JPH11157080A - Ink jet recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To protect an ink guide protrusion from wiping or paper jam. SOLUTION: The ink jet recorder for recording a recording medium by flying an ink droplet containing at least a colorant component of an ink obtained by dispersing the colorant component in a solvent by operating an electrostatic force at the ink toward the medium comprises a plurality of individual electrodes 20 having at least protruding ink guides 10 to operate electrostatic forces, an ink supply means for supplying the ink to the electrodes 20, and a protective member 30 protruding from ends of the guides 10 to become an ink droplet flying position to the medium side to protect the individual electrodes.

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 a recording method using a liquid ink in which a colorant is dispersed, by flying at least a colorant component in the ink as an ink droplet onto a recording medium. The present invention relates to an ink jet recording apparatus that performs the following.

[0002]

2. Description of the Related Art A device 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. Ink jet printers have less noise than other recording methods,
It has the advantage that processing such as development and fixing is unnecessary,
It is drawing attention as a plain paper recording technology. Many ink jet printer systems have been proposed so far. In particular, (a) a system in which ink droplets fly by the pressure of steam generated by the heat of a heating element (for example, Japanese Patent Publication No. 56-942)
9, and JP-B-61-59911) and (b) a method in which an ink droplet is caused to fly by a mechanical pressure pulse generated by a piezoelectric element (for example, JP-B-53-12138).

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, main scanning direction) orthogonal to a conveying direction of recording paper (hereinafter, sub scanning direction). A serial scanning head that performs recording while moving has been put to practical use. With this serial scanning head, it is difficult to increase the recording speed. Therefore, a line-scanning type printer that uses a long head in which the length of the recording head is the same as the width of the recording paper has been considered, but practical use of such a line-scanning type head has been considered. It is not easy for the following reasons.

[0004] In the ink jet recording system, a large number of individual fine nozzles corresponding to the resolution are provided. However, evaporation or volatilization of a solvent is liable to cause local concentration of ink in nature, which causes clogging of the nozzles. Cause. Furthermore, in the method using the pressure of steam for forming the ink jet, the adhesion of the insoluble substance formed by reacting with the ink thermally or chemically induces nozzle clogging, and the method using the pressure by the piezoelectric element In addition, a complicated structure such as an ink flow path makes it easier to induce clogging. In a line scanning head using a large number of nozzles as many as thousands, which is even more than a serial scanning head using tens to hundreds of tens of nozzles, clogging occurs with a high probability in probability, There was a problem of lack of practical reliability.

[0005] Further, in the method using the pressure of steam, the diameter 2 corresponding to a recording dot having a diameter of more than 50 μm on recording paper is used.
Since it is difficult to generate ink particles having a particle size of 0 μm or less, it is difficult to manufacture a high-resolution head. Further, in the method using the pressure generated by the piezoelectric element, it is difficult to manufacture a high-resolution head due to a processing technology problem because the recording head has a complicated structure. For this reason, in the conventional ink jet system, there is a problem that it is difficult to improve the resolution in any system.

In order to solve these problems, a voltage is applied to an electrode array formed by arranging a plurality of individual electrodes formed of a thin film on a substrate, and the ink or the ink is moved from the ink liquid level using an electrostatic force. There has been proposed an ink jet recording method in which a colorant component in the ink composition is made to fly as an ink droplet. Specifically, a method of flying ink droplets using electrostatic attraction (Japanese Patent Application Laid-Open Nos.
Japanese Patent Application Laid-Open Publication No. 7-502218) and a method of increasing the concentration of a colorant using an ink containing a charged colorant component to fly ink droplets (see Japanese Patent Publication No. 7-502218). In these methods, since the recording head has a slit-shaped nozzle structure that does not require a nozzle for each individual dot, or a nozzleless structure that does not require a partition of an ink flow path for each individual dot, line scanning is performed. This is effective for preventing and recovering from clogging, which has been a major obstacle in realizing the type recording head. The latter is also suitable for high resolution because it can stably generate and fly ink droplets having a very small diameter.

However, in the ink jet recording apparatus of the type in which the colorant component is ejected as ink droplets by the above-described electrostatic force, since the recording head is nozzleless, it is effective in preventing clogging, but on the substrate of the recording head. There has been a problem that the ink droplets can be freely moved in the main scanning direction, so that the ejection positions of the ink droplets become unstable. In addition, since the ink droplets are ejected at a voltage having the same polarity as the charge polarity of the colorant and fly on the recording medium, the colorant component repels and escapes from the electrode position on the recording head, and the colorant component is converted into an ink droplet. However, there is also a problem that the ink cannot be supplied stably to the discharge position. Therefore, it is difficult to eject and fly a sufficient amount of ink droplets from a predetermined ejection point in a stable state, and there has been a problem that characters and images cannot be well recorded on a recording medium.

