JP2734403B2 - Ink jet print head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet type print head, and more particularly to an ink jet type print head which prints on recording paper by flying a color material such as ink by electrostatic force.

[0002]

2. Description of the Related Art Conventionally, a so-called non-impact recording method has recently been receiving much attention from the viewpoint that noise during recording is extremely small to a negligible level. Among them, an ink jet recording method capable of recording directly on a recording medium at a high speed with a simple mechanism and recording on plain paper is an extremely effective recording method, and various methods have been used so far. Proposed.

A predetermined voltage is applied between an electrode provided on the back surface of the recording paper and a needle-shaped recording electrode facing the recording paper, and a color of ink or the like is generated by an electrostatic force of the generated electric field. There is a method of recording by flying a material.

FIG. 5 shows an example. In FIG. 5, reference numeral 34 denotes a slit-shaped ink ejection port. This slit-shaped ink ejection port 34 is formed by the substrate 30 and the cover member 32. Of these, a plurality of recording electrodes 36 are disposed on the substrate 30 at intervals in the width direction of the ink ejection ports 34. These recording electrodes 3
Numeral 6 is connected to a driver (not shown) so that a high-voltage pulse is selectively applied to the recording electrode 36 during recording.

On the other hand, a recording paper 38 facing the recording electrode 36
The counter electrode 40 is provided on the back surface in FIG. 5 and generates an electric field between the counter electrode 40 and the recording electrode 36 during recording. Further, since the recording electrode 36 has a needle shape, an electric field concentrates on the tip of the recording electrode 36, and electric charges are accumulated in the ink near the recording electrode 36. In this case, the process of accumulating charges differs depending on the type of ink used. That is, electrostatic induction is the dominant mechanism in the conductive ink, and polarization is the dominant mechanism in the dielectric ink. Furthermore, in the ink in which the color material particles are dispersed, the color material particles themselves have an apparent charge due to the zeta potential, and the charged color material migrates due to the electric field.

In either case, the ink or the coloring material particles in the ink are pulled in the direction of the counter electrode 40, that is, in the direction of the recording paper 38 by the Coulomb force acting on the accumulated electric charge, and the Coulomb force is reduced by the surface tension of the ink. When the ink is overcome, the ink flies and adheres to the recording paper 38. Therefore, desired recording can be performed by controlling the high voltage pulse applied to the recording electrode 36 according to the image.

On the other hand, since the conductivity and permittivity of the ink used for recording are higher than the conductivity and permittivity of air, strictly speaking, the location where the electric field is concentrated is not determined only by the arrangement of the recording electrodes 36, It also depends on the state of the ink meniscus of the ejection port 34. That is, in FIG. 5, the ink meniscus is expected to be uniform in the width direction of the ink ejection port 34. However, in actuality, the processing accuracy of the opening, the vibration of the meniscus after performing the ink ejection, and the Has slight irregularities due to natural fluctuation of the meniscus.

In this case, the electric field concentrates on the minute convex portion of the meniscus near the recording electrode due to the conductivity or dielectric property of the ink, and once the meniscus starts to be deformed by the Coulomb force, the electric field concentrates more strongly. Eventually, the part where the ink flies depends on the initial minute meniscus irregularities. In other words, even if a high voltage pulse is applied to a certain recording electrode, the ink may fly from a position that does not correspond to the recording electrode, so that recording may not be performed at a desired position. Causes a significant deterioration in quality.

Japanese Patent Application Laid-Open No. Sho 60-228162 discloses a measure for solving the above-mentioned problem. As shown in FIG. It has been proposed to provide unevenness in the ink meniscus in advance to concentrate the electric field on the recording electrode 44 by providing the recording meniscus.

[0010]

However, the pitch of the recording electrodes corresponding to the resolution of the printer, for example, 300 [dpi] is about 85 [μm], and the recording electrode portion formed at such a fine pitch is used. It is very difficult to accurately form a convex portion at a position corresponding exactly to the above. In particular, in order to have sufficient mechanical strength, the substrate needs to have a thickness of several hundred [μm] or more, but since the pitch of the unevenness is less than a fraction of this thickness, processing is extremely difficult. Difficult.

