JP2000238271A - Ink jet recording device - Google Patents

Abstract

(57) Abstract: Provided is an ink jet recording apparatus including a recording head configured to suppress electrical mutual interference between adjacent ink ejection units. An insulating substrate, a discharge unit disposed on the substrate via an auxiliary unit, a discharge electrode disposed to sandwich the discharge unit, and discharging ink from the discharge unit, And a covering portion to be included.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording apparatus, and more particularly to an ink jet recording head for discharging a pigment-based ink containing charged colorant particles onto a recording medium by electrostatic force to perform printing, and an apparatus using the same. .

[0002]

2. Description of the Related Art An apparatus that forms recording dots and records an image by discharging liquid ink as small droplets onto a recording medium has been put to practical use as an ink jet printer. This ink jet printer has advantages such as lower noise compared to other recording methods, and realization of the printer with a smaller number of parts than other recording methods because recording is performed directly on a recording medium. Therefore, it is attracting attention as plain paper recording technology. As a recording method of an ink jet printer, a method of ejecting ink droplets at a pressure of a bubble generated by heat of a heating element (for example,
56-9429) and a method of ejecting ink droplets by mechanical pressure accompanying a volume change caused by distortion of a piezoelectric element (for example, Japanese Patent Publication No. 53-12138).
In the above two methods, since the ejection amount of ink droplets for each recording dot on the recording medium is constant, in printing a color image, the density between recording dots is spatially changed to generate a pseudo The gradation expression is performed. But,
With this gradation expression method, it is difficult to print a high gradation color image equivalent to a photograph. In order to print an image with higher gradation, gradation expression by so-called area modulation for changing the area of the recording dot is required. However, in the above two methods, since the ejection amount of the ink droplet is constant, it is extremely difficult to express the gradation by the area modulation.

As a recording method for overcoming this drawback, a method has been devised in which a voltage is applied to a plurality of electrodes arranged in parallel on a substrate, and ink or colorant particles in the ink is discharged using electrostatic force. . Specifically, JP-A-56-4467
No. 6,086,067, a method of discharging ink by electrostatic attraction as disclosed in Japanese Patent Application Laid-Open No. 7-502218, and a method of using an ink containing charged colorant particles as disclosed in Japanese Patent Publication No. 7-502218. There has been proposed a method of increasing the ejection rate. As a specific shape of the ink jet recording head in the latter method, an insulating electrode substrate having an ink discharging electrode formed on one surface is laminated via a spacer to form a multi-head having a plurality of discharging electrodes. Alternatively, there has been known a method in which ink discharge electrodes are formed in parallel as thin film electrodes at a printing interval of a desired resolution on a flat insulating substrate, and are configured as a multi-head. FIG. 11 shows an example of a multi-head basic configuration of a type in which thin-film electrodes are arranged in parallel on a flat insulating substrate. In the ink jet recording head, a plurality of ink ejection electrodes 2 are provided.
4 are arranged in parallel by the number of dots for one line corresponding to the desired resolution, and ink is supplied between the ink discharge electrodes 24 from an ink tank (not explicitly shown in the figure). A flat counter electrode 2 is disposed at a position, for example, 1 mm away from the tip of the ink discharge electrode 24 in the longitudinal direction, and a recording medium is placed on the counter electrode 2. A pulse power supply 9 for discharging ink and a bias power supply 8 for assisting ink discharge are connected to each ink discharge electrode 24. Each pulse power supply 9
Are individually transmitted from a drive circuit (not explicitly shown in the figure), whereby ink droplets are ejected independently from each ink ejection electrode 24 in accordance with print data. A bias voltage of, for example, about 1.5 to 2.0 kV is applied to all the ink discharge electrodes 24, and when ink is to be discharged, a pulse voltage of, for example, about 300 to 500 V is applied to the corresponding ink discharge electrodes 24. Are superimposed. Here, it is an advantage of this method that the amount of ejected ink can be controlled by changing the width of the pulse voltage, and the area of the recording dots formed on the recording medium can be controlled.

