JPH0226586B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in ink recording heads and ink recording apparatuses that utilize the electroosmotic phenomenon of liquid ink.

A thin two-dimensional porous body is placed on the surface of a dielectric support substrate having a first electrode forming a recording electrode, and liquid ink is applied to the opposite side of the porous body from the first electrode. A transparent second electrode is positioned to supply and impregnate the porous body with liquid ink, and a signal voltage is applied between the first and second electrodes to cause the liquid ink to pass through the porous body with electricity. An ink recording head and an ink using the ink recording head that is in a relationship to form a controlled liquid ink portion to be recorded on a recording medium in response to a signal voltage on one end side where the first electrode extends. A recording device has already been proposed by the present inventor. The first electrode forming the recording electrode is formed by disposing a plurality of electrodes adjacent to each other and separating them from each other depending on the recording density, and preferably includes liquid ink on the surface of the dielectric material forming the supporting base material surface. If the electroosmotic polarity of the electrode is selected to be the same as that of the porous body, and the on-voltage for ink recording as a signal voltage and the off-voltage for blocking ink recording are selected to have opposite polarities, the tip side of the first electrode causes a convergence effect of the liquid ink, a liquid ink portion is generated in response to the on voltage, and the liquid ink portion disappears in response to the off voltage, and the amount of recording ink is directly modulated by the signal voltage. Combined with the convergence effect, high-resolution ink recording becomes possible.

The first electrode can be directly attached to the surface of the dielectric support base material, or it can be placed inside a depression or recess formed on the surface of the support base material.

This method has the advantage of being able to perform low voltage, high resolution ink recording by directly contacting and moving a recording medium such as paper to the end of the ink recording head to transfer the ink. However, according to this contact method,
If dust or the like adheres to the surface of the recording medium or supporting base material, ink transfer to the recording medium may become insufficient.
Alternatively, when the liquid ink attached to the dust is transferred, the ink is transferred in a striped pattern, which may significantly deteriorate the quality of the recorded image.

The above-mentioned difficulties can be improved by adopting a non-contact flight recording method, but the ink in the liquid ink part generated in connection with the on-voltage
Sometimes the ink overflows from the edge, wets the side edge of the supporting base material that is connected to this edge, and the ink also flies from this area and adheres to the surface of the recording medium, resulting in a decrease in the quality of the recorded image. I'm reading.

With the above-mentioned technical problems as a background, the present invention aims to improve an ink recording head and an ink recording apparatus that improve the above problems.

To explain the present invention specifically, in the ink recording head, the side edge surface of the dielectric supporting base material that is in contact with one tip end side of the first electrode is made ink repellent to the liquid ink. The present invention relates to the constructed ink recording head and an ink recording apparatus using this ink recording head.

Hereinafter, aspects of the present invention will be described in detail with reference to Examples. FIG. 1 is a perspective partial structural view of an ink recording head and an ink recording apparatus according to the present invention. 1st
In the figure, 100 is an ink recording head, 200
is housed in the ink container 300, and the ink recording head 100 is partially immersed in the ink recording head 1.
This is a liquid ink that is supplied to and impregnated into 00. 40
0 is a signal voltage source, 500 is a recording sheet such as a recording medium, and 600 is a recording medium 500, which is indicated by the arrow 50 in the figure.
This is a roller-shaped auxiliary electrode that feeds paper in one direction and applies an auxiliary voltage V _A from an auxiliary voltage source 401 . The auxiliary electrode 600 can be fixed without being rotated, or can be placed on an insulator in a limited manner, facing the tip 21 of the first electrode 20.

10 is a dielectric support substrate made of a non-porous material such as borosilicate glass or cellulose acetate. Its surface 11
On the top, a first electrode 20 serving as a recording electrode has a density of, for example, 3 to 8 per mm, corresponding to a desired ink recording density.
They are arranged at the density of a book, and the width thereof is 50 to 200 μm depending on the above-mentioned recording density, and the conductive film of tin oxide or metal vapor deposition film is deposited and arranged extremely thinly to about 500 to 2000 Å. For stable flying ink recording, the first electrode 20 is preferably made of a so-called ink-philic conductive material that is well wetted by the liquid ink 200.

The side edge end surface 12 of the support base material 10 that is in contact with the tip 21 side of the first electrode 20 is substantially covered with liquid ink 20.
0 is configured to be ink repellent so that it does not get wet for the first time. An effective method is to apply an ink repellent agent 30 having a surface tension smaller than the surface tension of the liquid ink 200 used (usually about 30 dyne/cm or more) on the side edge surface 12.

For the ink repellent agent 30, a material with high specific resistance, preferably an insulating material, is selected so as not to cause dielectric breakdown due to the signal voltage applied between the first electrodes 20.

An example of the ink repellent agent 30 that satisfies the above-mentioned conditions is an insulating oil-repellent or water-repellent spill-preventing agent (for example, 3M's Florado FC-721, etc.) dissolved in a fluorine-based solvent, and its surface tension is
It has an extremely low value of 11 dyne/cm. This type of ink repellent agent 30 is applied to a thickness of about 1 μm to impart ink repellency to the side edge end surface 12. In this example, the ink repellent agent 30 is also applied to the side edge surface of the tip portion 21 of the first electrode 20 at the same time.
The ink repellent agent 30 applied to this portion can also be removed. In addition, ink repellent agent 30
It is not necessarily necessary to apply the coating to the entire surface of the side edge end surface 12, but it is sufficient if it is applied partially including the edge 13.

On the support substrate surface 11, a porous body 40 having holes or gaps that substantially penetrate in the thickness direction and through which the liquid ink 200 can permeate in the thickness direction is installed.
As the porous body 0, for example, a so-called microporous membrane filter made of cellulose acetate having a thickness of 20 to 200 μm, an average pore diameter of 0.1 to 8 μm, and a porosity of about 60 to 80% is used. As the porous body 40, other plastic materials, glass, porcelain materials, etc. can also be used.

The edge 41 of the porous body 40 is located, for example, about 50 to 300 μm from the edge 13 of the support substrate 10,
Desirably, an exposed edge surface 14 is formed on the support substrate surface 11. The formation of the edge surface 14 utilizes the electrical convergence effect of the liquid ink utilizing the electroosmotic property of the liquid ink 200 on this surface 14, which is useful for high-resolution recording.

The surface of the porous body 40 opposite to the supporting substrate 10 is provided with pores (not shown) that penetrate at a density of about 100 to 300 meshes per inch, and a liquid ink 200 with a thickness of about 50 to 300 μm permeates therethrough. A second electrode 50 made of stainless steel plate, metal mesh, etc.
is installed, and the porous body 40 is pressed and fixed.

Note that the second electrode 50 can also be constructed by applying a thin layer of conductive paint such as graphite to the surface of the porous body 40.

The end of the porous body 40 opposite to the recording body 500 installation surface is sealed to the support surface 11 and the first electrode surface using a sealing agent 60 such as an adhesive. This prevents backflow of liquid ink due to electroosmosis, which will be described later.

Liquid ink 200 is supplied to and impregnated into porous body 40 via second electrode 50 .

The liquid ink 200 is made of a liquid material made of, for example, γ-methacryloxypropyltrimethoxysilane, and a necessary binder agent and charge control agent to provide good electroosmotic properties to the above-mentioned porous body 40 and supporting substrate 10. The oil-soluble ink 200 is composed of, for example, about 2 to 5% by weight of an oil-soluble dye or the like mixed together with a surfactant or the like.

This type of ink electro-osmoses into the above-mentioned porous body 40 and supporting substrate 10 in the direction of the negative electrode. The speed of this electroosmosis increases with the applied signal voltage, but its maximum amplitude is set to an electric field strength of about 2 V/μm, taking into account dielectric breakdown. Each of the first electrodes 20 serving as recording electrodes is connected to a signal voltage source 400, and signal voltages V _B and V _B ' are selectively applied between them and the second electrodes 50.

Now, as a signal voltage as shown in the figure, the first electrode 2
Off-voltage at which the second electrode 50 is negative with respect to 0
_The operation will be explained by taking as an example a case where a negative ON voltage V _B is alternately applied to the first electrode 20 with respect to the electrode 50.

In the part where V _B ' is applied, the liquid ink 200 flows from the first electrode 20 side forming the positive electrode to the second electrode 50 side forming the negative electrode via the porous body 40 in the direction indicated by the arrow 210. Along with electroosmosis, the liquid ink 200 located on the electrode tip 21 side is also sucked up to the second electrode 50 side, as shown by the arrow 211 in the figure.

Furthermore, since the supporting substrate 10 is also configured to have the same electroosmotic property as the porous body 40,
Liquid ink 200 electroosmoses on the support surface 11 as shown by arrow 212 from the electrode 20 to which V _B ' is applied toward the adjacent electrode 20 to which V _B is applied and forms a negative electrode.

Therefore, the first electrode 20 to which V _B ' is applied
The exposed edge surface 1 on the tip 21 side and the surrounding area
4, the liquid ink 200 cannot exist.

On the other hand, in the first electrode 20 portion to which V _B is applied,
The liquid ink 200 passes through the second electrode 50 and electroosmoses as shown by the arrow 220 through the porous body 40, concentrates toward the electrode tip 21 of the first electrode 20, and flows toward the other end. Since the liquid ink 200 is sealed with the sealing agent 60, the liquid ink 200 spreads over the surface of the first electrode 20 by electroosmosis in the direction indicated by the arrow 221 in the figure.
The exposed edge surface 1 is pushed out toward the tip 21 as shown in FIG.
4, a liquid ink portion 222 corresponding to the electrode 20, whose ink amount is controlled with respect to the position and the amplitude of V _B.
form.

In addition, the liquid ink 200 electropenetrates from the side of the adjacent positive electrode electrode 0 through the supporting substrate surface 11 and the exposed edge surface 14 as indicated by the arrow 212 and collects on the surface of the electrode 20, resulting in extrusion convergence. As a result, the formation of liquid ink 222 becomes more effective.

In order to effectively utilize the suction, extrusion, and convergence effects of the liquid ink 200 as in the present principle, the edges 41 and 13 should be kept parallel in order to keep the distance between them constant. If the interval, that is, the width of the exposed edge surface 14 is too narrow, the convergence effect of the liquid ink 200 on the surface 14 will be reduced and the recording resolution will be lowered, and if it is too wide, when V _B ' is applied, 200 ink to be sucked
is not fully suctioned and remains, reducing the quality of recorded images. From the above, the width is usually 50~
The thickness is selected to be around 300μm. In this embodiment, the recording head 100 is held vertically, but if the width of the exposed edge surface 14 is wide, the formation of the liquid ink portion 222 by extrusion may be sufficiently prevented by the backflow caused by gravity. There are things that cannot be done. In such a case, hold the ink recording head 100 horizontally, or tilt it further and slightly tilt the tip 2.
You can use it by holding it diagonally so that 1 is at the bottom.

A recording paper with a thickness of about 80 μm is used as the recording medium 500, the distance of the gap 700 between the electrode tip 21 and the auxiliary electrode 600 is selected to be, for example, 200 μm, the maximum amplitude of each of V _B and V _B ′ is selected to be about 150 V, and the liquid Ink section 22
A high DC voltage _V
If is appropriately selected, the liquid ink portion 222 of the electrode tip 21 to which V _B is applied will cause an ink bulge on the gap 700 side due to the Coulomb force of V _A , as illustrated in the figure, and the ink will fly 230 from the tip. This causes ink adhesion 240 on the surface of the recording medium 500. On the other hand, since the liquid ink portion 222 cannot exist at the electrode tip 21 where V _B ' is applied, ink adhesion 240 cannot occur. In this way, unlike the conventional ink recording device using the Coulomb force method, the amount of ink at the electrode tip 21 is modulated and controlled by the low voltage signal voltages V _B and V _B ', and is controlled by the auxiliary voltage V _A corresponding to the flying voltage. Since no flight modulation is required, a simpler ink recording device with much lower voltage can be realized. Normally, a suitable amplitude of V _A can be operated by applying a DC voltage of about 1.5 to 2.0 KV as a bias, and V _B ' has a constant amplitude,
V _B is amplitude-modulated, pulse-width-modulated, and pulse-width-amplitude modulated with respect to the ink recording density.

However, in the conventional ink recording head, since no treatment was applied to the side edge surface 12 of the support substrate, the liquid ink portion 2 when V _B ' was applied
22 wraps around the side edge end surface 12 and forms this surface 1.
2, making the ink bulge incomplete, and the ink adhering to the side edge end surface 12 may fly, resulting in excessive ink flying 230.
This often causes unstable operation.

Furthermore, in the V _B ' application section, the wet and adhered ink on the side edge end surface 12 is difficult to attract to the porous body 40 side, causing ink flying 230, which significantly deteriorates the quality of the recorded image.

However, by applying the ink repellent agent 30 on the side edge end surface 12 as in this embodiment to make the side edge end surface 12 substantially ink repellent, ink adhesion to the side edge end surface 12 as described above can be prevented. can be prevented, and
The ink jet 230 is easily separated from the ink jet 230, and the ink jet 230 is generated accurately and stably from the electrode tip 21 in accordance with V _B and V _B ′, and correctly corresponds to its shape, resulting in high resolution, stability, and clarity. There is an advantage that image recording can be performed using the ink adhesion 240.

FIG. 2 is a perspective sectional partial structural view of another embodiment of the ink recording head and ink recording apparatus according to the present invention, and for convenience of explanation, the same parts as in FIG. 1 are designated by the same numbers.

In this embodiment, the ink recording head 100 is held substantially horizontally and a thin metal wire is used as the first electrode 20. The thin metal wire is made of an ink-philic material that is well wetted by the liquid ink 200, such as copper or tungsten, and has a thickness of about 20 to 50 μm. The surface 11 of the support substrate 10 is machined or etched to have a width and depth equal to or greater than that of the thin metal wire, for example, 20 to 30 mm.
70 μm, and so-called recesses or depression grooves 15 are provided at a pitch corresponding to the recording density. The thin metal wire is accommodated and fixed in this recessed groove 15, and its upper surface may protrude slightly above the support substrate surface 11, but is preferably located below the substrate surface 11, as illustrated in the figure. It will stick like this.
By doing so, effective ink control can be performed through the gap between the porous body 40 and the first electrode 20. The tip portion 21 may be the same as the edge 13, or may protrude a little inside the edge 13 or slightly toward the flying gap 700, but for effective ink flying 230 due to Coulomb force, the distance is about 10 to 100 μm, as illustrated in the figure. It is desirable to make it stick out like this.

Note that the tip portion 21 may be formed into a conical or truncated conical shape with the diameter decreasing toward the gap 700 side. In this case, more effective ink flying can be achieved by concentrating the electric lines of force.

In addition, when the wire diameter of the metal wire is made extremely thin, such as about 10 to 30 μm, it is also possible to directly fix it onto the substrate surface 11 without providing the depressed groove 15.

The liquid ink 200 is supplied and impregnated into the porous body 40 using a sponge band 8 installed on the second electrode 50.
This is done by 00. One end of the sponge band 800 is connected to the liquid ink 20 in the ink reservoir 300.
0 and is supplied by capillary action.

Auxiliary electrode 601 fixed toward electrode tip 21
A recording paper 50 is arranged in contact with this auxiliary electrode 601, and is fed in response to signal voltages V _B and V _B ' as shown by an arrow 502 in the figure.

The auxiliary electrode 601 receives an auxiliary voltage from the auxiliary power source 401.
V _A is applied. In this embodiment, the first electrode 1
0 as a reference potential, the second electrode 50 has a positive voltage V _B , and the auxiliary electrode 601 has a maximum amplitude |V _Bnax | of the on-voltage V _B that modulates the density of the ink deposit 240. Amplitude of auxiliary voltage V _A | V _A |
is selected to be large and a negative potential difference |V _A |−|V _Bnax |, that is, a voltage V _A of opposite polarity to V _B is applied.

By selecting the polarity relationship between V _B and _VA in this way, ink adhesion 240 can be obtained with a lower auxiliary voltage V _A than when the polarity of V _A is reversed. For example, when the material composition is the same as that shown in Fig. 1 and the gap 700 is 200 μm, the second
V _B =- for the first electrode 20 with respect to the electrode 50 of
When 150V is applied, the auxiliary electrode 601 has V _A =-
Applying 1500V causes ink adhesion 240,
If the polarity of V _A is reversed from the diagram, V _A +1800
~2000V is required, and the power supply method of this embodiment is effective for low voltage operation.

In this way, when the on-voltage V _B is V _Bnax , the amplitude of V _A is maintained in the polarity relationship shown in the figure, and the electrode tip 21
The liquid ink portion 222 generated in the ink flying 230
If we fix the bias of the amplitude of V _A so that
There is an advantage that the density of the ink deposit 240 can be controlled in response to the modulation amplitude of _VB .

Note that the first electrode 2 to which the off-voltage V _B ' is applied
At 0 part, if the amplitude of V _B ' is selected to be sufficiently large, the liquid ink part 222 disappears, so ink flying 230 cannot occur.

The reason for such low voltage operation can be interpreted as follows.

That is, taking as an example the case where the liquid ink 200 electroosmoses in the direction of the negative electrode as illustrated in FIGS.
In order to generate an interfacial electric double layer with the holes of 0 and the supporting substrate surface 11, and to charge the liquid ink 200 side positively, a negative polarity is transferred from the second electrode 50, which is a positive electrode.
Electroosmosis occurs on the first electrode 20 side where _VB is applied. Therefore, the liquid ink portion 222 on the electrode tip 21 is
Since the auxiliary electrode 601 is positively charged with the opposite polarity to the first electrode 20, the auxiliary electrode 601
If a negative electrode is formed at a more negative potential than 0, that is, opposite to the second electrode 50 which is a positive electrode, the Coulomb force will be more effective and the ink will fly at a lower voltage than when a positive electrode is formed. will occur.

As shown in FIG. 2, when installing the recessed groove 15, the first electrode 20 is not a metal wire electrode, but the recessed groove 15
It can be constructed by applying a thin layer of conductive paint or the like to the bottom of the holder. Including this case, if there is a gap between the depressed grooves 15 between the metal wire electrode 20 and the surface of the porous body 40 as described above, when the on-voltage _VB is applied, the liquid ink 200 flows through the depressed groove gap due to electroosmotic pressure. It can be ejected to the flight gap side, and the above-mentioned V _A and V _B
The selection of the polarity relationship between the two makes this even more effective, and the synergistic relationship with the Coulomb force allows for even more effective ink ejection 230.

In addition, in FIG. 2, the electrodes 20, 50, porous body 40, etc. were installed on the upper surface of the support substrate 10, but
It can be operated on the bottom side, that is, in a position where the ink recording head 100 is turned upside down.

The above description has been made by taking as an example the case where the liquid ink 200 is electroosmotic toward the negative electrode, but the same operation can be performed by reversing the voltage polarity relationship when electroosmoticing toward the positive electrode.

Although oil-based ink is used as an example of the liquid ink 200, water-based ink can be used as well, and the coloring material is not limited to dyes, but may also be pigments, and liquid ink is defined as a fluid colored body.

As described above, the present invention stabilizes the operation of an ink recording head and device using electroosmotic development of liquid ink by making the side edge surfaces of the dielectric supporting base material ink repellent to liquid ink. This enables simple and stable ink recording, making it extremely useful industrially.

[Brief explanation of drawings]

FIG. 1 is a perspective partial structural diagram of an embodiment of an ink recording head and an ink recording apparatus according to the present invention;
FIG. 2 is a perspective partial structural view of another embodiment of the ink recording head and ink recording apparatus according to the present invention. DESCRIPTION OF SYMBOLS 10... Dielectric support substrate, 20... First electrode, 30... Ink repellent agent, 40... Porous body, 5
0... Second electrode, 100... Ink recording head, 200... Liquid ink, 300... Ink container, 400... Signal voltage source, 401... Auxiliary voltage source, 500... Recording body, 600, 601 ...Auxiliary electrode, 700...Flight gap, 800...Sponge band.

Claims (1)

[Claims] 1. A porous body is installed on the surface of a dielectric support base material having a first electrode, and a second electrode is positioned on the side of the porous body opposite to the first electrode, Supplying and impregnating the porous body with liquid ink, and applying a signal voltage between the first and second electrodes to cause the liquid ink to electroosmote through the porous body, the tip of the first electrode In the ink recording head that forms a controlled liquid ink portion to be recorded on the recording medium in response to the signal voltage, the dielectric support base is in contact with the tip end side of the first electrode. An ink recording head characterized in that a side edge end face of the material is configured to be ink repellent to the liquid ink. 2. In claim 1, the first electrode is made of a metal wire, and the first electrode is provided on the surface of the dielectric support base material on the side of the porous body, or on the surface of the support base material. An ink recording head characterized in that it is disposed within a depressed groove. 3. An ink recording head according to claim 1 or 2, characterized in that the ink repellency is achieved by coating an ink repellent agent. 4 A porous body is placed on the surface of the dielectric supporting base material having the first electrode, a second electrode is positioned on the opposite side of the porous body to the first electrode, and a liquid is applied to the porous body. In addition to supplying and impregnating ink,
Applying a signal voltage between the first and second electrodes to cause the liquid ink to electroosmote through the porous body, and recording on the tip side of the first electrode in response to the signal voltage. in a relationship forming a controlled liquid ink portion to be recorded on the body;
an ink recording head in which a side edge end surface of the dielectric supporting base material in contact with the tip end side of the electrode is configured to be ink repellent to the liquid ink; A recording body is positioned with a distance therebetween, an auxiliary electrode is positioned on the side of the recording body opposite to the top surface of the first electrode, and an auxiliary voltage is applied between the auxiliary electrode and the first electrode. . A recording apparatus characterized in that the ink of the liquid ink portion is caused to fly and adhere to the surface of the recording medium. 5. In claim 4, the signal voltage applied between the first electrode and the second electrode is
The liquid ink is transferred from the second electrode side to the first electrode side.
an on-voltage that causes electroosmosis to form the liquid ink portion through the porous body on the electrode side of the auxiliary material, and an off-voltage that has a polarity opposite to this on-voltage and causes the liquid ink portion to disappear; The polarity of the voltage is when the first electrode is set as a reference potential,
A recording device characterized in that it is provided with means for selecting a polarity opposite to the on-voltage.