As shown in FIG. 6, a reinforcing plate 48 is provided at a position separating the recording electrodes 44 from each other.
In terms of strength, the substrate 42 can be formed of a thin and flexible material. However, in this case, the strength of the protruding portion at the leading end of the substrate 42 is inevitably reduced due to the reduction in thickness, and this causes the head 42 to be cleaned at the time of cleaning the leading end of the head or when a paper jam occurs in the recording paper. There has been an inconvenience that the projection 46 at the tip end is easily damaged.

[0012]

SUMMARY OF THE INVENTION An object of the present invention is to improve the disadvantages of the prior art and to reliably form a meniscus at a portion corresponding to a recording electrode without requiring processing accuracy, thereby suppressing a decrease in print quality. Its purpose is to provide a head.

[0013]

According to the first aspect of the present invention, there is provided a substrate, a cover member which is disposed opposite to the substrate with its tip retreated to form an ink ejection port between the substrate and the ink ejection port. A plurality of recording electrodes disposed on the substrate at intervals in the width direction, and further, a meniscus forming member that is disposed on each of the recording electrodes and guides the ink meniscus in a convex shape, and Is provided.

[0014] The invention according to claim 2 employs a configuration in which the meniscus forming member is positioned behind the front end of the substrate and protrudes from the front end of the cover member.

In the invention according to claim 3, claim 1 or 2
In the configuration described above, a configuration is adopted in which the meniscus forming member is formed integrally with the cover member. This aims to achieve the above-mentioned object.

[0016]

When ink is filled in the ink ejection port, the ink is guided to the periphery of each meniscus forming member by surface tension, and a convex meniscus is formed at the position of each meniscus forming member. Since each meniscus forming member corresponds to the position of each recording electrode, when a voltage is applied to a specific recording electrode, ink droplets surely fly from that recording electrode.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. In FIG. 1, reference numeral 2 denotes an overall perspective view of an ink jet print head. The ink jet print head shown in FIG.
A cover member 8 disposed opposite to the substrate 4 to form an ink ejection port 6 between the substrate 4 and a cover member 8 disposed on the surface of the substrate 4 at a predetermined interval in the width direction of the ink ejection port A plurality of needle-shaped recording electrodes 10 and a strip-shaped meniscus forming member 12 disposed on each recording electrode 10 are provided.

The substrate 4 is formed of an insulator such as glass. The recording electrode 10 is formed by patterning a conductive material such as chromium sputtered on the entire surface of the substrate 4 by photolithography. The recording electrode 10 is 300 [dpi]
They are arranged at a pitch, that is, at intervals of about 85 [μm]. The meniscus forming member 12 is obtained by processing a photosensitive polymer film laminated on the substrate 4 by photolithography, and is disposed at a position slightly retreated from the tip of the recording electrode 10. The thickness of the photosensitive polymer film is 3
0 [μm], the width of the meniscus forming member 12 is about 30
[Μm]. The tip of the meniscus forming member 12 is formed in an arc-shaped convex shape so that the convex guidance of the ink meniscus occurs smoothly.

The cover member 8 is formed of an insulating material, and is set so that its tip is located behind the tip of the substrate 4 and behind the tip of the meniscus forming member 12. Therefore, the tip of the meniscus forming member 12 described above is exposed. In the cover member 8, the outer corner of the tip portion forms an inclined surface. Further, an ink circulation port 14 is formed at a rear end of the cover member 8 on the upper surface of FIG.

Here, it is sufficient for the meniscus forming member 12 to be present locally in the portion of the ink ejection port 6 in terms of function. However, in this embodiment, the meniscus forming member 12 also serves to support the cover member 8. It has a length up to the rear end of the cover member 8. Also, when forming the meniscus forming member 12,
At the same time, a continuous wall surface is also formed on the side portion and the rear end portion of the cover member 8, thereby forming an ink chamber having the ink ejection ports 6 together with the substrate 4 and the cover member 8.

As described above, since the meniscus forming member 12 has a structure that also serves as the side wall of the ink chamber, it is not necessary to prepare a new side wall member, so that the material can be saved and the assembling effort can be reduced. The advantage that it can be omitted can be obtained.

The ink jet print head 2 according to the present embodiment is connected to an ink tank (not shown) via the above-described ink circulation port 14 by a tube.
A negative pressure of about [cmH ₂ O] is applied and ink is circulated forcibly.

The ink is a dispersion of fine particles of a thermoplastic resin, a so-called toner, adhered to a petroleum organic solvent (isoparaffin) together with a charge control agent, and the toner is apparently positively charged by the zeta potential.

