JP2001150683A - Electrostatic ink-jet recording device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent pigment adhesion and plating in an ink channel or an ink ejection opening of an electrostatic ink-jet recording device. SOLUTION: An electrostatic ink-jet recording device comprising a plurality of recording electrodes 1 formed on an electrode substrate 2 having the insulation property, disposed parallel with each other, notch parts 8 formed between the recording electrodes 1 for allowing passage of an ink, an upper head block 4 and a lower head block 5 for providing an ink ejection opening and an ink channel 7, disposed so as to interpose the recording electrodes 1 therebetween, with the tip end of the recording electrodes 1 projected, and a counter electrode disposed facing the recording electrodes 1, wherein a pigment in an ink is ejected an jumped by an electrostatic force for printing on a recording medium, is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic ink jet recording apparatus, and more particularly to an electrostatic ink jet recording apparatus capable of obtaining a stable print density.

[0002]

2. Description of the Related Art Ink jet technology is widely used in office automation and personal information recording devices such as copiers, facsimile machines, printers, word processors, etc., as a technology enabling low cost, high image quality and high speed printing.

[0003] Ink jets use a heating resistor such as an electrothermal conversion element as an energy generating means for flying a color material, use a piezo element such as an electromechanical conversion element, and further use an ink jet. There is an electrostatic type that uses electric energy as it is.

[0004] Among them, in the electrostatic ink jet, the production of the recording head is simpler than other methods, and the area gradation recording can be performed by controlling the electric signal applied to the recording electrode. . Further, the amount of current consumed at the time of recording is extremely small, and it can be said that this is a recording technology that is useful in the future as an energy-saving device. Furthermore, by using an oil-based pigment ink, printing with excellent water resistance can be performed, and the utility value is particularly high for office automation applications.

Here, the electrostatic type ink jet recording apparatus will be briefly described.

FIG. 6 is a perspective view showing a conventional electrostatic ink jet recording apparatus.

As shown in FIG. 1, an electrostatic ink jet recording apparatus includes a plurality of recording electrodes 1 formed on an electrode substrate 2.
And an upper head block 4 arranged so as to sandwich the recording electrode 1 to form an ink ejection port 3 from which the tip of the recording electrode 1 projects.

When a recording voltage of several kV is applied between a recording electrode 1 filled with ink and a counter electrode holding a recording medium, as reported in Japanese Patent Application Laid-Open No. 56-4467, When the recording voltage exceeds a certain threshold value, the electrostatic force acting on the ink overcomes the surface tension of the ink, and the ink droplet is ejected from the recording electrode 1 and flies to the counter electrode.

Regarding the structure of the head based on this principle,
For example, U.S. Pat.
No. -4467.

In the configuration of this example, a nozzle hole is not necessarily required for each recording electrode, and the ink ejection port can be formed in a so-called slit type common to a plurality of recording electrodes.

A feature of such a configuration is that clogging due to drying of ink is reduced because there is no need to provide a nozzle. Therefore, not only a so-called serial type head having a few hundred recording electrodes and scanning in the width direction of the recording medium, but also a so-called line type head having recording electrodes for the width of the recording medium is very useful. It is an effective technology.

In this electrostatic ink jet recording apparatus, when a plurality of recording electrodes are provided, it is necessary to prevent charge leakage due to forming a closed loop with adjacent electrodes in order to operate each recording electrode independently of each other. is there. For this purpose, an oily solvent having high electric resistance is usually used as a solvent for the ink. For example, in the example disclosed in JP-A-58-215353, the specific resistance is about 10 ⁸ Ωcm, the surface tension is 18 dyne / cm, the viscosity is 2 to 30 cP, and the specific gravity is 1.0.
g / cm ³ of oil-based ink is used. Oil-based pigments and oil-based dyes can be used as the coloring material, but mainly oil-based pigments are used because of their variety.

However, in an electrostatic ink jet recording apparatus using a pigment and an oily solvent, there is a problem that a certain proportion of the solvent is ejected together with the pigment in the ejection of ink, so that the print density does not increase. This was because the ratio between the pigment and the magnitude of the electrostatic force applied to the solvent was poor.

On the other hand, as disclosed in JP-A-8-295023 and JP-A-9-193389, the ratio of the force applied to the pigment and the solvent is controlled so that only the pigment is ejected from the ink. As a result, attempts have been made to solve these problems. In these documents,
Although the principle of the ejection is not always clearly explained, the above-mentioned problem is solved because only the pigment dispersed in the solvent is applied with electrostatic force to fly the pigment only, so that the carrier liquid is not contained in the ejected ink, and the above-mentioned problem is solved. Is done.

In order to move the pigment and the solvent independently as described above, the pigment must be dispersed without being dissolved in the solvent. This is because if the pigment is dissolved, it becomes impossible to distinguish between the pigment and the solvent, and it is not possible to selectively discharge only the pigment.

According to JP-A-8-295023,
In fact, by applying a voltage of the same polarity as the charged polarity of the pigment to the recording electrode, only the pigment migrates and aggregates at the tip of the recording electrode by electrostatic repulsion, and an ink droplet containing a large amount of pigment is ejected. ing.

[0017]

However, according to such a technique, although the printing density is increased by the aggregation of the pigment, the pigment is deposited on the electrode or the electrode substrate by the aggregation at an unnecessary timing or the aggregation at an unnecessary place. There has been a problem that the ink is fixed or the recording electrode or the electrode substrate is plated with a pigment, thereby causing an undesirable obstacle in the ink flow path.

It is known that such an obstacle caused by the fixation or plating of the pigment disturbs the flow of the ink in the ink flow path and hinders stable ink ejection. According to experiments by the inventors, in the case of a head using a slit-type ink ejection port common to all or a large number of recording electrodes, slight turbulence of ink flow causes variation of ink droplets and non-ejection of ink. It is known to be the cause.

Furthermore, in addition to the cause of aggregation, there is also a problem that the pigment sediments due to the use of the dispersed pigment and is fixed on the recording electrode or the electrode substrate on which the recording electrode is formed, and cannot be removed in due course. is there. Generally, maintenance processing is not performed in the ink flow path, so that even if the pigment is simply fixed, it cannot be easily removed once it has occurred. This also shortens the life of the printing apparatus.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an electrostatic ink jet recording apparatus capable of preventing pigment from sticking or plating in an ink flow path or an ink discharge port.

[0021]

To solve this problem, an electrostatic ink jet recording apparatus according to the present invention comprises a plurality of recording electrodes formed on an insulating electrode substrate and arranged in parallel with each other. A first head block and a second cutout formed between the recording electrodes and through which the ink passes, and an ink ejection port and an ink flow path which are arranged so as to sandwich the recording electrode and protrude from the tip of the recording electrode. And a counter electrode disposed opposite to the recording electrode, and prints on a recording medium by discharging and flying the pigment in the ink by electrostatic force.

With this arrangement, the pigment passes through the gap between the recording electrodes and does not adhere to the electrode substrate due to the cut portion, so that it is possible to prevent the pigment from sticking or plating in the ink flow path or the ink discharge port.

[0023]

DETAILED DESCRIPTION OF THE INVENTION According to the first aspect of the present invention, there are provided a plurality of recording electrodes formed on an insulating electrode substrate and arranged in parallel with each other, and formed between the recording electrodes. A first head block and a second head block, which are formed so as to sandwich the recording electrode, form an ink discharge port and an ink flow path which are disposed so as to sandwich the recording electrode, and which have a protruding tip of the recording electrode; An electrostatic ink jet recording apparatus that has a counter electrode arranged in a position and discharges and flies the pigment in the ink by electrostatic force to print on the recording medium, and the cutout allows the pigment to pass between the recording electrodes. Therefore, the pigment does not adhere to the electrode substrate, so that it has an effect that it is possible to prevent fixation and plating of the pigment in the ink flow path or the ink discharge port.

According to a second aspect of the present invention, in the first aspect of the present invention, a stirring electrode for stirring the ink flowing through the ink flow path with an electric force is provided in the ink flow path. This is an electrostatic ink jet recording apparatus, which has an effect that it is possible to more effectively prevent the fixation and deposition of the pigment in the recording electrode and the ink flow path.

According to a third aspect of the present invention, in the first or second aspect, the ink from the ink tank is circulated by an ink passage of the first head block and a second head block. This is an electrostatic ink jet recording apparatus in which an ink circulation system that returns to an ink tank through an ink flow path is configured. In the entire system from the ink tank to the head block, the flow of ink is obtained. It has the effect of making it possible to prevent sticking and deposition of pigments.

According to a fourth aspect of the present invention, there is provided an electrostatic ink jet recording apparatus according to the first, second or third aspect, wherein a tip of the recording electrode is supported by an electrode substrate. This has the effect that it is possible to prevent the electrode from bending and causing displacement.

According to a fifth aspect of the present invention, in the invention according to any one of the first to fourth aspects, the flow velocity of the ink is slow at the leading end of the recording electrode and is high at the ink flow path. This is an electrostatic ink jet recording device that is set so that a stable meniscus with good ink ejection characteristics and printing characteristics is formed, and the fixation and plating of the pigment near the recording electrode are reduced. Have.

According to a sixth aspect of the present invention, in accordance with the fifth aspect of the present invention, there is provided an electrostatic ink-jet apparatus in which the flow path on the leading end side of the recording electrode in the first head block is narrowed. The recording device has a function of forming a stable meniscus having good ink ejection characteristics and printing characteristics, and reducing fixation and plating of pigments near recording electrodes.

According to a seventh aspect of the present invention, in the invention according to any one of the first to sixth aspects, the ink flow path extends in a direction orthogonal to the recording electrode and extends from the recording electrode. This is an electrostatic ink jet recording apparatus provided with an aggregation electrode to which a high potential is applied, and has an effect that it is possible to increase the aggregation rate of a pigment to increase the print density.

According to an eighth aspect of the present invention, in the invention according to the seventh aspect, the distance from the ink discharge port to the portion where the depth of the ink flow path becomes deep is a, and the distance between the ink discharge port and the aggregation electrode is The distance between the ink ejection port and the opposite end is b,
When the distance from the ink ejection port to the end of the cut portion opposite to the ink ejection port is c, the electrostatic ink jet recording apparatus is set so as to satisfy the relationship of a ≦ c ≦ b. This has the effect of making it possible to prevent pigment sticking and plating more effectively while increasing the rate.

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. In these drawings, the same members are denoted by the same reference numerals, and duplicate description is omitted.

FIG. 1 is an exploded perspective view showing a main part of an electrostatic ink jet recording apparatus according to an embodiment of the present invention, FIG. 2 is a sectional view of the electrostatic ink jet recording apparatus of FIG. 1, and FIG. FIG. 4 is an exploded perspective view showing a main part of an electrostatic ink jet recording apparatus according to another embodiment, FIG. 4 is a sectional view of the electrostatic ink jet recording apparatus of FIG. 3, and FIG. FIG. 3 is a cross-sectional view illustrating a flow of ink in the recording apparatus.

As shown in FIGS. 1 and 2, the recording electrode 1
Are formed on a thin electrode substrate 2 having an insulating property such as a polyimide film, and are arranged in parallel with each other to be electrically independent. Preferably, the recording electrode 1 is provided with an insulating coating.

One end of the recording electrode 1 is electrically connected to a driver (not shown), and a recording signal is sent to the recording electrode 1 from the driver. An upper head block (first head block) 4 and a lower head block (second head block) 5 are arranged above and below the recording electrode 1 with the recording electrode 1 interposed therebetween. The blocks 4 and 5 form an ink discharge port 3 which is a slit-shaped opening. Note that the tip of the recording electrode 1 is attached so as to protrude from the ink ejection port 3.

As shown in FIG. 2, a counter electrode 10 is arranged at a position facing the recording electrode 1, and the ink discharged from the recording electrode 1 toward the counter electrode 10 is provided on the front surface of the counter electrode 10. The recording medium 11 to which is attached is set.

Here, the flow of ink in the electrostatic ink jet recording apparatus of the present embodiment will be described with reference to FIG.

The ink is filled from the ink tank 13 into a space sandwiched between the upper head block 4 and the lower head block 5 by a circulation device 14 such as a pump. An opening 6 is formed between the upper head block 4 and the lower head block 5.
An ink flow path 7 is formed which communicates with the ink flow path of the upper head block 4 from the ink tank 13 to the ink flow path 7 of the lower head block 5 through the opening 6. It is designed to flow in.

However, such an ink circulation mechanism and the ink flow path 7 of the lower head block 5 are not always necessary, and may be closed by the opening 6. In this case, the ink stays in the head blocks 4 and 5, but when an electric field is applied to the ink containing the charged pigment, convection called electric convection is generated. 4 causes the ink to flow to the lower head block 5.

In FIG. 5, a stirring electrode 12 is provided in the ink flow path of the upper head block 4. According to this, by giving a three-phase electric signal or the like, a convection of an arbitrary size can be generated in the ink by an electric force to stir the convection, so that the effect of preventing the adhesion of the pigment is further enhanced. Furthermore, if a pair of stirring electrodes are provided on the upper head block 4 and the lower head block 5 and an AC signal is applied to the stirring electrodes, the ink flows in the ink flow path 7 while vibrating. And the adhesion and deposition of the pigment in the ink flow path 7 can be prevented.

Further, as shown in FIG.
If a circulating device 14 such as a pump is provided between the head block 4 and the head blocks 4 and 5 so that the ink is forcibly circulated, the entire system from the ink tank 13 to the head blocks 4 and 5 has Fluidity is obtained, and sticking and deposition of the pigment throughout the system can be prevented.

Here, as shown in FIG. 1, slit-shaped cut portions 8 are formed between the recording electrodes 1 so that the ink can pass through.

The slit-shaped cut portion 8 between the recording electrodes 1 is processed by making a cut from the front end to the other end of the recording electrode 1 using, for example, a dicing saw. Therefore, in this case, the cut 8 has a shape that is open at the tip of the recording electrode 1. In addition,
The depth of the notch 8 is preferably long as long as each recording electrode 1 is not bent. The tip of the recording electrode 1 may be floating in the air, but it is desirable that the recording electrode 1 be supported by the electrode substrate 2 so that the recording electrode 1 does not bend and cause displacement.
The lower head block 5 and the electrode substrate 2 may be adhered to each other, but it is desirable not to adhere them from the viewpoint of ejection characteristics.

As shown in FIG. 3, the notch 9 between the recording electrodes 1 is TAB (Tape Automated).
After the recording electrode 1 is formed by using a bonding technique, the recording electrode 1 can be formed by partially removing the recording electrode 1 by performing wet etching from the back side of the substrate. When the notch 9 is formed by such a window processing, each recording electrode 1 is held in the electrode substrate 2 without floating, so that the recording electrode 1 does not bend. Note that the cut portion may be formed by directly performing a cut process, a window process, a hole process, or the like on the electrode substrate 2 using, for example, an excimer laser.

Here, the shape of the meniscus, which is a curved surface formed by the interface between ink and air at the tip of the recording electrode 1, is determined by the ink flow rate when circulating the ink. In order to form a meniscus shape having good printing characteristics, the ink flow rate near the meniscus must be relatively slow. Otherwise, the meniscus tends to swell and ink is erroneously ejected from the ink ejection port 3 all at once, or the individual recording electrodes 1 cannot eject ink independently.

For this reason, in order to prevent a pigment from sticking and plating and to form a meniscus having good printing characteristics, in the present embodiment, the ink flow rate near the tip of the recording electrode 1 is optimized to form the meniscus. It is designed to make

That is, the upper head block 4 is designed so that the ink flow speed is low only in the vicinity of the recording electrode 1 and the flow speed is high in other portions. Specifically, as shown in FIGS. 2 and 4, the processing is performed so that the flow path on the tip side of the recording electrode 1 in the upper head block 4 is narrowed. By processing in this manner, the conductance of the ink flow becomes worse near the ink discharge port 3, so that the ink flow rate in the ink flow path is such that the effect of preventing the fixation of the pigment and the plating can be sufficiently obtained. However, the ink flow velocity is relatively slow near the tip of the recording electrode 1 so that an appropriate meniscus can be formed.