Accordingly, the colorant component contained in the ink can be stably supplied to the leading edge of the individual electrode, which is the discharge position of the ink droplet, so that the ink droplet can be stably discharged and fly without clogging. A possible inkjet recording apparatus has been proposed.

FIG. 7 is a perspective view showing such a conventional ink jet recording apparatus. In FIG. 7, an ink guide 10 for guiding the ink 1 from the ink chamber to the ink ejection hole 4 is provided. This ink guide 10
Has a rod-shaped base 11 and a protruding portion 12 protruding from the base 11 in the direction of the control board 3. A slit 13 is formed at the center of the protruding portion 12, and a tip of the slit 13 is formed.
The inclined surface 14 is inclined downward from the side to the side wall. The ink guide 10 is made of an insulating resin, and is formed in the same pit as the ink protrusion hole 4 formed in the control electrode 5 and connected in a line. When a recording voltage is applied to the control electrode 5 from which ink is to be projected in a manner superimposed on a bias voltage with the head having such a structure, the ink that has risen to the tip of the projection 12 in the slit 13 by capillary force is controlled. Due to the electric field between the electrode 5 and the grounded counter electrode (not shown), the droplets fly out as ink droplets,
Image dots are formed on the recording paper in contact with the counter electrode.

Since the recording paper moves relatively to the ink guide 10, an image is continuously formed by selectively applying a 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 clear and stable image can be recorded. Further, since a plurality of recording heads having such a structure can be continuously formed on the same plane, high resolution of the head can be easily realized by arranging the control electrodes 5 in a staggered manner. .

However, the above-mentioned conventional ink jet recording apparatus has a large hole as compared with other ink jet recording systems, but has a structure in which ink is ejected from the ink ejection holes 4 again. For example, if the ink is not completely removed from the periphery of the ink ejection hole 4, the hole may be clogged. As a problem peculiar to the ink-jet recording apparatus, measures for solving the clogging have been considered for a long time. Conventionally, countermeasures such as capping, wiping, and suctioning ink have been taken to solve the problem of clogging. These methods reduce clogging extremely and also recover clogged heads. Now you can.

[0012]

However, since the above-described ink guide 10 is made of resin and has a structure that fits within a hole diameter of about 200 μm, the tip of the protrusion 12 is very fine. It is in a soft state. Therefore, if a measure against clogging as conventionally performed is taken, the possibility that the protruding portion 12 is damaged is increased. In particular, wiping that rubs the head surface is completely impossible. Further, the adhesion of the ink to the protruding portion 12 occurs even when continuous printing is performed for a long time, and the ink ejection characteristics may change. Further, once the protruding portion 12 has dried, there is a problem that the ink does not rise to the tip even if the ink is to be blown out next time. Even in such a case, it is difficult for the conventional inkjet recording apparatus to return the head. Further, when a paper jam occurs and the paper bends near the head or collides with the head, there is a problem that the protrusion 12 is damaged.
As described above, the use of the ink guide 10 having the protruding portions 12 has caused some new problems.

In order to solve the above problems, the present invention prevents ink clogging in the vicinity of the ink ejection holes and avoids damage to the ink guides due to paper jams in the recording medium, etc., and performs good recording with high resolution. It is an object of the present invention to provide an ink jet recording apparatus capable of performing the above.

[0014]

As a means for solving the above-mentioned problems, the present invention provides an ink in which a coloring agent component is dispersed in a solvent by applying an electrostatic force to the ink to contain at least the coloring agent component. In an ink jet recording apparatus that performs recording by flying ink droplets toward a recording medium,
A plurality of individual electrodes are provided for applying the electrostatic force, and have at least a convex ink guide,
An ink supply unit that supplies the ink to the individual electrode; and a protection member that protrudes toward a recording medium side from a tip end of the convex ink guide that is an ink droplet flying position and protects the individual electrode. It is characterized by.

The control electrode substrate is formed on an insulating substrate having a through hole formed in the ink droplet flying direction, and formed on at least one surface of the insulating substrate so as to correspond to the through hole. The protection member is disposed on the recording medium side on the control electrode substrate,
The convex ink guide is located substantially at the center of the through hole,
A tip portion serving as an ink droplet flying position may be arranged so as to protrude more toward the recording medium than the control electrode substrate surface, and to be located closer to the control electrode substrate than the recording medium side surface of the protection member. .

