JP3916184B2 - Inkjet recording device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
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 apparatus that performs recording by using a liquid ink in which a colorant is dispersed and causing at least a colorant component in the ink to fly onto a recording medium as ink droplets. It is.
[0002]
[Prior art]
An apparatus for recording an image by spraying liquid ink as small droplets called ink droplets on a recording medium to form recording dots has been put to practical use as an ink jet printer. Inkjet printers have the advantages of being less noisy than printers of other recording methods and requiring no processing such as development or fixing, and are attracting attention as plain paper recording technology. Many ink jet printer systems have been proposed so far. In particular, (a) systems in which ink droplets are ejected by the pressure of steam generated by the heat of a heating element (for example, Japanese Patent Publication Nos. 56-9429 and 61-59911). Etc.) and (b) a method of flying ink droplets by mechanical pressure pulses generated by a piezoelectric element (for example, Japanese Patent Publication No. 53-12138).
[0003]
A recording head (hereinafter referred to as an ink jet head) used in an ink jet printer is mounted on a carriage and moves in a direction (hereinafter referred to as a main scanning direction) orthogonal to a recording paper transport direction (hereinafter referred to as a sub scanning direction). Serial scanning heads for recording have been put into practical use. With this serial scanning head, it is difficult to increase the recording speed. Therefore, although a line scanning printer that uses a long head having the same length as the recording paper is used to increase the speed, a practical use of such a line scanning head is possible. This is not easy for the following reasons.
[0004]
Inkjet recording systems are provided with a large number of individual fine nozzles corresponding to the resolution, but local ink concentration tends to occur essentially due to evaporation or volatilization of the solvent, which causes clogging of the nozzles. ing. In addition, in the method using vapor pressure for forming an ink jet, adhesion of insoluble substances formed by thermal or chemical reaction with ink induces clogging of the nozzle, and in the method using pressure by a piezoelectric element. Further, a complicated structure such as an ink flow path makes it easier to induce clogging. Line scanning heads that use thousands of nozzles, more than thousands of serial scanning heads that use dozens to hundreds of nozzles, are clogged at a rather high frequency, It had the problem of lacking practical reliability.
[0005]
Furthermore, in the method using the vapor pressure, it is difficult to produce ink particles having a diameter of 20 μm or less corresponding to recording dots having a diameter of 50 to several μm on the recording paper. Have difficulty. In the method using the pressure generated by the piezoelectric element, since the recording head has a complicated structure, it is difficult to manufacture a high-resolution head due to a problem in processing technology. For this reason, the conventional inkjet system has a problem that it is difficult to improve the resolution regardless of which system is used.
[0006]
In order to solve these problems, a voltage is applied to an electrode array formed by arranging a plurality of individual electrodes formed by thin films on a substrate, and an electrostatic force is used from the ink liquid surface to the ink or the contents in the ink. An ink jet recording system in which a colorant component is allowed to fly as ink droplets has been proposed. Specifically, a method of flying ink droplets using electrostatic attraction (see JP-A-49-62024 and JP-A-56-4467), or an ink containing a charged colorant component is used. A method of increasing the concentration of the colorant and causing ink droplets to fly (see JP 7-502218A) has been proposed. In these systems, since the recording head configuration is a slit-like nozzle structure that does not require a nozzle for each individual dot, or a nozzleless structure that does not require a partition for an ink flow path for each individual dot, line scanning is performed. This is effective for the prevention and restoration of clogging, which was a major obstacle in realizing the type recording head. The latter is also suitable for increasing the resolution because ink particles having a very small diameter can be stably generated and fly.
[0007]
[Problems to be solved by the invention]
However, in the above-described ink jet recording apparatus in which the colorant component is ejected as ink droplets by electrostatic force, the recording head is nozzleless, which is effective for preventing clogging, but ink is mainly used on the substrate of the recording head. There is a problem that the ink droplet ejection position becomes unstable because it can move freely in the scanning direction. In addition, since the ink droplets are ejected at a voltage of the same polarity as the charging polarity of the colorant and fly to the recording medium, the colorant component repels and escapes from the electrode position on the recording head, and the colorant component is removed from the ink droplet. There is also a problem that it cannot be stably supplied to the discharge position. Therefore, it is difficult to eject ink droplets by a sufficient amount in a stable state from a predetermined ejection point, and it is difficult to record characters and images on a recording medium.