When a circulation mechanism is provided to control the ink flow velocity in the vicinity of the ink discharge port 3, the circulation velocity is proportional to the thickness of the recording head 1 of the upper head block 4 on the tip side. I just need. That is, if the circulation speed is increased in order to increase the effect of preventing the fixation of the pigment, the thickness of the tip of the recording electrode 1 in the upper head block 4 is increased. Conversely, if the circulation speed can be reduced, the wall thickness is also reduced.

Further, as shown in FIGS. 2 and 4, an aggregation electrode 15 extending in a direction perpendicular to the recording electrode 1 is connected to the ink flow of the upper head block 4 in order to increase the aggregation rate of the pigment to increase the printing density. It can also be provided in the road.

By providing the aggregation electrode 15 and providing a signal having a higher potential than that of the recording electrode 1 as described above, the positively charged pigment has a higher aggregation rate near the recording electrode 1.
In this case, while there is a merit that the agglomeration ratio increases, the problem due to fixation and plating of the pigment increases,
By increasing the ink flow rate near the aggregation electrode 15, it is possible to prevent pigment fixation and plating while increasing the pigment aggregation rate.

To do so, the aggregated electrode 15 is arranged in a wide portion of the ink flow path, and the slit-shaped cut portions 8 and 9 between the recording electrodes 1 are processed so as to extend directly below the aggregated electrode 15. The length of the narrow portion of the ink flow path and the length of the cut portions 8 and 9 between the recording electrodes 1 are adjusted according to the type of ink and the aggregation rate. That is, in the case of using an ink having a small ink particle diameter and in which the fixation and plating of the pigment are relatively unlikely to occur, the horizontal length of the portion where the ink flow path is narrowed can be shortened. 15 can be arranged near the tip of the recording electrode 1,
The length of the cut portions 8 and 9 between the recording electrodes 1 can be designed to be short. Conversely, when using ink having a large ink particle diameter and easily causing sticking or plating of the pigment, the horizontal length of the portion where the ink flow path is narrowed is increased, and the aggregated electrode 15 is moved away from the tip of the recording electrode 1. It is necessary to arrange them apart from each other and to make the cuts 8 and 9 between the recording electrodes 1 long.

In particular, as shown in FIG.
A to the portion where the depth of the ink flow path becomes deeper,
When the distance from the ink ejection port 3 to the end of the aggregation electrode 15 opposite to the ink ejection port 3 is b, and the distance from the ink ejection port 3 to the end of the cutout 8 opposite to the ink ejection port 3 is c. By arranging these so as to satisfy the relationship of a ≦ c ≦ b, it is possible to more effectively prevent the fixation and plating of the pigment while increasing the aggregation rate of the pigment.

As described above, according to the present embodiment, the cut portions 8 and 9 through which ink passes are formed between the recording electrodes 1, so that the pigment passes between the recording electrodes 1. The ink does not adhere to the electrode substrate 2, and it is possible to prevent the pigment from sticking and plating in the ink flow path 7 and the ink discharge port 3.

[0053]

As described above, according to the present invention, the cut portion allows the pigment to pass between the recording electrodes and not adhere to the electrode substrate. An effective effect that plating can be prevented is obtained.

The provision of the stirring electrode has an advantageous effect that it is possible to more effectively prevent the fixation and deposition of the pigment in the recording electrode and the ink flow path.

If the ink circulation system is constituted, the flow of ink can be obtained in the entire system from the ink tank to the head block, so that it is possible to prevent the pigment from being fixed or deposited in the entire system. Is obtained.

If the leading end of the recording electrode is supported by the electrode substrate, an effective effect is obtained in that it is possible to prevent the recording electrode from bending and causing displacement.

If the ink flow rate is set to be slow at the tip of the recording electrode and fast at the ink flow path, a stable meniscus with good ink ejection characteristics and printing characteristics is formed, and the ink flow rate near the recording electrode is improved. An effective effect of reducing fixation and plating of the pigment is obtained.