The convex ink guide may be formed so that at least a portion protruding from the surface of the through-hole in the direction in which the ink drops fly is substantially constant and the tip is thin. The convex ink guide may have a slit-like groove formed at a substantially central position. The coloring agent component is positively or negatively charged, and the recording is performed by causing an ink droplet containing at least the coloring agent component to fly toward a recording medium by applying an electrostatic force having the same polarity as the coloring agent component. It may be performed.

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 adhered to the tip from drying out. Since it is located closer to the recording medium than the leading end, even when paper jam occurs, the clogged paper is prevented from directly contacting the leading end of the ink guide.

[0018]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a perspective view of an ink jet recording apparatus provided with a line scanning type ink jet head according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view of FIG. 1A-A '. In the first embodiment, as will be described in detail with reference to FIG.
1 and a convex ink guide 10. The control electrode substrate 2 and the convex ink guide 10
Are supported in a predetermined manner. Further, a protective member 30 is formed around the convex ink guide 10, and the distal end of the convex ink guide 10 is disposed so as to be located between the protective member 30 and the control electrode substrate 2. In the drawing, ink 1 is a colloidal dispersion of a positively chargeable colorant component together with a charge control agent and a binder in an insulating solvent having a resistivity of 10 ⁸ Ωcm or more. The ink chamber 9 formed by the ink jet head 2 and the head block 21 is supplied and filled from an ink supply system (not shown). Although the head configuration in the first embodiment has a configuration in which two rows of eight ink guides are arranged in one row, it is needless to say that the present invention is not limited to this.

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 the 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 around the through hole 4 on the recording medium side. The convex ink guides 10 are made of an insulating member such as a plastic resin or ceramics, and are arranged at the same row interval and pits so that the center of each ink guide 10 is equal to the center of the through hole 4. Each of the convex ink guides 10 has a shape in which a flat plate having a constant thickness is cut into a triangular or trapezoidal shape, and a slit 13 having a width of about 30 to 50 μm is formed at the center. Further, as described above, each convex ink guide 10 has a tip position located between the protective member 30 and the control electrode substrate 2 surface.
It projects from the respective through-holes almost vertically in the ink droplet flight direction by a predetermined distance. Here the ink guide 10
Is formed integrally with eight ink guides.

A recording medium 17 which is a recording paper is disposed opposite the tip of the convex ink guide 10.
A counter electrode 18 also serving as a platen for guiding the recording medium 17 is arranged on the back surface of the recording medium 17.

Next, a specific example of the structure of the control electrode substrate 2 will be described with reference to FIG. FIG. 4 shows the control electrode substrate 2
FIG. 5 is a diagram viewed from the recording medium 17 side, and shows a through hole 4 formed in the insulating substrate 3 corresponding to the plurality of individual electrodes 20 and an individual hole provided around the through hole 4. And the control electrodes 5 are arranged in an array in two rows in the main scanning direction.

Here, in the first embodiment, the insulating substrate 3
Is made of a polyimide having a thickness of about 25 μm, the control electrode 5 is made of a copper foil having a thickness of about 18 μm, and the inner diameter of the through hole 4 is about 150 to 250 μmΦ.

Next, the recording operation of the ink jet recording apparatus according to the first embodiment will be described.

At the time of recording, the ink 1 filled in the ink chamber 9 shown in FIG.
0 is supplied to the ink flying position at the leading end. Here, a voltage of, for example, DC 1.5 kV is always applied as a bias to the control electrode 5 from the bias voltage source 6, and a pulse voltage of, for example, 500 V at the time of ON 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 the ground potential 0 V as shown in the figure.

Now, the control electrode 5 is turned on (in a state where 500 V is applied), and the bias voltage is reduced to 1.5 kV by 50 kV.
When a total voltage of 2 kV on which the 0V pulse voltage is superimposed is applied, the ink droplet 8 centering on the colorant component jumps out of the ink droplet flying position at the tip of the convex ink guide 10, and is pulled by the counter electrode 18. The image flies toward the recording medium 17 to form an image.

In this case, since the flow path of the ink 1 is determined, the flying position of the ink droplet is set to the convex ink guide 10.
And the colorant component does not escape in the main scanning direction due to the application of a voltage during flight. Further, as shown in the present embodiment, the liquid ink is conveyed into the independent through-hole 4 and the control electrode provided around the through-hole 4, and the surface of the convex ink guide 10 projecting substantially perpendicularly 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 are as follows. It is maintained stably without being affected by the state of the ink supply system such as pressure, the atmospheric pressure, or the influence of mechanical vibration. Therefore, the flight of the ink droplet 8 is stabilized, and a good image with a stable density can be recorded on the recording medium 17.