[0004]

By the way, in FIG. 11, each ink discharge electrode 24 discharges ink individually according to a print pattern. For example, paying attention to the third ink ejection electrode 24 from the left depending on the print pattern, if the voltages applied to the ink ejection electrodes 24 adjacent on both sides are different, for example, the second ink ejection electrode from the left whereas the pulse voltage V _p to the bias voltage V _b to 24 is superimposed, the fourth ink ejection electrode 24 from the left there is a case where only the bias voltage V _b is applied. In this case, the potential distribution at the tip of the third ink ejection electrode 24 from the left becomes asymmetric due to the electric mutual interference (crosstalk) between the ink ejection electrodes, and is distorted. As a result, when the ink is ejected from the tip of the third ink ejection electrode 24 from the left, the ink is not ejected straight, and stable ink ejection cannot be obtained. Therefore, there is a problem that a good printed image cannot be obtained. As an invention for solving such a problem, WO97 / 27057 has a configuration in which an ink discharge portion having a structure in which an ink discharge point is sandwiched between a pair of electrodes from both sides is laminated to suppress electrical mutual interference. Are known. However, an organic material having a relative dielectric constant of about 3 to 4 is used for a member serving as a discharge point in this configuration. Even when such a material is used in the above-described configuration, the electric mutual interference between the adjacent ejection portions remains, and the landing position deviation amount on the recording medium due to the electric mutual interference is calculated by a two-dimensional electric field calculation. Is estimated as shown in FIG. Here, when the relative permittivity of the ejection member is about 3, the gap between the tip of the ejection point and the counter electrode is 1 mm.
In the case of (2), the landing position shift amount is about 60 μm, and there is a problem that the effect of suppressing the electric mutual interference is hardly obtained.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problem, and suppresses electric mutual interference between electrodes in a multi-head in which a plurality of ink discharge electrodes are arranged, thereby achieving stable ink discharge. An object of the present invention is to realize and provide good color image printing.

[0006]

In order to achieve the above-mentioned object, the present invention employs the following configuration. An insulating substrate, a discharge unit disposed on the substrate via an auxiliary unit, a discharge electrode disposed to sandwich the discharge unit, the discharge electrode for discharging ink from the discharge unit, and a covering unit including the discharge electrode. The configuration is provided with.

According to the present invention, distortion of the potential distribution due to electrical mutual interference can be suppressed regardless of how the voltage is applied in any print pattern between adjacent ink discharge cells. Further, the ink is always ejected in the correct direction from the tip of the ejection member in the ink ejection cell, the displacement of the landing position on the recording medium can be reduced, and stable ink ejection characteristics can be obtained for a long period of time. Alternatively, an apparatus using the head can be realized.

Further, the discharge section is configured to be grounded via a switch.

According to the present invention, there is provided an ink jet recording apparatus capable of preventing the generation of an unnecessary electric field due to the trapped charges by periodically discharging the charges trapped at the interface between the ejection member and the auxiliary member. it can.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described with reference to the drawings.

FIG. 3 shows the configuration of a printer using the ink jet recording head 1 according to the present invention. The ink 6 is sucked from the ink tank 12 by a supply pump 13a and supplied to the recording head 1 through an ink circulation path 14a. Here, the ink 6 is supplied to the ink introduction path 15 between the ink circulation path 14a and the recording head 1.
, And flows through the flow path of the recording head 1 from the top to the bottom in the drawing. In the inkjet recording head 1, a plurality of ink ejection cells 3 are arranged in parallel in the main scanning direction of printing. A pulse power supply 9 and a common bias power supply 8 are individually connected to each ink ejection cell 3. Further, a control signal from a drive circuit 10 is connected to the pulse power supply 9, and the control signal is transmitted to each pulse power supply 9 independently according to print data sent from a personal computer or the like. Thus, application of a voltage to the ink discharge cells 3 is controlled. From the ink discharge cell 3 to which the voltage is applied from the pulse power supply 9, charged colorant particles dispersed in the ink 6 by an electric field near the tip of the ink discharge cell 3 (not explicitly shown in the drawing) ) Are aggregated, and the aggregated colorant particles are discharged toward the grounded counter electrode 2. As a result, dots are formed on the recording medium 5 on the counter electrode 2 by aggregates of colorant particles, and printing is performed. The ink 6 flowing through the flow path in the recording head 1 is sucked by the pump 13b for collection, and
The ink is returned to the ink tank 12 through 4b and used again for printing.

FIG. 1 is a top view showing the basic structure of the ink jet recording head 1 according to the first embodiment.
As shown in FIG. 1, the ink jet recording head 1 has a configuration in which ink discharge cells 3 are arranged in parallel at intervals of, for example, 250 μm. The ink discharge cell 3 includes a discharge member 32 and discharge electrodes 31 arranged on both sides of the discharge member 32 so as to sandwich the discharge member 32 therebetween. FIG. 2 is a perspective view of one ink discharge cell 3 in the ink jet recording head 1 according to the first embodiment. The ink jet recording head 1 has a structure in which the ink discharge cells 3 shown in FIG. 2 are arranged in parallel in the main scanning direction of printing. Discharge electrode 31 and discharge member 32
Is a metal formed on one insulating substrate 22 by a method such as vacuum evaporation or electroless plating. However,
The discharge member 32 is connected to the insulating substrate 2 via the auxiliary member 19.
2 and is in a state of being electrically insulated from the surroundings (floating state). The auxiliary member 19
For example, polyimide or the like is used. On the other hand, the ejection electrode 31 is coated with the covering member 4, and the covering member 4 has a structure including the ejection electrode 31. An ink flow path is formed between the ejection member 32 and the ejection electrode 31, and the ink 6 is always sucked up from the supply side by a capillary phenomenon, and the tip of the ejection member 32 is wet. The tip of the ejection member 32 projects from the ink surface by, for example, about 50 to 100 μm. The space between the discharge electrodes 31 of the adjacent ink discharge cells 3 is covered with the covering member 4 so that the ink 6 does not penetrate into the gap between the adjacent discharge electrodes 31. Discharge electrode 31
Since the intensity of the electric field at the end of the discharge electrode 31 is substantially the same as that of the end of the discharge member 32, when the ink 6 is filled around the discharge electrode 31, the ink 6 flows from the end of the discharge electrode 31. It will be ejected. Therefore, the adjacent discharge electrode 3
Unnecessary ejection is prevented by closing the space with the covering member 4. Further, as shown in FIG. 1, the counter electrode 2 is disposed at a position about 1 mm away from the tip of the discharge member 32 along the longitudinal direction of the discharge member 32, and the recording medium 5 placed thereon is disposed. Printing is performed on the top. The discharge electrodes 31 in the plurality of ink discharge cells 3 are connected to a common bias power supply 8 for assisting ink discharge and a pulse power supply 9 used for discharging ink. When printing is performed in the present invention, a printing signal is given from the drive circuit 10 to the pulse voltage source 9 connected to the ejection electrode 31 corresponding to the position of the dot to be printed in one line. As a result, the ink in which the colorant particles charged independently and simultaneously from the discharge member 32 sandwiched between the discharge electrodes 31 connected to all the pulse voltage sources 9 to which the print signal is applied is aggregated. 6 is ejected, and printing is performed. At this time, in the related art, the member for ejecting ink itself is an electrode. Regarding the electrode for ink ejection, the electrode to which the print signal is applied to the connected pulse voltage source 9 and the electrode to which no pulse signal is applied are connected. When they are adjacent to each other, the voltage applied between the adjacent ink discharging electrodes is different, so that electrical mutual interference (crosstalk) occurs between the ink discharging electrodes.

A feature of the present invention is that in the ink discharge cell 3 comprising the discharge electrode 31 and the discharge member 32 surrounded by the discharge electrode 31, the discharge member 32 is electrically insulated from the surroundings (in a floating state). The use of conductors. Note that the conductor in the floating state may be coated with a thin film of an insulating material such as polyimide to prevent the charged colorant particles in the ink 6 from adhering to the surface of the ejection member. Specifically, the ink discharge cells 3 having the above-described configuration can maintain the symmetry of the potential distribution at the tip of the discharge member 32 even when the voltage applied between adjacent ink discharge cells is different. it can. As a result, it is possible to suppress the deviation of the direction of the electric field at the tip portion of the discharge member 32 due to the distortion of the potential distribution, that is, the deviation of the ink discharge direction. This mechanism will be described in detail below.
FIG. 4 shows the result of two-dimensionally calculating the potential distribution between the ink discharge cell 3 and the counter electrode 2 as an equipotential line. The interval between the equipotential lines is 56V. In the figure, the horizontal direction on the paper is defined as the y-axis direction, and the vertical direction is defined as the x-axis direction. The calculation conditions in FIG. 4 are as follows. In FIG. 4, the voltages applied to the ejection electrodes 31 of the ink ejection cells 3 are respectively the ejection electrodes 31a, 31b, and 31e.
2.5 kV (only bias voltage), the ejection electrodes 31 c,
2.8 kV (pulse voltage 300 for bias voltage)
V superimposed). A grounded (0 V) flat counter electrode was placed at a position 1 mm away from the tip of the discharge member 32. The interval between adjacent ink ejection cells 3 is 250 μm. The width of the ejection electrodes 31a to 31e is 20 μm. The width of each of the ejection members 32a to 32b is 50 μm, the tip has a sharp angle of 60 °, and the tip has a radius of curvature of 10 μm. The width of the ink flow path between each discharge electrode and the discharge member is 20 μm. The relative permittivity of the covering member covering each discharge electrode is 3.4, and the relative permittivity of the ink is 2.6. Focusing on the ink ejection cell having the ejection member 32d in FIG. 4, a voltage of 2.8 kV is applied to the ink ejection cell having the ejection member 32c, whereas the ink ejection cell having the ejection member 32e is applied to the ink ejection cell having the ejection member 32c. Since a voltage of 2.5 kV is applied, the potential distribution around the ejection member 32d is asymmetric on the left and right (the same applies to the ejection member 32c). However, looking only at the potential distribution near the ejection member 32d, it can be seen that the shape of the equipotential lines is substantially symmetrical with respect to the central axis of the ejection member 32d.