Next, the ink discharge function of the ink jet print head 2 will be described with reference to FIGS.

FIG. 2 is an enlarged view of the vicinity of the ink ejection port 6 when ink is supplied, as viewed from above, and FIG.
FIG. 2 shows a cross-sectional view taken along line A. The ink forms an ink meniscus 16 at the ink ejection port 6 due to its surface tension. Since a negative pressure is applied to the ink in the head and the tip of the cover member 8 is retracted from the tip of the substrate 4, the ink meniscus 16 is viewed from the side as shown in FIG. And a concave shape diagonally downward.

Further, since the meniscus forming member 12 protrudes outside the ink ejection port 6, the ink meniscus 1
Numeral 6 is guided along the periphery of the tip of the meniscus forming member 12 and becomes convex at the position of the meniscus forming member 12 when viewed from above. The meniscus forming member 12 is provided for each recording electrode 1.
Since the ink meniscus 16 is disposed at a position corresponding to 0, in other words, the ink meniscus 16 protruding from a portion corresponding to each recording electrode 10 is reliably formed.

Therefore, when a high voltage pulse is applied to an arbitrary recording electrode 10, an electric field is concentrated on the tip of the ink meniscus 16 protruding from the recording electrode 10 site. The charged toner in the ink is drawn out from the tip of the ink meniscus 16 which is guided by this electric field and protrudes, and forms a toner group 18 in the direction of a not-shown counter electrode facing the inkjet print head 2, that is, in the direction of the recording paper. To fly. Thereafter, the toner that has adhered to the recording paper to form recording dots is heated by a heater and fixed.

Next, another embodiment will be described with reference to FIG. In FIG. 4, the ink jet print head 20 includes a substrate 4 and a plurality of recording electrodes 10 disposed on the substrate 4, as in the embodiment of FIG. 1 described above, and corresponds to each recording electrode 10. Meniscus forming member 22 in position
Is integrally provided with the cover member 24.

The meniscus forming member 22 includes the cover member 2
It is formed integrally with the mold 4 and is formed so as to protrude from the ink ejection port by tapering the tip. As in the case of FIG. 1 described above, the meniscus forming member 22 is disposed at the same pitch as the recording electrodes 10, and is positioned so as to overlap the recording electrodes 10.
And the cover member 34 are adhesively bonded. Other configurations are the same as those of the embodiment of FIG. 1 described above.

In each of the above-described embodiments, each component is shown in a specific shape and a specific arrangement is shown. However, the present invention is not limited to this. It can be appropriately modified and rearranged as long as the reliable ink discharge function is obtained.

[0031]

As described above, according to the present invention, it is possible to form a meniscus for easily flying to the recording electrode portion easily by patterning or the like without performing high-precision processing on the tip of the head. It is possible to provide an unprecedented excellent ink jet print head that can suppress deterioration in quality, can secure the mechanical strength of the head end portion, and can reduce the manufacturing cost by simplifying the configuration. .

[Brief description of the drawings]

FIG. 1 is a perspective view showing an embodiment of the present invention.

FIG. 2 is a plan view of a head end portion.

FIG. 3 is an enlarged sectional view taken along line AA in FIG.

FIG. 4 is a perspective view showing another embodiment of the present invention.

FIG. 5 is a perspective view showing a main part of a conventional example.

FIG. 6 is a perspective view showing another conventional example.

[Explanation of symbols]

 Reference Signs List 4 Substrate 6 Ink ejection port 8, 24 Cover member 10 Recording electrode 12, 22 Meniscus forming member 16 Ink meniscus

Claims (3)

(57) [Claims] 1. A substrate, a cover member which is disposed to face the substrate with its tip retreated to form an ink ejection port between the substrate and the substrate, and which is spaced apart in the width direction of the ink ejection port on the substrate. An ink-jet printhead comprising: a plurality of recording electrodes disposed on the recording medium; and a meniscus forming member disposed on each of the recording electrodes so as to project the ink meniscus in a convex shape. 2. The ink-jet printhead according to claim 1, wherein the meniscus forming member is located behind the front end of the substrate and protrudes from the front end of the cover member. 3. The device according to claim 1, wherein the meniscus forming member is formed integrally with the cover member.
Or the ink jet print head according to 2.