If the processing is performed so that the flow path on the leading end side of the recording electrode in the first head block is narrowed, a stable meniscus having good ink ejection characteristics and printing characteristics is formed, and the pigment in the vicinity of the recording electrode is formed. An effective effect that sticking and plating are reduced can be obtained.

By providing the aggregation electrode, an effective effect of increasing the aggregation rate of the pigment and increasing the printing density can be obtained.

The distance a from the ink discharge port to the portion where the depth of the ink flow path becomes deep, the distance b from the ink discharge port to the end opposite to the ink discharge port of the aggregation electrode, and the distance from the ink discharge port to the notch Assuming that the distance from the ink ejection port to the opposite end is c, if the relationship a ≦ c ≦ b is satisfied, the fixation and plating of the pigment are more effectively prevented while increasing the aggregation rate of the pigment. The effective effect that it becomes possible is obtained.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing a main part of an electrostatic inkjet recording apparatus according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of the electrostatic inkjet recording apparatus of FIG.

FIG. 3 is an exploded perspective view showing a main part of an electrostatic ink jet recording apparatus according to another embodiment of the present invention.

FIG. 4 is a cross-sectional view of the electrostatic inkjet recording apparatus of FIG.

FIG. 5 is a cross-sectional view illustrating the flow of ink in the electrostatic inkjet recording apparatus according to the embodiment.

FIG. 6 is a perspective view showing a conventional electrostatic ink jet recording apparatus.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 recording electrode 2 electrode substrate 3 ink ejection port 4 upper head block (first head block) 5 lower head block (second head block) 7 ink flow path 8 cut section 9 cut section 10 counter electrode 11 recording medium 12 stirring Electrode 13 Ink tank 14 Circulating device 15 Aggregation electrode

Continuing from the front page (72) Inventor Kenji Oshima 1006 Kazuma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. Person Kazunari Chinawa 1006 Kazuma Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. F term (reference) 2C057 AF25 AG90 AG93 AH07 BD07

Claims (8)

[Claims] A plurality of recording electrodes formed on an insulating electrode substrate and arranged in parallel with each other; a notch formed between the recording electrodes, through which ink passes; A first head block and a second head block which are arranged so as to form an ink discharge port and an ink flow path from which the tip of the recording electrode projects, and a counter electrode which is arranged to face the recording electrode. An electrostatic ink jet recording apparatus for printing on the recording medium by discharging and flying a pigment in the ink by electrostatic force. 2. The electrostatic ink jet recording apparatus according to claim 1, wherein a stirring electrode for stirring the ink flowing through the ink flow path by electric force is provided in the ink flow path. . 3. An ink circulation system in which the ink from the ink tank returns to the ink tank through an ink flow path of the first head block and an ink flow path of the second head block by a circulation device. The electrostatic ink jet recording apparatus according to claim 1 or 2, wherein: 4. An electrostatic ink jet recording apparatus according to claim 1, wherein a tip portion of said recording electrode is supported by said electrode substrate. 5. The ink jet printer according to claim 1, wherein the flow velocity of the ink is set to be lower at the tip of the recording electrode and higher at the ink flow path. The electrostatic type ink jet recording apparatus as described in the above. 6. The electrostatic ink jet recording apparatus according to claim 5, wherein the first head block is machined so that a flow path on the tip side of the recording electrode is narrowed. 7. An aggregating electrode which extends in a direction perpendicular to the recording electrode and is applied with a higher potential than the recording electrode is provided in the ink flow path. The electrostatic ink jet recording apparatus according to any one of the above. 8. A distance a from the ink discharge port to a portion where the depth of the ink flow path is increased, and a distance b from the ink discharge port to the end of the aggregation electrode opposite to the ink discharge port is b. If the distance from the ink discharge port to the end of the cut portion opposite to the ink discharge port is c, a
8. The electrostatic ink jet recording apparatus according to claim 7, wherein the relationship is set so as to satisfy a relationship of ≤c≤b.