[0008]
Therefore, ink-jet recording that can stably supply the colorant component contained in the ink to the tip of the individual electrode that is the discharge position of the ink droplet, and can stably discharge and fly the ink droplet without clogging. A device has been proposed.
[0009]
Figure 7 is a perspective view showing such Lee inkjet recording apparatus, in the figure, the ink guide 10 for guiding the ink 1 is provided toward the ink discharge hole 4 from the ink chamber. The ink guide 10 includes a rod-like base 11 and a protrusion 12 protruding from the base 11 toward the control board 3. A slit 13 is formed at the center of the protrusion 12, and the tip of the ink guide 10 extends from the slit 13. It becomes the inclined surface 14 which inclines toward the shoulder toward the side wall. The ink guide 10 is made of an insulating resin, and is formed in the same pit as the ink protruding hole 4 formed in the control electrode 5 and connected in a row. With the head having such a structure, when a recording voltage is superimposed on the bias voltage and applied to the control electrode 5 where the ink is to be projected, the ink that has risen up to the tip of the protruding portion 12 by the capillary force in the slit 13 is controlled. By an electric field between the electrode 5 and the grounded counter electrode (not shown), an ink droplet pops out and an image dot is formed on the recording paper in contact with the counter electrode.
[0010]
Since the recording paper moves relative to the ink guide 10, images are continuously formed by selectively applying the recording signal in accordance with the image signal. Since the ink guide 10 has the protruding portion 12, the ink discharge point is stabilized, so that a beautiful and stable image can be recorded. Furthermore, since a plurality of recording heads having such a structure can be continuously formed on the same plane, it is possible to easily realize high resolution of the heads by arranging the control electrodes 5 in a staggered manner. .
[0011]
However, ink jet recording apparatus of the above SL, albeit with a large hole when compared to other ink jet recording system, in order had a structure in which ink is ejected from the ink ejection holes 4 again, for example, when unused for long periods of time If the ink is not completely removed from the periphery of the ink ejection holes 4, clogging may occur. For this clogging, as a problem peculiar to the ink jet recording apparatus, a measure for solving it has been considered for a long time. For clogging problems, measures such as capping, wiping, and ink suction have been used in the past. By these methods, clogging is extremely reduced and clogged heads are also recovered. I can do it now.
[0012]
However, since the ink guide 10 described above is made of resin and has a structure that falls within a hole diameter of about 200 μm, the tip of the protruding portion 12 is very fine and soft. Therefore, if the countermeasure against clogging as conventionally performed is taken, the possibility of damaging the protruding portion 12 is increased. In particular, wiping that rubs the head surface is completely impossible. Ink adhesion to the protrusions 12 may occur even when continuous recording is performed for a long time, and the ink ejection characteristics may change. Further, once the protrusion 12 is dried, there is a problem that the ink does not rise to the tip even if the next ink is to be ejected. Even in such a case, it is difficult for the conventional ink jet recording apparatus to return the head. Further, when the paper jam occurs and the paper is bent near the head or collides with the head, the protrusion 12 is damaged. As described above, since the ink guide 10 having the protrusions 12 is used, some new problems have occurred.
[0013]
In order to solve the above problems, the present invention can prevent clogging of ink in the vicinity of the ink ejection holes and avoid damage to the ink guide due to paper jam of the recording medium, and can perform good recording with high resolution. An object is to provide an ink jet recording apparatus.
