JPH08156260A - Ink jet recording apparatus - Google Patents

Abstract

PURPOSE: To enable recording of uniform density and to prevent the leakage of ink by arranging an auxiliary electrode array for feeding a charged colorant component in ink to a flight start position on an auxiliary substrate. CONSTITUTION: An auxiliary substrate 15 forming a parallel flat plate along with a head substrate 11 and forming ink supply passages along with the substrate 11 is arranged on' the surface having a main electrode array 12 arranged thereof of the silicon substrate 11. An auxiliary electrode array 16 consisting of a plurality of stripe like electrodes crossing the main electrode array 12 at a right angle is arranged on the inner surface of the auxiliary substrate 15, that is, the surface opposed to the head substrate 11 thereof and the auxiliary electrode driver circuit 17 for driving the auxiliary electrode array 16 is also arranged thereon. The charged colorant component in ink is fed toward a flight start position by the auxiliary electrode array to be uniformly fed to a colorant flight point.

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 in particular, a liquid ink in which a colorant is dispersed in a solvent is used, and the colorant component in this ink is concentrated and ejected onto a recording medium. The present invention relates to an inkjet recording device for recording.

[0002]

2. Description of the Related Art An apparatus for ejecting liquid ink as small droplets called ink particles on a recording medium to form recording dots and recording an image has been put into practical use as an inkjet printer. This ink jet printer has the advantages that it is less noisy than other recording methods and does not require processing such as development and fixing, and is attracting attention as a plain paper recording technology. Many methods of inkjet printers have been devised up to now, but in particular, (a) a method of ejecting ink droplets by the pressure of steam generated by the heat of a heating element (for example, Japanese Patent Publication Nos. 56-9429 and 61-59).
911) or (b) a method in which ink droplets are ejected by a mechanical pressure pulse generated by a piezoelectric element (for example, Japanese Patent Publication No. 53-12138), and a multi-nozzle that records a plurality of dots in parallel. The type is typical.

A recording head used in an ink jet printer is mounted on a carriage and is in a direction (main scanning direction) orthogonal to a recording paper conveyance direction (sub scanning direction).
A serial scanning type head is used in which recording is performed while moving to. With this serial scanning type head, it is difficult to increase the recording speed because recording is performed while moving mechanically. Therefore, the recording head is made a long head of the same size as the width of the recording paper to reduce the mechanical moving parts,
A so-called line scanning head capable of increasing the recording speed is also considered, but it is not easy to realize such a line scanning head for the following reason.

In the ink jet recording system, the concentration and concentration of the ink are likely to occur locally due to the evaporation and volatilization of the solvent, which causes the clogging of individual thin nozzles corresponding to the resolution. Therefore, in the method of using the pressure of vapor for forming the inkjet, insoluble matter is attached by thermal or chemical reaction with the ink, and in the method of using the pressure of the piezoelectric element, the ink flow path is complicated. The different structure makes it easier to induce clogging. Serial scanning heads that use several tens to hundreds of nozzles can reduce the frequency of clogging, but line scanning heads that require thousands of nozzles. The probability of clogging occurs at a fairly high frequency, which is a major problem in terms of reliability.

Further, there is a problem that the conventional ink jet recording apparatus is not suitable for improving the resolution. That is, it is difficult to generate ink particles having a diameter of 20 μm or less (which corresponds to a recording dot having a diameter of about 50 and several μm on the recording paper) by the method using the pressure of vapor, and the pressure generated by the piezoelectric element is used. This is because in the method of using, the recording head has a complicated structure, and it is difficult to form a head with high resolution due to processing technology problems.

In order to overcome these drawbacks, an ink jet recording system has been devised in which a voltage is applied to an electrode array of a thin film and an electrostatic force is used to fly the ink or a colorant component therein from the liquid surface of the ink. Specifically, a method of ejecting ink using electrostatic attraction (Japanese Patent Laid-Open No. 49-6).
2024, Japanese Patent Laid-Open No. 56-4467, etc.) or a method of increasing the concentration of the colorant and flying it using an ink containing a charged colorant component (WO93 / 11866: PCT / AU92 / 0).
0665) and the like have been proposed. With these methods,
Since the recording head has a slit-shaped nozzle configuration that does not require a nozzle for each individual dot (FIG. 10) or a nozzleless configuration that does not require an ink flow path partition for each individual dot (FIG. 11) This is effective in preventing and recovering from clogging, which was a major obstacle in realizing a line scan recording head. The latter is particularly suitable for high resolution because it can stably generate and fly ink particles having a very small diameter.

However, the conventional ink jet recording head shown in FIGS. 10 and 11 has the following drawbacks. That is, in these inkjet recording heads, the ink existing over a wide area supplied on the head substrate is intensively pressed from a relatively narrow area such as a pump from the rear of the ink flow. The pressure is applied by using a pressurizing mechanism. Therefore, due to the frictional force between the ink and the narrow ink flow path wall, the flow of the ink becomes non-uniform depending on the location, and the density of the colorant flying on the recording medium becomes non-uniform, resulting in uneven recording density. . Further, even if there is a difference in the frequency of use of the color material for each dot on the recording medium, the difference in the supply of the color material causes uneven recording density.

Further, the nozzle having a slit-like opening without a wall separating each dot causes ink leakage when a physical shock is applied, as compared with a system having a nozzle separating each dot. There is a problem that it is easy.