The ejection member 32d is shown in FIG.
In consideration of the model as shown in (a), the landing position deviation amount of the ink droplet at the counter electrode was calculated. In FIG. 5A, when there is no electrical mutual interference, the ink droplet is ejected straight from the tip of the ejection member 32 toward the counter electrode 2 as an aggregate of colorant particles. However, the presence of electrical mutual interference is caused by the discharge member 32 as shown in the figure.
The direction of the electric field at the tip of the device is inclined by the influence of mutual interference.
The ink droplets can be ejected when the electrostatic repulsion between the electric field and the aggregate of the charged colorant particles at the tip of the ejection member 32 overcomes the surface tension of the ink 6. Here, the surface of the ink breaks from the point where the electric field is strongest at the tip of the ejection member 32, and the ink droplet is ejected. The ejection direction is ejected in a straight line with the direction of the electric field on the tip surface of the ejection member 32. Therefore, assuming that the inclination angle of the electric field vector from the ideal discharge direction is θ, the deviation amount δ from the ideal landing position on the counter electrode located at a distance D _gap from the tip of the discharge member 32 is It is given as follows.

Δ = D _gap × tanθ (1) The distance D between the tip of the discharge member 32 and the counter electrode 2 calculated by the equation (1) under the voltage application condition in the calculation of FIG.
The relationship between the _gap and the landing position deviation amount δ is as shown in the graph of FIG. The calculation in FIG. 4 is based on D _gap = 1 (mm), the discharge member 32 is a conductor, and the pulse voltage applied to the discharge electrode 31 is V _p = 300 (V).
From the graph of (b), the landing position deviation amount δ is approximately 20 μm.
It is estimated. By the way, the potential distribution in FIG. 4 is calculated in two dimensions, and it is implicitly assumed that the discharge electrode 31 and the discharge member 32 have an infinite thickness in a direction perpendicular to the paper surface. Included in the house. Since the potential distribution between the infinite conductors is proportional to the natural logarithm of the distance D between the conductors, the potential of each conductor is determined under long-range interaction. On the other hand, the actual discharge electrode 31 and the discharge member 32 have a finite thickness. The potential distribution in such a case is not the natural logarithm of the distance D between the conductors, but the distance D.
Alternatively, since it is inversely proportional to the square of the distance D, it is considered that the potential distribution is actually determined under an interaction of a shorter distance than in the two-dimensional case.

That is, in the two-dimensional electric field calculation, the calculation is performed under the condition of the strongest electric mutual interference, and the actual electric mutual interference is weaker than in the case of the two-dimensional calculation. Therefore, it is estimated that the displacement δ of the landing in actual printing is 20 μm or less. For example, in the case of printing at 600 dpi, the dot interval is approximately 42 μm, but the landing position deviation of 20 μm or less on the printed image is a level that does not cause any practical problem. Further, as is clear from the graph of FIG. 5B, by shortening the distance D _gap between the tip of the ejection member 32 and the opposing electrode, it is possible to further reduce the amount of landing position deviation.