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. Each row of the two rows of ink guides is slit 32
It may be formed so as to be surrounded by. Further, as shown in FIG. 6, two rows of ink guides each having eight rows may be formed so as to be individually surrounded by square holes 34.

In the above embodiment, the colorant component has been described as having a positive charge, but it goes without saying that the colorant component may have a negative charge. At that time, all the voltages applied to the electrodes described above may be considered to have opposite polarities. Further, although the inside diameter of the hole formed in the control electrode is the same as the through hole, it may be slightly larger. Further, although the control electrode 5 is arranged on the recording medium side on the insulating substrate 3, it may be arranged on the opposite surface.

[0029]

As described above in detail, according to the ink jet recording apparatus of the present invention, the protection member located closer to the recording medium than the tip of the convex ink guide is provided around the ink guide. In addition to preventing the ink from drying at the tip of the ink guide, the paper and brush can be prevented from directly hitting the tip of the ink guide with excessive force during paper jam or wiping. This has the effect of ensuring a long life and high-resolution recording.

[Brief description of the drawings]

FIG. 1 is a perspective view of an inkjet head according to a first embodiment of the invention.

FIG. 2 is a cross-sectional view taken along line AA ′ of FIG. 1 in the first embodiment.

FIG. 3 is a cross-sectional view illustrating a configuration of an inkjet head unit and a main part of the inkjet recording apparatus according to the first embodiment.

FIG. 4 is a plan view showing the shape of a control electrode substrate according to the first embodiment.

FIG. 5 is a perspective view showing a shape of a protection member in an ink jet recording apparatus according to a second embodiment of the present invention.

FIG. 6 is a perspective view showing a shape of a protection member in the inkjet recording apparatus according to the embodiment of the present invention.

FIG. 7 is a perspective view showing an ink guide of a conventional inkjet recording apparatus.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 ink 2 control electrode substrate 3 insulating substrate 4 through hole 6 bias voltage source 7 signal voltage source 8 ink drop 9 ink chamber 10 convex ink guide 11 base 12 protrusion 13 slit 20 individual electrode 30 protective member

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yuko Nomura 1 Koko Toshiba-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Prefecture Inside the Toshiba R & D Center Co., Ltd. Komukai Toshiba-cho 1 Toshiba R & D Center (72) Inventor Hideyuki Nakao 1 Komukai Toshiba-cho 1-City, Kawasaki City, Kanagawa Prefecture Toshiba R & D Center (72) Inventor Koichi Ishii 1 Toshiba R & D Center, Komukai Toshiba-cho, Saiwai-ku, Kawasaki-shi, Kanagawa

Claims (5)

[Claims] An ink jet recording apparatus which performs recording by applying an electrostatic force to an ink in which a colorant component is dispersed in a solvent to fly at least an ink droplet containing the colorant component toward a recording medium. A plurality of individual electrodes provided for applying the electrostatic force and having at least a convex ink guide; an ink supply means for supplying the ink to the individual electrodes; and the convex ink serving as an ink droplet flying position A protecting member that protrudes toward the recording medium side from a leading end of the guide and protects the individual electrodes. 2. The method according to claim 1, wherein the plurality of individual electrodes comprise a control electrode substrate and a convex ink guide, and the control electrode substrate has an insulating substrate having a through-hole formed in the ink droplet flying direction. And a control electrode formed on at least one surface of the insulating substrate so as to correspond to the through hole. The protection member is disposed on the control medium substrate on the recording medium side, and the convex ink The guide is located substantially at the center of the through hole,
A tip portion serving as an ink droplet flying position protrudes toward the recording medium side from the control electrode substrate surface, and is arranged so as to be located closer to the control electrode substrate side than the recording medium side surface of the protection member. The ink jet recording apparatus according to claim 1, wherein: 3. The convex ink guide according to claim 1, wherein at least a portion of the convex ink guide protruding from the surface of the through-hole in the direction in which the ink drops fly is substantially constant, and the tip is thin. The inkjet recording apparatus according to claim 2. 4. The ink jet recording apparatus according to claim 1, wherein said convex ink guide has a slit-like groove formed at a substantially central position of a front end portion. 5. The color material component is positively or negatively charged, and an electrostatic force having the same polarity as the color material component is applied to fly an ink droplet containing at least the color material component toward a recording medium. The ink jet recording apparatus according to claim 1, wherein the recording is performed by: