and one side thereof is opened, and an upper substrate 7 are laminated in this order.
It is fixed by means such as adhesion.

By forming the head portion 8 with such a structure, a gap having a certain height determined by the thickness of the spacer 6 is formed as an ink chamber 10 for filling the ink 9 between the two substrates. A slit-shaped opening 11 (hereinafter referred to as a slit opening) is formed toward the counter electrode 12 facing the portion 8.

The slit opening 1 on the inner surface of the upper substrate 7
A single auxiliary electrode 3 is provided in the vicinity of 1 over at least the recording electrode arrangement range of the opening, and a charge can be supplied to the ink by applying a voltage to the auxiliary electrode 3.

The upper substrate 7 is provided with an ink supply hole 16 for supplying the ink 9 to the ink chamber 10, and is constituted by an ink supply tank, a supply tube and the like via an ink supply connector. An ink supply means (not shown) is connected. At this time, the ink 9 is supplied to the slit opening 11 through the ink chamber 10 while receiving substantially constant pressure (hereinafter referred to as static pressure) due to its own weight and atmospheric pressure by the ink supply means. The static pressure applied to the ink 9 is balanced with the surface tension of the ink 9 at the slit opening 11, and as shown in FIG.
In 1, the ink 9 forms a semi-lunar convex protrusion, that is, a meniscus, and holds this state.

Further, as shown in FIG. 1B, the cross section of the portion constituting the slit opening 11 of the recording head has a wedge shape which is sharpened toward the slit opening 11, so that the meniscus is thinned and the ink is formed. The structure is such that the electric field is concentrated on 9.

In this embodiment, the recording electrode 2 on the lower substrate 1
Are arranged at a high density of about 8 lines / mm or more. In this embodiment, the lower substrate 1 and the upper substrate 7 are made of insulating and highly planar glass substrates, and the recording electrodes 2 and the auxiliary electrodes 3 are used. Patterning was performed by vacuum-depositing aluminum on a substrate and then performing chemical etching on the aluminum thin film. Further, in this embodiment, the lower substrate 1 and the upper substrate 7 are both glass substrates having a thickness of 0.5 to 1 mm, and are chamfered so that the tip on the side of the slit opening 11 has an acute angle of about 20 degrees. Further, an oil-repellent treatment was applied to the chamfered portion so that the ink did not get on. The spacer between the two substrates is set to have a thickness of about 50 μm, and the vertical height S of the substrate in the portion where the ink opening 11 is formed is about 100 μm.
m. Therefore, the height H at the bottom of the meniscus when the ink meniscus is formed in the ink opening 11 is set to about 250 μm.

In this embodiment, the recording electrode 2 and the auxiliary electrode 3 are formed using aluminum. However, the present invention is not limited to this, and a metal material such as copper, chromium, gold, nickel or the like may be used. The same effect can be obtained by using a method such as plating, screen printing, or machining.

The spacer 6 may be formed integrally with the upper substrate 7, and the shape of the spacer 6 may be the slit opening 1
1 is formed, and the head section 8 is formed by ink supply means.
The shape of the ink 9 is not limited as long as the ink 9 is supplied to the slit opening 11.

Next, the configuration of the opposing electrode 12 arranged to face the head section 8 will be described with reference to FIG.

The counter electrode 12 is located with a minute gap of about 0.8 to 1.5 mm from the slit opening 11 of the head section 8 and is made of a single conductive material. The counter electrode 12 is arranged at least over the recording electrode arrangement range of the slit opening.

In the gap, the recording paper 15 as a recording medium is interposed in the direction of the arrow by the conveying means, so that the ink 9 flying from the head portion 8 toward the opposing electrode 12 at the time of recording is recorded on the recording paper 15. Will adhere. Although a method of transporting the recording paper 15 is not shown because a known method is used, a transport mechanism such as a friction feed method using a pair of rollers is generally used to synchronize with the driving of the recording electrode 2 in the head unit 8. The recording paper 15 is scanned intermittently or continuously.