As described above, according to the present embodiment, the electric mutual interference between the adjacent ink discharge cells is suppressed, and the electric field distribution at the tip of the discharge member from which ink is discharged is not distorted. As a result, it is possible to suppress the displacement of the landing positions of the dots formed on the recording medium on the counter electrode.

Next, a second embodiment of the present invention will be described. FIG. 6A is a diagram showing a basic structure of a recording head for an ink jet recording apparatus according to the second embodiment. In the inkjet recording head 1, a plurality of ink ejection cells 3 are arranged in parallel by the number of dots for one line corresponding to a desired resolution. One ink ejection cell 3 includes an ejection member 32 and an ejection electrode 31 arranged so as to surround the ejection member 32. The gap between the ejection member 32 and the ejection electrode 31 is an ink flow path, and the ink 6 supplied from the ink tank 12 (not shown in the figure) is filled up to the tip of the ejection member 32 by a capillary phenomenon. ing. The tip of the ink discharge cell 3 projects, for example, 100 μm from the end face of the substrate. A plate-shaped counter electrode 2 is disposed at a position, for example, 1 mm away from the tip of the ink discharge cell 3 in the longitudinal direction, and a recording medium 5 is placed on the counter electrode 2. A pulse power supply 9 for discharging ink and a bias power supply 8 for assisting ink discharge are connected to the discharge electrodes 31 in each ink discharge cell 3. A control signal is individually sent from the drive circuit 10 to each pulse power supply 9, so that the charged colorant aggregated by the electric field around the discharge member 32 independently of each discharge member 32 according to print data. A collection of particles is ejected as ink droplets. In this embodiment, the ejection member 32 in the ink ejection cell 3 is a conductor, and the ejection member 32 is grounded (0 V) via the switching element 20a.
During the printing operation, that is, while the ink is ejected, the switching element 20a is in the open state.
2 is in a state of being electrically isolated (floated) from the surroundings. As shown in FIG. 6B, the cross-sectional structure of the discharge member 32 is formed on the insulating substrate 22 via the auxiliary member 19, and is formed at the interface between the discharge member 32 and the auxiliary member 19. There are a number of defects that serve as trap sites for electric charges due to mismatching. When a voltage is continuously induced in the discharge member 32 in a floating state, electric charges are still trapped in defects at these interfaces. Since the charges trapped at such an interface are non-uniformly distributed, a non-uniform electric field is generated from the trapped charges, so that the electric field near the ejection member 32 is disturbed. Ink ejection may become unstable. Therefore, for example, during a printing pause period from the end of the printing operation of one page to the start of the printing operation of the next one page, the voltage applied to the discharge electrode 31 is turned off, and the switching element 20a is short-circuited. By doing so, the charges trapped at the interface can be discharged. Therefore, according to the present embodiment, it is possible to discharge the charges trapped at the interface between the ejection member 32 and the auxiliary member 19, and it is possible to prevent the generation of a non-uniform electric field due to the charges trapped at the interface. As a result, stable ink ejection characteristics can be obtained.