Further, in the ink jet recording head shown in FIG. 10, since the colorant component is usually about several percent, the ink is about 20 times as much as the colorant even in the case of all mark recording corresponding to a continuous black image. It is necessary to supply 100 times the amount of solvent, and it is necessary to supply approximately 2000 times the amount of solvent when the coverage on the recording paper, which is said to be the actual printing rate, that is, the black area ratio is 5%. Therefore, compared with normal ink jet recording in which the ink is ejected as it is, there is a drawback in that the use efficiency of the ink is poor and a recovery mechanism is required.

Moreover, if the ink is circulated and repeatedly used in order to efficiently use the collected ink, the characteristics of the head may be changed or deteriorated due to the ink stain when the ink passes through the open-ended area of the head end. However, the life and maintenance of the material become a problem.

[0011]

As described above, in the ink jet recording apparatus for recording by ejecting the ink or the coloring material component in the ink by using the conventional electrostatic force, the large area supplied on the head substrate is recorded. By applying pressure to the ink that exists over the entire area using a pressure mechanism such as a pump, the ink is conveyed to the tip of the head, so the ink flow becomes uneven and the recording density becomes uneven. Occurs, and unevenness in the recording density occurs due to the difference in the colorant supply frequency due to the difference in the frequency of use of the colorant for each dot, and further ink leakage due to physical shock is likely to occur.
There was a problem.

Further, since the above-mentioned conventional ink jet recording apparatus basically performs recording by ejecting only the colorant component in the ink, the ordinary ink jet recording in which the ink is ejected as it is without separating the colorant component. The efficiency of ink use is lower than that of the device, and a recovery mechanism is also required. Furthermore, if the ink is circulated and used repeatedly in order to efficiently use the recovered ink, changes in the characteristics of the head due to ink stains, deterioration, etc. There is also a problem in that the service life is shortened due to the problem and maintenance becomes complicated.

The present invention has been made to solve the above-mentioned problems, and an ink jet recording apparatus using electrostatic force, which enables recording with uniform density and is less likely to cause ink leakage from the head due to physical impact. The purpose is to provide.

It is another object of the present invention to provide an ink jet recording apparatus in which the amount of ink supplied to the head is recovered after passing through the head, or the ink recovery is substantially unnecessary.

[0015]

SUMMARY OF THE INVENTION The present invention is an ink jet recording apparatus for condensing a colorant component in an ink in which a colorant is dispersed in a solvent and flying it to a recording medium by dispersing the colorant in the solvent. An auxiliary substrate is provided so as to face the head substrate to which the ink is supplied, and an auxiliary electrode array for transporting the charged coloring material component in the ink toward the flight start position is arranged on the auxiliary substrate. Is a basic feature.

More specifically, in the ink jet recording apparatus according to the present invention, a head substrate to which ink in which a colorant is dispersed in a solvent is supplied, a main electrode array arranged on the head substrate, and a head are provided. An auxiliary substrate provided to face the substrate, an auxiliary electrode array arranged on the surface of the auxiliary substrate facing the head substrate so as to be orthogonal to the main electrode array, and an auxiliary electrode array in the ink supplied on the head substrate. A voltage for concentrating the charged coloring material components and moving them to the auxiliary substrate side,
And a main electrode driving means for applying a voltage for flying the coloring material component to the main electrode array, and an auxiliary electrode array for feeding the charged coloring material component on the auxiliary substrate toward the flying start position. And an auxiliary electrode driving means for applying to the electrode.

The main electrode array is composed of, for example, a plurality of striped electrodes extending from a plurality of colorant flying start positions at the tip of the head, and the auxiliary electrode array is composed of, for example, a plurality of striped electrodes extending in a direction orthogonal to the main electrode array. Composed. The auxiliary electrode array is not limited to a stray electrode, but may be one in which a plurality of dot-shaped electrodes are arranged in a matrix or one in which curved electrodes are arranged, and the array shape is not particularly limited. Also,
As the voltage applied to the auxiliary electrode array, a multi-phase voltage such as two-phase or three-phase is used.

Further, according to the present invention, the transporting means for transporting the colorant component in the ink supplied onto the head substrate to be supplied toward the flying start position of the colorant component is orthogonal to the direction in which the colorant component is transported. It is characterized in that it is divided into a plurality of areas in the direction in which the colorant component is conveyed and the amount of the colorant component to be conveyed can be controlled independently for each area. This transfer means is composed of, for example, the above-mentioned auxiliary substrate and an auxiliary electrode array arranged on the auxiliary substrate, and the auxiliary electrode array is divided into a plurality of electrode groups corresponding to the plurality of regions in a direction orthogonal to the arrangement direction. And connected so that a voltage can be applied independently to each electrode group. Then, to each electrode group of the auxiliary electrode array, for example, a voltage having a different cycle is applied in consideration of the structure of the ink flow path formed by the head substrate and the auxiliary substrate, or the voltage is applied to each electrode group. By applying a voltage whose cycle is controlled according to the frequency of the print data to be recorded, the amount of the color material component conveyed in each region is controlled.

Further, the present invention is characterized by having a pressure applying means such as a pump for applying a pressure to the ink supplied onto the head substrate. When the voltage applied to the auxiliary electrode array by the auxiliary electrode array driving means has two phases, the carrying direction of the charged color material component on the auxiliary substrate may not be determined, but with respect to the ink supplied on the head substrate. Then, by applying an appropriate positive pressure by this pressure applying means, the colorant component can be transported toward the flight start position.

Further, the pressure applying means is more preferable so as to increase the speed difference between the moving speed of the coloring material component in the ink and the flow speed of the solvent in the ink with respect to the ink supplied onto the head substrate. May apply a negative pressure so that the average moving speed of the ink supplied onto the head substrate becomes substantially zero.

Further, in the present invention, the acceleration sensor for detecting the impact applied to the head, and the voltage applied to the auxiliary electrode array by the auxiliary electrode array driving means based on the output of the acceleration sensor and further the ink applied by the pressure applying means. You may further provide the control means which controls the applied pressure.

[0022]

As described above, according to the present invention, in addition to the head substrate to which the ink is supplied, the auxiliary substrate facing the head substrate is provided, and the coloring agent component in the ink is colored by the auxiliary electrode array arranged on the auxiliary substrate. By transporting the colorant components of the ink supplied onto the head substrate to the flying start position, that is, toward the plurality of colorant flying points arranged at the head tip (the tip of the head substrate and the auxiliary substrate), It can be transported uniformly with respect to the points.

More specifically, if the colorant is charged to the same polarity as the voltage applied to the main electrode, the colorant component in the ink is electrostatically repulsive when the ink passes over the head substrate. By this, it moves so as to be pressed against the auxiliary substrate side, and becomes a concentrated state. The colorant component thus moved to the auxiliary substrate side is driven by an electric field formed by applying a voltage applied to the auxiliary electrode array on the auxiliary substrate, for example, a voltage whose phase advances in the ink transport direction, Form a thin and fast flow toward the colorant flying point. From the flow of the charged coloring material component, a frictional force proportional to the viscosity of the solvent acts on the ink, causing the ink to flow as if it is pulled by the charged coloring material component. Can be transported to. In this way, even with a long line scanning type recording head, it is possible to supply a constant amount of color material from one end to the other, thus achieving uniform recording density.

Further, even in the portion near the tip of the slit-shaped nozzle which is the ink supply channel formed by the head substrate and the main electrode array, the electric field due to the voltage applied to the auxiliary electrode array is present between the auxiliary electrode array and the ink. Causes a relatively strong force at a short distance to act, and this force acts as a resistance force against a physical shock, which makes it difficult for ink to leak from the head due to the physical shock. When the acceleration sensor detects that a shock has been applied to the head,
By controlling the voltage applied to the auxiliary electrode and the pressure applied to the ink to increase the resistance to the ink flow or to retract the ink, it is possible to more reliably prevent the ink leakage.

On the other hand, the colorant component transporting means may be divided into a plurality of regions in the direction orthogonal to the colorant component transporting direction so that the transporting amount (flow rate) of the colorant component can be controlled independently for each region. For example, in the ink transport path formed between the head substrate and the auxiliary substrate, by setting the transport amount in both regions where the ink flow resistance is high to be larger than that in the central region, the ink flow The non-uniformity of the flow of the colorant component coming from the structure of the road is eliminated. Further, by controlling the transport amount of the coloring material according to the frequency of the print data corresponding to each area,
The problem of uneven recording density due to the difference in the amount of color material consumed depending on the frequency of recording data is solved.

Furthermore, the flow of the colorant component along the inner surface of the auxiliary substrate due to the voltage applied to the auxiliary electrode array has a large relative velocity difference with the solvent, so that even if the velocity of the entire ink is forcibly slowed down, there is little effect. Do not receive Therefore, by applying a negative pressure to the entire ink from the rear using a pressure applying means such as a pump, the flow of the solvent can be made slower than the flow of the colorant component while maintaining the required flow of the colorant. It will be possible. As a result, the flow rate of the ink is reduced to reduce the chance of the ink coming into direct contact with the outside air, thereby preventing contamination of impurities, evaporation of the solvent, denaturation of the ink, and the like, which contributes to a longer life of the solvent. Furthermore, by applying this negative pressure, it is also possible to keep the flow of the colorant component while making the average moving speed of the ink substantially zero, that is, making the entire ink in a stationary state, thereby improving the ink use efficiency and No recovery mechanism is required.

[0027]

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) FIG. 1 is a view showing the arrangement of a recording head portion in an ink jet recording apparatus according to an embodiment of the present invention. In the figure, a main electrode array 1 including a plurality of parallel stripe electrodes to which a recording signal voltage for flying the ink 10 is applied to the surface of a head substrate 11.
2 are arranged. On the surface of the head substrate 11 on which the main electrode array 12 is arranged, a thickness not shown of 300 μm
A parallel plate is formed together with the head substrate 11 via a spacer of a certain degree, and an ink supply channel 13 is formed between the head substrate 11 and the main substrate 11.
An auxiliary substrate 14 that forms a substrate is provided. On the inner surface of the auxiliary substrate 15, that is, on the surface facing the head substrate 11, an auxiliary electrode array 16 including a plurality of stripe-shaped electrodes orthogonal to the main electrode array 12 is arranged. The figure also shows the state where the auxiliary substrate 15 and the auxiliary electrode array 16 are viewed from the inside. An auxiliary electrode driver circuit 17 for driving the auxiliary electrode array 16 is also provided on the inner surface of the auxiliary substrate 15.

Ink 1 is supplied to the ink supply passage 13 from the right side of the drawing by an ink recirculation mechanism including a pump or the like (not shown).
0 is supplied. The ink 10 contains, for example, a positively chargeable colorant component together with a charge control agent and a binder at 10 ⁻⁸ Ωcm.
It is dispersed in a colloidal state in the above insulating solvent and suspended. Ink 1 supplied to the ink supply channel 13
0 is an ink recovery channel 1 formed in the head substrate 11 after passing through a coloring material flying point 12a at the head end, which is an opening at the tip of the head substrate 11 and the auxiliary substrate 14.
It is collected in the above-mentioned ink recirculation mechanism through 4.