In the embodiment shown in FIG.
Is made of a metal plate about the width of the slit opening 11, but it is needless to say that the shape is limited to this shape. In consideration of the above-mentioned transporting means, the counter electrode 12 is formed in a roller shape or a shape having a curvature toward the head portion 8. It is desirable to adopt a structure in which the recording paper 15 is conveyed while being closely contacted because the surface potential of the recording paper 15 is stabilized.

Next, the electrical wiring connection between the recording electrode 2, the auxiliary electrode 3, and the counter electrode 12 in the head section 8 will be described with reference to FIG. First, regarding the wiring, the recording electrode 2 and the auxiliary electrode 3 in the head unit 8 are wired to the high-voltage power supply 5, and the counter electrode 12 is wired to the high-voltage power supply 14. Each electrode is connected to the power supply via an independent drive circuit, and is controlled so as to apply a desired voltage pulse in synchronization with a control signal from the device.

In the present embodiment, a configuration is adopted in which a potential (hereinafter referred to as a bias potential) is applied to the counter electrode 12 side in order to prevent discharge or dielectric breakdown due to a potential difference between a selected electrode and a non-selected electrode in the recording electrode 2. The bias potential is provided on the recording electrode side, and only the head section 8 is driven;
The counter electrode side may be grounded to be in a state of 0V potential.

Next, the driving operation of the recording head according to the present embodiment will be described with reference to the block diagram shown in FIG. 4 and the timing chart shown in FIG.

Here, in the recording head having the structure as in the present embodiment, the ink is physically connected because the opening 11 is slit-shaped and communicates in the main scanning direction. Therefore, when the adjacent recording electrodes 2 are driven at the same time, the flying of the ink 9 is mutually affected. Therefore, in the present embodiment, in order to reduce this effect, it is necessary to perform driving (hereinafter, time-division driving) with a time lag from at least the adjacent recording electrodes 2.

In the driving operation described below, the recording head having the above-described configuration is used, and the driving method is such that one line of recording electrodes arranged in the head section 8 (hereinafter, one line of recording) is odd-numbered. An example of time-division driving in which an electrode and an even-numbered recording electrode are divided into two will be described.

As shown in FIG. 4, first, a parallel signal output from an external device 21 such as a PC terminal is input to an interface 22 which is an entrance / exit as a recording device, and controls a parallel image data signal and the device from the interface 22. A control signal including a signal for performing the operation is output.

The parallel image data signal output from the interface 22 is input to a signal processing circuit 23. The control signal output via one interface 22 is input to a control circuit 24.

The signal processing circuit 23 receives the control signal output from the control circuit 24 and converts the parallel image data signal output from the interface 22 into a serial binary signal. Only the third data is extracted and input to the recording electrode driver 4.

In the recording electrode driver 4, first, 2
A shift register type in which the odd-numbered data signals of the recording electrode 2 are stored as information of a selected electrode (a recording electrode at a position where ink is ejected) and a non-selected electrode (a recording electrode at a position where ink is not ejected). Is set by input to the latch. At this time, information of 0 is set for the selected electrode and information of 1 is set for the non-selected electrode. In the present embodiment, the ground voltage (0 V) is set when information is 0, and a desired potential Vs is set when information is 1. The data of the even-numbered recording electrodes 2 are all set to 1 information.

At this time, when the recording electrode driver 4 receives a control signal from the control circuit 24, it applies a desired voltage pulse Vs to the recording electrode 2, and the auxiliary electrode driver 18 is controlled by the control circuit 24. When a control signal is received from the auxiliary electrode 3, a desired voltage pulse Va is applied to the auxiliary electrode 3. Similarly, the counter electrode driver 13 is configured to apply a desired voltage pulse Vc when receiving a control signal from the control circuit 24.