Next, a third embodiment of the present invention will be described. In the graph of FIG. 5B, the difference between the landing position deviation amount δ when the dielectric material is used instead of the conductor that is floated as the material of the ejection member 32 and the distance D _gap between the tip of the ejection member 32 and the counter electrode 2 is shown. The relationship is also shown. FIG.
In (b), the displacement of the landing position is larger in the case of the relative dielectric constant of 7.5 than in the case of the relative dielectric constant of 3.4 with respect to the distance D _gap between the tip of the discharge member 32 and the counter electrode 2. It can be seen that δ is small. This is because, as the relative dielectric constant of the ejection particulate material 32 increases, the relationship between the landing position deviation amount δ and the distance D _gap between the tip of the ejection member 32 and the counter electrode 2 approaches the floated conductor. Is shown. FIG. 7 (a) and
(b) shows the ink discharge cell 3 and the counter electrode 2 when the relative permittivity of the discharge member 32 is 100 and 3000, respectively.
It is a result of calculating the potential distribution between. The calculation condition is
This is the same as the case of FIG. 4 except for the relative permittivity of the ejection member 32. Comparing FIGS. 7A and 7B focusing on the vicinity of the ejection member 32d, it can be seen that the potential distribution is almost the same in both cases. Therefore, in the case where the distance D _gap = 1 (mm) between the tip of the ejection member 32 and the counter electrode 2,
FIG. 8 is a plot of the relationship between the relative dielectric constant of the ejection member 32 and the landing position deviation amount δ. FIG. 8 shows that when the relative dielectric constant is 100 or more, the landing position deviation amount δ is constant at about 35 μm. This value is shown in FIG.
As can be seen from the figure, the landing position shift amount is almost the same as the case where the conductor floated on the ejection member 32 is used (the case where the relative dielectric constant is infinite), and is negligible in practical use. By the way, depending on the voltage applied to the ejection electrode 31, the shape of the ejection electrode 31, the ejection member 32, the arrangement pitch of the ink ejection cells 3, etc., the relative permittivity and the landing position deviation amount of the ejection member 32 in FIG. The curve indicating the relationship with δ changes, but qualitatively approaches the landing position shift amount in the case of a floating conductor as the relative dielectric constant of the discharge member 32 increases. This means that the ejection member 32 in FIG.
In the case where a dielectric having a relative permittivity that provides a potential distribution similar to the potential distribution around the ejection member in the case of a conductor is used instead of the conductor as the material of the ink, the adjacent ink ejection is performed as in the first embodiment. This shows that the displacement of the landing due to the electric mutual interference between the cells 3 can be suppressed. Therefore, in the present embodiment, the ejection member 32 in the ink ejection cell 3 is made of a dielectric material having a relative permittivity that provides a potential distribution similar to the potential distribution around the ejection member in the case of a conductor. Since the member 32 is no longer a conductor, no induced charge is generated on the surface of the ejection member 32 due to electrostatic induction by the ejection electrode 31. as a result,
Since charges are not trapped by defects at the interface with the auxiliary member 19, it is possible to continue to discharge ink stably even when printing is performed continuously without discharging the charges.

Next, a fourth embodiment of the present invention will be described. FIG. 9A is a diagram showing a basic structure of a recording head for an inkjet recording apparatus according to the fourth embodiment. In the ink jet recording head 1, a plurality of ink ejection cells 3 on one substrate correspond to a desired resolution.
The number of dots for the line is arranged in parallel. One ink discharge cell 3 includes a discharge member 32 and discharge electrodes 31 arranged so as to sandwich the discharge member 32. The gap between the ejection member 32 and the ejection electrode 31 is an ink flow path, and the ink 6 supplied from the ink tank 12 (not shown in the figure) is filled up to the tip of the ejection member 32 by capillary action. ing. Ink ejection cell 3
Is projected, for example, by 100 μm from the end face of the substrate. A plate-shaped counter electrode 2 is disposed at a position, for example, 1 mm away from the tip of the ink discharge cell 3 in the longitudinal direction, and a recording medium 5 is placed on the counter electrode 2.
A pulse power supply 9 for discharging ink and a bias power supply 8 for assisting ink discharge are connected to the discharge electrodes 31 in each ink discharge cell 3. Control signals are individually sent from the drive circuit 10 to each of the pulse power sources 9 so that the charged colorant particles aggregated by the electric field around the ejection member independently of each of the ejection electrodes 31 according to the print data. Are ejected as ink droplets. In this embodiment, the ejection member 32 in the ink ejection cell 3 is a dielectric having a relative dielectric constant of 100 or more, and the ejection member 32 is connected to the AC power supply 23 via the switching element 20b. During the printing operation, that is, while the ink is being ejected, the switching element 20b is in the open state, so that the ejection member 32 is in a state of being electrically insulated (float) from the surroundings. As shown in FIG. 9B, the sectional structure of the discharge member 32 is such that the thin film electrodes 21 a and
1b, but in the case of a high dielectric constant material, the polarization state does not return to the initial state due to the hysteresis characteristic when an electric field is applied from the outside, and remanent polarization occurs. I will. In order to prevent the ink ejection from becoming unstable due to an unnecessary electric field due to such remanent polarization,
In this embodiment, for example, the switching element 20b is short-circuited during the line printing operation, and the AC power supply 23 is applied between the thin film electrodes 21a and 21b sandwiching the ejection member 32. At this time, the waveform of the AC power supply 23 has a waveform whose amplitude attenuates with time as shown in FIG. By applying a voltage having such a waveform to the ejection member 32, the residual polarization can be returned to the initial state. Therefore, according to the present embodiment, it is possible to periodically initialize the remanent polarization generated in the discharge member 32 when a high dielectric constant material having a relative dielectric constant of 100 or more is used for the discharge member 32, and the discharge member 32 is stable for a long period of time. Ink discharge can be maintained.