Next, the operation of this embodiment will be described with reference to FIGS. 2 and 3. FIG. 2 is an enlarged view showing a part of the ink supply flow path 13 in FIG. 1 so that the movement of the colorant component 10a in the ink 10 can be seen together with the operation of the auxiliary electrode driver circuit 17. To the main electrode array 12, for example, a bias voltage of 1.5 kV and a recording signal voltage 21 of 500 V are superimposed and applied. The bias voltage is applied to all the electrodes of the main electrode array 12, and the recording signal voltage 21 is selectively applied to the electrodes of the main electrode array 12 corresponding to the image points to be recorded.

As described above, since a voltage of 1.5 kV or more is constantly applied to the main electrode array 12, a positively charged color that floats in a colloidal state in the ink 10 in the ink supply channel 13 on the upper surface thereof. The agent component 10 a is applied to the auxiliary substrate 15 by the electrostatic repulsive force received from the main electrode array 12.
It moves in a concentrated state so that it can be pressed against the inner surface of.

On the other hand, in the electrode groups 16a, 16b, 16c, 16d, 16e and 16f forming the auxiliary electrode array 16, the voltage application positions are sequentially changed with time as shown in FIG. 3A. The auxiliary electrode driver circuit 17 applies a three-phase voltage pulse train whose phase shift is controlled so as to move in the direction of. The phase velocity and voltage value of this voltage pulse train are the same as the colorant component 10a in the ink 10.
And the repetition interval of the auxiliary electrode array 16,
It is determined based on the three values of the colorant transport amount to the required colorant flying point 12a. Actually, however, from the condition that the ink flows most efficiently by an experiment using the voltage and the pulse application period as parameters. It can be easily guided.
However, the voltage value of the voltage pulse train applied to the auxiliary electrode array 16 is applied to the main electrode array 12 so as not to impede the effect of concentrating the colorant component 10a by the electric field force due to the voltage applied to the main electrode array 12. Since there is a restriction that it must be lower than the voltage, in this case 1.5k
It is necessary that the voltage is less than V, and if it is considered that the auxiliary electrode driver circuit 17 is realized by an IC, it is preferably several tens V or less.

When the voltage pulse train having the thus optimized voltage value and phase velocity is applied to the auxiliary electrode array 16, it moves from the ink 10 in the ink supply channel 13 to the inner surface of the auxiliary substrate 15. The charged color material component 10a is transported toward the color material flying point 12a while sliding on the surface of the auxiliary substrate 15 at the same speed as the phase speed of the voltage pulse train.

That is, the timing t shown in FIG.
1, the auxiliary electrodes 16a and 16a are connected to each other as shown in FIG.
Since a voltage pulse having a phase of φ1 is applied to d, the positively charged colorant component present on the left side of the auxiliary electrodes 16a and 16d is pushed to the left side by the electrostatic repulsive force from the auxiliary electrodes 16a and 16d. It receives force and moves by electrophoresis. Next, the coloring material component that has moved to the left side due to the electrostatic repulsion force from the auxiliary electrodes 16a and 16b is transferred to the auxiliary electrodes 16a and 1b.
When a voltage pulse having a phase of φ2 is applied to the auxiliary electrodes 16b and 16e as shown in FIG. 2B at a timing t2 when the auxiliary electrodes 16b and 16e on the left side of 6d have just passed, these colors The agent component is now the auxiliary electrode 16b
And 16e, the electrostatic repulsion force is applied to move further to the left. Next, the coloring material component that has moved to the left side due to the electrostatic repulsive force from the auxiliary electrodes 16b and 16e is transferred to the auxiliary electrodes 16b and 1e.
When a voltage pulse having a phase of φ3 is applied to the auxiliary electrodes 16c and 16f as shown in FIG. 2C at a timing t3 when they have just passed over the auxiliary electrodes 16c and 16f on the left of 6e, these colors This time, the agent component is auxiliary electrode 16c
And 16f receive the electrostatic repulsion force and move further to the left.

In this way, the colorant component 10a that has moved onto the auxiliary substrate 15 is supplied to the auxiliary electrodes 16a to 16f of the auxiliary electrode array 12 driven by the three-phase voltage pulses.
By sequentially receiving the electrostatic repulsive force from the, the electrophoretic migration continues to move toward the colorant flying point 12a at the same speed as the phase velocity of the voltage pulse train.

Considering the case where the colorant components are present on the right side of the auxiliary electrodes 16a and 16b when a voltage pulse is applied to the auxiliary electrodes 16a and 16d, these colorant components are directed in the right direction, that is, the colorant fly. The electrostatic repulsive force in the backward direction, which is the opposite side to the direction toward the point 12a, is received. Here, as is apparent from FIG. 3A, the backward phase velocity when the auxiliary electrode array 16 is driven by the three-phase voltage pulse train is twice the forward phase velocity. That is, at the timing t1 in FIG.
When a voltage pulse having a phase of φ1 is applied to 16 and 16d, the coloring material component existing on the right side of the auxiliary electrodes 16a and 16b retreats to the right side due to the electrostatic repulsive force in the receding direction, and the next timing At t2, the voltage pulse having a phase of φ2 applied to the auxiliary electrodes 16b and 16e causes the voltage pulse to further retreat to the right side. Therefore, between timing t1 and t2, the distance retreats to the right side, which is twice the distance to advance to the left side. After all, the backward phase velocity becomes twice the forward phase velocity. Therefore, if the voltage value and the period of the voltage pulse train are set so as to deviate from the electrophoretic response range of the colorant component determined by the electric field mobility at this double phase velocity, the colorant component 10a
Does not move backwards.

The kinetic energy generated by the movement of the colorant component 10a has less viscous colorant that forms a layered flow in a region further away from the auxiliary substrate 15, or the viscous resistance of the ink solvent to the liquid portion having no colorant. Is transmitted, and eventually the entire ink 10 in the ink supply channel 13 develops a steady state in which it flows at a constant speed.