After waiting for a state in which all data is set in the recording electrode driver 4, a control signal for driving each electrode is output from the control circuit 24. First, the driver 1 for driving the auxiliary electrode
A control signal is input to 8, whereby a voltage pulse having substantially the same potential as that of the recording electrode 2 is applied to the auxiliary electrode 3.

While the auxiliary electrode 3 is driven for a short time Δt, a control signal is input to the recording electrode driver 4 and the counter electrode driver 13, and a desired voltage pulse is applied to the selection electrode and the counter electrode. Applied.

With the above operation, the odd-numbered recording of the recording electrode 2 in one recording line is performed. By driving the auxiliary electrode first as described above, a sufficient charge is supplied to the ink in advance, so that the ink flies stably even in a weak electric field.

Next, the even-numbered data is input to the recording electrode driver 4 and the same operation is performed. When the even-numbered recording is performed, the recording for one recording line is completed.

The above is the operation for one line of recording, and the recording paper 15 is gradually conveyed in a direction perpendicular to the driving direction of the recording head while sequentially repeating this operation at the line cycle T, thereby recording a desired image. It will be output on paper 15.

In the recording head, the driving method, and the ink (described below) used in the present embodiment, stable ink jetting can be performed at a voltage value that is about half the conventional value without sacrificing the recording speed as described below. Could be realized.

The potential applied to the selection electrode in the recording electrode 2 is V
s, the potential Va applied to the auxiliary electrode 3 and the potential Vc applied to the counter electrode, Vs: potential −150 V, applied pulse width 1 ms Va: potential −150 V, applied pulse width 1.5 ms Vc: potential +1.5 kV, applied The pulse width was set at 1 ms.

The voltage pulse application cycle to the recording electrode 2 during the division driving was set to 2 ms. Auxiliary electrode 3
In this case, the voltage pulse application cycle is set to 2 ms in synchronization with the recording electrode 2. However, at this time, as shown in the above operation, the voltage application timing of the auxiliary electrode 3 is shorter than the driving of the recording electrode 2 by a small time Δt. The motor was driven quickly, and Δt at this time was set to 0.5 ms. The voltage pulse application cycle of the counter electrode 12 was also set to 2 ms in synchronization with the recording electrode 2. However, the counter electrode 12 is not limited to this set value, and the recording electrode 2 is similar to the auxiliary electrode 3.
By driving at an earlier timing, it is possible to further supply electric charges to the ink.

However, the set values shown here vary greatly depending on the gap distance between the slit opening 11 of the head section 8 and the counter electrode 12, the physical properties of the ink, the structure of the head tip, the physical properties of the recording medium, and the like. It is not limited to this value.

In this embodiment, the auxiliary electrode 3 is driven independently of the recording electrode 2 so as to supply electric charges to the ink more quickly, and is driven a minute time earlier than the recording electrode 2. Even if the timing for simultaneously driving the recording electrode 3 and the recording electrode 2 is set, the effect can be sufficiently obtained, and the control system can be simplified.

Next, the conditions of the ink used in the present invention will be described below.

Factors that greatly contribute to ink jump as physical properties of the ink include surface tension, viscosity, and electrical conductivity. As for the surface tension, the smaller the value is, the smaller the resistance in the ink discharging process is, and the ink can be discharged even in a weak electric field. In general, the surface tension of the aqueous ink is higher than that of the aqueous ink and is 72.8 dyn / cm (20 ° C.) in pure water, but the viscosity of the organic solvent is distributed in a range of about 20 to 35 dyn / cm. In the embodiment, an ink in which a dye is dissolved in an organic solvent having a low surface tension or a pigment is dispersed is used as an ink. The viscosity of the ink solvent can be selected in a wide range, and when the viscosity is low similarly to the surface tension, the resistance in the ink discharge process is reduced and the ink can be discharged even in a weak electric field. Since the ink has high volatility, the storage stability of the ink deteriorates, so that the actual viscosity range is preferably about 2.0 to 8.0 cP. In order for the ink to fly, it is necessary to supply a charge to the ink from the recording electrode in the head section.
(Ω · cm) or more.

