JPH0225336B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a recording head that utilizes the electroosmotic phenomenon of liquid ink.

A porous body is installed on a surface of a dielectric support base material having a plurality of first electrodes, a second electrode is positioned on the opposite side of the porous body to the first electrode, and an on-voltage signal that supplies and impregnates the liquid ink and electro-osmoses the liquid ink from the second electrode side to the first electrode side through the porous body, and also has a polarity opposite to this on-voltage signal. and an off signal voltage for electro-osmosis of the liquid ink from the first electrode side to the second electrode side via the porous body to the plurality of second electrodes. selectively applied to the first electrode of the signal voltage, and selectively forms a controlled liquid ink portion to be recorded on the recording medium on the tip side of the first electrode in response to the signal voltage. Electroosmotic ink recording heads have already been proposed by the present inventor.

In this ink recording head, a recording medium is brought into direct contact with the tip of the electrode to transfer and adhere a controlled liquid ink portion, or a recording medium is provided with a gap between the ends of the electrodes, and the back side thereof is An ink image can be recorded by installing an auxiliary electrode on the ink, applying a high voltage between the first or second electrode, and using the Coulomb force to cause the ink to fly and adhere to the recording medium from the liquid ink portion. An ink recording device can be realized.

However, in this type of ink recording head,
As a result of various experiments, when on-voltage signals are simultaneously applied to a plurality of consecutive first electrodes adjacent to each other,
The amount of ink in the liquid ink section is larger than in other cases, and the ink cannot be separated from each other between the first electrodes, so that the ink adhering to the recording medium is abnormally thick, dense, and strip-shaped. , it was found that point separation was not possible.

Therefore, in ink image recording using the conventional operation method, due to the above-mentioned development, depending on the application conditions of the on-voltage signal, there are areas where the ink is recorded in dots corresponding to the tip of the first electrode, and areas where the ink is recorded on a plurality of electrodes. Corresponding to the leading edge, thick, dark, band-shaped ink recording locations intersect with each other in the ink recorded image, degrading the image quality.

The object of the present invention is to propose a drive method that improves the drawbacks caused by the above-mentioned operational problems of the conventional method.

A feature of the present invention is that in the recording method using electroosmotic ink described above, an auxiliary electrode is disposed between the plurality of first electrodes, and the off-voltage signal is transmitted to the auxiliary electrode with respect to the second electrode. The purpose is to apply a bias voltage of the same polarity as the

Examples of the present invention will be described in detail below. Figure 1 shows
1 is a diagram illustrating a perspective partial structure and a power supply system of a recording apparatus to which an electroosmotic ink recording head and its driving system according to the present invention are applied; FIG.

In the figure, 100 is an electroosmotic ink recording head, and 200 is a liquid ink contained in an ink container, which is supplied to and impregnated into the ink recording head 100 by utilizing the capillary action of a sponge body 700.
400 is a signal voltage source, 401 is an auxiliary voltage source, 50
0 is a recording sheet such as paper as a recording medium, and 600 is a pressure roller such as rubber that presses the recording medium 500 against the side edges 12 and 13 of the ink recording head 100 and feeds the paper in the direction of arrow 501 in the figure. be.

10 is a dielectric support base material such as a borosilicate glass plate;
The surface 11 side is etched with a desired pitch depending on the ink recording resolution, for example, at a density of 4 lines per 1 mm, and with a width of 50 to 100 μm, for example, by etching or machining.
A depression structure 16 having a depth of about 20 to 70 μm is provided. A first electrode 20 made of a metal film of gold or the like formed by vapor deposition or plating is deposited on the bottom of the groove 16 and further over the side walls to a thickness of about 1 μm.

Also, between the first electrodes 20, for example, the gap surface 15 of the electrodes 20 on the supporting base material surface 11.
An auxiliary electrode 20' is provided. The auxiliary electrode 20', like the electrode 20, is made of, for example, a metal coating film of about 1 μm thick, such as gold. The deposition position and width of the electrode 2
It is also possible to install the electrode on the entire surface of the gap surface 15 without contacting the electrode 20, but from the viewpoint of effective control of the amount of ink recorded, it is necessary to place it approximately in the center of the gap surface 15 and to have the same width as the electrode 20. Alternatively, it is desirable that the thickness be smaller than that, for example, about 30 to 40 μm.

Thus, on this supporting base material surface 11, there is a porous body 4 having holes or gaps that substantially penetrate in the thickness direction, and through which the liquid ink 200 can permeate in the thickness direction.
0 to form a groove gap 30 with the surface of the first electrode 20.

The porous body 40 has a thickness of, for example, 20 to 200 μm,
A so-called microporous membrane filter made of cellulose acetate with an average pore diameter of 0.1 to 8 μm and a porosity of about 60 to 80% is used. porous body 4
Other materials such as plastic materials, glass, and porcelain materials can be used as the material for the material 0, if necessary.

It is preferable that the edge 41 of the porous body 40 be located inside the edge 13 of the support base material 10 by, for example, about 50 to 300 μm, so that an exposed edge surface 14 is formed on the surface 11 of the support base material. The exposed edge surface 14 can utilize the electrical convergence effect of the liquid ink utilizing the electroosmotic property of the liquid ink 200 on this surface 14, and is useful for high-resolution ink recording.

The surface side of the porous body 40 opposite to the supporting base material 10 has a thickness of pores penetrating in the thickness direction at a density of, for example, 100 to 300 meshes per inch.
A liquid ink-permeable second electrode 50 such as a stainless steel plate or metal mesh with a thickness of about 50 to 300 μm is installed, and the porous body 40 is pressed and fixed. In addition, the second
The electrode 50 can also be made into a liquid ink permeable electrode by directly applying a thin conductive paint containing lead, silver, etc. to the surface of the porous body 40.

The end of the porous body 40 on the opposite side to the installation surface of the recording medium 500 is sealed with a sealing agent 60 such as an adhesive to connect the porous body 40 to the surface of the supporting base material 11 and the surface of the first electrode 20. This seals the space between the two and 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 sponge body 700 and second electrode 50 .

As the liquid ink 200, the above-mentioned porous body 4 is used.
0 and the supporting base material 10 so that electroosmosis occurs in the same electric field polarity direction. liquid ink 20
0, an oil-soluble ink is used, in which, for example, about 2 to 5% by weight of an oil-soluble dye is mixed as a coloring agent into a liquid material made of γ-methacrylopropyltrimethoxysilane. Incidentally, a binder, a charge control agent, a surfactant, etc. can also be mixed as required.

This type of ink electroosmoses into the above-mentioned porous body 40 and supporting base material 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 within the range of electric field strength of about 2 V/μm, taking into account dielectric breakdown. Each of the first electrodes 20, which are recording electrodes, is connected to a signal voltage source 400, and receives signal voltages V _B ,
V _B ' is selectively applied between the second electrode 50 and the second electrode 50 . Further, the auxiliary electrodes 20' are collectively connected to an auxiliary voltage source 401, and a bias voltage V _A having the same polarity as the signal voltage V _B ' is applied.

Now, as a signal voltage as shown in the figure, the second electrode 5
The off-voltage signal V _B ′ and the bias voltage V _A , which are respectively positive with respect to 0, are applied to the first electrode 20 and the auxiliary electrode 2.
The operation will be explained by taking as an example a case where a negative on-voltage signal V _B is applied to a plurality of adjacent first electrodes 20.

In the part where V _B ′ and V _A are applied, the liquid ink 200 flows in the direction indicated by the arrow 210 from the first electrode 20 side forming the positive electrode to the second electrode 50 side forming the negative electrode.
At the same time, the liquid ink 200 located at the tips 21, 21' of the electrodes 20, 20' is also sucked up as shown by the arrow 211 in the figure. In particular, the liquid ink 20 located at the tip 21
0 is the depressed groove 16, the electrode 20, and the porous body 40.
It is effectively sucked up through the groove gap 30 between the two.

Therefore, in this state where V _B ' and _VA are applied, liquid ink 200, that is, liquid ink portion 222 cannot exist at the electrode tips 21, 21'.

On the other hand, in the first electrode 20 section to which V _B is applied,
The first electrode 20 which is a negative electrode from the second electrode 50 side
Electroosmosis occurs to the side through the porous body 40 as shown by the arrow 220 in the figure, and is concentrated toward the surface of the first electrode 20. On the other hand, the adjacent auxiliary electrode 20' is applied with V _A to form a positive electrode, and the second electrode 20 is
V _B is applied to form a negative electrode, and the support base material surface 11, that is, the electrode gap surface 15 is also applied to the porous body 4.
0, the liquid ink 200 electroosmoses from the electrode 20' side to the electrode 20 side through this electrode gap surface 15 as shown by arrow 212 in the figure.

However, the end opposite to the edge 13 is coated with the sealant 6.
0, it is pushed out toward the electrode tip 21 through the surface of the electrode 20, that is, through the groove gap 30, by the two types of electroosmotic pressures described above.

Due to this rapid extrusion, the liquid ink 200 may overflow from the recessed groove 16 on the exposed edge surface 14, but as described above, this overflowing ink is directed from the electrode 20' side as indicated by the arrow 212 illustrated in the figure. Due to the convergence effect of electro-osmosis on the exposed edge surface 14 toward the electrode 20 side, the amount of ink is controlled at the electrode tip 21 with respect to the position and amplitude of V _B in accordance with the shape of the electrode 20. Liquid ink section 222
form. Therefore, even if the on-voltage signal V _B is simultaneously applied to a plurality of adjacent first electrodes 20, the auxiliary electrode 2 on the exposed edge surface 14
Liquid ink 20 is applied to the electrode gap surface 15 including 0'.
0, and the liquid ink portion 222 will be formed only on the electrode tip 21.

Therefore, the thickness of the recording body 500 is, for example, 80 μm.
For example, a constant amplitude of 150V is used as the off-voltage signal V _B ′, and a bias voltage _V
The same polarity as V _B ′ and preferably the same degree as V _B ′, e.g.
Apply 150V DC voltage and turn on voltage signal V _B
The polarity is opposite to V _B ′ and the maximum amplitude is
When amplitude modulation, pulse width modulation, and pulse width amplitude modulation are performed at approximately 150V depending on the recording density, an independent liquid ink portion whose amount of ink is controlled is created at each of the common ends of the electrodes 21 to which _VB is applied according to the signal voltage. 222, and their contact and transfer causes independent ink adhesion 240 on the surface of the recording medium 500.

On the other hand, a liquid ink portion 22 is provided at the common end portion 21 of the first electrode to which V _B ′ is applied and the common end portion 21 of the auxiliary electrode to which V _A is applied.
2 cannot exist, so ink adhesion 240 does not occur.

Independent ink deposits 240 are formed on the electrode tip 2 in response to the applied signal voltages V _B and V _B ′.
1, and no ink adhesion occurs from the electrode gap 15 including the electrode tip 21'.

In addition, the mutually adjacent first electrodes 20 each have a V _A
isolated by an auxiliary electrode 20' biased by . Therefore, each of the first electrodes 20 is less affected by the signal voltage applied to the adjacent electrode 20, and the liquid ink portion 222 can be controlled by electroosmosis in accordance with the signal voltage applied to the first electrode 20. Uniform ink deposition 240 is obtained in exact response to the applied signal voltage.

However, conventional electroosmotic ink heads do not have auxiliary electrodes. Therefore, since the adjacent electrodes 20 are not electrically isolated from each other, the formation of the liquid ink portion 222 is influenced by this.

In other words, the off-voltage signal V _B ' is applied to both sides,
When the on-voltage signal V _B is applied to the middle one, and when the continuous electrodes 20 are adjacent to each other.
Comparing the amount of ink in the liquid ink portion 222 when V _B is applied, the latter is smaller than the unit liquid ink portion 222 due to the synergistic effect with the adjacent electrode 20 applying V _B.
The amount of ink per unit 2 increases, resulting in a thicker and thicker ink adhesion 240 compared to the former.

In other words, since the auxiliary electrode 20' is not present, there is no convergence effect on the liquid ink spilling out of the depressed groove 16. Therefore, in the latter case, the liquid ink portion 222 spreads over the edges 13 of the plurality of electrodes 20 to which V _B is applied, and the ink adheres 24 in a band shape.
yields 0.

Therefore, ink recorded images contain a mixture of dotted ink adhesion and banded ink adhesion, and the ink adhesion density in the banded parts is higher than that in the dotted parts, making it difficult to record uniform ink with good image quality. There is.

According to this embodiment, the above-mentioned conventional drawbacks are improved, and uniform ink recording with good image quality can be performed.

As in this embodiment, the first electrode 20 is connected to the recessed groove 1.
The configuration in which the ink is installed between six inks is useful for contact transfer recording because it allows a high ink adhesion density. In such a case, the electrode gap surface 15 is
The configuration in which the auxiliary electrode 20' is provided allows the pitch of the recessed grooves 16 to be narrowed during manufacturing, and is useful in the configuration of the ink head 100 for high resolution recording. However, if the resolution is not so important, a recessed groove 16 of the same size is installed in advance and an electrode is deposited therein, and then V _A is applied to every other electrode and used as the auxiliary electrode 20'. , the remainder can be used as the first electrode 20.

Further, like the auxiliary electrode 20', the first electrode 20 is placed on the supporting base material surface 1 without providing the recessed groove 16.
1.

In this case as well, parallel grid electrodes such as metal films are deposited on the support base surface 11 at regular intervals in advance, and then _VA is applied to every other electrode to form the auxiliary electrodes 20'.

The bias voltage V _A does not necessarily have a voltage value as long as it has the same polarity as the off-signal voltage V _B ', and can be selected as appropriate. However, if the voltage is too low, the liquid ink 200 electropenetrates on the exposed edge surface 14 from the first electrode 20 side, which has been switched to the off-voltage signal V _B ', and a liquid ink portion is formed on the electrode 20'. In addition, the electrical isolation effect between the electrodes 20 is also reduced. On the other hand, if the bias voltage V _A is extremely high, the electroosmosis effect of the adjacent electrode 20 to which the on-voltage signal V _B is applied is inhibited, and the formation of the liquid ink portion 222 is incomplete. becomes. Therefore, if the voltage value is set to be approximately the same as the voltage value of the off-voltage signal V _B ', and preferably a means for making this voltage value variable is provided, so that it can be finely adjusted as necessary, Furthermore, the operation becomes more stable.

FIG. 2 is a diagram showing a perspective partial structure and power supply system of another embodiment of the electroosmotic ink recording head and operation system according to the present invention. Note that for convenience of explanation, the liquid ink supply means is not shown.

In this example, we use a metal wire made of copper or the like with a thickness of about 20 to 60 μm, and a wire made of fluorinated ethylene polymer with a thickness of 20 to
The ink-repellent coating material 10'' with a thickness of about 50 μm is broken to form a band-like position, which is then bonded to an auxiliary support base 10' such as glass or plastic with an adhesive (not shown).The porous material in this area is The surface of the strip on the side 40 is polished flat, and the metal wire is exposed with a semicircular cross section. It consists of a supporting base material 10'. Every other metal wire is collectively connected to an auxiliary voltage source 401, and the bias voltage V _A described in FIG. 1 is applied to form the auxiliary electrode 20'. The remaining metal lines are connected to respective signal voltage sources 400 and are selectively applied with an on-voltage signal V _B ′ and an off-voltage signal V _B ′, thereby forming the first electrode 20 .

The second electrode 50 uses a metal plate having a through hole 51.

In this configuration, it is difficult for the liquid ink 200 to exist only on the electrodes 20, 21' on the exposed edge surface 14 due to the ink repellency of the ink-repellent coating material 10''.The tip of the auxiliary electrode 21'21', as mentioned above, there is no liquid ink 200 due to the suction effect of electroosmosis toward the electrode 50 side due to the effect of bias V _A , while on the other hand, V _B , V _B are present at the tip 21 of the first electrode 20. According to ', a controlled liquid ink portion is formed by the extrusion and suction effect of the liquid ink 200 by electroosmosis through the surface of the porous body 40 and the electrode 20.

The above configuration includes the auxiliary electrode 20' and the first electrode 2.
Since the same 0 is used and each is insulated by the ink-repellent coating 10'', there is an advantage that the pitch interval between them can be narrowed, that is, high resolution can be easily obtained in ink recording. However, since the first electrodes 20 are electrically isolated from each other due to the existence of the auxiliary electrode 20', the influence of the signal voltages V _B and V _B ' applied to the adjacent first electrodes 20 can be prevented. A stable ink image can be recorded by dotted ink adhesion.

This type of configuration can be used for contact and transfer recording as well as in FIG.
A recording paper is provided at a certain distance from the recording paper, a high voltage electrode is provided on the back side of the recording paper, and a high voltage is applied between the electrode 20 and the tip 21, so that a controlled liquid ink portion is sprayed onto the surface of the recording paper with a coulomb. It is useful for ink recording using the ink flying adhesion method.

As described above, the present invention provides a recording method using electroosmotic ink in which an auxiliary electrode is provided between each of a plurality of first electrodes, and the auxiliary electrode is connected to the second electrode. An ink recording head equipped with a means for applying a bias voltage of the same polarity as the off-voltage signal and its operating method enables stable ink recording separated in accordance with the signal voltage, and recording with excellent ink image quality. It is extremely useful in industry.

[Brief explanation of drawings]

FIG. 1 is a perspective partial structure and power supply system diagram of an electroosmotic ink recording head according to the present invention and a recording apparatus to which the operating system thereof is applied, and FIG. 2 is a diagram of an electroosmotic ink recording head according to the present invention and its operation system. It is a figure which shows the perspective partial structure of another Example of an operation method, and a power supply method. 10...Supporting base material, 20...First electrode, 2
0'...Auxiliary electrode, 30...Groove gap, 40...Porous body, 50...Second electrode, 60...Sealing agent,
100...Electroosmotic ink recording head, 200...
...Liquid ink, 300...Ink container, 400...
...Signal voltage source, 401...Auxiliary voltage source, 500...
... Recording body, 600 ... Pressure roller, 700 ...
Sponge body.

Claims (1)

[Claims] 1. A porous body is installed on a surface of a dielectric support base material having a plurality of first electrodes, and the first electrode of this porous body is
A second electrode is positioned on the opposite side to the electrode, and liquid ink is supplied to and impregnated into the porous body, and the first electrode is connected to the porous body through the porous body. an on-voltage signal that electroosmoses the liquid ink from the second electrode side to the first electrode side; and an on-voltage signal that electroosmoses the liquid ink from the second electrode side to the first electrode side; selectively applying a signal voltage to the plurality of first electrodes with respect to the second electrode, including an off-voltage signal that causes the liquid ink to electro-osmose on the electrode side of the electrode, and in response to the signal voltage, In an electroosmotic ink recording head that selectively forms a controlled liquid ink portion to be recorded on a recording medium on the tip side of the first electrode, between the plurality of first electrodes, A recording head using electroosmotic ink, characterized in that an auxiliary electrode is provided, and means is provided for applying a bias voltage having the same polarity as the off-voltage signal to the second electrode.