In this way, the main electrode array 12 of FIG.
When the recording signal voltage superimposed on the bias voltage is applied to the main electrode array 12 at that timing, the coloring material component 10a carried to the coloring material flying point 12a at the tip of the point becomes stronger due to the application of the recording signal voltage. The force acting on the charged particles from the electric field overcomes the surface tension of the ink 10 and flies in the air toward the counter electrode 19, forming an image point on the recording paper 18 which is a recording medium arranged in front of the counter electrode 19. . On the other hand, at this time, the remaining color material components that did not fly even though they were at the color material flying point 12a and the color material components that were not at the timing when the recording signal voltage was applied to the main electrode array 12 are From the agent flying point 12a to the ink recovery channel 14, the ink recovery channel 14
Recovered through.

According to this embodiment, the following effects can be obtained. First, in the conventional method of injecting ink into a thin ink supply channel of about 300 μm by a pressure of a mechanical pressurizing mechanism such as a pump, a portion far from the ink supply port or an ink supply channel due to resistance due to viscous friction. There is a problem that unevenness in recording density is likely to occur due to local decrease in flow velocity and pressure drop on the wall portion of the ink, non-uniform flow of ink, and difference in ink supply amount between places. .

On the other hand, according to this embodiment, the auxiliary substrate 1
The auxiliary electrode array 16 arranged on the upper surface 5 forms a kind of electrostatic pump which is uniformly distributed in the ink supply flow path 13, whereby the colorant component in the ink 10 is spatially uniform. Since the toner is conveyed toward the colorant flying point 12a while maintaining the state, such a problem is solved, and even if a long line scan type recording head is used, a recorded image can be obtained without density unevenness. To be

In addition, the head substrate 11 and the main electrode array 12
Even in the portion near the tip of the ink supply flow path 13 which is a slit-shaped nozzle formed by, the electric field generated by the voltage applied to the auxiliary electrode array 10 between the auxiliary electrode array 16 and the ink 10 causes a comparatively short distance. Since a strong force is exerted, this force acts as a resistance force against a physical shock, so that it is possible to obtain the effect of preventing the leakage of the ink 10 due to the physical shock.

The present embodiment can be implemented with various modifications as follows. For example, in the above description, when driving the auxiliary electrode array 16 in three phases, φ1, φ
Although the voltage pulse is always applied to only one of the three phases of 2 and φ3, there may be a period in which voltage pulses of a plurality of phases are simultaneously applied to different auxiliary electrodes. For example, as shown in FIG. 3B, voltage pulses of two phases out of three phases may be simultaneously applied to different auxiliary electrodes in a certain period.

In the above description, the auxiliary electrode array 12 is used.
Although the voltage waveform applied to the pulse waveform is a pulse waveform, it is not limited to this and, for example, as shown in FIG.
You may use sine waves with different phases.

Further, in the above description, the auxiliary electrode array 16 is used.
Although the number of phases (the number of phase divisions) N in multi-phase driving is set to 3, N may be any number as long as it is 2 or more. That is, N
It may be an integer of ≧ 2. FIG. 3D shows the timing of voltage application to the auxiliary electrode array 16 in the case of N = 4 phases. In general, the ratio of the phase velocity in the backward direction to the phase velocity in the forward direction is-(N-1), and the larger N is, the larger the difference is. However, when N = 2, the phase velocities have the same magnitude in the forward direction and the backward direction, and the directions are opposite. Therefore, some ingenuity is required to set the conveying direction of the colorant component to the forward direction. Become. Hereinafter, the case of N = 2, that is, the case of driving the auxiliary electrode array 16 in two phases will be described.

FIG. 4A is an explanatory diagram in the case of two-phase driving. The solid line represents the waveform of the voltage pulse and the movement of the colorant component position in the first phase of the two-phase drive, and the dotted line represents the waveform of the voltage pulse and the movement of the colorant component position in the second phase. The positions of the specific colorant components are represented by black circles, and the positions of the specific colorant components in the second phase are represented by white circles. The colorant component particles 10b, which have a slightly lower moving speed than the phase speed given to the auxiliary electrode array 16 by the auxiliary electrode drive circuit 17 or have a small amount of charge, reciprocate between the two auxiliary electrodes. On the contrary, is it moving a little faster?
Alternatively, the same number of colorant component particles 10c having a large amount of charge continue to move in the left-right direction. Therefore, only the auxiliary electrode array 1
When 6 is driven in two phases, the flow direction of the coloring material is not fixed.

However, when a pressure means such as a pump 23 is forced to generate a flow of velocity va in the forward direction with respect to the ink 10 as shown in FIG. The migration speed of the
e and the moving speed va due to external pressure of the pump 23 or the like (ve-va), and the moving speed in the forward direction is the sum (ve + va) of both, so that the particles of the charged colorant component in the same applied electric field are Velocity creates an asymmetry with respect to direction. Therefore, the phase velocity of the voltage pulse actually applied to the auxiliary electrode array 16 may be set to a velocity (ve + va) that is the sum of the velocity of movement Ve of the ink 10 due to electrophoresis and the velocity of movement Va due to the external pressure of the pump 23 or the like. For example, the ink 10 efficiently and uniformly flows in one direction, that is, in the forward direction.

As described above, by combining the two-phase drive and the pressure applying means from the outside such as the pump 23 to make the moving speed of the ink 10 asymmetrical in the forward and backward directions, the color in the ink 10 is changed. The transport direction of the agent component can be set to the forward direction, that is, the direction toward the color agent flying point.