[0021]

As described above, according to the present invention,
Suppresses electric mutual interference between adjacent ink ejection cells,
An ink jet recording head and an apparatus using the same, which do not distort the electric field distribution at the tip of the ejection member from which ink is ejected and can suppress the displacement of the landing position of dots formed on the recording medium on the counter electrode. Can be provided.

Further, it is possible to discharge an electric charge trapped at the interface between the discharge member and the auxiliary member, to prevent generation of an unnecessary electric field, and to provide an ink jet recording apparatus capable of obtaining stable ink discharge characteristics. Can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing a basic structure of an ink jet recording head according to a first embodiment of the present invention.

FIG. 2 is a perspective view showing an ink ejection cell in the ink jet recording head according to the first embodiment of the present invention.

FIG. 3 is a diagram showing an apparatus configuration using an ink jet recording head according to the present invention.

FIG. 4 is a diagram showing a calculation result of a two-dimensional potential distribution between an inkjet recording head and a counter electrode according to the first embodiment of the present invention, expressed by equipotential lines.

5A and 5B are a calculation model of a landing position shift amount due to crosstalk according to the first embodiment of the present invention (a) and a relationship between the landing position shift amount and a distance between a tip end of a discharge member and a counter electrode (b).
FIG.

FIG. 6 is a diagram showing a basic structure (a) and a sectional structure (b) of an ink jet recording head according to a second embodiment of the present invention.

FIG. 7 is a diagram showing a calculation result of a two-dimensional potential distribution between an inkjet recording head and a counter electrode according to a third embodiment of the present invention, represented by equipotential lines.

FIG. 8 is a view showing the relationship between the relative dielectric constant of an ejection member and the amount of landing position deviation according to a third embodiment of the present invention.

FIG. 9 is a diagram showing a basic structure (a) and a sectional structure (b) of an ink jet recording head according to a fourth embodiment of the present invention.

FIG. 10 is a diagram showing a waveform of a voltage applied to a thin-film electrode according to a fourth embodiment of the present invention.

FIG. 11 is a diagram showing a basic structure of an ink jet recording head according to a conventional technique.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Ink jet recording head, 2 ... Counter electrode, 3 ... Ink ejection cell, 4 ... Coating member, 5 ... Recording medium, 6 ... Ink, 8 ... Bias power supply, 9 ... Pulse power supply, 10 ... Drive circuit, 12 ... Ink tank , 13a, 13b ... pump, 1
4a, 14b: ink circulation path, 15: ink introduction path, 1
9: auxiliary member, 20a, 20b: switching element, 2
1a, 21b: thin-film electrode, 22: insulating substrate, 23: AC power supply, 24: ink discharge electrode, 31: discharge electrode,
32 ... Discharge member.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Atsushi Onose 7-1-1, Omikacho, Hitachi City, Ibaraki Prefecture Inside the Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor Seiji Yonekura 7-1 Omikacho, Hitachi City, Ibaraki Prefecture No. 1 F-term in Hitachi, Ltd. Hitachi Research Laboratory (reference) 2C057 AF30 AF71 AG16 AG32 AG37 AH07 AM04 AM16 AM40 AP14 AP54 AP55 AR20 BD07

Claims (7)

[Claims] An insulating substrate; a discharge unit disposed on the insulating substrate via an auxiliary unit; and a discharge electrode disposed between the discharge unit and discharging ink from the discharge unit. An ink jet recording head having a coating portion including the ejection electrode. 2. The ink jet recording head according to claim 1, wherein said discharge section is electrically insulated from surroundings. 3. The ink jet recording head according to claim 1, wherein said discharge section is made of a dielectric material. 4. An insulating substrate, a discharge unit disposed on the insulating substrate via an auxiliary unit, and a discharge electrode disposed to sandwich the discharge unit and discharging ink from the discharge unit. An ink-jet recording comprising: a covering portion including the ejection electrode; a counter electrode disposed to face the ejection portion; a first power supply for applying a voltage to the ejection electrode; and a second power supply. apparatus. 5. The ink jet recording apparatus according to claim 4, wherein said ejection section is a dielectric. 6. An ink jet recording apparatus according to claim 4, wherein said discharge section is grounded via a switch. 7. An ink jet recording apparatus according to claim 4, wherein said discharge section is connected to an AC power supply via a switch.