The set value of the ink characteristics depends on the voltage value supplied between the electrodes, the distance between the recording electrode 2 and the counter electrode 12, the structure of the head section 8, and the like, and whether or not ink jumps is possible. For optimal surface tension, viscosity,
It goes without saying that the characteristic range such as the resistance value is not necessarily limited to the above value. Further, since the ink used in the present embodiment has a characteristic of being easily charged to the negative electrode, the negative electrode is connected to the recording electrode 2 side and the positive electrode is connected to the counter electrode 12 side. However, the present invention is not limited to this. When the charging polarity is positive, the voltage polarities applied to the counter electrode 12 and the recording electrode 2 are also reversed.

Next, the recording operation of the apparatus will be described with reference to FIG.

In this embodiment, the recording head is connected to the recording paper 15.
A description will be given assuming that the line head has a slit opening 11 substantially equivalent to the above. At this time, the longitudinal direction of the slit opening 11, that is, the arrangement direction of the recording electrodes 2 is defined as the main scanning direction, and the direction orthogonal to the main scanning direction is defined as the sub-scanning direction. Will be described.

When a printing command is issued from the apparatus, first, as an initial operation, a recovery / cleaning operation such as suction / wiping of the slit opening 11 in the head unit 8 is performed by a recovery system mechanism of the head unit 8 (not shown), and recording is performed. The head is brought into a state in which ink can fly. When the recovery operation is completed, the recording paper 15 is transported using a paper supply mechanism such as an automatic sheet feeder and a roller pair (not shown).
By intervening in the minute gap formed by the head section 8 and the counter electrode 12, the position of the recording start portion is determined by controlling the transport mechanism using position detecting means such as a paper edge sensor.

When the initial operation is completed, one line of recording is driven as described in the driving operation of the recording head. That is, the auxiliary electrode 3 in the head 8
Is driven first to supply sufficient charge to the ink near the slit opening 11 to charge the ink, and then the recording electrode 2 and the counter electrode 12 are driven according to the image data signal. As a result, the ink in the slit opening portion 11 selectively receives Coulomb force corresponding to the recording electrode position and flies toward the counter electrode 12, and on the recording paper 15, one line of ink corresponding to the image data signal. Ink dots are recorded.

After completing the operation for one line of recording,
The recording paper 15 is conveyed in the sub-scanning direction (arrow direction) by an amount determined to a predetermined resolution in the sub-scanning direction, and the same recording operation is repeated in the second and subsequent lines according to a desired image data signal. Thus, a desired image corresponding to the image data can be output on the recording paper 15 within the range of the width of the recording head and the scanning amount of the recording paper 15. (Embodiment 2) FIGS. 2A, 2B, and 2C are perspective views showing other examples of the configuration of the head section 8 in the recording head of the present invention.

FIG. 2A shows a structure in which an insulating material is coated in a layer on the surface of the recording electrode 2 in the structure of the head portion shown in the first embodiment. In the present invention, the auxiliary electrode 3 is provided as a function of supplying electric charges to the ink, and the counter electrode 1 is provided.
A recording electrode 2 is provided as a function of generating an electric field between the two, so that the two functions are separated. Therefore, the recording electrode 2 only needs to have a structure that generates an electric field between the opposing electrodes 12, and the ink flies even if it has a structure that does not contact the ink, that is, a structure that covers the recording electrode 2 with an insulating material.