[0014]
[Means for Solving the Problems]
As a means for solving the above-described problems, the present invention applies an electrostatic force to ink in which a colorant component is dispersed in a solvent, and causes ink droplets containing at least the colorant component to fly toward a recording medium. In the ink jet recording apparatus for recording by performing the recording, a plurality of electrodes are provided for applying the electrostatic force, individual electrodes having at least a convex ink guide, and ink supply means for supplying the ink to the individual electrodes; A protection member that protects the individual electrodes by projecting toward the recording medium from the tip of the convex ink guide serving as an ink droplet flying position, and the plurality of individual electrodes includes a control electrode substrate and the plurality of individual electrodes. And the control electrode substrate is formed corresponding to the plurality of convex ink guides in the ink droplet flying direction. An insulating substrate having a plurality of through holes, the individually provided around the plurality of through-holes on at least one surface of the insulating substrate consists of a plurality of control electrodes having a bore which communicates with the through-hole The protective member is arranged on the control electrode substrate on the recording medium side, and the convex ink guide is positioned at the center of the through-hole, and the tip portion serving as the ink droplet flying position is the surface of the control electrode substrate The present invention also provides an ink jet recording apparatus that protrudes toward the recording medium.
[0015]
Further, the ink chamber has a head block that supports the convex ink guide and the control electrode substrate, and is filled with ink supplied from the ink supply means between the control electrode substrate and the head block. Is preferably formed.
The convex ink guide is preferably made of an insulating member.
Further, it is preferable that the tip of the convex ink guide is an ink droplet flying position.
[0016]
The convex ink guide may be formed such that at least a portion protruding from the surface of the through hole in the ink droplet flying direction has a substantially constant thickness and a thin tip. The convex ink guide may have a slit-like groove formed at a substantially central position. Further, the colorant component is positively or negatively charged, and recording is performed by causing an electrostatic force having the same polarity as the colorant component to act and causing ink droplets containing at least the colorant component to fly toward the recording medium. You may make it perform.
Preferably, the plurality of individual electrodes are arranged in a plurality of rows, and the protection member is arranged so as to surround each of the plurality of individual electrodes arranged in rows.
It is also preferable that the tip position of the convex ink guide is located between the recording medium side surface and the control electrode substrate side surface of the protective member.
[0017]
As described above, by covering the periphery of the tip of the convex ink guide with the protective member, it is possible to prevent the liquid ink adhering to the tip from drying out. Is located on the recording medium side, so that even when a paper jam occurs, the clogged paper is prevented from coming into direct contact with the tip of the ink guide.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a perspective view of an ink jet recording apparatus including a line scanning ink jet head according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view of FIG. In the first embodiment, as will be described in detail with reference to FIG. 3, the individual electrode 20 that ejects ink includes the control electrode substrate 2 and the convex ink guide 10. The ink guide 10 is supported on the head block 21 by a predetermined method. Further, a protective member 30 is formed around the convex ink guide 10, and the tip of the convex ink guide 10 is disposed between the protective member 30 and the control electrode substrate 2. In the figure, ink 1 is a colloidal dispersion of a positively chargeable colorant component together with a charge control agent, a binder and the like in an insulating solvent having a low efficiency of 10 @ 8 .OMEGA.cm or more. The ink chamber 9 formed by the head block 21 is supplied and filled from an ink supply system (not shown). Although the head configuration in the first embodiment is a configuration in which two rows of eight ink guides are arranged in a row, it goes without saying that the present invention is not limited to this.
[0019]
FIG. 3 is an enlarged view of the periphery of the individual electrode 20 corresponding to each recording dot shown in FIG. 2, and a diagram showing a configuration of an ink jet recording apparatus using this ink jet head. The control electrode substrate 2 includes an insulating substrate 3 having a through hole 4 and a control electrode 5 formed on the recording medium side around the through hole 4. The convex ink guide 10 is made of an insulating member such as plastic resin or ceramics, and is arranged with the same row interval and pits so that the center of each ink guide 10 and the center of the through hole 4 are equal. Each convex ink guide 10 has a shape in which the tip of a flat plate having a constant thickness is cut into a triangle or a trapezoid and a slit 13 having a width of about 30 to 50 μm is formed in the center, and the tip of the tip is the ink droplet flying position. Further, as described above, each convex ink guide 10 has a tip position located between the protective member 30 and the surface of the control electrode substrate 2 so that it is substantially perpendicular to each through hole by a predetermined distance in the ink droplet flight direction. It sticks out. Here, the ink guide 10 is formed integrally with eight ink guides.
[0020]
A recording medium 17, which is a recording sheet, is disposed opposite the tip of the convex ink guide 10, and a counter electrode 18 that also serves as a platen for guiding the recording medium 17 is disposed on the back surface of the recording medium 17.
[0021]
Next, a specific structural example of the control electrode substrate 2 will be described with reference to FIG. FIG. 4 is a view of the control electrode substrate 2 as viewed from the recording medium 17 side. The through hole 4 formed in the insulating substrate 3 corresponding to the plurality of individual electrodes 20, and the through hole 4. Are arranged in an array in two rows in the main scanning direction.
[0022]
Here, in the first embodiment, the insulating substrate 3 is made of polyimide having a thickness of about 25 μm, the control electrode 5 is made of copper foil having a thickness of about 18 μm, and the inner diameter of the through hole 4 is about 150 to 250 μmΦ. is there.
[0023]
Next, the recording operation of the ink jet recording apparatus according to the first embodiment will be described.
[0024]
At the time of recording, the ink 1 filled in the ink chamber 9 shown in FIG. 2 is supplied from the through hole 4 to the ink flying position at the tip of the convex ink guide 10. Here, a voltage of, for example, DC 1.5 kV is applied to the control electrode 5 from the bias voltage source 6 as a constant bias, and a pulse voltage of, for example, 500 V is superimposed on this as a signal voltage corresponding to the image signal from the signal voltage source 7. Is done. On the other hand, the counter electrode 18 provided on the back surface of the recording medium 17 is set to a ground potential of 0 V as shown in the figure.
[0025]
Now, when the control electrode 5 is in an ON state (a state in which 500 V is applied) and a voltage of 2 kV in total, in which a pulse voltage of 500 V is superimposed on a bias DC of 1.5 kV, is applied, the ink droplet flying position at the tip of the convex ink guide 10 Thus, the ink droplet 8 centering on the colorant component is ejected, pulled by the counter electrode 18, and then ejected toward the recording medium 17 to form an image.
[0026]
In this way, since the flow path of the ink 1 is determined, the ink droplet flying position is determined at the substantially central position of the convex ink guide 10, and the colorant component does not escape in the main scanning direction due to the application of voltage during the flight. . Further, as shown in the present embodiment, the liquid ink is transported into the independent through-hole 4 and the control electrode provided in the periphery thereof, and the surface of the convex ink guide 10 protruding substantially vertically from the through-hole 4 and Since the ink 1 is supplied to the ink droplet flying position by wetting or surface tension in the slit 13 formed at the center of the convex ink guide 10, the size and position of the meniscus formed at the ink droplet flying position is The ink supply system is stably maintained without being affected by conditions such as the pressure of the ink supply system, atmospheric pressure, and mechanical vibration. Accordingly, the flying of the ink droplets 8 is stabilized, and a good image with a stable density can be recorded on the recording medium 17.
[0027]
Here, the shape of the protective member 30 shown in FIG. 1 is formed so as to surround the entire two rows of ink guides consisting of eight rows, but as shown in FIG. 5, two rows consisting of eight rows as shown in FIG. The ink guides may be formed so as to be surrounded by the slits 32. Further, as shown in FIG. 6, each of the two rows of ink guides including eight rows may be individually surrounded by the square holes 34.
[0028]
In the above-described actual form, the colorant component has been described as having positive chargeability, but it goes without saying that it may have negative chargeability. At that time, it may be considered a voltage applied to the various electrodes described above as the polarity of all reversed. In addition, the inner diameter of the hole formed in the control electrode is the same as that of the through-hole, but it may be slightly larger, and the control electrode 5 is disposed on the recording medium side on the insulating substrate 3, It may be arranged on the opposite side.