FIG. 5 shows that the auxiliary electrode corresponding to one phase is removed when the auxiliary electrode array 16 is driven in three phases, and the voltage pulse applied to the remaining auxiliary electrodes corresponding to two phases is for three-phase driving. This is an example in which the asymmetry between the forward speed and the backward speed is created by maintaining the same phase relationship. In simple terms, it can be considered that two phases are driven by omitting the movement of one phase of the three-phase drive only by the inertia of the fluid. At the timings shown in FIGS. 5A and 5B, the electric field force represented by the solid arrow acts as a force for moving the colorant component 10a, and at the timing shown in FIG. 5C, the solvent of the ink represented by the dotted arrow is included. It moves by the inertial force due to the flow.

By performing the two-phase driving as described above, the following merits are newly obtained. That is, when the auxiliary electrode array 16 is driven in three phases, the lead lines of the plurality of auxiliary electrodes that are arranged in stripes and that form the auxiliary electrode array 16 intersect, so the auxiliary electrode array 1
6 needs to have a two-layer structure in which wiring layers are formed on both sides of the insulating layer, which complicates the manufacturing process. On the other hand, when the two-phase drive is used, it is not necessary to intersect the lead wires of the auxiliary electrodes, so that the auxiliary electrode array 16 can be easily manufactured by a single-layer pattern manufacturing process. Also,
As for the auxiliary electrode driver circuit 17, a common circuit can be used for more auxiliary electrodes that are driven in the same phase, and two driver circuits corresponding to two phases can be prepared as a whole. It is possible to simplify.

(Second Embodiment) FIG. 6 is a view showing a main part of a recording head portion in an ink jet recording apparatus according to this embodiment, which is an auxiliary substrate 15 and an auxiliary electrode array 16.
2 and a configuration of the auxiliary electrode driver circuit 17 are shown.

In FIG. 6, the auxiliary electrode array 16 formed on the inner surface of the auxiliary substrate 15 has three (3 in this example) regions divided in a direction orthogonal to the array direction. The auxiliary electrode groups 16x, 16y, 16z are divided, and the flow of the ink 10 in the ink flow path 13 can be independently driven or controlled. The auxiliary electrode groups 16x, 16y, 16z have a pattern of unequal intervals similar to that used for the two-phase driving described in FIG. The three pairs of lead wirings respectively led out from the auxiliary electrode groups 16x, 16y, 16z are three unit drivers 17x, 17 constituting the auxiliary electrode driver circuit 17.
y and 17z are respectively connected. The auxiliary electrode driver circuit 17 is supplied with an output signal from a recording data frequency detecting circuit 24 for detecting the deviation of the recording data, that is, the frequency of occurrence of significant data of the recording data for each area.

In such a structure, the ink supply hole 2
When ink is supplied to each region from 0, voltage pulses whose phase shift is controlled are applied to the respective auxiliary electrode groups 16x, 16y, 16z. The components are conveyed toward the flight point at the top of the figure.

Here, the auxiliary electrode groups 16x, 16y, 16
As shown in the z block, the drive voltage waveform of the unit driver 17y that drives the central auxiliary electrode group 16y becomes the drive waveforms of the unit drivers 17x and 17z that drive the auxiliary electrode groups 16x and 16z on both sides. Compared with this, the cycle is set longer. This is to match the ink flow rates in the ink flow in the central area and the ink flow in the areas on both sides where the resistance that the ink flow receives is greater, and to equalize the transport amount of the colorant component in the ink. is there. In addition, the unit driver 1 that drives the auxiliary electrode groups 16x and 16y on both sides
There is a difference in the cycle of the drive waveform between 7x and 17y,
By the instruction from the recording data frequency detection circuit 24,
In the case of FIG. 6, there is more significant print data in the left area than in the right area of the drawing, which means that ink is supplied to the left area in a large amount.

As described above, the colorant component transporting means constituted by the auxiliary electrode array 16 is divided into a plurality of regions in the direction orthogonal to the transporting direction, and the transporting amount of the colorant component is independently open looped for each region. Therefore, it is possible to compensate for not only the difference in the ink flow from the structure of the ink flow path, but also the influence due to the difference in the color material consumption amount according to the frequency of the print data. As a result, good image recording with even less density unevenness becomes possible.

(Third Embodiment) FIG. 7 is a schematic configuration diagram of an ink jet recording apparatus according to this embodiment. The recording head portion, which is shown by enlarging the portion near the ink flying point 12a, is the same as that described in the first embodiment. In this embodiment, a pump 23 is provided for applying a pressure (negative pressure) to the ink 10 supplied to the ink supply flow path 13 through the ink supply flow path 13. If only the colorant component 10a in the ink 10 is conveyed to the colorant flying point 12a at the head end, the auxiliary electrode array 16 plays the role, so the pump 23 is essentially unnecessary, but in the present embodiment. The pump 23 has the following functions.

That is, as shown in the velocity distribution 22 in FIG. 2C, the auxiliary electrode array 16 is electrostatically directly driven only by the colorant component 10a, which is a charged particle, in the ink 10. Other ingredients, such as the solvent, are moving color components 1
Since it moves by receiving a force due to viscous friction from 0a, a relative speed difference is generated between it and the colorant component 10a. Therefore, the main purpose of the present embodiment is to use the pump 23 as a means for applying a pressure for braking the flow of the entire ink 10 rather than for conveying the color material component 10a, and to further increase the speed difference. Is.

Even if the ink 10 is braked by the pressure (negative pressure) given by the pump 23, the speed of the coloring material component 10a conveyed by the auxiliary electrode array 16 does not decrease so much, and the speed distribution of FIG. As shown in FIG. 22, most of them are covered by slowing the speed of the ink at a portion away from the auxiliary electrode array 16 that contains little or no coloring material component.

As described above, according to this embodiment, the ink 10
It is possible to reduce the total flow rate of the ink and reduce the chance of the ink 10 coming into direct contact with the outside air, thereby preventing contamination of impurities, evaporation of the solvent, denaturation of the ink 10 and the like, thereby extending the life of the ink solvent. Can be planned.

(Fourth Embodiment) FIG. 8 is a schematic structural diagram of an ink jet recording apparatus according to this embodiment.
In this example, the negative pressure applied to the ink 10 by 3 is further increased to prevent the ink 10 from flowing around the colorant flying point 12a at the tip of the head and flowing back.

In order to realize such an action, the ink 1
Closed loop control is required to supply 0 while preventing 0 from overflowing from the tip of the head. In this embodiment, the light emitting element 2
5 and the light receiving element 26 provided so as to face it, the optical sensor detects the amount of protrusion of the ink 10 from the colorant flying point 12a at the tip of the head, and the pump 23 is driven by the pump control circuit 27 based on the detected amount. Controlled.

That is, when the amount of protrusion of the ink 10 at the head tip is too large, the output of the light receiving element 26 decreases, and the pump control circuit 27 correspondingly pumps the negative pressure acting on the ink 10 to be large. Control 23. When the amount of protrusion of the ink 10 at the tip of the head is too small, the output of the light receiving element 26 rises, and the pump control circuit 27 correspondingly controls the pump 23 so that the negative pressure acting on the ink 10 becomes small. To do. With such control,
Other ink components such as the colorant component 10a carried in the direction of the colorant flying point 12a at the head end and the solvent dragged by the colorant component 10a and the other ink components such as the solvent pulled back in the direction of the pump 23 become equal, It becomes possible to keep the state of the velocity distribution 22 of FIG. 8 stable.

Therefore, according to the present embodiment, since the recovery of the ink 10 is unnecessary, not only the life of the ink solvent can be extended, but also the reflux mechanism can be eliminated or simplified, and the cost of the apparatus can be reduced. It is possible to realize an ink jet recording apparatus which can reduce the cost and improve the reliability, and which does not easily cause ink leakage when an impact force is applied.

In the above description, an example of the closed loop control is shown, but instead of this, the fact that the surface tension acting from the ink projecting surface to the inside of the ink becomes stronger according to the projecting height is utilized, and the auxiliary electrode array is used. The open loop control may be such that the total of the pressures applied from 16 and the pump 23 is maintained in a balanced range.

Further, in FIG. 8, the method of irradiating the light beam from the light emitting element 25 for detecting the protrusion amount of the ink tip from the direction perpendicular to the ink meniscus is adopted, but the present invention is not limited to this. Instead, the light beam may be emitted from the horizontal direction.

(Fifth Embodiment) FIG. 9 is a schematic configuration diagram of a main part of an ink jet recording apparatus according to the present embodiment, in which ink leakage is less likely to occur against impact force than in the eighth embodiment. This is an example of the above. In this embodiment, an acceleration sensor 28 for detecting an impact applied to the recording head portion is provided. When the acceleration sensor 28 detects a shock applied to the recording head portion, its output is transmitted to the auxiliary electrode driver circuit 17 and the pump control circuit 27. The auxiliary electrode driver circuit 17 and the pump control circuit 27 which have received the shock detection output from the acceleration sensor 28.
Controls the ink 10 at the tip of the head to be instantaneously retracted into the head.

When the control system in which the voltage applied to the auxiliary electrode array 16 is controlled in this way to instantaneously apply a negative pressure to the ink 10, the response is very fast, and ink leakage can be reliably prevented. it can. In this example, a system having a pump 23 is shown, but the quick response required to prevent ink leakage is most effectively obtained by the auxiliary electrode array 16 which is located near the head tip and does not include mechanical inertia. As such, it does not matter if the system does not have a pump.

[0066]

As described above, according to the present invention, the auxiliary substrate facing the head substrate to which the ink is supplied is provided, and the colorant component in the ink is removed by the auxiliary electrode array arranged on the auxiliary substrate. By transporting the colorant toward the colorant flying start position, the colorant component of the ink supplied on the head substrate can be uniformly transported with respect to the colorant flying point, so long line scanning type recording is possible. Even with the head, it is possible to supply a constant amount of color material from one end to the other, and it is possible to realize image recording with uniform density.

Further, even in the portion near the tip of the ink supply flow path formed by the head substrate and the main electrode array, the electric field due to the voltage applied to the auxiliary electrode array causes a relatively short distance between the auxiliary electrode array and the ink. By applying a strong force, it is possible to prevent ink from leaking from the head due to a physical shock, and it is added to the voltage and ink applied to the auxiliary electrode by detecting that a shock is applied to the head with an acceleration sensor. By controlling the pressure to increase the resistance to the ink flow or to retreat the ink, it is possible to more reliably prevent the ink leakage.

On the other hand, the colorant component conveying means is divided into a plurality of regions in the direction orthogonal to the colorant component conveying direction, and the colorant component conveying amount (flow rate) can be controlled independently for each region. As a result, the non-uniformity of the flow of the colorant component that comes from the structure of the ink flow path is eliminated, and the amount of the colorant conveyed is controlled according to the frequency of the print data corresponding to each area. It is possible to solve the problem of uneven recording density due to the difference in the consumption amount of the colorant, which is caused by the frequency distribution of.