Accordingly, it is possible to prevent a discharge caused by a potential difference between the adjacent recording electrodes 2 at the time of driving and a discharge between the opposing electrodes, thereby ensuring safety and stability of ink flying. Furthermore, since the recording electrode is covered on the surface, the ink does not come into direct contact with the recording electrode, so that it is possible to prevent deterioration of the electrode due to electrolysis, oxidation, and the like, thereby improving the durability and extending the life of the recording head. . The insulating material is preferably a dielectric having a high dielectric constant in order to improve the generation of an electric field. In addition, as shown in FIG. 2, by exposing only the leading end of the recording electrode 2 on the side of the slit opening, the electric field can be more concentrated.

The position of the auxiliary electrode 3 may be any position as long as it comes into contact with the ink in the head portion 8 near the slit discharge port 11 and does not come into contact with the recording electrode. Therefore, the present invention is not limited to the upper substrate 7 on the side of the ink chamber 10 as shown in the first embodiment. For example, the upper substrate 7 may be laminated on an insulating layer provided on the recording electrode 2 as shown in FIG. Alternatively, it may be formed as a structure floating in the ink chamber 10.

Further, as shown in FIG. 2 (c), the upper substrate 7 may not be an insulating glass substrate, but may be formed of a conductive material. Thus, for example, the portion of the spacer 6 can be easily processed integrally, and the processing accuracy can be maintained in a good state.

In any of the cases shown in FIG. 2, the driving method and the device configuration are the same as those in the first embodiment. (Embodiment 3) FIG. 3 shows the configuration of a recording head for color printing.

A plurality of heads 8Y, 8M, 8C, 8Bk of any of the types described in the first and second embodiments are arranged in parallel one above the other as shown in FIG. (Y), magenta (M), cyan (C), and black (Bk) color inks, and one counter electrode 12 is arranged to face the head section 8 of the four colors. ing.

Next, the driving operation of the recording head having the above configuration will be described with reference to the block diagram shown in FIG.

As shown in FIG. 5, first, a parallel signal output from an external device 21 such as a PC terminal is input to an interface 22 which is an entrance / exit as a recording device. R
(GB) A control signal including an image data signal and a signal for controlling the apparatus is output.

The parallel R, G, and B recording image signals output from the interface 22 are input to a signal processing circuit 23. The control signal output through the interface 22 is input to a control circuit 24, and the signal processing circuit 23 and the counter electrodes 12 and the recording electrodes in the heads 8Y, 8M, 8C, and 8Bk of each color. , And the auxiliary electrodes are converted into control signals for synchronously operating the auxiliary electrodes.

While receiving the control signal from the control circuit 24, the signal processing circuit 23 converts the parallel R, G, and B recording data signals output from the interface 22 into the parallel data stored in the signal processing circuit 23.・ Y ・ M ・ C ・ with serial conversion circuit and color conversion circuit
The image data signal is converted into a Bk serial binary signal, and the image data signal is input to a recording electrode driver and an auxiliary electrode driver provided in the head unit of each color.

Thereafter, the respective head portions 8Y, 8M, 8
The driving method of the recording head described in the first embodiment is performed for each of the recording heads of C, 8Bk and the counter electrode for each color.

The above is the operation for one recording line. After that, the recording paper 15 is conveyed in the sub-scanning direction by an amount determined to a predetermined resolution in the direction of the arrow, and is again input to the next recording image signal. The same recording operation is repeated thereafter. As described above, a color image can be output on the recording paper within the range of the arrangement width of the recording electrode groups in the main scanning direction and the scanning amount of the recording paper in the sub-scanning direction.

Since the slit openings 11 of a plurality of recording heads are sequentially arranged at intervals in the sub-scanning direction (hereinafter referred to as the distance between recording heads), the recording heads 511 of each color divide one line of recording into each color. Cannot be simultaneously recorded on recording paper. Therefore, the recording image signal of each color from the signal processing circuit 23 is driven at a predetermined time via a circuit for delaying according to the distance between recording heads, or an image corresponding to the distance between recording heads is provided in advance by providing a memory. It is necessary to secure necessary data and determine necessary data and drive timing. (Embodiment 4) Another example of the driving means of the auxiliary electrode 3 in the present invention will be described with reference to timing charts shown in FIGS. The drive shown in FIGS. 7, 8 and 9 is premised on a two-division drive in which one-line recording is divided into two times and time-divided as in the first embodiment.

First, the driving means of the auxiliary electrode 3 shown in FIG. 7 will be described.

The driving method shown in FIG. 7 is a method in which the voltage pulse from the auxiliary electrode does not overlap with the voltage pulse applied to the recording electrode 2 and the auxiliary electrode 3 is driven before the recording electrode 2 is driven. is there.

As a timing, first, a desired voltage pulse is applied to the auxiliary electrode 3 as a drive for supplying a charge to the ink 9. At this time, a desired voltage pulse having a polarity opposite to that of the voltage pulse applied to the auxiliary electrode 3 is also applied to the counter electrode 12. Then, a short time after the application of the voltage pulse to both electrodes is completed, a voltage pulse for flying ink is applied to the recording electrode 2 and the counter electrode 12, respectively. The timing is realized by giving a control signal to each driver independently by the control circuit 24 shown in FIG.

By the above operation, the necessary and sufficient electric charges are supplied to the ink in advance, so that stable recording can be realized without lowering the driving frequency of the recording electrode 12, and the driving applied to the recording electrode 2 and the counter electrode 12 can be realized. Voltage can be set low. Conversely, when the voltage value is returned to the conventional value, electric charges are supplied to the ink quickly, and the electric field intensity between both electrodes is increased, so that the recording speed can be improved as compared with the conventional case.

Further, as shown in the first embodiment,
Although a sufficient effect can be obtained by only driving, the driving voltage of the recording electrode 2 can be further reduced by applying the voltage pulse to the auxiliary electrode 3 and simultaneously overlapping the counter electrode 12 in the driving method described above. The driving frequency can be improved.

Next, the driving means of the auxiliary electrode 3 shown in FIG. 8 will be described.

The driving method shown in FIG. 8 is also a method in which the voltage pulse from the auxiliary electrode 3 is driven without overlapping with the voltage pulse applied to the recording electrode 2, and the voltage pulse is applied between the driving in the sub-scanning direction. How to give.

In a line head, the paper feed period for one line, which is a sub-scan, is generally longer than the drive period T of the recording head because of the use of mechanical driving. Accordingly, during this time, the amount of charge of the ink secured during line recording is greatly reduced, and at the time of the next line recording, at least at the odd-numbered recording electrode position that is the first drive, the ink becomes less likely to fly or the dot diameter becomes smaller. The phenomenon of being lost occurs.

Accordingly, in the present driving method, the voltage pulse is applied from the auxiliary electrode 3 during the interval time before the recording head starts recording and after the driving for one line is completed and before shifting to the next line, and the charge amount of the ink is increased. This ensures that stable recording can be achieved even if the paper feed period for one line is long, and that the voltage applied to the recording electrode 2 and the counter electrode 12 can be set low.

Here, in FIG. 8, the voltage pulse width applied to the auxiliary electrode 3 is set sufficiently smaller than the voltage pulse width applied to the recording electrode, and the amount of charge supplied to the ink can be finely controlled by the number of pulses. However, the present invention is not particularly limited to this, and any drive that can supply charges to the ink at the above timing may be used.

Next, the driving means of the auxiliary electrode 3 shown in FIG. 9 will be described.

The driving method shown in FIG. 9 is a method in which the voltage pulse from the auxiliary electrode 3 is driven in synchronization with the voltage pulse applied to the recording electrode 2 and is driven continuously and periodically during the image recording operation. This is a method of continuously applying a voltage pulse.

In the method of driving the auxiliary electrode 3 as well, a sufficient charge can be supplied to the ink, so that the driving voltage of the recording electrode 2 can be reduced or the driving frequency can be improved in the same manner as in the above-mentioned driving method. This makes it possible to reduce the size of the device or increase the recording speed. Further, since the present driving method does not require complicated control, the driving control system of the auxiliary electrode 3 is also easy.

[0085]

As described above, the present invention relates to a recording head for ejecting ink using Coulomb force, in which an auxiliary electrode for supplying a desired charge to ink near the ink opening is provided. The following effects can be achieved by using a recording head having a structure in which a power supply for applying a voltage having the same polarity as the recording electrode to the auxiliary electrode and an auxiliary electrode driving unit are provided. (1) Since a recording head that does not require formation of fine nozzles can be realized, a low-cost, long-length recording head can be realized. (2) Since a sufficient charge can be supplied to the ink by applying a voltage to the auxiliary electrode,
The driving voltage of the recording head can be reduced without sacrificing the recording speed. Conversely, by maintaining the conventional driving voltage, the driving frequency can be increased, that is, the recording speed can be increased. (3) The ink receives a further sufficient charge by adopting a driving method of applying a voltage to the auxiliary electrode at a timing earlier than that of the recording electrode, or applying a voltage to the counter electrode at the same timing as the auxiliary electrode. Therefore, the drive voltage of the recording head can be further reduced.

Further, in the recording head of the present invention, the electric charge is supplied by the auxiliary electrode, so that the recording electrode can fly the ink even if the surface of the recording electrode is covered with an insulating material. Is also obtained. (1) Discharge between recording electrodes and discharge between opposed electrodes can be prevented, and safety and stability of ink flying can be ensured. (2) Since the surface of the recording electrode is covered, deterioration of the electrode due to electrolysis, oxidation, or the like can be prevented, and the durability and the life of the recording head can be improved.

Further, the recording head according to the present invention, the recording medium is arranged in a minute gap provided between the opening and the counter electrode, and the recording medium is scanned in synchronization with the operation of each recording head. The following effects can be obtained by configuring an image recording apparatus for attaching image pixels on the recording medium by having the means. (1) The size of the apparatus can be reduced by reducing the power supply voltage for driving the recording electrodes, and the life cycle can be increased by improving the durability and extending the life of the recording head.
Stable image output can be realized. (2) In addition, a plurality of recording heads are provided independently and arranged in parallel, means for supplying inks of different colors to the respective head portions are provided, and a minute gap provided between the opening and the counter electrode portion is provided. The recording medium is arranged on the recording medium, and the recording medium is transported in synchronization with the operation of each of the recording heads, so that a plurality of color images can be easily output on the recording medium. .

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating a first configuration of a recording head according to Embodiment 1 of the present invention.

FIG. 2 is an explanatory diagram showing another example of the structure of the head unit according to the second embodiment of the present invention.

FIG. 3 is an explanatory diagram illustrating a configuration of a recording head for recording a multicolor image according to a third embodiment of the present invention.

FIG. 4 is a block diagram illustrating a driving method when outputting an image of the recording head according to the first embodiment of the present invention.

FIG. 5 is a block diagram illustrating a driving method when a recording head performs multicolor image recording according to a second embodiment of the present invention.

FIG. 6 is a timing chart illustrating a method for driving the recording head according to the first embodiment of the present invention.

FIG. 7 is a timing chart illustrating another example of the method of driving the recording head according to the first embodiment of the present invention.

FIG. 8 is a timing chart showing another example of the method of driving the recording head according to the first embodiment of the present invention.

FIG. 9 is a timing chart showing another example of the method of driving the print head according to the first embodiment of the present invention.

FIG. 10 is an explanatory diagram showing an example of the related art.

[Explanation of symbols]

 Reference Signs List 1 lower substrate 2 recording electrode 3 auxiliary electrode 4 recording electrode driver 5 recording electrode / auxiliary electrode high voltage power supply 6 spacer 7 upper substrate 8 head 9 ink 10 ink chamber 11 slit opening 12 counter electrode 13 counter electrode driver 14 counter High voltage power supply for electrode 15 Recording paper 16 Ink supply hole 17 Insulation protective layer 18 Driver for auxiliary electrode

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Seiji Kuwahara 1-8-1 Nakase, Mihama-ku, Chiba-shi, Chiba Inside the SII IRD Center (72) Inventor Hiroyuki Muramatsu 1 Nakase, Mihama-ku, Chiba-shi, Chiba 8-8 chome S.I.R.D. Center Co., Ltd. (72) Inventor Atsuya Akase 1-8-8 Nakase, Mihama-ku, Chiba-shi, Chiba Co., Ltd. S.I.I.R.D. Center Co., Ltd. (72) Inventor Shunichi Tanaka 1-8-8 Nakase, Mihama-ku, Chiba F-term (reference) in SIIR D Center 2C057 AF01 AF55 AG22 AR03 AR06 BD05 DB01 DC08 DC15 EC03

Claims (10)

[Claims] A plurality of recording electrodes arranged at predetermined intervals on at least one inner surface of the substrate and a slit-shaped ink opening formed by a lower substrate and an upper substrate; Ink supply means arranged toward the opening, communicating with the ink opening through the two substrates and supplying ink, and a counter electrode arranged at a position facing the recording electrode via a minute gap, A recording head that has a power supply for applying a voltage pulse between the recording electrode and the counter electrode and a head driving unit and applies Coulomb force to the ink to fly ink at a desired position in an opening; An auxiliary electrode for supplying a desired charge to the ink, a power supply for applying a voltage having the same polarity as the recording electrode to the auxiliary electrode, and an auxiliary electrode driving unit. Recording head, characterized in that digit. 2. The recording head according to claim 1, wherein a surface of said recording electrode is covered with an insulating material. 3. The recording head according to claim 1, wherein the auxiliary electrode is formed on an inner surface of the substrate on which the recording electrode is not disposed. 4. The recording head according to claim 1, wherein said auxiliary electrode is formed on an insulating material provided on said recording electrode. 5. The auxiliary electrode driving means is a means for applying a voltage pulse to the auxiliary electrode by superimposing the voltage pulse applied to the recording electrode, and simultaneously or slightly with the voltage pulse applied to the recording electrode. 5. The recording head according to claim 1, wherein a voltage pulse is applied to the auxiliary electrode at an early timing. 6. The auxiliary electrode driving means is a means for applying a voltage pulse to an auxiliary electrode without overlapping with a voltage pulse applied to the recording electrode, and is configured to apply a voltage pulse to the auxiliary electrode rather than a voltage pulse applied to the recording electrode. 5. The recording head according to claim 1, wherein at least one or more voltage pulses are applied to the auxiliary electrode at a timing before the recording head. 7. The auxiliary electrode driving means is a means for applying a voltage pulse to the auxiliary electrode by superimposing the voltage pulse applied to the recording electrode, and applying a voltage pulse to the auxiliary electrode during a recording time. 5. The recording head according to claim 1, wherein the voltage is continuously applied without interruption. 8. The recording head according to claim 1, wherein said auxiliary electrode driving means applies a desired voltage to said counter electrode in synchronization with driving of said auxiliary electrode. 9. A recording head according to claim 1, wherein a recording medium is disposed in a minute gap provided between the opening and the counter electrode, and the operation of each of the recording heads is performed. Having transport means for scanning the recording medium synchronously,
An image recording apparatus, wherein a desired image is formed on the recording medium by controlling the driving of the recording head and the transport unit. 10. The recording head according to claim 1, wherein a plurality of recording heads are provided independently and arranged in parallel, and means for supplying inks of different colors to the respective head portions are provided. And a transport means for arranging the recording medium in a minute gap provided between the counter electrode portions and scanning the recording medium in synchronization with the operation of each of the recording heads. An image recording apparatus characterized in that a plurality of color image pixels are attached on the recording medium by controlling the driving of the image recording apparatus.