[0029]
【The invention's effect】
As described above in detail, according to the ink jet recording apparatus according to the present invention, the protective member positioned closer to the recording medium than the front end of the convex ink guide is provided around the ink guide. In addition to preventing the ink from drying, the paper and brush can be prevented from hitting the tip of the ink guide with excessive force during paper jams and wiping. There is an effect that can guarantee the record.
[Brief description of the drawings]
FIG. 1 is a perspective view of an ink jet head according to a first embodiment of the invention.
2 is a cross-sectional view taken along line AA ′ of FIG. 1 in the first embodiment.
FIG. 3 is a cross-sectional view showing a configuration of an ink jet head unit and main parts of the ink jet recording apparatus according to the first embodiment.
FIG. 4 is a plan view showing the shape of a control electrode substrate in the first embodiment.
FIG. 5 is a perspective view showing the shape of a protective member in an ink jet recording apparatus according to a second embodiment of the invention.
FIG. 6 is a perspective view showing the shape of a protective member in the ink jet recording apparatus according to the embodiment of the invention.
FIG. 7 is a perspective view showing an ink guide of a conventional ink jet recording apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Ink 2 Control electrode board 3 Insulating board 4 Through-hole 6 Bias voltage source 7 Signal voltage source 8 Ink droplet 9 Ink chamber 10 Convex ink guide 11 Base part 12 Protrusion part 13 Slit 20 Individual electrode 30 Protection member

Claims (9)

In an inkjet recording apparatus that performs recording by causing an electrostatic force to act on ink in which a colorant component is dispersed in a solvent and causing ink droplets containing at least the colorant component to fly toward the recording medium.
A plurality of electrodes for operating the electrostatic force, and individual electrodes having at least a convex ink guide;
Ink supply means for supplying the ink to the individual electrodes;
A protective member that protrudes toward the recording medium from the tip of the convex ink guide serving as an ink droplet flying position and protects the individual electrode,
The plurality of individual electrodes includes a control electrode substrate and the plurality of convex ink guides,
The control electrode substrate includes an insulating substrate having a plurality of through holes formed corresponding to the plurality of convex ink guides in the ink droplet flying direction, and the control electrode substrate on at least one surface of the insulating substrate. A plurality of control electrodes provided individually around the plurality of through holes , and having a hole communicating with the through hole ;
The protective member is disposed on the recording medium side on the control electrode substrate,
The ink jet recording apparatus according to claim 1, wherein the convex ink guide has a tip end portion serving as an ink droplet flying position protruding substantially closer to the recording medium than the surface of the control electrode substrate at a substantially central position of the through hole. And a head block that supports the convex ink guide and the control electrode substrate.
The control electrode substrate and between the head block, an ink jet recording apparatus according to claim 1 in which the ink to be supplied, characterized in that the ink chamber to be filled is formed from the ink supply means. The convex ink guide to an ink jet recording apparatus according to claim 1 or 2, characterized in that it consists of an insulating member. The convex ink guide to an ink jet recording apparatus according to any one of claims 1 to 3, characterized in that the tip portion becomes an ink droplet ejecting position. The convex ink guide in at least the thickness of the portion through which the pore surfaces projecting ink droplets flying direction is substantially constant, to any one of claims 1 to 4, characterized in that the tip is narrower The ink jet recording apparatus described. The convex ink guide to an ink jet recording apparatus according to any one of claims 1 to 5, characterized in that is formed slit-like grooves in a substantially center position of the tip portion. The colorant component is positively or negatively charged, and recording is performed by causing an electrostatic force having the same polarity as the colorant component to act and causing ink droplets containing at least the colorant component to fly toward the recording medium. An ink jet recording apparatus according to any one of claims 1 to 6 . The plurality of individual electrodes are arranged in a plurality of rows,
The protective member is an ink jet recording apparatus according to any one of claims 1 to 7, characterized in that it is arranged so as to surround the plurality of individual electrodes arranged in rows for each column, respectively. The inkjet recording according to any one of claims 1 to 8 , wherein a tip position of the convex ink guide is located between the recording medium side surface and the control electrode substrate side surface of the protective member. apparatus.

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