Further, by applying a negative pressure to the entire ink from the rear by using a pressure applying means such as a pump, the flow of the solvent is made slower than the flow of the colorant component while maintaining the required flow of the colorant. Therefore, it is possible to reduce the flow rate of the ink to reduce the chance of the ink coming into direct contact with the outside air, prevent the mixing of impurities, the evaporation of the solvent, the denaturation of the ink, and the prolongation of the life of the solvent. . Also,
By applying this negative pressure, it is possible to keep the average moving speed of the ink at almost zero while keeping the flow of the colorant component, that is, to make the entire ink in a stationary state, which improves the ink use efficiency and The mechanism can be eliminated, which can greatly contribute to simplification and downsizing of the device.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of a head unit of an inkjet recording apparatus according to a first embodiment of the present invention.

FIG. 2 is a conceptual diagram for explaining the operation of the embodiment.

FIG. 3 is a waveform diagram of a phase-controlled voltage pulse when driving the auxiliary electrode array in three phases in the same example.

FIG. 4 is a conceptual diagram for explaining an operation when the auxiliary electrode array is driven in two phases in the same example.

FIG. 5 is a conceptual diagram for explaining another operation when the auxiliary electrode array is driven in two phases in the same example.

FIG. 6 is a schematic configuration diagram of a main part of an ink jet recording apparatus according to a second embodiment of the present invention.

FIG. 7 is a schematic configuration diagram of a main part of an ink jet recording apparatus according to a third embodiment of the present invention.

FIG. 8 is a schematic configuration diagram of a main part of an ink jet recording apparatus according to a fourth embodiment of the present invention.

FIG. 9 is a schematic configuration diagram of a main part of an inkjet recording apparatus according to a fifth embodiment of the present invention.

FIG. 10 is a diagram showing an example of a conventional inkjet recording head.

FIG. 11 is a diagram showing another example of a conventional inkjet recording head.

[Explanation of symbols]

10 ... Ink 10a to 10c ... Coloring agent component 11 ... Head substrate 12 ... Individual electrode 12a ... Coloring agent flying point 13 ... Ink supply channel 14 ... Ink recovery channel 15 ... Auxiliary substrate 16 ... Auxiliary electrode array 16a-16f ... Auxiliary Electrodes 16x to 17z ... Auxiliary electrode group 17 ... Auxiliary electrode driver circuit 17x to 17z ... Unit driver 18 ... Recording paper 19 ... Counter electrode 20 ... Ink supply hole 21 ... Recording circuit 22 ... Velocity distribution 23 ... Pump 24 ... Recording data frequency detection Circuit 25 ... Light emitting element 26 ... Light receiving element 27 ... Pump control circuit 28 ... Acceleration sensor

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Koichi Ishii, 1 Komukai Toshiba-cho, Sachi-ku, Kawasaki-shi, Kanagawa Inside the Toshiba Research and Development Center (72) Inventor Yuko Nomura Toshiba, Komukai-shi, Kawasaki-shi, Kanagawa Town No. 1 Incorporated company Toshiba Research & Development Center (72) Inventor Yasuo Hosaka Komukai-shi, Kawasaki-shi, Kanagawa Prefecture Komukai Toshiba Town No. 1 Incorporated company Toshiba Research & Development Center (72) Inventor Teruo Murakami Kawasaki, Kanagawa Prefecture Komukai-Toshiba-cho 1-ku, Toshiba Research & Development Center

Claims (4)

[Claims] 1. An ink jet recording apparatus for condensing a colorant component in an ink in which a colorant is dispersed in a solvent and flying it to a recording medium. A head substrate to which ink in which the colorant is dispersed in a solvent is supplied. And an auxiliary substrate provided facing the head substrate, and an auxiliary substrate arranged on the auxiliary substrate for carrying the charged colorant component in the ink toward the flight start position of the colorant component. An ink jet recording apparatus comprising an electrode array. 2. A head substrate to which ink containing a colorant dispersed in a solvent is supplied, a main electrode array arranged on the head substrate, and an auxiliary substrate provided so as to face the head substrate. An auxiliary electrode array arranged orthogonal to the main electrode array on a surface of the auxiliary substrate facing the head substrate, and a charged colorant component in the ink supplied on the head substrate are concentrated. Main electrode driving means for applying a voltage for moving to the auxiliary substrate side and a voltage for causing the colorant component to fly toward the recording medium to the main electrode array; and a charged color on the auxiliary substrate. An ink jet recording apparatus, comprising: an auxiliary electrode driving unit that applies a voltage to the auxiliary electrode array to convey the agent component toward the flight start position of the colorant component. 3. An ink jet recording apparatus for concentrating a colorant component in an ink in which a colorant is dispersed in a solvent and flying it to a recording medium. A head substrate to which the ink in which the colorant is dispersed in the solvent is supplied. And a transport unit that transports the colorant component in the ink supplied onto the head substrate toward the flight start position of the colorant component, the transporting unit being orthogonal to the transport direction of the colorant component. The inkjet recording apparatus is characterized in that it is divided into a plurality of areas in a direction in which the colorant component is conveyed, and the amount of the conveyed colorant component can be independently controlled for each area. 4. An ink jet recording apparatus for condensing a colorant component in an ink having a colorant dispersed in a solvent and flying it onto a recording medium, to which a head substrate to which the ink having the colorant dispersed in the solvent is supplied is supplied. And an auxiliary substrate provided facing the head substrate, and an auxiliary substrate arranged on the auxiliary substrate for carrying the charged colorant component in the ink toward the flight start position of the colorant component. An inkjet recording apparatus comprising: an electrode array; and a pressure applying unit that applies a pressure to the ink supplied onto the head substrate.